Continuously variable transmission

• US 7,322,901 B2
• Filed: 07/07/2005
• Issued: 01/29/2008
• Est. Priority Date: 02/28/2003
• Status: Expired due to Fees

• Current Assignee: Fallbrook Intellectual Property Company LLC (Fallbrook Technologies Incorporated)
• Original Assignee: Fallbrook Technologies Incorporated
• Inventors: Allen, David J., Smithson, Robert A., Miller, Donald C.
• Primary Examiner(s): Wright; Dirk
• Application Number:
  US11/176,545
• Publication Number:
  US 20050255957A1
• Time in Patent Office: 936 Days
• Field of Search: 475/215, 475/189, 475/196
• US Class Current: 475/189
• CPC Class Codes: B62M 11/04 of changeable ratio
• CPC Class Codes: B62M 11/14 with planetary gears
• CPC Class Codes: B62M 9/08 involving eccentrically- mounted or elliptically-shaped driving or driven wheel; with expansible driving or driven wheel
• CPC Class Codes: F16H 15/28 with external friction surface
• CPC Class Codes: F16H 15/40 in which two members co-operative by means of balls, or rollers of uniform effective diameter, not mounted on shafts
• CPC Class Codes: F16H 15/50 Gearings providing a continuous range of gear ratios
• CPC Class Codes: F16H 15/503 in which two members co-operate by means of balls or rollers of uniform effective diameter, not mounted on shafts
• CPC Class Codes: F16H 15/52 in which a member of uniform effective diameter mounted on a shaft may co-operate with different parts of another member
• 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 2037/101 Power split variators with one differential at each end of the CVT
• CPC Class Codes: F16H 37/084 at least one power path being a continuously variable transmission, i.e. CVT
• CPC Class Codes: F16H 37/0853 CVT using friction between rotary members having a first member of uniform effective diameter cooperating with different parts of a second member
• CPC Class Codes: F16H 37/086 CVT using two coaxial friction members cooperating with at least one intermediate friction member
• CPC Class Codes: F16H 61/6649 characterised by the means for controlling the torque transmitting capability of the gearing
• CPC Class Codes: F16H 63/067 mechanical actuating means
• CPC Class Codes: Y10T 29/49464 Assembling of gear into force transmitting device
• CPC Class Codes: Y10T 408/65 Means to drive tool

Abstract

A variable speed transmission having a plurality of tilting balls and opposing input and output discs is illustrated and described that provides an infinite number of speed combinations over its transmission ratio range. The use of a planetary gear set allows minimum speeds to be in reverse and the unique geometry of the transmission allows all of the power paths to be coaxial, thereby reducing overall size and complexity of the transmission in comparison to transmissions achieving similar transmission ratio ranges.

Claims

1. A variable speed transmission, comprising:

a longitudinal axis;

a plurality of balls distributed radially about the longitudinal axis, each ball having a tiltable axis about which it rotates;

a rotatable input disc positioned adjacent to the balls and in contact with each of the balls;

a rotatable output disc positioned adjacent to the balls opposite the input disc and in contact with each of the balls;

a rotatable idler having a substantially constant outer diameter coaxial about the longitudinal axis and positioned radially inward of and in contact with each of the balls; and

a planetary gear set mounted coaxially about the longitudinal axis of the transmission.

2. The variable speed transmission of claim 1, wherein the balls sum a torque component transmitted from at least two power paths, which power paths are provided by the planetary gear set and wherein the at least two power paths are coaxial.

3. The variable speed transmission of claim 1, wherein at least one of the idler and the output disc provide a torque input to the planetary gearset.

4. The variable speed transmission of claim 1, wherein the idler has an irregular interior bore, and wherein the idler is supported in its radial position by first and second shift guide sleeves, which fit coaxially within the interior bore, and is further supported by first and second radial support bearings positioned between the each end of the idler interior bore and its respective guide sleeve.

5. The variable speed transmission of claim 4, wherein the transmission is shifted by axially moving the guide sleeves.

6. The variable speed transmission of claim 1, wherein the planetary gearset further comprises:

a ring gear mounted coaxially about the longitudinal axis and having teeth that face radially inward towards;

a plurality of planet gears distributed coaxially about the longitudinal axis within the ring gear and in engagement with the ring gear, each planet gear having a respective planet axis about which it rotates, and wherein the planet axes are located radially away from the longitudinal axis;

a plurality of planet shafts, one for each planet, about which the planet gears rotate;

a sun gear mounted coaxially about the longitudinal axis and radially within and in engagement with each of the plurality of planet gears; and

a planet carrier mounted coaxially about the longitudinal axis and adapted to support and position the planet shafts.

7. The variable speed transmission of claim 6, further comprising a cage adapted to align the tiltable axes of the balls and further adapted to maintain the angular and radial positions of the balls.

8. The variable speed transmission of claim 7, wherein at least one of the idler, the cage and the output disc provide a torque input to the planetary gearset.

9. The variable speed transmission of claim 7, wherein an input torque is supplied to the planet carrier and the planet carrier is coupled to the input disc, wherein the sun gear is coupled to the cage, wherein the ring gear is fixed and does not rotate, and wherein an output torque is supplied from the transmission by the output disc.

10. The variable speed transmission of claim 6, further comprising an axial force generator adapted to generate an axial force that increases the traction between the input disc, the balls, the idler and the output disc.

11. The variable speed transmission of claim 10, wherein an amount of axial force generated by the axial force generator is a function of the transmission ratio of the transmission.

12. The variable speed transmission of claim 11, wherein each of the input disc, the balls, the output disc, and the idler have contact surfaces that are coated with a friction increasing coating material.

13. The variable speed transmission of claim 12, wherein the coating material is a ceramic.

14. The variable speed transmission of claim 12, wherein the coating material is a cermet.

15. The variable speed transmission of claim 12, wherein the coating is a material selected from the group consisting of silicon nitride, silicon carbide, electroless nickel, electroplated nickel, or any combination thereof.

16. The variable speed transmission of claim 12, wherein the thickness of the coating material is between 0.25 and 5 microns.

17. The variable speed transmission of claim 12, wherein the thickness of the coating material is between 0.5 and 4 microns.

18. An automobile, comprising:

an engine;

a drivetrain; and

a variable speed transmission comprising;

a longitudinal axis;

a plurality of balls distributed radially about the longitudinal axis, each ball having a tiltable axis about which it rotates;

a rotatable input disc positioned adjacent to the balls and in contact with each of the balls;

a rotatable output disc positioned adjacent to the balls opposite the input disc and in contact with each of the balls;

a rotatable idler having a substantially constant outer diameter coaxial about the longitudinal axis and positioned radially inward of and in contact with each of the balls; and

a planetary gear set mounted coaxially about the longitudinal axis of the transmission.