JPH0718341B2 - Exhaust timing control device for 2-cycle engine - Google Patents

Description

The present invention relates to an engine exhaust timing control device, and in particular,
The present invention relates to an exhaust timing control device used in a two-cycle engine.

"Prior Art" Generally, the engine used in a vehicle or the like has a low rotation type that emphasizes power characteristics at low speed running (low speed) and a power characteristic at high speed running (high speed). It is roughly divided into a high-speed type with emphasis on the former, so that the peak of the engine output can be obtained in the low rotation range, and the latter can obtain the peak of the engine output in the high rotation range. However, in the former case,
It also has the characteristic that the output in the high rotation range reaches a peak, and in the latter case, the output in the low rotation range becomes lower than in the former case.

Therefore, by maintaining a high output in the high speed range and increasing the output in the low and medium speed range, a wide speed range from low speed running (low middle speed) to high speed running (high speed) Improving the power characteristics has been studied, and as an example of a specific means for solving the problem, changing the exhaust timing of the engine between low rotation speed and high rotation speed is mentioned.

By the way, in the two-cycle engine, the exhaust operation is performed by moving the piston to the bottom dead center side to open the exhaust port and connect the exhaust passage and the inside of the cylinder. In order to change the exhaust timing, the position of the upper edge of the exhaust port (hereafter, the top dead center side of the piston is up and the bottom dead center side is down) is changed along the moving direction of the piston. There is a need.

Therefore, conventionally, as a specific solution for opening and closing the upper part of the exhaust port, for example, the techniques disclosed in Japanese Patent Publication No. 47-36047 and Japanese Utility Model Publication No. 58-36818 have been proposed.

The former supports an arcuate movable plate disposed near the exhaust port of the exhaust passage by a swing lever positioned in the exhaust passage, and swings the lever to move the movable plate in the moving direction of the piston. By moving up and down along this, the movable plate is selectively positioned in either the upper part of the exhaust port or the recess formed in the lower part of the inner wall of the exhaust passage to change the position of the upper end edge of the exhaust port. In the latter, a control valve having a half-moon shaped cross section is rotatably disposed near the upper portion of the exhaust port, and a part of the outer peripheral surface of the control valve is rotated by the rotation of the control valve. By opening and closing the upper portion of the exhaust port by projecting and retracting the upper portion of the exhaust port, the timing of communication between the exhaust passage and the inside of the cylinder during the downward movement of the piston is changed.

"Problems to be Solved by the Invention" The present invention is intended to solve the following problems in the above-described conventional techniques.

That is, in a two-cycle engine, if the upper part of the exhaust port is closed and the exhaust timing is delayed, the start timing of the compression process is advanced accordingly, the compression ratio is increased, and the generated torque tends to increase. However, as in the prior art described above, if the upper part of the exhaust port is kept blocked by the movable plate and control valve while the engine is operating in the low speed range, The fresh air exchange rate is reduced. (Because the exhaust chamber is set for high-speed output characteristics, the fresh air exchange rate is low especially in the low speed range). As a result, there is a problem that irregular combustion and rotation fluctuation in the idle speed range increase.

Such a problem is particularly remarkable in a single-cylinder engine or a 90-degree V-type two-cylinder two-cycle engine.

On the other hand, one means for solving such a problem is to increase the inertial mass of a flywheel attached to the crankshaft. This method is used to smooth the engine rotation. To
Since the inertial mass of the crank system increases with the increase in the mass of the flywheel, which deteriorates the response of the engine, further improvement is required.

"Means for Solving Problems" The present invention can effectively solve the above-mentioned conventional problems 2
An exhaust timing control device for a cycle engine is provided, wherein the exhaust timing control device is attached to an upper wall of an exhaust passage near an exhaust port and opens and closes the upper part of the exhaust port. An actuator that opens and closes the control valve, a rotation speed detection unit that detects the rotation speed of the two-cycle engine, and the rotation speed of the two-cycle engine based on an output signal from the rotation speed detection unit. In the vicinity of the low speed range, the control valve is operated in the opening direction, and when it reaches the middle speed range of the low speed range or higher, the control valve is operated in the closing direction,
And a control unit that outputs a drive signal to the actuator so as to operate the control valve in the opening direction when the rotation speed reaches a high rotation range of the middle rotation range or higher.

"Operation" The exhaust timing control device for a two-cycle engine according to the present invention has the above-described configuration, and controls the exhaust timing when the engine is operated in a low speed region near the idling speed. By operating the control valve in the opening direction, the compression ratio of the engine is reduced to suppress fluctuations in the torque (rotation) of the crankshaft, and the explosion interval is narrowed, so the effects of the torque fluctuations described above are minimal. When it reaches the rotation range, the control valve is operated in the closing direction to improve the output characteristics, and when it reaches the high rotation range, the control valve is operated in the opening direction to improve the output characteristics in the high rotation range. To improve.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 show a main part of a two-cycle engine to which an exhaust timing control system according to this embodiment is applied. The two-cycle engine 1 includes a cylindrical cylinder block 2 and a cylinder. A cylinder head 4 attached to the block 2 to form a combustion chamber 3, a piston 5 slidably fitted in the cylinder block 2, and an opening on a sliding surface of the piston 5 of the cylinder block 2 , A plurality of scavenging ports 6 and a single exhaust port 7 that are opened and closed as the piston 5 slides, and inside the peripheral wall of the cylinder block 2 in succession to each of the scavenging ports 6 and the exhaust port 7. Formed scavenging passage 8
And an exhaust passage 9, and an exhaust timing control device 10 according to the present embodiment is provided on the upper wall of the exhaust passage 9 near the exhaust port 7.

As shown in FIG. 1, the exhaust timing control device 10 is attached to the upper wall of the exhaust passage 9 to connect the exhaust port 7 to the exhaust port 7.
As shown in FIG. 2, an upper control valve 11 for opening and closing, an actuator 12 for driving the control valve 11 to open and close, and a control unit 13 for controlling an operation amount of the actuator 12 are provided. The two-cycle engine 1
A rotation speed detection means 14 for detecting the rotation speed is attached, and the rotation speed of the two-cycle engine 1 is based on an output signal from the rotation speed detection means 14 in the vicinity of the idling rotation speed (for example, including the idling rotation speed). When it is in the low speed range (in the range of several thousand revolutions), the control valve 11 is operated in the opening direction, and when it reaches the middle speed range above the low speed range, the control valve 11 is closed. When the control valve 11 is actuated in the open direction and reaches a high speed range above the middle speed range, a drive signal is output to the actuator 12 in order to operate the control valve 11 in the opening direction.

Next, these will be described in detail. As shown in FIGS. 1 and 2, the upper wall of the exhaust passage 9 is
A recess 15 is formed which opens in the exhaust passage 9 at a predetermined distance from the vicinity of the exhaust port 7 toward the downstream side, and the center of the cylinder block 2 is formed so as to penetrate the downstream end of the recess 15. A rotary shaft 16 is attached along a direction orthogonal to the line, and a rib 17 is provided which divides the exhaust port 7 and the exhaust passage 9 in the circumferential direction of the cylinder block 2 from the exhaust port 7 toward the downstream side. Has been.

As shown in FIGS. 1 and 2, the control valve 11 is formed in a substantially plate shape and is divided into two in the circumferential direction of the cylinder block 2, one end of each of which is the rotary shaft.
By being connected to the rib 16 in a state in which the relative rotation is restricted, the ribs 17 are arranged on both sides of the rib 17, and the pivot shaft 16 is reciprocally pivoted within a predetermined angle range.
It can be oscillated synchronously around 16. Then, as shown by the chain line in FIG. 1, the control valve 11 is swung to the upper swing limit,
Its shape is set so as to be stored in the recess 15,
The end on the swing side is curved with a curvature substantially equal to the sliding surface of the piston 5 of the cylinder block 2, and in the state of swinging to the lower swing limit,
As shown in FIG. 2, the inner surface of the combustion chamber 3 is made substantially continuous. Further, the swing center side end of the control valve 11 generates a sealing function between itself and the inner wall surface of the recessed portion 15, and has a gap that allows the swing movement of the control valve 11 itself. Made to form also said recess
When housed in 15, the lower surface is a curved surface that is continuous with the inner surface of the exhaust passage 9.

Therefore, the control valve 11 formed in this way has the recess 15
The upper part of the exhaust port 7 is closed in a state in which the exhaust port 7 is protruded from and is positioned at the lower swing limit, and
In the state of being positioned at the upper swing limit, the upper portion of the exhaust port 7 is opened to change the distance between the exhaust port 7 and the combustion chamber 3.

On the other hand, one end of the rotary shaft 16 penetrates the wall of the cylinder block 2 and is projected to the outside, and the actuator 12 is connected to the projected part.

That is, the wire drum 18 is attached to one end of the rotating shaft 16.
Are integrally attached, and the actuator 12 is connected via a wire 19 wound around the wire drum 18.

For example, a servomotor is used as the actuator 12, and the actuator 12 is attached to the cylinder block 2 or other engine components or in the vicinity of the cylinder block 2 of the vehicle body frame. Then, by the controlled rotation, the rotating shaft 16 (that is, the control valve 11) is rotated or swung within the range of a predetermined angle via the wire 19 and the wire drum 18.

The rotation speed detection means 14 connected to the control unit 13,
For example, a pulse generator attached to the crankshaft (not shown) of the two-cycle engine 1,
A pulse is generated according to the number of revolutions of the two-cycle engine 1, and an electric signal proportional to the number of pulses is output to the control unit 13 in the subsequent stage.

The control unit 13 controls the lower limit engine speed A and the upper limit engine speed B in the range of several thousand revolutions including the idle revolution speed, the engine revolution speed C that sets the upper limit of the middle revolution range, and the high revolution range. The engine speed D for setting the lower limit is input in advance, and based on the information from the speed detecting means 14, as shown in FIG. 3, when the engine is less than the speed A, the control valve is When a drive signal is output to the actuator 12 so as to position 11 in the fully closed position and the speed is within the range of the rotational speed A or more and less than the rotational speed B, the control valve is
In order to position 11 at an intermediate position between the fully open position and the fully closed position, a drive signal is output to the actuator 12, and when the rotational speed is in the range of B or more and less than C,
When a drive signal is output to position the control valve 11 in the fully closed position and the rotation speed is C or higher and lower than D,
A drive signal is sent to the actuator 12 in order to move the control valve 11 proportional to the rotation speed from the fully closed position toward the fully open position and to position the control valve 11 at the fully open position when the rotation speed D or more is reached. Is output.

And, when the two-cycle engine 1 is applied to, for example, a motorcycle, the engine speed C is
The upper limit of the number of rotations that is often used in general city driving is about 5000 ~
It is 7,000 rpm.

Further, in the present embodiment, the control valve 11 is made to reciprocate once to the fully open position when the engine speed reaches the engine speed X which is equal to or higher than the idle speed after the two-cycle engine 1 is started. . The rotation speed X is set to a value very close to the idle rotation speed.

The operation of the exhaust timing control device 10 of the present embodiment thus constructed will be described below with reference to the flow chart of FIG.

When the two-cycle engine 1 is in a stopped state, the control valve 11 is located at the fully closed position and the upper portion of the exhaust port 7 is held in a closed state.

As a result, when the two-cycle engine 1 is started, the rotation speed of the two-cycle engine 1 is detected by the rotation speed detecting means.
At the same time as being detected by 14, the rotation speed information is converted into an electric signal and continuously output from the rotation speed detecting means 14 to the control unit 13.

When the number of revolutions of the two-cycle engine 1 after starting reaches the idling number of revolutions or more, a drive signal is output from the control unit 13 to the actuator 12, and the actuator is driven.
The control valve 11 is once moved to the fully open position by 12 and then moved in the closing direction.

By such reciprocating movement of the control valve 11, carbon attached to the control valve 11 is forcibly scraped off by sliding contact between the control valve 11 and the inner surface of the recess 15.

After the control valve 11 is reciprocated in this way,
When the rotation speed of the cycle engine 1 is in the low rotation speed range from the rotation speed A to the rotation speed B, this information is output from the rotation speed detection means 14 to the control unit 13 and a drive signal is sent from the control unit 13 to the actuator 12. The output causes the control valve 11 to swing to an intermediate position between the fully closed position and the fully open position. Thus, in the low rotation range,
When the control valve 11 is moved to the intermediate position, the exhaust port 6
The upper edge is displaced to the top dead center side and the compression ratio is reduced.As a result, the fresh air exchange rate near the idle speed range is improved and irregular combustion and the resulting torque fluctuation are reduced. To be made. And the control valve in the low speed range
Holding 11 at the intermediate position is to reduce the torque fluctuation by reducing the compression ratio as described above, and when the control valve 11 is fully opened in the low rotation range and set to the high speed rotation side,
The combustion noise tends to be loud, and is set in consideration of minimizing the combustion noise.

Further, when the two-cycle engine 1 reaches the above-described low rotation range to the middle rotation range, which is frequently used during normal traveling between the rotation speeds B to C, based on the signal from the rotation speed detection means 14, the control unit 13 to the actuator. A drive signal is output to 12 and the control valve 11 is swung to the fully closed position. As a result, the exhaust timing is set to an appropriate state at the time when the explosion interval, which has a small influence on the torque fluctuation, is reached, the fluctuation of the rotation during normal traveling is suppressed, and the output characteristic is improved.

On the other hand, when the rotation of the two-cycle engine 1 exceeds the upper limit rotation speed C in the middle rotation speed range, the control valve 11 gradually opens from the fully closed state while reaching the lower limit rotation speed D in the high rotation speed range. Is held in the fully open position when the number of rotations D is reached,
The exhaust timing of the two-cycle engine 1 is set to an appropriate state in the high rotation speed range.

By performing the above-mentioned operation in correspondence with the rotation speed of the two-cycle engine 1, the output characteristics can be improved in a wide rotation range from the low rotation range to the high rotation range, and particularly, the influence of the torque fluctuation with a long explosion interval. The torque fluctuation, that is, the rotation fluctuation in the low rotation range of several thousand rotations including the idling speed, which is the rotation range in which the output of the control valve 11 is reduced, and in the present embodiment, the opening of the control valve 11 in the low rotation range is controlled. Since the opening is at an intermediate level, the sound of explosion can be reduced.

On the other hand, when the rotation of the two-cycle engine 1 is in the low rotation range described above, the control valve 11 is placed under the condition that carbon is most likely to adhere. When the control valve 11 is swung to the intermediate opening degree through the fully closed position when it is lowered to the low rotational speed range below the rotational speed B, the number of times the control valve 11 is swung during operation is increased. The action of scraping off the carbon adhering to the control valve 11 is improved. Therefore, the smoothness of the operation of the control valve 11 is always ensured, and the exhaust timing can be controlled with high accuracy.

It should be noted that the shapes, dimensions, and the like of the respective constituent members shown in the above-mentioned embodiment are examples, and the two-cycle engine 1 to which the invention is applied
Various changes can be made based on the type, design requirements, and the like.

For example, the number of rotations that sets the range of each rotation range is changed according to the specifications of the vehicle and the two-cycle engine 1, and the holding position of the control valve 11 at the intermediate opening is also the two-cycle engine 1. Can be changed depending on the trade-off between the cylinder inner diameter and the process distance that determine the process volume. Further, the rotation speed can be detected by detecting the ignition pulse of the two-cycle engine, and the actuator is not limited to the one by electrical control, but the fluid pressure, for example, the air pressure. May be used.

[Advantages of the Invention] As described above, the exhaust timing control system for a two-cycle engine according to the present invention changes the distance between the exhaust port of the two-cycle engine and the combustion chamber and forms the exhaust port continuously. An exhaust timing control device for changing the timing of communication between the exhaust passage and the inside of the cylinder, the control valve being attached to an upper wall of the exhaust passage to open and close an upper portion of the exhaust port; An actuator that opens and closes the control valve, a rotation speed detection unit that detects the rotation speed of the two-cycle engine, and the rotation speed of the two-cycle engine based on an output signal from the rotation speed detection unit. When it is in the low rotation speed range, the control valve is operated in the opening direction, and when it reaches the middle rotation speed range above the low rotation speed, the control valve is operated in the closing direction. And a control unit that outputs a drive signal to the actuator in order to operate the control valve in the opening direction when a high rotation range of the middle rotation range or higher is reached. It is possible to improve the output characteristics in a wide rotation range from the rotation range to the high rotation range, and especially in the low rotation range near the idling speed, which is a rotation range where the explosion variation is likely to be affected by torque fluctuation. The compression ratio is reduced and the fresh air exchange rate is increased to suppress the torque fluctuation of the two-cycle engine, and as a result, the smooth output state is maintained while maintaining the high output characteristics from the low speed range to the high speed range. It has excellent effects such as being able to.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view showing a main part of a two-cycle engine to which the embodiment is applied, and FIG. 2 is taken along line II-II of FIG. Sectional view, 3rd
FIG. 4 is a diagram showing the correspondence between the operation timing of the control valve and the engine speed, and FIG. 4 is a flow chart. 1 ... 2-cycle engine, 5 ... piston, 7 ... exhaust port, 9 ... exhaust passage, 10 ... exhaust timing control device,
11 ... Control valve, 12 ... Actuator, 13 ... Control unit, 14 ... Rotation speed detecting means, 15 ... Recess, 16 ... Rotating shaft, 18 ... Wire drum, 19 ... Wire.

Claims (1)

[Claims] 1. An exhaust system in which a distance between an exhaust port of a two-cycle engine and a combustion chamber is changed to change a timing of communication between an exhaust passage continuously formed in the exhaust port and an inside of the cylinder. A timing control device, which is attached to an upper wall of the exhaust passage and opens and closes an upper portion of the exhaust port, an actuator that opens and closes the control valve, and detects a rotation speed of the two-cycle engine. Based on the rotation speed detection means and the output signal from the rotation speed detection means, when the rotation speed of the two-cycle engine is in a low rotation range near the idling rotation speed, the control valve is operated in the opening direction. , When the medium speed range above the low speed range is reached, the control valve is operated in the closing direction, and when the high speed range above the medium speed range is reached, the control valve is operated in the opening direction. Let Ku, 2, characterized in that it consists of a control unit for outputting a drive signal to the actuator
Exhaust timing control device for cycle engine.