A method of controlling a continuously variable electric drivetrain (CVED) including a high ratio traction drive transmission and at least one of a first motor-generator and a second motor-generator is disclosed. The method includes the steps of receiving a output speed, determining a kinematic output speed, and determining a slip state of the high ratio traction drive transmission based on a comparison of the output speed to the kinematic output speed.

A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.

A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.

A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.

A continuously variable gear is described having an input shaft, a plurality of traction balls distributed radially around the axis, each traction ball is mounted on an axle passing there through, the axles are tiltable in the radial grooves in the housing and support plate. To control the position of the traction balls, the axles are guided in curved slots of a turnable iris plate. To control the axial placement of the traction balls, there is a rotatable input disc positioned adjacent to the traction balls, a rotatable output disc positioned adjacent to the traction balls opposite the input disc, and a pre-spanning ring around the traction balls such that each of the traction balls is making three-point contact with the input disc, the output disc and the pre-spanning ring, the contact surface of the pre-spanning ring having a specific curvature larger than the radius of the traction balls.

A variator having at least one roller which runs upon at least one race to transfer drive from one to the other at variable ratio. The variator has a fluid supply for supplying fluid to the race and roller thereby to provide a fluid film by which the roller and the race are separated in use. The roller has a running surface with root means square roughness R.sub.q(roller) and the race having a root means square roughness R.sub.q(race). The variator's specific film thickness is the minimum thickness of the fluid film in normal operation divided by the composite roughness, and is less than 1.0. At least one of the roller and the race has a powder metal surface with a Ra roughness above 0.1 micrometers.

A variator having at least one roller which runs upon at least one race to transfer drive from one to the other at variable ratio. The variator has a fluid supply for supplying fluid to the race and roller thereby to provide a fluid film by which the roller and the race are separated in use. The roller has a running surface with root means square roughness R.sub.q(roller) and the race having a root means square roughness R.sub.q(race). The variator's specific film thickness is the minimum thickness of the fluid film in normal operation divided by the composite roughness, and is less than 1.0. At least one of the roller and the race has a powder metal surface with a Ra roughness above 0.1 micrometers.

Disclosed is a toroidal variable speed traction drive including a driving disc and a driven disc, with a plurality of roller assemblies in between. Each roller assembly has a toroidal rolling surface to contact the toroidal surface of the corresponding disc, and a conical surface, for engaging the other roller in the assembly. An engagement is provide to prevent or reduce axial movement between the first and second rollers along the conical surface.

Disclosed is a toroidal variable speed traction drive including a driving disc and a driven disc, with a plurality of roller assemblies in between. Each roller assembly has a toroidal rolling surface to contact the toroidal surface of the corresponding disc, and a conical surface, for engaging the other roller in the assembly. An engagement is provide to prevent or reduce axial movement between the first and second rollers along the conical surface.

Devices and methods are provided herein for the transmission of power in motor vehicles. Power is transmitted in a smoother and more efficient manner by splitting torque into two or more torque paths. A continuously variable transmission is provided with a ball variator assembly having an array of balls, a planetary gearset coupled thereto and an arrangement of rotatable shafts with multiple gears and clutches that extend the ratio range of the variator. In some embodiments, clutches are coupled to the gear sets to enable synchronous shifting of gear modes.