JPH0618008Y2 - Oil return device for 4-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an oil return device for a 4-cycle engine in which the sliding direction of a piston is set in the horizontal direction.

[Conventional technology]

In a 4-cycle engine, oil is supplied to the gap between the piston and the inner surface of the cylinder in order to make the piston slide smoothly. This oil may be mixed in the combustion chamber due to the negative pressure in the combustion chamber and the positive pressure in the crank chamber generated during the intake stroke of the engine.

Therefore, conventionally, a recess is formed in the side surface of the piston that moves up and down in the cylinder, and a communication hole is formed in the piston skirt so that the recess communicates with the crank chamber. It is known that the amount of oil mixed into the combustion chamber is reduced by allowing the oil to naturally flow from the hole to the crank chamber side (Shokai 60-147737).
(See Japanese Patent Publication).

[Problems to be solved by the device]

However, in the engine in which the sliding direction of the piston is set horizontally, when the recess and the communication hole are provided as in the above-described prior art, the oil below the sliding surface of the piston does not return to the crank chamber. Moreover, since the piston slides in the horizontal direction, the oil on the sliding surface of the piston naturally flows down on the sliding surface and collects under the sliding surface. Therefore,
This oil is caused by the pressure difference between the combustion chamber and the crank chamber,
Since it mixes in the combustion chamber, not only the consumption of oil increases, but also problems such as carbon adhering to the inner wall of the combustion chamber occur.

This is because, for example, as disclosed in Japanese Utility Model Laid-Open No. 52-18308, a plurality of small holes are bored in the inner peripheral wall of the cylinder liner, and the oil scraped up by the oil ring of the piston is Even if it is configured such that it is extruded through the small hole and penetrates into the gap formed in the fitting portion between the cylinder liner and the cylinder block, it has substantially the same problem.

Further, conventionally, an oil return passage that communicates a plurality of mutually shielded crank chambers is formed in the shield portion, and pistons that operate in reverse to each other are provided corresponding to each crank chamber,
In one of the descending strokes of one piston, the oil that is scraped out by the oil ring of that piston from the sliding surface of the cylinder part is returned to the crank chamber in the ascending stroke of the other piston through the oil return passage. It is known (see Japanese Utility Model Publication No. 60-24889).

According to the above configuration, even if the sliding direction of the piston is set to the horizontal direction, the positive pressure in the crank chamber during the downward stroke of the piston and the negative pressure in the other crank chamber during the upward stroke of the piston cause The oil on the sliding surface of one piston can be forcibly returned to the other crank chamber through the return passage.

However, according to the above configuration, it is possible to apply only to an engine in which a plurality of crank chambers are separated from each other, cannot be applied to an engine having a single crank chamber, and lacks versatility.

The present invention has been made in order to solve the above problems, and provides an oil return device for a four-cycle engine that effectively prevents oil from entering the combustion chamber and has a simple structure and versatility. With the goal.

[Means for Solving the Problems]

In the oil return device according to the present invention, a recess for oil storage is formed on the outer peripheral surface of the lower portion of the sliding surface of the piston, and a return passage having at least one end opened to the crank chamber is provided at the lower portion of the sliding surface of the cylinder portion. A check hole is formed in the wall below the sliding surface of the cylinder to form a communication hole that is formed within the wall thickness and that connects the recess to the return passage over the entire upward and downward strokes of the piston. Is provided, and the return passage is closed by the positive pressure of the crank chamber during the downward stroke of the piston, and the return passage is opened by the negative pressure of the crank chamber during the upward stroke of the piston. To do.

[Action]

According to the above configuration, in the state where the return passage is closed by the check valve during the downward stroke of the piston, the oil in the recess can be scraped out from the communication hole into the return passage by the top ring.

Next, during the upward stroke of the piston, the crank chamber side step of the recess can scrape out the oil in the recess into the return passage from the communication hole. At this time, the check valve is opened by the negative pressure in the crank chamber, and the oil in the return passage is sucked into the crank chamber.

As described above, according to the above configuration, even when the sliding direction of the piston is set to the horizontal direction, the positive pressure of the crank chamber during the downward stroke of the piston and the negative pressure of the other crank chamber during the upward stroke of the piston are both Then, the oil on the sliding surface of the piston can be forcibly returned to the crank chamber through the recess and the oil return passage to effectively prevent the oil from entering the combustion chamber.

Moreover, according to the above configuration, it is possible to apply to an engine having a single crank chamber, and it is possible to provide a versatile oil return device.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1 showing the first embodiment of the present invention, 1 is a piston, 2 is a cylinder barrel, 3 is a crank shaft, 4 is a crank chamber, 5 is a cylinder head, 6 is a combustion chamber, 7 is a rocker arm chamber, and 8 is a rocker arm chamber. Is an oil pan, 9 is an oil splasher,
10 is a flywheel, 11 is a recoil starter, 12
Is a return passage, and 13 is a communication hole.

This engine is a vertical shaft shift engine in which a crankshaft 3 is arranged in the vertical direction, and a sliding direction of a piston 1 is set to a horizontal direction. The cylinder barrel 2 is formed by integrally casting a cylinder portion 2a and a crankcase portion 2b, a return passage 12 is horizontally provided in a lower portion of the cylinder portion 2a, and a communication hole 13 is vertically provided.

The return passage 12 is for returning the oil A to the crank chamber 4 side, and the check valve 14 is provided at one end opened to the crank chamber 4.
Is provided. The communication hole 13 is the return passage 12 described above.
Is opened in the lower portion of the cylinder inner surface 2c, and is provided closer to the crank chamber 4 than the top ring 15 at the bottom dead center of the piston 1. The check valve 14 is operated by the positive pressure of the crank chamber 4 during the piston descending stroke to cause the return passage 12 to move.
The crank chamber 4 on the other hand
The negative pressure of 2 opens the return passage 12 to the crank chamber 4.

In the lower part of the sliding surface 1a of the piston 1, there is a recess 1b at a position facing the communication hole 13, the length from the step 1c to the oil ring 16 and at a predetermined angle in the circumferential direction of the piston 1. It has a width of eggplant. The recess 1b always faces the communication hole 13 when the piston 1 slides. That is, the step portion 1c and the oil ring 16 do not pass over the communication hole 13.

Reference numeral 17 is a breather that allows blow-by gas in the rocker arm chamber 7 to escape to the atmosphere or downstream of an air cleaner (not shown).

Next, the flow of oil accompanying the operation of the engine will be described.

The crankshaft 3 is rotated by the recoil starter 11 to start the engine, and finally the engine enters an operating state. Along with this operation, the oil A in the oil pan 8 is scattered in the crank chamber 4 by the oil splasher 9 operated by the rotation of the crankshaft 3. On the other hand, due to the sliding of the piston 1, the pressure in the crank chamber 4 rises and the pressure in the combustion chamber 6 falls during the piston descending stroke. As a result, the crank chamber 4 becomes higher in pressure than the combustion chamber 6, the check valve 14 closes the return passage 12, and the mist-like oil A is supplied to the gap between the piston 1 and the cylinder inner surface 2c. The supplied oil A naturally flows down the sliding surface 1a of the piston 1 and collects in the recess 1b of the piston 1.

The accumulated oil A is scraped out from the communication hole 13 to the return passage 12 by the oil ring 15 during the piston descending stroke, and by the step portion 1c during the piston ascending stroke.
At the same time, it is scraped out to the return passage 12. On the other hand, when the piston is in the upward stroke, the check valve 14 opens the return passage 12 due to the negative pressure in the crank chamber 4, and the oil A accumulated in the return passage 12 is sucked into the crank chamber 4. .

In the above configuration, since the piston 1 is arranged so as to slide in the horizontal direction, the oil A easily collects in the gap between the lower portion of the piston 1 and the cylinder inner surface 2c. Particularly, in the small general-purpose engine of this embodiment, the oil pan 8 is the piston 1.
Since it is close to the lower part of the oil, oil A is more likely to accumulate. here,
In this invention, a communication hole 13 is provided so that the accumulated oil A is stored.
Is discharged to the return passage 12, and the return passage 12
Is opened to the crank chamber 4 side to return the oil A to the crank chamber 4 side. Therefore, there is little risk that the oil A will be mixed in the combustion chamber 6.

Further, since the position of the communication hole 13 is closer to the crank chamber 4 than the top ring 15 at the bottom dead center of the piston 1,
The combustion chamber 6 and the return passage 12, that is, the crank chamber 4 do not communicate with each other through the communication hole 13. Therefore,
Since the air-fuel mixture compressed in the combustion chamber 6 does not escape to the crank chamber 4, normal operation of the engine is not hindered.

Particularly, in the above embodiment, the check valve 14 is provided in the return passage 12.
Since the check valve 14 closes the return passage 12 during the piston ascending stroke, it is possible to prevent the oil A from flowing from the crank chamber 4 into the return passage 12.
Further, since the recess 1b is provided at a position facing the communication hole 13 in the piston 1, the oil A accumulated in the gap between the piston 1 and the cylinder inner surface 2c is prevented by the oil ring 15 and the step portion 1c. Since the oil is scraped out to the return passage 12, the discharge of the oil A is promoted.

FIG. 2 shows a second embodiment of the present invention, in which 18 is an oil supply passage which is provided in the cylinder barrel 2 and the cylinder head 5 and which connects the crank chamber 4 and the rocker arm chamber 7. Accordingly, the oil A is supplied from the crank chamber 4 to the rocker arm chamber 7. 1
An oil return passage 9 returns the oil A from the rocker arm chamber 7 to the crank chamber 4, and a part of the oil return passage 19 serves as a return passage 12. Two
Reference numeral 0 is a check valve, which is a locker arm chamber 7 of the oil supply passage 18.
Is provided at the side outlet, and the crank chamber 4 and the locker arm chamber 7 are provided.
Due to the pressure difference between and, it closes during the piston ascending stroke and opens during the piston descending stroke. Other configurations are similar to those of the first embodiment, and the same components are designated by the same reference numerals and detailed description thereof will be omitted.

In the above structure, the mist-like oil A is supplied from the crank chamber 4 to the rocker arm chamber 7 through the oil supply passage 18 in which the check valve 20 is opened by the positive pressure of the crank chamber 4 during the piston lowering stroke. It The supplied oil A is sucked into the crank chamber 4 through the oil return passage 19 due to the negative pressure in the crank chamber 4 during the piston ascending stroke. Here, in this embodiment, since the check valve 20 that closes the oil supply passage 18 during the piston rising stroke is provided, only the oil return passage 19 is opened during the piston rising stroke. Therefore, the suction force of the oil A from the return passage 12 does not decrease during the piston ascending stroke.

Further, since the return passage 12 is a part of the oil return passage 19, it is not necessary to separately provide the return passage 12, so that the structure is simplified.

[Effect of device]

As described above, according to the present invention, the oil that collects in the lower portion of the piston of the engine in which the sliding direction of the piston is set in the horizontal direction is transferred from the communication hole to the return passage through the return passage.
It can be returned to the crankcase side. Therefore,
Oil is effectively prevented from being wasted, carbon is not accumulated in the combustion chamber, and white smoke is not emitted. Moreover, according to this invention, it is possible to apply to an engine having a single crank chamber, and it is possible to provide a versatile 4-cycle engine oil return device.

[Brief description of drawings]

1 is a longitudinal sectional view showing a first embodiment of the present invention, and FIG.
The drawing is a vertical cross-sectional view showing a second embodiment. DESCRIPTION OF SYMBOLS 1 ... Piston, 1a ... Sliding surface, 1b ... Recess, 2a ... Cylinder part, 2c ... Cylinder inner surface, 4 ... Crank chamber, 12 ...
Return passage, 13 ... Communication hole, 14 ... Check valve, 15 ... Top ring, 19 ... Oil return passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Showa 52-18308 (JP, U) Showa 60-24889 (JP, Y2)

Claims (2)

[Scope of utility model registration request] 1. A four-cycle engine oil return device in which the sliding direction of a piston is set horizontally.
A recess for oil storage formed on the outer peripheral surface of the lower part of the sliding surface of the piston, and a return passage formed in the lower wall thickness of the sliding surface of the cylinder part with at least one end opening into the crank chamber. , A communication hole formed in the lower part of the sliding surface of the cylinder portion and communicating the recess with a return passage over the entire upward and downward strokes of the piston, and the return passage through the normal passage of the crank chamber in the downward stroke of the piston. A check valve that closes with pressure and opens with negative pressure in the crank chamber during the upward stroke of the piston, and in the state where the return passage is closed with the check valve during the downward stroke of the piston, the recess is formed by the top ring. The oil in the station is scraped out from the communication hole into the return passage, and in the ascending stroke of the piston, the recess is formed by the step on the crank chamber side of the recess. The oil in the return passage is sucked out into the crank chamber by the negative pressure of the crank chamber while the oil in the return passage is being scraped out into the return passage. 4 cycle engine oil return device. 2. The four cycle according to claim 1, wherein the return passage constitutes a part of an oil return passage from a rocker arm chamber provided at the top of a cylinder head to the crank chamber. Engine oil return device.