JPH0811525B2 - Braking hydraulic pressure control method for hydraulic braking system for automobile - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking hydraulic pressure control method for an automotive hydraulic braking device.

2. Description of the Related Art In a brake system for an automobile, when sudden braking is applied while the vehicle is running, wheels are stuck (locked) on a road surface where the friction coefficient between the tire and the road surface is low, causing slippage or irregular rotation ( There is a case of swinging. In order to prevent this, an anti-skid device that detects a slip or irregular rolling state (wheel lock) in advance and controls the brake fluid pressure of the brake device based on the detected signal has already been developed (for example, Japanese Patent Application Laid-Open No. No. 60-61354).

A part-time four-wheel drive vehicle capable of switching between two-wheel drive and four-wheel drive has been conventionally developed (see, for example, Japanese Utility Model Publication No. 55-54573) and is already in general use.

Problems to be Solved by the Invention The above-described anti-skid device is provided in the hydraulic pipe extending from the master cylinder to the brake device of the wheel when the deceleration of the wheel exceeds a predetermined value during sudden braking and becomes large. The normally open type holding valve is closed to hold the brake fluid pressure, and when the wheel speed decreases to a certain point, the brake fluid pressure in the brake device of the wheel is released to the fluid pressure release tank using the pump mechanism. The release valve that controls the passage is operated to reduce the braking fluid pressure, and then the friction coefficient of the road surface is determined based on the recovery condition of the wheel speed due to the friction torque generated between the tire and the road surface, and the braking fluid pressure is reapplied based on the friction coefficient. It is configured to exert pressure.

In a part-time four-wheel drive vehicle equipped with the conventional anti-skid device as described above, the front and rear wheels are directly connected when switching to the four-wheel drive side, so the sum of the left and right front wheel rotation speeds and the left and right rear wheel rotations. Since the constraint condition that the sum of the numbers is equal must be satisfied, frequent pulsation of the wheel speed is caused by the transmission of the driving force or the braking force (internal circulation torque) from the wheel on the opposite side in the front-rear direction. Operations such as holding the brake fluid pressure, depressurizing, and repressurizing are frequently repeated to cause vibrations in the vehicle body and to make the anti-skid control unstable.

Means for Solving the Problems According to the present invention, during braking, the braking fluid pressure of the brake device of the wheel is reduced and then increased in accordance with the change of the wheel speed based on the wheel speed information from the wheel speed sensor. In a part-time four-wheel drive vehicle equipped with an anti-skid device that performs braking hydraulic pressure control with a control pattern that repeats the control described above,
A first pseudo vehicle body speed that is lower than the vehicle body speed and a second pseudo vehicle body speed that is lower than the first pseudo vehicle body speed are created and set with respect to the vehicle body speed during braking, and at the time of four-wheel drive, the first pseudo vehicle body speed is set. It is characterized in that the braking hydraulic pressure is controlled by ignoring the wheel speed information between the vehicle speed and the second simulated vehicle speed.

Action The present invention adopts the control method as described above,
It is possible to prevent the brake fluid pressure from being frequently interrupted and the pressure reducing operation to be frequently performed due to the frequent pulsation of the wheel speed based on the internal circulation torque at the time of wheel drive, and to enable stable control of the anti-skid device.

Embodiments The present invention will be described with reference to the accompanying drawings.

In FIG. 1, 1 is a brake pedal, 2 is a master cylinder, 3 is a reservoir tank for supplying brake fluid to the master cylinder 2, 4 is a brake device provided for each wheel (only one wheel is shown, and the other is omitted). 5 is a hydraulic pipe extending from the master cylinder 2 to the brake device 4, 6 is a holding valve which is interposed in the hydraulic pipe 5 and is closed when the solenoid is energized, and 7 is downstream of the holding valve 6. Is a release valve which is interposed in a bypass hydraulic pipe 8 which branches from the hydraulic pipe 5 on the side to reach the upstream side of the holding valve 6 and which opens when the solenoid is energized. A reservoir 9 for temporarily storing the brake fluid in the brake device 4 and the reverser 9 are provided in the pressure pipe 8 when the release valve 7 is opened.
A hydraulic pump 10 that stores the brake fluid stored in the accumulator 11 and a relief valve 12 that opens when the braking fluid pressure in the accumulator 11 is equal to or greater than a predetermined value are interposed, and between both ends of the holding valve 6. Is provided with a differential pressure valve 13 that operates when the braking fluid pressure on the downstream side of the holding valve 6 becomes lower than the braking fluid pressure on the upstream side and closes the hydraulic piping between the holding valve 6 and the master cylinder 2. Has been.

14 is a wheel speed sensor provided on each wheel, 15 is a brake pedal switch, 16 is a control circuit, and the control circuit 16 controls the reduction rate of the wheel speed signal V _W of the vehicle speed sensor 14 as shown in FIG. Corresponds to the deceleration of) is a set value θ ′, for example −
A signal for closing the holding valve 6 is output at the braking fluid pressure cutoff point a exceeding 2 g to shut off the supply of the braking fluid pressure from the master cylinder 2 to the brake device 4 to maintain the braking fluid pressure at that time. , The vehicle speed signal V _V set to decrease with a predetermined deceleration θ, for example, −1.1 g, with the maximum value of each wheel speed signal V _W at the time of braking when the brake pedal is depressed as an initial value.
The release valve 7 is opened at a braking hydraulic pressure release point b where the wheel speed signal V _W is below the first pseudo vehicle speed signal V _T, which is multiplied by a predetermined value less than 0.9, for example, and which follows the vehicle speed signal V _V. A signal is output to release the brake fluid of the brake device 4 to the reservoir 9 to reduce the braking fluid pressure, and the wheel pressure signal V _W reaches the minimum value during the transition from the decrease to the increase due to the reduction of the brake fluid pressure. When the signal for closing the release valve 7 is output at the lowest point c, the pressure reduction of the brake fluid pressure is stopped to make the brake fluid pressure constant, and then the wheel speed signal V _W recovers to the vicinity of the vehicle body speed signal V _V. After the highest point d, a signal for intermittently opening the holding valve 7 is output to gradually increase the braking fluid pressure, and the same operation as described above is repeated based on the subsequent wheel speed signal V _W.

In a vehicle equipped with the conventional anti-skid device configured as described above and a part-time four-wheel drive mechanism capable of switching between two-wheel drive and four-wheel drive, the present invention provides the first pseudo vehicle body speed signal V _T. In addition, the vehicle body speed signal V _V is multiplied by another predetermined value less than 1 such as 0.95 to follow the vehicle body speed signal V _V, and the second lower value is lower than the first pseudo vehicle body speed signal V _T. sets the estimated vehicle speed signal V _TV, at the time of four-wheel drive and the first estimated vehicle speed signal V _T lowest and highest values of the wheel speed signal V _W which is generated between the second estimated vehicle speed signal V _TV It is characterized in that the brake hydraulic pressure control operation is performed ignoring the above.

That is, when the part-time four-wheel drive mechanism is used by switching to the four-wheel drive side, the left and right front wheels and the left and right rear wheels, which are respectively coupled via the differential gear device, are directly connected to the engine via the drive shaft. Therefore, the constraint condition that the sum of the left and right front wheels and the sum of the left and right rear wheels are equal must be satisfied. It creates an internal circulating torque that tends to turn the wheels.

Thus anti-skid device which is adapted to control the detected and brake fluid pressure fluctuations in the wheel speeds, the holding valve operation to variations in the wheel speed signals V _W when switched part-time four-wheel drive mechanism in two-wheel drive side And the operation status of the pressure reducing valve is as shown in FIG.
When switched to the four-wheel drive side, the wheel speed signal V _W reaches the true lowest point c while repeating small pulsations as shown in the speed signal diagram of FIG.
After that, the true maximum point d is reached while repeating small pulsations, and in the conventional case, the body vibration is caused by the repeated pressurization and depressurization due to the small pulsations.

In the present invention, the lowest points c ₁ and c ₂ and the highest points d ₁ and d ₂ generated within the range sandwiched between the first pseudo vehicle speed side signal V _T and the second pseudo vehicle body speed signal V _TV are ignored. Therefore, it is possible to prevent the vibration of the vehicle body due to the frequent stop and repressurization of the braking hydraulic pressure.

In the above embodiment, the example in which the fluctuation of the wheel speed is detected for each wheel and the braking hydraulic pressure is controlled for each wheel has been described, but the present invention is applied to a braking device having a two-system piping system such as a cross piping system. Of course, you can do that.

Further, it goes without saying that the first pseudo vehicle body speed signal and the second pseudo vehicle body speed signal may be obtained by subtracting different predetermined values from the vehicle body speed during braking.

EFFECTS OF THE INVENTION As described above, according to the present invention, a part-time four-wheel vehicle equipped with an anti-skid device for a hydraulic braking system for an automobile, which detects fluctuations in wheel speed of each wheel during braking and controls the braking hydraulic pressure. In the driving vehicle, when the first pseudo vehicle body speed lower than the vehicle body speed during braking and the second pseudo vehicle body speed lower than that are created and set, and the part-time four-wheel drive mechanism is switched to the four-wheel drive side, By controlling the braking fluid pressure by ignoring the minimum and maximum values of the wheel speed generated between the first and second pseudo vehicle body speeds, the wheel speed is controlled by the internal circulation torque during four-wheel drive. Prevents abnormal vibration of the vehicle body by eliminating frequent depressurization stop and re-pressurization of the braking fluid pressure due to the pulsation in a small width and controlling the braking fluid pressure at the minimum value and the maximum value during the small pulsation of the wheel speed. Can also Therefore, in combination with the simple structure, it can bring a great effect in practical use.

Further, a small pulsation of the wheel speed is also generated by unsprung resonance during traveling on a bad road, but according to the present invention, when the vehicle is traveling on such a bad road (normally, four-wheel drive is used on a bad road). It is possible to prevent irregular pressurization / depressurization control caused by the pulsation of the wheel speed, which is extremely effective.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a braking hydraulic pressure system and control system diagram, and FIG. 2 is a vehicle speed signal, wheel speed signal, first and second simulated vehicle speed signals, etc. FIG. 3 is a time chart showing the relationship between the fluctuation of the speed signal and the operation of the pressure reducing valve and the operation of the holding valve, and FIG. 1 …… Brake pedal, 2 …… Master cylinder, 4 ……
Brake device, 5 ... hydraulic piping, 6 ... holding valve, 7
…… Release valve, 8 …… Bypass hydraulic piping, 9 …… Reservoir, 10 …… Hydraulic pump, 11 …… Accumulator, 12 ……
… Relief valve, 13 …… Differential pressure valve, 14 …… Wheel speed sensor, 15 …… Brake pedal switch, 16 …… Control circuit.

Claims (1)

[Claims] 1. A control pattern in which during braking, based on wheel speed information from a wheel speed sensor, control is repeated to reduce and then increase the braking hydraulic pressure of a brake device for a wheel in accordance with changes in the wheel speed. In a part-time four-wheel drive vehicle equipped with an anti-skid device that controls the braking hydraulic pressure,
A first pseudo vehicle body speed that is lower than the vehicle body speed and a second pseudo vehicle body speed that is lower than the first pseudo vehicle body speed are created and set with respect to the vehicle body speed during braking, and at the time of four-wheel drive, the first pseudo vehicle body speed is set. And a second pseudo vehicle body speed, ignoring wheel speed information to control the braking hydraulic pressure, and a braking hydraulic pressure control method for an automotive hydraulic braking device.