JPH0336146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input device for providing each output of a crank position sensor and a crank angle sensor as a rotation signal to a vehicle computer in an electronic control device related to fuel injection amount and ignition timing control.

The input circuit that inputs the output signal of the rotation angle sensor that detects the engine crank rotation angle to the vehicle computer always includes a CR delay circuit or a digital delay circuit that converts the output signal of the rotation angle sensor into a digital signal and then delays it. attached. This is intended to remove noise, but if the delay is unnecessarily long, malfunctions due to noise will be reduced, but the disadvantage is that the rotation angle of the crank per delay time will increase during high-speed rotation, making rotation angle detection inaccurate. was traditionally hot.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotation signal input device for a vehicle-mounted computer that overcomes the above-mentioned drawbacks of the prior art.

In order to achieve the above object, the present invention provides an engine rotation signal input device for an in-vehicle computer, which includes a detection signal representing a predetermined crank angle position of the engine, which is an engine rotation signal, and a detection signal generated at each predetermined crank angle. an engine rotation sensor using a magnetic detection element that outputs
a waveform shaping means for inputting a detection signal output from the engine rotation sensor, shaping the waveform, and outputting the waveform-shaped engine rotation signal; disposed between the engine rotation sensor and the waveform shaping means;
and a delay means for receiving the output signal of the engine rotation sensor and delaying the output signal through a delay circuit having a predetermined time constant in order to prevent the influence of noise voltage mixed into the output signal. In the rotation signal input device, the waveform shaping means includes a waveform shaping circuit for shaping the waveform of the engine rotation signal using a predetermined threshold level, and also includes a waveform shaping circuit for shaping the waveform of the engine rotation signal using a predetermined threshold level. The circuit includes a compensation circuit for preventing malfunctions caused by the noise voltage caused by the noise voltage and guaranteeing the accuracy of crank angle detection based on the engine rotation signal. On the other hand, a time constant changing means for changing the time constant of the delay circuit by connecting a time constant changing element; and a threshold level for changing the threshold level of the waveform shaping circuit according to the rotational speed of the engine. This is an engine rotation signal input device for a vehicle-mounted computer, characterized in that it includes a changing means.

Furthermore, the time constant changing means can be configured to change the time constant of the delay circuit so that it becomes larger on the low engine speed side and smaller on the high engine speed side.

Further, the threshold changing means may be configured to change the threshold level of the waveform shaping circuit such that it is lowered at low engine speeds and increased at high engine speeds.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a device according to the present invention applied to an electronic control device that controls the fuel injection amount of an engine, where 1 is the engine body, 2 is an air cleaner, and 3 is an air flowmeter that detects the intake air amount of the engine. 4 is a throttle valve; 5 is an ignition device distributor with a built-in reference crank position sensor A and crank angle sensor B; 6 is a water temperature sensor; 7 is a microcomputer circuit that calculates the fuel injection amount; 8 is a fuel It is an injection valve.

FIG. 2 is a block diagram of the computer circuit 7, in which 71 is a microprocessor (hereinafter referred to as CPU);
2 is an A-D converter that converts analog signals output from the airflow sensor 3 and water temperature sensor 6 into digital values; 73 is a storage device; 74 is an input/output device; 75 is an input/output device;
Data on the fuel injection amount calculated by the CPU 71 is supplied via the input/output device 74, and a drive circuit drives the fuel injection valve based on this data. 76 is a waveform shaping circuit that shapes the waveform of the detection signal of the crank angle sensor B. , 77 is a waveform shaping circuit that shapes the detection signal of the reference crank position sensor A.

The reference crank position sensor A and the crank angle sensor B are composed of magnetic detection elements in which a coil is wound around a magnet, and as schematically shown in FIG. The angle sensor B is installed opposite to a gear 5b, which has teeth twice as many as the number of engine cylinders (for example, 12 in the case of a 6-cylinder engine in this embodiment), and is connected to a predetermined crankshaft as shown in FIG. A detection signal is output for each corner (in this example, at intervals of 60 degrees from top dead center), and the reference crank position sensor A is installed facing the gear 5a, which has only one tooth. As shown in Fig. 4, a detection signal is output only once at every predetermined crank position (every one revolution of the distributor), that is, every two revolutions of the engine (720 degrees in terms of crank angle). Both gears 5a and 5b are installed on the shaft 5c of the distributor 5 so as to be overlapped with each other at an appropriate interval, and the sensors A and B are respectively arranged at predetermined positions on the outer periphery of each gear.

FIG. 3 shows details of the waveform shaping circuits 76 and 77 shown in FIG. 2, which delay the rise of the detection signals of the crank position sensors A and B and shape the waveforms of the apparatus according to the present invention. This shows a detailed electric circuit incorporating one embodiment, including resistors 9, 10, 11, 12, 13, 14, capacitors 15, 16, 17, 18, 19, 20, and a constant voltage for comparator protection. Diodes 21, 22,
NPN transistors 23, 24, comparator 2
5, 26, 27, analog switches C and D, and a frequency-voltage (F-V) converter E. Vc in the diagram
represents a constant voltage terminal of, for example, 5V, and 74 represents an input/output device. This waveform shaping circuit 76, 77
The two circuits have different constants but have similar configurations.

Next, the operation of the above-mentioned constituent devices will be explained with a focus on the waveform shaping circuit 77. The reference crank position sensor A outputs a voltage signal at a predetermined crank position every two revolutions of the engine, that is, every 720 degrees of crank angle, as shown in FIG. 4a. This voltage signal is input to the inverting input terminal of the comparator 26, and this voltage signal is compared with the level of the non-inverting input terminal of the comparator 26. That is, when the output of the comparator 26 is at a high level, the emitter potential of the transistor 24 is determined to be approximately equal to the output level of the F-V converter E, and the current flowing from the output terminal of the comparator 26 through the transistor 24 and the resistor 13 When the level becomes higher than the possible threshold level, the output terminal of the comparator 26 becomes a low level as shown in FIG. 5b. Therefore, the comparator 26
Since no current flows from the output terminal of the comparator 2, the threshold level drops to the ground level as shown by the dashed line in FIG.
The output terminal of 6 becomes high level. This low level signal is supplied to the input/output device 74 as a waveform-shaped signal, and is used as a signal to control the opening timing of the fuel injection valve. The waveform shaping circuit 76 also operates in the same manner as the waveform shaping circuit 77. Now, if the engine speed increases, the level of the output voltage signal of the reference crank position sensor A will increase.
As shown in FIG. 4, an interference voltage is superimposed and output due to the influence of the output of the crank angle sensor B, that is, the influence of magnetic induction, and as the engine speed increases, the level of this interference voltage also increases, so the comparator 26 If the threshold level is fixed at a constant value, there is a problem that this superimposed interference voltage also exceeds this threshold level and erroneously outputs a waveform-shaped signal. or,
The same applies to ignition noise. However, in the waveform shaping circuit incorporating the embodiment of the present invention shown in FIG. 3, the threshold level of the comparator 26 is continuously adjusted by the F-V converter E according to the engine speed as shown in FIG. As a result, the threshold level also increases at high engine speeds, and problems such as erroneous output of the interference voltage and ignition noise do not occur. On the other hand, as the engine speed decreases, the threshold level of the comparator 26 also decreases, and the noise waveform superimposed on the electrical path from the reference crank position sensor A to the comparator 26 becomes lower than the threshold level of the comparator.
When the level reaches a high level, there is a problem that the noise waveform may be reshaped and erroneously output. Therefore, in this circuit Figure 3, resistor 12 and capacitor 1
9 forms a CR filter circuit and applies a delay to the noise waveform (Figure 7a) as shown in Figure 7, lowering the level of the noise waveform (Figure 7b) so that it becomes lower than the threshold level of the comparator. Therefore, the problem of accidentally outputting a noise waveform does not occur. Now, if we consider the time constant of CR, the larger the time constant, the lower the noise waveform will be, but this will cause a delay in waveform shaping, and this will cause the engine to rotate at high speeds. This large delay makes angle detection by the reference crank position sensor inaccurate. Therefore, in this circuit, as shown in Fig. 3, the engine speed is converted into a voltage by the F-V converter E, and the level is converted to a voltage by the comparator 27.
Vc and compare its output with analog switch C,
Connect to capacitors 17 and 2 according to the output of comparator 27 using analog switches C and D.
0 is connected or disconnected in parallel with the capacitors 16 and 19. As a result, in this circuit, the eighth
As shown in Figures a and 8b, when the output of the F-V converter E is at a low level of rotation that is lower than the comparison voltage Vc of the comparator 27, analog switches C and D are connected, so when the CR is The constant is large, and as the rotation speed increases, the output of the F-V converter E becomes the comparison voltage.
When the level becomes higher than Vc, the output of the comparator 27 becomes low level, analog switches C and D are disconnected, and the time constant of CR becomes small. As a result, the circuit shown in FIG. 3 is a waveform shaping circuit that is not affected by noise waveforms and has good angle detection accuracy from low to high rotations.

The F-V converter E shown in FIG. 3 can have a circuit configuration as shown in FIG. 9, for example. The configuration is resistor 2
9, 33, 36, 38, capacitor 28, 39,
Diodes 30, 31, 32, 34, 37,
It consists of a PNP transistor 35, a constant voltage terminal +Vcc, an input terminal c, and an output terminal d. Input terminal c, points a and b shown in the circuit, and output terminal d
The voltage waveforms at the four points are shown in Figure 10,
At the output terminal d, as the engine speed increases, the period t becomes smaller, and the potential at point d becomes a high level on average.When the engine speed becomes low, the period t increases and the potential on average becomes a low level. I'm going with you. F-
The V converter uses this voltage d as its output.

In the embodiment shown in FIG. 3, the circuit is constructed with an analog circuit, but a similar construction can be implemented with a digital circuit in other embodiments. It is also possible to determine the rotation speed using a microcomputer and change the time constant of the CR circuit by turning an analog switch ON or OFF based on the determination result.

As described above, according to the present invention, when the output signal of the engine rotation sensor is delayed, the delay time constant is increased when the engine rotates at low speed and decreased when the engine rotates at high speed. The crank angle detection accuracy is improved by preventing the crank rotation angle per delay time from increasing even when the engine rotates, and the threshold level when shaping the waveform of the delayed output signal of the engine rotation sensor is improved. By increasing the rotational speed in proportion to the increase in engine rotational speed, it is possible to supply a rotational signal that is not affected by noise even if the noise level increases due to magnetic interference, etc. due to an increase in engine rotational speed. This provides an excellent effect in that the crank angle detection accuracy is high even when the engine rotation speed increases, and an engine rotation signal that is not affected by noise can be supplied to the on-vehicle computer.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a device according to the present invention applied to an electronic control device that controls the fuel injection amount of an engine, Fig. 2 is a block diagram of the computer circuit in Fig. 1, and Fig. 3 is a block diagram of the computer circuit shown in Fig. 2. An electric circuit diagram of a waveform shaping circuit incorporating an embodiment of the device according to the present invention, FIG. 4 shows the output waveform of the crank position sensor in FIG. 3, and FIG. A waveform diagram showing the relationship with the waveform shaping output, Figure 6 is a characteristic diagram showing the relationship between the engine speed and the threshold level in the electric circuit of Figure 3, and Figure 7 shows the noise waveform and its delayed waveform. Waveform diagrams 8a and 8b show the relationship between the output voltage of the frequency-voltage converter and the engine rotation speed in the electric circuit of FIG. 3, and the relationship between the rotation speed and the delay time. FIG. 9 is an electric circuit diagram showing an example of a frequency-voltage converter,
FIG. 10 is a waveform diagram showing voltage waveforms at various parts of the circuit of FIG. 9. 1...Engine, 2...Air cleaner, 3...
Air flow sensor, 4... Throttle valve, 5...
Distributor, A...Reference crank position sensor, B...Crank angle sensor, 6...Water temperature sensor, 7...Microcomputer circuit, 8...Fuel injection valve, 25, 26, 27...Comparator,
C, D...Analog switch, E...Frequency-voltage converter, 71...Microprocessor, 72...
...A-D converter, 73... Storage device, 74... Input/output device, 75... Drive circuit, 76, 77... Waveform shaping circuit.

Claims (1)

[Scope of Claims] 1. An engine rotation signal input device for a vehicle-mounted computer, which inputs a detection signal representing a predetermined crank angle position of the engine, which is the engine rotation signal, and a detection signal generated at each predetermined crank angle, respectively. an engine rotation sensor using a magnetic detection element to output; a waveform shaping means for inputting the detection signal output from the engine rotation sensor, shaping the waveform, and outputting the waveform-shaped engine rotation signal;
disposed between the engine rotation sensor and the waveform shaping means, receives the output signal of the engine rotation sensor, and in order to prevent the influence of noise voltage mixed into the output signal, the output signal is In the engine rotation signal input device, the engine rotation signal input device includes a delay means for delaying the engine rotation signal through a delay circuit having a predetermined time constant, wherein the waveform shaping means generates a waveform for shaping the engine rotation signal using a predetermined threshold level. In addition to the shaping circuit, it includes a compensation circuit for preventing malfunctions caused by noise voltage mixed in the engine rotation signal when the engine rotates at high speeds, and for guaranteeing the accuracy of crank angle detection using the engine rotation signal. and the compensation circuit includes a time constant changing means for changing the time constant of the delay circuit by connecting a time constant changing element to the delay circuit according to the rotation speed of the engine; an engine rotation signal input device for an on-vehicle computer, comprising: threshold level changing means for changing the threshold level of the waveform shaping circuit in accordance with the threshold level of the waveform shaping circuit. 2. A patent characterized in that the time constant changing means is configured to change the time constant of the delay circuit so as to increase it on a low engine rotation side and decrease it on a high engine rotation side. An engine rotation signal input device for a vehicle-mounted computer according to claim 1. 3. Claims characterized in that the threshold changing means is configured to change the threshold level such that the threshold level is lowered on a low engine speed side and raised on a high engine speed side. An engine rotation signal input device for a vehicle-mounted computer according to item 1 or 2.