Image forming apparatus

Abstract

An image forming apparatus includes an image bearing member, a transfer roller, a first bearing, a second bearing, a first holding member, a second bearing member, a first urging member, a second urging member, and a contact member. The contact member contacts the first bearing on the upstream side of the rotation center of the transfer roller so as not to be disposed on the downstream side of the rotation center of the transfer roller with respect to the direction in which the first holding member is pressed by the first pressing member.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus using an electrophotographic type or an electrostatic recording type, such as a copying machine, a printer, a facsimile machine, or a multifunctional machine having multiple functions of these machines. Background Art

[0002] Conventionally, for example, in an image forming apparatus (such as a copier) using an electronic photographic type, a toner image formed on an image bearing member (such as a photosensitive member or an intermediate transfer member) is transferred to a recording material by applying a transfer bias to a transfer roller. For example, an elastic roller provided with an elastic layer is used as a transfer roller, and conductivity is imparted to the elastic layer by dispersing an ionic conductive agent or the like. Then, a conductive brush or a carbon chip or the like contacts the shaft portion of the transfer roller, thereby electrically connecting the transfer roller to a power supply path. However, in the case of such a constitution, there is a possibility that a power-on failure due to wear of the conductive brush or the carbon chip and abnormal noise due to mutual sliding of metals may occur.

[0003] On the other hand, in Japanese Patent Laid-Open No. Hei 11 338280, a configuration is proposed in which a shaft portion of a roller is rotatably supported by a bearing formed of a conductive resin, and in which the bearing is pressurized and electrically connected by a conductive spring.

[0004] However, in the above-mentioned conventional configuration, the outer periphery of the shaft portion and the inner periphery of the bearing formed of the conductive resin slide against each other while being pressurized. Therefore, as the image forming apparatus is used, the shaft portion or the bearing is worn, so that there is a possibility that the set pressurizing force cannot be applied. As a result, inconveniences such as transfer characteristics of uneven images may occur. Summary of the invention

[0005] Therefore, the main object of the present invention is to provide an image forming device that can provide stable (electrical) power supply with a simple structure while suppressing the occurrence of inconvenience caused by wear of a roller shaft portion or an electrical connection portion (to which pressure and electricity are applied) in the image forming device.

[0006] This object has been achieved by the image forming apparatus according to the present invention.

[0007] According to one aspect of the present invention, an image forming device is provided, which includes: an image bearing member, which is configured to carry a colorant image; a transfer roller, which includes a rotatable roller portion and a shaft portion, the shaft portion protruding from each of one end portion and the other end portion of the roller portion relative to the rotation axis direction of the roller portion, and is configured to transfer the colorant image carried on the image bearing member under the application of a transfer voltage; a first bearing, which is mounted to the shaft portion at the one end portion; a second bearing, which is mounted to the shaft portion at the other end portion; a first retaining member, which is configured to be movable in a direction intersecting the rotation axis of the transfer roller and to retain the first bearing, wherein the first retaining member retains the first bearing so as to be detachably mounted to the first bearing in a direction intersecting the rotation axis of the transfer roller; a second bearing member, which is configured to be movable in a direction intersecting the rotation axis of the transfer roller The first bearing is movable in a direction intersecting the rotation axis and is capable of holding the second bearing, wherein the second holding member holds the second bearing so as to be detachably mounted on the second bearing in a direction intersecting the rotation axis of the transfer roller; a first pushing member, which is constructed to push the first holding member toward the image bearing member; a second pushing member, which is constructed to push the second holding member toward the image bearing member; a contact member, which is movably supported relative to the first holding member and is configured to be able to contact the outer peripheral surface of the first bearing, wherein the contact member forms a power supply path for the transfer roller, wherein, relative to the direction in which the first holding member is pushed by the first pushing member, the contact member is constructed to contact the first bearing on the upstream side of the rotation center of the transfer roller, so as not to be arranged on the downstream side of the rotation center of the transfer roller.

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

[0009] Figure 1 is a schematic cross-sectional view of the image forming apparatus (when the cover is closed).

[0010] Figure 2 is a schematic cross-sectional view of an image forming section.

[0011] Figure 3 is a schematic cross-sectional view of the image forming apparatus (when the cover is opened).

[0012] Figure 4 It is a perspective view of the external secondary transfer roller and bearing.

[0013] Figure 5 is a perspective view of an external secondary transfer roller unit.

[0014] Figure 6 It is a perspective view of the pressure applying / power supplying section of the external secondary transfer roller.

[0015] Figure 7 It is a cross-sectional view of the pressure applying / power supplying portion of the external secondary transfer roller.

[0016] Figure 8 is a cross-sectional view of the pressing portion of the external secondary transfer roller.

[0017] Fig. 9 It is a perspective view of the secondary transfer unit.

[0018] Fig.10 is a front view of the external secondary transfer roller unit on one end side of the external secondary transfer roller. DETAILED DESCRIPTION

[0019] Hereinafter, the image forming apparatus according to the present invention will be described in further detail with reference to the accompanying drawings.

[0020] [Example 1]

[0021] 1. Overall structure and operation of image forming apparatus

[0022] First, the overall structure and operation of the image forming apparatus of this embodiment will be described. Figure 1 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem laser beam printer of an intermediate transfer type, in which a full-color image can be formed on a sheet-like recording material S such as paper or a plastic sheet by using an electrophotographic type.

[0023] The image forming apparatus 100 includes four image forming sections PY, PM, PC, and PK for forming images of yellow (Y), magenta (M), cyan (C), and black (K), respectively, as a plurality of image forming sections (stations). The four image forming sections PY, PM, PC, and PK are juxtaposed along the conveying direction of the image transfer surface of the intermediate transfer belt 7 described later. Incidentally, in some cases, elements provided for each color and having the same or corresponding function or configuration are collectively described by omitting the suffixes Y, M, C, and K of the reference numerals or symbols indicating the elements provided for the associated one color. Figure 21 is a schematic cross-sectional view showing the configuration of the image forming section P in an enlarged manner. In the present embodiment, the image forming section P is composed of a photosensitive drum 1 (1Y, 1M, 1C, 1K), a charging roller 2 (2Y, 2M, 2C, 2K), an exposure device 3, a developing device 4 (4Y, 4M, 4C, 4K), a primary transfer roller 5 (5Y, 5M, 5C, 5K), a drum cleaning device 6 (6Y, 6M, 6C, 6K), etc. Incidentally, in the present embodiment, the exposure device 3 is configured as a single unit for exposing the photosensitive drums 1Y, 1M, 1C, and 1K of the four image forming sections PY, PM, PC, and PK, but the exposure device 3 may be independently provided for each image forming section P.

[0024] Here, regarding the image forming apparatus 100 and its constituent elements, Figure 1 The front side of the drawing page is referred to as the "front side (front surface side)", and Figure 1 The back side of the drawing sheet is referred to as the "back side (back surface side)". The front-to-back direction (perpendicular to Figure 1 The direction of the drawing page) is substantially parallel to the rotation axis direction of the photosensitive drum 1 and the rotation axis direction of the tension roller of the intermediate transfer belt 7. In addition, with respect to the image forming apparatus 100 and its constituent elements, up and down refer to up and down in the direction of gravity (vertical direction), and do not simply refer to "directly above" and "directly below", and include above and below passing through the reference position or the horizontal position of the element.

[0025] exist Figure 1 and Figure 2 In the embodiment, a photosensitive drum 1 (which is a drum-type photosensitive member (electrophotographic photosensitive member)) as a first image bearing member is rotationally driven in the direction of arrow R1 (clockwise). The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined polarity (negative polarity in this embodiment) and a predetermined potential by a charging roller 2 (which is a roller-type charging member) as a charging section. The charged surface of the photosensitive drum 1 is subjected to scanning exposure of light according to an image signal (image information) by an exposure device (laser scanner) 3 as an exposure section, so that an electrostatic latent image (electrostatic image) according to the image signal is formed on the photosensitive drum 1.

[0026] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer from a developing device 4 as a developing portion, so that a toner image (toner picture, developer image) is formed on the photosensitive drum 1 .

[0027] The intermediate transfer belt 7 is arranged opposite to the four photosensitive drums 1Y, 1M, 1C, and 1K, and is an intermediate transfer member composed of an endless belt as a second image bearing member. The intermediate transfer belt 7 is extended around an internal secondary transfer roller 71, a tension roller 72, a primary transfer pre-roller 73, and a secondary transfer pre-roller 74 as a plurality of tension rollers, and is stretched with a predetermined tension. The intermediate transfer belt 7 is rotated by the internal secondary transfer roller 71 serving as a driving roller, and a driving force is transmitted thereto. Figure 1 The intermediate transfer belt 7 rotates (circulates and moves) in the direction of arrow R2 (counterclockwise) in the figure. On the inner peripheral surface side of the intermediate transfer belt 7, primary transfer rollers 5Y, 5M, 5C and 5K are respectively provided corresponding to the four photosensitive drums 1Y, 1M, 1C and 1K, which are roller-type primary transfer members as primary transfer sections. The primary transfer roller 5 presses the intermediate transfer belt 7 against the photosensitive drum 1, and forms the following primary transfer section (primary transfer nip section) T1 (T1Y, T1M, T1C, T1K), which is the contact section between the photosensitive drum 1 and the intermediate transfer belt 7. That is, the primary transfer section T1 is formed by sandwiching the intermediate transfer belt 7 between the primary transfer roller 5 and the photosensitive drum 1. The toner image formed on the photosensitive drum 1 is transferred (primarily transferred) to the rotating intermediate transfer belt 7 in the primary transfer section T1 by the action of a predetermined pressing force and an electrical bias applied by the primary transfer roller 5. During the primary transfer, a primary transfer voltage (primary transfer bias) of a polarity opposite to the normal charge polarity (positive polarity in the present embodiment), which is the charge polarity of the toner during development, is applied to the primary transfer roller 5. For example, during full-color image formation, the toner images of Y, M, C, and K colors formed on the photosensitive drum 1 are sequentially transferred in a superimposed manner onto the intermediate transfer belt 7 in the primary transfer portion T1.

[0028] On the outer peripheral surface side of the intermediate transfer belt 7, at a position opposite to the inner secondary transfer roller 71 as an opposing roller, an outer secondary transfer roller 200 is provided, which is a roller-type secondary transfer member (transfer roller) as a secondary transfer portion. The outer secondary transfer roller 200 is pressed toward the inner secondary transfer roller 71 through the intermediate transfer belt 7, and forms a secondary transfer portion (secondary transfer nip portion) T2 which is a contact portion between the intermediate transfer belt 7 and the outer secondary transfer roller 200. That is, the secondary transfer portion T2 is formed by sandwiching the intermediate transfer belt 7 between the inner secondary transfer roller 71 and the outer secondary transfer roller 200. The toner image formed on the intermediate transfer belt 7 is transferred (secondary transfer) in the secondary transfer portion T2 to the recording material S sandwiched between the intermediate transfer belt 7 and the external secondary transfer roller 200 and conveyed by the intermediate transfer belt 7 and the external secondary transfer roller 200 by the action of the pressing force and the electrical bias applied by the external secondary transfer roller 200. During the secondary transfer, a secondary transfer voltage (secondary transfer bias) of a polarity opposite to the normal charge polarity of the toner (positive polarity in this embodiment) is applied to the external secondary transfer roller 200. The internal secondary transfer roller 71 is electrically grounded. Incidentally, a secondary transfer voltage of the same polarity as the normal charge polarity of the toner may be applied to the internal secondary transfer roller 71, and the external secondary transfer roller 200 may be electrically grounded.

[0029] The recording material (transfer material, recording medium, sheet) S is stacked and accommodated in the recording material accommodating portion 11. The recording material S is fed one by one by a feeding roller 12 or the like as a feeding member, and the fed recording material S is conveyed toward the registration roller pair 13. Then, the recording material S is subjected to correction of tilt movement by the registration roller pair 13, and then is fed to the secondary transfer portion T2 at an appropriate timing.

[0030] The recording material S to which the toner image is transferred is sent to the fixing device 14. The fixing device 14 fixes (melts, adheres) the toner image on the recording material S by applying heat and pressure to the recording material S carrying the unfixed toner image. The recording material S to which the toner image is fixed is discharged (output) to the outside of the apparatus main assembly 110 of the image forming apparatus 100 by the discharge roller pair 15 as a conveying member. The recording material S discharged from the apparatus main assembly 110 is sequentially stacked on a stacking portion 16 provided outside the apparatus main assembly 110.

[0031] Furthermore, the toner remaining on the photosensitive drum 1 after the primary transfer step (primary transfer residual toner) is removed from the photosensitive drum 1 and collected by the drum cleaning device 6 as a photosensitive member cleaning section. Furthermore, on the outer peripheral surface side of the intermediate transfer belt 7, at a position opposed to the tension roller 72, a belt cleaning device 75 as an intermediate transfer member cleaning section is provided. Deposits such as toner (secondary transfer residual toner) remaining on the intermediate transfer belt 7 after the secondary transfer step are removed from the intermediate transfer belt 7 by the belt cleaning device 75 and collected.

[0032] In this embodiment, in each image forming portion P, a photosensitive drum 1 and a charging roller 2, a developing device 4 and a drum cleaning device 6 as a process portion actable on the photosensitive drum 1 constitute a process cartridge 8. The process cartridge 8 is made integrally detachably mountable to the apparatus main assembly 110.

[0033] Furthermore, the intermediate transfer belt 7, a plurality of tension rollers 71 to 74 for tensioning the intermediate transfer belt 7, the primary transfer roller 5, the belt cleaning device 75, and the like constitute an intermediate transfer unit 9. The intermediate transfer unit 9 is made integrally detachably mountable to the apparatus main assembly 110. Incidentally, the apparatus main assembly 110 of the image forming apparatus 100 is a portion obtained by removing the process cartridge 8 and the intermediate transfer unit 9 from the image forming apparatus 100.

[0034] 2. Opening / closing of the lid

[0035] When the image forming apparatus 100 is viewed from the front, a cover 10 as an openable (and closable) member that can be opened and closed is provided on the right-hand side of the image forming apparatus 100 of the present embodiment. This is because a jam of the recording material S occurring in the conveying path 17 of the recording material S is cleared or a component such as the external secondary transfer roller 200 or the intermediate transfer unit 9 is replaced.

[0036] The cover 10 is provided with a cover rotation shaft 18. The cover 10 is supported rotatably about a rotation axis extending substantially horizontally in the front-rear direction by engagement of the cover rotation shaft 18 with a frame (not shown) constituting a housing 120 of the image forming apparatus 100. Figure 3 1 is a schematic cross-sectional view showing a state where the cover 10 of the image forming apparatus 100 of the present embodiment is opened. Figure 3 As shown, the cover 10 is configured to stop at a predetermined position during opening by being supported by a link mechanism (not shown) provided to connect the frame of the image forming apparatus 100 and the cover 10. Incidentally, the cover 10 is configured to be opened and closed by a worker (operator) such as a user or a service person operating a handle (not shown).

[0037] In the present embodiment, a secondary transfer unit 220 as a supporting device for supporting the external secondary transfer roller 200 is mounted to the cover 10. Figure 1 As shown, in a state where the cover 10 is closed, the secondary transfer unit 220 is arranged at a predetermined position by being clamped by the components in the device main component 110 and the cover 10. In this embodiment, the secondary transfer unit 220 is arranged at a predetermined position by being positioned by the components in the device main component 110. In this state, the external secondary transfer roller 200 is pressed against the surface (peripheral surface) of the intermediate transfer belt 7 (which is the second image bearing member) as the contacted member wound around the internal secondary transfer roller 71, and is made operable (can form an image). In addition, as Figure 3 As shown, when the cover 10 is opened, the external secondary transfer roller 200 moves together with the cover 10 in a direction separating from the intermediate transfer belt 7 (internal secondary transfer roller 71), so that the operator can approach the secondary transfer unit 220. Figure 3 As shown, when the cover 10 is opened, the secondary transfer unit 220 not only exposes the external secondary transfer roller 200 upward, but also exposes at least a portion of its side surface toward the front side and the rear side on both sides of the front-to-back direction. By the way, in a state where the external secondary transfer roller 200 is supported by the secondary transfer unit 220 and mounted to the cover 10, the rotation axis direction (rotation axis direction) of the external secondary transfer roller 200 is substantially parallel to the front-to-back direction.

[0038] 3. Secondary transfer unit

[0039] 3-1. External secondary transfer roller

[0040] Next, the configuration of the external secondary transfer roller 200 as the roller member for replacement in the present embodiment will be described. Figure 4 : is a perspective view showing the appearance of the external secondary transfer roller 200 (and a bearing 203 fixed to the external secondary transfer roller 200 and described later) in this embodiment.

[0041] The external secondary transfer roller 200 includes a roller portion 201 and a shaft portion 202, the roller portion 201 is formed with an elastic member constituting an elastic layer (foamed elastic layer), and the shaft portion 202 constitutes a core metal portion. In the present embodiment, the roller portion 201 is composed of a sponge (foamed elastomer) formed by a metal complex, or a sponge (foamed elastomer) formed by NBR rubber or EPDM rubber containing a conductive agent such as carbon black. In addition, in the present embodiment, the shaft portion 202 is composed of metal. At each end of the external secondary transfer roller 200 relative to the direction of the rotation axis, the shaft portion 202 protrudes from the roller portion 201. In the present embodiment, the external secondary transfer roller 200 is formed so that the outer diameter of the roller portion 201 (sponge layer) is 24 mm and the thickness is 6 mm. However, the roller diameter, the thickness of the elastic layer, etc. are not limited to these values.

[0042] In addition, a pair of bearings 203 are mounted to the shaft portion 202, which is arranged at the opposite ends of the external secondary transfer roller 200 relative to the rotation axis direction. In the present embodiment, a ball bearing is used as the bearing 203. However, the bearing 203 is not limited thereto, but for example, typically, a ball bearing or a roller bearing as a rolling (anti-friction) bearing can be preferably used. The bearing 203 can have a general structure and include an outer ring, an inner ring, and a rolling element (a ball in this embodiment) arranged between these rings (and further, a holding device for holding the rolling element between the outer ring and the inner ring can be included). The bearing 203 contacts a pressing member (moving member) 216 used as an electrical connection portion described later, and has sufficient conductivity for connecting the external secondary transfer roller 200 to a power supply path (power-on path). In the present embodiment, regarding the bearing 203, the outer ring, the inner ring, and the ball are made of metal and have sufficient conductivity. In the present embodiment, the bearings 203 arranged at the opposite ends of the external secondary transfer roller 200 have substantially the same configuration.

[0043] Here, in the present embodiment, each bearing 203 is press-fitted and fixed to the shaft portion 202. The outer diameter of the shaft portion 202 before the press-fitting of the bearing 203 is slightly larger than the inner diameter of the inner ring of the bearing 203. The difference between these diameters becomes the press-fit margin (difference). Thus, after the bearing 203 is press-fitted to the shaft portion 202, the bearing 203 does not move on the shaft portion 202 in the direction of the rotation axis of the external secondary transfer roller 200, and does not come off from the shaft portion 202 due to the normal force applied in the replacement operation of the external secondary transfer roller 200 described later, etc.

[0044] 3-2. External secondary transfer roller unit

[0045] Next, the pressurizing / powering configuration of the external secondary transfer roller 200 in the present embodiment will be described.

[0046] Figure 5 FIG. 2 is a perspective view of the external secondary transfer roller unit 210 in this embodiment. Figure 5 , the rear side of the external secondary transfer roller 200 relative to the rotation axis direction is shown on the left hand side of the drawing page. Figure 6 2 is a perspective view showing a pressurizing / powering structure of the external secondary transfer roller 200 in this embodiment. Figure 6 In FIG. 1 , a pressurizing / power supplying structure provided at the rear end portion of the external secondary transfer roller 200 relative to the rotation axis direction is shown, and the illustration of the external secondary transfer roller 200 is omitted. Figure 7: is a cross-sectional view showing a pressurizing / powering configuration of the external secondary transfer roller 200 in the rear side end portion of the external secondary transfer roller 200 with respect to the rotation axis direction (showing a cross section substantially parallel to the rotation axis direction of the external secondary transfer roller 200). Figure 8 : is a sectional view showing a pressurizing configuration of the external secondary transfer roller 200 in the front side end portion of the external secondary transfer roller 200 with respect to the rotation axis direction (showing a cross section substantially parallel to the rotation axis direction of the external secondary transfer roller 200 ).

[0047] like Figure 5 As shown, the external secondary transfer roller 200 is supported by a support member R (rear support member, first support member) 211 and a support member F (front support member, second support member) 212 at opposite ends of the external secondary transfer roller 200 relative to the rotation axis direction through a bearing 203. In the present embodiment, each of the support member 211 and the support member 212 is formed integrally of an electrically insulating resin. In the present embodiment, the external secondary transfer roller unit 210 is composed of the external secondary transfer roller 200 (and the bearing 203 fixed to the external secondary transfer roller 200), the support member R211 (and the pressing member 216 held by it and described later) and the support member F212.

[0048] Incidentally, in the present embodiment, the supporting member R211 and the supporting member F212 have similar configurations (wherein these members are substantially symmetrical with respect to a flat surface substantially perpendicular to the rotation axis direction of the external secondary transfer roller 200 passing through the center of the external secondary transfer roller 200 with respect to the rotation axis direction) except that these members differ in points described later. As described later, the supporting member R211 and the supporting member F212 differ mainly in the presence / absence configuration of the pressing member 216 and the positioning configuration of the bearing 203.

[0049] First, refer to Figure 6 and Figure 7 , the pressurizing / powering structure of the external secondary transfer roller 200 in the rear side end portion with respect to the rotation axis direction of the external secondary transfer roller 200 will be described. The supporting member R211 is supported so as to be able to move relative to the secondary transfer guide 221 ( Fig. 9 ) slides in a predetermined direction. The predetermined direction is a direction toward the intermediate transfer belt 7 (internal secondary transfer roller 71) and a direction opposite thereto during the operation of the image forming apparatus 100. During the operation of the image forming apparatus 100, the supporting member R211 is pressed by the pressing member 217 in a predetermined direction in the direction toward the intermediate transfer belt 7 (internal secondary transfer roller 71).

[0050] In this embodiment, the pressure member 217 is composed of a compression coil spring formed of a nickel-based alloy. The pressure member 217 is arranged between the receiving portion 211a provided on the supporting member R211 and the bearing surface 221a provided on the secondary transfer guide 221 (see Figure 6 )between.

[0051] Furthermore, the supporting member R211 is provided with a supporting portion 213, and the bearing 203 which is press-fitted and fixed to the shaft portion 202 of the outer secondary transfer roller 200 is provided from Figure 6 The bearing 203 is installed in the upper part of the support portion 213. The installation direction (insertion / extraction direction) of the bearing 203 is a direction substantially perpendicular to the rotation axis direction of the external secondary transfer roller 200 when the external secondary transfer roller 200 is supported by the support member R211 and the support member F212, and is a direction along the pressure direction of the pressure member 217. The support portion 213 is provided with an opening 213a, which is located at Figure 6 The middle is opened upwardly to be able to receive the bearing 203 along the installation direction.

[0052] In addition, by the support member R211, the pressing member 216 as a moving member is held so as to be movable relative to the support member R211 along the pressurizing direction of the external secondary transfer roller 200 by the pressurizing member 217. The pressing member 216 is slidably accommodated in the pressing member holding portion 211d provided in the support member R211. The pressing member 216 is exposed to the opening 213a of the support portion 213 so as to contact the bearing 203. The bearing abutting portion (abutting surface in this embodiment) 216b of the pressing member 216 that can contact the outer periphery of the bearing 203 is arranged adjacent to the bearing abutting portion (abutting surface in this embodiment) 211b of the support member R211 that can contact the outer periphery of the bearing 203. Each of the bearing abutting portion 211b of the support member R211 and the bearing abutting portion 216b of the pressing member 216 can be a plane, a curved surface (arc-shaped or U-shaped) along the outer periphery of the bearing 203, a rib-shaped portion, etc.

[0053] The pressing member 216 is formed of a conductive material, and in particular, is formed of a conductive resin in this embodiment.

[0054] Incidentally, the pressing member 216 may also be formed of another conductive material such as metal. In addition, the pressing member 216 is pressurized by the pressing member 217 to pressurize the above-mentioned support member R211. The pressurization direction is along the sliding movement direction of the support member R211 as described above, and is in the direction toward the bearing 203 arranged on the support portion 213. That is, the pressing member 217 is not only arranged between the receiving portion 211a of the support member R211 and the bearing surface 221a of the secondary transfer guide 221 as described above, but also arranged between the receiving portion 216a provided on the pressing member 216 and the bearing surface 221a of the secondary transfer guide 221. Thus, the pressing member 217 contacts the support member R211 and presses the support member R211, and further, contacts the pressing member 216 and presses the pressing member 216 toward the bearing 203, so that the pressing member 216 contacts and presses the bearing 203. In addition, in this embodiment, if Figure 5 As shown, a pressing (energizing) member 218 supplied with a transfer current (transfer voltage) from a high-voltage power source provided in the image forming apparatus 100 is provided to contact the pressing member 217. In the present embodiment, the pressing member 218 is composed of a conductive spring. Thus, in the present embodiment, a power supply path (energizing path) from the high-voltage power source is connected to the external secondary transfer roller 200 through the pressing member 218, the pressing member 217, the pressing member 216 and the bearing 203.

[0055] In the state where the cover 10 is opened, that is, in the state where the external secondary transfer roller 200 is separated from the intermediate transfer belt 7, the pressing member 216 pressed by the pressing member 217 is locked by the supporting member R211. That is, the supporting member R211 is provided with a locking portion 211c, and the pressing member 217 is provided with a portion to be locked 216c engaged with the locking portion 211c. In addition, in the state where the locking portion 211c and the portion to be locked 216c are engaged with each other, the bearing abutting portion 216b of the pressing member 216 protrudes toward the bearing 203 side in the pressing direction of the pressing member 217 more than the bearing abutting portion 211b of the supporting member R211. In this state, at least a portion of the bearing abutting portion 216b of the pressing member 216 protrudes toward the bearing 203 side by a protruding amount W1 more than the bearing abutting portion 211b of the supporting member R211. When the external secondary transfer roller 200 contacts the intermediate transfer belt 7, the pressing force of the pressing member 217 is applied to the bearing 203 through the bearing abutment portion 211b of the supporting member R211. In addition, at this time, the bearing abutment portion 216b of the pressing member 216 is retracted to such an extent that the bearing abutment portion 216b is substantially flush with the bearing abutment portion 211b of the supporting member P211, and the pressing force is applied to the bearing 203 through the pressing member 217. From the viewpoint of the pressing stability of the external secondary transfer roller 200, the above-mentioned protrusion amount W1 is preferably 0.1 mm or more and about 1 mm or less, and is about 0.3 mm in the present embodiment.

[0056] By adopting this configuration, when the external secondary transfer roller 200 contacts the intermediate transfer belt 7, the bearing 203 and the pressing member 216 can be more reliably contacted with each other. Thus, the electrical connection between the bearing 203 and the pressing member 216 can be more reliably performed. In addition, the pressing force of the pressing member 217 is applied to the bearing 203 through the supporting member R211, which is easily constituted to be stronger than the pressing member 216 formed of a conductive resin, and in addition, the pressing force of the pressing member 217 can be used for pressurization between the pressing member 216 and the bearing 203.

[0057] Thus, the electrical connection between the bearing 203 and the pressing member 216 can be more reliably performed with a simple structure, and, further, the pressing force applied to the bearing 203 by the pressing member 217 can be more reliably performed. Furthermore, by adopting such a structure, the pressing member 216 is arranged in the area where the bearing 203 protrudes along the pressing direction of the pressing member 217. That is, when the pressing member 216 is observed from the external secondary transfer roller 200 side along the pressing direction of the pressing member 217, the pressing member 216 is hidden on the rear side of the bearing 203. Thus, the possibility that the operator touches the electrical connection portion connected to the external secondary transfer roller 200 in the state where the cover 10 is opened, thereby contaminating or damaging the external secondary transfer roller 200, can be reduced.

[0058] Next, refer to Figure 8 , the pressurizing structure of the external secondary transfer roller 200 in the front side end portion of the external secondary transfer roller 200 with respect to the rotation axis direction will be described. As described above, in the present embodiment, the supporting member F212 has a structure similar to that of the supporting member R211. However, in this embodiment, as Figure 8 As shown, the support member F212 is not provided with the above-mentioned pressing member 216 provided to the support member R211. The support member F212 receives the pressing force of the pressing member 217 through the receiving portion 212a, and also supports the bearing 203 through the bearing abutment portion 212b.

[0059] The support member F212 is similar to the support member R211, and is provided with a support portion 213, and is press-fitted and fixed to the bearing 203 of the shaft portion 202 of the outer secondary transfer roller 200. Figure 8 The upper part is mounted on the support part 213.

[0060] At this time, in the present embodiment, the external secondary transfer roller 200 is translated and moved in a predetermined direction (basically only by this translation movement), so that the bearings 203 arranged at the opposite ends relative to the direction of the rotation axis are respectively received by the support portions 213 of the support member R211 and the support member F212, so that the external secondary transfer roller 200 is assembled with the support member R211 and the support member F22, so that the position of the external secondary transfer roller 200 relative to the direction of the rotation axis can be determined. In the present embodiment, the support portion 213 of the support member R211 is constructed to engage with the bearing 203 of the external secondary transfer roller 200 relative to the direction of the rotation axis. On the other hand, the support portion 213 of the support member F212 is constructed to ensure the play with respect to the bearing 203 relative to the direction of the rotation axis of the external secondary transfer roller 200. Specifically, as Figure 7 As shown, for the support member R211, the following relationship is established: the engagement is achieved by setting the width W2 between the side walls 211e and 211e of the support portion 213 opposite to the opposite side of the bearing 203 with respect to the rotation axis direction of the external secondary transfer roller 200 to be substantially equal to the width W3 of the bearing 203. In this way, in the support member R211, the position of the external secondary transfer roller 200 to which the bearing 203 is fixed is determined. On the other hand, as Figure 8As shown, for the support member F212, the following relationship is established: the clearance is provided by setting the width W4 between the side walls 212c and 212c of the support portion 213 opposite to the opposite side of the bearing 203 relative to the rotation axis direction of the external secondary transfer roller 200 to be wider than the width W3 of the bearing 203. In this way, even if the length (between a pair of bearings 203) of the external secondary transfer roller 200 relative to the rotation axis direction changes, the external secondary transfer roller 200 can be assembled with the support member R211 and the support member F212. In order to more reliably achieve the contact between the pressing member 216 and the bearing 203 constituting the electrical connection portion, it is preferred to determine the position of the bearing 203 (external secondary transfer roller 200) on the side of the support member R211 as the power supply side.

[0061] Therefore, in the present embodiment, the external secondary transfer roller 200 is supported by the support member R211 and the support member F212 through a pair of bearings 203 fixed to the opposite ends of the external secondary transfer roller 200 with respect to the rotation axis direction, and is pressed toward the intermediate transfer belt 7. Furthermore, in the present embodiment, the pressing force of the pressing member 217 for pressing the support member R211 is also used to press the pressing member 216 constituting the electrical contact with the external secondary transfer roller 200 against the bearing 203. Here, when the external secondary transfer roller 200 rotates, the outer ring of the bearing 203 does not rotate, and therefore, the wear of the pressing member 216 formed of a conductive resin can be reduced (substantially eliminated) compared with a configuration in which a bearing formed of a conductive resin directly contacts the roller shaft portion.

[0062] Incidentally, a roller holding portion 214 is also provided to each of the supporting member R211 and the supporting member F212 , thereby suppressing the detachment of the mounted external secondary transfer roller 200 (the details of which will be described later).

[0063] 3-3. Secondary transfer guide

[0064] Next, refer to Fig. 9 and Fig.10 , the configuration of the secondary transfer guide 221 as a holding member, which is a mounted portion of the external secondary transfer roller unit 210 , and the configuration of the secondary transfer unit 220 will be described.

[0065] Fig. 9 2 is a perspective view of the appearance of the secondary transfer unit 220. Fig. 9 , the rear side of the external secondary transfer roller 200 relative to the rotation axis direction is shown on the left hand side of the drawing page. Fig.10 2 is a front view of the secondary transfer unit 220 on one end side of the external secondary transfer roller 200. Fig.10In the figure, the vicinity of the front end of the external secondary transfer roller 200 relative to the rotation axis direction is shown, and the secondary transfer guide 221 is omitted. Fig. 9 and Fig.10 As shown, the rotation axis direction of the external secondary transfer roller 200 is taken as the A1 direction, and the insertion / extraction direction of the external secondary transfer roller 200 in the secondary transfer unit 220 is taken as the A2 direction, wherein the installation direction is the + (positive) direction, and the direction perpendicular to the A1 direction and the A2 direction is taken as the A3 direction.

[0066] The secondary transfer unit 220 in this embodiment is configured by including a secondary transfer guide 221 provided with a sheet guide 222 for guiding a recording material (sheet) S conveyed from the upstream side of a conveying path and including an external secondary transfer roller unit 210 .

[0067] The secondary transfer guide 211 includes, at opposite ends with respect to the A1 direction, supporting member holding portions 221 b and 221 b for holding the supporting members R211 and F212 , respectively, so as to be slidably movable.

[0068] Between the support member retaining portions 221b, 221b at these opposite ends, an accommodation portion 221c is formed, in which the external secondary transfer roller 200 supported by the support member R211 and the support member F212 is accommodated. With respect to the A1 direction, the gap X1 between the support portion 213 of the support member R211 and the support portion 213 of the support member F212 is the area of ​​the accommodation portion 222b. In addition, the bearing 203 that is press-fitted and fixed to the external secondary transfer roller 200 is installed on the support portion 213 of each of the support member R211 and the support member F212, so that the external secondary transfer roller 200 is positioned relative to the A1 direction. In addition, similarly, with respect to the A3 direction, the external secondary transfer roller 200 is positioned by establishing a bonding relationship between the bearing 203 and the support portion 213 of the support member R211 and the support member F212.

[0069] In addition, if Fig.10 As shown, the roller holding portion 214 is formed integrally with each of the support member R211 and the support member F212. The roller holding portion 214 is arranged to be opposite to the shaft portion 202 on each of the two sides of the plane substantially parallel to the A2 direction passing through the center of the shaft portion 202 when viewed from the A1 direction. These roller holding portions 214 on both sides have flexibility so that each roller holding portion 214 can be sent out to separate from the above-mentioned plane. In addition, between these roller holding portions 214 on both sides, there is arranged Fig.10 The opening 214a is opened upward (ie, toward the upstream side of the installation direction (+A2 direction) of the external secondary transfer roller 200). Fig.10 As shown, when the width of the opening 214a between the roller holding portions 214 on the two sides is taken as X2 and the diameter of the shaft portion 202 is taken as D2 with respect to the A3 direction, the relationship: X2 < D2 holds. That is, the external secondary transfer roller 200 is configured such that as long as the roller holding portions on the two sides do not bend outward under the application of a predetermined load and separate from each other along the A3 direction, the external secondary transfer roller 200 will not be disengaged from the support member R211 and the support member F212 due to the movement in the -A2 direction.

[0070] 3-4. Replacement process of the external secondary transfer roller 200

[0071] Next, the process for replacing the external secondary transfer roller 200 will be described. In the case of replacing the external secondary transfer roller 200, first, as Figure 3 shown, the operator opens the cover 10 to expose the secondary transfer unit 220. At this time, the support member R211 and the support member F212 protrude by the force of the pressing member 217. However, a configuration is adopted in which the support member holding portions 219 ( Figure 6 and Fig.10 ) provided on each of the support member R211 and the support member F212 are locked by a joint portion (not shown) provided on the secondary transfer guide 221. Therefore, the support member R211 and the support member F212 stop at a predetermined position and do not protrude (disengage) from the secondary transfer guide 221.

[0072] The operator holds the shaft portion 202 of the external secondary transfer roller 200 and raises the external secondary transfer roller 200 (and the bearing 203 fixed thereto) along the insertion / extraction direction (A2 direction) of the external secondary transfer roller 200. Then, the shaft portion 202 of the external secondary transfer roller 200 bends the roller holding portion 214, so that the external secondary transfer roller 200 is disengaged from the secondary transfer unit 220. Thus, the operation for disengaging the external secondary transfer roller 200 from the apparatus main assembly 110 (secondary transfer unit 220) is completed.

[0073] Next, the external secondary transfer roller 200 for replacement (and the bearing 203 fixed thereto) as a new external secondary transfer roller 200 is usually mounted to the secondary transfer unit 220 through a process opposite to the process of the above-mentioned disengagement operation. In a state where the operator holds the shaft portion 202 of the external secondary transfer roller 200 for replacement, the operator presses the bearing 203 against the secondary transfer unit 220, engages the bearing 203 with the support portion 213, and bends the roller holding portion 214. Thus, the external secondary transfer roller 200 is mounted to the secondary transfer unit 220. At this time, the bearing 203 is in contact with the bearing abutment portion 211b of the support member R211 and the bearing abutment portion 216b of the pressing member 216, respectively, and is in contact with the bearing abutment portion 212b of the support member F212.

[0074] Finally, the operator closes the cover 10 , thereby completing the installation operation of the external secondary transfer roller 200 for replacement.

[0075] Therefore, according to the configuration of the present embodiment, when the outer secondary transfer roller 200 rotates, the outer ring of the bearing 203 does not rotate, and therefore, the pressing member 216 pressed against the bearing 203 is not worn. Therefore, for example, the risk of image defects such as uneven pitch due to changes in transfer pressure (pressing force) can be reduced.

[0076] Furthermore, according to the configuration of the present embodiment, when the replacement operation of the external secondary transfer roller 200 is performed, the bearing 203 is press-fitted to the shaft portion 202 and thus does not move and fall off.

[0077] Thus, the risk of difficulty in arranging the components at the predetermined positions and the risk of the components falling off during the replacement operation of the external secondary transfer roller 200 is reduced, thereby improving the operability of the replacement of the external secondary transfer roller 200. In addition, in the present embodiment, the function of the roller holding portion 214 is assigned to the supporting member R211 and the supporting member F212, that is, the apparatus main assembly 110 (secondary transfer unit 220) side. Thus, the configuration of the external secondary transfer roller 200 to be replaced can be minimized, thereby making it possible to reduce the cost required for replacement.

[0078] Incidentally, in the present embodiment, the case where the roller to be replaced is the external secondary transfer roller 200 is described, but the present invention is not limited thereto. The replacement object (roller) may also be another roller to be pressurized and energized in the image forming apparatus. In addition, the roller may also be a roller that is driven to rotate and a roller that is driven to rotate.

[0079] Furthermore, in the present embodiment, the supporting member F212 is not provided with the pressing member 216, but a configuration may be adopted in which a pressing member is provided to the supporting member on each of the opposite end sides of the roller with respect to the rotation axis direction.

[0080] In addition, in the present embodiment, the pressure member 217 constitutes a power supply path for the pressing member 216. Thus, as described above, the pressurization of the support member and the pressing member and the connection of the power supply path to the pressing member can be performed with a simple structure. However, the power supply path for the pressure member can also be provided separately from the pressure member. For example, a first pressure member for pressurizing the support member toward the bearing and a second pressure member (conductive spring) for pressurizing the pressing member toward the bearing can be provided separately from each other.

[0081] 4. Effect

[0082] As described above, in the present embodiment, the image forming apparatus 100 is provided with: an image bearing member (intermediate transfer belt) 7 for bearing a toner image; and a rotatable roller 200, the rotatable roller 200 including a shaft portion 202 protruding from each of one end portion and the other end portion relative to the direction of the rotation axis, and including a roller, (external secondary transfer roller) 200, which can contact the image bearing member 7; a first bearing 203, which is mounted to the shaft portion 202 at the above-mentioned one end portion; a second bearing 203, which is mounted to the shaft portion 202 at the above-mentioned other end portion; a first supporting member (supporting member R) 211, which is used to support the roller 200 through the first bearing 203; and a second supporting member (Support member F) 212, which is used to support the roller 200 through the second bearing 203; a first pressing member 217, which is used to pressurize the first supporting member 211 toward the image bearing member 7 in a predetermined direction; a second pressing member 217, which is used to pressurize the second supporting member 212 toward the image bearing member 7 in a predetermined direction; and a movable member (pressing member) 216, which is such a movable member 216 that is held by the first supporting member 211 to be movable relative to the first supporting member 211 in a predetermined direction and contacts the first bearing 203 by being pushed toward the first bearing 203, thereby forming a power supply path for the roller 200 through the first bearing 203.

[0083] In the present embodiment, the first pressing member 217 presses the first supporting member toward the image bearing member 7 in the above-mentioned predetermined direction, and further, presses the moving member 216 toward the first bearing 203 in the predetermined direction, so that the moving member 216 is pressed against the first bearing 203. In addition, in the present embodiment, in a state where the roller 200 is separated from the image bearing member 7, the moving member 216 is pushed so that at least a part of the abutting portion 216b of the moving member 216 that can contact the outer periphery of the first bearing 203 protrudes toward the first bearing 203 side in the predetermined direction compared with the protrusion of the abutting portion 211b of the first supporting member 211 that can contact the outer periphery of the first bearing 203. In addition, in the present embodiment, the moving member 216 is arranged in the region where the first bearing 203 protrudes in the predetermined direction. In addition, in the present embodiment, the first pressing member 217 constitutes a power supply path to the moving member 216. In addition, in the present embodiment, the moving member 216 is held only by the first supporting member 211 of the first supporting member 211 and the second supporting member 212. Furthermore, in the present embodiment, the roller 200 rotates in a state where the roller 200 is pressed against the image bearing member 7. Furthermore, in the present embodiment, a power supply path to the image bearing member 7 is formed. Furthermore, in the present embodiment, the moving member 216 is formed of a conductive resin. Furthermore, in the present embodiment, the roller 200 is a transfer roller for transferring toner from the image bearing member 7 to the recording material S while sandwiching the recording material S between the roller 200 itself and the image bearing member 7.

[0084] In addition, according to this embodiment, the pressing member having the functions of applying pressure and electrically connecting contacts the outer periphery of the bearing mounted to the roller, so the occurrence of inconvenience due to wear can be suppressed. In addition, according to this embodiment, the component mounted to the roller does not move in the axial direction, so the replacement of the roller can be easily performed.

[0085] According to the present invention, it is possible to provide an image forming apparatus capable of performing stable power supply with a simple configuration while suppressing the occurrence of inconveniences caused by wear of a shaft portion of a roller that applies pressure and electricity or wear of an electrical connection portion in the image forming apparatus.

[0086] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming device, comprising: an image bearing member configured to bear a toner image; a transfer roller including a rotatable roller portion and a shaft portion protruding from each of one end portion and the other end portion of the roller portion with respect to a rotation axis direction of the roller portion and configured to transfer a toner image carried on an image bearing member under application of a transfer voltage; a first bearing mounted to the shaft portion at the one end; a second bearing mounted to the shaft portion at the other end; a first holding member configured to be movable in a direction intersecting the rotation axis of the transfer roller and capable of holding the first bearing, wherein the first holding member holds the first bearing so as to be detachably mounted on the first bearing in the direction intersecting the rotation axis of the transfer roller; a second bearing member configured to be movable in a direction intersecting the rotation axis of the transfer roller and to hold the second bearing, wherein the second holding member holds the second bearing so as to be detachably mountable to the second bearing in the direction intersecting the rotation axis of the transfer roller; a first urging member configured to urge the first holding member toward the image bearing member; a second urging member configured to urge the second holding member toward the image bearing member; a contact member that is movably supported relative to the first holding member and is configured to be able to contact an outer peripheral surface of the first bearing, wherein the contact member forms a power supply path to the transfer roller, The contact member is configured to contact the first bearing on the upstream side of the rotation center of the transfer roller relative to the direction in which the first holding member is urged by the first urging member, so as not to be arranged on the downstream side of the rotation center of the transfer roller.

2. The image forming apparatus according to claim 1, wherein: The contact member is arranged to be disposed in a protruding region of the first bearing protruding in a moving direction of the first holding member.

3. The image forming apparatus according to claim 1, wherein: The first holding member is provided with a curved surface for holding the outer peripheral surface of the first bearing and an opening provided in the curved surface, and The contact member is supported so as to be able to contact the first bearing through the opening.

4. The image forming apparatus according to claim 1, wherein: The first urging member urges the first holding member toward the image bearing member, and presses the contact member against the first bearing by urging the contact member toward the first bearing.

5. The image forming apparatus according to claim 1, wherein: When the transfer roller is separated from the image bearing member, the contact member is pushed, and at least a portion of the abutment portion of the contact member that can contact the outer periphery of the first bearing protrudes toward the first bearing side more than at least a portion of the abutment portion of the first retaining member that can contact the outer periphery of the first bearing.

6. The image forming apparatus according to claim 1, wherein: The first urging member constitutes a power supply path to the contact member.

7. The image forming apparatus according to claim 1, wherein: The contact member is held by only the first holding member of the first holding member and the second holding member.

8. The image forming apparatus according to claim 1, wherein: The contact member is composed of a conductive resin.

9. The image forming apparatus according to claim 1, wherein: The first bearing and the second bearing are fixed by press-fitting to the shaft portion, The first holding member is provided with a positioning portion for positioning the first bearing relative to the rotation axis direction of the transfer roller, and The second holding member is configured to hold the second bearing with play relative to a rotation axis direction of the transfer roller.

Images