JPH0534292Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brake device for a four-wheel drive vehicle that can prevent wheels from locking during braking.

[Prior Art] Wheel locking during braking of a four-wheel drive vehicle occurs when the wheel driving force is smaller than the braking force. Here, the wheel driving force is the sum of the engine driving force transmitted to the wheels and the road surface driving force due to friction between the road surface and the wheels. Therefore, in a four-wheel drive vehicle, brake lock occurs at the wheel with the smallest road friction force among the four wheels.

Since the four wheels of a four-wheel drive vehicle are mechanically connected via gears or the like, a one-wheel lock immediately becomes a four-wheel lock state. For this reason, four-wheel drive vehicles have the disadvantage that the four wheels can easily become locked due to the poorest road surface conditions among the four wheels, that is, a road surface with low frictional force, making it impossible to control the vehicle.

Therefore, in a part-time 4-wheel drive system or a full-time 4-wheel drive system with a center differential lock device, when the center differential lock is applied, the wheel speed of each of the four wheels is A 4-channel, 4-sensor anti-lock brake system has been proposed (Japanese Patent Application Laid-Open No. 1989-1999) that detects the brake fluid pressure on wheels that are likely to lock up and releases the brake fluid pressure to the wheels that are likely to lock up.
No. 143170).

[Problems to be Solved by the Invention] However, the conventional anti-lock brake system described above has a problem in that the mechanism is complicated and the cost is extremely high. Furthermore, in the early stages of braking, the vehicle continues to run without decelerating even though the brake pedal is depressed, giving the driver a sense of uneasiness or a feeling of empty running.

The present invention was devised to solve the problems of the prior art described above, and the purpose of the present invention is to prevent the wheels from locking with a simple structure and to provide a four-wheel system that eliminates the feeling of free running at the initial stage of braking. The purpose of the present invention is to provide a brake device for a driving vehicle.

[Means for solving the problem] The present invention has a sensor that detects the drive torque and brake fluid pressure of each wheel of a four-wheel drive vehicle, and a sensor that is installed in the power transmission system that transmits engine power to each wheel. An actuator for engaging and disengaging the clutch, and an engine throttle for engaging the clutch when a predetermined brake fluid pressure is reached and preventing the wheels from locking when the ratio of wheel drive torque/brake fluid pressure is below a predetermined value. It consists of a control unit that operates the tutle valve in the opening direction.

[Operation] When the ratio of wheel drive torque/brake fluid pressure in any of the four wheels is below a predetermined value, that is, when the wheels are locked or there is a risk of locking, the engine throttle valve is operated in the opening direction. (idle up) to actively increase the engine driving force transmitted from the engine to the wheels to prevent the wheels from locking.

[Examples] Examples of the present invention will be described in detail below based on the drawings.

FIG. 1 shows the overall structure of a brake system for a four-wheel drive vehicle according to the present invention. As shown in the figure, each of the four wheels 1 is provided with a torque sensor 2 for detecting the wheel drive torque, and the detection signals of these torque sensors 2 are input to a control unit 3. There is. The control unit 3 also includes a brake fluid pressure sensor 4,
A detection signal is also input from the vehicle speed sensor 5. Furthermore, the control unit 3 is connected to a clutch actuator 6 that connects and disconnects a clutch provided in a power transmission system that transmits engine power to each wheel 1, and a throttle valve actuator 7 that opens and closes a throttle valve of the engine. It is designed to output a control signal.

As the torque sensor 2 that detects the wheel drive torque, for example, as shown in FIGS. 2 and 3, there is a stroke sensor provided at the rotating end of a caliper 9 rotatably attached to the knuckle 8 at one point. 10 is used. When the disk 11 is grasped by the pad 12 in the caliper 9, the stroke of the stroke sensor 10 changes depending on the wheel drive torque, so the wheel drive torque is detected from the stroke of the stroke sensor 10. Stroke sensor 1
0 has a built-in spring 13 as shown in FIG. In addition, the torque sensor is attached to the strain cage 1 on the arm 14 of the knuckle 8, as shown in FIG.
5 may be provided to detect the wheel drive torque from the stress sensed by the strain cage 15.

Next, the operation of this embodiment will be explained according to the flowchart of FIG.

When braking, that is, the brake switch is ON
When the vehicle speed V at which brake lock becomes a problem is higher than the set speed V ₀ and the brake fluid pressure is higher than a, a control signal is output from the control unit 3 to the clutch actuator 6, and the control signal is outputted from the control unit 3 to the clutch actuator 6, and the clutch actuator 6 outputs a control signal to the clutch actuator 6. The clutch is connected. Then, the control unit 3 calculates the ratio of the wheel drive torque input from the torque sensor 2 of each wheel to the brake fluid pressure input from the brake fluid pressure sensor 4, and the wheel drive torque/brake fluid pressure for each wheel. When this ratio is less than a predetermined value b for any wheel, it is determined that the wheels are locked or there is a strong risk of wheel locking, and the throttle valve actuator 7 is operated to open the throttle valve. Outputs a control signal to control operation in the direction (idle up). This increases the engine drive torque from the engine to the wheels 1 and therefore the wheel drive torque. When the wheel drive torque/brake fluid pressure is still below b, a control signal is output to further open the throttle opening. When the wheel drive torque/brake hydraulic pressure is greater than b and the vehicle speed V is less than the set vehicle speed _V1 , a signal to disengage the clutch is sent to the clutch actuator 6 to disengage the clutch.

In this way, when the wheels lock or are about to lock, the engine drive torque transmitted from the engine to the wheels 1 is increased, so the wheel lock is released or avoided, improving the vehicle's attitude stability during braking. will improve. Furthermore, since the system increases the engine drive torque rather than decreasing the brake fluid pressure, there is no feeling of dry running during the initial braking period.

[Effects of the Invention] In summary, the present invention provides the following excellent effects.

(1) When the wheels lock or there is a risk of locking, the throttle valve is operated in the opening direction to increase the driving force transmitted from the engine to the wheels, thereby preventing the wheels from locking up. Since it is a throttle valve opening control method, it can be realized at low cost without complicating the mechanism.

(2) Also, unlike the conventional method that reduces brake fluid pressure, this method increases the engine's driving force, so there is no feeling of dry running during the initial braking period.

(3) Since the clutch is connected when a predetermined brake fluid pressure is reached, the increased engine drive torque can be reliably transmitted to the wheels regardless of the position of the clutch pedal.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing an embodiment of a brake device according to the present invention, Fig. 2 is a front sectional view of a torque sensor that detects wheel drive torque, and Fig. 3 is a side sectional view of the same torque sensor. Fig. 4 is a longitudinal sectional view of a stroke sensor used as the torque sensor in Fig. 2, Fig. 5 is a sectional view showing another example of a torque sensor for detecting wheel drive torque, and Fig. 6 is a diagram illustrating operation control of a brake device. It is a flowchart showing an example. In the figure, 1 is a wheel, 2 is a torque sensor, 3 is a control unit, 4 is a brake fluid pressure sensor, and 5 is a
is the vehicle speed sensor, 6 is the clutch actuator, 7
is the throttle valve actuator, 8 is the knuckle, 9 is the caliper, 10 is the stroke sensor, 1
1 is a disk, and 15 is a strain cage.

Claims (1)

[Scope of utility model registration request] A sensor that detects the drive torque and brake fluid pressure of each wheel of a four-wheel drive vehicle, an actuator that connects and disconnects a clutch installed in a power transmission system that transmits engine power to each wheel, and a predetermined brake fluid. and a control unit that connects a clutch when the pressure reaches a predetermined value and operates an engine throttle valve in the opening direction to prevent the wheels from locking when the ratio of wheel drive torque/brake fluid pressure is less than a predetermined value. Brake equipment for four-wheel drive vehicles.