JP2012247627A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a toner pattern detection means for density adjustment to always properly determine the state of use of an intermediate transfer body without any influence of a recording medium or an image area ratio.SOLUTION: On a surface of an intermediate transfer belt 10, in an area of a width of Woutside an area which can be brought into contact with a maximum-width sheet P, or in an area of a width of Wwhich is not brought into contact with a secondary transfer roller 18, a toner pattern 100 for density adjustment is formed. A photosensor 7 is arranged opposite the area, as toner pattern detection means for optically detecting the toner pattern 100. The toner density is adjusted on the basis of a result obtained by the photosensor 7 optically detecting the toner pattern 100. The photosensor 7 optically detects the surface state of the area of the width of Wor Won the intermediate transfer belt 10 to determine the state of use of the intermediate transfer belt 10, on the basis of the detection result.

Description

  The present invention relates to an electrophotographic copying machine, a printer, a printing apparatus, a facsimile machine, and an image forming apparatus such as a multi-function machine having a plurality of these functions, and more particularly to an intermediate transfer member such as an intermediate transfer belt and an intermediate transfer drum. The present invention relates to an intermediate transfer type image forming apparatus that uses it to form color images.

  Such a conventional intermediate transfer type image forming apparatus sequentially superimposes toner images of different colors (for example, yellow, cyan, magenta, and black) formed on the photosensitive member on the surface of the intermediate transfer member. The toner image primarily transferred onto the intermediate transfer member is secondarily transferred onto a recording medium such as paper (transfer paper) to form a color image.

For example, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed, an intermediate transfer belt on which the toner image on the photosensitive drum is transferred intermediately, and the photosensitive drum with respect to the intermediate transfer belt 2. Description of the Related Art A color image forming apparatus is known that includes a primary transfer device that transfers an upper toner image and a secondary transfer device that collectively transfers a toner image transferred onto an intermediate transfer belt onto a sheet. .
The intermediate transfer belt has a multilayer structure, and the base layer is made of, for example, a fluororesin, PVDF sheet, or polyimide resin with little elongation, and the surface is covered with a smooth coat layer such as a fluororesin. ing.

  An image forming apparatus using such an intermediate transfer belt is generally called a tandem type, and a photosensitive drum for sequentially forming toner images of respective colors at predetermined intervals along the moving direction of the surface of the intermediate transfer belt. An image forming unit including a toner image formed on the photosensitive drum, and sequentially transferring the toner image formed on the surface of the intermediate transfer belt to the primary transfer, and then transferring the full-color toner image to paper or the like. A secondary image is collectively transferred onto the recording medium to form a color image.

  Some image forming apparatuses use an intermediate transfer drum as an intermediate transfer member. In that case, generally, only one photoconductor is provided, and an electrostatic latent image for each color that is sequentially formed on the surface is developed by the developing unit by sequentially switching the developing portion with each color toner, and developing for each color. The toner images thus formed are sequentially superimposed on the surface of the intermediate transfer drum for primary transfer, and then the full-color toner images are collectively transferred to a recording medium such as paper to form a color image.

  In such an intermediate transfer type image forming apparatus, in order to ensure image stability, it is necessary to adjust the toner image density when the power is turned on or every time a predetermined number of sheets are printed. For this purpose, a toner pattern for density adjustment is formed on the intermediate transfer member, and the toner density is detected by reading the reflected light with a photo sensor, and the charging bias and developing bias in the image forming unit are set according to the detection result. A method of correcting and adjusting the toner density is widely used.

  Such toner density adjustment is generally performed during non-image formation where there is no image output. However, in order to detect density fluctuations during continuous paper feeding, density adjustment is performed during the period between papers during image formation. A method of adjusting the toner density by creating a toner pattern is also known.

Further, since the intermediate transfer member deteriorates due to filming or scratches on the surface with use, its life is about a fraction of the life of the image forming apparatus main body. Therefore, it is necessary to replace the intermediate transfer member several times before the image forming apparatus main body reaches the end of its life.
Therefore, it is possible to automatically determine the deterioration state of the intermediate transfer member and the replacement of the new one so that the user can be notified of the replacement timing of the intermediate transfer member and can perform a necessary reset or initial setting when it is replaced with a new one. It is desirable to make it.

  Therefore, using the fact that the gloss level of the surface of the intermediate transfer belt changes due to aging filming, scratches, etc., whether or not the toner density detection means has been detected for use of the intermediate transfer member or has been replaced with a new one. Technology to be used for the determination of this has been developed. For example, Patent Literature 1, Patent Literature 2, Patent Literature 3, and the like disclose such techniques.

  By adopting such a technique, it is not necessary to mount a fuse for distinguishing between old and new, a memory storing life information, and the like on the intermediate transfer member. Further, it is possible to deal with the case where the intermediate transfer belt alone is difficult to detect.

  However, a conventional image forming apparatus employing such a technique has a region that can contact a recording medium (paper or the like) on the surface of an intermediate transfer member such as an intermediate transfer belt or an intermediate transfer drum, that is, within a maximum sheet passing width. A toner pattern for density adjustment was formed in the image forming area for printing, and this was detected by a toner pattern (toner density) detection means such as a photosensor, and the toner density was adjusted according to the detection result. . Then, the glossiness of the surface of the intermediate transfer member in the area where the toner pattern is formed is detected by the same toner pattern detection means to determine whether the intermediate transfer member is used or not.

  However, there are various factors that affect the detection result of the toner pattern detection means, and individual factors cannot be separated. For example, a filming phenomenon occurs in which residual toner adheres to the surface of the intermediate transfer member in the form of a film and cannot be easily removed. There are various factors such as the type of toner and the image area ratio, the amount and type of paper powder by the recording medium, and the bleeding from bleeding from the secondary transfer roller. Since each of these factors increases or decreases the glossiness of the surface of the intermediate transfer member, the change in glossiness varies depending on the use conditions, and the use state (number of sheets used) of the intermediate transfer member is constant. It was impossible to accurately determine the glossiness threshold.

  The present invention has been made to solve the above problems. Even if the toner pattern detecting means for adjusting the density is used, the influence of the amount and type of paper dust by the recording medium, the influence of the image area ratio, etc. An object of the invention is to make it possible to accurately determine the use state of the intermediate transfer member by a constant threshold (determination reference value) at all times.

An image forming apparatus according to the present invention includes a photosensitive member and an intermediate transfer member, and sequentially superimposes toner images of different colors formed on the photosensitive member on the surface of the intermediate transfer member. The image forming apparatus forms a color image by secondarily transferring a toner image primarily transferred onto an intermediate transfer member onto a recording medium by a secondary transfer unit.
In order to achieve the above object, a toner pattern forming means for forming a toner pattern for density adjustment in an area outside the area in contact with the recording medium on the surface of the intermediate transfer body; A toner pattern detecting unit that is provided opposite to the outer region on the surface and optically detects the toner pattern, and a toner that adjusts the toner density based on a result of optical detection of the toner pattern by the toner pattern detecting unit An intermediate for optically detecting the surface state of the outer region of the surface of the intermediate transfer member by the density adjusting unit and the toner pattern detecting unit, and determining the use state of the intermediate transfer member based on the detection result And a transfer body usage state determining means.

The image forming apparatus according to the present invention also forms a toner pattern for density adjustment in a region outside the region that can contact the recording medium on the surface of the intermediate transfer member, and also serves as a toner pattern detection unit that optically detects the toner pattern. Thus, the surface state of the outer region on the surface of the intermediate transfer member is optically detected, and the use state of the intermediate transfer member is determined based on the detection result.
For this reason, the influence of the amount and type of paper dust due to the recording medium can be eliminated, and the influence of the image area ratio can be eliminated because the density adjustment toner pattern is a constant pattern. Therefore, the use state of the intermediate transfer member can always be accurately determined based on a certain threshold value.

1 is a schematic diagram illustrating an overall configuration of an embodiment of an image forming apparatus according to the present invention. It is the enlarged view of the principal part similarly. FIG. 5 is a perspective view of a main part showing a toner pattern forming position on the intermediate transfer belt and a photo sensor for detecting the toner pattern. It is the typical top view similarly. FIG. 6 is a diagram showing the relationship between the number of recording medium passing sheets and the surface glossiness of an intermediate transfer belt in an example of the present invention and a conventional example. It is a diagram which shows the relationship between the light emission control current for obtaining the fixed detection signal from the number of sheets of the recording medium in Example of this invention and a prior art, and a photo sensor.

It is a block diagram which shows the function structure concerning this invention in the control part shown in FIG. FIG. 8 is a flowchart of an intermediate transfer belt use state determination process by a control unit shown in FIG. 7. FIG. 7 is a flowchart of the intermediate transfer member discrimination process. FIG. 2 is a schematic plan view showing a state in which an intermediate transfer belt unit for explaining an example of a desorption detection unit in the embodiment of the present invention is completely attached to the image forming apparatus main body. FIG. 6 is a schematic plan view showing a state where the intermediate transfer belt unit is being pulled out from the image forming apparatus main body. FIG. 6 is a diagram illustrating a change in light emission control current of a photosensor when an intermediate transfer belt unit is attached / detached.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of an image forming apparatus according to the present invention, which is a tandem type intermediate transfer type color image forming apparatus (color printer). FIG. 2 is an enlarged view of the main part.

  In an image forming apparatus main body (hereinafter referred to as “apparatus main body”) 1 shown in FIG. 1, an endless belt-like intermediate transfer belt 10 as an intermediate transfer member is provided in a substantially horizontal direction at the center. The intermediate transfer belt 10 has a multilayer structure, and the base layer is made of, for example, a fluororesin, a PVDF sheet, or a polyimide resin with little elongation, and the surface thereof is covered with a smooth coat layer such as a fluororesin. ing. The intermediate transfer belt 10 may be composed of a single layer polyimide resin.

  Then, the intermediate transfer belt 10 is wound around the support rollers 11, 12, 13 and the tension roller 14, and is rotated counterclockwise as indicated by an arrow A in the drawing. The support roller 11 is a drive roller that rotates by being driven by a motor (not shown) to rotate the intermediate transfer belt 10. The support rollers 12 and 13 and the tension roller 14 are driven rollers. The support roller 13 is urged by a spring 15 and applies a certain tension to the intermediate transfer belt 10 together with the tension roller 14. The support roller 11 also serves as a secondary transfer counter roller facing a secondary transfer roller 18 described later.

Further, an intermediate transfer belt cleaning device 17 for removing residual toner on the intermediate transfer belt 10 after image transfer is provided below the position close to the support roller 13.
Further, four image forming portions 2K, 2Y, and 2M of black, yellow, magenta, and cyan along the moving direction of the lower surface of the portion stretched between the tension roller 14 and the support roller 12 of the intermediate transfer belt 10. , 2C are arranged to constitute a tandem intermediate transfer type color image forming unit.

Each of the image forming units 2K, 2Y, 2M, and 2C includes a photosensitive drum 21 as a photosensitive member that is an image carrier, and a charger 22 along a rotation direction indicated by an arrow of the photosensitive drum 21 around the photosensitive drum 21. The developing unit 23, the cleaning blade 24, and the charge eliminating lamp 25 are sequentially arranged.
In FIG. 1, reference numerals 22 to 25 are given only to the respective parts around the photosensitive drum 21 of the image forming unit 2 </ b> C, but as shown in FIG. 2, other image forming units 2 </ b> K, 2 </ b> Y, and 2 </ b> M are provided. The same is provided around the photosensitive drum 21. However, the reference numerals of the cleaning blade 24 and the charge removal lamp 25 are also found in the image forming section 2C for convenience of illustration in FIG.

The developing units 23 of the image forming units 2K, 2Y, 2M, and 2C develop with toners of black, yellow, magenta, and cyan, respectively.
A process cartridge that can be attached to and detached from the apparatus main body 1 by forming all of these members, or at least the photosensitive drum 21 and the developing unit 23 integrally, for each of the image forming units 2K, 2Y, 2M, and 2C. You may comprise as.

Under the image forming units 2K, 2Y, 2M, and 2C, an exposure device 3 including a laser light source, a polygon mirror, a large number of mirrors, an fθ lens, and the like is provided. The laser beam exposes the position between the charger 22 and the developing unit 23 on the surface of each photosensitive drum 21 of the image forming units 2K, 2Y, 2M, and 2C.
Primary transfer rollers 26 are provided at positions facing the respective photosensitive drums 21 with the intermediate transfer belt 10 therebetween. In FIG. 1, only the primary transfer roller 26 of the image forming unit 2 </ b> C is provided with a reference numeral, but in FIG. 2, the primary transfer roller 26 of all image forming units is provided with a reference numeral.

Further, a secondary transfer roller 18 urged by a spring 19 is provided as a secondary transfer means on the outside across the intermediate transfer belt 10 so as to face the support roller 11 that also serves as a secondary transfer counter roller.
On the other hand, the paper cassettes 41 and 42 of the paper feed unit 4 are arranged in two stages at a position below the exposure apparatus 3, and the paper P having different sizes or orientations as recording media is respectively provided in the paper cassettes 41 and 42. Loaded and stored.

  Paper feed rollers 43 and 44 are provided at upper ends of the respective paper cassettes 41 and 42, respectively. Further, a paper feed path 45 that guides the paper fed by the paper feed rollers 43 and 44 toward the secondary transfer portion, and a registration roller pair 46 for taking a paper feed timing in the middle thereof are also provided.

Above the secondary transfer roller 18, the fixing device 5 and the subsequent discharge path 53 and discharge roller 54 are provided, and a discharge tray 40 is formed on the upper surface of the case of the apparatus main body 1. A bottle container 6 is disposed in the upper part of the apparatus main body 1. The bottle container 6 accommodates four toner bottles filled with toner of each color for replenishing toner of each color of the developing units 23 of the image forming units 2K, 2Y, 2M, and 2C.
Further, a pair of photosensors 7 are disposed as toner pattern detection means so as to oppose the vicinity of both ends in the width direction (direction perpendicular to the paper surface) of the upper surface slightly downstream from the support roller 12 of the intermediate transfer belt 10. Yes.

  The apparatus body 1 further includes a control unit (controller) 8 as shown in FIG. 2, and a display unit 9 using a liquid crystal display or the like is provided at a position where it can be easily seen from the outside. The control unit 8 controls each unit described above to execute the image forming process described below, and also functions as an intermediate transfer member use state determination unit and an intermediate transfer member determination unit according to the present invention. The display unit 9 displays the status of the image forming apparatus and the like, and also displays an exchange request for an intermediate transfer member described later.

  In this image forming apparatus, when an image formation is instructed, the support roller 11 is rotationally driven by a drive motor (not shown), and the other three support rollers 11, 12, 13 and the tension roller 14 are driven and rotated. The intermediate transfer belt 10 rotates in the arrow A direction.

Then, in each of the image forming units 2K, 2Y, 2M, and 2C, the respective photosensitive drums 21 are rotated in the directions of the arrows, and the surface of the photosensitive drum 21 is uniformly charged by the charger 22, and then the exposure apparatus 3 is used. Exposure is performed while scanning in the main scanning direction (axial direction of the photosensitive drum 21) with the laser beam from the laser beam, and an electrostatic latent image corresponding to the image data of each color is formed.
Each electrostatic latent image is developed with each color toner by each developing unit 23 to form black, yellow, magenta, and cyan single color toner images on the surface of each photoconductive drum 21.

In this manner, the toner images of the respective colors sequentially formed on the surface of the photosensitive drum 21 by the respective image forming units 2K, 2Y, 2M, and 2C are sequentially applied to the respective primary transfer rollers 26 to apply intermediate voltages. The image is sequentially superimposed and transferred onto the surface (lower surface in the figure) of the transfer belt 10 to form a composite color image (toner image).
Thereafter, the residual toner on each photosensitive drum 21 is removed by the cleaning blade 24, and the residual charge is removed by light irradiation of the static elimination lamp 25 to prepare for the next image formation.
The residual toner on the intermediate transfer belt 10 is removed by the intermediate transfer belt cleaning device 17 to prepare for the next primary transfer.

  On the other hand, the paper feed unit 4 selects and rotates either the paper feed roller 43 or 44 in accordance with the selected paper size or paper feed direction, and feeds the paper P from one of the paper cassettes 41 and 42. The paper is separated one by one from the separation roller that has not been fed and fed to the paper feed path 45. Further, the sheet is further conveyed by a conveyance roller (not shown), and is abutted against the registration roller pair 46 and stopped.

  Thereafter, the registration roller pair 46 is rotated in synchronization with the composite color image on the intermediate transfer belt 10, and the sheet P is fed into the nip portion between the intermediate transfer belt 10 and the secondary transfer roller 18. Then, the composite color image on the intermediate transfer belt 10 is transferred onto the paper by the secondary transfer roller 18. The sheet after transfer of the composite color image is sent to the fixing device 5, where heat and pressure are applied by the fixing roller 51 and the pressure roller 52, and the composite color image is conveyed while being fixed. Then, the sheet is discharged onto the discharge tray 40 by the discharge roller 54 through the discharge path 53 and stacked there.

  As the secondary transfer means, a secondary transfer belt that rotates around a plurality of support rollers can be used instead of the secondary transfer roller 18.

Next, with reference to FIGS. 3 and 4, the density adjustment toner pattern forming position and the photo sensor serving as the toner pattern detecting means in this embodiment will be described.
FIG. 3 is a perspective view of a main part showing a toner pattern forming position on the intermediate transfer belt and an arrangement position of a photosensor for detecting the toner pattern in the embodiment shown in FIGS. 1 and 2. In FIG. 3, arrow A indicates the rotation direction of the intermediate transfer belt 10, and arrow B indicates the conveyance direction of the paper P. FIG. 4 is also a schematic plan view showing the photosensor 7 in a state parallel to the surface of the intermediate transfer belt 10 for convenience of illustration.

  In this image forming apparatus, as shown in FIGS. 3 and 4, a toner pattern 100 for density adjustment is formed on the surface of the intermediate transfer belt 10 in a region outside the region that can come into contact with the sheet P as a recording medium. A pair of photosensors 7 serving as toner pattern detection means are disposed facing the area. Each photosensor 7 includes a reflection type photo sensor provided with a light emitting element 71 such as a light emitting diode and a light receiving element 72 such as a phototransistor so that their optical axes intersect at a position corresponding to the surface of the intermediate transfer belt 10. It is a sensor.

The available space in contact with the sheet P on the surface of the intermediate transfer belt 10, as shown in FIG. 4, the sheet P _M of the maximum width W _M that can be used in the image forming apparatus, the intermediate transfer belt 10 secondarily transferred it is a region of width W _M of contact with the surface of the intermediate transfer belt 10 as it passes through the nip between the roller 18. The image pattern 90 shown hatched in Figure 3 is formed in the region of the width W _M.

(Both side ends 10a of the intermediate transfer belt 10, 10b side) The width _W outside the region of the _M is a region having a width _{W 1} of, respectively outside the region. Forming a toner pattern 100 for adjusting the concentration to within the region the width W _1.
More preferably, when the axial length of the roller portion 18a which contacts the surface of the intermediate transfer belt 10 of the secondary transfer roller 18 is W _18, both sides of the intermediate transfer belt 10 that is not in contact with the secondary transfer roller 18 end 10a, and 10b side width _{W 2} in the region of, it is preferable to form an toner pattern 100 for adjusting the concentration.

The pair of photosensors 7 irradiates the toner pattern 100 for density adjustment formed on the outer region of the surface of the intermediate transfer belt 10 with light from the light emitting element 71 and receives the reflected light with the light receiving element 72. . Then, a signal corresponding to the amount of received light, that is, the density of the toner pattern 100 is output. When the surface state of the intermediate transfer belt 10 is detected, a signal corresponding to the reflectance (corresponding to the surface glossiness described later) in the area of the width W ₁ or W ₂ of the surface of the intermediate transfer belt 10 is generated. Output.

Here, the effects of the above-described embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a diagram showing the relationship between the number of sheets of the recording medium passed and the surface glossiness of the intermediate transfer belt (hereinafter referred to as “belt surface glossiness”) in the embodiment of the present invention and the conventional example. “Belt surface glossiness (20 degrees)” is a belt surface glossiness measured in a state where the incident angle and reflection angle of light with respect to the belt surface are 20 degrees.
Then, assuming the initial glossiness as 100, the belt glossiness transition is shown for every 50K (50,000 sheets). □ is the initial value of the belt surface glossiness in the conventional example and each value when the number of sheets to be passed increases by 50K, and x is the same value of the belt surface glossiness in the embodiment of the present invention.

  Usually, since the belt surface is filmed as the paper passes, the glossiness of the belt surface tends to decrease. However, in the case of the conventional example in which the glossiness is detected in the area in contact with the sheet on the surface of the intermediate transfer belt, the image area ratio (the amount of toner used per unit number) varies depending on the content of the image. Due to the influence, the belt surface glossiness does not necessarily decrease linearly with respect to the number of sheets passed.

  For example, in FIG. 5, in the conventional example, the belt surface glossiness is drastically reduced until point a is reached. This is presumably because many images with a high image area ratio were output, and the surface of the intermediate transfer belt was rapidly filmed with toner. At point b, the belt surface glossiness has once increased. This is because paper having a low image area was passed, and the belt was filmed with precipitates from the secondary transfer roller rather than toner filming. Conceivable.

  Since the secondary transfer roller is usually made of rubber or the like, the inside is bleed by application of a bias voltage, and the glossiness is temporarily increased by adhering to the surface of the intermediate transfer belt. In addition, the belt surface glossiness changes as shown by a line J in FIG. 5 because it is also affected by the amount of paper dust due to the type of paper, and it is difficult to determine the number of sheets to be passed based on this. It was.

On the other hand, in the embodiment of the present invention, as described above, the toner pattern 100 for density adjustment is formed on the surface of the intermediate transfer belt 10 outside the region that can be in contact with the paper P, and faces the region. The surface of the intermediate transfer belt 10 is detected by using the photosensor 7 for detecting the toner pattern disposed in the same manner.
Its outer region of the surface of the intermediate transfer belt 10 (area indicated by a width W ₁ in FIG. 4), only the toner pattern for toner density detection is formed, the amount of toner used since the pattern shape is the same each time Is also constant. Since the surface is filmed only by the toner, the gloss reduction ratio does not change depending on the change in the image area ratio, the type of paper, and the like.

Furthermore, in the area shown in FIG. 4 that do not contact both the secondary transfer roller 18 in the width W _2, it suffices to detect the surface of the intermediate transfer belt 10, also eliminates bleeding effects of the secondary transfer roller 18, The belt surface glossiness can be prevented from fluctuating up and down due to filming with toner and filming with the secondary transfer roller.

Further, the toner density adjustment is generally executed for every fixed number of sheets. Therefore, a predetermined toner pattern is formed for every predetermined number of sheets, that is, for every predetermined number of image formations, so that a predetermined amount of toner adheres to the outer region of the surface of the intermediate transfer belt 10, thereby a predetermined ratio. With toner filming.
For this reason, in the embodiment of the present invention, the belt surface glossiness linearly decreases with respect to the number of sheets to be passed, as indicated by a line K connecting the values indicated by x in FIG. Therefore, it becomes easy to determine the number of sheets to be passed based on the change in the belt surface glossiness.

  FIG. 6 is a diagram corresponding to FIG. 5 showing the relationship between the number of sheets passed and the emission control current for obtaining a constant detection signal from the photosensor in the embodiment of the present invention and the conventional example. □ is each value of the light emission control current in the conventional example and every time the number of sheets to be passed is increased by 50K, and × is a similar value of the light emission control current in the embodiment of the present invention.

  In this case, the surface of the intermediate transfer belt is detected by a reflection photosensor composed of a light emitting element and a light receiving element, and a constant detection signal is always output from the light receiving element, that is, the amount of light received by the photosensor is always constant. Thus, the light emission control current that flows through the light emitting element is controlled to change the light emission amount of the light emitting element.

Therefore, when the glossiness of the surface of the intermediate transfer belt (belt surface glossiness) is lowered and the reflectance is lowered, the light emission control current value is increased in order to increase the light emission amount of the light emitting element.
Therefore, when the belt surface glossiness changes as shown in FIG. 5 with respect to the number of sheets passed, the light emission control current changes as shown in FIG.

As can be seen from FIG. 6, in the case of the conventional example in which the glossiness is detected in a region in contact with the sheet on the surface of the intermediate transfer belt, the change in the light emission control current with respect to the number of sheets passing is a line connecting the points □. As shown by J, it fluctuated irregularly, and it was difficult to determine the number of sheets to be passed depending on the change in the light emission control current.
On the other hand, in the embodiment of the present invention, the emission control current increases linearly as shown by a line K connecting the dots in FIG. Therefore, it is easy to determine the number of sheets to be passed based on the change in the light emission control current.

  Therefore, it is possible to determine the state of the intermediate transfer belt by this light emission control current and control the transfer bias, the development bias, and the like. Further, for example, when the light emission control current reaches 20 mA, the intermediate transfer belt is found to be in a state where 250K sheets (250,000 sheets) have been passed, and at this point, it is determined that the intermediate transfer belt is in the replacement period. It is also possible.

  In addition, if a desorption detection unit for detecting the desorption of the intermediate transfer belt 10 from the apparatus main body 1 is provided, the desorption detection unit detects the desorption of the intermediate transfer belt 10 and then attaches the intermediate transfer belt 10 to the mounted intermediate transfer belt 10. The surface state of the outer region on the surface can be optically detected by the photosensor 7, and it can be determined whether or not it is a new product based on the value of the light emission control current that is the detection result.

Next, the functional configuration and operation related to the present invention in the control unit (controller) 8 shown in FIG. 2 in the image forming apparatus of the above-described embodiment will be described with reference to FIGS.
FIG. 7 is a block diagram showing a functional configuration according to the present invention in the control unit shown in FIG.

The control unit 8 includes a light emission control unit 81, a light reception output value detection unit 82, a density adjustment toner pattern formation control unit 83, a toner density adjustment unit 84, an intermediate transfer member use state determination unit 85, a desorption detection unit 86, and Intermediate transfer member discrimination means 87 is provided. In addition, a function for executing a normal image forming process and the like is naturally provided, but the description thereof is omitted here.
The control unit 8 is mainly configured by a microcomputer including a CPU, a ROM, a RAM, a nonvolatile memory, and the like.

The light emission control unit 81 causes a light emission control current to flow through the light emitting element 71 of the photosensor 7 serving as a toner pattern detection unit to emit light, and the light reception output value detection unit 82 receives light according to the amount of light received by the light receiving element 72 of the photosensor 7. Detect the output signal.
The density adjustment toner pattern formation control unit 83 performs image forming units 2K, 2Y, 2M, and 2C shown in FIG. By operating the intermediate transfer belt 10 and the like, the toner pattern 100 for density adjustment shown in FIGS. 3 and 4 is formed in a region outside the region of the intermediate transfer belt 10 that can contact the paper. Therefore, these constitute a toner pattern forming means.

  When the density adjustment toner pattern formation control unit 83 forms a toner pattern for each color in the region of the intermediate transfer belt 10, the light emission control unit 81 is operated, and a predetermined light emission control current is supplied to the light emitting element 71 of the photosensor 7. The received light output value corresponding to the amount of light received by the light receiving element 72 when each toner pattern is detected is detected by the received light output value detector 82.

  When the toner adhesion amount of the toner pattern increases, the light reception amount of the light receiving element 72 decreases and the light reception output value decreases. When the toner adhesion amount of the toner pattern decreases, the light reception amount of the light receiving element 72 increases and the light reception output value increases. Therefore, each of the image forming units 2K, 2Y, and 2M is set so that the toner concentration adjusting unit 84 can obtain an appropriate toner concentration according to the detection result (toner pattern optical detection result) by the received light output value detecting unit 82. , 2C development bias or charging bias is controlled.

  In this embodiment, since a pair of photosensors 7 are provided as toner pattern detection means on both sides in the width direction of the intermediate transfer belt 10, the light reception output values by the light receiving elements 72 of the two photosensors 7 are averaged. The result is an optical detection result of the toner pattern.

The intermediate transfer member use state determination unit 85 optically detects the surface state of the outer region of the surface of the intermediate transfer belt 10 that is an intermediate transfer member by the photo sensor 7 that is a toner pattern detection unit. Based on this, the use state of the intermediate transfer belt 10 is determined.
The use state determination process by the intermediate transfer member use state determination unit 85 will be described with reference to the flowchart of FIG. This process is actually executed by a microcomputer constituting the control unit 8.

This use state determination process is executed when the apparatus is turned on, or after a predetermined time interval, except when the toner density is adjusted.
When this process is started, first, the light emission control unit 81 is operated in step S1 to cause the light emitting element 71 of the photosensor 7 to emit light. The light emission control unit 81 stores the value of the previous light emission control current. At this time, the light emitting element 71 is caused to emit light with the light emission control current Is based on the previous stored value.

  Then, in step S2, the light reception output value of the light receiving element 72 of the photosensor 7 is detected by the light reception output value detection unit 82, and in step S3, whether or not the light reception output value of the light emission control unit 81 is equal to or greater than a predetermined value set in advance. Make them judge. If the result is not equal to or greater than the specified value, the light emission control current Is is increased by one step in step S4. That is, the light emission amount of the light emitting element 71 is increased.

  Thereafter, in step S2, the light reception output value of the light receiving element 72 of the photosensor 7 is detected by the light reception output value detection unit 82. In step S3, the light emission control unit 81 determines whether the light reception output value is equal to or greater than a predetermined value. Make a decision. The light emission control current Is is increased by one step at step S4 until the light reception output value exceeds the specified value. However, when the light reception output value exceeds the specified value, the process proceeds to step S5, and the light emission control current Is at that time is increased. Store the value in non-volatile memory. In this case, the previous stored value is overwritten.

  Then, in step S6, it is determined whether or not the value of the light emission control current Is is 20 mA or more (Is ≧ 20 mA). If it is not 20 mA or more, the process ends without doing anything. After determining that the transfer body (intermediate transfer belt in this embodiment) is in the use limit state and displaying the replacement request on the display unit 9 in step S7, the process is terminated.

  In this example, it is assumed that the value of the light emission control current Is becomes 20 mA when the number of sheets to be passed is 250K, and this state is set as the use limit state of the intermediate transfer belt. It is also possible to determine when the light emission control current Is is slightly smaller than this, for example, 18 mA or more, and to display a notice that the replacement timing of the intermediate transfer belt is near. These threshold values can be appropriately set according to the actual image forming apparatus.

In this embodiment, as described above, since a pair of photosensors 7 is provided, the light emitting elements 71 of the respective photosensors 7 are caused to emit light, and the light receiving output values of the respective light receiving elements 72 are equal to or higher than a specified value. The average value of the emission control current Is of each light emitting element 71 is stored, and it is determined whether the value is 20 mA or more.
In step S1 of the next use state determination process, the light emitting element 71 of each photosensor 7 is caused to emit light with the stored light emission control current Is.

  7 is a means for detecting the attachment / detachment of the intermediate transfer belt, which is an intermediate transfer member, that is, the attachment of the intermediate transfer belt after it is taken out from the apparatus main body. That is, it is possible to detect attachment / detachment of the intermediate transfer belt by a change in the light emission control current in the light emission control unit 81 as in an example described later.

  However, the intermediate transfer belt, the plurality of support rollers, and the supporting side plates that support them are unitized and turned on when the intermediate transfer belt unit is pulled out from the apparatus main body and when it is correctly attached to the apparatus main body. It is also possible to provide a switch or sensor that reverses the / OFF state, and to detect the attachment / detachment of the intermediate transfer belt by the change of the ON / OFF state.

  After the intermediate transfer belt is detected by the attachment / detachment detection unit 86, the intermediate transfer body determination unit 87 detects the surface of the intermediate transfer belt from the attached intermediate transfer belt by the photosensor 7 serving as the toner pattern detection unit. The surface state of the outer region is optically detected, and it is determined whether or not it is a new product based on the detection result.

  The intermediate transfer body discrimination process by the intermediate transfer body discrimination means 87 will be described with reference to the flowchart of FIG. This process is also actually executed by the microcomputer constituting the control unit 8. This intermediate transfer member determination process is executed when the attachment / detachment detection means 86 detects the attachment / detachment of the intermediate transfer belt (the intermediate transfer belt has been attached after being removed from the apparatus main body).

When this process is started, first, the light emission control unit 81 is operated in step S11 to cause the light emitting element 71 of the photosensor 7 to emit light. In this case, the light emission control unit 81 first causes the light emitting element 71 to emit light with the initial light emission control current (the smallest value, for example, 10 mA).
In step S12, the light reception output value of the light receiving element 72 of the photosensor 7 is detected by the light reception output value detection unit 82. In step S13, the light emission control unit 81 determines whether or not the light reception output value is equal to or greater than a predetermined value. Make them judge. If the result is not equal to or greater than the specified value, the light emission control current Is is increased by one step in step S14. That is, the light emission amount of the light emitting element 71 is increased.

  Thereafter, in step S12, the light reception output value of the light receiving element 72 of the photosensor 7 is detected by the light reception output value detection unit 82. In step S13, the light emission control unit 81 determines whether the light reception output value is equal to or greater than a predetermined value. Make a decision. The light emission control current Is is increased by one step at step S14 until the light reception output value exceeds the specified value. When the light reception output value exceeds the specified value, the process proceeds to step S15, and the light emission control current Is at that time is increased. Store the value in non-volatile memory.

Then, in step S16, it is determined whether or not the value of the light emission control current Is is 12 mA or less (Is ≦ 12 mA) as a threshold value. If 12 mA or less, the mounted intermediate transfer belt is new in step S17. And various setting values relating to the intermediate transfer belt are reset or initialized, or the counter for the number of sheets to be passed is reset.
If it is not less than 12 mA, it is determined in step S18 that a used product is mounted again or a used product is mounted, and the process is terminated without doing anything.

The threshold value to be compared with the value of the light emission control current Is in step S16 is preferably set to a slightly larger value when the initial light emission control current for the new intermediate transfer belt is 10 mA as described in FIG. . In this example, it is 12 mA, but this is not restrictive.
Further, in this embodiment, as described above, since a pair of photosensors 7 are provided, the light emitting elements 71 of the respective photosensors 7 are caused to emit light, and the light receiving output value of each of the light receiving elements becomes equal to or more than a predetermined value. The average value of the light emission control current Is of each of the light emitting elements 71 is stored, and it is determined whether or not the value is equal to or less than a threshold value (12 mA).

As described above, in this embodiment, the light emission control current for causing the light emitting element 71 to emit light is gradually increased so that the light reception output value of the light receiving element 72 of the photosensor 7 maintains a constant specified value. Thus, it is determined whether to replace the intermediate transfer belt or whether the attached intermediate transfer belt is new.
However, the light emitting element 71 of the photosensor 7 is always caused to emit light with a constant light emission control current, and due to a decrease in the light receiving output value of the light receiving element 72, the replacement timing of the intermediate transfer belt and whether or not the attached intermediate transfer belt is new. You can also make a judgment.

  As shown in FIG. 5, the surface glossiness of the intermediate transfer belt decreases with an increase in the number of sheets passed, so that the amount of light received by the light receiving element 72 decreases and the light reception output value decreases. Therefore, by comparing the light reception output value with a preset threshold value, it is possible to determine whether to replace the intermediate transfer belt or whether the attached intermediate transfer belt is new.

Next, as an example of the desorption detection means 86 in FIG. 7, an embodiment using the photosensor 7 which is a toner pattern detection means will be described with reference to FIGS.
10 shows a state in which the intermediate transfer belt unit of the embodiment is completely attached to the image forming apparatus main body provided with the photosensor, and FIG. 11 shows a state in which the intermediate transfer belt unit is being pulled out from the image forming apparatus main body. It is a typical top view which shows each. In these drawings, portions corresponding to those in FIGS. 1 to 4 are denoted by the same reference numerals.

  However, in FIG. 1 to FIG. 4, a pair of photosensors 7 are provided on both sides facing the upper portion of the intermediate transfer belt 10 near the support roller 11, but in FIG. 10 and FIG. For easy explanation, only one intermediate transfer belt 10 is provided facing the side of the support roller 13 on the side of the intermediate transfer belt 10. Further, portions not related to the desorption detection means are simplified by omitting illustration.

In this embodiment, the intermediate transfer belt 10, the supporting rollers 11 to 13 and the tension roller 14 that support and stretch the intermediate transfer belt 10, and a pair of side plates 111 that support both ends of the shafts of the rollers via bearings, 112 constitutes an intermediate transfer belt unit 110.
The intermediate transfer belt 10 and the intermediate transfer belt unit 110 can be attached to and detached from the apparatus main body 1.

  The photo sensor 7 is fixedly provided in the apparatus main body 1 at a position facing the side portion of the intermediate transfer belt 10 on the support roller 13 side. The photosensor 7 has a front surface 7a on which light from the detection portion, that is, the light emitting element 71 is emitted and reflected light from the surface of the intermediate transfer belt 10 enters the light receiving element 72, and the toner on the surface of the intermediate transfer belt 10. It is made to oppose the area | region which forms a pattern.

  A shielding plate 75 having a shielding portion 75a and a window hole 75b as shielding means is provided between the front surface 7a, which is the detection site of the photosensor 7, and the surface of the intermediate transfer belt 10, as a shielding means. (13 axial directions) is slidable. The compression coil spring 77 is fixed at both ends thereof to the bent portion 75c between the bent portion 75c bent at a right angle of the shielding plate 75 and extending to the side and the fixing piece 76 fixed to the apparatus main body 2. It is fixed to the piece 76. Therefore, the shielding plate 75 is always given a force that moves to the left in FIG. 10 by the restoring force of the compression coil spring 77.

However, in a state where the intermediate transfer belt unit 110 is completely mounted in the apparatus main body 1, the state is as shown in FIG. That is, the extended portion 111 a of the side plate 111 in the intermediate transfer belt unit 110 hits the bent portion 75 c of the shielding plate 75 and pushes it over the force of the compression coil spring 77.
Therefore, the shielding plate 75 moves leftward to the position shown in FIG. 10, and the window hole 75 b becomes a position corresponding to the front surface 7 a of the photosensor 7. Therefore, the photosensor 7 can detect the glossiness of the surface of the intermediate transfer belt 10 through the window hole 75b of the shielding plate 75.

  However, as shown in FIG. 11, when the intermediate transfer belt unit 110 is pulled out from the apparatus main body 1, the extending portion 111a of the side plate 111 is separated from the bent portion 75c of the shielding plate 75, so that the shielding plate 75 is a compression coil spring. It is moved to the left by 77 restoring force. Thereby, the shielding part 75a becomes a position where the front surface 7a of the photosensor 7 is shielded. Therefore, the light emitted from the light emitting element 71 of the photosensor 7 does not reach the surface of the intermediate transfer belt 10, and the light reflected by the shielding portion 75 a of the shielding plate 75 is hardly received by the light receiving element 72.

  Therefore, as described above, the light emission control unit 81 flows to the light emitting element 71 so that the light reception output value detecting unit 82 shown in FIG. 7 always detects a constant light reception output value from the light receiving element 72 of the photosensor 7. When the light emission control current is controlled, the value of the light emission control current changes as shown in FIG.

  That is, as shown in FIG. 10, in a state where the intermediate transfer belt unit 110 is mounted in the apparatus main body 1, if the intermediate transfer belt 10 is in the replacement period, the light emission control current becomes about 20 mA. Yes. When the intermediate transfer belt unit 110 is pulled out and detached from the apparatus main body 1 as shown in FIG. 11, the front surface 7 a that is a detection portion of the photosensor 7 is shielded by the shielding plate 75. Thereafter, this state continues until the intermediate transfer belt unit 110 is mounted. Therefore, during that period, the light emission control current is greatly increased, and a state of shielding by the shielding means is detected.

  When the intermediate transfer belt unit 110 is mounted again in the apparatus main body 1, the front surface 7 a that is a detection part of the photosensor 7 is opened by the window hole 75 b of the shielding plate 75, so that the light emission control current is about 10 to 20 mA. Become. The removal of the intermediate transfer belt 10 can be detected by the change in the light emission control current.

As a result of determining the use state of the attached intermediate transfer belt 10 after detecting the desorption, if the emission control current is about 10 mA as shown by the solid line in FIG. It can be determined that the intermediate transfer belt (intermediate transfer belt unit) is attached.
However, if the light emission control current is about 20 mA as shown by a broken line in FIG. 12 and exceeds a threshold (for example, 12 mA), it can be determined that the used intermediate transfer belt (intermediate transfer belt unit) is mounted again.

  In this case, if the value of the light emission control current after the intermediate transfer belt unit 110 is mounted is substantially the same as the value before being detached, it is determined that the same used intermediate transfer belt unit 110 is mounted again. If it is different from the value before separation, it can be determined that another used intermediate transfer belt unit 110 is attached.

  According to this embodiment, since the attachment / detachment of the intermediate transfer belt can be detected by using the photo sensor 7 which is a toner pattern detection means, it is not necessary to install a switch or a sensor dedicated to the detection of the attachment / detachment of the intermediate transfer belt. Cost is advantageous. However, in the case of this embodiment, the photosensor 7 and the control unit 8 must always be in an operating state. Therefore, in the apparatus in which the main power supply is turned off when a cover (not shown) of the apparatus main body 1 is opened when the intermediate transfer belt unit 110 is detached, the power supply of at least the control unit 8 shown in FIG. It is necessary to turn it on.

  In the above-described embodiments, the present invention is applied to a tandem type color image forming apparatus that uses an intermediate transfer belt as an intermediate transfer member. However, the present invention is directed to image formation using an intermediate transfer drum as an intermediate transfer member. The device (simplely described in the background section) is equally applicable.

  Also in this case, a toner pattern for density adjustment is formed in an area outside the area (in this case, the outside in the axial direction) that is in contact with a recording medium such as paper on the surface of the intermediate transfer drum. A toner pattern detection means such as a photosensor that optically detects the toner pattern is provided opposite to it. Then, the toner pattern detection means optically detects the surface state of the outer region on the surface of the intermediate transfer drum, and the use state of the intermediate transfer drum is determined based on the detection result.

  Also, a desorption detecting means for detecting the desorption of the intermediate transfer drum is provided, and after the desorption of the intermediate transfer drum is detected thereby, the surface of the intermediate transfer drum is detected by the toner pattern detection means with respect to the mounted intermediate transfer drum. It is also possible to optically detect the surface state of the outer region and determine whether or not it is new based on the detection result.

  The present invention is not limited to the above-described embodiments, and it goes without saying that it can be added, omitted, or changed as appropriate without departing from the scope defined in the claims.

1: Image forming apparatus main body 2K, 2Y, 2M, 2C: Image forming unit 3: Exposure device 4: Paper feeding unit 5: Fixing device 6: Bottle container
7: Photo sensor (toner pattern detection means)
7a: Front surface (detection part) of photo sensor 8: Control unit 9: Display unit 10: Intermediate transfer belt 11, 12, 13: Support roller 14: Tension roller 15: Spring 17: Intermediate transfer belt cleaning device 18: Secondary transfer Roller 19: Spring 21: Photosensitive drum 22: Charger 23: Developer 24: Cleaning blade 25: Static elimination lamp 40: Paper discharge tray 41, 42: Paper cassette 43, 44: Paper feed roller 45: Paper feed path 46: Registration roller pair 51: Fixing roller 52: Pressure roller

53: Discharge path 54: Discharge roller 71: Light emitting element 72: Light receiving element 75: Shielding plate 75a: Shielding part 75b: Window hole 75c: Bending part
76: Fixed piece 77: Compression coil spring 81: Light emission control unit
82: Light reception output value detection unit 83: Toner pattern formation control unit for density adjustment
84: Toner density adjusting unit 85: Intermediate transfer member use state determining means
86: Desorption detection means 87: Intermediate transfer member discrimination means 90: Image pattern
100: Toner pattern for density adjustment 110: Intermediate transfer belt unit 111, 112: Side plate 111a: Extension portion

JP 2002-351269 A JP-A-2005-181974 JP 11-84959 A

Claims (5)

A photosensitive member and an intermediate transfer member are provided, and toner images of different colors formed on the photosensitive member are sequentially superimposed on the surface of the intermediate transfer member to be primarily transferred, and then primary transferred onto the intermediate transfer member. An image forming apparatus for forming a color image by secondarily transferring the toner image onto a recording medium by a secondary transfer unit,
A toner pattern forming means for forming a toner pattern for density adjustment in a region outside the region that can contact the recording medium on the surface of the intermediate transfer member;
A toner pattern detecting means provided opposite to the outer region of the surface of the intermediate transfer member and optically detecting the toner pattern;
Toner density adjusting means for adjusting the toner density based on the optical detection result of the toner pattern by the toner pattern detecting means;
Intermediate transfer member use state determination unit that optically detects the surface state of the outer region of the surface of the intermediate transfer member by the toner pattern detection unit and determines the use state of the intermediate transfer member based on the detection result An image forming apparatus comprising: The toner pattern forming unit is a unit that forms the toner pattern for density adjustment in a region outside the region that can contact the recording medium on the surface of the intermediate transfer member and that does not contact the secondary transfer unit. Yes,
The image forming apparatus according to claim 1, wherein the toner pattern detection unit is provided opposite to a region outside the surface of the intermediate transfer member and not in contact with the secondary transfer unit. .   The image forming apparatus according to claim 1, wherein the toner pattern forming unit forms the toner pattern every predetermined number of times of image formation. The image forming apparatus according to any one of claims 1 to 3,
A desorption detecting means for detecting desorption of the intermediate transfer member;
After the removal of the intermediate transfer body is detected by the desorption detection means, the surface state of the outer region of the surface of the intermediate transfer body is optically detected by the toner pattern detection means with respect to the mounted intermediate transfer body. An image forming apparatus comprising: an intermediate transfer body discriminating unit that detects and discriminates whether or not the product is new based on the detection result.   The desorption detection means has a shielding means for shielding a detection portion of the toner pattern detection means in a state where the intermediate transfer member is detached, and the toner pattern detection means detects a shielding state by the shielding means, 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is means for detecting desorption of the intermediate transfer member.

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