JPH0152572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an oil-free two-stroke engine used, for example, in a brush cutter.

(Prior art) A general two-stroke engine (for example,
No. 56-2425), oil and air are mixed with fuel and turned into a mist. Normally, each bearing part of the shaft is lubricated.

Mixing oil in fuel in this way
This has the disadvantage of not only wasting oil, but also requiring special mixing equipment and lubrication operations. Moreover, when oil is mixed with fuel and combusted, not only does the exhaust gas turn blue, but a large amount of carbon adheres to the combustion chamber, exhaust port, and muffler, resulting in a change in the volume of the combustion chamber and a decrease in the compression ratio. As a result, output performance may be reduced, or the muffler's muffler muffling holes may become clogged, resulting in a loss of durability.

In addition, such carbon adheres to the piston surface, impairing the heat dissipation of the piston, resulting in thermal troubles. Furthermore, such carbon also adheres to the inside of the crankcase, and when the air is scavenged, it adheres to the sliding surface of the cylinder, resulting in the disadvantage that the sliding surface of the cylinder becomes poor due to the adhesion of carbon. Also,
Carbon also adhered to the electrodes of spark plugs, causing bridging and short-circuiting, which sometimes resulted in poor starting. Furthermore, when oil is used, the outside of the engine is stained by oil due to oil spillage or oil leakage during refueling, resulting in the inconvenience of deteriorating the appearance of the engine.

(Object of the invention) This invention was made in view of the above problems, and eliminates oil consumption while maintaining the performance that sliding surfaces and bearing parts should have. The purpose is to eliminate the need for additional work, drastically reduce carbon adhesion to various parts due to oil, and effectively maintain engine performance.

(Structure of the Invention) The present invention has been made to achieve the above object, and includes a piston pin that connects a piston and a conrod, and a piston pin that connects a piston and a connecting rod, and a piston pin that connects a piston and a connecting rod. The bearings installed between the large end of the connecting rod and the crankshaft, and the crankshaft bearings are dry type or oil-sealed bearings, and the piston rings are made of low-friction, heat-resistant synthetic resin. By coating the outer circumference of the piston with a low-friction, heat-resistant synthetic resin, the entire operating system within the engine, from the piston sliding surface to the crankshaft bearing, is completely oil-free. .

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

Figure 1 shows a two-wheel drive system mainly configured for brush cutters.
This is a first embodiment regarding a cycle engine.

Here, 1 is a crankcase made of aluminum material, and this crankcase 1 is
It has a fan case 2 integrally.

The crankcase 1 has shaft support walls 3, 3 facing each other, and a crankshaft 4 is rotatably supported by these shaft support walls 3, 3.

In this case, the crankshaft 4 has the first and second crankshafts.
Both shaft support bearings 5, 5 are supported by fitting into shaft support walls 3, 3, respectively, and in this case, the first and second shaft support bearings 5, 5 are both sealed with rubber plates. It is a sealed ball bearing with a packing 6. Here, the first and second shaft support bearings 5, 5 are arranged closer to the outside of the crankcase 1, while oil seals 7, 7 are fitted inside the respective bearings 5, 5, respectively. It is provided.

The reason why the oil seals 7, 7 are placed inside and the first and second shaft support bearings 5, 5 are placed outside is to protect the first and second shaft support bearings 5, 5 from the high temperature gas in the crankcase 1 as much as possible. This is to protect the bearings and effectively maintain the bearing function and sealing function. Here, there is no oil between the first and second shaft support bearings 5, 5 and the oil seals 7, 7 inside them. is filled.

In this case, each of the bearings 5, 5 is
While the crankcase 1 is made of aluminum, the crankshaft 4 is not allowed to slide against the crankcase 1 in consideration of the fact that it is made of an iron-based material that has higher wear resistance than the crankcase 1. While it is fitted tightly to the crankshaft 4, it is loosely fitted to the crankshaft 4. From this, the first and second shaft support bearings 5,
The oil seal 7 is provided to prevent leakage of oil from between the engine 5 and the crankshaft 4 due to pressure fluctuations.

In addition, the first and second support bearings 5, 5
For example, recently developed dry bearings made of ceramic can be used.

A cooling fan 9 having a mounting portion 8 for the brush cutter main shaft is attached to one end of the crankshaft 4 supported in this way protruding from the crankcase 1.
Cooling air is taken in from a cooling air intake port 10 opened at the bottom of the fan case 2, and the cooling air is guided from the fan case 2 to a cylinder 11, which will be described later.

Further, a driven-side locking plate 13 that constitutes a part of the recoil starter 12 is attached to the other end of the crankshaft 4, and a driving-side locking plate 14 that locks onto this is formed in an annular shape from the crankcase 1. The starter case 16 is attached to a mounting receiving portion 15 that projects integrally with the starter case 16 .

On the other hand, an aluminum cylinder 11 whose inner periphery is plated with Cr is attached to the upper part of the crankcase 1 to reduce friction.A spark plug 18 extending into the combustion chamber 17 and a piston 19 are installed in the cylinder 11. It is provided.

Here, the outer peripheral surface of the piston 19 is coated with a low-friction, heat-resistant synthetic resin by thermal spraying.

The coating material is fluorocarbon resin paint Xylan (trade name, manufactured by Whitford, USA) NO1052 or XYLAR.
(Trade name, manufactured by Whitford, USA) NO201 is suitable. The general properties of the above coating materials include low friction, high wear resistance, and impact resistance.

A piston ring 20 is fitted onto the outer periphery of the piston 19, and the piston ring 20 in this case is made of a low-friction, heat-resistant synthetic resin, such as Vespel (trade name, manufactured by Teikoku Piston Ring Co., Ltd.), which is an ultra-heat-resistant polyimide resin. ) is used.

Further, the piston pin 21 fitted into the piston 19 is fixed to the piston 19 by a rotation prevention pin 22 made of a spring pin, which is connected to the sliding surface between the piston pin 21 and the piston 19. However, in consideration of the fact that the piston pin 21 is not only exposed to high temperatures but also subjected to high loads, the piston pin 21 is fixed to the piston 19 to eliminate the need for lubrication.
Note that other means such as splines may be used to prevent rotation.

On the other hand, the small end 24 of the connecting rod 23 connected to the piston pin 21 and the piston pin 21
There is a bush 2 made of dry bearing between
5 is fitted.

Furthermore, the following oil-sealed bearing is provided between the large end portion 26 and the crank pin 27.

In other words, the oil-sealed bearing in this case consists of the needle bearing 28 arranged around the outer periphery of the crank pin 27, and the outer race 2 around the outer periphery of the needle bearing 28.
9 and a pair of oil seals 30, 30.

The crankshaft 4 has a crank pin 27
The oil seals 30, 30 are fitted into the inner groove 32 of the web 31, and then the needle bearing 28 and the outer race 29 are fitted between the big end 26 and the crank pin 27. The structure is such that the opposing crankshafts 4 are connected by a press-fit type crank pin 27 by fitting them together.

Here, in the outer lace 29,
A pair of oil seals 30, 30 are provided to prevent the grease from leaking out, and are filled with grease in advance.
In order to avoid interference between the oil seal 30 and the connecting rod 23, a thrust gap 33 is provided between the oil seal 30 and the oil seal 30, thereby effectively preventing grease leakage.

FIG. 2 relates to a second embodiment, particularly to a type in which the crankshaft 4 is supported in a cantilevered manner.

Here, oil-sealed bearings are used for the small end 24 and large end 26 of the connecting rod 23. However, the small end 2 in FIG.
The dry bearing shown in No. 4 can be selected as required.

In the case of the second embodiment shown in FIG. 2, the recoil starter 12 is arranged at the lower part (corresponding to the side part in the actual machine) of the crankcase 1. Further, the first and second shaft support bearings 5, 5 each have a pair of sealing gaskets 6, 6 and are arranged in parallel, and an oil seal 7 is arranged between both bearings 5, 5.

As shown above, connect the piston pin 21 to the piston 19.
Since the piston pin 21 and the piston 19 are prevented from rotating, lubrication between the piston pin 21 and the piston 19 is not required.

Additionally, a bearing provided between the small end 24 of the connecting rod 23 and the piston pin 21,
The bearing provided between the big end 26 of 3 and the crankshaft 4 and the bearing of the crankshaft 4 are dry type or oil-sealed bearings, and the piston ring 20 is made of low-friction, heat-resistant synthetic resin. and the piston 19
By coating the outer circumference with a low-friction, heat-resistant synthetic resin, there is no need to replenish oil to the sliding surfaces of the entire operating system from the piston 19 to the crankshaft 4, as well as to the bearings. Now, it has become possible to provide a so-called oil-free two-stroke engine.

As a result, since oil is not mixed with fuel and combusted, not only does the exhaust gas become transparent, but also carbon does not adhere to the combustion chamber 17, exhaust port, and muffler, resulting in a change in the volume of the combustion chamber 17.
This eliminates the inconveniences such as a decrease in compression ratio, resulting in a decrease in output performance, or a clogging of the muffler's muffler muffling holes, which impairs durability.

Moreover, since such carbon does not adhere to the surface of the piston 19, the heat dissipation performance of the piston 19 is not impaired, and therefore thermal troubles are less likely to occur. Furthermore, such carbon does not adhere to the inside of the crankcase 1, so that carbon does not adhere to the sliding surface of the cylinder 11 during scavenging, and the sliding surface of the cylinder 11 does not adhere to the inside of the crankcase 1. It no longer becomes inferior due to the adhesion of. Also, carbon spark plug 18
Since it does not adhere to the electrode portion of the battery and therefore does not cause bridging, there is no possibility of short-circuiting and starting problems. Furthermore, since no oil is used, the outside of the engine is not contaminated by oil due to oil spills or oil leaks during refueling, thereby eliminating the inconvenience of damaging the engine's appearance.

(Effects of the Invention) As explained above, according to the present invention, the entire operating system in the engine from the piston sliding surface to the crankshaft bearing is completely oil-free, so the sliding surface and While effectively maintaining the lubrication performance of the bearing part, it eliminates oil consumption, eliminates the need for special equipment for oil mixing or refueling work, and dramatically reduces carbon adhesion to various parts due to oil, improving engine performance. It has become possible to maintain the system effectively.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the invention;
FIG. 2 is a sectional view showing a second embodiment of the invention. 4...Crankshaft, 19...Piston, 20
...Piston ring, 21...Piston pin, 23...
Storing rod, 24...small end, 26...large end.

Claims (1)

[Claims] 1. A bearing that prevents the piston pin that connects the piston and connecting rod from rotating on the piston, and that is provided between the small end of the connecting rod and the piston pin, and a bearing that is provided between the large end of the connecting rod and the crankshaft. , and the crankshaft bearing is a dry type or oil-sealed bearing, the piston ring is made of a low-friction, heat-resistant synthetic resin, and the outer periphery of the piston is coated with a low-friction, heat-resistant synthetic resin. This is an oil-free two-stroke engine.