Fluid pressure pulsation damper mechanism and high-pressure fuel pump equipped with fluid pressure pulsation damper mechanism

The present application claims priority from Japanese application serial No. 2007-133612, filed on May 21, 2007, the content of which is hereby incorporated by reference into this application.

1. Field of the Invention

The present invention relates to a fluid pressure pulsation damper mechanism, and more particularly to a fluid pressure pulsation damper mechanism in which a metal damper is disposed between a main body and a cover attached to the main body and thereby held, the metal damper being formed by joining two metal diaphragms and filling a gas between them.

The present invention also relates to a high-pressure fuel pump that is equipped with the above fluid pressure pulsation damper mechanism and used with an internal combustion engine.

2. Description of Related Art

With known conventional fluid pressure pulsation damper mechanisms of this type, two metal diaphragms are joined by being welded along their outer peripheries, a gas is filled between them to form a discal bulge, and a ring-shaped flat, plate part formed by overlapping the two metal diaphragms is disposed between the peripheral welded part and the discal bulge. Two outer surfaces of the flat plate part are held between the cover and a thick part of the main body. Alternatively, to hold the two outer surfaces, elastic bodies are disposed between the cover and ring-shaped flat plate part and between the main body and the ring-shaped flat plate part (see Japanese Patent Application Laid-open No. 2004-138071, Japanese Patent Application Laid-open No. 2006-521487, Japanese Patent Application Laid-open No. 2003-254191, and Japanese Patent Application Laid-open No. 2005-42554.)

Patent Document 1: Japanese Patent Application Laid-open No. 2004-138071 Patent Document 2: Japanese Patent Application Laid-open No. 2006-521487 Patent Document 3: Japanese Patent Application Laid-open No. 2003-254191 Patent Document 4: Japanese Patent Application Laid-open No. 2005-42554

The technology described above prior arts has a problem in that the cover is made of a thick material and thus increases the weight of the fluid pressure pulsation damper mechanism.

An object of the present invention is to reduce the weight of a fluid pressure pulsation damper mechanism or a high-pressure fuel pump equipped with a fluid pressure pulsation damper mechanism.

To achieve the above object, a fluid pressure pulsation damper mechanism according to the present invention comprising: a metal damper having two metal diaphragms joined together with a hermetic seal for forming a sealed spacing filled with a gas between the two metal diaphragms, an edge part at which are overlapped along outer peripheries thereof; a main body having a damper housing in which the metal damper is accommodated; and a cover attached to the main body to cover the damper housing and isolate the damper housing from an outside air, the metal damper being held between the cover and the main body; wherein the cover is further comprising: a metal plate for making the cover, a peripheral edge of the cover being joined to the main body, a plurality of inner convex curved parts extending toward the main body and a plurality of outer convex curved parts extending in a direction away from the main body, and a plurality of the inner convex curved parts and a plurality of the outer convex parts being disposed alternately inside the peripheral edge of the cover at which the cover is joined to the main body; wherein the cover is attached to the main body, ends of the plurality of inner convex curved parts touch one side of the edge part of the metal damper, which are outwardly formed in radial directions of a part including the sealed spacing in the metal damper; and the metal damper is held between the cover and a metal damper holding part of a holding member placed on the main body.

According to the present invention, the cover is made of a thin metal plate, but the inner convex curved parts have necessary stiffness. In addition, the outer convex curved parts form channels through which spacings inside and outside the metal diaphragm communicate with each other. Accordingly, the fluid pressure pulsation damper mechanism can be made lightweight.

FIG. 1 is an entire longitudinal sectional view of a high-pressure fuel pump equipped with a fluid pressure damper-mechanism in a fourth embodiment of the present invention.

FIG. 2 is a structural view illustrating an example of a fuel supply system of an internal combustion engine to which a high-pressure fuel pump equipped with a fluid pressure damper mechanism of the present invention is applied.

FIG. 3 is a partially enlarged view of the fluid pressure damper mechanism in the fourth embodiment of the present invention.

FIG. 4 is a partially exploded perspective view of the fluid pressure damper mechanism in the fourth embodiment of the present invention.

FIG. 5 is a partially enlarged view of a fluid pressure damper mechanism in a fifth embodiment of the present invention.

FIG. 6 is a partially exploded perspective view of the fluid pressure damper mechanism in the fifth embodiment of the present invention.

FIG. 7 is a partially enlarged view of the fluid pressure damper mechanism in the first embodiment and the fourth embodiment of the present invention.

FIG. 8 is a partially enlarged view of a fluid pressure damper mechanism in a sixth embodiment of the present invention.

FIG. 9 is a partially exploded perspective view of the fluid pressure damper mechanism in the sixth embodiment of the present invention.

FIG. 10 is a longitudinal sectional view showing section X-X, in FIG. 11 , of the high-pressure fuel pump equipped with the fluid pressure damper mechanism in the first embodiment and the fourth embodiment of the present invention.

FIG. 11 is a plan view of a high-pressure fuel pump equipped with the fluid pressure damper mechanism in the first embodiment and the fourth embodiment of the present invention.

FIG. 12 is a longitudinal sectional view of a fluid pressure damper mechanism in a first embodiment of the present invention.

FIG. 13 is a longitudinal sectional view of a fluid pressure damper mechanism in a second embodiment of the present invention.

FIG. 14 is a longitudinal sectional view of a fluid pressure damper mechanism in a third embodiment of the present invention.

An object of an embodiment of the present invention is to reduce the weight of a fluid pressure pulsation damper mechanism or a high-pressure fuel pump equipped with a fluid pressure pulsation damper mechanism.

Accordingly, the damper cover in the embodiment of the present invention is made by pressing a thin metal plate.

When the damper cover is made of a thin metal plate, some problems arise; there is a fear that necessary stiffness is not obtained, it is difficult to configure a part for pressing the damper, and it is also difficult to configure channels through which the inside and outside of the damper communicate with each other.

In a fluid pressure pulsation damping mechanism in the embodiment of the present invention, inner convex curved parts and outer convex curved parts are alternately formed along the periphery of the cover. The cross sectional shape of a part between the inner convex curved part and outer convex curved part has a combined stiffness greater than the stiffness of the flat part. The thickness of the cover is substantially uniform over its entire area. The flat part has prescribed elasticity. The inner convex curved part has prescribed stiffness.

A part for pressing the metal diaphragms is formed on each inner convex curved part having the prescribed stiffness, and channels through which the inner periphery and outer periphery of the metal diaphragm pressing part communicate with each other are formed with the outer convex curved parts.

Accordingly, means for pressing the dumper and fluid communicating channels can be formed by the convex and concave parts disposed to obtain stiffness. The weight of the cover can thereby be reduced without losing necessary functions as the cover member of the metal damper mechanism.

A fluid pressure pulsation damping mechanism in embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment

FIG. 12 is a longitudinal cross sectional view of a fluid pressure pulsation damping mechanism in a first embodiment of the present invention.

The metal damper 120 in the fluid pressure pulsation damping mechanism D 12 comprises two metal diaphragms 121 and 122 , between which there is a sealed spacing 123 filled with a gas.

An edge part 124 of the metal damper 120 is formed by overlapping the peripheries of the two metal diaphragms 121 and 122 ; welding is performed over the entire peripheries of the outer edge 125 of the edge part 124 , maintaining a hermetic seal inside the sealed spacing 123 .

A damper housing part 120 A accommodates the metal damper 120 , and its frame 127 is formed on the outer surface of a main body 126 .

The frame 127 on the main body 126 is ring-shaped; the internal periphery of a skirt 129 of a cover 128 fits into the outer periphery of the frame 127 of the main body 126 , and the damper housing part 120 A is formed by welding their entire peripheries at Z 1 . The metal damper 120 internally disposed is covered with the cover 128 to isolate it from the outside air, and the metal damper 120 is held between the main body 126 and cover 128 .

The cover 128 , which is formed by pressing a thin metal plate having a uniform thickness, has inner convex curved parts 130 extending toward the main body 126 and outer convex curved parts 131 extending in a direction away from the main body 126 ; these convex curved parts are both inside the skirt 129 (the joint part along the peripheral edge) of the cover 128 , are alternately formed. With the cover 128 attached to the main body 126 , the end of each inner convex curved part 130 touches the surface of one side of the edge part 124 of the metal damper 120 (the upper surface in FIG. 12 ), which are outwardly formed in radial directions of a part including the sealed spacing in the metal damper 120 ; the edge part 124 being formed in a radial direction outside the sealed spacing formed in the metal damper 120 . A metal damper holding part 132 facing the main body 126 touches the surface of the other side of the edge part 124 (the lower surface in FIG. 12 ). The metal damper 120 is held between the metal damper holding part 132 and inner convex curved parts 130 .

The metal damper 120 is discal, and has bulges 121 A and 122 A, between which a sealed spacing is formed. The ring-shaped flat part 124 is formed along the peripheral edge part. The outer peripheral edges of the ring-shaped flat part 124 are joined by being welded at 125 over their entire peripheries. The ends of the inner convex curved parts 130 on the cover 128 touch the ring-shaped flat part 124 , which is more inside than the welded part 125 along the outer peripheral edge part.

The end of the inner convex curved part 130 on the cover 128 is a flat part 130 F (see FIG. 7 ), which is flattened by being pressurized during pressing. The flat part 130 F is thereby placed in tight contact with the edge part 124 on the peripheral edge part of the metal damper 120 , reducing uneven contact. Accordingly, a force for holding the metal damper 120 falls within a prescribed range even when any fluid pressure pulsation damping mechanism is used, and thus a high yield is obtained.

As shown in FIG. 7 , the metal damper 120 is placed on a cup-shaped holding member 133 , and the cover 128 is placed thereon. The cover 128 is then pressed against the main body 126 , and the skirt 129 and the frame 127 of the main body are welded at Z 1 over the entire periphery. When the dimension between the bottom surface of the skirt 129 and the flat part 130 F at the end of the inner convex curved part 130 is managed so that the dimension becomes prescribed dimension L 1 , variations in the dimension are eliminated and thus variations in holding force are also eliminated.

The cup-shaped holding member 133 , which faces the main body 126 , is provided separately from the main body 126 , and set to a ring-shaped positioning protrusion 126 P disposed at the center of the damper housing part 120 A on the main body 126 . A curled part 132 formed on the upper end of the holding member 133 supports the lower surface of the peripheral edge part 124 of the metal damper 120 .

The holding member 133 is elastically deformed and adjusts its holding force when the inner convex curved parts 130 press the metal damper 120 toward the main body 126 .

As shown in FIG. 12 , a fluid inlet 126 C, through which fluid is supplied to the damper housing part 120 A, is attached to the main body 126 . The fluid inlet 126 C and a hole 126 a formed in the damper housing part 120 A communicate with each other through an inlet channel 126 A formed in the main body 126 . A fluid outlet 126 D, through which fluid is expelled from the damper housing part 120 A, is also attached to the main body 126 . A hole 126 b formed in the damper housing part 120 A and the fluid outlet 126 D communicate with each other through an outlet channel 126 B.

The outer convex curved parts 131 formed on the cover 128 are used to allow a spacing S 1 below the cover 128 in the metal damper 120 and a spacing S 2 above the main body 126 in the metal damper 120 to communicate with each other.

The spacing in the holding member 133 and the spacing S 2 above the main body 126 communicate with each other through an opening (the same opening as the opening 30 a in FIG. 4 is present) that appears when a cross section at a different angle is viewed.

In the metal damper 120 accommodated in the damper housing part 120 A, the metal diaphragms 121 and 122 are exposed to a flow of fluid supplied between the fluid inlet 126 C and fluid outlet 126 D, and contracts and expands in response to changes in the dynamic pressure of pressure pulsation generated in the flow, eliminating the pulsation.

The cover 128 in this embodiment is made of a thin metal plate. If, therefore, pressure pulsation that is too large for the metal damper 120 to eliminate occurs, a discal dent 135 formed in the cover 128 at the center eliminates the pulsation by contracting and expanding.

The cover 128 is formed by pressing a rolled steel, so its thickness is uniform over all parts including the skirt 129 , inner convex curved parts 130 , outer convex curved parts 131 , and discal dent 135 . The stiffness of the cover 128 varies with the area; it is lowest at the discal dent 135 , and becomes higher little by little at the skirt 129 and outer convex curved part 131 in that order. The stiffness at an area around the end of the inner convex curved part 130 is highest. The force to hold the edge part 124 of the metal damper 120 can thereby be accepted.

The skirt 129 is press-fitted along the periphery of the frame 127 , causing a tight contact between the inner peripheral surface of the skirt 129 of the cover 128 and the outer peripheral surface of the frame 127 , after which their peripheries are welded at Z 1 . Due to thermal distortion generated during the welding, the cover 128 is displaced in a direction in which it presses the edge part 124 of the metal damper 120 against the holding member 133 . This prevents the force to hold the metal damper from being reduced.

A plurality of outer convex curved parts 130 A, each of which has a larger curvature than the outer convex curved part 131 , is formed on the inner convex curved part 130 toward the skirt 129 , and a plurality of outer convex curved parts 130 B, each of which has approximately the same curvature as the outer convex curved part 131 , is also formed on the inner convex curved part 130 toward the discal dent 135 . A set of these plurality of curved parts ensure a prescribed high stiffness. Accordingly, in this embodiment, the area having high stiffness refers to the area including these curved parts, and the elastic areas or the areas having low stiffness refer to the discal dent 135 and skirt 129 . The outer convex curved part 131 has intermediate stiffness and elasticity.

Second Embodiment

In a fluid pressure pulsation damping mechanism in a second embodiment shown in FIG. 13 , a fluid inlet channel 126 A is formed at the center of the main body 126 ; a hole 126 a , which is linked to the fluid inlet channel 126 A and open to the damper housing part 120 A, is formed at the center of an extrusion 126 P; another hole 133 A is also formed at the center of the holding member 133 .

Accordingly, fluid flows from a fluid inlet 126 C connected to an upstream pipe at a threaded part 126 F through the fluid inlet channel 126 A, holes 126 a , 133 A, and 126 b , the fluid outlet channel 126 B, and fluid outlet 126 D, to a downstream pipe connected at a threaded part 126 G.

Third Embodiment

A fluid pressure pulsation damping mechanism in a third embodiment shown in FIG. 14 indicates that an O-ring 126 H can be applied to a connection part of the fluid inlet 126 C to which the upstream pipe is connected.

Fourth Embodiment

A high-pressure fuel pump equipped with a fluid pressure pulsation damping mechanism will be described as a fourth embodiment in the present invention in detail, with reference to FIGS. 1 to 4 , 7 , 10 , and 11 .

The basic features of the high-pressure fuel pump equipped with a fluid pressure pulsation damping mechanism will be described first while being compared with the fluid pressure pulsation damping mechanism D 12 in the first embodiment.

In the embodiment described below, the main body 126 of the fluid pressure pulsation damping mechanism D 12 in the first embodiment is configured as a pump body 1 of the high-pressure fuel pump; the pump body 1 has a low-pressure fuel inlet (referred to below as the intake joint) 10 and a fuel outlet (referred to below as the expelling joint) 11 .

The pump body 1 also has a fuel pressurizing chamber 12 , in which a cylinder 20 is fixed. A plunger 2 is slidable fitted to the cylinder 20 . When the plunger 2 reciprocates, fuel supplied through an intake joint 10 is delivered to the pressurizing chamber 12 through an intake valve 203 provided at an intake 12 A of the pressurizing chamber 12 . The fuel is pressurized in the pressurizing chamber 12 and the pressurized fuel is expelled to the expelling joint 11 through an outlet valve 6 provided at the outlet 12 B of the pressurizing chamber 12 .

The damper housing part 120 A is disposed at an intermediate point of a low-pressure channel formed between the intake joint 10 and intake valve 203 . The damper housing part 120 A is formed as spacing partitioned by the pump body 1 and cover 128 ; it internally includes the fluid pressure pulsation damping mechanism D 12 equipped with the metal damper 80 .

A shown in FIG. 10 , the damper housing part 120 A includes a first opening 10 A communicating with the intake joint 10 and a second opening 10 B communicating with the fuel intake 12 A, in which the intake valve 203 is disposed. The fuel intake 12 A in the pressurizing chamber 12 and the second opening 10 B open to the damper housing part 120 A are interconnected by an intake channel 10 a.

The first opening 10 A corresponds to the fluid intake 126 a of the fluid pressure pulsation damping mechanism in FIG. 12 , and the second opening 10 B corresponds to the fluid outlet 126 b of the fluid pressure pulsation damping mechanism in FIG. 12 .

As shown in FIG. 1 and FIG. 10 , a seal 2 A is attached to an outer periphery of the plunger 2 at a outside of the pressurizing chamber 12 . A cylinder holder 21 holds the seal 2 A to the outer peripheral surface of the plunger 2 . The seal 2 A and cylinder holder 21 constitute a fuel reservoir 2 B that collects fuel that leaks from the end of the sliding part between the plunger 2 and cylinder 20 . Fuel return channels 2 C and 2 D allow the fuel reservoir 2 B to communicate with a low-pressure fuel channel 10 e formed between the first opening 10 A of the damper housing part 120 A and the intake joint 10 of the pump body 1 .

The diameter d 1 of a part on the plunger 2 to which the seal 2 A is attached is smaller than the diameter d 2 of another part on the plunger 2 over which the plunger 2 fits to the cylinder 20 .

As shown in FIG. 10 , the first opening 10 A in the damper housing part 120 A is open to a wall 10 D that faces the metal damper 80 in the damper housing part 120 A. The low-pressure fuel channel 10 e disposed between the first opening 10 A and the intake joint 10 of the pump body 1 is formed as a first blind hole 10 E starting from the first opening 10 A and extending parallel to the plunger 2 . The fuel reservoir 2 B is connected to the blind hole 10 E through the fuel return channels 2 C and 2 D.

As shown in FIG. 1 , the second opening 10 B in the damper housing part 120 A is open to a position other than the first opening 10 A in the wall 10 D facing the metal damper 80 in the damper housing part 120 A. The low-pressure fuel channel 10 a disposed between the second opening 10 B and the intake joint 10 of the pressurizing chamber 12 is formed as a second blind hole 10 F starting from the second opening 10 B and extending parallel to the plunger 2 . A hole 10 G for attaching the intake valve 203 to the pump body 1 starts from the outer wall 10 H of the pump body 1 , traverses the second blind hole 10 F, and extends to the pressurizing chamber 12 .

The damper housing part 120 A is an isolating wall, which is part of the pressurizing chamber 12 of the pump body 1 . The damper housing part 120 A isolates a wall 1 A facing the end surface 2 A, close to pressurizing chamber 12 , of the plunger 2 , and is formed on the outer wall of the pump body 1 located outside the pressurizing chamber 12 .

The first and second openings 10 A and 10 B are made on this outer wall. The cover 40 is fixed to the pump body 1 in such a way that it covers these openings 10 A and 10 B.

The embodiment will be described below in detail with reference to FIGS. 1 to 4 , 7 , 10 , and 11 .

As shown in FIG. 1 , the expelling joint 11 has an expelling valve 6 . The expelling valve 6 is urged by a spring 6 a in a direction in which the expelling hole 12 B in the pressurizing chamber 12 is closed. The expelling valve 6 is a so-called non-return valve that limits a direction in which fuel flows.

An intake valve mechanism 200 A is unitized as an assembly comprising a solenoid 200 , a plunger rod 201 , a spring 202 , and a flat valve, the intake valve 203 being attached to the assembly. The intake valve 203 inserted from the hole 10 G through the intake channel 10 a into the fuel take 12 A of the pressurizing chamber 12 . The solenoid 200 blocks the hole 10 G and the intake valve mechanism is fixed to the pump body 1 .

When the solenoid 200 is turned off, the plunger rod 201 is urged by the spring 202 in a direction in which a flat valve of the intake valve 203 closes the fuel intake 12 A. Accordingly, when the solenoid 200 is turned off, the plunger rod 201 and intake valve 203 are in a closed state, as shown in FIG. 1 .

As shown in FIG. 2 , fuel is supplied under a low pressure by a low-pressure pump 51 , from a fuel tank 50 to the intake joint 10 of the pump body 1 . In this case, the fuel is regulated to a fixed pressure by a pressure regulator 52 operating at a low pressure. The fuel is then pressurized by the pump body 1 and the pressurized fuel is delivered from the expelling joint 11 to a common rail 53 .

The common rail 53 includes injectors 54 and a pressure sensor 56 . The number of injectors 54 included is equal to the number of cylinders of the engine. Each injector 54 injects fuel into the cylinder of the engine in response to a signal from an engine control unit (ECU) 60 . When the pressure in the common rail 53 exceeds a prescribed value, a relief valve 15 in the pump body 1 opens and part of the high-pressure fuel is returned through a relief channel 15 A to an opening 10 f open to the damper housing part 120 A, thereby preventing the high-pressure piping from being damaged.

A lifter 3 , which is disposed at the bottom of the plunger 2 , is placed in contact with a cam 7 by means of a spring 4 . The plunger 2 is slidably held in the cylinder 20 , and reciprocates when the cam 7 is rotated an engine cam shaft or the like, changing the volume of the pressurizing chamber 12 .

As shown in FIG. 1 , the cylinder 20 is held by a cylinder holder 21 on its outer surface. When threads 20 A formed on the outer surface of the cylinder holder 21 are screwed into threads 1 B formed on the pump body 1 , the cylinder holder 21 is fixed to the pump body 1 .

In this embodiment, the cylinder 20 just slidably holds the plunger 2 , and lacks a pressurizing chamber, providing the effect that the cylinder made of a hard material, which is hard to machine, can be machined to a simple shape.

When the solenoid 200 of the intake valve mechanism 200 A is turned off during a compressing process of the plunger 2 and then the plunger rod 201 moves to the left side in FIG. 1 due to the force by the spring 202 and the fuel pressure in the pressurizing chamber 12 , the intake valve 203 closes the fuel intake 12 A of the fuel pressurizing chamber 12 . The pressure in the pressurizing chamber 12 then starts to rise. In response to this, the expelling valve 6 automatically opens and the pressurized fuel is delivered to the common rail 53 .

When the pressure in the fuel pressurizing chamber 12 falls below the pressure in the intake joint 10 or low-pressure fuel channel 10 a , the plunger rod 201 in the intake valve mechanism 200 A opens the intake valve 203 . When to open the intake valve 203 is set according to the force by the spring 202 , a difference in fluid pressure between the front and back of the intake valve 203 , and the electromagnetic force of the solenoid 200 .

With the solenoid 200 turned on, an electromagnetic force greater than the force of the spring 202 is generated, so the plunger rod 201 opposes the force of the spring 202 and is pushed to the right side in the drawing. The intake valve 203 is then separated from the seat, opening the intake valve 203 .

With the solenoid 200 turned off, the plunger rod 201 engages the seat due to the force of the spring 202 , keeping the intake valve 203 closed.

The solenoid 200 is kept turned on and fuel is supplied to the pressurizing chamber 12 while the plunger 2 is in an intake process (it moves downward in the drawing). The solenoid 200 is turned off at an appropriate point in time in a compression process (it moves upward in the drawing) and the intake valve 203 is moved to the left side in the drawing to close the fuel intake 12 A, causing the fuel remaining in the pressurizing chamber 12 to be delivered to the common rail 53 .

When the solenoid 200 is kept turned on in the compression process, the pressure in the pressurizing chamber 12 is kept to a low level almost equal to the pressures in the intake joint 10 or low-pressure fuel channel 10 a , preventing the expelling valve 6 from being opened. Fuel is returned to the low-pressure fuel channel 10 a by the amount by which the volume of the pressurizing chamber 12 is reduced.

Accordingly, if the solenoid 200 is turned back off in the middle of the compression process, fuel is then delivered to the common rail 53 , so the amount of fuel expelled by the pump can be controlled.

While the plunger 2 is reciprocating, three processes, that is, intake from the intake joint 10 to the pressurizing chamber 12 , expelling from the pressurizing chamber 12 to the common rail 53 , and return from the pressurizing chamber 12 to the fuel intake channel, are repeated. As a result, fuel pressure pulsation occurs in the low-pressure fuel channel.

A mechanism for reducing fuel pressure pulsation in the fourth embodiment will be described next with reference to FIGS. 3 and 4 . FIG. 3 is an enlarged view of the mechanism, and FIG. 4 is a perspective view of a holding mechanism of a damper for reducing fuel pressure pulsation.

A two-metal-diaphragm damper 80 is formed by welding the outer edges 80 d of two diaphragms 80 a and 80 b ; an internal spacing 80 c includes a sealed gas. Since the two-metal-diaphragm damper 80 changes its volume in response to an external change in pressure, it functions as a sensing element that has a pulsation damping function.

Each of the two diaphragms 80 a and 80 b is a thin disk having a bulge at its center. Their dents are made to face each other, and the two diaphragms 80 a and 80 b are concentrically matched. A gas is included in the sealed spacing 80 c formed between the two diaphragms 80 a and 80 b . A plurality of concentric pleats is formed on the diaphragms 80 a and 80 b so that they can be elastically deformed with ease in response to a change in pressure; their cross sections are wavy. The two diaphragms 80 a and 80 b each have a flat part 80 e along the outer periphery of the bulge on which the pleats are formed. The outer edges 80 d of the two matched diaphragms 80 a and 80 b are joined by being welded over their entire peripheries. Due to the welding, the gas in the sealed spacing 80 c does not leak.

The pressure of the gas in the sealed spacing 80 c is higher than the atmospheric pressure, but the gas pressure can be adjusted to any level during manufacturing, according to the pressure of the fluid to be handled. The gas filled is, for example, a mixture of argon gas and helium gas. A leak detector is sensitive to a leak of the helium gas from the welded part, and the argon gas is hard to leak. Accordingly, a leak from the welded part, if any, can be easily detected, and it cannot be considered that the gasses leak completely. The ratios of the mixed gases are determined so that a leak is hard to occur and, if any, can be easily detected.

The diaphragms 80 a and 80 b are made of precipitation hardened stainless steel, which is superior in corrosion in fuel and strength. The two-metal-diaphragm damper 80 is included in the damper housing part 120 A disposed between the intake joint 10 and low-pressure fuel channel 10 a , as the mechanism for reducing the fuel pressure pulsation.

The two-metal-diaphragm damper 80 is held between the damper holder 30 held on the pump body 1 and the damper cover 40 forming the damper housing part 120 A.

Although the entire cross section of the damper holder 30 is a cup-shaped cross section, it has cutouts 30 e formed by cutting part of the damper holder 30 in the peripheral direction, so as to obtain fuel channels through which the inside and outside communicate with each other.

Along the outer edge of the damper holder 30 , peripheral walls 30 c and 30 d erect on areas, which have a diameter larger than the bulge on which concentric pleats are formed on the metal diaphragm damper 80 . Curled parts 30 f and 30 g are respectively formed on the upper ends of the peripheral walls 30 c and 30 d . The curled parts 30 f and 30 g touch the flat part of the lower ring-shaped flat part 80 e formed along the outer periphery of the metal diaphragm dampers 80 , supporting the metal diaphragm damper 80 and radially positioning it.

A downward protrusion 30 e is formed at the center of the damper holder 30 . When the downward protrusion 30 e is inserted into the inner peripheral part of a ring-shaped extrusion 1 a formed on the wall 10 D of the pump body 1 , the damper holder 30 is radially positioned with respect to the pump body 1 .

A plurality of inner convex curved parts 40 a is formed on the inner surface of a damper cover 40 . The inner convex curved parts 40 a is corresponding to the inner convex curved part 130 shown in FIG. 12 . The vertexes of the plurality of inner convex curved parts 40 a are formed at intervals on a circumference positioned inside the outer diameter of the metal diaphragm damper 80 , so that the vertexes are positioned on the ring-shaped flat parts 80 e of the metal diaphragm damper 80 . When the damper cover 40 is joined to the pump body 1 , the metal diaphragm damper 80 is also held between the pump body 1 and the curled parts 30 f and 30 g of the damper holder 30 . As in the embodiment in FIG. 12 , the end of the inner convex curved part 40 a is flattened as shown in FIG. 7 to form a flat part 40 f , providing the same effect as illustrated in FIG. 12 .

An outer convex curved part 40 B is formed between two adjacent inner convex curved parts 40 a . The outer convex curved parts 40 B is corresponding to the outer convex curved part 131 shown in FIG. 12 . The outer convex curved part 40 B functions as a fuel channel through which the inside and outside of the two-metal-diaphragm damper 80 communicate with each other, and thereby can provide a dynamic pressure in the same low-pressure fuel channel to the outer peripheries of the metal diaphragms 80 a and 80 b , improving the pulsation elimination function of the damper.

The inner convex curved part 40 a and outer convex curved part 40 B on the damper cover 40 are formed by pressing, so their costs can be reduced. A ring-shaped skirt 40 b of the damper cover 40 is disposed so that its inner periphery faces the outer periphery of a ring-shaped frame 1 F protruding up to the outer surface of the pump body 1 (the outer surface of the isolating wall 1 A of the pressurizing chamber 12 corresponding to the end of the plunger 2 ). In this state, the entire outer periphery of the skirt 40 b of the damper cover 40 is welded. Accordingly, the damper cover 40 can be fixed to the pump body 1 and hermetic seal in the internal damper housing part 120 A can also be obtained.

The damper cover 40 is formed by pressing a rolled steel, so its thickness is uniform over all parts including the skirt 40 b , inner convex curved parts 40 a , outer convex curved parts 40 B, and discal dent 45 . The stiffness of the cover depends on the area; it is lowest at the discal dent 45 , and becomes higher little by little at skirt 40 b and outer convex curved part 40 B in that order. The stiffness around the end of the inner convex curved part 40 a is highest. The force to hold the ring-shaped flat parts 80 e of the metal diaphragm damper 80 can thereby be accepted.

The skirt 40 b is press-fitted along the periphery of the frame 1 F, causing a tight contact between the inner peripheral surface of the skirt 40 b of the damper cover 40 and the outer peripheral surface of the frame 1 F, after which their peripheries are welded at Z 1 . Due to thermal distortion generated during the welding, the damper cover 40 is displaced in a direction in which it presses the ring-shaped flat parts 80 e disposed around the outer periphery of the metal diaphragm damper 80 against the damper holder 30 , which is used as a holding member. This prevents the force to hold the metal diaphragm damper from being reduced.

A plurality of outer convex curved parts 40 X, each of which has a larger curvature than the outer convex curved parts 40 B, is formed toward the skirt 40 b of the inner convex curved part 40 a , and a plurality of outer convex curved parts 40 Y, each of which has approximately the same curvature as the outer convex curved parts 40 B, is formed toward the discal dent 45 in the inner convex curved part 40 a . A set of these plurality of curved parts ensures a prescribed high stiffness. Accordingly, in this embodiment, the area having a high stiffness refers to the area including these curved parts, and the elastic areas or the areas having low stiffness refer to the discal dent 45 and skirt 40 b . The outer convex curved part 40 B has intermediate stiffness and elasticity.

Accordingly, the ring-shaped flat parts 80 e on the outer periphery of the two-metal-diaphragm damper 80 are held between the flat part 40 f at the end of the inner convex curved part 40 a on the damper cover 40 and the curled parts 30 f and 30 g of the damper holder 30 . Since the force to hold the metal diaphragm damper 80 does not act on the outer peripheral edge 80 d , it can be possible to prevent the two-metal-diaphragm damper 80 from being damaged due to concentrated stress.

Due to the holding force, the damper cover 40 causes a tight contact between the damper holder 30 and metal diaphragm damper 80 . The lower edge of the skirt 40 b of the damper cover 40 is placed in contact with the pump body 1 while the damper cover 40 is pressed against the pump body 1 . The entire periphery of the skirt 40 b of the damper cover 40 is then welded at Z 1 to fix it. Thermal shrinkage caused by the welding further causes distortion in a direction in which the inner convex curved parts 40 a on the damper cover 40 are always pressed against the pump body 1 , making the holding force after the welding stable.

Accordingly, the metal diaphragm damper 80 can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper 80 , so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper 80 in the damper chamber can be lessened, so the whole length of the pump along the plunger can be shortened, enabling the size and cost of the pump to be reduced.

To eliminate variations in manufacturing, it is also possible for the damper holder 30 to have distortion to a certain level in advance during a process of assembling. In this case, the metal diaphragm damper 80 is supported by the cup-shaped outer periphery and fixed to the pump body 1 by means of the ring-shaped protrusion 30 e formed at the center. The cross section of this structure is shaped like a cantilever, so the amount of distortion can be adjusted easily by changing the plate thickness or positioning at the center. However, the amount of distortion must be adjusted so that the holding force is kept greater than an external force exerted on the metal diaphragm damper 80 because of pressure pulsation of the fuel.

When the number of inner convex curved parts 40 a on the damper cover 40 and their width are determined according to the shape of the touched part of the damper holder 30 , the ring-shaped flat parts 80 e on the outer periphery of the two-metal-diaphragm damper 80 can be held in a well-balanced state.

Fuel chambers 10 c and 10 d used as the damper housing part 120 A, in which the metal diaphragm damper 80 is accommodated, communicate with the low-pressure fuel channel 10 a , which leads to the inlet of the pressurizing chamber 12 .

Accordingly, the fuel can also flow freely into and out of the fuel chamber 10 c through the low-pressure fuel channel 10 b formed by the outer convex curved part 40 B on the damper cover 40 , enabling the fuel to be supplied to both surfaces of the two-metal-diaphragm damper 80 . The fuel pressure pulsation can then be eliminated efficiently.

Fifth Embodiment

A fluid pressure pulsation damping mechanism in a fifth embodiment of the present invention will be described next with reference to FIGS. 5 and 6 .

The ring-shaped flat parts 80 e on the outer periphery of the two-metal-diaphragm damper 80 are held between the damper holder 30 and the inner convex curved parts 40 a on the damper cover 40 , as in the fourth embodiment.

The damper cover 40 internally has a plurality of inner convex curved parts 40 a , as described above. The lower peripheral ring-shaped flat part 80 e of the metal diaphragm damper 80 is supported by the vertexes of the inner convex curved parts 40 a.

The damper holder 30 includes a cylindrical metal member 30 F having stiffness, which is formed separately from the pump body 1 . A curved surface 30 f , which is curved toward the inner diameter, is formed on the upper surface of the cylindrical metal member 30 F. The metal diaphragm damper 80 is set so that the lower surface of the ring-shaped flat parts 80 e on the outer periphery of the metal diaphragm damper 80 touches the curved surface 30 f . The ring-shaped flat parts 80 e on the outer periphery of the metal diaphragm damper 80 are held between the damper holder 30 and the inner convex curved parts 40 a on the damper cover 40 placed from above.

The inner diameter of the curved surface 30 f at the upper end of the damper holder 30 is a little larger than the diameter of the bulge of the metal diaphragm damper 80 . The bulge on which pleats of the metal diaphragm damper 80 are formed fits to the inside of the cylindrical metal member 30 F, radially positioning the metal diaphragm damper 80 .

Several cutouts 30 a are formed on the outer cylindrical part 30 c of the damper holder 30 so as to obtain fuel channels. The fuel flows into and out of the fuel chamber 10 d through the cutouts 30 a . The fuel also flows into and out of the fuel chamber 10 c through a low-pressure fuel channel 10 b formed by the outer convex curved parts 40 B formed on the damper cover 40 . As a result, the fuel can be delivered to both sides of the two-metal-diaphragm damper 80 , effectively eliminating the fuel pressure pulsation.

The damper holder 30 is radially positioned by the outer cylindrical part 30 c attached along the frame 1 F, which forms the damper housing part 120 A of the pump body 1 .

In this embodiment, the axial positioning of the damper cover 40 is determined by managing a dimension from the lower end of the cylindrical metal member 30 F to its upper end. For this reason, the dimension of the skirt 40 b of the damper cover 40 is determined so that the lower surface of the skirt 40 b does not touch the pump body 1 .

As described above, the two-metal-diaphragm damper 80 is held by the front and back of the peripheral ring-shaped flat parts 80 e , and the outer peripheral edge 80 d is not held, so there is no risk that the two-metal-diaphragm damper 80 is damaged due to concentrated stress.

The lower side of the two-metal-diaphragm damper 80 fits to the entire periphery of the damper holder 30 , so it can be freely set to the positions at which the inner convex curved parts 40 a are formed on the damper cover 40 disposed at the opposite position.

The damper holder 30 is formed by pressing, so its cost can be reduced.

Due to the holding force, the damper cover 40 causes a tight contact between the damper holder 30 and metal diaphragm damper 80 , as described above. The entire periphery of the skirt 40 b is then welded at Z 1 to the pump body 1 to fix the skirt 40 b while the damper cover 40 is pressed against the pump body 1 . Thermal shrinkage caused by the welding further causes distortion by which the inner convex curved parts 40 a on the damper cover 40 are always deformed toward the pump body 1 . Accordingly, there is no risk that the holding force is weakened after the welding and thereby the metal diaphragm damper 80 becomes unstable.

Accordingly the metal diaphragm damper 80 can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper 80 , so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper 80 in the damper chamber can be lessened, so the whole length of the pump can be shortened, enabling the size and cost of the pump to be reduced.

Sixth Embodiment

A fluid pressure pulsation damping mechanism in a sixth embodiment of the present invention will be described next with reference to FIGS. 8 and 9 .

As shown in FIGS. 8 and 9 , the two-metal-diaphragm damper 80 is structured so that the peripheral ring-shaped flat parts 80 e are held between the inner convex curved parts 40 a on the damper cover 40 and the upper ends of a plurality of arc-shaped protrusions 1 c integrally formed on the pump body 1 .

The damper cover 40 internally has a plurality of inner convex curved parts 40 a , as described above. The upper peripheral ring-shaped flat parts 80 e of the metal diaphragm damper 80 are supported by the vertexes of the inner convex curved parts 40 a . The low-pressure fuel channel 10 a communicates with the fuel chamber 10 c through the low-pressure fuel channel 10 b , which is formed by the outer convex curved part 40 B formed between the inner convex curved part 40 a on the inner surface of the metal diaphragm damper 80 and the inner convex curved part 40 a.

The pump body 1 is made of cast metal, and integrally has a plurality of arch-shaped protrusions 1 c in the damper housing part 120 A. The protrusions 1 c , which are formed along a diameter a little greater than the pleat of the metal diaphragm damper 80 , protrude from the outer surface 10 D of the pump body 1 at positions opposite to the inner convex curved parts 40 a on the damper cover 40 . The ends of the protrusions 1 c support the lower peripheral ring-shaped flat part 80 e of the metal diaphragm damper 80 , and radially position the metal diaphragm damper 80 . Since the dumper holders 1 c are integrated with the pump body 1 in this way, the number of parts can be reduced.

In this embodiment as well, the outer peripheral edge 80 d of the two-metal-diaphragm damper 80 is not held, so there is no risk that the two-metal-diaphragm damper 80 is damaged due to concentrated stress.

Cutouts 1 d are partially formed on the ring-shaped protrusion 1 c on the pump body 1 , enabling the fuel chamber 10 c and low-pressure fuel channel 10 a to communicate with each other. As a result, the fuel can be delivered to both sides of the two-metal-diaphragm damper 80 , effectively eliminating the fuel pressure pulsation.

Due to the holding force, the damper cover 40 is placed in tight contact with the metal diaphragm damper 80 . The outer surface 40 b of the damper cover 40 is fixed to the pump body 1 by welding at Z 1 while the damper cover 40 is pressed against the pump body 1 . Thermal shrinkage caused by the welding further causes distortion in a direction in which the inner convex curved parts 40 a on the damper cover 40 are always pressed against the pump body 1 . Accordingly, there is no risk that the holding force of the two-metal-diaphragm damper 80 is weakened after the welding and thereby the metal diaphragm damper 80 becomes unstable.

Accordingly the metal diaphragm damper 80 can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper 80 , so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper 80 in the damper chamber can be lessened, so the whole length of the pump can be shortened, enabling the size and cost of the pump to be reduced.

To achieve the object of providing a compact, inexpensive high-pressure fuel pump that ensures stable pulsation reduction, a metal damper has been formed by welding two metal diaphragms along their peripheries in the fourth to sixth embodiments described above. An entire or partial periphery of the metal damper is held inside the welded part between a pair of pressing members, which are oppositely disposed, and fixed to the damper chamber.

One of the pair of the pressing members is the damper cover 40 , which is part of the damper chamber. The inner convex curved parts 40 a formed on the inner surface of the damper cover 40 , which extrude toward the pump body 1 , directly support the damper. The opposite pressing member is a cup-shaped damper holder 30 , a ring-shaped protrusion formed integrally with the pump body 1 , or a plurality of protrusions formed integrally with the pump body 1 with a predetermined spacing.

Accordingly, the two-metal-diaphragm damper 80 with two metal diaphragms 80 a , 80 b welded on their peripheries can be fixed in a simple manner, and thereby these embodiments can provide a high-pressure fuel pump 1 with less parts that has easy-to-adjust fuel pressure pulsation elimination characteristics and can supply fuel to the fuel injection valve under stable pressure.

Specifically, the peripheral ring-shaped flat part 80 e of the two-metal-diaphragm damper 80 is directly supported by a plurality of inner convex curved parts 40 a formed on the inner surface of the damper cover 40 to reduce the number of parts. In addition, outer convex curved parts 40 B, which are formed among the plurality of inner convex curved parts 40 a , can be used as fuel channels, so a structure for delivering fuel to both sides of the two-metal-diaphragm damper 80 can be formed with less parts and by simple machining.

The features of these embodiments are summarized below as specific aspects.

(First Aspect)

A high-pressure fuel pump having a damper chamber that includes a discal damper formed by joining two metal diaphragms and is disposed in an intermediate point of a channel between an intake channel and a pressurizing chamber, the damper chamber being formed by joining the outer wall of a pump body and a damper chamber cover to the edge of the pump body; the discal damper is disposed in such a way that the damper chamber is partitioned into two parts, one part facing the pump body and the other facing the damper cover; the damper is held between a damper holder supported on the pump body and the inner surface of the damper cover, one side of the damper being supported by the damper holder, the other side being directly supported by the inner surface of the damper cover.

(Second Aspect)

In the high-pressure fuel pump described in the first aspect, the damper cover has a plurality of protrusions on its inner surface; the plurality of protrusions supports one side of the damper at two or more point or on two or more planes.

(Third Aspect)

In the high-pressure fuel pump described in the second aspect, the plurality of protrusions on the inner surface of the damper cover is convex-concave protrusions formed integrally with the pump body by pressing.

(Fourth Aspect)

In the high-pressure fuel pump described in the third aspect, the damper holder, which supports the one side of the damper, is a ring-shaped protrusion formed integrally with the pump body by casting or the like.

(Fifth Aspect)

In the high-pressure fuel pump described in the fourth aspect, the damper holder formed integrally with the pump body is a plurality of protrusions and supports the damper at two or more points or on two or more planes.

(Sixth Aspect)

In the high-pressure fuel pumps described in the first to third aspects, the damper holder supported on the pump body is an elastic member.

(Seventh Aspect)

In the high-pressure fuel pump described in the sixth aspect, the damper holder is discal, the cross section of which is cup-shaped; the outer periphery of the damper holder supports the damper; a protrusion provided at the center of the damper holder fits to a housing part formed on the pump body, positioning and fixing the damper.

(Eighth Aspect)

In the high-pressure fuel pump described in the seventh aspect, the damper holder has cutouts or holes at some parts to form fuel channels.

(Ninth Aspect)

In the high-pressure fuel pumps described in the first to eighth aspects, the damper cover, which directly supports the damper, is an elastic member.

(Tenth Aspect)

In the high-pressure fuel pumps described in the first to ninth aspects, the outer periphery of the damper cover is welded to the pump body, and thereby a welded joint structure is provided in which the damper cover is deformed by contraction after the welding in a direction in which the inner surface of the damper cover is pressed toward the pump body and thereby the dumper is held between the damper cover and the damper holder.

According these aspects of the embodiments described above, the following results can be achieved.

In the embodiments of the present invention, inner convex curved parts used as the damper holder are formed by pressing a thin metal plate. Each inner convex curved part has significant stiffness, and prescribed elasticity is posed around the inner convex curved part. A resulting effect is that a force to hold the damper can be adjusted in a wide range.

The metal diaphragm assembly (also referred to as the two-metal-diaphragm damper) can be held by a simple structure, and the effect of reducing pressure pulsation of low-pressure fuel can be stabilized. The fuel can thereby be supplied to the fuel injection valve under stable pressure.

The cover itself has elasticity, by which if pulsation that is too large for the damper to eliminate occurs, the pulsation can be eliminated. Accordingly, a compact damper mechanism having a large effect of reducing fuel pressure pulsation is obtained.

The cover itself is also used to hold the damper, reducing the number of parts and achieving a simple structure.

The number of parts for fixing the metal damper can be reduced, and thereby the structure is simplified. The force to hold the metal damper can be adjusted with ease. As a result, a stable pulsation reduction effect is obtained.

In addition to the features described above, the high-pressure fuel pump equipped with this fluid pulsation damper mechanism is compact and lightweight, and can be assembled easily, when compared with a fuel pump to which a damper mechanism is integrally attached.

The present invention can be applied to various types of fluid transfer systems as a damper mechanism for reducing fluid pulsation. The present invention is particularly preferable when the damper mechanism is used as a fuel pressure pulsation mechanism attached to a low-pressure fuel channel of a high-pressure fuel pump that pressurizes gasoline and expels the pressurized gasoline to the injector. It is also possible to integrally attach the damper mechanism to the high-pressure fuel pump, as embodied in the present invention.