JP2009234491A - Master cylinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a master cylinder capable of preventing the interference of a retainer with an outermost circumference of an inner bottom part of a piston even when it is formed by forging and of securing the good sliding performance of the piston. <P>SOLUTION: The master cylinder has a bottomed cylinder body, the piston 18 formed into a bottomed cylinder shape by forging and sliding in the cylinder body, and a spring assembly 79 having a spring 78 for urging the piston 18 to the opening side of the cylinder body and regulating the length of the spring 78 by the retainer 82 coming into contact with the inner bottom part 91 of the piston 18. An annular groove 99 is formed at the outermost circumference of the inner bottom part 91 of the piston 18 by forging. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a master cylinder.

For example, a master cylinder used in an automobile brake device has a bottomed cylindrical cylinder body, a piston that slides inside the cylinder body, and a spring assembly that biases the piston toward the opening side of the cylinder body. There is one in which a piston is formed in a bottomed cylindrical shape and a spring assembly is disposed in an inner hole thereof. And the technique which forms the inner hole of such a bottomed cylindrical piston by forging is disclosed (for example, refer patent document 1).
JP 2002-104164 A

  If the inner hole of the piston is formed by forging as described above, an arcuate wall surface portion connected in an arc shape to the inner wall portion is formed on the outermost periphery (boundary with the inner wall portion) of the inner bottom portion. On the other hand, since the spring assembly inserted into the piston is centered by the inner wall portion of the piston, the outer diameter of the retainer contacting the inner bottom portion needs to be slightly smaller than the inner diameter of the inner wall portion of the piston. is there. As a result, the retainer interferes with the outermost arcuate wall surface of the inner bottom of the piston, resulting in poor seating, and the entire spring assembly is tilted, causing a twisting moment in the piston and sliding. This could affect performance and impair brake operation feeling.

  Therefore, an object of the present invention is to provide a master cylinder capable of preventing the retainer from interfering with the outermost periphery of the inner bottom portion of the piston even if it is formed by forging, and ensuring good sliding performance of the piston. .

  In order to achieve the above object, in the present invention, an annular groove is formed by forging on the outermost periphery of the inner bottom portion of the piston.

  According to the invention of claim 1, since the annular groove is formed by forging on the outermost periphery of the inner bottom portion of the piston, the arc-shaped wall surface portion is formed on the outermost periphery of the annular groove. The inner bottom retainer can be shifted to the back side from the seating surface of the retainer. Therefore, even if the piston is formed by forging, it is possible to prevent the retainer from interfering with the outermost periphery of the inner bottom portion and to ensure good sliding performance of the piston.

  A master cylinder according to an embodiment of the present invention will be described below with reference to the drawings.

  Reference numeral 11 in FIG. 1 indicates a master cylinder according to the present embodiment that generates brake fluid pressure with a force corresponding to an operation amount of a brake pedal introduced via a brake booster (not shown). A reservoir 12 for supplying and discharging brake fluid is attached to the upper side of the reservoir 12.

  The master cylinder 11 is formed by processing a single material into a bottomed cylindrical shape having a bottom portion 13 and a cylindrical portion 14 and is disposed in the vehicle in a posture along the lateral direction, and the cylinder main body 15. A tandem type piston having a primary piston (piston) 18 slidably inserted into the opening 16 side and a secondary piston 19 slidably inserted into the bottom 13 side of the primary piston 18 of the cylinder body 15. Is. The primary piston 18 and the secondary piston 19 are slidably guided by a sliding inner diameter portion 20 having a circular cross section perpendicular to the axis of the cylinder portion 14 of the cylinder body 15 (hereinafter referred to as a cylinder shaft).

  The cylinder body 15 has mounting bases 21 and 22 that project outward in the radial direction of the cylindrical portion 14 (hereinafter referred to as the cylinder radial direction), in the circumferential direction of the cylindrical portion 14 (hereinafter referred to as the cylinder circumferential direction). The mounting holes 24 and 25 for mounting the reservoir 12 to the mounting bases 21 and 22 are formed in a state where the positions in the cylinder circumferential direction are matched with each other.

  A secondary discharge passage 26 and a primary discharge passage 27 to which a brake pipe (not shown) for supplying brake fluid to a brake device (not shown) is attached are formed on the mounting base portions 21 and 22 side of the cylinder portion 14 of the cylinder body 15. Has been. Note that the secondary discharge path 26 and the primary discharge path 27 are formed by shifting the positions in the cylinder axial direction in a state in which the positions in the cylinder circumferential direction coincide with each other.

  A plurality of, specifically, four seal grooves 30, seal grooves 31, seal grooves 32, and seal grooves 33 are formed in order from the bottom 13 side in the sliding inner diameter portion 20 of the cylinder body 15 by shifting the position in the cylinder axial direction. Has been. These seal grooves 30 to 33 have an annular shape in the cylinder circumferential direction and are recessed outward in the cylinder radial direction.

  The seal groove 30 on the most bottom 13 side is formed in the vicinity of the mounting hole 24 on the bottom 13 side, and an annular cup seal 35 is fitted in the seal groove 30.

  A sliding inner diameter portion of the cylinder portion 14 is formed so that a communication hole 36 formed from the mounting hole 24 on the bottom portion 13 side is opened in the cylinder portion 14 on the opening portion 16 side of the seal groove 30 in the cylinder body 15. An annular opening groove 37 that is recessed from the cylinder 20 outward in the cylinder radial direction is formed. Here, the opening groove 37 and the communication hole 36 are always in communication with the reservoir 12 so as to connect the inside of the cylindrical portion 14 and the reservoir 12.

  The cylinder body 15 is formed with the above-described seal groove 31 on the opposite side to the seal groove 30 of the opening groove 37 in the cylinder axial direction, that is, on the opening 16 side. A seal 42 is fitted.

  The above-described seal groove 32 is formed on the opening 16 side of the cylinder body 15 and in the vicinity of the mounting hole 25 on the opening 16 side. An annular cup seal 45 is formed in the seal groove 32. Is fitted.

  In the cylinder body 15, the sliding inner diameter of the cylinder portion 14 is formed on the opening portion 16 side of the seal groove 32 so that a communication hole 46 drilled from the mounting hole 25 on the opening portion 16 side is opened in the cylinder portion 14. An annular opening groove 47 that is recessed outwardly from the portion 20 in the cylinder radial direction is formed. Here, the opening groove 47 and the communication hole 46 are always in communication with the reservoir 12 so as to connect the inside of the cylindrical portion 14 and the reservoir 12.

  The above-mentioned seal groove 33 is formed on the cylinder body 15 on the opposite side to the seal groove 32 of the opening groove 47, that is, on the opening 16 side, and an annular partition seal 52 is fitted in the seal groove 33. .

  The secondary piston 19 fitted to the bottom 13 side of the cylinder body 15 has a bottomed cylindrical shape (cup shape) having a cylindrical portion 55 and a bottom portion 56 formed on one side in the axial direction of the cylindrical portion 55. The cylinder portion 55 is slidably fitted to the sliding inner diameter portion 20 of the cylinder body 15 in a state where the cylinder portion 55 is disposed on the bottom 13 side of the cylinder body 15. Further, an annular step 59 having a slightly smaller diameter than the other portions is formed on the outer peripheral side of the end opposite to the bottom 56 of the cylindrical portion 55, and the bottom 59 has a bottom 56. A plurality of ports 60 penetrating in the cylinder radial direction are formed radially.

  Between the secondary piston 19 and the bottom 13 of the cylinder body 15, a spring assembly 63 including a secondary piston spring 62 that biases the secondary piston 19 toward the opening 16 of the cylinder body 15 in a contracted state is a cylindrical portion 55. It is provided in the state inserted in. The spring assembly 63 includes a retainer 64 that contacts the bottom 13 of the cylinder body 15, a retainer 65 that contacts the bottom 56 of the secondary piston 19, one end fixed to the retainer 65, and the retainer 64 within a predetermined range. The secondary piston spring 62 is interposed between the retainers 64 and 65 on both sides in a state in which the length thereof is regulated. The distance between the secondary piston 19 in the initial state where no input is made from the brake pedal side (the right side in FIG. 1) (not shown) and the bottom 13 of the cylinder body 15 is determined by the spring assembly 63.

  Here, the portion surrounded by the bottom portion 13 of the cylinder body 15 and the bottom portion 13 side of the cylinder portion 14 and the secondary piston 19 is a secondary pressure chamber 68 for supplying hydraulic pressure to the secondary discharge passage 26. The pressure chamber 68 communicates with the reservoir 12 when the secondary piston 19 is in a position for opening the port 60 into the opening groove 37. On the other hand, the cup seal 35 provided in the seal groove 30 on the bottom 13 side of the cylinder body 15 has an inner circumference that is in sliding contact with the outer circumference side of the secondary piston 19, and the secondary piston 19 connects the port 60 to the cup seal 35. In the state of being positioned on the bottom 13 side, communication between the reservoir 12 and the secondary pressure chamber 68 can be blocked. In this state, the secondary piston 19 slides on the inner diameter of the sliding inner diameter portion 20 of the cylinder body 15 and the inner periphery of the cup seal 35 and the partition seal 42 held by the cylinder body 15, whereby the brake in the secondary pressure chamber 68. The liquid is pressurized and supplied from the secondary discharge passage 26 to the brake device.

  The primary piston 18 fitted to the opening 16 side of the cylinder body 15 includes an inner cylindrical portion 71, a bottom portion 72 formed on one side in the axial direction of the inner cylindrical portion 71, and an inner cylindrical portion 71 of the bottom portion 72. On the other hand, it has a shape having an outer cylindrical portion 73 formed on the opposite side, and the inner cylindrical portion 71 is inserted into the cylinder body 15 in a state of being disposed on the secondary piston 19 side in the cylinder body 15. Here, an output shaft of a brake booster (not shown) is inserted inside the outer cylindrical portion 73, and this output shaft presses the bottom portion 72.

  On the outer peripheral side of the end opposite to the bottom 72 of the inner cylindrical portion 71, an annular recess 75 having a slightly smaller diameter than the other portions is formed. Furthermore, a plurality of ports 76 are formed radially in the recess 75 of the inner cylindrical portion 71 so as to penetrate in the radial direction on the bottom 72 side.

  Between the secondary piston 19 and the primary piston 18, a spring assembly 79 including a primary piston spring (spring) 78 that biases the primary piston 18 toward the opening 16 of the cylinder body 15 in a contracted state is an inner cylindrical portion. 71 is provided in a state of being inserted. The spring assembly 79 includes a retainer 81 that contacts the bottom 56 of the secondary piston 19, a retainer 82 that contacts the bottom 72 of the primary piston 18, one end fixed to the retainer 82, and the retainer 81 within a predetermined range. The primary piston spring 78 is interposed between the retainers 81 and 82 on both sides in a state in which the length thereof is regulated. An interval between the secondary piston 19 and the primary piston 18 in an initial state where there is no input from the brake pedal side (the right side in FIG. 1) (not shown) is determined by the spring assembly 79.

  Here, the portion surrounded by the opening 16 side of the cylinder portion 14 of the cylinder body 15, the primary piston 18 and the secondary piston 19 is a primary pressure chamber 85 for supplying hydraulic pressure to the primary discharge passage 27, The primary pressure chamber 85 communicates with the reservoir 12 when the primary piston 18 is in a position for opening the port 76 into the opening groove 47. On the other hand, the cup seal 45 provided in the seal groove 32 of the cylinder body 15 has an inner periphery that is in sliding contact with the outer periphery side of the primary piston 18, and the primary piston 18 places the port 76 closer to the bottom 13 than the cup seal 45. In the positioned state, communication between the reservoir 12 and the primary pressure chamber 85 can be blocked. In this state, the primary piston 18 slides on the inner diameter of the sliding inner diameter portion 20 of the cylinder body 15 and the inner periphery of the cup seal 45 and the partition seal 52 held by the cylinder body 15, whereby the brake in the primary pressure chamber 85 is reached. The liquid is pressurized and supplied from the primary discharge passage 27 to the brake device.

  A cover 86 is attached to the opening 16 side of the cylinder body 15 so as to cover the primary piston 18 protruding from the opening 16.

  The primary piston 18 shown in FIG. 2 includes an inner wall portion 90 on the inner peripheral side of the inner cylindrical portion 71, an inner bottom portion 91 on the inner cylindrical portion 71 side of the bottom portion 72, and an inner wall portion on the inner peripheral side of the outer cylindrical portion 73. 92 and the inner bottom portion 93 on the outer cylindrical portion 73 side of the bottom portion 72 are formed by forging.

  The inner wall 90 on the inner circumferential side of the inner cylindrical portion 71 is formed with an inner wall surface portion 95 having a constant diameter on the side opposite to the inner bottom portion 91, and a tapered surface portion 96 is formed on the inner bottom portion 91 side of the inner wall surface portion 95. An inner wall surface 97 having a constant diameter smaller than the inner wall surface 95 is formed on the inner bottom 91 side of the tapered surface 96. The inner diameter wall 97 having the smallest diameter is slightly larger than the diameter of the retainer 82 so that it can be inserted while the retainer 82 of the spring assembly 79 is centered. Further, the inner bottom portion 91 has a flat portion 98 along the direction orthogonal to the axis of the primary piston 18.

  An annular groove 99 is formed on the outermost outer periphery of the inner bottom portion 91 of the primary piston 18 so as to be recessed toward the outer cylindrical portion 73 by forging. As shown in FIG. 3, the annular groove 99 is formed on the opposite side of the inner wall surface portion 97 of the wall surface portion 102 from the inner wall surface portion 97 on the side opposite to the inner wall surface portion 97. The smaller the diameter, the smaller the diameter, and the arc-shaped wall surface portion 103 in which the axial section of the primary piston 18 forms an arc shape, and the inner side along the axis-perpendicular direction of the primary piston 18 from the opposite side of the wall surface portion 102 of the arc-shaped wall surface portion 103. It has an annular groove bottom surface portion 104 that extends, and a wall surface portion 105 that rises from the inner diameter side of the groove bottom surface portion 104 toward the inner cylindrical portion 71 with a constant diameter. The wall surface portion 105 is connected to the flat surface portion 98 of the inner bottom portion 91.

  Here, the distance A from the groove bottom surface portion 104 to the end opposite to the groove bottom surface portion 104 of the arc-shaped wall surface portion 103 is the groove to the end portion of the wall surface portion 105 opposite to the groove bottom surface portion 104. The distance is less than the distance B from the bottom surface portion 104 (that is, the distance from the groove bottom surface portion 104 to the flat surface portion 98). In this embodiment, the distance B is set to about 1 mm. Further, in the present embodiment, the distance from the wall surface portion 102 to the wall surface portion 105 is set to about 2 mm. In the retainer 82, the inner diameter of the flat end surface portion 107 along the direction orthogonal to the axis opposite to the primary piston spring 78 is smaller than the outer diameter of the plane portion 98. As a result, the retainer 82 abuts at the end surface portion 107 on the flat surface portion 98 formed on the inner peripheral side of the annular groove 99 of the inner bottom portion 91 while the outer diameter side is centered by the inner wall surface portion 97.

  According to the master cylinder 11 according to the present embodiment described above, the annular groove 99 is formed on the outermost periphery of the inner bottom portion 91 of the primary piston 18 by forging. It will be formed in the outer periphery, and it can shift to the back | inner side rather than the plane part 98 used as the seat surface of the retainer 82 of the inner bottom part 91. FIG. Therefore, even if the primary piston 18 is formed by forging, interference of the retainer 82 of the spring assembly 79 with the outermost periphery of the inner bottom portion 91 can be prevented, and the seating property of the retainer 82 is improved. Therefore, the uprightness of the spring assembly 79 can be ensured, and good sliding performance of the primary piston 18 can be ensured. As a result, a good brake operation feeling can be obtained. Further, since the slidability is improved, it is possible to improve the damage due to the prying of the primary piston 18.

  Further, since the retainer 82 of the spring assembly 79 abuts on a flat surface portion 98 formed on the inner peripheral side of the annular groove 99 of the inner bottom portion 91 of the primary piston 18, the retainer 82 reaches the outermost periphery of the inner bottom portion 91 of the primary piston 18. Interference of the retainer 82 of the spring assembly 79 can be reliably prevented, and good sliding performance of the primary piston 18 can be ensured.

  The shape of the annular groove 99 is not limited to the above as long as the seating property of the retainer 82 of the spring assembly 79 can be improved, and can be appropriately changed according to the shape of the forging die.

  For example, as shown in FIG. 4, at the boundary between the groove bottom surface portion 104 and the wall surface portion 105, an arcuate wall surface portion 110 having a smaller diameter as the distance from the groove bottom surface portion 104 increases and the axial section of the primary piston 18 forms an arc shape. It may be formed.

  In addition, as shown in FIG. 5, the wall surface portion 105 may have a tapered shape having a smaller diameter as the distance from the groove bottom surface portion 104 increases.

  Further, as shown in FIG. 6, a tapered surface portion 111 having a smaller diameter as the distance from the groove bottom surface portion 104 may be formed at the boundary between the groove bottom surface portion 104 and the wall surface portion 105.

It is sectional drawing which shows the master cylinder which concerns on one Embodiment of this invention. It is sectional drawing which shows the primary piston of the master cylinder which concerns on one Embodiment of this invention. It is an expanded sectional view of the A section of Drawing 2 showing the master cylinder concerning one embodiment of the present invention. It is an expanded sectional view of the A section of Drawing 2 showing the modification of the master cylinder concerning one embodiment of the present invention. It is an expanded sectional view of the A section of Drawing 2 showing the modification of the master cylinder concerning one embodiment of the present invention. It is an expanded sectional view of the A section of Drawing 2 showing the modification of the master cylinder concerning one embodiment of the present invention.

Explanation of symbols

11 Master cylinder 15 Cylinder body 18 Primary piston (piston)
78 Primary piston spring (spring)
79 Spring assembly 82 Retainer 91 Inner bottom 98 Flat surface 99 Annular groove

Claims (2)

A bottomed cylindrical cylinder body,
A piston that is formed into a bottomed cylinder by forging and slides within the cylinder body;
A spring assembly that includes a spring that biases the piston toward the opening side of the cylinder body, and the length of the spring is regulated by a retainer that can contact the inner bottom of the piston;
In a master cylinder having
An annular groove is formed on the outermost periphery of the inner bottom portion of the piston by forging.   2. The master cylinder according to claim 1, wherein the retainer is in contact with a flat portion formed on an inner peripheral side of the annular groove of the inner bottom portion.

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