JPH066894B2 - Exhaust timing control device for 2-cycle engine - Google Patents

Description

TECHNICAL FIELD 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.

"Prior Art" Generally, the engine installed in a vehicle is roughly divided into a low rotation type that emphasizes power characteristics during low speed traveling and a high rotation type that emphasizes power characteristics during high speed traveling. The former is designed so that the peak of the engine output can be obtained in the low engine speed range of the engine, and the latter can obtain the peak of the engine output in the high engine speed range. As a result, the output in the high speed range reaches a ceiling, and in the latter case, the output in the low speed range becomes lower than that in the former case.

Therefore, it has been considered to improve the power characteristics in the entire range from low speed running to high speed running by increasing the output in the low speed range while maintaining the high output in the high speed range. As a means, it is mentioned that the exhaust timing of the engine is changed between low rotation speed and high rotation speed. As a structural example thereof, the technique disclosed in Japanese Patent Laid-Open No. 56-92314 has been already proposed.

As shown in FIG. 1, this technique is designed so that, in the upper part of the exhaust passage 3 communicating with the inside of the cylinder 2 of the two-cycle engine 1, in the vicinity of the opening 3a of the exhaust passage 3, the piston 4 is inclined with respect to the sliding direction. A through hole 2a which is made to communicate with the exhaust passage 3 is formed, a control valve 5 is slidably provided in the through hole 2a, and the control valve 5 is advanced and retracted above the opening 3a. When the engine speed is high, as shown by the solid line in FIG. 1, the control valve 5 is retracted from the opening 3a of the exhaust passage 3 to open the entire surface of the opening 3a. Raise the upper edge 3b, and at the time of low rotation,
As shown by the chain line in FIG. 1, the control valve 5 is projected above the opening 3a of the exhaust passage 3 to close the upper part of the opening 3a, and the projecting end 5a of the control valve 5 is extended to the inner surface of the cylinder 2. The opening 3a can be formed by locating the same level as the line.
The upper edge 3b is shifted downward to the protruding end 5a of the control valve 5 by an apparent distance L ₁ , whereby the communication timing between the inside of the cylinder 2 and the exhaust passage 3 due to the lowering of the piston 4 is set to the above distance.
L It was designed to be delayed by ₁ minute.

"Problems to be Solved by the Invention" The present invention is intended to solve the following problems in the above-described conventional techniques.

That is, in the above-described technique, the control valve 5 is formed by the through hole 2a formed in the cylinder 2, but the through hole 2a must support the control valve 5 over the entire width. Further, since it is necessary to secure a length capable of preventing the swing of the control valve 5 in the protruding state, the through hole 2a has a wide and deep shape, which causes
This is a problem that the distortion due to heat generated in the through hole 2a may become large.

In order to improve the exhaust efficiency and improve the output of the engine, the above-mentioned engine tends to increase the opening area of the exhaust passage, but in this case, the entire width of the control valve 5 must be increased as well. However, this tends to promote the above-mentioned problems.

Further, the change amount L ₁ of the exhaust timing is uniquely determined by the positional relationship of the through hole 2a with respect to the cylinder 2 and the shape of the control valve 5, but the change amount L ₁ needs to be changed. In that case, the formation position of the through hole 2a must be changed. Therefore, for example, when manufacturing various types of engines having different characteristics, the cylinder 2 must be prepared for each type. It also has points.

"Means for Solving Problems" The present invention is intended to provide an exhaust timing control device for a two-cycle engine that can effectively solve the problems in the above-mentioned conventional technology. In particular, a plate-like hole is formed in the upper wall of the exhaust passage, the through-hole extending toward the center of the cylinder, and the through-hole moves forward and backward toward the upper portion of the opening of the exhaust passage to vertically change the upper edge of the opening of the exhaust passage by a predetermined distance. The control valve is slidably fitted, and a plate-shaped guide member that slidably supports the plate-shaped control valve is provided on the cylinder side at least above the plate-shaped control valve. And

[Operation] The exhaust timing control device according to the present invention guides and supports the control valve by supporting the control unit on the cylinder through the guide member and guiding the sliding movement of the control valve by the guide member. The amount of distortion of the hole is suppressed, the movement of the control valve is made smooth, and the shape of the guide member is changed so that the change in engine characteristics can be dealt with.

"Example" Hereinafter, a preferred example of the present invention will be described in detail with reference to Figs.

In FIG. 2, reference numeral 6 indicates a two-cycle engine to which the present embodiment is applied, and includes a cylinder 7, a piston 8 slidably fitted in the cylinder 7, and a space in the circumferential direction of the cylinder 7. And a plurality of scavenging passages 9 opened at the inner surface of the cylinder 7 and opened at the inner surface of the cylinder 7.
An exhaust passage 10 having an exhaust passage 10a and a reinforcing rib H that divides the opening 10a of the exhaust passage 10 into two in the circumferential direction of the cylinder 7 are provided. A timing control device 11 is provided.

Explaining these in detail, the cylinder 7 is provided with two parallel portions extending in the radial direction of the cylinder 7 on both sides of the rib H from the vicinity of the opening 10a of the exhaust passage 10 to the outside of the cylinder 7. A through hole 12 is formed. A large-diameter portion having a predetermined depth is provided at the outer end of the through hole 12.
12a is formed, and a step portion 12b orthogonal to the length direction of the through hole 12 is formed at the end portion on the inner side.

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

The guide member 13 is formed of a material having higher hardness and strength than aluminum, which is a general forming material of the cylinder 7, such as iron, and one end portion located inside the cylinder 7 is The inner peripheral shape and the inner peripheral shape of the exhaust passage 10 are formed to have a shape, and a step portion 15 orthogonal to the length direction of the guide hole 13a is provided at one end edge thereof toward the inner side of the guide hole 13a. Is formed.
On the other hand, at the other end of the guide member 13 outside the cylinder 7, a flange 16 having substantially the same shape as the large diameter portion 12a of the through hole 12 and a thickness equivalent to the depth thereof is integrally formed. As shown in FIG. 2, a slight gap is formed between the one end surface of the guide member 13 and the step portion 12b of the through hole 12 by being fitted and locked in the large diameter portion 12a. The guide member 13 is positioned with respect to the cylinder 7 so as to be formed.

The control valve 14 is slidably fitted to each guide member 13, and has one end surface located inside the cylinder 7 along the moving direction of the piston 8 as shown in FIG. Cylinder 7 has a small width and as shown in FIG.
A control surface 14a is formed substantially along the inner peripheral surface of the exhaust passage 10, and the remaining portion is substantially continuous with the inner peripheral surface of the exhaust passage 10 when the control valve 14 is housed inside the guide hole 13a. The curved surface 14b forms a part of the curved surface. And
In the state where the control valve 14 is most protruded toward the inside of the cylinder 7, one end surface of the control valve 14 has a step portion 15 of the guide member 13.
As shown in FIG. 3, the control surface 14a is locked to the exhaust passage 10 side with respect to the inner surface of the cylinder 7 by a slight distance from the inner surface of the cylinder 7.
An operation rod 17 protruding outward from the guide member 13 is integrally connected to the other end of the control valve 14,
Driving means (not shown) via the operating rod 17, for example,
It is designed to be connected to a governor, a servomotor, a fluid pressure cylinder, etc.
Two control valves 14 are linked so as to be interlocked.

Thus, the exhaust timing control device 11 of this embodiment having such a configuration simultaneously molds the through hole 12 at a predetermined position above the exhaust passage 9 when the cylinder 7 is cast, and the inside of the through hole 12 is molded. After fitting and fixing the guide member 13 to the guide member 12,
It is assembled to the engine 6 by inserting the control valve 14 therein and then connecting the drive means to the control valve 14 via its operating rod 17.

Then, by sliding the control valve 14 in a predetermined direction based on the operating state of the engine 6, the output characteristic of the engine 6 can be enhanced in the entire rotation range.

That is, when the engine 6 is operating in the low speed region, the control valve 14 is projected 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, the control surface 14a is positioned near the inner surface of the cylinder 7 as shown by the solid line in FIGS. 2 and 3. As a result, the opening 10 of the exhaust passage 10
While the upper part of a is closed, the upper edge 10b of the opening 10a is apparently lowered by the distance L ₂ to the lower edge 14c of the control surface 14a.

Therefore, the position of the piston 8 for establishing communication between the cylinder 7 and the exhaust passage 10 is displaced by the distance L ₂ described above, which delays the exhaust timing and ensures proper exhaust at low revolutions. As a result, the engine output can be improved in the low speed region.

On the other hand, when the engine 6 reaches the high speed range,
By moving the control valve 14 in the opposite direction to the above and accommodating the control valve 14 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 to accelerate the exhaust timing. As a result, it is possible to perform appropriate exhaust at the time of high rotation and improve the engine output in the high rotation range.

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

Then, due to the temperature rise accompanying the continuous operation of the engine 6,
Although distortion due to heat is generated in each component such as the cylinder 7, the guide member 13 that supports the control valve 14 is formed separately from the cylinder 7, and since the volume thereof is small, the absolute distortion amount is small. As a result, the deformation amount of the guide hole 13a into which the control valve 14 is fitted is also suppressed, and the control valve 14
Smooth sliding is secured. Therefore, the above-described control operation of the exhaust timing can be surely obtained.

Further, when various kinds of engines 6 having different output characteristics are manufactured by changing the timing of changing the exhaust timing, the sliding direction of the piston 8 with respect to the position of the guide hole 13a formed in the guide member 13 Guide hole 18a
The guide member 18 (19) having the (19a) is formed in accordance with the type of the engine 6, and these guide members 13, 18,
By selectively setting 19 in the cylinder 7, as shown in FIGS. 4A and 4B, the distance between the lower edge 14c of the control valve 14 in the protruding state and the upper edge 10b of the opening 10a is set to L ₃ , L 2. It can be dealt with by changing to ₄ . As a result, the cylinder 7 can be used as a common member, which is advantageous in terms of productivity and cost even in high-mix low-volume production.

It should be noted that the shapes, sizes, combinations and the like of the respective constituent members shown in the above embodiment are merely examples, and can be variously changed based on design requirements and the like.

[Advantages of the Invention] As described above, in the exhaust timing control system for a two-cycle engine according to the present invention, a through hole extending toward the center of the cylinder is formed in the upper wall of the exhaust passage, and the exhaust gas is exhausted through the through hole. A plate-like control valve that moves back and forth to the upper part of the opening of the passage to change the upper edge of the opening of the exhaust passage up and down by a predetermined distance is slidably fitted, and at least the upper part of the plate-like control valve has the plate-like control. A plate-shaped guide member that slidably supports the valve,
It is characterized in that it is provided on the cylinder side, and even when distortion occurs in each component of the engine due to the temperature rise of the engine, the control valve is formed by a guide member formed separately from the cylinder. Since it is supported, the distortion of each component of the engine is absorbed by the guide member,
It is possible to ensure smooth sliding of the control valve and reliably control the exhaust timing. Moreover, when the guide member is provided only above the control valve, the thickness of the guide member and the control valve is changed, and when the guide member is provided above and below the control valve, only the guide member is provided. By changing the thickness of the cylinder, the amount of change in the timing of communication between the inside of the cylinder and the exhaust passage can be changed very easily without changing the position or size of the through hole formed in the cylinder (output characteristics). Different types of engines can be manufactured. In other words, many types of engines with different output characteristics can be manufactured using cylinders with through holes formed at the same position and with the same size. It has excellent effects such as being advantageous.

[Brief description of drawings]

In the drawings, FIG. 1 is a vertical cross-sectional view showing a structural example of a two-cycle engine equipped with a conventional exhaust gas timing control device, and FIGS. 2 to 4 show one embodiment of the present invention. The figure is the same as FIG. 1 to which one embodiment is applied, and FIG. 3 is II of FIG.
FIG. 4 is a schematic cross-sectional view taken along the line I-IIIIII, and FIG. 4 is a schematic view of a main part showing a configuration for changing the exhaust timing. 6 ... (2-cycle) engine, 7 ... cylinder, 8 ... piston, 10 ... exhaust passage, 10a ... opening, 10b ... upper edge, 11 ... exhaust timing control device, 12 ... through hole, 12a ... large diameter part, 12b ... step part, 13 ... guide member, 13a ... guide hole, 14 ... control valve, 14a ... control surface, 14b ... curved surface, 14c ... bottom edge, 15 …… Step, 16 …… Flange, 17 …… Operating rod.

Claims (1)

[Claims] Claim: What is claimed is: 1. An exhaust passage communicating with the inside of a cylinder of a two-cycle engine is opened and closed to change a timing of communication between the inside of the cylinder and the exhaust passage by a piston slidably fitted inside the cylinder. In the exhaust timing control device, a through hole is formed in the upper wall of the exhaust passage toward the center of the cylinder, and the through hole is moved forward and backward toward the upper portion of the exhaust passage to open the exhaust passage. A plate-shaped control valve that slidably moves the upper edge up and down by a predetermined distance is slidably mounted, and a plate-shaped guide that slidably supports the plate-shaped control valve is provided at least on the upper part of the plate-shaped control valve. An exhaust timing control device for a two-cycle engine, wherein a member is provided on the cylinder side.