JPS6141986Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an overspeed prevention device installed in a non-contact ignition system of an engine. Directional voltage is only short-circuited by a diode, but the current generated by the next generated positive direction voltage is controlled on and off by a transistor.This is a so-called primary coil current cutoff type non-contact ignition device, and the present invention is This makes it extremely easy to install this type of non-contact ignition device into an engine. In particular, it relates to a positive voltage short-circuit type overspeed prevention device.

Figure 1 shows an example of the non-contact ignition device of the primary coil current cutoff type, which is the basis of the present invention (Utility Application No. 55-
012635, Utility Model Application Publication No. 56-115574), the detailed explanation will be omitted as it will be described later, but to briefly explain its operation, the magnet generator G rotates in synchronization with the engine, and its ignition Negative direction voltage V ₁ shown by the broken line arrow generated in the primary coil W ₁ of coil 1
The current caused by this is only short-circuited by the diode D ₁ of the transistor ignition control circuit K ₁ , but the current generated by the positive voltage shown by the solid line arrow turns on the power transistor T ₁ of the control device K ₁ .
By performing off control, a high voltage is induced in the secondary coil _W2 of the ignition coil 1, which causes a high voltage spark to fly to the ignition plug P, thereby igniting the engine.

Accordingly, as a positive direction voltage short-circuit type overspeed prevention device to be installed in an engine having a non-contact ignition device as shown in FIG. 1, the one shown in FIG. 2 has been proposed. What is shown in this Figure 2 is
First, when a negative direction voltage V ₁ is generated in the primary coil W ₁ of the ignition coil 1, as shown by the dashed arrow, current is passed through the circuit of the diode D ₂ of the overspeed prevention device K ₂ , the capacitor C, and the diode D ₃ , and the capacitor Charge C to the polarity shown. The charge in the capacitor C is discharged into the circuit of resistors _R1 and _R2 , and is also discharged between the gate and cathode of the thyristor S, turning on the thyristor. In the following cases, the on state of the thyristor S shifts to the off state before the positive direction voltage V ₂ shown by the solid line arrow is generated in the primary coil W ₁ , so that the over-rotation prevention device K ₂ is substantially activated. will not work. However, when the rotational speed of the engine increases to a predetermined value or higher, the on state of the thyristor S causes a positive voltage V ₂ to be generated in the primary coil W ₁ as shown by the solid arrow, and that voltage V ₂ is applied to the thyristor S. The thyristor S continues to be on until the positive voltage V ₂ disappears.

The positive voltage V ₂ of the primary coil W ₁ is then short-circuited by the thyristor S and is no longer applied to the transistor ignition control device K′ ₁ , which prevents the engine from igniting, thereby preventing engine overspeed. It becomes like this.

However, in order to install the conventional overspeed prevention device K ₂ shown in Fig. 2 on an engine that has already been equipped with the non-contact ignition device K ₁ shown in Fig. 1, the first
Since the diode _D1 connected between the collector and emitter of the power transistor _T1 of the transistor ignition control device _K1 shown in the figure must be removed as in the diode ignition control device _K'1 shown in FIG. The drawback was that the overspeed prevention device K ₂ could not be installed as is.

Furthermore, the over-rotation prevention device shown in Fig. 2
When K ₂ is installed, the transistor ignition control device K′ ₁ has a negative direction voltage generated in the primary coil W ₁ .
Since the diode shorting V ₁ has been removed, a reverse voltage is repeatedly applied between the base and emitter of the power transistor T ₁ , which causes the temperature of this power transistor T ₁ to rise abnormally and shorten its lifetime. It had a serious drawback that it became shorter.

The present invention has been particularly devised for the purpose of eliminating the above-mentioned drawbacks, and an embodiment of the present invention shown in FIG. 3 will be described below. In this figure, 1 is a spark plug of the engine, 2 is a magnet generator driven in synchronization with the engine, and this magnet generator 2 includes a magnet rotor 3 and an ignition coil consisting of a primary coil 5 and a secondary coil 6. 4 and more. Next, reference numeral 7 denotes an over-rotation prevention device which has been specially devised according to the present invention.
13 and 14, a constant voltage time constant circuit 11 having a capacitor 15 and a resistor 16 connected in parallel. Next, 17 is a transistor ignition control device, and this mounting 17 has diodes 18, 19, 20.
, a power transistor 21, a control transistor 22, resistors 23 to 27, and a capacitor 28, each connected as shown.

The embodiment of the present invention shown in FIG. 3 constructed as described above operates as follows. First, the magnet rotor 3 of the magnet generator 2 rotates in synchronization with the engine.
When the negative direction voltage V ₁ shown by the broken arrow is generated in the primary coil 5 of the ignition coil 4, the primary coil 5 connects the diodes 8, 12, 13, 14 of the overspeed prevention device 7 and the transistor ignition control device. Current flows through a circuit consisting of 17 diodes 18, but since the plurality of diodes 12, 13, 14 of the overspeed prevention device 7 constitute a constant voltage time constant circuit 11 with a capacitor 15 and a resistor 16, The capacitor 15 is charged to the polarity shown, and a gate current is applied to the thyristor 10 to turn it on, and the on state of the thyristor 10 is maintained for a predetermined period of time. However, when the rotational speed of the engine is below a predetermined value, the on state of the thyristor 10 shifts to the off state before the next positive direction voltage V ₂ shown by the solid line arrow is generated in the primary coil 5. Therefore, when the rotational speed of the engine is low and below a predetermined value, the overspeed prevention device 7 does not operate substantially.

Then, when a positive voltage V ₂ is generated in the primary coil 5 as shown by the solid arrow, the base current is first supplied to the power transistor 21 via the resistor of the transistor ignition control device 17, and the power transistor 21 is turned on. Collector current begins to flow. When this collector current approaches its peak value, the base current is supplied to the control transistor 22 via the resistors 24 and 25, and the control transistor 22 is turned on, thereby turning the power transistor 21 off. Since the current flowing through the primary coil 5 is abruptly cut off, a high voltage is induced in the secondary coil 6, causing a high voltage spark to fly to the ignition plug 1 and igniting the engine.

If the rotational speed of the engine is below a predetermined value, the above-described operation is repeated and the engine is ignited. Note that the transistor ignition control device 17
When the positive direction voltage V ₂ of the primary coil 5 is rising, the capacitor ₂₈ provided at , the charge in the capacitor 28 is transferred to the resistors 27, 26,
25 to the base and emitter circuit of the control transistor 22 to stabilize the operation of the control transistor 22 and to prevent the ignition timing of the engine from changing as the engine speed increases. It is something.

Next, the operation when the rotational speed of the engine increases to a predetermined value or more will be explained.

As mentioned above, when the rotational speed of the engine is below a predetermined value, the thyristor 10 of the overspeed prevention device 7 is turned on when the negative direction voltage _V1 is generated in the primary coil 5, and the turned-on operation is performed at a constant voltage. Although it lasts for a predetermined period of time due to the time constant circuit 11, the thyristor 10 is turned off before the positive direction voltage _V2 is generated in the primary coil 5, so the over-speed prevention device 7 is not actually activated. It is.

However, when the engine speed increases above a predetermined value, a negative voltage is generated in the primary coil 5.
Although the generation period of V ₁ and the positive voltage V ₂ becomes short, the duration of the on state of the thyristor 10 is almost constant, so when the thyristor 10 is in the on state, the positive voltage V ₂ is A positive voltage is generated in the coil 5 and applied to the anode of the thyristor 10.
Since V ₂ is applied and a current flows between the anode and cathode, the on state of the thyristor 10 is a positive voltage.
It will continue to last longer from the time V ₂ occurs until it disappears. Therefore, the positive direction voltage generated in the primary coil 5
V ₂ is short-circuited through the thyristor 10 and diode 9 of the overspeed prevention device 7, and the ignition operation of the transistor ignition control device 17 is no longer performed and the engine is not ignited, so that if the engine speed exceeds a predetermined value, Over-speeding is completely prevented.

As is clear from the above explanation, according to the present invention,
A magnet generator driven in synchronization with the engine is provided with an ignition coil consisting of a primary coil and a secondary coil, and a spark plug is connected to the secondary coil of the ignition coil, and the primary coil is connected to the secondary coil of the ignition coil. In a non-contact ignition system for an engine, a transistor ignition control circuit is connected to short-circuit the generated negative direction voltage via a diode, and to turn on and off the same positive direction voltage. A thyristor configured to short-circuit the positive direction voltage is connected via a diode for preventing reverse current, and is turned on by the negative voltage generated in the primary coil between the gate and cathode of this thyristor, and the on-state is turned on. When the engine rotational speed is about to rise above a predetermined value, the thyristor is turned on. Since the operation is continued from the generation of the positive direction voltage to the disappearance of the primary coil, the positive direction voltage is short-circuited, and the ignition operation of the transistor ignition control device is disabled.
It is possible to completely prevent the engine from overspeeding.

The overspeed prevention device according to the present invention is similar to the conventional overspeed prevention device shown in FIG. There are some models that can be equipped with an overspeed prevention device without removing the diode, so they can be easily installed even on engines that are equipped with a non-contact ignition system without an overspeed prevention device as shown in Figure 1. At the same time, it completely eliminates the serious drawback of the conventional transistor shown in FIG. 2, in which a reverse voltage is repeatedly applied to the power transistor and the control transistor, causing abnormal temperature rise of the transistor and shortening its life. This has the practical effect of being able to eliminate the problem.

[Brief explanation of drawings]

Figure 1 is an electric circuit diagram showing the non-contact ignition system for an engine, which is the basis of the present invention, Figure 2 is an electric circuit diagram of a non-contact ignition system connected to a conventional overspeed prevention device, and Figure 3 is the electrical circuit diagram of the non-contact ignition system of the engine FIG. 2 is an electrical circuit diagram of a non-contact ignition device to which an embodiment of the overspeed prevention device is connected. In the figure, 1 is a spark plug, 2 is a magnet generator, 4 is an ignition coil, 5 is a primary coil, 6 is a secondary coil,
7 is an overspeed prevention device, 8 and 9 are diodes for backflow prevention, 10 is a thyristor, 11 is a constant voltage time constant circuit, 17 is a transistor ignition control device, 18,
19 and 20 are diodes, 21 is a power transistor, and 22 is a control transistor.

Claims (1)

[Scope of utility model registration request] A magnet generator driven in synchronization with the engine is provided with an ignition coil consisting of a primary coil and a secondary coil, a spark plug is connected to the secondary coil of this ignition coil, and the primary coil is connected to the same primary coil. In a non-contact ignition system for an engine, a diode 18 is connected to short-circuit the generated negative voltage, and a transistor ignition control circuit is connected to turn on and off the positive voltage. A thyristor that short-circuits the positive voltage is connected to both ends of the coil via a diode 9 for preventing backflow, and the connection point between the diode 9 and the primary coil is connected to the thyristor via the diode 8 for preventing backflow. A plurality of diodes 12,1 are connected to the gate of the thyristor, and further turn on the thyristor by a negative voltage generated in the primary coil between the gate and cathode of the thyristor, and maintain the on state for a predetermined time.
3, 14, a capacitor 15, and a resistor 16 connected in parallel to form a constant voltage time constant circuit.