JPH0245619A - Unit swing type engine - Google Patents

Abstract

PURPOSE:To reduce the flexible deformation rate of a crank shaft, in an unit swing type engine having a vertically divided crank case, by offsetting the center of a connecting rod from the center of a piston. CONSTITUTION:An unit case 2 vertically divided into two parts along the surface in parallel with a crank shaft 8, is provided so as to integrate a crank case and a transmission case with the unit case 2. The center of a connecting rod 12 is offset to an extent epsilon from the center of a piston 6 toward a ball bearing 9b side. Thereby, the overhang rate l of the crank shaft, namely, the distance between the large end part connecting point of the connecting rod and the center of the ball baring 9b, can be shortened, so that the flexible deformation rate of the crank shaft can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a unit swing type engine having a crankcase that is divided into upper and lower parts.

(Prior art) This type of unit swing type engine is mounted on, for example, a scooter-type motorcycle, or it is constructed by compactly combining the cylinder, crankcase, transmission system, and intake/exhaust system into one unit. be done.

By the way, in such a unit swing type engine, the cylinder and the crankcase are constructed as separate members made of different materials, and these are assembled into one piece.

(Problem to be solved by the invention) However, in conventional unit swing engines, the cylinder and crankcase were constructed separately as mentioned above, which simplified the structure and reduced the number of assembly steps. There were limits to efforts to reduce costs.

Therefore, a proposal has been made to integrate the cylinder and the crankcase, or if they are integrated in this way, the cylinder will be placed in a position offset from the crankcase compared to the conventional one in order to enable honing inside the cylinder. If such a configuration is adopted, a cantilever crank type must be adopted.

However, if a cantilevered crank type is adopted, the amount of flexural deformation of the crankshaft increases, so it is necessary to take measures to minimize the amount of overhang of the crankshaft.

The present invention has been made based on the above circumstances, and its purpose is to enable honing of the inside of a cylinder integrated into the crankcase, and to minimize the amount of bending deformation of the crankshaft. It is possible to provide a unit swing type engine.

(Means for Solving the Problems) In order to achieve the above object, the present invention has an upper and lower split crankcase that is divided into upper and lower parts on a plane parallel to the crankshaft, and employs a cantilevered crank type. A unit swing type engine in which a cylinder and a crankcase are integrated is characterized in that the center of the connecting rod is offset from the center of the piston.

Further, the present invention is a similar unit swing type engine, and is characterized in that a bearing that supports one end of the crankshaft is supported by the crankcase boss via a cover member that partially covers the bearing.

(Function) So, should the center of the connecting rod be offset toward the crankshaft bearing side with respect to the center of the piston?

Alternatively, if the crankshaft bearing protrudes toward the connecting rod side, the amount of overhang of the crankshaft, that is, the length between the center of the crankshaft bearing and the connecting point of the large end of the connecting rod, can be minimized. The amount of bending deformation of the crankshaft can be minimized. Incidentally, even if the piston center is offset from the connecting rod center, honing of the cylinder can be performed without any problem. or,
During honing, the crankshaft bearing and the cover member covering it are removed, so these bearing songs and cover members do not interfere with the honing of the cylinder.

(Example) Embodiments of the present invention will be described below based on the accompanying drawings.

Fig. 1 is a side view of a unit swing type engine according to the present invention, Fig. 2 is a sectional view taken along line II-II in Fig. 1, and Fig. 3 is a side view of a shifter type motorcycle equipped with the unit swing type engine. be.

As shown in FIG. 3, the unit swing type engine l according to the present invention is a two-stroke engine that is disposed at the rear of a motorcycle 30 and drives a rear wheel 31, and its front end is connected to a main frame 33 by a vehicle 32. 8.
The rear end portion is suspended from the main frame 33 via a reaction 34. In addition, in the motorcycle 30.

35 is a front wheel, and 36 is a seat.

Details of the unit swing type engine 1 are shown in FIGS. 1 and 2, and the engine 1 has a unit case 2 that is divided into upper and lower halves in a plane parallel to a crankshaft 8, which will be described later. , upper and lower parts 2a, 2 of the unit case 2
b is constructed by integrally including a crankcase and a transmission case.

Further, the cylinder 3 is constructed integrally with the unit case upper part 2a, and this is formed at a position offset from the center of the unit case 2.

By the way, the middle part 2c of the unit case 2.

It extends long in the front-rear direction, and on the outside of this intermediate portion 2c, 1. A vertically divided muffler 4 consisting of lower parts 4a and 4b is integrally attached. The unit case upper part 2a, the cylinder 3, the muffler upper part 4a, and the unit case lower part 2b and the muffler 5 part 4b are integrally formed by aluminum casting or the like.

As shown in FIG. 2, a piston 6 is provided in the cylinder 3.
is fitted in a slidable manner, and an ignition plug 7 is screwed onto the top of the cylinder 3.

On the other hand, in the front part (crankcase part) 2d of the unit case 2, a crankshaft 8 is rotatably supported by two left and right ball bearings 9a, 9b. A flywheel magneto 10 is connected to the outwardly extending end (the left end in FIG. 2), and the outwardly extending end of the other ball bearing 9b of the crankshaft 8 is connected to the flywheel magneto 10. A crank web 11 is tied to the right end (in FIG. 2).

The large end of a connecting rod 12 is rotatably connected to the crank web 11 via a crank pin 13, and the small end of the connecting rod 12 is connected to a piston pin 14.
It is connected to the piston 6 via. As described above, in this embodiment, a so-called cantilever crank type is adopted, and one end of the connecting rod I2 is supported by the single bar hang portion of crank #+8.

However, in this embodiment, the center of the connecting rod 12 is offset from the center of the piston 6 by ε toward the ball bearing 9b as shown.

Further, a centrifugal clutch 15, a chain sprocket 16, and a one-way clutch 17 are installed between both bearings 9a and 9b of the crankshaft 8. In addition, in Figure 2,
18 is a starter motor, and 19 is a kick shaft.

Furthermore, a transmission shaft 20 is rotatably supported in the rear part (transmission case part) 2e of the unit case 2 by a ball bearing 21.21, and a large diameter chain sprocket 22 is attached to the end of the transmission shaft 20. A drive chain 23 is wound between the chain sprocket 22 and the chain sprocket 16. A small-diameter gear 24 is fitted onto the transmission shaft 20, and a rear axle 25 is rotatably supported by ball bearings 26 and 26 and arranged parallel to the transmission shaft 20. A large-diameter gear 27 that meshes with the gear 24 is fitted onto the rear axle 25 . The rear wheel 31 is supported at the end of the rear vehicle 25 that extends outside the unit case 2.

When the unit swing type engine 1 is driven and the rotational speed of the crankshaft 8 reaches a certain value or more, the centrifugal clutch 15 is turned on and the rotation of the crankshaft 8 is transferred to the chain sprocket 16 via the centrifugal clutch 15. The chain sprocket 16 is then rotated. In this way, when the chain sprocket 16 is rotationally driven, this rotation causes the drive chain 23, chains sprockets 1 to 22, . Transmission shaft 20. Gear 24.27 and rear axle 25
The signal is transmitted to the rear wheel 31 through the rotor, and the rear wheel 31 is rotationally driven to move the motorcycle 30 shown in FIG. 3 forward.

In the above, since the center of the connecting rod 12 is offset from the center of the piston 6 by an amount ε toward the ball bearing 9b side, the center of the connecting rod 12 is offset by the amount ε of the oversolder of the crankshaft 8 (the center of the ball bearing 9b As a result, the amount of flexural deformation of the crankshaft 8 can be suppressed to a small value. Since only the center position of the connecting rod is offset without changing its position relative to the belt case 2, the crank 3 can be honed without any problem.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 to 6. In addition, FIG. 4 is a view similar to FIG. 2 of the main part of a unit swing type engine according to another embodiment, FIG. In these figures, the same elements as in the previous embodiment are given the same reference numerals.

The unit swing type engine 1 according to this embodiment also has a unit case 2 divided into upper and lower parts, employs a single cantilever crank type, and has a cylinder 3 integrated with the upper part 2a of the unit case.

In this embodiment, the center of the connecting rod 12 is aligned with the center of the piston 6, or the ball bearing 9b is moved toward the connecting rod 12, and the two halves of the ball bearing 9b are placed on the unit case. It protrudes by a length e from the boss portion 2a-1 of the half portion 2a, and this protrusion is covered by a half-link-shaped cover member 40 interposed between the ball ring 9b and the boss portion 2a-1. It is being said.

Therefore, the overhang kl of the crankshaft 8 becomes smaller as the ball bearing 9b is moved closer to the connecting rod 12, so that the amount of bending deformation of the crankshaft 8 can be kept small.

Furthermore, when honing the cylinder 3 formed integrally with the unit case upper part 2a, the cover member 40 can be removed as shown in FIG. Even though the overhang image of No. 8 is kept small, the honing process of Cylinder 3 can be performed without any problem.

By the way, when the cylinder 3 in the embodiment described above is viewed from a plane (when viewed from the direction of arrow A in FIGS. 1, 2, 4, and 5), the cylinder bore as shown in FIG. Two scavenging ports 41a with 3Noi on 3a,
41b and the exhaust port 42 so that they do not overlap with the ball bearing 9b, the boss f42a-1 (see FIGS. 2 and 4) of the upper part of the unit case 2a will not have insufficient strength or rigidity. It's convenient.

(Effects of the Invention) As is clear from the above description, the present invention has a vertically split crankcase that is divided into upper and lower parts on a plane parallel to the crankshaft, adopts a cantilever crank type, and has a cylinder and a crankcase. In a unit swing type engine that is integrated with the crankcase, the center of the connecting rod is offset from the center of the piston, or the bearing that supports one end of the crankshaft is connected to the crankcase through a cover member that partially covers the bearing. Since it is supported by the boss, it is possible to perform honing inside the cylinder integrated with the crankcase, and it also has the effect of minimizing the amount of bending deformation of the crankshaft.

[Brief explanation of the drawing]

FIG. 1 is a side view of a unit swing type engine according to the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a side view of a scooter type motorcycle equipped with the unit swing type engine. 4 is a view similar to FIG. 2 of the main part of a unit swing type engine according to another embodiment, FIG. Fig. 7 is a schematic view of a cylinder viewed from above, showing the arrangement of scavenging ports and exhaust ports. 1...Unit swing type engine, 2...Unit case, 2a...Unit case upper part, 2a-1・
...Unit case boss part, 2b...Unit case lower part, 3...Cylinder, 6...Piston, 8...
Crankshaft, 9a, 9b...ball bearing, 12
...Conrod, 40...Cover member, 41a, 4
1b...Scavenging port, 42...Exhaust port.

Claims (3)

[Claims] (1) In a unit swing type engine that has a vertically split crankcase that is divided into upper and lower parts on a plane horizontal to the crankshaft, adopts a cantilever crank type, and integrates the cylinder and crankcase, the connecting rod A unit swing type engine characterized by having its center offset from the piston center. (2) In a unit swing type engine that has a vertically split crankcase that is divided into upper and lower parts on a plane horizontal to the crankshaft, adopts a cantilever crank type, and integrates the cylinder and crankcase, the crank A unit swing type engine characterized in that a bearing that supports one end of a shaft is supported by a crankcase boss via a cover member that partially covers the bearing. (3) Claim 1, wherein the scavenging port and the exhaust port are arranged so as not to overlap the crankshaft bearing in plan view.
Or the unit swing type engine described in 2.