| 摘要 |
PROBLEM TO BE SOLVED: To stabilize frictional characteristics and improve heat resistant durability by providing a sliding surface of a brake drum with a groove parallel with the sliding direction. SOLUTION: A groove 21 parallel with the sliding direction of a brake drum 20 on the sliding surface thereof is provided. The pitch, depth and width thereof should be 0.3-2 mm, 2-100μm, and 0.1-1.4 mm, respectively. The groove 21 has a semi-sperical, angular or tapered form. Accordingly, the contact with a frictional member is a linear contact, thereby eliminating an influence of oil film at the initial stage of fastening in a brake band for ennacing the biting characteristic. Lublicant is fully held in the groove 21 under the fastening sliding operation, on the other hand, to always lublicate the frictional face for restraining the increase of frictional coefficient, resulting in reduction in the temperature of the frictional surface. Furthermore, in the groove 21 parallel with the sliding direction, no face angle generates to the frictional sliding and thus wear caused by cutting is relaxed. In this way a smooth speed change characteristic is obtained and kept for a long period of time.
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