Patent Application
20210246860
The present invention relates to a structure for attaching a metal diaphragm damper for pulsation absorption that is used at a position where pulsation is generated in a high-pressure fuel pump and the like.
There is a high-pressure fuel pump for pumping fuel, which is supplied from a fuel tank, to an injector. The high-pressure fuel pump pressurizes and discharges fuel by the reciprocation of a plunger that is driven by the rotation of a cam shaft of an internal-combustion engine. Since pulsation is generated in a fuel chamber due to a change in the amount of fuel discharged to the injector from the high-pressure fuel pump or a change in the amount of fuel injected from the injector, a metal diaphragm damper for reducing pulsation generated in the fuel chamber is generally built in the high-pressure fuel pump.
For example, two disc-shaped diaphragms are welded to each other at the outer peripheral edge portions thereof, so that a hermetically sealed space filled with gas having a predetermined pressure is formed in a metal diaphragm damper disclosed in Patent Citation 1; and the metal diaphragm damper is provided in a fuel chamber. The fuel chamber is a space formed between a housing and a housing cover, and an annular attachment member is mounted on the inner peripheral surface of the fuel chamber by frictional engagement. The attachment member includes clip-shaped holders at a plurality of positions thereon in a circumferential direction and the outer peripheral edge portions of the diaphragms are held by the holders, so that the metal diaphragm damper is installed so as to partition the fuel chamber. Further, fuel can flow around to the spaces formed on both the surface side and back side of the metal diaphragm damper in the fuel chamber through a radial gap between the attachment member and the metal diaphragm damper.
Since the respective diaphragms of the metal diaphragm damper are elastically deformed by fuel pressure accompanied by pulsation, the volume of the fuel chamber can be changed and pulsation is reduced. For example, the metal diaphragm damper is adapted to be capable of reducing pulsation while the outer peripheral edge portions of the diaphragms or the attachment member is deformed and both the diaphragms are integrally moved to the other side when the metal diaphragm damper receives pulsation accompanied by shock waves from one side thereof.
Patent Citation 1: JP 2014-190188 A (page 7, FIG. 2)
Since the metal diaphragm damper disclosed in Patent Citation 1 allow the elastic deformation of the respective diaphragms and the integrated movement of both the diaphragms, high pulsation reduction capability can be achieved. However, since the separate attachment member is used to hold the metal diaphragm damper, the number of parts is large and the structure is complicated. For this reason, assembly work and the like are inconvenient. Further, since the clip-shaped holders hold the diaphragms over the inner peripheral side from the outer peripheral edge portions that are welded portions of the diaphragms, the holders affect the deformation of deformable portions of the diaphragms closer to the inner peripheral side than the welded portions.
The present invention has been made in consideration of such problems, and an object of the present invention is to provide a structure for attaching a metal diaphragm damper that can fulfill an excellent pulsation-reducing function with a simple structure.
In order to solve the above-mentioned problem, a structure for attaching a metal diaphragm damper according to the present invention includes: a housing; a housing cover that cooperates with the housing to define a space between the housing and the housing cover; and a pair of diaphragms each formed in a disk shape, the pair of diaphragms having weld portions on an outer periphery side thereof, the weld portions being welded to each other in an annular shape to form the metal diaphragm damper of which inside is filled with gas, the metal diaphragm damper being attached to the housing and the housing cover so as to be disposed in the space between the housing and the housing cover, wherein the pair of diaphragms is provided with outer peripheral portions on the outer peripheral side of the welded portions, and the outer peripheral portions of the pair of diaphragms are held by the housing and the housing cover in a thickness direction of the pair of diaphragms. According to the aforesaid feature, since the outer peripheral portions of the diaphragms are directly held by the housing and the housing cover, a separate attachment member and the like do not need to be prepared. Further, when the metal diaphragm damper receives pulsation accompanied by shock waves from one side of the diaphragms, the outer peripheral portions are deformed so that the portions of the diaphragms closer to the inside than the welded portion are allowed to move to the other side. Accordingly, an excellent pulsation-reducing function can be achieved with a simple structure.
It may be preferable that the outer peripheral portions of the pair of diaphragms are formed to be opened in a direction where the outer peripheral portions are spaced apart from each other as going toward the outside in a radial direction. According to this preferable configuration, since elastic restoring forces act when the outer peripheral portions are held by the housing and the housing cover, the metal diaphragm damper can be reliably attached.
It may be preferable that the outer peripheral portions are provided with communication passages which allow both sides of the outer peripheral portions in a thickness direction thereof to communicate with each other. According to this preferable configuration, communication passages allowing fluid to flow around to the diaphragms provided on both the surface side and back side of the metal diaphragm damper can be easily formed.
It may be preferable that the communication passages are formed by cutouts of outer edges of the outer peripheral portions. According to this preferable configuration, the communication passages can be formed even though the outer peripheral portions are small.
It may be preferable that communication grooves are formed over the housing and the housing cover. According to this preferable configuration, communication passages of which the cross-sectional area of flow channels is large can be formed by the communication passages of the diaphragms and the communication grooves of the housing.
It may be preferable that the pair of diaphragms is provided with curved portions which are formed on an inner peripheral side of the weld portions so as to be spaced apart from each other as going toward a radially inward side from base end portions inwardly continuous with the welded portions, the base end portions being brought into contact with each other. According to this preferable configuration, it is possible to suppress the application of stress to the welded portion by concentrating stress on the base end portions of the curved portions.
It may be preferable that the outer peripheral portions of the pair of diaphragms are held by the housing and the housing cover in a state where the outer peripheral portions of the pair of diaphragms are spaced from each other. According to this preferable configuration, the metal diaphragm damper can be reliably attached by the elastic restoring forces of the outer peripheral portions regardless of the dimensional accuracy of the housing and the housing cover.
It may be preferable that the outer peripheral portions of the pair of diaphragms are held by the housing and the housing cover in a state where the outer peripheral portions of the pair of diaphragms are in contact with each other. According to this preferable configuration, the outer peripheral portions can be made to be deformed integrally.
Modes for implementing a metal diaphragm damper according to the present invention will be described below on the basis of embodiments.
A structure for attaching a metal diaphragm damper according to a first embodiment of the present invention will be described with reference to
As illustrated in
As a mechanism for pressurizing and discharging fuel in the high-pressure fuel pump 10, an intake stroke for opening an intake valve 13 and taking in fuel to a pressurizing chamber 14 from a fuel chamber 11 formed on a fuel inlet side, when the plunger 12 is moved down, is performed first. Then, an amount adjustment stroke for returning a part of the fuel of the pressurizing chamber 14 to the fuel chamber 11, when the plunger 12 is moved up, is performed, and a pressurization stroke for pressurizing fuel, when the plunger 12 is further moved up after the intake valve 13 is closed, is performed. As described above, the high-pressure fuel pump 10 repeats a cycle that includes the intake stroke, the amount adjustment stroke, and the pressurization stroke, to pressurize fuel, to open a discharge valve 15, and to discharge the fuel to the injector. In this case, pulsation in which high pressure and low pressure are repeated is generated in the fuel chamber 11 due to a change in the amount of fuel discharged to the injector from the high-pressure fuel pump 10 or a change in the amount of fuel injected from the injector.
The metal diaphragm damper 1 of the present embodiment is used to reduce such pulsation that is generated in the fuel chamber 11 of the high-pressure fuel pump 10 (i.e., a space between the housing and the housing cover). Meanwhile, the metal diaphragm damper 1 is disposed to partition the fuel chamber 11 of the high-pressure fuel pump 10 into an upper space and a lower space. The fuel chamber 11 is formed by a recessed portion 16a that is formed in a housing 16 of the high-pressure fuel pump 10 to be recessed down and a housing cover 17 that has a downward U-shaped cross-section and closes the recessed portion 16a. Outer peripheral portions 21 and 21, which are to be described later, of the metal diaphragm. damper 1 are held between the housing 16 and the housing cover 17.
As illustrated in
A tubular portion 17a to be externally fitted to the wall portion 16b is formed at the lower end portion of the housing cover 17. In a state where the tubular portion 17a is externally fitted to the wall portion 16b, the lower end face of the tubular portion 17a is in contact with the horizontal surface 16f of the stepped portion 16e and is positioned in a vertical direction.
Convex portions 17b and concave portions 17c are formed on the inner peripheral side of the tubular portion 17a. The convex portions 17b extend toward the convex portions 16c so as to face the convex portions 16c with a distance L1 (see
That is, in a state where the housing cover 17 is attached to the housing 16, a distance L2 (see
As illustrated in
In detail, a welded portion W (see particularly
A hermetically sealed space S3 formed between the diaphragms 2a and 2b joined to each other (that is, the interior space of the metal diaphragm damper 1 (see
As illustrated in
Particularly, as illustrated in
The deformable-action portion 23 is a portion that is formed in a dome shape and is to be elastically deformed by differential pressure between external pressure and the pressure of gas to be filled in the hermetically sealed space S3. Meanwhile, the shape of the deformable-action portion 23 may be the shape of a single continuous curved surface, or may be a shape including a plurality of curved surfaces, for example, the shape of a corrugated plate in cross-sectional view. That is, the shape of the deformable-action portion 23 may be freely changed.
As illustrated in
Specifically, in a state where the plate-like portions 21b and 21b, which are the outer peripheral portions 21 and 21, are not yet held between the convex portions 16c and 17b (see
As illustrated in
Further, the respective notches 21a communicate with the gaps S2 (i.e., communication grooves) formed between the concave portions 16d and 17c, and the gaps S2 are larger than the gaps S1 in the vertical direction. That is, since the respective notches 21a and the gaps S2 function as communication passages that allow one side and the other side of the metal diaphragm damper 1 to communicate with each other, the cross-sectional area of the flow channels of the communication passages can be increased. Furthermore, since the gaps S1 and S2 are continuous over the circumferential direction, the cross-sectional area of the flow channels of the communication passages can be increased in comparison with a case where the gaps S1 and S2 are discontinuous in the circumferential direction. Moreover, since the notches 21a are formed by notching of the outer edges of the outer peripheral portions 21 and 21, the communication passages can be formed even in a case where the widths of the outer peripheral portions 21 and 21 in the radial direction are small.
Next, an operation will be described. When fuel pressure accompanied by pulsation is changed to high pressure from low pressure and the diaphragms 2a and 2b substantially uniformly receive fuel pressure from the fuel chamber 11, the deformable-action portions 23 and 23 are deformed to be crushed toward the hermetically sealed space S3 as illustrated in
When the deformable-action portions 23 and 23 are crushed toward the hermetically sealed space S3, the diameters of the diaphragms 2a and 2b are increased outward in the radial direction. Since a gap is formed between the metal diaphragm damper 1 and the tubular portion 17a in the radial direction as described above, an increase in the diameters of the diaphragms 2a and 2b is allowed and the curved portions 22 and 22 provided closer to the inner peripheral side than the welded portion W are deformed. Particularly, since the curved portions 22 and 22 are deformed in a direction where the curved portions 22 and 22 approach each other, the first curved portions 22a and 22a are more strongly pushed against each other. Accordingly, stress is concentrated on the first curved portions 22a and 22a. Therefore, since it is difficult for high stress to be applied to the welded portion W, the breakage of the welded portion W is prevented.
Since the outer peripheral portions 21 and 21 closer to the outer peripheral side than the welded portion W are held by the housing 16 and the housing cover 17 as described above, the housing 16 and the housing cover 17 are not in contact with the deformable-action portions 23 and 23 disposed closer to the inner peripheral side than the welded portion W. Accordingly, the housing 16 and the housing cover 17 do not inhibit the elastic deformation of the deformable-action portions 23 and 23. That is, the housing 16 and the housing cover 17 can be adapted not to affect a pulsation-reducing function.
Further, since the outer peripheral portions 21 and 21 of the diaphragms 2a and 2b are directly held by the housing 16 and the housing cover 17, a separate attachment member and the like do not need to be prepared. Accordingly, the number of parts can be reduced. That is, in the structure for attaching the metal diaphragm damper 1 according to the present embodiment, an excellent pulsation-reducing function can be achieved with a simple structure. Further, since the housing 16 and the housing cover 17 having high strength hold the outer peripheral portions 21 and 21, the metal diaphragm damper 1 can be reliably held in comparison with a case where the metal diaphragm damper 1 is held by the separate attachment member.
Further, when the metal diaphragm damper 1 receives large pulsation accompanied by shock waves from one side (lower side) thereof as illustrated in
Specifically, when portions of the diaphragms 2a and 2b closer to the inside than the welded portion W receive a force, which is applied toward the upper side of the metal diaphragm damper 1, as a whole, the outer peripheral portion 21 of the diaphragm 2a and the outer peripheral portion 21 of the diaphragm 2b are elastically deformed or start to move rotationally from the gap S1 substantially at the same time. Since fuel is present on the upper side of the curved portion 22 and the deformable-action portion 23 of the diaphragm 2a, the curved portion 22 and the deformable-action portion 23 of the diaphragm 2a are slightly bent upward. On the other hand, the curved portion 22 and the deformable-action portion 23 of the diaphragm 2b are further pushed up and is deformed to be crushed toward the hermetically sealed space S3 (see
Since the welded portion W is provided closer to the inside than the outer peripheral portions 21 and 21 that are the fixed portions of the metal diaphragm damper 1 as described above, the portions of the diaphragms 2a and 2b closer to the inside than the welded portion W can be moved through the deformation of the outer peripheral portions 21 and 21. Accordingly, large pulsation accompanied by shock waves can be reduced.
Further, when the metal diaphragm damper 1 receives large pulsation accompanied by shock waves and is moved to the other side from one side, the outer peripheral portion 21 of the diaphragm 2a and the outer peripheral portion 21 of the diaphragm 2b are separately elastically deformed or move rotationally and the outer peripheral portion 21 of the diaphragm 2a and the outer peripheral portion 21 of the diaphragm 2b are subjected to different deformation. Accordingly, stress can be distributed to different positions on the outer peripheral portions 21 and 21, so that the breakage of the outer peripheral portions 21 and 21 can be suppressed.
Meanwhile, the portions of the diaphragms 2a and 2b closer to the inside than the welded portion W may be moved to the lower side from the upper side in some types of high-pressure fuel pump 10 to which the metal diaphragm damper 1 is applied.
Next, a structure for attaching a metal diaphragm damper according to a second embodiment will be described with reference to
Since a convex portions 16c′ of a housing 16 and a convex portions 17b′ of a housing cover 17 of the second embodiment are disposed close to each other in comparison with the first embodiment as illustrated in
As illustrated in
Meanwhile, the edge portions of the outer peripheral portions 21 and 21 close to the inner peripheral sides of the convex portions 16c′ and the convex portions 17b′ may be formed thin so that the edge portions are easily deformed, or may be formed thick so that the strength of the edge portion is increased.
Next, a structure for attaching a metal diaphragm damper according to a third embodiment will be described with reference to
As illustrated in
The embodiments of the present invention have been described above with reference to the drawings, but specific configuration is not limited to the embodiments. Even though modifications or additions are provided without departing from the scope of the present invention, the modifications or additions are included in the present invention.
For example, the diaphragms 2a and 2b have been joined to each other by laser welding in the description of the first to third embodiments, but are not limited thereto. As long as the hermetically sealed space S3 can be formed between the diaphragms 2a and 2b, the diaphragms 2a and 2b may be joined to each other by various types of welding, caulking, or the like.
Further, forms that include both the communication passages (the notches 21a or the through-holes 211b) of the metal diaphragm damper and the communication passages (the gaps S1 and S2) of the housing and the housing cover have been exemplified in the first to third embodiments, but at least any one of the metal diaphragm damper or the housing and the housing cover may be provided with the communication passages.
The first curved portions 22a and 22a have been in contact with each other over the circumferential direction in the first to third embodiments, but are not limited thereto. A plurality of protrusions may be provided in the circumferential direction on the base end portions (portions close to the welded portion W) of the curved portions, and the protrusions may be in contact with each other.
Further, a restriction member for restricting excessive elastic deformation of the diaphragms 2a and 2b (particularly, curved portions 22) may be disposed in the metal diaphragm damper 1. In this case, it is preferable that the restriction member has a shape allowing the appropriate volume change ratios of the diaphragms 2a and 2b. Furthermore, it is preferable that the restriction member is made of a material not allowing the breakage of the diaphragms 2a and 2b caused by the contact between the restriction member and the diaphragms when the diaphragms 2a and 2b are elastically deformed.
Moreover, the diaphragms 2a and 2b that include the curved portions 22 having an S-shaped cross-section and the dome-shaped deformable-action portions 23 have been described in the embodiments, but the shape of the diaphragm may be freely designed. For example, the diaphragm may have a shape that includes a deformable-action portion having a linear cross-section and a curved portion provided at the outer edge of the deformable-action portion and having a circular arc-shaped cross-section.
1 Metal diaphragm damper
2
a,
2
b Diaphragm
10 High-pressure fuel pump
11 Fuel chamber (space)
16 Housing
16
c,
16
c′ Convex portion
16
d Concave portion
17 Housing cover
17
b,
17
b′ Convex portion
17
c Concave portion
21 Outer peripheral portion
21
a Notch (communication passage)
22 Curved portion
22
a First curved portion (contact portion)
22
b Second curved portion
23 Deformable-action portion
S1, S2 Gap (communication passage, communication groove)
S3 Hermetically sealed space
W Welded portion
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-096188 | May 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/019616 | 5/17/2019 | WO | 00 |
