JPH0791259A - Exhaust timing control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To smoothly discharge exhaust gas during low speed and low load operation so as to stabilize the output power of an engine with the use of a rotary control valve which is located in the upper part of an exhaust port and which is opened and closed in dependence upon an operating condition of an engine, by specifying the surface shape of the barrel part of the valve, the effective exhaust port shape and the timing thereof. CONSTITUTION:An exhaust port and a scavenge port 18 which are adapted to be opened and closed by a piston are formed in the inner peripheral wall of a cylinder 8. A rotary control valve 24 adapted to be rotated in its closing direction upon low speed and low load operation but in its opening direction upon high speed and high load operation is located in the upper part of the exhaust port. In this arrangement, the outer surface of the barrel part of the rotary control valve 24 is aligned with the inner peripheral surface of the cylinder 8 in its center part 24c, but it is separated therefrom at its both side parts 24d. Further, the effective exhaust shape of the rotary control valve 24 is set to be such that the exhaust timing is earlier in the side parts 24d than in the center part 24c, when the control valve 24 is closed. Further, the it is set to be such that the difference in timing between the center part 24c and the side parts 24d is small, when the control valve 24 is closed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust timing control device for a two-cycle engine which can change the exhaust timing according to the engine speed.

[0002]

2. Description of the Related Art In a two-cycle engine, an exhaust port and a scavenging port which are opened and closed by a piston are formed on an inner peripheral wall of a cylinder, and an upper portion of the exhaust port is rotated in a closing direction at a low speed and / or a low load. At the same time, there is a device which is provided with a rotation control valve for rotating in the opening direction at high speed and / or high load so as to obtain high output over the entire rotation range.

An example thereof is Japanese Examined Patent Publication Sho 63-3048.
As disclosed in Japanese Patent Publication No. 5, a rotation control valve is provided with a plate-shaped valve, and the tip end edge of this plate-shaped valve has a radius of curvature substantially the same as the inner surface of the cylinder, and the valve bottom surface is exhausted when the valve is opened. The upper surface of the passage is located substantially at the same position as the upper edge of the passage so that there is no flow resistance in the exhaust passage when the valve is opened during high-speed operation, so that the exhaust gas is discharged smoothly.

[0004]

By the way, the exhaust gas is smoothly discharged by eliminating the one that causes the flow resistance in the exhaust passage when the valve is opened at the time of high speed operation, but at the low speed when the valve is closed. However, there is a problem in that the effective exhaust port has a center-height shape, and exhaust cannot be smoothly discharged at low speed and / or at low load.

The present invention has been made in view of the above problems, and provides an exhaust timing control device for a two-cycle engine, which can smoothly discharge exhaust gas at a low speed and / or at a low load and can obtain a stable output. It is intended to be provided.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 forms an exhaust port and a scavenging port which are opened and closed by a piston in an inner peripheral wall of a cylinder, and an upper part of the exhaust port is provided. An exhaust timing control device for a two-cycle engine, comprising a rotation control valve for rotating in a closing direction at a low speed or / and a low load, and rotating in a opening direction at a high speed or / and a high load. The central surface of the body of the rotation control valve is made to be approximately the same as the inner peripheral surface of the cylinder, and is separated from the inner peripheral surface of the cylinder on both sides, and effective exhaust when the rotation control valve is closed Mouth shape, exhaust timing is early on both sides,
It is characterized in that the central portion is set to be slower, and when the rotation control valve is opened, the difference in timing between the central portion and both side portions is reduced.

Further, according to a second aspect of the invention, an exhaust port and a scavenging port which are opened and closed by a piston are formed on the inner peripheral wall of the cylinder, and the upper portion of the exhaust port is closed in a closing direction at a low speed and / or a low load. In an exhaust timing control device for a two-cycle engine, which is provided with a rotation control valve that is rotated and is rotated in the opening direction at high speed and / or high load, the body surface of the rotation control valve or the rotation control valve The leading edge of the plate valve provided has a radius of curvature substantially the same as the inner peripheral surface of the cylinder, and the effective exhaust port shape when the rotation control valve is closed is such that the exhaust timing is fast on both sides and the central part Is set so that when the rotation control valve is opened, the difference in timing between the central portion and both side portions is reduced.

[0008]

According to the first aspect of the invention, the surface of the body of the rotation control valve is made to be substantially the same as the inner peripheral surface of the cylinder in the central portion, and is separated from the inner peripheral surface of the cylinder at both sides, and The effective exhaust port shape when the rotation control valve is closed,
Set the exhaust timing to be early in both sides and to be late in the center so that the difference in timing between the center and both sides is small when the rotation control valve is opened, and at low speed and / or low load. Because the exhaust timing of both sides of the exhaust port is early in the scavenging of the exhaust gas, exhaust gas is discharged from both sides of the exhaust port, and the amount of exhaust gas remaining in the combustion chamber decreases, so the scavenging efficiency is low and / or low. A stable output can be obtained without deterioration even under load.

According to the second aspect of the present invention, the body surface of the rotation control valve or the leading edge of the plate-shaped valve provided on the rotation control valve has a radius of curvature substantially the same as that of the inner peripheral surface of the cylinder.
In addition, the effective exhaust port shape when the rotation control valve is closed is set so that the exhaust timing is early in both sides and late in the center, while when the rotation control valve is opened, the timing of the center and both sides is Try to reduce the difference at low speed or
Also, because the exhaust timing of both sides of the exhaust port is early during scavenging at low load, exhaust gas is discharged from both sides of the exhaust port, and the amount of exhaust gas remaining in the combustion chamber decreases, so the scavenging efficiency is low Alternatively, and / or a stable output can be obtained without deterioration even under a low load.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust timing control device for a two-cycle engine according to the present invention will be described below with reference to the drawings.

1 to 9 show a first embodiment of an exhaust timing control device for a two-cycle engine, FIG. 1 is a longitudinal sectional view of the two-cycle engine, and FIG. 2 is a sectional view taken along line II-II of FIG. 3 is a sectional view showing a mechanism for operating the rotation control valve, FIG. 4 is a side view showing a mechanism for operating the rotation control valve, FIG. 5 is a sectional view taken along line VV of FIG. 2, and FIG. VI-VI of 2
2 is a sectional view taken along line VII-VII of FIG. 2, FIG. 8 is a view showing an effective exhaust port shape when the rotation control valve is closed, and FIG. 9 is a line IX-IX of FIG. FIG.

Cylinder block 1 of a two-cycle engine
Is mounted on a crankcase 2, a crank chamber 3 is formed by the cylinder block 1 and the crankcase 2, and a crankshaft 4 is supported by the crankcase 2 via a bearing 5. A connecting rod 7 is provided on the crankshaft 4 via a crankpin 6, and the connecting rod 7 is connected to a piston 9 reciprocally provided in a cylinder 8 of a cylinder block 1 via a piston pin 10.

The cylinder block 1 has a cylinder head 1
1 is provided, and an ignition plug 12 is provided on the cylinder head 11 so as to face the combustion chamber 13. The combustion chamber 13 includes a cylinder 8 formed in the cylinder block 1,
A piston 9 reciprocally provided in the cylinder 8.
And the cylinder head 11.

The cylinder block 1 has an intake passage 15 communicating with the intake port 14 and an exhaust passage 1 communicating with the exhaust port 16.
7. A scavenging passage 19 communicating with the scavenging port 18 and an opposing scavenging passage 21 communicating with the opposing scavenging port 20 are formed.
4, the exhaust port 16, the scavenging port 18, and the counter scavenging port 20 are open to the inner peripheral wall of the cylinder. Further, an auxiliary exhaust passage 22 is formed on both sides of the exhaust passage 17 in the cylinder block 1, and the auxiliary exhaust port 2 of the auxiliary exhaust passage 22 is formed.
3 is open in the inner peripheral wall of the cylinder. The intake port 14, the exhaust port 16, the scavenging port 18, the counter scavenging port 20, and the auxiliary exhaust port 23 are opened and closed by the vertical movement of the piston 9.

The two-cycle engine is provided with an exhaust timing control device, and a rotation control valve 24 of this exhaust timing control device is rotatably supported above the exhaust passage 17 close to the exhaust port 16. The rotation control valve 24 is configured to open and close via a governor mechanism 25 in conjunction with the engine speed. The rotating shaft 26 of the governor mechanism 25 is rotatably supported by the cover 27 and the crankcase 2,
The governor gear 28 integrally rotatably provided on the rotary shaft 26 meshes with a drive gear 29 integrally rotatably provided on the crankshaft 4, and the rotational force of the crankshaft 4 is transmitted via the drive gear 29 and the governor gear 28. It is transmitted to the rotating shaft 26 and rotates in conjunction with it.

A fixed cam 30 and a movable cam 31 are provided at the end of the rotary shaft 26, and a flyweight 32 is arranged between the fixed cam 30 and the movable cam 31. Movable cam 31
Is provided on the rotary shaft 26 so as to be movable in the axial direction, and a compression spring 33 is arranged between the movable cam 31 and the governor gear 28. The movable cam 31 is moved by the compression spring 33.
Is always biased toward the fixed cam 30. Rotating shaft 26
The flyweight 32 moves outward due to the centrifugal force in accordance with the rotation speed of the movable cam 31.
The upper part is moved against the compression spring 33.

A lever 35 is provided on the movable cam 31 via a pin 34, and the lever 35 is connected to an operating shaft 36, whereby the lever 35 is moved in response to the movement of the movable cam 31.
The operating shaft 36 rotates via the. A link 37 is fixed to the operating shaft 36, an arm 39 is connected to the link 37 via a pin 38, and the arm 39 is connected to a link 40 fixed to the rotation control valve 24 via a pin 41. As a result, the rotational force of the operating shaft 36 is transmitted to the rotation control valve 24 via the link 37, the arm 39, and the link 40, and the rotation control valve 24 rotates in conjunction with the rotation of the operating shaft 36.

A small diameter shaft portion 24a is formed in the rotation control valve 24, and a recess 24b is formed in the small diameter shaft portion 24a. Due to the small diameter shaft portion 24a having the concave portion 24b, the body surface of the rotation control valve 24 is made to be substantially the same as the cylinder inner peripheral surface 8a at the central portion 24c as shown in FIGS. At 24d, the cylinder inner peripheral surface 8
As shown in FIG. 8, the effective exhaust port shape 42 when the rotation control valve 24 is closed is separated from the a
2a is set so that the exhaust timing is early and the central portion 42b is delayed, and when the rotation control valve 24 is opened, the central portion 4
The difference in timing between 2b and both side portions 42a is configured to be small.

As described above, the rotation control valve 24 is opened / closed via the governor mechanism 25 in conjunction with the engine speed, and the rotation control valve 24 is closed at low speed and / or at low load, and effective exhaust gas at this time is obtained. The mouth shape 42 is as shown in FIG. Therefore, at low speed and / or at low load, the exhaust efficiency is reduced, but both sides of the exhaust port 16 are blown down first, so that the combustion gas is likely to remain in the exhaust port 1.
Gas exchange by scavenging and exhaustion is ensured in the portions of the combustion chambers 13 on both sides of 6, and incomplete combustion at low speeds can be reduced, and stable output can be derived.

As described above, since the exhaust timing of both sides of the exhaust port 16 is early in the scavenging at low speed and / or low load, the exhaust gas is exhausted from both sides of the exhaust port 16 and remains in the combustion chamber. Since the amount of exhaust gas decreases, stable output can be obtained without deteriorating the scavenging efficiency at low speed and / or at low load, and similarly stable output at medium speed and / or medium load. Can be obtained.

In particular, the facing scavenging port 2 facing the exhaust port 16
When 0 is provided, and when the second scavenging port 18 is provided on both sides of the line L connecting the exhaust port 16 and the opposed scavenging port 20, both sides of the exhaust port 16 blow first at low speed and / or low load. When it is downed, the opposing scavenging port 20 and the second
Of the combustion chamber 13 on both sides of the exhaust port 16
It is possible to ensure gas exchange by scavenging and exhaustion in the part of, and to derive stable output at a lower speed.

Further, the effective exhaust port shape 42 when the rotation control valve 24 is closed is set so that the exhaust timing is early in both side portions 42a and delayed in the central portion 42b, while the rotation control valve 24 is opened, The difference in the exhaust timing between the central portion 42b and the both side portions 42a is made small so that the exhaust timing has a wide range, whereby the set width of the exhaust pulsation can be increased. Therefore, it is possible to set the exhaust timing according to the exhaust pulsation in the middle speed range, improve the combustion efficiency in the middle speed range, and eliminate the valley of the output in the middle speed range.

Further, the rotation control valve 2 is controlled by the governor mechanism 25.
4 is opened and closed, the accelerator grip and the opening of the throttle valve are increased during acceleration, but the rotation control valve 24 is closed at a low speed due to a decrease in engine speed, and the rotation control valve 24 is controlled by the governor mechanism 25. Therefore, the advance of the exhaust timing is delayed, but even if the advance of the exhaust timing during acceleration is delayed, a stable output can be obtained without deteriorating the scavenging efficiency even at a low speed. Compared to the ones, the valley of the output is less likely to occur, there is no rattling during acceleration, and the acceleration is improved.

As shown in FIG. 9, the auxiliary passage 22 has its passage cross-sectional area variable along the way by a rotation control valve 24. At high speeds and / or high loads, the recess 24e maximizes the passage cross-sectional area. Therefore, the exhaust blowdown is performed not only from the exhaust port 16 but also from the auxiliary exhaust port 23, so that the efficiency of gas exchange is improved and the engine exhibits sufficient performance.

Further, the concave portion 24e at the time of low speed and / or low load minimizes the cross-sectional area of the passage as shown by the chain double-dashed line in FIG. As a result, the blowdown of the exhaust gas above the second scavenging port 18 on both sides of the line L and above the second scavenging port 18 where gas exchange is difficult can be performed within a range where blow-through does not occur, resulting in deterioration of fuel efficiency. Low speed stability can be improved without causing

10 and 11 show a second embodiment of the exhaust timing control system for a two-cycle engine, FIG. 10 is a cross-sectional view of the two-cycle engine, and FIG. 11 is XI- of FIG.
It is sectional drawing which follows the XI line.

A two-cycle engine to which the exhaust timing control device for a two-cycle engine of this embodiment is applied is
Since it has the same configuration as the two-cycle engine of the first embodiment, the same reference numerals are given and description thereof is omitted.

In the exhaust timing control system for the two-cycle engine, the rotation control valve 50 is rotated in conjunction with the accelerator grip 51 or the throttle valve 52. The rotation control valve 50 is provided with a plate-shaped valve 53. When the tip end 53a of the plate-shaped valve 53 has a radius of curvature substantially the same as the cylinder inner peripheral surface 8a, and the rotation control valve 50 is closed. When the rotation control valve 50 is opened, the difference in timing between the central portion 42b and the both side portions 42a is set to be equal to the effective exhaust port shape 42 of FIG. It is configured to be small.

In this way, the rotation control valve 50 opens and closes in conjunction with the accelerator grip 51 or the throttle valve 52,
The rotation control valve 50 is closed at low speed and / or at low load, and the effective exhaust port shape 42 formed by the plate valve 53 at this time is as shown in FIG. For this reason,
At low speeds and / or low loads, exhaust efficiency decreases, but both sides of the exhaust port 16 are blown down first, so that combustion gas 1 on both sides of the exhaust port 16 where combustion gas tends to remain.
Gas exchange by scavenging and exhaustion is ensured at the portion 3 and incomplete combustion at low speed can be reduced to derive stable output.

FIG. 12 shows a third embodiment of the exhaust timing control system for a two-cycle engine, and FIG. 12 is a vertical sectional view of the two-cycle engine.

The two-cycle engine to which the exhaust timing control device for the two-cycle engine of this embodiment is applied is
Since it has the same configuration as the two-cycle engine of the first embodiment, the same reference numerals are given and description thereof is omitted.

In this exhaust timing control system for a two-cycle engine, the body surface 60a of the rotation control valve 60 has a radius of curvature substantially the same as that of the cylinder inner peripheral surface 8a.
In addition, the effective exhaust port shape 42 when the rotation control valve 60 is closed
The exhaust timing is early at both sides 42a,
When the rotation control valve 60 is opened, the difference between the timings of the central portion 42b and the both side portions 42a becomes small.

Thus, the rotation control valve 60 is opened and closed, and the rotation control valve 60 is closed at low speed and / or at low load, and the effective exhaust gas formed by the body surface 60a of the rotation control valve 60 at this time. The mouth shape 42 is as shown in FIG. Therefore, at low speed and / or at low load, exhaust efficiency is reduced, but both sides of the exhaust port 16 are blown down first, so that the combustion gas is likely to remain in the combustion chamber 13 on both sides of the exhaust chamber 16. It is possible to ensure the gas exchange by the sweep exhaust, reduce the incomplete combustion at low speed, and derive a stable output.

[0034]

As described above, the invention according to claim 1 is
The center surface of the body of the rotation control valve is made to be approximately the same as the cylinder inner peripheral surface, and it is separated from the cylinder inner peripheral surface on both sides, and the effective exhaust port when the rotation control valve is closed The shape is set so that the exhaust timing is early on both sides and delayed at the center, and when the rotation control valve is opened,
Since the difference in timing between the central part and both sides is made small, because the exhaust timing of both sides of the exhaust port is early in scavenging at low speed or / and at low load,
Exhaust gas is discharged from both sides of the exhaust port, and the amount of exhaust gas remaining in the combustion chamber is reduced, so that stable output can be obtained without deterioration in scavenging efficiency even at low speed and / or low load.

According to the second aspect of the present invention, the surface of the body of the rotation control valve or the leading edge of the plate-shaped valve provided on the rotation control valve has a radius of curvature substantially the same as that of the inner peripheral surface of the cylinder.
In addition, the shape of the effective exhaust port when the rotation control valve is closed is set so that the exhaust timing is early in both sides and late in the center, while when the rotation control valve is opened, the timing of the center and both sides is Since the difference is made small, the exhaust gas is discharged from both sides of the exhaust port and remains in the combustion chamber due to the early exhaust timing of both sides of the exhaust port during scavenging at low speed and / or low load. Since the amount of exhaust gas decreases, a stable output can be obtained without deterioration in scavenging efficiency at low speed and / or at low load.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a two-cycle engine.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view showing a mechanism for operating a rotation control valve.

FIG. 4 is a side view showing a mechanism for operating a rotation control valve.

5 is a cross-sectional view taken along the line VV of FIG.

6 is a sectional view taken along line VI-VI in FIG.

7 is a cross-sectional view taken along the line VII-VII of FIG.

FIG. 8 is a view showing a shape of an effective exhaust port when the rotation control valve is closed.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a cross-sectional view of a two-cycle engine.

11 is a sectional view taken along line XI-XI of FIG.

FIG. 12 is a vertical sectional view of a two-cycle engine.

[Explanation of symbols]

 8 Cylinder 8a Cylinder Inner Surface 9 Piston 16 Exhaust Port 18 Scavenging Port 24 Rotation Control Valve 24c Central Part 24d Both Sides 42 Effective Exhaust Port Shape 42a Both Sides 42b Central Part

Claims (2)

[Claims] 1. An exhaust port and a scavenging port which are opened and closed by a piston are formed on an inner peripheral wall of a cylinder, and an upper portion of the exhaust port is rotated in a closing direction at a low speed and / or a low load, and at the same time at a high speed. And / or an exhaust timing control device for a two-cycle engine, which is provided with a rotation control valve that is rotated in the opening direction at the time of high load, in the center portion of the body surface of the rotation control valve, which is substantially the same as the inner peripheral surface of the cylinder. In this way, both sides are separated from the inner surface of the cylinder, and the effective exhaust port shape when the rotation control valve is closed is set so that the exhaust timing is early in both sides and late in the center. On the other hand, an exhaust timing control device for a two-cycle engine, characterized in that, when the rotation control valve is opened, a difference in timing between a central portion and both side portions becomes small. 2. An exhaust port and a scavenging port which are opened and closed by a piston are formed on an inner peripheral wall of a cylinder, and an upper portion of the exhaust port is rotated in a closing direction at a low speed and / or a low load, and at the same time at a high speed. And / or an exhaust timing control device for a two-cycle engine, which is provided with a rotation control valve that is rotated in the opening direction at the time of high load, in the body surface of the rotation control valve or the leading edge of a plate valve provided on the rotation control valve. To have a radius of curvature substantially the same as the cylinder inner peripheral surface,
Moreover, the shape of the effective exhaust port when the rotation control valve is closed is set so that the exhaust timing is early in both sides and delayed in the center part, while when the rotation control valve is opened, the center part and both side parts are An exhaust timing control device for a two-cycle engine, characterized in that the difference in timing is reduced.