JP2011154109A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves high image quality without a drastic increase in cost. <P>SOLUTION: A control part of the image forming apparatus applies a charging bias to a charging part 2 upon the start-up of a machine lower than that upon usual imaging to lower charging potential on a photoreceptor 1 and forms an image pattern of predetermined image density on the photoreceptor 1. At the same time, the control part of the image forming apparatus operates a displacement motor 81 and reads image density on the whole width in the main scanning direction on the photoreceptor 1 by using the image density sensor 3 while displacing an image density sensor 3 in the main scanning direction. Then, from the read value of the image density, the control part of the image forming apparatus detects a lowering part and a lowered content of the charging potential on the photoreceptor 1 and corrects the charging bias upon the usual imaging in accordance with the lowered content of the lowering part of the charging potential. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic digital copying machine, a facsimile machine, and a digital multifunction machine (multifunction printer: MFP) equipped with an image density detecting means (image density sensor) or a potential detecting means (potential sensor). About.

  In the electrophotographic image forming apparatus as described above, an image carrier that is rotated in the sub-scanning direction (previously charged uniformly) is exposed to form a latent image on the image carrier. The latent image is developed with toner to form a toner image (hereinafter also simply referred to as “image”), the image is transferred onto a recording medium such as paper, and then the image on the recording medium is fixed. The image forming process is performed.

By the way, with increasing awareness of the environment, recycling, high reliability, and long life have become increasingly important. In addition, due to consideration for the office environment, awareness of ozone generation and dust generation is increasing.
For this reason, in the electrophotographic image forming apparatus as described above, a charging roller system that generates less ozone is often used as the charging means (charging member) (FIG. 5). Furthermore, with the aim of prolonging the life, a charging roller facing the photoconductor (image carrier) with a small gap may be employed. In addition, due to the demand for higher image quality, there are an increasing number of cases where an AC voltage is sufficiently applied to the charging roller to apply an alternating voltage that stabilizes the charging potential.

However, in such an image forming apparatus, since the charging roller is in contact with or close to the surface of the photoreceptor, dirt such as toner tends to adhere to the surface of the charging roller from the surface of the photoreceptor. If dirt on the surface of the charging roller accumulates over time, the resistance of the charging roller increases and charging failure occurs.
Therefore, in order to prevent the charging roller from being soiled, a charging roller cleaner using a cleaning member such as a sponge roller or a brush roller that removes a deposit such as toner from the surface of the charging roller is mounted.

However, the capacity of the charging roller cleaner is also limited, and the cleaning capacity deteriorates with time. As a result, dirt is accumulated on the surface of the charging roller, and the resistance of the charging roller increases.
In addition, in order to prevent charging failure due to an increase in the resistance of the charging roller, a process control may be implemented in which a potential sensor that detects the charging potential on the charging roller is mounted and the charging bias applied to the charging roller is changed to an appropriate value. is there.
Further, there may be a case where process control is performed to change the charging bias by detecting background contamination on the photosensitive member.

However, in these detection methods, only the location where the potential detection means and the image density detection means are arranged is detected in the main scanning direction, so that it is not possible to detect an increase in resistance due to accumulation of partial contamination on the charging roller. . Therefore, partial charging failure may occur.
This problem will be described more specifically with reference to FIG.

FIG. 5 is a diagram for illustrating a portion of the image forming unit of the conventional image forming apparatus excluding the exposure unit and explaining a problem due to conventional image density detection.
In this image forming unit, as shown in FIG. 5A, a charging roller (charging unit) 2 that is opposed to the photoreceptor 1 with a gap and to which an AC voltage is applied is provided with the aim of improving the image quality and extending the life. It has been adopted. An image density sensor 3 for detecting the image density on the photoreceptor 1 is disposed between the developing unit 4 (developing unit) and the transfer unit 5 (transfer unit).

  The control unit of the image forming apparatus including the image forming unit configured as described above is arranged on the photoreceptor 1 by an exposure unit (exposure unit) (not shown) according to, for example, image information read from a document or image information received from the outside. An image forming process in which a latent image is formed on the photosensitive member 1 and the latent image is developed with toner from the developing unit 4 to form a toner image (hereinafter also simply referred to as “image”). Thereafter, the image is transferred onto a recording medium such as paper, and a series of image forming processes for fixing the image on the recording medium is performed.

  Further, a predetermined pattern image for detecting the image density by a process slightly different from the above-described image forming process (for example, the exposure process is omitted and the developing bias applied to the developing unit 4 and the charging bias applied to the charging roller 2 are changed). Is formed on the photosensitive member 1, and the image density is read (detected) by the image density sensor 3, and process control such as development bias and charging bias change is executed based on the read value. I also try to make adjustments.

  For example, in an image forming apparatus provided with an image forming unit, when the machine is started up, the charging bias (charging applied voltage) is lowered and the charging potential on the charging roller 2 is lowered as compared with that during normal image forming, whereby the photoreceptor 1 An analog halftone image pattern is created on the image, the image density is read by the image density sensor 3, and the decrease in the charge potential (image density is greater than the appropriate value: charge potential decrease) is detected from the read value. The process control for correcting the charging bias during normal image formation is performed to prevent the occurrence of charging failure.

  However, in this image forming apparatus, the image density can be detected only at the place where the image density sensor 3 in the main scanning direction is arranged, as shown in FIG. Since the density cannot be detected, it cannot be detected whether the charged potential is properly maintained over the entire main scanning direction. Even if the charging roller resistance other than the image density detection unit increases due to contamination of the charging roller over time and the charging potential locally decreases, the decrease in charging potential cannot be detected by the image density sensor 3, Charging failure occurs locally, and image problems such as streak images occur.

Therefore, in order to solve such a problem, for example, what is found in Patent Documents 1 and 2 has been proposed.
Japanese Patent Application Laid-Open No. 2004-228688 detects density unevenness of an image on a photoconductor from the output of a photoelectric element that is long in the main scanning direction for measuring (detecting) the image density on the photoconductor, and based on the detected density nonuniformity. Discloses a configuration for controlling the amount of laser light emitted to form a latent image on a photosensitive member.

  Japanese Patent Application Laid-Open No. 2004-228867 describes a method for producing an image based on detection results obtained by a plurality of toner adhesion amount detection units that detect toner adhesion amounts per unit area with respect to an image (reference toner image) on a photoreceptor at different positions in the main scanning direction. An arrangement for adjusting the image forming ability of the image means is disclosed.

  However, in the device described in Patent Document 1, in order to detect the image density of the full width in the main scanning direction on the photosensitive member, a photoelectric element having the full width in the main scanning direction has to be prepared, which is a significant cost. It will be high. Further, in the device described in Patent Document 2, in order to detect the image density of the entire width in the main scanning direction on the photosensitive member, a plurality of toner adhesion amount detection means must be prepared, which also increases the cost significantly. End up.

  The present invention has been made in view of the above points, and by performing process control by detecting the image density and potential in the main scanning direction on the image carrier without significantly increasing the cost, The purpose is to improve image quality.

In order to achieve the above object, the present invention provides the following image forming apparatuses (1) and (2).
(1) Charging means for charging the image carrier, exposure means for exposing the image carrier charged thereby to form a latent image, and latent image formed on the image carrier by the exposure means An image forming apparatus of an electrophotographic system having a developing means for developing an image with toner and an image density detecting means for detecting an image density on the image carrier, wherein the image density detecting means comprises: Moving means for moving in the main scanning direction orthogonal to the sub-scanning direction, which is the rotation direction of the image carrier, is provided.

The image density detecting means is moved on the image carrier by the moving means in the main scanning direction while moving on the image carrier by the image density detecting means over the entire width of the image carrier. It is preferable to provide control means for detecting the image density.
The control means outputs an image having a predetermined density on the image carrier by the charging means and the developing means at a predetermined timing different from the normal image formation timing over the entire width of the image carrier in the main scanning direction. The image density detecting means is moved by the moving means on the image carrier in the main scanning direction by the moving means, and the image density detecting means is used by the image density detecting means over the entire width of the image carrier. It is desirable to detect the upper image density.

(2) Charging means for charging the image carrier, exposure means for exposing the image carrier charged thereby to form a latent image, and latent image formed on the image carrier by the exposure means An electrophotographic image forming apparatus having a developing means for developing an image with toner and forming an image and a potential detecting means for detecting a potential on the image carrier, wherein the potential detecting means is connected to the image carrier. Moving means for moving in the main scanning direction orthogonal to the sub-scanning direction, which is the rotation direction of the body, is provided.

The potential detecting means is moved by the moving means on the image carrier in the main scanning direction, and the potential on the image carrier is measured by the potential detecting means over the entire width of the image carrier in the main scanning direction. It is preferable to provide control means for detecting
The control means applies a predetermined charging bias to the charging means over the entire width of the image carrier in the main scanning direction at a predetermined timing different from the normal image formation timing to charge the image carrier. The potential detecting means moves the image carrying member on the image carrier in the main scanning direction by the moving means, and the potential on the image carrier is applied by the potential detecting means over the entire width of the image carrier in the main scanning direction. It is desirable to detect.

In addition, the charging means contacts the image carrier and charges the image carrier, or a charging roller that faces the image carrier with a small gap and charges the image carrier. It may be a roller.
When such a charging roller is used, the control means may apply a charging bias in which an AC voltage is superimposed on a DC voltage to the charging roller.
Further, a polymerized toner may be used as the toner.
Furthermore, as an image forming unit, a process cartridge including the image carrier and including at least one of the charging unit, the exposure unit, and the developing unit may be used.

  According to the present invention, the image density detecting means (image density sensor) and the potential detecting means (potential sensor) are moved in the main scanning direction orthogonal to the sub-scanning direction that is the rotation direction of the image carrier. The image quality can be improved by detecting the image density and potential in the main scanning direction on the image carrier and performing process control without increasing the cost.

1 is a configuration diagram illustrating an example of a mechanism unit of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a portion excluding an exposure unit in the image forming unit of the image forming apparatus in FIG. 1 and a diagram for explaining a portion related to the present invention. FIG. 2 is a block diagram illustrating a configuration example of a control unit of the image forming apparatus illustrated in FIG. 1. It is a figure for magnifying and showing the part except an exposure part among the image forming units of the image forming apparatus which is 2nd Embodiment of this invention, and demonstrating the part relevant to this invention. It is a figure for demonstrating the subject by the conventional image density detection while showing the part except the exposure part among the image forming units of the conventional image forming apparatus.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
First, a first embodiment of the present invention will be described.
FIG. 1 is a block diagram showing an example of a mechanism portion of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is an enlarged view of a portion excluding an exposure portion of an image forming unit of the image forming apparatus. And it is a figure for demonstrating the part relevant to this invention, and the same code | symbol is attached | subjected to the same part as FIG.

  The image forming apparatus according to the first embodiment is an image forming apparatus such as an electrophotographic digital copying machine, a facsimile machine, or a digital multifunction machine. As shown in FIG. 1 and FIG. 10 is provided. The image forming unit 10 is provided with a drum-shaped (or belt-shaped) photosensitive member 1 that is an image carrier so as to be rotatable in the direction of the arrow, and a charging unit that charges the photosensitive member 1 around the photosensitive member 1. 2 (charging means), an exposure portion 11 (exposure means) for exposing the charged surface to form an electrostatic latent image, and a developing portion 4 (developing the electrostatic latent image with toner to form a toner image) Developing means), a transfer unit 5 for transferring the toner image onto a sheet (or other recording medium), and a photoconductor cleaning for removing dirt such as residual toner remaining on the photoconductor 1 after the transfer of the toner image. A unit 6 (image carrier cleaning unit) and a charging unit cleaning unit 7 (charging unit cleaning unit) for removing dirt such as toner adhering to the charging unit 2 are provided.

Of these components, the components other than the exposure unit 11 are integrally coupled as a process cartridge and detachable from the main body of the image forming apparatus. At least one of the units including the exposure unit 11 is included. It is also possible to adopt a configuration in which one is removable as a process cartridge.
The charging unit 2 is a charging roller that comes into contact with the photosensitive member 1 and charges the surface thereof, but may be opposed to the photosensitive member 1 with a small gap. A charging bias obtained by superimposing an AC voltage on a DC voltage can be applied to the charging unit 2. A charging charger can also be used as the charging unit 2.

  As shown in FIG. 2A, an image density sensor 3 (image density detecting means) for detecting the image density on the photosensitive member 1 is disposed between the developing unit 4 and the transfer unit 5. As shown in FIG. 5B, a moving motor 81 and a feed screw mechanism 82 for moving the image density sensor 3 in the main scanning direction orthogonal to the sub-scanning direction that is the rotation direction of the photosensitive member 1 are provided. The moving motor 81 and the feed screw mechanism 82 function as moving means. Also, a mechanism other than the feed screw mechanism 82 can be used to move the image density sensor 3.

In the image forming apparatus configured as described above, for example, when image information (image data) of a document is read by an image reading unit such as a scanner (not shown) or image information is received from the outside, the image forming process starts. The photoconductor 1 is rotated at a predetermined speed by a main motor (not shown), the surface of the photoconductor 1 is uniformly charged by the charging unit 2, and the charged surface is in accordance with image information from the laser diode of the exposure unit 11. And an electrostatic latent image is formed by exposure with the modulated laser beam. An LED array can be used instead of the laser diode.
Next, the electrostatic latent image is developed with toner from the developing unit 4 to form a visualized toner image. The toner used in the developing unit 4 is supplied from the toner bottle 20 of FIG.

On the other hand, among the two-stage paper feeding cassettes 21 and 22, the paper in the paper feeding cassette selected in advance is fed by a paper feeding roller 23 or 24 at a predetermined timing and conveyed. After waiting at the position where the leading edge is sandwiched, the toner image on the photosensitive member 1 is electrostatically transferred onto a sheet by a transfer unit (transfer roller) 5 with the timing of re-transporting with the photosensitive member 1.
Thereafter, the toner image on the paper is heated and fixed by the fixing unit 26 and discharged to the outside by the paper discharge roller 27.
After the electrostatic transfer, the photosensitive member 1 is cleaned of unnecessary toner and the like remaining on its surface by the photosensitive member cleaning unit (cleaning blade) 6 shown in FIG. To wait. Further, dirt such as toner adhering to the charging unit 2 is removed by the charging unit cleaning unit 7.

  In addition, at a predetermined timing different from the normal image forming timing, a process slightly different from the above-described image forming process (the exposure process is omitted and the developing bias applied to the developing unit 4 and the charging bias applied to the charging roller 2 are changed. A predetermined pattern image is formed on the photosensitive member 1 and the image density is read (detected) by the image density sensor 3, and the developing bias applied to the developing unit 4 or the charging unit 2 is read based on the read value. The process control such as the change of the charging bias applied to is performed, and will be described in detail later.

FIG. 3 is a block diagram illustrating a configuration example of a control unit of the image forming apparatus illustrated in FIG. 1.
The control unit of the image forming apparatus includes a controller board 51, an engine main board 52, an engine sub board 53, a power supply unit (hereinafter referred to as “PSU”) 54, and the like.

  The controller board 51 uses a microcomputer including a CPU, a ROM, a RAM, and an ASIC (Application Specific Integrated Circuit), and an external device (not shown) such as a personal computer and a network interface such as a LAN (Local Area Network) (hereinafter “interface”). Is abbreviated as "I / F") 71, IEEE1284 / I / F72, IEEE1394 / I / F73, IEEE802.11b / I / F74 Data such as a character code received from an external device under control is developed on a memory (RAM) 75 and converted into image information (bitmap data) in a format printable by the engine unit, and output to the engine main board 52 To do.

  The controller board 51 sets information used for control input from the operation unit 204 or the like, and stores and saves it in the NVRAM 76, HDD (hard disk device) 77, SD card 78, or the like, which is a non-volatile storage means. be able to. Further, image information or the like for creating a predetermined image pattern for image density detection is stored in advance in any one of these nonvolatile storage means, or in a ROM in the controller board 51 or the engine main board 52. It can also be left. The controller board 51, together with an engine main board 52 and an engine sub board 53, which will be described later, fulfills a function as control means according to the present invention.

  The engine main board 52 uses a microcomputer similar to the controller board 51, exchanges various signals with the engine sub board 53, and sets the LD in the exposure unit 11 based on image information from the controller board 51. (Laser diode) 101 is modulated and driven, and the high voltage power source 102 is controlled to drive the charging unit 2, the developing unit 4, and the transfer unit 5.

The engine sub board 53 also uses the same microcomputer as the controller board 51, and based on signals from the various sensors 201 including the image density sensor 3 of FIG. The motor 202 and various clutches 203 are controlled, and a PSU (power supply unit) 54 is controlled based on a thermistor (temperature sensor) (not shown) in the fixing unit 26 of FIG. The PSU 54 controls on / off of energization to the heater 103 built in the fixing roller constituting the fixing unit 26.
The operation unit 204 includes an input unit for performing various settings and a display unit for displaying various information.

Next, the parts relating to the present invention in the image forming apparatus shown in FIGS. 1 to 3 will be described in detail. In this image forming apparatus, as shown in FIG. 5, the image density sensor 3 disposed between the photosensitive member 1 and the feed screw mechanism 82 can be moved to the full width in the main scanning direction of the photosensitive member 1 as shown in FIG.

The control unit of the image forming apparatus performs charging bias control (charging bias correction) that is process control when the image forming apparatus (machine) is started up.
That is, when the machine is started up, the charging bias (charge application voltage) applied to the charging unit 2 is lowered from that during normal image formation to reduce the charging potential on the photoconductor 1, and an image pattern having a predetermined image density ( For example, an analog halftone image pattern) is created on the photoreceptor 1. In addition, in order to create an image pattern having a predetermined image density, it is possible to change the charging bias and cause the exposure unit 11 to perform exposure based on predetermined image information.

  At the same time, the moving motor 81 is operated to move the image density sensor 3 in the main scanning direction, and the image density sensor 3 reads (detects) the image density of the entire width in the main scanning direction on the photoconductor 1. Then, from the image density reading value (image density detection result) of the full width in the main scanning direction, the lowering portion and the lowering portion of the charging potential on the photoconductor 1 are detected, and the normal portion is matched with the lowering portion of the charging potential lowering portion. Correct the charging bias during image formation. Therefore, charging failure does not occur over the entire width of the photoconductor 1 in the main scanning direction. Further, when the charged potential lowering portion is detected, the operation time of the charging portion cleaning portion 7 (charging roller cleaner) is increased to suppress the surface of the charging portion (charging roller) 2 from being stained. Thereby, an increase in the resistance of the charging unit 2 is suppressed, and the occurrence of charging failure is prevented over a long period of time.

  It should be noted that development bias control for correcting the development bias applied to the developing unit 4 may be performed instead of or together with the charging bias control. Further, the above-described process control is performed not only when the machine is started up but also every other timing, for example, every time the normal number of image formation (corresponding to the number of copies, etc.) reaches a predetermined number of times set in advance. Also good. Further, the image density detection by the image density sensor is not necessarily performed over the entire width of the photoconductor in the main scanning direction. This is because, for example, the vicinity of both ends of the photoconductor in the main scanning direction is not used for image formation. Furthermore, as the image density sensor, a CCD image sensor whose performance has been improved and the price has been reduced in recent years may be used.

  In this way, by moving the image density sensor in the main scanning direction orthogonal to the sub-scanning direction, which is the rotation direction of the photoconductor (image carrier), the main density on the photoconductor is not increased without significant cost increase. Process control can be performed by detecting the image density in the scanning direction. That is, partial image density unevenness in the main scanning width direction on the photoconductor (that is, partial resistance increase in the main scanning direction of the charging unit) can be detected. It is possible to change process conditions such as increasing the cleaning time of the roller) and increasing the charging bias. Therefore, it is possible to prevent the occurrence of an image problem (abnormal image due to defective charging) and to improve the image quality.

  Further, when the image density sensor detects the image density on the photoconductor over the entire width of the photoconductor while moving the image density sensor in the main scan direction, the image of the full width in the main scan width direction on the photoconductor is detected. It is possible to detect density unevenness (that is, increase in resistance across the main scanning direction of the charging unit), and change process conditions such as increasing the cleaning time of the charging unit and increasing the charging bias in response to the image density unevenness. It is possible to reliably prevent the occurrence of image problems.

  Further, an image pattern having a predetermined image density is formed on the photosensitive member by a charging unit and a developing unit over a full width in the main scanning direction of the photosensitive member at a predetermined timing different from the normal image forming timing. When the image density sensor detects the image density on the photoconductor over the entire width of the photoconductor in the main scan direction while moving in the main scan direction, the image forming throughput is reduced due to the influence of stopping the image forming operation on the way. Further, the image density unevenness of the full width in the main scanning width direction on the photosensitive member can be detected with high accuracy by the image pattern having a predetermined image density.

Furthermore, the following effects can also be obtained. This effect can also be obtained by a second embodiment described later.
If a charging roller (contact charging roller) that contacts the photosensitive member and charges the photosensitive member is used as the charging unit, the generation of ozone is reduced and the generation of ozone can be suppressed. Alternatively, if a charging roller that faces the photoconductor with a small gap and charges the photoconductor is used, dirt from toner and the like is less likely to adhere from the photoconductor to the surface of the charging roller. Can be extended and the service life can be extended.

When such a charging roller is used, if a charging bias in which an AC voltage is superimposed on a DC voltage is applied to the charging roller, the charging current sufficiently flows through the charging roller, so that the charging potential on the photosensitive member is stable. In addition, higher image quality can be achieved.
If a polymerized toner having a uniform shape is used as a toner used for development, development characteristics and transferability are improved, and image quality is further improved.
When a process cartridge including a photoconductor and including at least one of a charging unit, an exposure unit, a developing unit, and a cleaning unit is used as an image forming unit, the image forming unit is integrated, and setability and maintenance are improved. Get better. Furthermore, the integration improves the position accuracy of the photosensitive member such as the charging unit, the exposure unit, the developing unit, and the cleaning unit.

Next explained is the second embodiment of the invention. In the second embodiment, the image forming apparatus shown in FIG. 1 and the control unit shown in FIG. 3 are used. However, it is assumed that a potential sensor is provided instead of the image density sensor.
FIG. 4 is an enlarged view of a portion of the image forming unit of the image forming apparatus according to the second embodiment of the present invention excluding the exposure portion, and is a view for explaining a portion related to the present invention. The same parts as those in FIG.

  In this image forming apparatus, as shown in FIG. 4B, a potential sensor 8 (potential detection means) for detecting a charged potential on the photosensitive member 1 is disposed between the charging unit 2 and the developing unit 4. As shown in FIG. 5A, a moving motor 91 and a feed screw mechanism 92 are provided for moving the potential sensor 8 in the main scanning direction orthogonal to the sub-scanning direction that is the rotation direction of the photosensitive member 1. . Note that the moving motor 91 and the feed screw mechanism 92 function as moving means. Also, a mechanism other than the feed screw mechanism 92 can be used to move the potential sensor 8.

In this image forming apparatus, as shown in FIG. 4B, the electric potential sensor 8 disposed between the charging unit 2 and the developing unit 4 includes a moving motor 91 as shown in FIG. In addition, the feed screw mechanism 92 can move the entire width of the photosensitive member 1 in the main scanning direction.
The control unit of the image forming apparatus performs charging bias control, which is process control, when the machine is started up.
That is, when the machine is started, a predetermined charging bias (charging applied voltage) is applied to the charging unit 2 to charge the surface of the photoreceptor 1.

  At the same time, the moving motor 91 is operated to move the potential sensor 8 in the main scanning direction, and the potential sensor 8 detects the charged potential of the entire width in the main scanning direction on the photoreceptor 1. Then, from the charging potential detection result of the full width in the main scanning direction, the lowering portion and the lowering portion of the charging potential on the photoconductor 1 are detected, and the charging bias at the time of normal image formation is matched with the lowering portion of the charging potential lowering portion. Correct. Therefore, charging failure does not occur over the entire width of the photoconductor 1 in the main scanning direction. Further, when the charged potential lowering portion is detected, the operation time of the charging portion cleaning portion 7 is increased to suppress the surface of the charging portion (charging roller) 2 from being stained. Thereby, an increase in the resistance of the charging unit 2 is suppressed, and the occurrence of charging failure is prevented over a long period of time.

  Note that the above-described process control (charging bias control) may be performed not only at the time of starting the machine but also at other timing, for example, every time the normal number of image formation reaches a predetermined number of times set in advance. Further, the potential detection by the potential sensor is not necessarily performed over the entire width of the photoconductor in the main scanning direction.

  In this way, the main scanning on the photoconductor is performed without significant increase in cost by moving the potential sensor in the main scanning direction orthogonal to the sub-scanning direction that is the rotation direction of the photoconductor (image carrier). Process control can be performed by detecting the potential in the direction. In other words, it is possible to detect partial charging unevenness in the main scanning width direction on the photosensitive member, and in response to the charging unevenness, the cleaning time of the charging unit (charging roller) is increased or the charging bias is increased. Process conditions can be changed. Therefore, the occurrence of an image problem can be prevented and high image quality can be achieved.

  Further, when the potential on the image carrier is detected by the potential sensor over the entire width of the photosensitive member in the main scanning direction while moving the potential sensor in the main scanning direction, the charging unevenness of the entire width of the photosensitive member in the main scanning width direction is reduced. It becomes possible to detect, and it is possible to change the process conditions such as increasing the cleaning time of the charging portion or increasing the charging bias in response to the charging unevenness, and it is possible to reliably prevent the occurrence of an image problem.

  Further, at a predetermined timing different from the normal image forming timing, a predetermined charging bias is applied to the charging unit over the entire width of the photosensitive member in the main scanning direction to charge the photosensitive member, and the potential sensor is moved in the main scanning direction. When the potential on the photoconductor is detected by the potential sensor over the entire width of the photoconductor in the main scanning direction while moving, the image forming throughput is not reduced due to the influence of stopping the image forming operation in the middle. It is possible to detect the charging unevenness on the photoconductor in the full width direction in the main scanning width with high accuracy.

  As is apparent from the above description, according to the present invention, it is possible to detect the image density and potential in the main scanning direction on the image carrier and perform process control without significantly increasing the cost. Can be achieved. Therefore, it is possible to provide an image forming apparatus that can acquire a high-quality image at low cost.

1: Photoconductor 2: Charging unit 3: Image density sensor 4: Development unit 5: Transfer unit 6: Photoconductor cleaning unit 7: Charging unit cleaning unit 8: Potential sensor 11: Exposure unit 20: Toner bottle 51: Controller board 52 : Engine main board 53: Engine sub board 76: NVRAM
77: HDD 78: SD card 101: LD 102: High voltage power supply 81, 91: Moving motor 82, 92: Feed screw mechanism

JP 7-225508 A JP 2006-234862 A

Claims (11)

A charging unit that charges the image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form a latent image, and a latent image formed on the image carrier by the exposure unit. An electrophotographic image forming apparatus comprising: a developing unit that develops an image with toner to form an image; and an image density detecting unit that detects an image density on the image carrier,
An image forming apparatus comprising: a moving unit that moves the image density detecting unit in a main scanning direction orthogonal to a sub-scanning direction that is a rotation direction of the image carrier. The image forming apparatus according to claim 1.
While moving the image density detecting means on the image carrier in the main scanning direction by the moving means, the image density detecting means moves the image on the image carrier over the entire width in the main scanning direction. An image forming apparatus comprising a control means for detecting density.   The control means outputs an image having a predetermined density on the image carrier by the charging means and the developing means over a full width of the image carrier in the main scanning direction at a predetermined timing different from a normal image forming timing. The image carrier is formed by the image density detector over the entire width in the main scanning direction of the image carrier while moving the image density detector in the main scanning direction on the image carrier by the moving unit. The image forming apparatus according to claim 2, wherein the upper image density is detected. A charging unit that charges the image carrier, an exposure unit that exposes the image carrier charged by the charging unit to form a latent image, and a latent image formed on the image carrier by the exposure unit. An electrophotographic image forming apparatus comprising: a developing unit that develops an image with toner to form an image; and a potential detecting unit that detects a potential on the image carrier.
An image forming apparatus comprising: moving means for moving the potential detection means in a main scanning direction orthogonal to a sub-scanning direction that is a rotation direction of the image carrier. The image forming apparatus according to claim 4.
The potential detection means detects the potential on the image carrier over the entire width of the image carrier in the main scanning direction while moving the potential detection means on the image carrier in the main scanning direction by the moving means. An image forming apparatus comprising a control unit for controlling the image forming apparatus.   The control unit applies a predetermined charging bias to the charging unit over a full width in the main scanning direction of the image carrier at a predetermined timing different from a normal image forming timing to charge the image carrier. The potential detection means moves the potential on the image carrier by the potential detection means over the entire width in the main scanning direction of the image carrier while moving the potential detection means on the image carrier in the main scanning direction by the moving means. The image forming apparatus according to claim 5, wherein the image forming apparatus is detected.   The image forming apparatus according to claim 1, wherein the charging unit is a charging roller that comes into contact with the image carrier and charges the image carrier.   7. The image forming apparatus according to claim 1, wherein the charging unit is a charging roller that faces the image carrier with a minute gap and charges the image carrier. .   The image forming apparatus according to claim 7, wherein the control unit applies a charging bias in which an AC voltage is superimposed on a DC voltage to the charging roller.   The image forming apparatus according to claim 1, wherein a polymerized toner is used as the toner.   11. The process cartridge according to claim 1, wherein a process cartridge including the image carrier and including at least one of the charging unit, the exposure unit, and the developing unit is used as the image forming unit. The image forming apparatus described in the item.

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