JPH08296444A - Exhaust timing control structure for 2-cycle engine - Google Patents

Abstract

(57) [Summary] [Purpose] In a two-cycle engine with multiple exhaust openings on the inner peripheral surface of the cylinder, each exhaust control valve installed at each exhaust opening is controlled by a single rotating shaft. , Operate surely in each operating range. [Structure] A plurality of exhaust ports 5 opening on the inner peripheral surface 2 of the cylinder
Exhaust control valves 8 for opening and closing the upper portions of the exhaust ports 5a are provided for the respective a, and the plurality of exhaust control valves 8 are interlocked with the rotation of one common rotary shaft 9. In an exhaust timing control structure of a two-cycle engine configured to slide, a coil spring 13 that is fitted into a rotation shaft 9 and that is interlocked with the rotation is individually provided for each exhaust control valve 8. The exhaust control valves 8 are individually linked to the rotary shaft 9 via the respective ends of the coil springs 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust timing control structure for a two-cycle engine provided with an exhaust control valve that opens and closes an upper portion of an exhaust port opened on an inner peripheral surface of a cylinder in accordance with a rotation speed of the engine.

[0002]

2. Description of the Related Art In a two-cycle engine in which the piston itself acts as an exhaust valve, and the exhaust timing is set by the upper edge position of the exhaust port opening on the inner peripheral surface of the cylinder, the exhaust timing matches the engine speed. Optimally, in order to increase the gas filling rate in each rotation range and improve the output, an exhaust control valve that opens and closes the upper part of the exhaust port according to the engine speed is provided. It has been conventionally performed to control the exhaust timing from the exhaust port by opening and closing.

In a two-cycle engine provided with such an exhaust control valve, in order to open and close each exhaust control valve installed for each of a plurality of exhaust ports, a reciprocating operation is performed in response to a change in the rotational speed of the engine. It is conventionally known that one rotating shaft that rotates is provided and all exhaust control valves are interlocked with the rotation of this rotating shaft to synchronously control the exhaust timing of a plurality of exhaust ports. Has become.

[0004]

By the way, in the exhaust gas timing control structure of the conventionally known two-cycle engine as described above, if the operating ranges of all the exhaust gas control valves are not the same for some reason, one of them is used. There is a problem that all the exhaust control valves are restricted within the operating range and other exhaust period control valves having different operating ranges cannot be reliably operated within the original operating range.

An object of the present invention is to eliminate the above-mentioned disadvantages of the conventional exhaust control structure for a two-cycle engine. More specifically, a plurality of exhaust ports are opened on the inner peripheral surface of the cylinder. In a two-stroke engine,
To provide an exhaust timing control structure of a two-cycle engine capable of reliably operating each exhaust control valve installed in each exhaust port in each operating range by one common rotating shaft. It is what

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention provides a plurality of exhaust ports which are opened in the inner peripheral surface of a cylinder, as described in claim 1. An exhaust control valve that opens and closes the upper portion of the exhaust port is installed for each, and the plurality of exhaust control valves are configured to slide in conjunction with the rotation of a single common rotating shaft. In the exhaust timing control structure for a two-cycle engine, a coil spring that is fitted into a rotation shaft and interlocks with the rotation is individually provided for each exhaust control valve, and both ends of each coil spring are provided. The exhaust control valves are individually linked to the rotary shafts via the parts.

[0007]

[Operation] According to the above configuration, when the rotating shaft rotates in response to a change in the number of rotations of the engine, each coil spring rotates in association with the rotating shaft. Each exhaust control valve slides in the same direction in association with either end of the exhaust control valve.

At this time, even if one of the exhaust control valves slides to the limit of its operating range and stops, the movement of the coil spring end portion linked to the exhaust control valve is prevented. Nevertheless, the elastic deformation of the coil spring itself allows the rotary shaft to continue to rotate in the same direction.

Therefore, if the turning range of the turning shaft is set to an appropriate range, the turning shaft further turns in the same direction even after one of the exhaust control valves first stops, Other exhaust control valves can be slid to the limits of their operating range.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust timing control structure for a two-cycle engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a cylinder block portion of a two-cycle engine to which an embodiment of the exhaust timing control structure of the present invention is applied. The cylinder head has crankcases integrally connected therebelow, and a crankshaft, which is connected to a piston via a connecting rod, is pivotally supported in the crankcase, and an intake passage that follows the carburetor is inside the crankcase. And a piston is arranged in the cylinder of the cylinder block 1 so as to be vertically slidable.

As shown in the figure, the cylinder block 1 has a cooling water jacket 3, a scavenging passage 4 and an exhaust passage 5 formed in its peripheral wall portion, and each end of a plurality of scavenging passages 4 communicating with the inside of the crankcase. Each of the parts is opened as a scavenging port 4a on the cylinder inner peripheral surface 2, and the upstream end of the exhaust passage 5 is an exhaust port 5a so that the upper end of the opening is located above the scavenging port 4a. Inner surface of cylinder 2
It is open to.

The exhaust passage 5 is formed with a vertical center rib 6 which integrally connects the upper surface and the lower surface of the passage at the center in the left-right direction and extends from the exhaust port 5a to a predetermined location downstream thereof. The exhaust passage 5 is divided into two left and right by a center rib 6 at the upstream portion and merges into one at the downstream portion, and the exhaust port 5a of the exhaust passage 5 has a center in the left-right direction. The cylinder inner peripheral surface 2 is opened as two exhaust ports which are divided into right and left with the rib as a boundary.

As a result, the exhaust port 5a of the exhaust passage 5 as a whole has its left and right ends largely expanded in the circumferential direction of the cylinder inner peripheral surface so that a high output can be obtained by increasing the exhaust flow rate. Nevertheless, since the end portion of the center rib 6 located at the center thereof serves as a piston sliding surface as a part of the cylinder inner peripheral surface 2, the piston ring is connected to the exhaust port 5a.
The center rib 6 reinforces the vicinity of the exhaust port 5a of the exhaust passage 5 without catching on the upper edge or the lower edge.

At the upstream portion of the exhaust passage 5 which is separated by the center rib 6, there is a sliding valve which goes in and out obliquely downward from the upper wall of the exhaust passage 5 toward the exhaust port 5a with respect to each exhaust port 5a. Exhaust control valves 8 are installed respectively.

FIG. 2 shows the arrangement of the exhaust control valve 8 and its related structure. The two exhaust control valves 8 are installed at each of the two exhaust ports 5a defined by the center rib 6. The exhaust control valves 8 are arranged in parallel, and a single rotating shaft 9 for operating the exhaust control valves 8 is provided near the rear of the exhaust control valves 8 in the sliding direction of the exhaust control valves 8. It is extended in the direction orthogonal to.

In each of the exhaust control valves 8, a valve portion 8a for opening and closing above the exhaust port 5a is integrally extended from the front end of the sliding shaft 8b, and a stopper is provided at the front portion of the sliding shaft 8b. A portion 8c is formed, and an engaging pin 8d is provided on one side of the rear portion of the sliding shaft 8b so that the sliding shaft 8b of the exhaust control valve 8 is mounted on the cylinder block 1 through the bearing portion 7. It is held slidably on.

The rotary shaft 9 is rotatably supported by the cylinder block 1, and a link mechanism 10 composed of a plurality of link members is connected to one end of the rotary shaft 9 so as to apply centrifugal force due to rotation of the engine. By interlocking with a used drive mechanism (not shown) via the link mechanism 10, the reciprocating rotation is performed according to the change in the rotation speed of the engine.

FIG. 3 shows a structure in which the rotary shaft 9 and the exhaust control valves 8 are linked to each other. The rotary shaft 9 is located in the central portion between the sliding shafts 8b of the exhaust control valves 8. The spring rotation member 11 is fixed by the bolt 12,
Coil springs 13 are fitted on the rotating shafts 9 on both sides of the spring rotating member 11, respectively.

Each of the exhaust control valves 8 and the rotating shaft 9 as described above.
The linkage structure will be further explained by disassembling the structure with reference to FIGS. 4 to 6. First, as shown in FIG. 4, the spring rotating member 11 fixed to the central portion of the rotating shaft 9 with a bolt 12. The engagement pins 11a are provided on both sides of the projection, respectively.

As shown in FIG. 5, both ends 13a, 13b of the springs of the coil springs 13 fitted into the rotating shaft 9 on both sides of the spring rotating member 11 are substantially parallel and long. It was extended,
With the coil spring 13 fitted into the rotating shaft 9,
The engagement pin 11a of the spring rotation member 11 is located between the both ends 13a and 13b.

Further, as described above, the coil spring 1
As shown in FIG. 6, the exhaust control valve is provided between the both ends 13a and 13b of the coil spring 13 with the engaging pin 11a of the spring rotating member 11 in a state where the exhaust control valve 3 is fitted into the rotating shaft 9. An engaging pin 8d is provided at the rear of the sliding shaft 8b of No. 8 so as to project.

The operating state of each exhaust control valve 8 individually linked to the rotating shaft 9 via the coil spring 13 and the engaging pin 8d as described above will be described below.

A rotating shaft 9 is provided in response to a change in the engine speed.
When is rotated, each of the coil springs 13 is rotated by being interlocked with the rotating shaft 9 by being pushed by each engaging pin 11a of the spring rotating member 11 fixed to the rotating shaft 9.

When each coil spring 13 rotates in conjunction with the rotating shaft 9, both end portions 13 of each coil spring 13 are rotated.
One of a and 13b pushes the engagement pin 8d of each exhaust control valve 8, and each exhaust control valve 8 slides in the same direction in conjunction with the rotation of each coil spring 13.

As shown in FIG. 7, the sliding of each exhaust valve 8 causes the stopper 8c to abut on the bearing portion 7 when fully opened, and as shown in FIG. 8, when the stopper 8c is fully closed.
When c touches the cylinder block 1, its operating range is restricted.

The two exhaust control valves 8 slide simultaneously,
When the stopper 8c of one of the exhaust control valves 8 comes into contact with the cylinder block 1 or the bearing portion 7, the exhaust control valve 8 is stopped by it, and the engagement pin 8d of the exhaust control valve 8 moves further. Disappear.

In such a state, the rotating shaft 9 is in contact with the stopped engaging pin 8d and the coil spring 1 is in contact therewith.
3 elastically deforms to continue to further rotate to the rotation set position, and the rotation of the other exhaust control valve 8 causes the stopper 8c to come into contact with the cylinder block 1 or the bearing portion 7. Slide.

As a result, during high-speed operation with a high engine speed, each exhaust control valve 8 slides until the stopper 8c contacts the bearing 7, as shown in FIG. The leading edge of the exhaust passage 5 is retracted from the inside of the exhaust passage 5 until it substantially coincides with the upper wall of the exhaust passage 5,
Each of the exhaust ports 5a is in a fully opened and fully opened state.

On the other hand, during low-speed operation at a low engine speed, each exhaust control valve 8 slides until the stopper 8c contacts the cylinder block 1 as shown in FIG. The tip edge portion is brought close to the inner surface of the cylinder 2 and largely advances into the exhaust passage 5, and each exhaust port 5a is in a fully closed state in which the upper portion is closed by the valve portion 8a.

According to the exhaust timing control structure of the two-cycle engine of the present embodiment as described above, the two exhaust control valves 8 installed respectively for the two exhaust ports 5a separated by the center rib 6 are provided. , Even if each operating range is different for some reason,
If the turning range of the turning shaft 9 is set to an appropriate range, the respective exhaust control valves 8 are individually interlocked with the turning of the turning shaft 9 and are reliably operated in their respective working ranges. be able to.

The exhaust timing control structure for a two-cycle engine according to the present invention has been described with reference to an embodiment of a two-cycle engine in which two exhaust control valves 8 are installed in an exhaust passage 5 having a center rib 6. Although described, the present invention is not limited to only such specific structures.

That is, auxiliary exhaust passages are further provided on both sides of the main exhaust passage having the center rib, and exhaust control valves (two main exhaust control valves,
Auxiliary exhaust control valves (two auxiliary exhaust control valves) are installed, or auxiliary exhaust passages are provided on both sides of the main exhaust passage without a center rib, and each exhaust control valve (one main exhaust control valve, auxiliary exhaust control valve) It is needless to say that the present invention can be applied to a two-cycle engine having another structure, such as one provided with two exhaust control valves).

[0034]

According to the exhaust timing control structure of the two-cycle engine of the present invention as described above, one exhaust control valve is installed at each of the plurality of exhaust ports opened in the inner wall of the cylinder. It becomes possible to reliably operate the respective exhaust control valves within the operating range by the common rotating shaft of the above.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a cylinder block portion of a two-cycle engine to which an embodiment of an exhaust timing control structure of the present invention is applied.

FIG. 2 is a top view showing an exhaust control valve and its related structure in the two-stroke engine shown in FIG.

FIG. 3 is a top view showing a structure in which the exhaust control valve shown in FIG. 2 and a rotary shaft are linked together.

4A is a top view and FIG. 4B is a side view showing a spring rotating member in the linkage structure shown in FIG.

5 (A) is a top view and FIG. 5 (B) is a side view showing an arrangement state of a spring rotating member and a coil spring in the linkage structure shown in FIG.

6 is a side view showing an arrangement state of coil springs with respect to the exhaust control valve in the linkage structure shown in FIG.

FIG. 7 is a vertical cross-sectional view showing a fully open state of the exhaust control valve in the embodiment shown in FIG.

8 is a vertical cross-sectional view showing a fully closed state of the exhaust control valve in the embodiment shown in FIG.

[Explanation of symbols]

 1 Cylinder Block 2 Cylinder Inner Surface 5 Exhaust Passage 5a Exhaust Port 8 Exhaust Control Valve 9 Rotating Shaft 13 Coil Spring

Claims (1)

[Claims] 1. An exhaust control valve that opens and closes an upper portion of each of the plurality of exhaust ports that open on the inner peripheral surface of the cylinder is installed, and the plurality of exhaust control valves are one common. In the exhaust timing control structure of a two-cycle engine configured to slide in conjunction with the rotation of the rotating shaft, the exhaust control valve is fitted into the rotating shaft for each of the exhaust control valves. Exhaust gas of a two-cycle engine, characterized in that interlocking coil springs are individually provided, and each exhaust control valve is individually linked to a rotating shaft via both ends of each coil spring. Timing control structure.