Sheet feeding device and image forming apparatus

A sheet feeding device comprising:

• a lift plate on which a sheet is set;
• a feeding portion that contacts the sheet on the lift plate from above to pull and feed the sheet out from the lift plate;
• a lifting member that is disposed under the lift plate, the lifting member lifting the lift plate by making one end of the lifting member in a feeding direction pivot upward about another end of the lifting member in the feeding direction serving as a pivot fulcrum, the lifting member thereby bringing the sheet on the lift plate into contact with the feeding portion;
• a motor that is coupled to a pivot shaft serving as a pivot fulcrum of the lifting member, the motor rotating the pivot shaft and thereby making the one end of the lifting member pivot upward;
• a control portion that controls the motor, the control portion stopping driving the motor when the sheet on the lift plate contacts the feeding portion;
• and
• an encoder that outputs a pulse signal according to rotation of the pivot shaft, wherein
• the encoder includes:
• a rotary member that has a plurality of sensing targets arranged at intervals from each other in a circumferential direction of the pivot shaft, the rotary member rotating together with the pivot shaft;
• and
• an optical sensor that has a light emitter and a light receiver disposed so as to face each other across a movement path of the plurality of the sensing targets, the optical sensor changing a level of the pulse signal between when the light from the light emitter reaches the light receiver and when the light from the light emitter does not reach the light receiver,
• the control portion recognizes a remaining quantity of the sheets on the lift plate based on a count value of the pulse signal,
• when the motor stops being driven, the control portion thereafter does not count the pulse signal until a predetermined period elapses,
• when the motor stops being driven, the rotary member swings in the circumferential direction under vibration generated in the sheet feeding device,
• when the level of the pulse signal changes from a first level to a second level, the control portion increments the count value,
• when the motor stops being driven at a timing of the pulse signal changing from the first level to the second level, even if the pulse signal changes from the first level to the second level in the predetermined period, the control portion increments the count value only once, and,
• when the light from the light emitter does not reach the light receiver, the pulse signal at the first level is output from the encoder, and, when the light from the light emitter reaches the light receiver, the pulse signal at the second level is output from the encoder.