JPH077546Y2 - Exhaust timing control device for 2-cycle engine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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]

2. Description of the Related Art In a two-cycle engine, a reflected wave in an exhaust passage is used as a means for increasing a combustion gas filling efficiency, and a fuel gas (so-called blow-through gas) blown from a combustion chamber to a discharge passage during scavenging The technique of pushing back to is known.

In applying this technique to an actual engine, it must be kept 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. This 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 point just before the exhaust port is blocked at a certain rotational speed, and combustion is performed. Even if the gas filling 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 present inventors, as shown in the above-mentioned Japanese Utility Model Application No. 60-97274,
A valve element is provided in the upper part of the exhaust passage in the vicinity of the opening to the inner peripheral surface of the cylinder, and by swinging this valve element in accordance with the engine speed, the upper part of the exhaust passage is opened and closed, thereby enabling full rotation. We devised a technology that improves the gas filling efficiency in the region to improve the output.

[0006]

Some conventional engines have a wide opening so that the exhaust port occupies nearly half of the inner peripheral surface of the cylinder in the circumferential direction for the purpose of improving the output. In such an engine, the exhaust passage is formed such that the opening to the inner peripheral surface of the cylinder, that is, the exhaust port portion is widest in the left-right direction, and gradually narrows 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, a dead space occurs between the valve body and the cylinder inner peripheral surface. To minimize this dead space, the swing center should be located as far away from the cylinder inner peripheral surface as possible. It is advantageous to arrange it at a position, that is, at a position as downstream as possible from the exhaust passage.

If the exhaust port is wide, as described above, the elasticity of the piston ring will cause the piston ring to expand radially outward, and the piston ring will hit the upper and lower edges 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 and the valve It becomes impossible to wear the body.

[0008] Therefore, the inventors of the present invention, the actual public Sho 58-36
As disclosed in Japanese Patent No. 818, it was devised that the valve body was divided into two parts in the left-right direction, and the valve halves were individually inserted into the exhaust passage and attached to an exhaust port having a rib at the center.

However, the technique described in the above publication, that is, the valve body is divided into left and right parts, and the valve halves are individually inserted into predetermined positions of the exhaust passage, and the mating surfaces of the valve halves are joined. Insert the pin provided on one side into the hole provided on the mating surface of the other valve half, and position so that the rotary shafts integrally provided on these valve half are on the same axis,
In this state, if the technique of inserting the fixing bolts into the location that is displaced radially outward from the center and assembling the valve body together is adopted as it is, the diameter of the mating faces of the valve halves should be fixed. The bolts must be set large enough to be inserted, the valve body cannot be thinned to a certain extent, the number of parts is large, and the assembly work of the valve body is troublesome.

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

[0011]

In order to achieve the above-mentioned object, in the exhaust timing control device according to the present invention, an upper portion of the exhaust passage having a rib at the center in the left-right direction of the exhaust port opening on the inner peripheral surface of the cylinder is provided. The timing of communication between the inside of the cylinder and the exhaust passage is controlled by a piston that is slidably inserted into the cylinder by opening and closing with a valve body that is swingable about a rotation axis that is orthogonal to the cylinder centerline. In the exhaust timing control device to be changed, a control surface having a curvature substantially the same as that of the cylinder inner peripheral surface and aligned with the cylinder inner peripheral surface is provided at a portion of the valve body facing the cylinder inner peripheral surface. The valve element has a structure that can be divided into right and left parts with a portion facing the rib as a boundary, and the valve element is such that the rotation axis rotates around through holes formed in the left and right valve halves constituting the valve element. In a stopped state Is characterized by being assembled is input.

[0012]

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

The left and right valve halves are simply inserted by inserting ribs between exhaust valve passages and inserting a common rotary shaft into the through holes of the valve halves. Can be integrally assembled, and the assembling work of 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 bolts are inserted at the eccentric positions. Compared to other valve body fixing means such as fixing, there is an advantage that the thickness of the valve body around the shaft support can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a longitudinal 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 a piston slidably fitted in 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 inner peripheral surface of the cylinder is provided so that both the 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. The exhaust passage 5 is provided with a rib 6 extending from the upper surface to the lower surface at a center in the left-right direction near the port 5a and extending to a predetermined downstream side. The lip 6 serves to reinforce the vicinity of the opening of the exhaust passage 5 to the inner peripheral surface of the cylinder and to prevent the piston ring from spreading radially outward and hitting the upper edge or the lower edge of the exhaust port 5a.

The upper part of the exhaust passage 5 and the exhaust port 5a
A recess 7 is formed on the slightly downstream side. This recess 7
Guide holes 8, 8 continuous with the recess 7 and extending obliquely with respect to the longitudinal direction of the cylinder 1 are provided on the upper side of the cylinder 2 on both sides of the rib 6 when viewed in plan as shown in FIG. Is formed so as to extend in the circumferential direction along the inner peripheral surface of the. 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). In the upper large-diameter portion 9b, a guide cylinder 11 integrally provided with a cover 10 screwed to the cylinder head 2 is coaxially fitted.

In the recess 7, a plate-shaped first valve body 13 having a control surface 12 having substantially the same curvature as the inner peripheral surface of the cylinder 1 and aligned with the inner peripheral surface of the cylinder is provided. It is arranged so that it can swing around an axis perpendicular to the center line,
A second valve body having a control surface 14 in each of the guide holes 8 and 9 that has substantially the same curvature as the inner peripheral surface of the cylinder 1 and is aligned with the inner peripheral surface of the cylinder similarly to the first valve body 13. 15
Is movably fitted (see FIG. 7).

The first valve body 13 has a structure in which it is divided into two parts 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 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 that rotation can be prevented. Rotating shaft 17
Are arranged so as to extend in a direction orthogonal to the center line of the cylinder 1, and are arranged so as to be located downstream of the ribs 6. When the rotary shaft 17 is rotated, the first valve body 13 is either housed in the recess 7 or projected to a predetermined position above the exhaust port 5a. It is supposed to be located alternatively.

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 one end of the rotary shaft 17 and protruding to the outside of the cylinder 1.
It comprises 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 is the cylinder 1
Bifurcated action part 2 inserted into the guide holes 8 of the
1 and 21, and a bottomed cylindrical base 22 provided only at the center of the upper part thereof. The base 22 is
It is movably fitted 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 repelled toward the first valve body 13 side.

Therefore, the second valve body 15 is always brought into contact with the upper part of the swinging tip of the first valve body 13 to follow the swinging of the first valve body 13 and the guide holes 8, When the first valve body 13 is swung to a position that closes the upper portion of the exhaust port 5a, the
Enters between the upper end of the valve body 13 and the upper edge 5b of the exhaust port to fill the gap between them, and its control surface 14 cooperates with the control surface 12 of the first valve body 13. A surface substantially continuous with the inner peripheral surface of the cylinder 1 is formed above the exhaust port 5a.

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 passed from the downstream side opening of the exhaust passage 5 to the passage. The rib 6 is inserted into the inside, and is fitted into the recesses 7 on both sides of the rib 6 so that the rib 6 is sandwiched 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.
Insert. Next, 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.

The valve bodies 13 and 15 and the drive mechanism 18 are assembled as described above. In the above installation,
The valve body 13 has a wide rocking tip side where the overall shape matches the cylinder inner peripheral surface, and the rocking center is located on the downstream side of the rib 6 of the exhaust passage 5. Since the 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 cylinder inner peripheral surface and the exhaust passage 5, and the cylinder inner peripheral portion. The 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 constructed can be operated based on the operating condition of the engine to enhance the output characteristics of the engine in the entire rotation range.

That is, when the engine is operated at a low speed, the drive mechanism 18 rotates the rotating shaft 17 in a predetermined direction to swing the first valve body 13, and is shown by a solid line in FIG. Thus, the valve element 13 is projected into the exhaust port 5a. With such movement of the valve body 13, the second valve body 15
Also moves downward while being in contact with the first valve body 13 by the action of the coil spring 23. 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, resulting in exhaust gas. The upper edge of the 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.

Thus, when the engine is running at a low speed, the exhaust port 5a is opened late and closed late in response to the long vertical movement cycle of the piston 3, which causes the exhaust port 5a to be closed just before it is 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 that shown in FIG.
It is stored in the recess 7 as shown by the middle two-dot chain line. 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 just 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 engine exhaust timing is set to the first,
The second valve elements 13 and 15 are controlled so that the combustion gas charging efficiency is increased to improve the output characteristics in the entire rotation range.

The control method of the valve element 13 is not limited to stepwise control such as 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]

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

The left and right valve halves are individually inserted by inserting ribs between exhaust valve passages, and inserting a common rotary shaft into the through holes of the valve halves. Can be integrally assembled, and the assembling work of 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 hole of the valve half, and the bolts are inserted at the eccentric positions. Compared to other valve body fixing means such as fixing, there is an advantage that the 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 sectional view taken along the line AA of FIG.

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

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

6 is a view showing a state in which a cover of a cylinder head is removed, as viewed in 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 element that is swingably arranged around a rotation axis that is orthogonal to the cylinder center line. An exhaust timing control device for changing the timing of communication between an exhaust passage and the inside of a cylinder by a piston slidably inserted therein, wherein a cylinder inner peripheral surface is provided at a portion of the valve body facing the cylinder inner peripheral surface. 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 left and right 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 left and right valve halves constituting a valve body in a state in which the rotation shaft is stopped.