Vehicle power unit

Patent metadata

Field	Value
Publication number	US-11293527-B2
Application number	US-201916370158-A
Country	US
Kind code	B2
Filing date	Mar 29, 2019
Priority date	Apr 5, 2018
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

A vehicle power unit has a transmission apparatus including a transmission, and a transmission actuating mechanism including a speed reduction gear train having multiple speed reduction stages for transmitting power from a drive gear on a drive shaft of a shift motor to a driven gear on a drum turning shaft of a shift drum. The speed reduction gear train has a speed reduction ratio ranging from 23 to 45, and the shift motor is a DC electric motor that produces a pulsating cogging torque having a maximum value ranging from 0.04 to 0.07 Nm. The vehicle power unit enables the transmission actuating mechanism to be made up of a reduced number of parts and to be simple in structure, making the transmission apparatus small in size, and ensures quicker and smoother gear changes with an electric motor.

First claim

The invention claimed is:

1. A vehicle power unit having an internal combustion engine and a transmission apparatus integrally supported in a crankcase,
the transmission apparatus including a transmission having gear pairs of different speed reduction ratios for transmitting power from the internal combustion engine to a vehicle, and a transmission actuating mechanism having a shift drum angularly movable by a shift motor to move shift forks guided by the shift drum for changing gear pairs of the transmission to transmit power, wherein:
a speed reduction gear train has multiple speed reduction stages for transmitting power from a drive gear, on a drive shaft of the shift motor, to a driven gear on a drum turning shaft of the shift drum;
a shift drum adjustment torque, for angularly moving the shift drum from a 0-degree angular position to change gear positions, is set to be 1.15 Nm or larger, the shift drum adjustment torque being provided primarily by the shift motor and the speed reduction gear train without a star-shaped cam,
the speed reduction gear train has a speed reduction ratio ranging from 23 to 45; and
the shift motor includes a direct current electric motor which produces a pulsating cogging torque having a maximum value in a range from 0.04 to 0.07 Nm.

2. The vehicle power unit as claimed in claim 1 , wherein:
the vehicle power unit is configured to be laterally mounted on a small-sized vehicle with a crankshaft oriented in leftward and rightward directions transversely across the small-size vehicle;
the shift drum has left and right drum turning shafts rotatably supported respectively on left and right side walls of the crankcase;
the driven gear is mounted on one of the left and right drum turning shafts of the shift drum;
the transmission actuating mechanism includes an extension support wall extending rearward from one of the left and right side walls of the crankcase, the one of the left and right side walls rotatably supporting the one of the left and right drum turning shafts with the driven gear mounted thereon;
the shift motor is mounted on the extension support wall with the drive gear protrusively disposed in the leftward and rightward directions; and
the speed reduction gear train is supported on the extension support wall and arranged in an array.

3. The vehicle power unit as claimed in claim 2 , wherein:
the shift motor is mounted on a rear portion of the extension support wall with the drive gear protrusively disposed in one of the leftward and rightward directions which is the same as the direction in which the one of the left and right drum turning shafts with the driven gear mounted thereon extends.

4. The vehicle power unit as claimed in claim 3 , wherein:
the crankcase is of a vertical split structure including an upper crankcase member and a lower crankcase member; and
the extension support wall is mounted on the lower crankcase member.

5. The vehicle power unit as claimed in claim 4 , wherein:
the speed reduction gear train is arrayed longitudinally of the vehicle between the drive gear and the driven gear.

6. The vehicle power unit as claimed in claim 5 , wherein:
the speed reduction gear train includes an idle gear.

7. The vehicle power unit as claimed in claim 6 , wherein:
the speed reduction gear train is disposed above an oil level line of oil kept in the lower crankcase member.

8. The vehicle power unit as claimed in claim 6 , wherein:
an endless chain is trained around a drive sprocket fitted over an output shaft of the vehicle power unit and a driven sprocket fitted over a rear axle; and
the shift motor is disposed transversely inwardly of the endless chain at a position superposed on the endless chain as viewed in side elevation.

9. The vehicle power unit as claimed in claim 5 , wherein:
the speed reduction gear train is disposed above an oil level line of oil kept in the lower crankcase member.

10. The vehicle power unit as claimed in claim 5 , wherein:
an endless chain is trained around a drive sprocket fitted over an output shaft of the vehicle power unit and a driven sprocket fitted over a rear axle; and
the shift motor is disposed transversely inwardly of the endless chain at a position superposed on the endless chain as viewed in side elevation.

11. The vehicle power unit as claimed in claim 4 , wherein:
the speed reduction gear train is disposed above an oil level line of oil kept in the lower crankcase member.

12. The vehicle power unit as claimed in claim 11 , wherein:
an endless chain is trained around a drive sprocket fitted over an output shaft of the vehicle power unit and a driven sprocket fitted over a rear axle; and
the shift motor is disposed transversely inwardly of the endless chain at a position superposed on the endless chain as viewed in side elevation.

13. The vehicle power unit as claimed in claim 4 , wherein:
an endless chain is trained around a drive sprocket fitted over an output shaft of the vehicle power unit and a driven sprocket fitted over a rear axle; and
the shift motor is disposed transversely inwardly of the endless chain at a position superposed on the endless chain as viewed in side elevation.

14. The vehicle power unit as claimed in claim 3 , wherein:
the crankcase is of a vertical split structure including an upper crankcase member and a lower crankcase member; and
the extension support wall is mounted on the upper crankcase member.

15. The vehicle power unit as claimed in claim 1 , wherein the shift motor comprises a motor casing which is aligned with the crankcase in a manner so as to be positioned within a transverse width of the crankcase without projecting transversely out beyond the crankcase.

16. A vehicle power unit having an internal combustion engine and a transmission apparatus integrally supported in a crankcase,
the transmission apparatus including a transmission having gear pairs of different speed reduction ratios for transmitting power from the internal combustion engine to a vehicle, and a transmission actuating mechanism having a shift drum angularly movable by a shift motor to move shift forks guided by the shift drum for changing gear pairs of the transmission to transmit power, wherein:
a speed reduction gear train has multiple speed reduction stages for transmitting power from a drive gear on a drive shaft of the shift motor to a driven gear on a drum turning shaft of the shift drum;
the speed reduction gear train has a speed reduction ratio ranging from 23 to 45;
a shift drum adjustment torque, for angularly moving the shift drum from a 0-degree angular position to change gear positions, is provided primarily by the shift motor and the speed reduction gear train without a star-shaped cam;
the shift motor comprises a motor casing which is aligned with the crankcase in a manner so as to be positioned within a transverse width of the crankcase without projecting transversely out beyond the crankcase;
an endless chain is trained around a drive sprocket fitted over an output shaft of the vehicle power unit and a driven sprocket fitted over a rear axle;
the shift motor is disposed transversely inwardly of the endless chain at a position superposed on the endless chain as viewed in side elevation;
and the shift motor includes a direct current electric motor which produces a pulsating cogging torque having a maximum value in a range from 0.04 to 0.07 Nm.

Assignees

• Honda Motor Co Ltd

Inventors

• Kittaka Eiji
• Kudo Takashi

Classifications

• F16H63/18 Primary

  the final actuating mechanism comprising cams · CPC title

• F16H63/32

  Gear shift yokes, {e.g. shift forks} · CPC title

• F16H3/006

  power being selectively transmitted by parallel flow paths, e.g. dual clutch transmissions · CPC title

• F16H63/304

  the final output mechanisms comprising elements moved by electrical or magnetic force (band brake actuating mechanisms F16H63/3003) · CPC title

• B60Y2200/12

  Motorcycles, Trikes; Quads; Scooters · CPC title