JPS63625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a starting device for a two-stroke engine mounted on a two-wheeled motor vehicle.

Conventionally, this type of device involves intervening a one-way clutch in the starting system that transmits the rotational driving force of a kickshaft or other starting shaft to the crankshaft of a two-cycle engine, and returns the starting shaft to a non-driving position after a starting operation. It is known that the crankshaft is prevented from reversing when the engine is stopped; however, in this case, the clutch is configured to immediately engage and stop the reversal of the crankshaft when the crankshaft is reversed. According to this, if abnormal combustion occurs due to a misalignment of ignition timing and the crankshaft is reversed, an abnormal non-return load immediately after the explosion may act on the starting system. It is desirable to reduce this and ensure the strength of the starting system.

It is an object of the present invention to provide a device that satisfies such demands, and in which a one-way clutch is inserted into a starting system that transmits the rotational driving force of a starting shaft to the crankshaft of a two-stroke engine, the clutch is configured in a ratchet type, and its meshing position is set within a crank angle range between the valve closing point of the exhaust port of the engine and 20 degrees from the bottom dead center side with the starting shaft in the non-driving position. It is characterized by what it did.

Next, one example of implementing the present invention will be explained with reference to attached drawings.

The drawing shows a power unit mounted on a two-wheeled motor vehicle, and the unit is of a so-called swing type in which a transmission case 2 with an engine 1 attached to one side of its front end is pivotally supported on an axle 3a of a rear wheel 3 on one side of its rear end. The engine 1 is a two-stroke engine having an exhaust port 6 and a scavenging port 7, which are opened and closed by an internal piston 5, on the side of the cylinder 4,
The case 2 has a chain or other power transmission system 10 therein which connects a crankshaft 8 connected to the piston 5 to the axle 3a via an automatic centrifugal clutch 9 at its outer end, and further includes a power transmission system 10 in the middle of the case 2. The crankshaft 8 is provided with a starting system 12 that connects a starting shaft 11 to the crankshaft 8. The starting shaft 11 is constituted by a kick shaft having a kick arm 11a at the outer end, and is always stopped at the non-drive position shown in the second figure by a return spring 13 and a stopper 14.

The starting system 12 includes a gear mechanism 17 and a chain mechanism 18 that connect the starting shaft 11 to a driven shaft 16 via an intermediate shaft 15, and a one-way clutch 19 that connects the driven shaft 16 to the crankshaft 8. , the clutch 19 functions to prevent a counterclockwise reversal of the crankshaft 8 relative to the driven shaft 16 in FIG. When the starting rotation is clockwise, normal clockwise rotation is applied to the crankshaft 8 via the clutch 19;
When the clutch 1 returns to the non-driving position by the return spring 13, the driven shaft 16 is prevented from rotating, and the clutch 1
9 prevents the crankshaft 8 from rotating in reverse. In this case, the check load is received by the stopper 14 of the starting shaft 11 via the starting system 12.

Although the above is not particularly different from the conventional type described above, according to the present invention, the clutch 19 is configured as a ratchet type, and its meshing position is set to the exhaust gas when the starting shaft 11 is in the non-driving position. The crank angle was set within a range of 20 degrees between the valve closing point A of port 6 and the bottom dead center B side.

More specifically, the clutch 19 has a ratchet wheel 20 on the driven shaft 16 and a pair of symmetrically positioned pawls attached to the drive plate 21 of the centrifugal clutch 9 on the crankshaft 8. Piece 2
2, 22, the ratchet wheel 20
A pair of first claw teeth 23, 23 are formed in symmetrical positions to each other, so that when the crankshaft 8 is reversed from the top dead center C side, each claw piece 22 touches each first claw tooth 23. In the illustrated example, the ratchet wheel 20 is provided with a pair of second pawl teeth 2.
4 and 24, so that each claw piece 22 is engaged with each second claw tooth 24 at a second engagement position near the bottom dead center B in addition to the first engagement position in the above range.

In the illustrated example, the valve closing point A is at a crank angle of 115 degrees from the top dead center C, and the first meshing position is set at a crank angle of 120 degrees from the top dead center C.
Further, the second meshing position is preferably shifted by 50 degrees from the first meshing position between the first meshing position and the bottom dead center B.

Next, to explain its operation, the one-way clutch 19 prevents the crankshaft 8 from reversing when the engine is stopped and the crankshaft 8 receives the compression reaction force of the piston 5 from near the top dead center C and reverses, or when the one-way clutch 19 prevents the crankshaft 8 from reversing. It is carried out when a reversal occurs,
In the case of the explosion, the pressure in the combustion chamber due to the explosion is gradually reduced by the downward movement of the piston 5 as the crankshaft 8 reverses, and when the closing point A of the exhaust port 6 is exceeded, the explosion pressure is released from the port 6 and the reverse occurs. The dead load is also reduced.

Figure 3 is a diagram showing the change in check load with respect to the change in the first meshing position of the one-way clutch 19 when a lock occurs, where the horizontal axis is the crank angle from top dead center C and the vertical axis is when the engine is stopped. It shows the ratio of the check load when the check load due to the reverse rotation of the crankshaft 8 is set to 1.

From the diagram, if the crank angle from the top dead center C of the engagement position is set above the valve closing point A, the check load due to the butt will be smaller than the normal check load when the engine is stopped, but from the valve closing point A. If it exceeds 20 degrees, it will not decrease any further, and in this case, considering that it is desirable to move the meshing position closer to the top dead center C side in order to reduce the starting load, the first meshing position should be closed as described above. It turns out that it is best to set the crank angle between point A and 20 degrees from bottom dead center B.

In this case, the angle between the first meshing position and bottom dead center B increases, so that when the engine is stopped, the crankshaft 8 rotates forward past top dead center C and stops near bottom dead center B. If this happens, the play between the crankshaft 8 being rotated through the one-way clutch 19 at the time of starting becomes large and operability deteriorates. If provided, the crankshaft 18 will be rotated via the clutch 19 immediately upon startup, and operability will not be impaired. As described above, according to the present invention, the engagement position of the one-way clutch is set at a crank angle between the valve closing point of the exhaust port and 20 degrees toward the bottom dead center.
According to this, without increasing the starting load,
This has the effect of reducing as much as possible the check load acting on the starting system due to the butt.

[Brief explanation of the drawing]

Fig. 1 is a cutaway plan view of a power unit of a two-wheeled motor vehicle equipped with the device of the present invention, Fig. 2 is a cutaway side view of the main parts of the device of the present invention, and Fig. 3 is a non-return check against changes in the engagement position of the one-way clutch. FIG. 3 is a diagram showing changes in load. 1...Engine, 6...Exhaust port, 8...Crankshaft, 11...Starting shaft, 12...Starting system, 1
9... One-way clutch, A... Valve closing point, B...
...Bottom dead center, C...Top dead center.

Claims (1)

[Scope of Claims] 1. In a system in which a one-way clutch intervenes in a starting system that transmits rotational driving force of a starting shaft to a crankshaft of a two-cycle engine, the clutch is constructed in a ratchet type, and its meshing position is adjusted according to A starting device for a two-stroke engine, characterized in that the crank angle is set within a range of 20 degrees between the valve closing point of the exhaust port of the engine and the bottom dead center side when the starting shaft is in a non-driving position. 2. The two-stroke engine starting device according to claim 1, wherein the clutch has a second engagement position near the bottom dead center of the crank angle in this state.