JPH0134666Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a crank web for a four-stroke engine.

In an engine, a crank web is attached to the crank arm to improve the rotational balance of the crankshaft, and its inertial efficiency is proportional to the weight and proportional to the square of the diameter. On the other hand, in engines such as motorcycles, the crankshaft and transmission shaft are installed side by side inside the engine case, and in 4-stroke engines, the crank chamber and the transmission chamber are not separated and both shafts are placed adjacent to each other. is normal. In this case, the crank web and the outer periphery of the transmission gear face each other most closely. In this situation,
In order to reduce the weight of the crank web without reducing its inertial efficiency, it is necessary to increase the outer diameter as described above, but this increases the distance between the crankshaft and the transmission shaft. This results in an increase in the size of the interlocking gear and case. Conversely, when the crankshaft and transmission axis are brought closer together, the outer diameter of the crank web is compressed, and in order to compensate for the decrease in inertial efficiency, which is proportional to the square of the outer diameter, considerable measures such as increasing the width of the crank web are required. It is necessary to increase the weight.

This idea was developed in view of these contradictory conditions.
To provide a crank web for a four-stroke engine that can be made lighter without increasing the distance between the crankshaft and the transmission shaft and without reducing inertial efficiency.

The figure shows an embodiment of this invention.

A crank case 1 and a transmission case 2 are installed in series without providing a partition wall. A crank mechanism supported by a crankshaft 3 is housed in the crankcase 1 . 4 is a crank web, 5 is a crank pin, and 6 is a connecting rod large end. A transmission shaft consisting of a counter shaft 7 and a drive shaft 8 is mounted on the transmission case 2, and a transmission gear train 9 is pivotally supported between the two shafts 7 and 8 so that a combination of meshing can be selected. A drive gear 10 is disposed on the crankshaft 3 and meshes with a driven gear 11 on the countershaft 7, and the driven gear 11 transmits rotation to the countershaft 7 via an opening/closing clutch 12.

Next, some gears of the transmission gear train 9, for example gears 9a and 9b, are connected to the crank web 4.
It is in the same axial position as. If the outer diameters of the gears 9a and 9b are da and db, the outer diameter of the crank web 4 is D, and the distance between the crankshaft 3 and the countershaft 7 is L, then L<D+da/2 or D+db/2 is set. . A circumferential groove 13 is formed on the outer peripheral surface of the crank web 4.
is provided to prevent gears 9a, 9b and crank web 4 from interfering with each other. The outer diameter of the bottom of the circumferential groove 13
If Da, Db, L>Da+da/2 and Db/
A relationship of db/2 is established.

The above configuration increases the degree of freedom in setting the weight and inertia efficiency of the crank web and the distance between the crankshaft and the countershaft. In other words, if Db is the outer diameter of the conventional crank web, the inertia efficiency increases in proportion to the square of the diameter in the outer diameter part that is enlarged so as not to contact the gears 9a and 9b, so the weight of the crank web increases accordingly. In addition, the distance between the shafts can be reduced without increasing the weight of the crank web or reducing inertial efficiency, and the case, drive, and driven gears 10 and 11 can be made smaller.

In this way, the crank web of the 4-cycle engine according to this invention has a circumferential groove and an enlarged outer diameter so as not to come into contact with the opposing transmission gear, and the inertial efficiency is proportional to the weight and increases to the square of the diameter. Utilizing the proportionality point, it is possible to reduce the weight of the crank web or the distance between the crankshaft and the transmission axis, making the engine smaller and lighter and reducing costs without reducing engine performance. It has the effect that it can.

[Brief explanation of drawings]

The figure is a sectional view of a crank chamber and a transmission chamber of a four-stroke engine showing an embodiment of this invention. 1... Crank room, 2... Mission room, 3...
... Crankshaft, 4 ... Crank web, 7 ... Counter shaft, 8 ... Drive shaft, 9 ... Mission gear train, 9a, 9b ... Mission gear, 10 ...
...Drive gear, 11...Driven gear, 12...
...Opening/closing clutch, 13... Circumferential groove.

Claims (1)

[Scope of utility model registration request] In a 4-cycle engine in which a transmission chamber is connected to a crank chamber and a crank web and a transmission gear are placed close to each other, the distance between the crankshaft and the transmission shaft is determined by the maximum radius of the crank web and the gear facing it. A crank web for a four-stroke engine, characterized in that the web is set smaller than the sum of the sums of the crank webs, and a circumferential groove is provided on the outer peripheral surface of the crank web to avoid contact with overlapping gears.