JP2017217966A - Brake booster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make rigidity reduction and durability of a reaction disk 100 compatible.SOLUTION: The reaction disk 100 is provided in a power transmission passage between: an output rod 40; and a power piston 30 and an operating rod 50. The reaction disk 100 comprises a discoid body part 101 made of rubber, a liquid chamber 102 is formed inside the body part 101, and liquid W (water) is encapsulated in the liquid chamber 102. Consequently, even when using rubber material having high rigidity almost the same level as that of a conventional reaction disk, the deformation volume of the whole of the reaction disk 100 can be increased, and restriction of an adjustment width of the brake operation feeling can be reduced.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a brake booster that assists a driver to operate a brake pedal.

  A brake booster (brake booster) is used in a hydraulic brake device of a vehicle to amplify a driver's brake pedal depression force to operate a master cylinder. Such a brake booster is provided with a reaction disk as described in Patent Document 1, for example. The reaction disk is a rubber member provided in a force transmission path between the output rod and the operating rod and the power piston. Therefore, the reaction disk transmits a reaction force acting on the output rod to the operating rod, and thus affects the brake operation feeling.

  Patent Document 1 describes that the brake operation feeling can be improved by changing the hardness of the rubber of the reaction disk.

Japanese Patent Laid-Open No. 5-16793

  If the rubber hardness of the reaction disk is changed, the brake operation feeling can be adjusted by increasing or decreasing the hysteresis of the brake booster. FIG. 5 shows the hysteresis characteristic of the brake booster. This hysteresis represents the difference in the booster output with respect to the pedal depression force when the brake pedal is depressed and released. For example, if the hysteresis is zero, when the pedal is held, the booster output is changed by a slight change in the pedaling force, that is, the braking force is changed, so that the pedal holding operation becomes difficult. On the other hand, if the hysteresis is set excessively, the braking force remains even if the pedal effort is reduced, so that the brake release operation becomes difficult. Therefore, the hysteresis characteristic of the brake booster is an important factor in the brake operation feeling.

  In the conventional apparatus, the hysteresis characteristic is changed by changing the rubber hardness. However, when the reaction disk is changed to the side where the rubber hardness is reduced, the durability performance of the reaction disk is lowered. For this reason, a restriction occurs in the adjustment range of the brake operation feeling, and a case where a desired brake operation feeling cannot be obtained occurs.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to achieve both reduction in the hardness of the reaction disk and durability.

In order to achieve the above object, the features of the present invention are:
A housing (10) partitioned into a constant pressure chamber (11) to which negative pressure is constantly supplied and a variable pressure chamber (12) in which the pressure is changed;
A power piston (30) that operates with an operating force based on a pressure difference between the constant pressure chamber and the variable pressure chamber;
An operating rod (50) provided at an axial center portion of the power piston so as to be movable relative to the power piston, to which a pedaling force input to a brake pedal is input;
A valve (21) that can be switched between a state in which the variable pressure chamber communicates with the constant pressure chamber and a state in which the variable pressure chamber is blocked from the constant pressure chamber and communicates with the atmosphere according to relative movement of the operating rod with respect to the power piston. 22)
An output rod (40) for outputting a driving force by a total input which is a sum of an operating force of the power piston and a force applied to the operating rod;
A brake booster comprising: the output rod; and an elastically deformable reaction disk (100) provided in a force transmission path between the power piston and the operating rod.
The reaction disk is configured by sealing a liquid (W) inside a rubber material (101).

  In the present invention, when the operating pedal moves forward when the brake pedal is depressed, the variable pressure chamber is switched from the state communicating with the constant pressure chamber to the state disconnected from the constant pressure chamber and communicated with the atmosphere by the operation of the valve. And the power piston moves forward due to the pressure difference between the variable pressure chamber. Thus, the total input, which is the sum of the operating force of the power piston and the force applied to the operating rod, is transmitted to the output rod. As a result, the brake pedal operating force of the driver is assisted and transmitted to the master cylinder of the hydraulic brake device. Thus, a braking force is generated in the hydraulic brake device.

  A reaction disk capable of elastic deformation is provided in a force transmission path between the output rod and the power piston and the operating rod. Accordingly, the reaction force acting on the output rod from the master cylinder is distributed and transmitted to the power piston and the operating rod by the reaction disk. Thereby, the driver can perceive the reaction force according to the braking force generated in the vehicle via the operating rod.

  The brake operation feeling can be adjusted by changing the hardness of the reaction disk. However, if the hardness of the rubber material forming the reaction disk is lowered, the durability performance of the reaction disk may be lowered. Therefore, the reaction disk provided in the brake booster of the present invention is configured by enclosing a liquid in a rubber material. As this liquid, for example, water can be used.

  The force required to deform the liquid is very small relative to the force necessary to deform the rubber material. Therefore, the reaction disk of the present invention is deformed with a smaller force than a conventional reaction disk formed of only a rubber material. That is, the rubber material is deformed in the same manner as the one with reduced hardness. For this reason, the rubber material used for the reaction disk can be the same as that of a conventional reaction disk, or a rubber material having a hardness higher than that of a conventional reaction disk. The amount of deformation can be increased. That is, it is possible to obtain an amount of deformation equivalent to that formed by a rubber material having a low hardness on the entire reaction disk. For this reason, it is possible to reduce the hardness of the reaction disk while securing the durability performance of the reaction disk, and to reduce the restriction on the adjustment width of the brake operation feeling.

  In addition, by appropriately setting the viscosity or volume of the liquid sealed in the rubber material, the force (energy) required for the deformation of the reaction disk can be adjusted, so the tuning of the reaction disk hardness, Brake operation feeling can be easily adjusted.

  In the above description, in order to assist the understanding of the invention, the reference numerals used in the embodiments are attached to the constituent elements of the invention corresponding to the embodiments in parentheses. It is not limited to the embodiment defined by.

It is a whole lineblock diagram showing the outline of the brake booster concerning this embodiment. It is a partial expanded sectional view of the piston main-body part at the time of non-operation of a brake booster. It is sectional drawing of a reaction disk. It is sectional drawing of the reaction disk which concerns on a modification. It is a graph showing the hysteresis characteristic of a brake booster. It is a simplified diagram for explaining the function of the reaction disk. It is a simplified diagram for explaining a mechanism in which hysteresis occurs. It is a simplified diagram for explaining a reaction disk manufacturing method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram showing an outline of a brake booster 1 of the present embodiment.

  The brake booster 1 includes a housing 10 that forms a pressure chamber, and a piston body 20 that adjusts the pressure in the housing 10. The interior of the housing 10 is partitioned into a constant pressure chamber 11 and a variable pressure chamber 12 by a diaphragm 15. The constant pressure chamber 11 communicates with a pipe connected to an intake pipe of an engine as a negative pressure source via a check valve 13. Therefore, when the engine is started, negative pressure is introduced into the constant pressure chamber 11 through the piping. For this reason, the constant pressure chamber 11 is always supplied with negative pressure when the engine is operating. A return spring 17 is provided in the constant pressure chamber 11 for returning to the state before the brake pedal BP is depressed.

  As shown in FIG. 2, the piston body 20 includes a power piston 30 to which the diaphragm 15 is fixed, an operating rod 50 connected to the brake pedal BP, and an output rod connected to the piston of a master cylinder (not shown). 40. FIG. 2 shows a state when the brake booster 1 is not operated. The operating rod 50 is disposed at the axial center of the power piston 30 so that the operating rod 50 can move relative to the power piston 30 in the axial direction. The pedaling force input by the driver to the brake pedal BP is transmitted to the piston of the master cylinder via the operating rod 50, the power piston 30, the output rod 40, etc., and the output of the braking device is increased.

  The power piston 30 is formed in a stepped cylindrical shape, and is assembled to the rear end portion of the housing 10 so as to be airtight and movable in the front-rear direction, and is urged rearward by a return spring 17. In this specification, the forward direction is the direction in which the operating rod 50 moves when the brake pedal BP is depressed, that is, the left direction in the drawing, and the rear direction is the operating rod 50 when the brake pedal BP is released. Is the moving direction, that is, the right direction of the drawing. The power piston 30 has an outer peripheral surface at the front end thereof assembled to the center of the diaphragm 15. A seal member 16 is fixed to the inner peripheral surface of the rear end portion of the housing 10, and the power piston 30 is supported by the seal member 16 so as to be airtight and slidable with respect to the housing 10.

  The power piston 30 has a double tube structure on the front side, and an output rod 40 is attached to the front end portion thereof. Inside the power piston 30, a reaction disk 100, a plunger 35, an air valve 60, a valve seat forming member 70, a spring receiving member 80, a filter 90 and the like are provided in order from the front side to the rear side.

A communication hole 18 for communicating the inside of the power piston 30 and the constant pressure chamber 11 is formed in a portion having a double pipe structure on the front side of the power piston 30, and the rear side of the inner cylindrical portion of the double pipe structure is formed. On the side, a ring-shaped first valve forming portion 31 is formed. In addition, communication holes 19 for communicating the inside of the power piston 30 with the variable pressure chamber 12 are formed at a plurality of locations on the side of the power piston 30.

  A key member 110 is inserted into the power piston 30. The key member 110 is a stopper that regulates a limit position when the power piston 30 is displaced in the axial direction. When the key member 110 hits and is engaged with a stepped portion formed at the rear end of the housing 10, the key member 110 restricts the displacement of the power piston 30 to the rear at that position.

  A bellows 120 that covers the sliding portion of the power piston 30 from the outside is provided at the rear end of the housing 10. The bellows 120 is made of a flexible member, and has a front end attached to the rear end of the housing 10 and a rear end fitted to the outer peripheral surface of the operating rod 50. A plurality of vent holes 121 are formed in the rear end surface of the bellows 120, and air can be introduced into the inside from the rear end opening of the power piston 30.

  The output rod 40 has a cylindrical accommodating portion 41 that accommodates the reaction disk 100 at the input side end.

  As shown in FIG. 3, the reaction disk 100 includes a disc-shaped main body 101 made of rubber, and a liquid chamber 102 is formed inside the main body 101, and a liquid W (this embodiment) is formed in the liquid chamber 102. In the form, water) is enclosed. The liquid chamber 102 is a circular chamber as viewed from the front-rear direction. The reaction disc 100 is in contact with the front end portion of the power piston 30 while being accommodated in the accommodating portion 41 of the output rod 40. The front end of the power piston 30 is provided in contact with the inner peripheral surface of the accommodating portion 41 of the output rod 40 so as to be able to advance and retreat in the axial direction, and its front surface is formed in a donut shape and is an outer peripheral portion on the rear surface of the reaction disk 100 It becomes the press surface 30a which presses.

  A plunger 35 and an air valve 60 are provided between the reaction disk 100 and the operating rod 50. Plunger 35 and air valve 60 are provided in contact with the inner peripheral surface of the double pipe portion of power piston 30 so as to advance and retract in the axial direction. The plunger 35 is formed in a cylindrical shape, is provided between the reaction disk 100 and the air valve 60, and has a pressing surface 35 a that presses the rear surface of the reaction disk 100. The center of the pressing surface 35a of the present embodiment is formed in a convex shape, but this is a booster input / output characteristic tuning element, which is not necessarily required, and may be a flat surface. The plunger 35 may be formed integrally with the air valve 60.

  The rear side of the air valve 60 is formed in a cylindrical shape, and the distal end portion of the operating rod 50 is inserted and crimped. The force transmitted to the operating rod 50 is transmitted to the air valve 60 via the spherical tip, and becomes a propulsive force forward of the air valve 60. The driving force of the air valve 60 is transmitted to the output rod 40 via the plunger 35 and the reaction disk 100.

  The rear end of the air valve 60 can be attached to and detached from a second valve seat 72a of a valve seat forming member 70, which will be described later, and a ring-shaped second valve forming portion 62 that introduces or blocks air to the variable pressure chamber 12 is formed. .

  The valve seat forming member 70 is provided in contact with the inner peripheral surface on the rear side of the power piston 30 so as to be able to advance and retreat in the axial direction, and a first support portion 71 formed in a ring shape at the front end portion of the cylindrical main body, and a cylinder And a second support portion 72 formed in a ring shape at the rear end of the main body. A ring-shaped first valve seat 71a made of rubber is attached to the front surface of the first support portion 71, and a ring-shaped second valve seat 72a made of rubber is attached to the front surface of the second support portion 72. Has been. As a result, the first valve forming portion 31 of the power piston 30 is attached to and detached from the first valve seat 71a, and the second valve forming portion 62 of the air valve 60 is attached to and detached from the second valve seat 72a. A valve portion 22 is formed.

  The spring receiving member 80 is a ring-shaped member that is press-fitted into the inner peripheral surface in the vicinity of the rear end portion of the power piston 30. A first spring 81 that biases the valve seat forming member 70 forward is interposed between the spring receiving member 80 and the valve seat forming member 70. In addition, a seal member 75 made of rubber that can be expanded and contracted in the front-rear direction is disposed between the spring receiving member 80 and the valve seat forming member 70, and the atmosphere introduced from the rear end of the power piston 30 communicates. Leakage to the constant pressure chamber 11 through the hole 18 is prevented.

  The filter 90 is fixed to the rear end opening of the power piston 30 and prevents inflow of dust and the like from the outside. The air introduced from the vent hole 121 of the bellows 120 flows into the power piston 30 through the filter 90. An operating rod 50 is inserted in the center of the filter 90 so as to be able to advance and retreat, and a ring plate-like spring seat 85 is provided on the front side thereof. The spring seat 85 is engaged with the step portion of the operating rod 50. A second spring 82 is interposed between the spring seat 85 and the spring receiving member 80. The second spring 82 urges the spring seat 85 rearward to contact the filter 90. Since the spring seat 85 is engaged with the step portion of the operating rod 50, the operating rod 50 is urged rearward by the urging force of the second spring 82.

<Brake booster operation>
Next, the operation of the brake booster 1 will be described. When the brake is not applied to the brake pedal BP, the power piston 30 is pushed back to the base of the housing 10 by the urging force of the return spring 17. In this state, the operating rod 50 is pushed back to the initial position (right side in the drawing) by the urging force of the second spring 82. At this time, as shown in FIG. 2, the urging force of the first spring 81 pushes back until the second valve seat 72a of the second support portion 72 comes into contact with the second valve forming portion 62 of the air valve 60 (left side in the drawing). It is. Further, the first valve forming portion 31 of the power piston 30 and the first valve seat 71a formed on the first support portion 71 are in a non-contact state, and a predetermined gap is formed between them. Accordingly, the first valve portion 21 is opened and the second valve portion 22 is closed. As a result, the constant pressure chamber 11 and the variable pressure chamber 12 communicate with each other through the communication holes 18 and 19. Therefore, a negative pressure from an intake manifold (not shown) acts on both the constant pressure chamber 11 and the variable pressure chamber 12, so that no pressure difference occurs between the two chambers. That is, the brake booster 1 is in an inoperative state. In this state, the pressing surface 35 a of the plunger 35 is not in contact with the rear end surface of the reaction disk 100.

  From this state, if the pedaling force is slightly applied to the brake pedal BP, the power piston 30 is still in the initial position, but the operating rod 50 is pressed forward (to the left in the drawing) against the urging force of the second spring 82. Is done. At this time, as the air valve 60 moves forward, the urging force of the first spring 81 moves the valve seat forming member 70 forward, and the first valve seat 71a contacts the first valve forming portion 31 of the power piston 30. . Accordingly, since the first valve portion 21 is closed, the communication between the constant pressure chamber 11 and the variable pressure chamber 12 is interrupted after this point, and no negative pressure is introduced into the variable pressure chamber 12.

  From this state, when the operating rod 50 moves further forward by the depression force of the brake pedal BP, the displacement is transmitted only to the air valve 60. As a result, the second valve forming portion 62 of the air valve 60 is moved to the valve seat forming member 70. This leaves the second valve seat portion 72a and the inside of the power piston 30 is released to the atmosphere. That is, since the second valve portion 22 is opened, the variable pressure chamber 12 communicates with the atmosphere through the communication hole 19 after this point. Thereby, the atmosphere is guided to the variable pressure chamber 12 through the communication hole 19 and the internal pressure thereof increases.

  As the air is introduced into the variable pressure chamber 12 in this way, a pressure difference is generated between the variable pressure chamber 12 and the constant pressure chamber 11, and the power piston 30 moves forward from the time when the pressure difference exceeds the urging force of the return spring 17 ( In the left direction of the drawing), the output rod 40 is pressed through the reaction disk 100. The brake booster 1 generates the assisting force regardless of the input of the operating rod 50 until the plunger 35 contacts the reaction disk 100.

  When the reaction disc 100 is pressed against the pressing surface 30a of the power piston 30 (that is, the donut-shaped region on the outer peripheral side is pressed), the central portion of the rear side surface (the right side surface in the figure) rises backward. It contacts the pressing surface 35a of the plunger 35. In this state, the total input, which is the sum of the operating force (the operating force due to the pressure difference) of the power piston 30 and the force of the operating rod 50 advanced by the brake pedal depression force, is output via the reaction disk 100 to the output rod 40. Is transmitted to. This force ratio is an area ratio of the power piston 30 and the plunger 35 contacting the reaction disk 100, that is, a servo ratio.

  When the brake pedal depression force is increased and the variable pressure chamber 12 is completely at atmospheric pressure, the force acting on the power piston 30 is maximized and the assisting force is limited. In this state, the balancing action of the reaction disk 100 is lost.

  When the brake pedal BP is returned and the brake depression force is reduced, the balance of the reaction disk 100 is lost and the plunger 35 is pushed back. Thereby, the 2nd valve part 22 will be in a valve closing state, the 1st valve part 21 will be in a valve opening state, and the variable pressure chamber 12 and the constant pressure chamber 11 will connect. Then, there is no pressure difference between the constant pressure chamber 11 and the variable pressure chamber 12, and the power piston 30 is pushed back.

<Reaction Disc Function>
Here, the function of the reaction disk 100 will be described. FIG. 6 is a simplified diagram for explaining the function of the reaction disk 100.

  As shown in FIG. 6A, the force that the plunger 35 presses the reaction disk 100 is f, the contact area between the plunger 35 and the reaction disk 100 is a, the force that the power piston 30 presses the reaction disk 100 is F, and the power When the contact area between the piston 30 and the reaction disk 100 is A, the pressure generated in the reaction disk 100 is expressed by f / a = F / A according to Pascal's principle.

Therefore, the ratio between the force generated by the plunger 35 and the force generated by the power piston 30 is constant.
F / f = A / a = constant value As described above, the reaction disc 100 is adjusted so that the ratio of the force generated by the plunger 35 and the force generated by the power piston 30 is constant.

  When the input from the operating rod 50 increases, as shown in FIG. 6 (b), the reaction disc 100 is pushed forward by the pressing surface 35a of the plunger 35 at its center portion (contact portion with the plunger 35). At the same time, the peripheral portion pushes the pressing surface 30a of the power piston 30 backward. At this time, when the second valve portion 22 is opened, the force pushing the power piston 30 forward (force due to the pressure difference) increases. As a result, the power piston 30 pushes the reaction disk 100 forward and returns to the state of FIG. Thereby, the 2nd valve part 22 closes and an operation | movement is complete | finished.

  When the input from the operating rod 50 decreases, as shown in FIG. 6C, the plunger 35 moves backward due to the reaction force from the reaction disk 100, and at the same time, the power piston 30 moves forward. At this time, the opening of the first valve portion 21 reduces the force pushing the power piston 30 forward (force due to the pressure difference). As a result, the reaction disk 100 pushes the power piston 30 backward and returns to the state of FIG. Thereby, the 2nd valve part 22 closes and an operation | movement is complete | finished.

<Relationship between hardness and hysteresis of reaction disc>
Next, the relationship between the hardness of the reaction disk 100 and hysteresis will be described. As shown in FIG. 7, the deformation amount of the reaction disk 100 differs between when the operating rod 50 moves forward and when the operating rod 50 moves backward. If the output is the same when the operating rod 50 moves forward and backward (the reaction force from the output rod 40 to the reaction disk 100 is the same), the amount of deformation of the reaction disk 100 is larger during the backward movement. The force to return to the shape of the work greatly. For this reason, the force acting on the power piston 30 from the reaction disk 100 is larger and the force acting on the plunger 35 is smaller when the operating rod 50 is retracted than when it is advanced. Thereby, hysteresis occurs.

  If the hardness of the reaction disk 100 is reduced, the force required for deformation of the reaction disk 100 (= force for the reaction disk 100 to return to the original shape) is reduced, so that the difference between the forward force and the reverse force, Hysteresis can be reduced.

  Therefore, the brake operation feeling can be adjusted by changing the hardness of the reaction disk 100. However, if the hardness of the rubber material (elastic material) forming the reaction disk 100 is lowered in order to reduce hysteresis, the durability performance of the reaction disk 100 may be lowered. Therefore, as described above, the reaction disk 100 used in the brake booster 1 of the present embodiment is configured such that the liquid W (water) is sealed inside the rubber material.

  The force required to deform the liquid is very small relative to the force necessary to deform the rubber material. Accordingly, the reaction disk 100 is deformed with a smaller force than a conventional reaction disk formed only of a rubber material. That is, the rubber material is deformed in the same manner as the one with reduced hardness. Therefore, even if a rubber material having a hardness as high as that of the conventional reaction disk is used as the rubber material used for the reaction disk 100 or a rubber material having a hardness higher than that of the conventional reaction disk is used, the reaction disk is used. The overall deformation amount can be increased. That is, it is possible to obtain an amount of deformation equivalent to that formed by a rubber material having a low hardness on the entire reaction disk. For this reason, the hardness of the reaction disk 100 can be reduced while ensuring the durability performance of the reaction disk 100, and the restriction on the adjustment width of the brake operation feeling can be reduced.

  In addition, since the force (energy) necessary for deformation of the reaction disk 100 can be adjusted by appropriately setting the viscosity or volume of the liquid W sealed in the rubber material, the hardness of the reaction disk 100 can be adjusted. That is, the brake operation feeling can be easily adjusted.

  As a method of enclosing the liquid W inside the rubber material, for example, as shown in FIG. 8A, a rubber base 100b having a recess S1 formed on the surface and a rubber lid 100a are used to form the recess S1. A method of adhering the surface of the rubber base 100b with the rubber lid 100a in a state where the liquid W is filled can be employed. Further, as shown in FIG. 8B, after the rubber material body 100c having the cavity S2 formed therein is blow-molded, and the cavity S2 is evacuated by the syringe T, the liquid W is injected into the cavity S2 by the syringe T. In addition, a method of closing the hole formed by the syringe T with an adhesive may be employed.

  Although the brake booster according to the present embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, a reaction disk 100 'as shown in FIG. 4 may be used. In the reaction disk 100 ′, a plurality of liquid chambers 102 ′ are provided in a main body 101 ′, and liquid W (water) is sealed in each liquid chamber 102 ′. Thus, by appropriately setting the capacity of the liquid chamber 102 ', tuning of the hardness of the reaction disk, that is, adjustment of the brake operation feeling can be facilitated.

  Further, in this embodiment, water is used as the liquid W sealed inside the rubber material of the reaction disk 100, but it is not always necessary to use water, and other liquids may be used. For example, by appropriately selecting and using a liquid W having a viscosity different from that of water, it becomes easy to tune the hardness of the reaction disk, that is, to adjust the brake operation feeling.

  DESCRIPTION OF SYMBOLS 1 ... Brake booster, 10 ... Housing, 11 ... Constant pressure chamber, 12 ... Transformer chamber, 20 ... Piston main-body part, 21 ... 1st valve part, 22 ... 2nd valve part, 30 ... Power piston, 31 ... 1st valve formation 35, plunger, 40 output rod, 50 operating rod, 60 air valve, 62 second valve forming portion, 70 valve seat forming member, 71 first support portion, 71a first valve seat, 72 ... 2nd support part, 72a ... 2nd valve seat, 80 ... Spring receiving member, 81 ... 1st spring, 82 ... 2nd spring, 85 ... Spring seat, 100 ... Reaction disk, 101 ... Body part, 102 ... Liquid chamber , W ... Liquid.

Claims (1)

A housing partitioned into a constant pressure chamber to which negative pressure is constantly supplied and a variable pressure chamber in which the pressure is changed;
A power piston that operates with an operating force based on a pressure difference between the constant pressure chamber and the variable pressure chamber;
An operating rod provided at the axial center of the power piston so as to be movable relative to the power piston, to which a pedaling force input to a brake pedal is input;
A valve capable of switching between a state in which the variable pressure chamber communicates with the constant pressure chamber and a state in which the variable pressure chamber is blocked from the constant pressure chamber and communicates with the atmosphere according to relative movement of the operating rod with respect to the power piston;
An output rod that outputs a driving force by a total input that is the sum of the operating force of the power piston and the force applied to the operating rod;
A brake booster comprising: the output rod; and an elastically deformable reaction disk provided in a force transmission path between the power piston and the operating rod.
The reaction disk is a brake booster configured by sealing a liquid inside a rubber material.

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