DE3112222A1 - SPEED CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINES - Google Patents

Description

HITACHI, LTD., Tokyo, Japan

Speed control device for internal combustion engines

The invention relates to a device for the electronic control of the speed of an internal combustion engine such that the speed is kept at a desired constant value.

For internal combustion engines (hereinafter referred to as motor for short) with intermittent combustion, e.g. B. in gasoline engines and diesel engines, the generation takes place Engine output power takes place intermittently, so that pulsations in the speed of an output or crankshaft of the engine. Particularly in the case of a diesel engine which has a high compression ratio is used, the pulsation in the speed of the output shaft occurs more strongly than in a gasoline engine.

If the output power of the engine is used to drive an electrical generator, the Frequency of the generated electrical energy disadvantageously fluctuations due to the pulsation in the speed the output shaft of the motor. Needless to say, computers, precision electronic devices, -Instruments or the like. Need a power supply in which practically no frequency change occurs.

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According to a known method for detecting or measuring the engine speed, a crank angle pulse train becomes synchronous generated at the speed of the engine crankshaft, the speed of the crankshaft being detected by clock pulses are counted during an interval between the individual pulses of the crank angle1 pulse train (i.e. during a period of the crank angle signal), where dlo number of counted Fdktimpulse then a measure for is the speed of the engine crankshaft. However, the known system for detecting the crankshaft speed takes into account in no way the pulsation in the engine speed. In these circumstances the undesirable one occurs every now and then Appearance of a beat or flutter due to the non-collapse of the period the speed pulsation and the period for detecting the speed.

According to a method for detecting the engine speed (US Pat. No. 3,969 61A-), the speed is determined as a function of the time interval between crank angle pulse trains is detected, which is generated synchronously with the speed of the crankshaft will. With this known method, the speed is recorded for practically every cylinder (for every crank angle of 90 in the case of an eight-cylinder engine) and thus synchronous with the periodic pulsation in the crankshaft speed. As a result, the rotational speed of the crankshaft is detected by the pulsations strongly influenced. It can thus be seen that to control the engine speed in such a way that it is with sufficient accuracy is constant, the detection of the engine speed is to be carried out so that it is not subject to the influence of pulsations.

The object of the invention is to create a speed control device for internal combustion engines, the speed being kept at a desired constant value with high accuracy.

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The invention is based on the observation that the pulsation in the speed of an internal combustion engine synchronously with the period of the engine cycle occurs, and suggests that the speed is detected by the fact that a cycle period, d. H. one for the execution of an engine stroke, consisting of suction, compression, combustion and exhaust stroke, required period or an integer multiple of this clock period is measured, the speed of the Motor is controlled on the basis of the measured value, which is used as basic information, so that the engine speed is maintained at a predetermined value.

The speed control device according to the invention is characterized by a sensor unit which is operatively connected to a crankshaft of the internal combustion engine and the rotation of the crankshaft detects, by a first signal generator, the signals corresponding to a clock period of the internal combustion engine or a clock period which is equal to an integral multiple of this clock period is generated on the basis of the output signal of the sensing unit by a counter which is one of the Clock period corresponding digital count value generated by a comparator, which the digital count value with compares a predetermined value indicative of a reference speed, and by a second signal generator, which, based on the output signal of the comparator, provides a control signal for one of the combustion conditions regulating actuator generated.

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The invention is explained in more detail, for example, with the aid of the drawing. Show it:

1 shows a graph of pulsations

a speed and a revolution period in a known speed control device for internal combustion engines;

FIG. 2 shows a larger partial representation of the graphic from FIG. 1; FIG.

3 shows the block diagram of an exemplary embodiment the control device according to the invention;

FIG. K shows a diagram of signal profiles of various signals to illustrate the mode of operation of the control device according to FIG. 3;

Fig. 5 is a block diagram showing in detail part of the controller of Fig. 3;

Fig. 6 is a flow chart showing control operations performed by the apparatus of Fig. 3; and

FIG. 7 is a block diagram showing in detail a part of the control device of FIG.

Fig. 1 shows changes in the speed RV and the revolution period RT obtained experimentally with a known speed control device for a three-cylinder four-stroke diesel engine driving an electric generator with a rated output frequency of 50 Hz. Part of the diagram of FIG. 1 is shown enlarged in FIG. According to FIG. 1, the engine is operated under load up to a point in time T _Q and then at idle. As can be seen from the figures, the speed change is essentially limited around 50 Hz to the range of 50.25-50.75 Hz. In idle mode

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However, the speed increases to 51.61 Hz. The The maximum value of the speed is determined by the operation of the control device (circuits 11, 12, 13, 14 and 15, the to be explained) progressively decreased. in the During load operation, the cycle period VT changes in the range from approx. 50.25 Hz to approx. 49.75 Hz, while in idle operation the period of rotation itself compared to the speed gets shorter. So if the period of revolution is VT as the frequency is reproduced, it is 51.15 Hz.

The pulsations explained above become more pronounced with increasing load. This can be explained by the fact that when the engine is running under high load, the speed is abruptly reduced on all strokes except the combustion stroke is, which in turn requires the generation of a higher power, which intermittently in a certain time interval he follows.

The known device for controlling the engine speed cannot control the speed with high accuracy as the device is subject to the influences caused by the pulsations explained. The expert may attempt to remove the pulsation components by filtering the speed signal. However, such a filter cannot follow very rapid changes in the speed.

Fig. 2 shows in time intervals t ,, t _? and t, those changes in the speed signal which can be assigned to the first cylinder (T), the second cylinder (2) and the third cylinder (3). In the case of the three-cylinder four-stroke engine, the crankshaft of the engine revolves twice during a period T ~ which is required for the repeated speed change attributable to the same cylinder. That is, the crankshaft threatens to move 720. In the case of a two-stroke engine

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the crankshaft performs a single revolution during the period T ^. In the explanation of the invention, this period T. is referred to as the "clock period". In an engine with several cylinders, of course, there are differences in the amount of combustion energy between the individual cylinders, as can be seen from FIG. 2, which shows the differences in the peak value of the speed signal RV of the individual cylinders. For this reason, there is _{a difference in the periods T 1} and T 1 of the successive revolutions during the clock period T 3.

However, it has been found experimentally that in operation of a four-stroke engine in a constant medium speed range, the period T ^, during which the Crankshaft rotates twice (i.e. the clock period) is subject to very little changes over time, namely regardless of the number of cylinders. Thus, it becomes possible to detect even a very small speed change, and this is because, in the case of the four-stroke engine, the crankshaft rotates twice during the individual engine cycle and the repetition accuracy of such an engine stroke is high.

Fig. 3 shows the basic layout of an embodiment the speed control device, which can advantageously be used with a four-stroke engine. The following is used to explain 4-7 of this speed control device is also referred to.

According to FIG. 3, fuel is supplied from an injection pump 2 to a diesel engine 1. The fuel injection amount is determined by an actuator 3, which has a shut-off element, the position of which is controlled electromagnetically will. The diesel engine 1 has an output shaft 4

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on, on the free end of which a disk is placed in a rotationally fixed manner. On an outer surface of the disc, a single projection 5 is secured from magnetic material which is a magnetic sensor 6 arranged opposite, so that a pulse-shaped output signal P (see. Fig. 4 (A)) generated by the sensor 6 during each full revolution of the output shaft 4 will. The pulse-shaped signal P is fed to a signal shaper 7 and converted into a square-wave signal P (see FIG. 4 (B)) so that it is suitable for the subsequent processing operations. On the basis of the signal P 1 and a clock signal 55 which is generated by a clock signal generator 12, a control signal generator 8 generates a clear signal 8a for resetting the contents of a clock period counter 9 to zero and a hold signal 8b, whereby the contents of the counter 9 in a data holding element 10 are held.

The counter 9 counts a counting clock signal 51 which is generated by the clock signal generator 12, whereby a data signal 49 is generated relating to the cycle period of the engine. The clock period information is fetched from the hold signal 8b into the data holding element 10 and a processing unit 13 supplied via a data connection 11. The processing unit 13 operates in synchronism with a clock signal 53 generated by clock signal generator 12.

The processing unit 13 operates with a random access memory or RAM and a read-only memory or ROM and performs control operations in accordance with the Flow chart according to FIG. 6.

Clock period information relating to the engine becomes off the holding element 10 is read out to the processing unit 13 via the data connection 11 (cf. step 602 of FIG. 6) By the processing unit 13 is the read

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Clock period information from the holding element 10 is compared with reference information of the clock period which is stored in the KOM and denotes a predetermined speed (step 60k). When the clock period is smaller than the reference clock period (that is, when the speed is high), information 63 for shortening a time period T " _N during which the actuator 3 is operated and thus for lengthening the clock period is arithmetically determined on the basis of the comparison results ( Step 606). The information determined in this way is fed to an output counter 15 via a data connection 14. The output counter 15 is activated by a clock signal (42; 43) with an invariable width, which is fed from the output of the clock signal generator 12, and thereby generates a predetermined control signal 68 for a duration which corresponds to the control information 63 generated by the processing unit 13. Then a transistor 16 is switched on for a duration corresponding to the pulse width Tq., Of the signal 68 and actuates the electromagnetic actuator 3, which in turn sets the fuel injection quantity by positioning an actuating rod of the injection pump 2 in accordance with the control information 63 generated by the processing unit 13, and as a result, the engine speed is controlled to be kept at the reference value.

Fig. 5 shows in detail the control signal generator 8 and the clock signal generator 12 as circuits associated with one another. The magnetic sensor 6 generates a pulse-shaped signal in response to each passage of the projection 5, d. H. every revolution of the output shaft 4 of the motor 1, as already explained. As a result of the output signal of the sensor 6, a transistor 32 of the signal shaper 7 is switched on immediately, whereby an output signal is generated at a low level, which is then sent to a C-

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Connection of a frequency divider flip-flop 33 is applied, which together with other flip-flops 34, 35 and 36 one Part of the control signal generator 8 forms. Each flip-flop 33, 34, 35 and 36 is a D flip-flop. With this type of flip-flop is caused by the transition of the electrical state of the input signal applied to the clock input terminal C from a low level "L" to a high level The "H" level has the effect that the data signal with the L level or Η level applied to the data input D is positive Output Q appears. If, on the other hand, the input signal at input C changes its state from Η level to L level changes, the data signal applied to the data input D appears at a complementary output Q. Thus appears at the moment in which the transistor 32 from the conductive state to the non-conductive state passes, the signal appearing at the complementary Q output of the flip-flop 33 at the positive Q output. As a result, the Q output of the flip-flop changes its state or level every other revolution of the motor (see. Fig. 4 (C)).

As can be seen from the signal curve of FIG. 4 (C), this is subject to each revolution of the output shaft 4 of the Motor 1 generated sensor signal of frequency division by 2 for the purpose of detecting the clock period T ~. These Frequency division can be omitted if the magnetic sensor 6 is mounted on a valve drive shaft (i.e. camshaft) Four-stroke engine is attached, or in the case of a two-stroke engine. In these cases the Q output decreases of the flip-flop 33 for one revolution (half a cycle) of the motor the Η level and for a subsequent one Revolution (a following half cycle) of the motor to the L level; this process is repeated over and over again.

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The Taktsiynalgeber 12 includes an oscillator 37, the a clock signal 53 is generated, which is used for the processing unit 13. From the output of the oscillator 37 are further through frequency dividing elements 38 and 39 a clock signal 51, which will be explained later, and a clock signal 55 with a repetition frequency that is sufficiently higher than that of the output signal of the magnetic sensor 6 (see. Fig. 4 (D)) derived. The clock signal 55 is applied to the C terminals of the successive D flip-flops 34 or 35 created. As a result, the Q output of flip-flop 34 is due to the rising edge R, of the C terminal (i applied C input signal to H level is set immediately after the Η signal is applied to the D terminal of flip-flop 34. The Q output signal with Η level of flip-flop 34 is applied to the D input of the following flip-flop 35, the Q output of which as a result of the rising edge R- of the subsequent one the input signal applied to the C terminal of the flip-flop 35 is set to the Η level. In this way, each once during two. Revolutions of the output shaft 4, the output signal of the flip-flop 34 first to the H level set, whereupon the Q output with Η level of the flip-flop 35 follows with a sufficiently short delay. The Q output of flip-flop 34 and the Ti output of the flip-flop 35 are fed to a NAND gate 45, the output of which has the signal level L during a Assumes duration that a single pulse of the clock signal 55 once for two revolutions of the output shaft is equivalent to. The L level output of the NAND gate is fed to one input of a NOR element 46, the other input of which is that which is inverted by a non-element 44 Clock signal 55 is supplied. Thus, the signal 8b is obtained at the output of the NOR gate 46, which only then the Assumes Η level when the clock signal 55 has the Η level (see. Fig. 4 (I)). This signal 8b is used as an input signal

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-lodern data holding element 10 is supplied and holds the there instantaneous output signal 49 of the counter 9. The Q output signal of the flip-flop 35 is applied to the D input of the Flip-flops 36 applied, the C input of which is fed the periodic clock signal, which after inversion by the non-element 44 is derived from the clock signal 55. Thus, the Q output of the flip-flop 36 is due the trailing edge of the clock signal 55 is set to the H level, whereby the Q output of the flip-flop 35 on H is set. The Q output signal of the flip-flop 35 and the Q output signal of the flip-flop 36 are sent to the NOR gate 47 is applied, which thus at its output the signal 8a with a sufficiently short duration in each case once generated for two revolutions of the output shaft 4. The signal 8a is used to clear the contents of the counter 10 utilized. In this way, the hold signal 8b is generated once for every two revolutions of the motor output shaft 4 Short duration obtained, followed with a slight delay by the clear signal 8a, which is also short in duration. In In this connection it should be noted that the time interval between the signals 8b and 8a is provided to be to rule out an incorrect operation. In this way, after the contents 49 of the counter 9 into the Data holding element 10 are transferred, the counter 9 prepares for a subsequent counting process. That for the Counting process of the counter 9 used counting clock signal 51 is from the clock signal 53 at the output of the oscillator 37 derived and has by frequency divisions which are carried out by the frequency dividers 38 and 40, a high pulse repetition rate. Thus, the count clock signal 51 a sufficiently lower repetition frequency in comparison with the clock signal 55. An increase in frequency of the counting clock signal naturally has an increase in the contents of the counter 9 with a correspondingly increased rate Episode. Therefore, the contents 49 form the signal for the

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Clock period T. ,, d. H. for one of the two turns of the Motor output shaft Λ corresponding period. As the engine speed increases, the cycle period T-, shorter, which causes a correspondingly reduced count.

The resolving power of the time measurement and the required counting capacity of the counter 9 are determined as a function of the choice of the repetition frequency of the counting pulse signal 51. Although the counting clock signal 51 is the same signal as the counting clock signal 42 which is used in the output counter 15 (FIG. 3), it should be noted, however, that the latter signal can differ from the former. A frequency divider 41 generates a switch-on start signal 43 (corresponding to the pulse duration T ₀ ) for periodically switching on the output counter 15, the duration preferably being 5-20 ms.

FIG. 7 shows in detail the design of the output counter 15 from FIG. 2.

_{The switch-on start signal 43 (T Q} ) generated by the clock generator 12 in FIG. 5 is fed to the input of a monostable multivibrator 64 and converted into a periodic signal with a sufficiently short pulse duration. This signal is fed to an S input of an RS flip-flop 66 , whereby the Q output of the flip-flop 66 is immediately set to the Η level. The Q output signal is fed to a D input of a D flip-flop 61 with a reset input, whereby the Q output of the flip-flop 61 to the Η level as a result of the rising edge of the counting clock signal 42 of the clock signal generator 12 of FIG. Input of the flip-flop 61 is supplied, is set. The Q output signal of the flip-flop 61 , which is now at the L level, is fed to a terminal 69 which is used both for data input and for counting control. If the

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Terminal 69 has the Η level, actuator switch-on time information 63 is entered into the counter 62 and is supplied by the processing unit 13 via the data connection 14 while the counting process is interrupted. On the other hand, when terminal 69 is low, output counter 62 begins counting, thereby decreasing the contents of counter 62 by one in response to each clock pulse 44 applied to the clock input. When the contents of the counter 62 are counted down to zero, the H-level signal appears at the zero output 71. Assuming that the Q output of the flip-flop 62 now has the L level, the counting process of the counter is initiated, whereby the Η level appears at the zero output 71 of the counter 62 after a time which corresponds to a product of the output time information and the clock duration . As a result, the flip-flop 66 is reset immediately, whereby its Q output is L and the ^ output is high. The {J output signal is applied to the reset terminal of the flip-flop 67, so that the Q output of the flip-flop 67 immediately becomes the L level. In this way, the signal 68 is periodically obtained at the Q terminal of the flip-flop 67 which assumes the Η level during a time which corresponds to the product of the actuator switch-on time information and the duration of the clock signal 42. During the pulse duration Tq _{n of} the signal 68, the transistor 16 (FIG. 3) is switched on so that the actuator 3 can determine the fuel injection quantity. In this connection it should be mentioned that the method for controlling the actuator with the aid of the members 11, 12, 13, 14 and 15 is already known per se.

As can be seen from the above explanation, the invention teaches that the speed of the motor in each Cycle period T, which is detected with the stroke cycle of the engine

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is synchronized. In the case of the conventional speed detection method in which the engine speed is for every revolution of the crankshaft (see. Fig. 2) is detected, the revolution period signal is obtained, which is a significant Shows pulsation (cf. the thick solid lines in Fig. 2). Even if the control with the help of members 11-15 of Fig. 3 is done by this round trip period signal that subject to pulsation, is used, the output power of the motor is inevitably of the undesirable Pulsations according to fig. I accompanied. If against it the rotational speed of the motor output shaft for every clock period or every integer multiple of the clock period is detected, a round trip period signal RT, (corresponding to the content 49 in counter 9) are obtained, which has essentially no pulsation and practically the desired speed (corresponding to 50 Hz) represents, as indicated by hatched longitudinal areas in FIG. When the controller is using the signal RT, is carried out in the manner previously explained in connection with the members 11-15 according to FIG. 3, the speed can be kept at a setpoint value in a simple manner, the response characteristic being considerable is improved.

If the detected speed, which forms the basis for the speed control, is subject to considerable pulsations, Of course, the controlled variable cannot be increased, otherwise the pulsation will be even stronger and thus control would become more difficult. If the controlled variable is limited for the reason given above, the response characteristic is naturally deteriorated.

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Claims (5)

Expectations [Iy speed control device for internal combustion engines for maintaining the speed at a predetermined value while adjusting the combustion conditions in the internal combustion engine,
marked by - A sensor unit (6, 7), which is operationally with a Crankshaft (A-) of the internal combustion engine (1) connected and the rotation of the crankshaft (4 ·) is detected; - A first signal generator (8), the signals (8a, 8b) corresponding to a clock period (T,) of the internal combustion engine or a clock period which is equal to an integral multiple of this clock period (T.,), generated on the basis of the output signal of the sensing unit (6, 7); - A counter (9) _f which generates a digital count value (4-9) corresponding to the clock period (T _3); - A comparator (13), which the digital count (ή-9) with a reference speed designating predetermined Value compares; and - A second signal generator (15) based on the output signal of the comparator (13) a control signal (68) for a regulating the combustion conditions Adjusting device (2, 3) generated. 81- (A 5378-03) -Schö 13006A / 071 7 -Z- 2. Device according to claim 1,
characterized, - That the internal combustion engine is a four-stroke engine, and - That the first signal generator (8) sends a signal corresponding to a period (T.,) during which the crankshaft (4 ·) of the four-stroke engine rotates two times, or a signal corresponding to an integral multiple of this clock period (T ₃ ) generated. 3. Device according to claim 1,
characterized, - That the internal combustion engine is a two-stroke engine, and - That the first signal generator (8) sends a signal corresponding to a period (T.,) during which the crankshaft (4 ·) of the two-stroke engine performs a single revolution, or a signal corresponding to an integral multiple of this period (T ₃ )
generated. 4. Device according to claim 1,
characterized, - That the output signal of the sensor unit (6, 7) consists of a train of pulses, each for each
Rotation of the crankshaft (4) is generated, - That the first signal generator (8) has a frequency divider element for dividing the frequency of this pulse train
includes. 130064/0717 5. Device according to claim 1, characterized in that - that the internal combustion engine is a diesel engine, whose output shaft is connected to an electric generator via a gear unit. 130064/0717