JPS6044173B2 - Deceleration sensing proportioning valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deceleration-sensing proportioning valve that is interposed in hydraulic pressure transmission to a rear wheel brake system of a vehicle and is used to obtain a rear wheel brake force that approximates an ideal brake force distribution ratio between the front and rear wheels. It is something.

It is known that the front and rear wheel brake force distribution ratio during vehicle braking is not fixed, but changes in response to changes in the vehicle's carrying load. This means that it is desirable to properly brake a vehicle by maintaining a constant, suitable slip ratio between the wheels and the road surface.
When this slip rate increases, it causes wheel lock phenomenon. In other words, wheel lock occurs due to a decrease in the conformity between the wheels and the road surface, but this is greatly influenced by the weight of the vehicle that presses the wheels against the road surface. The load on the front wheels does not vary much due to the vehicle's own equipment, such as the engine, whereas the load on the rear wheels varies greatly depending on the amount of cargo loaded. This results in a change in the ideal brake power distribution ratio between the front and rear wheels. Conventionally, in consideration of this point, various mechanisms have been provided for reducing the brake oil pressure of the rear wheel brake system at a certain ratio with respect to the brake oil pressure of the front wheel brake system. For example, the proportioning valve uses a certain oil pressure value as the turning point, and when the brake oil pressure is lower than that, the master cylinder and the rear wheel brake system are directly connected, and the brake oil pressure is increased at a rate of 1/1.
If the brake oil pressure is higher than this, the oil pressure increase rate of the rear wheel brake device is made to gradually increase to TanO<1 with respect to the master cylinder, and the limiter valve increases the oil pressure of the rear wheel brake device at a constant oil pressure value. I'm trying to cut it.

However, since these control valves only reduce or cut the increase in rear wheel brake oil pressure using a fixed brake oil pressure value as a turning point, it is not possible to modify the front and rear brake power distribution ratio in accordance with the fluctuations in vehicle payload mentioned above. Furthermore, in consideration of this point, a load response mechanism has been added that takes into account that fluctuations in the vehicle load appear in the relative movement of the axle and the vehicle body, and the turning point oil pressure of the proportioning valve etc. can be varied. Although methods have been proposed to do so, they have drawbacks such as complicating the mechanism and increasing costs. Furthermore, a so-called G valve is provided which cuts off communication of the flow path not by constant oil pressure but by constant deceleration during braking of the vehicle.

This is because the brake force required to obtain a constant deceleration increases approximately in proportion to the increase in vehicle load, so there is a correlation between the load and the hydraulic cut point, but in reality the value of vehicle deceleration depends on the front wheel brake force. Since the degree of brake force distribution is large and the hydraulic pressure transmission is cut at a constant hydraulic pressure, the deviation from the ideal brake force distribution mentioned above becomes large. The present invention takes into consideration the various points mentioned above, and the G valve shows a correlation between the vehicle load and the oil pressure cut point within a certain range, and the proportioning valve changes the rear wheel brake oil pressure with the constant oil pressure as the turning point. This deceleration-sensing proportioning valve is capable of controlling braking force as closely as possible to the ideal brake force distribution curve, which shows a curve that varies depending on the amount of vehicle payload. We aim to provide the following. Specifically, the control piston, which has hydraulic pressure receiving surfaces with different areas, moves in the axial direction against the biasing spring due to hydraulic action, thereby blocking the communication path between the input oil chamber and the output oil chamber. In a proportioning valve that obtains a gradual increase in the oil pressure in the output oil chamber by balancing the hydraulic action in both directions of the shaft and the biasing spring, the corner oil pressure is determined by the hydraulic pressure acting on the area difference in both directions of the shaft and the spring force. By paying attention to the fact that it is determined by the value, this spring is used to control the corner oil pressure by utilizing the correlation between the vehicle load of the G valve and the oil pressure cut point. That is, G
The above-mentioned correlation of the valves was expanded by using a piston with a different area (stepped piston), and linked to the increase in the spring force of the proportioning valve. The present invention will be described below based on embodiments shown in the drawings.

In FIG. 1, 1 is a valve body, and 2, 2'' are stepped cylinders, which include a proportioning actuating mechanism 3 and a pressing force control mechanism 14 that changes the corner oil pressure of the mechanism and the spring load of a load spring 4. It is accommodated.

The proportioning operation mechanism 3 includes stepped cylinders 2, 2
The adjustment spring 5 is slidably fitted to be movable in the axial direction within the
adjusting pistons 6 and 7 (cylindrical first part 6, one end open cylindrical second part) of different diameters, which are biased toward the large diameter cylinder 2'' side and constitute one stepped piston; One end of the cylinder 6'' is formed to penetrate through the axial center of the small-diameter adjusting piston 6, and a compression-type load spring 4 is connected to the other large-diameter adjusting piston 7 in a water-tight manner. a control piston 8 with a tensioned control piston 8, and an annular valve seat 9 that is fixed to the stepped cylinder 2 and cooperates with the large-diameter flange portion 8'' at the tip of the control piston 8 to constitute an opening/closing valve portion of the flow path.
, the "large diameter flange portion 8" of the control piston 8 is located,
An output oil chamber 10 communicates with a wheel cylinder (not shown) of a rear wheel brake device, and is separated from the output oil chamber 10 by a valve portion constituted by a control piston 8 and a valve seat 9, and is connected to a master cylinder (not shown). The input oil chamber 11 is connected to the input oil chamber 11.

In addition, 12 is a piston cup, which ensures watertightness of the sliding surfaces of the control piston 8 and the adjustment piston 6.
13 is the same adjustment piston 6, 7 and stepped cylinder 2, 2''
This is an O-ring that ensures watertightness.

Next, the operation of the proportioning actuation mechanism 3 will be explained.

The cross-sectional area of the shaft of the control piston 8 is A1, the cross-sectional area of the large diameter flange 8'' is A2, and the initial pressing force of the load spring 4 (
If F1 is the initial load (initial load) and K1 is the spring constant, the control piston 8 is moved to the tip side (
The input/output oil chamber 10 is biased and locked in a predetermined position on the left side of the figure.
, 11 are opened, and the hydraulic pressure from the master cylinder is transmitted to the input oil chamber 11, the output oil chamber 10, and then to the rear wheel brake system.

Therefore, a hydraulic pressure Pi, O-A1 acts on the control piston 8 toward the rear end (to the right in the figure), and when this exceeds the initial load F1 of the load spring 4 as shown in the following equation, the control piston 8 moves as shown in the figure. Moving to the right, the large-diameter flange portion 8'' comes into contact with the valve seat 9, cutting off communication between the input oil chamber 11 and the output oil chamber 10.

Hydraulic pressure at this time (when communication is cut off) (However, S.

is the amount of contraction of the load spring 4 when the control piston 8 moves from the illustrated position until it abuts the valve seat 9), then below this oil pressure Pc, the input and output oil pressures are Pi = PO
Above this state, the valve part repeats opening and closing according to the balance between the hydraulic pressure acting on the control piston 8 and the pressing force of the load spring 4, and A2-Altanθ=
The output oil P with respect to the input oil chamber Pi with a slope of ~.

A gradual rise in the temperature is obtained. That is, the oil pressure P. is the corner oil pressure value. The pressing force adjustment mechanism 14 for the load spring 4 includes an adjustment oil chamber 15 provided in a stepped cylinder 2'' facing the closed rear end surface of a large-diameter adjustment piston 7 having a cylindrical shape with one end open, and a G valve mechanism 16. A small-diameter adjusting piston 6 and a large-diameter adjusting piston 7 are connected to the input oil chamber 11 through the piston, and the tip end face faces the input oil chamber 11, and the large-diameter adjusting piston 7 is provided so as to function as one stepped piston.

The configuration of the G valve mechanism 16 is the same as the known one,
Guided by a guide surface 17 that forms an elevation angle of θ with respect to the forward direction of the vehicle as shown by the arrow in the figure, the ball 19 abuts against the valve seat 18 at a constant deceleration GO during vehicle braking and moves through the flow path 20. It has a configuration that blocks it.

Further, the valve seat 18 is provided with a throttle portion 21 for regulating the speed of oil flowing into the regulating oil chamber 15. This is to delay the increase in vehicle deceleration due to the hydraulic pressure transmission speed, that is, to block the flow path 20 of the ball 19 at an appropriate hydraulic pressure. Next, the operation of the pressing force adjustment mechanism 14 for the load spring 4 will be explained.

For convenience of explanation, the hydraulic pressure receiving areas facing the input oil chamber 11 and the adjustment oil chamber 15 of one stepped piston consisting of the adjustment pistons 6 and 7 mentioned above are respectively referred to as A3-Al and A4 (A3-Ai), and for convenience of explanation, the adjustment spring 5 Assuming that the load is zero, the force acting on the stepped pistons 6 and 7 to the left in the figure when the G valve mechanism 16 opens the flow path 20 is as follows.

Here, when Pi,O(A4-A3+A1)≦F1, the stepped piston continues to stand still in the state shown. Since the stepped piston and the control piston 8 are in a sliding relationship, the initial load F1 of the load spring 4 is controlled by the hydraulic pressure (Pi
, O(A4-A3+A1)), the stepped piston moves to the left in the figure while bending the load spring 4.
Next, when the G valve mechanism 16 blocks the flow path 20, the stepped piston is stopped at that position. If the amount of movement of the stepped piston at this time is the sealed oil pressure in the S1 adjustment oil chamber 15 as Pa, the pressing force of the load spring 4 when the stepped piston is stationary increases by that amount, and the above-mentioned equation (1) is It is expressed as

It can be rewritten as

And the corner oil pressure of the proportioning actuation mechanism 3 (P″
C) is expressed as.

The hydraulic pressure P8 sealed in the adjustment oil chamber Pa is PaO because the brake force required to obtain a constant deceleration GO of the vehicle increases approximately in proportion to the vehicle carrying load W, as described above.
(-W (5), and the amount of movement S in the equations (3), (1)″, and (4) also increases approximately in proportion to the vehicle carrying load W.

From the above, it is clear that the corner oil pressure of the proportioning actuating mechanism 3 increases approximately in proportion to the increase in the oil pressure Pa sealed in the adjustment oil chamber 15, but the corner oil pressure when the vehicle is not loaded (PCl The initial load F1 of the load spring 4 can be calculated from It is desirable to facilitate the setting of the corner oil pressure value by setting the size of the oil pressure approximately equal to the oil pressure applied to the stepped piston due to the oil pressure sealed in the adjustment oil chamber 15 when the vehicle is not loaded. As in the present embodiment shown in the drawings, an adjustment spring 5 is provided to apply a pressing force against the moving force due to the hydraulic action of the stepped piston, and the movement start point at which the load spring 4 of the stepped piston is bent. It will also be easily understood that the configuration is such that the amount of movement thereof is adjusted.

As described above, the deceleration sensing type proportioning valve according to the present invention has an ideal brake force distribution curve for the front and rear wheels during vehicle braking as shown in FIG.
Corresponding to the change from the curve state to the state of PO2 at the time of high load loading, the corner oil pressure PO also increases, and the gradual rise rate A2 is determined by the hydraulic pressure receiving area Al, A2 which differs in the longitudinal direction of the axis of the control piston 8. The characteristic of the rear wheel brake oil pressure that increases when -AltanO= ~ is obtained by extremely approximating the oil pressure curve Px.

Another feature of the present invention is that the adjustment mechanism 14 for the pressing force of the load spring 4 is connected to the input oil chamber 11 of the proportioning actuating mechanism 3 and the input oil chamber 11 via the G valve mechanism 16. It operates based on the hydraulic balance of the adjustment oil chamber 15.

In other words, in the case of sudden braking, the brake oil pressure may rise rapidly, and the stepped piston may cause the load spring 4 to increase due to the balance between the oil pressure from the adjustment oil chamber and the mechanical spring force that resists this. If the method is to determine the amount of deflection,
Abnormally high pressure may be transmitted before the G valve mechanism blocks the oil inflow path to the adjustment oil chamber (before constant vehicle deceleration Gc is obtained), leading to malfunction of oil pressure corner adjustment. In the present invention, even if such abnormal high pressure is transmitted to the adjustment oil chamber 15, the corresponding abnormal high pressure acts on the stepped piston from the input oil chamber 11 side, so the degree of malfunction is extremely reduced, and the flow path 20 In addition to the provision of the throttle portion 21 in the hydraulic pressure Pc, damage caused by incorrect adjustment of the corner oil pressure Pc is effectively prevented.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional view of a deceleration sensing type proportioning valve, and FIG. 2 is a diagram showing the increase characteristic of front and rear wheel brake oil pressure. 1...Valve body, 2,2''...Stepped cylinder nodder, 3...Proportioning operation mechanism, 4...Load spring, 5... Adjustment spring, 6, 7...Adjustment piston, 6''...Cylinder, 8...Control piston, ``...Large diameter flange section, 9...Valve seat , 10...
...Output oil chamber, 11...Input oil chamber 1, 12.
... Zeston cup, 13 ... O-ring, 14 ... Pressure force adjustment mechanism, 15 ... Adjustment oil chamber, 16 ... G valve mechanism, 17...
...Guide surface, 18... Valve seat, 19...
-Ball, 20...flow path, 21...throttle section.

Claims (1)

[Claims] 1. A control piston that moves in one direction with different hydraulic forces in the longitudinal direction of the shaft against the biasing spring force of a load spring has a valve seat that divides the inside of the cylinder into two oil chambers, an input oil chamber and an output oil chamber. Proportioning is a method in which a cooperating flow passage opening/closing valve part is configured, and when the input oil pressure exceeds a corner oil pressure value determined by the urging spring force, the rate of increase in output oil pressure is reduced by opening/closing the valve part. In the valve, a stepped piston with a small diameter end face facing an input oil chamber is arranged approximately concentrically with the control piston moving direction side in the cylinder, and an adjustment oil chamber is formed with the other end of the stepped piston facing the large diameter end face. The load spring that applies a spring force in the span extension direction is tensioned between these two pistons, and the input oil chamber and the adjustment oil chamber are connected via a G valve mechanism that closes the flow path at a constant deceleration. A deceleration-sensing proportion characterized in that the stepped piston compresses the load spring substantially in proportion to an increase in the oil pressure value sealed in the adjustment oil chamber, thereby increasing the corner oil pressure value. ning valve. 2. The deceleration sensing device according to claim 1, characterized in that a cylinder with one end open is formed in either the small diameter portion of the stepped piston or the one end portion of the control piston, and these two pistons are slid together in a watertight manner. Type proportioning valve. 3. The deceleration sensing type proportioning valve according to claim 1 or 2, further comprising a load adjustment spring that presses the stepped piston toward the adjustment oil chamber. 4. A patent claim characterized in that the stepped piston is divided into two independent members: a cylindrical first part that slides through one end of the control piston, and a second cylindrical part that is open at one end and holds a load spring. Deceleration sensing type proportioning valve described in range 2 or 3.