JPH0425909B2 - - Google Patents

Description

[Detailed description of the invention] A. Purpose of the invention (1) Industrial application field The present invention calculates an estimated vehicle speed based on wheel speed, and sets a reference value and wheel speed based on the estimated vehicle speed. This invention relates to an anti-lock control method that controls the supply of braking hydraulic pressure to wheel brakes by comparison with the above.

(2) Prior Art Conventionally, such an anti-lock control method is known as disclosed in Japanese Patent Publication No. 56-47010, for example.

(3) Problems to be Solved by the Invention In the above-mentioned known technology, the estimated vehicle speed is calculated based on the maximum value of the speeds of a plurality of wheels including the driving wheels.

However, depending on the driving mode of the vehicle, the brake pedal and the accelerator pedal may be depressed at the same time, and in such cases, if the vehicle is driving on a slippery road such as an ice slope, the drive wheels may spin. Since the estimated vehicle speed is calculated based on the idling wheel speed, there is a risk that the estimated vehicle speed will be significantly higher than the actual vehicle speed and anti-lock control will be performed at an unnecessary time.

The present invention has been made to solve this problem, and even if the drive wheels spin in the above-mentioned special driving mode, the estimated vehicle speed will be higher than the actual vehicle speed. It is an object of the present invention to provide an anti-lock control method that can avoid calculations and prevent unnecessary anti-lock operations from occurring.

B. Structure of the Invention (1) Means for Inventing the Problem In order to achieve the above object, the present invention calculates an estimated vehicle speed based on the wheel speed, and calculates a reference value set based on the estimated vehicle speed. In an antilock control method that controls the supply of braking hydraulic pressure to wheel brakes by comparison with wheel speed, when calculating the estimated vehicle speed, if the rate of change in wheel speed is within a predetermined limit, The estimated vehicle speed is tracked, and when the rate of change exceeds a predetermined limit, the sensitivity of the tracking is reduced, and the drive wheels are controlled based on a signal indicating that the wheel speed of the drive wheels is greater than the estimated vehicle speed. Determine idle speed,
The present invention is characterized in that when it is determined that the vehicle is idling, the estimated vehicle speed is calculated based on the wheel speed of a wheel different from the driving wheel that is involved in the determination.

(2) Effect If the driving wheels should spin in a special driving mode such as pressing both the brake and accelerator pedals simultaneously, the estimated vehicle speed is calculated based on the wheel speed of a wheel different from the wheel that is spinning. Therefore, it is possible to prevent the estimated vehicle speed calculated at the time of idling from becoming higher than the actual vehicle speed, and it is possible to prevent anti-lock control from being performed unnecessarily.

Furthermore, when calculating the estimated vehicle speed, if the rate of change in wheel speed is within a predetermined limit, the estimated vehicle speed is made to follow the wheel speed, and when the rate of change exceeds a predetermined limit, the sensitivity of the tracking is reduced. Therefore, if the drive wheel is spinning in the special driving mode mentioned above and the other wheels are about to lock up,
Even if the estimated vehicle speed is calculated based on the wheel speed of the wheel that is about to lock, there is no risk that the calculated value will suddenly decrease following the sudden decrease in the wheel speed.

(3) Embodiment Hereinafter, an embodiment of the present invention will be explained with reference to the drawings. First, in FIG. 1 showing an embodiment of the present invention, a brake pedal 1 is operatively connected to a master cylinder M, and during operation. When a person depresses the brake pedal 1, the master cylinder M generates hydraulic pressure in the oil passage 2. This oil passage 2 is connected to a hydraulic control circuit 3, and a braking hydraulic pressure corresponding to the hydraulic pressure is output from the hydraulic control circuit 3.

Wheel brakes are mounted on the left and right driving wheels and the left and right driven wheels of the vehicle, respectively, and braking oil pressure is supplied from the hydraulic control circuit 3 to these wheel brakes. For example, in a front-wheel drive vehicle, the left and right front wheels as driving wheels are equipped with a left front wheel brake Blf and a right front wheel brake Blf, and the left and right rear wheels as driven wheels are equipped with a left rear wheel brake Blr and a right rear wheel. Brake Brr is installed. The brakes Blf, Blf, Blr, and Brr are, for example, drum brakes, and the brakes for the left front wheel and right front wheel are Blf,
An oil passage 5 from the hydraulic control circuit 3 is communicated with the brake oil chamber 4 of the BRF, and the brake for the left rear wheel and the right rear wheel is connected to the brake oil chamber 4 of the BRF.
An oil passage 5' from the hydraulic control circuit 3 is communicated with the brake oil chambers 4 of Blf and Brr.

When braking oil pressure is supplied to each brake oil chamber 4 in each brake Blf, Blf, Blr, Brr, the pistons 7 and 8 operate in the direction of separating from each other, and the brake shoes 9 and 10 respectively act on the brake drums. (not shown) to generate braking torque. Furthermore, if the braking oil pressure in each brake oil chamber 4 is too large, the braking torque generated between each brake shoe 9, 10 and the brake drum becomes too large, and as a result, the wheels become locked. Therefore, when the wheels are about to lock, the hydraulic control circuit 3
This reduces the pressure in the brake oil chamber, thereby preventing the wheels from becoming locked.

The hydraulic control circuit 3 includes brakes Blf for left and right front wheels,
Modulator 11 compatible with BRF, and modulator 1 compatible with left and right rear wheel brakes Blr and Brr.
1', both modulators 11, 1
Since both modulators 1' have basically the same structure, the structure of only one modulator 11 will be described in detail.

That is, the modulator 11 includes a cylinder portion 14 that is closed at both ends and partitioned in the middle by a partition wall 13, and a pair of pistons 15 at each end.
16, the rod 17 passes through the partition wall 13 in a portion between each piston 15, 16 so as to be able to freely slide in the axial direction.
Equipped with. A cylinder chamber between the partition wall 13 and one piston 15 serves as a primary braking hydraulic chamber 18 and communicates with the master cylinder M via the oil passage 2 . Further, the cylinder chamber between the partition wall 13 and the other piston 16 serves as a secondary braking hydraulic chamber 19 and is communicated via an oil passage 5 with the braking oil chamber 4 of the left and right front wheel brakes Blf, Blf. An anti-lock control hydraulic chamber 20 is defined between one end wall of the cylinder section 14 and one piston 15, and a release oil chamber is defined between the other end wall of the cylinder section 14 and the other piston 16. 21 is defined, and the release oil chamber 21 is communicated with the reservoir R of the master cylinder M. Further, a spring 22 that biases the piston 16 away from the partition wall 13 is housed in the secondary brake hydraulic chamber 19, and a spring 23 that biases the piston 15 toward the partition wall 13 is housed in the anti-lock control hydraulic chamber 20. It will be stored.

An oil passage 24 is connected to the anti-lock control hydraulic chamber 20, and this oil passage 24 is connected to a hydraulic pump P via a normally closed inlet valve Vi, and is also connected to a hydraulic pump P via a normally open outlet valve Vo. Connected to oil tank T. Further, an accumulator Ac is connected between the inlet valve Vi and the hydraulic pump P.

In the other modulator 11', the primary brake hydraulic chamber 18' is also communicated with the master cylinder M.
The secondary braking hydraulic chamber 19' is communicated with the braking oil chamber 4 of the left and right rear wheel brakes Blr and Brr via an oil passage 5'.
The release oil chamber 21' is communicated with the reservoir R. Further, the anti-lock control hydraulic chamber 20' is connected to a hydraulic pump P via a normally closed inlet valve Vi', and a normally open outlet valve Vi'.
It is connected to the oil tank T via Vo'.

Both inlet valves Vi, Vi' and both outlet valves Vo, Vo' are solenoid valves,
Its opening and closing operations are controlled by control means 32.

When inlet valves Vi, Vi' are closed and outlet valves Vo, Vo' are open,
The anti-lock control hydraulic chambers 20, 20' are open to the oil tank T, and when the brake pedal 1 is depressed, the master cylinder M is connected to the primary brake hydraulic chambers 18, 18'.
When hydraulic pressure is supplied from the secondary brake hydraulic pressure chamber 19,
The volume of 19' is reduced and each wheel brake Blf,
Braking oil pressure corresponding to the oil pressure from the master cylinder M is supplied to the brake oil chambers 4 of Brf, Blr, and Brr.
Therefore, the torque during braking can be freely increased according to the driver's braking operation.

When the outlet valves Vo, Vo' are closed with the inlet valves Vi, Vi closed, the control oil in the anti-lock control hydraulic chambers 20, 20' is locked, so each modulator 11,
The volume of the secondary brake hydraulic chambers 11', 11' remains unchanged regardless of the increase or decrease in the hydraulic pressure supplied to the primary brake hydraulic chambers 18, 18', and therefore the torque during braking is controlled by the driver. It is maintained at a constant size regardless of the braking operation. Such an operating condition is suitable when the possibility of wheel locking arises.

Furthermore, when the inlet valves Vi, Vi' are opened and the outlet valves Vo, Vo' are closed, anti-lock control hydraulic pressure is supplied to the anti-lock control hydraulic chambers 20, 20', so that the master cylinder M
Although the hydraulic pressure from the
The volume of 9' increases, and each wheel brake Blf, Brf,
The oil pressure in the brake oil chambers 4 of Blr and Brr decreases, and the braking torque is weakened. Therefore, when the wheels are about to enter the lock state, the inlet valve Vi,
By opening valve Vi′ and closing outlet valves Vo and Vo′, it is possible to avoid the wheels from entering a locked state.

In FIG. 2, the configuration of the control means 32 will be explained, including a configuration for controlling the inlet valves Vi and outlet valves Vo corresponding to the wheel brakes Blf and Blf of one set, and the configuration for controlling the wheel brakes of the other set. The configurations for controlling inlet valve Vi' and outlet valve Vo' corresponding to Blf and Brr are basically the same, so here we will explain how to control one inlet valve Vi and outlet valve Vo. I will only discuss the configuration of .

The control means 32 includes a judgment circuit 33 such as a microcomputer, and this judgment circuit 33 judges whether the wheels are in a locked state or not, and opens and closes the inlet valve Vi and the outlet valve Vo based on the judgment result. Outputs a signal for activation.

Now, if we consider the criteria for determining which conditions should be met to output a signal for antilock control, there are generally four types (a) to (d) below. A method has been proposed.

(a) A method that outputs a signal β and releases the braking pressure when wheel acceleration N〓w < reference wheel deceleration - N〓w ₀ holds.

(b) A method of outputting a signal _S1 when wheel speed Vw<first reference wheel speed _Vr1 to loosen the braking oil pressure. However, in this case, when the vehicle speed is Vv and the wheel slip rate is λ ₁ , Vr ₁ = Vv・
(1−λ ₁ ), so the slip rate of the wheel is λ
When Vw<Vr ₁ is the same as λ>λ ₁ , the signal S ₁ is output when Vw′Vr ₁ or λ>λ ₁ holds true.

(c) A method in which the braking hydraulic pressure is relaxed when either of the above (a) or (b) is satisfied.

(d) A method in which the braking hydraulic pressure is relaxed when (a) and (b) above are satisfied at the same time.

In the method (a) above, the reference wheel deceleration _-N〓w0 is set to a value that does not occur during braking in a state where there is no risk of wheel locking, for example, normally -2.0.
It is set to ~1.2G. However, according to this method, during braking operations performed on snowy roads or icy roads, wheel deceleration of approximately -1.0 to -0.5G may occur, and in the latter half of braking, the wheels may lock. However, the signal to loosen the brake hydraulic pressure is not output. Furthermore, when driving on a rough road, the wheel acceleration Nw pulsates finely even during normal braking, and the signal β is output even when the wheels are not locked, reducing braking efficiency.

Furthermore, in the method (b) above, even if the slip rate λ is high, that is, even if the signal _S1 is output, as long as the wheel speed Vw is increasing, the brake hydraulic chamber is sufficiently relaxed. However, even within this period, the braking oil pressure will be loosened, resulting in a decrease in braking efficiency.

It is clear that the method (c) has the drawbacks of (a) and (b).

Finally, the method (d) above solves the problem of reduced braking efficiency when driving on a rough road, and the problem of reducing braking efficiency by loosening the brake hydraulic pressure while the wheel speed Vw is increasing. Furthermore, the reference wheel deceleration −N〓w ₀ ,
Within the range of wheel deceleration that occurs during braking under normal road running conditions, for example -1.0 to 0G, preferably -0.3 to
When set to -0.6G, wheel deceleration will be - during braking operations performed on snowy roads or on the autobahn.
It is possible to detect a lock state even when the pressure is between 1.0 and -0.5G, and to loosen the brake hydraulic pressure.

Therefore, the judgment circuit 33 includes the wheel speed detector 3.
A signal corresponding to the wheel speed Vw is input from 4,
The wheel speed Vw and the wheel acceleration N〓w calculated based on the wheel speed Vw are compared with the first reference wheel speed Vr ₁ and the reference wheel deceleration −N〓w ₀ , respectively, as described above. , N〓w<−N〓w ₀ Vw<Vr ₁ are established, high level signals β and S ₁ are outputted from the judgment circuit 33, respectively. These signals β, S ₁ are input to the AND gate 35,
Transistor 3 when both signals are high level
6 becomes conductive, the solenoid 38 is energized, and the inlet valve Vi is opened. Further, when the high level signal _S1 is output, the transistor 37 becomes conductive, the solenoid 39 is energized, and the outlet valve Vo is closed.

By the way, when the braking torque is weakened with the signal β, S ₁ as described above, the wheel speed is still decelerating, which means that the braking torque is still larger than the driving wheel torque on the road surface. At this point, concerns about wheel locking have not been completely eliminated.
However, since the system typically has an activation delay of about 10ms, the brake oil pressure is further relaxed even after the release signal disappears, so this method usually yields good results. However, depending on road surface conditions, loosening may not be sufficient and the wheel speed may continue to lock. In order to eliminate such a phenomenon, when λ>λ ₁ , a signal to reduce the wheel speed Vw may be generated until the wheel speed Vw is reliably increased. However, usually
Although good control can be obtained even if the loosening signal is stopped when N〓w＞−N〓w, the loosening signal continues until N〓w＞0, so the braking torque is too loose. However, this does not pose a practical problem for wheels with smaller braking load distribution.

Therefore, a second reference wheel speed Vr ₂ corresponding to the second reference slip rate λ ₂ where λ ₂ > λ ₁ is set, and Vw <
Only when Vr ₂ , that is, λ>λ ₂ , and the possibility of locking increases, is the loosening signal maintained until the wheel speed Vw starts to increase. That is, in the judgment circuit 33, Vw<Vr ₂ or λ>λ ₂
It is determined whether or not the condition is satisfied, and when the condition is satisfied, a signal _S2 is output. In addition, in order to judge that the wheel speed Vw is increasing, increase reference value +
Set N〓w ₀ , and output signal α when Vw>+N〓w ₀ .

The signal S ₂ is inputted to one input terminal of the AND gate 40 and also inputted to the OR gate 41 , and the signal α is inputted to the OR gate 41 and is inverted and inputted to the AND gate 40 . Furthermore, the signal _S1 is also input to the OR gate 41, and the OR gate 4
The output of 1 is given to the base of transistor 37. Further, the outputs of both AND gates 35 and 40 are input to an OR gate 42, and the output of the OR gate 42 is applied to the base of a transistor 36.

According to such a control means 32, the signals S ₁ ,
If either α or S ₂ becomes high level, transistor 37 becomes conductive and outlet valve Vo closes, and both signals β and S ₁ are at high level, or
When the signal _S2 is high level and the signal α is low level, the inlet valve Vi opens.

Next, the first and second reference wheel speeds Vr ₁ , Vr ₂
To explain how to set these, it is ideal to detect the vehicle speed V, add appropriate reference slip rates λ ₁ and λ ₂ to this, and determine them as shown in the following equation.

Vr ₁ =V(1-λ ₁ ) Vr ₂ =V(1-λ ₂ ) However, no practical means for detecting the wheel speed V has been found so far. Therefore, the wheel speed
This method estimates a temporary vehicle speed Vv from the state of change in Vw, and its calculation circuit is shown in FIG.

In FIG. 3, a first input terminal 51 is connected to a first arithmetic circuit 52, and a second input terminal 51' is connected to a second arithmetic circuit 52.
It is connected to an arithmetic circuit 52'. Both arithmetic circuits 52,
The output end of the switch 52' is connected to individual contacts 53a and 53b of the changeover switch 53, respectively, and the common contact 53c of the changeover switch 53 is connected to the output terminal 54. Moreover, the changeover switch 53 is switched and driven by an idle detection circuit 55 connected to the second arithmetic circuit 52'.

The wheel speed Vwr of a driven wheel, such as a rear wheel, is input to the first input terminal 51, and the wheel speed Vwf of a driving wheel, such as a front wheel, is input to a second input terminal 51'. 52' calculates wheel speeds Vv ₁ and Vv ₂ based on these wheel speeds Vwr and Vwf, respectively.

In the first arithmetic circuit 52, the input terminal 51 is connected to the inverting input terminal of the comparator circuit 56. The output terminal of this comparison circuit 56 is a PNP connected in series.
Transistor 52 and NPN transistor 58
are connected to the base terminals of each. Further, a DC power supply 59 is connected to the emitter terminal of the PNP transistor 57 via a constant current circuit 60, and the emitter terminal of the NPN transistor 58 is grounded via a constant current circuit 61. A connection point between both transistors 57 and 58 is connected to a non-inverting input terminal of a buffer circuit 62, and a capacitor 63 is connected between the connection point and the buffer circuit 62 and grounded. Moreover, the output terminal of the buffer circuit 62 is connected to one individual contact 53a of the changeover switch 53, and is also connected to the non-inverting input terminal of the comparison circuit 56.

In the first arithmetic circuit 52, the buffer circuit 6
The estimated vehicle speed Vv ₁ output from 2 is the wheel speed
When it is smaller than Vwr, the output of the comparator circuit 56 becomes low level, and the PNP transistor 57
conducts, the NPN transistor 58 is cut off, and the constant current circuit 60 charges the capacitor 63 with a constant current. Also, estimated vehicle speed Vv ₁
When is greater than the wheel speed Vwr, the output of the comparison circuit 56 becomes high level, the PNP transistor 57 is cut off, the NPN transistor 58 is turned on, and the constant current circuit 61 discharges a constant current from the capacitor 63. Therefore, when the wheel speed Vwr changes gradually, the estimated vehicle speed Vv ₁ also changes gradually, but when the wheel speed Vwr changes suddenly, a predetermined value is added or subtracted from the estimated vehicle speed Vv ₁ . The value is inputted to the individual contact 53a of the changeover switch 53 as a new estimated vehicle speed _Vv1 .
That is, when the wheel speed Vwr is larger than the estimated vehicle speed Vv ₁ , the value obtained by adding a predetermined value, for example, the speed equivalent to 1G, becomes the new estimated vehicle speed Vv ₁ , and when the wheel speed Vwr is smaller than the estimated vehicle speed Vv ₁ . , a value obtained by subtracting a speed corresponding to a predetermined value, for example, 1G, becomes the new estimated vehicle speed _Vv1 .

The second arithmetic circuit 52' includes a comparison circuit 56', a PNP transistor 57', an NPN transistor 58', a DC power supply 59', constant current circuits 60', 61', a buffer circuit 62' and a capacitor 63'. 1 arithmetic circuit 52. Moreover, the signal output from the buffer circuit 62', that is, the estimated vehicle speed Vv ₂ , is transmitted to the individual contact 5 of the changeover switch 53.
3b. In this second arithmetic circuit 52', when the wheel speed Vwf is larger than the estimated vehicle speed _Vv2 , the value obtained by adding a predetermined value, for example, a speed corresponding to 1G, becomes the estimated vehicle speed _Vv2 , and the wheel speed Vvf is When the estimated vehicle speed Vv ₂ is smaller than the estimated vehicle speed Vv 2 , a value obtained by subtracting a predetermined value, for example, a speed corresponding to 1 G, becomes the new estimated vehicle speed Vv ₂ .

The idle detection circuit 55 includes an inversion circuit 64, a timer 65, and a flip-flop 66. Second
The output terminal of the comparison circuit 56' in the arithmetic circuit 52' is connected to the base terminals of the PNP transistor 57' and the NPN transistor 58', and
It is connected to the inverting circuit 64. The signal inverted by the inverting circuit 64 is input to the timer 65 and also to the clear input terminal C of the flip-flop 66, and the output of the timer circuit 65 is input to the set input terminal S of the flip-flop 66.
Moreover, when a high level signal is input for a certain period of time, for example, 30ms or more, the timer 65
A high level signal is output as the certain period of time elapses.

After a high-level signal is input to the clear input terminal C, the flip-flop 66 outputs a high-level signal from the set output terminal Q in response to a high-level signal input to the set input terminal S, and then outputs a high-level signal from the set output terminal Q. It is reset when a high level signal is input to the clear input terminal C.
Further, when the output of the set output terminal Q is at a low level, the changeover switch 53 connects the common contact 53c to one of the individual contacts 53b, and when the output of the set output terminal Q is at a high level, it connects the common contact 53c to the other individual contact. 53a.

Therefore, if the driving wheels idle and the wheel speed Vwf is greater than the estimated vehicle speed _Vv2 for a certain period of time, for example, 350 ms or more, the idle detection circuit 55
is detected to be in a idling state, and the estimated vehicle speed Vv ₁ based on the wheel speed Vwr on the driven wheel side is outputted from the output terminal 54 as the estimated vehicle speed Vv.

Next, the operation of this embodiment will be explained with reference to FIG. This Fig. 4 shows an example of the operating state of the anti-lock braking system. The horizontal axis shows the time elapsed after the start of braking, and the vertical axis shows the actual vehicle speed Vv ^* and wheel speed Vw at the top. , 1st
A reference wheel speed Vr ₁ and a second reference wheel speed Vr ₂ are shown, and below them, wheel acceleration N〓w, speed increase reference value +N〓w ₀ and reference wheel deceleration -N〓w ₀ are shown, Further below, the signals α, β, S ₁ , S ₂ and the operating states of the solenoids 38 and 39 are shown.
Braking oil pressure Pb is shown at the bottom.

First, at time t=0, immediately after starting braking, the outputs of the signals α, β, S ₁ and S ₂ are at a low level, the braking oil pressure Pb gradually increases, and along with this, the wheel speed Vw and the wheel Both accelerations N〓w gradually decrease.

When the wheel acceleration N〓w becomes smaller than the reference wheel deceleration −N〓w ₀ at time t ₁ (N〓w<−N〓w ₀ ),
The signal β becomes high level, but at this time the wheel speed
Since Vw is greater than the first reference wheel speed Vr ₁ , the signal S ₁ remains at a low level. Therefore, the braking oil pressure Pb continues to increase, and the wheel speed Vw and wheel acceleration N〓w also continue to decrease.

At time _t2 , when the wheel speed Vw falls below the first reference wheel speed _Vr1 , the signal _S1 goes high, and in response to the output of the AND gate 35 going high, the output of the OR gate 42 goes high. At the same time, the output of the OR gate 42 becomes high level. This energizes the solenoids 38 and 39, opening the inlet valve Vi and closing the outlet valve Vo. As a result, the braking oil pressure Pb begins to decrease, and the wheel acceleration N〓w changes to the speed increasing side. At this time, wheel speed Vw
continues to decline.

At time _t3 , when the wheel acceleration N〓w becomes larger than the reference wheel speed −N〓w (N〓w>−N〓w ₀ ), the signal β becomes low level, and the AND gate 35 is activated accordingly. Output becomes low level. Therefore, the solenoid 38 of the inlet valve Vi is demagnetized,
The inlet valve Vi is closed and the braking oil pressure Pb is kept constant. In other words, the braking torque is kept substantially constant. After this, the wheel speed Vw begins to increase.

At time _t4 , when the wheel acceleration N〓w becomes larger than the speed increase reference value +N〓w ₀ (N〓w>+N〓w ₀ ), the signal α becomes high level. Further, at time _t5 , when the wheel speed Vw exceeds the first reference wheel speed _Vr1 ,
Signal _S1 becomes low level. Furthermore, at time _t6 , when the wheel acceleration N〓w falls below the speed increase reference value + _N〓w0 , the signal α becomes low level and the outlet valve _V0 opens. Braking oil pressure Pb increases accordingly.

At time _t7 , when the wheel acceleration N〓w becomes smaller than the reference wheel deceleration _-N〓w0 (N〓w< _-N〓w0 ),
When the signal β becomes high level and the wheel speed Vw decreases below the first reference wheel speed Vr ₁ (Vw<Vr ₁ ) at time t ₈ , the signal S ₁ becomes high level, and the AND gate 35 is activated accordingly. As the output becomes high level and the inlet valve Vi closes, the outlet valve _V0 opens and the braking oil pressure Pb begins to decrease. Next, at time _t9 , the brake hydraulic pressure chamber Vw decreases below the second reference wheel speed _Vr2 (Vw
<Vr ₂ ) and the possibility of wheel lock increases, the signal S ₂ becomes high level.

At time t ₁₀ , wheel acceleration N〓w becomes reference wheel deceleration −
When it becomes larger than N〓w, the signal β becomes low level, but the brake hydraulic pressure chamber Pb further decreases and the wheel speed
Vw starts accelerating. When the wheel acceleration N〓w exceeds the speed increase reference value + _N〓w0 at time _t11 , the signal α becomes high level, and the output of the AND gate 40 becomes low level. At this time, since the output of the AND gate 35 is at a low level, the output of the OR gate 42 is at a low level, so the solenoid 38 is demagnetized and the inlet valve Vi is closed. As a result, the braking oil pressure Pb is maintained constant.

At time _t12 , when the wheel speed Vw exceeds the second reference wheel speed _Vr2 , the signal _S2 becomes low level, and at time _t13 , the wheel speed Vw reaches the first reference wheel speed.
When Vr ₁ is exceeded, the signal S ₁ becomes low level, but the braking oil pressure Pb is kept almost constant, and a locked state is avoided. Also, at time t ₁₄ , when the wheel acceleration N〓w falls below the speed increase reference value + N〓w ₀ ,
The signal α becomes low level, and the outlet valve Vo opens accordingly. For this reason, the braking oil pressure
Pb starts to increase.

At time t ₁₅ , wheel acceleration N〓w becomes reference wheel deceleration −
When N〓w becomes smaller than ₀ , the signal β becomes a high level, and at the next time _t16 , the wheel speed Vw decreases below the first reference wheel speed _Vr1 and the signal _S1 becomes a high level. Inlet valve Vi opens and inlet valve Vo closes. Therefore, the braking oil pressure Pb begins to decrease. Furthermore, at time t ₁₇ , the wheel acceleration N〓w becomes the reference wheel deceleration − N〓wo
, the outlet valve Vo opens in response to the signal β going low, and the braking oil pressure Pb
is maintained constant.

At time t ₁₈ , wheel acceleration N〓w reaches the speed increase reference value +
When N〓wo is exceeded, the signal α becomes high level,
When the wheel speed Vw exceeds the first reference wheel speed Vr ₁ at time ₁₉ , the signal S ₁ becomes low level. Further, at time _t20 , when the wheel acceleration N〓w falls below the speed increase reference value + _N〓w0 , the signal α becomes low level, the outlet valve Vo opens accordingly, and the braking oil pressure Pb starts to decrease.

Thereafter, the above process is repeated in the same way, and the wheel speed decreases without the wheels locking.

Next, referring to FIG. 5, assume that the wheel speed Vw pulsates during braking while driving on a rough road. At this time, when the driving wheels, for example, the front wheels, are not spinning, the vehicle speed Vv ₂ calculated by the second calculation circuit 52' based on the wheel speed Vwf of the driving wheels is used as the estimated vehicle speed Vv.

In this state, when the wheel speed Vw becomes higher than the estimated vehicle speed Vv, in the second arithmetic circuit 52', the PNP transistor 57' becomes conductive, and the NPN transistor 58' becomes conductive. Therefore, the capacitor 63' is charged with a constant current, and the value obtained by adding the speed equivalent to 1G becomes the new estimated vehicle speed.
It becomes Vv. As a result, the increase rate of the estimated vehicle speed Vv is suppressed lower than the wheel speed Vw, and the first
The second reference wheel speeds Vr ₁ and Vr ₂ are also kept low. As a result, the wheel speed Vw is prevented from becoming smaller than the first reference wheel speed Vr ₁ , and the braking oil pressure is prevented from decreasing.

Further, when the drive wheels are idling, the idling state is detected by the idling detection circuit 55 when a state in which the wheel speed Vwf of the driving wheels is greater than the estimated vehicle speed Vv ₂ continues for a certain period of time, for example, 350 ms or more. and the changeover switch 53 is connected to the common contact 53c.
is operated to connect to the individual contact 53a. Therefore, the vehicle speed Vv ₁ calculated by the first calculation circuit 52 is used as the estimated vehicle speed Vv. As a result, the estimated vehicle speed Vv is prevented from becoming higher than the actual vehicle speed Vv ^* ,
Antilock activation is prevented from occurring when unnecessary.

FIG. 6 shows another embodiment of the present invention, in which two input terminals 70 and 71 are provided corresponding to the first arithmetic circuit 52, and the second arithmetic circuit 52 is provided with two input terminals 70 and 71.
Two input terminals 73 and 74 are provided corresponding to 2'.

The wheel speed Vvr of the driven wheel is input to the input terminal 70, and the wheel speed of the driving wheel is input to the input terminal 71.
VWF is input. Both input terminals 70 and 71 are connected to a low select circuit 72, and the lower wheel speed is selected and input to the inverting input terminal of the comparative example circuit 56 in the first arithmetic circuit 52. That is, the estimated vehicle speed Vv ₁ is calculated by the first calculation circuit 52 based on the minimum value of the wheel speeds of all wheels.

Further, the wheel speed Vwr of the driven wheel and the wheel speed Vwf of the driving wheel are input to the input terminals 73 and 74, respectively, and these wheel speeds Vwr and Vwf are input to the high select circuit 75. The wheel speed selected by the high select circuit 75, that is, the maximum value of all wheel speeds, is input to the inverting input terminal of the comparison circuit 56' in the second calculation 52'.

According to this embodiment, the second calculation circuit 52' calculates the estimated vehicle speed Vv ₂ based on the maximum wheel speed of each wheel including the driving wheels, and the time during which the maximum wheel speed exceeds the estimated vehicle speed Vv ₂ is constant. When the time T has passed, it is determined that the drive wheels are idling, and in this case, the estimated vehicle speed Vv ₁ based on the minimum wheel speed is used as the estimated vehicle speed Vv. Therefore, even when the vehicle is idling, the estimated vehicle speed Vv is prevented from becoming higher than the actual vehicle speed, and anti-lock control is prevented from being performed when unnecessary.

C. Effects of the Invention As described above, according to the present invention, it is determined whether the driving wheels are spinning based on a signal indicating that the wheel speed of the driving wheels is higher than the estimated vehicle speed, and when the wheel slipping is determined, the Since the estimated vehicle speed is calculated based on the wheel speed of a wheel different from the drive wheel involved in the judgment, even if the drive wheel were to spin in a special driving mode such as pressing both the brake and accelerator pedals at the same time. It is possible to prevent the estimated vehicle speed calculated at the time of idle rotation from becoming higher than the actual vehicle speed, and to prevent unnecessary anti-lock operation from occurring.

Furthermore, when calculating the estimated vehicle speed, if the rate of change in wheel speed is within a predetermined limit, the estimated vehicle speed is made to follow the wheel speed, and when the rate of change exceeds a predetermined limit, the sensitivity of the tracking is reduced. Therefore, if the drive wheel is spinning in the special driving mode mentioned above and the other wheels are about to lock up,
Even if the estimated vehicle speed is calculated based on the wheel speed of the wheel that is about to lock, there is no risk that the calculated value will suddenly decrease following the sudden decrease in the wheel speed, and therefore, in such a case, Anti-lock control can be performed with high precision.

[Brief explanation of drawings]

Figures 1 to 5 show an embodiment of the present invention. Figure 1 is a hydraulic control circuit diagram, Figure 2 is a simplified circuit diagram showing the configuration of the control means, and Figure 3 is a calculation diagram. A circuit diagram showing the configuration of the circuit and the slip detection circuit,
FIG. 4 is a characteristic diagram showing the anti-lock operating state, FIG. 5 is a characteristic diagram when the wheel speed is pulsating, and FIG. 6 is a circuit diagram corresponding to FIG. 3 of another embodiment of the present invention. Blf, Brf, Blr, Brr...Wheel brake, Vv...
...Estimated vehicle speed, Vw...Wheel speed.

Claims (1)

[Claims] 1. An estimated vehicle speed is calculated based on the wheel speed, and the supply of braking hydraulic pressure to the wheel brakes is controlled by comparing the wheel speed with a reference value set based on the estimated vehicle speed. In the above anti-lock control method, when calculating the estimated vehicle speed, if the rate of change in wheel speed is within a predetermined limit, the estimated vehicle speed follows the wheel speed, and if the rate of change exceeds the predetermined limit, the estimated vehicle speed follows the wheel speed. The sensitivity of the tracking is reduced, and whether the driving wheels are spinning is determined based on a signal indicating that the wheel speed of the driving wheels is higher than the estimated vehicle speed, and when the wheel slipping is determined, the driving related to the determination is made. An antilock control method characterized in that the estimated vehicle speed is calculated based on the wheel speed of a wheel different from the wheels. 2. According to claim 1, the estimated vehicle speed is calculated based on the wheel speed of the driving wheels during normal operation, and the estimated vehicle speed is calculated based on the wheel speed of the driven wheels when the driving wheels are idling. Anti-lock control method. 3. The anti-lock control method according to claim 1, wherein the estimated vehicle speed is calculated based on the maximum value of the speeds of a plurality of wheels including the drive wheels during normal times.