JPH0325610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable exhaust expansion chamber device for a two-stroke engine that changes the volume of the exhaust expansion chamber in relation to engine speed, etc. .

(Prior Art) A two-stroke engine is characterized in that its output characteristics are influenced by the structure of its exhaust system. Specifically, it is said that the volume of the exhaust system should be large in the low-speed range, but not so large in the high-speed range. So, to solve this problem all at once,
An expansion chamber of an appropriate volume is provided in the middle of the exhaust passage by branching off, and this expansion chamber is communicated with the exhaust passage, and a valve is provided in the middle of the passage to communicate and cut off the expansion chamber and the exhaust passage. There is something set up.

(Problems to be Solved by the Invention) In a two-stroke engine having such a structure, it is only possible to effectively improve the output of the engine by optimizing the opening and closing timing of the valves. Further, when this valve is closed, it is preferable that the state is the same as that in which no expansion chamber is provided when viewed from the exhaust passage side. In this case, the valve should be located as close to the cylinder as possible, and the valve and the gear that drives the valve should be easily attached and operated accurately.

The present invention has been made to meet such demands.

(Means for Solving the Problems) As a means for solving the above problems, the present invention provides a valve chamber with a circular cross section formed integrally with the cylinder in the exhaust passage of a two-stroke engine, and a valve chamber formed in the back of the valve chamber. An expansion chamber is provided, at least a portion of which is integral with the cylinder, and a rotary valve is installed in the valve chamber between the expansion chamber and the exhaust passage to communicate with and shut off the expansion chamber and the exhaust passage. The rotary valve is configured to be rotated by the output of a converter that rotates depending on the engine speed, etc., so that the valve opens when the engine rotates at low speed and closes when the engine rotates at high speed. be.

(Function) With such a configuration, by rotating the rotary valve at an appropriate timing, the expansion chamber can be communicated with or shut off from the exhaust passage. As a result, the expansion chamber acts in the low rotation range, and in the high rotation range it is possible to create a state similar to not having an expansion chamber, so the exhaust condition from the low rotation range to the high rotation range can be improved. ,
This means that it can be ideally controlled.

(Embodiment) Next, an embodiment of the present invention will be explained with reference to the drawings. 1 is a cylinder of a two-stroke engine;
3 is an intake passage, and 3 is an exhaust passage. The casing 4 forming the exhaust passage 3 is formed thick,
As shown in the figure, it is formed integrally with the cylinder 1. A valve chamber 5 having a circular cross section and extending in a direction perpendicular to the cylinder 1 is formed here. A rotary valve 7 that rotates around a shaft 6 is rotatably provided in the valve chamber 5 . An expansion chamber 8 is formed outside the valve chamber 5, that is, on the other side of the valve chamber 5 in the direction shown in FIG. A portion of this expansion chamber 8 protrudes toward the valve chamber 5 as shown in FIG. 7a is a seal ring.

As shown in FIGS. 1 and 2, the rotary valve 7 is a hollow body provided with a radial hole 9, and furthermore, as shown in FIG. An axial notch 9a is provided in the part to communicate with the hole 9 (second
(see figure). This notch 9a communicates with the notch 9a when the rotary valve 7, which is bored in the casing 4 as shown in FIG. 2, is in a predetermined position (in the posture shown in FIG. 1). It communicates with a passage 8' in the casing 4 through the hole 4a, and communicates with the expansion chamber 8 through this passage 8'. If the rotary valve 7 is rotated by the shaft 6 and the position of the notch 9a is changed, this communication will be cut off. The rotation angle of the rotary valve 7 is such that the line passing through the hole 9 is from a position (a) where it is perpendicular to the exhaust passage 3 to a position (b) where it is parallel to the exhaust passage 3, as shown in FIG. . As mentioned above, the exhaust passage 3 and the expansion chamber 8 communicate with each other at the position (a), and the
(b) will cut it off.

As shown in FIG. 2, the rotary valve 7 is
A shaft 6 is integrally formed at both ends thereof. This shaft 6 is rotatably supported by the casing 1 via a bearing 10. A gear 11 is attached to one end of the shaft 6, and a converter 12
It is meshed with a gear 14 attached to a shaft 13 of. In this case, one side of the bearings of the gears 11 and 14 is formed integrally with the cylinder 1. The converter 12 is composed of, for example, a servo motor, and is configured to rotate a shaft 13 in accordance with the number of rotations of the engine in conjunction with an engine tachometer or the like.

This device configured in this way operates the rotary valve 7 in the low rotation range where the engine speed is low.
The center of the hole 9 is controlled to be at position (a), and the center of the hole 9 is controlled to be at position (b) in the high rotation range. As a result, the volume of the exhaust system increases when the rotation speed is low, and decreases when the rotation speed is high, making it possible to stably improve output from the low rotation speed range to the high rotation speed range. It will be possible.

(Effects of the Invention) Since the present invention has the configuration described above, the rotary valve opens when the engine rotates at low speed and closes when the engine rotates at high speed. In addition to stably improving output up to high rotational speeds, the rotary valve has a state equivalent to not having an expansion chamber at all when closed, and can be installed in a dead space, reducing overall size. It also has the advantage of not affecting the

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the main parts of an embodiment of the present invention, and a diagram showing the part along the line - in FIG.
FIG. 2 is a longitudinal cross-sectional view showing the rotary valve driving portion of the rotary valve drive portion of FIG. 1... Cylinder, 3... Exhaust passage, 4... Casing, 5... Valve chamber, 6... Shaft, 7... Rotary valve, 8... Expansion chamber, 9... Hole, 9a...
Notch, 12...transducer.

Claims (1)

[Claims] 1. A valve chamber with a circular cross section formed integrally with the cylinder is provided in the exhaust passage of a two-stroke engine, and an expansion chamber at least partially integral with the cylinder is provided in the back of the valve chamber, and the expansion chamber is provided in the valve chamber. A rotary valve is installed between the expansion chamber and the exhaust passage to communicate and cut off the expansion chamber and the exhaust passage, and the rotary valve is connected to the output of the converter that rotates according to the engine speed, etc. 1. A variable exhaust expansion chamber device for a two-cycle engine, characterized in that the valve is configured to rotate at a low speed, and the valve is opened when the engine rotates at a low speed, and closed when the engine rotates at a high speed.