JP2757256B2 - Brake hydraulic pressure control method for hydraulic brake system for automobile - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake hydraulic pressure control method for a hydraulic brake system for an automobile. 2. Description of the Related Art In a braking device for an automobile, when sudden braking is applied during running of a vehicle, wheels are stuck (locked) on a road surface having a low friction coefficient between a tire and a road surface to cause slipping or irregular rolling ( Ass). In order to prevent this, an anti-skid device has been developed which detects a slipping state or a turning state (wheel lock) in advance and controls the brake fluid pressure of the braking device based on the detected signal (for example, Japanese Patent Application Laid-Open No. 60-1985). -61354). A part-time four-wheel drive vehicle capable of switching between two-wheel drive and four-wheel drive has been developed (see, for example, Japanese Utility Model Publication No. 5554573) and is already in general use. Problems to be Solved by the Invention The anti-skid device as described above is interposed in the hydraulic pipe from the master cylinder to the wheel brake device when the deceleration of the wheel exceeds a set value during sudden braking. A normally closed type holding valve is closed to hold the brake fluid pressure, and when the wheel speed is reduced to a certain level, the hydraulic fluid in the brake device of the wheel is released to a fluid pressure release tank by using a pump mechanism. A release valve for controlling the pressure passage is actuated to reduce the brake fluid pressure. Thereafter, the friction coefficient of the road surface is determined based on the recovery state of the wheel speed based on the friction torque generated between the tire and the road surface, and the brake fluid pressure is reset based on the friction coefficient. It is configured to apply pressure. When the conventional anti-skid device as described above is applied to a part-time four-wheel drive vehicle, when switching to the four-wheel drive side, the front and rear wheels are directly connected. Since the constraint condition that the sum of the rotation speeds is equal to that of the vehicle must be satisfied, the driving force or the braking force can be transmitted (internal circulating torque) from the opposite wheel in the front-rear direction. Causes a problem that the anti-skid control is not properly performed. The present invention relates to a copper pressure control method for minimizing the influence of the internal circulation torque as described above. Means for Solving the Problems The present invention directly connects an anti-skid device and a front and rear wheel drive mechanism of an automotive hydraulic braking device that detects fluctuations in wheel speed of each wheel during braking and controls braking hydraulic pressure. In an automobile equipped with a four-wheel drive mechanism capable of switching and using the direct-coupled four-wheel drive, the main control system including the wheels at one diagonal position on the plane is used as the main control system during the direct-coupled four-wheel drive. Of the wheels that belong, the wheel with the lower initial wheel speed is selected as the reference wheel, and the fluctuation of the wheel speed of the reference wheel is detected to control the brake fluid pressure of each wheel that belongs to the main control system. The slave control system composed of the wheels at diagonal positions opposite to the main control system is at least a magnitude relationship between the wheel speeds of the wheels belonging to the slave control system and the wheel speed of the reference wheel of the main control system. Fluctuations such as wheel speed change rate The control of the brake fluid pressure of each wheel belonging to the slave control system is performed in accordance with the increase or decrease of the vehicle speed. Function The present invention adopts the above-described configuration, and when the part-time four-wheel drive mechanism is switched to the four-wheel drive side, the sum of the rotation speeds of the left and right front wheels and the sum of the rotation speeds of the left and right rear wheels are more than a certain distance apart. Can be prevented, and the effect of the internal circulation torque can be reduced. 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, and when the brake pedal 1 is depressed, the master cylinder 2 is operated. 4
The brake hydraulic pressure is supplied to the wheel cylinders of the brake device 5a of the left front wheel 5 and the brake device 6a of the right rear wheel 6 while the right front wheel brake device and the left rear wheel brake device (both are shown) from the other hydraulic pressure pipe 7. (Omitted) The brake fluid pressure is supplied to the wheel cylinder to apply the brake. Reference numeral 8 denotes a hydraulic pipe branched from the one hydraulic pipe 4 to the left front wheel brake device 5a, 9 is a holding valve interposed in the hydraulic pipe 8 and closed when the solenoid is energized, and 10 is a holding valve. A release valve that is interposed in a bypass pipe 11 that branches off from the hydraulic pressure pipe 8 on the downstream side by the holding valve 9 and reaches the upstream side of the holding valve 9 and that opens when the solenoid is energized;
A release valve 10 is connected to a bypass pipe 11 downstream of the release valve 10.
A reservoir 12 for temporarily storing the brake fluid in the left front wheel brake device 5a when opened, a hydraulic pump 13 for storing the brake fluid stored in the reservoir 12 in the accumulator 14, and a brake fluid pressure in the accumulator 14 which is equal to or higher than a predetermined value. The relief valve 15 which is opened when the
When the brake fluid pressure on the downstream side of the holding valve 9 becomes lower than the brake fluid pressure on the upstream side, the holding valve 9 is activated.
Differential pressure valve that closes the hydraulic line between the master cylinder 2
16 are provided. 17 is a hydraulic pipe branching from the one hydraulic pipe 4 and reaching the right rear wheel brake device 6a, 18 is a holding valve interposed in the hydraulic pipe 17, and 19 is a downstream side of the holding valve 18. A differential pressure valve 21 is provided between both ends of the holding valve 18 and is a release valve interposed in a hydraulic pressure pipe 20 branched from the hydraulic pressure pipe 17 and reaching the reservoir 12. 5b and 6b are wheel speed sensors for the front left wheel 5 and the rear right wheel 6, 22 is a brake pedal switch for detecting that the brake pedal 1 is depressed and outputting a signal, 23 is a control circuit, and 23 is a control circuit. the holding valve 9 when the reduction rate at the time of braking of the wheel speed signals V _W exceeds the set value theta 'example -2g as shown in FIG. 3 from each wheel separately e.g. wheel speed sensor 5b for the left front wheel 5 Close holding the brake fluid pressure at that time to interrupt the supply of the brake fluid pressure to the left front wheel 5a from the master cylinder 2 and outputs a signal, for each wheel speed signal V _W during braking the brake pedal 1 is depressed pseudo signal V _T the left front wheel to follow the maximum value at an initial value to a predetermined speed △ V for example 5K / mh only low value vehicle speed signal V _V which is set to decrease at a predetermined deceleration example -1.1g 5 wheel speed sensor accumulator 5b To release the reservoir 12 to reduce the pressure of the brake fluid pressure of the brake fluid in the left front wheel brake device 5a outputs a signal for opening the relief valve 10 when the wheel speed signal V _W is below the, by vacuum of the braking pressure discontinue minimum value and outputs a signal to close the release valve 10 when it reaches the vacuum of the brake fluid pressure between the wheel speed signal V _W is moved from decreasing to increasing the brake fluid pressure is constant, then the wheel and the road surface by friction braking to output intermittently open signal to duty ratio retaining valve 9 recovered to vehicle speed signal V _V vicinity increased wheel speed signal V _W is is proportional to the acceleration of the left front wheel 5 with Increasing the fluid pressure step by step, and then the wheel speed signal
Based on the variation of V _W is configured to repeat the same operation as described above. Although not shown, the hydraulic pressure pipe 7 to the right front wheel brake device and the left rear wheel brake device also has the same holding valve, release valve, hydraulic pump, differential valve as the left front wheel brake device and the right rear wheel brake device. Needless to say, a pressure valve is provided and the control circuit 23 controls the brake hydraulic pressure holding, pressure reduction and re-pressurization in the same manner. The present invention relates to a two-wheel drive in an automobile having a conventional anti-skid device having the above-described structure and a part-time four-wheel drive mechanism capable of switching between two-wheel drive and four-wheel drive using a drive system changeover switch 24. Sometimes, the control of the brake fluid pressure is performed by detecting the fluctuation of the wheel speed for each wheel, and the main control system composed of the wheels at one diagonal position on the plane at the time of the four-wheel drive is the main control system belonging to the main control system. Of the wheels, a wheel having a lower initial wheel speed is selected as a reference wheel, and a change in wheel speed of the reference wheel is detected to control brake fluid pressure of each wheel belonging to the main control system. A sub-control system composed of wheels at diagonal positions opposite to the main control system is used to determine the magnitude relationship between the wheel speeds of the wheels belonging to the sub-control and the fluctuation of the wheel speed of the reference wheel of the main control system, for example, a wheel. Depending on the increase or decrease in speed change rate It is characterized in that configured to perform the control of each wheel brake fluid pressure belonging to the control system. That is, in the two-wheel drive mode in which the drive system changeover switch 24 is switched to the two-wheel drive side, similar to the conventional anti-skid device which detects the fluctuation of the wheel speed for each wheel and controls the brake fluid pressure for each wheel. Is controlled. At the time of four-wheel drive in which the drive system changeover switch 24 is switched to the four-wheel drive side, a combination of wheels at diagonal positions on a plane, for example, a system consisting of a right front wheel and a left rear wheel is used as a main control system. A combination of wheels located at opposite diagonal positions to the system, for example, a system consisting of a front left wheel and a rear right wheel is set as a slave control system, and controls as described below. For the main control system, the control circuit 23 selects a wheel that issues a lower wheel speed signal in the initial stage of braking from both wheel speed signals from the right front wheel and left rear wheel speed sensors (not shown) ( Low select) to use it as a reference wheel. Based on the fluctuation of the wheel speed signal of the reference wheel, the brake fluid of each wheel belonging to the main control system is applied to the brake device in the same manner as in the conventional anti-skid device. Pressure control is performed. For the left front wheel 5 and the right rear wheel 6 which are the slave control systems,
The control circuit 23 changes as shown in the velocity signal diagram of the wheel speed signals V _WF and V _WR is braked, for example, a second view of the wheel speed sensor 5b and 6b of the left front wheel 5 and the right rear wheel 6, the Assuming that the speed change of the wheel speed signal of the reference wheel of the main control system changes as shown in the reference wheel acceleration / deceleration signal diagram of FIG. 2, the lower one of the left front wheel 5 and the right rear wheel 6 at the beginning of braking. the left front wheel 5 that emits a speed signal V _WF and a main control wheel in accordance control system, select each right rear wheel 6 that emits a wheel speed signal V _WR of higher as slave control wheel in accordance control system. Then, the control circuit 23, to the left front wheel 5 is the main control loop, when the reduction rate of the wheel speed signals V _WF during braking which exceeds the set value theta 'example -2 g, brake system of the left front wheel 5 Main control wheel holding valve 9 for controlling the brake fluid pressure of 5a
Is output from the master cylinder 2 to the left front wheel 5
The supply of the brake fluid pressure to the brake device 5a is interrupted to maintain the brake fluid pressure at that time. Then, the left front wheel 5 the pseudo signal V _T to follow only low predetermined speed removed by ΔV to the vehicle speed signal V _V
When the wheel speed signal _VWF falls below, the main control wheel release valve 10 is opened and a signal is output to release the brake fluid of the left front wheel 5 to the reservoir 12 to reduce the brake fluid pressure. Due to the decrease in the brake fluid pressure, the reduction rate of the wheel speed signal _VWF of the left front wheel 5 becomes gradually smaller. In addition, the control circuit 23 for the right rear wheel 6 which is a slave control wheel in the slave control system, reduces the wheel speed of the reference wheel by reducing the brake fluid pressure in the brake device of the reference wheel of the master control system. Changes from an increase to a decrease (when the point a in the reference wheel acceleration / deceleration signal _{F in} FIG. 2 is reached), the secondary control provided in the hydraulic pressure pipe 17 to the brake device 6a of the right rear wheel 6 A signal for closing the wheel holding valve 18 is output, and the supply of the brake fluid pressure from the master cylinder 2 to the brake device 6a of the right rear wheel 6 is interrupted to maintain the brake fluid pressure at that time. When the wheel speed of the right rear wheel 6 gradually decreases due to the holding of the braking pressure of the right rear wheel 6, and the wheel speed signal V _WR falls below the wheel speed signal V _WF of the left front wheel 5 which is the main control wheel ( When the point b in the speed signal diagram of FIG. 2 is reached), a signal is output to close the main control wheel release valve 10 for controlling the brake hydraulic pressure of the left front wheel 5, which is the main control wheel, to reduce the brake hydraulic pressure. At the same time, the signal for opening the secondary control wheel release valve 19 for controlling the braking hydraulic pressure of the right rear wheel 6 which is the secondary control wheel is output to output the right rear wheel 6
The brake fluid in the brake device 6a is released to the reservoir 12 to reduce the brake fluid pressure. On the other hand, the reference wheel of the main control system, which is controlled independently,
Vacuum In conjunction to the brake fluid pressure in the brake system of the reference wheel, while the friction wheel speed approaches the increased vehicle speed V _V by the wheels and the road surface, the rate of increase in the wheel speed at this time is increased When it starts to decrease (when it reaches the point c in the reference wheel acceleration / deceleration signal _F diagram in FIG. 2), the control circuit 23
Is a signal for intermittently opening the main control wheel holding valve 9 for controlling the brake hydraulic pressure of the left front wheel 5, which is the main control wheel of the slave control system, so that its duty ratio is proportional to the acceleration of the reference wheel of the main control system. A signal for outputting the brake fluid pressure of the brake device 5a of the left front wheel 5 in a stepwise manner and closing the slave control wheel release valve 19 for controlling the brake fluid pressure of the right rear wheel 6, which is the slave control wheel of the slave control system. And the reduction of the brake fluid pressure in the brake device 6a of the right rear wheel 6 is stopped. Migration and to reduce the increase in the wheel speed signals V _WF by gradual pressurization of the brake fluid pressure of the left front wheel 5 is the main control loop, the vacuum withdrawal of the brake fluid pressure of the right rear wheel 6 is slave control wheel by the gradual increase of the wheel speed signals V _WR accompanied, (when it reaches the point d in the rate signal diagram of FIG. 2) when the V _WR is caught up with the V _WF, the control circuit 23 is a main control wheel left A signal for opening the main control wheel holding valve 9 for controlling the brake fluid pressure of the front wheel 5 is output to re-pressurize the brake fluid pressure of the left front wheel 5 and to control the brake fluid pressure of the right rear wheel 6 which is a slave control wheel. Secondary wheel holding valve
A signal for intermittently opening the duty ratio 18 so that its duty ratio is proportional to the acceleration of the reference wheel of the main control system is output to gradually increase the brake fluid pressure of the brake device 6a of the right rear wheel 6. Thereafter, the same operation as described above is performed based on the two wheel speed signals V _WF and V _WR of the left front wheel 5 which is the main control wheel and the right rear wheel 6 which is the slave control wheel, and the acceleration / deceleration signal _F of the reference wheel of the main control system. Is repeated to control the slave control system. In the above, the operation of the brake fluid pressure control device of the slave control system including the master control wheel holding valve 9, the master control wheel release valve 10, the slave control wheel holding valve 18, the slave control wheel release valve 19, and the hydraulic pump 13 The mode is as shown in the operation diagram of the main control wheel holding valve, the operation diagram of the main control wheel release valve, the operation diagram of the slave control wheel holding valve, the operation diagram of the slave control wheel release valve, and the operation diagram of the hydraulic pump in FIG. Fluctuations in the brake fluid pressure applied to the brake devices of the main control wheels and the slave control wheels of the slave control system are as shown in the brake fluid pressure diagram of FIG. Effect of the Invention As described above, according to the present invention, an anti-skid device, a two-wheel drive, and a four-wheel drive of a hydraulic brake system for a vehicle that controls a brake hydraulic pressure by detecting a change in wheel speed of each wheel during braking. In an automobile equipped with a part-time four-wheel drive mechanism that can switch between driving and driving, when two wheels are driven, fluctuations in wheel speed are detected for each wheel to control brake hydraulic pressure. The main control system composed of the wheels at the diagonal positions of the main control system selects a wheel having a lower wheel speed at the initial stage of braking among the wheels belonging to the main control system and uses the selected wheel as a reference wheel to change the wheel speed of the reference wheel. Detects and controls the brake fluid pressure of each wheel belonging to the main control system, and the slave control system including the wheels at diagonal positions opposite to the main control system includes the respective wheels belonging to the slave control system. Of the wheel speeds of the By controlling the brake fluid pressure of each wheel belonging to the slave control system in accordance with the fluctuation of the wheel speed of the reference wheel, for example, the increase and decrease of the wheel speed change rate, the rotation speed between the front and rear wheels at the time of four-wheel drive is reduced. The difference can be limited within a predetermined value, and the front and rear wheels are directly connected, so the constraint that the sum of the rotation speeds of the left and right front wheels and the sum of the rotation speeds of the left and right rear wheels must be satisfied must be satisfied. Therefore, the effect of the internal circulation torque can be minimized, and a great effect in practical use can be obtained in combination with the simplification of the configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 is a diagram of a braking hydraulic system and a control system. FIG. 2 is a diagram showing various speeds such as a vehicle speed signal, a wheel speed signal, and a pseudo signal. The relationship between signal fluctuation, main control wheel acceleration / deceleration signal fluctuation, main control wheel holding valve and release valve operation, slave control wheel holding valve and release valve operation, hydraulic pump operation and hydraulic pressure fluctuation FIG. 3 is a time chart for a conventional apparatus. 1 ... Brake pedal, 2 ... Master cylinder, 3 ...
Reservoir tank, 4,7,8,17,20 ... hydraulic piping, 5 ... Left front wheel, 6 ... Right rear wheel, 9,18 ... Holding valve, 10,19 ...
Release valve, 11 Bypass piping, 12 Reservoir, 13
... hydraulic pump, 14 ... accumulator, 15 ... relief valve, 16, 21 ... differential pressure valve, 22 ... brake pedal switch, 23 ... control circuit, 24 ... drive system changeover switch.

Claims (1)

(57) [Claims] A four-wheel drive that can switch between an anti-skid device of a hydraulic brake system for an automobile that detects fluctuations in wheel speed of each wheel during braking and controls a braking hydraulic pressure and a direct-coupled four-wheel drive that directly connects a drive mechanism of front and rear wheels. In a vehicle equipped with a mechanism, at the time of the direct connection type four-wheel drive, a main control system including wheels at one diagonal position on a plane has a low wheel speed at the beginning of braking among wheels belonging to the main control system. One of the wheels is selected as a reference wheel to detect a change in the wheel speed of the reference wheel to control the brake fluid pressure of each wheel belonging to the main control system, and to control the diagonal on the opposite side to the main control system. The slave control system composed of the respective wheels at the position is at least one of the wheels belonging to the slave control system according to the magnitude relationship between the wheel speeds of the wheels belonging to the slave control system and the fluctuation of the wheel speed of the reference wheel of the main control system. Control the brake fluid pressure Braking force control method of automotive hydraulic braking device according to claim.