JP2009063909A - Belt device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt device and an image forming device capable of efficiently suppressing generation of color shift even when connection and disconnection operation of a belt member is conducted by switching from a monochrome mode to a color mode. <P>SOLUTION: In the color mode, the belt member is faced to all of a plurality of image carriers. In the monochrome mode, the belt member is faced to one image carrier out of the plurality of the image carriers, and the other image carriers are relatively separated from the belt member. When the mode is switched from the monochrome mode to the color mode (steps S1-S2), a color image is not formed until a detection result by a detection means becomes less than a predetermined value (steps S5-S7). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a belt apparatus in which belt members such as an intermediate transfer belt and a transfer conveyance belt are installed. The present invention relates to a tandem belt device and an image forming apparatus formed to be switchable between modes.

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, a tandem type color image forming apparatus provided with an intermediate transfer belt (belt device) is known (for example, see Patent Document 1 and Patent Document 2).
Specifically, four photosensitive drums (image carriers) are arranged side by side so as to face the intermediate transfer belt (belt member). On these four photosensitive drums, black (black), yellow, magenta, and cyan toner images are formed, respectively. Then, the toner images of the respective colors formed on the respective photoconductive drums are transferred onto the intermediate transfer belt in an overlapping manner. Further, the toner images of a plurality of colors carried on the intermediate transfer belt are transferred onto a recording medium as a color image.

  In such an image forming apparatus, a technique is known in which the displacement in the width direction of the intermediate transfer belt is detected and the displacement in the width direction of the intermediate transfer belt is corrected based on the detection result (for example, Patent Document 1). , See Patent Document 2). Such a technique has a problem that the quality of the color image is deteriorated due to the meandering of the intermediate transfer belt, or the intermediate transfer belt comes into contact with other members after the intermediate transfer belt is largely displaced in the width direction (close to the belt). The purpose is to prevent breakage and other problems.

  Specifically, in Patent Document 1 and the like, the amount of displacement of the contact that abuts on the widthwise end of the intermediate transfer belt (endless belt) and swings following the displacement is detected by a detecting means (displacement sensor). Detected. Then, based on the detection result of the detection means, the displacement (meander) of the intermediate transfer belt is corrected by the correction means (meandering correction roller).

On the other hand, such an image forming apparatus is configured such that an operator can select either a color mode or a monochrome mode (monochrome mode).
Specifically, in Patent Document 2 and the like, when the color mode (color print mode) is selected, all four photosensitive drums (image carriers) are opposed (contacted) to the belt member (transfer belt), and the single color is selected. When the mode (monochrome print mode) is selected, only one of the four photosensitive drums (image carrier) is made to face (contact) the belt member, and the other three photosensitive drums are belted. It is relatively spaced from the member. By performing such contact / separation operation, it is possible to suppress “color mixing” in which other colors are mixed on the output image in the single color mode, wear deterioration of the image forming member not related to the single color mode, and the like.

  In Patent Document 2, etc., the belt member is changed from the separated state to the contact state with respect to the photosensitive drum for the purpose of preventing the occurrence of color misalignment due to the separation operation of the belt member (transfer belt). A technique for performing a displacement detection operation after a predetermined time has elapsed is disclosed.

JP 2006-343629 A Japanese Patent No. 3799763

  In the above-described conventional technology, when switching between the monochromatic mode and the color mode, the belt member is brought into and out of contact with the image carrier, so that the balance of the tension of the belt member slightly changes. The belt member was likely to meander. In particular, if a large meandering of the belt member occurs in the color mode, color misregistration (a phenomenon in which a good color image is not formed due to a shift in the image forming position of each color) has occurred.

Such a problem cannot be ignored particularly in a high-speed machine (an image forming apparatus having a high process line speed) in which a belt member travels at a high speed.
Further, such a problem is not limited to a belt device using an intermediate transfer belt as a belt member, but may be a belt device in which a belt member in which toner images of a plurality of colors are superimposed and a contact / separation operation is performed is installed. For example, the belt device using the transfer conveyance belt as the belt member is also common.

  On the other hand, since the technique disclosed in Patent Document 2 described above performs the positional deviation amount detection operation after a predetermined time has elapsed after the belt member changes from the separated state to the contact state with respect to the image carrier, Even if a meandering correction mechanism for the member is installed, even if the belt member is not sufficiently corrected for meandering, printing may start and color misalignment may occur, or even if the meandering correction for the belt member is sufficient There is a problem that an extra waiting time occurs because printing is performed after a predetermined time.

  The present invention has been made to solve the above-described problems, and even when the belt member is brought into contact with or separated from the single-color mode by switching to the color mode, the occurrence of color misregistration is efficiently suppressed. The present invention provides a belt device and an image forming apparatus.

  A belt device according to a first aspect of the present invention is a belt device that faces a plurality of image carriers, and includes an endless belt member that travels in a predetermined direction, and a displacement in the width direction of the belt member. Detecting means for detecting; correcting means for correcting displacement in the width direction of the belt member based on a detection result of the detecting means; and the belt member on all of the plurality of image carriers in a color mode for forming a color image. In the monochromatic mode for forming a monochrome image, the belt member is opposed to one of the plurality of image carriers, and the other image carrier is separated from the belt member. A separation unit, and when the monochrome mode is switched to the color mode, a color image is not formed until a detection result by the detection unit becomes a predetermined value or less. And it is controlled so.

  According to a second aspect of the present invention, the belt device according to the first aspect of the present invention is controlled such that the color misregistration correction mode for correcting the color misregistration of the color image is performed at a predetermined timing. When the monochrome mode is switched to the color mode, the color misregistration correction mode is controlled not to be performed until the detection result by the detection means becomes equal to or less than a second predetermined value.

  The belt device according to a third aspect of the invention is the belt device according to the second aspect, wherein the second predetermined value is set to a value lower than the predetermined value.

  According to a fourth aspect of the present invention, there is provided the belt device according to any one of the first to third aspects, wherein the detection means detects when the color mode is switched to the single color mode. Control is performed so that a monochromatic image is formed even if the result is not less than the predetermined value.

  A belt device according to a fifth aspect of the present invention is the belt device according to any of the first to fourth aspects, wherein when the monochrome mode is switched to the color mode, the operator selects it. The color image is controlled to be formed even if the detection result by the detection means is not below the predetermined value.

  The belt device according to a sixth aspect of the present invention is the belt device according to any one of the first to fifth aspects, wherein the detection means calculates a displacement amount per unit time in the width direction of the belt member. It is something to detect.

  An image forming apparatus according to a seventh aspect of the present invention includes the belt device according to any one of the first to sixth aspects.

  In the present invention, even when the belt member is moved toward and away from the monochrome mode to the color mode, the color image is formed until the detection result by the detecting means for detecting the meandering of the belt member becomes a predetermined value or less. Therefore, it is possible to provide a belt device and an image forming apparatus in which the occurrence of color misregistration is efficiently suppressed.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIGS.
FIG. 1 is a block diagram showing a printer as an image forming apparatus, and FIG. 2 is an enlarged view showing an image forming unit thereof.
As shown in FIG. 1, an intermediate transfer belt device 15 as a belt device is installed in the center of the image forming apparatus main body 100. Further, image forming portions 6Y, 6M, 6C, and 6K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 8 (belt member) of the intermediate transfer belt device 15. Yes.

  Referring to FIG. 2, an image forming unit 6Y corresponding to yellow includes a photosensitive drum 1Y as an image carrier, a charging unit 4Y disposed around the photosensitive drum 1Y, a developing unit 5Y, and a cleaning unit 2Y. , And a static elimination unit (not shown). Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photosensitive drum 1Y, and a yellow image is formed on the photosensitive drum 1Y.

  The other three image forming units 6M, 6C, and 6K have substantially the same configuration as that of the image forming unit 6Y corresponding to yellow except that the color of the toner used is different. A corresponding image is formed. Hereinafter, description of the other three image forming units 6M, 6C, and 6K will be omitted as appropriate, and only the image forming unit 6Y corresponding to yellow will be described.

Referring to FIG. 2, the photosensitive drum 1Y is driven to rotate counterclockwise in FIG. 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 1Y is uniformly charged at the position of the charging unit 4Y (a charging process).
Thereafter, the surface of the photosensitive drum 1Y reaches the irradiation position of the laser beam L emitted from the exposure unit 7, and an electrostatic latent image corresponding to yellow is formed by exposure scanning at this position (in the exposure process). is there.).

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the developing portion 5Y, and the electrostatic latent image is developed at this position to form a yellow toner image (developing process).
Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the intermediate transfer belt 8 (belt member) and the transfer roller 9Y (primary transfer roller), and the toner image on the photosensitive drum 1Y is intermediately transferred at this position. Transferred onto the belt 8 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drum 1Y.

Thereafter, the surface of the photosensitive drum 1Y reaches a position facing the cleaning unit 2Y, and untransferred toner remaining on the photosensitive drum 1Y at this position is collected in the cleaning unit 2Y by the cleaning blade 2a (cleaning). Process.)
Finally, the surface of the photosensitive drum 1Y reaches a position facing a neutralization unit (not shown), and the residual potential on the photosensitive drum 1 is removed at this position.
Thus, a series of image forming processes performed on the photosensitive drum 1Y is completed.

The image forming process described above is performed in the other image forming units 6M, 6C, and 6K in the same manner as the yellow image forming unit 6Y. That is, a laser beam L based on image information is irradiated from the exposure unit 7 disposed above the image forming unit onto the photosensitive drums 1M, 1C, and 1K of the image forming units 6M, 6C, and 6K. Is done. Specifically, the exposure unit 7 emits laser light L from a light source, and irradiates the photosensitive drum through a plurality of optical elements while scanning the laser light L with a polygon mirror that is rotationally driven.
Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 8 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 8.

  Here, the intermediate transfer belt device 15 (belt device) includes an intermediate transfer belt 8, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, a secondary transfer counter roller 12B, a tension, with reference to FIG. The roller 12C, the correction roller 13 (correction unit), the regulation roller 14, the meandering detection unit 80 (detection unit), the abnormality detection unit 88, the photo sensor 90, the intermediate transfer cleaning unit 10, and the like. The intermediate transfer belt 8 is stretched and supported by a plurality of roller members 12A to 12C, 13, and 14, and is endlessly moved in the direction of the arrow in FIG. 3 by the rotational drive of one roller member (drive roller) 12A. .

Four transfer rollers 9Y, 9M, 9C, and 9K (primary transfer rollers) respectively sandwich the intermediate transfer belt 8 between the photosensitive drums 1Y, 1M, 1C, and 1K to form primary transfer nips. Yes. Then, a high voltage (transfer bias) opposite to the polarity of the toner is applied to the transfer rollers 9Y, 9M, 9C, and 9K.
The intermediate transfer belt 8 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the transfer rollers 9Y, 9M, 9C, and 9K. In this way, the toner images of the respective colors on the photosensitive drums 1Y, 1M, 1C, and 1K are primarily transferred while being superimposed on the intermediate transfer belt 8.

  Thereafter, the intermediate transfer belt 8 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 19. At this position, the secondary transfer counter roller 12B sandwiches the intermediate transfer belt 8 with the secondary transfer roller 19 to form a secondary transfer nip. Then, a high voltage (secondary transfer bias) opposite to the polarity of the toner is applied to the secondary transfer roller 19. As a result, the four-color toner images formed on the intermediate transfer belt 8 are transferred onto a recording medium P such as transfer paper conveyed to the position of the secondary transfer nip (secondary transfer step). ). At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 8.

Thereafter, the intermediate transfer belt 8 reaches the position of the intermediate transfer cleaning unit 10. At this position, the untransferred toner on the intermediate transfer belt 8 is removed.
Thus, a series of transfer processes performed on the intermediate transfer belt 8 is completed. The configuration and operation of the intermediate transfer belt device 15 as a belt device will be described in more detail later with reference to FIGS.

Here, referring to FIG. 1, the recording medium P transported to the position of the secondary transfer nip is fed to the paper feeding unit 26 (or laterally fed) disposed below the apparatus main body 100. From the paper section) via the paper feed roller 27, the registration roller pair 28, and the like.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 26 in a stacked manner. When the paper feed roller 27 is driven to rotate counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the rollers of the registration roller pair 28.

  The recording medium P transported to the registration roller pair 28 temporarily stops at the position of the roller nip of the registration roller pair 28 whose rotation drive has been stopped. Then, the registration roller pair 28 is rotationally driven in synchronization with the color image on the intermediate transfer belt 8, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
Thereafter, the recording medium P is discharged out of the apparatus by a pair of discharge rollers (not shown). The transferred P discharged from the apparatus by the pair of paper discharge rollers is sequentially stacked on the stack unit as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the developing unit in the image forming unit will be described in more detail with reference to FIG.
The developing unit 5Y includes a developing roller 51Y that faces the photosensitive drum 1Y, a doctor blade 52Y that faces the developing roller 51Y, two transport screws 55Y disposed in the developer containing unit, and an opening in the developer containing unit. A toner replenishment path 43Y that communicates with each other via a toner density, a density detection sensor 56Y that detects a toner density in the developer, and the like. The developing roller 51Y includes a magnet fixed inside, a sleeve rotating around the magnet, and the like. In the developer accommodating portion, a two-component developer composed of a carrier and toner is accommodated.

The developing unit 5Y configured as described above operates as follows.
The sleeve of the developing roller 51Y rotates in the direction of the arrow in FIG. The developer carried on the developing roller 51Y by the magnetic field formed by the magnet moves on the developing roller 51Y as the sleeve rotates. Here, the developer in the developing device 5Y is adjusted so that the toner ratio (toner concentration) in the developer is within a predetermined range.
Thereafter, the toner replenished in the developer accommodating portion circulates through the two separated developer accommodating portions while being mixed and stirred together with the developer by the two conveying screws 55Y (movement in the direction perpendicular to the paper surface of FIG. 2). .) The toner in the developer is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller 51Y together with the carrier by the magnetic force formed on the developing roller 51Y.

  The developer carried on the developing roller 51Y is conveyed in the direction of the arrow in FIG. 2 and reaches the position of the doctor blade 52Y. The developer on the developing roller 51Y is conveyed to a position facing the photosensitive drum 1Y (development area) after the developer amount is made appropriate at this position. The toner is attracted to the latent image formed on the photosensitive drum 1Y by the electric field formed in the development area. Thereafter, the developer remaining on the developing roller 51Y reaches the upper portion of the developer accommodating portion as the sleeve rotates, and is detached from the developing roller 51Y at this position.

Next, the intermediate transfer belt device 15 (belt device) characteristic of the image forming apparatus according to the present embodiment will be described in detail with reference to FIGS.
FIG. 3 is a configuration diagram showing an intermediate transfer belt device 15 as a belt device. FIG. 4 is a schematic view of a part of the intermediate transfer belt device 15 as viewed in the width direction. FIG. 5 is a perspective view showing the vicinity of the meandering detection unit 80 in the intermediate transfer belt device 15. FIG. 6 is a perspective view showing the vicinity of the abnormality detection unit 88 in the intermediate transfer belt device 15.

  3 and 4, the intermediate transfer belt device 15 (belt device) includes an intermediate transfer belt 8 as a belt member, four transfer rollers 9Y, 9M, 9C, and 9K, a driving roller 12A, and a secondary transfer counter. The roller 12B, the tension roller 12C, a correction roller 13 as a correction unit, a regulation roller 14, a meandering detection unit 80 as a detection unit, an abnormality detection unit 88, a photo sensor 90, an intermediate transfer cleaning unit 10, and the like.

  The intermediate transfer belt 8 as a belt member is disposed so as to face the photosensitive drums 1Y, 1M, 1C, and 1K as four image carriers that respectively carry toner images of respective colors. The intermediate transfer belt 8 is stretched and supported mainly by five roller members (a driving roller 12, a secondary transfer counter roller 12B, a tension roller 12C, a correction roller 13, and a regulating roller 14).

In the present embodiment, the intermediate transfer belt 8 is made of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), etc. in a single layer or multiple layers. A conductive material such as carbon black is dispersed. The intermediate transfer belt 8 is adjusted so that the volume resistivity is in the range of 10 ⁷ to 10 ¹² Ωcm and the surface resistivity on the back side of the belt is in the range of 10 ⁸ to 10 ¹² Ωcm. The intermediate transfer belt 8 is set to have a thickness in the range of 80 to 100 μm. In the present embodiment, the thickness of the intermediate transfer belt 8 is set to 90 μm. The peripheral length of the intermediate transfer belt 8 is set to 2197.5 mm.
If necessary, a release layer can be coated on the surface of the intermediate transfer belt 8. At that time, materials used for the coating are ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluororesin), FEP (four A fluororesin such as fluorinated ethylene-hexafluoropropylene copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.
Further, as a method for manufacturing the intermediate transfer belt 8, there are a casting method, a centrifugal molding method, and the like, and a step of polishing the surface is performed as necessary.

  The transfer rollers 9Y, 9M, 9C, and 9K are opposed to the corresponding photosensitive drums 1Y, 1M, 1C, and 1K through the intermediate transfer belt 8, respectively. More specifically, the yellow transfer roller 9Y faces the yellow photosensitive drum 1Y via the intermediate transfer belt 8, and the magenta transfer roller 9M contacts the magenta photosensitive drum 1M via the intermediate transfer belt 8. The cyan transfer roller 9C faces the cyan photosensitive drum 1C via the intermediate transfer belt 8, and the black (black) transfer roller 9K passes through the intermediate transfer belt 8 for black (black). For example).

The four transfer rollers 9Y, 9M, 9C, and 9K are configured to separate the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K by contact / separation means (contact / separation mechanism).
Specifically, among the four transfer rollers 9Y, 9M, 9C, and 9K, the three color transfer rollers 9Y, 9M, and 9C are integrally held by a holding member (not shown) and integrated in the vertical direction. It is configured to be movable. Further, the black transfer roller 9K is configured to be movable up and down independently. Then, the four transfer rollers 9Y, 9M, 9C, and 9K move to the positions indicated by broken lines in FIG. 3, so that the intermediate transfer belt 8 is separated from the photosensitive drums 1Y, 1M, 1C, and 1K (to the positions indicated by broken lines). Move.) The operation of separating the intermediate transfer belt 8 from the photosensitive drums 1Y, 1M, 1C, and 1K is performed in order to reduce wear deterioration of the intermediate transfer belt 8, and is performed mainly during non-image formation. . The black transfer roller 9K can be moved up and down independently in the single color mode (when a monochrome image is formed), and the three color transfer rollers 9Y, 9M, and 9C. Is moved downward to separate the color photosensitive drums 1Y, 1M, and 1C from the intermediate transfer belt 8 (the state shown in FIG. 7).

  As described above, in this embodiment, when the color mode (the mode for forming a color image) is selected, the four photosensitive drums 1Y, 1M, and 1C are used by the contact / separation means (contact / separation mechanism). The intermediate transfer belt 8 is configured to face (contact) all of 1K (the state shown in FIG. 3). When the single color mode (a mode for forming a single color image) is selected, the intermediate transfer belt 8 faces (contacts) only one photosensitive drum 1K by the contact / separation means (contact / separation mechanism). The other three photosensitive drums 1Y, 1M, and 1C are configured to be relatively separated from the intermediate transfer belt 8 (the state shown in FIG. 7).

The drive roller 12A is rotationally driven by a drive motor 70. As a result, the intermediate transfer belt 8 travels in a predetermined traveling direction (clockwise in FIG. 3). The drive motor 70 is a stepping motor and is operated by a drive signal (pulse signal) from the drive 71 controlled by the control unit 72.
The secondary transfer counter roller 12 </ b> B is in contact with the secondary transfer roller 19 through the intermediate transfer belt 8. Another tension roller 12 </ b> C is in contact with the outer peripheral surface of the intermediate transfer belt 8. An intermediate transfer cleaning unit 10 (cleaning blade) is installed between the secondary transfer counter roller 12B and the tension roller 12C.

Here, in the intermediate transfer belt device 15 in the present embodiment, a meandering detection unit 80 is installed as detection means for detecting the displacement of the intermediate transfer belt 8 in the width direction (the vertical direction in FIG. 3). ing. Specifically, the meandering detection unit 80 as detection means detects a displacement amount (meandering speed) per unit time in the width direction of the intermediate transfer belt 8.
More specifically, with reference to FIG. 5, the meandering detection unit 80 (detection means) is a swinging member 82 that contacts the end of the intermediate transfer belt 8 in the width direction, and a distance measurement that detects the amount of displacement of the swinging member 82. The sensor 81 and the spring 83 that urges the swinging member 82 in a direction to contact the intermediate transfer belt 8 are formed.

The swing member 82 includes a first arm portion 82a, a rotation support shaft 82b, a second arm portion 82c, and the like. One end of the first arm portion 82a is in contact with the end portion in the width direction of the intermediate transfer belt 8, and the other end is fixed to the rotation support shaft 82b. The rotation spindle 82b is rotatably supported by a housing (not shown) of the intermediate transfer belt device 15. One end of the second arm portion 82c is fixed to the rotation support shaft 82b. One end of a spring 83 is connected to the center of the second arm portion 82c. The other end of the spring 83 is connected to the housing.
With such a configuration, the swinging member 82 swings following the displacement in the width direction of the intermediate transfer belt 8 (closer to the belt in the direction indicated by the broken line in FIG. 5) (FIG. 5). (It is a swing in the direction of the solid double arrow in the middle.) In the present embodiment, the intermediate transfer belt 8 is set to travel at 440 mm / second in the traveling direction (in the direction of the arrow in FIG. 5) during normal operation.

  A distance measuring sensor 81 is installed above the other end of the second arm portion 82c of the swing member 82 (fixed to the housing). The distance measuring sensor 81 is mainly composed of a light emitting element (infrared light emitting diode) and a position detecting element (PSD) arranged side by side in the horizontal direction. Infrared light emitted from the light emitting element is reflected by the surface of the second arm portion 82c and enters the position detection element as reflected light. At this time, the incident position of the reflected light incident on the position detecting element changes depending on the distance between the distance measuring sensor 81 and the surface of the second arm portion 82c, and the output value of the light receiving element (ranging sensor 81) is proportional to the change. Changes. Thereby, the amount of displacement in the width direction of the intermediate transfer belt 8 (distance from the surface of the second arm portion 82c) can be detected. Specifically, when the output value of the distance measuring sensor 81 is smaller than a predetermined value (voltage V0), the intermediate transfer belt 8 is displaced in the plus direction with respect to the target position (position displacement to the right in FIG. 5). When the output value of the distance measuring sensor 81 is larger than a predetermined value (voltage V0), the intermediate transfer belt 8 is displaced in the minus direction with respect to the target position (to the left in FIG. 5). This is a displacement of.

Further, in the present embodiment, during normal image formation (printing) or the like, the meander detection unit 80 also detects abnormal belt deviation (abnormality detection).
Specifically, the belt by the correction roller 13 is set based on the detection result of the meandering detection unit 80, with a belt shift (position shift) of ± 0.5 mm with respect to the target position (position shift 0 mm) as an allowable range (print allowable range). Perform misalignment correction. Then, when the belt shift (position shift) of the intermediate transfer belt 8 is outside the detection range (± 1 mm) of the meander detection unit 80, it is assumed that a relatively large belt shift has occurred, and the apparatus is forcibly stopped. At the same time, the abnormality detection is displayed on the display unit (not shown) of the apparatus main body 100.
In addition to the abnormality detection by the meandering detection unit 80, abnormality detection by the abnormality detection unit 88 is also performed. The reason for detecting the belt-side anomaly in this way is to reliably detect the anomaly even if the meandering detector 80 breaks down or the control software runs away.

Here, in the vicinity of the meandering detection unit 80 (detection means), a regulation roller 14 that regulates displacement in a direction different from the width direction and the traveling direction of the intermediate transfer belt 8 is installed. Specifically, the regulating roller 14 is close to the contact position between the swing member 82 (first arm portion 82a) and the intermediate transfer belt 8 (upstream in the running direction of the intermediate transfer belt 8 with respect to the contact position). Side.)
With such a configuration, the direction perpendicular to the width direction of the intermediate transfer belt 8 in the meandering detection unit 80 (the contact position between the swinging member 82 and the intermediate transfer belt 8) is the direction perpendicular to the paper surface of FIG. Is reduced. In other words, since the belt tension of the intermediate transfer belt 8 is increased by the restriction roller 14, the displacement of the meandering detection unit 80 in the orthogonal direction is restricted. Therefore, the meandering detection unit 80 detects a displacement component in a direction different from the width direction and the traveling direction in addition to a detection component (a detection component in the width direction) that should be detected originally. It is reduced. That is, the accuracy of detection of the intermediate transfer belt 8 near the belt by the meandering detection unit 80 is improved.

Then, when the displacement (meandering speed) of the intermediate transfer belt 8 is detected by the meandering detection unit 80, the displacement in the width direction of the intermediate transfer belt 8 is corrected by the correction roller 13 as correction means based on the detection result. .
Here, referring to FIG. 3, the correction roller 13 is on the upstream side in the running direction of the intermediate transfer belt 8 with respect to the photosensitive drums 1 </ b> Y, 1 </ b> M, 1 </ b> C, and 1 </ b> K, and It arrange | positions so that it may contact | connect. Then, referring to FIG. 4, the correction roller 13 swings in the X1 and X2 directions around the swing center 13a by a drive cam (not shown) of the swing mechanism 73 operating at a predetermined angle. It is configured to move.
With this configuration, when the intermediate transfer belt 8 is displaced to the right (belt side) in FIG. 4, the correction roller 13 is swung in the X2 direction by the swing mechanism 73 based on the detection result, and the intermediate transfer belt The displacement correction of the belt 8 is performed. On the other hand, when the intermediate transfer belt 8 is displaced to the left side, based on the detection result, the correction roller 13 is swung in the X1 direction by the swing mechanism 73, and the displacement of the intermediate transfer belt 8 is corrected. As a result, the quality of the color image is deteriorated due to the meandering of the intermediate transfer belt 8, or the intermediate transfer belt 8 is greatly displaced in the width direction (being close to the belt) and comes into contact with other members to cause the intermediate transfer belt 8 to move. Defects etc. that are damaged are suppressed.

In the intermediate transfer belt device 15 according to the present exemplary embodiment, referring to FIG. 4, an abnormality detection unit 88 is installed at a position that is a predetermined distance away from both ends in the width direction of the intermediate transfer belt 8.
As shown in FIG. 6, the abnormality detection unit 88 optically moves the arm member 90 that contacts the intermediate transfer belt 8 that is largely deviated from the belt, and the movement of the arm member about the rotation support shaft 90 b caused by the contact of the intermediate transfer belt 8. An overrun detection sensor 89 (optical sensor) for detecting the position of the arm member 90, a spring 91 for maintaining the posture of the arm member 90, and the like.

  Specifically, referring to FIG. 6, the arm member 90 includes a first arm portion 90 a, a rotation support shaft 90 b, a second arm portion 90 c, and the like. The first arm portion 90a is disposed at a position 5 mm away from the widthwise end portion of the intermediate transfer belt 8 having one end at a normal position, and the other end is fixed to the rotation support shaft 90b. The rotation spindle 90b is rotatably supported by a housing (not shown) of the intermediate transfer belt device 15. One end of the second arm portion 90c is fixed to the rotation support shaft 90b, and the other end is disposed between the light emitting portion 89a and the light receiving portion 89b of the overrun detection sensor 89. One end of a spring 91 is connected to the center of the second arm portion 90c. The other end of the spring 91 is connected to the housing. Although not shown, a part of the second arm portion 90c is in contact with the positioning portion of the housing by the biasing force of the spring 91.

With such a configuration, the arm member 90 swings in contact with the intermediate transfer belt 8 when a large belt shift exceeding 5 mm occurs on the intermediate transfer belt 8 (in the direction of the solid arrow in FIG. 6). Oscillating.)
Such a state is detected by the overrun detection sensor 89. That is, the state where the tip of the second arm portion 90c is separated from the light emitting portion 89a and the light receiving portion 89b is recognized by the light emitted from the light emitting portion 89a being received by the light receiving portion 89b.
When abnormality is detected by the abnormality detection unit 88 (overrun detection sensor 89) in this way, the driving of the intermediate transfer belt 8 (drive roller 12A) is stopped, the photosensitive drums 1Y, 1M, 1C, 1K, and the first. 2 The driving of the transfer roller 19 is stopped, and the photosensitive drums 1Y, 1M, 1C, and 1K and the second transfer roller 19 are forcibly separated from each other. The serviceman call is displayed on the display (the serviceman needs to be repaired).
In the present embodiment, referring to FIG. 3, the secondary transfer roller 19 is configured to move in a freely detachable manner relative to the intermediate transfer belt 8 (movement in the direction of the arrow).

  In addition, the intermediate transfer belt device 15 in the present exemplary embodiment is provided with a photo sensor 90 with reference to FIGS. 3 and 4. Here, the photo sensor 90 detects the position and density of the toner image (patch pattern) carried on the intermediate transfer belt 8, and optimizes the image forming conditions. Specifically, the position shift of each color toner image (patch pattern) formed on the intermediate transfer belt 8 through the image forming process described above is optically detected by the photosensor 90, and exposure is performed based on the detection result. The exposure timing of the photosensitive drums 1Y, 1M, 1C, and 1K by the unit 7 is adjusted. Further, the density (toner density) of the toner image (patch pattern) formed on the intermediate transfer belt 8 through the above-described image forming process is optically detected by the photosensor 90 and developed based on the detection result. The toner density of the developer stored in the unit 5 is adjusted.

Hereinafter, characteristic control performed by the intermediate transfer belt device 15 will be described in detail with reference to FIGS. 8 and 9.
In the intermediate transfer belt device 15 according to the present embodiment, when the monochrome mode (monochrome print mode) is switched to the color mode (color print mode), the detection result by the meandering detection unit 80 (detection means) is a predetermined value (A ) Control is performed so that color image formation (color printing) is not performed until the following occurs.

Specifically, the control is performed according to the flow of FIG.
Referring to FIG. 8, first, it is determined whether the selected mode is a color mode (step S1). The mode may be selected manually by an operator by operating an operation panel (not shown) or may be automatically selected on the image forming apparatus main body 100 side.
As a result, when it is determined that the color mode is selected, it is determined whether or not the switching from the single color mode has been performed (step S2). That is, it is determined whether the mode (job) immediately before the color mode is performed is the single color mode. When switching from the monochrome mode to the color mode is performed, the contact / separation operation of the intermediate transfer belt 8 by the contact / separation means accompanying the mode switching is performed as described above.

  As a result, when it is determined that the switching from the single color mode to the color mode has been performed, it is determined whether the high-speed mode is selected by the operator (step S3). Here, “high-speed mode” means that even if the image quality of the output image has deteriorated to some extent, when priority is given to shortening the output time (first print time) of the output image, This mode is arbitrarily selected. The operator selects the “high speed mode” by operating an operation panel (not shown) of the apparatus main body 100.

As a result, when it is determined that the high-speed mode is not selected, the meander detection of the intermediate transfer belt 8 is performed by the meander detection unit 80 (detection means) (step S4), and the detection result is a predetermined value ( A) It is determined whether or not the following is true (step S5). Specifically, the meandering detection unit 80 as detection means detects a displacement amount (meandering speed) per unit time in the width direction of the intermediate transfer belt 8. In the present embodiment, the predetermined value (A) is set to ± 19.5 μm / second. That is, in step S5, it is determined whether the meandering speed of the intermediate transfer belt 8 is within a range of ± 19.5 μm / second with respect to the target value. This discriminant value (A) is defined as the distance from the transfer of the first color (yellow) image to the transfer of the final color (black) on the intermediate transfer belt 8 as D. If the linear velocity is v and the color misregistration allowable value set in the image forming apparatus 100 is x,
x> A · D / v
Is set so that the following relationship is established. Here, the color misregistration allowable value x is preferably 100 μm or less (more preferably 60 μm or less).

  As a result, when it is determined that the detection result by the meander detection unit 80 is not less than or equal to the predetermined value (A) (within ± 19.5 μm / second), meander correction by the correction roller 13 (correction means) is performed. This is done (step S6), and the flow after step S4 is repeated until it is determined that the detection result is equal to or less than the predetermined value (A). Then, when it is determined that the detection result by the meandering detection unit 80 is equal to or less than the predetermined value (A) (within a range of ± 19.5 μm / sec), printing (color image formation) is performed (step S7). .

  As described above, in the present embodiment, even when the contact / separation operation of the intermediate transfer belt 8 is performed by switching from the single color mode to the color mode, the detection result by the meander detection unit 80 is less than or equal to the predetermined value (A). Since a color image is not formed, the occurrence of color misregistration can be efficiently suppressed in a state where the meandering correction of the intermediate transfer belt 8 is sufficiently performed with a sufficient waiting time.

  Here, in this embodiment, when it is determined in step S1 that the color mode is not selected, printing is started immediately without performing the flow after step S2 (step S7). That is, when the color mode is switched to the monochromatic mode, it is difficult to cause a problem on the image without correcting the meandering of the intermediate transfer belt 8 with high accuracy, and the monochromatic mode is continuously selected. Since large meandering of the intermediate transfer belt 8 is unlikely to occur, an unnecessary waiting time required for meander correction is eliminated (even if the detection result of the meandering detection unit 80 is not less than the predetermined value A), and monochrome printing (monochrome) Image formation) is started.

  In this embodiment, if it is determined in step S2 that the switching from the single color mode to the color mode has not been performed, printing is started immediately without performing the flow after step S3 (step S3). S7). That is, when the color mode is continuously selected, the intermediate transfer belt 8 does not contact and separate, and the intermediate transfer belt 8 does not easily generate a large meander, so that a wasteful waiting time required for meander correction is eliminated. Immediately start color printing.

  In this embodiment, if it is determined in step S3 that the high-speed mode has not been selected, printing is started immediately without performing the flow from step S4 onward (step S7). That is, when the high-speed mode is selected, the useless waiting time required for meander correction is eliminated in accordance with the operator's intention to give priority to shortening the print time regardless of the image quality of the output image ( Even if the detection result of the meandering detection unit 80 is not less than the predetermined value A), color printing (color image formation) is started immediately.

FIG. 9 is a flowchart showing the control when the color misregistration correction mode is started.
As shown in FIG. 9, first, it is determined whether the start condition of the color misregistration correction mode is set (step S11). Here, the color misregistration correction mode can be performed every predetermined number of prints (for example, every 100 sheets), or can be performed when a change in ambient temperature becomes a predetermined value or more. In the “color misregistration correction mode”, a toner image (patch pattern) of each color is formed on the intermediate transfer belt 8, and the amount of misregistration of each color toner image is optically detected by a photo sensor (not shown). This is a mode for detecting and performing color misregistration correction (for example, adjustment of writing timing and writing position) based on the detection result, and is performed separately from the normal image forming operation (printing operation) in the color mode. .

  As a result, when it is determined that the start condition of the color misregistration correction mode is satisfied, it is determined whether or not switching from the single color mode has been performed (step S12). That is, it is determined whether the mode (job) immediately before the color mode is performed is the single color mode. When switching from the monochrome mode to the color mode is performed, the contact / separation operation of the intermediate transfer belt 8 by the contact / separation means accompanying the mode switching is performed as described above.

As a result, when it is determined that the switching from the monochromatic mode to the color mode has been made, the meandering detection of the intermediate transfer belt 8 is performed by the meandering detection unit 80 (detection means) (step S14), and the detection result thereof. Is less than or equal to the second predetermined value (B) (step S15).
Here, in the present embodiment, the second predetermined value (B) is set to a value lower than the predetermined value (A) in FIG. 8 (A> B). Specifically, the second predetermined value (B) is set to ± 6 to 10 μm / second. That is, in step S15, it is determined whether the meandering speed of the intermediate transfer belt 8 is within a range of ± 6 to 10 μm / second with respect to the target value. Accordingly, it is possible to perform highly accurate color misregistration correction in a state where the intermediate transfer belt 8 is meandered with high accuracy.

  As a result, when it is determined that the detection result by the meandering detection unit 80 is not less than or equal to the second predetermined value (B) (within ± 6 to 10 μm / second), the correction roller 13 (correction means) The meandering correction is performed (step S16), and the flow after step S14 is repeated until it is determined that the detection result is equal to or smaller than the second predetermined value (B). When it is determined that the detection result by the meander detection unit 80 is equal to or less than the second predetermined value (B) (within a range of ± 6 to 10 μm / second), the color misregistration correction mode is started (step S17). ).

  As described above, in the present embodiment, even if the contact / separation operation of the intermediate transfer belt 8 is performed by switching from the single color mode to the color mode, the detection result by the meander detection unit 80 is equal to or less than the second predetermined value (B). Since the color misregistration correction mode is not performed until the time becomes, the color misregistration correction can be efficiently performed in a state where the meandering correction of the intermediate transfer belt 8 is sufficiently performed in a waiting time with no excess or deficiency.

  Here, in this embodiment, when it is determined in step S12 that the switching from the single color mode to the color mode has not been performed, the color misregistration correction mode is immediately set without performing the flow from step 14 onward. Start (step S17). That is, when the color mode is continuously selected, the intermediate transfer belt 8 does not contact and separate, and the intermediate transfer belt 8 does not easily generate a large meander, so that a wasteful waiting time required for meander correction is eliminated. Immediately start the color misregistration correction mode.

  As described above, in this embodiment, meandering detection for detecting meandering of the intermediate transfer belt 8 even when the intermediate transfer belt 8 (belt member) is brought into contact with and separated from the single color mode by switching from the color mode. Since the color image is not formed until the detection result by the unit 80 (detection means) is equal to or less than the predetermined value (A), the occurrence of color misregistration can be efficiently suppressed.

  In the present embodiment, the present invention is applied to a belt device (intermediate transfer belt device 15) using the intermediate transfer belt 8 as a belt member. On the other hand, the present invention is also applied to a belt device using a transfer conveyance belt as a belt member (a belt device that transfers a plurality of color toner images onto a recording medium while conveying the recording medium on the belt member). The invention can be applied. In this case as well, the same effect as that of the present embodiment can be obtained when the transfer / conveying belt is brought into and out of contact.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. Further, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating an image forming unit in the image forming apparatus of FIG. 1. FIG. 2 is a configuration diagram illustrating a belt device installed in the image forming apparatus of FIG. 1. It is the schematic which looked at a part of belt device in the width direction. It is a perspective view which shows a detection means. It is a perspective view which shows an abnormality detection part. It is the schematic which shows the belt apparatus at the time of monochromatic mode. It is a flowchart which shows the control at the time of switching from a monochromatic mode to a color mode. It is a flowchart which shows the control at the time of color shift correction mode.

Explanation of symbols

8 Intermediate transfer belt (belt member),
12A-12C roller member,
13 Correction roller (correction means),
15 Intermediate transfer belt device (belt device),
80 Meander detection part (detection means),
81 ranging sensor,
82 rocking member,
83 Spring,
100 Image forming apparatus main body (apparatus main body).

Claims (7)

A belt device facing a plurality of image carriers,
An endless belt member traveling in a predetermined direction;
Detecting means for detecting displacement in the width direction of the belt member;
Correction means for correcting displacement in the width direction of the belt member based on the detection result of the detection means;
In the color mode for forming a color image, the belt member is opposed to all of the plurality of image carriers, and in the single color mode for forming a monochrome image, the belt member is attached to one of the plurality of image carriers. Contacting / separating means for opposing the other image carrier relative to the belt member,
With
The belt device is controlled so that, when the mode is switched from the single color mode to the color mode, a color image is not formed until a detection result by the detection unit becomes a predetermined value or less. Control is performed so that a color misregistration correction mode for correcting color misregistration of a color image is performed at a predetermined timing.
The color misregistration correction mode is controlled so that the color misregistration correction mode is not performed until the detection result by the detection unit becomes equal to or lower than a second predetermined value when the monochrome mode is switched to the color mode. Item 2. The belt device according to Item 1.   The belt device according to claim 2, wherein the second predetermined value is set to a value lower than the predetermined value.   The control is performed so that when the color mode is switched to the single color mode, a single color image is formed even if a detection result by the detection unit is not less than the predetermined value. The belt device according to any one of claims 1 to 3.   When switching from the single color mode to the color mode, control is performed so that a color image is formed even if the detection result by the detection means is not less than or equal to the predetermined value by the operator's selection. The belt device according to any one of claims 1 to 4, wherein:   The belt device according to claim 1, wherein the detection unit detects a displacement amount per unit time in the width direction of the belt member.   An image forming apparatus comprising the belt device according to claim 1.

Images