JPH01159413A - Exhaust timing variable device for two-cycle engine - Google Patents

Abstract

PURPOSE:To secure a variation in a smooth compression ratio at the whole rotational range by setting up two disc valve bodies on an upper wall of an exhaust passage after superposing them on each other free of rising and setting, driving these valve bodies according to an engine speed state, and advancing or retreating them to or from the exhaust passage. CONSTITUTION:Two disc valve bodies 11, 12 are superposed on each other, and each of them is inserted into a hole 2b formed in an upper wall 2a of an exhaust passage 1 free of sliding motion. At this time, each of stepped parts 11a, 12a is formed in each upper end of these valve bodies 11, 12, each of these stepped parts 11a, 12a is made contact with a housing 2 and each of tips 11b, 12b of these valve bodies 11, 12 is positioned to each of upper parts A1, A2 of an exhaust port 5. In addition, an actuator 13 is clamped to the housing 2, and each of pins 11c, 12c installed in each upper end of these valve bodies 11, 12 is fitted in a notch groove 14a of a lever 14 attached to the shaft 13a. Then, each of these valve bodies 11, 12 is driven by the actuator 13 via the lever 14, and each of these upper parts A1, A2 of the exhaust port 5 is opened or closed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable exhaust timing device for a two-stroke engine.

[Prior art]

2 cycles] - The engine has an upper wall 2 of a housing 2 forming an exhaust passage 1, as shown in FIGS. 3 and 4.
A is provided with a valve body 3 so as to be freely retractable, and the valve body 3 is made to protrude in the low speed range of the engine, and the tip 3a of the valve body 3 faces the upper part A of the exhaust port 5 of the cylinder 4, and the exhaust gas is The upper part of the port 15 is closed to bring the exhaust timing closer to increase the compression ratio, thereby improving the output in the low speed range, and in the high speed range of the engine, the tip 3a of the valve body 3 is connected to the exhaust gas of the cylinder 4. Some engines are equipped with a variable exhaust timing device that retracts from the port 5 and lowers the compression ratio by adjusting the exhaust timing to improve output in a high speed range.

By the way, with this kind of exhaust timing variable device lead,
The valve body 3 is retracted from the exhaust port 5 between the engine's low speed range and high speed range, but since the compression ratio changes rapidly before and after that, a valley is created in the output characteristics. Put it away.

(Object of the invention) The object of the invention is to obtain optimal output characteristics in each rotation speed range! An object of the present invention is to provide a variable exhaust timing device for a two-stroke engine that can smoothly change the compression ratio of ζ.

(Structure of the Invention) In the variable exhaust timing device for a two-stroke engine according to the present invention, a plurality of plate-shaped valve bodies are stacked one on top of the other and arranged so as to be freely retractable from the upper wall of the exhaust passage. implanting pins, and inserting the pins into the notched grooves of one lever so that the pins of the lower valve body are located farther from the center of rotation of the lever than the pins of the upper valve body, and The lever is linked to an actuator that is driven in accordance with the engine speed.

(Embodiment) FIGS. 1(a) to 1(C) show an embodiment of a variable exhaust timing device for a two-stroke engine according to the present invention.

This device uses two plate-shaped valve bodies 11 and 12, which are stacked one on top of the other and fitted into a hole 2b formed in the upper wall 2a of the exhaust passage 1. The valve bodies 11, 12 are each movably disposed relative to 7t2b. Steps 11a, 12a are formed at the upper ends of these valve bodies 11.12, and when these steps 11a, 12a abut against the housing 2, the tip 11b of the valve body 11.12.

12b at the upper part of the exhaust port 5, and the upper part Δ1. A2 is blocked respectively. In addition, the valve bodies 11 and 12
Pins 11c and 12c are implanted at the upper end of the holder.

On the other hand, this device uses an actuator 1 such as a servo motor.
It has 3. This actuator 13 is controlled based on a pulse signal output from a pickup coil provided in an AC generator, and the valve body 11,
12 and is fixed to the housing 2. This actuator 13 is equipped with a lever 14 at the tip of its shaft 13a. A notch groove 14a is formed in this lever 14 from the distal end to the proximal end. The pins 11c and 12c of the valve bodies 11 and 12 are fitted into the notch groove 14a in this order from the base end to the distal end.

The operation of the above device will be explained below, and the configuration will also be explained in more detail.

During the low speed range of the engine, the valve body 11.12 is in the state shown in FIG. 1(a). That is, the valve bodies 11 and 12 protrude from the upper part A1 of the exhaust port 5. A2 is respectively occluded. Therefore, during this period, the compression ratio is high and stable combustion can be achieved in the low rotational speed range.

When the rotation of the crankshaft becomes faster and the CPU, etc. confirms that it has reached the medium speed range based on the pulse signal from the pickup coil, the CPU, etc. outputs the actuator drive (number 0). Actuator 1
3 is rotated by a certain angle. This actuator 13 rotates the lever 14 to the position shown in FIG. 1(b).

Therefore, the valve body 12 is pulled up greatly, opening the upper part A2 of the exhaust port 5. At the same time, the valve body 11 is also pulled up, but the amount of movement of the valve body 11 is small, and the upper part A1 of the exhaust port 5
It has not yet reached the point where it can be released. As a result, the compression ratio is maintained at a moderate level in the medium speed range.

Furthermore, the rotation of the crankshaft becomes faster, and as above, CP
When it is confirmed that the high speed range has been reached in the CPU, etc., the actuator 1-13 is actuated by the output signal from the CPU, etc., and the lever 14 is rotated to the position shown in FIG. 1(C). Ru. Therefore, the valve body 11 is located on the upper wall 2a of the exhaust passage 1.
The upper part A1 of the exhaust port 5 is opened. At the same time, the valve body 12 is also pulled up, and the upper wall 2 of the exhaust passage 1
completely immersed in a. As a result, the compression ratio is maintained low in the high speed range, ensuring stable combustion.

In addition, when the rotation of the engine becomes slow, each valve body 11.12
The operation returns to the state shown in FIG. 1(a) by following the reverse operation to the above operation.

FIG. 2 shows a modification of the above embodiment.

In this device, the actuator 13 is connected to the valve bodies 11' and 12.
It is located below the moving area of '.

Even when the actuator 13 is arranged in this manner, the pin 11C' of the upper valve body 11' must be located closer to the center of rotation of the lever 14 than the pin 12C' of the lower valve body 12'. Therefore, in the device shown in FIG. 2, a hole 15 is formed in the valve body 11', the valve body 12' is inserted into the hole 15, and the pin 11C' of the valve body 11' is connected to the pin 120' of the valve body 12'. It is located below. If you cover it like this,
Sufficient stroke suspension of the lower valve body 12' is ensured.

Note that the operation of the device of this modification is completely the same as that of the device of the above embodiment, so a description thereof will be omitted.

Further, in the above embodiment, the actuator 13 is operated in three stages of the engine's low speed range, middle speed range, and high speed range, but it is operated in six stages including the middle of each speed range. It can also be activated.

[Effect of light]

As described above, according to the variable exhaust timing device for a two-stroke engine according to the present invention, the compression ratio changes smoothly from low speed rotation to high speed rotation of the engine, and the R-shaped output corresponds to the rotation speed. Moreover, since one actuator can actuate a plurality of valve bodies, the device becomes extremely I11 pure.

[Brief explanation of the drawing]

FIGS. 1(a) to (C) are conceptual cross-sectional views showing the operation mode of a variable exhaust timing device for a two-stroke J engine according to the present invention, and FIG. FIG. 3 is a conceptual sectional view showing a modified example of the variable timing device, FIG. 3 is a conceptual sectional view showing a conventional variable exhaust timing device, and FIG. 4 is a front view showing a state in which the exhaust port is closed. be. DESCRIPTION OF SYMBOLS 1... Exhaust passage, 2... Housing, 2a... Upper wall, 4... Cylinder, 5... Exhaust port, 11.12.
... Valve body, 11a, 12a... Step portion, 11b, 12b
・'Tip, 11C, 12G...pin, 13...actuator, 14...lever, 14a...notch full,
A1. A2...excluding, upper part of appearance. Fig. 1 (b) (C No. 1 Fig. 2

Claims (1)

[Claims] A plurality of plate-shaped valve bodies are stacked one on top of the other and arranged so that they can appear and retract freely on the upper wall of the exhaust passage, pins are installed in each of the valve bodies, and the pins are inserted into the notch groove of one lever in the lower direction. The pin of the valve body is inserted so that it is located further from the center of rotation of the lever than the pin of the upper valve body, and the lever is linked to an actuator that is driven in accordance with the rotation speed of the engine. A variable exhaust timing device for a 2-cycle engine featuring: