JPH09228840A - Exhaust control device of two cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the rate of exhaust gas at the time of part load operation, in an exhaust control device of a two cycle engine. SOLUTION: An exhaust control device 1 is provided with a first valve element 4 arranged on the upper wall 10 of an exhaust passage 9 communicated with the exhaust port 8 of a cylinder 7, a second valve element 5, and a third valve element 6, the first valve element 4 and the second valve element 5 are projected/retreated to the exhaust port 8 according to engine rotational speed so as to change the upper rim position of the exhaust port 8. In this case, the first valve element 4 is provided with a vent hole for circulating exhaust gas on a top end part, the first valve element 4 is projected to the exhaust port 8 in the low rotational speed range of the engine, the lower rim part of the exhaust port 8 is closed, only communication of the vent hole 16 and a cylinder bore 12 is allowed, and thereby, a fully closing position is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine equipped with an exhaust timing valve which can fully close the exhaust port of a cylinder in a low engine speed range and has a vent hole through which exhaust gas can flow out. Exhaust control device.

[0002]

2. Description of the Related Art Conventionally, various measures have been taken to improve the output of a two-cycle engine. For example, in Japanese Utility Model Laid-Open No. 53-165922, a butterfly valve is provided in the exhaust pipe portion of a muffler, and the throttle amount of the butterfly valve is changed according to the negative pressure of the intake system.
Japanese Unexamined Patent Publication No. 59-28018 discloses that a rotary valve that rotates in synchronization with the crankshaft is provided in the vicinity of the exhaust port of the cylinder.

Further, in Japanese Patent Laid-Open No. 3-275930, the position of the upper edge of the exhaust port is raised and lowered according to the engine speed to ensure the optimum exhaust timing corresponding to each engine speed range. An exhaust control device that improves output in a wide range of engine speed is disclosed.

This will be described with reference to FIGS. 3 to 5. 101 is an exhaust control device, and the exhaust control device 101 is
It has a plate-shaped first valve body 104 and a second valve body 105 that are arranged so as to be retractable in the upper wall 103a of the exhaust passage 103, and as shown in FIG. Also, both the second valve body 104 and the second valve body 105 are projected toward the exhaust port 106 side, and the upper edge position of the exhaust port 106 is lowered by A by the tip of the first valve body 104, thereby delaying the exhaust timing and lowering the rotation speed. As shown in FIG. 4, the first valve body 10 is improved in the middle rotation range while improving the engine output in the range.
4 is retracted from the exhaust port 106 and the second valve body 105
The upper edge position of the exhaust port 106 is raised by B by the tip of the engine, thereby slightly speeding up the exhaust timing to improve the output of the engine in the medium revolution range, and in the high revolution range, as shown in FIG. Both of the two valve bodies 104 and 105 are retracted from the exhaust port 106, and the upper edge position of the exhaust port 106 is further raised by C, whereby the exhaust timing is most accelerated and the engine output is improved in the high revolution range. ing.

The first and second valve bodies 104 and 105 are arranged so as to overlap each other, and a pin 107 penetrating the second valve body 105 is fixed to the second valve body 105.
Has a long groove 1 formed on the upper surface of the first valve body 104.
When the first valve element 104 is inserted into the exhaust passage 08 and is retracted by a predetermined distance, the tip of the pin 107 engages with the end of the long groove 108, whereby the second valve element 105 causes the exhaust valve 103 to move.
The upper wall 103a can be retracted.
Reference numeral 109 denotes a spring arranged in the cylinder, which is the second valve body 1
05 is constantly elastically urged toward the exhaust port 106 by the spring force of the spring 109 via the pin 107.

A shaft 110 is projectingly provided at the rear end of the first valve body 104, and the shaft 110 is slidably engaged with a U-shaped notch formed at the tip of a lever 111. Lever 11
The drive shaft 112 is attached to the base portion of No. 1, and when the drive shaft 112 rotates, the lever 111 swings by this, and the swing causes the first valve body 104 to project toward the exhaust port 106 side or the exhaust port 106. Be evacuated from.

A drive pulley (not shown) is attached to the drive shaft 112, and a drive cable (not shown) is wound around the drive pulley. Driven according to.

[0008]

In the case of using the butterfly valve of the above-mentioned conventional example, not only the throttle amount at the time of idling is unstable, but also a phenomenon such as flapping of the butterfly valve at the time of idling may occur. Therefore, the values of CO gas, HC gas, etc. to be discharged are not constant, and thus the stability of the exhaust gas is lacking, and thus the output improvement in a wide range of engine speed is insufficient.

On the other hand, the above-mentioned exhaust control device for improving the output by raising and lowering the position of the upper edge of the exhaust port is called a piston valve type exhaust device in contrast to the above rotary valve type exhaust device and has a wide range. Although the output can be improved in the engine speed range, there is a problem that the amount of HC gas blown through at the time of idling is large.

The present invention has been made in view of the above problems, and an object thereof is to provide an exhaust control device capable of reducing the amount of exhaust gas during partial load operation.

[0011]

The present invention has the following configuration to achieve the above object. That is, the present invention has a plurality of valve elements which are provided on the upper wall of the exhaust passage leading to the exhaust port of the cylinder and which are vertically stacked, and at least the lowest end of the plurality of valve elements according to the engine speed. In the exhaust control device of the two-cycle engine, the valve element of which is slid in and out of the exhaust port to change the upper edge position of the exhaust port, the valve element at the lowermost end is a vent hole through which exhaust gas can flow. And has a fully closed position that allows the vent hole and the cylinder bore to communicate with each other by protruding to the exhaust port in the low engine speed range and closing the lower edge of the exhaust port. It is an exhaust control device for a cycle engine.

According to the present invention, in the low engine speed range, the valve body at the lowermost end closes the lower end portion of the exhaust port to fully close the exhaust port, so that blow-through of HC gas is prevented. The displacement can be reduced as much as possible. Further, in the low engine speed range, the exhaust port is fully closed as described above, but since the valve body at the lowest end has a vent hole, exhaust gas from the cylinder bore passes through the vent hole. Can flow out to the exhaust passage, and therefore rotation at idling can be secured. Further, unlike the adjustment of the position of the valve element, the diameter of the vent hole can be set accurately and its selection is easy, so that the exhaust gas can be stably reduced even during idling. Further, since the constituent parts are the same as those of the conventional exhaust control device, the above effects can be obtained with a minimum cost increase.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust control system for a two-cycle engine according to the present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a schematic vertical cross-sectional view taken along the cylinder axis of an exhaust control device 1 according to the present invention, and FIG. 2 is AA of FIG.
It is sectional drawing which follows a line. The exhaust control device 1 is roughly composed of an exhaust timing valve 2 and a lever 3, and the exhaust timing valve 2 is a vertically stacked first valve body 4 (corresponding to the valve body at the lowermost end), a second valve body 5 and The third valve body 6 is roughly configured.

The first valve body 4 and the second valve body 5 located above the first valve body 4 have holes 11 formed in the upper wall 10 of the exhaust passage 9 connected to the exhaust port 8 of the cylinder 7. And is freely retractable into and out of the exhaust port 8, and these slidably contact each other. The third valve body 6 is fixed to the upper wall 10 of the exhaust passage 9, and the second valve body 5 slidably contacts from the lower side. The cross-sectional shape of the first valve body 4, the second valve body 5 and the third valve body 6 in a superposed state is substantially circular as shown in FIG.

The first valve body 4 has a low engine speed range,
As shown in FIG. 1, it is in a fully closed position where it projects into the exhaust passage 9 and faces the cylinder bore 12 from the exhaust port 8. The first valve body 4 has an arcuate cross-sectional shape, and an exhaust port 8 is provided at the tip thereof.
A tapered surface 14 is provided so as to substantially match the taper angle of the peripheral wall 13, and the tapered surface 14 is in contact with the peripheral wall 13 at the lower edge of the exhaust port 8 at the fully closed position.
Further, the tip end surface of the first valve body 4 has the exhaust port 8 at the fully closed position.
Is formed so as to be substantially parallel to the opening surface 15, and when fully closed, the lower edge portion of the opening surface 15 is closed so as to extend parallel to the opening surface 15. Further, the first valve body 4 is formed with a vent hole 16 penetrating its tip end and through which exhaust gas can flow, and an inlet 17 of the vent hole 16 is opened to a flat surface 18 of the first valve body 4 and an outlet 19 thereof. Is open to the curved surface 20 rearward of the tapered surface 14 so that the cylinder bore 12 and the exhaust passage 9 communicate with each other when fully closed. As described above, the first valve body 4 can freely retract into and out of the exhaust passage 9, and is located in the hole 11 formed in the upper wall 10 of the exhaust passage 9 when retracted.

The upper and lower surfaces of the second valve body 5 are flat, and both side surfaces are curved so as to fit the peripheral wall surface of the exhaust port 8 and slidably contact the upper surface of the first valve body 4. ing. The tip end surface of the second valve body 5 is inclined so that a space 22 having a triangular cross section is formed between the inclined surface 21 and the upper surface of the first valve body 4 in the low engine speed range. At the same time, its tip reaches the opening surface 15 of the exhaust port 8 and faces the cylinder bore 12. In the second valve body 5,
A screw hole 23 is formed so as to penetrate therethrough, and the screw hole 2
A bolt 24 is screwed into the screw 3. Head 25 of bolt 24
Is slidably inserted into a long groove 26 formed in the upper surface of the first valve body 4. The long groove 26 is located rearward of the inlet 17 of the ventilation hole 16.

The second valve body 5 can be retracted into and out of the exhaust passage 9 as described above, and at the time of retreat, the hole 1 is formed like the first valve body 4.
Located within 1. The third valve body 6 is formed in an arcuate cross section so as to fit the peripheral wall surface of the upper edge portion of the exhaust port, and is in contact with the upper surface of the second valve body 5. Further, the tip end surface of the third valve body 6 is inclined, and the cross-sectional shape is triangular between the inclined surface 27 and the upper surface of the second valve body 5 in the low rotation speed region and the middle rotation speed region of the engine. A space 28 is formed, and the tip of the space 28 reaches the opening surface 15 of the exhaust port 8 and faces the cylinder bore 12.

A coil spring 30 is compressed and disposed in a space 29 surrounded by the base of the third valve body 6, the upper wall surface of the hole 11 and the upper surface of the second valve body 5, and the coil spring 30 and the third The tip of the shaft of the bolt 24 projects from the valve body 6, and the coil spring 30 elastically urges the tip of the bolt 24 toward the base of the third valve body 6. As a result, the second valve body 5 is constantly urged toward the exhaust passage 9 via the bolt 24.

As described above, the first valve body 4 has the exhaust passage 9
The operation of the first valve body 4 is performed by turning the lever 3. That is, a U-shaped notch 32 is formed at the tip of the lever 3, and the notch 32 is slidably engaged with a shaft 33 protruding from the base of the first valve body 4. A drive shaft 34 is attached to the base portion of the lever 3, and when the drive shaft 34 rotates, the lever 3 rotates by this rotation, and this rotation causes the first valve body 4 to protrude into the exhaust passage 9 or the exhaust passage 9. Be evacuated from.

A drive pulley (not shown) is attached to the drive shaft 34, and a drive cable (not shown) is wound around the drive pulley. The drive shaft 34 rotates a predetermined engine by a servo motor (not shown) via the drive cable. It is driven according to the number.

Next, the operation of the present embodiment will be described. In the low engine speed range, the first valve body 4 and the second valve body 5 project into the exhaust passage 9, and the tip of the first valve body 4 is shown in FIG.
As shown in FIG. 4, the exhaust port 8 is in a fully closed position that closes the lower edge thereof, and the respective tip portions of the second valve body 5 and the third valve body 6 face the cylinder bore 12 from the exhaust port 8.

As described above, in the low rotation speed range, the exhaust port 8 is fully closed by the first valve body 4, the second valve body 5 and the third valve body 6, but the vent hole 16 is formed in the first valve body 4. The exhaust gas from the cylinder bore 12 can flow out to the exhaust passage 9 through the vent hole 16 because of the formation of the.

Therefore, it is of course possible to prevent the HC gas from passing through in the low rotation speed range and reduce the exhaust amount as much as possible, and the exhaust gas can flow out from the vent hole 16 as shown by the arrow G. Therefore, it is possible to secure the rotation during idling.

When the engine reaches the middle speed range, the lever 3 is rotated counterclockwise in FIG. 1 by the rotation of the drive shaft 34, whereby the first valve body 4 is moved backward to the left, The right end of the long groove 26 is retracted until it engages with the head 25 of the bolt 24.

On the other hand, the second valve body 5 maintains the same position as in the low rotational speed range, and the tip thereof sets the upper edge position of the exhaust port 8 above the fully closed position, and the first valve body 4 Does not affect the exhaust timing.

When the engine reaches the high speed range, the lever 3 further rotates counterclockwise, and in response to this, the first valve body 4 further moves backward. When the first valve body 4 starts to move, the bolt 24 engaged with the right end portion of the long groove 26 overcomes the spring force of the coil spring 30 and is pushed to the left, so that the second valve body 5 also moves backward to the left. start. Then, when the first valve body 4 and the second valve body 5 are retracted into the hole 11 and the exhaust port 8 is fully opened, the backward movement of the first valve body 4 and the second valve body 5 is stopped. At this time, it is the third valve body 6 that sets the upper edge position of the exhaust port 8.

When the engine speed decreases from the high speed range to the medium speed range, the drive shaft 34 rotates in the clockwise direction and the lever 3 also rotates in the clockwise direction, whereby the first valve body 4 is rotated. Moves forward by a predetermined distance and projects into the exhaust passage 9. On the other hand, the second valve body 5 moves forward in the direction of the exhaust port 8 by the spring force of the coil spring 30 acting through the bolt 24, and when the tip end of the shaft portion of the bolt 24 abuts the base portion of the third valve body 6. The movement is stopped and the tip of the second valve body 5 is moved to the position shown in FIG.
As shown in, the upper edge position of the exhaust port 8 is set so as to face the cylinder bore 12 from the exhaust port 8.

Further, when the engine speed decreases from the medium speed range to the low speed range, the drive shaft 34 further rotates clockwise and the lever 3 further rotates clockwise. Then, the first valve body 4 separates from the head portion 25 of the bolt 24, and further moves forward to take a fully closed position for closing the lower edge portion of the exhaust port 8 as shown in FIG.

According to the present embodiment which operates as described above, it is possible to prevent blow-through of the HC gas in the low engine speed range to reduce the exhaust gas volume as much as possible, and in the low engine speed range described above. As described above, the exhaust port 8 is fully closed, but the exhaust gas from the cylinder bore 12 can flow out to the exhaust passage 9 through the ventilation hole 16,
Therefore, the rotation at the time of idling can be secured. Further, unlike the adjustment of the position of the valve element, the diameter of the vent hole 16 can be accurately set, and its selection is easy,
It is possible to stably reduce the exhaust gas even when idling. Further, since the constituent parts are the same as those of the conventional exhaust control device, the above effects can be obtained with a minimum cost increase.

[0030]

As described above, it is possible to prevent blow-through of the HC gas in the low rotation speed range and reduce the exhaust amount as much as possible. Also, in the low engine speed range, the exhaust port is fully closed, but the exhaust gas from the cylinder bore can flow out to the exhaust passage through the ventilation hole, thus ensuring the rotation during idling. be able to.
Furthermore, exhaust gas can be stably reduced even when idling. Further, since the constituent parts are the same as those of the conventional exhaust control device, the above effects can be obtained with a minimum cost increase.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a main part of an exhaust control device for a two-cycle engine according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram illustrating the operation of a conventional example.

FIG. 4 is a diagram for explaining the operation of the conventional example.

FIG. 5 is an operation explanatory view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust control device 2 Exhaust timing valve 4 First valve body (corresponding to the lowermost valve body) 5 Second valve body 6 Third valve body 7 Cylinder 8 Exhaust port 9 Exhaust passage 10 Upper wall 12 Cylinder bore 16 Vent hole

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F16K 3/06 F16K 3/06 A

Claims (1)

[Claims] 1. A plurality of valve bodies which are provided on an upper wall of an exhaust passage communicating with an exhaust port of a cylinder and which are vertically stacked, and at least a lowermost end of the plurality of valve bodies corresponding to an engine speed. In a two-cycle engine exhaust control device in which a valve element slides in and out of an exhaust port to change an upper edge position of the exhaust port, the valve element at the lowermost end has a vent hole through which exhaust gas can flow, at a tip portion. A two-cycle that has a fully closed position that has a protrusion to the exhaust port in the low engine speed range and closes the lower edge of the exhaust port to allow only communication between the vent hole and the cylinder bore. Engine exhaust control device.