Integrated power unit including split crankcase with reinforced fastening arrangement, and vehicle including same

Abstract

An integrated power unit for a small vehicle is configured to permit a compact engine design in a power unit having a crankcase that is split into upper and lower portions. The power unit includes a crankshaft supported by the crankcase and oriented transverse to the running direction of the vehicle. A transmission shaft is rotatably supported in a transmission chamber formed on the rear side of the crank chamber. The respective split surfaces of the upper and the lower crankcase portions are provided plural fastening boss portions arranged as vertically opposed pairs. The plural fastening boss portions are respectively joined using fastening bolts to integrate the upper crankcase and the lower crankcase, thereby forming the crankcase. A clutch is disposed at one end of the transmission shaft, and the rearmost fastening boss portions overlap with a rear portion of the clutch in the front-rear direction of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall right side view of a motorcycle on which an integrated power unit according to an embodiment of the present invention is mounted.

FIG. 2 is a left side view of the integrated power unit of FIG. 1.

FIG. 3 is a partial right side view of the integrated power unit of FIG. 1.

FIG. 4 is a partial plan view of the integrated power unit of FIG. 1.

FIG. 5 is a sectional view of the integrated power unit of FIG. 1 taken along line V-V of FIG. 2.

FIG. 6 is a schematic sectional view of a portion of the integrated power unit of FIG. 1 taken along line VI-VI of FIG. 5.

FIG. 7 is a bottom view of the crankcase of the integrated power unit of FIG. 1.

FIG. 8 is a front view of the crankcase of the integrated power unit of FIG. 1.

FIG. 9 is a sectional view of an upper crankcase of the integrated power unit of FIG. 1.

Claims

1. An integrated power unit for a small vehicle, the power unit comprising: a crankshaft;a transmission shaft;a crankcase, the crankcase being split into an upper crankcase and a lower crankcase;a crank chamber within the crankcase, the crankshaft rotatably supported within the crank chamber and having an axis which is oriented in a transverse direction which is orthogonal to a forward travel direction of the vehicle;a transmission chamber within the crankcase on the rear side of the crank chamber, the transmission shaft rotatably supported within the transmission chamber; anda clutch which permits connection and disconnection of power of the crankshaft to and from the transmission shaft, the clutch disposed at one end of the transmission shaft, whereinrespective confronting surfaces of the upper crankcase and the lower crankcase are provided with plurality of fastening boss portions arranged as vertically opposed pairs,the upper crankcase and the lower crankcase are fastened together by fastening respective vertically opposed pairs of the fastening boss portions using fastening bolts so as to integrate the upper crankcase and the lower crankcase into a single entity,and wherein rearmost fastening boss portions of the plurality of fastening boss portions are located so as to be vertically overlapping with a rear portion of the clutch.

2. The integrated power unit for a small vehicle as set forth in claim 1, wherein the crankshaft is rotatably supported between the respective confronting surfaces of the upper crankcase and the lower crankcase, the crankshaft comprising at least one crankpin connecting at least one pair of crank webs; and wherein the crankshaft has a drive gear provided thereon,and wherein the clutch comprises: a driven gear, the driven gear meshed with the drive gear provided on the crankshaft; anda clutch mechanism;wherein the outside diameter of the driven gear is greater than the outside diameter of the clutch mechanism; andwherein one of the rearmost fastening boss portions is substantially aligned, along said transverse direction, with said at least one crank pin.

3. The integrated power unit for the small vehicle as set forth in claim 2, wherein the crankshaft comprises four pairs of crank webs, and wherein the one of the rearmost fastening boss portions is disposed adjacent to a transverse side of the crankcase corresponding to the one end of the transmission shaft.

4. The integrated power unit for the small vehicle as set forth in claim 1, wherein the power unit further comprises a drive gear provided on the crankshaft, and wherein the clutch comprises: a driven gear, the driven gear meshed with the drive gear provided on the crankshaft; anda clutch mechanism,wherein the outside diameter of the driven gear is greater than the outside diameter of the clutch mechanism; andone of the rearmost fastening boss portions, provided at an end of the crankcase corresponding to the one end of the transmission shaft, is disposed rearward of both the clutch and the driven gear as viewed in a plane corresponding to the confronting surfaces of the upper crankcase and the lower crankcase.

5. The integrated power unit for the small vehicle as set forth in claim 1, wherein: the transmission further comprises an output shaft and plural speed change gear groups, the output shaft operatively connectable to the transmission shaft via one of the plural speed change groups,the transmission shaft is located at a position that is above and in front of the output shaft, andthe output shaft is supported by and retained between the confronting surfaces of the upper crankcase and the lower crankcase at a location on the rear side of the crankshaft.

6. A vehicle, comprising: an integrated power unit comprising:a crankshaft;a transmission shaft;a crankcase, the crankcase being split into an upper crankcase and a lower crankcase;a crank chamber within the crankcase, the crankshaft rotatably supported within the crank chamber and having an axis which is oriented in a transverse direction which is orthogonal to a forward travel direction of the vehicle;a transmission chamber within the crankcase on the rear side of the crank chamber, the transmission shaft rotatably supported within the transmission chamber; anda clutch which permits connection and disconnection of power of the crankshaft to and from the transmission shaft, the clutch disposed at one end of the transmission shaft, whereinrespective confronting surfaces of the upper crankcase and the lower crankcase are provided with plurality of fastening boss portions arranged as vertically opposed pairs,the upper crankcase and the lower crankcase are fastened together by fastening respective vertically opposed pairs of the fastening boss portions using fastening bolts so as to integrate the upper crankcase and the lower crankcase into a single entity, and wherein rearmost fastening boss portions of the plurality of fastening boss portions are located so as to be vertically overlapping with a rear portion of the clutch;wherein the vehicle further comprises a vehicle body frame upon which the integrated power unit is mounted; and a swing arm pivotally mounted to the vehicle body frame and rotatable about a pivot axis,and wherein the pivot axis is disposed adjacent a rear side of the crankcase at a location adjacent to the rearmost fastening boss portions, and underlying a portion of the upper crankcase.

7. The vehicle of claim 6, wherein the crankshaft is rotatably supported between the respective confronting surfaces of the upper crankcase and the lower crankcase, the crankshaft comprising at least one crankpin connecting at least one pair of crank webs; and wherein the crankshaft has a drive gear provided thereon,and wherein the clutch comprises: a driven gear, the driven gear meshed with the drive gear provided on the crankshaft; anda clutch mechanism;wherein the outside diameter of the driven gear is greater than the outside diameter of the clutch mechanism; andwherein one of the rearmost fastening boss portions is substantially aligned, along said transverse direction, with said at least one crank pin.

8. The vehicle of claim 7, wherein the crankshaft comprises four pairs of crank webs, and wherein the one of the rearmost fastening boss portions is disposed adjacent to a transverse side of the crankcase corresponding to the one end of the transmission shaft.

9. The vehicle of claim 6, wherein the power unit further comprises a drive gear provided on the crankshaft, and wherein the clutch comprises: a driven gear, the driven gear meshed with the drive gear provided on the crankshaft; anda clutch mechanism,wherein the outside diameter of the driven gear is greater than the outside diameter of the clutch mechanism; andone of the rearmost fastening boss portions, provided at an end of the crankcase corresponding to the one end of the transmission shaft, is disposed rearward of both the clutch and the driven gear as viewed in a plane corresponding to the confronting surfaces of the upper crankcase and the lower crankcase.

10. The vehicle of claim 6, wherein: the transmission further comprises an output shaft and plural speed change gear groups, the output shaft operatively connectable to the transmission shaft via one of the plural speed change groups,the transmission shaft is located at a position that is above and in front of the output shaft, andthe output shaft is supported by and retained between the confronting surfaces of the upper crankcase and the lower crankcase at a location on the rear side of the crankshaft.