Recording medium conveyance device, recording medium conveyance method and non-transitory computer-readable recording medium encoded with recording medium conveyance instructions

A recording medium conveyance method executed in an image forming apparatus, the method comprising:

• determining whether a type of an object, conveyed by a conveyor of the image forming apparatus, is stored in a storage of the image forming apparatus;
• upon determining that the type is not stored in the storage, switching to a type detection process of detecting the type based on output of an ultrasonic sensor of the image forming apparatus and storing the type in the storage, wherein the ultrasonic sensor indicates an attenuation amount of an ultrasonic wave caused by the conveyed object;
• upon determining that the type is stored in the storage, switching to an overlay detection process of detecting whether the conveyed object is in an overlay state in which a gap is present based on a result of output of the ultrasonic sensor;
• and
• determining whether a conveyance state of the conveyed object is normal or abnormal based on the type and whether the conveyed object is in the overlay state.

A non-transitory computer-readable recording medium encoded with recording medium conveyance instructions executed by a computer that controls an image forming apparatus,

• the image forming apparatus comprising:
• a storage;
• a conveyer that conveys an object;
• and
• an ultrasonic sensor that outputs a value indicating an attenuation amount of an ultrasonic wave caused by the conveyed object, and
• the recording medium conveyance instructions causing the computer to:
• determine whether a type of the conveyed object is stored in the storage;
• upon determining that the type is not stored in the storage, switch to a type detection process of detecting the type based on a result of output of the ultrasonic sensor and executing a type detection process of storing the type in the storage;
• upon determining that the type is stored in the storage, switch to an overlay detection process of detecting whether the conveyed object is in an overlay state in which a gap is present based on a result of output of the ultrasonic sensor;
• and
• determine whether a conveyance state of the conveyed object is normal or abnormal based on the type and whether the conveyed object is in the overlay state.