JPS62189322A - Exhaust timing controller 2-cycle engine - Google Patents

Abstract

PURPOSE:To prevent carbon from deposition by swinging a swing valve body for opening and closing the upper edge of an exhaust port of a 2-cycle engine and making the valve body end face side inner surface of a valve receiving chamber have an arc having the same center as the valve body end in opening the valve body. CONSTITUTION:An exhaust port 5 of a 2-cycle engine is provided with a valve body 19 swung about a shaft 18 to open and close the upper edge of a port opening 15a. The opening 19a side end face 23 of valve body 19 has an arc centering around a pivot 18 with a radius l1 and the inner surface 28a to the opening side edge 28 of a valve body 19 receiving chamber is an arcuate one centering around the same pivot with a radius l2. Thus, a gap between the end face of valve body and the inner surface of edge can be reduced so that carbon depositing in the gap can be scavenged by the swing of the valve body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to exhaust timing control of a two-stroke engine, and more specifically, a plate-shaped valve body is provided at the upper part of an exhaust passage, and this plate-shaped valve body This invention relates to an exhaust timing control device for a two-stroke engine, in which the timing of communication between the inside of a cylinder and an exhaust passage is changed by swinging the engine according to the rotational speed of the engine.

``Prior art'' Various technologies have been proposed for two-stroke engines to change the exhaust timing according to the engine speed so that high output can be obtained in both low and high speed ranges. , FIG. 1 shows an example of an exhaust timing control device devised by the inventors of the present invention. In this exhaust timing control device, an opening (exhaust boat) Ia to the inner surface of the cylinder at the upper part of the exhaust passage l A shaft 2 is installed nearby so as to be orthogonal to the cylinder axis, a plate-shaped valve body 3 is attached to this shaft 2, and a valve body storage recess 4 is provided at a location opposite to the valve body 3 on the upper surface of the exhaust passage 1. It is at the installation size.

Further, on the upper edge of the exhaust boat Ia, when the valve body 3 is housed in the recess 4, there is a dead space between the control surface 3a, which is the swinging tip of the valve body 3, and the inner surface of the cylinder. In order to prevent the formation of a turbulent flow when the exhaust gas in the cylinder flows out and increase flow resistance, an arcuate protrusion 5 (hereinafter referred to as an edge) 5 hanging down from the top surface of the exhaust boat Ia is provided. ing.

According to this device, the valve body 3 is oscillated by a drive mechanism (not shown) according to the rotational speed of the engine. For example, when the engine rotates at a low speed, the valve body 3 is moved as shown by the solid line in the figure. When the engine rotates at high speed, the valve body 3 is positioned at the upper part of the exhaust passage as shown by the two-dot chain line in the figure. It is operated so that it is stored in the recess 4 provided in the. In this way, the upper edge position of the exhaust boat 1a is moved up and down according to the rotation speed of the engine, so that even when the engine rotates at low speed or high speed, the exhaust boat 1a is moved up and down after the scavenging boat (not shown) is closed. The exhaust timing is controlled so that the exhaust reflected wave returns to the exhaust boat 1a just before the boat 1a closes, and the gas that has blown into the exhaust passage 1 is pushed back into the cylinder to improve gas filling efficiency. It is now possible to improve the output of the

``Problems to be Solved by the Invention'' However, when the above-mentioned exhaust timing control device is used for a long period of time, the gap between the valve body 3 and the valve body housing recess 4, especially the edge. Carbon contained in the air-fuel mixture adheres to the inner surface of the portion 5, and by depositing this carbon, the valve body 3 can be housed in the recess 4 as desired, as shown by the two-dot chain line in the figure. It has been found that this causes a problem in that the exhaust timing cannot be controlled as expected.

``Object of the Invention'' The present invention has been made in view of the above circumstances, and provides a two-stroke engine that can prevent carbon from adhering to the inner surface of the edge portion and ensure exhaust timing control over a long period of time. The purpose of the present invention is to provide an exhaust timing control device.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention has a swinging tip facing the inner surface of the cylinder of the valve body and an inner surface of the valve body housing facing the swinging tip, respectively. Formed so that the cross section is arcuate when cut on a plane parallel to the axis,
Moreover, both of them are formed into arcuate surfaces whose centers of curvature coincide with the center of swing of the valve body.

"Example" Hereinafter, an example of the present invention will be described with reference to FIGS. 2 to 4.

FIG. 3 is a sectional view taken along the line 1--■ in FIG. 2.

In the figure, numeral 11 is a cylinder block, I2 is a cylinder head, 13 is a piston slidably inserted into the cylinder, 14 is a scavenging passage, and 15 is an exhaust passage. A reinforcing rib 16 is provided at the center of the exhaust passage 15 in the left-right direction, and a reinforcing rib 16 extends from the opening (exhaust boat) 15a to the inner surface of the cylinder to the exhaust passage 15.
It is provided so as to extend downstream to a predetermined location. This rib I6 strengthens the vicinity of the opening of the exhaust passage 15 to the inner surface of the cylinder, and also prevents the piston ring from expanding radially outward due to its own elasticity and hitting the upper or lower edge of the exhaust boat 15a. fulfill a function.

A recess 17 is provided at the upper part of the exhaust passage I5 and slightly downstream of the exhaust boat 15a. Shaft 1 is placed in recess 17.
8 is rotatably provided so as to be perpendicular to the central axis of the cylinder. The central part of the shaft 18 is formed to have a rectangular cross-section, and there is a plate-shaped (upper handle) - 7-hi-shu 114 tRIh.
l m m yTh /su In IQ? +(
71 are arranged on both sides of the rib 16 so as to sandwich the rib 16 therebetween.

Both valve bodies 19.19 are symmetrical. As shown in FIG. 4, the valve body 1 consists of a shaft insertion portion 20, a flat plate portion 21 extending from the shaft insertion portion 20 to one side, and a flange portion 22 provided at the top of the tip of the flat plate portion 21. There is. Surface 23 of the flat plate portion 21 and the collar portion 22 on the opposite side to the shaft insertion portion 20
is a surface that functions as a control surface that actually performs exhaust timing control by facing the inner surface of the cylinder, and this surface 23
The cross-sectional shape is formed into an arcuate shape with approximately the same curvature as the inner surface of the cylinder (see Fig. 3). Further, as shown in FIGS. 2 and 4, the control surface 23 is formed so that its cross section is arcuate when cut along a plane parallel to the cylinder axis, and the center of curvature is located at the valve body 19. It is formed to coincide with the center of oscillation.

The flat plate portion 21 of the valve body 19 is provided with a plurality of elongated through holes 26 that reach from the upper surface to the lower surface. These through holes 26 are formed when the valve body 19 is set in the exhaust passage 15.
It is provided to be inclined with respect to the length direction of the valve body so as to follow the flow of exhaust gas flowing in the exhaust passage 15. Through hole 2
The upper part of the hole 6 is chamfered, and an edge portion 27 is formed at the boundary of the through hole 26.

Furthermore, an edge portion 28 is formed at the cylinder inner peripheral surface opening (exhaust port 15a) of the exhaust passage 15 so as to hang down from the upper ceiling portion so as to prevent the generation of the dead space. Similar to the control surface 23 of the valve body 19, the inner surface of the edge portion 28 is formed so that its cross section is arcuate when cut along a plane parallel to the cylinder axis, and the center of curvature is located at the center of the valve body 19. It is formed to coincide with the center of oscillation. Then, the radius of curvature ρ of the inner surface 28a of the edge portion
, is set to a value slightly larger than the radius of curvature a1 of the valve body control surface 23 (see FIG. 2).

Further, the valve body 19 is operated by the drive mechanism 2 according to the rotational speed of the engine.
The swing operation is performed by 9. The drive mechanism 29 is connected to the shaft 18
, a wire guide 30 attached to one end of the shaft 18 and protruding to the outside of the cylinder block 11;
It consists of a motor (not shown) connected to the wire guide 30 via a wire 31, a controller (not shown) that rotates the motor in forward and reverse directions according to the rotational speed of the engine, and the like. Note that R in FIGS. 2 and 3 indicates a passage for passing cooling water.

According to the exhaust timing control device configured in this manner, the output characteristics of the engine can be improved over the entire rotation range by swinging the valve body 19 based on the operating state of the engine.

That is, when the engine is operated at low rotation speed, the shaft 18 is rotated in a predetermined direction to swing the valve body 19,
The valve body 19 is made to protrude into the exhaust passage 15. By such movement of the valve body 19, the control surface 23 is moved to the exhaust port 1.
5a, thereby closing the upper part of the exhaust port 15a as shown by the solid line in FIG.
Lower it to the bottom edge of. For this reason, lower the control surface 23 and
(exhaust bow opened and closed by movement of piston 13)
15a can be opened later and closed earlier.

In this way, when the engine is running at low speed, the piston 1
In response to the long vertical movement period of No. 3, the exhaust port 15a
is opened late and closed early, thereby transmitting the exhaust reflected wave to the exhaust port 1 just before the exhaust port 15a is closed.
It has been returned to 5g to improve combustion gas filling efficiency.

On the other hand, when the engine reaches a high speed range, the valve body 19
is rotated in the opposite direction to that described above and housed in the recess 17 as shown by the two-dot chain line in FIG. That is, in this case, in response to the shorter vertical movement period of the piston 13, the exhaust port 15a is opened earlier and closed later than in the case described above. Therefore, in this case as well, the exhaust reflected waves are returned to the exhaust port 15a just before the exhaust port 15a is closed, and as in the case described above, the combustion gas filling efficiency is improved by effectively utilizing the reflected waves.

In this way, the exhaust timing of the engine is controlled by the control surface 2 of the valve body 19.
3 to improve output characteristics over the entire rotation range.

The method of controlling the valve body 19 may be either step control such as two-position control or continuous proportional control.

Further, in the above exhaust timing control device, the swinging tip of the valve body, that is, the control surface 23, and the inner surface of the valve body housing recess 17, that is, the inner and back surface 28a of the edge portion facing thereto, are arranged in a plane parallel to the cylinder axis. The valve body 1 is formed so that its cross section becomes an arc shape when cut at the center of curvature of the valve body 1.
Since it is formed to coincide with the center of oscillation of 9, it is possible to set the gap formed between the opposing 23 and 28a to the minimum necessary, and furthermore, it is possible to set the gap formed between the opposing 23 and 28a to the necessary minimum, and also prevent carbon from adhering to the gap. Even if it does, it can be scraped off by the upper end corner 23a of the control surface 23 when the valve body 19 is rotated toward the concave MI7 side. Therefore, as seen in the conventional example shown in FIG. 1, a large amount of carbon adheres to the inner surface 28a of the edge portion, making it impossible to accommodate the valve body 19 in the recess 17 as desired. It is possible to prevent this from happening. The carbon scraped off by the upper peak 23a of the control surface 23 is removed from the exhaust gas or the atrium by the through hole 26 into the exhaust passage 15.
It is discharged to the side.

Furthermore, in the above configuration, the through hole 26 is provided in the valve body 19, and the atrium guides gas or exhaust gas to the upper side of the valve body 19. This is to clean the top surface and the valve body storage portion 17 and prevent carphones from adhering to them.

Further, in this embodiment, the through hole 26.2 in the upper part of the valve body 19
6, an edge portion 27 is provided between the valve body storage recess 17. Even if carbon adheres to the lower surface of the valve body storage recess 17 and solidifies, the edge portion 27 can knock off the carbon.
This is to discharge the knocked down carbon from the through hole 26 to the exhaust passage 15.

Furthermore, in this embodiment, a flange portion 22 that projects upward is provided at the swinging end of the valve body 19, but this is to increase the height of the valve body control surface 23 while keeping the valve body thin. This makes it possible to reduce the weight of the valve body 19 and to operate the valve body 19 even with a drive mechanism with a small output.

"Effects of the Invention" As explained above, according to the exhaust timing control device of the present invention, the swinging tip of the valve body and the valve body storage recess 1 facing thereto
7 is formed so that its cross section becomes an arc when cut along a plane parallel to the cylinder axis, and the arcuate surfaces are formed so that their centers of curvature coincide with the center of swing of the valve body. Because of this shape, the gap formed between these opposing surfaces can be set small, and even if carbon adheres to the gap, it will not be removed when the valve body is rotated toward the storage recess. The car phone can be scraped off at the top of the control surface. As a result, it is possible to prevent the occurrence of problems such as the conventional problem where a large amount of carbon adheres to the inner surface of the edge part and the valve body cannot be housed in the recess as desired. Reliable exhaust timing control can be performed throughout the period.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a part of a conventional exhaust timing control device, FIGS. 2 to 4 show an embodiment of the exhaust timing control device according to the present invention, and FIG. Figure 3 is the second
A sectional view taken along the line ■-■ in the figure, and FIG. 4 is a perspective view of the valve body. 11... Cylinder block, 12... Cylinder head, 15... Exhaust passage, 15a... Opening (exhaust boat), 17...
...Valve body storage recess, 19...Valve body, 22...Brim part, 23...Control surface, 28...Edge part, 29... ...Valve body drive device. Applicant Honda Motor Co., Ltd. Agent Patent Attorney Masaaki Shuga; ＼ Figure 3

Claims (1)

[Claims] A method for controlling the timing of communication between the inside of the cylinder and the exhaust passage by a piston slidably inserted into the cylinder by opening and closing the upper part of the opening of the exhaust passage communicating with the inside of the cylinder of a two-cycle engine. The exhaust timing control device is configured to change the exhaust timing, and includes: a plate-shaped valve body provided near the top of the opening of the exhaust passage and swingable about an axis perpendicular to the cylinder axis; The valve body is provided with a valve body storage recess that is provided in the upper part and stores the valve body when the valve body is in an open state, and a valve body drive mechanism that opens and closes the valve body according to the engine rotation speed, The swinging tip of the valve body facing the inner surface of the cylinder and the inner surface of the valve body housing facing the swinging tip are each formed so that the cross section thereof becomes an arc shape when cut along a plane parallel to the cylinder axis, An exhaust timing control device for a two-stroke engine, characterized in that both of the surfaces are arcuate surfaces formed such that their centers of curvature coincide with the center of swing of the valve body.