JPH0660566B2 - 2-cycle engine - Google Patents

Description

Description: [Industrial field of use] The present invention relates to a separated refueling type two-cycle engine in which the exhaust timing can be changed.

[Prior Art] In a separate refueling type two-cycle engine, lubricating oil is supplied to each part of the engine by a plunger type oil pump driven by a crankshaft, and the oil discharge amount per one revolution of the engine is the above-mentioned plunger. Is determined by the stroke amount.

In this conventional oil pump, the plunger is linked to the throttle, and the stroke amount of this plunger is
It is designed to be changed according to the throttle opening.
Therefore, the amount of oil corresponding to the engine load is supplied to each part of the engine through the oil pump, and the oil discharge amount of this oil pump is linearly compared with the engine speed at each throttle opening. There is.

On the other hand, in a 2-cycle engine, the higher the opening height of the exhaust port and the earlier the exhaust timing, the higher the rotational speed and the high output type. Conversely, the lower the opening height of the exhaust port and the later the exhaust timing, the lower speed type engine. Becomes

In order to achieve both of these contradictory output characteristics, a two-cycle engine is conventionally known in which the exhaust timing can be freely changed according to the engine speed.

In this engine, a recess facing the upper edge of the opening of the exhaust port is formed in the exhaust passage communicating with the exhaust port, and a substantially drum-shaped exhaust valve that is rotated according to the engine speed is provided in the recess in the axial direction. It is configured to be rotatably attached to. When the engine speed becomes lower than a preset value, this exhaust valve rotates in a direction in which its outer peripheral surface advances to the upper edge of the opening of the exhaust port, lowering the opening height of this exhaust port, The exhaust timing is delayed. Then, when the engine speed exceeds the set value, the exhaust valve rotates in a direction in which the outer peripheral surface of the exhaust valve recedes from the upper edge of the opening of the exhaust port, and the height of the exhaust port is increased to set the exhaust timing. It is designed to be hastened.

Therefore, the optimum exhaust timing can be obtained over the entire rotation range from the low rotation range to the high rotation range.

[Problems to be Solved by the Invention] In a two-cycle engine equipped with an exhaust valve of this kind, when the exhaust valve is opened and the exhaust timing is advanced, the engine output rises in a quadratic curve, so that it is added to the piston. The heat load also increases in proportion to the output. Therefore, in order to prevent the seizure of the piston, it becomes necessary to increase the supply amount of the lubricating oil.

However, the amount of oil discharged per engine revolution is
In a conventional engine that controls according to the throttle opening,
As indicated by the broken line in FIG. 8, if the throttle opening (engine load) is constant, the oil discharge amount per engine revolution becomes substantially constant even if the engine speed changes.

As a result, when the throttle opening is fully open and the engine speed is in a high rotation range that exceeds the set value, and when the exhaust valve is open and high output, the throttle opening is fully open and the engine speed is low. If the amount of oil discharged per engine revolution is the same when the exhaust valve is in the region and the exhaust valve is closed and the output is low, the heat load on the piston is as described above.
Since it is proportional to the output, it is impossible to supply a sufficient amount of oil commensurate with the amount of heat generation to the portion of the piston or the like that requires lubrication, and there is a problem that the lubrication reliability decreases.

The present invention has been made under such circumstances, and an object of the present invention is to provide a two-cycle engine capable of supplying an appropriate amount of oil in conjunction with the operation of an exhaust valve and significantly improving the reliability of lubrication. And

[Means for Solving the Problem] Therefore, in the present invention, by changing the opening height of the exhaust port opened and closed by the piston, the exhaust valve for changing the exhaust timing and the power transmission from the crankshaft are used. An oil pump provided with an axially reciprocating plunger, and an adjusting means for increasing / decreasing the oil discharge amount per engine revolution by changing the stroke amount of the plunger of the oil pump were provided.
In a cycle engine, when the engine speed is lower than a preset value, the exhaust valve is actuated in the direction in which the opening height of the exhaust port is lowered, and the adjusting means is actuated in the direction in which the stroke of the plunger is shortened. The exhaust valve is operated in a direction in which the opening height of the exhaust port is increased and the adjusting means is operated in a direction in which the stroke of the plunger is increased when the engine speed exceeds the set value. It is characterized in that a control means for controlling is provided.

[Operation] With this configuration, since the adjusting means for adjusting the stroke of the exhaust valve and the plunger are linked through the control means, the exhaust valve operates in the direction of increasing the opening height of the exhaust port. As long as the adjustment means of the oil pump is operated, the stroke of the plunger is lengthened.

Therefore, in an operating state in which the exhaust valve is opened and the heat load on the piston is particularly large, a sufficient amount of oil can be supplied to the piston side, and seizure or overheating of the engine can be reliably prevented.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings applied to a motorcycle.

FIG. 9 shows the front part of the motorcycle, and reference numeral 1 is a frame. A steering head pipe 2 that pivotally supports a front fork 3 is provided at the front end of the frame 1. The steering head pipe 2 is connected with a main pipe 4 extending obliquely rearward and downward and a down tube 5 extending downward. In the space surrounded by the main pipe 4 and the down tube 5, a separate refueling type two-cycle engine 6 is mounted.

In the cylinder block 17 of the engine 6, a pair of cylinders 7 are arranged in parallel. As shown in FIG. 6, an intake port 9, an exhaust port 10, and a scavenging port 11 opened and closed by a piston 8 are opened on the inner surface of each cylinder 7. The exhaust port 10 is connected to the exhaust passage 12 in the cylinder block 17. The exhaust port 10 has a substantially rectangular shape as shown in FIG.
The exhaust timing determined by the height of 0a is set to a high rotation type in advance.

The exhaust port 10 is provided on the upper surface of the exhaust passage 12 facing the exhaust port 10.
An exhaust valve 13 for changing the exhaust timing by changing the height of the exhaust valve is mounted. Exhaust valve 13
Has a substantially hourglass shape, and a cutout portion 14 matching the opening shape of the opening upper edge 10a of the exhaust port 10 is provided on a part of the outer peripheral surface of the exhaust valve 13. Shaft portions 15 are provided at both ends of the exhaust valve 13 along the axial direction, and these shaft portions 15 are axially supported by a cylinder block 17 via bearings 16. Then, as shown in FIG. 1, the exhaust valves 13 of each cylinder 7 are coaxially connected via a joint 13 a, and these exhaust valves 13 are rotated by a servomotor 19.

That is, the shaft portion 15 of the one exhaust valve 13 is led out to the outside of the cylinder block 17. This shaft 15
A pulley 18 is bolted to the lead-out end of the wire, and a wire 21 is wound between the pulley 18 and a pulley 20 driven by a servomotor 19. The servo motor 19 is rotated by a predetermined angle in the forward and reverse directions according to the rotation speed of the engine 6. In the case of this embodiment, the rotation speed (rpm) of the engine 6 is set to CDI as shown in FIG.
The pulse signal is detected from the ignition pulse of the unit 22 and the pulse signal is equal to or higher than a predetermined level.
000 (rpm), control unit 2
3 outputs a drive signal to the servomotor 19. In this case, the rotation speed of the engine 6 is 5000 (r
pm), the exhaust valve 13
The outer peripheral surface of the exhaust port 10 has advanced to the upper edge 10a of the opening of the exhaust port 10, and the opening height of the exhaust port 10 is correspondingly lowered, and the exhaust timing is delayed. When the rotation speed of the engine 6 exceeds 5000 (rpm), the servo motor 1
Since 9 rotates the exhaust valve 13 by a predetermined angle in the clockwise direction in FIG. 6 via the pulleys 18, 20 and the wire 21, the outer peripheral surface of the exhaust valve 13 recedes from the opening upper edge 10a of the exhaust port 10, Notch 14 of exhaust valve 13
Coincides with the opening upper edge 10 a of the exhaust port 10. For this reason,
The opening height of the exhaust port 10 becomes high, and the exhaust timing becomes early.

On the other hand, the crankcase 24 of the engine 6 is provided with an oil pump 25 that supplies lubricating oil to the lubricated portion of the engine 6 including the crankshaft 6a. Details of the oil pump 25 are shown in FIGS. 3 and 4.

That is, reference numeral 26 in the drawing is a pump case, and a guide hole 27 is formed in the pump case 26.
A plunger 28 is fitted in the guide hole 27 so as to be rotatable about the axis and reciprocally movable in the axis direction. The plunger 28 includes a large diameter shaft portion 29 and a small diameter shaft portion 30. A worm wheel 31 is formed on the outer peripheral surface of the large-diameter shaft portion 29, and the worm wheel 31 meshes with a worm 32 that is rotationally driven by the crankshaft 6a.

Therefore, the plunger 28 has the worm wheel 31.
Also, it is interlocked with the crankshaft 6a via the worm 32, and is rotationally driven by power transmission from the crankshaft 6a.

At the boundary between the large-diameter shaft portion 29 and the small-diameter shaft portion 30, there is formed a groove 33 that is continuous in the circumferential direction. The concave groove 33 faces the step portion 34 on the inner surface of the guide hole 27, and forms an annular first pump chamber 35 between the groove 33 and the step portion 34.
Inside the small-diameter shaft portion 30, a cylinder hole 3 extending in the axial direction is formed.
6 is formed. In the cylinder hole 36, the rod 3
7 is slidably inserted in the axial direction.
A second pump chamber 38 is formed between the tip surface of 7 and the end of the cylinder hole 36. On the outer peripheral surface of the small-diameter shaft portion 30, a suction switching port 40 that communicates with the first pump chamber 35 via a communication hole 39 that extends in the radial direction of the plunger 28, a discharge switching port 41, and a suction that communicates with the second pump chamber 38. The switching port 42 and the discharging switching port 43 are opened, and these switching ports 40 and 41 and 42 and 43 are provided at positions facing each other in the radial direction of the small-diameter shaft portion 30.

As shown in FIG. 4, on the inner surface of the guide hole 27, a pair of suction ports 44 that are opposed to and match the suction switching ports 40 and 42 as the plunger 28 rotates are formed opposite to each other. These suction ports 44 are connected to a suction passage 46 in the pump case 26. Also, on the inner surface of the guide hole 27,
At the position orthogonal to the suction port 44, the discharge switching port 41,
Four discharge ports 45, which are momentarily opposed to each other with 43, are provided so that two discharge ports 45 face each other. These discharge ports 45 are
It is connected to each lubricated portion of the engine 6 via four discharge passages 47 in the pump case 26.

A rotation shaft 48 extending in a direction orthogonal to the plunger 28 is housed in the pump case 26 so as to be rotatable about its axis. A peripheral surface of the rotary shaft 48 faces one end surface of the plunger 28, and a cylindrical cam 29 is coaxially formed on the one end surface of the plunger 28. The end surface of the cylindrical cam 49 has a cam surface 50 having valleys and peaks alternately.
Are continuously formed in the circumferential direction, and the cam surface 50 is pressed against the circumferential surface of the rotary shaft 48 by the urging force of the spring 51. At the center of one end surface of the plunger 28, a protrusion 52 having a height higher than the maximum lift amount of the cylindrical cam 49 is formed. On the peripheral surface of the rotary shaft 48 facing the protrusion 52, a recess 53 continuous in the circumferential direction is formed. The bottom surface of the recess 53 is eccentric with respect to the rotary shaft 48, and forms a cam surface 54 that comes into contact with and separates from the protrusion 52 according to the rotation of the rotary shaft 48. The recess 53 and the projection 52 of the plunger 28 constitute an adjusting means for changing the stroke amount of the plunger 28.

Therefore, when the rotary shaft 48 is rotated to the fully closed position, the protrusion 52 is closest to the cam surface 54, the stroke of the plunger 28 is limited, and the rotary shaft 48 is opened from the fully closed position. When rotated in the direction, the cam surface 54 separates from the protrusion 52, and the stroke of the plunger 28 increases.

The tip of the rotary shaft 48 is led out of the pump case 26. A lever 55 for rotating the rotating shaft 48 in the axial direction according to the opening degree of the throttle 56 and the rotation speed of the engine 6 is attached to the lead-out portion of the rotating shaft 48. The operation system of the rotary shaft 48 will be described with reference to FIGS. 1 and 2, and reference numeral 57 in the drawings is a flexible operation wire. The operation wire 57 includes an outer tube 58 and an inner wire 59 slidably inserted in the outer tube 58. Wire holders 60 and 61 are caulked to both ends of the outer tube 58 of the operation wire 57. One wire holder 60 is fixed near the pulley 20 of the servomotor 19 and the other wire holder 6
1 is rotatably connected to a lever 55 of the rotary shaft 48 via a pin 62. The operation wire 57 is curved in an arc shape between the pulley 20 and the lever 55, one end of the inner wire 59 is locked to the pulley 20, and the other end is linked to the throttle 56. .

Therefore, when the throttle 56 is opened, the operation wire 57
Since the inner wire 59 is pulled in the direction of arrow A in FIG. 1, as shown in FIG. 2, the portion from the curved portion of the operation wire 57 to the other wire holder 61 moves in the pulling direction of the inner wire 59, The lever 55 is rotated from the fully closed position in the opening direction by a predetermined angle. Further, when the rotation speed of the engine 6 exceeds 5000 (rpm) and the pulley 20 is rotated in the direction of the arrow B for opening the exhaust valve 13 by the operation of the servomotor 19, only the inner wire 59 is pulled in the opposite direction this time. Therefore, the portion from the curved portion of the outer tube 58 to the other wire holder 61 moves in the pulling direction of the inner wire 59 similarly to the above. Therefore, the wire holder 61 is pushed out, and the lever 55 is rotated in the opening direction by a predetermined angle in the same manner as when the throttle 56 is opened.

From this, in the case of this embodiment, the pulleys 18, 20,
The wire 21 and the operation wire 57 are the exhaust valve 1 described above.
3 constitutes a control means for linking the rotary shaft 48 with the rotary shaft 3.

Next, the operation of the above configuration will be described.

When the plunger 28 is rotated by the power transmission from the crankshaft 6a as the engine 6 is started, the cylindrical cam 49 is rotated.
The cam surface 50 is in sliding contact with the peripheral surface of the rotating shaft 48, and the plunger 28 reciprocates according to the shape of the cam surface 50. When the plunger 28 is slid to the right side in FIG. 3 by the urging force of the spring 51, the inner volumes of the first pump chamber 35 and the second pump chamber 38 are expanded, and at the same time the suction switching ports 40, 42 are sucked. Matches mouth 44. Therefore, the plunger 28 enters the suction stroke, and the lubricating oil is discharged from the suction port 4
4 is sucked into the pump chambers 35 and 38.

Next, the plunger 28 moves to the third position depending on the shape of the cam surface 50.
When it is slid to the left in the figure, this time the first pump chamber 35
And the internal volume of the second pump chamber 38 is reduced, and the sucked lubricating oil is pressurized, and at the same time, the discharge switching port 4
1, 43 match the one discharge port 45. For this reason, the lubricating oil pressurized in the pump chambers 35, 38 is
5 is discharged to each lubrication part of the engine 6 through the discharge passages 5 and the discharge passages 47 connected thereto.

In addition, such a discharging operation of the lubricating oil is performed by the discharge port 45.
Are opened at opposite positions on the inner surface of the guide hole 27, that is, they are opened with a phase difference of 180 ° in the rotation direction of the plunger 28. Therefore, the rotation is performed twice during one rotation of the plunger 28. It will be.

By the way, since the amount of lubricating oil discharged per one revolution of the engine 6 (crankshaft 6a) is determined by the stroke amount of the plunger 28, the opening of the throttle 56 is small and the number of revolutions of the engine 6 is 5000. (R
When it is in a low rotation region where it does not reach pm), since the displacement amount of the operation wire 57 is small, the rotation shaft 48 is rotated to the fully closed position. When the rotary shaft 48 is at the fully closed position, the cam surface 54 of the recess 53 and the protrusion 52 of the plunger 28 are in the closest positional relationship. For this reason,
With the rotation of the plunger 28, the cam surface 5 of the cylindrical cam 49
The projection 52 comes into contact with the recess 53 before the valley of 0 comes into sliding contact with the rotary shaft 48. Due to this contact, the plunger 28
Can no longer make a stroke, and the lift amount of the cylindrical cam 49 is apparently reduced. Therefore, the stroke of the plunger 28 is shortened and the amount of lubricating oil discharged is also reduced.

In such an operating state, when the throttle 56 is fully opened, that is, when the opening degree of the throttle 56 is 1/1, the rotary shaft 48 is moved in a predetermined opening direction from the fully closed position via the operation wire 57 and the lever 55. The bottom surface of the recess 53 of the rotary shaft 48 is rotated by an angle, and is separated from the projection 52 of the plunger 28. For this reason, the sliding contact range of the cam surface 50 with respect to the rotating shaft 48 becomes long, and as shown in FIG.
The stroke of No. 8 increases, and the amount of oil discharged per one revolution of the engine 6 increases.

When the rotation speed of the engine 6 exceeds 5000 (rpm) by the opening operation of the throttle 56 and reaches the middle / high rotation range, the servo motor 19 operates and the pulley 20 rotates. Therefore, the exhaust valve 13 starts to open, and the exhaust timing becomes earlier. Further, since the inner wire 59 of the operation wire 57 is connected to the pulley 20, the inner wire 59 is wound around the pulley 20, and the bent portion of the outer tube 58 causes the inner wire 59 to be wound on the other wire holder 6.
The part up to 1 moves in the pulling direction of the inner wire 59. Therefore, since the lever 55 is further rotated in the opening direction, the sliding contact range of the cam surface 50 with respect to the rotating shaft 48 becomes longer.

Therefore, the stroke of the plunger 28 becomes longer, and the rotation speed of the engine 6 becomes 500 as shown in FIG.
At the time of reaching 0 (rpm), the discharge amount of the lubricating oil rapidly increases.

On the other hand, when the engine 6 is in the high rotation speed range of more than 5000 (rpm) and the engine brake is operated with the throttle 56 fully closed, for example, if the rotation speed of the engine 6 is 5000 (rpm) or more. The exhaust valve 13 is held in the open position retracted from the upper edge of the opening of the exhaust port 10. Therefore, the lever 55 of the rotating shaft 48 is kept rotated in the opening direction by the operation wire 57, and as long as the engine load is small, the rotation speed of the engine 6 is in the high rotation range. The stroke of the plunger 28 is maintained in a long state, and the amount of lubricating oil discharged can be increased.

According to such an embodiment of the present invention, the oil pump 2
The rotary shaft 48 for increasing / decreasing the oil discharge amount of No. 5 is linked to the servomotor 19 for opening / closing the exhaust valve 13 via the operation wire 57, so that the exhaust valve 13 can adjust the opening height of the exhaust port 10. As long as it is actuated in the raising direction, the rotation shaft 48 moves the plunger 28 of the oil pump 25.
Is operated to lengthen the stroke of.

For this reason, the exhaust timing is particularly early and the piston 8
In an operating state in which the heat load is high, it is possible to supply a sufficient amount of lubricating oil to the lubricated portion of the engine 6 including the piston 8. Therefore, the seizure of the piston 8 and the overheating of the engine 6 can be reliably prevented, and the reliability of lubrication is significantly improved.

Further, in the case of the present embodiment, the stroke of the plunger 28 of the oil pump 25 is controlled by both the rotation speed of the engine 6 and the opening degree of the throttle 56, so that the discharge amount of the lubricating oil can be controlled in any operation of the engine 6. The required amount can be automatically adjusted according to the situation, and there is an advantage that it contributes to the improvement of the reliability of lubrication.

In the above embodiment, the rotary shaft of the oil pump is operated by the power transmission from the servo motor that drives the exhaust valve, but the present invention is not limited to this, and for example, to operate the rotary shaft. Alternatively, the rotation shaft may be operated by providing a dedicated motor and controlling the motor according to the rotation speed of the engine.

[Effect of the Invention] According to the present invention described in detail above, as long as the exhaust valve is operated in the direction of increasing the opening height of the exhaust port, the plunger of the oil pump is continuously operated in the direction of increasing the stroke. Therefore, especially in an operating state in which the exhaust timing is advanced and the heat load on the piston is high, a sufficient amount of oil can be supplied to the lubricated portion of the engine including the piston.

Therefore, seizure of the piston and overheating of the engine can be reliably prevented, and the reliability of lubrication is significantly improved.

[Brief description of drawings]

The drawings show one embodiment of the present invention, FIG. 1 is a configuration diagram showing a control system of an oil pump and an exhaust valve, FIG. 2 is an operation explanatory diagram of a lever of an oil pump, and FIG. 1 is a sectional view taken along line III-III in FIG. 4, FIG. 4 is a sectional view taken along line IV-IV in FIG. 3, and FIG. 5 is a sectional view taken along line VV in FIG. FIG. 7 is a cross-sectional view of a two-cycle engine, FIG. 7 is a block diagram showing a control system of an exhaust valve, FIG. 8 is a characteristic diagram showing a relationship between an engine speed and a stroke of a plunger, and an oil discharge amount. The figure is a side view around the front of the motorcycle. 6a ... crankshaft, 8 ... piston, 10 ... exhaust port, 13 ... exhaust valve, 18, 20, 21, 57 ...
Control means (pulley, wire, operation wire), 25 ... Oil pump, 28 ... Plunger, 48, 52, 53 ...
... Adjusting means (rotating shaft, protrusion, recess).

Claims (1)

[Claims] 1. An oil equipped with an exhaust valve for changing exhaust timing by changing an opening height of an exhaust port opened and closed by a piston, and a plunger reciprocating in an axial direction by power transmission from a crankshaft. In a two-cycle engine equipped with a pump and an adjusting means for increasing / decreasing the oil discharge amount per engine revolution by changing the stroke amount of the plunger of the oil pump, the engine speed is set to a preset value. When it is lower than the above, the exhaust valve is operated in a direction in which the opening height of the exhaust port is lowered, the adjusting means is operated in a direction in which the stroke of the plunger is shortened, and the engine speed is set to the set value. When it exceeds the above, operate the exhaust valve in the direction in which the opening height of the exhaust port increases and A two-cycle engine characterized by comprising control means for operating the adjusting means in a direction in which the stroke of the plunger becomes longer.