JPH0250296B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention aims to increase output by increasing the area of the exhaust passage by using a sub-exhaust passage in addition to the main exhaust passage in combination with the main exhaust passage at high rotation speeds, and The present invention relates to an exhaust control device that suppresses a decrease in output by sometimes 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, the sixth
As shown in the figure, in addition to providing a main exhaust passage 5 that communicates with the inside of the cylinder 4 of the cylinder block 2, the inside of the cylinder 4 and the main exhaust passage 5 are connected by a sub-exhaust passage 6. , an on-off valve 7 is provided. The opening/closing valve 7 is controlled so as to open the sub-exhaust passage 6 when the engine is running at a high speed (FIG. 6), and to close the sub-exhaust passage 6 when the engine is running at a low speed as shown in FIG.

In this way, during high rotation as shown in FIG. 6, 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 that at low rotation (FIG. 7). At high rotation speeds in Figure 6, it is a high speed, high output type, that is, on the output curve, the output peak shifts to the higher rotation side than the output peak when the sub exhaust passage 6 is not used, so the output is high in the high rotation range. is obtained.

On the other hand, at low speeds shown in FIG. 7, if the sub exhaust passage 6 is left open as at high speeds (FIG. 6), the area of the exhaust passage is too large, resulting in the high-speed, high-output type described above. As a result, the output at low rotation speeds decreases, so the opening/closing valve 7
For example, by rotating the sub-exhaust passage 6 by 90 degrees in the counterclockwise direction shown in the figure from the state at high rotation speed (Fig. 6), the sub-exhaust passage 6 is closed, and exhaust is exclusively performed through the main exhaust passage 5. By doing so, the output decrease at low rotation speeds shown in FIG. 7 is suppressed.

In such an exhaust control device, it is required not only to suppress a decrease in output at low rotation speeds, but also to actively increase output.

In contrast, in conventional exhaust control devices,
As shown in FIG. 8, an on-off valve 7 has a valve pinion 14 meshed with a drive rack 15 provided at the end of the cylinder block 2 in the exhaust direction E.
were arranged parallel to the center O of the cylinder 4.

Therefore, the on-off valve 7 is located near the end of the sub-exhaust passage 6, and as a result, at low rotation speeds as shown in FIG. However, the output power could not be effectively increased.

In order to meet the demand for increased output, the applicant discovered that the volume of the sub-exhaust passage 6, which forms part of the volume of the combustion chamber at low engine speeds, should be made as small as possible.

To achieve this, the opening/closing valve 7 should be placed as close to the cylinder 4 as possible than the position shown in FIG. 6, that is, the position near the end of the sub-exhaust passage 6.

As a concrete plan, as shown by the broken line in FIG. 8, the on-off valves 7, which were provided parallel to the center O of the cylinder 4 and separated in the exhaust direction E, are moved in parallel to each other while maintaining the parallel relationship. As shown by the dotted chain line, we are considering moving it directly to the cylinder 4 side.

However, when the on-off valve 7 is brought closer to the cylinder 4 side as described above, the circumferential wall of the cylinder 4 becomes thinner as a result of the above-mentioned arrangement, and in particular, when the on-off valve 7 is brought closer to the cylinder 4 side while maintaining a parallel relationship. The thinned part is the opening/closing valve 7.
Since it extends over a wide range corresponding to the entire length of the cylinder, the portion of the cylinder block 2 corresponding to the peripheral wall of the cylinder 4 lacks strength.

Furthermore, if the opening/closing valve 7 is brought closer to the cylinder 4 side while maintaining the above-mentioned parallel relationship, it becomes necessary to bring the drive rack 15 closer to the cylinder 4 side as well.

When the drive rack 15 is brought closer to the cylinder 4 in this way, a stud bolt (not shown) arranged parallel to the center O of the cylinder 4 for connecting the cylinder block 2 and the cylinder head 3 shown in FIG. , and the drive rack 15. As a result, it remains difficult to adopt the idea of placing the opening/closing valves 7 in parallel.

(Purpose of the Invention) This invention was made in view of the above problems, and it not only prevents interference between the drive rack and the stud bolt, but also suppresses a significant decrease in the strength of the cylinder block, while reducing the speed at low rotation speeds. The purpose is to effectively increase the output at the same time.

(Structure of the Invention) In order to achieve the above object, the present invention disposes the drive rack near the end of the sub-exhaust passage in the cylinder block on the exhaust direction side, and at the same time disposes the opening/closing valve so that the valve portion thereof By arranging it so that it is inclined toward the center of the cylinder so that it is located closer to the cylinder than the pinion, only the valve part is brought closer to the cylinder side to prevent a decrease in the strength of the cylinder block, and the valve pinion side is separated from the cylinder as before. The valve pinion is arranged to prevent the risk of interference between the stud bolt and the drive rack that engages with the valve pinion.

(Example) Hereinafter, an example of the present 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 by stud bolts (not shown). Here, F in the figure corresponds to the front when the vehicle is mounted on a two-wheeled motor vehicle.

The above cylinder block 2 has its upper part facing forward F.
The cylinder 4 inside is inclined so that it comes to
As with cylinder block 2, its center O is at the front F.
is inclined to. At the front side of the cylinder 4, a main exhaust passage 5 and a sub-exhaust passage 6 are provided, as shown in FIG. Main exhaust passage 5 above
has a circular main exhaust port 5A at the end on the cylinder 4 side, and is formed as a passage tapering in the direction corresponding to the front F of the engine, as shown in FIG. As you can see, it is formed with the center of the passage slanting downward in the F direction in front of the engine.

On the other hand, the sub-exhaust passage 6 connects the cylinder 4 and the main exhaust passage 5 as a passage narrower than the main exhaust passage 5, as shown in FIG.

Each of the sub-exhaust passages 6 is provided with an on-off valve 7 that opens and closes the sub-exhaust passage 6.

As shown in FIG. 4, this on-off valve 7 has a valve part 8 at its upper part, a valve shaft 9 at its lower part, an upper pivot part 10 at its upper end, and a lower pivot part at its lower end. Part 11
has.

The valve portion 8 has a vertically elongated valve passage 12 extending therethrough, and as shown in FIG. It is formed as a passage inclined around the axis.

Here, a pair of crescent-shaped closing walls 13, 13 are formed on the outer periphery of the valve passage 12, as shown in a cross section in FIG. 2, which face each other with the valve passage 12 in between.

In such an opening/closing valve 7, when the rotation speed exceeds a certain level (FIG. 2), the passage center in the penetrating direction of the valve passage 12 is concentric with the sub-exhaust passage 6, so that the cylinder 4 and the main exhaust passage 5 are connected to each other. On the other hand, at low rotation speed as shown in Fig. 3,
By rotating both on-off valves 7, 7 by 90 degrees in the same direction counterclockwise from the state shown in FIG.
As shown in FIG. 3, one closing wall 13 always closes the sub-exhaust passages 6, 6 closer to the cylinder 4 than the valve passage 12, thereby cutting off communication between the cylinder 4 and the main exhaust passage 5. In this case, 30
is a first common communication passage, which is formed at an opposing position on the inner wall of the main exhaust passage 5, and this first common communication passage 30 is connected to the main exhaust passage 5 and the second common passage only at the time of low rotation as shown in FIG. By communicating with the communication path 31,
The resonance chamber 32 is activated during low rotation.

Here, the opening/closing valve 7, as shown in FIG. 4 (corresponding to the high rotation in FIG. 2),
It has a valve pinion 14 at its lower part, and for this valve pinion 14, as shown in FIG.
The drive racks 15 are engaged.

As shown in FIG. 5, the drive rack 15 in this case is arranged in a rack insertion hole 35 formed near the lower end of the cylinder block 2 below the main exhaust passage 5 (FIG. 1). The longitudinal direction of the engine is oriented in the left-right direction of the engine. The sliding shaft portion 16 shown in FIG. 2 provided at one end of the drive rack 15 has a rack support boss 2A.
A cylindrical rack sliding hole 17 formed in the cylinder block 2 as the inner periphery of one end, and a rack support shaft 18 with a circular cross section provided at the other end are connected to the screw hole 2.
It is slidably supported by a rack bearing bushing 19 screwed into B.

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 level of engine rotation is provided on the outer periphery of the governor sleeve 21 in the governor mechanism. An engagement pin 24 provided at one end of the drive 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 swing 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 swing arm 26. , this rack drive pin 28 engages a rack sleeve 27 attached to one end of the drive rack 15, as shown in FIG. In addition, 29 in Figure 1
is a drive case, which is attached to the right side of the cylinder block 2, and this drive case 29 extends from one end of the rack drive shaft 23 to the drive rack 15.
It is said to be a case body that covers up to one end of the. Also,
Reference numeral 33 in FIG.
8 is slidably supported.

This exhaust control device is characterized by a drive rack 15 as shown in FIG.
is disposed on the front F side of the engine, that is, near the end of the lower end of the cylinder block 2 on the exhaust direction E side, while the on-off valve 7 is placed in the state shown by the two-dot chain line in FIG. The angle θ is based on the opening/closing valve 7 whose valve center is parallel to
It is said to be tilted toward the rear of the engine (almost vertically when mounted on a vehicle).

Here, as a result of the above-mentioned inclination, the on-off valve 7
The valve portion is located closer to the cylinder 4 than the 8-valve pinion 14.

In the above configuration, the above valve section 8 has a third
As shown by the solid line in the figure, since it is moved closer to the cylinder 4 side, the volume of the part of the combustion chamber formed between the cylinder 4 and the opening/closing valve 7 at low rotational speeds is
This is much smaller than that of the on-off valve 7 shown by the two-dot chain line in FIG.

Here, the purpose of making a part of the combustion chamber smaller is not to move the entire on-off valve 7 closer to the cylinder 4 side, but to move only the valve part 8 side closer to the cylinder 4 side.
As a result, the range in which the peripheral wall of the cylinder block 2 corresponding to the outer periphery of the cylinder 4 is thinned is limited only to the upper part of the cylinder, and as a result, it is possible to increase the output at low rotation speeds. Therefore, there is little possibility that the strength of the cylinder block 2 will be reduced.

In addition, the drive rack 15 that engages with the valve pinion 14 provided at the lower end of the opening/closing valve 7 in FIG. There is no possibility that this drive rack 15 will interfere with a stud bolt (not shown) provided near the rear. This possibility of interference is also eliminated even when the drive rack 15 is disposed above the cylinder block 2 (FIG. 8).

In the above embodiment, both of the pair of on-off valves 7 are provided at an angle to the cylinder 4, but a type in which only one of them is provided at an angle may also be used. Further, in FIG. 2 of the embodiment, the sub-exhaust passage 6
Although one pair is provided, the configuration may include only one of them. Furthermore, although the opening/closing valve 7 is provided with a pair of closing walls 13, 13, it is also possible to omit one of them. Further, in the above embodiment, the valve pinion 14 is arranged below the valve part 8, but as in the conventional example shown in FIG. Also cylinder block 2
It may be placed at the top of the . Furthermore, in the above embodiment, the resonance chamber 32 was specially provided in order to more effectively increase the output at low rotation speeds by also utilizing the resonance effect, but in this invention, the volume of the combustion chamber is kept small. Since the purpose is to increase the output by this, the resonance chamber 32 may not be provided.

(Effects of the Invention) As explained above, according to the present invention, the drive rack is disposed near the end of the sub-exhaust passage in the cylinder block on the exhaust direction side;
The opening/closing valve mentioned above is arranged at an angle to the center of the cylinder so that the valve part is located closer to the cylinder than the valve pinion, which not only prevents interference between the drive rack and stud bolt, but also prevents the cylinder block from collapsing significantly. It is possible to effectively increase the output at low rotation speeds while suppressing the reduction in strength.

[Brief explanation of drawings]

Fig. 1 is a right side view of a two-stroke engine showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the line shown in Fig. 1 at high speed, and Fig. 3 is a sectional view taken along the line shown in Fig. 1 at low speed. 4 is a perspective view of the opening/closing valve, FIG. 5 is a sectional view taken along the line of FIG. 2, and FIG.
The figure is a sectional view showing an example of a conventional exhaust control device at high speeds, FIG. 7 is a sectional view of an example of a conventional exhaust control device at low speeds, and FIG. 8 is a right side view of a conventional exhaust control device. It is a front view. 2...Cylinder block, 4...Cylinder, 5...Main exhaust passage, 6...Sub exhaust passage, 7...Opening/closing valve, 8...Valve portion, 14...Valve pinion, 15
...Easy to drive.

Claims (1)

[Claims] 1. 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 are formed in the cylinder block. Opens the sub-exhaust passage during rotation,
An exhaust system is provided with an opening/closing valve that closes the sub-exhaust passage at low engine speeds, a valve pinion is provided in the opening/closing valve, and a drive rack is engaged with the valve pinion, which is driven according to the high or low engine speed. In the control device, the driving rack is arranged near the end of the sub-exhaust passage in the cylinder block on the exhaust direction side, and the opening/closing valve is arranged near the center of the cylinder so that its valve portion is located closer to the cylinder than the valve pinion. An exhaust control device characterized by being arranged at an angle.