Patent Application
20200355150
The present invention relates to a metal diaphragm damper for absorbing pulsation, which is used in a location where pulsation occurs in a high-pressure fuel pump or the like.
Conventionally, at the time of driving an engine or the like, a high-pressure fuel pump is used to pump fuel supplied from a fuel tank toward an injector. The high-pressure fuel pump is configured to pressurize and discharge the fuel by reciprocating movement of a plunger driven by rotation of a camshaft of an internal combustion engine.
The conventional mechanism for pressurizing and discharging the fuel in the high-pressure fuel pump is as below. First, when the plunger moves downward, a suction process is performed in which a suction valve is opened to suck the fuel from a fuel chamber formed adjacent to a fuel inlet into a pressurizing chamber. Next, when the plunger moves upward, a volume adjustment process of returning a portion of the fuel in the pressurizing chamber to the fuel chamber is performed. Then, the suction valve is closed; thereafter, when the plunger moves further upward, a pressurizing process of pressurizing the fuel is performed. As just described, the high-pressure fuel pump repeats the cycle of the suction process, the volume adjustment process, and the pressurizing process and thus pressurizes the fuel to discharge the fuel toward the injector. At this time, pulsation is generated in the fuel chamber by a change in the discharge volume of the fuel discharged from the high-pressure fuel pump to the injector or a change in the injection volume of the injector.
A metal diaphragm damper configured to reduce pulsation occurring in the fuel chamber is internally disposed in such a high-pressure fuel pump. For example, as illustrated in
As illustrated in
Thus, the diaphragm described in Patent Citation 1 is designed such that the first curved portion 101 bulging out is disposed at the center of the meal diaphragm damper to secure a large elastic deformation allowance. Accordingly, when the first curved portion 101 is axially deformed by external pressure (e.g., fuel pressure), a radially outward end portion of the first curved portion 101 is deformed to radially outward expand. Then, the radially outward stress generated by the radially outward deformation of the first curved portion 101 acts on the second curved portion 102; therefore, the second curved portion 102 is deformed radially outward. Consequently, the stress acts on the diaphragm is dispersed.
Patent Citation 1: JP 2016-113922 A (page 5, FIG. 3)
Here, the metal diaphragm damper disclosed in the Patent Citation 1 is configured such that the first curved portion 101 at the radially inward side of the diaphragm has the large curvature radius and thus is easily deformed axially and such that the second curved portion 102 at the radially outward side is located adjacent to the outer circumferential fixation portion and has the small curvature radius and thus is not easily deformed axially compared with the first curved portion 101. In addition, the first curved portion 101 and the second curved portion 102 are formed in curved shapes protruding outward, and when being deformed axially, the first curved portion 101 is deformed to radially expand. Accordingly, when the first curved portion 101 is deformed radially outward under external pressure, stress may concentrate on a periphery P1 around a flexion point between the first curved portion 101 and the second curved portion 102 or a boundary periphery P2 between the second curved portion 102 and the outer circumferential fixation portion. Consequently, the diaphragm may be fractured by pulsation repeating high pressure and low pressure. Moreover, when the external force is large, the second curved portion 102 may be partially reversed (see
The present invention is thus made in view of such a problem, and an object of the present invention is to provide a metal diaphragm damper which is hard to fracture even when being applied with repeated stress.
To solve the foregoing problem, a metal diaphragm damper according to a first aspect of the present invention includes a diaphragm including: a deformable portion disposed in a center thereof; and an outer circumferential fixation portion formed by an outer circumferential rim of the diaphragm, the metal diaphragm damper being filled with gas inside and formed in a disk shape. The deformable portion includes: a third curved portion located at a radially outward side thereof and formed to be bulged out; a first curved portion located radially inward of the third curved portion and formed to be bulged out; and a second curved portion located between the first curved portion and the third curved portion. The second curved portion includes at least a curved wall part formed to be dented in.
According to the first aspect, the second curved portion includes the curved wall part formed to be dented in. Accordingly, the second curved portion is deformed inward of the diaphragm in accordance with deformation of the first curved portion under external pressure; therefore, stress acting inward of the diaphragm is applied to the radially inward side of the third curved portion by the deformation of the second curved portion to deform the third curved portion such that the curvature radius thereof is reduced. Consequently, the diaphragm absorbs radially outward stress generated by the deformation of the first curved portion. Thus, the stress is inhibited from concentrating on the third curved portion and the surroundings around a boundary between the third curved portion and the outer circumferential fixation portion. As a result, the metal diaphragm damper can be effectively prevented from being fractured. In addition, the stress to reduce the curvature radius acts on the third curved portion; therefore, the third curved portion is not easily reversed. As a result, the metal diaphragm damper can be effectively prevented from being fractured.
In a second aspect of the present invention, the second curved portion consists of the curved wall part.
According to the second aspect, a large region of variable volume can be secured in the center of the diaphragm.
In a third aspect of the present invention, the curved wall part of the second curved portion is formed so as to have a curvature radius smaller than a curvature radius of a curved wall part forming the third curved portion.
According to the third aspect, the third curved portion can be easily deformed radially outward, and the second curved portion having the curved wall part formed to be dented in can be prevented from being axially and largely deformed.
In a fourth aspect of the present invention, the diaphragm is connected to another diaphragm such that the metal diaphragm damper is constituted by a pair of diaphragms having an identical shape and reversely oriented to each other, and the outer circumferential rims of the diaphragms are fixed to each other so as to form the outer circumferential fixation portion.
According to the fourth aspect, the respective diaphragms can absorb pulsation, and thus the metal diaphragm damper can sufficiently secure pulsation absorption performance.
In a fifth aspect of the present invention, the second curved portion has a point defining a shortest distance from the curved wall part of the second curved portion to the outer circumferential fixation portion in an axial direction is larger than a maximum length of deformation of the first curved portion in the axial direction.
According to the fifth aspect, even when the first curved portions of the pair of diaphragms are respectively deformed to the maximum, the points of the second curved portions defining the shortest distances are not brought into contact with each other. Therefore, the pair of diaphragms may not be fractured.
In a sixth aspect of the present invention, a radially inward distance between the point of the second curved portion and another point of the second curved portion opposite to each other over the center of the diaphragm is larger than a radially outward distance from each of the points of the second curved portion to a radially outward end of the third curved portion.
According to the sixth aspect, the first curved portion functions as the region of variable volume and the third curved portion functions as a stress absorption region. Accordingly, the radial dimension of the first curved portion is set to be larger than that of the third curved portion, and thus the region of large variable volume can be secured.
Modes for carrying out a metal diaphragm damper according to the present invention will be described below based on embodiments.
A metal diaphragm damper according to an embodiment of the present invention will be described with reference to
As illustrated in
The mechanism for pressurizing and discharging the fuel in the high-pressure fuel pump 10 is as below. First, when the plunger 12 moves downward in
As just described, the high-pressure fuel pump 10 repeats the cycle of the suction process, the volume adjustment process, and the pressurizing process and thus pressurizes the fuel and opens a discharge valve 15 to discharge the fuel toward the injector. At this time, pulsation repeating high-pressure and low-pressure is generated in the fuel chamber 11 by a change in the discharge volume of the fuel discharged from the high-pressure fuel pump 10 to the injector or a change in the injection volume of the injector. The metal diaphragm damper 1 is used to reduce the pulsation occurring in the fuel chamber 11 of the high-pressure fuel pump 10 as just described.
As illustrated in
Gas made of argon and helium or the like at a predetermine pressure is filled in an enclosed space formed between the connected diaphragms 2 and 3 (i.e., inside the metal diaphragm damper 1). In addition, the metal diaphragm damper 1 adjusts a change in the volume by inner pressure of the gas filled in the enclosed space and thus can obtain a desired pulsation absorption performance.
The diaphragms 2, 3 are formed by pressing a metallic plate of the same material into the same dish shape, and thus the diaphragms 2, 3 have substantially the same shape and thickness, the thickness being entirely uniform. A deformable portion 19 is formed in the center of each of the diaphragms 2, 3, and a connection end portion 21 is formed by an outer circumferential rim of each of the diaphragms 2, 3. The connection end portion 21 of the diaphragm 2 and the connection end portion 21 of the diaphragm 3 are configured such that parallel portions thereof are entirely and circumferentially connected in an airtight manner by laser welding, thereby forming an outer circumferential fixation portion 20.
Herein, the diaphragms 2, 3 will be described in detail; however, in the descriptions related to the diagrams in
As illustrated in
The first curved portion 22, the second curved portion 23, and the third curved portion 24 are configured to have respective constant curvatures. The first curved portion 22 is formed to protrude toward the outer side of the diaphragm 2 (or toward the fuel chamber 11 in
In the present embodiment, as illustrated in
In addition, the first curved portion 22, the second curved portion 23, and the third curved portion 24 are connected via the connection portion 25 and the connection portion 26 that are formed in the aforementioned shapes, i.e., curved wall shapes but are not limited thereto. Alternatively, the first curved portion 22, the second curved portion 23, and the third curved portion 24 may be connected via linear or substantially S-shaped connection portions or may be directly connected with each other not via the connection portion 25 and the connection portion 26.
As illustrated in
Further, as illustrated in
As illustrated in
As illustrated in
Next, the pulsation absorption of the metal diaphragm damper 1 under the fuel pressure associated with pulsation repeating high-pressure and low-pressure will be described with
As illustrated in
Specifically, the first curved portion 22 is deformed axially (i.e., toward the inner side of the diaphragm 2) by the fuel pressure that is external pressure and, at the same time, is deformed to expand radially outward. In other words, the boundary (A) that corresponds to a radially outward end portion of the first curved portion 22 moves radially outward. Stress acting radially outward is applied by the radially outward movement of the boundary A to a portion of the diaphragm 2 located radially outward of the boundary A.
The third curved portion 24 is deformed by the stress acting radially outward so as to be compressed radially outward; therefore, the axial stress applied by external pressure to the first curved portion 22 is converted into the radially outward stress and the third curved portion 24 is deformed such that the curvature radius thereof is reduced. Consequently, the axial stress applied to the first curved portion 22 is absorbed, and thus the diaphragm 2 can be effectively prevented from being fractured.
Specifically, the radially outward stress applied to a portion of the diaphragm 2 located radially outward of the boundary A is transmitted along the outer or inner surface of the diaphragm 2. The second curved portion 23 is constituted by the curved wall part dented in; therefore, the stress also acts axially inward of the diaphragm 2 in such a manner as to, at the radially inward of a point T2 of the second curved portion 23, be guided via the connection portion 25 in accordance with the shape of the second curved portion 23, the point T2 defining the shortest distance from the second curved portion to the connection end portion in the axial direction. Accordingly, as illustrated in
As just described, the second curved portion 23 is deformed such that the point T2 moves axially inward of the diaphragm 2 and radially outward, and thus not only the radially outward stress but also the force pulling axially inward of the diaphragm 2 acts radially inward from the point T3 of the third curved portion 24 continuously formed via the connection portion 26 with the second curved portion 23. Therefore, as illustrated in
In addition, the stress acts on the third curved portion so as to reduce the curvature radius of the third curved portion 24; therefore, the third curved portion 24 is not easily reversed. As a result, the diaphragm 2 can be effectively prevented from being fractured.
Subsequently, the fuel pressure associated with pulsation shifts from high to low and thus the fuel pressure applied from the fuel chamber 11 to the diaphragm 2 decreases. At this time, the first curved portion 22 comes to protrude outward of the diaphragm 2 into the dome shape, and then the shape of the diaphragm 2 is restored. Additionally, in response to the restoring force of the first curved portion 22, the shapes of the second curved portion 23 and the third curved portion 24 are restored.
Moreover, the larger the curvature radius is, the more easily deformation occurs. Accordingly, the first curved portion 22 having the largest curvature radius is disposed in the center of the diaphragm 2, and thus a sufficient volume variable region (i.e., a large area of pulsation absorption) can be secured in the center of the diaphragm 2. Note that the radially inward distance between the points T2, opposite to each other over the center of the diaphragm 2, of the curved wall part of the second curved portion 23 is formed to be larger than the radially outward distance from each of the points T2 to a radially outward end portion (i.e., the boundary E) of the third curved portion 24. In other words, the region radially occupied by the first curved portion 22 is formed to be larger than the region radially occupied by the third curved portion 24. Thus, the first curved portion 22 functions as the volume variable region and the third curved portion 24 functions as a stress absorption region.
Accordingly, the radial dimension of the first curved portion 22 is designed to be larger than the radial dimension of the third curved portion 24; therefore, the large volume variable region can be secured. Additionally, since the first curved portion 22 is formed in a curved shape protruding outward, i.e., is formed to be bulged out, the first curved portion 22 is not easily reversed by external force.
Further, the diaphragm 2 includes from the radially inward side: the first curved portion 22 formed to be bulged out; the second curved portion 23 formed to be dented in; and the third curved portion 24 formed to be bulged out and thus is configured to be curved outward, inward, and outward. Accordingly, when the radially outward stress acts on the diaphragm 2 under external force, the diaphragm 2 deforms while keeping the shape curved outward, inward, and outward. As a result, portions of the diaphragms 2, which are respectively located between the first curved portion 22 and the second curved portion 23 and between the second curved portion 23 and the third curved portion 24 are not easily reversed.
Furthermore, as described above, the curvature radius R23 of the second curved portion 23 is formed to be smaller than the curvature radius R24 of the third curved portion 24; therefore, the third curved portion 24 can be easily deformed radially outward and the second curved portion 23 having the inward curved surface can be inhibited from being axially and largely deformed. Accordingly, the second curved portions 23 of the diaphragms 2, 3 located opposed to each other are prevented from being brought into contact with each other, and thus the diaphragms 2, 3 can be prevented from being fractured.
In addition, the diaphragm 2 is formed such that a distance H2 (see
Further, as illustrated in
Furthermore, as illustrated in
The deformable portion 19 is formed such that the area radially inward of the point T2 of the second curved portion 23 is larger than the area radially outward of the point T2 of the second curved portion 23; therefore, the large volume variable region of the diaphragm 2 can be secured.
As described above, the embodiment of the present invention is described with the drawings; however, the concrete structure is not limited to the embodiment. Even modifications or additions may be made to the present invention without departing from the scope of the present invention.
For example, in the foregoing embodiment, a case where the diaphragms 2, 3 are connected by laser welding is described, but not limited thereto. Alternatively, as long as the diaphragms 2, 3 can include an enclosed space therebetween, the diaphragms 2, 3 may be connected by a variety of welding methods such as swaging, friction stir welding, and the like.
Further, in the foregoing embodiment, the relationship between the curvature radii of the first curved portion 22, the second curved portion 23, and the third curved portion 24 is described in such a way that the curvature radius R22 of the first curved portion 22 is greater than the curvature radius R24 of the third curved portion 24 and the curvature radius R24 of the third curved portion 24 is greater than the curvature radius R23 of the second curved portion 23, but not limited thereto. Alternatively, for example, the first curved portion 22 and the third curved portion 24 may have the same curvature radius.
Furthermore, as long as the first curved portion 22 and the third curved portion 24 are formed to be bulged out and the second curved portion 23 is formed to be dented in, the radially outward stress can be converted into the force to bend the third curved portion 24 inward. Therefore, for example, the curvature radius of the second curved portion 23 may be greater than the curvature radius of the third curved portion 24.
Additionally, in the foregoing embodiment, the second curved portion 23 is formed by the curved wall part having the constant curvature radius to be dented in, but not limited thereto. Alternatively, the second curved portion 23 may be formed in a waved shape such that the waved shape includes, for example, two or more inward curved wall parts formed to be dented in and such that the inward curved wall part located at the most radially outward side is continuously formed with the third curved portion 24.
Further, in the foregoing embodiment, the first curved portion 22 is formed by the curved wall part having the constant curvature radius. Alternatively, the first curved portion 22 may be formed by, for example, two or more curved wall parts which is formed to bulged out and which has different curvature radii. Additionally, likewise, each of the second curved portion 23 and the third curved portion 24 may be formed similarly to the aforesaid modification of the first curved portion 22.
Further, the diaphragm 2 and the diaphragm 3 may not have the same shape.
Furthermore, in the foregoing embodiment, the metal diaphragm damper 1 including the diaphragm 2 and the diaphragm 3 connected to each other is configured such that the fuel pressure in the fuel chamber 11 is absorbed by both the diaphragm 2 and the diaphragm 3, but not limited thereto. Alternatively, for example, as illustrated in
Moreover, in the foregoing embodiment, the metal diaphragm damper 1 is provided in the fuel chamber 11 of the high-pressure fuel pump 10 and is configured to reduce pulsation in the fuel chamber 11, but not limited thereto. Alternatively, the metal diaphragm damper 1 is provided in a fuel pipe or the like connected to the high-pressure fuel pump 10 and thus may reduce pulsation.
Further, as long as airtightness and connection strength can be maintained, at least only the radially outermost parts of the connection end portions 21 of the diaphragm 2 and the diaphragm 3 may be connected to each other.
Furthermore, a core member made of an elastically deformable synthetic resin or the like may be disposed in the enclosed space formed between the diaphragm 2 and the diaphragm 3 connected to each other (i.e., inside of the metal diaphragm damper 1), and thus the diaphragm 2 and the diaphragm 3 may be prevented from being brought into contact with each other under high pressure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-225530 | Nov 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/042765 | 11/20/2018 | WO | 00 |
