JPH0656018A - Anti-skid controller - Google Patents

Abstract

PURPOSE:To improve the quality of brake while the operation stability of a vehicle is being secured on a split road. CONSTITUTION:Counters CTR, CTL respectively count time in which right and left front wheel brake oil pressure is considered to be in a depressurization mode or in a retention mode. When a difference between the CTR and the CTL values is larger than a predetermined value K1 (Step 5241; YES), a split road travel time is determined, and a split road flag is set (Step 5249). When one side has a certain degree of a friction coefficient (Steps 5253, 5257: YES), independent limit control is selected as rear wheel control. As a result, the quality of brake can be improved while operation stability at the split road is being secured.

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 preventing wheel lock during wheel braking,
Particularly, the present invention relates to achieving both braking performance and steering stability on a traveling road (hereinafter referred to as a split road) having different friction coefficients with wheels on the left and right.

[0002]

2. Description of the Related Art In conventional anti-skid control,
Emphasizing steering stability on a split road, the braking force of the left and right rear wheels is controlled by so-called select low control in which the braking force of the other wheel is controlled in accordance with the wheel on the side with large slip. By doing so, it is possible to prevent a large braking force from being applied to the wheels on the high friction coefficient side and improve the steering stability of the vehicle.

[0003]

However, in a device adopting select low control, a relatively large slip occurs on a wheel on the low friction coefficient side (hereinafter referred to as a low μ wheel). Therefore, it is necessary to absorb this slip. Control is frequently performed to reduce the braking force of the low μ wheels. Then, the braking force of the wheel on the high friction coefficient side (hereinafter referred to as the high μ wheel) with relatively small slip is also similarly reduced, so that the braking force of the vehicle is reduced.

In the conventional anti-skid control, the slip reference speed is set based on the maximum rotation speed of the four wheels, and the braking force is set when the wheel rotation speed falls below the slip reference speed. The control is performed such that it decreases and increases when the slip reference speed is exceeded. Then, this slip reference speed is the maximum braking force on the assumption that a significant slip has occurred on each wheel, that is, the rotation speed of each wheel is smaller than the actual vehicle speed to some extent. Is set to obtain.

However, when the select low control is executed on the split road, only a braking force equal to that of the low μ wheels is applied to the high μ wheels, and the force applied to the wheels from the road surface is much larger than this braking force. Therefore, almost no slip occurs. Therefore, the rotation speed of this wheel (in most cases, it becomes the maximum of the rotation speeds of the four wheels) substantially coincides with the actual vehicle body speed, and the slip reference speed set on the basis of this also has a large value. Then, even if the rotational speed of the wheels is slightly reduced, the braking force is reduced and the braking force is further reduced.

Therefore, the present invention has been made for the purpose of providing an anti-skid control device capable of improving the braking performance while ensuring the steering stability of a vehicle on a split road.

[0007]

The invention according to claim 1 made to achieve the above object (hereinafter referred to as the first invention).
As illustrated in FIG. 12, the braking force adjusting means for individually adjusting the braking force of the left and right wheels, the rotation speed detecting means for individually detecting the rotation speeds of the respective wheels, and the rotation speed detecting means are used. Based on the detected rotational speed of the two wheels, a slip state detecting means for individually detecting the slip state of each wheel, and a road surface state determining means for determining whether or not the road surface friction coefficient is uniform on the left and right. When the road surface condition judging means judges that the road surface friction coefficient is uniform on the left and right, the control of each wheel is controlled to be a select low control for controlling the braking force of the other wheel in accordance with a wheel having a large slip, or The road surface condition determining means is selected from a single or a plurality of controls including at least an independent control for independently controlling the braking force of each wheel in accordance with the slip state of each wheel. When it is determined that the surface friction coefficient is not uniform on the left and right, wheel control selecting means for selecting the control of each wheel as an independent limit control for limiting and controlling the increasing tendency of the braking force of the other wheel by the wheel with large slip. The anti-skid control device is characterized by comprising: a control unit that outputs a control signal to the braking force adjustment unit based on the selected control to adjust the slip state of each wheel. The invention according to claim 2 (hereinafter referred to as the second invention), as illustrated in FIG. 13, has a road surface condition determining means for determining whether or not the road surface friction coefficient is uniform on the left and right, and at least the road surface condition determining means. When the means determines that the road surface friction coefficient is not uniform, either the front wheel or the rear wheel is controlled, and the braking force of each wheel is controlled independently according to the slip state of each wheel. Independent control is selected and the other control is controlled by limiting the increasing tendency of the braking force of the other wheel by the wheel with large slip, or by controlling the braking force of the other wheel according to the wheel with large slip. Selecting means for selecting the select low control, a braking force adjusting means for individually adjusting the braking force of the four wheels, a rotational speed detecting means for individually detecting the rotational speeds of the four wheels, and the select low control. The slip reference speed for detecting the slip state of the wheel is set based on the maximum rotation speed of the plurality of wheel rotation speeds including at least the rotation speeds of the two wheels controlled by the control or the independent limit control. When the slip reference speed setting means and the road surface condition determining means determine that the road surface friction coefficient is not uniform on the left and right, the slip reference speed A slip reference speed decrease correction means for reducing the quasi-speed to calculate a corrected slip reference speed, and a rotation speed of a wheel on the side having a lower road surface friction coefficient among the two wheels controlled based on the independent control and the above The slip reference speed is compared to output the control signal of the braking force adjusting means for the wheel, and the rotational speed of the wheel on the higher road friction coefficient is compared with the corrected slip reference speed for the brake for the wheel. Control means for outputting a control signal of the force adjusting means,
The gist is an anti-skid control device that is equipped with.

[0008]

In the first aspect of the invention thus constituted, the road surface condition determining means determines whether or not the road surface friction coefficient is uniform on the left and right. Then, when the road surface condition judging means judges that the road surface friction coefficient is not uniform on the left and right, that is, the road is a split road, the wheel control selecting means selects the independent limiting control for controlling the left and right wheels. Then, the control means outputs a control signal to the braking force adjusting means based on the independent limit control to adjust the slip state of each wheel.

The independent limiting control is a control method for limiting the tendency of the other wheel to increase the braking force by the wheel with large slip. Therefore, the braking force corresponding to the slip of the low-μ wheel is applied to the low-μ wheel, but the braking force of the low-μ wheel is smaller than the braking force corresponding to the slip of the high-μ wheel to the high-μ wheel. Greater braking force is applied.
Therefore, the braking force can be improved while ensuring the steering stability as follows. That is, since the slip generated on the high μ wheels is relatively small, the braking force is improved by making the braking force of the high μ wheels larger than the braking force of the low μ wheels. Further, since the increasing tendency of the braking force of the high μ wheel is limited by the low μ wheel, it is possible to prevent the application of the braking force which is largely biased to the high μ wheel side. Therefore, the steering stability of the vehicle is not impaired.

Further, on a traveling road where the road surface friction coefficient is uniform on the left and right (hereinafter referred to as a uniform road), the wheel control selection means controls the wheel from among a single or a plurality of controls including at least select low control or independent control. select. Therefore, on a uniform road, the braking force can be controlled by a method suitable for the road surface condition and the running condition of the vehicle.

On the other hand, in the second aspect of the invention, the road surface condition judging means judges whether the road surface friction coefficient is uniform on the left and right. When it is determined that the wheel control selecting means is not uniform, the wheel control selecting means selects the independent control for the control of either the front wheel or the rear wheel, and selects the independent limiting control or the select low control for the other control.

Further, the slip reference speed setting means sets the wheel based on the maximum rotational speed of the plurality of wheel rotational speeds including at least the rotational speeds of the two wheels controlled based on the select low control or the independent limit control. The slip reference speed for detecting the slip state of is set. Here, when the select low control is selected for the control of the pair of left and right wheels, the high μ wheel has a rotation speed substantially equal to the actual vehicle body speed as described above. Similarly, when the independent limit control is selected, the increasing tendency of the braking force of the high μ wheels is limited by the low μ wheels, so that the high μ wheels have a rotation speed close to the actual vehicle speed. Therefore, the slip reference speed set based on this rotation speed becomes a relatively large value with respect to the rotation speed at which the maximum braking force is obtained.

Therefore, when the road surface condition determining means determines that the road surface friction coefficient is not uniform on the left and right, the slip reference speed decrease correcting means reduces and corrects the slip reference speed to calculate a corrected slip reference speed. Then, the control means compares the rotation speed of the low μ wheel with the slip reference speed among the two wheels controlled based on the independent control, and outputs the control signal of the braking force adjusting means relating to the wheel, The rotation speed of the high μ wheel is compared with the corrected slip reference speed, and the control signal of the braking force adjusting means for the wheel is output.

Therefore, of the two wheels controlled on the basis of the independent control, the low μ which can hardly give the braking force to the vehicle.
The wheel is controlled to a relatively high rotation speed based on the slip reference speed. Therefore, the side force of the low μ wheels is increased, and the steering stability of the vehicle is secured. Also,
The high μ wheels that can apply the braking force to the vehicle are controlled to a small rotation speed that is closer to the rotation speed at which the maximum braking force is obtained based on the corrected slip reference speed. Therefore, the high μ wheels give a good braking force to the vehicle.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the antiskid control device of the present invention will be described below. FIG. 1 shows the configuration of an anti-skid control device as an embodiment of the present invention.
The present embodiment is an example in which the present invention is applied to a front-wheel steering / rear-wheel drive four-wheel vehicle.

Rotation speed sensors 9, 11, 13, 15 of electromagnetic pickup type or photoelectric conversion type are arranged on each of the right front wheel 1, the left front wheel 3, the right rear wheel 5 and the left rear wheel 7, and each wheel 1 , 3, 5, 7 are output in accordance with the rotation. That is, the rotation speed sensors 9, 11, 13, 1
Reference numeral 5 corresponds to a rotation speed detecting means. Furthermore, each wheel 1, 3,
Hydraulic brake devices 17, 19, 21 and 2 are provided at 5 and 7, respectively.
3 is provided, and actuators 27, 29 for hydraulic control serving as brake pedal 25 or braking force adjusting means are provided.
The hydraulic pressure is supplied to the respective hydraulic pipelines 35, 37, 3 by 31, 33.
Each of the hydraulic brake devices 17, 19, 2 via 9, 41
Sent to 1, 23. Therefore, the actuator 27,
The braking force on the wheels 1, 3, 5, and 7 can be adjusted by 29, 31, 33 or the brake pedal 25. An oil temperature sensor 42 that detects the temperature of the brake fluid is provided in the hydraulic line 37 and outputs an electric signal according to the oil temperature.
The oil temperature sensor 42 may be provided in the hydraulic lines 35, 39, 41, but in the present embodiment, the oil temperature sensor 42 is provided only in the hydraulic line 37 on the assumption that the oil temperature difference between the four paths is small. The stepped state of the brake pedal 25 is detected by the stop switch 43, and an ON signal is output during braking and an OFF signal is output during non-braking. Normally, the brake pedal 2
By depressing 5, hydraulic pressure is generated in the hydraulic cylinder 45, and each wheel 1, 3, 5, 7 can be braked.
Separately, as a hydraulic pressure source for slip control, a hydraulic pump 47 that generates hydraulic pressure by driving an engine or driving an electric motor is also provided. The electronic control circuit 49 controls the actuators 27, 29, 31, 33 to adjust the hydraulic pressure from the hydraulic cylinder 45 or the hydraulic pump 47 and send the hydraulic pressure to the hydraulic brake devices 17, 19, 21, 23. The braking force can be adjusted for each wheel 1, 3, 5, 7.

The actuators 27, 29, 31,
Reference numeral 33 is a well-known one which has a three-position valve and changes the setting of the hydraulic pressure of the hydraulic brake device 17 into three modes of increasing pressure, holding, and reducing pressure according to the electric current flowing through the solenoid coil provided inside. . Since the structure of this type of actuator is detailed in, for example, Japanese Patent Laid-Open No. 3-54058, it will not be described in detail here.

The main relay 51 switches the connection between the actuators 27, 29, 31, 33 and the power supply source according to the output of the electronic control circuit 49. Further, the indicator lamp 53 is connected to the rotational speed sensors 9, 11, 13, and 15 by disconnecting each actuator 27,
When a failure occurs in the anti-skid control device such as a break in the solenoid coil of 29, 31, 33 or a break in the stop switch 43, the driver is notified of the occurrence of a system abnormality based on the output of the electronic control circuit 49. .

The electronic control circuit 49 has a circuit configuration as shown in FIG. Here, the waveform shaping amplifier circuits 60, 6
2, 64, 66 are the rotational speed sensors 9, 11, 13, 1
5 as a pulse signal suitable for processing by the microcomputer 68, the buffer circuit 70 temporarily holds the signal from the stop switch 43, and the power supply circuit 72.
Supplies a constant voltage to the microcomputer 68 and the like when the ignition switch 50 is turned on. Further, the A / D converter 73 converts the voltage of the battery power supply and the output signal of the oil temperature sensor 42 into a digital amount, and the microcomputer 68 has a CPU 76, a ROM 78, a RAM 80, an I / O.
By including the circuit 82 and the like, a control signal is output to each of the following drive circuits based on the input data.

Drive circuits 84, 86, 88, 90, 92,
Reference numeral 94 denotes an output in accordance with a control signal from the microcomputer 68. Among these, actuator drive circuits 84, 86, 88, 90 drive the 3-position valves of the actuators 27, 29, 31, 33. Then, the main relay drive circuit 92 energizes the coil 98 of the main relay 51 having the normally open contact 96 to turn on the normally open contact 96. The indicator lamp driving circuit 94 lights the indicator lamp 53.

Next, the processing and operation of the anti-skid control device thus constructed will be described. When the ignition switch 50 is turned on, a constant voltage from the power supply circuit 72 is applied to the microcomputer 68 and the like, and the CPU 76 of the microcomputer 68 starts execution of arithmetic processing according to a program previously stored in the ROM 78.

FIG. 3 is a flow chart showing the main routine of the anti-skid control processing executed by the electronic control circuit 49. When the ignition switch 50 is turned on, first, in step 100, initialization of the inside of the CPU such as resetting various flags is performed. Continued Step 200
Then, the rotation speed signals from the rotation speed sensors 9 to 15 are detected and the pulse input time is stored. In step 300, the rotational speed Vw and acceleration Vw ′ of each wheel 1 to 7 are individually calculated based on the time in step 200. At the same time, the slip reference speed V0 is set based on the maximum rotation speed Vw of the wheels 1 to 7. The method for setting the slip reference speed V0 is described in JP-A-3-54058.
Since it is detailed in the publication, it will not be detailed here.

Subsequently, when the process proceeds to step 400, step 300 is executed by the operation mode setting routine described later.
The slip state of the wheels 1 to 7 is determined from the rotation speed Vw, the acceleration Vw ', and the slip reference speed V0 obtained in
The operation mode of the actuators 27 to 33 is the pressure increasing mode,
Switch between holding mode and decompression mode.

In the following step 500, step 400
A rear wheel control process is executed to appropriately change the operation mode set in step 6 for each rear wheel control. Then, the following step 600
Then, the actuators 27 to 33 are driven according to the operation mode set in steps 400 and 500, and the process proceeds to step 200 again.

The method of the rear wheel control processing in step 500 will be described. This processing is sequentially performed for each wheel 1 to 7, for example, right front wheel 1 → left front wheel 3 → right rear wheel 5 → left rear wheel 7. Are executed in order. Then, in the first step 510, it is determined whether or not the control target is the rear wheels 5, 7. Rear wheels 5,7
If not, proceed directly to step 600, step 60
At 0, the actuators 27 and 29 are driven according to the operation mode set in step 400. When the controlled object is the rear wheels 5 and 7, the process proceeds to step 520. Step 520
Then, by the rear wheel control selection routine described later, the rear wheels 5, 7
Control is selected, and if select low control is selected, the process proceeds to step 530, and the rear wheel (5
Alternatively, the operation mode of 7) is controlled according to the rear wheel (7 or 5) having the larger slip. When the independent limiting control is selected in step 520, the process proceeds to step 540, and the operation mode of the rear wheel (7 or 5) on the small slip side is limited by the rear wheel (5 or 7) on the large slip side. When the independent control is selected in step 520, the process proceeds to step 550, and the actuators 31, 33 are driven according to the operation mode set in step 400 for each of the rear wheels 5, 7.

Next, the rear wheel control selection routine of step 520 will be described with reference to the flowcharts of FIGS. In the first step 5201, the brake pedal 25
Is operated to determine whether or not the stop switch 43 is turned on. When the stop switch 43 is not turned on, the routine proceeds to step 5203, and the counters CTR and CTL that count the time when the right front wheel 1 and the left front wheel 3 are set to the pressure reduction mode or the holding mode are reset. In the following step 5205, the split road flag Fs indicating that the vehicle is traveling on the split road is reset and the low μ flag Fμ indicating that the vehicle is traveling on the low μ road is set, and the routine proceeds to step 530 of FIG. Therefore, when the brake pedal 25 is not operated, the select low control is selected.

On the other hand, when it is determined in step 5201 that the stop switch 43 is turned on, the following step 52
Move to 07. In step 5207, it is determined whether or not the right front wheel 1 has started the pressure reduction mode. Immediately after starting the depressurization mode, the counter CTR is reset in the following step 5209, and then the process proceeds to step 5211.
If it is not immediately after starting the pressure reduction mode, the process directly proceeds to step 5211. Similarly, the following steps 5211,
At 5213, if the front left wheel 3 has just started the pressure reduction mode, the counter CTL is reset and then step 52 is executed.
If not immediately after starting the depressurization mode, the process proceeds directly to step 5215.

In step 5215, it is determined whether the right front wheel 1 is in the pressure reducing mode or the holding mode. If it is the depressurization mode or the holding mode, the following step 5217
After incrementing the counter CTR at step 5,
If the mode is not the pressure reducing mode or the holding mode, that is, if the pressure increasing mode, the process proceeds to step 52.
Move to 19. Similarly, the following steps 5219 and 52
In step 21, if the left front wheel 3 is in the pressure reducing mode or the holding mode, the counter CTL is incremented and then step 5 is performed.
231, and if it is the pressure increasing mode, the process directly proceeds to step 5231.

By the processing of steps 5207 to 5221, the counter CTR (CTL) is reset every time the front wheel 1 (3) is switched to the pressure reducing mode, and the front wheel 1 (3) is reset.
It is possible to count the time when is set to the decompression mode or the holding mode. Next, at step 5231, it is determined whether any one of the front wheels 1 or 3 has started the pressure increasing mode. When either one starts the pressure increasing mode, it is determined in step 5233 that follows whether or not both front wheels 1 and 3 are set to the pressure increasing mode. If a negative determination is made in either step 5231 or step 5233, the process moves to step 5235.

In step 5235, it is determined whether the low μ flag Fμ is set. If it is set, the process proceeds to step 530 of FIG. 3 to select the select low control, and if not set, step 523.
Move to 7. In step 5237, it is determined whether the split road flag Fs is set. If it is set, the process proceeds to step 540 in FIG. 3 to select the independent limiting control, and if it is not set, the process proceeds to step 550 in FIG. 3 to select the independent control.

Next, when an affirmative determination is made in steps 5231 and 5233, that is, immediately after one of the front wheels 1 or 3 has started the pressure increasing mode, and both of the front wheels 1 and 3 are in the pressure increasing mode. Then, the processing shifts to step 5241 and subsequent steps to change the settings of the low μ flag Fμ and the split road flag Fs described above.

First, at step 5241, the counter CT
The absolute value of the difference between the value of R and the value of the counter CTL is calculated, and it is judged whether or not it is larger than the predetermined value K1. If a negative determination is made here, the process proceeds to step 5243. Step 5
At 243, the split road flag Fs is reset. On the other hand, when it is determined in step 5241 that the absolute value of the difference between the counters CTR and CTL is larger than the predetermined value K1, the process proceeds to step 5245 and the counters CTR and CTL are counted.
Compare the size with. When the counter CTL is larger, the right wheel high μ flag Fr indicating that the right side is the high μ side is set in step 5247, and the process proceeds to step 5249. If the counter CTR is larger, the right wheel height μ flag Fr is reset and the routine proceeds to step 5249. Then, in step 5249, the split road flag Fs is set.

That is, since the counters CTL and CTR increase / decrease in inverse proportion to the friction coefficient of the left and right road surfaces, step 5
In the processing of 241-step 5249, step 524
Based on the difference between the counters CTR and CTL, it is determined whether the vehicle is traveling on a split road or a uniform road. The right wheel high μ flag Fr is used in an operation mode setting routine described later.

When the split road flag Fs is set in step 5243 or 5249, the process proceeds to step 5253. In step 5253, it is determined whether or not the counter CTR is smaller than a predetermined value K2 separately set from the predetermined value K1. When it is determined that the value is smaller than the predetermined value K2, the routine proceeds to step 5255, and at least the right side of the road surface is not low μ and the low μ flag Fμ is reset. Counter C
If TR is equal to or greater than the predetermined value K2, the process proceeds to step 5257, and it is determined whether the counter CTL is smaller than the predetermined value K2. If it is judged to be small, the same as the previous step 52
After shifting to 55, the low μ flag Fμ is reset and the predetermined value K
If it is determined to be 2 or more, the process proceeds to step 5259.
In step 5259, the low μ flag is set because both sides of the road surface are low μ.

As described above, steps 5241 to 5255
After the setting of the low μ flag Fμ and the split road flag Fs is changed in, the control shifts to the control from step 5235 and thereafter, and the rear wheel control is selected based on the new setting.
Next, the processes of the select low control, the independent limiting control, and the independent control will be described with reference to a control flowchart.

FIG. 6 shows a control flowchart of the select low control. First, at step 531, it is determined whether the operation mode of the rear wheels 5, 7 is one pressure increasing mode and the other one pressure reducing mode. In the one-wheel depressurization mode and the one-wheel pressure increase mode, the process proceeds to step 532, and step 532 is performed.
The control mode on the pressure increasing mode side is switched to the pressure reducing mode with. If neither the single-wheel depressurization mode nor the single-wheel pressure-increasing mode, the routine proceeds to step 533, where it is determined whether or not one wheel is in the holding mode and the other one is in the pressure-increasing mode. In the one-wheel holding mode and the one-wheel pressure increasing mode, the process proceeds to step 534, and in step 534, the control mode on the pressure increasing mode side is switched to the holding mode.

As described above, the select low control is a mode in which the left and right rear wheels 5, 7 are controlled in accordance with the mode on the pressure reducing side. In the control flow chart of the independent control, as shown in FIG. 7, in step 551, the operation mode of each wheel remains the mode currently selected.

FIG. 8 is a control flowchart of the independent limit control.
Shown in. In step 541, it is determined whether one wheel is in the pressure reducing mode and the other wheel is in the pressure increasing mode. In the case of the one-wheel depressurization mode and the one-wheel pressure increasing mode, the routine proceeds to step 542, and the operation mode of the rear wheel (5 or 7) for which the pressure increasing mode is selected is switched to the holding mode. On the other hand, in the cases other than the above modes, the control mode as it is is executed.

Here, select low control, independent limit control,
The characteristics of the rear wheel control by the independent control will be seen in the image graph of the rear wheel control in FIG. This graph represents changes in the brake hydraulic pressure applied to the left and right rear wheels 5, 7 and changes in the rotational speed when the road surface friction coefficients of the left and right rear wheels 5, 7 are different. In FIG. 9, the right rear wheel 5 is a high μ wheel, its rotation speed is a right rear wheel speed V WRR, and the left rear wheel 7 is a low μ wheel, and its rotation speed is a left rear wheel speed V WRL. There is.

Before the time t1, the select low control shown by the solid line is performed, and the brake oil pressures PRR of the left and right rear wheels 5, 7 are set.
Both PRL repeats increasing and releasing the brake hydraulic pressure based on the left rear wheel speed V WRL. When hydraulic pressure is applied, the left rear wheel speed V WRL
Gradually decreases the speed while repeatedly adding and releasing hydraulic pressure. Then, the change of the hydraulic pressure applied to the right rear wheel 5 when the control method is changed from the time point t1 will be observed. A solid line is shown for the select low control, a broken line is shown for the independent limit control, and a dashed-dotted line is shown for the independent control.

According to this, in the select low control, the pressure increase / release of the right rear wheel brake oil pressure PRR is continued at the same cycle as the left rear wheel brake oil pressure PRL, and in the independent control, the right rear wheel brake oil pressure PRR is continued. Rapidly increases in accordance with the right rear wheel speed V WRR, and the right rear wheel brake hydraulic pressure PRR has a control mode that continues to increase at a slow speed in the independent limiting control, and in the independent limiting control, is substantially the same as the hydraulic pressure in the select low control. It can be seen that the right rear wheel 5 is controlled by the brake hydraulic pressure that is intermediate to the hydraulic pressure during the independent control.

As described above, in the independent limiting control, when there is a difference in the slip state between the left and right rear wheels, the brake hydraulic pressure difference between the rear wheels 5 and 7 is not as large as that in the independent control, and the select low control and the independent control are performed. It is an intermediate brake hydraulic pressure control. Next, the operation mode setting routine of step 400 is shown in FIG.
This will be described based on the flowchart of No. 0. The operation mode setting routine is a process of calculating all the wheels 1 to 7, for example, the right front wheel 1-> the left front wheel 3-> the right rear wheel 5-> the left rear wheel 7, and then proceeding to step 500.

In the first step 401, it is judged whether or not the controlled objects are the rear wheels 5, 7. In the case of the rear wheels 5 and 7, the process proceeds to step 403, and the slip reference speed V0 obtained in step 300 is set as the judgment value V1 which is a reference for judging the slip state of the wheels.

On the other hand, when it is determined in step 401 that the control targets are the front wheels 1 and 3, the process proceeds to the following step 407. In step 407, it is determined whether or not the above-mentioned split road flag Fs is set. If the vehicle is traveling on a uniform road and the split road flag Fs is reset, the routine proceeds to step 403, and if the split road flag Fs is set, the routine proceeds to subsequent step 409. In step 409, it is determined whether or not the control target is the high μ wheel based on the value of the right wheel high μ flag Fr. If the control target is a low μ wheel, step 403
If the control target is the high μ wheel, the process proceeds to step 41.
Move to 1. In step 411, the slip reference speed V0 is multiplied by a positive predetermined count k smaller than 1 and the value kV0 reduced and corrected is set as the judgment value V1.

That is, when the vehicle is traveling on the split road and the control target is the front wheel (1 or 3) on the high μ side by the processing of steps 401 to 411, the judgment value V1
Is set to kV0 as the control target is the front wheel (3 or 1) on the low μ side, and the control target is the rear wheels 5 and 7
If it is, the slip reference speed V0 is set as the judgment value V1.
To set.

Next, step 403 or step 41
After setting the judgment value V1 in 1, the process proceeds to step 415. In step 415, the rotation speed Vw of the wheel to be controlled is compared with the set judgment value V1. When the rotation speed Vw is smaller than the judgment value V1, the following step 4
Moving to 17, it is determined whether or not the acceleration Vw 'is positive. If the acceleration Vw 'is positive, the process proceeds to step 419 to select the holding mode, and if it is negative, the process proceeds to step 421 to select the depressurization mode. On the other hand, when it is determined in step 415 that the rotation speed Vw is equal to or higher than the determination value V1, the process proceeds to step 423 and the pressure increasing mode is selected.

The processing of steps 415 to 423 increases the brake hydraulic pressure when the rotation speed Vw is equal to or higher than the judgment value V1 (small slip), and when the rotation speed Vw becomes smaller than the judgment value V1 (large slip). This is a well-known process in anti-skid control in which the brake oil pressure is reduced and the brake oil pressure at that time is maintained when the rotation speed Vw starts to increase.

As a result, the left and right front wheel speeds on the split road change as illustrated in FIG. Note that FIG.
1, the right front wheel 1 is a high μ wheel. First, when the brake pedal 25 is depressed at time T1 and the stop switch 43 is turned on, the left front wheel speed on the low μ side decelerates faster and becomes lower than the judgment value V1 (= V0) at time T2. . Then, the brake oil pressure of the left front wheel 3 enters the pressure reducing mode, and at the same time, the counter CTL starts counting up. Then, when the right wheel speed becomes equal to or lower than the determination value V1 at time T3, the brake hydraulic pressure of the right front wheel 1 enters the pressure reducing mode and the counter CTR starts counting up.

When the left front wheel speed and the right front wheel speed start increasing at time points T4 and T5, the respective brake hydraulic pressures are in the holding mode. Then, at time T6, when the speed of the right front wheel exceeds the determination value V1, the brake hydraulic pressure of the right front wheel 1 enters the pressure increasing mode again, and the counter CTR stops counting. Low μ
Since the frictional force from the road surface is not much applied to the left front wheel 3 on the side, the front left wheel speed gradually increases and exceeds the judgment value V1 at time T7 which is delayed from time T6. Then left front wheel 3
The brake hydraulic pressure of becomes the pressure increasing mode, and the counter CTL stops counting.

Further, at time T7, the right front wheel 1 is held in the pressure increasing mode, so that steps 5241 to 5241 in FIG.
The processing of 5259 is executed. Since the vehicle is traveling on the split road, CTL-CTR becomes larger than the predetermined value K1 and the split road flag Fs is set. As a result, the judgment value V1 relating to the right front wheel speed is reduced and corrected to kV0. Thereafter, the brake hydraulic pressure of the right front wheel 1 repeats the above-described operation mode based on the newly set determination value V1. As a result, after time T7, the time during which the brake hydraulic pressure of the right front wheel 1 is in the pressure increasing mode increases. Also, at times T8 and T9 when the counters CTR and CTL start counting for the second time, the counters CTR and CTL are once reset and then start counting up.

In the above anti-skid control processing, the processing of steps 5241 to 5249 is the first.
Step 4 in the road surface condition judging means of the invention and the second invention.
15 and step 417 are the slip state detection means of the first invention, steps 5235 and 5237 are the wheel control selection means of the first invention, and step 600 is the control means of the first and second inventions. , Steps 510, 5235, and 5237 are the wheel control selecting means of the second invention, step 200 is the slip reference speed setting means of the second invention, and step 411 is the slip reference speed decrease correcting means. Equivalent to each.

As described above, in the anti-skid control device of this embodiment, the independent limiting control is selected for controlling the left and right rear wheels 5 and 7 on the split road where one side has a certain friction coefficient. Therefore, the brake oil pressure (for example, PRL in FIG. 9) corresponding to the slip of the low μ wheel is applied to the low μ wheel,
A brake oil pressure (for example, FIG. 9: broken line) smaller than the braking force corresponding to the slip of the high μ wheel and larger than the braking force of the low μ wheel can be applied to the high μ wheel.
Therefore, the braking force can be improved while ensuring the steering stability as follows. That is, since the slip generated on the high μ wheels is relatively small, the braking force applied to the vehicle can be increased by increasing the braking force on the high μ wheels. Further, since the increasing tendency of the braking force of the high μ wheel is limited by the low μ wheel, it is possible to prevent the application of the braking force that is largely biased to the high μ wheel side, and to secure the steering stability of the vehicle. .

Further, in this embodiment, the select low control is selected on a road having a small friction coefficient (step 5).
235: YES), the stability of the vehicle can be ensured, and independent control can be selected on a uniform road having a large friction coefficient (step 5237: NO) to exhibit excellent braking force. .

Further, in the anti-skid control device of the present embodiment, among the front wheels 1 and 3 which are controlled based on the independent control during traveling on the split road, the low μ wheel which gives almost no braking force to the vehicle is set to the slip reference speed. A relatively high rotation speed is controlled based on V0. Therefore, it is possible to increase the side force related to the low μ wheels and ensure the steering stability of the vehicle. Further, the high μ wheel that applies the braking force to the vehicle can be controlled to a smaller rotation speed based on the value obtained by multiplying the slip reference speed V0 by the coefficient k and correcting the decrease, and the braking force can be increased. Therefore, in this embodiment, it is possible to improve the braking performance extremely well while ensuring the steering stability of the vehicle on the split road.

In the above embodiment, during braking on the split road, the control for reducing the slip reference value V0 of the front wheel (1 or 3) on the low μ side and the control for the rear wheels 5, 7 are switched to the independent limiting control. Although the control and the control are executed at the same time, the provisional effect can be obtained by executing only one of the control. Further, although the front wheels are independently controlled and various controls are applied to the rear wheels in the above embodiment, even if various controls are applied to the front wheels and the rear wheels are independently controlled, various controls are also applied to the four wheels. May be applied.

Further, in the above embodiment, the rear wheel control is selected from the independent control when the road surface friction coefficient is large and the select low control when the road surface friction coefficient is small on the uniform road. Various other control selection methods are possible. For example, the rear wheel control may be selected depending on the vehicle speed and the steering angle. Further, in the above embodiment, the front wheels 1, 3
It is determined whether or not the friction coefficient of the road surface is uniform based on the rotation speed of No. 1. However, various methods other than this determination method are possible. For example, unevenness of the road surface, friction torque applied to wheels,
The yawing moment applied to the vehicle body may be detected by another sensor.

[0057]

As described above in detail, in the antiskid control device of the first invention, the independent limit control is selected for controlling the left and right wheels on the split road. Therefore, the braking force corresponding to the slip of the low-μ wheel is applied to the low-μ wheel, but the braking force of the low-μ wheel is smaller than the braking force corresponding to the slip of the high-μ wheel to the high-μ wheel. Greater braking power can be applied. Therefore, the braking force can be improved while ensuring the steering stability as follows. That is, since the slip generated on the high μ wheels is relatively small, the braking force applied to the vehicle can be increased by increasing the braking force on the high μ wheels. Further, since the increasing tendency of the braking force of the high-μ wheels is limited by the low-μ wheels, it is possible to prevent the application of a braking force that is largely biased to the high-μ wheels to ensure the steering stability of the vehicle. . In the first aspect of the invention, the wheel control can be selected from a single control or a plurality of controls including at least select low control or independent control on a uniform road. Therefore, on a uniform road, the braking force can be controlled by a method suitable for the road surface condition and the running condition of the vehicle.

On the other hand, in the anti-skid control device of the second invention, the independent control is selected for the control of either the front wheels or the rear wheels on the split road, and the independent limit control or the select low control is selected for the other control. Then, of the two wheels that are controlled based on the independent control, the low μ wheel that can hardly apply the braking force to the vehicle is controlled to a relatively high rotation speed based on the slip reference speed. Therefore, this low μ
It is possible to increase the side force on the wheels and ensure the steering stability of the vehicle. Further, it is possible to increase the braking force by controlling the high μ wheels that can apply the braking force to the vehicle to a smaller rotation speed based on the corrected slip reference speed.

Therefore, in the first invention and the second invention, it is possible to improve the braking performance while ensuring the steering stability of the vehicle on the split road.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an anti-skid control device of an embodiment.

FIG. 2 is a block diagram of an electronic control circuit of the anti-skid control device.

FIG. 3 is a flowchart showing a main routine of anti-skid control of the embodiment.

FIG. 4 is a flowchart showing a rear wheel control selection routine of anti-skid control.

FIG. 5 is a flowchart showing a rear wheel control selection routine of anti-skid control.

FIG. 6 is a control flowchart showing select low control.

FIG. 7 is a control flowchart showing independent control.

FIG. 8 is a control flowchart showing an independent limiting control.

FIG. 9 is a graph showing changes in brake hydraulic pressure in various controls.

FIG. 10 is a flowchart showing an operation mode setting routine for anti-skid control.

FIG. 11 is a graph showing changes in left and right front wheel speeds on a split road.

FIG. 12 is a diagram illustrating the configuration of the first invention.

FIG. 13 is a diagram illustrating the configuration of a second invention.

[Explanation of symbols]

1, 3, 5, 7 ... Wheels 9, 11, 13, 15 ... Rotational speed sensor 17, 19, 21, 23 ... Hydraulic brake device
25 ... Brake pedal 27, 29, 31, 33 ... Hydraulic control actuator 43 ... Stop switch 49 ... Electronic control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiaki Tsuchiya 1 Toyota-cho, Toyota-shi, Aichi Toyota Automobile Co., Ltd.

Claims (4)

[Claims] 1. A braking force adjusting means for individually adjusting the braking forces of the left and right wheels, a rotation speed detecting means for individually detecting the rotation speeds of the respective wheels, and two rotation speed detecting means. Slip state detecting means for individually detecting the slip state of each wheel based on the rotational speed of the wheels, road surface state determining means for determining whether or not the road surface friction coefficient is uniform on the left and right, and the road surface state determining means When the means determines that the road surface friction coefficient is uniform on the left and right, the control of each wheel is selected low control for controlling the braking force of the other wheel according to the wheel with large slip,
Alternatively, the road surface condition determination means selects one or a plurality of controls including at least an independent control for independently controlling the braking force of each wheel in accordance with the slip state of each wheel, and the road surface state determination means does not have a uniform road surface friction coefficient on the left and right. When it is determined that the control of each wheel, the wheel control selection means for selecting an independent limit control for controlling by controlling the braking force increase tendency of the other wheel by the wheel with large slip, and based on the selected control And a control means for adjusting the slip state of each wheel by outputting a control signal to the braking force adjusting means. 2. Road surface condition determining means for determining whether or not the road surface friction coefficient is uniform on the left and right, and at least when the road surface condition determining means determines that the road surface friction coefficient is not uniform, either the front wheel or the rear wheel. For one of the controls, select the independent control that independently controls the braking force of each wheel according to the slip state of each wheel, and for the other control, limit the tendency of the braking force of the other wheel to increase due to the wheel with large slip. Wheel control selecting means for selecting independent limit control for controlling the brake force of the other wheel or a select low control for controlling the brake force of the other wheel according to the wheel with large slip, and a brake force for individually adjusting the brake force of the four wheels. Adjusting means, rotation speed detecting means for individually detecting the rotation speeds of the four wheels, and two control means based on the select low control or the independent limiting control. Based on the maximum rotation speed of a plurality of wheel rotation speeds including at least the rotation speed of the wheels, a slip reference speed setting means for setting a slip reference speed for detecting the slip state of the wheels, and the road surface state determination means When it is determined that the road surface friction coefficient is not uniform on the left and right, slip reference speed decrease correction means for reducing and correcting the slip reference speed to calculate a corrected slip reference speed, and two wheels controlled based on the independent control Among these, the rotation speed of the wheel on the side with the high road surface friction coefficient is output by comparing the rotation speed of the wheel on the side with the low road surface friction coefficient with the slip reference speed, and outputting the control signal of the braking force adjusting means for the wheel. And a control means for comparing the corrected slip reference speed with the corrected slip reference speed and outputting a control signal of the braking force adjusting means for the wheel. A characteristic anti-skid control device. 3. A road surface friction coefficient detecting means for detecting a road surface friction coefficient is provided, wherein the wheel control selecting means always selects the independent control for front wheel control, and the road surface friction coefficient is uniform for rear wheel control. When the road friction coefficient is high, the independent control is selected, when the road friction coefficient is uniform and low, the select low control is selected, and when the road friction coefficient is uneven, the independent limit control is selected. Or the anti-skid control device described in 2. 4. The anti-rotation system according to claim 1, wherein the road surface condition determining means makes a determination based on the rotational speeds of the left and right wheels detected by the rotational speed detecting means. Skid control device.