JPH065014B2 - Exhaust control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust control device for a two-cycle engine.

(Prior art and its problem) A conventional exhaust control device includes, for example, a sub-exhaust port on the side of a main exhaust port, and opens the sub-exhaust port with respect to the main exhaust port during high-speed rotation, thereby overrunning during high-speed rotation. The run characteristics are improved. Also, the auxiliary exhaust port is completely closed from the time the engine is stopped until the engine rotates at high speed.

(Object) An object of the present invention is to make the auxiliary exhaust port open even when the engine is stopped and at extremely low speed rotation, thereby reducing the compression ratio when the engine is stopped and at extremely low speed rotation and causing it to function as a decompression device. , Thereby improving the engine starting performance and improving the instability of rotation at extremely low speed rotation due to torque fluctuation.

(Means for Achieving the Purpose) In order to achieve the above-mentioned object, the present invention forms a sub-exhaust port on the side of a main exhaust port opening in a cylinder, and an outlet end of the sub-exhaust port on the main exhaust port side. An opening / closing valve is provided in the section to open the auxiliary exhaust port to the main exhaust port when the engine is stopped or at extremely low speed, close the auxiliary exhaust port to the main exhaust port at medium speed rotation, and open the auxiliary exhaust port at high speed rotation. The auxiliary exhaust port is configured to open with respect to the main exhaust port, and the upper end edge of the auxiliary exhaust port is located closer to the top wall than the upper end edge of the main exhaust port, so that the auxiliary exhaust port has an exhaust timing that is higher than that of the main exhaust port. The cylinder is opened at an early position.

(Embodiment) FIG. 4 is a development view of the inner peripheral surface of a cylinder of a two-cycle engine to which the present invention is applied. In FIG. 4, auxiliary cylinders on both left and right sides of a main exhaust port 2 opening in the cylinder 1 are shown. An exhaust port 3 is formed, and each sub exhaust port 3 opens in the cylinder 1. The upper edge (edge on the top dead center side) of the opening of the sub exhaust port 3 is formed higher than the upper edge of the opening of the main exhaust port 2, so that the exhaust timing of the sub exhaust port 3 is better. Is configured to be earlier than the exhaust timing of the main exhaust port 2.

1, the main exhaust port 2 extends forward from the cylinder 1 and is connected to, for example, an exhaust pipe (not shown). The sub exhaust port 3 extends forward, and the front end thereof faces the middle portion of the main exhaust port 2. A column-shaped on-off valve 6 is rotatably provided at an outlet portion of the sub-exhaust port 3 on the main exhaust port 2 side, and a passage 7 perpendicular to the axial direction of the on-off valve 6 is formed in the on-off valve 6. .

The open / close valve 6 is integrally provided with a drive pinion 8 on the same axis, and each drive pinion 8 engages with a drive rack 10 parallel to a line connecting the centers of both the open / close valves 6 and the rack length of the drive rack 10. Both opening / closing valves 6 simultaneously rotate in the same rotation direction by the movement in the vertical direction, whereby the auxiliary exhaust port 3 is opened / closed with respect to the main exhaust port 2.

The drive rack 10 is supported in the hole of the cylinder block 4 so as to be movable in the rack length direction, protrudes to the outside of the cylinder block 4, and the rack sleeve 1 is attached to the protruding tip.
Equipped with 2. A pin 13 is engaged with the rack sleeve 12, and the pin 13 is fixed to a rack drive shaft 16 via an arm 15 that swings left and right. The rack drive shaft 16 extends rearward and is rotatably supported by the cylinder block 4, and a pin 20 is fixed to a rear end of the rack drive shaft 18 via a swing arm 18. The pin 20 is engaged with a governor sleeve 22 of a governor mechanism 21. is doing.

5, the governor mechanism 21 is, for example, a mechanical governor using a ball weight 24, and the concave body 26 fixed to the governor shaft 25 and the governor shaft 25. Is provided with a governor sleeve 22 that is axially movably fitted to the concave surface body 26 side and is biased by a spring 27. The governor sleeve 22 is integrally provided with a dish-shaped cam surface body 28 facing the concave surface body 26. A plurality of ball weights 24 are sandwiched between the cam surface body 28 and the concave surface body 26. A first cam surface 30 on the axial center side and a second cam surface 31 on the radially outer side are formed on the cam surface body 28.

The state of the governor mechanism 21 of FIG. 5 corresponds to the state of FIG. 1, the state of the governor mechanism 21 of FIG. 6 corresponds to the state of FIG. 2, and the state of the governor mechanism 21 of FIG. 7 is the third state. It corresponds to the state in the figure. Specifically, the open / close valve 6 and the governor mechanism 2
1 is linked and linked in the following relationship.

When the engine speed is from 0 to 2000 rpm, the ball weight 24 is located on the axial center side as shown in FIG. 5, and the auxiliary exhaust port 3 is positioned relative to the main exhaust port 2 as shown in FIG. Keep it slightly open.

When the engine speed is around 2000 rpm, the ball weight 24 shown in FIG. 5 moves outward while pushing the first cam surface 30 in the direction of arrow B, and reaches the outer peripheral end of the first cam surface 30 as shown in FIG. As a result, the rack 10 is moved in the direction of arrow A from the state of FIG. 1 to rotate the opening / closing valve 6 in the direction of arrow S, and the auxiliary exhaust port 3 is closed as shown in FIG.

The state shown in FIG. 2 and FIG. 6 is maintained between about 2000 rpm and 5500 rpm.

And around 5500 rpm, the ball weight 2 in FIG.
4 moves outward while pushing in the direction of arrow B on the second cam surface 31, thereby moving the rack 10 from the state shown in FIG.
Direction to rotate the open / close valve 6 in the direction of arrow S,
The auxiliary exhaust port 3 is fully opened as shown in FIG.

At 5500 rpm or more, the governor mechanism 21 is held in the state shown in FIG. 7, and the open / close valve 6 is held in the fully opened state shown in FIG.

That is, when the rack 10 is moved by the operation of the governor mechanism 21, the opening / closing valve 6 partially opens the auxiliary exhaust port 3 with respect to the main exhaust port 2 as shown in FIG. The auxiliary exhaust port 3 is completely closed during rotation as shown in FIG. 2, and the auxiliary exhaust port 3 is fully opened with respect to the main exhaust port 2 during high speed rotation as shown in FIG.

(Operation) When the engine is stopped, the governor mechanism 21 is in the state shown in FIG. 5, and therefore the auxiliary exhaust port 3 is partially opened to the main exhaust port 2 as shown in FIG. , The compression ratio becomes low.

Therefore, the operation force at the time of starting, for example, the kick force in a motorcycle or the like can be small, and the starting becomes easy.

Even when the engine is rotating at an extremely low speed (for example, about 1600 rpm), the governor mechanism 21 is in the state shown in FIG. 5, so that the auxiliary exhaust port 3 partially includes the main exhaust port 2 as shown in FIG.
, The exhaust timing is early, and the compression ratio is low.

Therefore, the instability of the engine rotation due to the torque fluctuation at the extremely low speed rotation is improved, and the torque fluctuation becomes smooth, and the stable engine rotation can be obtained.

When the engine is rotating at a medium speed (approximately 2000 to less than 5500 rpm), the governor mechanism 21 is in the state shown in FIG. 6, and therefore, as shown in FIG. 2, the sub exhaust port 3 is fully closed and the compression ratio becomes high. The engine output is improved.

When the engine is rotating at high speed (more than 5500 rpm),
The governor mechanism 21 is in the state shown in FIG. 7. Therefore, as shown in FIG. 3, the auxiliary exhaust port 3 is fully opened with respect to the main exhaust port 2, and the compression ratio is lowered and the exhaust cross-sectional area is increased.

Therefore, the output at high speed rotation is improved and the overrun characteristic is also improved.

(Another embodiment) (1) The embodiment shown in FIGS. 8 to 10 is provided with an exhaust resonator chamber 32, and the opening / closing valve 6 of the auxiliary exhaust port 3 is used to open / close the resonator chamber 32 to / from the main exhaust port 2. This is a free example.

That is, when the engine is stopped and at extremely low speed, the resonator chamber 32 is closed to the main exhaust port 2 as shown in FIG. 8, and when the engine is rotating at medium speed, the resonator chamber 32 is opened to the main exhaust port 2 as shown in FIG. At the time of high speed rotation, the resonator chamber 32 is configured to be closed to the main exhaust port 2 as shown in FIG.

Since the resonator chamber 32 is opened during the medium speed rotation in FIG. 9, the resonance action of the resonator chamber 32 improves the output during the medium speed rotation.

(2) FIGS. 11 and 12 show a modified example of the auxiliary exhaust port 3, in which the slit 3a extending upward is formed at the upper edge of the auxiliary exhaust port 3. As shown in FIG. 12, the slit 3a has a substantially triangular cross section.

By providing the slit 3a, the compression ratio can be further reduced during extremely low speed rotation, while the influence on the speedup of the performance curve during high speed rotation can be reduced.

For example, if the slit 3a shown in FIG.
Assuming that characteristics such as the graph X1 in the figure are obtained, the entire sub exhaust port 3 is set to the first
If the position is high like the phantom line in FIG.
When the auxiliary exhaust port is fully opened as shown in graph X3 (range L)
The performance of moves to the high speed side too much, and the balance of the output characteristics as a whole is destroyed. On the other hand, the eleventh
By providing the slit 3a as shown in the figure, the compression ratio at the time of extremely low speed rotation can be made sufficiently small, but on the other hand, the overall balance of the output characteristics can be kept good as shown by the graph X2 in FIG.

(3) In the illustrated embodiment, one pair of left and right auxiliary exhaust ports 3 are provided, but the auxiliary exhaust port 3 may be provided on only one of the left and right sides.

(4) In the illustrated embodiment, the open / close valve is switched using a mechanical governor, but it may be electrically switched. For example, a rotation speed detection device and an opening / closing valve control device connected to the detection device are provided, and when the engine speed reaches 2000 rpm, the opening / closing valve 6 is switched from the state shown in FIG. 1 to the state shown in FIG. It is configured to switch from the state of 1 to the state of FIG.

(Effects of the Invention) According to the present invention as described above: (1) The auxiliary exhaust port 3 is formed on the side of the main exhaust port 2 opening in the cylinder 1, and the auxiliary exhaust port 3 is provided more than the main exhaust port. An opening / closing valve 6 is provided at the outlet end of the main exhaust port side of the sub exhaust port 3 that opens to the cylinder 1 at a position where the exhaust timing is early, and the sub exhaust port 3 is used as the main exhaust port 2 when the engine is stopped and at extremely low speed rotation. Since it is opened to the opposite side, the compression ratio can be lowered when the engine is stopped and at extremely low speed rotation.

As a result, when the engine is started, the starting operation force, for example, the starting kick force of a motorcycle or the like, is small, which facilitates starting, and when the engine is started at an extremely low speed such as idling, the compression ratio becomes low, which reduces the torque. The instability of the engine rotation due to the fluctuation is improved, the torque fluctuation becomes smooth, and the stable engine rotation can be obtained.

(2) Since the auxiliary exhaust port 3 is closed and the compression ratio is increased during the medium speed rotation, the output in the medium speed range is improved and the pickup (rapid acceleration performance) is also improved.

(3) The sub-exhaust port 3 opens during high-speed rotation, the compression ratio decreases and the exhaust cross-sectional area increases, so the output in the high-speed rotation range is improved and the overrun characteristic is also improved.

The important features and advantages of the present invention are summarized as follows.

(a) Secondary exhaust port 3 formed on the side of the main exhaust port 2
Is configured to be opened / closed with respect to the main exhaust port 2 and controlled to be opened / closed in three stages of a high speed rotation range, a medium speed rotation range, an extremely low speed rotation range or a rotation stop range. (B) Close the main exhaust port 2 in the extremely low speed rotation range or rotation stop range, and (c) make the upper edge of the auxiliary exhaust port 3 closer to the top wall than the upper edge of the main exhaust port 2. The auxiliary exhaust port 3 is opened in the cylinder at a position where the exhaust timing is earlier than that of the main exhaust port 2.

That is, as described above, by opening the auxiliary exhaust port 3 at a high timing position in the extremely low rotation range or rotation stop range, it is possible to expand the exhaust cross-sectional area and simultaneously reduce the compression ratio. Since a so-called decompression action can be performed, kick start of a motorcycle or the like becomes easy, torque fluctuation during idling is reduced, and stable engine rotation can be obtained.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing a state of a two-cycle engine to which the present invention is applied when the engine is stopped or at extremely low speed, and FIGS. 2 and 3 show states at medium speed and high speed, respectively. 1 is a horizontal sectional view of the same portion as FIG. 1, FIG. 4 is a developed view taken along the arrow IV in FIG. 1, and FIG. 5 is a sectional view taken along line VV in FIG. 1 showing a state when the engine is stopped or at extremely low speed. 6 and 7 are sectional views taken along line VV of FIG. 1 showing states during medium speed rotation and high speed rotation, respectively, and FIG. 8 is a state during engine stop or extremely low speed rotation of another embodiment. And FIG. 9 and FIG. 10 are horizontal cross-sectional views of the same portion as FIG. 8 showing the states at medium speed rotation and high speed rotation, respectively, and FIG. 11 shows a modification of the auxiliary exhaust port. FIG. 12 is a development view corresponding to a view taken along the line IV in FIG. 1, FIG. 12 is a sectional view taken along line XII-XII in FIG. 11,
FIG. 13 is an output characteristic diagram when the auxiliary exhaust port of FIG. 11 is adopted. 1 ... Cylinder, 2 ... Main exhaust port,
3 ... Sub-exhaust port, 6 ... Open / close valve

Claims (1)

[Claims] 1. A sub-exhaust port is formed on a side of a main exhaust port opening in a cylinder, and an opening / closing valve is provided at an outlet end of the sub-exhaust port on the main exhaust port side, when the engine is stopped or at extremely low speed rotation. The auxiliary exhaust port is opened to the main exhaust port, the auxiliary exhaust port is closed to the main exhaust port at medium speed rotation, and the auxiliary exhaust port is opened to the main exhaust port at high speed rotation. By positioning the upper edge of the port closer to the top wall than the upper edge of the main exhaust port, the auxiliary exhaust port is opened to the cylinder at an earlier exhaust timing than the main exhaust port. Exhaust control device.