JPS634006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust valve that is housed near the upper edge of an exhaust port of a two-stroke engine and that changes exhaust timing by its rotation.

In a port exhaust type two-stroke engine, it is preferable to advance the exhaust timing in order to improve power performance at high speeds. On the other hand, in order to reduce blow-by of fresh air at low speeds, improve fuel efficiency, and stabilize combustion, it is preferable to delay the exhaust timing compared to when the engine is at high speeds. Therefore, in order to change the exhaust timing in accordance with the operating conditions, it has been considered to provide a rotatable exhaust valve near the upper edge of the exhaust port.

However, this exhaust valve is exposed to exhaust gas, especially when operating at low speeds for long periods of time.
Lubricating oil may adhere to the exhaust valve, and the lubricating oil may be baked and solidified by the high-temperature exhaust gas, resulting in carbon deposits. In such a case, the deposits tend to get stuck between the exhaust valve and the exhaust valve accommodating portion, and the exhaust valve may not rotate smoothly.

This invention was made in view of the above circumstances, and an object of the present invention is to provide an exhaust valve for a two-stroke engine that can quickly remove even if carbon is deposited and can rotate smoothly at all times. shall be.

In order to achieve this object, the present invention includes a rotatable drive plate and a large number of laminated plates stacked along the rotational axis of the drive plate, the laminated plates having adjacent laminated plates out of phase. The laminates are connected to each other so as to rotate together with the drive plate, and the adjacent laminated plates are slightly shifted from each other when the drive plate is rotated in the forward and reverse directions. The present invention will be described in detail below based on embodiments shown in the drawings.

Fig. 1 is a cross-sectional view showing one embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the line - Fig. 3 is a vertical cross-sectional view of the exhaust valve, Fig. 4 is a right side view thereof, and Fig. 5 is a cross-sectional view of the exhaust valve. 4 is a sectional view taken along the line -V in FIG. 4. FIG. In Figs. 1 and 2, reference numeral 10 indicates a water-cooled cylinder block;
2 is a cylinder sleeve cast into this cylinder block 10. 14 is a combustion chamber,
It is formed by a cylinder head 16, a piston 18 and a cylinder sleeve 12. Reference numeral 20 denotes an intake passage, and a reed valve (not shown) is installed in this intake passage 20 to prevent intake air from blowing back. This intake passage 20 opens into the cylinder sleeve 12, and this opening opens into the piston 1.
The intake port 24 communicates with the crank chamber 22 when the piston 8 is raised, and the combustion chamber 1 when the piston 18 is lowered.
This is a scavenging port 26 that communicates with 4. 2
Reference numerals 8 and 30 are a main scavenging port and an auxiliary scavenging port that open into the cylinder sleeve 12, respectively.

32 is an exhaust passage, and 34 is an exhaust port. An exhaust valve accommodating portion 36 is formed on the inner wall of the exhaust passage 32 near the upper edge of the exhaust port 34 . A part of this exhaust valve accommodating portion 36 is the exhaust passage 3.
2, and both axial ends thereof are opened to the outer surface of the cylinder block 10 through passages 38 and 40 having substantially the same cross section as both ends of the clutch-shaped portion. (Figure 2). Note that 42 is a spark plug, and 44 is a cooling water passage. Cooling water flows into this cooling water passage 44 from an inlet 46 (FIG. 2) that opens on the side of the cylinder block 10, and this cooling water flows into the cylinder head. The water flows out through 16 outlets (not shown).

50 is an exhaust valve. This exhaust valve 50
comprises a disk-shaped drive plate 52 and an end plate 54, and a large number of laminated plates 56 laminated along the rotational axis A between the drive plate 52 and the end plate 54, and a second,
As is clear from FIG. 5, the entire structure is formed into a substantially cylindrical shape. The exhaust valve 50 is housed in the exhaust valve accommodating portion 36 as shown in FIGS.
6 is cut out so as to be smoothly continuous with the inner surface of the exhaust passage 32, and this cutout 58 forms a part of the exhaust passage 32.
It becomes part of the inner world of 2.

A drive shaft 60 is integrally formed on the drive plate 52,
The rotation axis A of these drive plates 52 and drive shafts 60
A support shaft 62 is press-fitted and fixed to the drive plate 52 in parallel with (FIGS. 3 and 4). In this embodiment, the center axis B of the support shaft is eccentric from the rotation axis A by a distance a. A large number of laminated plates 56 are supported on the support shaft 62 so that each of the laminated plates 56 can rotate independently, and furthermore, the end plate 54 is similarly rotatably attached to the end thereof, These are prevented from falling off by a retaining ring 64 attached to the support shaft 62. 66 is a tapered pin. This pin is press-fitted into the drive plate 52 so as to be eccentric to the rotational axis A and parallel to the support shaft 62. On the other hand, this pin 6 is attached to a large number of laminated plates 56 and end plates 54.
A through hole 68 is formed at a position corresponding to 6 so as to have the same diameter in the longitudinal direction, and this pin 66 is inserted into this through hole 68. Therefore, the rotational gap formed between the inner surface of the through hole 68 and the pin 66 gradually becomes larger as the distance from the drive plate 52 increases. That is, this gap is different for adjacent laminates.

Note that this exhaust valve 50 is provided with a second through hole 70 that is different from the through hole 68, as is clear from FIGS. 1, 4, and 5. This second through hole 70 is used when processing the surfaces of a large number of laminated plates 56. That is, the pin 66 is connected to the drive plate 5.
2, the laminated plate 56 and the end plate 54 are attached to the support shaft 62 that has been press-fitted and fixed to the drive plate 52 in advance, and a cylindrical shaft (see FIG. After inserting a long bolt (not shown) into the second through hole 70, the whole is firmly connected. In this state, the laminate 5
6 is processed into a smooth substantially concave shape, and a notch 58 is formed. After this process is completed, the long bolt is removed and the tapered pin 66 is press-fitted into the drive plate 52 in place of the cylindrical shaft. Then, half of the large number of laminated plates 56 is attached to the support shaft 62 and pin 66 on the drive plate 52 side, and inserted into the valve housing part 36 from the passage 38 side shown in FIG. 2, while the remaining laminated plates 56 and The end plate 54 is inserted from the other passage 40 and attached to the support shaft 62 and pin 66. Finally, by attaching the retaining ring 64 to the end 62, loading of the exhaust valve 50 into the exhaust valve accommodating portion 36 is completed.

In FIG. 2, 72 and 74 are bearing members,
The bearing member 72 is fitted into the passage 38 so that the drive shaft 60 is supported by a bearing 76, and a seal member 78 is fitted between the bearing member 72 and the drive shaft 60. The bearing member 74 is fitted from the passage 40 and supports the inner surface of the cylindrical portion 80 formed in the end plate 54 by the bearing 82 .

Next, the operation of this exhaust valve 50 will be explained. FIG. 6 is a sectional view taken along the line -- in FIG. 3 to show its operating state. The drive plate 52 is a drive shaft 60
The valve is rotated by a valve drive mechanism (not shown) in accordance with the engine rotation speed. When the engine speed decreases, the drive plate 52 rotates clockwise for the first time to delay the exhaust timing, but at this time, the gap between the pin 66 and the through hole 68 in the rotational direction is Since the direction changes, each laminated plate 56 sequentially rotates with a delay as it moves away from the drive plate 52, causing a phase shift. FIG. 6A shows this situation. Conversely, when the engine speed increases,
The drive plate 52 rotates counterclockwise in FIG. 1, and each laminated plate 56 rotates with a delay as it moves away from the drive plate 52, causing a phase shift. FIG. 6B shows this situation. In this way, when the driving plate 52 is forward or reversed, each adjacent laminated plate 56 rotates with a phase shift, so carbon adhering to the outer periphery of each laminated plate 56, that is, the surface of the exhaust valve 50, is easily removed. take off.

Next, the effect of the center axis B of the support shaft 62 being eccentric with respect to the rotation axis A of the exhaust valve 50 will be explained. FIG. 7 is an explanatory diagram showing the effect in an exaggerated manner. If the drive plate 52 now rotates clockwise about the rotation axis A, the central axis B of the support shaft 62 moves in the same direction on an arc with an eccentric distance a. Therefore, since the gap between the pin 66 and the through hole 68 has the effect of delaying rotation, each laminated plate 56 is displaced so as to twist the surface of the exhaust valve 50, thereby further preventing carbon from falling off. It can be promoted.

In the above embodiment, the pin 66 is tapered, and the diameter of the through hole 68 is constant in the length direction, so the delay in rotation of the laminated plate 56 increases as it moves away from the drive plate 52. However, it goes without saying that the intended purpose of the present invention can be achieved by connecting the laminated plates so that adjacent laminated plates rotate with a phase shift. Therefore, for example, the pin may be formed with two tapered surfaces such that both ends have the same diameter and the center portion becomes narrower, or it may be formed with two or more tapered surfaces. Further, the inner surface of the through hole may be tapered.

Further, in this embodiment, the drive plate 52 is connected to the valve 50.
Although it is provided at one end, a drive plate is placed near the center of the valve, and half of the laminated plates are pivotally supported by the drive shaft of this drive plate, and pins are provided protruding from both sides of the drive plate. is also possible.

Furthermore, the exhaust valve 50 in this embodiment
As is clear from the figure, the surface of the exhaust valve is formed smoothly, but if a large number of grooves approximately parallel to the rotational axis A are formed on the surface of the exhaust valve facing the inner surface of the exhaust valve accommodating portion 36, carbon can be removed. Even if carbon adheres, the area in contact with the inner surface of the accommodating portion 36 is reduced, and the carbon falls into this groove, allowing the exhaust valve to rotate more smoothly.

As described above, in this invention, when the drive plate is rotated, the adjacent laminated plates are rotated with a phase shift, so that the carbon attached to the adjacent laminated plates is removed from the exhaust gas. The carbon is easily crushed by the relative movement between the laminated plates when the valve is rotated, and the carbon easily falls off. As a result, even if carbon adheres to the exhaust valve surface, such as after operating the engine at low speed for a long time, rotating the exhaust valve will cause the carbon to fall off and the exhaust valve will always rotate smoothly.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an engine showing an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the line - Fig. 3 is a vertical cross-sectional view of an exhaust valve, and Fig. 4 is a right side view thereof.
5 is a cross-sectional view taken along the line -- in FIG. 4, FIG. 6 is a cross-sectional view taken along the line -- in FIG. 3 to show the operation of the exhaust valve, and FIG. 34...Exhaust port, 50...Exhaust valve, 5
2... Drive plate, 56... Laminate plate, A... Rotation axis line.

Claims (1)

[Claims] 1. A rotatable drive plate in a two-cycle engine exhaust valve that is housed near the upper edge of the exhaust port and changes the exhaust timing by its rotation;
A large number of laminated plates are stacked along the rotational axis of the driving plate, and the laminated plates are connected so that adjacent laminated plates rotate with a phase shift. Exhaust valve for 2-stroke engine.