| 摘要 |
PURPOSE:To find out an output variation due to a real internal wear with no relation to temperature variation by providing a permanent magnet inside of a ball joint for providing a Hall element for sensing magnetic force facing to the permanent magnet and another Hall element for referring to temperature nonsensible of magnetic force apart from said magnet to operate subtraction between outputs of both Hall elements. CONSTITUTION:A magnetic field due to a permanent magnet (11) stretches to outside of a closedown plate (10), and the magnetic force of said field is sensed strongly by a Hall element (12). But, a magnetic force is scarcely sensed by a Hall element (13) for referring to temperature because of its position apart from the permanent magnet (11). Supposing that a ball joint wears abnor mally and a cylinder (9) of a wear compensating bearing (8) restores by its elastic spring force, a ball head (5) and the permanent magnet 11 move in the direction to a socket opening (6). Then, a facing distance (L) between the perma nent magnet (11) and the Hall element (12) gets large. And, when the facing distance (L) reaches the set value, it is sensed to be the wear limit of the ball joint. Thus, an output variation due to a real internal wear can be find out with no relation to temperature variation.
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