JPH07121687B2 - Vehicle brake fluid pressure control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake fluid that maintains good turning performance by controlling the hydraulic pressure of the brake fluid supplied to the left and right wheels during braking while the vehicle is turning. The present invention relates to a pressure control device.

2. Description of the Related Art Generally, when braking during turning of a vehicle, the vehicle tends to oversteer and spin due to the braking force. Therefore, there is a so-called anti-skid control device that applies an optimal braking force without locking the wheels. Known,
In this type of control device, when braking, the braking force applied to the wheels on the inner side of the turning center is made lower than the braking force applied to the wheels on the outer side of the turning center, thereby increasing the frictional force between the tire and the road surface. In addition, a means for preventing the vehicle from becoming oversteer is common. As one example of the above-mentioned means, for example, in Japanese Patent Laid-Open No. 57-144158, a brake fluid pressure increase for the rear wheels on the inner side of the turning center is provided in the middle of a brake pipe arranged between the master cylinder and the rear wheels. The left and right hydraulic pressure control device is provided so that the rate is lower than the braking hydraulic pressure increase rate for the rear wheels on the outer side of the turning center, and based on the movement action of the weight body according to the lateral acceleration applied to the vehicle body, A configuration example is disclosed in which the left and right hydraulic pressure control devices are operated to cause a difference in brake fluid pressure between the left and right wheels during braking during turning.

Incidentally, in general, the load on the rear wheels is reduced as compared with the load on the front wheels during braking, and the rear wheels tend to be easily locked.
A proportioning valve is usually arranged in the middle of the brake pipe to the rear wheels for the purpose of matching the front-rear distribution ratios of the vehicle weight and the braking force. The proportioning valve is configured to reduce the subsequent rear-wheel-side hydraulic pressure increase rate at a constant rate with respect to the front wheels when the brake hydraulic pressure becomes equal to or higher than a constant hydraulic pressure that is an operation start point.

Further, by providing a separate hydraulic pressure control valve, by using the movement of the suspension arm during turning, etc. to open and close the control valve, the brake hydraulic pressure applied to the wheels is appropriately controlled,
An example of a device that prevents a spin during vehicle braking is also known.

SUMMARY OF THE INVENTION However, such a conventional brake fluid pressure control device,
In particular, in the example of the device disclosed in JP-A-57-144158, by detecting the lateral acceleration applied to the vehicle, that is, the turning state of the vehicle, the braking fluid pressure to the rear wheels inside the turning center is detected. Since the rate of increase is controlled to be lower than the rate of increase in braking fluid pressure for the rear wheels on the outside of the turning center, it is possible to prevent the vehicle from spinning during slow braking, while the vehicle is running laterally during sudden braking. There is a problem that the so-called trift moment that is swept away by the vehicle increases and the behavior of the vehicle tends to become unstable. Furthermore, since the rate of increase in the braking fluid pressure is kept low compared to that during normal braking, the deceleration required during sudden braking is reduced, and the sudden braking may not work. There is.

Therefore, the present invention solves the problem of such a conventional vehicle brake fluid pressure control device, can reduce both the spin moment and the drift moment of the wheels during turning braking, and can also perform sudden braking during an emergency. It is intended to provide a device that can be operated.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention relates to a vehicle brake fluid pressure control device that independently controls brake fluid pressure applied to wheels, and detects a turning state of a vehicle. Means, a braking state detecting means for detecting the braking state of the vehicle, and when the detected value of the turning state detecting means is equal to or more than a predetermined value, the brake fluid pressure of the wheel on the inner side of the turning center is greater than that of the wheel on the outer side of the turning center. In addition to limiting the brake fluid pressure to a value lower than the brake fluid pressure, during sudden braking when the detection value of the braking state detection means reaches a predetermined value or more, the brake fluid pressure of the wheel on the inner side of the turning center is set to the outer side of the turning center. The control means for releasing the above-mentioned restriction for lowering the brake fluid pressure of the wheel to return to the normal braking state is provided.

According to this configuration, when the driver depresses the brake pedal while the vehicle is turning in either the left or right direction, when the detection value of the turning state detection means reaches a predetermined value, control by a controller or the like is performed. From the means, a signal for limiting the brake fluid pressure of the wheel on the inner side of the turning center to be lower than the brake fluid pressure of the wheel on the outer side of the turning center is output,
As a result, the spin moment of the wheel is kept low.

On the other hand, at the time of sudden braking when the detection value of the braking state detection means reaches a predetermined value or more, the brake fluid pressure of the wheel located on the inner side of the turning center from the control means is higher than the brake fluid pressure of the wheel located on the outer side of the turning center. A signal to release the lower limit is output,
The same brake fluid pressure is supplied to the left and right wheels, and the vehicle returns to the normal braking state. As a result, the drift moment of the wheels can be suppressed to a low level, and moreover, sudden braking can be performed.

Embodiment An embodiment of a vehicle brake fluid pressure control device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic view showing the present invention as a whole. In FIG. 1, reference numeral 1 is a brake pedal, 2 is a master cylinder which is linked to the brake pedal 1, and a brake fluid 4 in a reservoir tank 3 is mastered. From the rear wheel fluid chamber 2a and the front wheel fluid chamber 2b in the cylinder 2 through the brake pipes 5, 6, 7, 8 respectively, the right rear wheel 9, the left rear wheel 10, the right front wheel 11, the left front wheel 12 The wheel cylinders 9a, 10a, 11a, 12a are supplied. or,
A proportioning valve 30 for reducing the hydraulic pressure generated in the master cylinder 2 at a predetermined ratio is provided between the rear wheel liquid chamber 2a and the brake pipes 5 and 6.

In the middle of the brake pipes 5, 6 for the rear wheels, solenoid valves 13, 14 consisting of two-position valves are installed. Solenoid valve 1 above
As shown in the figure, 3 and 14 are normally positioned to allow the brake fluid 4 from the master cylinder 2 to flow to the rear wheels 9 and 10, and when the solenoids 13a and 14a of the solenoid valves 13 and 14 are energized. The solenoid valves 13 and 14 are switched by the action of the solenoids 13a and 14a, and the flow of the brake fluid 4 is shut off.

Reference numeral 15 denotes a lateral acceleration sensor as a turning detection means for detecting turning of the vehicle. The lateral acceleration sensor 15 detects the magnitude of lateral acceleration applied to the vehicle body when the vehicle turns.

Reference numeral 16 is a longitudinal acceleration sensor as a braking state detecting means of the vehicle. The longitudinal acceleration sensor 16 detects the magnitude of acceleration applied in the longitudinal direction of the vehicle body during braking.

Reference numeral 20 denotes a controller as a control means, and the controller 20 includes the lateral acceleration sensor 15 and the longitudinal acceleration sensor.
Upon receiving the detection signal of 16, the open / closed states of the solenoid valves 13 and 14 are controlled by signal output lines 21 and 22.

The basic operation of the device of the present invention having such a configuration is as follows. That is, when the driver depresses the brake pedal 1 from the state shown in the figure, the pressure of the brake fluid 4 inside the rear wheel fluid chamber 2a and the front wheel fluid chamber 2b of the master cylinder 2 increases, and the brake fluid from the reservoir tank 3 increases. 4 is the brake pipe 5,
The braking force is generated in each wheel by being supplied to each wheel cylinder 9a, 10a, 11a, 12a of the four wheels via 6, 7, 8 and solenoid valves 13, 14. At this time, the solenoid valves 13 and 14 provided on the brake pipes 5 and 6 on the rear wheels 9 and 10 side are still released.

Next, assume that the driver depresses the brake pedal 1 while the vehicle is turning at high speed. Then, when the detection value of the lateral acceleration sensor 15 as the turning state detecting means becomes equal to or more than a predetermined value,
A signal is transmitted from the controller 20 to the solenoid on the rear wheel side inside the turning center of the solenoids 13a and 14a, and this solenoid is switched to the closing side. Therefore, at the time of gentle braking, the brake fluid pressure of the rear wheel on the inner side of the turning center is limited to be lower than the brake fluid pressure of the wheel on the outer side of the turning center, and the spin moment of the rear wheel is suppressed low. FIG. 2 shows the relationship between the braking force X applied to the automobile and the lateral force Y. Generally, when the braking force X is reduced by ΔFx as shown in the figure, the lateral force Y increases by ΔFy. It has been known. FIG. 3 shows a state in which a spin moment is generated by the braking force when the brake pedal is depressed while the vehicle is turning. That is, when the brake pedal is depressed while the vehicle body 45 is turning left as shown by arrow A, a moment M indicated by a broken line is generated around the center of gravity O. In this case, the braking force applied to the left rear wheel 10 is Fx and the lateral force is Fy, but the hydraulic pressure of the brake fluid 4 supplied to the wheel cylinder 10a (FIG. 1) of the left rear wheel 10 is reduced to When the braking force Fx is reduced by ΔFx, the lateral force Fy increases by ΔFy. Therefore, around the center of gravity O of the vehicle body 45, a moment M ₁ indicated by the solid line, that is, a moment in a direction of canceling the moment M indicated by the broken line is generated, and the moment causing the spin due to braking is reduced. be able to.

On the other hand, during the above operation, during the sudden braking when the detection value of the longitudinal acceleration sensor 16 as the braking state detecting means reaches a predetermined value or more, the solenoid is switched again from the controller 20 to the solenoid switched to the closing side. A signal for switching to the disengagement side is transmitted, and the above-mentioned restriction that lowers the brake fluid pressure of the rear wheel on the inner side of the turning center than the brake fluid pressure of the rear wheel on the outer side of the turning center is released. Therefore, the same brake fluid pressure is supplied to the rear wheels 9 and 10, and the vehicle returns to the normal braking state.

The behavior of such a vehicle will be described based on the graphs of FIGS. 4 and 5. All of the graphs show the relationship between the yawing moment of the vehicle and the deceleration, and FIG. 4 shows the case of a vehicle equipped with a normal proportioning valve, in the region where the deceleration is small, that is, the slow braking region. Has a characteristic that the spin moment becomes large and the vehicle easily spins, and conversely, the drift moment becomes large in a region where the deceleration is large, that is, a sudden braking region. Lines H and L show the limit values of the spin moment and the drift moment, respectively, and the inside of both lines H and L is the stable region. Point P is the maximum braking acceleration that the vehicle can generate (1G = 9.8m
/ S ² ) is shown.

The graph in the figure shows a case where the brake fluid pressure of the rear wheels on the inner side of the turning center is lowered as described above in order to prevent spin in the slow braking region during such a high-speed turning,
According to this graph, it is understood that the spin moment in the slow braking region decreases, while the drift moment becomes large in the rapid braking region, and the maximum braking acceleration does not reach 1G.

On the other hand, the graph shown in FIG. 5 shows the behavior of the vehicle when the present invention is applied. By executing the above-mentioned control for the left and right rear wheels 9 and 10, the graph in FIG. While the spin moment is reduced, the drift moment in the sudden braking region is also reduced, and the moving vehicle is always in the stable region indicated by the lines H and L. Further, since the maximum braking acceleration 1G (point P) that can be depressed by a general driver during braking has been reached, the effect of sudden braking is obtained.

The operation of the present invention will be described in more detail based on the time chart of FIG.

That is, it is assumed that the driver turns the steering wheel to the left or right at time t ₀ while the vehicle is traveling. Then, the lateral acceleration of the vehicle gradually increases, and reaches the predetermined value Y _g0 at time t ₁ . In this example, the above Y _g0 is set to 0.6G.

Next, at time t ₁ , the lateral acceleration sensor 15 detects that the lateral acceleration reaches a predetermined value Y _g0 , and when this detection signal is input to the controller 20, the controller 20 outputs a control signal Q. Of the solenoid valves 13 and 14, only the solenoid valve of the rear wheel on the inner side of the turning center is closed. However, at this time, since the brake pedal 1 is not depressed by the driver, the braking force is not applied to the vehicle. Further, as shown in the graph C, the yaw rate is also generated by a predetermined amount.

The next when the brake is depressed by the driver at time t _2, the brake fluid pressure in the master cylinder 2 by the depression force is increased from 0 to P _0, the brake fluid pressure P ₀ is depressurized by proportioning valve 30 As a result, the wheel cylinder of the rear wheel on the outer side of the turning center is set to 0 as shown in a.
To P ₁ are supplied. At this time, since the electromagnetic valve of the rear wheel on the inner side of the turning center is closed, the brake fluid pressure is not supplied to the rear wheel on the inner side of the turning center. Therefore, the spin moment of the vehicle at the time of gentle braking is reduced based on the above-described operating principle.

When the braking force acts on the vehicle in this way, the longitudinal acceleration of the vehicle changes, but at time t ₃ , the longitudinal acceleration reaches a predetermined value X _g0. The sensor 16 detects, and this detection signal is sent to the controller 20.
Entered in. Then, a signal for turning off the control signal Q is output from the controller 20, and accordingly, the solenoid valve of the rear wheel on the inner side of the turning center of the electromagnetic valves 13 and 14 is released, and the inner side of the turning center is released. The brake fluid pressure shown in b is supplied to the wheel cylinder of the rear side wheel. Therefore, the same brake fluid pressure is supplied to the left and right rear wheels 9 and 10, and the vehicle returns to the normal braking state. In the case of this example, X _g0 above is 0.5 G
Is set to.

Thus, as shown in the graph C ′ from time t ₃ ,
The yaw rate gently approaches zero, and braking ends at time t ₅ .

For comparison with the operation of the present invention described above, even if the longitudinal acceleration exceeds the predetermined value _Xg0 , the energization to the rear wheel on the inner side of the turning center is continued and the lateral acceleration is the predetermined value _Yg0. The change in the yaw rate when the energization of the solenoid valve is stopped for the first time when the following occurs is indicated by the broken line C ″ in the figure. In this case, the yaw rate greatly fluctuates toward the drift side at time t ₄ . Is observed.

Therefore, it is clear that if the energization of the solenoid valves of the rear wheels 9 and 10 is controlled only by the factor of the lateral acceleration, it is not possible to prevent a rapid drift of the vehicle.

Although the longitudinal acceleration sensor 16 is used as the vehicle braking state detecting means in this embodiment, the longitudinal acceleration sensor 15 is used.
Instead of change in brake fluid pressure or brake pedal 1
It is also possible to detect the braking state from the pedaling force of. Further, in the case of a vehicle equipped with an anti-skid device or a traction control system, it is possible to replace the solenoid valves provided in these devices with the solenoid valves 13 and 14 in the above-mentioned embodiment.

EFFECTS OF THE INVENTION As described in detail above, the vehicle brake fluid pressure control device according to the present invention provides the following operation effects. That is, during turning braking of the vehicle, when the turning state detecting means detects this and the detected value of the turning detecting means reaches a predetermined value, the brake fluid pressure of the wheel on the inner side of the turning center from the control means is outside the turning center. Since a signal that limits the brake fluid pressure to the wheels on the other side is output,
The spin moment of the wheel can be reduced.

Further, during the above-described operation, when the value detected by the braking state detecting means reaches a predetermined value or more and the vehicle is suddenly braked, the brake fluid pressure of the wheel on the inner side of the turning center is changed from the control means to the rear wheel on the outer side of the turning center. Since the signal for releasing the above restriction that lowers the brake fluid pressure is output to the left and right wheels, the same brake fluid pressure is supplied, the vehicle returns to the normal braking state, and the drift moment of the wheels is kept low. As a result, the behavior of the vehicle is stabilized, and the sudden braking operation required in an emergency can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a vehicle brake fluid pressure control device according to the present invention, FIG. 2 is a graph showing a relationship between a braking force applied to an automobile and a lateral force, and FIG. Schematic diagrams showing practical examples of braking and lateral force, FIGS. 4 and 5
FIG. 6 is a graph showing the relationship between the yawing moment and deceleration of the vehicle between the conventional example and the present invention, and FIG. 6 is a time chart showing an operation example of the present invention. 1 ... Brake pedal, 2 ... Master cylinder, 3 ...
Reservoir tank, 5,6,7,8 …… Brake pipe, 9 ……
Right rear wheel, 10 …… left rear wheel, 11 …… right front wheel, 12 …… left front wheel,
13,14 ... Solenoid valve, 15 ... Lateral acceleration sensor, 16 ... Longitudinal acceleration sensor, 20 ... Controller,

Claims (1)

[Claims] 1. A vehicle brake fluid pressure control device for independently controlling a brake fluid pressure applied to a wheel, a turning state detecting means for detecting a turning state of a vehicle, and a braking state detecting means for detecting a braking state of the vehicle. When the detected value of the turning state detecting means is equal to or more than a predetermined value, the brake fluid pressure of the wheel on the inner side of the turning center is restricted to be lower than the brake fluid pressure of the wheel on the outer side of the turning center, and In the case of sudden braking when the detection value of the braking state detection means reaches a predetermined value or more, the above-mentioned restriction that the brake fluid pressure of the wheel inside the turning center is made lower than the brake fluid pressure of the wheel outside the turning center is released. Then, the vehicle brake hydraulic pressure control device is provided with a control means for returning to a normal braking state.