US3916865A

US3916865A - Electronic governor for internal combustion engine

Info

Publication number: US3916865A
Application number: US478594A
Authority: US
Inventors: Uwe Kiencke; Martin Zechnall
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1973-07-12
Filing date: 1974-06-12
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04
Also published as: GB1477365A; JPS5037926A; DE2335440A1

Abstract

To provide for speed governing of internal combustion engines having an electronic fuel control, typically an electronic fuel injection system in which the pulse duration of generated injection control pulses determines the amount of fuel being supplied, in a given time, to the engine, a pulse source generates a series of pulses at a frequency determinative of maximum speed of the engine. This frequency is compared with a frequency representative of actual engine speed and, when the actual speed frequency exceeds the maximum generated speed frequency, a switch (typically a flip-flop) is controlled to change state, the switch being connected to interrupt fuel injection pulses, thereby cutting fuel from the engine. Preferably, the comparator includes an EXCLUSIVE OR-gate.

Description

COMBUSTION ENGINE United States Patent 1 91 1111 3, Kiencke et al. Nov. 4, 1975 [5 ELECTRONIC GOVERNOR FOR INTERNAL 3,757,571 9/1973 Chamberas 123/118 Primary ExaminerCharles J. Myhre [75] Inventors: Uwe Kiencke, Moglingen; Martin Zechnall, Schwieberdingen, both of Assistant Examiner-Ronald COX Germany Attorney, Agent, or FzrmF1ynn & Frlshauf [73] Assignee: Robert Bosch GmbH,

Gerlingen-Schillerhohe, Germany ABSTRACT [22] Filed: June 12, 1974 To provide for speed governing of internal combustion engines having an electronic fuel control, typically an [21] APPI' N05 478,594 electronic fuel injection system in which the pulse duration of generated injection control pulses determines [30 Foreign Application priority Data the amount of fuel being supplied, in a given time, to the engine, a pulse source generates a series of pulses July 12, 1973 Germany 2335440 at a frequency determinative of maximum Speed of the 52 us. c1. 123/198 DB- 123/32 EA' 123/118 i frequency COTTPaYCd with a frequency [51] Int C12 6 77/00 1502? 9/00 representative of actual engine speed and, when the S actual speed frequency exceeds the maximum gener- [58] Field of 23/32 198 DB ated speed frequency, a switch (typically a flip-flop) is controlled to change state, the switch being connected [56] References Clted to interrupt fuel injection pulses, thereby cutting fuel 1 UNITED STATES PATENTS from the engine. Preferably, the comparator includes 3,572,302 3/1971 Wollesen 123/118 an EXCLUSIVE OR-gate. 3,651,793 3/1972 Roth 123/32 EA 3,659,571 5/1972 Lang 123/102 7 Claims, 1 Drawing Figure "FUEL "FUEL INJECTION INJECTION TERMINATE START PULSE PULSE 0 ENGINE PULSE SCANNING COMPARATOR 301 3 i SPEED CIRCUITS STAGE FREQUENCY i a j 150 171 I I 293 29] 296 51 B I "i5 (170 1 l 5 E D I' 11 111 153 62 M I 1 J 31, 1 I K "TX 1.1 32 STROBE 158 62 D 0 I I I 300 O2 REFERENCE I D 1 173 I I 292 f f I 15% (MAXIMUM SPEEDl' 172 [172 l CLOCK FREQUENCY ELECTRONIC GOVERNOR FOR INTERNAL COMBUSTION ENGINE The present invention relates to a governing system for internal combustion engines and particularly to such a system which can be combined with a fuel injection system described, for example, in US. Pat. No. 3,483,851, Reichardt, assigned to the assignee of the present application.

The speed of internal combustion engines depends, at a given load, on the amount of fuel being supplied. Frequently there is a time delay between change in loading and supply of fuel or, for some other reason for example malfunction of control systems or the like, excessive fuel may be supplied. This may cause the engine to run faster than desired. Particularly modern internal combustion engines can easily reach speeds in excess of maximum design speed, without any indications to the engine operator, such as excessive noise, valve chatter or the like being apparent. It is therefore frequently necessary to include a maximum speed governing arrangement in any control system for an internal combustion engine. lntemal combustion engines, in which the fuel supply is controlled electronically, permit electronic governing since signals representative of engine operation are already available in the electronic fuel supply control system.

Governing systems have been proposed which prevent excessive fuel supply, typically excessively long opening times of fuel injection valves under given load conditions, by using analog computation circuits to prevent excessive engine speeds and, particularly, run-away of the engine. Such analog computation systems or circuits are not suitable, however, when com bined with an internal combustion engine control system which uses a digitally operating circuit, particularly an incremental digital circuit.

It is an object of the present invention to provide a speed governing system for internal combustion engines which are controlled by means of digital controllers, and more particularly digital controllers using in cremental digital circuits controlling the opening time. or duration of fuel injection valves.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, a comparator stage is provided to compare a frequency proportional to speed of the engine with another frequency which is pre-set and is representative of maximum permissible engine speed. When the frequency, and particularly when using pulse techniques, the pulse repetition rate (PRR) of the engine speed signal exceeds the frequency (or the PRR) of the reference or governing command frequency, a signal is ob tained at the comparator stage which is transmitted to a controlled switch, typically a JK flip-flop, the switch (i.e. the FF) changing state and, due to its connection, interrupting the injection pulse.

In a preferred form, the comparator state is an EX- CLUSIVE OR-gate, each input to which has a time di vision, or strobing, or time scanning circuit connected thereto.

The arrangement has the particular advantage that a fair number of the circuit elements, and the signals required to control the arrangement, are already present in digital incremental internal combustion engine control systems. The governing arrangement can. there- 2 fore, be easily and simply constructed by minor modification, or addition to already present circuit components.

The invention will be described by way of example with reference to the accompanying drawings, wherein the single FIGURE illustrates a schematic block diagram of a digital speed governing arrangement for an internal combustion engine fuel injection system.

Output pulses f3 are applied to a terminal 62, representative of speed of the engine. These pulses may be derived, as shown schematically, by a tachometer generator 41, connected to the crankshaft 40 of the engine (not shown). Speed signals, in digital form, are available in electronic fuel injection systems. The speed signal pulses f3, at terminal 62, are applied to the D input of a first D flip-flop (FF) 167, which forms part of a first time scanning stage 97. The first time scanning stage 97 further includes a second D-FF 170, the D input of which is connected to the output Q1 of the first D-FF 167. The output Q2 of the second D-FF is connected to one input of an NAND-gate 171. The out put Q1 of the first D-FF 167 is connected to the other input of the NAND-gate 171.

An oscillator, providing pulses at a PRR corresponding to the highest permissible speed of the internal combustion engine is connected to terminal 62a of a second time scanning circuit 970. The second time scanning circuit 97a is, generally, similar to the first time scanning circuit 97. Two D-

FFs

172a and 172 as well as a NAND-gate 173 are connected identically to the connection of the first time scanning stage 97.

An input terminal 168 is connected to an inverter 169, the inverter being connected to the clock inputs of the four D-

FFs

167, 170, 172a, 172. The input terminal 168 has a clock frequency applied thereto. This clock frequency is readily available in digital circuits, particularly in incremental digital circuits, in which a stepping clock generator provides for uniform, even stepping of the incrementally operating circuit.

The two

time scanning circuits

97, 97a are then connected to a comparator stage 98a. Comparator stage 98a is constructed as a modified exclusive OR-gate. It has an input AND-gate 291 to which the direct output from NAND-gate 173 is connected as well as the inverted output from NAND-gate 171, over an inverter 293. A second input AND-gate 292 is provided, connected in complementary manner to AND-gate 291, that is, having the output of NAND-gate 171 applied and the inverted output from NANDgate 173, over an inverter 294. The comparator stage 980 further includes a J K-F F 295. The strobe, or clock pulse terminal of the FF 295 is connected to terminal 168a, to which a clock frequency or clock pulse sequence is connected. The JK-FF 295 operates as a pulse correcting stage. Its J input is connected to the output of AND- gate 291. Its K input is connected to the output of AND-gate 292.

The positive or Q1 output of the J K-FF 295 is connected to an AND-gate to which further the output from AND-gate 291 is connected as a second input. The gates, and the FF, together, form the comparator stage.

The output from the comparator stage, that is. the output from AND-gate 296, is connected to the first input of an OR-gate 300. The second input of OR-gate 300 is connected to a terminal 301. Terminal 301 is connected to the digital electronic circuit for a fuel injection system. This digital electronic circuits provides a stop or terminate pulse at terminal 301 when a previously commanded fuel injection pulse is to be terminated. Some fuel injection systems provide a pulse, the duration of which determines the opening time of a fuel injection valve. Other systems provide a pulse when the valve is to be opened, and another pulse when the valve is to close. The second type system can readily be instrumented from the first type by differentiating the fuel injection valve opening pulse, first in one direction (when the pulse starts) and then by differentiating the trailing flank of the pulse, that is, differentiating with respect to the other direction, to obtain the fuel injection terminate pulse. It is this type of pulse which is applied to terminal 301. This pulse can be derived, therefore, for example from the type of electronic circuit disclosed in the foregoing patent; in an incrementally, digitally operating fuel injection control system, the terminate pulse would be directly available.

The output of the OR-gate 300 is connected to the K input of a second JK-F F 152. The J input of the FF 152 is connected to a switch 150 and then to a terminal 302. Terminal 302' has a constant l-signal applied, which is transferred over switch 150 when the switch is closed, which occurs over a predetermined portion of crankshaft revolution. Terminal 302 likewise is connected to the electronic control system for the fuel injection valve and provides the signal which enables the fuel injection valve of the injection system to be open. Terminal 302 or terminal 302' in connection with switch 150 may be used alternatively.

The switch 150 is periodically opened and closed by a cam 151, connected to the crankshaft of the engine and operating in synchronism therewith. When closed,

it applies a l-signal to the J input of FF 152. The clock pulse input of the FF 152 is connected to a clock pulse terminal 168b, to which a further clock pulse frequency is connected. The direct output Q1 of FF 152 is connected to the input of a power amplifier 153 which controls from its output terminal 134 the energization of the magnet or solenoid winding 32 of a fuel injection valve. Only one such winding is shown as an example for all the injection valves associated with all the cylinders. In many systems it is sufficient that all injection valves open and close simultaneously, although they may be associated with different cylinders.

Operation: Thebasic principle of the system is based on comparing an engine speed frequency f derived from a tachometer generator 41, coupled to the engine, with a fixed or reference frequency f, which corresponds to the maximum permissible speed of the engine. These two pulse sequences, or frequencies, are scanned or strobed in the

circuits

97, 97a and compared in the comparator stage 98a. If the speed of the engine exceeds the highest maximum speed, the sign of the pulses at the output of thecomparator stage 98 will reverse, and a pulse applied to the J input of the FF 152, by providing a pulse to the K input of FF 152, similar to the terminate pulse, immediately interrupts a previously triggered or started fuel injection pulse by re-setting of the FF 152.

The circuit components, themselves, are well known and reference may be had, for example, to Logic Handbook, by Digital Equipment Corporation, 1968, which describes digital components, including the flipflops in question. The D-type FF, such as

FF

167, 170; 1720, 172, uses single-ended data inputs, connected to the D terminal, has an additional clock input and is'triggered or provides an output on the flank or edge of the clock pulse provided that the D input has a l-signal applied. The leading, or trailing flank of the pulse may be selected by suitable connecting circuitry. The JK-FF, such as FF 295, or 152, is also a clocked general-purpose FF which, however, has two inputs which are complementary. Either the J, or the K input can have a l-signal applied and upon the occurrence of the clock pulse connected to the clock pulse input (terminals 168a, 1681)), the FF will assume the state commanded by whether the J, or K input has a l-signal applied, and

provide a l-signal at the Q1 output, or, respectively, at the complementary, or Q2 output. Of course, if the complementary output has a l-signal, the other output has a O-signal. These outputs will remain until there is a change in input signals which will be transferred to the output of the occurrence of the next clock pulse. Timing relations and details are well known, and reference may be made to the aforementioned publication.

Operation of

pulse scanning circuits

97, 97a: An input pulse f3 on terminal 62 is transferred through the FF 167 upon occurrence of the negative flank of the immediately succeeding strobe pulse from terminal 168. Upon occurrence of the next following strobe pulse applied from terminal 168 over the inverter 169, the ouput pulse from FF 167 is transferred through the FF 170. The NAND-gate 171 provides a negative output pulse when the input pulse f3 was transferred through the first D-FF 167, but not yet to the second D-FF 170. The pulse duration of the output pulse of the NAND-gate 171 thus is equal to the pulse duration of the strobe frequency at terminal 168. The D-FF is generally characterized by the fact that a signal at its D, or data input is transferred at the next occurring clock pulse to theoutput Q1.

The pulse duration of the pulses derived from the NAND-

gates

171, 173 is thus equalized; comparison of the pulse repetition rate (PRR) or frequency of the pulse train supplied by the NAND-

gates

171, 173 is done in the comparator stage 980. The O-pulses at the outputs from the NAND-

gates

171, 173 are inverted in the inverter stages 293, 294, respectively, into l-pulses. The l-pulses derived from the outputs of the

inverters

292, 293 are not transferred through the AND-

gates

291, 292, however, under usual conditions. Let it be assumed that inverter 293 provides a l-signal. The

AND-gate 291 can transfer this l-signal only if, simultaneously, the NAND-gate 193 provides a l-signal. This, however, is the case only during a pulse interval of the pulse from NAN D-gate 193. The JK-FF 295, in cooperation with the AN D-gate 296, provides for pulse correction. The signals at the inputs J, K of the .lK-FF 295 are transferred to the Q1 output only upon occurrence of the next clock pulse from clock terminal 1683. The first positive pulse at the output of the AND-gate 291 thus does not provide a l-signal at the output of the AND-gate 296. Only if a second pulse, to be counted in the same direction, is provided, will both inputs of the AN D-gate 296 have l-signals applied. Thus, if the speed of the engine exceeds the highest permissible level, terminal 62 will have more pulses applied thereto than the reference frequency terminal 62a. This increase in pulses results in l-signals at the output of the AND-gate 291. If at least two extra l-signals occur thereat, the output of the AND-gate 296 will likewise have a l-signal arise thereat which is transferred over the OR-gate 300 to the K input of the second JK-FF 152.

The timing of a single injection cycle will now be described. It is, again, assumed that the injection valves of the engine are all triggered simultaneously; that is, that their windings are all in parallel to the 'winding 32. Common triggering of all injection valves is customary in many fuel injection systems.

At a predetermined angle of the crankshaft, switch 150 is closed by the cam 151. A l-signal is thus applied to the J input of the JK-FF 152. At the next following clock pulse from clock terminal 168b, the FF 152 is triggered or placed in the state which provides a l-signal at the direct Q1 output. The l-signal at the Q1 output is amplified in the power amplifier 153 and applied to the winding 132, thus opening winding 132. Let it be assumed that the engine operates below the highest permissible speed. The output of the AND-gate 296 will thus have a O-signal. The injection pulse is then terminated only when the fuel injection terminate pulse is applied to terminal 301 from the fuel injection system. This pulse will be applied to the K input of the FF 152. At the next following clock pulse from the clock 168b, the FF 152 is re-set, providing a O-signal at the direct Q1 output of FF 152, disabling amplifier 153 and deenergizing the solenoid 32. Fuel injection is thus terminated.

If the highest speed is exceeded then, as above described, a l-signa] will appear at the output of the AND-gate 296 which is applied to the K input of FF 152. Fuel injection is thus immediately interrupted. If the speed should have been too high at the beginning of the injection cycle, fuel injection will nevertheless be started at the occurrence of the first clock pulse from clock 168 after closing of switch 150 but will be immediately interrupted at the occurrence of the next succeeding clock pulse at terminal 168b. Very little fuel will thus be injected and the speed of the engine will rapidly decrease.

Various changes and modifications may be made within the scope of the inventive concept.

The rates of the clock pulses at the strobe terminal 168, and at the

clock terminals

168a, 168b may be suitably selected, (i.e. the basic clock frequency of the fuel injection computer) matched to the operating cycles of the fuel injection valves, maximum design speeds of the engine and the like. In a typical four-cylinder engine, having a maximum permissible speed of 6,500 rpm, the following pulse repetition rates, or frequencies are suitable:

tion pulse, or the fuel injection terminate pulse determines the length of the open time of the injection valve; after the terminate pulse has been applied, a l-signal is placed on terminal 302', which is connected through switch 150 to the J input of FF 152. Alternatively, or additionally, at a time determined in accordance with the electronic circuitry of the fuel injection system, a

l-signal is applied to terminal 302 to reliably ensure starting of fuel injection. The pulse of terminal 302 may occur before, or after closing of switch 150, since exact synchronism may not be obtainable in all instances for structural reasons. An electronic control system with 6 which the present application can be used is described in co-pending application Ser. 3,65';729, filed May 31, 1973, now U.S. Pat. No.- 3,898,962, assigned to the assignee of the present application. Weclaim: I

1. Governor arrangement for an internal combustion engine, having an electronic control system including a digital circuit providing fuel supply and fuel tennination signals to the engine, and means (41) providing a speed signal ()3) having a frequency proportional to engine speed, said governor arrangement comprising means (62a) providing a reference signal frequency proportional to maximum permissible governed engine speed;

comparator means (98a) having said speed signal 3) and said reference signal (f applied thereto and providing an output signal when the frequency of the speed signal exceeds the frequency of the reference signal;

a digital switch (152) connected to control termination of fuel supply to the engine when controlled to change state, the output signal from said comparator means (98a) being connected to the digital switch to cause said switch to change state when said output signal from the comparator means is generated; and

pulse scanning or strobing circuits (97, 97a) connected to said speed signal generating means (41) and said reference signal generating means (62a), respectively, and equalizing the pulse durations of the signals provided by said respective signal generating means.

2. Arrangement according to claim 1, wherein the fuel control comprises a fuel injection system (153, 32) 35 in which the duration of the fuel injection pulses determines the amount of fuel being applied to the engine, said duration being defined when said switch changes to one (set) state and terminating when said switch changes to the other (re-set) state.

3. Arrangement according to claim 1, wherein the comparator means (98a) comprises a comparator stage including an EXCLUSlVE OR-gate.

4. Arrangement according to claim 1, wherein the comparator means comprises an EXCLUSIVE OR- 45 gate having two inputs, one input, each, being connected to the output of a respective pulse scanning or strobing circuit.

5. Arrangement according to claim 1, wherein at least one of the pulse scanning or strobing circuits (97, 97a) comprises two D-tlip-flops (167, 170; 172a, 172); a strobe pulse source (168, 169) connected to the clock inputs of both the flip flops;

the D input of the first D-FF (167, 172a) having the input frequency applied thereto;

and a NAND-gate (171, 173) having its inputs connected to the output of the first D-flip-flop (167, 1720) and the further input connected to the inverse output of the second D-flip-flop (170, 172).

6. Arrangement according to claim 1, wherein said digital switch comprises a JK-flip-tlop (152).

7. Arrangement according to claim 1, wherein the electronic control system provides a control pulse defining termination of fuel supply, at a given instant of 65 time (terminal 301);

means (300) connecting said terminate pulse to said digital switch to control said digital switch to terminate fuel supply to the engine;

8 stant of generation of the output signal from said comparator means and regardless of presence of a terminate pulse from said electronic control system.

Claims

1. Governor arrangement for an internal combustion engine, having an electronic control system including a digital circuit providing fuel supply and fuel termination signals to the engine, and means (41) providing a speed signal (f3) having a frequency proportional to engine speed, said governor arrangement comprising means (62a) providing a reference signal frequEncy proportional to maximum permissible governed engine speed; comparator means (98a) having said speed signal (f3) and said reference signal (fr) applied thereto and providing an output signal when the frequency of the speed signal exceeds the frequency of the reference signal; a digital switch (152) connected to control termination of fuel supply to the engine when controlled to change state, the output signal from said comparator means (98a) being connected to the digital switch to cause said switch to change state when said output signal from the comparator means is generated; and pulse scanning or strobing circuits (97, 97a) connected to said speed signal generating means (41) and said reference signal generating means (62a), respectively, and equalizing the pulse durations of the signals provided by said respective signal generating means.

2. Arrangement according to claim 1, wherein the fuel control comprises a fuel injection system (153, 32) in which the duration of the fuel injection pulses determines the amount of fuel being applied to the engine, said duration being defined when said switch changes to one (set) state and terminating when said switch changes to the other (re-set) state.

3. Arrangement according to claim 1, wherein the comparator means (98a) comprises a comparator stage including an EXCLUSIVE OR-gate.

4. Arrangement according to claim 1, wherein the comparator means comprises an EXCLUSIVE OR-gate having two inputs, one input, each, being connected to the output of a respective pulse scanning or strobing circuit.

5. Arrangement according to claim 1, wherein at least one of the pulse scanning or strobing circuits (97, 97a) comprises two D-flip-flops (167, 170; 172a, 172); a strobe pulse source (168, 169) connected to the clock inputs of both the flip-flops; the D input of the first D-FF (167, 172a) having the input frequency applied thereto; and a NAND-gate (171, 173) having its inputs connected to the output of the first D-flip-flop (167, 172a) and the further input connected to the inverse output of the second D-flip-flop (170, 172).

6. Arrangement according to claim 1, wherein said digital switch comprises a JK-flip-flop (152).

7. Arrangement according to claim 1, wherein the electronic control system provides a control pulse defining termination of fuel supply, at a given instant of time (terminal 301); means (300) connecting said ''''terminate'''' pulse to said digital switch to control said digital switch to terminate fuel supply to the engine; and wherein the output signal from said comparator means (98a) is connected to said connection means (300) to provide a signal to said digital switch and cause said digital switch to change state and terminate fuel supply to the engine at the instant of generation of the output signal from said comparator means and regardless of presence of a terminate pulse from said electronic control system.