Abstract: An image forming apparatus includes: a conveyance roller configured to convey recording sheets; a brush motor configured to drive the conveyance roller to rotate; and a control unit configured to control a rotational speed of the brush motor, wherein while the conveyance roller conveys a recording sheet, (i) the control unit applies voltage to an outer circumferential surface of a commutator of the brush motor to drive the brush motor to rotate by a predetermined rotation amount, so as to perform a cleaning operation to remove a film deposited on the outer circumferential surface, and (ii) the control unit reduces the rotational speed of the brush motor while not performing the cleaning operation, so as to correct a conveyance distance of the recording sheet.

Abstract: An image forming apparatus includes a longitudinally conveying motor, a main-body-side control board, and a sensor. In the longitudinally conveying motor, an encoder generates an encoder signal having a frequency corresponding to the number of rotations of the longitudinally conveying motor, and a sensor signal superimposing unit receives an input of a logical state of the sensor. The sensor signal superimposing unit superimposes the logical state of the sensor on the encoder signal by modulating a duty ratio of the encoder signal based on the logical state of the sensor, and outputs a post-superimposition encoder signal. In the main-body-side control board, a sensor signal separating unit obtains the logical state of the sensor by demodulating the input encoder signal.

Abstract: A sheet conveying device includes: a roller that conveys a sheet; a leading end retaining member that temporarily retaining a front portion in a conveying direction of the sheet conveyed by the roller; a moving unit that moves a rear portion of the sheet toward a direction intersecting the conveying direction using a pushing member while the sheet is retained by the leading end retaining member, the pushing member being located on a downstream side of the roller; and an inverting and conveying roller that, after the moving unit moves the sheet, conveys the sheet while the rear portion of the sheet is set to a head.

Abstract: An image forming apparatus includes: a stepping motor arranged in a conveying path for a paper; a driver for driving the stepping motor; a current detecting unit for detecting an actual current value; and a control unit for providing a set current value for every predetermined cycle. The control unit determines an estimated load torque value corresponding to the set current value in a previous cycle and the actual current value in a present cycle, by referring to a relationship between actual current and load torque of the stepping motor with respect to the set current value, determines a target load torque value based on the estimated load torque value, and determines, as the set current value, a current value corresponding to the target load torque value, by referring to a relationship between maximum output torque of the stepping motor and current supplied to the stepping motor.

Abstract: A control device for generating a second trigger with a delay of a predetermined time from generation of a first trigger, said control device having; a counter for counting numbers from 0 to n?1 at a frequency with cycles of a first period; a control section, which operates at a frequency with cycles of a second period that is longer than the first period, for calculating a remainder of a division by adding a number of counts of the counter corresponding to the predetermined time to a count value of the counter at the time of generation of the first trigger and by dividing a result of the addition by n; and an output section for outputting the second trigger at a time when the count value of the counter becomes equal to the remainder.

Abstract: A sheet detection unit of an image forming apparatus includes a light receiving unit including a plurality of light receiving elements arranged in a sheet feeding direction. A computation processing unit shifts signals from the elements in synchronization with a sheet feeding speed and makes additions, increases a signal change level, and stores the signals in buffers in a result storage unit. A sheet position determination unit detects a position of an edge portion of a sheet being fed based on distribution of data stored in the buffers.

Abstract: A variable frequency clock output circuit, comprising: a target value register which stores a target value corresponding to an arbitrarily set target frequency; an increase/decrease value register which stores an arbitrarily set increase/decrease value; an adder-subtractor which has an input portion into which a current output value is inputted and outputs a calculation result obtained by adding/subtracting the increase/decrease value stored in the increase/decrease value register to/from the current output value inputted into the input portion based on an addition/subtraction instruction signal; a comparator which compares an output value of the adder-subtractor to the target value stored in the target value register, and outputs an addition/subtraction instruction signal to the adder-subtractor until the output value of the adder-subtractor and the target value coincide; and a clock generator which outputs a clock signal having a frequency proportional to the output value of the adder-subtractor.

Abstract: A sheet feeding device that is suited to be employed in an image forming apparatus having a printing section for printing an image on a sheet. The sheet feeding device has feed rollers for feeding a sheet at a speed “Va” and timing rollers for feeding a sheet fed by the feed rollers to the printing section at a speed “Vb”. Sensors are provided between the feed rollers and the timing rollers, so that the gap between a foregoing sheet and a following sheet can be detected at a plurality of detection points while the foregoing sheet is being fed by the timing rollers and the following sheet is being fed by the feed rollers. When one of the sensors detects that there is a gap between the sheets, a control unit controls the feed rollers such that the speed “Va” will be higher than the speed “Vb”.

Abstract: A sheet detection unit of an image forming apparatus includes a light receiving unit including a plurality of light receiving elements arranged in a sheet feeding direction. A computation processing unit shifts signals from the elements in synchronization with a sheet feeding speed and makes additions, increases a signal change level, and stores the signals in buffers in a result storage unit. A sheet position determination unit detects a position of an edge portion of a sheet being fed based on distribution of data stored in the buffers.

Abstract: A variable frequency clock output circuit, comprising: a target value register which stores a target value corresponding to an arbitrarily set target frequency; an increase/decrease value register which stores an arbitrarily set increase/decrease value; an adder-subtractor which has an input portion into which a current output value is inputted and outputs a calculation result obtained by adding/subtracting the increase/decrease value stored in the increase/decrease value register to/from the current output value inputted into the input portion based on an addition/subtraction instruction signal; a comparator which compares an output value of the adder-subtractor to the target value stored in the target value register, and outputs an addition/subtraction instruction signal to the adder-subtractor until the output value of the adder-subtractor and the target value coincide; and a clock generator which outputs a clock signal having a frequency proportional to the output value of the adder-subtractor.

Abstract: A controller of a color copier according to the invention includes a drive controller section, a pattern generation section, and a velocity information acquisition section. The drive controller section changes the phase relationship in rotation angle between a drive roller driving the transfer belt and individual photosensitive drums of a plurality of imaging sections. The pattern generation section forms registered marks on the transfer belt by using the plurality of imaging sections before and after the drive controller section changes the phase relationship. The velocity information acquisition section acquires at least one of a velocity fluctuation component of individual photosensitive drums and a velocity fluctuation component of the transfer belt in accordance with the result of sensing by a mark sensor for two registered marks formed by the pattern generation section.

Abstract: A controller of a color copier according to the invention includes a drive controller section, a pattern generation section, and a velocity information acquisition section. The drive controller section changes the phase relationship in rotation angle between a drive roller driving the transfer belt and individual photosensitive drums of a plurality of imaging sections. The pattern generation section forms registered marks on the transfer belt by using the plurality of imaging sections before and after the drive controller section changes the phase relationship. The velocity information acquisition section acquires at least one of a velocity fluctuation component of individual photosensitive drums and a velocity fluctuation component of the transfer belt in accordance with the result of sensing by a mark sensor for two registered marks formed by the pattern generation section.