Monochromatic imaging device

Abstract

The present invention relates to a monochromatic imaging device. A control section controls a change mechanism so as to pass through a third tension form when switching the tension form of a belt member from a second tension form to a first tension form. The first tension form is a tension form capable of transferring a toner image from a photosensitive drum to the belt member by positioning a transfer member at a first position and positioning a separation roller at a second position. The second tension form is a tension form that separates each of the transfer member and the separation roller from the transfer surface to the opposite side of the photosensitive drum. The third tension form is a tension form in which the transfer member is positioned at the first position and the separation roller is positioned at a third position away from the transfer surface toward the opposite side of the photosensitive drum.

Description

Technical Field

[0001] The present invention relates to an imaging apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction printer having a plurality of these functions, and more particularly to a monochromatic imaging apparatus. Background Art

[0002] Hitherto, in an electrophotographic type imaging apparatus, an intermediate transfer system configuration is known, which primarily transfers a toner image from an image carrier member (e.g., a photosensitive drum) to an intermediate transfer belt (i.e., a belt member) and secondarily transfers the toner image from the intermediate transfer belt to a recording material. Further, for example, in Japanese Patent Application Laid-Open No. 2014-232130, a configuration is proposed in which a full-color image is formed by using a plurality of imaging units and a monochromatic image is formed by removing a color imaging unit from the plurality of imaging units and using only a black imaging unit in a configuration having a plurality of imaging units.

[0003] In a configuration capable of forming a full-color image and a monochromatic image as described in the above-mentioned Japanese Patent Application Laid-Open No. 2014-232130, in addition to a configuration for installing and removing a color imaging unit, there is also a configuration in which the intermediate transfer belt is brought into contact with or separated from the image carrier member when all imaging units are installed. When the intermediate transfer belt is tensioned by a plurality of tension rollers, one of the tension rollers is set as a movable separation roller for bringing the intermediate transfer belt into contact with or separating the intermediate transfer belt from the image carrier member by moving the separation roller. For example, in the case of forming a full-color image, the separation roller is moved so that the intermediate transfer belt comes into contact with all image carrier members (this state will be hereinafter referred to as "the first tension cross section"). At the same time, in the case of forming only a monochromatic image, the separation roller is moved so that the intermediate transfer belt comes into contact only with the black image carrier member and is separated from other image carrier members (this state will be hereinafter referred to as "the second tension cross section").

[0004] In the case of forming a monochromatic image by setting the tension cross section of the intermediate transfer belt to the second tension cross section by removing the color imaging unit as in Japanese Patent Application Laid-Open No. 2014-232130, the tension of the intermediate transfer belt becomes lower than that in the case of the first tension cross section. Therefore, the image quality of the image to be transferred to the recording material is likely to deteriorate due to the impact caused when the recording material enters the secondary transfer portion where the toner image is transferred from the intermediate transfer belt to the recording material.

[0005] Accordingly, it is contemplated to form an image by setting a first tension section in a monochromatic imaging device. At the same time, there is a case where each primary transfer roller is separated from the intermediate transfer belt when an image is not formed (this state will be hereinafter referred to as the "fully separated mode" or "third tension section"). Such an arrangement makes it possible to suppress the friction between the intermediate transfer belt and the photosensitive drum when replacing the intermediate transfer belt. It is also possible to suppress the curling of the intermediate transfer belt by releasing the tension of the intermediate transfer belt. However, in the case of the arrangement of switching the intermediate transfer belt from the third tension section to the first tension section, the following problem occurs. That is, when switching from the third tension section to the first tension section as an image is formed, the torque of the motor increases. SUMMARY OF THE INVENTION

[0006] The present invention provides a monochromatic imaging device capable of suppressing a decrease in the image quality of an image to be transferred while suppressing an increase in torque when changing the tension shape of an intermediate transfer belt as the imaging operation changes.

[0007] According to one aspect of the present invention, a monochromatic imaging device includes: a single photosensitive drum configured to carry a toner image; a belt member to which the toner image formed on the photosensitive drum is transferred; a transfer member configured to transfer the toner image from the photosensitive drum to the belt member; a plurality of tension rollers that tension the belt member, the plurality of tension rollers including a separation roller movably provided upstream of the transfer member and adjacent to the transfer member in the rotational direction of the belt member; a changing mechanism configured to change the tension shape of the belt member by changing the positions of the transfer member and the separation roller, the changing mechanism being configured to switch the tension form of the belt member to a plurality of tension forms including a first tension form, a second tension form, and a third tension form, the first tension form being a tension form capable of transferring the toner image from the photosensitive drum to the belt member by forming a transfer surface between the transfer member and the separation roller by positioning the transfer member at a first position and positioning the separation roller at a second position, the second tension form being a tension form in which each of the transfer member and the separation roller is separated from the transfer surface to the opposite side of the photosensitive drum, the third tension form being a tension form in which the transfer member is positioned at the first position and the separation roller is positioned at a third position away from the transfer surface toward the opposite side of the photosensitive drum; and a control section configured to control the changing mechanism. The control section is configured to control the changing mechanism so as to pass through the third tension form when switching the tension form of the belt member from the second tension form to the first tension form.

[0008] Other features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional view schematically illustrating the configuration of the full-color imaging device of the exemplary embodiment.

[0010] Figure 2 It is a cross-sectional view schematically showing the structure of the monochromatic imaging device of the present exemplary embodiment.

[0011] Figure 3A It is a perspective view showing the full-color intermediate transfer unit.

[0012] Figure 3B It is a perspective view showing the full-color intermediate transfer unit from which the intermediate transfer belt has been removed.

[0013] Figure 4 It is a perspective view showing the belt automatic alignment mechanism.

[0014] Figure 5 It is an enlarged perspective view showing the end portion of the belt automatic alignment mechanism.

[0015] Figure 6A It is a schematic view showing the belt winding area in the belt stable state.

[0016] Figure 6B It is a schematic view showing the belt winding area in the state where the belt is offset.

[0017] Figure 7 It is a schematic view showing the separation slider of the present exemplary embodiment.

[0018] Figure 8A It is a schematic view showing the state of the separation mechanism in the full-color intermediate transfer unit in the full-color mode.

[0019] Figure 8B It is a schematic view showing the state of the separation mechanism in the full-color intermediate transfer unit in the separated monochromatic mode.

[0020] Figure 8C It is a schematic view showing the state of the separation mechanism in the full-color intermediate transfer unit in the fully separated mode.

[0021] Figure 9 It is a schematic cross-sectional view showing the structure for installing / removing the intermediate transfer unit to / from the device main body.

[0022] Figure 10A It is a perspective view showing the monochromatic intermediate transfer unit.

[0023] Figure 10B It is a perspective view showing the monochromatic intermediate transfer unit from which the intermediate transfer belt has been removed.

[0024] Figure 11A It is a schematic view showing the state of the separation mechanism in the monochromatic intermediate transfer unit in the monochromatic mode.

[0025] Figure 11BIt is a schematic diagram showing the state of the separation mechanism in the monochromatic intermediate transfer unit in the complete separation mode. Detailed implementation

[0026] Reference will be made to Figures 1 to 11B to describe the exemplary embodiments. In this exemplary embodiment, Figure 1 the full-color imaging device 200 configured to form an image with toner of multiple colors and Figure 2 the basic structure or at least a part of the monochromatic imaging device 200K in Figure 1 the full-color imaging device 200 used as Figure 2 the intermediate transfer unit 20 of the belt transfer unit used in Figure 1 is the same as the basic structure of the intermediate transfer unit 20K of the belt transfer unit used in the monochromatic imaging device 200K as

[0027] Full-color imaging device

[0028] The full-color imaging device 200 as the first imaging device is a so-called intermediate transfer cascade type printer, which includes four imaging units Pa, Pb, Pc, and Pd and an intermediate transfer unit 20 in the device main body. Note that the number of imaging units, that is, the number of multiple second image-bearing members, is not limited to the above number and can be any plural number of two or more. The device main body is composed of a housing 201 (i.e., the main body frame) configured to support the imaging units Pa, Pb, Pc, and Pd and the intermediate transfer unit 20, a decorative cover (not shown), and the like.

[0029] The full-color imaging device 200 is configured to form and output an image on the recording material S based on the image information read from the manuscript or the image information input from an external device. Note that in addition to ordinary paper sheets, the recording material S also includes special sheets such as coated sheets, special-shaped sheets such as envelopes and index sheets, sheets such as plastic films for overhead projectors, and cloth.

[0030] The imaging units Pa, Pb, Pc, and Pd as multiple second imaging units are configured to form toner images of yellow, magenta, cyan, and black, and include photosensitive drums 1a, 1b, 1c, and 1d as electrophotographic second image-bearing members respectively. Since the structure of each imaging unit is basically the same except for the color of the toner used for image development, the structure of the yellow imaging unit Pa will be described by way of example below.

[0031] The imaging unit Pa includes a charging unit 2, an exposure unit 3, a developing unit 4, and a drum cleaner 6 arranged around a photosensitive drum 1a which is a drum-shaped photosensitive member. When the imaging operation starts, the photosensitive drum 1a is rotationally driven to uniformly charge the surface of the photosensitive drum 1a by the charging unit 2, and then an electrostatic latent image is formed on the drum surface by the exposure unit 3. The electrostatic latent image formed on the photosensitive drum 1a is visualized as a toner image by the yellow toner supplied from the developing unit 4, and the developing unit stores a developer in a developing container 41. That is, the charging unit 2, the exposure unit 3, and the developing unit 4 constitute a toner image forming unit for forming a toner image on the photosensitive drum 1a which is a second image bearing member.

[0032] Note that the developer storage containers Ta, Tb, Tc, and Td for storing the developer to be replenished are removably mounted on the housing 201. For example, the developer storage container Ta stores a developer containing a yellow toner to be appropriately replenished to the developer container 41 by the replenishing unit 70a. As the developer, a two-component developer containing a magnetic carrier and a non-magnetic toner, a one-component developer containing a magnetic toner, or a liquid developer in which toner particles are dispersed in a carrier liquid can be used.

[0033] The intermediate transfer unit 20 as a second intermediate transfer unit includes an intermediate transfer belt 7 (which is an annular second belt member), and a plurality of tension rollers as tension members, and the intermediate transfer belt 7 is tensioned by these tension rollers. Specifically, the intermediate transfer belt 7 is wound around second tension rollers (i.e., a secondary transfer inner roller 8, a turning roller 17, a separating roller 19, and an upstream guide roller 18) such that the outer peripheral surface of the intermediate transfer belt 7 faces the photosensitive drums 1a to 1d of the imaging units Pa to Pd.

[0034] Arranged on the inner peripheral side of the intermediate transfer belt 7 are primary transfer rollers 5a, 5b, 5c, and 5d (which are used as a plurality of transfer members) as an example of a primary transfer unit. The primary transfer rollers 5a to 5d are arranged at positions corresponding to the photosensitive drums 1a to 1d of the imaging units Pa to Pd respectively to form primary transfer portions T1a, T1b, T1c, and T1d where the toner images are transferred from the photosensitive drums 1a to 1d onto the intermediate transfer belt 7.

[0035] As the secondary transfer inner roller 8 as a secondary transfer roller is rotationally driven in a predetermined direction indicated by an arrow R8 (not shown) by a motor, along with the rotation of the photosensitive drums 1a to 1d indicated by arrows R1, R2, R3, and R4, the intermediate transfer belt 7 rotates in the direction indicated by an arrow R7. That is, the secondary transfer inner roller 8 also serves as a driving roller for rotationally driving the intermediate transfer belt 7. Figure 1

[0036] ​With respect to the rotation direction of the intermediate transfer belt 7, the secondary transfer inner roller 8 is disposed more downstream than the upstream guide roller 18. The secondary transfer inner roller 8 faces the secondary transfer outer roller 9 across the intermediate transfer belt 7, and a secondary transfer portion T2 serving as a clamping portion is formed between the portion of the intermediate transfer belt 7 tensioned by the secondary transfer inner roller 8 and the secondary transfer outer roller 9. The secondary transfer inner roller 8 also serves as a roller for transferring the toner image from the intermediate transfer belt 7 to the recording material S.

[0037] With respect to the rotation direction of the intermediate transfer belt 7, the turning roller 17 is disposed more upstream than the separation roller 19. As will be described in detail later, the turning roller 17 has an alignment function of controlling the position in the width direction of the intermediate transfer belt 7, which intersects the rotation direction of the intermediate transfer belt 7 or is orthogonal to the rotation direction in the present exemplary embodiment. The turning roller 17 also serves as a tension roller for applying tension to the intermediate transfer belt 7.

[0038] With respect to the rotation direction of the intermediate transfer belt 7, the upstream guide roller 18 is disposed upstream of the secondary transfer inner roller 8 and downstream of the primary transfer rollers 5a to 5d to guide the intermediate transfer belt 7 such that the intermediate transfer belt 7 enters the secondary transfer portion T2 from a constant direction. The upstream guide roller 18 and the separation roller 19 are a pair of tension rollers disposed upstream and downstream of the portion of the intermediate transfer belt 7 facing the plurality of photosensitive drums 1a to 1d with respect to the rotation direction of the intermediate transfer belt 7. The upstream guide roller 18 is the tension roller disposed downstream of the portion facing the photosensitive drums 1a to 1d among the pair of tension rollers. The upstream guide roller 18 and the separation roller 19 may form a transfer surface on which the toner image is transferred from the plurality of photosensitive drums 1a to 1d to the intermediate transfer belt 7.

[0039] The separation roller 19 as the second separation roller is movable and is disposed downstream of the turning roller 17 and upstream of the primary transfer rollers 5a to 5d with respect to the rotation direction of the intermediate transfer belt 7. The separation roller 19 can change the tension cross-section, which is the cross-section of the intermediate transfer belt 7 along the rotation direction, by being moved by a separation mechanism 300 (see Figures 8A to 8C ) that is a separation mechanism described later. That is, the separation roller 19 corresponds to at least any one of a plurality of tension members. As will be described in detail later, the separation mechanism 300 can separate the outer peripheral surface of the intermediate transfer belt 7 from a part or all of the photosensitive drums 1a to 1d by moving the separation roller 19 and the primary transfer rollers 5a to 5d.

[0040] Magenta, cyan, and black toner images are also formed on the photosensitive drums 1b to 1d in the other imaging units Pb to Pd by imaging operations similar to that of the imaging unit Pa. The toner images formed on the photosensitive drums 1a to 1d are primarily transferred to the intermediate transfer belt 7 at the primary transfer portions T1a to T1d by an electrostatic bias (i.e., transfer bias) applied to the primary transfer rollers 5a to 5d. At this time, when forming a color image, multiple transfers are performed so that the toner images carried on the photosensitive drums 1a to 1d are superimposed on each other. After the sheet S on which the toner image has been transferred passes through the primary transfer portions T1a to T1d, the attachments remaining on the photosensitive drums 1a to 1d (e.g., transfer residual toner) are removed by the drum cleaners 6.

[0041] The toner image carried on the intermediate transfer belt 7 is secondarily transferred to the recording material S at the secondary transfer portion T2 by an electrostatic bias applied to the secondary transfer outer roller 9. The attachments remaining on the intermediate transfer belt 7 after passing through the secondary transfer portion T2 (e.g., transfer residual toner) are removed by the belt cleaning unit 11.

[0042] In parallel with this imaging operation, the recording material S placed in the feed cassette 60 is fed by a feeding mechanism 61 (e.g., a sheet feeding roller) toward the registration roller pair 62. The registration roller pair 62 is configured to correct the skew of the recording material S and send the recording material S toward the secondary transfer portion T2 in synchronization with the progress of the imaging operations performed by the imaging units Pa, Pb, Pc, and Pd.

[0043] The recording material S on which the unfixed toner image has been transferred at the secondary transfer portion T2 is delivered to the fixing unit 13. The fixing unit 13 includes a heating roller 14 heated by a heat source such as a halogen heater and an opposing roller 15 in pressure contact with the heating roller 14, and is configured to heat and press the toner image while clamping and conveying the recording material S. Thereby, the toner particles are melted and fixed, so that the toner image is fixed onto the recording material S.

[0044] Then, the recording material S that has passed through the fixing unit 13 is discharged to a discharge tray 63 provided at the upper part of the apparatus main body. In the case of performing double-sided printing, the recording material S having a first side and a second side (i.e., the front and back sides) is flipped through an inversion conveyance path (not shown) and is conveyed again to the registration roller pair 62. Then, the recording material S on which another image has been formed on its back side passes through the secondary transfer portion T2 and the fixing unit 13 and is discharged to the discharge tray 63.

[0045] Note that the operation display section 40 of the user interface is provided on the upper surface of the apparatus main body. The operation display section 40 includes a liquid crystal panel capable of displaying current setting information and other information, and various buttons through which the user can input various information, and can be set to switch the output image between a color image and a monochrome image.

[0046] The apparatus main body is also provided with a control section 50 as a second control section for comprehensively controlling the operation of the full-color imaging apparatus 200 based on the information input through the operation display section 40. The control section 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each part when reading a program corresponding to the control program stored in the ROM. The RAM stores working data and input data, and the CPU performs control by referring to the data stored in the RAM based on the above program and other programs.

[0047] The apparatus main body also includes a color patch sensor PS as a density detection unit, which can detect the density of the toner image carried on the outer periphery of the intermediate transfer belt 7. The color patch sensor PS is arranged downstream of the photosensitive drum 1d of the imaging unit Pd that is the most downstream in terms of the rotation direction of the intermediate transfer belt 7 and upstream of the upstream guide roller 18 to face the outer peripheral surface of the intermediate transfer belt 7. Such a color patch sensor PS includes, for example, a light emitting part and a light sensing part, and can detect the density of the toner image on the intermediate transfer belt 7 by emitting light from the light emitting part to the outer peripheral surface of the intermediate transfer belt 7 and receiving the light reflected by the outer peripheral surface by the light sensing part. The control section 50 can perform control to adjust the density of the output image by using the color patch sensor PS. For example, the control section 50 forms a color patch image as a control image on the outer peripheral surface of the intermediate transfer belt 7 every predetermined number of sheets, and detects the density of the color patch image by the color patch sensor PS. Then, the control section 50 keeps the density of the output image at an appropriate level by adjusting the amount of toner to be supplied to the developing unit 4 based on the detection result.

[0048] The full-color imaging device 200 configured as described above can execute a full-color mode as a first mode, a separated monochromatic mode as a second mode, and a contact monochromatic mode. The full-color mode is a mode of forming a toner image by using a plurality of photosensitive drums 1a to 1d. The separated monochromatic mode and the contact monochromatic mode are modes of forming a toner image by using one of the plurality of photosensitive drums 1a to 1d, i.e., the photosensitive drum 1d. In the separated monochromatic mode in a state where one of the photosensitive drums 1d is in contact with the outer peripheral surface of the intermediate transfer belt 7 and the remaining photosensitive drums 1a to 1c are separated from the intermediate transfer belt 7, a black toner image is formed only on the photosensitive drum 1d. Meanwhile, the contact monochromatic mode is a mode of forming a black toner image only on the photosensitive drum 1d and not forming a toner image on the other photosensitive drums 1a to 1c in a state where all of the plurality of photosensitive drums 1a to 1d are in contact with the outer peripheral surface of the intermediate transfer belt 7.

[0049] The full-color imaging device 200 can also execute a complete separation mode in which all of the plurality of photosensitive drums 1a to 1d are separated from the intermediate transfer belt 7. The intermediate transfer unit 20 can change the tension cross-section of the intermediate transfer belt 7 to execute each mode, as will be described in detail later.

[0050] Monochromatic imaging device

[0051] Next, reference will be made to Figure 2 the monochromatic imaging device 200K as a second imaging device. The monochromatic imaging device 200K is a so-called intermediate transfer type printer, which includes an imaging unit Pd as a first imaging unit and an intermediate transfer unit 20K as a first intermediate transfer unit corresponding to the monochromatic imaging device 200K in a housing 201.

[0052] The monochromatic imaging device 200K uses the same housing 201 as that of the above-described full-color imaging device 200, and is constructed by removing the imaging units Pa, Pb, and Pc, the developer storage containers Ta, Tb, and Tc, and the replenishing units 70a, 70b, and 70c (not shown) corresponding to the respective developer storage containers. The intermediate transfer belt 7 as a first belt member is wound around a plurality of first tension rollers including a secondary transfer inner roller 8, a turning roller 17, a separating roller 19, and an upstream guide roller 18, and the photosensitive drum 1d whose outer peripheral surface faces the imaging unit Pd. The position of the photosensitive drum 1d as a first image carrier member of the monochromatic imaging device 200K with respect to the intermediate transfer belt 7 as a first belt member is the same as the position of the photosensitive drum 1d as a second image carrier member of the full-color imaging device 200 with respect to the intermediate transfer belt 7 as a second belt member. Since the other elements and operations of the monochromatic imaging device 200K are the same as those of the above-described full-color imaging device 200, the same constituent elements will be denoted by the same reference numerals and their description will be omitted here.

[0053] Note that, although the housing 201 that is the same as the housing of the full-color imaging device 200 is used as the device body of the monochrome imaging device 200K, a decorative cover can be used specifically for the monochrome imaging device because the decorative cover is used to cover the area where the imaging units Pa, Pb, Pc, and other components have been removed. Note that the housing 201 in this exemplary embodiment is the frame portion of the imaging device and is composed of metal components. Further, although the housing 201 of this exemplary embodiment is described by giving an example in which the housing 201 of the monochrome imaging device 200K is exactly the same as the housing 201 of the full-color imaging device 200, they do not need to be exactly the same. For example, a mark can be provided to distinguish the full-color imaging device 200 from the monochrome imaging device 200K. Further, although most of the components of the housing are the same, a reinforcing bracket can be added to partially reinforce only one device. In this case, the basic structure of the housing 201 is also considered to be substantially the same.

[0054] Further, in order to prevent the intermediate transfer unit 20 corresponding to the full-color imaging device 200 from being erroneously installed on the monochrome imaging device 200K, an incompatible structure can be provided so that the intermediate transfer unit 20 cannot be installed on the monochrome imaging device 200K. In the same way, an incompatible structure can be provided so that the intermediate transfer unit 20K cannot be installed on the full-color imaging device 200. The incompatible structure can be provided on either the main body of the imaging device or the intermediate transfer unit.

[0055] Except that the monochrome imaging device 200K only includes one imaging unit Pd, the operations and configurations for forming a toner image on the recording material S based on the image information read from the document or the image information input from an external device are the same as those of the full-color imaging device 200. Note that the configuration and operation of the intermediate transfer unit 20K will be described later.

[0056] The monochrome imaging device 200K constructed as described above can execute a monochrome mode and a monochrome complete separation mode. The monochrome mode is a mode in which a toner image is formed by using one photosensitive drum 1d as the first image carrier member. The monochrome complete separation mode is a mode in which the one photosensitive drum 1d is separated from the intermediate transfer belt 7 as the first belt. To execute these respective modes, the intermediate transfer unit 20K is configured to be able to change the tension cross-section of the intermediate transfer belt 7, as described in detail later.

[0057] Intermediate transfer unit

[0058] Next, the internal structure of the intermediate transfer unit 20 (which is an example of a belt conveyance unit) and the structure for turning the intermediate transfer belt 7 will be described with reference to Figures 3A to 6B and Figure 3A and3B The intermediate transfer unit 20 shown in [figure] shows the structure when the intermediate transfer unit 20 is installed on the full-color imaging device 200. First, reference will be made to Figure 3A and 3B to schematically describe the structure of the intermediate transfer unit 20. Although Figure 3A and 3B are both perspective views showing the intermediate transfer unit 20, Figure 3A shows the state where the intermediate transfer belt 7 is tensioned, while Figure 3B shows the state where the intermediate transfer belt 7 is removed.

[0059] As Figure 3A and 3B shown, the intermediate transfer unit 20 includes a front frame 21F and a rear frame 21R supported by a housing 201. The front frame 21F is a frame member arranged on the front side of the intermediate transfer unit 20 (i.e., the forward direction in Figure 1 or the side where the user operates), and the rear frame 21R is a frame member arranged on the opposite side, i.e., the rear side. The two-side transfer inner roller 8, the upstream guide roller 18, and the separation roller 19 are rotatably supported at both ends in the rotational axial direction in such a manner as to be sandwiched between the front frame 21F and the rear frame 21R. The rotational axial direction of these rollers 8, 18, and 19 is parallel to the width direction W of the intermediate transfer belt 7. A belt automatic alignment mechanism 17U (described later) including a turning roller 17 is supported by a frame support plate 28 extending across the front frame 21F and the rear frame 21R.

[0060] A drive coupling 22 is attached to one end in the rotational axial direction of the two-side transfer inner roller 8. In a state where the intermediate transfer unit 20 is installed on the device main body, the drive coupling 22 is coupled to an output shaft of a belt drive unit (not shown) to transmit the driving force of the belt drive unit to the two-side transfer inner roller 8. The belt drive unit includes a drive source such as a motor and a coupling member configured to engage with the drive coupling 22, and is installed inside the device main body.

[0061] The surface of the two-side transfer inner roller 8 is made of a material (e.g., rubber) having a relatively high coefficient of friction, and conveys and drives the intermediate transfer belt 7 in the direction of arrow R7 along Figure 3A . Note that although the drive coupling 22 is used as a drive transmission unit in this exemplary embodiment, the drive source of the device main body can be coupled to the intermediate transfer unit 20 by using, for example, attachable / detachable gears.

[0062] Regarding the intermediate transfer belt 7 driven and conveyed as described above, according to this exemplary embodiment, the turning roller 17 has a belt automatic alignment mechanism that can align or turn the belt, i.e., control the position in the width direction, by maintaining the frictional force balance at both end portions. Below, reference will be made toFigure 4 and 5 Describe the structure of the automatic alignment mechanism 17U as an example of a steering mechanism. Figure 4 is a perspective view showing the automatic alignment mechanism 17U, Figure 5 is an enlarged perspective view of an end portion of the automatic alignment mechanism 17U.

[0063] As Figure 4 shown, the steering roller 17 includes a cylindrical roller body 17a and roller shafts 17b that project from the roller body 17a toward both sides in the rotational axial direction. Steering bearings 23 are respectively arranged at positions corresponding to both end portions of the rotational axis of the steering roller 17. Each roller shaft 17b is rotatably supported by the steering bearing 23 in such a manner that it is inserted through a support hole 10a provided in the corresponding steering bearing 23.

[0064] The pair of steering bearings 23 are attached to the swing plate 26 while supporting both end portions of the steering roller 17 in the axial direction. The steering roller 17 is one of a plurality of tension rollers by which the intermediate transfer belt 7 is tensioned. Each steering bearing 23 is slidably supported by a sliding guide portion 24 at both end portions of the swing plate 26. A tension spring 25 is provided in a contracted state between the steering bearing 23 and the sliding guide portion 24 to serve as a compression spring.

[0065] The swing plate 26 is an example of a swing member that supports the steering roller 17 in a state where the relative alignment with the secondary transfer inner roller 8 can be changed by swinging. The tension spring 25 is also an example of a pressing member that applies the tension acting on the inner circumference of the intermediate transfer belt 7 to the steering roller 17. That is, the tension spring 25 as the pressing member of the present exemplary embodiment is composed of a pair of spring members that respectively apply a pressing force to the pair of steering bearings 23 at both end portions of the swing plate 26.

[0066] As Figure 4 and 5 shown, the sliding guide portion 24 has a mating groove for guiding the steering bearing 23 to move along the pressing direction of the tension spring 25 (i.e., the direction of arrow K1). That is, the sliding guide portion 24 constitutes a guiding portion for guiding the pair of steering bearings 23 in the pressing direction of the tension spring 25. The sliding guide portion 24 also has a stopper portion (not shown) that can limit the movement of the steering bearing 23 in the pressing direction of the tension spring 25. This stopper portion prevents the steering bearing 23 and the steering roller 17 from falling off in an assembled state where the automatic alignment mechanism 17U is not mounted on the intermediate transfer unit 20. These arrangements enable the pressing force of the tension spring 25 located at both end portions to be effectively transmitted to each corresponding steering bearing 23.

[0067] In as Figure 3AWhile the intermediate transfer belt 7 shown is being tensioned by the turning roller 17 and other roller members 8, 18, and 19, the turning bearing 23 moves in the direction of the compression tension spring 25 from the position restricted by the stopper portion. Accordingly, the turning roller 17 is pressed against the inner peripheral surface of the intermediate transfer belt 7 by the elastic force of the tension spring 25, and in this state, a tension is generated in the intermediate transfer belt 7. That is, the turning roller 17 in the present exemplary embodiment also serves as a tension roller that applies sufficient tension to the intermediate transfer belt 7 by the pressing force from the pressing member.

[0068] As Figure 4 shown, the swing plate 26 as a swing member is fixed in a state where: the pivot member 27 (serving as a support shaft) disposed at the width center portion of the swing plate 26 projects rearward in Figure 4 and the slide guide portions 24 are respectively fixed to both end portions of the swing plate 26. The pivot member 27 rotatably or swingably supports the swing plate 26 by being pivotally fitted into a fitting portion (not shown) provided in the through-frame support plate 28.

[0069] Thereby, the swing plate 26 can swing in the swing direction Ro about the turning axis J (which is the axis of the pivot member 27) while supporting the turning roller 17. That is, the belt automatic alignment mechanism 17U (which is an example of an alignment change unit for changing the alignment of the belt member) is constructed as a swingable unit that can swing relative to the frame of the intermediate transfer unit 20 together with the turning roller 17.

[0070] Operating principle of the belt automatic alignment mechanism

[0071] Next, the configuration and operation of the belt automatic alignment mechanism of the present exemplary embodiment will be described in detail with reference to Figure 5 、 6A and 6B. Figure 6A and 6B are both plan views or top views from the perspective pointing in the arrow TV direction along Figure 3A . Figure 6A shows a stable state in which the width direction force acting on the intermediate transfer belt 7 is balanced by the operation of the belt automatic alignment mechanism 17U, that is, a state in which the hanging position of the intermediate transfer belt 7 is located at the nominal position. Figure 6B shows a state in which the intermediate transfer belt 7 is skewed to the left in Figure 6B when the intermediate transfer belt 7 is conveyed in the direction of arrow R7.

[0072] As Figure 5As shown, the turning bearing 23 configured to support the turning roller shaft 17b includes a friction surface 231 for generating a turning torque by sliding contact with the inner peripheral surface of the intermediate transfer belt 7. Here, the turning torque refers to the torque that attempts to change the alignment of the turning roller 17 in a direction that can reduce the skew of the intermediate transfer belt 7. As described above, the moving direction of the turning bearing 23 is restricted by the sliding guide portion 24 and moves in the direction of arrow K1. Therefore, when the intermediate transfer belt 7 is conveyed and driven in the direction of arrow R7, the turning bearing 23 (which is an example of a friction portion) slidably contacts the inner peripheral surface of the belt without being driven.

[0073] The friction surface 231 is formed in a conical shape such that its outer diameter gradually increases as it approaches outward in the axial direction of the turning roller 17, and has a maximum diameter larger than the outer diameter of the cylindrical turning roller 17. In the present exemplary embodiment, as Figure 6B shown, the outer diameter of the turning roller 17 is set to 16 mm, for example. Although the friction surface 231 of the turning bearing 23 has a cylindrical outer peripheral portion of 16 mm at the portion where it engages with the turning roller 17, the friction surface 231 has a curved shape in which the outer diameter gradually increases outward from the outer peripheral portion, and the degree of curvature is such that the taper angle ψ is 10 degrees.

[0074] Furthermore, according to the present exemplary embodiment, the dimension of the intermediate transfer belt 7 in the width direction of the intermediate transfer belt 7 (i.e., the direction orthogonal to the conveying and driving direction or the direction orthogonal to the direction of arrow R7) is set to extend at least partially over the region of the friction surface 231 having the taper angle ψ. In other words, the width Lb of the intermediate transfer belt 7 is set to be greater than the axial length (Lr) of the roller body of the turning roller 17 and shorter than the width (Lr + 2Lf) between the two ends of the turning bearing 23, that is, Lr < Lb < Lr + 2Lf. Here, Lf is the length in the width direction of the friction surface 231 of each turning bearing 23.

[0075] Reference will be made to Figure 6A and 6B to describe the operating principle of achieving automatic belt alignment by slidably contacting the intermediate transfer belt 7 with the turning bearing 23. Since the turning bearing 23 is supported in a manner not to be driven by the intermediate transfer belt 7 as described above, the turning bearing 23 can slidably contact the inner peripheral surface of the belt when the intermediate transfer belt 7 is driven and conveyed. At this time, since a frictional force is generated in the region where the intermediate transfer belt 7 is wound around the turning bearing 23 (i.e., the right region facing downward when viewed from the direction of arrow G of Figure 5 ), a downward frictional force acts on the turning bearing 23.

[0076] As described above, the width direction dimension (Lb) of the intermediate transfer belt 7 is set to extend on the slidable conical contact surface 231 of the turning bearing 23. Therefore, in Figure 6A the stable state or nominal state shown, the intermediate transfer belt 7 slidably contacts the friction surfaces 231 of the two turning bearings 23 with equal hanging widths (for example, 2 mm). In this state, the torques generated by the frictional forces acting on the two turning bearings 23 from the intermediate transfer belt 7 cancel each other out.

[0077] That is, the frictional force received by the turning bearing 23 from the intermediate transfer belt 7 acts as torques acting on the turning bearing 23 and the swing plate 26 in opposite directions centered on the turning axis J. Therefore, the frictional forces received by the respective turning bearings 23 are substantially equal and the torques cancel each other out, thereby maintaining the posture of the swing plate 26. As a result, the turning roller 17 is held in a posture in which its axial direction is substantially parallel to the axial direction of other roller members (for example, the secondary transfer inner roller 8), that is, it is held in a state of maintaining alignment.

[0078] In contrast, in a state where the intermediate transfer belt 7 deviates to either side in the width direction, that is, in a state of so-called skew, the hanging width of the intermediate transfer belt 7 with respect to one turning bearing 23 is larger than the hanging width of the intermediate transfer belt 7 with respect to the other turning bearing 23. In Figure 6B the example shown, the hanging width of the intermediate transfer belt 7 with respect to the left turning bearing 23 is D mm, while the hanging width of the intermediate transfer belt 7 with respect to the right turning bearing 23 is zero. That is, this is a state where the intermediate transfer belt 7 deviates from the friction surface 231.

[0079] In this case, if the vertically downward frictional force received by the friction surface 231 within a certain hanging width range from the intermediate transfer belt 7 is F(ST), then the magnitude of the force received by one turning bearing 23 is F(ST)×D. At the same time, since the hanging width of the other turning bearing 23 is zero, this turning bearing 23 basically does not receive a force from the intermediate transfer belt 7. Therefore, in Figure 6B the state shown, a turning torque is generated that attempts to move the left end portion of the turning roller 17 downward (that is, Figure 6B the rear side in

[0080] ). The turning angle of the turning roller 17 (that is, the inclination angle of the turning roller 17) generated by the above principle in a state where the turning roller 17 swings according to the turning torque is consistent with the direction in which the skew of the intermediate transfer belt 7 returns to the original state. Therefore, the skew of the intermediate transfer belt 7 decreases as the belt is conveyed. That is, the belt automatic alignment mechanism 17U has an automatic alignment effect of controlling the width direction position of the intermediate transfer belt 7 by converting a part of the driving force for conveying and driving the intermediate transfer belt 7 into a turning torque.

[0081] Note that this exemplary embodiment is configured to set a relatively low coefficient of friction μS by setting a taper angle ψ for the steering bearing 23 to avoid sudden steering operations. Specifically, by using a resin material (e.g., POM (polyoxymethylene)) having sliding characteristics (i.e., low friction) as the material of the steering bearing 23, and by setting the coefficient of friction μS to about 0.3 and the taper angle ψ to about 5 to 10 degrees, favorable results can be obtained. Further, in consideration of the adverse electrostatic effects caused by triboelectrification with the intermediate transfer belt 7, the steering bearing 23 is made conductive. However, other configurations with different taper angles ψ and friction characteristics may also be employed as long as the required steering torque can be obtained. For example, the friction surface 231 of the steering bearing 23 may be formed in a cylindrical shape.

[0082] Separation mechanism of the intermediate transfer belt

[0083] Next, reference will be made to Figure 7 and 8A to 8C to describe the separation mechanism 300 (as the second separation mechanism) for separating the intermediate transfer belt 7 from the photosensitive drums 1a to 1d. The separation mechanism 300 as a moving mechanism includes a separation slider 30 as a sliding member and a separation cam 31 as a cam member. The control section 50 as the second control section can change the tension cross-section, which is the cross-section of the intermediate transfer belt 7 in the rotational direction, by controlling the separation mechanism 300 to move the separation roller 19 (which is at least any one of the plurality of tension members). The separation mechanism 300 can also move the plurality of primary transfer rollers 5a to 5d. Thus, when the intermediate transfer unit 20 is installed in the full-color imaging device 200, the separation mechanism 300 can change the tension cross-section of the intermediate transfer belt 7 corresponding to the full-color mode, the separated monochromatic mode, the contact monochromatic mode, and the fully separated mode.

[0084] Specifically, in the full-color mode (i.e., the first mode) and the contact monochromatic mode, the tension cross-section of the intermediate transfer belt 7 takes the first tension cross-section as shown in Figure 8A . In the first tension cross-section, the outer peripheral surface of the intermediate transfer belt 7 contacts all of the plurality of photosensitive drums 1a to 1d. In the separated monochromatic mode, i.e., the second mode, the tension cross-section of the intermediate transfer belt 7 takes the second tension cross-section as shown in Figure 8B . In the second tension cross-section, the outer peripheral surface of the intermediate transfer belt 7 contacts one photosensitive drum 1d and is separated from the other photosensitive drums 1a to 1c. In the fully separated mode, the tension cross-section of the intermediate transfer belt 7 takes the fourth tension cross-section as shown in Figure 8C . In the fourth tension cross-section, the outer peripheral surface of the intermediate transfer belt 7 is separated from all of the plurality of photosensitive drums 1a to 1d.

[0085] In short, Figures 8A to 8C The relationship with the tensioning section is as follows:

[0086] Figure 8A : The first tensioning section (full-color mode (first mode or CL mode) and contact monochromatic mode)

[0087] Figure 8B : The second tensioning section (separated monochromatic mode (second mode or BK mode))

[0088] Figure 8C : The fourth tensioning section (fully separated mode)

[0089] The configuration for separating the intermediate transfer belt 7 by the separating mechanism 300 will be specifically described below. As described above, the primary transfer rollers 5a to 5d of the photosensitive drums 1a to 1d facing the image forming units Pa to Pd are arranged on the inner peripheral side of the intermediate transfer belt 7 (see Figure 1 ). These primary transfer rollers 5a to 5d and the separating roller 19 located upstream of the primary transfer rollers 5a to 5d can move relative to the frame member of the intermediate transfer unit 20.

[0090] The movement of the primary transfer rollers 5a to 5d and the separating roller 19 is performed by Figure 7 the sliding motion of the separating slider 30 shown. Figure 7 The state of the separating slider 30 as viewed from the front is shown. Each separating slider 30 is respectively stored in the front frame 21F and the rear frame 21R (see FIG. 3) of the intermediate transfer unit 20 and has the same shape. That is, each separating slider 30 has four cam surfaces 30a, 30b, 30c, and 30d corresponding to the primary transfer rollers 5a to 5d and a cam surface 30e corresponding to the separating roller 19. Two separating sliders 30 slide synchronously in the lateral direction (i.e., the direction in which the primary transfer rollers 5a to 5d are arranged or the direction orthogonal to the rotational axial direction of the primary transfer rollers 5a to 5d) as the moving direction in FIG. 8 with respect to the front frame 21F and the rear frame 21R.

[0091] Each of the cam surfaces 30a to 30e includes an inclined surface inclined in the sliding direction of the separating slider 30 so as to enable the operation of each of the rollers 5a to 5d and 19 in each switching mode, as described below. For example, the cam surface 30e corresponding to the separating roller 19 includes a flat portion 302 corresponding to the middle section position of the separating roller 19 and an inclined surface 301 extending from the flat portion 302 in the sliding direction and corresponding to the lower section position of the separating roller 19. The same applies to the cam surfaces 30a to 30d.

[0092] As Figures 8A to 8CAs shown, the axial ends of the primary transfer rollers 5a to 5d are rotatably supported by corresponding primary transfer bearings 29a to 29d. The primary transfer bearings 29a to 29d are arranged at the axial ends of the primary transfer rollers 5a to 5d and are respectively supported by the front frame 21F and the rear frame 21R. Any one of the primary transfer bearings 29a to 29d is also supported by the front frame 21F and the rear frame 21R in a state of being movably engaged in the vertical direction in FIG. 8 (i.e., the direction orthogonal to the moving direction of the separation slider 30 or the direction orthogonal to the rotational axial direction of the primary transfer rollers 5a to 5d). Further, the primary transfer bearings 29a to 29d are restricted from moving in the direction along the conveyance direction of the intermediate transfer belt 7 (i.e., the direction of arrow R7).

[0093] Each of the primary transfer bearings 29a to 29d is provided with contact portions a1 to d1 that contact the cam surfaces 30a to 30d of the separation slider 30. Further, primary transfer springs Spa to SPd that push downward in FIG. 8 to press the primary transfer bearings 29a to 29d against the cam surfaces 30a to 30d are provided between the primary transfer bearings 29a to 29d and the front and rear frames 21F and 21R. The pushing direction of the primary transfer springs Spa to Spd is the direction in which the primary transfer rollers 5a to 5d point toward the photosensitive drums 1a to 1d.

[0094] As the separation slider 30 slides and moves laterally in FIG. 8, the primary transfer bearings 29a to 29d move in the vertical direction in FIG. 8 with the contact portions a1 to d1 in contact with the cam surfaces 30a to 30d, thereby moving the primary transfer rollers 5a to 5d.

[0095] A moving structure similar to that of the primary transfer rollers 5a to 5d is also provided for the separation roller 19. That is, the axial ends of the separation roller 19 are rotatably supported by separation roller bearings 29e arranged at the axial ends. Each of the separation roller bearings 29e is held by the front frame 21F and the rear frame 21R in a state where the separation roller bearing 29e can move in the vertical direction in FIG. 8, and is restricted from moving along the conveyance direction of the intermediate transfer belt 7 (i.e., along the direction of arrow R7). Further, the separation roller bearing 29e includes a contact portion e1 that contacts the cam surface 30e of the separation slider 30 and is pressed toward the cam surface 30e by the separation roller spring SPe. As the separation slider 30 slides and moves in the lateral direction in FIG. 8, the separation roller bearing 29e moves in the vertical direction in FIG. 8 with the contact portion e1 in contact with the cam surface 30e. Thereby, the separation roller 19 moves.

[0096] The separation slider 30 includes a slider push surface 30f that engages with a separation cam 31 attached to a separation cam shaft 32 (see Figure 7) and is pushed in the lateral direction in FIG. 8 as the slider pressing surface 30f is pressed by the separation cam 31. The separation coupling 33 (see FIG. 3), which is drivingly coupled to a drive source (such as a motor) installed in the apparatus main body, is attached to the axial end of the separation camshaft 32 in a state where the intermediate transfer unit 20 is installed to the apparatus main body.

[0097] The separation slider 30 corresponds to a movable member that can move in a direction intersecting the moving direction of the separation roller bearing 29e corresponding to the bearing member in the present exemplary embodiment, that is, Figures 8A to 8C the vertical direction in. The separation roller spring SPe corresponds to a pressing unit that causes the bearing member to follow the cam surface by pressing the bearing member toward the cam surface.

[0098] According to the present exemplary embodiment, the primary transfer rollers 5a to 5d and the separation roller 19 are moved by the separation mechanism 300 including the separation slider 30 and the separation cam 31 to switch the modes as Figures 8A to 8C respectively shown in. The following mode switching operation is achieved by controlling the rotation phase of the separation camshaft 32 based on a control signal issued from the control section 50 (see Figure 1 ) installed in the full-color imaging apparatus 200. Although this operation will be described by taking an example of switching in the order of the full-color mode (i.e., the CL mode), the separated monochromatic mode (i.e., the BK mode), and the fully separated mode, switching can also be performed in any mode according to the reverse operation.

[0099] In the full-color mode as Figure 8A shown, that is, in the CL mode, all the primary transfer rollers 5a to 5d and the separation roller 19 are held at the lower position, and the intermediate transfer belt 7 is in contact with the photosensitive drums 1a to 1d of the respective imaging units Pa to Pd. That is, the primary transfer roller 5d is positioned at the first position and the separation roller 19 is positioned at the second position. In this state, a color image can be formed on the recording material by performing an imaging operation by the respective imaging units Pa to Pd and transferring the toner image formed on the photosensitive drums 1a to 1d to the recording material by the intermediate transfer belt 7.

[0100] When switching from the CL mode to the separated monochromatic mode (i.e., the BK mode) as Figure 8B shown, the separation cam 31 rotates 90 degrees in the direction of arrow R9 and the separation slider 30 moves toward Figure 8BSlide to the right side (i.e., in the direction of arrow K2) in it. In the BK mode, the primary transfer rollers 5a to 5c move to the upper position to separate from the inner peripheral surface of the intermediate transfer belt 7, and the separation roller 19 moves to the middle position. At this time, the intermediate transfer belt 7 is tensioned by the separation roller 19 located at the middle position and the black primary transfer roller 5d held at the lower position, and separates from the photosensitive drums 1a to 1c except for the black primary transfer roller 5d. In this state, by performing an imaging operation by the black imaging unit Pd and transferring the toner image formed on the photosensitive drum 1d to the recording material by the intermediate transfer belt 7, a monochromatic image can be formed on the recording material.

[0101] In the case of switching from the BK mode to the fully separated mode as shown in Figure 8C , the separation cam 31 further rotates 90 degrees in the direction of arrow R9 and the separation slider 30 slides to the Figure 8C right side (i.e., in the direction of arrow K2) in it. In the fully separated mode, all the primary transfer rollers 5a to 5d move to the upper position to separate from the inner peripheral surface of the intermediate transfer belt 7, and the separation roller 19 moves to the upper position. At this time, the intermediate transfer belt 7 is tensioned by the upstream guide roller 18 (see Figure 1 ) and the separation roller 19 at the upper position, and separates from all the photosensitive drums 1a to 1d. The control section 50 controls the separation mechanism 300 so as to adopt the fully separated mode in cases other than when performing the replacement work of the intermediate transfer unit 20 and also when the full-color imaging device 200 is waiting for a signal (e.g., a print job) instructing the start of the imaging operation.

[0102] The separation roller 19 is an example of a roller member of its tension belt member. Figure 8A The lower position in it corresponds to the second position. Figure 8B And 8C the upper position in it corresponds to the third position where the separation roller 19 moves toward the inner peripheral side of the belt member compared with the second position. In the case of performing the full-color mode, the control section 50 moves the separation roller 19 to the second position, and in the case of performing the separated monochromatic mode, the control section 50 moves the separation roller 19 to the third position. The separation mechanism 300 is an example of a moving mechanism for moving such a roller member to the second position and the third position.

[0103] Here, when the type of the recording material is, for example, 150 g / m 2 or more in grammage, there is a case where the shock caused when the recording material enters the secondary transfer section T2 propagates to the intermediate transfer belt 7 and vibrates the photosensitive drum 1d. Since it is effective to increase the tension of the intermediate transfer belt 7 to suppress the propagation of the shock, it is preferable to also switch to the Figure 8A CL mode shown in it when forming a monochromatic image on the recording material.

[0104] Thus, the present exemplary embodiment is arranged such that the monochromatic mode in which an image is formed in a single color of black can be executed by a contact monochromatic mode (i.e., the sixth mode) in addition to the above-described separated monochromatic mode. For example, the control section 50 may be arranged to execute the contact monochromatic mode when forming a monochromatic image on a recording material having a predetermined grammage value of 150 g / m 2 or more. It may also be arranged to enable the user to select the separated monochromatic mode or the contact monochromatic mode, etc. from the operation display section 40.

[0105] In the contact monochromatic mode, all of the primary transfer rollers 5a to 5d and the separation roller 19 are held in the lower position, and the intermediate transfer belt 7 is in contact with the photosensitive drums 1a to 1d of the respective image forming units Pa to Pd (see Figure 1 ), as Figure 8A shown. When executing the contact monochromatic mode, a toner image is formed on the black photosensitive drum 1d, and no toner image is formed on the other photosensitive drums 1a to 1c. However, since the other photosensitive drums 1a to 1c are in contact with the intermediate transfer belt 7, it is preferable to rotate the respective photosensitive drums and charge the surfaces of the photosensitive drums by the charging unit 2 when forming an image. That is, although the image forming units Pa, Pb, and Pc perform imaging operations at this time, the exposure units 3 corresponding to the yellow, magenta, and cyan image forming units do not form an electrostatic latent image on the drum surface.

[0106] Furthermore, in Figure 8A the first tensioning section shown, the tension of the intermediate transfer belt 7 is higher than Figure 8B the tension in the second tensioning section shown, so that the intermediate transfer belt 7 can be stably driven. Because of this, it is preferable to perform control based on the density of the color patch image detected by the above-described color patch sensor PS in the state of the first tensioning section. This is because if the intermediate transfer belt 7 is not stably driven, the distance between the detection surface of the color patch sensor PS and the outer peripheral surface of the intermediate transfer belt 7 changes, and the detection accuracy decreases.

[0107] Thus, according to the present exemplary embodiment, the control section 50 periodically or appropriately uses the color patch sensor PS to perform control in the full-color mode. At the same time, in the monochromatic mode, the control section 50 uses the color patch sensor PS to perform control when the contact monochromatic mode is being executed. That is, the control section 50 uses the color patch sensor PS to perform control when the tensioning section of the intermediate transfer belt 7 is Figure 8A the first tensioning section shown.

[0108] Installation and removal of the intermediate transfer unit

[0109] Next, the structure for installing / removing the intermediate transfer unit 20 to / from the apparatus main body in the case of replacing the intermediate transfer belt 7, etc. will be described.Figure 9 The intermediate transfer unit 20 shown in Figure 9 can be mounted to the apparatus main body of the full-color imaging apparatus 200 and removed from the apparatus main body while being held in the above-described fully separated mode. That is, the intermediate transfer unit 20 can be mounted to and removed from the apparatus main body in the state of the fourth tension cross-section shown in Figure 8C . Figure 8C Specifically, the intermediate transfer unit 20 is exposed by opening the right door RD provided on the right side when viewed from the front side of the apparatus main body, and can be removed from the apparatus main body by moving in the lateral direction (i.e., the direction of arrow K3).

[0110] Specifically, the intermediate transfer unit 20 is exposed by opening the right door RD provided on the right side when viewed from the front side of the apparatus main body, and can be removed from the apparatus main body by moving in the lateral direction (i.e., the direction of arrow K3).

[0111] Monochrome intermediate transfer unit

[0112] Next, the internal structure of the intermediate transfer unit 20K corresponding to the monochrome imaging apparatus 200K will be described with reference to Figure 10A and 10B . FIGS. 10A and 10B are perspective views showing the intermediate transfer unit 20K, where Figure 10A shows a state in which the intermediate transfer belt 7 is tensioned, and Figure 10B shows a state in which the intermediate transfer belt 7 is removed. Figure 10A and 10B Next, the internal structure of the intermediate transfer unit 20K corresponding to the monochrome imaging apparatus 200K will be described with reference to Figure 10A and 10B . FIGS. 10A and 10B are perspective views showing the intermediate transfer unit 20K, where Figure 10A shows a state in which the intermediate transfer belt 7 is tensioned, and Figure 10B shows a state in which the intermediate transfer belt 7 is removed. Figure 10A shows a state in which the intermediate transfer belt 7 is tensioned, Figure 10B shows a state in which the intermediate transfer belt 7 is removed.

[0113] The intermediate transfer unit 20K is a unit in which the primary transfer rollers 5a to 5c, the primary transfer bearings 29a to 29c, and the primary transfer springs Spa to SPc are removed from the intermediate transfer unit 20 corresponding to the above-described full-color imaging apparatus 200. This arrangement can reduce the cost of the intermediate transfer unit 20. Note that the structure other than this is the same as the structure of the intermediate transfer unit 20. That is, the primary transfer rollers 5a to 5c and other components are only removed from the intermediate transfer unit 20, and the other structures are the same. That is, the basic structure of the intermediate transfer unit 20K is the same as the basic structure of the intermediate transfer unit 20 corresponding to the above-described full-color imaging apparatus 200. Note that in the present exemplary embodiment, an example in which the intermediate transfer units in the full-color imaging apparatus 200 and the monochrome imaging apparatus 200K are completely the same except that the primary transfer rollers 5a to 5c and the above-described other components are removed is exemplified, but they do not always need to be completely the same. For example, a mark for distinguishing the intermediate transfer unit of the full-color imaging apparatus 200 and the intermediate transfer unit of the monochrome imaging apparatus 200K may be provided. Further, although most of the outer shell (i.e., the frame) of the intermediate transfer unit is the same, a reinforcing bracket for partially reinforcing only one apparatus may be added. In this case, the basic structure of the intermediate transfer unit is also considered to be substantially the same.

[0114] Accordingly, the positions of the tension rollers 8, 17, 18, and 19 for tensioning the intermediate transfer belt 7 and the separating mechanism 300 (i.e., the first separating mechanism) of the separating roller 19 (i.e., the first separating roller) are the same in the intermediate transfer unit 20 and the intermediate transfer unit 20K. The structure for turning the intermediate transfer belt 7 is also the same. Therefore, the structures of the intermediate transfer unit 20K that are the same as those of the intermediate transfer unit 20 will be denoted by the same reference numerals, and their descriptions will be omitted below.

[0115] Separation mechanism of the intermediate transfer belt in the monochromatic intermediate transfer unit

[0116] Next, with reference to Figure 11A and 11B the structure for separating the intermediate transfer belt 7 of the monochromatic intermediate transfer unit 20K from the photosensitive drum 1d will be described. The intermediate transfer unit 20K also includes the above-described separating mechanism 300. Then, the control section 50 as the first control section can change the tension cross-section, which is the cross-section of the intermediate transfer belt 7 along its rotation direction, by controlling the separating mechanism 300 to move the separating roller 19. The separating mechanism 300 can also move a primary transfer roller 5d. Then, when the intermediate transfer unit 20K is installed in the monochromatic imaging device 200K, the separating mechanism 300 can change the tension cross-section of the intermediate transfer belt 7 corresponding to the monochromatic mode as the third mode and the monochromatic full separation mode as the fifth mode.

[0117] Specifically, the tension cross-section of the intermediate transfer belt 7 takes the Figure 11A third tension cross-section shown in, in which the outer peripheral surface of the intermediate transfer belt 7 contacts the photosensitive drum 1d. That is, the third tension cross-section (i.e., the first tension form) is a tension form that can form a transfer surface between the primary transfer roller 5d and the separating roller 19 by positioning the primary transfer roller 5d at the first position and the separating roller 19 at the second position to transfer the toner image from the photosensitive drum 1d to the intermediate transfer belt 7. In the monochromatic full separation mode, the tension cross-section of the intermediate transfer belt 7 takes the fifth tension cross-section as shown in Figure 11B in which the outer peripheral surface of the intermediate transfer belt 7 is separated from one photosensitive drum 1d. That is, the fifth tension cross-section (i.e., the second tension form) is a tension form for separating each of the primary transfer roller 5d and the separating roller 19 from the transfer surface.

[0118] In short, Figure 11A and 11B the relationship with the tension cross-section is as follows:

[0119] Figure 11A : Third tension cross-section (monochromatic mode)

[0120] Figure 11B: Fifth Tension Section (Monochromatic Complete Separation Mode)

[0121] Here, in the case of the present exemplary embodiment, as Figure 11A shown, the third tension section is the same as the first tension section shown as Figure 8A . That is, when forming a monochromatic image in the monochromatic imaging device 200K, a monochromatic image can also be formed in a state where the tension section of the intermediate transfer belt 7 is changed to the second tension section shown as Figure 8B . However, when changing the tension section of the intermediate transfer belt 7 to the second tension section, the tension of the intermediate transfer belt 7 decreases compared to the case of the first tension section. Therefore, due to the impact generated when the recording material enters the secondary transfer portion T2, the image quality of the image to be transferred to the recording material is likely to deteriorate. Specifically, when the recording material has a large grammage of 150 g / m 2 or more, the impact caused when the recording material enters the secondary transfer portion T2 is large. This impact is likely to propagate through the intermediate transfer belt 7 and cause the photosensitive drum 1d to vibrate.

[0122] Thus, when forming an image by mounting the intermediate transfer unit 20 to the monochromatic imaging device 200K, the tension section of the intermediate transfer belt 7 is changed to the third tension section that is the same as the first tension section. That is, a tension section is set that is the same as the tension section when performing the full-color mode or the contact monochromatic mode in the full-color imaging device 200. In other words, the control section 50 controls the separation mechanism 300 such that the separation roller 19 is positioned at the second position when forming an image. This arrangement makes it possible to suppress a deterioration in the image quality of the image to be transferred to the recording material S. Even when the grammage of the recording material is particularly large, it is possible to suppress a deterioration in the image quality of the image to be transferred.

[0123] As Figure 11B shown, the fifth tension section is the same as the fourth tension section shown as Figure 8C . That is, when separating the photosensitive drum 1d in the monochromatic imaging device 200K, the tension section of the intermediate transfer belt 7 is changed to a tension section similar to the tension section in the complete separation mode of the full-color imaging device 200. In other words, when separating the photosensitive drum 1d from the intermediate transfer belt 7, the control section 50 controls the separation mechanism 300 such that the separation roller 19 is positioned at the third position. This arrangement makes it possible to share the separation mechanism 300 between the full-color imaging device 200 and the monochromatic imaging device 200K and reduce costs.

[0124] The following will specifically describe this arrangement. As described above, the primary transfer roller 5d of the photosensitive drum 1d facing the imaging unit Pd is arranged inside the inner peripheral side of the intermediate transfer belt 7 (see Figure 2)。In the present exemplary embodiment, the primary transfer roller 5d and the separation roller 19 located upstream of the primary transfer roller 5d are relatively movable with respect to the frame member of the intermediate transfer unit 20K.

[0125] The movement of the primary transfer roller 5d and the separation roller 19 is effected by the sliding movement of a separation slider 30 as shown in Figure 7 which is the same as that of the above-described intermediate transfer unit 20. In the present exemplary embodiment, the movement of the primary transfer roller 5d and the separation roller 19 is thus effected by a separation mechanism 300 including the separation slider 30 and a separation cam 31, and the modes as shown in Figure 11A and 11B are switched. Note that the following mode switching operation is achieved by controlling the rotational phase of the separation cam shaft 32 based on a control signal issued from a control section 50 (see Figure 2 ) installed in the monochromatic imaging device 200K. Further, although the following description will exemplify the operation of switching modes in the order of the monochromatic mode and the full separation mode, the reverse operation can be performed to switch between any modes.

[0126] In the monochromatic mode as shown in Figure 11A , both the primary transfer roller 5d and the separation roller 19 are held in the lower positions, i.e., the first position and the second position, and the intermediate transfer belt 7 is in contact with the photosensitive drum 1d of the imaging unit Pd (see Figure 2 ). In this state, by performing an imaging operation by the imaging unit Pd and transferring the toner image formed on the photosensitive drum 1d to the recording material by the intermediate transfer belt 7, a monochromatic image can be formed on the recording material. That is, the tension cross section in the monochromatic mode is the same as that of the intermediate transfer belt 7 in the full-color mode as shown in Figure 8A .

[0127] In the case where the mode is switched from the monochromatic mode to the Figure 11B shown full separation mode, the separation cam 31 rotates 180 degrees in the direction of arrow R9 and the separation slider 30 slides to the right side (i.e., in the direction of arrow K2) in Figure 11B . That is, in the case where the mode is switched from the monochromatic mode (i.e., the third tension cross section or the first tension form) to the monochromatic full separation mode (i.e., the fifth tension cross section or the second tension form), when the separation cam 31 rotates 90 degrees in the direction of arrow R9, the tension cross section of the intermediate transfer belt 7 is switched to the same as that in Figure 8BThe tensioning section corresponding to the second tensioning section in [reference], i.e., the third tensioning form. The second tensioning section, i.e., the third tensioning form, is a tensioning form in which the primary transfer roller 5d is positioned at the transfer surface and the separation roller 19 is separated from the transfer surface. Therefore, the torque required for the separation operation can be reduced because the mode passes through the second tensioning section once when switching to the third and fifth tensioning sections. That is, compared with the case of directly switching from the monochromatic mode (i.e., the third tensioning section) to the monochromatic complete separation mode (i.e., the fifth tensioning section) without passing through the second tensioning section, the torque required in the separation movement can be suppressed. This is because when the monochromatic mode passes through the second tensioning section, the separation roller 19 and the primary transfer roller 5d are moved sequentially. In contrast, when directly switching from the monochromatic mode to the monochromatic complete separation mode, the primary transfer roller 5d and the separation roller 19 are both moved simultaneously. That is, when switching from the monochromatic mode to the second tensioning section, the separation roller 19 moves and the primary transfer roller 5d does not move, and when subsequently switching from the second tensioning section to the monochromatic complete separation mode, the primary transfer roller 5d moves.

[0128] It is arranged such that the second tensioning section is also passed through when switching from the monochromatic complete separation mode to the monochromatic mode. Compared with the case of directly switching the mode from the monochromatic complete separation mode to the monochromatic mode, the torque required for the switching operation can be suppressed. This is because, for similar reasons as above, the primary transfer roller 5d and the separation roller 19 are moved sequentially due to passing through the second tensioning section. Note that although in the present exemplary embodiment, control is performed such that the second tensioning section is always passed through when switching between the monochromatic complete separation mode and the monochromatic mode, the present disclosure is not limited to this case. For example, the monochromatic complete separation mode and the monochromatic mode can be switched without passing through the second tensioning section.

[0129] In the complete separation mode, the primary transfer roller 5d moves to the upper position to separate from the inner peripheral surface of the intermediate transfer belt 7, and the separation roller 19 moves to the upper position, i.e., the third position. At this time, the intermediate transfer belt 7 is in a state of being tensioned by the upstream guide roller 18 (see Figure 2 ) and the separation roller 19 at the upper position and is separated from the photosensitive drum 1d. The intermediate transfer unit 20K can be mounted to and removed from the device main body of the monochromatic image forming apparatus 200K while being held in the above-described complete separation mode, as shown in the above Figure 9 . That is, the intermediate transfer unit 20K can be mounted to and removed from the device main body in a state where the tensioning section of the intermediate transfer belt 7 is the Figure 11B fifth tensioning section shown.

[0130] The control section 50 performs control so as to enter the fully separated mode when the monochromatic image forming apparatus 200K is waiting for a signal (e.g., a print job) instructing the start of the image forming operation, except when the intermediate transfer unit 20K is being replaced. Specifically, when the user replaces the intermediate transfer unit 20K, the power is turned off. Upon receiving the power-off signal, the control section 50 is arranged to turn off the power after entering the fully separated mode. The control section 50 is also arranged to enter the fully separated mode when the control section 50 detects that the right door is opened to replace the intermediate transfer unit 20. The control section 50 is also arranged to enter the fully separated mode when the image forming unit (e.g., a drum cartridge) is removed from the apparatus main body to replace the photosensitive drum, in order to prevent the photosensitive drum and the intermediate transfer belt 7 from rubbing against each other and being damaged. Specifically, when the control section 50 detects that the front door is opened to replace the photosensitive drum, the control section 50 enters the fully separated mode. Further, when the intermediate transfer unit 20K is left for a long time, there is a case where a curl remains in the area of the intermediate transfer belt 7 facing and wound around the tension roller, that is, the bent shape of the tension roller is temporarily left on the belt. Thus, the control section 50 is arranged to enter the fully separated mode when the state of not forming an image continues for a predetermined time.

[0131] In the intermediate transfer unit 20, the image forming operation in the tension cross section corresponding to the BK mode of the intermediate transfer unit 20 shown Figure 8B is not normally performed. This is because it is preferable to always keep the intermediate transfer unit 20 in Figure 11A the monochromatic mode shown, because it is effective to increase the tension of the belt member to prevent the propagation of shock, as described above regarding switching the intermediate transfer unit 20 to the CL mode corresponding to the type of recording material. This is also because there is no need to worry about the deterioration of the developer and the photosensitive drum due to the image forming operation, nor about the running cost, because the yellow, magenta, and cyan image forming units Pa, Pb, and Pc are removed in the monochromatic image forming apparatus 200K. That is, the monochromatic image forming apparatus 200K is arranged to form an image through Figure 11A the third tension cross section, regardless of the grammage of the recording material.

[0132] The separation roller 19 is an example of a roller member that tensions the belt member, Figure 11A the lower position in Figure 11B corresponds to the second position, and the upper position in

[0133] corresponds to the third position where the separation roller 19 moves to the inner peripheral side of the belt member compared to the second position. The separation mechanism 300 is an example of a moving mechanism for moving such a roller member to the second and third positions. Figure 11A shown in the third tension cross section, the tension of the intermediate transfer belt 7 is, for example, Figure 8BThe tension of the second tension section shown is high, so the intermediate transfer belt 7 can be stably driven. Because of this, it is preferable to perform control according to the density of the color patch image detected by the color patch sensor PS in the state of the third tension section. Thus, according to the present exemplary embodiment, the control section 50 periodically or appropriately uses the color patch sensor PS to perform control in the monochromatic mode. That is, the control section 50 uses the color patch sensor PS to perform control when the tension section of the intermediate transfer belt 7 is Figure 11A the third tension section shown or when the separation roller 19 is positioned at the second position.

[0134] In the case of the present exemplary embodiment, the intermediate transfer unit 20 used in the full-color imaging device 200 including a plurality of photosensitive drums 1a to 1d is the same as the intermediate transfer unit 20K used in the monochromatic imaging device 200K including one photosensitive drum 1d. Thus, according to the present exemplary embodiment, it is possible to suppress a decrease in the image quality of the image transferred in the monochromatic imaging device 200K. That is, when an image is formed by installing the intermediate transfer unit 20K in the monochromatic imaging device 200K, the tension section of the intermediate transfer belt 7 is switched to the third tension section that is the same as the first tension section. The first tension section is the tension section in the case of performing the full-color mode or the contact monochromatic mode in the full-color imaging device 200, so the tension of the intermediate transfer belt 7 is high. This arrangement makes it possible to suppress a decrease in the image quality of the image to be transferred to the recording material S. Even when the basis weight of the recording material is particularly large, it is possible to suppress a decrease in the quality of the transferred image.

[0135] Other embodiments

[0136] Embodiments of the present invention can also be implemented by a computer of a system or device. The computer reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which can also be more fully referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more of the above embodiments, and / or the computer includes one or more circuits (e.g., an application specific integrated circuit (ASIC)) for performing the functions of one or more of the above embodiments. Embodiments of the present invention can also be implemented by a method performed by the computer of the system or device by, for example, reading and executing computer-executable instructions from the storage medium to perform the functions of one or more of the above embodiments and / or by controlling the one or more circuits to perform the functions of one or more of the above embodiments. The computer can include one or more processors (e.g., a central processing unit (CPU), a microprocessing unit (MPU)) and can include a network of stand-alone computers or stand-alone processors to read and execute the computer-executable instructions. The computer-executable instructions can be provided to the computer, for example, from a network or a storage medium. The storage medium can include, for example, one or more of a hard disk, a random access memory (RAM), a read only memory (ROM), the memory of a distributed computing system, an optical disk (e.g., a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD)) TM ), a flash device, a memory card, etc.

[0137] Embodiments of the present invention can also be implemented by the following method, i.e., by providing software (a program) that performs the functions of the above embodiments to a system or device through a network or various storage media, and the method by which the computer or the central processing unit (CPU), the microprocessing unit (MPU) of the system or device reads and executes the program.

[0138] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications as well as equivalent structures and functions.

Claims

1. A monochromatic imaging device, comprising: A single photosensitive drum configured to carry a toner image; A belt member onto which the toner image formed on the photosensitive drum is transferred; A transfer member configured to transfer the toner image from the photosensitive drum to the belt member; A plurality of tension rollers that tension the belt member, the plurality of tension rollers including a separation roller movably disposed upstream of the transfer member and adjacent to the transfer member in the rotational direction of the belt member; A changing mechanism configured to change the tensioned shape of the belt member by changing the positions of the transfer member and the separation roller, the changing mechanism being configured to switch the tensioned form of the belt member to a plurality of tensioned forms including a first tensioned form, a second tensioned form, and a third tensioned form, the first tensioned form being a tensioned form capable of transferring the toner image from the photosensitive drum to the belt member by forming a transfer surface between the transfer member and the separation roller by positioning the transfer member at a first position and the separation roller at a second position, the second tensioned form being a tensioned form in which each of the transfer member and the separation roller is separated from the transfer surface to the opposite side of the photosensitive drum, and the third tensioned form being a tensioned form in which the transfer member is positioned at the first position and the separation roller is positioned at a third position away from the transfer surface toward the opposite side of the photosensitive drum; And A control section configured to control the changing mechanism; Wherein, when the tensioned shape of the belt member is the first tensioned form, the tension of the belt member is a first tension, and when the tensioned shape of the belt member is the third tensioned form, the tension of the belt member is a second tension, and the first tension is higher than the second tension; Wherein, the control section is configured to control the changing mechanism so as to pass through the third tensioned form when switching the tensioned form of the belt member from the second tensioned form to the first tensioned form.

2. The monochromatic imaging device according to claim 1, wherein, In the case where the tensioned form of the belt member is the third tensioned form, the imaging operation is not performed.

3. The monochromatic imaging device according to claim 1 or 2, wherein, The control section is configured to control the changing mechanism so as to change the tensioned form of the belt member to the second tensioned form when the power of the imaging device is turned off.

4. The monochromatic imaging device according to claim 1 or 2, wherein, The control section is configured to control the changing mechanism so as to change the tensioned form of the belt member to the second tensioned form according to the time elapsed since the end of the imaging operation.

5. The monochromatic imaging device according to claim 1 or 2, wherein, The control section is configured to control the changing mechanism so as to pass through the third tensioned form when switching the tensioned form of the belt member from the first tensioned form to the second tensioned form.

6. The monochromatic imaging device according to claim 1 or 2, wherein, The changing mechanism includes a sliding member and a rotating cam. The sliding member is arranged to be movable and includes a first cam surface for moving the transfer member and a second cam surface for moving the separation roller. The rotating cam is arranged to contact the sliding member and move the sliding member, and Wherein, the control section controls the phase of the rotating cam.

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