JPS637981B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tandem master cylinder device for a vehicle brake.

[Prior Art] When the brakes are applied while a vehicle is running, the load moves forward, and the frictional engagement force of the rear wheels with the road surface becomes extremely small. When the rear wheels lock, the vehicle loses lateral stability, causing the rear of the vehicle to swing sideways and turn. In order to prevent the wheels from locking up, the relationship between the front wheel brake fluid pressure P _F and the rear wheel brake fluid pressure P _R must have characteristics expressed by ideal curves 70 and 71 in response to the braking force, as shown in Figure 1. This is desirable.

Techniques for obtaining the above-mentioned braking characteristics are disclosed, for example, in Japanese Patent Application Laid-Open No. 53-99172 and Japanese Patent Application Laid-Open No. 49-119069. The tandem master cylinder device disclosed in Japanese Patent Application Laid-Open No. 53-99172 includes an intermediate piston between a driving piston and a floating piston, and a stopper that protrudes from the cylinder body into an annular groove provided on the outer circumferential side of the intermediate piston. The return position of the floating piston is regulated, and the forward movement of the intermediate piston is regulated during braking, and the pressure in the intermediate fluid chamber is maintained constant by the hydraulic pressure control valve. but,
The hollow shaft extending from the hydraulic control valve to the liquid chamber is supported through the intermediate piston, so if the hollow shaft is not held in the axial position when the intermediate piston is assembled into the cylinder body, the stopper will fit into the cylinder body. I can't. If the hollow shaft is fitted into the intermediate piston and then assembled, assembly becomes even more difficult and time-consuming.

Further, in the tandem master cylinder device disclosed in Japanese Patent Application Laid-open No. 49-119069, a stepped piston that is pushed by the hydraulic pressure of the front wheel brake fluid chamber is housed inside the floating piston, and the end of the stepped piston is The passage connecting the fluid tank and the rear wheel brake fluid chamber is closed by the valve body provided in the rear wheel brake fluid chamber. Therefore, in order to close the passage with the valve body and lock the operation of the floating piston, the outer diameter of the end of the floating piston on the front brake fluid chamber side is large, and the outer diameter of the end of the floating piston on the rear brake fluid chamber side is large. It is necessary to use a stepped piston with a small outer diameter, and the cylinder body must also be a stepped cylinder, and both ends of the cylinder body must be opened for convenience in assembling the floating piston. Furthermore, it is no longer possible to use the same cylinder body as the conventional cylinder body, and accurate concentricity is required for machining the stepped cylinder, which also increases costs.

Therefore, the present applicant previously proposed a floating piston fitted into a general straight cylinder body with only one end open, according to Japanese Patent Application No. 52-48786 (see Japanese Patent Application Laid-open No. 53-134176). We are proposing a tandem master cylinder device with an integrated hydraulic control valve. In this application, the stepped piston is fitted into a stepped cylinder formed inside the floating piston, and the movement of the stepped piston causes the stepped piston to form a valve body on the stepped piston side with respect to an immovable valve body supported by the floating piston. When the valve seat moves and opens and closes, and the brake fluid pressure exceeds a predetermined value, the fluid pressure to the rear wheel brake is reduced. However, due to the relationship with the direction of movement of the stepped piston, the valve body is supported so as to pass through the valve seat passage of the stepped piston, and is pressed against the end wall of the stepped cylinder by a spring to prevent it from coming off the stepped piston. Since the valve body is held in a closed state, the shape of the valve body is complicated and it takes time to assemble it, making it difficult to automate the assembly and affecting the cost.

[Problems to be Solved by the Invention] The purpose of the present invention is to provide a structure in which a hydraulic pressure control valve is incorporated into a floating piston fitted into a straight cylinder body with one end open, which has a simple configuration and a small number of parts. An object of the present invention is to provide a tandem master cylinder device whose parts can be easily machined and assembled.

[Means for Solving the Problem] In order to achieve the above object, the configuration of the present invention includes a first cylinder that fits into the cylinder body and is connected to the front wheel brake.
A drive piston that partitions a liquid chamber, a floating piston that partitions a second liquid chamber, a large-diameter cylinder that is coaxially arranged inside the floating piston and that is connected to the rear wheel brake at its end, and a compression spring that accommodates the drive piston and the second liquid chamber. A stepped cylinder consisting of a small diameter cylinder connected to two liquid chambers, a stepped piston that fits into the stepped cylinder and has an internal passage that communicates both end chambers with each other, and a stepped piston that is fitted and fixed to the end chamber of the large diameter cylinder. The valve body includes an annular valve seat and a valve body formed as a flange on a stem extending from a stepped piston and abutted against the valve seat by movement of the stepped piston against the compression spring.

[Function] Hydraulic pressure control valve A provided inside the floating piston
is equipped with a stepped piston 12 that has a different area for receiving the hydraulic pressure in the first (for front wheel brake) liquid chamber and an area for receiving the liquid pressure in the second liquid chamber, and The passage extending through the interior of the piston 12 to the rear brake is constricted by the movement of the stepped piston 12, and the hydraulic pressure of the rear brake is reduced.

The valve body 90 constituting the hydraulic control valve is connected to the piston 1
Since the stepped piston 12a is integrally formed as a flange on the stepped piston 12, the number of parts is reduced and machining can be performed together with the stepped piston 12. On the other hand, an annular valve seat 80 of the hydraulic pressure control valve is fitted and fixed to a large diameter cylinder 81 of the stepped cylinder. Therefore, the valve seat 80 and the valve body 90 as a hydraulic pressure control valve for the floating piston are neatly assembled into the stepped cylinder of the floating piston 12 from this side.

[Embodiments of the Invention] As shown in FIG. 2, the tandem master cylinder device according to the present invention includes a liquid tank 55, a cylinder body 32, a driving piston 50, and a floating piston 43.
, a stepped cylinder disposed inside the floating piston 43, and a hydraulic pressure control valve A integrated with the stepped piston 12.

The liquid tank 55 is provided with pipes 22 and 26 that protrude from the bottom and supply brake fluid to a pair of liquid chambers in the cylinder body 32. One end of the cylinder body 32 is closed by an end wall 42, and at the open end, a flange 35 integral with the cylinder body 32 is fixed to the vehicle body side with bolts. A floating piston 43 and a driving piston 50 are fitted inside the cylinder body 32, and a return spring 41 is inserted between the end wall 42 and the floating piston 43.
A return spring 38 is interposed between each of them. The drive piston 50 is stopped by a retaining ring 36 that engages the open end of the cylinder body 32. The floating piston 43 creates a second liquid chamber 57 and a first liquid chamber 5.
8 will be divided.

A liquid chamber C communicating with the second liquid chamber 57 via the inlet passage 23 is formed on the upper circumferential wall of the cylinder body 32, and the pipe 22 of the liquid tank 55 described above is connected to this liquid chamber C via an elastic seal ring 24. be done. Similarly, a liquid chamber D communicating with the first liquid chamber 58 is formed in the upper circumferential wall of the cylinder body 32, and the pipe 26 of the liquid tank 55 is connected to this liquid chamber D via an elastic seal ring 29.

A stepped sleeve 28 coupled to a valve seat 31 is fitted inside the cylindrical liquid chamber D, and a retaining ring 27 is fitted inside the cylindrical liquid chamber D.
is held by A conical valve body 52 is brought into contact with the valve seat 31 by a spring 53 . However, normally it projects from the liquid chamber D to the liquid chamber 58. Valve body 52
leg is tilted by the floating piston 43 to open the inlet passage 30.

A rod 48 is provided at one end of the drive piston 50 to restrict the extension of the return spring 38, and seal rings 33, 37 are fitted to the outer periphery of the piston 50 to ensure fluid tightness of the sliding portion with the cylinder body 32.

The floating piston 43 has a seal ring 63 in the center.
, a pair of seal rings 18 and 19 on the right end,
A cup-shaped seal ring 67 is fitted to the left end of each. Seal ring 67 is held by spring seat 39. A pair of wide annular grooves 61 and 65 are provided on the outer periphery of the floating piston 43, and the annular groove 61 is constantly communicated with the liquid chamber C through the passage 25, and is connected to the gap on the back side of the seal ring 67 through the passage 68. communicated.

The annular groove 65 communicates with the rear brake through the outlet passage 14, and the first fluid chamber 58 communicates with the front brake through the outlet passage 20.

According to the invention, a hydraulic pressure control valve A is provided inside the floating piston 43. As shown in FIGS. 3 and 4 (FIG. 4 is a schematic diagram), the floating piston 43 has a cylinder 87 whose inner diameter gradually decreases from the base end (right end).
88 , 81 , and 85 are provided, the left end portion of the cylinder 81 is communicated with the annular groove 61 through the passage 83 , and the cylinder 85 is communicated with the second liquid chamber 57 through the passage 40 .

The closing body 86 is press-fitted into the cylinder 88 via the seal ring 77. The stepped piston 12 is fitted into a stepped cylinder consisting of cylinders 81 and 85, and the cylinder 85 has an end chamber 85a.
An end chamber 81a is defined (FIG. 4).

A valve body 90 is configured as a flange on a stem 12a protruding from the right end portion of the stepped piston 12.
The stem 12a is fitted into the cylinder 76 of the closure body 86 and is moved by the spring 62 housed in the end chamber 85a.
It is biased against the end wall of the cylinder 76.

The right end flange of the closing body 86 is fitted into the cylinder 87 together with the spring seat 47, and is fixed to the floating piston 43 by the retaining ring 46. The closing body 86 is provided with the cylinder 76 and a cylinder 89 having a larger diameter than the cylinder 76. The cylinder 76 is communicated with the first liquid chamber 58 through the passage 45 . The cylinder 89 communicates with the annular groove 65 via radial passages 75 and 64. An annular valve seat 80 made of an elastic material is supported at the left end of the closing body 86 . It is preferable that the valve seat 80 is held between a step between the cylinders 81 and 88 by a closing body 86 .

The stepped piston 12 has a seal ring 84 on the left end side.
The stem 12a has a small diameter portion that fits into the cylinder 85 through the cylinder 85 and a large diameter portion that fits into the cylinder 81 through the seal ring 82, while the stem 12a fits into the cylinder 76 through the seal ring 78 on the right end side.
It is equipped with A passage 74 crossing the central portion of the stepped piston 12 opens into the end chamber 81a, and further communicates with the end chamber 85a via an axial passage 73.

An annular valve body 90 that can abut against the valve seat 80 is provided on the stem 12a, and the spring 62 of the stepped piston 12
Due to the movement against the force of
a, passages 75, 64, annular groove 65, outlet passage 14
The path leading to the rear brake is opened and closed.

Next, the operation of the tandem master cylinder device according to the present invention will be explained. When the drive piston 50 is pushed to the left in FIG. 2 during braking, the floating piston 43, which is regulated by the return springs 41 and 38, also moves to the left. Valve body 52
becomes an upright position under the force of the spring 53, and when the inlet passage 30 is closed, the liquid in the first liquid chamber 58 flows into the outlet passage 20 as the driving piston 50 moves to the left.
from there to the front brakes. At the same time, when the floating piston 43 moves to the left and passes through the inlet passage 23, the liquid in the second liquid chamber 57 flows into the passage 40 and into the end chamber 85.
a, passages 73, 74, end chamber 81a, passages 75, 64 through the gap between valve seat 80 and valve body 90, annular groove 6
5. Pressurized from the outlet passage 14 to the rear wheel brakes.

To simplify the explanation, it is assumed that the cross-sectional area of the small diameter portion of the stepped piston 12 and the cross-sectional area of the stem 12a are equal. The fluid pressures in the first fluid chamber 58 and the second fluid chamber 57 are always equal, and when the braking force is weak, the second fluid chamber 58
7 is equal to the hydraulic pressure sent from this liquid chamber 57 to the rear wheel brake via the hydraulic pressure control valve A. However, if the brake fluid pressure exceeds a predetermined value (Pc in Figure 5),
The hydraulic pressure acting on the right end surface of the stepped piston 12 from the end chamber 81a becomes greater than the force of the spring 62, and the stepped piston 12 moves to the left. At this time, the valve body 90 approaches the valve seat 80 and the passage is narrowed, so
The fluid pressure applied to the rear brake from the second fluid chamber 57 is reduced as shown by line 17 in FIG.

When the brake is released, the floating piston 43 is returned by the force of the return spring 41, and the driving piston 50 is returned by the force of the return spring 38, resulting in the state shown in FIG. The legs of the valve body 52 are tilted by the floating piston 43 to open the inlet passage 30.

In the present invention, the hydraulic control valve A consisting of the valve seat 80 and the valve body 90 has the valve body 90 integrally formed as a flange on the stem 12a of the stepped piston 12, so the number of parts is reduced and the machining process is also stepped. Since it can be processed integrally with the attached piston 12, it is useful for reducing costs. Furthermore, the valve body 80 made of a relatively soft material such as rubber is easily assembled because it fits into the large diameter cylinder 81 and is fixed with an adhesive or the like.

[Effects of the Invention] As described above, the present invention provides a tandem master cylinder device that includes a driving piston that fits into the cylinder body and defines a first fluid chamber connected to a front wheel brake, and a floating piston that defines a second fluid chamber. , a stepped cylinder consisting of a large-diameter cylinder coaxially arranged inside the floating piston and connected to the rear wheel brake at its end, and a small-diameter cylinder that accommodates a compression spring and connected to the second liquid chamber; A stepped piston having an internal passage that fits and communicates both end chambers with each other, an annular valve seat that is fitted and fixed in the end chamber of the large diameter cylinder, and a stem extending from the stepped piston that is formed as a flange. Since the stepped piston is brought into contact with the valve seat by movement of the stepped piston against the compression spring, when the liquid pressure in the second liquid chamber becomes higher than a predetermined value, the stepped piston is moved by the force of the spring. The engine moves backward, narrowing the passage connecting the second fluid chamber and the rear brake fluid chamber, and reducing the fluid pressure to the rear brake. As a result, hydraulic pressure corresponding to changes in the load on the vehicle body during braking is distributed between the front and rear brakes, ensuring maximum braking performance is achieved safely.

According to the present invention, the following effects can be obtained compared to the conventional example.

(a) Since the hydraulic control valve is completely assembled inside the floating piston, it is only necessary to fit it into the cylinder body, and there is no need to assemble a special stopper, so assembly is very easy. be.

(b) The cylinder body may be a general straight type, with no changes in external dimensions, etc., and does not affect assembly to the vehicle body or piping.

(c) Fit the spring, stepped piston, and valve seat to the stepped cylinder of the floating piston from one side, fit and fix the closing body, and fit the stem of the stepped piston to the cylinder of the closing body. Because it is a hydraulic control valve, the number of parts such as springs is small, assembly is easy, and the hydraulic control valve operates reliably and provides stable performance.

(d) Since the annular valve seat and valve body are arranged in the large diameter cylinder of the stepped cylinder, its size and shape can be increased, and accidents such as clogging due to foreign matter mixed in the brake fluid can be avoided. .

The hydraulic control valve according to the present invention is different from that of Japanese Patent Application No. 52-48786 (see Japanese Unexamined Patent Publication No. 134176/1988), which is the applicant's earlier application. It is pressed against the floating piston side (the end wall of the large diameter cylinder) by a spring, but this valve body is divided into a part that abuts against the valve seat of the assembled upper piston and a part that is pressed against the floating piston side. The configuration is complex and requires a lot of effort to assemble. Multiply.

Compared to this, in the present invention, the structure of the valve body itself is formed integrally with the stepped piston, so there is no need to provide the stepped piston with a spring that presses the valve body against the floating piston or a slit that guides the valve body. , the number of parts and processing man-hours are reduced, and assembly work becomes easier.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of the hydraulic pressure distribution required for front wheel brakes and rear wheel brakes as a tandem master cylinder device, Fig. 2 is a longitudinal sectional view of the tandem master cylinder device according to the present invention, and Fig. 3 is a FIG. 4 is an enlarged schematic diagram of the essential parts of the device, and FIG. 5 is an operating characteristic diagram of the device. 12: stepped piston, 14, 20: outlet passage,
23, 30: inlet passage, 80: valve seat, 32: cylinder body, 38, 41: return spring, 43: floating piston, 50: drive piston, 57: second liquid chamber,
58: first liquid chamber, 90: valve body.

Claims (1)

[Claims] 1 A driving piston that fits into the cylinder body and defines a first fluid chamber connected to the front wheel brake, a floating piston that defines a second fluid chamber, and a floating piston that is disposed coaxially inside the floating piston and that connects the rear wheel at the end. It accommodates a large diameter cylinder connected to the brake and a compression spring, and a second
A stepped cylinder consisting of a small diameter cylinder connected to a liquid chamber, a stepped piston that fits into the stepped cylinder and has an internal passage that communicates both end chambers with each other, and an annular shaped cylinder that is fitted and fixed to the end chamber of the large diameter cylinder. The valve seat and
A tandem master cylinder device comprising: a valve body formed as a flange on a stem extending from a stepped piston and brought into contact with the valve seat by movement of the stepped piston against the compression spring.