JP2017177835A - Master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master cylinder capable of smoothing a flow of brake fluid in the replenishment of the fluid.SOLUTION: A master cylinder includes: a pressure chamber 68 which is formed by a piston 19 and a cylinder body 15 so as to change pressure according to the operation of a pedal; a replenishing chamber 38 which is formed by an inner peripheral surface 15A of the cylinder body 15 and an outer peripheral surface 19A of the piston 19 and is communicated with a reservoir; a piston seal 35 which annularly seals between the inner peripheral surface 15A of the cylinder body 15 and the outer peripheral surface 19A of the piston 19 and partitions the replenishing chamber 38 and the pressure chamber 68; and a relief port 60 which passes through the piston 19 at the radial direction inside of the piston seal 35 so as to communicate the replenishing chamber 38 with the pressure chamber 68. A portion 60a on a side close to the pedal in at least an end section on the outer peripheral surface 19A side of the piston 19 of an inner wall surface 60A of the relief port 60 is inclined so as to be closer to the pedal toward the outer peripheral surface 19A side.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a master cylinder that supplies hydraulic pressure to a brake cylinder of a vehicle.

  Some master cylinders are provided with a relief port on a piston in order to replenish liquid from a reservoir to a pressure chamber (see, for example, Patent Document 1).

Japanese Patent No. 4141548

  In the above master cylinder, there is a possibility that the flow of the brake fluid may not be smooth when replenishing the pressure chamber from the reservoir through the relief port.

  Accordingly, an object of the present invention is to provide a master cylinder capable of smoothing the flow of brake fluid when replenishing fluid.

  In order to achieve the above object, a master cylinder of the present invention includes at least an end on the outer peripheral surface side of the piston of the inner wall surface of the relief port of the relief port that penetrates the piston and communicates the replenishing chamber and the pressure chamber. The portion closer to the pedal is inclined so that the outer peripheral surface is closer to the pedal.

  According to the master cylinder of the present invention, it becomes possible to make the flow of the brake fluid smooth when the fluid is replenished.

It is sectional drawing which shows the master cylinder of 1st Embodiment. It is a partial expanded sectional view which shows the principal part of the master cylinder of 1st Embodiment. It is sectional drawing which shows the piston of the master cylinder of 1st Embodiment. It is sectional drawing which shows the piston of the master cylinder of 2nd Embodiment. It is a partial expanded sectional view which shows the principal part of the master cylinder of 2nd Embodiment. It is a partial expanded sectional view which shows the principal part of the master cylinder of 3rd Embodiment.

[First Embodiment]
1st Embodiment which concerns on this invention is described based on FIGS. 1-3. A master cylinder 11 of the first embodiment shown in FIG. 1 is connected to a pedal 1 and a brake booster 2 schematically shown in a reduced scale in FIG. 1, and a force corresponding to the operation amount of the pedal 1 is applied to the brake booster 2. It is introduced via the output shaft 3. Then, the master cylinder 11 generates a brake fluid pressure corresponding to the operation amount of the pedal 1 introduced through the brake booster 2 in this way. A reservoir 12 (only a part of which is shown in FIG. 1) for supplying and discharging brake fluid is attached to the master cylinder 11 on the upper side in the vertical direction. In the first embodiment, the reservoir 12 is directly attached to the master cylinder 11, but the reservoir is arranged at a position separated from the master cylinder 11, and the reservoir and the master cylinder 11 are connected by piping. good.

  The master cylinder 11 has a metal cylinder body 15 formed by processing a single material into a bottomed cylindrical shape having a bottom portion 13 and a cylindrical portion 14. As for the cylinder main body 15, the bottom part 13 is arrange | positioned on the opposite side to the pedal 1, and the opening part 16 is arrange | positioned at the pedal 1 side.

  A metal primary piston 18 (piston) is movably disposed on the opening 16 side in the cylinder body 15 so as to partially protrude from the cylinder body 15. Similarly, a metal secondary piston 19 (piston) is movably disposed on the bottom 13 side of the primary piston 18 in the cylinder body 15. An inner peripheral hole 21 having a bottom surface is formed in the primary piston 18. The secondary piston 19 has an inner peripheral hole 22 having a bottom surface. The master cylinder 11 is a so-called plunger type. The master cylinder 11 is a tandem type master cylinder having the two primary pistons 18 and the secondary piston 19 as described above. The present invention is not limited to the application to the tandem type master cylinder, and if it is a plunger type master cylinder, a single type master cylinder in which one piston is arranged in the cylinder body, or three or more types. The present invention can be applied to any plunger type master cylinder such as a master cylinder having a plurality of pistons.

  The cylinder body 15 has a mounting base portion 23 protruding outward in the radial direction of the cylindrical portion 14 (hereinafter referred to as the cylinder radial direction), and in the circumferential direction of the cylindrical portion 14 (hereinafter referred to as the cylinder circumferential direction). Are integrally formed at predetermined positions. The mounting base 23 is formed with mounting holes 24 and mounting holes 25 for mounting the reservoir 12. In the first embodiment, the mounting hole 24 and the mounting hole 25 are in the axial direction of the cylinder portion 14 of the cylinder main body 15 (hereinafter referred to as the cylinder axis) in a state where the positions in the cylinder circumferential direction coincide with each other. It is formed at the top in the vertical direction by shifting the position. The cylinder body 15 is disposed in the vehicle in a posture in which the cylinder axial direction is along the vehicle front-rear direction, and at that time, the bottom portion 13 is disposed on the vehicle front-rear direction front side and the opening 16 is disposed on the vehicle front-rear direction rear side.

  A secondary discharge path 26 is formed in the vicinity of the bottom 13 on the mounting base 23 side of the cylinder portion 14 of the cylinder body 15. Further, a primary discharge path 27 is formed closer to the opening 16 side of the cylinder body 15 than the secondary discharge path 26. Although not shown, the secondary discharge path 26 and the primary discharge path 27 communicate with a brake cylinder such as a disc brake or a drum brake via a brake pipe, and discharge brake fluid toward the brake cylinder. In the first embodiment, the secondary discharge passage 26 and the primary discharge passage 27 are formed so that the positions in the cylinder axial direction are shifted in a state where the positions in the cylinder circumferential direction coincide with each other.

  A sliding inner diameter portion 28 that protrudes inward in the cylinder radial direction and forms an annular shape in the cylinder circumferential direction is formed on the inner peripheral portion on the bottom 13 side of the cylinder portion 14 of the cylinder body 15. The secondary piston 19 is slidably fitted to the minimum inner diameter surface 28a of the sliding inner diameter portion 28, and is guided by the minimum inner diameter surface 28a to move in the cylinder axis direction. A sliding inner diameter portion 29 that protrudes inward in the cylinder radial direction and forms an annular shape in the cylinder circumferential direction is formed on the inner peripheral portion on the opening 16 side of the cylinder portion 14 of the cylinder body 15. The primary piston 18 is slidably fitted to the minimum inner diameter surface 29a of the sliding inner diameter portion 29, and is guided by the minimum inner diameter surface 29a to move in the cylinder axis direction. The minimum inner diameter surface 28 a and the minimum inner diameter surface 29 a are part of the inner peripheral surface 15 </ b> A of the cylinder body 15. The inner peripheral surface 15 </ b> A of the cylinder body 15 is also the inner peripheral surface of the cylindrical portion 14.

  The sliding inner diameter portion 28 is formed with a circumferential groove 30 and a circumferential groove 31 that are formed in this order from the bottom portion 13 side in a plurality of positions, in the cylinder axis direction, in a plurality of shapes, specifically in any two places. Also, the sliding inner diameter portion 29 is formed with a circumferential groove 32 and a circumferential groove 33 that are formed in this order from the bottom 13 side in a plurality of positions, in the cylinder axis direction, in a plurality of positions, specifically in any two places. . The circumferential grooves 30 and 31 have an annular shape in the cylinder circumferential direction and are recessed outward in the cylinder radial direction from the minimum inner diameter surface 28a. The circumferential grooves 32 and 33 have an annular shape in the cylinder circumferential direction and have a minimum inner diameter. It is shaped to be recessed outward in the cylinder radial direction from the surface 29a. The circumferential grooves 30 to 33 are all formed by cutting.

  Of the circumferential grooves 30 to 33, the circumferential groove 30 closest to the bottom 13 is formed in the vicinity of the mounting hole 24 on the bottom 13 side of the mounting hole 24 and the mounting hole 25. An annular piston seal 35 is disposed in the circumferential groove 30 so as to be held in the circumferential groove 30. The radially outer side of the piston seal 35 abuts on the inner peripheral surface of the circumferential groove 30. Further, the secondary piston 19 is fitted inside the piston seal 35 in the radial direction. Here, the inner surface of the circumferential groove 30 constitutes a part of the inner peripheral surface 15A of the cylinder body 15, and therefore the piston seal 35 includes the inner peripheral surface 15A of the cylinder body 15 and the outer peripheral surface of the secondary piston 19. 19A is sealed in an annular shape. The secondary discharge path 26 described above is formed at a position between the bottom 13 of the cylinder body 15 and the circumferential groove 30 and in the vicinity of the bottom 13.

  An annular opening groove 37 that is recessed from the minimum inner diameter surface 28 a is formed on the outer side in the cylinder radial direction on the opening 16 side of the circumferential inner diameter 30 in the sliding inner diameter portion 28 of the cylinder body 15. The opening groove 37 opens the communication hole 36 formed in the mounting portion 24 on the bottom portion 13 side into the cylindrical portion 14. Here, the opening groove 37, the portion of the circumferential groove 30 closer to the opening groove 37 than the piston seal 35, and the secondary piston 19 diametrically opposed thereto are always connected to the reservoir 12 through the communication hole 36. An annular secondary supply chamber 38 (supply chamber) that communicates with each other is formed. In other words, the secondary supply chamber 38 communicating with the reservoir 12 is formed by the inner peripheral surface 15 </ b> A of the cylinder body 15 including the inner surface of the opening groove 37 and the outer peripheral surface 19 </ b> A of the secondary piston 19.

  A communication groove 41 that opens to the circumferential groove 30 on the bottom 13 side of the sliding inner diameter portion 28 of the cylinder body 15 and extends linearly from the circumferential groove 30 toward the bottom 13 side in the cylinder axial direction. Is formed so as to be recessed from the minimum inner diameter surface 28a on the outer side in the cylinder radial direction.

  In the sliding inner diameter portion 28 of the cylinder body 15, the circumferential groove 31 is formed on the side opposite to the circumferential groove 30 of the opening groove 37 in the cylinder axial direction, that is, on the opening 16 side. An annular partition seal 42 is disposed in the circumferential groove 31 so as to be held in the circumferential groove 31.

  The above-mentioned circumferential groove 32 is formed in the sliding inner diameter portion 29 of the cylinder body 15 in the vicinity of the mounting hole 25 on the opening 16 side. An annular piston seal 45 is disposed in the circumferential groove 32 so as to be held in the circumferential groove 32. The piston seal 45 is in contact with the inner peripheral surface of the circumferential groove 32 on the radially outer side. Further, the primary piston 18 is fitted inside the piston seal 45 in the radial direction. Here, the inner surface of the circumferential groove 32 constitutes the inner circumferential surface 15A of the cylinder body 15, and therefore the piston seal 45 is formed between the inner circumferential surface 15A of the cylinder body 15 and the outer circumferential surface 18A of the primary piston 18. Seal the space in a ring. The primary discharge path 27 described above is formed at a position between the circumferential groove 31 and the circumferential groove 32 and in the vicinity of the circumferential groove 31.

  On the opening 16 side of the circumferential groove 32 in the sliding inner diameter portion 29 of the cylinder body 15, an annular opening groove 47 that is recessed from the minimum inner diameter surface 29 a is formed on the outer side in the cylinder radial direction. The opening groove 47 opens a communication hole 46 formed from the attachment hole 25 on the opening 16 side into the cylindrical portion 14. Here, the opening groove 47, the portion of the circumferential groove 32 closer to the opening groove 47 than the piston seal 45, and the primary piston 18 diametrically opposed thereto are always in communication with the reservoir 12 via the communication hole 46. An annular primary supply chamber 48 (supply chamber) is mainly configured. In other words, the primary supply chamber 48 communicating with the reservoir 12 is formed by the inner peripheral surface 15A of the cylinder body 15 including the inner surface of the opening groove 47 and the outer peripheral surface 18A of the primary piston 18.

  A communication groove 51 that opens to the circumferential groove 32 on the bottom 13 side of the sliding inner diameter portion 29 of the cylinder body 15 and extends linearly from the circumferential groove 32 toward the bottom 13 side in the cylinder axial direction. However, it is formed so as to be recessed in the cylinder radial direction outer side than the minimum inner diameter surface 29a.

  A circumferential groove 33 is formed on the side of the sliding inner diameter portion 29 of the cylinder body 15 opposite to the circumferential groove 32 of the opening groove 47, that is, on the opening portion 16. An annular partition seal 52 is disposed in the circumferential groove 33 so as to be held in the circumferential groove 33.

  The secondary piston 19 disposed on the bottom 13 side of the cylinder body 15 includes a first cylindrical portion 55, a bottom portion 56 formed on one side in the axial direction of the first cylindrical portion 55, and a first cylinder of the bottom portion 56. It has the shape which has the 2nd cylindrical part 57 formed in the opposite side to the shape part 55. FIG. The inner peripheral hole 22 is formed by the first cylindrical portion 55 and the bottom portion 56 among these. The secondary piston 19 has inner circumferences of the piston seal 35 and the partition seal 42 provided on the sliding inner diameter portion 28 of the cylinder body 15 in a state where the first cylindrical portion 55 is disposed on the bottom 13 side of the cylinder body 15. And is slidably fitted. The secondary piston 19 has its center axis aligned with the center axis of the cylinder portion 14 of the cylinder body 15, and therefore the radial direction of the secondary piston 19 matches the cylinder radial direction, and the circumferential direction of the secondary piston 19 is the cylinder circumference. The direction of the secondary piston 19 coincides with the direction of the cylinder axis.

  A circle recessed inward in the radial direction from the largest outer diameter surface 19a having the largest diameter in the outer peripheral surface 19A on the radially outer side of the secondary piston 19 is disposed on the outer peripheral portion on the end side opposite to the bottom portion 56 of the first cylindrical portion 55. An annular recess 59 is formed. The recess 59 has a plurality of relief ports 60 penetrating the first cylindrical portion 55 in the radial direction of the secondary piston 19 on the bottom 56 side, and the circumferential direction of the secondary piston 19 is aligned with the axial position of the secondary piston 19. Are formed so as to be radial at equal intervals.

  Between the secondary piston 19 and the bottom portion 13 of the cylinder body 15, there is provided an interval adjusting portion 63 including a secondary piston spring 62 that determines these intervals in a non-braking state where the pedal 1 is not operated. The interval adjusting portion 63 is connected to the locking member 64 that contacts the bottom portion 13 of the cylinder body 15 and the locking member 64 so as to slide only within a predetermined range, and contacts the bottom portion 56 of the secondary piston 19. And a locking member 65. The secondary piston spring 62 is interposed between the locking member 64 and the locking member 65.

  Here, a portion formed by being surrounded by the bottom portion 13 of the cylinder body 15 and the bottom portion 13 side of the cylinder portion 14 and the secondary piston 19 generates a brake fluid pressure and supplies the brake fluid pressure to the secondary discharge passage 26. It is a secondary pressure chamber 68 (pressure chamber). In other words, the secondary piston 19 forms a secondary pressure chamber 68 that supplies hydraulic pressure to the secondary discharge passage 26 between the secondary piston 19 and the cylinder body 15. A portion of the circumferential groove 30 closer to the communication groove 41 than the piston seal 35 and the communication groove 41 form a secondary pressure chamber 68. The piston seal 35 includes a secondary pressure chamber 68 including a communication groove 41 closer to the bottom 13 than the piston seal 35, and the piston seal 35 between the inner peripheral surface 15 A of the cylinder body 15 and the outer peripheral surface 19 A of the secondary piston 19. Also defines a secondary supply chamber 38 including an opening groove 37 on the opening 16 side.

  The relief port 60 passes through the secondary piston 19 on the radially inner side of the piston seal 35. When the secondary piston 19 positions the relief port 60 closer to the opening groove 37 than the piston seal 35 disposed in the circumferential groove 30 and opens the opening in the opening groove 37, the secondary pressure chamber 68 is the secondary supply chamber 38, that is, the reservoir 12. It has come to communicate with. In other words, the relief port 60 allows the secondary supply chamber 38 and the secondary pressure chamber 68 to communicate with each other.

  The relief port 60 is a straight hole having a constant inner diameter, and the central axis thereof is inclined so as to be closer to the pedal 1 in the axial direction of the secondary piston 19 as it is positioned closer to the outer peripheral surface 19A in the radial direction of the secondary piston 19. ing. In other words, the relief port 60 is inclined so as to approach the opening 16 side of the cylinder body 15 in the cylinder axial direction as the central axis thereof is positioned on the secondary supply chamber 38 side in the cylinder radial direction. The relief port 60 is inclined at a predetermined angle with respect to the radial direction of the secondary piston 19.

  Here, the peripheral surface 37a of the opening groove 37 on the opposite side to the pedal 1 is inclined so as to be closer to the opening 16 side in the cylinder axial direction as it is located on the outer side in the cylinder radial direction. Therefore, the relief port 60 is inclined in the same manner as the peripheral surface 37a. The inclination angle of the relief port 60 with respect to the radial direction of the secondary piston 19 is equal to the inclination angle of the circumferential surface 37a of the opening groove 37 with respect to the cylinder radial direction.

  The partition seal 42 held in the circumferential groove 31 of the cylinder body 15 is an integrally molded product made of synthetic rubber, and one side shape of the radial cross section including the center line thereof is C-shaped. The partition seal 42 is in sliding contact with the outer peripheral surface 19 </ b> A of the secondary piston 19 that moves in the cylinder axial direction, and the outer periphery contacts the peripheral groove 31 of the cylinder body 15. Thus, the partition seal 42 always seals the gap between the secondary piston 19 and the partition seal 42 of the cylinder body 15.

  The piston seal 35 held in the circumferential groove 30 of the cylinder body 15 is an integrally molded product made of synthetic rubber such as EPDM, and is a cup seal in which one side shape of the radial cross section including the center line forms an E shape. . The inner periphery of the piston seal 35 is in sliding contact with the outer peripheral surface 19A of the secondary piston 19 that moves in the cylinder axial direction. Further, the outer periphery of the piston seal 35 is in contact with the circumferential groove 30 of the cylinder body 15. The piston seal 35 can seal between the secondary supply chamber 38 and the secondary pressure chamber 68 in a state where the secondary piston 19 has the relief port 60 positioned on the bottom 13 side of the piston seal 35. That is, the piston seal 35 can block communication between the secondary pressure chamber 68 and the secondary supply chamber 38 and the reservoir 12. In this sealed state, the secondary piston 19 slides on the sliding inner diameter portion 28 of the cylinder body 15 and the inner periphery of the piston seal 35 and the partition seal 42 held by the cylinder body 15 and moves to the bottom 13 side. The brake fluid in the secondary pressure chamber 68 is pressurized. The brake fluid pressurized in the secondary pressure chamber 68 is supplied from the secondary discharge passage 26 to the brake cylinder on the wheel side.

  When there is no input from the output shaft 3 of the brake booster 2 and the secondary piston 19 is in a basic position (non-braking position) where the relief port 60 is opened in the opening groove 37 as shown in FIG. In the recess 59 of the secondary piston 19, a part of the relief port 60 wraps in the cylinder axial direction. When the secondary piston 19 moves to the bottom 13 side of the cylinder body 15 and the inner peripheral portion of the piston seal 35 overlaps with the relief port 60, the communication between the secondary pressure chamber 68 and the reservoir 12 is blocked. ing.

  The primary piston 18 disposed on the opening 16 side of the cylinder body 15 includes a first cylindrical portion 71, a bottom portion 72 formed on one side in the axial direction of the first cylindrical portion 71, and a first of the bottom portion 72. The shape which has the 2nd cylindrical part 73 formed in the opposite side to the cylindrical part 71 is comprised. The inner peripheral hole 21 is formed by the first cylindrical portion 71 and the bottom portion 72 among them. The primary piston 18 has the first cylindrical portion 71 disposed on the secondary piston 19 side in the cylinder body 15 and each of the piston seal 45 and the partition seal 52 provided on the sliding inner diameter portion 29 of the cylinder body 15. The inner periphery is slidably fitted. The primary piston 18 has its central axis aligned with the central axis of the cylinder portion 14 of the cylinder body 15, and therefore the radial direction of the primary piston 18 matches the cylinder radial direction, and the circumferential direction of the primary piston 18 is the cylinder circumferential direction. The axial direction of the primary piston 18 matches the cylinder axial direction. Here, the output shaft 3 of the brake booster 2 is inserted inside the second cylindrical portion 73, and the bottom portion 72 is pressed by the output shaft 3.

  In the outer peripheral portion on the end side opposite to the bottom portion 72 of the first cylindrical portion 71, an annular concave portion 75 that is recessed radially inward from the largest outer diameter surface 18 a having the largest diameter on the outer peripheral surface 18 A of the primary piston 18. Is formed. The recess 75 has a plurality of relief ports 76 penetrating the first cylindrical portion 71 in the radial direction of the primary piston 18 on the bottom 72 side, and the axial direction of the primary piston 18 is aligned with the circumferential direction of the primary piston 18. Are formed so as to be radial at equal intervals.

  Between the secondary piston 19 and the primary piston 18, there is provided an interval adjusting portion 79 including a primary piston spring 78 that determines these intervals in a non-braking state where the pedal 1 is not operated. The gap adjusting portion 79 includes a locking member 81 that contacts the bottom 72 of the primary piston 18, a locking member 82 that contacts the bottom 56 of the secondary piston 19, and one end fixed to the locking member 81. And a shaft member 83 that slidably supports the stop member 82 only within a predetermined range. The primary piston spring 78 is interposed between the locking member 81 and the locking member 82.

  Here, a portion surrounded by the cylinder portion 14 of the cylinder body 15, the primary piston 18 and the secondary piston 19 generates a brake fluid pressure and supplies a brake fluid to the primary discharge passage 27 (primary pressure chamber ( Pressure chamber) 85. In other words, the primary piston 18 forms a primary pressure chamber 85 that supplies hydraulic pressure to the primary discharge passage 27 between the secondary piston 19 and the cylinder body 15. A portion of the circumferential groove 32 closer to the communication groove 51 than the piston seal 45 and the communication groove 51 form a primary pressure chamber 85. The piston seal 45 includes a primary pressure chamber 85 including a communication groove 51 closer to the bottom portion 13 than the piston seal 45 between the inner peripheral surface 15 A of the cylinder body 15 and the outer peripheral surface 18 A of the primary piston 18, and the piston seal 45. Also defines a primary supply chamber 48 including an opening groove 47 on the opening 16 side.

  Here, the relief port 76 passes through the primary piston 18 on the radially inner side of the piston seal 45. The primary pressure chamber 85 has a primary replenishment chamber 48 when the primary piston 18 is positioned so that the relief port 76 is positioned closer to the opening groove 47 than the piston seal 45 disposed in the circumferential groove 32 and is opened to the opening groove 47. That is, it communicates with the reservoir 12. In other words, the relief port 76 allows the primary supply chamber 48 and the primary pressure chamber 85 to communicate with each other.

  The relief port 76 is a straight hole having a constant inner diameter, and the central axis thereof is inclined so as to be closer to the pedal 1 in the axial direction of the primary piston 18 as it is positioned closer to the outer peripheral surface 18A in the radial direction of the primary piston 18. ing. In other words, the relief port 76 is inclined so as to be closer to the opening 16 side of the cylinder body 15 in the cylinder axial direction as the central axis thereof is positioned closer to the primary supply chamber 48 side in the cylinder radial direction. The relief port 76 is inclined at a predetermined angle with respect to the radial direction of the primary piston 18.

  Here, the peripheral surface 47a of the opening groove 47 on the side opposite to the pedal 1 is inclined so as to be closer to the opening 16 side in the cylinder axial direction as it is located on the outer side in the cylinder radial direction. Therefore, the relief port 76 is inclined in the same manner as the peripheral surface 47a. The inclination angle of the relief port 76 with respect to the radial direction of the primary piston 18 is equal to the inclination angle of the peripheral surface 47a of the opening groove 47 with respect to the cylinder radial direction.

  The partition seal 52 held in the circumferential groove 33 of the cylinder body 15 is a component common to the partition seal 42 and is an integrally molded product made of synthetic rubber, and the one-side shape of the radial cross section including the center line thereof is C. It has a letter shape. The partition seal 52 is in sliding contact with the outer peripheral surface 18 </ b> A of the primary piston 18 moving in the cylinder axial direction, and the outer periphery is in contact with the peripheral groove 33 of the cylinder body 15. Thereby, the partition seal 52 always seals the gap between the primary piston 18 and the position of the partition seal 52 of the cylinder body 15.

  The piston seal 45 held in the circumferential groove 32 of the cylinder body 15 is a common part with the piston seal 35, and is an integrally formed product made of synthetic rubber such as EPDM, and one side of the radial cross section including the center line thereof. The cup seal has an E-shape. The inner periphery of the piston seal 45 is in sliding contact with the outer peripheral surface 18A of the primary piston 18 that moves in the cylinder axial direction. The outer periphery of the piston seal 45 is in contact with the circumferential groove 32 of the cylinder body 15. The piston seal 45 can seal between the primary replenishing chamber 48 and the primary pressure chamber 85 in a state where the primary piston 18 has the relief port 76 positioned on the bottom 13 side of the piston seal 45. That is, the piston seal 45 can block communication between the primary pressure chamber 85 and the primary supply chamber 48 and the reservoir 12. In this sealed state, the primary piston 18 slides on the sliding inner diameter portion 29 of the cylinder body 15 and the inner periphery of the piston seal 45 and the partition seal 52 held on the cylinder body 15 and moves to the bottom 13 side. The brake fluid in the primary pressure chamber 85 is pressurized. The brake fluid pressurized in the primary pressure chamber 85 is supplied from the primary discharge passage 27 to the brake cylinder on the wheel side.

  When there is no input from the output shaft 3 of the brake booster 2 and the primary piston 18 is in a basic position (non-braking position) where the relief port 76 is opened in the opening groove 47 as shown in FIG. In the recess 75 of the primary piston 18, a part of the relief port 76 wraps in the cylinder axial direction. When the primary piston 18 moves to the bottom 13 side of the cylinder body 15 and the inner peripheral portion of the piston seal 45 is entirely overlapped with the relief port 76, the communication between the primary pressure chamber 85 and the reservoir 12 is blocked. ing.

  When the pedal 1 is operated, the primary piston 18 slides relative to the cylinder body 15 in accordance with the operation. The primary pressure chamber 85 formed by the primary piston 18, the secondary piston 19, and the cylinder body 15 changes in volume and pressure according to the operation of the pedal 1.

  When the pedal 1 is operated, the secondary piston 19 receives a pressing force from the primary piston 18 that slides with respect to the cylinder body 15 in response to the operation via the distance adjusting unit 79 and slides with respect to the cylinder body 15. Will do. The volume and pressure of the secondary pressure chamber 68 formed by the secondary piston 19 and the cylinder body 15 change according to the operation of the pedal 1.

  Here, the structure part which consists of the circumferential groove 30 of the cylinder main body 15 and its vicinity part, the piston seal 35, and the front-end | tip part of the 1st cylindrical part 55 of the secondary piston 19 which is a sliding contact part of the piston seal 35 is made into secondary. This is referred to as a side seal structure SS. Further, the structure portion including the circumferential groove 32 of the cylinder body 15 and the vicinity thereof, the piston seal 45, and the tip end portion of the first cylindrical portion 71 of the primary piston 18 which is a sliding contact portion of the piston seal 45 is provided on the primary side. This is referred to as a seal structure SP. The piston seal 35 and the piston seal 45 are common parts, and the secondary-side seal structure portion SS and the primary-side seal structure portion SP have the same structure. Therefore, in the following, these details will be described with reference to FIGS. 2 and 3 mainly by taking the secondary seal structure SS as an example.

  As shown in FIG. 2, the circumferential groove 30 has a groove bottom surface 30a on the outer side (upper side in FIG. 2) in the cylinder radial direction. Further, the circumferential groove 30 is a groove wall surface 30b that extends inward in the cylinder radial direction from the edge of the groove bottom surface 30a on the opening 16 side of the cylinder body 15 (right side in FIG. 2; hereinafter referred to as the cylinder opening side). have. Further, the circumferential groove 30 has a groove wall surface 30c extending inward in the cylinder radial direction from an end edge of the bottom surface 30a of the cylinder body 15 on the bottom 13 side (left side in FIG. 2; hereinafter referred to as the cylinder bottom side). Have. The groove bottom surface 30 a and the groove wall surfaces 30 b and 30 c are formed on the cylinder body 15 itself, and are formed by cutting the cylinder body 15.

  The recess 59 formed in the secondary piston 19 has a cylindrical surface 59a, a tapered surface 59b, and a tapered surface 59c. The cylindrical surface 59a has a smaller diameter than the cylindrical outer surface 19a having the largest diameter in the secondary piston 19, and has a constant width in the axial direction. The tapered surface 59b extends so as to increase in diameter from the edge of the cylindrical surface 59a on the cylinder opening side toward the cylinder opening side, and is connected to a portion on the cylinder opening side of the concave portion 59 of the maximum outer diameter surface 19a. Yes. The tapered surface 59c extends so as to increase in diameter from the edge of the cylindrical surface 59a on the cylinder bottom side toward the cylinder bottom side, and is connected to a portion on the cylinder bottom side of the concave portion 59 of the maximum outer diameter surface 19a. Yes.

  The cylindrical surface 59a, the tapered surface 59b, and the tapered surface 59c are formed around the central axis of the secondary piston 19 similarly to the maximum outer diameter surface 19a. The relief port 60 that is always in communication with the secondary pressure chamber 68 is formed at a position that spans both the cylindrical surface 59a and the tapered surface 59b. In other words, the end of the cylinder bottom side is formed on the cylindrical surface 59a and the cylinder opening. The end portions on the side are respectively located on the tapered surface 59b.

  The piston seal 35 disposed in the circumferential groove 30 has a base portion 101, an inner peripheral lip portion 102, an outer peripheral lip portion 103, and an intermediate lip portion 104. The base 101 is disposed on the cylinder opening side of the piston seal 35, and has an annular plate shape parallel to the axis orthogonal surface of the piston seal 35. The inner peripheral lip 102 has an annular cylindrical shape that protrudes from the inner peripheral edge of the base 101 toward the cylinder bottom along the cylinder axial direction. The outer peripheral lip 103 has an annular cylindrical shape that protrudes from the outer peripheral edge of the base 101 toward the cylinder bottom along the cylinder axial direction. The intermediate lip 104 is in the shape of an annular cylinder between the outer lip 103 and the inner lip 102 and protruding from the base 101 toward the cylinder bottom along the cylinder axial direction. In the intermediate lip 104, the amount of protrusion in the cylinder axial direction from the base 101 is larger than the amount of protrusion from the base 101 of the inner peripheral lip 102 and outer peripheral lip 103.

  The piston seal 35 is in sliding contact with the outer peripheral surface 19A of the secondary piston 19 including the cylindrical surface 59a, the tapered surface 59b, the tapered surface 59c, and the maximum outer diameter surface 19a of the secondary piston 19 that moves in the cylinder axial direction. As a result, the outer peripheral lip 103 abuts against the groove bottom surface 30 a of the peripheral groove 30 constituting the inner peripheral surface 15 A of the cylinder body 15.

  As shown in FIG. 3, the plurality of relief ports 60 formed in the first cylindrical portion 55 of the secondary piston 19 are, as shown in FIG. 2, the pedal 1 in the direction of the central axis of the secondary piston 19 on the inner wall surface 60 </ b> A. 2a (the right side in FIG. 2; hereinafter referred to as the pedal side) is inclined so that the outer peripheral surface 19A side in the radial direction of the secondary piston 19 is positioned on the pedal side in the axial direction of the secondary piston 19. doing. Similarly, the inclined portion 60b of the inner wall surface 60A on the side farther from the pedal 1 in the direction of the central axis of the secondary piston 19 (left side in FIG. 2; hereinafter referred to as the non-pedal side) is also the outer peripheral surface 19A in the radial direction of the secondary piston 19. The side is inclined so as to be located on the pedal side in the axial direction of the secondary piston 19.

  The relief port 60 is inclined in the same manner as the circumferential surface 37a of the opening groove 37 on the counter pedal side, and the inclination angle α with respect to the radial direction of the secondary piston 19 is inclined with respect to the cylinder radial direction of the circumferential surface 37a of the opening groove 37. It is equivalent to the angle β. Therefore, the inclination angle of the inclined portions 60a and 60b with respect to the radial direction of the secondary piston 19 is also equal to the inclination angle β of the peripheral surface 37a of the opening groove 37 with respect to the cylinder radial direction.

  When there is no input from the output shaft 3 side of the brake booster 2 shown in FIG. 1 and the master cylinder 11 is in the basic state, the secondary piston 19 is located at the basic position (non-braking position) shown in FIG. When the secondary piston 19 is in this basic position, the relief port 60 is positioned closer to the opening groove 37 than the piston seal 35 disposed in the circumferential groove 30, and the secondary piston 19 is positioned so as to open to the opening groove 37. ing. In this state, the inclined portion 60 a of the relief port 60 and the peripheral surface 37 a of the opening groove 37 wrap the position in the cylinder axial direction, and the secondary pressure chamber 68 and the secondary supply chamber 38 communicate with each other via the relief port 60. It is supposed to be. When the secondary piston 19 is in the basic position, the piston seal 35 has an inner peripheral portion at the position of the cylindrical surface 59 a of the concave portion 59 of the secondary piston 19, and an inner peripheral portion of the base 101 is one of the relief ports 60. The position in the cylinder axial direction is superimposed on the part.

  When there is input from the output shaft 3 side of the brake booster 2 and the secondary piston 19 moves from the basic position to the cylinder bottom side, the piston seal 35 slides on the outer peripheral surface 19A of the secondary piston 19 and the base 101 Rides on the tapered surface 59b of the recess 59.

  When the secondary piston 19 further moves to the cylinder bottom side, the piston seal 35 that is in sliding contact with the outer peripheral surface 19A of the secondary piston 19 passes over the relief port 60 and closes the relief port 60, and the secondary pressure chamber 68 and the secondary replenishing chamber 38. The secondary pressure chamber 68 is sealed by blocking communication with the secondary pressure chamber 68. As a result, the hydraulic pressure in the secondary pressure chamber 68 is increased by the movement of the secondary piston 19 to the cylinder bottom side, and the brake fluid in the secondary pressure chamber 68 is supplied from the secondary discharge passage 26 shown in FIG. Will be. When the secondary piston 19 further moves to the cylinder bottom side after the relief port 60 is closed, the piston seal 35 rides on the cylinder opening side portion of the maximum outer diameter surface 19a of the secondary piston 19 as a whole.

  If the pedal 1 shown in FIG. 1 is returned from the state in which the secondary piston 19 has moved to the cylinder bottom side, the secondary piston 19 attempts to return to the basic position by the interval adjusting unit 63. The movement of the secondary piston 19 increases the volume of the secondary pressure chamber 68. At that time, the return of the brake fluid through the brake pipe cannot catch up with the volume expansion of the secondary pressure chamber 68. Then, after the hydraulic pressure in the secondary supply chamber 38 that is atmospheric pressure and the hydraulic pressure in the secondary pressure chamber 68 become equal, the hydraulic pressure in the secondary pressure chamber 68 becomes negative, and the secondary supply chamber 38 that is atmospheric pressure has a negative pressure. The hydraulic pressure in the secondary pressure chamber 68 is lower than the hydraulic pressure.

  Then, the negative pressure in the secondary pressure chamber 68 separates the outer peripheral lip 103 shown in FIG. 2 of the piston seal 35 from the groove bottom surface 30a. As a result, the brake fluid in the secondary supply chamber 38 is supplied to the secondary pressure chamber 68 via the outer peripheral lip 103, the groove bottom surface 30a, and the gap. As a result, the speed at which the hydraulic pressure in the secondary pressure chamber 68 is returned from the negative pressure state to the atmospheric pressure is increased.

  Further, at the time when the secondary piston 19 returns to the basic position, the relief port 60 of the secondary piston 19 communicates with the secondary replenishing chamber 38 beyond the piston seal 35, and the brake fluid in the secondary replenishing chamber 38 is discharged to the relief port. As a result, the hydraulic pressure in the secondary pressure chamber 68 is returned from the negative pressure state to the atmospheric pressure.

  In the master cylinder described in Patent Document 1, a relief port is provided in the piston in order to replenish liquid from the reservoir to the pressure chamber. The relief port is a straight hole orthogonal to the axial direction of the piston. When the pedal suddenly returns, the pressure difference between the negative pressure chamber and the atmospheric pressure replenishment chamber rapidly increases, so it is not sufficient to replenish the fluid at the piston seal, and even at the end of the pedal return, The differential pressure between the pressure chamber and the supply chamber is large. For this reason, when the piston relief port crosses the piston seal and communicates with the replenishing chamber at the end of the return of the pedal, the brake fluid in the replenishing chamber is introduced into the pressure chamber all at once in order to release the negative pressure in the pressure chamber. Will be. At that time, if the relief port is a straight hole orthogonal to the axial direction of the piston, the flow of brake fluid during fluid replenishment may not be smooth. For example, the brake fluid flow may be separated at the edge of the relief port on the replenishment chamber side, and it may take time to replenish the fluid. In some cases, abnormal noise such as canning noise may occur. .

  In contrast, in the master cylinder 11 of the first embodiment, the central axis of the relief port 60 provided in the first cylindrical portion 55 of the secondary piston 19 approaches the pedal 1 toward the outer peripheral surface 19A side of the secondary piston 19. So as to be inclined. For this reason, the liquid flows from the secondary supply chamber 38 including the opening groove 37 positioned on the pedal 1 side relative to the relief port 60 to the secondary pressure chamber 68 inside the first cylindrical portion 55 via the relief port 60. Brake fluid flows smoothly. Therefore, separation of the brake fluid flow that occurs at the edge portion of the relief port 60 on the secondary supply chamber 38 side can be suppressed, the time for supplying the fluid can be reduced, and abnormal noise such as canning noise can be generated. Can be suppressed.

“Second Embodiment”
Next, the second embodiment will be described mainly with reference to FIGS. 4 and 5 focusing on the differences from the first embodiment. In addition, about the site | part which is common in 1st Embodiment, it represents with the same name and the same code | symbol. Also in the second embodiment, the secondary-side seal structure SS including the secondary piston 19 will be described in detail as an example, but the primary-side seal structure SP is the same structure as the seal structure SS, and the same There is an effect.

  In the second embodiment, as shown in FIG. 4, a relief port 160 different from the relief port 60 of the first embodiment is provided at the position of the recess 59 in the first cylindrical portion 55 of the secondary piston 19. . The relief port 160 is a tapered hole whose central axis extends in the radial direction of the secondary piston 19 and has a larger diameter toward the outer peripheral surface 19 </ b> A side of the secondary piston 19. The relief port 160 is a tapered hole over the entire length in the central axis direction.

  Accordingly, as shown in FIG. 5, the relief port 160 has a pedal-side inclined portion 160 a in the central axis direction of the secondary piston 19 of the inner wall surface 160 </ b> A that is closer to the outer peripheral surface 19 </ b> A side in the radial direction of the secondary piston 19. Inclined so as to be located on the pedal side in the axial direction of the piston 19. In addition, the relief port 160 has an inner wall surface 160 </ b> A that is inclined in the axial direction of the secondary piston 19 such that the inclined portion 160 b on the counter pedal side in the central axis direction of the secondary piston 19 is closer to the outer peripheral surface 19 </ b> A side in the radial direction of the secondary piston 19. Inclined to be located on the pedal side.

  Here, in the relief port 160, the inclined portion 160a of the inner wall surface 160A is inclined in the same manner as the peripheral surface 37a of the opening groove 37, and the inclination angle γ of the inclined portion 160a with respect to the radial direction of the secondary piston 19 is: This is equal to the inclination angle β of the circumferential surface 37a of the opening groove 37 with respect to the cylinder radial direction.

  When the secondary piston 19 is located at the basic position (non-braking position) shown in FIG. 5, the relief port 160 is positioned closer to the opening groove 37 than the piston seal 35 disposed in the circumferential groove 30. It is located at a position opening in the groove 37. In this state, the inclined portion 160a of the relief port 160 and the peripheral surface 37a of the opening groove 37 wrap the position in the cylinder axial direction, and the secondary pressure chamber 68 and the secondary supply chamber 38 communicate with each other via the relief port 160. It is supposed to be.

  The relief port 160 of the second embodiment described above is the same as the first embodiment because the inclined portion 160a of the inner wall surface 160A is inclined in the same manner as the peripheral surface 37a on the side opposite to the pedal of the opening groove 37. The brake fluid that flows from the secondary supply chamber 38 including the opening groove 37 positioned on the pedal 1 side relative to the relief port 160 to the secondary pressure chamber 68 inside the first cylindrical portion 55 via the relief port 160 when the fluid is supplied. The flow becomes smooth. Therefore, separation of the brake fluid flow that occurs at the edge portion of the relief port 160 on the secondary supply chamber 38 side can be suppressed, the time for supplying the fluid can be reduced, and abnormal noise such as canning noise can be generated. Can be suppressed.

  Further, the relief port 160 in the second embodiment has a central axis extending in the radial direction (axial orthogonal direction) of the secondary piston 19. For this reason, when the secondary piston 19 is made of, for example, an aluminum alloy, the relief port 160 can be formed by punching with a press. Therefore, the productivity of the secondary piston 19 can be improved.

  In addition, in the relief port 160 in the second embodiment, the inclined portion 160b on the counter-pedal side in the central axis direction of the secondary piston 19 of the inner wall surface 160A is counter-pedal in the axial direction of the secondary piston 19 toward the outer peripheral surface 19A side. Since it inclines so that it may be located in the side, when the secondary piston 19 returns, it will contact an obtuse angle with respect to the piston seal 35. Therefore, the relief port 160 can move smoothly with respect to the piston seal 35.

“Third Embodiment”
Next, the second embodiment will be described mainly based on FIG. 6 with a focus on differences from the second embodiment. In addition, about the site | part which is common in 2nd Embodiment, it represents with the same name and the same code | symbol. Also in the third embodiment, the secondary-side seal structure portion SS will be described in detail by way of example, but the primary-side seal structure portion SP has the same structure as the seal structure portion SS, and has the same effects.

  In the third embodiment, a relief port 260 different from the relief port 160 of the second embodiment is provided at the position of the recess 59 in the first cylindrical portion 55 of the secondary piston 19. The relief port 260 has a central axis extending in the radial direction of the secondary piston 19. In the relief port 260, the end of the secondary piston 19 on the outer peripheral surface 19A side is a tapered hole portion 261 having a larger diameter on the outer peripheral surface 19A side, and the end on the opposite side of the outer peripheral surface 19A is The straight hole 262 has a constant diameter.

  Thereby, the relief port 260 is on the pedal side of the inner wall surface 260 </ b> A in the central axis direction of the secondary piston 19, and the inclined portion 260 a provided in the tapered hole portion 261 is closer to the outer peripheral surface 19 </ b> A side in the radial direction of the secondary piston 19. The secondary piston 19 is inclined so as to be positioned on the pedal side in the axial direction. In addition, the relief port 260 is located on the inner wall surface 260 </ b> A on the side opposite to the pedal in the central axis direction of the secondary piston 19, and the inclined portion 260 b provided in the tapered hole portion 261 is closer to the outer peripheral surface 19 </ b> A side in the radial direction of the secondary piston 19. Further, the secondary piston 19 is inclined so as to be located on the side opposite to the pedal in the axial direction.

  Here, in the relief port 260, the inclined portion 260a of the inner wall surface 260A is inclined in the same manner as the peripheral surface 37a on the counter pedal side of the opening groove 37, and the inclined portion 260a is inclined with respect to the radial direction of the secondary piston 19. The angle γ is equal to the inclination angle β of the circumferential surface 37a of the opening groove 37 with respect to the cylinder radial direction.

  When the secondary piston 19 is located at the basic position (non-braking position) shown in FIG. 6, the relief port 260 is positioned closer to the opening groove 37 than the piston seal 35 disposed in the circumferential groove 30. It is located at a position opening in the groove 37. In this state, the inclined portion 260a of the relief port 260 and the circumferential surface 37a of the opening groove 37 wrap the position in the cylinder axial direction, and the secondary pressure chamber 68 and the secondary supply chamber 38 communicate with each other via the relief port 260. It is supposed to be.

  In the relief port 260 of the third embodiment described above, the inclined portion 260a of the inner wall surface 260A is inclined in the same manner as the peripheral surface 37a of the opening groove 37 on the side opposite to the pedal. For this reason, as in the first and second embodiments, the first cylindrical portion 55 is provided via the relief port 260 from the secondary supply chamber 38 including the opening groove 37 positioned on the pedal side of the relief port 260 when replenishing liquid. The flow of the brake fluid flowing into the secondary pressure chamber 68 on the inner side of the engine becomes smooth. Therefore, separation of the brake fluid flow that occurs at the edge portion of the relief port 260 on the secondary supply chamber 38 side can be suppressed, the time for supplying the fluid can be shortened, and abnormal noise such as canning noise can be generated. Can be suppressed.

  The relief port 260 in the third embodiment also has a central axis extending in the radial direction of the secondary piston 19. For this reason, the relief port 260 can be formed in the secondary piston 19 by punching by pressing. Therefore, the productivity of the secondary piston 19 can be improved.

  In addition, the relief port 260 in the third embodiment is inclined so that the inclined portion 260b of the inner wall surface 260A is located on the counter pedal side in the axial direction of the secondary piston 19 as the outer peripheral surface 19A side. When the secondary piston 19 returns, it comes into contact with the piston seal 35 at an obtuse angle. Therefore, the relief port 260 can move smoothly with respect to the piston seal 35.

  According to the second and third embodiments described above, the relief port has a central axis extending in the radial direction of the secondary piston 19, and at least the end portion on the outer peripheral surface 19A side of the secondary piston 19 is larger toward the outer peripheral surface 19A side. If it becomes the diameter, it will suffice.

  According to the first to third embodiments described above, the relief port is connected to the pedal 1 so that at least the portion of the inner wall surface closer to the pedal 1 at the outer peripheral surface 19A side of the secondary piston 19 is closer to the outer peripheral surface 19A side. It suffices if it is inclined to approach.

  In the first to third embodiments described above, the first of the secondary piston 19 having the circumferential groove 30 and the opening groove 37 of the cylinder body 15, the piston seal 35, the recess 59 and the relief ports 60, 160, 260. The secondary seal structure SS including the cylindrical portion 55 has been described in detail as an example, but the circumferential groove 32 and the opening groove 47 similar to the circumferential groove 30 and the opening groove 37 and the piston seal similar to the piston seal 35 are described. 45 and the primary side seal structure SP including the first cylindrical portion 71 of the primary piston 18 having the recess 75 and the relief port 76 similar to the recess 59 and the relief port 60 have the same structure. Therefore, the seal structure SP can achieve the same effects as the seal structure SS.

  In the above embodiment, a cylinder body, a piston that slides with respect to the cylinder body in response to an operation of the pedal, and a pressure that is formed by the piston and the cylinder body and changes in volume in accordance with the operation of the pedal. A chamber, an inner peripheral surface of the cylinder body and an outer peripheral surface of the piston, and an annular seal between the replenishing chamber communicating with the reservoir, and the inner peripheral surface of the cylinder body and the outer peripheral surface of the piston. And a piston seal that divides the replenishing chamber and the pressure chamber, and the piston penetrates the piston radially inward of the piston seal and communicates the replenishing chamber and the pressure chamber. A port is formed, and the relief port is a portion of the inner wall surface of the relief port on the side closer to the pedal at the end on the outer peripheral surface side of the piston , I am inclined as the outer peripheral surface closer to the pedal. For this reason, the flow of the brake fluid flowing from the replenishment chamber to the primary pressure chamber through the relief port at the time of fluid replenishment becomes smooth.

  Since the central axis of the relief port is inclined so as to approach the pedal toward the outer peripheral surface side of the piston, the brake fluid flowing from the replenishing chamber to the primary pressure chamber via the relief port at the time of replenishing the fluid. The flow becomes smooth.

  The relief port has a central axis extending in the radial direction of the piston, and at least an end portion on the outer peripheral surface side of the piston has a larger diameter toward the outer peripheral surface side. It is possible to improve the performance.

DESCRIPTION OF SYMBOLS 1 Pedal 11 Master cylinder 12 Reservoir 15 Cylinder main body 15A Inner peripheral surface 18 Primary piston (piston)
18A, 19A Outer peripheral surface 19 Secondary piston (piston)
35, 45 Piston seal 38 Secondary supply chamber (supply chamber)
48 Primary supply room (supply room)
60, 76, 160, 260 Relief port 60A, 160A, 260A Inner wall surface 60a, 160a, 260a Inclined portion (portion close to pedal)
68 Secondary pressure chamber (pressure chamber)
85 Primary pressure chamber (pressure chamber)

Claims (3)

A cylinder body,
A piston that slides relative to the cylinder body in response to an operation of the pedal;
A pressure chamber formed by the piston and the cylinder body, the volume of which changes according to the operation of the pedal;
A replenishment chamber formed by an inner peripheral surface of the cylinder body and an outer peripheral surface of the piston, and in communication with a reservoir;
A piston seal that annularly seals between the inner peripheral surface of the cylinder body and the outer peripheral surface of the piston to partition the replenishing chamber and the pressure chamber;
The piston is formed with a relief port that penetrates the piston radially inward of the piston seal and communicates the replenishing chamber and the pressure chamber.
The relief port is inclined such that at least a portion of the inner wall surface of the relief port on the outer peripheral surface side of the piston closer to the pedal is closer to the pedal toward the outer peripheral surface side. Cylinder.   2. The master cylinder according to claim 1, wherein the relief port is inclined such that a central axis thereof approaches the pedal toward an outer peripheral surface side of the piston.   2. The master cylinder according to claim 1, wherein a central axis of the relief port extends in a radial direction of the piston, and at least an end portion on an outer peripheral surface side of the piston has a larger diameter toward the outer peripheral surface side.

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