JPS6113090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive device for a rotary exhaust valve in a two-stroke engine.

In general, in a two-stroke engine that opens and closes the exhaust port, scavenging port, etc. provided in the cylinder by piston action, the exhaust timing is changed slowly or quickly according to the rotational speed of the engine, and the output is adjusted to suit low speed and high speed respectively. I'm trying to get it, but
As a means for changing the exhaust timing, a rotary exhaust valve whose upper edge of the opening is movable is used at the exhaust port.

However, as previously proposed by the present applicant in Utility Application No. 51-42497, an electric method using a servo motor has been adopted for driving the rotary exhaust valve. Since it is operated separately from the motor that serves as the power source, the number of parts for the device increases and it is inconvenient to manufacture, and since it is an electric system, batteries must be kept at all times, and maintenance is not easy. There is.

The present invention has been made in view of the above-mentioned conventional circumstances, and uses the discharge pressure of a lubricating oil pump driven by the crankshaft to mechanically detect the engine rotation speed, and also detects the exhaust valve. By using this as a power source for rotation, the present invention aims to solve the conventional problems and provide a mechanical drive device with a simple structure and excellent durability.

According to the present invention, a piston that is displaced by receiving the discharge pressure of the pump is provided in the discharge side passage of a lubricating oil oil pump that rotates in conjunction with the rotation of the crankshaft, and the displacement of the piston is determined by the amount of change. It is characterized by being linked to the rotation of a rotary exhaust valve according to the requirements.

An example of carrying out the present invention will be explained with reference to the drawings. Fig. 1 shows a two-stroke engine A, in which a is a cylinder, b is a cylinder head, c is a piston, and d is a cylinder head.
is a crankcase, 1 is an exhaust port, 2 is an exhaust valve, 3 is a crankshaft, 4 is a crankcase cover, 5 is a clutch, and p is an oil pump. A housing portion 6 is formed between the crankcase d and the crankcase cover 4.
A crankshaft 3 protrudes inside, and a clutch 5 is housed therein.

The crankshaft 3 has a driving gear 7 pivotally attached to its projecting end, and the gear 7 meshes with a driven gear 8 of the clutch 5.

The housing portion 6 forms an oil reservoir 9 at its bottom to store lubricating oil 10, and an oil pump p is provided in front of the oil reservoir 9.

The oil pump p is a centrifugal pump, and the oil sump 9
A rotating shaft 14 is installed in a pump chamber 11 equipped with a suction side passage 12 communicating with the pump chamber 11 and a discharge side passage 13 rising upward.
is inserted into the shaft 14, and an impeller 15 is pivotally attached to the shaft 14.

Further, a driven gear 16 is attached to the rotating shaft 14 and meshed with the driving gear 7 of the crankshaft 3.

Therefore, the oil pump p rotates in conjunction with the rotation of the crankshaft 3, and the discharge amount increases or decreases depending on the rotational speed of the crankshaft, that is, the rotational speed of the engine A.
The discharge pressure in the discharge side passage 13 also increases or decreases approximately proportionally accordingly. A discharge side passage 13 of the oil pump p is continuous with a discharge side passage 13' formed in a housing 17 constituting a drive device B, which will be described later. The discharge port 18 is connected to the discharge port 18.

Therefore, the lubricating oil 10 is forced into the discharge side passages 13, 13' by the oil pump p, drops from the discharge port 18 into the oil sump 9, and is circulated.

Further, the discharge side passage 13' of the housing 17 is provided with a constriction part 19 having a constant opening amount, and
A sub-passage 20 bypassing the constricted portion 19 is formed.

This secondary passage 20 is provided with a spring 21,
A relief valve 22 is provided which is always biased towards the valve closing side.

The relief valve 22 is configured to open when the pump discharge pressure applied to the auxiliary passage 20 reaches a predetermined pressure or higher, and the opening timing is set by the strength of the spring 21.

Incidentally, the discharge side passage 13' may be provided with a passage communicating with a mission chamber (not shown) in the middle thereof to supply the lubricating oil 10 to the transmission gear. In this case, a communication path communicating with the housing section 6 is provided in the mission chamber to circulate the lubricating oil 10.

The drive device B for the exhaust valve 2 is installed in this discharge side passage 13' so that the pressure in the passage 13' is received.

The drive device B is formed by a housing 17, and includes a cylinder part 23 whose lower end communicates with the discharge passage 13', a piston 24 slidably fitted in the cylinder part 23 in a liquid-tight manner, and the piston 24. The exhaust valve 2 is made of a material whose displacement is linked to the exhaust valve 2.

The bottom surface of the piston 24 faces the discharge side passage 13', and the bottom face receives the pressure inside the discharge side passage 13', that is, the discharge pressure of the oil pump p.

At the upper end of the cylinder portion 23 is a cap 2 that slidably supports a rod 25 connected to a piston 24.
6 is removably attached.

A spring 27 is fitted onto the outer periphery of the rod 25, and the upper and lower ends of the spring 27 are engaged with the cap 26 and the piston 24, respectively.
The piston 24 is always urged downward, and a discharge pressure greater than the elastic force of the spring 27 is applied to the piston 24.
The piston 24 is made to move upward against the spring 27 when it is applied.

The upper end of the rod 25 is made to protrude above the cap 26, and a lever 28 that protrudes radially from the support shaft 2' of the exhaust valve 2 is engaged with the upper end of the rod 25 using a screw 25' and an elongated hole 28'. Lever 28
The vertical movement of the rod 25 is transmitted to the rotational movement of the exhaust valve 2 through the vertical movement of the rod 25.

Therefore, the increase or decrease in the rotational speed of the engine A corresponds to the increase or decrease in the discharge pressure of the oil pump p, and the piston 24 detected by the piston 24 is vertically displaced. The rotation amount of the exhaust valve 2 is converted into the rotation amount of the exhaust valve 2 through the rotation amount.

The exhaust valve 2 is rotatably fitted and supported on the upper surface of the exhaust port 1, and has a substantially semicircular cross section, and its rotation causes the portion that projects into the exhaust port 1 to define the upper opening edge 1' of the exhaust port 1. This constitutes a movable wall.

The rotation of the exhaust valve 2 is set to reciprocate in a predetermined angular range in conjunction with the vertical movement of the piston 24, and when the piston 24 is at the lowest stage, the upper opening edge of the exhaust port 1 is set to the lower limit. When the piston 24 reaches the upper stage position, the upper edge 1' of the opening is set as the upper limit, and the section from the lower limit to the upper limit position is rotated in proportion to the amount of displacement of the piston 24.

When the upper opening edge 1' of the exhaust port 1 is at the lower limit position, the exhaust timing is the latest, that is, the exhaust start time is the latest, the exhaust end time is the earliest, and the exhaust operation time is the shortest, so that engine A can be operated at low speed. As the upper edge of the opening moves upward, the exhaust timing becomes progressively earlier, making it suitable for high-speed operation.

As the engine A operates, the oil pump p operates via the crankshaft 3 and the gears 7 and 16, and discharges the lubricating oil 10 to the discharge side passages 13 and 13', thereby increasing the discharge pressure in the passage 13'. is received by the piston 24. As the rotational speed of the engine A increases, the discharge amount of the oil pump p increases, and the discharge pressure in the discharge side passage 13' increases, and as the pressure increases, the piston 24 resists the elastic force of the spring 27. and moves upward, and the amount of displacement is engine A
Rod 25 and lever 2 change depending on the increase or decrease of rotation speed.
8 to the exhaust valve 2;
is rotated to raise and lower the opening upper edge 1' of the exhaust port 1.

When the engine A reaches a medium to high speed operating range, the exhaust valve 2 is held in the fully open position, but even with the discharge pressure of the oil pump p at that time, the relief valve 22 opens against the elastic force of the spring 21. , secondary passage 2
0 is open, the lubricating oil 10 passing through the discharge side passage 13' reaches the accommodating part 6 through the sub passage 20 in addition to passing through the constriction part 19.

Therefore, after the exhaust valve 2 is fully opened, even if the rotational speed of the engine A increases and the discharge amount of the oil pump p increases, the flow rate passing through the discharge side passages 13, 13' increases, so that the flow rate through the passages 13, 13' The increase in the pump discharge pressure inside the pump is suppressed.

As described above, the present invention uses a piston to receive the discharge pressure of an oil pump operated by the rotation of the crankshaft, detects the engine speed based on the displacement of the piston, and converts the amount of displacement into the rotation of a rotary exhaust valve. Since it is a mechanical device that is linked, the detection part that detects the engine rotation speed and the power source of the exhaust valve are integrated, making it possible to create a device with a simple structure and excellent durability, and it can be done without using conventional electrical devices. It has fewer breakdowns than the previous model, and can be used even in vehicles that do not have a battery as a power source.

By using an oil pump, the engine can be equipped with either a water-cooled or air-cooled cooling system, and maintenance becomes free.

Thus, the intended purpose can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of a two-stroke engine, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is an enlarged sectional view showing the oil pump, and Fig. 4 is a main part of the device of the present invention. FIG. 5 is an enlarged cross-sectional side view of FIG. In the figure, A: 2-stroke engine, B: drive device, a: cylinder, 1: exhaust port, 2: rotary exhaust valve, p: oil pump, 3: crankshaft, 24: piston, 25: rod, 28 :lever.

Claims (1)

[Claims] 1 A piston that receives the discharge pressure of the pump and is displaced is provided in the discharge side passage of a lubricant oil pump that rotates in conjunction with the rotation of the crankshaft, and the displacement of the piston is adjusted according to the amount of displacement. A rotary exhaust valve drive device in a 2-cycle engine that is linked to the rotation of the exhaust valve.