DE2050328B2 - Arrangement of an anti-skid device for vehicle wheels, in particular for road vehicles - Google Patents

Description

The invention relates to an arrangement : iner anti-skid device for vehicle wheels, especially of road vehicles with one of the Monitored vehicle wheel-driven generator that sends a signal proportional to the wheel speed generated from which a vehicle speed corresponding signal is derived; with an electronic Speed comparison device, which compares both signals and if the difference exceeds a predetermined value, emits a first control signal; with an electronic, the wheel deceleration sensor differentiating the wheel speed signal, which emits a second control signal, as soon as the wheel deceleration exceeds a predetermined value; with a valve device that receives both control signals and operates in such a way that when a control signal is received, the brake pressure is constant held, when the other control signal is added, the brake pressure is reduced and at the end a wheel acceleration signal, the brake pressure is released, the constant hold time after Pressure increase is dependent on a damping of the wheel decelerator.

Arrangements of anti-skid devices of this type are used to block and when braking thus preventing the vehicle wheels from sliding. It is advantageous here as a criterion for achieving it the sliding threshold to use the amount of slip that occurs between the wheel and the roadway. In such arrangements, this slip is determined by comparing one of the vehicle speed corresponding reference variable, preferably derived from the wheel speed, with one of the wheel speeds corresponding size with the help of a speed comparison device, which when reached of a critical slip indicating the sliding threshold, switching of the brake pressure control valve device caused in terms of a reduction in the slip. But since the not directly sampled, but a reference variable derived from the actual course of the vehicle speed These types of anti-skid devices are independent and therefore not always analogous to this in principle unstable.

In order to stabilize the facilities, el. H. To avoid the triggering of false signals as a result of the between the reference variable and the actual vehicle speed intermittently occurring deviations To prevent this, it is necessary to use wheel decelerators that depend on the reference value correct the deceleration of the wheel. In a known arrangement of an anti-skid In the direction of the genre, the decelerators are assigned to the non-driven wheels (OS 19 61 741). A reference signal derived from the speed of these wheels is only used at Exceeding a certain deceleration of these wheels delivered. In another known arrangement an anti-skid device of the type, the decelerator is used to track the course of the subsequently influencing the reference signal output (OS 18 10 163).

To make a sufficiently accurate correction of the vehicle speed To achieve an analog reference value, it is necessary that the delay generator used very weakly attenuated, d. H. are very easily approachable. Such delay generators are however, it is particularly complex and therefore very expensive.

It is an anti-skid device is known in which

the braking force of rotation deceleration signals, the supported by a speed difference signal.

With this arrangement, the delay signal - b experiences a delay similar to attenuation (FR-PS 15 92 594, DT-OS 16 55 454).

A complex signal generator is also required with this arrangement of an anti-skid device.

The invention is based on the object of this -o To avoid the disadvantage and to arrange an anti-skid device of the type mentioned above create, using relatively simple and thus cheaper electronic means "a Control of the brake pressure in the sense of a reduction that corresponds exactly to the respective conditions of the slip guaranteed.

This object is achieved according to the invention by the combination of the features:

a) the wheel deceleration sensor (16 a) has - as is known per se - strong damping;

b) the valve device (13 a) is first switched by Jas's first control signal and, after the hold time (T ₁ ), by the second control signal - formed by the wheel decelerator.

It is advantageous if the dependent on the damping of the wheel decelerator when the expires Time before the specified holding time has elapsed, the brake pressure control valve device is triggered by the wheel displacement sensor output control signal in the second switching position causing a brake pressure reduction is switchable.

To adjust the brake pressure on each individual wheel according to the conditions prevailing on it control and thereby simplify the entire anti-skid system of the vehicle is also according to the invention provided that each vehicle wheel has a speed comparison device, a wheel deceleration sensor and a brake pressure control valve means associated therewith, the wheel speed signal by a known electronic device assigned to the corresponding wheel and the vehicle speed signal through a signal common to all wheels, also known per se electronic device for deriving a reference signal corresponding to the vehicle speed is formed from the wheel speed of all wheels.

The inventive arrangement of an anti-skid device is based on the knowledge that heavily damped electronic deceleration and acceleration sensors are structurally simpler and therefore much cheaper than weakly damped sensors, the strong damping leading to a strongly delayed output of the corresponding -b or -ffc signal but does not affect the instantaneous fall of the signal. Under heavily damped deceleration and acceleration sensors are to be understood in principle sensors whose damping is set so that there is a speed drop on the controlled wheel, iier 1.5 to 3.5 km / h greater than with conventional encoders, which in the Usually show a speed drop of 1.5 to 3 km / h. The drop in speed occurs in the time from exceeding the response threshold until the signal is emitted. Ultimately, however, a damping value is decisive, which prohibits the use of the encoder in the known anti-skid device arrangements of the type, which are subject to high requirements with regard to operational safety and the utilization of the braking force absorption capacity of the wheels in all operating states.

The use of such strongly damped deceleration and acceleration sensors in three arrangements of anti-skid devices is made possible according to the invention in that the brake pressure is first applied immediately as a function of a zl _v signal emitted by the speed comparison device (15α) and only after one of the damping has elapsed of the sender as well as the time dependent on the respective wheel speed is controlled by a - ύ signal emitted by the sender. This eliminates the disadvantageous effect of the strong damping and, on the other hand, stabilizes the anti-skid device arrangement in the area of the brake pressure reduction even with a relatively low response threshold of the speed comparison device. The latter, however, has the advantage that after braking has been initiated, the increase in brake pressure is interrupted as soon as a relatively small slip is reached, whereby 2. B. the compressed air consumption in compressed air burner systems is lower. The brake pressure curve following the interruption of the increase in brake pressure according to the invention ensures good utilization of the braking force absorption capacity of the wheel as a function of the respective road condition and a soft brake pressure regulation.

Through the use of heavily damped wheel accelerators can be both a response of the sender in the braking phase, in the high wheel decelerations occur, as well as an incorrect response of the encoder caused by vibrations on the wheel be avoided. In addition, the number of poles of the generators can be reduced or it can simple signal generators with a small number of teeth can be used.

The use of delay allowances for Controlling the brake pressure in the last brake pressure reduction area also offers the option of dropping of the - b signal to maintain a residual pressure, without impairing the anti-skid function of the facility.

Since the pressure rise again is not affected by the strong damping, instantaneous Fall of the + fe signal and not of, as a rule, the actual fall below the critical one The time-dependent decrease in the / ((- signal is made dependent on the slip, is the one according to the invention Arrangement of an anti-skid device stable even when the wheel starts up again.

Another advantage is that the inventive arrangement of the anti-skid device in the event of failure the speed comparison device or the deceleration and acceleration sensor the encoder or the speed bits comparison device (15a) remains functional to a limited extent, so that the entire arrangement does not fail completely.

An exemplary embodiment of the invention is described in greater detail below with reference to the drawing explained. It shows

Fig. 1 is a schematic block diagram of a Anti-skid system consisting of four inventive arrangements of anti-skid devices with

The voltage supplied by the converters 3 a, 3 b, 3 c, 3d is present, so that only the speed of the faster wheel, which is less prone to sliding, is decisive for the formation of the reference voltage analogous to the vehicle speed.

The response threshold of the speed comparison device 15 a is chosen so low that the device 15 a a control signal Δ _ν already after reaching a relatively very small difference

Pulses, the frequency of which is a measure of the speed of the wheel is, furthermore a frequency-voltage converter 3 a, which converts these pulses into a

a common device for generating a reference signal corresponding to the vehicle speed,

F i g. 2 a logic circuit for the arrangement of an anti-skid device according to FIG. 1, symbolically shown,

F i g. 3 shows a time-pressure-speed diagram for the arrangement of the anti-skid device according to FIG the Fi g. 1 and 2.

As can be seen from FIG. 1 of the drawing, the anti-skid system shown relates to a four-way reference voltage between the speed of the vehicle and that of the wheel-wheel vehicle, each wheel emitting a voltage corresponding to the speed of the invention,
according to the arrangement of an anti-skid device la, the generator 2a, the converter 3a, the

Ib, Ic, lrf is assigned. In the following, the decorative element 6a, the damping elements 1a , 8a and the arrangement 15 assigned to the right front wheel FR, the triggers 9a, 10a forming an electronic wheel-Ia, are described in more detail. The deceleration and acceleration sensors 16a associated with the other wheels, the ordered arrangements Ib, lc, Id are identically strongly damped and are thus designed to be relatively sluggish. ^{ur |} d display the sliding threshold when a

The anti-skid device la has, in its and the wheel deceleration and a restart order, a wheel acceleration driven by the vehicle wheel, each one generator la for generating electromagnetic control signal -b or + b with one of the damping and the respective Wheel speed dependent deceleration emits. The -b- or + b- signals are also converted to the voltage proportional to the logic circuit 12a, one with the 25 «.
Converter 3.j in operative connection via diode 4a. The logic circuit 12a is in accordance with FIG. 2

standing signal converter 5 for generating one from a first timing element 17 with dynamic reference voltage, which went to the vehicle speed 18, 19, a second timing element 20 with two inputs 21, 22 dynamic with maximum permissible deceleration of the vehicle and a third as analog Differentiator 6a to the DiiTcren 30 signal delay element designed timing element 23 decorate the voltage output by converter 3a. An input signal is at the inputs 18 and 21 attenuators Ta and 8a for the differentiating only at the transition from 0 to 1 and at the element 6a. a trigger 9 a for outputting a gear 19 and 22 only on the transition from 1 to 0 - b signal when one of the value -b is reached . The timers 17 and 20 deliver a speaking wheel deceleration, a trigger 10a 35 an output signal until their _{hold time Z 1} or Z ₂ for emitting a -fb signal has expired when a signal is reached, or at their inputs 19 and 22 the value + b corresponding wheel acceleration an input signal becomes effective. The timing element 23 and an output signal, for example as a differential trigger, are provided by a comparator 11a which is formed with respect to the input signal to compare the signal converter 5 delayed by a certain delay time T ₁ and output signal from the converter 3a until the input signal is deleted , benen voltages that are generated by the speed comparison device via a logic circuit Das

12 a with a brake pressure control valve 13 a in active 15 a delivered .1 _v signal is the input 18 of the connection. first timing element 17 and the input of the third

The generator 2 a, the converter 3 a, which is fed to the four timing element 23. The one from the wheel deceleration arrangements delivered by sliding protection devices la, Ib, 45 and wheel acceleration sensors 16a - feie. 1 rf common signal converter 5 and the ver signal is available at input 21 of the second simulator 11a form an electronic speed element 20 and the negated input of an AND speed comparison device 15 a, the one of the driving gate 24 at. The + fe signal is applied to input 19 generating speed corresponding, from the wheel of the first timing element 17 and the input 22 of the Speed-derived reference value with a 50 second timing element 20 is supplied. That from the first the variable speed corresponding to the wheel speed time element 17 output signal is a

OR gate 25 and an AND gate 26, at whose negated input the output from the timer 23 Output signal is available to an OR gate 27 trains-55 leads. The output signal of the timing element 20 is fed to the OR gates 25 and 27.

The anti-skid device la has in its order a brake designed as a directional control valve pressure control valve 13, which is shown in FIG. 2 in a

converter 5 pending input signal depends 60 from a compressed air tank 31 to a on there and whose further course of the Entladi.kurve of the right front wheel VR acting brake cylinder 3: capacitor corresponds approximately. The course of the leading line 33, 34, 35 is arranged. The output signal can be set in a known manner in such a way that the signal voltage of the vehicle is connected upstream. Two solenoid valves 37, 37 'serve the speed at maximum permissible deceleration 6 ₅ for switching the brake pressure control valve 13 to one of the vehicle. With the help of the four diodes of the three switch positions 4a shown schematically. 4fr. 4r, 4rf it is achieved that on the signal, both solenoid valves 37, 37 'are de-energized, then only the converter 5 is the highest of the four, then the brake pressure control valve 13 is in one

equals and when a certain difference is reached between the two variables (response threshold) emits a control signal that the logic circuit 12 a is fed.

The signal converter 5 consists in a known manner in principle of a resistor-capacitor circuit (RC element) and emits an output signal, the initial value of which depends on the value of the

(ι

a switching position causing a brake pressure increase 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, the brake pressure control valve 13 is then in a position which causes the brake pressure to be kept constant Switching position in which the brake cylinder 32 both from the atmosphere and from the compressed air tank 31 is separated. If the solenoid valve 37 is energized, but the solenoid valve 37 'is de-energized, so is then the brake pressure control valve 13 in a brake pressure reduction causing Switching position in which the brake cylinder 32 is connected to the atmosphere. The solenoid valves 37 and 37 'are controlled by the signals emitted by the OR gate 25 and the AND gate 24, respectively.

The mode of operation of the arrangement according to the invention according to FIGS. 1 and 2 will be explained below with reference to the diagram according to FIG. 3, where V _{r is} the time profile of the vehicle speed, V _{R is} the time profile of the wheel speed, Vf 'is the time profile of the pseudo vehicle speed, which is formed by the reference voltage output by the signal converter 5 , and P _{n represents} the time curve of the brake pressure acting on the right front wheel VR.

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 one hand, supplied to the Verglcicher 11a on the other hand via the diode 4 a the transducer 5 and, finally, the differentiator 6 a. The signal converter 5 supplies a reference voltage that is dependent on the highest of the voltages supplied by the four converters 3 a, 3 b, 3 r, 3d. which represents one of the vehicle speed analog and the so-called pseudo vehicle speed forming reference variable and is also fed to the comparator 11 α.

The differentiator 6 a differentiates the signal supplied by the converter 5 and emits an output signal corresponding to the respective deceleration or acceleration of the wheel, which is damped by the strongly damping damping elements 7 a, 8 a and by the trigger 9 a, 10 a when the corresponding sliding brw. Restart threshold is converted into a constant - b or + fc signal.

When the brake is not actuated, the brake pressure control valve 13 is in the position shown in FIG. 2 switching position shown. If a braking process is triggered by actuating the brake valve 36, the compressed air tank 31 is connected to the brake cylinder 32 via line 33.34, brake pressure control valve 13 and line 35 and a brake pressure increasing in accordance with the curve P _{B (l} -P _{Bi) is applied in the latter.}

It is assumed that when the effective brake pressure P _ßl (time /,) is reached, the wheel speed V _R has decreased compared to the pseudo vehicle speed Vf to such an extent that the response threshold of the speed _{comparison device 15a is exceeded, so that it emits an / I v} signal. This response threshold is selected to be so small that the device ensures that a / fy signal is output as soon as the critical slip is reached.

The ziy signal is on the one hand the first timing element 17, on the other hand fed to the third timing element 23, whereby both timing elements become effective without delay. The output signal given by the timer 17 excites the solenoid valve via the OR gate 25 37 and via the AND gate 26 the OR gate 27 in the AND gate 24, the solenoid valve 37 ', so that

ίο keep the brake pressure control valve 13 in its a constant the switching position causing the brake pressure is switched.

After the delay time T ₁ specified by the third timer 23 has elapsed (time t ₂ ) ,

_{the J v} signal present at the Zcit member 23 at the negated input of the AND gate 26 effective, whereby the output signal emitted by this is deleted. This also clears the signals emitted by the OR gate 27 and the AND gate 24. The solenoid valve 37 'is de-energized and the brake pressure control valve 13 is switched to its switching position causing a brake pressure reduction.

It is now assumed that when the brake pressure P _{B: t is reached} (point in time J ₃ ), a - b signal emitted by the wheel decelerator 16 ″ becomes effective on the timing element 20. As a result, the latter emits an output signal which superimposes the output signal of the timer 17 in the OR gate 25 and causes the solenoid valve 37 to remain energized as long as the -5 signal is effective. The -. "Signal also has the effect that the negated input of the AND gate 24 is also deleted, so that the solenoid valve 37 'remains de-energized.

The brake pressure control valve 13 thus remains in its switching position which brings about a brake pressure reduction _{even after the point in time J 3. However, the I 1} signal emitted by the speed comparison device 15a is no longer decisive for the extent to which the brake pressure is further reduced, but rather that of the wheel deceleration sensor 16i? delivered - b-signal. Has the wheel deceleration infoige the brake pressure reduction decreased so far that the - b signal is deleted (time r ₄ ). the solenoid valve 37 'is then again excited 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 - fc signal, for example, as a result of a deterioration in the road conditions before the delay time T ₁ expires, e.g. B. effective at time t "' , the deletion de:

at the negated input of the AND gate 24, the immediate de-excitation of the solenoid valve 37 'and thus there immediate switching of the brake pressure control valve 1'. in its switching position causing a brake pressure reduction. The delay time 7 ″ given by the timer 23 is dimensioned so that the point in time at which a -b signal becomes effective, if the road condition is good, shortly after the expiry of the delay time T ₁ T ₁ liegi It is now assumed that at time point t _5, the wheel acceleration sensor 16a emits a + fo signal during the restart of the wheel, which the inputs 19 and 22 of the timers 17 and 17 respectively

10 is fed. Due to the design of these inputs described at the beginning, however, the members 17 and 20 are only deleted when the + b signal drops out again after the wheel has restarted (time f ₇ ). The deletion of the two timing elements 17 and 20 and thus the de-excitation of the two solenoid valves 37, 37 'as well as the subsequent switching of the brake pressure control valve 13 α into a switching position causing a renewed increase in the brake pressure corresponding to the _{initial position it assumed at time / 0} thus depends, according to the invention, on the drop of the + b signal and not the 4 _V signal. The stop characters Z ₁ and Z ₂ are chosen so that they only expire after the fall of the + fe signal. They are used to store the - fo signal until they are deleted by the fall of a + b signal.

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

In the above-described arrangement of an anti-skid device, that of the vehicle speed corresponding reference variable derived from a variable corresponding to the wheel speed. However, within the scope of the invention it is possible to use the vehicle speed as the reference variable from others related sizes, such as

z. B. derived from the deceleration of the wheel.

For this purpose 3 sheets of drawings

Claims (3)

Patent claims: 1. Arrangement of an anti-skid device for vehicle wheels, in particular for road vehicles, with a generator driven by the monitored vehicle wheel, which is one of the wheel speed proportional signal generated from which a signal corresponding to the vehicle speed is derived; with an electronic speed comparison device, which compares the two signals and, if the difference exceeds a predetermined value, a first control signal gives up; with an electronic wheel deceleration sensor that differentiates the wheel speed signal, which emits a second control signal, if the wheel deceleration is a predetermined one Value exceeds; with a valve device that receives both control signals and such works so that when a control signal is received, the brake pressure is kept constant when stepping on of the other control signal, the brake pressure is lowered and at the end of a wheel acceleration signal the brake pressure is released, the hold time after the pressure increase is dependent on a damping of the wheel deceleration sensor, characterized by the combination of features: a) the wheel deceleration sensor (16 a) has - as is known per se - strong damping; b) the valve device (13 α) is first switched by the first control signal and, after the hold time (T ₁ ), by the second control signal - formed by the wheel decelerator. 2. Arrangement according to claim 2, characterized in that upon expiry of the damping of the wheel deceleration sensor (16 a) dependent tent before the end of the certain holding time (T ₁ ) the Brcmsdrucksteuerventileinrichtung (13 a) through the control signal emitted by the wheel deceleration sensor in the second, a switching position causing a brake pressure reduction is switchable. 3. Arrangement according to claim 1 or 2, characterized in that each vehicle wheel has a speed comparison device (ISa, b, 15 c, ISd), a wheel deceleration sensor (16 a, b, 16 c, 16 d) and a brake pressure control valve device (13a, 13 b , 13 c, 13 d) , wherein the wheel speed signal is assigned to the corresponding wheel, known electronic device (3 α, 3 b, 3c, 3d) and the vehicle speed signal is common to all wheels, also known per se electronic device (5) for deriving a reference signal corresponding to the vehicle speed from the wheel speed of all wheels.