JPH0238018Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" The invention relates to a cooling structure for a two-stroke engine, and more specifically, a control valve for changing the exhaust timing is installed near the opening of the exhaust passage to the inner peripheral surface of the cylinder. The present invention relates to a cooling structure for an engine equipped with a cooling structure.

"Conventional technology" In a two-stroke engine, as a means to increase the combustion gas filling efficiency, reflected waves in the exhaust passage are used to combust the fuel gas that blows from the combustion chamber to the exhaust passage during the scavenging stroke (so-called blow-through gas). Techniques for pushing it back into the room are known.

When applying this technology to an actual engine, it is important to keep in mind that the exhaust reflected wave must be returned to the exhaust port after the scavenging port is closed, but just before the exhaust port is closed. This is an essential point.

By the way, the 2 installed on motorcycles and cars
In the case of a cycle engine, since the rotational speed is varied, at a certain rotational speed the reflected waves can be returned to the point where the exhaust port is on the verge of being blocked, and even if it is possible to increase the combustion gas filling efficiency, At other rotational speeds, the timing at which the reflected waves return and the timing at which the exhaust port or scavenging port closes are different from each other, resulting in a phenomenon in which the reflected waves are unable to push back the blow-by gas.

As a solution to this problem, a structure is known in which a sliding control valve is provided on the upper edge of the exhaust port and the valve is moved according to the rotational speed of the engine. reference).

``Problem to be solved by the invention'' When the above-mentioned slide type control valve is installed in an engine, the contact area between the control valve and the housing part on the cylinder side that houses the control valve is large, so carbon in the exhaust gas is The control valve tends to stick to the control valve storage part due to the influence of carbon and tar, and it is necessary to periodically remove these carbons and the like in order to ensure the desired performance.

Similarly, since the contact area between the control valve and the control valve storage portion is large, the control valve is susceptible to distortion due to the influence of exhaust heat, which is a factor that promotes the above-mentioned stalemate phenomenon. Therefore, in order to suppress the adhesion of carbon and the like, it is effective to cool the area around the control valve.

The present invention has been developed in view of the above circumstances, and can efficiently cool a slide type control valve, thereby making it difficult for the control valve to become stuck due to adhesion of carbon or the like. The purpose is to provide a cooling structure for a two-stroke engine.

"Means for Solving the Problems" In order to achieve the above-mentioned object, in the present invention, the cylinder is provided with a cooling water jacket connected to the radiator, and the cooling water jacket includes the area around the exhaust passage, A water passage surrounding the control valve is integrally formed.

Further, a valve chamber is defined behind the control valve,
Preferably, this valve chamber is covered with a removable lid.

``Operation'' By passing cooling water around the control valve, the control valve can be efficiently cooled from all directions outside.

Efficiently cooling the control valve has two important meanings: making it difficult for carbon and tar to adhere to the control valve, and reducing thermal distortion that tends to occur in the control valve. can prevent stalemate.

Furthermore, since the exhaust passage can also be efficiently cooled, thermal distortion around the exhaust port can be reduced, thereby further preventing the control valve from sticking.

``Example'' Below, an example of the present invention will be described in Figures 1 to 9.
This will be explained with reference to the figures.

FIG. 1 shows a longitudinal sectional view of a two-stroke engine according to the present invention, and in the figure, reference numeral 1 indicates a cylinder;
2 is a cylinder head, 3 is a piston slidably inserted into the cylinder, 4 is a scavenging passage, and 5 is an exhaust passage. The opening (exhaust port) 5a of the exhaust passage 5 to the cylinder inner circumferential surface is provided so that both left and right ends thereof extend to approximately half of the cylinder inner circumferential surface in the circumferential direction. The exhaust passage 5 is provided with a rib 6 extending from the upper surface to the lower surface at the center in the left-right direction near the port 5a and extending to a predetermined location on the downstream side. This rib 6 serves to reinforce the vicinity of the opening of the exhaust passage 5 to the inner peripheral surface of the cylinder, and also serves to prevent the piston ring from expanding radially outward and hitting the upper or lower edge of the exhaust port 5a. .

A recess 7 is formed in the upper part of the exhaust passage 5 and slightly downstream of the exhaust port 5a. The upper part of this recess 7 is connected to the recess 7 and has a cylinder 1.
Guide holes (valve chambers that accommodate slide valves to be described later) 8, 8 extending obliquely with respect to the length direction of the
are formed on both sides of the rib 6 so as to extend in the circumferential direction along the inner peripheral surface of the cylinder 2, as shown in FIG. 2 when viewed from above. Further, the cylinder head 2 is formed with a guide hole (valve chamber) 9 that is continuous with the guide holes 8, 8. The guide hole 9 is provided with lower small diameter portions 9a, 9a which are bifurcated so as to be continuous with the guide holes 8, 8 on the cylinder side, and located at the upper center of the lower small diameter portion 9a so as to be continuous with the lower small diameter portion 9a. (See FIG. 7). Inside the upper large diameter portion 9b is a cover (lid) 1 which is screwed onto the cylinder head 2.
A guide tube 11 integrally provided with the guide tube 11 is coaxially fitted into the guide tube 11.

Inside the recess 7, a driving member 13 having a surface 12 having substantially the same curvature as the inner circumferential surface of the cylinder 1 and aligned with the inner circumferential surface of the cylinder 1 swings about an axis perpendicular to the cylinder centerline. The cylinder 1 is movably arranged in the guide holes 8 and 9.
The drive member 1 has approximately the same curvature as the inner circumferential surface of the drive member 1.
3, a slide valve (control valve) 15 having a control surface 14 aligned with the cylinder inner circumferential surface is fitted so as to be movable in the longitudinal direction at a required angle to the cylinder inner circumferential surface. (See Figure 9).

The drive member 13 has a structure in which it is divided into two parts at the center in the left-right direction, that is, at the portion facing the rib 6. A support tube 16 is integrally formed on each drive member half body 13A, 13B constituting the drive member 13 on the side opposite to the side on which the surface 12 is formed. The support tube 16 is connected to a rotation shaft 17 provided through the recess 7. The rotation shaft 17 is arranged to extend in a direction perpendicular to the center line of the cylinder 1, and is arranged so as to be located downstream of the rib 6. And this rotation shaft 17
is rotated, the driving member 1
3 is selectively located in either a state where it is housed in the recess 7 or a state where it is projected at a predetermined position above the exhaust port 5a.

A drive mechanism 18 for rotating the rotation shaft 17 is connected to the end of the rotation shaft 17 that projects outward from the cylinder 1 (see FIG. 3). The drive mechanism 18 includes a wire guide 19 attached to one end of the rotating shaft 17 and a portion protruding to the outside of the cylinder 1;
It consists of a motor (not shown) connected to the engine 9 via a wire 20, and a controller (not shown) that rotates the motor in forward and reverse directions according to the rotational speed of the engine.

On the other hand, the slide valve 15 is connected to the cylinder 1.
It is composed of working parts 21, 21 which are divided into two and have a circular arc cross section, which are inserted into the guide holes 8, 8, and a base part 22 which is a single cylinder with a bottom and is provided at the center of the upper part thereof. The base 22 is connected to the guide tube 1
1 so as to be movable. Further, a coil spring 23 is interposed between the base 22 and the cover 10, and thereby the slide valve 15
is constantly fired toward the driving member 13 side.

Therefore, the slide valve 15 is always brought into contact with the upper part of the swinging tip of the drive member 13, and can slide within the guide holes 8 and 9 following the swing of the drive member 13. and the drive member 13
When it is swung to the position where it closes the upper part of the exhaust port 5a, it enters between the upper end of the drive member 13 and the upper edge 5b of the exhaust port, fills the gap between them, and controls the The surface 14 cooperates with the surface 12 of the drive member 13 to open the exhaust port 5a.
A surface substantially continuous with the inner circumferential surface of the cylinder 1 is formed on the upper part of the cylinder 1.

Further, this engine is water-cooled and includes a cooling water jacket 30 spanning the cylinder 1 and cylinder head 2. The cooling water jacket 30 is connected to a radiator (not shown) via a pump, and when the engine temperature exceeds a certain level, the pump is activated and the cooling water flowing from the radiator cools the cylinder 1 and the cylinders. The head 2 is cooled appropriately.

To explain the cooling water jacket 30, 31 in FIGS. 1, 2, and 4 is installed at the front lower side of the cylinder 1 (in this specification, the left side in FIG. 1 is the front, and the right side is the rear). As shown in FIG. 4, the inside of this member 31 connects the scavenging passage 4 with the side of the cylinder inner circumference from the front of the cylinder inner circumference formed at the lower part of the cylinder. It is communicated with a water passage 32a which is U-shaped in plan view and extends to the rear of the cylinder through the gap. The water passage 32a is communicated with a water passage 32d formed in the upper part of the cylinder via water passages 32b, 32b rising on both sides of the front part of the cylinder, and water passages 32c, 32c rising on both sides of the rear part of the cylinder (Fig. 3). reference). The water passage 32d is formed continuously in the circumferential direction on the outside so as to surround the inner peripheral part of the cylinder, except for the part where the exhaust passage 5 is provided.

As shown in FIG. 2, the water passage 32d includes a water passage 32e standing up at the front of the cylinder, a water passage 32f standing up at the front of the inner circumference of the cylinder, and a water passage 32f standing up at the rear of the cylinder divided into left and right parts. 32g, 32g, and the cylinder head 2 via a water passage 32h rising up behind them.
It communicates with a water passage 32i formed inside. Further, a water passage 32j is formed in the center of the inside of the rib 6 and extends in the vertical direction.
The lower end of j is communicated with the water passage 32a provided at the lower part of the cylinder, and the upper end thereof is communicated with the water passage 32d.

Here, the water passages 32b, 32d, 32e, 3
2f, 32g, 32i, and 32j collectively constitute a water passage surrounding the slide valve 15.
The water passages 32e to 32h are formed astride both the cylinder 1 and the cylinder head 2, as shown in FIGS. 2 and 7. Also,
Water passage 3 rising in front of the inner circumference of the cylinder
2h is constituted by a single passage extending in an arcuate cross section on the cylinder side, while on the other hand, the cylinder head 2 side is constituted by four holes communicating with the passage. Further, 33 indicates the cylinder head 2 so as to communicate with the water passage 32i.
This is a tube connecting member implanted in the tube.

Thus, the exhaust timing control device configured as described above can improve the output characteristics of the engine over the entire rotation range by being operated based on the operating state of the engine.

That is, when the engine is operated at low rotation speed, the drive mechanism 18 rotates the rotation shaft 17 in a predetermined direction to swing the drive member 13, and the first
The drive member 13 is made to protrude into the exhaust port 5a as shown by the solid line in the figure. Along with such movement of the drive member 13, the slide valve 15 also moves downward while remaining in contact with the drive member 13 due to the action of the coil spring 23. In this state, the drive member and control surfaces 12, 14 of the slide valve
is positioned substantially on the same plane as the inner circumferential surface of the cylinder 1, and the upper part of the exhaust port 5a is closed. As a result, the upper edge of the exhaust port 5a is apparently distance l from the lower edge of the drive member 13. It will be lowered by a minute. Therefore, the exhaust port 5a, which is opened and closed by the movement of the piston 3, opens later and closes earlier because the upper edge of the exhaust port 5a is apparently lowered by a distance l.

In this way, when the engine is running at low speed, the exhaust port 5a is opened late and closed late in response to the long vertical movement period of the piston 3, and as a result, the exhaust reflection occurs just before the exhaust port 5a is closed. The waves are returned to the exhaust port 5a to improve combustion gas filling efficiency.

On the other hand, when the engine reaches a high rotation range,
The drive member 13 is moved in the opposite direction to the first
It is housed in the recess 7 as shown by the two-dot chain line in the figure.
At this time, the slide valve 15 is pressed upward by the drive member 13 and moved upward against the biasing force of the spring 23. That is, in this case, in response to the shorter vertical movement period of the piston 3, the exhaust port 5a is opened earlier and closed later than in the case described above. Therefore, in this case as well, the exhaust reflected waves are returned to the exhaust port 5a just before the exhaust port 5a is closed, and as in the case described above, the combustion gas filling efficiency is improved by effectively utilizing the reflected waves.

In this way, the exhaust timing of the engine can be controlled by the driving member 1.
3 and slide valve 15 to increase the combustion gas filling efficiency, thereby improving output characteristics over the entire rotation range.

Here, the main function of the driving member 13 is to operate the slide valve 1 along with the coil spring 23.
It is to move 5 up and down. As an auxiliary function, the exhaust timing is also controlled at the lower part of the slide valve 15.

The method of controlling the driving member 13 is not limited to step-type control such as two-position control, but may also be continuous proportional control.

In addition, in the above engine, the slide valve 1
The water passage for the cooling water jacket 30 is formed so as to surround the slide valve 15.
can be efficiently cooled from all directions outside. Therefore, problems such as distortion of the slide valve 15 due to the influence of heat will not occur, the operation of the slide valve 15 will be stabilized, and the durability will be increased.

In addition, the slide valve 15 is constantly driven by the drive member 13.
, and cooling the slide valve 15 efficiently also leads to efficient cooling of the drive member 13. As a result, the drive member 1
3, the operation can be stabilized and durability can be improved.

Further, in the above-mentioned engine, a water passage 32a extending between the inner circumference of the cylinder and the scavenging passage 4 is provided in the lower part of the cylinder, and a water passage 32d is provided in the upper part of the cylinder so as to surround the inner circumference of the cylinder.
The inner circumference of the cylinder and the boss for attaching it to the crankcase or cylinder head on the outside are made independent of each other. Therefore, when fixing the cylinder 1 to the crankcase side, the tightening strain does not affect the inner circumference of the cylinder, and when fixing the cylinder 1 and the cylinder head 2, the tightening strain does not affect the inner circumference of the cylinder. It does not even affect. In this way, it is possible to minimize the influence of tightening strain on the inner circumferential side of the cylinder, making it easier to set the distance between the inner circumferential surface of the cylinder and the piston to an optimal value, and suppressing the occurrence of piston slap noise. Moreover, the advantage is that the influence of unavoidable thermal distortion can be minimized.

Furthermore, the rib 6 is one of the parts that is most likely to reach a high temperature because it is constantly exposed to exhaust gas while the engine is running. In the embodiment described above, a cooling water passage 32j is formed in the center of the inside of the rib 6 to directly cool the rib 6, thereby preventing heat sagging and thermal distortion due to abnormally high temperature of the rib.

"Effects of the Invention" As explained above, according to the invention, the cylinder is provided with a cooling water jacket connected to the radiator, and the cooling water jacket has water surrounding the control valve including the area around the exhaust passage. Since the passage is integrally formed, the control valve can be efficiently cooled from all directions outside. Therefore, carbon and tar are less likely to adhere to the control valve, and thermal distortion that tends to occur in the control valve can be suppressed, thereby preventing the control valve from sticking.

Furthermore, since the exhaust passage can also be efficiently cooled at the same time, thermal distortion around the exhaust port can be reduced, and therefore, control valve sticking can be further prevented.

Further, if a valve chamber is defined behind the control valve and the valve chamber is covered with a removable lid, there is an advantage that maintenance can be facilitated.

[Brief explanation of the drawing]

1 to 9 show an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view of a two-stroke engine, FIG. 2 is a plan view of a cylinder, and FIG.
4 is a sectional view taken along the - line in Fig. 1, Fig. 5 is a sectional view taken along the - line in Fig. 2, and Fig. 6 is a sectional view taken along the - line in Fig. 2. ,
7 is a bottom view of the cylinder head, FIG. 8 is a view of the cylinder head with the cover removed, viewed from the direction of the arrow in FIG. 1, and FIG. 9 is a perspective view of the driving member and the slide valve. 1...Cylinder, 2...Cylinder head, 4...
Scavenging passage, 5... Exhaust passage, 5a... (exhaust port) opening, 6... Rib, 7... Recess, 8, 9...
Guide hole (valve chamber), 10...Cover (lid body), 14
... Control surface, 13 ... Drive member, 15 ... Slide valve (control valve), 17 ... Rotating shaft, 18 ...
Drive mechanism, 30...Cooling water jacket, 32a~
32j...Water passage.

Claims (1)

[Claims for Utility Model Registration] (1) At the upper part of the exhaust passage, near the opening to the inner circumferential surface of the cylinder, it is provided so as to be slidable in the longitudinal direction at a required angle with respect to the inner circumferential surface of the cylinder. and a control valve having a control surface having approximately the same curvature as the inner peripheral surface of the cylinder, the cylinder is provided with a cooling water jacket connected to a radiator, and the cooling water jacket is connected to a radiator. A cooling structure for a two-stroke engine, characterized in that a water passage surrounding the control valve including the periphery of the exhaust passage is integrally formed in the jacket. (2) A two-stroke engine according to claim 1, characterized in that a valve chamber is defined at the rear of the control valve, and the valve chamber is covered with a removable lid. Cooling structure.