JP3149473B2 - Exhaust control device for two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control system for a two-stroke engine, and more particularly, to an exhaust control system for changing the exhaust timing by moving a valve disposed on an upper wall of an exhaust passage.

[0002]

2. Description of the Related Art An exhaust control device of this type includes a valve body disposed on an upper wall of an exhaust passage so as to be able to move forward and backward, and an operating mechanism for moving the valve body forward and backward on the back side of the valve body. I have. The operating mechanism is provided in a valve operating chamber, and receives power from an actuator such as a servomotor provided outside the valve operating chamber.

When the valve body is advanced by the operating mechanism, the tip of the valve body projects above the exhaust gas inlet in the exhaust passage, and the upper edge position of the exhaust gas inlet is substantially lowered. As a result, the exhaust timing is delayed as compared with the case where the valve element is at the retracted position.

When the engine is operated in the low rotation speed range and the high rotation speed range, the valve body is in the forward position and the reverse position, respectively, whereby the wide rotation speed from the low rotation speed to the high rotation speed is increased. High engine output can be obtained in the range. By the way, the exhaust gas flows into the valve working chamber through a minute gap existing between the valve body and the guide means, but the flowed exhaust gas has no escape place, and as a result, the internal pressure of the valve working chamber is reduced. Is higher than the pressure at the exhaust inlet. The pressure in the valve working chamber acts in a direction that hinders the retreating operation when the valve element in the forward position is retracted, so that rapid retraction of the valve element is hindered, and in some cases, the valve element is moved to a predetermined position. Is caused to be unable to fully retract to the position. Therefore, attempts have conventionally been made to communicate the valve working chamber with an exhaust passage.

[0005]

However, when the valve working chamber is communicated with the exhaust passage, the following inconveniences are caused. That is, in the two-cycle engine, the exhaust system is configured to obtain a good exhaust pulsation effect in a wide rotation speed range. However, when the valve operating chamber is communicated with the exhaust passage, the valve operating chamber is exhausted. Since it functions as an exhaust chamber that expands the volume of the passage, the synchronized state of the exhaust pulsation is disturbed, and as a result, the disadvantage that the engine output is reduced occurs.

SUMMARY OF THE INVENTION In view of such circumstances, it is an object of the present invention to quickly and surely retreat a valve body without adversely affecting the exhaust pulsation effect, and at the same time, to diffuse impurities into the atmosphere as much as possible. An object of the present invention is to provide an exhaust emission control device for a two-stroke engine that prevents the exhaust emission control.

[0007]

According to the present invention, there is provided a piston, a cylinder on which the piston slides, an exhaust gas inlet opening to the cylinder, and an exhaust gas inlet and outlet disposed on an upper wall of an exhaust passage. A two-stroke engine including a valve body projecting above the inlet to substantially lower the upper edge position of the exhaust gas inlet, an operating mechanism for moving the valve body forward and backward, and a valve operating chamber accommodating the operating mechanism. In the exhaust control device of
The exhaust control device for a two-stroke engine includes a hole formed in a valve operating chamber, a tubular member mounted in the hole to maintain the internal pressure of the valve operating chamber at atmospheric pressure, and an oil catch in the middle of the tubular member. A tubular member that connects the oil catch tank and the valve actuation chamber is interposed between the oil catch tank and the valve operating chamber in a substantially vertical arrangement.

[0008]

Since the valve working chamber is at atmospheric pressure, the pressure in the valve working chamber becomes lower than the pressure at the exhaust inlet during exhaust. This pressure difference urges the valve body in the retreating direction, so that the retreating operation of the valve body is performed quickly and reliably, and the tar contained in the exhaust gas is accommodated in the valve working chamber without leaking to the outside. .

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a two-stroke engine 1 for a motorcycle to which an embodiment of the present invention is applied. On the upper wall 3 of the exhaust passage 2 of the engine 1, a valve element 4 which is a component of the exhaust control device according to the present embodiment, a valve element 5 superposed on the lower surface of the valve element 4, and a valve element 4 And a guide member 6 having a substantially L-shaped cross section for slidably supporting the guide member 5.

The valve body 4 is located between the valve body 5 and the guide member 6, and a pin 4a is implanted at an intermediate portion thereof. The upper end and the lower end of the pin 4a protrude from the upper and lower surfaces of the valve body 4, respectively.
The lower end is slidably fitted into a groove 6a formed on the lower surface side of the valve body 5 and the lower end is slidably fitted into a groove 5a formed on the upper surface side of the valve body 5. A spring 7 is interposed between the upper end of the pin 4 a and the base of the guide member 6, and the valve body 4 is urged by the spring 7 toward the exhaust inlet 8 of the exhaust passage 2. On the other hand, the base end of the valve body 5 is slidably penetrated through the base of the guide member 6, and a pin 5 and a stopper 5 c are provided at the base end.

A valve operating chamber 9 is provided on the back side of the valve elements 4 and 5, and the base end of the valve element 5 is located in the valve operating chamber 9. In the valve working chamber 9, the base is
A lever 11 fixed to the lever 1 is provided.
The pin 5 of the valve element 5 is fitted to the forked tip 11a of the first valve body. The shaft 10 is rotatably supported, and is provided with rotational power from outside the valve operating chamber 9. The shaft 10
In this embodiment, a servomotor M is used as an actuator for rotating.

A hole 9 is provided above the lid 9a of the valve operating chamber 9.
b is formed through the hole 9 b and the lower opening 1 of the spherical catch tank 12 located above the valve actuation chamber 9.
2a is connected via a pipe 13. The upper opening 12b of the catch tank 12 is open to the atmosphere via the pipe 14, so that the pressure in the valve operating chamber 9 is maintained at the atmospheric pressure.

FIGS. 4 and 5 conceptually show a motorcycle on which the two-cycle engine 1 is arranged. As shown in these figures, the pipe 14 connected to the catch tank 12 extends to the rear end of the tank rail 15 along the inner surface of the tank rail 15 as a frame component, It is lowered to the position outside the first muffler. The first end of the first muffler is connected to the exhaust outlet of the exhaust passage 2 shown in FIG.
It is connected to the muffler 17.

Next, the operation of this embodiment will be described. The control unit 18 shown in FIG.
Based on the engine speed detected in step 9, it is determined whether the speed indicates a value belonging to a predetermined low speed range, middle speed range, or high speed range. And
When the control unit 18 determines that the engine speed indicates a value in the low speed range, the control unit 18 controls the motor M so that the lever 11 assumes the posture illustrated in FIG. 5 both project above the exhaust inlet 8. At this time,
The pin 4a of the valve body 4 has an upper end formed with a groove 6 of the guide member 6.
The lower end abuts on the right wall of the groove 5 a of the valve body 5. In the state where the valve bodies 4 and 5 are positioned as shown in FIG. 1, the upper edge position of the exhaust gas inlet 8 is substantially lowered to the tip position of the valve body 5, and as a result, the exhaust gas inlet 8 is adapted to a low rotation speed region. Exhaust timing is achieved.

When the control unit 18 determines that the engine speed has reached a value in the middle engine speed range, the motor M is controlled so that the lever 11 assumes the posture shown in FIG.
As a result, only the valve element 5 is retracted, and its distal end surface coincides with the distal end surface of the valve element 4. At this time, the pin 4 of the valve body 4
The lower end of a is in contact with the left wall of the groove 5a of the valve body 5. In this state, the upper edge position of the exhaust gas inlet 8 is substantially lowered to the position of the tip of the valve body 4, and as a result, exhaust timing suitable for the middle rotation speed range is realized.

When the control unit 18 determines that the engine speed has reached a value in the high engine speed range, the motor M is controlled so that the lever 11 assumes the posture shown in FIG. 3 (b). As a result, the valve element 5 is retracted to a position where the front end surface of the valve element 5 coincides with the inner surface of the upper wall of the exhaust passage 2.
By the retraction force applied from the valve body 5 side via the pin 4a, the valve is operated to retreat to a position where the front end surface coincides with the inner surface of the upper wall of the exhaust passage 2. At this time, the rear end surfaces of the valve element 4 and the valve element 5 are in contact with the inner surface of the base of the guide member 6, respectively. In the state of FIG. 3B in which both the valve body 4 and the valve body 5 do not protrude into the exhaust passage 2, the actual upper edge position of the exhaust gas inlet 8 becomes the exhaust start position, so that the high rotational speed region can be obtained. Suitable exhaust timing is achieved.

In this embodiment, the valve operating chamber 9 shown in FIG.
And open to the atmosphere through the pipe 14,
The pressure in the valve operating chamber 9 becomes atmospheric pressure. Therefore, the pressure in the valve operating chamber 9 becomes lower than the pressure in the exhaust gas inlet 8, so that the front end faces of the valve bodies 4 and 5 have positive pressure, that is, these valve bodies 4 and 5 are moved toward the valve operating chamber 9. The urging pressure acts, and as a result, the retreating operation of the valve bodies 4 and 5 described above is quickly and reliably performed. Further, since the valve operating chamber 9 is isolated from the exhaust passage 2, the valve operating chamber 9 does not function as an element of the exhaust system, and therefore, the valve operating chamber 9 has no adverse effect on the pulsation of the exhaust. Do not give.

In the above embodiment, there are slight gaps between the valve body 4 and the guide member 6, between the valve body 4 and the valve body 5, and between the valve body 5 and the upper wall of the exhaust passage 2. A small amount of exhaust gas flows into the valve operating chamber 9 therethrough. Tar is contained in the exhaust gas flowing into the valve operating chamber 9, and the tar is collected by the catch tank 12. That is, when the exhaust containing tar flows into the catch tank 12, the exhaust is expanded. As a result, the tar component in the exhaust gas is condensed and liquefied and collected in the catch tank 12. As a result, according to this embodiment, the disadvantage that the tar leaks outside through the pipe 14 is avoided.

Instead of the catch tank 12, a box-shaped catch tank 20 shown in FIG. 2 can be used. The catch tank 20 has openings 20a and 2a corresponding to the openings 12a and 12b of the catch tank 12.
0b, and a partition plate 20c that is inclined inside.
The tar is efficiently liquefied and collected by the expansion action and the collision action of the exhaust gas against the partition plate 20c. The liquefied tar collected by the catch tanks 12 and 20 naturally falls into the valve operating chamber 9 via the pipe 12 after the engine 1 is stopped.

In the above embodiment, the two valve bodies 4 and 5 are used. However, it is also possible to change the exhaust timing by using only the valve body 5, and in this case, the rotation speed of the engine 1 is set to a predetermined value. The valve body 5 is protruded when the rotation speed indicates a value in a low rotation speed range, and the valve body 5 is retracted when the rotation speed indicates a value in a predetermined middle and high rotation speed range.

In the above-described embodiment, the lever 11 is operated by the servo motor M. However, the lever 11 is operated by inputting the rotational power of the crankshaft.
It is also possible to use a mechanical actuator as shown in No. 02.

[0023]

According to the present invention, a hole is formed in a valve operating chamber, a tube is attached to the hole to maintain the internal pressure of the valve operating chamber at atmospheric pressure, and oil is provided in the middle of the tubular member. Since the catch tank is interposed and the tubular member connecting the oil catch tank and the valve operating chamber is arranged in a substantially vertical shape, the output of the engine can be reduced without adversely affecting the exhaust pulsation effect. The valve body can be quickly and reliably moved backward without lowering, so that the output of the two-stroke engine can be further improved and the tar contained in the exhaust gas can be naturally dropped without leaking to the outside. As a result, the two-stroke engine is provided to prevent the diffusion of impurities into the atmosphere as much as possible and to reduce the adverse effects on the atmosphere as much as possible. Door can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view conceptually showing one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view conceptually showing another configuration example of the catch tank.

FIG. 3 is a sectional view showing an operation mode of the valve body.

FIG. 4 is a side view conceptually showing attachment positions of a frame and a pipe of the motorcycle.

FIG. 5 is a plan view conceptually showing attachment positions of a frame and a pipe of the motorcycle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 2 cycle engine 2 Exhaust passage 3 Exhaust passage upper wall 4,5 Valve 6 Guide member 8 Exhaust inlet 9 Valve working chamber 9b Hole 10 Shaft 11 Lever 12 Catch tank 13,14 Pipe

Claims (1)

(57) [Claims] A piston, a cylinder on which the piston slides, an exhaust inlet opening to the cylinder, and an exhaust passage disposed at an upper wall of the exhaust passage so as to be able to advance and retreat, and projecting above the exhaust inlet to exhaust the exhaust gas. An exhaust control device for a two-stroke engine, comprising: a valve body for substantially lowering an upper edge position of an inflow port, an operating mechanism for moving the valve body forward and backward, and a valve operating chamber accommodating the operating mechanism. An exhaust control device for a cycle engine has a hole formed in a valve working chamber, a tube-shaped member attached to the hole to maintain the internal pressure of the valve working chamber at atmospheric pressure, and an oil catch tank in the middle of the tubular body. An exhaust control device for a two-stroke engine, wherein a tubular member that intervenes and connects the oil catch tank and the valve working chamber is disposed substantially vertically.