Troidal-type continuously variable transmission and a ball spline for use in the same

• US 6,071,210 A
• Filed: 11/12/1998
• Issued: 06/06/2000
• Est. Priority Date: 11/11/1997
• Status: Expired due to Term

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Fujinami, Makoto, Kato, Hiroshi, Machida, Hisashi, Imanishi, Takashi, Goto, Nobuo
• Primary Examiner(s): Herrmann, Allan D.
• Application Number:
  US09/189,933
• Time in Patent Office: 572 Days
• Field of Search: 384/49, 464/167, 464/168, 476/40, 476/42
• US Class Current: 476/42
• CPC Class Codes: F16H 15/38 with two members B having hollow toroid surfaces opposite to each other, the member or members A being adjustably mounted between the surfaces

Abstract

The ball spline for use in a troidal-type continuously variable transmission comprises a plurality of spline grooves and a plurality of balls which are arranged in series within spline gaps each constituted by a set of mutually opposing spline grooves, in which, while allowing the movement of the input disc in the direction of an input shaft by means of contact between the spline gaps and balls, the input shaft and input disc can be drivingly connected to each other. In the ball spline, the number of spline gaps is set different from integral multiples of the number of power rollers which are held by and between the input and output discs in contact with the two discs in order to transmit a rotation torque between the input and output discs. Further, each of the spline grooves includes inner and outer peripheral surface side spline grooves, and the shape of each of the sections of the two inner and outer peripheral surface side spline grooves respectively forming the ball spline is formed as a Gothic arch shape. And, the radius of curvature of the section of the groove bottom portion arc surface forming the groove bottom portion of each of the spline grooves is set more than or equal to 15% of the diameter of the ball. Also, the outer peripheral surface side chamfers of the outer peripheral surface side spline groove are set smaller to thereby be able to secure the effective grinding surface of the outer peripheral surface side spline groove.

Claims

1. A ball spline for use in a troidal-type continuously variable transmission, comprising:

a plurality of spline grooves respectively formed in an outer peripheral surface of an input shaft and in an inner wall surface of a mounting hole opened up in a central portion of an input disc in such a manner that they extend along a direction of said input shaft and are opposed to each other, thereby forming spline gaps by two mutually opposing spline grooves respectively formed in the outer peripheral surface of the input shaft and in the inner wall surface of the mounting hole of said spline grooves; and

a plurality of balls arranged in series within said spline gaps, wherein, while allowing a movement of said input disc in the direction of said input shaft by means of contact between said spline gaps and said balls, said input shaft and said input disc are drivingly connected to each other,

wherein the number of said spline gaps is set different from integral multiples of the number of power rollers which are held by and between said input disc and an output disc in contact with said two discs in order to transmit a rotation torque between said input and output discs.

2. A ball spline for use in a troidal-type continuously variable transmission according to claim 1, wherein the number of said spline gaps and the number of said power rollers are mutually prime to each other.

3. A ball spline for a troidal-type continuously variable transmission, wherein a disc is supported through a said ball spline on an outer peripheral surface of a rotary shaft so as to be freely shifted in an axial direction of the rotary shaft, said ball spline comprising:

a plurality of first spline grooves respectively formed in an inner peripheral surface of the disc;

a plurality of second spline grooves respectively formed in the outer peripheral surface of the rotary shaft, wherein said first spline grooves and said second spline grooves respectively extend along a direction of said rotary shaft and are opposed to each other respectively, thereby forming a plurality of spline gaps; and

a plurality of balls arranged in series within said spline gaps,

wherein said first spline groove comprises;

two side surface arc portions respectively formed on two circumferential-direction inner surfaces of said first spline groove, each of said side surface arc portions having a larger radius of curvature than a radius of curvature of a rolling surface of said ball;

a bottom arc surfaces formed on a bottom portion of said first spline groove,

wherein said bottom arc surface has a radius of curvature which is smaller than the radius of curvature of the rolling surface of said ball and is 0.15 or more times an outside diameter of said ball, so that said first spline groove has a cross section of a Gothic arch shape, and after execution of heat-treatment on said first spline groove, a heat-treated abnormal layer are removed from a surface of each of said bottom portion of said first spline groove.

4. A ball spline for a troidal-type continuously variable transmission according to claim 3, wherein a radius of curvature of said side surface arc portion is set in a range of 52-57% of the outside diameter of said ball.

5. A ball spline for a troidal-type continuously variable transmission, wherein a disc is supported through a said ball spline on an outer peripheral surface of a rotary shaft so as to be freely shifted in an axial direction of the rotary shaft, said ball spline comprising:

a plurality of first spline grooves respectively formed in an inner peripheral surface of the disc, each of said first spline grooves having two first chamfers respectively formed in circumferential-direction two end opening edge portions of said first spline groove;

a plurality of second spline grooves respectively formed in the outer peripheral surface of the rotary shaft, each of said second spline grooves having two second chamfers respectively formed in circumferential-direction two end opening edge portions of said second spline groove, wherein said first spline glooves and said second spline grooves respectively extend along a direction of said rotary shaft and are opposed to each other respectively, thereby forming a plurality of spline gaps; and

a plurality of balls arranged in series within said spline gaps,

wherein said second chamfers are set smaller than said first chamfers.

6. A troidal-type continuously variable transmission comprising:

an input shaft

an input disc supported by said input shaft;

an output shaft;

an output disc coupled to said output shaft, wherein said input disc and said output disc respectively have a concave surface formed on an axial-direction one-side surface having a cross section of an arc shape, and said two discs can be freely rotated coaxially with and independently of each other with said respective concave surfaces being opposed to each other;

a pair of trunnions swingable about pivots respectively situated at twisted positions with respect to a center of rotation of said two discs;

a plurality of power rollers respectively interposed between said concave surfaces of said two discs, supported rotatably on shift shafts respectively, and each of said power rollers including a peripheral surface as a rotation-arc-surface shaped convex surface; and

a ball spline for supporting said input disc on an outer peripheral surface of said input shaft so that said input disc can be freely shifted in an axial direction of said input shaft, said ball spline comprising;

a plurality of spline grooves respectively formed in the outer peripheral surface of said input shaft and in an inner wall surface of a mounting hole opened up in a central portion of said input disc in such a manner that they extend along a direction of said input shaft and are opposed to each other, thereby forming spline gaps by two mutually opposing spline grooves respectively formed in the outer peripheral surface of said input shaft and in the inner wall surface of the mounting hole of said spline grooves; and

a plurality of balls arranged in series within said spline gaps, wherein, while allowing a movement of said input disc in the direction of said input shaft by means of contact between said spline gaps and said balls, said input shaft and said input disc are drivingly connected to each other,

wherein the number of said spline gaps is set different from integral multiples of the number of power rollers which are held by and between said input disc and an output disc in contact with said two discs in order to transmit a rotation torque between said input and output discs.

7. A troidal-type continuously variable transmission according to claim 6, wherein the number of said spline gaps and the number of said power rollers are mutually prime to each other.

8. A troidal-type continuously variable transmission comprising:

an input shaft

an input disc supported by said input shaft;

an output shaft;

an output disc coupled to said output shaft, wherein said input disc and said output disc respectively have a concave surface formed on an axial-direction one-side surface having a cross section of an arc shape, and said two discs can be freely rotated coaxially with and independently of each other with said respective concave surfaces being opposed to each other;

a pair of trunnions swingable about pivots respectively situated at twisted positions with respect to a center of rotation of said two discs;

a plurality of power rollers respectively interposed between said concave surfaces of said two discs, supported rotatably on shift shafts respectively, and each of said power rollers including a peripheral surface as a rotation-arc-surface shaped convex surface; and

a ball spline for supporting said input disc on an outer peripheral surface of said input shaft so that said input disc can be freely shifted in an axial direction of said input shaft, said ball spline comprising;

a plurality of first spline grooves respectively formed in an inner peripheral surface of said input disc;

a plurality of second spline grooves respectively formed in the outer peripheral surface of said input shaft, wherein said first spline glooves and said second spline grooves respectively extend along the axial direction of said input shaft and are opposed to each other respectively, thereby forming a plurality of spline gaps; and

a plurality of balls arranged in series within said spline gaps,

wherein said first spline groove comprises;

two side surface arc portions respectively formed on two circumferential-direction inner surfaces of said first spline groove, each of said side surface arc portions having a larger radius of curvature than a radius of curvature of a rolling surface of said ball;

a bottom arc surfaces formed on a bottom portion of said first spline groove,

wherein said bottom arc surface has a radius of curvature which is smaller than the radius of curvature of the rolling surface of said ball and is 0.15 or more times an outside diameter of said ball, so that said first spline groove has a cross section of a Gothic arch shape, and after execution of heat-treatment on said first spline groove, a heat-treated abnormal layer are removed from a surface of each of said bottom portion of said first spline groove.

9. A troidal-type continuously variable transmission according to claim 8, wherein a radius of curvature of said side surface arc portion is set in a range of 52-57% of the outside diameter of said ball.

10. A troidal-type continuously variable transmission comprising:

an input shaft

an input disc supported by said input shaft;

an output shaft;

an output disc coupled to said output shaft, wherein said input disc and said output disc respectively have a concave surface formed on an axial-direction one-side surface having a cross section of an arc shape, and said two discs can be freely rotated coaxially with and independently of each other with said respective concave surfaces being opposed to each other;

a pair of trunnions swingable about pivots respectively situated at twisted positions with respect to a center of rotation of said two discs;

a plurality of power rollers respectively interposed between said concave surfaces of said two discs, supported rotatably on shift shafts respectively, and each of said power rollers including a peripheral surface as a rotation-arc-surface shaped convex surface; and

a ball spline for supporting said input disc on an outer peripheral surface of said input shaft so that said input disc can be freely shifted in an axial direction of said input shaft, said ball spline comprising;

a plurality of first spline grooves respectively formed in an inner peripheral surface of said input disc, each of said first spline grooves having two first chamfers respectively formed in circumferential-direction two end opening edge portions of said first spline groove;

a plurality of second spline grooves respectively formed in the outer peripheral surface of said input shaft, each of said second spline grooves having two second chamfers respectively formed in circumferential-direction two end opening edge portions of said second spline groove, wherein said first spline glooves and said second spline grooves respectively extend along a direction of said rotary shaft and are opposed to each other respectively, thereby forming a plurality of spline gaps; and

a plurality of balls arranged in series within said spline gaps,

wherein said second chamfers are set smaller than said first chamfers.