US3736910A

US3736910A - Control circuit for controlling a fuel injecting system

Info

Publication number: US3736910A
Application number: US00165797A
Authority: US
Inventors: L Raff
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1970-07-14
Filing date: 1971-07-13
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05
Also published as: AT311126B; SE368260B; DE2034764A1; SU442614A3; CH526042A; FR2101674A5; GB1335893A

Abstract

A control arrangement in internal combustion engines for controlling a group of electromagnetically actuated injection valves simultaneously. A monostable multivibrator provides pulses synchronously with the rotational speed of the engine for the purpose of determining the opening duration of the injection valves as a function of at least one operating parameter, particularly the intake manifold pressure. A first electronic circuit operable only when the throttle valve is closed, inhibits the pulses when the engine is above an upper limit, and switches the pulses back on when the engine speed is below a lower limit which is above the idling speed. A second electronic circuit which is operable at all positions of the throttle, serves to switch off the pulses when the engine speed is above a maximum value, and then switches the pulses back on when the speed drops below this maximum value.

Description

United States Patent [191 Raff CONTROL CIRCUIT FOR CONTROLLING A FUEL INJECTING SYSTEM Inventor: Lothar Raff, 7141 Hochberg, Germany Robert Bosch GmbH, Stuttgart, Germany Filed: July 13, 1971 Appl. No.: 165,797

Assignee:

Foreign Application Priority Data July 14, 1970 Germany ..P 20 34 764.2

U.S. Cl ..123/32 EA, 123/198 DB, 123/139 E, 123/139 DE, 123/97 B Int. Cl. ..F02d 31/00, F02b 3/00 Field of Search ..123/32 EA, 198 DB, 123/134 E, 139 DE, 97 B References Cited UNITED STATES PATENTS 3,522,794 8/1970 Reichardt ..123/32 EA Primary ExaminerLaurence M. Goodridge Assistant Examiner-Ronald B. Cox Att0rneyMichael S. Striker [57] ABSTRACT A control arrangement in internal combustion engines for controlling a group of electromagnetically actuated injection valves simultaneously. A monostable multivibrator provides pulses synchronously with the rotational speed of the engine for the purpose of determining the opening duration of the injection valves as a function of at least one operating parameter, particularly the intake manifold pressure. A first electronic circuit operable only when the throttle valve is closed, inhibits the pulses when the engine is above an upper limit, and switches the pulses back on when the engine speed is below a lower limit which is above the idling speed. A second electronic circuit which is operable at all positions of the throttle, serves to switch off the pulses when the engine speed is above a maximum value, and then switches the pulses back on when the speed drops below this maximum value.

15 Claims, 2 Drawing Figures CONTROL CIRCUIT FOR CONTROLLING A FUEL INJECTTNG SYSTEM BACKGROUND OF THE INVENTION The present invention relates to a control arrangement for controlling at least one group of simultaneously actuated electromagnetic injection valves in an internal combustion engine. The control arrangement has at least one switching transistor for actuating the injection valves, and is provided with a monostable multivibrator which is, in turn, actuated synchronously with the rotational speed of the crank shaft. The monostable multivibrator provides pulses for determining the opening duration of the injection valves as a function of at least one operating parameter as, for example, the intake manifold pressure or vacuum of the engine.

Heretofore in the art, control arrangement of these species possessed two deficiencies which become noticeable under particular operating conditions of the engine. First of all, when the engine is used for braking purposes, fuel is further injected so that the braking effect is diminished, and unnecessary quantities of injurious gases are emitted. Secondly, it is easily possible that when the gas pedal or accelerator is fully depressed, the maximum engine speed becomes exceeded when driving downhill, since a considerable amount of fuel is injected under this condition.

To eliminate the first deficiency, heretofore, a bistable multivibrator was provided with two RC networks which close or cut off the fuel injection above an upper limit of the engine speed. First when the engine speed drops back to a value below a lower speed limit, can fuel again be injected. For eliminating the second deficiency, it is known in the art, to interrupt the ignition with the aid of a centrifugal governor when the maximum speed of the engine is exceeded. The combination of these two known arrangements, however, involves considerable design complexity and equipment.

Accordingly, it is an object of the present invention to provide a simple auxiliary arrangement which eliminates both of the deficiencies described above. A particularly satisfactory solution results when, in accordance with the present invention, a first electronic circuit is provided which is operable only when the throttle valve is closed. This first electronic circuit-serves to switch off or inhibit the transmission of pulses for the fuel injection valves when the engine speed is above an upper speed limit. The pulses are again switched on or allowed to be transmitted when the engine speed drops below a lower limit which is, however, above the idling speed. A second electronic circuit which operates at all throttle positions, serves to switch off or inhibit the transmission of the pulses when the engine speed is above a maximum value. This circuit then allows the pulses to be switched back on when the engine speed drops below this maximum speed limit.

This control arrangement, in accordance with the present invention, can be designed through different embodiments. The-control arrangement has two electronic circuits which serve to close the injection valves. One of the electronic circuits is operable when the engine is used for braking purposes, and the second electronic circuit is operable when'the maximum engine speed is exceeded. It is possible to also apply the present invention in control arrangements which are more complex than the arrangements discussed above.

LII

From the viewpoint of safety, it is particularly advantageous when the first electronic circuit possesses a switching hysteresis, while the second electronic circuit does not possess such switching hysteresis. As a result of such hysteresis relationship, engine braking is made possible when the accelerator is in its un-depressed position. When the maximum permissible engine speed is exceeded, on the other hand, a speed limiting is applied without braking effects. The second electronic circuit must not possess any switching hysteresis under any conditions, since such hysteresis effects could prove dangerous under conditions of passing on a highway.

SUMMARY OF THE INVENTION An arrangement used in internal combustion engines for controlling a group of electromagnetic fuel injection valves which are simultaneously actuated. The valves are actuated through the use of at least one switching transistor. A monostable multivibrator is driven synchronously with the crank shaft rotation through a cam and switch arrangement. The multivibrator provides pulses which determine the opening duration of the injection valves as a function of at least one operating parameter, preferably the intake manifold vacuum pressure. A first electronic circuit is provided which is operable only when the throttle of the engine is closed. This first circuit serves to switch off or inhibit transmission of the pulses from the multivibrator when the engine speed is above an upper limit. When the engine speed drops below a lower limit which is above the idling speed, the pulses are switched back on. A second electronic circuit which is operable or effective for all throttle positions, switches the pulses off when the maximum permissible engine speed is exceeded. When the speed drops again below this maximum limit, the pulses are again switched on.

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.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electronic circuit diagram and shows the arrangement of the components and their interconnections for carrying out one embodiment of the present invention; and

FIG. 2 is an electronic circuit diagram and shows the components and their interconnections for carrying out a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS by an amplifier T5. In the first embodiment, the pulse generator consists of a switch 17 and of a monostable multivibrator 16. The switch 17 is operated in synchronism with the rotation of the engine by a cam 88, which is turned by the crank shaft 32, as shown by the broken line 89. The monostable multivibrator 16 includes two transistors 18 and 19, which have the

respective load resistors

22 and 23. These two transistors are mutually coupled together by a resistor 21 and by a transformer 24 so as to obtain the desired monostable operation. When the switch 17 is open, the monostable multivibrator 16 is in the stable state, the transistor 18 being conductive and the transistor ll9 being cut off. When the multivibrator 116 is in the stable state, a first connecting terminal 67, which is connected to the collector of the transistor 19, is at the voltage of the positive rail 66.

When the switch 17 is momentarily closed, the monostable multivibrator 16 is triggered to the unstable state. The length of time of the unstable state depends on the amount of mutual inductance between the two windings of the transformer 24. The mutual inductance can be varied by shifting the movable iron core 25 of the transformer. The iron core 25 is shifted in dependence on the intake manifold pressure by a pressure box 83 that is coupled to the iron core by a rod that is symbolized by the broken line 91. In this way it is possible to vary the length of the fuel injection pulses in dependence on the intake manifold pressure, so that with an open throttle valve 85 more fuel is injected.

In the control arrangements of the prior art, the output pulses of the multivibrator 16 are strengthened in the amplifier l and then conducted directly to the switching transistor 11. There will now be described what constitutes the core of the invention: namely, two bistable triggered

circuits

45 and 46 and two passive networks 30 and 3th. The purpose of these passive networks is to determine certain limiting engine speeds, the purpose of the triggered circuits being to prevent the pulses from the multivibrator 116 from being conducted to the switching transistor 11 when these limiting speeds are exceeded. Since both of the triggered

circuits

45 and 46 have the same purpose, it is possible to omit one transistor and to use the transistor 48 in both of the circuits 415 and 416.

The first bistable triggered circuit 45 includes a first transistor 47 and a second transistor 48 respectively having the

load resistors

49 and 55. The resistor 55 connects the base of the transistor 48 to the collector of the transistor 47, and the resistor 51 connects the base of this transistor to the collector of the transistor 48. The

resistors

56, 57, and 58, constitute a base voltage divider for the transistor 43, the base of this transistor and the resistor 52 being connected to the junction between the

resistors

56 and 57. An RC network, composed of the resistor 59 and the capacitor 60, is connected in parallel with the resistor 57. A pulse conductor 73 connects the junction between the

resistors

57 and 58 to the collector of resistor 19 of the monostable multivibrator 16. This collector is the output of the multivibrator.

The base of the first transistor 47 is connected to the positive voltage supply line 66 by way of the series circuit containing the diode 411i and two resistors 4ll and 42. The junction between the

resistors

41 and 42 can be connected to the negative voltage supply line 65 through a switch 39. This switch 39 is actuated through the gas pedal 84, or accelerator 84, as indicated through the broken line 86. The switch 39 is closed when the gas pedal or accelerator is in its un-actuated or un-depressed position. The base of the first transistor 47 is, aside from this, connected to a third terminal 68 through a diode 37. This terminal 68 serves as a connecting terminal for the first passive network 30.

This first passive network 30 has three

terminals

67, 68 and 69. The first terminal 67 is connected to the collector of the transistor 19. The second terminal is, as already described, connected to the base of the first transistor 47, through the diode 37. The third terminal 69, on the other hand, is connected to the negative voltage supply line 65.

In the first passive network 30, the first terminal 67 leads to the second terminal 68, through the series circuit containing the first charging resistor 29 and a first capacitor 36. The junction 71 between the first charging resistor 29 and the first capacitor 36 is connected to the third terminal 69, through the series circuit containing a diode 34, a second capacitor .32, and a second charging resistor 31. The junction 72 between the diode 34 and the second capacitor 32 leads to the junction 71 through a third charging resistor 33. This junction 72 also leads to the second terminal 68 through a fourth charging resistor 35.

The collector of the first transistor 47 also leads to the junction between the second charging resistor 31 and the second capacitor 32, through a resistor 53.

The components of the second passive network 30' differ from those of the first passive network 30, only in their component values. Otherwise, the arrangement is the same. However, no corresponding resistor is provided for the element 53. This resistor must be omitted in the second passive network, since it gives rise to switching hysteresis.

The second bistable circuit stage 46 is a simplified version of the first bistable switching stage 45, since the switch 39 actuated by the gas pedal or accelerator, is omitted. The third transistor 47 has a resistor 49 which is connected between the collector of this transistor 47 and the positive voltage supply line 66. The two diodes S0 and 50' decouple the transistor 47 from the transistor 47. The collector of the second transistor 48 is coupled to the base of the third transistor 47', through a resistor 51.

In the stable inoperative state of the circuit, the transistor 18 within the control multivibrator 16, conducts,

whereas the transistor 19 is non-conducting. The collector of the transistor 19 is, thereby, at positive potential. Through the line 73 and the

base voltage divider

56,57,58, the base potential of the second transistor 48 is driven in the positive direction to the extent that this transistor 48 becomes conducting. The amplifier stage 15 is arranged so that the output pulses of the second transistor 48 are only amplified and not inverted. As a result, the switching transistor 11 is non-conducting in its inoperative or initial state, and the injection valves remain closed.

If, now, the monostable multivibrator 16 is switched to its unstable state by closing the switch 17, then the collector potential of the transistor 19 is driven into the negative region. The processes in the first passive network 30 and in the first transistor 47 are for the time being disregarded. The negative step voltage at the collector of the transistor 19, is applied to the base of the second transistor 48 through the connecting line 73,

the resistor 57, and the RC network 59,60. As a result, the second transistor 38 becomes non-conducting. The collector potential of the second transistor lb becomes driven thereby in positive direction, and the switching transistor 11 becomes thereby conducting so that the injection valves l3 become opened. The monostable multivibrator 16 is switched back to its stable state, these steps or processes are carried out in reverse, and the injection valves become again closed. After the functional operation that was described above, the second transistor 48 functions simply as an inverting stage. The second transistor 48 must, thereby, become nonconducting when the injection valves are to be opened.

When the two

diodes

37 and 37, which form the coupling between the passive networks 30 and 3d, and the

bistable stages

45, 46 become isolated, the base electrode of the transistors d7 and 47 are affected only through the

resistors

51 and 51'. in this case, the transistor 47' switches in the reverse direction from the transistor 48 with which it forms a bistable stage as. Thus, the transistor 47' is turned off when the second transistor 48 becomes conducting or is turned on. When the switch 39 becomes closed, the same situation applies for the transistor 47 which also forms. a bistable stage 45, together with the second transistor 48. When the diodes 37 and 37' are in the circuit, they influence or affect the switching of the

bistable stage

45 and 46 only when the passive networks 361) and 3% have negative output pulses.

The control arrangement has the purpose or object of preventing the opening of the injection valves '70 under two operating conditions of the engine. This task is achieved through the passive networks 3i) and 3b which provide negative output pulses so that the switching of the bistable stages 45 and as is prevented or inhibited. These two operating conditions of the engine are as follows:

1. Under general conditions when the maximum rotational speed of the engine of, for example, 6,000 revolutions per minute, is exceeded.

2. When the upper limit of the engine speed is exceeded as, for example, 1,800 revolutions per minute while driving with the accelerator or gas pedal in the un-depressed position. Since in this case, the engine is to be used for braking purposes, the opening of the injection valves must also be prevented even after the drop in engine speed. in this case, the stopping or blocking arrangement must possess hysteresis characteristics from a safety point of view. First when the speed has dropped below, for example, 1,000 revolutions per minute, thus the injection valves be allowed to open again, in order to prevent the engine from becoming stalled. The switching hysteresis described above, makes thereby possible the engine braking. it is to be noted, at the same time, that the lower limit speed lies above the idling speed of, for example, 800 revolutions per minute.

The functional mode under engine operation under which the maximum speed is exceeded, as described in (l will now be described. in order to prevent the opening of the injection valves, the base electrode or the base terminal of the third transistor 47' must receive a negative pulse, so that the second transistor d8 is prevented from being turned off. When the monostable multivibrator i6 is in its stable state, the collector of the transistor 19 is at positive potential. At that time, the second capacitor 32 becomes charged through the resistors 29', 33, and 311'. Both terminals of the first capacitor 36' are connected with the positive terminal 72' of the second capacitor 32, through resistors 33' or 35'. As a result, these two terminals of the first capacitor as receive the same potential variation as the terminal 72'. The capacitance of the condenser or capacitor 36' is substantially smaller than that of the second capacitor 32.

At the instant of time 1 a pulse is transmitted through the closing of the switch E7. The collector potential of the transistor 3Q switches by the amount of U in the negative direction. The second capacitor 32 becomes charged through the positive voltage U until time The two terminals 71' and 68' of the first capacitor 36 are also subjected substantially to this potential. The junction 73' does not receive the full step voltage of U instead, it receives only a step of U U in the negative direction. When this potential drops further below this value, the diode 3 conducts, and the second capacitor 32 becomes discharged through the resistors 3i and 29. For accurate computation, U must be multiplied by the factor in order to take into account the voltage divider composed of resistors 29 and Bi. Since, however, the second resistor 31' can be omitted without causing the circuit to become inoperative, this factor can be neglected from qualitative considerations.

The voltage step U U K becomes transmitted to the second terminal on, from the first capacitor 36'. This terminal as has substantially the potential +U directly before the instant of time Immediately after the time instant this terminal 6% has the potential U (U, U,,) 2 U, U This potential 2 U U must become negative in order to turn off the transistor d7" through the diode 37' and the resistor 54. This potential, however, becomes negative when U,, becomes smaller than in U This situation prevails, consequently, at higher pulse frequency when only a substantially small time interval is available for charging the second capacitor 32'.

The second passive network 30 applies to its second terminal (98', negative output pulses when the maximum speed of the engine is exceeded. The maximum engine speed limit can be set through the third resistor 33' which is constructed in the form of a trimming potentiometer, for the purpose of accurate setting. The output pulses of the second passive network 30' have a steep leading edge, and decay exponentially, since the first capacitor as discharges through the fourth resistor 35'.

in order to establish unique switching relationships, it is possible to apply also exponentially decaying pulses to the base of the second transistor lb. The RC network consisting resistor 59 and capacitor 6% serves for this purpose. The time constant of this RC network has a substantially short magnitude of approximately 10 microseconds. in contrast to this, the output pulses of the second passive network 30' decay with a longer time constant of at least lOO microseconds. The functional operation of securing against excessive speed is briefly summarized below:

Below the maximum engine speed, the second transistor 48 has applied to it pulses of alternating polarity, through the line 73 and the RC network 59,6ll. The second bistable stage as switches thereby to its other stable state. As long as the second transistor 48 can remain turned off, fuel is injected. As soon as the maximum engine speed becomes exceeded, the short negative pulse of approximately 10 microseconds is applied to the base of the second transistor 48, through the line 73. At the same time, however, a positive pulse with longer duration is obtained from the third transistor 47 Since the pulse height of the short negative pulse is larger than that of the positive pulse, the second transistor 48 still remains turned off for 10 microseconds. However, the injection valves are not capable of opening within 10 microseconds because of their substantially large inertia. The longer positive pulse then causes the second transistor 48 to be conducting after the approximately 10 microseconds, and prevents the opening, thereby, of the injection valve 90.

The first bistable stage 45 functions in a similar manner in maintaining the valves closed during operation. The base of the first transistor 47 is joined with the positive voltage supply line, through the

resistors

41 and 42. As a result, the first transistor is continuously maintained conducting, since the pulses applied through the high-resistance resistor 51 are not sufficient to turn this transistor off. The first transistor 47 can first be turned off when, at the same time, the switch 39 is closed (in the unactuated position of the gas pedal) and the first passive network 30 provides negative output pulses. When the first transistor 47 does become turned off, the terminal of the second capacitor 32, which is connected to the second resistor 31, receives potential determined from the voltage divider consisting of

resistors

49,53 and 31. The voltage U,, at the capacitor 32 becomes, thereby, smaller. In accordance with what was said above in relation to the second passive network 30, the upper frequency limit of the first passive network 30 becomes, thereby, smaller, as soon as the first passive network 30 provided a negative output signal. The resistor 53 provides the required hysteresis as follows:

The fuel injection is prevented or inhibited when the gas pedal is un-depressed or un-actuated, and the engine speed is above an upper speed limit. This speed limit can, for example, be 1,500 revolutions per minute. When the engine speed decreases thereupon, no further fuel is injected as a result of the hysteresis. Only when the lower speed limit is first reached, is fuel injection again initiated, in order to avoid stalling of the eng The two

diodes

50 and 50 decouple the first transistor 47 from the third transistor 47'.

the second transistor 48 can be accomplished through the first transistor 47 as well as through the third transistor 47.

The number and complexity of components which one would expect in a control arrangement which is so versatile, was considerably reduced in the aforementioned first example. Thus, the second transistor 48 was utilized three times, and the first transistor 47 was utilized twice. The second transistor 48 serves first as an inverter (when no passive network is applicable), and then this transistor serves as part of the first bistable stage 45. Thirdly, this transistor 48 serves as part of the second bistable stage 46. The transistor 47 serves in the first place as part of the first bistable stage 45, and then in the second place the transistor 47 serves to form an AND gate together with the

diodes

37 and 40, the

resistors

41 and 42, and the switch 39.

The turning off of so FIG. 2 illustrates the switching circuit for a second embodiment of the control arrangement. This embodiment shows that the application of the invention is not limited to particularly simple injection arrangements. The four injection valves are subdivided into two groups of two injection valves each. Each one of these groups has its own control channel. The power transistor 11 forms together with the transistor 219, the first control channel. This transistor 219 in front of the power transistor 11 serves in the form of an AND gate. The power transistor 11 forms the second control channel together with the transistor 220 which also serves as an AND gate. Each of the two control channels can be selected through one common bistable multivibrator 200, in an alternating manner for a subsequent injection process with two of the four injection valves. The multivibrator 200 is bordered with a dashed line in the drawing. This multivibrator has two

transistors

201 and 202 of npn type. The emitters of these two transistors are directly connected to the negative supply line 65, whereas their collectors lead to the positive voltage supply line 66 through

resistors

203 and 204, respectively. From the collector or from the resistor 204 of the transistor 202, stems a feedback network consisting of the series circuit of resistors 205, resistor 206 and a diode base of the transistor 201. The base of the transistor 201 leads to the negative voltage supply line 65 through a resistor 208. The collector of the transistor 201 is connected, in an analogous manner, to the base of the transistor 202, through the two

resistors

211 and 212, as well as the diode 213. The base of the transistor 202 leads to the negative voltage supply line 65 through the resistor 214. The selection of the control channel is performed through the two switches 209 and 215 which are present in the distributor, not shown, of the high voltage ignition arrangement of the internal combustion engine. The fixed contacts of these switches are connected to the negative voltage supply line 65. The switching arm of the switch 209 is joined to the junction of the two

feedback resistors

205 and 206. The switching arm or movable contact of the switch 215, on the other hand, is connected to the junction of the

resistors

211 and 212, which are connected in series and lead to the base of the transistor 202.

The bistable multivibrator 200 does not have only the task of selecting one of the control channels. This multivibrator 200 also delivers control pulses for the monostable multivibrator 16. These pulses are provided by the switch 17 in the first embodiment. Two differentiating networks are provided for this purpose. These differentiating networks are composed of the series circuits of a

capacitor

229 or 230 and a

resistor

231 or 232, respectively. The free terminal of the capacitor 229 is connected to the collector of the transistor 202, and the free terminal of the capacitor 230 is connected to the collector of the transistor 201. The free terminals of the two

resistors

231 or 232 are connected to the negative voltage supply line 65. From the terminal of this capacitor with the resistor, a

respective diode

233 and 234 lead to the base of the transistor 18 which forms a part of the monostable multivibrator 16. The monostable multivibrator 16 is thereby actuated when either the switch 209 or the switch 215 are closed. For this reason the monostable multivibrator 16 can determine the pulse duration of both control channels for the fuel injection arrangement.

207. This feedback circuit leads to the The output pulses provided by the collector of the transistor 19 are processed further in a circuit which is similar to the one used in the first embodiment. Under normal operation, the second transistor 48 functions again as an inverting stage. The transistor 48 controls the switching transistor 226 which has its collector joined to the bases of the two

transistors

219 and 220 through

resistors

222 and 223, respectively. These two

transistors

219 and 220 function as AND gates. The operational mode of the AND gate is explained in the example related to the first control channel: the switching transistor 11 can conduct only when the transistor 219 is turned off. Two conditions must be fulfilled therewith. First of all, the transistor 201 within the bistable multivibrator 200 must conduct, and secondly, the switching transistor 226 must conduct. The transistor 226, however, conducts only when the second transistor 48 is turned off. i

The two

cams

210 and 216 actuate the switches 209 and 215 in a synchronous manner, and they are adjusted so that one switch is closed when the other is opened. When, now, the switch 215 closes, for example, the transistor 202 is turned off and the transistor 201 becomes conducting. The monostable multivibrator 16 becomes actuated over the differentiating networks, and as a result the second transistor 48 becomes also turned off. The two inputs to the AND gate in the form of transistor 219, aquire thereby negative potential, and this transistor 219 becomes turned off. The switching transistor 11 conducts thereby and actuates both injection valves of the first group.

In the second embodiment, means are further provided in order to make the switch-off speed and the switch-on speed dependent upon the engine temperature variations in operation. For this purpose a voltage divider is provided with resistor 133 and the resistor 132, as well as the thermistor 131. In the first embodi' ment, the charging voltage of the first capacitor 36 becomes determined through the resistor 35 and the magnitude of the voltage across the second capacitor 32. The resistor 35 is omitted in the second embodiment. The charging voltage of the first capacitor 36 becomes determined through the voltage divider 132, 131. The thermistor 131 is in thermal contact with the engine block, and has a high resistance at low temperatures. As a result, the first capacitor 36 becomes charged to a higher voltage at lower temperatures, so that the frequency limit of the first passive network 30 shifts to higher values. It is achieved therewith that the switchon speed becomes set to the required higher idling speed when the engine is cold. This is required in order that the engine can freely operate or turn over even at low temperatures.

The second embodiment illustrates still a further essential improvement over that from the first embodiment:

The first terminal 67' of the second passive network 30 is not connected with the output of the multivibrator 16, but is instead connected with the collector of the transistor 202 in the bistable multivibrator 200. This switching arrangement is advantageous because the phase relationship of the output pulses of the monostable multivibrator 16, i.e., the relationship of pulse duration to period, is dependent upon the manifold intake pressure of the engine. Since the charging voltage of the second capacitor 32' is determined from the levels of the pulse dwell intervals, the frequency limit of the second passive network 30' depends on the intake manifold pressure, in the first embodiment. In the case of the first passive network 30,, this is of no consequence, since the throttle is closed during operation. In contrast to this, the maximum speed varies as a function of the intake manifold pressure up to approximately 15 per cent, in the first embodiment in which the second passive network 30' interconnects the fuel injection.

In the second embodiment, pulses are applied to the second passive network 30', which have a duration to period ratio that is not dependent upon the intake manifold pressure. These pulses appear only when a single control channel is actuated, so that when the maximum engine speed is exceeded, only the valves of a single valve group becomes closed. In spite of this, effective safety against excessive speeds is obtained in smaller engines of lower power, since the power of the engine drops to less than half, when half of the fuel injection valves are closed. If the arrangement in accordance with the present invention is to be installed in engines with large power output, then all injection valves must be made closeable when the maximum engine speed is exceeded. The first embodiment is basically applicable to this purpose. It is necessary to insert the resistor 33' in the second passive network 30', so that the frequency limit of the second passive network does not lie above the maximum permissible speed of the engine for any intake manifold pressure that may be encountered in operation. It is essential to recognize, however, that safety against excessive speeds becomes effective dependent upon the intake manifold pressure at different maximum speeds.

When it is not possible to take into account the dependency of maximum engine speed on intake manifold pressure, the control arrangement can be modified without the use of large equipment or complex design. It is only necessary to provide a pulse emitter or generator which applies a pulse to the second passive network 30' when each control channel is actuated. The pulse duration to period ratio of the pulses is thereby not dependent on the intake manifold pressure or manifold vacuum. In this case, it is possible to apply the output pulses of the monostable multivibrator 16 to a further monostable multivibrator. This further monostable multivibrator then provide pulses which no longer have a duration to period ratio which is dependent upon the intake manifold pressure. These pulses can then be used for controlling or applying to the second passive network.

From the preceding explanations, it is evident that the basic concept of the present invention is to provide an arrangement that safely secures against excessive speeds during operation of an engine, through the use of two electronic circuits which are used to control the injection valves. The present invention is applicable to different circuitry. It is also possible, in accordance with the present invention, to design the circuits so that they can take into account still further parameters as, for example, the engine temperature. It is possible, for example, to modify the second passive network 30' by inserting a temperature dependent resistor, so that the maximum engine speed is also limited to lower values at lower temperatures. This is of advantage because when the engine is cold, the lubrication presents difficulties and problems.

ill

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 a control circuit for controlling a fuel injecting system, it is not intended to be limited to the details shown, since various modifications, structural and circuit 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.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. Control circuit for controlling the operation of at least one group of simultaneously opened and closed electromagnetic fuel injection spray valves of a fuel injection system of an internal combustion engine, comprising, in combination, a monostable multivibrator for producing, in dependence on at least one engine operating parameter, control pulses in time with the rotation of the engine crankshaft for determining the length of the open times of the fuel injection spray valves; switching means for controlling the opening and closing of the fuel injection spray valves, said switching means being connected to receive said control pulses as input for controlling said switching means; first circuit means connected to said monostable multivibrator and to said switching means for preventing, only when the throttle valve is closed, said control pulses from controlling said switching means when the engine rpm exceeds an upper limit that is above the idling rpm so as to prevent the injection of fuel by at least one group of valves and for allowing, only when the throttle valve is closed, said control pulses to control said switching means at an engine rpm that is below said upper limit but above the idling rpm so as again to permit the injection of fuel by said at least one group of valves; and second circuit means, connected to said switching means, for preventing, at all positions of the throttle valve, said control pulses from controlling the switching means when the engine rpm exceeds the maximum engine rpm so as to prevent the injection of fuel by at least one group of valves, and for allowing, at all positions of the throttle valve, said control pulses to control the switching means at any engine speed below said maximum engine rpm so as again to permit the injection of fuel by said at least one group of valves, each ofsaid first and second circuit means including a respective bistable triggered circuit, each said bistable triggered circuit having at least one input, said first and second circuit means further including each a respective passive network, said passive network of said first circuit means being connected between said input of said bistable triggered circuit of said first circuit means and the output of said monostable multivibrator, said passive network of said second circuit means being connected to the input of said bistable triggered circuit of said second circuit means.

2. Control circuit for controlling the operation of two groups of simultaneously opened and closed electromagnetic fuel injection spray valves of a fuel injection system of an internal combustion engine of which the valves of each group are simultaneously opened and closed, comprising, in combination, a monostable multivibrator for producing, in dependence on at least one engine operating parameter, control pulses in time with the rotation of the engine crankshaft for determining the length of the open times of the fuel injection spray valves; switching means for controlling the opening and closing of the fuel injection spray valves, said switching means being connected to receive said control pulses as input for controlling said switching means; first circuit means connected to said monostable multivibrator and to said switching means for preventing, only when the throttle valve is closed, said control pulses from controlling said switching means when the engine rpm exceeds an upper limit that is above the idling rpm so as to prevent the injection of fuel by at least one group of valves and for allowing, only when the throttle valve is closed, said control pulses to control said switching means at an engine rpm that is below said upper limit but above the idling rpm so as again to permit the injection of fuel by said at least one group of valves; second circuit means, connected to said switching means, for preventing, at all positions of the throttle valve, said control pulses from controlling the switching means when the engine rpm exceeds the maximum engine rpm so as to prevent the injection of fuel by at least one group of valves, and for allowing, at all positions of the throttle valve, said control pulses to control the switching means at any engine speed below said maximum engine rpm so as again to permit the injection of fuel by said atleast one group of valves, a bistable multivibrator having two inputs and two outputs, respective switch means for each input of said bistable multivibrator operated in synchronism with the engine crankshaft for triggering said bistable multivibrator back and forth between the two stable states thereof; and first and second control paths connected to respective ones of said two outputs of said bistable multivibrator for controlling the opening and closing of respective ones of the two groups of fuel injection spray valves, and wherein one of said first and second control paths includes said switching means, and both of said outputs of said bistable multivibrator are connected to the input of said monostable multivibrator.

3. The control arrangement as defined in claim i, wherein said passive network of said first circuit means has first, second and third external connections, said first external connection being connected to the output of said monostable multivibrator, said second external connection being connected to said input of said bistable triggered circuit of s'aidfirst circuit means, said third external connection being connected to one polarity of a source of voltage.

4. The control arrangement as defined in claim 3, further including a diode connected between said second external connection and said input of said bistable triggered circuit of said first circuit means.

5. The control arrangement as defined in claim 3, wherein said passive network of said first circuit means further includes a first resistor and a first capacitor connected in series between said first and second external connections, a diode, and a second capacitor and a second resistor connected in series between said third external connection and the junction between said first resistor and said first capacitor, a third resistor connected between the junction between said diode and said second capacitor and said junction between said first resistor and said first capacitor, and a fourth resistor connected between the junction between said diode and said second capacitor and said second connection.

6. The control arrangement as defined in claim 1, wherein each said passive network has the same component, the values of which are different in dependence on said upper limit and said maximum engine rpm.

7. The control arrangement as defined in claim 1, wherein said bistable triggered circuit of said first circuit means includes first and second transistors, a resistor connecting the output electrode of the first transistor to the input electrode of the second transistor, and a resistor connecting the output electrode of the second transistor and the input electrode of the first transistor.

8. The control arrangement as defined in claim 7, wherein the output electrodes of said first and second transistors are the collectors and the input electrodes of said first and second transistors are the bases.

9. The control arrangement as defined in claim 7, further including first and second source polarities, said bistable triggered circuit of said first circuit means further including a resistor connecting said input electrode of said second transistor to the first source polarity, two series connected resistors connecting said input electrode of said second transistor to the second source polarity, a series connected capacitor and resistor connecting said input electrode of said second transistor to the output of said monostable multivibrator, the junction between said two series connected resistorsbeing connected to the output of said monostable multivibrator.

10. The control arrangement as defined in claim 7, wherein said bistable triggered circuit of said second circuit means includes said second transistor of said bistable circuit of said first circuit means and a third transistor, said resistor connecting the output electrode of said first transistor to the input electrode of said second transistor also connecting the output electrode of said third transistor to the input electrode of said second transistor, and a resistor connected between the input electrode of said third transistor and the output electrode of said second transistor.

11. The control arrangement as defined in claim 10, including a respective diode connecting the output electrode of each of said first and third transistor to said resistor connecting the output electrode of said first transistor to the input electrode of said second transistor, for mutually decoupling the first and third transistor.

12. The control arrangement as defined in claim 10, wherein the passive network of said second circuit means has first, second and third external connections, said first external connection being connected to the output of said monostable multivibrator, said second external connection being connected to the input electrode of said third transistor, said third external connection being connected to one polarity of a source of voltage, and further wherein said switching means is a switching transistor and the output electrode of said second transistor is connected to the control electrode of said switching transistor.

13. The control arrangement as defined in claim 12, further including a series connected diode and resistor connecting said second external connection to the input electrode of said third transistor.

14. The control arrangement as defined in claim 12, further including an amplifier connecting the output electrode of said second transistor to the control electrode of said switching transistor.

15. The control arrangement as defined in claim 5, wherein said bistable triggered circuit of said first circuit means includes first and second transistors, a resistor connecting the output electrode of the first transistor to the input electrode of the second transistor, a resistor connecting the output electrode of the second transistor to the input electrode of the first transistor, and further wherein a resistor connects the output electrode of said first transistor of said bistable triggered circuit of said first circuit means to the junction between said second capacitor and said second resistor of said passive network of said first circuit means for obtaining a switching hysteresis.

Claims

1. Control circuit for controlling the operation of at least one group of simultaneously opened and closed electromagnetic fuel injection spray valves of a fuel injection system of an internal combustion engine, comprising, in combination, a monostable multivibrator for producing, in dependence on at least one engine operating parameter, control pulses in time with the rotation of the engine crankshaft for determining the length of the open times of the fuel injection spray valves; switching means for controlling the opening and closing of the fuel injection spray valves, said switching means being connected to receive said control pulses as input for controlling said switching means; first circuit means connected to said monostable multivibrator and to said switching means for preventing, only when the throttle valve is closed, said control pulses from controlling said switching means when the engine rpm exceeds an upper limit that is above the idling rpm so as to prevent the injection of fuel by at least one group of valves and for allowing, only when the throttle valve is closed, said control pulses to control said switching means at an engine rpm that is below said upper limit but above the idling rpm so as again to permit the injection of fuel by said at least one group of valves; and second circuit means, connected to said switching means, for preventing, at all positions of the throttle valve, said control pulses from controlling the switching means when the engine rpm exceeds the maximum engine rpm so as to prevent the injection of fuel by at least one group of valves, and for allowing, at all positions of the throttle valve, said control pulses to control the switching means at any engine speed below said maximum engine rpm so as again to permit The injection of fuel by said at least one group of valves, each of said first and second circuit means including a respective bistable triggered circuit, each said bistable triggered circuit having at least one input, said first and second circuit means further including each a respective passive network, said passive network of said first circuit means being connected between said input of said bistable triggered circuit of said first circuit means and the output of said monostable multivibrator, said passive network of said second circuit means being connected to the input of said bistable triggered circuit of said second circuit means.

2. Control circuit for controlling the operation of two groups of simultaneously opened and closed electromagnetic fuel injection spray valves of a fuel injection system of an internal combustion engine of which the valves of each group are simultaneously opened and closed, comprising, in combination, a monostable multivibrator for producing, in dependence on at least one engine operating parameter, control pulses in time with the rotation of the engine crankshaft for determining the length of the open times of the fuel injection spray valves; switching means for controlling the opening and closing of the fuel injection spray valves, said switching means being connected to receive said control pulses as input for controlling said switching means; first circuit means connected to said monostable multivibrator and to said switching means for preventing, only when the throttle valve is closed, said control pulses from controlling said switching means when the engine rpm exceeds an upper limit that is above the idling rpm so as to prevent the injection of fuel by at least one group of valves and for allowing, only when the throttle valve is closed, said control pulses to control said switching means at an engine rpm that is below said upper limit but above the idling rpm so as again to permit the injection of fuel by said at least one group of valves; second circuit means, connected to said switching means, for preventing, at all positions of the throttle valve, said control pulses from controlling the switching means when the engine rpm exceeds the maximum engine rpm so as to prevent the injection of fuel by at least one group of valves, and for allowing, at all positions of the throttle valve, said control pulses to control the switching means at any engine speed below said maximum engine rpm so as again to permit the injection of fuel by said at least one group of valves, a bistable multivibrator having two inputs and two outputs, respective switch means for each input of said bistable multivibrator operated in synchronism with the engine crankshaft for triggering said bistable multivibrator back and forth between the two stable states thereof; and first and second control paths connected to respective ones of said two outputs of said bistable multivibrator for controlling the opening and closing of respective ones of the two groups of fuel injection spray valves, and wherein one of said first and second control paths includes said switching means, and both of said outputs of said bistable multivibrator are connected to the input of said monostable multivibrator.

3. The control arrangement as defined in claim 1, wherein said passive network of said first circuit means has first, second and third external connections, said first external connection being connected to the output of said monostable multivibrator, said second external connection being connected to said input of said bistable triggered circuit of said first circuit means, said third external connection being connected to one polarity of a source of voltage.

9. The control arrangement as defined in claim 7, further including first and second source polarities, said bistable triggered circuit of said first circuit means further including a resistor connecting said input electrode of said second transistor to the first source polarity, two series connected resistors connecting said input electrode of said second transistor to the second source polarity, a series connected capacitor and resistor connecting said input electrode of said second transistor to the output of said monostable multivibrator, the junction between said two series connected resistors being connected to the output of said monostable multivibrator.