JP2593179B2 - Anti-skid control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an anti-skid control device for preventing wheel lock during braking in such a manner that maximum braking efficiency is achieved.

(Prior Art) The anti-skid control device is designed such that when the wheel speed during braking has a predetermined slip relationship with the vehicle speed (for example, when the road surface friction coefficient of the wheel exceeds an ideal slip ratio at which the road surface friction coefficient is maximized),
The brake fluid pressure is reduced so as to prevent slip (lock) of the wheel.

By the way, when the speed of the brake fluid pressure is reduced, if the speed is high, the brake fluid pressure becomes too low on a high friction road, so that the braking distance becomes long, and the imbalance of the braking force between the wheels becomes large, and the steering becomes unstable. On the other hand, if the pressure reduction speed is low, the brake fluid pressure is too high on the low friction road, and the braking distance is increased due to slip, and in any case, the braking efficiency is reduced. In this sense, it is preferable to reduce the brake fluid pressure reduction speed on a high friction road and increase the brake fluid pressure reduction speed on a low friction road.

For this reason, conventionally, as described in Japanese Patent Application Laid-Open No. 60-261769, a pseudo vehicle speed calculated by imitating the vehicle speed from the wheel speed (because a Doppler radar that directly detects the vehicle speed is expensive and impractical) A technique has been proposed in which the road surface friction coefficient is determined from the decreasing gradient, and the result is used to control the pressure reduction speed.

(Problems to be Solved by the Invention) However, in this technique, although the decrease gradient of the pseudo vehicle speed in the second and subsequent skid cycles can substantially correspond to the road surface friction coefficient by calculation, the decrease gradient of the pseudo vehicle speed in the first skid cycle is Since calculation is impossible, there is no other way than to determine in advance to correspond to either the high or low friction road, so it does not necessarily correspond to the road surface friction coefficient, and the braking efficiency decreases without obtaining the required pressure reduction speed control described above. And the problem of steering instability occurred.

(Means for Solving the Problems) In the present invention, the time from the start of braking indicated by ΔT in FIG. 10 to the start of the first anti-skid depressurization becomes longer on the high friction road, and this time can be detected in the first skid cycle. However, if the time contributes to the brake fluid pressure reduction speed control, this control can be performed as required from the first skid cycle and the above problem can be solved. When the generated braking wheel is determined to be locked based on a comparison between the wheel speed and the pseudo vehicle speed, the device that performs anti-skid control to reduce the brake fluid pressure and prevent the wheel from being locked, A timer for measuring the time during which the pseudo vehicle speed is decreasing until at least the first depressurization for anti-skid control is started; and The longer the time measured by the regimen time means when pressure is initiated and is characterized in that a pressure reducing speed control means for reducing the speed of the vacuum.

(Operation) When the anti-skid control device determines that the braking wheel that has generated the brake fluid pressure has locked in comparison between the wheel speed and the pseudo vehicle speed, the anti-skid control device reduces the brake fluid pressure to prevent the wheel from being locked.

Here, the time measuring means measures a period of time during which the pseudo vehicle speed is decreasing from the start of braking until at least the first depressurization for anti-skid control is started. The longer the above measurement time of the start of decompression for, that is,
The higher the friction road, the lower the speed of the pressure reduction.

Therefore, the pressure reduction for the anti-skid control is set to a gentle pressure reduction on the high friction road, and the pressure reduction for the anti-skid control is set to the rapid pressure reduction on the low friction road.

Therefore, it is possible to prevent the brake fluid pressure from becoming too low on the high friction road, thereby preventing the braking distance from being lengthened, and the imbalance of the braking force between the wheels to become large, thereby preventing the steering from becoming unstable. It is possible to prevent the braking distance from being lengthened due to slippage due to the brake fluid pressure being too high, and to secure high braking efficiency and steering stability on any road surface.

In addition, the above-described time can be detected during the first skid cycle, and the above-described pressure reduction speed control and the operation and effect thereof can be achieved from the first skid cycle.

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

FIG. 1 is an overall system diagram showing an embodiment of the anti-skid control device of the present invention. In the figure, reference numeral 1 denotes a right front wheel, 1a denotes a wheel shifter thereof, 2 denotes a left front wheel, 2a denotes a wheel cylinder thereof, and 3 denotes a right rear wheel. The wheel, 3a is its wheel cylinder, 4 is the left rear wheel, and 4a is its wheel cylinder. 5 is an engine, 6 is a transmission, 7 is a propeller shaft, 8 is a differential gear, 9 and 10 are rear axles, respectively, which can drive the rear two wheels 3 and 4 to drive the vehicle. .

The brake system is one of the two-system master cylinder 11
11a is connected to the right front wheel cylinder 1a by a pipe 12, the left front wheel cylinder 2a is connected to a pipe 13 by a pipe 13, and the other system 11b is connected to the right rear wheel cylinder 3a by a pipe 14 and the pipe 14 is connected. , 15, a so-called front-back split type hydraulic brake device connected to the left rear wheel cylinder 4a. This brake device is generated by the depression of the brake pedal 16 and the two systems 11a,
Actuated by the master cylinder pressure output from 11b, the vehicle can be decelerated.

A total of three anti-skid control means are provided for the right front wheel 1, the left front wheel 2, and the two rear wheels 3, 4, which are provided with conduits 12, 13,
It is composed of actuators 17a, 17b, 17c respectively inserted in and an anti-skid control circuit 18 for controlling the operation thereof.

Since the actuators 17a, 17b, and 17c are the same, the corresponding parts are indicated by the same reference numerals with different suffixes a, b, and c, and only the right front wheel actuator 17a will be described in detail below. Actuator 17a is an inflow valve (EV
A valve 19a, a discharge valve (AV valve) 20a, a pump 21a, an accumulator 22a, and a check valve 23a are connected as shown in the figure. The EV valve 19a and the AV valve 20a are individually controlled by the EV ₁ signal and the AV ₁ signal from the anti-skid control circuit 18, and the pump 21a is appropriately driven by the common motor 24 together with the pumps 21b and 21c in the other actuators 17b and 17c. The driving is controlled by the MR signal from the anti-skid control circuit 18. When the EV ₁ signal opens the EV valve 19a at L level and the AV ₁ signal closes the AV valve 20a at L level, the brake fluid pressure to the wheel shifter 1a rises until it becomes the same value as the master cylinder fluid pressure. Is done. In this state, EV ₁
When the signal changes to the H level and the EV valve 19a is also closed, the brake fluid pressure to the wheel cylinder 1a is held. Then open the AV valve 20a in turn AV ₁ signal is the H level in this state, is added to conduct the transistor 25 by the H level of the MR signals, when the motor 24 is energized by the power source + E to drive the pump 21a Wheel The brake fluid pressure of cylinder 1a is the master cylinder
Return to 11 and decompress. The above operation is summarized in a table as shown in the following table.

The anti-skid control circuit 18 includes a circuit portion 18a that emits the EV ₁ signal and the AV ₁ signal based on a signal from a wheel speed sensor 26a that detects the rotation speed of the right front wheel 1, and a wheel that detects the rotation speed of the left front wheel 2. A circuit portion 18b for generating an EV ₂ signal and an AV ₂ signal for the left front wheel actuator 17b based on a signal from the speed sensor 26b, and a rotation speed of the propeller shaft 7, which is an average rotation speed of the rear two wheels 3, 4, Wheel speed sensor 26c to detect
₃ for rear wheel actuator 17c based on signals from
A circuit portion 18c for emitting signals and AV ₃ signal, the pseudo vehicle speed generator 27, the circuit 28a for generating a target wheel speed corresponding to the desired slip rate from coming pseudo vehicle speed, 28b, and 28c, A
_{V 1, AV 2, AV 3} AV 1 becomes a signal source _{', AV 2', AV 3} '(H
OR gate 29 which takes the logical sum of (OR) level, and MR of H level for a predetermined time triggered by the rising of the output of the OR gate
A retriggerable timer 30 that emits a signal.

Since the circuit portions 18a, 18b, 18c have the same configuration,
Corresponding portions are indicated by the same reference numerals with different suffixes a, b, and c, and only the circuit portion 18a will be described in detail. 31a is a wheel speed detection circuit, calculates the right front wheel rotational speed (pulse) signal and the peripheral speed of the right front wheel turning radius (wheel speed) V _w1 from the wheel speed sensor 26a. The wheel speed V _w1 is input to the wheel acceleration detection circuit 32a and is used for calculating a wheel acceleration α _w1 (negative is deceleration). The wheel acceleration α _w1 is compared with the deceleration reference value b ₁ and the acceleration reference value a ₁ by the comparators 33a and 34a, and the comparator 33a
Outputs an H level signal when the wheel deceleration α _w1 becomes larger than the reference value b ₁ , and the comparator 34a outputs an H level signal when the wheel acceleration α _w1 becomes larger than the reference value a _1. . The comparator 35a compares the wheel speed V _w1 with the target wheel speed generation circuit 28a.
The comparator 35a outputs an H level signal while the wheel speed V _w1 is equal to or lower than the target wheel speed (V _fH × 0.85) described below. The OR gate 36a is connected to the H of the comparators 33a to 35a.
The level output is ORed to generate an H level signal, which passes through an OR gate 40a and is output as an EV ₁ signal to an amplifier 37a.
Is supplied to the EV valve 19a. AND gate 38a emits an H level output of the comparator 35a, the H-level AV ₁ 'signal of the logical product of the L-level signal from the comparator 34a, decompression rate control according to the subject matter of the present invention the signal after the AV ₁ signal by the circuit 90a, and supplies the AV valve 20a via an amplifier 39a.

The output of the AND gate 41a is connected to the remaining input of the OR gate 40a, and a variable timer 42a and a pulse generator (OSC) 4 for generating a rectangular pulse of a constant frequency are respectively connected to three inputs of the AND gate.
3a and the MR signal from the retriggerable timer 30 are supplied. Variable timer 42a is triggered by the fall of the output of the comparator 34a, and shall only outputs an H level signal time corresponding to the peak value αmax of the wheel acceleration alpha _w1 detected by the peak value detection circuit 44a, the peak value detecting circuit Reference numeral 44a detects the peak value α _max of the wheel acceleration α _w1 from the fall of the output from the comparator 33a to the next rise.

For this reason, the peak value detection circuit 44a is constituted by buffer amplifiers 45 and 46, a peak hold circuit including a die auto 47 and a capacitor 48, and an analog switch 49 as shown in FIG. The wheel acceleration α _w1 is input to the input, the output signal of the comparator 33a is input to the gate of the analog switch 49, and the buffer amplifier 46
It is assumed that a peak value α _max is output.

The operation of the peak value detection circuit 44a is based on the wheel acceleration α
_{The case where w1} is as shown in FIG. 3 and the output of the comparator 33a is as shown in FIG. 3 will now be described. That wheel deceleration alpha _w1 is beyond the reference value b ₁ comparator 33a
While the output of the comparator is at the H level, this comparator output resets the capacitor 48 by turning on the analog switch 49, and charges the capacitor 48 with a voltage corresponding to the peak value α _max of the wheel acceleration α _w1 during this reset. The peak value α _max can be output from the buffer amplifier 46.

The variable timer 42a is provided with a first timer 5 as shown in FIG.
The output of the comparator 34a is supplied to the input B of the first timer 50 via the inverters 52 and 53, and the first timer 50 is activated at the falling edge of the input B to start the timer. output resulting from the terminal Q _a a. The set time of the timer output is determined by terminals T ₁ and T ₂
Is determined by the time constant of the externally connected capacitor 54 and the variable resistance circuit 55, and the resistance value of the variable resistance circuit 55 is the peak value α.
_It shall increase in proportion to _max . Therefore, the timer output set time from the terminal Q _A of the first timer 50 is a peak value α
_It becomes longer in proportion to the size of _max . Output Q of first timer 50
_A is supplied to an input B of a second timer 51, and a time constant determined by an externally connected capacitor 56 and a variable resistor 57 is fixedly set in the second timer 51. And the second timer 51
It is started by the fall of the first timer output Q _A, terminal
From Q _B to the AND gate 41a outputs a H level only signal the time constant.

Operation of the variable timer 42a is in as wheel acceleration alpha _w1 of Figure 5, therefore the output of the comparator 34a is explained if it is as shown in the figure, the wheel acceleration alpha _w1 is the reference value a ₁ or less the more the instantaneous output of the comparator 34a falls by Te' 1 output Q _a of the timer 50 becomes H level only time T ₁ corresponding to the peak value alpha _max, the output Q fall instantly from the second timer _a 51 output Q _B becomes constant time T ₂ by H-level.

Pseudo vehicle speed generator 27 pseudo vehicle speed based on the wheel speed V _w1 ~V _w3
Circuits 27a to 27c for individually generating V _{f1 to} V _f3 and a select high switch 58 for selecting the highest value of these pseudo vehicle speeds closest to the vehicle speed, and the switch 58 _{controls the} select high pseudo vehicle speed V _fH . The target wheel speed generation circuits 28a to 28c are supplied. The simulated vehicle speed generation circuits 27a to 27c have wheel speeds _{Vw1 to} Vw, respectively.
While inputting _w3 and supplying the MR signal, the circuits 27a to 27c
To the respective same configuration, pseudo than the wheel speed V _w1 vehicle speed V
Only the circuit 27a for producing _f1 will be described below with reference to FIG.

That is, the pseudo vehicle speed generating circuit 27a and the comparator 59 and 60 to be supplied to the wheel speed V _w1 to first input, the other input of the comparator 59 and 60 to set the dead zone of ± 1km / h to the pseudo vehicle speed V _f1 Adder 61 to supply
And a subtractor 62 and a NOR gate 63 to which the outputs C ₁ and C ₂ of the comparators 59 and 60 are supplied. Comparator 59 is V _w1 ≧ V _f1 +1 km / h
, The output C _{1 is set} to the H level, and the comparator 60 outputs V _w1 <V _f1 −1 km /
when h is the output C ₂ to H level. Thus, the NOR gate 63 outputs V _f1 −1 km / h ≦ V _w1 <V _{f1 at} which both the outputs C ₁ and C ₂ are at the L level.
Outputs H level at + 1km / h. The output of the NOR gate 63 is input to the timer 64, the OR gate 65, and the shot pulse generation circuit 66. The timer 64 is started by the fall of the signal from the NOR gate 63, and outputs an H level signal for a fixed time T ₃ (for example, 0.1 seconds, which will be described later with reference to FIG. 7).
Supply to gate 65.

The output of the OR gate 65 is supplied as a select signal S ₃ to the gate of the analog switch 67 is supplied to one input of AND gate 69 is inverted by inverter 68. A C ₁ signal to the other input of the AND gate 69, and the C ₂ signal respectively supplied to the other input of the AND gate 70, an analog switch the output of AND gate 69 as a select signal S _2, S ₄ 71,72
Supply to the gate. Analog switch 67 is set to zero the supply voltage E to the select signal S ₃ of the H-level during the integration circuit 73 is turned ON, the analog switch 71 is H level during ON of the select signal S _2, possible vehicle acceleration (speed increase Rate of change)
, For example, a voltage E corresponding to +0.4 g
Is supplied to the analog switch 72 is H level during ON of the select signal S _4, possible vehicle deceleration maximum value (the vehicle speed reduction rate of change), for example, supply a voltage E corresponding to -1.2g to the integrating circuit 73 I do.

Integrating circuit 73 amplifier 74, well known consisting capacitor 75 and the analog switch 76 is reset when the analog switch 76 is turned ON by the H-level reset signals S ₁ to its gate, after the reset signal S ₁ is lost It is assumed that the voltage E is continuously integrated. Reset signals S ₁ is to obtain by-shot pulse from the circuit 66, the shot pulse generating circuit 66 is an ignition-on signal at the start of the engine by IG first one shot pulse reset signal
Output as S _1, then outputs the shot pulse for each output of the NOR gate 63 rises as a reset signal S _1.

Also used to reset the reset signals S ₁ sample-and-hold circuit 77 to the other, this circuit also buffer amplifier 78,7
9. A well-known device comprising a capacitor 80 and an analog switch 81 is inputted with the wheel speed _Vw1 . Sample-and-hold circuit 77 is reset when the analog switch 81 is turned ON by the H-level reset signal S _1, it continues to store the wheel speed V _w1 at that time as a wheel speed sampling value V _s, and inputs it to the adder circuit 82. Adder circuit 82 is the integral value of circuit 73 It was added to the wheel speed sampling value V _s, and inputs the addition value V _s + V _e to the change-over switch 83. Separately wheel speed V _w1 is also input to the change-over switch 83, the changeover switch H level MR signal and H level C ₁ signal and the wheel speed V _w1 pseudo vehicle speed V by H level output of the AND gate 84 for taking a logical product of _f1 and otherwise functions to set the output of the adder circuit 82 to the pseudo vehicle speed _Vf1 .

When the wheel speed V _w1 is as shown in FIG. 7, the pseudo vehicle speed generation circuit 27a can generate the pseudo vehicle speed V _f1 as shown by a dotted line in FIG. However, in FIG. 7 Fig. 6 in the AND gate 84 does not output the H level, ie (anti-skid control is not executed in as described below) MR signal is L level or the signal C ₁ is L level (wheel speed V _w1 is not accelerating), the AND gate 84 does not output the H level, and the changeover switch 83 sets the output of the adding circuit 82 to the pseudo vehicle speed V _f1 .

When starting the engine in FIG. 7 instant t _0, the ignition switch signal IG is one-shot pulse (reset signal) from the time circuit 66 to output the S _1. The signals S ₁ during the seventh figure wheel speed V _w1 at that time as a wheel speed sampling value V _s to reset the sample-and-hold circuits 77 1
Hold as shown by the dotted line. Signals S ₁ resets the integrating circuit 73 on the other hand, the output V _e is 0, and therefore, the output V _s + V _e is V _s and is in this pseudo vehicle speed V _f1 of the adder circuit 82. By the way, since V _s is initially V _w1 , V _f1 = V _w1 , the comparator outputs C ₁ and C ₂ are both at L level, and the NOR gate 63 outputs an H level signal. The output is also at the H level. The H-level output is provided as the select signal S ₃ to the ON of the analog switch 67 is inverted to L level by the inverter 68 on the other hand, it prohibits the generation of the select signal S _2, S _4. The ON of the analog switch 67 is determined by the input voltage E of the integrating circuit 73.
Kept at 0, the pseudo vehicle speed V _f1 by the integrated value V _e remains 0 is maintained at the same constant value as the wheel speed sampling value V _s.

When the wheel speed V _w1 increases due to the acceleration of the wheel after the instant t _1, the signal C ₁ from the comparator 59 is obtained when V _w1 ≧ V _f1 +1 km / h.
Goes high, and the output of the NOR gate 63 goes low. However, since the timer 64 outputs the H-level signal only ₃ hours T than its instantaneous, until the output S ₃ of the OR gate 65 is T ₃ hours elapses keeps the H level, starts to L level to the instant t ₂ . Therefore, the pseudo even between instant t ₁ ~t ₂ vehicle speed V
_f1 is still kept at the same constant value as the original wheel speed sampling value V _s.

In instant t ₂ after the output of OR gate 65 is at L level, by the output C ₁ of the comparator 59 is H level, the AND gate 69 outputs a (select signal S ₂₎ to H level, the analog When the switch 71 is turned on, the input voltage E of the integration circuit 73 is switched to a value corresponding to the vehicle acceleration of +0.4 g. Therefore, its integral value Speed + 0.4 g acceleration increases at a speed corresponding to the addition value by the circuit 82 between this and the wheel speed sampling value V _s, i.e. also the pseudo vehicle speed V _f1 corresponding to the acceleration of the seventh diagram as + 0.4 g To rise.

As a result, the pseudo vehicle speed V _f1 catches up with the wheel speed V _w1 (V _w1
<A V _f1 + 1.0km / h) signal C ₁ at instant t ₃ is turned to L level, the output of NOR gate 63 starts to H level. The instant shot pulse generating circuit 66 issues a reset signal S _1,
Reset integrating circuit 73 and the sample hold circuit 77, but since then also up to instant t ₄ when increasing the wheel speed V _w1 is with a similar trend, the pseudo vehicle speed V _f1 by the action similar to the above
Is produced.

By the way, during the instants t _{4 to} t ₅ , the wheel speed V _w1 is equal to the time T ₃
Since the fluctuation is repeated in a shorter cycle, the output of the OR gate 65 is kept at the H level by the timer 64 even if the output of the NOR gate 63 repeats the corresponding level change. Therefore, the integrated value V _e by H level holding the select signal S ₃ which is the output of OR gate 65 is held at 0, the wheel speed sampling value V _s at the instant t ₄ is output as a pseudo vehicle speed V _f1, the pseudo vehicle speed Can be kept constant while the fluctuation cycle of the wheel speed V _w1 is short.

The instant t ₅ hereinafter, a _{V w1 <V f1 -1km / h} , also this state to follow after a lapse T ₃ hours the fall of the output of the NOR gate 65, in the course instant t ₆ of T ₃ hours The output of the OR gate 65 turns to L level. Since the output of the comparator 60 is at the H level due to V _w1 <V _f1 -1 km / h, the AND gate 7
0 sets the select signal S ₄ to the H level and sets the analog switch 7
By turning on 2, the input voltage E of the integration circuit 73 is switched to a value corresponding to the vehicle deceleration of -1.2 g. Therefore, its integral value Becomes smaller at a speed corresponding to the deceleration of -1.2 g, which the addend by the circuit 82 and the wheel speed sampling value V _s, i.e. corresponding to the deceleration of the pseudo vehicle speed V _f1 also as Figure 7 -1.2 g At a reduced speed.

As a result, the pseudo vehicle speed V _f1 catches up with the wheel speed V _w1 (V _w1
≧ a V _f1 -1km / h) signal C ₂ at moment t ₇ is turned to L level, the output of NOR gate 63 starts to H level. The instant shot pulse generating circuit 66 issues a reset signal S _1,
While resetting the integrating circuit 73 and the sample hold circuit 77, described above followed for up to instant t ₈ do not vary or vary the period of the wheel speed V _w1 is less than T _3, the pseudo vehicle speed V _f1 is per between instant t ₄ ~t ₅ It is maintained at the same constant value as the wheel speed sampling value V _s at the instant t ₇ in the same manner as the.

In addition, since the instant t ₈ thereafter to decrease the wheel speed V _w1, instant t ₅
In the same manner as described above per between ~t _7, the pseudo vehicle speed V _f1 T ₃
During the time keeping the value of the heretofore, it can be lowered at a speed corresponding to the deceleration of the instant t ₉ hereinafter -1.2 g.

In the pseudo vehicle speed generating circuit of FIG. 6, between MR signal is H level, ie in the anti-skid control performed as apparent from processing described later, when the wheel is accelerated C ₁ signal becomes H level, the AND the gate 84 switches the changeover switch 83 to the output to H level, during which the pseudo vehicle speed V _f1 ignoring the effect match the wheel speed V _w1. This is because during this period also the anti-skid control too slow than directing the wheel speed V _w1 at a speed corresponding pseudo vehicle speed V _f1 to + 0.4 g becomes inaccurate by the action of the.

Next, the decompression speed control circuit 90a in FIG.
This circuit includes an AND gate 91a to which the AV ₁ 'signal is input, and supplies the output of the change-over switch 92a to the other input of the AND gate. Changeover switch 92a outputs an H-level signal from between the power source + E of the control signal S ₅ is L level, the pulse signal having a constant period of the control signal S ₅ is between the pulse generator at the H level (OSC) 93a (AV ₁ 'Generated during the H level of the signal). AND gate 91a is therefore, the brake fluid pressure reduction in the pressure (in the anti-skid control performed) to AV ₁ 'signal as is clear from processing to be described later becomes H level, when the control signal S ₅ is at L level, AV ₁ 'to execute the rapid decompression by the output signal as it is AV ₁ signal, if the control signal S ₅ is at H level, to execute the gradual decompression by outputting a pulse signal from the OSC 93a as AV ₁ signal.

Control signal S _5, all of the anti-skid control channel 18a for determining Such a decompression rate, 18b, decompression rate control circuit 90a in 18c, 90b, 90c to a common flip-flop circuit 9
4, and the level is determined according to the time indicated by ΔT in FIG. That is, a flip-flop circuit
94 a signal S ₅ by the set at the rising edge of the output is connected to the output of the AND gate 95 to the set input to the H level, at the fall of the input to the MR signals to the reset input MR signal, i.e. antiskid the end reset control shall signal S ₅ to the L level. One input of an AND gate 95 receives a shot pulse from a circuit 96 that generates one shot pulse each time the MR signal rises, and the other input of the AND gate 95 supplies the output of a comparator 97. I do.

The comparator 97 is supplied with the output voltage TM of the timer 98 at one input and the voltage corresponding to the set time T _s at the other input. When the measured time TM of the timer 98 becomes longer than the set time T _{s, the} comparator 97 outputs the output. Assume that the level is H level. Timer 98 is a deceleration detection circuit 99
Corresponding to the output of this output, and when this output rises,
The level time is integrated, and the integrated value is reset when the output falls.

As shown in FIG. 8, the deceleration detecting circuit 99 has the same configuration as the pseudo vehicle speed generating circuit shown in FIG. For this reason, FIG.
Shows view as corresponding parts and signals in the same reference numerals, the input signal is a select-high pseudo vehicle speed V _fH, the output signal which the timer as C ₂ signal which becomes apparent slowdown in H level from processing described above 98, and the set deceleration gradient selected by the analog switch 72 is set to a small value of about -1.2 g, which is slightly larger than the engine brake equivalent value.

The operation of the deceleration detection circuit 104 will be described with reference to the case where the select high pseudo vehicle speed _VfH is as shown in FIG. 9, as is clear from the above description with reference to FIGS. 6 and 7.
The output of the changeover switch 83 is turned as the dotted line in FIG. 9, the sample hold value V _s is as the one-dot chain line in the figure by the circuit 77. Starts braking in FIG. 9 in instant t _1, when the wheel speed V _w1 of the front right wheel is to have dropped to as the two-dot chain line, than the instantaneous t ₂ when the set time T ₃ has elapsed since the start of braking instant t ₁ begins to decrease select-high pseudo vehicle speed V _fH (deceleration), the time between C ₂ signal is at the H level, that is, the deceleration time TM timer
98 is measured as shown in FIG.

The comparator 97 in FIG. 1 is to output the H-level signal when the deceleration time TM exceeds the setting time T _s, the AND gate 95, the circuit 9
When shot pulse from 6 is input, that is, if the above TM ≧ T _s state occurs in the anti-skid start the MR signal rises, the signal S ₅ and sets a flip-flop circuit 94 by H-level output Set to H level.

Incidentally set time T _s is previously determined by the set time T ₃ from FIG. 9 during the braking start instant t ₁ until the reduced initial instant t ₂ of the select high pseudo vehicle speed V _fH previously considered, so that the output of the comparator 97 has an H level when the braking time from the start of braking instant t ₁ is T ₃ + T _s or more. And at the start of braking, as shown in FIG.
The high friction path time ΔT is longer from t ₁ until the anti-skid control is started when t _3, the output of the comparator 97 becomes H level before the instant t _3, in response to the rise of the MR signal at the instant t ₃ Receiving a shot pulse from the circuit 96 generated by the
H level and no flip-flop circuit of the output to the instant t ₃ is
94 output (control signal) S ₅ to H level.

The operation of the above embodiment will be representatively described by taking an anti-skid control operation relating to the right front wheel 1 as an example. However, in the following, the select-high pseudo vehicle speed V _fH selected by the wheel speed V _w1 and select-high Sutchi 58 of the right front wheel 1 is FIG. 10 (V _c is the actual vehicle speed as shown by reference) and in as, therefore wheel acceleration alpha _w1 is intended as shown in the drawing, to deploy described that the change-over switch 92a for low friction road is the first solid line in the figure located at the L-level control signal S _5.

In the depression of the brake pedal 16 (see FIG. 1), the brake fluid pressure P _w than in FIG. 10 instant t ₀ is generated, the wheel speed V _w1 is first
0 Figure Initially braking drops as the, wheel deceleration alpha _w1 is less than the reference value b _1, the output of the comparator 33a is L level,
Of course, since α _w1 <a ₁ , the output of the comparator 34a is also at the L level. Since the wheel speed V _w1 is not less than the target wheel speed V _fH × 0.85 without causing any wheel slip, the output of the comparator 35a is also at the L level. Level. Therefore, the output of the OR gate 36a is at L level and A
The output (AV1 'signal) of the ND gate 38a is also at the L level,
Since the output of the OR gate 29 which takes the logical sum of the 1 'signal to the AV3' signal is kept at L level and the MR signal from the retriggerable timer 3 is kept at L level, the output of the AND gate 41a is also at L level. The output of the OR gate 40a (EV1 signal) is also at the L level. EV1 signal L level opens the EV valve 19a, AV1 'L-level signal closes the AV valve 20a to the AV1 signals to the L level, thus from the brake fluid pressure P _w is the master cylinder 11 to the meantime wheel cylinder 1a It rises towards hydraulic pressure and normal braking is obtained.

During the braking, the instantaneous wheel deceleration alpha _w1 exceeds the reference value b ₁
t ₁ between ~t _2, comparators 33a between t ₁ '~t _2' outputs the H level, instant t ₃ the wheel acceleration alpha _w1 exceeds the reference value a ₁ ~
During t ₄ , after t ₃ ′, the comparison 34a outputs an H level,
Between instant t ₂ ~t ₆ of the wheel speed V _w1 is equal to or less than the target wheel speed, t ₅ '
The comparator 35a outputs the H level during ~t ₆ '. Therefore, EV1 signal EV valve 19a becomes H level between instant t ₁ ~t ₄
Closed, AV1 'signal to open the AV valve 20a to the AV1 signals to the H level to the H level during this period in instant t ₂ ~t _3. This is the brake fluid pressure P _w in between instant t ₁ ~t ₂ for being held, as well as the road surface friction coefficient can be determined by keeping the braking force constant, eliminating this in increase of more brake fluid pressure Ensure that antiskid control is not delayed.

Then, at moment t ₂ when the wheel speed V _w1 is less than the target wheel speed V _fH × 0.85, closed holding of the EV valve 19a, the opening of the AV valve 20a,
Also, when the AV1 'signal rises, M
R signal rises, by driving the pump 21a in energizing the motor 24, reducing the pressure of the brake fluid pressure P _w. The locking of the wheel 1 is thus prevented. By the way, as described above, since the changeover switch 92a is in the solid line position and the corresponding input of the AND gate 91a is kept at the H level by the power supply + E because of the low friction road, the AV1 'signal becomes the AV1 signal as it is, and Then, a rapid decompression is performed. For this reason, anti-skid control is performed on the low friction road due to rapid pressure reduction, and it is possible to prevent the brake fluid pressure from being too high and the braking distance being lengthened by slip. Incidentally, the retriggerable timer 30 is triggered for each rise of AV1'～AV3 'signal, but as it emits MR signals of a predetermined time H level, instant t ₂ after the retrigger within a predetermined time in FIG. 10
It is assumed that the MR signal is kept at the H level.

By AV valve 20a is closed at instant t ₃ when the wheel acceleration alpha _w1 reaches the reference value a ₁ by the above vacuum switched to hold the brake fluid pressure P _w I closed state held coupled with the EV valve 19a, This makes it possible to determine the degree of change in the road surface friction coefficient, and to prevent delay in canceling the anti-skid control for increasing the brake fluid pressure again when the brake fluid pressure further decreases.

During the holding of such a brake fluid pressure, while the wheel speed V _w1 by recovery of the road friction force is increased toward the vehicle speed corresponding value, the vehicle speed value corresponding wheel speed at moment t ₄ when wheel acceleration alpha _w1 is equal to or less than the reference value a ₁ Therefore, the brake fluid pressure _Pw is increased again as follows. That is, at moment t _4, the comparator
Since the outputs of 33a, 34a and 35a are all at L level, AV1
The (AV1 ') signal is kept at the L level, and the level of the EV1 signal is determined by the signal from the AND gate 41a. The variable timer 42a connected to the input of the AND gate 41a outputs a time T corresponding to the peak value α _max of the wheel acceleration α _w1 detected by the circuit 44a.
₁ only later than instant t ₄ emits output for a predetermined time T ₂ in the H level, and a pulse generator (OSC) 43a has issued a rectangular pulse of a constant frequency shown in Figure 10. AND gate 41a from taking the logical product of these signals and the MR signal (in H level), keeping the L level during the time T ₁ the EV1 signal from the instantaneous t _4, the pulse signal from OSC43a during subsequent T ₂ hours The level is changed at the same cycle as the above. Therefore, the brake fluid pressure P _w in time T ₁ is pressurized surge toward the master rosewood da pressure, T ₂ hours in the brake fluid pressure P _w becomes be pressed Yuruzo, the brake fluid pressure P _w
The can be kept long in the lock near the hydraulic P _L corresponding to the desired slip rate maximum braking efficiency, it can shorten the braking distance.

Thereafter, the instant t ₁ ′ at which the wheel deceleration α _w1 exceeds the reference value b ₁
Then, the operation proceeds to the next skid cycle, and by repeating the same operation as described above, the brake fluid pressure of the right front wheel 1 is controlled so as to maintain the ideal slip ratio, and the anti-skid such that the braking distance becomes as short as possible. Control is executed.

The above is the anti-skid control for the right front wheel on a low friction road.
t ₁ long time ΔT until the anti-skid start t ₃ from the comparator 97 has an output from the previous instant t ₃ the H level. Therefore, when the circuit 96 at the rising edge of MR signals instantaneously t ₃ emits shot pulse, turn signal S ₅ to H level AND gates 95 and sets a flip-flop circuit 94 by the H level output. As a result, the changeover switch 92a is at the position indicated by the dotted line, and the AND gate 91a uses the pulse signal shown in FIG. 9 from the OSC 93a during the anti-skid when the AV1 'signal is at the H level as the AV1 signal. Therefore, the the anti-skid control in the brake fluid pressure P _w in the high friction road will be intermittently reduced pressure, pressure reduction rate is in a low friction path of FIG. 10 is a rapidly as indicated by a dotted line in FIG. 9 On the other hand, on a high friction road, the speed becomes low. Therefore, it is possible to prevent the brake fluid pressure from becoming too low on the high friction road, thereby increasing the braking distance, and preventing the steering stability from being deteriorated due to a large imbalance in the inter-wheel braking force.

The left wheel 2 and the two rear wheels 3, 4 are also similarly subjected to anti-skid control by the same operation as described above based on the corresponding wheel speeds _Vw2 , _Vw3 .

FIG. 11 shows another example of the deceleration detection circuit 104. In this example, the normal brake switch 110 and the stop lamp 111
Connect the base of transistor 112 between
Connect the 12 collectors to the power supply + E and the input of timer 98,
The emitter of transistor 112 is grounded. Timer 9
A NOT gate 113 is provided for the input 8.

In this example, when the braking is started, the brake switch 110 is turned off.
The transistor 112 is turned on by N and the collector potential is set to 0, the input of the timer 98 is set to H level by the NOT gate 113, and this state is maintained during braking. Therefore, the signal directed from the NOT gate 113 to the timer 93 becomes those similar to C ₂ signal in FIG. 8, it is possible to measure the deceleration time TM by the timer 93.

(Effects of the Invention) As described above, the anti-skid control device of the present invention determines the road surface friction coefficient and controls the pressure reduction rate of the brake fluid pressure during the anti-skid control according to the determination result. It is possible to prevent the braking distance from being excessively reduced on the road, thereby preventing the braking distance from being extended or the steering stability from being deteriorated, and to prevent the brake hydraulic pressure from being delayed on a low friction road and the braking distance from being extended due to slippage. Can be.

Moreover, in determining the road surface friction coefficient, the time during which the pseudo vehicle speed is decreasing from the start of braking is measured at least until the first depressurization for anti-skid control is started, and the depressurization for the first anti-skid control is measured. The road surface friction coefficient is determined from the length of the measurement time at the start of the operation, so that the road surface friction coefficient can be determined from the first skid cycle. From the first skid cycle.

[Brief description of the drawings]

FIG. 1 is an overall system diagram showing one embodiment of the anti-skid control device of the present invention, FIG. 2 is an electronic circuit diagram of a peak value detection circuit in the anti-skid control device, FIG. 4 is a circuit diagram of a variable timer in the anti-skid control device of FIG. 1, FIG. 5 is an explanatory diagram of operation waveforms of the variable timer, and FIG. 6 is a diagram of a pseudo vehicle speed generation circuit in the anti-skid control device of FIG. Electronic circuit diagram, FIG. 7 is an explanatory diagram of operation waveforms of the circuit, FIG. 8 is an electronic circuit diagram of the deceleration detection circuit in FIG. 1, FIG. 9 is an operation waveform diagram of the circuit, FIG. 10 is FIG. FIG. 11 is an operation waveform diagram of the anti-skid control device shown in FIG. 11, and FIG. 11 is an electronic circuit diagram showing another example of the deceleration detection circuit. 1 ... Right front wheel 2 ... Left front wheel 3,4 ... Rear wheel 1a ~ 4a ... Wheel cylinder 7 ... Propeller shaft 8 ... Differential gear 9,10 ... Axle 11 ... 2 system master cylinder 16 ... Brake pedal 17a, 17b, 17c Actuator 18 Anti-skid control circuit 19a, 19b, 19c EV valve 20a, 20b, 20c AV valve 21a, 21b, 21c Pump 22a, 22b, 22c Accumulators 23a, 23b, 23c Check valve 24 Pump drive motor 25 Transistors 26a, 26b, 26c Wheel speed sensor 27 Simulated vehicle speed generator 27a, 27b, 27c Simulated vehicle speed generation circuit 28a, 28b, 28c: Target wheel speed generation circuit 29: OR gate 30: Retriggerable timer 31a, 31b, 31c: Wheel speed detection circuit 32a, 32b, 32c: Wheel acceleration detection circuit 33a-33c, 34a- 34c, 35a to 35c ...... Comparator 36a to 36c, 40a to 40c ...... OR gate 37a to 37c, 39a to 39c ...... Amplifier 38a to 38c ...... AND gate 41a to 41c ... AND gates 42a-42c Variable timers 43a-43c Pulse generators 44a-44c Peak value detection circuit 58 Select high switch 59,60 Comparator 61 Adder 62 Subtraction Unit 63 NOR gate 64 Timer 65 OR gate 66 Shot pulse generation circuit 67, 71, 72 Analog switch 68 Inverter 69, 70 AND gate 73 Integration circuit 77 … Sample hold circuit 82… Addition circuit 83… Changeover switches 90a to 90c… Decompression speed control circuit 91a, 95… AND gate 92a… Changeover switch 93a… Pulse generator 94… Flip flop circuit 96… Shot pulse generation circuit 97 Comparator 98 Timer 99 Deceleration detection circuit 110 Brake switch 111 Stop lamp 112 Transistor 113 NOT gate

Claims (1)

(57) [Claims] (1) A braking wheel that generates a brake fluid pressure,
A device that performs anti-skid control to reduce the brake fluid pressure to prevent wheel lock when it is determined that the vehicle is locked in the comparison between the wheel speed and the pseudo vehicle speed, wherein the pseudo vehicle speed is decreasing from the start of braking. The time between
A timer for measuring at least until the first depressurization for anti-skid control is started; and the longer the measurement time by the timing means when the first depressurization for anti-skid control is started, the lower the speed of decompression. An anti-skid control device comprising: a pressure reduction speed control means for causing the pressure to decrease.