The disclosure provides rotary machines that include, in one embodiment, a shaft defining a central axis A, the shaft having a first end and a second end. The shaft can have a first gearbox disposed thereon defining one or more cavities therein. At least one contour is slidably received into an arcuate cavity in an exterior surface of the gearbox. The contour has a convex outer surface that cooperates with an inwardly facing curved surface of a housing to form a working volume. A gearbox mechanism consisting of gears, crankshafts, bearings and connecting rod creates an oscillatory motion 2 times per revolution such that the contour can navigate about the arcuate cavity without contacting the cavity at a high rate of rotating speed. Thus, said working volume can expand and compresses twice per rotatable shaft revolution.

An outboard motor having an internal combustion engine that rotates a driveshaft disposed in a driveshaft housing, a transmission that is operatively connected to the driveshaft and is disposed in a transmission housing located below the driveshaft housing, a set of angle gears that operatively connect the transmission to a propulsor for imparting a propulsive force in a body of water, wherein the set of angle gears are located in a lower gearcase located below the transmission housing, and a lubrication system that circulates lubricant to and from the transmission.

An engine includes a cylinder portion under which a crankshaft portion is arranged. A transmission box is arranged at one side of the crankshaft portion and includes a continuously variable transmission system arranged therein. The transmission box includes a cooling air inlet opening and a cooling air outlet opening. A cooling air intake tube is arranged on the cooling air inlet opening. The cooling air intake tube includes a cooling air ingress port. An air collection box is arranged on the cooling air ingress port. The cooling air intake tube includes a curved section posterior to the cooling air ingress port and the curved section includes a riser section. This helps ensure cleanliness of the external fresh cold air entering the air collection box and guided into the cooling air intake tube to prevent external water and dust from entering the transmission box to cause damage to the continuously variable transmission system.

A vehicle includes three pairs of wheels, each pair being spaced apart in a right-left direction, three differential gears, respectively corresponding to the three pairs of wheels, and an engine that generates a rotation to be transmitted to the three pairs of wheels through the three differential gears. The engine is located rearward of a front differential gear that is any one of the three differential gears and is fixed to the front differential gear.

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.

A vehicle power unit is disclosed which prevents a transmission apparatus from becoming large in size and promotes reduction in size by reducing the number of parts. A transmission shift drum has a driven gear mounted on a shift drum rotary shaft portion on one end of the shift drum. An extended support wall is formed to extend to outside in a vehicle width direction in parallel with a first case side wall of a crankcase. The case side wall supports the first drum rotary shaft portion on which the driven gear is mounted. The extended support wall and the first case side wall support thereon gears of a reduction gear train between a drive gear of a shift motor mounted on the extended support wall and the driven gear.

In a vehicle power unit, a drum rotary shaft member on one side of a shift drum is provided with a driven gear. A case side wall on one side of an engine crankcase supporting the drum rotary shaft member is covered by a case cover member in opposing relation thereto. A shift motor is mounted to the case cover member, with a driving gear thereof directed to protrude toward the case side wall. A speed reducing gear train has gear shafts and provides a multiplicity of speed reduction stages for transmitting power from the driving gear to the driven gear. The speed reducing gear train is arranged with both ends of its gear shafts thereof supported on the case side wall and the case cover member, respectively. Such arrangement provides a vehicle power unit for a fast and smooth shift by an electric motor.

A gear shift control system controls an actuator so that a pushing force will be a constant gearing-phase pushing force, during a gearing phase. The gear shift control system performs control on the basis of the number of rotation of the engine in the gearing phase, which is measured at the start of the gearing phase, so that the constant gearing-phase pushing force will increase as a number of rotation of the engine in the gearing phase increases. Thus, the hitting sound due to collision between the sleeve and the shift gear in shifting gears is reduced.

As viewed from a side, an output shaft is disposed rearward of a crankshaft, and an odd-numbered stage shaft and an even-numbered stage shaft are disposed rearward of the crankshaft. Moreover, the odd-numbered stage shaft is provided on a side opposite to the even-numbered stage shaft relative to a line connecting the crankshaft and the output shaft, and a shift drum is disposed on a side opposite to the output shaft relative to a line connecting the odd-numbered stage shaft and the even-numbered stage shaft. This structure reduces dimensions of the power unit for the saddled vehicle.

A vehicle casing includes a metal frame and a resin cover that covers the metal frame. The resin cover accommodates vehicle components inside the metal frame. The metal frame includes a bearing supporting boss portion that rotatably supports, inside the resin cover, a shaft member that is one of the vehicle components and rotates about a shaft center, and a mount boss portion that is for fixing the vehicle casing to a vehicle body. The bearing supporting boss portion is disposed at a position separate from an inner surface of the resin cover. The resin cover is disposed to cover the entire metal frame except a portion provided with the mount boss portion.