JPH0745813B2 - Exhaust control device for 2-cycle engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust control device for a two-stroke engine.

[Prior Art] In a two-cycle engine, a so-called scavenging process, which pushes out combustion gas with a mixture gas, is added to perform exhaust. Therefore, compared with an engine having an independent exhaust valve such as a four-cycle engine, a more modest gas There is a drawback that the exchange, that is, the mixture of air and exhaust gas cannot be performed. Therefore, in the conventional two-cycle engine, a part of the air-fuel mixture comes out from the exhaust port during exhaust (so-called blow-through phenomenon), the efficiency of filling the air-fuel mixture is reduced, and the output is reduced. Further, conventionally, in order to prevent such a blow-through phenomenon, a sub-chamber is formed in the exhaust port, the blow-through is prevented by utilizing the exhaust pressure pulsation generated in the sub-chamber, and the filling efficiency of the air-fuel mixture is improved. Although the output is improved, the optimum volume for forming this sub-chamber also differs depending on each rotation range of the two-cycle engine.
It was not possible to improve the output of the two-cycle engine according to the full speed range.

Incidentally, in order to solve the above-mentioned problems, Japanese Patent Application Laid-Open No. 60-2496
As disclosed in JP-A-15, the cylindrical valve that opens and closes between the exhaust port and the subchamber and the plate-shaped valve that changes the upper edge position of the exhaust port are interlocked via interlocking means composed of gears, It is conceivable that the exhaust pipe volume and the exhaust timing are changed at the same time. However, in the one disclosed in JP-A-60-249615, the plate valve immediately follows the rotation of the cylindrical valve. Since the exhaust timing is changed by changing the exhaust timing, the change in the exhaust timing is greatly affected by the transient exhaust gas accompanying the change in the exhaust pipe volume. There was a risk of becoming. [Object of the Invention] In view of the above-mentioned circumstances, the present invention has a smooth engine output characteristic, and is designed to improve the output over a wide range of engine speeds from a low speed range to a high speed range.
An object is to provide an exhaust control device for a cycle engine.

[Structure of Invention]

In order to achieve the above-mentioned object, in a two-cycle engine exhaust control device of the present invention, a cylindrical valve disposed between an exhaust port and an exhaust pipe volume varying sub-chamber, and a lower valve forming an upper surface of the exhaust port. A plate-shaped valve that has an end surface and is slidably disposed on an upper wall located behind the cylinder side opening of the exhaust port, and an arc-shaped groove formed on the end surface of the cylindrical valve and the plate-shaped valve. Interlocking means for activating the plate-shaped valve by delaying the rotation of the cylindrical valve, the cylindrical valve being arranged at the upper end of the cylindrical valve and engaging with the arc-shaped groove; Drive means for opening and closing in a region, the drive means rotates the cylindrical valve to move the exhaust port to the sub-chamber. When passed, the interlocking means delays the rotation of the cylindrical valve to cause the lower end surface of the plate-shaped valve to project into the exhaust hoat to lower the upper edge position of the cylinder side opening and When the cylindrical valve is rotated by means to close the space between the sub-chamber and the exhaust port, the interlocking means delays the rotation of the cylindrical valve to cause the plate valve to escape from the exhaust port. The upper edge position of the cylinder opening is raised.

〔Example〕

An embodiment of the exhaust control device according to the present invention will be described in detail below.

FIG. 1 is a fragmentary cross-sectional view of a two-cycle engine 2 equipped with an exhaust control device 1 according to the present invention.

The exhaust control device 1 includes a sub-chamber 4 for varying the exhaust pipe volume, which is connected to the exhaust port 3 of the two-cycle engine 1, and a cylindrical valve 5 which opens and closes between the sub-chamber 4 and the exhaust port 3. And a plate-like valve 6 which is interlocked with the valve 5 and moves up and down the upper edge position 3b of the cylinder side opening 3a of the exhaust port 3.

Of these, the plate-shaped valve 6 is slidable through a communication hole 7a formed in the cylinder block 7 into a hole 7b having a rectangular cross section, which is bored toward the cylinder side opening 3a of the exhaust port 3. It is arranged and its lower end face
6a forms the upper surface 3c of the exhaust port 3.
Slide the valve 6 along the hole 7b,
When projected into the exhaust port 3, as shown in the figure, the upper edge 3b of the cylinder side opening 3a is formed by the lower end surface 6a thereof.
Apparently moves down by H. On the other hand, a hole 5a for communicating the sub-chamber 4 with the exhaust port 3 is formed on the peripheral surface of the cylindrical valve 5, and the cylinder 5 is driven by a driving means composed of a servo motor or a mechanical governor mechanism (not shown). When the shaped valve 5 is rotated in a predetermined rotation range of the engine, the hole 5a and the peripheral surface of the valve 5 open and close between the sub chamber 4 and the exhaust port 3. Further, between the cylindrical valve 5 and the plate-shaped valve 6, an interlocking device 8 for sliding the plate-shaped valve 6 according to the rotation of the cylindrical valve 5 is provided. 8 is both end surfaces of the cylindrical valve 5 as shown in FIG. 2 which is an enlarged perspective view showing the concept of the main part of FIG.
5b, 5c, and an arc-shaped groove 5d formed concentrically with respect to the axial direction of the valve 5, and a roll-shaped groove which is disposed on the upper end 6b of the plate-shaped valve 6 and engages with the guide groove 5d. It is constituted by the pin 9. Such interlocking means 8
According to this, when the cylindrical valve 5 shown in FIG. 2 rotates clockwise, only the cylindrical valve 5 initially rotates, and when it exceeds a predetermined rotation angle, the pin 9 and one end 5d 'of the groove 5d are not connected. Engage with each other to move the plate-like valve 6 upward along the hole 7b shown in FIG. 1 and raise the upper edge 3b of the cylinder side opening 3a by H. At the initial position of the plate-like valve 6 shown in FIG. 2, the pin 9 of the interlocking means 8 and the groove 5d are in contact with each other to restrict the movement thereof.

Next, the operation of the above-described exhaust control device 1 will be described, and the configuration will also be described in more detail.

When the two-cycle engine 1 is started and its rotational speed range is within a predetermined low / medium rotational speed range, the cylindrical valve 5 is rotated by the drive means and stopped at the initial position shown in FIG. At the stop position of the cylindrical valve 5 shown in FIG. 1, the sub-chamber 4 and the exhaust port 3 communicate with each other,
The volume of the exhaust pipe expands, and the volume of the exhaust pipe required mainly in the low / medium speed range is secured, and the plate-shaped valve 6 is lowered by the interlocking means 8 and the upper edge 3b of the cylinder side opening 3a. Since H is decreased by H, suitable exhaust timing is secured in the low / medium speed range at the same time.

On the other hand, when the rotation speed of the engine 2 reaches a predetermined high rotation speed range, the cylindrical valve 5 is rotated clockwise from the initial position shown in FIG. 1 by the driving means to move to the rotation position shown in FIG. Via, stop at the position shown in FIG.

According to the stop position of the cylindrical valve 5 shown in FIG. 4, the space between the sub-chamber 4 and the exhaust port 3 is closed, and the volume of the exhaust pipe is reduced. Therefore, the exhaust pipe mainly required in the high rotation speed range is provided. While the volume is secured, the plate-like valve 6 is moved upward by the interlocking means 8 and the upper edge 3b of the cylinder side opening 3a is raised by H, so that a suitable exhaust timing is secured at the same time in a high rotational speed range. It will be. As shown in FIG. 3, while the cylindrical valve 5 and the plate-shaped valve 6 reach the position shown in FIG. 4, there is a time delay with respect to the movement of the plate-shaped valve 6 by the interlocking means 8, that is, Since the change of the exhaust timing is started after the exhaust pipe volume change by the cylindrical valve 5 is completed, the exhaust timing is changed without being affected by the transient exhaust gas accompanying the change of the exhaust pipe volume, and the exhaust timing is changed. Therefore, the engine output is improved based on the smoother engine output characteristic.

〔The invention's effect〕

This invention is a cylindrical valve that changes the exhaust pipe volume,
The plate-shaped valve for changing the exhaust timing is operated by delaying the rotation of the cylindrical valve through the interlocking means composed of the arc-shaped groove and the pin engaging with the groove, thereby operating the plate-shaped valve. The change in the exhaust timing can be made to follow the change in the exhaust pipe volume with a time delay, and as a result, a wider range from the low rpm range to the high rpm range with smoother output characteristics. It is possible to improve the output of the 2-cycle engine over a wide range of engine speeds.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view of a main part of a two-cycle engine showing an exhaust control device according to the present invention, FIG. 2 is an enlarged perspective view of the main part of FIG. 1, and FIGS. It is a principal part conceptual sectional view of a 2-cycle engine which shows the effect | action of the exhaust control device which concerns. 1 ... Exhaust control device, 2 ... 2-cycle engine, 3 ...
… Exhaust port, 3a …… Cylinder side opening, 3b…
… Top edge, 3c… Top surface, 4… Subchamber, 5… Cylindrical valve, 5d… Groove, 6… Plate valve, 6a…
Lower end face, 6b ... Upper end, 7a ... Hole, 8 ... Interlocking means, 9 ...
…pin.

Claims (1)

[Claims] 1. A cylindrical valve disposed between an exhaust port and a sub-chamber for varying the exhaust pipe volume, and a lower end surface forming an upper surface of the exhaust port, the exhaust port being located behind a cylinder side opening. A plate-shaped valve slidably disposed on the upper wall, an arc-shaped groove formed on the end surface of the cylindrical valve, and a pin disposed on the upper end of the plate-shaped valve and engaging with the groove. And a driving means for opening and closing the cylindrical valve at a predetermined engine speed range, the interlocking means delaying the rotation of the cylindrical valve to operate the plate valve, and the cylindrical valve by the driving means. When the exhaust port is communicated with the sub-chamber by rotating the cylinder, the interlocking means delays the rotation of the cylindrical valve before While lowering the upper edge position of the cylinder side opening by projecting the lower end surface of the plate-shaped valve into the exhaust hoat, the cylindrical valve is rotated by the driving means, and between the sub chamber and the exhaust port. When closed, the interlocking means delays the rotation of the cylindrical valve to cause the plate-shaped valve to escape from the exhaust port and raise the upper edge position of the cylinder opening. Exhaust control device for 2-cycle engine.