JPH10299629A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure igniting energy at the time of high temperatures of an ignition coil and suppress temperature rise of the ignition coil to provide high out put and high reliability in relation to the ignition device for internal combustion engines, in which a switching module which conducts or shuts off the primary current of the ignition coil, is arranged integrally with the ignition coil or in the neighborhood of the ignition coil. SOLUTION: This ignition device is provided with a switching module 2 which conducts or shuts off a primary current 11 of an ignition coil 1. In this case, the switching module 2 is provided with a current limiting circuit 20 which limits the primary current 11 below a current limiting value, and which is capable of setting the current limiting value. By setting the current limiting value by the current limiting circuit 20, the current limiting value is adapted to be increased as the temperature of the switching module 2 rises from the room temperature.

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 more particularly to a spark plug using a high voltage induced in a secondary coil when a current flowing through a primary coil of an ignition coil is cut off by a semiconductor switching element. Ignite,
The present invention relates to an ignition device for an internal combustion engine such as an automobile gasoline engine.

[0002]

2. Description of the Related Art FIG. 1 is a circuit diagram showing a configuration of a general ignition device for an internal combustion engine. The ignition device for an internal combustion engine includes an ignition coil 1, a switching module 2, a control module 3, an ignition plug 4, a battery 5, and a key switch 6. Usually, the switching module 2 is integrated with the ignition coil 1 or is arranged in the vicinity.

The primary coil 1a of the ignition coil 1 and the power transistor 2a and the current detection resistor 2b constituting a part of the switching module 2 are connected in series, and when the key switch 6 is closed, the battery mounted on the vehicle A voltage from 5 is applied.

With the key switch 6 closed, the voltage of the energizing signal (ignition signal) Sg from the control module 3 goes to a high level “H” and is applied to the input terminal of the switching module 2. The power transistor 2a is turned “ON”, and the primary current I1 flows through the primary coil 1a of the ignition coil 1.

Next, the voltage of the energization signal Sg becomes low level "L".
, The power transistor 2a of the switching module 2 is turned “OFF”, the primary current I1 is cut off, and at this time, the secondary coil 1b of the ignition coil 1 has a voltage of 30 kV.
A secondary voltage V2 of the order is generated.

[0006] The secondary voltage V2 is guided to a spark plug 4 provided in the cylinder of the engine (not shown).
A spark discharge is generated between the electrodes of the spark plug 4 to ignite the fuel mixture in the cylinder.

The switching module 2 is provided with a current limiting circuit 20 including a current detecting resistor 2b and a switching transistor 2g. The primary current I1 changes from zero to a maximum current value in a transient state according to the energizing signal Sg. When the current limit value I0 is reached during the rising process, the current limiter 20 sets the primary current I as shown in FIG.
1 is limited to the current limit value I0 to avoid destruction of the ignition coil 1 and the switching module 2 due to overcurrent.

[0008] The current limiting operation of the current limiting circuit 20 is roughly as follows. In the course of the rise of the primary current I1, the product of the primary current I1 and the resistance value of the current detection resistor 2b increases and the switching transistor 2g
When the base-emitter voltage V _BE becomes equal to the ON voltage V _BEON , the switching transistor 2g is turned on, and the base voltage of the power transistor 2a is pulled down. Therefore, the power transistor 2a is turned off, or at least the conductivity is greatly reduced, and the primary current I1 of the ignition coil 1 tends to decrease. as a result,
When the voltage V _BE between the base and the emitter of the switching transistor 2g decreases again and falls below the on-voltage V _BEON , the switching transistor 2g is turned off again, and the power transistor 2a is turned on or the conductivity increases, and the primary current I1 Tends to increase. By repeating such an operation, the primary current I1 flowing through the power transistor 2a is substantially limited to a predetermined current value (current limit value I0) or less.

The current limiting value I0 is determined by the current limiting circuit 2
0, and the resistance values of the current limit value setting resistors 2c, 2d, 2e, and the thermistor 2f, and B of the thermistor 2f.
The temperature characteristics of the current limit value I0 can be arbitrarily set by selecting / combining constants, including the temperature characteristics. Generally, the temperature characteristics of the current limit value I0 are made as constant as possible over the entire temperature range in which the switching module 2 is used. Is set.

As shown in FIG. 4, the rise of the primary current I1 differs depending on the temperature of the ignition coil 1 and the switching module 2. At a high temperature indicated by a broken line, the rise is larger than at a normal temperature indicated by a solid line. Becomes moderate, and it takes more time to reach the current limit value I0 at a high temperature. This is because the resistance of the primary coil 1a of the ignition coil 1 increases when the ambient temperature increases. Further, as the primary current I1 approaches the current limit value I0, the voltage V _BE between the base and the emitter of the switching transistor 2g increases, and the switching transistor 2g approaches an active state and draws the base current flowing into the power transistor 2a. The transistor 2a also approaches the active state, the voltage V _CE between the collector and the emitter of the power transistor 2a increases, and the voltage applied to the primary coil 1a relatively decreases.
The rise of the primary current I1 is further delayed. Even a switching module that uses a thermistor or the like to perform temperature compensation cannot correct the phenomenon that the rise of the primary current I1 at high temperatures is delayed as the current limit value I0 is approached.

On the other hand, in order to supply sufficient ignition energy to the ignition plug 4, the necessary energy must be stored in the primary coil 1a of the ignition coil 1. The energy stored in the primary coil 1a is determined by the inductance of the primary coil 1a and the current value when the primary current I1 is cut off.
It is half of the product of the powers. That is, in order to store the necessary energy in the ignition coil 1, it is necessary to supply a sufficient current to the primary coil 1a.

[0012]

However, in the above conventional ignition device for an internal combustion engine, when the primary current I1 at room temperature reaches the current limit value I0 in the energizing time ΔT, it is determined that a sufficient current has been obtained. And the same energizing time ΔT is applied even at a high temperature, so that at a high temperature where a rise is delayed, the current is cut off without obtaining a sufficient primary current (current limit value I0). A situation has arisen in which it is not possible to supply sufficient ignition energy.

In order to obtain a sufficient primary current (current limit value I0) even at a high temperature, the energizing time may be increased to ΔT1, but if the energizing time is increased, the effective current of the primary current I1 increases. However, there is a problem that overheating is caused by an increase in temperature rise of the ignition coil 1 and eventually durability is impaired, and it has been difficult to achieve both output securing and durability of the ignition coil 1 at a high temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a high-output and high-reliability ignition device for an internal combustion engine which secures ignition energy at a high temperature of an ignition coil and has a small rise in temperature of the ignition coil. It will not be provided.

[0015]

In order to achieve the above object, an ignition device for an internal combustion engine according to the present invention is an ignition device for an internal combustion engine having a switching module for conducting and cutting off a primary current of an ignition coil. The switching module has a current limiting circuit that limits the primary current to a current limit value or less and can set the current limit value. The current limit circuit sets the current limit value to the temperature of the switching module. Is characterized by increasing from room temperature to higher.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described. The circuit configuration of the ignition device for an internal combustion engine of the present invention is shown in FIG.
Since the description of the circuit configuration and operation is redundant, description thereof will be omitted.

FIG. 2 shows the temperature characteristic of the current limit value in the present invention. As described above, the current limit value I0 is determined by the current limit value setting resistors 2c, 2d, 2e and the thermistor 2f.
In this embodiment, the current limit value I0R of the switching module 2 at normal temperature is the output of the ignition energy required for the ignition device for the internal combustion engine. In order to obtain a value obtained by adding a margin to the primary current value necessary for the operation, specifically, to be 6.5 A, the current limit value I
0H is set to increase by about 0.3 A to 0.5 A with respect to the room temperature.

FIG. 3 shows the relationship between the primary current and the set value of the conduction time in the present invention. Here, the current limit value I0R of the switching module 2 at normal temperature is 6.5.
A, the current limit value I0H at high temperature is set to 7.0A. In the figure, the primary current rise curve N at high temperature is more gradual than the primary current rise curve M at room temperature, and the current limit value IOH is higher. At the intersection, the energization time is 4.0 ms and the primary current is 6.5 A
It is. When the energizing time is set to 4.0 ms, the same primary current I1 (= I
OR) can be secured, and the primary current I1 is a value sufficient to output the required ignition energy.

That is, the primary current I1 at the time of interruption is a current limit value IOR near normal temperature, becomes a value determined by the energization time without the current limitation at a high temperature, and a necessary and sufficient primary current with a minimum energization time at a high temperature. The current I1 can be obtained.

When a conventional switching module in which the current limit value is set to be constant over the entire temperature range is used, the current limit value is 6.5 A even at a high temperature as shown by the broken line in FIG. As described above, the rise curve of the primary current is rounded in the vicinity of the current limit value, specifically, from 6.0 A to 6.5 A, and the energization time for the primary current to reach 6.5 A is 4.4 ms. (FIG. 3). That is, according to the embodiment of the present invention, the primary current I required at high temperature is increased by raising the current limit value at high temperature with respect to normal temperature.
1 can be shortened by 10%.

When the energizing time is reduced by 10%, the rising waveform of the primary current I1 is substantially a triangular wave, so that the effective current is about 87%, and the heat generated by the ignition coil 1 is proportional to the square of the effective current of the primary current I1. Therefore, the effective current can be suppressed to about 76%, and the heat generation of the ignition coil 1 can be effectively suppressed.

At high temperatures, the operating conditions are such that current is not limited. Therefore, the power transistor 2a does not operate in the active state, and the heat generation of the power transistor 2a can be greatly reduced.

[0023]

As described above, the ignition device for an internal combustion engine according to the present invention can shorten the energization time for outputting the ignition energy required at a high temperature, so that the ignition coil and the power transistor at a high temperature can be reduced. The temperature rise can be greatly reduced. Therefore, a high-output and highly reliable ignition device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an ignition device for an internal combustion engine according to the present invention.

FIG. 2 is a graph showing a temperature characteristic of a current limit value of the switching module according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a primary current and a set value of a conduction time according to the present invention.

FIG. 4 is a diagram showing how a conventional primary current rises.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Ignition coil 1a Primary coil 1b Secondary coil 2 Switching module 2a Power transistor 2b Current detection resistance 2c Current limit value setting resistor 2d Current limit value setting resistor 2e Current limit value setting resistor 2f Thermistor 2g Switching transistor 3 Control module 4 Spark plug 5 Battery 6 Key switch I1 Primary current IOR Current limit value set for switching module at normal temperature IOH Current limit value set for switching module at high temperature ΔT Energizing time

Claims (2)

[Claims] An ignition device for an internal combustion engine, wherein a switching module for conducting and interrupting a primary current of an ignition coil is integrated with or disposed near an ignition coil, wherein the switching module limits a primary current to a current. A current limiting circuit capable of setting the current limiting value to a value equal to or less than the current limiting value, and by setting in the current limiting circuit, the current limiting value is increased as the temperature of the switching module increases from normal temperature. An ignition device for an internal combustion engine, comprising: 2. The ignition device for an internal combustion engine according to claim 1, wherein when the switching module is at a high temperature, the primary current has reached a value substantially equal to a current limit value set for the switching module at around normal temperature. An ignition device for an internal combustion engine, wherein the primary current is sometimes interrupted.