| 摘要 |
Provided are a pair of pressure plates and a spring unit 2 situated between the pair of pressure plates. The spring unit 2 has a plurality of springs 20. The spring 20 each has, in a longitudinally sectional shape thereof, a curved central portion 21 having a substantially arc shape projecting in a direction perpendicular to an expansion/contraction direction, a pair of curved end portions 22 each having a substantially arc shape projecting at extensions of both ends of the curved central portion 21 in a direction opposite to the projecting direction of the curved central portion 21, and base portions 23 formed by extending edges of the curved end portions 22 in substantially parallel with in the direction perpendicular to the expansion/contraction direction, wherein the base portions 23 are respectively secured to the pair of pressure plates so that the spring 20 is located between the pair of pressure plates. The spring 20 with a length in natural state has linear straight portions 24 between the curved central portion 21 and the curved end portions 22. |
