JPH09203323A - Two cycle engine with scavenging valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scavenge a cylinder by a large quantity of fresh air in a low load area by pushing back supply air in the cylinder by a specified quantity, and thereby reduce the amount of remaining burned gas in the cylinder to improve the ignitability. SOLUTION: A scavenging valve 10 rotating (operating) in synchronizm with a main shaft of an engine, is provided at a cylinder head 4. After an exhaust passage 8 is opened, the scavenging valve 10 is opened to allow the fresh air to flow into a cylinder 1 to scavenge it. By a timing variable means 13, the closing timing of the scavenging valve 10, in low load area, is delayed enough later than that of the exhaust passage 8 to push back the supply air in the cylinder 1 a specified quantity by a piston 2. The closing timing of the scavenging valve 10 in high load area is controlled to be hastened much more than that in the low load area.

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 with a scavenging valve, which has improved ignitability by controlling the closing timing of the scavenging valve.

[0002]

2. Description of the Related Art Generally, a two-cycle engine has a scavenging process for expelling burnt gas by fresh air, and in a low load region of the engine including an idle state, the charge ratio is small and the fresh air supplied to the cylinder is small. On the other hand, since the residual amount of burned gas is very large, the ignitability deteriorates, causing unpleasant irregular combustion.
As a result, harmful components in the exhaust gas increased, and fuel efficiency also deteriorated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to scaveng with a large amount of fresh air by pushing back the supply air in the cylinder by a predetermined amount in the low load region of the engine. It is trying to improve the ignitability by reducing the residual amount of burnt gas inside.

[0004]

In order to solve the conventional drawbacks, the present invention provides a cylinder head with a scavenging valve that operates in synchronization with the main shaft of an engine, and opens the scavenging valve after the exhaust passage is opened. Fresh air into the cylinder to scaveng the burned gas, and in the low load region of the engine, the timing of closing the scavenging valve is sufficiently delayed from the timing of closing the exhaust passage in the low load region of the engine. A predetermined amount of the supplied air is pushed back by the piston so that the closing timing of the scavenging valve is sufficiently advanced in the high load region than in the low load region.

[0005]

In the low load region, the timing varying means delays the closing timing of the scavenging valve sufficiently later than that in the exhaust passage so that the supply air in the cylinder is pushed back into the scavenging passage by the piston. Therefore, in the scavenging process corresponding to this pushback amount, it is necessary to scavenge with a larger amount of fresh air,
As a result, the amount of residual gas in the cylinder is reduced and the ignitability is improved. In the high load range, the closing timing of the scavenging valve is made sufficiently earlier than that in the low load range so that high output can be obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows an embodiment of a two-cycle engine with a scavenging valve according to the present invention, in which a scavenging valve 10 provided in a cylinder head 4 is a rotary that rotates in synchronization with a main shaft (crankshaft) of the engine. A valve is used, and the speed is reduced to 1/2 of the rotation axis of the main shaft of the engine (1/1 via the chain and sprocket 5).
It is also possible) to be driven. The scavenging valve 10 has rotary sliding surfaces 11 arranged so as to face each other, and if the rotary sliding surface 11 is perpendicular to the axis, the scavenging valve 10 has a shaft on which a radial load due to gas pressure is applied. Is not added.
The combustion chamber 3 is provided with a seal device S that allows fresh air to pass through, and seals the pressure inside the combustion chamber by bringing them into close contact with the rotary sliding surface 11, and the in-valve scavenging passage 12 formed in the scavenging valve 10 ( (A type of scavenging passage) communicates with the combustion chamber 3 so that fresh air flows into the cylinder 1 through the scavenging passage 9, the axis of the scavenging valve 10, and the combustion chamber 3. As a result, the burnt gas in the cylinder 1 is exhausted through the exhaust passage 8
And the scavenging process ends. Continued piston 2
When the exhaust passage 8 is closed as the temperature rises (scavenging valve 10
(The communication between the inside of the shaft and the combustion chamber 3 is also cut off), the supply air in the cylinder 1 is compressed, ignited and burned near the top dead center, and an explosive force is generated. As a result, when the piston 2 descends and the exhaust passage 8 is opened, the burned gas in the cylinder 1 is discharged, and as described above, due to the subsequent scavenging process, the cylinder 1
The inside is scavenged. The scavenging passage 9 is normally connected to the crank chamber, but it may be connected to a scavenging pump. The sealing device S includes a seal cylinder a (the outer periphery of which has a slight gap with the surrounding wall surface) and a seal ring b (the outer periphery of which is attached to the surrounding wall surface) without a gap.
It is desirable that the seal ring b is composed of a pressing spring C, and the seal ring b has a special closed end (known). Lubrication of the rotary sliding surface 11 is done by the fact that in a two-cycle engine, the fresh air generally contains oil. Next, in the shaft of the scavenging valve 10, there is provided a timing varying means 13 that comes into close contact with or contacts the inner peripheral surface of the shaft. That is, the outer periphery of the timing varying means 13 is brought into close contact with the inner peripheral surface of the shaft of the scavenging valve 10 (having a minute gap between them), or a slit 17 is formed as shown in FIG. Thus, the scavenging valve 10 is lightly contacted with the inner peripheral surface of the shaft. The timing varying means 13 is the scavenging valve 1.
Although it does not rotate together with 0, the closing timing of the scavenging valve 10 is controlled by rotating it to an arbitrary position. Explaining in detail with the above configuration, the exhaust passage 8 opens at a crank angle of, for example, 70 ° before bottom dead center, closes at 70 ° after bottom dead center, and the scavenging valve 10 opens at, for example, 35 ° before bottom dead center ( The start of communication between the scavenging passage 9 and the in-valve scavenging passage 12 and the combustion chamber 3, that is, the start of communication between the inside of the scavenging valve 10 shaft and the combustion chamber 3),
It is closed at 100 ° after bottom dead center (blocking the same communication),
As a result, after the exhaust passage 8 is closed in accordance with the upward stroke of the piston 2, the supply air in the cylinder 1 is pushed back through the in-valve scavenging passage 12 by a predetermined amount (a period of 30 °). As a result, in the low load region of the engine (including the idle state), it becomes necessary to scavenge with a larger amount of fresh air during the scavenging process,
The amount of residual gas is reduced by that amount, and the ignitability is improved. In this case, the flow of fresh air in the scavenging process is the combustion chamber 3
Since it is a uniflow type that flows from the exhaust side to the exhaust passage 8 side, the inside of the combustion chamber 3 is occupied by the supply air with almost no burned gas (improved ignitability), and the one returned by the rise of the piston 2 is almost burned gas. There is no air supply. In the high load region, if the timing varying means 13 is rotated clockwise to the position shown in FIG. 2A, even if the communication between the sealing device S and the in-valve scavenging passage 12 connected thereto remains. The communication between the in-valve scavenging passage 12 connected to the sealing device S and the control passage 14, that is, the communication between the in-valve scavenging passage 12 connected to the sealing device S and the in-valve scavenging passage 12 in the shaft of the scavenging valve 10 is, for example, Since it is cut off at 70 ° after bottom dead center, it has the same effect as cutting off the communication between the shaft of the scavenging valve 10 and the combustion chamber 3 at this time, and the supply of air in the cylinder 1 rises in the piston 2. High output can be obtained without being pushed back by. In this case, if the portion of the scavenging passage 12 in the valve connected to the sealing device S in FIG. 1A is connected to the timing varying means 13 in the axial direction as shown by the chain double-dashed line, the valve connected to the sealing device S is expanded. It is possible to reduce the throttling resistance when the communication between the internal scavenging passage 12 and the control passage 14 is interrupted. In the present invention, since the opening timing of the scavenging valve 10 is delayed compared to the conventional case, fresh air is not blown through much, but if the exhaust passage is throttled by a throttle valve, the pulsation phenomenon in the exhaust passage 8 will be in the cylinder 1. Therefore, the effect is further enhanced (the same effect can be obtained because the scavenging is performed slowly even if the scavenging passage 9 is throttled by the throttle valve). These throttle valves are optimally controlled according to the engine operating state. Figure 1 (b),
In (c), a cylindrical rotary valve is used as the scavenging valve 10 (the former is decelerated to 1/2 of the rotation of the engine main shaft, and the latter is driven at 1/1). In FIG. 1D, a spherical rotary valve is used as the scavenging valve 10. In either case, by rotating the timing varying means 13, the closing timing of the scavenging valve 10 is the closing timing of the exhaust passage (not shown) in the low load region. It is controlled so that the supply air in the cylinder 1 is pushed back by a predetermined amount by the piston with a sufficient delay, and the closing timing of the scavenging valve 10 in the high load region is made to be earlier than that in the low load region. Next, as a driving method of the timing varying means 13, there is a method of driving the driving piece 15 by an accelerator pedal (not shown), and further, there is a method of using the servo motor 20 as shown in FIG. That is, in FIG. 2C, the accelerator opening signal obtained from the accelerator opening sensor 18 is input to the microcomputer 19, calculated, and an output signal is sent to the servo motor 20. This output signal follows the relationship between the accelerator opening degree stored in the microcomputer 19 in advance and the desired amount of rotation of the timing changing means 13. The output signal drives the servo motor 20, and the worm gear 21, rod 22,
The timing varying means 13 is optimally controlled according to the accelerator opening via the drive piece 15. In controlling the closing timing of the scavenging valve 10, the present invention shown in FIG.
By using the timing varying means 23 of (b), fresh air in the scavenging passage 9 flows into the cylinder 1 from the outer periphery of the scavenging valve 10 through the in-valve scavenging passage 12 to scavenge burned gas. It has become. The timing varying means 23 has helical splines 25 and 26 which are cut in opposite directions, and the helical spline 25 is the shaft 2 of the scavenging valve 10.
4, the helical spline 26 has a sprocket 5
The helical splines 25 and 26 are designed to rotate integrally with each other through a sleeve 27 into which they are fitted, as they are integrated (they are not fixed to the shaft 24 and can rotate freely). Therefore, if the sleeve 27 is moved in the axial direction by the slide ring 28 (using hydraulic pressure or the like), the phase changes, and the closing timing of the scavenging valve 10 can be changed. For example, assuming that the opening / closing timing of the exhaust passage 8 is the same as in FIG. 1A, in the low load range, the scavenging valve 10 is opened at 5 ° before bottom dead center and closed at 100 ° after bottom dead center. The ignitability is improved by pushing back the supply air in 1 by a predetermined amount. In the high load range, the scavenging valve 10 is advanced by 30 ° and controlled to close at 70 ° after bottom dead center to ensure high output. At this time, the scavenging valve 10
Will open earlier, reaching 35 ° before bottom dead center (Fig. 1 (a))
Does not change). FIG. 3C uses a conical rotary valve as the scavenging valve 10. If the timing varying means 23 of FIG. 3B is used, the same object of the present invention can be achieved. In the present invention, it is possible to use a poppet valve as the scavenging valve 10, and as shown in FIG.
In the low load range, the scavenging valve 10 is opened at 5 ° before bottom dead center against the closing spring by the cam 16 rotating at a speed ratio of / 1,
The valve is closed at 100 ° after bottom dead center (interruption of communication between the scavenging passage 9 and the combustion chamber 3), and the scavenging process is completed. The object of the present invention can be achieved by controlling the closing timing of the scavenging valve 10 by the timing varying means 23 shown in FIG. 3B (the opening timing naturally changes). still,
In the present invention, the exhaust passage 8 may be opened, for example, at 50 ° before bottom dead center and closed at 50 ° bottom dead center, and the closing timing of the scavenging valve 10 may be delayed later than that of the exhaust passage 8 in the high load range. (Reduction of fresh air). In this case, the exhaust period is 100
Although apparently small, the cross-sectional area of the opening of the exhaust passage 8 can be 1.5 to 2 times or more as compared with the conventional one, so that a sufficient angular area can be provided. Next, in FIG. 2A, the timing changing means 13 is at the position shown in the high load region.
During the period from the valve closing timing of the scavenging valve 10 to the timing when the communication between the seal device S and the in-valve scavenging passage 12 connected thereto (crank angle of 30 °), the piston 2 rises and The supply air enters the in-valve scavenging passage 12 connected to the sealing device S, and the substantial supply air amount in the cylinder 1 is slightly reduced. In order to prevent this, the in-valve scavenging passage 12 on the downstream side of the timing varying means 13 as shown in FIG.
Is divided by a separation wall 29 (divided into 12a and 12b),
The scavenging valve 10 while communicating with the combustion chamber 3 in the scavenging passage in the valve.
The volume of the portion that does not communicate with the shaft of the valve is reduced by separating it with the timing varying means 13 and the separating wall 29 (reducing the total volume of the in-valve scavenging passage 12 from the volume of 12b). Is good. FIG. 4B shows an embodiment in which the scavenging valve 10 is driven at 1/1 of the rotation of the engine main shaft in FIG. 4A. Here, in FIG. 4B, when the communication between the in-valve scavenging passage 12a and the inside of the scavenging valve 10 is interrupted, there is a throttling resistance that is throttled by the timing changing means 13. To prevent this, Ingenuity is needed. That is, in FIG. 4C, when the separation wall 29 approaches the part of the combustion chamber 3 connected to the scavenging valve 10 (the part where the sealing device S is located), the valve scavenging passage 12a on the advancing side of the separation wall 29 is located. The timing variable means 13 is formed (the central angle is made small) so that the communication area is communicated with the inside of the shaft of the scavenging valve 10 with a sufficiently large communication cross-sectional area.
In this case, when the separation wall 29 passes through the part of the combustion chamber 3 connected to the scavenging valve 10 (the part where the sealing device S is located), fresh air is supplied from the in-valve scavenging passages 12a, 12b on both sides of the separation wall 29 to the cylinder. It is desirable to form the timing varying means 13 so that it can flow into 1. In FIG. 4C, a state of 70 ° after bottom dead center is shown in FIG.
Until the communication between the scavenging passage 12b and the valve scavenging passage 12b connected thereto is cut off, the communication between the valve scavenging passage 12b and the shaft of the scavenging valve 10 is blocked by the timing varying means 13 (see FIG. )reference). An embodiment in which the above is applied to the present invention of FIG. 1C is shown in FIG. By the way, in the present invention, in the high load region, the opening timing of the scavenging valve 10 is 35 ° before bottom dead center. Therefore, if this is delayed to 5 ° before bottom dead center, blow-through of fresh air can be prevented. That is, in FIG. 5A, the in-valve scavenging passages on the downstream side of the timing varying means 13 'are separated by the separating walls 30 and 31 to be 12e, 12f, 1 and 1.
It is divided into 2g, and the timing changing means 1 is used in the low load region.
3'is at the position shown in the figure. If the communication between the in-valve scavenging passage 12e and the shaft of the scavenging valve 10 is blocked by the timing varying means 13 'up to 5 ° before bottom dead center, the scavenging valve 3'is provided. 1
When 0 opens, the bottom dead center is 5 °, and blow-through of fresh air is completely prevented. The in-valve scavenging passages 12f and 12g communicate with the inside of the shaft of the scavenging valve 10 up to 100 ° after the bottom dead center, so that the supply air in the cylinder 1 is returned by a predetermined amount to achieve the object of the present invention. In the high load / low speed range, the timing varying means 13 'is located at the position shown in FIG. 5B.
Similarly, the opening timing of the scavenging valve 10 is 5 ° before bottom dead center, while the closing timing is such that the communication between the valve scavenging passage 12g and the shaft of the scavenging valve 10 is after bottom dead center as shown in FIG. Since it is cut off from 70 ° by the timing varying means 13 ', 70 after the bottom dead center.
And high output can be obtained. In the high load / medium speed range, if the timing varying means 13 'is rotated clockwise, the scavenging valve 10 opens earlier, and a sufficient scavenging period is given (the closing time of the scavenging valve 10 does not change). However, FIG.
Rotate within the range of θ as shown. In the high load / high speed range, the timing varying means 13 'is rotated to the position shown in FIG. 5 (e) so as not to interfere with the inflow. This time,
The opening time of the scavenging valve 10 is 35 ° before bottom dead center, and the closing time thereof is 70 ° after bottom dead center. Incidentally, each timing changing means 13 '
Rotate integrally, but each may be configured to rotate independently and may rotate separately. Figure 1 above
An embodiment applied to the present invention in (c) is shown in FIG. 5 (f).
Since the description is the same, it will be omitted.

[0007]

According to the present invention, since the closing timing of the scavenging valve 10 is sufficiently delayed from that of the exhaust passage 8 in the low load range to push back the supply air in the cylinder by a predetermined amount, a larger amount of fresh air is supplied. Therefore, it becomes necessary to perform scavenging, and as a result, the residual gas amount in the cylinder is reduced and the ignitability is improved. Therefore, fuel efficiency is greatly improved and exhaust gas is purified.

[Brief description of drawings]

FIG. 1 is a diagram of a two-cycle engine with a scavenging valve according to the present invention.

FIG. 2 is a diagram showing a timing varying means and a driving device.

FIG. 3 is a diagram of another embodiment of a two-cycle engine with a scavenging valve according to the present invention.

FIG. 4 is a diagram of a scavenging valve according to the present invention.

FIG. 5 is a diagram of a scavenging valve according to the present invention.

[Explanation of symbols]

1 is a cylinder, 2 is a piston, 3 is a combustion chamber, 4 is a cylinder head, 5 is a sprocket, 6 and 7 are bearings, 8 is an exhaust passage, 9 is a scavenging passage, 10 is a scavenging valve, 11 is a rotary sliding surface, 12, 12a, 12b, 12e, 12f, 12g
Is a scavenging passage in the valve, 13 and 23 are timing variable means, 1
4 is a control path, 15 is a driving piece, 16 is a cam, 17 is a slit, 18 is a sensor, 19 is a microcomputer,
20 is a servo motor, 21 is a warm gear, 22 is a rod, 24 is a shaft, 25 and 26 are helical splines, 2
7 is a sleeve, 28 is a sliding ring, 29, 30 and 31 are separating walls, a is a seal tube, b is a seal ring, c is a pressing spring, S is a sealing device, and 13 'is a timing varying means.

Claims (6)

[Claims] 1. In a two-cycle engine having a scavenging process for expelling burnt gas by fresh air, a cylinder head is provided with a scavenging valve that operates in synchronization with the main shaft of the engine, and the scavenging valve is opened after the exhaust passage is opened. Open and let fresh air flow into the cylinder through the scavenging passage and the combustion chamber to scaveng burnt gas.In addition, the timing variable means controls the closing timing of the scavenging valve in the low load region of the engine to close the exhaust passage. It is constructed so that the supply air in the cylinder is pushed back by a predetermined amount with a sufficient delay from the timing, and the closing timing of the scavenging valve is controlled to be advanced earlier than that in the low load area in the high load region of the engine. With a scavenging valve that is characterized by 2
Cycle agency. 2. A scavenging valve is a rotary valve that allows fresh air to pass through the shaft thereof, and the scavenging valve is provided with a timing varying means in the shaft of the scavenging valve, the timing varying means being in close contact with or in contact with the inner peripheral surface of the shaft. By rotating the scavenging valve shaft and the combustion chamber so as to change the timing for shutting off communication between the scavenging valve and the combustion chamber, that is, the closing timing of the scavenging valve. And a structure in which the volume of a portion which communicates with the combustion chamber of the scavenging passage in the valve and does not communicate with the shaft of the scavenging valve can be reduced by separating with the timing varying means and the separation chamber. 1
2-cycle engine with scavenging valve described. 3. When the separation wall approaches a portion of the combustion chamber connected to the scavenging valve, the in-valve scavenging passage on the advance side of the separation wall has a sufficiently large communicating cross-sectional area so that the inside of the scavenging valve has a shaft. The two-cycle engine with a scavenging valve according to claim 2, wherein the timing varying means is formed so as to communicate with the engine. 4. The timing varying means is formed so that fresh air can flow into the cylinder through the in-valve scavenging passages on both sides of the separation wall when the separation wall passes through a portion of the combustion chamber connected to the scavenging valve. A two-cycle engine with a scavenging valve according to claim 3. 5. The scavenging passage in the valve downstream of the timing varying means is divided by another separating wall, and the opening timing of the scavenging valve is delayed by the timing varying means in the high load / low speed region of the engine. A two-cycle engine with a scavenging valve according to any one of claims 2 to 4. 6. The engine according to claim 1, wherein the scavenging valve is closed later than the exhaust passage in the high load region of the engine.
A two-cycle engine with a scavenging valve according to any one of 1.