JPH04105068A - Ignition pulse detection circuit - Google Patents

Abstract

PURPOSE:To enable the quantity of high voltage resistant parts to be reduced, and measures against a noise to be simplified by introducing a part of the output current of an ignition coil to the input side of a photo coupler, and obtaining an ignition pulse via the half-wave shaping of an output signal from the photo coupler. CONSTITUTION:The negative voltage component of an ignition pulse generated at an ignition coil 1 is eliminated at a diode D1, and the aforesaid ignition pulse is inputted to a photo coupler 2 after overcurrent protection with a resistor R1 and overvoltage protection with a Zener diode Z1. The photo coupler 2 transmits only a signal component to the output side thereof via the photo coupling of an internal light emitting diode and photo transistor. Then, a waveform shaping circuit 3 comprising Schmitt trigger buffer shapes an output signal from a low-pass filter, and generates a desired output signal. This signal does not contain surge voltage. According to the aforesaid construction, the quantity of high voltage resistant parts can be reduced, and the protection of a circuit against a noise can be simplified.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ignition pulse detection circuit, and particularly to an ignition pulse detection circuit for detecting and using engine rotation speed from ignition pulses to control and measure an engine. This relates to a detection circuit.

[Conventional technology]

Conventionally, the engine's ignition cord is controlled? il.

When inputting to an electronic circuit for the purpose of measurement, etc., a waveform shaping circuit consisting of resistors, capacitors, diodes, etc. is used to shape the pulses into TTL, CMO3, etc. level pulses.

FIG. 6 shows the configuration of a waveform shaping circuit in a conventional ignition pulse detection circuit.

In FIG. 6, the low voltage side (-
The ignition pulse from the
After the voltage is divided by a voltage divider consisting of
The peak value is limited by Dll, and only the positive polarity component is extracted via diode Dll and load resistor R13.

This signal is filtered by a filter circuit consisting of a capacitor C11, a resistor R14, a capacitor C12, and a resistor R15, and is then applied to the base of a transistor Trll, which constitutes a common emitter circuit, and is connected to its collector circuit. A required waveform-shaped pulse output is generated at the load resistor R16.

[Problem to be solved by the invention]

The peak value of the engine's ignition pulse varies depending on the engine speed and includes a surge voltage of several hundred volts. Therefore, in the conventional ignition pulse detection circuit, as shown in FIG. 6, the waveform shaping circuit becomes complicated and it is necessary to use expensive high-voltage components.

Furthermore, in the ignition pulse detection circuit shown in Fig. 6, the ignition pulse voltage is detected with respect to the circuit ground, but since the ignition coil l generates a voltage with respect to the vehicle body ground, it is connected to the circuit ground. If the potential difference with the vehicle body ground is large, it may not be possible to operate correctly.

Furthermore, noise voltage from the input section may cause malfunctions in the equipment's circuits, incorrect signal input to other input sections, or radiated noise from the harness (wiring) that transmits the ignition pulses. occurs,
It may affect other signals and car radios.

[Object of the Invention] The present invention aims to solve the problems of the prior art, and is to reduce the noise countermeasures of the circuit by preventing high surge voltage from being input to the ignition pulse detection circuit. In addition, it is possible to operate correctly even if the circuit ground and the vehicle body ground are not at the same potential, and the number of parts that require high withstand voltage can be reduced. The purpose of this is to suppress the influence of other circuits on other circuits.

[Means for Solving the Problems] The present invention is a circuit that detects an ignition pulse from the output current of an ignition coil 1, which includes a photocoupler 2, which shunts a part of the output current of the ignition coil to the photocoupler 2. A waveform shaping circuit 3 is provided to shape the signal on the output side of the photocoupler 2, thereby obtaining a waveform shaped ignition pulse as the output of the waveform shaping circuit 3. ing. This aims to achieve the above-mentioned purpose.

[Effect]

A part of the ignition coil's output current is shunted and connected to the input side of the photocoupler, and the signal obtained at the output side of the photocoupler is waveform-shaped to obtain the ignition pulse, so high surges from the ignition coil can be avoided. Since no voltage is applied to the ignition pulse detection circuit, the number of high-voltage components can be reduced, and noise countermeasures for the circuit can be simplified.

Furthermore, since the input side and output side are electrically separated, it can operate even if the ground of the ignition pulse detection circuit and the ground of the vehicle body are not at the same potential. influence will be suppressed.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 indicates an ignition coil of an engine, reference numeral 2 indicates a photocoupler, and reference numeral 3 indicates a waveform shaping circuit including a Schmitt trigger buffer for waveform shaping. Further, Di is a diode for removing negative voltage components, Zl is a Zener diode for overvoltage protection at the input of photocoupler 2, and R1
is a resistor for overcurrent protection at the input of photocoupler 20, R2 is a pull-up resistor for the output of photocoupler 2,
R3 and CI are a resistor and a capacitor forming a waveform shaping filter, and voc is a power supply for operating the electronic circuit. Note that in FIG. 1, A, B, C, and D indicate points at which voltage waveforms in the circuit should be compared.

The present invention provides a circuit for detecting an ignition pulse from an output current of an ignition coil 1, which is provided with a photocoupler 2 to connect a part of the output current of the ignition coil to the input side of the photocoupler 2, and also includes a waveform shaping circuit 3. By shaping the signal on the output side of the photocoupler 2, a desired ignition pulse whose waveform has been shaped by the output of the waveform shaping circuit 3 can be obtained.

Figure 2 shows the voltage waveform (
A) and includes a surge voltage of several hundred square meters. If such a signal is connected to a circuit that includes electrical connections as shown in Figure 6, the surge current will flow into the circuit's power supply or ground, which can cause equipment malfunction due to noise. Become.

In the embodiment shown in FIG. 1, the ignition pulse generated in the ignition coil 1 has its negative voltage component removed by the diode D1, overcurrent protection is provided by the resistor R1, overvoltage protection is provided by the Zener diode Z1, and the ignition pulse is sent to the photocoupler 2. is input.

In the photocoupler 2, only the signal component is transmitted to the output side through optical coupling between a light emitting diode and a phototransistor inside the photocoupler 2.

FIG. 3 shows the output voltage waveform (B) of the photocoupler, the peak value of which is the power supply voltage V((), which is a waveform from which surges have been removed.

In this case, by installing the circuit up to the photocoupler 2 near the ignition coil 1, no surge current will flow through the harness up to the circuit, so noise radiation and induction into nearby harnesses can be suppressed.

However, even in this case, the output waveform of the photocoupler 2 often contains unnecessary pulses, so the resistor R3
, a low-pass filter consisting of a capacitor C1 removes noise components.

FIG. 4 shows the output waveform (C) of the low-pass filter consisting of resistor R3 and capacitor C1, and shows that noise consisting of high frequency components has been removed.

Next, a waveform shaping circuit 3 consisting of a Schmitt trigger buffer (or hysteresis comparator) shapes the output signal of the low-pass filter to generate a desired output signal.

FIG. 5 shows the output waveform (D) of the waveform shaping circuit 3, and shows that a square wave output from which noise has been removed can be obtained.

The output of the waveform shaping circuit 3 is a constant peak value V. has C,
TTL since it does not include surge voltage.

It can be used as an input signal for elements such as CMO3.

〔Effect of the invention〕

As described above, according to the present invention, high surge voltage from the ignition coil is not applied to the ignition pulse detection circuit, so the number of high-voltage components can be reduced and noise countermeasures for the circuit can be simplified.

In addition, in the ignition pulse detection circuit of the present invention, since the input side and the output side are electrically separated, the ignition pulse detection circuit can operate even if the ground of the ignition pulse detection circuit and the ground of the vehicle body are not at the same potential. radiation from,
The influence of induction on other circuits is now suppressed.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an embodiment of the present invention, Figure 2 is a diagram showing the voltage waveform generated by the ignition coil, Figure 3 is a diagram showing the output voltage waveform of the photocoupler, and Figure 4 is the output of the low-pass filter. FIG. 5 is a diagram showing the output waveform of the waveform shaping circuit, and FIG. 6 is a diagram showing the conventional ignition pulse detection circuit. 1-Ignition coil, 2-Photocoupler, 3-waveform shaping circuit. Applicant: Suzuki Motor Co., Ltd. Agent Patent Attorney Isamu Takahashi Figure 2 (Equipment coil) Figure 4 (Rono de file comparison) Figure 3 (Hotokaara Koun) Figure 5 (7!2 type) Vertical circuit output)

Claims (1)

[Claims] (1) In a circuit that detects an ignition pulse from the output current of an ignition coil, there is a photocoupler connected to the input side of a part of the output current of the ignition coil, and a waveform shaping circuit that shapes the waveform of the signal on the output side of the photocoupler. An ignition pulse detection circuit comprising: an ignition pulse detection circuit which obtains an ignition pulse by the output of the waveform shaping circuit.