JP2000335401A - Booster device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower an operation starting input by lowering a spring setting load compared with a conventional common booster device. SOLUTION: A valve plunger 16 consists of a plurality of members 45 to 48. An annular space 49 is formed between an inner circumference of a cylindrical member 48 and an outer circumference of a rod member 45, therein disposing a closing member 44. The closing member 44 is connected to a valve body 6 through a connecting member 21. The closing member 44 can slide airtightly with respect to the valve plunger 16. The closing member 44 is capable of reducing an area than conventional in which a differential pressure acts on a valve element 19 under an inoperative condition of a tandem brake booster device 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a booster used for a brake or the like of an automobile, and more particularly to an improvement of a valve mechanism thereof.

[0002]

2. Description of the Related Art Conventionally, a cylindrical valve body slidably provided in a shell, a power piston provided in the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston, An annular vacuum valve seat formed on the inner periphery of the body, a valve plunger slidably fitted to the valve body, an annular atmospheric valve seat provided on the valve plunger, and an annular air valve seat provided on the valve body. A valve body seated on the vacuum valve seat and the atmospheric valve seat by the resilient force of the first spring, an input shaft having one end connected to the valve plunger and the other end connected to the brake pedal, A booster with a second spring positioned in the operating position is known. A booster disclosed in, for example, Japanese Patent Application Laid-Open No. H08-113137 is known as a booster in which the operation start input is reduced by improving the above-mentioned valve element and both valve seats. In the booster disclosed in the above publication, the vacuum valve seat and the atmospheric valve seat are provided apart from each other in the axial direction, and the diameters of the vacuum valve seat and the atmospheric valve seat are set to substantially the same size. . As a result, the set load of the second spring can be reduced,
The operation start input of the booster can be reduced.

[0003]

However, the conventional booster disclosed in the above-mentioned publication can reduce the operation start input, but on the other hand, the axial dimension of the valve body becomes longer, and the shaft of the valve body is eventually increased. There is a disadvantage that the directional dimension is long.

[0004]

[Means for Solving the Problems] In view of such circumstances,
The present invention provides a cylindrical valve body slidably provided in a shell, a power piston provided in the valve body,
A constant-pressure chamber and a variable-pressure chamber formed before and after the power piston, an annular vacuum valve seat formed on an inner peripheral portion of the valve body, a valve plunger slidably fitted to the valve body, and a valve plunger; An air valve seat provided in the valve body, a valve body provided in the valve body and seated on the vacuum valve seat and the air valve seat by a resilient force of a first spring, and one end connected to the valve plunger. In a booster provided with an input shaft having the other end connected to a brake pedal and a second spring for positioning the input shaft at a non-operating position, the booster device includes a ring arranged radially inward of the atmospheric valve seat of the valve plunger. Is formed, and an annular closing member is slidably provided in the space while maintaining airtightness, and the closing member is connected to the inner peripheral portion of the valve body via a connecting member.

[0005]

According to such a configuration, when the booster is not operated, the valve body is seated on the atmospheric valve seat, so that the valve body has a negative pressure on the front side and an atmospheric pressure on the rear side. When the booster is not operated, the differential pressure between the negative pressure acting on the inner side of the atmospheric valve seat and the atmospheric pressure is applied to the closing member. Will work.
Here, since the closing member is connected to the valve body by the connecting member, the valve body is moved forward in a non-operating state as compared with a conventional general booster by an amount corresponding to the differential pressure acting on the closing member. The biasing force for biasing to the side becomes small. Therefore, the set load of the second spring for positioning the input shaft connected to the valve plunger at the non-operation position can be made smaller than before. Accordingly, it is possible to suppress the valve body and the valve body from becoming longer in the axial direction, thereby reducing the operation start input of the booster and, at the same time, reducing the change in the operation start input due to the negative pressure fluctuation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, the inside of a shell 2 of a tandem brake booster 1 is divided into a front chamber 4 on the front side and a rear chamber 5 on the rear side by a center plate 3. It is partitioned. The substantially cylindrical valve body 6 is connected to the rear opening 2 of the shell 2.
A and the inner peripheral portion of the center plate 3 are slidably penetrated by sealing members 7 and 8 while maintaining airtightness. A front power piston 9 and a rear power piston 11 are connected to the outer periphery of the valve body 6 located in the front chamber 4 and the rear chamber 5, respectively. The diaphragm 12 and the rear diaphragm 13 are stretched. Thereby, the front diaphragm 12 in the front room 4 is
A constant-pressure chamber A and a variable-pressure chamber B are formed before and after, and a constant-pressure chamber C and a variable-pressure chamber D are formed before and after the rear diaphragm 13 in the rear chamber 5. In the valve body 6, a valve mechanism 14 for switching a communication state between the constant pressure chambers A and C and the variable pressure chambers B and D is provided. The valve mechanism 14 includes an annular vacuum valve seat 15 formed on the inner peripheral surface of the valve body 6, a valve plunger 16 slidably provided on the valve body 6, and an annular atmospheric valve seat formed on the valve plunger 16. 1, and a valve body 19 which is seated on both valve seats 15, 17 from the right side in FIG.

The valve body 19 is formed in a substantially cylindrical shape, and a base 19a, which is a rear end portion, is formed on the inner peripheral portion of the valve body 6 by a substantially cylindrical connecting member 21 and an annular retainer 22. It is fixed. A vacuum valve 23 is constituted by the vacuum valve seat 15 and a seat portion of a valve body 19 which comes into contact with and separated from the vacuum valve seat 15. A space outside the vacuum valve 23 is formed by a first constant pressure passage 24 formed in the valve body 6. The inside of the constant-pressure chamber A communicates with the constant-pressure chamber C via the second constant-pressure passage 25. Since the inside of the constant pressure chamber A communicates with the negative pressure source via the negative pressure introducing pipe 26, the constant pressure chambers A and C
Negative pressure is always introduced inside. An atmosphere valve 27 is constituted by the atmosphere valve seat 17 and a seat portion of the valve body 19 which comes into contact with / separates from the atmosphere valve seat 17. A space between the atmosphere valve 27 and the vacuum valve 23 is a space formed in the valve body 6. The first pressure passage 28 communicates with the variable pressure chamber D. The variable pressure chamber D is provided with a second variable pressure passage 3 formed in the valve body 6.
1 is always in communication with the transformer chamber B. Atmospheric valve 2
The space inside the portion 7 is communicated with the atmosphere through an atmosphere passage 32 formed by the inner peripheral portion of the valve body 6, and a filter 33 is provided in the atmosphere passage 32. The distal end of an input shaft 34 is pivotally connected to the valve plunger 16, and the distal end of the input shaft 34 is connected to a brake pedal (not shown). The input shaft 34 is urged to the rear side by a resilient force of a spring 36 mounted between the annular retainer 35 fitted on the step portion and the connecting member 21 to stop at the inoperative position in the drawing. I have.

The first variable pressure passage 28 in the valve body 6
In the area on the front side, the radial insertion holes 6
A is formed. The key member 37 is inserted through the insertion hole 6A and is engaged with the valve plunger 16, thereby preventing the valve plunger 16 from dropping from the valve body 6 to the rear side. In the non-operating state shown in FIG. 1, the key member 37 and the valve plunger 16 are held at the forward position with respect to the valve body 6 by bringing the key member 37 into contact with the rear wall surface of the shell 2. Thereby, the loss stroke of the input shaft 34 at the time of starting the operation of the tandem brake booster 1 is reduced. The plunger plate 3 is provided on the inner peripheral portion of the valve body 6 on the front side of the valve plunger 16.
8 is slidably fitted, and a reaction disk 41 is disposed on the front side of the plunger plate 38. The reaction disk 41 is housed in a recess 42 a on the rear side of the output shaft 42.
The left end of the output shaft 42 is slidably protruded from the front wall surface of the shell 2 to the outside, and is interlocked with a piston of a master cylinder (not shown). The valve body 6 is urged rearward by a return spring 43 and is normally located at a non-operating position in the drawing. When the tandem brake booster 1 is not operated, the key member 37 is in contact with the rear wall surface of the shell 2, and the valve body 6 and the valve plunger 16 are in contact with the key member 37. The seat portion of the valve body 19 is separated from the vacuum valve seat 15 and the vacuum valve 23 is opened, while the seat portion of the valve body 19 comfortably seats on the atmosphere valve seat 17 and the atmosphere valve 27 is closed. In this state, the front side (outside) of the valve body 19 has a negative pressure, and the rear side (inside side) of the valve body 19 has an atmospheric pressure. For this reason, the valve element 19 is urged toward the front side by the differential pressure before and after the valve element 19, but the differential pressure is larger than the urging force for urging the valve element 19 toward the front side. , The valve body 19 and the input shaft 34 are stopped at the non-operating position in the figure. The configuration described above is the same as that of a conventionally known tandem brake booster.

In this embodiment, the valve plunger 16
And the connecting member 21 is improved, and an annular closing member 44 is provided inside the valve plunger 16.
Thereby, the set load of the spring 36 is reduced. That is, as shown in an enlarged manner in FIG. 2, the valve plunger 16 of the present embodiment includes a stepped rod-shaped member 45 located on the shaft side and an annular fitting fitted to the outer periphery of the rod-shaped member 45 from the front side. A member 46, an arc-shaped locking member 47 fitted to the outer peripheral portion of the rod-shaped member 45 from the front side of the annular member 46 to prevent the annular member 46 from dropping off, and a front side attached to the outer peripheral portion of the annular member 46. And a cylindrical member 48 fitted with the inner peripheral portion of the cylindrical member. The rod-shaped member 45 has a small-diameter portion 45a on the front side and a middle-diameter portion 45b on the center side,
Further, the rear side has a large diameter portion 45c, and the small diameter portion 45a
And the middle diameter portion 45b penetrates the connecting member 21 and the closing member 44 from the rear side. An annular groove is formed at a predetermined position in the axial direction of the small diameter portion 45a, and an arc-shaped locking member 47 is engaged therewith. Thus, the annular member 46 is integrally fixed to the rear side of the small diameter portion. The annular member 46 and the locking member 47 are sequentially fitted to the small diameter portion 45a of the rod-shaped member 45 from the front side, and the small diameter portion 45a
The inner peripheral portion of the locking member 47 is engaged with the annular groove. Thus, the rod-shaped member 45, the annular member 46, and the locking member 47 are integrally connected. The outer peripheral portion on the front side of the annular member 46 is a small diameter portion, and the key member 37 is engaged with the small diameter portion. An axial hole 46a is formed in the large-diameter portion on the rear side of the annular member 46, so that the front and rear spaces of the annular member 46 can communicate with each other through the axial hole 46a. The rod-like member 4
The input shaft 34 is pivotally connected to a rear shaft portion of the large-diameter portion 45c.

The cylindrical member 48 has a large diameter portion 48 on the front side.
a, the rear side is defined as a small diameter portion 48b,
A radial portion extending inward in the radial direction is formed at an end on the rear side of b. This radial portion is referred to as the atmospheric valve seat 17. A caulking portion 48c extending toward the front side is formed at a plurality of circumferential locations at the front end of the large diameter portion 48a. After the rear side of the rod-shaped member 45 is inserted into the cylindrical member 48, a large-diameter portion 48a which is the front side of the cylindrical member 48 is fitted to the outer peripheral portion of the annular member 46 from the rear side, and then the swaged portion 48c Is bent in the radial direction to be in close contact with the end surface of the annular member 46. Thus, the members 45 to 48 constituting the valve plunger 16 are integrally connected, and the cylindrical member 48 is disposed between the annular member 46 and the atmospheric valve seat 17.
And the outer peripheral surface of the middle diameter portion 45a of the rod-shaped member 45, an annular space portion 49 is formed. The closing member 44 is arranged in the annular space 49. The closing member 44 includes a plate-shaped member 51 having rigidity, and an annular sealing member 52 that is in close contact with the rear end surface of the plate-shaped member 51. A cylindrical engaging projection 51a protruding toward the rear side in the axial direction is formed at an equidistant circumferential position on the rear end surface of the plate-like member 51. Through holes 52 at intervals
a. Both the inner peripheral portion and the outer peripheral portion of the seal member 52 at the rear edge are formed in a lip shape. Each of the engagement projections 51a of the plate-shaped member 51 is penetrated and engaged with each of the through holes 52a of the seal member 52, and the front end surface of the seal member 52 is
In close contact with the rear end surface. Thus, the plate member 51 and the seal member 52 are integrally connected.

The plate member 51 and the seal member 5
The inner peripheral portion of the valve plunger 16 is slidably penetrated the outer peripheral portion of the middle diameter portion 45b of the rod-shaped member 45 in the valve plunger 16, and the outer peripheral portions of the plate-like member 51 and the seal member 52 are cylindrical members 48 Is slidably fitted to the inner peripheral portion of the. The inner peripheral portion of the seal member 52 is a medium diameter portion 45.
b, the airtightness between them is maintained, and the outer peripheral portion of the seal member 52 is
, So that airtightness between them is maintained. The seal member 52 is in close contact with the rear end surface of the plate-shaped member 51 to maintain airtightness therebetween. Therefore, in the non-operating state shown in the drawing, the atmospheric pressure acts on the rear side of the closing member 44 while the closing member 4
4 to the front side of the closing member 44,
The negative pressure in the variable pressure chamber D acts through the insertion hole 6A of the valve body 6, the axial hole 46a of the annular member 46, and the like. In the present embodiment, the closing member 44 thus formed is connected to the valve body 6 via the connecting member 21. Therefore, when the valve plunger 16 is advanced and retracted in conjunction with the input shaft 34, the inner peripheral portion and the outer peripheral portion of the closing member 44 maintain airtightness between the cylindrical member 48 and the rod-shaped member 45 on the valve plunger 16 side. The valve is moved relative to the valve plunger 16 in the axial direction.

Next, the connecting member 21 is made of a stepped cylindrical metal having a small diameter on the front side. Connecting member 21
Is a small diameter portion 21a, and a rear portion is a large diameter portion 21b. A flange 21c is formed on the outer periphery of the front end of the small-diameter portion 21a, and the flange 2c is formed on the rear end of the large-diameter portion 21b.
1d. A support portion 21 that extends from the front end of the large-diameter portion 21b to the inner side thereof in the radial direction.
The supporting portion 21e is connected to the small diameter portion 21a by a tapered portion 21f. A plurality of through holes 21g are formed at predetermined positions of the tapered portion 21f of the connecting member 21 and a portion on the outer side of the radial direction portion. The passage 32 can communicate. On the other hand, the structure of the valve body 19 is the same as that of the conventional one, and the thick base 19a at the rear end thereof is fitted to the inner peripheral portion between the steps 6B and 6C of the valve body 6. ing. The large-diameter portion 21b of the connecting member 21e is connected to the valve body 19
Of the base member 19a and the support member 2
The first flange portion 21d is brought into contact with the base portion 19a of the valve body 19 and the end face of the step portion 6C from the rear side. Further, the annular retainer 22 is pressed into the inner peripheral portion of the valve body 6 and pressed against the flange portion 21d of the support member 21 from the rear side. In this manner, the base 19 of the valve body 19
a and the flange 21d of the support member 21 are connected to the position of the step 6C. The spring 31 is elastically mounted on the support portion 21 e of the connecting member 21 and the back surface of the seat portion of the valve element 19, and the spring is mounted on the support portion 21 e of the connecting member 21 and the retainer 35 on the input shaft 34 side. 36 are loaded.

The small-diameter portion 21a of the connecting member 21 is fitted with play to the outer peripheral portion of the middle-diameter portion 45b of the rod-shaped member 45, and the flange portion 21c is located inside the tubular member 48 and the closing member. 44 and the atmosphere valve seat 17. An engagement hole 21h is formed in the flange portion 21c of the connecting member 21 at a position in the circumferential direction at equal intervals. And these engagement holes 21
The front end side of the engaging projection 51a of the plate-shaped member 51 on the closing member 44 side is engaged with h so that they cannot be detached. Thereby, the closing member 44 is connected to the connecting member 21, and is connected to the valve body 6 via the connecting member 21. As described above, in the present embodiment, the valve plunger 16 is constituted by the plurality of members 45 to 48, and the closing member 44 is provided in the annular space 49 formed in the valve plunger 16. Valve mechanism 14, closing member 4
The configuration other than 4 and the connecting member 21 is the same as that of the conventional tandem brake booster.

In the above configuration, in the non-operating state, the seat portion of the valve body 19 is separated from the vacuum valve seat 15 so that the vacuum valve 23 is opened, while the seat portion of the valve body 19 is open to the atmosphere valve. Since the seat 17 is seated, the atmosphere valve 27 is closed. Therefore, negative pressure is introduced into the constant pressure chambers A and C and the variable pressure chambers B and D. In this non-operating state, the rear side (inward side) of the valve body 19 and the closing member 44
, A negative pressure acts on the front side (outward side) of the valve element 19 and the front side of the closing member 44. Therefore, a differential pressure between the negative pressure and the atmospheric pressure acts on the valve element 19 and the closing member 44, and they are urged toward the front side. Since the closing member 44 is connected to the valve body 6 by the connecting member 21, in this non-operating state, the spring 36 causes the input shaft 34 and the valve plunger 16 to move more than the urging force due to the differential pressure acting on the valve body 19. Since the elasticity at the inoperative position is greater, the vacuum valve 23 is open and the atmosphere valve 27 is closed. Here, the effective diameter of the valve element 19 is Dv, the radial sectional area of the valve element 19 at the effective diameter Dv is Sv, and the diameter of the atmospheric valve seat 17 (atmospheric valve 27) is Dp. Atmospheric valve seat 17 at diameter Dp (atmospheric valve 2
The sectional area in the radial direction of 7) is defined as Sp. Further, the outside diameter of the middle diameter portion 45b of the rod-shaped member 45 constituting the valve plunger 16 is Do, the sectional area of the middle diameter portion 45b is So, the set load of the spring 36 is F, and the difference between the inside and outside of the valve body 19 is set. Pressure P
And In the non-operating state shown in the drawing, the relationship between the set load of the spring 36 and the differential pressure P between the inside and outside of the valve body 19 can be expressed as follows. F> P * (Sv-Sp + So) On the other hand, in the case of the valve mechanism of the conventional general booster without the closing member 44, the set load of the spring 36 and the differential pressure P between the inside and outside of the valve body 19 Is as follows. F> P * Sv

Next, when the brake pedal is depressed from the inoperative state, the input shaft 34 and the valve plunger 16 are depressed.
Is advanced, so that the seat portion of the valve body 19 is
And the vacuum valve 23 is closed, while the seat portion of the valve body 19 is separated from the atmospheric valve seat 17 and the atmospheric valve 27 is opened. Therefore, the atmosphere is introduced into the two transformation chambers B and D, and the valve body 6 is advanced by the pressure difference between the atmosphere in the two transformation chambers B and D and the negative pressure in the two constant pressure chambers A and C. That is, the tandem brake booster 1 is operated. Here, the input at the start of the operation of the tandem brake booster 1 is F1, and the reaction disc 41
Is assumed to be F2. Then, the input F1 at the start of the operation of the tandem brake booster 1 is input.
, The relationship between the set load F of the spring 36 and the differential pressure P between the inside and outside of the valve body 19 is as follows. F1 = P * (SV-SP + S0) On the other hand, in the valve mechanism of the conventional general booster, the relationship between the input F1 at the start of operation, the set load of the spring 36, and the differential pressure P between the inside and outside of the valve body 19 is obtained. Is as follows. F1 = P * SV Further, in the intermediate load state after the tandem brake booster 1 is operated, in this embodiment, the relationship between the input F1, the brake reaction force F2, and the load F of the spring 36 is as follows. Become. F1 = F2 + FP * Sp On the other hand, the configuration of the valve mechanism of the conventional general booster is as follows. F1 = F2 + FP * S0 In other words, according to the present embodiment, by providing the closing member 44, at the start of the operation, the air valve seat 17 (atmosphere valve 27) and the outer peripheral surface of the middle diameter portion 45b are in contact with each other. The urging force due to the differential pressure that urges the valve element 19 to the front side is smaller than that of the related art by an amount corresponding to the cross-sectional area of the space between them (substantially the cross-sectional area of the space 49). Therefore, according to the present embodiment, the set load of the spring 36 can be made smaller than that of a conventional general booster.

As described above, in the present embodiment, the annular space 49 of the valve plunger 16 is formed and the closing member 44 is provided therein, so that the set load of the spring 36 can be reduced. Therefore, the operation start input can be reduced as compared with a conventional booster including a general valve mechanism. Further, as compared with a conventional booster equipped with a general valve mechanism, the valve element 19 of the present embodiment can reduce the area receiving the differential pressure before and after the valve element 19, so that the atmospheric valve seat 17 is provided.
The diameter of the (atmospheric valve 27) can be increased. Therefore, it is possible to provide the tandem brake booster 1 having good responsiveness during operation. Further, when the negative pressure fluctuates and the negative pressure in the variable pressure chambers B and D increases, the urging force due to the differential pressure urging the valve element 19 to the front side increases. Since the area where the valve element receives the differential pressure is reduced, the fluctuation of the input can be reduced. Furthermore, in comparison with the booster disclosed in Japanese Patent Application Laid-Open No. H08-113137, in which the atmospheric valve 27 and the vacuum valve 23 are provided to be separated from each other in the axial direction, in the present embodiment, the shafts of the valve body 19 and the valve body 6 are different. Directional dimensions can be reduced. Further, in this embodiment, as compared with the valve mechanism of the booster disclosed in JP-A-8-113137, the number of parts is small, the configuration is simple, and the assemblability is good.

[0017]

As described above, according to the present invention, the set load of the second spring for positioning the input shaft at the non-operation position can be made smaller than before, and at the same time, the change in the operation start input due to the negative pressure fluctuation can be made smaller. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1;

[Explanation of symbols]

Reference Signs List 1 tandem brake booster 6 valve body 9 front power piston 11 rear power piston 15 vacuum valve seat 16 valve plunger 17 atmospheric valve seat 18 spring (first
Spring 19 Valve Element 21 Connecting Member 34 Input Shaft 36 Spring (Second)
Spring) 44 Closing member 45 Rod member 46 Annular member 48 Cylindrical member A, C Constant pressure chamber B, D Transformation chamber

Claims (3)

[Claims] 1. A cylindrical valve body slidably provided in a shell, a power piston provided in the valve body, a constant pressure chamber and a variable pressure chamber formed before and after the power piston. An annular vacuum valve seat formed on an inner peripheral portion, a valve plunger slidably fitted to the valve body, an annular atmospheric valve seat provided on the valve plunger, and a second air valve seat provided in the valve body. A valve body seated on the vacuum valve seat and the atmospheric valve seat by the resilience of one spring, an input shaft having one end connected to the valve plunger and the other end connected to the brake pedal, And a second spring positioned at a position closer to the valve plunger, wherein an annular space is formed radially inward of the atmospheric valve seat in the valve plunger, and an airtight seal is maintained in the space to form an annular space. Provided member slidably, booster, characterized in that coupled to the inner periphery of the valve body via a connecting member to the closure member. 2. The valve plunger according to claim 1, wherein said valve plunger is a rod-shaped member which is located on a shaft portion side and to which said input shaft is connected to a rear end, an annular member fitted to an outer peripheral portion of said rod-shaped member, A cylindrical member having a front-side inner peripheral portion fitted to the outer peripheral portion of the member and the above-described atmospheric valve seat formed on the rear side; and the annular space portion includes an inner peripheral portion of the cylindrical member and a rod-shaped member. The booster according to claim 1, wherein the booster is constituted by: 3. The closing member is made of a rigid body and has a plate-shaped member having a plurality of engaging protrusions on a rear end surface, and a through-hole through which the engaging protrusions of the plate-shaped member are inserted at a plurality of circumferential positions. An annular seal member having a hole and having an outer peripheral portion in close contact with the inner peripheral portion of the cylindrical member, and an inner peripheral portion in close contact with the outer peripheral portion of the rod-shaped member; A flange portion formed at the front end and having a plurality of engagement holes at predetermined positions in the circumferential direction, and a radially extending support portion formed at the rear side in the axial direction. An outer peripheral portion on the rear side of the connecting member is fixed to an inner peripheral portion of the valve body, and a flange portion of the connecting member is located inside the tubular member from the rear side of the closing member, and Engagement projection 51a of the annular member at
Is engaged with the engaging hole of the flange portion of the connecting member, thereby connecting to the inner peripheral portion of the closing member via the connecting member, and extending over the radial portion of the connecting member and the back surface of the seat portion of the valve body. 3. The apparatus according to claim 1, wherein the first spring is mounted on the connecting member, and the second spring is mounted on a radial portion of the connecting member and a retainer fitted on a stepped portion of the input shaft located on a rear side of the connecting member. A booster according to claim 1 or 2.