JPH0524866Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crankshaft seal structure for an engine used to drive, for example, a scooter or an automatic tricycle.

[Conventional technology]

In many engines of this type, the crankshaft is rotatably supported via a bearing in a through hole formed in the crankcase, and conventionally, an oil seal installed in the through hole seals the inside and outside of the crank. . This oil seal generally has an outer diameter smaller than the inner diameter of the outer ring of the bearing, and is inserted from the outside of the through hole holding the bearing inside with a gap between it and the bearing. It is prevented from slipping out by a member such as a mounting plate attached to the outside of the chamber.

[Problem that the invention attempts to solve]

However, in such a seal structure, the oil seal sometimes moves toward the bearing due to vibrations generated in the crankcase during engine operation. As a result, the lip of the oil seal may slide against the inner ring of the bearing, or the outer circumferential portion of the oil seal may enter the rolling motion of the bearing and become jammed, resulting in shortened lifespans of the oil seal and bearing.

In particular, in two-stroke engines, the crank chamber is used as a pre-pressure chamber, and the negative pressure generated in the crank chamber can cause the oil seal to be sucked toward the bearing, so this tendency is noticeable.

[Means for solving problems]

The present invention has been devised in view of these circumstances, and it is an object of the present invention to provide a crankshaft seal structure that has a simple structure and can extend the life of oil seals and bearings. The crankshaft seal structure according to the present invention holds the bearing in the crankcase by fixing the outer ring inside the through hole, and has a lip on the inner periphery outside of the bearing in the crankcase. An oil seal having a seal body with a U-shaped cross section that is open toward The lip is located further outward in the radial direction and protrudes further toward the bearing in the axial direction than the lip.

[Effect]

In the present invention, the outer circumferential portion of the oil seal is prevented from entering the rolling portion of the bearing by bringing the outer circumferential portion of the oil seal into contact with the outer ring of the bearing.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a sectional view showing a part of an engine in which the crankshaft seal structure according to the present invention is implemented, Fig. 2 is a half sectional view showing an oil seal, and Fig. 3 is a rear view. The reference numeral 1 indicates a crank chamber precompression air-cooled two-stroke engine. This engine 1 includes a cylinder 2 having a cooling fan 2a, a piston 3 held in the cylinder 2 so as to be able to rise and fall, and a crank that is connected to the piston 3 via a connecting rod 4 and rotates as the piston 3 moves up and down. It consists of a shaft 5, a crank case 7 which covers the lower part of the cylinder 2 and a weight 5a which also serves as a crank arm of the crankshaft 5 to form a crank chamber 6.

The crankcase 7 is divided into right and left crankcases 7a and 7b.
Cylindrical portions 8a and 8b are integrally formed in 7b. These cylindrical parts 8a, 8b have through holes 10a, 10b through which the crankshaft 5 is passed, and press-fit parts 12a, 12b for press-fitting and fixing the outer rings 11a, 11a of the bearings 11, 11 are formed inside the through-holes. ing. Inner rings 11b, 1 of press-fitted bearings 11, 11
A crankshaft 5 is inserted into 1b. Therefore, the crankshaft 5 is rotatably supported in the through holes 10a, 10b via bearings 11,11. Here, the inner diameter of the portion of the through hole 10b outside the press-fitting portion 12b where an oil seal (to be described later) is mounted is larger than the inner diameter of the bearing outer ring 11a and smaller than the outer diameter of the outer ring 11a.

Reference numeral 15 denotes an oil seal for sealing between the inner peripheral surface of the through hole 10a and the crankshaft 5, and the oil seal is mounted by sandwiching the flange 16 integrally provided on the outer peripheral edge between the end surface of the cylindrical portion 8a and the mounting plate 17. It is being

Reference numeral 20 denotes an oil seal installed outside the press-fit portion 12b of the through hole 10b. This oil seal 20 includes a reinforcing ring 21 formed in a cylindrical shape having an inner flange 21a, and a synthetic rubber seal that covers this reinforcing ring 21 and has a U-shaped cross section that is open toward the bearing 11. The main body 22 has an annular spring 2 on the bearing side of the inner circumference 20a.
A main lip 26 is integrally formed with the seal body 22 and is biased radially inwardly by the main lip 26 . This main lip 26 slides on the crankshaft 5 and seals between the crankshaft 5 and the inner peripheral surface of the through hole 10b. Further, a dust strip 27 is formed on the outside of the inner peripheral portion 20a to mainly seal off dust. The outer diameter of the oil seal 20 is set to be slightly larger than the inner diameter of the through hole 10b so that the oil seal 20 is held in the through hole 10b by the elasticity of the seal body 22 itself. Therefore, the bearing side end of the outer peripheral portion 20b is
It faces 1a.

The outer peripheral portion 20b of the oil seal 20 projects further than the main lip 26 in the axial direction. In the embodiment, three protrusions 30 having a height h are provided on the bearing side end surface of the reinforcing ring 21 at equal intervals.

Reference numeral 40 denotes an annular groove provided on the inner circumferential surface of the through hole 10b, and an annular protrusion 41 that protrudes in the outer radial direction from the outer circumferential edge of the oil seal 20 is engaged in the annular groove 40. Since the annular protrusion 41 is formed integrally with the seal main body 22 and has elasticity, it does not prevent the oil seal 20 from being inserted into the through hole 10b, and after entering the annular groove 40, the oil seal Prevent 20 from getting out.

Note that 50a and 50b are scavenging passages that communicate between the crank chamber 6 and the inside of the cylinder, and 51a and 51b are the bearings 11 of these scavenging passages and through holes 10a and 10b.
This is a lubricating oil passage that communicates with a portion on the outside, and is used to circulate lubricating oil in the air-fuel mixture to lubricate the bearing 11 and the oil seals 15 and 20.

In the crankshaft seal structure configured in this way, the inner diameter of the portion of the through hole 10a on the outside of the press-fit portion 12a is larger than the inner diameter of the bearing outer ring 11a, but smaller than the outer diameter of the outer ring 11a. Since the outer peripheral part 20b of the oil seal 20 installed in the hole 10b is made to protrude further in the axial direction than the main lip 26, vibrations of the cylindrical part 8b that occur with the operation of the engine 1 and the crank chamber 6 after engine assembly are avoided. When the oil seal 20 moves toward the bearing 11 due to the negative pressure inside the oil seal 20,
The protrusion 30 abuts on the end surface of the outer ring 11a of the bearing 11.

Therefore, the movement of the oil seal 20 is stopped,
It is possible to prevent the outer circumferential portion 20b from entering the rolling portion of the bearing 11 and to prevent it from being bitten. In addition, the main lip 26 is connected to the inner ring 11b of the bearing 11.
There is no sliding contact. In addition, oil seal 20
and the outer ring 11 of the bearing 11 is the crankcase 7
Since the protrusion 30 and the outer ring 11a are fixed to each other and do not rotate relative to each other, the contact portion between the protrusion 30 and the outer ring 11a will not be damaged.

In the embodiment, in order to protrude the outer circumferential portion 20b, three protrusions 30 are provided at intervals, so even if the protrusions 30 abut against the outer ring 11a, there is no gap between the outer circumferential portion 20b and the end surface of the outer ring. can be formed. This gap allows the lubricating oil passage 51b and the through hole 10b to communicate with each other and allowing the lubricating oil to flow, so that the bearing 11 and the oil seal 20 can be properly lubricated.

In the above embodiment, an example was explained in which the reinforcing ring 21 was provided with a protrusion 30 so that the outer peripheral part 20b protruded, but the present invention is not limited to this. Alternatively, the seal body 22 may be made to protrude.

[Effect of idea]

As explained above, according to the present invention, the bearing can be
A seal body is held in the crankcase by fixing an outer ring inside the through hole, and has a lip on the inner circumference outside the bearing in the crankcase and has a U-shaped cross section and is open toward the bearing. A crankshaft is rotatably inserted into the oil seal, and the outer circumference of the oil seal is positioned radially outward from the inner ring of the bearing so that the axis line Since the oil seal protrudes toward the bearing along the direction, the outer circumferential portion of the oil seal can be brought into contact with the outer ring of the bearing, and the oil seal can be locked.

Therefore, even if the engine vibrates, the lip of the oil seal will not come into sliding contact with the inner ring of the bearing, and the outer periphery will not get caught in the rolling parts of the bearing, extending the life of the oil seal and bearing. The transformation is measured. Furthermore, when the oil seal moves toward the bearing, the outer circumference of the oil seal contacts the outer ring of the bearing and does not contact the inner ring. Therefore, since the parts that are fixed to the crankcase and do not rotate relative to each other come into contact with each other, the contact parts are not damaged. This also makes it possible to extend the life of the oil seal and bearing. In addition, if the outer periphery of the oil seal is in contact with the bearing, no force is applied to bend the contact part, compared to a structure in which the inner diameter side is in contact with the bearing.
This has the effect that the oil seal does not need to be formed with high strength. Further, by adjusting the inner diameter of the through hole, it can be implemented without requiring any special members, so the structure does not become complicated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a part of an engine in which the crankshaft seal structure according to the present invention is implemented, FIG. 2 is a half sectional view showing an oil seal, and FIG. 3 is a rear view. 5...Crankshaft, 8b...Cylinder part, 10b...
Through hole, 11...bearing, 11a...outer ring, 20...
...Oil seal, 20a...Inner peripheral part, 20b...
Outer peripheral part, 21... Reinforcement ring, 22... Seal body,
26...Main lip, 30...Protrusion.

Claims (1)

[Scope of utility model registration request] In a structure in which a crankshaft rotatably supported in a crankshaft through-hole of a crankcase via a bearing is sealed with an oil seal attached to the through-hole, the bearing is fixed to an outer ring inside the through-hole. In this way, it is held in the crankcase, and on the outside of the bearing in the crankcase, there is a cylindrical reinforcing ring, and a cross-sectional core that covers the reinforcing ring and has a lip on the inner circumference and is open toward the bearing. An oil seal consisting of a letter-shaped seal body is fixed, a crankshaft is rotatably inserted into this oil seal, and the outer circumference of this oil seal is positioned radially outward from the inner ring of the bearing. A crankshaft seal structure characterized in that the lip protrudes toward the bearing along the axial direction.