JPH0531216Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an exhaust system for a two-stroke engine in which the piston itself acts as an exhaust valve.

[Prior Art] Conventionally, in a two-stroke engine, there is an exhaust system in which an auxiliary exhaust passage is provided in addition to the main exhaust passage, and the auxiliary exhaust passage is opened and closed by a rotary valve (for example, Japanese Patent Laid-Open No. 60-249614 discloses an auxiliary exhaust passage). reference).
This exhaust system improves output at high speeds by closing the auxiliary exhaust passage at low speeds and opening it at high speeds, making the cross-sectional area of the exhaust passage commensurate with the rotational speed of the engine.

By the way, in this type of exhaust system, a driving device such as a motor is provided outside the engine body, and on the other hand, the shaft portion of each rotary valve is made to protrude from the engine body, and the motor and each shaft portion are connected by a connecting member. There is one that rotates a rotary valve. By transmitting the driving force outside the engine body in this way, for example, it becomes easier to handle the connecting member and to arrange the water jacket.

[Problems to be Solved by the Invention] However, since the driving machine and the rotary valve are generally far apart from each other, each connecting member becomes long and the entire driving device becomes large.

Therefore, the inventor first thought of connecting the motor and one rotary valve with a connecting member, and connecting the rotary valves in close position with each other with a short rod, thereby reducing the size of the drive device. . However, in this case, the operation of the rod that connects the rotary valves to each other is not smooth, resulting in problems such as an increase in the load on the motor.

This idea was made in view of the above points,
It is an object of the present invention to provide an exhaust system for a two-stroke engine in which the drive device can be downsized and the rod connecting rotary valves can smoothly operate.

[Means for Solving the Problems] In order to achieve the above object, this invention first provides a pulley rotated by a drive machine outside the engine body, and on the other hand, the shaft of each rotary valve is connected to the engine body. It protrudes from the main body. First and second levers projecting in the radial direction of the shaft are fixed to each of the shafts. The above pulley and the first
The levers are connected by a cable that transmits the rotational force of the pulley to the first lever, and each lever is connected by a rod that transmits the rotational force of the first lever to the second lever. There is. The rod is rotatably supported by each lever by a spherical slide bearing.

[Operation] According to this invention, the rod connecting the first lever and the second lever is provided between the rotary valves that are in a close positional relationship, so that the pulley and the first lever are connected. shorter than the cable.

Here, the position at which the above rod is supported by both levers is misaligned in the axial direction of the rotary valve due to manufacturing errors, causing the rod connecting the shaft parts to tilt. Since the rod is supported, its error can be sufficiently tolerated, and the rod can be supported without changing the gap in the rod direction, so the resistance in the bearing is small.

[Example] An example of this invention will be described below with reference to the drawings.

FIG. 1 shows a longitudinal section of a two-cylinder two-stroke engine mounted on a two-wheeled motor vehicle, for example, in which 1 is a cylinder head, 2 is a cylinder block, 3 is a piston, and 4 is a water jacket. A main exhaust port 5 communicates the cylinder 6 with the main exhaust passage 7 shown in FIG. Reference numeral 9 denotes an auxiliary exhaust passage, which includes an auxiliary exhaust port 8 on the side of the main exhaust port 5 and a main exhaust passage 7.
and is connected as an auxiliary exhaust passage.
That is, the cross-sectional area of the auxiliary exhaust passage 9 is smaller than that of the main exhaust passage 7. In addition,
Reference numeral 30 denotes a resonance chamber that communicates with the main exhaust passage 7 at low speeds to prevent a decrease in output at low speeds.
Although the resonance chamber 30 is provided only on one side,
It may be provided on both sides, and it is not always necessary to provide it.

Reference numeral 10 denotes a rotary valve, which is provided in the middle of the auxiliary exhaust passage 9, and is operated by a drive device 11, which will be described later, in response to changes in operating conditions such as engine rotational speed.
(Fig. 4), the auxiliary exhaust passage 9
It opens and closes. This rotary valve 1
0, a valve passage 10a and a valve body 10b are formed in a cylindrical portion 10c in FIG. This rotary valve 10 has its axial direction set in the sliding direction of the piston 3 of the engine, and its shaft portion 10d.
is pivotally supported by the cylinder head 1 and cylinder block 2, and rotates in both directions around this shaft portion 10d. Shaft portion 10d of this rotary valve 10
protrudes from the cylinder block 2 through the cylinder head 1, and is connected to the drive device 11 above the cylinder head 1, as shown in FIG. In addition, 31 in Fig. 1 is a spacer, 3
2 is an oil seal. Although not shown, the right cylinder 6 is also provided with the rotary valve.

Next, the above drive device will be explained.

In FIG. 4, reference numeral 15 denotes a motor (driver) that can freely rotate in forward and reverse directions, and rotates the pulley 16 via a reduction gear (not shown). The motor 15 is provided with a potentiometer 40 for detecting its rotational angular position. The motor 15, potentiometer 40, and pulley 16 are integrally assembled with each other to constitute a motor unit 33, and this motor unit 33 is fixed to the main frame of the motorcycle via a plate (not shown). ing. Therefore, the motor unit 33
is provided outside the engine body.

Reference numeral 41 denotes a control means, which is composed of, for example, a microcomputer, and essentially controls the ignition timing of the engine. This control means 41 uses the engine rotation speed signal a detected by the detector 42 and the motor 1 detected by the potentiometer 40.
It inputs the rotation angle signal b of No. 5 and outputs a drive signal c for rotating the motor 15 in accordance with changes in the engine speed.

17 is the opening cable, 18 is the closing cable,
It connects the pulley 16 and the two first levers 19 and 20. Both cables 17 and 18 above
are cable outer 17a, 18a, respectively.
and cable inners 17b and 18b,
A cylindrical engagement member 34 is fixed to both ends of the inners 17b, 18b. This engaging member 34 is connected to the notch 35 of the levers 19, 20 or the pulley 16.
The cables 17 and 18 connect the pulley 16 and the first levers 19 and 20 by being fitted into and engaged with the notches 35 of the to communicate.

One end of the outer parts 17a, 18a is fixed to a clamp 21 connected to the cylinder head 1 (FIG. 3). On the other hand, at the other ends of the outer parts 17a and 18a, a male threaded part 37 is fixed to a female threaded part 36 provided on the motor unit 33.

The first levers 19, 20 are connected to each other via a first rod 22, and are connected to a second lever via a second rod 23, 24, respectively.
levers 25 and 26, and its rotational force is transmitted to the second levers 25 and 26. The four levers 19, 20, 25, 26 are each
It is screwed to the protruding shaft portion 10d of the rotary valve 10 in FIG. 3, and protrudes in the radial direction of the shaft portion 10d. Note that 60 in FIG. 4 is a mark for rotationally positioning the first lever 20.

Each rod 22, 23, 24 has the same structure,
If one rod 23 is shown as a representative, as shown in FIG.
9 and 25 so as to be rotatable. In FIG. 5 which clearly shows this, 51 is a spherical surface formed on the outer surface of the barrel-shaped member 52. 53 is a male screw,
The barrel-shaped member 52 is fixed to the lever 25, for example, by passing through the barrel-shaped member 52. Rod 2 above
The end portion 54 of 3 is hollow, and a concave spherical surface 55 that slides into contact with the spherical surface 51 is formed in this end portion 54. Grease is inserted between both spherical surfaces 51 and 55. The upper and lower surfaces 57 of the end portion 54 are maintained so as not to contact the male screw 53 and each lever 25 .

Next, an example of the operation of the above configuration will be described.

First, when the engine speed is low, the levers 19, 20, 25, and 26 shown in FIG. 4 are held at the positions shown, and the auxiliary exhaust passage 9 shown in FIG. 2 is closed by the rotary valve 10. . Therefore, the exhaust A is exhausted only from the main exhaust passage 7, and as is well known, the cross-sectional area of the entire exhaust passage becomes small enough to be suitable for low speeds, and a decrease in output at low speeds is prevented.

Thereafter, when the rotational speed of the engine reaches a predetermined speed, the detector 42 shown in FIG. 4 detects this, and
The rotational speed signal a is output to the control means 41. On the other hand, the rotation angle signal b of the motor 15 is input from the potentiometer 40 to the control means 41 . Based on these signals a and b, a drive signal c is output from the control means 41 to the motor 15, the motor 15 rotates by a predetermined angle, and the pulley 16 rotates. With this rotation, the inner 17b is pulled in the direction of the arrow, and the first lever 19 on the left side is rotated. This rotation causes the first lever 20 on the right side to rotate via the first rod 22, and the inner 18b is pulled in the direction of the arrow. At the same time, the first levers 19, 2
0 rotates, the second rods 23, 24
The second levers 25, 26 are rotated via the.
The rotation of the four levers 19, 20, 25, and 26 causes the four shaft portions 10d to rotate in the directions of the arrows, and the rotary valve 10 in FIG. 2 rotates approximately 90 degrees. As a result, the auxiliary exhaust passage 9 communicates with the main exhaust passage 7, and exhaust air is discharged from both exhaust passages 7 and 9. Therefore, when the engine rotational speed is high, the cross-sectional area of the entire exhaust passage becomes large enough to correspond to the high speed, and as is well known, the output is improved.

In the above configuration, this invention has a shaft portion 10d (the first
Figure) Move the comrade to the second rod 2 as shown in Figure 4.
3, 24 and levers 19, 20, 25, 26 to transmit the rotational force of the first levers 19, 20 to the second levers 25, 26. Therefore, the second levers 25 and 26
The rotational force is transmitted by short rods 23, 24 instead of 7, 18. Therefore, the drive device 11
can be made smaller.

By the way, the rotary valve 10 and cylinder block 2 shown in FIG. 1, and the lever 19 shown in FIG.
25, manufacturing errors occur. Therefore, the upper surfaces 19a, 25a of both levers 19, 25 are
d are mutually displaced in the axial direction (vertical direction), and the rods 23 are inclined as shown by the dashed line L. Here, if the end portion 54 of the rod 23 is supported by a plain bearing as in the conventional case, the rod 23 is Since the rod 23 is inclined, the rotation of the rod 23 is not smooth. On the other hand, if the clearance of the sliding contact portion of the plain bearing is increased, the accuracy of the rotational position of the rotary valve 10 will decrease, leading to a decrease in output, for example.

In contrast, in this invention, the rod 23 is supported by a spherical sliding bearing 50. Therefore,
Even if the rod 23 is tilted, both spherical surfaces 5 in Fig. 5
1 and 55 are in smooth sliding contact with each other. Therefore, the clearance between both spherical surfaces 51 and 55 can be kept small, and the rods 23, 22, 24 can operate smoothly. As a result, for example, the load on the motor 15 shown in FIG. 4 is reduced, and the rotational position accuracy of the rotary valve 10 shown in FIG. 2 is improved.
Output is improved. Also, both spherical surfaces 51, 5 in FIG.
Since the bearing parts 5 smoothly slide into contact with each other, the durability of the bearing portion is improved.

By the way, in this embodiment, as shown in FIG.
Four rotary valves 10 are provided. Here, a pair of cables 17 and 18 are provided on the pulley 16, and as the pulley 16 rotates, the cables 17 and 18 operate in opposite directions to rotate the four rotary valves 10 simultaneously. Therefore, since the position of the rotary valve 10 can be restrained by the two inners 17b, 18b, return springs for the inners 17b, 18b are not required.

By the way, although the motor 15 is used as the driving device in the above embodiment, in this invention, the driving device can also be mechanical. In addition,
As a mechanical drive device, when the rotational speed of the crankshaft exceeds a predetermined value by the rotation of a governor (not shown) connected to the crankshaft, the steel balls are moved along the slope of the dish-shaped spherical plate. There is a well-known moving device (see the above-mentioned prior art document), and its rotating shaft may be projected outside the engine body and connected to the pulley 16.

[Effects of the invention] As explained above, according to this invention, the rods connecting each lever are installed between rotary valves that are necessarily in close positional relationship, so they are shorter than the cables. , Therefore, it is possible to downsize the drive device.

In addition, since the rod, which tilts in the vertical direction, is rotatably mounted on the lever using a spherical sliding bearing, the rod rotates smoothly. Therefore,
For example, as the load on the drive machine becomes smaller,
It is possible to improve engine output. Additionally, the durability of the bearing portion is improved.

[Brief description of the drawings]

Fig. 1 is a longitudinal sectional view of an engine showing an embodiment of this invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a sectional view taken along the - line in Fig. 4, and Fig. 4 is a drive unit. FIG. 5 is a vertical cross-sectional view of the spherical plain bearing. 6...Cylinder, 7...Main exhaust passage, 9...Auxiliary exhaust passage, 10...Rotary valve, 10d
... Shaft portion, 11 ... Drive device, 15 ... Motor (driver), 16 ... Pulley, 17, 18 ... Cable, 19, 20 ... First lever, 23, 24
... (second) rod, 25, 26 ... second lever, 50 ... spherical plain bearing.

Claims (1)

[Claims for Utility Model Registration] A main exhaust passage communicating with the inside of the cylinder, a plurality of auxiliary exhaust passages connecting the inside of the cylinder and the main exhaust passage as auxiliary exhaust passages, and the auxiliary exhaust passages. An exhaust passage for a two-cycle engine, which is equipped with rotary valves that open and close, and a drive device that rotates each rotary valve in accordance with changes in the operating state of the engine, the drive device being installed outside the engine body. a pulley that is rotated by the rotary valve; a drive machine that rotates the pulley; a shaft that is provided on each of the rotary valves and projects from the engine body; a second lever, a cable that connects the pulley and the first lever and transmits the rotational force of the pulley to the first lever, and a cable that connects each of the levers and transfers the rotational force of the first lever to the first lever. 1. An exhaust system for a two-stroke engine, comprising a rod for transmitting power to two levers, and a spherical slide bearing for rotatably supporting the rod on each of the levers.