Horizontal step scroll compressor with bypass ports

The present invention relates to a horizontal step scroll compressor in which step parts are provided in positions of a stationary scroll and a revolving scroll following a spiral direction.

A so-called step scroll compressor, in which step parts are provided in each of positions of tooth crests and tooth bases in spiral wraps of a stationary scroll and a revolving scroll along the spiral directions thereof, and a height of the spiral wrap on an outer peripheral side thereof is greater than a height of the wrap on an inner peripheral side thereof on the respective sides of the step parts, is capable of compressing a refrigerant gas not only in a circumferential direction of the spiral wraps but also in a wrap height direction (that is, is capable of three-dimensional compression). The step scroll compressor is thus capable of a greater amount of displacement and a higher compressor volume than a scroll compressor not provided with steps (two-dimensional compression). Accordingly, the compression ratio can be increased and the performance of the compressor can be improved without increasing the outer diameter of the compressor, and thus the compressor can be made smaller and more lightweight.

Among such step scroll compressors, Patent Document 1 discloses a step scroll compressor provided with an overcompression prevention mechanism that, when the pressure in a compression chamber rises abnormally and reaches or exceeds a set pressure before the pressure communicates with a discharge port, diverts the pressure to a discharge chamber via a bypass port and a bypass valve. On the other hand, Patent Document 2 discloses a two-dimensional compression-type scroll compressor, in which the stationary scroll and the revolving scroll have different numbers of turns, where bypass ports provided in a posterior compression chamber and an anterior compression chamber that form a pair are given different positions and sizes (numbers) in order to alleviate overcompression and liquid compression.

Additionally, Patent Document 3 discloses a horizontal scroll compressor in which a drive shaft is arranged in the horizontal direction, where at least four relief ports and one discharge port are provided between a compression chamber formed by the two scrolls and a discharge chamber, a relief valve is provided in each port, and one of the relief ports or the discharge port is configured to constantly communicate with the compression chamber. This makes it possible to prevent liquid compression and overcompression throughout the entire compression stroke.

Patent Literature

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-287512A

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-270667A

Patent Document 3: Japanese Unexamined Patent Application Publication No. 2000-345976A

Technical Problem

However, none of Patent Documents 1 to 3 disclose a technique for effectively preventing liquid compression when a horizontal step scroll compressor is started up from a state in which liquid refrigerant has migrated and accumulated within the compression chamber while the operation of the compressor is stopped. If a scroll compressor is started up in a state where liquid refrigerant has accumulated, the scroll wraps may be damaged by liquid compression. Techniques that provide a bypass port and divert the liquid refrigerant to a discharge chamber are thus employed to prevent excessive liquid compression.

In the case of a horizontal scroll compressor in which the drive shaft is arranged horizontally, refrigerant liquid typically migrates to the compression chamber on the lower side in the gravitational direction and accumulates therein. It is thus thought that liquid compression arises more easily in the compression chamber on the lower side of the gravitational direction. Under these circumstances, analysis carried out by the inventors revealed that in a horizontal step scroll compressor, the posterior compression chamber and anterior compression chamber that form a pair communicate when the step parts disengage from each other. Accordingly, it is not always the case that liquid compression arises more easily in the compression chamber on the lower side in the gravitational direction; rather, it was discovered that liquid compression will arise more easily in the compression chamber where the step parts are present on the lower side in the gravitational direction when the step parts begin to engage. The result of this analysis will be described hereinafter.

FIGS. 6A to 6D illustrate compression operations in the case where the compressor is started up from a state in which liquid refrigerant has accumulated to a height position of approximately 50% in the compression chamber. Here, step parts 13 D and 13 E, and 14 D and 14 E, are provided in predetermined positions along a spiral direction of tooth crests and tooth bases of spiral wraps 13 B and 14 B of a stationary scroll 13 and a revolving scroll 14 , respectively. The drawings illustrate a case where the step part 13 E in the tooth base and the step part 14 D in the tooth crest on the lower side in the gravitational direction that engage with each other are set to a position of 45° on the lower-left when the scrolls 13 and 14 are engaged.

FIG. 6A illustrates a state where a scroll turn angle is at a suction cutoff position, and the step parts 13 E and 14 D and the step parts 13 D and 14 E are in engagement end positions. It is assumed in this case that the liquid refrigerant has accumulated within a lower-side compression chamber (stationary anterior compression chamber) 15 A up to the level of a horizontal line passing through the centers of the scrolls. FIG. 6B illustrates a state arrived at after the turn angle has advanced by 90° from the state illustrated in FIG. 6A . Here, the step parts 13 E and 14 D and the step parts 13 D and 14 E disengage, and thus the stationary anterior compression chamber 15 A and the stationary posterior compression chamber 15 B that form a pair communicate, and the liquid refrigerant that had been accumulated in the stationary anterior compression chamber 15 A in FIG. 6A moves toward the stationary posterior compression chamber 15 B that forms the pair therewith.

FIG. 6C illustrates a state arrived at after the turn angle has advanced by 90° from the state illustrated in FIG. 6B . At this position, the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage, and the liquid refrigerant is trapped within both compression chambers 15 A and 15 B. At this time, a greater amount of the liquid refrigerant is trapped in the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction than is trapped in the stationary anterior compression chamber 15 A. This liquid refrigerant is compressed in the subsequent process leading to the state illustrated in FIG. 6D , arrived at after the turn angle has advanced by another 90°, and liquid compression arises as a result.

Thus, in the case of a horizontal step scroll compressor, liquid compression does not necessarily arise easily in the compression chamber (stationary anterior compression chamber) 15 A located on the lower side in the gravitational direction at the time of startup, as with a two-dimensional compression-type horizontal scroll compressor that lacks step parts. Liquid compression will arise more easily on the side of the compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage.

Although FIGS. 6A to 6D illustrate a case where the step parts 13 E and 14 D on the lower side in the gravitational direction are set to a position of 45° on the lower-left relative to the horizontal direction, it was discovered that by changing the positions of the step parts 13 E and 14 D, the amount of liquid refrigerant trapped in the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction changes when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage. The circumstances of this change will be described using FIGS. 7A to 9D .

FIGS. 7A to 7D illustrate compression operations in the case where the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction are set to a center-bottom position, FIGS. 8A to 8D illustrate compression operations in the case where the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction are set to a position of 45° on the lower-right, and FIGS. 9A to 9D illustrate compression operations in the case where the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction are set to a center-side position (a horizontal position). In these diagrams, it can be seen that the amount of liquid refrigerant trapped in the compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction is different when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage, as is clear by comparing FIGS. 7C, 8C, and 9C .

In other words, in the case of FIG. 6C , when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage, there is a far greater amount of liquid refrigerant trapped on the side of the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction than in the stationary anterior compression chamber 15 A that forms a pair therewith, making it easy for liquid compression to arise. Meanwhile, in the case of FIG. 7C , there is a far greater amount of liquid refrigerant trapped on the side of the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction than in the stationary anterior compression chamber 15 A that forms a pair therewith, as in the case of FIG. 6C .

As opposed to this, in the case of FIG. 8C , it can be seen that the amount of liquid refrigerant trapped on the side of the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction has dropped to slightly more than approximately half the amount of the refrigerant trapped in the stationary anterior compression chamber 15 A that forms a pair therewith. Furthermore, in the case of FIG. 9C , it can be seen that the amount of liquid refrigerant trapped on the side of the stationary posterior compression chamber 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction is slightly less but still approximately half the amount of the refrigerant trapped in the stationary anterior compression chamber 15 A that forms a pair therewith.

Having been achieved in light of the above-described knowledge, an object of the present invention is to provide a horizontal step scroll compressor with which liquid compression can be effectively prevented even when starting up from a liquid migration state in which liquid refrigerant has migrated into the compressor while operation of the compressor is stopped.

Solution to Problem

A horizontal step scroll compressor of the present invention employs the following means to solve the problems described above.

That is, a horizontal step scroll compressor according to a first aspect of the present invention is a horizontal step scroll compressor in which step parts are provided in each of positions of tooth crests and tooth bases in spiral wraps of a stationary scroll and a revolving scroll forming a pair of compression chambers along the spiral directions thereof, and in which a height of the spiral wrap on an outer peripheral side thereof is greater than a height of the wrap on an inner peripheral side thereof on the respective sides of the step parts. Here, bypass ports that, when a pressure in the pair of compression chambers reaches or exceeds a set pressure at an intermediate compression position between a suction cutoff position and a position communicating with a discharge port, divert the pressure into the discharge chamber are provided along a spiral direction of spiral wraps. Among the bypass ports, an opening area of the bypass port that opens into a first compression chamber including the step parts on a lower side in a gravitational direction when the step parts begin to engage is greater than an opening area of the bypass port that opens into a second compression chamber forming a pair with the first compression chamber.

In the horizontal scroll compressor, refrigerant liquid migrates and accumulates in a compression chamber located on a lower side in the gravitational direction while the compressor is stopped, and it is thus easier for liquid compression to arise on the side of the compression chamber located on the lower side in the gravitational direction when the compressor is started. However, in the case of a so-called step scroll compressor, a posterior compression chamber and an anterior compression chamber that form a pair communicate when the step parts disengage. As such, it is not necessarily the case that liquid compression arises easily in the compression chamber on the lower side in the gravitational direction; rather, liquid compression arises more easily on the side of the compression chamber including the step parts on the lower side in the gravitational direction when the step parts begin to engage.

According to the present invention, bypass ports that, when a pressure in the pair of compression chambers reaches or exceeds a set pressure at an intermediate compression position between a suction cutoff position and a position communicating with a discharge port, divert the pressure into the discharge chamber are provided along a spiral direction of spiral wraps. Among the bypass ports, an opening area of the bypass port that opens into a first compression chamber including the step parts on the lower side in a gravitational direction when the step parts begin to engage is greater than an opening area of the bypass port that opens into a second compression chamber forming a pair with the first compression chamber. As such, even if the horizontal step scroll compressor has been started up in a state where liquid refrigerant has accumulated, excessive liquid compression can be prevented from arising on the first compression chamber side, where it is easy for liquid compression to arise, by diverting the liquid refrigerant trapped in the first compression chamber including the step parts on the lower side in the gravitational direction when the step parts begin to engage, to the discharge chamber via the bypass port whose opening area is greater. Thus liquid compression can be effectively prevented during liquid migration startup of the horizontal step scroll compressor, which makes it possible to reduce the risk of damage or the like to the scrolls caused by liquid compression and improve the reliability thereof.

Additionally, in the horizontal step scroll compressor according to the first aspect of the present invention, it is preferable that an opening area of a second bypass port open in a range from a position before the first compression chamber is closed to the bypass port to a position where the first compression chamber communicates with the discharge port also be greater than an opening area of a second bypass port open in a range from a position before the second compression chamber is closed to the second bypass port to a position where the second compression chamber communicates with the discharge port.

According to the present invention, an opening area of a second bypass port open in a range from a position before the first compression chamber is closed to the bypass port to a position where the first compression chamber communicates with the discharge port is also greater than an opening area of a second bypass port open in a range from a position before the second compression chamber is closed to the second bypass port to a position where the second compression chamber communicates with the discharge port. As such, when liquid compression arises in the first compression chamber in a range of engagement from a position where the first compression chamber is closed to the bypass port to when the first compression chamber communicates with the discharge port as well, that liquid refrigerant can be diverted to the discharge chamber via the second bypass port whose opening area is greater. Accordingly, liquid compression in the first compression chamber can be reliably prevented in the overall compression process following the beginning of engagement of the step parts, and the durability and reliability of the horizontal step scroll compressor can be ensured with respect to liquid migration startup.

Furthermore, in the horizontal step scroll compressor according to the first aspect of the present invention, it is preferable that the opening area be increased by providing a greater number of bypass ports and/or second bypass ports opening into the first compression chamber than bypass ports and/or second bypass ports opening into the second compression chamber.

According to the present invention, the opening area is increased by providing a greater number of bypass ports and/or second bypass ports opening into the first compression chamber than bypass ports and/or second bypass ports opening into the second compression chamber. As such, in a situation where the diameter of this type of port is limited to no greater than a predetermined diameter, the opening area can be increased easily by increasing the number of ports. Accordingly, during liquid migration startup, liquid refrigerant trapped in the first compression chamber can be diverted smoothly through the bypass ports and/or second bypass ports whose opening area has been increased by increasing the number of ports, and thus liquid compression can be reliably prevented on the first compression chamber side.

Furthermore, in the horizontal step scroll compressor according to the first aspect, it is preferable that the opening area be increased by giving the bypass ports and/or second bypass ports opening into the first compression chamber a greater port area per port than the port area per port of the bypass ports and/or second bypass ports opening into the second compression chamber.

According to the present invention, the opening area is increased by giving the bypass ports and/or second bypass ports opening into the first compression chamber a greater port area per port than the port area per port of the bypass ports and/or second bypass ports opening into the second compression chamber. As such, in a situation where the diameter of this type of port is limited to no greater than a predetermined diameter, the opening area can be increased easily by making each port a long hole, for example, to change the port area thereof. Accordingly, during liquid migration startup, liquid refrigerant trapped in the first compression chamber can be diverted smoothly through the bypass ports and/or second bypass ports whose opening area has been increased by increasing the port area per port, and thus liquid compression can be reliably prevented on the first compression chamber side.

Furthermore, a horizontal step scroll compressor according to a second aspect of the present invention is a horizontal step scroll compressor in which step parts are provided in each of positions of tooth crests and tooth bases in spiral wraps of a stationary scroll and a revolving scroll forming a pair of compression chambers along the spiral directions thereof, and in which a height of the spiral wrap on an outer peripheral side thereof is greater than a height of the wrap on an inner peripheral side thereof on the respective sides of the step parts. Here, bypass ports that, when a pressure in the pair of compression chambers reaches or exceeds a set pressure at an intermediate compression position between a suction cutoff position and a position communicating with a discharge port, divert the pressure into the discharge chamber are provided along a spiral direction of spiral wraps. Among the pairs of step parts, step parts located on a lower side in a gravitational direction are located in a range of from 0° to 45° in a scroll turn direction relative to a horizontal direction.

According to the present invention, bypass ports that, when a pressure in the pair of compression chambers reaches or exceeds a set pressure at an intermediate compression position between a suction cutoff position and a position communicating with a discharge port, divert the pressure into the discharge chamber are provided along a spiral direction of spiral wraps. Among the pairs of step parts, step parts located on a lower side in a gravitational direction are located in a range of from 0° to 45° in a scroll turn direction relative to a horizontal direction. Even if the horizontal step scroll compressor is started up in a state where liquid refrigerant has accumulated, the step parts, among the pairs of step parts, located on the lower side in the gravitational direction are located in a range of from 0° to 45° in a scroll turn direction relative to a horizontal direction. By making the amount of liquid refrigerant trapped in the first compression chamber including the step parts located on the lower side in the gravitational direction when the step parts begin to engage equal to the amount of liquid refrigerant trapped in the second compression chamber forming a pair therewith, and diverting the liquid refrigerants to the discharge chamber through the bypass ports, a risk of liquid compression arising in the first and second compression chambers, or in other words, in the posterior compression chamber and the anterior compression chamber forming a pair, can be reduced. Accordingly, liquid compression can be effectively prevented during liquid migration startup of the horizontal step scroll compressor, which makes it possible to reduce the risk of damage or the like to the spiral wraps caused by liquid compression and improve the reliability thereof.

Furthermore, in the horizontal step scroll compressor according to the second aspect, it is preferable that the step parts located on the lower side in the gravitational direction be located in a range of from 20° to 40° in the scroll turn direction relative to the horizontal direction.

According to the present invention, the step parts located on the lower side in the gravitational direction are located in a range of from 20° to 40° in the scroll turn direction relative to the horizontal direction. Accordingly, the amount of liquid refrigerant trapped in the first compression chamber including the step parts on the lower side in the gravitational direction when the step parts begin to engage and the amount of liquid refrigerant trapped in the second compression chamber that forms a pair therewith can be brought closer in the direction of being equal, and the risk of liquid compression arising in the first and second compression chambers can be reduced. As a result, liquid compression in the respective compression chambers can be reliably prevented in the compression process following the beginning of engagement of the step parts, and the durability and reliability of the horizontal step scroll compressor can be ensured with respect to liquid migration startup.

Furthermore, in the horizontal step scroll compressor according to the second aspect, it is preferable that the step parts located on the lower side in the gravitational direction be located at a position of 30° in the scroll turn direction relative to the horizontal direction.

According to the present invention, the step parts located on the lower side in the gravitational direction are located at a position of 30° in the scroll turn direction relative to the horizontal direction. Accordingly, the amount of liquid refrigerant trapped in the first compression chamber including the step parts on the lower side in the gravitational direction when the step parts begin to engage and the amount of liquid refrigerant trapped in the second compression chamber that forms a pair therewith can be made essentially equal, and the risk of liquid compression arising in the first and second compression chambers can be reduced even further. Accordingly, liquid compression in the respective compression chambers can be reliably prevented in the compression process following the beginning of engagement of the step parts, and the durability and reliability of the horizontal step scroll compressor can be ensured with respect to liquid migration startup.

Advantageous Effects of Invention

According to the present invention, even if the horizontal step scroll compressor has been started up in a state where liquid refrigerant has accumulated, excessive liquid compression can be prevented from arising on the first compression chamber side, where it is easy for liquid compression to arise, by diverting the liquid refrigerant trapped in the first compression chamber including the step parts on the lower side in the gravitational direction when the step parts begin to engage, to the discharge chamber via the bypass port whose opening area is greater. Accordingly, liquid compression can be effectively prevented during liquid migration startup of the horizontal step scroll compressor, which makes it possible to reduce the risk of damage or the like to the scrolls caused by liquid compression and improve the reliability thereof.

Additionally, according to the present invention, even if the horizontal step scroll compressor is started up in a state where liquid refrigerant has accumulated, the step parts, among the pairs of step parts, located on the lower side in the gravitational direction are located in a range of from 0° to 45° in a scroll turn direction relative to a horizontal direction. By making the amount of liquid refrigerant trapped in the first compression chamber including the step parts located on the lower side in the gravitational direction when the step parts begin to engage equal to the amount of liquid refrigerant trapped in the second compression chamber forming a pair therewith, and diverting the liquid refrigerants to the discharge chamber through the bypass ports, a risk of liquid compression arising in the first and second compression chambers, or in other words, in the posterior compression chamber and the anterior compression chamber forming a pair, can be reduced. Accordingly, liquid compression can be effectively prevented during liquid migration startup of the horizontal step scroll compressor, which makes it possible to reduce the risk of damage or the like to the spiral wraps caused by liquid compression and improve the reliability thereof.

FIG. 1 is a vertical cross-sectional view of a horizontal step scroll compressor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along A-A in FIG. 1 .

FIGS. 3A to 3D are explanatory diagrams of compression operations illustrating a transition in a state of engagement of stationary and revolving scrolls in the stated scroll compressor.

FIGS. 4A to 4E are explanatory diagrams of compression operations illustrating a transition in a state of engagement of both scrolls in a horizontal step scroll compressor according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a relationship between a liquid surface height of liquid refrigerant that has accumulated in a compression chamber of the stated scroll compressor and a liquid compression pressure that is produced.

FIGS. 6A to 6D are explanatory diagrams of compression operations during liquid migration startup in the case where step parts of a horizontal step scroll compressor, on the lower side in the gravitational direction, are in a position of 45° on the lower-left relative to the horizontal direction.

FIGS. 7A to 7D are explanatory diagrams of compression operations during liquid migration startup in the case where the step parts of the stated compressor, on the lower side in the gravitational direction, are positioned at a center-bottom position relative to the horizontal direction.

FIGS. 8A to 8D are explanatory diagrams of compression operations during liquid migration startup in the case where the step parts of the stated compressor, on the lower side in the gravitational direction, are in a position of 45° on the lower-right relative to the horizontal direction.

FIGS. 9A to 9D are explanatory diagrams of compression operations during liquid migration startup in the case where the step parts of the stated compressor, on the lower side in the gravitational direction, are positioned at a center-side position (a horizontal position) relative to the horizontal direction.

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]

A first embodiment of the present invention will be described below, using FIGS. 1 to 3D and 5 .

FIG. 1 is a vertical cross-sectional view of a horizontal step scroll compressor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along A-A in FIG. 1 , and FIGS. 3A to 3D are explanatory diagrams of compression operations of the stated scroll compressor.

A horizontal step scroll compressor 1 includes a housing 2 constituting an outer shell. The housing 2 is formed from a closed-ended cup-shaped housing 3 that is sealed on one end and a front housing 4 fitted and mounted to the open-ended side of the cup-shaped housing 3 , with the two housings fastened and fixed to each other using bolts or the like to form an integrated unit.

Inside the front housing 4 , a crank shaft 5 is supported by a main bearing 6 and a sub bearing 7 so as to be capable of freely rotating around an axis of the crank shaft 5 . One end side of the crank shaft 5 (a left end side in FIG. 1 ) serves as a small-diameter shaft part 5 A, and the small-diameter shaft part 5 A passes through the front housing 4 and protrudes to the left in FIG. 1 . A known electromagnetic clutch, pulley, or the like that receives motive power from the exterior is provided on an end of the small-diameter shaft part 5 A protruding to the exterior, and motive power is inputted from an external driving source such as an engine via a belt. A lip seal 8 is installed between the main bearing 6 and the sub bearing 7 , forming a seal between the interior of the housing 2 and the atmospheric air.

A large-diameter shaft part 5 B is provided on another end side of the crank shaft 5 (a right end side in FIG. 1 ). A crank pin 5 C that is decentered from the axis of the crank shaft 5 by a predetermined dimension is provided integrally with the large-diameter shaft part 5 B. By the large-diameter shaft part 5 B and the small-diameter shaft part 5 A being supported via the main bearing 6 and the sub bearing 7 , the crank shaft 5 is supported by the front housing 4 so as to be capable of freely rotating. A revolving scroll 14 , which will be described later, is connected to the crank pin 5 C via a drive bushing 9 and a revolving bearing 10 , and the revolving scroll 14 is driven to revolve by rotational driving of the crank shaft 5 .

A pin hole 9 A into which the crank pin 5 C is fitted is provided in the drive bushing 9 . The crank pin 5 C and the revolving scroll 14 are connected by fitting, via the revolving bearing 10 , a boss part 14 C of the revolving scroll 14 onto the outer circumference of the drive bushing 9 that is fitted to the crank pin 5 C. A known slave crank mechanism that makes the turn radius of the revolving scroll 14 variable may be provided between the drive bushing 9 and the crank pin 5 C. Additionally, a balance weight 11 for eliminating unbalanced loads produced by the revolving scroll 14 revolving is provided on the drive bushing 9 , and is driven to revolve along with the revolving scroll 14 .

A scroll compressor mechanism (compression mechanism) 12 constituted of a stationary scroll 13 and the revolving scroll 14 , which form a pair, is incorporated into the housing 2 . The stationary scroll 13 is constituted of an end plate 13 A and a spiral wrap 13 B erected from the end plate 13 A, and the revolving scroll 14 is constituted of an end plate 14 A and a spiral wrap 14 B erected from the end plate 14 A.

The stationary scroll 13 and the revolving scroll 14 according to the present embodiment include step parts 13 D and 13 E and step parts 14 D and 14 E, respectively, provided in predetermined positions of tooth crests and tooth bases of the spiral wraps 13 B and 14 B along the spiral directions thereof (see FIG. 2 ). The tooth crests of the spiral wraps 13 B and 14 B are formed such that a tooth crest on an outer peripheral side in a revolution axial direction is higher and a tooth crest on an inner peripheral side is lower on the respective sides of the step parts 13 D and 13 E and step parts 14 D and 14 E. On the other hand, the tooth bases are formed such that a tooth base on the outer peripheral side in the revolution axial direction is lower and a tooth base on the inner peripheral side is higher. As a result, the spiral wraps 13 B and 14 B have a higher wrap height on the outer peripheral side than the wrap height on the inner peripheral side.

The stationary scroll 13 and the revolving scroll 14 are engaged with each other such that the centers thereof are separated by an amount equivalent to the turn radius and the phases of the spiral wraps 13 B and 14 B shifted by 180 degrees, and are assembled such that a small clearance in the wrap height direction is present between the tooth crests and the tooth bases on the spiral wraps 13 B and 14 B of the respective scrolls at normal temperature. As a result, as illustrated in FIG. 1 , a pair of compression chambers 15 delimited by the end plates 13 A and 14 A and the spiral wraps 13 B and 14 B are formed between the scrolls 13 and 14 so as to be symmetrical relative to the scroll centers, and the revolving scroll 14 revolves smoothly around the stationary scroll 13 .

The compression chambers 15 are formed such that a height thereof in the revolution axial direction is greater on an outer peripheral side of the spiral wraps 13 B and 14 B than on an inner peripheral side, thus forming the compression mechanism 12 capable of three-dimensional compression in which a gas can be compressed not only in a circumferential direction of the spiral wraps 13 B and 14 B but also in a wrap height direction. Note that in the tooth crests of the spiral wraps 13 B and 14 B, a tip seal 16 that seals a tip seal surface formed with the tooth base of the partner scroll is fitted into a groove provided in the tooth crest. The horizontal step scroll compressor 1 configured in this manner is well-known.

The stationary scroll 13 is fixed to an inner bottom surface of the cup-shaped housing 3 by a plurality of bolts 17 . Additionally, with the revolving scroll 14 , the crank pin 5 C provided on one end side of the crank shaft 5 is connected to the boss part 14 C provided on a rear surface of the end plate 14 A via the drive bushing 9 and the revolving bearing 10 as described above. Furthermore, the rear surface of the end plate 14 A is supported by a thrust bearing surface of the front housing 4 , and the revolving scroll 14 is driven so as to orbitally revolve around the stationary scroll 13 while being prevented from self-rotating by a self-rotation prevention mechanism 18 such as an Oldham coupling provided between the thrust bearing surface and the rear surface of the end plate 14 A. The self-rotation prevention mechanism 18 may be a known pin-ring type self-rotation prevention mechanism.

A discharge port 13 C that discharges compressed refrigerant gas is formed in the stationary scroll 13 in a central area of the end plate 13 A. A discharge lead valve 19 is installed in the discharge port 13 C via a retainer. Additionally, in the rear surface side of the end plate 13 A of the stationary scroll 13 , a seal member 20 such as an O-ring is provided so as to make tight contact with the inner surface of the cup-shaped housing 3 , and a discharge chamber 21 sectioned off from the internal space of the housing 2 is formed with the inner surface of the cup-shaped housing 3 . As a result, the configuration is such that the internal space of the housing 2 aside from the discharge chamber 21 functions as an intake chamber 22 .

In the horizontal step scroll compressor 1 configured as described thus far, overcompression, liquid compression, and the like may arise in response to changes in operation conditions. In this case, excessive stress caused by the overcompression, liquid compression, or the like may be applied to, for example, base parts of the step parts 13 D and 14 D on the tooth crest sides of the spiral wraps 13 B and 14 B in the stationary scroll 13 and the revolving scroll 14 . There is a risk that this stress will cause cracks to form in the bases of the step parts 13 D and 14 D and damage the spiral wraps 13 B and 14 B.

Accordingly, the present embodiment employs a configuration in which a plurality of pairs of bypass ports, namely first bypass ports 23 A and 23 B, second bypass ports 24 A and 24 B, and third bypass ports 25 A and 25 B, are provided along the spiral direction, opening into the respective compression chambers 15 and preventing overcompression or liquid compression in the overall compression stroke from a suction cutoff position of the pair of compression chambers 15 (θd), to when the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage (a θs position), through a position where that engagement ends (θs+π), and finally to a position where the pair of compression chambers 15 merge and communicate with the discharge port 13 C (θp).

It is assumed that lead valves (not illustrated) that open the bypass ports 23 A and 23 B, 24 A and 24 B, and 25 A and 25 B to the discharge chamber 21 when pressure within the compression chambers 15 has reached or exceeded a set pressure are provided in the openings of the first bypass ports 23 A and 23 B, the second bypass ports 24 A and 24 B, and the third bypass ports 25 A and 25 B leading into the discharge chamber 21 . Note that providing lead valves in this manner is known.

Furthermore, as described earlier, it has been discovered that in the horizontal step scroll compressor 1 , liquid compression arising when starting up the compressor in a liquid migration state in which liquid refrigerant has migrated into the compressor while operation of the compressor is stopped arises more easily not in the compression chamber located on the lower side in the gravitational direction at the time of startup, but rather on the side of a first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage. On the basis of this knowledge, the following configuration is employed in addition to the above-described first bypass ports 23 A and 23 B, second bypass ports 24 A and 24 B, and third bypass ports 25 A and 25 B in order to effectively prevent liquid compression arising when starting up from a liquid migration state.

That is, an additional first bypass port 23 B 1 is provided in addition to the first bypass port 23 B that opens into the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage, so that an opening area of the first bypass ports 23 B and 23 B 1 that open into the first compression chamber (stationary posterior compression chamber) 15 B side is greater than an opening area of the first bypass port 23 A that opens into a second compression chamber (stationary anterior compression chamber) 15 A that forms a pair with the first compression chamber 15 B. This makes it easier to divert the liquid refrigerant, and as a result prevents liquid compression.

Moreover, an additional second bypass port 24 B 1 is provided in a position of the second bypass port 24 B that opens into the first compression chamber (stationary posterior compression chamber) 15 B while the first compression chamber (stationary posterior compression chamber) 15 B is moving from the position of the beginning of engagement (θs), through the engagement end position (θs+π), and to the position of communicating with the discharge port 13 C (θp). As a result, an opening area of the second bypass ports 24 B and 24 B 1 that open into the first compression chamber (stationary posterior compression chamber) 15 B side is greater than an opening area of the second bypass port 24 A that opens into the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair with the first compression chamber 15 B. This makes it easier to divert the liquid refrigerant, and as a result ensures that liquid compression does not arise.

Note that it is assumed that lead valves that open the bypass ports 23 B 1 and 24 B 1 to the discharge chamber 21 when the pressure within the first compression chamber 15 B has reached or exceeded a set pressure are also provided in the additionally-provided first bypass port 23 B 1 and second bypass port 24 B 1 . The lead valves for the first bypass port 23 B 1 and the second bypass port 24 B 1 may be common with the lead valves provided for the first bypass port 23 B and the second bypass port 24 B.

According to the configuration described above, the present embodiment has the following operational effects.

In the horizontal step scroll compressor 1 , a low-pressure refrigerant gas sucked into the intake chamber 22 within the housing 2 from an intake port (not illustrated) is sucked into the pair of compression chambers 15 by the revolving driving of the revolving scroll 14 . This refrigerant gas undergoes three-dimensional compression while the compression chambers 15 move from the outer peripheral side toward the center side in the circumferential direction and wrap height direction of the spiral wraps 13 B and 14 B and decrease in volume, after which the pair of compression chambers 15 merge and communicate with the discharge port 13 C. The discharge lead valve 19 opens and discharges into the discharge chamber 21 as a result. This high-pressure gas is sent to the exterior through a discharge port provided in the housing 2 .

In this compression process, there are cases, depending on the operation conditions, where the pressure within the compression chambers 15 rises abnormally and produces a state of overcompression, liquid refrigerant is sucked in and the pressure rises abnormally under liquid compression, or the like. In such a case, there are cases where excessive stress caused by the overcompression, liquid compression, or the like is applied to base parts of the step parts 13 D and 14 D on the tooth crest sides of the spiral wraps 13 B and 14 B in the stationary scroll 13 and the revolving scroll 14 . There is a risk that this concentration of stress will produce cracks in the bases of the step parts 13 D and 14 D and damage the spiral wraps 13 B and 14 B.

However, in the present embodiment, the plurality of pairs of bypass ports, namely the first bypass ports 23 A and 23 B, the second bypass ports 24 A and 24 B, and the third bypass ports 25 A and 25 B, are provided along the spiral direction, opening into the respective compression chambers 15 in the overall compression stroke from the suction cutoff position of the pair of compression chambers 15 (θd) to the position where the compression chambers 15 communicate with the discharge port 13 C (θp). Accordingly, abnormal pressure caused by overcompression or liquid refrigerant under liquid compression in the compression chambers 15 can be diverted from the first bypass ports 23 A and 23 B, the second bypass ports 24 A and 24 B, and the third bypass ports 25 A and 25 B to the discharge chamber 21 sequentially via the lead valves. The risk of the spiral wraps 13 B and 14 B being damaged can be eliminated as a result.

On the other hand, liquid refrigerant may migrate and accumulate within the compression chambers 15 while operation of the horizontal step scroll compressor 1 is stopped. When the compressor is started up from this liquid migration state, it is known that in the horizontal step scroll compressor 1 , liquid compression arises more easily on the side of the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage. The opening area of the first bypass ports 23 B and 23 B 1 that open into the first compression chamber (stationary posterior compression chamber) 15 B is greater than the opening area of the first bypass port 23 A that opens into the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair with the first compression chamber (stationary posterior compression chamber) 15 B.

Accordingly, it can be made easier to divert the liquid refrigerant on the first compression chamber (stationary posterior compression chamber) 15 B side, where liquid compression arises more easily. This makes it possible to effectively prevent liquid compression in the horizontal step scroll compressor 1 .

Meanwhile, the additional second bypass port 24 B 1 is provided in the position of the second bypass port 24 B that opens into the first compression chamber (stationary posterior compression chamber) 15 B while the first compression chamber (stationary posterior compression chamber) 15 B is moving from the position of the beginning of engagement (θs), through the engagement end position (θs+π), and to the position of communicating with the discharge port 13 C (θp), and thus provides a greater opening area than the second bypass port 24 A that opens into the second compression chamber (stationary anterior compression chamber) 15 A forming a pair with the first compression chamber 15 B. Accordingly, liquid compression in the first compression chamber (stationary posterior compression chamber) 15 B can be reliably suppressed in the entire compression process following the beginning of engagement of the step parts 13 D and 14 E and the step parts 13 E and 14 D.

Furthermore, in the above embodiment, the additional first bypass port 23 B 1 and second bypass port 24 B 2 are provided for the first bypass port 23 B and the second bypass port 24 B, respectively, in order to increase the opening area of the openings into the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage. This makes it easy to increase the opening area, which in turn makes it easy to divert the liquid refrigerant.

Note that rather than increasing the number of ports as described above, the first bypass port 23 B and the second bypass port 24 B themselves may, for example, be formed as long holes or the like in order to increase the opening area of the first bypass port 23 B and the second bypass port 24 B opening into the first compression chamber (stationary posterior compression chamber) 15 B.

It goes without saying that the degree of the aforementioned liquid compression is affected by the amount of liquid refrigerant accumulated within the compression chambers 15 . As illustrated in FIG. 5 , in a case where the liquid refrigerant has accumulated to where the pair of compression chambers 15 are full (a liquid surface height of 100%) at, for example, the suction cutoff position (θd), there is no point in making it easy to discharge liquid from one of the compression chambers 15 . That is, additional measures are necessary in such a case. Conversely, in a case where the liquid surface height is less than or equal to 30%, pressure produced by liquid compression will be less than or equal to a permissible range and thus poses no problem. The above-described effects are thus thought to be useful when the liquid surface height is in a range greater than 30% and up to approximately 70%.

[Second Embodiment]

A second embodiment of the present invention will be described below, using FIGS. 4A to 4E .

The present embodiment differs from the above-described first embodiment in that liquid compression is prevented by setting the positions of the step parts 13 E and 14 D located on the lower side in the gravitational direction to an appropriate range, without changing the opening area of the bypass ports. Other points are similar to the first embodiment, so descriptions thereof will be omitted here.

In other words, the present embodiment was arrived at on the basis of knowledge that changing set positions of the step parts 13 E and 14 D located on the lower side in the gravitational direction produces a change in the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage.

As illustrated in FIGS. 4A to 4E , even if the same amount of liquid refrigerant is trapped in the compression chambers 15 , changing the positions of the step parts 13 E and 14 D produces a change in the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage. This is as described earlier with reference to FIGS. 6A to 9D , and FIGS. 4A to 4D are diagrams corresponding to FIGS. 6C, 7C, 8C, and 9C , respectively.

FIG. 4A illustrates the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction being set to a position of 45° on the lower-left relative to the horizontal direction. FIGS. 4B, 4C, 4D, and 4E illustrate states of compression in the case where the positions of the step parts 13 E and 14 D are set to a center-bottom position, the positions of the step parts 13 E and 14 D are set to a position of 45° on the lower-right, the positions of the step parts 13 E and 14 D are set to a center-side position (a horizontal position), and the positions of the step parts 13 E and 14 D are set to a position of 30° on the lower-right, respectively. As illustrated in these drawings, the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage changes.

In the cases of FIGS. 4A and 4B , the amount of liquid refrigerant trapped on the first compression chamber (stationary posterior compression chamber) 15 B side is far greater than the amount of liquid refrigerant trapped in the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair therewith, and thus it is easier for liquid compression to arise in the first compression chamber (stationary posterior compression chamber) 15 B. However, in the cases of FIGS. 4C and 4D , the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B is essentially the same as the amount of liquid refrigerant trapped in the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair therewith (there is slightly more on the first compression chamber 15 B side in the case of FIG. 4C and slightly more on the second compression chamber 15 A side in the case of FIG. 4D ). In the case of FIG. 4E , the amount of liquid refrigerant trapped in the compression chambers 15 A and 15 B is closer to being equal.

In this manner, making the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage equal to the amount of liquid refrigerant trapped in the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair with the compression chamber 15 B means that the amounts of liquid refrigerant trapped in the compression chambers 15 A and 15 B can be reduced and the risk of liquid compression can be reduced.

On the basis of the stated knowledge, in the horizontal step scroll compressor 1 provided with the first bypass ports 23 A and 23 B, the second bypass ports 24 A and 24 B, and the third bypass ports 25 A and 25 B that are open in the overall compression stroke from the suction cutoff position of the pair of compression chambers 15 (θd) to the position where the compression chambers 15 communicate with the discharge port 13 C (θp) and prevent overcompression or liquid compression in the compression chambers 15 as in the first embodiment, the present embodiment sets the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction to the ranges indicated in FIGS. 4C to 4E , or in other words, to a range of from 0° to 45° in the clockwise direction (the scroll turn direction) relative to the horizontal direction, preferably to a range of from 20° to 40° in the scroll turn direction relative to the horizontal direction, and more preferably to a position of 30° (ϕ=30° in FIG. 4E ) in the scroll turn direction relative to the horizontal direction.

As described above, the positions of the step parts 13 E and 14 D on the lower side in the gravitational direction are set to a range of from 0° to 45° in the scroll turn direction relative to the horizontal direction, preferably to a range of from 20° to 40°, and more preferably to a position of 30°. In this manner, the amount of liquid refrigerant trapped in the first compression chamber (stationary posterior compression chamber) 15 B including the step parts 13 E and 14 D on the lower side in the gravitational direction when the step parts 13 E and 14 D and the step parts 13 D and 14 E begin to engage can be made approximately equal to the amount of liquid refrigerant trapped in the second compression chamber (stationary anterior compression chamber) 15 A that forms a pair with the compression chamber 15 B.

Thus, according to the present embodiment as well, liquid compression can be effectively prevented during liquid migration startup of the horizontal step scroll compressor 1 , which makes it possible to reduce the risk of damage or the like to the scrolls caused by liquid compression and improve the reliability thereof.

Note that the present invention is not limited to the invention according to the above-described embodiments and can be modified as appropriate without departing from the spirit of the present invention. For example, although the foregoing embodiments describe examples in which the present invention is applied in a type of horizontal step scroll compressor 1 in which a first end portion of the crank shaft 5 protrudes outward from the housing 2 and the compressor is driven by motive power received from the exterior, the present invention can of course be similarly applied in a hermetically sealed horizontal step scroll compressor in which an electric motor is installed integrally within the housing 2 and the compressor is driven by that electric motor.

Additionally, although the foregoing embodiments describe a configuration in which the first bypass ports 23 A and 23 B, the second bypass ports 24 A and 24 B, or the third bypass ports 25 A and 25 B open into the pair of compression chambers 15 in the overall compression stroke from the suction cutoff position (θd) to the position where the compression chambers 15 communicate with the discharge port 13 C (θp), it goes without saying that the present invention can be similarly applied in a horizontal step scroll compressor 1 in which bypass ports are provided in a range from a position where the step parts 13 D and 14 E and the step parts 13 E and 14 D begin to engage (the θs position) to the position of communication with the discharge port 13 C (θp) or a range from a position where those step parts begin to engage (the θs position) to the position where the engagement ends (θs+π).

1 Horizontal step scroll compressor

13 Stationary scroll

13 B, 14 B Spiral wrap

13 C Discharge port

13 D, 14 D Step part of tooth crest

13 E, 14 E Step part of tooth base

14 Revolving scroll

15 Compression chamber

15 A Second compression chamber (stationary anterior compression chamber)

15 B First compression chamber (stationary posterior compression chamber)

21 Discharge chamber

23 A, 23 B, 23 B 1 First bypass port

24 A, 24 B, 24 B 1 Second bypass port

25 A, 25 B Third bypass port