JPH0527241U - Exhaust timing control device for 2-cycle engine - Google Patents

Abstract

(57) [Abstract] [Purpose] A two-cycle engine in which an exhaust timing control valve element can be assembled very easily even in an engine having an exhaust passage having a wide exhaust port having a rib in the center. The exhaust timing control device is provided. [Structure] A control surface is provided at a portion of the valve body facing the cylinder inner peripheral surface so as to have substantially the same curvature as the cylinder inner peripheral surface so as to be aligned with the cylinder inner peripheral surface. The structure is divided into right and left, and the valve body is inserted and assembled in a through hole formed in the left and right valve halves forming the valve body with the rotation shaft being stopped.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an engine exhaust timing control device, and more particularly to an exhaust timing control device used in a two-cycle engine.

[0002]

[Prior Art]

 In a two-cycle engine, there is a known technology for pushing back the fuel gas (so-called blow-through gas) blown from the combustion chamber during scavenging to the exhaust chamber by using reflected waves in the exhaust passage, as a means to increase the combustion gas filling efficiency. Has been.

When applying this technique to an actual engine, it is important to keep in mind that the reflected exhaust wave is returned to the exhaust port after the scavenging port is closed and just before the exhaust port is closed. That is something that must be done.

By the way, in the case of a two-cycle engine mounted on a motorcycle or an automobile, since the rotational speed is changed and used, the reflected wave can be returned to a position just before the exhaust port is blocked at a certain rotational speed. Even if the combustion gas charging efficiency can be increased, a phenomenon occurs in which it cannot be performed at other rotation speeds.

In order to deal with such a problem, the inventors of the present invention, as disclosed in the above-mentioned Japanese Utility Model Application No. 60-97274, propose that the valve body is located in the upper part of the exhaust passage and near the opening to the inner peripheral surface of the cylinder. Is provided, and by swinging this valve element according to the engine speed, the upper part of the exhaust passage is opened and closed, thereby improving the gas filling efficiency and improving the output in the entire rotation range. Devised.

[0006]

[Problems to be solved by the device]

 By the way, some conventional engines have a wide opening so that the exhaust port occupies nearly half of the inner circumferential surface of the cylinder for the purpose of improving the output. The opening to the peripheral surface, that is, the exhaust port portion is widest in the left-right direction, and is formed so as to gradually narrow toward the downstream side. In order to assemble the exhaust control valve element into the exhaust passage having such a shape, the valve element must have a shape that is widest on the exhaust port side according to the exhaust passage and narrows toward the downstream side. Also, when the valve body is assembled, there is a dead space between the valve body and the inner peripheral surface of the cylinder.To keep this dead space as small as possible, keep the swing center as far away from the inner peripheral surface of the cylinder as possible. It is advantageous to arrange them at a separated position, that is, at a position as downstream as possible from the exhaust passage.

Further, as described above, if the exhaust port is wide, the piston ring expands radially outward due to its elasticity, and hits the upper edge or the lower edge of the exhaust port. To prevent this, it is effective to provide a rib that is flush with the inner peripheral surface of the cylinder at the center of the exhaust port. However, when this rib is provided, when trying to assemble the valve body having the swing center on the downstream side of the rib and the swing tip facing the exhaust port, the valve body and the rib interfere with each other. It becomes impossible to attach the valve body.

Therefore, the inventors of the present invention have a structure in which the valve element is divided into two parts in the left-right direction as shown in Japanese Utility Model Publication No. 58-36818, and the valve halves are individually inserted into the exhaust passage, and the central portion is inserted. I devised to attach it to the exhaust port which has a rib.

However, the technique described in the above publication, that is, the valve body is divided into left and right halves, and the valve halves are individually inserted into predetermined positions of the exhaust passage, and the mating surfaces of the valve halves are inserted. Insert the pin provided on one side into the hole provided on the mating surface of the other valve half and position them so that the rotary shafts integrally provided on those valve half are on the same axis. If the technology of assembling the valve body by inserting the fixing bolt at a position that is displaced radially outwards from is adopted as it is, the diameter of the mating surfaces of the valve halves can be inserted with the fixing bolt. It had to be set to a large value, and it was not possible to reduce the thickness of the valve disc to a certain extent, there were many parts, and the assembly work of the valve disc was troublesome.

The present invention has been made in view of the above circumstances, and even in an engine having an exhaust passage having a wide exhaust port having a rib in the center, the cylinder inner peripheral surface is aligned with the exhaust passage. A 2-cycle exhaust valve that has the widest side and has a swing center on the downstream side of the rib can be assembled very easily, and the wall thickness near the shaft support part of the valve can be set thin. An object is to provide an exhaust timing control device for an engine.

[0011]

[Means for solving problems]

 In order to achieve the above-mentioned object, in the exhaust timing control device according to the present invention, the upper portion of the exhaust passage having a rib at the center in the left-right direction of the exhaust port opening on the cylinder inner peripheral surface is provided with An exhaust timing control device that opens and closes with a valve body that is swingable around the center of the cylinder to change the timing of communication between the inside of the cylinder and the exhaust passage by a piston that is slidably inserted into the cylinder. In addition, a control surface that has substantially the same curvature as the cylinder inner peripheral surface and is aligned with the cylinder inner peripheral surface is provided at a portion of the valve body facing the cylinder inner peripheral surface, and the valve body is provided on the rib. The valve element is structured so that it can be divided into left and right parts with the opposing parts as boundaries, and the valve body is in a state in which the rotary shaft is stopped from rotating through the through holes formed in the left and right valve halves constituting the valve element. Inserted in and assembled It is characterized in Rukoto.

[0012]

[Action]

 When assembling the valve body to the upper part of the exhaust passage, the valve halves divided into two parts can be inserted separately into one side and the other side of the rib, respectively, and the rib is arranged at the center of the exhaust passage. Despite that, the valve body can be assembled.

Further, the left and right valve halves are individually inserted so that a rib is sandwiched between the exhaust passages, and a common rotary shaft is inserted into the through holes of the valve halves. Can be integrally assembled, and the work of assembling the valve body itself can be simplified.

Further, as described above, the common rotary shaft is inserted into the through hole of the valve half body to integrally assemble the left and right valve half bodies, and the bolt is inserted into the eccentric position. Compared with other valve body fixing means such as fixing the valve body, the wall thickness of the valve body around the shaft support can be reduced.

[0015]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional view of a two-cycle engine equipped with an exhaust timing control device according to the present invention. In the figure, reference numeral 1 is a cylinder, 2 is a cylinder head, and 3 is slidably inserted in the cylinder. A piston, 4 is a scavenging passage, and 5 is an exhaust passage. The opening (exhaust port) 5a of the exhaust passage 5 to the inner peripheral surface of the cylinder is provided so that both left and right ends extend to approximately half of the inner peripheral surface of the cylinder in the circumferential direction so that high output can be obtained. In the exhaust passage 5, a rib 6 extending from the upper surface to the lower surface is provided in the vicinity of the port 5a at the center in the left-right direction and extends to a predetermined downstream side. The lip 6 reinforces the vicinity of the opening of the exhaust passage 5 to the inner surface of the cylinder, and also prevents the piston ring from spreading radially outward and hitting the upper edge or the lower edge of the exhaust port 5a. ..

A recess 7 is formed above the exhaust passage 5 and slightly downstream of the exhaust port 5a. Guide holes 8, 8 continuous with the recess 7 and extending obliquely with respect to the longitudinal direction of the cylinder 1 are provided in the upper portion of the recess 7 in a plan view as shown in FIG. It is formed on both sides along the inner peripheral surface of the cylinder 2 so as to extend in the circumferential direction. Further, the cylinder head 2 is formed with guide holes 8 and guide holes 9 continuous with the guide holes 8. The guide hole 9 is composed of a lower small-diameter portion 9a which is bifurcated so as to be continuous with the guide holes 8 on the cylinder side, and a single upper large-diameter portion 9b provided at the center of the upper portion (FIG. 4). reference). A guide cylinder 11 that is integrally provided with a cover 10 that is screwed to the cylinder head 2 is coaxially fitted in the upper large diameter portion 9b.

In the recess 7, a plate-shaped first valve body 13 having a control surface 12 having substantially the same curvature as that of the inner peripheral surface of the cylinder 1 and aligned with the inner peripheral surface of the cylinder is provided. The guide holes 8 and 9 are arranged so as to be swingable about an axis perpendicular to the center line, and the guide holes 8 and 9 have substantially the same curvature as the inner peripheral surface of the cylinder 1 so that they are similar to the first valve body 13. A second valve body 15 having a control surface 14 aligned with the inner surface of the cylinder is movably fitted (see FIG. 7).

The first valve body 13 has a structure in which the first valve body 13 is divided into two at the center in the left-right direction, that is, at a portion facing the rib. A support cylinder 16 is integrally formed on each of the valve halves 13A and 13B forming the first valve body 13 on the side opposite to the side on which the control surface 12 is formed. The support cylinder 16 is connected to a rotary shaft 17 that penetrates through the recess 7. The outer shape of the support cylinder 16 and the rotary shaft 17 fitted into the support cylinder 16 are both formed in a rectangular cross-section so as to prevent rotation. The rotating shaft 17 is arranged so as to extend in a direction orthogonal to the center line of the cylinder 1, and is arranged so as to be located on the downstream side of the rib 6. Then, when the rotating shaft 17 is rotated, the first valve body 13 is housed in the recess 7 or is projected to a predetermined position above the exhaust port 5a. It is designed to be positioned as one of the alternatives.

A drive mechanism 18 for rotating the rotating shaft 17 is connected to the end of the rotating shaft 17 protruding outward of the cylinder 1 (see FIG. 3). .. The drive mechanism 18 includes a wire guide 19 attached to a portion of the rotary shaft 17 protruding to the outside of the cylinder 1, and a motor (not shown) connected to the wire guide 19 via a wire 20. ) And a controller (not shown) for operating the motor in forward / reverse rotation according to the rotation speed of the engine.

On the other hand, the second valve body 15 includes bifurcated action portions 21 and 21 to be fitted into the guide holes 8 and 8 of the cylinder 1 and a bottomed sole provided at the center of the upper portions thereof. It is composed of a cylindrical base portion 22. The base portion 22 is movably inserted into the guide cylinder 11. A coil spring 23 is interposed between the base 22 and the cover 10, whereby the second valve body 15 is constantly repulsed toward the first valve body 13 side.

Therefore, the second valve body 15 is always brought into contact with the upper end of the swing tip of the first valve body 13 and follows the swing of the first valve body 13 to guide the guide hole 8 , 9 inside, and when the first valve body 13 is swung to a position that closes the upper part of the exhaust port 5a, the upper end of the first valve body 13 and the above It penetrates into the space between the upper edge 5b of the exhaust port and fills the gap between the two, and its control surface 14 cooperates with the control surface 12 of the first valve body 13 so that it is located above the exhaust port 5a. It is formed so as to form a surface substantially continuous with the inner peripheral surface of the cylinder 1.

Here, the method of assembling the first and second valve bodies 13 and 15 will be described. First, the valve halves 13A and 13B constituting the first valve body 13 are connected to the downstream side opening of the exhaust passage 5. The rib 6 is inserted into the passage, and the rib 6 is fitted into the recesses 7 on both sides of the rib 6 so as to sandwich the rib 6 therebetween. Next, the rotary shaft 17 is inserted from the side of the cylinder 1 and inserted into the support cylinders 16 of both valve halves.

Next, the cylinder head 2 is screwed to the cylinder 1, and the second valve body 15 is inserted into the continuous guide holes 8 and 9. Then, the coil spring 23 is interposed between the cover 10 and the second valve body 15 and the cover 10 is screwed to the cylinder head 2. On the other hand, the drive mechanism 18 is set at the end of the rotary shaft 17 protruding from the cylinder 1.

As described above, the valve bodies 13 and 15 and the drive mechanism 18 are assembled. In the above-mentioned assembly, the valve body 13 is widened on the swing tip side where the overall shape matches the cylinder inner peripheral surface, and the swing center is located on the downstream side of the rib 6 of the exhaust passage 5. However, since the valve body itself has a structure that can be divided into two parts on the left and right, it can be set near the exhaust port 5a of the exhaust passage 5.

Reference numeral 31 in FIG. 2 indicates a cooling water inlet, and the cooling water introduced therein passes through a water passage 32 formed so as to surround the inner peripheral surface of the cylinder and the exhaust passage 5, and thus the inside of the cylinder. The peripheral surface and the exhaust passage 5 are appropriately cooled, and then collected at the upper cooling water outlet 33 and sent from there to a radiator (not shown).

Thus, the exhaust timing control device thus configured can be operated based on the operating state of the engine to enhance the output characteristics of the engine in the entire rotation range.

That is, when the engine is operating at a low rotation speed, the drive mechanism 18 rotates the rotating shaft 17 in a predetermined direction to swing the first valve body 13, and is indicated by a solid line in FIG. So that the valve body 13 is projected into the exhaust port 5a. With such movement of the valve body 13, the second valve body 15 also moves downward due to the action of the coil spring 23 while being in contact with the first valve body 13. In this state, the control surfaces 12 and 14 of the first and second valve bodies are positioned substantially on the same plane as the inner peripheral surface of the cylinder 1, and the upper portion of the exhaust port 5a is closed. The upper edge of the exhaust port 5a is apparently lowered by a distance 〓 to the lower edge of the first valve body 13. Therefore, since the upper edge of the exhaust port 5a is apparently reduced by a distance, the exhaust port 5a opened and closed by the movement of the piston 3 is opened late and closed early.

As described above, when the engine is running at low speed, the exhaust port 5a is opened and closed slowly in response to the long vertical movement cycle of the piston 3, which causes the exhaust port 5a to be closed on the verge of being closed. The exhaust reflected wave is returned to the exhaust port 5a to enhance the combustion gas filling efficiency.

On the other hand, when the engine reaches the high speed range, the first valve body 13 is moved in the opposite direction to the above and is housed in the recess 7 as shown by the chain double-dashed line in FIG. .. At this time, the second valve body 15 is pressed upward by the first valve body 13 and moved upward against the biasing force of the spring 23. That is, in this case, the exhaust port 5a is opened earlier and closed later than in the case described above in response to the shortening of the vertical movement cycle of the piston 3. Therefore, also in this case, the exhaust reflected wave is returned to the exhaust port 5a immediately before the exhaust port 5a is closed, and the combustion gas filling efficiency is enhanced by the effective use of the reflected wave, as described above.

In this way, the exhaust timing of the engine is controlled by the first and second valve bodies 13 and 15 so that the combustion gas filling efficiency is increased, and the output characteristics in the entire rotation range are improved.

The control method of the valve element 13 is not limited to the step-type control such as the two-position control, but continuous proportional control may be performed.

Further, in the above embodiment, both the first valve body 13 and the second valve body 15 are provided, but the second valve body 15 has an auxiliary function of the first valve body 13. This is done and is not always necessary in the present invention.

[0033]

[Effect of the device]

 As described above, according to the exhaust timing valve body device of the present invention, since the valve body has a structure in which the valve body can be divided into left and right parts, the upper portion of the exhaust passage having the wide exhaust port having the rib in the center is provided. It is possible to assemble the valve body to the. Further, as described above, since the rib is arranged at the center of the exhaust port in the left-right direction, the piston ring does not spread and the knocking sound that hits the upper edge or the lower edge of the exhaust port is not generated.

Further, the left and right valve halves are individually inserted so that the ribs are sandwiched between the exhaust passages, and the common rotary shaft is inserted into the through holes of the valve halves. Can be integrally assembled, and the work of assembling the valve body itself can be simplified.

Further, as described above, the left and right valve halves are integrally assembled by inserting the common rotary shaft into the through holes of the valve halves, and the bolt is inserted at the eccentric position. Compared with other valve body fixing means such as fixing the valve body, the wall thickness of the valve body around the shaft support can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a two-stroke engine according to an embodiment of the present invention.

FIG. 2 is a plan view of a cylinder.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a bottom view of the cylinder head.

5 is a cross-sectional view taken along the line BB of FIG.

FIG. 6 is a diagram showing a state in which a cover of a cylinder head is removed, as seen from the direction of arrow C in FIG.

FIG. 7 is a perspective view of first and second valve bodies.

[Explanation of symbols]

 1 cylinder 2 cylinder head 4 scavenging passage 5 exhaust passage 5a (exhaust port) opening 6 rib 7 recess 8 guide hole 9 guide hole 12 control surface 13 first valve body 13A valve half body 13B valve half body 14 control surface 15th 2 valve body 17 rotating shaft 18 drive mechanism

Claims (1)

[Scope of utility model registration request] The upper part of the exhaust passage, which has a rib at the center in the left-right direction of the exhaust port that opens on the inner peripheral surface of the cylinder, is opened and closed by a valve body that is swingably arranged around a rotation axis that is orthogonal to the cylinder center line. An exhaust timing control device for changing a communication timing between an inside of a cylinder and an exhaust passage by a piston slidably inserted therein, wherein a cylinder inner peripheral surface is provided at a portion facing the cylinder inner peripheral surface of the valve body. A control surface having substantially the same curvature and aligned with the inner peripheral surface of the cylinder is provided, and the valve body has a structure that can be divided into right and left with a portion facing the rib as a boundary, and the valve body has the same structure. An exhaust timing control device for a two-cycle engine, characterized in that the rotary shaft is inserted and assembled in a through hole formed in the left and right valve halves constituting the valve body in a state where the rotation shaft is stopped.