JP2016101898A - Master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master cylinder capable of suppressing deterioration in performance of replenishing brake liquid.SOLUTION: A step part 91 having an inner peripheral face 89a extending toward a cylinder opening is formed in a circumferential wall 89 at the cylinder opening side of a circumferential wall 32. A piston seal 45 has a toric base part 101 in which are protrudingly provided an inner peripheral lip part 102 that slidably contacts an outer peripheral face 18A of a piston 18 and an outer peripheral lip part 103 that contacts a circumferential groove 32. In the base part 101 are formed protrusions 122 that protrude toward the cylinder opening. The protrusions 122 are configured so that outer faces 122a thereof in a radial direction are arranged at positions slidable relative to the inner peripheral face 89b of the step part 91 with the piston 18 moved to a position for generating liquid pressure.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 have a cup seal disposed in a circumferential groove of a cylinder body (see, for example, Patent Document 1).

International Publication No. 2014/119611

  In the above master cylinder, a step portion having an inner peripheral surface extending toward the opening portion is formed on the peripheral wall of the peripheral groove on the opening portion side of the cylinder main body. When a hydraulic pressure is generated, a cup seal is formed on the step portion. An annular projecting piece projecting from the base portion is pressed. The cup seal regulates the leakage of brake fluid from the pressure chamber to the replenishment chamber, while allowing the brake fluid to be replenished from the replenishment chamber to the pressure chamber, but the annular protrusion is pressed against the step. If the frictional resistance between them increases, the cup seal cannot move smoothly in the circumferential groove, and the brake fluid supply performance from the supply chamber to the pressure chamber may deteriorate.

  Therefore, an object of the present invention is to provide a master cylinder capable of suppressing a decrease in brake fluid replenishment performance.

  In order to achieve the above object, in the master cylinder of the present invention, the peripheral wall on the opening side of the cylinder body in the circumferential groove is formed with a step portion having an inner peripheral surface extending to the opening side. Has an annular base portion protruding from an inner peripheral lip portion that is in sliding contact with the outer peripheral surface of the piston and an outer peripheral lip portion that is in contact with the peripheral groove of the cylinder body. A protrusion is formed, and the protrusion has a radially outer surface disposed at a position where the piston can slide with respect to the inner peripheral surface of the stepped portion in a state where the piston moves to a position where hydraulic pressure is generated. The configuration was made.

  According to the master cylinder of the present invention, it is possible to suppress a decrease in brake fluid supply performance.

It is sectional drawing which shows the master cylinder of embodiment. It is a partial expanded sectional view which shows the principal part of the master cylinder of embodiment, Comprising: (a) shows the state at the time of hydraulic pressure generation | occurrence | production, (b) shows the state at the time of replenishment of brake fluid. The piston seal of the master cylinder of embodiment is shown, Comprising: (a) is a front view, (b) is a side view. The piston seal of the master cylinder of embodiment is shown, Comprising: (a) is XX sectional drawing of FIG. 3, (b) is a rear view. It is a perspective view which shows the piston seal of the master cylinder of embodiment.

  An embodiment according to the present invention will be described with reference to the drawings. In the master cylinder 11 of the present embodiment shown in FIG. 1, a force corresponding to an operation amount of a brake pedal (not shown) is introduced via an output shaft of a brake booster (not shown). The brake fluid pressure is generated. 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 present embodiment, the reservoir 12 is directly attached to the master cylinder 11, but the reservoir may be disposed at a position separated from the master cylinder 11, and the reservoir and the master cylinder 11 may be connected by piping. .

  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. A metal primary piston (piston) 18 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 (piston) 19 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 present embodiment, the mounting hole 24 and the mounting hole 25 are positioned in the axial direction (hereinafter referred to as the cylinder axis) of the cylinder portion 14 of the cylinder body 15 in a state where the positions in the cylinder circumferential direction coincide with each other. Is formed at the top in the vertical direction. The cylinder body 15 is disposed on the vehicle in a posture in which the cylinder axis direction is along the vehicle front-rear direction.

  A secondary discharge passage (discharge passage) 26 is formed in the vicinity of the bottom portion 13 on the mounting base portion 23 side of the cylinder portion 14 of the cylinder body 15. Further, a primary discharge path (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 present embodiment, the secondary discharge path 26 and the primary discharge path 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 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.

  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 and the communication hole 36 constitute a secondary supply path (supply path) 38 provided in the cylinder body 15 and always communicating with the reservoir 12.

  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. The communication groove 41 communicates the secondary discharge passage 26 and the circumferential groove 30 formed at a position between the bottom portion 13 and the circumferential groove 30 and in the vicinity of the bottom portion 13 via a secondary pressure chamber 68 described later. Is.

  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.

  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 and the communication hole 46 mainly constitute a primary supply path (supply path) 48 provided in the cylinder body 15 and always communicating with the reservoir 12.

  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. The communication groove 51 has a primary discharge passage 27 formed between the circumferential groove 31 and the circumferential groove 32 and in the vicinity of the circumferential groove 31, and the circumferential groove 32 via a primary pressure chamber 85 described later. To communicate.

  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.

  In the outer peripheral portion on the end side opposite to the bottom portion 56 of the first cylindrical portion 55, an annular concave portion 59 that is recessed radially inward from the largest outer diameter surface 19 a having the largest diameter on the outer peripheral surface 19 A of the secondary piston 19. Is formed. In the recess 59, a plurality of ports 60 penetrating in the cylinder radial direction are formed on the bottom 56 side so as to be radially arranged at equal intervals in the cylinder circumferential direction.

  Between the secondary piston 19 and the bottom 13 of the cylinder body 15, there is provided an interval adjusting portion 63 including a secondary piston spring 62 that determines the interval in a non-braking state in which there is no input from an output shaft of a brake booster (not shown). ing. 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. A secondary pressure chamber (pressure chamber) 68 is formed. 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. The secondary pressure chamber 68 communicates with the secondary supply path 38, that is, the reservoir 12 when the secondary piston 19 is in a position for opening the port 60 into the opening groove 37.

  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 one side shape of the radial cross section including the center line thereof is 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 passage 38 and the secondary pressure chamber 68 in a state where the secondary piston 19 positions the port 60 closer to the bottom 13 than the piston seal 35. That is, the piston seal 35 can block communication between the secondary pressure chamber 68 and the secondary supply path 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 of a brake booster (not shown) and the secondary piston 19 is in a basic position (non-braking position) where the 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 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 is entirely overlapped with the port 60, the communication between the secondary pressure chamber 68 and the reservoir 12 is blocked. Yes.

  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. Here, an output shaft of a brake booster (not shown) is inserted inside the second cylindrical portion 73, and the bottom portion 72 is pressed by this output shaft.

  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 is formed with a plurality of ports 76 penetrating in the radial direction on the bottom 72 side so as to be radially arranged at equal intervals in the cylinder circumferential direction.

  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 without input from an output shaft of an unillustrated brake booster. 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. The primary pressure chamber 85 communicates with the primary replenishment path 48, that is, the reservoir 12 when the primary piston 18 is in a position where the port 76 is opened to the opening groove 47.

  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 shape is E-shaped. 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 supply passage 48 and the primary pressure chamber 85 in a state where the primary piston 18 has the 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 path 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 of a brake booster (not shown) and the primary piston 18 is in the basic position (non-braking position) where the 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 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 overlaps with the port 76, the communication between the primary pressure chamber 85 and the reservoir 12 is blocked. Yes.

  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 to 5 mainly using the seal structure portion SP on the primary side as an example.

  As shown in FIG. 2, the circumferential groove 32 has a groove bottom portion 88 on the outer side in the cylinder radial direction (upper side in FIG. 2). Further, the circumferential groove 32 has a circumferential wall 89 extending inward in the cylinder radial direction from the edge of the groove bottom 88 on the side of the opening 16 of the cylinder body 15 (the right side in FIG. 2; hereinafter referred to as the cylinder opening side). Have. Furthermore, the circumferential groove 32 has a circumferential wall 90 that extends inward in the cylinder radial direction from the edge of the groove bottom 88 on the bottom 13 side of the cylinder body 15 (left side in FIG. 2; hereinafter referred to as the cylinder bottom side). doing. The groove bottom portion 88, the peripheral wall 89, and the peripheral wall 90 are formed in the cylinder body 15 itself, and are formed by cutting the cylinder body 15.

  The groove bottom portion 88 has a groove bottom surface 88a. The groove bottom surface 88a has a cylindrical surface centered on the cylinder axis, and the length in the cylinder axis direction is constant.

  The peripheral wall 89 on the cylinder opening side of the peripheral groove 32 has an outer wall surface 89a, an inner peripheral surface 89b, and an inner wall surface 89c. The outer wall surface 89a extends inward in the cylinder radial direction from the edge of the groove bottom surface 88a on the cylinder opening side. The outer wall surface 89a is a flat surface parallel to the orthogonal surface of the cylinder axis. The outer wall surface 89a has a constant inner diameter and a constant outer diameter, a constant width in the cylinder radial direction, and an annular surface centered on the cylinder axis.

  The inner peripheral surface 89b extends from the inner end edge in the cylinder radial direction of the outer wall surface 89a to the cylinder opening side. The inner peripheral surface 89b forms a cylindrical surface centered on the cylinder axis, and the length in the cylinder axis direction is constant over the entire periphery. The inner peripheral surface 89b is orthogonal to the outer wall surface 89a.

  The inner wall surface 89c extends inwardly in the cylinder radial direction from the edge of the inner peripheral surface 89b on the cylinder opening side. The inner wall surface 89c is a flat surface parallel to the orthogonal surface of the cylinder axis. The inner wall surface 89c has a constant inner diameter and a constant outer diameter, a constant width in the cylinder radial direction, and has an annular shape centering on the cylinder axis. The edge portion on the small diameter side of the inner wall surface 89c and the minimum inner diameter surface 29a of the sliding inner diameter portion 29 are connected by R chamfering.

  By providing the cylindrical inner peripheral surface 89b between the inner wall surface 89c and the outer wall surface 89a, the inner wall surface 89c as a whole is offset from the outer wall surface 89a toward the cylinder opening side. A step including a portion including the inner peripheral surface 89b side of the outer wall surface 89a, the inner peripheral surface 89b, and the inner peripheral surface 89b side of the inner wall surface 89c so that the inner side in the cylinder radial direction is located closer to the cylinder opening than the outer side. The step part 91 which makes a shape is comprised. The width of the outer wall surface 89a in the cylinder radial direction is wider than the width of the inner wall surface 89c in the cylinder radial direction, and the inner peripheral surface 89b of the step 91 is located on the inner peripheral side of the peripheral wall 89 in the cylinder radial direction. ing. In other words, the distance between the inner peripheral surface 89 b of the step portion 91 and the groove bottom surface 88 a of the groove bottom portion 88 is larger than the distance from the minimum inner diameter surface 29 a of the sliding inner diameter portion 29.

  A peripheral wall 90 on the cylinder bottom side of the peripheral groove 32 faces the peripheral wall 89 and has an outer wall surface 90a, a curved surface 90b, and an inner wall surface 90c. The outer wall surface 90a extends inward in the cylinder radial direction from the cylinder bottom side of the groove bottom portion 88. The outer wall surface 90a is a flat surface parallel to the orthogonal surface of the cylinder axis. The outer wall surface 90a has a constant inner diameter and a constant outer diameter, a constant width in the cylinder radial direction, and has an annular shape centering on the cylinder axis. The edge on the large diameter side of the outer wall surface 90a and the edge on the cylinder bottom side of the groove bottom surface 88a are connected by R chamfering.

  The curved surface 90b extends from the inner end edge in the cylinder radial direction of the outer wall surface 90a to the inside in the cylinder radial direction so as to be located on the cylinder bottom side toward the inner side in the cylinder radial direction. The curved surface 90b has an arc shape in which the cross section of the surface including the cylinder axis has a center inside the circumferential groove 32.

  The inner wall surface 90c extends inwardly in the cylinder radial direction from the inner edge of the curved surface 90b in the cylinder radial direction. The inner wall surface 90c is a flat surface parallel to the orthogonal surface of the cylinder axis. The inner wall surface 90c has a constant inner diameter, a constant outer diameter, and a constant width in the cylinder radial direction except for the opening portion of the communication groove 51, and has an annular shape centering on the cylinder axis. The edge portion on the small diameter side of the inner wall surface 90c and the minimum inner diameter surface 29a of the sliding inner diameter portion 29 are connected by R chamfering.

  Since the curved surface 90b is provided between the inner wall surface 90c and the outer wall surface 90a, the inner wall surface 90c is provided offset to the cylinder bottom side from the outer wall surface 90a as a whole. Thus, the width in the cylinder axial direction between the outer wall surface 90a parallel to each other and the outer wall surface 89a of the peripheral wall 89 is narrower than the width in the cylinder axis direction between the inner wall surface 90c parallel to each other and the inner wall surface 89c of the peripheral wall 89. Yes. The width of the curved surface 90b in the cylinder radial direction is wider than the width of the outer wall surface 90a in the cylinder radial direction and narrower than the width of the inner wall surface 90c in the cylinder radial direction.

  The recess 75 formed in the primary piston 18 has a cylindrical surface 75a, a tapered surface 75b, and a tapered surface 75c. The cylindrical surface 75a has a smaller diameter than the cylindrical outer surface 18a having the largest diameter in the primary piston 18, and has a constant width in the axial direction. The tapered surface 75b is inclined and extended so as to increase in diameter from the end of the cylinder surface 75a on the cylinder opening side toward the cylinder opening side, and is connected to a portion closer to the cylinder opening than the concave portion 75 of the maximum outer diameter surface 18a. Yes. The tapered surface 75c is inclined and extended so as to increase in diameter from the edge of the cylindrical surface 75a 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 75 of the maximum outer diameter surface 18a. Yes.

  The cylindrical surface 75a, the tapered surface 75b, and the tapered surface 75c are formed around the central axis of the primary piston 18 similarly to the maximum outer diameter surface 18a. The port 76 that is always in communication with the primary pressure chamber 85 is formed at an end position on the tapered surface 75b side of the cylindrical surface 75a.

  The piston seal 45 disposed in the circumferential groove 32 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 45 and has an annular plate shape parallel to the axial orthogonal surface of the piston seal 45. 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 45 is in sliding contact with the outer peripheral surface 18A including the cylindrical surface 75a, the tapered surface 75b, the tapered surface 75c, and the maximum outer diameter surface 18a of the primary piston 18 whose inner peripheral lip portion 102 moves in the cylinder axial direction. As a result, the outer peripheral lip 103 comes into contact with the groove bottom surface 88 a of the groove bottom 88 of the peripheral groove 32 of the cylinder body 15. In other words, the piston seal 45 includes an annular base portion 101 provided with a projecting inner peripheral lip portion 102 that is in sliding contact with the outer peripheral surface 18A of the primary piston 18 and an outer peripheral lip portion 103 that is in contact with the peripheral groove 32 of the cylinder body 15. The intermediate lip portion 104 is provided between the inner peripheral lip portion 102 and the outer peripheral lip portion 103 so as to protrude further in the axial direction of the cylinder body 15.

  The piston seal 45 in the natural state before being incorporated in the master cylinder 11 will be described with reference to FIGS. As shown in FIG. 3A, the base 101, the inner peripheral lip 102, the outer peripheral lip 103, and the intermediate lip 104 have the same central axis, and this central axis is the central axis of the piston seal 45. ing. Hereinafter, the central axis direction of the piston seal 45 is referred to as a seal axial direction, the circumferential direction of the piston seal 45 is referred to as a seal circumferential direction, and the radial direction of the piston seal 45 is referred to as a seal radial direction.

  As shown in FIG. 4A, the inner peripheral lip portion 102 and the intermediate lip portion 104 have a substantially cylindrical shape, and the outer peripheral lip portion 103 has a tapered cylindrical shape with a larger diameter as the distance from the base portion 101 increases. ing.

  As shown in FIG. 3, the piston seal 45 includes a plurality of intermediate grooves 106 that penetrate the intermediate lip portion 104 in the radial direction of the seal on the extending tip side of the intermediate lip portion 104 at equal intervals in the seal circumferential direction. 8 places). Further, the piston seal 45 has a plurality of inner lip grooves 107 that penetrate the inner peripheral lip portion 102 in the radial direction of the seal on the leading end side of the inner peripheral lip portion 102 at equal intervals in the seal circumferential direction (specifically, 8 places).

  The outer peripheral lip 103 extends in the opposite direction from the base 101 from the inner peripheral side of the distal end of the main body 111 and the main body 111 extending in a tapered cylindrical shape having a larger diameter as the distance from the base 101 increases. And a plurality of (specifically, eight) protruding pieces 112 that are thinner than the main body 111. The plurality of projecting piece portions 112 are formed at equal intervals in the seal circumferential direction, and the space between the projecting piece portions 112 adjacent to each other in the seal circumferential direction penetrates the outer peripheral lip portion 103 in the seal radial direction. An outer lip groove 113 is formed. Therefore, the same number of outer lip grooves 113 as the protruding piece portions 112 are provided.

  The base 101 includes an annular base body 121 centered on the central axis of the piston seal 45 as shown in FIGS. 4B and 5, and an inner peripheral lip from the base body 121 as shown in FIG. The protrusion 102 protrudes in the opposite direction to the part 102, the outer peripheral lip part 103, and the intermediate lip part 104. As shown in FIG. 4B, a plurality of protrusions 122 (specifically, 24 locations) are formed at predetermined positions in the seal radial direction at intervals in the seal circumferential direction. That is, the plurality of protrusions 122 are arranged on the same circle.

  As shown in FIG. 4A, the base main body 121 has a base surface 121a located in the direction opposite to the innermost lip 102, outer lip 103, and intermediate lip 104 in the seal axis direction. It is a flat surface parallel to the axis orthogonal plane. The base body 121 is formed with a back surface groove 125 that is recessed from the base surface 121a toward the inner peripheral lip portion 102, the outer peripheral lip portion 103, and the intermediate lip portion 104 in the seal axis direction. The back groove 125 crosses the base surface 121a in the seal radial direction. As shown in FIG. 4B, a plurality of back surface grooves 125 (specifically, eight locations) are formed at equal intervals in the seal circumferential direction.

  Three projections 122 are formed at equal intervals at each position between the back groove 125 and the back groove 125 adjacent in the seal circumferential direction. All the protrusions 122 are arranged such that the outer surface 122a on the outer side in the radial direction of the seal is disposed on the same cylindrical surface with the central axis of the piston seal 45 as the center. The diameter is a predetermined amount smaller than the diameter of the surface 89b. The plurality of protrusions 122 are formed within the range of the inner and outer diameters of the base surface 121 a of the base body 121. More specifically, the plurality of protrusions 122 are slightly separated from each of the circular outer peripheral edge and the circular inner peripheral edge of the base surface 121a, and closer to the inner edge than the outer peripheral edge of the base surface 121a. It is formed by approaching. The plurality of protrusions 122 are formed closer to the inner peripheral side in the piston seal 45, and are also formed closer to the inner peripheral side in the base 101.

  Next, with reference to FIG. 2, the master cylinder 11 is demonstrated according to a state. FIG. 2 (a) shows a hydraulic pressure generation state in which the primary piston 18 has moved to a position where a hydraulic pressure exceeding atmospheric pressure is generated.

  In this hydraulic pressure generation state, the piston seal 45 that is in sliding contact with the outer peripheral surface 18A of the primary piston 18 on the inner peripheral surface 45a closes the port 76 with the base 101 positioned on the cylinder opening side with respect to the port 76. The communication between the pressure chamber 85 and the primary supply path 48 is blocked and the space between them is sealed. Thus, when the primary piston 18 moves to the cylinder bottom side, the brake fluid in the primary pressure chamber 85 is supplied from the primary discharge path 27 shown in FIG. 1 to the brake cylinder on the wheel side. In this hydraulic pressure generation state, the piston seal 45 is positioned on the primary supply path 48 side, that is, on the peripheral wall 89 side in the circumferential groove 32 by the hydraulic pressure exceeding the atmospheric pressure of the primary pressure chamber 85, and the base surface of the base main body 121. 121 a is brought into contact with the outer wall surface 89 a of the peripheral wall 89, while the intermediate lip 104 is separated from the peripheral wall 90.

  Here, when the hydraulic pressure is generated, the base 101 of the piston seal 45 may receive a lifting force in the direction away from the outer peripheral surface 18A of the primary piston 18 in the cylinder radial direction due to the hydraulic pressure of the primary pressure chamber 85. . In the present embodiment, the plurality of protrusions 122 formed on the base 101 of the piston seal 45 are wrapped with the inner peripheral surface 89b of the step 91 of the circumferential groove 32 in the cylinder axial direction. Therefore, the inner peripheral surface 89b of the stepped portion 91 suppresses the base 101 from being lifted by bringing the protrusion 122 into contact with the outer surface 122a. Thereby, it is suppressed that the surface pressure between the base 101 of the piston seal 45 and the outer peripheral surface 18A of the primary piston 18 decreases and the sealing performance is deteriorated.

  In the present embodiment, when the hydraulic pressure is generated, the outer surface 122a of the plurality of protrusions 122 is slidable with respect to the inner peripheral surface 89b of the step portion 91 except when the hydraulic pressure is raised. Has been placed. Specifically, in the hydraulic pressure generation state other than when the lift occurs, the outer surface 122a of the protrusion 122 and the inner peripheral surface 89b of the step portion 91 are in contact with each other without tightening. In other words, the diameter A of the cylindrical inner peripheral surface 89b is equal to the diameter B of the cylinder connecting the outer surfaces 122a of the plurality of protrusions 122 in a state where the hydraulic pressure is generated except when the lift occurs. It has become.

  When the primary piston 18 moves toward the bottom of the cylinder and generates hydraulic pressure, when the brake pedal (not shown) is started to release the brake, the primary piston 18 is moved by the interval adjusting unit 79 shown in FIG. Try to return to the basic position. Although the volume of the primary pressure chamber 85 is expanded by the movement of the primary piston 18, the return of the brake fluid through the brake pipe cannot catch up with the volume expansion of the primary pressure chamber 85. Then, after the hydraulic pressure in the primary supply passage 48 that is atmospheric pressure and the hydraulic pressure in the primary pressure chamber 85 become equal, the hydraulic pressure in the primary pressure chamber 85 becomes negative, and the primary supply passage 48 that is atmospheric pressure has a negative pressure. The hydraulic pressure in the primary pressure chamber 85 is lower than the hydraulic pressure.

  Then, the negative pressure in the primary pressure chamber 85 separates the outer peripheral lip 103 of the piston seal 45 from the groove bottom 88 and also separates the base body 121 from the peripheral wall 89 as shown in FIG. . At this time, since the inside of the primary pressure chamber 85 is a negative pressure, the above-described lifting force is not applied to the piston seal 45, and accordingly, the outer surface 122 a of the protrusion 122 of the piston seal 45 and the inner peripheral surface 89 b of the step portion 91. Are in contact with each other without tightening. Therefore, the sliding resistance between them is small, and the base body 121 can be smoothly separated from the peripheral wall 89.

  The brake fluid in the primary replenishment path 48 passes through the gaps between the plurality of protrusions 122 of the piston seal 45 and the gaps and grooves between the peripheral wall 89 and the base main body 121 as indicated by a one-dot chain line arrow F in FIG. The primary pressure chamber 85 is supplied through the gap between the bottom 88 and the outer peripheral lip 103, the gap between the peripheral wall 90 and the intermediate groove 106 of the intermediate lip 104, and the flow path such as the communication groove 51. As a result, the speed at which the hydraulic pressure in the primary pressure chamber 85 is returned from the negative pressure state to the atmospheric pressure is increased.

  In the master cylinder described in Patent Document 1, a step portion having an inner peripheral surface extending toward the opening portion is formed on the peripheral wall of the peripheral groove on the opening portion side of the cylinder body, and a piston is formed on the step portion. An annular protrusion protruding from the base of the seal is in contact with the seal. And if a piston moves to the position which generate | occur | produces a hydraulic pressure, the cyclic | annular protrusion of a piston seal will be pressed and contact | adhered to the inner peripheral surface of a step part with the allowance in radial direction. Then, the frictional resistance between them increases, and the piston seal may not be able to move smoothly in the circumferential groove. As a result, when the brake pedal is returned from the hydraulic pressure generation state, the gap between the piston seal and the peripheral wall of the peripheral groove on the supply chamber side cannot be expanded smoothly, and replenishment is performed via the gap between the piston seal and the peripheral groove. There is a possibility that the brake fluid cannot sufficiently flow from the chamber to the pressure chamber, that is, the replenishment performance of the brake fluid to the pressure chamber may be deteriorated.

  The master cylinder 11 of the present embodiment also has a step portion 91 having an inner peripheral surface 89b extending to the cylinder opening side on the peripheral wall 89 on the cylinder opening side in the peripheral groove 32 in order to suppress the lifting of the piston seal 45 when hydraulic pressure is generated. And a protrusion 122 protruding toward the cylinder opening is formed on the base 101 of the piston seal 45. And the protrusion 122 of this embodiment has the outer surface 122a of radial direction in the position which can slide with respect to the internal peripheral surface 89b of the step part 91 in the state which the primary piston 18 moved to the position which generate | occur | produces a hydraulic pressure. Has been placed. Therefore, sliding resistance due to friction between the protrusion 122 and the step portion 91 is suppressed, and the piston seal 45 moves smoothly in the circumferential groove 32 when the brake pedal is returned from the hydraulic pressure generation state, and the base main body 121. Is separated from the peripheral wall 89. Therefore, it is possible to suppress a decrease in brake fluid supply performance.

  In the above embodiment, the primary seal structure SP including the piston seal 45 has been described in detail as an example. However, the piston seal 45 and the peripheral groove 32 having the same shape as the piston seal 45 and the common groove 32 have been described in detail. The secondary-side seal structure SS including the first cylindrical portion 55 having the same shape as the groove 30 and the first cylindrical portion 71 has the same structure. Therefore, the seal structure portion SS can achieve the same effect as the seal structure portion SP.

  The above embodiment is provided with a bottomed cylindrical cylinder body having a brake fluid discharge path and a replenishment path communicating with the reservoir, and is movably disposed in the cylinder body. A piston that forms a pressure chamber that supplies hydraulic pressure to the discharge path, and an inner circumference that is provided in a circumferential groove formed in the cylinder body and that is in sliding contact with the piston to seal between the supply path and the pressure chamber And a step portion having an inner peripheral surface extending toward the opening portion is formed on the peripheral wall of the peripheral groove on the opening portion side of the cylinder body. The inner peripheral lip portion that is in sliding contact with the outer peripheral surface and the outer peripheral lip portion that is in contact with the peripheral groove of the cylinder body have an annular base portion that protrudes, and the base portion has a protrusion that protrudes toward the opening portion side. Formed , The piston is in a state of being moved to a position for generating a hydraulic pressure, the outer surface of the radial at a position where the slidable is disposed against the inner peripheral surface of the stepped portion. Therefore, it is possible to suppress a decrease in brake fluid supply performance.

11 Master cylinder 12 Reservoir 13 Bottom 15 Cylinder body 16 Opening 18 Primary piston (piston)
18A, 19A Outer peripheral surface 19 Secondary piston (piston)
26 Secondary discharge path (discharge path)
27 Primary discharge path (discharge path)
30, 32 Circumferential groove 35, 45 Piston seal 38 Secondary supply path (supply path)
48 Primary supply path (supply path)
68 Secondary pressure chamber (pressure chamber)
85 Primary pressure chamber (pressure chamber)
89 Perimeter wall (peripheral wall on the opening side)
89b Inner peripheral surface 91 Step part 101 Base part 102 Inner peripheral lip part 103 Outer peripheral lip part 122 Projection 122a Outer surface

Claims (1)

A bottomed cylindrical cylinder body having a brake fluid discharge path and a supply path communicating with the reservoir;
A piston that is movably disposed within the cylinder body, and that forms a pressure chamber between which the fluid pressure is supplied to the discharge passage;
A piston seal provided in a circumferential groove formed in the cylinder body and having an inner circumference slidingly contact the piston and sealing between the supply path and the pressure chamber;
On the peripheral wall on the opening side of the cylinder body in the peripheral groove, a step portion having an inner peripheral surface extending to the opening side is formed,
The piston seal has an annular base portion in which an inner peripheral lip portion that is in sliding contact with the outer peripheral surface of the piston and an outer peripheral lip portion that is in contact with the peripheral groove of the cylinder body are protruded.
The base is formed with a protrusion protruding toward the opening,
The protrusion is a master cylinder in which a radially outer surface is disposed at a position where the protrusion is slidable with respect to an inner peripheral surface of the stepped portion in a state where the piston is moved to a position where hydraulic pressure is generated.

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