JP2012071753A - Master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master cylinder which can suppress an increase of manufacturing cost.SOLUTION: A cup seal 35 is integrally formed of a ringlike base 90 disposed at the cylinder body opening side of a seal groove 30, and lips 91, 92 extending on a cylinder body bottom side from the inner circumferential side and the outer circumferential side of the base 90. A recess 95 is formed at least at the radial intermediate part on the cylinder body open side of the base 90, and an O-ring 99 disposed in the seal groove 30 is embedded in the recess 95 side by side the cup seal 35 in the cylinder body axis direction with the diameter of the O-ring 99 set larger than the space between the cup seal 35 and the seal groove 30 in the cylinder body axis direction.

Description

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

  In order to suppress deformation of the cup seal arranged in the seal groove, the master cylinder is provided with a protrusion on the back surface of the cup seal, and this protrusion is fitted in the recess of the piston guide facing the back surface of the cup seal. Yes (see, for example, Patent Document 1).

Japanese Utility Model Publication No. 63-53862

  In the above structure, it is necessary to form the seal groove with a plurality of members in order to suppress deformation of the cup seal, and the cost for forming the seal groove increases.

  Therefore, an object of the present invention is to provide a master cylinder capable of suppressing an increase in manufacturing cost.

  In order to achieve the above object, according to the present invention, a concave portion is formed at least in a radially intermediate portion on the cylinder body opening side of the base portion of the cup seal, and the cup seal and the cylinder body are arranged side by side in the axial direction in the concave portion. An O-ring disposed in the groove was embedded, and the diameter of the O-ring was made larger than the gap between the cup seal and the seal groove in the cylinder body axial direction.

  According to the present invention, an increase in manufacturing cost can be suppressed.

It is sectional drawing which shows the master cylinder of one Embodiment. It is a fragmentary sectional view at the time of the assembly which shows the principal part of the master cylinder of one embodiment. It is a fragmentary sectional view showing a cup seal and O ring in a free state used for a master cylinder of one embodiment. It is a fragmentary sectional view showing the important section of the master cylinder of one embodiment, and shows the time of normal piston return stroke. It is a fragmentary sectional view showing an important section of a master cylinder of one embodiment, and shows a state when a cup seal is going to reverse in a piston pushing stroke. It is a fragmentary sectional view showing an important section of a master cylinder of one embodiment, and shows a state when a cup seal tries to reverse in a piston return stroke. The 1st modification of the cup seal used for the master cylinder of one embodiment is shown, (a) is a fragmentary sectional view and (b) is a partial back view. The 2nd modification of the cup seal used for the master cylinder of one embodiment is shown, (a) is a fragmentary sectional view and (b) is a partial back view. The 3rd modification of the cup seal used for the master cylinder of one embodiment is shown, (a) is a fragmentary sectional view and (b) is a partial back view. The 4th modification of the cup seal used for the master cylinder of one embodiment is shown, (a) is a fragmentary sectional view and (b) is a partial back view. The 5th modification of the cup seal used for the master cylinder of one embodiment is shown, (a) is a fragmentary sectional view and (b) is a partial back view.

  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 has a cylinder main body 15 that is formed by processing a single material into a bottomed cylindrical shape having a bottom portion 13 and a cylindrical portion 14 and that is disposed in the vehicle in a posture in which the longitudinal direction is along the vehicle front-rear direction. is doing. A primary piston (piston) 18 that is slidably inserted is provided on the opening 16 side of the cylinder body 15. A secondary piston (piston) 19 that is slidably inserted into the cylinder body 15 is provided 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 and the secondary piston 19 have inner peripheral holes 18a and 19a each having a bottom surface, and the master cylinder 11 is a so-called plunger type. Thus, the master cylinder 11 in the present embodiment is of a tandem type having two pistons. 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 22 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 22. In the present embodiment, the mounting holes 24 and 25 are formed by shifting the positions in the cylinder axial direction in a state in which the positions in the cylinder circumferential direction coincide with each other.

  A secondary discharge passage 26 and a primary discharge passage 27 to which a brake pipe (not shown) for supplying brake fluid to a brake device (not shown) is attached are formed on the mounting base 22 side of the cylinder portion 14 of the cylinder body 15. Yes. In the present embodiment, the secondary discharge passage 26 and the primary discharge passage 27 are formed so that the positions in the cylinder axial direction are shifted in a state where the positions in the cylinder circumferential direction coincide with each other.

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

  The seal groove 30 closest to the bottom 13 is formed in the vicinity of the mounting hole 24 on the bottom 13, and an annular cup seal 35 is disposed in the seal groove 30.

  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 seal 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 replenishment path 38 that connects the cylinder body 15 and the reservoir 12 in a communicable manner and always communicates with the reservoir 12.

  The sliding inner diameter portion 20 of the cylinder body 15 has an opening in the seal groove 30 on the mounting base portion 22 side in the cylinder circumferential direction and extends slightly from the seal groove 30 toward the bottom portion 13 in a straight line in the cylinder axial direction. The connecting communication 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 seal groove 30 formed between the bottom portion 13 and the seal groove 30 in the vicinity of the bottom portion 13 through a secondary pressure chamber 68 described later. Is.

  The cylinder body 15 is formed with the seal groove 31 on the opposite side to the seal groove 30 of the opening groove 37 in the cylinder axial direction, that is, on the opening 16 side, and an annular partition is formed in the seal groove 31. A seal 42 is disposed.

  The above-described seal groove 32 is formed on the opening 16 side of the cylinder body 15 and in the vicinity of the mounting hole 25 on the opening 16 side. An annular cup seal 45 is disposed in the seal groove 32 so as to be held in the seal groove 32.

  In the cylinder body 15, the sliding inner diameter of the cylinder portion 14 is formed on the opening portion 16 side of the seal groove 32 so that a communication hole 46 drilled from the mounting hole 25 on the opening portion 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 48 that connects the cylinder body 15 and the reservoir 12 in a communicable manner and always communicates with the reservoir 12.

  On the bottom 13 side of the seal groove 32 of the sliding inner diameter portion 20 of the cylinder body 15, the seal groove 32 opens on the mounting base 22 side in the cylinder circumferential direction and linearly extends from the seal groove 32 in the cylinder axial direction. A communication groove 51 that extends slightly toward the bottom 13 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 seal groove 31 and the seal groove 32 via a primary pressure chamber 85 described later.

  A seal groove 33 is formed on the cylinder body 15 on the opposite side of the opening groove 47 to the seal groove 32, that is, on the opening 16 side, and an annular partition seal 52 is disposed in the seal groove 33.

  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 19 a 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 cup 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. It can be fitted. In addition, an annular step 59 having a slightly smaller outer diameter than the other portions is formed on the outer peripheral side of the end opposite to the bottom 56 of the cylindrical portion 55. A plurality of ports 60 penetrating in the cylinder radial direction are formed radially on the stepped portion 59 on the bottom 56 side.

  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 to the secondary discharge passage 26. It is a pressure chamber (pressure chamber) 68. 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 cup seal 35 held in the seal groove 30 on the bottom 13 side of the cylinder body 15 includes an annular plate-shaped base portion 90 disposed on the opening 16 side of the seal groove 30 and an inner peripheral side of the base portion 90. An annular inner peripheral lip portion (lip portion) 91 extending substantially along the axial direction of the base portion 90 toward the bottom portion 13 side, and extending from the outer peripheral side of the base portion 90 to the bottom portion 13 side, like the inner peripheral lip portion 91. It is an integrally molded product having an annular outer peripheral lip portion (lip portion) 92 to be taken out, and one side shape of the radial cross section including the center line thereof is C-shaped.

  In the cup seal 35, the inner periphery of the inner peripheral lip portion 91 is in sliding contact with the outer periphery of the secondary piston 19. With the cup seal 35, the secondary piston 19 can seal between the secondary supply passage 38 and the secondary pressure chamber 68 in a state where the port 60 is positioned on the bottom 13 side of the cup 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 body 15 and the inner periphery of the cup seal 35 and the partition seal 42 held by the cylinder 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 brake device.

  When there is no input from the brake pedal (not shown) and the secondary piston 19 is in a position (non-braking position) for opening the port 60 into the opening groove 37, the inner peripheral side of the base portion 90 of the cup seal 35 is the above-mentioned. In the step part 59 of the secondary piston 19, it arrange | positions in the position which does not contact the step part 59. FIG. Then, the secondary piston 19 moves to the bottom 13 side of the cylinder body 15 and the inner peripheral side of the base portion 90 of the cup seal 35 contacts the stepped portion 59, so that the communication between the secondary pressure chamber 68 and the reservoir 12 is blocked. It has become so. With such a configuration, it is possible to shorten the so-called invalid stroke from when the piston starts to move until the pressure in the pressure chamber is generated.

  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 with respect to the part 71 is comprised. The inner peripheral hole 18a is formed by the first cylindrical portion 71 and the bottom portion 72 among them. The primary piston 18 includes a cup seal 45 and a partition seal 52 provided in the sliding inner diameter portion 20 of the cylinder body 15 in a state where the first cylindrical portion 71 is disposed on the secondary piston 19 side in 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. Furthermore, a plurality of ports 76 are formed radially in the concave portion 75 of the first cylindrical portion 71 so as to penetrate the bottom portion 72 in the radial 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 82. And a shaft member 83 that slidably supports the stop member 81 only within a predetermined range. The primary piston spring 78 is interposed between the locking members 81 and 82 on both sides.

  Here, the portion formed by the opening 16 side of the cylinder portion 14 of the cylinder body 15 and the primary piston 18 and the secondary piston 19 generates brake fluid pressure and supplies the brake fluid to the primary discharge passage 27. The primary pressure chamber (pressure chamber) 85 is used. 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.

  Similarly to the cup seal 35, the cup seal 45 held in the seal groove 32 of the cylinder body 15 also has an annular plate-like base portion 90 disposed on the opening 16 side of the seal groove 32, and an inner periphery of the base portion 90. An annular inner peripheral lip portion 91 that extends from the side toward the bottom portion 13 substantially along the axial direction of the base portion 90, and extends from the outer peripheral side of the base portion 90 to the bottom portion 13 side, similar to the inner peripheral lip portion 91. It is an integrally molded product having an annular outer peripheral lip portion 92, and the one-side shape of the radial cross section including the center line is C-shaped.

  In the cup seal 45, the inner periphery of the inner peripheral lip portion 91 is in sliding contact with the outer periphery of the primary piston 18. With the cup seal 45, the primary piston 18 can seal between the primary supply passage 48 and the primary pressure chamber 85 in a state where the port 76 is positioned on the bottom 13 side of the cup 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 body 15 and the inner periphery of the cup seal 45 and the partition seal 52 held by the cylinder body 15, whereby the brake in the primary pressure chamber 85 is reached. The liquid is pressurized and supplied from the primary discharge passage 27 to the brake device.

  When there is no input from the brake pedal side (not shown) and the primary piston 18 is in a position (non-braking position) for opening the port 76 to the opening groove 47, the inner peripheral side of the base portion 90 of the cup seal 45 is The primary piston 18 is arranged in a position where it does not come into contact with the recess 75 in the recess 75. The primary piston 18 moves to the bottom 13 side of the cylinder body 15 and the inner peripheral side of the base portion 90 of the cup seal 45 abuts against the recess 75, so that the communication between the primary pressure chamber 85 and the reservoir 12 is blocked. It is like that. With such a configuration, it is possible to shorten the so-called invalid stroke from when the piston starts to move until the pressure in the pressure chamber is generated.

  Here, a secondary-side seal structure SS composed of a portion near the seal groove 30 of the cylinder body 15 shown in FIG. 1, a sliding contact portion of the cup seal 35 and the cup seal 35 of the secondary piston 19, The primary side seal structure SP composed of the vicinity of the seal groove 32, the cup seal 45, and the sliding contact portion of the cup seal 45 of the primary piston 18 has the same structure. This will be described mainly with reference to FIGS. 2 to 6 by taking the seal structure portion SS on the secondary side as an example.

  The seal groove 30 has a cylindrical groove bottom portion 30a that is the outermost in the cylinder radial direction and extends along the cylinder axis direction, and a cylinder shaft at the end of the groove bottom portion 30a on the cylinder body bottom portion 13 side (left side in FIG. 2). An annular wall 30b orthogonal to the direction and an annular wall 30c orthogonal to the cylinder axial direction at the end edge of the groove bottom 30a on the cylinder body opening 16 side (right side in FIG. 2) are provided. The groove bottom 30a, the annular wall 30b, and the annular wall 30c are formed integrally with the cylinder body 15 and are all formed by cutting the cylinder body 15.

  The cup seal 35 comes into sliding contact with the outer peripheral surface 19b of the secondary piston 19 at the inner peripheral surface 91a of the inner peripheral lip portion 91, and behind the back surface 90a of the base body 90 on the cylinder body opening 16 side. It faces the annular wall 30c of the seal groove 30 and contacts the groove bottom portion 30a of the seal groove 30 at the outer peripheral surface 92a of the outer peripheral lip portion 92.

  The cup seal 35 is formed with a concave portion 95 formed of an annular groove that is coaxial with the base portion 90 and is recessed in the axial direction at the radial intermediate portion of the back surface 90 a of the base portion 90. Thereby, an annular convex portion 96 that protrudes toward the cylinder body opening 16 side is formed on the base portion 90 on the radially outer side of the recessed portion 95, and the cylinder body opening portion 16 side is formed on the radially inner side of the recessed portion 95. An annular convex portion 97 is formed so as to protrude from the center. Accordingly, the concave portion 95 is closed on both the inner and outer sides in the radial direction and is opened outward only on one side in the axial direction. The recess 95 is formed close to the outer peripheral lip 92 side of the back surface 90 a of the base 90.

  In the recess 95 of the cup seal 35, an O-ring 99 is embedded in which one side of the radial cross section including the center line has a circular shape. The O-ring 99 is embedded in the recess 95, and is arranged in the seal groove 30 side by side in the axial direction of the cup seal 35 and the cylinder body 15.

  Here, as shown in FIG. 3, in the natural state, the length in the axial direction of the cup seal 35 is Lcup, the depth of the concave portion 95 is Hcup, and the inner diameter on the small side of the concave portion 95 (the outer diameter of the convex portion 97) is Dcup1. 2, the outer diameter on the large side of the concave portion 95 (the inner diameter of the convex portion 96) is Dcup 2, and in the natural state, the axial length of the O-ring 99, that is, the diameter is Hring, the inner diameter is Dring 1, and the outer diameter is Dring 2. As shown, when the axial width of the seal groove 30 (distance between the annular walls 30b and 30c) is Lmizo, the cup seal 35, the O-ring 99 and the seal groove 30 are set to a dimensional relationship that satisfies the following relationship. ing.

Hcup> Hring
Dcup1 <Dring1
Dcup2> Dring2
Lmizo> Lcup
Hring> (Lmizo-Lcup)

  Here, Lmizzo-Lcup is a gap between the cup seal 35 and the seal groove 30 in the axial direction of the cylinder body 15, and the diameter Hring of the O-ring 99 is larger than this gap.

  In the piston pushing stroke in which the secondary piston 19 moves to the cylinder body bottom 13 side (left side in FIG. 2), the O-ring 99 is recessed in the state in which the secondary piston 19 slides smoothly with respect to the cup seal 35. 95, the O-ring 99 is deformed integrally with the cup seal 35 in the recess 95, and the cup seal 35 is deformed into the O-ring 99 and the recess 95. It works in the same way as no state. In this piston pushing stroke, the outer peripheral surface 92 a of the outer peripheral lip portion 92 of the cup seal 35 is in close contact with the groove bottom portion 30 a of the seal groove 30, and the inner peripheral surface 91 a of the inner peripheral lip portion 91 of the cup seal 35 is the outer periphery of the secondary piston 19. Closely contacted with the surface 19b, the gap between the cylinder body 15 and the secondary piston 19 is sealed, and the escape of hydraulic pressure from the secondary pressure chamber 68 to the atmospheric pressure reservoir 12 and the secondary supply path 38 shown in FIG. To do.

  In the piston return stroke in which the secondary piston 19 moves to the cylinder body opening 16 side (the right side in FIG. 2), the O-ring 99 is in a state where the secondary piston 19 slides smoothly with respect to the cup seal 35. A force that moves from the inside of the recess 95 to the outside is not received from the outside, and the cup seal 35 is deformed integrally with the cup seal 35 as in the piston pushing process, and the cup seal 35 does not have the O-ring 99 and the recess 95. Works the same as the state. In this piston return stroke, the secondary pressure chamber 68 shown in FIG. 1 becomes negative pressure, so that the outer peripheral surface 92a of the outer peripheral lip 92 of the cup seal 35 is separated from the groove bottom 30a of the seal groove 30 as shown in FIG. The liquid supply from the atmospheric pressure reservoir 12 and the secondary supply path 38 shown in FIG. 1 to the secondary pressure chamber 68 through the gap between the cylinder body 15 and the secondary piston 19 is enabled.

  Further, as shown by an arrow A1 in FIG. 5, in the piston pushing process in which the secondary piston 19 moves to the cylinder body bottom 13 side, the friction coefficient becomes high for some reason such as catching or sticking, and the secondary piston 19 becomes a cup seal. When the inner lip 91 of the cup seal 35 cannot move smoothly with respect to the cylinder 35, the inner lip 91 of the cup seal 35 is pulled to the cylinder body bottom 13 side (left side in FIG. 5) to move together with the secondary piston 19. The part 90 starts to deform radially inward. That is, a force in the direction indicated by R1 in FIG. As a result, the concave portion 95 of the cup seal 35 tends to move inward in the radial direction, so that the outer diameter thereof is reduced and the overall shape is reduced. Immediately after the start of the reversal of the cup seal 35, the O-ring 99 set so as to fit in the recess 95 is also deformed so that the outer diameter is reduced.

  Then, when the inversion of the cup seal 35 further proceeds and the concave portion 95 further moves inward in the radial direction, the elastic energy of compression due to the diameter reduction stored in the O-ring 99 increases, and this elastic energy causes the O-ring to be compressed. 99 has a restoring force to return to the original diameter as indicated by f1 in FIG. At this time, since a gap in the axial direction of the cylinder body 15 for replenishing liquid is formed between the O-ring 99 and the seal groove 30, the O-ring 99 is moved from the recess 95 to the direction of the gap by the restoring force. It moves until it contacts the annular wall 30c. Since the diameter of the O-ring 99 is larger than the gap between the cup seal 35 and the seal groove 30 in the axial direction of the cylinder body 15, when the O-ring 99 comes into contact with the annular wall 30c as shown in FIG. And the annular wall 30c, the restoring force is applied in a direction that restrains the movement of the concave portion 95 inward in the radial direction, and the reversal of the cup seal 35 is restricted.

  6, when the secondary piston 19 does not slide smoothly with respect to the cup seal 35 in the piston return stroke in which the secondary piston 19 moves toward the cylinder body opening 16, The inner peripheral lip portion 91 of the seal 35 is pulled toward the cylinder body opening 16 side (the right side in FIG. 6) in an attempt to move together with the secondary piston 19, and accordingly, the base portion 90 starts to deform radially outward. That is, a force in the reverse direction indicated by R2 in FIG. 6 is generated on the cup seal 35 in the direction opposite to the piston pushing stroke. Then, the concave portion 95 of the cup seal 35 tends to move outward in the radial direction, and the inner diameter is enlarged. Immediately after the start of the reversal of the cup seal 35, the O-ring 99 set so as to fit in the recess 95 is also deformed so that the inner diameter is enlarged.

  When the inversion of the cup seal 35 further proceeds and the concave portion 95 further moves outward in the radial direction, the elastic energy of pulling due to the enlarged diameter that is stored inside the O-ring 99 increases. 99 has a restoring force to return to the original diameter as indicated by f2 in FIG. The O-ring 99 moves from the recess 95 by this restoring force in the axial gap direction of the cylinder body 15 between the O-ring 99 and the seal groove 30 until it contacts the annular wall 30c. Since the diameter of the O-ring 99 is larger than the gap between the cup seal 35 and the seal groove 30 in the axial direction of the cylinder body 15, when the O-ring 99 comes into contact with the annular wall 30c as shown in FIG. And the annular wall 30c, and the restoring force is applied in a direction that restrains the movement of the concave portion 95 in the radially outward direction, thereby restricting the reversal of the cup seal 35.

  In this way, a recess 95 is formed in the radially intermediate portion of the base portion 90 of the cup seal 35 on the cylinder body opening 16 side, and in this recess 95, the seal groove is aligned in the axial direction of the cup seal 35 and the cylinder body 15. An O-ring 99 disposed at 30 is embedded, and the diameter of the O-ring 99 is larger than the gap between the cup seal 35 and the seal groove 30 in the axial direction of the cylinder body 15. For this reason, even if the entire seal groove 30 is formed by cutting the cylinder body 15, the inversion of the cup seal 35 can be regulated by the O-ring 99. Therefore, the reliability of the master cylinder can be improved while suppressing an increase in manufacturing cost.

  In addition, in order to improve the replenishment property at the time of liquid replenishment from the reservoir 12 to the secondary pressure chamber 68, the convex portion 196 is intermittently provided in the circumferential direction like the cup seal 135 of the first modified example shown in FIG. A plurality of arc-shaped convex portions 196A are formed, and a passage groove 196B penetrating in the radial direction is formed between adjacent convex portions 196A, and the convex portions 197 are intermittently formed in the circumferential direction. A plurality of arc-shaped convex portions 197A may be formed, and a passage groove 197B penetrating in the radial direction may be formed between adjacent convex portions 197A.

  Next, in the above description, the concave portion 95 in which both the inner and outer sides in the radial direction are closed on the cylinder body opening 16 side of the base portion 90 of the cup seal 35 and the axial cylinder body opening 16 side is opened to the outside. The case of having 195 has been described as an example. However, the cup seal only needs to have a portion that is recessed in the axial direction from the end surface of the base portion at least in the radially intermediate portion of the base portion on the cylinder body opening 16 side.

  For example, like the cup seal 235 of the second modification shown in FIG. 8, the recess 295 has a shape in which the outer side in the radial direction is closed and the inner side in the radial direction and the cylinder opening 16 side in the axial direction are opened outward. May be. In other words, the concave portion 295 has a shape widened in the direction in which the diameter is reduced, and the convex portion 297 on the inner peripheral side of the base portion 290 is not formed, and protrudes toward the cylinder body opening 16 side on the outer peripheral side of the base portion 290. An annular convex portion 296 is formed. By satisfying other than the relational expression related to Dcup 1 described above, the recess 295 can prevent reversal in the piston pushing stroke by the O-ring 99.

  In this case, in order to improve the replenishment performance when the liquid is replenished from the reservoir 12 to the secondary pressure chamber 68, the convex portion 396 is intermittently provided in the circumferential direction like the cup seal 335 of the third modified example shown in FIG. Alternatively, a plurality of arc-shaped convex portions 396A may be formed, and a passage groove 396B penetrating in the radial direction may be formed between adjacent convex portions 396A.

  Further, like the cup seal 435 of the fourth modified example shown in FIG. 10, the concave portion 495 has a shape in which the radially inner side is closed and the radially outer side and the axial cylinder opening 16 side are opened to the outer side. May be. In other words, the concave portion 495 has a shape widened in the direction in which the diameter increases, the convex portion 496 on the outer peripheral side of the base portion 490 is not formed, and protrudes toward the cylinder body opening 16 side on the inner peripheral side of the base portion 490. In this shape, an annular convex portion 497 is formed. The concave portion 495 satisfies the relational expression other than the relational expression related to Dcup 2 described above, whereby the inversion in the piston return stroke can be prevented by the O-ring 99.

  Also in this case, in order to improve the replenishment property when replenishing the liquid from the reservoir 12 to the secondary pressure chamber 68, the convex portion 597 is arranged in the circumferential direction like the cup seal 535 of the fifth modified example shown in FIG. A plurality of arc-shaped convex portions 597A formed intermittently may be formed, and a passage groove 597B penetrating in the radial direction may be formed between adjacent convex portions 597A.

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

11 Master cylinder 15 Cylinder body 18 Primary piston (piston)
19 Secondary piston (piston)
30, 32 Seal groove 35, 45, 135, 235, 335, 435, 535 Cup seal 68 Secondary pressure chamber (pressure chamber)
85 Primary pressure chamber (pressure chamber)
90 Base part 91 Inner lip part (lip part)
92 Outer lip (lip)
95 Concave 99 O-ring

Claims (1)

A piston slides on the inner periphery of a cup seal held in an annular seal groove formed in a bottomed cylindrical cylinder body, and brake fluid pressure is applied in a pressure chamber formed by the piston and the cylinder body. In the generated master cylinder,
The cup seal is integrally formed with an annular base portion disposed on the cylinder body opening side of the seal groove and a lip portion extending from the inner peripheral side and the outer peripheral side of the base portion to the cylinder main body bottom side, respectively.
A recess is formed at least in a radially intermediate portion on the cylinder body opening side of the base portion,
The recess is embedded with an O-ring that is arranged in the seal groove side by side in the axial direction of the cup seal and the cylinder body,
A diameter of the O-ring is larger than a gap between the cup seal and the seal groove in the cylinder body axial direction.

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