Patent Application
20240377771
This application relates to and claims priority rights from Japanese Patent Application No. 2023-078374, filed on May 11, 2023, the entire disclosures of which are hereby incorporated by reference herein.
The present disclosure relates to an image forming apparatus.
An image forming apparatus includes a light beam scanning device that performs scanning of a light beam using a polygon mirror. In such a light beam scanning device, lengths of plural reflection surfaces of the polygon mirror have fluctuation, and therefore, in order to restrain a fluctuation of a scanning period in a primary scanning direction, each reflection surface is identified and correction of the scanning period is required for each reflection surface.
An image forming apparatus detects a mark attached on an axis of motor that rotates a polygon mirror using a reflective-type optical sensor to identify each reflection surface, and thereby identifies each reflection surface. Further, the aforementioned mark is detected on the basis of a sensor signal outputted from the reflective-type optical sensor, a detection timing of the mark is set as a reference, each reflection surface is identified on the basis of a relative light beam detection timing of a BD sensor (a sensor that detects a scanned light beam at a predetermined position), and the aforementioned correction is performed. For example, identified as the first surface is a reflection surface that reflects the light beam from the first light beam detection timing after the detection timing of the mark to the next light beam detection timing; and afterward, the second and subsequent surfaces are identified using the light beam detection timings.
In the aforementioned image forming apparatus, an output waveform (waveform of the sensor signal) of the reflective-type optical sensor varies due to an operational condition of the image forming apparatus (the light beam scanning device), and therefore, a wrong reflection surface of the polygon mirror is detected in error due to overlapping of the detection timing of the mark and the light beam detection timing of the BD sensor or misdetecting as the mark a balancer (a weight such as sticky substance or adhesive) attached to the motor axis for restraining eccentricity.
An image forming apparatus according to an aspect of the present disclosure includes a photoconductor drum, an exposure device, a development device, and a controller. The exposure device is configured to irradiate the photoconductor drum with a light beam and thereby form an electrostatic latent image. The development device is configured to cause toner to adhere to the electrostatic latent image and thereby generate a toner image. The controller is configured to control the exposure device. Further the exposure device includes a polygon mirror, a polygon motor, a mark detector, and an actuator. The polygon mirror is configured to scan the light beam. The polygon motor is configured to rotate the polygon mirror. The mark detector is configured to detect a mark attached to a motor axis of the polygon motor. The actuator is configured to be enabled to move the mark detector. Furthermore, the controller moves the mark detector using the actuator to a position corresponding to an operation condition of the exposure device.
These and other objects, features and advantages of the present disclosure will become more apparent upon reading of the following detailed description along with the accompanied drawings.
Hereinafter, embodiments according to an aspect of the present disclosure will be explained with reference to drawings.
The image forming apparatus in this embodiment includes a tandem-type color development device. This color development device includes photoconductor drums 1a to 1d, exposure devices 2a to 2d, and development devices 3a to 3d. The photoconductor drums 1a to 1d are photoconductors of four toner colors: Cyan, Magenta, Yellow and Black.
The exposure devices 2a to 2d irradiate the photoconductor drums 1a to 1d with laser light beams and thereby form electrostatic latent images. The exposure devices 2a to 2d are laser scanning units that have laser diodes as light sources of the laser light beams, optical elements (such as lens, mirror and polygon mirror) that guide the laser light beams to the respective photoconductor drums 1a to 1d.
Further, the periphery of each one of the photo conductor drums 1a to 1d includes a charging unit such as scorotron, a cleaning device, a static electricity eliminator and the like. The cleaning device removes residual toner on each one of the photo conductor drums 1a to 1d after primary transfer. The static electricity eliminator eliminates static electricity of each one of the photoconductor drums 1a to 1d after primary transfer.
Toner cartridges which contain toner of four colors: Cyan, Magenta, Yellow and Black are attached to the development devices 3a to 3d, respectively. In the development devices 3a to 3d, the toner is supplied from the toner cartridges, and this toner and carrier compose developer. The development devices 3a to 3d causes the toner to adhere to the photoconductor drums 1a to 1d and thereby forms toner images.
The photoconductor drum 1a, the exposure device 2a and the development device 3a perform development of Magenta. The photoconductor drum 1b, the exposure device 2b and the development device 3b perform development of Cyan. The photoconductor drum 1c, the exposure device 2c and the development device 3c perform development of Yellow. The photoconductor drum 1d, the exposure device 2d and the development device 3d perform development of Black.
The intermediate transfer belt 4 is a loop-shaped image carrier, and contacts the photoconductor drums 1a to 1d. Toner images on the photoconductor drums 1a to 1d are primarily transferred onto the intermediate transfer belt 4. The intermediate transfer belt 4 is hitched around driving rollers 5, and rotates by driving force of the driving rollers 5 towards the direction from the contact position with the photoconductor drum 1d to the contact position with the photoconductor drum 1a.
A transfer roller 6 causes an incoming paper sheet in transportation to contact the transfer belt 4, and secondarily transfers the toner image on the transfer belt 4 to a print sheet. The print sheet on which the toner image has been transferred is transported to a fuser 9, and consequently, the toner image is fixed on the print sheet.
A roller 7 has a cleaning brush, and removes residual toner on the intermediate transfer belt 4 by contacting the cleaning brush to the intermediate transfer belt 4 after transferring the toner image to a print sheet.
A sensor 8 is an optical sensor that measures a density of a developed toner patch image in the calibration, and irradiates the intermediate transfer belt 4 with a light beam and detects its reflected light. For example, when adjusting a toner density in the calibration, the sensor 8 irradiates a predetermined area (toner patch image or surface material of the intermediate transfer belt 4) on the intermediate transfer belt 4, detects its reflected light, and outputs an electric signal corresponding to a light amount of the reflected light.
A registration roller 10 temporarily stops the incoming print sheet transported from a print sheet feeding tray or the like in primary paper sheet feeding, and at a second feeding timing, transports the print sheet to a transfer position between the intermediate transfer belt 4 and the transfer roller 6. The second feeding timing is specified so as to cause a toner image on the intermediate transfer belt 4 to be transferred to a specified position on the print sheet. A registration sensor 11 is a sensor that is arranged near the registration roller 10, and optically detects that a print sheet reaches the registration roller 10 (i.e. registration position).
In
Further, the polygon mirror 23 is an element connected to a motor axis 24a of the polygon motor 24 such that the motor axis 24a is perpendicular to an axis of the photoconductor drum 1a, a cross section of the polygon mirror 23 perpendicular to the motor axis 24a has a polygon shape (e.g. hexagon shape), and plural side surfaces of the polygon mirror 23 are planar mirrors (reflection surfaces).
The polygon mirror 23 rotates around the motor axis 24a, and scans the laser light emitted from the light source 21, along an axis direction of the photoconductor drum 1a (i.e. along a primary scanning direction). A polygon motor 24 causes the polygon mirror 23 to rotate in accordance with a control signal supplied from a controller 31. For example, the polygon motor 24 causes the polygon mirror 23 to rotate at a rotation speed (rotation frequency) specified by the control signal.
Further, the BD (Beam Detection) sensor 25 is a sensor that receives at a predetermined position the laser light beam scanned by the polygon mirror 23 to generate a primary-scanning-directional synchronization signal. When light enters the BD sensor 25, the BD sensor 25 induces an output voltage corresponding to an amount of the light beam. The BD sensor 25 is arranged at a predetermined position on a scanning line of the light beam, detects a timing that a spot of the light beam passes through this position, and outputs as the primary-scanning-directional synchronization signal a pulse formed at this timing.
The controller 31 includes an ASIC (Application Specific Integrated Circuit), a computer and/or the like and performs control of an internal device of this image forming apparatus, a data process and the like, and controls the exposure device 2a (the light source 21, the polygon motor 24, an actuator 42 mentioned below and the like) and thereby exposures the photoconductor drum 1a with the laser light beam correspondingly to an image to be formed. The light source 21 is controlled such that the photoconductor drum 1a is exposed with the laser light beam of a pattern corresponding to an image to be formed in synchronization with the primary-scanning-directional synchronization signal.
Further, the exposure device 2a includes a mark detector 41, and the actuator 42 that is enabled to move the mark detector 41. The mark detector 41 is a sensor that detects a mark attached to a motor axis of the polygon motor, and here a reflective-type optical sensor that performs irradiation with light and detects reflection light of the irradiation light. Furthermore, the controller 31 moves the mark detector 41 using the actuator 42 to a position corresponding to an operation condition of the exposure device 2a.
The controller 31 moves the mark detector 41 using the actuator 42 to a position corresponding to a rotation speed of the polygon motor 23 in the radial direction of the motor axis 24a. Specifically, the mark detector 41 is approached closer to the motor axis 24a (the mark 24b) correspondingly to a higher rotation speed of the polygon mirror 23. The higher the rotation speed is, the shorter the time that the mark 24b passes through a detection area of the mark detector 41 is and the lower the peak of a pulse in an output signal of the mark detector 41, and therefore, the mark detector 41 is approached closer to the motor axis 24a (the mark 24b). Consequently, a received light amount of the mark detector 41 (i.e. a received light amount of reflection light from the mark 24b) gets large, and therefore, a favorable pulse is detected in the output signal of the mark detector 41. When the rotation speed is low, a light amount of the reflection light from the mark 24b is sufficiently large, and therefore, the mark detector 41 is arranged at a proper position corresponding to a sensitivity of the mark detector 41.
Further, if the rotation speed of the polygon mirror 23 exceeds a predetermined value, the controller 31 may move the mark detector 41 using the actuator 42 to a height position (a position in the axial direction) that the aforementioned balancer does not exist. Specifically, as mentioned, if the rotation speed is high, a peak of the pulse in the output signal of the mark detector 41 is low and reflection light from the aforementioned balancer may be misdetected as reflection light from the mark 24b; and therefore the mark detector 41 may be moved as mentioned.
The following part explains a behavior of the aforementioned image forming apparatus 1.
In a print job, the controller 31 controls the polygon motor 24 and thereby rotates the polygon mirror at a rotation speed corresponding to a specified linear velocity, and controls the actuator 42 and thereby arranges the mark detector 41 at a position corresponding to the rotation speed.
Further, the controller 31 determines a detection timing of the mark 24b on the basis of an output waveform (i.e. a waveform of the output signal) of the mark detector 41, and causes the light source 21 to emit a laser light beam of a pattern corresponding to an image to be printed while identifying each reflection surface of the polygon mirror 23 on the basis of the detection timing as the reference and performing the correction corresponding to the identified reflection surface.
In the aforementioned manner, each of the photoconductor drums 1a to 1d is irradiated with a laser light beam and thereby an electrostatic latent image is formed, the electrostatic latent image is developed with toner, primary transfer and secondary transfer of the developed image are performed and thereby a color toner image is formed on a print sheet, and fixing of the toner image is performed by the fuser 9.
As mentioned, in the aforementioned embodiment, the exposure device 2a, 2b, 2c or 2d includes the polygon mirror 23 that scans the light beam, the polygon motor 24 that rotates the polygon mirror 23, the mark detector 41 that detects the mark 24b attached to the motor axis 24a of the polygon motor 24, and the actuator 42 that is enabled to move the mark detector 41. Further, the controller 31 moves the mark detector 41 using the actuator 42 to a position corresponding to an operation condition of the exposure device 2a, 2b, 2c or 2d.
Consequently, even if a characteristic of an output waveform of the mark detector 41 changes correspondingly to an operation condition of the exposure device 2a, 2b, 2c or 2d, the change of the characteristic is compensated by the movement of the mark detector 41, and therefore it is restrained that a reflection surface of the polygon mirror is wrongly identified.
In Embodiment 2, each of the exposure devices 2a to 2d includes a nonvolatile storage device (EEPROM (Electrically Erasable Programmable Read-Only Memory) or the like) that stores setting data for this exposure device 2a, 2b, 2c or 2d, and the controller 31 individually controls the exposure devices 2a to 2d in accordance with the setting data.
Here, the setting data includes data that indicates a relationship between rotation speeds of the polygon mirror 23 and positions of the mark detector 41, and the controller 31 determines a position of the mark detector 41 corresponding to a rotation speed of the polygon mirror 23 on the basis of the setting data, and moves the mark detector 41 to the determined position using the actuator 42.
The rotation speed of the polygon mirror 23 is set correspondingly to a linear velocity (number of printed sheets per unit time), and therefore, the controller 31 determines a position corresponding to the set rotation speed of the polygon mirror 23 on the basis of the setting data, and moves the mark detector 41 to the determined position.
Further, the setting data includes data that indicates a timing to be detected as a detection timing of the mark 24b among a rising timing and a falling timing in an output waveform of the mark detector 41. The controller 31 detects as a detection timing of the mark 24b a rising timing or a falling timing in an output waveform of the mark detector 41 in accordance with the setting data.
Other parts of the configuration and behaviors of the image forming apparatus in Embodiment 2 are identical or similar to those in Embodiment 1, and therefore not explained here.
As mentioned, in Embodiment 2, the controller 31 individually controls the exposure devices 2a to 2d in accordance with characteristics individually set in the respective storage devices of the exposure devices 2a to 2d, and consequently, it is further restrained that a reflection surface of the polygon mirror is wrongly identified.
It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.
For example, in the aforementioned embodiments, the controller 31 arranges the mark detector 41 at a position corresponding to a rotation speed of the polygon mirror 23, and further may set a position of the mark detector 41 correspondingly to a change of a peak level of the output waveform of the mark detector 41 that occurs due to aging changes of the exposure device 2a, 2b, 2c or 2d.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-078374 | May 2023 | JP | national |
