JPH045811B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention prevents damage caused by over-speeding of an engine.
This invention relates to an overspeed prevention device for a two-stroke internal combustion engine.

[Prior Art] Two-stroke internal combustion engines tend to have small displacements due to their characteristics, and are sometimes equipped with a diaphragm type carburetor to enable full-circle operation, making them suitable for hand-held or backpack-type portable working machines. For example, it is widely used as a power source for power saws, brush cutters, etc.

Since power saws and brush cutters require relatively light and simple operation, the majority of drivers these days are unskilled people, such as women, the elderly, and young people. What you need to be careful about when working is that the load on the engine suddenly decreases immediately after cutting off trunks, branches, etc. with a power saw, and immediately after cutting off shrubs, weeds, etc. with a brush cutter, so the engine speed will suddenly increase and reach the overspeed range. enter abruptly. At this time, it is necessary to quickly close the throttle valve of the carburetor to suppress the rapid increase in engine speed, but unskilled operators tend to be slow in closing the whitening valve mentioned above, and Sometimes it is not done. If the above-mentioned operating procedures are neglected, the engine will overspeed, resulting in insufficient lubrication, which often leads to engine seizure and damage.

In particular, depending on the chain bar length for power saws, the cutter diameter for brush cutters, the length and number of nylon thread blades used, the speed and temperature of the work area, etc., the fuel metering needle valve of the carburetor is adjusted. Properly adjusting the opening requires considerable skill and experience.
If you mistakenly adjust the mixture to be too lean, the engine will overspeed, resulting in insufficient lubrication and damage.

In particular, recently, the structural strength of engines has been reduced to the minimum necessary to reduce costs and weight.
It has become increasingly important to prevent damage due to over-speeding.

Conventionally used overspeed prevention devices include the so-called rich-down system, in which a vibrating fuel valve opens when the engine overspeeds, supplying excess fuel to the engine and suppressing the rise in engine speed due to an overrich mixture. However, if an engine is equipped with this overspeed prevention device, a large amount of fuel will be wasted, the engine will malfunction due to fouled spark plugs, the working environment will deteriorate due to highly concentrated exhaust gas (white smoke) with odor, and the mixture will become too rich. There are problems such as poor idling and engine failure due to the generation of

In addition, when the engine overspeeds, the vane governor rotates the throttle valve in the closing direction together with the valve shaft that connects the control blades when the engine overspeeds due to the wind pressure applied to the control blades located in the wind area of the engine cooling fan. In order to achieve both the rotational force of the control blades due to wind pressure and an appropriate amount of cooling air, the prevention device requires a larger cooling fan than a normal fan, which causes power loss and increased weight.

In the overspeed prevention device for a two-stroke internal combustion engine disclosed in Japanese Patent Application Laid-open No. 59-46344, when the engine overspeeds, only the positive pressure of the pulsating pressure in the crank chamber is supplied to the actuator via a check valve. The actuator rotates the throttle valve in the closing direction. However, since the crank chamber is filled with gas containing lubricating oil and unburned fuel, if the unburned gas is led directly to the actuator, the unburned gas will eventually be released from the actuator through the throttle hole and into the atmosphere. , harm the environment. In addition, there is a problem in that when the engine is not used for a long period of time, oil from unburned gas adheres to the check valve and solidifies, causing a delay in the check valve's operation due to overspeeding of the engine, thereby interfering with normal operation.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, the object of the present invention is to provide a system that operates reliably and does not harm the environment, and that automatically rotates the throttle valve in the closing direction when the engine overspeeds. An object of the present invention is to provide an overspeed prevention device for a two-stroke internal combustion engine.

[Means for solving the problem] In order to achieve the above object, the configuration of the present invention connects the discharge port of the vibratory air pump that resonates when the engine overspeeds to the working chamber of the actuator, and connects it to the diaphragm of the actuator. The rod is brought into contact with a control lever connected to the valve shaft together with the throttle valve of the carburetor, and the throttle valve is rotated to the closed position.

[Operation] When the engine overspeeds, pressurized air is supplied to the actuator from a vibrating air pump equipped with a weight, a spring, and a diaphragm that resonates with the vibrations of the engine, and a rod connected to the diaphragm of the actuator is protruded. Regardless of the position of the throttle lever, the actuator rod rotates a control lever coupled to a valve shaft supporting the throttle valve in the direction of closing the throttle valve. Therefore, the amount of fuel supplied to the engine is reduced, and the engine speed is reduced.

[Embodiments of the Invention] Fig. 1 is a front sectional view showing an over-speed prevention device during normal operation of an engine according to the present invention, and Fig. 2 is a front sectional view showing an over-speed prevention device during over-speed operation of the engine. FIG. 3 is a side sectional view taken along the line - in FIG. 1.

In FIG. 1, 1 is a diaphragm type carburetor, a control lever 7 is connected to the outer end of a valve shaft 3 that connects a butterfly-shaped throttle valve 2, and a throttle lever 4 is supported for free rotation. Ru. The throttle lever 4 is moved in the closing direction of the throttle valve 2 by a spring 5 (FIG. 3) that is wound around the valve shaft 3 and that has one end locked to the throttle lever 4 and the other end locked to the wall of the carburetor 1. It is urged to rotate in the direction of the arrow y. One end of an operating rod 6 is connected to the throttle lever 4. The other end of the operating rod 6 is connected to an operator's operating lever (not shown).

As shown in FIG. 3, the control lever 7 is wound around the valve shaft 3 and is fixed at one end to the control lever 7 and at the other end to the wall of the carburetor 1, so that the throttle valve 2 is fully opened. The protruding piece 7a of the control lever 7 comes into contact with the edge of the throttle lever 4. The valve shaft 3 is supported on the inner surface of a bearing 10 supported on the wall of the carburetor 1, and the throttle lever 4 is supported on the outer surface of the bearing 10.

As shown in FIG. 1, a rod 9 of a pressure/displacement transducer or actuator 17 rests on the edge of the control lever 7. Actuator 17 is connected to container 2
The working chamber 23 and the atmospheric chamber 25 are separated by a diaphragm 18 supported inside the engine. At the same time, rotate the throttle valve 2 in the closing direction.

For this reason, the vibrating air pump 11 is connected to the working chamber 23.
is connected. The vibrating air pump 11 is connected to the container 28
A pump chamber 26 and an atmospheric chamber 27 are partitioned by a diaphragm 12 supported inside.

A weight 13 is coupled to the diaphragm 12, and a spring 14 that contacts the diaphragm 12 is housed in the atmospheric chamber 27. The vibrating air pump 11 is preferably disposed on the wall of the engine, and resonates with vibrations caused by overspeeding of the engine to cause the diaphragm 12 to reciprocate up and down, thereby pumping atmospheric air from the inlet 15 through the check valve to the pump chamber 26. It is inhaled and exhaled from the outlet 16 through a check valve.

During normal load operation of the engine, when the throttle lever 4 is rotated by the operating rod 6 in the direction opposite to the arrow y to the position shown in FIG. , the throttle valve 2 rotates following the throttle lever 4, and the throttle valve 2 is almost fully opened. At this time, the vibration of the engine is small, and the diaphragm 12 of the vibratory air pump 11 hardly moves back and forth. The rod 9 of the actuator 17 is in the state shown in FIG. 1 and does not prevent movement of the control lever 7 to the fully open position.

When the engine overspeeds, the vibration of the engine becomes intense.
The diaphragm 12 of the vibrating air pump 11 resonates and reciprocates, and pressurized air is pumped from the vibrating air pump 11 to the working chamber 23 of the actuator 17 . The rod 9 connected to the diaphragm 18 moves to the right. The rod 9 rotates the throttle valve 2 together with the control lever 7 in the closing direction. Therefore, the amount of fuel supplied to the engine is reduced, the engine speed is lowered, and overspeeding of the engine is prevented.

The throttle holes 20 and 19 provided in the container 24 of the actuator 17 facilitate smooth operation when the engine output is restored.

[Effects of the Invention] As described above, the present invention connects the discharge port of the vibrating air pump that resonates when the engine overspeeds to the working chamber of the actuator, and connects the rod connected to the diaphragm of the actuator to the throttle valve of the carburetor. Since it comes into contact with a control lever connected to the valve stem and rotates the throttle valve in the closing direction, it does not require any effort and is supplied to the engine regardless of the operating position of the throttle lever. The fuel quantity is automatically reduced. Therefore, the engine rotational speed is reduced, and damage to the engine due to overspeeding can be prevented.

The present invention utilizes the vibration energy of the engine to move the throttle valve in the closing direction when the engine is overspeeding, reducing the amount of fuel and reducing the engine speed. Therefore, fuel is not wasted and exhaust gas is reduced. can prevent environmental pollution caused by

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view showing an over-speed prevention device during normal operation of an engine according to the present invention, FIG. 2 is a front cross-sectional view showing an over-speed prevention device during over-speed operation of the engine, and FIG. FIG. 1: Diaphragm type carburetor, 2: Throttle valve, 4:
Throttle lever, 7: Control lever, 7a: Protrusion, 9: Rod, 11: Vibrating air pump, 1
7: Actuator.

Claims (1)

[Claims] 1 Connect the discharge port of the vibrating air pump that resonates when the engine overspeeds to the working chamber of the actuator, and touch the rod connected to the diaphragm of the actuator to the control lever connected to the valve shaft together with the throttle valve of the carburetor. An overspeed prevention device for a two-stroke internal combustion engine, characterized in that the throttle valve is rotated in the closing direction.