Disk-mounting structure for optical encoder

提供一种转盘不偏心的光学式编码器。该光学式编码器备有：支承在外壳(1)的轴承(3)上的转轴(2)、固定在转轴(2)上有码图形的转盘(4)、接受通过转盘(4)的来自发光元件(10)的光后变换成电信号的受光元件(12)、以及安装了根据电信号进行检测的电路的基板(13)，在该光学式编码器中备有：在中央设有转轴(2)贯通的孔，背面被置于转轴(2)的台阶面(2a)上的转盘(4)；置于涂敷在转盘(4)的上表面上的粘合剂(6)的表面上、以一定的间隙嵌合在转轴(2)上的衬垫(5)；压入到转轴(2)上，以使衬垫(5)和转盘(4)固定在转轴(2)上的临时止动环(7)；以及涂敷在衬垫(5)、临时止动环(7)及转轴(2)上的粘合剂(8)。因此，粘合剂(8)不会流入转轴(2)的小直径部(2b)的外周和转盘(4)的孔部(4a)的内周之间、以及转盘(4)的下表面和台阶面(2a)之间。 An optical encoder is provided in which a disk is prevented from eccentric rotation. An optical encoder comprises a shaft (2) supported on a bearing (3) in a housing (1), a rotating disk (4) having a code pattern and fixed to the shaft (2), a photodetector element (12) which receives light passing through the rotating disk (4) from a light-emitting element (10) and converts it into an electric signal, and a substrate (13) on which is mounted a circuit for detecting a signal in the electric signal. The shaft (2) is inserted in a hole (4a) opened in the center of the rotating disk (4), the backside of which is seated on a step (2a) of the shaft (2). The optical encoder further comprises a spacer (5) fitted loosely over the shaft (2) and placed on an adhesive (6) spread on the rotating disk (4), a ring (7) for fixing the spacer (5) and the disk (4) tentatively to the shaft (2), arid adhesive (8) spread on the spacer (5), the ring (7) and the shaft (2). This structure prevents the adhesive (8) from entering between the thinner part (2b) of the shaft (2) and the hole (4a) of the disk (4) and between the backside of the disk (4) and the step (2a).