JPS62166152A - Antiskid device for vehicle - Google Patents

Abstract

PURPOSE:To satisfactorily maintain the feeling of brakeage by providing a means for detecting a coefficient of friction between a road surface and a vehicle and a means for detecting a slip late, and adjusting a reincreasing rate of brake power in accordance with a ratio of the variation of the slip rate to the variation of the coefficient of friction. CONSTITUTION:There is provided a brake adjusting means 'b' for adjusting brake power, which acts on a wheel 'a' in the braking time of a vehicle, in each mode of relaxation, holding and increment. Further, there are provided first detecting means 'c' for detecting a coefficient of friction between the wheel 'a' and a road surface, and second detecting means 'd' for detecting a slip rate during the braking. And, a reincreasing rate of the brake power, after once it is relaxed, is adjusted by a control means 'e' in accordance with a ratio of the variation of the momentary slip rate per unit time to the variation of the coefficient of friction, so that suitable control for all kinds of the road surfaces is possible. Therefore, fluctuating width of the brake power can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an anti-skid device for a vehicle that prevents wheels from locking during braking of a vehicle.

[Conventional technology]

The conventional anti-skid device is disclosed in Japanese Patent Application Laid-Open No. 60-3.564.
As shown in No. 7, etc., a wheel speed, wheel acceleration/deceleration, or a reference speed that approximates the vehicle speed is created based on the signal of the wheel speed sensor, and the optimal braking force modulation is obtained by combining these. That's what I do.

In addition, the method of adjusting the braking force to the wheels by selecting and switching the modes of loosening, holding, and increasing the braking force is disclosed in Japanese Patent Application Laid-open No. 59-2.
06250 etc.

[Problem that the invention seeks to solve]

In these conventional devices, the wheel acceleration/deceleration is calculated based on the wheel speed, and the braking force is adjusted by comparing it with various setting levels.When the wheel acceleration/deceleration falls below a certain setting level G, The system starts to release the brake, monitors the start-up of wheel rotation due to the release of the brake, and controls whether or not the brake is maintained or increased again. Therefore, control is performed without detecting the μmS characteristics (friction coefficient - slip rate characteristics) between the road surface and the wheels, which change from moment to moment, resulting in a slight time delay in control depending on the various road surfaces, and the braking force applied to the wheels. There is a problem in that the fluctuation range of the brake becomes large and the brake feeling worsens.

The present invention has been made in view of the above problem, and an object of the present invention is to monitor the μmS characteristic, which changes moment by moment when the vehicle is braking, to optimally control the re-increase after the brake is released, and thereby to reduce the fluctuation range of the braking force.

Means for Solving Problem C] To this end, in the present invention, as shown in the schematic diagram of FIG. A first detecting means C for determining the coefficient of friction between the wheel a and the road surface, a second detecting means d for determining the slip rate during braking, A control means e is provided for adjusting the rate at which the braking force is increased again after it has been loosened, depending on the ratio between the change in the slip ratio and the change in the friction coefficient.

[Effect]

According to the above configuration, when the vehicle is braking, the slope of the friction coefficient-slip rate characteristic of the wheel is monitored, and based on the level of the slope, the rate of re-increase of the brake force that has been loosened is adjusted to increase or decrease to suit various road surfaces. Take control.

〔Example〕

The present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 2 is an overall configuration diagram showing the overall configuration of the device.

In this Fig. 2, 1 is a brake booster that increases the pressing force of the brake pedal, and 2 is the brake booster 1.
A mask cylinder 3 generates brake fluid pressure according to force, and 3 is an actuator that loosens, holds, and increases the brake fluid pressure from the mask cylinder 2, and includes a right front wheel actuator 3a, a left front wheel actuator 3b, and a rear wheel actuator 3C. have. 4 is the vehicle wheel (right front wheel),
4a is a left front wheel, 4b is a right rear wheel, and 4C is a left rear wheel. 5
is the vehicle brake of the right front wheel 4, and the right front wheel actuator 3
A frictional force is applied to a brake disc 6 connected to the right front wheel 4 in order to apply a braking force to the wheel 4 in response to the hydraulic pressure from a. Reference numeral 7 indicates a hydraulic pressure sensor for detecting the hydraulic pressure in the wheel brake 5, and 7a, 7b, and 7c indicate hydraulic pressure sensors corresponding to the front left wheel 4a, the rear right wheel 4b, and the rear left wheel 4C. 8
8 is a wheel sensor that detects the wheel speed of the right front wheel and generates a wheel speed signal with a frequency proportional to the magnitude thereof, and 8a, 8b, and 8c are wheel sensors corresponding to each wheel 4a, 4b, and 4c. It is.

The same wheel brake 5, brake disc 6, oil pressure sensor 7, and wheel sensor 8 associated with the right front wheel 4 are installed corresponding to the left front wheel 4a, right rear wheel 4b, and left rear wheel 4, respectively. ing.

9 is a signal line that transmits the oil pressure signal from the oil pressure sensor 7; 10
1 is a signal line that transmits the wheel speed signal from the wheel sensor 8;
1 is a signal line that transmits loosening commands, holding commands, and pressure increase commands to the actuator 3; 12 is an electronic control unit;
Said oil pressure sensor 7.7a, 7b, 7c corresponding to each wheel
, the signals from wheel sensors 8.8a, 8b, and 8c are signal vA9.

The control signal is received from the IO, performs various calculations, and applies a control signal to the actuator 3 from the signal line 11 to prevent wheel lock.

And between the actuators 3a, 3b, 3c and each wheel, and between the mask cylinder 2 and the actuators 3a, 3b, 3.
C is connected by respective hydraulic piping.

Further, as shown in FIG. 3, the right front wheel actuator 3a, the left front wheel actuator 3b, and the f&transport actuator 3C are each equipped with a liquid? It is equipped with an electromagnetic solenoid valve 31 that switches the brake fluid between pressure increase, hold, and pressure reduction modes, and a reservoir and pump section 32 that temporarily stores the brake fluid when the brake fluid pressure is released and then returns it to the mask cylinder side. , the hydraulic pressure output from each actuator 3a, 3b, 3c is transmitted to the wheel cylinder of each wheel brake 5 via each hydraulic pressure pipe, and brakes are applied to the wheels.

The electromagnetic solenoid valve 31 in the actuator operates in three modes: a pressure increase mode (a-b-) in which it communicates with the wheel cylinder side, a depressurization mode (b-c) in which it communicates with the pump section 32 side, and a holding mode in which it communicates with neither. It is configured as a 3-position valve with modes.

Next, the specific configuration of the electronic control unit 12 will be explained according to FIG. 4. In FIG. 4, 40 is a battery, 41 is an ignition switch that is turned on when the vehicle starts driving, and 42 is a brake switch that is closed in conjunction with the brake operation.

7. 7a, 7b, 7c are oil pressure sensors attached to the wheel brakes of each wheel to detect the oil pressure; 8° 8a, 8b, 8
c is a wheel sensor that detects the speed of each wheel; 43 is a control circuit that receives various signals from the above-mentioned sensors and performs calculation control;
45 is an A/D that sequentially converts analog oil pressure signals from the oil pressure sensors 7.7a, 7b, and 7c into digital signals.
Converters 46 to 49 are waveform shaping circuits that shape wheel speed signals of frequencies corresponding to the wheel speeds from the respective wheel sensors 8, 8a, 8b, and 8c into rectangular wave wheel pulse signals. 50 is a buffer circuit that is electrically connected to the stop switch 42 and converts the signal; 51 is a power supply circuit; when the ignition switch 41 is turned on, the battery 40 is
This converts the power supply voltage supplied by the converter into a constant voltage and supplies it to the entire device.

52 is a microcomputer, CPU52a.

It is composed of a ROM 52b, a RAM 52c, an I10 circuit 52d, etc., and receives signals from each sensor, performs predetermined digital arithmetic processing according to a control program recorded in advance in the ROM 52b, and generates various control signals. Reference numerals 53, 54, and 55 are actuator drive circuits that receive control signals such as a loosening command, a holding command, and a pressure increase command from the microcomputer 52 and generate drive outputs, which actuate the right rear wheel reactor 3a and the left front wheel actuator 3b.
.

It drives each electromagnetic solenoid valve of the rear wheel actuator 3C. Reference numeral 56 denotes a main relay drive circuit, which energizes the coil 57b of the main relay 57 having a normally open contact 57a to close the contact 57a and put the actuators 3a, 3b, and 3c into an operation standby state by supplying power to them. . Reference numeral 58 denotes a lamp drive circuit for lighting the indicator lamp 59.

Next, the operation of the above configuration will be explained with reference to the flowchart in FIG. 5 and the characteristic diagrams in FIGS. 6 and 7.

First, in FIG.
Starting from wheel sensors 8.8a, 8b.

Wheel speed from 8C ■8, oil pressure sensor 7.7a.

Read the wheel cylinder (W/C) pressure P from 7b and 7c. In the following step 104, the coefficient of friction μ between the road surface and the wheels is determined from the following equation.

11= ((1/r2)Vw + (k/r)P)/W
......(1) Here, ■ is the moment of inertia of the wheel, r is the effective radius of the wheel, and ■ is the acceleration/deceleration of the wheel. Find it as the time derivative of . k is a conversion coefficient from W/C pressure to braking torque, and P is W/C pressure. W is the wheel load, which is measured and stored in advance using a load meter, but may also be calculated and estimated using the following equation.

WF=WFO+ΔW・・・・・・(2) W, 1=WRo
−ΔW ・−−−−・(31Δw=
(WIl/2) ・ (H/L) ・ (Vs/
g)...(4) Here, W is the front wheel load, W. is the front wheel load at rest,
ΔW is the amount of load movement, WR is the rear wheel load, and W4° is the rear wheel load when stationary. W8 is the total vehicle weight, H is the height of the center of gravity, L is the wheel base, ■8 is the vehicle deceleration, and g is the gravitational acceleration. Note that equations (2) to (4) are calculation equations assuming that the vehicle is in straight-line control and that the spring constant of the suspension is extremely large.

In the subsequent step 106, the wheel slip rate S is calculated using the following equation.

s= (Vll V, ) / VIl= t
VW /v11... (5) In the above formula, ■ is the vehicle speed, which can be measured by a ground speed meter or vehicle acceleration sensor, but it can also be calculated using the following formula using a W/C pressure sensor. I'm looking for it.

v, -v. −gΣ(SaP idt” b Vwt)・
...(6) In the above formula, a=/ (rW), b= I/ (
r''W)i = 1~n (n = 2or3or4
).

In the following step 1108, the ratio Δμ/Δ between the difference in friction coefficient μ in minute time (per unit time): Δμ (−μm−μ.) and the difference in slip rate S: ΔS (” Sl so )
S (tangential slope of μmS characteristic) in steps 104 and 106
Calculate using the following formula based on the calculated value obtained in .

Δμ/ΔS = (μ, -μo) / (St -3o
)...(7) In addition, μ. +Sl) are both given zero as initial values. After calculating Δμ/ΔS using equation (7), the next Δ
For the calculation of μ/ΔS, variables are replaced as follows.

S0←S1 ・・・・・・(
8) μ. 18m...
- (9) In the subsequent judgment step 110, Δμ/ΔS is compared with the criterion, and if Δμ/ΔS>Kl holds, the road surface friction coefficient μ is at the peak part of the μmS characteristic (dμ/
ds=o), the process proceeds to step 112, where a drive signal is applied to the actuator 3, and the pressure is simply increased for the first time and again after loosening, and after maintaining stability, 'r, =T.
After the holding time of , pulse pressure increase control with a time width of tup2 is performed. In this case, the pulse pressure increase time tup=tup2 is relatively large as shown in the characteristic diagram of FIG.
Let p2=6 msec. Further, the W/C pressure holding time T, = T2 before the pulse pressure increase in step 112 is relatively small, as shown in the characteristic diagram of FIG. 7, for example, T, = 3.
0 m5ec.

On the other hand, if Δμ/ΔS>Kl does not hold in decision step 110, the process proceeds to decision step 114, where K is compared with 2 and Δμ/ΔS using the smaller criterion. Step 1
If Δμ/Δs>Kg is established in step 14, it is determined that there is still a slight margin until the μ peak, and the process proceeds to step 116, where the pressure is simply increased in the same way as step 112, and after maintaining stability, T, -T After the holding time of , pulse pressure increase control with a time width of tupl is performed. Pulse pressure increase time t in this case
up=tupl is relatively small as shown in FIG.
For example, let tupl=3 msec. Also, step 1
As shown in FIG. 7, the W/C pressure holding time Th-T before the pulse pressure increase at step 16 is relatively long, for example, T + -
It will be 75m56c.

If Δμ/ΔS>Kt does not hold in determination step 114, the process proceeds to determination step 118, where 3 (=O) and Δμ/ΔS are compared as a determination criterion smaller than K2. If Δμ/ΔS>K3 holds true, it is determined that the μ peak has been reached, and the process proceeds to step 120, where a drive signal is applied to the actuator 3 to perform holding control of the wheel brake chamber.

If Δμ/ΔS>K3 does not hold in judgment step 118, it is determined that the μ peak is likely to be exceeded and the wheels are likely to lock, and the process proceeds to step 122, where a drive signal is applied to the actuator 3 and the wheel brake is applied. Perform pressure reduction control.

The above operation is shown in the waveform diagram of FIG. That is, time t
When the brake pedal is depressed at 0 and a sudden braking operation is performed, the oil pressure of each wheel brake 5 of the wheels 4.4a, 4b, and 4c increases rapidly.

Then, as shown in the characteristic diagram of FIG. 9 showing the relationship between the friction coefficient μ and the slip rate S, the slope of the characteristic line Δμ/ΔS decreases rapidly, and at time t1, Δμ/ΔS is less than 3. Then, a loosening command is applied to the actuator 3, and the hydraulic pressure of the wheel brake 5 is loosened.

As a result of this loosening control, the wheel rotation begins to recover, and as a result, Δμ/ΔS gradually increases, and when it becomes larger than K3 (time tz), the control shifts to holding control, and the brake oil pressure at that time is maintained. Then, at time t3, the pressure is increased again, and at time t4, the pressure is increased again and the state shifts to stable maintenance.

If the wet road in Figure 9 changes to a dry road when the stability is maintained, the P on the wet road
P on dry road from control based on IIHAXI, □
It is necessary to change to control based on 8□.

Therefore, at time t, Δμ/ΔS is larger,
Proceeding to step 112 in FIG. 5, the pulse is increased after stability is maintained. That is, after the holding time of Th=Tt, a pulse pressure increase of pulse width tup=tup2 is performed, and thereby Δ
When μ/ΔS is larger than 2 and K is less than or equal to K, the process proceeds to step 116, and after the holding time of T, = T, pulse pressure is increased with a pulse width of tup = tupl, and the brake oil pressure of the wheels is gradually increased. , shifts to control suitable for dry roads. Then, the control oil pressure PBHAlt that exhibits optimal performance on dry roads and the oil pressure when the wheel speed suddenly drops are detected, and after the next pressure increase, the control is switched to that based on PIIMAM□.

Also, when changing from a dry road to a wet road,
At that point, the wheel speed suddenly drops, and as above, after the ground pressure is re-established, control is switched to one that is suitable for the wet road.

In addition, in the above-mentioned embodiment, the pulse pressure increase time tup is set to Δμ
/ΔS is shown, but a pressure increase pump may be added and the pressure increase 1pup may be made variable by Δμ/ΔS. In that case, in the flow chart of FIG. 5 and the characteristic diagram of FIG.
By replacing 2 with P and p2, control can be achieved without any other major changes.

〔Effect of the invention〕

As described above, according to the present invention, when the vehicle is braking, the inclination of the μmS characteristic of the wheel is monitored moment by moment, and the rate of re-increase of the once-relaxed braking force is sequentially adjusted to perform control suitable for various road surfaces. This has the excellent effect of reducing the variation range of braking force and maintaining good brake feeling.

[Brief explanation of drawings]

Fig. 1 is a schematic block diagram showing an overview of the present invention, Fig. 2 is a general block diagram showing an embodiment of the present invention, Fig. 3 is a block diagram showing a block diagram of its actuator, and Fig. 4 is a block diagram showing its electronic structure. A block diagram showing the detailed configuration of the control unit, Fig. 5 is a flowchart showing the arithmetic processing of the microcomputer, Fig. 6 is a characteristic diagram showing the pressure increase time of pulse pressure increase, and Fig. 7 is a holding at pulse pressure increase. FIG. 8 is a waveform diagram showing the control state, and FIG. 9 is a characteristic diagram showing μmS characteristics. a...Wheel, b...Brake adjustment means, C...First detection means, d...Second detection means, e...Control means, 3...Actuator, 5...Wheel brake, 6
...Brake disc, 7.7a, 7b, 7c...
oil pressure sensor. 8.8a, 8b, 8c...Wheel sensor, 12...Electronic control unit.

Claims (1)

[Scope of Claims] An anti-skid device for a vehicle equipped with a brake adjustment means that detects a tendency of a wheel to lock when braking a vehicle and adjusts the brake force applied to the wheel in each mode of loosening, holding, and increasing. , a first step of determining the coefficient of friction between the road surface and the vehicle during braking;
a detection means, a second detection means for determining the slip rate during the braking, and a second detection means for determining the slip rate during the braking, and a second detection means for determining the slip rate during the braking, An anti-skid device for a vehicle, comprising: a control means for adjusting the rate of increase.