JPS6347663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-skid control device that smoothly converges wheel speed to a braking target wheel speed during braking.

In general, anti-skid control devices, which prevent slips caused by wheels locking during sudden braking, have a maximum coefficient of friction with the road surface when the slip rate is around 15%, resulting in the highest braking efficiency. Since, the slip rate during braking is 15
The intention is to control the wheel speed so that it is around %.

For this reason, conventional anti-skid control devices
If this occurs while braking at the target wheel speed where the slip rate is 15% relative to the vehicle speed, and the brake oil pressure is increased and the wheel speed falls below the target wheel speed, the brake oil pressure is switched to decrease and the wheel speed is restored. The basic principle is to increase the brake oil pressure again when the braking target wheel speed is exceeded, but there are various methods such as changing the rate of increase and decrease of the brake oil pressure, and changing the time ratio for repeating pressure increase and decrease. Hydraulic control is performed to converge the wheel speed to the braking target wheel speed using the following method (see, for example, Japanese Patent Laid-Open No. 138286/1986). With this kind of hydraulic control, if the friction coefficient with the road surface changes only slightly during braking, the wheel speed follows the braking target well, but if the friction coefficient changes significantly during braking, This change in the friction coefficient appears as a disturbance that prevents the wheel speed from converging, resulting in a problem that the followability of the wheel speed to the target value is reduced.

In order to solve these conventional problems, the inventors of the present application have developed a system that reduces the time ratio between brake hydraulic pressure reduction and pressure reduction stop while the wheel speed of the wheel to be skid-controlled falls below the braking target wheel speed. It is repeatedly changed according to the magnitude of the wheel deceleration, and while the wheel speed is equal to or higher than the braking target wheel speed, the time ratio between increasing the brake hydraulic pressure and stopping the pressure increase is changed according to the wheel deceleration. We have proposed an anti-skid control device that allows repeated changes.

The above device is designed to repeatedly change the time ratio of brake hydraulic pressure reduction and pressure reduction stop, or pressure increase and pressure increase stop depending on the magnitude of wheel deceleration, based on the braking target wheel speed. The wheel speed in the middle quickly converges to the braking target wheel speed.

By the way, when the skid control by the above device reaches a convergence state where the wheel speed approaches the braking target wheel speed, the wheel speed V _w gradually oscillates around the braking target wheel speed V _w0 as shown in Fig. 1. Draw and follow the waveform. However, as shown at times t ₁ , t ₂ , t ₃ , ..., when the wheel speed V _w crosses the braking target wheel speed V _w0 , in the control cycle immediately after the cross, a relatively large Brake oil pressure P _w
causes a change in Such a relatively large change in brake oil pressure will cause the wheel speed to change depending on the magnitude of the change.
Since it brings about a deceleration or recovery of V _w , it helps the vibration of the wheel speed V _w , which greatly affects the ability to follow the braking target wheel speed.

The present invention has been made in view of the above, and in order to suppress the generation of extra vibration due to hydraulic on/off control, the wheel speed converges within a predetermined fluctuation range determined based on the braking target wheel speed. Moreover, when the deceleration is below a predetermined value, control of the brake hydraulic pressure is stopped and the hydraulic pressure is maintained.

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

FIG. 2 is a diagram showing an embodiment of the present invention. First, to explain the configuration, 1a and 1b are differentiating circuits, and 2a and 2b are amplifiers, which differentiate the wheel speed V _w and generate a wheel deceleration signal e ₁ for skid control.
Output e ₂ respectively. R ₁ , R ₂ and R ₃ , R ₄ are
This is a voltage dividing resistor for biasing the deceleration signals from the amplifiers 2a and 2b. 3 is a comparator that determines the magnitude relationship between the wheel speed signal V _w and the braking target wheel speed signal V _w0 , and when V _w > V _w0 , the determination output _e3 becomes H level, and when V _w > V _w0 The discrimination output _e3 becomes L level.

Reference numeral 4 denotes a triangular wave oscillator, which forms a positive feedback loop with amplifiers 4a and 4b, and outputs a triangular wave signal _et with a predetermined period determined by the charging and discharging of the capacitor _C0 .
Or, set a control cycle that changes the time ratio between pressure increase and pressure increase stop. For example, the skid cycle drawn by the wheel speed is generally several hundred milliseconds, whereas the period of the triangular wave signal e _t is sufficiently short, about 10 milliseconds.

5a and 5b are comparators that operate as pulse modulators, and when e ₁ , e ₂ > e _t , comparison outputs e ₄ ,
e ₅ becomes H level, and conversely, when e ₁ , e ₂ < _et , comparison outputs e ₄ , e ₅ become L level.

6 and 7 are inverters, 8 is a NAND gate, 9 is an AND gate, 10a and 10b are amplifiers, and 11 is a hydraulic adjustment device.

In addition to the above configuration, as a circuit means that first determines whether the wheel speed V _w is within a predetermined braking target range centered on the braking target wheel speed V _w0 ,
12 is an upper limit setting device for setting the upper limit of the braking target range which is β ₁ times the braking target wheel speed V _w0 to β ₁ ·V _w0 ;
13 is a lower limit setter that sets the lower limit of the braking target range which is β ₂ times the braking target wheel speed V _w0 to β ₂ ·V _w0 ; for example, β ₁ = 1.05, β ₂ = 0.95; ±5
% range as the braking target range. 14 is a comparator that determines the magnitude relationship between the wheel speed V _w and the upper limit setting value β ₁ · V _w0 , and when V _w > β ₁ · V _w0 , the comparison output e ₆
becomes an L level, and when it falls within the range of V _w <β ₁ ·V _w0 , the comparison output e ₆ becomes an H level. Also, comparator 15
is a comparator that determines the magnitude relationship between the wheel speed V _w and the lower limit setting value β ₂ · V _w0 . When V _w < β ₂ · V _w0 , the comparison output e ₇ becomes L level. , V _w ＞
When the lower limit value is exceeded like β ₂ ·V _w0 , the comparison output e ₇ becomes H level.

In addition, 1c is a differentiating circuit, and 2c is an amplifier as a circuit means for determining whether the wheel deceleration ±(dV _w /dt) is between a predetermined value α ₁ and −α ₂ . By differentiating the wheel speed V _w , the deceleration ±(dV _w /dt) is outputted and subjected to a predetermined bias through resistors R ₅ and R ₆ . 16 is deceleration (dV _w /
dt) and the set value α _1. When the comparison output e ₈ is larger than the set value α 1 such as (dV _w t/dt) > α ₁ , the comparison output e ₈ becomes L level, and (dV _w t/dt) > α 1. t/
dt)< _α1 , when the comparison output e8 is smaller than the set value _α1 , the comparison output _e8 becomes H level. In addition, 17 is the deceleration (-
This is a comparator that determines the magnitude relationship between the set value α ₂ (dV _w t/dt) and the set value α 2, and when it is larger than the set value α ₂ , such as (dV _w t/dt) > α ₂ , the comparison output e ₉ becomes L level. ,
When it is smaller than the set value α ₂ such as (dV _w t/dt)<α ₂ , the comparison output e ₉ becomes H level.

Reference numeral 18 denotes a NAND gate having four inputs of signals e ₆ , e ₇ , e ₈ , and e _9. When all of the input signals e ₆ to e ₉ are at H level, the L level output outputs the NAND gate 8 and AND gate 9. is prohibited. That is, the NAND gate 18 has a wheel speed V _w of β ₂ .
V _w0 <V _w <β ₁・V _w0 , and the deceleration (dV _w
t/dt) is −α ₂ (dV _w t/dt) < α ₁ , then L
A level output is generated, and an H level output is generated at other times.

In addition, as another configuration for determining the braking target range centered on the braking target wheel speed V _w0 by the upper limit setter 12 and the lower limit setter 13, for example, in a device that can obtain the vehicle speed V _c during braking, this vehicle The upper limit β ₁ ·V _c and the lower limit β ₂ ·V _c may be determined based on the speed V _c , and in this case, they may be determined as β ₁ =0.85 and β ₂ =0.80.

In addition, when V _w > V _w0 , the EV signal output from the NAND gate 8 increases the pressure at the H level, which repeatedly changes the time ratio of brake hydraulic pressure increase and pressure increase stop depending on the magnitude of deceleration. On the other hand, the AV signal output from the AND gate 9 is a rectangular pulse train that increases the pressure at the L level.When V _w < V _w0 , the AV signal is a rectangular pulse train that changes the time ratio between brake hydraulic pressure reduction and pressure reduction stop to the deceleration. Since the pulse train is a rectangular pulse train that reduces the pressure at the H level and stops the pressure reduction at the L level, which is repeatedly changed depending on the magnitude, the hydraulic pressure adjustment device 11 has two pressure increasing valves (EV valves) and pressure reducing valves (AV valves).
The EV has an actuator using two solenoid valves.
The valve operates to stop the supply of brake hydraulic pressure when activated by the H level of the EV signal, and supplies brake hydraulic pressure to increase the pressure when deenergized by the L level of the EV signal.On the other hand, the AV valve operates to The brake hydraulic pressure is reduced when the AV signal is energized by the H level, and the reduction of the brake hydraulic pressure is stopped when the AV signal is deenergized by the L level.

Next, the action will be explained.

Figure 3 shows the wheel speed during braking according to the above embodiment.
FIG. 2 is a graph diagram showing changes over time in V _w , wheel deceleration, EV and AV signals, and brake oil pressure P _w .

Therefore, to explain the operation of the embodiment shown in FIG. 2 with reference to FIG. 3, in addition to the braking target wheel speed V _w0 generated during braking, the upper limit setter 12
Based on each setting value of the lower limit setter 13, a braking target range as shown by the diagonal line is set around the braking target wheel speed _Vw0 .

Immediately after stepping on the brake, the amplitude of the wheel speed V _w is large, and the wheel deceleration (dV _w t/dt) also changes significantly.

In such a case, when the wheel speed V _w falls below the braking target value V _w0 at time t ₁ , the time ratio for increasing brake hydraulic pressure and stopping the pressure increase is controlled.
As for the EV signal, the output _e3 of the comparator 3 goes to L level due to _Vw < _Vw0 and disables the NAND gate 8, so the output of the pulse width modulation signal _e4 generated by the comparator 5a is prohibited. The EV signal becomes H level (pressure increase is stopped). Conversely, the L level output of the comparator 3 is applied to the AND gate 9 via the inverter 7, so the AND gate 9 enters the allowable state and the time
After _t1 , the pulse width modulated signal _e5 produced by the comparator 5b passes through the AND gate 9 and is applied to the hydraulic pressure adjustment device 11 as an AV signal. The AV signal increases as the magnitude of deceleration increases in the positive direction.
Since the time width for reducing the brake oil pressure is a rectangular pulse train that decreases with respect to the time width for stopping the reduction, the brake oil pressure P _w decreases at a greater rate immediately after time t ₁ , but as time passes, the reduction in pressure decreases. The degree changes gradually.

At time _t2 , the wheel speed _Vw recovers and exceeds the braking target value _Vw0 , so under the condition of _Vw > _Vw0 , the output of the comparator 3 becomes H level, Therefore, the AND gate 9 becomes prohibited, and the AV signal maintains the L level (stopping decompression), and conversely, the NAND gate 8 becomes allowed, and the pulse width modulation signal e ₄ generated by the comparator 5a again of
A rectangular pulse train is outputted as an EV signal, and as the wheel deceleration goes in the negative direction, a rectangular pulse train is given to the hydraulic pressure adjustment device 11 such that the pressure increase time width decreases sequentially with respect to the pressure increase stop time width. , the rate of increase in brake oil pressure immediately after time _t2 is large, but the degree of pressure increase changes to become more gradual as time passes.

Such control of the brake hydraulic pressure P _w using the EV signal or the AV signal is performed under the condition that the output of the NAND gate 18 is at the H level. In other words, even if the wheel speed V _w is within the braking target range, if the deceleration (dV _w t/dt) is not between α ₁ and −α ₂ ,
The output of the NAND gate 18 is at H level, putting the NAND gate 8 and the AND gate 9 in a permissible state. Conversely, even if the wheel speed V _w is outside the braking target range and the deceleration (dV _w t/dt) is between α ₁ and −α ₂ , the output of the NAND gate 18 will be at the H level. Then, the NAND gate 8 and the AND gate 9 are set to an allowable state.

That is, the NAND gate 18 determines that the wheel speed V _w is within the braking target range and the deceleration (dV _w t/
dt) is between α ₁ and −α ₂ , all of its inputs are at H level and the output is at L level, and this L level output disables NAND gate 8 and AND gate 9, and outputs the EV signal. is set to H level, and the AV signal is fixed to L level.

The above condition in which the output of the NAND gate 18 becomes L level occurs at time _t3 in the graph of FIG.

That is, at time _t3 , the wheel speed _Vw falls below the upper limit of the braking target range ( _β1 · _Vw0 ), and the deceleration ( _dVwt /dt) at this time is equal to the set deceleration _α1 − _α2. Since the outputs of comparators 14, 15, 16, and 17 are between
Each of e ₆ , e ₇ , e ₈ , and e ₉ becomes H level, so the H level output of NAND gate 18 switches to L level, and AND gate 9, which had been outputting the AV signal until time t ₃ , is prohibited. and set the AV signal to L.
Fixed to level.

Therefore, the brake oil pressure _Pw , which had been increasing through time ratio control up to time _t3 , is maintained at a constant brake oil pressure at time _t3 , and the wheels are braked using this constant brake oil pressure.

Maintaining the brake oil pressure in this way reduces the wheel speed V _w
This will continue as long as the braking is within the target braking range, and changes in wheel speed within the target braking range will not result in large decelerations outside the range determined by the set decelerations _α1 and _-α2 . , wheel speed V _w
is 15% when the braking target wheel speed V _w0 is converged.
It will now decelerate while maintaining the nearby slip rate.

Of course, if the road surface condition changes while the wheel speed is within the target braking range, the wheel speed _Vw may deviate from the target braking range, but in such a case, the output of the NAND gate 18 will return to the H level again. Then,
Since the control of the brake oil pressure is switched to the same as that up to time _t3 , even if the wheel speed deviates from the target braking range, it will return quickly.

FIG. 4 shows a differential circuit 1c in the embodiment shown in FIG.
The deceleration (dV _w t/dt) of the wheel composed of the amplifier 2c and the comparators 16 and 17 is -α ₂ <(dV _w t/dt)
This shows another embodiment that performs the same function as the circuit unit that determines whether < _α1 .

That is, in the embodiment of FIG. 2, the thresholds α ₁ and −α ₂
However, in the embodiment shown in Fig. 4, the difference between the deceleration of the braking target wheel speed V _w0 or the vehicle speed V _c and the deceleration of the wheels is determined, and this difference is set to a predetermined value. It is determined whether the value is between δ ₁ and −δ ₂ .

First, to explain the configuration, 20 differentiates the wheel speed V _w and calculates the wheel deceleration (dV _w t/
dt) = α _w , 22 is a differentiation circuit that differentiates the braking target wheel speed V _w0 and outputs the deceleration of the braking target wheel speed (dV _w0 t/dt) = α _w0 from the amplifier 23, 24 25 is a differential amplifier that calculates the difference in deceleration (α _w0 −α _w ) from amplifiers 21 and 23, and 25 outputs an L level output when (α _w0 − α _w )> _{δ 1} ;
−α _w ) < δ ₁ , a comparator that outputs an H level;
26 outputs L level when (α _w0 −α _w )<−δ ₂ ,
The comparator outputs an H level output when (α _w0 -α _w )>-δ ₂ , and the comparator outputs e' ₈ and e' ₉ are applied to the NAND gate 18 in FIG.

Next, the action will be explained.

First, the wheel deceleration α _w created by the differentiating circuit 20 and the amplifier 21 is the same wheel speed V _w as in FIG.
For example, the change is shown in FIG. 5A. On the other hand, if the rate of decrease of the target braking wheel speed V _w0 is constant, the deceleration α _w0 produced by the differentiating circuit 22 and the amplifier 23 will be a constant negative value.

In such a case, the output of the differential amplifier 24 (α _w0 −α _w ) is a curve obtained by inverting the deceleration α _w with the deceleration V _w0 in FIG. 5A as the original axis, as shown in FIG. 5B. becomes.

For the curve showing this (α _w0 −α _w ), the comparator 2
5, 26, the threshold values δ ₁ and −δ ₂ are set, and −δ ₂ <
When (α _w0 - α _w ) < δ ₁ , the outputs e' ₈ and e' ₉ of comparators 25 and 26 both become H level, creating a condition for setting the output of NAND gate 18 in FIG. 2 to L level. .

The feature of the embodiment shown in FIG. 4 is that in the embodiment shown in FIG. 2, even if the slope of the braking target wheel speed V _w0 changes, the wheel deceleration α _w remains at the set value regardless of this change. In the embodiment shown in FIG _{. 4} , the curve of (α _w0 −α _w ) is determined depending on the change in the slope of the braking target wheel speed V _w0 . is shifted, and it is possible to set a braking target range for deceleration according to changes in vehicle deceleration.

Therefore, control to stop increasing or decreasing the brake oil pressure and maintain the brake oil pressure at the current brake oil pressure is performed more accurately depending on the actual road surface condition.

Note that the same effect as the control shown in FIG. 3 that reflects the slope of the braking target wheel speed described above is as follows depending on the magnitude of the slope (deceleration) of the braking target wheel speed V _w0 in the graph of FIG. This can also be achieved by shifting each of the threshold values α ₁ and −α ₂ set for the wheel deceleration α _w .

Furthermore, although the above embodiment uses the braking target wheel speed V _w0 , the same effect can be achieved by using the vehicle speed V _c detected by a Doppler radar etc. instead of V _w0 , and by using a G sensor etc. It is also possible to directly detect the deceleration of the vehicle and provide it to the comparator 24.

As explained above, according to the present invention, the configuration is such that the wheel speed converges within a predetermined braking target range centered on the braking target wheel speed, and the magnitude of deceleration when the wheel speed converges within a predetermined braking target range centered on the braking target wheel speed. When is less than a predetermined value,
We stopped increasing or decreasing the brake hydraulic pressure and kept the brake hydraulic pressure constant at that time.
It is possible to suppress vibrations in the wheel speed when the wheel speed has converged to the braking target wheel speed, and it is possible to decelerate while keeping the actual wheel speed consistent with the braking target wheel speed, which is the maximum braking efficiency. This makes it possible to shorten the braking stopping distance and suppress vibrational changes in wheel speed during braking, resulting in the effect that the braking feeling for the occupants can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a graph diagram showing skid control using only time ratio control, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a diagram showing wheel speed during braking according to the embodiment of Fig. 2. , its deceleration, hydraulic control output,
and a graph showing changes in brake oil pressure over time,
Fig. 4 is a block diagram showing another embodiment of the circuit section used in the embodiment of Fig. 2, and Fig. 5 shows the discrimination operation according to the embodiment of Fig. 4, corresponding to the graph of Fig. 3. It is a graph diagram. 1a, 1b, 1c, 20, 22... Differential circuit, 2
a, 2b, 2c, 10a, 10b, 21, 23...
Amplifier, 3, 5a, 5b, 14, 15, 16, 1
7, 25, 26... Comparator, 4... Triangular wave oscillator,
6, 7... Inverter, 8, 18... NAND gate,
9...And gate, 11...Hydraulic pressure adjustment device, 12...
Upper limit setter, 13...lower limit setter, 24...differential amplifier.

Claims (1)

[Scope of Claims] 1. Brake hydraulic pressure adjustment means for increasing, decreasing, or maintaining brake hydraulic pressure so that the wheel speed becomes a braking target wheel speed, and a braking target that defines a predetermined variation range based on the braking target wheel speed. a range setting means; a determining means for determining and outputting whether the wheel speed is within the fluctuation range and the wheel deceleration is below a predetermined value; and when the determining means outputs, the brake 1. An anti-skid control device comprising: holding signal output means for outputting a signal for stopping brake oil pressure pressure increase and pressure reduction by the oil pressure adjusting means and maintaining the oil pressure.