JPH0337008B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inhalation device for a two-stroke engine used, for example, in a power sprayer, and particularly relates to an inlet opening/closing timing and an inlet opening/closing timing in relation to engine load. This invention relates to an intake device for a two-stroke engine whose opening area is controlled.

[Conventional technology]

A conventional two-cycle engine intake device will be explained with reference to FIGS. 12 and 13.

In FIG. 12, a two-stroke engine 10
has a cylinder 12 and a crankcase 14 joined and fixed to the lower end of the cylinder 12. The piston 16 is slidably installed within the cylinder 12 and defines the lower end of the combustion chamber 18 . The spark plug 20 is mounted on the top of the cylinder 12 and has a discharge gap facing the top of the combustion chamber 18 . The crankshaft 22 is disposed in the crankcase 14 at its axial center, rotatably supported by the crankcase 14 via ball bearings (not shown) at both ends, and has a balance weight 24. There is. The connecting rod 26 is rotatably coupled to the piston 16 and the pin portion of the crankshaft 22 at both upper and lower ends, respectively. The suction port 28 and the exhaust port 30 are formed in the cylinder 12 so as to open into the bore circumferential surface of the cylinder 12 at piston-side openings 40 and 44, respectively, and the piston-side opening 44 is closer to the piston 16 than the piston-side opening 40. It is located on the spark plug 20 side in the axial direction. These openings 40 and 44 are opened and closed by the side surface of the piston 16, and communication with the crankcase interior space 42 and the combustion chamber 18 is controlled, respectively. The carburetor 32 has a throttle valve 36 rotatably supported via a throttle valve shaft 34,
The air cleaner 38 and the inlet 2 of the two-stroke engine 10 at the upstream and downstream ends, respectively.
It is joined to the partition wall of No.8. The muffler 39 is joined to the downstream end of the partition wall of the exhaust port 30.

The air-fuel mixture generated in the carburetor 32 is introduced into the crankcase interior space 42 from the piston-side opening 40 via the intake port 28, and then sent to the combustion chamber 18 via a scavenging passage (not shown). Exhaust gas generated as a result of combustion of the air-fuel mixture in the combustion chamber 18 is discharged from the piston-side opening 44 to the exhaust port 30 and sent to the muffler 39 via the exhaust port 30.

FIG. 13 shows the piston side opening 40 of the suction port 28.
The opening/closing timing is indicated by the crank angle of the crankshaft 22. During the upward stroke of the piston 16, when the lower end of the side surface of the piston 16 passes upwardly through the lower edge of the piston-side opening 40, the piston-side opening 40 is opened and the crankcase inner space 42 is opened from the piston-side opening 40. The introduction of the air-fuel mixture begins. During the downward stroke of the piston 16, the lower end of the side surface of the piston 16 opens into the piston side opening 40.
When passing through the lower edge of the piston side opening 4
0 is closed, and the introduction of the air-fuel mixture from the piston-side opening 40 into the crankcase internal space 42 is completed.

In the conventional two-stroke engine 10, the intake port 2
The opening/closing timing of the piston side opening 40 of No. 8 is fixed and generally only adapted to the normal rotational speed of the two-stroke engine 10, and it is difficult to control it to an appropriate value depending on the engine rotational speed. It was hot.

[Problem that the invention seeks to solve]

Therefore, the conventional two-stroke engine 10 has the following problems.

(a) When the two-stroke engine 10 rotates at low speed,
Since the negative pressure in the crankcase internal space 42 decreases, the piston side opening 40 of the suction port 28 opens too early, that is, when communication between the suction port 28 and the crankcase internal space 42 starts,
Sufficient negative pressure is not generated in the crankcase internal space 42, and a sufficient amount of air-fuel mixture cannot be introduced.

(b) When the two-stroke engine 10 rotates at low speed,
The speed of the airflow at the intake port 28 decreases, the diameter of the fuel particles increases, and the combustion state of the fuel in the combustion chamber 18 deteriorates.

(c) When the two-stroke engine 10 rotates at low speed,
The piston-side opening 40 of the suction port 28 closes too late, that is, the positive pressure in the crankcase internal space 42 increases when the communication between the suction port 28 and the crankcase internal space 42 ends, and the internal pressure inside the crankcase increases. The air-fuel mixture in the space 42 is
8, and a so-called blowback phenomenon occurs.

An object of the present invention is to overcome such problems of the prior art and to provide a two-cycle engine intake in which the opening/closing timing and opening area of the intake port can be controlled to appropriate values regardless of engine speed and load. The purpose is to provide equipment.

[Means for solving problems]

According to the present invention, in a two-stroke engine in which an outwardly protruding inlet is integrally formed on the side edge of the cylinder, and a carburetor is connected to and installed in this inlet, one end is provided in the radial direction near the lower part of the inlet. An L-shaped rotating shaft that protrudes outward and has an arm is rotatably fitted on the rotating shaft, and a rotating valve that projects toward the cylinder side and that can open and close the suction port is attached to the rotating shaft. The arm of the rotating shaft is connected to the arm of the throttle valve shaft disposed in the carburetor via a spring member, and the opening/closing timing and opening area of the intake port can be adjusted according to the rotational displacement of the engine. Allows displacement.

[Effect]

The throttle valve shaft rotates in relation to the opening degree of the throttle valve of the carburetor. The rotation of the throttle valve shaft is controlled by the arms of the throttle valve shaft,
It is transmitted via the spring element and the L-shaped pivot shaft to the pivot valve, which pivots in relation to the throttle valve of the carburetor. The free end of the rotary valve forms the lower side of the effective opening of the inlet through which the air-fuel mixture is introduced into the piston-side opening, so as the rotary valve rotates, the free end of the rotary valve is displaced. The timing at which the side surface of the piston passes the free end of the rotary valve, that is, the timing at which the inlet opens and closes, changes. Furthermore, the area of the effective opening of the suction port changes depending on the displacement of the free end of the rotary valve.

When the opening degree of the throttle valve of the carburetor is small, that is, when the two-stroke engine is running at low speed or under low load, the free end of the rotary valve, which serves as the lower edge of the effective opening of the inlet, rises. The mouth opens later, the inlet closes earlier, and the opening area of the inlet decreases. Due to the reduction in the opening area of the inlet, the velocity of the airflow at the inlet increases.

The spring element creates a damping effect when transmitting the movement of the rotary valve to the throttle valve shaft of the carburetor, so that the spring element rotates against the spring element in relation to the velocity of the airflow at the inlet. This adjusts the flow cross-sectional area of the suction port and automatically adjusts the flow velocity at the suction port to an appropriate value.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 11.

FIG. 1 is a sectional view showing the overall configuration of the embodiment;
FIG. 2 is a perspective view showing the range including the inlet 28 from the outside, FIG. 3 is a cross-sectional view of the range including the inlet 28 and the carburetor 32, and FIGS. 4 and 5 are respectively taken along the line - It is a sectional view taken along the and - lines.

In FIGS. 1 and 2, the rotary valve 46 is disposed within the suction port 28, and is rotatably supported by the partition wall of the suction port 28 at its upstream end via a rotation shaft 48. , the free end 50 as the downstream end is
As the rotary valve 46 rotates, the piston side opening 4
It is adapted to be displaced along the surface of the piston-side opening 40 in a range from the lower side of 0 to a little above it.

3 and 4, the manner in which the rotary valve 46 and the rotary shaft 48 are coupled is shown in detail. A C-shaped retaining ring 5 is inserted through the wall portion and rotatably supported by the partition wall portion, and is mounted on the outside of the two-stroke engine 10.
2, 52 is fitted to prevent it from coming off from the two-stroke engine 10. Round machine screws 54, 54
is inserted through an insertion hole at the upstream end of the rotary valve 46 and then screwed onto the rotary shaft 48, thereby fixing the upstream end of the rotary valve 46 to the rotary shaft 48. Arm portion 56
is fixed to the end of the rotating shaft 48 protruding from the two-cycle engine 10, and rotates integrally with the rotating shaft 48. L due to the rotation shaft 48 and the arm portion 56
A letter-shaped member is formed. Note that, as clearly shown in FIG. 3, the free end 50 is formed to have an arcuate profile that substantially matches the circumferential profile of the bore of the two-stroke engine 10.

As shown in FIGS. 3 and 5 in detail in the manner in which the throttle valve shaft 34 and the throttle valve 36 are connected, the throttle valve shaft 34 is inserted into the passage wall of the carburetor 32, and It is pivotably supported,
C-shaped retaining rings 58, 58 on the outside of the carburetor 32
is fitted and prevented from coming off from the carburetor 32. The round machine screws 60 , 60 are inserted through the insertion holes in the centerline portion of the throttle valve 36 and then screwed onto the throttle valve shaft 34 to fix the throttle valve 36 to the throttle valve shaft 34 . The arm portion 62 is fixed to the end of the throttle valve shaft 34 that protrudes from the carburetor 32 and rotates integrally with the throttle valve shaft 34 .

In FIGS. 1 to 3, the coil spring 64
is fastened to the arm portion 56 and the arm portion 62 at both ends to connect the two.

FIG. 6 shows the position of the free end 50 of the rotary valve 46 in the piston-side opening 40. Rotary valve 4
6, the free end 50 is displaced along the piston-side opening 40 in the axial direction of the combustion chamber 18 in a range from the lower side of the piston-side opening 40 to slightly above the lower side.

FIG. 7 is an exploded perspective view of a rotary valve 46b and a rotary shaft 48b as a modification of the rotary valve 46 and rotary shaft 48 shown in FIGS. 1 to 6, and FIG. 8 is an exploded perspective view of a rotary valve 46b and a rotary shaft 48b.
9 is a side view of the rotary valve 46 to the cylinder 12.
FIG. 4 is a diagram illustrating an assembled state of the rotating shaft 48b and the rotating shaft 48b. The rotary valve 46b has a rectangular through hole 66 at its upstream end, and the rectangular through hole 66 is formed into a pair of plane portions parallel to each other. Rotation axis 4
8b has an angular insertion portion 68 that matches the circumferential contour of the angular insertion hole 66, and the angular insertion portion 68 is inserted into and fitted into the angular insertion hole 66. In addition, in FIG. 7, an annular groove 70 is provided at both ends of the rotation shaft 48b.
70 is shown, and C-shaped retaining rings 52, 52 are fitted into the annular grooves 70, 70. The rotary valve 46b and the rotary shaft 48b are fixed to each other and prevented from rotating relative to each other by fitting their rectangular insertion hole 66 and rectangular insertion portion 68. The round machine screw 54 can be omitted.

The operation of the embodiment will be explained.

The opening degree of the throttle valve 36 is manually operated by a throttle lever (not shown), and is approximately related to the engine rotational speed or load. The throttle valve shaft 34 rotates integrally with the throttle valve 36, and the arm portion 62 rotates integrally with the throttle valve shaft 3.
It swings with the rotation of 4. The coil spring 64 causes the arm portion 56 to swing in relation to the swing of the arm portion 62, thereby causing the rotation shaft 48 and the rotation valve 46 to rotate. As the opening degree of the throttle valve 36 decreases, the free end 50 of the rotary valve 46 rises, the lower side of the effective opening of the piston-side opening 40 rises, and the cross-sectional area of the effective opening decreases. In FIGS. 1 and 6, the solid line position and the two-dot chain line position of the rotary valve 46 correspond to the fully open and fully closed positions of the throttle valve 36, respectively. The opening/closing timing of the piston-side opening 40 coincides with the timing when the lower edge of the piston 16 passes the free end 50 of the rotary valve 46, so as the free end 50 of the rotary valve 46 rises, the piston-side opening 40 opens and closes. Part 4
The opening timing and closing timing of 0 are later and earlier, respectively. FIG. 10 shows the opening/closing timing of the piston-side opening 40 when the throttle valve 36 is fully open and fully closed, in terms of the rotation angle of the crankshaft 22.

When the opening degree of the throttle valve 36 is small, that is, when the two-cycle engine 10 is rotating at low speed or under low load, the opening timing and closing timing of the piston-side opening 40 become late and early, respectively, so that the crankcase inner space 42 The suction port 28 and the crankcase internal space 4 when the negative pressure is not large enough.
In addition, communication between the intake port 28 and the crankcase inner space 42 is prevented from continuing even though the positive pressure in the crankcase inner space 42 is increasing. This increases the filling efficiency of the air-fuel mixture into the crankcase internal space 42, avoids blowing back of the air-fuel mixture from the crankcase internal space 42 to the intake port 28, and increases the output of the two-stroke engine 10. Can be done.

When the two-cycle engine 10 rotates at low speed or under low load, the speed of the airflow at the intake port 28 decreases and the diameter of the fuel particles increases, which may cause deterioration of combustion. In the cycle engine 10, the free end 50 of the rotary valve 46 rises during such low speed rotation or low load, thereby reducing the opening area of the piston side opening 40, and as a result, the airflow at the intake port 28 is reduced. speed can be increased. Therefore,
The size of the fuel particles is reduced, which can improve combustion and enhance the performance of the two-stroke engine 10.

FIG. 11 shows the relationship between engine rotational speed and output horsepower by comparing two-stroke engines 10 based on the present invention and the prior art. In the two-cycle engine 10 according to the present invention, the timing of opening and closing of the piston-side opening 40 of the intake port 28 is controlled in relation to the opening degree of the throttle valve 36, so that the filling efficiency of the air-fuel mixture into the crankcase internal space 42 is improved. As the torque increases, the atomization of the fuel improves, thus increasing the horsepower output.

The coil spring 64 is provided between the arm portion 56 and the arm portion 62, and acts as a buffer for the transmission force between them. Therefore, fluctuations in the throttle valve 36 or the rotary valve 46 are appropriately damped, and minute fluctuations can be prevented from affecting each other. Furthermore, when the velocity of the airflow at the intake port 28 increases despite the same throttle valve opening, the rotary valve 46 rotates against the coil spring 64, causing the free end 50 of the rotary valve 46 to rotate. As a result, the opening/closing timing and opening area of the suction port 28 are automatically adjusted to appropriate values according to the velocity of the airflow at the suction port 28.

〔Effect of the invention〕

Thus, according to the invention, the free end of the rotary valve forms the lower side of the effective opening of the inlet through which the air-fuel mixture is introduced into the crankcase internal space, and is displaced in conjunction with the throttle valve of the carburetor. The opening/closing timing and opening area of the inlet are changed. Therefore, when a two-cycle engine is running at low speed or under low load, the opening timing and closing timing of the intake port are delayed and early, respectively, and the intake port is delayed and closed when the negative pressure in the crankcase interior space is not large enough. This prevents the intake port from starting to communicate with the crankcase interior space, and also prevents the suction port from continuing to communicate with the crankcase interior space despite the increased positive pressure in the crankcase interior space. It is possible to increase the filling efficiency of the air-fuel mixture into the crankcase internal space, avoid blowing back of the air-fuel mixture from the crankcase internal space to the intake port, and increase the output of the two-cycle engine.

When a two-stroke engine runs at low speed or under low load, the speed of the airflow at the intake port decreases and the size of the fuel particles increases, which can lead to deterioration of combustion. By raising the free end of the rotary valve at low speed rotation or under low load, the opening area of the suction port can be reduced, and as a result, the speed of airflow at the suction port can be increased. Therefore, the size of the fuel particles can be reduced, improving combustion and increasing the performance of the two-stroke engine.

In this invention, a spring member is provided between the throttle valve shaft and the rotation shaft of the rotary valve, and acts as a buffer for the transmission force between the throttle valve shaft and the rotation shaft. Therefore, fluctuations in the throttle valve or rotary valve are appropriately damped, and minute fluctuations can be prevented from affecting each other. Also, despite the same throttle valve opening,
When the velocity of the airflow at the inlet increases, the rotary valve rotates against the spring member, and the free end of the rotary valve properly lowers, so that the opening/closing timing and the opening area of the inlet become smaller than the inlet. Automatically adjusts to the appropriate value depending on the speed of airflow in the mouth.

[Brief explanation of the drawing]

1 to 11 relate to an embodiment of the present invention, in which FIG. 1 is a sectional view showing the overall structure, FIG. 2 is a perspective view showing the area including the inlet from the outside, and FIG.
The figure is a cross-sectional view of the area including the inlet and the vaporizer.
5 and 5 are sectional views taken along lines - and -, respectively, in FIG. 3, FIG. 6 is a diagram showing the position of the free end of the rotary valve in the piston side opening, and FIG. FIG. 6 is an exploded perspective view of a modification of the rotary valve and rotary shaft in FIG. 6, FIG. 8 is a side view of the rotary valve in FIG. 7, and FIG. 9 is an exploded perspective view of the rotary valve in FIG. FIG. 10 is a diagram showing the assembled state of the rotating shaft, FIG. 10 is a diagram showing the opening/closing timing of the piston-side opening when the throttle valve is fully open and fully closed, in terms of the rotation angle of the crankshaft, and FIG. 11 is a diagram showing the invention and A graph showing the relationship between engine speed and output horsepower comparing two-stroke engines based on conventional technology. Figure 12 is a cross-sectional structural diagram of a conventional two-stroke engine. Figure 13 is a diagram of the piston-side opening of the intake port. FIG. 6 is a diagram showing the opening/closing timing in terms of the crank angle of the crankshaft. 10...Two-stroke engine, 12...Cylinder, 28...Intake port, 32...Carburizer, 34...
Throttle valve shaft, 46, 46b...Rotary valve, 48, 48
b... Rotation shaft, 56, 62... Arm portion, 64... Coil spring (spring member).

Claims (1)

[Claims] 1. In a two-cycle engine in which a suction port protruding outward is integrally formed on the side edge of the cylinder, and a carburetor is connected to and installed in this suction port, one end extends outward in the radial direction near the bottom of the suction port. A protruding L-shaped rotary shaft provided with an arm is rotatably fitted, and a rotary valve that protrudes toward the cylinder side and is capable of opening and closing the suction port is fixed to the rotary shaft. is,
The arm of the rotating shaft is connected to the arm of a throttle valve shaft disposed in the carburetor via a spring member, and the opening/closing timing and opening area of the intake port are controlled according to the rotational displacement of the engine. A two-stroke engine intake device that allows displacement.