JPH0717781Y2 - Exhaust control valve for 2-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an exhaust control valve provided in an exhaust port of a cylinder in a two-stroke engine.

[Prior Art] In a two-cycle engine, intake (scavenging) into the combustion chamber
The gas passage for exhaust is opened and closed by the reciprocating movement of the piston. In other words, a 2-cycle engine does not have a valve (mushroom valve) like a 4-cycle engine, and the scavenging port and exhaust port opened in the cylinder are opened and closed using the piston itself as a kind of valve body to introduce and exhaust gas. .

By the way, the output characteristic of a two-cycle engine is greatly affected by the timing of exhaust from the combustion chamber. The one with early exhaust timing is a high-speed type engine (which produces the maximum output at a relatively high speed rotation), and the one with a late exhaust timing is a low speed type engine (which produces the maximum output at a relatively low speed rotation).

Due to the structure described above, the exhaust timing is determined by the height of the exhaust port in the cylinder, especially the height of the upper edge of the port in a 2-cycle engine. Therefore, the output position of the engine is roughly determined by the opening position of the exhaust port. Become. Therefore, for the purpose of constantly generating a high output from low speed to high speed without biasing the characteristics of the engine, a control valve is provided at the upper edge of the exhaust port, and by opening and closing this valve according to the engine speed. The technology of changing the exhaust timing has already been introduced in Shokai 63-11553.
No. 0, JP-A-63-173817, etc.

FIG. 4 is a diagram showing an outline of a conventional exhaust control valve based on the device of the above publication (former). The control valve 41 formed in the shape of an integral plate is used for the exhaust port 1 formed in the cylinder 10 '.
A support shaft 41c swingably supports the upper edge of 1 ', and a driving force is transmitted from a driving means (not shown) to the pin 41b to swing up and down. In this way, by swinging the control valve 41 and changing the height of the protruding end 41a at the lower end of the tip, the exhaust port 11 'is moved when the piston (not shown) slides down the inner wall surface of the cylinder 10'. The opening timing will change, and the exhaust timing will change. Therefore, when the rotation speed of the engine is high, the control valve 41 is set to the position shown by the solid line to accelerate the exhaust timing, while when the rotation speed is low, the control valve 41 is lowered to the position of the phantom line (chain line) to delay the exhaust timing. If so, the engine characteristics are improved as described above.

[Problems to be Solved by the Invention] It is desirable that the tip of the control valve for changing the exhaust timing be as close as possible to the outer peripheral surface of the reciprocating piston. This is because if there is a large gap between the piston and the piston, the exhaust gas blows through the gap even if the control valve is below, so the exhaust timing cannot be determined by its height.

The exhaust control valve 41 shown in FIG.
The projecting end 41a is made as close as possible to the inner wall surface of the cylinder 10 '(thus, the outer peripheral surface of the piston) in consideration of manufacturing errors, etc., but that state is always maintained while the control valve 41 moves up and down. Not always maintained. That is, when the control valve 41 is at the position shown by the solid line in the figure, the distance between the projecting end 41a and the inner wall surface of the cylinder 10 'is extremely small and is a0 as described above, but it is swung downward with the support shaft 41c as the fulcrum. Sometimes the distance spreads to a1. This spread is even larger at the end portion of the control valve 41 in the width direction (direction perpendicular to the paper surface). Therefore, the control valve 41
When is swung downward, the exhaust gas blows through here (the gap of the dimension a1), and the exhaust timing may not be substantially delayed.

In order to solve the above problems, the present invention provides an exhaust control valve capable of effectively changing the exhaust timing by keeping the distance between the tip of the valve and the inner wall surface of the cylinder small while the valve moves up and down to prevent gas blow-through. It is the one we are trying to provide.

[Means for Solving the Problems] An exhaust control valve for a two-cycle engine according to the present invention is guided by a cylinder or a member fixed to the cylinder so as to be vertically movable in parallel with the cylinder, and a tip portion thereof is an inner wall surface of the cylinder. And a valve body that is formed in the vicinity of the valve body, and swings up and down by being driven according to the rotation speed of the engine with a portion on the downstream side of the exhaust as a fulcrum, and engages with the valve body near the swinging end to engage the valve body. An arm member for moving the main body up and down is assembled, and the arm member is formed so that the height of the lower surface is continuous with the lower surface of the valve main body and the upper wall surface of the subsequent exhaust passage (that is, there is no large step). Is.

[Operation] In the exhaust control valve of the present invention, since the valve body is engaged with the arm member that swings up and down about the exhaust downstream side as a fulcrum, it moves up and down as the arm member swings. This operation is a vertical movement parallel to the cylinder due to the valve body being guided by the cylinder or a member fixed to the cylinder. Since the swinging of the arm member is driven according to the rotation speed of the engine, the vertical movement of the valve body is performed according to the rotation speed of the engine.

The valve body is provided at the upper edge of the exhaust port, the tip of which is close to the inner wall surface of the cylinder, and because it moves up and down in parallel with the cylinder as described above, the tip and the inner wall surface of the cylinder are The distance is always kept small.

From the above, according to the exhaust control valve of the invention, regardless of the opening of the valve, that is, the height of the exhaust port of the valve body,
The gas blow-by is kept to a minimum, and the exhaust timing is effectively changed according to the engine speed.

Further, the arm member is formed such that the height of the lower surface is continuous with the lower surface of the valve main body and the upper wall surface of the subsequent exhaust gas flow path, so that in the exhaust flow path from the valve main body to the downstream side,
There is no sudden change in cross-sectional area due to the valve body or arm member. This also holds true when the valve body is lowered by swinging the arm member. That is, since the arm member is engaged with the valve body near the swing end, when the valve body is lowered, the side close to the valve body (that is, the swing end side) is lowered and the lower surface is inclined. The reason is that the lower surface of the valve body and the upper wall surface of the exhaust passage on the downstream side are continuously formed with almost no step, and a portion where the cross-sectional area suddenly changes is not formed. For this reason, the flow of exhaust gas becomes smooth, and deterioration of engine performance is prevented regardless of the vertical position of the valve body (that is, during high speed rotation and low speed rotation).

[Embodiment] FIG. 1 is a longitudinal sectional view showing a part of a cylinder 10 and a cylinder head 20 of an engine 1, which relates to a two-cycle engine equipped with an exhaust control valve according to an embodiment of the present invention. A cylinder head 20 is integrally connected to the upper portion of the cylinder 10 by a bolt 15 and a nut 22. A combustion chamber is formed inside by both, and a spark plug 23 is attached to the cylinder head 20. A piston (not shown) reciprocates up and down while slidingly contacting the inner wall surface of the cylinder 10. Reference numeral 14 is a cooling water passage provided in the cylinder 10, and 21 is a cooling water passage provided in the cylinder head 20.

As shown in the figure, on the inner wall of the cylinder 10, the scavenging port 13 and
Exhaust port 11 is opened. The scavenging port 13 communicates with a crankcase (not shown) below the cylinder 10, but the exhaust port 11 passes through an illustrated exhaust passage 12 and an exhaust pipe (not shown) including a muffler (not shown). It is an opening leading to ().

An exhaust control valve 30 shown in the figure is provided along the upper wall of the most upstream portion of the exhaust passage 12 facing the exhaust port 11. Hereinafter, the control valve 30 will be described with reference to FIG. 1 (plan view) and FIG. 3 (partial front view) in addition to FIG. 1. In addition, each figure (solid line portion in FIG. 1) shows the control valve 30.
Fully open (when engine 1 speed is high)
Is shown. The control valve 30 is composed of the following parts.

Valve body 31: It moves up and down at the upper edge of the exhaust port 11, and when it descends, it serves as a partition for the upper edge of the port 11. The lower end of the tip is projected, and its protruding end 31a is extremely close to the inner wall surface of the cylinder 10 (gap a0 ≈ 0.1 m in the figure).
m) as formed. Since the protruding end 31a is formed in an arc shape as shown in FIG. 2 and extends along the inner wall surface of the cylinder 10, it is close to the inner wall surface of the cylinder 10 anywhere in the width direction. Two guide pins 31b are provided on the top of the valve body 31,
The guide pin 31b was inserted into the guide hole 16 (FIG. 1) formed in the cylinder 10 to provide vertical movement guide. Since the orientation of the guide hole 16 is parallel to (the axis of) the cylinder 10, the valve body 31 moves up and down in the direction parallel to the cylinder 10. Further, a recess 31c having a U-shaped cross section is formed in the rear portion of the valve body 31 so as to engage with an arm member 32 (described later).

Arm member 32: A member that engages with the valve body 31 described above and transmits the driving force to move the valve body 31 up and down. Pin to the above
Since 32a is attached and inserted into and engaged with the recess 31c of the valve body 31, only the vertical movement component of the swing displacement of the pin 32a is transmitted to the valve body 31. The rear end portion of the arm member 32, in other words, the portion on the exhaust downstream side, is rotatably supported by a holder 33 (described later) via a support pin 32c. In other words, the arm member 32 can swing about the support pin 32c as a fulcrum, and when swinging, the valve body that engages near its swing end
31 will be displaced up and down. A pin 32b is provided on one side as shown in FIG. 2 as a portion for receiving a driving force for swinging, and is engaged with a driving member 34 (described later).

Holder 33: As shown in FIG. 1, the arm member 32 is rotatably supported via a support pin 32c, and is fixed to the cylinder 10 by a bolt 33a at a bent rear portion. 33b
Is a cap for sealing the opening after the bolt 33a is attached. In addition, from the lower surface of the valve body 31 to the arm member
32, each lower surface of the holder 33 and the upper surface of the subsequent exhaust passage 12 are connected to each other in a continuous manner, that is, the upper wall of the exhaust passage is not substantially stepped. .

Driving member 34: A member that transmits a driving (swinging) force to the arm member 32 via the pin 32b described above. As shown in FIG. 3, a cam groove 34b is rotatably attached to the peripheral surface of a cylindrical portion 34a integral with the shaft portion 34c, and the pin 32b of the arm member 32 is engaged with the cam groove 34b. The cam groove 34b is provided with a spiral portion, and the shaft portion 34c is connected to a servo motor (not shown) that outputs a rotational displacement according to the rotation speed of the engine 1, so that the drive member 34 is set to the rotation speed of the engine 1. The arm member 32 is swung accordingly, and the arm member 32 is swung accordingly. Specifically, when the rotation speed of the engine 1 becomes low, the drive member 34 rotates clockwise from the state shown in the drawing to rotate the arm member.
Swing 34 downwards.

The exhaust control valve 30 configured as described above functions as follows to change the exhaust timing of the engine 1.

First, when the rotation speed of the engine 1 is high, the valve body 31 is located above and the exhaust port 11 is fully opened as shown in FIG. 1 (solid line portion). The valve body 31 is located above because the servo motor gives a predetermined rotational displacement to the drive member 34 (FIG. 3), and the arm member 32 engaging with the cam groove 34b swings upward. This is because the valve body 31 is pushed up via the pin 32a. At this time, the timing when the piston descends in the cylinder 10 and exhaust begins is the earliest.

When the rotational speed of the engine 1 decreases, the drive member 34 (FIG. 3) is rotated by the servomotor in accordance with the ratio, and the arm member 32 is swung downward to lower the valve body 31. The phantom line (chain line) in FIG. 1 shows the valve body 31 and the arm member 32 in that state. Since the valve body 31 moves up and down only in the direction parallel to the cylinder 10 as described above, the distance between the protruding end 31a and the inner wall surface of the cylinder 10 is maintained at a0 even in this state. This distance
Since a0 is an extremely small value as described above, almost no gas blows through the combustion chamber before the piston head is below the projecting end 31a. That is, the exhaust timing is delayed according to the descending amount of the valve body 31.

The exhaust control valve 30 also has a function of reducing the flow path resistance to the exhaust in the portion from the exhaust port 11 to the exhaust passage 12 to smooth the flow of the exhaust. As described above, there is no large step on the lower surfaces of the valve body 31, the arm member 32, and the holder 33 in the above state, but the valve body 31 is lowered as described above (see the phantom line in FIG. 1). Even at this time, since the lower surface of the inclined arm member 32 is continuous from the rear end of the lower surface of the valve body 31 to the holder 33, a sudden change in the cross-sectional area does not occur in the exhaust passage. With this function, it is possible to prevent the performance of the engine from deteriorating despite the vertical movement of the valve body 31.

Although one embodiment of the present invention has been introduced above, the present invention can also be implemented as follows.

B) The guide pin 31b for guiding the valve body 31 in parallel with the cylinder 10 may be fixed to the cylinder 10 side instead of being provided in the valve body 31. In this case, a hole into which the pin is fitted is provided on the valve body 31 side so that the fitting of the two guides the vertical movement of the valve body 31.

B) Without using the holder 32, the above-mentioned official gazette (Actual exploitation 63-115)
Based on the example described in No. 530), the support pin 3 of the arm member 32
The 2c may be directly attached to the cylinder 10.

C) For driving the arm member 32, refer to the driving member 34 described above.
Various methods are possible regardless of the above. For example,
The pin 32c is integrally fixed to the arm member 32 and is directly rotated, or a push / pull wire is passed from the upper surface of the arm member 32 to the outside of the engine 1 to push / pull the wire to swing the arm member 32. It may be something to let you do.

D) The auxiliary exhaust port (passage) opened and closed by a rotary valve is provided on the side of the exhaust port (passage), which is disclosed in the above-mentioned publication (JP-A-63-173817).
It goes without saying that it can also be applied to a cycle engine. Further, according to the invention, the arm member 32 may be driven by the rotation of the rotary valve to swing.

E) In the present specification, the term “upper” or “lower” (for example, “upper edge”, “vertical movement”) means “top dead center”,
According to words such as "bottom dead center", the one in the cylinder closer to the cylinder head is called "upper" and the opposite is called "lower". That is, the present invention is not limited to two-stroke engines in which the cylinders are arranged vertically or close thereto.

[Advantages of the Invention] According to the exhaust control valve of the present invention, the gas blow-through is kept to a minimum regardless of the opening of the valve, that is, the height of the valve body at the exhaust port. This is done effectively and the output characteristics of the engine are improved. Since the minimum blow-through of gas is not related to the vertical stroke of the valve body, it is effective even when the stroke is required to be large due to the characteristics of the engine.

Further, this control valve does not form a portion where the cross-sectional area changes suddenly in the exhaust flow passage and keeps the flow of exhaust gas smoothly, so that deterioration of engine performance can be avoided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a two-stroke engine equipped with an exhaust control valve according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and is a plan view of the exhaust control valve, and FIG. 3 is a cross-sectional view taken along the line III-III in FIG. Further, FIG. 4 is a vertical sectional view showing an outline of a conventional exhaust control valve. 10 …… Cylinder, 11 …… Exhaust port, 20 …… Cylinder head, 30 …… Exhaust control valve, 31 …… Valve body, 32 …… Arm member.

Claims (1)

[Scope of utility model registration request] 1. An exhaust control valve of a two-cycle engine, which is provided at an upper edge portion of an exhaust port formed in a cylinder and is driven in accordance with an engine speed to move up and down to change an exhaust timing. The valve body is guided by a member fixed to the cylinder and can move up and down in parallel with the cylinder, and the tip of the valve body is formed close to the inner wall surface of the cylinder. And an arm member that is vertically driven to move in the vicinity of the swing end and moves the valve body up and down by engaging with the valve body in the vicinity of the swing end. An exhaust control valve for a two-cycle engine, wherein the height of the lower surface is continuous with the upper wall surface of the road.