JPH0316488B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust valve driving device for a two-stroke engine having an exhaust valve whose exhaust timing can be adjusted.

[Prior Art] In a two-stroke engine, the timing of exhaust from the exhaust port affects the output performance of the engine, so an exhaust valve is provided at the exhaust port, and this exhaust valve is driven by a governor mechanism that is linked to the crankshaft. The applicant has attempted to increase the output performance by advancing the exhaust start timing when the engine rotates at high speeds and by delaying the exhaust start timing when the engine rotates at low speeds. (For example, see Utility Model Application Publication No. 55-23421.) In addition, a piston that is displaced by receiving the discharge pressure of the pump is provided in the discharge side passage of the lubricant oil pump that rotates in conjunction with the rotation of the crankshaft. The applicant has attempted an exhaust valve driving device in which the displacement of the piston is linked to the rotation of the exhaust valve in accordance with the amount of displacement. (For example, JP-A-55-19968
By the way, in the above-mentioned conventional technology, the former uses a clutch drive gear to extract power for driving the governor mechanism from the crankshaft, and a primer drive for extracting the power through the clutch. There was a problem in that it was taken out from a separate gear, making it difficult to select its installation position. In addition, since the rotor shaft for the governor is arranged perpendicular to the crankshaft, a worm gear must be used for transmission between the two, which is disadvantageous in terms of power transmission and cost. Since the movable member is provided on a cantilevered shaft, the axis line is tilted, making it difficult to accurately control the exhaust valve.

Furthermore, the latter method uses fluid pressure from a pump to transmit power to the governor, and because the pump is located below the crankshaft, the fluid flow path is long, resulting in poor responsiveness during gear changes. It was hot.

The present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to provide a system in which both a clutch drive gear and a governor drive gear are engaged with the primary drive gear for power extraction. In addition, the present invention aims to provide an exhaust valve driving device in which a governor mechanism for driving the exhaust valve is arranged on the opposite side of the clutch with respect to the crankshaft, thereby solving the above-mentioned problems and facilitating the installation of the governor mechanism. It is.

[Means for Solving the Problems] In order to achieve the above object, the exhaust valve drive device of the present invention includes an exhaust valve that is arranged in front of the cylinder block to drive the exhaust timing from the exhaust port in an adjustable manner. In a two-stroke engine,
A clutch drive gear is engaged with the primary drive gear at the end of the crankshaft, a rotor shaft parallel to the crankshaft is supported between the crankcase and the crankcase cover, and a governor drive is pivotally supported by the rotor shaft. meshing the gears so that they are above the primary drive gear and forward of the clutch drive gear;
A governor mechanism for driving the exhaust valve is disposed on the governor drive gear, and a slider of the governor mechanism is provided so as to be slidable in the axial direction on the rotor shaft shaft.

[Function] The rotation of the engine is extracted from the crankshaft through a transmission mechanism such as a clutch and a transmission as power for driving the wheels, but this rotation of the crankshaft is extracted from the crankshaft through a governor mechanism for driving the exhaust valves. The exhaust timing is adjusted and driven according to the engine rotation speed. The rotor shaft of this governor is arranged parallel to the crankshaft, so a spur gear is used for power transmission, and the rotorshaft is supported on both ends, so it is supported reliably, and the governor mechanism is parallel to the crankshaft. Since the governor mechanism is installed on the opposite side from the clutch, a sufficient installation space can be secured, and since the slider of the governor mechanism is provided so as to be slidable in the axial direction on the rotor shaft shaft, a wide sliding range can be obtained.

[Embodiments] Examples of the present invention will be described below with reference to the drawings.

In the figure, numeral 1 is a cylinder block, 2 is a cylinder head, 3 is a connecting rod, and 4 is a crankshaft. The conrod 3 is connected to a crankshaft 4 via a crank 4a. crankshaft 4
A primary drive gear 7 is fixed to the shaft end of the primary drive gear 7, and the primary drive gear 7 meshes with a governor drive gear 8 at its upper portion to drive the governor mechanism 6. The governor drive gear 8 is fixed to the rotor shaft 9 by a key 10a and rotates as a unit, and its movement in the axial direction is fixed by a washer 11 and a circlip 12. The rotor shaft 9 is parallel to the crankshaft 4 and is supported on both sides by a crank case 38 and a crank case cover 39. A slider 13 is further rotatable integrally with the rotor shaft 9 and is axially supported. It is fixed by a key 10b so as to be slidable.
A plurality of steel balls 1 are disposed between the outer end of the slider 13 and a guide plate 14 fixed to the rotor shaft 9.
A spring guide 17 is provided at the inner end of the slider 13, and a spring 18 is provided on the governor drive gear 8 side and tensioned between the spring guide 16 and the spring guide 16. . The spring 18 provides an elastic force that presses the slider 13 toward the guide plate 14. Shift fork 19 for slider 13
The other end of the shift fork 19 is fixed to the shaft lever 20. Therefore,
When the slider 13 slides in the axial direction, the engaging portion of the shift fork 19 also moves accordingly.
The shift fork 19 swings about the shaft lever 20, and the shaft lever 20 rotates. A lever 21 is further fixed to the other end of the shaft lever 20, and swings as the shaft lever 20 rotates. Lever 2
A joint 22 is rotatably attached to the swinging end of 1. On the other hand, at the exhaust port 23, another joint 26 is rotatably attached to a holder 25 fixed to the shaft end of the exhaust valve 24. An adjustment bolt 27 whose length is adjustable is connected between the joints 22 and 26. and,
The exhaust valve 24 is arranged in front of the cylinder block 1.

A shift fork 28 different from the shift fork 19 is engaged with the slider 13 at the same time,
The shift fork 28 is swingable about a shaft 28a, and a rod 29 having a spherical end is rotatably engaged with the other end.
The rod 29 is integrally fixed to the axis of the screw 30, and is adapted to move in the front and rear directions as the screw 30 rotates. An arm 31 is integrally fixed to the shaft end of the screw 30, and one end of a wire 32 is engaged with the end of the arm 31. The other end of the wire 32 is engaged with the end of a claw arm 33 that is pivotally supported by a shaft 33a. The claw portion 33b of the claw arm 33 is in contact with the circumferential surface of a cam 35 fixed to a kick shaft 34 for starting the engine. The cam 35 has a plurality of protrusions 35a and recesses 35b arranged alternately on its circumferential surface, and the claws 33b of the claw arm 33 are normally in contact with the recesses 35b.

The primary drive gear 7 fixed to the shaft end of the crankshaft 4 further includes a clutch drive gear 3.
6, and as used in general motorcycles, the power from the engine is transmitted to the primary drive gear 7 and the clutch drive gear 3.
6. Transmit driving power to the wheels via a transmission mechanism such as a clutch 37 and a transmission. The governor drive gear 8 is connected to the clutch drive gear 3.
Primary drive gear 7 ahead of 6
It has become a good fit.

Generally, the power take-off section from the crankshaft is constructed in this way, so as can be seen from the drawings, there is a fairly large space in the front upper part of the crankshaft on the opposite side of the clutch. This invention places a governor mechanism in this space.

In the above-mentioned device, when the engine is started, the rotor shaft 9 rotates due to the engagement between the primary drive gear 7 and the governor drive gear 8 as the crankshaft 4 rotates, so that the steel balls 15 are rotated in the radial direction by centrifugal force. The slider 13 is moved toward the outside of the governor drive gear 8 against the elastic force of the spring 18.
By sliding this slider 13, the shift fork 1
9 swings, the shaft lever 20 rotates,
This rotation causes the lever 21, joint 22, adjustment bolt 27, joint 26, holder 2
5 to drive the exhaust valve 24.

Since the centrifugal force of the steel ball 15 is approximately proportional to the rotation speed of the crankshaft 4, the exhaust valve 24 is driven early when the speed is high, and slowly when the speed is low, and the exhaust timing is adjusted to optimize the engine output. Will have to adjust.

On the other hand, when starting the engine by rotating the kick shaft 34 via a kick pedal (not shown) from a stopped state of the engine, the cam 35
4, so the protrusion 35 on the circumferential surface of the cam 35
a and the recess 35b cause the claw arm 33 to swing. Due to the swinging movement of the claw arm 33,
The screw 30 rotates via the wire 32, and this rotation causes the rod 29 to move back and forth. Since the shift fork 28 swings due to the back and forth movement of the rod 29, the slider 13 slides back and forth, and thereafter the exhaust valve 24 is driven via the shift fork 19 in the same manner as in the case described above.

[Effects of the Invention] In this invention, a clutch drive gear is engaged with the primary drive gear at the end of the crankshaft, and the governor drive gear, which is supported by a rotor shaft parallel to the crankshaft, is connected to the primary drive gear at the upper part of the primary drive gear. The clutch is engaged forward of the clutch drive gear, and the governor mechanism for driving the exhaust valve is placed on the governor drive gear, so the power for driving the governor mechanism can be extracted easily and efficiently. It is possible to easily install the governor mechanism by making effective use of the upper space, and since the rotor shaft is parallel to the crankshaft, spur gears are used for transmission, allowing for quick transmission of power at low cost. It becomes possible. In addition, since the rotor shaft is supported on both sides, it is securely supported between the crankcase and crankcase cover, and since the governor mechanism is installed on the opposite side of the crankshaft from the clutch, there is sufficient installation space. Since the slider of the governor mechanism is provided so as to be able to slide in the axial direction on the rotor shaft shaft, a large sliding range can be obtained, so even if the displacement of the transmission member from the slider to the exhaust valve is small, the exhaust valve will not move. It can operate reliably and the transmission member can be made smaller. Furthermore, since the governor mechanism is located above and in front of the primary drive gear and the exhaust valve is installed in front of the cylinder block, the link mechanism that drives the exhaust valve becomes shorter, and the response of the exhaust valve becomes shorter. This has advantages such as improved properties.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a partial cross section of an embodiment of the present invention, and FIG. 2 is a longitudinal front view thereof. 1...Cylinder block, 4...Crankshaft,
6... Governor mechanism, 7... Primary drive gear, 8... Governor drive gear, 9... Rotor shaft, 13... Slider, 23... Exhaust port, 24... Exhaust valve, 36... Clutch drive gear, 37...Clutch, 38...Crankcase, 39...Crankcase cover.

Claims (1)

[Claims] 1. In a two-stroke engine equipped with an exhaust valve installed in front of the cylinder block to adjust the timing of exhaust from the exhaust port, a clutch drive gear is engaged with the primary drive gear at the end of the crankshaft, and the clutch drive gear is engaged with the primary drive gear at the end of the crankshaft. The rotor shaft parallel to the is supported on both sides between the crankcase and the crankcase cover,
A governor drive gear pivotally supported by the rotor shaft is engaged with the primary drive gear so as to be forward of the clutch drive gear, and a governor mechanism for driving an exhaust valve is disposed on the governor drive gear. 1. An exhaust valve driving device characterized in that a slider is provided on the rotor shaft shaft so as to be slidable in the axial direction.