JPH0348329B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention extracts a portion of exhaust gas from an exhaust port of an internal combustion engine, and controls the flow of exhaust gas by opening and closing a butterfly valve disposed near the exhaust port. The present invention relates to an apparatus, and particularly to an improvement in the structure of the butterfly valve.

(Prior Art) The applicant has already developed and filed an application for an exhaust system for a two-stroke engine as shown in FIG.
(Japanese Patent Application Laid-Open No. 61-118525) This device includes a first cylinder 10a and a second cylinder 10b which are connected to each other with a phase difference of 180°, and exhaust ports 12a and 12b are connected by a pressure propagation passage 14. Butterfly valves 16 are provided near the 14 exhaust ports 12a and 12b, respectively, and the butterfly valves 16 are opened and closed by a drive mechanism (not shown).For example, the drive mechanism is operated at 7000 rpm. The structure is such that the butterfly valve 16 is opened and closed in the high speed range.

According to the above device, at low speed when the butterfly valve 16 is open, a positive pressure wave is transmitted to the exhaust port 12 by mutual resonance of the pressure propagation passage 14 and the mufflers 13a, 13b connected to the respective mechanisms.
a, 12b to prevent the air-fuel mixture from blowing through and improve the output, resulting in the output curve 18c in Figure 9.
(when the valve is open) and 18 (when the valve is closed), when the pressure propagation passage 14 is in communication, the output will decrease. At high speeds, the butterfly valve 16 is closed to improve the output, and the output is improved in the entire rotation speed range. It is designed to produce high output.

However, in the exhaust system of such a two-stroke engine, when the butterfly valve 16 is closed, the pressure propagation passage 14 and the exhaust port 12a,
There is a problem that the shapes of the exhaust ports 12a and 12b change at the boundary portion of the exhaust port 12b, and the flow of exhaust gas is disturbed at this boundary portion, thereby inhibiting the flow of exhaust gas.

(Objective of the Invention) The present invention provides an exhaust system for an internal combustion engine that can prevent the shape of the exhaust port from changing at the boundary between the pressure propagation passage and the exhaust port and obstructing the flow of exhaust gas when a butterfly valve is closed. The purpose is to

(Structure of the Invention) The present invention provides a guide passage within the cylinder wall thickness for guiding exhaust gas from a position immediately behind the exhaust ports of a pair of internal combustion engines in a direction crossing the exhaust ports, and connects both guide passages to an external connection passage. A butterfly valve is provided near the exhaust port of the guide passage, and the butterfly valve closes the guide passage so that when the butterfly valve is closed, the surface of the butterfly valve facing the exhaust port is substantially continuous with the inner surface of the exhaust port. an internal combustion engine comprising: a plate-shaped valve body; and a protrusion formed on one surface of the valve body so as not to obstruct opening and closing of the valve body, and a protrusion that smoothly connects with the inner surface of the exhaust port when the valve is closed. This is an exhaust system.

(Example) In FIG. 1 showing the case where the present invention is applied to a water-cooled in-line two-cylinder two-stroke engine for a motorcycle, parts given the same reference numerals as in FIG. 8 indicate the same or equivalent parts.

FIG. 1 is a side view of the cylinder and cylinder head portion of the engine of the present invention viewed from the left side when facing the direction of travel of the motorcycle, and this engine is shown in the direction of the cylinder arrangement in FIG. is mounted on the vehicle body along the front and rear direction of the vehicle body.

In FIG. 1, cooling water hoses 2 are installed on the sides of the first cylinder 10a and the second cylinder 10b, respectively.
0a is connected to the cooling water hose 20a, and cooling water is supplied from a cooling water pump (not shown) to the cooling water hose 20a. The first cylinder 10a and the second cylinder 10b are provided with exhaust ports 12a and 12b, respectively, and the exhaust port 12a of the first cylinder 10a is
is opened toward the front of the vehicle body, and the second cylinder 1
The exhaust port 12b of 0b is open toward the rear.

Exhaust ports 12a, 12b as shown in FIG.
The upper end of the guide passage 22a communicates with the upper surface (FIGS. 1 and 2), that is, the portion facing the cylinder head 10c. The guide passage 22a is formed within the wall thickness of the first cylinder 10a so as to rise toward the cylinder head 10c. The second cylinder 10b (FIGS. 1 and 2) is similarly provided with a guide passage 22b (FIGS. 1 and 2).

The upper end of the guide passage 22a is a direction change passage 24a.
The direction change passage 24a is formed within the wall thickness of the cylinder head 10c. The direction change passage 24a is bent in a so-called 90° elbow shape as shown in FIG.
The other end portion 4a extends toward the left side of the first cylinder 10a (FIG. 2). Further, the direction change passage 24b of the second cylinder 10b is formed in the same manner, and the direction change passage 24b is formed in the direction change passage 24b of the 1 cylinder head 1.
It extends in a curved line toward the left side of the second cylinder 10b along the outer periphery of the cylinder 0c (FIG. 2).

The direction change passages 24a and 24b are connected by an external connection passage 26 as shown in FIGS. 1 and 2, and the external connection passage 26 extends in the front-rear direction so as to surround the cooling water outlet 20b along the left side of the engine. has passed. These external connection passages 26, direction change passages 24a, 24b, and guide passages 22a, 2
The pressure propagation passage 14 is formed by 2b.
Note that the cooling water outlet 20b is a radiator (not shown).
It is connected to the.

Exhaust ports 12a, 12b of pressure propagation passage 14
As shown in FIG. 3, a butterfly valve 16 (opening/closing valve) is provided in the vicinity, that is, at the boundary between the guide passages 22a, 22b and the exhaust ports 12a, 12b. It has a curved surface that is substantially continuous with the inner surface 28 of the exhaust port 12. As shown in FIG. 4, the butterfly valve 16 is rotatably supported by a rotating shaft 30, and the end of the rotating shaft 30 protrudes from the left side of the engine. Note that in FIGS. 3 and 4, 32a and 32b are cooling water jackets.

Next, referring to FIG. 1, the guide passages 22a and 22b
A drive mechanism 34 that opens and closes the butterfly valve 16 of
Explain. The drive mechanism 34 is formed of a rotary solenoid 36, a bell crank 38, rods 40a, b, an arm 42, etc., and is arranged below the external connection passage 26 on the left side of the engine.

The rotary solenoid 36 is connected to the first cylinder 10
It is fixed to the left side surface of part a with a bolt 44b via a flange 44a with a slight gap. A rotating shaft 46 of the rotary solenoid 36 projects into this gap, and a bell crank 38 is fixed to the rotating shaft 46. One end of a rod 40a and a rod 40b are rotatably supported at both ends of the bell crank 38.

The other end of the rod 40a extends in front of the rotary solenoid 36 and is connected to an arm 42 of the butterfly valve 16 that opens and closes the guide passage 22a. The other end of the rod 40b extends rearward and is connected to an arm 42 of a butterfly valve 16 that opens and closes the guide passage 22b.

The rotary solenoid 36 is connected to a control unit 48, and in response to an input from the control unit 48, the rotation shaft 46 is rotated in the direction of arrow A at a rotation angle of, for example, 67.5°, as shown by the two-dot chain line in the figure. The butterfly valve 16 is closed by rotating the arm 42. The rotary solenoid 36 is normally biased in the direction of the reverse arrow A by the spring force of a built-in spring. The control unit 48 receives a rotational speed detection signal from the ignition device 50, and has a function of outputting a drive current to the rotary solenoid 36 when the engine rotational speed reaches, for example, 7000 rpm.

The arm 42 is connected to the rotating arm 5 as shown in FIG.
2, a fixed arm 54, a holding spring 56, etc. The fixed arm 54 is the rotating arm 5
2 and is pressed into contact with the rotating shaft 30 and fitted so as to rotate together with the rotating shaft 30. The rotating arm 52 is tightened with a nut 60 via a collar 58, and the rotating arm 52 is attached to the rotating shaft 30.
A rod 40a is rotatably fitted to the tip of the rotary arm 52.
The rotating arm 52 and the fixed arm 54 are supported by a retaining spring 5 that is wound around the rotating shaft 30.
The rotation axes 3 overlap each other at the ends 62 of 6.
It is biased in the circumferential direction of 0.

Next, details of the butterfly valve 16 will be explained. As shown in FIG. 5, the butterfly valve 16 includes a substantially disk-shaped valve body 70 that closes the inner surfaces of the guide passages 22a, 22b (FIG. 4) and closes the guide passages 22a, b, and an exhaust port 12a of the valve body 70. , 12b
A protrusion 7 protruding from the lower surface facing (Fig. 4)
It consists of 2. The valve body 70 and the protrusion 72 are integrally molded from a sintered metal. As shown in FIG. 6, the protrusion 72 protrudes from the lower surface of the valve body 70 except for the central portion where the rotating shaft 30 is fixed, and the diameter D ₂ of the protrusion 72 is equal to the diameter D of the valve body 70. It is set to have a slightly smaller diameter than ₁ . Two holes 74 are provided in the center of the valve body 70 for fixing the rotation shaft 30 with screws.

The shape of the lower surface 76 of the protrusion 72 is as shown in FIG. 5, which is a cross-sectional view taken along the center line 78 of FIG. The radius as shown in Figure 7 and Figures 7a to 7b.
It is formed into a substantially continuous curved surface on the inner surface 28 of the exhaust port 12 according to the radius R ₁ to radius R ₄ (R ₁ <R ₂ <R ₃ <R ₄ ). Note that the center line 78 in FIG. 5 is the rotation axis 30.
It forms an angle of 24° with the center line 80, which is perpendicular to the center line 80.

Next, the effect will be explained. The pressure propagation passage 14 includes guide passages 22a, 22b and direction change passages 24a, 24.
b. Since the external connection passage 26 is formed, a space for arranging the drive mechanism 34 is secured on the left side of the engine. Also, the guide passages 22a, 22
b is formed within the wall thickness of the first cylinder 10a and the second cylinder 10b, and the direction change passages 24a, 24b
are formed within the wall thickness of the cylinder head 10c, so the structure is simple and the guide passages 22a, 22
b and the external connection passage 26 can be easily connected. Further, since the external connection passage 26 is arranged along the left side of the engine, a space is secured for fixing the rotary solenoid 36 to the first cylinder 10a below the external connection passage 26. Therefore, the pressure propagation passage 14 and the drive mechanism 34 are arranged centrally on the left side of the engine.

The drive mechanism 34 has an engine rotation speed of, for example,
Rotary solenoid 36 when below 7000rpm.
The butterfly valve 16 is held open by the spring force of the built-in spring, thereby improving the output of the engine at low speeds. On the other hand, if the engine speed is, for example, 7000 rpm or more, the control unit 48
The output current from the rotary solenoid 36
rotates in the direction of arrow A to guide the guide passages 22a and 22b.
The butterfly valve 16 of the engine is closed at the same time to improve output at high speed.

When the butterfly valve 16 is closed, the holding spring 56 of the arm 42 uses its own elastic force to displace the fixed arm 54 and the rotating arm 52 in the circumferential direction of the rotating shaft 30, so that the valve body 7 of the butterfly valve 16
0 to the inner surfaces of the guide passages 22a and 22b, and prevents excessive load from being applied to the valve body 70.

Diameter D ₂ of the protrusion 72 of the butterfly valve 16
is smaller in diameter than the diameter D ₁ of the valve body 70, so when the butterfly valve 16 is attached to the guide passages 22a, 22b, the protrusion 72 and the guide passages 22a, 22
As shown in FIG. 3, there is a gap δ between the inner surface of the guide passages 22a and 22b, and even when the butterfly valve 16 is rotated, the protrusion 72 collides with the inner surfaces of the guide passages 22a and 22b, preventing the butterfly valve 16 from rotating. There is no risk of interfering with the movement, and it rotates smoothly.

When the butterfly valve 16 is closed, as shown in FIG. 3, the lower surface 76 of the protruding portion 72 is approximately continuous with the inner surface 28, so that the lower surface 76 has a radius R _{1 to 4} in FIGS. 7a to 7d. Since it is formed in a curved shape, the flow of exhaust gas that is rapidly discharged to the exhaust ports 12a, 12b at the initial stage of opening of the exhaust ports 12a, 12b by the piston shown by the two-dot chain line in FIG. Guide the crab to the guide passage 22a,
The exhaust flow is prevented from being obstructed at the boundary between the exhaust port 22b and the exhaust ports 12a and 12b, thereby improving engine output. According to experiments conducted by the inventor of the present invention, by providing the protrusion 72, the engine output can be reduced by approx.
Experimental results have shown an improvement of 10%.

Valve body 70 and protrusion 72 of butterfly valve 16
Since the butterfly valve 16 is integrally formed of a sintered metal, it is easy to manufacture the butterfly valve 16 having the lower surface 76 having a complicated curved shape.

(Effects of the Invention) When the butterfly valve 16 is closed, the lower surface 76 has the radius shown in FIGS. 7a to 7d so that the lower surface 76 of the protrusion 72 is substantially continuous with the inner surface 28 as shown in FIG. Since the curved surface of R1 _{to R4} is formed, the flow of exhaust gas is rapidly discharged to the exhaust ports 12a and 12b at the beginning of opening of the exhaust ports 12a and 12b by the piston shown by the two-dot chain line in FIG. are smoothly guided by the lower surface 76, and the guide passages 22a,
It is possible to prevent the exhaust flow from being obstructed at the boundary between the exhaust port 22b and the exhaust ports 12a and 12b, thereby improving engine output.

The butterfly valve 16 can close the guide passage 2 in a shorter time than other types of valves, such as slide valves.
2a and 22b can be opened and closed, and is suitable for a vehicle engine in which the engine speed changes rapidly. In addition, after long-term use, the guide passage 22a,
Even if carbon adheres to the inner surface of the guide passage 22b, the butterfly valve 16 operates reliably and the guide passage 22
Since a and 22b can be opened and closed, the reliability of the device is improved.

Furthermore, the diameter of the protrusion 72 of the butterfly valve 16
Since D ₂ is smaller in diameter than the diameter D ₁ of the valve body 70, when the butterfly valve 16 is attached to the guide passages 22a, 22b, the protrusion 72 and the guide passages 22a, 2
There is a gap δ between the inner surface of 2b and the inner surface of 2b as shown in FIG.
Even if the butterfly valve 16 is rotated, the protrusion 72 can separate the guide passages 22a and 22b.
There is no risk of collision with the inner surface of the butterfly valve 16 and hindering the rotation of the butterfly valve 16, and the butterfly valve 16 can be moved smoothly.
can be rotated.

In the present invention, the butterfly valve 16 is located immediately at the outlet of the exhaust port 12a (immediately after exhaust gas exits from the combustion chamber to the exhaust port side).
Because of this arrangement, if a depression is formed in the butterfly valve 16 area that causes a sudden change in the exhaust port area in the high speed range where the engine is operated with the butterfly valve 16 closed, performance will be significantly degraded.
In the present invention, the protruding part 72 is provided on the valve body 70, and the lower surface 76 of the protruding part 70 is smoothly continuous with the inner surface 28 of the exhaust port.
There is no risk of performance deterioration in the high speed range when the engine is fully closed. In addition, since the protrusion 72 is provided, when the valve is fully closed, the valve body 70 is moved around the protrusion 72, and the contact area between the inner surface of the guide passage 22a and the valve body 70 is separated from the high-temperature exhaust gas, thereby making it possible to lower the temperature. can.
Moreover, since the guide passage 22a is located within the cylinder wall thickness immediately after the exhaust port exit, and the guide passages 22a and 22b of the pair of cylinders communicate through the external connection passage 26, the external connection passage 26 and the muffler are connected when the butterfly valve is fully opened. can effectively give the mutual resonance effect to the exhaust port outlet, and the external connection passage 2
6 is also compact.

(Another embodiment) (1) The protruding portion 72 of the butterfly valve 16 is not limited to the shape shown in FIG.
As shown in the figure, the lower surface 90 may be formed into a flat shape to simplify the shape of the butterfly valve 16. However, in this case as well, the lower surface 90 is formed so as to be substantially continuous with the inner surface 28 of the exhaust ports 12a, 12b.

(2) The present invention is not limited to the two-stroke engine of the embodiment, but can also be applied to other internal combustion engines, such as when an exhaust chamber is provided at the exhaust port of a four-stroke engine.

[Brief explanation of drawings]

Figure 1 is a partial side view of a two-stroke engine to which the present invention is applied, Figure 2 is a view taken in the direction of the arrows in Figure 1, and Figure 3
The figure is a partial sectional view of FIG. 2, FIG. 4 is a sectional view of FIG. 3, FIG. 5 is a plan view of the butterfly valve, FIG. 5
Figure 7a is a cross-sectional view taken along line a-a in figure 7, figure 7b is a cross-sectional view taken along line bb in figure 7, and figure 7c is
The figure is a sectional view taken along the line CC in FIG. 7, FIG. 7D is a sectional view taken along the DD line in FIG. 7, FIG. 7E is a plan view showing another embodiment of the butterfly valve, and FIG. f
Fig. 7g is a cross-sectional view taken along line ii in Fig. 7e, Fig. 8 is a structural schematic diagram showing a conventional example, and Fig. 9 is a graph showing engine output. 10a...first cylinder, 10b...second cylinder, 12a, 12b...
...Exhaust port, 14...Pressure propagation passage, 16...
Butterfly valve, 22a, 22b...Guide passage, 24a, 24b...Direction change passage, 26...
External connection passage, 28...inner surface, 30...rotation shaft,
34... Drive mechanism, 36... Rotary solenoid, 38... Bell crank, 40a, b... Rod, 42... Arm, 70... Valve body, 72... Projection, 76, 90... Bottom surface.

Claims (1)

[Claims] 1 A guide passage that guides exhaust gas from a position immediately behind the exhaust ports of a pair of internal combustion engines in a direction that intersects with the exhaust ports is provided within the cylinder wall thickness, and both guide passages are communicated by an external connection passage, and the guide passages are A butterfly valve is provided near the exhaust port, and the butterfly valve is connected to a plate-shaped valve body that closes the guide passage so that when the butterfly valve is closed, the surface of the butterfly valve facing the exhaust port is substantially continuous with the inner surface of the exhaust port. An exhaust system for an internal combustion engine, characterized in that a protruding portion is formed on one surface of the valve body so as not to obstruct opening and closing of the valve body, and is smoothly continuous with the inner surface of the exhaust port when the valve is closed.