JP4664529B2 - Reaction mechanism of brake booster - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake booster used for boosting a brake master cylinder of an automobile, and in particular, a reaction force piston connected to an input rod, and a part of a rear end surface on a front end surface of the reaction force piston. A reaction force mechanism for a brake booster, wherein the reaction force mechanism includes a resilient piston that receives the booster output over the entire front end surface, and transmits a part of the booster output to the reaction force piston via the resilient piston. Alternatively, the reaction force piston connected to the input rod, the elastic piston that makes a part of the rear end surface contact the front end surface of the reaction force piston, and the entire front end surface of the elastic piston are contacted in the contact direction. An output pressure receiving member that receives the booster output, and a part of the booster output received by the output pressure receiving member is transmitted to the reaction force piston via an elastic piston. It relates to an improvement of the reaction force mechanism of use booster.
[0002]
[Prior art]
In the brake booster, it is desired in terms of brake operation that the jumping characteristic (brake assist) of the booster output is enhanced as the input speed with respect to the input rod increases. Conventionally, as a means for making the jumper characteristic of the booster output variable as described above, an electric type and a mechanical type are known.
[0003]
[Problems to be solved by the invention]
By the way, in the electric type, the input speed to the input rod is detected by a sensor, and the auxiliary pump is operated based on the detection signal to generate the brake assist force, but the system itself is complicated, There are many components and it becomes very expensive. In the mechanical type, a device called “ADAM” manufactured by Continental Thebes is known, but this also has a complicated structure and is expensive. In addition, these conventional devices show a characteristic that the output rapidly increases when the input speed exceeds the threshold value, so that it is difficult to say that the operation feeling is good.
[0004]
The present invention was made in view of such circumstances, and with a simple and inexpensive structure, the jumper characteristic of the booster output (brake assist) can be increased substantially linearly as the input speed increases, It is an object of the present invention to provide a reaction force mechanism for the brake booster that can obtain a good operation feeling.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a reaction force piston connected to an input rod, a part of the rear end surface abutting against the front end surface of the reaction force piston, and a booster output on the entire front end surface. In the reaction force mechanism of a brake booster, comprising an elastic piston and transmitting a part of the booster output to the reaction force piston via the elastic piston, the reaction force piston is directed toward the elastic piston. While forming a taper convex portion having a small diameter, a taper concave portion corresponding to the taper convex portion is formed in the elastic piston, and the taper convex portion and the taper concave portion are fitted and brought into contact with each other, and the inner periphery of the taper concave portion is formed. A first feature is that a plurality of grooves extending in the generatrix direction of the inner peripheral surface are formed on the surface .
[0006]
According to the first feature, at the time of sudden braking in which the input rod is rapidly moved forward, the taper convex portion of the reaction force piston pushes and expands the taper concave portion of the elastic piston, and enters the elastic piston. A jumping characteristic (brake assist) that increases rapidly can be obtained, and the characteristic changes substantially linearly according to the input speed to the input rod, so that the braking operation feeling can be improved. In addition, this reaction force mechanism has a simple structure and can be provided at a low cost. Furthermore, since a plurality of grooves extending in the generatrix direction of the inner peripheral surface are formed on the inner peripheral surface of the tapered recess, the taper convex portion of the reaction force piston can easily enter the elastic piston, and the jumping characteristics can be improved. Can be encouraged.
[0007]
The present invention also includes a reaction force piston connected to the input rod, an elastic piston that makes a part of the rear end surface contact the front end surface of the reaction force piston, and the entire front end surface of the elastic piston. An output pressure receiving member that receives a booster output in the contact direction, and a part of the booster output received by the output pressure receiving member is transmitted to the reaction force piston via an elastic piston. And forming at least one of the reaction force piston and the output pressure receiving member a taper convex portion having a small diameter toward the elastic piston, and forming a taper concave portion corresponding to the taper convex portion on the elastic piston. tapered protrusions and the tapered recess for engagement with one another, brought into contact, said the inner peripheral surface of the tapered recess, the inner circumferential surface the second Japanese that groove was formed plural rows extending in the generatrix direction of the To.
[0008]
The output pressure receiving member corresponds to the output pressure receiving cylinder 21 in each embodiment of the present invention described later.
[0009]
According to the second feature, at the time of sudden braking in which the input rod is rapidly advanced, the taper convex portion of the reaction force piston or the output pressure receiving member pushes the taper concave portion of the elastic piston and enters the elastic piston. A jumping characteristic (brake assist) that increases the booster output rapidly can be obtained, and the characteristic changes substantially linearly according to the input speed to the input rod, so that the braking operation feeling can be improved. . In addition, this reaction force mechanism has a simple structure and can be provided at a low cost. Furthermore, since a plurality of grooves extending in the generatrix direction of the inner peripheral surface is formed on the inner peripheral surface of the tapered recess, it is easy to enter the reaction piston or the tapered convex portion of the output pressure receiving member into the elastic piston, The jumping characteristic can be promoted.
[0010]
Furthermore, in addition to the first or second feature, the third feature of the present invention is that the elastic piston is provided with an axial through hole that opens at the bottom of the tapered recess.
[0011]
According to the third feature, entry into the reaction piston or output pressure receiving member of the tapered protrusions in the elastic piston is facilitated, Ru can promote the jumping characteristics.
[0012]
[Embodiment]
Embodiments of the present invention will be described based on examples of the present invention shown in the accompanying drawings.
[0013]
1 is a longitudinal sectional view of a negative pressure booster for braking of an automobile according to a first embodiment of the present invention, FIG. 2 is an enlarged view of two parts of FIG. 1 (when not braking), and FIG. 3 is the same booster during sudden braking. FIG. 4 is a front view of the elastic piston in the reaction force mechanism of the booster, FIG. 5 is an input / output characteristic diagram of the booster, and FIG. 6 is a second embodiment of the present invention. It is a longitudinal cross-sectional view corresponding to FIG. 2 which shows an example.
[0014]
First, the description starts with the description of the first embodiment of the present invention. 1 and 2, a booster shell 1 of a negative pressure type booster B is composed of a pair of front and rear shell halves 1a and 1b that connect opposite ends to each other, and a rear shell half 1b is a front wall of a vehicle cabin. The cylinder body Ma of the brake master cylinder M operated by the booster B is fixed to the front shell half 1a by a bolt 9 and fixed to the F by a bolt 8.
[0015]
The booster shell 1 has a booster piston 4 accommodated therein so as to be capable of reciprocating back and forth, and a diaphragm 5 which is attached to the rear surface of the booster shell 1 and is sandwiched between the front and rear shell halves 1a and 1b. The front negative pressure chamber 2 and the rear working chamber 3 are partitioned. The negative pressure chamber 2 is connected to a negative pressure source V (for example, inside the intake manifold of the internal combustion engine) via a negative pressure introduction pipe 14.
[0016]
The booster piston 4 is formed in an annular shape from a steel plate, and a synthetic resin valve cylinder 10 is integrally connected to the central portion thereof. The valve cylinder 10 is slidably supported via a seal member 13 on a rear extension cylinder 12 formed at the center of the rear shell half 1b, and the backward limit of the booster piston 4 is raised on the rear surface of the diaphragm 5. The protrusion 5a is defined by contacting the rear wall of the booster shell 1.
[0017]
In the valve cylinder 10, an input rod 20 that is connected to the brake pedal P and can be advanced and retracted, and the working chamber 3 is moved to the atmosphere at the rear end portions of the negative pressure chamber 2 and the rear extension cylinder 12 according to the advancement and retraction of the input rod 20. A control valve 38 that switches to the introduction port 39 is provided.
[0018]
The control valve 38 includes a valve piston 18 connected to the front end of the input rod 20 via a ball joint 20a so as to be able to swing relatively. An annular atmosphere introduction valve seat 30 is formed at the rear end of the valve piston 18, and an annular negative pressure introduction valve seat 31 that concentrically surrounds the atmosphere introduction valve seat 30 with the first annular passage 32 interposed therebetween, A second annular passage 33 surrounding the negative pressure introducing valve seat 31 is formed in the valve cylinder 10. The first and second annular passages 32 and 33 communicate with the working chamber 3 and the negative pressure chamber 2 through first and second ports 29A and 29B formed in the valve cylinder 10, respectively. A valve body 34 that cooperates with both the valve seats 30 and 31 is attached to the valve cylinder 10.
[0019]
The valve body 34 has an annular valve portion 34a opposed to the atmospheric introduction valve seat 30 and the negative pressure introduction valve seat 31 so as to be seated at the front end, and an annular mounting bead portion 34b at the rear end, and both portions 34a, 34b. In the middle part, a diaphragm part 34c is connected to each other so as to be axially displaceable. The mounting bead part 34b is a cylindrical valve holder 35 fitted to the inner peripheral surface of the rear part of the valve cylinder 10. The front end is attached to the inner peripheral surface of the valve cylinder 10. And the valve spring 36 which urges | biases the valve part 34a to the seating direction with both the valve seats 30 and 31 is contracted between the valve part 34a and the input rod 20. FIG. Thus, the control valve 38 is configured.
[0020]
An output rod 25 disposed in the negative pressure chamber 2 coaxially with the input rod 20 is connected to the valve cylinder 10 and the valve piston 18 via the reaction force mechanism 24 of the present invention.
[0021]
As clearly shown in FIG. 2, the reaction force mechanism 24 includes a piston 15 formed at the front end of the valve piston 18 and a cup formed at the rear end of the output rod 25 and slidably fitted to the outer periphery of the piston 15. And a rubber disc-like elastic piston 22 filled in the reaction force chamber 19 defined between the piston 18 and the output pressure cylinder 21, and a front end of the valve piston 18. The reaction tube 17 is configured to include a reaction force piston 17 having a diameter smaller than that of the elastic piston 22 slidably penetrating the guide hole 16 of the valve cylinder 10 and contacting the rear end surface of the elastic piston 22. A front end portion of the reaction force piston 17 is formed in a taper convex portion 17a having a smaller diameter toward the front, and a taper concave portion 22a corresponding to this is formed in the rear end surface of the elastic piston 22, and the taper convex portion and the concave portion 17a, It arrange | positions so that 22a may mutually fit and contact | abut. The elastic piston 22 is formed with either or both of a through-hole 44 that opens at the bottom of the tapered recess 22a and a plurality of grooves 45 that extend in the generatrix direction of the inner peripheral surface of the tapered recess 22a.
[0022]
In FIG. 1 again, the output rod 25 is connected to the piston Mb of the brake master cylinder M. A retainer 26 is disposed in contact with the output pressure receiving cylinder 21 and the front end face of the valve cylinder 10, and a valve cylinder return spring 27 is contracted between the retainer 26 and the front wall of the booster shell 1.
[0023]
An inward flange 12a having an air introduction port 39 opened at the center is integrally formed at the rear end of the rear extension cylinder 12, and abutting the inner surface of the flange 12 defines the retreat limit of the input rod 20. The stopper plate 40 is fixed to the input rod 20 so as to be adjustable in the front-rear direction, and the input rod 20 is urged by the input return spring 41 supported by the valve holder 35 toward the retreat limit.
[0024]
An air filter 42 is attached to the inner periphery of the rear end of the valve cylinder 10, and the inner peripheral side of the atmosphere introduction valve seat 30 is always in communication with the atmosphere introduction port 39 through the air filter 42. The air filter 42 has flexibility so as not to hinder the forward / backward movement of the input rod 20 relative to the valve cylinder 10.
[0025]
Next, the operation of this embodiment will be described.
<When the negative pressure booster is stopped>
In the resting state of the negative pressure booster B, as shown in FIG. 1 and FIG. 2, the input rod 20 is positioned in the backward limit, and the control valve 38 moves the valve body 34 to the atmosphere introduction valve seat 30 and the negative pressure introduction valve seat 31. The operation chamber 3 is in a neutral state in which neither the negative pressure chamber 2 nor the air introduction port 39 is in communication, and the negative pressure chamber 2 is supplied to the negative pressure chamber 2 through the negative pressure introduction pipe 14 by such a control valve 38. The negative pressure of the negative pressure source is stored, and the working chamber 3 holds a negative pressure appropriately diluted with the atmosphere. In this way, a small forward force is given to the booster piston 4 by a slight difference in atmospheric pressure generated between the front negative pressure chamber 2 and the rear working chamber 3, and the forward force and the force of the valve barrel return spring 27 are increased. In balance, the booster piston 4 stops at a slight advance from the retreat limit.
<When braking>
If the brake pedal P is depressed to brake the vehicle and the atmosphere introduction valve seat 30 is advanced via the input rod 20 and the valve piston 18, the booster piston 4 is initially immobile. Immediately away from the body 34, the first port 29 </ b> A is communicated with the atmosphere inlet 39 via the first annular passage 32. As a result, the air flowing into the valve cylinder 10 from the air introduction port 39 passes through the air introduction valve seat 30 and is introduced into the working chamber 3 through the first port 29A. As a result, the working chamber 3 has a higher pressure than the negative pressure chamber 2, and the booster piston 4 moves forward by obtaining a forward thrust based on the pressure difference generated between the two chambers 2 and 3.
[0026]
The booster piston 4 moving forward in this way follows the movement of the input rod 20 against the force of the valve barrel return spring 27 while accompanying the valve cylinder 10. Then, the piston 15 integrated with the valve cylinder 10 pushes the output pressure receiving cylinder 21, that is, the output rod 25 forward via the elastic piston 22, and the input rod 20 also presses the elastic piston 22 via the reaction force piston 17. Therefore, the output rod 25 obtains the total thrust of the booster piston 4 and the input rod 20, drives the piston Mb of the brake master cylinder M forward, and operates a wheel brake (not shown) by the output hydraulic pressure.
[0027]
When the input rod 20 is stopped at an arbitrary forward position so as to maintain the braking force, the booster piston 4 is stopped at the time when the control valve 38 is neutralized, and therefore, the pressure difference between the negative pressure chamber 2 and the working chamber 3. Can be held at any value.
[0028]
During braking, in the reaction force mechanism 24, the resultant force of the thrust of the piston 15 connected to the booster piston 4 and the thrust (input) of the reaction force piston 17 connected to the input rod 20 is transferred from the output rod 25 to the output pressure receiving cylinder 21. Since the operating reaction force is balanced, a part of the operation reaction force of the output rod 25 is fed back to the reaction force piston 17, that is, the input rod 20 through the elastic piston 22. The magnitude of the braking force can be perceived, and therefore the output to the output rod 25 can be controlled by adjusting the input to the input rod 20.
[0029]
By the way, the reaction force piston 17 and the elastic piston 22 are fitted and brought into contact with each other with the taper convex portion 17a and the taper concave portion 22a. As shown, since the taper convex portion 17a of the reaction force piston 17 pushes the taper concave portion 22a of the elastic piston 22 and expands into the elastic piston 22, the valve piston 18 integrated with the reaction force piston 17 As a result, the opening degree of the air introduction valve seat 30 increases, and the air introduction flow rate into the working chamber 3 increases substantially linearly accordingly, and the booster piston 4 The forward thrust and the output of the output rod 25 also increase substantially linearly.
[0030]
Therefore, at the time of sudden braking in which the input rod 20 is rapidly advanced, the amount of the reaction force piston 17 entering the elastic piston 22 suddenly increases. Therefore, the atmosphere introduction valve seat 30 is largely opened to introduce the atmosphere into the working chamber 3. The jumping characteristic (brake assist) (see dotted line A in FIG. 5) that rapidly increases the output of the output rod 25 can be obtained, and the characteristic is approximately linear according to the input speed to the input rod 20. Since it changes, the braking operation feeling can be improved.
[0031]
In this case, as described above, forming the through-hole 44 opening in the bottom of the tapered recess 22a and the plurality of grooves 45 extending in the generatrix direction of the inner peripheral surface of the tapered recess 22a in the elastic piston 22 is a reaction force. This is effective for facilitating the entry of the taper convex portion 17a of the piston 17 into the elastic piston 22 and promoting the jumping characteristics.
[0032]
Further, when the taper convex portion 17a of the reaction force piston 17 enters the elastic piston 22 while expanding the taper concave portion 22a, the force of the elastic piston 22 against the taper convex portion 17a increases, and the friction generated during that time. However, since it exerts a resistance force on the reverse movement of the input rod 20, a large hysteresis is given to the input and output characteristics, and even if there is some fluctuation in the input to the input rod 20 when holding the braking force, Since the holding of the braking force can be stably and continuously, the braking operation is facilitated.
[0033]
In addition, the reaction force mechanism 24 has no increase in the number of parts and is very simple in structure as compared with a conventional general mechanism, and therefore can be provided at a low cost.
<When releasing the brake>
When the pedaling force is released from the brake pedal P in order to release the brake state, the input rod 20 first retracts with the force of the input return spring 41. At that time, the valve piston 18 seats the air introduction valve seat 30 on the valve body 34, and the valve body 34 is largely separated from the negative pressure introduction valve seat 31 to open the negative pressure introduction valve seat 31. The chamber 3 communicates with the negative pressure chamber 2 through the first port 29A, the first annular passage 32, the negative pressure introduction valve seat 31, and the second port 29B. As a result, the introduction of the atmosphere into the working chamber 3 is blocked, and at the same time, a negative pressure is introduced into the working chamber 3, eliminating the pressure difference between the negative pressure chamber 2 and the working chamber 3. The cylinder is retracted by the force of the cylinder return spring 27 and the operation of the master cylinder M is released.
[0034]
When the input rod 20 reaches the retreat limit in which the stopper plate 40 is brought into contact with the inward flange 12 of the rear extension cylinder 12 due to the retraction of the booster piston 4, the booster piston 4 temporarily moves the protrusion 5a of the diaphragm 5 to the booster shell 1. Returning to the rearward limit to be brought into contact with the rear wall, this time the negative pressure introduction valve seat 31 is seated on the valve body 34 and the valve body 34 is separated from the atmosphere introduction valve seat 30. However, if the booster piston 4 slightly moves forward due to the pressure difference caused thereby, the valve element 34 is also seated on the atmosphere introduction valve seat 30 and the control valve 38 is brought into the initial neutral state. In this way, the working chamber 3 holds the negative pressure diluted in the atmosphere, and the negative pressure booster B enters the resting state shown in FIG.
[0035]
In the above embodiment, in order to improve the jumping characteristic of the output at the initial stage of input, a gap is provided between the reaction force piston 17 and the elastic piston 22 in the idle state of the negative pressure booster B, or the valve piston 18 and the reaction force piston 17. Can be separated from each other with a gap therebetween. However, in the latter case, it is not possible to expect hysteresis as in the above embodiment.
[0036]
Next, a second embodiment of the present invention shown in FIG. 6 will be described.
[0037]
On the inner end face of the output pressure receiving cylinder 21 facing the reaction force chamber 19, a tapered convex part 21a having a smaller diameter toward the rear is formed, and a corresponding tapered concave part 22a is formed on the front end face of the elastic piston 22. These tapered convex portions and concave portions 21a and 22a are arranged so as to fit and abut each other. The elastic piston 22 is formed with either or both of a through-hole 44 that opens at the bottom of the tapered recess 22a and a plurality of grooves 45 that extend in the generatrix direction of the inner peripheral surface of the tapered recess 22a.
[0038]
The opposing surfaces of the reaction force piston 17 and the elastic piston 22 are formed flat, and a small gap is provided between the opposing surfaces of the reaction force piston 17 and the elastic piston 22 in the resting state of the negative pressure booster B.
[0039]
Since the other configuration is the same as that of the previous embodiment, the same reference numerals are assigned to the parts corresponding to those of the previous embodiment in FIG.
[0040]
According to the second embodiment, the same operational effects as those of the first embodiment can be achieved except for the hysteresis characteristic.
[0041]
The present invention is not limited to the above embodiments, and various design changes can be made without departing from the scope of the invention. For example, the taper convex portion 17a of the reaction force piston 17 can be formed in a truncated cone or a wedge shape. Further, the negative pressure booster B can be configured in a tandem type in which a pair of front and rear booster pistons are connected to each other. Furthermore, the reaction force mechanism 24 of the present invention can be applied to a hydraulic booster.
[0042]
【The invention's effect】
As described above, according to the first feature of the present invention, the reaction force piston connected to the input rod, a part of the rear end surface abuts on the front end surface of the reaction force piston, and the booster is applied to the entire front end surface. In the reaction force mechanism of a brake booster, comprising: an elastic piston for receiving an output; and a part of the booster output is transmitted to the reaction force piston via the elastic piston. The taper convex portion corresponding to the taper convex portion is formed in the elastic piston, and the taper convex portion and the taper concave portion are fitted and brought into contact with each other. At the time of sudden braking that rapidly advances the rod, the taper convex part of the reaction piston pushes and expands the taper concave part of the elastic piston and enters the elastic piston, so the booster output increases rapidly. That the jumping characteristics can be obtained (brake assist), yet its properties are varied approximately linearly in accordance with the input speed of the input rod, it is possible to improve the braking operation feeling. In addition, this reaction force mechanism has a simple structure and can be provided at a low cost. Furthermore, since a plurality of grooves extending in the generatrix direction of the inner peripheral surface are formed on the inner peripheral surface of the tapered recess, the taper convex portion of the reaction force piston can easily enter the elastic piston, and the jumping characteristics can be improved. Can be encouraged.
[0043]
According to the second aspect of the present invention, the reaction force piston connected to the input rod, the elastic piston that makes a part of the rear end surface abut on the front end surface of the reaction force piston, and the front end surface of the elastic piston. An output pressure receiving member that contacts the whole and receives a booster output in the contact direction, and transmits a part of the booster output received by the output pressure receiving member to the reaction force piston via an elastic piston. In the reaction force mechanism of the brake booster, at least one of the reaction force piston and the output pressure receiving member is formed with a taper convex portion having a small diameter toward the elastic piston, and a taper concave portion corresponding to the taper convex portion is formed in the taper concave portion. Since it is formed on an elastic piston and these taper convex part and taper concave part are fitted and brought into contact with each other, the reaction force piston or the output pressure receiving part at the time of sudden braking to rapidly advance the input rod Since the taper convex part of the elastic piston pushes the taper concave part of the elastic piston and enters into the elastic piston, it is possible to obtain a jumping characteristic (brake assist) that increases the booster output rapidly, and the characteristic is to the input rod. It is possible to improve the braking operation feeling by changing the linear velocity according to the input speed. In addition, this reaction force mechanism has a simple structure and can be provided at a low cost. Furthermore, since a plurality of grooves extending in the generatrix direction of the inner peripheral surface is formed on the inner peripheral surface of the tapered recess, it is easy to enter the reaction piston or the tapered convex portion of the output pressure receiving member into the elastic piston, The jumping characteristic can be promoted.
[0044]
Furthermore, according to the third feature of the present invention, in addition to the first or second feature, the elastic piston is provided with an axial through-hole opened at the bottom of the tapered recess, so that the reaction force piston or entry into the tapered protrusions in the elastic piston an output pressure receiving member is facilitated, Ru can promote the jumping characteristics.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a negative pressure booster for a vehicle brake according to the present invention.
FIG. 2 is an enlarged view of part 2 in FIG. 1 (when not braking).
FIG. 3 is a view corresponding to FIG. 2 showing an operating state of the negative pressure booster during sudden braking.
FIG. 4 is a front view of an elastic piston in the reaction force mechanism of the booster.
FIG. 5 is an input / output characteristic diagram of the negative pressure booster.
6 is a longitudinal sectional view corresponding to FIG. 2, showing a second embodiment of the present invention.
[Explanation of symbols]
B ··· Booster 15 ··· Piston 17 · · · Reaction piston 17a · · · Tapered protrusion 19 · · · Reaction chamber 20 · · · Input 21 ... Output pressure receiving member (Output pressure receiving cylinder)
21a ··· Taper convex portion 22 ··· Elastic piston 22a ··· Tapered concave portion 24 ··· Reaction force mechanism 25 ··· Output rod 44 ··· Through hole 45 · · ····groove

Claims (3)

A reaction force piston (17) connected to the input rod (20), and an elastic piston (a part of the rear end surface abuts against the front end surface of the reaction force piston (17)) and receives the booster output over the entire front end surface ( 22), and a part of booster output is transmitted to the reaction force piston (17) via the elastic piston (22).
The reaction force piston (17) is formed with a taper convex portion (17a) having a smaller diameter toward the elastic piston (22), while a taper concave portion (22a) corresponding to the taper convex portion (17a) is formed into the elastic piston (17a). Formed in the piston (22), the tapered convex portion (17a) and the tapered concave portion (22a) are fitted and brought into contact with each other ;
A reaction force mechanism for a brake booster, wherein a plurality of grooves (45) extending in the direction of the generatrix of the inner peripheral surface are formed on the inner peripheral surface of the tapered recess (22a) . A reaction force piston (17) connected to the input rod (20), an elastic piston (22) in which a part of the rear end surface is brought into contact with the front end surface of the reaction force piston (17), and the elastic piston (22). And an output pressure receiving member (21) that receives a booster output in the abutting direction, and a part of the booster output received by the output pressure receiving member (21) is passed through an elastic piston (22). In the reaction force mechanism of the brake booster that is transmitted to the reaction force piston (17),
At least one of the reaction force piston (17) and the output pressure receiving member (21) is formed with tapered convex portions (17a, 21a) having a smaller diameter toward the elastic piston (22), while the tapered convex portion (17a , 21a) is formed in the elastic piston (22), and the tapered convex portions (17a, 21a) and the tapered concave portion (22a) are fitted and brought into contact with each other ,
A reaction force mechanism for a brake booster, wherein a plurality of grooves (45) extending in the direction of the generatrix of the inner peripheral surface are formed on the inner peripheral surface of the tapered recess (22a) . In the reaction force mechanism of the brake booster according to claim 1 or 2,
Wherein the resilient piston (22), characterized in that a axial through hole opened in the bottom of the tapered recess (22a) (44), the reaction force Organization of the booster brake.

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