KR930007726B1 - Antilock brake control device - Google Patents

Abstract

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Description

Anti-lock brake control device that switches between simultaneous 2-wheel control and independent control

1 is a block diagram of an electronic control circuit of an embodiment of an anti-lock brake control apparatus according to the present invention.

2 is a block diagram of a hydraulic circuit.

3 is a flowchart art of a program in an electronic control circuit.

4 is a partial flow chart of normal actilock control.

5 is a flowchart art of a main program.

6 is another embodiment of the flowchart art of FIG.

7 and 8 illustrate a failure state of the operation of the conventional example.

* Explanation of symbols for main parts of the drawings

10 electronic control circuit 13 microcomputer

22, 22 °: solenoid valve 23: hydraulic pump

S1 to S4: Wheel speed sensor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-lock brake control apparatus for performing two-wheel simultaneous control and independent control in which the brake braking efficiency of wheels of automobiles, in particular, left and right rear wheels, is improved.

When brake braking a wheel of an automobile or the like, an anti-lock control method is preferable in order to operate the brake device with high efficiency in response to a change in the friction coefficient of the road surface. According to this anti-lock control method, the brake is controlled so that the brake braking and opening can be repeated within a short time by pressurizing, maintaining, or depressurizing the brake pressure in the brake pipe even though the brake is being braked. do.

The control apparatus used for the anti-lock control generally includes a wheel speed sensor for detecting wheel speed and a wheel speed, estimated vehicle speed (reference wheel speed), slip ratio, and the like calculated from the detected wheel speed signal. An electronic control circuit for outputting control signals such as depressurization, holding, and pressurization based on the result, and a hydraulic control unit for inputting and adjusting the braking pressure from the master cylinder by the control signal from the control circuit.

When the wheel speed signal is input, the electronic control circuit performs various calculations based on the input information and determines whether the braking state of each wheel is in the lock direction or the recovery direction from the lock, based on the change of the slip ratio, the deceleration value, and the like. Based on the result, a control signal such as depressurizing, holding, or pressurizing is output to the hydraulic control unit.

Hydraulic control units generally include solenoid valves (or these and shutoff valves or flow control valves), check valves, hydraulic pumps and motors, accumulators, reservoir tanks, and the like. It consists of a hydraulic pressure circuit which opens and closes a flow of a braking pressure or a pump liquid pressure by the valve of any of the above provided in the braking pressure path.

In the case of brake braking of each wheel by the hydraulic circuit as described above, a method of opening / closing and controlling the flow of hydraulic pressure to the wheel cylinder is provided. For each wheel, and for the rear wheels, a 3-channel system is provided for each pair of left and right pairs of rear wheels, and solenoid valves are installed only for the left and right front wheels. There is a two-channel system that follows.

A method of applying a hydraulic control signal to the hydraulic circuit, in which the left and right wheels are considered as a pair of front and rear wheels, respectively, and based on the side controlled by the low hydraulic pressure among the pair of wheels (surface friction coefficient sound). Therefore, when the low pressure side turns to lock, both control methods reduce pressure (hereinafter referred to as select low). On the contrary, when the high pressure side turns toward lock, both pressure control means (referring to select high) Or a method of independently controlling the hydraulic pressure of each wheel according to the road surface situation (hereinafter referred to as independent) is known.

In general, the select low is effective for securing the lateral force of the wheel, and affects the directional stability and steering of the vehicle, but has a disadvantage in that the braking distance is extended because the braking force is insufficient. On the contrary, the select high can secure the braking force, but has a disadvantage in that the direction stability is insufficient. Independent has a cost, but there is an advantage that it can be finely controlled according to the situation of each road surface. In consideration of the advantages and disadvantages of the respective control methods, it is generally said that the independent or select is preferable for securing the braking force on the front wheel, and the select low is preferable for securing the direction stability of the vehicle for the rear wheel.

However, in the conventional anti-lock brake control apparatus, in general, all the wheels are always independently controlled, or the select wheel control method is always applied to the rear wheels regardless of how the road surface condition changes.

In the case where the select control of the rear wheel is applied to the rear wheel, there is a manufacturing error in the hydraulic control unit that performs the hydraulic control. Therefore, as shown in FIG. Hydraulic pressure difference may occur from side to side. In this case, if it is always controlled by the select low, the slight nonuniformity is piled up every time the operation is repeated, and if there is no nonuniformity of the acceleration / deceleration characteristic, the wheel speed and acceleration / deceleration curve such as curves b and b 'should be. It becomes like curve a, a ', and the difference by the nonuniformity expands. Therefore, the brake braking force of the rear wheel which becomes the low pressure side is not effectively utilized, resulting in extremely low efficiency.

When the front wheels are always independently controlled, the friction coefficients of the left and right road surfaces are greatly different, and when the sum of slips of both rear wheels is greater than or equal to a predetermined value, the braking force of the left and right rear wheels is greatly different. As shown (curves c, c ', d, d'), the braking timing, acceleration and deceleration time, etc. are all different, and driving stability of the vehicle is impaired (stability is likely to be lost in the vicinity of A and B). Therefore, in such a case, it is effective to secure directional stability by controlling with select.

However, if the rear wheels are always controlled by the select low, when the sum of the slips of the left and right rear wheels is less than a certain value, this means that the slip amount of the left and right rear wheels is respectively reduced, so even if there is a difference in braking force between the left and right rear wheels, It does not have a big influence anymore so as to impair stability, and in such a state, controlling the rear wheels by the select row unnecessarily results in the loss of the braking force, thereby extending the braking distance.

The present invention has been made in view of the above-described state of the art of the anti-lock brake control device, and an object thereof is to improve the control method of the rear brake in the above-described conventional anti-lock brake control device. If the sum of the slip amounts is greater than or equal to the fixed value, select lock is applied to the rear wheel, and if it is less than or equal to the anti-lock, the two-wheel simultaneous control and independent control can be switched to control the switch to independent. It is to provide a brake control device.

Thus, in the present invention, as a means for solving the above problems, the wheel speed sensor for detecting the rotational speed of each wheel and the detected wheel speed signal to calculate the wheel speed, estimated vehicle speed, deceleration, slip ratio and the like An electronic control circuit for outputting a hydraulic pressure control signal based on the result, and a hydraulic pressure control unit capable of independently adjusting at least the braking force of the left and right rear wheels by the control signal. When the sum of the slip amounts exceeds a predetermined value, either of the left and right rear wheels simultaneously controls both rear wheels based on information from the lower rotation speed, and when the sum of the slip amounts exceeds a predetermined value, A configuration is adopted in which the wheels are independently controlled based on the speed information of each wheel.

When the brake is braked by stepping on the brake pedal, the anti-lock control is started. When the wheel speeds are decelerated due to the pressurization by brake braking, these wheel speed changes are calculated by the electronic control circuit, and the slip amount, deceleration, and slip of the left and right rear wheels are calculated for each wheel. As a result of this calculation, it is judged whether or not the slip sum of the rear wheel exceeds a predetermined value, and when the predetermined value is more than the predetermined value, the speeds of both rear wheels are also compared, and the high speed wheel speed is replaced by the low speed wheel speed, Using these wheel speeds, the deceleration and slip ratios of each wheel are further determined to determine whether each wheel is in the lock direction or the recovery direction from the lock, and whether to pressurize, maintain, or depress the rear wheel according to each judgment. Control signal is output. As a result, the select wheel is controlled on the rear wheel side.

When the predetermined value is less than or equal to the predetermined value, the control of the select row is released, and each wheel performs normal anti-lock control independently according to its own input information.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing an outline of an electric control system of an anti-lock brake control apparatus according to the present invention. Each wheel speed signal detected by the wheel speed sensors S1 to S4 for detecting the rotational state of each wheel in the front, rear, left and right of the vehicle is input to the A / D converter 11 of the electronic control circuit 10 and pulsed. The signal is converted into a signal, processed by the pulse processing signal 12, and sent to the microcomputer 13.

In the microcomputer 13, deceleration, vehicle estimation speed, slip ratio and the like are calculated based on the wheel speed pulse signal, and the solenoid driving circuit 14 and the motor driving circuit 15 are calculated based on the calculation result. Each will send the necessary control signal. In addition to the drive circuit, a double safety device relay drive circuit 16 and an alarm lamp drive circuit 17 are provided. W.L is an alarm light.

The solenoid drive circuit 14 sends control signals of four systems as shown in FIG. 1, and turns on four sets of each pair of solenoid valves 22 and 22 '(2-position switching valve). (ON) and OFF (OFF), each brake cylinder of each wheel is switched to an operation mode of pressurizing, holding or depressurizing to brake braking.

As shown in FIG. 2, the hydraulic circuit of this embodiment includes a pair of solenoid valves 22, 22 'and a hydraulic pump disposed on the master cylinder 21, its braking pressure circuit, and its return path. 23, a motor 24, an accumulator 25, a reserve tank 26, a check valve 27, and the like. The braking pressures of the two systems from the master cylinder 21 are supplied to the left and right front wheels, respectively, and the braking pressure to the left front wheel is branched on the way and sent to the right rear wheel, and the right rear wheel is symmetrical with this. The dynamic pressure gauge consists of X piping. A pair of solenoid valves 22, 22 'and a check valve 27 are provided for each wheel, and the hydraulic pump 23, the accumulator 25, and the reservoir tank 26 are right and left two. It is provided for each system of two braking pressure systems, and the motor 24 drives two hydraulic pumps 23 by a biaxial drive type. This hydraulic circuit is generally referred to as reflux.

Anti-lock control by the anti-lock brake control device is performed as follows (see FIGS. 3 to 8).

When the power is turned on and the vehicle starts, the wheel speed signal of each wheel while driving is input to the electronic control circuit 10, and the wheel speed of each wheel V _FLH , V _FRH , V _RLH , by the microcomputer 13. The calculation of V _RRH is performed. When the brake is braked by the brake pedal, anti-lock control is started.

As shown in FIG. 3, after calculating the wheel speed that is changed by brake braking, the estimated vehicle speed V _REF and rear wheel slip sum S _R = (2V _REF -V _RLH -V _RRH ) And the like are calculated.

Next, it is determined whether S _R is larger than the reference value THR (threshold). The reference value is determined based on whether the slip of the rear wheel affects the stability of the vehicle. Therefore, if S _R is less than or equal to the reference value THR, there is little influence on the stability, and each wheel may be controlled independently according to the road surface situation. Therefore, the wheel speeds are respectively V (1) to V (4).

If it is larger than THR, the operation for controlling the selector of the rear wheel is performed. That is, the wheel speeds of the left and right rear wheels are compared, and when the wheel speed V _RRH of the right rear wheel is smaller than the wheel speed V _RLH of the left rear wheel, the speed of the left rear wheel is V (3) = V _RRH . On the contrary, when large, V (4) = V _RLH . As a result, the rear wheels are controlled by the information on the low speed side.

Which of the three cases is V (i) (i = 1 to 4) is different depending on the road surface situation. Therefore, using this new wheel speed V (i), the deceleration Dv, the slip ratio S, and the like are obtained as in the normal anti-lock control, and V (i) is evaluated. As a result, the liquid-up control signal is determined by? (I). It is determined whether the pressure is reduced, maintained or pressurized. The control signal can be determined according to, for example, the flowchart art used for normal anti-lock control shown in FIG.

Before entering the flowchart art of FIG. 4, the initialization process is performed in the main program described later, and then, the phase of the command in which the respective modes of decompression, retention and pressurization of the control signal are combined is set to I. Three phases are generally used for this phase, and the pressurization is phase I, the combination of the decompression and the maintenance command is phase II, and the combination of the pressurization and the maintenance command is phase III.

In this state, when the flowchart art of FIG. 4 is processed and the deceleration obtained by V (i) (i = 1 to 4) is not determined that the slip ratio value is the lock tendency, it is determined by the initial setting. Since the phase is set to I, the processing of the phase I is performed as it is, outputting to the solenoid for each wheel. For this reason, each wheel remains pressurized, and while returning to the beginning of the flowchart art and repeating the same processing, the deceleration and slip ratio change due to the pressurization command, and the vehicle is gradually moved toward the lock direction.

When the lock tendency is detected, the command is switched to the processing of phase II. In this case, since the decompression and the holding command are output, the decompression and the holding command are directed to the direction in which the lock is recovered. If a lock recovery trend is detected, it is changed to the treatment of phase III. When there is no large change in the road surface situation, the brake braking is most efficiently carried out by the processing of the above phases I → II → III, and the vehicle rapidly decreases or stops. However, if the frictional coefficient of the road surface greatly changes in the middle, the phase returns to II again and then changes to transition to Phase III again.

5 shows an example of a main program in the microcomputer 13. With respect to this main program, the subprograms shown in the flowchart arts of FIGS. 3 and 4 are configured as a program for interrupting timely intervention, performing initialization processing after initial check, setting a phase to I, and then permitting interruption. Then, the judgment is made as shown in Fig. 1, and the endless loop is repeated as long as there is no abnormality. If there is an interruption at regular intervals, the main loop suspends and executes the subprogram.

FIG. 6 is another embodiment of the subprogram of FIG. It is basically the same program, but V (i) (i = 1 to 4) is evaluated first, and the resultant θ (i) (i = 1 to 4) such as deceleration and slip ratio obtained as a result is obtained. When selecting a select, the only difference is that the result is replaced with a lower speed result.

As described in detail above, in the present invention, the speed of the rear wheel is replaced by the value of the rear wheel, or the speed of the high speed is replaced with that of the low speed, according to the magnitude of the rear wheel slip sum. The lock direction of each wheel or recovery direction from the lock was determined from the slip ratio, and the control signal was outputted according to each judgment. Therefore, even if there is a non-uniformity caused by the error of the hydraulic control unit, the friction coefficient of the left and right road surfaces is large. Even when they are different, when the slip sum of the rear wheels is large, the direction stability of the rear wheels is secured by the select low, and when the slip sum is small, the respective wheels are controlled independently so that the braking force can be secured and extremely efficient brake braking can be performed.

Claims (3)

At least the wheel speed and the estimated vehicle speed are calculated from the wheel speed sensors S1 to S4 for detecting the wheel speed signal corresponding to the rotation speed of each wheel, and the detected wheel speed signal, and the hydraulic control signal (θ) is calculated based on the calculation result. an electronic control circuit 10 for outputting (i)) and hydraulic control units 22 to 24 for independently adjusting at least the braking force of the left and right rear wheels according to the control signal. Has a means for evaluating the sum of slip amounts of the left and right rear wheels, and when the sum of the slip amounts exceeds a predetermined value, both of the left and right rear wheels simultaneously control both rear wheels by information from the lower rotation speed, When the wheel is less than the predetermined value, the anti-lock brae that switches between the two-wheel simultaneous control and the independent control configured to independently control all the wheels based on the speed information of each wheel. Control device. 2. The electronic control circuit according to claim 1, wherein the electronic control circuit calculates a slip sum of at least the wheel speeds, the estimated vehicle speeds, and the rear wheels of at least all wheels from the wheel speed signals detected by the wheel speed sensors S1 to S4. Compared with stationary, when the slip sum exceeds a predetermined value, the wheel speeds of the left and right rear wheels are further compared, and either the high speed wheel speed is replaced with the low speed wheel speed, and the low speed wheel speed is used. Hydraulic control unit calculates the deceleration and slip amount, controls the rear wheels based on the calculation result, and controls all the wheels independently at each wheel speed without performing the above replacement when the slip sum is less than a predetermined value. And an anti-lock brake control device for switching between two-wheel simultaneous control and independent control. The wheel of claim 1, wherein the electronic control circuit calculates at least the wheel speeds and the estimated vehicle speeds of all the wheels from the wheel speed signal detected by the wheel speed sensor, calculates the slip sum of the rear wheels, and calculates the slip sum of the rear wheels. With respect to the control signal θ (i), when the slip sum of the rear wheels exceeds a predetermined value, the wheel speeds of the left and right rear wheels are compared and either the high speed calculation result is replaced with the low speed calculation result. An anti-lock brake control device for switching between two-wheel simultaneous control and independent control as a control signal and outputting it to the hydraulic control unit as a control signal as it is as a result of calculation for each wheel when the slip sum is less than a predetermined value.

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