JPS6339447Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a two-stroke multi-cylinder internal combustion engine such as a motorcycle, and particularly to a crank chamber preload type internal combustion engine.

In order to improve vehicle stability and turning performance, this type of internal combustion engine should be placed as low as possible in the vehicle body to lower the center of gravity, and the bank angle should be increased by sandwiching the lateral width. good.

However, when the power extraction gear is attached to the end of the crankshaft, the clutch, reducer, etc. protrude sideways, making it impossible to increase the bank angle. Also, the weight is biased to one side, resulting in poor balance.

Therefore, it is conceivable to arrange the power extraction gear approximately in the center of the crankshaft, for example between adjacent cylinders, but this requires some ingenuity in attaching the gear, oil seal, etc. to the crankshaft.

The present invention has been proposed in view of the above points, and as shown in FIG. Crank pins 22a and 22b for each of the cylinders 1a and 1b are integrally molded on both ends of the intermediate shaft portion 21, and a gear chamber 12 accommodates crank chambers 7a and 7b for each of the cylinders 1a and 1b and the power extraction gear 3. so that a ring-shaped oil seal 11 separating the two can be installed from the end of each crank pin 22a, 22b to the intermediate shaft portion 21 on both sides of the power extraction gear 3.
The intermediate shaft portion 21 and each crank pin 22a, 22
The crank webs 24a and 24b between the crankshaft and the crankshaft are formed separately from the intermediate shaft portion and the crank pin, and are assembled after the oil seal 11 is installed.

The tips of the crank pins 22a and 22b are press-fitted into holes 4a and 4b formed in the outer crank webs 23a and 23b, respectively. , 23b can be formed thickly as shown in the illustrated example. Therefore, crank pin 22
It becomes possible to form the crank webs 24a, 24b between a, 22b and the intermediate shaft portion 21 to be correspondingly thinner. Also, the crank webs 24a, 24b
As shown in FIG. 2, the crank web 24 is mounted between the intermediate shaft portion 21 and the crank pins 22a, 22b with screws 31, etc.
Before installing a and 24b, install the oil seal 1
1 to the crank pin 22a, as shown by the chain line in FIG.
It can be easily loaded by inserting from 22b.

In the figure, 5a and 5b are pistons, 6a and 6b are connecting rods, 8a and 8b are crankcases that are divided into upper and lower parts, and 9 and 10 are bearings that support both ends and the middle part of the crankshaft 2, respectively, and a bearing 10 in the middle part. is structured in two parts.

In the present invention, the intermediate shaft 21 between the adjacent cylinders 1a, 1b of the crankshaft 2 and the gear 3 are integrally formed as described above, so that the connection strength between the two 21, 3 is strong, and furthermore, the crank pins 22a, 22b for each cylinder are integrally formed at both ends of the intermediate shaft 21, so that the strength against the twisting force generated in the crankshaft 2 due to torque fluctuation is strong and durable.
A ring-shaped oil seal 11 is attached to each of the crank pins 22a, 22b, and separates the crank chambers 7a, 7b and the gear chamber 12 that houses the power take-off gear 3.
2b from the end of the intermediate shaft portion 21 so that it can be attached to the intermediate portion 21 on both sides of the power take-off gear 3.
The crank webs 24a, 24b between the crank pins 22a, 22b are formed separately and are configured to be attached after the oil seal 11 is installed. This makes it possible to make the diameter of the seal 11 as small as possible, thereby reducing friction and improving durability by reducing seizure and wear.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of the two-stroke multi-cylinder internal combustion engine of the present invention, and FIG. 2 is an exploded perspective view of a portion of the crankshaft. 1a and 1b are cylinders, 2 is a crankshaft, 21
is an intermediate shaft portion, 22a, 22b are crank pins, 2
3a, 23b, 24a, 24b are crank webs, 3 is a power take-off gear, 7a, 7b is a crank chamber, and 11 is an oil seal.

Claims (1)

[Scope of utility model registration request] A power extraction gear is integrally molded on the intermediate shaft between adjacent cylinders of the crankshaft, and crank pins for each of the cylinders are integrally molded on both ends of the intermediate shaft. The intermediate shaft portion and each crank pin are connected so that a ring-shaped oil seal that partitions the gear chamber housing the extraction gear can be installed from the end of each crank pin to the intermediate shaft portions on both sides of the power extraction gear. A two-stroke multi-cylinder internal combustion engine, characterized in that a crank web between the intermediate shaft portion and the crank pin is formed separately from the intermediate shaft portion and the crank pin, and is assembled after the oil seal is installed.