JP6099482B2 - Booster - Google Patents

Description

  The present invention relates to a booster incorporated in a brake device of a vehicle such as an automobile.

  For example, in the electric booster described in Patent Document 1, when the brake pedal is released to release the brake operation, the input rod moves backward together with the brake pedal, and the enlarged diameter portion is formed in the housing. Abutting on the lateral projections, they are positioned at the non-braking position.

JP 2009-202867 A

  However, in the electric booster according to Patent Document 1, when the input rod is retracted, there is a possibility that a collision sound is generated when the diameter-enlarged portion of the input rod interferes with the inward projection of the housing.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a booster device that reduces a collision sound when an input rod is retracted.

  In order to solve the above-described problems, the present invention moves the input rod back and forth according to the operation of the brake pedal, and boosts the operating force of the brake pedal according to the amount of movement of the input rod. In the booster in which the housing is provided with boosting means for propelling the piston, the input rod has one end side disposed in the housing and the other end side extended from the housing and connected to the brake pedal, A stopper portion for restricting the retracted position of the input rod is provided in contact with a restricting portion provided in the housing at an intermediate portion in the axial direction, and the input rod is retracted to a non-braking position on the input rod. In this case, a buffer mechanism is provided that decelerates the retraction speed of the input rod before the stopper portion abuts on the restricting portion.

  According to the booster according to the present invention, it is possible to reduce the collision sound when the input rod moves backward.

It is sectional drawing of the electric booster which concerns on one Embodiment. It is sectional drawing of the buffer mechanism employ | adopted as this electric booster. It is sectional drawing for demonstrating the effect | action of a buffer mechanism. It is sectional drawing for demonstrating the effect | action of a buffer mechanism.

Hereinafter, an embodiment will be described in detail based on the drawings.
As shown in FIG. 1, the booster according to the present embodiment is an electric booster 1, and the electric booster 1 includes a tandem master cylinder 2 and an actuator 3 as a booster. Housing 4. A reservoir 5 is connected to the master cylinder 2. A controller C is attached to the upper part of the housing 4. The housing 4 includes a substantially bottomed cylindrical housing body 4A made of an aluminum alloy and the like, and a rear cover 4B made of cast iron or the like, which is coupled to the opening side of the housing body 4A by a plurality of bolts 4C. The rear cover 4B is formed with a cylindrical portion 8 that is concentric with the master cylinder 2 and protrudes rearward. A pair of anti-rotation portions 39 and 39 projecting radially inward from the rear end portion is formed at the rear end portion of the cylindrical portion 8. The rear cover 4B is formed by casting including the cylindrical portion 8, and the anti-rotation portions 39, 39 are formed by cutting the inner surface of the rear cover 4B.

  The master cylinder 2 includes a cylinder body 2A having a substantially bottomed cylindrical shape, and an opening side of the master cylinder 2 is coupled to an opening at the bottom of the housing 4 by a stud bolt 6A and a nut 6B. In the cylinder main body 2A of the master cylinder 2, a cylindrical primary piston 10 whose tip is formed in a cup shape is inserted on the opening side, and a cup-shaped secondary piston 11 is inserted on the bottom side. The rear end portion of the primary piston 10 protrudes from the opening of the master cylinder 2 into the housing 4 and extends to the cylindrical portion 8 of the rear cover 4B. In the cylinder body 2 </ b> A, two pressure chambers of a primary chamber 16 and a secondary chamber 17 are formed by the primary piston 10 and the secondary piston 11. The primary chamber 16 and the secondary chamber 17 are respectively provided with hydraulic pressure ports 18 and 19. Two hydraulic pressure circuits (not shown) for supplying hydraulic pressure to the brake calipers of the wheels are connected to the hydraulic pressure ports 18 and 19, respectively.

  Reservoir ports 20 and 21 for connecting the primary chamber 16 and the secondary chamber 17 to the reservoir 5 are provided on the upper side of the side wall of the cylinder body 2A. The cylinder bore 12 of the cylinder body 2A and the primary piston 10 and the secondary piston 11 are sealed by two seal members 22A, 22B and 23A, 23B, respectively. The seal members 22A and 22B are arranged so as to sandwich the reservoir port 20 along the axial direction. When the primary piston 10 is in the non-braking position shown in FIG. 1, the seal member 22 </ b> A allows the primary chamber 16 to communicate with the reservoir port 20 via the port 24 provided on the side wall of the primary piston 10, and the primary piston 10 Is moved from the non-braking position over the seal member 22 </ b> A to shut off the primary chamber 16 from the reservoir port 20. Further, the seal members 23A and 23B are arranged so as to sandwich the reservoir port 21 along the axial direction. When the secondary piston 11 is in the non-braking position shown in FIG. 1, the seal member 23 </ b> A communicates the secondary chamber 17 with the reservoir port 21 via the port 25 provided on the side wall of the secondary piston 11, and the secondary piston 11. Is moved from the non-braking position over the seal member 23 </ b> A so that the secondary chamber 17 is blocked from the reservoir port 21.

  A spring assembly 26 is interposed between the primary piston 10 and the secondary piston 11 in the primary chamber 16. A return spring 27 that is a compression coil spring is interposed between the bottom of the master cylinder 2 in the secondary chamber 17 and the secondary piston 11. The spring assembly 26 holds the compression coil spring 28 in a predetermined compression state by a retractable retainer 29 and can be compressed against the urging force thereof. A cylindrical spacer 29 </ b> A is interposed between the retainer 29 and an intermediate wall 30 (described later) of the primary piston 10.

  The primary piston 10 is formed in a cylindrical shape as a whole and includes an intermediate wall 30 that partitions the inside in the axial direction. A guide bore 31 is passed through the intermediate wall 30 along the axial direction. A small-diameter tip end of a stepped input piston 32 having a step portion 32A is slidably and liquid-tightly inserted into the guide bore 31. The gap between the guide bore 31 and the tip of the input piston 32 is sealed by two seal members 33A and 33B, and the intermediate wall 30 of the primary piston 10 has an opening between the seal members 33A and 33B of the guide bore 31. The passage 33 is penetrated along the radial direction. The passage 33 is opened inside the seal member 22B.

  An intermediate portion of the primary piston 10 extending into the housing 4 is inserted into a cylindrical spring receiving member 70 that fits into an opening at the bottom of the housing main body 4A, and is slidably guided along the axial direction. The spring receiving member 70 is connected to the cylinder bore 12 of the master cylinder 2 with an outer flange portion 71 formed at one end thereof being fitted into and fixed to the opening at the bottom of the housing body 4A. The space between the primary piston 10 is sealed by a seal member 72 attached to the inner periphery of the rear end of the spring receiving member 70.

  The rear end portion of the input piston 32 is connected to the cylindrical portion 8 of the rear cover 4 </ b> B and the front end portion of the input rod 34 inserted into the rear portion of the primary piston 10. The rear end side of the input rod 34 extends from the cylindrical portion 8 to the outside. A threaded portion 34B is formed at the rear end portion of the input rod 34 that extends from the cylindrical portion 8 to the outside. A clevis 73 and a lock nut 74 for connecting a brake pedal (not shown) are screwed onto the screw portion 34B. A flange-shaped spring receiver 35 is attached to the rear end portion of the primary piston 10, and the primary piston 10 is a return that is a compression coil spring interposed between the rear end portion of the spring receiving member 70 and the spring receiver 35. The spring 36 is biased in the backward direction. Further, the input piston 32 is neutrally shown in FIG. 1 by springs 37 and 38 which are compression coil springs interposed between the intermediate piston 30 of the primary piston 10 and the spring receiver 35 of the primary piston 10. Elastically held in place. The retracted position of the input rod 34 is defined by a large diameter contact portion 34A provided at the intermediate portion of the input rod 34 contacting a pair of rotation preventing portions 39 provided on the cylindrical portion 8 of the rear cover 4A. Yes.

  A cylindrical covering member 76 is provided at the rear end of the cylindrical portion 8 of the rear cover 4B. The covering member 76 is attached to the rear end portion of the cylindrical portion 8 of the rear cover 4B so as to cover the outer periphery of the screw shaft 47. The covering member 76 is fixed to the rear end portion of the cylindrical portion 8 by a retaining ring 84. A spring support portion 77 is provided on the pair of detent portions 39. Specifically, the spring support portion 77 is provided on the rear side of the pair of detent portions 39 and 39 provided integrally with the cylindrical portion 8 of the rear cover 4B of the housing 4. The spring support portion 77 is configured to support one end portion of the reaction force spring 79 so as to connect the distal ends of a pair of rotation preventing portions 39 provided integrally with the cylindrical portion 8 of the rear cover 4B. The spring support portion 77 is formed as a concave wall portion that extends in an annular shape so as to connect the tip ends of the pair of detent portions 39. An elliptical opening 86 through which the input rod 34 is inserted is formed inside the spring support 77. A washer 80 and a spring washer 82 are overlaid on the outer periphery of the anti-rotation portion 39 on the spring support portion 77 side.

  The movable spring receiver 78 is supported by the covering member 76 so as to be movable within a predetermined range along the axial direction in the covering member 76. The movable spring receiver 78 is engaged with a guide groove 47A of the screw shaft 47 and a guide groove 81 of the cover member 76, which will be described later, by a guide portion 78A projecting radially outward, with respect to the cover member 76 and the screw shaft 47. And is supported so that it cannot rotate relative to each other. The movable spring receiver 78 has an opening 78B formed in the center in the radial direction, and the inner diameter of the movable spring receiver 78 is set so that the opening edge abuts on a spring receiver 54 of the buffer mechanism 51 described later. On the rear surface (surface on the screw shaft 47 side) of the opening 78B of the movable spring receiver 78, a recess for receiving the other end of the reaction force spring 79 is formed. The reaction force spring 79 is a compression coil spring that is interposed between a spring support portion 77 and a movable spring receiver 78 that are connected to the pair of detent portions 39. The reaction force spring 79 is movable with the spring support 77 in a natural length or a state compressed with a predetermined set load (in this embodiment, a state slightly compressed in order to suppress rattling between components). It is interposed between the spring receiver 78. When the input rod 34 moves forward by a predetermined distance L with respect to the cylindrical portion 8, that is, the housing 4, a spring receiving portion 54 of the buffer mechanism 51 described later comes into contact with the movable spring receiver 78, and the input rod 34 is When the advancing further, the reaction force spring 79 is compressed, and the urging force is applied as a reaction force against the advance of the input rod 34.

  In addition, as shown in FIG. 2, the input rod 34 is provided with a buffer mechanism 51 between the movable spring receiver 78 and the lock nut 74 to reduce the reverse speed of the input rod 34 when the input rod 34 is retracted to the non-braking position. It has. The buffer mechanism 51 is configured to decelerate the retraction speed of the input rod 34 before the abutting portion 34A as the stopper portion of the input rod 34 abuts against the pair of detent portions 39 as the restricting portions. Specifically, the buffer mechanism 51 includes a cylindrical portion 52, a flange portion 53 provided at the front end portion of the cylindrical portion 52, a flange-shaped spring receiving portion 54 provided near the rear end of the cylindrical portion 52, A coil spring 55 is provided between the spring receiving portion 54 and the lock nut 74 and includes a lock nut 74 that is screwed to the rear end of the input rod 34. The input rod 34 is inserted into the cylindrical portion 52 so as to be relatively movable in the axial direction. The cylindrical portion 52 is inserted into the opening 78B of the movable spring receiver 78 so as to be relatively movable in the axial direction. The flange portion 53 is disposed on the rear surface (surface on the screw shaft 47 side) side of the movable spring receiver 78 and extends in the radial direction. The outer diameter of the flange portion 53 is smaller than the inner diameter of the reaction force spring 79. The spring receiving portion 54 extends in a radial shape from the outer peripheral surface of the cylindrical portion 52 in a flange shape. The rear end 52 </ b> A of the cylindrical portion 52 is disposed so as to face the front surface 74 </ b> A of the lock nut 74 so as to be able to come into contact therewith. The coil spring 55 has a front end fixed to the spring receiving portion 54 and a rear end fixed to the front surface 74A side of the lock nut 73 by caulking. The coil spring 55 is configured to apply a biasing force that pulls the lock nut 74 against the spring receiving portion 54 in a non-braking state where the brake pedal is not operated.

  In the housing 4, there is provided an actuator 3 including an electric motor 40 and a ball screw mechanism 41 that converts the rotation of the electric motor 40 into a linear motion and applies thrust to the primary piston 10. The electric motor 40 is a permanent magnet embedded synchronous motor, and includes a stator 42 and a rotor 45. The stator 42 has a plurality of coils fixed by a plurality of bolts 69 to a step on the rear side of the bottom of the housing body 4A. The rotor 45 has a plurality of permanent magnets that are formed in a cylindrical shape and are disposed along the circumferential direction so as to face the inner peripheral surface of the stator 42. The electric motor 40 may be a synchronous motor in which a permanent magnet is arranged inside the rotor 45, or another type of motor such as an induction motor.

  The ball screw mechanism 41 includes a plurality of nut members 46, a hollow screw shaft 47, a plurality of screw grooves provided between an inner peripheral surface of the nut member 46 and a screw groove provided on the outer peripheral surface of the screw shaft 47. And a ball 48. The nut member 46 extends in the axial direction from the vicinity of the bottom of the housing body 4A to the vicinity of the rear cover 4B, and both ends thereof are rotatably supported by the housing body 4A and the rear cover 4B by bearings 43 and 44. The inner peripheral portion of the rotor 45 is fixed to the outer peripheral portion on the front side of the nut member 46. The screw shaft 47 is inserted into the nut member 46 and the cylindrical portion 8 of the housing 4, is movable along the axial direction, and is supported so as not to rotate about the axis. Specifically, at the rear end portion of the screw shaft 47 protruding from the cylindrical portion 8, guide grooves 47A extending to the end portion along the axial direction are formed at two locations in the diameter direction. A pair of detents 39 provided on the cylindrical portion 8 of the rear cover 4B of the housing 4 are engaged with the guide grooves 47A, respectively, so that the screw shaft 47 can be moved within a predetermined range in the axial direction and around the axis. It supports so as not to rotate.

  In the ball screw mechanism 41, the screw shaft 47 moves in the axial direction when the ball 48 rolls along the screw groove by the rotation of the nut member 46 accompanying the rotation of the rotor 45 of the electric motor 40. ing. Further, the ball screw mechanism 41 can mutually convert rotation and linear motion between the nut member 46 and the screw shaft 47. Although not provided in the present embodiment, a known speed reduction mechanism such as a planetary gear mechanism or a differential speed reduction mechanism is interposed between the electric motor 40 and the ball screw mechanism 41, and the electric motor 40 is provided. The rotation of the motor may be decelerated and transmitted to the ball screw mechanism 41.

  As shown in FIG. 1, the screw shaft 47 of the ball screw mechanism 41 is biased in the backward direction by a return spring 49 that is a compression taper coil spring interposed between the outer flange portion 71 of the spring receiving member 70. . The screw shaft 47 is regulated in its retracted position by the bottom portion of the guide groove 47A coming into contact with the anti-rotation portion 39 provided in the cylindrical portion 8 of the rear cover 4B. The rear end portion of the primary piston 10 is inserted into the screw shaft 47, and the retracted position of the primary piston 10 is regulated by the spring receiver 35 coming into contact with the step portion 50 formed on the inner peripheral portion of the screw shaft 47. ing. As a result, the primary piston 10 is pushed forward by the stepped portion 50 by the advancement of the screw shaft 47, and can move forward separately from the stepped portion 50. As shown in FIG. 1, the non-braking position of the primary piston 10 is defined by the screw shaft 47 that is in contact with the anti-rotation portion 39, and the primary piston 10 and the spring assembly 26 in the non-braking position are A retracted position of the piston 11, that is, a non-braking position is defined.

  A resolver 60 as a rotational position sensor that detects the rotational position of the rotor 45 of the electric motor 40 is provided in the housing 4. The resolver 60 includes a sensor rotor 60A fixed to the outer peripheral portion on the rear side of the nut member 46, and a sensor stator 60B attached to the rear cover 4B so as to face the sensor rotor 60A.

  Further, the controller C of the electric booster 1 operates a brake pedal, that is, a stroke sensor (not shown) for detecting the displacement of the input piston 32 and the input rod 34, and the rotational position of the rotor 45 of the electric motor 40. Various sensors (all not shown) such as a resolver 60 for detecting, a current sensor for detecting a current supplied to the electric motor 40, a hydraulic pressure sensor for detecting the hydraulic pressure in the primary chamber 17, and the secondary chamber 18 are connected, respectively. The detection signal is received. The controller C is a microprocessor-based electronic control device including an ECU and a RAM, and based on detection signals from the various sensors, the relative position between the input rod 34 and the screw shaft 47 (primary piston 10) of the ball screw mechanism 41. The operation of the electric motor 40 is controlled so as to adjust. By this control, the electric booster 1 generates brake fluid pressure in the primary chamber 17 and the secondary chamber 18 in the master cylinder 2 with a desired boost ratio.

Next, the operation of the electric booster 1 according to this embodiment will be described. In the following description, since the primary piston 10 and the secondary piston 11 operate in the same manner, only the primary piston 10 will be described.
First, as the operation amount of the brake pedal, the displacement of the input piston 32 from the input rod 34 is detected by a stroke sensor, the operation of the electric motor 40 is controlled by the controller C based on the displacement of the input piston 32, and the ball screw mechanism 41 is controlled. Thus, the primary piston 10 is advanced to follow the displacement of the input piston 32. That is, based on the displacement of the input piston 32, the nut member 46 of the ball screw mechanism 41 is rotated in the direction in which the brake fluid pressure is generated by the operation of the electric motor 40, and the rotation preventing portions 39 of the housing 4 and the screw shaft 47 are When the guide groove 47A comes into contact, the rotation of the screw shaft 47 is restricted and the screw shaft 47 moves forward. As the screw shaft 47 advances, the primary piston 10 is pushed forward by the stepped portion 50 of the screw shaft 47. Thereby, a hydraulic pressure is generated in the primary chamber 16, and this hydraulic pressure is transmitted to the secondary chamber 17 via the secondary piston 11. In this way, the brake fluid pressure generated in the master cylinder 2 is supplied to the brake calipers of the respective wheels via the fluid pressure ports 18 and 19, and braking force is generated.

  At this time, when the brake pedal is operated, a part of the hydraulic pressure in the primary chamber 16 is received by the input piston 32, and the reaction force is fed back to the brake pedal via the input rod 34. Thereby, a desired braking force can be generated with a predetermined boost ratio. The controller C can adjust the relative position between the input piston 32 and the primary piston 10 that follows the input piston 32. The displacement amount of the primary piston 10 can be adjusted with respect to the displacement amount of the input piston 32. The hydraulic pressure output with respect to the operation of the brake pedal can be increased by adjusting forward, and the hydraulic pressure output with respect to the operation of the brake pedal can be decreased by adjusting backward. Accordingly, brake control such as boost control, brake assist control, inter-vehicle stability control, inter-vehicle control, and regenerative cooperative control can be executed. Particularly, by adjusting the input piston 32 so that the primary piston 10 is rearward, the hydraulic pressure output for the operation of the brake pedal is reduced, and the hydraulic pressure in the primary chamber 16 is reduced, so that the braking force by the hydraulic pressure is reduced. The amount of regeneration during regeneration coordination can be increased by suppressing the above. Further, when adjusting the relative position of the input piston 32 with respect to the primary piston 10, the biasing force of the spring 37 or the spring 38 acts on the input piston 32 to increase or decrease the reaction force against the input rod 34. Variations in pedal effort can be suppressed.

  When the output of the electric motor 40 controlled by the controller C reaches the maximum output and the hydraulic pressure in the primary chamber 16 and the thrust of the primary piston 10 are balanced, the primary piston 10 can no longer move forward and stops. When the brake pedal is further depressed in such a full load state, only the input piston 32 moves forward by compressing the spring 37 while the primary piston 10 remains stopped with respect to the advancement of the input rod 34. However, since the primary piston 10 is stopped, an increase in the pedal reaction force fed back to the brake pedal via the input piston 32 and the input rod 34 due to the increase in the hydraulic pressure in the primary chamber 16 with respect to the advance amount of the input piston 32 is caused. The percentage decreases compared to before full load. For this reason, the driver may experience a sense of incongruity because the pedal reaction force decreases during the braking operation. However, when the movement distance of the input piston 32 relative to the housing 4 by the operation of the brake pedal reaches a predetermined distance L, that is, the position where the input piston 32 is in a full load state, the spring receiving portion 54 of the buffer mechanism 51 receives the movable spring support. 78, the reaction force spring 79 is compressed, and the biasing force is applied to the brake pedal as a reaction force to compensate for the decrease in the pedal reaction force. For this reason, it can suppress giving a discomfort to a driver. When the brake pedal is further depressed after the full load state, the step 32A of the input piston 32 comes into contact with the intermediate wall 30 of the primary piston 10, and the primary piston 10 moves forward together with the input piston 32. The reaction force due to the increase in hydraulic pressure increases.

  On the other hand, when the operation of the brake pedal is released, the input piston 32, the primary piston 10 and the secondary piston 11 are retracted to reduce the brake fluid pressure of the master cylinder 2, and the brake pad is retracted to release the brake.

  Next, the operation when the buffer mechanism 51 decelerates the reverse speed of the input rod 34 before coming into contact with the anti-rotation portion 39 will be described with reference to FIGS. First, as shown in FIG. 3A, at the non-braking position of the input rod 34, a gap is generated between the rear end 52A of the cylindrical portion 52 of the buffer mechanism 51 and the front surface 74A of the lock nut 74. ing. In this state, the distance between the spring receiving portion 54 of the cylindrical portion 52 and the front surface 74 </ b> A of the lock nut 74 is set to be longer than the natural length of the coil spring 55. A biasing force that pulls the lock nut 74 is applied.

  When the brake pedal is operated and the input rod 34 moves forward from the non-braking position in FIG. 3A, the coil spring 55 returns to the natural length in the buffer mechanism 51 as shown in FIG. 3B. The front surface 74A of the lock nut 74 abuts on the rear end 52A of the cylindrical portion 52 and moves forward while pushing the cylindrical portion 52. Accordingly, the flange portion 53 of the buffer mechanism 51 is separated from the movable spring receiver 78.

  When the brake pedal is operated so as to release the brake release, the buffer mechanism 51 moves the input rod 34 back together with the cylindrical portion 52 of the buffer mechanism 51 at a constant retraction speed. As shown in (c), the flange portion 53 of the buffer mechanism 51 is in contact with the movable spring receiver 78. Thereafter, when the brake pedal is further operated to be retracted, when a force in the retracting direction is applied to the input rod 34, the cylindrical portion 52 of the buffer mechanism 51 is connected to the flange portion 53 as shown in FIG. Since the movement in the retreating direction is restricted by the contact with the movable spring receiver 78, only the input rod 34 is relatively retreated, and the rear end 52A of the cylindrical portion 52 and the front surface 74A of the lock nut 74 are moved. A gap is created between them. At this time, the distance between the spring receiving portion 54 of the cylindrical portion 52 and the front surface of the lock nut 74 is longer than the natural length of the coil spring 55, and the coil spring 55 is extended from the natural length. A biasing force (tensile force) of the coil spring 55 is applied in the forward direction. Then, as shown in FIG. 4 (e), the urging force of the coil spring 55 is applied to the input rod 34 in the forward direction, so that the retreating speed of the input rod 34 is reduced, and the contact portion 34A of the input rod 34 is contacted. Comes in contact with the pair of detents 39 and retracts to the non-braking position. Thereby, when the input rod 34 is retracted, the flange portion 53 of the buffer mechanism 51 and the movable spring receiver 78 are in contact before the contact portion 34A of the input rod 34 contacts the pair of rotation preventing portions 39. Thereafter, the retreating speed of the input rod 34 is decelerated by the biasing force of the coil spring 55, so that it is possible to reduce the impact when the abutting portion 34A of the input rod 34 abuts against the pair of detent portions 39.

  As described above, according to the electric booster 1 according to the embodiment of the present invention, when the input rod 34 is retracted to the non-braking position, the contact portion 34A is provided with the pair of rotation preventing portions 39. Before the contact, a buffer mechanism 51 that decelerates the retreating speed of the input rod 34 is provided. Thereby, when the input rod 34 is retracted, the shock when the abutting portion 34A of the input rod 34 abuts against the pair of detent portions 39 can be reduced by the operation of the buffer mechanism 51, and the collision noise is reduced. It becomes possible.

  DESCRIPTION OF SYMBOLS 1 Electric booster (boost device), 2 Master cylinder, 3 Actuator (boost means), 4 Housing, 10 Primary piston, 11 Secondary piston, 34 Input rod, 34A Contact part (stopper part), 39 rotations Stopping part (regulating part), 51 shock absorbing mechanism, 52 cylindrical part, 53 flange part, 54 spring receiving part, 55 coil spring

Claims (1)

The input rod moves back and forth in accordance with the operation of the brake pedal, and a boosting means is provided in the housing for propelling the piston of the master cylinder by boosting the operation force of the brake pedal in accordance with the amount of movement of the input rod. In the booster,
One end side of the input rod is disposed in the housing, the other end side extends from the housing, is connected to the brake pedal, and abuts on a restriction portion provided in the housing at an intermediate portion in the axial direction. A stopper portion for restricting the retracted position of the input rod,
The input rod is provided with a buffer mechanism for reducing a reverse speed of the input rod before the stopper portion comes into contact with the restricting portion when the input rod retracts to the non-braking position. Force device.

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