JPS6155623B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition detection circuit for detecting operation of an engine ignition system.

If the spark plug in the engine ignition device fails to generate a spark for some reason, fuel gas continues to be supplied without combustion occurring within the engine, resulting in problems such as incomplete combustion.

Conventionally, spark plugs operate normally,
An ignition detection circuit for detecting whether fuel gas is reliably ignited has been developed and put into practical use. FIG. 1 is a block diagram of an ignition detection circuit provided in a vehicle such as an automobile, and FIGS. 2a to 2c are waveform diagrams showing signal waveforms at each portion thereof. In the circuit shown in Fig. 1, 1 is supplied with various input signals including a pulsed axle synchronization input signal obtained from a magnetic induction pickup coil, and is used to cause current to flow through the ignition coil 2 for an appropriate time. A digital central processing unit (hereinafter abbreviated as CPU) calculates and outputs a signal that determines the duty of the on period and off period of the output transistor 3, and also calculates and outputs a signal for controlling an electronic fuel injection device (not shown), etc. It is. This signal from the CPU 1 is then supplied to the output circuit 4. The output circuit 4 actually performs switch control of the output transistor 3. Incidentally, a spark plug 5 for generating a spark is provided on the secondary side of the ignition coil 2.

On the other hand, in FIG. 1, the circuit surrounded by a dashed line is a pulse generating circuit 6, and this circuit 6 is constructed as shown. That is, a pair of dividing resistors 7 and 8 for detecting this primary side voltage is connected between a point P1 on the primary side of the ignition coil 2 and a ground potential point. The anode of a reverse voltage blocking diode 9 is connected to the series connection point of the pair of resistors 7 and 8, and the cathode of this diode 9 is connected to the positive input terminal of a voltage comparator 10. Further, a capacitor 11 and a resistor 12 are connected in parallel between the cathode of the diode 9 and the ground potential point. A DC power supply 13 that generates a reference voltage V _th is connected between the negative input terminal of the voltage comparator 10 and the ground potential point with the polarity shown.

That is, the voltage comparator 10 generates a pulse signal φ by comparing the terminal voltage of the capacitor 11 (the voltage at the connection point P2 between the cathode of the diode 9 and the capacitor 11) with the reference voltage V _th of the DC power supply 13.
This pulse signal φ is supplied to the CPU 1.

The operation of the circuit configured as described above is as follows. First, by turning off the output transistor 3 at a predetermined timing under the control of the CPU 1, the primary side current of the ignition coil 2 is cut off, a high voltage (for example, 30 kV) is generated on the secondary side, and the ignition is started. Overcome the spark discharge with plug 5. At this time, the primary side voltage of the ignition coil 2, that is, the voltage at the P1 point V
_P1 is the output transistor 3 as shown in Figure 2a.
A pulse-like _high voltage (for _{example ,} a pulse width of 20 μ
S, the peak voltage is about 350V). P1 above
The voltage V _P1 at the point is divided by a pair of resistors 7 and 8, and the peak voltage is, for example, several to several tens of volts. And this divided voltage is
1, the capacitor 11 is rapidly charged to the above voltage immediately after each timing of t ₁ , t ₂ , t ₃ , . . . . Therefore, the voltage V _P2 at point P2 is
As shown in FIG. 2b, it rises rapidly. Further, since a resistor 12 is connected in parallel to the capacitor 11, the charged capacitor 11 is
The voltage is discharged through the resistor 12 with a time constant determined by the value of the resistor 12. Therefore, the voltage V _P2 at point P2 after charging gradually decreases to OV with a predetermined slope as shown in FIG. 2b.

On the other hand, the voltage comparator 10 compares the voltage V _P2 with the reference voltage V _th and outputs a high level signal when V _P2 > V _th and a low level signal when V _P2 < V _th . If a voltage as shown in Figure 2a is generated on the primary side of
Pulse signals φ as shown in FIG. 2c are sequentially output.

Pulse signal φ output from pulse generation circuit 6
is supplied to the CPU 1, so when the pulse signal φ as described above is output from the pulse generation circuit 6, the CPU 1 knows that the spark plug 5 is operating normally and the fuel gas is reliably ignited. It is determined that the calculation operation is continued. On the other hand, if the pulse signal φ as described above is not output from the pulse generation circuit 6, the CPU 1 determines that the spark plug 5 does not operate and the fuel gas is not ignited, and performs a fuel injection operation in an electronic fuel injection device, for example. By stopping the fuel gas, incomplete combustion of the fuel gas is prevented.

By the way, the circuit shown in Figure 1 has one ignition coil.
However, when there are a plurality of such devices, for example two, the conventional structure is as shown in FIG. 3 or 4.

In the circuit shown in FIG. 3, two output transistors 3 are activated by a pair of signals INa and INb having different phases from the CPU 1 and supplied to an output circuit 4'.
a, 3b, thereby spark plug 5
In this case, the high voltage generated on the primary side of the two ignition coils 2a and 2b is supplied to one pulse generation circuit 6 via the OR circuit 14. A synthesized pulse signal φ' is obtained.

Further, in the circuit shown in FIG. 4, pulse generating circuits 6 are prepared in a number equal to the number of ignition coils (in this case, two circuits 6a and 6b), and each pulse generating circuit 6a and 6b separately generates a pulse signal φ. _a and φ _b are obtained.

However, in the circuit shown in FIG. 3, the spark plugs 5a,
Even if one of 5b is not generating a spark, if the other is generating a spark, the pulse signal φ' can be obtained, so it is not possible to confirm which spark plug is not working. There is. In addition, in the circuit shown in Figure 4, there are as many pulse generating circuits as there are ignition coils, so it is easy to check which spark plugs do not generate sparks, but on the other hand, the number of parts increases and the manufacturing cost increases. The disadvantage is that it is expensive. That is, the fourth
When the circuit shown in the figure is integrated, the remaining parts except for the two capacitors 11 and resistor 12 can be made monolithic, but since capacitors 11 and resistor 12 require high precision, they are external components. Therefore, the total number of parts is at least five. Furthermore, since two types of pulse signals φ _a and φ _b are obtained by different pulse generating circuits 6 a and 6 b, there arises an inconvenience that the pulse widths of the two pulse signals do not match.

This invention was made in consideration of the above circumstances, and its purpose is to easily check which ignition coils are not generating sparks and are not working, even when there are multiple ignition coils. It is an object of the present invention to provide an ignition detection circuit that can be manufactured at low cost by reducing the number of parts.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a configuration diagram of an embodiment of the present invention,
This is a case where two ignition coils 2a and 2b are provided. Note that the same reference numerals are given to the parts of this embodiment circuit that correspond to those of the conventional circuit shown in FIGS. 3 and 4, and the explanation thereof will be omitted.

In this embodiment circuit, P _1a on the primary side of the ignition coil 2a for driving one spark plug 5a
High voltage generated at the point, and the other spark plug 5
P on the primary side of the ignition coil 2b for driving b
Each high voltage generated at point _1b is connected to OR circuit 14.
A pulse signal _{φ '} is obtained by supplying it to one pulse generation circuit 6 via This is what I did.

Further, the high voltage at point P _1a is supplied to the set side of the set-reset type flip-flop circuit 16 as a set signal, and the high voltage at point P _1b is supplied to the reset side of this flip-flop circuit 16 as a reset signal. The output Q of this flip-flop circuit 16 is supplied to the pulse distribution circuit 15.

The pulse distribution circuit 15 includes, for example, an AND circuit 17 to which the pulse signal φ' from the pulse generation circuit 6 and the Q output of the flip-flop circuit 16 are supplied, and a Q output of the flip-flop circuit 16, as shown in FIG. Inverter 18 to invert
and another AND circuit 19 to which the pulse signal φ' and the output of the inverter 18 are supplied.

Next, the operation of the circuit configured as described above will be explained using the waveform diagrams shown in FIGS. 7a to 7h.
First, the output circuit 4' is configured as shown in Fig. 7a and b.
Signals INa and INb of opposite phase from CPU1 are input. At this time, if all the circuits are normal, one output transistor 3a is turned off in synchronization with the falling timing of the signal INa, and at this timing, the pulse width is 20 μS and the peak voltage is applied to the primary side of the ignition coil 2a. A high voltage V _P1a of about 350V is generated, and a high voltage of about 30kV is generated on the secondary side. In addition, the other output transistor 3b is connected to the signal INb.
It turns off in synchronization with the falling timing of , and at this timing, a high voltage V _P1b similar to the above is generated on the primary side of the ignition coil 2b, and a high voltage similar to the above is also generated on the secondary side. do.

The high voltages V _P1a and V _P1b generated on the primary sides of the two ignition coils 2a and 2b are inputted to the pulse generation circuit 6 via the OR circuit 14, so the pulse generation circuit 6 is shown in FIG. 7e. A pulse signal φ' having a predetermined pulse width is output in synchronization with both high voltages V _P1a and V _P1b .

On the other hand, the flip-flop circuit 16 is set when one high voltage V _P1a is input, and reset when the other high voltage V _P1b is input, so its output Q becomes as shown in FIG. 7f. . In the pulse distribution circuit 15, one AND circuit 17 is opened when the Q output is at a high level, and the other AND circuit 19 is opened when the Q output is at a low level, so that the pulse signal φ' output from the pulse generation circuit 6 is As shown in Figure 7g and h, the output is distributed to φ _a and φ _b for each of the two spark plugs 5 a and 5 b.

Here, for example, if the circuit of one spark plug 5a system fails and high voltage is not generated on the primary side of the ignition coil 2a, high voltage V _P1b is generated only on the primary side of the ignition coil 2b. The pulse signal φ' is output from the pulse generating circuit 6 at the same timing as shown in FIG. 7h. On the other hand, since the flip-flop circuit 16 is only reset, its output Q is always at a low level. Therefore, at this time, the pulse distribution circuit 15
In this case, only one AND circuit 19 is always open, and the pulse signal φ' output from the pulse generating circuit 6 is output as is as φ _b . At this time, the other AND circuit 17 in the pulse distribution circuit 15 remains closed, so it does not output anything, and its output is at a low level. Therefore, in this case, it can be easily confirmed that the spark plug 5a does not generate sparks.

Also, if the circuit of the other spark plug 5b fails and high voltage is not generated on the primary side of the ignition coil 2b, high voltage V _P1a is generated only on the primary side of the ignition coil 2a. Therefore, the pulse signal φ' is outputted from the pulse generating circuit 6 at the same timing as shown in FIG. 7g. At this time, since the flip-flop circuit 16 is only set, its output Q is always at a high level. Therefore, at this time, only one AND circuit 17 in the pulse distribution circuit 15 is always open, and the pulse signal φ' output from the pulse generation circuit 6 is output as is as φ _a . At this time, the other AND circuit 19 in the pulse distribution circuit 15 remains closed, so it does not output anything, and its output is at a low level. Therefore, in this case, it can be easily confirmed that the spark plug 5b is not generating sparks.

As described above, according to the above embodiment, even if there are two ignition coils, it is possible to easily check which one does not generate a spark and is not working. In addition, when integrating this circuit, the capacitor 1 in the pulse generation circuit 6, which requires high precision and is an external component,
1 and resistor 12, the remaining parts can be made monolithic into one chip, so the number of parts can be reduced to three at the minimum. Therefore, it is possible to significantly reduce the cost compared to the conventional method, and it can be manufactured at low cost. Furthermore, since the pulse signal φ' is generated by one pulse generation circuit 6 and distributed by the pulse distribution circuit 15, the pulse widths of the pulse signals φ _a and φ _b can be made equal. , for this purpose, the signals φ _a and φ _b are
This facilitates the processing when the CPU 1 performs the processing.

Furthermore, in the above embodiment circuit, in response to all the primary side high voltage inputs of the plurality of ignition coils 2a, 2b,
The pulses generated by the pulse generating circuit 6 are distributed to each ignition coil. Since the pulses are distributed in accordance with the primary side signals of all the ignition coils in this way, correct output cannot be obtained if the ignition coils are fired in different orders. Therefore, with this embodiment circuit, it is also possible to determine whether the ignition order of the ignition coils is good or bad. For example, when starting, one ignition coil 2a must be started, but if the other ignition coil 2b is used, the phase of the Q output of the flip-flop circuit 16 will change from the waveform in FIG. is the opposite, and in this case, the two types of pulse signals φ _a and φ _b are not output. This is extremely effective when two or more ignition coils are provided.

Note that the present invention is not limited to the above embodiments; for example, in the above embodiments, the case where there are two ignition coils has been described, but this invention can be implemented regardless of the number of ignition coils. Needless to say, it is. Further, the pulse generating circuit 6 may be configured as shown in FIGS. 8 and 9, for example.

The pulse generating circuit of FIG. 8 is constructed by inserting an emitter-collector circuit of a PNP transistor 21 whose base input is a predetermined voltage E _B of positive polarity between the anode of the diode 9 and the ground potential point. The anode voltage of diode 9 is E _B +V _BE
(V _BE is the voltage between the base and emitter of the transistor 21). Note that the two resistors 22 and 23 and the diode 24 are for protecting each element.

The pulse generating circuit shown in FIG. 9 consists of a pair of resistors 7 and 8.
Instead of directly charging the capacitor 11 with the divided voltage, a high level or low level signal is obtained by comparing the primary side voltage of the ignition coil with the reference voltage V _th2 by another voltage comparator 25,
The capacitor 11 is charged by the high level signal from the voltage comparator 25.

As explained above, according to the present invention, even if there are multiple spark plugs, it is possible to easily check which ones are not generating sparks and are not working, and by reducing the number of parts. It is possible to provide an ignition detection circuit that can be manufactured at low cost.

[Brief explanation of the drawing]

Figure 1 is a general configuration diagram of the ignition detection circuit, Figure 2 is a general configuration diagram of the ignition detection circuit.
Figures a to c are waveform diagrams, Figures 3 and 4 are configuration diagrams of a conventional ignition detection circuit when a plurality of ignition coils are provided, and Figure 5 is a configuration of an embodiment of the present invention. 6 are specific diagrams of a part thereof, FIGS. 7a to 7h are waveform diagrams for explaining the above embodiment, and FIGS. 8 and 9 are configuration diagrams of modified examples of the above embodiment, respectively. . 1...Digital central processing unit (CPU),
2...Ignition coil, 3...Output transistor, 4
... Output circuit, 5 ... Spark plug, 6 ... Pulse generation circuit, 14 ... OR circuit, 15 ... Pulse distribution circuit, 16 ... Set-reset type flip-flop circuit.

Claims (1)

[Claims] 1. A plurality of ignition coils, a pulse generating means that generates a pulse each time a high voltage is generated on the primary side of each of the plurality of ignition coils, and a high voltage generated on the primary side of all of the plurality of ignition coils. 1. An ignition detection circuit comprising pulse distribution means for receiving an input and distributing pulses generated by the pulse generation means to each ignition coil in accordance with the input.