| 摘要 |
A hollow crank spindle unit for bicycles includes a crank spindle (2) having an outer peripheral surface defining a first end, a second end and a hollow central portion (3). A plurality of first serrations (4) are formed on the first end of the crank spindle (2) and a plurality of second serrations (4) are formed on the second end of the crank spindle (2). A first guide surface (10) having a first guides surface diameter (d2) is formed on the outer peripheral surface continuously with and inwardly from the plurality of first serrations (4), and a second guide surface (10) having a second guide surface diameter (d2) is formed on the outer peripheral surface continuously with and inwardly from the plurality of second serrations (4). A first track groove (12) is formed on the outer peripheral surface in proximity to the first end of the crank spindle (2) wherein a lowermost surface of the first track groove has a first track groove diameter (D1). Similarly, a second track groove (13) formed on the outer peripheral surface in proximity to the second end of the crank spindle, wherein a lowermost surface of the second track groove (13) has a second track groove diameter (D2). A diameter of the central portion between the first track groove (12) and the second track groove (13) is less than the first guide surface diameter (d2) and the second guide surface diameter (d2). <IMAGE> |
