PURPOSE: To obtain a sufficient damping effect without need of an oil damper or the like and to reduce number of components by providing a grease pool for torque grease with a step or a groove formed thereto between a turning shaft and a bearing section.

CONSTITUTION: An open cover 1 of an electronic device is engaged with a turning shaft of an operation panel through a bearing section 4 in a turnable way. Plural grease pools 7 are arranged to the bearing section 4 in the circumferential direction and torque grease with high viscosity used for an oil damper is sealed in the grease pools 7. In order obtain a sufficient damping effect, it is effective to increase a contact area of the turning shaft and the bearing section 4, and then a step or a groove is provided to at least one of the surface of the both. Through the constitution above, a sufficient damping effect is enhanced even when an oil damper is omitted through the constitution above.