GB2117070A

GB2117070A - Motor vehicle control arrangement

Info

Publication number: GB2117070A
Application number: GB08306451A
Authority: GB
Inventors: Marcel Andrei-Alexandru; Rudi Plog; Hans Prohaska; Wolfgang Scholl
Original assignee: SWF Spezialfabrik fuer Autozubehoer Gustav Rau GmbH
Current assignee: SWF Auto Electric GmbH
Priority date: 1982-03-22
Filing date: 1983-03-09
Publication date: 1983-10-05
Also published as: GB8306451D0; DE3210469A1; FR2523536A1; JPS58174054A

Abstract

In a control arrangement for a motor vehicle including a brake system and an engine, which can be arbitrarily switched off by the driver via a switching device, for example by a so-called stop-start device 40, the brake is arranged to be automatically applied when the vehicle speed is below a set value, or negative, upon switching-off of the vehicle engine (by switch 42). This saves an application of the handbrake at every stop such as at a traffic light which has been necessary until now. In the circuit shown, a switching signal for switching off the engine is tapped off at the output 36 of the "stop-start device" 40 and conducted to a switching stage 34 which produces the adjusting signal for the adjusting element in the form of an electric motor 15 acting on the parking brake linkage. Alternatively the adjusting element acts to retain foot brake pressure. <IMAGE>

Description

SPECIFICATION Motor vehicle control arrangement This invention relates to a control arrangement for a motor vehicle comprising at least one brake system and an engine, which may be switched on or off by switching commands of a switching device to be arbitrarily actuated by the driver.

Today's motor vehicles licensed for traffic are equipped with two brake systems on the ground of safety. The foot brake is mainly applied en route, while the parking brake is applied for stopping the vehicle at its destination or in front of a traffic light. Both brake systems are normally applied by a respective actuating lever which has to be operated by the driver. In particular at a stoppage in front of a traffic light a plurality of actuating operations are necessary. In the interest of saving of fuel the engine should be switched off.

Due to this measure the brake booster of most vehicles fails, so that the driver must bring about a considerable braking force, when the vehicle is to be held at a standstill on an inclined road. In order to avoid accidents caused by a vehicle rolling back the parking brake should be applied on the ground of safety. Before continuing the drive the engine has to be started again and the parking brake released. These complicated actuating operations distract the driver from his real task, namely observing the traffic. Thus the overall security of road traffic is impaired.

According to the invention in its broadest aspect there is provided a control arrangement for a motor vehicle comprising at least one brake system and an engine, which may be switched on or off by switching commands of a switching device to be arbitrarily actuated by the driver, characterised in that below a given road speed an adjusting signal for actuating an adjusting element is released by the switching command for switching off the motor vehicle engine, which adjusting element puts the brake system in its operating position and/or holds it in its operating position.

The invention is thereby based on the idea that in all situations of traffic in which the motor vehicle engine is arbitrarily switched off, a simultaneous braking of the vehicle seems to be reasonable. It is essential for the present invention that only a switching command for switching off the engine arbitrarily initiated by the driver releases and adjusting signal for applying the brake. If, for instance, the engine fails en route because of a defect, the brake must not be applied. A further contribution to safety is that in principle the brake is only automatically applied below a given driving speed. If thus the driver switches off the engine en route intentionally or unintentionally the brake is applied as late as when the driving speed amouhts to zero or nearly to zero.

The switching command for switching off the engine and thus for an automatic application of the foot brake can for example be tapped off from the ignition starter switch. In the switching position "ignition off" of the ignition starter switch a brake thus is applied in principle at a low driving speed or at a standstill of the vehicle. Thus, when the driver leaves the vehicle, he has not to apply the so-called handbrake in addition to switching off the engine, as has been usual until now.

The present invention is however of particular advantage for vehicles equipped with a so-called "stop-start device". In vehicles of this kind a solenoid valve in the fuel supply pipe is closed via a circuit upon actuation of a switch, so that the engine is stopped. Upon the actuation of other switches, for example upon the actuation of the clutch or accelerator pedals, the engine is started again, because the starter is controlled via a relay and the solenoid valve is opened again. In vehicles of this kind according to the present invention the adjusting signal for the adjusting element is to be derived from these switching commands for a short-duration switching on and off of the engine via a so-called "stop-start device". Thus at any stop in front of a traffic light, when the "stop-start device" is normally actuated, one brake system is also brought into the operating position.This is especially advantageous and reasonable with regard to vehicles comprising an automatic transmission. As is known the brake system of these vehicles need not be actuated even if the vehicle is to be stopped on a hill in front of a traffic light, because via the automatic transmission a low driving torque from the engine acts on the wheels. If however the engine were switched off by using the "stop-start device" this driving torque would no longer be available and the vehicle would roll back, if it were not equipped in accordance with the present invention. Thus in these vehicles traffic safety is decisively improved by the present invention because it ensures that in spite of an installation of the "stop-start device" the driver need not change the usual actuating operations.

According to an advantageous embodiment of the invention in addition to the application of the brake system the release of the brake system is also to be automatically coupled with the operating condition of the engine. By a switching command for switching on the engine arbitrarily released by the driver the brake system is thus also to be released again. In this case it should be ensured in the interest of traffic safety that the brake is only released, when the engine is running again. This can be achieved by a retarded release of the brake system. But better is a solution in which the operating condition of the engine is monitored and the release of the brake is only possible, when the engine has reached its idle speed.

The adjusting element automatically controlled upon switching off of the engine can act upon the parking brake or upon the normal foot brake. A version comprising an adjusting element acting upon the parking brake is especially preferred, if a switching command is evaluated by the ignition starter switch. Such a version meets today's normal standard and the foot brake system is not unnecessarily applied for days. In a system in which the switching command is utilised for the control of a "stop-start device" the adjusting member will, in contrast thereto, preferably act upon the foot brake system, because in this case the foot brake system is mostly only applied for a short time.

The present invention can be realised on the basis of two differing principles. In one case the brake system is to be brought into the operating position by the adjusting element and to be held in this operating position thereafter. Thus this principle will preferably be used, when the adjusting element acts upon the parking brake.

With regard to the other principle one assumes that the driver himself has already applied the brake. In this case the adjusting element is merely intended to hold the brake system in its operating position. This principle is preferably applicable to systems of a kind in which the adjusting element acts upon the foot brake system. Thus in the latter principle it is assumed that, in front of a traffic light, the driver brakes the vehicle by means of the foot brake anyhow, so that the adjusting element has merely to maintain the braking force already brought about by the driver.

Vehicles which have already been licensed can relatively simply be developed in the sense of the present invention, if one provides that one adjusting element, for example a reversible electric motor, directly acts upon the actuating lever of the brake system and thus displaces this actuating lever in a way in which the driver would normally do it. However solutions in which the adjusting member acts upon the brake system anywhere else, for instance upon the brake cable of a parking brake, have a simpler design.

Solutions of this kind should in any case ensure that in addition to the automatic course of applying the foot brake an arbitrary application is also possible. This is achieved by a clutch between the adjusting element and the actual brake system, which clutch may be manually operated.

The basic idea of the invention can be realised without a considerable amount of additional technique in vehicles comprising a brake booster which supports the braking force produced by the driver via a brake pedal. In such a version the adjusting element need not bring about the total braking force. A version of this kind is especially advantageous in so-called motor-driven brake boosters, because in this case the electric motor can also bring about a torque supporting the braking force, when the motor vehicle engine is switched off.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of an embodiment in which the adjusting member acts upon the parking brake system, Fig. 2 is a circuit diagram for controlling the adjusting element according to Fig. 1, Fig. 3 is a different embodiment comprising an adjusting element acting upon the parking brake, Fig. 4 is a third embodiment of an adjusting element acting upon the parking brake, Fig. 5 is a circuit diagram of an embodiment in which the adjusting element controls a solenoid valve in the brake line, Fig. 6 is an embodiment comprising a brake booster, Fig. 7 is a circuit diagram for the embodiment according to Fig. 6, Fig. 8 is a further embodiment of a motordriven power booster, and Fig. 9 is a circuit diagram for the embodiment according to Fig. 8.

In Fig. 1 parts of a motor vehicle parking brake are shown. In particular this comprises an actuating lever 10, which acts upon a brake cable 1 The position of the actuating lever 10 can be arrested by a pawl 12, which may be actuated via a push-button 1 3. The pawl 12 co-operates with a toothed segment 1 4. Such versions are known in the art and need not be described in detail.In the present example the toothed segment 1 4 serves as an output element of a reversible electric motor 15, which drives the toothed wheel 1 6 cooperating with the toothed segment 1 4. The electric motor 1 5 serves as an adjusting element for applying this parking brake, because it may displace the toothed segment and thus also the actuating lever 10 in both directions of displacement, as long as the pawl 12 is in gear with the toothed segment 14. It is important that the parking brake can be arbitrarily applied by the driver independently of the position of the electric motor and of the toothed segment 14 driven by this motor.This is ensured by the pawl 12, by means of which a clutch is realised between the actuating lever and the toothed segment 14, which forms the output element of a self-retarding gear. In the present case a wiper motor known as such is namely used as electric motor 15, in which the armature shaft has a worm mating with a worm wheel which is connected with the toothed wheel 1 6 in a manner protected against twisting.

Thus in this version according to Fig. 1 the adjusting element, namely the electric motor 15, acts upon the parking brake system. Moreover this version includes the feature that the actuating lever is directly displaced by the adjusting element. Thus the adjusting member provides in practice the displacement formerly carried out by the driver himself. From the position of the actuating lever 10 it can be seen at any time, whether the parking brake occupies its operating position or is released.

Fig. 2 shows a circuit diagram for controlling the electric motor 1 5 of the version according to Fig. 1.

The electric motor 1 5 is controlled via a reversing switch 20, which is operated by a relay 21. The reversing switch 20 comprises two movable bridging contacts 22 and 23 which may be connected in an electrically conductive manner with the terminals 24 and 25 of a voltage source not shown in detail. In the rest position, the movable bridging contacts rest upon the stationary contacts 26 and 27, but in the operating position, that means when the relay 21 is energised, a circuit to the stationary contacts 28 and 29 is closed. From Fig. 2 it can be seen that between the stationary contact 26 and one motor terminal a position switch 30 is looped which is closed in the operating position of the brake system and which is only open when the brake system is fully released.Furthermore, a brake indicator lamp 31 is controlled via the position switch - as shown in Fig. 2. This means in practice that the brake light indicator switch known as such has to be provided with a second bridging contact which is looped in the circuit of the electric motor 1 5.

The operating current of the electric motor 1 5 is controlled via a relay 32. This relay 32 is controlled via a pulse generator 33, whose pulse time is greater than the time of displacement maximally necessary for an action of displacement. The pulse generator 33 is triggered by an AND-gate 34, to which switching signals for switching on and off the motor vehicle engine are conducted as well as a speed-dependent control signal via the leads 35, 36 and 37. The control signal 37 originates from a driving-speed detector 38 and is released as soon as the driving speed falls below a given limit value. This limit value can be the driving speed zero, which means the control signal is only released at a standstill of the vehicle. Other versions are, however, also conceivable in which the driving speed detector only releases a control signal when the vehicle moves backwards.Combinations are also conceivable in which the detector 38 releases a control signal in the case of moving ahead only below a given driving speed, but, in the case of moving backwards, independently of the driving speed. The switching signal for switching off the motor vehicle engine on the lead 36 is conducted to an AND-gate 39, whose other input is connected to the output of the pulse generator 33 and controls the relay 21 of the reversing switch 20. A circuit of a so-called "stop-start device" is designated with the reference numeral 40. Such a circuit is known in the art.The total wiring of such a circuit is for example described on page 1 31 of the technical journal "Krafthand", No. 3 of February 7, 1 981. For the present invention it is sufficient to state that the circuit 40 supplies a signal for switching off the motor vehicle engine on the lead 36 and a signal for switching on the motor vehicle engine on the lead 35. For example, the lead 36 is conducted to a solenoid valve which interrupts the fuel supply to the engine, while the lead 35 is conducted to a starter relay. Moreover this circuit 40 can also comprise an output on which a road-speed-dependent signal may be tapped off. This signal is conducted to the roadspeed detector 38.

To the circuit 40 are conducted signals of a switching device designated as a whole with the reference numeral 41. This switching device 41 may be arbitrarily actuated by the driver and releases switching commands for switching on and off the engine. For example this switching device 41 can comprise a switch 42 arranged on the steering column switch of the motor vehicle, through which the vehicle engine can be switched off in front of a traffic light in a known manner by touching this switch 42 for a short time. The engine can be started again in a known manner via further switches 43 and 44 which are coupled with the clutch pedal or the accelerator pedal. In Fig. 2 it is indicated by broken lines, upon which leads 35 or 36 these switches act. The two leads 35 and 36 are decoupled via diodes 45 and are conducted to a common input of the AND-gate 34.Instead of these diodes 45 and OR-gate could also be provided. Moreover in Fig. 2 a road-speed generator, for example a speedometer generator 46, is indicated whose signal is processed by the circuit 40.

The circuit arrangement according to Fig. 2 operates as follows: In the switching position of the various switching elements shown in Fig. 2 the indicator lamp 31 is not illuminated: this indicates that the parking brake which may be actuated by the motor-driven adjusting element 15, is released, If now the switch 42 of the switching device 41 is arbitrarily actuated by the driver at a stop before a traffic light, a switching command is released for switching off a motor vehicle engine not shown in detail. The switching signal of this switch 42 is conducted to the circuit 40 of the "stop-start device". When the road-speed is below a given speed of, for example 10 km per hour, which speed is measured by the speedometer generator 46, the circuit 40 produces a signal on the lead 36.When the speed detector 38 detects that the vehicle is idle a signal may also be measured at the other input of the AND-gate 34. Thus this AND-gate 34 produces a trigger signal for the pulse generator 33, so that the relay 32 is energised for a given period of time.

Simultaneously the AND-gate 39 supplies a signal to energise the relay 21, so that the reversing switch 20 is changed over. Thus the electric motor 1 5 is connected to operating voltage via the movable bridging contacts 22 and 23, which rest upon the stationary contacts 28 or 29, and rotates in a direction of rotation which displaces the actuating lever 10 and thus also the parking brake into the operating position. When the pulse time of the pulse generator 33 has expired, the relays 32 and 21 are de-energised and the electric motor is dead. Thus the parking brake is applied and the vehicle is stopped by a switching command which serves for switching off the engine.Because the actuating lever is connected with the electric motor via a selfretarding gear, the parking brake is also locked in its operating position, because the pawl 12 remains in gear with the toothed segment 14. By releasing this pawl the parking brake can however be manually released at any time. When the switches 43 and 44 are actuated at a later time, whereby a switching element is released for starting the engine, signals may be measured on the leads 35 and 37, so that the AND-gate 34 again triggers the pulse generator 33. Thus the relay 32 is energised. However the relay 21 continues to be de-energised, because now no signal is conducted from the control lead 36 to one input of the AND-gate 39.Because the parking brake is locked in its operating position and thus the position switch 30 is closed, the contact of the relay 32 closes the operating circuit of the motor in such a way that the latter now rotates in the opposite direction of rotation and thus resets the actuating lever 10 into its rest position and simultaneously releases the parking brake. Because the pulse time of the pulse generator 33 is greater than the maximum time of displacement, the operating circuit of the electric motor 1 5 is now opened by the position switch 30 in dependence on the brake pressure or on the path, when this switch changes over into its rest position with fully released brake, in which rest position the indicator lamp 31 is no longer applied to voltage either.In one direction of rotation for applying the parking brake thus the motor 1 5 is controlled in dependence on time, but in the other direction of rotation is controlled in dependence on path or on brake pressure. This is advantageous, because in the course of its service time the displacement path for applying the parking brake increases and thus the displacement path necessary for stopping the vehicle cannot be detected by a path-dependent position switch.

This is, however, possible when the brake is released. It is thereby ensured by the position switch 30 that the electric motor does not run for an unnecessarily long time or remains locked in the end position for an unnecessarily long time.

Furthermore disturbing noises are avoided in a version in which the pawl 1 2 is provided with an inciined stop face on one side, so that, when the toothed segment 14 has a counter-clockwise direction of rotation the pawl 1 2 can jump from tooth to tooth.

Moreover, the position switch 30 ensures that the electric motor is not unnecessarily controlled, if upon release of a switching command for switching on the engine again the parking brake has already been released manually.

When the motor-driven adjusting element 1 5 is controlled by a circuit arrangement according to Fig. 2 the switching commands for switching on and off are conducted to the circuit 40 of a "stopstart device" and the switching signals are tapped off at the output of this circuit 40. These switching signals are eventually evaluated in a switching stage, namely the AND-gate 34 for producing an adjusting signal for the motor-driven adjusting element 1 5. Thus this switching stage 34 evaluates a switching signal on the lead 35 or 36 with a control signal of the speed detector 38 in the way of a logical AND-operation in that an adjusting signal, namely a trigger signal for the pulse generator 33, is only released, when the road-speed is below a given limit value.The circuit arrangement could, of course, be also modified in a way that the switching commands of the switches 42 or 43 or 44 are directly conducted to the leads 35 or 36. Moreover a delay element could be looped in the lead 35, so that the adjusting signal for the electric motor 1 5 is retardedly released upon switching-on of the engine. Thereby the delay time should be greater than the maximally necessary time interval for starting the motor vehicle engine. In this way it is to be ensured that the brake system is only reset into its rest position, when the engine of the motor vehicle has reached its idling speed and thus in vehicles comprising an automatic transmission a certain driving torque is again available.In an improved version a monitoring stage for the revolutional speed of the engine could be inserted instead of this delay element, which monitoring stage provides that even if the starting operation lasts for a long time the parking brake can only be released, after the engine has reached its idling speed.

Figs. 3 and 4 are schematic views of embodiments in which the adjusting element does not act upon the actuating lever 10 of a parking brake system. In the embodiment according to Fig. 3 the electric motor 1 5 serving as an adjusting element drives a drum 49 via a self-retarding gear, which drum serves for winding up and off a brake cable 11. On the actuating lever 10 a pull member 50 is suspended in a way that the brake cable 11 may be deflected from the stretched position into a bent position shown by broken lines, thus substantially perpendicularly to the pull direction of the cable. The electric motor 1 5 could, for example, be controlled via a circuit 48 similarly to Fig. 2. In one direction of rotation the brake cable 11 is wound up the drum 49 and thus the parking brake is brought into the operating position.In the other direction of rotation of the electric motor the brake cable 11 can be wound off again. The position switch 30, which in this case is closed in the rest position of the actuating lever 10 and open in the operating position of the parking brake provides that the electric motor 1 5 is only controlled upon switching off the motor vehicle engine, when the parking brake still occupies its rest position. But when the actuating lever 10 is already in its operating position shown by broken lines and thus the brake cable 11 is already tensioned, the electric motor is not controlled unnecessarily. As compared to the embodiment of Fig. 2 this solution according to Fig. 3 has indeed the disadvantage that the parking brake can only be released via the motor-driven adjusting element. Furthermore, it is disadvantageous that the position of the actuating member 10 does not correspond to the actual operation condition of the parking brake. However the parking brake can be manually applied, when the brake cable 1 is wound off.

In the version according to Fig. 4 the electric motor 1 5 with the drum 49 for the brake cable 11 is directly secured on the actuating lever 1 0. This version is advantageous because of its compact and uncomplicated mode of construction.

In the embodiments described so far the adjusting element acts upon the parking brake.

Furthermore, in these embodiments the adjusting member has to bring the parking brake into its operating position and hold it in the latter. In the embodiment schematically shown in Fig. 5, in contrast thereto, the adjusting element acts upon the foot brake, whereby merely the braking force produced by the driver is to be maintained by an adjusting element. Two brake lines 61 and 62 are conducted from a brake master cylinder to two differing brake circuits. The brake pressure in one circuit can be maintained by a solenoid valve 63 closing the brake line 61. From the schematic circuit diagram it can be seen that again a switching signal for switching on and off the engine is derived from a circuit 40 of a "stop-start device". On the signal lead 64 a signal is to be retained after switching off of the engine until the engine is started again.With this switching signal a signal of a speed detector 38 and a signal of a brake-pressure dependent position switch 30 are interconnected via a switching stage comprising an AND-gate 34. The adjusting signal released by the AND-gate is conducted to the solenoid valve 63. This version operates as follows: It is assumed that prior to a stop before a traffic light the driver has applied the foot brake system via the actuating lever 10. This means that in both brake circuits 61 and 62 a sufficiently high brake pressure is built up, so that the position switch 30 responds. This position switch can be combined in a constructional unit with the stop-lamp switch.

The vehicle is thus braked, so that a control signal may eventually also be measured at the output of the speed detector 38. If the driver now actuates the switch 42 and thus releases a switching command for switching off the motor vehicle engine all conditions are met that the switching stage with the AND-gate 34 releases an adjusting signal to the solenoid valve 63, which responds.

Then the brake pressure in one brake circuit with the brake line 61 is maintained, even if the actuating lever 10 is no longer depressed. If a switching command for switching on the motor vehicle engine is released at a later time, the signal disappears on the lead 64, so that at the output of the AND-gate 34 a signal can no longer be measured. The solenoid valve 63 to be regarded as an adjusting element again occupies its rest position, whereby the brake pressure in the brake line 61 is reduced. This version is especially suitable for motor vehicles equipped with a socalled anti-blocking system, because in that case a solenoid valve 63 is necessary anyhow.Then the corresponding signals from the "stop-start device" or the speed detector 38 or the stop-lamp switch 30 have only to be supplied to the electronic regulator of this anti-blocking system correspondingly logically interconnected.

Figs. 6 to 9 relate to embodiments comprising a motor-driven power booster. Power boosters of this kind are described in all details in the German patent application P 30 31 643.9 to which reference is explicitly made. It is therefore sufficient when the components essential for the functioning are described below.

The power booster unit according to Fig. 6 designated as a whole with the reference numeral 70 has an input rod 71, which is connected to an actuating lever, for example a pedal. An output rod 72 is operated by a spindle 90 and presses against a brake master cylinder, not shown in detail. An electric motor, not shown in detail, has a worm shaft 73, whose rotary movement is transmitted to a sleeve 76 via a worm wheel 74 and an overrunning clutch 75. This sleeve 76 has to be regarded as a first element of a screw-and-push gear whose second element is the spindle 90 which is axially displaceable in the sleeve 76. The spindle 90 has an external thread in whose grooves the balls 77 roll, which are supported on the sleeve 76. The first half 78 of a clutch 79 is longitudinally displaceably, but non-rotatably guided in the casing 80 of the brake booster 70.

The second half 81 of the clutch 79 is seated at the end of the spindle 90 in a manner protected against twisting. The two clutch halves, of which each can comprise several friction disks, are pressed against each other by a pressure exerted on the input rod, thus by the braking force brought about by the driver. Because one clutch half is non-rotatable the rotary motion of the spindle 90 is braked or impeded, when the two clutch halves rest firmly against each other. Thereby the mode of operation of this brake booster can already be illustrated. If the first element of the screw-andpush gear, namely the sleeve 76, is turned and the two clutch halves are out of gear, the spindle 90, which has to be regarded as the second element of the screw-and-push gear, is turned together with the sleeve 76 due to the friction. Then an axial displacement of the spindle 90 does not result.If the clutch 79 is now operated and thus the rotary motion of the spindle 90 is impeded, the latter is screwed within the sleeve 76 in the direction of arrow A, so that the foot brake system is operated. Thereby the supporting braking torque brought about by the electric motor is the greater the greater is the braking force the driver provides via the input rod 71. When the braking force produced by the driver diminishes, the spindle 90 is reset into the starting position shown by a pressure spring 82. So far, the functioning of a normal braking operation fully corresponds to that of known systems.

A brake booster of this kind can now be further developed in the sense of the present invention in that it is provided that the adjusting element causes a displacement motion in the brake booster having the same effect as a displacement of the actuating lever and thus of the input rod 71.

To achieve this it is obviously necessary to brake the rotary motion of the spindle 90. In the embodiment according to Fig. 6 this is achieved by an electromagnetic adjusting element 83 whose winding 84 is arranged in the bell-shaped part 85 of the first clutch half 78. The end 86 of the spindle 90 emerges into this winding. An inner ring 87 of a ball bearing is pressed onto this spindle, which inner ring serves as a stop for the second clutch half 81. When the electromagnetic adjusting element is energised the clutch 79 is thus brought into its operating position. When the electric motor rotates, the spindle 90 is moved in the direction of arrow A, even if the brake pedal is not actuated. Thus the foot brake system is brought into its operating position and held therein until the electromagnet 83 is switched off again.

Fig. 7 shows a schematic circuit diagram for the version according to Fig. 6. This circuit diagram shows that the electromagnetic adjusting element 83 is controlled via the relay 33, when an appropriate switching signal of the circuit 40 in the "stop-start device" and of the speed detector 38 appears. The electric motor 1 5 of the brake booster 70 is controlled via a switch 88, which is actuated via the brake pedal 1 0. In such a version it is assumed that the driver applies the brake pedal prior to a stop before a traffic light and thus puts into operation the electric motor 1 5 of the brake booster 70. If now the motor vehicle engine is switched off, the electromagnetic adjusting element 83 is controlled via the relay 33 and thus the clutch 79 is actuated.Thereby the torque of the electric motor 1 5 of the brake booster is transformed into an axial displacement of the spindle 90 and thus of the output rod 72, whereby possibly the input rod 71 is also displaced. The relay 33 and thus also the electromagnetic adjusting element 81 remains energised and the operating position of the foot brake system is retained, until a switching command for switching on the motor vehicle engine is again released.

Whereas in the version according to Figs. 6 and 7 a displacement action is initiated through an additional electromagnetic adjusting element, which displacement action corresponds to that initiated by the driver in applying the brake pedal.

In the version according to Figs. 8 and 9 the engagement of the clutch is effected by a reversal of the direction of rotation of the electric motor 1 5 of the brake booster 70. The design of this brake booster substantially corresponds to that of Fig. 6, so that only the modifications of the design will be described. To begin with, there is no overrunning clutch between the worm wheel 74 and the sleeve 76, so that the latter can also be driven in both directions of rotation. The sleeve 76 has an internal thread, which is indicated at 91. In the grooves of this thread 91 the balls 77 can roll. The spindle 90 has a stop plate 92 on the end of its output side. The internal thread 91 of the sleeve 76 has a different direction of the thread pitch in comparison with the external thread on the spindle 90.Between the end 86 of the spindle 90 and one clutch half 78 an overrunning clutch 93 is provided, which in a second direction of rotation of the drive motor 1 5 impedes the rotary motion of the spindle 90. This sytem operates as follows: When, during normal operation, the electric motor 1 5 rotates in one direction, the sleeve and the spindle can rotate with it, because the overrunning clutch 93 does not impede the rotary motion of the spindle in this direction of rotation.

The rotary motion of this spindle 90 is only impeded, when due to a pressure exerted on the brake pedal and thus on the input rod 71 the clutch halves 78 and 81 are pressed against each other. So far the mode of operation corresponds to that of Fig. 6. But if now the direction of rotation of the electric motor is changed and the sleeve 76 rotates in the reverse direction, the spindle 90 is only taken along until the overrunning clutch becomes effective. Then the rotary motion of the spindle is impeded by the overrunning clutch 93, which takes the place of the clutch 79. Now the balls 77 move in the grooves of the internal thread 91 of the sleeve, whereby again a displacement motion of the spindle in the direction of arrow A is effected.Thus the foot brake system of the motor vehicle is also brought into the operating position and held therein in this manner, as long as the electric motor 1 5 is switched on. In this version the particular design of the screw-and-push gear is essential in that in spite of the change in the direction of rotation of the electric motor the same displacement motion of the spindle 90 is achieved. The mode of operation of this gear can easily be illustrated, if in one case the balls 77 are assigned to the sleeve 76 and it is assumed that these balls run in the external thread of the spindle. In the other case the balls, which rest against the stop plate 92, are to be assigned to the spindle 90 and run in the thread grooves 91 of the sleeve 76.

Fig. 9 shows a circuit diagram for the version of Fig. 8. From this circuit diagram it is to be seen that the electric motor 1 5 is controlled via a reversing switch 100, which is switched by a relay 101. in the rest position shown the operating circuit for this electric motor 1 5 is prepared. It is closed by a switch 88, which may be actuated by the brake pedal 10. So far the control of the electric motor 1 5 corresponds to that of the version according to Fig. 7. However the direction of rotation of the electric motor is reversed, when an adjusting signal appears at the output of the AND-gate 34 and thus the relay 101 becomes energised. Simultaneously a second relay 102 in the operating circuit of the motor is energised, whose switch contact bridges the brake pedal switch 88. In the then effected circuit with changed over reversing switch 101 a brakepressure-dependent switch 103 is also inserted, which at first is closed, but is opened with a given brake pressure. This means that the electric motor 1 5 is switched off as soon as the necessary brake pressure is built up in the brake system. Although the electric motor is switched off by this brakepressure-dependent switch 103, the spindle 90 cannot reset, because for this purpose a rotary motion of the spindle would be necessary, which rotary motion is impeded by the overrunning clutch 93. For resetting the spindle rather a rotary motion of the electric motor in the reverse direction of rotation is necessary. This rotary motion is initiated, when the relay 101 becomes de-energised again. It is true that also the relay 102 de-energises, but the brake pedal switch 88 maintains the circuit to the electric motor 87 until the rest position is reached again. Thus in this embodiment it is absolutely necessary that the input rod 71 is operatively connected with the bell-shaped part 85 of the first clutch half 78, because only in this case the brake pedal switch 88 remains closed, even if the driver removes his foot from the brake pedal 10 at a standstill of the vehicle.

Claims

1. A control arrangement for a motor vehicle comprising at least one brake system and an engine, which may be switched on or off by switching commands of a switching device to be arbitrarily actuated by the driver, characterised in that below a given road speed an adjusting signal for actuating an adjusting element (1 5, 63, 83) is released by the switching command for switching off the motor vehicle engine, which adjusting elements puts the brake system in its operating position and/or holds it in its operating position.

2. A control arrangement according to claim 1, comprising a so-called "stop-start system" including a circuit controlled via switches of a switching device on which circuit signals for switching on and off the motor vehicle engine may be tapped off, characterised in that a switching signal for switching off the motor vehicle engine to be tapped off at the output of the circuit (40) is conducted to a switching stage (34) which produces the adjusting signal for the adjusting element (15, 63, 83).

3. A control arrangement according to claim 1, comprising a so-called "stop-start system" including a circuit controlled via switches of a switching device, on which circuit signals for switching on and off the motor vehicle engine may be tapped off, characterised in that the switching signal of a switch (42; 43, 44) conducted to the circuit (40) for switching off the motor vehicle engine is directly conducted to a switching stage (34), which produces the adjusting signal for the adjusting element (1 5, 63, 83).

4. A control arrangement according to any one of the preceding claims, characterised in that a rod speed detector (38) releases a control signal as soon as the road speed is below a particular limit value, and that the control signal and a switching signal released by the switching command for switching off the motor vehicle engine are conducted to a switching stage (34), which evaluates the control signal and the switching signal in the way of a logical AND-operation and produces the adjusting signal for the adjusting element (15).

5. A control arrangement according to claim 4, characterised in that the road speed detector (38) releases a control signal, when the road speed is zero.

6. A control arrangement according to claim 4 or 5, characterised in that the road speed detector (38) releases a control signal when the vehicle moves in the reverse direction.

7. A control arrangement according to any one of the preceding claims, characterised in that by a switching command for switching on the motor vehicle engine the brake system is released.

8. A control arrangement according to claim 7, characterised in that in comparison with the time of release of the switching command for switching on the motor vehicle engine the brake system is released with a delay.

9. A control arrangement according to claim 7 or 8, characterised in that the brake system is only released when the motor vehicle engine is running.

10. A control arrangement according to any one of the preceding claims, characterised in that the adjusting element (15) acts upon the parking brake system.

11. A control arrangement according to any one of the preceding claims, characterised in that the adjusting element (63) acts upon the foot brake system.

12. A control arrangement according to claim 10 or 11 , characterised in that an actuating lever (10) of the brake system is displaced by the adjusting element (15).

1 3. A control arrangement according to claim 12, characterised in that the adjusting element is a reversible electric motor (15), which displaces the actuating lever (10) in both adjusting directions via an output element (14) of a selfretarding gear, preferably a worm gear, and that between the output element (14) and the actuating lever (10) is provided a coupling which may be manually operated and, for example, has the shape of a pawl (12).

1 4. A control arrangement according to claim 10, characterised in that the adjusting element is a reversible electric motor (15), which drives a drum (49) for winding up and off a brake cable (11) of the parking brake system via a selfretarding gear, and that via an actuating lever (10) of the parking brake system the brake cable (11) is deflectable substantially perpendicularly to the pull direction of the cable.

1 5. A control arrangement according to claim 10, characterised in that the adjusting element is a reversible electric motor (1 5), which drives a drum (49) for winding up and off a brake cable (11) of a parking brake system via a selfretarding gear and that the electric motor (1 5) with the drum (49) is secured to an actuating lever (10) of the parking brake system.

16. A control arrangement according to any one of claims 13 to 15, characterised in that in one direction the electric motor (15) is controlled in dependence on time for operating the brake system and in the other direction it is controlled in dependence on the path or brake force for releasing the brake system.

1 7. A control arrangement according to claim 16, characterised in that to the brake system is assigned a position switch (30) which in the operating condition of the brake system occupies a switching position which is different from that of the rest position of the brake system, and that the motor circuit in one direction of rotation of the motor is switched for releasing the brake.

1 8. A control arrangement according to claim 17, characterised in that to the electric motor (1 5) operating voltages of different polarities are conducted via a relay-operated reversing switch (20) comprising two movable bridging contacts (22, 23) which by turns rest upon stationary contacts (26, 28;; 27, 29), whereby between one terminal of the motor and one stationary contact (26) controlled for releasing the brake system is looped the position switch (30), which is closed in the operating position of the brake system and is only opened with completely released brake, and that the operating circuit of the electric motor is furthermore switched via a contact of a relay (32), which is controlled by a pulse generator (33) triggered by the adjusting signal, which pulse generator energises the reversing relay (21).

1 9. A control arrangement according to claim 11, characterised in that the adjusting element in its operating position arrests the actuating lever of the foot brake system.

20. A control arrangement according to claim 11, characterised in that the adjusting element is a solenoid valve (63) which in its operating position maintains the brake pressure of the foot brake system.

21. A control arrangement according to claim 20, characterised in that the solenoid valve (63) is cor,trolled via an AND-gate (34) to whose inputs is conducted a signal of the circuit (40) of the "stop-start system" as well as a control signal of the speed detector (38) and a signal of a brake pressure switch (30).

22. A control arrangement according to claim 11, characterised in that the foot brake system includes a so-called brake booster (70) comprising a drive element (1 5) which supports the brake force produced by the driver via a brake pedal, and that upon release of an adjusting signal this drive element brings the foot brake system into its operating position and/or holds it in its operating position.

23. A control arrangement according to claim 22, characterised in that the brake booster comprises an adjusting member (83) which produces an adjusting motion having the same effect as a displacement of the brake pedal.

24. A control arrangement according to claim 23, characterised in that the brake booster (70) comprises a pressure-sensitive element (79) actuated by the brake pedal via which pressuresensitive element the braking force brought about by the brake booster is controlled, and that the adjusting member (83) acts upon this pressuresensitive element (79).

25. A control arrangement according to any one of the preceding claims with a brake booster, which comprises an input rod to be actuated by a brake pedal and an output rod acting upon the piston of a brake master cylinder and an electric motor with an output element the direction of rotation of which is transformed in an axial displacement of the output rod via a gear and a clutch and a clutch torque dependent on the brake pedal pressure, characterised in that the clutch (79) is operated upon release of an adjusting signal and thus the output rod (72) is brought into an operating position, when the electric motor is running and/or is held in the operating position.

26. A control arrangement according to claim 25, characterised in that the first element (76) of a screw-and-push gear may be driven by the output element (73) of the electric motor and the second element (90) of this screw-and-push gear acts upon the output rod (72), that one half (81) of the clutch (79) is coupled with this second element (90) in a manner protected against twisting and that the other half (78) of the clutch (79) is non-rotatably held, that the latter half (78) of the clutch (79) is pressed against the other clutch half (81) by a movement of the input rod (71) and thus in its operating position a rotary motion of the second element (90) of the screwand-push gear is braked, which entails an axial motion of this second element (90) of the screwand-push gear and that furthermore the rotary motion of the second element (90) of the screwand-push gear is braked, when an adjusting signal appears.

27. A control arrangement according to claim 25 or 26, characterised in that the adjusting signal is conducted to an electromagnetic adjusting element (83) which brings the clutch (79) into its operating position.

28. A control arrangement according to claim 27, characterised in that the first element of the screw-and-push gear is a sleeve (76), that a spindle (90) as a second element is rotatably mounted in this sleeve and that on one end of this spindle the first clutch half (81) is held in a manner protected against twisting and that this spindle end is developed as an armature (86) of the electromagnetic adjusting element (83) the winding (84) of which is seated on the other clutch half (78).

29. A control arrangement according to claim 28, characterised in that the torsionally firm clutch (78) comprises a bell-shaped member (85) which is mounted non-rotatably but axially displaceably and on which is secured at least one friction disk of the clutch (79), that this bellshaped member (85) has a bobbin for the winding (84) of the electromagnetic adjusting element (83) and that the end of the spindle (90) emerges into this bobbin.

30. A control arrangement according to claim 29, characterised in that the input rod (71) is coupled with the bell-shaped member (85), whereby this coupling may only be loaded by pressure.

31. A control arrangement according to claim 25, characterised in that a rotary motion of the electric motor in both directions of rotation is transformed into an axial displacement of the output rod (72) effective in the same direction by an appropriate screw-and-push gear, whereby one direction of rotation of the electric motor is determined by the adjusting signal and, when the electric motor has this direction of rotation, one element (90) of the screw-and-push gear is braked by a clutch (93) operating in dependence on the direction of rotation.

32. A control arrangement according to claim 31, characterised in that the electric motor drives a sleeve (76) with an internal thread (91), that in this sleeve a spindle (90) is axially displaceable, whereby balls (77) running in the grooves (91) of the sleeve (76) are supported on a stop plate (92) on the spindle, that this spindle (90) has an external thread with a thread pitch in the opposite direction to that of the internal thread, in which thread the balls (77) run as long as they are supported on a stop of the sleeve (76), and that the spindle (90) may be braked by the clutch (93) through the reversal of the electric motor.

33. A control arrangement for a motor vehicle substantially as described with reference to the accompanying drawings.