JPH01249555A - Antiskid control device - Google Patents

Abstract

PURPOSE:To improve braking performance on an icy road or the like by increasing an engine speed while setting it so as to be in a higher value in a two-wheel- drive side condition than in a four-wheel-drive side condition when a predetermined slip condition is decided. CONSTITUTION:The captioned device calculates a slip rate of a wheel by a slip rate arithmetic means C being based on output signals of a wheel speed detecting means A and a car body speed estimating means B and controls a brake pressure of the wheel by a control means D being based on these slip rate and wheel speed detection value. Here the device provides a drive condition detecting means E detecting a vehicle for whether it is in a two-wheel-drive side condition (2W) or in a four-wheel-drive side condition (4W) and a target value setting means F setting a speed target value in the time of braking with the 2W in a higher value than in the 4W. When the condition is decided to be in a predetermined slip condition by a decision means G, an engine speed adjusting means H increases the engine speed in accordance with the above described speed target value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an anti-skid control device that prevents wheel locking during braking of a vehicle, and particularly relates to an anti-skid control device that prevents wheel locking during braking of a vehicle.
2WD) and four-wheel drive (4WD) are selectable.
This is a selective four-wheel drive vehicle, or a so-called vehicle in which the driving force distribution ratio between the front and rear wheels is continuously variable controlled by the engagement force of the clutch.

The present invention relates to an anti-skid control device used in Torx brift type four-wheel drive vehicles, etc.

[Prior Art] In recent years, from the viewpoint of improving braking performance and turning performance during braking, anti-scissor IS control devices that prevent wheels from locking have been proposed everywhere.

Examples of this prior art include, for example, Japanese Unexamined Patent Publication No. 60-25955;
The one described in Publication No. 9 is known. Generally, such a device detects the rotational speed and rotational acceleration/deceleration of the wheels, estimates the vehicle speed to obtain a pseudo vehicle speed, and then calculates the slip ratio of the wheels from the pseudo vehicle speed and the wheel rotational speed. It has become. Then, the brake fluid pressure is at least increased or maintained depending on the slip situation (slip rate).

It is adjusted in three modes of pressure reduction, and controlled so that the ideal braking condition, that is, the slip ratio is within a predetermined range (for example, 10 to 20%).

To explain this in detail, the wheel speed is decelerated as the brake pressure increases rapidly at the start of braking, and at the point when this deceleration passes a preset deceleration reference level (e.g., a value corresponding to -1,0G). Set to hold mode. After this, the wheel circumferential speed is set to the wheel target value (for example, (100(%) - of the pseudo vehicle speed).
When the pressure drops below a value equivalent to 15C%)), the system enters the depressurization mode, and the rotational acceleration of the wheels, which increases with this depressurization, passes through the acceleration side level (e.g., a value equivalent to 0.6G). At this point, the pressure holding mode is set, and when the wheel deceleration, which decreases due to this hydraulic pressure holding, passes the acceleration side reference level again, the pressure is increased, thereby forming a skid cycle. That is, the wheels themselves are repeatedly accelerated and decelerated in accordance with such pressure regulation, and as a result, the slip ratio with respect to the vehicle body is controlled within a predetermined range.

[Problem to be Solved by the Invention] However, in such a conventional device, the recovery of the wheel rotational speed toward the weight speed after the brake fluid pressure is reduced is due to a road reaction force, that is, generated between the wheel rotational speed and the road surface. Since the vehicle is dependent on torque due to frictional force, for example, when braking is performed on a low μ road, the engine brake acting on the wheels acts as a braking torque, resulting in a significant delay in the above-mentioned recovery of the wheel speed. As a result, the time it takes to pass the acceleration-side reference level, that is, the command state of the decompression mode, becomes significantly longer, so on such a low μ road, the braking distance becomes longer than necessary.
There are problems in that this results in a decrease in braking performance and also in the stability of the vehicle.

In particular, in vehicles 2 in which the driving force distribution state between the front and rear wheels changes, for example the aforementioned selective type four-wheel drive vehicle, since the wheel inertia differs in each drive state, braking by the engine brake]. Therefore, it has been desired that braking performance would not be affected by the difference in drive system even when installed in such a vehicle.

Therefore, the present invention was made in view of the above problems and circumstances, and is a four-wheel drive vehicle in which the driving force distribution state between the front and rear wheels is variable, and which is capable of being set in either the two-wheel drive side or the four-wheel drive side. The system also speeds up the recovery of wheel speed after depressurization during braking, thereby preventing a state where the brakes are not applied or an extension of the braking distance, regardless of the road surface condition, and improving braking performance. , which is the problem we are trying to solve.

[Means for Solving the Problems] Therefore, in order to solve the above problems, the present invention provides the first
As shown in the figure, a wheel speed detection means for detecting wheel speed, a vehicle speed estimation means for estimating vehicle speed, and a slip ratio for calculating a wheel slip ratio based on the detected wheel speed value and the estimated vehicle speed value. In an anti-skid fffff device comprising a calculation means and a control means for controlling brake pressure of a wheel based on the detected wheel speed value and according to the slip ratio, the vehicle is in a two-wheel drive state or a four-wheel drive state. a driving state detecting means for detecting whether or not the vehicle is running, and a target rotation speed value for the engine idling rotation base during braking. a predetermined engine speed target value setting means for setting a target value of engine rotation speed to a higher value in the four-wheel drive side state than in the four-wheel drive side state; a slip state determining means for determining whether or not the slip state is present; and when the slip state determining means determines that the slip state is a predetermined slip state, the engine revolution speed is determined according to a target value set by the engine revolution target value setting means. and engine speed adjustment means for increasing the engine speed.

[Operation] In the present invention, the slip ratio of the wheels is calculated based on the detected wheel speed value and the estimated vehicle speed value by the slip ratio calculation. The control means controls the brake pressure during braking based on the wheel speed and according to the slip ratio.

On the other hand, the drive state detection means detects whether the vehicle is in a two-wheel drive state or a four-wheel drive state, and the engine rotation speed target value setting means detects a rotation speed that is higher than the idling rotation of the engine during braking. A target value is set, and the target value is set to a higher value in the two-wheel drive state than in the four-wheel drive state by being energized by the detection information of the drive state detection means.

Further, the slip state determining means constantly determines whether or not the slip state is a predetermined slip state in which the slip ratio calculation value is equal to or greater than a predetermined value for a predetermined period of time or more. Therefore, when the determination means determines that the predetermined slip condition is present, the engine rotation speed adjustment means increases the engine rotation speed to the target value set by the engine rotation speed target value setting means. As a result, the idling rotational speed during braking is increased in accordance with the driving state.

〔Example] Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 to 6 are diagrams showing an embodiment of the present invention. Note that this embodiment is applied to a selectizo four-wheel drive vehicle.

In FIG. 2, reference numeral 2 indicates a hydraulic drum brake mounted on a vehicle, and reference numeral 4 indicates an anti-skid control device for four-wheel independent control for this brake 2.

The brake 2 includes a brake pedal 6 and a master cylinder 8.
, wheel cylinders l0FL to l0RI of wheels 9FL to 9RR on the front side to the rear right side? have.

The anti-skid control device 4 includes a wheel speed sensor IIFI, ~111?, which detects the rotational status of the wheels. R, a drive state detection switch 12 as a drive state detection means for detecting the drive state of the vehicle, a controller 15 that commands anti-skid control and engine rotation speed control during braking based on each detected value; The wheel cylinders 10r'L~
l0RI? actuator 16 that individually adjusts the hydraulic pressure of the
FL~16RJ? , and a throttle actuator unique 17 consisting of a proportional electromagnetic solenoid that similarly adjusts the opening degree of the throttle valve 17A based on a control signal from the controller 15.

Wheel speed sensors IIFL to IIRR are for each wheel 9FL to 9.
It is composed of an electromagnetic pickup installed at a predetermined position of the RR, and outputs sinusoidal AC voltage signals v1 to v4 each having a frequency proportional to the rotation speed of the wheel. Further, a drive state detection switch 12 is provided at a predetermined position of the transfer,
In the two-wheel drive state, a logic H level (or logic 'IJ) is output, and in the four-wheel drive state, a logic - level (or logic "0") detection signal ■□ is output.

As shown in FIG. 3 (the signal processing circuits from the front side to the rear right side have the same configuration, only the front left side of these is shown in the figure), the wheel speed sensor IIFL
The front left signal processing circuit 1 performs signal processing of the detection signal ■,
8FL, a slip state determining means 20 that determines the slip state of four wheels 9F+, ~9RR, and an engine rotation speed target value setting means that adds the output signal (1) of the drive state detection switch 12 and the logic H level signal (2). an adder circuit 22, a switch circuit 24 and a drive circuit 26 interposed between the adder circuit 22 and the throttle actuator 1f.
It has Here, switch circuit 24. Drive circuit 26. and the throttle actuator 17 form an engine rotation speed adjusting means 28.

The front left signal processing circuit 18FL has a frequency/voltage (F/V) at its input stage that converts the detection signal V of the wheel speed sensor 11FL into a voltage signal proportional to the frequency, and uses this as the wheel speed signal Vwl. A converter 30 is provided. The output side of this frequency/voltage converter 30 is connected to a wheel deceleration comparison circuit 34A and a wheel acceleration comparison circuit 34A through a differentiation circuit 32.
A pseudo vehicle speed generating circuit 35.B serves as a vehicle speed estimating means. Slip rate calculation circuit 36 as slip rate calculation means. and a wheel speed comparison circuit 37, respectively.

The reference input terminals of both comparison circuits 34A and 34B each have
A reference voltage signal -2 corresponding to a wheel deceleration reference value -α2 (for example, -1G) and a reference voltage signal -2 corresponding to an acceleration reference value α (for example, 0.6G) are applied. For this reason, the comparator circuit 34A calculates that in summer, 1≦−V2
Logic H level when .

When Vw+>v, the comparison circuit 34B outputs a logic L level signal, and when Vw I≧v1, the comparison circuit 34B outputs a logic H level signal.
When Vw+<V+, a logic L level signal is output. Furthermore, the output side of these comparison circuits 34A, 34B is
Along with each input to the ND (and) circuit 46, the output of the comparator circuit 34B is also connected to the 3 through another inverter 48.
Human power A N 1) Leads to circuit 50. Furthermore, the output of the comparison circuit 34A is input to a pseudo vehicle speed generation circuit 35.

The pseudo vehicle speed generating circuit 35 normally outputs the wheel speed VWI as a pseudo vehicle speed, and when the wheels tend to lock such that the wheel deceleration exceeds a predetermined reference value, the wheel speed no longer imitates the vehicle speed. Therefore, the instantaneous wheel speed with lock tendency is the initial value of the pseudo vehicle speed signal V with a constant deceleration gradient.
ref is calculated and outputted to the slip ratio calculation circuit 36.

Here, wheel speed detection means 62 is formed by wheel speed sensor IIFL and frequency/voltage converter 30.

Further, the slip ratio calculation circuit 36 includes a subtracter and a divider, and inputs the pseudo vehicle body speed signal V raf and the wheel speed signal (2). 1, calculate the slip rate S of the front left wheel 9FL based on ref 2,
A slip rate signal S, which is a voltage signal corresponding to this, is output to the next stage slip rate comparison circuit 70.

The output side of this comparison circuit 70 is connected to the AND circuit 50.
It is also connected to the AND circuit 46 via an inverter 72.

The comparison circuit 70 stores a predetermined slip rate S at which the coefficient of friction between the road surface and the wheels is in the highest range. (in this case, 15%). is applied as a reference value.

Therefore, the comparison circuit 70 outputs the slip rate signal S.

When ≧30, a logic H level signal is output, and S+ <s. When , a signal of logic 17 level is output.

By the way, the aforementioned wheel speed comparison circuit 37 has, as its reference value, a voltage signal (2) corresponding to a vehicle speed (5 km/h in this case) that can be considered to be in a pseudo stopped state. is applied. Therefore, the comparison circuit 37 calculates that VWI≧V0
When V, <V, a logic H level signal is supplied to the AND circuit 50 and the RS flip-flop 74.

The output terminal of the AND circuit 50 reaches the recent input terminal of the flip-flop 74, and the Q output terminal of this flip-flop 74 reaches the AND circuit 46 via the OR circuit 76 at the subsequent stage. Further, the output of the pulse generator 77 that generates the pulse signal pi for gradual pressure increase serves as the other power of the OR circuit 76.

Also, the output side of the AND circuit 50.46 is an amplifier 78.8.
0 of the actuator 16FL, respectively, through outflow valves 91.0, which will be described later. This leads to the inflow valve 90, which causes each valve 91,
Hydraulic pressure control signals AV and E■ are supplied to 90, respectively. In other words, the AND circuit 50 outputs a signal of logic 1 level only when all of the three human forces are at logic 1 level, turns on the hydraulic control signal AV in response to this, and
Similarly, the D circuit 46 turns on the hydraulic pressure control signal EV only when all four human forces are at the logic H level.

Furthermore, the output side of the AND circuit 50 is connected to a retriggerable timer 81 . The signal is connected to the pump 93 of the actuator 16FL via the amplifier 82, thereby making it possible to supply the pump control signal MR. Retriggerable timer 8■
Each time the output of the AND circuit 50 rises to logic 1 level, it outputs a logic H level set for a time longer than one skid cycle, and correspondingly, the pump control signal MR is turned on.

On the other hand, the slip state determining means 20 includes an OR circuit 85 which inputs each output signal of the AND circuits 50 from the front side to the rear right side, and a monostable which is triggered in synchronization with the rise of the output of this OR circuit 85. Multivi Break 86 and OR
Inverters 87A and 87B invert the outputs of the circuit 85 and the monostable multi-bi break 86, respectively, a NAND circuit 88A whose input signals are the outputs of the inverter 87A and the monostable multi-bi break 86, and the inverter 87.
NAND circuit 88B which uses the output of B and OR circuit 85 as input signals, and R which uses the output of NAND circuit 88A as set input and the output of NAND circuit 88B as reset input.
S flimp flop 89. The metastable time T of the monostable multibibreak 86 is Q6 in Fig. 5)
As shown in , the depressurization command time on the low μ road (AND circuit 5
0 output becomes logic H level), and
It is set longer than that of the high μ road.

Further, the switch circuit 24 includes a flip-flop 8
The Q output of No. 9 is used as a control input, so that it is "on (closed)" when the Q output is at the logic H level, and "off (open)" when it is at the logic L level.

Therefore, when the switch circuit 24 is in the on state, the output of the adder circuit 22 is supplied to the drive circuit 26.
6 rotates the throttle actuator 17 by an amount proportional to the addition result of the addition circuit 22. As a result, the opening degree of the throttle valve 17A becomes larger than the fully closed degree during idling rotation, and the engine speed increases.

On the other hand, each of the actuators 16FL to 16RR has an inlet valve 90 connected between the master cylinder 8 and the wheel cylinder 10FL (~101?R), and a wheel cylinder 10FL (~10R), as shown in FIG.
R), an accumulator 92 for accumulating pressure and an oil pump 93 for oil recovery connected to the output side of the outflow valve 91, and a check valve 94 between the oil pump 93 and the master cylinder 8. It is equipped with

Of these, the inflow valve 90 and the outflow valve 91 are connected to the controller 1.
It is a normally closed solenoid valve whose opening and closing are controlled by hydraulic control signals EV and AV from 5.

In the pressure increase mode, the control signal EV is turned on.

By turning off the control 'lo signal AV, the inflow valve 9
0 is "open" and the outflow valve 91 is "closed", and the brake fluid pressure from the master cylinder 8 can be supplied to the wheel cylinder l0FL (~l0RR) via the inflow valve 90. As a result,
Cylinder pressure increases. In the decompression mode, the control signal EV
By turning off the control signal AV and turning on the control signal AV, the inflow valve 90 is “closed” and the outflow valve 91 is “opened”, allowing the oil in the wheel cylinder 10FL (~l0RR) to be recovered to the master cylinder 8 side. As a result, the cylinder hydraulic pressure decreases. Furthermore, in the hold mode, control signals EV, A
By turning off V, the inflow valve 90. Outflow valve 91 closes,
The oil in the wheel cylinder PL (~lol?R) can be trapped and its pressure can be maintained.

The control signal MR is turned on during anti-skid control, thereby driving the pump 93.

Here, the frequency/voltage converter 30. Simulated vehicle continuous generation circuit 3
5. A control unit 96 is formed by the signal processing circuit excluding the slip ratio calculation circuit 36, and the control unit 96 and the actuator 16FL (˜16RR) constitute a control means.

Next, the operation of the above embodiment will be explained with reference to FIGS. 5 and 6. For simplicity, the wheel speed is 9FL for all four wheels.
Assuming that everything is equal at ~9RR, the front left side will be described.

This device starts when the ignition switch is turned on.

First, when driving in a non-braking state where the wheel slip rate is almost zero (before to), the wheel speed sensor 11FL sends a sine wave signal v corresponding to the circumferential speed of the wheel 9F+ to the controller. 15 signal processing circuits 18F
Output each to L.

The input AC signal (2) is converted by the frequency/voltage converter 30 into a wheel speed signal VWI proportional to its frequency. This signal Vwl is converted by a differentiation circuit 32 into a wheel acceleration/deceleration signal indicating the rate of change per minute time, and is converted by a comparison circuit 34A, 34B into a reference value -V2. V, and the outputs of the comparison circuits 34A and 34B are both set to logic 1.
− level (see FIG. 5 (31+41)). In addition, in the slip ratio calculation circuit 36, the pseudo vehicle speed signal V rer
Since =+= V Wl, the slip ratio s, =O is calculated, and the output of the comparator circuit 70 is at the logic L level ((5) in the same figure).
)), and the output of the inverter 72 becomes a logic H level (see (9) in the figure). Furthermore, since the vehicle is currently running at a speed higher than the speed equivalent to stopping, the output of the comparator circuit 37 is at the logic H level (see (6) in the figure), which sets the flip-flop 74 (OIJ in the figure). reference),
The Q output is at the logic I] level, which is the OR circuit 7
6. On the other hand, the pulse signal PI for slow pressure increase from the pulse generator 77 (see 0 in the same figure) is also supplied to the OR circuit 7G, and its output becomes logic I (level 0 in the same figure).
reference).

Therefore, in one AND circuit 46, all of the four human forces are at the logic II level, so the output is also at the logic H level (see 04 in the same figure), and the hydraulic pressure control signal for the inflow valve 90 of the actuator 16FL is at a predetermined level. turns on. At this time, in the other AND circuit 50, the output of the comparison circuit 70 among the three circuits is at the logic L level, so A
The output of the ND circuit 50 is held at the logic L level (see 00 in the same figure).

Therefore, the hydraulic pressure control signals A and V for the outflow valve 91 of the actuator 16FL are turned off at zero level, the retriggerable timer 81 is not activated, and the pump control signal MR is turned off.

That is, in this normal running state, the inflow valve 90 is open and the outflow valve 91 is closed, allowing oil from the master cylinder 8 to flow into the wheel cylinder 10FL (-10RR).

At this time, the pressure reduction signal, that is, the output of the AND circuit 50 is
Since it is at the logic L level as described above, the monostable multi-bi break 86 is not triggered, and therefore the Q output of the flip-flop 89 is maintained at the logic L level (0 in the same figure).
(See 0 to 0).

On the other hand, the drive state detection switch 12 sends a logic H level detection signal 4 if the vehicle is in a two-wheel drive state, and a logic L level detection signal ■4 if the vehicle is in a four-wheel drive state to an adding circuit 22.
is supplied to one input end of the

As a result, the addition result in the adding circuit 22 becomes (V, 10V,) in the two-wheel drive state, and becomes v, (<(v, +Vb)) in the four-wheel drive state.

However, during normal driving, as described above, the switch circuit 24 is off, so the opening control of the throttle valve 17A related to this device is carried out regardless of the driving state. There isn't.

Assume that from this state, sudden braking is performed on a low μ road at time t0. That is, when the brake pedal 6 is depressed, oil flows from the master cylinder 8 to the wheel cylinder l0FL (~10R1?) via the inflow valve 90, and the cylinder pressure (brake pressure) rapidly increases (see αωA in the same figure). The wheel speed begins to decrease (see Figure 11). In this state, when the wheel speed has decreased below the actual vehicle speed, the pseudo vehicle speed generation circuit 35 causes the wheel speed to decrease as shown in Figure 1 (1). , or a constant slope of the vehicle body speed V raf toward the deceleration side is estimated, and hydraulic pressure control is performed based on this.

Also, in this state, the wheel acceleration/deceleration signal V w I output from the differentiating circuit 32 becomes a signal that gradually increases in the negative direction (see (2) in the same figure), and the wheel acceleration/deceleration signal V w I outputted from the differentiating circuit 32 becomes a signal that gradually increases in the negative direction (see (2) in the same figure). At , the deceleration side reference value -■2 is reached. Activated by this, the output of the comparison circuit 34A becomes a logic H level, the output of the inverter 44A becomes a logic I'IL level, and the output of the AND circuit 46 becomes a logic logic (see +3) +8) 04) in the figure). In other words, from the above-mentioned rapid pressure state, the hydraulic pressure control signal EV turns off (the signal ■ is off), and that pressure is maintained (OJ in the same figure).
(See B).

Although this holding pressure slows down the decrease in wheel speeds ■ and 1,
At time t2, the calculated value of the slip ratio calculation circuit 36 is 8.
1≧80. As a result, the output of the comparator circuit 70 becomes a logic H level, and all three inputs of the AND circuit 50 become a logic H level, so the output also becomes a logic H level (see (5) 0ω in the same figure), and the hydraulic pressure is controlled. When the signal AV is turned on, the retriggerable timer 81 is activated and the pump control signal MR is turned on. On the other hand, at this time, since the output of the AND circuit 46 is at the logic L level, the hydraulic pressure control signal EV is turned off, and the aforementioned pressure reduction mode is commanded.
The cylinder 1 pressure decreases (see Fig. 5 f19C).

At this time t2, the output of the AND circuit 50 is activated to rise, and the monostable multi-high break 86 is triggered, and the output is kept at the logic H level for a preset time T from time t2 ((I6) )reference). However, N
The output of the AND circuit 88A becomes a logic L level, and the flip-flop 89 is not set (αηθ in the figure).
), the switch circuit 24 remains off.

As a result of the above pressure reduction, the wheel speed - gradually recovers in the direction of the vehicle body speed, and at time t3, the wheel acceleration and deceleration stand. 1-1α
2, and after t3, the output to the comparison circuit 34 becomes logic L.
level, but the AND circuit 50 is still logic! 4
level, AND circuit 46 outputs a logic L level. In other words, the pressure reduction mode is continued since the recovery of the wheel speed ■1 is not sufficient.

Furthermore, at time t3' (=t2+T), the output of the monostable multi-bi break 86 becomes a logic L level, and at this time, the output of the AND circuit 50 is a logic H level, so that
The NAND circuit 88A rises to the logic H level (see Q71 in (16) in the figure). Activated by this, the flip-flop 89 is set (see FIG. 09), and the switch circuit 24 is turned on. Therefore, the output of the adder circuit 22 reaches the drive circuit 26, the drive circuit 26 drives the throttle actuator 17, and the throttle valve 17A increases its opening in proportion to the output of the adder circuit 22 corresponding to the drive method at that time. As a result, the engine speed starts to increase accordingly.

Then, at time t4, wheel acceleration/deceleration V ii I
-α1, the comparator circuit 34B outputs a logic T level, and while maintaining the logic L level of the output of the AND circuit 46, the output of the AND circuit 50 also outputs a logic I, level tonal ((5) in the same figure). 7) QI (see Q4)). In other words,
As described above, both the hydraulic pressure control signals EV and AV are turned off and the pressure holding state is entered (see QSID in the figure).

At t4, the NAND circuit 88A also returns to the logic L level.

Then, at time t, the wheel speed VW+ recovers and the slip rate s becomes <S. Therefore, the output of the comparison circuit 70 falls to the logic L level (see (5) in the same figure), but the hydraulic pressure control signals EV and AV are maintained off. As a result, the pressure holding mode continues, and the wheel speed V,1 changes to the vehicle body speed V.
It fully recovers to near ref.

Then, at time t6 when the road surface changes to a high μ road at the end of the pressure holding period and the wheel acceleration/deceleration signal becomes Vw+-V+ again, the comparator circuit 34B is at the logic L level, and the AND circuit 50 is at the logic
7 levels, the AND circuit 46 outputs a pulse-like output (+41 (7) QOI (see 141) in the figure). In other words,
While keeping the hydraulic pressure control signal AV off, the hydraulic control signal EV is turned on for a predetermined minute period of time, and this is repeated at a predetermined period. As a result, the hydraulic pressure increases in a substantially stepwise manner as shown in FIG. 5 (Is) A'.

In this slow pressure increase mode, Vii+=-■2
This continues until time t7 when S+=So.
The pressure holding mode is commanded until Il. Hereinafter, in the same way, reduce pressure (ta """Q) + hold pressure (tq ~ L1 °),
A skid cycle in which slow pressure increases (too~L, ), . . . , are repeated continues until braking is completed. The control direction of the hydraulic mode related to this skid cycle is as follows:
As shown in FIG. 6, the starting point is the origin as shown by an arrow.

On the other hand, at time t, the NAND circuit 88B becomes logic 1 (level), so the output of the flip-flop 89 becomes logic logic (see QI 0m in the figure), and the switch circuit 24 is turned off. As the road surface changed to a high-μ road, the engine recognized that the state of recovery from the large slip due to pressure reduction was good, and stopped the increase control of the engine speed that had been commanded after time L3', and returned to the original idling state. do.

In this way, on a low μ road, the recovery of the wheel speed is slow, so the engine speed is increased at an appropriate timing, whereas on a high μ road, such a situation hardly occurs, so the normal idling speed is returned. In other words, when the engine speed is increased, the recovery of the wheel speed VWI is accelerated by the engine drive l/lux, and the state of high slip ratio is suppressed for as short a time as possible, which reduces braking performance and vehicle stability. Deterioration can be avoided.

To explain this in more detail, the equation of motion for one wheel is expressed as Iω=μrW −TBO−TEO−・−(21), where: wheel inertia, ω: wheel angular velocity, μ:
Road surface H friction coefficient, r: wheel radius, W: wheel load, TBO brake torque, TEO: engine torque. What has been described above is that in this equation (2), engine torque T
When EO is negative during engine braking, the torque that turns the wheel due to frictional force μ becomes larger than W, the wheel angular acceleration eccentricity is not positive, and the state in which the wheel does not recover from slip is increased by increasing the engine speed and increasing the engine torque. This corresponds to making T[EO positive, thereby making the wheel angular acceleration ω positive.

On the other hand, for any throttle opening, the engine torque T
Although EO is constant, in a 2WD vehicle, it is divided into three equal parts and applied to each wheel, and in a 4WD vehicle, it is distributed to all four wheels. Therefore, the value of the engine torque to be applied to each wheel differs depending on the road surface μ. Therefore, in this embodiment, in the case of 2WD, the throttle is opened so that a larger engine torque is obtained than in the case of 4WD. The engine torque is increased by widening the engine torque.This compensates for the difference in engine torque due to the difference in drive system, and ensures a reliable and appropriate increase in engine torque regardless of the drive system. .

Note that the controller 15 in the embodiment described above can also be configured entirely by a controller.

In addition, although the above embodiment has been applied to a vehicle that selectively switches between two-wheel drive and four-wheel drive as a four-wheel drive vehicle, the driving force distribution ratio between the front and rear wheels can be adjusted continuously using the clutch engagement pressure. Needless to say, it can also be used in variable control, so-called torque split type four-wheel drive vehicles. In this type of vehicle, the target value of the engine speed may be determined in accordance with the signal that determines the clutch engagement pressure.

Further, although the above embodiments have been described in the case where the present invention is applied to a drum type brake, the same can be applied to a disc type brake as well. In addition to the four-wheel independent control system, it can also be applied to anti-lock brakes that control the rear two wheels.

[Effects of the Invention] As explained above, according to the present invention, when a predetermined slip condition occurs, the engine speed is increased and the engine speed is set to be lower than that of the four-wheel drive side. The configuration is configured so that the value is higher in the driving side state, so even when braking is applied on a low μ road such as an icy road, the wheel speed recovers quickly after the brake pressure decreases, and the time for excessive slip is reduced. This reduces the time required by increasing the engine torque, thereby reliably eliminating the situation where the braking performance deteriorates and the vehicle becomes unstable due to a tendency to no-brake. An excellent effect can be obtained in that the above-mentioned advantages can be reliably enjoyed even when the drive is performed.

[Brief explanation of the drawing]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a block diagram showing the overall configuration of an embodiment of the present invention, and FIG. 3 is a block diagram showing the configuration of the controller in FIG. 2.
FIG. 4 is a block diagram showing the configuration of the actuator shown in FIG. 2, FIG. 5 is a timing chart showing the operation of each part of this embodiment, and FIG. 6 is a graph showing a control map. In the figure, 2 is a brake, 4 is an anti-skid control device, 9
FL~9RR are wheels, l0FL~l0RR are wheel cylinders, IIFL~IIRR are wheel speed sensors, 12 is a drive state detection switch, 15 is a controller, 16FL
~16RR is an actuator forming part of the control means; 2
0 is a slip state judgment means, 22 is an addition circuit (engine speed target value setting means), 28 is an engine speed adjustment means, 35 is a pseudo vehicle speed generation circuit (vehicle speed estimation means), 3
6 is a slip rate calculation circuit (slip rate calculation means), 62
96 is a wheel speed detection means, and 96 is a control section forming a part of the control means.

Claims (1)

[Claims] (1) Wheel speed detection means for detecting wheel speed, vehicle speed estimation means for estimating vehicle speed, and slip rate calculation means for calculating a wheel slip ratio based on the detected wheel speed value and the estimated vehicle speed value. , a control means for controlling brake pressure of the wheels based on the detected wheel speed value and according to the slip ratio, the anti-skid control device comprising: detecting whether the vehicle is in a two-wheel drive state or a four-wheel drive state; The driving state detecting means sets a target value of rotation speed that is higher than the idling revolution of the engine during braking, and is energized by the detection information of the driving state detecting means to change the target value to four wheels in the two-wheel drive state. and engine rotational speed target value setting means for setting a target value higher than the drive side state, and determining whether or not a predetermined slip state exists in which the calculated value of the slip ratio calculation means continues for a predetermined time or more. and an engine rotation speed adjustment for increasing the engine rotation speed according to the target value set by the engine rotation speed target value setting means when the slip condition determination means determines that a predetermined slip condition is present. An anti-skid control device characterized by comprising means.