JP2716151B2 - Unit swing engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a unit swing type engine having a vertically divided unit case.

(Prior Art) A unit swing type engine is mounted on, for example, a scooter type motorcycle, which is configured as a single unit by compactly integrating a cylinder, a crankcase, a transmission system, an intake / exhaust system, and the like. .

By the way, in this type of unit swing type engine, a crankcase is integrally formed with a transmission case to form a unit case for the purpose of simplification of structure, simplification of manufacture and assembly, cost reduction, and the like. May be divided into upper and lower parts by dividing the upper and lower parts with a plane parallel to the crankshaft.

(Problems to be Solved by the Invention) However, in the unit swing type engine having the vertically divided unit case as described above, the front and rear of the unit case are required in order to secure a storage space for a rear wheel such as a motorcycle. The width of the middle part in the direction must be narrowed, which causes a problem that the strength and rigidity of this part are insufficient.If the thickness of the middle part is increased to solve this problem, the unit swing type engine Another problem arises in that the overall weight increases and the cost increases.

The present invention has been made in view of the above-described problems, and the object thereof is to reinforce the unit case while suppressing an increase in the overall weight and cost, and to have a sufficient strength of the unit case.
It is an object of the present invention to provide a unit swing type engine that secures rigidity.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a unit swing type engine having an upper and lower unit case divided vertically in a plane parallel to the crankshaft. The muffler upper and lower parts are integrated with the unit case together with the upper and lower parts.

(Function) According to the present invention, since the unit case is reinforced by the muffler integrally formed with the unit case, sufficient strength and rigidity are secured in the unit case.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is a side view of a unit swing type engine according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a bottom view of the engine, and FIG. -IV line sectional view,
5 (a) to 5 (c) are cross-sectional views taken along the line VV of FIG. 2 showing an integrated structure of a muffler and a unit case, and FIG. 6 is a scooter type equipped with a unit swing type engine according to the present invention. FIG. 2 is a side view of the motorcycle.

As shown in FIG. 6, a unit swing type engine 1 according to the present invention is a two-stroke engine arranged at the rear of a motorcycle 30 and driving a rear wheel 31.
The rear end is suspended from the main frame 33 via a rear cushion 34. In the motorcycle 30, 35 is a front wheel,
36 is a sheet.

The details of the unit swing type engine 1 are shown in FIGS. 1 to 5, and the engine 1 has a vertically divided unit case 2 which is vertically divided into two parts by a plane parallel to a crankshaft 8 described later. , Upper and lower portions 2a, 2b of the unit case 2
Is constituted integrally with the crankcase and the transmission case. The cylinder 3 is formed integrally with the unit case upper part 2a.

Incidentally, an intermediate portion 2c of the unit case 2 is elongated in the front-rear direction in order to secure a space for arranging the rear wheel 31, and a crankshaft 8 to be described later is provided outside the intermediate portion 2c.
The upper and lower split mufflers 4 which are vertically divided into two on a horizontal surface (the same as the division surface of the unit case 2) are integrally attached. That is, the muffler 4 is configured by joining and integrating the upper part 4a and the lower part 4b. In this embodiment,
As shown in FIG. 5 (a), the muffler upper part 4a is integrated with the unit case upper part 2a, and the muffler lower part 4b is integrated with the unit case lower part 2b. A pipe 5 is interposed between the upper and lower portions 4a and 4b in the muffler 4.

Thus, the unit case upper part 2a and the cylinder 3 and the muffler upper part 4a, and the unit case lower part 2b and the muffler lower part 4b are integrally formed by aluminum casting or the like.

As shown in FIG. 2, a piston 6 is slidably fitted in the cylinder 3, and an ignition plug 7 is screwed to the top of the cylinder 3.

On the other hand, a crankshaft 8 is rotatably supported by two ball bearings 9a and 9b on the left and right sides in a front portion (crankcase portion) 2d of the unit case 2. A flywheel magneto is provided at the end extending outward (the left end in FIG. 2).
The end of the crankshaft 8 extending outwardly from the other ball bearing 9b (the right end in FIG. 2)
Is connected to a crank web 11. The large end of the connecting rod 12 is attached to the crank web 11 by a crank pin.
13 are connected rotatably via the connecting rod 12
Is connected to the piston 6 via a piston pin 14.

A centrifugal clutch 15, a chain sprocket 16 and a one-way clutch 17 are mounted between the two bearings 9a and 9b of the crankshaft 8. In FIG. 2, reference numeral 18 denotes a starter motor, and 19 denotes a kick shaft.

Further, a transmission shaft 20 is rotatably supported by ball bearings 21 and 21 in a rear portion (transmission case portion) 2e of the unit case 2, and a large-diameter chain sprocket 22 is attached to an end of the transmission shaft 20. The drive chain 23 is wound between the chain sprocket 22 and the chain sprocket 16. A small-diameter gear 24 is fitted on the transmission shaft 20, and a rear axle 25 is disposed behind the transmission shaft 20 in parallel with the rear axle 25 so as to be rotatably supported by ball bearings 26, 26. The rear axle 25 has the gear 24
A large-diameter gear 27 meshing with the gear is fitted. The rear wheel 31 is supported at an end of the rear axle 25 extending outside the unit case 2.

By the way, an exhaust groove 18 (see FIG. 4) having a U-shaped cross section for guiding exhaust gas discharged from the cylinder 3 to the muffler 4 is formed on the bottom surface of the unit case 2 as shown in FIG. The exhaust groove 28 is closed by a lid member 29 fixed to the bottom of the unit case 2.

When the unit swing type engine 1 is driven and the rotation speed of the crankshaft 8 reaches a certain value or more,
The centrifugal clutch 15 is turned on, the rotation of the crankshaft 8 is transmitted to the chain sprocket 16 via the centrifugal clutch 15, and the chain sprocket 16 is driven to rotate. Thus, when the chain sprocket 16 is rotationally driven, this rotation is transmitted to the rear wheel 31 via the drive chain 23, the chain sprocket 22, the transmission shaft 20, the gears 24 and 27, and the rear axle 25,
The rear wheel 31 is driven to rotate, and the motorcycle 30 shown in FIG. 6 is advanced.

On the other hand, the exhaust gas generated by the combustion of the air-fuel mixture in the combustion chamber S (see FIG. 2) in the cylinder 3 reaches the muffler 4 via the exhaust groove 28 formed on the bottom surface of the unit case 2, where the exhaust gas After the noise energy has been attenuated,
It is discharged from the muffler 4 into the atmosphere.

In the above, the narrow middle portion 2c of the unit case 2
Is reinforced by a muffler 4 integrally provided on the side thereof, so that the intermediate portion 2c has sufficient strength and rigidity. Therefore, it is not necessary to increase the thickness of the intermediate portion 2c, and there is no increase in weight and cost of the entire unit swing type engine 1.

In the above embodiment, both the upper part 4a and the lower part 4b of the muffler 4 are integrally formed with the unit case 2.
Even if only the lower muffler 4b is integrally formed with the unit case 2 as shown in FIG. 5 (b) or only the upper muffler 4a is integrally formed with the unit case 2 as shown in FIG. 5 (c). The same effect can be obtained.

(Effects of the Invention) As is apparent from the above description, according to the present invention, in a unit swing type engine having an upper and lower split unit case vertically divided by a plane parallel to the crankshaft, the muffler is parallel to the crankshaft. The upper and lower parts of the muffler are divided into upper and lower parts, and one or both of the lower part and the lower part are integrally formed with the unit case, so that the unit case is reinforced by a muffler integrally formed with the unit case. The effect of securing sufficient strength and rigidity in the unit case is obtained.

[Brief description of the drawings]

1 is a side view of a unit swing type engine according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a bottom view of the engine, and FIG. FIG. 5 is a sectional view taken along the line VV of FIG. 2 showing an integrated structure of the muffler and the unit case, and FIG. 6 is a unit swing according to the present invention. FIG. 1 is a side view of a scooter-type motorcycle including an expression engine. DESCRIPTION OF SYMBOLS 1 ... Unit swing type engine, 2 ... Unit case, 4 ... Muffler, 4a ... Upper muffler, 4b ... Lower muffler, 8 ... Crankshaft.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-42163 (JP, A) JP-A-2-4924 (JP, U) JP-A-63-177615 (JP, U)

Claims (1)

(57) [Claims] In a unit swing type engine having an upper and lower split unit case which is vertically split on a plane parallel to a crankshaft, a muffler is vertically split on a plane parallel to the crankshaft to form an upper and lower split. A unit swing type engine, wherein one or both of an upper part and a lower part of a muffler are integrally formed with the unit case.