JPH1029527A - Master cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation of a sleeve during operation of a brake, facilitate manufacturing of guide grooves, and eliminate any regulation of retreating limits of a primary piston and a secondary piston. SOLUTION: A master cylinder is so constituted that a cylinder housing 1 is composed of a body main body 2 and a cap 3, first and second pistons 4, 5 guided by sleeves fitted in the cylinder housing 1 are slidably provided, first and second pressure chambers 9, 10 are partitioned, and spring mechanisms 11, 12 are arranged therein so that the first and second pistons 4, 5 are energized thereby in the retreating direction, projecting ends 17c projecting in the radially outer direction are formed on a spring retainer 17 of a spring mechanism 11 for energizing the first piston 4, and trapezoidal guide grooves whose groove widths become wider toward their sleeve ends and which penetrate the outer circumferential surface of the sleeve 8 in the axial direction, where the projecting parts 17c are inserted and engaged, and locking parts 20a which are brought in contact with the projecting ends 17c in such positions as a little extended from the retreating limit are formed in the sleeve 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a master cylinder used for various brake devices of an automobile.

[0002]

2. Description of the Related Art Conventionally, as this type of master cylinder, for example, there is a tandem master cylinder mc shown in FIG. 5, which is mounted in front of a brake booster (brake booster) mv. In the master cylinder mc, a cylinder housing 41 is configured by coupling or screwing a cap 43 to an opening of a body main body 42. In the cylinder housing 41, a primary piston 44 and a secondary piston 45 are fitted with the cap 43 and piston guides 46, 47 are inserted.
And is slidably disposed through. In the cylinder housing 41, a resin sleeve 48 for positioning the primary piston 44 is fitted and slidably mounted on the primary piston 44.

A primary piston 44 and a secondary piston 45 are provided inside a cylinder housing 41.
The sleeve 48 forms a first pressure chamber 49, and the secondary piston 45 and the inner wall surface of the body 42 form a second pressure chamber 50. The first pressure chamber 49 and the second pressure chamber 50 are provided with spring mechanisms 51 and 52, respectively, for urging the primary piston 44 and the secondary piston 45 in the retreating direction, respectively.

In such a master cylinder mc, when the primary piston 44 and the secondary piston 45 are pushed leftward in the drawing into the first pressure chamber 49 and the second pressure chamber 50, respectively, the pressure chambers 49 and 50 are pressed. The internal fluid pressure is increased, and the hydraulic fluid is sent from the outlets 53 and 54 to a brake system (not shown).

Incidentally, the conventional master cylinder mc
The spring mechanism 51 includes a return spring 55 and a guide screw 5
6 and a spring retainer 57. The large head 56a is formed on the primary piston 44 so as to protrude forward.
The guide screw 56 is screwed and protruded so that the spring retainer 57 can slide on the guide screw 56 and abut on its large head 56a. Then, a return spring 55 is contracted between the spring retainer 57 and the primary piston 44.

The spring retainer 57 has a projection 57a projecting outward in the radial direction, and the sleeve 48 is axially oriented so that the projection 57a is slidably engaged with the bottom. A guide groove 58 having a
and a stopper portion 59 for receiving the "a" and restricting the retreat thereafter. With such a structure, the conventional master cylinder mc has a compact shape and regulates the retreat limit of the primary piston 44 and the secondary piston 45. (Tokuhei 4-27060
No.)

[0007]

However, the conventional master cylinder mc has the following problems. (1) During the brake operation of the primary piston 44 to the left in the drawing, only the inner diameter side of the sleeve 48 of the first pressure chamber 49 is pressurized, but the replenishing liquid passage on the outer diameter side of the sleeve 48 is increased. Since the pressure at the peripheral edge is always low, a pressure difference is generated therebetween. For this reason, the sleeve 48 made of resin expands so as to fill the clearance at the peripheral edge and the like, and its shape and dimensions change.

(2) Since the protruding end 57a of the spring retainer 57 is slidably guided in the guide groove 58 having the bottom of the sleeve 48, the sleeve 48 is worn when the protruding end 57a slides. Then, the abrasion powder is generated, which may affect the operation of the master cylinder mc. (3) The retreat limit of the primary piston 44 and the secondary piston 45 constitutes the retreat limit mechanism 4
8, since the spring retainer 57 and the stopper 59 of the guide groove 58 restrict the variation, the dimensional accuracy varies, the variation of the invalid stroke of the master cylinder mc increases.

(4) Since the guide screw 56 is screwed into and protruded from the primary piston 44, if there is an eccentric load on the primary piston 44, the guide screw 56 and the spring retainer 57 are twisted. (5) A guide groove 58 having a bottom is required on the inner peripheral surface of the sleeve 48, and this groove processing is extremely troublesome, and the cost increases.

[0010] The present invention has been made in view of such a point,
The purpose is to solve the above-mentioned problems, to prevent the deformation of the sleeve during the operation of the brake, to facilitate the processing of the guide groove, and to limit the retreat limit of the primary piston and the secondary piston to reduce the ineffective stroke and the brake doubling. An object of the present invention is to provide a master cylinder that can be freely set in combination with a force device (brake booster).

[0011]

According to a first aspect of the present invention, there is provided a cylinder housing comprising a body having an opening at one end and a cap coupled to the opening of the body. First and second pistons, which are inserted into the cap and guided by a sleeve fitted in the cylinder housing, are slidably provided. The first and second pistons and the cap are used to slide the first and second pistons. A first pressure chamber, a second pressure chamber is defined by the second piston and the body body, and a spring mechanism is disposed in each of the first and second pressure chambers; 1. In the master cylinder that urges the second piston in the backward direction, the following is performed.

(1) The spring mechanism disposed in the first pressure chamber has a substantially cylindrical spring retainer abutting on a rear end surface of the second piston, and a head inserted through the retainer. A guide pin engaged with the retainer, a guide pin engaging member abutting on a bottom surface of a concave portion formed on the distal end side of the first piston and being engaged with an end of the guide pin; and the spring retainer. A return spring contracted between the guide pin engaging member and the spring retainer, a protruding end protruding outward in the radial direction is formed on the spring retainer, and the protruding end is inserted into the sleeve and engaged. In the axial direction
Among them, a guide groove penetrating the outer peripheral surface and a locking portion for abutting the protruding end portion at a position slightly beyond the retreat limit are formed.

(2) In the above (1), the guide groove is a trapezoidal groove having a wide groove width at the sleeve end and a narrow groove width at the locking portion.

Since the present invention is configured as described above, the inner diameter of the sleeve (the first
Since the pressure is increased to the same hydraulic pressure at the same time through the penetrated guide groove, a pressure difference is generated between the inner and outer diameter portions of the sleeve. Therefore, deformation and dimensional change of the sleeve can be prevented.

Since the guide groove is a groove penetrating between the outer diameter portions of the sleeve, the processing is easy and the processing cost can be reduced. Further, since the retraction limit of the primary piston and the secondary piston is not restricted, the invalid stroke of the master cylinder can be freely adjusted and set in a state where the invalid stroke is combined with the brake booster.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. 1 and 2 show an embodiment of the master cylinder of the present invention. FIG. 1 is a longitudinal sectional view of the master cylinder, and FIG. 2 is an enlarged view of a portion A in FIG.

In FIG. 1, MC is a tandem master cylinder, which is mounted in front of a brake booster (brake booster) MV, not shown. The cylinder housing 1 of the master cylinder MC includes a body main body 2 having an opening at one end, and a cap 3 coupled to the opening of the body main body 2 (prevented from being removed by a retainer). A sleeve 8 is fitted in the cylinder housing 1, and a primary piston 4 and a secondary piston 5 are fitted into the cap 3, and a piston guide portion 3 a formed in the cap 3, It is guided and supported by the sleeve 4 and is slidably disposed.

A first pressure chamber 9 is defined inside the cylinder housing 1 by the primary piston 4, the secondary piston 5 and the cap 3. The first pressure chamber 9 is defined by the secondary piston 5 and the inner wall surface of the body 2. 2
A pressure chamber 10 is defined. The primary piston 4 and the secondary piston 5 are formed with concave portions 4a, 5a each having an opening at the distal end, and small holes 4b, 5b as replenishing liquid passages are formed in peripheral walls forming the concave portions 4a, 5a. Are provided respectively.

The first pressure chamber 9 and the second pressure chamber 10 are provided with spring mechanisms 11 and 12, respectively. The spring mechanisms 11 and 12 are connected to the recess 4a of the primary piston 4 and the secondary Between the piston 5 and between the recess 5a of the secondary piston 5 and the body 2
The primary piston 4 and the secondary piston 5 are respectively urged in the retreating direction.

The spring mechanism 11 includes a return spring 15, a guide pin 16 having a large head 16a, a spring retainer 17 in the shape of a mountain hat, and a guide pin engaging member 18. The return spring 15 is contracted between the peripheral edge of the guide pin engaging member 18 and the peripheral edge 17a of the spring retainer 17, and one end thereof is formed on the bottom surface of the recess 4a of the primary piston 4. Fitted on the enlarged diameter part. The guide pin 16 is disposed so as to protrude in the axial direction of the piston at a predetermined distance from the bottom surface of the recess 4a, and the engaging member 18 is engaged with an engaging groove formed at an end thereof. Is being worn. In addition, the spring retainer 17
The hole 17b provided at the top of the mountain hat shape slides freely on the guide pin 16 within a predetermined stroke range (range slightly beyond the retreat limit of the primary piston 4), and the large head 16a To be engaged. The spring mechanism 12 is only a return spring.

On the peripheral edge 17a of the spring retainer 17, a plurality (4 in this embodiment) projecting outward in the radial direction is provided.
) Are formed integrally with each other, and the sleeve 8 is formed in the sleeve 8 with a constant width and a wide guide groove penetrating the outer peripheral surface thereof in the axial direction in which the protrusion 17c is inserted and engaged. 20 are formed. These guide grooves 20 are inserted into the primary piston 4 from the end of the sleeve 8.
A locking portion 20a is formed at a position slightly beyond the retreat limit so that the protruding end portion 17c abuts and locks. As shown in FIG. 3, a trapezoidal guide groove 2 having a wide groove width 21a at the end of the sleeve 4 and a narrow groove width at the locking portion 20a is used instead of the wide guide groove 20 having a constant width.
1 is preferably formed.

As shown in FIG. 4, the guide groove 20 (or 21) formed in the sleeve 8 penetrates the inner and outer peripheral surfaces thereof and is wider than the width of the protruding end portion 17c. Even if the protruding end 17c is inserted along the groove 20 (or 21), there is no hindrance to the flow of hydraulic oil, and the protruding end 17c slides into the groove 20 (or 21) to slide the sleeve 8 Is hardly worn.
Further, the reciprocation of the primary piston 4 does not hinder the movement of the spring retainer 17.

Next, the replenishing liquid passage 2 from the oil reservoir 23 is provided in the cap 3 of the cylinder housing 1.
A passage 26 communicating with the piston guide 4 is formed on the piston sliding surface of the piston guide portion 3a. A passage 28 is formed in the sleeve 8 in the cylinder housing 1 so as to communicate with a replenishing liquid passage 27 from the oil reservoir 23, and is opened on the piston sliding surface.

In the first pressure chamber 9 on the primary piston 4 side, the sleeve 8 and the piston guide portion 3a
And a sliding surface between the piston guide 3a and the primary piston 4 to form a liquid supply path when the brake operation is released.
An annular one-way seal member 29 is provided. That is, since the inside of the first pressure chamber 9 becomes a negative pressure when the brake operation is released, the one-way seal member 29 is deformed and loses its sealing function, thereby promoting the replacement fluid from the fluid supply path. Similarly, in the second pressure chamber 10 on the secondary piston 6 side, an annular one-way seal member 30 is disposed on the side surface of the sleeve 8.

When the primary piston 4 and the secondary piston 5 are pushed into the first and second pressure chambers 9, 10, respectively, when the brakes are operated, the pressure chambers 9, 10
Of the one-way sealing members 29, 3
0 is pressed against the respective sealing surfaces by the liquid pressure to seal.

The small holes 4b, 5b formed in the peripheral walls of the respective recesses 4a, 5a of the primary piston 4 and the secondary piston 5 respectively move from the oil reservoir 23 to the first and second pressure chambers 9, 9 at the brake release position.
A replenishment fluid passage to 10 is formed.

The annular seal members 31, 32, 33,
34 and 35 are provided in the cylinder housing 1.

As described above, the tandem master cylinder MC
When the primary piston 4 and the secondary piston 5 are pushed leftward in FIG. 1 into the first pressure chamber 9 and the second pressure chamber 10, respectively, the pressure chambers 9, 10
The internal fluid pressure is increased, and the hydraulic fluid is configured to be fed from the delivery ports 13 and 14 to a brake system (not shown).

In the case of such a brake operation, since the guide groove 20 (or 21) is a wide groove penetrating through the outer diameter surface of the sleeve 8, the inner diameter portion of the sleeve 8 (the primary piston The guide portion) side and the outer diameter portion side pass through the guide groove 20 (or 21),
At the same time, the pressure is increased to the same hydraulic pressure.
There is no pressure difference between the outer diameters, so the shape and dimensions of the sleeve 8 do not change.

Further, the locking portion 20a of the guide groove 20 (or 21) of the sleeve 8 is formed at a position slightly beyond the retreat limit of the primary piston 4 from the end of the sleeve 8, so that when the brake is released, The retraction limit of the primary piston 4 is determined by the position of the push rod of the brake booster MV.
In a state where the master cylinder MC and the brake booster MV are connected, c is at a position not in contact with the locking portion 20a.

As described above, since the retreat limit of the primary piston 4 and the secondary piston 5 is not restricted, the invalid stroke of the master cylinder MC can be freely adjusted and set in a state combined with the brake booster MV. Can be. Therefore, the retreat limit of the primary piston 4 is restricted by the output shaft of the brake booster MV.

The technique of the present invention is not limited to the technique in the above-described embodiment, but may be implemented by means of other modes that perform the same function. Can be changed or added.

[0033]

As is apparent from the above description, according to the master cylinder of the present invention, the spring mechanism disposed in the first pressure chamber is substantially in contact with the rear end face of the second piston. A cylindrical spring retainer; a guide pin inserted into the retainer, the head of which is engaged with the retainer; and an end of the guide pin which abuts against a bottom surface of a concave portion formed on the tip side of the first piston. And a return spring contracted between the spring retainer and the guide pin engaging member. The spring retainer has a protruding end protruding radially outward. Forming
In the sleeve, in the axial direction in which the protruding end portion is inserted and engaged, a guide groove penetrating the outer peripheral surface thereof, and a locking portion for abutting the protruding end portion at a position slightly beyond the retreat limit. During the operation of the brake, the shape and dimensions of the sleeve are prevented from changing, and the processing of the guide groove is easy, the processing cost can be reduced, and the retraction limit of the primary piston and the secondary piston is limited. Without restriction, the invalid stroke can be freely set in combination with a brake booster (brake booster).

Further, since the protruding end of the spring retainer is guided so as to be freely inserted into the guide groove formed in the sleeve without sliding, it is possible to prevent generation of wear powder of the sleeve. Further, since the guide pin is engaged in front of the primary piston, it is possible to prevent the guide pin and the spring retainer from being twisted even when the primary piston has an eccentric load.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a master cylinder of the present invention.

2 is an enlarged view of a portion A in FIG. 1, wherein FIG. 2 (a) is a sectional view thereof, and FIG. 2 (b) is a bottom view thereof.

3 is an enlarged view showing another example of FIG. 2, wherein FIG. 3 (a) is a sectional view thereof, and FIG. 3 (b) is a bottom view thereof.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 1;

FIG. 5 is a longitudinal sectional view showing a conventional master cylinder.

[Explanation of symbols]

 MC master cylinder 1 cylinder housing 2 body main body 3 cap 4 primary piston 5 secondary piston 8 sleeve 9 first pressure chamber 10 second pressure chamber 11 spring mechanism 12 spring mechanism (return spring) 15 return spring 16 guide pin 16a large head 17 Spring retainer 17a Peripheral edge 17b Hole 17c Protrusion 18 Guide pin engaging member 20 Guide groove 20a Locking portion 21 Trapezoidal guide groove 21a Groove width

Claims (2)

[Claims] 1. A cylinder housing comprising a body having an opening at one end and a cap coupled to the opening of the body, which is inserted into the cap and fitted into the cylinder housing. First and second pistons guided by the sleeve are slidably provided, and a first pressure chamber is formed by the first and second pistons and the cap. A second pressure chamber is defined by each of the first and second pressure chambers, and a spring mechanism is disposed in each of the first and second pressure chambers to urge the first and second pistons in a backward direction. The spring mechanism disposed in the first pressure chamber includes a substantially cylindrical spring retainer abutting on a rear end surface of the second piston, and a head inserted into the retainer and having a head portion formed by the retainer. A guide pin engaged with the spring retainer, a guide pin engaging member abutting against a bottom surface of the concave portion formed on the distal end side of the first piston, and being engaged with an end of the guide pin; A return spring that is contracted between the attachment member and the spring retainer, the spring retainer is formed with a protruding end protruding radially outward, and the sleeve is inserted into and engaged with the sleeve. A master groove formed in the outer peripheral surface of the guide cylinder, and a locking portion for abutting the protruding end portion at a position slightly beyond the retreat limit. 2. The master cylinder according to claim 1, wherein the guide groove is a trapezoidal groove having a wide groove width at the sleeve end and a narrow groove width at the locking portion.