Traction-drive transmission

• US 4,098,146 A
• Filed: 09/10/1976
• Issued: 07/04/1978
• Est. Priority Date: 09/10/1976
• Status: Expired due to Term

• Current Assignee: The Torrington Company (The Timken Company)
• Original Assignee: Textron Inc
• Inventors: McLarty, Daniel R.
• Primary Examiner(s): Scott, Samuel
• Assistant Examiner(s): Chandler, Lance W.
• Application Number:
  US05/721,938
• Time in Patent Office: 662 Days
• Field of Search: 74/190, 74/200, 74/194, 74/690
• US Class Current: 475/186
• CPC Class Codes: F16H 15/50 Gearings providing a continuous range of gear ratios
• CPC Class Codes: F16H 37/084 at least one power path being a continuously variable transmission, i.e. CVT

Abstract

The invention contemplates an improved mechanical traction drive providing a single control whereby a desired range of speed ratios between input and output shafts is selectively available, without requiring clutch connection to the power source, such as an internal-combustion engine. The transmission involves a combination of completely mechanical friction-roller and meshing-gear planetary systems which are connected at all times, whether the single control is operated to call for a forward drive, a stop or a reverse drive of the output shaft. For the particular disclosed form, provision is made for automatic downshifting reaction to increasing load, the major axial-reaction forces are self-contained by rotating mechanism, thus (a) avoiding substantial axial force components on main-bearings of the mechanism, and (b) reducing to very small magnitudes the requisite force for selective control actuation.

Claims

1. A transmission comprising a housing, a drive shaft and a driven shaft journaled for rotation in said housing on a common axis, a variable-ratio coupling mechanism coupling said shafts, said mechanism including reaction means having torsionally resilient antirotational support about said axis in said housing, whereby in reaction to increasing torsional load said mechanism will be displaced in rotation about said axis and against increasing torsional resistance by said resilient means, said mechanism further including a control member for changing the coupling ratio between said input and output shafts, cam and follower elements reacting to such displacement and including a cam carried by said housing and a follower connected to said control member for modifying the instantaneous control condition of said control member, and means for varying the effective slope orientation of said cam, whereby the rate at which the coupling ratio is varied in response to load torque is a function of the instantaneous slope orientation of said cam.

2. In a traction-drive transmission, comprising a housing, a drive shaft journaled for rotation in said housing, two spaced sun wheels having keyed longitudinally relatively slidable support on said shaft, a sun gear keyed to said shaft, Belleville-washer means carried by said shaft and axially pre-loading said sun wheels in the direction of relative axial approach to each other, plural like planet wheels axially interposed between and in rolling contact with said sun wheels, a planet-member carrier supported for rotation about the shaft axis and including spaced radial guides positioning said planet wheels on angularly spaced axes offset front the shaft axes and in said planet-member carrier, whereby each of said planet wheels may have at least a degree of generally radial freedom at its guided angular position with respect to said carrier, planet gears carried by said planet-member carrier and meshing with said sun gear on angularly spaced axes offset from the shaft axis, two axially movable reaction rings having torsionally resilient anti-rotational support in said housing and in constant rolling contact with said planet wheels, an output shaft journaled for rotation in said housing on the alignment axis of said drive shaft, and a ring gear carried by said output shaft and meshing with said planet gears;

and selectively operable shift means for varying the relative axial spacing of said reaction rings, said shift means including a yoke having arms pivotally supported by said housing on opposite sides of the shaft axis, first control connections of one reaction ring to said arms at a first location of offset from the pivot axis, and second control connections of the other reaction ring to a second location of offset from the pivot axis, said first and second control connections being at opposite offsets from the pivot axis of said yoke;

the improvement in which said shift means comprises a yoke-actuating follower element carried by said yoke at a location radially offset from the yoke-pivot axis, a control member pivotally referenced to said housing and having an elongate guide in constant engagement with said follower element through the range of torsionally reactive angular displacement of said reaction rings in response to a range of output-drive loading, said control member being positioned such that one end of said guide positions said yoke for lowest transmission ratio at maximum output-drive loading, and selectively operable means for setting the pivoted orientation of said control member such that a maximum range of transmission ratios is available for lesser output-drive loading.

3. The transmission of claim 2, in which said guide is a cam forming part of said control member, and in which said follower element is a cam follower tracking said cam.

4. The transmission of claim 2, in which said selectively operable means includes a shift rod longitudinally guided in and by said housing, said rod having an actuating connection to said control member.

5. The transmission of claim 4, in which said control member comprises an arm connected at one end to said shift rod and in longitudinal abutment with said housing at its other end, said guide extending between said ends.

6. A traction-drive mechanism, comprising a housing, input and output shafts journaled for rotation on the same alignment in said frame, a variable-ratio assembly including a carrier mounted on one of said shafts and constantly engaged rotatable elements on said carrier and on said shafts for variable-ratio coupling of said shafts, torsionally compliant means coactive between said housing and said assembly for torsionally compliant angular displaceability of said assembly about said shaft alignment as a function of load-torque reaction, axially displaceable reaction rings forming part of said variable-ratio assembly for varying the input-output transmission ratio in accordance with the relative axial displacement of said rings, differentially operative means including a cam carried by said housing and a cam-follower carried by said assembly for varying the axial separation of said rings and thus for varying the input-output transmission ratio;

and selectively operable means for varying the effective slope of said cam as encountered by said cam-follower in the course of a load-reacting torsional displacement of said assembly about said shaft alignment, the placement of said cam being such with respect to a no-load position of said cam-follower that increasing load-torque reaction displacement about said shaft alignment is operative to drive said cam-follower in the direction of lower transmission-ratio adjustment of said assembly.

7. A traction-drive mechanism according to claim 6, in which said cam is straight and is pivotally related to said housing at one end and is connected at its other end to said selectively operable means.

8. Traction-drive mechanism according to claim 6, in which said cam is elongate and wherein the range of cam orientation by said selectively operable means extends through a range of slopes with respect to a single radial plane containing said cam-follower under zero-transmission ratio conditions.

9. Traction-drive mechanism according to claim 6, in which said selectively operable means includes a control rod longitudinally guided with respect to said housing, said control rod being connected to said cam for selectively changing the orientation thereof.

10. A traction-drive mechanism, comprising a housing, input and output shafts journaled for rotation on the same alignment in said frame, a variable-ratio assembly including a carrier mounted on one of said shafts and constantly engaged rotatable elements on said carrier and on said shafts for variable-ratio coupling of said shafts, torsionally compliant means coactive between said housing and said assembly for torsionally compliant angular displaceability of said assembly as a function of load-torque reaction, axially displaceable reaction rings forming part of said variable-ratio assembly for varying the input-output transmission ratio in accordance with the relative axial displacement of said rings, differentially operative means including a cam carried by said housing and a cam-follower carried by said assembly for varying the axial separation of said rings and thus for varying the input-out transmission ratio;

and selectively operable means including a control rod longitudinally guided with respect to said housing, said control rod being connected to said cam for varying the effective slope of said cam as encountered by said cam-follower in the course of a load-reacting torsional displacement of said assembly, the placement of said cam being such with respect to a no-load position of said cam-follower that increasing load-torque reaction displacement is operative to drive said cam-follower in the direction of lower transmission-ratio adjustment of said assembly, said control rod being also mounted for limited angular displaceability, and clutch means disengageably connecting coacting elements of said assembly, said clutch means having an operative connection of said control rod and being responsive solely to rotational displacement thereof.

11. Traction-drive mechanism according to claim 10, and including guidance means fixed with respect to said housing and coacting with said rod to constrain said rod for substantially purely longitudinal displacement for all positions except substantially at the zero-transmission ratio position.

12. Traction-drive mechanism according to claim 11, wherein said control rod includes a radial-arm portion, and wherein said guidance means includes a control plate fixed with respect to said housing, said plate having slot formations for guidance of said arm.

13. Traction-drive mechanism according to claim 12, in which said slot formations include a transversely extending region at substantially the zero-transmission ratio position, the transverse extent of said region being such as to enable a clutch-disengaging rotational displacement of said arm and control rod.