JP2600252B2 - Anti-skid control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an anti-skid control device for preventing a wheel from being locked during braking of a vehicle, and particularly when a change in a wheel speed in a locking direction is detected. The present invention relates to an anti-skid control device that estimates a vehicle body speed using a longitudinal acceleration of a vehicle.

[Conventional technology]

Conventionally, as this type of anti-skid control device, for example, a device described in Japanese Patent Application Laid-Open No. 57-11149 is known.

This conventional device integrates a longitudinal acceleration sensor that detects the longitudinal acceleration of the vehicle and a detection value of the longitudinal acceleration sensor from when the brake pedal is depressed, and subtracts the integral value from the wheel speed when the brake pedal is depressed. Vehicle speed calculating means for setting the vehicle speed.

[Problems to be solved by the invention]

However, in such a conventional device, when the wheel speed is about to be converted to the lock direction, the vehicle speed is obtained by integrating the detection of the longitudinal acceleration sensor, so that the vehicle speed is continuously long. When the integral calculation is performed, the actual vehicle deceleration and the sensor detection value may be different due to a change in the gain of the longitudinal acceleration sensor itself, a change over time due to the occurrence of a DC offset, or a detection error due to a slope such as a slope. Different situations frequently occurred.
In this case, especially when the detected deceleration is smaller than the actual deceleration, the estimated vehicle speed is calculated to be larger than the actual vehicle speed.
There has been an unsolved problem that the vehicle slip ratio is erroneously determined to be large, and the brake cylinder such as a wheel cylinder is continuously depressurized to fall into a no-brake state.

On the other hand, when the estimated vehicle speed is not accurately calculated and the actual vehicle speed> estimated corporate speed, the wheel cylinder pressure reduction start timing performed because the wheel slip rate exceeds a predetermined value is delayed, The time when the slip ratio was large became long, and the vehicle behavior during the anti-skid control became unstable.

Therefore, the present invention has been made in view of such a situation, and when the vehicle speed is obtained by integrating the detection value of the longitudinal acceleration sensor during the anti-skid control, the detection error of the acceleration sensor is caused. It is an object of the present invention to provide an anti-skid control device capable of accurately avoiding a no-brake state, optimizing decompression start timing during braking, and performing high-precision anti-skid control. .

[Means for solving the problem]

Therefore, in order to achieve the above object, the present invention provides the first
As shown in the drawing, in an anti-skid control device including a plurality of actuators each of which adjusts the pressure of a braking cylinder of each wheel according to a predetermined command signal, a longitudinal acceleration sensor that detects a longitudinal acceleration of the vehicle, A wheel speed detecting means for individually detecting the wheel speed of each wheel, and a maximum value of each wheel speed obtained based on each wheel speed detected value by the wheel speed detecting means as an initial value, the longitudinal acceleration sensor Means for calculating an estimated vehicle speed by integrating a value obtained by adding an offset amount to the absolute value of the detected value of the vehicle speed in the deceleration direction, and braking the vehicle based on the estimated vehicle speed and each wheel speed by the wheel speed detecting device. Actuator control means for individually supplying the command signal of a value corresponding to a state to each of the actuators, and a calculation time by the vehicle speed calculation means The offset amount increases with the passage are provided with offset amount supply means for supplying to said vehicle speed calculating means.

[Action]

In the present invention, the vehicle speed calculating means integrates a value obtained by adding an offset value to an absolute value of the longitudinal acceleration output from the longitudinal acceleration sensor, using a maximum value of the wheel speeds by the wheel speed detecting means as an initial value. Thus, the estimated body side degree is calculated. Then, the actuator control means individually supplies a command signal of a value corresponding to a braking state to each actuator based on the estimated vehicle speed and each wheel speed according to the wheel speed detection means, thereby providing a brake cylinder for each wheel. The pressure is controlled. At this time, an offset amount that increases as the calculation time of the vehicle speed calculating means elapses is supplied to the vehicle speed calculating means by the offset amount supplying means. For this reason, when the longitudinal acceleration detection value includes an error biased toward the no brake side, the error increases as the calculation time (integration time) elapses, but the error is appropriately offset by the offset amount, and the estimated vehicle body Speed is more accurate.

〔Example〕

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

2 to 8 are views showing an embodiment of the present invention.

In FIG. 2, reference numeral 2 denotes a hydraulic brake system mounted on a four-wheel drive vehicle, and reference numeral 4 denotes an anti-skid control device for the brake system 2.

The brake system 2 includes a brake pedal 6, a master cylinder 8, and a wheel cylinder 10 serving as a cylinder for braking a drum-type brake on the front left to rear right wheels 9 FL to 9 RR.
It has FL ~ 10RR.

On the other hand, the anti-skid control device 4 controls each of the wheels 9FL to 9RR.
Wheel speed sensors 12FL to 12RR for detecting wheel speeds
, A longitudinal acceleration sensor 13 for detecting the longitudinal acceleration of the vehicle, wheel speed sensors 12FL to 12RR and a longitudinal acceleration sensor
13, a controller 14 for instructing anti-skid control based on each detection signal, and actuators 16FL to 16RR for individually adjusting the hydraulic pressures of the wheel cylinders 10FL to 10RR by a control signal output from the controller 14. .

Each of the wheel speed sensors 12FL~12RR is formed by an electromagnetic pickup provided at a predetermined position in conjunction with each wheel, and outputs an AC voltage signal v ₁ to v ₄ with a frequency proportional to the rotational speed of the wheel. Also, the longitudinal acceleration sensor 13 outputs is provided at a predetermined position of the vehicle body, the acceleration signal G _X comprising an analog DC voltage corresponding thereto to detect the acceleration in the longitudinal direction, in the case of deceleration as a positive.

The controller 14, on the input side, as shown in Figure 2, the detection signal v ₁ to v ₄ of the wheel speed sensor 12FL~12RR F-V
(Frequency - voltage) are equipped with wheel speed calculation circuit 18FL~18RR for calculating sales is wheel speed signals V _w1 ~V _w4 converted. The output side of the wheel speed calculation circuits 18FL to 18RR outputs a wheel speed signal V
The _w1 ~V _w4 together leads to the microcomputer 22 via respective A / D converters 20A~20D to digitize, leading to the wheel speed filters 24FL~24RR as wheel speed limiting circuit consisting of a second-order lag digital filter. This wheel speed filter 24FL
Each of ~ 24RR has an A / D converter on its input side and a D / A converter on its output side, and the input wheel speed signal V _w1 (~ V _w4 ) corresponds to the deceleration side when changes have a negative slope that may limit so as not to change beyond a predetermined inclination -k _1, when changing with a positive slope which corresponds to the acceleration side so as not to change beyond a predetermined slope k ₂ It has a limiter function to limit. This filter 24FL ~ 24RR
Is provided to prevent a value different from the actual wheel speed from being input to the controller 22 due to road surface unevenness, electric noise, or the like.

Each output terminal of the wheel speed filters 24FL to 24RR reaches a select high switch 25 for determining a wheel speed signal closest to the actual vehicle speed. In other words, select high switch
25, the wheel speed signal V _w1 filter 24FL~24RR '~V _w4'
Is selected (select high), and this is set as the maximum wheel speed signal _VwMAX , and the integrating circuit 26 provided in the next stage is selected.
Is applied to a predetermined initial value input terminal and the microcomputer 22. In this way, the wheel speed calculating means includes the wheel speed calculating circuits 18FL to 18RR and the wheel speed filter 24F.
L to 24RR, a high select switch 25, an offset generator 27 described later, and a gate circuit 30.

On the other hand, the controller 14 is provided with an offset amount supply means for compensating for the variation in the detected value that fluctuates toward the no brake side (a direction lower than the actual vehicle acceleration / deceleration) due to the characteristic change of the longitudinal acceleration sensor 13 or the road surface inclination. The offset generator 27 is provided. This offset generator 27
Uses a later-described switching control signal CS as a control input, outputs an initial value A ₀ when the switching control signal CS is at a logic L (low) level, and is determined by the following equation when the switching control signal CS is at a logic H (high) level. The positive offset A is output to one input terminal of the adder 28 at the next stage (see FIG. 7).

A = A ₀ + K ₃ · t _C (t _C ≦ t _D ) A = A ₁ (t _C > t _D ) where k ₃ is a positive coefficient of t _C and 5t _c is the switching control signal C
S is the time from Na to a logic H level, t _D is the reference time.

Further, the output terminal of the longitudinal acceleration sensor 13 reaches the other input terminal of the adder 28 via an absolute value circuit 29 in consideration of a case where sudden braking is performed during retreat in the controller 14, and the output of the adder 28 The terminal reaches the input terminal of the integration circuit 26 via the gate circuit 30. The gate circuit 30 is configured to open the gate when a later-described switching control signal CS is at a logic H (high) level, and to close the gate when the switching control signal CS is at a logic L (low) level. Therefore, when the gate circuit 30 is “open”, a signal of | G _X | + A is input to the integration circuit 26, and when the gate circuit 30 is “closed”, there is no input to the integration circuit 26.

The integration circuit 26 sets the initial value signal to V _wMAX and the input signal to | G _X | +
_Assuming that A, V _ref = V _wMAX ∫ (| G _X | + A) dt (1) The integral calculation of (1) is performed to obtain an estimated vehicle speed signal V _ref that changes to the vehicle body speed decreasing side. ing. And
The output side of the integration circuit 26 reaches the microcomputer 22 via the A / D converter 31.

The microcomputer 22 has an interface circuit 3
3. It comprises at least an arithmetic processing unit 34 and a storage device 35. The arithmetic processing unit 34 reads the digitized detection signals V _{w1 to} V _w4 , V _ref via the interface circuit 33, and performs predetermined arithmetic and processing according to a predetermined program stored in advance (see FIGS. 4 to 6). ), And outputs control signals for driving the actuators 16FL to 16RR, the offset generator 27, and the gate circuit 30 via the interface circuit 33 as necessary. The storage device 35 stores in advance programs and fixed data such as a control map necessary for execution of the arithmetic processing device 34, and can temporarily store the processing results.

On the other hand, on the output side of the microcomputer 22, amplifiers 36A to 36C are provided for each of the actuators 16FL to 16RR. Therefore, the microcomputer 22 outputs a control signal of a logical level to each of the amplifiers 36A to 36C, so that the amplifiers 36A to 36C in each group respectively transmit the hydraulic pressure control signals EV, AV, MR each having a current value to the actuator. It is configured to output to 16FL-16RR.

Further, as shown in FIG. 3, each of the actuators 16FL to 16RR has an inflow valve connected between the hydraulic pressure inflow side of the master cylinder 8 and the wheel cylinder 10FL (to 10RR).
42 and the output side of the inflow valve 42, that is, the wheel cylinder 10
Outflow valve 44 connected to FL (（10RR), accumulator 46 for accumulating pressure and oil pump 48 for oil recovery connected to the output side of this outflow valve 44, and between oil pump 48 and master cylinder 8 And a check valve 50 provided in the apparatus.

The opening and closing of the inflow valve 40 and the outflow valve 42 are controlled by hydraulic pressure control signals EV and AV from the controller 14. That is, in the pressure increasing mode, the control signals EV and AV are turned off, so that the inflow valve 42 is opened and the outflow valve 44 is closed,
The brake fluid pressure from the master cylinder 8 can be supplied to the wheel cylinders 10FL (to 10RR) via the inflow valve 42, and as a result, the cylinder pressure increases. Control signal E in decompression mode
By turning on V and AV, the inflow valve 42 is closed and the outflow valve 44 is opened, and the wheel cylinders 10FL to (10RR)
The oil inside can be recovered to the master cylinder 3 side, and as a result, the cylinder hydraulic pressure decreases. Further, in the holding mode, the control signal EV is turned on and the AV is turned off, so that the two inflow valves 4 are turned off.
2. The outflow valve 44 is closed, and the oil in the wheel cylinders 10FL to (10RR) can be confined and the pressure can be maintained. The control signal MR is turned on during the anti-skid control, whereby the pump 48 is driven.

Next, the operation of the above embodiment will be described with reference to FIGS.

When the ignition switch is turned on, the power is turned on and the apparatus starts.

In other words, the AC voltage signal v ₁ to v ₄ detected by the wheel speed sensors 12FL~12RR is converted respectively to the wheel speed signal V _w1 ~V _w4 in the wheel speed calculation circuit 18FL~18RR, D / A converters 20A
2020D, each of which is digitized and supplied to the microcomputer 22, and a wheel speed filter 24FL〜24
Each is supplied to RR.

The wheel speed filters 24FL to 24RR output the input wheel speed signals.
The change amount of V _{w1 to} V _w4 per fixed time (for example, 5 msec)
When exceeding a predetermined value corresponding to the slope -k ₁ (e.g. -0.2km / h) and a constant value corresponding to the slope k ₂ (e.g. 0.8km / h) is in a state of being restricted to their constant values, the opposite If it is below a certain value, the wheel speed signal
V _wi ′ to V _w4 ′ are output to the select high switches 25. In other words, even when noise is mixed in the wheel speed signals V _w1 ~V _w4 by disturbance or the like, hardly influenced by the noise, more accurate estimated vehicle speed is detected.

Then, the select switch 25, of the wheel speed signals V _wi '~V _w4' input, the selection signal of the largest value, which is the maximum wheel speed signals V _Wmax, the integration circuit 26
And output to the microcomputer 22.

On the other hand, the longitudinal acceleration detection signal G _X is converted into its absolute value signal | G _X | by an absolute value circuit 29, and the adder 28 converts the absolute value signal | G _X |
Is added (see FIG. 7). This added signal | G _X | + A
Is supplied to the integration circuit 26 when the gate circuit 30 is “open”, and is not supplied when the gate circuit 30 is “closed”.

As a result, when the gate circuit 30 is “open”, the integration circuit 26
In the above, the estimated vehicle speed signal V _ref according to the above-mentioned equation (1) is calculated and supplied to the microcomputer 22 via this signal V _ref A / D converter 31.

Subsequently, a certain period of time (for example,
The timer interrupt processing of FIGS. 4 to 6 executed every 20 msec) and for each wheel will be described. These processes are performed only when a switch signal from a brake switch (not shown) is turned on.

First, the arithmetic processing unit 34 sequentially performs the estimated vehicle speed signal V _ref and the maximum wheel speed signal V
_Wmax, reads the wheel speed signals V _wi (i = 1~4), the value of the estimated vehicle body speed V _ref, the maximum wheel speed V _Wmax, the wheel speed V _wi
As temporary storage.

Next, at step, the wheel speed according to the previous control cycle
After calculating the wheel acceleration / deceleration _wi from _Vwi , the process _proceeds to step.

In the step, a flag F indicating whether or not the vehicle speed related to the longitudinal acceleration is estimated is determined. If the flag F = 0 in this determination, it is determined that the vehicle speed is estimated based on the wheel speed, and the process then proceeds to step
In order to determine whether or not the wheel acceleration / deceleration _wi increases toward the deceleration side and is in the locking direction, it is determined whether or not _wi ≦ −α ₀ (α ₀ is a predetermined reference value).

In the case of _{wi> -α 0} in this decision, and not a locking tendency, in followed by step, to see whether or not the wheel speed has been restored to the actual vehicle speed direction, V _ref ≦ V
_Judge whether it is _wMAX or not. If _Vref ≦ _VwMAX in this determination, it is determined that the wheel speed has recovered, the switching control signal CS is set to the logic L level in a step, the flag F is cleared in a step, and the program returns to the main program. Thus, the gate circuit 30 (a or which maintains) "closed" and the (1) operation value equation is the same as has been reset to the initial value V _Wmax, a V _ref = V _wMAX.

If the above-mentioned step _Vref > _VwMAX , it is determined that the wheel speed has not been sufficiently recovered yet, and the steps
To skip.

Furthermore, if the _wi ≦-.alpha. ₀ in the step as being toward the locking direction, the switching control signal CS to a logic H level in step, after the flagged F at step returns. As a result, the gate circuit 30 is opened, and the calculation of the expression (1) is performed.

Furthermore, if it is determined that the flag F has been set at step, as a calculation in based on the longitudinal acceleration G _X, the process proceeds to step ~.

Next, the processing of FIG. 5 will be described. In steps 1 to 5, the estimated vehicle speed _Vref and the wheel speed _Vwi are the same as described above.
To calculate the wheel acceleration / deceleration _wi . Then move on to the steps, The slip ratio S _i is calculated based on the following formula, and this is temporarily stored, and the process returns to the main program.

Next, the processing of FIG. 6 will be described with reference to the hydraulic control example of FIG. 7 and the control map of FIG. Note that the speed curve in FIG. 7 shows the speed slightly shifted and also shows an arbitrary wheel in order to make it easy to determine a change in each output.

Now, the pressure reduction timer L described later in the previous timer interrupt control
And the control flag AS are both cleared and the vehicle is traveling at a constant speed. It is assumed that the brake pedal 6 is depressed at an arbitrary time from this state to enter a braking state.

At the start of the braking, since the wheel acceleration / deceleration _wi and the slip ratio S _i (i = 1 to 4) are substantially zero, the starting point in the control map of FIG. , Arrows simply indicate the control direction of the hydraulic mode). Therefore, in the determination of the slip ratio S _i ≧ S ₀ (S ₀ is the reference slip ratio, which is set to 15% here) according to the step of FIG. In the determination of whether or not> 0, the result is "NO", and the process proceeds to the determination of whether or not the control end condition of the step is satisfied. Specifically, this determination is based on the assumption that the estimated vehicle speed _Vref is a predetermined value V corresponding to the stopped state.
Whether V _ref ≦ V _{ref0 with} respect to _{ref 0} , whether the number of gentle _pressure increase N is N ≧ N _{0 with} respect to a predetermined value N ₀ , or whether a switch signal from a brake switch (not shown) is turned off And so on, so “NO”. Further, in the determination of whether or not the pressure reduction timer L> 0 in the step, "N
O ", step wheel acceleration _wi ≧ _{α 1 (α 1} is accelerated side of the reference value: positive) whether the" NO "in the determination, the step of _wi ≦ _{-α 2 (α 2} the reference deceleration side (Value: positive value) is determined to be “NO”, and the process proceeds to step. In the step, it is determined whether or not the control flag AS is 0. However, since the control flag AS is still cleared before the start of the anti-skid control, the determination becomes “YES” and the process proceeds to the step to perform the rapid pressure increase mode (normal brake Mode) is commanded.

In other words, the arithmetic processing unit 34 sets each of the actuators 16FL to
The hydraulic pressure control signals EV, AV, MR output to 16RR are turned on. For this reason, the inflow valve 42 is opened and the outflow valve 44 is closed, and the oil from the master cylinder 8 is discharged from the wheel cylinder 10FL (up to 10
RR). Therefore, the brake pedal 6
When the operation is performed, a braking state (see section a in FIG. 7) due to a sudden increase in the cylinder hydraulic pressure (sudden pressure increase) is established. On the other hand, when the brake pedal 6 is not operated, it is in a non-braking state.

In this manner, when the hydraulic pressure rapidly increases, decreases the wheel speed V _wi gradually, as shown by a solid line arrow in FIG. 8, the wheel deceleration _wi increases in the negative direction, the slip ratio S _i increases. The wheel deceleration _wi falls below the reference value-.alpha. _2, the determination is "YES" in step mentioned above, commands the holding mode of the high pressure side goes to step.

That is, the arithmetic processing unit 34 turns on the hydraulic pressure control signal EV,
V and MR are turned off. As a result, the oil in the wheel cylinder 10FL (（10RR) is confined and the pressure is maintained, as shown in a section b in FIG.

Even during this pressure holding, since the braking by the high pressure is performed, the slip ratio S _i gradually increases, and the value becomes the reference value.
Suppose _S0 is exceeded. Thus, the in the Fig. 6 step the determination is "YES", "NO" in step _wi ≧ alpha ₁ determines whether a set a predetermined initial value L ₀ in vacuum timer L proceeds to step Control flag
Set AS to indicate the start of anti-skid control. After that, the process proceeds to the step via the step, and the decompression mode is commanded.

That is, the arithmetic processing unit 34 turns on both the pressure reduction control signals EV and AV. As a result, the pressure reduction of the wheel cylinders 10FL (RR10RR) decreases as described above (see section c in FIG. 7).

This vacuum, since changes to approach the vehicle body speed to recover the wheel speed V _wi gradually, its wheel acceleration _wi
Gradually increases. Then, when _{the wi} becomes the reference value alpha ₁ or more, the determination is "YES" in step,
The process proceeds to the step and the pressure reducing timer L is cleared. After this, the process moves to steps through steps ~,
Command the low pressure holding mode again.

That is, the arithmetic processing unit 34 performs control in the same manner as in the above-described steps. As a result, the hydraulic pressure is maintained (see section d in FIG. 7).

Then, by maintaining the hydraulic pressure, the slip ratio _Si recovers, and when S _i <S ₀ , the process sequentially shifts to steps through steps 1 to 3 to instruct the slow pressure increase mode.

That is, the arithmetic processing unit 34 controls the hydraulic pressure control signal AV to be off, and repeatedly turns off and on the control signal EV intermittently at a predetermined minute interval. As a result, the fluid pressure rises in a substantially step-like manner as shown in section a 'in FIG.

Hereinafter, the pressure is reduced for each of the wheel cylinders 10FL to 10RR until the braking is completed and the above-described control end condition is satisfied.
The holding, slowly increasing, and holding modes are repeated. Then, when the control end condition is satisfied, the pressure reduction timer L and the control flag AS are cleared in step and the process returns to the normal brake mode in step.

If the slip ratio S _i is reduced to the reference value S ₀ or less earlier than the recovery of the wheel acceleration _wi while the pressure is being reduced during braking on a road with a high friction coefficient or the like, the steps Transition. Then, in this step, a pressure reduction timer L = L-1 is performed. Thereafter, the gradual pressure increase mode relating to the step is commanded prior to the holding mode via steps (1) to (4) (see the dotted line in FIG. 8).

Here, the overall operation will be outlined over time with reference to FIG.

Now, assuming that carried out the sudden braking at the time t _0, together with a positive longitudinal acceleration occurs, the wheel cylinder 10FL~
Each wheel speed is increased by a sudden increase in pressure of 10RR (step in Fig. 6).
V _wi starts to drop (for simplicity, _assume that the speeds of the four wheels are the same).

Then, in _wi ≦-.alpha. _{0 (Fig.} 4 step) and time t ₁ is determined gate circuit 30 is opened (Fig. 4 step), the wheel speed V _wi no longer show the vehicle speed longitudinal acceleration G _X By switching, the correct vehicle speed _Vref is estimated. Based on the estimated vehicle speed, the subsequent high pressure holding, pressure reduction, and low pressure holding (steps in FIG. 6) are performed, while the offset amount A increases in proportion to the elapse of the integration time as shown in FIG. I will do it.

Therefore, even if an error is contained biased to no brake side acceleration detection value G _X, wherein (1) the offset amount corresponding to the integration error is immediately after operation start is smaller by Formula A also small. Since the accurate vehicle speed _{Vref at the time} is estimated from the variable offset amount in this manner, the actual vehicle speed does not exceed the estimated vehicle speed, and a more accurate slip ratio is obtained. For this reason, the time at which the step rate is large is suppressed to a minimum without delaying the pressure reduction timing, and the vehicle behavior during the anti-skid control is stabilized.

Thereafter, as the integration time becomes longer, the offset amount A
There was increased, because the shortage of the longitudinal acceleration detection value G _X are integrated after being compensated appropriately, integral error almost eliminated. Therefore, even in the worst case, the estimated vehicle speed is not calculated to be higher than the actual vehicle speed, and a situation in which the vehicle is continuously depressurized due to an erroneous determination that the slip ratio is large and falls into the no-brake state is reliably avoided. .

Then, FIG. 6 of the decompression, to come to recover the wheel speed V _wi by the holding process, V _ref ≦ V _Wmax next (Figure 4 at an arbitrary time t ₁ 'based on the slip ratio S _i and the wheel acceleration _wi Step), the gate circuit 30 is closed (Step in the figure). Thus, t ₁ 'and later, the vehicle speed estimation according to the time t ₂ in again the wheel speed V _wi, performs hydraulic control is switched to the vehicle speed estimation according to the longitudinal acceleration G _X in the same manner as described above again at time t ₂ Thereafter, the hydraulic pressure control is performed based on the estimated value until t ₂ ′.

 Hereinafter, a skid cycle is formed by this repetition.

Here, in the present embodiment, the wheel speed sensors 12FL to 12RR and the wheel speed calculation circuits 18FL to 18RR (or these and the A / D converter 2
0A to 20D, the processing in FIG. 5) constitutes the wheel speed detecting means. Further, the select high switch 25, the integrating circuit 26, the adder 28, the absolute value circuit 29, the gate circuit 30, the A / D converter 31, and the processing in FIG. 4 and the processing in FIG. The actuator control means is constituted by the steps of FIG. 5 and the steps of FIG. 6 and the amplifiers 36A to 36C.

It should be noted that the controller 14 in the above embodiment can be entirely constituted by a computer, while the microcomputer 22 can be constituted by an electronic circuit such as a counter, a comparator, and a flip-flop.

Further, the above embodiment shows a case where the present invention is applied to a drum type brake, but this is similarly applicable to a disk type brake.

Further, in the above-described embodiment, the anti-skid control device of the four-wheel independent control has been described. However, the present invention is not necessarily limited to this, and can be applied to, for example, an anti-lock brake of the rear two-wheel control.

Furthermore, in the above-described embodiment, the maximum value of each wheel speed was calculated after controlling the detected value of each wheel speed using the wheel speed filter. Not required. In other words, although the accuracy is somewhat reduced, the detected wheel speed values may be directly compared to determine the maximum wheel speed.

〔The invention's effect〕

As described above, according to the present invention, when it is detected that the wheel speed tends to be locked, when estimating the vehicle speed based on the detected longitudinal acceleration value, the offset amount that increases with the calculation time elapses. The longitudinal acceleration detection value is compensated for in addition to the absolute value of. For this reason, even when the longitudinal acceleration sensor detects a value deviating toward the no-brake side due to, for example, a characteristic change, drift occurrence, road surface inclination, or the like, if the elapsed time from the start of integration is short, the vehicle speed calculation error also decreases. Since it is small, an accurate vehicle body speed is estimated by setting an offset amount corresponding to this, whereby a time period in which the wheel slip ratio is larger than the set value is suppressed to a minimum without delaying the decompression start timing, Therefore, the effect that the vehicle behavior during the anti-skid control is stabilized can be obtained.

In addition, in the detection state of the longitudinal acceleration, the offset amount to be added increases with the lapse of time from the start of the integration, so that the calculation error due to the integration is almost eliminated, and the accurate vehicle speed is estimated. As a result, the estimated vehicle speed is calculated to be higher than the actual vehicle speed, and it is not erroneously determined that the slip ratio is large. As a result, the brake cylinder continues to be depressurized as in the case where the offset amount is not added. In this case, the worst no-brake condition can be reliably avoided, and the fail-safe function has the effect of significantly improving the reliability of the brake.

Furthermore, in the device according to the second aspect of the present invention, even when high-frequency noise is mixed into each vehicle speed detection value by the road surface unevenness, this is appropriately suppressed by the wheel speed limiting means, and the noise resistance is improved. It has the effect of becoming.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the actuator of FIG. 4 to 6 are schematic flowcharts each showing a processing procedure executed in the microcomputer, FIG. 7 is a timing chart showing a control example, and FIG. 8 is a graph showing a control map. In the figure, 4 is an anti-skid control device, 10FL-10RR is a wheel cylinder, 12FL-12RR is a wheel speed sensor, 13 is a longitudinal acceleration sensor, 14 is a controller, 16FL-16RR is an actuator, 22 is a microcomputer, and 27 is offset generation. It is a vessel.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) The inventor Takeshi Fujishiro 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-1-218954 (JP, A) JP-A-1- 101260 (JP, A) JP-A-64-63456 (JP, A) JP-A-62-146761 (JP, A) JP-A-62-146757 (JP, A) JP-A-60-25836 (JP, A)

Claims (2)

(57) [Claims] An anti-skid control device comprising a plurality of actuators for adjusting pressure of a braking cylinder of each wheel according to a predetermined command signal, a longitudinal acceleration sensor for detecting longitudinal acceleration of a vehicle, A wheel speed detecting means for individually detecting a wheel speed of each wheel; and a maximum value of each wheel speed obtained based on each wheel speed detected by the wheel speed detecting means as an initial value, the longitudinal acceleration sensor Vehicle speed calculating means for integrating the value obtained by adding the offset amount to the absolute value of the detected value in the deceleration direction to obtain the estimated vehicle body side degree, and the vehicle speed based on the estimated vehicle body speed and each wheel speed by the wheel speed detecting means. Actuator control means for individually supplying the command signal having a value corresponding to a braking state to each of the actuators, and Antiskid control device according to claim offset amount that increases with the lapse of that provided with the offset amount supply means for supplying to said vehicle speed calculating means. 2. The vehicle speed calculating means limits a wheel speed detection value by providing a fixed upper limit to a speed change amount for a predetermined time with respect to each wheel speed detection value by the wheel speed detection means. The maximum value of the wheel speeds is set as the initial value,
2. The anti-skid control device according to claim 1, wherein a value obtained by adding the offset value to an absolute value of the value detected by the longitudinal acceleration sensor is integrated in a deceleration direction to obtain an estimated vehicle speed.