JPS62122860A - Lock preventing method for wheel in vehicle - Google Patents

Abstract

PURPOSE:To enable control of brake torque during brake so that the slip rate of a wheel is adjusted to a value within a proper range, by a method wherein, togetherwith acceleration and deceleration of wheels, the slip rate of the wheel is added to a control factor. CONSTITUTION:The peripheral velocity of a wheel is detected by a wheel speed detecting device 34 to fetch it as a wheel speed signal Uwi, and a car body speed is detected thereby. In the formation wherein a reference wheel speed signal is comparable with the wheel speed signal Uwi, a reference wheel speed signal UR, to which a slip rate lambdao of a wheel is added, is set. A wheel acceleration signal U'wi is drived from the wheel speed signal Uwi, and in the formation of comparison with the wheel acceleration speed signal, a reference wheel reduction speed signal -V'wo is set. Further, based on a car body speed, a low reference wheel speed UR' is derived. In which case, during brake, in the case of Uwi<UR and U'wi<-V'wo, or Uwi<UR', electromagnetic valves 20 and 21 are actuated, and brake torque T is decreased. Thus, a momentary lock state due to a rapid change in a road surface can be prevented from continuance.

Description

[Detailed Description of the Invention] A0 Object of the Invention fil Industrial Application Field The present invention relates to a method for preventing wheel locking in a vehicle, in which the slip rate of the wheel is added to the control factors as well as the acceleration/deceleration of the wheel. be.

(2) Conventional technology When a vehicle suddenly brakes, if the braking input to the wheels is too large, the wheels lock and the braking efficiency decreases.

In order to prevent such a situation, when there is a risk of wheel locking, it is necessary to keep the wheel slip rate within an appropriate range, for example 1, regardless of the braking input by the driver.
It is known that the braking torque of the wheels may be automatically controlled so that it is within a range of about 5 to 25%.

Therefore, various types of anti-rotation and brake braking devices have been proposed as devices for automatically controlling the braking torque of wheels.

(3) Problems to be solved by the invention Conventional anti-lock brake devices have poor performance, reliability,
It cannot be said that it is still sufficient from the viewpoint of economic efficiency.

In addition, in conventional anti-lock brake devices, wheel acceleration and deceleration, which is negative acceleration, are detected.
The braking torque is controlled while determining whether there is a risk of wheel locking based on the magnitude of the acceleration/deceleration of the wheel. However, depending on the control method based only on the wheel acceleration/deceleration, the Since it is difficult to control the braking torque so that the slip ratio of the wheels falls within an appropriate range, it is desirable to add the slip ratio of the wheels to the control factor in some way.

Here, the wheel slip rate λ is defined as λ=1-Vw/V, where the circumferential speed of the wheel is Vw and the vehicle body speed is V. As is clear from this equation, the wheel slip rate There is no direct relationship between λ and the wheel acceleration, that is, the differential value 9w of the wheel peripheral speed Vw. Therefore, in order to detect the slip rate of the wheels during braking, it is first necessary to detect the vehicle body speed at that time.

Conventional methods for detecting vehicle speed include (detection method using Doppler radar installed on 11 wheels), (
2) A method in which a non-braking wheel is specially installed and the vehicle speed is detected from the circumferential speed of that wheel, and (3) a method in which the acceleration/deceleration of the vehicle body is detected and the vehicle speed is determined from the integral value have been proposed. However, depending on these conventional methods, the structure is complicated, the accuracy and reliability are insufficient,
Or the number of parts and processing and assembly man-hours increase,
It is not easy to obtain a vehicle speed detection device that is technically and economically satisfactory.

In view of the above-mentioned circumstances, the present invention adds the wheel slip rate as well as the wheel acceleration/deceleration to the control factors, thereby controlling the braking torque so that the wheel slip rate falls within an appropriate range during braking. The main purpose of this invention is to provide a method for preventing locking of wheels in a vehicle, which can control.

Structure of B8 invention! 11 Means for Solving the Problems In order to achieve the above object, the present invention provides a method that can detect the circumferential speed of a wheel and extract it as a wheel speed signal, as well as detect the vehicle body speed and compare it with the wheel speed signal. A reference wheel speed signal is set in consideration of a predetermined slip rate of the wheel, and an acceleration signal of the wheel is derived from the wheel speed signal, and a reference wheel deceleration signal is generated in a form that can be compared with the acceleration signal. Further, a low reference wheel speed signal is derived based on the vehicle body speed so as to be at a lower level than the reference wheel speed signal, and when braking, the wheel speed signal, the reference wheel speed signal and the low A reference wheel speed signal is compared, and the wheel acceleration signal and the reference wheel deceleration signal are compared, and the value of the wheel speed signal is smaller than the value of the reference wheel speed signal, and the wheel acceleration signal is smaller than the reference wheel speed signal. a braking device so as to reduce the braking torque of the wheels whenever the value is smaller than the value of the reference wheel deceleration signal or when the value of the wheel speed signal is smaller than the value of the low reference wheel speed signal; It is characterized by control.

(2) Effect According to the above configuration, since the slip rate of the wheel is added to the control factors as well as the acceleration/deceleration of the wheel, the braking torque can be controlled so that the slip rate is always within an appropriate range. .

In particular, there is a condition in which the value of the wheel speed signal is smaller than the value of the reference wheel speed signal and the value of the wheel acceleration signal is smaller than the value of the reference wheel deceleration signal, that is, the risk of wheel lock is immediately present. Since the braking torque is always reduced under imminent conditions, the risk of wheel locking can be reliably avoided, and strong braking torque continues to be applied until the danger of wheel locking approaches. Is possible.

Furthermore, even under conditions where the value of the wheel speed signal is smaller than the value of the low reference wheel speed signal, it is not affected by the magnitude relationship between the wheel acceleration signal and the reference wheel deceleration signal or the control state of the braking torque. Since the braking torque is constantly reduced, during braking the vehicle suddenly changes from a road surface with a high coefficient of friction (such as a dry paved road) to a road surface with a low coefficient of friction (such as a dry paved road).
For example, when approaching an Asbahn, even if the wheels lock momentarily due to a delay in the response of the control system,
It can always be released instantly.

(3) Embodiment Hereinafter, the present invention will be explained in detail according to the drawings. First, in FIG. 1, a brake pedal 1 is connected to a master cylinder 2.
When the driver depresses the brake pedal 1, the master cylinder 2 generates braking hydraulic pressure. The master cylinder 2 communicates via an oil passage 3 with a brake oil chamber 11 formed between a pair of pistons 7 and 8 in a wheel cylinder 6 mounted on the vehicle body. The rods 9° IO of each piston 7.8 each extend outwardly through the end wall of the wheel cylinder 6, and the outer ends of each rod 9, 10 engage in friction with the brake drum 4 mounted on the wheel. They are respectively connected to a pair of brake shoes 5.5' which generate braking torque when they come into contact with each other. Therefore, when the master cylinder 2 generates braking oil pressure when the brake pedal 1 is depressed, this braking oil pressure is transmitted through the oil passage 3 into the brake oil chamber 11, and as a result, each piston 7.8 separates from each other. direction, and each brake shoe 5 is moved accordingly.
．． 5' is pressed toward the friction surface of the brake drum 4,
It cooperates with the brake drum 4 to generate braking torque to the wheels.

If the brake oil pressure in the brake oil chamber 11 is too large, the braking torque generated between each brake shoe 5,5' and the brake drum 4 will be too large, resulting in the wheels being locked. To prevent this dangerous situation, each piston 7.
A pair of control oil chambers 12 and 12' are formed between the wheel cylinder 8 and the end wall of the wheel cylinder 6.
2. By controlling the control oil pressure in the brake oil chamber 11, when the brake oil pressure in the brake oil chamber 11 is too large and there is a possibility or danger of wheel locking, each piston 7.8 is moved by the brake oil pressure. is configured to suppress.

Therefore, a control device for controlling the control oil pressure in the control oil chambers 12, 12' will be described below.

The pressurized control oil sucked up from the oil tank T by the pump P is sent through the oil line 15 and the pressure accumulator 13 to the artificial side boat of the inlet valve 14 which is switched and controlled by the electromagnetic coil 20. At the same time, the outlet side boat of the inlet valve 14 is connected to the control oil chamber 12 via an oil passage 16, and further to the control oil chamber 12' via an oil passage 17.
are connected to each other. Further, the control oil chamber 12 is further connected to the control oil chamber 1 through an oil passage 16, an oil passage 17, and an oil passage 18.
2' communicates via an oil passage 18 with an inlet side boat of an outlet valve 19, each of which is switched and controlled by an electromagnetic coil 21, and an outlet side boat of the outlet valve 19 communicates with an oil tank T.

The in-left valve 14 is normally kept switched to the right position in FIG. When the electromagnetic coil 20 is actuated by a signal sent to the electromagnetic coil 20, the inlet valve 14 is switched to the left position in FIG. Via the left pulp 14, it is forced into each control oil chamber 12, 12', and presses each piston 7.8 toward each other against the braking oil pressure in the brake oil chamber 11.

In addition, the outleft valve 19 is normally kept in the left position in FIG. It's open. When the electromagnetic coil 21 is activated by a signal sent to the electromagnetic coil 21, the outlet valve 19 is activated.
In the figure, the control oil chambers 12, 12' are switched to the right-hand position, so that each control oil chamber 12, 12' is isolated from the oil tank T.

Therefore, as the first operating state, the inlet pulp 14
is switched to the right-hand position and the outlet valve 19 is switched to the left-hand position, that is, no signal is sent to any of the electromagnetic coils 20, 21. In this state, each control oil Room 12, 12'
is open in the oil tank T, so each piston 7.8
is pressed and moved depending only on the brake oil pressure in the brake oil chamber 11, and as a result, the braking torque during braking can be freely increased depending on the driver's braking operation.

Next, as a second operating state, the outlet valve 19
is switched to the right position, that is, electromagnetic coil 2
Considering the state in which the signal is sent to 1, in this state, each control oil chamber 12, 12' is cut off from the oil tank T, and the control oil in each control oil chamber 12, 12' is in a locked state. Therefore, each piston 7.8 is prevented from further movement even if the brake oil pressure in the brake oil chamber 11 continues to increase. As a result, the braking torque during braking is maintained at a constant level regardless of the driver's braking operation.
This second operating state is suitable in the event of a possible locking of the wheels.

Then, as the third operating state, the inlet valve 14
is switched to the left position and the outlet valve 19 is switched to the right position, that is, each electromagnetic coil 20
．． Considering the state in which signals are sent to both pumps 21 and 21, in this state, the control oil sent from pump P is
3. Each control oil chamber 12.12 via the inlet valve 14
' and each control oil chamber 12.12'
are cut off from the oil tank T, so the pistons 7.8 are pushed toward each other against the braking oil pressure in the braking oil chamber 11. As a result, the braking torque during braking is reduced independently of the driver's braking action, so that this third operating state is suitable when there is a risk of wheel locking.

By the way, in order to determine the slip rate of the wheels, it is first necessary to estimate the vehicle speed, so a specific example of a practical vehicle speed estimating device 32 for this purpose will be described below with reference to FIGS. 2 and 3. . First, in Figure 2,
Each wheel is equipped with wheel speed detection devices 22, 23, 24, and 25 that individually detect the circumferential speed of the corresponding wheel. Proportional values of wheel speed signals are generated as frequency signals fl, rz, fz and f4. Each wheel speed frequency signal f,,f,.

In order to convert fz and ra into easy-to-handle signal formats,
They are immediately sent to frequency-to-voltage converters 26, 27, 28 and 29, respectively, where voltage signals L1w, , Uw1, Uw3 and [Jw
, is converted to In Fig. 3, each wheel speed voltage signal U
The state of change of the values of w 1 , U w z , U w 3, and 0 w4 with respect to time when the skid prevention device is activated is exemplarily shown.

Referring again to FIG. 2, each frequency-to-voltage converter 26.27
．． 28. The wheel speed voltage signal [Jw
, , Uw, LJw3.0w4 are subsequently sent to the high select circuit 30, respectively.

The high select circuit 30 receives each wheel speed voltage signal IJ W, , U Wt , U as an input signal.
W3.

Select only the signal that always has the value of Agricultural University from LJw,
As shown by the thick solid line in FIG. 3, the maximum wheel speed voltage signal Uwmax is generated as an output signal.

The maximum wheel speed voltage signal Uwmax generated by the high select circuit 30 is then sent to a storage circuit 31 having a constant current discharge characteristic commensurate with standard vehicle body deceleration during braking. As shown by the chain line in FIG. 3, the memory circuit 31 receives the maximum wheel speed voltage signal Uwm, which is an input signal.
An estimated wheel speed voltage signal U, which is a damping signal having a slope determined by the discharge characteristics of the ax, is generated as an output signal.

The vehicle body speed voltage signal U estimated in this manner is sent to a reference wheel speed setting circuit 33 as shown in FIG. The reference wheel speed setting circuit 33 sets a predetermined slip rate λO with respect to the estimated vehicle speed voltage signal U.
This circuit sets the wheel speed so that the following equation is true: um=(1-λo)U.

Since the reference wheel speed is set as described above, only specific examples of the method and device for adding the wheel slip rate to the control factor in the anti-skid device will be described below.

In FIG. 4, the circumferential speed of the wheel whose braking torque is to be controlled is first determined by the wheel speed detection device ll! attached to the wheel. Detected by 34.

The wheel speed detection device 34 generates a wheel speed frequency signal fi proportional to the wheel speed as its output signal, but this signal is immediately converted into a wheel speed voltage signal proportional to the wheel speed by the frequency-voltage converter 35. ■Converted to wi. In order to obtain this wheel speed voltage signal Uwi, as the wheel speed detection device 34 and the frequency-voltage converter 35,
Each wheel speed detection device 22, 23, 24, 25 and each frequency-voltage converter 26, 27, 28, 29 constituting the vehicle body speed estimating device 32 shown in FIG. 2 can be used for each wheel. can.

The wheel speed voltage signal Uwi is subsequently sent to a comparator circuit 36, a differentiator circuit 37 and a comparator circuit 38. Comparison circuit 3
6 compares the wheel speed voltage signal Uwi and the reference wheel speed voltage signal U which is the output signal of the reference wheel speed setting circuit 33, and determines whether the value of the wheel speed voltage signal Uwi is greater than the true value of the reference wheel speed voltage signal U. When it is small, that is, Uwi<U+
It is configured to generate an output signal only when the voltage is +.

Differentiating circuit 37 differentiates wheel speed voltage signal Uwi and generates wheel acceleration voltage signal [Jwi as an output signal. This wheel acceleration voltage signal wi is immediately sent to comparison circuits 40, 41 and 42.

Here, the comparison circuit 40 compares the wheel acceleration voltage signal ■wi with a reference wheel deceleration voltage signal -ywo indicating a preset negative reference wheel acceleration, and compares the wheel acceleration voltage signal Qw
The output signal is generated only when the value of + is smaller than the value of the reference wheel deceleration voltage signal -QWO, that is, when ■wi<-ywo.

Further, the comparison circuit 41 compares the wheel acceleration voltage signal ■wi and a preset first reference wheel acceleration voltage signal yWl, and determines that the value of the wheel acceleration voltage signal ■wi is the first reference wheel acceleration voltage signal *w, It is configured to generate an output signal only when the value is larger than the value of Qw, that is, when Qw<■wi.

Further, the comparison circuit 42 outputs the wheel acceleration voltage signal ■wi and a preset second reference wheel acceleration voltage signal* having a larger value than the first reference wheel acceleration voltage signal Vwr.
w2, and the value of the wheel acceleration voltage signal ■wi is the second
When the reference wheel acceleration voltage signal is larger than the value of wz,
That is, it is configured to generate an output signal only when 9w2<■wi. The output side of this comparison circuit 42 is connected to the input side of an inversion circuit 45, and while the comparison circuit 42 is generating an output signal, the inversion circuit 45 cancels the signal and produces no output signal. However, while the comparison circuit 42 is not generating an output signal, it is configured to always generate an output signal. That is, the inversion circuit 45 functions to invert the output signal of the comparison circuit 42.

By the way, the comparison circuit 38 receives the wheel speed voltage signal (Jwi
is compared with a preset second reference wheel speed voltage signal Vwo indicating an extremely low wheel circumferential speed, and the value of the wheel speed voltage signal [Jwi is determined to be the second reference wheel speed voltage signal Vwo.
, that is, when [J w i < V
It is configured to generate an output signal only when W O. The output side of this comparator circuit 38 is connected to the input terminal of a pulse generator 39, and this pulse generator 39 operates for a certain period of time T (for example, 300~ It is configured to generate a pulse of 500 m5ec).

Now, the output signals of each of the comparison circuits 36, 40, 41, 42 and the pulse generator 39 are processed through a logical judgment process, and the output signals of the electromagnetic coil 20. The signal is sent as an operation command signal to the electromagnetic coil 21 for operating the outlet pulp 19, and the logic circuit device therefor will be explained below.

The output sides of the comparison circuits 36 and 40 are both connected to the AND circuit 4.
3 and the input side of the OR circuit 44, and the comparison circuit 4
1 and the output side of the pulse generator 39 are connected to the input side of the OR circuit 44. The output sides of AND circuit 43 and pulse generator 39 are further connected to the input side of OR circuit 46, and the output sides of OR circuit 46 and inverting circuit 45 are connected to the input side of AND circuit 47. The output sides of the OR circuit 44 and the inverting circuit 45 are AN
It is connected to the input side of the D circuit 48. AND circuit 47
is connected to the electromagnetic coil 20, and when the AND circuit 47 generates an output signal, the electromagnetic coil 20 is activated to switch the in-left pulp 14 from the right position to the left position in FIG. , the AND circuit 48 is connected to the electromagnetic coil 21, and when the AND circuit 48 generates an output signal, the electromagnetic coil 21 is activated to switch the out-left pulp 19 from the left position to the right position in FIG. has been done.

Since the logic circuit device is configured as described above, the output signals of each comparison circuit 36, 40, 41, inversion circuit 45 and pulse generator 39 are processed as follows.

First, the circumferential speed of the wheel is greater than the second reference wheel circumferential speed, which is set extremely low, and therefore the wheel speed voltage signal Uwi
Considering a state in which the O value is larger than the value of the second reference wheel speed voltage signal Vwo and the pulse generator 39 does not generate an output signal, the value of the wheel speed voltage signal Uwi is larger than the value of the reference wheel speed voltage signal UII. , and when the value of the wheel acceleration voltage signal ■wi is larger than the reference wheel deceleration voltage signal -〇WOO value and smaller than the value of the first reference wheel acceleration voltage signal 'I>Wl, that is, when the value of the first reference wheel acceleration voltage signal 'I>Wl is
When <■wi<Ωw, or wheel speed voltage signal U
Regardless of the value of wi, when the value of the wheel acceleration voltage signal ■wi is larger than the value of the second reference wheel acceleration voltage signal *W2, that is, when yw<■wi, there is no possibility of wheel locking. Since both the AND circuits 47 and 48 do not generate an output signal and therefore the electromagnetic coils 20.21 do not operate together at this time, the inlet pulp 14 and the outlet pulp 19 are
The brake torque during braking is freely increased according to the driver's braking operation.

Further, when the value of the vehicle speed voltage signal [Jwi is larger than the value of the reference wheel speed voltage signal Ull and the value of the wheel acceleration voltage signal IJw+ is smaller than the value of the reference wheel deceleration voltage signal -9Wo, that is, U, I<Uwi and [Jw
When i<-■wo or wheel speed voltage signal Uwi
Regardless of the value of , when the value of the wheel acceleration voltage signal ■wi is larger than the value of the first reference wheel acceleration voltage signal *W1 and smaller than the value of the second reference wheel acceleration voltage signal QWg, that is, *w< ■When wi<*W2, or when the wheel speed voltage signal UwiO value is equal to the reference wheel speed voltage signal Ul
and the value of the wheel acceleration voltage signal Uwi is larger than the reference wheel deceleration voltage signal -9Wo and smaller than the second reference wheel acceleration voltage signal *W2, that is, when the value of the wheel acceleration voltage signal Uwi
When <U, and -9Wo<■wi<QWz, it is determined that there is a possibility of wheel locking, and AN
D circuit 47 does not generate an output signal, but only AND circuit 48 generates an output signal. Therefore, at this time, the electromagnetic coil 20 does not operate, but the electromagnetic coil 21 operates, so that the in-left pulp 14 and the outlet pulp 1
9 is placed in the second operating state, and the braking torque during braking is kept constant so as not to increase any further regardless of the driver's braking operation.

Furthermore, the value of the wheel speed voltage signal [Jwi is smaller than the value of the reference wheel speed voltage signals U, l, and the value of the wheel acceleration voltage signal ■wi is the reference wheel deceleration voltage signal -? When it is smaller than the WOO value, that is, UwilU, and ■wi<
-ywo, it is determined that there is a risk of wheel locking, and AND circuits 47 and 48 both generate output signals. Therefore, at this time, the electromagnetic coils 20 and 21 operate together, so that the in-left valve 1
4 and the outlet valve 19 are placed in the third operating state, and the braking torque during braking is reduced regardless of the driver's braking operation.

By the way, when the circumferential speed of the wheel becomes extremely low and the value of the wheel speed voltage signal Uwi becomes smaller than the value of the second reference wheel speed voltage signal Vwo, the comparison circuit 38 generates an output signal and the pulse generator 39 generates a pulse with a constant time width T as an output signal. In such a case, the value of the wheel acceleration voltage signal Qw+ is smaller than the value of the second reference wheel acceleration voltage signal *w2, and therefore the inverting circuit 45 is generating an output signal, so the AND circuits 47 and 48
is the time width T of the pulse generated by the pulse generator 39, regardless of the output signals of the comparison circuits 36, 40 and 41.
Generates an output signal only during this period.

The electromagnetic coils 20 and 21 operate together only during this time width T, the in-left valve 14 and the out-left valve 19 are placed in the third operating state, and the braking torque during braking is dependent on the driver's braking operation. will be reduced regardless.

The comparison circuit 38 and the pulse generator 39 are configured to detect, for example, when the vehicle suddenly enters a road surface with a low friction coefficient from a road surface with a high friction coefficient while braking, the wheels may momentarily lock due to a delay in response of the control system. Even if this occurs, it immediately releases the lock and functions as an additional circuit to reliably prevent continued wheel locking.

Comparison circuit 38 and pulse generator 39 shown in FIG.
A dividing circuit 49 and a comparing circuit 50 as shown in FIG. 5 can be provided to perform the same functions as those shown in FIG. 5, instead of providing the comparator circuit 38 and pulse generator 39 in FIG. 49, and in this dividing circuit 49, a low reference wheel speed voltage signal URj having a value smaller than the value of the reference wheel speed voltage signal Ull than the estimated vehicle body speed voltage signal U is set, and this low reference wheel speed voltage signal Ul' is sent to the comparison circuit 50 as an output signal of the division circuit 49, and the comparison circuit 50 compares the wheel speed voltage signal Uwi and the low reference wheel speed voltage signal Ul', and the wheel speed voltage signal UwiO value is determined to be the low reference wheel speed. The configuration differs from that of FIG. 4 in that an output signal is generated only when the value is smaller than the voltage signal UR' and is sent to the OR circuits 44 and 46, but the other configuration is as shown in FIG. is exactly the same.

Therefore, in the circuit arrangement shown in FIG. 5, when the value of the wheel speed voltage signal UwiO becomes smaller than the value of the low reference wheel speed voltage signal U8', that is, when Uwi<U,'
When this happens, the electromagnetic coils 20 and 21 operate together, and the inlet valve 14 and the out left valve 1
9 is placed in the third operating state, and the braking torque during braking is reduced regardless of the driver's braking operation.

FIG. 6 shows an example of the operation mode of the anti-skid device when the logic circuit device shown in FIG. 4 is employed. In FIG. 6, the horizontal axis shows the passage of time after the start of braking, and the vertical axis shows the estimated vehicle speed voltage signal U, the wheel speed voltage signal Uwi, and the reference wheel speed voltage signal at the top position. UR is shown, and at a position below it, a wheel acceleration voltage signal ■wi is shown, and further below that, in order, the output signal A of the comparison circuit 36 and the comparison circuit 4
0 output signal B, output signal C1 of comparison circuit 41, output signal D of comparison circuit 42, third operating state (■) of inlet pulp 14 and outleft valve 19, also second operating state (2), same first operation BI and braking torque Ts are shown, respectively.

Immediately after starting braking at time 1=0, neither of the AND circuits 47 and 48 generates an output signal, and therefore the hydraulic control system of the braking device is in the first operating state BI, so the braking torque T, gradually increases, and along with this, the wheel speed voltage signal LJwi and the wheel acceleration voltage signal ■wi
Both gradually decrease.

Time 1. When the value of the wheel acceleration voltage signal ■wi becomes smaller than the value of the reference wheel deceleration voltage signal −■wo,
The output signal B of the comparison circuit 40 is generated, and it is determined that there is a possibility of wheel locking, and the AND circuit 48 generates an output signal, but at this time, the output signal A of the comparison circuit 36 has not yet been generated. Therefore, the AND circuit 47 does not generate an output signal, and the hydraulic control system of the braking device is in the second operating state (2), and the braking torque T is held substantially constant.

At this time, the braking torque T8 due to a delay in the operation of the hydraulic control system, etc.
is excessive, the wheel speed voltage signal Uwi continues to decrease further, and as a result, at time t2, the comparison circuit 3
6 generates an output signal A.

At this point, the output signal A of the comparison circuit 36 and the output signal B of the comparison circuit 40 are both generated, and it is determined that there is a risk of wheel locking, and the AND circuits 47 and 48 both output signals. each electromagnetic coil 20.2
1 operate together, the hydraulic control system enters the third operating state (2), and the braking torque T8 is reduced.

As the braking torque T decreases, the wheel acceleration gradually increases, and as a result, at time t, the value of the wheel acceleration voltage signal wi becomes the reference wheel deceleration voltage signal - wo
becomes larger than the value of , the output signal B of the comparison circuit 40 disappears, and it is determined that there is no risk of wheel locking, and the output signal of the AND circuit 47 disappears, but the output signal A of the comparison circuit 36 continues to be generated. Therefore, the output signal of the AND circuit 48 does not disappear, so the hydraulic control system returns to the second operating state (3), and the braking torque T8 is maintained substantially constant.

At this time, the braking torque T,
has decreased too much, so as the wheel acceleration voltage signal ■wi continues to rise, the wheel speed voltage signal Uwi begins to rise, and at time t4, the value of the wheel acceleration voltage signal ■wi becomes the first reference wheel acceleration voltage signal *W. , the value of the wheel acceleration voltage signal □wiO becomes larger than the value of the second reference wheel acceleration voltage signal Qwz and the output signal C of the comparison circuit 41 is generated. A signal is generated. As a result, it was determined that there was no possibility of the wheels locking, and the AND circuit 4
7 and 48 do not generate any output signals, the electromagnetic coils 20, 21 are both inactive, the hydraulic control system is in the first operating state 1, and the braking torque Tm begins to increase again.

As the braking torque Tll increases, the value of the wheel acceleration signal white wi becomes smaller than the value of the second reference wheel acceleration voltage signal QW2 at time 1h, and the output signal of the comparison circuit 42 disappears. Since the output signal C of 41 still remains, it is determined that there is a possibility of wheel locking, and the AND circuit 48 generates an output signal, the electromagnetic coil 21 is activated, and the hydraulic control system is activated. The operating state becomes (■), and the braking torque T is held almost constant.

When the wheel speed voltage signal Uwi increases to the extent that an appropriate wheel slip rate can be maintained, the value of the wheel acceleration voltage signal Qw+ becomes smaller than the value of the first reference wheel acceleration voltage signal QW at time t7, and the comparison is made. The output signal C of the circuit 41 disappears, and it is determined that there is no possibility of the wheels locking, so the AND circuits 47 and 48 do not generate output signals, and the electromagnetic coils 20 and 21 are both inactive. Then, the hydraulic control system enters the first operating state 6r, and the braking torque T8 begins to increase.

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

In the above explanation, the reference wheel speed voltage signal Ua constitutes the reference wheel speed signal of the present invention, and the wheel speed voltage signal
i constitutes the wheel speed signal of the present invention, wheel acceleration voltage signal ■wi constitutes the wheel acceleration signal of the present invention, and further,
The reference wheel deceleration voltage signal -9WO constitutes the reference wheel deceleration signal of the present invention.

C1 Effect of the Invention As described above, according to the present invention, the slip rate of the wheel is added to the control factors as well as the acceleration/deceleration of the wheel, so that braking is performed so that the slip rate of the wheel is always within an appropriate range. Torque can be controlled.

In particular, in the present invention, the wheel speed signal Uwi and the reference wheel speed signal UN are compared, and the wheel acceleration signal
wi and the reference wheel deceleration signal -9WO are compared, and the braking torque pressure reduction control timing is determined based on the magnitude relationship of the values of each signal, so the braking torque pressure reduction control can be performed automatically and accurately. It can be carried out.

In particular, a condition in which the value of the wheel speed signal UwiO is smaller than the value of the reference wheel speed signal U8 and the value of the wheel acceleration signal ■wi is smaller than the value of the reference wheel deceleration signal -9WOO, that is, the risk of wheel locking. Since the braking torque is always reduced under conditions where the risk of wheel locking is imminent, it is possible to reliably avoid the risk of wheel locking, and the strong braking torque continues until the point where the risk of wheel locking approaches. Therefore, the overall braking efficiency is improved.

Furthermore, a low reference wheel speed signal U is derived based on the vehicle body speed so as to be at a lower level than the reference wheel speed signal UR.
Even under conditions where the wheel speed signal UwiO value is smaller than the value of l', it is not affected by the magnitude relationship between the wheel acceleration signal ■wi and the reference wheel deceleration signal -■wo, the control state of the braking torque, etc. Since the braking torque is constantly reduced, the vehicle is not affected by the road surface with a high coefficient of friction (
Even if the wheels lock momentarily due to a delay in the response of the control system when the vehicle suddenly enters a road surface with a low coefficient of friction (for example, an icy road) from a dry paved road, the system always releases the lock instantly. Therefore, it is possible to prevent the wheels from being locked continuously, and to minimize the decrease in braking efficiency that accompanies locking of the wheels.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional conceptual diagram of main parts showing a wheel braking device and a hydraulic control device for controlling the braking torque of the braking device;
FIG. 2 is a block diagram showing an example of a vehicle speed estimation device,
3 is a graph diagram for explaining an example of the operation of the vehicle speed estimating device shown in FIG. 2, FIG. 4 is a signal processing circuit and logic circuit diagram for operating the hydraulic control device shown in FIG. 1, and FIG. The figure is a signal processing circuit and logic circuit diagram similar to that in FIG. 4 showing a modification of FIG. 4, and FIG. 6 is a diagram of the braking device and hydraulic control device in FIG. It is an explanatory view showing an example of each operation mode with a circuit device. UN...Reference wheel speed signal, Uyo'...Low reference wheel speed signal, Uwi...Wheel speed signal, (Jwi...
Wheel acceleration signal, -■wo...Reference wheel deceleration signal,
λo...Slip rate

Claims (1)

[Claims] The circumferential speed of the wheel is detected and taken out as a wheel speed signal (Uwi), and the vehicle body speed is detected and a predetermined slip ratio (λo) of the wheel is added in a manner that can be compared with the wheel speed signal (Uwi). A reference wheel speed signal (U_R) is set, and an acceleration signal (■wi) of the wheel is derived from the wheel speed signal (Uwi), and the acceleration signal (■wi) is derived from the wheel speed signal (Uwi).
The reference wheel deceleration signal (-■wo
), and further derives a low reference wheel speed signal (U_R') based on the vehicle body speed so that it is at a lower level than the reference wheel speed signal (U_R), and during braking,
The wheel speed signal (Uwi) and the reference wheel speed signal (
The wheel acceleration signal (■wi) is compared with the reference wheel deceleration signal (-■wo), and the wheel speed signal (Uwi) is compared with the low reference wheel speed signal (U_R'). ) is the reference wheel speed signal (
U_R) and the wheel acceleration signal (
■wi) is smaller than the reference wheel deceleration signal (-■wo), or when the wheel speed signal (Uw
Prevention of wheel locking in a vehicle, characterized in that when the value of i) is smaller than the value of the low reference wheel speed signal (U_R'), a braking device is controlled to always reduce the braking torque of the wheel. Method.