JPS6260920A - Exhaust timing control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To have sure control of exhaust timing by furnishing a valve, whose incoming and outgoing angles are right across the axis of cylinder, at the upper edge of exhaust port of a 2-cycle engine and by installing a close position restricting part at the end of a valve guide. CONSTITUTION:A control valve 14, whose incoming and outgoing angles are right across the axis of cylinder, is installed at the upper edge of an opening for the exhaust port 10 of 2-cycle engine. This control valve 14 slides within a valve guide 13, and a valve closing position restricting part 15 is installed at that end of valve guide 13 situated on the opening side. During high speed operation of engine, the control valve 14 is positioned on the left in the attached illustration and opens to quicken the exhaust timing. During low speed operation, the valve 14 moves to the right and comes in contact with the closing position restricting part 15 to provide valve closing in specified position, when the exhaust timing will be delayed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an exhaust timing control device for an engine, and particularly to an exhaust timing control device used in a two-stroke engine.

"Conventional Technology" In general, the engines installed in vehicles, etc. are roughly divided into low-speed types that emphasize power characteristics when driving at low speeds, and high-speed types that emphasize power characteristics when driving at high speeds. The former is designed so that the peak of engine output is obtained in the low rotation range of the engine, and the latter is designed so that the peak of engine output is obtained in the high rotation range, but the former In the latter case, the output in the high rotation range reaches a ceiling, and in the latter case, the output in the low rotation range becomes lower than that in the former.

Therefore, efforts are being made to improve power characteristics across the entire range from low-speed driving to high-speed driving by increasing output in the low-speed range while maintaining high output in the high-speed range, and specific solutions are being developed. As a means of changing the exhaust timing of the engine between low and high rotations, an example of this structure is disclosed in Japanese Patent Application Laid-Open No. 56-9231.
The technology shown in Publication No. 4 has already been proposed.

As shown in Figure 1, this technology is a two-stroke engine! A through hole 2a, which is inclined with respect to the sliding direction of the piston 4 and communicated with the exhaust passage 3, is provided in the upper part of the exhaust passage 3 communicating with the inside of the cylinder 2, near the opening 3a of the exhaust passage 3. A control valve 5 is slidably provided in the through hole 2a, and the control valve 5 is moved forward and backward into the upper part of the opening 3a.
As shown by the solid line in FIG. 1, by retracting the control valve 5 from the opening 3a of the exhaust passage 3, the opening 3a
The entire surface of the exhaust passage 3 is opened to raise its upper edge 3b, and at low speed, the control valve 5 is made to protrude above the opening 3a of the exhaust passage 3, as shown by the chain line in FIG. By closing the upper part of the opening 3a and positioning the protruding end 5a of the control valve 5 at approximately the same level as the extension line of the inner surface of the cylinder 2, the upper edge 3b of the opening 3a can be extended up to the protruding end 5a of the control valve 5. The hook is shifted downward by an upper distance L1, thereby delaying the communication timing between the inside of the cylinder 2 and the exhaust passage 3 as the piston 4 descends by the distance ML.

"Problems to be Solved by the Invention" The present invention aims to solve the following problems in the conventional technology described above.

That is, as described above, when controlling the exhaust timing using the sliding control valve 5, it is necessary to restrict the protruding position of the control valve 5 so as not to interfere with the sliding movement of the piston 4. Therefore, in the conventional technology described above, the control valve 5
A collar 5b is integrally formed on the end opposite to the projecting end of the control valve 5, and a step 2b is formed in a part of the through hole 2a, and the projecting position of the control valve 5 is regulated by abutting the two. However, the following problems arise due to such a structure.

■In order to allow the control valve 5 on which the flange 5b is formed to slide and to form the stepped portion 2b, it is necessary to form a large diameter portion from the middle of the through hole 2a to the outer surface of the cylinder 2. However, this may lead to a decrease in the strength of the cylinder 2.

■Increasing the weight of the control valve 5 by forming the flange 5b;
In other words, the weight of the reciprocating part increases, which tends to reduce the responsiveness of the control valve 5.

■ The variation in the position when forming the flange 5b and the variation when forming the step portion 2b directly affect the regulation of the protruding position of the control valve 5, and as a result, the control valve 5 and the cylinder 2 requires high-precision processing.

"Means for Solving the Problems" The present invention aims to provide an exhaust timing control device for a two-stroke engine that can effectively solve the problems in the conventional techniques described above, and the exhaust timing control device has the following features: In particular, a through hole directed toward the center of the cylinder is formed in the upper wall of the exhaust passage, and the upper edge of the opening is slidable by the piston being moved forward and backward into the through hole to the upper part of the opening of the exhaust passage. A control valve that changes the direction of movement is slidably fitted, and
The present invention is characterized in that an engaging portion is provided at the end of the through hole on the inside side of the cylinder, with which the end of the control valve comes into contact, thereby regulating the protruding position of the control valve.

"Function" The exhaust timing control device according to the present invention has the following advantages:
The cross-sectional shape of the control valve and the through hole that guides the control valve is made substantially uniform over its entire length, thereby suppressing an increase in the weight of the control valve itself and preventing the cylinder from becoming thinner.

"Example" Hereinafter, a preferred embodiment of the present invention will be described in detail based on FIGS. 2 to 4.

In FIG. 2, reference numeral 6 indicates a two-stroke engine to which this embodiment is applied, which includes a cylinder 7, a piston 8 slidably inserted into the cylinder 7, and a piston 8 that is spaced apart in the circumferential direction of the cylinder 7. A plurality of scavenging passages 9 are provided at intervals and open on the inner surface of the cylinder 7; an exhaust passage 10 having an opening 10a on the inner surface of the cylinder 7; An exhaust timing control device 11 according to this embodiment is provided near the opening 10a of the exhaust passage 10.

To explain these details, the cylinder 7 has a cylinder 7 on both sides of the rib I (from the vicinity of the opening 10a at the upper part of the exhaust passage 10 to the outside of the cylinder 7).
Two parallel through holes 12 are formed along the radial direction. A large diameter portion 12a having a predetermined depth is formed at the outer end of the through hole 12, and a stepped portion 12b perpendicular to the length direction of the through hole 12 is formed at the inner end. has been done.

As shown in FIGS. 2 and 3, the exhaust timing control device 11 includes a guide member 13 that is fitted and fixed in each of the through holes 12 and has a guide hole 13a having a substantially rectangular cross section, and each of the guide members. 13 and a control valve 14 slidably fitted within the control valve 13.

The guide member 13 is made of a material having higher hardness and strength than aluminum, which is a general material for forming the cylinder 7, such as iron. It has a shape that follows the inner peripheral shape and the inner peripheral shape of the exhaust passage 10, and
A stepped portion 15 serving as an engaging portion is formed on one end edge of the guide hole 13a, and is perpendicular to the length direction of the guide hole 13a. On the other hand, the guide member 13
A flange 16 having approximately the same shape as the large diameter portion +2a of the through hole 12 and a thickness equivalent to the depth thereof is integrally formed on the other outer end of the cylinder 7. By being fitted and locked into the portion 12a, the second
As shown in the figure, the guide member 13 is positioned relative to the cylinder 7 so that a slight gap is formed between one end surface of the guide member 13 and the stepped portion 12b of the through hole 12.

The control valve 14 is slidably fitted into each guide member 13, and has a groove on one end surface located inside the cylinder 7 along the moving direction of the piston 8, as shown in FIG. A control surface 14a having a slight width and substantially along the inner circumferential surface of the cylinder 7 as shown in FIG. In this state, the curved portion 14b is substantially continuous with the inner circumferential surface of the exhaust passage 10 and forms a part thereof. When the control valve 14 is in its most protruded state toward the inside of the cylinder 7, its one end surface is brought into contact with the stepped portion 15 of the guide member 13, as shown in FIG. , the control surface 14a is locked in a state shifted by a minute distance 9 to the downstream side of the exhaust passage 10 from the inner surface of the cylinder 7. An operating rod 17 protruding outward from the guide member 13 is integrally connected to the other end of the control valve 14, and a driving means (not shown), such as a governor, It is configured to be connected to a servo motor, a fluid pressure cylinder, etc., and two control valves 4 are operatively connected by the driving means.

Therefore, in the exhaust timing control device 11 of this embodiment having such a configuration, when the cylinder 7 is cast, the exhaust passage 9 is
After simultaneously molding the through hole 12 at a predetermined position on the upper part of the through hole 12 and fitting and fixing the guide member 13 into the through hole 12, the control valve 14 is inserted into the guide member 12, and then the control valve 14 is inserted into the guide member 12. It is assembled into the engine 6 by connecting a driving means to the engine 6 via its operating rod 17.

By sliding the control valve 14 in a predetermined direction based on the operating state of the engine 6, the output characteristics of the engine 6 can be increased over the entire rotation range.

That is, when the engine 6 is operated in a low rotation range, the control valve 14 should protrude into the exhaust passage 10. That is, it is moved toward the inside of the cylinder 7. By such movement of the control valve 14, its control surface 1.4
a is located near the inner surface of the cylinder 7, as shown by solid lines in FIGS. 2 and 3. As a result, the upper part of the opening 10a of the exhaust passage 10 is closed, and the upper edge i0b of the opening 10a appears to be the lower edge 1 of the main control surface 14a.
The distance to 4c is lowered by 2 minutes.

Therefore, the position of the piston 8 for communicating the cylinder 7 and the exhaust passage 10 is shifted by the above-mentioned distance ML, thereby delaying the exhaust timing and ensuring proper exhaust at low rotation speeds. As a result, the output of the engine in the low rotation range can be improved.

On the other hand, when the engine 6 reaches a high rotation range,
By moving the control valve 14 in the opposite direction to that described above and housing it in the guide member 13 as shown by the chain line in FIGS. 2 and 3, the upper part of the opening 10a is opened and the exhaust timing is advanced. As a result, it is possible to perform appropriate exhaust gas at high speeds and improve engine output in the high speed range.

Therefore, the output characteristics of the engine 6 can be improved over the entire rotation range.

When the control valve 14 is moved in the protruding direction as shown in FIG.
By being brought into contact with the stepped portion 15 of the cylinder 7, the control surface 14a is locked so as to be positioned a minute distance 2 toward the downstream side of the exhaust passage 10 than the inner circumferential surface of the cylinder 7, and the control valve 14 and Interference with the piston 8 is prevented. Therefore, the control valve 14 is positioned in front of the control valve 14 in its movement direction.
The cross-sectional shape of the guide hole 13a that guides the control valve 14 is maintained to be approximately the same cross-sectional shape as the control valve 14 over its entire length, and the cylinder 7 is prevented from becoming thinner, thereby increasing the strength of the cylinder 7. is ensured. Further, there is no need to provide a large diameter portion in the control valve 14, an increase in the weight of the control valve 14 itself is suppressed, and the position of the control valve 14 is regulated by locking one end surface of the control valve 14. Therefore, the relative positional relationship between the control surface 14a and the inner circumferential surface of the cylinder 7 is maintained substantially constant without being affected by the machining accuracy of the control valve 14 or the like.

In addition, in this embodiment, since the control valve 14 is guided and supported by the guide member 13 fitted into the through hole 12 of the cylinder 7, the temperature rise due to continued operation of the engine 6 may cause the various components of the cylinder 7, etc. Even if distortion or the like occurs in the member due to heat, the cylinder 7 is reinforced by the guide member 13, and the above-mentioned distortion is suppressed to a minimum, allowing the control valve 14 to operate smoothly. This ensures smooth sliding movement.

Therefore, the above-mentioned exhaust timing control operation can be reliably achieved.

Furthermore, in this embodiment, when manufacturing many types of engines 6 with different output characteristics by changing the exhaust timing change timing, the formation position of the guide hole 13a is changed to the piston 8.
By preparing various types of guide members 13 that are shifted in the sliding direction according to the type of engine 6, and selectively setting these guide members 13 on the cylinder 7,
The lower edge 14c of the control valve 14 in the protruding state and the opening 10a
This can be solved by changing the distance between the upper edge 10b and the upper edge 10b. As a result, the cylinder 7 can be used as a common member, which is advantageous in terms of productivity and cost even in the production of a wide variety of small bonds.

Note that the shapes, dimensions, combinations, etc. of each component shown in the above embodiments are merely examples, and can be variously changed based on design requirements and the like. For example, the guide member 13
Although an example has been shown in which the stepped portion 15 formed in the cylinder 7 is used as an engaging portion and the position of the control valve 14 is regulated by the stepped portion 15, the guide member 13 is omitted and the stepped portion of the through hole 12 formed in the cylinder 7 is used. 12b can also be used as an engaging portion for regulating the position of the control valve 14.

"Effects of the Invention" As explained above, the exhaust timing control device for a two-stroke engine according to the present invention includes a through hole extending toward the center of the cylinder in the upper wall of the exhaust passage, and a through hole extending toward the center of the cylinder. , a control valve is slidably fitted therein to change the upper edge of the opening in the sliding direction of the piston by being moved forward and backward toward the upper part of the opening of the exhaust passage; The device is characterized in that the end portion is provided with an engaging portion that restricts the protruding position of the control valve by being brought into contact with the end portion of the control valve, and the control valve is moved in the protruding direction. When the control valve is moved, the protruding position of the control valve is restricted at the front in the direction of movement of the control valve, so that the cross-sectional shape of the through hole that guides the control valve is almost the same as the cross-sectional shape of the control valve over its entire length. With the same shape, it is possible to prevent the cylinder from becoming thinner and ensure the strength of the cylinder,
In addition, by eliminating the need to provide a large diameter part in the control valve and suppressing an increase in the weight of the control valve itself, the response of the control valve is improved. By regulating the position of the control valve, the relative positional relationship between the inner end surface of the cylinder of the control valve and the inner circumferential surface of the cylinder is almost directly regulated, and the position regulation of the control valve is controlled by the machining accuracy of the control valve. It has the effect of being able to maintain an almost constant level without being influenced by the

[Brief explanation of drawings]

In the drawings, FIG. 1 is a vertical sectional view showing an example of the structure of a two-stroke engine equipped with a conventional exhaust timing control device, and FIGS. 2 and 3 show an embodiment of the present invention. The figure is similar to FIG. 1 to which one embodiment is applied, and FIG. 3 is a sectional view taken along the line III--III in FIG. 2. 6... (2 cycle) engine, 7...
・Cylinder, 8...Piston, 1
0...Exhaust passage, 10g...Opening,
IOb...Top edge, 11...Exhaust timing control device, 12...Through hole, 12
a...Large diameter part, +2b...
・Stepped portion, 13...Guide member, 13
a... Guide hole, 14... Control valve,
14a-...Control unit, 14b...
...Curved surface, 14c...Town edge, 15...Step, 16...Flange, 1
7... Operation rod.

Claims (1)

[Claims] An exhaust system that opens and closes the upper part of the exhaust passage that communicates with the inside of the cylinder of a two-cycle engine to change the timing of communication between the inside of the cylinder and the exhaust passage through a piston that is slidably fitted inside the cylinder. In the timing control device, a through hole directed toward the center of the cylinder is formed in the upper wall of the exhaust passage, and the timing control device is configured to advance and retreat into the through hole to the upper part of the opening of the exhaust passage. A control valve whose upper edge changes in the sliding direction of the piston is slidably fitted, and the end of the control valve is brought into contact with the end of the through hole on the inside of the cylinder, An exhaust timing control device for a two-stroke engine, characterized in that an engaging portion is provided for regulating the protruding position of the control valve.