JPH0346228Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a safety braking device for emergency braking of an engine chain saw in order to prevent accidents caused by the jerking phenomenon that occurs unexpectedly during sawing operations with an engine chain saw.

Generally, the safety braking device is mainly of a mechanical braking operation type, and is intended to shorten the braking time to the maximum extent possible.

However, there are limits to what mechanical braking methods can do, and considering the need to reduce the weight and size of engine chainsaws, it is undesirable to complicate the structure and increase the number of attached parts.

Furthermore, as in Japanese Patent Publication No. 47-47157, it has been proposed to cut off the engine's ignition current and stop the engine itself at the same time as the safety braking device is activated. , it is necessary to perform restart work such as pulling the recoil rope.

In view of these conventional problems, the present invention not only shortens braking time, but also operates the engine at a low speed below the clutch-in rotation speed of the centrifugal clutch so that the engine is not driven during braking, eliminating the need to restart the engine. The purpose of this invention is to provide a chain saw safety braking device that enables efficient work.

That is, by operating the detection lever that detects the jerking phenomenon, the electronic ignition system for steady engine operation switches to the overspeed prevention ignition circuit at the idling limit, and the engine is reduced to a low speed below the clutch-in rotation speed of the centrifugal clutch so that the engine is not driven. To achieve this, the mechanical braking action is added to the braking action, the braking action is quickly effective, the braking effect is enhanced and the braking time is shortened, and the engine continues idling without stopping.

Below, the configuration of the present invention will be explained according to the embodiments shown in the drawings.

Figure 1 shows a CDI type electronic ignition system for an engine chain saw that has only a conventional mechanical braking device. Regardless of the high or low engine speed, the ignition is performed every cycle of the engine, so that the engine produces the best output. The ignition system is also designed to operate so as to emit . Therefore, when the safety braking device (not shown) enters the braking state, the engine speed is reduced by its braking force, but the rate of decrease in engine speed is significantly affected by the difference between the braking force and the engine output. box office. This means that the greater the engine output of the chain saw, the greater the braking force required, and the longer it takes for the chain to stop. Here, braking is completed when the engine speed drops to the speed at which the clutch of the chain saw's centrifugal clutch separates from the clutch drum that drives the saw chain.If the engine output is not transmitted to the saw chain during this period, then Since the braking force of the mechanical braking device only needs to brake the motion equivalent to the inertial mass of the rotating parts of the engine, the braking time is significantly shortened. Therefore, the above object can be achieved by preventing the engine output from being transmitted to the chain engine during the braking period. As a specific method, in the above-mentioned Japanese Patent Publication No. 47-47157, the operation of the ignition system is stopped in the above-mentioned braking rotation range (revolution speed above clutch-in), but in order to resume work, the braking must be released. In this case, it is necessary to restart the engine.

In an example of the engine ignition system used in the present invention shown in FIG. 2, an electronic ignition circuit B for steady engine operation, which is the same as that shown in FIG. Prevention electronic circuit A is connected. Although not shown, the circuit changeover switch 17, which is linked to the displacement of a known jerk-back detection lever in a mechanical braking system for an engine chain saw, is shown open and in a non-braking position.

In this ignition system, an electromotive force is generated in a power generating coil 2 by the rotation of a magnet rotor 1 connected to the crankshaft of the engine. The ignition capacitor 11 is charged by the forward electromotive force that passes through the diode 9 out of this electromotive force. That is, a circuit is formed in which the generating coil 2 → the diode 9 → the ignition capacitor 11 → the primary winding a of the ignition coil 4 → the ground → the generating coil 2.

Next, when an electromotive force in the opposite direction to the above is generated in the generating coil 2, the generating coil 2
→ Ground → Resistor 10 → Gate of SCR3 → SCR3
A circuit of cathode → diode 8 → generator coil 2 is formed, and SCR 3 is triggered.

When the SCR 3 is triggered, the electric charge charged in the ignition capacitor 11 is transferred to the ignition coil 4.
It is rapidly discharged through the primary winding a, forming a circuit of ignition capacitor 11 -> anode of SCR 3 -> cathode of SCR 3 -> diode 7 -> ground -> primary winding a of ignition coil 4 -> capacitor 11.

At this point, a current suddenly flows through the primary winding a of the ignition coil 4, so a high voltage is induced in the secondary winding b, generating a spark at the ignition plug 5, which is used to ignite the engine.

As described above, when the saw chain is not braking, the circuit is exactly the same as the conventional ignition circuit shown in FIG. does not affect the electronic ignition circuit B for steady engine operation at all.

Next, when brake is applied, the circuit changeover switch 17 is activated in conjunction with the displacement of the kickback sensing lever.
is closed. The signal coil 18 of the spark-cut type overspeed prevention electronic circuit A is manufactured so that its electromotive force is approximately proportional to the engine rotation, and when the engine is in the clutch-in rotation range, the signal coil 18 passes through the diode 15 as shown in Fig. 3 A and B. The forward electromotive force of the signal coil 18 peaks at the time when the ignition capacitor 11 starts charging. Note that there is no problem even if the electromotive force of the signal coil 18 varies slightly, as shown by the dotted line in FIG. 3B.

Here, when the saw chain is braked at a steady engine operating speed higher than the clutch-in speed, the over-speed prevention electronic circuit A acts to conduct the SCR3 with the electromotive force of the signal coil 18, and when the SCR3 conducts, the ignition capacitor 11 is not charged, and the electromotive force of the generating coil 2 is short-circuited by the SCR 3.

That is, signal coil 18 → circuit changeover switch 17
→ Diode 15 → Voltage regulator diode 13 → Resistor 12 → Diode 19 → Gate of SCR3 → SCR
3 cathode → diode 7 → ground → signal coil 18 circuit is formed, SCR 3 becomes conductive, generating coil 2 → diode 9 → anode of SCR 3 → cathode of SCR 3 → diode 7 → earth →
Since the circuit of the generating coil 2 is formed, the electromotive force of the generating coil 2 is short-circuited, and the ignition capacitor 11
is never charged. Therefore, since high voltage is no longer generated in the ignition coil 4, no ignition operation is performed, and the engine speed, combined with the action of the mechanical braking device, rapidly decreases.

Next, if the engine speed falls below the clutch-in speed while braking, the signal coil 18
The electromotive force becomes less than the Zener voltage of the constant voltage diode 13, and no current is supplied to the gate of the SCR3 from the spark cut type overspeed prevention electronic circuit A side, so that the SCR3 is connected to the electronic ignition circuit B for steady operation.
does not conduct until triggered by the current passing through the resistor 10, again producing a spark for ignition below the clutch-in speed.

Above, the case of the embodiment in which the signal coil 18 and the generator coil 2 are wound around different iron cores has been explained in FIGS.
No protection circuit is required. Note that the diode 16 and the diode 20 are also used to protect the circuit.

Next, when the signal coil 18 and the generator coil 2 are wound on the same iron core, the signal coil 18 is set so that the electromotive force has the opposite polarity to the generator coil 2.
By charging the capacitor 14 with an electromotive force shown by Va in FIG. 3C of the signal coil 18 and discharging it through the resistor 12, the phase of the current flowing to the gate of the SCR 3 is changed as shown by the dotted line in FIG. 3C. By keeping the SCR 3 in a conductive state until the electromotive force of the generator coil 2 that charges the ignition capacitor 11 is generated, charging of the ignition capacitor 11 can be prevented and the engine speed can be lowered.

As mentioned above, when the circuit selection switch 17 is closed, the ignition operation is stopped when the engine rotation is high and the voltage generated by the signal coil 18 is high.
The engine speed is low and therefore the signal coil 18
When the generated voltage is low, the ignition operation is performed below the clutch-in rotation speed. In other words, when the engine speed is high immediately after braking, the ignition does not operate, but when the engine speed is low and the centrifugal clutch is disengaged, the ignition operates, so the engine speed is set to the preset speed by the spark-cut type overspeed prevention electronic circuit A. It will not rise any higher. If this rotation is set below the clutch-in rotation speed of the chain saw, the engine rotation will be cut off from the saw chain immediately after the mechanical braking device operates while the safety braking device is operating. The time required to stop can be significantly shortened. During braking, transmission of the engine output to the saw chain side is stopped, so the service life of each part of the chain saw is extended.

In other words, in the conventional system, the engine continues to rotate at high speed even after the chain stops, and the centrifugal clutch remains engaged, but with the system of the present invention, the clutch is immediately disengaged, which prevents clutch slippage. It has advantages such as less damage due to overload.

Further, as shown in FIG. 4, it is also possible to connect the circuit changeover switch 17 shown in FIG. 2 in parallel with the signal coil 18. In this case, ON and OFF are reversed from the circuit changeover switch 17 shown in FIG.

FIG. 5 shows an example with a period detection type over-rotation prevention circuit C. This circuit C is slightly different from the voltage detection type one shown in FIG. 2 in its circuit configuration.

In other words, over-speed prevention circuit C is added to the CDI circuit in Figure 1.
(Diode D ₁ , D ₂ , D ₃ , SCR21, capacitor
C ₂ , resistors R ₂ and R ₃ ), and when the circuit selector switch 17 is opened in conjunction with the displacement of the kickback sensing lever, as in the embodiment shown in FIG.
Spark cut type overspeed prevention electronic circuit C is activated.
When the circuit changeover switch 17 is closed, the overspeed prevention circuit C is not activated, and the electronic ignition circuit B for steady engine operation is activated.

The over-rotation prevention circuit C shown in FIG. 5 is configured such that when the circuit changeover switch 17 is opened and an electromotive force is generated in the generating coil ₂ with the waveform shown in FIG. ₃ → Capacitor C ₂ → Diode 8 → Capacitor in the circuit of generator coil 2
By charging C ₂ and the voltage formed by resistors R ₂ and R ₃
When the voltage on capacitor _C2 rises to a voltage at which the gate of SCR21 is triggered, SCR21 becomes conductive. When this SCR21 becomes conductive, the capacitor
During the time constant determined by C ₂ and resistor 10, the charge on capacitor C ₂ changes from capacitor C ₂ → SCR21 → resistor 1
0 → gate of SCR3 → cathode of SCR3 → capacitor C ₂ The circuit of C2 discharges through the gate and cathode of SCR3, and SCR3 becomes conductive.
Capacitor 11 → SCR 3 → Diode D ₁ → Diode 7 → Primary winding a of ignition coil 4
→A circuit of the capacitor 11 is formed, and the charge of the capacitor 11 flows to the primary winding a of the ignition coil 4, is transmitted to the secondary winding b, and is discharged at the ignition plug 5. Then, as the rotation increases, charging should be performed in the circuit of capacitor C ₂ → primary winding a → capacitor 11 → generator coil 2 during the conduction period of the time constant determined by the capacitor C ₂ and resistor 10 of SCR 3. An electromotive force of V ₂ is generated, but the electromotive force of the generating coil 2 is short-circuited via the SCR 3, and the ignition capacitor 11 is not charged. When the braking device is released and the circuit selection switch 17 is closed,
During the period of V ₁ in Figure 6, generator coil 2 → switch 1
7 -> resistor 10 -> gate of SCR3 -> cathode of SCR3 -> diode 8 -> generating coil 2 circuit is formed, capacitor _C2 of overspeed prevention circuit C is not charged, and normal ignition is performed.

As described above, according to the configuration of the present invention, when the sensing lever is in the non-braking position, the electronic ignition circuit for steady engine operation is activated, and when it is in the braking position, the spark cut type over-speed prevention electronic circuit is activated.
In addition to significantly shortening the braking time of Sochien,
Since the engine does not stop even when the brake system is activated, work can be resumed immediately, and wear and tear on the clutch and brake system can be reduced, which has great practical effects.

[Brief explanation of the drawing]

Figure 1 shows a conventional CDI ignition system, Figure 2 shows an ignition system with a spark cut type overspeed prevention electronic circuit according to the present invention, and Figure 3 A and B show the voltage of the electromotive force generated in the generator coil and signal coil. 4 is another actual circuit diagram of the circuit changeover switch, and FIG. 5 is another embodiment of the spark cut type according to the present invention. FIG. 6 is a cycle diagram showing the voltage of the generating coil of the ignition device of FIG. 5. A...Voltage detection type spark cut type overspeed prevention electronic circuit, B...Electronic ignition circuit for steady engine operation,
C...Periodic detection type spark cut type overspeed prevention electronic circuit.

Claims (1)

[Scope of utility model registration request] A sensing lever is provided which detects the jerking phenomenon and induces mechanical braking of the soot chain, and a circuit changeover switch is provided which operates an electronic ignition circuit B for steady engine operation when the sensing lever is in a non-braking position. When the sensing lever is in the braking position, a spark cut-type overspeed prevention electronic circuit A is operated to operate the engine at a speed below the clutch-in speed, and the engine is operated at a low speed even during braking, so that restarting the engine is not required. A safety braking device for engine chainsaws featuring: