JP5674111B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine.

  In an electrophotographic image forming apparatus, a plurality of reference toner images, which are toner images having a predetermined shape, are formed on the surface of a photoconductor as an image carrier, and then the development potential at the time of forming the reference toner image and the reference A potential set value adjustment control for obtaining various development potentials for forming a toner image by obtaining a development potential for obtaining a desired toner adhesion amount from a linear approximation formula of the toner adhesion amount of a toner image is widely performed (for example, Patent Documents). 1). The developing potential is a potential difference between the potential of the electrostatic latent image on the photosensitive member and the potential of the developing sleeve surface to which the developing bias is applied.

  It is known that a so-called edge effect occurs in which the electric field at the boundary portion of the electrostatic latent image formed on the image carrier is strengthened. Due to this edge effect, the amount of toner developed in the electrostatic latent image of the line image on the image carrier increases and the toner layer height increases, and when transferring the line image to the intermediate transfer member or recording material, Toner scattering (hereinafter simply referred to as “transfer dust”) may occur in the peripheral portion of the line image. Further, the influence of the charging characteristics of the developer is large, the charge amount and the edge effect overlap, and the transfer dust appears most remarkably in a low temperature and low humidity environment.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus that can reduce transfer dust caused by the edge effect.

In order to achieve the above object, the invention of claim 1 is directed to irradiating a charged image carrier with a writing light to write a latent image, developing the latent image on the image carrier and developing the image carrier. Image forming means for forming a toner image on the body, and the transfer means transfers the toner image formed on the image carrier to a recording material conveyed by the surface moving member, or transfers the toner image to the surface moving member; In the image forming apparatus for forming an image on the recording material by transferring the toner image on the surface moving member to the recording material after being transferred to the surface of the recording medium, optical detection means for detecting reflected light from the toner image, and at least a line Information on the toner layer height of the line-shaped toner image is acquired based on the detection result of the optical detection means that detects the reflected light from the toner image, and the toner layer height of the line-shaped toner image is transferred. Pre-set to generate Chile It has a control means for controlling the image forming means so that the toner layer height becomes lower when the above semi-height, wherein the imaging means includes the image bearing member, the image bearing member having a predetermined potential A charging means for charging the toner, a latent image forming means for forming a latent image by irradiating the surface of the image carrier charged to a predetermined potential with a writing light, and a developer carrier for carrying a developer containing at least toner. And developing means for developing the latent image by transferring the toner on the developer carrier to a latent image on the image carrier while applying a developing bias, and the toner layer height is equal to or higher than the reference height In this case, the peripheral speed ratio between the image carrier and the developer carrier is increased, and a gradation pattern composed of a plurality of toner patches formed under image forming conditions having different adhesion amounts is formed. Detecting the gradation pattern detected by the optical detecting means Based on the results set the development potential is the difference between the potential and the developing bias of the electrostatic latent image portion, and is characterized in that for controlling said image forming means by said control means.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus further includes a toner adhesion amount detection unit that detects a toner adhesion amount per unit area of the toner image based on a detection result of the optical detection unit. The control means controls to increase the peripheral speed ratio when the development γ, which is the slope of the relational expression of the toner adhesion amount with respect to the development potential, is smaller than a preset reference development γ. Is.
Further, the invention of claim 3, the image forming apparatus according to claim 1, wherein said control means, the development potential for the image density of the solid-like toner image is obtained a toner adhesion amount as a target value, is preset If the reference development potential is greater than the reference development potential, control is performed to increase the peripheral speed ratio.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, the image forming apparatus further includes a humidity detecting unit that detects a humidity around the developing unit, and the control unit is detected by the humidity detecting unit. When the absolute humidity in the surrounding environment of the developing unit is lower than a preset reference absolute humidity, control for increasing the peripheral speed ratio is performed.
The invention of claim 5, claim 1, in 3 or the image forming apparatus 4, before the start of the normal image forming operation for imaging an image on the recording material, a desired image forming condition The image forming means is controlled by the control means so that

  In the present invention, when the toner layer height of the linear toner image is equal to or higher than a preset reference height at which transfer dust occurs, the image forming means is controlled by the control means so that the toner layer height is lowered. Since the toner layer is controlled, the transfer dust caused by the edge effect can be reduced as much as the height of the toner layer can be reduced.

  As described above, according to the present invention, there is an excellent effect that transfer dust caused by the edge effect can be reduced.

3 is a flowchart showing a control flow in potential set value adjustment control according to Embodiment 1; 1 is a schematic configuration diagram showing a copier according to an embodiment. FIG. 2 is an enlarged configuration diagram showing an intermediate transfer unit and its peripheral configuration in the copier. FIG. 3 is an enlarged configuration diagram showing two of four image forming units in the copier. FIG. 2 is a block diagram showing a main part of an electric circuit of the copier. FIG. 3 is a schematic diagram showing an intermediate transfer belt of the copier and a gradation pattern image formed on the surface thereof. The figure which shows the relationship between the toner adhesion amount of a line pattern and a solid pattern. (A) a graph showing a photoreceptor potential exposed by image data in a solid pattern and an electric field latent image corresponding to the photoreceptor potential; (b) a photoreceptor potential and photoreceptor exposed by image data in a line pattern; The graph which shows the electric field latent image corresponding to an electric potential. 6 is a graph showing the relationship between the line width and the toner adhesion amount per unit area. 6 is a graph showing characteristics of development γ specified based on a detection result of a gradation pattern image in the copier. A graph showing the relationship between development γ and transfer dust rank of the copier. 3 is a graph showing the relationship between the development linear speed ratio and development γ of the copier. 9 is a flowchart illustrating a control flow in potential set value adjustment control according to the second embodiment. 9 is a flowchart illustrating a control flow in potential set value adjustment control according to a third embodiment.

Hereinafter, an embodiment of a copying machine as an image forming apparatus to which the present invention is applied will be described. First, a basic configuration of the copying machine according to the present embodiment will be described.
FIG. 2 is a schematic configuration diagram showing the copying machine according to the present embodiment. In FIG. 1, a copying machine includes a printing unit 100 that forms an image, a paper feeding device 200 on which the printing unit 100 is mounted and that supplies a transfer sheet 5 as a recording member to the printing unit 100, and a printing unit. A scanner 300 that is mounted on 100 and reads a document image, and an automatic document feeder (ADF) 400 that is mounted on the scanner 300 are provided. The print unit 100 is provided with a manual feed tray 6 for manually feeding the transfer paper 5 and a paper discharge tray 7 for discharging the transfer paper 5 on which an image has been formed.

  FIG. 3 is an enlarged configuration diagram illustrating the configuration of the printing unit 100 in an enlarged manner. The print unit 100 is provided with an endless intermediate transfer belt 10 that is an intermediate transfer body and is a surface endless moving body. As the material of the intermediate transfer belt 10, polyimide, which is a material excellent in mechanical characteristics, is used in order to prevent displacement due to belt elongation. In this polyimide, carbon is dispersed as an electric resistance adjusting agent in order to achieve high image quality and high stability, that is, to always obtain stable transfer performance regardless of the temperature and humidity environment. For this reason, the intermediate transfer belt 10 is black.

  The intermediate transfer belt 10 is rotationally driven in the clockwise direction in FIG. 3 while being stretched around the three support rollers 14, 15, and 16. As shown in FIG. 3, yellow (Y), cyan (C), and magenta are provided on the belt stretch portion between the first support roller 14 and the second support roller 15 of the support rollers 14, 15, and 16. Four image forming units 18Y, 18C, 18M, and 18K of (M) and black (K) are arranged side by side. An optical sensor 110 for detecting a density patch as a reference toner image formed on the intermediate transfer belt 10 is attached to a belt stretch portion between the first support roller 14 and the third support roller 16. Yes.

  A laser writing device 21 is provided above the image forming units 18Y, 18C, 18M, and 18K as shown in FIG. The laser writing device 21 emits writing light by driving a semiconductor laser (not shown) by a laser control unit (not shown) based on image information of an original read by the scanner 300. Then, the writing light exposes and scans the drum-shaped photoconductors 20Y, 20C, 20M, and 20K, which are latent image carriers provided in the image forming units 18Y, 18C, 18M, and 18K, and electrostatically scans the photoconductors. A latent image is formed. Note that the light source of the writing light is not limited to the laser diode, and may be an LED, for example.

  FIG. 4 is an enlarged configuration diagram showing two of the four image forming units 18Y, 18C, 18M, and 18K. The four image forming units 18Y, 18C, 18M, and 18K have the same configuration except that the colors of the toners used are different from each other. Therefore, in FIG. The subscripts Y, C, M, and K are omitted. In the following description, these subscripts are omitted as appropriate.

  In the image forming unit 18, a charging device 60, a developing device 61, a photoconductor cleaning device 63, and a charge removal device 64 are provided around the photoconductor 20. A primary transfer device 62 is provided at a position facing the photoconductor 20 via the intermediate transfer belt 10.

  The charging device 60 is of a contact charging type employing a charging roller, and uniformly charges the surface of the photoconductor 20 by applying a voltage in contact with the photoconductor 20. As the charging device 60, a non-contact charging type using a non-contact scorotron charger or the like can be used.

  The developing device 61 uses a two-component developer composed of a magnetic carrier and a non-magnetic toner. The developing device 61 can be broadly divided into a stirring unit 66 and a developing unit 67 provided in the developing case 70. In the agitating unit 66, a two-component developer (hereinafter simply referred to as “developer”) is conveyed while being agitated and supplied onto a developing sleeve 65, which will be described later, as a developer carrying member. The stirring unit 66 is provided with two parallel screws 68, and a partition plate is provided between the two screws 68 for partitioning so that both ends communicate with each other. Further, a toner concentration sensor 71 for detecting the toner concentration of the developer in the developing device 61 is attached to the developing case 70. On the other hand, in the developing unit 67, the toner in the developer attached to the developing sleeve 65 is transferred to the photoconductor 20. The developing portion 67 is provided with a developing sleeve 65 that faces the photoreceptor 20 through the opening of the developing case 70, and a magnet (not shown) is fixedly disposed in the developing sleeve 65. Further, a doctor blade 73 is provided so that the tip approaches the developing sleeve 65. If the peripheral speed of the photosensitive member 20 is Vp and the peripheral speed of the developing sleeve is Vs, this peripheral speed ratio can be expressed as Vs / Vp. Hereinafter, it is simply referred to as “development linear velocity ratio”).

  In the developing device 61, the developer is conveyed and circulated while being stirred by the two screws 68 and supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is pumped up to the sleeve surface by the magnetic force generated by the magnet roller disposed in the developing sleeve 65. The developer pumped up by the developing sleeve 65 is conveyed along with the rotation of the developing sleeve 65 and is regulated to an appropriate amount by the doctor blade 73. The regulated developer is returned to the stirring unit 66. Thus, the developer conveyed to the developing area facing the photoconductor 20 becomes a spiked state by the magnetic force generated by the magnet roller, and forms a magnetic brush. In the developing region, a developing electric field that moves the toner in the developer to the electrostatic latent image portion on the photoreceptor 20 is formed by the developing bias applied to the developing sleeve 65. As a result, the toner in the developer is transferred to the electrostatic latent image portion on the photoreceptor 20, and the electrostatic latent image on the photoreceptor 20 is visualized to form a toner image. The developer that has passed through the developing region is transported to a portion where the magnetic force of the magnet is weak, and thus is separated from the developing sleeve 65 and returned to the stirring unit 66. When the toner concentration in the stirring unit 66 becomes light by repeating such an operation, the toner concentration sensor 71 detects this, and the toner is supplied to the stirring unit 66 based on the detection result.

  As the primary transfer device 62, a primary transfer roller is employed, and is installed so as to be pressed against the photoconductor 20 with the intermediate transfer belt 10 interposed therebetween. The primary transfer device 62 is not limited to a roller shape, and may be a conductive brush shape, a non-contact corona charger, or the like.

  The photoconductor cleaning device 63 includes a cleaning blade 75 made of, for example, polyurethane rubber, which is disposed so that the tip thereof is pressed against the photoconductor 20. In this embodiment, in order to improve the cleaning performance, a conductive fur brush 76 that contacts the photoconductor 20 is also used. The toner removed from the photoconductor 20 by the cleaning blade 75 and the fur brush 76 is accommodated in the photoconductor cleaning device 63. The static eliminator 64 including a static eliminator lamp irradiates light to initialize the surface potential of the photoreceptor 20.

  The image forming unit 18 is provided with a potential sensor 120 facing the photoconductor 20. The potential sensor 120 is provided to face the photoconductor 20 and detects the photoconductor surface potential.

  In FIG. 4, the surface of the photoconductor 20 is uniformly charged to, for example, −760 V by the charging device 60, and the potential of the electrostatic latent image portion irradiated with the laser by the laser writing device 21 is, for example, −200 V. . On the other hand, the developing bias voltage is set to −560V, and a developing potential of 360V is secured. The developing potential is a potential difference between the electrostatic latent image on the surface of the photoreceptor and the developing sleeve surface to which a developing bias is applied. Such process conditions are changed as appropriate according to the result of potential set value adjustment control described later.

  As shown in FIG. 2, in the image forming unit 18, first, the surface of the photoconductor 20 is uniformly charged by the charging device 60 as the photoconductor 20 rotates. Next, based on the image information read by the scanner 300, laser writing light is emitted from the laser writing device 21 to form an electrostatic latent image on the photoconductor 20. Thereafter, the electrostatic latent image is visualized by the developing device 61 to form a toner image. This toner image is primarily transferred onto the intermediate transfer belt 10 by the primary transfer device 62. The transfer residual toner remaining on the surface of the photoconductor 20 after the primary transfer is removed by the photoconductor cleaning device 63, and then the surface of the photoconductor 20 is discharged by the charge removal device 64 and used for the next image formation. .

  As shown in FIG. 3, a secondary transfer roller 24 as a secondary transfer device is provided at a position facing the third support roller 16 among the support rollers. When the toner image on the intermediate transfer belt 10 is secondarily transferred onto the transfer paper 5, the secondary transfer roller 24 is pressed against the intermediate transfer belt 10 portion wound around the third support roller 16 and the second transfer roller 24 is pressed. Next transfer is performed. The secondary transfer device may not be configured using the secondary transfer roller 24 but may be configured using, for example, a transfer belt or a non-contact transfer charger. A roller cleaning unit 91 for cleaning the toner attached to the secondary transfer roller 24 is in contact with the secondary transfer roller 24.

  Further, an endless belt-like transport belt 22 is stretched between the two rollers 23 a and 23 b on the downstream side of the secondary transfer roller 24 in the transport direction of the transfer paper 5. Further, a fixing device 25 for fixing the toner image transferred onto the transfer paper 5 is provided further downstream in the transport direction. The fixing device 25 has a configuration in which a pressure roller 27 is pressed against a heating roller 26. Further, a belt cleaning device 17 is provided at a position facing the second support roller 15 among the support rollers of the intermediate transfer belt 10. The belt cleaning device 17 is for removing residual toner remaining on the intermediate transfer belt 10 after the toner image on the intermediate transfer belt 10 is transferred to the transfer paper 5.

  As shown in FIG. 2, the printing unit 100 is provided with a conveyance path 48 that guides the transfer paper 5 fed from the paper feeding device 200 to the paper discharge tray 7 via the secondary transfer roller 24. Yes. Along the conveyance path 48, a conveyance roller 49a, a registration roller 49b, a discharge roller 56, and the like are also provided. A switching claw 55 is provided on the downstream side of the transport path 48 to switch the transport direction of the transfer paper 5 after transfer to the paper discharge tray 7 or the paper reversing device 93. The paper reversing device 93 reverses the transfer paper 5 and sends it again toward the secondary transfer roller 24. Further, the print unit 100 is provided with a manual paper feed path 53 that joins from the manual feed tray 6 to the conveyance path 48, and the transfer paper 5 set on the manual feed tray 6 is placed upstream of the manual paper feed path 53. A paper feed roller 50 and a separation roller 51 are provided for feeding paper one by one.

  The paper feeding device 200 includes a plurality of paper feeding cassettes 44 that store the transfer paper 5, a paper feeding roller 42 and a separation roller 45 that feed the transfer papers stored in these paper feeding cassettes 44 one by one, and the fed transfer paper Is composed of a transport roller 47 that transports the paper along the paper feed path 46. The paper feed path 46 is connected to the transport path 48 of the printing unit 100.

  In the scanner 300, first and second traveling bodies 33 and 34 mounted with a document illumination light source and a mirror reciprocate in order to read and scan a document (not shown) placed on the contact glass 31. To do. The image information scanned by the traveling bodies 33 and 34 is collected by the imaging lens 35 on the imaging surface of the reading sensor 36 installed behind the imaging lens 35 and read by the reading sensor 36 as an image signal.

  When copying a document using the copying machine, first, the document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 31 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it. Thereafter, when the user presses a start switch (not shown), when the document is set on the automatic document feeder 400, the document is conveyed onto the contact glass 31. Then, the scanner 300 is driven and the first traveling body 33 and the second traveling body 34 start traveling. Thereby, the light from the first traveling body 33 is reflected by the document on the contact glass 31, and the reflected light is reflected by the mirror of the second traveling body 34 and guided to the reading sensor 36 through the imaging lens 35. . In this way, the image information of the original is read.

  When the start switch is pressed by the user, a drive motor (not shown) is driven, and one of the support roller 14, the support roller 15, and the support roller 16 is driven to rotate, and the intermediate transfer belt 10 is driven to rotate. . At the same time, the photosensitive member 20 and the developing sleeve 65 of each image forming unit 18 are rotationally driven, and the photosensitive member 20 is irradiated with laser writing light from the laser writing device 21 to form an electrostatic latent image on the photosensitive member 20. Form. Thereafter, toner is supplied from the developing sleeve 65 to the electrostatic latent image formed on the photoconductor 20, and a toner image is formed on the photoconductor 20.

  Each color toner image formed in this way is primarily transferred by the primary transfer devices 62Y, 62C, 62M, and 62K so as to sequentially overlap the intermediate transfer belt 10. As a result, a composite toner image in which the toner images of the respective colors overlap is formed on the intermediate transfer belt 10. The transfer residual toner remaining on the intermediate transfer belt 10 after the secondary transfer is removed by the belt cleaning device 17.

  When the user presses the start switch, the paper feed roller 42 of the paper feed device 200 corresponding to the transfer paper 5 selected by the user rotates, and the transfer paper 5 is sent out from one of the paper feed cassettes 44. The transferred transfer paper 5 is separated into one sheet by the separation roller 45 and enters the paper feed path 46, and is conveyed by the conveyance roller 47 to the conveyance path 48 in the printing unit 100. The transfer sheet 5 thus transported is stopped when it abuts against the registration roller 49b.

  The registration roller 49b starts to rotate in accordance with the timing at which the composite toner image formed on the intermediate transfer belt 10 as described above is conveyed to the secondary transfer unit facing the secondary transfer roller 24. The transfer paper 5 sent out by the registration roller 49b is sent between the intermediate transfer belt 10 and the secondary transfer roller 24, and the secondary transfer roller 24 causes the composite toner image on the intermediate transfer belt 10 to be transferred onto the transfer paper 5. Secondary transfer. Thereafter, the transfer sheet 5 is conveyed to the fixing device 25 while being attracted to the secondary transfer roller 24, and heat and pressure are applied by the fixing device 25 to perform a toner image fixing process. The transfer paper 5 that has passed through the fixing device 25 is discharged to the paper discharge tray 7 by the discharge roller 56 and stacked. When image formation is also performed on the back surface of the surface on which the toner image is fixed, the transfer paper 5 that has passed through the fixing device 25 is switched by the switching claw 55 and sent to the paper reversing device 93. The transfer paper 5 is then reversed and guided to the secondary transfer roller 24 again.

  In this embodiment, the toner image on the photosensitive member 20 as a latent image carrier is transferred to the transfer paper 5 as a recording member via the intermediate transfer belt 10 as a surface endless moving member. Such a configuration may be adopted. In other words, a paper transport belt, which is a surface endless moving body, is disposed at a position facing the photoconductor, and the toner image on the photoconductor is directly applied to the transfer paper transported while being held on the surface of the paper transport belt. It is transcribed. Even in such a configuration, the reference patch is transferred to the surface of the paper conveyance belt instead of the transfer paper held on the surface of the paper conveyance belt. 110 can be detected.

  In this embodiment, a color type copying machine that forms a multicolor toner image by superimposing transfer has been described. However, the present invention can also be applied to a single color type image forming apparatus that forms only a single color toner image. Is possible.

[Example 1]
FIG. 5 is a block diagram showing the main part of the electric circuit of the copying machine according to the present embodiment. As shown in the figure, the copying machine is provided with a main control unit 500 having a computer configuration, and the main control unit 500 drives and controls each unit. The main control unit 500 includes a ROM (Read Only Memory) 503 that stores in advance fixed data such as a computer program via a bus line 502 in a CPU (Central Processing Unit) 501 that executes various calculations and drive control of each unit. A RAM (Random Access Memory) 504 that functions as a work area for storing various data in a rewritable manner is connected.

  The ROM 503 stores a conversion table (not shown) that stores information related to conversion of the output value of the optical sensor 110 into toner adhesion amount per unit area.

  The main control unit 500 is connected to each unit of the printing unit 100, the paper feeding device 200, the scanner 300, and the automatic document feeder 400. Here, the optical sensor 110 and the potential sensor 120 of the printing unit 100 send the detected information to the main control unit 500.

  A main control unit (a combination of a CPU 501, a ROM 503, and a RAM 504) 500 serving as a control unit of the copier performs image forming condition adjustment control called potential set value adjustment control immediately after a power switch (not shown) is turned on. Configured to do. As a result, the main control unit 500 sets the desired image forming conditions before the start of a normal image forming operation for forming an image on the transfer paper 5 (before the transfer paper 5 is fed by the paper feeding device 200). Since the image forming condition adjustment control is performed, an image can be formed on the transfer paper 5 under the optimized image forming condition, and good image quality can be obtained.

  In this potential set value adjustment control, in the four image forming units 18Y, 18C, 18M, and 18K, gradation pattern images are formed on the surfaces of the photoreceptors 20Y, 20C, 20M, and 20K, respectively. Transcript to. The gradation pattern images of Y, M, C, and K are each composed of a plurality of reference patches (reference toner images) having different toner adhesion amounts per unit area. For example, the intermediate transfer belt in the state shown in FIG. 10 is transferred. Specifically, an M gradation pattern image Tm composed of a plurality of M reference patches, a C gradation pattern image Tc composed of a plurality of C reference patches, and a Y gradation pattern image Ty composed of a plurality of Y reference patches are respectively belts. The images are transferred so that they are aligned in the order of M, C, and Y in the moving direction. On the other hand, the K gradation pattern image Tk composed of a plurality of K reference patches is transferred to a position different from other gradation pattern images in the belt width direction.

  In the potential setting value adjustment control, each reference patch in a gradation pattern image (for example, 10 gradation pattern) formed on the intermediate transfer belt 10 is detected by the optical sensor 110 including the optical elements 110a and 110b, and the reference patch is detected. An appropriate development γ is calculated based on the corresponding output voltage value. Then, based on the calculation result, the photosensitive member uniform charging potential, the developing bias, and the optical writing intensity capable of obtaining the target image density are specified and set as the set values.

  The development γ is the slope of a graph showing the relationship between the development potential and the toner adhesion amount per unit area. The development potential is a potential difference between the potential of the electrostatic latent image on the surface of the photoconductor and the potential of the surface of the developing sleeve to which the developing bias is applied.

  Here, in the potential setting adjustment control, when a line pattern and a solid pattern are created on the intermediate transfer belt 10 as shown in FIG. 7 and these line pattern and solid pattern are detected by the optical sensor 110, each of the line pattern and the solid pattern is detected. The toner adhesion amount can be obtained according to the image density. The adhesion amount data obtained with the line pattern is V_Line, the adhesion amount data obtained with the solid pattern is V_beta, and the line solid ratio = V_Line ÷ V_beta is defined as the adhesion amount ratio between the line pattern and the solid pattern.

Here, the definition of the line pattern and the solid pattern will be described.
In FIG. 8A, (A) shows the photosensitive member potential exposed by the image data in the solid pattern, and (B) shows the electric field latent image corresponding to the photosensitive member potential. In FIG. 8B, (A) shows the photosensitive member potential exposed by the image data in the line pattern, and (B) shows the electric field latent image with respect to the photosensitive member potential.

  An electric field corresponding to a place where the photoreceptor potential changes is greatly emphasized. At this time, the shape of the edge electric field changes according to the line width L. That is, when the line width L is large as shown in FIG. 8A (specifically, when the line width is 12 lines or more in the present configuration example), the electric field is emphasized only at the edge of the image. On the other hand, when there are less than 12 lines as shown in FIG. 8B, the edge electric fields at the edge of the image are combined to generate a large edge electric field.

  Since the solid pattern and the line pattern differ slightly depending on the system, the actual machine outputs an image based on data in which the line width is changed from one line to a plurality of lines, and determines the amount of toner attached to each line image. Measured and converted into toner adhesion amount per unit area, as shown in FIG. 9, the horizontal axis represents the line width and the vertical axis represents the toner adhesion amount per unit area. The result of an experiment in advance may be used as the threshold for distinguishing the solid line width from the line pattern with the saturated line width.

  The closer the line solid ratio, which is the ratio of the toner adhesion amount per unit area of the line pattern and the toner adhesion amount per unit area of the solid pattern, to 1, the lower the height of the toner layer of the line pattern, The margin will increase.

  The threshold value α of the line solid ratio at which transfer dust occurs is different depending on the characteristics of the system and the developer used. Therefore, it is necessary to set according to the characteristics of each electrophotographic apparatus. Only when α is exceeded, the potential setting adjustment is performed after changing the peripheral speed ratio of the developing sleeve to reduce the edge effect. As a result, there is an effect that “transfer dust” can be improved without giving extra stress to the developer or the electrophotographic apparatus.

  The value of the development γ varies greatly depending on the surrounding environment of the developer. More specifically, development is performed in a high temperature and high humidity environment (here, 27 [° C.] 80 [%]) as compared with an environment of normal temperature and normal humidity (here, 23 [° C.] 50 [%]). γ increases, and development γ decreases in a low temperature and low humidity environment (10 [° C.] 15 [%]). This is because the charge amount of the developer that is frictionally charged by the stirring unit 66 decreases in a high-temperature and high-humidity environment and increases in a low-temperature and low-humidity environment. This is a phenomenon that occurs because the toner adhesion amount per unit area increases and the toner adhesion amount per unit area decreases in a low temperature and low humidity environment.

  In the copying machine of this embodiment, it is assumed that the actual use environment of the user is 10 [° C.] 15 [%] (low temperature and low humidity environment) to 27 [° C.] 80 [%] (high temperature and high humidity environment). When developing γ at 15 ° C. [15 ° C.] (low temperature and low humidity environment) is the lower limit γmin, and developing γ at 27 ° C. 80% (high temperature and high humidity environment) is the upper limit γ MAX γ varies between γmin and γMAX. The copying machine is designed so that the development γ becomes γref in the range of γmin to γMAX under 23 [° C.] 50 [%] (normal temperature and humidity environment).

FIG. 10 is a graph showing the relationship between the development potential and the toner adhesion amount of each reference patch in the development γ = γmin, γref, γMax. Here, the toner adhesion amount for obtaining a predetermined solid density is referred to as a target adhesion amount, and in this copying machine, the target adhesion amount is set to 0.55 [mg / cm ² ].

The development potentials for obtaining the target adhesion amount of 0.55 [mg / cm ² ] at the development γ = γMax, γref, γmin from the linear approximation formula of the plot points of each reference patch in FIG. 10 are Vpot1, Vpot2, Vpot3, respectively. And The unit of development γ is [(mg / cm ² ) / − kV], and the unit of development potential is [−kV].

As shown in FIG. 10, the development potential for obtaining the target adhesion amount of 0.55 [mg / cm ² ] changes according to the development γ, and when the development γ becomes smaller, the target adhesion amount of 0.55 [mg / cm ² ]. The development potential for obtaining cm ² ] is increased. That is, in the development γ = γmin, γref, γMax shown in FIG. 10, when the development γ is γmin, the development potential for obtaining the target adhesion amount 0.55 [mg / cm ² ] is the largest, and then becomes γref. , The development potential for obtaining the target adhesion amount of 0.55 [mg / cm ² ] becomes the smallest when γMax.

  FIG. 11 is a graph showing the relationship between development γ and transfer dust rank. The transfer dust rank is obtained by visually observing the degree of toner scattering in the character portion (line pattern). If the transfer dust rank allowed by the user is 4 or more, the transfer dust rank is 4 or more as shown in FIG. For this purpose, the development γ needs to be γth or more.

  As described above, in the electrophotographic image forming apparatus, a phenomenon that the electric field at the boundary portion of the electrostatic latent image formed on the image carrier is strengthened, that is, a so-called edge effect occurs. The edge effect increases as the development potential increases. For this reason, the smaller the development γ, the larger the development potential for obtaining the target adhesion amount, and the greater the influence of the edge effect. The conventional copying machine has a problem that transfer dust occurs when development γ <γth in a low temperature and low humidity environment and the development potential increases.

  For this reason, it is conceivable to reduce the development potential so that transfer dust due to the edge effect does not occur. However, if the development potential is simply reduced, the toner adhesion amount becomes smaller than the target adhesion amount for obtaining a predetermined solid density. This leads to a decrease in the solid density.

As in FIG. 10, when the target adhesion amount for obtaining a predetermined solid density is 0.55 [mg / cm ² ], the target adhesion amount 0.55 [mg / cm ² ] when development γ = γth. The development potential for obtaining the above is Vpot_th [−kV].

  Next, FIG. 12 is a graph showing the relationship between the development linear velocity ratio and development γ. As shown in FIG. 12, when the development linear velocity ratio is Ksafe (Vs / Vp = 1.7) or more, the development γ is γth (development γ = 1.3) or more. This is because the developing linear velocity ratio increases, that is, the number of toner supply per unit time from the developing sleeve 65 to the electrostatic latent image formed on the photosensitive member 20 increases by increasing the rotation speed of the developing sleeve. This is considered to be because the toner adhesion amount per unit area increases even with the same development potential.

  Considering the above points, the copying machine of this embodiment is equipped with potential set value adjustment control shown in the flowchart of FIG.

  In the potential set value adjustment control, first, a Y-10 gradation pattern image, a C-10 gradation pattern image, an M-10 gradation pattern image, and a K-10, each consisting of 10 reference patches each having a different toner adhesion amount. A gradation pattern image is formed. In addition to these gradation pattern images, a line pattern and a solid pattern are created on the intermediate transfer belt 10 under normal image forming conditions (S1: S is an abbreviation of step).

  The gradation pattern image, line pattern, and solid pattern are detected by the optical sensor 110, and the output result is stored in the RAM 504 (S2). At the same time, the output value of the potential sensor 120 for each gradation pattern portion potential on the photoconductor 20 is read and stored in the RAM 504 (S4).

  Next, the toner adhesion amount in each gradation pattern image, line pattern, and solid pattern is obtained from the output value of the optical sensor 110 stored in the RAM 504 and an adhesion amount conversion table (not shown) (S3). At the same time, the development potential is calculated from the potential output value of the potential sensor 120 stored in the RAM 504 and the pattern image development bias (S5).

  When the toner adhesion amount is obtained, development γ is calculated based on the development potential and toner adhesion amount in each gradation pattern image (S6).

  Next, the toner adhesion amount per unit area is calculated for each of the line pattern and the solid pattern from the toner adhesion amount of the line pattern and the solid pattern, and the image data of the line pattern and the solid pattern, and the per unit area of the line pattern is calculated. Line solid ratio = V_Line ÷ V_beta is calculated as a ratio between the toner adhesion amount V_Line and the toner adhesion amount V_beta per unit area of the solid pattern, and the calculated line solid ratio is V_Line ÷ V_beta <α with respect to the threshold α. (NO in S7), it is determined that the height H of the toner layer of the line pattern does not exceed the specified value of the toner layer height at which transfer dust occurs, and a target adhesion amount that provides a desired solid density is obtained. The development potential necessary for the calculation is calculated and specified based on the calculated development γ (S1). 0).

  On the other hand, when the calculated line solid ratio is V_Line ÷ V_beta ≧ α with respect to the above-described line solid ratio threshold α at which transfer dust occurs (YES in S7), the toner layer height H of the line pattern becomes the transfer dust. It is determined that the specified value of the toner layer height at which the toner occurs is exceeded.

  If the calculated development γ is smaller than γth where the transfer dust rank allowed by the user is 4 or more (NO in S8), the development linear velocity ratio Vs / Vp is developed as described above. The developing speed ratio Ksafe is changed so that γ becomes γth (S9). That is, it is determined that the developing capability of the developing device has decreased, and the developing linear speed ratio is increased to increase the toner supply amount per unit time from the developing sleeve 65 to the electrostatic latent image formed on the photoreceptor 20. The toner adhesion amount per unit area at the same development potential is increased to increase the development γ. After changing the development linear speed ratio to Ksafe, the process returns to S1 again and a series of control is repeated.

  Then, when the re-calculated line solid ratio becomes V_Line ÷ V_beta ≧ α with respect to the threshold α (YES in S7), and the re-calculated development γ is equal to or greater than γth (YES in S8), the desired solid The development potential necessary to obtain the target adhesion amount that can obtain the density is calculated and specified based on the calculated development γ (S10).

  At this time, by changing to the development linear velocity ratio Ksafe and increasing the development γ so that the development γ <γth becomes the development γ = γth, the target adhesion amount can be obtained compared to before the development linear velocity ratio is changed to Ksafe. Development potential can be reduced. Therefore, by changing the imaging condition so that the specified development potential can be obtained as described above, the development potential necessary to obtain the target adhesion amount becomes smaller than before the imaging condition change. The degree of influence of the edge electric field in the line pattern is reduced. Accordingly, the toner adhesion amount of the line pattern is reduced and the height of the toner layer is lowered, so that transfer dust caused by the edge electric field of the line pattern can be reduced.

  Even if the development potential is reduced in order to reduce the degree of influence of the edge electric field in the line pattern, a target adhesion amount for obtaining a desired solid density is ensured, so that a reduction in the density of the solid pattern can be suppressed.

  Thus, the potential set value adjustment control process is completed. Then, by performing such potential set value adjustment control processing and changing the image forming conditions such as the charging potential and developing bias of the photoconductor so as to obtain the specified developing potential, a decrease in the density of the solid pattern is suppressed. However, transfer dust caused by the edge electric field of the line pattern can be reduced.

[Example 2]
In the potential set value adjustment control flow in the first embodiment shown in FIG. 1, the same effect can be obtained even if the development linear velocity ratio is changed to Ksafe after calculating the development potential. Since the development potential at the time of development γ = γth is Vpot_th [−kV], the development linear speed ratio may be changed to Ksafe when the development potential is larger than Vpot_th. FIG. 13 shows a potential set value adjustment control flow in the second embodiment.

  In the potential set value adjustment control, first, a Y-10 gradation pattern image, a C-10 gradation pattern image, an M-10 gradation pattern image, and a K-10, each consisting of 10 reference patches each having a different toner adhesion amount. A gradation pattern image is formed on the intermediate transfer belt 10. In addition to these gradation pattern images, a line pattern and a solid pattern are created on the intermediate transfer belt 10 under normal image forming conditions (S1).

  The gradation pattern image, line pattern, and solid pattern are detected by the optical sensor 110, and the output result is stored in the RAM 504 (S2). At the same time, the output value of the potential sensor 120 for each gradation pattern portion potential on the photoconductor 20 is read and stored in the RAM 504 (S4).

  Next, the toner adhesion amount in each gradation pattern image, line pattern, and solid pattern is obtained from the output value of the optical sensor 110 stored in the RAM 504 and the adhesion amount conversion table (not shown) (S3). At the same time, the development potential is calculated from the potential output value of the potential sensor 120 stored in the RAM 504 and the pattern image development bias (S5).

  When the toner adhesion amount is obtained, development γ is calculated based on the development potential and toner adhesion amount in each gradation pattern image (S6).

  Next, the toner adhesion amount per unit area is calculated for each of the line pattern and the solid pattern from the toner adhesion amount of the line pattern and the solid pattern, and the image data of the line pattern and the solid pattern, and the per unit area of the line pattern is calculated. The line solid ratio = V_Line ÷ V_beta is calculated as the ratio of the toner adhesion amount V_Line and the toner adhesion amount V_beta per unit area of the solid pattern. When the calculated line solid ratio is V_Line ÷ V_beta <α with respect to the threshold value α of the line solid ratio at which the above-mentioned transfer dust occurs (NO in S7), the height H of the toner layer of the line pattern is Based on the calculated development γ, specify the development potential necessary to obtain the target adhesion amount that determines the toner layer height at which transfer dust is generated does not exceed the specified value. (S10).

  On the other hand, when the calculated line solid ratio is V_Line ÷ V_beta ≧ α with respect to the threshold value α (YES in S7), the toner layer height H of the line pattern is the specified value of the toner layer height at which transfer dust occurs. It is judged that it exceeded.

  Then, a development potential necessary to obtain a target adhesion amount that can obtain a desired solid density from the calculated development γ is obtained, and when the obtained development potential is larger than Vpot_th (NO in S8), a development linear velocity ratio is obtained. Is changed to Ksafe, and the process returns to S1 again to repeat a series of controls (S9).

  The recalculated line solid ratio becomes V_Line ÷ V_beta ≧ α with respect to the threshold value α (YES in S7), and the development necessary for obtaining the target adhesion amount that can obtain the desired solid density from the recalculated development γ. A potential is obtained, and it is determined whether or not the obtained development potential is equal to or less than Vpot_th. Here, as described above, the development linear velocity ratio Ksafe is a value at which the development γ = γth can be obtained. Therefore, by setting the development linear velocity ratio to Ksafe, the development γ = γth is obtained, and the desired solid density can be obtained. Since the development potential necessary to obtain the adhesion amount can be set to Vpot_th, when it is determined that the obtained development potential is equal to or less than Vpot_th (YES in S8), the target adhesion amount at which a desired solid density is obtained. The development potential necessary to obtain the above is calculated and specified based on the calculated development γ (S10).

  Here, the development linear velocity ratio is changed to Ksafe, and the development potential necessary to obtain the target adhesion amount that can achieve a desired solid density is set to Vpot_th, so that the development linear velocity ratio is changed to Ksafe before the change. However, the development potential for obtaining the target adhesion amount is reduced. Therefore, by changing the imaging condition so that the specified development potential can be obtained as described above, the development potential necessary to obtain the target adhesion amount becomes smaller than before the imaging condition change. The degree of influence of the edge electric field in the line pattern is reduced. Accordingly, the toner adhesion amount of the line pattern is reduced and the height of the toner layer is lowered, so that transfer dust caused by the edge electric field of the line pattern can be reduced.

  Even if the development potential is reduced in order to reduce the degree of influence of the edge electric field in the line pattern, a target adhesion amount for obtaining a desired solid density is ensured, so that a reduction in the density of the solid pattern can be suppressed.

  Thus, the potential set value adjustment control process is completed. Then, by performing such potential set value adjustment control processing and changing the image forming conditions such as the charging potential and developing bias of the photoconductor so as to obtain the specified developing potential, a decrease in the density of the solid pattern is suppressed. However, transfer dust caused by the edge electric field of the line pattern can be reduced.

[Example 3]
In this embodiment, a temperature / humidity sensor (not shown) is attached in the vicinity of the developing device 61, and the same effect can be obtained even when the developing linear velocity ratio is changed to Ksafe according to the change in the surrounding environment of the developing device (developer). Is obtained. Here, the absolute humidity in the surrounding environment of the developer satisfying development γ ≧ γth varies depending on the device characteristics and is not specified. Here, assuming that the absolute humidity threshold value indicating whether or not transfer dust occurs is δ [g / m ³ ], transfer dust occurs when the absolute humidity is smaller than the threshold value δ by the temperature and humidity sensor. If the absolute humidity detected by the above is smaller than the threshold value δ, the development linear speed ratio may be changed to Ksafe. FIG. 14 shows a potential set value adjustment control flow in the third embodiment.

  In the potential set value adjustment control, first, a Y-10 gradation pattern image, a C-10 gradation pattern image, an M-10 gradation pattern image, and a K-10, each consisting of 10 reference patches each having a different toner adhesion amount. A gradation pattern image is formed. In addition to these gradation pattern images, a line pattern and a solid pattern are created on the intermediate transfer belt 10 under normal image forming conditions (S1).

  The gradation pattern image, line pattern, and solid pattern are detected by the optical sensor 110, and the output result is stored in the RAM 504 (S2). At the same time, the output value of the potential sensor 120 for each gradation pattern portion potential on the photoconductor 20 is read and stored in the RAM 504 (S4).

  Next, the toner adhesion amount in each gradation pattern image, line pattern, and solid pattern is obtained from the output value of the optical sensor 110 stored in the RAM 504 and an adhesion amount conversion table (not shown) (S3). At the same time, the development potential is calculated from the potential output value of the potential sensor 120 stored in the RAM 504 and the pattern image development bias (S5).

  When the toner adhesion amount is obtained, development γ is calculated based on the development potential and toner adhesion amount in each gradation pattern image (S6).

  Next, the toner adhesion amount per unit area is calculated for each of the line pattern and the solid pattern from the toner adhesion amount of the line pattern and the solid pattern, and the image data of the line pattern and the solid pattern, and the per unit area of the line pattern is calculated. A line solid ratio = V_Line ÷ V_beta is calculated as a ratio between the toner adhesion amount V_Line and the toner adhesion amount V_beta per unit area of the solid pattern. If the calculated line solid ratio is V_Line ÷ V_beta <α with respect to the threshold α (NO in S7), the height H of the toner layer of the line pattern is equal to the height of the toner layer where transfer dust occurs. It is determined that the specified value is not exceeded, and a development potential necessary to obtain a target adhesion amount that provides a desired solid density is calculated and specified based on the calculated development γ (S11).

  On the other hand, when the calculated line solid ratio is V_Line ÷ V_beta ≧ α with respect to the above-described line solid ratio threshold α at which transfer dust occurs (YES in S7), the toner layer height H of the line pattern becomes the transfer dust. It is determined that the specified value of the toner layer height at which the toner occurs is exceeded.

Then, the ambient environment such as the humidity of the developing device 61 is detected by a temperature / humidity sensor attached in the vicinity of the developing device 61 (S8). Based on the detection result, whether or not the transfer humidity is generated or not is absolute. When the humidity is smaller than the threshold value δ [g / m ³ ] (NO in S9), the development linear velocity ratio is changed to Ksafe, and the process returns to S1 again to repeat the series of controls (S10).

  When the absolute humidity is smaller than the threshold value δ, the development γ <γth is obtained. As described above, the development linear velocity ratio Ksafe is a value at which the development γ = γth can be obtained. The toner supply amount per unit time from 65 to the electrostatic latent image formed on the photoconductor 20 is increased, the toner adhesion amount per unit area at the same development potential is increased, and the development γ is increased, thereby developing γ By setting γth, the development potential for obtaining the target adhesion amount can be made smaller than before the development linear velocity ratio is changed to Ksafe.

  Therefore, the degree of influence of the edge electric field in the line pattern is reduced as the development potential is reduced, and the toner adhesion amount of the line pattern is reduced and the toner layer height is lowered. Therefore, transfer dust caused by the edge electric field of the line pattern is reduced. Can be reduced.

  Even if the development potential is reduced in order to reduce the degree of influence of the edge electric field in the line pattern, a target adhesion amount for obtaining a desired solid density is ensured, so that a reduction in the density of the solid pattern can be suppressed.

  Thus, the potential set value adjustment control process is completed. Then, by performing such potential set value adjustment control processing and changing the image forming conditions such as the charging potential and developing bias of the photoconductor so as to obtain the specified developing potential, a decrease in the density of the solid pattern is suppressed. However, transfer dust caused by the edge electric field of the line pattern can be reduced.

  In each embodiment, the determination as to whether or not the toner layer height H of the line pattern exceeds the specified value of the toner layer height at which transfer dust occurs is based on at least the detection result of the line pattern by the optical sensor 110. Thus, it is possible to obtain information (toner adhesion amount V_Line per unit area) related to the toner layer height of the line pattern, and the toner layer height H of the line pattern is generated based on the obtained information. Even if the potential set value adjustment control process is executed so that the toner layer height is lowered when the toner height is equal to or greater than the specified value, the same effect as described above can be obtained. Further, as in each of the embodiments, the toner adhesion amount per unit area of the line pattern is used to determine whether the toner layer height H of the line pattern exceeds the specified value of the toner layer height at which transfer dust occurs. It is preferable to use a line / solid ratio that is a ratio between V_Line and a toner adhesion amount V_beta per unit area of the solid pattern because a determination can be made in consideration of a margin with respect to transfer dust.

As described above, in this embodiment, the latent image is written by irradiating the charged light on the photosensitive member 20 that is a charged image carrier, the latent image on the photosensitive member 20 is developed, and the toner on the photosensitive member 20 is developed. An image forming unit for forming an image, and the transfer unit transfers the toner image formed on the photosensitive member 20 to the transfer sheet 5 which is a recording material conveyed by a paper conveyance belt which is a surface moving member; In an image forming apparatus that forms an image on transfer paper 5 by transferring the toner image on intermediate transfer belt 10 to transfer paper 5 after transferring the image to the surface of intermediate transfer belt 10 that is a surface moving member, the toner image The toner layer height of the line-shaped toner image is based on the detection result of the optical sensor 110 which is an optical detection means for detecting the reflected light from the optical sensor 110 and at least the reflected light from the line-shaped toner image. And the image forming means is controlled so that the toner layer height is lowered when the toner layer height of the line-shaped toner image is equal to or higher than a preset reference height at which transfer dust occurs. And a main control unit 500 which is a control means. Accordingly, when the toner layer height of the line-shaped toner image is equal to or higher than a preset reference height at which transfer dust occurs, the main controller 500 controls the image forming unit so that the toner layer height is lowered. Since the toner layer is controlled, the transfer dust caused by the edge effect can be reduced as much as the height of the toner layer can be reduced.
The upper Kisakuzo means includes a photosensitive member 20 as an image carrier, a charging device 60 is a charging means for charging the photosensitive member 20 to a predetermined potential, writing light to the charged photoreceptor surface to a predetermined potential A developing sleeve while applying a developing bias to a laser writing device 21 that is a latent image forming means for forming a latent image by irradiating the toner and a developing sleeve 65 that is a developer carrying member carrying a developer containing at least toner. And a developing device 61 that is a developing means for developing the latent image by transferring the toner on the photosensitive member 20 to a latent image on the photosensitive member 20, and when the toner layer height is equal to or higher than the reference height, the photosensitive member The development linear speed ratio, which is the peripheral speed ratio between the toner 20 and the developing sleeve 65, is increased, and a gradation pattern composed of a plurality of toner patches formed under different image forming conditions is formed. Tone Putter The development potential, which is the difference between the potential of the latent image portion and the development bias, is set based on the detection result detected by the optical sensor 110, and the image forming means is controlled by the main control portion 500, whereby the density of the solid pattern is determined. It is possible to reduce transfer dust caused by the edge electric field of the line pattern while suppressing the decrease.
Further, according to the present embodiment, the main control unit 500 that also functions as a toner adhesion amount detection unit that detects the toner adhesion amount per unit area of the toner image based on the detection result of the optical sensor 110 is provided. The main control unit 500 performs control to increase the development linear velocity ratio when the development γ, which is the slope of the relational expression of the toner adhesion amount with respect to the development potential, is smaller than the preset reference development γ, γth, The toner supply amount per unit time from the developing sleeve 65 to the latent image formed on the photoconductor 20 can be increased, the toner adhesion amount per unit area at the same development potential can be increased, and the development γ can be increased. . By increasing the development γ, the development potential for obtaining the target adhesion amount can be made smaller than before the development linear velocity ratio is increased, and the degree of influence of the edge electric field in the line pattern can be reduced accordingly. Accordingly, the toner adhesion amount of the line pattern is reduced and the height of the toner layer is lowered, so that transfer dust caused by the edge electric field of the line pattern can be reduced.
Further, according to the present embodiment, the main control unit 500 determines that the development potential for obtaining the toner adhesion amount at which the image density of the solid toner image becomes the target value is based on the preset reference development potential Vpot_th. If it is too large, the development potential necessary to obtain the target adhesion amount can be reduced by controlling the development linear velocity ratio to be large, and the degree of influence of the edge electric field in the line pattern is reduced accordingly. be able to. Accordingly, the toner adhesion amount of the line pattern is reduced and the height of the toner layer is lowered, so that transfer dust caused by the edge electric field of the line pattern can be reduced.
Further, in the present embodiment, a temperature / humidity sensor that is a humidity detecting unit that detects the humidity around the developing device 62 is provided, and the main control unit 500 detects the periphery of the developing device 62 detected by the temperature / humidity sensor. When the absolute humidity of the environment is lower than an absolute humidity threshold value δ, which is a preset reference absolute humidity, control is performed to increase the development linear velocity ratio. When the absolute humidity is smaller than the threshold value δ, the development γ <γth, so that the development linear velocity ratio is increased and the toner supply amount per unit time from the developing sleeve 65 to the latent image formed on the photoconductor 20 is increased. Thus, by increasing the toner adhesion amount per unit area at the same development potential and increasing the development γ, the development potential for obtaining the target adhesion amount can be made smaller than before the development linear speed ratio is changed. Therefore, the degree of influence of the edge electric field in the line pattern is reduced as the development potential is reduced, and the toner adhesion amount of the line pattern is reduced and the toner layer height is lowered. Therefore, transfer dust caused by the edge electric field of the line pattern is reduced. Can be reduced.
Further, according to the present embodiment, before the normal image forming operation for forming an image on the transfer paper 5 is started, the image forming unit is controlled by the main control unit 500 so as to satisfy a desired image forming condition. Thus, an image can be formed on the transfer paper 5 under the optimized image forming conditions, and good image quality can be obtained.

5 Transfer Paper 6 Manual Tray 7 Discharge Tray 10 Intermediate Transfer Belt 14 Support Roller 15 Support Roller 16 Support Roller 17 Belt Cleaning Device 18 Image Forming Unit 20 Photosensitive Member 21 Laser Writing Device 22 Conveying Belt 23a Roller 23b Roller 24 Secondary Transfer Roller 25 Fixing device 26 Heating roller 27 Pressure roller 30 Document table 31 Contact glass 33 Traveling body 34 Traveling body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 44 Paper feed cassette 45 Separating roller 46 Paper feed path 47 Transport roller 48 Transport Path 49a Conveying roller 49b Registration roller 50 Feeding roller 51 Separating roller 53 Manual feed path 55 Switching claw 56 Discharging roller 60 Charging device 61 Developing device 62 Primary transfer device 62 Developing device 63 Photoconductor cleaning device 64 Removal Electric device 65 Developing sleeve 66 Stirrer 67 Developing unit 68 Screw 70 Developing case 71 Toner concentration sensor 73 Doctor blade 75 Cleaning blade 76 Fur brush 91 Roller cleaning unit 93 Paper reversing device 100 Print unit 110 Optical sensor 110a Optical element 110b Optical element 120 Potential sensor 200 Paper feeding device 300 Scanner 400 Automatic document feeder 500 Main control unit 501 CPU
502 Bus line 503 ROM
504 RAM

JP 2007-33770 A

Claims (5)

Image forming means for irradiating writing light onto the charged image carrier to write a latent image, developing the latent image on the image carrier to form a toner image on the image carrier, and transferring The toner image formed on the image carrier is transferred onto the recording material conveyed by the surface moving member, or the toner image on the surface moving member is recorded after the toner image is transferred to the surface of the surface moving member. In an image forming apparatus that forms an image on a recording material by transferring it to the material,
Optical detecting means for detecting reflected light from the toner image;
Information on the toner layer height of the line-shaped toner image is obtained based on the detection result of the optical detection means that has detected reflected light from at least the line-shaped toner image, and the toner layer height of the line-shaped toner image There have a control means for controlling the image forming means so that the toner layer height becomes lower when the above reference height previously set to the generation of transfer dust,
The image forming means includes the image carrier, charging means for charging the image carrier to a predetermined potential, and a latent image for forming a latent image by irradiating the surface of the image carrier charged to a predetermined potential with writing light. The toner on the developer carrying member is transferred to a latent image on the image carrying member while applying a developing bias to the image forming means and the developer carrying member carrying the developer containing at least toner. And developing means for developing
When the toner layer height is equal to or higher than the reference height, a plurality of image forming conditions are formed such that the peripheral speed ratio between the image carrier and the developer carrier is increased and the adhesion amounts are different from each other. Forming a gradation pattern composed of toner patches, and setting a development potential that is a difference between the potential of the electrostatic latent image portion and the development bias based on the detection result obtained by detecting the gradation pattern by the optical detection unit, An image forming apparatus, wherein the image forming means is controlled by the control means . The image forming apparatus according to claim 1 .
A toner adhesion amount detection means for detecting a toner adhesion amount per unit area of the toner image based on a detection result of the optical detection means;
The control means performs control to increase the peripheral speed ratio when the development γ, which is the slope of the relational expression of the toner adhesion amount with respect to the development potential, is smaller than a preset reference development γ. apparatus. The image forming apparatus according to claim 1 .
The control means controls to increase the peripheral speed ratio when the development potential for obtaining the toner adhesion amount at which the image density of the solid toner image becomes a target value is larger than a preset reference development potential. An image forming apparatus. The image forming apparatus according to claim 1 .
Having humidity detecting means for detecting the humidity around the developing means,
The control means performs control to increase the peripheral speed ratio when the absolute humidity of the surrounding environment of the developing means detected by the humidity detection means is lower than a preset reference absolute humidity. Image forming apparatus. Claims 1, 3 or in the image forming apparatus 4,
An image forming apparatus, wherein the image forming unit is controlled by the control unit so as to satisfy a desired image forming condition before a normal image forming operation for forming an image on the recording material is started.

Images