JPH071332Y2 - Vehicle braking system - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) [0001] The present invention relates to a vehicle brake system, and more particularly to a vehicle brake including a hydraulic pressure control valve such as a proportioning valve and a brake with an adjusting mechanism for adjusting a brake gap. Regarding the system.

(Prior Art) Generally, in a vehicle brake system, in order to prevent the rear wheels from prematurely locking and shorten the braking distance by approximating the braking force distribution at the time of braking to the ideal distribution, the hydraulic pressure of the rear wheels is reduced. Some are equipped with a hydraulic control valve that limits the pressure to a value lower than the hydraulic pressure.

A conventional braking system for this type of vehicle is, for example, a proportioning valve (hereinafter referred to as P valve).
Or load saving valve (hereinafter referred to as LSV)
It is equipped with the "Automotive Engineering Complete Book 12 tires,
Brakes (see Sankaido Co., Ltd. issued in January 1980). "

The P valve is provided between the master cylinder and the rear wheel cylinder that generate brake oil pressure in response to the depression of the brake pedal. When the brake oil pressure from the master cylinder reaches the set oil pressure, the oil pressure on the rear wheel cylinder side is changed to the front. For the hydraulic pressure on the wheel cylinder side,
The pressure is reduced at a constant rate to prevent early locking of the rear wheels. Like the P valve, the LSV is provided between the master cylinder and the rear wheel cylinder. For example, a link mechanism interposed between the vehicle body and the axle allows the LSV to respond to the axial load, that is, the relative distance between the vehicle body and the axle. The set hydraulic pressure is changed according to the displacement.

On the other hand, in the case of a drum brake mounted on the rear wheels of a vehicle, the lining that slides on the drum wears as the vehicle is repeatedly braked. An adjusting mechanism for adjusting the clearance between the shoe and the drum is provided as necessary so as not to hinder the operation.

As this adjusting mechanism, for example, a service adjuster is known which receives a hydraulic pressure from a wheel cylinder and adjusts a brake clearance, which is a clearance between the brake shoe and the inner peripheral surface of the drum.

(Problems to be Solved by the Invention) However, in such a conventional vehicle braking system, the P valve and the LSV are configured to limit the hydraulic pressure on the rear wheel cylinder side at or above the set hydraulic pressure. For example, during parking, the brake oil pressure supplied to the rear wheel cylinders may not rise sufficiently compared to the brake oil pressure supplied from the master cylinder to the front wheel cylinders, and the rear wheel side automatic adjustment mechanism may not operate. It was That is, when a vehicle equipped with a P valve having a small set hydraulic pressure or a vehicle equipped with an LSV is lightly loaded, as shown in FIG. Since the valve characteristic has (the set hydraulic pressure), the rear wheel side hydraulic pressure does not rise sufficiently unless the front wheel side hydraulic pressure is made sufficiently high. on the other hand,
Since the adjusting mechanism is set so that it does not operate unless the hydraulic pressure of the rear wheel cylinder reaches the value indicated by A in FIG. 4, therefore, the adjusting mechanism does not operate even when the brake pedal is depressed, and the shoe and drum Since the brake clearance cannot be adjusted even if the clearance is greater than the specified value, an initial loss stroke occurs in the stroke of the brake pedal,
There was a problem that the operation feeling of the brake pedal deteriorated.

(Purpose of the Invention) Therefore, in the present invention, when the vehicle is stopped, the hydraulic pressure is supplied to the rear wheel brakes directly from the master cylinder to the rear wheel brakes without passing through the control valve, so that the hydraulic pressure of the rear wheel cylinder is sufficient when the vehicle is stopped. To activate the adjustment mechanism,
The purpose is to improve the operation feeling of the brake pedal.

(Means for Solving the Problem) In order to achieve the above-mentioned object, a vehicle brake system according to the present invention adjusts a brake clearance by a master cylinder that generates brake hydraulic pressure in response to depression of a brake pedal and a brake hydraulic pressure from the master cylinder. It has an adjusting mechanism and is provided on the rear wheel brake that brakes the rear wheels according to the brake hydraulic pressure and the oil passage from the master cylinder to the rear wheel brake, and can limit the brake hydraulic pressure supplied to the rear wheel brake. In a vehicle brake system including a hydraulic pressure control valve, a bypass supply path for supplying brake hydraulic pressure from the master cylinder to a rear wheel brake by bypassing the hydraulic pressure control valve, and traveling for detecting a traveling state of the vehicle Bypass when the vehicle is stopped based on the state detection means and the detection information from the traveling state detection means Switching means for supplying the brake oil pressure to the rear wheel brakes via the supply passage is provided.

(Operation) In the present invention, when the vehicle is stopped, the brake hydraulic pressure is directly supplied from the master cylinder to the rear wheel brakes through the bypass supply passage by the operation of the switching means, while the hydraulic pressure is supplied to the rear wheel brakes when the vehicle is running. The brake hydraulic pressure is supplied via the pressure control valve. Therefore, when the vehicle is stopped, the hydraulic pressure of the rear wheel cylinder is sufficiently increased and the adjusting mechanism operates. As a result, the initial loss stroke of the brake pedal is prevented and the operation feeling is improved.

(Example) Hereinafter, the present invention will be described with reference to the drawings. 1 to 3 are views showing an embodiment of the present invention and show a brake system of a vehicle having a drum brake.

First, the configuration will be described. In FIG. 1, reference numeral 1 is a tandem type master cylinder, and the master cylinder 1 has a primary piston and a secondary piston that partition the inside into a first liquid chamber and a second liquid chamber, although not shown in detail. The master cylinder 1 is connected to a negative pressure booster 2, and the negative pressure booster 2 doubles the depression force of a brake pedal (not shown) to generate a brake hydraulic pressure according to the depression amount of the brake pedal.
Further, the first liquid chamber of the master cylinder 1 is connected to the front wheel brake 4 via the front side hydraulic pressure supply passage 3, and the second liquid chamber is connected to the rear wheel brake 6 via the rear side hydraulic pressure supply passage 5. Therefore, the front and rear wheels (not shown) are braked according to the brake hydraulic pressure from the master cylinder 1. The front wheel brake 4 and the rear wheel brake 6 are known ones,
The rear wheel brake 6 has, for example, a rear wheel cylinder and a known adjusting mechanism for adjusting the clearance between the brake shoe and the drum. This adjusting mechanism is operated by the brake hydraulic pressure supplied from the master cylinder 1 to the rear wheel cylinders via the hydraulic pressure supply passage 5, and sets a so-called brake gap between the lining surface of the brake shoe and the inner peripheral surface of the drum to a predetermined value. (For example, 0.3 mm to 0.4 mm).

Further, a known hydraulic pressure control valve 7 such as a P valve is provided in the oil passage from the master cylinder 1 to the rear wheel brake 6, that is, the hydraulic pressure supply passage 5, and the hydraulic pressure control valve 7 is provided from the master cylinder 1 to the hydraulic pressure control valve 7. The brake hydraulic pressure supplied to the rear wheel brake 6 can be limited. Specifically, this hydraulic control valve 7 has a predetermined set hydraulic pressure (valve breaking point), and when the brake hydraulic pressure supplied from the master cylinder 1 reaches this set hydraulic pressure, it is supplied to the front wheel brake 4. It has a function of reducing the brake oil pressure supplied to the rear wheel brakes 6 at a constant ratio with respect to the brake oil pressure.

On the other hand, a bypass supply passage 8 is provided in the hydraulic pressure supply passage 5, and the bypass supply passage 8 supplies the brake hydraulic pressure from the master cylinder 1 to the rear wheel brake 6 by bypassing the hydraulic pressure control valve 7. Further, a variable valve 9 such as a switching valve is provided at the connection between the hydraulic pressure supply passage 5 and the bypass supply passage 8, and the variable valve 9 transfers the brake hydraulic pressure from the master cylinder 1 to the rear via the hydraulic pressure supply passage 5. The first switching position supplied to the wheel brakes 6 and the brake hydraulic pressure from the master cylinder 1 are passed through the bypass supply passage 8 to the rear wheel brakes 6.
Has a second switching position for supplying to. The variable valve 9 is connected to an actuator 10 such as a solenoid valve and is switched by the actuator 10. For example,
The variable valve 9 is in the first switching position when the actuator 10 is activated, and is in the second switching position when the actuator 10 is not activated. Reference numeral 11 denotes a rotation speed sensor as a running state detection means, and this rotation speed sensor 11 detects the rotation speed of the rear wheel based on the unevenness of the rotor or the like mounted on the rear wheel, and the detected information is sent to the actuator 10. Output. Based on this detection information, the actuator 10 sets the variable valve 9 to the first switching position when traveling and when the vehicle is stopped, the variable valve 9
To the second switching position. That is, these variable valve 9 and actuator 10 constitute a switching means.
Reference numeral 12 is a reservoir tank for supplying brake oil to the master cylinder 1.

Next, the operation will be described.

First, since the front wheels and the rear wheels do not rotate when the vehicle is stopped, the actuator 10 switches the variable valve 9 to the second switching position based on the detection information from the rotation speed sensor 11.
At this time, when the brake pedal is depressed, the brake hydraulic pressure from the master cylinder 1 is supplied to the variable valve 9 and the bypass valve in the same manner as the brake hydraulic pressure from the master cylinder 1 is supplied to the front wheel brake 4 via the hydraulic pressure supply passage 3. It is directly supplied to the rear wheel brake 6 via the road 8. At this time, the relationship between the front wheel side oil pressure and the rear wheel side oil pressure is approximately the same as shown in FIG. That is, the brake hydraulic pressure from the master cylinder 1 is not restricted by the hydraulic pressure control valve 7, and even if the front wheel hydraulic pressure is low by the hydraulic pressure difference B shown in FIG. The adjustment mechanism can be activated by raising it. Therefore, the brake gap can be adjusted to a predetermined value (for example, 0.3 mm to 0.4 mm) to prevent the initial stroke loss of the brake pedal, and the pedal operation feeling can be improved.

On the other hand, since the front wheels and the rear wheels rotate when the vehicle is running, the rotation speed sensor 11 sends a signal corresponding to the rotation speed of the rear wheels to the actuator 10, and the actuator 10 causes the variable valve 9 to move the first variable valve 9 based on this signal. Switch to the switching position. Therefore, when the vehicle is operating, the brake hydraulic pressure from the master cylinder 1 is supplied to the rear wheel brake 6 via the hydraulic pressure supply passage 5 and the hydraulic pressure control valve 7. At this time, the relationship between the front wheel side oil pressure and the rear wheel side oil pressure has a break point P ₁ generated by the hydraulic pressure control valve 7 as shown in FIG. 3, and the normal valve characteristics similar to those of the conventional example are obtained. The function of preventing the lock or the like can be sufficiently exerted.

Although the rotation speed sensor 11 for detecting the rotation speed of the rear wheels is used as the traveling state detecting means in the present embodiment, the invention is not limited to this, and the rotation speed sensor 11 for detecting the rotation speed or the vehicle speed of the front wheels may be used. Good. The point is that it suffices to detect whether or not the vehicle is traveling. Further, although the adjusting mechanism adjusts the brake gap of the drum brake in the present embodiment, it is needless to say that the adjusting mechanism can be applied to a structure for adjusting the brake gap of the disc brake.

As described above, in the present embodiment, the brake hydraulic pressure is directly supplied from the master cylinder 1 to the rear wheel brake 6 via the bypass supply passage 8 when the vehicle is stopped by the operation of the switching means, and at the time of traveling the rear wheel. Since the brake hydraulic pressure is supplied to the brake 6 through the hydraulic pressure control valve 7, the hydraulic pressure of the rear wheel cylinder can be sufficiently increased to operate the adjustment mechanism when necessary, and the initial loss of the brake pedal can be lost. The stroke can be prevented and the operation feeling can be improved.

(Effect) According to the present invention, the switching means is operated based on the detection information of the traveling state detection means, and when the vehicle is stopped, the brake oil pressure is directly supplied from the master cylinder to the rear wheel brakes via the bypass supply passage. At the same time, the control oil pressure is supplied to the rear wheel brakes via the hydraulic pressure control valve when the vehicle is running, so that the hydraulic pressure in the rear wheel cylinders can be sufficiently increased to operate the adjustment mechanism when necessary. It is possible to prevent the initial loss stroke of the pedal and improve the operation feeling.

[Brief description of drawings]

1 to 3 are views showing an embodiment of a vehicle brake system according to the present invention, and FIG. 1 is an overall configuration diagram thereof, and FIG.
FIG. 3 is a valve characteristic diagram showing the relationship between the front wheel side hydraulic pressure and the rear wheel side hydraulic pressure when the vehicle is stopped, and FIG. 3 is a valve characteristic diagram showing the relationship between the front wheel side hydraulic pressure and the rear wheel side hydraulic pressure when the vehicle is running, FIG. 4 is a valve characteristic diagram showing a relationship between a front wheel side hydraulic pressure and a rear wheel side hydraulic pressure in a conventional vehicle brake system. 1 ... Master cylinder, 5 ... Hydraulic pressure supply passage (oil passage),
6 ... rear wheel brake, 7 ... hydraulic pressure control valve, 8 ... bypass supply passage, 9 ... variable valve (switching means), 10 ... actuator (switching means), 11 ... rotation speed sensor (running state) Detection means).

Claims (1)

[Scope of utility model registration request] 1. A master cylinder that generates a brake hydraulic pressure in response to depression of a brake pedal, and an adjusting mechanism that adjusts a brake gap by the brake hydraulic pressure from the master cylinder, and the rear wheel is braked in accordance with the brake hydraulic pressure. A brake system for a vehicle, comprising: a wheel brake; and a hydraulic pressure control valve provided on an oil passage from a master cylinder to a rear wheel brake and capable of limiting a brake hydraulic pressure supplied to the rear wheel brake. A bypass supply path for supplying brake hydraulic pressure from a cylinder to the rear wheel brakes by bypassing the hydraulic control valve, a running state detecting means for detecting a running state of the vehicle, and a vehicle based on detection information from the running state detecting means. Switching means for supplying the brake oil pressure to the rear wheel brakes via the bypass supply passage when stopped. Brake system for a vehicle according to claim.