JPS6158971A - Igniter for automobile - Google Patents

Abstract

PURPOSE:To continues a normal ignition function in time of short breakdown in a switching element, by installing a conductor made up of a fusible material in a circuit serving as a current passage of the switching element for driving a DC-DC converter. CONSTITUTION:There are provided with an ignition circuit, continuing a primary side current for an ignition coil, and a DC-DC converter feeding voltage to a spark gap of a spark plug. Pads 28-38, terminals 22-26 and switching transistor part 42 and 43 set up on a base plate 27 are all connected together through Al wires 41a-41l. If a current of 35-40A flows in time of short breakdown of a switching transistor 4d, any of these Al wires 41c, 41d, and 41f is fused down in a moment, stopping the current at once. Thus, even in time of the short breakdown of the switching element for driving the DC-DC converter, an engine is operatable without entailing any damage to an ignition function.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ignition system for an automobile, and more particularly to a fail-safe in the event of short-circuit destruction of a switching element provided in an output stage of an ignition system.

[Background of the invention]

In conventional automobile ignition systems, the power line for the ignition circuit that destroys the insulation of the ignition plug and the power line for the primary coil of the DC-DC converter transformer are separated, and the DC-
When a switching transistor for driving a DC converter is damaged by a short circuit, there is a method of cutting off the power supply for the DC-DC converter using a relay. This method is disclosed in, for example, Japanese Patent Laid-Open Nos. 58-70059 and 5B-88468. This conventional method had the drawbacks of increasing the number of parts, being expensive, and requiring complicated wiring.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fail-safe ignition system for an automobile that does not impair the ignition function even if a switching transistor for driving a DC-DC converter is short-circuited.

[Summary of the invention]

The present invention provides an ignition system for automobiles made of a material that can be blown out when a current of a predetermined value or more flows through a circuit that constitutes a DC-DC converter and serves as a current path for a switching element that performs switching operation in response to an oscillator output. It is characterized in that the circuit is mounted so as to provide a formed conductor.

[Embodiments of the invention]

Embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of an automobile ignition system to which the present invention is applied. In the figure, 1 is a battery, 2 is a key switch, 1 is an ignition signal generating circuit 3, a switching transistor 4a, and an ignition coil. 5 constitutes an ignition circuit, and power distributor 9 and spark plugs 10 to 13 constitute a power distribution section.

The power distributor 9 includes a rotor 9a and a side plug 9b. Also, an operation time determining circuit 4b.

The oscillator 4c, PwTR 54d, transformer 6, high voltage diode 7, and capacitor 8 constitute a DC-DC converter.

The switching transistor 4a is connected to the ignition signal generation circuit 3
The primary coil current of the ignition coil 5 is intermittent at appropriate timings based on the output signal. When the switching transistor 4a switches from ON to OFF when the rotor 9a and the side plug 9b face each other, a high voltage is generated on the secondary side of the first ignition coil 5, and about -20 KV is applied to the rotor 9a of the power distributor 9. 1 The insulation between the electrodes of any one of the spark plugs 10 to 13 is destroyed, causing sparks to fly. switching transistor 4a
In response to the output signal of the oscillator 4c, the primary coil current of the transformer 6 is switched on and off, and the terminal of the capacitor 8 on the high voltage diode 7 side is charged to about -2 KV. Here, the collector current of the switching transistor 4d when it is turned on is about 30A, and the average current is about 2A. 4b is a DC-DC converter operating time determining circuit, which operates the oscillator 4c and switches the switching transistor 4d only within a time period more appropriate than the OFF start timing of the switching transistor 4a.

During arc discharge after breaking the insulation between the electrodes of the spark plugs 10 to 13, -IKV~ is applied to continue the discharge of the spark plugs.
A medium-high voltage of about -2KV is sufficient, and by superimposing the discharge current of the DC-DC converter on the discharge current of one ignition circuit, the discharge of the ignition plug is continued and the energy is increased.

FIG. 2 shows an example of how the control circuit section 4 in FIG. 1 is mounted. 20 is a molded case, and terminals 22 to
26 are integrally molded. The A side of the terminal 23 is connected to the battery 1 via the key switch 2, and the B side is connected to the ignition coil 5 and the primary coil of the transformer 6.

The other primary coil of the ignition coil 5 is connected to a terminal 25 , and the other primary coil of the transformer 6 is connected to a terminal 26 . The A side of the terminal 22 is connected to the negative terminal of the battery 1, and the B side is connected to the secondary coil of the transformer 6 and the ground of the capacitor 8. The terminal 24 is connected to the 1 ignition signal generation circuit 3. 21 is a discharger, case 2
It is glued to o. 27 is a hybrid thick film integrated circuit board (hereinafter referred to as the board), which is bonded to the discharger 21.

Further, insulating plates 44 and 45 are bonded to the discharger 21,
Switching transistors 42, 43 and pads 39.40 are soldered onto the insulating plates 44, 45, respectively. The switching transistor 42 is the switching transistor 4a in FIG. 1, and the switching transistor 43 is the switching transistor 4d.

Connection pads 28 to 38 are arranged on the substrate 27, and the pads 28 to 38, the terminals 22 to 26, and the switching transistor parts 42 and 43 are all connected to the AQ wire 4.
It is connected by 1a-41Q.

Also, on the substrate 27, between pads 30 and 38, between pads 36 and 37,
Between, 32, 33, 34, and 29 and 31rt! J is directly connected by printed wiring.

In the switching transistor 42, 411 is the emitter, 41j is the base, and 41 is A that connects the collector.
It is a Q wire. Further, in the switching transistor 43, 41f is an emitter, 41e is a base, and 41d is an AM wire connecting the collector. There are two AQ wires only between pad 33 and ground terminal 22 (41
g+41h).

As mentioned above, during normal DC-DC converter operation, the switching transistor 4d (FIG. 2 43) is turned ON.
The collector current at this time is about 30A, and the average current is about 2A. However, if the switching transistor 4d is destroyed by a short circuit, a current of 35 to 40 A will constantly flow, so a fail-safe is required.

The route of the current when the switching transistor 4d is short-circuited is terminal 23 → primary coil of transformer 6 → terminal 26 → Aρ wire 41c → pad 37 → pad 36 → A
Q wire 41d → collector of switching transistor 43 emitter of switching transistor 43 → AQ
Wire 41f → Pad 34 → Pad 33 → AQ wire 4
1g.

41b-+ terminal 22. When a current of 35 to 40 A constantly flows, An wires 41 c, 41 d, 41 f
One of them will instantly melt, blocking the flow of current.

Since the pad 33 and the terminal 22 are double wire bonded, it is difficult to melt. Therefore, the ground of the ignition switching transistor 42 and the substrate 27 will not melt even when the switching transistor 43 is short-circuited, and the ignition function will not be impaired.

According to this embodiment, even when the switching transistor for driving the DC-DC converter is destroyed by a short circuit, the engine can be operated without impairing the ignition function. Furthermore, since only one AQ wire is required as a component count, costs can be reduced.

〔Effect of the invention〕

According to the present invention, there is an effect that the ignition function is not impaired even when the switching transistor for driving the DC-DC converter is destroyed by a short circuit6.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an ignition device to which the present invention is applied;
FIG. 2 is a diagram showing an embodiment of the circuit of the ignition device shown in FIG. 1. 1...Battery, 3...Ignition signal generation circuit, 4...
- Control circuit section, 4a, 4b...operation time determining circuit, 5
...Ignition coil, 9...Power distribution diagram, 20...Mold case, 21...Radiator, 22-26...Terminal,
28-40...pad, 41a-412...AQ wire.

Claims (1)

[Claims] 1. An ignition circuit that intermittents the primary side current of the ignition coil, and a DC-DC that shares a power source with the ignition circuit and supplies a voltage to the secondary side of the ignition coil to continue the discharge between the spark plug electrodes.
In an automobile ignition system having a DC converter,
A circuit is constructed so that a conductor made of a material that can be blown out when a current exceeding a predetermined value flows is provided in the circuit that constitutes a DC-DC converter and serves as a current path for a switching element that performs a switching operation in response to an oscillator output. An ignition device for an automobile characterized by being implemented.