JPH0238031Y2 - - Google Patents

Description

[Detailed explanation of the invention] (Field of industrial application) This invention aims to increase output by increasing the area of the exhaust passage by using a main exhaust passage and a sub-exhaust passage together at high speeds, but at low speeds. The present invention relates to an exhaust control device that suppresses a decrease in output by closing a sub-exhaust passage to reduce the area of the exhaust passage.

(Prior art) For example, in a two-stroke engine installed in a motorcycle, a fifth exhaust control device is used.
As shown in the figure, in addition to providing a main exhaust passage 5 that communicates with the inside of the cylinder 4, the inside of the cylinder 4 and the main exhaust passage 5 are connected by a pair of sub-exhaust passages 6, 6. On top, open/close valve 7
is provided. The opening/closing valve 7 is controlled to allow the sub-exhaust passage 6 to communicate when the engine is running at high speeds, and to close the sub-exhaust passage 6 when the engine is running at low speeds.

In this way, at high rotation speeds as shown in FIG. 5, by using the sub exhaust passage 6 in addition to the main exhaust passage 5 as an exhaust passage, the area of the exhaust passage can be obtained larger than at low rotation speeds. High output type, that is, the output peak shifts to the higher rotation side on the output curve than the output peak when the sub-exhaust passage 6 is not used, so that high output can be obtained in the high rotation range.

On the other hand, at low speeds shown in FIG. 6, if the sub exhaust passage 6 is left open as at high speeds (FIG. 5), the area of the exhaust passage is too large, resulting in the high-speed, high-output type mentioned above. As a result, the output at low rotation speeds decreases, so the on-off valve 7
For example, by rotating the sub-exhaust passage 6 by 90 degrees in the counterclockwise direction shown in the figure from a high-speed state, the sub-exhaust passage 6 is closed and exhaust is exclusively carried out through the main exhaust passage 5, thereby reducing the low-speed rotation. It is designed to suppress the output drop during the time.

On the other hand, at low engine speeds, the exhaust pressure wave from the main exhaust passage 5 is applied to the resonance chamber 32 to cause it to resonate, in order to actively increase the output rather than simply suppressing a decrease in the output.

However, as shown in FIG. 7, the conventional on-off valve 7 has a cylindrical valve portion 8 (fourth
The valve passage 12 was formed by a closing wall portion 13 having a crescent-shaped cross section and a valve passage 12 which was cut out leaving the closing wall portion 13 on one side of the outer periphery.

Here, the opening/closing valve 7 is used to open the sub-exhaust passage 6 in order to obtain a high output type at the above-mentioned high speed, while communicating the main exhaust passage 5 and the resonance chamber 32 in order to obtain a resonance effect at low speed. In addition, in order to more effectively obtain a high-speed, high-output type by cutting off communication between the main exhaust passage 5 and the resonance chamber 32 during high rotation, the exhaust control device shown in FIG. 5 is suitable. There is.

In this exhaust control device, during high rotation, each of the closing walls 13, 13 is located on the outer side of the sub-exhaust passages 6, 6, respectively, and opens the sub-exhaust passages 6, 6, respectively, and the main exhaust passage 5 and the resonance chambers 32, 32, the above-mentioned predetermined function can be obtained. When the engine rotates in the same direction (counterclockwise) and reaches low rotation, the closing wall portion 13 on the right side in the drawing closes the sub-exhaust passage 6 and contributes to suppressing a decrease in output.

However, the sub-exhaust passage 6 on the left side of the drawing
communicates with the resonance chamber 32, so the area of the exhaust passage becomes larger than that of the case where only the main exhaust passage 5 is used, which is not preferable for low rotation speeds. As shown by the solid line, without providing the resonance chamber 32,
Only the resonance chamber 32 on the right side was provided.

If low-speed operation is performed using only the right resonance chamber 32 in this manner, a large resonance effect cannot be obtained, and therefore, an output increase at low rotation speeds cannot be effectively obtained.

Here, the on-off valve 7 on the left side in FIG. 6 can also be brought into a rotational state in which it has the same function as the on-off valve 7 on the right side. That is, the drive rack 15 that rotates the opening/closing valve 7 is
As shown in FIG. 8, drive racks 15 are provided so as to be inclined when seen in plan, that is, to mesh with the outer periphery of one on-off valve 7 on the cylinder 4 side and on the outer periphery of the other on-off valve 7 on the opposite cylinder side, respectively. This can be achieved by rotating both on-off valves 7, 7 in opposite directions, as shown in FIG. However, as mentioned above, the drive rack 1
5 is installed at an angle, each opening/closing valve 7
It becomes difficult to accurately determine the dimensions between the drive rack 15 and the drive rack 15, and as a result, manufacturing becomes troublesome and disadvantageous in terms of mass production.

In view of this, the applicant devised an on-off valve 7 shown in FIG. 10.

This opening/closing valve 7 has a pair of closing walls 13, 1
This type has a valve passage 12 between the three.

When the on-off valve 7 having such a pair of closing walls 13, 13 is used, as shown in FIG.
In addition to opening the sub-exhaust passages 6, 6 at high rotation speeds, in particular, at low rotation speeds shown in FIG. By being able to communicate with the exhaust passage 5, the resonance chamber 32
It is now possible to provide a pair of the two on the left and right sides, which is convenient for increasing the output at low rotation speeds.

However, at the time of high rotation as shown in FIG. 10 (or at the time of low rotation as shown in FIG. 11), such opening/closing valve 7
However, in this case, in order to further increase the output from another aspect, a wider main exhaust passage 5 is formed within a certain cylinder block width to improve the exhaust flow. It is desirable to facilitate this process.

To do this, the width of the main exhaust passage 5 can be increased by positioning the on-off valves 7, 7 slightly upstream of the outlet of the sub-exhaust passage 6.
The width of the main exhaust passage 5 is increased by widening it as shown by the dotted chain line (the former), or by moving the on-off valve 7 to the position B (broken line) of the sub-exhaust passage 6, that is, near the cylinder 4 side. I've been thinking about (the latter).

However, if the opening/closing valve 7 is placed in the former position, that position may correspond to a passage, so in order to avoid this and smooth the flow of exhaust, the sub-exhaust passage 6 is shown in Fig. 10. As shown by the two-dot chain line, A on the long straight passage is assumed to have a large curved passage and a longer straight passage.
It becomes necessary to arrange the on-off valve 7 at the position.

If this happens, the angle θ1 at the connecting portion between the sub-exhaust passage 6 and the main exhaust passage 5 becomes large as θ2, which poses a problem in that the smooth flow of exhaust from the sub-exhaust passage 6 is obstructed.

On the other hand, if the opening/closing valve 7 is brought to the latter position, that is, the B position, this B position corresponds to a location close to the cylinder 4, and the cylinder 4 and the crankcase (not shown) are located near the B position. In practice, it is difficult to arrange the on-off valve 7 here because of conditions such as the provision of stud bolts for connecting the two.

After all, it is most convenient for the on-off valve 7 to be disposed at the C position (solid line), that is, near the exit which is the terminal end of the sub-exhaust passage 6, also for the above reasons.

However, if the opening/closing valve 7 is placed at position C and the width of the main exhaust passage 5 is widened as shown by the two-dot chain line in Figure 10 in order to increase the output, the output will be increased only at the high speeds shown in Figure 10. Even at low rotation speeds as shown in FIG.
13 protrudes into the main exhaust passage 5.

If the closing wall portion 13 protrudes into the main exhaust passage 5 in this manner, exhaust resistance is generated, making it impossible to effectively increase the output.

(Purpose of the invention) This invention was devised in view of the above-mentioned problems.It does not obstruct the outflow of exhaust gas from the sub-exhaust passage, and also prevents interference with the cylinder and stud bolt. It is possible to increase the output by widening the width of the passage, and in particular, the purpose is to prevent the opening/closing valve from interfering with the smooth flow of exhaust gas in the main exhaust passage when the width of the main exhaust passage is widened. do.

(Structure of the invention) In order to achieve the above object, this invention provides a cylinder block with a main exhaust passage that communicates with the inside of the cylinder, and a sub-exhaust that connects the inside of the cylinder and the main exhaust passage as an auxiliary exhaust passage. a valve passage for opening the sub-exhaust passage at high speeds and a closing wall portion for closing the sub-exhaust passage at low speeds near the outlet of the sub-exhaust passage to the main exhaust passage; A cylindrical opening/closing valve is provided which is rotatably driven by a drive rack depending on the speed of rotation, and a cut surface is formed on the closing wall of the opening/closing valve to match the inner wall of the main exhaust passage when the valve is fully opened. By becoming
Even if the width of the main exhaust passage is widened, the opening/closing valve does not resist the flow of exhaust gas through the main exhaust passage.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

FIG. 1 shows a two-stroke engine mounted on a two-wheeled motor vehicle, in which 1 is a crankcase, and the crankcase 1 is provided with a crankshaft (not shown).

A cylinder block 2 is attached to the upper part of the crankcase 1, and a cylinder head 3 is attached to the upper part of the cylinder block 2. Here, F in the figure corresponds to the front when the vehicle is mounted on a two-wheeled motor vehicle.

The cylinder block 2 is formed with a cylinder 4 whose center is inclined forward F.
As shown in Figure 2, there is a main exhaust passage 5 on the front side of the
and a pair of left and right sub-exhaust passages 6, 6 are provided. As shown in Fig. 4, the main exhaust passage 5 has a rectangular main exhaust port 5A with a bulge on the cylinder 4 (Fig. 2) side, and is tapered in a direction corresponding to the front of the engine. It is formed as a passage, and as shown in FIG. 1, when viewed from the right side of the engine, it is formed with the passage center slanting downward toward the front F direction of the engine.

The main exhaust passage 5 has second exhaust passages on both sides thereof.
A pair of left and right sub-exhaust passages 6, 6 shown in the figure are provided, and the sub-exhaust passages 6, 6 connect the cylinder 4 and the main exhaust passage 5 as passages narrower than the main exhaust passage 5.

Opening/closing valves 7, 7 for opening and closing the sub-exhaust passages 6, 6 are provided near the passage outlet of each of the sub-exhaust passages 6, 6.

As shown in FIG. 4, each opening/closing valve 7 is
It has a cylindrical valve part 8 at its upper part, a valve shaft 9 at its lower part, and at its upper end,
It has an upper pivot section 10 and a lower pivot section 11 at its lower end. This opening/closing valve 7 is a first
As shown in the figure, it is arranged parallel to the center of the cylinder 4. A vertically elongated valve passage 12 is formed in the valve portion 8 of each of the on-off valves 7, and as shown in FIG. It is formed as a passage inclined at the center of the axis of the on-off valve 7.

Here, on the outer periphery of the valve passage 12, a pair of crescent-shaped closing walls 13, 13 are formed which face each other with the valve passage 12 in the center, as shown in the cross section in FIG. There is.

The opening/closing valve 7 allows the cylinder 4 and the main exhaust passage 5 to communicate with each other by making the center of the valve passage 12 concentric with the sub-exhaust passage 6 when the rotation speed exceeds a certain level (FIG. 2).
At low engine speeds, both opening and closing valves 7, 7 are rotated 90 degrees in the same direction, that is, counterclockwise, from the state shown in FIG. 2, so that the sub-exhaust passage opens as shown in FIG. 6, 6 are always closed by one of the closing wall portions 13 closer to the cylinder 4 than the valve passage 12, thereby cutting off communication between the cylinder 4 and the main exhaust passage 5.

Here, as shown in FIG. 4, the opening/closing valve 7 has a valve pinion 14 at its lower part, and a drive rack 15 meshes with the valve pinion 14.

As shown in FIG. 1, the drive rack 15 in this case is arranged near the lower end of the cylinder block 2 below the main exhaust passage 5, and is located at the longitudinal center of the cylinder block 2 in the left-right direction of the engine. It is aimed at

The sliding piece 16 shown in FIG. 2 provided at one end of the drive rack 15 is connected to a sliding hole 1 formed in the cylinder block 2 as the inner periphery of one end of the rack support boss 2A.
7, and a rack support shaft 18 provided at the other end,
It is slidably supported by a rack bearing bush 19 screwed into the rack support boss 2A.

Here, the means for driving the drive rack 15 is constructed as follows.

That is, as shown in FIG. 1, an engagement sleeve 22 that reciprocates in the axial direction of the governor shaft 20 according to the height of the engine rotation is provided on the outer periphery of the governor sleeve 21 in the governor mechanism, and the engagement sleeve 22 is provided with an easy drive mechanism. An engagement pin 24 provided at one end of the shaft 23 is engaged.

The rack drive shaft 23 is supported by a clutch cover 25 attached to the right side of the crankcase 1, and its axial center corresponds to the longitudinal direction of the engine.

A swinging arm 26 that swings in the left-right direction of the engine is attached to one end corresponding to the front of the rack drive shaft 23, and a rack drive pin 28 is protruded from the tip of the swinging arm 26. , this rack drive pin 28 is connected to the drive rack 15
It engages a rack sleeve 27 attached to one end of the holder.

In addition, 29 is a drive case, which is attached to the right side of the cylinder block 2.
is a case body that covers from one end of the rack drive shaft 23 to one end of the drive rack 15. Further, FIG. 2 31 shows a resonance communication passage, which communicates the main exhaust passage 5 with the resonance chamber 32 through the valve passage 12 during low rotation as shown in FIG. 3 .

The feature of such an exhaust control device is that the opening/closing valve 7 is located in the vicinity of the outlet of the sub-exhaust passage 6 to the main exhaust passage 5, that is, in the main exhaust passage of a constant width (shown by two dotted lines in FIG. 2). 5, the outer periphery of the on-off valve 7 (closing wall portion 13) does not protrude, and the on-off valve 7 does not protrude from the outer periphery of the on-off valve 7 (closing wall portion 13), and the on-off valve 7 does not protrude from the outer periphery of the on-off valve 7 (closure wall portion 13).
It is arranged near the exit so that the outer periphery of the (closing wall portion 13) protrudes. And open/close valve 7
One of the closing wall portions 13 is formed with a cut surface 7A that matches the inner wall of the wide main exhaust passage 5 when the engine is fully opened at high speeds.

In the above configuration, the on-off valve 7 is closed near the outlet of the sub-exhaust passage 6 to the main exhaust passage 5, that is, the on-off valve 7 (closed off) Wall part 1
3) The outer periphery of the open/close valve 7 (closing wall portion 13) does not protrude, and the outer periphery of the on-off valve 7 (closing wall portion 13) protrudes from the main exhaust passage 5 (solid line in Figure 2), which has a wider width. Because of this arrangement, there is no risk of interference with the cylinder 4 and stud bolts, and there is no need to raise the sub-exhaust passage 6. From sub exhaust passage 6 to main exhaust passage 5
There is no risk of impeding the smooth flow of exhaust gas flowing out.

In particular, in the wide main exhaust passage 5, the portion of the opening/closing valve 7 that protrudes into the main exhaust passage 5 when fully opened is cut.
The exhaust gas flowing through the main exhaust passage 5 is not resisted by the closing wall portion 13 of the opening/closing valve 7, and the flow of exhaust gas at high engine speeds is smoothed, thereby increasing the output.

This increase in output is not only achieved by a simple structure in which only a portion of the opening/closing valve 7 is cut out, but it is also extremely beneficial because it is achieved while preventing interference with the other members mentioned above.

In the above embodiment, only the part of the opening/closing valve 7 that corresponds to high rotation is cut off, but as shown by X in FIG. 3, the part that protrudes at low rotation can also be cut off. In addition, the on-off valve 7
In the above embodiment, one pair is provided, but only one may be provided. Furthermore, the resonance chamber 32
can also be omitted. In addition, this idea
It is also applicable to a structure in which the closing wall portion 13 is provided at one location as shown in FIG. In this case, the closing wall portion 13
The condition is that the engine protrudes into the main exhaust passage at high or low rotations.

(Effect of the invention) As explained above, according to this invention, the closing wall of the on-off valve is formed with a cut surface that matches the inner wall of the main exhaust passage when the valve is fully opened, so the sub-exhaust passage It is possible to increase the output by widening the width of the main exhaust passage while not obstructing the outflow of exhaust gas from the engine and preventing interference with the cylinder and stud bolt. It is possible to prevent the opening/closing valve from interfering with the smooth flow of exhaust gas in the main exhaust passage.

[Brief explanation of the drawing]

Fig. 1 is a right side view of a two-stroke engine showing an embodiment of this invention, Fig. 2 is a sectional view taken along the line of Fig. 1 shown at high speed, and Fig. 3 is a sectional view of Fig. 1 shown at low speed. - Line sectional view, Figure 4 is a line sectional view shown at high speed, Figure 2 - Line sectional view, Figure 5
The figure is a cross-sectional view of an example of a conventional exhaust control device at high speeds, FIG. 6 is a cross-sectional view of the exhaust control device of FIG. 5 at low speeds, and FIG. 7 is a conventional opening/closing valve. A perspective view, FIG. 8 is a cross-sectional view showing a conventional example in which the drive rack is tilted, FIG. 9 is a cross-sectional view showing the conventional example of FIG. 8 at low rotation speed,
FIG. 10 is a cross-sectional view showing an example of an exhaust control device equipped with an on-off valve having a pair of closing walls at high speed, and FIG. 11 is a cross-sectional view of the example of FIG. 10 at low speed. It is. 2...Cylinder head, 4...Cylinder, 5...
...Main exhaust passage, 6...Sub exhaust passage, 7...
Opening/closing valve, 7A... cut surface, 12... valve passage, 13... closing wall portion.

Claims (1)

[Scope of utility model registration request] The cylinder block is provided with a main exhaust passage that communicates with the inside of the cylinder, and a sub-exhaust passage that connects the inside of the cylinder and the main exhaust passage as an auxiliary exhaust passage, and an outlet of the sub-exhaust passage to the main exhaust passage. A cylindrical cylinder that has a nearby valve passage that opens the sub-exhaust passage at high engine speeds and a closing wall that closes the sub-exhaust passage at low engine speeds, and is rotated by a drive rack depending on the engine speed. An exhaust control device comprising: an opening/closing valve; and a cut surface formed on a closing wall of the opening/closing valve to match an inner wall of a main exhaust passage when the valve is fully opened.