JPH0510242A - Ignition signal generator - Google Patents

Abstract

PURPOSE:To always generate optimum ignition signal, by preventing the missing of the ignition signal when the number of engine revolution varies sharply, in an ignition signal generator used for am internal combustion engine. CONSTITUTION:The signal of an engine revolution angle sensor is compared with a threshold value by using a comparator 10, and wave-shaped, and the lapse time from the pulse signal which is obtained through the differentiation of the output by a differentiation circuit 13 is measured by a timer 14, and the threshold value is varied by using a correction circuit 15 and a D/A converter 15 according to the lapse time, and the threshold value is set always to an optimum value according to the level of the sensor signal. Accordingly, independently of the number of revolution of the engine, the timing far starting the charge to an ignittor and the time interval of the ignition timing are made always optimum, and the optimum ignition signal can be always obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition signal generator for an engine by digital signal processing.

[0002]

2. Description of the Related Art FIG. 3 is a schematic block diagram showing an example of a conventional engine ignition signal generator. In FIG. 3, 10 is a comparator, 11 is an input terminal, 12 is an output terminal,
Reference numeral 19 is an F / V converter. A sensor signal output from a rotation angle sensor of the engine (not shown) is input to the input terminal 11, is subjected to signal processing by an ignition signal generator configured by the comparator 10 and the F / V converter 19, and is output terminal 12. The ignition signal is output from. When the engine reaches a certain rotation angle, charging the igniter starts
Ignition timing is when the engine reaches near top dead center. Timing for starting charging and ignition for the igniter is determined by the ignition signal generator.

Next, the operation of the above-mentioned conventional ignition signal generator will be described. Conventionally, microprocessor (MPU)
In the engine control system used, a magnetic detection type sensor is often used as an engine rotation angle sensor. Since this magnetic detection type sensor utilizes the fact that the voltage across the detection coil changes due to the change in magnetic flux due to the rotation of the shaft, the output of the sensor, that is, the sensor signal, is a function of the engine speed. .. In order to use the sensor signal as an ignition signal, it is necessary to shape the waveform using the comparator 10, but the threshold value of the comparator 10 is lowered because the level of the sensor signal is low at low revolutions, and induced noise etc. at high revolutions. It is necessary to increase the threshold value of the comparator 10 in order to avoid the influence of. Furthermore, in order to generate the energy required for ignition, it is necessary to optimally control the energization time from the timing to start charging the igniter to the timing to output the ignition signal,
For this purpose, it is necessary to measure the engine speed and generate a threshold value corresponding to the engine speed to determine the timing to start charging the igniter. The F / V converter 19 generates this threshold value. F / V converter 19
Converts the frequency (F) of the sensor signal indicating the engine speed into a voltage (V), and uses the converted voltage (V) as a comparison voltage (threshold value) for the comparator 10.

[0004]

However, in the above-mentioned conventional ignition signal generator, an optimum threshold value can be obtained when there is a large change in the number of revolutions, that is, a change in the output voltage of the magnetic detection type sensor, such as during cranking. However, there is a problem in that it is difficult to obtain an optimum energization time. For example, when the rotation speed suddenly drops, the output voltage of the sensor becomes a value smaller than the threshold voltage, resulting in signal loss and misfire.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and an object thereof is to provide an excellent ignition signal generator capable of generating an accurate ignition signal without signal omission.

[0006]

In order to achieve the above object, the present invention compares the signal of the engine rotation angle sensor with a threshold value by a comparator to shape the waveform so that an optimum energization time can be obtained. , The threshold value to the comparator is changed according to the elapsed time from the pulse signal obtained by differentiating the output.

[0007]

According to the present invention, an optimum threshold value can be obtained by the above means, and an accurate ignition signal can be generated without signal omission.

[0008]

1 is a block diagram showing the construction of an ignition signal generator according to an embodiment of the present invention, in which components having the same functions as those in FIG. 3 are designated by the same reference numerals. FIG. 2 is a signal waveform diagram of essential parts of the ignition signal generator shown in FIG.

In FIG. 1, 10 is a comparator, which shapes the waveform of the signal from the engine rotation angle sensor. Reference numeral 11 is its input terminal, and 12 is an output terminal. A differentiating circuit 13 differentiates the output of the comparator 10 to detect a change point. 1
Reference numeral 4 is a timer, which counts up the time at regular intervals (for example, every 0.5 mS). Reference numeral 15 is a correction circuit, a correction circuit that decodes the digital value of the timer 14 in accordance with a predetermined relationship, and 16 is a D / A converter that converts the decoding result of the correction circuit 15 into an analog voltage,
Generate a threshold of. Reference numeral 17 denotes a hysteresis generating resistor, which prevents an error in threshold setting caused by noise or power supply voltage fluctuation. Reference numeral 18 is a count pulse input terminal.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 shows the waveform of each part. In FIG. 2, 20 is a signal waveform of the engine rotation angle sensor input to the input terminal 11. 20a is a waveform 20 of the engine rotation angle sensor
Is the point where the output (threshold value) 24 of the D / A converter 16 intersects, and 20b is the point (zero cross) where the waveform 20 also intersects the zero level. Reference numeral 21 is a waveform of the ignition signal obtained by shaping the waveform 20 by the comparator 10. 21a is an energization time. An energization time 21a is between the point 20a and the zero cross 20b. That is, the charging of the igniter is started at the point 20a, and the zero cross 20b becomes the ignition timing. The ignition signal 21 whose waveform is shaped by the comparator 10 is differentiated by the differentiating circuit 13. 22 is a differentiated waveform, that is, the waveform of the output pulse of the differentiating circuit 13. Reference numeral 23 is a count pulse for a timer which is generated at intervals of 0.5 mS. The count pulse 23 is input to the timer 14 from the count pulse input terminal 18 and counts up. The timer 14 is reset by the plus side of the waveform 22 of the output pulse of the differentiating circuit 13, and when reset, starts counting up again with the count pulse 23. The correction circuit 15 is provided with a read-only memory having conversion contents as shown in (Table 1) below.
4. Convert the output value of 4 into the appropriate digital value. This digital value is converted into an analog voltage value by the D / A converter 16 according to the relationship shown in (Table 1). The output of the D / A converter 16 is the threshold value 24 and is given to the comparator 10.

[0011]

[Table 1]

In this way, as is clear from the relationship between the signal waveform 20 of the engine rotation angle sensor shown in FIG. 2 and the output of the D / A converter 16, that is, the threshold value 24, the level of the sensor signal changes. However, since the threshold value changes, it is possible to always generate an optimal ignition signal between the ignition start timing and the ignition start timing, that is, the energization time, at any engine speed.

The differentiating circuit 13, the timer 14, the correcting circuit 15, and the D / A converter 16 may be those having a built-in microprocessor. In this case, the effect of cost reduction by reducing the number of parts is achieved. can get.

[0014]

As is apparent from the above embodiment, the present invention compares the signal of the engine rotation angle sensor with the threshold value to perform waveform shaping, and compares the output according to the elapsed time from the pulse signal obtained by differentiating the output. It changes the threshold value of the instrument, and the threshold value becomes the optimum value according to the level of the sensor signal,
This has the effect of always generating the optimum ignition signal for the time period during which the igniter is charged.

[Brief description of drawings]

FIG. 1 is a block diagram of an ignition signal generator according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of essential parts of the device.

FIG. 3 is a block diagram of a conventional ignition signal generator.

[Explanation of symbols]

 10 comparator 11 input terminal 12 output terminal 13 differentiating circuit 14 timer 15 correction circuit 16 D / A converter 21 ignition signal

Claims (1)

Claim: What is claimed is: 1. A comparator for waveform shaping by comparing an input signal from an engine rotation angle sensor with a threshold value, a differentiation circuit for differentiating the output of the comparator, and a differentiation circuit for the differentiation circuit. A timer for measuring the elapsed time from the output pulse generation, a correction circuit for reading a threshold value according to the elapsed time as a digital value, and a D / A converter for D / A converting the output of the correction circuit An ignition signal generator that uses the output of the comparator as an ignition signal.