JPS5823271A - Electronic advance device of ignition unit for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain an optimum conduction time of electric current, by smoothing primary current detection output of an ignition coil, converting the output through an A/D converter and feedback controlling the current conduction time of the primary coil in such a manner as to obtain always a fixed value of this converted value. CONSTITUTION:A timing generator circuit 5 controls electric conduction of a primary current in an ignition coil 7 by a switching circuit 6. A level detector circuit 1 detects a signal b to be at least a preset value and outputs a signal c. An integrating circuit 2 switches charge and discharge to output a smoothed signal d to an A/D converter 3, here the signal is converted into a digital value. An arithmetic unit 4 firstly initializes a time of electric conduction, then reads the digital value to correct the electric conduction time. Thereafter, this loop is repeated to perform feedback control of the conduction time with an A/D value always to a target value, thus an optimum conduction time of current is always obtained.

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 as a map in the microcomputer's memory in advance as a function of the power supply voltage and engine speed, and this map can be changed as needed. In ignition timing generation circuits that use a microcomputer, counter, etc., the trailing edge of the signal corresponds to a constant rotation angle of the engine. This signal was used to create the ignition coil energization time using another analog circuit.

First, in the former method, since the energization time is determined in advance, 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 it is not possible to ensure an adequate energization time. ignition performance cannot be obtained. 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 does require a separate circuit for controlling the energization time, which increases costs.

The present invention has been developed in view of the above problems, and it 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 S A/D exchanger. However, it is necessary to control the energization time of the primary coil so that this value is always constant, regardless of changes in the supply voltage of the ignition coil and coil constants (primary inductance, primary resistance). An object of the present invention is to provide an electronic advance device for an igniter for an internal combustion engine, which can always obtain the optimum energization time without any problems.

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 the electronic advance device of the present invention. 01 is a level detection circuit that detects that the primary current of the ignition coil is higher than a set value, and 2 is an integration circuit that smoothes the output of the level detection circuit 1. , 3 is an A/D converter, 4 is a microcomputer (computer), 5 is a timing generation circuit, and 6 is a switch circuit for controlling the primary current of the ignition coil 7.

FIG. 2 shows waveforms of the main parts of FIG. 1. a) is the output of the timing generation circuit 5, which controls the primary current supply to the ignition coil 7 through the switch circuit 6; b) is a signal representing the magnitude of the primary current; by inserting a resistance element on 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) has exceeded the set value, and outputs the signal shown in C). The integrating circuit 2 switches between charging and discharging according to the signal C), and outputs a smoothed signal like d) to the A/D converter 3 as an output.
A/D converter 3 converts this smoothed signal into a digital value.

The arithmetic unit 4 executes the program according to the flowchart 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 this loop is repeated and the energization time is feedback-controlled so that the A/D value always becomes the target value, the optimum energization time is always determined. shall be. K is a constant obtained by taking into account the Rouboud successive 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 is determined.

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 12 are input resistors 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 base current to the transistor 24; 22. 23 is a resistor that supplies the base current to the transistor 25; 27 is a resistor that charges the capacitor 28 with a current from the power source 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 element 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, the time required to reach the constant current can be reduced and the circuit can be prevented from generating heat. 201 is a resistor that supplies the base current to the transistor 204, 202 and 203 are resistors that supply the base current to the transistor 205, 206 is a diode for preventing current backflow, and 207 is used to charge the capacitor 208 from the primary side power supply of the coil. Resistor, 211 is transistor 2140
212, 213 is a resistor that supplies base current to transistor 215; 216 Fi is a resistor that supplies base current to transistor 215;
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, by changing the ratio of the resistors 207 and 217, the coil It is possible to give power supply voltage characteristics to the 1' sleep time control.

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, it is possible to control the energization of the coil primary current. Time can be controlled.

In contrast to the conventional method of storing a map of energization time in the computer's memory as a function of power supply voltage and engine speed, a large number of programs can be reduced and the memory used can be reduced. The calculation for determining the energization time can be performed asynchronously with the rotation of the engine. Since it can be executed in the main routine or monitor routine, the degree of freedom in programming is increased, and the optimal energization time can always be obtained in response to changes in progere inductance, resistance, power supply voltage, and ambient temperature.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electronic advance angle device according to the present invention, and FIG.
The figure is a waveform diagram of the main blocks in Figure 1, and Figure 6 is the arithmetic unit (
FIG. 4 is an electrical circuit diagram of the main blocks of FIG. 1, and FIG. 5 is another electrical circuit diagram of the main blocks 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 agent Asamura Kogai 4 people

Claims (1)

[Claims] 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 level of the smoothing circuit. an A/D converter that converts the value into a digital value, an arithmetic unit that performs a predetermined operation based on the digital output of the A/D converter, and an arithmetic unit that drives the switch circuit based on the arithmetic output of the arithmetic unit. An electronic advance device for an igniter for an internal combustion engine, characterized in that it comprises a timing generation circuit.