JPH0562098B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a braking device for a four-wheel drive automobile, and more particularly to a braking device that can perform suitable braking according to the drive mode of the wheels.

(Prior Art) In automobile braking systems, if the rear wheels lock before the front wheels during braking, there is a risk of dangerous situations such as tail swing or spin.
The rear wheel brake system is equipped with a hydraulic pressure regulating valve that reduces the brake hydraulic pressure from the master cylinder. An example of this regulating valve is disclosed in Japanese Patent Publication No. 55-164549, and if this valve is used, the ratio of front wheel brake fluid pressure and rear wheel brake fluid pressure can be adjusted according to the load conditions of the front and rear wheels during braking. It can be almost adapted and varied.

(Problems to be Solved by the Invention) However, when this braking device is provided in a four-wheel drive vehicle, there is a problem that braking efficiency deteriorates depending on the driving form. In other words, in the case of a full-time four-wheel drive system, the front wheel drive system and the rear wheel When the vehicle is directly connected to the drive train, the front and rear wheels always lock at the same time. Therefore, in such a direct connection state,
Reducing the brake force on the rear wheels in order to obtain a brake force distribution that locks the front wheels first will result in poor braking efficiency.

Additionally, it is desirable to change the brake force distribution between the front and rear wheels depending on the road surface conditions, but with conventional automobile braking systems, it is not possible to arbitrarily change the brake force distribution between the front and rear wheels. Nakatsuta.

The present invention has been made to solve such problems, and its object is to perform appropriate braking in a four-wheel drive vehicle according to its driving form.

(Means for Solving the Problems) The present invention provides a braking system for a four-wheel drive vehicle that can directly connect the rear wheel drive system and the front wheel drive system. When the brakes are in the directly connected state, the brake adjustment valve controls the increase in the brake fluid pressure acting on the rear wheel cylinders from the point at which a higher brake fluid pressure is applied than when the brakes are not in the directly connected state. More specifically, in the present invention, the hydraulic pressure regulating valve includes a spring for determining a set hydraulic pressure at which brake hydraulic pressure is controlled by the valve, and a spring load setting for changing the load applied by this spring. means.
and a detection means for detecting that the rear wheel drive system is directly connected to the front wheel drive system, and based on the detection result of the detection means, while the rear wheel drive system is in the directly connected state to the front wheel drive system, A controller is provided for operating the spring load setting means by a desired amount so as to increase the set hydraulic pressure by a desired value.

(Function) In the present invention configured as described above, the braking force acting on the rear wheels differs depending on whether the front wheel drive system and the rear wheel drive system are directly connected. First, when there is no direct connection, the brake fluid pressure applied to the wheel cylinders of the front wheels is controlled by the action of the brake fluid pressure regulating valve so that the brake force distribution is such that the front wheels are locked first. That is, when the brake fluid pressure of the master cylinder exceeds a predetermined setting fluid pressure value, the increase in the brake fluid pressure acting on the wheel cylinder of the rear wheel is controlled. For example, when a proportioning valve is used as a hydraulic pressure regulating valve, as shown by the broken line in Fig. ₂ , the brake applied to the front wheel cylinder becomes The rate of increase in brake fluid pressure acting on the rear wheel cylinder decreases.

However, when the front and rear wheel drive systems are directly connected, the set hydraulic pressure value at which the brake hydraulic pressure regulating valve starts controlling the increase in brake hydraulic pressure is changed to a high value. As a result, when brake fluid pressure higher than the predetermined set fluid pressure value is applied,
Compared to the case where the rear wheels are not directly connected, a larger brake fluid pressure is applied to the wheel cylinders of the rear wheels. In other words, as shown by the broken line in Figure 2, the rate of increase in brake fluid pressure acting on the rear wheel wheel cylinder from the changed set fluid pressure value P ₁ is limited, so large brake fluid pressure is applied to the rear wheels. is supplied.

In particular, in the present invention, the hydraulic pressure regulating valve has a spring for determining a set hydraulic pressure at which brake hydraulic pressure is controlled by the valve, and a spring load setting means for changing the load by this spring, Since this spring load setting means is actuated by a desired value by the controller, a desired brake force distribution can be set for the front and rear wheels according to road surface conditions.

(Effects of the Invention) According to the present invention, in a braking system for a four-wheel drive vehicle, the control of the brake fluid pressure acting on the rear wheel cylinder by the brake fluid pressure regulating valve is performed by the front and rear drive systems. When the vehicle is not directly connected, braking is performed from a predetermined set hydraulic pressure value to prevent the rear wheels from locking first, so the vehicle body does not spin due to braking and running stability is ensured. In addition, in the direct connection state, the set hydraulic pressure value is changed to a high value, so the rate at which the brake hydraulic pressure applied to the rear wheel cylinder by the brake hydraulic pressure adjustment valve is reduced is reduced. A large brake fluid pressure is applied to the brake, making it possible to improve brake efficiency.

As described above, according to the present invention, since the braking of the rear wheels is controlled according to the drive mode, it is possible to improve both running stability and braking efficiency.

Further, the present invention has the advantage that a desired brake force distribution can be set for the front and rear wheels according to the road surface conditions.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows a brake system in one embodiment of the present invention. In the figure, reference numeral 1 denotes a brake pedal disposed on the floor of the vehicle interior, and the force applied to this pedal is amplified via a vacuum servo 2 and transmitted to a master cylinder 3. In the master cylinder 3, the pressing force from the pedal is converted into corresponding brake fluid pressure. The brake fluid pressure generated in the master cylinder 3 is supplied to the wheel cylinders of each wheel through two piping systems. 1st
The piping system extends from the master cylinder via the brake tube 4 to the hydraulic pressure regulating valve 5, and from this hydraulic pressure regulating valve 5 via the brake tube 6R and brake hose 7R to the wheel cylinder 8R of the right front wheel. The regulating valve 5 is connected to a wheel cylinder 12L of the left rear wheel via brake tubes 10L and 11L. The second piping system extends from the master cylinder 3 via the brake tube 9 to the hydraulic pressure regulating valve 5, and from this valve 5 via the brake tube 6L and brake hose 7L to the wheel cylinder 8L of the left front wheel. 5 to a wheel cylinder 12R of the right rear wheel via brake tubes 10R and 11R. When hydraulic pressure is supplied from the master cylinder 3 to each wheel cylinder 8R, 8L, 12R, 12L via such a piping system, the brake piece of each wheel is driven by the hydraulic pressure, and each wheel is braked.

The hydraulic pressure regulating valve 5 is for adjusting the distribution of hydraulic pressure, that is, braking pressure, supplied to the front wheels and rear wheels, and brings the distribution close to the ideal state to prevent dangerous rear wheel locking. It is for.
In this example, a proportioning valve is used as the hydraulic pressure adjustment valve, and its brake force distribution state is
Indicated by dashed lines in the figure.

In FIG. 2, the solid line is an ideal brake force distribution curve showing the most efficient distribution of brake force to each of the front wheels and rear wheels, and the broken line is the actual brake force distribution curve distributed by the proportioning valve 5 as described above. It is an actual brake force distribution line showing force distribution. As shown in the figure, the actual brake force distribution line is in the area below the ideal brake force distribution curve,
The rear wheel brake force distribution is kept lower than the ideal brake force distribution, so that the front wheels lock first.

Next, in FIG. 1, a controller 13 is used to control the action of the proportioning valve 5, as will be described later. A sensor 14 detects whether or not the rear wheel drive system is directly connected to the front wheel drive system. This sensor output, which constitutes a detection means, is supplied to the controller 13. In addition, 16 is a parking brake lever arranged on the floor surface of the vehicle interior, and by pulling up this lever 16, cables 17 and 18R, 1
The control piece for the rear wheel is driven via the 8L, and braking force is applied to the rear wheel.

FIG. 3 shows the structure of the proportioning valve 5. In this example, the brake hydraulic piping system is
Since it is a system, a dual type is used, and one valve 5R and the other valve 5L have the same structure, so the valve 5R distributes brake fluid pressure to the left front wheel and the right rear wheel. I will explain about it. In the figure, 51 is a housing, and a cylindrical space 5 formed by this housing 51
2 is equipped with a plunger 53. The plunger 53 has a large diameter at its base end, and a small diameter at its distal end connected to the poppet valve 54. A ring member 55 having a hole with an inner diameter slightly larger than the outer diameter of the poppet valve 54 is fitted into the inner peripheral wall of the cavity 52 in which the poppet valve 54 is located. A communication hole 56 extending in the direction is formed. The communication hole 56 communicates with an outlet port 57 formed in the housing 51 for applying a brake to the right rear wheel. A poppet valve 5 is provided at the lower end of the ring member 55.
A ring member 59 forming the seat surface 58 of 4 is also fitted into the cavity 52. On the other hand, a spring receiving portion 61 is disposed at a large diameter portion 60 of the plunger 53, and a spring 62 is interposed between this spring receiving portion 61 and the lower end surface of the ring member 59. Reference numeral 63 is an outlet port that supplies brake fluid pressure to the left front wheel, and the space 52 is an outlet port that supplies brake fluid pressure to the left front wheel.
It communicates at the lower part of 9. Further, in the lower part of this ring member 59, the hollow space 5
2 communicates with the master cylinder 3 side.

The proximal end of the plunger 53 protrudes from the cavity 52 of the housing 51 and is supported by an equalizer 64. Reference numeral 65 denotes a support for the equalizer 64, which has an inverted hat shape as a whole, and a contact portion 652 with the equalizer 65 is formed at a portion of a flange 651 bent outward. The outer peripheral end of this flange 651 is bent upward and fixed to the lower part of the housing 51. In addition, the hollow space 6 of the protrusion formed in the center of this support 65
A spring 66 is attached to the spring 53 , the upper end of which is supported by the center of the equalizer 65 via a ball 67 , and the lower end of which is supported by a spring receiving member 71 . This receiving member 71 is supported by a push screw 72, which allows the receiving member 71 to be pushed toward the ball 67 side. 73 is a sleeve nut screwed onto the push screw 72, and is attached to the bottom 6 of the support 65.
54, and a gear 74 is fixed to the outer periphery thereof. On the other hand, 75 is a support 65
A small gear 76 is fixed to the output shaft of the motor, and a small gear 76 is fixed to the output shaft of the motor.
6 meshes with the gear 74 mentioned above. motor 7
5 is controlled by a controller 13. Here, push screw 72, sleeve nut 7
3. Gear 74, small gear 76 and motor 75,
This constitutes a spring load setting means for changing the load applied by the spring 66. That is, when the front and rear wheel drive systems are directly connected, the motor is driven to rotate in the forward direction, and the push screw 72 is pushed up from its initial position. However, when the direct connection state is released, the motor is driven to rotate in the opposite direction, and the push screw 72 is pushed down to return to the initial position again.

Here, in the plunger 53, the outer diameter of the large diameter portion 60 is set to be smaller than the inner diameter of the ring member 59 forming the seat surface, and this difference in pressure receiving area causes the brake fluid pressure to increase. When applied, a force is generated that pushes up the plunger 53. Further, the force of pushing up the plunger 53 by the spring 6 is set to a value larger than twice the force of pushing down the plunger 53 by the spring 62. As a result, when the brake fluid pressure is not applied, the plunger 53 is biased upward by the upward force of the spring 66, as shown by the dashed line in the figure.
In this state, within the cavity 52, the hydraulic pressure chamber 68 formed above the poppet valve 54 and the hydraulic pressure chamber 69 formed below it are in communication.

The operation of this embodiment configured as described above will be explained. First, when the front wheel and rear wheel drive systems are not directly coupled, the push screw 72 is at the initial position. Therefore, the spring set load, which is the force of the spring 66 pushing up the plunger 53, remains at a predetermined magnitude. As a result, as shown by the broken line in FIG. 2, when the brake (initial setting hydraulic pressure) P ₀ corresponding to the break point is reached, the downward force of the plunger 53 becomes greater than the upward force, and the plunger 53 moves downward. , the poppet valve 54 comes into close contact with the seat surface 58. In detail, when the brake pedal 1 is depressed, the brake fluid pressure generated in the master cylinder 3 is transferred to the proportioning valves 5, 5.
It is added to the hydraulic pressure chamber 69 of R and 5L. As described above, since the plunger 53 is biased upward by the force of the spring 67, both hydraulic chambers 68 and 69 are in communication. Therefore, the brake fluid pressure of the master cylinder 3 is directly applied to both the fluid pressure chambers 68 and 69. As a result, the same hydraulic pressure acts on each of the front and rear wheels. However, the break point in Figure 2
When the brake fluid pressure (initial setting fluid pressure) is reached as indicated by _P0 , the downward force of the plunger 53 becomes greater than its upward force, the plunger 53 moves downward, and the poppet valve 54 comes into close contact with the seat surface. As a result, both hydraulic pressure chambers 68, 69 are suddenly cut off. Thereafter, when the brake fluid pressure further increases, the force pushing up the plunger 53 increases, the poppet valve 54 separates from the seat surface, and the fluid pressure in the fluid pressure chamber 68 increases. When the hydraulic pressure in the hydraulic pressure chamber 68 increases by a predetermined rate, the force pushing down the plunger 53 becomes large, the plunger 53 moves downward, and the poppet valve 54 comes into close contact with the seat surface 58 again. Such operations are repeated to maintain a balanced state between the two hydraulic pressure chambers 68 and 69 even as the brake hydraulic pressure in the master cylinder 3 increases. As a result of this operation, the rate of increase in the brake fluid pressure acting on the rear wheels is a predetermined ratio with respect to the brake fluid pressure acting on the front wheels, as shown after the turning point P ₀ in Figure 2. It is only held down low.

Next, when the front and rear wheel drive systems are directly connected,
The controller 13 detects this from the output of the sensor 14 and drives the motor 75 to rotate in the forward direction for a predetermined period. As a result, the push-in screw 72 moves upward by a predetermined amount, and the movement of the receiving member 71 supported on this screw 72 compresses the spring 67 by a predetermined amount. As a result, the set load of the spring 67 increases, and the corner hydraulic pressure of the proportioning valve 5, which changes depending on this set load, increases to P ₀ or P ₁ . Therefore, under such a set load, the brake fluid pressure of the master cylinder 3 is supplied to the front and rear wheel cylinders as shown by the broken line in FIG. As is clear from Figure 2, when a brake fluid pressure greater than the turning point fluid pressure P ₀ , which is the initial setting fluid pressure, is applied, the brake fluid pressure is greater than when the front and rear wheel drive systems are not directly connected. will act on the rear wheels.

Note that when the direct connection between the front and rear wheels is released, the motor 75 is driven by the controller 13 to rotate in the reverse direction, and the push screw 72 returns to its initial position.
As a result, the set load of the spring 67 also decreases and returns to its initial value.

As mentioned above, in this embodiment, when the front and rear wheel drive systems are directly connected, the corner hydraulic pressure is increased by increasing the spring setting load of the proportioning valve, so that the rear wheel The brake fluid pressure acting on the brake increases, making it possible to improve brake efficiency.

Furthermore, in this embodiment, the spring setting load can be set to a desired value by changing the amount of movement of the push-in screw 72, resulting in the effect that the brake fluid pressure acting on the rear wheels can be controlled to a suitable value. It will be done.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Figure 2 is a characteristic curve diagram showing the distribution of brake fluid pressure.
FIG. 3 is a sectional view showing the configuration of the proportioning valve of FIG. 1. 3... Master cylinder, 5... Proportioning valve, 8R, 8L, 12R, 12L... Wheel cylinder, 13... Controller, 14... Sensor, 53
...Plunger, 54...Poppet valve, 68, 69...
Hydraulic pressure chamber, 72...push screw, 75...motor.

Claims (1)

[Claims] 1. Fluid pressure adjustment that controls the increase in brake fluid pressure that acts on the rear wheel cylinder when the master cylinder brake fluid pressure exceeds a predetermined set fluid pressure so that the front wheels lock before the rear wheels. In a braking device for a four-wheel drive vehicle that is equipped with a valve and is capable of switching whether or not to directly connect a rear wheel drive system to a front wheel drive system, the hydraulic pressure regulating valve determines the set hydraulic pressure. a detection means for detecting that the rear wheel drive system is directly connected to the front wheel drive system, the detection means having a spring and a spring load setting means for changing the load by the spring; Based on the results, a controller is provided that operates the spring load setting means by a desired amount so as to increase the set hydraulic pressure by a desired value while the rear wheel drive system is directly connected to the front wheel drive system. An automobile braking device characterized by: