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

A fluid pressure pulsation damper mechanism includes: 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 overlapping 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 outside air.

CLAIM OF PRIORITY

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.

BACKGROUND OF THE INVENTION

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

SUMMARY OF THE INVENTION

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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

The metal damper120in the fluid pressure pulsation damping mechanism D12comprises two metal diaphragms121and122, between which there is a sealed spacing123filled with a gas.

An edge part124of the metal damper120is formed by overlapping the peripheries of the two metal diaphragms121and122; welding is performed over the entire peripheries of the outer edge125of the edge part124, maintaining a hermetic seal inside the sealed spacing123.

A damper housing part120A accommodates the metal damper120, and its frame127is formed on the outer surface of a main body126.

The frame127on the main body126is ring-shaped; the internal periphery of a skirt129of a cover128fits into the outer periphery of the frame127of the main body126, and the damper housing part120A is formed by welding their entire peripheries at Z1. The metal damper120internally disposed is covered with the cover128to isolate it from the outside air, and the metal damper120is held between the main body126and cover128.

The cover128, which is formed by pressing a thin metal plate having a uniform thickness, has inner convex curved parts130extending toward the main body126and outer convex curved parts131extending in a direction away from the main body126; these convex curved parts are both inside the skirt129(the joint part along the peripheral edge) of the cover128, are alternately formed. With the cover128attached to the main body126, the end of each inner convex curved part130touches the surface of one side of the edge part124of the metal damper120(the upper surface inFIG. 12), which are outwardly formed in radial directions of a part including the sealed spacing in the metal damper120; the edge part124being formed in a radial direction outside the sealed spacing formed in the metal damper120. A metal damper holding part132facing the main body126touches the surface of the other side of the edge part124(the lower surface inFIG. 12). The metal damper120is held between the metal damper holding part132and inner convex curved parts130.

The metal damper120is discal, and has bulges121A and122A, between which a sealed spacing is formed. The ring-shaped flat part124is formed along the peripheral edge part. The outer peripheral edges of the ring-shaped flat part124are joined by being welded at125over their entire peripheries. The ends of the inner convex curved parts130on the cover128touch the ring-shaped flat part124, which is more inside than the welded part125along the outer peripheral edge part.

The end of the inner convex curved part130on the cover128is a flat part130F (seeFIG. 7), which is flattened by being pressurized during pressing. The flat part130F is thereby placed in tight contact with the edge part124on the peripheral edge part of the metal damper120, reducing uneven contact. Accordingly, a force for holding the metal damper120falls within a prescribed range even when any fluid pressure pulsation damping mechanism is used, and thus a high yield is obtained.

As shown inFIG. 7, the metal damper120is placed on a cup-shaped holding member133, and the cover128is placed thereon. The cover128is then pressed against the main body126, and the skirt129and the frame127of the main body are welded at Z1over the entire periphery. When the dimension between the bottom surface of the skirt129and the flat part130F at the end of the inner convex curved part130is managed so that the dimension becomes prescribed dimension L1, variations in the dimension are eliminated and thus variations in holding force are also eliminated.

The cup-shaped holding member133, which faces the main body126, is provided separately from the main body126, and set to a ring-shaped positioning protrusion126P disposed at the center of the damper housing part120A on the main body126. A curled part132formed on the upper end of the holding member133supports the lower surface of the peripheral edge part124of the metal damper120.

The holding member133is elastically deformed and adjusts its holding force when the inner convex curved parts130press the metal damper120toward the main body126.

As shown inFIG. 12, a fluid inlet126C, through which fluid is supplied to the damper housing part120A, is attached to the main body126. The fluid inlet126C and a hole126aformed in the damper housing part120A communicate with each other through an inlet channel126A formed in the main body126. A fluid outlet126D, through which fluid is expelled from the damper housing part120A, is also attached to the main body126. A hole126bformed in the damper housing part120A and the fluid outlet126D communicate with each other through an outlet channel126B.

The outer convex curved parts131formed on the cover128are used to allow a spacing S1below the cover128in the metal damper120and a spacing S2above the main body126in the metal damper120to communicate with each other.

The spacing in the holding member133and the spacing S2above the main body126communicate with each other through an opening (the same opening as the opening30ainFIG. 4is present) that appears when a cross section at a different angle is viewed.

In the metal damper120accommodated in the damper housing part120A, the metal diaphragms121and122are exposed to a flow of fluid supplied between the fluid inlet126C and fluid outlet126D, and contracts and expands in response to changes in the dynamic pressure of pressure pulsation generated in the flow, eliminating the pulsation.

The cover128in this embodiment is made of a thin metal plate. If, therefore, pressure pulsation that is too large for the metal damper120to eliminate occurs, a discal dent135formed in the cover128at the center eliminates the pulsation by contracting and expanding.

The cover128is formed by pressing a rolled steel, so its thickness is uniform over all parts including the skirt129, inner convex curved parts130, outer convex curved parts131, and discal dent135. The stiffness of the cover128varies with the area; it is lowest at the discal dent135, and becomes higher little by little at the skirt129and outer convex curved part131in that order. The stiffness at an area around the end of the inner convex curved part130is highest. The force to hold the edge part124of the metal damper120can thereby be accepted.

The skirt129is press-fitted along the periphery of the frame127, causing a tight contact between the inner peripheral surface of the skirt129of the cover128and the outer peripheral surface of the frame127, after which their peripheries are welded at Z1. Due to thermal distortion generated during the welding, the cover128is displaced in a direction in which it presses the edge part124of the metal damper120against the holding member133. This prevents the force to hold the metal damper from being reduced.

A plurality of outer convex curved parts130A, each of which has a larger curvature than the outer convex curved part131, is formed on the inner convex curved part130toward the skirt129, and a plurality of outer convex curved parts130B, each of which has approximately the same curvature as the outer convex curved part131, is also formed on the inner convex curved part130toward the discal dent135. 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 dent135and skirt129. The outer convex curved part131has intermediate stiffness and elasticity.

Second Embodiment

In a fluid pressure pulsation damping mechanism in a second embodiment shown inFIG. 13, a fluid inlet channel126A is formed at the center of the main body126; a hole126a, which is linked to the fluid inlet channel126A and open to the damper housing part120A, is formed at the center of an extrusion126P; another hole133A is also formed at the center of the holding member133.

Accordingly, fluid flows from a fluid inlet126C connected to an upstream pipe at a threaded part126F through the fluid inlet channel126A, holes126a,133A, and126b, the fluid outlet channel126B, and fluid outlet126D, to a downstream pipe connected at a threaded part126G.

Third Embodiment

A fluid pressure pulsation damping mechanism in a third embodiment shown inFIG. 14indicates that an O-ring126H can be applied to a connection part of the fluid inlet126C 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 toFIGS. 1 to 4,7,10, and11.

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 D12in the first embodiment.

In the embodiment described below, the main body126of the fluid pressure pulsation damping mechanism D12in the first embodiment is configured as a pump body1of the high-pressure fuel pump; the pump body1has a low-pressure fuel inlet (referred to below as the intake joint)10and a fuel outlet (referred to below as the expelling joint)11.

The pump body1also has a fuel pressurizing chamber12, in which a cylinder20is fixed. A plunger2is slidable fitted to the cylinder20. When the plunger2reciprocates, fuel supplied through an intake joint10is delivered to the pressurizing chamber12through an intake valve203provided at an intake12A of the pressurizing chamber12. The fuel is pressurized in the pressurizing chamber12and the pressurized fuel is expelled to the expelling joint11through an outlet valve6provided at the outlet12B of the pressurizing chamber12.

The damper housing part120A is disposed at an intermediate point of a low-pressure channel formed between the intake joint10and intake valve203. The damper housing part120A is formed as spacing partitioned by the pump body1and cover128; it internally includes the fluid pressure pulsation damping mechanism D12equipped with the metal damper80.

A shown inFIG. 10, the damper housing part120A includes a first opening10A communicating with the intake joint10and a second opening10B communicating with the fuel intake12A, in which the intake valve203is disposed. The fuel intake12A in the pressurizing chamber12and the second opening10B open to the damper housing part120A are interconnected by an intake channel10a.

The first opening10A corresponds to the fluid intake126aof the fluid pressure pulsation damping mechanism inFIG. 12, and the second opening10B corresponds to the fluid outlet126bof the fluid pressure pulsation damping mechanism inFIG. 12.

As shown inFIG. 1andFIG. 10, a seal2A is attached to an outer periphery of the plunger2at a outside of the pressurizing chamber12. A cylinder holder21holds the seal2A to the outer peripheral surface of the plunger2. The seal2A and cylinder holder21constitute a fuel reservoir2B that collects fuel that leaks from the end of the sliding part between the plunger2and cylinder20. Fuel return channels2C and2D allow the fuel reservoir2B to communicate with a low-pressure fuel channel10eformed between the first opening10A of the damper housing part120A and the intake joint10of the pump body1.

The diameter d1of a part on the plunger2to which the seal2A is attached is smaller than the diameter d2of another part on the plunger2over which the plunger2fits to the cylinder20.

As shown inFIG. 10, the first opening10A in the damper housing part120A is open to a wall10D that faces the metal damper80in the damper housing part120A. The low-pressure fuel channel10edisposed between the first opening10A and the intake joint10of the pump body1is formed as a first blind hole10E starting from the first opening10A and extending parallel to the plunger2. The fuel reservoir2B is connected to the blind hole10E through the fuel return channels2C and2D.

As shown inFIG. 1, the second opening10B in the damper housing part120A is open to a position other than the first opening10A in the wall10D facing the metal damper80in the damper housing part120A. The low-pressure fuel channel10adisposed between the second opening10B and the intake joint10of the pressurizing chamber12is formed as a second blind hole10F starting from the second opening10B and extending parallel to the plunger2. A hole10G for attaching the intake valve203to the pump body1starts from the outer wall10H of the pump body1, traverses the second blind hole10F, and extends to the pressurizing chamber12.

The damper housing part120A is an isolating wall, which is part of the pressurizing chamber12of the pump body1. The damper housing part120A isolates a wall1A facing the end surface2A, close to pressurizing chamber12, of the plunger2, and is formed on the outer wall of the pump body1located outside the pressurizing chamber12.

The first and second openings10A and10B are made on this outer wall. The cover40is fixed to the pump body1in such a way that it covers these openings10A and10B.

The embodiment will be described below in detail with reference toFIGS. 1 to 4,7,10, and11.

As shown inFIG. 1, the expelling joint11has an expelling valve6. The expelling valve6is urged by a spring6ain a direction in which the expelling hole12B in the pressurizing chamber12is closed. The expelling valve6is a so-called non-return valve that limits a direction in which fuel flows.

An intake valve mechanism200A is unitized as an assembly comprising a solenoid200, a plunger rod201, a spring202, and a flat valve, the intake valve203being attached to the assembly. The intake valve203inserted from the hole10G through the intake channel10ainto the fuel take12A of the pressurizing chamber12. The solenoid200blocks the hole10G and the intake valve mechanism is fixed to the pump body1.

When the solenoid200is turned off, the plunger rod201is urged by the spring202in a direction in which a flat valve of the intake valve203closes the fuel intake12A. Accordingly, when the solenoid200is turned off, the plunger rod201and intake valve203are in a closed state, as shown inFIG. 1.

As shown inFIG. 2, fuel is supplied under a low pressure by a low-pressure pump51, from a fuel tank50to the intake joint10of the pump body1. In this case, the fuel is regulated to a fixed pressure by a pressure regulator52operating at a low pressure. The fuel is then pressurized by the pump body1and the pressurized fuel is delivered from the expelling joint11to a common rail53.

The common rail53includes injectors54and a pressure sensor56. The number of injectors54included is equal to the number of cylinders of the engine. Each injector54injects 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 rail53exceeds a prescribed value, a relief valve15in the pump body1opens and part of the high-pressure fuel is returned through a relief channel15A to an opening10fopen to the damper housing part120A, thereby preventing the high-pressure piping from being damaged.

A lifter3, which is disposed at the bottom of the plunger2, is placed in contact with a cam7by means of a spring4. The plunger2is slidably held in the cylinder20, and reciprocates when the cam7is rotated an engine cam shaft or the like, changing the volume of the pressurizing chamber12.

As shown inFIG. 1, the cylinder20is held by a cylinder holder21on its outer surface. When threads20A formed on the outer surface of the cylinder holder21are screwed into threads1B formed on the pump body1, the cylinder holder21is fixed to the pump body1.

In this embodiment, the cylinder20just slidably holds the plunger2, 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 solenoid200of the intake valve mechanism200A is turned off during a compressing process of the plunger2and then the plunger rod201moves to the left side inFIG. 1due to the force by the spring202and the fuel pressure in the pressurizing chamber12, the intake valve203closes the fuel intake12A of the fuel pressurizing chamber12. The pressure in the pressurizing chamber12then starts to rise. In response to this, the expelling valve6automatically opens and the pressurized fuel is delivered to the common rail53.

When the pressure in the fuel pressurizing chamber12falls below the pressure in the intake joint10or low-pressure fuel channel10a, the plunger rod201in the intake valve mechanism200A opens the intake valve203. When to open the intake valve203is set according to the force by the spring202, a difference in fluid pressure between the front and back of the intake valve203, and the electromagnetic force of the solenoid200.

With the solenoid200turned on, an electromagnetic force greater than the force of the spring202is generated, so the plunger rod201opposes the force of the spring202and is pushed to the right side in the drawing. The intake valve203is then separated from the seat, opening the intake valve203.

With the solenoid200turned off, the plunger rod201engages the seat due to the force of the spring202, keeping the intake valve203closed.

The solenoid200is kept turned on and fuel is supplied to the pressurizing chamber12while the plunger2is in an intake process (it moves downward in the drawing). The solenoid200is turned off at an appropriate point in time in a compression process (it moves upward in the drawing) and the intake valve203is moved to the left side in the drawing to close the fuel intake12A, causing the fuel remaining in the pressurizing chamber12to be delivered to the common rail53.

When the solenoid200is kept turned on in the compression process, the pressure in the pressurizing chamber12is kept to a low level almost equal to the pressures in the intake joint10or low-pressure fuel channel10a, preventing the expelling valve6from being opened. Fuel is returned to the low-pressure fuel channel10aby the amount by which the volume of the pressurizing chamber12is reduced.

Accordingly, if the solenoid200is turned back off in the middle of the compression process, fuel is then delivered to the common rail53, so the amount of fuel expelled by the pump can be controlled.

While the plunger2is reciprocating, three processes, that is, intake from the intake joint10to the pressurizing chamber12, expelling from the pressurizing chamber12to the common rail53, and return from the pressurizing chamber12to 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 toFIGS. 3 and 4.FIG. 3is an enlarged view of the mechanism, andFIG. 4is a perspective view of a holding mechanism of a damper for reducing fuel pressure pulsation.

A two-metal-diaphragm damper80is formed by welding the outer edges80dof two diaphragms80aand80b; an internal spacing80cincludes a sealed gas. Since the two-metal-diaphragm damper80changes 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 diaphragms80aand80bis a thin disk having a bulge at its center. Their dents are made to face each other, and the two diaphragms80aand80bare concentrically matched. A gas is included in the sealed spacing80cformed between the two diaphragms80aand80b. A plurality of concentric pleats is formed on the diaphragms80aand80bso that they can be elastically deformed with ease in response to a change in pressure; their cross sections are wavy. The two diaphragms80aand80beach have a flat part80ealong the outer periphery of the bulge on which the pleats are formed. The outer edges80dof the two matched diaphragms80aand80bare joined by being welded over their entire peripheries. Due to the welding, the gas in the sealed spacing80cdoes not leak.

The pressure of the gas in the sealed spacing80cis 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 diaphragms80aand80bare made of precipitation hardened stainless steel, which is superior in corrosion in fuel and strength. The two-metal-diaphragm damper80is included in the damper housing part120A disposed between the intake joint10and low-pressure fuel channel10a, as the mechanism for reducing the fuel pressure pulsation.

The two-metal-diaphragm damper80is held between the damper holder30held on the pump body1and the damper cover40forming the damper housing part120A.

Although the entire cross section of the damper holder30is a cup-shaped cross section, it has cutouts30eformed by cutting part of the damper holder30in 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 holder30, peripheral walls30cand30derect on areas, which have a diameter larger than the bulge on which concentric pleats are formed on the metal diaphragm damper80. Curled parts30fand30gare respectively formed on the upper ends of the peripheral walls30cand30d. The curled parts30fand30gtouch the flat part of the lower ring-shaped flat part80eformed along the outer periphery of the metal diaphragm dampers80, supporting the metal diaphragm damper80and radially positioning it.

A downward protrusion30eis formed at the center of the damper holder30. When the downward protrusion30eis inserted into the inner peripheral part of a ring-shaped extrusion1aformed on the wall10D of the pump body1, the damper holder30is radially positioned with respect to the pump body1.

A plurality of inner convex curved parts40ais formed on the inner surface of a damper cover40. The inner convex curved parts40ais corresponding to the inner convex curved part130shown inFIG. 12. The vertexes of the plurality of inner convex curved parts40aare formed at intervals on a circumference positioned inside the outer diameter of the metal diaphragm damper80, so that the vertexes are positioned on the ring-shaped flat parts80eof the metal diaphragm damper80. When the damper cover40is joined to the pump body1, the metal diaphragm damper80is also held between the pump body1and the curled parts30fand30gof the damper holder30. As in the embodiment inFIG. 12, the end of the inner convex curved part40ais flattened as shown inFIG. 7to form a flat part40f, providing the same effect as illustrated inFIG. 12.

An outer convex curved part40B is formed between two adjacent inner convex curved parts40a. The outer convex curved parts40B is corresponding to the outer convex curved part131shown inFIG. 12. The outer convex curved part40B functions as a fuel channel through which the inside and outside of the two-metal-diaphragm damper80communicate with each other, and thereby can provide a dynamic pressure in the same low-pressure fuel channel to the outer peripheries of the metal diaphragms80aand80b, improving the pulsation elimination function of the damper.

The inner convex curved part40aand outer convex curved part40B on the damper cover40are formed by pressing, so their costs can be reduced. A ring-shaped skirt40bof the damper cover40is disposed so that its inner periphery faces the outer periphery of a ring-shaped frame1F protruding up to the outer surface of the pump body1(the outer surface of the isolating wall1A of the pressurizing chamber12corresponding to the end of the plunger2). In this state, the entire outer periphery of the skirt40bof the damper cover40is welded. Accordingly, the damper cover40can be fixed to the pump body1and hermetic seal in the internal damper housing part120A can also be obtained.

The damper cover40is formed by pressing a rolled steel, so its thickness is uniform over all parts including the skirt40b, inner convex curved parts40a, outer convex curved parts40B, and discal dent45. The stiffness of the cover depends on the area; it is lowest at the discal dent45, and becomes higher little by little at skirt40band outer convex curved part40B in that order. The stiffness around the end of the inner convex curved part40ais highest. The force to hold the ring-shaped flat parts80eof the metal diaphragm damper80can thereby be accepted.

The skirt40bis press-fitted along the periphery of the frame1F, causing a tight contact between the inner peripheral surface of the skirt40bof the damper cover40and the outer peripheral surface of the frame1F, after which their peripheries are welded at Z1. Due to thermal distortion generated during the welding, the damper cover40is displaced in a direction in which it presses the ring-shaped flat parts80edisposed around the outer periphery of the metal diaphragm damper80against the damper holder30, 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 parts40X, each of which has a larger curvature than the outer convex curved parts40B, is formed toward the skirt40bof the inner convex curved part40a, and a plurality of outer convex curved parts40Y, each of which has approximately the same curvature as the outer convex curved parts40B, is formed toward the discal dent45in the inner convex curved part40a. 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 dent45and skirt40b. The outer convex curved part40B has intermediate stiffness and elasticity.

Accordingly, the ring-shaped flat parts80eon the outer periphery of the two-metal-diaphragm damper80are held between the flat part40fat the end of the inner convex curved part40aon the damper cover40and the curled parts30fand30gof the damper holder30. Since the force to hold the metal diaphragm damper80does not act on the outer peripheral edge80d, it can be possible to prevent the two-metal-diaphragm damper80from being damaged due to concentrated stress.

Due to the holding force, the damper cover40causes a tight contact between the damper holder30and metal diaphragm damper80. The lower edge of the skirt40bof the damper cover40is placed in contact with the pump body1while the damper cover40is pressed against the pump body1. The entire periphery of the skirt40bof the damper cover40is then welded at Z1to fix it. Thermal shrinkage caused by the welding further causes distortion in a direction in which the inner convex curved parts40aon the damper cover40are always pressed against the pump body1, making the holding force after the welding stable.

Accordingly, the metal diaphragm damper80can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper80, so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper80in 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 holder30to have distortion to a certain level in advance during a process of assembling. In this case, the metal diaphragm damper80is supported by the cup-shaped outer periphery and fixed to the pump body1by means of the ring-shaped protrusion30eformed 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 damper80because of pressure pulsation of the fuel.

When the number of inner convex curved parts40aon the damper cover40and their width are determined according to the shape of the touched part of the damper holder30, the ring-shaped flat parts80eon the outer periphery of the two-metal-diaphragm damper80can be held in a well-balanced state.

Fuel chambers10cand10dused as the damper housing part120A, in which the metal diaphragm damper80is accommodated, communicate with the low-pressure fuel channel10a, which leads to the inlet of the pressurizing chamber12.

Accordingly, the fuel can also flow freely into and out of the fuel chamber10cthrough the low-pressure fuel channel10bformed by the outer convex curved part40B on the damper cover40, enabling the fuel to be supplied to both surfaces of the two-metal-diaphragm damper80. 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 toFIGS. 5 and 6.

The ring-shaped flat parts80eon the outer periphery of the two-metal-diaphragm damper80are held between the damper holder30and the inner convex curved parts40aon the damper cover40, as in the fourth embodiment.

The damper cover40internally has a plurality of inner convex curved parts40a, as described above. The lower peripheral ring-shaped flat part80eof the metal diaphragm damper80is supported by the vertexes of the inner convex curved parts40a.

The damper holder30includes a cylindrical metal member30F having stiffness, which is formed separately from the pump body1. A curved surface30f, which is curved toward the inner diameter, is formed on the upper surface of the cylindrical metal member30F. The metal diaphragm damper80is set so that the lower surface of the ring-shaped flat parts80eon the outer periphery of the metal diaphragm damper80touches the curved surface30f. The ring-shaped flat parts80eon the outer periphery of the metal diaphragm damper80are held between the damper holder30and the inner convex curved parts40aon the damper cover40placed from above.

The inner diameter of the curved surface30fat the upper end of the damper holder30is a little larger than the diameter of the bulge of the metal diaphragm damper80. The bulge on which pleats of the metal diaphragm damper80are formed fits to the inside of the cylindrical metal member30F, radially positioning the metal diaphragm damper80.

Several cutouts30aare formed on the outer cylindrical part30cof the damper holder30so as to obtain fuel channels. The fuel flows into and out of the fuel chamber10dthrough the cutouts30a. The fuel also flows into and out of the fuel chamber10cthrough a low-pressure fuel channel10bformed by the outer convex curved parts40B formed on the damper cover40. As a result, the fuel can be delivered to both sides of the two-metal-diaphragm damper80, effectively eliminating the fuel pressure pulsation.

The damper holder30is radially positioned by the outer cylindrical part30cattached along the frame1F, which forms the damper housing part120A of the pump body1.

In this embodiment, the axial positioning of the damper cover40is determined by managing a dimension from the lower end of the cylindrical metal member30F to its upper end. For this reason, the dimension of the skirt40bof the damper cover40is determined so that the lower surface of the skirt40bdoes not touch the pump body1.

As described above, the two-metal-diaphragm damper80is held by the front and back of the peripheral ring-shaped flat parts80e, and the outer peripheral edge80dis not held, so there is no risk that the two-metal-diaphragm damper80is damaged due to concentrated stress.

The lower side of the two-metal-diaphragm damper80fits to the entire periphery of the damper holder30, so it can be freely set to the positions at which the inner convex curved parts40aare formed on the damper cover40disposed at the opposite position.

The damper holder30is formed by pressing, so its cost can be reduced.

Due to the holding force, the damper cover40causes a tight contact between the damper holder30and metal diaphragm damper80, as described above. The entire periphery of the skirt40bis then welded at Z1to the pump body1to fix the skirt40bwhile the damper cover40is pressed against the pump body1. Thermal shrinkage caused by the welding further causes distortion by which the inner convex curved parts40aon the damper cover40are always deformed toward the pump body1. Accordingly, there is no risk that the holding force is weakened after the welding and thereby the metal diaphragm damper80becomes unstable.

Accordingly the metal diaphragm damper80can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper80, so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper80in 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 toFIGS. 8 and 9.

As shown inFIGS. 8 and 9, the two-metal-diaphragm damper80is structured so that the peripheral ring-shaped flat parts80eare held between the inner convex curved parts40aon the damper cover40and the upper ends of a plurality of arc-shaped protrusions1cintegrally formed on the pump body1.

The damper cover40internally has a plurality of inner convex curved parts40a, as described above. The upper peripheral ring-shaped flat parts80eof the metal diaphragm damper80are supported by the vertexes of the inner convex curved parts40a. The low-pressure fuel channel10acommunicates with the fuel chamber10cthrough the low-pressure fuel channel10b, which is formed by the outer convex curved part40B formed between the inner convex curved part40aon the inner surface of the metal diaphragm damper80and the inner convex curved part40a.

The pump body1is made of cast metal, and integrally has a plurality of arch-shaped protrusions1cin the damper housing part120A. The protrusions1c, which are formed along a diameter a little greater than the pleat of the metal diaphragm damper80, protrude from the outer surface10D of the pump body1at positions opposite to the inner convex curved parts40aon the damper cover40. The ends of the protrusions1csupport the lower peripheral ring-shaped flat part80eof the metal diaphragm damper80, and radially position the metal diaphragm damper80. Since the dumper holders1care integrated with the pump body1in this way, the number of parts can be reduced.

In this embodiment as well, the outer peripheral edge80dof the two-metal-diaphragm damper80is not held, so there is no risk that the two-metal-diaphragm damper80is damaged due to concentrated stress.

Cutouts1dare partially formed on the ring-shaped protrusion1con the pump body1, enabling the fuel chamber10cand low-pressure fuel channel10ato communicate with each other. As a result, the fuel can be delivered to both sides of the two-metal-diaphragm damper80, effectively eliminating the fuel pressure pulsation.

Due to the holding force, the damper cover40is placed in tight contact with the metal diaphragm damper80. The outer surface40bof the damper cover40is fixed to the pump body1by welding at Z1while the damper cover40is pressed against the pump body1. Thermal shrinkage caused by the welding further causes distortion in a direction in which the inner convex curved parts40aon the damper cover40are always pressed against the pump body1. Accordingly, there is no risk that the holding force of the two-metal-diaphragm damper80is weakened after the welding and thereby the metal diaphragm damper80becomes unstable.

Accordingly the metal diaphragm damper80can be reliably held with a small number of parts, and the pressure pulsation of fuel can be stably transmitted to the metal diaphragm damper80, so the pulsation can be stably eliminated. In addition, members for pressing the metal diaphragm damper80in 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 cover40, which is part of the damper chamber. The inner convex curved parts40aformed on the inner surface of the damper cover40, which extrude toward the pump body1, directly support the damper. The opposite pressing member is a cup-shaped damper holder30, a ring-shaped protrusion formed integrally with the pump body1, or a plurality of protrusions formed integrally with the pump body1with a predetermined spacing.

Accordingly, the two-metal-diaphragm damper80with two metal diaphragms80a,80bwelded on their peripheries can be fixed in a simple manner, and thereby these embodiments can provide a high-pressure fuel pump1with 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 part80eof the two-metal-diaphragm damper80is directly supported by a plurality of inner convex curved parts40aformed on the inner surface of the damper cover40to reduce the number of parts. In addition, outer convex curved parts40B, which are formed among the plurality of inner convex curved parts40a, can be used as fuel channels, so a structure for delivering fuel to both sides of the two-metal-diaphragm damper80can be formed with less parts and by simple machining.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.