A wheel-type resistance device for providing a resisting force to a bicycle exerciser which includes an axle defining an axial direction, and a hub member mounted rotatably on the axle and driven to rotate by a pedaling action of a user, said wheel-type resistance device comprising:
- a flywheel having left and right end walls, said flywheel being adapted to be mounted rotatably on the axle such that said left end wall is proximate to and is rotated together with the hub member around the axle, and such that said right end wall is distal to the hub member, said right end wall having an accommodation chamber therein indented axially and leftward so as to form a dragging force generating wall which is spaced apart from said right end wall in the axial direction and which has a first circumferential portion extending in a radial direction relative to the axle;
- a plurality of magnetically attractive members angularly provided on said first circumferential portion;
- a dragging force adjusting member adapted to be mounted on the axle and having a right major surface and a left major surface which is spaced apart from and opposing said dragging force generating wall and which is provided with a second circumferential portion that is registered with said first circumferential portion;
- upper and lower magnetic members disposed movably on said second circumferential portion and defining respectively upper and lower magnetic zones with upper and lower leading and tailing ends respectively, said upper leading and tailing ends being diametrically opposite to said lower tailing and leading ends respectively so that said upper and lower magnetic members are spaced apart from and are in symmetry with each other relative to a horizontal line that is transverse to the axial direction;
- a cam mechanism including a cam member adapted to be mounted rotatably on the axle and having a pair of cam surfaces disposed diametrically opposite to each other, and a pair of cam followers disposed respectively on said upper and lower magnetic members and engaged movably and respectively by said cam surfaces such that a counterclockwise angular displacement of said cam member will impart linear movements of said upper and lower magnetic members towards the horizontal line along a transverse direction relative to the horizontal line;
- a first biasing member disposed to bias said cam followers to engage movably and respectively said cam surfaces;
- and
- a tensioning member having a proximate end fixed at said cam member and a distal end mounted on said dragging force adjusting member such that a pulling force applied on said tensioning member will result in a clockwise angular displacement of said cam member for counteracting biasing action of said first biasing member to retain each of said cam surfaces at a first angular position, where said cam followers are lifted to a farthest position relative to the horizontal line, and where overlapping area of said upper and lower magnetic members with said second circumferential portion is largest;
- and
- a second biasing member disposed to bias against the pulling force applied on said tensioning member so as to place said tensioning member in a tense state when said tensioning member counteracts the biasing action of said first biasing member;
- whereby, a decrease in the pulling force applied on said tensioning member will result in the counterclockwise angular displacement of said cam member, thereby decreasing the overlapping area of said upper and lower magnetic members with said second circumferential portion.