Arrangement For Limiting The Speed Of Internal Combustion Engines

Abstract

An arrangement through which the speed of an internal combustion engine is limited by inhibiting the generation of ignition or fuel injection pulses. An alternating current voltage generator is driven from the crank shaft of the engine and provides a voltage signal which is dependent upon the speed of the engine. A monitoring unit connected to the voltage generator provider pulses with amplitudes or pulse levels dependent upon the speed of the engine. When the amplitudes of the pulses exceed a predetermined magnitude corresponding to a predetermined engine speed, an electronic switch becomes actuated so that electrical pulses used for ignition and fuel injection are inhibited. Inhibition of the pulses takes place during a time interval determined by a monostable multivibrator, with the time interval being at least as long as necessary for suppressing the next oncoming pulse used for ignition or fuel injection purposes. BACKGROUND OF THE INVENTION The present invention resides in an internal combustion engine with a monitoring arrangement for limiting the rotational speed of the engine. The arrangement has, furthermore, a unit for ignition and fuel injection, which are rendered ineffective when the maximum permissible rotational speed is exceeded. The internal combustion engine becomes provided, for this reason, with a monitoring unit for purpose of limiting the rotational speed. This arrangement is intended to avoid the destruction of parts as a result of overloading due to increase rotational speed. An internal combustion engine is known in the art which has a monitoring unit for limiting the rotational speed through a centrifugal force regulator which actuates a short-circuiting switch. This switch lies in the circuit of the ignition interrupter or circuit breaker, and becomes closed when the maximum permissible speed is exceeded. In this conventional case, no further ignition prevails, since the ignition circuit breaker or interrupter is short-circuited and is rendered, thereby, ineffective. When the engine has a plurality of cylinders, the short-circuiting switch is connected in series with a control switch which provides for suppression of the ignition in only a few of the available cylinders, so that a relatively soft limiting of the rotational speed is realized. In the preceding conventional monitoring arrangement for the regulation of speed of an engine, it is possible that when opening the short-circuiting switch, an ignition cycle is produced at the improper instant of time, so that damaging effects result. Furthermore, the monitoring function can be easily interfered with through soiling and wear of the switching contacts. Finally, the setting of the centrifugal regulator corresponding to the maximum permissible speed is a complex procedure, and as a result the desired limiting effect cannot be attained with assurance and reliability in each case. Accordingly, it is an object of the present invention to provide an internal combustion engine which has means for ignition and fuel injection, and which is provided with a monitoring unit for limiting the rotational speed, so that the disadvantages of the aforementioned conventional arrangement are avoided. The object of the present invention is achieved by providing a control voltage generator from which a monitoring pulse may be derived for the initiating of each ignition or fuel injection cycle. The amplitude of the monitoring pulse is made dependent upon the rotational speed. When this amplitude of the monitoring pulse corresponds to a level which exceeds the maximum permissible rotational speed, an electronic protective circuit path is actuated in the monitoring arrangement. When thus actuated, the monitoring pulse is intercoupled with the ignition or fuel injection arrangement. A monostable multivibrator maintains the protective circuit path in actuated state, so that within the period of the monostable multivibrator, the time of the multivibrator coincides with the following pulses for initiating the ignition of fuel injection cycles. SUMMARY OF THE INVENTION An arrangement for limiting the speed of an internal combustion engine by inhibiting the ignition or fuel injection pulses. A voltage generator in the form of an alternating current generator is mechanically coupled to the engine and produces a cyclic voltage from which monitoring pulses are derived. The amplitudes of the monitoring pulses are made dependent upon the rotational speed of the engine, and when the speed exceeds a predetermined magnitude, the level of the pulses also exceed a predetermined magnitude. A transistor switch becomes actuated when the monitoring pulses exceed the predetermined magnitude in amplitude, and thereby prevents the application of further ignition or fuel injection pulses by short-circuiting the alternating current generator. A monostable multivibrator is also actuated so that inhibition of the ignition or fuel injection pulses is realized for at least a time interval corresponding to the prevalence of the next oncoming ignition or fuel injection pulse. The alternating current generator may be one in which the rotor is unsymmetrically mounted with respect to the stator poles. The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a circuit diagram and shows the monitoring arrangement for limiting the speed of an internal combustion engine;

FIG. 2 is an isometric view with partial cross section of a voltage generator used in conjunction with the arrangement of FIG. 1; and

FIG. 3 is a circuit diagram for using the monitoring arrangement of FIG. 1 in conjunction with a fuel injection arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawing and in particular to FIG. 1, an internal combustion engine B is used for driving a motor vehicle, not shown, and a monitoring unit W is used to limit the speed of the engine. The limiting of the speed is accomplished in a manner whereby combustion control means, e.g., an ignition arrangement Z, associated with the internal combustion engine B is disconnected or rendered inoperative through the monitoring unit W, when the speed exceeds a predetermined maximum permissible value.

The internal combustion engine B is, for example, equipped with a conventional coil ignition arrangement. This ignition arrangement Z has a circuit junction 11 which leads to the positive terminal of a DC current source 14, by way of the circuit path 12 and the switch 13 in the form of an operating switch. The DC current supply 14 is provided with a battery of the motor vehicle. The negative terminal of this DC current source or battery 14 is connected to ground potential. A negative circuit path 15 applies ground potential to the circuit junction or terminal 16 of the ignition arrangement Z. Connected between the circuit junctions or terminals 11 and 16 of the ignition arrangement Z, is a series combination of the emitter-collector path 17-18 of a transistor 19 and the primary winding 20 of an ignition coil 21. One terminal of the secondary winding 22 of the ignition coil 21, is connected to both the circuit junction 16 and to one terminal of a spark plug 23. The second terminal of the secondary winding 22 is connected, on the other hand, to the other terminal of the spark plug 23. A monostable multivibrator 24 is, furthermore, connected across the terminals or circuit junctions 11 and 16. The control input 25 of the ignition arrangement Z is applied to the monostable multivibrator 24, through the circuit path 26 which, in turn, leads to the base 27 of the transistor 19.

The control input 25 of the ignition arrangement Z is connected to the output 29 of a control voltage generator 30 which has one terminal 31 connected to ground potential through the circuit path 32.

A substantially small alternating current generator is used for the control voltage generator 30, and is coupled to the crank shaft K of the engine B through linkage denoted in the drawing by dash-dot lines. The alternating current generator provides an AC voltage with amplitude dependent upon the rotational speed of the crank shaft. The positive half-wave 34 is used, in this embodiment, for providing the ignition pulse, whereas the negative half-wave 33 is used as a monitoring pulse in the monitoring unit W.

The principle of the speed regulation through the monitoring unit W resides on the basis that when the monitoring pulse has an amplitude exceeding the maximum permissible level, corresponding to the maximum permissible speed, an electronic protection circuit H is actuated. In the actuated state of the circuit H, the ignition arrangement Z is interconnected, so that the ignition pulse for this ignition arrangement is held up through a predetermined state of a monostable timing means, such as a multivibrator, M. This ignition pulse is thus held up for a period of time extending at least for the duration of the ignition pulse.

The monitoring unit W has a first power supply line 35 provided with a circuit junction or terminal 36, and a second power supply line 37 provided with a circuit terminal or junction 38. The circuit junction 36 of the first power supply line 35 is connectable to the positive terminal of the direct current source 14, through the operating switch 13. The circuit terminal 38, on the other hand, and associated with the second power supply line 37, is connected to ground potential.

In order to provide for constant voltage supply, the monitoring unit W is equipped with a voltage stabilizer G at its input. This voltage stabilizer G includes a zener diode 39 with anode connected to the circuit junction or terminal 38 of the second power supply line 37. The cathode of the zener diode, on the other hand, leads to the circuit junction 36, through a resistor 40. In addition, the voltage stabilizer G includes a stabilizing transistor 41 with base 42 connected to the cathode of the zener diode 39. The emitter-collector path 43-44 of the transistor 41, is connected in series with the power supply line 35. The emitter 43 of the transistor is connected in series with a capacitor 45 leading, in turn, to the power supply line 37.

The monitorin unit W contains, moreover, a threshold-detecting control input branch E which has one terminal connected to the first power supply line 35, and another terminal connected to the circuit junction 46. The circuit junction 46 is connected directly to the output terminal 29 of the voltage generator 30. At least one threshold-detecting switching element 47 is provided in the control branch E, and has a predetermined threshold value. This switching element 47 is switched to the conducting state when the applied voltage to the monitoring pulse exceeds the threshold value associated with this switching element. The threshold value of this element 47 is made such that it corresponds to maximum permissible rotational speed.

In an exemplary case, the switching element 47 with a predetermined threshold value is in the form of a zener diode. The switching element can, however, also be constructed through a plurality of series connected zener diodes 47, 47' and 47", as represented by dashed lines in the drawing. Aside from this, it is also possible to use a single diode 48 or a chain of series-connected diodes 48, 48', 48" which are also shown in dashed or broken lines.

Assume that the engine B drives a load L through a conventional gear shift arrangement R, as is the usual case in motor vehicles. Under these conditions, it is possible to link the gear shift R to a switching arrangement which includes of number of switching elements 47, 47a, 47b . . . which exhibit different threshold values. The arrangement is such that when the gear shift R shifts to another gear stage, a different one of the switching elements 47a, 47b . . . becomes correspondingly switched into the circuit. The rotational speed can then become limited in another manner through the individual gear stages. The switching function can be accomplished whereby a selector switch 49 is used with a movable contact arm 50 denoted by dash-dot lines. This movable arm 50 is connected to the shifting lever 51 used to shift gears. At the same time, the movable arm 50 may be brought into electrical contact with a plurality of fixed contacts 52, 52a, and 52b which are, in turn, connected to respective switching elements 47, 47a, 47b. The other terminals of these switching elements are connected jointly and to the circuit junction 46, and the movable contact arm 50 also leads to the second power supply line 35.

It is further desirable to provide a monitoring resistor 53 in the form of an adjustable resistor, in the threshold-detecting control branch E. This adjustable resistor 53 allows precise setting of the level corresponding to the maximum permissible speed. In a particular case, it is also possible to couple the sliding contact 54 of the adjustable resistor 53, to the shifting lever 51 for regulation purposes.

It is also possible to provide a temperature dependent resistor 55 in the control input branch E. This temperature dependent resistor 55 is situated so that it is influenced preferably from the thermal state of the internal combustion engine B. As a result of such an arrangement, the speed limitation or regulation is attained whereby such speed regulation is made dependent upon the temperature of the engine B.

The control branch E is connected to the first power supply line 35 to a resistor 56 which is also in the form of an adjustable resistor and establishes the circuit potential P at the base 60 of the transistor 57.

In the simplest case, the monostable multivibrator M can be directly controlled from the circuit point P. It is, however, more advantageous to connect the monostable multivibrator M to the circuit point P, through a trigger stage T subjected to rectangular-shaped trigger pulses, and a differential network D. With this arrangement, each monitoring pulse from the monitoring arrangement W can be processed with reliability.

The trigger stage T has a first triggering transistor 57, a second transistor 58, and a control transistor 59. The base 60 of the first triggering transistor 57 is connected to the circuit point P, whereas the emitter of this transistor is connected to the second power supply line 37. The collector 62 of this transistor 57 is connected directly to the base 63 of the second trigger transistor 58, while it is simultaneously connected to a resistor 64 leading to the first power supply line 35. The second triggering transistor 58 has its emitter 65 also connected to the second power supply line 37, whereas the collector 66 is directly connected to the base 67 of the control transistor 59, as well as to a resistor 68 leading to the first power supply line 35. The control transistor 59 has its collector 69 connected to the first power supply line 35, whereas its emitter 70 leads to the second power supply line 37 through a resistor 71.

The differentiating network D is formed through a capacitor 72 having one electrode connected to the emitter 70 of the control transistor 59. The other electrode of this capacitor 72 is joined to a circuit junction F. Connected to this circuit junction F, is the monostable multivibrator M. The arrangement is such that when the trigger pulse is differentiated, the voltage spike resulting from the trailing edge, switches the monostable multivibrator M to the "on" state. The spike voltage resulting from the differentiating process of the leading edge of the trigger pulse, on the other hand, terminates the "on" state of the monostable multivibrator when the latter has not already returned to its initial state.

The monostable multivibrator M contains a first switching transistor 73 and a second switching transistor 74. The base 75 of the first transistor 73 is connected to the circuit junction F to which also a resistor 76 is connected. The other terminal of this resistor 76 is joined to the second power supply line 37. The circuit junction F and hence the base 75 of the transistor 73 is also connected to the collector 78 of the second transistor 74, through a resistor 77. The emitter 79 of the first transistor 73 is connected also to the circuit junction F through a capacitor 80 which serves to bypass disturbing pulse signals. This emitter 79, at the same time, leads to the second voltage supply line 37 through a resistor 81. The collector 82 of the first switching transistor 73 is joined to the first power supply line 35, through a resistor 83, while this collector is coupled to the base 85 of the transistor 74, through a coupling capacitor 84. Aside from this, the base 85 of the second switching transistor 74 also leads to the first power supply line 35 through a resistor 86. This resistor 86 forms a timing network together with a coupling capacitor 84, which has a duration corresponding to the duration of the interval of the monostable multivibrator. The resistor 86 is made variable or adjustable so that the time interval may be precisely set in a simple manner. The second switching transistor 74 has its emitter 87 directly connected to the second power supply line 37, while the collector 78 of this transistor 74 is connected to the first supply line 35, through a resistor 88.

The electronic protective circuit path H for limiting the rotational speed, is formed from a transistor 91 having an emitter-collector path 89-90. The base 92 of the transistor 91 is directly connected to the emitter 79 of the switching transistor 73, whereas the emitter 89 is connected to the second power supply line 37 and hence to ground potential. The collector 90 of the transistor 91 is connected in series with a diode 93 which, in turn, is connected directly to the control output terminal 29 of the voltage generator 30, by being connected to the terminal 46 of the control input branch E.

In operation of the arrangement of FIG. 1, the operating switch 13 becomes closed for the purpose of operating the driving engine B, and as a result voltage from the DC source 14 is applied to the ignition arrangement Z with terminals 11 and 16, as well as the monitoring unit with terminals 36 and 38 used to monitor and regulate the rotational speed. The emitter-collector path 17-18 of the pnp switching transistor 19 is normally conducting in the ignition arrangement Z. Accordingly, current flows, in this state of operation, through the primary winding 20 of ignition coil 21. At the instant of ignition, the positive half-wave 34 appears at the control output terminal 29 of the voltage generator 30. This half-wave 34 reaches, in the form of an actuating pulse, to the control input 25 of the ignition arrangement Z, through the circuit path 28. From there, the actuating pulse reaches the base 27 of the switching transistor 19, through the monostable multivibrator 24 lying within the circuit path 26. The applied signal to the base 27 causes the potential of this base to become positive to the extent that its emitter-collector path 17-18 of the transistor 19 becomes cutoff or nonconducting. Current flow in the primary winding 20 of the ignition coil 21 becomes thereby interrupted, and as a result a high voltage pulse is generated in the secondary winding 22. Due to the high voltage pulse induced in the secondary winding 22, an igniting spark appears across the spark plug 23, and the compressed fuel-air mixture within the cylinder becomes thereby ignited. With the aid of the monostable multivibrator 24, the emitter-collector path 17-18 of the switching transistor 19 is maintained nonconducting until the high voltage pulse has again become terminated.

The negative half-wave 33 which precedes the positive half-wave 34 at the control output terminal 29 of the generator 30 described above, reaches the terminal 46 of the control input branch E of the monitoring arrangement W, and serves as a monitoring pulse. For purposes of simplicity and maintaining the description of the embodiment in clarified form, the switching element with predetermined threshold value is used only in the form of a single zener diode 47.

If, now, the internal combustion engine B has exceeded the maximum permissible rotational speed, the control voltage generator 30 provides a monitoring pulse which gives rise to a signal exceeding the threshold value of the zener diode 47. As a result, the zener diode 47 becomes conducting and the circuit point P becomes thereby negative, so that the base 60 of the first NPN trigger transistor 57 also becomes negative. During the duration of the conducting state of the zener diode 47, the emitter-collector path 61-62 of this transistor 57 becomes cutoff or nonconducting, and the base 63 of the second NPN trigger transistor 58 becomes positive, through the resistor 64, to the extent that the emitter-collector path 65-66 of the last-mentioned transistor 58 becomes switched to the conducting state. Since the switching takes place very rapidly, a substantially rectangular-shaped pulse is produced across the resistor 68.

This pulse across the resistor 68 appears at the resistor 71 in the form of a trigger pulse due to the use of the NPN control transistor 59. At the same time, the emitter-collector path 65-66 of the second trigger transistor 58 conducts, and the base 67 of the control transistor 59 becomes negative to the extent that the emitter-collector path 70-69 attains the cutoff state. By differentiating the trigger pulse through the differentiating capacitor 72, a negative and afterward a positive voltage spike is realized at the circuit junction F. If the monostable multivibrator M is in its stable state, then this negative voltage spike has no effect upon the multivibrator M. The monostable multivibrator is in its stable state when the emitter-collector path 79-82 of the first NPN transistor 73 is cutoff and the emitter-collector path 87-78 of the second NPN transistor 74 is conducting. When, however, the positive voltage spike appears, the potential at the base 75 of the first transistor 73 rises briefly in positive direction to the extent that the emitter-collector path 79-82 becomes conducting. Following the discharge of the coupling capacitor 84, the base 85 of the second transistor 74 acquires negative potential, so that the emitter-collector path 87-78 is cutoff or nonconducting. A feedback effect then appears through the resistor 77 and to the base 75 of the first switching transistor 73, whereby a rapid switching of the multivibrator M takes place to the astable state, as well as back to the stable state.

The duration of the switching process, or the duration in which the emitter-collector path 79-82 of the first switching transistor 73 conducts and the emitter-collector path 87-78 of the second switching transistor 74 is cutoff or nonconducting, is determined by the discharging of the coupling capacitor 84 through its capacitance value, and the magnitude of the resistor 86. When the discharge of the coupling capacitor 84 has terminated or become ended, the emitter-collector path 87-78 of the second switching transistor 74 becomes again conducting, and the emitter-collector path 79-82 of the first switching transistor 73 becomes again cutoff or nonconducting.

Since the first switching transistor 73 conducts through its emitter-collector path 79-82 during the preceding switching process, the NPN transistor 91 acquires positive potential at its base 92, so that the protective path through the emitter-collector path 89-90 is also in the conducting state. The positive half-wave voltage 34 can, consequently, not be effective for initiating the ignition process during the switching step of the multivibrator M, since this positive half-wave voltage 34 is conducted away from the diode 93 and the emitter-collector path 89-90 of the protective path H. Thus, the half-wave 34 is conducted to ground. Since the fuel-air mixture in the engine B cannot be further ignited, the rotational speed also cannot assume higher values.

When, now, the further negative half-wave voltage of the generator 30 produces a monitoring pulse with amplitude also again exceeding the threshold value of the zener diode 47, a new trigger pulse appears across the resistor 71 in a manner described above. Should the switching state of the multivibrator M not yet be terminated, whereby the first transistor 73 with its emitter-collector path 79-82 is still in the conducting state, the negative voltage spike resulting from the differentiation of the trigger pulse at the leading edge, takes effect. Thus, this negative spike provides for the condition that the multivibrator M is returned to the stable state prior to the appearance of the following positive voltage spike. This negative voltage spike causes the base 75 of the first switching transistor 73 to become negative to the extent that the emitter-collector path 79-82 is again switched to the cutoff state and the emitter-collector path 87-78 of the second switching transistor 74 is again made conducting. As a result of these conditions, rapidly following monitoring pulses can be processed and evaluated through the monitoring arrangement.

If a soft speed limit is to be attained, it is necessary to care for the condition that after exceeding the maximum permissible speed and hence the corresponding voltage level, the ignition processes are not entirely rendered ineffective immediately thereafter. This is accomplished in a simple manner by providing that a plurality of monitoring pulses are taken from the generator 30 when the latter executes one revolution. These monitoring pulses are then set so that they have different amplitudes corresponding to a predetermined rotational speed.

FIG. 2 illustrates an alternating current generator with the aforementioned specification. This generator has a stator 94 with two poles 95 and 96. The rotor 97 is mounted within the stator in an unsymmetrical manner upon a shaft 98, and is rotatable with respect to the fixed poles 95 and 96 of the stator. The rotor 97 consists of material which is nonmagnetic. Thus, the rotational axis 99 of the rotor shaft 98 is displaced from the line of symmetry 100 of these stator poles 95 and 96. The axis of rotation 99 is parallel to the line of symmetry 100. Aside from this, the poles 101 and 102 of the rotor 97 are spaced at different radial lengths 11 and 12, respectively. The rotor shaft 98 is surrounded by a permanent magnet 103 which is preferably a conventional oxide magnet. The North pole N of this permanent magnet 103 faces the rotor 97 whereas the South pole S faces the stator 94. A coil 104 surrounding the magnet 103 provides the control voltage made available at the terminals 29 and 31 in FIG. 1. In accordance with this embodiment of the control voltage generator in FIG. 2, two control voltage periods are realized during one rotation of the rotor 97, and a negative half-wave 33 as well as a positive half-wave 34 are realized. When such a control voltage generator is used in accordance with the embodiment of FIG. 1, the rotor shaft 98 is driven at only half the rotational speed applied to the crank shaft K. This results from the condition that only a single cylinder internal combustion engine is applicable there, and accordingly, only a single actuating pulse for initiating the ignition and a monitoring pulse are required for one rotation of the crank shaft K. A speed-changing mechanism 105 is, accordingly, provided and shown in the drawing in schematic form. This speed-changing mechanism 105 is coupled between the crank shaft K and the rotor shaft 98, and provides for the required reduction in rotational speed.

If, now, pole 101 of the rotor moves past the stator pole 95, and the pole 102 of the rotor moves past the stator pole 96, then the first control voltage period takes place. The second control voltage period is produced when the rotor pole 101 moves past the stator pole 96 and the rotor pole 102 moves past the stator pole 95. From the drawing, it is possible to observe that in generating the first control voltage period, the air gap between the stator pole 95 and the rotor pole 101 is substantially small, whereas the air gap between the stator pole 96 and the rotor pole 102 is relatively large. In generating the second control voltage period, an air gap of intermediate length prevails between the stator pole 95 and the rotor pole 102, as well as between the stator pole 96 and the rotor pole 101. In this manner, it is possible to achieve the condition wherein the magnetic stray flux and thereby the variation in the magnetic flux is different when generating the first control period than when the second control period prevails. Accordingly, a first control voltage period is realized for a predetermined rotational speed, in which the amplitude of the half-waves are, for example, larger than those of the half-waves in the second control period. In this case, the monitoring pulse realized from the negative half-wave of the first control voltage period when exceeding the maximum permissible rotational speed, is used to influence the following ignition process. The arrangement is such that the monitoring pulse derived from the negative half-wave of the second control voltage period, is not sufficient to exceed the threshold level of the zener diode 47 and thereby affect the now-following ignition process. As a result of this arrangement and through the preceding conditions, only a portion of the following ignition cycles are suppressed when the maximum permissible speed is exceeded.

This situation applies when the maximum permissible speed is exceeded in a gradual manner.

When, however, the maximum permissible speed is exceeded suddenly and by a substantial amount, severe braking of the engine takes place, since all monitoring pulses will then exceed the threshold level of the zener diodes 47 with their amplitudes, so that all following pulses for initiating the ignition cycles are rendered ineffective. Sudden and abrupt exceeding of the maximum permissible speed may take place when the motor vehicle, for example, operates in the gear-shift position and the driven wheels are lifted from the road, or when the gear-shift lever drops out of the selected position.

The monitoring unit W can also be operatively coupled with the unit F.sub.0 used for fuel injection, instead of the ignition arrangement Z. Such a fuel injection arrangement is shown in FIG. 3. The latter contains an electromagnetically actuated injection valve 106 which is provided with a control winding 107. This control winding 107 is connected in series with the emitter-collector path 108-109 of an npn switching transistor 110. The series circuit has a terminal 111 on the transistor end, and a terminal 112 at the valve end. The base 113 of the switching transistor 110 leads to a control input terminal 115, through a monostable multivibrator 112. For purposes of applying supply voltages to the monostable multivibrator 114, the latter is also connected to the terminals 111 and 112. If, now, the injection unit F.sub.0 is inserted in FIG. 1, in place of the ignition arrangement Z, the positive supply line 12 is connected to the terminal 111, and the negative supply line 15 is connected to the terminal 112, whereas the control line 28 is connected to the control input 115.

The emitter-collector path 108-109 of the switching transistor 110 is, consequently, not conducting and the injection valve 106 is closed, when in the normal or inoperative quiescent state. As soon as the positive half-wave 34 generated by the control voltage generator 30 reaches the control input 115, the base 113 of the transistor 110 becomes positive to the extend that the emitter-collector path 108-109 conducts and the injection valve 106 becomes thereby opened. The opening duration of the injection valve 106 and hence the quantity of injected fuel are determined by the associated time interval of the monostable multivibrator 114. When operating together with the monitoring arrangement W, the fuel injection unit F differs from the ignition arrangement Z solely in the respect that when the permissible rotational speed is exceeded, no fuel injection cycle takes place. As a result of this feature, no fuel-air mixture is made available within the cylinder of the engine for ignition.

It is, of course, within the frame of the present invention that the arrangement described above may be used in conjunction with an internal combustion engine having a plurality of cylinders operating in conjunction with a rotating distributor which applies the necessary ignition pulses from the ignition coil 21 to the individual spark plugs within the cylinders from the secondary winding 22. For purposes of generating the control voltage, an embodiment as shown in FIG. 2 can then also be used. It is only necessary to provide that the rotational speed of the crank shaft K is properly changed to drive the rotor shaft 98 through the coupling 105. The alternating current generator used to provide the control voltage can, at the same time, be designed so that it has a number of stator and rotor poles corresponding to the number of cylinders so that a direct coupling between the crank shaft K and the rotor shaft 98 is possible. For the purpose of realizing a soft rotational speed limiting, the stator poles can also have, for example, elliptical surfaces, and the rotor poles may have circumferential lines also corresponding to an ellipse.

In the embodiment of FIG. 1, furthermore, a conventional high voltage capacitor ignition arrangement can also be used for ignition purposes. In this case, the control input 25, for example, leads to the control electrode of a thyristor which becomes triggered or fired through the positive half-wave 34 from the generator 30 when in the state of ineffective monitoring pulses. The charged ignition capacitor is then made to discharge through the primary winding 20 of the ignition coil 21 as a result of the conducting state of the thyristor.

Assume that the ignition arrangement consists, for example, of two arrangements commonly known as double-ignition arrangements. Each of them has a control voltage generator 30 connected to a terminal output 29 and a control input terminal 25. In such a case, the control output terminal 29 as the terminal 46, in FIG. 1, can be connected only to the protective path H through the diode 93 and a control output terminal of the other voltage generator, so that only a single monitoring unit W is used.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in monitoring arrangement for speed limiting of internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

Claims

What is claimed as new and desired to be protected by Letters Patent is:

1. An arrangement for limiting the speed of an internal combustion engine, comprising, in combination, oscillating-voltage generator means coupled with a shaft driven by said engine, and adapted to provide an oscillating voltage whose amplitude is representative of engine speed; combustion control means connected with said generator means and adapted to produce combustion control signals, timed with rotation of said shaft, for producing combustion in the engine; electronic protective circuit means adapted, when actuated, to turn off said combustion control means; threshold-detecting means adapted to produce threshold signals in response to generation by said generator means of a voltage beyond a predetermined value, said predetermined value corresponding to the maximum engine speed permissible; trigger means adapted to produce trigger pulses in response to said threshold signals; and timing means actuated in response to some of said trigger pulses and serving to switch on said protective circuit means.

2. An arrangement as defined in claim 1; and further comprising differentiating means associated with said trigger means and adapted to produce trigger pulses having the form of voltage spikes.

3. The arrangement as defined in claim 1, wherein said combustion control means comprises ignition pulse generating means for igniting the fuel-air mixture within the cylinders of said engine.

4. The arrangement as defined in claim 1, wherein said combustion control means comprises fuel injection pulse generating means for the injection of fuel into said engine.

5. The arrangement as defined in claim 1 wherein said timing means comprises a monostable multivibrator.

6. The arrangement as defined in claim 1 wherein said protective circuit means comprises a transistor with emitter-collector path in parallel with said voltage generating means and base connected to said timing means, said emitter-collector path being in the conducting state during said interval of said timing means.

7. The arrangement as defined in claim 1, including diode means connected in series with said emitter-collector path of said transistor.

8. The arrangement as defined in claim 1 including a source of DC voltage; and voltage stabilizing means associated with said threshold-detecting means and connected to said source of DC voltage for providing a source of constant voltage.

9. The arrangement as defined in claim 1 wherein said timing means comprises a monostable multivibrator with adjustable resistor means for varying the on time duration of said protective circuit.

10. The arrangement as defined in claim 1 including at least one diode connected to said threshold detecting means.

11. The arrangement as defined in claim 1 wherein said detecting means comprises at least one zener diode.

12. The arrangement as defined in claim 1 wherein said threshold means comprises at least one diode connected in series with a zener diode.

13. The arrangement as defined in claim 1 including at least one adjustable resistor connected to said threshold detecting means.

14. The arrangement as defined in claim 1 including at least one temperature dependent resistor connected to said threshold detecting means.

15. The arrangement as defined in claim 1 wherein said temperature dependent resistor controls the cylinder temperature of said engine.

16. The arrangement as defined in claim 1 wherein said threshold detecting means comprises a plurality of switching elements with different threshold values; and selector means for selecting a predetermined one of said threshold elements with a predetermined threshold value.

17. The arrangement as defined in claim 1 wherein said voltage generating means comprises an alternating current generator whereby a plurality of pulses are generated for one revolution of said alternating current generator, said plurality of pulses during one revolution of said rotor having different amplitudes for a predetermined speed of said engine.

18. The arrangement as defined in claim 1 wherein said voltage generating means comprises an alternating current generator with magnetic field generated through at least one oxide magnet.

19. An arrangement for limiting the speed of an internal combustion engine, comprising, in combination, voltage generating means coupled to the crank shaft of said engine and providing a voltage signal with amplitude dependent upon the speed of said engine, said amplitude exceeding a predetermined level when said speed exceeds a predetermined magnitude; electronic switching means connected to said voltage generating means and actuated when said amplitude exceeds said predetermined level, said switching means providing upon being actuated a regulating signal representing that the speed of said engine is above said predetermined magnitude; engine control means connected to said voltage generating means and applying controlling pulses from said voltage signal to said engine for controlling the speed of said engine, the speed of said engine being dependent on the pulse repetition frequency of said controlling pulses; inhibiting means connected between said switching means and said engine control means and actuated by said regulating signal, said inhibiting means inhibiting the application of said controlling pulses to said engine when actuated by said regulating signal; and timing means connected to said switching means for maintaining said switching means actuated for an interval so that at least the next controlled pulse to be applied to said engine is inhibited, whereby inhibiting the application of said controlling pulses to said engine reduces the speed of said engine, said voltage generating means comprising an alternating current generator providing an alternating current having a cycle constituted of two half-waves, the leading half-wave being the source for said signal amplitude for actuating said switching means means and the trailing half-wave being the source of said controlling pulses.

20. An arrangement for limiting the speed of an internal combustion engine, comprising, in combination, voltage generating means coupled to the crank shaft of said engine and providing a voltage signal with amplitude dependent upon the speed of said engine, said amplitude exceeding a predetermined level when said speed exceeds a predetermined magnitude; electronic switching means connected to said voltage generating means and actuated when said amplitude exceeds said predetermined level, said switching means providing upon being actuated a regulating signal representing that the speed of said engine is above said predetermined magnitude; engine control means connected to said voltage generating means and applying controlling pulses from said voltage signal to said engine for controlling the speed of said engine, the speed of said engine being dependent on the pulse repetition frequency of said controlling pulses; inhibiting means connected between said switching means and said engine control means and actuated by said regulating signal, said inhibiting means inhibiting the application of said controlling pulses to said engine when actuated by said regulating signal; and timing means connected to said switching means for maintaining said switching means actuated for an interval so that at least the next controlling pulse to be applied to said engine is inhibited, whereby inhibiting the application of said controlling pulses to said engine reduces the speed of said engine, said voltage generating means comprising an alternating current generator whereby a plurality of pulses are generated for one revolution of said alternating current generator, said plurality of pulses during one revolution of said rotor having different amplitudes for a predetermined speed of said engine, the rotor of said current generator being unsymmetrically mounted with respect to the stator poles of said alternating current generator, the radial lengths from the rotational axis of said rotor to the stator poles of said generator being different for each pole of the stator.