This invention relates to variable speed drive systems and more particularly to torque sensing pulleys for such drive systems.
Variable speed drive systems utilizing a V-belt and pulley drive system for transferring power from a driving pulley to a driven pulley are well known. In such systems a driving pulley, connected with the output shaft of an engine or other source of power, and a driven pulley connected with driven shaft, are made to include a fixed pulley-half and a movable pulley-half, with the spacing between the respective pulley-halves determining the drive ratio from the input shaft to the output shaft. Such variable speed drive systems are used as a part of the drive system of such devices as agricultural machines, snowmobiles, automobiles, golf carts, utility vehicles, and the like.
In one example of a torque-sensing variable speed drive, the driven pulley relies on the combination of a pretension spring and a torque feedback ramp to exert the required pressure on the movable pulley pulley to maintain the optimum side load on the belt. The floating pulley-half is pushed towards the fixed pulley-half using a fixed-angle set of cams and a spring. This pushing action and associated mechanism utilizes the driven shaft for support and torsional constraint. With prior torque-sensing pulleys, this pushing action changes proportionally with torque to provide sufficient belt squeeze and belt tension at peak torque but less squeeze and tension at lower torque. This reduction at lower torque improves belt life. The previously mentioned spring is needed to maintain a prevailing squeeze between the pulley-halves and the belt so that friction is always present, as some friction is required for the torque-sensing reaction to develop. However, this pre-load provided by the spring is only in the axial direction and does not prevent separation (backlash) of the otherwise mating cams in rotational direction during deceleration and back-driving. Cam separation can result in rapid closure or slamming and damage to cams when forward-driving is resumed.
In one embodiment, the invention is directed to a variable speed belt drive system having a driving pulley, a V-belt, and a driven pulley connected to the driving pulley with the V-belt. The driven pulley includes a pulley shaft rotatable about a pulley axis, an inboard pulley-half having a first contact surface that is inclined relative to the axis of the pulley shaft that defines a first belt-contacting wall of driven pulley, wherein the first contact surface is fixed relative to the pulley shaft. The driven pulley has an outboard pulley-half having a second contact surface that is opposite the first contact surface and that is inclined relative to the axis of the pulley shaft, the outboard pulley-half being movable relative the inboard pulley-half such that the second contact surface is moveable relative to the driven pulley shaft. The inboard pulley-half is connected to the outboard pulley-half with two or more tension struts. Each strut extends through a slot in the outboard pulley-half so that the length of each strut is greater than spacing between the pulley-halves. A first end of each of the struts is connected to a hub of the inboard pulley-half and a second end of each of the struts is connected to a hub of the outboard pulley-half so that the outboard pulley-half can rotate relative to inboard pulley-half.
These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.
The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the views of the drawings.
The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.
Referring now to the drawings, and particularly to
Turning now to
According to the invention, the inboard pulley-half 30 is connected to the outboard pulley-half 40 with two or more tension struts 50. The struts 50 extend beyond the outboard pulley-half 40 through a slot 52 in the outboard pulley-half 40 so that the length of each strut 50 is greater than spacing between the pulley-halves 30, 40. A first end 54 of each of the struts 50 is connected to the hub 38 of the inboard pulley-half 30 as best seen in
Desirably, the struts 50 are solid spring-grade wire with the ends 54, 56 anchored such that any windup between pulley-halves 30, 40 applies a torsional action to the cross-section of the struts 50. In affect these tension struts 50 then also become torsional members and can function as springs to provide a prevailing closing (squeeze) force between pulley-halves 30, 40.
The foregoing has broadly outlined some of the more pertinent aspects and features of the present invention. These should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be obtained by applying the disclosed information in a different manner or by modifying the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings.
Filing Document | Filing Date | Country | Kind |
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PCT/IB2018/055044 | 7/9/2018 | WO | 00 |
Number | Date | Country | |
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62543843 | Aug 2017 | US |