JPH0343421Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to chain saws, and when a chain saw jerks during use, the driving force of the internal combustion engine can be applied in advance of the saw chain's mechanical braking without any special operation. This feature is characterized in that the saw chain can be braked smoothly in a short period of time during back-up, and there is no risk of damage to various parts.

[Conventional technology]

Chain saws are used for felling wood, but a phenomenon called stubble may occur during cutting operations such as twig cutting, plunge cutting, and round cutting that are performed after felling wood. Kickback refers to a phenomenon in which the chain saw itself instantaneously bounces back from the wood toward the operator at the beginning of cutting or during cutting.For example, the size of the twig to be cut does not match the cutting blade pitch of the saw chain, This is caused by the cutting blade of the saw chain not being sharpened enough.

As described above, when a backlash occurs, the chain saw itself is instantly thrown back toward the operator, which is extremely dangerous and can cause personal injury.

Therefore, conventionally, a chain saw 1 as shown in FIG. 4 has been provided. The chain saw 1 is provided with a front hand guard 4 which can be rotated forward by a predetermined angle at a position in front of the front handle 3 of the chain saw body 2, and when the front hand guard 4 is rotated forward, a link mechanism (not shown) is provided. The brake shoe of a brake (not shown) that applies a mechanical braking force to stop the saw chain 5 is pulled via the brake switch 5). Note that once the front hand guard 4 is rotated forward, it is locked in that position. In FIG. 4, 6 is a saw chain guide plate, 7 is a rear handle, 8 is a throttle lever, and 9 is a stop switch. The chain saw main body 2 houses an internal combustion engine that provides driving force to the saw chain 5, its ignition device (not shown), and the like.

Therefore, the conventional chain saw 1 described above has the fifth
As shown in the figure, a worker 10 grasps a front handle 3 and a rear handle 7 to cut a piece of wood 11, etc., and this is to ensure safety in the event that a backlash occurs during the cutting operation. Ta. In other words, when a bump occurs, the arrow X in Figure 5
As shown in the figure, the chain saw 1 itself bounces back toward the worker 10, but at this time, the worker 10
The back of the hand gripping the front handle 3 is protected by the front hand guard 4, and as a result of the back of the hand coming into contact with the front hand guard 4, the front hand guard 4 is rotated forward by a predetermined angle. The brake was activated and mechanical braking force was applied to stop the saw chain 5 from driving, thereby ensuring safety.

However, in the conventional chain saw 1 described above, even when the brake is activated and mechanical braking is applied when a backlash occurs, the ignition operation of the internal combustion engine continues, and the saw chain 5 continues to provide driving force. Therefore, if the braking force of the brake is small, it will not be possible to stop the Saw Chain 5 in a short period of time.On the other hand, if the braking force of the brake is large, conflicting forces will be applied, so the internal combustion An extremely large force was applied to various parts surrounding the brake, such as the engine's crankshaft and centrifugal clutch, and there was a risk that these parts would be damaged. In addition, as mentioned above, if the ignition operation continues and the saw chain stops and the internal combustion engine becomes idling, there is a great danger that the saw chain will start rotating when the front hand guard is unlocked to try to work again. It was hot.

[Problem that the invention attempts to solve]

The present invention eliminates the above-mentioned drawbacks of the prior art, and when a kickback occurs during use, the drive of the internal combustion engine is completely stopped and the saw chain is braked smoothly in a short period of time, thereby preventing damage to various parts. The aim is to provide a chain saw that is free from damage.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has a configuration in which a misfire switch is provided on the inner surface of the front hand guard to cause the ignition device of the internal combustion engine to misfire.

[Effect]

According to this invention, since the misfire switch is provided on the inside surface of the front hand guard, when a backlash occurs and the chain saw itself bounces back toward the operator, the back of the hand that is gripping the front handle will be the first to misfire. When the misfire switch comes into contact with the misfire switch, the misfire switch is activated, and the front hand guard then rotates forward. Therefore, when a knockback occurs, the brake that stops the saw chain is automatically activated without any special operation after the internal combustion engine's ignition device misfires. That is, when a kickback occurs, the driving force of the internal combustion engine is stopped without any special operation, and the driving force of the internal combustion engine is stopped prior to mechanical braking of the saw chain.

As a result, compared to the conventional chain saw mentioned above, even if the mechanical braking force is reduced, the saw chain can be stopped in a short time, and the engine crankshaft, centrifugal clutch, and other parts surrounding the brake can be overloaded. There is no risk of damage to these parts as no excessive force is applied to them.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows a chain saw 20 of the present invention, and the same components as those of the chain saw 1 shown in FIG. 4 are given the same reference numerals. That is, a front hand guard 4 is provided at a position in front of the front handle 3 of the chain saw main body 2 and is rotatable by a predetermined angle in front, and when the front hand guard 4 rotates forward, a link mechanism (not shown) etc. A brake shoe of a brake (not shown) that applies a mechanical braking force to stop the saw chain 5 is pulled through the saw chain. Further, once the front hand guard 4 is rotated forward, it is locked in that position. Furthermore, in the figure, 6 is a saw chain guide plate, 7 is a rear handle, 8 is a throttle lever,
9 is a stop switch. Furthermore, the chain saw main body 2 houses an internal combustion engine that provides driving force to the saw chain 5, an ignition device thereof, and the like.
In the case of the embodiment shown in FIG. 1, the front hand guard 4 is rotatably provided on the chain saw main body 2 as described above, but it may also be rotatably provided on the front handle 3.

In the present invention, a misfire switch 21 is provided on the inner surface of the front hand guard 4 to cause the ignition device of the internal combustion engine to misfire. As the misfire switch 21, various types of switches such as an ordinary push switch, a conductive rubber switch, and a tab-shaped switch can be used, but a thin switch is preferable. In addition, in order to ensure that the hand holding the front handle 3 comes into contact with the pressing part of the misfire switch 21 in the event of a backlash, the pressing part of the misfire switch 21 is pressed against the entire inner surface of the front hand guard 4. It is desirable to provide it so that it spans the
However, it is not necessarily necessary to provide it over the entire area, and it may be located only in a part of the inner surface of the misfire switch 21, for example, in the center. Note that the pressing portion herein refers to a portion that receives pressure and operates the switch. Furthermore, it is preferable that the switch 21 be operated not with a slight pressure but with a considerably strong pressure such as in the case of a kickback phenomenon.

Note that switches are generally divided into self-holding types and self-resetting types, but the misfire switch 21 of the present invention
can be used with any type of switch.

Next, the electrical connection between the misfire switch 21 and the ignition device 22 will be explained.

FIG. 2 is an electrical circuit diagram showing the relationship between the misfire switch 21 and the ignition device 22 when a self-holding type switch is used as the misfire switch 21. In the figure, 23 is a rotor that rotates in synchronization with the internal combustion engine, 24 is an ignition generator coil in which voltage is induced by the rotation of the rotor 23, and 25 is a rotor that rotates in synchronization with the internal combustion engine.
26 is the spark plug, and 26 is the ignition generator coil 24.
A well-known ignition control circuit that receives the induced voltage of and supplies high voltage to the spark plug 25 at a predetermined timing, 9
1 is the stop switch also shown in FIG. 1, and these constitute the ignition device 22. The misfire switch 21 has its a contact connected in series with the ignition generator coil 24 and in parallel with the stop switch 9. Therefore, when the misfire switch 21 is activated, both ends of the ignition generator coil 24 are maintained in a short-circuited state, and no spark is generated in the ignition plug 25. As a result, the output of the internal combustion engine is lost and the power of the saw chain 5 is reduced. The driving force is stopped.

Note that the ignition device 22 is not limited to the above configuration, and may be of a battery type, for example. In the case of the embodiment shown in FIG. 2, as described above, the a contact of the misfire switch 21 is connected to the ignition generator coil 2.
4 and in parallel with the stop switch 9, its b contact may be connected in series between the generator coil 24 and the ignition control circuit 26.

FIG. 3 shows another embodiment of the misfire switch 21 and the ignition device 22 in the case where a self-reset type switch is used as the misfire switch 21.
It is an electric circuit diagram showing the relationship between the two. It should be noted that the ignition device 22 in this embodiment is completely similar to that in the embodiment shown in FIG. 2, and the same components are given the same reference numerals.

In this embodiment, since a self-reset type switch is used as the misfire switch 21, once the misfire switch 21 is activated, the ignition device 22 is kept in the misfire state at least until the saw chain 5 stops driving. In order to maintain this, the misfire switch 21 is not directly connected to the ignition device 22 through a holding circuit 36, unlike the embodiment shown in FIG.

That is, the anode of the thyristor 27 is connected to one end of the ignition generating coil 24, the cathode of the thyristor 27 is connected to the other end of the ignition generating coil 24 via the resistor 28, and the thyristor 27 is connected to the other end of the thyristor 27.
The gate of is connected to the other end of the ignition generating coil 24 via a resistor 29 and a capacitor 30, and a resistor 31 is connected between the gate and cathode of the thyristor 27, and the middle point of the connection between the resistor 29 and the capacitor 30 and the thyristor 27 are connected to each other. A diode 32 is connected between the cathode of thyristor 27 and
Resistors 28, 29, 31, capacitor 30, and diode 32 constitute a holding circuit 36. A misfire switch 21 is connected between the anode and cathode of the thyristor 27. In addition,
In this embodiment, the misfire switch 21 is made conductive when activated. Note that the constant is determined so that the CR time constant due to the resistor 29 and capacitor 30 becomes large.

Therefore, when the misfire switch 21 is activated, the induced voltage of the ignition generator coil 24 causes
Path for misfire switch 21 → resistor 28 and misfire switch 21 → diode 32 → capacitor 30
A current flows through the path, charges the capacitor 30, and the voltage supplied to the ignition control circuit 26 drops, causing no spark to be generated in the spark plug 25, resulting in a misfire condition. Since the fire is instantaneous, the misfire switch 21
Even if the capacitor 30 is immediately released and becomes non-conductive, the charge in the capacitor 30 is discharged through the path of the resistor 29 → the gate/cathode of the thyristor 27 → the resistor 28 and the path of the resistor 29 → the resistor 31 → the resistor 28, and the thyristor 27 is triggered and becomes conductive. Then, due to the resistor 29 and capacitor 30
Since the CR time constant is set to be large, the thyristor 27 is maintained in a conductive state until the next induced voltage is obtained in the ignition generator coil 24. When the next induced voltage is obtained in the ignition generator coil 24, current flows in the path from the anode/cathode of the thyristor 27 to the resistor 28 and from the anode/cathode of the thyristor 27 to the diode 32 to the capacitor 30, and the capacitor 30 is charged with electric charge, and the voltage supplied to the ignition control circuit 26 is maintained in a decreased state, and the misfire state is maintained. Then, the above operation is repeated,
After all, once the misfire switch 21 is activated, the misfire state is maintained until the saw chain 5 stops driving.

Note that the holding circuit 36 is not limited to the circuit configuration shown in FIG. 3, and of course may have other circuit configurations.

According to the present invention having the above configuration, the front hand guard 4
Since the misfire switch 21 is provided on the inner surface of the machine, when a backlash occurs and the chain saw 1 bounces back toward the operator, the back of the hand that is gripping the front handle 3 will first hit the misfire switch 21.
When the misfire switch 21 comes into contact with the holder, the misfire switch 21 is activated, and the front hand guard 4 then rotates forward. Therefore, when a crisis occurs,
The brake that stops the drive of the saw chain 5 is automatically operated without any special operation after the ignition device of the internal combustion engine has misfired. That is, when a kickback occurs, the driving force of the internal combustion engine is stopped prior to mechanical braking of the saw chain 5, and the driving force of the saw chain 5 is stopped without any special operation.

As a result, compared to the conventional chain saw 1 mentioned above, even if the mechanical braking force is reduced, the saw chain 5 can be stopped in a short time, and various parts around the brake such as the engine crankshaft and centrifugal clutch can be stopped. No excessive force is applied to the parts, and there is no risk of damage to these parts.

[Effect of idea]

According to the present invention, the safety of workers is ensured, and when a backlash occurs during use, the driving force of the internal combustion engine is automatically stopped without any special operation, and the brake of the saw chain at the time of a backlash is automatically stopped. The effect is that the process is carried out smoothly and there is no risk of damage to various parts.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; Fig. 1 is a perspective view, Fig. 2 is an electric circuit diagram thereof, Fig. 3 is an electric circuit diagram showing another embodiment, and Fig. 4 is a conventional chain saw. FIG. 5 is a perspective view showing the state in which it is used. 3...Front handle, 4...Front hand guard, 5
...Sochien, 6...Sochien information board, 20
... Chain saw, 21 ... Misfire switch, 22
...Ignition device.

Claims (1)

[Scope of utility model registration request] This chain saw is characterized in that a misfire switch is provided on the inner surface of the front hand guard to cause the ignition device of the internal combustion engine to misfire.