JP2008179364A - Master cylinder - Google Patents

Abstract

A master cylinder suitable for combination with a braking / driving force control device without lengthening an invalid stroke is provided.
A liquid replenishing chamber formed by a cylinder and an outer peripheral surface of a piston is defined with respect to a pressure chamber, so that the inner surface of the cylinder can be slidably contacted with the outer peripheral surface of the piston. The piston 13 has an annular cup seal 46 held on the circumferential side, and the piston 13 has one side opened on the outer circumferential surface and the other side always opened to the pressure chamber 17 so that the pressure chamber 17 can communicate with the liquid supply chamber 34. A relief port 56 is formed, and a control taper surface 86 having a small diameter on the front side is formed behind the opening 88 of the relief port 56 on the outer peripheral portion of the piston 13, and the inner peripheral portion of the cup seal 46. It is formed so that it can contact.
[Selection] Figure 2

Description

  The present invention relates to a master cylinder that generates hydraulic pressure for operating a brake device.

A conventional master cylinder is disclosed in Patent Document 1, for example. As shown in FIG. 12, the master cylinder includes a cylinder 111 and a pressure chamber 112 that is slidably provided on the cylinder 111 and generates hydraulic pressure on the forward side (left side in FIG. 2) with the cylinder 111. The liquid supply chamber 114 formed by the piston 113 to be formed and the cylinder 111 and the outer peripheral surface of the piston 113 and communicating with a reservoir (not shown) is partitioned from the pressure chamber 112. Therefore, the piston 113 slides on the straight outer peripheral surface of the piston 113. The piston 113 has an annular cup seal 115 held on the inner peripheral side of the cylinder 111 so as to be able to come into contact with the piston 113. One side opens on the outer peripheral surface of the piston 113, and the other side always opens on the pressure chamber 112. A relief port 116 capable of communicating the chamber 112 with the liquid supply chamber 114 is formed. Here, in the cup seal 115 used in this master cylinder, as indicated by X0 in FIG. 13, the peak position of the surface pressure with respect to the piston 113 is arranged on the front side in the moving direction of the piston 113. As shown in FIG. 14, in the initial state where the piston 113 is at the most opposite position with respect to the pressure chamber 112, the relief port 116 moves the pressure chamber 112 to the liquid supply chamber 114 as shown by the solid line. When the piston 113 starts to advance toward the pressure chamber 112 and the relief port 116 advances to a position exceeding a predetermined position near the surface pressure peak of the cup seal 115 as indicated by a two-dot chain line, the pressure chamber 112 The fluid supply chamber 114 is completely cut off, and the piston 113 presses the brake fluid in the pressure chamber 112 to generate fluid pressure.
JP-A-2-136363

  By the way, in the master cylinder, because of the brake feeling in the vehicle, the so-called invalid stroke A of the piston 113 from the initial position to the start of hydraulic pressure generation is determined to some extent (A = about 1.2 mm to 1.5 mm). The initial position of the piston 113 must be a position where the relief port 116, which is the fluid pressure generation start position, returns from the position exceeding the predetermined position near the surface pressure peak of the cup seal 115 by this invalid stroke value A. When the initial position of the piston 113 is set in this way, in the master cylinder described above, the relief port 116 of the piston 113 has to be largely closed at the opening 117 by the rear end portion of the cup seal 115. There is a problem that the opening amount, that is, the communication amount with respect to the supply chamber 114 cannot be sufficiently secured. For this reason, even if this master cylinder is combined with a braking / driving force control device such as a traction control device and the brake fluid is forced to be sucked from the piping communicating with the pressure chamber for traction control, etc., the brake fluid is pressured from the reservoir. There is a problem that it is difficult to flow into the chamber and is not suitable for combination with a braking / driving force control device.

  Therefore, an object of the present invention is to provide a master cylinder that is suitable for combination with a braking / driving force control device without lengthening the invalid stroke.

  In order to achieve the above object, a master cylinder according to claim 1 of the present invention includes a cylinder and a piston that is slidably provided in the cylinder and that forms a pressure chamber that generates hydraulic pressure on the front side with the cylinder. The liquid replenishing chamber formed by the cylinder and the outer peripheral surface of the piston and communicating with the reservoir is partitioned from the pressure chamber, so that it is held on the inner peripheral side of the cylinder so as to be slidable in contact with the outer peripheral surface of the piston. An annular cup seal, and the piston has a relief port whose one side is open on the outer peripheral surface and the other side is always open to the pressure chamber, and the pressure chamber can communicate with the liquid supply chamber. A control taper surface having a small diameter on the front side is in contact with the inner peripheral portion of the cup seal on the rear side of the opening portion of the relief port on the outer peripheral portion of the piston. It is characterized by comprising a can formed.

  As described above, the control taper surface having a small diameter on the front side is formed behind the relief port opening on the outer peripheral portion of the piston so as to be able to contact the inner peripheral portion of the cup seal. When the control taper surface is brought into contact with the rear end side of the inner peripheral portion of the cup seal and the cup seal is expanded along the control taper surface, the surface pressure between the cup seal and the piston is increased. Can be partially elevated. As a result, a sufficient surface pressure can be generated on the rear end side of the cup seal, the pressure chamber and the fluid supply chamber can be shut off, and the brake fluid in the pressure chamber can be pressed by the piston to generate fluid pressure. It becomes. Therefore, it is possible to generate a surface pressure sufficient to shut off the pressure chamber and the liquid supply chamber on the rear end side of the cup seal, so the opening of the relief port is positioned in front of the control taper surface. If you do it, it will do. As a result, the relief port of the piston in the initial position can be disposed further rearward than the cup seal without lengthening the invalid stroke, and the opening amount, that is, the communication amount with respect to the liquid replenishing chamber can be sufficiently increased. It can be secured.

  According to the master cylinder of claim 2 of the present invention, with respect to the one according to claim 1, a recess is formed in the outer peripheral portion of the piston, and an opening of the relief port is arranged in the recess, and the relief port is further provided. The concave portion on the rear side of the opening is formed as the control tapered surface.

  Thus, since the concave portion on the rear side from the opening portion of the relief port becomes the control tapered surface, the cross-sectional area of the flow path on the relief port side of the liquid supply chamber provided outside the outer peripheral portion of the piston can be increased. .

  As described above in detail, according to the master cylinder of the first aspect of the present invention, the control taper surface having a small diameter on the front side is formed behind the opening of the relief port on the outer peripheral portion of the piston. Since it is formed so as to be able to contact the peripheral portion, when the piston is advanced, the control taper surface is brought into contact with the rear end side of the inner peripheral portion of the cup seal and the cup seal is moved along the control taper surface. When the diameter is increased, the surface pressure between the cup seal and the piston can be partially increased. As a result, a sufficient surface pressure can be generated on the rear end side of the cup seal, the pressure chamber and the fluid supply chamber can be shut off, and the brake fluid in the pressure chamber can be pressed by the piston to generate fluid pressure. It becomes.

  As described above, since it is possible to generate a surface pressure sufficient to shut off the pressure chamber and the liquid replenishing chamber on the rear end side of the cup seal, the opening of the relief port is on the front side of the control taper surface. It will suffice if it is located at. As a result, the relief port of the piston in the initial position can be disposed further rearward than the cup seal without lengthening the invalid stroke, and the opening amount, that is, the communication amount with respect to the liquid replenishing chamber can be sufficiently increased. It can be secured. Therefore, it is suitable for combination with the braking / driving force control device without lengthening the invalid stroke. In addition, since the relief port of the piston in the initial position can be arranged further rearward with respect to the cup seal, the communication amount can be effectively increased by increasing the diameter of the relief port. it can. In addition, since it is not necessary to make the shape of the cup seal itself special, the reliability of the cup seal can be ensured.

  According to the master cylinder of the second aspect of the present invention, the concave portion on the rear side from the opening portion of the relief port serves as a control taper surface, so that the liquid replenishing chamber provided outside the outer peripheral portion of the piston is provided on the relief port side. The cross-sectional area of the flow path can be increased. Accordingly, the flow rate of the brake fluid from the fluid supply chamber to the relief port can be further increased, which is more suitable for combination with the braking / driving force control device.

A master cylinder according to a first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 shows the overall configuration of the master cylinder 10. In FIG. 1, reference numeral 11 denotes a substantially bottomed cylindrical cylinder whose one end is open, and reference numeral 12 denotes an opening side of the cylinder 11 (the right side in the figure). Reference numeral 13 denotes a primary piston that is movably fitted, and reference numeral 13 denotes a secondary piston that is slidably fitted to the bottom side (left side in the drawing) of the primary piston 12 of the cylinder 11.

  Reference numeral 14 denotes an initial state that is disposed between the primary piston 12 and the secondary piston 13 and is not input from a brake pedal side (right side in the drawing) (the position of each part at this time is hereinafter referred to as an initial position). ), An initial interval maintaining mechanism for determining these intervals is arranged between the secondary piston 13 and the bottom of the cylinder 11, and the initial interval is maintained in the initial state where there is no input from the brake pedal side. The mechanical part 16 is a primary pressure chamber defined by the primary piston 12, the secondary piston 13 and the cylinder 11, and a reference numeral 17 is a secondary pressure chamber defined on the bottom side of the secondary piston 13 and the cylinder 11. Respectively.

  Here, the depression force of the brake pedal assisted by, for example, a booster is input to the master cylinder 10 from the opposite side to the secondary piston 13 of the primary piston 12, whereby the primary piston 12 is moved into the primary pressure chamber. 16 side (left side in each figure) moves forward, and secondary piston 13 moves forward to secondary pressure chamber 17 side (left side in each figure), while the brake pedal depression force is released, so that each reverse side (each figure). Go back to the right). Note that this direction is used before and after in the following.

  The cylinder 11 is coaxial with the cylinder hole 20 on the side closest to the bottom of the first member 21 and the first member 21 constituting the front of the cylinder hole 20 into which the primary piston 12 and the secondary piston 13 are fitted. A substantially annular second member 22 to be fitted, and a perforated disk-shaped second member which is adjacent to the rear side of the second member 22 and is fitted to the first member 21 so as to be coaxial with the cylinder hole 20. A third member 23, a substantially cylindrical fourth member 24 that is fitted to the first member 21 so as to be adjacent to the rear side of the third member 23, and constitutes an intermediate portion of the cylinder hole 20, and a fourth member A substantially cylindrical fifth member 25 fitted to the rear side of the cylinder 24 so as to be coaxial with the cylinder hole 20, and fitted to the outside of the fourth member 24 and the fifth member 25 while being screwed to the first member 21. And a substantially cylinder constituting the most rear side of the cylinder hole 20 And a sixth member 26.

  The first member 21 is formed with an attachment portion 28 to which a reservoir (not shown) is attached, and the attachment portion 28 has two liquid passages 29 and 30 communicating individually with the interior of the attached reservoir. They are arranged in the direction. One of the liquid passages 29 on the front side is always in communication with a liquid passage 32 formed through the second member 22 in the radial direction. Here, an annular step 33 having a diameter larger than the outer diameter of the secondary piston 13 is formed on the inner peripheral side of the second member 22, whereby the step 33 of the second member 22 and the secondary piston are formed. An annular liquid replenishing chamber 34 is formed between the outer peripheral surface of 13 and the third member 23. The liquid passage 32 is opened on the inner peripheral surface of the stepped portion 33, and is always in communication with the liquid supply chamber 34.

  The other liquid passage 30 is also always communicated with a liquid passage 36 formed in the sixth member 26 in a radial direction, and the liquid passage 36 is formed in the fifth member 25 in a radial direction. 37 is always in communication. Here, an annular step portion 38 having a diameter larger than the outer diameter of the primary piston 12 is formed on the inner peripheral side of the fifth member 25, whereby the step portion 38 of the fifth member 25 and the primary piston are formed. An annular liquid replenishing chamber 39 is formed between the outer peripheral surfaces of the twelve. The liquid passage 37 is opened on the inner peripheral surface of the stepped portion 38, and is always in communication with the liquid supply chamber 39.

  A liquid chamber 41 communicating with the primary pressure chamber 16 through a gap between the secondary piston 13 and the fourth member 24 is formed in the fourth member 24 and the like, and the first outer periphery of the fourth member 24 has a first An annular seal member 42 and a seal member 43 are provided to prevent the liquid chamber 41 from communicating with the liquid passage 29 and the liquid passage 30 through a gap between the member 21 and the fourth member 24. An annular seal member 44 that prevents the liquid passage 30 from communicating with the outside through a gap between the first member 21 and the sixth member 26 is also provided on the outer peripheral portion of the sixth member 26.

  Between the fourth member 24, the third member 23, and the secondary piston 13, the liquid replenishing chamber 34 and the liquid chamber 41 are prevented from communicating with each other through a gap between the secondary piston 13 and the fourth member 24. An annular seal member 45 having a concave cross section in the plane including the axis is provided. The seal member 45 is arranged such that the opening side in the cross-sectional shape is on the liquid chamber 41 side.

  Between the inner peripheral side of the first member 21 of the cylinder 11, the second member 22, and the secondary piston 13, the liquid supply chamber 34 and the secondary pressure chamber 17 are interposed via a gap between the secondary piston 13 and the first member 21. The annular cup seal 46 having a concave cross section on the surface including the axis thereof for preventing the fluid communication, that is, partitioning the liquid supply chamber 34 and the secondary pressure chamber 17 slidably slides on the outer peripheral surface of the secondary piston 13. It is held so that contact is possible. The cup seal 46 is arranged such that the opening side in the cross-sectional shape is on the secondary pressure chamber 17 side.

  Between the sixth member 26, the fifth member 25, and the primary piston 12, an axis that prevents the liquid replenishing chamber 39 from communicating with the outside through a gap between the primary piston 12 and the sixth member 26 is included. An annular seal member 48 having a concave cross section on the surface is provided. The seal member 48 has an opening side in a cross-sectional shape arranged on the liquid supply chamber 39 side.

  Between the inner peripheral side of the fourth member 24 of the cylinder 11, the fifth member 25, and the primary piston 12, the liquid replenishing chamber 39 and the primary pressure chamber 16 are interposed via a gap between the primary piston 12 and the fourth member 24. An annular cup seal 49 having a concave cross section on the surface including the axis thereof for preventing the fluid communication, i.e., partitioning the liquid replenishing chamber 39 and the primary pressure chamber 16, slides on the outer peripheral surface of the primary piston 12. It is held so that contact is possible. The cup seal 49 is arranged with the opening side in the cross-sectional shape facing the primary pressure chamber 16 side.

  A hole 51 is formed in the front portion of the secondary piston 13 along the axial direction, and an initial interval maintaining mechanism 15 is provided in the hole 51. The initial gap maintaining mechanism 15 is slidably fitted to the retainer 52 that is in contact with the bottom of the cylinder 11 and the secondary piston 13 side of the retainer 52, and the movement limit to the secondary piston 13 side is determined. The connecting rod 53, the retainer 54 fixed to the secondary piston 13 side of the connecting rod 53 and abutted against the bottom surface of the hole 51 of the secondary piston 13, and the retainer 52 and the retainer 54 in a direction opposite to each other. And an urging spring 55. As a result, in a state where the secondary piston 13 is not input from the primary piston 12 side, the retainer 52 and the retainer 54 are separated to the limit determined by the connecting rod 53 by the biasing force of the spring 55, and the secondary piston 13 The distance from the bottom of the 13 cylinders 11 is a predetermined distance.

  In the vicinity of the front end portion of the secondary piston 13, the secondary pressure chamber 17 is always opened by passing through the hole 51 in the outer peripheral surface of the secondary piston 13 in the radial direction, and depending on the position of the secondary piston 13, the secondary pressure chamber 17. A relief port 56 capable of communicating with the liquid supply chamber 34 is formed.

  In the primary piston 12, a hole 58 is formed in the rear portion along the axial direction, and an output shaft of a booster (not shown) is disposed in the hole 58. And the output which assisted the depression of the brake pedal with this booster is input via an output shaft.

  A hole 59 is formed in the front portion of the primary piston 12 along the axial direction, and the initial interval maintaining mechanism 14 is provided in the hole 59. The initial interval maintaining mechanism 14 is a retainer 60 that is in contact with the rear side of the secondary piston 13 and is slidably fitted to the primary piston 12 side of the retainer 60 and has a limit of movement toward the primary piston 12 side. The connecting rod 61 is fixed, the retainer 62 fixed to the primary piston 12 side of the connecting rod 61 and abutted against the bottom surface of the hole 59 of the primary piston 12, and the retainer 60 and the retainer 62 are opposed to each other. And a spring 63 biasing in the direction. As a result, in a state where the primary piston 12 is not input from the brake pedal side, the retainer 60 and the retainer 62 are separated to the limit determined by the connecting rod 61 by the biasing force of the spring 63, and the primary piston 12 The distance from the secondary piston 13 is a predetermined distance. The initial position of the primary piston 12 and the secondary piston 13 is determined to be a predetermined position by the initial interval maintaining mechanism parts 14 and 15 described above.

  In the vicinity of the front end portion of the primary piston 12, the primary pressure chamber 16 is always opened by passing through the hole 59 in the radial direction from the outer peripheral surface of the primary piston 12, and depending on the position of the primary piston 12, the primary pressure chamber A relief port 64 capable of communicating 16 with the liquid supply chamber 39 is formed.

  A communication switching portion 66 including a cup seal 46 is provided in the vicinity of the relief port 56 of the secondary piston 13, and a similar communication switching including a cup seal 49 is also provided in the vicinity of the relief port 64 of the primary piston 12. A portion 67 is provided. Hereinafter, the communication switching portion 66 in the vicinity of the relief port 56 of the secondary piston 13 will be described as an example with reference to FIG.

  A large-diameter hole 69 having a diameter larger than that of the cylinder hole 20 is formed on the inner peripheral surface of the front side of the first member 21 so as to be coaxial with the cylinder hole 20. An annular projecting portion 70 projecting rearward along the axial direction is formed. The bottom surface 71 on the outer peripheral side is disposed on the front side with respect to the bottom surface 72 on the inner peripheral side via the protrusion 70. The second member 22 is fitted in the large-diameter hole 69 of the first member 21, and the above-described cup seal 46 is held between the first member 21 and the second member 22. .

  The cup seal 46 includes a substantially perforated disk-shaped bottom 74, an annular inner lip 75 projecting from the inner peripheral side of the bottom 74 to one side, and the inner lip 75 from the outer peripheral side of the bottom 74. And an annular outer lip 76 projecting to the side. The cup seal 46 is slightly inclined so that the inner lip portion 75 has a smaller diameter on the protruding tip side in a free state where no external force is applied, and the outer lip portion 76 has a larger diameter on the protruding tip side in the free state. Slightly inclined. In the free state, the inner lip portion 75 includes a sliding contact surface 77 on the inner peripheral side that is slightly inclined so that the diameter on the protruding tip side becomes small, and a protruding tip side of the sliding contact surface 77 that is connected to the protruding tip side. And a chamfered surface 78 that is inclined so as to increase in diameter.

  The cup seal 46 is configured so that the bottom 74 is brought into contact with the second member 22 and the projecting portion 70 of the first member 21 is interposed between the inner lip portion 75 and the outer lip portion 76. It is held by the member 22.

  The stepped portion 33 on the inner peripheral side of the second member 22 has an inclined surface 80 whose front portion is slightly larger in diameter than the inner diameter of the rear end portion of the cup seal 46 and gradually increases in diameter toward the rear side. The rear surface of the inclined surface 80 is a cylindrical surface 81 having the same diameter regardless of the position. The liquid passage 32 described above opens at a position slightly extending from the end of the cylindrical surface 81 on the inclined surface 80 side to the inclined surface 80.

  Further, the inner lip portion of the cup seal 46 in the initial state in which the secondary piston 13 is not input from the brake pedal side and is in the initial position located on the most opposite side with respect to the secondary pressure chamber 17. An annular recess 83 is formed in which 75 can be stored in a free state or with a tightening margin that does not impair the tightening margin of the outer lip 76.

  The concave portion 83 is disposed at the foremost portion and is inclined so that the rear side has a small diameter, and the second tapered portion is provided continuously with the rear side of the first tapered surface 84 and inclined so that the rear side has a large diameter. A taper surface 85 and a third taper surface (control taper) that is connected to the rear side of the second taper surface 85 and inclines with a larger taper than the second taper surface 85 so that the rear side has a large diameter (the front side has a small diameter). Surface) 86.

  In the initial position, the first taper surface 84 is disposed so as to face the chamfered surface 78 of the cup seal 46 in the initial state so as to be slightly parallel with each other while being substantially parallel to each other. Here, in the initial position, the front end portion of the first taper surface 84 is located on the front side of the front end portion of the chamfered surface 78 of the cup seal 46.

  In the initial position, the second tapered surface 85 is disposed so as to be substantially parallel to the sliding contact surface 77 of the cup seal 46 in the initial state in a state where the second taper surface 85 is overlapped with the front-rear direction position. Here, in the initial position, the front end portion of the second taper surface 85 is located in front of the front end portion of the sliding contact surface 77 of the cup seal 46, and the rear end portion of the second taper surface 85 is the cup The seal 46 is located on the rear side from the rear end portion of the sliding contact surface 77.

  The front end portion of the third tapered surface 86 is located at an intermediate position in the front-rear direction of the inclined surface 80 of the second member 22 at the initial position, and the rear end portion of the third tapered surface 86 is at the initial position. The position in the front-rear direction is arranged inside the liquid passage 32 of the second member 22. As a result, the rear end portion of the recess 83 overlaps the liquid supply chamber 34 in the front-rear direction.

  The rear end portion of the third taper surface 86 is the outer peripheral surface of the maximum outer diameter of the secondary piston 13 and is larger in diameter than the maximum inner diameter of the sliding contact surface 77 of the inner lip portion 75 of the cup seal 46. 46 is continuous with a tightening / sliding contact surface 87 slidably contacting with 46. The opening 88 on the outer peripheral side of the relief port 56 of the secondary piston 13 is formed on the second tapered surface 85 up to the boundary position with the third tapered surface 86 of the second tapered surface 85.

  Thus, the third taper surface 86 can be brought into contact with the rear end portion of the sliding contact surface 77 of the cup seal 46 on the rear side of the opening portion 88 of the relief port 56, and the relief port 56 is recessed. An opening 88 is disposed at 83, and the entire recess 83 on the rear side of the opening 88 of the relief port 56 has a third tapered surface 86.

  In the initial position, the relief port 56 of the secondary piston 13 has a front end portion located slightly in front of the rear end face of the cup seal 46 and a rear end portion located in the rear side of the rear end face of the cup seal 46. . That is, the relief port 56 partially overlaps with the cup seal 46 in the front-rear direction, and a part of the rear side differs from the cup seal 46 in the front-rear direction.

  The operation of the master cylinder 10 configured as described above will be described by taking the secondary piston 13 side as an example. When the input to the brake pedal is started, the output assisted by the booster is input to the secondary piston 13 via the primary piston 12 and the initial interval maintaining mechanism 14, and the secondary piston 13 is moved from the initial position in the cylinder 11. Advance. Then, the secondary piston 13 brings the third tapered surface 86 into contact with the rear end portion side of the sliding surface 77 of the cup seal 46.

  When the secondary piston 13 further advances, as shown in FIG. 3, the rear end portion of the sliding contact surface 77 of the cup seal 46 is expanded in diameter by the third taper surface 86, so that the tightening margin, that is, the tightening force on the secondary piston 13 is increased. The surface pressure (X1 shown in FIG. 3 indicates the surface pressure distribution at this time) is generated so as to be partially increased and partially have a peak with the secondary piston 13. As a result, the cup seal 46 blocks communication between the secondary pressure chamber 17 and the liquid supply chamber 34 via the relief port 56 and presses the brake fluid in the secondary pressure chamber 17 with the secondary piston 13 to increase the hydraulic pressure. Will be generated.

  Further, when the secondary piston 13 moves forward and the rear end portion of the cup seal 46 is placed on the interference sliding contact surface 87 of the third taper surface 86 and the corner 90 at the boundary, as shown in FIG. 46 is in line contact with the secondary piston 13 at the corner 90, and the peak of the surface pressure is located at this line contact portion (X2 shown in FIG. 4 indicates the surface pressure distribution at this time). As a result, the cup seal 46 continues to block the communication between the secondary pressure chamber 17 and the liquid supply chamber 34 via the relief port 56, and the brake fluid in the secondary pressure chamber 17 is pressed by the secondary piston 13 to hydraulic pressure. Will continue to be generated.

  While the cup seal 46 is in contact with the corner 90 during further advancement of the secondary piston 13, the surface pressure peak is maintained at the position of the corner 90 as shown in FIG. X3 shown indicates the surface pressure distribution at this time), and the communication between the secondary pressure chamber 17 and the liquid replenishing chamber 34 continues to be shut off. When the secondary piston 13 further moves forward and the cup seal 46 as a whole rests on the interference sliding contact surface 87, the peak of the surface pressure moves to the front of the cup seal 46 as shown in FIG. However, X4 shown in FIG. 6 indicates the surface pressure distribution at this time, and the communication between the secondary pressure chamber 17 and the liquid replenishing chamber 34 is continuously cut off at this portion.

  On the other hand, when the input of the brake pedal is released, the secondary piston 13 returns to the initial position shown in FIG. When the brake fluid is forcibly sucked from the pipe communicating with the secondary pressure chamber 17 for traction control or the like in the state of returning to the initial position as described above, the fluid passages 29 and 32 and the fluid supply chamber 34 from the reservoir. The brake fluid flows through the relief port 56.

  As described above, the third taper surface 86 having a small diameter on the front side behind the opening 88 of the relief port 56 on the outer peripheral portion of the secondary piston 13 can come into contact with the inner peripheral portion of the cup seal 46. Thus, when the secondary piston 13 is moved forward, the third taper surface 86 is brought into contact with the rear end side of the sliding contact surface 77 of the cup seal 46 and the cup seal is moved along the third taper surface 86. When the diameter of 46 is increased, the surface pressure between the rear end portion of the cup seal 46 and the secondary piston 13 can be partially increased. As a result, a sufficient surface pressure is generated on the rear end side of the cup seal 46 to shut off the secondary pressure chamber 17 and the liquid replenishing chamber 34 and press the brake fluid in the secondary pressure chamber 17 by the secondary piston 13. Pressure can be generated. Further, the peak of the surface pressure (X1, X2, X3, X4) of the inner lip portion 75 of the cup seal 46 moves on the inner lip portion 75 from the rear end side to the front end side as the secondary piston 13 advances. Therefore, an efficient sealing effect can be exhibited at the forward movement position of the secondary piston 13, and therefore brake fluid pressure can be generated as in the conventional case without impairing efficiency.

  As described above, since it is possible to generate a surface pressure sufficient to shut off the secondary pressure chamber 17 and the liquid supply chamber 34 on the rear end side of the cup seal 46, the opening 88 of the relief port 56 is It suffices if it is positioned in front of the third tapered surface 86. As a result, as shown in FIG. 7, the relief port 56 of the secondary piston 13 in the initial position can be disposed further rearward than the cup seal 46 without increasing the invalid stroke A. That is, when the relief port 56 moves forward to the position indicated by the two-dot chain line in FIG. 7 with respect to the cup seal 46, a surface pressure sufficient to shut off the secondary pressure chamber 17 and the liquid supply chamber 34 is generated. The relief port 56 at the initial position can be arranged at a position further rearward than the cup seal 46 shown by a solid line in FIG. Therefore, the opening amount, that is, the communication amount with respect to the liquid supply chamber 34 can be sufficiently secured.

  Therefore, since a sufficient amount of brake fluid can flow from the reservoir through the fluid passages 29 and 32, the fluid supply chamber 34, and the relief port 56 without increasing the invalid stroke, the braking / driving force control device It becomes suitable for the combination.

  In addition, since the relief port 56 of the secondary piston 13 in the initial position can be disposed further rearward with respect to the cup seal 46 as described above, the communication amount can be effectively increased by increasing the diameter of the relief port 56. Can be increased.

  In addition, the recess 83 on the rear side of the opening 88 of the relief port 56 is a third taper surface 86, and the position of the rear end of the third taper surface 86 in the front-rear direction is set to the liquid supply chamber 34 at the initial position. Since they are overlapped, the cross-sectional area of the flow path on the relief port 56 side of the liquid supply chamber 34 provided outside the outer peripheral portion of the secondary piston 13 can be increased. Therefore, a further sufficient flow rate of brake fluid can be allowed to flow from the reservoir through the fluid passages 29 and 32, the fluid supply chamber 34, and the relief port 56, which is further suitable for combination with a braking / driving force control device.

  Furthermore, since it is not necessary to make the shape of the cup seal 46 special, the reliability of the cup seal 46 can be ensured. In addition, when the secondary piston 13 advances from the initial position to the secondary pressure chamber 17 side, the second taper surface 85 and the third taper surface 86 of the recess 83 move relative to the cup seal 46 in a direction in which the diameter gradually increases. The cup seal 46 moves while being guided by the second tapered surface 85 and the third tapered surface 86 so as to maintain the posture. Therefore, the invalid stroke can be stabilized.

  Further, the recessed portion 83 is more than the tightening force when the inner lip portion 75 of the cup seal 46 is in a free state or when the inner lip portion 75 is placed on the tightening sliding contact surface 87 when the secondary piston 13 is in the initial position. Since it can be arranged in a weak tightening force state, the cup seal 46 is in a free state when it is in the initial position, and it is difficult to cause settling. Therefore, the life of the cup seal 46 can be extended.

  Here, the communication switching unit 66 is not limited to the above and can have various structures as long as a tapered surface is formed on the rear side of the opening of the relief port 56 on the outer peripheral portion of the secondary piston 13. For example, as shown in FIG. 8, the recess 83 is formed so that the cross-sectional shape of the surface including the axis of the secondary piston 13 is an arc, and in accordance with this, the sliding contact surface 77 of the cup seal 46 is moved along its axis. The cross-sectional shape of the surface to be included is an arc-shaped convex shape, or the third tapered surface 86 is eliminated as shown in FIG. 9, and the second tapered surface 85 is connected to the interference sliding contact surface 87, as shown in FIG. As shown, the first taper surface 84 and the third taper surface 86 are eliminated, the front end of the second taper surface 85 is connected to the end surface 92 orthogonal to the axis, and the rear end is connected to the interference sliding contact surface 87. In accordance with this, the chamfered surface is eliminated from the inner peripheral portion of the cup seal 46, or the first tapered surface is eliminated and the secondary piston 13 is straight from the front end of the second tapered surface 85 as shown in FIG. Cylindrical surface extending to the front end face of 3 to form the can be a rear end portion of the second tapered surface 85 or to continuously to tighten Daisuri contact surface 87.

  In the above description, the communication switching unit 66 on the secondary piston 13 side has been described as an example. However, the communication switching unit 67 on the primary piston 12 side also employs the same structure as described above, and therefore exhibits the same effect. It will be.

It is sectional drawing which shows the whole structure of one Embodiment of the master cylinder of this invention. It is a partial expanded sectional view which shows the communication switching part of one Embodiment of the master cylinder of this invention. FIG. 3 is a partial enlarged cross-sectional view showing a communication switching portion of one embodiment of the master cylinder of the present invention including a surface pressure distribution by a cup seal, and shows one state when the piston advances. It is the elements on larger scale which show the communication switching part of one embodiment of the master cylinder of the present invention including the surface pressure distribution by a cup seal, and shows another state at the time of piston advance. It is the elements on larger scale which show the communication switching part of one embodiment of the master cylinder of the present invention including the surface pressure distribution by a cup seal, and shows another state at the time of piston advance. It is the elements on larger scale which show the communication switching part of one embodiment of the master cylinder of the present invention including the surface pressure distribution by a cup seal, and shows another state at the time of piston advance. It is a partial expanded sectional view which shows the communication switching part of one Embodiment of the master cylinder of this invention, Comprising: The relationship between the invalid stroke of a piston and a relief port is shown. It is a partial expanded sectional view which shows another example of the communication switching part of one embodiment of the master cylinder of the present invention. It is a partial expanded sectional view which shows another example of the communication switching part of one embodiment of the master cylinder of the present invention. It is a partial expanded sectional view which shows another example of the communication switching part of one embodiment of the master cylinder of the present invention. It is a partial expanded sectional view which shows another example of the communication switching part of one embodiment of the master cylinder of the present invention. It is sectional drawing which shows a master cylinder. It is a partial expanded sectional view which shows the principal part of a master cylinder including the surface pressure distribution by a cup seal. It is a partial expanded sectional view which shows the principal part of a master cylinder.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Master cylinder 11 Cylinder 13 Secondary piston 34 Liquid supply chamber 46 Cup seal 56 Relief port 83 Recessed part 86 3rd taper surface (control taper surface) 88 Opening part

Claims (2)

A cylinder,
A piston that is slidably provided in the cylinder and forms a pressure chamber that generates hydraulic pressure on the front side with the cylinder;
A liquid replenishing chamber formed by the cylinder and the outer peripheral surface of the piston and communicating with the reservoir is partitioned with respect to the pressure chamber, so that it is held on the inner peripheral side of the cylinder so as to be slidable in contact with the outer peripheral surface of the piston. An annular cup seal,
Have
In the master cylinder in which the piston is provided with a relief port in which one side is open to the outer peripheral surface and the other side is always open to the pressure chamber and the pressure chamber can be communicated with the liquid supply chamber.
A master cylinder, wherein a control taper surface having a small diameter on the front side is formed on the rear side of the opening portion of the relief port in the outer peripheral portion of the piston so as to be in contact with the inner peripheral portion of the cup seal. .   A concave portion is formed in an outer peripheral portion of the piston, an opening portion of the relief port is disposed in the concave portion, and the concave portion on the rear side of the opening portion of the relief port is used as the control tapered surface. Item 1. The master cylinder according to item 1.

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