JPH0441253Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to an improvement of an overspeed prevention device for an internal combustion engine to prevent damage to the engine due to overspeed.

[Conventional technology]

Conventionally, as a method to prevent engine overspeed,
For example, as shown in Japanese Patent Publication No. 53-13740, a method is used in which the ignition spark of the engine is extinguished when the engine speed exceeds a predetermined speed, thereby limiting the increase in engine speed. In this method, the engine is ignited intermittently to prevent overspeed. That is, when the rotational speed exceeds a predetermined rotational speed, the ignition spark is extinguished, resulting in no engine output and the rotational speed decreases, and when it falls below the predetermined rotational speed, ignition sparks are generated again and the engine rotational speed increases.

[Problem that the invention attempts to solve]

When the engine's ignition sparks become intermittent, the engine generates a shock and a greater force is applied to each part of the engine than during normal operation. Therefore, if the user of the engine continues to operate without noticing the overspeed prevention state, there are problems such as shortening the life of the engine and wasting fuel.

This invention was developed to solve the problems mentioned above. It prevents the life of the engine from being shortened, prevents unnecessary fuel consumption, and informs the user that the overspeed is prevented. The purpose of the present invention is to obtain an overspeed prevention device for an engine that can be tightened.

[Means for solving problems]

The over-rotation prevention device according to this invention lowers the predetermined number of revolutions at which over-rotation is prevented when the over-rotation prevention state continues for a certain period of time.

[Effect]

The over-rotation prevention circuit in this invention enables the first
If it continues to be controlled by a predetermined value for a certain period of time or more, it will switch to a second predetermined value that is lower than the first predetermined value, thereby preventing continued strong impact, reducing fuel consumption, and informs the driver that it is in the overspeed prevention state.

[Example of idea]

An embodiment of this invention will be described below with reference to the drawings. In Figure 1, 1 is a generator coil of a magnet generator driven by the engine, 2 is a diode that rectifies the alternating current output of this generator coil 1, 3 is a capacitor that is charged by the rectified output of diode 2, and 4 is the ignition of the engine. 5 is a diode that rectifies the AC output of the signal coil 4, 6 is a resistor that limits the rectified output current of the diode 5, and 7 is a signal coil that receives the output of the signal coil 4 and adjusts the ignition timing of the engine. A first SCR conducts to discharge the charge charged in the capacitor 3; 8 is an ignition coil that conducts the discharged charge of the capacitor 3 to the primary coil and generates a high voltage in the secondary coil; 9 is a high voltage of the ignition coil 8; Spark plug that receives voltage and discharges to ignite the engine, 1
0 is a diode that rectifies the alternating current output of the signal coil 4, 11 is a capacitor that is charged by the rectified output of the diode 10, 12 is a resistor that discharges the charge of the capacitor 11, and 13 is a generator coil that conducts in response to the output of the resistor 12. The second short-circuiting the output of the first
SCR, 14 is a resistor that allows the short-circuit current of the generator coil 1 that flows when the second SCR 13 is conductive to generate a voltage drop, 15 is a diode that allows the voltage drop that occurs in the resistor 14 to pass and prevents reverse current, 16 is a diode 15 A resistor 17 limits the current flowing through the diode 15. A capacitor 17 is charged by the current flowing through the resistor 16. A transistor 18 conducts in response to the voltage of the capacitor 17. A resistor 19 limits the collector current of the transistor 18. The resistor 20 is connected through the resistor 19 when the transistor 18 is conductive.
A transistor becomes conductive when a base current flows through it, a resistor 21 limits the collector current of the transistor 20, and a resistor 22 connected between the gate of the second SCR 13 and ground. The above-mentioned diode 10 and capacitor 11 constitute a rotation speed detection circuit.
22, constitutes an over-speed prevention circuit with the second SCR 13, and also includes the above-mentioned resistors 14, 16, 19, 21,
The diode 15, the capacitor 17, and the transistors 18 and 20 constitute a switching means.

Next, the operation will be explained.

The AC output generated in the generator coil 1 is rectified by the diode 2 and charged into the capacitor 3 in the direction shown. When a signal is generated in the signal coil 4, it is applied to the gate of the first SCR 7 through the diode 5 and the resistor 6, and the first SCR 7 becomes conductive. The charge in the capacitor 3 is discharged through the primary coil of the ignition coil 8, and A high voltage is generated in the secondary coil of 8. The high voltage generated in the secondary coil of the ignition coil 8 is applied to the ignition plug 9, and the ignition plug 9 discharges to ignite the engine.

On the other hand, the AC output of the signal coil 4 is connected to the diode 1.
0, and the capacitor 11 is charged. The signal coil 4 is a coil built into the magnet generator, and generates a voltage proportional to the rotation speed of the magnet generator, that is, the engine rotation speed. Therefore, the voltage across the capacitor 11 becomes a DC voltage that increases or decreases in proportion to the engine speed. The engine speed is low and the second SCR13
When the capacitor 17 is in a non-conducting state, the voltage of the capacitor 17 is zero (volt), the transistor 18 is in a non-conducting state, and therefore the transistor 20 is also in a non-conducting state. In this state, the voltage of the capacitor 11 is divided by the resistors 12 and 22 and applied to the gate of the second SCR 13. When the engine speed increases and the terminal voltage of the capacitor 1 increases, the gate voltage of the second SCR 13 also increases, and when this voltage reaches the gate trigger voltage, the second SCR 13 becomes conductive and the generator coil 1
output is shorted. If the output of the generator coil 1 is short-circuited, the capacitor 3 will not be charged.
Therefore, the discharge of the spark plug 9 is stopped, and overspeeding of the engine is prevented. When the second SCR 13 becomes conductive, current flows through the resistor 14, causing a voltage drop. This voltage drop is charged to the capacitor 17 through the diode 15 and the resistor 16, but since the charging current is limited by the resistor 16, the terminal voltage of the capacitor 17 gradually increases. When the terminal voltage of capacitor 17 reaches VBE of transistor 18, transistor 18 becomes conductive, a base current flows to the base of transistor 20 through resistor 19, and transistor 20 also becomes conductive. transistor 2
0 becomes conductive, the terminal voltage of the capacitor 11 is supplied to the gate of the second SCR 13 through the series circuit of the transistor 20 and the resistor 21 and the resistor 12, so that the second SCR 13 is triggered at a lower rotation speed. Become. The above operation will be explained with respect to the engine speed characteristics shown in FIG. In the figure, between points a and b, the engine is operating normally and ignition is performed normally. When the rotation speed increases from point b and the second SCR 13 is triggered at point c, ignition is stopped and the rotation decreases. When the rotation decreases, the second SCR 13 is no longer triggered, fires again, and the rotation increases. In this way, the engine speed is limited in a wave-like manner at the speed _n1 , but if the engine is operated continuously in this state, the capacitor 17 will be gradually charged due to the voltage drop that occurs across the resistor 14, and the terminal voltage will gradually rise. . When the terminal voltage of the capacitor 17 reaches the base-emitter forward voltage of the transistor 18 at point d in the figure, the transistor 18,
20 becomes conductive, and the second SCR 13 is triggered at a lower rotation speed, so the engine rotation drops below point d as shown in the figure, and the rotation speed is limited to _n2 .

By lowering the engine speed from n ₁ to n ₂ in this way, the force applied to each part of the engine can be reduced, and since the rotation speed is greatly reduced, the user is informed that the engine is under overspeed prevention control. You can make something obvious.

[Effect of idea]

As described above, according to this invention, when the overspeed prevention state continues for a certain period of time, the rotation speed at which overspeed prevention is performed is lowered, so that the engine is no longer used in the overspeed prevention state continuously at high speed. The service life of the engine will not be shortened, and unnecessary fuel consumption will be eliminated.Also, the user can be clearly notified that the overspeed prevention control is in effect, and the rotation speed detection circuit can be activated by the output of the signal coil. This configuration has the effect of reliably preventing engine overspeed regardless of changes in engine load.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing one implementation of the present invention.
FIG. 2 is a rotation speed characteristic diagram of the engine according to the present invention. In the figure, 1 is a power generation coil, 4 is a signal coil,
7 is the first SCR, 8 is the ignition coil, 10, 15
is a diode, 11 and 17 are capacitors, 12,
14, 16, 19, 21, and 22 are resistors, 13 is a second SCR, and 18, 20 are transistors.

Claims (1)

[Scope of utility model registration request] An ignition coil that ignites the engine, a generator coil that outputs a current that flows through this ignition coil, a signal coil that generates an ignition signal at the ignition timing of the engine, and a current that flows through the ignition coil in response to the output of this signal coil. a semiconductor switching element for controlling the engine; a rotation speed detection circuit that receives the output of the signal coil and detects the rotation speed of the engine; an overspeed prevention circuit that prevents engine overspeed by short-circuiting an output that contributes to ignition of the generator coil to eliminate ignition sparks generated in the ignition coil when the speed exceeds An over-rotation prevention device for an engine, comprising a switching means for switching the operating rotation speed of the over-rotation prevention circuit to a second predetermined value lower than the first predetermined value when the over-rotation prevention circuit continues to operate.