JP2013071507A - Master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master cylinder, preventing a piston seal from being damaged.SOLUTION: The piston seal 45 includes: a ring-like base part 90; an inner peripheral lip part 91 projected from an inner peripheral side of the base part 90 to be in slide-contact with an outer peripheral face of a piston; an outer peripheral lip part 92 projected from an outer peripheral side of the base part 90 to be in contact with a circumferential groove of a cylinder body; and an intermediate projection part 93 projected more than the outer peripheral lip part 92 from between the inner peripheral lip part 91 and the other peripheral lip part 92 of the base part 90. A plurality of projections 96 are circumferentially arranged on a tip side of the intermediate projection part 93, and the projection 96 is formed so that the rigidity of one side in the circumferential direction is different from that of the other side.

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 piston seal that performs sealing while allowing sliding of the piston (see, for example, Patent Document 1).

JP 2006-123879 A

  In the master cylinder, the piston seal may be damaged, so-called biting may occur.

  Therefore, an object of the present invention is to provide a master cylinder capable of suppressing damage caused to the piston seal.

  In order to achieve the above object, the present invention provides a piston seal having an annular base portion, an inner peripheral lip portion protruding from the inner peripheral side of the base portion and slidably contacting the outer peripheral surface of the piston, and an outer peripheral side of the base portion. An outer peripheral lip portion that protrudes and abuts against a peripheral groove of the cylinder body, and an intermediate protrusion portion that protrudes from between the inner peripheral lip portion and the outer peripheral lip portion of the base portion to beyond the outer peripheral lip portion. In the master cylinder, a plurality of protrusions arranged along the circumferential direction are provided on the tip side of the intermediate protrusion, and the protrusions are formed with different rigidity at both ends in the circumferential direction.

  ADVANTAGE OF THE INVENTION According to this invention, the damage which arises in a piston seal can be suppressed.

It is sectional drawing which shows the master cylinder of embodiment. It is a fragmentary sectional view showing an important section of a master cylinder of an embodiment. It is a front view which shows the piston seal of the master cylinder of embodiment. (a) is XX sectional drawing of FIG. 3, (b) is YY sectional drawing of FIG. 3, (c) is ZZ expanded sectional drawing of FIG. It is sectional drawing corresponding to FIG.4 (c) explaining the rotation principle of the piston seal of the master cylinder of embodiment. It is sectional drawing which shows the piston seal of the state in which the pressure chamber of the master cylinder of embodiment became negative pressure. It is sectional drawing corresponding to FIG.4 (c) which shows the 1st modification of the piston seal of the master cylinder of embodiment. It is sectional drawing corresponding to FIG.4 (c) which shows the 2nd modification of the piston seal of the master cylinder of embodiment. It is sectional drawing corresponding to FIG.4 (c) which shows the 3rd modification of the piston seal of the master cylinder of embodiment. The 4th modification of the piston seal of the master cylinder of an embodiment is shown, (a) is a partial front view, and (b) is a sectional view corresponding to Drawing 4 (c).

  A master cylinder according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a master cylinder 11 that generates a brake fluid pressure with a force corresponding to an operation amount of a brake pedal introduced via a brake booster (not shown). A reservoir 12 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 arranged at a position separated from the master cylinder 11 and connected by piping.

  The master cylinder 11 is a cylinder body made of metal that is formed in a bottomed cylinder having a bottom portion 13 and a cylinder portion 14 from a single material and that is disposed in a vehicle in a posture in which the longitudinal direction is along the vehicle front-rear direction. 15. A metal primary piston (piston) 18 is slidably inserted into the opening 16 side of the cylinder body 15. Similarly, a metal secondary piston (piston) 19 is slidably inserted on the bottom 13 side of the cylinder body 15 with respect to the primary piston 18.

  The primary piston 18 and the secondary piston 19 are slidably guided by a sliding inner diameter portion 20 having a circular cross section perpendicular to the axis of the cylinder portion 14 of the cylinder body 15 (hereinafter referred to as a cylinder shaft). The primary piston 18 is formed with an inner peripheral hole 21 having a bottom surface, and the secondary piston 19 is formed with an inner peripheral hole 22 having a bottom surface, and the master cylinder 11 is of a so-called plunger type. Thus, the master cylinder 11 in this embodiment is a tandem type having two pistons 18 and 19. 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) at a predetermined position in the circumferential direction of the cylindrical portion 14 (hereinafter referred to as the cylinder circumferential direction). Are integrally formed. Mounting holes 24 and 25 for mounting the reservoir 12 are formed in the mounting base portion 23. In the present embodiment, the mounting holes 24 and 25 are formed by shifting the positions in the cylinder axial direction in a state where the positions in the cylinder circumferential direction coincide with each other.

  On the mounting base 23 side of the cylinder portion 14 of the cylinder body 15, there is a secondary discharge path (discharge path) 26 in the vicinity of the bottom portion 13, and a primary discharge path (discharge path) 27 on the opening 16 side than this, respectively. Is formed. 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 passage 26 and the primary discharge passage 27 are formed by shifting the positions in the cylinder axial direction in a state where the positions in the cylinder circumferential direction coincide with each other.

  The sliding inner diameter portion 20 of the cylinder body 15 has a circumferential groove 30, a circumferential groove 31, a circumferential groove 32, and a circumferential groove 33 that are arranged in a plurality of positions, in particular, at four positions by shifting the position in the cylinder axial direction. They are formed in order from the bottom 13 side. These circumferential grooves 30 to 33 have an annular shape in the cylinder circumferential direction and have a shape that is recessed outward in the cylinder radial direction, and all are formed by cutting.

  The circumferential groove 30 closest to the bottom 13 is formed in the vicinity of the mounting hole 24 on the bottom 13, and an annular piston seal 35 is held in the circumferential groove 30 so as to be held by the circumferential groove 30. Is arranged.

  A sliding inner diameter portion of the cylinder portion 14 is formed so that a communication hole 36 formed from the mounting hole 24 on the bottom portion 13 side is opened in the cylinder portion 14 on the opening portion 16 side of the circumferential groove 30 in the cylinder body 15. An annular opening groove 37 that is recessed from the cylinder 20 outward in the cylinder radial direction is formed. Here, the opening groove 37 and the communication hole 36 mainly constitute a secondary supply path (supply path) 38 provided in the cylinder body 15 and always communicating with the reservoir 12.

  The sliding inner diameter portion 20 of the cylinder body 15 is open in the circumferential groove 30 on the mounting base portion 23 side in the cylinder circumferential direction and extends slightly from the circumferential groove 30 toward the bottom 13 side in a straight line in the cylinder axial direction. The communicating groove 41 is formed so as to be recessed outward 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 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. In the circumferential groove 31, the circumferential groove 31 is formed. An annular section seal 42 is arranged so as to be held in the space.

  The above-described circumferential groove 32 is formed on the opening 16 side of the circumferential groove 31 of the cylinder body 15 and 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 side of the opening 16 of the circumferential groove 32 in the cylinder body 15, the sliding inner diameter of the cylinder portion 14 is formed so that a communication hole 46 formed from the mounting hole 25 on the opening 16 side is opened in the cylinder portion 14. An annular opening groove 47 that is recessed outwardly from the portion 20 in the cylinder radial direction is formed. 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.

  On the bottom 13 side of the circumferential groove 32 of the sliding inner diameter portion 20 of the cylinder body 15, on the mounting base 23 side in the cylinder circumferential direction, the circumferential groove 32 opens to the bottom and linearly extends from the circumferential groove 32 in the cylinder axial direction. A communication groove 51 extending slightly toward the 13 side is formed so as to be recessed outward in the cylinder radial direction. The communication groove 51 communicates the primary discharge passage 27 formed at a position near the circumferential groove 31 and the circumferential groove 32 via a primary pressure chamber 85 described later.

  A circumferential groove 33 is formed on the opposite side of the opening groove 47 in the cylinder body 15 from the circumferential groove 32, that is, on the opening 16 side. A circular groove 33 is held in the circumferential groove 33 so as to be held by the circumferential groove 33. An annular compartment seal 52 is disposed.

  The secondary piston 19 fitted to the bottom 13 side of the cylinder body 15 has a bottomed cylindrical shape having a cylindrical portion 55 and a bottom portion 56 formed on one side in the axial direction of the cylindrical portion 55. The inner peripheral hole 22 is formed by the cylindrical portion 55 and the bottom portion 56. The secondary piston 19 slides on the inner periphery of each of the piston seal 35 and the partition seal 42 provided on the sliding inner diameter portion 20 of the cylinder body 15 with the cylindrical portion 55 disposed on the bottom 13 side of the cylinder body 15. Can be fitted. On the outer peripheral side of the end portion on the opposite side to the bottom portion 56 of the cylindrical portion 55, an annular step portion 59 having a slightly smaller outer diameter than the other portions is formed. In the stepped portion 59, a plurality of ports 60 penetrating in the cylinder radial direction are formed on the bottom 56 side so as to be radially formed at equal intervals in the cylinder circumferential direction.

  An interval adjustment unit including a secondary piston spring 62 between the secondary piston 19 and the bottom portion 13 of the cylinder body 15 for determining these intervals in a non-braking state without input from a brake pedal (not shown) (right side in FIG. 1). 63 is provided. The gap adjusting portion 63 includes a locking member 64 that contacts the bottom 13 of the cylinder body 15, a locking member 65 that contacts the bottom 56 of the secondary piston 19, and one end fixed to the locking member 64. And a shaft member 66 that slidably supports the stop member 65 only within a predetermined range. The secondary piston spring 62 is interposed between the locking members 64 and 65 on both sides.

  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 and the cylinder body 15 form a secondary pressure chamber 68 that supplies a hydraulic pressure to the secondary discharge passage 26. The secondary pressure chamber 68 communicates with the secondary supply path 38 when the secondary piston 19 is in a position where the port 60 is opened in 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 periphery of the secondary piston 19 and the outer periphery is in contact with the circumferential groove 31 of the cylinder body 15 so as to always seal 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, and one side shape of the radial cross section including the center line thereof is an E shape. That is, the piston seal 35 extends from the inner peripheral side of the base 90 to the bottom 13 side substantially along the axial direction of the base 90 from the inner peripheral side of the base 90. An annular inner peripheral lip 91, an annular outer peripheral lip 92 extending from the outer peripheral side of the base 90 toward the bottom 13, similar to the inner peripheral lip 91, and the inner peripheral lip 91 and the outer periphery of the base 90 An annular intermediate projecting portion 93 projecting from between the lip portion 92 and the inner peripheral lip portion 91 and the outer peripheral lip portion 92 to the front side (the side opposite to the base portion 90) is provided.

  The piston seal 35 is configured such that the inner periphery of the inner peripheral lip 91 is in sliding contact with the outer periphery of the secondary piston 19 and the outer periphery of the outer peripheral lip 92 is in contact with the peripheral 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 in which the secondary piston 19 positions the port 60 on the bottom 13 side of the piston seal 35, that is, the secondary pressure chamber 68. The communication with the secondary supply path 38 and the reservoir 12 can be blocked. In this state, the secondary piston 19 slides on the inner diameter of the sliding inner diameter portion 20 of the cylinder main body 15 and the piston seal 35 and the partition seal 42 held by the cylinder main body 15, whereby the brake in the secondary pressure chamber 68. The liquid is pressurized and supplied from the secondary discharge passage 26 to the braking cylinder on the wheel side.

  Note that when there is no input from the brake pedal (not shown) and the secondary piston 19 is in a position (non-braking position) where the port 60 is opened in the opening groove 37, the piston seal 35 is a step portion of the secondary piston 19. 59 partially overlaps the port 60. 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 the port 60, the communication between the secondary pressure chamber 68 and the reservoir 12 is blocked. Yes.

  The primary piston 18 fitted to 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 cylinder of the bottom portion 72. The shape which has the 2nd cylindrical part 73 formed in the opposite side to the 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 a first cylindrical portion 71 disposed on the side of the secondary piston 19 in the cylinder body 15, and each of the piston seal 45 and the partition seal 52 provided on the sliding inner diameter portion 20 of the cylinder body 15. The 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.

  On the outer peripheral side of the end opposite to the bottom 72 of the first cylindrical portion 71, an annular recess 75 having a slightly smaller outer diameter than the other portions 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 a distance adjusting portion 79 including a primary piston spring 78 that determines these distances in a non-braking state without input from a brake pedal side (right side in FIG. 1). It has been. The gap adjusting portion 79 includes a locking member 81 that contacts the bottom 56 of the secondary piston 19, a locking member 82 that contacts the bottom 72 of the primary piston 18, 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 members 81 and 82 on both sides.

  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, in the primary piston 18, the secondary piston 19 and the cylinder body 15 form a primary pressure chamber 85 that supplies hydraulic pressure to the primary discharge path 27. The primary pressure chamber 85 communicates with the primary supply path 48 when the primary piston 18 is in a position where the port 76 is opened in the opening groove 47.

  The partition seal 52 held in the circumferential groove 33 of the cylinder body 15 is the same component as the partition seal 42, and is an integrally molded product made of synthetic rubber. The one-side shape of the radial cross section including the center line is C-shaped. It has a shape. The partition seal 52 is slidably in contact with the outer periphery of the primary piston 18, and the outer periphery is in contact with the circumferential groove 33 of the cylinder body 15 to always seal the gap between the position of the partition seal 52 of the primary piston 18 and the cylinder body 15.

  The piston seal 45 held in the circumferential groove 32 of the cylinder body 15 is the same component as the piston seal 35, and is an integrally molded product made of synthetic rubber, and the one-side shape of the radial cross section including the center line is E-shaped. It has a shape. That is, the piston seal 45 extends from the inner peripheral side of the base 90 to the bottom 13 side along the axial direction of the base 90 from the inner peripheral side of the base 90. An annular inner peripheral lip 91, an annular outer peripheral lip 92 extending from the outer peripheral side of the base 90 toward the bottom 13, similar to the inner peripheral lip 91, and the inner peripheral lip 91 and the outer periphery of the base 90 An annular intermediate projecting portion 93 projecting from between the lip portion 92 and the inner peripheral lip portion 91 and the outer peripheral lip portion 92 (the side opposite to the base portion 90) is provided.

  The piston seal 45 is configured such that the inner periphery of the inner peripheral lip 91 is in sliding contact with the outer periphery of the primary piston 18 and the outer periphery of the outer peripheral lip 92 is in contact with the peripheral 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 when the primary piston 18 has the port 76 positioned on the bottom 13 side of the piston seal 45, that is, the primary pressure chamber 85. And communication with the primary supply path 48 and the reservoir 12 can be blocked. In this state, the primary piston 18 slides on the inner diameter of the sliding inner diameter portion 20 of the cylinder main body 15 and the piston seal 45 and the partition seal 52 held by the cylinder main body 15, so that the brake in the primary pressure chamber 85 is maintained. The liquid is pressurized and supplied from the primary discharge passage 27 to the braking cylinder on the wheel side.

  When there is no input from the brake pedal (not shown) and the primary piston 18 is in a position (non-braking position) where the port 76 is opened in the opening groove 47, the piston seal 45 is in the recess 75 of the primary piston 18. A part of the port 76 overlaps the inside of the port 76. 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 entirely overlaps the port 76, the communication between the primary pressure chamber 85 and the reservoir 12 is blocked. Yes.

  Here, a secondary-side seal structure SS composed of a portion near the circumferential groove 30 of the cylinder body 15 shown in FIG. 1, a sliding contact portion of the piston seal 35 and the piston seal 35 of the secondary piston 19, and the circumference of the cylinder body 15. The primary-side seal structure SP composed of the vicinity of the groove 32, the piston seal 45 and the sliding contact portion of the piston seal 45 of the primary piston 18 has the same structure. The primary-side seal structure SP will be described as an example with reference mainly to FIGS.

  As shown in FIG. 2, the circumferential groove 32 has a cylindrical groove bottom portion 32a that is the outermost in the cylinder radial direction and extends along the cylinder axial direction, and the opening 16 side of the cylinder body 15 in the groove bottom portion 32a (on the right side in FIG. 2). ) In the direction perpendicular to the cylinder axis at the position of the annular wall 32b along the direction orthogonal to the cylinder axis at the edge of the cylinder shaft and the edge of the groove bottom 32a on the bottom 13 side (left side in FIG. 2) of the cylinder body 15 And an annular wall 32c. The groove bottom portion 32a, the annular wall 32b, and the annular wall 32c are formed integrally with the cylinder body 15, and are all formed by cutting the cylinder body 15.

  The piston seal 45 is in sliding contact with the outer peripheral surface 18a of the primary piston 18 at the inner peripheral surface 91a of the inner peripheral lip 91, and is on the opening 16 side (right side in FIG. 2) of the cylinder body 15 in the base 90. The rear surface 90a faces the annular wall 32b of the circumferential groove 32 behind it. Further, the outer peripheral surface 92 a of the outer peripheral lip 92 is in contact with the groove bottom 32 a of the peripheral groove 32, and is opposed to the annular wall 32 c of the peripheral groove 32 in front of the intermediate protrusion 93.

  As shown in FIG. 3, the piston seal 45 has the inner peripheral lip portion 91, the outer peripheral lip portion 92, and the intermediate projecting portion 93 arranged concentrically. As shown in FIG. 4, the piston seal 45 includes a cylindrical portion 95 extending from the base portion 90 along the axial direction of the base portion 90 at a constant height, and a base portion 90 from the opposite end to the base portion 90 of the cylindrical portion 95. And a plurality of protrusions 96 protruding on the opposite side. As shown in FIG. 3, the plurality of protrusions 96 on the distal end side of the intermediate protrusion 93 are disposed at a plurality of positions, specifically 12 positions along the circumferential direction of the intermediate protrusion 93. All the protrusions 96 have the same shape, and are arranged at equal intervals in the circumferential direction of the intermediate protrusion 93. Between the protrusions 96 adjacent to each other in the circumferential direction, there is a slit 97 penetrating in the radial direction of the intermediate protrusion 93.

  The cylindrical portion 95 has an end face 95 a opposite to the base portion 90 at a position between the adjacent projections 96 and constitutes a slit 97. The end surface 95a is along the direction perpendicular to the axis of the intermediate protrusion 93. In the state where the piston seal 45 is disposed in the circumferential groove 32, the intermediate projecting portion 93 is disposed so that the central axis of the cylinder body 15 coincides with the central axis.

  The protrusion 96 has a distal end surface 96 a opposite to the base portion 90 along the axial orthogonal direction of the intermediate protrusion 93. In the protrusion 96, one end side in the circumferential direction of the intermediate protruding portion 93 is a side surface portion 96 b that connects the end surface 95 a of the cylindrical portion 95 and the distal end surface 96 a of the protrusion 96 along the radial direction and the axial direction of the intermediate protruding portion 93. ing. Further, the projection 96 has a side surface portion 96c that slightly rises from the end surface 95a of the cylindrical portion 95 along the radial direction and the axial direction of the intermediate protrusion portion 93, and a side surface portion 96c of the side surface portion 96c. It has a side surface portion 96d that extends from the opposite end to the end surface 95a along the radial direction of the intermediate projecting portion 93 and is inclined with respect to the axial direction and is connected to the front end surface 96a of the projection 96. In other words, in the protrusion 96, one side surface portion 96b in the circumferential direction is orthogonal to the tip surface 96a, and the other side surface portion 96d in the circumferential direction is inclined with an obtuse angle with respect to the tip surface 96a. . Therefore, in other words, in the protrusion 96, the angle of the side surface portions 96b and 96d extending to the tip end surface 96a with respect to the axial direction of the cylinder body 15 is different between the one side surface portion 96b and the other side surface portion 96d.

  As described above, the protrusions 96 are formed with different rigidity on both ends in the circumferential direction of the intermediate protrusion 93. Here, the rigidity is specifically the rigidity when the projection 96 abuts against the annular wall 32c of the circumferential groove 32 at the tip surface 96a and receives an axial force. The side surface 96b side orthogonal to 96a has higher rigidity, and the side surface portion 96d side inclined with respect to the front end surface 96a has lower rigidity. All the protrusions 96 have a side surface portion 96b orthogonal to the tip surface 96a on the same side in the circumferential direction of the intermediate projection portion 93, and form an obtuse angle on the tip surface 96a on the same other side in the circumferential direction of the intermediate projection portion 93. A side surface portion 96d is disposed.

  When the pressure in the primary pressure chamber 85 fluctuates with respect to the pressure in the reservoir 12 (atmospheric pressure), the piston seal 45 is repeatedly pressed and released from the annular wall 32c of the circumferential groove 32 at the plurality of protrusions 96. In each case, due to the unbalance of the rigidity of the plurality of protrusions 96 in which the rigidity on the same side in the circumferential direction is high and the rigidity on the other side is low, the rotation around the central axis is performed in the circumferential groove 32. Become.

  More specifically, a conceptual diagram of the deformation history of the protrusion 96 at the time of releasing the brake fluid pressure shown in FIG. 5 will be described. In the conceptual diagram, the side surface portion 96c that is negligible for rotational operation is omitted.

  FIG. 5 shows one protrusion 96, a part of the cylindrical portion 95 in the vicinity thereof, and the annular wall 32 c of the circumferential groove 32. As shown in FIG. 5A, the angular position between the side surface portion 96b of the projection 96 and the end surface 95a of the cylindrical portion 95 is the point A, the angular position between the side surface portion 96b and the distal end surface 96a is the B point, and the side surface portion 96d. And the distal end surface 96a is the point C, the angular position of the side surface portion 96d and the end surface 95a is the point D, the base end position of the center of the circumferential width of the projection 96 is the point O, and the tip end position of the center of the circumferential width Is the O ′ point, the symmetrical position with respect to the center of the circumferential width of the C point is the C ′ point, the entire volume of the protrusion 96 is V, and the volume on the side surface 96b side of the center line OO ′ is The difference ABCC ′ that is larger than the volume on the side surface portion 96d side will be described as v.

  For example, when a brake pedal (not shown) is started to release the brake, the primary piston 18 tries to return to the standby position as shown in FIG. Although the volume of the primary pressure chamber 85 is increased by the movement of the primary piston 18, the return of the brake fluid through the thin brake pipe cannot catch up with the volume expansion from the middle, and the hydraulic pressure in the primary pressure chamber 85 is increased. Changes from positive pressure to negative pressure P0. The piston seal 45 is pulled toward the primary pressure chamber 85 by the negative pressure P0, and the tip surface 96a of the protrusion 96 of the intermediate protrusion 93 is annular in the circumferential groove 32 as shown in FIGS. It contacts the wall 32c.

  When the brake pedal is further returned, the negative pressure in the primary pressure chamber 85 increases, but in the initial state, that is, in the state of the small negative pressure P1, the rising state of the frictional force generated at the tip surface 96a and the annular wall 32c is brought about. Accordingly, the point B stays at the same position, or slides as shown in FIG. 5B and moves to the point B1 in the direction opposite to the point C (the left direction in FIG. 5). The rising state of the frictional force depends on the shape of the protrusion 96, the surface state of the tip surface 96a of the protrusion 96, and the surface state of the annular wall 32c.

  The case where the rising of the frictional force is slow and the point B moves to the point B1 will be described. This is because the rigidity on the side surface 96b side is larger than the rigidity on the side surface portion 96d side by the ratio v / V of the volume difference v between the side surface portion 96b side and the side surface portion 96d side to the total volume V of the protrusion 96. It depends. That is, as shown in FIGS. 5A and 5B, when the base end portion A-O-D of the projection 96 is attracted to the annular wall 32c by the action of the initial negative pressure P1 due to the difference in rigidity, the rigidity is increased. The side surface 96d side having low rigidity, that is, the C-D surface is deformed earlier than the side surface 96b side having high A, that is, the AB surface side, and the AB surface is inclined at the point A before being deformed. start. Once point A breaks, while the negative pressure is high, the broken state will not be resolved. Therefore, even if v / V is small, point A breaks before point D, and point B The distance δ1 is shifted in the direction opposite to the point C (the left direction in FIG. 5) and located at the point B1. Further, the point A maintains the point A1 which is the same position. In this way, the point B shifts to the point B1 before the point A moves in the direction D (the right direction in FIG. 5) because the mass of the piston seal 45 is sufficiently larger than the mass of the protrusion 96. Because it is large, it depends on its inertia. By shifting the point B to the point B1, the point C is also shifted in the direction of the point B (leftward in FIG. 5) and located at the point C1. It is shifted to the left of FIG.

  When the negative pressure is further increased to the negative pressure P2, the projection 96 is strongly pressed against the annular wall 32c and the frictional force is increased. Therefore, as shown in FIGS. 5B and 5C, the point B1 is the same. The side surface 96d, that is, the C1-D1 surface is attracted to the annular wall 32c while the C1 point is located at the same C2 point, and is deformed into a barrel shape, and the D1 point is the D2 point on the annular wall 32c side. Located in. Thus, when the C1-D1 plane is attracted to the annular wall 32c, the point A1 is shifted by the distance δ2 in the direction of the point D1 (right direction in FIG. 5) and is positioned at the point A2.

  After the above, as shown by a broken line in FIG. 6, the gap between the annular wall 32b of the circumferential groove 32 and the back surface 90a of the base 90, the space between the groove bottom 32a and the outer peripheral surface 92a of the outer lip 92, and the annular wall 32c. And the brake fluid is returned to the primary pressure chamber 85 via the flow path between the intermediate protrusion 93 and the slit 97, and the negative pressure in the primary pressure chamber 85 gradually decreases. At the same time, when the primary piston 18 returns to the standby position, the port 76 shown in FIG. 1 communicates with the reservoir 12 via the primary supply path 48, and the hydraulic pressure in the primary pressure chamber 85 rises to the atmospheric pressure P3. . Then, since the negative pressure changes to the atmospheric pressure, the projection 96 that has been compressed and deformed as shown in FIG. 5C extends to a free length as shown in FIG. 5D, and the annular wall 32c. The frictional force is lost. At this time, due to the inertia of the piston seal 45, the point A2 maintains the same position and becomes the point A3, and the point B2 moves to the position of the point A3 in the direction of the point C2 (right direction in FIG. 5). Accordingly, the point C2 is also shifted to the point C3 in the opposite direction (right direction in FIG. 5) to the point B2, and the point D2 is also shifted to the point D3 in the opposite direction (right direction in FIG. 5).

  Through the above-described deformation process, all the protrusions 96 are moved to the one side in the circumferential direction by the distance δ2 in one return stroke of the primary piston 18. As a result, the piston seal 45 rotates to one side in the circumferential direction. In the initial stage of expansion of the negative pressure in the primary pressure chamber 85 (FIG. 5 (a) to FIG. 5 (b)), when the frictional force between the protrusion 96 and the annular wall 32c immediately rises, the point B becomes the distance δ1. Since there is no deviation, each projection 96 moves a distance obtained by adding the above-described distance δ1 and distance δ2.

  The conditions under which the entire piston seal 45 moves in the circumferential direction by the elastic force of the projection 96 corresponding to the distance δ2 with respect to the distance δ2 that is the circumferential movement amount of the projection 96 will be described. FIG. 6 shows the load condition of FIG. 5C, and the contact points with the other of the piston seal 45 at this time are the tip of the intermediate protrusion 93 and the inner periphery of the inner peripheral lip 91. ing. Assuming that the frictional force between the inner peripheral lip 91 and the primary piston 18 is Fin and the frictional force between the intermediate protrusion 93 and the circumferential groove 32 is Fcen, the conditions for the entire piston seal 45 to rotate in the circumferential direction are as follows: The piston seal 45 satisfies the expression (1).

  Fin <Fcen (1)

  Here, Fin takes a value close to zero because a force acts in a direction in which the inner diameter lip portion 91 moves away from the primary piston 18 due to a high negative pressure. On the other hand, Fcen has a sufficiently large value as compared with Fin because the force acts in the direction in which the entire piston seal 45 is sucked into the annular wall 32c by high negative pressure and is supported by the intermediate protrusion 93. Therefore, even if the shape of the piston seal 45 is arbitrary, the above equation (1) is established, and the piston seal 45 rotates.

  As shown in FIG. 2, a plurality of ports 76 are formed in the above-described primary piston 18 at intervals in the circumferential direction, and the piston seal 45 opens and closes the ports 76 while being in sliding contact with the primary piston 18. When the port 76 passes through a specific position in the circumferential direction of the piston seal 45 in the axial direction of the cylinder body 15, there is a possibility of causing so-called biting that damages the piston seal 45 at the corner of the port 76.

  On the other hand, in the master cylinder 11 of the above-described embodiment, the protrusions 96 of the intermediate protrusion 93 of the piston seal 45 are formed with different rigidity at both ends in the circumferential direction. Each time the pressure release of 85 is performed, the piston seal 45 rotates little by little, and the situation where the port 76 repeatedly passes through a specific position in the circumferential direction of the piston seal 45 is suppressed. Therefore, damage that occurs in the piston seal 45 can be suppressed.

  In addition, in the outer diameter sliding type master cylinder that holds the piston seal on the outer periphery of the piston, there is a cylinder that has a winding spring mechanism to rotate the piston seal during the reciprocating motion of the piston. In the present embodiment in which the piston seal 45 is held on the inner peripheral side of the cylinder body 15, the piston seal 45 and the winding spring cannot be contacted due to the structure and cannot be applied. In the present embodiment, as described above, the piston seal 45 is provided on the inner peripheral side of the cylinder body 15 by providing the piston seal 45 with the projection 96 that rotates due to a change in the received pressure. The piston seal 45 can also be rotated. In addition, since only the shape of the piston seal 45 is changed, an increase in the number of parts and cost can be suppressed. Of course, the present invention can also be applied to an outer-diameter sliding type master cylinder. In this case as well, an increase in the number of parts and cost can be suppressed.

  In order to rotate the piston seal 45, it is only necessary that the projections 96 are formed with different rigidity at both ends in the circumferential direction, and various modifications can be made to the above.

  For example, as in the first modification shown in FIG. 7, the angle of both side surfaces 96b and 96d extending to the front end surface 96a with respect to the front end surface 96a is obtuse, and the angle of one side surface 96b with respect to the front end surface 96a is You may make smaller than the angle with respect to the front end surface 96a of the side part 96d. In other words, the length of O′-C <the length of B−O ′. Also in this case, the angle of the cylinder body 15 with respect to the axial direction differs between the side surface portion 96b on one side and the side surface portion 96d on the other side, and the rigidity differs between the side surface portion 96b side and the side surface portion 96d of the projection 96. It will be.

  Further, for example, as in the second modification shown in FIG. 8, the angle of one side surface 96b with respect to the tip surface 96a is made smaller than the angle of the other side surface portion 96d with respect to the tip surface 96a and the side surface portion 96b is concave. The side surface portion 96d may have a convex arc shape. Also in this case, the angle of the cylinder body 15 with respect to the axial direction differs between the side surface portion 96b on one side and the side surface portion 96d on the other side, and the rigidity differs between the side surface portion 96b side and the side surface portion 96d of the projection 96. It will be.

  Further, for example, as in the third modification shown in FIG. 9, the angle of both side surfaces 96b and 96d extending to the front end surface 96a with respect to the front end surface 96a is an obtuse angle, and the angle of one side surface 96b with respect to the front end surface 96a is set. The angle of the other side surface portion 96d may be smaller than the angle with respect to the tip end surface 96a, and each of the angular positions A to D may be arcuate. Also in this case, the angle of the cylinder body 15 with respect to the axial direction differs between the side surface portion 96b on one side and the side surface portion 96d on the other side, and the rigidity differs between the side surface portion 96b side and the side surface portion 96d of the projection 96. It will be. Each corner position may be chamfered.

  Further, for example, as in the fourth modification shown in FIG. 10, the radial thickness on one side of the protrusion 96 may be different from the radial thickness on the other side in the circumferential direction. That is, the side surface portion 96d of the projection 96 is aligned along the radial direction and the axial direction of the intermediate protrusion portion 93 so as to connect the end surface 95a and the front end surface 96a, and the radial thickness is constant from the side surface portion 96b side to the center. The chamfer 100 is formed on both sides in the radial direction so as to become thinner toward the side surface 96d side of the projection 96, and the rigidity is reduced. Of course, the structure of the fourth modified example can be applied to the first embodiment and the first to third modified examples.

  In the above description, the primary-side seal structure portion SP has been described in detail as an example, but the secondary-side seal structure portion SS has the same structure, and thus the same effect can be achieved.

11 Master cylinder 12 Reservoir 15 Cylinder body 18 Primary piston (piston)
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)
90 Base 91 Inner peripheral lip 92 Outer peripheral lip 93 Intermediate protrusion 96 Projection

Claims (3)

A bottomed cylindrical cylinder body having a brake fluid discharge path and a supply path communicating with the reservoir;
A piston that is slidably inserted into the cylinder body and forms a pressure chamber that supplies hydraulic pressure to the discharge passage with the cylinder body;
A piston seal provided in a circumferential groove formed in the cylinder body and having an inner circumference that is in sliding contact with the piston and capable of sealing between the supply path and the pressure chamber;
The piston seal includes an annular base, an inner peripheral lip projecting from the inner peripheral side of the base and slidingly contacting the outer peripheral surface of the piston, and projecting from the outer peripheral side of the base to the circumferential groove of the cylinder body. In a master cylinder comprising an outer peripheral lip portion that abuts, and an intermediate protruding portion that protrudes from between the inner peripheral lip portion and the outer peripheral lip portion of the base portion to beyond the outer peripheral lip portion,
A plurality of protrusions are provided along the circumferential direction on the tip side of the intermediate protrusion,
The master cylinder according to claim 1, wherein the protrusions are formed with different rigidity at both ends in the circumferential direction.   2. The master cylinder according to claim 1, wherein an angle of the side surface portion extending to the tip surface with respect to the axial direction of the cylinder body is different between the one side surface portion and the other side surface portion.   2. The master cylinder according to claim 1, wherein the protrusion has a radial thickness on one side in the circumferential direction and a radial thickness on the other side in the circumferential direction.

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