JPH0811524B2 - 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 of an automobile, when sudden braking is applied while the vehicle is running, wheels are stuck (locked) on a road surface with a low friction coefficient between the tire and the road surface, 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 anti-skid device as described above is installed in the hydraulic pipe from the master cylinder to the wheel braking device when the wheel deceleration exceeds the set value θ ′ during sudden braking. The normally open type holding valve is closed to hold the braking fluid pressure, and the pseudo signal V _T which is lower than the wheel speed signal V _W by a constant ΔV and the descending slope θ is θ <θ ′ and the wheel speed is When the signal V _W crosses, after reducing the braking fluid pressure by operating the release valve that controls the fluid pressure passage to release the braking fluid pressure in the brake device of the wheel to the fluid pressure release tank using the pump function. The road friction coefficient is determined based on the state of wheel speed recovery due to the friction torque generated between the tire and the road surface, and the braking fluid pressure is repressurized based on the friction coefficient.

Also, when the part-time four-wheel drive vehicle is switched to the four-wheel drive side, the front and rear wheels are directly connected, and therefore the constraint condition that the sum of the left and right front wheel rotation speeds and the left and right rear wheel rotation speeds are equal is satisfied. It has anti-skid characteristics that even if one of the wheels is locked, it will be turned from the other wheels and it will not easily lock, and either the front wheel on either the left or right side When one rear wheel is about to lock at the same time, the wheel that is about to lock due to road surface conditions, front and rear wheel load distribution and braking force distribution, etc. is connected to the wheel by rotating the differential gear and the opposite wheel. And may be turned in the opposite direction by the drive shaft from the engine.

The present invention is intended to provide a braking hydraulic pressure control method that allows accurate braking to be performed in either two-wheel drive or four-wheel drive.

Means for Solving the Problems The present invention relates to an anti-skid device for a hydraulic brake system for an automobile, which detects fluctuations in wheel speed of each wheel belonging to the same hydraulic piping system during braking and controls the braking hydraulic pressure, and 2 In a vehicle equipped with a part-time four-wheel drive mechanism capable of switching between four-wheel drive and four-wheel drive, the braking hydraulic pressure control for each wheel belonging to the same hydraulic piping system is performed for two-wheel drive. It is characterized in that it is configured to be performed based on an average value of the wheel speeds of the above-mentioned wheels during four-wheel drive, which is performed based on the lower one of the speeds.

Action The present invention adopts the above-described configuration, and the braking fluid is generated by the internal circulation torque generated based on the constraint condition of the direct-coupled four-wheel drive system when the part-time four-wheel drive mechanism is switched to the four-wheel drive side. It is possible to prevent the timing of pressure holding and pressure reduction from being advanced.

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, and when the brake pedal 1 is depressed, the master cylinder 2 is actuated, and the brake device 3a for the right front wheel 3 and the brake for the left rear wheel 6 are provided from one cross pipe A. The brake fluid pressure is supplied to the wheel cylinder of the device 6a, and the brake fluid pressure is supplied from the other cross pipe B to the wheel cylinders of the brake device 4a of the left front wheel 4 and the brake device 5a of the right rear wheel 5 to apply the brake. It is like this.

Numeral 7 is a proportioning valve interposed in the pipes to the brake devices on the rear wheels of both of the above cross pipes A and B. When the brake pedal 1 is depressed by the proportioning valve 7, the braking fluid pressure on the front wheels is increased. On the other hand, the braking fluid pressure on the rear wheel side is controlled so that the rate of increase is lower than a certain point, and when the front wheel is locked, the rear wheel is not yet locked. It is designed to prevent irregular rotation (swinging phenomenon) due to locking.

Actuators 8a and 8b for controlling the braking fluid pressure are respectively installed in both of the cross pipes A and B,
The actuators 8a and 8b detect the depression of the brake pedal 1 and output a signal, and a signal from a brake pedal switch 9 and a wheel speed sensor 3b for the front wheels 3 and 4,
4b and the pressurization of the control circuit 10 for issuing a brake hydraulic pressure increase / decrease signal for each hydraulic pipe system based on the wheel speed signals V _W output from the wheel speed sensors 5b, 6b of the rear wheels 5 and 6, It is designed to be controlled by the pressure reduction signal.

That is, the control circuit 10 controls the wheel speed sensors 3b of the right front wheel 3 and the left rear wheel 6 belonging to the same hydraulic piping system, for example, the cross piping A system, as shown in the speed signal diagram of FIG.
Both wheel speed signals V _WR from 6b, select wheel speed signal V _WR lower of the V _WL to (low-select), the reduction rate of the low-select to the wheel speed signal V _WR (i.e. deceleration of the wheel (Equivalent) becomes larger than the set value θ, for example, −2 g, the holding valve (not shown) in the actuator 8a is closed to supply the braking fluid pressure from the master cylinder 2 to the right front wheel braking device 3a and the left rear wheel braking device 6a. By shutting off and holding the braking fluid pressure at that time (Fig. 2, holding valve operation diagram,
Predetermined speed dotted shown) braking (vehicle speed signal V _V which is set to the maximum value of each wheel speed signal in the breaking point) decreases the initial value and a predetermined deceleration example -1.1g in the brake fluid圧図When the low-selected wheel speed signal V _WR falls below the pseudo signal V _T which follows at a value lower by the difference ΔV, the pressure reducing valve (not shown) in the actuator 8a is opened to open the right front wheel braking device 3a and the left rear wheel. Reduce the braking fluid pressure held in the braking device 6a (dotted line in FIG. 2 pressure reducing valve operation diagram, braking fluid pressure diagram),
When the wheel speed signal V _WR reaches a low peak value due to the reduction of the braking fluid pressure, the pressure reduction of the braking fluid pressure is stopped to make the braking fluid pressure constant, and then the wheel speed signal V _WR is reduced due to the friction between the wheel and the road surface. When increasing and reaching a high peak value, the holding valve in the actuator 8a is intermittently opened to increase the braking fluid pressure stepwise, and the same operation as above is repeated based on the subsequent wheel speed signal. There is.

Front wheel 4 and right rear wheel 5 belonging to the other cross piping system B
The control circuit 10 is configured to operate in the same manner as for the cross pipe A system with respect to the wheel speed signals from the wheel speed sensors 4b and 5b.

Part time 4 in which the conventional anti-skid device configured as described above can be used by switching between two-wheel drive and four-wheel drive.
When applied to a four-wheel drive vehicle, when the four-wheel drive is used, the left and right front wheels and the left and right rear wheels, which are respectively coupled via a differential gear device, are directly connected to the engine through a drive shaft, and therefore the rotational speed of the left and right front wheels is reduced. Since the constraint condition that the sum is equal to the sum of the rotational speeds of the left and right rear wheels must be satisfied, the wheel on the side with the larger sum of rotational speeds tries to turn the wheel on the side with the smaller sum of rotational speeds in the front and rear. Creates a circulating torque.

The internal circulating torque the wheel speed signals V _WR which is low-select as a reference for controlling the brake fluid pressure, wheel 3 wheel speed signal V _WR is issued belongs to the side the sum of the rotational speed is greater The brake fluid pressure is held or reduced early if sufficient reduction is performed. It will not be effective.

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 a four-wheel drive changeover switch 11 for four-wheel drive. When the four-wheel drive is switched to the side, the average value of the wheel speed signals from the wheel speed sensors of the wheels belonging to the same hydraulic piping system is obtained, and the braking hydraulic pressure is controlled based on the average value of the wheel speed signals. It is characterized by that.

That is, when the four-wheel drive changeover switch 11 is changed over when the two-wheel drive is changed over, the four pressure-reducing valve operation diagrams, the holding valve operation diagram, and the braking fluid pressure diagram follow the processes indicated by the dotted lines. When the drive changeover switch 11 is switched to the four-wheel drive side, both wheel speed signals V _WR and V _WL from the wheel speed sensors 3b and 6b of the right front wheel 3 and the left rear wheel 6 as shown in FIG. 2 speed signal diagram. When the rate of decrease of the average value V _M of the actuators exceeds the set value θ and becomes large, the holding valve (not shown) in the actuator 8a is closed to hold the braking fluid pressure (see the operation of the holding valve in FIG. 2 and the solid line in the braking fluid pressure chart). ), Pseudo signal V _T
When the average value V _{M of the} wheel speed signals V _WR and V _WL falls below, the pressure reducing valve (not shown) in the actuator 8a is opened to reduce the braking fluid pressure (see Fig. 2 pressure reducing valve operation diagram, braking fluid pressure diagram (Shown by a solid line), when the average value V _M reaches a low peak value due to the pressure reduction of the brake fluid pressure, the pressure reduction of the brake fluid pressure is stopped to keep the brake fluid pressure constant, and then the average value is obtained due to friction between the wheel and the road surface. When the value V _M starts to increase and reaches a high peak value, the holding valve in the actuator 8a is intermittently opened to increase the braking fluid pressure stepwise, and then the average value of the wheel speed signals V _WR and V _WL . It is configured to repeat the same operation as above based on V _M.

In the above embodiment, the example applied to the cross pipe type two-system braking device was described, but it is needless to say that it may be applied to the two-system braking device divided into the left and right front wheels and the left and right rear wheels.

EFFECTS OF THE INVENTION As described above, according to the present invention, an anti-skid device for a hydraulic braking system for an automobile, which detects a variation in wheel speed of each wheel belonging to the same hydraulic piping system during braking and controls the braking hydraulic pressure, and In a vehicle equipped with a part-time four-wheel drive mechanism capable of switching between two-wheel drive and four-wheel drive, control of braking hydraulic pressure for each wheel belonging to the same hydraulic piping system is performed.
Part-time four-wheel drive is configured by performing the two-wheel drive based on the lower wheel speed of the wheels and the four-wheel drive based on the average value of the wheel speeds of the wheels. It is possible to prevent the timing of holding and reducing the braking fluid pressure from being accelerated by the internal annular torque generated based on the constraint conditions of the direct-coupled four-wheel drive system when the mechanism is switched to the four-wheel drive. In this case, accurate braking can be performed even when the vehicle is driven or when the vehicle is driven by four wheels, and it is possible to bring about a great practical effect in combination with the simple structure.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 shows a braking fluid pressure system and a control system diagram, and FIG. 2 shows variations in various speed signals and pressure reducing valve operation, holding valve operation, and braking fluid pressure fluctuation. It is a time chart which shows a relation. 1 ... Brake pedal, 2 ... Master cylinder, 3,4 ...
… Front wheel, 5,6 …… Rear wheel, 7 …… Proportioning valve, 8a, 8b …… Actuator, 9 …… Brake pedal switch, 10 …… Control circuit, 11 …… 4-wheel drive selector switch.

Claims (1)

[Claims] 1. An anti-skid device, a two-wheel drive, and a four-wheel drive for a hydraulic brake system for an automobile, which detects a variation in wheel speed of each wheel belonging to the same hydraulic piping system during braking and controls the braking hydraulic pressure. In a vehicle equipped with a part-time four-wheel drive mechanism capable of switching between two wheels, the control of the braking hydraulic pressure for each wheel belonging to the same hydraulic piping system is carried out when the two wheels are driven, and the lower wheel speed of the respective wheels is used. A braking hydraulic pressure control method for a hydraulic braking system for an automobile, characterized in that it is configured to be performed based on an average value of wheel speeds of the respective wheels when four wheels are driven based on speed.