CN104661885B - Master cylinder - Google Patents

Abstract

The piston seal has an annular base, an inner lip protruding from the inner peripheral side of the base and slidingly contacting the outer peripheral surface of the piston, and an outer peripheral lip protruding from the outer peripheral side of the base and contacting the peripheral groove of the cylinder body. part, an intermediate protruding part protruding forward from between the inner peripheral lip and the outer peripheral lip of the base part than the outer peripheral lip. A connection portion is provided between the inner peripheral lip and the middle protrusion, and the connection portion is formed extending in the axial direction of the piston seal to connect the inner peripheral lip and the middle protrusion.

Description

main tank

technical field

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

this application claims priority based on Japanese Patent Application No. 2012-241198 for which it applied to Japan on October 31, 2012, and uses the content here.

Background technique

In a master cylinder, a piston seal having an inner peripheral lip is provided in a peripheral groove of a cylinder body, and the inner peripheral lip of the piston seal is brought into sliding contact with the piston (for example, refer to Patent Document 1).

In another master cylinder, a cup seal and a slide ring slidingly connected to the cylinder main body are provided in an annular groove of the piston (for example, refer to Patent Document 2).

prior art literature

patent documents

Patent Document 1: (Japanese) Unexamined Patent Application Publication No. 2006-123879

Patent Document 2: (Japanese) Unexamined Patent Publication No. 9-136641

Name content

The problem to be solved by the invention

If it is a structure in which a piston seal is provided in the peripheral groove of the cylinder body as in the master cylinder described in Patent Document 1, and the piston is in sliding contact with the piston seal, the inner surface of the piston seal may be damaged due to the movement of the piston. The peripheral lip enters between the cylinder body and the piston.

The present invention provides a master cylinder capable of suppressing entry of an inner peripheral lip between a cylinder body and a piston due to movement of the piston.

Technical solutions for solving problems

The master cylinder provided by the first aspect of the present invention has: a bottomed cylindrical cylinder main body having a brake fluid discharge passage and a supply passage communicating with the liquid storage chamber; a piston movably provided on the cylinder main body Inside, a pressure chamber for supplying hydraulic pressure to the discharge passage is formed between the piston and the cylinder main body; a piston seal is provided in a peripheral groove formed on the cylinder main body, and the inner circumference and the A piston slides to seal between the supply passage and the pressure chamber. The piston seal includes an annular base, an inner lip protruding from the inner peripheral side of the base and slidingly contacting the outer peripheral surface of the piston, protruding from the outer peripheral side of the base and contacting the cylinder main body. The outer peripheral lip abutted by the peripheral groove, and the intermediate protrusion protruding forward from between the inner peripheral lip and the outer peripheral lip of the base portion further forward than the outer peripheral lip. A connection portion is provided between the inner peripheral lip and the middle protrusion, and the connection portion is formed extending in the axial direction of the piston seal and connects the inner peripheral lip and the middle protrusion.

A plurality of the coupling portions may be provided separately from each other along the circumferential direction of the base portion.

The connecting portion may also be formed extending from the base portion along the front end direction of the middle protruding portion.

In the master cylinder provided by the second aspect of the present invention, a tapered surface may be formed on the opening side of the peripheral groove on the peripheral wall of the peripheral groove on the bottom side of the cylinder main body. The front end of the connecting portion may be arranged to face a boundary between the tapered surface and a wall surface of the peripheral wall that is closer to the bottom of the peripheral groove than the tapered surface.

The connecting portion may also be formed to extend at least to a maximum interference portion of the inner peripheral lip.

Invention effect

According to the master cylinder described above, it is possible to prevent the inner peripheral lip from entering between the cylinder body and the piston due to the movement of the piston.

Description of drawings

FIG. 1 is a sectional view showing a master cylinder according to an embodiment of the present invention;

2 is a partially enlarged cross-sectional view showing a main part of a master cylinder according to an embodiment of the present invention, showing a state where a piston is in a basic position;

3A is a front view showing a piston seal of a master cylinder according to an embodiment of the present invention;

3B is a side view showing a piston seal of the master cylinder according to an embodiment of the present invention;

Fig. 4A is a diagram showing a piston seal of a master cylinder according to an embodiment of the present invention, and is a sectional view taken along line AA of Fig. 3A;

Fig. 4B is a diagram showing a piston seal of the master cylinder according to an embodiment of the present invention, and is a cross-sectional view along BB of Fig. 3A;

5A is a partially enlarged cross-sectional view showing a main part of the master cylinder according to an embodiment of the present invention, and is a view showing a state of an initial movement of a piston;

5B is a partially enlarged cross-sectional view showing a main part of the master cylinder according to an embodiment of the present invention, and is a view showing a state after FIG. 5A;

Fig. 6 is a cross-sectional view of a modified example of the piston seal;

Fig. 7 is a cross-sectional view showing a modified example of the piston seal.

detailed description

One embodiment of the present invention will be described with reference to the drawings. The master cylinder 11 of this embodiment shown in FIG. 1 receives a force corresponding to the operation amount of the brake pedal (not shown) via the output shaft of the brake booster (not shown), and generates a force corresponding to the operation amount of the brake pedal. brake hydraulic pressure. The master cylinder 11 is equipped with a reservoir chamber 12 (only a part of which is shown in FIG. 1 ) for supplying brake fluid upward in the vertical direction. It should be noted that, in this embodiment, although the liquid storage chamber 12 is directly installed on the master cylinder 11, it is also possible to arrange the liquid storage chamber at a position separate from the master cylinder 11, and use piping to connect the liquid storage chamber and the main cylinder. Cylinder 11.

The master cylinder 11 has a metal cylinder main body 15 processed into a bottomed cylindrical shape having a bottom 13 and a cylindrical portion 14 using one material. The cylinder main body 15 is arranged on the vehicle with the axial direction along the vehicle front-rear direction. A metal primary piston (piston) 18 is movably disposed on the opening 16 side of the cylinder main body 15 . The same metal secondary piston (piston) 19 is arranged movably on the bottom 13 side of the cylinder body 15 relative to the primary piston 18 . An inner peripheral hole 21 having a bottom surface is formed in the primary piston 18 . An inner peripheral hole 22 having a bottom surface is formed in the secondary piston 19 . The master cylinder 11 is a so-called plunger type master cylinder. The master cylinder 11 is a tandem master cylinder having two pistons 18 and 19 as described above. It should be noted that the embodiment is not limited to the above-mentioned tandem master cylinder, as long as it is a plunger-type master cylinder, it can be applied to a single-type master cylinder with one piston disposed in the cylinder body or a single-type master cylinder with three or more pistons. master cylinder and any plunger type master cylinder.

The cylinder main body 15 is integrally formed with a mount portion 23 projecting 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). . Mounting holes 24 and 25 for mounting the liquid storage chamber 12 are formed in the mount portion 23 . In this embodiment, the positions of the mounting holes 24 and 25 in the direction of the axis of the cylindrical portion 14 of the cylinder body 15 (hereinafter referred to as the cylinder axis) are shifted in a state where the positions in the cylinder circumferential direction are aligned. formed in the upper part.

A secondary discharge passage (discharge passage) 26 is formed in the vicinity of the bottom 13 on the mounting table portion 23 side of the cylindrical portion 14 of the cylinder main body 15 . A primary discharge passage (discharge passage) 27 is formed on the opening portion 16 side of the secondary discharge passage (discharge passage) 26 . Although not shown, these secondary discharge passages 26 and primary discharge passages 27 communicate with brake cylinders such as disc brakes and drum brakes via brake pipes, and discharge brake fluid to the brake cylinders. In this embodiment, these secondary discharge passages 26 and primary discharge passages 27 are formed so that their positions in the cylinder axial direction are shifted from each other while aligning their positions in the cylinder circumferential direction.

The secondary piston 19 is slidably guided in a cylindrical sliding inner diameter portion 28 centered on the cylinder axis formed on the inner peripheral portion of the cylinder portion 14 on the bottom 13 side of the cylinder body 15 . The primary piston 18 is slidably guided in a cylindrical sliding inner diameter portion 29 centered on the cylinder axis formed on the inner peripheral portion of the cylinder portion 14 on the opening 16 side of the cylinder body 15 .

In the sliding inner diameter portion 28 , a plurality of circular grooves 30 and 31 are formed sequentially from the bottom 13 side with shifted positions in the cylinder axial direction. In addition, in the sliding inner diameter portion 29 , a plurality of circular grooves 32 and 33 are formed in order from the bottom 13 side, and are located at two locations with shifted positions in the cylinder axial direction. These peripheral grooves 30 to 33 are formed in an annular shape along the cylinder circumferential direction and are formed in a concave shape outward in the cylinder radial direction. The entire peripheral grooves 30 to 33 are formed by cutting.

The peripheral groove 30 on the bottommost 13 side is formed near the mounting hole 24 on the bottom 13 side among the mounting holes 24 , 25 . An annular piston seal 35 is disposed in the peripheral groove 30 so as to be held by the peripheral groove 30 .

In the sliding inner diameter portion 28 of the cylinder main body 15, on the opening portion 16 side of the peripheral groove 30, an annular opening groove 37 recessed outward in the cylinder radial direction is formed so that the mounting hole 24 on the bottom 13 side can pass through. The provided communicating hole 36 opens into the cylindrical portion 14 . Here, the open groove 37 and the communication hole 36 mainly constitute a secondary supply passage (supply passage) 38 provided in the cylinder main body 15 and always in communication with the liquid storage chamber 12 .

In the sliding inner diameter portion 28 of the cylinder main body 15, a groove opening into the peripheral groove 30 and extending linearly from the peripheral groove 30 toward the bottom 13 side along the cylinder axial direction is formed so as to be recessed outward in the cylinder radial direction. Connecting slot not shown. The communication groove communicates with the secondary discharge passage 26 formed in the vicinity of the bottom 13 and the peripheral groove 30 through a secondary pressure chamber 68 described later.

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

The aforementioned peripheral groove 32 is formed in the sliding inner diameter portion 29 of the cylinder main body 15 in the vicinity of the attachment hole 25 on the opening portion 16 side. An annular piston seal 45 is arranged in the peripheral groove 32 so as to be held by the peripheral groove 32 .

On the opening 16 side of the circumferential groove 32 in the sliding inner diameter portion 29 of the cylinder main body 15, an annular opening groove 47 recessed outward in the radial direction of the cylinder is formed so that the mounting hole 25 on the opening 16 side passes through. The provided communicating hole 46 opens into the cylindrical portion 14 . Here, the open groove 47 and the communication hole 46 mainly constitute a primary supply passage (supply passage) 48 provided in the cylinder main body 15 and always in communication with the liquid storage chamber 12 .

On the bottom 13 side of the peripheral groove 32 of the sliding inner diameter portion 29 of the cylinder main body 15 , a groove opening to the peripheral groove 32 and extending linearly from the peripheral groove 32 in the cylinder axial direction is formed so as to be recessed outward in the cylinder radial direction. A communication groove (not shown) extending toward the bottom 13 side. The communication groove communicates with the primary discharge passage 27 formed in the vicinity of the peripheral groove 31 and the peripheral groove 32 via a primary pressure chamber 85 described later.

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

The secondary piston 19 fitted on the bottom 13 side of the cylinder main body 15 is formed in a bottomed cylindrical shape having a cylindrical portion 55 and a bottom 56 formed on one side in the axial direction of the cylindrical portion 55 . The above-mentioned inner peripheral hole 22 is formed by these cylindrical portion 55 and bottom portion 56 . With the cylindrical portion 55 disposed on the bottom 13 side of the cylinder main body 15, the secondary piston 19 is connected to the respective piston seal 35 and the partition seal 42 provided on the sliding inner diameter portion 28 of the cylinder main body 15. The inner circumference is slidably fitted. On the outer peripheral portion of the end side opposite to the bottom 56 of the cylindrical portion 55 , a stepped annular step portion 59 is formed, and the stepped portion 59 is located closer to the outer diameter portion 58 of the largest diameter in the secondary piston 19 . Radially inside. On the bottom 56 side of the stepped portion 59 , a plurality of ports 60 penetrating in the cylinder radial direction are radially formed at positions at equal intervals in the cylinder circumferential direction.

Between the secondary piston 19 and the bottom 13 of the cylinder main body 15, there is provided an interval adjusting portion 63 including a secondary piston spring 62 on the side of the brake pedal (not shown in FIG. 1 ). Right side) The separation between the secondary piston 19 and the bottom 13 of the cylinder body 15 is determined in the non-braking state with no input. The gap adjusting portion 63 has a locking member 64 and a locking member 65 that are in contact with the bottom 13 of the cylinder main body 15, and the locking member 65 is connected to the locking member 64 so as to slide only within a predetermined range. The bottom 56 of the secondary piston 19 abuts. The secondary piston spring 62 is installed between the locking members 64 and 65 on both sides.

Here, the portion surrounded by the bottom 13 of the cylinder main body 15 , the bottom 13 side of the cylindrical portion 14 , and the secondary piston 19 serves as a secondary pressure chamber that generates brake hydraulic pressure and supplies the brake hydraulic pressure to the secondary discharge passage 26 . (pressure chamber)68. In other words, the secondary piston 19 has a secondary pressure chamber 68 that supplies hydraulic pressure to the secondary discharge passage 26 between the secondary piston 19 and the cylinder main body 15 . When the secondary piston 19 is at a position where the port 60 opens to the opening groove 37 , the secondary pressure chamber 68 communicates with the secondary supply passage 38 , that is, the reservoir chamber 12 .

The partition seal 42 held in the peripheral groove 31 of the cylinder main body 15 is an integrally molded product made of synthetic rubber. The one-sided shape of the radial section of the zoned seal 42 including its center line is formed in a C-shape. The zoned seal 42 has its inner periphery in sliding contact with the outer periphery of the secondary piston 19 that moves axially along the cylinder, and its outer periphery abuts against the peripheral groove 31 of the cylinder main body 15 to always seal the secondary piston 19 and the cylinder. The cylinder main body 15 has a gap at the position of the partition seal 42 .

The piston seal 35 held in the peripheral groove 30 of the cylinder main body 15 is an integrally molded product made of synthetic rubber such as EPDM. The piston seal 35 is configured such that its inner circumference is in sliding contact with the outer circumference of the secondary piston 19 that moves in the cylinder axial direction, and its outer circumference is in contact with the peripheral groove 30 of the cylinder main body 15 . The piston seal 35 can seal between the secondary supply passage 38 and the secondary pressure chamber 68 when the port 60 of the secondary piston 19 is located on the bottom 13 side of the piston seal 35, that is, the secondary pressure chamber 68 can be blocked. The pressure chamber 68 communicates with the secondary supply passage 38 and the liquid storage chamber 12 . In this state, the secondary piston 19 slides on the sliding inner diameter portion 28 of the cylinder main body 15 and the inner circumference of the piston seal 35 and the partition seal 42 held in the cylinder main body 15 and moves toward the bottom 13 side, thereby The brake fluid in the secondary pressure chamber 68 is pressurized and supplied from the secondary discharge passage 26 to the brake cylinder on the wheel side.

It should be noted that when there is no input from the not-shown brake pedal side and the secondary piston 19 is at a position (non-braking position) where the port 60 is opened to the opening groove 37 as shown in FIG. 1 , the piston A part of the seal 35 overlaps the port 60 within the stepped portion 59 of the secondary piston 19 . Then, when the secondary piston 19 moves toward the bottom 13 of the cylinder body 15 and the inner peripheral portion of the piston seal 35 completely overlaps the port 60 , communication between the secondary pressure chamber 68 and the reservoir chamber 12 is cut off.

The primary piston 18 fitted to the opening 16 side of the cylinder main body 15 is formed to have a first cylindrical portion 71 , a bottom 72 formed on one side in the axial direction of the first cylindrical portion 71 , and a bottom portion 72 formed on the bottom 72 . The shape of the second cylindrical portion 73 formed on the opposite side to the first cylindrical portion 71 . The above-mentioned inner peripheral hole 21 is formed by the first cylindrical portion 71 and the bottom portion 72 among them. The primary piston 18 is slidably fitted to a piston seal provided on the sliding inner diameter portion 29 of the cylinder body 15 with the first cylindrical portion 71 disposed on the side of the secondary piston 19 inside the cylinder body 15 . 45 and the inner circumference of the zone seal 52 respectively. Here, the output shaft of the brake booster is inserted inside the second cylindrical portion 73 , and the bottom portion 72 is pressed by the output shaft.

On the end side outer peripheral portion of the first cylindrical portion 71 opposite to the bottom portion 72 , a stepped annular step portion 75 is formed. More radially inward. On the bottom 72 side of the stepped portion 75 , a plurality of ports 76 penetrating in the cylinder radial direction are radially formed at positions 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, and the interval adjusting portion 79 has no input on the brake pedal side (right side in FIG. 1 ), not shown. The distance between the secondary piston 19 and the primary piston 18 is determined in the non-braking state. The gap adjustment part 79 has a locking member 81 that abuts on the bottom 72 of the primary piston 18, a locking member 82 that abuts on the bottom 56 of the secondary piston 19, and has one end portion fixed to the locking member 81, and only in a predetermined position. The shaft member 83 slidably supports the locking member 82 within a range. The above-mentioned primary piston spring 78 is installed between the locking members 81 and 82 on both sides.

Here, a portion surrounded by the cylindrical portion 14 of the cylinder main body 15 , the primary piston 18 , and the secondary piston 19 serves as a primary pressure chamber (pressure chamber) 85 that generates brake hydraulic pressure and supplies the brake hydraulic pressure to the primary discharge passage 27 . . In other words, the primary piston 18 forms a secondary primary pressure chamber 85 that supplies hydraulic pressure to the primary discharge passage 27 between the secondary piston 19 and the cylinder main body 15 . When the primary piston 18 is at a position where the port 76 opens to the opening groove 47 , the primary pressure chamber 85 communicates with the primary supply passage 48 , that is, the reservoir chamber 12 .

The partition seal 52 held in the peripheral groove 33 of the cylinder main body 15 is the same component as the partition seal 42 and is an integrally molded product made of synthetic rubber. The one-sided shape of the radial cross-section including the center line of the zone seal 52 is formed in a C-shape. The zoned seal 52 has its inner periphery in sliding contact with the outer periphery of the primary piston 18 that moves axially along the cylinder, and its outer periphery abuts against the peripheral groove 33 of the cylinder main body 15 to always seal the primary piston 18 and the cylinder. The gap of the body 15 at the location of the zone seal 52 .

The piston seal 45 held in the peripheral groove 32 of the cylinder main body 15 is the same component as the piston seal 35 and is an integrally molded product made of synthetic rubber. The piston seal 45 is configured such that its inner circumference is in sliding contact with the outer circumference of the primary piston 18 that moves in the cylinder axial direction, and its outer circumference is in contact with the peripheral groove 32 of the cylinder main body 15 . In the state where the primary piston 18 is located so that the port 76 is closer to the bottom 13 side than the piston seal 45, the piston seal 45 can seal between the primary supply passage 48 and the primary pressure chamber 85, that is, can cut off the primary pressure chamber 85. It communicates with the primary supply passage 48 and the liquid storage chamber 12 . In this state, the primary piston 18 slides on the sliding inner diameter portion 29 of the cylinder main body 15 and the inner circumference of the piston seal 45 and the partition seal 52 held in the cylinder main body 15 and moves toward the bottom 13 side, thereby, The brake fluid in the primary pressure chamber 85 is pressurized and supplied from the primary discharge passage 27 to the brake cylinder on the wheel side.

It should be noted that when there is no input from the brake pedal side (not shown) and the primary piston 18 is at a position (non-braking position) where the port 76 is opened to the opening groove 47 as shown in FIG. 1 , the piston seal Part 45 overlaps the port 76 in the stepped portion 75 of the primary piston 18 . Then, when the primary piston 18 moves toward the bottom 13 of the cylinder body 15 and the inner peripheral portion of the piston seal 45 completely overlaps the port 76 , communication between the primary pressure chamber 85 and the reservoir chamber 12 is cut off.

The structure of the seal structure part SS on the secondary side, which is composed of the peripheral groove 30 of the cylinder main body 15 and its vicinity, the piston seal 35, and the part where the secondary piston 19 slides with the piston seal 35, is identical to that of the cylinder main body. The structure of the primary-side seal structure SP formed by the peripheral groove 32 of 15 and its vicinity, the piston seal 45 , and the sliding contact between the primary piston 18 and the piston seal 45 is the same. Therefore, in the following, the primary-side seal structure portion SP will be described in detail mainly with reference to FIGS. 2 to 7 .

As shown in FIG. 2 , the peripheral groove 32 has a cylindrical groove bottom (the bottom of the peripheral groove 32 ) which is located on the outermost side in the radial direction of the cylinder (upper side in FIG. 2 ) and is centered on the cylinder axis. ) 88, a peripheral wall 89 extending radially inward from the groove bottom 88 near the opening 16 side of the cylinder main body 15 (the right side in FIG. 2 ) in a direction perpendicular to the cylinder axis A peripheral wall 90 extending radially inward of the cylinder radially from an edge portion of the groove bottom 88 on the bottom 13 side (left side in FIG. 2 ) of the cylinder main body 15 in a direction perpendicular to the cylinder axis. These groove bottoms 88 , peripheral walls 89 , and peripheral walls 90 are formed integrally with the cylinder body 15 by cutting the cylinder body 15 .

The peripheral wall 89 has a flat surface 89a formed of a flat surface parallel to a plane perpendicular to the cylinder axis, and an R-chamfered portion 89b provided on the inside of the flat surface 89a in the cylinder radial direction. The flat surface portion 89a has a constant inner diameter and a constant outer diameter and has a constant width in the cylinder radial direction, and is formed in an annular shape centered on the cylinder axis.

The R-chamfered portion 89b extends obliquely with respect to the cylinder axial direction so that the inner end edge portion from the flat surface portion 89a in the cylinder radial direction is closer to the inner side in the cylinder radial direction and is located on the opening portion 16 side of the cylinder main body 15 ( the right side in Figure 2). The cross-sectional shape of the R-chamfered portion 89 b including the cylinder axis is formed in an arc shape having a center on the outside of the peripheral groove 32 . The R chamfered portion 89b is formed in an annular shape centering on the cylinder axis, and the inner edge portion in the radial direction of the cylinder and the sliding inner diameter portion 29 are closer to the opening portion 16 than the peripheral groove 32 (right side in FIG. 2 ). ) part of the connection.

The peripheral wall 90 facing the peripheral wall 89 has a flat surface (wall surface) 90a formed by a flat surface parallel to a plane perpendicular to the cylinder axis, and a tapered cone provided on the inside of the flat surface 90a in the cylinder radial direction. The shaped surface portion 90b and the R-chamfered portion 90c provided on the inner side in the cylinder radial direction than the tapered surface portion 90b. The flat surface portion 90 a has a constant width in the cylinder radial direction with a constant inner diameter and a constant outer diameter, and is formed in an annular shape centered on the cylinder axis.

The tapered surface portion 90b is formed so that the diameter decreases toward the bottom 13 side from the inner end edge portion of the flat surface portion 90a in the cylinder radial direction to the bottom 13 side in the cylinder axial direction (left side in FIG. 2 ). Extends in a tapered shape centered on the cylinder axis. The tapered surface portion 90b is formed on the opening side (radially inner side) of the peripheral groove 32 in the peripheral wall 90 on the bottom 13 side (left side in FIG. 2 ) of the cylinder body 15 of the peripheral groove 32 . A flat surface portion 90a is formed adjacent to the tapered surface portion 90b on the groove bottom 88 side in the cylinder radial direction. The maximum diameter of the tapered surface portion 90b is larger than the minimum diameter of the flat surface portion 89a of the peripheral wall 89 . The angle formed by the tapered surface portion 90b and the flat surface portion 90a is an obtuse angle.

The R-chamfered portion 90c extends obliquely with respect to the cylinder axial direction so that the inner end edge portion of the tapered surface portion 90b in the cylinder radial direction is located on the bottom 13 side of the cylinder main body 15 ( left in Figure 2). The cross-sectional shape of the R-chamfered portion 90 c including the cylinder axis is formed in an arc shape having a center on the outside of the peripheral groove 32 . The entirety of the R chamfered portion 90c is formed in an annular shape centered on the cylinder axis, and the inner edge portion in the radial direction of the cylinder and the sliding inner diameter portion 29 are closer to the bottom 13 side than the peripheral groove 32 (in FIG. 2 ). Partial connections on the left).

The stepped portion 75 formed in the primary piston 18 is formed from a cylindrical surface portion 75a having a fixed diameter smaller than the cylindrical surface-shaped outer diameter portion 74 having the largest diameter in the primary piston 18. The end edge portion on the opening 16 side (the right side in FIG. 2 ) of the cylinder main body 15 has a tapered surface portion 75b that extends obliquely so that its diameter increases toward the opening portion 16 side of the cylinder main body 15 . The end edge portion of 75a on the bottom 13 side of the cylinder main body 15 (left side in FIG. 2 ) is constituted by a tapered surface portion 75c extending obliquely so as to increase in diameter toward the bottom 13 side of the cylinder main body 15 .

The cylindrical surface 75 a , tapered surface 75 b , and tapered surface 75 c are formed around the central axis of the primary piston 18 in the same manner as the outer diameter portion 74 . The large diameter side of the tapered surface portion 75b and the large diameter side of the tapered surface portion 75c are respectively connected to the outer diameter portion 74 . The port 76 that always communicates with the primary pressure chamber 85 is formed at a position straddling both the cylindrical surface portion 75a and the tapered surface portion 75b. In other words, the end portion of the port 76 on the bottom 13 side (left side in FIG. 2 ) of the cylinder main body 15 is located on the cylindrical surface portion 75 a. The end portion of the port 76 on the opening portion 16 side of the cylinder main body 15 is located on the tapered surface portion 75b.

The piston seal 45 disposed in the peripheral groove 32 is an integrally molded product made of synthetic rubber such as EPDM. The piston seal 45 has an annular plate-shaped base 101 disposed on the opening 16 side of the cylinder main body 15 (right side in FIG. The annular cylindrical inner peripheral lip 102 protruding from the bottom 13 side (left side in FIG. 2 ) of the cylinder body 15 protrudes from the outer peripheral end of the base 101 toward the bottom 13 side (left side in FIG. 2 ) of the cylinder main body 15. Between the outer peripheral lip 103 and the inner peripheral lip 102, the annular cylindrical outer peripheral lip 103 is further from the base 101 toward the bottom 13 side of the cylinder main body 15 (left side in FIG. 2 ) than the outer peripheral lip 103. An annular cylindrical middle protruding part 104 protruding forward. As shown in FIG. 3A , the central axes of the base portion 101 , the inner peripheral lip portion 102 , the outer peripheral lip portion 103 , and the middle protrusion portion 104 coincide. This central axis becomes the central axis of the piston seal 45 . The piston seal 45 is shown in FIG. 2 , and the inner peripheral lip 102 is in sliding contact with the outer peripheral surface 18 a of the primary piston 18 that moves in the axial direction of the cylinder. The outer peripheral lip 103 is in contact with the peripheral groove 32 of the cylinder body 15 .

Referring to FIG. 3A , FIG. 3B , FIG. 4A and FIG. 4B , the piston seal 45 in a natural state before being installed in the master cylinder 11 will be described.

As shown in FIG. 4A , the back surface 101 a of the base 101 , which is an end surface opposite to the protruding directions of the inner peripheral lip 102 , the outer peripheral lip 103 , and the middle protrusion 104 , is parallel to the axis-orthogonal surface of the piston seal 45 . The back surface portion 101 a has a constant width in the radial direction with a constant inner diameter and a constant outer diameter, and is formed in an annular shape centered on the central axis of the piston seal 45 .

In addition, the base portion 101 has an R-chamfered portion 101b formed on the inner side in the radial direction of the back portion 101a. An R-chamfered portion 101c is formed on the radially outer side of the rear surface portion 101a. The R-chamfered portion 101b is located on the inner peripheral lip portion 102 side in the axial direction from the radially inner end edge portion of the back surface portion 101a toward the inner side in the radial direction farther from the back surface portion 101a. The central axis extends obliquely. The cross-sectional shape of the chamfered portion 101 b including the central axis of the piston seal 45 is formed in an arc shape having a center on the inner side of the base portion 101 . The entirety of the R-chamfered portion 101 b is formed in an annular shape centered on the central axis of the piston seal 45 . The R-chamfered portion 101c is located relative to the center of the piston seal 45 in such a manner that the radially outer end edge portion of the rear surface portion 101a is further away from the rear surface portion 101a in the radial direction, and the more it is located on the axially outer peripheral lip portion 103 side. The shaft extends obliquely. The cross-sectional shape of the chamfered portion 101 c including the central axis of the piston seal 45 is formed in an arc shape having a center on the inner side of the base portion 101 . The entirety of the R-chamfered portion 101c is formed in an annular shape centering on the central axis of the piston seal 45 .

The inner peripheral lip portion 102 is formed in a tapered cylindrical shape with a smaller diameter as a whole as it moves away from the base portion 101 in the axial direction. On the inner peripheral side of the inner peripheral lip 102, a reduced-diameter inner peripheral surface 102a, an enlarged-diameter inner peripheral surface 102b, and a cylindrical inner peripheral surface 102c are formed sequentially from the axial base 101 side. The reduced-diameter inner peripheral surface portion 102a is formed from the radially inner end edge portion of the R-chamfered portion 101b of the base portion 101 in the radial direction of the piston seal 45 in such a manner that the diameter becomes smaller (i.e., the diameter decreases) as it moves away from the base portion 101 in the axial direction. It extends in a tapered shape centered on the central axis of the piston seal 45 . The diameter-enlarged inner peripheral surface 102b is formed from the edge portion of the reduced-diameter inner peripheral surface 102a on the opposite side to the base 101 so that the diameter becomes larger (that is, the diameter expands) as it moves away from the base 101 in the axial direction. The central axis extends for a central tapered shape. The cylindrical inner peripheral surface 102c extends from the end edge of the enlarged diameter inner peripheral surface 102b on the opposite side to the base 101 in a cylindrical shape centered on the central axis of the piston seal 45 .

On the outer peripheral side of the inner peripheral lip portion 102, a reduced-diameter outer peripheral surface portion 102d and an R-chamfered portion 102e are formed in this order from the base portion 101 side in the axial direction. The reduced-diameter outer peripheral surface portion 102d extends in a tapered shape centered on the central axis of the piston seal 45 such that the diameter becomes smaller as it moves away from the base portion 101 in the axial direction. The R-chamfered portion 102e extends obliquely with respect to the central axis of the piston seal 45 from the end edge portion of the reduced-diameter outer peripheral surface portion 102d on the opposite side to the base portion 101 so that the diameter becomes smaller as it moves away from the base portion 101 in the axial direction. The cross-sectional shape of the chamfered portion 102 e including the central axis of the piston seal 45 is formed in an arc shape having a center on the inner side of the inner peripheral lip portion 102 . The entirety of the R-chamfered portion 102e is formed in an annular shape centered on the central axis of the piston seal 45 .

End edges on the side opposite to the base 101 of the cylindrical inner peripheral surface 102c and the R-chamfered portion 102e are connected to a front end surface 102f on the opposite side of the base 101 of the inner peripheral lip 102 . The front end surface portion 102f is parallel to the surface perpendicular to the axis of the piston seal 45 and has a constant width in the radial direction of the piston seal 45 with a constant inner diameter and a constant outer diameter. The front end surface portion 102f is formed in an annular shape centering on the central axis of the piston seal 45 .

Here, in the inner peripheral lip portion 102 , the boundary portion between the reduced-diameter inner peripheral surface portion 102 a and the enlarged-diameter inner peripheral surface portion 102 b becomes a minimum diameter portion 106 having the smallest inner diameter. In the inner peripheral lip portion 102, the portion between the base portion 101 and the smallest diameter portion 106 becomes a thicker head portion 107 that becomes thicker as it moves away from the base portion 101 in the axial direction, and the wall thickness at the smallest diameter portion 106 in the axial direction is the thickest. . In addition, in the inner peripheral lip portion 102, the portion of the axially enlarged diameter inner peripheral surface portion 102b becomes the head thin portion 108, which becomes thinner as it is farther away from the base portion 101. Except for the R chamfered portion 102e, the axial cylindrical A portion of the peripheral surface portion 102c becomes a front end portion 109 having a constant thickness.

The outer peripheral lip portion 103 is formed in a tapered cylindrical shape such that its overall diameter increases as it moves away from the base portion 101 in the axial direction. On the inner peripheral side of the outer peripheral lip portion 103 , an enlarged-diameter inner peripheral surface portion 103 a and a cylindrical inner peripheral surface portion 103 b are formed in this order from the base portion 101 side in the axial direction. The diameter-enlarged inner peripheral surface 103 a is formed in a tapered shape centered on the center axis of the piston seal 45 so as to increase in diameter (that is, expand in diameter) as it moves away from the base 101 in the axial direction. The cylindrical inner peripheral surface 103b is formed in a cylindrical shape centered on the central axis of the piston seal 45 and extends from the end edge of the enlarged diameter inner peripheral surface 103a on the opposite side to the base 101 .

On the outer peripheral side of the outer peripheral lip 103, an enlarged diameter outer peripheral surface 103c, a cylindrical outer peripheral surface 103d, a segment surface 103e, and a cylindrical outer peripheral surface 103f are formed in this order from the axial base 101 side. The diameter-enlarged outer peripheral surface portion 103c is formed in a tapered shape centered on the central axis of the piston seal 45 and extends so as to increase in diameter as it moves away from the base portion 101 in the axial direction. The cylindrical outer peripheral surface 103 d is formed in a cylindrical shape centered on the central axis of the piston seal 45 and extends from the end edge of the enlarged diameter outer peripheral surface 103 c on the opposite side to the base 101 . The segment surface portion 103e extends radially inward in parallel to the plane perpendicular to the axis of the piston seal 45 from the end edge portion of the cylindrical outer peripheral surface portion 103d on the opposite side to the base portion 101 . The cylindrical outer peripheral surface portion 103f is formed in a cylindrical surface shape centered on the central axis of the piston seal 45 and extends from the inner peripheral edge portion of the segment surface portion 103e. Each end edge of the cylindrical inner peripheral surface 103 b and the cylindrical outer peripheral surface 103 f opposite to the base 101 is connected to a front end surface 103 g of the outer peripheral lip 103 opposite to the base 101 . The front end surface 103g is parallel to the surface perpendicular to the axis of the piston seal 45, has a certain width in the radial direction of the piston seal 45 with a certain inner diameter and a certain outer diameter, and is formed as a ring centered on the central axis of the piston seal 45. shape.

Here, the portion of the cylindrical outer peripheral surface portion 103f of the outer peripheral lip portion 103 is a thin portion 112 whose thickness in the radial direction is thinner than that of the other main body portion 111 in the outer peripheral lip portion 103 .

On the inner peripheral side of the intermediate projecting portion 104 , an enlarged-diameter inner peripheral surface portion 104 a and an R-chamfered portion 104 b are formed in this order from the base portion 101 side in the axial direction. The diameter-enlarged inner peripheral surface portion 104a is formed in a tapered shape centered on the central axis of the piston seal 45 and extends so as to increase in diameter as it moves away from the base portion 101 in the axial direction. The R-chamfered portion 104b extends obliquely with respect to the central axis of the piston seal 45 so that the diameter of the end edge portion on the opposite side to the base portion 101 becomes larger as the distance in the axial direction from the expanded-diameter inner peripheral surface portion 104a increases. The cross-sectional shape of the chamfered portion 104 b including the central axis of the piston seal 45 is formed in an arc shape having a center on the inner side of the intermediate protrusion 104 . The entirety of the R-chamfered portion 104 b is formed in an annular shape centered on the central axis of the piston seal 45 .

On the outer peripheral side of the intermediate projecting portion 104, a reduced-diameter outer peripheral surface portion 104c and an R-chamfered portion 104d are formed in this order from the base portion 101 side in the axial direction. The reduced-diameter outer peripheral surface portion 104c is formed to extend in a tapered shape centered on the central axis of the piston seal 45 such that the diameter becomes smaller as it moves away from the base portion 101 in the axial direction. The R-chamfered portion 104d extends obliquely with respect to the central axis of the piston seal 45 such that the diameter of the end edge portion opposite to the base portion 101 becomes smaller as it moves away from the reduced-diameter outer peripheral surface portion 104c in the axial direction. The cross-sectional shape of the chamfered portion 104 d including the central axis of the piston seal 45 is formed in an arc shape having a center on the inner side of the intermediate protrusion 104 . The entirety of the R-chamfered portion 104d is formed in an annular shape centering on the central axis of the piston seal 45 .

End edge portions on the opposite side to the base portion 101 of the R-chamfered portions 104 b and 104 d are connected to a front end surface portion 104 e on the opposite side to the base portion 101 of the intermediate protrusion portion 104 . The front end surface 104e is parallel to the surface perpendicular to the axis of the piston seal 45 and has a constant width in the radial direction of the piston seal 45 with a constant inner diameter and a constant outer diameter. The front end surface portion 104e is also formed in an annular shape centered on the central axis of the piston seal 45 . It should be noted that the front end surface 104e of the intermediate protrusion 104 is aligned with the front end surface 102f of the inner peripheral lip 102 in the axial direction of the piston seal 45, and the front end surface 103g of the outer peripheral lip 103 is located at a position lower than the front end surface 104e and the front end surface 102f of the inner peripheral lip 102. The front end surface 102f is closer to the base 101 side.

The base 101 side of the reduced-diameter outer peripheral surface 102 d of the inner peripheral lip 102 and the base 101 side of the enlarged-diameter inner peripheral surface 104 a of the intermediate protrusion 104 are connected at a curved surface 114 . The cross-sectional shape of the curved surface portion 114 including the central axis of the piston seal 45 is formed in an arc shape having a center in the space between the inner peripheral lip portion 102 and the intermediate protrusion portion 104 . In addition, the base 101 side of the enlarged-diameter inner peripheral surface 103 a of the outer peripheral lip 103 and the reduced-diameter outer peripheral surface 104 c of the intermediate protrusion 104 are connected at a curved surface 115 . The cross-sectional shape of the curved surface portion 115 including the central axis of the piston seal 45 is formed in an arc shape having a center in a space between the outer peripheral lip portion 103 and the intermediate protrusion portion 104 . The respective bottom positions of the curved surface portions 114 and 115 constitute the base portion 101 . Therefore, in the base portion 101 , the base end portions of the inner peripheral lip portion 102 and the intermediate protrusion portion 104 are thick in the axial direction, and the proximal end portions of the outer peripheral lip portion 103 are thin in the axial direction.

Furthermore, in the present embodiment, a connection portion 120 for connecting the inner peripheral lip portion 102 and the intermediate protrusion portion 104 as shown in FIG. 4B is provided between the inner peripheral lip portion 102 and the intermediate protrusion portion 104 . As shown in FIG. 3A, the connecting portion 120 is formed in an arc shape centered on the central axis of the piston seal 45, and the connecting portion 120 is spaced at equal intervals in the circumferential direction of the piston seal 45, that is, in the circumferential direction of the base portion 101. Multiple (specifically, 8 sites) are formed. As a result, a portion between the inner peripheral lip portion 102 and the middle protrusion portion 104 where the connecting portion 120 is not formed becomes a gap 121 . The slits 121 are also formed in an arc shape centering on the central axis of the piston seal 45, and a plurality of the slits 121 are formed at equal intervals in the circumferential direction of the piston seal 45, that is, in the circumferential direction of the base 101 (specifically, , 8 parts). The circumferential length of one slit 121 is longer than the circumferential length of one connecting portion 120 . In other words, compared with the central angle of the sector formed by linking one connecting portion 120 , its circumferential ends and the center of the piston seal 45 , the sector formed by linking one slit 121 , its circumferential ends and the center of the piston seal 45 The central angle is large.

The front end surface 120 a of the connecting portion 120 opposite to the base portion 101 is parallel to the plane perpendicular to the axis of the piston seal 45 and has a constant width in the radial direction of the piston seal 45 with a constant inner diameter and a constant outer diameter. The coupling portion 120 is opposed to the piston seal 45 passing through the center of the coupling portion 120 in such a manner that the distance between the pair of side surfaces 120b, 120b on both sides in the circumferential direction of the arc-shaped front end surface portion 120a becomes narrower as the distance between the base portion 101 and the distance between the coupling portion 120 and the coupling portion 120 decreases. The central axis is parallel to the line forming the line symmetrically inclined.

As shown in FIG. 4B , the connecting portion 120 is integrated with the reduced-diameter outer peripheral surface 102d of the inner peripheral lip 102 , the enlarged-diameter inner peripheral surface 104a of the intermediate protrusion 104 , and the curved surface 114 therebetween. More specifically, the connecting portion 120 is integrated with the curved surface 114 over the entire axial and radial length of the piston seal 45, and is also integrated with the piston seal 45 in the reduced-diameter outer peripheral surface 102d and the enlarged-diameter inner peripheral surface 104a. 45 is integrated over substantially the entire length in the axial direction. That is, the connecting portion 120 is formed along the axial direction of the piston seal 45 , and is formed from the base portion 101 along the axial direction of the piston seal 45 and along the direction of the protruding tip of the intermediate protrusion 104 and the inner peripheral lip 102 . The front end surface 120a of the connecting portion 120 extends to the side opposite to the base 101 from the smallest diameter portion 106 of the inner peripheral lip 102, and extends to an axially intermediate position of the cylindrical inner peripheral surface 102c.

Next, referring mainly to FIG. 2 , the side of the bottom 13 which is installed in the peripheral groove 32 of the cylinder main body 15 and which is in proper contact with the axial middle position of the cylindrical surface portion 75 a of the step portion 75 of the primary piston 18 and away from the peripheral groove 32 will be described. Piston seal 45 in basic state (non-braking state before brake pedal operation) of peripheral wall 90 (left side in FIG. 2 ).

In this basic state, the piston seal 45 is located closest to the opening 16 side of the cylinder main body 15 (the right side in FIG. 2 ) with the base 101 parallel to the plane perpendicular to the cylinder axis. Therefore, the base part 101 is arrange|positioned so that it may oppose the peripheral wall 89 of the peripheral groove 32, and will contact the flat surface part 89a of the peripheral wall 89 at the back part 101a. In addition, the inner peripheral lip portion 102 located on the innermost peripheral side is in contact with the cylindrical surface portion 75 a of the step portion 75 in the outer peripheral surface 18 a of the primary piston 18 at its inner peripheral portion. At this time, in the inner peripheral lip portion 102, a part of the reduced diameter inner peripheral surface portion 102a side of the reduced diameter inner peripheral surface portion 102a shown in FIG. 4A and FIG. The surface 75a contacts, and the pseudo-cylindrical surface 75a deforms into a cylindrical shape having a larger diameter than before deformation. Therefore, the inner peripheral lip 102 is in contact with the cylindrical surface 75a with an interference. At this time, the minimum diameter portion 106 with the smallest inner diameter becomes the maximum interference portion with the largest interference with the cylindrical surface 75a, and extends The connecting portion 120 is formed to the smallest diameter portion 106 which becomes the portion of the largest interference.

In addition, in the basic state, in the piston seal 45, the cylindrical inner peripheral surface 102c and a part of the cylindrical inner peripheral surface 102c side of the enlarged diameter inner peripheral surface 102b are away from the cylindrical surface 75a of the piston 18 in the cylinder radial direction. , and a gap portion 125 is formed between it and the cylindrical surface portion 75a. The gap portion 125 is formed in an annular shape centered on the central axis of the piston seal 45 , and opens toward the bottom 13 side (left side in FIG. 2 ) in the cylinder axial direction. Furthermore, the connecting portion 120 extends from an end position on the base portion 101 side of the gap portion 125 toward the side opposite to the base portion 101 .

Further, in the basic state, in the piston seal 45 , the outermost peripheral lip 103 is in contact with the groove bottom 88 of the peripheral groove 32 at its outermost cylindrical outer peripheral surface 103 d. At this time, the middle protrusion 104 is in the same state as the natural state, and the front end surface 104e thereof is parallel to the plane perpendicular to the cylinder axis. The middle protrusion 104 extends further toward the bottom 13 side of the cylinder main body 15 (left side in FIG. 2 ) than the outer peripheral lip 103 by the same length as the inner peripheral lip 102 .

Here, in the basic state, the entire front end surface 104e of the intermediate protrusion 104 is aligned with the flat surface 90a of the peripheral wall 90 of the peripheral groove 32 in the cylinder radial direction. The middle protrusion 104 is disposed so as to face the flat surface 90a in the cylinder axial direction and be capable of abutting against the flat surface 90a. However, at this time, the intermediate protrusion 104 is separated from the peripheral wall 90 including the flat surface portion 90a in the cylinder axial direction.

In addition, in the basic state, the front end surface 102f of the inner peripheral lip 102, the tapered surface 90b and the R-chamfered portion 90c of the peripheral wall 90 of the peripheral groove 32, and the tapered surface 75c of the stepped portion 75 of the primary piston 18 are in the cylinder bore. Align the positions radially. The inner peripheral lip portion 102 is disposed so as to face the tapered surface portion 90b, the R-chamfered portion 90c, and the tapered surface portion 75c. However, at this time, the inner peripheral lip portion 102 is separated from the peripheral wall 90 including the tapered surface portion 90b and the R-chamfered portion 90c in the cylinder axial direction, and also separated from the tapered surface portion 75c in the cylinder axial direction. In addition, at this time, the front end surface 102f of the inner peripheral lip 102 does not overlap the flat surface 90a of the peripheral wall 90 in the cylinder radial direction.

In addition, in the basic state, the boundary portion 127 between the front end surface 120a of the connecting portion 120, the tapered surface 90b of the peripheral wall 90 of the peripheral groove 32, and the flat surface 90a on the side of the groove bottom 88 from the tapered surface 90b of the peripheral wall 90 is formed. The cylinder bores are aligned radially. The front end surface portion 120a is disposed so as to face the boundary portion 127 upward in the cylinder axial direction. In other words, the front end surface 120a of the connecting portion 120 is arranged to be aligned with both the tapered surface 90b and the flat surface 90a in the cylinder radial direction, and to face both the tapered surface 90b and the flat surface 90a in the cylinder axial direction. .

When there is no input from the brake pedal side (not shown) and the primary piston 18 is in the basic position (non-braking position) in which the port 76 opens to the opening groove 47 as shown in FIG. The inner peripheral portion of the lip portion 102 and the base portion 101 is located at the cylindrical surface portion 75a of the step portion 75 of the primary piston 18, and the inner peripheral portion of the base portion 101 coincides with a portion of the port 76 in the cylinder axial direction.

In addition, when there is an input from the brake pedal side and the primary piston 18 moves toward the bottom 13 side of the cylinder body 15 (the left side in FIGS. 5A and 5B ) as shown in FIG. The tapered surface 75b on the opening 16 side (the right side in FIGS. 5A and 5B ) of the cylinder main body 15 abuts on the R-chamfered portion 101b of the base 101 of the piston seal 45 to press the piston seal 45 . Then, the piston seal 45 moves integrally with the primary piston 18 , and as a result, the base 101 moves in the peripheral groove 32 toward the peripheral wall 90 and away from the peripheral wall 89 as shown in FIG. 5A . At the same time, the front end surface 104 e of the intermediate protrusion 104 comes into contact with the flat surface 90 a of the peripheral wall 90 .

When the primary piston 18 moves further toward the bottom 13 side of the cylinder main body 15 (the left side in FIGS. 5A and 5B ), the inner peripheral lip 102 receives the force of movement together with the primary piston 18 , but is not in contact with the peripheral wall of the peripheral groove 32 . The middle protruding part 104 abutting against the 90 strongly pulls the inner peripheral lip part 102 connected by the connecting part 120 to restrain its movement. Accordingly, it is possible to prevent the inner peripheral lip portion 102 from entering into a gap between the step portion 75 of the primary piston 18 and the sliding inner diameter portion 29 of the cylinder body 15 and being bitten by them.

In addition, at this time, with respect to the intermediate protrusion 104 that is in contact with the flat surface 90a of the peripheral wall 90 and is actually in a stopped state, the R-chamfered portion 101b of the base 101 pressed by the tapered surface 75b moves toward the bottom of the cylinder body 15 . 13 side (left side in FIGS. 5A and 5B ), but in the piston seal 45 centering on the R-chamfered portion 101b of the base portion 101, the front end surface 104e of the intermediate protrusion 104 moves toward the groove bottom 88 side. moment in the direction of . As a result, as shown in FIG. 5B , the middle protrusion 104 rotates slightly so that the front end surface 104 e approaches the groove bottom 88 . At this time, the inner peripheral lip 102 connected to the intermediate protrusion 104 by the connecting portion 120 is also strongly pulled by the intermediate protrusion 104 to move integrally therewith while suppressing contact with the peripheral wall 90 by the tapered surface portion 90b, and moves radially. The step portion 75 of the primary piston 18 abuts against the flat surface portion 90 a side of the tapered surface portion 90 b, and is positioned radially outward from the sliding inner diameter portion 29 of the cylinder main body 15 . Accordingly, it is possible to further suppress entry of the inner peripheral lip portion 102 into the gap between the step portion 75 of the primary piston 18 and the sliding inner diameter portion 29 of the cylinder main body 15 .

When the primary piston 18 moves further toward the bottom 13 side of the cylinder main body 15 (the left side in FIGS. 5A and 5B ), the piston seal 45 maintains the state where the middle protrusion 104 is in contact with the flat surface 90 a of the peripheral wall 90 . Movement is restricted. Therefore, the piston seal 45 rides on the tapered surface portion 75 b of the stepped portion 75 to go over the port 76 to block the port 76 , thereby blocking the communication between the primary pressure chamber 85 and the primary supply passage 48 . It should be noted that the piston seal 45 seals the primary pressure chamber from the range where the primary piston 18 is located on the bottom 13 side of the cylinder main body 15 (the left side in FIGS. 5A and 5B ) including this position. 85 and the primary supply passage 48 are cut off to seal the primary pressure chamber 85 . In this state, the hydraulic pressure in the primary pressure chamber 85 is basically higher than the hydraulic pressure in the primary supply passage 48 which is atmospheric pressure, and is supplied into the primary pressure chamber 85 from the primary discharge passage 27 shown in FIG. 1 to the brake cylinder on the wheel side. brake fluid.

After the port 76 is blocked, if the primary piston 18 moves further toward the bottom 13 side of the cylinder main body 15 (the left side in FIGS. 5A and 5B ), the base 101 of the piston seal 45 rides over the tapered surface 75b and rides on the outer surface. Diameter portion 74. At the same time, the inner peripheral lip 102 rides on the tapered surface portion 75 b, and then, the inner peripheral lip 102 rides on the outer diameter portion 74 . Then, the piston seal 45 moves toward the peripheral wall 89 in the peripheral groove 32 by the above-mentioned hydraulic pressure rise of the primary pressure chamber 85 . Thereby, the intermediate protrusion part 104 and the inner peripheral lip part 102 are separated from the peripheral wall 90, and the base part 101 contacts the peripheral wall 89 at the back part 101a.

As described above, when the primary piston 18 moves to the bottom 13 side of the cylinder main body 15 (the left side in FIGS. With the spacing adjustment 79 shown in FIG. 1 , the primary piston 18 is to be returned to the basic position shown in FIG. 2 . The volume of the primary pressure chamber 85 gradually expands by the movement of the primary piston 18 . At this time, if the return of the brake fluid via the brake pipe cannot keep up with the expansion of the volume of the primary pressure chamber 85, after the hydraulic pressure of the primary supply passage 48 which is atmospheric pressure and the hydraulic pressure of the primary pressure chamber 85 become equal, the primary pressure chamber 85 The hydraulic pressure inside becomes a negative pressure, and the hydraulic pressure of the primary pressure chamber 85 is lower than the hydraulic pressure of the primary supply passage 48 which is atmospheric pressure. Then, the negative pressure in the primary pressure chamber 85 deforms the outer peripheral lip 103 side of the base 101 of the piston seal 45 away from the peripheral wall 89 and deforms the outer peripheral lip 103 away from the groove bottom 88 . As a result, a gap is formed between the peripheral groove 32 and the piston seal 45 , and the brake fluid is supplied from the primary supply passage 48 to the primary pressure chamber 85 through the flow path in the gap. Thereby, the hydraulic pressure of the primary pressure chamber 85 can be returned to atmospheric pressure from a negative pressure state.

Here, when setting the connecting portion 120 on the piston seal 45 , it is preferable to set the formation angle θ of the gap 121 shown in FIG. 3A around the central axis of the piston seal 45 according to the following formula.

θ≦(360/(D*π))*((384*δmax*E*I)/5(W/(b*L)))1/4

In the formula, δmax is the allowable displacement of the inner peripheral lip 102 being pressed down along the inner radial direction, W is the radial reaction force equivalent to the width of the slit 121 received by the inner peripheral lip 102 when sliding on the tapered surface 75b, L is the width of the gap 121 (L=D*π*θ/360), b is the axial length of the inner peripheral lip 102, H is the radial height of the inner peripheral lip 102, and D is the conical surface of the primary piston 18 75b is the diameter of the position where the piston seal 45 is in contact, I is the secondary moment of section (I=bh3/12), and E is Young's modulus of elasticity.

In the master cylinder described in the aforementioned Patent Document 1, a piston seal, which is in sliding contact with the piston, is provided in a peripheral groove of the cylinder main body. In this master cylinder, as a piston seal, an annular base, an inner peripheral lip protruding from the inner peripheral side of the base and slidingly contacting the outer peripheral surface of the piston, protruding from the outer peripheral side of the base and contacting the cylinder The outer peripheral lip which the peripheral groove of the cylinder main body abuts on, and the intermediate protrusion which protrudes forward from the space between the inner peripheral lip and the outer peripheral lip of the base, than the outer peripheral lip. In addition, in the master cylinder described in the above-mentioned Patent Document 2, a cup-shaped seal having an annular base and an inner peripheral lip and an outer peripheral lip protruding from the inner and outer peripheries is provided in the annular groove of the piston. A slide ring sliding in the cylinder bore is provided between the cup seal of the annular groove and the cylinder bore of the cylinder main body.

In the master cylinder described in Patent Document 1, when the piston moves, the piston seal moves together with the piston, and its inner peripheral lip may enter the gap between the piston and the cylinder main body. On the other hand, according to the master cylinder 11 of the above-mentioned embodiment, the piston seal 45 provided in the peripheral groove 32 of the cylinder main body 15 is provided with the connection part 120 which connects the inner peripheral lip part 102 and the middle protrusion part 104, therefore, even The inner peripheral lip 102 moves together with the primary piston 18 , and the middle protrusion 104 abutting on the peripheral wall 90 of the peripheral groove 32 strongly pulls the inner peripheral lip 102 to suppress its movement. Therefore, entry of the inner peripheral lip 102 into the gap between the primary piston 18 and the cylinder body 15 can be suppressed, and the influence on the piston seal 45 caused by the movement of the primary piston 18 can be suppressed.

It should be noted that, in the master cylinder described in Patent Document 2, a thick portion is formed at the base, but the inner peripheral lip and the outer peripheral lip are not in sliding contact with the cylinder body or the piston, so the thick portion has no Aids in the effect on the cup seal caused by the movement of the piston.

In addition, according to the master cylinder 11 of the above-described embodiment, since the plurality of connection portions 120 are provided separately from each other in the circumferential direction of the base portion 101 , it is possible to suppress a decrease in the flexibility of the inner peripheral lip portion 102 .

In addition, since the connecting portion 120 is formed extending from the base portion 101 in the direction of the front end of the intermediate protrusion portion 104 , molding is easy.

Moreover, the front end of the connection part 120 is arrange|positioned so that it may face the boundary part 127 of the tapered surface part 90b and the flat surface part 90a. Therefore, the inner peripheral lip part 102 can be made to face the tapered surface part 90b, and the distance between the inner peripheral lip part 102 and the peripheral wall 90 can be ensured.

In addition, the connecting portion 120 is formed to extend to the smallest diameter portion 106 which is the largest interference portion of the inner peripheral lip portion 102 . Therefore, the rigidity of the smallest diameter portion 106 can be increased by the connection portion 120 , and the surface pressure applied to the primary piston 18 by the inner peripheral lip portion 102 can be increased.

Here, the piston seal 45 may be partially changed as shown in FIGS. 6 and 7 . That is, as shown in FIG. 6, the protruding length of the inner peripheral lip portion 102 from the base portion 101 may be shorter than that of the intermediate protruding portion 104, or the connecting portion 120 may be shortened so as to be formed on the smallest diameter portion 106 side of the enlarged diameter inner peripheral surface portion 102b. s position. It should be noted that even in the case of shortening the connecting portion 120 , it is preferable to extend at least to the position of the smallest diameter portion 106 .

In addition, as shown in FIG. 7, the connecting portion 120 may be extended to the position of the front end surface 102f of the inner peripheral lip 102 and the front end surface 104e of the intermediate protrusion 104, or the substantially constant wall thickness of the inner peripheral lip 102 may be eliminated. The front end portion 109 either forms a radially penetrating slit 130 on the thin-walled portion 112 of the outer peripheral lip portion 103, or makes the protruding length of the inner peripheral lip portion 102 from the base portion 101 shorter than that of the middle protrusion portion 104 and in the middle protrusion portion. A radially penetrating slit 131 is formed at an end portion of 104 opposite to the base portion 101 . It should be noted that when the connecting portion 120 is extended to the position of the front end face 102f of the inner peripheral lip 102 and the front end face 104e of the intermediate protrusion 104, if the front end faces 102f, 104e deviate in the axial direction, the connection portion 120 The front end surface 120a is formed in a tapered shape.

It should be noted that by forming a slit 130 penetrating in the radial direction on the thin-walled portion 112 of the outer peripheral lip portion 103 or forming a slit 131 at the end portion of the middle protrusion 104 opposite to the base portion 101, when the above-mentioned brake is released, Therefore, a wider flow path can be formed between the peripheral wall 89 and the piston seal 45 , and the brake fluid in the primary supply passage 48 can be smoothly supplied to the primary pressure chamber 85 .

In addition, in the above embodiment, the primary-side seal structure portion SP was described in detail as an example, but since the secondary-side seal structure portion SS also has the same structure, the same effect can be achieved. able to make the same changes.

The above embodiment relates to a master cylinder including: a bottomed cylindrical cylinder main body having a brake fluid discharge passage and a supply passage communicating with a fluid storage chamber; and a piston movably provided in the cylinder. In the main body, a pressure chamber for supplying hydraulic pressure to the above-mentioned discharge passage is formed between the piston and the cylinder main body; a piston seal is provided in a peripheral groove formed on the above-mentioned cylinder main body, and the inner periphery slides with the above-mentioned piston. and sealing between the above-mentioned replenishment passage and the above-mentioned pressure chamber; the piston seal has: an annular base, an inner peripheral lip protruding from the inner peripheral side of the base and slidingly contacting with the outer peripheral surface of the piston, and a The outer peripheral lip protruding from the outer peripheral side of the cylinder main body and in contact with the peripheral groove of the cylinder body, and the middle part protruding forward from the outer peripheral lip between the inner peripheral lip and the outer peripheral lip of the base. The protruding portion; the master cylinder is characterized in that a connection portion is provided between the above-mentioned inner peripheral lip and the above-mentioned middle protruding portion, and the connection portion is formed along the axial direction of the above-mentioned piston seal, and connects the above-mentioned inner peripheral lip and the above-mentioned The middle protrusion is connected. In this way, the piston seal provided in the peripheral groove of the cylinder main body is provided with a connecting portion connecting the inner peripheral lip and the middle protrusion, so even if the inner peripheral lip moves together with the piston, it will abut against the peripheral wall of the peripheral groove. The attached central protrusion also strongly pulls on the inner peripheral lip and inhibits its movement. Therefore, it is possible to suppress the inner peripheral lip from entering between the cylinder body and the piston due to the movement of the piston.

In addition, since the plurality of connecting portions are provided separately from each other in the circumferential direction of the base portion, it is possible to suppress a decrease in flexibility of the inner peripheral lip portion.

In addition, since the connection portion is formed extending from the base portion in the direction of the front end of the intermediate protrusion portion, molding is easy.

In addition, a tapered surface is formed on the opening side of the above-mentioned peripheral groove in the peripheral wall of the bottom side of the above-mentioned cylinder main body of the above-mentioned peripheral groove, and the front end of the above-mentioned connecting part is arranged so as to be in contact with the above-mentioned tapered surface and smaller than the above-mentioned tapered surface of the above-mentioned peripheral wall. Since the surface faces closer to the boundary portion of the wall surface on the bottom side of the peripheral groove, the inner peripheral lip can be made to face the tapered surface and a distance from the peripheral wall can be ensured.

In addition, the connection portion is formed to extend at least to the maximum interference portion of the inner peripheral lip, so that the rigidity of the maximum interference portion can be improved by the connection portion, and the surface pressure applied to the piston by the inner peripheral lip can be increased. .

Industrial Applicability

According to the master cylinder of the present invention, it is possible to suppress the inner peripheral lip from entering between the cylinder body and the piston due to the movement of the piston.

Symbol Description

11 master cylinder

12 reservoir

13 bottom

15 cylinder body

16 opening

18 primary piston (piston)

18a Outer surface

19 Secondary piston (piston)

26 Secondary discharge passage (discharge passage)

27 Primary discharge passage (discharge passage)

30, 32 week slots

35, 45 Piston seal

38 Secondary supply pathways (supply pathways)

48 Primary Supply Pathway (Supply Pathway)

68 Secondary pressure chamber (pressure chamber)

85 primary pressure chamber (pressure chamber)

88 Groove bottom (bottom of peripheral groove)

90 Surrounding wall (surrounding wall on the bottom side of the cylinder body)

90a flat face (wall face)

90b tapered face

101 base

102 Inner peripheral lip

103 Peripheral lip

104 Middle protrusion

106 Minimum diameter part (maximum interference part)

120 link

127 Division

Claims (8)

1. A master cylinder having: a bottomed cylindrical cylinder main body, which has a discharge passage for brake fluid and a replenishment passage communicated with the liquid storage chamber; a piston movably disposed in the cylinder main body, and a pressure chamber for supplying hydraulic pressure to the discharge passage is formed between the piston and the cylinder main body; a piston seal provided in a peripheral groove formed on the cylinder main body, the inner periphery of which is in sliding contact with the piston to seal between the supply passage and the pressure chamber; The piston seal has: circular base; an inner peripheral lip protruding from the inner peripheral side of the base and slidingly engaged with the outer peripheral surface of the piston; an outer peripheral lip protruding from an outer peripheral side of the base and abutting against the peripheral groove of the cylinder main body; an intermediate protrusion protruding forward from between the inner peripheral lip and the outer peripheral lip of the base; The master cylinder is characterized in that, A connection portion is provided between the inner peripheral lip and the middle protrusion, and the connection portion is formed extending in the axial direction of the piston seal and connects the inner peripheral lip and the middle protrusion. 2. The master cylinder of claim 1, wherein: A plurality of the coupling portions are provided separately from each other in a circumferential direction of the base portion. 3. The master cylinder of claim 2, wherein: The connecting portion is formed extending from the base portion along the front end direction of the middle protruding portion. 4. The master cylinder of claim 3, wherein: A tapered surface is formed on the peripheral wall of the peripheral groove on the bottom side of the cylinder main body on the opening side of the peripheral groove, A front end of the connecting portion is arranged to face a boundary portion between the tapered surface and a wall surface of the peripheral wall that is closer to the bottom of the peripheral groove than the tapered surface. 5. The master cylinder of claim 1, wherein: The connecting portion is formed extending from the base portion along the front end direction of the middle protruding portion. 6. The master cylinder of claim 5, wherein: A tapered surface is formed on the peripheral wall of the peripheral groove on the bottom side of the cylinder main body on the opening side of the peripheral groove, A front end of the connecting portion is arranged to face a boundary portion between the tapered surface and a wall surface of the peripheral wall that is closer to the bottom of the peripheral groove than the tapered surface. 7. The master cylinder of claim 1, wherein: A tapered surface is formed on the peripheral wall of the peripheral groove on the bottom side of the cylinder main body on the opening side of the peripheral groove, A front end of the connecting portion is arranged to face a boundary portion between the tapered surface and a wall surface of the peripheral wall that is closer to the bottom of the peripheral groove than the tapered surface. 8. The master cylinder according to any one of claims 1 to 7, wherein: The connecting portion is formed to extend at least to a maximum interference portion of the inner peripheral lip.