Abstract: An image forming unit forms test images of a color of the same type as a first color using toner of a second color and toner of a third color, transfers first and second test images, fixes the test images on a sheet, controls a sensor to read the test images, determines sampling timings for the test images based on an output signal related to the first test image outputted from the sensor using a color filter of a fourth color, acquires a result of reading the test images based on a reading result of the test images on the sheet by the color sensor using a color filter of the first color and the sampling timing, and determines a transfer voltage based on the result of reading the test images.

Abstract: An image reading apparatus includes a conveyance roller to convey a sheet, a light source to illuminate an image on the sheet while being moved in a predetermined direction above the conveyed sheet, a reading sensor to read the image on the sheet while being moved in the predetermined direction above the conveyed sheet, and a controller. The controller controls the reading sensor to read a first image for generating a color profile on a first sheet after the light source emits light for a duration of a first time. The controller controls the reading sensor to read a second image for detecting density unevenness in a main scanning direction of the image forming apparatus on a second sheet after the light source emits light for a duration of a second time shorter than the first time.

Abstract: An image forming unit forms test images of a color of the same type as a first color using toner of a second color and toner of a third color, transfers a first and second test images, fixes the test images on a sheet, controls a sensor to read test images, determines sampling timings for the test images based on an output signal related to the first test image outputted from the sensor using a color filter of a fourth color, acquires a result of reading the test images based on a reading result of the test images on the sheet by the color sensor using a color filter of the first color, and the sampling timing, and determines a transfer voltage based on the result of reading the test images.

Abstract: An image reading apparatus includes a conveyance roller to convey a sheet, a light source to illuminate an image on the sheet while being moved in a predetermined direction above the conveyed sheet, a reading sensor to read the image on the sheet while being moved in the predetermined direction above the conveyed sheet, and a controller. The controller controls the reading sensor to read a first image for generating a color profile on a first sheet after the light source emits light for a duration of a first time. The controller controls the reading sensor to read a second image for detecting density unevenness in a main scanning direction of the image forming apparatus on a second sheet after the light source emits light for a duration of a second time shorter than the first time.

Abstract: An image forming apparatus that determines presence or absence of bubbles with a simple configuration. The image forming apparatus forms an image on a sheet using a liquid developer including toner and carrier liquid. An exposure unit exposes a photosensitive member charged by a charging unit to form an electrostatic latent image. A development unit stores the liquid developer and develops the electrostatic latent image using the liquid developer. A supplying unit supplies toner and carrier liquid to the development unit. A light receiving unit receives light that is emitted from a light emitting unit and passes through the liquid developer in the development unit, and to output an output value based on a light receiving amount. A controller determines whether a bubble is generating in the liquid developer according to a period after the output value exceeding the first threshold until falling below a second threshold.

Abstract: An image forming apparatus that determines presence or absence of bubbles with a simple configuration. The image forming apparatus forms an image on a sheet using a liquid developer including toner and carrier liquid. An exposure unit exposes a photosensitive member charged by a charging unit to form an electrostatic latent image. A development unit stores the liquid developer and develops the electrostatic latent image using the liquid developer. A supplying unit supplies toner and carrier liquid to the development unit. A light receiving unit receives light that is emitted from a light emitting unit and passes through the liquid developer in the development unit, and to output an output value based on a light receiving amount. A controller determines whether a bubble is generating in the liquid developer according to a period after the output value exceeding the first threshold until falling below a second threshold.

Abstract: An image forming apparatus calculates a speed correction amount obtained by correcting a gain and a phase of a speed fluctuation component by a gain phase correction unit and a correction speed calculation unit so as to cancel this speed fluctuation component and controls a rotation speed of a rotator by using the calculated speed correction amount.

Abstract: An image forming apparatus capable of preventing image defects, such as color shift, from being caused, by preventing increased transfer pressure from being applied by a primary transfer section to thereby prevent a surface speed difference from being generated between the photosensitive drum and the intermediate transfer belt. The image forming apparatus includes a photosensitive drum and an intermediate transfer belt that rotates in contact with the photosensitive drum, respective brushless DC motors for driving the photosensitive drum for rotation and the intermediate transfer belt for rotation, and a controller for controlling the brushless DC motors. The controller performs control such that the brushless DC motor applies assist torque to the photosensitive drum, for offsetting load torque acting thereon, thereby enabling the photosensitive drum to be friction-driven by the intermediate transfer belt.

Abstract: An image forming apparatus calculates a speed correction amount obtained by correcting a gain and a phase of a speed fluctuation component by a gain phase correction unit and a correction speed calculation unit so as to cancel this speed fluctuation component and controls a rotation speed of a rotator by using the calculated speed correction amount.

Abstract: An image forming apparatus that is capable of forming an electrostatic latent image on the surface of a photosensitive member with high position accuracy even when the shaft of the photosensitive member is off-centered. In the apparatus, exposure devices form electrostatic latent images on respective photosensitive drums, and developing devices develop the electrostatic latent images. An intermediate transfer belt rotates in contact with the photosensitive drums. A rotary encoder detects a rotational speed of a drum shaft of each photosensitive drum. An amount of off-centering of the drum shaft is detected, and a correction coefficient for correcting positional displacement of electrostatic latent images is calculated. A control unit corrects timing of exposure using the calculated correction coefficient, and controls the exposure device to form the image on the photosensitive drum based on the corrected timing of exposure.

Abstract: An image forming apparatus stabilized in transferability of an image from the photosensitive member to the intermediate transfer belt. The image forming apparatus includes photosensitive drums and an intermediate transfer belt (ITB) that rotates in contact with each drum, brushless DC motors for driving the drum and the ITB for rotation. Rotary encoders associated with the drum and the ITB detect respective rotational speeds thereof. A controller sets a target value for the drum-associated rotary encoder for making the surface speeds of the drum and the belt equal to each other during normal printing operation, from a detection value from the drum-associated rotary encoder in a state of the drum being friction-driven by the belt at the primary transfer section, and controls the drum-associated motor such that the target value becomes a detection value.

Abstract: An image bearing member drive unit which is capable of performing excellent follow-up of random disturbances without increasing the costs and further with reduced energy loss. The image bearing member drive unit is formed by a brushless DC motor, a rotational position detector, a rotary encoder, a drive circuit, a motor driver IC, and a controller. The rotary encoder detects a drive speed of an image bearing member driven by the brushless DC motor. Drive current for the brushless DC motor is controlled according to the detected drive speed and a target speed. When a short brake signal for braking the brushless DC motor is on, current in a direction opposite to the drive current is generated to thereby brake the brushless DC motor.

Abstract: An image forming apparatus stabilized in transferability of an image from the photosensitive member to the intermediate transfer belt. The image forming apparatus includes photosensitive drums and an intermediate transfer belt (ITB) that rotates in contact with each drum, brushless DC motors for driving the drum and the ITB for rotation. Rotary encoders associated with the drum and the ITB detect respective rotational speeds thereof. A controller sets a target value for the drum-associated rotary encoder for making the surface speeds of the drum and the belt equal to each other during normal printing operation, from a detection value from the drum-associated rotary encoder in a state of the drum being friction-driven by the belt at the primary transfer section, and controls the drum-associated motor such that the target value becomes a detection value.

Abstract: An image forming apparatus that is capable of forming an electrostatic latent image on the surface of a photosensitive member with high position accuracy even when the shaft of the photosensitive member is off-centered. In the apparatus, exposure devices form electrostatic latent images on respective photosensitive drums, and developing devices develop the electrostatic latent images. An intermediate transfer belt rotates in contact with the photosensitive drums. A rotary encoder detects a rotational speed of a drum shaft of each photosensitive drum. An amount of off-centering of the drum shaft is detected, and a correction coefficient for correcting positional displacement of electrostatic latent images is calculated. A control unit corrects timing of exposure using the calculated correction coefficient, and controls the exposure device to form the image on the photosensitive drum based on the corrected timing of exposure.

Abstract: An image forming apparatus capable of preventing image defects, such as color shift, from being caused, by preventing increased transfer pressure from being applied by a primary transfer section to thereby prevent a surface speed difference from being generated between the photosensitive drum and the intermediate transfer belt. The image forming apparatus includes a photosensitive drum and an intermediate transfer belt that rotates in contact with the photosensitive drum, respective brushless DC motors for driving the photosensitive drum for rotation and the intermediate transfer belt for rotation, and a controller for controlling the brushless DC motors. The controller performs control such that the brushless DC motor applies assist torque to the photosensitive drum, for offsetting load torque acting thereon, thereby enabling the photosensitive drum to be friction-driven by the intermediate transfer belt.

Abstract: An image bearing member drive unit which is capable of performing excellent follow-up of random disturbances without increasing the costs and further with reduced energy loss. The image bearing member drive unit is formed by a brushless DC motor, a rotational position detector, a rotary encoder, a drive circuit, a motor driver IC, and a controller. The rotary encoder detects a drive speed of the image bearing member driven by the brushless DC motor. Drive current for the brushless DC motor is controlled according to the detected drive speed and a target speed. When a short brake signal for braking the brushless DC motor is on, current in a direction opposite to the drive current is generated to thereby brake the brushless DC motor.