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(11) | EP 0 036 396 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Device for controlling the fuel feed for Otto-cycle internal combustion engines for motor vehicles Vorrichtung zum Steuern der Kraftstoffversorgung für eine Ottozyklusbrennkraftmaschine eines Motorfahrzeuges Dispositif pour commander l'alimentation en carburant d'un moteur à combustion interne à cycle Beau de Rochas, de véhicule |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to a device for controlling the fuel feed for Otto-cycle internal combustion engines for motor vehicles. In particular the present invention relates to a control device of the type including:
-speed sensor means arranged to provide at its output an electrical signal indicative of the speed of rotation of the engine.
-generator means arranged to generate a reference electrical signal having a constant amplitude ,
-a threshold comparison circuit with an upper and a lower operating threshold having first and second inputs connected respectively to the speed sensor means and the generator means and arranged to supply a control signal when the signal provided by the speed sensor means exceeds the upper operating threshold value; the said control signal being provided till when the said speed signal is lower than the lower operating threshold value.
-first electrical position-detector means arranged to detect the position of the accelerator pedal and to provide an electrical enabling signal when the accelerator pedal is released.
-shut off means intended to be disposed in the fuel feed pipe of the engine, and
-an enabling logic circuit connected to the comparison circuit and to the said first position-detector means and arranged to actuate the shut off means only when the said control signal and the said enabling signal are simultaneously present at the inputs of the said logic circuit.
[0002] Known devices of the above specified type, as somewhat illustrated for instance in FR-A-2 376 948 and FR-A-2 101 674 bring about the closure of the fuel feed pipe of the engine of the vehicle when the accelerator pedal is released and the speed of rotation of the engine exceeds a predetermined minimum value during running of the vehicle.
[0003] The fuel feed is restored again when the speed of rotation of the engine falls below the predetermined minimum value or when the accelerator pedal is again pressed.
[0004] These control devices for the fuel feed allow atmospheric pollution to be reduced. Indeed, as is known, when the accelerator pedal is released during running of the vehicle, the engine emits considerable quantities of unburnt hydrocarbons. The emission of unburnt hydrocarbons is greater the higher the speed of revolution of the engine at the moment at which the accelerator pedal is released.
[0005] The fuel-feed control devices further allow a saving in fuel, for example on all occasions when the engine is driven by the vehicle wheels through the transmission system. These conditions occur rather frequently, particularly during urban driving, for example when the vehicle slows to stop at traffic lights. Under these conditions, the accelerator pedal has barely been released before the fuel feed pipe is closed. The engine does not stall since it is driven by the transmission system. Immediately the speed of rotation of the engine falls below a predetermined minimum value the fuel feed is restored.
[0006] The adoption of fuel feed control devices is particularly convenient for carburettor engines provided with catalytic silencers. During periods in which the engine is driven by the transmission, a considerable quantity of unburnt hydrocarbons reaches the catalytic silencer. Thanks to the oxygen present in the catalytic silencer, partial combustion of these hydrocarbons occurs with an exothermic reaction which results in an increase in the temperature of the so-called catalytic bed. Such temperature increases may result in progressive damage to the catalytic bed. This disadvantage may be eliminated by means of the fuel feed control device of the type specified above, which allows the quantity of unburnt hydrocarbons passed into the catalytic silencer to be reduced.
[0007] Fuel feed control devices of the type described above made up till now, establish a minimum threshold value for the speed of rotation of the engine, above which the fuel feed duct can be closed, and below which the feed is re-established. This threshold value is fixed.
[0008] A disadvantage of known devices is related to the fact that there is a period of delay, which cannot be ignored, between the instant at which the fuel feed to the engine is re-established and the instant at which the engine again supplies driving torque. This period of delay may result in stalling of the engine, particularly when the engine is uncoupled from the transmission (friction clutch disengaged) and hence is no longer driven.
[0009] According to the known art, this disadvantage was avoided by using a threshold speed value which was rather high (about 2000 rpm). The use of a high speed threshold value allows stalling of the engine to the averted. However, as is clear, a high speed threshold value involves a drastic reduction in the benefits resulting from the use of the fuel feed control device, so that the use of such a control device has a rather limited economic advantage.
[0010] The object of the present invention is to provide a fuel feed control device for Otto-cycle internal combustion engines for vehicles, which is both simple and economical to manufacture, easy to instal, and which is free from the present disadvantages of the devices of the prior art.
[0011] In order to achieve this object, the present invention provides a fuel speed control device of the type specified above, the main characteristic of which lies in the fact that it further includes a processing circuit connected to the speed sensor means and arranged to generate an electrical signal having an amplitude which increases with time according to a predetermined law when the signal provided at the output of the speed sensor means falls at a rate greater than a predetermined rate; the output of the said processing circuit being connected to the second input of the said comparison circuit, increasing thereby the level of the said lower operating threshold.. Further characteristics and advantages of the present invention will emerge from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which:
Figure 1 is a circuit diagram, partly in block form, of a control device according to the invention,
Figure 2 illustrates four cartesian graphs of electrical signals present, in operation, at the output of respective component circuits of the device of Figure 1,
Figure 3 is a circuit diagram, partly in block form, of a second embodiment of the device according to the invention.
Figure 4 is a series of four cartesian graphs which illustrate, as a function of time, the changes in four voltage signals provided at the outputs of component circuits of the device illustrated in Figure 3,
Figure 5 is a circuit diagram, partly in block form, of a third embodiment of the device according to the invention, and
Figure 6 is a series of seven cartesian graphs which illustrate, as a function of time, seven wave forms provided at the outputs of the component circuits making up the device of Figure 5.
[0012] In Figure 1, by 1 there is indicated in its entirety, an analog circuit arranged to provide at its output an eiectrical signal the amplitude of which is substantially proportional to the speed of rotation of the engine of the vehicle (not shown). The analog circuit 1 has an input terminal 1 a intended to be connected to the induction coil (not shown) of the ignition circuit of the vehicle. The terminal 1a constitutes the input of a pulse shaping circuit 2 the output of which is connected to a monostable circuit 3. This latter is connected to the input of a filter 4 the output of which is connected to the input of an amplifier 5. The output of this amplifier constitutes the output of the analogue circuit 1 and is indicated by 1 b
[0013] The output 1 b of the analogue circuit 1 is connected to the input of a processing circuit 6 and to a first input 7a of a threshold comparison circuit 7 exhibiting hysteresis. The second input 7b of this circuit is connected through a resistor 8, to a d.c. reference voltage source 9 constituted, for example, by a potentiometer 10 the resistive element of which is connected between a d.c. voltage supply and earth.
[0014] The output of the processing circuit 6 is connected to the input 7b of the comparison circuit 7 by means of a resistor 11. The output of the comparison circuit 7 is connected to a first input 12a of a logic AND gate 12, the output of which is connected to a shut off device 13 by means of a transistorised power output stage 14. The shut off device 13 may, for example, be constituted by an electrovalve disposed in the fuel feed pipe of the engine.
[0015] A position detector device 15, arranged to provide an enabling electrical signal when the accelerator pedal (not shown) of the engine is released, is connected to the second input 12b of the logic AND gate 12 through an inverter 16.
[0016] The position detector device 15 may be constituted by a switch associated with the accelerator pedal Alternatively, the position detector device 15 may be constituted by a switch associated with a butterfly valve (not shown) of the carburettor, and, in general, by any device capable of providing a signal of the on/off type when the accelerator pedal is pressed/released.
[0017] In the following description it will be assumed that the detector device 15 provides at its output a signal "1" when the accele- ratory pedal is pressed, and a signal "0" when the accelerator is released.
[0018] The threshold comparison circuit 7 includes an operational amplifier 17, an input resistor 18 and a feedback resistor 19.
[0019] The feedback operational amplifier 17, together with the resistors 8 and 11, constitute an analogue summing circuit.
[0020] The processing circuit 6 includes a memory circuit 20 constituted by a diode 21 having its anode connected to the output of the amplifier 5, and a capacitor 22 and a resistor 23 connected in parallel with each other between the cathode of the diode 21 and earth. The memory circuit 20 is connected to a first input 24a of a differential amplifier 24 a second input 24b of which is connected to the output of the amplifier 5. The output of the differential amplifier 24 is connected to the input 7b of the threshold comparison circuit 7, through the resistor 11.
[0021] The operation of the embodiment of the control device according to the invention illustrated in Figure 1 will now be described with reference to the wave forms illustrated in Figure 2.
[0022] In the said Figure 2, by A, B, C and D are illustrated four wave forms provided at the outputs of the analogue circuit 1, the threshold comparison circuit 7, the logic inverter 16 and the logic AND gate 12, respectively.
[0023] A curve A shows a possible variation of the signal provided at the output of the amplifier 5 as a function of time t. The amplitude of this signal is proportional to the speed of rotation of the engine. In the graph which illustrates the progression of curve A, two parallel lines L 21 Li have been drawn which represent the levels of the upper and lower operating thresholds of the threshold comparator 7. These levels may correspond for example, to 1700 rpm and 1300 rpm respectively.
[0024] Supposing initially that the accelerator pedal is pressed by the driver, in this situation, the output of the position detector device 15 is at level "1", and therefore the output of the inverter 16 is at the level "0" (signal C of Figure 2).
[0025] The speed of rotation of the engine increases, and correspondingly, the curve A rises. At the instant t=to, the signal A intersects the level L2. Consequently the output of the threshold comparison circuit 7 is brought to level "1" (signal B of Figure 2).
[0026] Supposing the accelerator pedal is released at the instant indicated by tj, at the instant t, the signal provided at the output of the logic inverter 16 passes to level "1", as indicated by the wave form C of Figure 2. During the whole period of time preceding the instant t,, or else for the entire period of time during which the signal A rises or is substantially constant, the inputs 24a, 24b of the differential amplifier 24 are fed with the same signal. Indeed, the memory circuit 20 is arranged to reproduce at its output the same signal which is received at its input, as long as this signal increases or is substantially constant. Consequently for t<t,, there is no signal present at the output of the differential amplifier 24 and only the constant reference voltage provided by the potentiometer 10 is present at the input 7b of the threshold comparator 7..
[0027] Subsequent to the instant t1, the signal A, which is proportional to the speed of the engine, starts to fall. The rate at which the signal falls depends on numerous factors. For example, after release of the accelerator pedal, the rate at which the signal A falls will be greater or smaller according to whether or not the brakes are applied.
[0029] If, after the instant t,, the signal A falls (branch A, of the curve A of Figure 2) with a time constant less than the discharge time constant of the R-C circuit constituted by the capacitor 22 and the resistor 23, the diode 21 isolates this R-C circuit from the output of the amplifier 5. The capacitor 22 discharges through the resistor 23 and the voltage there- across, the variation of which is indicated by S in Figure 2, is fed to the input 24a of the differential amplifier 24. This differential amplifier 24 provides at its output an increasing signal the instantaneous amplitude of which corresponds to the difference between the instantaneous amplitudes of the curve S and the branch A, of the curve A. This signal is superimposed on the constant reference fed to the input 7b of the threshold comparison circuit 7. Hence, from the instant t, the level of the lower operating threshold of the comparator 7 ceases to be constant, and starts to increase in accordance with the curve indicated by T in Figure 2.
[0030] At the instant t,, the output of the logic AND gate 12 will have changed to level "1" bringing about, through the power stage 14, the actuation of the shut off device 13 is disposed in the fuel feed pipe of the engine.
[0031] At the instant t2 the branch A, of the curve A intersects the curve T, and consequently the output of the threshold comparison circuit 7 changes again to level "0" (signal B of Figure 2). Correspondingly the output of the logic AND gate 12 (signal D of Figure 2) changes to level "0", resulting in the deactivation of the shut off means 13. The engine feed is re-established.
[0032] Summing up what has been explained above, when the speed of rotation of the engine falls with a time constant less than that of the R-C circuit 22, 23 the processing circuit 6 causes a progressive increase in the level of the lower operating threshold of the threshold comparison circuit 7. This increase in the lower operating threshold is greater the more rapid the fall in speed of the engine. Without the use of the processing circuit 6, the restoration of the fuel feed would occur at the instant indicated by t3 in Figure 2. The effect of the use of the processing circuit 6 is thus to advance the restoration of the fuel feed to an extent which is greater the faster the fall in speed of the engine. This ensures that the fuel feed is restored in time, before the engine can stall.
[0033] The control device according to the invention operates in a rather different manner from that indicated above when .subsequent to the instant t1, the speed of rotation of the engine falls with a time constant greater than the discharge time constant of the R--C circuit 22, 23. Supposing, in fact, that from the instant t,, the curve A of Figure 2 decreases along the branch A2 located above the curve S which corresponds to the discharge of the said R-C circuit, in this situation the diode 21 remains conductive, and the memory circuit 20 continues to reproduce at its output the signal provided to it by the amplifier 5, that is, the signal A. As a result, the differential amplifier 24 provides a zero signal at the input 7b of the comparison circuit 7. Therefore the level of the lower operating threshold of this comparison circuit 7 remains, again subsequent to the instant t1, constant at the level L1. Correspondingly, the output of the threshold comparison circuit 7 (signal B) and the logic AND gate 12 (signal D) will change to level "0" only at the instant indicated by t4 in Figure 2.
[0034] The processing circuit 6 is thus arranged to maintain the level of the lower operating threshold of the threshold comparison circuit 7 unaltered when the speed of rotation of the engine increases, is constant, or decreases with a time constant greater than the time constant of the R-C circuit 22, 23.
[0035] As has been described above, if, instead, the speed of rotation of the engine decreases with a time constant less than that of the said R-C circuit, the processing circuit 6 superimposes on the level of the lower operating threshold L" a signal of an amplitude which increases in time to a proportionally larger extent the greater the decrease in the speed of rotation of the engine.
[0036] The processing circuit 6 thus enables the setting of a lower operating threshold of the comparison circuit 7 which has a value less than the threshold values which could be set for the control devices of the prior art.
[0037] When, with the accelerator pedal released, the speed of rotation of the engine falls slowly, the control device according to the invention provides for the restoration of the feed only when the speed of the engine has reached a threshold value less than that of the devices of the prior art. Consequently the device according to the invention allows the emission of unburnt hydrocarbons and the heating of the catalytic silencer to be greatly reduced. A greater fuel saving is also possible.
[0038] Figure 3 shows a second embodiment of the device according to the invention. In this Figure, the same elements already described with reference to Figure 1 have been given the same reference numerals.
[0039] In the variant illustrated in Figure 3, the processing circuit 6 further includes a generator circuit 25 having its input connected to the output of the logic inverter 16, and its output connected to the input 7b of the threshold comparison circuit 7 through a resistor 26. The generator circuit 25 is arranged to generate a signal of increasing amplitude when its input is fed with a signal at level "1". This circuit may be constituted, for example, by a ramp voltage generator circuit.
[0040] In operation, immediately the accelerator pedal is released, the detector device 15 activates the generator circuit 25 through the logic inverter 16. The generator circuit provides a signal of increasing amplitude to the input 7b of the threshold comparison circuit 7. Consequently, as is seen from Figure 4, from the instant t, at which the accelerator pedal is released, the level of the-lower operating threshold of the comparison circuit 7 ceases to be constant and starts to increase. If the speed of rotation of the engine decreases with a time constant less than that of the R-C circuit 22, 23, the level of the lower operating threshold of the comparator 7 increases according to the curve T' of Figure 4. If, however, the speed of the engine falls with a time constant greater than that of the said R-C circuit, the lower operating threshold of the comparator 7 increases according to the curve T" of Figure 4.
[0041] In each case, the effect of the generator circuit 25 is to being about a progressive increase in the level of the lower operating threshold of the threshold comparator 7 when the accelerator is released.
[0042] As is known, when the accelerator pedal is released during running of the vehicle, progressive drying of the induction manifold of the engine occurs, this manifold previously having been wetted by the fuel. The drying of the induction manifold occurs progressively, on average in about 15 seconds. As soon as the accelerator pedal is released, and the fuel feed pipe closed, the induction manifold is again partially wetted by the fuel. If the deactivation of the shut off device of the fuel feed pipe occurs a few seconds after its activation, the fuel feed will be restored very quickly. On the other hand, if this shut off device is deactivated after the manifold has completely dried, the fuel feed will be restored after a certain delay. This delay could result in stalling of the engine. The control device illustrated in Figure 3 provides for the gradual raising of the level of the lower operating threshold of the comparison circuit 7 so as to ensure that the fuel feed is restored earlier and earliest as the induction manifold dries. In the case of Figure 4, the fuel feed is restored at the instant ti rather than at the instant t2.
[0043] Figure 5 illustrates a further embodiment of the device according to the invention. In this Figure, the elements common to the embodiments previously described have been indicated by the same reference numerals.
[0044] In the embodiment illustrated in Figure 5, the processing circuit 6 further includes a control circuit 27 having a first input 27a connected to the output of the amplifier 5, and a second input 27b connected to the output of a device 28 for detecting the position of the friction-clutch control pedal. The detector device 28 may, for example, be constituted by a switch associated with the friction-clutch control pedal, and arranged to provide at its output a signal at level "0" when this pedal is released (friction clutch engaged) and a signal at level "1" when this pedal is depressed (friction clutch disengaged).
[0045] The output of the control circuit 27 is connected to a third input 12c of the logic AND gate 12. The control circuit 27 includes a threshold comparison circuit 29 having a first input 29a connected to the output of the amplifier 5, and a second input 29b connected to a d.c. reference voltage supply constituted, for example, by a potentiometer 30 connected between a voltage supply source and earth. The output of the threshold comparison circuit 29 is connected to a first input 31 a of a logic OR gate 31 which has a second input 31 b connected to the detector device 28 via a logic inverter 32.
[0046] The operation of the Figure 5 embodiment of the device according to the invention is essentially similar to that of the embodiments described above. In Figure 6 are illustrated the wave forms A to G of signals provided at the respective outputs of the analogue circuit 1, the threshold comparison circuit 7, the logic inverter 16, the logic AND gate 12, the logic inverter 32, the threshold comparator 29, and the logic OR gate 31.
[0047] In operation, when the vehicle is running, immediately at the instant t, at which the accelerator pedal is released, the speed of rotation of the engine starts to fall. At the instant t" as described above, the shut off device 13 is activated. If, in these circumstances, the friction clutch is engaged, the engine does not stop since it continues to be driven by the transmission shaft. If, however, under these conditions the friction clutch is disengaged, the vehicle engine could stop before the fuel feed has been restored. The embodiment of the device according to the invention illustrated in Figure 5 allows this eventuality to be avoided.
[0048] Supposing the friction clutch is disengaged at instant t5 which is subsequent to the instant t,. At the instant t5 the output of the logic inverter 32 changes to level "0". If, at this moment, the speed of rotation of the engine resides above the operating threshold value of the comparison circuit 29, the output of this comparison circuit 29 and of the logic OR gate 31 remain at level "1". In this situation the operation of the control device proceeds exactly in the manner already illustrated above. Whenever, before the control device has allowed the fuel feed to be restored, the speed of rotation of the engine falls below the operating threshold of the comparison circuit 29 (at the instant t6; Figure 6) the outputs of the comparison circuit 29 and of the logic OR gate 31 change to level "0". Consequently, the output of the logic AND gate 12 changes suddenly to level "0" advancing the restoration of the fuel feed. This prevents the engine from stopping before the fuel feed has been effectively restored.
[0049] Whenever, between the instants t, and t2 (t12) the friction clutch is not disengaged, the device illustrated in Figure 5 functions exactly in the same manner as the device illustrated in Figure 3.
[0050] The device illustrated in Figure 5 allows the restoration of the fuel feed to be advanced whenever, in the period in which the fuel feed is interrupted, the friction clutch is disengaged and- the speed of rotation of the engine falls below the operating threshold of the comparator 29.
[0051] The device illustrated may be used to advantage f6r controlling the fuel feed to carburettor, Otto-cycle, internal combustion engines. It may also, however, be used with injection engines. When the device is used for this latter type of engine, the position detector device 15 may be constituted by an electrical air-flow meter disposed in the induction manifold. A threshold comparison circuit connected to the output of the flow meter may, in this case, provide a signal of the on/off type when the accelerator pedal is pressed/released.
-speed sensor means (1) arranged to provide at its output an electrical signal (A) indicative of the speed of rotation of the engine,
-generator means (9) arranged to provide at its output an electrical reference signal having a constant amplitude,
-a threshold comparison circuit (7) with an upper and a lower operating threshold (L,, L2) having first and second inputs (7a, 7b) connected respectively to the speed sensor means (1) and to the generator means (9), and arranged to provide a control signal (B) when the signal (A) provided by the speed sensor means (1) exceeds the upper operating threshold value (L2); the said control signal (B) being provided till when the said signal (4) is lower than the lower operating threshold value (L,),
-first electrical position detector means (15) arranged to detect the position of the accelerator pedal and to provide an electrical enabling signal (C) when the accelerator pedal is released,
-shut-off means (13) intended to be disposed in the fuel feed pipe of the engine,
-an enabling logic circuit (12) connected to the threshold comparison circuit (7) and to the said first position-detector means (15), and arranged to actuate the shut-off means (13) only when the said control signal (B) and enabling signal (C) are present simultaneously at the inputs to the said logic circuit (12), characterised in that it further includes a processing circuit (6) connected to the speed sensor means (1) and arranged to generate an electrical signal having an amplitude which increases in time according to a predetermined law when the signal (A) provided at the output of the speed sensor means (1) falls at a rate greater than a predetermined rate; the output of the said processing circuit (6) being connected to the second input (7b) of the said threshold comparison circuit (7) increasing threby the level of the said lower operating threshold (L,).
-a memory circuit (20) connected to the speed sensor means (1) and arranged to:
(a) provide at its output an electrical signal having an initial amplitude equal to the instantaneous amplitude of the signal (A) emitted by the speed sensor means (1) and decreasing in time with a predetermined time constant; when the signal (A) emitted by the speed sensor means (1) falls with a time constant less than said predetermined time constant;
(b) reproduce at its output the signal (A) emitted by the speed sensor means (1), when the amplitude of the said signal (A) is increasing, is constant, or decreases with a time constant greater than the said predetermined time constant,
-a differential amplifier circuit (24) having first and second inputs (24a, 24b) connected respectively to the output of the speed sensor means (1) and the output of the memory circuit (20).
-second electrical position-detector means (28) intended to be associated with the friction-clutch control pedal, and
-a control circuit (27) connected to the speed sensor means (1), to the said second electrical position-detector means (28), and to the said enabling logic circuit (12); the said control circuit (27) being arranged to provide an inhibit signal (G) to the said enabling logic circuit (12) when the signals (A; E) emitted by the speed sensor means (1) and by the second electrical position-detector means (28) indicate that the speed of rotation of the engine is less than a predetermined value and that the friction-clutch control pedal has been depressed.
-mit einer Geschwindigkeitsensoreinrichtung ( 1 an deren Ausgang ein für die Drehgeschwindigkeit der Brennkraftmaschine kennzeichnendes elektrisches Signal (A) erzeugt wird
-mit einer Generatoreinrichtung (9), die an ihrem Ausgang ein elektrisches Referenzsignal mit konstanter Amplitude erzeugt,
-mit einer einen oberen und einen unteren Betriebsschwellwert (L1, L2) aufweisenden Schwellwertvergleicherschaltung (7), die eine ersten mit der Geschwindigkeitsensoreinrichtung (1) verbundenen Eingang (7a) und einen zweiten mit der Generatoreinrichtung (9) verbundenen Eingang (7b) besitzt und derart angeordnet ist, daß sie ein Steuersignal (b) liefert, wenn das von Geschwindigkeitsensoreinrichtung (1) erzeugte Signal (A) den oberen Betriebsschwellwert (L2) überschreitet, wobei dieses Steuersignal (B) solange erzeugt wird, bis das Signal (A) der Geschwindigkeitsensoreinrichtung (1) den unteren Betriebsschwellwert (L1) unterschreitet,
-mit einer ersten elektrischen Positionsdetektoreinrichtung (15) zur Erfassung der Position des Beschleunigungspedals und zur Erzeugung eines elektrischen Aktivierungssignals (C), wenn das Beschleunigungspedals losgelassen ist,
-mit einer in der Kraftstoffversorgungsleittung der Brennkraftmaschine einefügten Absperreinrichtung (13),
-sowie mit einer logischen Aktivierungsschaltung (12), die mit der Schwellwertvergleicherschaltung (7) und der ersten Positionsdetektoreinrichtung (15) verbunden und derart angeordnet ist, daß sie die Absperreinrichtung (13) (13) nur dann betätigt, wenn das genannte Steuersignal (B) und das Aktivierungssignal (C) gleichzeitig an den Eingängen der logischen Aktivierungsschaltung (12) anliegen,
dadurch gekennzeichnet,
daß ferner eine Prozessorschaltung (6) vorgesehen ist, die mit der Geschwindigkeitsensoreinrichtung (1) verbunden und derart angeordnet ist, daß sie ein elektrisches Signal erzeugt, dessen Amplitude nach einer vorgegebenen Gesetzmäßigkeit zeitlich ansteigt, wenn das am Ausgang der Geschwindigkeitsensoreinrichtung (1) erzeugte Signal (A) mit einer Geschwindigkeit abfällt, die größer ist als eine vorbestimmte Geschwindigkeit, wobei der Ausgang der Prozessorschaltung (6) mit dem zweiten Eingang (7b) der genannten Schwellwertvergleicherschaltung (7) verbunden ist, derart daß der Pegel des genannten unter Betriebsschwellwerts (L1) hierdurch vergrößert wird.
―eine Speicherschaltung (20), die mit der Geschwindigkeitsensoreinrichtung (1) verbunden und derart angeordnet ist, daß sie
a) an ihrem Ausgang ein elektrisches Signal liefert, dessen Amplitude anfänglich gleich der Momentanamplitude des von der Geschwindigkeitsensoreinrichtung (1) gelieferten Signals (A) ist und zeitlich mit einer vorbestimmten Zeitkonstanten abfällt, wenn das von der Geschwindigkeitsensoreinrichtung (1) erzeugte Signal (A) mit einer Zeitkonstanten abfällt, die kleiner ist als die genannten vorbestimmte Zeitkonstante,
b) an ihrem Ausgang das von der Geschwindigkeitsensoreinrichtung (1) abgegebene Signal (A) reproduziert, wenn die Amplitude des genannten Signals (A) entweder an wächst oder konstant ist oder mit einer Zeitkonstanten abfällt, die größar ist als die genannte vorbestimmte Zeitkonstante,
-sowie eine Differentialverstärkerschaltung (24) mit einem ersten Eingang (24), der mit dem Ausgang der Geschwindigkeitsensoreinrichtung (1) verbunden ist, und einem zweiten Eingang (24b), der mit dem Ausgang Speicherschaltung (20) verbunden ist.
-daß die Prozessorschaltung (6) ferner eine Generatorschaltung (25) umfaßt, deren Eingang mit der Positionsdetektoreinrichtung (15, 16) verbunden ist und deren Ausgang mit dem zweiten Eingang (7b) der Schwellwertvergleicherschaltung (7) verbunden ist,
-und daß diese Generatorschaltung (25) ein elektrisches Signal erzeugt, dessen Amplitude von dem Zeitpunkt (t1) an nach einer vorgegebenen Gesetzmäßigkeit anwächst, in welchem das von der ersten Positionsdetektoreinrichtung (15, 16) im Betrieb abgegeben Signal (C) das Loslassen des Beschleunigungspedals anzeigt.
―eine zweite dem Kupplungsbetätigungspedal zugeordnete elektrische Positionsdetektoreinrichtung 28,
-sowie eine Steuerschaltung (27), die mit der Geschwindigkeitsensoreinrichtung (1), der zweiten elektrischen Positionsdetektoreinrichtung (28)
―sowie eine Steuerschaltung (27), die mit der Geschwindigkeitsensoreinrichtung (1), der zweiten elektrischen Positions detektoreinrichtung (28) und der logischen Aktivierungsschaltung (12) verbunden ist und die ein Sperrsignal (G) an die logische Aktivierungsschaltung (12) liefert, wenn die von der Geschwindigkeitsensoreinrichtung (1) und von der zweiten elektrischen Positionsdetektoreinrichtung (28) erzeugten Signale (A bzw. E) anzeigen, daß die Drehgeschwindigkeit der Brennkraftmaschine einen vorbestimmten Wert unterschreitet und das Kupplungsbetätigungspedal niedergedrückt ist.
-daß die genannte Steuerschaltung (27) eine Schwellwertvergleicherschaltung (29) beinhaltet, die mit der Geschwindigkeitsensoreinrichtung (1) verbunden ist sowie eine logische ODER-Schaltung (31) mit einem ersten und einem zweiten Eingang (31a, 31 b), die mit dem Ausgang der Schwellwertvergleichschaltung (29) bzw. mit dem Ausgang der zweiten elektrischen Positionsdetektoreinrichtung (28) verbunden sind
-und daß der Ausgang der logischen ODER-Schaltung (31) mit einem dritten Eingang (12c) der logischen Aktivierungsschaltung (12) verbunden ist,
-un capteur des vitesse (1) agencé pour délivrer à sa sortie un signal électrique (A) indiquant la vitesse de rotation du moteur,
-un générateur (9) agencé pour produire à sa sortie un signal électrique de référence ayant une amplitude constante,
-un circuit comparateur à seuil avec un seuil de fonctionnement supérieur et un seuil de fonctionnement inférieur (L,, L2) dont une première et une seconde entrées (7a, 7b) sont connectées respectivement au capteur de vitesse (1) sont connectées respectivement au capteur de vitesse (1) et au générateur (9), et agencé pour produire un signal de commande (B) quand le signal (A) produit par le capteur de vitesse (1) dépasse la valeur seuil supérieure de fonctionnement (LZ); ledit signal de commande (B) étant produit jusqu'à ce que ledit signal de vitesse (4) soit inférieur à la valeur seuil inférieure de fonctionnement (L,),
-un premier détecteur électrique de position (15) agencé pour détecter la position de la pédale d'accélérateur et pour produire un signal électrique d'autorisation (C) quand la pédale l'accélérateur est relâchée,
-un dispositif de coupure (13) destiné à être disposé dans la conduite d'alimentation en combustible du moteur,
-un circuit logique d'autorisation (12) connecté au circuit comparateur à seuil (7) et audit premier détecteur de position (15) et agencé pour actionner le dispositif de coupure (13) seulement quand ledit signal de commande (B) et le signal d'autorisation (C) sont présents simultanément aux entrées dudit circuit logique (12), caractérisé en ce qu'il comporte en outre un circuit de traitement (6) connecté au capteur de vitesse (1) et agencé pour produire un signal électrique ayant une amplitude qui augmente dans le temps selon une loi prédéterminée quand le signal (A) produit à la sortie du capteur de vitesse (1) décroît à une vitesse supérieure à une valeur prédéterminée; la sortie dudit circuit de traitement (6) étant connectée à la seconde entrée (7b) dudit circuit comparateur à seuil (7), en augmentant ainsi le niveau dudit seuil inférieur de fonctionnement (L,).
-un circuit à mémoire (20) connecté au capteur de vitesse (1) et agencé pour:
(a) produire à sa sortie un signal électrique ayant une amplitude initiale égale à l'amplitude instantanée due signal (A) émis par le capteur de vitesse (1) diminuant dans le temps avec une constante de temps prédéterminée quand le signal (A) émis par le capteur de vitesse (1) diminue avec une constante de temps inférieure à ladite constante de temps prédéterminée;
(b) reproduire à sa sortie le signal (A) émis par le capteur de vitesse (1) quand l'amplitude dudit signal (A) augmente, est constante, ou diminue avec une constante de temps supérieure à ladite constante de temps pré- determinée,
-un amplificateur différentiel (24) dont une première et une seconde entrées (24a, 24b) sont connectées respectivement à la sortie du capteur de vitesse (1) et à la sortie du circuit à memoire (20).
-un second détecteur électrique de position (28) destiné à être associé avec la pédale de commande d'embrayage à friction, et
-un circuit de commande (27) connecté au capteur de vitesse (1), audit second détecteur électrique de position (28) et audit circuit logique d'autorisation (12); ledit circuit de commande (27) étant agencé pour produire un signal d'inhibition (G) pour ledit circuit logique d'autorisation (12) quand les signaux (A; E) émis par le capteur de vitesse (1) et par le second détecteur électrique de position (28) indique que la vitesse de rotation du moteur est inférieure à une valeur prédéterminée et que la pédal de commande d'embrayage à friction a été manoeuvrée.