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An automatically adjusting magnetic resistance unit for an exercise device such as a bicycle trainer, in which the degree of resistance is automatically and non-linearly adjusted in relation to the rotational speed of a rotating member caused by the input of a user. The rotating member may be in the

An automatically adjusting magnetic resistance unit for an exercise device such as a bicycle trainer, in which the degree of resistance is automatically and non-linearly adjusted in relation to the rotational speed of a rotating member caused by the input of a user. The rotating member may be in the form of a flywheel having a number of supports extending between a hub and a rim. The supports define longitudinal grooves which slidably retain magnets that are biased inwardly toward the hub by biasing members. An electrically conductive member is located adjacent the flywheel. As the flywheel rotates in response to rotation of the bicycle wheel, the magnets interact with the conductive member to establish eddy currents that provide resistance to the rotation of the flywheel. The speed of rotation of the flywheel increases as the speed of rotation of the bicycle wheel increases, and centrifugal forces act on the magnets to cause the magnets to slide outwardly along the grooves in opposition to the bias of the biasing members. The outward movement of the magnets causes outward movement of the eddy current forces, to increase the resistance provided to rotation of the flywheel and the bicycle wheel. The variable resistance due to the increased or decreased rotational speed of the flywheel is smooth, based on the constant interaction of the counteracting forces of the biasing members and the centrifugal forces acting on the magnets.

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We claim: 1. A bicycle trainer, comprising: a frame configured to support a bicycle having a driven wheel; and a resistance device secure as a unit to the frame, wherein the resistance device comprises: a housing supported by the frame; a roller rotatably supported by the housing, wherein the rolle

We claim: 1. A bicycle trainer, comprising: a frame configured to support a bicycle having a driven wheel; and a resistance device secure as a unit to the frame, wherein the resistance device comprises: a housing supported by the frame; a roller rotatably supported by the housing, wherein the roller is arranged engage the driven wheel of the bicycle for rotation in response to rotation of the driven wheel; a rotatable member rotatably supported by the housing and interconnected with the roller for rotation in response to rotation of the driven wheel, wherein the rotatable member is rotatable about an axis of rotation in response to rotation of the driven wheel; a stationary electrically conductive member mounted to the housing adjacent the rotatable member; and one or more magnetic members movably mounted to the rotatable member, wherein the magnetic members are movable relative to the stationary electrically conductive member and relative to the axis of rotation in response to variations in the speed of rotation of the rotatable member; wherein the one or more magnetic members and the electrically conductive member cooperate to form an eddy current force which resists rotation of the rotatable member and thereby resists rotation of the roller and the driven wheel, wherein movement of the one or more magnetic members relative to the stationary electrically conductive member functions to alter the location of the eddy current force relative to the axis of rotation to vary the resistance to rotation of the rotatable member in response to the speed of rotation of the rotatable member caused by rotation of the roller and the driven wheel. 2. The bicycle trainer of claim 1, wherein the rotatable member comprises a flywheel mounted to a shaft which in turn is interconnected with the roller, and wherein the roller is adapted to be engaged by the driven wheel of the bicycle such that the flywheel imparts resistance to rotation of the driven wheel. 3. The bicycle trainer of claim 1, wherein the one or more magnetic members are each located within an open groove associated with the rotatable member, and further including a retainer positioned over the open groove to retain the magnetic member within the groove. 4. The bicycle trainer of claim 3, wherein the magnetic member is slidably retained within the groove. 5. The bicycle trainer of claim 3, further comprising a biasing member positioned within the groove, wherein the biasing member engages the magnetic member to bias the magnetic member radially inwardly. 6. The bicycle trainer of claim 1, wherein the rotatable member includes a plurality of vanes which circulate air upon rotation of the rotatable member. 7. The bicycle trainer of claim 1 wherein the electrically conductive member comprises a primary wall located adjacent a side of the rotatable member and an outer flange located radially outwardly of the rotatable member. 8. The bicycle trainer of claim 1, wherein each magnet is movably mounted to a radially extending support that extends outwardly from a hub section defined by the rotatable member, wherein each magnet is biased inwardly toward the hub section and is moved outwardly against the inward bias by centrifugal force caused by rotation of the rotatable member. 9. The bicycle trainer of claim 1 wherein the rotatable member is formed of a non-magnetic material. 10. The bicycle trainer of claim 9, wherein each magnetic member is positioned within a groove defined by the rotatable member, and is maintained in position on the rotatable member by means of a non-magnetic cover secured to the rotatable member over the groove. 11. The bicycle trainer of claim 1, wherein the one or more magnetic members are mounted to the rotatable member for radially inward and outward movement relative to the axis of rotation in response to variations in the speed of rotation of the rotatable member, and wherein the stationary electrically conductive member includes a radially outwardly extending surface that is axially spaced from the one or more magnetic members, wherein the radially outwardly extending surface of the conductive member lies in a plane that is parallel to the direction of movement of the one or more magnetic members. 12. The bicycle trainer claim 11, wherein the electrically conductive member comprises a disc-shaped member located adjacent the rotatable member. 13. A bicycle training apparatus, comprising: a) a support frame adapted to support a bicycle having a driven wheel; and b) a resistance unit attached to the support frame, wherein the resistance unit includes a housing, a roller rotatably supported by the housing and engageable with the driven wheel of the bicycle, a shaft extending outwardly from the roller, a stationary electrically conductive member secured to the housing, and a rotatable member attached to the shaft and located adjacent the stationary electrically conductive member, wherein the roller, the shaft and the rotatable member rotate about an axis of rotation, and wherein the rotatable member has at least one radially outwardly movable magnetic element that interacts with the stationary electrically conductive member to establish a resistive eddy current force upon rotation of the rotatable member, wherein the magnetic member is radially movable relative to the axis of rotation in response to the speed of rotation of the rotatable member caused by rotation of the driven wheel of the bicycle to resist rotation of the bicycle wheel. 14. The bicycle training apparatus of claim 13, wherein outward movement of the magnetic element is resisted by a biasing member that engages the magnetic element. 15. The bicycle training apparatus of claim 14 wherein the biasing member is a spring. 16. The bicycle training apparatus of claim 13 wherein the rotatable member comprises a flywheel having a number of vanes to circulate air relative to the conductive member. 17. The bicycle training apparatus of claim 16 wherein the vanes are positioned at an angle with respect to the axis of rotation of the rotatable member. 18. The bicycle training apparatus of claim 13, wherein the radially outwardly movable magnetic element is mounted to the rotatable member for radially inward and outward movement relative to the axis of rotation in response to variations in the speed of rotation of the rotatable member, and wherein the stationary electrically conductive member includes a radially outwardly extending surface that is axially spaced from the magnetic element, wherein the radially outwardly extending surface of the conductive member lies in a plane that is parallel to the direction of movement of the magnetic element. 19. A resistance unit for an exercise device, comprising: a rotatable member, wherein the rotatable member is rotatable about an axis of rotation; a disc-shaped electrically conductive member located adjacent the rotatable member; a magnetically attractive member mounted to the disc-shaped member to direct the magnetic flux of the magnetic member through the disc-shaped member; and one or more magnetic members movably mounted to the rotatable member, wherein the magnetic members are movable relative to the axis of rotation in response to variations in the speed of rotation of the rotatable member; wherein the one or more magnetic members and the electrically conductive member cooperate to form an eddy current force which resists rotation of the rotatable member, wherein movement of the one or more magnetic members functions to alter the location of the eddy current force relative to the axis of rotation to vary the resistance to rotation of the rotatable member in response to the speed of rotation of the rotatable member. 20. A resistance unit for an exercise device, comprising: a rotatable member, wherein the rotatable member is rotatable about an axis of rotation; an electrically conductive member located adjacent the rotatable member; and one or more magnetic members movably mounted to the rotatable member, wherein the magnetic members are movable relative to the axis of rotation in response to variations in the speed of rotation of the rotatable member; wherein the one or more magnetic members and the electrically conductive member cooperate to form an eddy current force which resists rotation of the rotatable member, wherein movement of the one or more magnetic members functions to alter the location of the eddy current force relative to the axis of rotation to vary the resistance to rotation of the rotatable member in response to the speed of rotation of the rotatable member; wherein the rotatable member includes a plurality of vanes which circulate air upon rotation of the rotatable member, and wherein the rotatable member is contained within a housing having a plurality of openings to allow circulation of air through the housing upon rotation of the rotatable member. 21. An bicycle trainer, comprising: a stationary frame configured to support a driven wheel of a bicycle; and a resistance unit mounted to the frame, wherein the resistance unit comprises a housing supported by the frame; a roller rotatably mounted to the housing, wherein the roller is configured to engage the driven wheel of the bicycle for rotation in response to rotation of the driven wheel; a stationary electrically conductive member interconnected with the housing, a rotatable member rotatably mounted to the housing and adapted to rotate in response to rotation of the roller caused by rotation of the driven wheel, and an automatically variable magnetic resistance arrangement carried by the rotatable member which interacts with the stationary electrically conductive member to provide eddy current resistance to the roller through the rotatable member, wherein the automatically variable magnetic resistance arrangement is operable to provide an automatically variable non-linear relationship between the speed of the rotatable member and the resistance provided to the roller in response to the speed of rotation of the rotatable member. 22. The bicycle trainer of claim 1, wherein the automatically variable magnetic resistance arrangement comprises at least one radially movable magnet carried by the rotatable member, and wherein the stationary electrically conductive member includes a radially outwardly extending surface that is axially spaced from the at least one radially movable magnet, wherein the radially outwardly extending surface of the conductive member lies in a plane that is parallel to the direction of movement of the at least one radially movable magnet. 23. An exercise method, comprising the acts of: providing a bicycle having a driven wheel; providing a bicycle trainer having a wheel engaging frame assembly and a resistance unit, the resistance unit including housing; a stationary electrically conductive member mounted to the housing, a shaft rotatably mounted to the housing, wherein the shaft is connected to a wheel-engaging roller and to a rotatable member, the rotatable member including at least one support, the at least one support having at least one movable magnetic element located adjacent the stationary electrically conductive member that is urged radially inwardly by a biasing member; engaging the driven wheel of the bicycle with the wheel engaging frame assembly so that the driven wheel is supported by the frame assembly and the driven wheel of the bicycle contacts the roller; rotating the driven wheel of the bicycle to rotate the roller, the shaft and the rotatable member about an axis of rotation, wherein the magnetic element interacts with the stationary electrically conductive member to establish an eddy current force that resists rotation of the rotatable member and thereby the bicycle wheel; and varying the radial position of the magnetic element relative to the axis of rotation against the force of the biasing member in response to variations in the speed of rotation of the rotatable member caused by variations in the speed of rotation of the driven wheel of the bicycle, wherein the act of varying the radial position of the magnetic element relative to the stationary electrically conductive member functions to vary the radial position of the eddy current force to vary the degree of resistance to rotation of the rotatable member. 24. The method of claim 23, wherein the stationary electrically conductive member includes a radially outwardly extending surface that is axially spaced from the magnetic element and parallel to the direction of movement of the magnetic element, and wherein the act of varying the radial position of the magnetic element is carried out by varying the radial position of the magnetic element along the radially outwardly extending surface of the electrically conductive member in response to variations in the speed of rotation of the driven wheel of the bicycle.