Automatic document feeder, image forming apparatus, and fault detection method

An image forming apparatus comprising an image reading device, an operation and display component, and an automatic document feeder configured to feed documents one by one to the image reading device, wherein

• the automatic document feeder comprises
• a multi-feed detection sensor configured to detect multi-feed of the documents,
• a sensor controller configured to control the multi-feed detection sensor, and
• a control board on which the sensor controller is mounted,
• the multi-feed detection sensor comprises
• a transmission sensor configured to transmit a detection wave,
• a current detection circuit configured to detect a drive current of the transmission sensor,
• a transmission board on which the transmission sensor and the current detection circuit are mounted,
• a reception sensor configured to receive the detection wave,
• an amplifier circuit configured to amplify an amplitude of a reception signal of the reception sensor,
• a reception board on which the reception sensor and the amplifier circuit are mounted,
• a drive circuit configured to supply the drive current to the transmission sensor,
• a comparator configured to compare an output value of the amplifier circuit with a threshold set by the sensor controller, and
• a relay board on which the drive circuit and the comparator are mounted, and
• when the image forming apparatus is activated and returned, in order to detect a fault in the multi-feed detection sensor,
• the sensor controller checks connection between the control board and the relay board, and stores first fault information indicating disconnection of the relay board if the relay board is in a disconnected state,
• the sensor controller sets the threshold to a first threshold, and stores second fault information indicating that the reception board is at fault if a comparison result of the comparator indicates that the output value of the amplifier circuit is equal to or less than the first threshold,
• the sensor controller causes the drive circuit to start supplying the drive current, and stores third fault information indicating that the transmission board is at fault if the current detection circuit does not detect the drive current,
• the sensor controller sets the threshold to a second threshold, and stores fourth fault information indicating that the transmission sensor or the reception sensor is damaged if the comparison result of the comparator indicates that the output value of the amplifier circuit is equal to or less than the second threshold,
• the sensor controller causes the drive circuit to stop supplying the drive current,
• the sensor controller determines whether any of the first fault information to the fourth fault information is stored, and transmits, to the image forming apparatus, an instruction signal for causing the fault information to be displayed on the operation and display component if the fault information is stored, and
• the image forming apparatus displays the fault information on the operation and display component.

A fault detection method for detecting a fault in a multi-feed detection sensor of an automatic document feeder, wherein

• the automatic document feeder is configured to feed documents one by one to an image reading device of an image forming apparatus, and comprises
• the multi-feed detection sensor configured to detect multi-feed of the documents,
• a sensor controller configured to control the multi-feed detection sensor, and
• a control board on which the sensor controller is mounted, and
• the multi-feed detection sensor comprises
• a transmission sensor configured to transmit a detection wave,
• a current detection circuit configured to detect a drive current to be supplied to the transmission sensor,
• a transmission board on which the transmission sensor and the current detection circuit are mounted,
• a reception sensor configured to receive the detection wave,
• an amplifier circuit configured to amplify an amplitude of a reception signal of the reception sensor,
• a reception board on which the reception sensor and the amplifier circuit are mounted,
• a drive circuit configured to supply the drive current to the transmission sensor,
• a comparator configured to compare an output value of the amplifier circuit with a threshold set by the sensor controller, and
• a relay board on which the drive circuit and the comparator are mounted,
• the fault detection method comprising, when the image forming apparatus is activated and returned:
• checking connection between the control board and the relay board, and storing first fault information indicating disconnection of the relay board if the relay board is in a disconnected state;
• setting the threshold to a first threshold, and storing second fault information indicating that the reception board is at fault if a comparison result of the comparator indicates that the output value of the amplifier circuit is equal to or less than the first threshold;
• causing the drive circuit to start supplying the drive current, and storing third fault information indicating that the transmission board is at fault if the current detection circuit does not detect the drive current;
• setting the threshold to a second threshold, and storing fourth fault information indicating that the transmission sensor or the reception sensor is damaged if the comparison result of the comparator indicates that the output value of the amplifier circuit is equal to or less than the second threshold;
• causing the drive circuit to stop supplying the drive current;
• and
• determining whether any of the first fault information to the fourth fault information is stored, and displaying the fault information on the image forming apparatus if the fault information is stored.