JP3292633B2 - Anti-skid control system for four-wheel drive vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device for controlling a braking force on each drive wheel to prevent locking of each drive wheel in a four-wheel drive vehicle in which all wheels of the vehicle can be used as drive wheels. More particularly, the present invention relates to an anti-skid control device for a four-wheel drive vehicle that appropriately performs braking force control even when traveling on a low friction coefficient road surface such as on ice or a snowy road.

[0002]

2. Description of the Related Art As four-wheel drive (4WD) vehicles in which all of the front and rear wheels can be used as drive wheels, various types such as part-time and full-time are known. In the full-time system, the drive wheels in front of the vehicle and the drive wheels in the rear of the vehicle are generally connected via a differential device (a so-called center differential), but a part for switching between two-wheel drive (2WD) and four-wheel drive is provided. In the time method, a so-called direct connection type having no center differential is used, and front and rear wheels are directly connected at the time of four-wheel drive.

[0003] With respect to the four-wheel drive vehicle of the part-time system, in Japanese Patent Application Laid-Open No. 4-50067, when anti-skid brake control of a three-channel system is applied,
It is described that the anti-skid brake control is not performed when traveling with four-wheel drive. The reason for this is that in the publication, the front wheel side and the rear wheel side are directly connected via the drive system, so if the brake pressure on the front wheel side and the rear wheel side is independently controlled, the drive system It is described that the torsional torque of the front wheel increases and the wheel speeds of the front wheel and the rear wheel vibrate. Therefore, in the same publication, at the time of control in four-wheel drive traveling, simultaneously with the reduction of the brake pressure at both rear wheels, the brake pressure of the front wheel on the same side as the rear wheel that tends to lock is also changed to the rear wheel side. A method has been proposed in which the pressure is reduced in the same manner as described above, and the brake pressure is controlled substantially in phase between the front wheel side and the rear wheel side.

On the other hand, in Japanese Patent Application Laid-Open No. 63-222962, in a drive wheel brake control device including a slip detection means and a brake fluid pressure control means, an output signal from the slip detection means should increase the brake fluid pressure. At least one of when the value indicating that the pressure has been reduced and when the value indicating that the pressure should be reduced has been reached, the brake fluid pressure control means starts increasing or decreasing the pressure at least once in one control cycle for a certain period of time. A delay means is provided to delay the control of the drive wheel brake control device from falling into a vibration state. It is desirable that the delay time is set to a value suitable for each case by experiment or the like. In many cases, however, the purpose can be achieved by delaying the time corresponding to 1/2 of the resonance cycle of the drive system. It states that it can be done.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The device described in Japanese Patent No. 2962 relates to the brake fluid pressure control on the rear wheel side in a rear wheel drive vehicle. However, in the above-described direct connection type four wheel drive vehicle, a sudden wheel speed When the front wheel and the rear wheel are displaced by about 1/2 cycle of the resonance cycle of the drive system, torsional torque is easily accumulated in the drive system, and the front wheel and the rear wheel There is a possibility that the wheel speed of the wheels vibrates, which in turn causes vehicle body vibration. This is particularly noticeable when the anti-lock brake control is performed while traveling on ice or a snowy road with a low coefficient of road surface friction.

Therefore, the present invention provides an anti-skid control device for a four-wheel drive vehicle that causes vehicle body vibration even when the anti-lock brake control is performed while traveling on ice, a snowy road, or the like having a low coefficient of road surface friction. It is an object of the present invention to be able to appropriately perform braking force control without causing any problem.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a wheel cylinder mounted on each of the front and rear wheels of a vehicle for performing four-wheel drive control to apply a braking force, and the wheel cylinder. A hydraulic pressure generating device for supplying brake hydraulic pressure to each of the cylinders, a hydraulic pressure control device interposed between the hydraulic pressure generating device and the wheel cylinder to control brake hydraulic pressure of the wheel cylinder, and the wheel Wheel speed detecting means for detecting the wheel speed of each of the wheels, each of the wheels by controlling the brake fluid pressure supplied to the wheel cylinder by driving the hydraulic pressure control device according to the detection output of the wheel speed detecting means An anti-skid control device for a four-wheel drive vehicle provided with braking force control means for controlling braking force on the vehicle, wherein the braking force control means is controlled at least in accordance with a detection output of the wheel speed detection means. Wherein determining the pressure boosting starting timing in the control of the brake fluid pressure supplied to the wheel cylinder, it determines an increase of pressure start control whether they meet the condition for performing a predetermined pressure increase start control in bulking pressure start timing by When the pressure increasing start control determining means determines that the condition for performing the predetermined pressure increasing start control is satisfied, the pressure increasing start timing is set to a predetermined pressure set according to the characteristics of the vehicle. A pressure-intensification start delay means for delaying by a delay time; and, after elapse of a predetermined delay time by the pressure-intensification start delay means, when starting the pressure increase in controlling the brake fluid pressure supplied to the wheel cylinder, And a pressure increasing gradient adjusting means for adjusting the pressure increasing gradient to be gentler than the pressure increasing gradient at the time of the normal brake fluid pressure control.

In the above-described anti-skid control device, the pressure increase start control determining means includes a traveling road surface state determining means for determining a road surface state on which the vehicle travels, and a vehicle deceleration state determining for determining a deceleration state of the vehicle. Means, and four-wheel drive control start determining means for determining whether or not the vehicle has started four-wheel drive control, the four-wheel drive control start determining means, the traveling road surface state determining means, It may be configured to determine whether or not to perform the pressure increase start control based on a determination result of the vehicle deceleration state determination means.

[0009]

FIG. 1 shows an embodiment of the present invention having the above-mentioned structure. FIG. 1 shows an anti-skid control device for a four-wheel drive vehicle. Wheel cylinders Wfr, Wfl, Wfl, Wfl, which are mounted on front wheels FR, FL and rear wheels RR, RL of the vehicle to apply a braking force, respectively.
Wrr, Wrl, a hydraulic pressure generator PG for supplying brake hydraulic pressure to each of the wheel cylinders Wfr and the like, and a brake for the wheel cylinder Wfr and the like interposed between the hydraulic pressure generator PG and the wheel cylinder Wfr and the like. Hydraulic pressure control device FV for controlling hydraulic pressure, and wheel speed detecting means Sfr, Sfl, Srr, Srl for detecting wheel speed of each wheel
And a braking force for driving the hydraulic pressure control device FV in accordance with the detection output of the wheel speed detecting means Sfr and the like to control the brake fluid pressure supplied to the wheel cylinder Wfr and the like to control the braking force for each of the wheels FR and the like. Control means BC is provided. Then, at least the pressure increase start timing in the control of the brake fluid pressure supplied to the wheel cylinder Wfr and the like by the braking force control means BC is determined in accordance with the detection output of the wheel speed detection means Sfr and the like. Pressure increase start control determining means SC for determining whether or not conditions for performing the pressure increase start control are satisfied, and pressure increase start control determining means S
When it is determined that the condition C for performing the pressure increase start control is satisfied, the pressure increase start delay means DS for delaying the pressure increase start time by a predetermined delay time set according to the characteristics of the vehicle.
When the pressure increase in the control of the brake fluid pressure supplied to the wheel cylinder Wfr or the like is started after the elapse of a predetermined delay time by the pressure increase start delay means DS, the pressure increase gradient of the brake fluid pressure is reduced by the normal brake. Pressure increasing gradient adjusting means RP for adjusting the pressure increasing gradient to be gentler than the pressure increasing gradient at the time of hydraulic pressure control.
And

When the hydraulic pressure generating device PG is driven, the wheel cylinders Wfr, Wfr are controlled via the hydraulic pressure control device FV.
The brake fluid pressure is supplied to each of fl, Wrr, Wrl, and the front wheels FR, FL and the rear wheels RR, R
A braking force is applied to L. On the other hand, the wheels FR and F are detected by the wheel speed detecting means Sfr, Sfl, Srr and Srl.
The wheel speeds of L, RR and RL are detected, and the hydraulic pressure control device FV is driven by the braking force control means BC in accordance with the wheel speeds, and the brake hydraulic pressure supplied to the wheel cylinder Wfr and the like is controlled. The braking force against FR and the like is controlled. On the other hand, in the pressure increase start control determining means SC, a braking force control
The pressure increase start time in the control of the brake fluid pressure by the stage BC is determined, and it is also determined whether or not the condition for performing the predetermined pressure increase start control is satisfied at the pressure increase start time. When the pressure increase start control determining means SC determines that the condition for starting the pressure increase start control is satisfied, the pressure increase start delay means DS sets the pressure increase start timing according to the characteristics of the vehicle. After the elapse of the predetermined delay time, when the pressure increase in the control of the brake fluid pressure supplied to the wheel cylinder Wfr and the like starts, the pressure increase gradient of the brake fluid pressure is adjusted by the pressure increase gradient adjusting means RP. It is adjusted so that it becomes gentler than the pressure increase gradient at the time of normal brake fluid pressure control.

The pressure increase start control determining means SC is, for example, as shown in FIG.
As shown by the broken line, a traveling road surface state determining means RC for determining the road surface state on which the vehicle travels, a vehicle deceleration state determining means DC for determining the deceleration state of the vehicle, and whether the vehicle has started four-wheel drive control There is provided a four-wheel drive control start determining means WD for determining whether or not to perform the pressure increase start control based on the determination results of these means. As the vehicle deceleration state determining means DC, for example, a vehicle body acceleration sensor that outputs a signal corresponding to the acceleration (including deceleration) of the vehicle is used. As the four-wheel drive control start determining means WD,
For example, a 4WD switch that is turned on during four-wheel drive control is used. The traveling road surface condition determination means RC is configured to estimate the friction coefficient of the traveling road surface based on, for example, the output of the wheel speed detection means Sfr and the like. It is determined whether or not the vehicle is traveling on a friction coefficient road surface.

[0012]

FIG. 2 shows an anti-skid control device according to an embodiment of the present invention. The anti-skid control device comprises a master cylinder 2a and a booster 2b, and is driven by a brake pedal 3; , RR, and RL, the pumps 21, 22 and the reservoirs 23, 24,
Dampers 25 and 26 and solenoid valves 31 to 36 are interposed. Wheel FR indicates the front right wheel when viewed from the driver's seat, hereinafter wheel FL is the front left side, wheel RR is the rear right side,
The wheel RL indicates the rear left wheel. In this embodiment, a direct-coupled four-wheel drive vehicle in which all the wheels are drive wheels is configured. As for the brake system, the front and rear pipes are configured as is apparent in FIG. 2, and the rear wheel side is a common hydraulic system, but may be an independent hydraulic system similarly to the front wheel side. Further, diagonal piping may be used.

An actuator 30 as a hydraulic control device according to the present invention is interposed between the hydraulic pressure generator 2 and the wheel cylinders 51 to 54. This actuator 3
Numeral 0 indicates that solenoid valves 31, 32 and solenoid valves 33, 34 are interposed in a hydraulic passage connecting one output port of the master cylinder 2a and each of the wheel cylinders 51, 52, respectively. A pump 21 is interposed therebetween. On the other hand, solenoid valves 35 and 36 are interposed in a hydraulic passage communicating with the other output port of the master cylinder 2a and both the wheel cylinders 53 and 54, and the pump 22 is interposed between these and the master cylinder 2a. Is equipped.
The proportioning valve 4 is arranged on the wheel cylinders 53 and 54 as shown in FIG. The pumps 21 and 22 are driven by the electric motor 20, and the brake fluid, which has been boosted to a predetermined pressure, is supplied to these fluid pressure paths. Therefore, these hydraulic paths are normally open solenoid valves 31,
It is on the supply side of the brake fluid pressure to 33 and 35.

The discharge-side hydraulic pressure paths of the normally closed solenoid valves 32 and 34 are connected to the pump 21 via a reservoir 23, and the discharge-side hydraulic pressure paths of the normally closed solenoid valve 36 are connected to the pump 22 via a reservoir 24. It is connected to the. Each of the reservoirs 23 and 24 has a piston and a spring, and the solenoid valves 32 and 3
The brake fluid that is recirculated from the pumps 4 and 36 via the discharge-side hydraulic pressure path is accommodated, and the brake fluid is supplied to these when the pumps 21 and 22 are operated.

The solenoid valves 31 to 36 are two-port two-position solenoid switching valves, each of which is shown in FIG.
, Each wheel cylinder 51 to 54 is in communication with the hydraulic pressure generator 2 and the pump 21 or 22. When the solenoid coil is energized, it is in the second position, and each of the wheel cylinders 51 to 54 is
And the pumps 21 and 22 are shut off and communicate with the reservoir 23 or 24. Note that the check valve in FIG. 2 allows return from the wheel cylinders 51 to 54 and the reservoirs 23 and 24 to the hydraulic pressure generator 2 side, and shuts off the flow in the reverse direction.

The brake fluid pressure in the wheel cylinders 51 to 54 can be increased, decreased, or maintained by controlling the energization and non-energization of the solenoid coils of the solenoid valves 31 to 36. That is, the solenoid valve 3
When the solenoid coils 1 to 36 are not energized, brake fluid pressure is supplied to the wheel cylinders 51 to 54 from the hydraulic pressure generator 2 and the pump 21 or 22 to increase the pressure. . When the solenoid coils of the solenoid valves 31, 33 and 35 are energized and the remaining solenoid coils of the solenoid valves are de-energized, the brake fluid pressure in the wheel cylinders 51 to 54 is maintained. Therefore, by adjusting the time interval between energization and non-energization, so-called pulse pressure increase (step pressure increase) or pulse pressure reduction is performed, and control can be performed so as to increase or decrease the pressure gradually.

The solenoid valves 31 to 36 are connected to the electronic control unit 1
0, energizing each solenoid coil,
De-energization is controlled. The electric motor 20 is also the electronic control unit 1
0, which controls the drive. The wheels FR, FL, RR, RL are provided with wheel speed sensors 41 to 44 as wheel speed detecting means according to the present invention, respectively.
These are connected to the electronic control unit 10 so that the rotation speed of each wheel, that is, a wheel speed signal is input to the electronic control unit 10. Each of the wheel speed sensors 41 to 44 is a well-known electromagnetic induction type sensor including, for example, a toothed rotor that rotates with the rotation of each wheel and a pickup provided to face the tooth portion of the rotor. A device that outputs a voltage having a frequency proportional to the rotation speed of the wheel is used, but another system may be used.

Further, the brake switch 45 which is turned on when the brake pedal 3 is depressed is set to the electronic control unit 10.
It is connected to the. In addition, as one embodiment of the vehicle deceleration state determination means DC shown in FIG. 1, a vehicle acceleration sensor, that is, a so-called G, which outputs a signal corresponding to the acceleration (including deceleration) of the vehicle.
A sensor 46 is provided, and as an embodiment of the four-wheel drive control start determining means WD of FIG. 1, for example, a 4WD switch 47 which is turned on when switching to four-wheel drive control is provided. The G sensor 46 and the 4WD switch 47 are connected to the electronic control unit 10.

The electronic control unit 10, as shown in FIG.
CPU 14 and ROM 1 interconnected via a bus
5, a microcomputer 11 comprising a RAM 16, a timer 17, an input port 12 and an output port 13. Each output signal of the wheel speed sensors 41 to 44, the brake switch 45, the G sensor 46, and the 4WD switch 47 is configured to be input to the CPU 14 from the input port 12 via the amplifier circuits 18a to 18g, respectively. Further, a control signal is output from the output port 13 to the electric motor 20 via the drive circuit 19a, and the solenoid valves 31 to 3 are respectively provided via the drive circuits 19b to 19g.
6 is configured to output a control signal. In the microcomputer 11, the ROM 15 stores programs corresponding to the flowcharts shown in FIGS. 4 and 5 (or FIG. 6), and the CPU 14 executes the programs while an ignition switch (not shown) is closed. The RAM 16 is configured to temporarily store variable data necessary for executing the program.

In the embodiment constructed as described above and storing a program corresponding to the flow charts of FIGS. 4 and 5, when the ignition switch (not shown) is closed, the execution of the program starts. I do. When the execution of the program is started, the microcomputer 11 is first initialized in step 101 of FIG. 4, and various calculated values, the estimated vehicle speed Vso representing the vehicle speed, the wheel speed Vw of each wheel, the wheel acceleration DVw, and the like are cleared. You. And
In step 102, the wheel speeds VwFR, VwFL, VwR of each wheel are obtained from the output signals of the wheel speed sensors 41 to 44.
R, VwRL (represented by Vw) are calculated, and the routine proceeds to step 103, where the wheel accelerations DVwFR, Dw are calculated from these values.
VwFL, DVwRR, DVwRL (represented by DVw)
Is calculated. Next, in step 104, the control sensitivity is set according to, for example, the road surface condition.

Then, the routine proceeds to step 105, where it is determined whether or not each wheel is under anti-skid control (shown as ABS control in FIG. 4). It is determined whether or not the anti-skid control start condition is satisfied for each wheel. If the start is determined, the process proceeds to step 107. If the anti-skid control start condition is not satisfied, the process directly jumps to step 113. Step 1
07, the wheel speed Vw and the wheel acceleration DVw
The control mode is set to one of pressure reduction, pulse pressure increase, and hold control in accordance with a braking situation determined based on an estimated vehicle body speed Vso, which will be described later, and a road surface friction coefficient (μ).
The coefficient of friction of the road surface is specified as one of high μ, medium μ and low μ according to, for example, the slip ratio.

At step 108, it is determined whether or not the control mode is the pressure reduction mode. If the control mode is the pressure reduction mode, the flow proceeds to step 109, where a pressure reduction signal is output. Is determined. If it is determined that the mode is the pulse pressure increasing mode, step 111
, A pulse pressure increase signal that alternately repeats pressure increase and hold is output, and the control target of the wheel cylinders 51 to 54 is gradually increased in pressure. The processing at this time will be described later in detail with reference to FIGS. If the mode is not the pulse pressure increasing mode, the routine proceeds to step 112, where a holding signal is output, and the wheel cylinder hydraulic pressure is held. The setting of the control mode and the output of the pressure increasing / decreasing signal are similarly performed for the wheel cylinders of the respective wheels. In step 113, it is determined whether or not the processing has been performed for all four wheels FR, FL, RR, RL. The above routine is repeated until the processing is completed for all four wheels. In this embodiment, the wheels RR, RL at the rear of the vehicle are connected to the solenoid valve 35,
At the same time, the hydraulic pressure control is performed by 36. When this is completed, the estimated vehicle speed Vso is calculated in step 114, and the process returns to step 102.

The flowchart of FIG.
11 shows a process at the time of pulse boosting output. When it is determined in step 110 of FIG. 4 that the pulse boosting mode is set, the pulse boosting output process is performed at step 111. In the example, the following processing is performed according to the flowchart of FIG. 5, and an example of the control situation at this time is shown in FIG. In FIG. 7A,
The dashed-dotted line VA represents the actual vehicle speed, the solid line Vw represents the wheel speed of any of the wheels by the brake fluid pressure control of the present embodiment, and the broken line Vn represents the wheel speed by the normal brake fluid pressure control. I have. FIG. 7B shows a brake fluid pressure control situation of the present embodiment, and FIG. 7C shows a normal brake fluid pressure control situation. Pw represents the wheel cylinder pressure corresponding to the wheel speed Vw, and Pn represents the wheel speed Vn.
Represents the wheel cylinder hydraulic pressure corresponding to. Then, the pressure reducing operation is started at the point a, the pressure is maintained at the point b, and the pressure increasing operation in the normal brake hydraulic pressure control is started at the point c.

When the pulse pressure increasing mode is set in step 110 of FIG. 4, it is determined in step 201 of FIG. 5 whether or not the supply of the pressure increasing output has been completed. Then, the process proceeds to step 202. That is, if the wheel cylinder hydraulic pressure of the wheel to be controlled is being increased and the braking force is not being applied, it is determined in step 202 whether or not it is time to increase the pressure, that is, whether or not it is time to start increasing the pressure. Is determined, and when it is determined that it is time to start increasing the pressure, the routine proceeds to steps 203 and 204, where predetermined pressure increase start control is performed. As the predetermined pressure increase start control, the pressure increase start timing is delayed by a predetermined delay time set in accordance with the characteristics of the vehicle, and the pressure increase gradient of the brake fluid pressure is normally set at the time of the pressure increase after the delay time. Is performed so as to be gentler than the pressure increase gradient at the time of the brake fluid pressure control. That is, in step 203, the pressure increase start time is delayed by a predetermined time Td as compared with the pressure increase start time at the time of the normal brake fluid pressure control indicated by the point c in FIG. 7, and the pulse pressure increase control is performed at the point d in FIG. Set to start. Then, the process proceeds to step 204, where a short cycle pulse pressure increase signal having a short pressure increase and hold cycle is output, and pulse pressure increase control is performed as shown in FIG.

The above-mentioned predetermined time Td is desirably set to a time corresponding to about 1/2 cycle of the resonance cycle of the drive system or longer. Since the resonance cycle is peculiar to each vehicle, this embodiment Is set according to the vehicle in which the anti-skid control device is mounted. Further, the specific value of the cycle of the short cycle pulse pressure increasing signal in step 204 is set for each vehicle according to the characteristics. If it is determined in step 201 that the pressure increase output has not been completed, the pressure increase control is being performed, and the process proceeds to step 205, where the desired pulse pressure increase signal is output. Step 2
If it is determined at 02 that it is not the pressure increase output timing, a holding signal is output.

FIG. 6 is a flowchart according to another embodiment of the present invention.
6, 307, 308 and 310 are the same as steps 201 to 206 in the flowchart of FIG. 5, but in this embodiment, steps 303, 304, 305 and 309 are added. That is, as shown in FIG. 1, it is assumed that the pressure increase start control determining means SC includes a traveling road surface state determining means RC, a vehicle deceleration state determining means DC, and a four-wheel drive control start determining means WD. This shows a specific example of a configuration in which it is determined whether or not to perform the pressure increase start control based on the result. As described above, the G sensor 46 shown in FIGS. 2 and 3 is used as the vehicle deceleration state determination means DC, and the 4WD switch 47 is used as the four-wheel drive control start determination means WD. As the traveling road surface state determination means RC, for example, the aforementioned step 107 in FIG.
As in the estimation of the friction coefficient (μ) in, the slip ratio is calculated based on the detection signals of the wheel speed sensors 41 to 44, and is specified as one of high μ, medium μ and low μ according to the slip ratio. Is configured.

If it is determined in step 303 of FIG. 6 that the friction coefficient of the traveling road surface is low μ, step 304
Proceed to. In step 304, the detection output of the G sensor 46 is compared with a predetermined value. If it is determined that the value is low G, the process proceeds to step 305, and it is determined whether the 4WD switch 47 is on. If it is determined that the 4WD switch is on and four-wheel drive control is being performed, steps 306 and 307 are performed.
The pressure increase timing is delayed as in step 203 of FIG. 5 and a short cycle pulse pressure increase signal is output. If it is determined to be no in any of steps 303 to 305, the above-described pressure increase start control is not performed, and the routine proceeds to step 309, where a normal pressure increase output is made.

FIG. 8 shows the state of anti-skid control on the front and rear wheels of the vehicle according to the above-mentioned embodiment.
The front wheel side wheel speed Vwf (solid line) recovers and approaches the actual vehicle body speed VA (dashed line). Then, at time t2, with a slight time delay, the wheel cylinder hydraulic pressure Pr on the rear wheel side
Is reduced, the rear wheel speed Vwr (broken line) starts to recover, but as described above, both wheel speeds Vwf, Vwr
If, for example, a shift corresponding to a half cycle of the resonance cycle of the drive system occurs, the body vibration may be caused. In contrast,
In the above embodiment, the pressure increase control is started at a timing (t5) at which the front wheel-side wheel cylinder hydraulic pressure Pf is delayed by a predetermined time Td from the normal pressure increase timing (t3), and this pressure increase control is performed. As described above, short cycle pulse pressure increase control with a short cycle is performed. On the other hand, the pulse pressure increase control of the wheel cylinder pressure Pr on the rear wheel side is started at t4, but the interval between t4 and t5 is short. Thus, the front wheel speed Vwf is equal to the rear wheel speed Vwr.
Therefore, there is no significant difference between the two wheel speeds, and stable braking control is performed without causing vehicle body vibration.

[0029]

The present invention has the following effects because it is configured as described above. That is, according to the anti-skid control apparatus for a four-wheel drive vehicle of the present invention, the pressure increase start control determining means determines the pressure increase start time in the control of the brake fluid pressure supplied to the wheel cylinder. At the same time, it is determined whether or not a condition for performing a predetermined pressure increase start control is satisfied at a pressure increase start time. When it is determined that this condition is satisfied, the pressure increase The timing is delayed by a predetermined delay time set according to the characteristics of the vehicle. After the predetermined delay time has elapsed, when the pressure increase in the control of the brake fluid pressure supplied to the wheel cylinder is started, the pressure increase gradient adjustment is performed. Since the pressure increasing gradient of the brake fluid pressure is configured to be gently adjusted by the means as compared with the pressure increasing gradient at the time of normal brake fluid pressure control,
Even when traveling on a low friction coefficient road surface such as a snow-covered road, appropriate brake fluid pressure control can be performed without causing vehicle body vibration, and stable braking operation can be ensured.

In the anti-skid control device according to the second aspect, the pressure increase start control determining means includes a four-wheel drive control start determining means, a traveling road surface state determining means, and a vehicle deceleration state determining means. It is configured to determine whether to perform the pressure increase start control based on
The pressure increase start control can be performed quickly and accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an anti-skid control device for a four-wheel drive vehicle according to the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of an anti-skid control device for a four-wheel drive vehicle according to the present invention.

FIG. 3 is a block diagram illustrating a configuration of the electronic control device of FIG. 2;

FIG. 4 is a flowchart illustrating an anti-skid control process according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating a process of pulse boost output in one embodiment of the present invention.

FIG. 6 is a flowchart showing a process of pulse boost output in another embodiment of the present invention.

FIG. 7 is a graph showing a comparison between brake fluid pressure control and normal brake fluid pressure control in one embodiment of the present invention.

FIG. 8 is a graph showing control states of a front wheel side and a rear wheel side at the time of brake fluid pressure control in one embodiment of the present invention.

[Explanation of symbols]

 2 Hydraulic pressure generator 2a Master cylinder 2b Booster 3 Brake pedal 10 Electronic control unit 20 Electric motor 21,22 Pump 23,24 Reservoir 30 Actuator (hydraulic pressure control unit) 31-36 Solenoid valve 41-44 Wheel speed sensor (wheel speed) Detecting means) 45 Brake switch 46 G sensor (vehicle deceleration state determining means) 47 4WD switch (four-wheel drive control start determining means) 51-54 Wheel cylinder FR, FL, RR, RL Wheel

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiko Takahashi 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Toshihisa Nihei 1-Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hiroyuki Matsubayashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-63-222962 (JP, A) JP-A-63-203862 (JP, A) JP-A-6-24317 (JP, A) JP-A-6-24319 (JP, A) JP-A 8-34333 (JP, A) JP-A 7-165049 (JP, A) (58) Int.Cl. ⁷ , DB name) B60T 8/58

Claims (2)

(57) [Claims] 1. A wheel cylinder mounted on each of the front and rear wheels of a vehicle that performs four-wheel drive control to apply a braking force, a hydraulic pressure generator that supplies brake hydraulic pressure to each of the wheel cylinders, A fluid pressure control device interposed between the fluid pressure generating device and the wheel cylinder to control a brake fluid pressure of the wheel cylinder, a wheel speed detecting means for detecting a wheel speed of each of the wheels, A four-wheel drive including braking force control means for driving the hydraulic pressure control device in accordance with the detection output of the speed detection means and controlling the brake hydraulic pressure supplied to the wheel cylinder to control the braking force on each of the wheels in the antiskid control device of the car, at least control of the brake fluid pressure supplied to the wheel cylinder by the braking force control unit in accordance with a detection output of said wheel speed detecting means It determines the pressure boosting starting timing in your and determining pressure increasing start control determining means for determining whether they meet the condition for performing a predetermined pressure increase start control in bulking pressure start timing, bulking pressure starts the control determination unit When it is determined that the condition for performing the predetermined pressure increase start control is satisfied, the pressure increase start timing is delayed by a predetermined delay time set according to the characteristics of the vehicle, When the pressure increase in the control of the brake fluid pressure supplied to the wheel cylinder is started after a predetermined delay time has elapsed by the pressure increase start delay unit, the pressure increase gradient of the brake fluid pressure is controlled by the normal brake fluid pressure control. An anti-skid control device for a four-wheel-drive vehicle, comprising: a pressure-increase gradient adjusting means for adjusting the pressure-increase gradient to be gentler than the pressure-increase gradient at the time. 2. The vehicle according to claim 1, wherein the pressure increase start control determining means determines a road surface state on which the vehicle travels, a vehicle deceleration state determining means determines a deceleration state of the vehicle, and Four-wheel drive control start determining means for determining whether or not wheel drive control has been started, the determination results of the four-wheel drive control start determining means, the traveling road surface state determining means, and the vehicle deceleration state determining means 2. The anti-skid control device for a four-wheel drive vehicle according to claim 1, wherein it is configured to determine whether or not to perform the pressure increase start control based on the following.