JP2710149B2 - Exhaust pipe connection structure for two-cycle engine - Google Patents

Description

The present invention relates to an exhaust pipe connection structure of a two-stroke engine employed in, for example, a motorcycle, and more particularly, to an increased degree of freedom of a connection angle between an exhaust port and an exhaust pipe. The present invention relates to an improvement in a connection structure capable of improving exhaust efficiency and securing a required exhaust pipe length.

[Conventional technology]

Conventionally, as an exhaust pipe connection structure for a two-cycle engine,
For example, as described in Japanese Utility Model Application Laid-Open No. 58-33722, an exhaust opening on the inner surface of a cylinder bore is led out to an outer wall of a cylinder body by an exhaust port, and an exhaust pipe is connected to the outlet opening. In general, the shape of the vicinity of the exhaust port and the exhaust pipe connection is set so that the connection to the exhaust pipe is linear or continuous in a curved line.

By the way, in order to improve engine performance, it is necessary to discharge exhaust gas efficiently. To improve this exhaust efficiency, in the case of a two-stroke engine, the port angle between the exhaust port and the cylinder axis is made as small as possible. That is, it is effective to set the exhaust port as downward as possible. In order to improve engine performance, it is also important to secure a sufficient exhaust pipe length, particularly in the case of a two-stroke engine.

[Problems to be solved by the invention]

However, in the case of the conventional exhaust pipe connection structure, since the exhaust port and the exhaust pipe are continuously connected,
The port angle of the exhaust port with respect to the cylinder axis is substantially the same as the exhaust pipe angle with respect to the cylinder axis near the connection of the exhaust pipe. Therefore, the more the exhaust port is directed downward, the shorter the exhaust pipe length becomes.Therefore, the exhaust pipe length for reducing the port angle and improving the exhaust efficiency may be insufficient. The angle increases. After all, in the case of the above-described conventional structure, the degree of freedom of the connection angle is low, and it is difficult to secure both the port angle and the exhaust pipe length.

The present invention has been made in view of the above-described conventional circumstances, and provides an exhaust pipe connection structure of a two-stroke engine that can increase the degree of freedom of an exhaust pipe connection portion, improve exhaust efficiency, and sufficiently secure an exhaust pipe length. It is intended to be.

[Means for solving the problem]

The present invention relates to an exhaust pipe connection structure for a two-stroke engine, wherein an exhaust opening opening on an inner surface of a cylinder bore is led to an outer wall of a cylinder body by an exhaust port, and an exhaust pipe is connected to the leading opening. A port angle formed by an exhaust straight line connecting the exhaust pipe and the upper edge of the exhaust opening to a cylinder axis is set to be smaller than an exhaust pipe angle formed by the exhaust pipe axis and the cylinder axis at the connecting portion of the exhaust pipe. An adapter that absorbs the deviation between the port angle and the exhaust pipe angle is interposed between the outlet opening of the exhaust pipe and the connection end face of the exhaust pipe.

[Action]

According to the exhaust pipe connection structure for a two-stroke engine according to the present invention, the port angle between the exhaust straight line and the cylinder axis is set smaller than the exhaust pipe angle between the exhaust pipe axis and the cylinder axis, and the difference between the two angles is set. Since absorption is performed by the adapter, the degree of freedom in setting the port angle and the exhaust pipe angle is expanded, and the angle can be set freely as required. Therefore, it is possible to increase the exhaust pipe angle so as to increase the exhaust pipe length while setting the port angle to be small so that the flow of the exhaust gas is smooth. As a result, the required exhaust pipe length can be secured while improving the exhaust efficiency.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 6 are views for explaining an exhaust pipe connection structure of a two-stroke engine according to one embodiment of the present invention. FIG. 1 is a sectional side view, and FIG. 2 is II- in FIG. FIG. 3 is a front view of the exhaust pipe connection flange portion, FIG. 4 is a side view of the engine of the embodiment, FIG. 5 is a cross-sectional side view showing a modification of the adapter, and FIG. 1 is a left side view of a motorcycle equipped with an example engine. Note that, unless otherwise specified, the description will be made in a state in which the user gets on the vehicle.

In the drawing, reference numeral 1 denotes a motorcycle on which the engine of the present embodiment is mounted, and a body frame 2 of the motorcycle 1 has a main pipe 2b having a pair of left and right rectangular cross sections on a head pipe 2a.
The main frame 2b is extended leftward and rightward while extending diagonally downward and rearward, and a rear arm bracket 2c is welded and fixed to the extended rear end, and the two brackets 2c are connected to each other by three crosses. It has a structure that is welded and connected with a pipe. A front fork 4 that supports the front wheel 3 at the lower end by a head pipe 2a of the vehicle body frame 2 is rotatably supported left and right, and a rear arm 6 that supports the rear wheel 5 at the rear end by the rear arm bracket 2c. Is pivotally supported up and down freely. Reference numeral 7 denotes a fuel tank arranged to cover the left and right main frames 2b, 2b, and 21 denotes a radiator.

A water-cooled two-cycle V-type two-cylinder engine unit 8 is suspended from the vehicle body frame 2. The crankcase 9 of the engine unit 8 includes a front case 26 and a rear case 27. A crankshaft 28 is provided at a mating portion between the front and rear cases 26 and 27, and a main shaft 29 is provided at a lower rear portion of the main case 29. A drive shaft 30 is arranged above the rear side of the shaft 29, and a balancer shaft 42 is arranged above the main shaft 29 in parallel. 39 is an operating mechanism of the clutch device, and 51 is an operating mechanism of the clutch device.
Is an inner case of the cooling water pump.

An upper cylinder body 10 is connected to the upper left side of the front wall of the front case 26 constituting the crankcase 9 by bolting, and an upper cylinder head 66a is fixed to the upper surface of the cylinder body 10 by bolting. . A lower cylinder body 11 and a lower cylinder head 66b are stacked and connected to the lower right side of the front case 26. The upper and lower cylinder bodies 10, 11 and the cylinder heads 66a and 66b are viewed from the side. The V banks are arranged in a V-shape, and the V bank forms 90 degrees and opens toward the front of the vehicle.

An upper intake opening 9a communicating with the upper cylinder body crank chamber is formed on the back side of the upper cylinder body 10, that is, outside the V bank. An upper reed valve 12a is inserted into the upper intake opening 9a, and further connected to an upper carburetor 14a via an upper cab joint 13a. The left and right main frames 2a are connected to the carburetor 14a.
The upper air cleaner 15 located between b and the upper air duct 1
Connected via 7. 26a is the above-mentioned front case 26.
Is a cooling water inlet formed in a lower portion of the upper cylinder body 10, and is closed by a cover plate 54.

A lower intake opening 9b communicating with the lower cylinder body crank chamber is formed on the back side of the lower cylinder body 11, that is, in the V bank of the front case. A lower reed valve 12b is inserted into the lower intake opening 9b, and a lower carburetor 14b is connected to the lower carburetor 14b via a lower cab joint 13b.The carburetor 14b is disposed on the right side of the engine. The connected lower air cleaner 18 is connected.

An exhaust opening 10b formed in the inner surface of the cylinder bore of the upper cylinder body 10 is led out to the front wall of the cylinder body 10 by an exhaust port 10a, and the outlet opening 10c
The port angle formed by the cylinder axis A and the exhaust straight line a connecting the center of the exhaust opening 10b and the upper edge of the exhaust opening 10b is θ1. An exhaust timing valve 57 adjusts the opening timing of the exhaust opening 10b.

The upper exhaust pipe 22 is connected to the outlet opening 10c via a disk-shaped adapter 58 with the following configuration. First, the rear surface of the adapter 58 is brought into contact with the sealing surface of the outlet opening 10c with a gasket 59 interposed between the two surfaces, and a connection fitting 61 welded to the exhaust pipe main body 22a is provided on the front surface of the adapter 58. A disc spring-like seal member 63 is sandwiched between the flanges 61a of the connection fitting 61, and a holding bracket 60 is also brought into contact with the flange 61a, which is fixed by a fixing bolt 62 and a nut 62a implanted in the cylinder body 10. The structure is fixed by pressing.

Here, the exhaust pipe angle θ2 between the cylinder axis A and the exhaust pipe axis b near the connection part of the exhaust pipe main body 22a and the connection fitting 61 is set to be larger than the port angle θ1, and the connection fitting 61 The center of the end face is the exhaust port
It deviates slightly upward from the center of the lead-out opening 10c of 10a.
The exhaust passage 58b of the adapter 58 has an axis c
Are formed so as to connect the center of the outlet opening 10c of the exhaust port 10a and the center of the front end of the connection fitting 61. That is, the adapter 58 is connected to the port angle θ1 and the exhaust pipe angle θ2.
And the deviation is absorbed.

10d and 10g are the lower part of the upper cylinder body 10,
The lower and upper water cooling jackets 10d and 10g have an exhaust port 10a side portion connected to a lower passage 10e communicating with the lower water cooling jacket 10d and an exhaust port 10a side portion of the adapter 58. The formed intermediate passage 5
8a, and the upper passage 10f communicating with the upper water cooling jacket 10g.
Are communicated through.

The front wall of the lower cylinder body 11, that is, the V
The lower exhaust pipe 23 is provided on the wall outside the bank via an adapter 58.
Is connected. The port angle of the lower cylinder body 11, the axis of the adapter 58, the exhaust pipe angle, and the like are set in the same angular relationship as the exhaust pipe connection of the upper cylinder body 10. The structure of the communication passage connecting the upper and lower water cooling jackets is the same as that of the upper cylinder body 10.

 Next, the operation and effect of this embodiment will be described.

In the engine of this embodiment, the port angle θ1 is set to be smaller than the exhaust pipe angle θ2, and the difference between the two is absorbed by the adapter. Therefore, the conventional exhaust port and the vicinity of the exhaust pipe connection are linearly or circularly connected. The degree of freedom in setting each of the angles is increased as compared with the case where the arcs are continuously formed.

Therefore, by setting the port angle θ1 to be smaller, the exhaust port 10a can be formed downward, thereby improving the exhaust efficiency. The required exhaust pipe length can be secured by setting the exhaust pipe angle θ2 larger.

Further, in the present embodiment, the exhaust port 10a and the exhaust pipe 22 are connected via the adapter 58, so that various combinations of the exhaust port and the exhaust pipe can be realized by appropriately selecting the adapter. For example, as shown in FIG. 5, a cylinder body 10 having an exhaust port 10a having the same dimensions as FIG.
Alternatively, an exhaust pipe 22 'having an exhaust pipe angle θ2' can be connected.

Here, the exhaust pipe 22 in FIG. 1 is an exhaust pipe for a commercial vehicle, and the exhaust pipe 22 'in FIG. 5 is an exhaust pipe for a competition running vehicle. Since the adapter is interposed in this way, the exhaust port
The exhaust pipe according to the purpose can be easily connected while using 10a in common. In this case, it is of course possible to connect the same exhaust pipe as in FIG. 1 to a cylinder body having an exhaust port different from that in FIG. 1 by appropriately selecting the shape of the adapter.

〔The invention's effect〕

As described above, according to the exhaust pipe connection structure of the two-stroke engine according to the present invention, the port angle is set smaller than the exhaust pipe angle, and the adapter that absorbs the difference between the two angles is interposed between the two. The degree of freedom in setting the above angles is improved, the port angle can be set smaller to improve the exhaust efficiency, and the exhaust pipe angle can be set larger to secure the required exhaust pipe length,
This has the effect of improving engine performance.

[Brief description of the drawings]

1 to 6 are views for explaining an exhaust pipe connection structure of a two-stroke engine according to one embodiment of the present invention. FIG. 1 is a sectional side view, and FIG. 2 is II- in FIG. FIG. 3 is a front view of the exhaust pipe connection flange portion, FIG. 4 is a side view of the engine of the embodiment, FIG. 5 is a cross-sectional side view showing a modification of the adapter, and FIG. 1 is a left side view of a motorcycle equipped with an example engine. In the figure, 8 is a two-stroke engine, 10 is a cylinder body, 10a is an exhaust port, 10b is an exhaust opening, 10c is an outlet opening, 22 is an exhaust pipe, 58 is an adapter, A is a cylinder axis, a
Is the exhaust straight line, b is the exhaust pipe axis, θ1 is the port angle, θ2
Is the exhaust pipe angle.

Claims (1)

(57) [Claims] 1. An exhaust pipe connection structure for a two-stroke engine, wherein an exhaust opening opening on an inner surface of a cylinder bore is led to an outer wall of a cylinder body by an exhaust port, and an exhaust pipe is connected to the outlet opening. The port angle between the exhaust straight line connecting the center and the upper edge of the exhaust opening and the cylinder axis is set smaller than the exhaust pipe angle between the exhaust pipe axis and the cylinder axis at the connection part of the exhaust pipe, An exhaust pipe connection structure for a two-stroke engine, characterized in that an adapter for absorbing a deviation between the port angle and the exhaust pipe angle is interposed between a port outlet opening and an exhaust pipe connection side end face.