JP2010117534A - Image forming apparatus, method for adjusting image forming item, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus measuring toner density of a toner image formed on an image carrier with a small number of parts, and to provide a method for adjusting image forming items and an image forming method. <P>SOLUTION: The image forming apparatus includes a transparent photoreceptor belt 9, an electrifying part 10, an exposure part 11, a developing part 2, a transfer part 3, a fixing part 4, and a photodetector 16, wherein the photodetector 16 is installed at a position where it is opposed to the exposure part 11 across the photoreceptor belt 9. The image forming apparatus further includes a toner density-measuring means for measuring the toner density of the toner image formed on the photoreceptor belt 9 by using intensity of light radiated from the exposure part 11 and detected by the photoreceptor 16. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine, an image forming item adjusting method, and an image forming method using an electrophotographic system.

  In general, an image forming apparatus using an electrophotographic system forms a desired image through each process of charging, exposure, development, transfer, peeling, cleaning, static elimination, and fixing. In recent years, with the widespread use of color inkjet image forming apparatuses, electrophotographic color image forming apparatuses are also required to be smaller and less expensive.

  In order to realize downsizing and cost reduction of the image forming apparatus, it is necessary to perform at least one of downsizing of the components of the image forming apparatus and reduction of the number of components. Therefore, as one of the methods for reducing the size and reducing the price, there has been proposed an image forming apparatus that superimposes a plurality of color toner images on one photoconductor and collectively transfers the image onto a recording medium (paper). This image forming apparatus does not require an intermediate transfer body because it is not a system in which a toner image is superimposed on an intermediate transfer body and then transferred to a recording medium. Further, since the toner image is not superposed on the recording medium held on the recording medium holder, the recording medium holder is not required. Therefore, the size is significantly reduced as compared with an image forming apparatus employing these methods.

  On the other hand, an electrophotographic image forming apparatus has a characteristic that the image quality of a recorded image is likely to change due to environmental changes and usage conditions. An image forming apparatus capable of measuring the toner density in order to stabilize the image quality is described in Patent Document 1 and Patent Document 2.

  The image forming apparatuses described in Patent Document 1 and Patent Document 2 create a toner patch for detecting an image density on the surface of a toner image carrier such as a photoreceptor or an intermediate transfer member, and the toner density (toner adhesion amount) of the toner patch. ) Is measured using an optical sensor including a light emitting unit and a light receiving unit.

  As shown in FIGS. 9 (a1) and 9 (a2), the image forming apparatus described in Patent Document 1 emits light toward the toner patches Tb and Tc on the photosensitive member 52 by the light emitting unit 50a. Reflected light generated by the light is detected by the light receiving unit 51a, and the toner concentrations of the toner patches Tb and Tc are measured from the received light amount. When measuring the toner density of the black toner patch Tb, as shown in FIG. 9 (a1), the light emitting unit 50a and the light receiving unit 51a are installed so that regular reflection light from the photoconductor 52 can be detected. This is because the black toner absorbs light, so that it is necessary to detect specularly reflected light that reaches the photoreceptor and is reflected without being absorbed by the toner. When measuring the toner density of the color toner patch Tc, as shown in FIG. 9 (a2), the light emitting unit 50a and the light receiving unit 51a are installed so as not to detect the regular reflection light from the photosensitive member 52. Since the color toner absorbs light of a specific wavelength and reflects light of other wavelengths, the toner density can be measured only by the reflected light from the color toner patch Tc, and the regular reflected light from the photoconductor 52 is detected. This is because the toner density cannot be accurately measured if both the reflected light from the color toner patch Tc and the regular reflected light from the photoconductor 52 are detected. In the image forming apparatus described in Patent Document 1, by measuring at least one of the light emitting unit 50a and the light receiving unit 51a, the toner density of both the black toner patch Tb and the color toner patch Tc is measured by a pair of optical sensors. It is possible.

  As shown in FIG. 9B, the image forming apparatus described in Patent Document 2 uses a recording medium holder 53 as a transparent member, and a light emitting unit 50b and a light receiving unit 51b so as to face each other with the recording medium holder 53 interposed therebetween. , The light passing through the toner patch T and the recording medium holding member 53 can be detected by the light receiving unit 51b, and the toner density is measured by the detected light intensity. The toner density of both the black toner patch and the color toner patch can be measured.

JP-A 61-209470 Japanese Patent Laid-Open No. 3-174560

  However, in order to stabilize the image quality of the recorded image by the image forming apparatus, it is necessary to install at least both the light emitting unit 50 and the light receiving unit 51 when applying the technique described in Patent Document 1 or Patent Document 2. Therefore, the image forming apparatus is increased in size and is contrary to the trend of downsizing.

  The present invention has been made to solve the above-described problems, and an image forming apparatus and an image forming apparatus capable of measuring the toner density of a toner image formed on an image carrier with a small number of parts. An object is to provide an item adjustment method and an image forming method.

The present invention comprises a transparent image carrier,
Charging means for charging the surface of the image carrier;
Exposure means for irradiating light to the charged image carrier to form an electrostatic latent image;
Developing means for supplying toner to the image carrier on which an electrostatic latent image is formed;
Transfer means for transferring the toner image formed on the image carrier to a recording medium;
Fixing means for fixing the toner image on the recording medium to the recording medium;
A light receiving means provided at a position facing the exposure means across the image carrier;
And a toner density measuring unit that measures the toner density of the toner image on the image carrier using the intensity of light emitted from the exposure unit, which is detected by the light receiving unit. Forming device.

  According to the present invention, the light emitted from the exposure means is detected based on the intensity of the light emitted from the exposure means and transmitted through the area where the toner is not carried on the image carrier. Emission intensity changing means for changing the intensity is provided.

The present invention also provides a transparent image carrier,
Charging means for charging the surface of the image carrier;
Exposure means for irradiating light to the charged image carrier to form an electrostatic latent image;
Developing means for supplying toner to the image carrier on which an electrostatic latent image is formed;
Neutralizing means for performing neutralization by irradiating the image carrier with light;
Transfer means for transferring the toner image formed on the image carrier to a recording medium;
Fixing means for fixing the toner image on the recording medium to the recording medium;
A light receiving means provided at a position facing the exposure means across the image carrier;
And a toner density measuring unit that measures the toner density of the toner image on the image carrier using the intensity of light emitted from the charge eliminating unit, which is detected by the light receiving unit. Forming device.

  Further, the present invention is directed to the light emitted from the charge eliminating unit based on the intensity of the light detected by the light receiving unit and emitted from the charge eliminating unit and transmitted through the area of the image carrier where the toner is not carried. Emission intensity changing means for changing the intensity is provided.

  Further, the present invention is characterized by further comprising an item changing means for changing the image forming item according to the measurement result of the toner density of the toner image on the image carrier.

  In the invention, it is preferable that the item changing unit changes an image forming item so that a toner density of a specific toner patch on the image carrier approaches a specific value.

In the present invention, the developing means is a developing means for applying a developing bias when supplying toner to the image carrier.
The image forming item is a value of a developing bias.

  In the invention, it is preferable that the image forming item is intensity of light irradiated by the exposure unit.

In the present invention, the image carrier is movably provided,
A plurality of the light receiving means are provided in a direction parallel to the image carrying surface of the image carrier and perpendicular to the moving direction of the image carrier.

The present invention also includes a charging step for charging the surface of the image carrier,
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
Intensity of light irradiated from the exposure unit and transmitted through the transparent image carrier detected by a light receiving unit provided at a position facing the exposure unit across the image carrier with the toner density of the toner image on the image carrier A toner concentration measuring step to measure using
And an item changing step for changing an image forming item so that a measurement result obtained by the toner concentration measuring step approaches a predetermined reference value.

The present invention also includes a step of changing an image forming item by the adjustment method,
A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
A transfer step of transferring a toner image formed on the image carrier to a recording medium;
And a fixing step of fixing the toner image transferred onto the recording medium to the recording medium.

The present invention also includes a charging step for charging the surface of the image carrier,
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
Intensity of light irradiated from the charge eliminating unit and transmitted through the transparent image carrier detected by a light receiving unit provided at a position opposite to the charge eliminating unit with the image carrier sandwiched between the toner density of the toner image on the image carrier A toner concentration measuring step to measure using
And an item changing step for changing an image forming item so that a measurement result obtained by the toner concentration measuring step approaches a predetermined reference value.

The present invention also includes a step of changing an image forming item by the adjustment method,
A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
A charge removal step of removing light by irradiating the image carrier with light;
A transfer step of transferring a toner image formed on the image carrier to a recording medium;
And a fixing step of fixing the toner image transferred onto the recording medium to the recording medium.

  According to the present invention, a transparent image carrier, a charging means for charging the surface of the image carrier, an exposure means for forming an electrostatic latent image by irradiating light to the charged image carrier, Developing means for supplying toner to the image carrier on which the electrostatic latent image is formed, transfer means for transferring the toner image formed on the image carrier to a recording medium, and recording the toner image on the recording medium A fixing unit for fixing to a medium; a light receiving unit provided at a position facing the exposure unit across the image carrier; and a toner density of a toner image on the image carrier is detected by the light receiver. There is provided an image forming apparatus comprising: a toner concentration measuring unit that measures the intensity of light emitted from the exposing unit.

  According to this apparatus, the light irradiated by the exposure unit is detected by the light receiving unit, and the toner concentration is measured by the detected light intensity, so that a light emitting unit used only for toner concentration measurement is not provided. It is possible to measure the toner concentration.

  According to the invention, the exposure means irradiates on the basis of the intensity of light detected by the light receiving means and irradiated from the exposure means and transmitted through a region of the image carrier where no toner is carried. A light emission intensity changing means for changing the light intensity is provided.

  When at least one of the image carrier, the exposure unit, and the light receiving unit is contaminated with toner or deteriorated with time, the exposure unit irradiates and the toner of the image carrier is not carried. The intensity of light transmitted through the region changes. According to the apparatus, even when the intensity of detected light changes due to such contamination and deterioration with time, the intensity of light irradiated by the exposure unit can be changed by the emission intensity changing unit. Therefore, it is possible to irradiate light with a certain intensity by the exposure means.

  According to the invention, the transparent image carrier, the charging unit for charging the surface of the image carrier, the exposure unit for irradiating the charged image carrier with light to form an electrostatic latent image, A developing unit that supplies toner to the image carrier on which an electrostatic latent image is formed, a neutralizing unit that performs light neutralization by irradiating the image carrier with light, and a toner image formed on the image carrier. Transfer means for transferring to a recording medium; fixing means for fixing a toner image on the recording medium to the recording medium; light receiving means provided at a position facing the exposure means across the image carrier; and the image carrier There is provided an image forming apparatus comprising: a toner density measuring unit that measures a toner density of a toner image on a body using an intensity of light emitted from the charge removing unit, which is detected by the light receiving unit.

  According to this apparatus, the light irradiated by the charge eliminating unit is detected by the light receiving unit, and the toner concentration is measured based on the detected light intensity. Therefore, a light emitting unit used only for toner concentration measurement is not provided. It is possible to measure the toner concentration.

  According to the invention, the static eliminator irradiates on the basis of the intensity of the light detected by the light receiver and irradiated from the static eliminator and transmitted through the area of the image carrier where the toner is not carried. A light emission intensity changing means for changing the light intensity is provided.

  When at least one of the image carrier, the exposure unit, and the light receiving unit is contaminated with toner or deteriorated with time, the toner is irradiated from the charge eliminating unit and the toner of the image carrier is not carried. The intensity of light transmitted through the region changes. According to the apparatus, even when the intensity of detected light changes due to such contamination and deterioration with time, the intensity of light emitted by the static eliminating means can be changed by the emission intensity changing means. Therefore, it is possible to irradiate light with a certain intensity by the static eliminating means.

  According to the invention, there is provided item changing means for changing the image forming item according to the measurement result of the toner density of the toner image on the image carrier. According to the apparatus, it is possible to change the image formation item according to the measurement result of the toner density of the toner image on the image carrier. Therefore, it is possible to obtain an image with a constant image quality regardless of changes in the environment and usage conditions.

  According to the invention, the item changing unit changes the image forming item so that the toner density of a specific toner patch on the image carrier approaches a specific value. According to the apparatus, it is possible to suitably adjust the image forming items in accordance with the measurement result of the toner density of the toner image on the image carrier, so that regardless of changes in environment and changes in use conditions, etc. It is possible to obtain an image having a constant image density.

  According to the invention, the developing means is a developing means for applying a developing bias when supplying toner to the image carrier, and the image forming item is a value of the developing bias. According to the apparatus, the value of the developing bias can be changed according to the measurement result of the toner density of the toner image on the image carrier.

  According to the invention, the image forming item is intensity of light irradiated by the exposure unit. According to the apparatus, it is possible to change the intensity of light irradiated by the exposure unit in accordance with the measurement result of the toner density of the toner image on the image carrier.

  According to the invention, the image carrier is movably provided, and the light receiving means is in a direction parallel to the image carrier surface of the image carrier and the moving direction of the image carrier. A plurality are provided along a direction perpendicular to. According to the apparatus, the toner density of the toner image formed on the image carrier can be measured at a plurality of positions in the width direction of the image carrier. Further, when changing the image formation item according to the measurement result of the toner density, the image formation item can be changed according to the measurement result of the toner density measured at a plurality of positions in the width direction. Even if the toner density of the toner image formed on the carrier has unevenness in the width direction, the image forming items can be suitably adjusted.

  According to the invention, the charging step for charging the surface of the image carrier, the exposure step for irradiating the charged image carrier with light to form an electrostatic latent image, and the image on which the electrostatic latent image is formed. The developing process for supplying toner to the carrier and forming a toner image, and the toner density of the toner image on the image carrier are detected by a light receiving means provided at a position facing the exposure means across the image carrier. A toner concentration measuring step for measuring using the intensity of light irradiated from the exposure means and transmitted through the transparent image carrier, and an image so that the measurement result obtained by the toner concentration measuring step approaches a predetermined reference value. There is provided an adjustment method including an item changing step of changing a formation item.

  According to the adjustment method, the light irradiated by the exposure unit is detected by the light receiving unit, and the toner density is measured by the detected light intensity. Therefore, a light emitting unit used only for toner density measurement is provided. The toner density can be measured, and the image forming item can be changed according to the measurement result of the toner density.

  According to the invention, the step of changing the image forming item by the adjustment method, the charging step of charging the surface of the image carrier, and the electrostatic latent image is formed by irradiating the charged image carrier with light. An exposure step, a developing step for supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image; a transfer step for transferring the toner image formed on the image carrier to a recording medium; And a fixing step of fixing the toner image transferred onto the recording medium to the recording medium.

  According to the image forming method, since the image is formed using the image forming item changed by the adjustment method, an image having a constant image quality can be obtained regardless of a change in environment or a change in use conditions. Is possible.

  According to the invention, the charging step for charging the surface of the image carrier, the exposure step for irradiating the charged image carrier with light to form an electrostatic latent image, and the image on which the electrostatic latent image is formed. A developing process for supplying toner to the carrier and forming a toner image, and a toner density of the toner image on the image carrier are detected by a light receiving means provided at a position facing the charge eliminating unit with the image carrier interposed therebetween. A toner concentration measurement step for measuring using the intensity of light irradiated from the charge eliminating means and transmitted through the transparent image carrier, and an image so that the measurement result obtained by the toner concentration measurement step approaches a predetermined reference value. There is provided an adjustment method including an item changing step of changing a formation item.

  According to the adjustment method, the light irradiated by the charge eliminating unit is detected by the light receiving unit, and the toner concentration is measured based on the detected light intensity. Therefore, a light emitting unit used only for toner concentration measurement is provided. The toner density can be measured, and the image forming item can be changed according to the measurement result of the toner density.

  According to the invention, the step of changing the image forming item by the adjustment method, the charging step of charging the surface of the image carrier, and the electrostatic latent image is formed by irradiating the charged image carrier with light. An exposure step, a developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, forming a toner image, a static elimination step of irradiating the image carrier with light to neutralize, and an image carrier There is provided an image forming method including a transfer step of transferring the toner image formed on the recording medium to a recording medium, and a fixing step of fixing the toner image transferred onto the recording medium to the recording medium.

  According to the image forming method, since the image is formed using the image forming item changed by the adjustment method, an image having a constant image quality can be obtained regardless of a change in environment or a change in use conditions. Is possible.

  FIG. 1 is a schematic diagram schematically showing a cross section of an image forming apparatus 100 according to the first embodiment of the present invention. The image forming apparatus 100 includes a photosensitive belt unit 1, a developing unit 2, a transfer unit 3, a fixing unit 4, a paper feeding unit 5, a conveyance path 6, and a paper discharging unit 7. Here, in order to correspond to the image information of each color of black (b), cyan (c), magenta (m), and yellow (y) included in the color image information, each of the four members is provided for each color. The alphabet which represents is distinguished by attaching | subjecting to the end of a reference code, and when referring generically, it represents only with a number. Although the image forming apparatus 100 shown in FIG. 1 is a color printer having only a printer function, embodiments of the present invention may be a copying machine having an image reading unit or a facsimile apparatus having a communication unit. Good.

  An elongated photoconductor belt unit 1 is installed at substantially the center of the cabinet 8 of the image forming apparatus 100. The photosensitive belt unit 1 includes a photosensitive belt 9, a charging unit 10, an exposure unit 11, a neutralizing unit 12, a pre-transfer neutralizing unit 13, a pre-transfer charging unit 14, a cleaning unit 15, and a light receiving unit. 16, a driving roller 17, a driven roller 18, a tensioner (not shown), and a frame (not shown) that stores and supports them.

  Along the surface of the photoreceptor belt 9, a charging unit 10 on the outside of the photoreceptor belt 9, an exposure unit 11 on the inside, a developing unit 2 on the outside, a charge eliminating unit 13 on the inside, a charging unit 14 on the outside, and a pre-transfer charging unit 14 on the outside, The cleaning unit 15, the neutralization unit 12 on the inner side, and the light receiving unit 16 on the outer side of the photosensitive belt facing the neutralization unit 12 are arranged in this order.

  The driving roller 17, the driven roller 18, and the tensioner are disposed inside the photosensitive belt 9 and wrap around the photosensitive belt 9. The driving roller 17 and the driven roller 18 support the photosensitive belt 9 so as to be rotatable in the direction of an arrow 19, and the tensioner applies a predetermined tension so that the photosensitive belt 9 does not loosen. The drive shaft 17a of the drive roller 17 and the support shaft 18a of the driven roller 18 are supported rotatably on the frame. A gear (not shown) is attached to one end of the drive shaft 17a, meshed with a gear connected to a drive unit provided in the cabinet 8, and the drive roller 17 is rotated by the rotation of the drive unit.

The photoreceptor belt 9 as an image carrier is obtained by laminating a translucent conductive film and a photoconductive layer on the surface of a transparent support having translucency, and has an insulating property in a dark place. It has conductivity at the place. Here, the term “transparent and translucent” means that light having a specific wavelength is transmitted without being absorbed and reflected. In the present embodiment, a laminate of a 500 積 層 ITO (Indium Tin Oxide) film and a 500 Ｓ SnO ₂ film is used as the translucent conductive film. The photoconductive layer includes a blocking layer made of a hydrogenated amorphous silicon (a-Si: H) film having a layer thickness of 0.2 μm and 5000 ppm boron added, and a boron layer having a thickness of about 3 μm and 5 ppm boron. A laminate of an a-Si: H film to which is added and a surface protective layer made of an a-SiC: H film having a layer thickness of 0.1 μm is used.

  The charging unit 10 serving as a charging unit is disposed so as to face the photosensitive belt 9 and be separated from the surface of the photosensitive belt 9 with a gap, and charges the surface of the photosensitive belt 9 to a predetermined polarity and potential. For the charging unit 10, a charger-type charger, a saw-tooth type charger, an ion generator, or the like can be used. In the present embodiment, the charging unit 10 is provided so as to be separated from the surface of the photoreceptor belt 9, but includes a plurality of photoreceptors corresponding to each developer, and after developing for each developer, a toner image is formed. In another embodiment that employs a method of transferring to a recording medium, a charging roller may be used as the charging unit 10, and the charging roller may be disposed so that the charging roller and the photosensitive member are pressed against each other. A contact charging type charger such as a brush may be used.

  The exposure unit 11 serving as an exposure unit separates image information into light of each color information of b, c, m, and y in the exposure unit 11 and is charged to a uniform potential by the charging unit 10. Is exposed with light of one color of each color information to form an electrostatic latent image. Since only the exposed portion of the photosensitive belt 9 is conductive, only the exposed surface is neutralized, and the potential is greatly different from the other portions. Surfaces with different potentials are electrostatic latent image portions, and an image represented by the electrostatic latent image portion is an electrostatic latent image. For the exposure unit 11, for example, an LED (Light emitting diode) array can be used. In addition, a laser scanning unit including a laser irradiation unit and a plurality of reflection mirrors, or a unit in which a liquid crystal shutter and a light source are appropriately combined may be used.

  The neutralization unit 12 which is one of the neutralization units irradiates the photosensitive belt 9 with light by irradiating light to the charged photosensitive belt 9. A member such as a halogen lamp can be used for the static elimination unit 12.

  The developing unit 2 that is a developing unit includes a developing tank 20 that contains a developer, a stirring roller 21 that stirs the developer, a developing roller 22 that carries the developer, and a developer amount that is carried on the developing roller 22. And a layer thickness regulating member 23 for regulating. The developing tank 20b contains black toner, the developing tank 20c contains cyan toner, the developing tank 20m contains magenta toner, and the developing tank 20y contains yellow toner. The developer stored in the developing tank 20 is charged by being stirred by the stirring roller 21, and the charged developer is carried on the developing roller 22, and is regulated to a predetermined amount by the layer thickness regulating member 23. The photosensitive belt 9 is conveyed to the vicinity of the outer surface. The proximity of the developing roller 22 to the outer surface of the photosensitive belt 9 and the outer surface of the photosensitive belt 9 have a distance of about 200 μm, and the developer moves from the developing roller 22 to the outer surface of the photosensitive belt 9. This is done by causing a large potential difference between the developing roller 22 and the electrostatic latent image portion of the photosensitive belt 9 by the developing bias applied to the developing roller 22. In the present embodiment, as described above, the developer is moved by the potential difference due to the developing bias. Therefore, although a one-component developer composed only of toner is used, a plurality of photoconductors corresponding to each developer are provided. In another embodiment that employs a system in which development is performed for each developer and then a toner image is transferred to a recording medium, a two-component developer can also be used.

  A process of forming a color toner image on the outer surface of the photosensitive belt 9 by the driving roller 17, the driven roller 18, the photosensitive belt 9, the charging unit 10, the exposure unit 11, the charge removing unit 12, and the developing unit 2 will be described. .

  First, the photosensitive belt 9 is rotated in the direction of the arrow 19 by the driving roller 17 and the driven roller 18. Along with the start of rotation, a high voltage is applied to the charging unit 10, and the outer surface of the photoreceptor belt 9 is uniformly charged by corona discharge. The charged area of the photosensitive belt 9 is irradiated with light by an exposure unit 11 provided inside the photosensitive belt 9, and an electrostatic latent image corresponding to one of the colors b, c, m, and y. Is formed.

  Next, as the photosensitive belt 9 rotates, the area where the electrostatic latent image is formed moves to the vicinity of the developing unit 2, and the toner of the color corresponding to the light on which the electrostatic latent image is formed in the developing unit 2. The toner is supplied to the photosensitive belt 9 by the developing unit 2 having the same. In accordance with the timing at which the area where the electrostatic latent image is formed passes through the vicinity of the developing unit 2, toner is conveyed by the developing roller 22 and a developing bias is applied so that only one color toner is applied to the photosensitive belt 9. A one-color toner image is formed.

  Due to the rotation of the photosensitive belt 9, the area carrying the toner image of one color passes near the transfer unit 3 and the cleaning unit 15, but the transfer unit 3 and the cleaning unit 15 are separated from the outer surface of the photosensitive belt 9. Since the toner image is separated from the outer surface of the photosensitive belt 9 until all color toners are developed, the toner image is not disturbed, and the transfer unit 3 and the cleaning unit 15 are not disturbed. Pass nearby. Thereafter, the area carrying the toner image moves to the vicinity of the static eliminating unit 12, and the photosensitive belt 9 is neutralized by light irradiation by the static eliminating unit 12 from the inside of the photosensitive belt 9.

  The area carrying the toner image moves to the vicinity of the charging unit 10, and the outer surface of the photosensitive belt 9 is charged again by the corona discharge of the charging unit 10 while carrying the toner image. Thereafter, in the same manner as described above, toners of other colors are superimposed on the outer surface of the photoreceptor belt 9 to form a color toner image. The above is the color toner image forming process.

  When a color toner image is formed on the outer surface of the photoreceptor belt 9 by the above-described color toner image forming process, the pre-transfer charge removal unit 13 as another charge removal unit performs charge removal on the photoreceptor belt 9. For the pre-transfer charge removal unit 13, the same member as the charge removal unit 12 can be used.

  After the color toner image is formed and discharged by the pre-transfer charge eliminating unit 13, the pre-transfer charging unit 14 charges the color toner image for transfer described later. A member similar to the charging unit 10 can be used for the pre-transfer charging unit 14. After charging the color toner image, the area carrying the color toner image moves to the vicinity of the transfer unit 3.

  The transfer unit 3 serving as a transfer unit includes a transfer roller 24 that is disposed to face the driving roller 17 on the inner side of the photosensitive belt 9 and is configured to be detachable from the outer surface of the photosensitive belt 9. A high voltage is applied by the power source. The transfer roller 24 is rotatably supported by a bearing attached to the cabinet 8. As described above, the transfer roller 24 is attached to the outer surface of the photoreceptor belt 9 before the color toner image is formed by a separation mechanism such as a motor and a solenoid. They move away from each other and come into contact after formation. The position where the transfer roller 24 and the photosensitive belt 9 come into contact is the transfer execution position. When the area carrying the color toner image moves to the vicinity of the transfer roller 24, the color toner image charged by the pre-transfer charging unit 14 is transferred from the photoreceptor belt 9 to the recording paper by the high voltage applied to the transfer roller 24. The

  In this embodiment, as described above, development and transfer are performed by one photoconductor without using an intermediate transfer member, but in other embodiments, development and transfer are performed using a plurality of photoconductors and intermediate transfer members. Transcription can also be performed.

  The residual toner remaining on the outer surface of the photoreceptor belt 9 is collected by the cleaning unit 15. As described above, the cleaning unit 15 is moved away from the outer surface of the photosensitive belt 9 before the formation of the color toner image by the contact / separation mechanism such as a motor and a solenoid, and moves after the formation. This separation / contact timing is synchronized with the separation / contact timing of the transfer roller 24.

  The paper feed unit 5 includes a paper feed tray 25, a pickup roller 26, and a registration roller 27. A paper feed tray 25 on which recording paper as a recording medium is detachably provided is provided on the outer wall of the cabinet 8, and the recording paper placed on the paper feed tray 25 is conveyed by a pickup roller 26 one by one. Supplied to the path 6. The conveyance path 6 is formed so as to extend from the paper feed tray 25 to the paper discharge unit 7 on the upper surface of the cabinet 8. A pickup roller 26, a registration roller 27, a transfer unit 3, and a fixing unit 4 are provided along the conveyance path 6 from the upstream side in the conveyance direction. The recording paper picked up from the paper feed tray 25 is conveyed to the transfer execution position by the registration roller 27 in accordance with the toner image formation timing on the photosensitive belt 9. The transfer roller 24 comes into contact with the photosensitive belt 9 and the recording paper is conveyed toward the transfer execution position by the registration roller 27.

  The recording paper on which the color toner images are collectively transferred is conveyed to a fixing unit 4 as a fixing unit, where the toner on the recording paper is melted and pressed by heating and pressurization, and the color image is transferred onto the recording paper. To be established. The recording sheet on which fixing has been completed is discharged to the paper discharge section 7 through the conveyance path 6 and image formation is completed.

Further, the image forming apparatus 100 includes a control unit (not shown). For example, the control unit is provided in an upper part of the internal space of the image forming apparatus 100 and includes a storage unit, a calculation unit, and a control unit. The storage unit stores various setting values via an operation panel (not shown) arranged on the upper surface of the image forming apparatus 100, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus 100, and external devices. Image information and the like are input. Various programs are written. As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). As the external device, an electric / electronic device capable of forming or obtaining image information and electrically connected to the image forming apparatus can be used. For example, a computer, a digital camera, a television, a video recorder, a DVD (Digital Versatile
Disc) recorder, HDDVD (High Definition Digital Versatile Disc), Blu-ray disc recorder, facsimile apparatus, and portable terminal apparatus. The arithmetic unit takes out various data (image formation command, detection result, image information, etc.) written in the storage unit and programs for executing various means, and performs various determinations. The control unit sends a control signal to the corresponding device according to the determination result of the calculation unit, and performs operation control. The control unit and the calculation unit include a processing circuit realized by a microcomputer and a microprocessor including a central processing unit (CPU). The control unit includes a main power source together with the processing circuit, and the main power source supplies power not only to the control unit but also to each member in the image forming apparatus 100. The image forming apparatus 100 described above can measure the toner density of the toner image formed on the photoreceptor belt 9, and further, the image forming items of the image forming apparatus 100 can be determined based on the measured toner density. It is possible to change and adjust to stabilize the image quality of the recorded image. Hereinafter, measurement of toner density and adjustment of image formation items will be described.

  The image forming apparatus 100 forms a plurality of toner patches on the outer surface of the photoreceptor belt 9 in order to measure the toner density. This toner patch is formed for each color by developing only one color in the color toner image forming process. In the present invention, for each color, a square toner patch having a side L of 20 mm is formed at a pitch P of 15 mm in the moving direction of the photosensitive belt 9. For example, three toner patches are formed as shown in FIG. The toner patches T1, T2, and T3 are moved to a position facing the neutralization unit 12 provided 15 mm away from the surface of the photosensitive belt 9 by the rotation of the photosensitive belt 9, and are irradiated with light by the neutralization unit 12. A light receiving unit 16 as a light receiving unit is provided 10 mm away from the surface of the photosensitive belt 9 at a position facing the neutralizing unit 12 with the photosensitive belt 9 interposed therebetween, and the light irradiated by the neutralizing unit 12 is It is detected by the light receiving unit 16.

  FIG. 3 shows a state in which the light irradiated by the charge eliminating unit 12 passes through the toner patch T1 and the photoreceptor belt 9 and is detected by the light receiving unit 16. A part of the light irradiated by the static eliminating unit 12 is absorbed or reflected by the colorant particles in the toner patch T1. If the toner patch T1 is a black toner patch, the irradiated light is absorbed, and if it is any other color toner patch, the irradiated light is absorbed or reflected. The light that has not been absorbed or reflected passes through the photosensitive belt 9 and is detected by the light receiving unit 16. In the present embodiment, a halogen lamp is used for the static elimination unit 12 and a photodiode is used for the light receiving unit 16. As the halogen lamp, for example, a halogen lamp (JE type) manufactured by Harrison Toshiba Lighting Co., Ltd. can be used. As the photodiode, for example, a photodiode (model number KD834) manufactured by Shinko Denshi Co., Ltd. can be used.

  The image forming apparatus 100 measures the toner density of the toner image from the detected light intensity. Specifically, the intensity of irradiation light from the static eliminating unit 12 is unified, and the light receiving intensity N detected by the light receiving unit 16 when a toner image is present on the surface of the photoreceptor belt 9, and the light receiving unit when there is no toner image. The ratio S / N of the received light intensity S detected by 16 is calculated. This calculation is performed by the control unit which is a toner density measuring unit.

  This received light intensity ratio S / N has a one-to-one correspondence with the toner concentration represented by the toner adhesion amount per unit area, and is in a proportional relationship. Therefore, if the irradiation light of the static eliminating unit 12 is always kept constant, the toner density can be expressed by the light reception intensity ratio S / N. In the present invention, the toner density represented by the toner adhesion amount per unit area is referred to as toner density (attachment amount), and the toner density represented by the received light intensity ratio S / N is referred to as toner density S / N.

  As described above, in this embodiment, the toner density S / N can be measured from the photosensitive belt 9 formed of a transparent member, the charge eliminating unit 12 and the light receiving unit 16. Further, if the correspondence between the toner density S / N and the toner density (attachment amount) is stored in the storage unit in advance, the toner density (attachment amount) can be measured from the toner density S / N. . Therefore, in the present invention, it is possible to measure the toner concentration S / N and the toner concentration (attachment amount) of the toner image formed on the photosensitive belt 9 without newly providing a light emitting portion for measuring the toner concentration. Therefore, it is possible to reduce the size of the image forming apparatus.

  Next, adjustment of image formation items for stabilizing the image quality of the recorded image will be described. Table 1 shows the toner density S / N for each of the black toner patch (b), cyan toner patch (c), magenta toner patch (m), and yellow toner patch (y) formed as described above. This represents the relationship with the image density (Image Density) of the recorded image. As shown in Table 1, there is a one-to-one correspondence between toner density S / N and image density. FIG. 4 is a graph of Table 1.

  FIG. 4A is a graph showing the relationship between the toner density S / N and the image density in the black toner patch, and FIG. 4B shows the relationship between the toner density S / N and the image density in the cyan toner patch. FIG. 4C is a graph showing the relationship between the toner density S / N and the image density in the magenta toner patch, and FIG. 4D is the relationship between the toner density S / N and the image density in the yellow toner patch. It is a graph which shows. Each point in FIG. 4 represents each value in Table 1, and the straight line is a straight line calculated by linear approximation from the value of each point using the least square method. As shown in FIG. 4, it can be seen that the toner density S / N is proportional to the image density. Therefore, the image quality of the recorded image can be adjusted using the toner density S / N instead of the toner density (attachment amount).

  Hereinafter, image quality adjustment by adjusting the toner density S / N will be described. As described above, in the electrophotographic image forming apparatus 100, the image quality of a recorded image is likely to change due to environmental changes and usage conditions. Therefore, the image forming apparatus 100 is required to stably form a high density image. From Table 1 and FIG. 3, in order to stabilize the image density of the recorded image, the image forming item may be adjusted so that the toner density S / N becomes constant, and the image forming apparatus 100 is the control that is the item changing unit. Adjust the image forming items.

  In order to make the toner density S / N constant, it is necessary to store the reference value of the toner density S / N in the storage unit before adjusting the image forming items. This reference value can be stored in the image forming apparatus 100 in advance, and can be changed by the user. In this embodiment, the reference value for the black toner patch is 0.33, the reference value for the cyan toner patch is 0.42, the reference value for the magenta toner patch is 0.43, and the reference value for the yellow toner patch is 0.47. . When the toner density S / N in each toner patch deviates from the reference value, the image forming apparatus 100 adjusts the image forming item so as to approach these reference values. For example, when the toner density S / N is not within a predetermined range from the reference value, the image forming item is adjusted so that the toner density S / N falls within the range. The predetermined range can be changed by the user.

  The image forming items include the value of the developing bias and the light emission intensity of the exposure unit 11. The developing bias is a voltage applied to the developing roller 22, and a large potential difference is generated between the electrostatic latent image portion and the developing roller 22 by the developing bias, and the charged toner moves. As the potential difference increases, the toner concentration (attachment amount) increases. Therefore, the toner concentration S / N can be brought close to the reference value by adjusting the value of the developing bias. Further, if the light emission intensity of the exposure unit 11 is increased, the charge removal amount on the surface of the photoreceptor belt 9 after charging by the charging unit 10 increases, and the potential difference increases even if the developing bias is constant. By adjusting the light emission intensity, the toner density S / N can be brought close to the reference value.

  First, a development bias adjustment process using the development bias value as an image formation item will be described. The image forming apparatus 100 forms three toner patches on the surface of the photoreceptor belt 9 as shown in FIG. In this embodiment, the number of toner patches to be created is three, but the toner density S / N can be adjusted if the number is two or more. In the developing bias adjustment process, the toner patches are formed by different potential differences. Hereinafter, a process for adjusting the developing bias applied to the developing roller 22b using the black toner patch will be described.

  In the developing bias adjustment process, for example, as shown in FIG. 5A, the outer surface potential V1 of the photosensitive belt 9 after being charged by the charging unit 10 is −850 V, and is uniformly charged. Thereafter, three latent image patches are created by the exposure unit 11. The surface potentials V2 of the photoreceptor belt 9 in the three latent image patches are all -100V, and are made the same by making all the emission intensities of the exposure unit 11 equal.

  The developing bias applied to the developing roller 22 is adjusted to develop each latent image patch to form toner patches T1, T2, and T3. The toner patch T1 is formed with a potential difference V6 between the latent image patch and the developing roller of 600 V by applying a developing bias V3 (−700 V). The toner patch T2 is formed with a potential difference V7 between the latent image patch and the developing roller of 550 V by applying a developing bias V4 (−650 V). The toner patch T3 is formed by applying a developing bias V5 (−600V) so that the potential difference V8 between the latent image patch and the developing roller is 500V. In the present embodiment, the toner patch is formed by the above-described potentials, but these potentials can be appropriately changed according to the embodiment.

  The image forming apparatus 100 measures the toner density S / N of the toner patch formed as described above using the charge removal unit 12 and the light receiving unit 16. Assuming that the toner concentrations S / N of the toner patches T1, T2, and T3 are 0.31, 0.36, and 0.42, respectively, the control unit determines the toner concentration S / N based on these values. A developing bias value that approaches the reference value 0.33 is calculated. Specifically, the least square method is used from each toner density S / N, 0.31, 0.36, 0.42, and the respective development biases, −700V, −650V, and −600V. The developing bias −679 V approaching the reference value 0.33 is calculated using the linear approximation. The control unit changes the setting of the image forming apparatus 100 so as to apply the calculated developing bias of −679 V to the developing roller 22b. The above is the developing bias adjustment process corresponding to the developing roller 22b.

  The image forming apparatus 100 adjusts the developing bias to be applied to the developing rollers 22c, 22m, and 22y by the same process. The image forming apparatus 100 can always form an image with a stable image density by adjusting the developing bias.

  Next, a light emission intensity adjustment process using the light emission intensity of the exposure unit 11 as an image formation item will be described. The image forming apparatus 100 forms three toner patches on the surface of the photoreceptor belt 9 as shown in FIG. In the light emission intensity adjustment process, the toner patches are formed with different light emission intensities. Hereinafter, a process for adjusting the light emission intensity when forming a latent image corresponding to black toner, which is performed using the black toner patch, will be described.

  In the light emission intensity adjustment process, for example, as shown in FIG. 5B, the outer surface potential V11 of the photosensitive belt 9 after being charged by the charging unit 10 is −850 V, and is uniformly charged. Thereafter, three latent image patches are created by the exposure unit 11. In the present embodiment, an LED is used as the exposure unit 11, and the light emission intensity of the LED changes depending on the applied current. Therefore, the light emission intensity is adjusted by adjusting the current applied to the LED, and the latent image patch is exposed to light. The surface potential of the body belt 9 is adjusted. When a current of 1.34 mA is applied to the LED, the surface potential V12 in the latent image patch corresponding to the toner patch T1 is −100V. When a current of 1.23 mA is applied to the LED, the surface potential V15 in the latent image patch corresponding to the toner patch T2 is −150V. When a current of 1.1 mA is applied to the LED, the surface potential V14 in the latent image patch corresponding to the toner patch T3 is -200V.

  Then, a developing bias V13 (−750 V) is applied to the developing roller 22 to develop each latent image patch, thereby forming toner patches T1, T2, and T3. The toner patch T1 is formed in a state where the potential difference V16 between the latent image patch and the developing roller is 650V. The toner patch T2 is formed in a state where the potential difference V17 between the latent image patch and the developing roller is 600V. The toner patch T3 is formed in a state where the potential difference V18 between the latent image patch and the developing roller is 550V. In this embodiment, the latent image patch is formed by each of the applied currents and the toner patch is formed by the above potentials. However, the applied currents and the potentials can be appropriately changed according to the embodiment.

  The image forming apparatus 100 measures the toner density S / N of the toner patch formed as described above using the charge removal unit 12 and the light receiving unit 16. Assuming that the toner concentrations S / N of the toner patches T1, T2, and T3 are 0.24, 0.29, and 0.35, respectively, the control unit determines that the toner concentration S / N is based on these values. The value of the applied current is calculated so as to approach the reference value 0.33. Specifically, the toner density S / N, 0.24, 0.29, and 0.35, and the applied current values that are the values, 1.34 mA, 1.23 mA, and 1.1 mA, are set to a minimum of 2. An applied current value of 1.14 mA, which is a reference value of 0.33, is calculated using linear approximation using multiplication. Further, from the surface potentials of −100 V, −250 V, and −200 V, the surface potential of −183 V that is the reference value of 0.33 is calculated using linear approximation using the least square method, and the surface potential becomes −183 V. Such an applied current value of 1.14 mA may be calculated. The control unit changes the setting of the image forming apparatus 100 so as to apply the calculated applied current of 1.14 mA to the LED. The above is the light emission intensity adjustment process of the exposure unit 11 corresponding to the black toner.

  The image forming apparatus 100 performs the same process to adjust the light intensity corresponding to each color. The image forming apparatus 100 can always form an image having a stable image density by adjusting the light emission intensity. In the present embodiment, the exposure unit 11 is an LED. However, when a laser scanning unit is used as the exposure unit 11, the emission intensity can be adjusted by adjusting the laser power, similarly to the above emission intensity adjustment process. The emission intensity can be adjusted so that the toner density S / N approaches the reference value.

  In addition to the adjustment of the image formation item based on the reference value of the toner density S / N, the image forming apparatus 100 can adjust the image formation item using the image density set by the user as the reference value. When adjusting the image forming item using the image density as a reference value, the image forming apparatus 100 uses the data representing the correspondence relationship between the toner density S / N and the image density stored in the storage unit. The reference value of the image density set by the above is converted into the reference value of the toner density S / N so that the converted reference value of the toner density S / N can be obtained in the same manner as the adjustment process of the image forming item. Next, the image forming items are adjusted. The data representing the correspondence between the toner density S / N and the image density is, for example, Table 1 and FIG.

  In addition, the image forming apparatus 100 detects light that is irradiated by applying a predetermined current or voltage to the static eliminating unit 12 and passes through a region on the outer surface of the photosensitive belt 9 where toner is not carried, and the light emission. The intensity and a predetermined current or voltage value can be stored. For example, if the light emission intensity of light irradiated by applying a predetermined current or voltage to the charge removal unit 12 is different from the stored light emission intensity, at least one of the charge removal unit 12, the photoreceptor belt 9, and the light receiving unit 16. One of them is that there are problems such as toner contamination and deterioration over time. According to the image forming apparatus 100, such a problem can be found immediately. For example, if the light emission intensity and the value of a predetermined current or voltage are stored immediately after the image forming apparatus 100 is manufactured, a problem that occurs after the storage can be found immediately.

  When the emission intensity changes due to a malfunction, the image forming apparatus 100 changes the setting of the current or voltage applied to the charge removal unit 12 by the control unit, which is the emission intensity changing unit, using the stored emission intensity as a reference value. As a result, the emission intensity is changed to approach the reference value. Therefore, the image forming apparatus 100 can always stably measure the toner density S / N, and can also stably adjust the image forming items based on the toner density S / N.

  Next, a second embodiment of the present invention in which the toner density S / N can be measured at a plurality of positions will be described. In the second embodiment, as shown in FIG. 6, the direction of movement of the photosensitive belt 9, which is parallel to the image carrying surface that is the surface carrying the image of the photosensitive belt 9, and is indicated by an arrow 19. A plurality of light receiving portions 16 are provided along a direction perpendicular to the pitch P2 of 100 mm. That is, as shown in FIG. 6, three light receiving portions 16 are provided in the width direction of the photosensitive belt 9. Further, in the present embodiment, the three light receiving portions 16 are all provided 10 mm away from the surface of the photoreceptor belt 9. The members other than the light receiving unit 16 have the same configuration as that of the image forming apparatus 100.

  The developer is carried as a thin layer on the developing roller 22 by the layer thickness regulating member 23. Although a thin SUS plate, phosphor bronze, or the like is used for the layer thickness regulating member 23, it is very difficult to uniformly press the layer thickness regulating member 23 over the entire surface of the developing roller 22. Therefore, unevenness in the thickness of the developer layer may occur locally. When development is performed in a state where unevenness occurs in the thickness of the developer layer, unevenness also occurs in the toner density S / N on the photosensitive belt 9. In this embodiment, since the three light receiving portions 16 are provided in the width direction of the photosensitive belt 9, the toner density S / N can be measured at three positions aligned in the width direction. By averaging the three toner density S / N values in the direction, the image forming items can be adjusted by the average value in the width direction of the toner density S / N.

  For example, in the present embodiment, nine toner patches T11 to T33 are formed as shown in FIG. Toner patches formed side by side with a pitch P3 of 100 mm in the width direction, for example, T11 to T13, are formed by common image forming items (development bias, emission intensity, etc.). In the present embodiment, similar to the image formation item adjustment process described above, suitable image formation items (development bias, light emission intensity, etc.) are calculated from the average values in the width direction of the three toner densities S / N, and the image formation is performed. Set to perform image formation using items. Therefore, in this embodiment, an image with a more stable image density can be formed. Further, since the static eliminating unit 12 irradiates light in the entire width direction, it is not necessary to irradiate light for each toner patch in the width direction, and the toner density S / N can be measured in a short time.

  Further, like the image forming apparatus 200 according to the third embodiment of the present invention illustrated in FIG. 7, the installation position of the light receiving unit 16 may be set to a position facing the exposure unit 11 with the photosensitive belt 9 interposed therebetween. . The image forming apparatus 200 forms an image by the same process as the image forming apparatus 100. The image forming apparatus 200 can measure the toner density S / N by the exposure unit 11 and the light receiving unit 16. The toner density S / N is measured by irradiating the photosensitive belt 9 and the toner image with light and detecting the transmitted light by the light receiving unit 16, as in the image forming apparatus 100. However, in the image forming apparatus 200, the exposure unit 11 irradiates light from the outside of the photosensitive belt 9. In the present embodiment, the above-described photodiode can be used for the light receiving portion 16, and the light receiving portion 16 is provided 10 mm away from the inner surface of the photosensitive belt 9. The exposure unit 11 can be an LED. In this embodiment, the toner density S / N is measured by irradiating the exposure unit 11 with light having a wavelength of 760 to 780 nm.

  Similarly to the image forming apparatus 100, the image forming apparatus 200 is irradiated by applying a predetermined current or voltage to the exposure unit 11, and passes through a region on the outer surface of the photosensitive belt 9 where toner is not carried. The detected light is detected and the emission intensity and a predetermined current or voltage value are stored. Then, the stored light emission intensity is used as a reference value, and the control unit, which is a light emission intensity changing unit, changes the light emission intensity by changing the setting of the current or voltage applied to the exposure unit 11, and returns to the reference value. You can get closer.

  Further, as in the second embodiment, it is also possible to provide a plurality of light receiving portions 16 in the width direction and measure the toner density S / N of the toner patches arranged in the width direction.

  As described above, the image forming apparatus 200 can measure the toner density by using the exposure unit 11 without newly providing a light emitting unit, so that the size of the apparatus can be reduced. Further, since the exposure unit 11 is an indispensable member in the electrophotographic image forming apparatus, the toner density S / N can be measured even if the apparatus does not include the charge removal unit 12, and the apparatus can be downsized. It is possible to Further, the image forming apparatus 200 can change the image forming item by the same process as the image forming apparatus 100 using the measured toner density S / N.

  Further, like the image forming apparatus 300 according to the fourth embodiment of the present invention shown in FIG. 8, the installation position of the light receiving unit 16 is set to a position facing the pre-transfer charge eliminating unit 13 with the photoreceptor belt 9 interposed therebetween. Also good. The image forming apparatus 300 forms an image by the same process as the image forming apparatus 100. The image forming apparatus 300 can measure the toner density S / N by the pre-transfer charge eliminating unit 13 and the light receiving unit 16. The toner density S / N is measured by irradiating the photosensitive belt 9 and the toner image with light and detecting the transmitted light by the light receiving unit 16, as in the image forming apparatus 100. However, in the image forming apparatus 300, the pre-transfer charge eliminating unit 13 emits light. In the present embodiment, the above-described photodiode can be used for the light receiving unit 16, and the light receiving unit 16 is provided 10 mm away from the outer surface of the photosensitive belt 9. Further, the halogen lamp described above can be used for the pre-transfer charge eliminating unit 13, and the pre-transfer charge eliminating unit 13 is provided 10 mm away from the inner surface of the photosensitive belt 9.

  Similarly to the image forming apparatus 100, the image forming apparatus 300 is irradiated with a predetermined current or voltage applied to the pre-transfer charge eliminating unit 13 and is an area on the outer surface of the photosensitive belt 9 where toner is not carried. Is detected, and the light emission intensity and a predetermined current or voltage value are stored. Then, the stored light emission intensity is used as a reference value, and the control unit, which is the light emission intensity changing means, changes the light emission intensity by changing the setting of the current or voltage applied to the pre-transfer charge eliminating unit 13, and the reference value Can be close to.

  Further, as in the second embodiment, it is possible to provide a plurality of light receiving portions 16 in the width direction and measure the toner density S / N of the toner patches arranged in the width direction. Since the pre-transfer charge eliminating unit 13 irradiates the entire width of the photosensitive belt 9 with light, similarly to the charge eliminating unit 12, a plurality of toner densities S / N can be measured by one light irradiation.

  As described above, the image forming apparatus 300 can measure the toner concentration by using the pre-transfer charge eliminating unit 13 without newly providing a light emitting unit, so that the size of the apparatus can be reduced. Further, the image forming apparatus 300 can change the image forming item by the same process as the image forming apparatus 100 using the measured toner density S / N.

  In addition, after adjusting the image forming item, and adjusting the image forming item, the toner density S / N is measured using any one of the image forming apparatuses 100, 200, and 300, and the image forming item is adjusted. Each of the image forming methods for forming an image is another embodiment of the present invention.

1 is a schematic diagram schematically showing a cross section of an image forming apparatus 100 of the present invention. 3 is a diagram showing that three toner patches T1, T2, and T3 are formed on the photosensitive belt 9. FIG. FIG. 6 is a diagram illustrating a state in which light emitted from the charge removal unit 12 passes through the toner patch T1 and the photosensitive belt 9 and is detected by the light receiving unit 16. 6 is a graph showing a relationship between toner density S / N and image density in each toner patch. It is a figure for demonstrating a development bias adjustment process and light emission intensity adjustment process. FIG. 4 is a diagram for explaining an image forming apparatus of the present invention that can measure toner density S / N at a plurality of positions. 1 is a schematic diagram schematically showing a cross section of an image forming apparatus 200 of the present invention. FIG. 2 is a schematic diagram schematically showing a cross section of an image forming apparatus 300 of the present invention. 6 is a diagram for explaining a toner density measuring method in the image forming apparatuses described in Patent Documents 1 and 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor belt unit 2 Developing part 3 Transfer part 4 Fixing part 5 Paper feed part 6 Carriage path 7 Paper discharge part 9 Photoconductor belt 10 Charging part 11 Exposure part 12 Electric discharge part 13 Pre-transfer charge removal part 16 Light receiving part 100,200, 300 Image forming apparatus

Claims (13)

A transparent image carrier,
Charging means for charging the surface of the image carrier;
Exposure means for irradiating light to the charged image carrier to form an electrostatic latent image;
Developing means for supplying toner to the image carrier on which an electrostatic latent image is formed;
Transfer means for transferring the toner image formed on the image carrier to a recording medium;
Fixing means for fixing the toner image on the recording medium to the recording medium;
A light receiving means provided at a position facing the exposure means across the image carrier;
And a toner density measuring unit that measures the toner density of the toner image on the image carrier using the intensity of light emitted from the exposure unit, which is detected by the light receiving unit. Forming equipment.   Light emission that is detected by the light receiving means and that changes the intensity of light emitted by the exposure means based on the intensity of light emitted from the exposure means and transmitted through a region of the image carrier that does not carry toner. The image forming apparatus according to claim 1, further comprising an intensity changing unit. A transparent image carrier,
Charging means for charging the surface of the image carrier;
Exposure means for irradiating light to the charged image carrier to form an electrostatic latent image;
Developing means for supplying toner to the image carrier on which an electrostatic latent image is formed;
Neutralizing means for performing neutralization by irradiating the image carrier with light;
Transfer means for transferring the toner image formed on the image carrier to a recording medium;
Fixing means for fixing the toner image on the recording medium to the recording medium;
A light receiving means provided at a position facing the exposure means across the image carrier;
And a toner density measuring unit that measures the toner density of the toner image on the image carrier using the intensity of light emitted from the charge eliminating unit, which is detected by the light receiving unit. Forming equipment.   Light emission that is detected by the light receiving means and that changes the intensity of light emitted from the charge eliminating means based on the intensity of light emitted from the charge eliminating means and transmitted through a region of the image carrier where toner is not carried. The image forming apparatus according to claim 3, further comprising an intensity changing unit.   The image forming apparatus according to claim 1, further comprising an item changing unit that changes an image forming item according to a measurement result of a toner density of a toner image on the image carrier.   The image forming apparatus according to claim 5, wherein the item changing unit changes an image forming item so that a toner density of a specific toner patch on the image carrier approaches a specific value. The developing means is a developing means for applying a developing bias when supplying toner to the image carrier;
The image forming apparatus according to claim 5, wherein the image forming item is a value of a developing bias.   The image forming apparatus according to claim 5, wherein the image forming item is an intensity of light irradiated by the exposure unit. The image carrier is provided movably,
2. The plurality of light receiving means are provided along a direction parallel to an image carrying surface of the image carrier and perpendicular to a moving direction of the image carrier. The image forming apparatus according to any one of 8 to 8. A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
Intensity of light irradiated from the exposure unit and transmitted through the transparent image carrier detected by a light receiving unit provided at a position facing the exposure unit across the image carrier with the toner density of the toner image on the image carrier A toner concentration measuring step to measure using
An image forming item adjusting method comprising: an item changing step for changing an image forming item so that a measurement result obtained by the toner density measuring step approaches a predetermined reference value. Changing the image forming item by the adjustment method according to claim 10;
A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
A transfer step of transferring a toner image formed on the image carrier to a recording medium;
And a fixing step of fixing the toner image transferred onto the recording medium to the recording medium. A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
Intensity of light irradiated from the charge eliminating unit and transmitted through the transparent image carrier detected by a light receiving unit provided at a position opposite to the charge eliminating unit with the image carrier interposed therebetween, the toner density of the toner image on the image bearing member A toner concentration measuring step to measure using
An image forming item adjusting method comprising: an item changing step for changing an image forming item so that a measurement result obtained by the toner density measuring step approaches a predetermined reference value. Changing the image forming item by the adjustment method according to claim 12;
A charging step for charging the surface of the image carrier;
An exposure step of forming an electrostatic latent image by irradiating light on the charged image carrier;
A developing step of supplying toner to the image carrier on which the electrostatic latent image is formed, and forming a toner image;
A charge removal step of removing light by irradiating the image carrier with light;
A transfer step of transferring a toner image formed on the image carrier to a recording medium;
And a fixing step of fixing the toner image transferred onto the recording medium to the recording medium.

Images