JPH09256855A - Exhaust control device of two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas control device of a two-cycle engine capable of correctly controlling the exhaust gas, easy in setting the position of a slide valve. SOLUTION: In an exhaust control device, a plurality of laminated valve disks 8, 11 are provided in a retractable manner on an exhaust gas passage 7 to be communicated with an exhaust port 4 of a cylinder 2, and exhaust of the exhaust gas is controlled by projecting the prescribed valve element 8, 11 according to the engine speed. The exhaust gas port 4 is split into upper and lower parts to form a main exhaust port 5 and a sub exhaust port 6, a bulkhead 9a to demarcate the main exhaust port 5 and the sub exhaust port 6 in the vertical direction is extended into the exhaust passage 7, and a rib 9 on which the prescribed valve element 8 is abutted is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for a two-cycle engine that controls exhaust gas exhaust by vertically changing the upper edge position of an exhaust port of a cylinder by means of a sliding valve body.

[0002]

2. Description of the Related Art Aiming to improve the output of a two-cycle engine 1
Control of exhaust gas emission is performed as one means. For example, in Japanese Patent Laid-Open No. 59-25030, as shown in FIG. 7, an exhaust port of a cylinder is vertically divided into two parts, and a rotary valve that rotates in synchronization with a crankshaft is arranged close to an upper exhaust port a. It is shown that the output is improved by providing b. Further, Japanese Patent Laid-Open No. 3-2759
In JP-A No. 31, the position of the upper edge of the exhaust port is raised and lowered according to the engine speed, thereby ensuring optimum exhaust timing according to each engine speed range and improving output in a wide range of engine speed ranges. An exhaust control device for achieving the above is disclosed.

This will be described with reference to FIGS. 101 is an exhaust control device, and the exhaust control device 101 is
It has a plate-shaped first valve body 104 and a second valve body 105 that are arranged so as to be retractable in the upper wall 103a of the exhaust passage 103, and as shown in FIG. And the second valve bodies 104 and 105 both project toward the exhaust port 106, and the tip of the first valve body 104 lowers the upper edge position of the exhaust port 106 by L, thereby delaying the exhaust timing and reducing the rotation speed. As shown in FIG. 9, the first valve body 10 is improved in the middle rotation range while improving the engine output in the range.
4 is retracted from the exhaust port 106 and the second valve body 105
10 raises the upper edge position of the exhaust port 106 by the front end of the exhaust port 106, thereby slightly speeding up the exhaust timing to improve the output of the engine in the middle revolution range, and FIG.
As shown in FIG. 3, both the first and second valve bodies 104 and 105 are retracted from the exhaust port 106 to further raise the upper edge position of the exhaust port 106 by N, thereby maximizing the exhaust timing and increasing the high revolution range. The engine output is being improved.

[0004]

In either case of the drum valve system or the slide valve system, it is preferable that the drum valve and the slide valve are as close to the exhaust port as possible. However, in the drum valve system shown in FIG. 7, the thin portion A of the Cinder wall on the upper side of the exhaust port increases, so the valve cannot be brought closer to the exhaust port as compared with the slide valve system, and the exhaust control It will be less accurate. In the slide valve method, it is easy to bring the slide valve close to the cylinder bore without reducing the wall thickness of the cylinder wall above the exhaust port, but in order to avoid contact with the piston,
As shown in Fig. 4, the clearance B between the slide valve c and the cylinder bore d must be secured, and on the other hand, if the clearance B is large, the exhaust control accuracy is low as in the drum valve system. It was difficult to set the gap B.

On the other hand, even if the optimum clearance setting is obtained, if the clearance B exists, the exhaust control at low speed is inaccurate, and the output at low speed cannot be reliably ensured. The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust control device for a two-cycle engine in which exhaust control can be accurately performed and the position of a slide valve can be easily set.

[0006]

In order to achieve the above object, the invention according to claim 1 provides a plurality of valve elements which are superposed on each other so as to be retractable in an exhaust passage communicating with an exhaust port of a cylinder. In an exhaust control device for a two-cycle engine, which controls the exhaust of exhaust gas by projecting a predetermined valve body according to the number of revolutions, the exhaust port is divided into upper and lower parts to form a main exhaust port and a sub exhaust port. Further, a partition wall that vertically separates the main exhaust port and the sub exhaust port is extended into the exhaust passage to provide a rib with which the predetermined valve body can abut. Since the invention according to claim 1 is configured as described above, at the time of low speed of the engine, a predetermined valve body is made to project into the exhaust passage, and its tip end is brought into contact with the rib to make the predetermined valve body Make sure there are no gaps between the ribs. As described above, at a low speed, the predetermined valve element comes into contact with the rib and the upper edge of the exhaust port descends to the rib, so that the exhaust is performed only by the main exhaust port, and the exhaust efficiency at the low speed is improved. On the other hand, when the engine is operating at high speed, the predetermined valve element retracts from the exhaust passage and the upper edge of the exhaust port rises, so that exhaust is performed by the main exhaust port and the sub-exhaust port, improving the output at high speed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an exhaust control device for a two-cycle engine according to the present invention will be described below with reference to the drawings. FIG. 1 shows an entire motorcycle incorporating an exhaust control device for a two-cycle engine according to an embodiment of the present invention. FIG. 2 is an enlarged view of the engine 1.

As shown in FIGS. 3 and 4, the cylinder wall 3 of the cylinder 2 constituting the engine 1 has a main exhaust port 5 formed by vertically dividing an exhaust port 4 into two parts, and a main exhaust port 5. And an auxiliary exhaust port 6 located above the. Main exhaust port 5
And the auxiliary exhaust port 6 communicate with the exhaust passage 7. A partition wall 9a that vertically separates the main exhaust port 5 and the sub exhaust port 6 extends obliquely downward in the exhaust passage 7 and forms a rib 9 with which a first valve body 8 described later can contact.

Two auxiliary exhaust ports 6 are provided side by side in the circumferential direction of the cylinder 2. In other words, the sub exhaust port 6 is the reinforcing wall 6a.
Although the rib 9 is divided into two in the circumferential direction, it is possible to omit the reinforcing wall 6a and make it one if the strength of the rib 9 is sufficient. The upper wall 10 of the exhaust passage 7 is provided with a first valve body 8 and a second valve body 11 stacked on the upper side of the first valve body 8. The first valve body 8 is retractable in the exhaust passage 7, and its tip portion has an inclined surface having an angle substantially the same as the inclination angle of the rib 9 so that it can come into contact with the upper surface of the rib 9 that faces obliquely downward. Is formed. Therefore, when the first valve body 8 is in contact with the rib 9, the exhaust gas does not leak from both contact surfaces. The length of the first valve body 8 in the cylinder circumferential direction is substantially the same as the length of the rib 9 in the same direction.

The second valve body 11 is fixed, and the tip portion thereof is formed as an inclined surface having an inclination angle substantially the same as the inclined surface of the first valve body 8, and this inclined surface forms the upper surface of the exhaust passage 7. When the engine is running at high speed, the auxiliary exhaust port 6
It becomes the upper edge. It is also possible to provide a plurality of valve elements that appear and disappear. A timing mechanism 12 shown in FIG. 5 controls the timing at which the first valve body 8 appears and disappears from the exhaust passage 7. That is, the governor 1 is synchronized with the engine speed.
The rod 1 is driven by the centrifugal force generated by driving the rod 3.
4, the shaft 15 is rotated by this, and the first valve body 8 is operated via the arm 16 to change the timing at low speed and at high speed.

Next, the operation will be described. When the engine is running at a low speed, the first valve body 8 is projected into the exhaust passage 7 and its tip is brought into contact with the rib 9 so that no gap is created between the first valve body 8 and the rib 9. In other words, the first valve body 8
There should be no gap between the cylinder and the cylinder 2 as in the conventional case. By doing so, the accuracy of exhaust control is ensured. Thus, at low speed, the first valve body 8 has the rib 9
, And the upper edge of the exhaust port descends to the rib 9,
Exhaust is performed only by the main exhaust port 5, and the exhaust efficiency at low speed is improved.

On the other hand, when the engine is running at high speed, the first valve body 8
Is withdrawn from the exhaust passage 7, and the upper edge of the exhaust port is the second valve body 11
Since it rises up to the tip, the exhaust is performed by the main exhaust port 5 and the auxiliary exhaust port 6, and the output at high speed is improved. FIG.
Is a graph comparing the above-mentioned conventional device of this type and the device according to the present embodiment, the vertical axis represents the output, the horizontal axis represents the engine speed, the dotted line graph represents the present embodiment,
The solid line shows the conventional example. From this, it can be seen that the output improvement in the present embodiment is remarkable from low speed to medium speed of the engine.

[0013]

As described above, according to the first aspect of the present invention, since the valve body is provided with the rib which can freely abut, the valve body can be formed without reducing the wall thickness of the cylinder wall above the exhaust port. Since the gap with the cylinder can be eliminated, the accuracy of exhaust control can be maintained. Moreover, the provision of the ribs reduces the work load required for setting the clearance between the valve body and the cylinder and adjusting the position of the valve body.

[Brief description of drawings]

FIG. 1 is a side view showing an entire motorcycle to which an exhaust control device for a two-cycle engine according to the present invention is applied.

FIG. 2 is likewise an enlarged view showing the engine of FIG.

FIG. 3 is likewise a vertical cross-sectional view showing a main part.

FIG. 4 is likewise a sectional view taken along line XX of FIG.

FIG. 5 is likewise an exploded perspective view of a timing mechanism that controls the timing of the valve element appearing and retracting.

FIG. 6 is a graph similarly comparing outputs of the present embodiment and a conventional example.

FIG. 7 is a sectional view of a conventional drum valve system.

FIG. 8 is likewise an operation explanatory view of a slide valve system.

FIG. 9 is likewise an operation explanatory diagram of a slide valve system.

FIG. 10 is likewise an operation explanatory diagram of a slide valve system.

FIG. 11 is likewise a sectional view of a slide valve system.

[Explanation of symbols]

 2 Cylinder 4 Exhaust port 5 Main exhaust port 6 Sub-exhaust port 7 Exhaust passage 8, 11 Valve body 9 Rib 9a Partition wall

Claims (1)

[Claims] 1. Exhaust gas discharge is controlled by providing a plurality of valve elements that are overlapped with each other so as to be retractable in an exhaust passage communicating with an exhaust port of a cylinder, and projecting a predetermined valve element according to an engine speed. In the exhaust control device for a two-cycle engine, the exhaust port is divided into upper and lower parts to form a main exhaust port and a sub exhaust port, and a partition wall that vertically separates the main exhaust port and the sub exhaust port is provided in the exhaust passage. An exhaust control device for a two-cycle engine, which is provided with a rib extending inward so that the predetermined valve body can come into contact therewith.