JPH09112280A - Exhaust control device for two cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the capacity of an exhaust passage, facilitate work of a constitution parts, and also operate each valve efficiency and smoothly. SOLUTION: In a this device 28, an auxiliary exhaust passage 32 through which a cylinder 10 communicates with a main exhaust passage is formed integratedly with a cylinder main body 8, a power chamber 34 which communicates with the auxiliary exhaust passage 32 is arranged on the cylinder main body 8, the communicating condition of the auxiliary exhaust passage 32 and the power chamber 34 is opened/closed, and thereby controlling the capacity of the exhaust passage. A nearly cylindrical piston valve 36 which is projected/retreated in the auxiliary exhaust passage 32 is slidably arranged on the cylinder main body 8, the piston valve 36 is projected/retreated following with projected/retreated operation of the main exhaust valve 30, and thereby, the communication condition of the auxiliary exhaust passage 32 and the pwoer chamber 34 is opened/closed simultaneously with change of an exhaust timing.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As conventional exhaust control devices for two-cycle engines, there are those disclosed in Japanese Utility Model Publication No. 63-151936 and Japanese Utility Model Publication No. 3-42028. The apparatus disclosed in Japanese Utility Model Laid-Open No. 63-151936 discloses a timing valve that appears in and out of the exhaust passage to change the upper edge position of the exhaust port, and is rotatably arranged in the cylinder body to provide a power chamber and an exhaust passage. With a power valve that opens and closes the communication state with, the timing valve controls the exhaust timing, and the power valve allows the volume of the exhaust passage according to the engine speed to be obtained.
The desired exhaust pulsation effect is obtained.

[0003]

However, in the apparatus disclosed in Japanese Utility Model Laid-Open No. 63-151936, the power valve is used only for opening and closing the exhaust passage and the power chamber, and this power is not used. No measures have been taken to increase the volume of the exhaust passage by the valve. In addition, the shape of the power valve is complicated, and it takes time to process the power valve and the cylinder body.

Further, especially in Japanese Utility Model Laid-Open No. 63-511936, since the central axis of the timing valve and the central axis of the power valve are not in the same direction due to the mechanism, each of them may cause a slight machining error in the cylinder body. The valve may not operate smoothly. At the same time, since the timing valve is interlocked by the rotational force of the power valve, there is a time lag between the operation of the timing valve and the operation of the power valve. Therefore, it is desired to operate both valves more efficiently. .

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to secure a large volume of the exhaust passage,
Moreover, it is an object of the present invention to provide an exhaust control device for a two-cycle engine in which the constituent parts can be easily processed and each valve operates efficiently and smoothly.

[0006]

The present invention has the following configuration to achieve the above object. That is, the invention of claim 1 controls the exhaust timing by retracting the main exhaust valve into and out of the main exhaust passage, and at the same time, integrally forming an auxiliary exhaust passage communicating with the cylinder and the main exhaust passage in the cylinder body, A two-cycle engine in which a power chamber that can communicate with the auxiliary exhaust passage is provided in the cylinder body, and the volume of the exhaust passage is controlled by opening and closing the communication state between the auxiliary exhaust passage and the power chamber according to the engine speed. In the exhaust control device, a substantially cylindrical piston valve capable of retracting into and out of the auxiliary exhaust passage is slidably disposed in the cylinder body, and the piston is adjusted according to the retracting operation of the main exhaust valve. By opening and closing the valve, the communication state between the auxiliary exhaust passage and the power chamber is opened and closed at the same time when the exhaust timing is changed. Cycle is an exhaust control device for an engine.

According to a second aspect of the present invention, there is provided the exhaust control device for a two-cycle engine according to the first aspect, wherein an inner cavity portion of the substantially cylindrical piston valve is formed as a part of the power chamber. .

According to the invention of claim 1, since the piston valve opens and closes the communication state between the auxiliary exhaust passage and the power chamber, the auxiliary exhaust passage is opened when the piston valve opens the communication state. Since the flowing exhaust gas is sent to the power chamber, the volume of the exhaust passage is increased by the amount of the auxiliary exhaust passage. Further, since the piston valve has a substantially cylindrical shape, the piston valve and the cylinder body can be easily processed. Moreover, since the piston valve is retracted and retracted in accordance with the retracting operation of the main exhaust valve, each valve operates efficiently. Furthermore, since the main exhaust valve and the piston valve are both slide type, the direction of the central axis of each valve can be set to be almost the same,
The cylinder body can be machined easily and the machining cost can be reduced. At the same time, each valve operates smoothly even if there is some machining error.

According to the second aspect, since the inner cavity of the piston valve is formed as a part of the power chamber, the volume of the exhaust passage can be further increased.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a two-cycle engine according to this embodiment. FIG. 2 is an enlarged view of part A in the engine low speed range in FIG. FIG. 3 is a view on arrow B in FIG. 4A and 4B are views showing the piston valve according to the present embodiment, where FIG. 4A is a view taken in the direction of arrow B in FIG. 2, and FIG. 4B is a view taken in the direction of arrow C in FIG. FIG.
It is a sectional view showing the structure of the piston valve circumference concerning this embodiment, and is a figure showing the state in an engine low-speed range. FIG. 6 is an enlarged view of part A in the engine high speed range in FIG. FIG. 7 is a cross-sectional view showing the structure around the piston valve according to the present embodiment, and is a view showing a state in the engine high speed range.

In this embodiment, the present invention is applied to an exhaust control system for a two-cycle engine of a motorcycle.
As shown in FIG. 1, a two-cycle engine (hereinafter, referred to as an engine) 2 according to the present embodiment is fixed to a crankcase 6 that rotatably supports a crankshaft 4 and a front upper surface of the crankcase 6. And a cylinder body 8.

The cylinder body 8 is formed with a cylinder 10 having a central axis extending in the vertical direction.
On the inner wall of the piston, the piston 14 slides up and down by the connecting rod 12. An intake passage 18 connected to the carburetor 16 via an intake pipe 16a is provided on one side of the cylinder body 8, and a main exhaust passage 20 is formed obliquely downward on the other side of the cylinder body 8. To be done. The intake passage 18 is provided with a reed valve 22 that opens and closes the passage. In addition, on the upper end surface of the cylinder 10,
A cylinder head 26 having a spark plug 24 in the center is fastened.

The exhaust control device 28 of this embodiment controls the exhaust timing by retracting the main exhaust valve 30 into and out of the main exhaust passage 20, and at the same time, the cylinder 10 and the main exhaust passage 2
The auxiliary exhaust passage 32 communicating with 0 is integrally formed in the cylinder body 8, and the power chamber 34 capable of communicating with the auxiliary exhaust passage 32 is provided in the cylinder body 8 so that the auxiliary exhaust passage 32 and the power chamber can be connected in accordance with the engine speed. The volume of the exhaust passage is also controlled by opening and closing the communication state with 34. That is, the substantially cylindrical piston valve 36 capable of projecting and retracting in the auxiliary exhaust passage 32 is attached to the cylinder body 8
The piston valve 36 is slidably arranged at the same time as the main exhaust valve 30 is moved in and out to open / close the communication state between the auxiliary exhaust passage 32 and the power chamber 34 at the same time when the exhaust timing is changed.

The structure of the exhaust control device 28 will be described in detail. First, the configuration related to the main exhaust valve 30 will be described. As shown in FIG. 2, a hole 40 that opens to the main exhaust passage 20 near the exhaust port 38 of the cylinder 10 is integrally formed in the cylinder body 8, and the main exhaust valve 30 is slidably arranged in the hole 40. To do. As shown in FIG. 3, the main exhaust valve 30 is a plate-shaped cross section having a substantially oval shape, and has a drive shaft portion 30a at the rear portion. As shown in FIGS. 2 and 3, a plate 42 is fastened to the inner wall of the power chamber 34 with a screw 42a. The plate 42 is attached to the drive shaft portion 30a of the main exhaust valve 30 when the main exhaust valve 30 is projected. A substantially cylindrical spacer 44 that abuts the plate 42
Is fitted. Further, the spacer 44 and the drive shaft portion 3
A drive pin 46 penetrates in the left-right direction at 0a, and both ends of the drive pin 46 are driven by a pair of left and right arms 48a. A boss portion 48b is integrally formed at the base of the arm 48a.
Is fastened with a screw 52 to a drive shaft 50 rotated by an actuator (not shown).

Next, the structure of the piston valve 36 will be described. The auxiliary exhaust passage 32 is provided on both the left and right sides of the main exhaust passage 20, and as shown in FIG.
The sub-exhaust port 32a is opened at and the outlet 32b is opened at the main exhaust passage 20. In the state shown in FIG. 2, the piston valve 36 is slidably assembled in the cylinder body 8 with its lower end protruding into the auxiliary exhaust passage 32, and its upper part faces the power chamber 34.

As shown in FIGS. 4 (a) and 4 (b), the piston valve 36 has a bottomed cylindrical shape that opens upward, and has an inlet port 36a and an outlet port 36b arranged vertically. As shown in FIG. 2, the lower inlet port 36a faces the outlet 32b side in a state where the piston valve 36 projects into the auxiliary exhaust passage 32, and exhausts the exhaust gas that has entered the auxiliary exhaust passage 32 from the outlet 32b side. It is installed in the inner cavity portion 36c of the piston valve 36. Further, in this state, the upper outlet 36b coincides with the power chamber hole 34a (see FIG. 5) communicating with the power chamber 34,
The exhaust gas taken into the piston valve 36 is led to the power chamber hole 34a. Further, a drive pin 36d penetrates in the left and right direction above the piston valve 36,
The drive pin 36d is driven in the vertical direction by arms 48c integrally formed at both left and right ends of the boss portion 48b. The arm 48c is inserted from a notch 36e (see FIG. 4B) provided at the upper end of the piston valve 36. The power chamber 34 is formed by attaching a cover 8a, which is separate from the cylinder body 8, to a flange portion 8b of the cylinder body 8, as shown in FIG.

According to the present embodiment thus constructed, when the engine speed is in the low speed range, the drive pins 46 and 36d are driven via the arms 48a and 48c by the actuator (not shown), and the main exhaust gas is discharged. The valve 30 and the piston valve 36 simultaneously project into the main exhaust passage 20 and the auxiliary exhaust passage 32, respectively (see FIG. 2).
At this time, the front edge of the main exhaust valve 30 reaches the exhaust port 38 and is positioned flush with the inner wall of the cylinder 10. This slightly lowers the upper edge position of the exhaust port 38 and delays the exhaust timing. On the other hand, the piston valve 36 shuts off the middle of the auxiliary exhaust passage 32 at the lower end thereof, and closes the auxiliary exhaust port 32.
In addition to blocking the inflow of exhaust gas from a, the main exhaust passage 20
The exhaust gas that has flowed in through the outlet 32b via the inlet is introduced into the inner hollow portion 36c through the inlet 36a. Inner cavity 36c
As shown in FIG. 5, the exhaust gas introduced into the power chamber hole 3 passes through the inner cavity 36c and the outlet 36b.
4a, the volume of the exhaust passage becomes large and the exhaust path length becomes long in the low engine speed range.

When the engine speed increases from this state, the arms 46 and 48c rotate in the opposite direction, and the main exhaust valve 30 and the piston valve 36 simultaneously enter the cylinder body 8 from the main exhaust passage 20 and the auxiliary exhaust passage 32, respectively. Immerse yourself (see Figure 6). In this state, as the main exhaust valve 30 moves backward, the upper edge position of the exhaust port 38 rises to its original position, and the exhaust timing corresponds to the high engine speed range. On the other hand, for the auxiliary exhaust passage 32,
When the piston valve 36 is retracted, the auxiliary exhaust port 32a and the outlet 32b are completely communicated with each other, and at the same time, the power chamber hole 34a is closed by the peripheral wall of the piston valve 36 as shown in FIG. As a result, the volume of the exhaust passage and the length of the exhaust path are reduced, and the engine can be used in the high speed region of the engine.

According to this embodiment that operates in this way,
Since the piston valve 36 opens and closes the communication state between the auxiliary exhaust passage 32 and the power chamber 34, when the piston valve 36 opens the communication state, exhaust gas passes through the auxiliary exhaust passage 32 to the power chamber 34. Because of the flow, the volume of the exhaust passage is increased by the amount of the auxiliary exhaust passage 32 as compared with the conventional one in which the main exhaust passage and the power chamber are simply connected. Further, since the inner cavity portion 36c of the piston valve 36 is configured as a part of the power chamber 34, the volume of the exhaust passage can be further increased.

Further, since the piston valve 36 has a substantially cylindrical shape, the piston valve 36 and the cylinder body 8 can be easily processed. Further, since the piston valve 36 is retracted at the same time as the main exhaust valve 30 is retracted and retracted, each valve operates efficiently (there is no time difference in operation). Further, since the main exhaust valve 30 and the piston valve 36 are both slide type, the directions of the central axes of the respective valves can be set to the same or substantially the same direction, which facilitates the machining of the cylinder body 8 and reduces the machining cost. At the same time, each valve operates smoothly even if there is some processing error. Further, the power chamber hole 34a
The position of can be freely changed with the setting of the position of the outlet port 36b of the piston valve 36.

The present embodiment is a preferred embodiment of the present invention, and the technical scope of the present invention is not limited to this embodiment.

[0022]

As described above, according to the present invention, 2
In the exhaust control device of the cycle engine, it is possible to secure a large volume of the exhaust passage. Further, the constituent parts can be easily processed, and the valves can be operated efficiently and smoothly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a two-cycle engine according to this embodiment.

FIG. 2 is an enlarged view of part A in the engine low speed range in FIG.

FIG. 3 is a view taken in the direction of arrow B in FIG. 2;

4A and 4B are views showing a piston valve according to the present embodiment, in which FIG. 4A is a view taken in the direction of arrow B in FIG. 2, and FIG. 4B is a view taken in the direction of arrow C in FIG.

FIG. 5 is a cross-sectional view showing a structure around a piston valve according to the present embodiment, and is a view showing a state in a low engine speed range.

FIG. 6 is an enlarged view of part A in the engine high speed range in FIG. 1.

FIG. 7 is a cross-sectional view showing a structure around a piston valve according to the present embodiment, and is a view showing a state in an engine high speed range.

[Explanation of symbols]

 2 2 cycle engine 8 Cylinder body 10 Cylinder 20 Main exhaust passage 28 Exhaust control device 30 Main exhaust valve 32 Auxiliary exhaust passage 34 Power chamber 36 Piston valve 36c Inner cavity

Claims (2)

[Claims] 1. A main exhaust valve is projected from and retracted into the main exhaust passage to control the exhaust timing, and at the same time, an auxiliary exhaust passage that connects the cylinder and the main exhaust passage is formed integrally with the cylinder body. An exhaust control device for a two-cycle engine in which a power chamber capable of communicating with the power chamber is provided in the cylinder body, and the volume of the exhaust passage is controlled by opening and closing the communication state between the auxiliary exhaust passage and the power chamber according to the engine speed. A substantially cylindrical piston valve that can be retracted into and out of the auxiliary exhaust passage is slidably arranged in the cylinder body, and the piston valve is retracted according to the retracting operation of the main exhaust valve. Thus, the communication state between the auxiliary exhaust passage and the power chamber is opened / closed at the same time when the exhaust timing is changed. Exhaust control device. 2. The exhaust control device for a two-cycle engine according to claim 1, wherein an inner hollow portion of the substantially cylindrical piston valve is formed as a part of the power chamber.