Rotary compressor

FIG. 1 is a longitudinal sectional view illustrating an example of a rotary compressor according to the invention and FIG. 2 is a lateral sectional view of a first compressing unit and a second compressing unit of the example as viewed from above.

As illustrated in FIG. 1 , a rotary compressor 1 includes a compressing unit 12 which is disposed in a lower portion of a sealed vertically-placed cylindrical compressor housing 10 , and a motor 11 which is disposed in an upper portion of the compressor housing 10 and drives the compressing unit 12 via a rotation shaft 15 .

A stator 111 of the motor 11 is formed in a cylindrical shape and is fixed by shrinkage fitting to an inner circumferential surface of the compressor housing 10 . A rotor 112 of the motor 11 is disposed in an inside portion of the cylindrical stator 111 and is fixed by shrinkage fitting to the rotation shaft 15 which mechanically connects the motor 11 and the compressing unit 12 to each other.

The compressing unit 12 includes a first compressing unit 12 S and a second compressing unit 12 T, and the second compressing unit 12 T is disposed above the first compressing unit 120 . As illustrated in FIG. 2 , the first compressing unit 120 includes an annular first cylinder 121 S. The first cylinder 121 S includes a first side-flared portion 122 S extending from an annular outer circumference thereof, and a first inlet hole 135 S and a first vane groove 128 S are radially provided in the first side-flared portion 122 S. In addition, the second compressing unit 12 T includes an annular second cylinder 121 T. The second cylinder 121 T includes a second side-flared portion 122 T extending from an annular outer circumference thereof and a second inlet hole 135 T and a second vane groove 128 T are radially provided in the second side-flared portion 122 T.

As illustrated in FIG. 2 , a circular first cylinder inner wall 123 S is formed concentrically with the rotation shaft 15 of the motor 11 in the first cylinder 121 S. A first annular piston 125 S having an outer diameter smaller than an inner diameter of the first cylinder 121 S is disposed in the first cylinder inner wall 123 S and a first cylinder chamber 130 S which sucks, compresses and discharges a refrigerant is formed between the first cylinder inner wall 123 S and the first annular piston 125 S. A circular second cylinder inner wall 123 T is formed concentrically with the rotation shaft 15 of the motor 11 in the second cylinder 121 T. A second annular piston 125 T having an outer diameter smaller than an inner diameter of the second cylinder 121 T is disposed in the second cylinder inner wall 123 T and a second cylinder chamber 130 T which sucks, compresses and discharges a refrigerant is formed between the second cylinder inner wall 123 T and the second annular piston 125 T.

The first vane groove 128 S extending in the radial direction from the first cylinder inner wall 123 S over the entire cylinder height is formed in the first cylinder 121 S and a flat plate-shaped first vane 127 S is slidably fitted into the first vane groove 128 S. The second vane groove 128 T extending in the radial direction from the second cylinder inner wall 123 T over the entire cylinder height is formed in the second cylinder 121 T and a plate-shaped second vane 127 T is slidably fitted into the second vane groove 128 T.

As illustrated in FIG. 2 , a first spring hole 124 S is formed on an outer side of the first vane groove 128 S in the radial direction so as to communicate with the first vane groove 128 S from an outer circumferential portion of the first side-flared portion 122 S. A first vane ring (not illustrated) which presses a back surface of the first vane 127 S is inserted into the first spring hole 124 S. A second spring hole 124 T is formed on an outer side of the second vane groove 128 T in the radial direction so as to communicate with the second vane groove 128 T from an outer circumferential portion of the second side-flared portion 122 T. A second vane spring (not illustrated) which presses a back surface of the second vane 127 T is inserted into the second spring hole 124 T.

When the rotary compressor 1 is started up, the first vane 127 S protrudes into the first cylinder chamber 130 S from an inside of the first vane groove 128 S into the first cylinder chamber 130 S by repulsive force of the first vane spring, a tip thereof is in contact with the outer circumferential surface of the first annular piston 125 S, and the first vane 127 S divides the first cylinder chamber 130 S into a first inlet chamber 131 S and a first compression chamber 133 S. In addition, similarly the second vane 127 T protrudes from an inside of the second vane groove 128 T into the second cylinder chamber 130 T by repulsive force of the second vane spring, the tip thereof is in contact with an the outer circumferential surface of the second annular piston 125 T, and the second vane 127 T divides the second cylinder chamber 1301 into a second inlet chamber 131 T and a second compression chamber 133 T.

In addition, a first pressure guiding-in path 129 S which communicates an outside of the first vane groove 123 S in the radial direction and an inside of the compressor housing 10 by an opening portion R (see FIG. 1 ), in which the compressed refrigerant in the compressor housing 10 is introduced, and which applies a back pressure by a pressure of the refrigerant to the first vane 1270 is formed in the first cylinder 121 S. The compressed refrigerant in the compressor housing 10 is also introduced from the first spring hole 124 S. In addition, a second pressure guiding-in path 129 T which communicates an outside of the second vane groove 128 T in the radial direction and an inside of the compressor housing 10 by the opening portion R (see FIG. 1 ), in which the compressed refrigerant in the compressor housing 10 is introduced, and which applies a back pressure by the pressure of the refrigerant to the second vane 127 T is formed in the second cylinder 121 T. The compressed refrigerant in the compressor housing 10 is also introduced from the second spring hole 124 T.

A first inlet hole 135 S which communicates the first inlet chamber 131 S and the outside portion with each other is provided in the first side-flared portion 122 S of the first cylinder 121 S so as to suck a refrigerant from the outside portion into the first inlet chamber 131 S. A second inlet hole 135 T which communicates the second inlet chamber 131 T and the outside portion with each other is provided in the second side-flared portion 122 T of the second cylinder 121 T so as to suck a refrigerant from the outside portion into the second inlet chamber 131 T. The cross sections of the first inlet hole 135 S and the second inlet hole 135 T are circular.

In addition, as illustrated in FIG. 1 , a intermediate partition plate 140 is disposed between the first cylinder 121 S and the second cylinder 121 T and partitions between the first cylinder chamber 130 S (see FIG. 2 ) of the first cylinder 121 S and the second cylinder chamber 130 T (see FIG. 2 ) of the second cylinder 121 T. The intermediate partition plate 140 closes an upper end portion of the first cylinder 121 S and a lower end portion of the second cylinder 121 T.

A lower end plate 160 S is disposed at the lower end portion of the first cylinder 121 S and closes the first cylinder chamber 130 S of the first cylinder 121 S. In addition, an upper end plate 160 T is disposed at the upper end portion, of the second cylinder 121 T and closes the second cylinder chamber 130 T of the second cylinder 121 T. The lower end plate 160 S closes the lower end portion of the first cylinder 121 S and the upper end plate 160 T closes the upper end portion of the second cylinder 121 T.

A sub-bearing unit 161 S is formed on the lower end plate 160 S and a sub-shaft unit 151 of the rotation shaft 15 is rotatably supported by the sub-bearing unit 161 S. A main bearing unit 161 T is formed on the upper end plate 160 T and a main shaft unit 153 of the rotation shaft 15 is rotatably supported by the main bearing unit 161 T.

The rotation shaft 15 includes a first eccentric portion 152 S and a second eccentric portion 152 T which are eccentrically shifted by 180° phase from each other, the first eccentric portion 152 S is rotatably fitted to the first annular piston 125 S of the first compressing unit 12 S, and the second eccentric portion 152 T is rotatably fitted to the second annular piston 125 T of the second compressing unit 12 T.

When the rotation shaft 15 rotates, the first annular piston 125 S revolves clockwise in FIG. 2 along the first cylinder inner wall 123 S in the first cylinder 121 S and the first vane 127 S reciprocates following the first annular piston 125 S. Due to the movement of the first annular piston 125 S and the first vane 127 S, the capacities of the first inlet chamber 131 S and the first compression chamber 133 S are continuously changed, and the compressing unit 12 continuously sucks, compresses and discharges a refrigerant. In addition, when the rotation shaft 15 rotates, the second annular piston 125 T revolves clockwise in FIG. 2 along the second cylinder inner wall 123 T in the second cylinder 121 T and the second vane 127 T reciprocates following the second annular piston 125 T. Due to the movement of the second annular piston 125 T and the second vane 127 T, the capacities of the second inlet chamber 131 T and the second compression chamber 133 T are continuously changed, and the compressing unit 12 continuously sucks, compresses and discharges a refrigerant.

As illustrated in FIG. 1 , a lower end plate cover 170 S is disposed under the lower end plate 160 S and a lower muffler chamber 180 S is formed between the lower end plate 160 S and the lower end plate cover 170 S. The first compressing unit 12 S opens into the lower muffler chamber 180 S. In other words, a first discharge hole 190 S (see FIG. 2 ) communicating the first compression chamber 133 S of the first cylinder 121 S and the lower muffler chamber 180 S with each other is provided in the vicinity of the first vane 127 S of the lower end plate 160 S and a reed valve type of first discharge valve 200 S for preventing back-flow of the compressed refrigerant is disposed in the first discharge hole 190 S.

The lower muffler chamber 180 S is one annularly formed chamber, and is a portion of a communication path which communicates a discharge side of the first compressing unit 12 S and an inside of an upper muffler chamber 180 T with each other through a refrigerant path hole 136 (see FIG. 2 ) which passes through the lower end plate 160 S, the first cylinder 121 S, the intermediate partition plate 140 , the second cylinder 121 T, and the upper end plate 160 T. The lower muffler chamber 180 S reduces pressure pulsation of the discharged refrigerant. In addition, a first discharge valve cap 201 S for limiting the flexural valve opening amount of the first discharge valve 200 S, which overlaps the first discharge valve 200 S, is fixed together with the first discharge valve 200 S by rivets. The first discharge hole 190 S, the first discharge valve 200 S, and the first discharge valve cap 201 S constitute a first discharge valve unit of the lower end plate 160 S.

As illustrated in FIG. 1 , an upper end plate cover 170 T is disposed above the upper end plate 160 T and the upper muffler chamber 180 T is formed between the upper end plate 160 T and the upper end plate cover 170 T. A second discharge hole 190 T (see FIG. 2 ) communicating the second compression chamber 133 T of the second cylinder 121 T and the upper muffler chamber 180 T with each other is provided in the vicinity of the second vane 127 T of the upper end plate 160 T, and a reed valve type of second discharge valve 200 T for preventing back-flow of the compressed refrigerant is disposed in the second discharge hole 190 T. In addition, a second discharge valve cap 201 T for limiting the flexural valve opening amount of the second discharge valve 200 T, which overlaps the second discharge valve 200 T, is fixed together with the second discharge valve 200 T by rivets. The upper muffler chamber 180 T reduces pressure pulsation of the discharged refrigerant. The second discharge hole 190 T, the second discharge valve 200 T, and the second discharge valve cap 201 T constitute a second discharge valve unit of the upper end plate 160 T.

The lower endplate cover 170 S, the lower end plate 160 S, the first cylinder 121 S and the intermediate partition plate 140 are inserted from the lower side and are fastened to the second cylinder 121 T by a plurality of penetrating bolts 175 screwed into female screws provided in the second cylinder 121 T The upper end plate cover 1701 and the upper end plate 160 T are inserted from the upper side and fastened to the second cylinder 121 T by a penetrating bolt illustrated) screwed into the female screws provided in the second cylinder 121 T. The lower end plate cover 170 S, the lower end plate 160 S, the first cylinder 121 S, the intermediate partition plate 140 , the second cylinder 121 T, the upper end plate 160 T, and the upper end plate cover 170 T integrally fastened by the plurality of penetrating bolts 175 or the like constitute the compressing unit 12 . An outer circumferential portion of the upper end plate 160 T of the compressing unit 12 is fixed to the compressor housing 10 by spot welding and thus the compressing unit 12 is fixed to the compressor housing 10 .

A first through hole 101 and a second through hole 102 are spaced apart from each other in the axial direction and sequentially provided on the outer circumferential wall of the cylindrical compressor housing 10 from the lower portion thereof so as to make a first inlet pipe 104 and a second inlet pipe 105 pass through the holes respectively. In addition, an accumulator 25 formed of an independent cylindrical sealed container is held by an accumulator holder 252 and an accumulator band 253 on an outside portion of the compressor housing 10 .

A system connecting pipe 255 which is connected to an evaporator of a refrigerant circuit is connected to a center of a top portion of the accumulator 25 and a first low-pressure communication tube 31 S and a second low-pressure communication tube 31 T of which one end extends to an upper side of an inside portion of the accumulator 25 and of which the other end is connected to the other end of each the first inlet pipe 104 and the second inlet pipe 105 are fixed to a bottom through hole 257 provided to a bottom portion of the accumulator 25 .

The first low-pressure communication tube 3 which guides a low-pressure refrigerant of the refrigerant circuit to the first compressing unit 12 S via the accumulator 25 is connected to the first inlet hole 135 S (See FIG. 2 ) of the first cylinder 121 S via the first inlet pipe 104 as an inlet portion. In addition, The second low-pressure communication tube 31 T which guides the low-pressure refrigerant of the refrigerant circuit to the second compressing unit 121 via the accumulator 25 is connected to the second inlet hole 135 T (See FIG. 2 ) of the second cylinder 121 T via the second inlet pipe 105 as an inlet portion. In other words, the first inlet hole 135 S and the second inlet hole 135 T are connected in parallel to the evaporator of the refrigerant circuit.

A discharge pipe 107 as a discharge portion, which is connected to the refrigerant circuit and discharges a high-pressure refrigerant to a condenser side of the refrigerant circuit, is connected to a top portion of the compressor housing 10 . In other words, the first discharge hole 190 S and the second discharge hole 190 T are connected to a condenser of the refrigerant circuit.

Lubricant oil is enclosed to approximately the height of the second cylinder 121 T in the compressor housing 10 . In addition, the lubricant oil is sucked up from an oil feeding pipe 16 attached to the lower end portion of the rotation shaft 15 by a pump impeller (not illustrated) inserted into a lower portion of the rotation shaft 15 , circulates through the compressing unit 12 , lubrication of the sliding component (first annular piston 125 S and second annular piston 125 T) is performed and minute gaps of the compressing unit 12 are sealed.

Next, with reference to FIG. 1 to FIG. 6 , a characteristic configuration of the rotary compressor 1 of the example using a refrigerant R32 will be described. The temperature increase Δt [K] of the intake refrigerant in the first cylinder chamber 130 S and the second cylinder chamber 130 T is expressed by the following expression (1).

Δ t=h·S ·Δθ/( m·c )  (1)

where,

h: heat transfer coefficient [W/(mm 2 ·K)] S: wall surface area of cylinder chamber ( 130 S and 130 T) [mm 2 ] Δθ: difference between wall surface temperature and refrigerant temperature [K] m: refrigerant mass [g/s]=(cylinder chamber capacity V [mm 3 /rev])×(intake refrigerant density ρ [g/mm 3 ]) c: refrigerant specific heat [J/(g·K)]

The intake refrigerant density ρ of the refrigerant R32 is about 70% of a refrigerant R410A and the evaporation enthalpy is about 140%. Therefore, substantially, the same exclusion capacity V (cylinder chamber capacity) can be applied. Since the exclusion capacities V are equal to each other, the size of the compressing unit 12 for the refrigerant R410A can be used and the wall surface areas S are also the same. Therefore, Δt in the above expression (1) is increased for the refrigerant R32 having a smaller intake refrigerant density ρ than for the refrigerant R410A and the refrigerant R32 is likely to be heated compared to the refrigerant R410A. From this, in a case where the refrigerant R32 is adopted, suppression of refrigerant heating is effective for improving compression efficiency compared to a case where refrigerant R410A is used.

In the invention, when the wall surface area of the cylinder chamber ( 130 S and 130 T) is referred to as and the exclusion capacity (cylinder chamber capacity) is referred to as V, the refrigerant heating is suppressed by the sizes of the compressing units 12 S and 12 T being set so that S/V is decreased.

The wall surface area S of one cylinder chamber (first cylinder chamber 130 S or second cylinder chamber 130 T) of the rotary compressor 1 of the example is expressed by the following expressions (2) to (5).

S= 2 Sb+Sc+Sr   (2)

Sb =( Dc 2 −( Dc− 2 e ) 2 )π/4  (3)

Sc=π·Dc·Hc   (4)

Sr =π·( Dc −2 e )· Hc   (5)

where,

Sb: area of the end plate ( 160 S and 160 T) portion or the intermediate partition plate ( 140 ) portion of the cylinder chamber [mm 2 ]

Sc: inner ( 121 S and 121 T) inner circumferential wall area [mm 2 ]

Sr: annular piston ( 125 S and 125 T) outer circumferential wall area [mm 2 ]

Dc: cylinder ( 121 S and 121 T) inner diameter [mm]

e: eccentric portion ( 152 S and 152 T) eccentric amount [mm]

Hc: cylinder ( 121 S and 121 T) height [mm]

In addition, the exclusion capacity (cylinder chamber capacity) V of one cylinder chamber (first cylinder chamber 130 S or second cylinder chamber 130 T) of the rotary compressor 1 is expressed by the following expression (6).

V=π·e ·( Dc−e )· Hc   (6)

From expressions (2) and (6), S/V is expressed by the following expression (7).

S/V= 2( e+Hc )/( e−Hc )  (7)

Since as the exclusion capacity V is increased, S/V is decreased, in order to evaluate the size of the cylinder chamber, it is necessary to eliminate the influence of the exclusion capacity V. Therefore, let S/V multiplied by V 1/3 be referred to as parameter A [dimensionless]. Parameter A is expressed by the following expression. (8), and as parameter A is decreased, the influence of the refrigerant heating is decreased.

A =( e+He )·( Dc−e ) 1/3 /( e·Hc ) 2/3   (8)

Next, in Japanese Patent No. 4864572, it is described that the compression efficiency is improved by reducing the refrigerant leak amount by decreasing the ratio Hc/Dc of the cylinder height He and the cylinder inner diameter Dc.

FIG. 3 is a diagram illustrating relationship between parameter A and Hc/Dc. As illustrated in FIG. 3 , as parameter A is decreased, Hc/Dc tends to be increased. In Examples 1 to 3 illustrated in FIG. 3 , the exclusion capacity V, the inner diameter of the compressor housing 10 and the cylinder height. Hc of the rotary compressor 1 are the same, and the eccentric portion eccentric amount e is changed. Calculation is made for two patterns with cylinder height Hc large and cylinder height Hc small.

In the calculation example (Hc large), the cross-sectional areas of the inlet holes 135 S and 135 T are set to the cylinder height Hc which can be commonly secured in the related art. As the eccentric portion eccentric amount e increases, the cylinder inner diameter Dc is decreased and thus Hc/Dc is increased. However, parameter A can be decreased.

In the calculation example (Hc small), the cylinder height Hc is set to be low until the cross-sectional areas of the inlet holes 135 S and 135 T become about 80% of those in the related art. By the cylinder height Hc being set to be low, in a case of the same parameter A value, Hc/Dc can be decreased and the amount of refrigerant leakage can be reduced. In this case, although since the cross-sectional areas of the inlet holes 135 S and 1357 are decreased, the pressure loss of the intake refrigerant is increased, since the refrigerant R32 has a lower density than the refrigerant R410A, the influence of pressure loss is decreased.

In the rotary compressor of the related art using the refrigerant R410A, since decrease in the Hc/Dc is effective for improving the compression efficiency, as a result of selecting the sizes of the compressing units 12 S and 12 T with a small Hc/Dc, the sizes of the compressing units 12 S and 12 T are not set so that parameter A is decreased. In the rotary compressor 1 using the refrigerant R32 which is greatly affected by the refrigerant heating, compression efficiency can be further improved than the rotary compressor of the related art by setting parameter A to a value smaller than the lower limit value 4.1 (see FIG. 3 ) of the rotary compressor of the related art.

FIG. 4 is a diagram illustrating relationship between parameter A and the sub-shaft unit ( 151 ) surface pressure. The sizes of the compressing units 12 S and 12 T with small parameter A are increased in the eccentric amount e of the eccentric portions ( 152 S and 152 T). When the eccentric amount e increases, it is necessary to decrease the diameter of the sub-shaft unit 151 for the convenience of assembling the rotation shaft 15 and the annular pistons 125 S and 125 T and when the sub-shaft diameter is decreased, the sub-shaft surface pressure P is increased. Therefore, parameter A has a lower limit value.

Next, a calculation method of the sub-shaft surface pressure P will be described. The axial load F [N] is expressed by the following expression (9).

F=W /(2π· e·N ).

where,

W: compression power [W] e: eccentric amount of the eccentric portion ( 152 S and 152 T) [mm] N. rotation speed of the rotation shaft 15 [rev/s]

In addition, the compression power W is expressed by the following expression (10).

W=Δh·V·ρ·N   (10)

where,

Δh: difference between discharge enthalpy and inlet enthalpy [J/g] V: exclusion capacity (cylinder chamber capacity) [cc/rev] ρ: intake refrigerant density [g/mm 3 ] N: rotation speed of the rotation shaft 15 [rev/s] Δh, ρ, N are determined by operating conditions.

The shaft load F [mm 2 /rev] is set to the following expression (11) by leaving only the parameters related to the sizes of the compressing units 12 S and 12 T.

F=V/e   (11)

In addition, the area of the sub-shaft unit 151 is assumed to be the square of the diameter Ds of the sub-shaft unit 151 .

From the above, the sub-shaft surface pressure P is calculated by the following expression (12).

P=V /( e·Ds 2 )  (12)

where,

V: exclusion capacity (cylinder chamber capacity) [cc/rev] e: eccentric amount of the eccentric portion ( 152 S and 152 T) [mm] Ds: diameter [mm] of sub-shaft unit 151

According to the experience value in the related art, the allowable maximum surface pressure of the sub-shaft unit 151 is 22 to 23. As illustrated in FIG. 4 , in the calculation example (Hc small), the sub-shaft surface pressure P can be made smaller than in the calculation example (Hc large). In the calculation example (Hc small) in which parameter A an be decreased, the point at which the sub-shaft surface pressure P becomes 22 is a measure of the lower limit value of parameter A. As will be described below, by taking means to improve the durability of the sub-shaft unit 151 , parameter A can be further decreased.

From the above, it is desirable that the range of parameter A is 3.9<parameter A<4.1 as illustrated in FIG. 4 . In addition, in a case where adopting the cylinder height Hc (trial calculation example (Hc large)) which can ensure the cross-sectional area of the inlet holes 135 S and 135 T as in the related art, it is desirable that the range of parameter A is 4.0<Parameter A<4.1, as illustrated in FIG. 4 .

Next, as a parameter simpler than parameter A, parameter B [dimensionless] is defined by the following expression (13).

B=e/V 1/3   (13)

where,

V: exclusion capacity (cylinder chamber capacity) [cc/rev] e: eccentric amount of the eccentric portion ( 152 S and 152 T) [mm]

FIG. 5 is a diagram illustrating relationship between parameter A and parameter B. As illustrated in FIG. 5 , parameter. A and parameter B have a correlation between each other. As a range corresponding to a range 3.9<parameter A<4.1 of parameter A, the range of parameter B may be set to the range of 0.215<parameter B<0.240.

FIG. 6 is a table illustrating Embodiments 1 to 3 of the sizes of the compressing units 12 S and 12 T of the two-cylinder type of rotary compressor 1 using the refrigerant R32. In Embodiments 1 to 3, the exclusion capacity V is 14.5 [mm 3 /rev], and the inner diameter of the compressor housing 10 is fixed at ϕ112 mm.

As illustrated in FIG. 6 , in Embodiment 1, parameter A is the smallest among the three embodiments, and the influence of the refrigerant heating can be minimized. However, the sub-shaft surface pressure P is high. Although the sub-shaft surface pressure P of Example 1 does not exceed the allowable maximum surface pressure 23 of actual results of the related art, one of the following countermeasures may be taken.

a. An extreme pressure additive is added to lubricant oil.

b. The refrigerant melt viscosity of the lubricant oil is increased.

b 1 . Viscosity grade is further increased than conventional viscosity grade (ISO VG68) b 2 . lubricant oil for refrigerant R410A which is not compatible with refrigerant R32 is used. b 3 . A mixture of lubricant oil for refrigerant R32 and lubricant oil for refrigerant R410A which are compatible with each other is used.

Here, the lubricant oil which is not compatible with the refrigerant means a lubricant oil having a region in which the refrigerant and the lubricant oil are separated into two layers irrespective of the temperature in a certain ratio range among ranges in which the ratio of the lubricant oil to the refrigerant is 0 to 100%.

In Embodiment 2, although parameter A is increased than that in Example 1, the sub-shaft surface pressure P is the smallest among the three embodiments. Therefore, it is suitable for a rotary compressor (for tropical area or for hot water heater) with a wide operating range. In addition, reliability can be maintained without adding an extreme pressure additive to the lubricant oil.

In Embodiment 3, parameter A has an intermediate value between Embodiment 1 and Example 2. Since the cylinder height Hc is higher than in Embodiment 1 and Embodiment 2, the cross-sectional areas of the inlet holes 135 S and 135 T can be increased, the pressure loss of the intake refrigerant can be reduced, and compression efficiency at high speed rotation is excellent. The sub-shaft surface pressure P is within the range of the sub-shaft surface pressure P of the rotary compressor of the related art, and reliability can be maintained without adding an extreme pressure additive to the lubricant oil. Since the rotary compressor 1 of Embodiment 3 can secure the cross-sectional area of the inlet holes 135 S and 135 T similar to the rotary compressor using the refrigerant R4101, the rotary compressor 1 of Embodiment 3 can be used for both the refrigerant R32 and the refrigerant R410A.

FIG. 7 is a diagram illustrating relationship between parameter B and the surface pressure of the sub-shaft unit ( 151 ) As illustrated in FIG. 7 , even in the same parameter B value, the sub-shaft surface pressure P can be decreased by the cylinder height Hc being decreased than by the cylinder height Hc being increased, there is a margin for reliability, and parameter B value can be further increased. As described above, the refrigerant heating is suppressed by the cylinder height Hc being decreased, and thus it is effective for improving the compression efficiency of the rotary compressor using the refrigerant R32.

However, in the related art, since the rotary compressor using the refrigerant R32 and the rotary compressor using the refrigerant R410A can obtain the substantially same refrigerating capacity by the same exclusion capacity (cylinder chamber capacity), components thereof are shared by the same compressing unit size being adopted, and thus it is not the compressing unit size which is particularly effective for refrigerant R32 only.

As described above, the intake refrigerant density of the refrigerant R32 is about 70% of that of the refrigerant. R41A. Therefore, in the case of using the refrigerant R32, even if the cross-sectional areas (inlet path area) of the inlet holes 135 S and 1357 the cylinders 121 S and 121 T are made smaller than those for the refrigerant R410A, the pressure loss of the intake refrigerant is not increased.

The inlet holes 135 S and 135 T are provided on the side portions of the cylinders 121 S and 121 T, and in the cylinder height Hc, a height to which the inlet pipes 104 and 105 are attached is secured. Since the wall thicknesses of the inlet, holes 135 S and 135 T are required to secure the wall thickness to secure 2 to 4 mm or more for the strength thereof, the cylinder height Hc is required to satisfy the following expression (14).

cylinder height Hc ≥inlet hole diameter Dk+ 2×(2 to 4)  (14)

According to expression (14), the cylinder height Hc can be decreased by decreasing the inlet hole diameter Dk.

In JP-A-2010-121481, a configuration in which cross-sectional shapes of the inlet holes 135 S and 135 T are long holes which are long in the circumferential direction is disclosed as a technique in which, even when the cylinder height Hc is decreased, the inlet path area can be secured and the intake pressure loss of the refrigerant is reduced. However, when the cross-sectional shapes of the inlet holes 135 S and 135 T are long holes, the cross-sectional shapes of the inlet pipes 104 and 105 and the low-pressure communication tubes 31 S and 31 T connecting the accumulator 25 and the inlet holes 135 S and 135 T to each other are also required to be long holes.

Although the inlet holes 135 S and 135 T are sealed by press-fitting the inlet pipes 104 and 105 , the long hole shape is difficult to form with high accuracy, the seal becomes insufficient, the high-pressure refrigerant in the compressor housing 10 leaks from the press-fitted seal portion, and thus the compression efficiency is decreased. Therefore, in the invention, the cross-sectional shapes of the inlet holes 135 S and 135 T are formed in a circular shape.

The pressure loss of the intake refrigerant is generally proportional to the density of the refrigerant and is proportional to square of the inlet flow rate. Since the inlet flow rate is obtained by dividing the exclusion capacity (cylinder chamber capacity) per one cylinder by the inlet path area (proportional to square of inlet hole diameter), the intake pressure loss is represented by parameter C of the following expression (15).

C=β·V 2 /Dk 4   (15)

where,

β: intake refrigerant density ratio (refrigerant R410A is referred to as 100 and refrigerant R32 is referred to as 70) [dimensionless] V: exclusion capacity (cylinder chamber capacity) [cc/rev] Dk: inlet hole diameter [mm]

FIG. 8 is a diagram illustrating relationship between the exclusion capacity V and the intake pressure loss C (parameter C) of the rotary compressor for refrigerant R410A. As illustrated, in FIG. 8 , in the rotary compressor for refrigerant R410A, the exclusion capacity V and the inlet hole diameter Dk are set so as to suppress the intake pressure loss C to 2.0 or less. The intake pressure loss C is large when the exclusion capacity V is 60 cc or more. This is because a pipe with a small diameter is used for reason that the pipe diameter becomes too thick, there is no margin in the pressure resistance strength, the availability and assembly of the pipe are deteriorated or the like, if the inlet hole diameter Dk (inlet, pipe diameter, low-pressure communication tube diameter) corresponding to the large exclusion capacity V is set.

If parameter C is 1.5 or less, it can be said that the pressure loss is decreased. When parameter C is 1.0 or less, although the pressure loss is decreased, it cannot be said that the pressure loss is low despite having a margin to decrease the cylinder height Hc. If it is the rotary compressor for the refrigerant R32, in order to suppress the refrigerant heating, the cylinder height He should be decreased.

From the above, in the rotary compressor dedicated to the refrigerant R32, by setting parameter C representing the intake pressure loss within the range of 1.0 to 1.5, the compression efficiency can be improved. The cylinder height Hc [mm] needs to satisfy the following expression (16) when the inlet hole diameter is Dk [mm].

( Dk+ 4)≤ Hc ≤( Dk+ 8)  (16)

FIG. 9 is a table illustrating Embodiments 4 to 6 of the sizes of the compressing units 12 S and 12 T of the two-cylinder type of rotary compressor 1 using the refrigerant R32. In Embodiments 4 to 6, the exclusion capacity V was 14.5{cc/rev} and the inner diameter of the compressor housing 10 is fixed at ϕ112 mm.

As illustrated in FIG. 9 , in Embodiments 4 and 5, in a case where the refrigerant R410A is used, parameter C indicating the intake pressure loss exceeds 1.5, and there is concern that the intake pressure loss will be increased. However, in a case where the refrigerant R32 is used, parameter C is within the range of 1.0 to 1.5, and the cylinder height Hc is decreased while the intake pressure loss is suppressed. Since the refrigerant heating and the intake pressure loss can be suppressed, a rotary compressor having high efficiency is obtained.

In Embodiment 6, it is assumed that the same compressing unit sizes are used for the refrigerant R410A and the refrigerant R32. Even in a case where the refrigerant R410A is used, parameter C indicating the intake pressure loss can be suppressed to 1.5 or less, and the intake pressure loss is decreased. However, in a case where the refrigerant R32 is used, parameter C is less than 1.0, and there is margin to decrease the cylinder height Hc.

FIG. 5 is a diagram illustrating relationship between parameter A and parameter B. As illustrated in FIG. 5 , parameter A and parameter B have a correlation between each other. As a range corresponding to a range 3.9<parameter A<4.1 of parameter A, the range of parameter B may be set to the range of 0.215<parameter B<0.240. By e and V being set such that the range of the value of parameter B exceeds 0.215, the ratio of the wall surface area of the cylinder chamber to the exclusion capacity V can be decreased, and decrease in the compression efficiency by heating of the intake refrigerant can be suppressed.

In order to increase parameter B, the eccentric amounts e of the eccentric portions 152 S and 152 T are required to be increased. However, as described above, when the eccentric amount e is increased, there is a problem that the annular pistons 125 S and 125 T cannot be assembled to the eccentric portions 152 S and 152 T. Therefore, even if the diameter of the sub-shaft unit 151 is made smaller than the diameter of the main shaft unit 153 and the eccentric amount e is large, the annular pistons 125 S and 125 T can be assembled to the eccentric portions 152 S and 152 T.

FIG. 7 is a diagram illustrating relationship between parameter B and the sub-shaft surface pressure. As illustrated in FIG. 7 , when the diameter of the sub-shaft unit 151 is decreased, the sub-shaft surface pressure P is increased, and the margin of reliability is decreased. Therefore, according to the experience value in the related art, since the allowable maximum surface pressure of the sub-shaft unit 151 is 22 to 23, the upper limit value of parameter B is set to 0.240 or less in order to suppress the sub-shaft surface pressure P to about 22 to 23.

In addition, to improve reliability, one of the following countermeasures may be taken.

a. An extreme pressure additive is added to lubricant oil.

b. The refrigerant melt viscosity of the lubricant oil is increased.

b 1 . Viscosity grade is further increased than conventional viscosity grade (ISO VG68) b 2 . A lubricant oil for refrigerant R410A which is not compatible with refrigerant R32 is used (since the refrigerant R410A is not compatible with the refrigerant R32, the decrease in viscosity due to the refrigerant dissolving into the lubricant oil is decreased). b 3 . A mixture of lubricant oil for refrigerant R32 and lubricant oil for refrigerant R410A which are compatible with each other is used.

Here, the lubricant oil which is not compatible with the refrigerant means a lubricant oil having a region in which the refrigerant and the lubricant oil are separated into two layers irrespective of the temperature in a certain range among ranges in which the ratio of the lubricant oil to the refrigerant is to 100%.

FIG. 10 is a longitudinal sectional view illustrating another example of the rotary compressor according to the invention, FIG. 11-1 is a bottom view illustrating a first compressing unit of another example, FIG. 11-2 is a top view illustrating a second compressing unit of another example, FIG. 12 is a top view illustrating a compressing unit of another example, FIG. 13 is a longitudinal sectional view taken along the line A-A of FIG. 12 , FIG. 14 is a top view illustrating an upper end plate of another example, FIG. 15 is a bottom view illustrating a compressing unit of another example, FIG. 16 is a bottom view illustrating a lower end plate of another example, and FIG. 17 is an exploded perspective view illustrating a lower end plate and a lower end plate cover of another example.

As illustrated in FIG. 10 , the rotary compressor 1 includes the compressing unit 12 which is disposed in a lower portion of the sealed vertically-placed cylindrical compressor housing 10 and the motor 11 which is disposed in an upper portion of the compressor housing 10 and drives the compressing unit 12 via the rotation shaft 15 .

The stator 111 of the motor 11 is formed in a cylindrical shape and is fixed by shrinkage fitting to an inner circumferential surface of the compressor housing 10 . The rotor 112 of the motor 11 is disposed in an inside portion of the cylindrical stator 111 and is fixed by shrinkage fitting to the rotation shaft 15 which mechanically connects the motor 11 and the compressing unit 12 to each other.

The compressing unit 12 includes the first compressing unit 12 S and the second compressing unit 12 T, and the second compressing unit 12 T is disposed above the first compressing unit 12 S. As illustrated in FIG. 11-1 , the first compressing unit 12 S includes the annular first cylinder 121 S. The first cylinder 121 S includes the first side-flared portion 122 S extending from an annular outer circumference thereof, and the first inlet hole 135 S and the first vane groove 128 S are radially provided in the first side-flared portion 122 S, In addition, as illustrated in FIG. 11-2 , the second compressing unit 12 T includes the annular second cylinder 121 T. The second cylinder 121 T includes the second side-flared portion 122 T extending from an annular outer circumference thereof and the second inlet hole 135 T and the second vane groove 128 T are radially provided in the second side-flared portion 122 T.

As illustrated in FIG. 11-1 , the first cylinder 121 S is formed with the circular first cylinder inner wall 123 S concentrically with the rotation shaft 15 of the motor 11 . The first annular piston 125 S having an outer diameter smaller than an inner diameter of the first cylinder 121 S is disposed in the first cylinder inner wall 123 S and the first cylinder chamber 130 S which sucks, compresses and discharges a refrigerant is formed between the first cylinder inner wall 123 S and the first annular piston 125 S. As illustrated in FIG. 11 - 2 , the circular second cylinder inner wall 123 T is formed concentrically with the rotation shaft 15 of the motor 11 in the second cylinder 121 T. The second annular piston 125 T having an outer diameter smaller than an inner diameter of the second cylinder 121 T is disposed in the second cylinder inner wall 123 T and the second cylinder chamber 130 T which sucks, compresses and discharges a refrigerant is formed between the second cylinder inner wall 123 T and the second annular piston 125 T.

The first vane groove 128 S extending in the radial direction from the first cylinder inner wall 123 S over the entire cylinder height is formed in the first cylinder 121 S and the flat plate-shaped first vane 127 S is slidably fitted into the first vane groove 128 S. The second vane groove 128 T extending in the radial direction from the second cylinder inner wall 123 T over the entire cylinder height is formed in the second cylinder 121 T and the plate-shaped second vane 127 T is slidably fitted into the second vane groove 128 T.

As illustrated in FIG. 11-1 , the first spring hole 124 S is formed on an outer side of the first vane groove 128 S in the radial direction so as to communicate with to the first vane groove 128 S from an outer circumferential portion of the first side-flared portion 122 S. A first vane spring 126 S which presses the back surface of the first vane 127 S is inserted into the first spring hole 124 S. As illustrated in FIG. 11-2 , the second spring hole 124 T is formed on an outer side of the second vane groove 128 T in the radial direction so as to communicate with the second vane groove 128 T from an outer circumferential portion of the second side-flared portion 122 T. A second vane spring 126 T which presses the back surface of the second vane 127 T is inserted into the second spring hole 124 T.

When the rotary compressor 1 is started up, the first vane 127 S protrudes from an inside of the first vane groove 128 S into an inside of the first cylinder chamber 130 S by repulsive force of the first vane spring 126 S, a tip thereof is in contact with the outer circumferential surface of the first annular piston 125 S, and the first vane 127 S divides the first cylinder chamber 130 S into the first inlet chamber 131 S and the first compression chamber 133 S. In addition, the second vane 127 T protrudes from an inside of the second vane groove 128 T into an inside of the second cylinder chamber 130 T by the repulsive force of the second vane spring 126 T, the tip thereof is in contact with the outer circumferential surface of the second annular piston 125 T, and the second vane 127 T divides the second cylinder chamber 1301 into the second inlet chamber 131 T and the second compression chamber 133 T.

In addition, the first pressure guiding-in path 129 S which communicates an outside of the first vane groove 128 S in the radial direction and an inside of the compressor housing 10 with each other, in which the compressed refrigerant in the compressor housing 10 is introduced, and which applies a back pressure to the first vane 127 S by the pressure of the refrigerant is formed in the first cylinder 121 S. The compressed refrigerant in the compressor housing 10 is also introduced from the first spring hole 124 S. In addition, the second pressure guiding-in path 129 T which communicates an outside of the second vane groove 128 T in the radial direction and an inside of the compressor housing 10 with each other, in which the compressed refrigerant in the compressor housing 10 is introduced, and which applies a back pressure to the second vane 127 T by the pressure of the refrigerant is formed in the second cylinder 121 T. The compressed refrigerant in the compressor housing 10 is also introduced from the second spring hole 124 T.

The first inlet hole 135 S which communicates the first inlet chamber 131 S and the outside portion with each other is provided in the first side-flared portion 122 S of the first cylinder 121 S so as to suck a refrigerant from the outside portion into the first inlet chamber 131 S. The second inlet hole 135 T which communicates the second inlet chamber 121 T and the outside portion with each other is provided in the second side-flared portion 122 T of the second cylinder 121 T so as to suck a refrigerant from the outside portion into the second inlet chamber 131 T.

In addition, as illustrated in FIG. 10 , the intermediate partition plate 140 is disposed between the first cylinder 121 S and the second cylinder 121 T and partitions into the first cylinder chamber 130 S (see FIG. 11-1 ) of the first cylinder 121 S and the second cylinder chamber 130 T (see FIG. 11-2 ) of the second cylinder 121 T. The intermediate partition plate 140 closes an upper end portion of the first cylinder 121 S and a lower end portion of the second cylinder 121 T.

The lower end plate 160 S is disposed at the lower end portion of the first cylinder 121 S and closes the first cylinder chamber 130 S of the first cylinder 121 S. In addition, the upper end plate 160 T is disposed at the upper end portion of the second cylinder 121 T and closes the second cylinder chamber 130 T of the second cylinder 121 T. The lower end plate 160 S closes the lower end portion of the first cylinder 121 S and the upper end plate 160 T closes the upper end portion of the second cylinder 121 T.

The sub-bearing unit 161 S is formed on the lower end plate 160 S and the sub-shaft unit 151 of the rotation shaft 15 is rotatably supported by the sub-bearing unit 161 S. The main bearing unit 161 T is formed on the upper end plate 160 T and the main shaft unit 153 of the rotation shaft 15 is rotatably supported by the main bearing unit 161 T.

The rotation shaft 15 includes the first eccentric portion 152 S and the second eccentric portion 152 T which are eccentrically shifted by 180° phase from each other, the first eccentric portion 152 S is rotatably fitted to the first annular piston 125 S of the first compressing unit 12 S, and the second eccentric portion 152 T is rotatably fitted to the second annular piston 125 T of the second compressing unit 12 T.

When the rotation shaft 15 rotates, the first annular piston 125 S revolves clockwise in FIG. 11-1 along the first cylinder inner wall 123 S in the first cylinder 121 S and the first vane 127 S reciprocates following the revolution of the first annular piston 125 S. Due to the movement of the first annular piston 125 S and the first vane 127 S, the capacities of the first inlet chamber 131 S and the first compression chamber 133 S are continuously changed, and the compressing unit 12 continuously sucks, compresses and discharges a refrigerant. In addition, when the rotation shaft 15 rotates, the second annular piston 125 T revolves counterclockwise in FIG. 11-2 along the second cylinder inner wall 123 T in the second cylinder 121 T and the second vane 127 T reciprocates following the revolution of the second annular piston 125 T. Due to the movement of the second annular piston 125 T and the second vane 127 T, the capacities of the second inlet chamber 131 T and the second compression chamber 133 T are continuously changed, and the compressing unit 12 continuously sucks, compresses and discharges a refrigerant.

As illustrated in FIG. 10 , a communication portion 180 S is formed under the lower end plate 160 S by the flat plate-shaped lower end plate cover 170 S being disposed and covering a concave portion 163 S provided to the lower end plate 160 S. The first compressing unit 12 S opens into the communication portion 180 S. In other words, in the vicinity of the first vane 127 S of the lower end plate 160 S, a first discharge hole 190 S communicating the first compression chamber 133 S of the first cylinder 121 S and the communication portion 180 S with each other is provided and the reed valve type of first discharge valve 200 S for preventing back-flow of the compressed refrigerant is disposed in the first discharge hole 190 S.

The communication portion 180 S communicates a discharge side of the first compressing unit 12 S and an inside of the upper muffler chamber 180 T with each other through the refrigerant path hole 136 (see FIG. 10 , FIGS. 11-1, and 11-2 ) which passes through the lower end plate 160 S, the first cylinder 121 S, the intermediate partition plate 140 , the second cylinder 121 T, and the upper end plate 160 T. In addition, the tip portion of the first discharge valve cap 201 S for limiting the flexural valve opening amount of the first discharge valve 200 S, which overlaps the first discharge valve 200 S, is accommodated in the concave portion 163 S provided in the lower end plate 160 S, together with the tip portion of the first discharge valve 200 S. The first discharge hole 190 S, the first discharge valve 200 S, and the first discharge valve cap 201 S constitute a first discharge valve unit of the lower end plate 160 S.

As illustrated in FIG. 10 to FIG. 14 , the upper end plate cover 170 T having five bulging portions 171 T is disposed above the upper end plate 160 T and the upper muffler chamber 180 T is formed between the upper end plate 160 T and the upper end plate cover 170 T. The upper muffler chamber 180 T communicates with the inside portion of the compressor housing 10 by an annular muffler discharge hole 172 T formed between the main bearing unit 161 T of the upper end plate 160 T and the upper end plate cover 170 T, and the compressed refrigerant in the upper muffler chamber 180 T is discharged from the muffler discharge hole 172 T into the compressor housing 10 . In the vicinity of the second vane 127 T of the upper end plate 160 T, a second discharge hole 190 T communicating the second compression chamber 133 T of the second cylinder 121 T and the upper muffler chamber 180 T with each other is provided and a reed valve type of second discharge valve 200 T for preventing back-flow of the compressed refrigerant is disposed in the second discharge hole 190 T.

In addition, the tip portion of the second discharge valve cap 201 T for limiting the flexural valve opening amount of the second discharge valve 200 T, which overlaps the second discharge valve 200 T, is accommodated in the concave portion 163 T provided in the upper end plate 160 T, together with the tip portion of the second discharge valve 200 T. The upper muffler chamber 180 T reduces pressure pulsation of the discharged refrigerant. The second discharge hole 190 T, the second discharge valve 200 T, and the second discharge valve cap 201 T constitute a second discharge valve unit of the upper end plate 160 T.

As illustrated in FIG. 12 to FIG. 15 , the lower end plate cover 170 S, the lower end plate 160 S, the first cylinder 121 S, the intermediate partition plate 140 , the second cylinder 121 T, the upper end plate 160 T, and the upper end plate cover 170 T are integrally fastened by a plurality of bolts in a manner which will be described below and thus become the compressing unit 12 . An outer circumferential portion of the upper end plate 160 T of the compressing unit 12 fastened integrally is fixed to the compressor housing 10 by spot welding, and thus the compressing unit 12 is fixed to the compressor housing 10 .

The first through hole 101 and the second through hole 102 are spaced apart from each other in the axial direction and sequentially provided on the outer circumferential wall of the cylindrical compressor housing 10 from the lower portion thereof such that the first inlet pipe 104 and the second inlet pipe 105 pass through the holes. In addition, the accumulator 25 formed of an independent cylindrical sealed container is held by the accumulator holder 252 and the accumulator band 253 on an outside portion of the compressor housing 10 .

The system connecting pipe 255 which is connected to an evaporator of a refrigerant circuit (refrigeration cycle) is connected to a center of a top portion of the accumulator 25 and the first low-pressure communication tube 31 S and the second low-pressure communication tube 31 T of which one end extends to an upper side of an inside portion of the accumulator 25 and of which the other end is connected to the other ends of the first inlet pipe 104 and the second inlet pipe 105 are fixed to the bottom through hole 257 provided to a bottom portion of the accumulator 25 .

The first low-pressure communication tube 31 S which guides the low-pressure refrigerant of the refrigerant circuit to the first compressing unit 12 S via the accumulator 25 is connected to the first inlet hole 135 S (See FIG. 11-1 ) of the first cylinder 121 S via the first inlet pipe 104 as the inlet portion. In other words, the first inlet hole 135 S is connected to the evaporator of the refrigerant (refrigeration cycle). The second low-pressure communication tube 31 T which guides the low-pressure refrigerant of the refrigerant circuit to the second compressing unit 12 T via the accumulator 25 is connected to the second inlet hole 135 T (See FIG. 11-2 ) of the second cylinder 121 T via the second inlet pipe 105 as the inlet portion. In other words, the second inlet hole 135 T is connected to the evaporator of the refrigerant circuit (refrigeration cycle).

The discharge pipe 107 as a discharge portion, which is connected to the refrigerant circuit (refrigeration cycle) and discharges a high-pressure refrigerant to a condenser side of the refrigerant circuit, is connected to a top portion of the compressor housing 10 . In other words, the first discharge hole 190 S and the second discharge hole 190 T are connected to the condenser of the refrigerant circuit (refrigeration cycle).

Lubricant oil is enclosed to approximately the height of the second cylinder 121 T in the compressor housing 10 . In addition, the lubricant oil is sucked up from the oil feeding pipe 16 attached to the lower end portion of the rotation shaft 15 by a pump impeller (not illustrated) inserted into a lower portion of the rotation shaft 15 , circulates through the compressing unit 12 , lubrication of the sliding component (first annular piston 125 S and second annular piston 125 T) is performed and minute gaps of the compressing unit 12 are sealed.

As illustrated in FIG. 11-1 to FIG. 15 , the lower end plate cover 170 S, the lower end plate 160 S, the first cylinder 121 S, the intermediate partition plate 140 , the upper end plate 160 T, and the upper end plate cover 170 T are provided with five (a plurality of) bolt through holes 137 at the same phase position on a substantially concentric circle, respectively. Five screw holes 138 are provided at the same phase position on the substantially concentric circle with the five bolt through holes 137 in the second cylinder 121 T. The bolt through hole 137 and the screw hole 138 are collectively referred to as bolt holes ( 137 and 138 ). The bolt hole is a through hole. Although the five (a plurality of) bolt holes may be disposed at regular intervals (equal phase angle=72°), the bolt holes may be disposed at unequal intervals with slightly shifted spacing to avoid wrong assembly. Five penetrating bolts 174 are inserted into the bolt holes from the upper end plate cover 170 T side, the five penetrating bolts 175 are inserted into the bolt holes from the lower end plate cover 170 S side and thus the entire compressing unit 12 is fastened. The number of bolt holes is not limited to five, and may be four or six or more.

Two auxiliary bolt through holes 300 are provided in the lower end plate 160 S, two auxiliary screw holes 301 are provided in the first cylinder 121 S, two auxiliary bolts 176 are inserted into the auxiliary bolt through holes 300 and the auxiliary screw holes 301 , and thus the lower end plate 160 S and the first cylinder 121 S are fastened to each other. The lower end plate 160 S and the first cylinder 121 S are fastened in advance before the entire compressing unit 12 is fastened.

As illustrated in FIG. 11-1 , FIG. 11-2 , FIG. 14 and FIG. 16 , the refrigerant path hole 136 is provided in a range (in range of phase angle≈90° in Example 1) between the adjacent two bolt holes 137 which sandwich the vicinity of the first discharge hole 190 S and the second discharge hole 190 T, for example, the first discharge hole 190 T, the second discharge hole 190 S, the first vane 127 S, and the second vane 127 T. The number of the refrigerant path holes 136 is not limited to one, and two or three holes may be provided adjacent to each other.

The circular concave portion 1638 is formed on the lower end plate 160 S. The concave portion 163 S accommodates the tip portion of the first discharge valve 200 S and the tip portion of the first discharge valve cap 201 S and constitutes the communication portion 180 S which communicates the first discharge hole 190 S and the lower end portion of the refrigerant path hole 136 with each other. A circular concave portion 163 T is formed on the upper end plate 160 T. The concave portion 163 T accommodates the tip portion of the second discharge valve 200 T and the tip portion of the second discharge valve cap 201 T and constitutes a part of the upper muffler chamber 180 T which communicates the second discharge hole 190 T and the upper end portion of the refrigerant path hole 136 with each other.

In addition, a groove 164 S is formed in the lower end plate 160 S which attaches a base end portion of the first discharge valve 200 S and a base end portion of the first discharge valve cap 201 S by rivets. A groove 164 T is formed in the upper end plate 160 T which attaches a base end portion of the second discharge valve 200 T and a base end portion of the second discharge valve cap 201 T by rivets. On the lower surface of the first cylinder 121 S and the upper surface of the second cylinder 121 T, a recess 303 for accommodating the head of the rivet is formed. Since the first discharge valve 200 S and the first discharge valve cap 201 S are attached to fill the space, the groove 164 S does not constitute the communicating portion 180 S. Since the second discharge valve 200 T and the second discharge valve cap 201 T are attached to fill the space, the groove 164 T does not constitute the upper muffler chamber 180 T.

The lower end plate 160 S is formed to be thick, and the concave portion 163 S and the groove 164 S are formed to a depth which can completely accommodate the first discharge valve 200 S and the first discharge valve cap 201 S.

In the rotary compressor 1 of another example, although the upper muffler chamber 180 T is formed as a chamber having the five bulging portions 171 T formed by press-molding the upper end plate cover 170 T, the lower end plate cover 170 S of another example is a plate shape having no irregularities covering the first discharge valve unit and the refrigerant path hole 136 of the lower end plate 160 S, and the communication portion 180 S is formed by only the circular concave portion 163 S of the lower end plate 160 S as a small capacity path smaller than the volume of the upper muffler chamber 180 T in order to communicate the first discharge hole 190 S and the refrigerant path hole 135 with each other.

In the rotary compressor 1 of another example, since the communicating portion 180 S is a path having a small capacity smaller than the volume of the upper muffler chamber 180 T by only the concave portion 163 S of the lower end plate 160 S, the space into which the refrigerant compressed by the second cylinder 121 T flows by flowing through the refrigerant path hole 136 in a reverse direction is decreased, and the back-flow is suppressed and thus decrease in efficiency of the rotary compressor 1 can be prevented. The lower end plate cover 170 S may be press molded in the same manner as the upper end plate cover 170 T to form the bulging portions and thus forms a lower muffler chamber.

Next, with reference to FIG. 10 to FIG. 17 , the characteristic configuration of the rotary compressor 1 of the example using the refrigerant R32 will be described, which overlaps with the description in Example 1. The temperature increase Δt [K] of the intake refrigerant in the first cylinder chamber 130 S and the second cylinder chamber 130 T is expressed by the following expression (1).

Δ t=h·S ·Δθ/( m·c )  (1)

where,

h: heat transfer coefficient [W/(mm 2 ·K)] S: wall surface area of cylinder chamber ( 130 S and 130 T) [mm 2 ] Δθ: difference between wall surface temperature and refrigerant temperature [K] m: refrigerant mass [g/s]=(cylinder chamber capacity V [mm 3 /rev])×(intake refrigerant density ρ [g/mm 3 ]) c: refrigerant specific heat [J/(g·K)]

The intake refrigerant density ρ of the refrigerant R32 is about 70% of the refrigerant R410A and the evaporation enthalpy is about 140%. Therefore, substantially the same exclusion capacity V (cylinder chamber capacity) can be applied. Since the exclusion capacities V are equal to each other, the size of the compressing unit 12 for the refrigerant R410A can be used and the wall surface areas S are also the same. Therefore, Δt in the above expression (1) is increased for the refrigerant R32 having a smaller intake refrigerant density ρ than for the refrigerant R410A and the refrigerant R32 is likely to be heated compared to the refrigerant R410A. From this, in a case where the refrigerant R32 is adopted, suppression of refrigerant heating is effective for improving compression efficiency compared to a case where the refrigerant R410A is used.

In the invention, when the wall surface area of the cylinder chamber ( 130 S and 130 T) is referred to as S and the exclusion capacity (cylinder chamber capacity) is referred to as V, the refrigerant heating is suppressed by the sizes of the compressing units 12 S and 12 T being set so that S/V is decreased.

The wall surface area S of one cylinder chamber (first cylinder chamber 130 S or second cylinder chamber 130 T) of the rotary compressor 1 of another example is expressed by the following expressions (2) to (5).

S= 2 Sb+Sc+Sr   (2)

Sb =( Dc 2 −( D− 2 e ) 2 )π/4  (3)

Sc=π·Dc·Hc   (4)

Sr =π·( Dc −2 e )· Hc   (5)

where,

Sb: area of the end plate ( 160 S and 160 T) portion or the intermediate partition plate ( 140 ) portion of the cylinder chamber [mm 2 ] Sc: cylinder ( 121 S and 121 T) inner circumferential wall area [mm 2 ] Sr: annular piston ( 125 S and 125 T) outer circumferential wall area [mm 2 ] Dc: cylinder ( 121 S and 121 T) inner diameter [mm] e: eccentric portion ( 152 S and 152 T) Eccentric amount [mm] Hc: cylinder ( 121 S and 121 T) height [mm]

In addition, the exclusion capacity (cylinder chamber capacity) V [cc/rev] of one cylinder chamber (first cylinder chamber 130 S or second cylinder chamber 130 T) of the rotary compressor 1 is expressed by the following expression (6).

V=π·e ·( Dc−e )· Hc   (6)

From expressions (2) and (6), S/V is expressed by the following expression (7).

S/V= 2( e+HC )/( e·HC )  (7)

Since as the exclusion capacity V is increased, S/V is decreased, in order to evaluate the size of the cylinder chamber, it is necessary to eliminate the influence of the exclusion capacity V. Therefore, let S/V multiplied by V 1/3 be referred to as parameter A [dimensionless]. Parameter A is expressed by the following expression (8), and as parameter A is decreased, the influence of the refrigerant heating is decreased.

A =( e+Hc )·( Dc−e ) 1/3 /( e·Hc )  (8)

Next, in Japanese Patent No. 4864572, it is described that the compression efficiency is improved by reducing the refrigerant leak amount by decreasing the ratio Hc/Dc of the cylinder height Hc and the cylinder inner diameter Dc.

FIG. 3 is a diagram illustrating relationship between parameter A and Hc/Dc. As illustrated in FIG. 3 , as parameter A is decreased, Hc/Dc tends to be increased. In Embodiments 1 to 3 illustrated in FIG. 3 , the exclusion capacity V, the inner diameter of the compressor housing 10 and the cylinder Height Hc of the rotary compressor 1 are the same, and the eccentric portion eccentric amount e is changed. Calculation is made for two patterns with cylinder height Hc large and cylinder height Hc small.

In the calculation example (Hc large), the cross-sectional areas of the inlet holes 135 S and 135 T are set to the cylinder height Hc which can be commonly secured in the related art. As the eccentric portion eccentric amount e increases, the cylinder inner diameter Dc is decreased and thus Hc/Dc is increased. However, parameter A can be decreased.

In the calculation example (Hc small), the cylinder height Hc is set to be low until the cross-sectional areas of the inlet holes 135 S and 135 T become about 80% of those in the related art. By the cylinder height Hc being set to be low, Hc/Dc can be decreased and the amount of refrigerant leakage can be reduced in a case of the same parameter A value. In this case, although since the cross-sectional areas of the inlet holes 135 S and 135 T are decreased, the pressure loss of the intake refrigerant is increased, since the refrigerant R32 has a lower density than the refrigerant R410A, the influence of pressure loss is decreased.

In the rotary compressor of the related art using the refrigerant R410A, since decrease in the Hc/Dc is effective for improving the compression efficiency, as a result of selecting the sizes of the compressing units 12 S and 12 T with a small Hc/Dc, the sizes of the compressing units 12 S and 12 T are not set so that parameter A is decreased. In the rotary compressor 1 using the refrigerant R32 which is greatly affected by the refrigerant heating, compression efficiency can be further improved than the rotary compressor of the related art by setting parameter A to a value smaller than the lower limit value 4.1 (see FIG. 3 ) of the rotary compressor of the related art.

FIG. 4 is a diagram illustrating relationship between parameter A and the sub-shaft unit ( 151 ) surface pressure. The sizes of the compressing units 12 S and 12 T with small parameter A are increased in the eccentric amount e of the eccentric portions ( 152 S and 152 T). When the eccentric amount e increases, it is necessary to decrease the diameter of the sub-shaft unit 151 for the convenience of assembling the rotation shaft 15 and the annular pistons 125 S and 125 T and when the sub-shaft diameter is decreased, the sub-shaft surface pressure P is increased. Therefore, parameter A has a lower limit value.

Next, a calculation method of the sub-shaft surface pressure P will be described. The axial load F [N] is expressed by the following expression (9).

F=W /(2π· e·N )  (9)

where,

W: compression power [W] e: eccentric amount of the eccentric portion ( 152 S and 152 T) [mm] N: rotation speed of the rotation shaft 15 [rev s]

In addition, the compression power W is expressed by the expression (10).

W=Δh·V·ρ·N   (10)

where,

Δh: difference between discharge enthalpy and inlet enthalpy [j/g] V: exclusion capacity (cylinder chamber capacity) [cc/rev] ρ: intake refrigerant density [g/mm 3 ] N: rotation speed of the rotation shaft 15 [rev/s]

Δh, ρ, N are determined by operating conditions.

The shaft load F [mm 2 /rev] is set to the following expression (11) by leaving only the parameters related to the sizes of the compressing units 12 S and 12 T.

F=V/e   (11)

In addition, the area of the sub-shaft unit 151 is assumed to be the square of the diameter Ds of the sub-shaft unit 151 .

From the above, the sub-shaft surface pressure P is calculated by the following expression (12).

P=V /( e·Ds 2 )  (12)

where,

V: exclusion capacity (cylinder chamber capacity) [cc/rev] e: eccentric amount of the eccentric portion ( 152 S and 132 T) [mm] Ds: diameter [mm] of sub-shaft unit 151

According to the experience value in the related art, the allowable maximum surface pressure of the sub-shaft unit 151 is 22 to 23. As illustrated in FIG. 4 , in the calculation example (Hc small), the sub-shaft surface pressure P can be made smaller than the calculation example (Hc large). In the calculation example (Hc small) in which parameter A can be decreased, the point at which the sub-shaft surface pressure P becomes 22 is a measure of the lower limit value of parameter A. By taking means to improve the durability of the sub-shaft unit 151 , parameter A can be further decreased.

From the above, it is desirable that the range of parameter A is 3.9<parameter A<4.1 as illustrated in FIG. 4 . In addition, in a case where adopting the cylinder height Hc (trial calculation example (Hc large)) which can ensure the cross-sectional area of the inlet holes 135 S and 135 T as in the related art, it is desirable that the range of parameter A is 4.0<Parameter A<4.1, as illustrated in FIG. 4 .

Next, as a parameter simpler than parameter A, parameter B [dimensionless] is defined by the following expression (13).

B=e/V 1/3   (13)

where,

V: exclusion capacity (cylinder chamber capacity) [cc/rev] e: eccentric amount of the eccentric portion ( 152 S and 152 T) [non]

FIG. 5 is a diagram illustrating relationship between parameter A and parameter B. As illustrated in FIG. 5 , parameter A and parameter B have a correlation between each other. As a range corresponding to a range 3.9<parameter A<4.1 of parameter A, the range of parameter B may be set to the range of 0.215<parameter B<0.240. The description described above overlaps with the description in Example 1.

Although overlapping with the description in Example 2, FIG. 7 is a diagram illustrating relationship between parameter B and the surface pressure of the sub-shaft unit ( 151 ). As illustrated in FIG. 7 , even in the same parameter B value, the sub-shaft unit surface pressure P can be decreased by the cylinder height Hc being decreased than by Hc being increased, there is a margin for reliability, and parameter B value can be further increased. As described above, the refrigerant heating is suppressed by the cylinder height Hc being decreased, and thus it is effective for improving the compression efficiency of the rotary compressor using the refrigerant R32.

However, in the related art, since the rotary compressor using the refrigerant R32 and the rotary compressor using the refrigerant R410A can obtain the substantially same refrigerating capacity by the same exclusion capacity (cylinder chamber capacity), components thereof are shared by the same compressing unit size being adopted, and thus it is not the compressing unit size which is particularly effective for refrigerant R 32 only.

As described above, the intake refrigerant density of the refrigerant R32 is about 70% of that of the refrigerant R410A. Therefore, in the case of using the refrigerant R32, even if the cross-sectional areas (inlet path area) of the inlet holes 135 S and 135 T of the cylinders 121 S and 121 T are made smaller than that for the refrigerant R410A, the pressure loss of the intake refrigerant is not increased.

The inlet holes 135 S and 135 T are provided on the side portions of the cylinders 121 S and 121 T, and in the cylinder height Hc, a height to which the inlet pipes 104 and 105 are attached is secured. Since the wall thicknesses of the inlet holes 135 S and 135 T are required to secure the wall thickness to secure 2 to 4 mm or more for the strength thereof, the cylinder height Hc is required to satisfy the following expression (14).

cylinder height Hc ≥inlet hole diameter Dk+ 2×(2 to 4)  (14)

According to expression (14), the cylinder height Hc can be decreased by decreasing the inlet hole diameter Dk.

In JP-A-2010-121481, a configuration in which cross-sectional shape of the inlet holes 135 S and 135 T are long holes which are long in the circumferential direction is disclosed as a technique in which, even when the cylinder height Hc is decreased, the inlet path area can be secured and the intake pressure loss of the refrigerant is reduced. However, when the cross-sectional shapes of the inlet holes 135 S and 135 T are long holes, the cross-sectional shapes of the inlet pipes 104 and 105 and the low-pressure communication tubes 31 S and 31 T connecting the accumulator 25 and the inlet holes 135 S and 135 T to each other are also required to be long holes.

Although the inlet holes 135 S and 135 T are sealed by press-fitting the inlet pipes 104 and 105 , the long hole shape is difficult to form with high accuracy, the seal becomes insufficient, the high-pressure refrigerant in the compressor housing 10 leaks from the press-fitted seal portion, and thus the compression efficiency is decreased. Therefore, in the invention, the cross-sectional shapes of the inlet holes 135 S and 135 T are formed in a circular shape.

The pressure loss of the intake refrigerant is generally proportional to the density of the refrigerant and is proportional to square of the inlet flow rate. Since the inlet flow rate is obtained by dividing the exclusion capacity (cylinder chamber capacity) per one cylinder by the inlet path area (proportional to square of inlet hole diameter), the intake pressure loss is represented by parameter C of the following expression (15).

C=β·V 2 /Dk 4   (15)

where,

β: intake refrigerant density ratio (refrigerant R410A is referred to as 100 and refrigerant R32 is referred to as 70) [dimensionless] V: exclusion capacity (cylinder chamber capacity) [cc/rev] Dk: inlet hole diameter [mm]

FIG. 8 is a diagram illustrating relationship between the exclusion capacity V and the intake pressure loss C (parameter C) of the rotary compressor for refrigerant R410A. As illustrated in FIG. 8 , in the rotary compressor for refrigerant R410A, the exclusion capacity V and the inlet hole diameter Dk are set so as to suppress the intake pressure loss C to 2.0 or less. The intake pressure loss C is large when the exclusion capacity V is 60 cc or more. This is because a pipe with a small diameter is used for reason that the pipe diameter becomes too thick, there is no margin in the pressure resistance strength, the availability and assembly of the pipe are deteriorated or the like, if the inlet hole diameter Dk (inlet pipe diameter, low-pressure communication tube diameter) corresponding to the large exclusion capacity V is set.

If parameter C is 1.5 or less, it can be said that the pressure loss is decreased. When parameter C is 1.0 or less, although the pressure loss is decreased, it cannot be said that the pressure loss is low despite having a margin to decrease the cylinder height Hc. If it is the rotary compressor for the refrigerant R32, in order to suppress the refrigerant heating, the cylinder height Hc should be decreased. The description described above overlaps with the description in Example 2.

In an inverter type of air conditioner, the operating hours at low capacity (low load) is long, and efficiency at low capacity operation greatly affects annual efficiency. Therefore, even if the efficiency at the maximum capacity operation somewhat deteriorates, if the efficiency at the low capacity operation can be improved, the annual efficiency can be improved.

FIG. 18 is an enlarged view of portion B in FIG. 13 . The range of the cylinder height Hc is set to the range illustrated in the following expression (16) regardless of the securing of the cross-sectional areas (inlet path area) of the inlet holes 135 S and 135 T of the cylinders 121 S and 121 T (see FIG. 18 ).

2×( d+M )+1.0 ≤Hc≤ 2×( d+M )+2.5  (16)

where,

d: nominal diameter of penetrating bolts 174 and 175 [mm] M: chamfer size of screw hole 138 [mm] Hc: cylinder height

By setting the range of the cylinder height Hc to the range illustrated in the expression (16), the diameters of the inlet holes 135 S and 135 T are decreased, and the efficiency at the maximum capacity operation may be decreased in some cases. However, since the efficiency at the low capacity operation is improved by decreasing the cylinder height Hc, the annual efficiency can be improved.

When the cylinder height Hc is decreased, the screwing lengths of the penetrating bolts 174 and 175 fixing the compressing unit 12 are decreased. If the screwing lengths of the penetrating bolts 174 and 175 are too decreased, the screw threads are collapsed by tightening and the necessary fastening force cannot be secured. By setting the cylinder height Hc to the range of above expression (16), screwing lengths of the same lengths as the nominal diameters of the penetrating bolts 174 and 175 can be secured, even if the penetrating bolts 174 and 175 are tightened until the required fastening force is obtained, the threads are not collapsed.

The chamfer size M of the screw hole 138 in the expression (16) considers the fact that the effective threaded length is decreased by the chamfer size M. In addition, in the expression (16), it is intended to set the gap between the tip of the penetrating bolt 174 and the tip of the penetrating bolt 175 to be in the range of 1.0 [mm] to 2.5 [mm]. The minimum value 1.0 [mm] of the gap is set by considering the length tolerance of the penetrating bolts 174 and 175 and the height tolerance of the fastening components (lower end plate cover 170 S, lower end plate 160 S, first cylinder 121 S, intermediate partition plate 140 , upper end plate 160 T, and upper end plate Cover 170 T).

For example, if the length tolerance of the penetrating bolts 174 and 175 is set to ±0.3 mm and the height tolerance of the fastening components is set to ±0.2 mm, the gap between the both bolt tips is decreased by 0.8 [mm] at the maximum tolerance. Further, the gap is also decreased due to the elastic deformation of the penetrating bolts 174 and 175 or permanent set-in fatigue of the seating surface. In order to prevent the contact between the both bolt tips, the minimum value of the gap is 1.0 [mm]. On the other hand, if the gap is too increased, since the cylinder height which can reduce refrigerant heating cannot be set, the maximum value of the gap is 2.5 [mm].

The rotary compressor 1 of another example has a structure in which the penetrating bolt 174 is tightened from the upper side and the penetrating bolt 175 is tightened from the lower side of the same screw hole 138 of the second cylinder 121 T (see FIG. 13 and FIG. 18 ). This structure is advantageous in that the number of screw holes 138 to be machined is decreased compared to a case where screw holes 138 for fastening the penetrating bolts 174 and screw holes 138 for fastening the penetrating bolts 175 are separately provided and the structure can be manufactured at low cost. The second cylinder 121 T provided with the screw hole 138 and the first cylinder 121 S provided with the bolt through hole 137 may be made of cast iron (FC250 or the like) which can be manufactured at low cost. It is desirable that screw tip incomplete screw portion length (see FIG. 18 ) of the penetrating bolts 174 and 175 is equal to or less than 1 times the screw pitch.

FIG. 19 is a table illustrating Embodiments 7 to 9 of the sizes of the compressing units 12 S and 12 T of the two-cylinder type of rotary compressor 1 using the refrigerant R32. In Embodiments 7 to 9, the exclusion capacity V is fixed at 14.5 [cc/rev] and the inner diameter of the compressor housing 10 is fixed at ϕ112 mm.

The cylinder height Hc can be lowered to Hc=2×(d+M)+1.0, regardless of securing the cross-sectional area (inlet path area) of the inlet holes 135 S and 135 T of the cylinders 121 S and 121 T and in the case of Embodiments 7 and 8, the cylinder height Hc can be decreased to 12.0 [mm].

When the cylinder height Hc is set to be higher than 13.4 [mm] illustrated in Embodiment 9, parameters A and B are unlikely to put in the specified range, the influence of the refrigerant heating is increased and thus the efficiency is likely to be decreased. Therefore, the cylinder height may be Hc=2×(d+M)+2.5 or less. In the embodiment, the upper limit of the cylinder height Hc is 13.5 [mm].

In the invention, by appropriately setting the size of the compressing unit 12 without providing a hole or the like penetrating the cylinders 121 S and 121 T in the axial direction, heat transfer from the cylinders 121 S and 121 T and the end plates 160 S and 160 T to the refrigerant in the compressing unit 12 can be suppressed and increase in cost can be suppressed. In addition, the efficiency at the low capacity (low load) operation can be improved and the annual efficiency can be improved. The invention can be applied to a single cylinder system rotary compressor and a two-stage compression system rotary compressor.

As described above, although the examples are described, the examples are not limited by the contents described above. In addition, configuration elements described above include those easily assumed by those skilled in the art, substantially the same ones, and so-called equivalents. Further, the configuration elements described above can be appropriately combined with each other. Further, at least one of various omission, substitution, and change of the configuration elements can be performed without departing from the gist of the example.