JP4892526B2 - Tandem master cylinder - Google Patents

Description

  According to the present invention, a primary piston and a secondary piston are slidably fitted to a cylinder main body whose axis is arranged to rise forward, and a coil spring is formed between a recess formed on the rear surface of the primary piston and the front surface of the secondary piston. The present invention relates to a tandem master cylinder in which return springs are arranged.

In a tandem master cylinder that includes a primary piston and a secondary piston that are operated by a pedaling force of a driver stepping on a brake pedal and that generates brake fluid pressure that operates two wheel cylinders, the tandem master cylinder is disposed between the primary piston and the secondary piston. Patent Document 1 below discloses that the front end of the return spring is engaged with a recess formed on the rear surface of the primary piston.
JP-A-2005-59700

  In general, the master cylinder is mounted on the vehicle body with its axis line horizontal, but the master cylinder may be mounted on the vehicle body in a front-up posture due to layout restrictions. In such a case, when air is released after the brake fluid is replaced, if the air bubbles accumulated in the hydraulic pressure chamber between the primary piston and the secondary piston enter the recess formed on the rear surface of the primary piston, the recess rises forward. Since it inclines, there exists a possibility that a bubble may remain there and it becomes difficult to be discharged. If air bubbles stay in the recess facing the hydraulic chamber in this way, when the volume of the hydraulic chamber is reduced and the brake hydraulic pressure is generated, the bubbles are compressed and the rise of the brake hydraulic pressure is delayed, and the brake pedal There is a possibility that the brake fluid pressure with respect to the stroke is reduced, and the braking performance and the braking feeling are affected.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to prevent air bubbles from staying in a concave portion on the rear surface of a primary piston of a tandem master cylinder that is disposed in a front-up state.

In order to achieve the above object, according to the first aspect of the present invention, a primary piston and a secondary piston are slidably fitted to a cylinder body having an axially upwardly arranged axis, and a rear surface of the primary piston In the tandem master cylinder in which a return spring made of a coil spring is disposed between the recess formed in the front surface and the front surface of the secondary piston, a spring seat for supporting the front end side of the return spring on the inner peripheral surface of the recess Forming a stepped portion that engages, expanding the inner peripheral surface of the concave portion from the outer periphery of the stepped portion toward the rear, and reducing the outer diameter of the return spring toward the front, A tandem master cylinder is proposed in which the inclination of the upper part of the inner peripheral surface of the recess is raised rearward from the horizontal line (H) .

  The second return spring 38 of the embodiment corresponds to the return spring of the present invention.

According to the first aspect of the present invention, when the concave portion is formed on the rear surface of the primary piston that is fitted to the cylinder body that is disposed so that the axis is raised forward, air bubbles are retained in the concave portion and the pedal stroke is increased. Although the brake fluid pressure may decrease, a step portion for supporting the spring seat is formed on the inner peripheral surface of the concave portion, and the inner peripheral surface of the concave portion behind the outer periphery of the step portion is directed rearward. By expanding the diameter, the inclination of the upper part of the inner peripheral surface of the recess is raised behind the horizontal line, so that bubbles are easily discharged from the recess to prevent an increase in pedal stroke and a decrease in brake fluid pressure. Can do. Moreover, since the outer diameter of the return spring is reduced toward the front, the degree of expansion can be increased when the inner peripheral surface of the concave portion on the rear surface of the primary piston is expanded toward the rear. The upward angle of the axis of the cylinder body can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 and 2 show an embodiment of the present invention. FIG. 1 is a diagram showing a negative pressure booster and a master cylinder of a vehicle brake device, and FIG. 2 is an enlarged sectional view of the master cylinder. In addition, the definition of the front and back in this specification is that the master cylinder side is the front, and the negative pressure booster side is the back.

  As shown in FIG. 1, a negative pressure booster 12 is supported on the front surface of the toe board 11 in front of the driver's seat of the automobile, and a tandem master cylinder 13 is provided on the front surface of the negative pressure booster 12. A first reservoir 14 is integrally provided on the upper portion of the master cylinder 13, and the first reservoir 14 is connected to a second reservoir 15 disposed on the front upper side via a hose 16.

  Since the axis L of the master cylinder 13 is arranged to rise forward by an angle θ1 with respect to the horizontal line H, and the reservoir is divided into the first and second reservoirs 14 and 15, the negative pressure booster 12 in the narrow engine room, the master The layout of the cylinder 13 and the first and second reservoirs 14 and 15 is facilitated.

  Thus, when the driver steps on a brake pedal (not shown), the push rod 17 of the negative pressure booster 12 is pushed forward by the depression force, and the master cylinder 13 is operated by the depression force boosted by the negative pressure booster 12. Thus, the brake hydraulic pressure can be output from the first and second output ports 18 and 19 to a wheel cylinder (not shown).

  As shown in FIG. 2, the master cylinder 13 includes a cylinder body 21 formed in a bottomed cylindrical shape whose front end is closed, and a primary piston 22 and a secondary piston 23 are provided at the front portion and the rear portion of the cylinder body 21, respectively. The first hydraulic pressure chamber 24 is defined on the front side of the primary piston 22, and the second hydraulic pressure chamber 25 is defined between the primary piston 22 and the secondary piston 23.

  A front first cup seal 26 and a rear second cup seal 27 provided on the inner peripheral surface of the cylinder body 21 are in sliding contact with the outer peripheral surface of the primary piston 22, and the first and second cup seals 26, 27, a first input port 28 communicating with the first reservoir 14 is formed. When the primary piston 22 is at the most retracted initial position, openings 22a... Are formed in the primary piston 22 so as to be located immediately after the first cup seal 26.

  A first return spring 31 that urges the primary piston 22 backward between a spring seat 29 disposed on the bottom wall 21 a of the cylinder body 21 and a spring seat 30 disposed in a recess 22 b formed on the front surface of the primary piston 22. Is reduced. The front and rear spring seats 29 and 30 are connected by a connecting pin 32 slidable with respect to them in order to restrict the backward limit while allowing the primary piston 22 to move forward.

  A front third cup seal 33 and a rear fourth cup seal 34 provided on the inner peripheral surface of the cylinder body 21 are in sliding contact with the outer peripheral surface of the secondary piston 23, and the third and fourth cup seals 33, A second input port 35 communicating with the first reservoir 14 is formed between 34. When the secondary piston 23 is at the most retracted initial position, openings 23a are formed in the secondary piston 23 so as to be located immediately after the third cup seal 33.

A step portion 22d is formed at an intermediate position in the front-rear direction of the concave portion 22c formed on the rear surface of the primary piston 22, and a spring seat 36 supported by the step portion 22d and a concave portion 23b formed on the front surface of the secondary piston 23 are disposed. Between the spring seat 37, a second return spring 38 that biases the secondary piston 23 backward with respect to the primary piston 22 is contracted. The front end of the connecting pin 39 that slidably penetrates the rear spring seat 37 is screwed into the front spring seat 36 in order to restrict the backward limit while allowing the secondary piston 23 to advance.

  The first cup seal 26, the third cup seal 33, and the fourth cup seal 34 are disposed forward, and the second cup seal 27 is disposed rearward.

  Accordingly, the brake fluid pressure can be generated in the first fluid pressure chamber 24 by the first cup seal 26, and the brake fluid pressure can be generated in the second fluid pressure chamber 25 by the second and third cup seals 27, 33. In addition, the fourth cup seal 34 can prevent leakage of brake fluid from the cylinder body 21.

  Thus, when the driver steps on the brake pedal, the secondary piston 23 is pushed forward by the push rod 17 that is operated by the negative pressure booster 12, and the second hydraulic pressure is instantaneously passed through the third cup seal 33 by the opening 23 a. The brake fluid pressure generated in the chamber 25 is transmitted to the wheel cylinder via the second output port 19. Also, the brake pressure generated in the first hydraulic pressure chamber 24 at the moment when the primary piston 22 is pushed forward by the brake hydraulic pressure generated in the second hydraulic pressure chamber 25 and the opening 22a... Passes through the first cup seal 26. Is transmitted to the wheel cylinder via the first output port 18.

  When the driver returns the brake pedal, the primary piston 22 is retracted by the first return spring 31 and the secondary piston 23 is retracted by the second return spring 38. At this time, the retreat limit of the primary piston 22 with respect to the cylinder body 21 is regulated by the front and rear spring seats 29 and 30 and the connecting pin 32, and the retreat limit of the secondary piston 23 with respect to the primary piston 22, that is, the secondary piston 23 with respect to the cylinder body 21. The backward limit is regulated by the front and rear spring seats 36 and 37 and the connecting pin 39.

  The inner peripheral surface of the concave portion 22c on the rear surface of the primary piston 22 is formed in a partial conical shape that expands rearward, and the upper portion of the inner peripheral surface of the concave portion 22c rises rearward by an angle θ2 with respect to the horizontal line H. It has become. Accordingly, the bubbles generated in the second hydraulic pressure chamber 25 are discharged outside the recess 22c without accumulating in the recess 22c, and eventually pass through the second output port 19 to the outside from the air bleeding bleeder provided in the brake caliper. Discharged. Thereby, when the 2nd hydraulic pressure chamber 25 which the said recessed part 22c faces generate | occur | produces a brake hydraulic pressure, it can prevent that a bubble is compressed and a pedal stroke becomes long or a brake hydraulic pressure reduces.

  Further, the second return spring 38 has a rear end in contact with the rear spring seat 37 having a maximum diameter and a front end in contact with the front spring seat 36 having a minimum diameter. The diameter is reduced. If the second return spring 38 has the same diameter over its entire length, the diameter of the portion that abuts the front spring seat 36 increases, so the upper part of the inner peripheral surface of the recess 22c becomes the horizontal line H. There is a possibility that the angle θ2 formed with respect to the rear side cannot be raised rearward. However, the diameter of the portion contacting the front spring seat 36 is reduced by reducing the diameter of the second return spring 38 forward, and the inner circumference of the recess 22c is reduced. The angle θ2 formed by the upper part of the surface with respect to the horizontal line H can be reliably raised rearward.

  In addition, since the diameter of the second return spring 38 changes in the direction of the axis L, the wires of the second return spring 38 are less likely to come into contact with each other at the time of compressive deformation, and the compressible amount is reduced. Can be increased.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design settings can be made without departing from the present invention described in the claims. Is possible.

  For example, the second return spring 38 does not need to be reduced in diameter toward the front as a whole, and only the portion located inside the recess 22c on the rear surface of the primary piston 22 may be reduced toward the front. good.

The figure which shows the negative pressure booster and master cylinder of the brake device for vehicles Enlarged sectional view of the master cylinder

21 Cylinder body 22 Primary piston 22c Recess
22d step 23 secondary piston
36 Spring seat 38 Second return spring (return spring)
L Axis line H Horizontal line

Claims (1)

A primary piston (22) and a secondary piston (23) are slidably fitted to a cylinder body (21) having an axial line (L) arranged to rise forward, and a recess formed on the rear surface of the primary piston (22) ( 22c) and a tandem master cylinder in which a return spring (38) made of a coil spring is disposed between the secondary piston (23) and the front surface thereof.
A step portion (22d) that engages with a spring seat (36) for supporting the front end side of the return spring (38) is formed on the inner peripheral surface of the recess (22c). The diameter of the peripheral surface is increased from the outer periphery of the stepped portion (22d) toward the rear, and the outer diameter of the return spring (38) is reduced toward the front , whereby the inner peripheral surface of the recess (22c). A tandem master cylinder characterized in that the inclination of the upper part of the cylinder is raised rearward from the horizontal line (H) .

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