JP2001193618A - Overspeed governor for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably and inexpensively prevent an internal combustion engine from having an over speed without complicating a circuit structure. SOLUTION: Charging a charge and discharge capacitor 10 is banned by a switching element switched on based on the discharge time constant of a charge and discharge circuit when an internal combustion engine has a set engine speed or higher, by providing the charge and discharge circuit to charge the positive induced voltage of a trigger coil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact ignition device for a capacitor charge / discharge type internal combustion engine, and more particularly to an overspeed prevention device for an internal combustion engine which can prevent overspeed of the internal combustion engine.

[0002]

2. Description of the Related Art As a conventional contactless ignition device for an internal combustion engine, for example, when a rotor having magnetic poles rotates, a voltage induced by an exciter coil is charged in an ignition charge / discharge capacitor, and the charge / discharge capacitor is charged. In some devices, charge is supplied to an ignition coil through a switching element that is switched by a voltage induced by a trigger coil.

In this non-contact ignition device, when the rotation speed of the internal combustion engine, that is, the rotation speed of the rotor increases, the charging / discharging timing of the ignition charge / discharge capacitor is advanced, and finally the rotation speed of the internal combustion engine is reduced. The rotation speed may exceed the set rotation speed and cause seizure of the internal combustion engine.

[0004] On the other hand, an overspeed prevention device for an internal combustion engine employing a governor mechanism has been widely provided. However, since this governor mechanism expands and contracts while rotating integrally with the crankshaft, it requires a large working space,
In addition, there is a problem that the life is short due to the mechanical operation.

Further, in order to reduce the working space and extend the life of the engine, the internal combustion engine uses a plurality of switching elements and impedance elements for monitoring the engine speed. When the internal combustion engine reaches the threshold, the ignition timing of the charge / discharge capacitor for ignition is delayed, and the overspeed of the internal combustion engine can be prevented by electrical control in a narrow space. Has been provided.

[0006]

However, such a conventional overspeed prevention device for an internal combustion engine by electrical control uses two or more switching elements and impedance elements, so that it is occupied for mounting. In addition to an increase in space, the circuit configuration becomes complicated, and therefore, there is a problem that an increase in the cost of the entire apparatus is inevitable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. A point number circuit for setting a switch timing of a switching element for controlling charging / discharging of a charging / discharging capacitor for ignition is provided in the non-contact ignition device of the internal combustion engine. An object of the present invention is to provide an overspeed prevention device for an internal combustion engine that reliably prevents overspeed of the internal combustion engine at low cost without complicating the circuit configuration only by adding.

[0008]

To achieve the above object,
An over-rotation prevention device for an internal combustion engine according to the invention according to claim 1, wherein a rotor having magnetic poles disposed with a magnet interposed therebetween, a core disposed opposite to the rotor and wound with an exciter coil and a trigger coil, and an exciter coil An ignition charge / discharge capacitor for charging the positive induced voltage of the ignition coil, and when the positive induced voltage of the trigger coil reaches a predetermined trigger level, the charge is triggered to conduct, and the charge of the ignition charge / discharge capacitor is transferred to the ignition coil. In the contactless ignition device for an internal combustion engine having a switching element to supply, a charging and discharging circuit for charging the positive induced voltage of the trigger coil is provided,
When the rotation speed of the internal combustion engine becomes equal to or higher than a set rotation speed, charging of the ignition charge / discharge capacitor is prohibited by turning on the switching element based on a discharge time constant of the charge / discharge circuit.

According to a second aspect of the present invention, there is provided an overspeed prevention device for an internal combustion engine, wherein the time constant circuit includes a control capacitor and a control resistor.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an arrangement relationship between an exciter coil 1 and a trigger coil 2 constituting a non-contact ignition device for an internal combustion engine according to the present invention with respect to a rotor 3. In the figure, a rotor 3 is formed by burying a pair of magnetic poles 6 and 7 so as to sandwich a magnet 5 in a non-magnetic body 4 made of aluminum. Each of the magnetic poles 6 and 7 is partially exposed on the outer peripheral surface of the rotor 3 as shown in the figure, and can be opposed to a leg end surface of a core described later during rotation of the rotor 3.

Reference numeral 8 denotes the U-shaped core facing the rotor 3. The exciter coil 1 and the trigger coil 2 are wound around the legs 8 and 8b. The surfaces of the legs 8a and 8b facing the rotor 3 are formed in an arc shape so that the distance from the rotor 3 is kept constant.

FIG. 2 is a circuit diagram showing an overspeed prevention device for an internal combustion engine according to the present invention. In the figure, the exciter coil 1
Is connected in series with a diode 9, an ignition charge / discharge capacitor 10, and a primary coil 11a of an ignition coil 11, which constitutes a charging circuit for charging a positive voltage induced by the exciter coil 1.

An ignition charge / discharge capacitor 10 includes an anode / cathode of a thyristor 12 as a switching element and a primary coil 1 of an ignition coil 11.
1a are connected in series, and these constitute a discharge circuit for discharging the charge of the ignition charge / discharge capacitor 10. According to this, when the thyristor 12 is triggered and becomes conductive, the thyristor 12 functions to discharge the charge of the ignition charge / discharge capacitor 10 to the ignition coil 11.

Further, a spark plug 13 is connected to the secondary coil 11b of the ignition coil 11, and a thyristor 12 has an anode plug and a cathode.
A backflow preventing diode 14 having a voltage charging function is connected.

On the other hand, the trigger coil 2 has a diode 15
And the control capacitor 16 are connected in series, and one end of a control resistor 17 is connected to a connection point of the diode 15 and the control capacitor 16, and the other end of the control resistor 17 is connected to the gate of the thyristor 12. Have been. Reference numeral 18 denotes a resistor for setting the trigger level of the thyristor 12, one end of which is connected to the gate of the thyristor 12,
The other end is connected to a connection point between the trigger coil 2 and the control capacitor 16.

Next, the operation of the overspeed prevention device for an internal combustion engine having the above configuration will be described. First, when the internal combustion engine operates and the rotor 3 rotates in the direction of arrow A in FIG. 1, the exciter coil 1 and the trigger coil 2 on the core 8 facing the rotor 3 have the configuration shown in FIGS. Are induced, respectively. The positive voltage of the induced voltage of the exciter coil 1 is transmitted through the diode 9 and the ignition charge / discharge capacitor 10 to the ignition 11.
Is applied to the primary coil 11a to charge the charge / discharge capacitor 10 for ignition.

On the other hand, the positive voltage of the induced voltage of the trigger coil 2 rises with a period τ1 later than the rising of the positive induced voltage of the exciter coil 1, and this voltage is
The control capacitor 16 is charged through the gate of the thyristor 12 via the control resistor 17. When the potential of the gate of the thyristor 12 reaches a set level, the thyristor 12 is turned on, and the charge of the ignition charging / discharging capacitor 10 is transferred by the exciter coil 1 to the ignition coil 11 through the thyristor 12 as described above. Supply. For this reason,
An ignition voltage is applied to the ignition plug 13 from the ignition coil 11 to ignite an air-fuel mixture in a combustion chamber of the internal combustion engine. By repeating this operation, the rotation speed of the internal combustion engine gradually increases.

At this time, the positive induced voltage of the trigger coil 2 is gradually attenuated from its peak value. However, the electric charge charged in the control capacitor 16 is discharged when the time constant circuit formed together with the control resistor 17 discharges. According to a constant, it is discharged to the gate of thyristor 12 and continues to trigger this gate,
The thyristor 12 is kept on for a predetermined time.

Therefore, during the predetermined time, charging of the ignition charge / discharge capacitor 10 is prohibited. That is, by setting the time constants of the control capacitor 16 and the control resistor 17 arbitrarily, the charge / discharge timing of the ignition charge / discharge capacitor 10 can be determined, whereby the timing of supplying the ignition voltage to the spark plug, The engine speed can be controlled below the set value.

Therefore, when the rotation speed of the internal combustion engine is gradually increased after the start, and the waveform of the induced voltage of the exciter coil 1 changes as shown in FIG.
Even if the positive induced voltage of the exciter coil 1 is generated within the discharge time constant by the control resistor 17 and the control capacitor 16, the exciter coil 1 is short-circuited by the thyristor 12 within the discharge time constant τ2, and the charge and discharge for ignition is performed. Charging of the capacitor 10 is prohibited within the period t,
During this period t, ignition energy is not accumulated, and the internal combustion engine is in a misfire state. Due to this misfire state, the rotation speed of the internal combustion engine does not further increase, that is, even if the internal combustion engine attempts to over rotate in the high speed rotation range, the engine is safely operated within the set rotation speed or less.

Accordingly, the conventional non-contact ignition device for an internal combustion engine is simply added with a discharge time constant circuit comprising a control capacitor 16 and a control resistor 17, and the high-speed rotation exceeding a set rotation speed, for example, an over-speed rotation. In the range, charging of the charging / discharging capacitor 10 for ignition can be prohibited, thereby forcibly setting the ignition circuit to a misfire state and preventing overspeed of the internal combustion engine.

[0022]

As described above, according to the present invention, a charge / discharge circuit for charging a positive induced voltage of a trigger coil is provided.
When the internal combustion engine becomes equal to or higher than the set number of revolutions, by turning on the switching element based on the discharge time constant of the charge / discharge circuit,
Since the charging of the ignition charge / discharge capacitor is prohibited, the rotation speed of the internal combustion engine can be kept below the set value only by adding a simple time constant circuit to the conventional non-contact ignition device. At the same time, there is obtained an effect that over rotation of the internal combustion engine, which is dangerous depending on the application, such as a rotary blade of a mower, can be effectively prevented.

Further, since the time constant circuit is composed of a control capacitor and a control resistor, there is an advantage that the overspeed prevention circuit can be formed in a simple configuration and small in size and formed at low cost.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing a configuration of a main part of an overspeed prevention device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an overspeed prevention device for an internal combustion engine according to the present invention.

FIG. 3 is a timing chart showing voltage waveforms at various parts of the circuit shown in FIG. 2;

FIG. 4 is a timing chart showing voltage waveforms at various parts of the circuit shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exciter coil 2 Trigger coil 3 Rotor 8 Core 10 Charging / discharging capacitor for ignition 11 Ignition coil 12 Thyristor (switching element) 13 Spark plug 16 Control capacitor 17 Control resistor

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Yoshiki Kitamura 1-1114 Oppama Honcho, Yokosuka City, Kanagawa Prefecture F-term in Oppama Industry Co., Ltd. 3G019 BA02 BA07 BA09 CB23 CB24 FA02 FA04 FA31 GA05

Claims (2)

[Claims] 1. A rotor 3 having magnetic poles 6 and 7 disposed with a magnet 5 interposed therebetween, and a core 8 disposed opposite to the rotor 3 and wound with an exciter coil 1 and a trigger coil 2.
An ignition charging / discharging capacitor 10 for charging a positive induced voltage of the exciter coil 1; and an ignition charging / discharging capacitor 10 for triggering when the positive induced voltage of the trigger coil 2 reaches a predetermined trigger level. A switching element 12 for supplying a charge of a capacitor 10 to an ignition coil 11
In the non-contact ignition device for an internal combustion engine having a charge / discharge circuit for charging the positive induced voltage of the trigger coil 2, a discharge time constant of the charge / discharge circuit when the internal combustion engine becomes equal to or higher than a set number of revolutions. The switching element 12 based on
An overspeed prevention device for an internal combustion engine, wherein charging of the charging / discharging capacitor for ignition 10 is prohibited by turning on the ignition switch. 2. The control circuit according to claim 1, wherein the time constant circuit is a control capacitor.
6. The overspeed prevention device for an internal combustion engine according to claim 1, comprising: a control resistor;