JPH0558949B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention calculates wheel acceleration/deceleration based on an output signal from a wheel speed sensor when braking a vehicle using brake fluid pressure, and calculates the brake fluid pressure based on the calculated wheel acceleration/deceleration. This invention relates to an improvement in an anti-skid control device which prevents wheels from locking by performing control. (Prior art) The coefficient of friction μ between the wheels of a vehicle and the road surface is generally determined by the slip rate λ of the wheels, as shown in FIG.
(λ=vehicle speed - wheel speed/vehicle speed) is the predetermined slip rate λ ₀ (
15%), the maximum μ (max) is reached, and at this time the braking efficiency of the vehicle is at its maximum. Therefore, in normal anti-skid control, when the vehicle is braking, the brake fluid pressure is controlled by increasing, decreasing, or maintaining the brake fluid pressure so that the slip rate λ of the wheels is always around a predetermined slip rate λ ₀ . It is. As a result, it is possible to shorten the stopping distance during braking, and to ensure steering stability. By the way, in such an anti-skid control device, in order to maintain the slip ratio λ as close to a predetermined slip ratio λ ₀ as possible under various road surface conditions, wheel acceleration/deceleration is taken into consideration, and the wheel deceleration is controlled while the brake fluid pressure is being increased. The pressure increase is interrupted when the speed exceeds a predetermined value (when the degree of decrease in wheel speed becomes large enough), and when the wheel acceleration exceeds a predetermined value while the brake fluid pressure is being reduced. It is being considered to interrupt the pressure reduction (when the degree of increase in wheel speed becomes large enough). In this case, the brake fluid pressure is not controlled to excessively high or low fluid pressure under any road surface condition, but always changes in the vicinity of the fluid pressure P (lock) at which the wheels are on the verge of locking. This makes it possible to shorten the stopping distance and ensure steering stability. Conventionally, there is an anti-skid control device that performs switching control of brake fluid pressure in consideration of wheel acceleration/deceleration as described above, as disclosed in Japanese Patent Laid-Open No. 137160/1983. (Problem to be Solved by the Invention) However, when detecting the wheel acceleration/deceleration, it is necessary to detect the acceleration/deceleration at a predetermined time point based on the output signal from a wheel speed sensor that detects the wheel speed (rotational speed of the wheel). Since the calculation is based on the difference between the wheel speed at and the wheel speed at other times (wheel speed change), the detection of the wheel acceleration/deceleration is delayed compared to the detection of the wheel speed. In other words, as shown in FIG. 16, for example, when the brake fluid pressure P is increased, the wheel speed Vw decreases as shown, and even if the actual wheel deceleration αw is as shown by the dashed line, the calculation The wheel deceleration αw is as shown by the solid line. Therefore, at the instant _t1 when the actual wheel deceleration αw reaches the predetermined value _b1 , the pressure increase of the brake fluid pressure P must be interrupted as shown by the dotted line, but the calculated wheel deceleration reaches the predetermined value _b1 . The interruption of the pressure increase is not started until the instant t ₂ when the brake fluid pressure P reaches the instant t 2 , and the undesired increase in the brake fluid pressure P continues between the instants t ₁ and _{t 2} . As a result, the brake fluid pressure rises considerably above the above-mentioned P (lock), and in some cases, there is a possibility that the wheels may lock. Similarly, when performing pressure reduction control, the timing of detecting wheel acceleration equal to or higher than a predetermined value is delayed, resulting in the brake fluid pressure being considerably lower than P (lock), which causes an increase in the stopping distance of the vehicle. (Means for Solving the Problems) The present invention has been made to solve the above problems, and the principle thereof will be explained as follows. Equation of motion of the wheel I・ω・=r・μ・W−Tb ...(1) I: Rotational inertia of the wheel ω・: Rotation angular acceleration of the wheel r: Wheel rotation radius μ: Coefficient of friction between the wheel and the road surface W :Wheel weight Tb: Brake torque: If the brake torque Tb changes by ΔTb in a minute time Δt, it can be assumed that the wheel weight W and the friction coefficient μ do not change during Δt, so from the above equation, I・Δω・=−ΔTb (where Δω・ is the amount of change in the wheel rotational angular acceleration during the ΔT time). Here, since the brake torque change ΔTb is considered to be proportional to the brake fluid pressure change ΔP during that time, I・Δω・=−β・ΔP (2) β: proportionality constant. From the above equation, it is found that the change in wheel acceleration/deceleration Δαw (=rΔω・) can be estimated from the amount of change in brake fluid pressure ΔP and the rotational inertia I of the wheel, and the calculated wheel acceleration/deceleration can be corrected from this estimation result. The present invention is based on the theory that the above-mentioned problem can be solved by: calculating the wheel acceleration/deceleration based on the output signal from the wheel speed sensor while the wheel is being braked by the brake fluid pressure;
The anti-skid control device controls the brake fluid pressure based on the calculated wheel acceleration/deceleration, comprising: a brake fluid pressure reduction detection means for detecting that the brake fluid pressure is being reduced; Brake fluid pressure increase detection means for detecting that the pressure is being increased; Brake fluid pressure change amount detection means for detecting the amount of change in the brake fluid pressure; Wheel rotation inertia detection means for detecting the rotational inertia of the wheel. Based on the detection outputs from both of these detection means,
wheel acceleration/deceleration change calculation means for calculating the amount of change in wheel acceleration/deceleration after the instant when the hydraulic fluid pressure starts to decrease and the instant when the hydraulic fluid pressure starts to increase by both of the detection means; While the braking fluid pressure is being depressurized, the corrected wheel deceleration speed is calculated by correcting the calculated wheel acceleration/deceleration in the acceleration direction according to the amount of change in the wheel acceleration/deceleration at the moment when the start of brake fluid pressure depressurization is detected by the means. In addition to contributing to the control of the brake fluid pressure, while the brake fluid pressure increase detection means detects that the brake fluid pressure is being increased, the calculated wheel acceleration/deceleration at the moment when the start of the brake fluid pressure increase is detected by the brake fluid pressure increase detection means. and a wheel acceleration/deceleration correction means that contributes to controlling the braking fluid pressure by correcting the wheel acceleration/deceleration in the deceleration direction according to the amount of change in the wheel acceleration/deceleration. (Operation) The anti-skid control device increases or decreases the brake fluid pressure based on the calculated wheel acceleration/deceleration while the brake fluid pressure is braking the wheels. Here, the wheel acceleration/deceleration change amount calculation means calculates the amount of change in wheel acceleration/deceleration after the moment when the start of pressure reduction and the start of pressure increase are detected by the brake fluid pressure reduction detection means and the brake fluid pressure increase detection means. The calculation is performed based on the detection results by the change amount detection means and the wheel rotation inertia detection means. The wheel acceleration/deceleration correcting means converts the calculated wheel acceleration/deceleration at the moment when the brake fluid pressure reduction start is detected by the brake fluid pressure reduction detection means to the wheel acceleration/deceleration while the brake fluid pressure reduction detection means detects that the brake fluid pressure is being reduced. The corrected wheel acceleration/deceleration corrected in the acceleration direction according to the amount of change contributes to the control of the brake fluid pressure, and while the brake fluid pressure increase detection means detects that the brake fluid pressure is being increased, the brake is applied by the means. The corrected wheel acceleration/deceleration, which is obtained by correcting the calculated wheel acceleration/deceleration at the moment when the start of the hydraulic pressure increase is detected, in the deceleration direction according to the amount of change in the wheel acceleration/deceleration, contributes to the control of the braking hydraulic pressure. Therefore, the problem of the delay in detection of wheel acceleration/deceleration that occurred when calculating wheel acceleration/deceleration from the amount of change in wheel speed within a unit time and using this directly for anti-skid control of brake fluid pressure, as in the past, is resolved. This eliminates the occurrence of situations in which the brake fluid pressure is excessively reduced or increased during anti-skid control, and control accuracy can be greatly improved. (Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing the basic configuration of an anti-skid control device according to the present invention. That is, basically, this anti-skid control device (anti-skid control circuit 100) controls the master brake hydraulic pressure system based on a detection signal with a frequency proportional to the rotational speed of the wheels 102 output from the wheel speed sensor 1 during braking. An inflow valve 14 (hereinafter referred to as an EV valve 14) provided in a path from the cylinder 101 to the wheel cylinder 103
) switching control and wheel cylinder 1
03 to the master cylinder 101 via the reservoir tank 104 and the pump 17 for hydraulic pressure recovery.
and switching control of an outflow valve 15 (hereinafter referred to as AV valve 15) provided at the front stage of the pump 17. Then, the hydraulic pressure of the wheel cylinder 103, that is, the braking hydraulic pressure, is controlled as shown in the following table by the switching signal of the EV valve 14 (hereinafter referred to as the EV signal) and the switching signal of the AV valve 15 (hereinafter referred to as the AV signal). shall be carried out.

[C is the brake fluid pressure change rate within a minute time]

Therefore, when estimating this change Δαw for the above correction, it is necessary to know what −r·β/I is in the above equation. On the other hand, r, β, and C are constants, but if this is a driving wheel, the rotational inertia I of the wheel includes the transmission and engine, so it depends on the selected gear position of the transmission. different. Therefore, the acceleration/deceleration correction circuit 18 also receives as signal B a value obtained by multiplying the value −r·β/I determined by the inertia determination circuit 70 described below by the brake fluid pressure change rate C during the minute time Δt. do. The inertia determination circuit 70 includes a gear position sensor 71 that detects the gear position of the transmission (in this example, neutral, 1st speed to 5th speed), and a power supply voltage E for each gear position.
switches 72 to 77 turned on by
8, a constant setter 79, and a division circuit 80. The switch 72 has one end directly grounded and the other end grounded via a resistor 81. switch 73~7
One end of 7 has a constant voltage of 9Va, 4Va, 1.5Va, respectively.
Connect to 1.0Va and 0.5Va, and the other end is a common resistor 81
Ground through. Thus, switch 72~
77 generates a voltage signal corresponding to the rotational inertia Ia from the transmission to the engine, which differs for each gear position of the transmission, and inputs this to an addition circuit 78. The adder circuit 78 is further supplied with a voltage signal Vb corresponding to the rotational inertia Ib from the wheels to the transmission, which is constant regardless of the gear position. The adder circuit 78 adds both voltage signals to obtain the rotational inertia I (=Ia+Ib) of the wheel.
is determined, and the corresponding signal is input to the division circuit 80. Therefore, the addition circuit 78, together with the circuit at the preceding stage, constitutes wheel rotation inertia detection means. The division circuit 80 divides the signal from the constant setter 79 that outputs the constant voltage corresponding to −r·β in the above equation (3) by the signal from the adder circuit 78 to obtain the above equation (3). Medium-r.β/I is determined, and the value is multiplied by the brake fluid pressure change rate C in the minute time Δt,
A signal B corresponding to (≡−r·β/I·C) is input to the acceleration/deceleration correction circuit 18. Therefore, the division circuit 80 serves as a means for detecting the amount of change in brake fluid pressure. A specific example of the configuration of the acceleration/deceleration correction circuit 18 is shown in FIG. In this figure, 21 is a switch controlled on/off by an AND signal from an AND gate 26 of the EV signal from the OR gate 11 and the inverted signal of the AV signal from the AND gate 10 in FIG. , a switch 23 which is controlled on and off by the NOR signal from the NOR gate 27 of the AV signal, and a switch 23 which is controlled on and off by the AND signal from the AND gate 28 of the EV signal and the AV signal. It should be noted that each switch 21, 22, 23 is turned on when its control signal is at H level. Reference numeral 25 denotes an integrating circuit composed of a resistor R, a capacitor C, and an operational amplifier 25a, which functions as wheel acceleration/deceleration change amount calculation means. To the input terminal of the integrating circuit 25, a ground potential is selectively applied via a switch 21, a potential +B is applied via a switch 22, and an inverted potential -B by a not gate 31 is applied via a switch 23. In addition, a bypass switch 24 is connected to both ends of the capacitor C.
This switch 24 is an OR gate 3 between the update signal Sa from the acceleration/deceleration detection circuit 3 and the inverted signal of the MR signal from the retriggerable timer 16 in FIG.
It is assumed that on/off control is performed by an OR signal of 0 (on state when at H level). Reference numeral 29 is an addition circuit that adds the calculated wheel acceleration/deceleration αw from the acceleration/deceleration detection circuit 3 and the output signal from the integration circuit 25, and constitutes wheel acceleration/deceleration correction means, and the output from this addition circuit 29 is corrected. It is input as wheel acceleration/deceleration [αw] to comparison circuits 8 and 9 in FIG. Here, as is clear from the table, the H level signal from the AND gate 26, the H level signal from the NOR gate 27, and the H level signal from the AND gate 28 are used to maintain, increase, and maintain the brake fluid pressure, respectively.
This serves as a detection signal for depressurization. Therefore, the gate 27 functions as a means for detecting an increase in brake fluid pressure, and the gate 28 serves as a means for detecting a decrease in brake fluid pressure. In addition, as mentioned above, the change in brake fluid pressure ΔP can be considered to be proportional to the change time Δt in the minute time Δt, and ΔP=(C)・Δt (C): Brake fluid pressure in the minute time The above potential |±B| is expressed by the equation on the right corresponding to this proportionality constant (C). |±B|=|−r·β/I·C| Next, the operation of this device will be explained. First, to explain the basic operation, when the driver depresses the brake pedal and the braking fluid pressure (hydraulic pressure in the foil cylinder 103) increases, the wheel speed decreases and the wheel deceleration αw (negative acceleration) increases. Here, when the wheel deceleration further increases and reaches the predetermined value _b1 , the _b1 signal is output from the comparison circuit 9, and the EV valve 14 is activated by the _b1 signal (EV signal) via the OR gate 11. The pressure increase control of the brake fluid pressure is interrupted and maintained at that point. At this time, when the wheel deceleration reaches a predetermined value _b1 , the pseudo vehicle speed generating circuit 4 outputs a pseudo vehicle speed Vi having a predetermined slope from the detected wheel speed at that time, and at the same time the target wheel speed From the generating circuit 6, the target wheel speed _Vwo (=Vi×
0.85) are output sequentially. When the wheel speed further decreases and falls below the target wheel speed Vwo by maintaining the brake fluid pressure at a high level as described above, a slip signal is output from the comparator circuit 7, and the AND gate 10 is activated. The AV valve 15 is actuated by the slip signal (AV signal) sent through the gate, and the OR gate 1 is activated.
By the same slip signal (EV signal) via 1
The operating state of the EV valve 14 is maintained and the brake fluid pressure is reduced. When the brake fluid pressure is reduced in this way, the wheel speed and wheel acceleration return accordingly, and when the wheel acceleration reaches the predetermined value _a1 , the _a1 signal is output from the comparator circuit 8, and the or gate 11 is activated. The _a1 signal (EV signal) causes the EV valve 14 to continue operating, while the _a1 signal disables the ungate 10, causing the AV valve 15 to return to its initial state and stop the brake fluid. The pressure reduction control is interrupted and maintained at that point. If the brake fluid pressure is maintained at a relatively low pressure in this way, once the wheel speed exceeds the target wheel speed and increases to a certain extent (at this point the slip signal disappears), it will start decreasing again. At the same time, the wheel acceleration is also the predetermined value a ₁
It decreases from the above value. Here, when this wheel acceleration falls below the predetermined value _a1 , the comparator circuit 8
When the _a1 signal falls and the outputs from the comparison circuits 7 and 9 are at L level at that time, the EV signal and AV signal become L level, and the brake fluid pressure is increased again. Then, the wheel speed and wheel acceleration further decrease, and thereafter, the same control of the brake fluid pressure as described above is repeated one after another. That is, the braking fluid pressure switching control during braking is performed according to a control mode determined based on the wheel acceleration/deceleration αw and the slip rate λ (actually Vw/Vi) as shown in FIG. become. Next, in the overall operation as described above, the more detailed operation including the operation of the acceleration/deceleration correction circuit 18 will be explained with reference to the timing chart shown in FIG. Until the moment t ₁ when braking is started and the detected wheel speed Vw reaches the target wheel speed Vwo (=Vi×0.85),
Since the AV signal is not output, that is, the MR signal is not output, the switch 24 is turned on and the output of the integrating circuit 25 is kept at "0", and the output from the acceleration/deceleration correction circuit 18 via the adding circuit 29 is The output (αw) is the update signal Sa from the acceleration/deceleration detection circuit 3.
This value is the same as the calculated wheel acceleration/deceleration αw that is output together with the calculated wheel acceleration/deceleration αw. At instant _t1, when the AV signal rises at the same time as the slip signal from the comparison circuit 7 rises, the MR signal is output accordingly, so the switch 24 is turned off, while the pressure is reduced (EV=H, AV=H). ) The switch 23 is turned on by the output signal from the AND gate 28 which becomes the detection signal. Then, the integral value -1/CR∫(-B)dt=B/CR・t by the integrating circuit 25 of potential -B is added to the calculated wheel acceleration/deceleration αw output at instant _t1 , and the acceleration/deceleration correction circuit 18 The output [αw] from the calculated wheel acceleration/deceleration αw at the instant _t1 increases with time with a slope corresponding to (B/CR), that is, it corrects in the direction of acceleration. And instantly
When the acceleration/deceleration detection circuit 3 outputs the new calculated wheel acceleration/deceleration αw along with the update signal Sa at t ₂ , the switch 24 is instantaneously turned on by the update signal Sa, and the integration circuit 25 is turned on at that moment. It is cleared, and the output [αw] from the acceleration/deceleration correction circuit 18 momentarily becomes the calculated wheel acceleration/deceleration αw at instant _t2 .
After that, since the switch 23 is kept on (during pressure reduction control), the output of the integration circuit 25 becomes the integral value of the potential -B, and the acceleration/deceleration correction circuit 1
The output [αw] from 8 increases again with time from this newly calculated wheel acceleration/deceleration αw with a slope corresponding to the above (B/CR). In this way, when the output [αw] of the acceleration/deceleration correction circuit 18 rises and reaches the predetermined value _a1 at the instant _t3 , the _a1 from the comparator circuit 8
The AV signal falls as the signal rises,
The brake fluid pressure at that point is maintained. At this time (instantaneous _t3 ), the output of the AND gate 28, which serves as a decompression detection signal, falls and the switch 23 turns off, and the output of the AND gate 26, which serves as a hold (EV=H, AV=L) detection signal, falls. Since the output becomes H level and the switch 21 is turned on, the integrating circuit 25 will integrate the ground potential from now on, and the output of the integrating circuit 25 will stop increasing, and the acceleration/deceleration correction circuit 18 The output [αw] from maintains the output value at instant _t3 . Then, at instant _t4, when the new calculated wheel acceleration/deceleration αw is output from the acceleration/deceleration detection circuit 3 together with the update signal Sa, the integration circuit 25 is cleared in the same way as above, and the output from the acceleration/deceleration correction circuit 18 is [ αw] becomes the calculated wheel acceleration/deceleration αw, and after that, the integration circuit 25 integrates the ground potential, so the acceleration/deceleration correction circuit 18
The output [αw] from the acceleration/deceleration detection circuit 3 has the same value as the calculated wheel acceleration/deceleration αw output together with the update signal Sa. Here, when the output [αw] from the acceleration/deceleration correction circuit 18 (the calculated output from the acceleration/deceleration detection circuit ₃ , which is the acceleration value) falls below the predetermined value a ₁ at the instant t 5 , the b ₁ from the comparison circuit 9 has already been Since the _signal is falling, EV
The signal falls, and from that point (instantaneous t ₅ )
The brake fluid pressure that had been maintained after _t3 is increased and
going up. At this time (instantaneous _t5 ), the output of the AND gate 26, which serves as the holding detection signal, falls and the switch 21 turns off, and at the same time, the pressure increase (EV
=L, AV=L) NOR gate 27 serving as a detection signal
Since the output of the switch 22 becomes the H level and the switch 22 is turned on, the integrating circuit 25 becomes
B will be integrated, and its output value (integral value)
becomes -1/CR∫+Bdt=-B/CR・t. Then, the output [αw] from the acceleration/deceleration correction circuit 18 becomes the sum of the calculated wheel deceleration αw at instant _t5 and the above integral value, and the output (αw)
is calculated from the calculated wheel deceleration αw at instant _t5 (-B/
CR) decreases over time with a slope corresponding to
That is, it is corrected in the direction of deceleration. When the output [αw] from the acceleration/deceleration correction circuit 18 decreases and reaches the predetermined value b ₁ (deceleration) at instant t ₆ , the b ₁ signal from the comparison circuit 5 causes the pseudo vehicle speed generation circuit 4 to , a new pseudo vehicle speed Vi is generated, the _b1 signal from the comparator circuit 9 rises, the EV signal rises, and the braking fluid pressure at that point is maintained. At this time (instant _t6 ), the output of the NOR gate 27, which serves as the pressure increase detection signal, disappears and the switch 22 turns off, and the output of the AND gate 26, which serves as the holding detection signal, becomes H level again, and the switch 21 is turned off. is turned on, from now on, the integrating circuit 25 integrates the ground potential as described above, the output of the integrating circuit 25 stops increasing, and the output [αw] from the acceleration/deceleration correction circuit 18 becomes instantaneous. Maintain the output value at t ₆ . Then, at instant _t7, when the acceleration/deceleration detection circuit 3 outputs the new calculated wheel acceleration/deceleration αw along with the update signal Sa, the integration circuit 25 is cleared in the same way as above, and the output from the acceleration/deceleration correction circuit 18 [αw ] becomes the calculated wheel acceleration/deceleration αw,
While the brake fluid pressure P is maintained and controlled, the integration circuit 25 integrates the ground potential, so the output [αw] from the acceleration/deceleration correction circuit 18 has the same value as the calculated wheel deceleration αw. Furthermore, after that, the target wheel speed _Vwo (=
From the instant _t8 onwards, the instant t below Vi × 0.85) is
The operations after t ₁ are repeated. As described above, according to this embodiment, while the reduced pressure state of the brake fluid pressure is being detected, the calculated wheel acceleration/deceleration value output at a predetermined point in time is determined by ΔV・w=(B)・Δt. A value corresponding to the integral value of the potential -B corresponding to the proportionality constant (B) is added to correct the wheel acceleration/deceleration so that it increases with time from the calculated value, while detecting an increase in the braking fluid pressure. During this period, a value corresponding to the integral value of the potential + B corresponding to the proportionality constant (B) is added to the calculated wheel acceleration/deceleration value output at a predetermined point during that period, and the wheel acceleration/deceleration is determined from the calculated value. Since it has been modified so that it decreases with time, the integration circuit 2
By appropriately determining the time constant CR in step 5 to suit the actual situation through experiments, etc., the wheel acceleration/deceleration, which is a control parameter while detecting the decrease and increase in brake fluid pressure, approaches the actual value. In Figure 6, the corrected wheel acceleration/deceleration [αw] reaches the predetermined value _a1 at an instant _t3 before the instant _t4 when the calculated wheel acceleration/deceleration αw exceeds the predetermined value _a1 , which is the condition for interrupting decompression. , and the instant t ₇ when the calculated wheel acceleration/deceleration exceeds a predetermined value b ₁ (deceleration) that is a condition for interrupting pressure increase.
Corrected wheel acceleration/deceleration [αw] at the earlier instant _t5
reaches the predetermined value _b1 . As a result, it is possible to prevent the brake fluid pressure from increasing or decreasing excessively. Moreover, since the potential B above takes into account the rotational inertia of the wheels, which differs depending on the gear position of the transmission, as mentioned above, the above-mentioned ability to bring the wheel acceleration/deceleration close to the actual value under any gear position is achieved. The effect can be achieved reliably. Next, other embodiments shown in FIGS. 8 to 11 will be described. Now, the wheel cylinder 103 in FIG. 1 generally has a fluid pressure increase characteristic as shown in FIG. 7 (the pressure decrease characteristic is reversed). In addition, when braking on a high μ road surface, the hydraulic pressure at which the wheels are on the verge of locking is relatively high Ph (lock), and when braking on a low μ road surface, the same hydraulic pressure is relatively low Pl.
(lock). Therefore, in the anti-skid control, the braking fluid pressure P is Ph
On a low μ road surface, the braking fluid pressure P will increase or decrease within _{the region E 2 near} Pl(lock), but the rate of change in fluid pressure at that time (ΔP /Δt) differs depending on whether the road surface is high μ or low μ (this is because the characteristics shown in FIG. 7 are not linear). In other words, the preferable constant of proportionality (C) at ΔP=(C)・Δt is the road surface μ,
That is, it changes depending on the brake fluid pressure P. In view of the above, in this other embodiment, the brake fluid pressure P corresponding to the road surface μ at that time is indirectly known, and the correction constant for the calculated wheel acceleration/deceleration is changed accordingly. As shown in FIG. 8, its basic configuration is approximately the same as that of the embodiment shown in FIG. Specifically, the configuration is shown in FIG. 9, and the inertia discrimination circuit 70
utilizes the fact that the slope A information of the pseudo vehicle speed Vi from the pseudo vehicle speed generation circuit 4 changes depending on the road surface μ,
Based on this slope A information, the acceleration/deceleration correction circuit 18
It is configured to change the correction constant B' of the calculated wheel acceleration/deceleration toward a. The specific configuration of the acceleration/deceleration correction circuit 18a is shown in FIG. Now, to explain the configuration of the pseudo vehicle speed generation circuit ₄ , in _FIG . A sample hold circuit 40b extracts and holds the detected wheel speed Vw from the wheel speed detection circuit 2 in synchronization with the AND signal from the AND gate _G1 , and a sample hold circuit 40b extracts and holds the detected wheel speed Vw in synchronization with the _b1 signal. In addition, 41 is a timer counter that increments at a predetermined period, 40c is a sample hold circuit that extracts and holds the value of the timer counter 41 in synchronization with the output signal from the AND gate _G1 , and 40d is the above _b1. This is a sample and hold circuit that extracts and holds the numerical value of the timer counter 41 in synchronization with the signal. 42 is a sample hold circuit 40a
A subtraction circuit 43 subtracts the sampling value Vb of the sample and hold circuit 40b from the sampled wheel speed value Vo of the sample and hold circuit 40.
44 is a subtraction circuit that subtracts the sampling value Tb of d, and 44 is the subtraction value (Vo−
Vb) from the subtraction circuit 43 (To−Tb)
This is a division circuit that divides by . Further, 45 is a slope generation circuit that generates a slope signal corresponding to a predetermined wheel speed slope signal, for example, 0.4G, and 46 is a slope generation circuit 45.
This is a changeover switch that switches between the slope signal from the divider circuit 44 and the calculation output (Vo-Vb)/(To-Tb) from the divider circuit 44.
47 is a subtraction circuit that subtracts the output value from the timer counter 41 from the sampling value Tb(n) held in the sample hold circuit 40d, and 48 is the subtraction value from this subtraction circuit 47 and the division value from the division circuit 44 or 49 is a multiplier circuit that multiplies the slope value from the slope generation circuit 45 via the changeover switch 46.
is a subtraction circuit that subtracts the calculation output from the multiplication circuit 48 from the detected wheel speed values that are sequentially sampled by the sample and hold circuit 40b. And 50
is an RS flip-flop (hereinafter simply referred to as FF50) which is set at the rising edge of the AND signal by the AND gate _G3 of the _b1 signal and the MR signal, and reset at the falling edge of the MR signal. When the output Q is at L level, it is switched to the slope generating circuit 45 side, and when the output Q is at H level, it is switched to the multiplier circuit 44 side. Further, 51 is a triggerable timer that outputs an H level signal for a predetermined period of time (for example, 2 seconds) from the rise of the _b1 signal from the comparison circuit 5, and 52 is a subtraction circuit for subtracting the pseudo vehicle speed Vi output to the target wheel speed generation circuit 6. 49 or the detected wheel speed Vw from the wheel speed detection circuit 2. This changeover switch 52 switches to the subtraction circuit 49 side when the output Q from the retriggerable timer 51 is at H level. shall be taken as a thing. Next, the operation of the above-mentioned pseudo vehicle speed generating circuit 4 during braking will be explained with reference to the timing chart shown in FIG. 10. Start braking and instantly to
When the wheel deceleration reaches the predetermined deceleration b ₁ for the first time,
The detected wheel speed from the wheel speed detection circuit 2 is sampled as a value Vb(O)=Vo in the sample and hold circuits 40a and 40b in synchronization with the rising edge of the b 1 signal from the comparison circuit ₅ , and the rising edge of the b ₁ signal Sample and hold circuits 40c and 40
d is the count value Tb(O) from the timer counter 41.
=To is sampled. Furthermore, since the AV signal in the control device is at L level at this point, FF50 is not set, and this FF50
The output Q of is held at L level and the changeover switch 46 is placed on the slope generation circuit 45 side. Then, as time elapses until the wheel deceleration reaches the predetermined value _b1 again, the subtraction circuit 47 outputs a count value Tc corresponding to the elapsed time Tc=T-Tb(O) T: the output value of the timer counter 41. Based on this count value Tc and the slope value Ao (0.4G) from the slope generating circuit 45, the multiplier circuit 48 sequentially outputs a value Ao×Tc corresponding to the speed reduction value. Further, the subtraction circuit 49 outputs Vb(O)-Ao×Tc as the pseudo vehicle speed Vi, and after the first rise of the _b1 signal, the retriggerable timer 51 switches to the subtraction circuit 49 side by the H level output. Vb(O)−Ao× as the above pseudo vehicle speed Vi via the switching switch 52
Tc is supplied to the target wheel speed generation circuit 6. That is, in the first skid cycle from when the wheel deceleration reaches the predetermined value _b1 at the instant to until the wheel deceleration reaches the same _b1 again, the detected wheel speed value V(O) at the instant to A pseudo vehicle speed Vi having a characteristic that decreases with a slope Ao from Ao is output. Next, when the wheel deceleration reaches the predetermined value _b1 again at instant _t1 , the detected wheel speed value Vb(1) at that time becomes
In synchronization with the b ₁ signal, the sample and hold circuit 40b newly samples the signal, and the count value Tb(1) from the timer counter 41 at the same time is the same as the b ₁ signal.
The signal is newly sampled by the sample and hold circuit 40d in synchronization with the signal. Also, at this time, the MR signal from the retriggerable timer 16 is at H level, and the AND gate _G1 is disabled and the values in the sample and hold circuits 40a and 40c are
Vb(O) and Tb(O) are further maintained, and FF50
is set, and the changeover switch 46 is switched to the division circuit 44 side and held (this state continues thereafter). Here, the difference ΔVb(1) between the detected wheel speed value Vb(O) at the instant to and the detected wheel speed value Vb(1) at the instant t ₁ is calculated from the subtraction circuit 42 ΔVb(1)=Vb(O )−Vb(1) is output, and the above instantaneous value is output from the subtraction circuit 43.
Count value Tb(O) at to and count value at instant t ₁
The difference value ΔTb(1) ΔTb(1)=Tb(O)−Tb(1) from Tb(1) is output, and the division circuit 44 operates based on these difference values ΔVb(1) and ΔTb(1). Calculate ΔVb(1)/ΔTb(1) and convert this calculated value A ₁ from Vb(O) to Vb(1)
Output as slope information leading to . Then, as the time elapses until the wheel deceleration further reaches the predetermined value _b1 , the subtraction circuit 47 sequentially outputs the count value Tc Tc=T-Tb(1) corresponding to the elapsed time, and this count Based on the value Tc and the slope information A ₁ (A ₁ =ΔVb(1)/ΔTb(1)) from the divider circuit 44, the value A ₁ ×Tc corresponding to the speed reduction value is sequentially output from the multiplier circuit 48. Ru. Further, the subtraction circuit 49 outputs Vb(1)-A ₁ ×Tc as a pseudo vehicle speed. That is, in the second skid cycle from when the wheel deceleration reaches the predetermined value b ₁ at the instant t ₁ until the wheel deceleration reaches the same value b ₁ again, the detected wheel speed value at the instant t ₁
A pseudo vehicle speed Vi having a characteristic that decreases from Vb(1) with a slope A ₁ is output. Similarly, each time the wheel deceleration reaches the predetermined value _b1 in each skid cycle, the difference between the detected wheel speed value at that time and the first detected wheel speed value Vb(O) under the same conditions and the time The inclination information is calculated based on the interval (count value), and then the wheel deceleration is set to a predetermined value.
Until b ₁ is reached, a pseudo vehicle speed Vi that decreases with the above slope from the detected wheel speed value at that time is output. By the way, as mentioned above, the detected wheel speed Vb(O) when the wheel deceleration reaches the predetermined value _b1 at the start of braking
and the detected wheel speed Vb(n) under the same conditions in each skid cycle, i.e., the slope A of the pseudo vehicle speed Vi that occurs in each skid cycle.
indicates a decreasing tendency of the vehicle speed at the time of occurrence. Therefore, when this slope A is large, it means that the road surface μ is relatively large, and the braking hydraulic pressure at that time is also controlled in a relatively high hydraulic pressure area.If the slope A is small, then ,
This is a case where the road surface μ is relatively small, and the braking fluid pressure at that time is also controlled in a relatively low fluid pressure region. Therefore, as shown in FIG. 8, the acceleration/deceleration correction circuit 18a
The inertia determination circuit 70 which inputs the acceleration correction constant into the inertia determination circuit 70 has almost the same configuration as that described above with reference to FIG. Input the constant −r·β. The multiplier circuit 82 supplies the calculation results of these input information -r, β, A to the division circuit 80, and this division circuit supplies the signal B' corresponding to -r, β, A/I to the acceleration correction circuit 18a. , so that the acceleration/deceleration correction constant can be appropriately changed by the pseudo vehicle speed slope information A, that is, by the road surface μ as is clear from the above. Therefore, as shown in FIG. 11, the acceleration/deceleration correction circuit 18a has the same basic configuration as the acceleration/deceleration correction circuit 18 shown in FIG. The above signal B' is applied to the switch 22, which is controlled on and off by the pressure reduction detection signal (output of the AND gate 28).
The inverted output -B' from the not gate 31 of B' is input. The correction operation of the acceleration/deceleration correction circuit 18a is substantially the same as that in the above-mentioned embodiment shown in the timing chart of FIG. To,
− Integral value of A signal (potential) −1/CR∫−B′dt=B′/CR・t is added, and the wheel acceleration/deceleration is determined by the slope of (B′/CR) from the calculated value. On the other hand, when the brake fluid pressure is increased, the integral value of the B' signal (potential) is added to the calculated wheel acceleration/deceleration value output at a predetermined point in time during the pressure increase. -1/CR∫B ′・dt=−B′/CR・t is added to correct the wheel acceleration/deceleration so that it decreases over time with a slope of (−B′/CR) from the calculated value. Become. As described above, according to the present embodiment, the slope A of the simulated vehicle Vi becomes large in control in a region where the brake fluid pressure P is high, that is, in a region where the rate of change ΔP/Δt is large, so that the wheel acceleration/deceleration is correction constant (B′/
CR) becomes large, while the slope A becomes small in control in a region where the braking fluid pressure P is low, that is, in a region where the rate of change ΔP/Δt is small, so the correction constant (B'/CR) becomes small. . Therefore, the corrected acceleration/deceleration [αw] can be brought closer to the actual value than in the above embodiment. FIGS. 12 to 14 show still other embodiments of the present invention. In this example, as is clear from FIG. 12 showing its basic configuration, the acceleration/deceleration detection circuit 3 detects the wheel acceleration/deceleration by performing differential processing on the detected wheel speed from the wheel speed detection circuit 2. Therefore, unlike the two embodiments described above, the update signal Sa is not output. Accordingly, the acceleration/deceleration correction circuit 18b in this example does not perform the synchronized operation using the update signal Sa as described above.
The configuration is as shown in FIG. This circuit 18
b is basically the same as that shown in FIG. 4, but is activated at the rise of the holding detection signal from the AND gate 26, the pressure increase detection signal from the NOR gate 27, or the pressure reduction detection signal from the AND gate 28. A retriggerable timer 33 is provided to output an H level signal for a predetermined period of time, and an OR gate 32 is provided.
Output Q ₁ from retriggerable timer 33 via
This controls the switch 24 which prohibits the correction operation by the integrating circuit 25. In such an acceleration/deceleration correction circuit 18b, the first
As shown in Fig. 4, while the MR signal is in the output state and the output of the retriggerable timer 33 is at H level, between instants t ₁ and t ₂ , t ₃ and t ₄ , and t ₅ and t ₆ , a similar correction is made to the calculated wheel acceleration/deceleration as shown in FIG. In addition, in the above three embodiments, focusing on the fact that the change in wheel acceleration/deceleration Δαw (∝Δω・) is proportional to the change in brake fluid pressure ΔP, I・Δω・=−β・ΔP, the brake fluid pressure is The change ΔP is calculated based on ΔP=(C)・Δt (in the second example, (C) is the pseudo vehicle speed).
Variable by the slope A of Vi), the change in wheel acceleration/deceleration Δαw, that is, the amount of correction of the wheel acceleration/deceleration αw, is estimated based on the degree of the braking fluid pressure change ΔP. The pressure change ΔP may be directly detected by providing a hydraulic pressure sensor in the wheel cylinder 103 (see FIG. 1). (Effects of the Invention) Thus, as described above, the anti-skid control device of the present invention calculates the amount of change in wheel acceleration/deceleration after the moment when the brake fluid pressure starts to decrease and the moment when the pressure starts to increase, based on the amount of change in the brake fluid pressure and the wheel rotation inertia. However, while the brake fluid pressure is being reduced, the calculated wheel acceleration/deceleration at the instant of the brake fluid pressure reduction is corrected in the acceleration direction according to the amount of change in wheel acceleration/deceleration, and the corrected wheel acceleration/deceleration is used for anti-skid control of the brake fluid pressure. During the pressure increase, the calculated wheel acceleration/deceleration at the instant when the brake fluid pressure starts to increase is corrected in the deceleration direction according to the amount of change in wheel acceleration/deceleration, and the corrected wheel acceleration/deceleration is used for anti-skid control of the brake fluid pressure. , This problem occurred when, as in the past, wheel acceleration/deceleration was calculated from the amount of change in wheel speed within a unit time and used as is for anti-skid control of brake fluid pressure.
It is possible to solve problems related to delays in wheel acceleration/deceleration detection, eliminate situations where brake fluid pressure is excessively reduced or increased during anti-skid control, and greatly improve control accuracy. can. In particular, since the above corrected wheel acceleration/deceleration is calculated taking into account the rotational inertia of the wheels,
Even in the case of drive wheels where wheel rotational inertia, which greatly affects wheel acceleration/deceleration, differs depending on the gear position of the transmission, the wheel acceleration/deceleration that contributes to anti-skid control can always be made extremely close to the actual value at all gear positions. This makes it possible to achieve more accurate anti-skid control.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the anti-skid control device of the present invention, FIG. 2 is an electronic circuit diagram showing an example of the anti-skid control circuit in the device of the present invention, and FIG. 3 is an illustration of the acceleration/deceleration detection circuit in the same example. A block diagram showing a specific example, FIG. 4 is an electronic circuit diagram showing a specific example of the acceleration/deceleration correction circuit in the same example, FIG. 2 to 4 are operation timing charts of the embodiments, FIG. 7 is a hydraulic pressure temporal change diagram showing how the hydraulic pressure changes in a general wheel cylinder, and FIG. 8 is a diagram showing another example of the present invention. 9 is an electronic circuit diagram of the anti-skid control circuit shown in FIG. 9, and FIG. 9 is an electronic circuit diagram of the pseudo vehicle speed generation circuit in the same example.
FIG. 10 is an operation timing chart of the pseudo vehicle speed generation circuit, FIG. 11 is an electronic circuit diagram of the acceleration/deceleration correction circuit in FIG. 8, and FIG. 12 is an electronic circuit diagram of an anti-skid control circuit showing still another example of the present invention. Fig. 13 is an electronic circuit diagram of the acceleration/deceleration correction circuit in the same example, Fig. 14 is an operation timing chart of the acceleration/deceleration correction circuit, and Fig. 15 shows the relationship between the coefficient of friction between the wheels and the road surface and the slip rate. diagram showing,
FIG. 16 is a time chart showing changes in wheel speed, brake fluid pressure, and wheel acceleration/deceleration during braking by a conventional anti-skid control device. 1...Wheel speed sensor, 2...Wheel speed detection circuit,
3... Acceleration/deceleration detection circuit, 4... Pseudo vehicle speed generation circuit, 5, 7, 8, 9... Comparison circuit, 6... Target wheel speed generation circuit, 12, 13... Driver, 14...
...Inflow valve (EV valve), 15...Outflow valve (AV valve),
16...Retriggerable timer, 17...Pump,
18, 18a, 18b...acceleration/deceleration correction circuit, 2
1, 22, 23, 24... switch, 25... integral circuit (wheel acceleration/deceleration change amount calculation means), 27...
... Gate (brake fluid pressure increase detection means), 28 ... Gate (brake fluid pressure reduction detection means), 29 ... Addition circuit (wheel acceleration/deceleration correction means), 31 ... Knot gate, 33 ... Retriggerable timer , 40a-4
0d... Sample hold circuit, 41... Timer counter, 42, 43, 47, 49... Subtraction circuit, 44... Division circuit, 45... Pseudo vehicle speed slope generation circuit, 46, 52... Changeover switch, 48
...Multiplication circuit, 50...Flip-flop, 51
... Retriggerable timer, 61 ... Wheel acceleration/deceleration calculation section, 62 ... Memory, 70 ... Inertia discrimination circuit (wheel rotation synergia detection means), 71 ...
...Gear position sensor, 72-77...Switch, 7
8...addition circuit (wheel rotation inertia detection means),
79... Constant setter, 80... Divider circuit (braking fluid pressure change detection means), 81... Resistor, 82... Multiplier circuit, 100... Anti-skid control circuit, 1
01... Brake master cylinder, 102...
Wheel, 103...Wheel cylinder, 104...
reservoir tank.

Claims (1)

[Scope of Claims] 1. While braking the wheels using the brake fluid pressure, wheel acceleration/deceleration is calculated based on the output signal from the wheel speed sensor, and the brake fluid pressure is controlled based on the calculated wheel acceleration/deceleration. In the anti-skid control device, the brake fluid pressure decrease detection means detects that the brake fluid pressure is decreasing, and the brake fluid pressure increase detection means detects that the brake fluid pressure is increasing. , a brake fluid pressure change amount detection means for detecting the amount of change in the brake fluid pressure, a wheel rotational inertia detection means for detecting the rotational inertia of the wheel, and based on detection outputs from both of these detection means,
wheel acceleration/deceleration change calculation means for calculating the amount of change in wheel acceleration/deceleration after the moment when the brake fluid pressure starts to decrease and the moment when the brake fluid pressure starts to increase by both of the detection means; While the brake fluid pressure is being reduced, the corrected wheel acceleration/deceleration is corrected in the acceleration direction according to the amount of change in wheel acceleration/deceleration from the calculated wheel acceleration/deceleration at the moment when the start of brake fluid pressure reduction is detected by the means. In addition to contributing to the control of the brake fluid pressure, while the brake fluid pressure increase detection means detects that the brake fluid pressure is being increased, the calculated wheel acceleration/deceleration at the moment when the start of the brake fluid pressure increase is detected by the brake fluid pressure increase detection means. and wheel acceleration/deceleration correction means that contributes to controlling the brake fluid pressure by correcting the wheel acceleration/deceleration in the deceleration direction according to the amount of change in the wheel acceleration/deceleration.