A straddle vehicle includes: a prime mover; a hydraulically actuated main clutch disposed in a power transmission route between the prime mover and a drive wheel; an oil control valve unit that controls flow of a hydraulic oil supplied to the main clutch; and a power unit case including a case body and a cover removably mounted on the case body, the power unit case accommodating at least the main clutch. The oil control valve unit is secured to the case body.

A utility vehicle includes: a pair of front wheels; a pair of rear wheels; at least one front wheel power source configured to drive the front wheels and not to drive the rear wheels; at least one rear wheel power source configured to drive the rear wheels and not to drive the front wheels; and a controller that controls the front wheel power source and the rear wheel power source. Upon receiving a predetermined two-wheel drive command, the controller brings the front wheel power source into a non-operative state while allowing the rear wheel power source to drive the rear wheels. Upon receiving a predetermined four-wheel drive command, the controller brings the front wheel power source into operation while allowing the rear wheel power source to drive the rear wheels.

A transmission system efficiently performs efficiently and also provides the ability to perform full-power shifts. For example, a secondary clutch actuator, independent of fluid actuation, may eliminate the need for a pump to continuously provide high pressure during regular vehicle operation such that high pressures are only required during a shift event. This eliminates the need for energy at the pump to maintain application of the clutch, thereby allowing such energy to be used of other systems in the EV or to facilitate increased vehicle range.

A method of setting a clutch control reference value may make it possible to more accurately learn the VKP of a hydraulic multi-plate clutch controlled by a solenoid valve, improving the accuracy of clutch control, and furthermore, to improve the quality of shifting a vehicle by the precise control of a transmission provided with such a clutch.

A method of setting a clutch control reference value may make it possible to more accurately learn the VKP of a hydraulic multi-plate clutch controlled by a solenoid valve, improving the accuracy of clutch control, and furthermore, to improve the quality of shifting a vehicle by the precise control of a transmission provided with such a clutch.

A continuous variable transmission (CVT) hydraulic pressure control device includes: a pressure regulation valve regulating an operation pressure of oil supplied to a friction element of a forward-rearward device; and a switch valve to respectively switch oil discharge paths through which the oil supplied to the friction element is discharged, respectively by a pilot pressure from the pressure regulation valve and an elastic force of a return spring. In particular, the oil discharge paths switched by the switch valve have oil flow resistances different from each other.

A shift control method of a transmission including an electric oil pump (EOP) directly connected to a friction clutch for a vehicle may include: when a shift is initiated, setting, by a controller, a predetermined first target RPM for controlling the EOP; determining, by the controller, a target current based on the first target RPM; maintaining, by the controller, the first target RPM until an EOP driving current reaches the target current; when the EOP driving current is greater than or equal to the target current, linearly reducing, by the controller, an RPM of the EOP from a predetermined second target RPM to a third target RPM; and increasing, by the controller, an EOP driving power to increase a friction force of the friction clutch such that a slip of the friction clutch is smaller than a predetermined reference slip.

A hydraulic clutch assembly includes a housing defining an internal cavity, a shaft, a clutch pack, a piston and a cylinder. The shaft extends within the internal cavity along a rotation axis for a rotatable member. The clutch pack includes interleaved plates and discs which are configured to rotationally couple the rotatable member to the shaft. The piston may be disposed within the internal cavity of the housing. The piston includes a first piston region and a second piston region. The first piston region is configured to engage the clutch pack while the second piston region is spaced radially from the first piston region. The piston may be arranged within the housing to define a first pressure chamber between the piston and the housing. The cylinder may be disposed within the internal cavity of the housing and may include a hollow interior for receiving the second piston region. The second piston region and the cylinder may define a second pressure chamber.

A shift control method of a transmission including an electric oil pump (EOP) directly connected to a friction clutch for a vehicle may include: when a shift is initiated, setting, by a controller, a predetermined first target RPM for controlling the EOP; determining, by the controller, a target current based on the first target RPM; maintaining, by the controller, the first target RPM until an EOP driving current reaches the target current; when the EOP driving current is greater than or equal to the target current, linearly reducing, by the controller, an RPM of the EOP from a predetermined second target RPM to a third target RPM; and increasing, by the controller, an EOP driving power to increase a friction force of the friction clutch such that a slip of the friction clutch is smaller than a predetermined reference slip.

A clutch assembly for a transmission of an agricultural work vehicle. The clutch assembly includes a housing, a clutch pack located within the housing, a piston chamber located within the housing, and a multipart piston located within and slidable relative to the piston chamber. The multipart piston is operably connected to the clutch pack for engaging and disengaging the clutch pack. The multipart piston includes a lower piston extension part. The clutch assembly further includes a balance chamber that is located within the housing. The lower boundary wall of the balance chamber and the lower boundary wall of the piston chamber are radially separated from one another by a substantial distance. The lower piston extension part is located within the balance chamber for adding to a collective surface area of the balance chamber.