This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-019904, filed Feb. 6, 2017, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to an image forming apparatus.
An image forming apparatus forms a visible image in an image carrier such as an intermediate transfer belt by using developer, and transfers the visible image onto a sheet. If the amount of developer which is used for the visible image of the image carrier is not appropriate, quality of the image which is formed on the sheet may be adversely affected. Accordingly, technology is proposed which appropriately controls density of an image by detecting the amount of developer on the basis of the amount of received light of the light which is reflected from the visible image formed on the image carrier.
However, ripple due to noise may occur in the amount of received light (output of sensor) due to various factors. There are concerns that detection accuracy of the amount of developer decreases due to the ripple.
An object of the invention is to provide an image forming apparatus which can increase detection accuracy of developer.
In general, according to one embodiment, an image forming apparatus includes an image carrier, a sensor, a light amount control unit, and an image formation control unit. The sensor detects the amount of developer in a visible image which is formed in the image carrier by emitting light to the image carrier and receiving light that is reflected from the image carrier. The light amount control unit determines the amount of light which is emitted by the sensor when the amount of developer is detected. The image formation control unit controls the amount of developer of a visible image which is formed in the image carrier in accordance with the amount of developer that is detected by the sensor. The light amount control unit determines the amount of light in accordance with a statistical value of the amount of received light of the reflected light in a region in which the visible image is not formed.
The display 110 is an image display device such as a liquid crystal display or an organic electro luminescence (EL) display. The display 110 displays various types of information on the image forming apparatus 100.
The control panel 120 has a plurality of buttons. The control panel 120 receives input data of a user. The control panel 120 outputs a signal according to an operation which is performed by the user to a control unit of the image forming apparatus 100. The display 110 and the control panel 120 may be configured with a touch panel of one piece.
The printer unit 130 prints an image on the sheet, based on image information which is generated by the image reading unit 200 or image information which is received through a communication path. The printer unit 130 includes an image forming unit 10, a fixing unit 30, a paper discharging unit 40, a transport unit, and the like which will be described below. The printer unit 130 prints an image by using, for example, developer such as toner. The sheet on which an image is formed may be contained in the sheet containing unit 140, or may be inserted by hand.
The sheet containing unit 140 contains sheets which are used for image formation of the printer unit 130.
The image reading unit 200 reads image information of a read target by using brightness and darkness of light. The image reading unit 200 records the read image information. The recorded image information may be transmitted to other information processing devices through a network. An image of the recorded image information may be formed on the sheet by the printer unit 130.
The image forming unit 10 operates in accordance with control of an image formation control unit 71. The image forming unit 10 includes an exposure unit, a development unit, a first transfer unit, a second transfer unit, and the like which will be described below. For example, the image forming unit 10 operates as follows. The exposure unit of the image forming unit 10 forms an electrostatic latent image on a photoconductive drum on the basis of image information which becomes a target of image formation. The development unit of the image forming unit 10 forms a visible image by adhering developer to the electrostatic latent image. The first transfer unit of the image forming unit 10 transfers the formed visible image to an image carrier. The second transfer unit of the image forming unit 10 transfers the visible image formed in the image carrier onto a sheet.
The adhesion amount sensor 20 detects the amount of adhesion of the developer of the visible image formed in the image carrier of the image forming unit 10. The adhesion amount sensor 20 may be configured with, for example, an optical sensor.
The storage unit 60 is configured with a storage device such as a magnetic hard disk device or a semiconductor device. The storage unit 60 functions as a light amount information storage unit 61. The light amount information storage unit stores light amount information. The light amount information is information which is obtained by associating an output of the adhesion amount sensor 20 in a light amount adjustment mode with a light emission voltage when the output is obtained.
The control unit 70 functions as an image formation control unit 71 and a light amount control unit 72, as a CPU executes a program. The image formation control unit 71 performs density adjustment processing. In the density adjustment processing, the image formation control unit 71 acquires detection results of the adhesion amount sensor 20 by using a toner adhesion amount pattern formed in the image carrier as a target. The image formation control unit 71 controls development conditions (for example, development potential) of the development unit in accordance with the detection results such that density of the visible image which is formed in the image carrier has an appropriate value. In a case where the detection results of the adhesion amount sensor 20 indicate that “the density is high”, the image formation control unit 71 controls the development conditions such that the amount of adhesion of the developer in the image carrier is decreased. In a case where the detection results of the adhesion amount sensor 20 indicate that “the density is low”, the image formation control unit controls the development conditions (for example, development potential) such that the amount of adhesion of the developer in the image carrier is increased.
The light amount control unit 72 controls the amount of light of the light emission unit of the adhesion amount sensor 20 in accordance with the detection results of the adhesion amount sensor 20 in the light amount adjustment mode.
The image forming apparatus 100 includes the image forming unit 10, the adhesion amount sensor 20, the fixing unit 30, and the paper discharging unit 40. The image forming unit 10 includes an intermediate transfer body 11, development units 12 to 16, a plurality of first transfer rollers 17 (17-1 to 17-5), a second transfer unit 18, and an exposure unit 19.
The intermediate transfer body 11 is a specific example of the image carrier. The intermediate transfer body 11 may be configured with, for example, an endless belt. The intermediate transfer body 11 rotates in a direction of an arrow 91 by rollers. In the embodiment, upstream and downstream are defined based on a direction in which the intermediate transfer body 11 moves. Visible images generated by the development units 12 to 16 are transferred onto a surface of the intermediate transfer body 11. Transferring the visible image to the intermediate transfer body 11 corresponds to a first transfer process.
The development units 12 to 16 form the visible images by using toners with respectively different properties. For example, a part of the development units may use the toners of respectively different colors. The toners of each color of yellow (Y), magenta (M), cyan (C), and black (K) may be used as the toners of different colors. For example, a part of the development units may use toner whose color disappears due to external stimulus (for example, heat). The development unit 12 is located at the most upstream among the five development units, and the development unit 16 is located at the most downstream among the five development units.
The development units 12 to 16 use toners with different properties, but have the same configurations. Hereinafter, the development units will be described by using the development unit 12 as an example.
The development unit 12 includes a development machine 12a, a photoconductive drum 12b, a charger 12c, and a cleaning blade 12d.
The development machine 12a contains developer. The development machine 12a makes the developer adhere to the photoconductive drum 12b.
The photoconductive drum 12b includes a photoreceptor (photosensitive region) on an outer circumference surface thereof. The photoreceptor is, for example, an organic photoconductor (OPC).
The charger 12c uniformly charges a surface of the photoconductive drum 12b.
The cleaning blade 12d is, for example, a member of a plate shape. The cleaning blade 12d is configured with rubber such as urethane resin. The cleaning blade 12d removes the developer which adheres to the photoconductive drum 12b.
Next, a schematic operation of the development unit 12 will be described. The photoconductive drum 12b is charged with a predetermined potential by the charger 12c. Subsequently, the exposure unit 19 irradiates the photoconductive drum 12b with light. Thereby, a potential of a region of the photoconductive drum 12b to which light is applied changes. An electrostatic latent image is formed on a surface of the photoconductive drum 12b by the change. The electrostatic latent image on the surface of the photoconductive drum 12b is developed by the developer of the development machine 12a. That is, a visible image which is an image developed by the developer is formed on the surface of the photoconductive drum 12b.
The first transfer rollers 17 (17-1 to 17-5) transfer the visible images which are formed on the photoconductive drum by the respective development units 12 to 16 to the intermediate transfer body 11.
The second transfer unit 18 includes a second transfer roller 181 and a second transfer counter roller 182. The second transfer unit 18 collectively transfers the visible images formed on the intermediate transfer body 11 to a sheet which becomes a target of image formation. The transfer which is performed by the second transfer unit 18 is realized by a potential difference between, for example, the second transfer roller 181 and the second transfer counter roller 182.
The exposure unit 19 forms the electrostatic latent image by irradiating the photoconductive drums of the development units 12 to 16 with light. The exposure unit 19 includes a light source such as laser or a light emitting diode (LED).
The adhesion amount sensor 20 is located between the development unit 16 in the most downstream and the second transfer unit 18, and is provided to detect the amount of adhesion of the developer on the intermediate transfer body 11.
The fixing unit 30 fixes the visible image on the sheet by heating and pressing the visible image transferred onto the sheet.
The paper discharging unit 40 discharges the sheet on which the visible image is fixed by the fixing unit 30.
Hereinafter, effects of the image forming apparatus 100 according to the embodiment will be described with reference to
Next, the density adjustment processing of the image forming apparatus 100 will be described.
Corrected voltage value=V60−α×(V50−statistical voltage value)
α is a constant value and is appropriately determined. For example, α is a value less than “1”. A value of α may be, for example, 0.2. The image formation control unit 71 performs the density adjustment processing by using the corrected voltage value. That is, the image formation control unit 71 detects the amount of the developer on the basis of the corrected voltage value.
Hereinafter, effects of the density adjustment processing of the image forming apparatus 100 according to the embodiment will be described with reference to
An operation of the light amount adjustment mode may be performed at timing when an image is not formed. For example, the operation of the light amount adjustment mode may be performed in parallel with processing in which the image carrier does not form the visible image, in processing that the image forming apparatus 100 requires. For example, the operation of the light amount adjustment mode may be performed in parallel with a calibration operation of a magnetic developer concentration sensor of the development machine. For example, the operation of the light amount adjustment mode may be performed in parallel with toner supplying to the development machine after the toner is emptied. By configuring so, the operation of the light amount adjustment mode can be efficiently performed.
The operation of the light amount adjustment mode may be performed each time the predetermined number of images is formed. The operation of the light amount adjustment mode may be performed at a predetermined time interval. The operation of the light amount adjustment mode may be performed at a predetermined time.
A statistical value of the voltage values of one rotation of the image carrier is acquired in the aforementioned light amount adjustment mode, but it does not always need to be one rotation. For example, a statistical value of the voltage values of half a rotation of the image carrier may be acquired, or a statistical value of the voltage values of one and a half rotation may be acquired.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2017-019904 | Feb 2017 | JP | national |