JPS6038067Y2 - Overspeed prevention device for internal combustion engines - Google Patents

Description

[Detailed description of the invention] The present invention relates to an overspeed prevention device for an internal combustion engine that stops the operation of the ignition device when the rotational speed of the internal combustion engine exceeds a certain level to prevent the engine from overspeeding. .

Conventional devices of this type detect the rotational speed of the engine based on the output frequency or peak value of the output voltage of a lamp lighting generator coil or a battery charging generator coil installed in a magnetic alternator that rotates synchronously with the internal combustion engine. However, when the rotational speed reaches a set value, the ignition device for the internal combustion engine is prevented from performing an ignition operation, thereby preventing the rotational speed of the engine from increasing excessively.

However, in small vehicles such as two-wheeled vehicles, the conventional overspeed prevention device described above cannot be used because the generator coil for lighting is equipped with a small high-voltage magnet generator that does not include a generator coil for battery charging. There wasn't.

In addition, many conventional overspeed prevention devices require changes to the structure of the internal combustion engine ignition device itself, and in addition to wiring to the ignition device, wiring to the lighting generator coil and battery charging generator coil is also required. Therefore, it could not be easily applied to existing internal combustion engines.

By detecting the peak of the reverse voltage (half-cycle voltage that does not contribute to the ignition operation) of the ignition power supply coil, and operating the semiconductor switch for stopping the ignition operation when the peak of the reverse voltage reaches a predetermined value. A device has been proposed (Utility Model Application No. 53-10772) which stops the ignition operation to prevent over-speeding of the engine.

According to this device, there is no need to use a special coil to detect the rotational speed of the engine, so it can be installed even in existing internal combustion engines.

In this stop circuit, when the peak of the reverse voltage of the ignition power supply coil exceeds a certain value, a capacitor is charged with the reverse voltage, and the terminal voltage of the capacitor triggers a semiconductor switch for stopping the ignition operation. There is.

In this case, there is no problem as long as the peak value of the induced voltage in the ignition power supply coil is always accurately proportional to the rotational speed of the engine.

However, in reality, the magnitude of each half-cycle of the induced voltage in the ignition power supply coil, especially the magnitude of the half-cycle voltage induced after the ignition operation, varies greatly depending on the combustion state of the engine. In such a configuration, the set rotational speed at which the engine's ignition operation stops will fluctuate, and the overspeed prevention operation will inevitably become inaccurate.

The purpose of this invention is to provide an internal combustion engine that can accurately prevent overspeed without using a generator coil for lighting or a generator coil for battery charging, and that can be easily installed in the ignition system. An object of the present invention is to provide an overspeed prevention device for an engine.

This invention connects an overspeed prevention semiconductor switch in parallel to the ignition power supply coil, and triggers the overspeed prevention semiconductor switch when the rotational speed of the internal combustion engine exceeds a set value. The present invention is an overspeed prevention device for an internal combustion engine that prevents overspeed, and is characterized in that a trigger circuit for triggering the overspeed prevention semiconductor switch is configured as follows.

That is, in the overspeed prevention device of the present invention, the trigger circuit includes a capacitor, a charging circuit that charges the capacitor to one polarity with a half-cycle voltage that does not contribute to the ignition operation of the ignition power supply coil, and a Zener diode connected in parallel to the capacitor with its cathode facing the terminal that becomes positive during charging;
The terminal voltage of the capacitor is applied between a discharge circuit that discharges the charge of the capacitor at a constant time constant, a circuit that supplies a trigger signal from the ignition power supply coil side to the overspeed prevention semiconductor switch, and the gate source. a trigger control switch circuit comprising a field effect transistor that conducts when the terminal voltage of the capacitor is below a certain value, and conducts when the field effect transistor is conductive to bypass the trigger signal from the overspeed prevention semiconductor switch; Equipped with

As mentioned above, when a capacitor is charged with a half-cycle induced voltage that does not contribute to the ignition operation of the always-igniting power supply coil and the capacitor is discharged at a certain time constant, when the terminal voltage of the capacitor becomes below a certain value, When configured to trigger the overspeed prevention semiconductor switch, the terminal voltage of the capacitor changes in proportion to the frequency of the output of the ignition power supply coil, so it is always constant without being affected by the magnitude of the induced voltage of the ignition power supply coil. It is possible to accurately detect the rotational speed of the engine and perform accurate overspeed prevention operation.

In addition, according to the above configuration, the terminals connected to both ends of the overspeed prevention semiconductor switch can be connected to both ends of the ignition power supply coil without wiring to the lighting generation coil or the battery charging generation coil, and the installation can be done on the engine. Therefore, it can be easily applied to existing internal combustion engines.

The apparatus of the present invention will be explained in detail below with reference to the illustrated embodiments.

Figure 1 shows an example of an ignition system for an internal combustion engine using a small high-pressure magnet generator. In the figure, 1 is a magnet rotor attached to the output shaft of the internal combustion engine (not shown), The child includes a cylindrical rotating body 2 made of a non-magnetic material whose boss portion 2a is fitted onto the output shaft of the engine, and magnetic pole portions 3a at both ends.
, 3a, and the magnetic pole component 3 is embedded in the rotating body 2 so that the outer circumferential surface of the magnetic pole parts 3a, 3a is exposed to the outer circumferential surface of the rotating body 2, and A permanent magnet 4 is embedded in the rotating body 2 and is magnetized in the radial direction of the rotating body, and a permanent magnet 4 is embedded in the rotating body 2 and is in contact with a magnetic pole surface on the outer circumferential side of the permanent magnet 4, and the outer circumferential surface is magnetized in the rotating body 2. 2 and a magnetic pole piece 5 exposed on the outer peripheral surface.

A primary coil 8a and a secondary coil 8 are connected to a substantially U-shaped iron core 7 having magnetic pole portions at both ends opposite to the magnetic poles of the rotor 1.
The armature is an armature wrapped with an ignition coil 8 consisting of a ignition coil 8, and is attached to a mounting part provided at a fixed position on the case or cover of the engine using screws or the like.

The primary coil 8a also serves as an ignition power supply coil, and the rotor 1 attached to the output shaft of the engine is rotated in the direction of the arrow shown in the figure.
When rotated, FIG. 3 (the horizontal axis indicates time t).

) As shown in A, an alternating voltage consisting of two negative half cycles with a relatively small peak value and one positive half cycle with a large peak value is generated.

One end of the primary coil 8a is grounded, and the other end is connected to the secondary coil 8.
connected to one end of b.

Connected between one end of the secondary coil 8b and the ground is a contact of a circuit breaker 9, which is driven to open and close by a cam (not shown) that rotates synchronously with the engine, and a capacitor 10 is connected in parallel to both ends of this contact.

A spark plug 11 attached to a cylinder of the engine is connected between the other end of the secondary coil 8b and ground.

In this ignition system, when the output shaft of the engine rotates, the third
As shown in FIG. As shown in Figure 3C, the primary current I□ begins to flow.

Note that FIG. 3A shows the no-load voltage of the primary coil 8a.

Next, when a positive half-cycle voltage v2 is generated in the primary coil 8a at time 1, the direction of the primary current 11 is reversed, and the primary current 11 increases as the voltage v2 increases.

Next, at the time when the primary current 11 reaches approximately its peak, the contact of the interrupter 9 opens, abruptly cutting off the primary current 1.

As a result, a high voltage υゎ is generated in the primary coil 8a as shown in the third diagram.

This voltage is further boosted by the ignition coil, a high voltage is generated in the secondary coil 8b, a spark flies to the ignition plug 11, and an ignition operation is performed.

FIG. 2 is a connection diagram showing the overspeed prevention device 12 of the present invention connected to the ignition device, and the overspeed prevention device 12 is connected to the ignition device via a connector 13, 13'.

14 is a thyristor as a semiconductor switch for overspeed prevention, and this thyristor has a primary coil (ignition power supply coil) 8.
A is connected in parallel to both ends of a through a resistor 15.

The anode of a diode 16 is connected to the connector 13 connected to the non-grounded terminal of the primary coil 8a, and the cathode of the diode 16 is connected to the connector 13 whose source is connected to the grounded side.
' through a series circuit of resistors 18 and 19.

Between the gate and source of the FET 19 are a capacitor 20, a resistor 21, and a Zener diode 2 whose cathode is grounded.
2 are connected in parallel, and a series circuit consisting of a resistor 23 and a diode 24 with its cathode facing the connector 13 is connected in parallel between the gate and the connector 13.

A connection point between the resistors 18 and 19 is connected to the gate of the thyristor 14 via a Zener diode 25.

In this embodiment, the capacitor 20, the resistor 23, the diode 24, and the primary coil (ignition power supply coil) 8a charge the capacitor 20 to one polarity with a half-cycle voltage that does not contribute to the ignition operation of the ignition power supply coil. The resistor 21 constitutes a discharge circuit for the capacitor 20.

Further, the diode 16, the resistor 18, and the Zener diode 25 constitute a circuit that supplies a trigger signal from the ignition power supply coil (primary coil 8a) side to the thyristor (semiconductor switch for overspeed prevention) 14, and the field effect transistor 17 and the resistor 19 constitutes a trigger control switch circuit that bypasses the trigger signal from cycle 14 when conductive.

The capacitor, the charging circuit and discharging circuit for the capacitor, the circuit that supplies a trigger signal to the overspeed prevention semiconductor switch, and the trigger control switch circuit cause the rotational speed of the internal combustion engine to exceed the set value. A trigger circuit that sometimes triggers the over-rotation prevention semiconductor switch (thyristor 14) is configured.

In the embodiment shown in FIG. 2, when a voltage in the direction of the dashed arrow shown in the figure (voltage υ3' in FIG. 3 D) is generated in the primary coil 8a, the capacitor 20 is charged to the shown polarity through the resistor 23 and the diode 24. (See Figure 3E).

The terminal voltage of this capacitor 20 is the Zener diode 2
2 constant voltage υ.

limited to.

When the capacitor 20 is charged in this way and its terminal voltage (absolute value) Vo is above the threshold level υ, the drain and source of the FET 17 are in a disconnected state as shown in FIG. 3F.

When the induced voltage υ3' of the primary coil 8a becomes lower than the terminal voltage of the capacitor 20, the electric charge of the capacitor 20 is transferred to the resistor 2.
1 is discharged with a constant time constant, and when the terminal voltage (absolute value) o of the capacitor 20 becomes lower than the level υ, FE
The drain and source of T17 become conductive (Fig. 3F)
reference).

The discharge time constant of the capacitor 20 is such that when the rotational speed of the engine is lower than the set value, a half-cycle voltage υ3 that does not contribute to the ignition operation is generated in the primary coil 8a, and then a voltage υ2 that contributes to the ignition operation is generated next. If the time until
, is set to be lower than that to make FET17 conductive, and if the engine speed exceeds the set value and the time from when voltage υ3 is generated to when voltage υ2 is generated becomes short, the capacitor The terminal voltage of 20 cannot go below level υ.

Furthermore, the resistance values of the resistors 18 and 19 are such that when the FET 17 is in a conductive state, the terminal voltage of the resistor 19 does not exceed the Zener voltage of the Zener diode 25 even if the voltage υ2 of the primary coil 8a reaches the maximum. In the cutoff state, the terminal voltage of the resistor 19 is set to be equal to or higher than the Zener voltage of the Zener diode 25 when the voltage υ of the primary coil 8a is equal to or higher than a certain value.

Therefore, if the engine speed is lower than the set value,
As shown in FIG. 3F, since the FET 17 is conductive at the ignition timing ζ, the thyristor 14 is not conductive, and the ignition operation is performed without any trouble.

In contrast, the engine rotation speed exceeds the set value and the fourth
As shown in the figure, the time from the generation of the half-cycle voltage υ3' that does not contribute to the ignition operation of the primary coil 8a until the generation of the half-cycle voltage υ2 that contributes to the ignition operation is short.
Then, the terminal voltage V of the capacitor 20 as shown in FIG. 4E.

is no longer lower than the level υ, so the FET 17 is no longer able to conduct.

Therefore, at time ζ, the contacts of the interrupter 9 open as shown in FIG. 4B, and at the moment a voltage appears across the primary coil 8a, the thyristor 14 becomes conductive as shown in FIG.
The primary coil 8a is substantially short-circuited through the resistor 15.

Therefore, current continues to flow through the primary coil 8a, and only a low voltage υ2' corresponding to the voltage drop due to the resistor 15 is generated in the primary coil 8a, as shown in FIG. Engine speed is limited.

In this way, in the present invention, the time from the generation of a half-cycle voltage that does not contribute to the ignition operation of the ignition power supply coil to the generation of the next half-cycle voltage that contributes to the ignition operation (this time is determined by the ignition power supply coil). The output frequency of the coil, i.e.
It is inversely proportional to the rotational speed of the engine.

), and when this time becomes shorter than the set value, the overspeed prevention semiconductor switch is triggered in the half cycle that contributes to the ignition operation, so the overspeed prevention device is operated only by the ignition power supply coil. and does not require any other generator coil.

Therefore, it can also be applied to internal combustion engines that use small high-pressure magnet generators.

In addition, since it can be attached to the ignition device by simply connecting both ends of the ignition power supply coil using the connectors 13, 13', it can be easily attached to an existing internal combustion engine.

In the above embodiment, the resistors 18 and 19 serve as a load for the primary coil 8a, so the combined resistance value of these resistors is:
It is necessary to set it to a sufficiently large value so that the induced voltage in the secondary coil 8b during the ignition operation does not drop too much.

In the above embodiment, the resistor 15 is used to stabilize the generation of reverse voltage due to armature reaction when the primary coil 8a is short-circuited by the thyristor 14, and to stabilize the generation of reverse voltage due to the armature reaction when the primary coil 8a is short-circuited by the thyristor 14.
This is provided to control the temperature rise of the thyristor 14 by minimizing the subsequent current.

The Zener diode 22 is provided to keep the terminal voltage of the capacitor 20 charged with the reverse voltage υ3' constant, and there is a possibility that this may occur due to variations in the magnetized state of the magnet of the magnet generator or due to operation. This is to prevent the charging voltage from fluctuating due to certain demagnetization.

Also, by providing this Zener diode 22,
The influence of fluctuations in output voltage due to axial errors of the magnet generator can be eliminated.

When the FET 17 is used as a semiconductor switch to control the trigger of the thyristor 14 as in the above embodiment, since the FET is a high input impedance element, a capacitor 20 with a small capacity can be used, and a small capacitor such as a plastic film capacitor can be used. An inexpensive one can be used.

For example, as shown in FIG. The drain of FET 17 whose source is connected to the base of the transistor 26 is connected to the base of the transistor 26.
A trigger control switch circuit may be configured by the FET17 and FET17.

If you insert an amplifier on the output side of FETl7 in this way,
An FET with a small drain current can be used.

In the embodiment of FIG. 5, an inductor 28 is connected in series with the resistor 23.
The purpose of this inductor is to suppress the high frequency noise current generated during spark discharge, prevent the capacitor 20 from being charged by the noise current, and make the operation more stable.

In the above embodiment, a current interrupting type ignition device using a circuit breaker was used as an example, but it can also be applied to a case where a current interrupting type ignition device is used in which the interrupter is replaced with a non-contact switch such as a transistor. The present invention can also be applied to a case where the ignition coil is disposed outside the magnet generator and only the ignition power supply coil is provided in the magnet generator.

Furthermore, the present invention can also be applied when a capacitor discharge type ignition device 30 is used as shown in FIG.

In the figure, 8' is an ignition coil disposed outside the magnet generator, and one end of the capacitor 31 is connected to one end of the non-grounded side of the primary coil 3a' of the ignition coil.

The other end of the capacitor 31 is connected to the anode of a thyristor 32 whose cathode is grounded, and an ignition power supply coil 34 arranged in the magnet generator is connected to both ends of the series circuit of the capacitor 31 and the primary coil $a' via a diode 33. connected in parallel.

A diode 35 is connected between the gate and cathode of the thyristor 32.
The signal coil 36 is connected in parallel through
7 are connected in parallel.

and connectors 13.13 at both ends of the ignition power coil 34.
An over-rotation prevention device 12 configured similarly to the embodiment shown in FIG. 2 is connected via '.

In the embodiment shown in FIG. 6, the capacitor 31 is charged to the polarity shown by the output voltage of the ignition power supply coil 34 in the direction of the solid arrow, and the thyristor 32 is triggered by a signal given from the signal coil 36 at the ignition timing.

When the thyristor 32 is triggered, the charge in the capacitor 31 is discharged through the thyristor 32 and the primary coil 8a', and a high voltage is induced in the secondary coil Bb', causing the spark plug 11
Sparks fly.

Then, the capacitor 20 is charged to the polarity shown in the figure by the output voltage of the ignition power supply coil 34 in the direction of the dashed arrow, and when the rotational speed of the engine reaches the set value, the capacitor 20 is charged to the polarity shown in the figure by the output voltage of the ignition power supply coil 34 in the direction of the solid arrow. Thyristor 14 becomes conductive during the cycle.

When the thyristor 14 becomes conductive, the output of the ignition power supply coil 34 is substantially short-circuited, so that the capacitor 31 is no longer charged and the ignition operation is blocked.

As described above, according to the present invention, the capacitor is charged to a constant voltage with a half-cycle induced voltage that does not contribute to the ignition operation of the always-igniting power supply coil, and the capacitor is discharged at a constant time constant. A voltage proportional to the engine rotation speed is obtained at both ends, and the overspeed prevention semiconductor switch is triggered when the terminal voltage of the capacitor is below a certain value, so the influence of the magnitude of the induced voltage in the ignition power supply coil is reduced. This has the advantage of being able to accurately detect the rotational speed of the engine and perform accurate overspeed prevention operations at all times.

In addition, it can be installed in the engine by simply connecting the terminals connected to both ends of the overspeed prevention semiconductor switch to both ends of the ignition power supply coil, without having to wire the generator coil for lighting or the generator coil for battery charging. It has the advantage that it can be easily applied to internal combustion engines.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway block diagram of the ignition device used in the present invention, Fig. 2 is a connection diagram showing an embodiment of the present invention, and Fig. 3
Figures A to F are diagrams explaining the operation when the engine rotation speed is lower than the set value, and Figures 4A to F are diagrams explaining the operation when the engine rotation speed is higher than the set value. FIG. 5 is a connection diagram showing the main parts of another embodiment of the present invention, and FIG. 6 is a connection diagram showing still another embodiment of the invention. 1... Magnet generator, 8, 8'... Ignition coil, 8a... Primary coil (ignition power supply coil), 9... Intermittent Contact, 12... Over-rotation prevention device, 14... Thyristor, 17...
...FET, 20... Capacitor, 21.
...Resistor, 26...Transistor, 34
...Ignition power coil.

Claims (5)

[Scope of utility model registration request] (1) an over-rotation prevention semiconductor switch connected in parallel to the ignition power supply coil of an ignition device for an internal combustion engine driven by an ignition power supply coil that induces an alternating voltage in synchronization with the rotation of the internal combustion engine; An overspeed prevention device for an internal combustion engine, comprising a trigger circuit that triggers the overspeed prevention semiconductor switch when the rotational speed of the internal combustion engine exceeds a set value, the trigger circuit comprising: a capacitor; and the ignition power source. a charging circuit that charges the capacitor to one polarity with a half-cycle induced voltage that does not contribute to the ignition operation of the coil; a discharging circuit that discharges the charge of the capacitor at a constant time constant; The circuit includes a circuit that supplies a trigger signal to a semiconductor switch for preventing rotation, and a field effect transistor that conducts when a terminal voltage of a capacitor is applied between the gate and source and the terminal voltage of the capacitor is below a certain value. An over-speed prevention device for an internal combustion engine, comprising: a trigger control switch circuit that is conductive when conductive and bypasses the trigger signal from the over-speed prevention semiconductor switch. (2) The internal combustion engine according to claim 1, wherein the field effect transistor of the trigger control switch circuit is connected in parallel to the trigger signal input terminals of the overspeed prevention semiconductor switch. Over-rotation prevention device. (3) The trigger control switch circuit includes a transistor whose emitter-collector circuit is connected in parallel to the trigger signal input terminal of the over-rotation prevention semiconductor switch, and when the field-effect transistor becomes conductive, The overspeed prevention device for an internal combustion engine according to claim 1, wherein the field effect transistor and the transistor are connected to each other so that a base current flows through the transistor. (4) The circuit for charging the capacitor through the diode with a half-cycle voltage that does not contribute to the ignition operation includes an inductance connected in series with the diode. The overspeed prevention device for an internal combustion engine according to any one of Item 3. (5) The overspeed prevention device for an internal combustion engine according to any one of claims 1 to 4, wherein the overspeed prevention semiconductor switch is a thyristor.