Continuously variable transmission unit

• US 6,251,038 B1
• Filed: 10/18/1999
• Issued: 06/26/2001
• Est. Priority Date: 10/21/1998
• Status: Expired due to Term

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Ishikawa, Kouji, Imanishi, Takashi
• Primary Examiner(s): Marmor, Charles A
• Assistant Examiner(s): Pang, Roger
• Application Number:
  US09/420,283
• Time in Patent Office: 617 Days
• Field of Search: 475/215, 475/216, 475/278
• US Class Current: 475/216
• CPC Class Codes: F16H 2037/088 Power split variators with summing differentials, with the input of the CVT connected or connectable to the input shaft
• CPC Class Codes: F16H 37/086 CVT using two coaxial friction members cooperating with at least one intermediate friction member

Abstract

A continuously variable transmission unit, which combines a toroidal-type continuously variable transmission of the double-cavity type and an epicyclic train, comprises a low-speed clutch and a high-speed clutch. In a low-speed drive mode, the low-speed clutch is connected to allow all torque to be transmitted to an output shaft through the toroidal-type continuously variable transmission. In a high-speed drive mode, the high-speed clutch is connected to allow most of torque to be transmitted to the output shaft through an epicyclic train and some of the torque to be applied to output discs of the toroidal-type transmission. The combination of the transmission and the epicyclic train serve to improve the transfer efficiency and durability of the continuously variable transmission unit.

Claims

1. A continuously variable transmission unit comprising:

an input shaft rotatable by means of a drive shaft;

an output shaft located parallel to the input shaft and capable of fetching power based on the rotation of the input shaft;

a toroidal continuously variable transmission of the double-cavity type including a pair of input discs arranged in parallel with each other with respect to the direction of power transmission and rotatable in concert with the input shaft, a pair of output discs opposed to the input discs, and power rollers located between the input discs and the output discs, the transmission being capable of synchronously changing the gear ratios between the input discs and the output discs by synchronously changing the respective angles of inclination of the power rollers;

an epicyclic train including a sun gear coupled to the output shaft, a ring gear located around the sun gear, planet gears in mesh with the sun gear and the ring gear, and a carrier provided with a plurality of pivots individually supporting the planet gears for rotation;

a first power transmission device for transferring turning effort between the carrier and output discs;

a second power transmission device for transferring turning effort between the input shaft and the ring gear, the second power transmission device being designed so that β

/α

is substantially equal to a reduction ratio for the maximum acceleration of the continuously variable transmission, where β and

α

are reduction ratios of the second and first power transmission devices, respectively;

a pressure device incorporated in the continuously variable transmission and located between the first and second power transmission devices with respect to the axial direction of the input shaft and the output shaft, the pressure device being designed to press the input discs and the output discs toward one another; and

switching means capable of switching a drive mode to a high- or low-speed drive mode, depending on the state of transmission between the input shaft and the output shaft, wherein said switching means include a low-speed clutch capable of fixing the sun gear and the carrier to each other and a high-speed clutch located between the second power transmission device and the ring gear.

2. A continuously variable transmission unit according to claim 1, further comprising a reverse clutch capable of reversing the output shaft by stopping the rotation of the ring gear.