JPH0160671B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic advance device for an igniter for an internal combustion engine that controls the energization time of a primary current in an ignition coil.

In the conventional ignition coil energization time control method using a microcomputer, the energization time is stored in advance as a map in the microcomputer's memory as a function of the power supply voltage and engine speed, and this map is referenced as necessary. In the ignition timing generation circuit, which is made up of a microcomputer, a counter, etc., a signal corresponding to a constant rotation angle of the engine is generated, with the trailing edge of the signal being the ignition timing. In some cases, the ignition coil energization time was created using a separate analog circuit from this signal.

First, in the former method, since the energization time is predetermined, it is not possible to secure the optimum energization time for changes in the coil primary current rise characteristics due to manufacturing variations or temperature rises, and sufficient ignition performance is not achieved. I can't get it. In a circuit that has a constant current control function that controls the coil primary current so that it does not exceed a set value, if the time during which the coil primary current reaches this constant current increases slightly, heat generation in the circuit elements will increase rapidly, and in the worst case This may lead to the destruction of the element.

Next, although the latter method does not have the same problems as the former method, it requires a separate circuit for controlling the energization time, which increases costs.

The present invention was made in view of the above problems, and smoothes the output of a detection circuit that detects that the primary current of the ignition coil is higher than a set value, and converts it into a digital value using an A/D exchanger. By controlling the energization time of the primary coil so that this value is always constant, the optimum value is always maintained regardless of changes in the ignition coil supply voltage or coil constants (primary inductance, primary resistance). The purpose of the present invention is to provide an electronic advance device for an igniter for an internal combustion engine, which can provide a sufficient energization time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electronic advance angle device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a block diagram of an electronic advance device according to the present invention. 1 is a level detection circuit that detects that the primary current of the ignition coil is higher than a set value, 2 is an integration circuit that smoothes the output of the level detection circuit 1, and 3 is an A/D
Converter, 4 is a microcomputer (calculating unit),
5 is a timing generation circuit, 6 is 1 of ignition coil 7
This is a switch circuit that controls the next current.

FIG. 2 shows waveforms of the main parts of FIG. 1. a is the output of the timing generation circuit 5, and the switch circuit 6 controls the supply of the primary current to the ignition coil 7. b is a signal representing the magnitude of the primary current,
By inserting a resistance element into the primary side of the coil,
A voltage proportional to the primary current can be obtained. The level detection circuit 1 detects that the signal b exceeds a set value, and outputs a signal indicated by c. The integrating circuit 2 switches between charging and discharging according to the signal c, and outputs a smoothed signal such as d to the A/D converter 3.
The A/D converter 3 converts this smoothed signal into a digital value.

The arithmetic unit 4 executes the program according to the program flow shown in FIG. That is, first, the energization time is initialized, then the digital value output from the A/D converter 3 is read, and the energization time is corrected according to the formula shown below.

Energization time ← Energization time + K (target value - A/D value) After that, this loop is repeated and the energization time is feedback-controlled so that the A/D value always becomes the target value, so that the optimum energization time is always maintained. K is a constant obtained by taking into consideration the loop round time, the time constant of the integrator 2, and the like. The timing generating circuit 5 generates a signal a having the energization time determined by the arithmetic unit 4 before the ignition timing.

FIG. 4 shows the electrical circuits of the level detection circuit 1 and the integration circuit 2. 61 is a current detection resistor, 11 and 1
2 is an input resistance of the comparator 14, 13 is a reference voltage generator for setting the detection level of the primary current of the coil, 21 is a resistor that supplies the base current to the transistor 24, and 22 and 23 are the transistors 25
27 is a resistor for charging the capacitor 28 with current from the power supply +B,
29 is a resistor for discharging the charge of the capacitor 28; the resistors 27, 29 and the capacitor 28 determine the charging time constant, and the capacitor 28 and the resistor 29 determine the discharging time constant. Here, the internal power supply +B of the circuit is generally created by stabilizing the power supply of the device.

FIG. 5 shows another electrical circuit of the integrating circuit having power supply voltage characteristics. This is very effective when performing constant current control of the primary current of the coil, and when the power supply voltage is high, it is possible to reduce the time during which the constant current is reached and prevent the circuit from generating heat. 201 is a resistor that supplies base current to the transistor 204;
2, 203 is a resistor that supplies base current to the transistor 205, 206 is a diode for preventing current backflow, and 207 is a resistor 208 from the primary side power supply of the coil.
211 is a resistor that supplies the base current of the transistor 214; 211 is a resistor that supplies the base current of the transistor 214;
2 and 213 are resistors for supplying base current to the transistor 215; 216 is a diode for preventing current backflow; 217 is a resistor for charging the resistor 208 from the internal power source of the circuit; and 209 is a resistor for discharging the charge of the resistor 208. In this circuit, resistors 207 and 217
By changing the ratio of , it is possible to give power supply voltage characteristics to the control of the energization time of the coil.

According to the present invention, there are the following effects.

Conventional electronic advance angle devices with a built-in microcomputer have an A/D converter to receive input from various sensors, so by adding a level detection circuit and an integration circuit to this, coil 1
It is possible to control the energization time of the next current.

In contrast to the conventional method of storing a map of energization time in computer memory as a function of power supply voltage and engine speed, large programs can be eliminated and the memory used can be reduced. The calculation for determining the energization time can be performed asynchronously with the rotation of the engine. In other words, since it can be executed in the main routine or monitor routine, the degree of freedom of the program is increased and the program execution time is improved.

Feedback control always provides the optimum energization time for changes in inductance and resistance during coil manufacturing, power supply voltage, and ambient temperature.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the electronic advance angle device according to the present invention, Fig. 2 is a waveform diagram of the main blocks of Fig. 1, Fig. 3 is a diagram of a program executed by an arithmetic unit (microcomputer), and Fig. 4 1 is an electrical circuit diagram of the main block of FIG. 1, and FIG. 5 is another electrical circuit diagram of the main block of FIG. 4. 1...Level detection circuit, 2...Integrator circuit, 3...
...A/D converter, 4... Arithmetic unit (microcomputer), 5... Timing generation circuit, 6... Switch circuit, 7... Ignition coil.

Claims (1)

[Claims] 1. A switch circuit that intermittents the primary current of the ignition coil, a detection circuit that detects that the primary current exceeds a set value, a smoothing circuit that smoothes the output of the detection circuit, and an output of the smoothing circuit. an A/D converter that converts the level into a digital value;
For an internal combustion engine, comprising: a computing unit that executes a calculation for correcting the energization time of the next current; and a timing generation circuit that drives the switch circuit based on the corrected energization time from the computing unit. Electronic igniter advance device.