Patent ID: 12210305

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.

DETAILED DESCRIPTION

In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Referring to drawings, a description is provided of embodiments of the present disclosure.

FIG.1is a schematic cross-sectional view of a printer100serving as an image forming apparatus according to an embodiment of the present disclosure, that is, a color printer that forms a color image by electrophotography.

The printer100includes four image forming units1Y,1M,1C, and1K that form toner images in yellow (Y), magenta (M), cyan (C), and black (K), respectively. The printer100further includes a transfer unit30serving as an intermediate transfer device, a secondary transfer device40, a sheet tray60that loads a plurality of sheets P serving as conveyed objects, recording materials, or recording media, and a fixing device90.

The four image forming units1Y,1M,1C, and1K serving as image forming devices use toners in different colors, that is, yellow, magenta, cyan, and black, as powder developers, respectively. Other than usage of the toners in the different colors, the image forming units1Y,1M,1C, and1K have a common construction. The image forming units1Y,1M,1C, and1K include drum-shaped photoconductors2Y,2M,2C, and2K serving as image bearers, drum cleaners3Y,3M,3C, and3K, dischargers, chargers6Y,6M,6C, and6K, and developing devices8Y,8M.8C, and8K, respectively.

The chargers6Y,6M,6C, and6K uniformly charge surfaces of the photoconductors2Y,2M,2C, and2K, respectively. The printer100further includes an optical writing unit101that is disposed above the image forming units1Y,1M,1C, and1K. The optical writing unit101emits exposure light such as laser beams that optically scan and expose the surfaces of the photoconductors2Y,2M,2C, and2K, forming electrostatic latent images thereon, respectively. The developing devices8Y,8M,8C, and8K containing yellow, magenta, cyan, and black toners develop the electrostatic latent images into yellow, magenta, cyan, and black toner images, respectively. Thus, the photoconductors2Y,2M,2C, and2K bear the yellow, magenta, cyan, and black toner images, respectively. The transfer unit30includes an intermediate transfer belt31serving as an endless belt. The transfer unit30primarily transfers the yellow, magenta, cyan, and black toner images formed on the photoconductors2Y,2M,2C, and2K, respectively, onto an outer circumferential surface (e.g., a front side) of the intermediate transfer belt31.

The transfer unit30serving as the intermediate transfer device is disposed below the image forming units1Y,1M,1C, and1K. The transfer unit30includes the intermediate transfer belt31that is the endless belt stretched and rotated clockwise inFIG.1. According to the embodiment, the outer circumferential surface of the intermediate transfer belt31rotates in a rotation direction a.

In addition to the intermediate transfer belt31, the transfer unit30includes a driving roller32, a secondary transfer backup roller33that contacts an inner circumferential surface of the intermediate transfer belt31, a cleaning backup roller34, four primary transfer rollers35Y,35M,35C, and35K, and a transfer upstream roller37. The intermediate transfer belt31is looped over and stretched taut across the driving roller32, the secondary transfer backup roller33, the cleaning backup roller34, the primary transfer rollers35Y,35M,35C, and35K, and the transfer upstream roller37that support the intermediate transfer belt31. The printer100further includes a driver such as a driving motor that drives and rotates the driving roller32. As the driving roller32rotates clockwise inFIG.1, the driving roller32generates a torque that rotates the intermediate transfer belt31clockwise inFIG.1.

The secondary transfer device40is disposed outside and below a loop formed by the intermediate transfer belt31. The secondary transfer device40includes a secondary transfer belt102that is an endless belt serving as a belt or a transfer belt. The secondary transfer belt102is looped over a plurality of tension rollers including a secondary transfer roller41. The secondary transfer device40further includes a cleaner42and an opposed roller106. The cleaner42cleans a surface of the secondary transfer belt102. The printer100further includes an adhesion amount detection sensor104serving as a detector. The adhesion amount detection sensor104is a reflection type optical sensor. The adhesion amount detection sensor104is disposed opposite the opposed roller106via the secondary transfer belt102. The opposed roller106is one of the tension rollers.

The sheet tray60is disposed below the secondary transfer device40. The sheet tray60is a storage that accommodates the plurality of sheets P layered into a sheaf of sheets P. The sheet tray60includes a roller60athat contacts an uppermost sheet P of the sheaf of sheets P. The printer100further includes a conveyance path65and a registration roller pair61. As the driver drives and rotates the roller60aat a predetermined time, the roller60afeeds the uppermost sheet P from the sheet tray60to the conveyance path65through which the uppermost sheet P is conveyed to a secondary transfer nip N2formed between the intermediate transfer belt31and the secondary transfer belt102. The registration roller pair61feeds the uppermost sheet P conveyed through the conveyance path65to the secondary transfer nip N2at a time when the yellow, magenta, cyan, and black toner images superimposed on the outer circumferential surface of the intermediate transfer belt31reach the secondary transfer nip N2.

The secondary transfer roller41secondarily transfers the yellow, magenta, cyan, and black toner images superimposed on the outer circumferential surface of the intermediate transfer belt31collectively onto the sheet P at the secondary transfer nip N2under pressure in a secondary transfer electric field. The yellow, magenta, cyan, and black toner images transferred onto the sheet P form a full color toner image with a background color of white of the sheet P.

The fixing device90is disposed downstream from the secondary transfer nip N2in a sheet conveyance direction b (e.g., a recording medium conveyance direction). The fixing device90includes a fixing belt94and a plurality of support rollers that supports the fixing belt94. The support rollers include a heating roller91, a fixing roller93, a support roller96, and a tension roller95serving as a tensioner. The fixing device90further includes a pressure roller92that presses against the fixing roller93via the fixing belt94to form a fixing nip between the pressure roller92and the fixing belt94. As the sheet P bearing the full color toner image is conveyed through the fixing device90, the pressure roller92and the fixing belt94that is contacted by the fixing roller93sandwich the sheet P at the fixing nip. As the sheet P receives pressure at the fixing nip and heat conducted from the heating roller91accommodating a heater to the fixing belt94, the pressure roller92and the fixing belt94melt and fix toner of the full color toner image on the sheet P. The sheet P bearing the fixed full color toner image is ejected from the fixing device90onto an outside of the printer100.

FIG.2is a schematic diagram of the secondary transfer device40.

In a description below, X-direction defines a belt width direction of the secondary transfer belt102. Y-direction defines a facing direction in which the adhesion amount detection sensor104is disposed opposite the opposed roller106. Z-direction defines an orthogonal direction perpendicular to X-direction and Y-direction. According to the embodiment, Z-direction defines a vertical direction.

The secondary transfer device40serving as a belt unit further includes a pair of roller support plates109aand109b. Each of the roller support plates109aand109bserves as a roller support that rotatably supports the plurality of tension rollers across which the secondary transfer belt102is stretched taut. The printer100further includes a drawer frame103serving as a support frame that supports the secondary transfer device40. An operator (e.g., a user or a service engineer) draws the drawer frame103from an apparatus body100A of the printer100depicted inFIG.1in X-direction (e.g., the belt width direction).

The drawer frame103includes side plates103aand103bthat mount positioners108and107, respectively, that position the secondary transfer device40. The positioner108disposed opposite one lateral end of the secondary transfer device40in X-direction is a sub reference for positioning. The positioner107disposed opposite another lateral end of the secondary transfer device40in X-direction is a main reference for positioning.

The positioner107, that is disposed opposite another lateral end of the secondary transfer device40in X-direction and serves as the main reference for positioning, includes an insertion hole into which a shaft106aof the opposed roller106, that is disposed at another lateral end of the opposed roller106in X-direction, is inserted. The insertion hole has an inner diameter that is slightly greater than an outer diameter of the shaft106aof the opposed roller106. As the shaft106adisposed at another lateral end of the opposed roller106in X-direction is inserted into the insertion hole of the positioner107disposed opposite another lateral end of the secondary transfer device40in X-direction, the positioner107positions another lateral end of the secondary transfer device40in Y-direction and Z-direction.

The positioner108, that is disposed opposite one lateral end of the secondary transfer device40in X-direction and serves as the sub reference for positioning, includes a groove having a mouth at an upper portion of the groove in the vertical direction. As one end of the shaft106aof the opposed roller106fits into the positioner108disposed opposite one lateral end of the secondary transfer device40in X-direction, the positioner108positions one lateral end of the secondary transfer device40in Y-direction.

The printer100further includes a support123that is mounted on an upper portion of each of the side plates103aand103bof the drawer frame103in +Z-direction. The support123supports a shaft41aof the secondary transfer roller41. The drawer frame103supports the secondary transfer device40through the supports123and the positioners108and107that are disposed opposite one lateral end and another lateral end of the secondary transfer device40in the belt width direction, respectively.

The positioner107disposed opposite another lateral end of the secondary transfer device40in the belt width direction is attached to the side plate103bdisposed at another lateral end of the drawer frame103in the belt width direction such that the positioner107slides in X-direction. As the positioner107disposed opposite another lateral end of the secondary transfer device40in the belt width direction slides in −X-direction, the positioner107releases supporting of the shaft106aof the opposed roller106, thus releasing positioning of the secondary transfer device40. Accordingly, the operator detaches the secondary transfer device40from the drawer frame103and attaches the secondary transfer device40to the drawer frame103in Z-direction (e.g., the vertical direction).

The printer100further includes a sensor unit110that is attached to the drawer frame103. The sensor unit110includes the adhesion amount detection sensor104serving as the detector and a sensor support105serving as a detector support. The adhesion amount detection sensor104is disposed opposite the opposed roller106via the secondary transfer belt102. The adhesion amount detection sensor104includes detection portions104aand a sensor substrate104b. The detection portions104aare disposed at a center and both lateral ends of the adhesion amount detection sensor104in X-direction (e.g., the belt width direction), respectively. The sensor substrate104bmounts the detection portions104a. Each of the detection portions104aincludes a light-emitting element and a light-receiving element. The adhesion amount detection sensor104is placed inside the apparatus body100A in a posture in which light emitted from the light-emitting element travels toward a rotation center O1of the opposed roller106depicted inFIG.3.

Each of the detection portions104areceives reflected light reflected by a detection pattern as a detection object or a toner image that is secondarily transferred from the intermediate transfer belt31onto the secondary transfer belt102. Each of the detection portions104aoutputs a voltage corresponding to a toner adhesion amount (e.g., an image density) of toner of the toner image as the detection pattern. The printer100further includes a controller that detects the toner adhesion amount (e.g., the image density) of toner of the toner image as the detection pattern based on the voltage output by each of the detection portions104a. The controller adjusts an image formation condition such as an exposure condition based on a detection result sent from each of the detection portions104aso that the printer100prints a toner image having a predetermined image density. Thus, according to the embodiment, the secondary transfer belt102serves as a toner image bearer that bears the toner image as the detection pattern.

The controller detects skew of the toner image based on differences between times at which the detection portions104adetect the detection pattern. The controller controls a skew correction mechanism incorporated in the optical writing unit101, thus correcting skew of the toner image.

The sensor support105includes a sensor mount105athat extends in X-direction (e.g., the belt width direction) and mounts the adhesion amount detection sensor104. The sensor support105further includes attachments105band105c(e.g., bearings) that project from both lateral ends of the sensor mount105ain X-direction toward the secondary transfer device40in +Y-direction. The attachment105cis disposed below the secondary transfer device40inFIG.2and disposed opposite another lateral end of the secondary transfer device40in the belt width direction. The printer100further includes a screw120that immovably fastens the attachment105cto the side plate103bdisposed at another lateral end of the drawer frame103in the belt width direction. Conversely, the attachment105bdisposed at one lateral end of the sensor support105in the belt width direction is attached to the side plate103adisposed at one lateral end of the drawer frame103in the belt width direction such that the attachment105bis movable relative to the side plate103a.

A description is provided of a construction of a comparative image forming apparatus.

The comparative image forming apparatus includes a belt unit including an intermediate transfer belt, a skew correction roller, a pivot plate, and a securing plate and a detector unit including a photosensor and a sensor support plate. The intermediate transfer belt serves as a belt. The skew correction roller serves as an opposed roller. The pivot plate serves as a roller support that rotatably supports one lateral end of the skew correction roller. The securing plate serves as a roller support that rotatably supports another lateral end of the skew correction roller. The photosensor serves as a detector. The sensor support plate serves as a detector support that supports the photosensor. The sensor support plate has one lateral end that is mounted on the pivot plate and another lateral end that is mounted on the securing plate.

As the pivot plate pivots in a pivot direction and one lateral end of the skew correction roller moves in the pivot direction of the pivot plate, the skew correction roller tilts and corrects skew of the intermediate transfer belt. As the pivot plate pivots, one lateral end of the sensor support plate moves in the pivot direction of the pivot plate. Accordingly, the sensor support plate tilts like the skew correction roller. Consequently, even if the skew correction roller tilts, the sensor support plate retains a posture of the photosensor with respect to the intermediate transfer belt.

However, the detector unit is attached to the securing plate of the belt unit and coupled with the belt unit. Hence, when an operator removes the belt unit from an apparatus body of the comparative image forming apparatus and installs the belt unit into the apparatus body, the operator unplugs a connector of the photosensor of the detector unit from a connector of the apparatus body and plugs the connector of the photosensor into the connector of the apparatus body. Thus, the operator may not perform removal and installation of the belt unit with respect to the apparatus body easily.

Referring toFIG.3, a description is provided of a construction of the attachment105bdisposed at one lateral end of the sensor support105in the belt width direction.

FIG.3has sections (a), (b), and (c). The sections (a) and (c) illustrate the attachment105bwhen the opposed roller106is not inclined. The section (b) illustrates the attachment105bwhen the opposed roller106is inclined in Z-direction (e.g., the vertical direction) and Y-direction (e.g., a facing direction in which the adhesion amount detection sensor104is disposed opposite the secondary transfer belt102).

The attachment105bdisposed at one lateral end of the sensor support105in the belt width direction includes a supported hole105d, that is, a slot or an elongated hole elongated in Y-direction. As illustrated inFIG.2, the printer100further includes a support projection113that projects from the side plate103adisposed at one lateral end of the drawer frame103in the belt width direction. As illustrated inFIG.3, the support projection113penetrates through the supported hole105d. As illustrated inFIG.2, the printer100further includes a spring116serving as a biasing member. The spring116has one end that is anchored to the side plate103adisposed at one lateral end of the drawer frame103in the belt width direction. As illustrated inFIG.3, the spring116has another end that is attached to a front end of the attachment105bdisposed at one lateral end of the sensor support105in the belt width direction. Accordingly, the support projection113and the spring116move the attachment105bdisposed at one lateral end of the sensor support105in the belt width direction relative to the side plate103adisposed at one lateral end of the drawer frame103in the belt width direction in a predetermined range in Y-direction. The attachment105bis attached to the drawer frame103through the support projection113and the spring116such that the attachment105bpivots about X-axis relative to the drawer frame103.

The sensor mount105aof the sensor support105is an elongated plate that has a thickness in Y-direction and is elongated in X-direction. The sensor mount105adeforms resiliently under torsion about X-axis. Since the sensor support105is shaped as described above, the sensor mount105aalso deforms resiliently about another lateral end of the sensor mount105ain the belt width direction such that the sensor mount105atilts in Y-direction. The sensor mount105aholds the adhesion amount detection sensor104that is mainly constructed of the sensor substrate104bthat is elongated in the belt width direction. The adhesion amount detection sensor104is mounted on the sensor mount105asuch that a thickness direction of the sensor substrate104bis parallel to Y-direction. Hence, the adhesion amount detection sensor104also deforms resiliently under torsion about X-axis.

The attachment105bdisposed at one lateral end of the sensor support105in the belt width direction includes an engaging groove115disposed in the front end of the attachment105b. The engaging groove115has a mouth115bthat is disposed at an upper portion of the engaging groove115in the vertical direction. One lateral end of the shaft106aof the opposed roller106, that penetrates through the roller support plate109aand is exposed to an outside of the secondary transfer device40, engages the engaging groove115. The spring116biases the front end of the attachment105bdisposed at one lateral end of the sensor support105in the belt width direction upward in the vertical direction (e.g., +Z-direction). The spring116generates a biasing force that presses a lower portion of the engaging groove115against the shaft106aof the opposed roller106. The biasing force of the spring116is greater than a force that deforms the sensor mount105aresiliently under torsion. Accordingly, if the shaft106adisposed at one lateral end of the opposed roller106in the belt width direction is shifted upward in the vertical direction, the sensor mount105adeforms resiliently under torsion about X-axis, fitting the engaging groove115to the shaft106a.

As illustrated inFIG.4, one lateral end of the secondary transfer device40in the belt width direction, that is installed inside the apparatus body100A, may be twisted in a direction A relative to another lateral end of the secondary transfer device40in the belt width direction by a manufacturing error or the like. In this case, the opposed roller106may tilt in Z-direction and Y-direction. If the opposed roller106tilts in Y-direction, a distance between the adhesion amount detection sensor104and the secondary transfer belt102may be uneven in X-direction (e.g., the belt width direction), degrading detection accuracy of the adhesion amount detection sensor104. If the opposed roller106tilts in Z-direction, a posture of the adhesion amount detection sensor104with respect to the secondary transfer belt102may vary in X-direction. Accordingly, the light-emitting element of at least one of the detection portions104amay emit light that does not travel to the rotation center O1depicted inFIG.3of the opposed roller106. Consequently, the light emitted from the light-emitting element of the at least one of the detection portions104aonto an outer circumferential surface of the secondary transfer belt102may have an incident angle that is deviated from a target incident angle in a rotation direction of the secondary transfer belt102. Thus, the adhesion amount detection sensor104may suffer from degradation in detection accuracy.

According to the embodiment, if the opposed roller106tilts in Y-direction and one lateral end of the opposed roller106in X-direction shifts from another lateral end of the opposed roller106in X-direction by a length α in a unit of mm in Y-direction as illustrated in the section (b) ofFIG.3, the sensor support105tilts in accordance with a tilt of the opposed roller106as described below. For example, the engaging groove115of the attachment105bdisposed at one lateral end of the sensor support105in X-direction engages the shaft106aof the opposed roller106. Hence, the engaging groove115is subject to shifting by the length α in the unit of mm in Y-direction together with the shaft106a. The attachment105bdisposed at one lateral end of the sensor support105in X-direction is movable in Y-direction relative to the side plate103adisposed at one lateral end of the drawer frame103in X-direction. Accordingly, the engaging groove115moves in Y-direction by the length α in the unit of mm in accordance with motion of one lateral end of the opposed roller106in X-direction. The sensor support105deforms resiliently about another lateral end of the sensor mount105aas a reference point. The sensor mount105atilts in Y-direction in accordance with motion of the opposed roller106. Accordingly, one lateral end of the adhesion amount detection sensor104in the belt width direction that is mounted on the sensor mount105ashifts with respect to another lateral end of the adhesion amount detection sensor104in the belt width direction by the length α in the unit of mm in a direction B depicted inFIG.4. Consequently, the adhesion amount detection sensor104tilts in accordance with motion of the opposed roller106, thus retaining a constant distance between each of the detection portions104aand the secondary transfer belt102.

If the opposed roller106tilts in Z-direction and one lateral end of the opposed roller106in X-direction shifts from another lateral end of the opposed roller106in X-direction by a length β in a unit of mm in Z-direction as illustrated in the section (b) ofFIG.3, the adhesion amount detection sensor104twists about X-axis in a direction C depicted inFIG.4together with the sensor support105as described below. For example, as the engaging groove115that engages the shaft106aof the opposed roller106shifts by the length β in the unit of mm in Z-direction, the attachment105bdisposed at one lateral end of the sensor support105in X-direction pivots about the support projection113as a fulcrum in γ-direction depicted in the section (b) ofFIG.3. The sensor substrate104bof the adhesion amount detection sensor104deforms resiliently under torsion about X-axis together with the sensor mount105a. Accordingly, the sensor substrate104bsuppresses change of a posture of each of the detection portions104aof the adhesion amount detection sensor104with respect to the secondary transfer belt102. Consequently, the sensor substrate104bprevents the light emitted from the light-emitting element of each of the detection portions104afrom travelling to a position deviating from the rotation center O1of the opposed roller106and prevents the incident angle at which the light emitted from the light-emitting element of each of the detection portions104atravels onto the outer circumferential surface of the secondary transfer belt102from deviating from the target incident angle.

As described above, according to the embodiment, even if the opposed roller106tilts in Y-direction and Z-direction due to the manufacturing error or the like, the adhesion amount detection sensor104retains detection accuracy.

According to the embodiment, as illustrated inFIG.2, the sensor unit110is mounted on the drawer frame103of the apparatus body100A. As illustrated inFIG.3, the engaging groove115has the mouth115bthat is disposed at the upper portion of the engaging groove115in the vertical direction. As one end of the shaft106aof the opposed roller106moves in the vertical direction (e.g., +Z-direction), the engaging groove115disengages the shaft106a. Accordingly, the operator removes and installs the secondary transfer device40with respect to the apparatus body100A while the sensor unit110remains inside the apparatus body100A and is mounted on the drawer frame103.

For example, in order to remove the secondary transfer device40from the apparatus body100A, the operator draws the drawer frame103from the apparatus body100A. Subsequently, the operator slides the positioner107disposed opposite another lateral end of the secondary transfer device40in the belt width direction, releasing positioning and supporting of the shaft106aof the opposed roller106by the positioner107. Thus, no element restricts upward motion of the secondary transfer device40in the vertical direction. Hence, as the operator moves the secondary transfer device40upward in the vertical direction, the operator removes the secondary transfer device40from the apparatus body100A in a state in which the sensor unit110is left inside the apparatus body100A.

If the sensor unit110is secured to the secondary transfer device40, when the operator removes the secondary transfer device40from the apparatus body100A or detaches the secondary transfer device40from the drawer frame103, the operator unplugs the connector that electrically connects the adhesion amount detection sensor104with the apparatus body100A. Thus, the operator may suffer from a disadvantage of degradation in removal and installation of the secondary transfer device40with respect to the apparatus body100A. Additionally, the sensor unit110secured to the secondary transfer device40may cause a disadvantage of increased costs for manufacturing, replacement, and maintenance of the secondary transfer device40. Further, in order to reuse the secondary transfer device40, the operator may suffer from a disadvantage of an additional process for detaching the sensor unit110from the secondary transfer device40.

To address the disadvantages described above, according to the embodiment, the operator removes the secondary transfer device40from the apparatus body100A or detaches the secondary transfer device40from the drawer frame103while the sensor unit110is left inside the apparatus body100A. Accordingly, in order to remove the secondary transfer device40from the apparatus body100A, the operator does not unplug the connector that electrically connects the adhesion amount detection sensor104with the apparatus body100A. Thus, the operator removes the secondary transfer device40from the apparatus body100A readily. Additionally, after the operator installs the secondary transfer device40into the apparatus body100A, the operator does not connect the connector of the adhesion amount detection sensor104with the connector of the apparatus body100A. Thus, the operator installs the secondary transfer device40with improved efficiency.

Compared to a configuration in which the sensor unit110is secured to the secondary transfer device40, the secondary transfer device40that is separable from the sensor unit110reduces costs. For example, the secondary transfer device40is replaced at reduced costs, resulting in reduced maintenance costs. The secondary transfer device40is reused with reduced processes.

According to the embodiment, the engaging groove115has the mouth115bthat is disposed at the upper portion of the engaging groove115in the vertical direction. Hence, when the operator removes the secondary transfer device40from the apparatus body100A, the operator does not disengage the opposed roller106from the engaging groove115. Thus, the operator removes the secondary transfer device40from the apparatus body100A readily.

According to the embodiment, as illustrated in the section (a) ofFIG.3, the engaging groove115further includes taper portions115aserving as guides. The taper portions115aabut on the mouth115band widen the mouth115bgradually upward in the vertical direction. Hence, as illustrated inFIG.5, when the operator attaches the secondary transfer device40to the drawer frame103of the apparatus body100A, the taper portions115aguide the shaft106aof the opposed roller106to the engaging groove115. Accordingly, the shaft106aof the opposed roller106engages the engaging groove115readily. Thus, the operator installs the secondary transfer device40into the apparatus body100A readily.

As illustrated inFIG.2, according to the embodiment, the attachment105cdisposed at another lateral end of the sensor support105of the sensor unit110in X-direction is secured to the side plate103bdisposed at another lateral end of the drawer frame103in X-direction. The side plate103bpositions another lateral end of the opposed roller106in X-direction (e.g., the belt width direction) in Y-direction and Z-direction. Accordingly, the attachment105cpositions another lateral end of the adhesion amount detection sensor104in X-direction with respect to the secondary transfer belt102at a target position precisely.

As illustrated inFIG.2, the positioner108disposed opposite one lateral end of the secondary transfer device40in X-direction positions one lateral end of the opposed roller106in X-direction (e.g., the belt width direction) in Y-direction. Accordingly, the opposed roller106tilts in Y-direction in a decreased amount. Hence, the decreased amount of a tilt of the opposed roller106in Y-direction may be neglectable according to a target detection accuracy. In this case, as illustrated inFIG.6A, a sensor support105A including an attachment105bA having a supported hole105dA may be employed. The supported hole105dA is a round hole through which the support projection113penetrates. The attachment105bA disposed at one lateral end of the sensor support105A in X-direction pivots about X-axis relative to the drawer frame103.

As illustrated inFIG.6B, a sensor support105B including a sensor mount105aB and an attachment105bB may be employed. The sensor mount105aB is a plate that is perpendicular to Z-direction (e.g., the vertical direction). The attachment105bB includes a supported hole105dB that is an elongated hole elongated in the vertical direction. The attachment105bB disposed at one lateral end of the sensor support105B in X-direction moves in the vertical direction relative to the side plate103a. Accordingly, when the opposed roller106tilts in Z-direction, the sensor support105B deforms resiliently about another lateral end of the sensor mount105aB in X-direction (e.g., the belt width direction). The sensor mount105aB tilts in Z-direction in accordance with motion of the opposed roller106. Accordingly, even if the opposed roller106tilts in Z-direction, the attachment105bB causes light emitted from the light-emitting element of each of the detection portions104ato travel to the rotation center O1of the opposed roller106, preventing the incident angle at which the light emitted from the light-emitting element of each of the detection portions104atravels onto the outer circumferential surface of the secondary transfer belt102from deviating from the target incident angle.

If another lateral end of the opposed roller106in X-direction is not positioned, the attachment105cdisposed at another lateral end of the sensor support105may preferably employ a construction similar to the construction of the attachment105bdisposed at one lateral end of the sensor support105in X-direction illustrated inFIG.3.

According to the embodiment, the adhesion amount detection sensor104is disposed opposite the secondary transfer belt102. Alternatively, the adhesion amount detection sensor104may be disposed opposite the intermediate transfer belt31. The sensor support105of the sensor unit110, that supports the adhesion amount detection sensor104disposed opposite the intermediate transfer belt31, is configured as described above. Thus, the adhesion amount detection sensor104detects the toner adhesion amount of toner of the detection pattern on the intermediate transfer belt31precisely. Additionally, the operator removes the transfer unit30serving as the intermediate transfer device from the apparatus body100A while the sensor unit110is left inside the apparatus body100A.

The detector incorporated in the sensor unit110may be a surface detection sensor that detects a condition of a surface of a belt or a temperature sensor that detects a temperature of the surface of the belt as a condition of the surface of the belt. Hence, for example, the technology of the present disclosure may be applied to a temperature detector unit that detects a temperature of the fixing belt94. As the temperature detector unit that detects the temperature of the fixing belt94is applied with the technology of the present disclosure, the temperature detector unit detects the temperature of the fixing belt94in a belt width direction thereof precisely. Additionally, in a state in which the temperature detector unit is left inside the fixing device90, the operator removes a fixing belt unit incorporating the fixing belt94from the fixing device90and installs the fixing belt unit into the fixing device90.

The embodiments described above are examples and achieve advantages peculiar to aspects below, respectively.

A description is provided of a first aspect of the technology of the present disclosure.

As illustrated inFIGS.1,2, and3, an image forming apparatus (e.g., the printer100) includes an apparatus body (e.g., the drawer frame103of the apparatus body100A), a belt unit (e.g., the secondary transfer device40), and a detector unit (e.g., the sensor unit110). The belt unit includes a plurality of tension rollers, for example, a first tension roller (e.g., the opposed roller106) and a second tension roller (e.g., the secondary transfer roller41), a belt (e.g., the secondary transfer belt102), and a roller support (e.g., the roller support plates109aand109b). The detector unit includes a detector (e.g., the adhesion amount detection sensor104) and a detector support (e.g., the sensor supports105,105A, and105B).

The first tension roller and the second tension roller, that rotate, stretch and support the belt. Thus, the belt is stretched across the first tension roller and the second tension roller. The roller support rotatably supports the first tension roller and the second tension roller. The detector is disposed opposite the first tension roller (e.g., the opposed roller106) as one of the plurality of tension rollers via the belt. The detector detects a condition of a belt surface of the belt or a condition of a detection object (e.g., a toner adhesion amount of toner of a detection pattern) on the belt surface of the belt. The detector support supports the detector. The first tension roller includes a shaft (e.g., the shaft106a) that is disposed at one lateral end of the first tension roller in an axial direction thereof, that is parallel to a belt width direction of the belt.

The belt unit is attachably detached from the apparatus body in a detaching direction, that is, an orthogonal direction perpendicular to the belt width direction of the belt. For example, the belt unit is attached in an attaching direction as the orthogonal direction and detached in the detaching direction as the orthogonal direction with respect to the apparatus body. The detector support of the detector unit includes both lateral ends in the belt width direction, that are attached to the apparatus body. For example, the detector support includes a first lateral end portion (e.g., the attachments105b,105bA, and105bB) that is disposed at one lateral end of the detector support in the axial direction of the first tension roller, that is parallel to the belt width direction of the belt, and attached to the apparatus body (e.g., the drawer frame103). The detector support further includes a second lateral end portion (e.g., the attachment105c) that is disposed at another lateral end of the detector support in the axial direction of the first tension roller, that is parallel to the belt width direction of the belt, and attached to the apparatus body (e.g., the drawer frame103). The first lateral end portion is attached to the apparatus body (e.g., the drawer frame103) such that the first lateral end portion is movable with respect to the apparatus body. At least the first lateral end portion of the detector support includes an engaging groove (e.g., the engaging groove115) that engages the shaft of the first tension roller. The shaft penetrates through the roller support. The engaging groove has a mouth (e.g., the mouth115b) that is disposed at a downstream end of the engaging groove in the detaching direction (e.g., Z-direction) in which the belt unit is detached from the apparatus body.

According to the first aspect, the image forming apparatus has a configuration described below. Hence, even if the first tension roller (e.g., the opposed roller106) tilts, the first lateral end portion of the detector support prevents a posture of the detector from shifting with respect to the belt. For example, at least the first lateral end portion of the detector support in the belt width direction includes the engaging groove that engages the shaft disposed at one lateral end of the first tension roller in the belt width direction. At least the first lateral end portion of the detector support in the belt width direction is attached to the apparatus body such that the first lateral end portion is movable relative to the apparatus body. Since the first lateral end portion is movably attached to the apparatus body, when the first tension roller tilts and the shaft of the first tension roller, that is disposed at one lateral end of the first tension roller in the belt width direction, shifts from a shaft of the first tension roller, that is disposed at another lateral end of the first tension roller in the belt width direction, the engaging groove that engages the shaft of the first tension roller moves in a shift direction in which the shaft shifts. Accordingly, the detector support tilts similarly to the first tension roller, retaining the posture of the detector with respect to the belt. Thus, the detector support prevents a distance from the detector to the belt surface of the belt from varying between positions on the belt surface, that are arranged in the belt width direction. The detector support also prevents an incident angle at which light emitted from the detector travels onto the belt surface of the belt from varying between the positions on the belt surface, that are arranged in the belt width direction. Accordingly, the detector detects the condition of the belt surface of the belt or the condition of the detection object such as the detection pattern on the belt surface of the belt properly.

According to the first aspect, the detector unit is attached to the apparatus body. The engaging groove has the mouth that is disposed at the downstream end of the engaging groove in the detaching direction in which the belt unit is detached from the apparatus body. Hence, as the operator detaches the belt unit in the detaching direction in which the belt unit is detached from the apparatus body, the engaging groove disengages the shaft disposed at one lateral end of the first tension roller in the belt width direction. Thus, the operator detaches the belt unit from the apparatus body in a state in which the detector unit is left inside the apparatus body. Accordingly, when the operator performs attachment and detachment of the belt unit with respect to the apparatus body, the operator does not disconnect and connect a connector of the detector of the detector unit with respect to a connector of the apparatus body. Thus, the operator performs attachment and detachment of the belt unit with respect to the apparatus body readily.

A description is provided of a second aspect of the technology of the present disclosure.

According to the second aspect based on the first aspect, at least the first lateral end portion of the detector support (e.g., the sensor support105) in the belt width direction moves in a facing direction in which the detector (e.g., the adhesion amount detection sensor104) is disposed opposite the first tension roller (e.g., the opposed roller106). The first lateral end portion of the detector support is attached to the apparatus body such that the first lateral end portion is pivotable about an axis that is parallel to the belt width direction. The detector support further includes a detector mount (e.g., the sensor mounts105aand105aB) that is elongated in the belt width direction and mounts the detector (e.g., the adhesion amount detection sensor104). The detector mount is deformable resiliently under torsion about the axis that is parallel to the belt width direction.

Accordingly, as described above, if the first tension roller tilts in the facing direction (e.g., Y-direction), the first lateral end portion of the detector support (e.g., the sensor support105) moves in the facing direction according to a shift amount of a shift in the facing direction of one lateral end of the first tension roller in the belt width direction with respect to another lateral end of the first tension roller in the belt width direction. Accordingly, the detector support tilts in the facing direction in accordance with the shift of the first tension roller, preventing a distance from the detector to the belt from varying between positions arranged on the belt in the belt width direction.

If the first tension roller tilts in an orthogonal direction (e.g., Z-direction) perpendicular to the facing direction (e.g., Y-direction) and the belt width direction (e.g., X-direction), the detector mount (e.g., the sensor mount105a) of the detector support deforms resiliently under torsion about the axis that is parallel to the belt width direction. The detector supported by the detector support includes a plurality of detection portions (e.g., the detection portions104a) arranged in the belt width direction. Each of the detection portions has an opposed face that is disposed opposite the belt surface of the belt. The detector retains a posture with which a line extending perpendicularly from a center of the opposed face passes through a rotation center (e.g., the rotation center O1) of the first tension roller. Accordingly, the detector support prevents the incident angle at which light emitted from the detector travels onto the belt surface from deviating from a target incident angle. Consequently, the detector detects the condition of the belt surface of the belt or the condition of the detection object (e.g., the toner adhesion amount of toner of the detection pattern) on the belt surface of the belt properly.

Accordingly, even if the first tension roller tilts in any manner, the detector detects the condition of the belt surface of the belt or the condition of the detection object (e.g., the toner adhesion amount of toner of the detection pattern) on the belt surface of the belt precisely.

A description is provided of a third aspect of the technology of the present disclosure.

According to the third aspect based on the first aspect or the second aspect, the image forming apparatus further includes a biasing member (e.g., the spring116) that biases the engaging groove (e.g., the engaging groove115) in the detaching direction of the belt unit.

Accordingly, as described above in the embodiment, even if one lateral end of the first tension roller (e.g., the opposed roller106) in the belt width direction shifts with respect to another lateral end of the first tension roller in the belt width direction in the detaching direction in which the belt unit (e.g., the secondary transfer device40) is detached from the apparatus body, the biasing member (e.g., the spring116) generates a biasing force that moves the engaging groove in a shift direction in which one lateral end of the first tension roller in the belt width direction shifts. Accordingly, the biasing member prevents the shaft of the first tension roller from falling off the engaging groove. Additionally, the biasing member adjusts the posture of the detector according to a tilt of the first tension roller in the detaching direction of the belt unit. Thus, the detector detects the condition of the belt surface of the belt or the condition of the detection object (e.g., the toner adhesion amount of toner of the detection pattern) on the belt surface of the belt properly.

A description is provided of a fourth aspect of the technology of the present disclosure.

According to the fourth aspect based on any one of the first aspect to the third aspect, the first tension roller further includes another shaft (e.g., the shaft106a) that is disposed at another lateral end of the first tension roller in the belt width direction. The another shaft penetrates through the roller support (e.g., the roller support plate109b). The image forming apparatus further includes a positioner (e.g., the positioner107) that is mounted on the apparatus body. The positioner positions the another shaft with respect to the apparatus body in the facing direction (e.g., Y-direction) in which the detector is disposed opposite the first tension roller and the detaching direction (e.g., Z-direction) of the belt unit. The second lateral end portion of the detector support in the belt width direction is secured to the apparatus body. For example, the image forming apparatus further includes a fastener (e.g., the screw120) that fastens the second lateral end portion to the apparatus body.

Accordingly, as described in the embodiment, the another shaft disposed at another lateral end of the first tension roller in the belt width direction is positioned in the facing direction (e.g., Y-direction) and the detaching direction (e.g., Z-direction). Hence, the another shaft does not shift in the facing direction (e.g., Y-direction) and the detaching direction (e.g., Z-direction). Accordingly, as the second lateral end portion of the detector support in the belt width direction is secured to the apparatus body, the detection portion (e.g., the detection portion104a) disposed at another lateral end of the detector in the belt width direction retains a target distance between the detection portion and the belt surface of the belt and retains a target posture with respect to the belt.

A description is provided of a fifth aspect of the technology of the present disclosure.

According to the fifth aspect based on any one of the first aspect to the fourth aspect, the detector support (e.g., the sensor support105) further includes a guide (e.g., the taper portion115a) that guides the shaft of the first tension roller to the engaging groove.

Accordingly, as described in the embodiment, the guide causes the shaft of the first tension roller to engage the engaging groove readily, facilitating attachment of the belt unit (e.g., the secondary transfer device40) to the apparatus body.

A description is provided of a sixth aspect of the technology of the present disclosure.

According to the sixth aspect based on any one of the first aspect to the fifth aspect, the belt is an image bearing belt that bears a toner image. The detector detects the toner image on the image bearing belt.

Accordingly, as described in the embodiment, the detector detects the toner image precisely.

A description is provided of a seventh aspect of the technology of the present disclosure.

According to the seventh aspect based on the sixth aspect, the image bearing belt is an intermediate transfer belt (e.g., the intermediate transfer belt31) onto which the toner image formed on an image bearer (e.g., the photoconductors2Y,2M,2C, and2K) is transferred intermediately.

Accordingly, the detector detects the toner image on the intermediate transfer belt precisely.

A description is provided of an eighth aspect of the technology of the present disclosure.

According to the eighth aspect based on the sixth aspect, the image bearing belt is a secondary transfer belt (e.g., the secondary transfer belt102). The secondary transfer belt is disposed opposite a primary transfer belt (e.g., the intermediate transfer belt31) onto which the toner image on the image bearer is transferred.

Accordingly, the detector detects the toner image as the detection pattern borne on the secondary transfer belt precisely.

According to the embodiments described above, the printer100serves as an image forming apparatus. Alternatively, the image forming apparatus may be a copier, a facsimile machine, a multifunction peripheral (MFP) having at least two of copying, printing, scanning, facsimile, and plotter functions, or the like.

The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.