JPH0725326A - Anti-skid control device - Google Patents

Abstract

PURPOSE:To perform appropriate braking force control according to the change state of the friction coefficient of the road surface in an anti-skid control device. CONSTITUTION:Brake fluid pressure is supplied to a wheel cylinder WC by a fluid pressure generating device PG through a fluid pressure control device AC so as to impart braking force to a wheel ML. On the other hand, the friction coefficient of the road surface is detected every specified time by a friction coefficient detecting means CD and stored, and the change state of the friction coefficient is judged by a change state judging means CD. Brake fluid pressure is increased/decreased by a braking force control means BC according to the change of the friction coefficient so as to control braking force to the wheel WL. At the time of judging the existence of peak in the friction coefficient after the change by a peak judging means PD, braking force control is started on the basis of the friction coefficient close to the peak, and at the time of judging no peak in the friction coefficient after the change, braking force control is started on the basis of the friction coefficient close by immediately after change.

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 applied to wheels when a vehicle is being braked to prevent the wheels from being locked. The present invention relates to an anti-skid control device that can be controlled.

[0002]

2. Description of the Related Art An anti-skid control device is widely used that controls braking force by increasing or decreasing a brake fluid pressure to a wheel cylinder of each wheel so that the wheel does not lock during sudden braking of a vehicle. This anti-skid control device generally detects the wheel speed of each wheel of the vehicle, controls the brake fluid pressure to the wheel cylinder of each wheel according to the detection result, and applies the braking force to obtain the maximum friction coefficient. It is supposed to be controlled. An anti-lock brake device for directly measuring the road surface friction force or the road surface friction coefficient has been proposed, and Japanese Patent Application Laid-Open No. 4-331336 discloses a wheel for detecting the road surface friction force, the vertical drag force, the road surface friction coefficient, and the like. A force measuring device has been proposed.

[0003]

However, even in the anti-skid control device that controls the braking force according to the friction coefficient between the wheel and the road surface, it is difficult to follow the change of the friction coefficient, and the control is difficult. There will be a delay. For example, when the wheel enters the high friction coefficient road surface from the low friction coefficient road surface during the anti-skid control, while taking the friction coefficient on the high friction coefficient road surface corresponding to the slip ratio immediately after entering,
Immediately after the friction coefficient is made the same as the friction coefficient on the road surface, the brake fluid pressure control is performed based on the friction coefficient-slip ratio characteristic on the high friction coefficient road surface. Therefore, even after entering the road surface having a high friction coefficient, the brake fluid pressure control is performed so that the friction coefficient gradually increases from the value of the low friction coefficient, so that the braking operation is delayed and the braking distance is extended. . On the contrary, when a road surface having a high friction coefficient enters a road surface having a low friction coefficient, a large brake fluid pressure is applied to immediately obtain the friction coefficient before entering while taking the friction coefficient corresponding to the slip ratio immediately after entering. Therefore, the slip ratio will be increased at once.

Therefore, in the present invention, in an anti-skid control device for controlling a braking force according to a friction coefficient between a wheel and a road surface, an appropriate braking force control is performed according to a changing state of the friction coefficient. With the goal.

[0005]

In order to achieve the above object, the anti-skid control device of the present invention has a wheel cylinder WC which is mounted on a wheel WL to apply a braking force, as shown in the outline of the construction of FIG. And a hydraulic pressure generator PG for supplying brake hydraulic pressure to the wheel cylinder WC, and a hydraulic pressure control for interposing between the hydraulic pressure generator PG and the wheel cylinder WC to control the brake hydraulic pressure of the wheel cylinder WC. Friction coefficient detecting means CF for detecting the friction coefficient between the device AC, the wheel WL and the road surface at predetermined time intervals and storing the detection result.
And a change state determination means CD for determining the change state of the friction coefficient based on the output of the friction coefficient detection means CF, and the presence or absence of a peak of the friction coefficient after the change based on the determination result and the output of the friction coefficient detection means CF. Peak judging means P for judging
D, the peak determining means PD and the friction coefficient detecting means C
Braking force control means BC for controlling the braking force by driving the hydraulic pressure control device AC in accordance with the output of F to increase / decrease the brake hydraulic pressure supplied to the wheel cylinders WC, and which has been changed by the peak determination means PD. When it is determined that the friction coefficient has a peak, control of the braking force is started based on the friction coefficient near the peak, and when the peak determination unit PD determines that the friction coefficient after the change has no peak, the friction immediately after the change occurs. Braking force control means B for starting control of braking force based on coefficient
C is provided.

In the anti-skid control device, the friction coefficient detecting means CF may be composed of a tire torque sensor for detecting the torque due to the frictional force of the wheel WL on the road surface.

Alternatively, the friction coefficient detecting means CF is provided with a braking torque sensor TS for detecting a braking torque applied to the wheel WL and a wheel speed sensor WS for detecting a rotational angular speed of the wheel WL. The friction coefficient may be calculated based on the rotational angular velocity.

Further, the anti-skid control device is provided with slip ratio calculating means for calculating the slip ratio of the wheel WL based on the output of the wheel speed sensor, and the peak judging means PD and the output of the change state judging means CD are output. When the slip ratio calculated by the slip ratio calculation means exceeds the first predetermined value after the change from the high friction coefficient to the low friction coefficient,
It is determined that there is no peak after the peak of the friction coefficient has passed, and after the output of the change state determination means CD has changed from the low friction coefficient to the high friction coefficient, the slip ratio calculated by the slip ratio calculation means is When the friction coefficient is below the second predetermined value, it can be determined that the friction coefficient has passed the peak and the peak is not determined.

Alternatively, the peak determining means PD in the anti-skid control device may be configured to determine no peak when there is no peak within a predetermined time after the output of the change state determining means CD has changed. .

[0010]

In the anti-skid controller having the above structure, when the hydraulic pressure generator PG is driven, the hydraulic pressure controller AC
The brake fluid pressure is supplied to the wheel cylinder WC via the wheel cylinder WC, and the braking force is applied to the wheel WL. On the other hand, the friction coefficient detecting means CF detects the friction coefficient between the wheel WL and the road surface at predetermined time intervals and stores the detection result. Then, the change state determination means CD determines the change state of the friction coefficient based on the output of the friction coefficient detection means CF, and based on the determination result and the output of the friction coefficient detection means CF, the peak determination means PD determines the changed friction. It is determined whether the coefficient has a peak. Thus, the braking force control means BC drives the hydraulic pressure control device AC in response to the change in the friction coefficient of the wheels WL, and the braking hydraulic pressure to the wheel cylinders WC is increased or decreased. Therefore, the braking force to the wheels WL is controlled. It In this case, when the peak determination means PD determines that the changed friction coefficient has a peak, control of the braking force is started based on the friction coefficient near the peak, and the peak determination means PD peaks the changed friction coefficient. When it is determined that the braking force is not present, the braking force control is started based on the friction coefficient immediately after the change.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an anti-skid control device according to an embodiment of the present invention, which includes a master cylinder 2a and a booster 2b.
The hydraulic pressure generating device 2 driven by the brake pedal 3 and each of the wheel cylinders 51 to 54 arranged on the wheels FR, FL, RR, RL are connected to the hydraulic pressure passage by the pump 21, 22, the reservoirs 23 and 24 and the solenoid valves 31 to 38 are interposed. Incidentally, the wheel FR indicates the wheel on the front right side as viewed from the driver's seat, hereinafter the wheel FL indicates the wheel on the front left side, the wheel RR indicates the wheel on the rear right side, and the wheel RL indicates the wheel on the rear left side. As is apparent from FIG. Piping is configured.

An actuator 30, which is a hydraulic pressure 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
No. 0 has solenoid valves 31, 32 and solenoid valves 33, 34, respectively, which are provided in the hydraulic passages connecting one output port of the master cylinder 2a and each of the wheel cylinders 51, 54. A pump 21 is interposed between them. Similarly, solenoid valves 35, 36 and solenoid valves 37, 38 are respectively provided in the hydraulic paths connecting the other output port of the master cylinder 2a and the wheel cylinders 52, 53, and these are connected to the master cylinder 2a. Pump 22 in between
Is installed. The pumps 21 and 22 are electric motors 20
The brake fluid, which is driven by, and is pressurized to a predetermined pressure, is supplied to these fluid pressure paths. Therefore, these hydraulic pressure passages are the supply side of the brake hydraulic pressure to the normally open solenoid valves 31, 33, 35, 37.

The discharge side hydraulic pressure passages of the normally closed solenoid valves 32 and 34 are connected to the pump 21 via the reservoir 23, and the discharge side hydraulic pressure passages of the normally closed solenoid valves 36 and 38 are also connected via the reservoir 24. It is connected to the pump 22. Reservoirs 23, 2
4 are each equipped with a piston and a spring, and the solenoid valve 3
The brake fluid, which is recirculated from 2, 34, 36, and 38 via the discharge-side hydraulic pressure passage, is stored, and the brake fluid is supplied to these when the pumps 21 and 22 are operated.

The solenoid valves 31 to 38 are 2-port 2-position solenoid switching valves, each of which is shown in FIG.
In the first position shown in FIG. 3, each wheel cylinder 51 to 54 communicates 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 the wheel cylinders 51 to 54 have the hydraulic pressure generator 2
Also, the pumps 21 and 22 are shut off and communicate with the reservoir 23 or 24. The check valve in FIG. 2 allows the flow from the wheel cylinders 51 to 54 and the reservoirs 23, 24 side to the hydraulic pressure generator 2 side and shuts off the flow in the opposite direction.

By controlling the energization and de-energization of the solenoid coils of these solenoid valves 31 to 38, the brake fluid pressure in the wheel cylinders 51 to 54 can be increased, reduced or maintained. That is, when the solenoid coils of the solenoid valves 31 to 38 are not energized, the hydraulic pressure generator 2 and the pump 21 are attached to the wheel cylinders 51 to 54.
Alternatively, the brake fluid pressure is supplied from 22 to increase the pressure, and when energized, the fluid is communicated with the reservoir 23 or 24 to reduce the pressure. If the solenoid coils of the solenoid valves 31, 33, 35, 37 are energized and the solenoid coils of the remaining solenoid valves are de-energized, the brake fluid pressure in the wheel cylinders 51 to 54 is maintained. Therefore, so-called pulse pressure increase (step pressure increase) or pulse pressure decrease can be performed by adjusting the time interval of energization / de-energization, and control can be performed so as to gradually increase or decrease the pressure.

The solenoid valves 31 to 38 are electronic control units 1
0 connected to each solenoid coil to energize,
De-energization is controlled. The electric motor 20 is also the electronic control unit 1
It is connected to 0, and is drive-controlled by this. Further, wheel speed sensors 41 to 44 are provided on the wheels FR, FL, RR, RL, respectively, and these are connected to the electronic control unit 10, and a signal corresponding to the rotational angular velocity of each wheel is sent to the electronic control unit 10. Is configured to be input to. The wheel speed sensors 41 to 44 are well-known electromagnetic induction type sensors including a toothed rotor that rotates with the rotation of each wheel, and a pickup provided so as to face the tooth portion of the rotor. A sensor or the like may be used. Although the rotational angular acceleration is obtained when the outputs of the wheel speed sensors 41 to 44 are differentiated, a wheel acceleration sensor that directly detects the rotational angular acceleration of the wheel may be provided.

Braking torque sensors 45 to 48 are provided on each of the wheels FR, FL, RR, RL. The braking torque sensors 45 to 48 have a strain sensor (not shown) arranged at the end of a brake pad (not shown) of a disc brake, and perform braking based on the detection output of this strain sensor, that is, the load applied to the brake pad. The torque is detected. Further, the electronic control unit 10 is connected with a brake switch 49 which is turned on when the brake pedal 3 is depressed.

The electronic control unit 10 is, as shown in FIG.
CPU14 and ROM1 connected to each other via a bus
5, a microcomputer 16 including a RAM 16, a timer 17, an input interface circuit 12 and an output interface circuit 13. The output signals of the wheel speed sensors 41 to 44, the braking torque sensors 45 to 48, and the brake switch 49 are amplified by the amplifier circuits 18a to 18a.
8i from the input interface circuit 12 to C respectively
It is configured to be input to the PU 14. A control signal is output from the output interface circuit 13 to the electric motor 20 via the drive circuit 19a, and solenoid valves 31 to 3 are output via the drive circuits 19b to 19i, respectively.
8 is configured to output a control signal. In the microcomputer 11, the ROM 15 stores a program corresponding to each flow chart shown in FIG. 4 and subsequent figures, and the CPU 14 executes the program while an ignition switch (not shown) is closed, and the RAM 1
6 temporarily stores variable data necessary for executing the program.

In the present embodiment constructed as described above, the anti-skid (ABS) is controlled by the electronic control unit 10.
A series of processing for control is performed, and the actuator 3
Although 0 is controlled and the brake fluid pressure is controlled, in order to facilitate understanding, first, the friction coefficient − shown in FIGS.
After the description using the slip ratio curve (μ-S curve), the basic control will be described based on the flowcharts of FIGS. 4 to 9.

As is well known, the friction coefficient μ and the slip ratio S
The relationship of n differs depending on the condition of the road surface, the type of tire, etc. For example, on a high friction coefficient road such as a dry asphalt road (hereinafter referred to as a high μ road), the slip ratio Sn is 15 as shown by the one-dot chain line in FIG. The friction coefficient μ shows a peak at 20% to 20%, and the friction coefficient μ and the slip ratio Sn are in a substantially proportional relationship until reaching the maximum value. When the friction coefficient μ exceeds the maximum value, the friction coefficient μ gradually increases as the slip ratio Sn increases. Get smaller.
On the other hand, on a low friction coefficient road such as a frozen snow road (hereinafter referred to as a low μ road), the maximum value of the friction coefficient μ becomes extremely low as shown by the broken line in FIG. 15, but the slip ratio Sn is about 20%. Shows a peak. On the other hand, in the gravel road or the like, as shown by the chain double-dashed lines in FIGS. 17 and 20, the friction coefficient μ gradually increases as the slip ratio Sn increases, but there is no peak.
It should be noted that FIG. 17 shows the case of FIG.
Shows the case where there is no peak on the low μ road.

When a vehicle enters a high μ road from a low μ road, it can be roughly classified into three situations shown in FIGS. First, in FIG. 15, the slip ratio when entering the high μ road from the low μ road is the peak (μ) of the friction coefficient μ of the high μ road.
p), the friction coefficient changes along the path indicated by the solid line in FIG. 15, and as shown by the broken line arrow, the friction coefficient μ of the friction coefficient μ at that moment is instantaneously passed through the peak on the high μ road side. The value will be reached. Further, even when the slip ratio when entering the high μ road from the low μ road is in front of the peak (μp) of the friction coefficient μ of the high μ road, as shown by the broken arrow in FIG. On the road side, the value of the friction coefficient at that time is reached via the vicinity of the peak. Further, when entering a high μ road where there is no peak, the friction coefficient μ is the value on the low μ road when entering the high μ road via a route as shown in FIG.

Therefore, when the vehicle enters the high μ road from the low μ road and travels on the high μ road for a while, the friction coefficient μ is controlled from a low value immediately after entering the high μ road. Therefore, the followability of the braking force control deteriorates. However, if the change state of the friction coefficient when entering the high μ road from the low μ road is the state shown in FIG. 15 and FIG. 16, it is once passing through the vicinity of the peak of the friction coefficient μ on the high μ road side. If the brake fluid pressure is controlled so that the tire torque corresponding to the value of the friction coefficient μ near the peak is obtained, the optimum braking force can be obtained. However, when there is no peak in the friction coefficient μ as shown in FIG. 17, in order to secure the side force, a predetermined ratio (for example, 80 to 80) of the value of the friction coefficient μ when the road enters from the low μ road to the high μ road. 95
%), The brake fluid pressure is controlled so that the tire torque corresponding to the value of (%) is obtained, and the slip ratio Sn is 15 to 20.
It is desirable to control so that it becomes%.

On the other hand, when a vehicle enters a low μ road from a high μ road, it can be roughly classified into three situations shown in FIGS. First, FIG. 18 shows that the slip ratio when entering the low μ road from the high μ road is the peak (μ) of the friction coefficient μ of the low μ road.
In FIG. 18, the friction coefficient changes along the solid line path. That is, since the brake fluid pressure is high on the high μ road side, when the vehicle enters the low μ road, the brake fluid pressure remains as it is in the locking direction. In this case, since it goes through the peak of the friction coefficient μ on the low μ road side, if this peak is detected and the brake fluid pressure is controlled so that the tire torque corresponds to the value of the friction coefficient μ at that time, it is optimal. It will be possible to obtain a sufficient braking force.

Further, when the slip ratio when entering the low μ road from the high μ road is past the peak (μp) of the friction coefficient μ of the low μ road, as shown by the solid line in FIG. However, if the brake fluid pressure is reduced to the value immediately after entering the low μ road, the optimum braking force is obtained. As for a road surface having no peak, as shown in FIG. 20, a tire torque corresponding to a friction coefficient μ of 1.2 times that value, for example, based on a value when the friction coefficient μ on the low μ road side is once changed as a reference. Optimum braking force can be obtained by controlling the brake fluid pressure so that

In this embodiment, the optimum brake hydraulic pressure control is performed as described below even when the vehicle enters a road surface having a different friction coefficient μ during the anti-skid control as described above. First, when the ignition switch (not shown) is closed, the microcomputer 11 starts executing the program corresponding to the flowcharts of FIGS. 4 to 9. FIG. 4 is a flowchart for obtaining the friction coefficient μ between each wheel and the road surface. The value tn of the timer is cleared (0) in step 100, and is incremented every time the processing of steps 120 to 150 is performed at predetermined time intervals ( Step 110). That is, the friction coefficient μ is calculated in a predetermined calculation cycle (for example, 1 mS), and the memory RA
Stored in M. First, in step 120, the torque (tire torque) Tt due to the frictional force of each wheel with respect to the road surface is detected, and subsequently, in step 130, the load (tire load) F on the wheel is detected. μ is calculated as μ = Tt / R · F. Here, R indicates the effective radius of each wheel. The friction coefficient μ calculated in this way is sequentially read into the memory RAM in step 150, and the latest calculation result A
The value of the friction coefficient μ for each piece is stored. This calculation is performed until it is determined in step 160 that the anti-skid (ABS) control has ended, and the value of the friction coefficient μ is sequentially updated for each calculation cycle. There are various means for detecting the tire torque and the tire load, but in this embodiment, as shown in FIG. 5, the braking torque sensors 45 to 4 shown in FIG.
8 and the wheel speed sensors 41 to 44, the tire torque is detected, and the tire load is detected by a height sensor (not shown) that detects the vehicle height, and the friction coefficient μ is calculated based on these detected values. I am going to do it. Of course, the friction coefficient μ may be directly detected without being limited to these methods.

In FIG. 5, steps 121 to 123 are performed as the processing corresponding to step 120 in FIG. 4, and steps 131 and 141 are performed as the processing corresponding to steps 130 and 140, respectively. That is, the braking torque Tb is detected by the braking torque sensor in step 121, and the wheel speed sensor 4 is detected in step 122.
The rotational angular velocities of the respective wheels detected by 1 to 44 are differentiated to detect the rotational angular acceleration DAw. Then, based on these detected values, the tire torque Tt is Tt = Tb-
It is calculated as It DAw. Here, It is a coefficient according to the inertial force of each wheel, and is set according to the size, weight, etc. of the wheel. Subsequently, in step 131, the height signal Ht is detected by the height sensor. Since the height signal Ht corresponds to the vehicle height value of the vehicle, it has a constant relationship with the vehicle load, and therefore the tire load F is Kh · Ht.
(However, Kh is a coefficient). The tire load F can be detected by a vertical G (acceleration) sensor or the like instead of the height sensor. Thus, the friction coefficient μ is μ = Tt / R · Kh · Ht in step 141.
Is required as.

FIG. 6 shows the processing of the anti-skid control in one embodiment of the present invention, which constitutes the basic control for the embodiment to be described later. First, when the anti-skid control is started, the timer is reset at step 201 (0), and the processing from step 203 onward is performed at every predetermined time (Δt) (step 202). Whether or not the anti-skid control is started may be performed by using the same start condition as in the conventional case. For example, the slip ratio is a predetermined value (for example, 5
% Or more) or the rotational angular acceleration of the wheel is a predetermined value (for example, −10 G) or less, or the difference between the braking torque estimated from the master cylinder pressure and the tire torque measured from the tire torque sensor is a predetermined value. The anti-skid control may be started in the above cases.

First, at step 203, the memory RA
The friction coefficient μ at that time (at time t) is called from M, the slope dμ / dt of the friction coefficient is obtained, and the change state of the friction coefficient is determined. Then, in step 210, it is determined whether the previous time is the pressure increasing state or the pressure reducing state, and if it is the pressure increasing state, the flag B is reset (0) in step 211, and then the process proceeds to step 212. The flag B is a flag that is set (1) when the friction coefficient μ changes in the depressurized state, and when the friction coefficient μ changes in the increased pressure state, the flag A is set as described later. . Step 212
, The slope dμ / dt of the friction coefficient μ is a predetermined value K1
It is determined whether or not (for example, K1 = -10). That is, it is determined whether or not the friction coefficient μ has changed (decreased) in a predetermined range or more. If it is determined that the friction coefficient μ has changed, the flag A is set (1) in step 213 and then the process proceeds to step 300, which will be described later. High μ → low μ determination processing is performed.

When it is determined in step 212 that the slope dμ / dt of the friction coefficient μ is not less than the predetermined value K1, it is determined in step 214 whether the flag A is set. Proceed to 300. If flag A is not set, step 215
Then, the slope dμ / dt at that time is compared with a predetermined value K2 (for example, K2 = 1), and if it is equal to or larger than the predetermined value K2, the pressure increasing state is maintained as it is, and the routine proceeds to step 230. On the other hand, when the gradient dμ / dt of the friction coefficient is smaller than the predetermined value K2, the friction coefficient at this time is set to the friction coefficient μ1 (μ1 is the peak value of the friction coefficient of this road surface) in step 216. Substituting, after that, in step 217, the operation is switched to the “pressure reduction” operation, and the process proceeds to step 230.

If it is determined in step 210 that the previous time was in the depressurized state, the processing shown in the flowchart of FIG. 7 is performed. First, in step 221, the flag A is reset (0), and then the process proceeds to step 222. . The flag A is a flag that is set when the friction coefficient μ changes in the increased pressure state. In step 222,
The slope dμ / dt of the friction coefficient is a predetermined value K4 (for example, K4 =
It is determined whether it is larger than 10). That is, it is determined whether or not the friction coefficient μ has changed within a predetermined range,
If it is determined that there is a change, the flag B is set (1) in step 223, and then the process proceeds to step 400, and low μ → high μ determination processing described later is performed. Step 222
When it is determined that the gradient dμ / dt of the friction coefficient is less than or equal to the predetermined value K4, it is determined in step 224 whether the flag B is set. If it is set, the process proceeds to step 400. If the flag B has not been set, the routine proceeds to step 225, where the friction coefficient μ
Is compared with a predetermined value μ1 · K5 (for example, K5 = 0.95), and if the value is equal to or larger than the predetermined value μ1 · K5, the reduced pressure state is maintained and the process proceeds to step 230. On the other hand, when the value of the friction coefficient μ is smaller than the predetermined value μ1 · K5, the operation is switched to the “pressure increase” operation at step 226, and the routine proceeds to step 230.

After the above-described processing is performed for each wheel (steps 230 and 231), it is determined in step 232 whether the pressure increasing operation is continuously performed a predetermined number of times K3 times (for example, K3 = 120) or more. If it is less than the predetermined number of times K3, the process returns to step 202. If the pressure increasing operation is performed K3 times or more, the vehicle is determined to be stopped and this routine is finished.

[High μ → Low μ in step 300]
The "determination process" is executed based on the flowchart shown in FIG. First, at step 301, the time tn at which the friction coefficient gradient dμ / dt reaches the minimum value (dμ / dt) min is detected, and the routine proceeds to step 302, where the minimum value (dμ / dt
It is determined whether or not the peak μp of the friction coefficient exists after the time tn of dt) min. When the peak μp of the friction coefficient is not detected, the routine proceeds to step 303, where after the flag A is set (1), it is judged whether or not this routine has been performed 10 times or more. If it is less than 10 times, the routine proceeds to step 304. The brake fluid pressure is maintained and the routine returns to the routine of FIG.

In step 302, when the peak μp of the friction coefficient is detected after the time tn of the minimum value (dμ / dt) min of the friction coefficient, or this routine is executed 10 times or more after the flag A is set. In step 305, the slope of the friction coefficient when the minimum value (dμ / dt) min has passed t1 hours from time tn dμ /
The direction of dt is determined. If the value of the slope dμ / dt of the friction coefficient is not positive (> 0) (if it is negative), the state is as shown in FIG. 19, so the flow proceeds to step 306, where the value of the friction coefficient μ at the time (tn + t1) (that is, the friction Minimum slope of coefficient (dμ
/ Dt) min, the pressure is reduced to the value at the time of the next routine). The friction coefficient slope dμ / dt is positive (>
If the value is 0), whether the time of the maximum value μmax of the friction coefficient and the time of the final value μend of the friction coefficient are the same in step 307, that is, the value (final value) of the friction coefficient at the time of determination is the maximum value. It is determined whether or not μmax. Where the maximum value μm
If it is determined that the value is ax (that is, the state of FIG. 20), the routine proceeds to step 308, where the minimum friction coefficient value μmin.
Value obtained by multiplying by a constant K6 (for example, K6 = 1.2) μmin
・ The pressure is reduced to K6. When the maximum value μmax is different from the final value μend, it has a peak μp there (that is, the state of FIG. 18), so the routine proceeds to step 309, where a constant K7 (for example, K7 = The pressure is reduced to a value multiplied by 0.95). It should be noted that although it is possible to reduce the pressure until the peak μp is reached by setting K7 = 1, the pressure is reduced to a value of 95% because control is difficult.

The "low μ → high μ determination process" in step 400 is executed based on the flowchart shown in FIG. First, at step 401, the time tn when the friction coefficient gradient dμ / dt reaches the maximum value (dμ / dt) max is detected, and the routine proceeds to step 402, where the maximum value (dμ
/ Dt) max of friction coefficient peak μp after time tn
Is determined. Friction coefficient peak μp
If no is detected, the routine proceeds to step 403, where after the flag B is set (1), it is determined whether or not this routine has been performed 10 times or more. If less than 10 times, the brake fluid pressure is determined at step 404. It is held, and the routine returns to the routine of FIG. In this way, the friction coefficient μ changes while the brake fluid pressure is held, and the peak μp is detected. When it is not detected, the value of the friction coefficient μ is measured every moment.

In step 402, when the peak μp of the friction coefficient is detected after the time tn of the maximum value (dμ / dt) max of the friction coefficient, or this routine is executed 10 times or more after the flag B is set. In step 405, the slope of the friction coefficient dμ / when the time t1 of the maximum value (dμ / dt) max elapses from time tn
The direction of dt is determined. The value of the slope dμ / dt is negative (<
If it is not 0) (if it is positive), the state is as shown in FIG. 15, so the routine proceeds to step 406, where the value μmax obtained by multiplying the maximum value μmax of the friction coefficient by a constant K8 (for example, K8 = 0.95).
The pressure is increased to K8, and if the value is negative (<0), the slope d of the friction coefficient at (tn + t1) at step 407.
It is determined whether or not μ / dt is less than a constant K9 (for example, K9 = −20). Here, when it is determined that the gradient dμ / dt of the friction coefficient at (tn + t1) is less than the constant K9 (that is, the state of FIG. 16), the process proceeds to step 408 until the maximum value μmax of the friction coefficient is reached. The pressure boosting operation is performed, and the slope dμ / dt of the friction coefficient at (tn + t1) is K
When it is 9 or more (that is, the state of FIG. 17), the process proceeds to step 409, and the pressure increasing operation is performed until the friction coefficient μ value at (tn + t1) is multiplied by a constant K10 (for example, K10 = 0.95). Be done.

FIGS. 10 to 12 relate to another embodiment of the present invention, in which wheel speed sensors 41 to 44 are not provided,
The antiskid control is performed according to the detection signal of the tire torque sensor (not shown) used in FIG. In this embodiment, since the slip ratio cannot be obtained, the pressure is switched to the reduced pressure when dμ / dt is in the decreasing direction during the pressure increase. However, for example, in FIG.
In the case of a low μ road to a high μ road, once the peak μp is passed and the friction coefficient decreases (in the region on the left side of μp in the figure), the pressure is increased. On the other hand, since the change of the wheel is delayed, the friction coefficient may decrease despite the pressure increase, and dμ / dt <1. For this reason, the pressure may be switched to the pressure increasing mode and then to the pressure reducing mode immediately, and the friction coefficient may continue to decrease in the direction away from the peak μp (in the left direction in the drawing). To prevent this, the pressure increase flag is used to increase the pressure a predetermined number of times (K
i) The next judgment is made when the process continues continuously. Similarly, in FIG. 15, when it is in the direction in which the friction coefficient decreases by moving to the right in the drawing and passing the peak μp (the region on the right side of μp in the drawing), the pressure is reduced. Since the change of the wheel is delayed, it moves away from the peak μp despite the pressure reduction,
It may be <μ1 · K5. For this reason, there is a possibility that the pressure will be switched to the depressurization once and then to the pressure boosting immediately, and the friction coefficient will continue to decrease in the direction away from the peak μp (to the right in the drawing). In order to prevent this, the decompression flag is used so that the next judgment is made when the decompression continues for a predetermined number of times (Kd). 10 to 12 are incorporated into the flows of FIGS. 6 to 9 to form one routine. That is, as shown in FIGS. 10 and 11, after the pressure reducing operation is switched in step 217 of FIG. 6, the pressure reducing flag is set (1) in step 218, and the pressure increasing operation is performed in step 226 of FIG. 7. After the switching, the pressure increase flag is set (1) in step 227.

Then, as shown in FIG. 12, after the gradient dμ / dt of the friction coefficient is calculated in step 203 of FIG. 6, it is judged whether or not the pressure increase flag is set (1), and it is set. If so, the number of times the pressure increase flag is set in step 205 is a predetermined number of times Ki (for example, Ki =
4) and if it is Ki or more times, the pressure increase flag is reset (0) in step 206, and then step 2 in FIG.
If it is less than Ki times, proceed to step 23.
Go to 0. When it is determined in step 204 that the pressure increase flag is not set, step 207
Then, it is judged whether the pressure reduction flag is set (1) or not, and if it is not set, the process directly proceeds to step 210 of FIG. If the pressure reduction flag is set, the number of times the pressure reduction flag is set to the predetermined number Kd in step 208.
(For example, Kd = 2). If Kd times or more, the pressure reduction flag is reset in step 209 and then the process proceeds to step 230. If it is less than Kd times, the process proceeds to step 230 as it is.

13 and 14 relate to still another embodiment of the present invention. Like the embodiment of FIG. 2, the wheel speed sensors 41 to 44 and the braking torque sensors 45 to 48 are provided and the former detection signal is provided. The slip ratio Sn is calculated based on
FIG. 6 shows a process of determining whether the slip μn is on the left side or the right side of the peak μp in FIG. 15 based on the change in the slip ratio Sn and the friction coefficient μ. 7 is replaced with steps 212 to 230 to form one routine. The calculation of the slip ratio Sn is well known and will not be described.
First, in FIG. 13, when it is determined in step 214 of FIG. 6 that the flag A is not set, the routine proceeds to step 501, where the friction coefficient slope dμ / dt is compared with a predetermined value K2, and the slip ratio is Sn is compared with a predetermined slip ratio S2 (set in step 602 of FIG. 14). If it is determined that the slope dμ / dt is below the predetermined value K2 and the slip ratio Sn at this time exceeds the slip ratio S2, the process proceeds to step 216 and subsequent steps. Proceed to 230. In step 216, the friction coefficient peak μp is set as the friction coefficient μ1, and subsequently, in step 502, the slip ratio Sn at this time is set as the slip ratio S1.
At step 217, the pressure reducing operation is switched to.

On the other hand, the flag A is set in step 214 and the minimum value of the slope of the friction coefficient (d
When the time tn of μ / dt) min is detected, the routine proceeds to step 500 of FIG. 13, where it is judged if the slip ratio Sn exceeds 30%. Here, the slip ratio Sn is 30
If it is determined to be equal to or less than%, the routine proceeds to step 304, where the brake fluid pressure is retained, but if it exceeds 30%, it is determined to be in a state of passing through the changed friction coefficient peak μp, After step 305, the processing is performed in the same manner as in FIG.

Further, in FIG. 14, step 224
If it is determined that the flag B is not set in step S601, the routine proceeds to step 601, where the friction coefficient slope dμ / dt is compared with a predetermined value K5, and the slip ratio Sn is compared with a predetermined value S1. Here, the slope dμ / dt is a predetermined value K
If it is determined that the slip ratio Sn is less than 5 and the slip ratio Sn at this time is less than the slip ratio S1, the slip ratio Sn at this time is set as the slip ratio S2 in step 602, and the pressure is switched to pressure increase in step 226. .

On the other hand, in step 224, the flag B is set, and in step 401 the maximum value of the slope of the friction coefficient (d
When the time tn of μ / dt) max is detected, the routine proceeds to step 600 in FIG. 14, where it is judged if the slip ratio Sn is below 10%. Here, the slip ratio Sn is 1
If it is determined that it is 0% or more, the routine proceeds to step 404, where the brake fluid pressure is held, but if it is less than 10%, it is determined that it is in a state of passing through the changed friction coefficient peak μp. The process proceeds to step 405 and subsequent steps, and is processed in the same manner as in FIG. Thus, according to the embodiment shown in FIGS. 13 and 14, the state in which the high friction coefficient is changed to the low friction coefficient,
Alternatively, it is possible to quickly determine whether or not the friction coefficient has passed the peak in a state where the friction coefficient has changed from the low friction coefficient to the high friction coefficient, so that the erroneous detection of the friction coefficient after the change can be prevented.

As described above, according to each embodiment of the present invention, the optimum braking force can be immediately secured even when the friction coefficient of the road surface changes, and the braking distance can be shortened as compared with the conventional device. be able to. FIG. 21 shows an example of an experimental result of an embodiment for carrying out the routines of FIGS. 5 to 7 and FIGS. 10 to 12. While traveling on a high μ road, a low μ road is entered at a point and a b point is reached. Shows the control situation when returning to the high μ road again. As is clear from the figure, when the vehicle enters the low μ road, the pressure is immediately reduced, and when the vehicle enters the high μ road, the pressure is immediately increased, and the wheel speed Vw is controlled so as to quickly approach the vehicle body speed Va.

[0043]

Since the present invention is configured as described above, it has the following effects. That is, according to the anti-skid control device of the present invention, when the peak determination means determines that the changed friction coefficient has a peak, the braking force control is started based on the friction coefficient near the peak, and the peak determination means causes When it is judged that the friction coefficient after the change has no peak, the braking force control is started based on the friction coefficient immediately after the change, so suddenly entering the road surface with a different friction coefficient during the anti-skid control. Even in this case, stable braking operation can be ensured and the braking distance can be shortened as compared with the conventional one.

In the anti-skid control device in which the friction coefficient detecting means is constituted by the tire torque sensor, the desired effect can be obtained with the minimum number of sensors, and wiring and assembly are easy.

Further, in the case where the friction coefficient detecting means is composed of the braking torque sensor and the wheel speed sensor, the detection output of the wheel speed sensor can be used for other control, so that various controls are possible. Becomes

Further, in the case where the anti-skid control device is provided with a slip ratio calculating means, a state in which a high friction coefficient is changed to a low friction coefficient or a low friction coefficient is changed to a high friction coefficient is obtained. Since it is possible to make a distinction without erroneously detecting whether or not the friction coefficient has passed the peak, it is possible to perform more rapid braking force control.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an anti-skid control device of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of an anti-skid control device of the present invention.

FIG. 3 is a block diagram showing a configuration of the electronic control device of FIG.

FIG. 4 is a flowchart of a friction coefficient calculation process according to an embodiment of the present invention.

FIG. 5 is a flowchart of a friction coefficient calculation process according to an embodiment of the present invention.

FIG. 6 is a flowchart showing a process of anti-skid control in one embodiment of the present invention.

FIG. 7 is a flowchart showing a process of anti-skid control in one embodiment of the present invention.

FIG. 8 is a flowchart showing a subroutine of anti-skid control in one embodiment of the present invention.

FIG. 9 is a flowchart showing a subroutine of anti-skid control in one embodiment of the present invention.

FIG. 10 is a flowchart showing a part of processing of anti-skid control in another embodiment of the present invention.

FIG. 11 is a flowchart showing a part of the processing of anti-skid control in another embodiment of the present invention.

FIG. 12 is a flowchart showing a part of the processing of anti-skid control in another embodiment of the present invention.

FIG. 13 is a flowchart showing a part of the processing of anti-skid control in still another embodiment of the present invention.

FIG. 14 is a flowchart showing a part of an anti-skid control process in still another embodiment of the present invention.

FIG. 15 is a flowchart showing a part of the processing of the anti-skid control in still another embodiment of the present invention.

FIG. 16 is a graph showing a relationship between a friction coefficient and a slip ratio for explaining control in one example of the present invention.

FIG. 17 is a graph showing a relationship between a friction coefficient and a slip ratio for explaining control in one example of the present invention.

FIG. 18 is a graph showing a relationship between a friction coefficient and a slip ratio for explaining control in one example of the present invention.

FIG. 19 is a graph showing a relationship between a friction coefficient and a slip ratio for explaining control in one example of the present invention.

FIG. 20 is a graph showing a relationship between a friction coefficient and a slip ratio for explaining control in one example of the present invention.

FIG. 21 is a graph showing a control situation in an example of the present invention.

[Explanation of symbols]

 WL wheel WC wheel cylinder PG hydraulic pressure generator AC hydraulic pressure controller BC braking force control means CF friction coefficient detection means CD change state determination means FR, FL, RR, RL wheel 2 hydraulic pressure generator 2a master cylinder 2b booster 3 brake Pedal 10 Electronic control device 11 Microcomputer 12 Input interface circuit 13 Output interface circuit 18a-18i Amplifying circuit 19a-19i Drive circuit 20 Electric motor 21,22 Pump 23,24 Reservoir 30 Actuator 31-38 Solenoid valve 41-44 Wheel speed sensor 45-48 Braking torque sensor 49 Brake switch 51-54 Wheel cylinder

Front page continuation (72) Inventor Go Naito 2-1, Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. (72) Inventor Naoyasu Enomoto 2-chome, Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. Within

Claims (5)

[Claims] 1. A wheel cylinder mounted on a wheel for applying a braking force, a hydraulic pressure generator for supplying a brake hydraulic pressure to the wheel cylinder, and an interposition between the hydraulic pressure generator and the wheel cylinder. A hydraulic pressure control device for controlling the brake hydraulic pressure of the wheel cylinder, a friction coefficient detecting means for detecting the friction coefficient between the wheel and the road surface at predetermined time intervals and storing the detection result, and the friction coefficient detecting means. A change state determination means for determining the change state of the friction coefficient based on the output, and a peak determination for determining the presence or absence of a peak of the friction coefficient after the change based on the determination result of the change state determination means and the output of the friction coefficient detection means. Means, and the hydraulic pressure control device is driven according to the outputs of the peak determining means and the friction coefficient detecting means to control the braking force by increasing or decreasing the brake hydraulic pressure supplied to the wheel cylinder. A braking force control means for controlling,
When it is determined by the peak determination means that the friction coefficient after the change has a peak, control of the braking force is started based on the friction coefficient near the peak, and the peak determination means does not peak the friction coefficient after the change. When it is determined that the anti-skid control device has a braking force control means for starting the control of the braking force based on the friction coefficient immediately after the change. 2. The anti-skid control device according to claim 1, wherein the friction coefficient detecting means is a tire torque sensor that detects a torque due to a frictional force of the wheel with respect to the road surface. 3. The friction coefficient detecting means includes a braking torque sensor for detecting a braking torque applied to the wheel, and a wheel speed sensor for detecting a rotational angular velocity of the wheel.
The anti-skid control device according to claim 1, wherein the friction coefficient is calculated based on the braking torque and the rotational angular velocity. 4. A slip ratio calculating means for calculating a slip ratio of the wheel based on an output of the wheel speed sensor, wherein the peak judging means changes the output of the change state judging means from a high friction coefficient to a low friction coefficient. After the change, when the slip ratio calculated by the slip ratio calculating means exceeds a first predetermined value, it is determined that the friction coefficient is in a state after passing a peak, and it is determined that there is no peak. After the output changes from the low friction coefficient to the high friction coefficient, when the slip ratio calculated by the slip ratio calculating means is below the second predetermined value, it is determined that the state is after the peak of the friction coefficient and no peak is determined. The anti-skid control device according to claim 1, wherein: 5. The peak determining means determines that there is no peak when there is no peak within a predetermined time after the output of the change state determining means has changed.
Antiskid control device as described.