A secondary drive unit (SDU) for the secondary axis of an all wheel drive vehicle consists of an SDU housing defining a first section for receiving a main shaft which is connected to a drive source and a second section for enclosing a twin clutch assembly. The twin clutch assembly has a common clutch housing connected to the main shaft, a left clutch for selectively connecting a left output shaft and the clutch housing, a right clutch for selectively connecting a right output shaft and the clutch housing, and a rigid center plate separating the left and right clutches. The twin clutch assembly may be activated by a dual action piston assembly to decrease all wheel drive synchronization and connection response times.

A secondary drive unit (SDU) for the secondary axis of an all wheel drive vehicle consists of an SDU housing defining a first section for receiving a main shaft which is connected to a drive source and a second section for enclosing a twin clutch assembly. The twin clutch assembly has a common clutch housing connected to the main shaft, a left clutch for selectively connecting a left output shaft and the clutch housing, a right clutch for selectively connecting a right output shaft and the clutch housing, and a rigid center plate separating the left and right clutches. The twin clutch assembly may be activated by a dual action piston assembly to decrease all wheel drive synchronization and connection response times.

Disclosed is a travel control apparatus for a four-wheel drive vehicle in which the states of engagements between a drive output part for secondary drive wheels and left and right secondary drive wheel axles are each changed to a torque transmission state or a torque transmission interruption state. The ratio of rotational speed of the drive output part to the average of rotational speeds of primary drive wheels is greater than 1. When the engagement states corresponding to the secondary drive wheels on the outer and inner sides of a turning locus have been set to the torque transmission state and the torque transmission interruption state, respectively, the engagement state having been set to the torque transmission state is changed to the torque transmission interruption state upon determination that an accelerator pedal is not operated and the magnitude of lateral acceleration is equal to or greater than a predetermined threshold.

A drive device includes a first clutch mechanism that couples or decouples power transmission systems for front and rear wheels, a first electric motor disposed on a front or rear wheel side and coupled to the first clutch mechanism, a second electric motor disposed on the other of the front and rear wheel sides and coupled to the first clutch mechanism, a second clutch mechanism that couples or decouples the first electric motor and front drive shafts, a planetary gear mechanism that distributes output of the first electric motor to the first and second clutch mechanisms, and a third clutch mechanism that limits a difference between a first rotational element that transmits the output of the first electric motor to the first clutch mechanism and a second rotational element that transmits the output of the first electric motor to the second clutch mechanism.

A drive device includes a first clutch mechanism that couples or decouples power transmission systems for front and rear wheels, a first electric motor disposed on a front or rear wheel side and coupled to the first clutch mechanism, a second electric motor disposed on the other of the front and rear wheel sides and coupled to the first clutch mechanism, a second clutch mechanism that couples or decouples the first electric motor and front drive shafts, a planetary gear mechanism that distributes output of the first electric motor to the first and second clutch mechanisms, and a third clutch mechanism that limits a difference between a first rotational element that transmits the output of the first electric motor to the first clutch mechanism and a second rotational element that transmits the output of the first electric motor to the second clutch mechanism.

A drive unit having motor output shaft that is connected to a sun gear is connected to one or more planetary gears that are connected to a planetary gear housing. The housing is connected to planetary gear assembly pinion gear, which is connected to a ring gear. A first side of the ring gear is connected to a first clutch drum and the second side of the ring gear is connected to a second clutch drum. Connected to the first clutch drum is a first plurality of clutch plates interleafed with a second plurality of clutch plates connected to a first clutch can. The first clutch can is connected to a first shaft. Connected to the second clutch drum is a third plurality of clutch plates interleafed with a fourth plurality of clutch plates connected to a second clutch can. The second clutch can is connected to a second shaft.

A driving force distribution apparatus includes a driving force connecting/disconnecting mechanism between a pinion gear shaft and an intermediate rotational member, a first driving force adjustment mechanism between the intermediate rotational member and a second output rotational member, a second driving force adjustment mechanism between the intermediate rotational member and a first output rotational member, and a hydraulic unit configured to generate pressures of hydraulic oil for operating the driving force connecting/disconnecting mechanism and the first and second driving force adjustment mechanisms. The hydraulic unit includes a single hydraulic pump and a hydraulic circuit configured to distribute a pressure of the hydraulic oil, which is discharged from the hydraulic pump, to cylinder chambers of pistons.

A driving force distribution apparatus includes a driving force connecting/disconnecting mechanism between a pinion gear shaft and an intermediate rotational member, a first driving force adjustment mechanism between the intermediate rotational member and a second output rotational member, a second driving force adjustment mechanism between the intermediate rotational member and a first output rotational member, and a hydraulic unit configured to generate pressures of hydraulic oil for operating the driving force connecting/disconnecting mechanism and the first and second driving force adjustment mechanisms. The hydraulic unit includes a single hydraulic pump and a hydraulic circuit configured to distribute a pressure of the hydraulic oil, which is discharged from the hydraulic pump, to cylinder chambers of pistons.

In a vehicular final speed reducing device, the intermediate, rear, bottom and the side walls define a breather chamber, and the partition wall divides the breather chamber into auxiliary and primary breather chambers. The auxiliary breather chamber is held in communication with a space outside the breather chamber and within the housing, through a first hole formed through the intermediate wall, and through an opening formed between the intermediate and bottom walls. The primary breather chamber is held in communication with an outside atmosphere outside the housing, and with the auxiliary breather chamber through a second hole formed through the partition wall. The bottom wall extends from the rear wall such that a front end of the bottom wall is located forwardly of the opening in the axial direction of the ring gear.

In a vehicular final speed reducing device, the intermediate, rear, bottom and the side walls define a breather chamber, and the partition wall divides the breather chamber into auxiliary and primary breather chambers. The auxiliary breather chamber is held in communication with a space outside the breather chamber and within the housing, through a first hole formed through the intermediate wall, and through an opening formed between the intermediate and bottom walls. The primary breather chamber is held in communication with an outside atmosphere outside the housing, and with the auxiliary breather chamber through a second hole formed through the partition wall. The bottom wall extends from the rear wall such that a front end of the bottom wall is located forwardly of the opening in the axial direction of the ring gear.