JPH0346649B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Use) The present invention relates to a two-stroke engine having a pair of cylinders, in which the exhaust ports of both cylinders are connected through a pressure propagation passage to improve output. This invention relates to a structure for applying an exhaust system to an actual engine.

(Prior Art) The applicant has already developed and filed an application for an exhaust system for a two-stroke engine as shown in FIG.
This device consists of a first
A cylinder 10a and a second cylinder 10b are provided, exhaust ports 12a and 12b are connected by a pressure propagation passage 14, and exhaust ports 12a and 1 of the pressure propagation passage 14 are provided.
An on-off valve 16 is provided near 2b, and the on-off valve 16 is opened and closed by a drive mechanism (not shown). For example, by operating the drive mechanism at 7000 rpm, the on-off valve 16 is opened in a low speed range, and is opened in a high speed range. It has a structure that closes the on-off valve 16.

According to the above device, at low speeds when the on-off valve 16 is open, a positive pressure wave is transmitted to the exhaust ports 12a, 12 by the resonance action of the pressure propagation passage 14 and the mufflers 13a, 13b connected to the respective cylinders.
b to prevent the air-fuel mixture from blowing through and improve the output, output curve 18c in Fig. 9 (when the valve is open),
As shown in 18 (when the valve is closed), when the pressure propagation passage 14 is in communication, the output will decrease.At high speeds, the on-off valve 16 is closed to improve the output, so that high output is achieved in the entire rotation speed range. It is set as.

However, when mounting such a two-stroke engine exhaust system on a motorcycle body, for example, a drive mechanism for driving the pressure propagation passage 14 and the opening/closing valve 16 must be placed in a narrow cylinder area, and it is difficult to The problem is how to make the entire device compact.

(Object of the Invention) An object of the present invention is to provide an exhaust system for a two-stroke engine that can be compactly attached to the two-stroke engine.

(Structure of the Invention) The present invention provides a pressure propagation passage that communicates the exhaust ports of both cylinders of a two-stroke engine having at least one pair of cylinders, and provides an on-off valve in the vicinity of the exhaust port of the pressure propagation passage. In an exhaust system for a two-stroke engine that controls the opening and closing of valves, a guide passage is formed toward the cylinder head to guide exhaust from the portions of both exhaust ports facing the cylinder head in a direction that intersects the exhaust ports. A direction change passage that is continuous with the guide passage and changes the direction of the passage toward one side of the engine is integrally provided in the cylinder head, and an external connection that is arranged along the one side of the engine and connects the ends of the bidirectional change passage. An exhaust system for a two-stroke engine, characterized in that a passage is provided, a pressure propagation passage is formed by these guide passages, a direction change passage, and an external connection passage, and a drive mechanism for opening and closing an on-off valve is disposed on the one side of the engine. It is a device.

(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.
A lower end portion 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 upwardly from the cylinder head 10c. Second
Similarly, the cylinder 10b has a guide passage 22b (first
(Fig. 2) are provided.

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. Although the details will be described later, when the butterfly valve 16 is closed, 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
The drive mechanism 34 that opens and closes the butterfly valve 16 (FIGS. 3 and 4) will be explained. The drive mechanism 34 includes a rotary solenoid 36, a bell crank 38,
It is formed of rods 40a, b, an arm 42, etc., and the drive mechanism 34 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 a butterfly valve 16 (FIGS. 3 and 4) 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 (FIGS. 3 and 4) 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 degrees, as shown by the two-dot chain line in the figure. By rotating the arm 42, the butterfly valve 16 (FIGS. 3 and 4) is closed. The rotary solenoid 36 is normally biased in the direction of the reverse arrow A by the spring force of a built-in spring (not shown). A rotation speed detection signal from the ignition device 50 is input to the control unit 48, and for example, the engine rotation speed is detected.
Control unit 4 when reaching 7000rpm.
8 to the rotary solenoid 36.

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 is 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 56 that is wrapped around the rotating shaft 30.
The pivot shafts 30 overlap each other at the ends 62 of the
is biased in the circumferential direction.

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 and 22b to close the guide passages 22a and 22b.
and a protrusion 72 protruding from the lower surface of the valve body 70 facing the exhaust ports 12a, 12b.
The valve body 70 and the protrusion 72 are integrally molded from a sintered metal. As shown in FIG. 6, the protruding portion 72 is attached to the valve body 70 except for the central portion where the rotating shaft 30 is fixed.
The diameter D ₂ of the protrusion 72 is set to be slightly smaller than the diameter D ₁ of the valve body 70 . 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 protruding portion 72 is as shown in FIG. 5, which is a cross-sectional view taken along the center line 78 of FIG. radius as shown in Figure 7 and Figures 7a to 7d.
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 degrees 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 drive mechanism 34 is provided on the left side of the cylinders 10a and 10b.
A space is secured for placing the . Furthermore, the guide passages 22a and 22b are formed within the thickness of the first cylinder 10a and the second cylinder 10b, and the external conversion passages 24a and 24b are formed within the thickness of the cylinder head 10c, so the structure is simple. Guide passages 22a, 22b and external conversion passages 24a, 24b
The connection is between cylinder head 10c and cylinder 10.
It can be easily completed by fastening parts a and 10b. Furthermore, the external connection passage 26 is connected to the cylinder head 10.
Since the rotary solenoid 36 is disposed along the left side surface of the rotary solenoid 36, a space for fixing the rotary solenoid 36 to the first cylinder 10a below the external connection passage 26 is secured. Therefore, the pressure propagation passage 14 and the drive mechanism 34 are concentrated on the left side of the engine.

The drive mechanism 34 has an engine rotation speed of, for example,
Rotary solenoid 3 when below 7000rpm.
The butterfly valve 16 is held open by the spring force of the spring built into the butterfly valve 6, thereby improving the output at low speeds of the engine. On the other hand, if the engine speed is, for example, 7000 rpm or higher, control unit 4
Rotary solenoid 3 due to the output current from 8
6 rotates in the direction of arrow A to guide the guide passages 22a, 22.
The butterfly valve 16 of b is closed at the same time to improve the 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 inner 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.

The protrusion 72 of the butterfly valve 16 is the valve body 70
Since it has a smaller diameter, the protrusion 7 is
2 and the inner surfaces of the guide passages 22a, 22b are separated by a gap δ as shown in FIG. There is no possibility that the rotation of the butterfly valve 16 will be hindered.

When the butterfly valve 16 is closed, the lower surface 76 of the protrusion 72 is substantially continuous with the inner surface as shown in FIG. This improves the output of the engine by smoothing the flow of exhaust gas rapidly discharged to the exhaust ports 12a and 12b.

(Effects of the Invention) As explained above, the exhaust system for a two-stroke engine according to the present invention provides a pressure propagation passage that communicates the exhaust ports of both cylinders of a two-stroke engine having a pair of cylinders, and exhausts the air from the pressure propagation passage. In an exhaust system for a two-stroke engine in which opening and closing valves are provided near each port and the opening and closing of the opening and closing valves are controlled, a guide for guiding exhaust from the portions of both exhaust ports facing the cylinder head in a direction that intersects the exhaust ports. A passage is formed toward the cylinder head, and a direction changing passage that is continuous with the guide passage and changes the direction of the passage toward one side of the engine is provided integrally with the cylinder head, and the passage is arranged along the one side of the engine and runs both ways. An external connection passage connecting the ends of the conversion passage is provided, a pressure propagation passage is formed by the guide passage, the direction change passage, and the external connection passage, and a drive mechanism for opening and closing the opening/closing valve is arranged on the one side of the engine. Therefore, the following effects can be achieved.

The pressure propagation passage 14 includes guide passages 22a, 22b,
An external connection passage 26 is connected to one side of the cylinder head 10c via the direction change passages 24a and 24b, and the cylinder 10 is connected to the cylinder head 10c on the same side.
Since the drive mechanism 34 is arranged on the side surfaces of a and 10b, the exhaust system including the pressure propagation passage 14 and the drive mechanism 24 is housed in a concentrated manner on the same side of the engine, resulting in a compact engine with good mounting ease. In addition, the drive mechanism 34 can be adjusted during assembly or use without having to move it facing the same side of the engine, which simplifies the work.

Further, the guide passages 22a and 22b are connected to the first cylinder 1.
0a, formed within the wall thickness of the second cylinder 10b,
The direction change passages 24a and 24b are connected to the cylinder head 1.
Since it is formed within a wall thickness of 0c, the structure is simple and the guide passages 22a, 22b and the direction change passages 24a, 24b can be easily connected. Therefore, in the process of assembling the engine, it is only necessary to fix the cylinder head 10c to the first cylinder 10a and the second cylinder 10b, and the number of man-hours required for assembling the engine can be reduced.

Furthermore, since the external connection passage 26 is arranged along the left side of the engine, a space for fixing the rotary solenoid 36 to the first cylinder 10a below the external connection passage 26 can be secured. Therefore, the pressure propagation passage 14 and the drive mechanism 34
Since the drive mechanism 34 is concentrated on the left side of the engine, adjustments during assembly and use of the drive mechanism 34 can be made without having to move the drive mechanism 34 to face the same side of the engine, which simplifies the work.

[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 cross-sectional partial view of FIG. 2, FIG. 4 is a cross-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 cross-sectional view taken along line CC in Figure 7, Figure 7d is a cross-sectional view taken along line dd in Figure 7, and Figure 8 is a structural diagram showing a conventional example.
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, 22
a, 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, 7
0...Valve body, 72...Protrusion, 76...Bottom surface.

Claims (1)

[Claims] 1 A pressure propagation passage is provided that communicates the exhaust ports of both cylinders of a two-stroke engine having a pair of cylinders, an on-off valve is provided near the exhaust port of each pressure propagation passage, and the opening and closing of this on-off valve is controlled. 2 In the exhaust system of cycle engines,
A guide passage is formed toward the cylinder head that guides exhaust gas from the parts facing the cylinder head of both exhaust ports in a direction that intersects with the exhaust port, and a guide passage that is continuous with this guide passage and faces one side of the engine is formed. A direction change passage to be changed is provided integrally with the cylinder head, an external connection passage is provided along the one side of the engine and connects the ends of the bidirectional change passage, and these guide passages, direction change passages and external connections are provided. An exhaust system for a two-cycle engine, characterized in that the passage forms a pressure propagation passage, and a drive mechanism for opening and closing an on-off valve is disposed on the one side of the engine.