DE2050328A1 - Anti-skid device for vehicle wheels, in particular for road vehicles - Google Patents

Description

Hanover, October 8, 1970 WP 3 * /? 0

Westinghouse Bremsen- und Apparatebau GmbH, Hanover

Anti-skid device for vehicle wheels, in particular for road vehicles,

The invention relates to an anti-skid device for vehicle wheels, especially road vehicles, with an electronic speed comparison device for comparing a vehicle speed signal corresponding to the vehicle speed, preferably derived from the wheel speed, with a wheel speed signal corresponding to the wheel speed and for emitting a control signal when the difference between the vehicle speed signal and the wheel speed signal exceeds a certain value, as well as with an electronic wheel deceleration sensor for emitting a control signal when the wheel deceleration exceeds a certain value, and a brake pressure control valve device, which is dependent on both control signals in the sense of reducing the difference between the vehicle speed and the wheel speed is controllable , d

Devices of this type are used to prevent the vehicle wheels from locking and thus from sliding when braking. It is advantageous here to use the amount of slip that occurs between the wheel and the roadway as the criterion for reaching the sliding threshold.

In the anti-skid devices of this type, this slip is determined by comparing one of the vehicle speed.

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ORIGINAL INSPECTED

the reference variable, preferably derived from the wheel speed, with a variable corresponding to the wheel speed with the aid of a speed comparison device, which at
Reaching a critical threshold indicating the sliding threshold
Slip causes the brake pressure control valve device to switch over in the sense of a reduction in the slip, but since the reference variable that is not directly sampled, but derived
has a course that is independent of the actual course of the vehicle speed and therefore usually not always analogous to it, such anti-skid devices are in principle
|| unstable.

In order to stabilize the devices, i.e. to prevent false signals from being triggered as a result of the occasional deviations between the reference variable and the actual vehicle speed, the use of wheel decelerators is required which correct the reference variable as a function of the deceleration of the wheel. In a known anti-skid device of the type, the delay sensors are the
assigned to non-driven wheels (OS 1 961 741). In this case, a reference signal derived from the speed of these wheels is only emitted when a certain deceleration of these wheels is exceeded. In another known Gleitachutseinrichtung of the type, the delay generator is used to
Subsequent influence on the course of the emitted reference signal (OS 1 810 163).

In order to achieve a sufficiently precise correction of the reference variable, which is analogous to the vehicle speed, it is necessary that the decelerators used are very weakly attenuated, that is to say very slightly _JM:; C \ * OO ^ - 3 - SÄD

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are easily approachable. However, such delay generators are particularly complex and therefore very expensive.

The invention is based on the object of addressing this disadvantage avoid and to create an anti-skid device of the type mentioned above, which is relatively easier to use and thus cheaper electronic means a control of the brake pressure exactly corresponding to the respective conditions guaranteed in terms of a reduction in slip.

This object is achieved according to the invention in that the ' electronic had decelerator a relatively strong one Having damping, and that the brake pressure control valve device first by that of the speed comparison device output control signal and after a time dependent on the damping of the wheel deceleration sensor has elapsed by the wheel deceleration sensor output control signal is controlled.

In order to further improve the effectiveness of the wheel slide protection device, is further provided according to the invention that the | Response threshold of the speed comparison device relatively is chosen low.

In a further embodiment according to the invention is the Fuel pressure freezing valve device by the speed comparison device output control signal in a first switching position that causes the brake pressure to be kept constant: and after a certain holding time has elapsed, in a second, fine switching position that brings about a reduction in fuel pressure

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switchable, in which after the expiry of the attenuation of the Wheel deceleration sensor dependent time by the wheel deceleration sensor output control signal is held. This enables better utilization of the braking force absorption capacity of the Wheel when using a speed comparison device that has a low response threshold and thus works without delay achieved «

It is advantageous if, when the time, which is dependent on the damping of the wheel deceleration sensor, has elapsed, before the specified time has elapsed Holding time the brake pressure control valve device by the from The control signal output by the wheel decelerator can be switched in the second switching position which causes a brake pressure reduction.

It is further provided according to the invention that the wheel deceleration sensor also serves as a wheel acceleration sensor, which when Exceeding a certain value of the wheel acceleration Outputs control signal, and that the brake pressure control valve device can be controlled as a function of this control signal, so $ ■ that when the signal falls, it rises again in a third the switching position causing the brake pressure is switchable » As a result, the anti-skid device is stabilized even when the wheel is restarted with the aid of strongly damped ^ Accelerator reached »

The brake pressure control valve device is expediently at a standstill with the speed adjustment facility and the wheel deceleration generator about a lögi§üh§ Böhaltung in WifkverbiMuagj die Preferably a member to store the control signals Evil *

certain time periods and / or for determining the holding time in which the brake pressure control valve means i _n the first, a constant holding of the brake pressure causing Sehaltstellung is switchable contains.

To adjust the brake pressure on each individual wheel according to the To control the prevailing conditions and thereby simplify the entire anti-skid system of the vehicle, is also According to the invention, it is provided that each vehicle wheel has a speed svergleichseinrichtung, a wheel deceleration sensor and a brake pressure control valve device is assigned, wherein the wheel speed signal through one of the corresponding Wheel assigned, known electronic device and the vehicle speed signal through a common to all wheels, also known electronic device for deriving a vehicle speed corresponding Reference signal formed from the wheel speed of all wheels will.

In the following an embodiment of the invention is explained in more detail with reference to the drawing:

Show it:

Pig, 1 is a schematic block diagram of an anti-skid system, consisting of four anti-skid devices according to the invention with a common device for generating composes a reference signal corresponding to the vehicle speed.

2 shows a logic circuit for the anti-skid device according to Fig. 1, shown symbolically.

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Pig. 3 shows a time-pressure-speed diagram for the anti-skid device according to FIGS. 1 and 2.

As can be seen from FIG. 1 of the drawing, the one shown relates Anti-skid system on a four-wheel vehicle, with each wheel having an anti-skid device according to the invention la, 1b, 1c, 1d is assigned »The device 1a assigned to the right front wheel VR is described in more detail below. The den Devices 1b, 1c, 1d associated with other wheels are identical educated.

The anti-skid device 1a has one driven by the vehicle wheel Generator 2a for generating electromagnetic pulses, the frequency of which is a measure of the speed of the wheel is, further a frequency-voltage converter 3a, which this Converts pulses into a proportional voltage, a signal converter which is operatively connected to the converter 3a via a diode 4a 5 for generating a reference voltage corresponding to the vehicle speed is analog at the maximum permissible deceleration of the vehicle, a differentiating element 6a for differentiating the from P converter 3a output voltage, attenuators 7a and 8a for the differentiator 6a, a trigger 9a for delivering a -b signal when a wheel deceleration corresponding to the value -b is reached, a trigger 10a for emitting a + b signal when a wheel acceleration corresponding to the value + b is reached and a comparator 11a designed as a differential trigger, for example, for comparing the signals from the signal converter 5 and from Converter 3a output voltages via a logic circuit 12a with a brake pressure control valve 13a in V / irkverbi.ndung stands.

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The generator 2a, the converter 3a, the four anti-skid devices 1a, 1b, 1c, 1d straight signal converter 5 and the Comparators 11a form an electronic speed comparison device 15a which measures one of the vehicle speed corresponding reference variable derived from the wheel speed with a variable corresponding to the wheel speed compares and when a certain difference is reached between the two variables (response threshold) it emits a control signal that . The logic circuit 12a is supplied.

The signal converter 5 basically consists of a V / resistance capacitor circuit (RC element) and emits an output signal, the initial value of which depends on the value of the input signal present at the signal converter 5 and the further course of which roughly corresponds to the discharge curve of the capacitor. The course of the output signal can be set in a known manner in such a way that the signal voltage is analogous to the vehicle speed at the maximum permissible deceleration of the vehicle. With the help of the four diodes 4a, 4b, 4c, 4d it is achieved that the signal converter 5 only has the highest of the four voltage supplied by the converters 3a, 3b, 3c, 3d, so that only the speed of the faster and thus less risk of sliding wheel is decisive for the formation of the reference voltage analogous to the vehicle speed «

The response threshold of the speed comparison device 15a is chosen very low according to the invention, d.lu that the device lpa a control signal .DELTA.y after reaching a relatively very small difference between the driving

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Stuff speed corresponding reference voltage and that of the Wheel speed emits corresponding voltage.

The generator 2a, the converter 3a, the differentiating element 6a, the damping elements 7a, 8a, and the triggers 9a,, 10a form an electronic wheel deceleration and acceleration sensor 16a _t which, according to the invention, is strongly damped and thus relatively sluggish, and when one is reached the sliding threshold wheel deceleration indicating the wheel deceleration and a wheel acceleration indicating the restart of the wheel each have a control signal -b or + b with one of

ider attenuation and the respective wheel speed dependent deceleration emits. The -b and + b signals are also the logic circuit 12a supplied.

The logic circuit 12a consists of a first timing element 17 with dynamic inputs 18, 19, a second timing element 20 with two dynamic inputs 21, 22 and a third timing element 23 designed as a signal delay element. An input signal is at the inputs 18 and 21 only effective on transition from 0 to 1 and at inputs 19 and 22 only effective on transition P from 1 to 0. Timers 17 and 20 provide an output signal until their hold time Z ₁ or Z2 has expired or an input signal becomes effective at their inputs 19 and 22, respectively. The timing element 23 supplies an _{output signal delayed by a certain delay time T 1} with respect to the input signal until the input signal is deleted.

The output of the speed comparison device 15a 'signal is the input 18 of the first timing element 17 and the

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■ ■■. ■ ■ "" ■ ■ ,, ", (y _mm

Input of the third timing element 23 is supplied. The -b signal emitted by the wheel deceleration and wheel acceleration sensor 16a is applied to the input 21 of the second timing element 20 and the negated input of an AND gate 24. The + b signal is fed to the input 19 of the first timing element 17 and the input of the second timing element 20. The output signal emitted by the first timing element 17 is fed to an OR gate 25 and an OR gate 27 via a UHD gate 26, at whose negated input the output signal emitted by the timing element 23 is present. The output of the timer 20 is the OR gates. 25 and 27 supplied.

The anti-skid device 1a also has a V / ege valve formed brake pressure control valve 13, which is shown in FIG. 2 in one of a compressed air tank 31 to one on the right Front wheel VR acting brake cylinder 32 leading line 33, 34, 35 is arranged. The brake pressure control valve 13 is a Brake valve 36 connected upstream. Two solenoid valves 37, 37 'are used to switch the brake pressure control valve 13 to one of the three switching positions shown schematically. Are both solenoid valves 37, 37 'de-energized, the brake pressure control valve 13 is then in a position causing a brake pressure increase Switching position in which, if the brake valve 36 is open, the brake cylinder 32 is connected to the compressed air tank 31. If both solenoid valves 37, 37 'are excited, then there is the brake pressure control valve 13 in a switching position which causes the brake pressure to be kept constant, in which the brake cylinder 32 from both the atmosphere and the compressed air tank 31 is separated. If the solenoid valve 37 is energized, the solenoid

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20b0328

valve 37 *, on the other hand, is de-energized, the brake pressure control valve is then located 13 in a switching position which brings about a brake pressure reduction, in which the brake cylinder 32 communicates with the atmosphere connected is. The solenoid valves 37 and 37 'are through the signals emitted by the OR gate 25 or the AND gate 24 are controlled.

The mode of operation of the anti-skid system according to the invention according to FIGS. 1 and 2 is illustrated below with the aid of the diagram according to Pig. 3 explains, where V ^, the time profile of the vehicle ^{speed, V ™ the time profile of the wheel speed, ν 1} -, the time profile of the pseudo vehicle speed, which is formed by the reference voltage output by the signal converter 5, and P ^ the time profile of the the right front wheel VR represents effective brake pressure.

The generator 2a driven by the right front wheel VR continuously supplies pulses, the frequency of which is a measure of the speed of the wheel. The converter 3a converts these voltage pulses to a corresponding one of the wheel speed voltage on the other hand supplied on the one hand, the comparator 11a W via the diode 4a the signal converter 5 and finally the Differerfzierglied 6a. The signal converter 5 supplies a reference voltage that is dependent on the largest of the voltages supplied by the four converters 3a, 3b, 3c, 3d, which represents a reference value analogous to the vehicle speed and the so-called pseudo vehicle speed, and is also fed to the comparator 11a.

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The differentiating element 6 a differentiates that supplied by the converter 5 Signal and gives one of the respective delay or

Acceleration of the bath from the corresponding output signal that by the strongly damping damping members 7a according to the invention, 8a is damped and by the trigger 9a, 10a when the corresponding sliding or restart threshold is reached constant -b or + b-signal is transformed.

When the brake is actuated, the brake pressure control valve 13 is located in Pig. 2 switching division shown. If a braking process is triggered by actuating the brake valve 36, the compressed air tank 3V is connected _{to the brake cylinder 32 via line 33 f} 34, brake pressure control valve 13 and line 35 and a brake pressure increasing in _{accordance with the curve ^ 0 -PjI is applied in the latter.}

Let it be assumed that when the effective brake pressure P _{B1 is reached} (time tj), the wheel _{speed V R} has decreased compared to the pseudo vehicle speed V * - ™ to such an extent that the response threshold of the speed comparison device 15a is exceeded, so that it emits a / \ y signal . In this case, according to the invention, this response threshold is selected to be very small, specifically in such a way that the device ensures the delivery of a Δν signal as soon as the critical slip is reached.

The Λψ signal is fed to the first timing element 17 on the one hand and the third timing element 23 on the other hand, whereby both timing elements become effective without delay. The from the timer 17

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given output signal energized via the OR gate 25 das.Magnetventil 37 and via the UMD gate 26, the OR gate 27 and the AND gate 24, the solenoid valve 57 ^f , so. that the brake pressure control valve 13 is switched into its switching position which causes the brake pressure to be kept constant.

_{After the delay time T 1} specified by the third timing element 23 has elapsed (time tp), the Δy signal present at the timing element 23 becomes effective at the negated input of the AND gate 26, whereby the output signal emitted by the latter is deleted. This also clears the signals emitted by the OR gate 27 and the IMD gate 24. The solenoid valve 37 ^f is de-energized and the brake pressure control valve 13 is switched to its switching position which brings about a brake pressure reduction.

It is now assumed that when the brake pressure Pt », (point in time t1) is reached, an output from the wheel deceleration sensor 16a -b signal at the timer 20 becomes effective. As a result, the latter emits an output signal which, in the OR gate 25, is the output signal of the timer 17 superimposed and causes the solenoid valve 37 remains energized as long as the -b signal is in effect. The ~ b signal also causes the negated input dea AND gate 24 is deleted, so that the solenoid valve 37 'is de-energized remain.

The brake pressure control valve 13 thus remains even after the time «'· point t, continue to bring about a reduction in pulp pressure switch position. However, the decisive factor for the further reduction in brake pressure is no longer that of the Velocity3Lg * '

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keitsvergleichseinrichtung 15a emitted Δy signal, but the -b signal emitted by the wheel deceleration sensor 16a. If the wheel deceleration has decreased so far as a result of the lowering of the Breinsdruek that the -b signal is deleted (time t.), The solenoid valve 37 'is then re-energized by the timer 20, while the solenoid valve 37 also remains energized by the timer 20. As a result, the brake pressure control valve 13 is switched back to its switching position which causes the brake pressure to be kept constant.

If the -b signal becomes effective, for example as a result of a deterioration in the road conditions before the expiry of the delay time T ₁ , e.g. at time t * p, then the deletion of the negated input of the UIID gate 24 causes the immediate de-energization of the solenoid valve 37 'and thus the immediate switching of the brake pressure control valve 13 into its switching position which brings about a brake pressure reduction. _{The delay time T 1} specified by the timer 23 is dimensioned so that the point in time at which a -b signal becomes effective is shortly after the delay time T has elapsed if the road condition is good, but shortly before the delay time T ^ has elapsed if the road conditions are poor lies.

It is now assumed that at time t, - the wheel acceleration sensor 16a emits a + b signal during the V / i ed eranlaufe s of the wheel, which is fed to the inputs 19 and 22 of the timers 17 and 20, respectively. Due to the above-described design of these inputs, however, the timers 17 and 20 are only deleted when the + b signal drops again after the wheel has restarted (time t ₇ ). The deletion of the two

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Timers 17 and 20 and thus the de-excitation of the two solenoid valves 37, 37 'and the subsequent switching of the Brake pressure control valve 13a into a switching position which causes the brake pressure to rise again, corresponding to that of the initial position it assumed at time t thus depends according to the invention from the fall of the + b signal and not of the Av signal away. The holding times Z., and Zp are chosen so that they only expire after the + b signal has dropped. So they are used to store the -b signal until it falls through of a + b signal can be deleted.

The anti-skid device according to the invention is based on the knowledge that heavily damped electronic deceleration and acceleration sensors are structurally simpler and therefore much cheaper than weakly damped sensors, although the strong damping leads to a strongly delayed output of the corresponding -b- or + b-signal, the undelayed one However, the drop in the signal is not affected. In principle, strongly damped deceleration and acceleration sensors are to be understood as sensors whose damping is set in such a way that there is a drop in speed on the controlled wheel that is 1.5-3.5 km / h greater than with conventional sensors, which are shown in FIG usually show a speed drop of 1.5 - 3 km / h. The drop in speed occurs in the time from exceeding the response threshold until the signal is emitted. Ultimately, however, the decisive factor is a damping value that prohibits the use of the encoder in the well-known anti-skid devices of the type, which have high requirements in terms of operational safety and utilization ^: the braking force absorption wedge?

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the wheels can be placed in all operating states.

The use of such strongly damped deceleration-and-acceleration sensors in such anti-skid devices is made possible according to the invention that the brake pressure is first in Dependence on a Δι / signal emitted without delay by the speed comparison device 15a and only after Sequence one of the damping of the encoder as well as of the respective Wheel speed dependent time from a given by the encoder -b signal is controlled. This is the disadvantageous The effect of the strong damping is eliminated and, on the other hand, a stabilization of the anti-skid device in the area of the Brake pressure reduction even with a relatively low response threshold achieved by the speed comparison device * but the latter has the advantage that after braking has been initiated the increase in brake pressure is interrupted when a relatively small sehlupfes is reached, which, for example, reduces the consumption of compressed air is lower in compressed air braking systems. The one on the Interrupting the increase in brake pressure according to the invention, the following brake pressure curve ensures good utilization of the braking force absorption capability of the wheel depending on the current road conditions as well as a soft brake pressure control

The use of heavily damped wheel accelerators can prevent the encoder from responding in the braking phase, in which high wheel decelerations occur, and from the encoder's incorrect response caused by vibrations on the wheel. In addition, the number of poles of the generators 2a, 2b, 2c , 2d decrease.

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The use of decelerators to control the brake pressure In the last brake pressure reduction area, there is also the option of a residual pressure when the -b signal drops without impairing the anti-skid function of the device.

Since the rise in pressure is made dependent on the instantaneous fall of the + b signal, which is not influenced by the strong damping, and not on the fall of the Δ ^ _ signal, which usually deviates over time from the actual fall below the critical sehlupfes, the slide according to the invention is dependent on - * Protective device stable even when the bike starts up again.

Another advantage is that the anti-skid device in the event of failure of the speed comparison device 15a or of the deceleration-and-acceleration transmitter 16a by the transmitter 16a or by the speed comparison device 15a remains functional to a limited extent, so that not the entire Anti-skid device totally fails.

| The elements shown symbolically in the drawings 1 and 2 are for example from the catalog "Integrated Digital Circuits in TTL" from Texas Instruments, May 1970 edition, known and therefore not described in detail.

In the anti-skid device described above, the reference variable corresponding to the vehicle speed is derived from a derived from the size corresponding to the wheel speed. It is

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However, within the scope of the invention it is possible to use the reference variable others related to vehicle speed To derive variables such as * from the deceleration of the wheel.

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Claims (8)

Patent or protection claims 1.:A skid protection device for vehicle wheels, in particular of ^ y road vehicles, with an electronic speed comparison device for comparing a vehicle speed corresponding, preferably from the wheel - "V MS" speed derived vehicle speed signal with a wheel speed corresponding to the wheel speed ssignal and for outputting a control signal when the difference between the vehicle speed signal and the wheel speed signal exceeds a certain value, as well as with an electronic wheel deceleration transmitter for emitting a control signal when the wheel deceleration exceeds a certain value, and a brake pressure control valve device, which depends on both control signals in the sense of reducing the difference is controllable between the vehicle speed and the wheel speed, characterized in that that the electronic wheel deceleration sensor (16a) has a relatively strong damping, and that the "Brake pressure control valve device (13a) first through that of the speed comparison device (15a) delivered Control signal and after a time dependent on the damping of the wheel deceleration sensor by the wheel deceleration sensor output control signal is controlled. 2. Anti-skid device according to claim 1, characterized in that that the response threshold of the speed comparison device (15a) is selected to be relatively low. - 2 209817/0428 or 2. 3. Anti-skid device according to claim 1, characterized in that that the brake pressure control valve device (13a) by the of the speed comparison device (15a) output control signal in a first, a constant holding of the brake pressure effecting holding position and after a certain holding time (T ..) in a second, a brake pressure reduction effecting switching position is switchable in which it after the time that is dependent on the damping of the wheel deceleration sensor (16a) has elapsed by the time given by the wheel deceleration sensor Control signal is held. 4. Anti-skid device according to claim 3, characterized in that upon expiry of the damping of the wheel deceleration sensor (16a) dependent time before the end of the certain holding time (T ₁ ), the brake pressure control valve device (13a) by the control signal emitted by the wheel deceleration sensor in the second, one Brake pressure reduction causing switching position is switchable. 5. Anti-skid device according to one or more of the claims 1 to 4, characterized in that the wheel deceleration sensor (16a) also serves as a wheel acceleration sensor, which emits a control signal when a certain value of the wheel acceleration is exceeded, and that the brake pressure control valve device (13a) can be controlled as a function of this control signal in such a way that when it drops of the signal in a third, a renewed increase in brake pressure causing switching position is switchable. _ 3 209817 / 0A28 Qo 6. Anti-skid device according to one or more of the claims 1 to 5, characterized in that the brake pressure control valve device (I3a) with the speed comparison device (15a) and the wheel deceleration sensor (16a) are in operative connection via a logic circuit (12a). 7. Anti-skid device according to claim 6, characterized in that the logic circuit (12a) timing elements (17, 20, 23) for storing the control signals over certain time periods and / or for determining the holding time (T ₁ ) in which the brake pressure * Control valve device (13a) is switchable in the first switching position which causes the brake pressure to be kept constant. 8. Anti-skid device according to one or more of claims 1 to 7, characterized in that .jedem vehicle wheel one Speed comparison device (15a, 15b, 15c, 15d), a wheel deceleration sensor (16a, 16b, 16c, I6d) and a brake pressure control valve device (13a, 13b, 13c, 13d) is assigned}, the wheel speed signal by one each Electronic device (3a, 3b, 3c, 3d) associated with the corresponding wheel and known per se, and the vehicle speed signal by an electronic device (5), which is also known per se and which is common to all wheels, for deriving one of the Vehicle speed corresponding reference signal from the Wheel speed of all wheels. 2 0 9g, l 7/0428