JP2862467B2 - Ignition device for internal combustion engine and failure detection device for ignition device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine and a failure detection device for detecting a failure of the ignition device.

[0002]

2. Description of the Related Art Conventionally, as an ignition device for an internal combustion engine, for example, there is one as shown in FIG. The ignition device includes an ignition plug 75, an ignition coil 70 for applying a high voltage to the ignition plug 75, a switching circuit 50 for operating the ignition coil 70, and an ECU (Electronic Controller).
ol Unit) 10c. The switching circuit 50 includes a power transistor 51, resistors 56 and 5
7, a current limiting circuit 58. ECU (Electr
onic Control Unit) 10c includes an arithmetic control circuit (microcomputer) 11c that executes various arithmetic operations, and an ignition signal that outputs an ignition signal to the power transistor 51 of the switching circuit 50 in response to an ignition control signal from the arithmetic control circuit 11c. And an output circuit 20c.

An ignition control signal from an arithmetic control circuit 11c turns on / off a transistor 22 via a resistor 21.
Control. By turning on / off the transistor 22, a current is output from the ECU power supply Vcc to the switching circuit 50 via the resistors 23 and 24 as an ignition signal. This ignition signal flows to the base of the power transistor 51 via the resistor 56 of the switching circuit 50. The power transistor 51 turns on when the ignition signal goes high, and turns off when the ignition signal goes low. By turning ON / OFF the power transistor 51, the application and interruption of the primary current flowing through the primary coil 71 of the ignition coil 70 are repeated, and a high voltage is induced in the secondary coil 72, and the spark plug 75 is discharged. I do.

[0004] The above series of operations will be described with reference to a waveform diagram shown in FIG. In the figure, (A) shows the operation control circuit 1
(B) is an ignition signal waveform from the ECU 10c, (C) is a primary current waveform of the ignition coil 70, (D) is a primary voltage waveform of the ignition coil 70, (E)
Shows the secondary voltage waveform of the ignition coil 70.

When the ignition control signal from the arithmetic control circuit 11c changes from high to low, the ignition signal from the ECU 11c changes from low to high, and a current flows through the primary coil 71 of the ignition coil 70. This primary coil 71
When the primary current flowing through the primary coil 71 is suddenly cut off, a high voltage is instantaneously applied to the primary coil 71 by so-called flyback. When a high voltage is applied to the primary coil 71, a very high voltage is instantaneously applied to the secondary coil 72 due to the amplifying action of the coil 70, and the spark plug 75 is sparked.

When the power transistor 51 is short-circuited for some reason, not only ignition control cannot be performed, but also a fire may occur. Therefore, it is necessary to detect this short-circuit immediately. Conventionally, as a type capable of detecting a short circuit of the power transistor, for example, Japanese Patent Application Laid-Open No. 63-295839 and
There is one described in Japanese Patent No. 295838. This technique detects a voltage between a collector terminal of a power transistor and a primary coil, and grasps a short circuit of the power transistor or the like from the value of the voltage.

[0007]

However, in such a conventional technique, a high voltage applied to the primary coil is also applied to the detection circuit when the power transistor is not short-circuited. There is a problem in that a pressure-resistant component must be used, and the manufacturing cost increases.

In view of the foregoing, the present invention focuses on such a conventional problem, and it is possible to detect a short circuit of a power transistor without using a high breakdown voltage component. It is an object to provide a detection device.

[0009]

A failure detection device for achieving the above object comprises an ignition plug, an ignition coil for applying a high voltage to the ignition plug, a primary coil and a secondary coil constituting the ignition coil. Among the side coils, an ignition signal output unit that outputs an ignition signal for controlling a current flowing through the primary side coil, and a switching circuit that controls a current flowing through the primary side coil according to the ignition signal, A switching element having a main current input terminal into which the current flowing through the primary coil flows, a main current output terminal from which the current flowing from the main current input terminal flows, and a signal input terminal to which the ignition signal is input And a resistor for connecting the main current output terminal and the signal input terminal of the switching element, and detecting a failure of the ignition device for the internal combustion engine having a resistor. In the device, an output terminal of the ignition signal output unit that outputs the ignition signal is connected to ground via a resistor, and a failure of the switching element occurs according to a waveform of a voltage applied to the output terminal of the ignition signal output unit. Is provided with a failure detection circuit for detecting

[0010]

[Function] Normally, from the ignition signal output section, High / Low
Are output to the switching circuit. When such an ignition signal is input to the signal input terminal of a switching element provided in the switching circuit, the switching element repeats ON / OFF, and the energization and interruption of the primary current flowing through the primary coil of the ignition coil are repeated. . When the supply and cutoff of the primary current is performed rapidly, a high voltage is instantaneously applied to the primary coil by so-called flyback. If a high voltage is applied to the primary coil, the secondary coil will
Very high voltages will be momentarily applied, sparking the spark plug.

By the way, since the failure detection circuit detects the voltage applied to the ignition signal output terminal, when the switching element is not short-circuited, the voltage based on the ignition signal,
That is, only a low voltage is applied. When the switching element is not short-circuited, the failure detection circuit includes Hig
A rectangular wave ignition signal that repeats h · Low is input.

When the switching element is short-circuited, that is, when the main current input terminal and the main current output terminal of the switching element are short-circuited, irrespective of the voltage applied to the signal input terminal, the primary side coil and the main current input terminal of the switching element. The primary current flows continuously between the output terminal and the main current output terminal. This primary current flows to the ground via a resistor connecting the signal input terminal of the switching element and the main current input terminal or the main current output terminal, and a grounded resistor. As a result, even if the ignition signal output section outputs a square wave ignition signal that repeats High / Low, a constant voltage corresponding to the voltage drop due to the grounded resistor is continuously applied to the ignition signal output terminal. Become.

Therefore, unlike the short circuit, a constant voltage is continuously applied to the failure detection circuit.
The short circuit of the switching element can be grasped.
Even if the switching element is short-circuited, the failure detection circuit receives only a voltage corresponding to the voltage drop due to the grounded resistor. Therefore, according to the present invention, a high voltage is not applied to the failure detection circuit regardless of whether the switching element is short-circuited or short-circuited. Can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments according to the present invention will be described below with reference to FIGS.

First, an ignition device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the ignition device of the present embodiment includes an ignition plug 75, an ignition coil 70 for applying a high voltage to the ignition plug 75,
The switching circuit 50 for operating the ignition coil 70 and the ECU 10 that outputs an ignition signal to the switching circuit 50 are provided.

The ECU 10 includes a calculation control circuit 11 for executing various calculations for controlling the fuel injection amount and the ignition timing;
An ignition signal output circuit 2 for outputting an ignition signal to a switching circuit 50 in response to an ignition control signal from an arithmetic control circuit 11
0, a fuel injection signal output circuit 40 that outputs a fuel injection signal to the fuel injection valve drive circuit 60 in response to a fuel control signal from the arithmetic and control circuit 11, and a failure detection circuit 30 that detects a failure of the switching circuit 50. It is configured to have.
The ignition coil 70 and the fuel injection valve drive circuit 60 are connected to the battery 90 by power lines 91 and 93, respectively, so that power is supplied from the battery 90. The power lines 91 and 93 are provided with switches 92 and 94 for interrupting the power supplied to the ignition coil 70 and the fuel injection valve driving circuit 60 through the power lines 91 and 93.

The arithmetic control circuit 11 is actually constituted by a microcomputer, and has a function as an ignition timing arithmetic section for setting an ignition timing based on a signal from a crank angle sensor 81 provided in the engine 80. 13
Similarly, the fuel injection amount calculation unit 14 that sets the fuel injection amount and the injection timing of the fuel injection valve 65 based on a signal from the crank angle sensor 81, and the power lines 91 and 93 when a failure is detected by the failure detection circuit 30. And a power cutoff signal output unit 12 for outputting a power cutoff signal to the provided switches 92 and 94.

As shown in FIG. 1, the ignition signal output circuit 20 of the ECU 10 includes resistors 21, 23, 24, 26 and NP
It comprises an N-transistor 22, a PNP transistor 25, and a Zener diode 27. NP
The base terminal of the N-transistor 22 is connected to the arithmetic control circuit 11 via the resistor 21 so that the ignition control signal from the arithmetic control circuit 11 is input thereto. Also, NP
The collector terminal of the N-transistor 22 includes resistors 23 and 24
Is connected to the ECU power supply Vcc, and the emitter terminal of the NPN transistor 22 is connected to the ground. P
The base terminal of the NP transistor 25 is connected to the collector terminal of the NPN transistor 22 via the resistor 24,
The emitter terminal of PNP transistor 25 is connected to ECU power supply Vcc. Also, the PNP transistor 25
Is connected to an ignition signal output terminal 2 via a resistor 26.
8 and connected to a Zener diode 27. The Zener diode 27 is provided to stabilize the voltage of the signal output from the collector terminal of the PNP transistor 25 to the ignition signal output terminal 28 via the resistor 26. The ignition signal output terminal 28 is connected to the switching circuit 50 and the failure detection circuit 30 and is also connected to the ground via the resistor 29.

The failure detection circuit 30 includes NPN transistors 31, 35, resistors 32, 33, 34, 36, a capacitor 37, and a comparator 38. The base terminal of the NPN transistor 31 is connected to the ignition signal output terminal 28. The collector terminal of the NPN transistor 31 is connected to the ECU power supply Vcc via the resistor 32, and the emitter terminal of the NPN transistor 31 is connected to the ground. The base terminal of the NPN transistor 35 is connected to the collector terminal of the NPN transistor 31. NPN transistor 3
5 is connected to the ECU power supply Vcc via the resistor 33.
, And to the (+) input terminal of the comparator 38 and the capacitor 37. NPN
The emitter terminal of the transistor 35 is connected to the ground. The (−) input terminal of the comparator 38 is connected to the ECU power supply Vcc via the resistor 34. Also,
The output terminal of the comparator 38 is connected to the operation control circuit 11.

The switching circuit 50 has a power transistor 51, resistors 56 and 57, and a current limiting circuit 58. The power transistor 51 has a collector terminal connected to the primary coil 71 of the ignition coil 70,
Its emitter terminal is connected to ground via a resistor 57, and its base terminal is connected to the ignition signal output terminal 28 of the ECU 10 via a resistor 56. The power transistor 51 includes two NPN transistors 52 and 53 and two resistors 54 and 55. NPN
The emitter terminal of the transistor 53 (= emitter terminal of the power transistor 51) and the base terminal of the NPN transistor 52 (= base terminal of the power transistor 51) are connected via two resistors 54 and 55. These two resistors 54 and 55 are provided so that the current flowing through the primary coil 71 of the ignition coil 70 changes more rapidly.

Next, the operation of the ignition device of this embodiment will be described. The ignition timing calculation unit 13 of the calculation control circuit 11
An ignition control signal is created based on a signal from a crank angle sensor 81 provided in the engine 80, and this signal is output to the ignition signal output circuit 20. This ignition control signal
The signal is input to the base terminal of the NPN transistor 22 via the resistor 3 and ON / OFF control of the transistor 22 is performed. When the NPN transistor 22 is ON, a current flows from the ECU power supply Vcc to ground via the resistors 23 and 24 and the NPN transistor 22. As a result, the base terminal of the PNP transistor 25 becomes low, the transistor 25 is turned on, and a current flows from the ECU power supply Vcc to the ignition signal output terminal 28 via the PNP transistor 25 and the resistor 26. When the NPN transistor 22 is OFF, the transistor 22 has an ECU power supply V
Since no current flows from cc, the base terminal of the PNP transistor 25 goes high. As a result, the PNP transistor 25 is turned off, and no current flows from the ECU power supply Vcc to the ignition signal output terminal 28 via the PNP transistor 25 and the resistor 26. That is, as shown in FIG. 3, when the arithmetic control circuit 11 outputs a rectangular wave that repeats High / Low as an ignition control signal (FIG. 3A), the ignition signal output terminal 28 outputs the rectangular wave from FIG. As shown in (2), a rectangular wave ignition signal that repeats High / Low is output to the switching circuit 50.

Such an ignition signal is supplied to the switching circuit 5
0, the power transistor 52 is turned on.
The turning off is repeated, and the primary current flowing through the primary side coil 71 of the ignition coil 70 is repeatedly turned on and off as shown in FIG. When the current supply and cutoff of the primary coil 71 is rapidly performed, a high voltage is instantaneously applied to the primary coil 71 by so-called flyback as shown in FIG. When a high voltage is applied to the primary coil 71, the secondary coil 7
2, a very high voltage is instantaneously applied to the spark plug 75, as shown in FIG.

When the power transistor 51 is not short-circuited, the failure detection circuit 30 operates as follows. Since the ignition signal output terminal 28 is connected to the base terminal of the NPN transistor 31 of the failure detection circuit 30, a rectangular wave ignition signal that repeats High / Low is input, and the NPN transistor 31 turns ON / OFF. Repeat. By the ON / OFF operation of the NPN transistor 31, the NPN transistor repeats OFF / ON.
When the ignition signal becomes high and the NPN transistor 31 is turned on and the NPN transistor is turned off, the voltage from the ECU power supply Vcc is applied to the capacitor 37 via the resistor 33, and the electric charge is gradually stored. Further, the ignition signal becomes low, the NPN transistor 31 is turned off, and NP
When the N transistor is turned on, the electric charge stored in the capacitor 37 is discharged to the ground via the NPN transistor 35. As described above, the charging and discharging of the capacitor 37 are repeated in accordance with the High / Low of the ignition signal, so that the voltage of the capacitor 37 has a waveform in which a triangular wave is repeated as shown in FIG. The resistor 33 and the capacitor 37 are normal (when not short-circuited)
The charging time constant is set so that the capacitor voltage does not exceed the reference voltage a applied to the (−) side input terminal of the comparator 38. Therefore, when the power transistor 51 is not short-circuited, the (+)
The capacitor voltage applied to the input terminal of the comparator 38
In order not to exceed the reference voltage a applied to the (−) side input terminal of the control operation circuit 11 from the output terminal of the comparator 38.
Is always Low.

Incidentally, if the power transistor 51 is short-circuited for some reason, not only the ignition control cannot be performed as described in the prior art, but also a fire may occur, so that it is necessary to detect this short-circuit immediately. . Therefore, in this embodiment, by detecting the voltage applied to the ignition signal output terminal 28, it is determined whether or not the power transistor 51 is short-circuited.

When the power transistor 51 is short-circuited, that is, when the collector terminal and the emitter terminal of the power transistor 51 are short-circuited, the current from the battery 90 flows through the primary coil 71 regardless of the voltage applied to the base terminal. It flows continuously to the power transistor 51. This primary current is supplied to the resistors 54 and 55 and the resistor 56 of the power transistor 10 and the resistor 29 of the ECU 10.
Flows to the ground via. As a result, a voltage corresponding to the voltage drop by the resistor 29 is continuously applied to the ignition signal output terminal 28. That is, when the power transistor 51 is short-circuited, the primary current (FIG. 3C) continuously flows regardless of the ignition signal from the ignition signal output circuit 20 as shown in FIG. , A constant voltage (High) is continuously applied.

Therefore, a constant voltage (High) is also applied to the base terminal of the NPN transistor 31 of the failure detection circuit 30.
It takes continuously. As a result, the NPN transistor 35
Maintain the OFF state, and the capacitor 37 continues to be charged. If the capacitor 37 continues to be charged,
As shown in FIG. 3F, the capacitor voltage is equal to the reference voltage a.
And the failure detection signal output from the output terminal of the comparator 38 to the control operation circuit 11 is High.
((F) in the figure). In the related art shown in FIG. 6, even if the power transistor 51 is short-circuited, the high and low voltages due to the ignition signal are repeatedly applied to the ignition signal output terminal.

When the failure detection signal becomes high, a power cutoff signal is output from the power cutoff signal output section 12 of the control arithmetic circuit 11 to the switches 92 and 94 in response to the signal, and the ignition coil 70 and the fuel The current supplied to the injection valve drive circuit 60 is cut off. When the current from the battery 90 to the ignition coil 70 is cut off, naturally, the primary current does not flow through the power transistor 51 and the spark plug does not spark. When the current is not supplied from the battery 90 to the fuel injection valve driving circuit 60, the fuel injection valve 65 is not driven, and the fuel is not supplied into the cylinder of the engine 80.

As described above, according to the present embodiment, when the power transistor 51 is short-circuited, the failure detection circuit 30
Detects this, and the current supplied from the battery 90 to the ignition coil 70 and the fuel injection valve drive circuit 60 is cut off. Therefore, the ignition coil 70 is ignited, and the unburned gas is burned in the exhaust pipe by the catalyst. Abnormal heating can be prevented.

Although the power transistor 51 may be short-circuited, no high voltage is applied to the base terminal of the power transistor 51. In the present embodiment, the failure detection circuit 30 detects a short circuit in the power transistor 51 based on the voltage applied to the ignition signal output terminal 28 connected to the base terminal of the power transistor 51. Therefore, it is not necessary to use a high breakdown voltage component for each element constituting the failure detection circuit 30, and the manufacturing cost can be reduced.

In a normal automobile, the ECU 10
The switching circuit 50 of the ignition plug 75 is provided with a certain distance. However, in this embodiment, the short circuit of the power transistor 51 is detected by the voltage applied to the ignition signal output terminal 28. There is no need to provide a signal line other than the ignition signal line, for example, a signal line for detecting a short-circuit of the power transistor 51, between the switch and the switching circuit 50, so that connection between the circuits can be simplified.

Next, a second embodiment according to the present invention and a third embodiment will be described.
Will be described with reference to FIGS. 5 and 6, respectively. In the first embodiment, the ignition signal output circuit 20 and the failure detection circuit 30 are provided in the ECU 10 and configured together with the arithmetic and control circuit 11 as one unit. EC
There is no particular positive reason that it must be provided in U10.

Therefore, for example, as in the second embodiment,
Part 2 of circuit elements constituting ignition signal output circuit 20a
5, 26, 26a, and 27 may be provided in the switching circuit 50a. Also, as in the third embodiment, some of the circuit elements constituting the ignition signal output circuit 20b,
26, 26a, 27 and the failure detection circuit 30 may be provided in the switching circuit 50b. However, in these embodiments, it is necessary to newly provide a signal line other than the ignition signal line between the ECUs 10a and 10b and the switching circuits 50a and 50b.

In these embodiments, the PNP transistors 25 of the ignition signal output circuits 20a and 20b are provided in the switching circuits 50a and 50b.
The emitter terminal of the P transistor 25 is connected to the ECU power supply Vcc
Instead, it is directly connected to the battery 90 via the resistor 26a.

[0034]

According to the present invention, the fault detection circuit detects the short-circuit of the switching element by the voltage applied to the ignition signal output terminal grounded via the resistor.
Only a voltage corresponding to the voltage drop due to the resistance is applied to the failure detection circuit. Therefore, it is not necessary to use a high breakdown voltage component as a circuit element constituting the failure detection circuit, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an ignition device according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram of an ignition device and a fuel injection device according to a first embodiment of the present invention.

FIG. 3 is a waveform diagram of a signal and the like in each part of the first embodiment according to the present invention.

FIG. 4 is a circuit diagram of an ignition device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram of an ignition device according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional ignition device.

FIG. 7 is a waveform diagram of signals and the like at various parts of the conventional ignition device.

[Explanation of symbols]

10, 10a, 10b, 10c ... ECU, 11, 11c
... Calculation control circuit, 12: power cutoff signal output unit, 13: ignition timing calculation unit, 14: fuel injection amount calculation unit, 20: ignition signal output circuit, 22: NPN transistor, 25: PNP
Transistor, 28: ignition signal output terminal, 29: resistor, 3
0: failure detection circuit, 31, 35: NPN transistor,
37, a capacitor, 38, a comparator, 40, a fuel injection signal output circuit, 50, a switching circuit, 51, a power transistor, 54, 55, a resistor, 60, a fuel injector drive circuit, 65, a fuel injector, 70, an ignition coil , 71
... Primary coil, 72 ... Secondary coil, 75 ... Spark plug, 80 ... Engine, 90 ... Battery, 92,94 ...
switch.

──────────────────────────────────────────────────続 き Continued on the front page Examiner Hozumi Yamamoto (58) Field surveyed (Int. Cl. ⁶ , DB name) F02P 3/055 F02P 11/00 F02P 17/00

Claims (3)

(57) [Claims] 1. An ignition plug, an ignition coil for applying a high voltage to the ignition plug, and a current flowing through the primary coil of the primary coil and the secondary coil constituting the ignition coil. An ignition signal output unit that outputs an ignition signal of the first order, and a switching circuit that controls a current flowing through the primary side coil in accordance with the ignition signal, wherein the switching circuit is configured to mainly receive the current flowing through the primary side coil. A switching element having a current input end, a main current output end through which a current flowing from the main current input end flows out, and a signal input end to which the ignition signal is input; the signal input end of the switching element and the main current input end Or a failure detection device for an ignition device for detecting a failure of an ignition device for an internal combustion engine having a resistor connected to the main current output terminal, wherein the ignition signal is output. An output terminal of the ignition signal output unit is connected to ground via a resistor, and includes a failure detection circuit that detects a failure of the switching element according to a waveform of a voltage applied to the output terminal of the ignition signal output unit. A failure detection device for an ignition device. 2. An ignition plug, an ignition coil for applying a high voltage to the ignition plug, and a current flowing through the primary coil of the primary coil and the secondary coil constituting the ignition coil. An ignition signal output unit that outputs an ignition signal of the first order, and a switching circuit that controls a current flowing through the primary side coil in accordance with the ignition signal, wherein the switching circuit is configured to mainly receive the current flowing through the primary side coil. A switching element having a current input end, a main current output end through which a current flowing from the main current input end flows out, and a signal input end to which the ignition signal is input; the signal input end of the switching element and the main current input end Alternatively, in the ignition device for an internal combustion engine having a resistor connected to the main current output terminal, an output terminal of the ignition signal output unit that outputs the ignition signal and ground. A failure detection circuit that detects a failure of the switching element according to a waveform of a voltage applied to the output terminal of the ignition signal output unit; and a failure of the switching element is detected by the failure detection circuit. And an ignition coil current interrupting means for interrupting the current supplied to the ignition coil. 3. An internal combustion engine ignited by said spark plug,
When a drive current is supplied, the fuel injection means injects fuel into a cylinder of the internal combustion engine. When the failure detection circuit detects a failure of the switching element, the fuel injection means 3. An ignition device for an internal combustion engine according to claim 2, further comprising a fuel injection current cutoff means for cutting off the drive current for driving the engine.