| 摘要 |
PURPOSE:To cause the uniform thermal expansion of a polygon mirror even if the temp. rises after the operation of the device and to prevent the deterioration in image grade, etc., by adjusting the coeffts. of thermal expansion of materials, such as polygon mirror, retaining member and set screws, and the wall thicknesses of respective parts. CONSTITUTION:The polygon mirror 1 is held by a seat 2a provided on a revolving shaft 2 and a retaining member 4. The screws 3 are passed through the retaining member 4 and the polygon mirror 1 and are screwed to the female thread parts formed on the seat 2a of the revolving shaft 2 and to fix the polygon mirror 1 to the revolving shaft 2. Namely, the constitution to transfer the pressure from the screws 5 to the polygon mirror 1 via the retaining member 4 is adopted and, therefore, the transmitted pressure is uniformized. The ratio of the thermal expansion from the part where the heads of the screws 3 come into contact with retaining member 4 up to the thread parts screwed to the seat 2a of the revolving shaft 2 is so adjusted as to be approximately equaled to the ratio of the thermal expansion of the thicknesses of the retaining member 4 and the polygon mirror 1 even when the temp. rises. The constitution to prevent the pressure transmitted from the heads of the screws 3 to the polygon mirror 1 via the retaining member 4 from being changed by the temp. rise is, therefore, obtd. and the deterioration in the image grade is prevented. |
