JP2006235391A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent image failure even in case where there is a change in the quality of an intermediate transfer belt, a primary charging roller, or a developing sleeve, which is different from the qualities of the others. <P>SOLUTION: The surface quality of the entire area of the intermediate transfer belt is detected by a density sensor (optical sensor)(S1). A toner image is formed in the entire area of the intermediate transfer belt (S2), and the density of a toner image (surface quality) is detected (S3). In the case where there is no differences between the result of the detection of the surface quality of the belt and the result of the surface quality of the toner image (S4 and S5), regular image formation is permitted (S9). In the case where there is a difference in the result of the detection of at least the intermediate transfer belt or the toner image (S6, S7, and S8), image formation is carried out at a part where there is no changes in the quality of the intermediate transfer belt and at a part where there is no change in the quality of development, primary transfer, etc. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus having an intermediate transfer member, such as a printer, a copying machine, or a facsimile.

  Patent Document 1 describes a so-called tandem type color image forming apparatus in which a plurality of image forming units (image forming portions) each containing toner of different colors are arranged side by side along an intermediate transfer belt.

  In this image forming apparatus, when a recording material such as paper or transparent film is jammed, the user takes out the recording material from the apparatus. When the toner in the image forming unit runs out, the user replaces the image forming unit.

  When removing the jammed paper or replacing the image forming unit, the surface of the intermediate transfer belt may be damaged. When scratches are formed, there is a problem that when an image is formed in the photographic mode, the halftone portion or highlight portion is affected by scratches on the intermediate transfer belt and the image deteriorates.

  In order to solve such a problem, Patent Document 2 detects a property change portion such as a scratch which causes image deterioration on the intermediate transfer belt. For example, when the image mode is a photographic mode, the image on the intermediate transfer belt is detected. Are described in which image formation is performed while avoiding the property change portion.

  Specifically, during the start-up operation of the image forming apparatus, the intermediate transfer belt is idled by one turn, a predetermined voltage is applied to the secondary transfer roller, and the current value at that time is measured by the current measuring unit. To do. A part having a current value different from the other part is detected as a property change part.

  Further, as a method for detecting the property change portion, there is a method using a density sensor (optical sensor) used for automatic density control. The amount of reflected light on the surface of the intermediate transfer belt over one round is compared, and a portion where the amount of reflected light is markedly different is detected as a property change portion. When there are a plurality of property change portions or when the image size to be formed is large, a warning is issued in advance to notify the user, or image formation itself is not permitted.

JP-A-7-28294 JP 2002-6645 PR

  However, in the above-described conventional example, the property change portion can be detected only for the intermediate transfer belt (intermediate transfer member), and other means related to image formation, such as charging, exposure, development, It is impossible to detect a change in properties of a primary charger, an exposure device, a developing sleeve, a primary transfer roller, etc. used for primary transfer. Accordingly, it is impossible to prevent image deterioration caused by property changes other than those of the intermediate transfer member.

  According to the present invention, the position of a property change portion of an intermediate transfer member and a means related to image formation other than the intermediate transfer member is specified, and image formation is avoided by avoiding the property change portion, thereby preventing image deterioration. An object of the present invention is to provide an image forming apparatus.

  The present invention relates to a toner image forming unit that forms a toner image on an image carrier, a transfer unit that transfers a toner image on the image carrier to an intermediate transfer member, and the toner image on the intermediate transfer member is transferred. In an image forming apparatus having an intermediate transfer body detection means for detecting a surface and a toner image detection means for detecting the toner image transferred to the intermediate transfer body, based on the detection result of the intermediate transfer body detection means, Control for variably controlling the area where the toner image is transferred on the intermediate transfer body and variably controlling the area where the toner image is formed on the image carrier based on the detection result of the toner image detecting means. It has the means, It is characterized by the above-mentioned.

  According to the present invention, the intermediate transfer body detection unit can detect a property change portion of the surface of the intermediate transfer body onto which the toner image is transferred. The toner image detecting means can detect a property change portion of the toner image transferred to the intermediate transfer member. Further, the control means can variably control the area where the toner image is transferred on the intermediate transfer body based on the detection result of the intermediate transfer body detection means, and the image carrier based on the detection result of the toner image detection means. The region where the toner image is formed on the body can be variably controlled. As described above, the region where the toner image on the image carrier is formed and the region where the toner image on the intermediate transfer member is transferred can be variably controlled. For this reason, for example, when there is a property change portion on the intermediate transfer member, the toner image can be transferred onto the intermediate transfer member while avoiding this. Further, for example, by detecting the toner image on the intermediate transfer member, it is possible to detect the property change portion of the toner image caused by other than the intermediate transfer member. The formation area can be changed so that the toner image is favorably formed on the image carrier.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in the same drawing or a different drawing performs the same structure or the same effect | action, The duplication description is abbreviate | omitted suitably about these.

<Embodiment 1>
FIG. 1 shows an image forming apparatus to which the present invention can be applied. The image forming apparatus shown in the figure is a four-color full-color printer of an electrophotographic system and an intermediate transfer body system. This figure is a schematic view corresponding to a longitudinal sectional view of the printer (hereinafter referred to as “image forming apparatus”) as seen from the front side. Here, the front side of the image forming apparatus refers to a side located when a user or a serviceman operates the printer.

  With reference to the figure, the overall configuration and operation of the printer will be described.

  The printer shown in the figure includes four image forming units PY, PM, PC, and PK from the left side to the right side. These image forming portions PY, PM, PC, and PK are image forming portions for forming toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) in this order. The intermediate transfer belt 7 is arranged in a state of being aligned at equal intervals from the upstream side to the downstream side along the rotation direction (arrow R7 direction) of the intermediate transfer belt 7 described later.

  Each of the image forming units PY, PM, PC, and PK includes drum-shaped electrophotographic photosensitive members (hereinafter referred to as “photosensitive drums”) 1Y, 1M, 1C, and 1K as image carriers. The photosensitive drums 1Y, 1M, 1C, and 1K are rotationally driven in the direction of the arrow R1. Around the photosensitive drums 1Y, 1M, 1C, and 1K, the primary chargers 2Y, 2M, 2C, and 2K, the exposure devices 3Y, 3M, 3C, and 3K, and the developing devices 4Y, 4M, and the like are arranged in almost the order along the rotation direction. 4C, 4K, primary transfer rollers 5Y, 5M, 5C, 5K as transfer chargers, and cleaning devices 6Y, 6M, 6C, 6K are arranged. Here, a toner image is formed on the photosensitive drums 1Y, 1M, 1C, and 1K by the primary fixing devices 2Y, 2M, 2C, and 2K, the exposure devices 3Y, 3M, 3C, and 3K and the developing devices 4Y, 4M, 4C, and 4K. Forming means, that is, toner image forming means.

  Below the photosensitive drums 1Y, 1M, 1C, and 1K, an intermediate transfer belt 7 is disposed as an intermediate transfer member. A secondary transfer counter roller 8 is disposed inside the intermediate transfer belt 7, and a secondary transfer roller 9 is disposed at a position corresponding to the secondary transfer counter roller 8 outside the intermediate transfer belt 7. A secondary transfer bias application power source 11 is connected to the secondary transfer roller 9 via an ammeter 10 as a current measuring means (detection means). Further, brush rollers 12 and 13 as belt cleaners are disposed on the downstream side of the secondary transfer roller 9 along the rotation direction of the intermediate transfer belt 7 (arrow R7 direction). Further, a registration roller 14 is disposed on the upstream side of the secondary transfer roller 9 along the conveyance direction (arrow Kp direction) of the recording material P. In the vicinity of the registration roller 14, a paper feed sensor 21 that detects the recording material P is disposed on the recording material conveyance path 19. Here, the recording material P is a recording medium used for image formation (on which a toner image is formed), and includes, for example, paper such as plain paper and cardboard, a transparent film for an overhead projector, and the like. A home position sensor 22 that detects the reference position of the intermediate transfer belt 7 and a density sensor 23 that detects a toner image on the intermediate transfer belt 7 are disposed so as to correspond to the surface of the intermediate transfer belt 7.

  The above-described photosensitive drums 1Y, 1M, 1C, and 1K include a drum base formed in a cylindrical shape with a conductive metal such as aluminum, and an organic optical semiconductor provided as a photosensitive layer on the outer peripheral surface (surface) of the drum base. (OPC). The photosensitive drums 1Y, 1M, 1C, and 1K are rotationally driven at a predetermined process speed (circumferential speed) in the direction of arrow R1 by a driving unit (not shown).

  The primary chargers 2Y, 2M, 2C, and 2K are long along the axes of the photosensitive drums 1Y, 1M, 1C, and 1K, and are disposed so as to face the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. ing. It is arrange | positioned so that the surface may be opposed. A primary transfer bias is applied to the primary chargers 2Y, 2M, 2C, and 2K by a primary transfer bias application power source (not shown). As a result, the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K are uniformly charged to, for example, −600 [V]. As the primary chargers 2Y, 2M, 2C, and 2K, the corona charger shown in FIG. 1 or a primary transfer roller (not shown) disposed in contact with the surface of the photosensitive drums 1Y, 1M, 1C, and 1K can be used. .

  The exposure devices 3Y, 3M, 3C, 3K form electrostatic latent images on the surfaces of the photosensitive drums 1Y, 1M, 1C, 1K after charging. As the exposure apparatuses 3Y, 3M, 3C, and 3K, laser optical units can be used. The exposure devices 3Y, 3M, 3C, and 3K irradiate the charged photosensitive drums 1Y, 1M, 1C, and 1K surfaces with laser light based on image information of each color of Y, M, C, and K. As a result, the electric charge of the laser beam irradiated portion is removed, and electrostatic latent images corresponding to the respective colors are formed on the photosensitive drums 1Y, 1M, 1C, and 1K. Note that the surface potential of the laser beam irradiated portions on the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K is neutralized by about −580 to −150 [V].

  Developing units 4Y, 4M, 4C, and 4K develop the electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1K. The developing devices 4Y, 4M, 4C, and 4K contain a two-component developer having toners of Y, M, C, and K colors and a carrier as main components. Each developing device 4Y, 4M, 4C, 4K has a developing sleeve 4a, and a developing bias is applied to the developing sleeve 4a by a developing bias applying power source (not shown). Thus, the electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1K are each developed with the toners of the respective colors Y, M, C, and K attached thereto, and developed as toner images of the respective colors.

  The primary transfer rollers 5Y, 5M, 5C, and 5K transfer the toner images on the photosensitive drums 1Y, 1M, 1C, and 1K to the intermediate transfer belt 7. The intermediate transfer belt 7 is formed by an endless belt that is stretched around a driving roller, a driven roller, and a tension roller (all not shown). The intermediate transfer belt 7 is sandwiched between the photosensitive drums 1Y, 1M, 1C, and 1K and the primary transfer rollers 5Y, 5M, 5C, and 5K. Accordingly, a primary transfer nip portion (primary transfer portion) T1 is formed between the photosensitive drums 1Y, 1M, 1C, and 1K and the intermediate transfer belt 7. The intermediate transfer belt 7 rotates (moves) in the direction of arrow R7 as the drive roller rotates. A primary transfer bias is applied to the primary transfer rollers 5Y, 5M, 5C, and 5K by a primary transfer bias application power source (not shown). As a result, the toner images of the respective colors Y, M, C, and K on the respective photosensitive drums 1Y, 1M, 1C, and 1K are primarily and electrostatically sequentially transferred onto the intermediate transfer belt 7 at the primary transfer nip portion T1. The Here, by shifting the electrostatic latent image writing timing on the photosensitive drums 1Y, 1M, 1C, and 1K for each color, the Y, M, C, and K toner images are appropriately superimposed on the intermediate transfer belt 7. It has come to be. The primary transfer bias for primarily transferring the toner images on the photosensitive drums 1Y, 1M, 1C, and 1K onto the intermediate transfer belt 7 is about +150 to +200 [V]. Here, the optimal primary transfer bias varies depending on the volume resistance of the roller, the charged state of the toner, the ambient temperature / humidity, and the like. For example, the charge amount of the toner is in the range of −20 to −35 [μC / g]. In the case of a normal temperature and humidity environment, it is about +800 [V]. Of the intermediate transfer belt 7 described above, the portion where the primary transfer of the toner image is performed, that is, the primary transfer region M is held substantially flat. The image forming portions PY, PM, PC, and PK are arranged at equal intervals from the upstream side to the downstream side along the rotational direction of the intermediate transfer belt 7 in the primary transfer region. The primary transfer is actually performed in the primary transfer nip T1 in the primary transfer region M. Although the primary transfer rollers 5Y, 5M, 5C, and 5K are used in FIG. 1, a transfer blade or a corona transfer charger can be used instead.

  The cleaning devices 6Y, 6M, 6C, and 6K remove unnecessary toner on the intermediate transfer belt 7. The cleaning devices 6Y, 6M, 6C, and 6K have cleaning blades (not shown) that are in contact with the surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K. The cleaning devices 6Y, 6M, 6C, and 6K scrape off the toner (primary transfer residual toner) remaining on the surface of the photosensitive drums 1Y, 1M, 1C, and 1K without being primarily transferred to the intermediate transfer belt 7 during the primary transfer. Note that the photosensitive drums 1Y, 1M, 1C, and 1K from which the primary transfer residual toner on the surface has been wiped off are used for the next image formation starting from the primary charging.

  A secondary transfer counter roller 8 is disposed inside the lower portion of the intermediate transfer belt 7. A secondary transfer roller 9 is disposed outside the intermediate transfer belt 7 at a position corresponding to the secondary facing roller 8. That is, the intermediate transfer belt 7 is sandwiched between the secondary transfer counter roller 8 and the secondary transfer roller 9. As a result, a secondary transfer nip portion (secondary transfer portion) T2 serving as a secondary transfer region of the toner image is formed between the secondary transfer roller 9 and the intermediate transfer belt 7. A secondary transfer bias application power source 11 is connected to the secondary transfer roller 9 via an ammeter 10 as a current detection means. The four-color toner images on the intermediate transfer belt 7 are collectively transferred onto the recording material P by applying a secondary transfer bias to the secondary transfer roller 9 from the secondary transfer bias application power source 11. Is done. Note that the secondary transfer roller 9 also serves as a detection unit, as will be described later.

  Here, the recording material P stored in a paper feed cassette (not shown) is conveyed to the registration roller 14 along the recording material conveyance path 19 by a feeding / conveying device (not shown) and temporarily stopped. After that, the registration roller 14 supplies the toner image on the intermediate transfer belt 7 to the secondary transfer nip portion T2 so as to be synchronized with the toner image.

  During the secondary transfer of the toner image, the toner (secondary transfer residual toner) that is not transferred to the recording material P and remains on the intermediate transfer belt 7 is removed by the brush rollers 12 and 13 as belt cleaners. The brush rollers 12 and 13 are disposed in contact with the intermediate transfer belt 7 and rotate in the directions of arrows R12 and R13, respectively. Thereby, the secondary transfer residual toner on the intermediate transfer belt 7 is removed. The intermediate transfer belt 7 from which the secondary transfer residual toner has been removed is used for the transfer of the next toner image.

  On the other hand, the recording material P onto which the toner image has been secondarily transferred is conveyed to a fixing device (not shown). Here, the recording material P is heated and pressed to fix the toner image on the surface. Thus, the four-color full-color image formation on one recording material P is completed.

  In the above-described image forming apparatus, a paper feed sensor 21, a home position sensor 22, and a density sensor 23 are disposed. Among these, the paper feed sensor 21 is disposed on the recording material conveyance path in the vicinity of the registration roller 14. The paper feed sensor 21 is for detecting that the leading edge of the recording material P fed and conveyed by a feeding and conveying device (not shown) is nipped by the registration roller 14. When the leading edge of the recording material P is detected by the paper feed sensor 21, the registration roller 14 temporarily stops its rotation, and then the recording material P is secondary-synchronized with the toner image on the intermediate transfer belt 7. It is sent out toward the transfer nip T2. The home position sensor 22 is downstream of the most downstream black primary transfer nip T1 and upstream of the secondary transfer nip T2 along the rotation direction of the intermediate transfer belt 7 (in the direction of arrow R7). The intermediate transfer belt 7 is disposed so as to face the surface. The home position sensor 22 detects a home position in the rotation direction of the intermediate transfer belt 7 by detecting a reference marker (not shown) attached to the intermediate transfer belt 7. The density sensor 23 is located downstream of the most downstream black primary transfer nip T1 along the rotation direction of the intermediate transfer belt 7 (in the direction of arrow R7) and upstream of the home position sensor 22 described above. It is disposed so as to face the surface of the intermediate transfer belt 7. The density sensor 23 includes an optical sensor having a light emitting unit (not shown) and a light receiving unit (not shown). The density sensor 23 detects the density of a patch image that is a density detection toner image formed on the intermediate transfer belt 7. That is, light is emitted from the light emitting unit to the toner image formed on the surface of the intermediate transfer belt 7, and the reflected light is received by the light receiving unit. Thereby, the density of the patch image is detected. As described above, the density sensor 23 detects the density of the patch image formed on the intermediate transfer belt 7 through a predetermined process during image formation or before and after image formation. Based on the detection result, the control unit 25 appropriately controls the charging bias, the exposure intensity of the laser beam, the developing bias, the transfer bias, and the like so as to maintain density stability in image formation.

  In the present embodiment, the density sensor 23 described above serves as an intermediate transfer body surface property detection means (intermediate transfer body detection means) for specifying the position of the property change portion on the surface of the intermediate transfer belt 7 and also on the surface of the intermediate transfer belt 7. It functions as a toner image surface property detecting means (toner image detecting means) for specifying the position of the property change portion of the formed toner image. That is, the density sensor 23 serves as both the intermediate transfer member surface property detection unit and the toner image surface property detection unit.

  The density sensor 23 irradiates light from the light emitting portion to the surface of the intermediate transfer belt 7 in a state where no toner image is formed, and receives the reflected light at the light receiving portion. Thereby, the surface property of the intermediate transfer belt 7 itself (hereinafter referred to as “belt surface property”) can be detected. Further, the density sensor 23 is a width direction of the intermediate transfer belt 7 (a direction orthogonal to the rotation direction of the intermediate transfer belt 7. Hereinafter, referred to as a belt width direction. The belt width direction is the developing sleeve 4a and the primary transfer roller 5Y. , 5M, 5C, and 5K in the same direction). The density sensor 23 can move in the belt width direction of the intermediate transfer belt 7 as described above, and the intermediate transfer belt 7 rotates, so that belts at a plurality of positions are provided over almost the entire surface of the intermediate transfer belt 7. The surface property can be detected. Similarly, the density of any toner image formed on any surface of the intermediate transfer belt 7 can be detected. That is, the density sensor 23 according to the present embodiment can detect the belt surface property of the intermediate transfer belt 7 itself and the toner image surface property (density of the formed toner image) over almost the entire surface of the intermediate transfer belt 7. It is like that.

  The image forming apparatus described above performs control as shown in FIG. Signals are input to the control means 25 from the ammeter 10, the paper feed sensor 21, the home position sensor 22, and the like. Based on these input signals, the control means 25 adjusts the timing (sub-scanning direction) and position (main scanning and sub-scanning directions) for forming the electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1K. Therefore, the exposure devices 3Y, 3M, 3C, 3K are controlled. As a result, an intermediate transfer belt drive motor (not shown) is controlled to adjust the transfer position of the toner image on the intermediate transfer belt 7, and the registration roller 14 is adjusted to adjust the conveyance of the recording material P. Control the rotation. Along with these, the rotation of a drive motor (not shown) for driving the fixing device is controlled.

  First, detection is started at a predetermined timing, for example, immediately after turning on the power of the image forming apparatus or at the time of post-rotation after performing predetermined image formation. Detection of the belt surface property of the entire area of the intermediate transfer belt 7 is performed at a plurality of positions of the intermediate transfer belt 7 by the rotation of the intermediate transfer belt 7 and the movement of the density sensor 23 in the belt width direction by the density sensor 23 also serving as surface property detection means. Execute (S1).

  After the detection of the belt surface property on the entire surface of the intermediate transfer belt 7 is completed, a toner image corresponding to the entire surface of the intermediate transfer belt 7 is formed on the photosensitive drum, and this toner image is transferred to the surface of the intermediate transfer belt 7. A toner image is formed on the entire area of the intermediate transfer belt 7 (S2). In this way, the toner image surface property of the toner image formed on the entire surface of the intermediate transfer belt 7 is detected by the density sensor 23 at a plurality of positions as described above (S3). If the toner image is formed on the intermediate transfer belt 7 for each color individually, the property change portions of the developing sleeve 4a and the primary transfer rollers 5Y, 5M, 5C, and 5K are detected for each color. can do.

  With respect to the belt surface property and toner image surface property of the entire area of the intermediate transfer belt 7, it is determined whether there are different detection results compared to other regions, that is, the presence or absence of different detection results (S4). In the present embodiment, a combination of presence / absence of different detection results for belt surface properties (belt: yes, belt: no) and presence / absence of different results for toner image surface properties (toner: yes, toner: no) Four types of S5 to S8 are determined. That is, in the case of “belt: none, toner: none”, the intermediate transfer belt 7, the developing sleeve 4a (indicated as “development” in FIGS. 2, 3, and 5), and the primary transfer rollers 5Y, 5M, and 5C. 5K (described as “primary transfer” in FIGS. 2, 3 and 5), it is determined that there is no property change portion (S5), and normal image formation is permitted (S9). On the other hand, if “belt: present, toner: absent” is determined, the intermediate transfer belt 7 is determined to have a property change portion (S6). If “belt: present, toner: present” is present, intermediate transfer is performed. It is determined that the belt 7 is present, and the developing sleeve 4a or the primary transfer rollers 5Y, 5M, 5C, 5K and others are possible (S7). Alternatively, it is determined that there is a property change portion in addition to the primary transfer rollers 5Y, 5M, 5C, 5K (S8). If it is determined that S6 to S8, all of the intermediate transfer belt 7 has no property change (no property change portion) and the development sleeve 4a or the primary transfer rollers 5Y, 5M, 5C, and 5K have no other property change. Image formation is selected (S10). That is, an area where an image can be formed is selected from areas excluding areas with different detection values. For example, in the case where a part of the intermediate transfer belt 7 shows different detection values in a belt shape in the entire belt width direction, an intermediate transfer belt drive motor, a fixing device drive motor, and an exposure device are used so as not to form an image in that region. The timing of image formation is changed by controlling 3Y, 3M, 3C, 3K and the like.

  Further, when different detection values are shown in the vicinity of one end of the intermediate transfer belt 7 in the belt width direction along the rotation direction of the intermediate transfer belt 7, the image is not formed in the vicinity of the end. A change is made to move the formation position in the belt width direction of the intermediate transfer belt 7.

  In the above description, the belt surface property and the toner image surface property are detected over the entire area of the intermediate transfer belt 7. However, instead of this, the detection may be limited to a region where a property change is expected. In addition, the detection timing is not limited to the above.

  In the present embodiment, the detection is performed by rotating the intermediate transfer belt 7 at the time of detection. In the present embodiment, the density sensor 23 is the surface property detection means, but the present invention is not limited to this, and a dedicated sensor may be used, and the number of surface detection means is not limited. In order to detect a wide area, a plurality of moving areas may be used for detection.

  In this embodiment, the toner image is an electrostatic latent image formed by laser light as normal image formation. However, the present invention is not limited to this, and analog development formed by a difference between a charging potential and a developing bias potential may be used. The density at which the toner image is formed, the image processing method, and the like are not limited, and a plurality of toner images may be formed, and detection may be performed with density and image processing that are more easily detected.

  Further, the recording material conveyance path 19 is configured to be movable in the paper width direction (a direction orthogonal to the recording material conveyance direction), and the recording material conveyance furnace 15 is moved in the paper width direction in correspondence with the image forming position. You may do it.

<Embodiment 2>
In the second embodiment, when continuous printing (for example, 500 sheets) is performed, the surface property of the entire area of the intermediate transfer belt 7 is detected when a predetermined number of sheets (50 sheets in this embodiment) are first printed. At the same time, the surface property of the toner image transferred over the entire surface of the intermediate transfer belt 7 is detected. And this detection result is preserve | saved at the memory (storage means) 26 (refer FIG. 1). The image forming apparatus according to the present embodiment is configured by adding a memory 26 to the image forming apparatus according to the first embodiment.

  Subsequently, only a partial area (area A) of the intermediate transfer belt 7 is detected when a predetermined number of prints are completed (in this embodiment, when 100 prints are completed). At this time, in the determination of the belt surface property and the toner image surface property in the region A, the detection result at the time when a predetermined number of prints are finished (in this embodiment, when 100 prints are finished) is used. It is done. The determination is made by the control means 25. Further, the determination of the belt surface property and the toner image surface property in the region other than the region A is performed by the control unit 25 based on the detection result stored in the memory 26 and previously detected.

  By doing so, the detection time can be shortened and the amount of toner used can be reduced.

  FIG. 3 shows a method for detecting only a part of a region, which is executed each time a predetermined number of sheets are printed in the case of continuous printing.

  First, at the start of detection, surface properties are detected at a plurality of positions in an area A of the intermediate transfer belt 7 (for example, the whole area in the belt width direction and a part of the belt-like area in the rotation direction) (S11). Subsequently, a toner image is formed in the area A, and the surface property of the toner image is detected (S13).

  Regarding the belt surface property and toner image surface property of the entire area of the intermediate transfer belt 7, there are different detection results (regions exceeding a predetermined threshold) in the region A compared to other regions, that is, the region A is different. The presence or absence of a detection result is determined (S14). In the case of “Belt: None, Toner: None”, it is determined that there is no property change portion in the area A in the intermediate transfer belt 7 and the developing sleeve 4a or the primary transfer rollers 5Y, 5M, 5C, and 5K ( S15). In this case, normal image formation is permitted until the next detection is performed (S19).

  On the other hand, in the case of “Belt: No, Toner: Yes”, other than the intermediate transfer belt 7, for example, uneven development toner amount due to property changes such as uneven developer in the rotation axis direction of the developing sleeve 4a, and the primary transfer roller 5Y. , 5M, 5C, and 5K are determined to be any of transfer irregularities in the rotation axis direction due to property changes such as resistance irregularities in the rotation axis direction (S18). In this case, since the property change affects the entire rotation direction of the position where the detection value is different, the toner image is moved in the rotation axis direction, and selection control is performed to the area where the image can be formed. Further, the recording material P is also moved in the rotation axis direction in accordance with the movement of the toner image.

  On the other hand, in the case of “belt: present”, if “toner: present” (S 17), the positions of both the intermediate transfer belt 7 and the toner image, and if “toner: absent” (S 16) in the intermediate transfer belt 7. The belt surface property and toner image surface property are similarly detected for adjacent undetected regions (in this case, regions adjacent in the rotation direction of region A) with respect to different positions (S20). This is performed until there are no positions where the detected values are different, and the areas having different detected values are specified. Thereafter, the image is moved so as not to form an image in a region having a different detection value depending on one of the rotation direction and the rotation axis direction or a combination of both directions (S21). When moving in the direction of the rotation axis, when the recording material conveyance path 19 is moved in the paper width direction to correspond to the change in the position of the recording material P in the rotation axis direction, the areas with slightly different detection values are large. But I can make it correspond. In the present embodiment, when the detected value exceeds a different threshold value, it is determined that the property has changed. However, the present invention is not limited to this. For example, when there are two threshold values and the second threshold value is exceeded, detection of the region is performed. If the frequency is increased and the second threshold value is exceeded, it may be determined that the property has changed completely, and the image forming position may be changed. Further, when the detected value is different from the other on the surface of the toner image, it is determined that the property of the developing sleeve 4a or the primary transfer rollers 5Y, 5M, 5C, and 5K is changed. However, the present invention is not limited to this. It is also possible to determine that the optical part is dirty.

<Embodiment 3>
FIG. 4 shows an image forming apparatus to which this embodiment can be applied. The image forming apparatus shown in the figure further includes resistance measuring means 18 for measuring the resistance of the intermediate transfer belt 7 in addition to the image forming apparatus shown in FIG. The resistance measuring means 18 detects an area (property change suspected area) that is an area on the surface of the intermediate transfer belt 7 and that may have changed characteristics. That is, this resistance measuring means 18 functions as a suspicious area detecting means.

  The resistance measuring unit 18 includes a roller 15 as a detection unit that is brought into contact with and separated from the surface of the intermediate transfer belt 7, a grounded backup roller 27 that sandwiches the intermediate transfer belt 7 between the roller 15, and the intermediate transfer belt 7. A power source 16 for applying a voltage and an ammeter 17 for detecting a current flowing through the backup roller 27 when a voltage is applied to the roller 15 by the power source 16 are provided. The outline of the resistance value of the intermediate transfer belt 7 is detected based on the voltage of the power supply 16 and the detection result of the ammeter.

  When the property changes, that is, when the surface of the intermediate transfer belt 7 is scratched or dust adheres, the area of the roller 15 in contact with the intermediate transfer belt 7 changes, and the current flowing through the backup roller 27 changes. . In this way, a change in the properties of the intermediate transfer belt 7 can be detected from the current detected by the ammeter 17.

  In the present embodiment, the resistance measurement unit 18 measures the resistance of the intermediate transfer belt 7 at a predetermined timing, and detects a belt surface property of the intermediate transfer belt 7 when a detection result different from the others is obtained. Detection is performed by the density sensor 23 as detection means. As a result, only the detection of one rotation of the intermediate transfer belt 7 is required, so that the belt surface property can be detected in a relatively short time.

  FIG. 5 shows the control in the present embodiment. The roller 15 of the resistance measuring means 18 is brought into contact with the surface of the intermediate transfer belt 7 at a predetermined timing, and the resistance is measured for one rotation of the intermediate transfer belt 7 (S31). Separate from the surface. As a result of the resistance measurement, it is determined whether there is a detection result where the resistance value is different from the others in the rotation direction of the intermediate transfer belt 7 (S32). If it does not exist (belt: none), normal image formation is permitted (S33).

  As a result of the resistance measurement, if there is a region A (for example, the entire region in the rotational axis direction and a part of the belt-shaped region in the rotational direction) having a detection value different from others, there is a suspicion of property change. That is, it is a property change suspicious area. Therefore, the area A of the intermediate transfer belt 7 (the rotation direction is the entire area) and the belt surface property of the adjacent portion thereof are detected at a plurality of positions by the density sensor 23 (S34).

  Further, a toner image is formed in the region A of the intermediate transfer belt 7 and its adjacent portion (S35), and the toner image surface property is detected at a plurality of positions by the density sensor 23 (S36). Then, it is determined whether a detection result in which the belt surface property and the toner image surface property are different from others exists in the region A (S37).

  As a result, in the case of “belt: none, toner: none”, the region A includes the intermediate transfer belt 7 and the developing sleeve 4a, or the primary transfer rollers 5Y, 5M, 5C, and 5K, as well as no property change portion. Judgment is made (S38), and normal image formation is permitted (S42). Regardless of “belt: present / absent”, if “toner: less than threshold value 1”, there is a possibility that the region A has a property change portion, but it is determined that there is no problem in image formation. (S39) In the same manner as S38 described above, normal image formation is permitted (S42).

  On the other hand, regardless of “belt: presence / absence”, in the case of “toner: threshold value 1 or more and less than threshold value 2”, the intermediate transfer belt 7 and the developing sleeve 4a or the primary transfer roller 5Y, Although there is a possibility that there is a property change portion in addition to 5M, 5C, and 5K, it is determined that there is no problem in image formation (S40), and the detection frequency of the region A and the adjacent portion is increased (S43). If the detection frequency is increased to reach the threshold value 2, it is determined that the property has changed, and the portion having no property change is selected as the image forming position (S44).

  On the other hand, regardless of “belt: presence / absence”, in the case of “toner: threshold value 2 or more”, the intermediate transfer belt 7 has a property change portion in the region A, and the developing sleeve 4a or the primary transfer rollers 5Y, 5M. , 5C, 5K and the like, there is a possibility that there is a leaf property changing portion, and it is determined that the image formation is hindered (S41). In this case, it is determined that the intermediate transfer belt 7, the developing sleeve 4a, or the primary transfer rollers 5Y, 5M, 5C, 5K and other properties have changed, and the non-existing portion is selected as the image forming position (S45).

  According to the present embodiment, by providing the resistance measuring means 18, it is possible to efficiently detect the possibility of the belt surface property change of the intermediate transfer belt 7. Further, the toner image surface property has two threshold values, threshold value 1 and threshold value 2. When the threshold value is 1 or more and less than threshold value 2, the detection frequency is increased, and when the value is 2 or more, the property is completely changed. And the image forming position is changed. If the threshold value is less than 1, normal image formation is performed as in the case of “toner: none”. Therefore, image formation is performed as long as there is no problem in image formation, and image formation is performed more than necessary. Prohibition can be prevented.

  In the present embodiment, the detection frequency and the image forming position are changed according to the threshold value. However, for example, when it corresponds to one of the threshold values, a notification may be given to the service person. In this case, it is possible to prepare in advance for countermeasures such as replacement of parts of the image forming apparatus, and it is possible to prevent image defects in advance.

  As a result of the detection, if the property change region is wide and the region where the image can be formed is extremely narrow, the size at which image formation is possible may be restricted or image formation may be prohibited.

  Similarly, the size of the toner image that can be formed is limited by the detection result of the intermediate transfer belt 17 of the resistance measuring unit 18 and the detection result of the toner image transferred to the intermediate transfer belt 17 of the density sensor 23, or the image You may make it prohibit formation. That is, the maximum size of the toner image transferred to the intermediate transfer belt 17 based on the detection result of the intermediate transfer belt 17 of the resistance measuring unit 18 and the detection result of the toner image transferred to the intermediate transfer belt 17 of the density sensor 23. Is variably controlled by the control means 25.

  In this embodiment, the resistance measurement unit 18 is provided as the suspicious area detection unit and the resistance measurement is performed. However, for example, the secondary transfer unit including the secondary transfer roller 9 and the current measurement unit 10 is used as the suspicious area detection unit. Thus, resistance measurement may be performed. In that case, initial data of the rotational direction resistance distribution of the secondary transfer roller 9 itself is obtained in advance, and fluctuations due to the rotational direction resistance distribution of the secondary transfer roller 9 itself calculated from the initial data are removed from the detected value to obtain resistance. It is preferable to roughly calculate the value, and it is more preferable that the initial data includes initial data that takes into account durability fluctuations and environmental fluctuations. Similarly, primary transfer means having primary transfer rollers 5Y, 5M, 5C, 5K and their current detection means (not shown) can be used as the suspected area detection means.

  In the above first to third embodiments, the case where the intermediate transfer member is the belt-like intermediate transfer belt 7 has been described as an example. However, in the present invention, instead of this, the intermediate transfer member is an intermediate transfer drum on the drum. It can also be applied to

1 is a diagram schematically illustrating a schematic configuration of an image forming apparatus according to a first embodiment to which the present invention can be applied. 3 is a flowchart for detecting a property change portion according to the first embodiment. 10 is a flowchart for detecting a property change portion according to the second embodiment. It is a figure which shows typically schematic structure of the image forming apparatus which concerns on Embodiment 3 which can apply this invention. 10 is a flowchart for detecting a property change portion according to the third embodiment.

Explanation of symbols

1Y, 1M, 1C, 1K
Photosensitive drum (image carrier)
5Y, 5M, 5C, 5K
Primary transfer roller (primary transfer means, suspicious area detection means)
7 Intermediate transfer belt (intermediate transfer member)
9 Secondary transfer roller (secondary transfer means, suspected area detection means)
10 Ammeter (Current measurement means)
18 Resistance measurement means (suspicious area detection means)
23 Density sensor (intermediate transfer body surface property detecting means, toner image surface property detecting means, optical sensor)
25 Control means P Recording material R7 Rotation direction of intermediate transfer belt (rotation direction of intermediate transfer member)

Claims (4)

A toner image forming unit that forms a toner image on the image carrier, a transfer unit that transfers the toner image on the image carrier to an intermediate transfer member, and a surface of the intermediate transfer member to which the toner image is transferred. In an image forming apparatus comprising: an intermediate transfer body detection unit; and a toner image detection unit that detects the toner image transferred to the intermediate transfer body.
Based on the detection result of the intermediate transfer body detection means, the area to which the toner image is transferred on the intermediate transfer body is variably controlled, and based on the detection result of the toner image detection means, the toner on the image carrier Having control means for variably controlling a region where an image is formed;
An image forming apparatus. The intermediate transfer body detection means substantially detects the shape of the surface of the intermediate transfer body onto which the toner image is transferred;
The image forming apparatus according to claim 1. The toner image detecting means detects a density of the toner image transferred to the intermediate transfer member;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Control means for variably controlling the maximum size of the toner image transferred to the intermediate transfer body based on the detection result of the intermediate transfer body detection means and the detection result of the toner image detection means;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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