JP2530174B2 - Breaking device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a braking device, and in particular, an optimal braking force distribution can be obtained even if the friction coefficient of a lining material of a disc brake provided on a front wheel changes. The braking device that is adapted to the above.

(Prior Art) Generally, the distribution of the braking force applied to the front wheels and the rear wheels of an automobile is a quadratic curve so that the front wheel side becomes effective as the braking force increases, as shown by line A in FIG. It is ideal to have a good relationship.

In this way, the braking force on the front wheel side is set to be large because the weight distribution before and after the vehicle is generally large on the front wheel side, and the load is applied to the front wheel due to the movement of the center of gravity caused by the inertia of the vehicle body when the vehicle is braked. For this reason, if the same braking force is applied to the front wheels and the rear wheels, the rear wheels may be locked before the front wheels, and the posture of the vehicle may become unstable.

Conventionally, as a means for bringing the actual braking force distribution of an automobile (hereinafter referred to as actual distribution) closer to the ideal braking force distribution, a hydraulic control valve (proportioning
There is a valve provided to control the hydraulic pressure supplied to the wheel cylinder of the rear brake.

An example of this hydraulic pressure control valve will be described with reference to FIG. 4, and the main body 1 is provided with a cylinder portion 2, an inflow port 3 and an outflow port 4 for inflowing and outflowing oil liquid, and the inflow port 3 Is connected to a master cylinder (not shown) by a pipe line, and the outlet 4 is connected to a wheel cylinder provided on a rear wheel brake (not shown) by a pipe line.

A piston 5 is slidably fitted in the cylinder portion 2. A liquid passage 6 that connects the inflow port 3 and the outflow port 4 is formed in the piston 5, and a valve body 7 is formed in the liquid passage 6.
Are arranged. And by the movement of the piston 5,
The valve body 7 contacts the valve seat 5a formed on the piston 5 so that the liquid passage 6 can be shut off. The piston 5 is biased by a spring 8 with a constant force in a direction in which the valve body 7 and the valve seat 5a are separated from each other.

The characteristics of the brake device provided with the hydraulic control valve having this structure will be described with reference to FIG.

First, as the hydraulic pressure supplied from the master cylinder to the wheel cylinder rises (line B), the piston 5 resists the biasing force of the spring 8 due to the difference in pressure receiving area between the inflow side and the outflow side of the piston 5. The valve seat 5a is moved and seated on the valve body 7, and the supply of hydraulic pressure to the wheel cylinder is cut off (cut point C). When the supply of hydraulic pressure is cut off, the pressure on the inlet side rises, the piston 5 moves, the valve seat 5a separates, and the hydraulic pressure is supplied again. In this way, the valve body 7 and the valve seat 5a
By repeatedly separating and seating and, it is possible to suppress the increase in the hydraulic pressure on the rear wheel side to a low ratio (D line).

In addition, in vehicles such as trucks where the load weight changes greatly, a load-sensing hydraulic pressure control valve (load sensing proportioning valve) that can adjust the brake fluid pressure to the rear wheels according to the load weight is provided. There are also things.

This is because the piston 5 of the hydraulic pressure control valve is attached to a wheel or the like that can detect a change in vehicle height via a spring so that the change in the vehicle load can be detected by the vehicle height. Make the cut point C higher,
When the load is small, the cut point C is lowered so that the actual distribution does not deviate from the ideal braking force distribution.

By the way, in an automobile that employs disc brakes on the front wheels, the braking force of the disc brakes varies with the same hydraulic pressure because the friction coefficient of the lining material changes depending on the weather conditions (fine, rain, snow, etc.) and the brake usage conditions. Even if given, it changes in various ways. In particular, since the front wheels have a larger burden of the braking force than the rear wheels, the temperature change tends to be large, and the braking force tends to largely change according to the usage situation.

(Problems to be Solved by the Invention) However, in the conventional brake device provided with the hydraulic pressure control valve, the cut point of the hydraulic pressure control valve is constant or changes only by the load, and the lining of the disc brake is increased. No consideration is given to the friction coefficient of the material. Therefore, if the braking force distribution is set with the average value of the friction coefficient of the lining material, if the friction coefficient of the lining material of the disc brake of the front wheels decreases, the cutting point is reduced even if the braking force on the front wheel side becomes small. Occurs at the same hydraulic pressure, the braking force of the rear wheels becomes relatively large, and the actual distribution largely deviates from the ideal braking force distribution. As a result, the road surface utilization efficiency decreases, and problems such as a longer braking distance and locking of the rear wheels occur.

The present invention has been made in view of the above problems, and an object of the present invention is to change the hydraulic pressure introduced to the rear wheels in accordance with the change of the friction coefficient of the lining material of the disc brake, thereby achieving a suitable control. It is to provide a braking device that can obtain power.

(Means for Solving Problems) As means for solving the above problems and achieving the object, a disc brake is attached to a vehicle body so as to be rotatable in a rotation direction of a rotor provided on a front wheel, and a master cylinder And a wheel cylinder for the rear wheel, a hydraulic pressure control valve is provided in the middle of the pipeline, and a piston that operates by the difference in pressure receiving area between the inlet side and the outlet side to open and close the valve is provided in the hydraulic pressure control valve. By engaging with the disc brake, the piston controls the opening / closing timing of the valve according to the rotational torque generated in the disc brake during braking.

(Operation) With this configuration, since the disc brake is rotatably provided, the rotation torque is generated in the rotation direction of the rotor by sandwiching the rotor during braking. Then, the rotational torque generated in the disc brake during braking is
It changes depending on the magnitude of the hydraulic pressure supplied to the disc brake and also changes depending on the friction coefficient of the lining material. That is, when the supplied hydraulic pressure is increased, the braking force of the disc brake is increased and the rotational torque is also increased. Further, when the friction coefficient of the lining material is high, a larger rotational torque is generated than when the friction coefficient of the lining material is small.

Therefore, when the friction coefficient of the lining material is high, the cut point of the hydraulic pressure control valve is high, and because the friction coefficient is high, the braking force of the disc brake is high and the hydraulic pressure supplied from the master cylinder increases. To change the cut point to a higher percentage,
The opened state of the hydraulic pressure control valve is maintained for a long time, and the hydraulic pressure is controlled to be substantially equal to the front wheels and the rear wheels.

When the friction coefficient of the lining material is small, the cut point of the hydraulic control valve is low, and since the friction coefficient is small, the braking force of the disc brake is small.
Even if the hydraulic pressure rises, the rate of increase of the cut point can be suppressed to a small level. Therefore, the opening time of the hydraulic pressure control valve is shortened, and the hydraulic pressure supplied to the rear wheels is controlled to be lower than the hydraulic pressure supplied to the front wheels.

In this way, by controlling the hydraulic control valve according to the friction coefficient of the lining material and adjusting the hydraulic pressure supplied to the front and rear wheels, even if the friction coefficient of the lining material changes, the braking force of the rear wheels can be reduced. It is possible to prevent the braking force of the front wheels from becoming relatively larger, and it is possible to prevent the actual distribution from deviating from the ideal braking distribution.

(Example) Next, the Example of this invention is described based on FIG.

The disc brake 9 is provided on a knuckle 10 provided on the vehicle body side through a bracket 11 so as to be rotatable in the rotation direction of the rotor 9a. A hydraulic control valve 12 is attached to the knuckle 10. The hydraulic pressure control valve 12 is provided in a pipe line 14 that communicates between a master cylinder (not shown) and a wheel cylinder 13 provided at a rear wheel side brake, and is the same as that described in FIG. It is the structure of. It should be noted that the pipe line 14 is laid so that the pipe line 14a branches off midway to supply hydraulic pressure to the disc brake 9.

Further, the piston 12a of the hydraulic pressure control valve 12 is axially abutted with the other end of a pressing member 16 whose one end is rotatably attached to the knuckle 10 by a pin 15. A bracket having the disc brake 9 attached to the pressing member 16.
Reference numeral 11 denotes the hydraulic pressure control valve according to the rotation of the disc brake 9.
Twelve pistons 12a are engaged so as to urge them in the axial direction.

The same hydraulic pressure control valve 17 as the conventional one is provided in the middle of the pipe line 14.

Reference numeral 18 is a stopper pin for restricting rotation of the disc brake 9 in the opposite direction.

 The operation of the above configuration will be described.

When hydraulic pressure is supplied from the master cylinder to the disc brake 9 during braking, the rotor 9a is sandwiched by a lining material (not shown) to brake the front wheels. At this time, the disc brake 9 rotates along with the rotor 9a, and a rotational torque T is generated. Then, this rotational torque T applies an urging force F to the piston 12a of the hydraulic pressure control valve 12 via the pressing member 16.

This rotational torque T changes as the braking force of the disc brake 9 changes, and also changes depending on the friction coefficient μ _f of the lining material of the disc brake 9. That is, when the brake pedal is depressed to increase the hydraulic pressure from the master cylinder, the force by which the disc brake 9 holds the rotor 9a also increases, so that the rotational torque T increases. In addition, the friction coefficient of the lining material μ _f
Is large, the rotational torque T is large, and when the friction coefficient μ _f of the lining material is small, the rotational torque T is small.

Therefore, the urging force F due to the rotational torque T also changes, so that the cut point of the hydraulic pressure control valve 12 changes. This characteristic is shown in FIG. 2. When the friction coefficient μ _f of the lining material is large (for example, μ _f : 0.5), a large urging force F is applied to the piston 12a.
Is applied to maintain the hydraulic pressure control valve 12 in the open state with a strong force, the cut point becomes higher, and as the hydraulic pressure supplied from the master cylinder rises, the friction coefficient μ _f becomes large and the disc brake The braking force of 9 increases, the rate of increase of the rotational torque T increases, and the cut point is changed to a higher rate at a large rate, resulting in a characteristic with a large gradient as shown in FIG. Liquid pressure is supplied to and at approximately the same rate. It should be noted that a clear cut point does not occur unlike the hydraulic pressure characteristics of the conventional hydraulic pressure control valve.

Further, when the friction coefficient μ _f of the lining material is small (for example, μ _f : 0.2), a small biasing force F is applied to the piston 12a, so that the hydraulic control valve 12 is maintained in the open state with a weak force. Since the cut point is low and the friction coefficient μ _f is small, the braking force is small even if the supplied hydraulic pressure rises, and the rate of increase of the rotational torque T is suppressed to a low level. The ratio becomes small, and the characteristics are obtained with a small gradient as shown in FIG. That is, the hydraulic pressure supplied to the rear wheels is controlled to be lower than the hydraulic pressure supplied to the front wheels.

Therefore, by utilizing this characteristic, it is possible to prevent the actual distribution from deviating from the ideal braking distribution even _if the friction coefficient μ _f of the lining material changes.

This will be described with reference to FIG. In this figure, three types of friction coefficient μ _f are set: maximum (MAX), average (NOM), and minimum (MIN).

Regarding the relationship between the braking force B _f of the front wheels and the hydraulic pressure P _f supplied to the front wheels, the larger the friction coefficient μ _f of the lining material of the disc brake 9 of the front wheels is, the larger the braking force can be obtained with the smaller hydraulic pressure. Further, the relationship between the hydraulic pressure P _f supplied to the front wheels and the hydraulic pressure P _r supplied to the rear wheels is that the hydraulic pressure control valve 12 of the present invention causes the hydraulic pressure supplied to the rear wheels to decrease as the friction coefficient μ _f decreases. Pressure P _r is kept low. Therefore, the control timing (cut points C _MAX , C _NOM , C _MIN ) of the hydraulic pressure control valve 17 provided on the rear wheels always starts at the same hydraulic pressure P _r1 on the rear wheels, so that at each friction coefficient μ _f , The same braking force B _{f1 is applied} to the front wheels at the control timing of the hydraulic control valve 17.
By setting the relationship between the front wheel hydraulic pressure P _f and the rear wheel hydraulic pressure P _r in order to obtain, the actual distribution (line B and line D) is always cut at the same time regardless of the friction coefficient μ _f. Point C occurs,
It does not deviate from the ideal braking force distribution curve A.

In this way, even if the friction coefficient μ _f changes, the hydraulic pressure of the rear wheels is optimally controlled so that the actual distribution always matches the ideal braking force distribution.

(Effects of the Invention) As described in detail above, the present invention optimally controls the hydraulic pressure supplied to the front wheels and the rear wheels by utilizing the rotational torque of the disc brake generated during braking, so that the friction of the lining material is reduced. It is possible to prevent the actual distribution from deviating from the ideal braking force distribution even if the coefficient changes.

Therefore, the road surface utilization efficiency is not reduced under any circumstances, and it is possible to reliably prevent the braking distance from becoming long and the rear wheels from locking.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a brake device of the present invention, and FIG. 2 is a relationship between front wheel hydraulic pressure and rear wheel hydraulic pressure for each friction coefficient μ _f which is a characteristic of the hydraulic pressure control valve of the present invention. FIG. 3 is a diagram showing the relationship between the hydraulic pressure and the braking force between the front wheels and the rear wheels controlled by the present invention, FIG. 4 is a longitudinal sectional view showing an example of the hydraulic control valve, FIG. FIG. 5 is a diagram showing the relationship between the ideal braking distribution and the braking force applied to the front wheels and the rear wheels by the brake device having the conventional hydraulic pressure control valve. 9 ... Disc brake 9a ... Rotor 12 ... Fluid pressure control valve 13 ... Rear wheel cylinder 14 ... Pipe line

Claims (1)

(57) [Claims] 1. A disc brake is attached to a vehicle body so as to be rotatable in a rotation direction of a rotor provided on a front wheel, and a hydraulic control valve is provided midway in a pipeline connecting a master cylinder and a wheel cylinder of a rear wheel. In the hydraulic control valve, a piston that operates by the difference in pressure receiving area between the inlet side and the outlet side to open and close the valve is engaged with the disc brake, and according to the rotational torque generated in the disc brake during braking. A brake device, wherein the piston controls opening / closing timing of the valve.