JPS61257352A - Brake liquid pressure control device - Google Patents

Abstract

PURPOSE:To approach an ideal brake force distributing characteristic with which the brake force of rear wheels lowers as the brake force of front wheels rises, by disposing a pressure reducing means in a brake hydraulic pipe line connecting between a brake hydraulic pressure control valve and a rear wheel cylinder. CONSTITUTION:A brake hydraulic pressure control valve 4 is disposed in a rear side brake hydraulic pipe line 3 connecting between a master cylinder 1 and rear wheel cylinders 2. A pressure reducing means 5 is disposed a control hydraulic pipe line 3' between the above-mentioned hydraulic pressure control valve 4 and the rear wheel cylinders 2. This pressure reducing means 5 lowers the rear hydraulic brake pressure as the pressure of the master cylinder rises when the master cylinder pressure exceeds a predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a brake fluid pressure control device, and particularly to a device that prevents rear wheels from locking first during braking.

(Prior Art) As a conventional brake fluid pressure control device, a device using a load-responsive hydraulic pressure control valve is known, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-164463.

This conventional hydraulic control valve is called a load sensing valve that moves the valve operation start point (split point) according to the weight of the vehicle.

In addition, in this load sensing valve, when a certain braking deceleration is exceeded, the G pole inside the valve moves to seal off the master cylinder hydraulic pressure, and the valve operation start point is set according to this sealed hydraulic pressure. 2 in Figure 6
As shown by the brake fluid pressure distribution characteristic H shown by the dotted chain line, after the valve operation start point p, the brake fluid pressure distribution characteristic exhibits a hydraulic pressure distribution characteristic in which the increase ratio of the rear brake hydraulic pressure Pr to the master cylinder hydraulic pressure Pm is suppressed.

(Problems to be Solved by the Invention) However, in such a conventional brake fluid pressure control device, although it is possible to suppress the rate of increase in the rear brake fluid pressure Pr, it is still possible to suppress the increase in the master cylinder fluid pressure Pm. Therefore, when applied to a vehicle with a large front load that has the ideal braking force distribution characteristic I as shown by the broken line in Fig. 6, the master cylinder hydraulic pressure Pm increases accordingly. In the high pressure region of (front braking force), there is a large difference between the ideal braking force distribution characteristic and the brake fluid pressure distribution characteristic H, and the rear brake fluid pressure P
There was a problem in that r became too high, leading to rear locking during braking.

As a brake fluid pressure control valve, in addition to the conventional example described above, there is a limit valve that does not increase the rear brake fluid pressure Pr after the master cylinder fluid pressure Pm exceeds a certain pressure (No. 6). The brake fluid pressure distribution characteristic J is shown by the dashed line in the figure).

However, even if this limit valve was applied, there still existed a difference from the ideal braking force distribution characteristic I, which led to rear locking during braking.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and to achieve this purpose, the present invention employs the following solving means.

The solution of the present invention will be explained with reference to the conceptual diagram of the claim shown in FIG. 1. In a brake fluid pressure control device equipped with a brake fluid pressure control valve 4 that controls rear brake fluid pressure Pr to .2, a control fluid pressure pipe that connects the brake fluid pressure control valve 4 and the rear wheel cylinder 2.2. A pressure reducing means 5 is provided at 3' to reduce the rear brake hydraulic pressure Pr in response to an increase in the master cylinder hydraulic pressure Pm.

(Function) Therefore, in the brake fluid pressure control device of the present invention, as described above, the master cylinder fluid is connected to the control fluid pressure pipe 3' that connects the brake fluid pressure control valve 4 and the rear wheel cylinders 2, 2. By providing the pressure reducing means 5 that lowers the rear brake fluid pressure Pr in response to an increase in the pressure Pm, the brake fluid pressure characteristics obtained by the device of the present invention can be adjusted to reduce the front braking force when the front braking force exceeds a predetermined braking force. It is possible to approach the ideal braking force distribution characteristic in which the rear braking force decreases as the vehicle rises.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing this embodiment, an example will be taken of an apparatus using a load sensing valve as the brake fluid pressure control valve and a pressure reducing valve as the pressure reducing means.

First, the configuration of the embodiment will be explained.

The brake fluid pressure control device A shown in FIG. 2 includes a brake pedal 10, a booster 11, a tandem master cylinder 12,
It is equipped with a front brake fluid pressure pipe 13, a rear brake fluid pressure pipe 14, front wheel cylinders 15, 18, rear wheel cylinders 17, 18, a load sensing valve 19, and a pressure reducing valve 20. Details of each configuration are as follows. state

The brake pedal 10 is connected to a valve operating rod of a booster 11, and the force applied to the brake pedal 10 is increased by the booster 11.

The booster 11 increases the pressing force from the brake pedal 10 and applies the increased force to the primary piston and secondary piston (not shown) of the tandem master cylinder 12 by means of a bushing rod.

The tandem master cylinder 12 converts the brake pedal force from the booster 11 into brake fluid pressure. Inside the tandem master cylinder 12, there are two independent fluid pressure generating chambers corresponding to the primary piston and the secondary piston. It is formed.

The front side brake hydraulic piping 13 is a piping that supplies brake hydraulic pressure from the first hydraulic port 21 of the tandem master cylinder 12 to the front wheel cylinders 15 and 16 of the left and right front wheels.

The rear brake hydraulic piping 14 is a piping that supplies the brake hydraulic pressure from the second hydraulic boat 22 of the tandem master cylinder 12 to the rear wheel cylinders 17 and 18 of the left and right rear wheels. control hydraulic piping) 142.

The front wheel cylinders 15, 16 and rear wheel cylinders 17, 18 actuate a brake device such as a drum brake or a disc brake, and the braking force is proportional to the magnitude of brake fluid pressure.

The load sensing valve 19 is installed in the middle of the rear brake fluid pressure pipe 14, and is a valve that takes advantage of the fact that the brake fluid pressure required to obtain a constant braking deceleration changes depending on the weight of the vehicle. , master cylinder hydraulic pressure Pm
However, when the valve starts operating, this load sensing valve 19 includes a valve body 23, an inlet hydraulic boat 24, an outlet hydraulic boat 25, a plunger 26, a poppet valve 27, a set spring 28, 29, 30, an actuating piston 31. M hydraulic pressure chamber 32, G pole 33. A pole seat 34 is provided.

The valve body 23 is arranged with respect to the longitudinal horizontal axis of the vehicle.
It can be installed in a tilted position with the rear side of the vehicle lowered.

The inlet hydraulic boat 24 is connected to the tandem master cylinder 1
Master cylinder hydraulic pressure Pm from the second hydraulic boat 22 of 2
is input, and when the hydraulic pressure is below the valve operation start point p, the poppet valve 27 is in an open state, and the master cylinder hydraulic pressure Pm is changed from the inlet hydraulic boat 24 to the communication path 35.
→It passes through the outlet hydraulic boat 25 and is directly supplied to the wheel cylinders 17, 18.

The plunger 26 is slidably provided on the valve body 23, and the plunger 26 has a large diameter (cross-sectional area Bl) on the outlet hydraulic boat 25 side and a small diameter on the set spring 2B, 29.30 side. (cross-sectional area B2).

The poppet valve 27 is disposed in a communication passage 35 formed in the plunger 26 and is a normally closed valve, and the valve is closed when the plunger 26 moves to the left in the drawing.

The set springs 28, 29, and 30 are springs for setting the valve operation starting point p, and one end side is supported by the seven-stroke piston 31, so that the containment hydraulic pressure Ps of the containment hydraulic pressure chamber 32 is controlled. Accordingly, the spring force SF applied to the plunger 26 becomes variable.

The G-pole 33 is provided in a brake hydraulic pressure chamber 36 communicating with the inlet hydraulic boat 24 so as to be able to move back and forth, and at the time of predetermined braking deceleration, the G-pole 33 is moved by the inertial force. to move forward and close the pole seat 34.

Note that this closing serves as the master cylinder Ps at the time of closing.

The pressure reducing valve 20 includes the load sensing valve 1
9 and the rear wheel cylinders 17 and 18, and when the valve opening point O of this pressure reducing valve 20 is reached, the subsequent rear brake fluid pressure Pr is applied.

This pressure reducing valve 20 includes a valve body 40, a piston 4
1. It includes a set spring 42, a poppet valve 43, a rear brake hydraulic pressure chamber 44, a valve chamber 45, a master cylinder hydraulic pressure chamber 46, a reservoir chamber 47, a reservoir piston 48, a reservoir spring 49, and a return valve 50.

The piston 41 is slidably arranged inside the valve body 40, and includes a large diameter piston portion 411 (cross-sectional area Cs), a small-diameter piston portion 412 (cross-sectional area C2), and a connecting portion 413 (cross-sectional area Cs). C3), and has a large diameter piston part 41
1 is biased toward the left in the drawing by a set spring 42, and movement of the small-diameter piston is restricted.

The poppet valve 43 is disposed in a communication passage 52 within the piston 41 that communicates the rear brake fluid chamber 44 and the valve chamber 45, and is a normally closed valve that allows the piston 41 to move to the right in the drawing. This opens the valve.

The rear brake hydraulic pressure chamber 44 is connected to the brake pipe 142.
A branch brake pipe 143 branched from is connected,
A set spring 42 is disposed in this rear brake hydraulic pressure chamber 44, which is a chamber into which rear brake hydraulic pressure Pr is input.

The valve chamber 45 is a chamber formed between the large diameter piston part 411 and the small diameter piston part 412.
5 is provided with a reservoir chamber 47 in communication with it.

The master cylinder hydraulic chamber 46 is connected to the brake pipe 14
The small diameter piston portion 412 is always pushed rightward in the drawing by the master cylinder hydraulic pressure Pm in the chamber to which the branch brake pipe 144 branched from the master cylinder hydraulic pressure Pm is connected.

The reservoir chamber 47 is provided with a reservoir piston 48 urged by a reservoir spring 49, and is a chamber that expands the volume Q of the valve chamber 45 until the reservoir piston 48 is fully stroked.

The return valve 50 is connected to a branch brake pipe 145.
and the valve chamber 45, and is provided between the piston 4 and the valve chamber 45.
This is a one-way valve for returning surplus brake fluid in the valve chamber 45 to the brake pipe 141 when the brake piston 1 and the reservoir piston 48 return to their original positions.

Next, the operation of the embodiment will be explained.

(a) Up to the valve opening point 0 Until the valve opening point 0, the pressure reducing valve 20 is in a closed state, so it does not take any part in controlling the rear brake fluid pressure Pr, and the pressure is adjusted based on the function of the load sensing valve 19. Pressure control is performed.

In other words, the master cylinder hydraulic pressure Pm remains unchanged until the valve operation start point p of the load sensing valve 19 becomes the brake hydraulic pressure Pr, and once the valve operation start point p is exceeded, the valve is repeatedly opened and closed due to the balance of the forces applied to the plunger 26. As a result, the rate of increase in rear brake fluid pressure Pr is reduced at a constant rate.

As shown in Fig. 5, the brake fluid pressure distribution characteristics up to the valve opening point O are as follows: Looking at the light load characteristic K, the valve operation start point p1 is the low pressure position characteristic, and the constant load characteristic is the characteristic K. , the valve operation start point p2 has a characteristic at a high pressure position, and exhibits a characteristic that approximates the respective ideal braking force distribution characteristics M and N.

(b) The force applied to the piston 41 of the pressure reducing valve 20 in the valve closed state from the valve opening point 0 to the pressure reduction limit boiling is the force in the right direction in the drawing (2XPm Force in the left direction in the drawing F+ +Ct ・Pr(Fl;
If the force in the right direction in the drawing overcomes the force in the left direction in the drawing, the piston 41 moves to the right and the valve becomes open.

In other words, the master cylinder hydraulic pressure P at the valve opening point 0
m is the hydraulic pressure when the forces in the left and right directions in the drawing are equal, and Pm1 = (Ft + Ct - Pr)/C2.

When the valve opening point 0 is exceeded, the brake fluid sealed in the brake pipe 142, rear wheel cylinder 17, 18, branch brake pipe 143, and rear brake fluid pressure chamber 44 passes through the communication passage 52 and enters the valve chamber. 45
The rear brake fluid pressure Pr gradually decreases due to the expansion of the brake fluid filling volume (Fig. 3).

The force applied to the piston 41 at this time is a force in the right direction in the drawing C2XPm+ (C-C2)Pv A force in the left-right direction in the drawing
F1+C1-Pr (Pv; hydraulic pressure in the valve chamber 45), and the force relationship is such that the force toward the right in the drawing is greater, and the difference in force gradually increases to move the piston 41 toward the right.

Next, as the hydraulic pressure Pv in the valve chamber 45 increases, the reservoir piston 48 starts to stroke, and finally makes a full stroke while decreasing the rear brake hydraulic pressure Pr.

After this full stroke, the volume of the valve chamber 45 does not increase, so the hydraulic pressure Pv of the valve chamber 45 matches the rear brake hydraulic pressure Pr, and at this time the pressure reduction limit (master cylinder hydraulic pressure Pm2) is reached ( Figure 4).

Furthermore, as shown in Fig. 5, the brake fluid pressure distribution characteristics from the valve opening point O to the pressure reduction limit boiling point are as follows from the valve opening point Of, 02 when looking at the light load characteristic K and the constant volume characteristic. Decompression limit boiling l, up to 12, master cylinder hydraulic pressure Pm
The characteristic is that the rear brake fluid pressure Pr decreases regardless of the increase of This is shown in a region where the pressure Pm is high.

(c) When the pressure rises above the reduced pressure limit or above the reduced pressure limit, the valve remains open,
The brake fluid pressure sealed volume and fluid pressure do not change, and the rear brake fluid pressure Pr is controlled again according to the operation of the load sensing valve 19.

In addition, the brake fluid pressure distribution characteristics that exceed the decompression limit opinion are as follows:
As shown in the figure, the rear brake fluid pressure Pr increases at the same rate as the fluid pressure increase ratio after the valve operation start point P1+p2, and the light load characteristic K is somewhat different from the ideal braking force distribution characteristic M. However, as for the constant volume characteristic, the deviation from the ideal braking force distribution characteristic N is corrected and the characteristic is approximated.

As described above, in the brake fluid pressure control device A of the embodiment, the characteristic of reducing the rear brake fluid pressure Pr with respect to the increase in the master cylinder fluid pressure Pm by the pressure reducing valve 20 is obtained after the predetermined master cylinder fluid pressure Pm1. This approximates the ideal braking force distribution characteristics M and N in which when the front braking force exceeds a predetermined braking force, as in a vehicle with a large front load, the rear braking force decreases as the front braking force increases. be able to.

In addition, in the example, if the reduced pressure limit boiling is exceeded.

Since the hydraulic pressure control characteristic by the load sensing valve 19 can be obtained again, it is possible to approximate the ideal braking force distribution characteristic N even in the constant volume characteristic.

And, as mentioned above, the brake fluid pressure characteristic K.

By making L approximate to the ideal braking force distribution characteristics M and H, it is possible to avoid a situation where the rear wheels lock first during braking.

Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention may be modified without departing from the gist of the present invention. included.

For example, in the embodiment, an example is shown in which a brake fluid pressure control valve, a brake fluid pressure control valve, and a load sensing valve are used, but other load sensing valves, provisioning valves, limit valves, etc. may be used.

Further, in the embodiment, an example is shown in which a pressure reducing valve is used as the pressure reducing means, but it is also possible to use a means for detecting rear brake fluid pressure and draining the rear brake fluid pressure by duty control or the like.

In addition, in the embodiment, the pressure reduction distribution area by the pressure reduction valve is limited to a predetermined range, and when the pressure reduction area is exceeded, the characteristics by the brake fluid pressure control valve are shown. However, the pressure reduction area is not necessarily limited, and moreover, the pressure reduction area It is also possible to allow multiple numbers to appear.

(Effects of the Invention) As explained above, in the brake fluid pressure control device of the present invention, the control pressure reducing pipe connecting the brake fluid pressure control valve and the rear wheel cylinder is provided with On the other hand, since the configuration is equipped with a pressure reducing means to reduce the rear brake fluid pressure, it is possible to prevent rear locking when braking in a vehicle that has ideal braking force distribution characteristics such that the rear braking force decreases as the front braking force increases. is obtained.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the claims showing the brake fluid pressure control device of the present invention, Fig. 2 is an overall view showing the brake fluid pressure control device of the embodiment, and Figs. 3 and 4 are the pressure reducing valve of the embodiment device. 5 is a brake fluid pressure distribution characteristic diagram of the embodiment device, and FIG. 6 is a brake fluid pressure distribution characteristic diagram of the conventional device. 1... Master cylinder 2... Rear wheel cylinder 3... Rear side brake fluid pressure piping 3'... Control fluid pressure piping 4... Brake fluid pressure control valve 5... Pressure reducing means Pm...・Master cylinder fluid pressure Pr...Rear brake fluid pressure

Claims (1)

[Claims] 1) A brake fluid pressure control valve provided in the middle of a rear brake fluid pressure pipe connecting a master cylinder and a rear wheel cylinder to control rear brake fluid pressure to the rear wheel cylinder. The brake fluid pressure control device is characterized in that the control fluid pressure piping connecting the brake fluid pressure control valve and the rear wheel cylinder is provided with a pressure reducing means for reducing rear brake fluid pressure in response to an increase in master cylinder fluid pressure. Brake fluid pressure control device.