JP2762468B2 - Anti-skid control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-skid control device, and more particularly to an anti-skid control device capable of reliably preventing wheels from locking even during turning braking of a vehicle.

[Conventional technology]

2. Description of the Related Art Conventionally, an anti-skid control device that controls a slip state of a wheel to an optimum value in order to prevent locking of a wheel during vehicle braking and to ensure running stability has been known. This anti-skid control device includes a wheel speed sensor, calculates a reference speed simulating each wheel speed and a vehicle speed from the output of this sensor, and calculates a slip ratio of each wheel by comparing these speeds. . When the calculated slip ratio of each wheel increases, the brake pressure of the wheel is reduced or held, and when the slip ratio decreases, the control cycle of increasing the brake pressure is repeated, whereby the slip ratio of the wheel is increased. Is optimally controlled to ensure running stability during braking.

In such an anti-skid control device, the slip ratio of the wheels is controlled to about 20%, but in order to perform the control, the vehicle speed must be accurately detected. For this reason, a method using a vehicle body speed sensor separately from the wheel speed sensor has been proposed, but it is not realistic because it is expensive.

Therefore, a method of calculating a reference speed as a vehicle speed in a pseudo manner from the wheel speed is generally used. Among them, a method of calculating a reference speed using the maximum value of the wheel speed of each wheel is widely used. However, when the vehicle is turning, since the turning inner wheel and the turning outer wheel have different speeds, optimal control cannot be performed by the method of controlling each wheel at one reference speed. For this reason, for example,
Japanese Patent Application Laid-Open No. 61-291261 proposes a method in which a steering sensor is provided and reference speeds of left and right wheels are separately created based on a steering angle.

[Problems to be solved by the invention]

However, in a vehicle, there is a problem that the steering angle and the turning state of the vehicle do not always match. Further, there is another problem that the cost is increased by providing the steering sensor.

The present invention has been made in view of the above-described problems, and provides an anti-skid control device that can always create a reference speed that appropriately simulates a traveling state of a vehicle without adding any special sensor or the like. With the goal.

[Means for solving the problem]

In order to achieve the above object, an anti-skid control device according to the present invention comprises a vehicle having a plurality of left and right wheels as shown in FIG. Based on the wheel speed of each of the left and right wheels detected by the detection unit, a reference speed calculation unit that calculates a reference speed corresponding to the left and right wheels for each of the left and right wheels, and a reference calculated separately for the left and right wheels by the reference speed calculation unit. A lock tendency determining unit that compares the speed with the wheel speeds of the left and right wheels and determines the locking tendency of the left and right wheels, respectively. The brake pressure of the left and right wheels is determined based on the locking tendency determined by the locking tendency determining unit. A brake pressure adjusting means for adjusting, and a reference speed having a higher speed among the reference speeds of the left and right wheels separately calculated by the reference speed calculating means. Speed difference limiting means for limiting the speed difference between the reference speeds of the left and right wheels as a reference; speed difference varying means for increasing the speed difference limited by the speed difference limiting means as the vehicle speed corresponding to the left and right wheels increases. The configuration is provided with.

[Action]

In the present invention, based on the wheel speed of each of the left and right wheels,
The reference speeds for the left and right wheels are separately calculated, and the locking tendency of each of the left and right wheels is determined based on the reference speeds, and the brake pressure is adjusted. At this time, the reference speed for the left and right wheels is
The speed is restricted based on the higher reference speed. In addition, a speed difference that is limited as the vehicle speed increases becomes larger. In this way, by limiting the reference speed difference and changing the speed difference limit, it is possible to suppress erroneous operation on a straight traveling crossroad or the like without adding a special sensor, and to set the right and left sides of the vehicle according to the turning state. The reference speeds of the left and right wheels that appropriately simulate the vehicle speed can be created. Therefore, appropriate control according to the turning state can be performed in the anti-skid control without a special sensor.

〔Example〕

Hereinafter, an embodiment of the anti-skid control device of the present invention will be described with reference to the drawings.

FIG. 2 is a configuration diagram schematically showing an overall configuration of an anti-skid control device applied to a rear-wheel drive vehicle.

In FIG. 2, 1,3,5,7 represent each wheel of the vehicle.
Denotes a front right wheel, 3 denotes a front left wheel, 5 denotes a rear right wheel, and 7 denotes a rear left wheel. Reference numerals 9, 11, 13, and 15 denote wheel speed sensors for detecting wheel speeds, respectively. Known wheel speed sensors such as an electromagnetic pickup type and a photoelectric conversion type can be used. And each wheel speed sensor 9,11,13,15 is connected to each wheel 1,3,
It is installed near 5, 7 and outputs a signal according to the rotation of the wheels. Also, 17,19,21,23 are wheel cylinders,
It is arranged on each wheel 1,3,5,7. These wheel cylinders 17, 19, 21, and 23 act to apply a braking force to each wheel with hydraulic pressure from a hydraulic cylinder 45 that generates a brake hydraulic pressure in response to a depression operation of a brake pedal 25. The hydraulic pressure from the hydraulic cylinder 45 is appropriately reduced by hydraulic control actuators 27, 29, 31, and 33 controlled by an electronic control unit 49 described below so as to optimize the braking force of each wheel, in other words, to optimize the slip ratio. -It is configured to hold and increase the pressure. 35, 37, 39, 41 are hydraulic conduits for guiding the hydraulic pressure adjusted by the hydraulic control actuators 27, 29, 31, 33 to the wheel cylinders 17, 19, 21, 23.

The electronic control unit 49 is operated by being supplied with power from a battery, and operates by various input signals related to the running / control state of the vehicle, such as a wheel speed signal from the wheel speed sensors 9, 11, 13, 15 and the brake pedal 25. A hydraulic control actuator that inputs a signal from a stop switch 43 that detects a braking operation of the vehicle, and adjusts a brake hydraulic pressure based on these signals.
Control signals are output to 27, 29, 31, and 33.

The electronic control unit 49 includes, as shown in FIG. 3, waveform shaping amplifier circuits 60 and 62 for converting the wheel speed signals from the wheel speed sensors 9, 11, 13, and 15 into pulse signals suitable for processing by the microcomputer 68. , 64, 66, a buffer circuit 70 connected to the stop switch 43, a power supply circuit 72 for supplying the power supply voltage supplied from the battery as a constant voltage when the ignition switch 50 is turned on to the entire apparatus, and each input signal. A microcomputer 68 that outputs a control signal to the actuator drive circuits 84, 86, 88, 90 for driving each of the actuators 27, 29, 31, 33 according to the control signal;
Main relay that controls power supply to the actuator
It comprises a main relay drive circuit 92 for driving 51 and an indicator lamp drive circuit 94 for driving an indicator lamp 53 for notifying an abnormality of the anti-skid control device.

When the ignition switch 50 is turned on, the electronic control device 49 configured as described above applies a constant voltage from the power supply circuit 72 to the microcomputer 68 and the like, and the CPU 76
The arithmetic processing is started according to a program stored in the OM78 in advance. This calculation process is executed based on the flowchart shown in FIG.

First, in step 100, initialization processing such as memory clear, flag reset, and I / O setting is executed. Step 200
In the above, the reading processing of the detection signals of the sensors and switches described above is executed. Based on the wheel speed signal read in step 200, in step 300 each wheel speed, that is, right front wheel speed V _WFR , left front wheel speed V _WFL , right rear wheel speed V _WRR , left rear wheel reference speed V _WRL Is calculated. Then the respective wheel speeds _{V WFR, V WFL, V WRR} , the reference speed of the left and right wheels from the V _WRL at step 400, i.e. the right wheel reference speed V _REFR and left wheel reference speed V _REFL is calculated. Subsequently, in step 500, each wheel speed calculated in steps 300 and 400 is compared with the left and right wheel reference speed, and the actuator operation mode is set so that the slip ratio of each wheel is optimized. In step 600, an actuator control signal is output to each of the hydraulic control actuators 27, 29, 31, and 33 according to the operation mode set in step 500. Thereafter, step 200
Repeat ~ 600.

Next, details of the basic control of step 400 will be described with reference to the flowchart of FIG. First, at step 402, the maximum value V of the right front wheel speed V _WFR and the right rear wheel speed V _WRR
Obtaining _{WRHi [V WRHi ← max (V WFR,} V WRR) ] as a right wheel reference speed. Next, in step 404, the maximum value V _WRHi as the right wheel reference speed, the right wheel reference velocity V _REFR which the last calculated
Comparing the preset value obtained by subtracting the rate K ₁ from. Here, the rate K ₁ is a constant for limiting below a certain value the deceleration reference speed. As a result of this comparison,
If the maximum value V _WRHi as right wheel reference speed is high, that is, when was the limitation of the deceleration of the previous reference velocity V _REFR, the process proceeds to step 406. In step 406, it compares the maximum value V _WRHi as right wheel reference speed, and a preset value obtained by adding the speed K ₂ was the right wheel reference velocity V _REFR which the last calculated. Wherein the rate K ₂ is a constant for limiting below a certain value of the acceleration of the reference velocity V _REFR. The result of this comparison, if the maximum value V _WRHi as right wheel reference velocity is small, that is, when was the limit of the acceleration of the previous reference velocity V _REFR, the process proceeds to step 408. The maximum value V _WRHi the right wheel in step 408 is set as the right wheel reference velocity V _REFR [V _REFR ← V _WRHi]. If the maximum value V _WRHi as right wheel reference velocity exceeds a limit deceleration of the previous reference velocity V _REFR at step 404, the process proceeds to step 412, the deceleration limit value as a right wheel reference speed V _REFR Set [V _REFR ← (V
_REFR -K _1)]. At step 406 the maximum value V _WRHi as right wheel reference speed when it exceeds the limits of acceleration of the previous reference velocity V _REFR, the process proceeds to step 410 to set the acceleration limit value as the right wheel reference speed V _REFR [V _REFR ← (V _REFR + K
₂ )].

As described above, at steps 402 to 412, the right wheel reference speed V
_Although REFR is obtained, the left wheel reference speed V _REFL can be similarly obtained in steps 452 to 462.

Next, the characteristic portion of the present invention in step 400 is shown in the flowchart of FIG. This flowchart differs from the basic flowchart shown in FIG.
403, 413, 453, and 463 are added, and the subsequent processing is the same, so that the description here is omitted. In step 403, it compares the value obtained by subtracting the rate K ₃ which is set in advance from the maximum value is V _WRHi symmetrical wheel left wheel reference speed V _REFL as right wheel reference speed. Here, this speed K ₃ is a constant to limit the difference between the left and right wheels reference speed. As a result of this comparison, when the maximum value V _WRHi as the right wheel reference speed is large,
That is, when the speed difference between the reference speeds of the left and right wheels is within the predetermined limit, the process proceeds to step 404, and the same process as the process described with reference to FIG. 5 is executed. If the maximum value V _WRHi as the right wheel reference speed is small, that is, if the speed difference between the reference speeds of the left and right wheels exceeds a predetermined limit, the process proceeds to step 413, where the high speed left wheel reference speed is used as a reference. as to set the limit value by a left wheel reference speed as the right wheel reference velocity V _REFR [V _REFR ← (V _REFL -
K _3)]. Also, regarding the left wheel reference speed, step 453,
At 463, it is obtained by the same processing as described above.

Note that as the speed limit difference K ₃ of the reference speed is shown in FIG. 7 for example, when the variable with respect to the reference speed, that estimated vehicle speed, it is possible to obtain a reference speed approximating more turning state of the vehicle. This is because, even when the turning radius at the time of turning the vehicle is the same, the speed difference between the turning inner wheel and the turning outer wheel increases as the vehicle speed increases.

Further, the limit speed difference K ₃ of the reference speed to the reference speed as described above as a method for the variable, the ratio of the lower reference speed for high reference speed is always may be made constant.

In step 403 of the sixth flowchart, the maximum value V _WRHi as the right wheel reference speed and the left wheel reference speed V
Compared with the value obtained by subtracting the predetermined speed K ₃ from _REFL ,
At this time, the left wheel reference speed V _REFL may be substituted with the left driven wheel speed. In steps 402 and 452, the reference speed of each of the left and right wheels may be created based only on the driven wheel speed, and the subsequent processing may be performed. This is because, during braking of the vehicle, the driven wheel speed indicates a value that is substantially closer to the vehicle speed than the drive wheel speed.

By limiting the speed difference between the left and right wheel reference speeds as described above, for example, as shown in FIG. 8, the wheel speeds (V _WFR , V _WFR , V _WFR , V _WFR ,
_{Even if the WRR} drops sharply, the reference speed (V
_REFR ) can be prevented from being excessively reduced. Therefore, based on the reference speeds (V _REFR , V _REFL ) obtained above, the slip ratio of each wheel is calculated, and the brake pressure of each wheel is adjusted according to the slip ratio, whereby
Even during turning braking, the braking distance can be shortened while securing running stability.

〔The invention's effect〕

As described above, according to the present invention, the reference speeds of the left and right wheels are separately calculated based on the maximum wheel speeds of the left and right wheels without adding any special sensor or the like, and the reference speeds of the left and right wheels are calculated. , The reference speeds of the left and right wheels that appropriately simulate the vehicle speeds on the right and left sides of the vehicle can always be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the outline of the present invention. FIG. 2 is a block diagram showing the overall configuration of one embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the electronic control unit of FIG. 2, and FIG. 4 shows an example of control of one embodiment. Flow chart, FIG.
6 is a flowchart showing a detailed processing procedure of step 400 of the flowchart shown in FIG. 6, FIG. 6 is a flowchart showing another processing procedure of step 400 of the flowchart shown in FIG. 4, and FIG. 7 is a flowchart of another embodiment of the present invention. FIG. 8 is an explanatory diagram for explaining the operation, and FIG. 8 is a waveform diagram for explaining the operation of the control according to the flowchart of FIG. 1 ... Right front wheel, 3 ... Left front wheel, 5 ... Right rear wheel, 7 ... Left rear wheel,
9,11,13,15 …… wheel speed sensor, 17,19,21,23 …… wheel cylinder, 27,29,31,33 …… hydraulic control actuator, 4
5… Hydraulic cylinder, 49 …… Electronic control device.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60T 8/66 B60T 8/58

Claims (2)

(57) [Claims] 1. A vehicle having a plurality of wheels on each of left and right sides, a wheel speed detecting means for detecting a speed of the wheel, and a left and right wheel based on each wheel speed detected by the wheel speed detecting means. A reference speed calculating means for calculating a reference speed corresponding to each of the left and right wheels, and a reference speed calculated separately for the left and right wheels by the reference speed calculating means and a wheel speed of the left and right wheels. Lock tendency determining means for respectively determining the tendency; brake pressure adjusting means for adjusting the brake pressure of the left and right wheels based on the lock tendency determined by the lock tendency determining means; Speed difference limiting means for limiting the speed difference between the reference speeds of the left and right wheels based on the higher reference speed at the reference speeds of the left and right wheels; The speed difference serial speed difference limiting means for limiting, antiskid control device, characterized in that it comprises a speed difference varying means to increase as the vehicle speed increases corresponding to the left and right wheels. 2. The reference speed calculating means calculates the reference speed of the left wheel based on a plurality of wheel speeds on the left side of the vehicle body, and calculates the reference speed of the right wheel based on a plurality of wheel speeds on the right side of the vehicle body. The anti-skid control device according to claim 1, wherein: