JPS6235902Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an automatic retardation circuit in an ignition system for an internal combustion engine, and its purpose is to demonstrate the retardation ability as set regardless of variations in the installation method of the ignition system. It is something.

By making the ignition system of the internal combustion engine non-contact, if the rotational speed of the internal combustion engine rises above a set value, the ignition timing is delayed to prevent the internal combustion engine from overspeeding.Overcircuit prevention methods are beginning to be adopted.

When the rotational speed of the internal combustion engine exceeds a set value, the means for retarding the ignition point and preventing the rotational speed of the internal combustion engine from increasing smoothly is implemented without causing a sudden change in the operation of the internal combustion engine. It has the advantage of helping you achieve your goals.

Conventionally, this retarding means has various configurations, but there is some variation in the assembly dimensions of the ignition device, especially between the magnetic pole face of the permanent magnet embedded in the flywheel and the pole face of the ignition coil. Due to variations in the dimensions of the air gap, variations occur in the voltage value induced in the ignition coil, which causes differences in the setting of the rotational speed value of the internal combustion engine at which retard operation should be started and in the degree of retardation. Ta.

For this reason, even if the same internal combustion engine is equipped with the same ignition device with a retardation circuit, there is a problem in that the retardation effect exerted differs.

The present invention was devised in order to eliminate the drawbacks of the conventional example described above, and it makes the voltage value charged to the capacitor that achieves the retard operation constant, and the discharging time of this capacitor constant, thereby making the air gap This is to obtain a constant reference time regardless of variations in induced voltage due to differences in voltage, etc.

An embodiment of the present invention will be described below with reference to the drawings.

Prior to explaining the retard circuit ESG according to the present invention, an example of the ignition circuit TCI to which the retard circuit ESG is attached will be described with reference to FIG.

The ignition circuit TCI shown in FIG.
Between both terminals of the primary winding T1 of the ignition coil T to which the plug P is connected to 2, a Darlington-coupled transistor circuit TrC and a low-resistance resistor R2 are connected.
A series circuit with a high-resistance resistor R3 and a silicon-controlled rectifier SCR (hereinafter simply referred to as a thyristor SCR)
A series circuit consisting of a resistor R1 having a high resistance value, a transistor Tr1, and a capacitor C2 is connected in parallel, and the base of the transistor Tr1 is connected to the emitter of the transistor circuit TrC, and the transistor The base of the circuit TrC is connected to the anode of the thyristor SCR, and a gate resistor R5 is inserted between the gate and the cathode.
It is constructed by connecting the collector of Tr1.

In addition, the Zener diode inserted in the opposite position between the collector and base of the transistor circuit TrC.
ZD1 is for protecting the transistor circuit TrC from surge voltage during ignition operation, and the resistor R4 inserted between the collector of the transistor Tr1 and the gate of the thyristor SCR is a current limiting resistor. The capacitor C1 connected in parallel with the series circuit of the transistor Tr1 and the capacitor C2 is a smoothing capacitor for smoothing the surge voltage so that the thyristor SCR is not triggered at an incorrect time.

The ignition circuit TCI configured as described above operates in the following order.

A portion of the reverse voltage induced in the primary winding T1 prior to the forward voltage passes through the transistor Tr1 as a reverse leakage current, thereby charging the capacitor C2 with the polarity shown.

The reverse voltage charged in this capacitor C2 is 1
Before the induced voltage in the next winding T1 is reversed from the reverse direction to the forward direction, the capacitor C2 → the resistor R2
→ Base of transistor Tr1 → Transistor Tr
The transistor Tr1 is discharged along the path from the emitter of the transistor Tr1 to the capacitor C2, and the transistor Tr1 is held in the triggered state.

When the induced voltage in the primary winding T1 is reversed in the forward direction, current flows through the resistor R3 to the base of the transistor circuit TrC.
turns on, and a primary short-circuit current flows through the transistor circuit TrC and the resistor R2 to the primary winding T1.

A part of the current flowing through the transistor circuit TrC flows into the base of the transistor Tr1 to keep the transistor Tr1 turned on, and by turning on the transistor Tr1, the capacitor C
2 is charged with an electric charge with a polarity opposite to that shown in the figure.

As the forward voltage charges to the capacitor C2 progresses, or as the current passing from the base to the collector of the transistor Tr1 increases, the thyristor
Since the SCR turns on and shunts the base current of the transistor circuit TrC, the transistor circuit TrC
turns off, thereby abruptly cutting off the primary short circuit current.

By interrupting this primary short circuit current, the secondary winding T2
A high voltage is induced in the plug P, and a spark discharge occurs in the plug P, causing an ignition operation.

The retard circuit ESG according to the present invention is used by being assembled into the ignition circuit TCI as described above.
A capacitor C3 charges part of the reverse voltage induced in the primary winding T1, and a capacitor C3 sets a rise in the voltage value charged to this capacitor C3.
a constant voltage switch circuit SWC connected in parallel to
A transistor Tr4 inserted between the gate and cathode of the thyristor SCR in the ignition circuit TC1.
The positive electrode of the capacitor C3 is connected to the base of the transistor Tr4 in order to trigger the transistor Tr4 by discharging the capacitor C3.

In the embodiment shown in FIG. 1, capacitor C3 is
The primary winding T1→
Resistor R2 → Capacitor C3 → Diode D → Resistor R6 → Zener diode ZD1 → Primary winding T1
is connected to charge a portion of the reverse voltage induced in the primary winding T1 by a charging circuit along the path shown in FIG.

A resistor R8 forming a part of the discharge circuit of the capacitor C3 is connected in parallel to this capacitor C3, and a resistor R7 is connected between the gate and the cathode.
and a constant voltage switch circuit SWC composed of a planar N-gate thyristor PUT with a Zenai diode ZD2 inserted in the opposite direction between the cathode and gate are connected in parallel, so that the charging voltage of the capacitor C3 is constant. When this value is exceeded, the Zener diode ZD2 goes down and the planar type N-gate thyristor PUT becomes conductive, thereby preventing further reverse voltage from being charged to the capacitor C3.

The configuration of this constant voltage switch circuit SWC is as follows:
For example, as shown in FIG. 2, a thyristor SCR1 is used instead of the planar N-gate thyristor PUT, and the gate and anode of this thyristor SCR1 are arranged in opposite directions. It may also be a circuit in which a Zener diode ZD3 is inserted.

The positive electrode of capacitor C3 is a transistor
It is connected via Tr3 to the base of a transistor Tr4 having a base resistor R11, and the base of the transistor Tr3 is connected via a resistor R9 to the negative electrode of a capacitor C3.

Note that the resistor R10 and capacitor C4 connected in parallel between the base and emitter of the transistor Tr4 are for ensuring the operation of the transistor Tr4.

Since the present invention is structured as described above,
According to the operation of the ignition circuit TCI, a portion of the reverse voltage induced in the primary winding T1 prior to the forward voltage is charged to the capacitor C3 at a constant voltage by the action of the constant voltage switch circuit SWC.

The reverse voltage charged in the capacitor C3 is discharged through the resistor R8 and at the same time
Tr3 is made conductive and a base current flows through the base of transistor Tr4, thereby triggering transistor Tr4.

When the speed of the internal combustion engine is below the set speed, the discharge time of the capacitor C3 ends earlier than the ignition time t1 in the diagram shown in FIG. A time retardation effect does not appear, but when the speed of the internal combustion engine exceeds a set value, the time interval between the start of discharge of capacitor C3 and the ignition time decreases, whereas the discharge time of capacitor C3 remains constant. As a result, the time when the discharge of the capacitor C3 is completed is delayed from the normal ignition time, and the ignition time is thereby delayed until the time when the discharge of the capacitor C3 is completed.

That is, as is clear from the voltage curve of the primary winding T1 shown in FIG. 3, when the speed of the internal combustion engine is below the set value, the voltage waveform shown by the solid line in FIG. 3 is drawn and the capacitor C3 is At time t3, the discharge curve CV1 is discharged and the discharge is completed before the ignition time t1, so that the ignition time of the ignition circuit TCI is not retarded.

In this state, if the speed of the internal combustion engine increases for some reason and exceeds the set value, the primary winding T1
The voltage waveform becomes as shown by the dotted line in Figure 3, and the start of discharge of capacitor C3 is delayed from t3 to t4, and the time t2 of completion of discharge of capacitor C3 is delayed from time t1, which is the normal ignition time. The ignition point of the ignition circuit TCI is from time t1 to time t.
It will be delayed by 2.

That is, in FIG. 1, if the discharge of capacitor C3 continues even if the voltage at primary winding T1 is reversed and a forward voltage is induced, the transistor maintained in a conductive state by the discharge of capacitor C3 The gate and cathode of the thyristor SCR are short-circuited by Tr4, and therefore the thyristor SCR is maintained in a state where it cannot be turned on.

When the discharge of the capacitor C3 is completed at time t2 from this state, the base current of the transistor Tr4 is cut off by turning off the transistor Tr3, and the transistor Tr4 is turned off, so that the thyristor SCR can be turned on, thereby causing ignition. The circuit TCI is now capable of performing ignition operations.

By the way, in the case of the present invention, as is clear from FIG. 3, the reverse voltage charged to the capacitor C3 is:
Since the constant voltage Vc is set, the discharge time is constant regardless of the rotational speed of the internal combustion engine, and the time point at which the discharge starts simply changes depending on the speed change of the internal combustion engine.

On the other hand, a method that does not regulate the reverse voltage charged to the capacitor C3, that is, a means in which the reverse voltage charged to the capacitor C3 increases in proportion to the speed of the internal combustion engine, as shown in FIG. The operation is such that the discharge start point of the capacitor C3 is almost constant and the discharge time itself changes.

However, as is well known, the voltage waveform in the primary winding T1 has a wave height that differs greatly due to the difference in air gap between the magnetic pole face of the permanent magnet embedded in the flywheel and the pole face of the ignition coil T. Therefore, even if the model is the same, there will be a difference in the voltage waveform at the primary winding T1 at the same speed between the case shown by the solid line and the case shown by the dotted line in Fig. 4 due to the difference in air gap. will occur.

This difference becomes a difference in the discharging time of capacitor C3 itself, so not only does the retard start speed itself that is set by the retard circuit ESG change, but the degree of retardation is also inconsistent, and after installation. , it is necessary to actually operate the machine and reset the discharge time constant for each machine.

Note that the retard operation of the retard circuit ESG according to the present invention has retard operation characteristics as shown in FIG.

As is clear from the above explanation, the retard circuit ESG according to the present invention can accurately set the discharge time of the capacitor C3 using only its own circuit time constant. Accurate and reliable retardation operation can be obtained regardless of the current, which eliminates the need for troublesome adjustments after installation.Furthermore, since capacitor C3 is charged with only a constant voltage, capacitor C3
3 has excellent functions and effects, such as being able to obtain stable operation without fear of causing voltage breakdown.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram showing an embodiment of the circuit of the present invention connected to an ignition circuit. FIG. 2 shows another embodiment of the constant voltage switch circuit. FIG. 3 is a voltage waveform diagram for explaining the retarding operation of the present invention. FIG. 4 is a voltage waveform diagram for explaining the operation of the conventional example. FIG. 5 is a diagram showing the retarding operation characteristics of the present invention. Explanation of symbols, T...Ignition coil, T1
...Primary winding, TrC...Transistor circuit,
SCR, SCR1...Silicon controlled rectifier, Tr
1, Tr3, Tr4...transistor, PUT...planar type N-gate thyristor, C1, C2, C
3, C4...Capacitor, RR1, R2, R3,
R4, R5, R6, R7, R8, R9, R10,
R11,... Resistor, ZD1, ZD2, ZD3... Zener diode, D... Diode, TCI... Ignition circuit, ESG... Retard circuit.

Claims (1)

[Scope of utility model registration request] In order to perform an ignition operation, the transistor circuit TrC inserted between both terminals of the primary winding T1 of the ignition coil T is turned off by turning on the silicon-controlled rectifier SCR connected to the base of the transistor circuit TrC. A retard circuit ESG connected to the configured internal combustion engine ignition circuit TCI includes a capacitor C3 that charges a portion of the reverse voltage induced in the primary winding T1, and a capacitor C3 that charges the capacitor C3. A constant voltage switch circuit SWC connected in parallel to the capacitor C3 to regulate the upper limit of the voltage, and a transistor Tr inserted between the gate and cathode of the silicon controlled rectifier SCR.
4, and the positive electrode of the capacitor C3 is connected to the transistor Tr4 so that the transistor Tr4 is triggered by the discharge of the capacitor C3.
An automatic retard circuit in an ignition system for an internal combustion engine connected to the base of Tr4.