JPS6161973A - transistor type ignition device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a transistor type ignition device used for ignition of an automobile engine.

<Prior art> In recent years, transistor-type ignition devices using microcomputers have been used in automobile engines (Japanese Patent Application No. 1983).
9-40474 etc.).

An example is shown in FIG.

To explain this, the primary current of the ignition coil 2 supplied from the common power supply line 1 is turned on and off by the transistor 3, so that a high voltage for ignition is obtained from the secondary side of the ignition coil 2. A vehicle battery 4 and an engine generator (alternator) 5 are connected to the 1ffl power supply line 1. However, the generated output of the generator 5 is supplied to the common power supply line 1 via a full-wave rectifier 6. And transistor 3 is
Continuity is controlled by timing control signals given from a control unit 7 using a microcomputer via a latch circuit 8 and a protection cutoff circuit 9, respectively. The control unit 7 generates predetermined timing signals Tl and T2 based on the rotational angle and rotational speed of the engine.
emits. By applying these timing signals Tl and T2 to the launch input and reset input R of the latch circuit 8, a timing control signal with a predetermined phase and period is output from the latch output Q of the latch circuit 8.

This control signal is applied to the base of the transistor 3 via the protection cutoff circuit 9. As a result, the conduction of the transistor 3 is controlled in a phase and period based on the rotational angle and rotational speed of the engine.

Here, the voltage V on the common power supply line 1 is the voltage V on the battery 4
Due to the voltage dump effect, the voltage is kept within an approximately constant range. However, if the battery 4 is accidentally disconnected from the common power supply line 1, the voltage dumping effect of the battery 4 is lost, and an abnormally high voltage, so-called surge voltage, is applied to the common power supply line 1. It will appear directly. Then, due to this surge voltage, an excessive surge current flows through the transistor 3 and the ignition coil 2, respectively, and as a result, the transistor 3 and the ignition coil 2
will be destroyed and burnt out. In this case, the surge voltage is mainly applied from the generator 5. Therefore, if the battery 4 is disconnected during high-speed driving, a particularly large surge current will flow.

Therefore, in the above-mentioned ignition device, the common power supply line 1
A surge detection circuit 10 is provided to detect surges on the upper side, and the protection cutoff circuit 9 is operated by the detection output from this surge detection circuit 10. The protection cutoff circuit 9 is configured to forcibly render the transistor 3 non-conductive by cutting off the base current of the transistor 3 through its operation. As a result, the transistor 3 and the ignition coil 2
Can be protected from excessive surge current.

Note that the surge detection circuit 10 is a circuit that determines whether the voltage V on the common power supply line 1 is within an allowable range,
For example, as shown in the figure, a Zener diode 11 and a resistor 12
Consisted of.

<Problems to be solved by the invention> However, in the above-mentioned transistor type ignition device,
Since it is necessary to provide an independent protection cut-off circuit 9 between the latch circuit 8 and the transistor 3, there is a problem in that the cost inevitably increases and it cannot be adopted in low-cost models.

The present invention overcomes the above-mentioned problems, and includes:
The purpose is to provide a transistor type ignition device that can protect the transistor and ignition coil from surge current without using an independent protection cut-off circuit, thereby reducing costs. It is in.

<Means for Solving the Problems> In order to achieve the above object, the present invention uses a transistor to intermittent the primary current of the ignition coil supplied from a common power supply line connected to the on-vehicle battery and the engine generator. Accordingly, a high voltage for ignition is obtained from the secondary side of the ignition coil, and conduction of the first helangistor is controlled by a timing control signal given from a control unit via a launch circuit. In this case, a surge detection circuit for detecting a surge on the common power supply line is provided, and a means for resetting the latch circuit by the detection output from the surge detection circuit is provided, so that the latch circuit is reset when a surge occurs. The transistor was configured to be forcibly rendered non-conductive.

(Function) With this configuration, the transistor can be forcibly rendered non-conductive via the latch circuit when a surge voltage is applied, without using an independent protection cutoff circuit, which makes it easy and low-cost. With this configuration, the transistor and the ignition coil can be protected from surge current.

<Example> Hereinafter, a preferred example of the present invention will be described based on FIG. 1. However, since its basic configuration is the same as the conventional one described above, the explanation will be omitted.

In FIG. 1, the major difference from the conventional one described above is that the part corresponding to the protective cut-off circuit 9 is omitted;
A launch output Q of the latch circuit 8 is directly connected to the base of the transistor 3. In addition, the reset manual power R of the latch circuit 8 is supplied with a timing signal T2 from the control unit 7.
In addition, a detection output from the surge detection circuit 10 is provided. In other words, the launch circuit 8 receives the timing signal T2 from the control unit 7 and the surge detection circuit 1.
It is reset by the logical sum of the surge detection output from 0. When the latch circuit 8 is reset, the transistor 3 is rendered non-conductive.

Next, the operation will be explained.

First, when the battery 4 is reliably connected to the common power supply line 1 and is operating normally, the timing signal T1. By T2, the setting and resetting of the latch circuit 8 are repeated at respective predetermined timings. The conduction of the transistor 3 is controlled by a control signal from the latch output Q of the latch circuit 8. As a result, the transistor 3 repeats conduction and non-conduction with a predetermined phase and period depending on the rotational angle and rotational speed of the engine. Then, each time this transistor 3 switches from conductive to non-Ni1ll, a high voltage for ignition is generated on the secondary side of the ignition coil 2, and this high voltage passes through a distributor (not shown) to the discharge electrode of the spark plug (not shown). ) is given to

Here, when a surge voltage appears on the common power supply line 1 due to the battery 4 being disconnected from the common power supply line 1 during high-speed driving, this surge voltage is detected by the surge detection circuit 10. Furthermore, this surge detection output is applied to the reset manual power R of the launch circuit 8, and the launch circuit 8 is forcibly reset regardless of the states of the timing signals TI and T2 from the control unit 7.

As a result, transistor 3 is forcibly rendered non-conductive. As a result, it becomes possible to avoid excessive surge currents from flowing into the transistor 3 and the ignition coil 2, respectively.

Therefore, the transistor 3 and the ignition coil 2 can be protected from destruction and burnout caused by surge current.

Incidentally, if the latch circuit is built into a one-chip microcomputer, the launch circuit may be reset by an interrupt or the like.

<Effects of the Invention> As is clear from the description of the embodiments above, in the transistor type ignition device according to the present invention, when a surge voltage is applied, the transistor is forcibly turned off without using an independent protection cut-off circuit. The transistor and ignition coil can be made non-conductive, thereby protecting the transistor and ignition coil from surge current with a simple and low-cost configuration.
This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a transistor type ignition device according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional transistor type ignition device.

Claims (1)

[Claims] By using a transistor to intermittent the primary current of the ignition coil supplied from a common power line connected to the vehicle battery and the engine generator, a high voltage for ignition is obtained from the secondary side of the ignition coil, and the control is performed. In a transistor type ignition device for an automobile engine, the conduction of the transistor is controlled by a timing control signal applied from the unit via a latch circuit, and a surge detection circuit for detecting a surge on the common power supply line is provided, The transistor type is characterized in that means is provided for resetting the latch circuit using a detection output from the surge detection circuit, and the latch circuit is reset when a surge occurs to forcibly render the transistor non-conductive. Ignition device.