JP2024027751A - image forming device - Google Patents

Abstract

An object of the present invention is to suppress deformation of an elastic layer of the transfer roller due to pressure applied from the conductive roller when the transfer roller is left unused, in a configuration including a conductive roller that contacts the surface of the transfer roller.
In the image forming apparatus 1, when the transfer roller 211 is separated from the intermediate transfer belt 61, the transfer roller 211 or a member moving together with the transfer roller 211 is in contact with a first regulating part 222. , the conductive roller 213 or a member 224 that moves together with the conductive roller is in contact with the second regulating portion 223, or when the transfer roller 211 is separated from the intermediate transfer belt 61, the conductive roller 213 or a member 224 that moves together with the conductive roller is in contact with the second regulating part 223, and neither the transfer roller 211 nor the member that moves together with the transfer roller 211 is in contact with the first regulating part 222. It is said that there is no configuration.
[Selection diagram] Figure 6

Description

The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine using an electrophotographic method or an electrostatic recording method, or a multifunction device having multiple functions among these.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine using an electrophotographic method, a toner image on an image carrier is transferred to a recording material in a transfer section to form an image on the recording material. Transfer of the toner image from the image carrier to the recording material is performed, for example, by applying a transfer voltage to a transfer roller that comes into contact with the image carrier to form a transfer portion.

As the transfer roller, for example, an elastic roller including an elastic layer provided with conductivity by dispersing an ion conductive agent or the like is used. When power is supplied to such a transfer roller from a rotating shaft (core metal), the electric resistance of the transfer roller may increase due to an increase in cumulative energization time. In that case, it is necessary to increase the transfer voltage applied to the transfer roller (increase its absolute value) as the electrical resistance of the transfer roller increases. Therefore, there was a problem in that the life span of the transfer roller was determined by the capacity of the high-voltage substrate.

Therefore, for example, there is a method in which a transfer voltage is applied to a conductive roller that contacts the surface of the transfer roller, and the transfer voltage is applied to the transfer roller via the conductive roller (Patent Document 1).

Japanese Patent Application Publication No. 2005-316200

In an image forming apparatus that uses a conductive roller that comes into contact with the surface of the transfer roller, the conductive roller is applied with a predetermined pressure to the transfer roller in order to enable stable driven rotation as the transfer roller rotates. Pressed.

However, if the transfer roller is configured to always receive the same pressing force from the conductive roller as during image formation, the elasticity of the transfer roller may Plastic deformation of the layer may result in indentations. If the elastic layer of the transfer roller is dented in this way, problems such as image unevenness may occur when images are formed thereafter.

Although the above description has been made using an example of a configuration in which the transfer voltage is applied to the conductive roller by applying the transfer voltage to the transfer roller via the conductive roller, the same problem may occur in the following configuration as well. In other words, a transfer voltage is applied to a tension roller placed on the inner circumference side of an intermediate transfer belt serving as an image carrier, and a conductive voltage is applied to the surface of the transfer roller that contacts the tension roller via the intermediate transfer belt. The configuration is such that the roller is electrically grounded. Even in this configuration, problems similar to those described above may occur if the unit including the transfer roller and the conductive roller is left alone.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to suppress deformation of the elastic layer of the transfer roller due to the pressure applied from the conductive roller when the transfer roller is left unused, in a configuration including a conductive roller that contacts the surface of the transfer roller.

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention includes an image carrier that carries a toner image, an intermediate transfer belt to which the toner image is transferred from the image carrier, a core bar, and an elastic layer provided around the core bar. a transfer roller that contacts the outer peripheral surface of the intermediate transfer belt to form a transfer portion; and a transfer roller that is disposed opposite to the transfer roller with the intermediate transfer belt in between and that contacts the inner peripheral surface of the intermediate transfer belt. an opposing roller that forms the transfer section together with the transfer roller; a power supply that supplies a current to the transfer section; and a counter roller that is in contact with the transfer roller and that is supplied from the power supply between the core bar of the transfer roller. a conductive roller that forms a current path through which a current flows, and first pressure members that are provided at both ends of the transfer roller in the rotational axis direction and press the transfer roller toward the intermediate transfer belt; a first holding part that is provided at both ends of the transfer roller in the rotational axis direction and holds the transfer roller rotatably and movably along the pressing direction of the first pressing member; a second pressure member that is provided at both ends of the conductive roller in the direction of the rotation axis and presses the conductive roller toward the transfer roller; and a second pressure member that is provided at both ends of the conductive roller in the direction of the rotation axis. , a second holding part that holds the conductive roller rotatably and movably along the pressing direction of the second pressing member and the transfer roller or a member that moves together with the transfer roller are in contact with each other; As a result, the first regulating portion that regulates the movement of the first pressure member of the transfer roller in the pressure direction comes into contact with the conductive roller or a member that moves together with the conductive roller. a second regulating portion that regulates movement of the conductive roller in the pressing direction of the second pressure member, and when the transfer roller is separated from the intermediate transfer belt, the transfer roller or a member that moves together with the transfer roller is in contact with the first regulating portion, and the conductive roller or a member that moves together with the conductive roller is in contact with the second regulating portion. This is an image forming apparatus with features.

According to another aspect of the present invention, there is provided an image carrier that carries a toner image, an intermediate transfer belt to which the toner image is transferred from the image carrier, a core bar, and an elastic belt provided around the core bar. a transfer roller that contacts the outer circumferential surface of the intermediate transfer belt to form a transfer portion; and an inner circumferential surface of the intermediate transfer belt that is disposed opposite to the transfer roller with the intermediate transfer belt in between. an opposing roller that comes into contact with the transfer roller and forms the transfer section together with the transfer roller; a power supply that supplies a current to the transfer section; and an opposing roller that comes into contact with the transfer roller and forms the transfer section between the core metal of the transfer roller and the power supply. a conductive roller that forms a current path through which a current supplied from the transfer roller flows; and a first pressurizer that is provided at both ends of the transfer roller in the rotational axis direction and presses the transfer roller toward the intermediate transfer belt. and a first holding part that is provided on both ends of the transfer roller in the rotational axis direction and holds the transfer roller rotatably and movably in the pressing direction of the first pressure member. and a second pressure member that is provided at both ends of the conductive roller in the direction of the rotation axis and presses the conductive roller toward the transfer roller; a second holding part which is provided respectively and holds the conductive roller rotatably and movably along the pressing direction of the second pressing member; and the transfer roller or a member that moves together with the transfer roller. When they come into contact with each other, a first regulating portion that regulates the movement of the first pressure member of the transfer roller in the pressing direction comes into contact with the conductive roller or a member that moves together with the conductive roller. and a second regulating portion that regulates movement of the conductive roller in the pressing direction of the second pressure member, when the transfer roller is separated from the intermediate transfer belt, The conductive roller or a member that moves together with the conductive roller is in contact with the second regulating section, and either the transfer roller or the member that moves together with the transfer roller is in contact with the first regulating section. Provided is an image forming apparatus characterized in that the two do not touch each other.

According to the present invention, in a configuration including a conductive roller that contacts the surface of the transfer roller, it is possible to suppress deformation of the elastic layer of the transfer roller due to pressure applied from the conductive roller when left unused.

FIG. 1 is a schematic cross-sectional view of an image forming apparatus. FIG. 3 is a schematic cross-sectional view showing a power supply mode of the secondary transfer section. FIG. 2 is a schematic cross-sectional view of the image forming apparatus with the right door unit opened. FIG. 2 is a perspective view showing a support structure for a secondary outer transfer roller and a conductive roller. FIG. 3 is a side view showing a pressure configuration of a secondary transfer outer roller and a conductive roller. FIG. 3 is a side view showing a pressure configuration of a secondary transfer outer roller and a conductive roller. FIG. 3 is a schematic diagram for explaining the amount of penetration of the conductive roller into the outer secondary transfer roller. FIG. 7 is a side view showing another example of the pressure configuration of the outer secondary transfer roller and the conductive roller. It is a perspective view for explaining a spacing member. FIG. 7 is a schematic cross-sectional view showing another example of the power supply mode of the secondary transfer section.

Hereinafter, the image forming apparatus according to the present invention will be explained in more detail with reference to the drawings.

[Example 1]
1. Overall Configuration and Operation of Image Forming Apparatus FIG. 1 is a schematic cross-sectional view of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 of this embodiment is a tandem-type multifunction device that uses an intermediate transfer method and is capable of forming full-color images using an electrophotographic method, and includes a copying machine, a printer (laser beam printer), It has the function of a facsimile machine.

Regarding the image forming apparatus 1 and its elements, the front side of the page in FIG. 1 when the image forming apparatus 1 is in operation is referred to as the "front side", and the back side of the page is referred to as the "rear side". The linear direction connecting the "front side" and the "rear side" ("backward direction") is the rotation of the photosensitive drum 11, the tension roller of the intermediate transfer belt 61, the secondary transfer outer roller 211, the conductive roller 213, etc., which will be described later. It is assumed to be approximately parallel to the axial direction. In addition, regarding the image forming apparatus 1 and its elements, the vertical direction refers to the vertical direction in the direction of gravity (vertical direction), but does not mean only directly above or directly below, respectively, but it also refers to the direction passing through the element or position of interest. It includes above and below the horizontal plane.

The image forming apparatus 1 includes four image forming sections SY and SM each forming yellow (Y), magenta (M), cyan (C), and black (K) toner images as a plurality of image forming sections (stations). , SC, and SK. Elements that have the same or corresponding functions or configurations provided for each color will be described generically by omitting the Y, M, C, or K at the end of the code indicating that the element is for one of the colors. There are things to do. In this embodiment, the image forming section S includes a photosensitive drum 11, a charging roller 12, an exposure device 13, a developing device 14, a drum cleaning device 15, etc., which will be described later.

The photosensitive drum 11, which is a drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as an image carrier (first image carrier) that carries a toner image, is rotated in the direction of arrow R1 (clockwise direction) in the figure. ) at a predetermined circumferential speed (process speed). The surface (outer peripheral surface) of the rotating photosensitive drum 11 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by a charging roller 12 serving as a charging means. The charged surface of the photosensitive drum 11 is scanned and exposed according to image information by an exposure device (laser scanner unit) 13 serving as an exposure means, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 11. Ru. For example, image information transmitted from an external connection cable (not shown) to the image forming apparatus 1 is processed by a control device (not shown), and a signal based on the processing result causes laser light to be emitted from the exposure device 13. is emitted, and an electrostatic latent image is formed on the photosensitive drum 11. The electrostatic latent image formed on the photosensitive drum 11 is developed (visualized) by being supplied with toner as a developer by a developing device 14 serving as a developing means, and a toner image is formed on the photosensitive drum 11 . In this embodiment, the exposed area (image area) on the photosensitive drum 11, whose absolute value has decreased by being exposed to light after being uniformly charged, has the same polarity as the charged polarity of the photosensitive drum 11 (in this embodiment). In this example, negatively charged toner is attached (reversal development method). In this embodiment, the normal charging polarity of the toner, which is the main charging polarity of the toner during development, is negative polarity.

An intermediate transfer belt 61, which is an endless belt and serves as an intermediate transfer member (second image carrier), is arranged opposite to the four photosensitive drums 11Y, 11M, 11C, and 11K. The intermediate transfer belt 61 is stretched by a plurality of tension rollers (support rollers) rotatably held by a frame (not shown). In this embodiment, the image forming apparatus 1 includes a secondary transfer inner roller 62, a secondary pre-transfer roller 63, a first auxiliary roller 64, a second auxiliary roller 65, as a plurality of tension rollers. It has a tension roller 66. The intermediate transfer belt 61 is driven by a driving force input to a secondary transfer inner roller 62 which functions as a facing member (counter electrode) of a secondary transfer outer roller 211 (described later) and also functions as a drive roller. The intermediate transfer belt 61 rotates (circularly moves) in the direction of arrow R2 (counterclockwise direction) in the figure at a circumferential speed (process speed) corresponding to the circumferential speed of the photosensitive drum 11. On the inner peripheral surface side of the intermediate transfer belt 61, between the first auxiliary roller 64 and the secondary pre-transfer roller 63, a primary transfer member constituting the primary transfer means is provided corresponding to each photosensitive drum 11. A primary transfer roller 68 is arranged. The primary transfer roller 68 is pressed toward the photosensitive drum 11 via the intermediate transfer belt 61, and forms a primary transfer portion (primary transfer nip portion) N1 where the photosensitive drum 11 and the intermediate transfer belt 61 are in contact. Among the plurality of tension rollers, the tension rollers other than the secondary transfer inner roller 62 and each primary transfer roller 68 are driven to rotate as the intermediate transfer belt 61 rotates.

The toner image formed on the photosensitive drum 11 is transferred (primary transfer) onto the rotating intermediate transfer belt 61 by applying a predetermined pressing force and electrostatic load bias in the primary transfer portion N1. Ru. During the primary transfer process, a primary transfer voltage (primary transfer voltage) is applied to the primary transfer roller 68 from a primary transfer power source (not shown), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner. bias) is applied. For example, when forming a full-color image, yellow, magenta, cyan, and black toner images formed on each photosensitive drum 11 are sequentially transferred onto the intermediate transfer belt 61 so as to be superimposed. Note that the image forming apparatus 1 is not limited to a configuration in which image forming sections S are provided for four colors, and the order in which the image forming sections S for each color are arranged is also limited to the order in this embodiment. It's not a thing. The toner remaining on the photosensitive drum 11 after the primary transfer process (primary transfer residual toner) is removed from the photosensitive drum 11 and collected by a drum cleaning device 15 serving as a photosensitive member cleaning means.

On the outer peripheral surface side of the intermediate transfer belt 61, an outer secondary transfer roller 211, which serves as a secondary transfer member constituting a secondary transfer means, is arranged at a position facing the inner secondary transfer roller 62. The secondary transfer outer roller 211 rotates as the intermediate transfer belt 61 rotates. The secondary transfer outer roller 211 is pressed toward the secondary transfer inner roller 62 as an opposing member via the intermediate transfer belt 61, and the secondary transfer portion where the intermediate transfer belt 61 and the secondary transfer outer roller 211 are in contact with each other. (Secondary transfer nip portion) N2 is formed. The toner image formed on the intermediate transfer belt 61 is sandwiched between the intermediate transfer belt 61 and the secondary transfer outer roller 211 by applying a predetermined pressing force and electrostatic load bias in the secondary transfer portion N2. The image is then transferred (secondary transfer) onto the recording material P that is being conveyed. The power supply mode of the secondary transfer portion N2 will be described later. The toner remaining on the intermediate transfer belt 61 after the secondary transfer process (secondary transfer residual toner) is removed from the intermediate transfer belt 61 and collected by a belt cleaning device 67 serving as intermediate transfer body cleaning means.

Recording materials (sheets, transfer materials, recording media) P are stored in a cassette (recording material storage) 21 serving as a recording material storage section, stacked on a lift-up that the cassette 21 has. The recording materials P stored in the cassette 21 are separated from the cassette 21 one by one and sent out by a feeding mechanism 22 having a pickup roller or the like as a feeding means. The recording material P sent out from the cassette 21 is conveyed through a conveyance path to a pair of registration rollers 23 serving as conveyance means. The recording material P hits the stopped pair of registration rollers 23 and is deflected, thereby correcting the skew. After skew correction is performed on the recording material P by the pair of registration rollers 23, the pair of registration rollers 23 synchronizes the timing with the toner image on the intermediate transfer belt 61 and sends it to the secondary transfer portion N2. Note that the conveyance path for conveying the recording material P includes, as conveyance means, conveyance members (for example, a pair of pre-registration rollers 24) disposed at appropriate intervals in order to transfer the recording material P while holding it, and the recording material P. It is configured to include a guide 25 that guides the vehicle while suppressing its behavior. Further, the recording material P is stacked on a multi-tray 26 provided on the right side of the image forming apparatus 1 when the image forming apparatus 1 is viewed from the front, and is transferred to a pair of pre-registration rollers 22 by a multi-feeding mechanism 27. , and can also be conveyed to a pair of registration rollers 23.

The recording material P onto which the toner image has been transferred is conveyed to a fixing device 40 as a fixing means. The fixing device 40 pressurizes and heats the recording material P carrying an unfixed toner image to fix (dissolve, fix) the toner image on the recording material P. The recording material P on which the toner image has been fixed is discharged as it is onto the discharge tray 52 by the branch conveyance mechanism 51, or if double-sided image formation is required, it is conveyed from the reversal conveyance mechanism 53 to the double-sided conveyance mechanism 54. A route selection is made as to whether the The image forming apparatus 1 of this embodiment includes a first conveyance path 55 for conveying the recording material P that has passed through the fixing device 40 to the reversing conveyance mechanism 53, and a recording material P conveyed from the first conveyance path 55. and a reversal conveyance path 56 in which the images are reversed and conveyed. Further, the image forming apparatus 1 of the present embodiment has a third transport path 57 to which the recording material P reversed by the reverse transport path 56 is discharged, and a first transport path 57 to which the recording material P reversed by the reverse transport path 56 is discharged. It has a double-sided conveyance path 58 for reconveying to the conveyance path 55.

In each image forming section S, the photosensitive drum 11, the charging roller 12, the developing device 14, and the drum cleaning device 15 are each singly or plurally integrated into a cartridge, and the photosensitive drum 11, the charging roller 12, the developing device 14, and the drum cleaning device 15 are installed in the main body 2 of the image forming device 1. It may be made removable from the . Further, in this embodiment, the intermediate transfer belt 61, the plurality of tension rollers 62 to 66, each primary transfer roller 68, the belt cleaning device 67, and the frame supporting these are integrally attached to and detached from the apparatus main body 2. A possible intermediate transfer belt unit 60 is configured.

Since the intermediate transfer type image forming apparatus 1 using the intermediate transfer belt 61 does not bring the recording material P into direct contact with the photosensitive drum 11, it is easy to form images on various recording materials P such as thin paper, plain paper, and thick paper. It has the characteristic of being

The intermediate transfer belt 61 is preferably made of a material made of a resin such as polyimide or polyamide, an alloy thereof, or various rubbers containing an appropriate amount of an antistatic agent such as carbon black. Further, the intermediate transfer belt 61 is formed to have a surface resistivity of 1×10 ⁹ to 5×10 ¹³ Ω/□, for example. The intermediate transfer belt 61 is, for example, a film-like endless belt with a thickness of about 0.04 to 0.5 mm.

2. Secondary transfer configuration FIG. 2 is a schematic cross-sectional view of the vicinity of the secondary transfer portion N2 in this embodiment (respective rotation axes of the secondary transfer inner roller 62, the secondary transfer outer roller 211, and the conductive roller 213 described later). (a cross section substantially perpendicular to the direction).

In the secondary transfer section N2, a secondary transfer outer roller 211 as a secondary transfer member (transfer member, transfer rotary body, transfer roller) performs secondary transfer as an opposing member (opposing roller) via an intermediate transfer belt 61. It is formed by contacting the inner roller 62. The secondary transfer inner roller 62 is arranged on the surface (inner peripheral surface) of the intermediate transfer belt 61 opposite to the toner image bearing surface. The secondary transfer outer roller 211 is arranged on the toner image bearing surface (outer peripheral surface) side of the intermediate transfer belt 61.

In this embodiment, the secondary transfer inner roller 62 is an elastic roller in which an elastic layer 62b of conductive rubber is formed around the outer periphery of a metal core 62a. In this embodiment, the elastic layer 62b of the secondary transfer inner roller 62 is formed using electrically conductive EPDM rubber. Further, in this embodiment, the secondary transfer inner roller 62 is formed so that the outer diameter is 16 mm and the thickness of the elastic layer 62b is 0.5 mm. Further, in this embodiment, the hardness of the elastic layer 62b is set to, for example, 70° (Asker C). In this embodiment, the secondary transfer inner roller 62 has the function of a driving roller that drives the intermediate transfer belt 61. However, the outer diameter of the secondary transfer inner roller 62 and the thickness of the elastic layer 62b are not limited to the above values.

In this embodiment, the secondary transfer outer roller 211 is an elastic roller in which an elastic layer 211b made of a conductive rubber sponge (foamed elastic material) is formed on the outer periphery of a metal core 211a. In this embodiment, the core bar 211a of the outer secondary transfer roller 211 is entirely solid. In this embodiment, the elastic layer 211b of the outer secondary transfer roller 211 is made of NBR rubber or EPDM which is imparted with conductivity by containing a metal complex (ionic conductive agent) or carbon (electronic conductive agent) as a conductive agent. It is formed using sponge such as rubber. Further, in this embodiment, the secondary transfer outer roller 211 is formed so that the outer diameter is 20 mm, and the thickness of the elastic layer 211b is 4 mm. Further, in this embodiment, the hardness of the elastic layer 211b is set to, for example, 28° (Asker C). Note that an elastic layer containing only an ion conductive agent as a conductive agent may be used. As will be described in detail later, the secondary transfer outer roller 211 applies a predetermined pressing force (pressing force, contact pressure, contact pressure) to the outer peripheral surface of the intermediate transfer belt 61 backed up by the secondary transfer inner roller 62. The intermediate transfer belt 61 is brought into pressure contact with the intermediate transfer belt 61 and rotates as the intermediate transfer belt 61 rotates. However, the outer diameter of the secondary transfer outer roller 211 and the thickness of the elastic layer 211b are not limited to the above values.

Further, in this embodiment, a conductive roller (power supply roller) 213 serving as a power supply member (power supply rotating body) that supplies electric charge (current) to the secondary transfer outer roller 211 comes into contact with the outer circumferential surface of the secondary transfer outer roller 211. being brought into contact with In this embodiment, a secondary transfer voltage (secondary transfer bias) is applied to the secondary transfer outer roller 211 via the conductive roller 213. A contact portion between the intermediate transfer belt 61 and the secondary transfer outer roller 211 is a secondary transfer portion (secondary transfer nip portion) N2. Further, the contact portion between the secondary transfer outer roller 211 and the conductive roller 213 is a power feeding portion (power feeding nip portion) N3. Note that the positions of the secondary transfer portion N2 and the power supply portion N3 are represented by the center positions in the circumferential direction (rotation direction) of the secondary transfer outer roller 211 and the conductive roller 213, respectively. Further, during operation of the image forming apparatus 1, the rotation axis directions of the inner secondary transfer roller 62, the outer secondary transfer roller 211, and the conductive roller 213 are substantially parallel.

In this embodiment, the conductive roller 213 is a metal roller made of a conductive metal such as SUM or SUS. In this embodiment, the metal roller constituting the conductive roller 213 has a roller portion 213b (FIG. 4) that can contact the secondary transfer outer roller 211, and a rotation shaft formed at both ends of the roller portion 213b in the rotation axis direction. 213a (FIG. 4), and is entirely made of metal. Note that the metal roller may be coated with a material other than metal on the surface of the roller portion 213b, for example. Further, in this embodiment, the conductive roller 213 is entirely solid. Further, in this embodiment, the outer circumferential surface of the roller portion 213b of the conductive roller 213 is substantially smooth. Further, in this embodiment, the outer diameter of the roller portion 213b of the conductive roller 213 is 8 mm. As will be described in detail later, the conductive roller 213 is pressed against the outer peripheral surface of the elastic layer 211b of the outer secondary transfer roller 211 with a predetermined pressure, and as the outer secondary transfer roller 211 rotates. Driven rotation. However, the outer diameter and material of the conductive roller 213 are not limited to those of this embodiment.

A secondary transfer power supply (high voltage power supply circuit) 301 is connected to the conductive roller 213 as a voltage application means (current supply means). The secondary transfer power source 301 applies a secondary transfer voltage, which is a DC voltage with a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment), to the secondary transfer outer roller 211 via the conductive roller 213. . In this embodiment, the secondary transfer power source 301 is a constant voltage power source. In this embodiment, the secondary transfer voltage is controlled at a constant voltage. Note that constant voltage control is control that adjusts the output of the power supply so that the voltage applied to the object is substantially constant at a target voltage. On the other hand, in this embodiment, the secondary transfer inner roller 62 is electrically grounded by connecting its core metal 62a to a ground potential (ground). Further, the secondary transfer outer roller 211 is electrically floated (in an electrically floating state). Note that in this embodiment, the secondary transfer voltage is controlled at a constant voltage, but the secondary transfer voltage may be controlled at a constant current. Note that constant current control is control that adjusts the output of the power supply so that the current supplied to the supply target is substantially constant at a target current.

The voltage applied to the conductive roller 213 is supplied to the electrically grounded inner secondary transfer roller 62 via the outer secondary transfer roller 211 . At this time, inside the secondary transfer outer roller 211, electricity flows from the contact point with the conductive roller 213 to the core bar 211a, and from the core bar 211a to the secondary transfer inner roller 62. In other words, the conductive roller 213 forms a current path between the conductive roller 213 and the core metal 211a of the outer secondary transfer roller 211 through which the current supplied from the power source flows. Therefore, by rotating the secondary transfer outer roller 211, it is possible to suppress the bias of the conductive agent inside the elastic layer 211b, and to reduce the increase in the electrical resistance of the secondary transfer outer roller 211.

In this embodiment, in the cross section shown in FIG. 2, when the position of the secondary transfer part N2 is set to 0 degrees with respect to the rotation center of the outer secondary transfer roller 211, the position of the power supply part N3 is approximately 180 degrees. A conductive roller 213 is disposed at a position. The above angle is defined by the straight line connecting the rotation center of the secondary transfer outer roller 211 and the rotation center of the secondary transfer inner roller 62, the rotation center of the secondary transfer outer roller 211, and the outer periphery of the secondary transfer outer roller 211. This is the angle formed by the straight line connecting the next transfer section N2 or the power supply section N3). That is, in this embodiment, the conductive roller 213 is arranged such that the secondary transfer portion N2 and the power supply portion N3 are located on opposite sides with the core metal 211a of the secondary transfer outer roller 211 interposed therebetween. This prevents current from flowing directly from the conductive roller 213 to the inner secondary transfer roller 62 via the elastic layer 211b of the outer secondary transfer roller 211 without passing through the core metal 211a of the outer secondary transfer roller 211. It's for a reason. However, in the case of the power supply mode as in this embodiment, the conductive roller 213 may be arranged so that the current flows to the secondary transfer portion N2 via the core bar 211a of the secondary transfer outer roller 211, for example, as described above. Preferably, the angle is within the range of 180 degrees ±15 degrees.

Here, unlike the present embodiment, in the configuration in which a voltage is applied to the core metal 211a of the secondary outer transfer roller 211, when paying attention to the elastic layer 211b at a certain position in the circumferential direction of the secondary outer transfer roller 211, The electric field applied to that position is always in the same direction. Therefore, in this configuration, polarization of the ion conductive agent in the elastic layer 211b of the outer secondary transfer roller 211 occurs, and the electrical resistance of the outer secondary transfer roller 211 increases as the outer secondary transfer roller 211 is used. To go. In contrast, in the power supply mode of this embodiment, the electric charge supplied from the conductive roller 213 is configured to reach the secondary transfer portion N2 via the core bar 211a of the outer secondary transfer roller 211. ing. As a result, when focusing on the elastic layer 211b at a certain position in the circumferential direction of the secondary transfer outer roller 211, the electric field applied to that position increases with the electric field in the opposite direction every time the secondary transfer outer roller 211 rotates approximately half a revolution. Become. Therefore, polarization of the ion conductive agent in the elastic layer 211b of the outer secondary transfer roller 211 can be suppressed, and an increase in electrical resistance of the outer secondary transfer roller 211 can be suppressed.

3. Secondary Transfer Unit FIG. 3 is a sectional view showing a state in which a right door unit 90 (described later) of the image forming apparatus 1 of the present embodiment shown in FIG. 1 is opened. The image forming apparatus 1 includes a right door unit 90 as an opening/closing member that opens the inside of the apparatus main body 2 on the right side when the apparatus main body 2 is viewed from the front side. The right door unit 90 is configured such that its upper part is rotated downward to open and conversely rotated upward to close around a rotating shaft 91 provided below and extending in the front-rear direction. The right door unit 90 is opened and closed by an operator such as a user or a service person operating an operating section (not shown) such as a handle provided on the right door unit 90.

The right door unit 90 connects at least a portion of the conveyance path of the recording material P from the cassette 21 to the fixing device 40 via the secondary transfer section N2 with the front side of the recording material P (the surface on which the toner image is transferred). It is opened by dividing it from the back side. A secondary transfer unit 200 including a secondary transfer outer roller 211, a conductive roller 213, a holder 201, and the like is attached to the right door unit 90. When the right door unit 90 is opened, the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61, and the secondary transfer unit 200 moves together with the right door unit 90. The operator can then access the secondary transfer unit 200 attached to the opened right door unit 90.

The operator can access the secondary transfer unit 200 by opening the right door unit 90 as described above, and can replace or clean the secondary transfer outer roller 211 and the conductive roller 213. Further, the secondary transfer unit 200 can be attached to and detached from the right door unit 90 together with the holder 201. Thereby, after removing the secondary transfer unit 200 from the right door unit 90, the secondary transfer outer roller 211 and the conductive roller 213 can be replaced or cleaned, or the secondary transfer unit 200 can be replaced entirely.

4. Support Structure Next, the support structure of the secondary transfer outer roller 211 and the conductive roller 213 in this embodiment will be described. FIG. 4 is a perspective view showing a support structure for the outer secondary transfer roller 211 and the conductive roller 213 in this embodiment.

The image forming apparatus 1 includes a holder 201 (FIG. 3) as a holding member for holding an outer secondary transfer roller 211, a conductive roller 213, and the like. The image forming apparatus 1 also includes a transfer roller bearing member 221 as a first bearing member for rotatably supporting the secondary transfer outer roller 211, and a second transfer roller bearing member 221 for rotatably supporting the conductive roller 213. It has a conductive roller bearing member 224 as a bearing member. The image forming apparatus 1 also includes a transfer roller pressure spring 225 as a first pressure member (biasing member) for biasing the transfer roller bearing member 221 and a transfer roller pressure spring 225 for biasing the conductive roller bearing member 224. It has a conductive roller pressure spring 226 as a second pressure member (biasing member). Note that the holder 201 has a substantially box-like shape with an opening at the top, for example, when it is attached to the right door unit 90 and when the right door unit 90 is opened. A structure for supporting the secondary transfer outer roller 211 and the conductive roller 213 is attached to both ends of the holder 201 in the front-rear direction.

The secondary transfer outer roller 211 is rotatably supported by transfer roller bearing members 221 at both ends in the direction of its rotational axis. More specifically, in the secondary transfer outer roller 211, a rotating shaft portion (protruding portion) 211c formed at an end in the rotational axis direction of the core metal 211a is rotated by a bearing (sliding bearing) 227 as a rotational support member. Possibly supported. The bearing 227 is held movably by the transfer roller bearing member 221 along the direction in which the outer secondary transfer roller 211 presses the inner secondary transfer roller 62 . The transfer roller bearing member 221 is held movably by the holder 201 along the direction in which the outer secondary transfer roller 211 presses the inner secondary transfer roller 62 . The transfer roller pressure spring 225 is composed of a compression coil spring, and is arranged so that one end is in contact with the transfer roller bearing member 221 and the other end is in contact with the holder 201. The transfer roller pressure spring 225 applies a predetermined pressure when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61 (during operation of the image forming apparatus 1). Pressure is applied to the transfer roller bearing member 221 (secondary transfer outer transfer roller 211). As a result, the outer secondary transfer roller 211 is pressed against the intermediate transfer belt 61 backed up by the inner secondary transfer roller 62 with a predetermined pressing force.

Further, the conductive roller 213 is rotatably supported by conductive roller bearing members 224 at both ends in the direction of its rotational axis. More specifically, the conductive roller 213 has a rotating shaft portion (projection) 213a formed at an end in the direction of its rotational axis, and is rotatably supported by a conductive roller bearing member 224. The conductive roller bearing member 224 is held movably by the transfer roller bearing member 221 along the direction in which the conductive roller 213 presses the secondary outer transfer roller 211 . The conductive roller pressure spring 226 is composed of a compression coil spring, and is arranged so that one end abuts the conductive roller bearing member 224 and the other end abuts the transfer roller bearing member 221. The conductive roller pressure spring 226 applies a predetermined pressure when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61 (during operation of the image forming apparatus 1). Pressure is applied to the conductive roller bearing member 224. As a result, the conductive roller 213 is pressed against the secondary transfer outer roller 211 with a predetermined pressure.

Thus, in this embodiment, the movable transfer roller bearing member 221 holds the conductive roller bearing member 224 and the conductive roller pressure spring 226. Thereby, the pressing force of the conductive roller 213 against the secondary transfer outer roller 211 can be made more stable, and the rotation of the secondary transfer outer roller 211 and the conductive roller 213 can be made more stable. That is, in this embodiment, the secondary transfer outer roller 211 is pressed with a predetermined pressing force (pressure regulation) by the transfer roller pressure spring 225 against the intermediate transfer belt 61 backed up by the secondary transfer inner roller 62. . Further, in this embodiment, the conductive roller 213 is pressed (pressure regulated) against the secondary transfer outer roller 211 by a conductive roller pressing spring 226 with a predetermined pressing force. In this embodiment, the conductive roller 213 and the conductive roller pressure spring 226 move the secondary transfer outer roller 211 along the pressure direction of the transfer roller pressure spring 225. It is now possible to move with it. That is, the conductive roller bearing member 224 and the conductive roller pressure spring 226 are held by the transfer roller bearing member 221. Therefore, even if there is a variation in the pressure applied by the transfer roller pressure spring 225, the conductive roller 213 and the conductive roller pressure spring 226, together with the secondary transfer outer roller 211, will act in the pressure direction of the transfer roller pressure spring 225. move along. Therefore, the influence of variations in the pressing force can be suppressed. Furthermore, even if there are variations in the outer diameters of the secondary transfer outer roller 211 and the conductive roller 213 (particularly the secondary transfer outer roller 211 having the elastic layer 211b), the conductive roller 213 is pressure regulated and its The position changes depending on the variation in the outer diameter. Therefore, the influence of variations in the outer diameter can be suppressed.

Here, as described above, when the secondary transfer unit 90 is left alone, for example, if the secondary transfer outer roller 211 continues to receive the same pressing force from the conductive roller 213 as during image formation, There is a possibility that the elastic layer 211b is plastically deformed and a dent occurs. If a dent occurs in the elastic layer 211b of the outer secondary transfer roller 211, problems such as image unevenness may occur when an image is formed thereafter.

In this embodiment, the secondary transfer outer roller 211 and the conductive roller 213 are configured to press as described later, so that it is possible to suppress the generation of dents in the elastic layer 211b of the secondary transfer outer roller 211 as described above. do it like this.

5. Pressure Configuration Next, the pressure configuration of the secondary transfer outer roller 211 and the conductive roller 213 will be further described using FIGS. 4, 5, and 6. 5 and 6 are side views showing the vicinity of one end of the secondary transfer outer roller 211 in the rotational axis direction (front-back direction) in more detail. Although FIGS. 5 and 6 only show the configuration of one end of the secondary transfer outer roller 211 in the rotation axis direction, in this embodiment, the configuration of the other end is also similar (the rotation (substantially symmetrical with respect to a plane passing through the center in the axial direction and substantially orthogonal to the rotational axis direction). Note that in FIGS. 5 and 6, illustration of the intermediate transfer belt 61 is omitted.

FIG. 5 shows a situation when the outer secondary transfer roller 211 is in contact with the inner secondary transfer roller 62 via the intermediate transfer belt 61 (during operation of the image forming apparatus 1). On the other hand, FIG. 6 shows a state in which the outer secondary transfer roller 211 is separated from the intermediate transfer belt 61 (inner secondary transfer roller 62). The outer secondary transfer roller 211 separates from the intermediate transfer belt 61 (inner secondary transfer roller 62) in the following cases. For example, this is the case when the right door unit 90 is opened as described above (FIG. 3). Further, for example, there is a case where the secondary transfer unit 200 is removed from the image forming apparatus 1 and left alone (such as when the secondary transfer unit 200 is stored in a warehouse). Another example is a case where the outer secondary transfer roller 211 is separated from the intermediate transfer belt 61 (inner secondary transfer roller 62) in the image forming apparatus by using a spacing member. An example of a spacing member that separates the secondary transfer outer roller 211 from the intermediate transfer belt 61 (secondary transfer inner roller 62) will be described in more detail later.

As shown in FIGS. 5 and 6, the transfer roller bearing member 221 has a transfer roller holding section 231 as a first holding section. The transfer roller holding section 231 allows the bearing 227, which rotatably supports the rotating shaft section 211c of the secondary transfer outer roller 211, to be movable (with play) along the pressure direction of the transfer roller pressure spring 225. )Hold. An abutment portion 232 against which the bearing 227 abuts is formed at the bottom of the transfer roller holding portion 231 on the opposite side of the intermediate transfer belt 61 (secondary transfer inner roller 62) in the pressure direction of the transfer roller pressure spring 225. There is. Further, the transfer roller bearing member 221 has a transfer roller slip-off preventing portion 222 as a first regulating portion outside the transfer roller holding portion 231 in the rotational axis direction of the secondary outer transfer roller 211. The transfer roller slip-off prevention portion 222 is capable of engaging with the rotating shaft portion 211c of the secondary transfer outer roller 211, and prevents the secondary transfer outer roller 211 from falling off from the transfer roller bearing member 221. Note that the transfer roller pressure spring 225 is arranged between a receiving surface 234 formed on the transfer roller bearing member 221 and a seat surface 235 formed on the holder 201.

Further, as shown in FIGS. 5 and 6, the transfer roller bearing member 221 includes a conductive roller holding section 233 as a second holding section. The conductive roller holding section 233 allows the conductive roller bearing member 224, which rotatably supports the rotating shaft section 213a of the conductive roller 213, to be movable (with play) along the pressing direction of the conductive roller pressure spring 226. )Hold. Further, the transfer roller bearing member 221 has a conductive roller bearing retaining portion 223 as a second regulating portion. The conductive roller bearing retaining portion 223 is capable of engaging with the conductive roller bearing member 244 and prevents the conductive roller bearing member 244 from falling off from the conductive roller holding portion 233 . Note that the conductive roller pressure spring 226 is arranged between a receiving surface 236 formed on the conductive roller bearing member 224 and a seat surface 237 formed on the transfer roller bearing member 221.

As shown in FIG. 5, when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61 (during operation of the image forming apparatus 1), the outer periphery of the bearing 227 is It abuts against the abutting portion 232 of the transfer roller bearing member 221. As a result, the transfer roller bearing member 221 is pressed with a predetermined pressure by the transfer roller pressure spring 225, so that the secondary transfer outer roller 211 is pressed against the secondary transfer inner roller 62 via the intermediate transfer belt 61. It is pressed with the pressure of . Furthermore, the conductive roller bearing member 224 is pressed with a predetermined pressure by the conductive roller pressure spring 226, so that the conductive roller 213 is pressed against the secondary transfer outer roller 211 with a predetermined pressure. At this time, the conductive roller bearing member 224 and the conductive roller bearing retaining portion 223 are separated by a gap G. Further, at this time, the rotation shaft portion 211c of the secondary transfer outer roller 211 and the transfer roller slip-off prevention portion 222 are separated by a play L.

As shown in FIG. 6, when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62), the conductive roller bearing member 224 pressurized by the conductive roller pressure spring 226 , the conductive roller 213 is displaced while pushing the secondary transfer outer roller 211. At this time, the secondary transfer outer roller 211 is displaced until its rotating shaft portion 211c comes into contact with the transfer roller slip-off prevention portion 222. Further, at this time, the conductive roller bearing member 224 is displaced until it comes into contact with the conductive roller bearing retaining portion 223. In other words, the positions (shapes) of the transfer roller retaining portion 222 and the conductive roller bearing retaining portion 223 are determined so as to achieve such a state. In this embodiment, the gap G and the play L have substantially the same dimensional relationship.

In this state, the conductive roller 213 is in contact with the outer secondary transfer roller 211, and the elastic layer 211b of the outer secondary transfer roller 211 is receiving pressure from the conductive roller 213. However, the conductive roller bearing retaining portion 223 also receives the pressing force of the conductive roller pressure spring 226. Therefore, compared to when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61, the elastic layer 211b of the secondary transfer outer roller 211 receives more force from the conductive roller 213. Pressure is relieved. As a result, it is possible to suppress the occurrence of dents in the elastic layer 211b of the secondary transfer outer roller 211 when the secondary transfer unit 90 is left alone, for example, and to prevent image unevenness caused by the dents. The risk of defects occurring can be reduced. Note that when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61, the conductive roller bearing member 224 is not in contact with the conductive roller bearing retaining portion 223, and the conductive roller The secondary transfer outer roller 211 directly receives the pressing force from the roller 213 .

Here, FIG. 7 is a schematic diagram of a cross section of the secondary transfer outer roller 211 that is substantially orthogonal to the rotational axis direction. As shown in FIG. 7, the amount by which the elastic layer 211b of the outer secondary transfer roller 211 is dented by the conductive roller 213 is defined as the amount of penetration I of the conductive roller 213 into the outer secondary transfer roller 211. In other words, the intrusion amount I is between the surface of the secondary transfer outer roller 211 at the contact portion of the conductive roller 213 assuming that there is no dent, and the surface of the secondary transfer outer roller 211 when the surface is dented by the conductive roller 213. is the distance between the surface of At this time, from the viewpoint of suppressing the above-mentioned dents, the intrusion amount I when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 is the amount I when the secondary transfer outer roller 211 is in contact with the intermediate transfer belt 61. It is desirable that the amount of intrusion I be smaller than the amount I when there is an intrusion. In addition, from the viewpoint of further suppressing the above-mentioned dents, the intrusion amount I when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 is determined by the intrusion amount I when the secondary transfer outer roller 211 is in contact with the intermediate transfer belt 61. It is preferable that the amount of intrusion I is 50% or less of the amount I when the intrusion occurs. The intrusion amount I when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 is substantially 0% of the intrusion amount I when the secondary transfer outer roller 211 is in contact with the intermediate transfer belt 61. It may be. Further, typically, it is preferable that the intrusion amount I when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 is 1.5% or less of the diameter of the secondary transfer outer roller 211.

In this embodiment, the secondary transfer outer roller 211 is held by the transfer roller bearing member 221 via the bearing 227, but the present invention is not limited to this. The bearing 227 may not be provided, and the rotating shaft portion 211c of the outer secondary transfer roller 211 may be directly rotatably supported (held) by the transfer roller bearing member 221.

Further, the first regulating portion may be configured to regulate the movement of the secondary outer transfer roller 211 by contacting the member (such as a bearing) that moves together with the outer secondary transfer roller 211 . Further, the conductive roller bearing member 224 in this embodiment is an example of a member that moves together with the conductive roller 213. Further, the second regulating portion may be configured to regulate the movement of the conductive roller 213 by directly contacting the rotating shaft portion 213a of the conductive roller 213, etc. Furthermore, the conductive roller 213 may be supported by a conductive roller bearing member 224 via a bearing that supports the rotating shaft portion 213a. The second regulating portion may be a member that moves together with the conductive roller 213, and may be configured such that the movement of the conductive roller 213 is restricted by, for example, a bearing thereof coming into contact with the second regulating portion.

As described above, in this embodiment, the image forming apparatus 1 includes the image carrier 11 that carries a toner image, the intermediate transfer belt 61 to which the toner image is transferred from the image carrier 11, the core bar 211a, and the core bar 211a. and an elastic layer 211b provided around the intermediate transfer belt 61, and a transfer roller 211 that contacts the outer circumferential surface of the intermediate transfer belt 61 to form the transfer portion N2, and is arranged opposite to the transfer roller 211 with the intermediate transfer belt 61 in between. an opposing roller 62 that contacts the inner peripheral surface of the intermediate transfer belt 61 and forms a transfer portion N2 together with the transfer roller 211; a power source 301 that supplies current to the transfer portion N2; A conductive roller 213 that forms a current path through which a current supplied from the power source 301 flows between the core bar 211a of the roller 211 and a conductive roller 213 that is provided at both ends of the transfer roller 211 in the rotational axis direction, and that connects the transfer roller 211 to the middle. A first pressure member 225 that applies pressure toward the transfer belt 61 and a first pressure member 225 that is provided at both ends of the transfer roller 211 in the rotational axis direction and that are capable of rotating the transfer roller 211 and pressurize the first pressure member 225. A first holding part 231 that holds the conductive roller 213 movably in the rotation axis direction, and a second pressurizing part that presses the conductive roller 213 toward the transfer roller 211, which is provided at both ends of the conductive roller 213 in the rotation axis direction. A second holding member is provided at both ends of the member 226 and the conductive roller 213 in the direction of the rotational axis, and holds the conductive roller 213 rotatably and movably along the pressing direction of the second pressing member 226. A first regulating section 222 that regulates the movement of the first pressing member 225 of the transfer roller 211 in the pressing direction by contacting the section 233 with the transfer roller 211 or a member that moves together with the transfer roller 211. and a second regulating portion 223 that regulates the movement of the second pressure member 226 of the conductive roller 213 in the pressing direction by contacting the conductive roller 213 or a member that moves together with the conductive roller 213; When the transfer roller 211 is separated from the intermediate transfer belt 61, the transfer roller 211 or a member that moves together with the transfer roller 211 is in contact with the first regulating portion 222, and the conductive roller 213 or the A member that moves together with the roller 213 is in contact with the second regulating portion 223 .

In this embodiment, the amount of penetration of the conductive roller 213 into the transfer roller 211 when the transfer roller 211 is separated from the intermediate transfer belt 61 is the same as the amount of penetration of the conductive roller 213 into the transfer roller 211 when the transfer roller 211 is in contact with the intermediate transfer belt 61. The amount of penetration of the conductive roller 213 is smaller than that of the conductive roller 213. Further, the amount of penetration of the conductive roller 213 into the transfer roller 211 when the transfer roller 211 is separated from the intermediate transfer belt 61 is the same as the amount of penetration of the conductive roller 213 into the transfer roller 211 when the transfer roller 211 is in contact with the intermediate transfer belt 61. It is preferable that the amount of intrusion of 213 is 50% or less. In this embodiment, the image forming apparatus 1 includes a bearing member 221 including a first holding section 231, a first regulating section 222, a second holding section 233, and a second regulating section 223, and a conductive roller 213. A conductive roller bearing member 224 is rotatably supported and movably held by a second holding part 233 in the pressing direction of the second pressure member 226, and the bearing member 221 is connected to the first pressure member. 225, the first pressure member 225 is disposed between the bearing member 221 and the holder 201, and the second pressure member 226 is It is arranged between the conductive roller bearing member 224 and the bearing member 221. Further, in this embodiment, a support member 227 that rotatably supports the transfer roller 211 and is movably held by the first holding portion 231 in the pressing direction of the first pressure member 225 is provided. , the first regulating section 222 regulates the movement of the transfer roller 211 when the transfer roller 211 comes into contact with the first regulating section 222 . Further, in this embodiment, the second regulating portion 223 regulates the movement of the conductive roller 213 by contacting the conductive roller bearing member 224, which is a member that moves together with the conductive roller 213. Further, in this embodiment, the transfer roller 211, the conductive roller 213, the first pressure member 225, the first holding part 231, the second pressure member 226, the second holding part 233, the first regulating part A unit 200 including a second regulating section 222 and a second regulating section 223 is detachable from the image forming apparatus 1 .

As described above, according to this embodiment, when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62), the conductive roller 213 is moved relative to the secondary transfer outer roller 211. Pressure force can be reduced. Therefore, according to the present embodiment, it is possible to suppress deformation of the elastic layer 211b of the secondary transfer outer roller 211 due to the pressing force received from the conductive roller 213 when left unused.

[Example 2]
Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of Embodiment 1 are given the same reference numerals as in Embodiment 1, and detailed explanation thereof will be omitted. .

In this embodiment, when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62), the rotating shaft portion 211c of the secondary transfer outer roller 211 is separated from the transfer roller stopper portion 222. They are now spaced apart. That is, in this embodiment, the position (shape) of the transfer roller slip-off prevention part 222 is determined so as to achieve this.

FIG. 8 shows the rotation axis direction (back and forth direction) of the secondary transfer outer roller 211 when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62) in this embodiment. FIG. 3 is a side view showing the vicinity of one end. Although FIG. 8 shows only the configuration of one end of the secondary transfer outer roller 211 in the direction of the rotation axis, in this embodiment, the configuration of the other end is also similar (in the direction of the rotation axis). (substantially symmetrical with respect to a plane passing through the center and substantially orthogonal to the direction of the rotation axis). Note that in FIG. 8, illustration of the intermediate transfer belt 61 is omitted. Further, in this embodiment, when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61, the area near the ends of the secondary transfer outer roller 211 and the conductive roller 213 is The state is similar to that shown in FIG. 5 described in the first embodiment.

As shown in FIG. 8, when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62), the conductive roller bearing member 224 pressurized by the conductive roller pressure spring 226 , the conductive roller 213 is displaced while pushing the secondary transfer outer roller 211. At this time, in this embodiment, the conductive roller bearing member 224 contacts the conductive roller bearing retaining portion 223 before the rotating shaft portion 211c of the outer secondary transfer roller 211 comes into contact with the transfer roller retaining portion 222. That is, in this embodiment, the above-mentioned gap G (FIG. 5) is smaller than the above-mentioned play L (FIG. 5).

Therefore, in this state, the conductive roller bearing retaining portion 223 receives the pressing force of the conductive roller pressure spring 226, and substantially only the dead weight of the secondary transfer outer roller 211 is applied to the conductive roller 213. It becomes the force that comes into contact with. Therefore, compared to when the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61, the elastic layer 211b of the secondary transfer outer roller 211 receives more force from the conductive roller 213. Pressure is relieved. In this embodiment, when the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61, the intrusion amount I is such that the secondary transfer outer roller 211 passes through the intermediate transfer belt 61 to the secondary transfer inner roller 62. The amount of intrusion I when in contact with is 10% or less, or substantially 0%. As a result, it is possible to suppress the occurrence of dents in the elastic layer 211b of the secondary transfer outer roller 211 when the secondary transfer unit 90 is left alone, for example, and to prevent image unevenness caused by the dents. The risk of defects occurring can be reduced.

Here, by adopting the following configuration, it is also possible to prevent the generation of pressing force of the secondary transfer outer roller 211 against the conductive roller 213 due to the above-mentioned own weight. That is, for example, the displacement direction of the secondary transfer outer roller 211 (more specifically, its rotating shaft portion 211c) in the transfer roller holding portion 231 is set to be perpendicular to the direction of gravity (ie, horizontal direction). Alternatively, the displacement direction is set to be a direction in which the inner secondary transfer roller 62 side faces downward rather than the horizontal direction (that is, a direction in which the outer secondary transfer roller 211 moves away from the conductive roller 213 due to gravity).

As described above, in this embodiment, when the transfer roller 211 is separated from the intermediate transfer belt 61, the conductive roller 213 or a member that moves together with the conductive roller 213 is in contact with the second regulating portion 223, Neither the transfer roller 211 nor any member that moves together with the transfer roller 211 is in contact with the first regulating portion 222 .

As explained above, according to this embodiment, when the secondary transfer outer roller 211 is spaced apart from the intermediate transfer belt 61 (secondary transfer inner roller 62), the secondary transfer outer roller The pressing force of the conductive roller 213 on the conductive roller 211 can be reduced. Therefore, according to the present embodiment, deformation of the elastic layer 211b of the secondary transfer outer roller 211 due to the pressure applied from the conductive roller 213 can be suppressed more than in the first embodiment.

[Example 3]
Next, other embodiments of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of the first embodiment. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of Embodiment 1 are given the same reference numerals as in Embodiment 1, and detailed explanation thereof will be omitted. .

In this embodiment, an example of a configuration in which the outer secondary transfer roller 211 is separated from the intermediate transfer belt 61 (inner secondary transfer roller 62) in the image forming apparatus 1 by using a spacing member will be described.

As described above, if the secondary transfer outer roller 211 is left under the same pressure from the conductive roller 213 as during image formation, the elastic layer 211b of the secondary transfer outer roller 211 will be plastically deformed and dented. may occur. This is not only the case where the secondary transfer unit 200 is removed from the image forming apparatus 1 and stored alone in a warehouse, but also the case where the image forming apparatus 1 is stored in a warehouse etc. before shipping. It can also occur in some cases. Therefore, in this embodiment, a spacing member is used to move the secondary transfer outer roller 211 to the intermediate transfer belt 61 (secondary the inner transfer roller 62). This makes it possible to reduce the pressing force that the secondary transfer outer roller 211 receives from the conductive roller 213 as in the first and second embodiments.

FIG. 9 is a perspective view showing a cross section of some elements near the transfer roller bearing member 221 for explaining the spacing member 202 in this embodiment. Although FIG. 9 shows only the configuration of one end of the secondary transfer outer roller 211 in the direction of the rotation axis, in this embodiment, the configuration of the other end is also similar (in the direction of the rotation axis). (substantially symmetrical with respect to a plane passing through the center and substantially orthogonal to the direction of the rotation axis). FIG. 9A shows a state in which the outer secondary transfer roller 211 is in contact with the inner secondary transfer roller 62 via the intermediate transfer belt 61 in the image forming apparatus 1 (during operation of the image forming apparatus 1). It shows. On the other hand, FIG. 9(b) shows a situation when the separation member 202 is used in the image forming apparatus 1 and the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62). It shows.

As shown in FIG. 9A, the transfer roller bearing member 221 is provided with a bearing-side engagement hole 241 as a bearing-side engagement portion. Further, the holder 201 is provided with a holder-side engagement hole 242 and a holder-side engagement groove 243 as a holder-side engagement portion. The holder-side engagement hole 242 is arranged on the outside of the transfer roller bearing member 221 in the direction of the rotational axis of the secondary transfer outer roller 211, and for example, when the right door unit 90 is opened as described above, the holder-side engagement hole 242 is located outside of the holder 201. It is provided so that the operator can access it from here. Further, the holder-side engagement groove 243 faces the holder-side engagement hole 242 on the opposite side of the holder-side engagement hole 242 with the transfer roller bearing member 221 in between in the rotation axis direction of the secondary transfer outer roller 211. placed in position. Further, in a state where the secondary transfer outer roller 211 is in contact with the secondary transfer inner roller 62 via the intermediate transfer belt 61, the situation is as follows. That is, in the movable direction of the transfer roller bearing member 221 (direction along the pressing direction of the transfer roller pressure spring 225), at least a part of the bearing side engagement hole 241, the holder side engagement hole 242, and the holder side engagement At least a portion of each of the grooves 243 overlaps with each other. That is, in this state, the bearing-side engagement hole 241, the holder-side engagement hole 242, and the holder-side engagement groove 243 each penetrate from the outside of the holder 201 to the holder-side engagement groove 243 at least in part. It is formed like this.

As shown in FIG. 9(b), the spacing member 202 has a generally rod-like or plate-like shape as a whole. The spacing member 202 has a width in the movable direction of the transfer roller bearing member 221 (a direction along the pressing direction of the transfer roller pressure spring 225) on one end (“tip portion”) 202a side, and a width on the other end portion 202a side. (“Base end”) It has a slope 202c that is formed to become wider toward the 202b side. The operator grasps the spacing member 202 with, for example, a finger and inserts the tip 202a of the spacing member 202 into the holder-side engagement hole 242 from outside the holder 201. As described above, a portion of each of the bearing-side engagement hole 241, the holder-side engagement hole 242, and the holder-side engagement groove 243 is open to the extent that the distal end portion 202a of the spacing member 202 can pass therethrough, and communicates with each other. Therefore, the spacing member 202 can be inserted from the distal end portion 202a side. Then, the first side surface 202d of the spacing member 202 opposite to the slope 202c engages with the holder-side engagement hole 242, and the slope 202c of the spacing member 202 engages with the bearing-side engagement hole 241. Then, as the spacing member 202 is inserted, the bearing side engagement hole 241 is pushed down by the slope 202c. As a result, the transfer roller bearing member 221 moves in a direction away from the intermediate transfer belt 61 (secondary transfer inner roller 62) along the pressing direction against the pressing force of the transfer roller pressing spring 225. Further, as shown in FIG. 9(b), the tip end 202c of the spacing member 202 reaches the holder-side engagement groove 243, and the first side surface 202d is connected to the holder-side engagement groove 243 and the holder-side engagement hole. 242. At the same time, a second side surface 202e formed on the side opposite to the first side surface 202d and closer to the base end 202b than the slope 202c engages with the bearing side engagement hole 241. As a result, the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62).

In this state, the transfer roller bearing member 221 is arranged closer to the holder 201 (on the opposite side to the intermediate transfer belt 61) than in the states shown in FIG. 6 (Example 1) and FIG. 8 (Example 2). However, in this state, the secondary transfer outer roller 211 is separated from the intermediate transfer belt 61 (secondary transfer inner roller 62). Therefore, the relative positions of the secondary transfer outer roller 211 and the conductive roller 213 (conductive roller bearing member 224) with respect to the transfer roller bearing member 221 are the same as those described in the first and second embodiments. Therefore, by separating the secondary transfer outer roller 211 from the intermediate transfer belt 61 (secondary transfer inner roller 62) by the spacing member 202, conductivity to the secondary transfer outer roller 211 can be improved as in the first and second embodiments. The pressing force of the roller 213 can be reduced.

As described above, in this embodiment, the image forming apparatus 1 separates the transfer roller 211 from the intermediate transfer belt 61 while the transfer roller 211 is disposed at a position facing the intermediate transfer belt 61 within the image forming apparatus. It has a spacing member 202.

In this embodiment, the image forming apparatus 1 is configured such that the right door unit 90 can be closed with the spacing member 202 attached. When the spacing member 202 is attached, the outer secondary transfer roller 211 remains separated from the intermediate transfer belt 61 (inner secondary transfer roller 62) even when the right door unit 90 is closed. Therefore, if the outer secondary transfer roller 211 is separated from the intermediate transfer belt 61 (inner secondary transfer roller 62) using the spacing member 202, the image forming apparatus 1 can be stored in a warehouse or the like before being shipped, for example. Also, by reducing the pressing force that the secondary transfer outer roller 211 receives from the conductive roller 213, it is possible to suppress the denting of the elastic layer 211b of the secondary transfer outer roller 211.

[others]
Although the present invention has been described above with reference to specific examples, the present invention is not limited to the above-mentioned examples.

In the above-described embodiment, a configuration has been described in which the secondary transfer voltage is applied from the conductive roller 213 to the secondary transfer portion N2 via the secondary transfer outer roller 211. However, the power supply mode of the secondary transfer portion N2 is as follows. You can do it like this. Note that elements having the same or corresponding functions or configurations as those of the above-described embodiments will be described with the same reference numerals. FIG. 10 is a schematic cross-sectional view showing another example of the power supply mode of the secondary transfer portion N2. A secondary transfer power supply (high voltage power supply circuit) 302 is connected to the secondary transfer inner roller 62 . During the secondary transfer process, the secondary transfer power source 302 applies a secondary transfer voltage (secondary transfer bias), which is a DC voltage with the same polarity (negative polarity in this example) as the normal charging polarity of the toner, to the secondary transfer process. A voltage is applied to the core bar 62a of the roller 62. In this example, the voltage applied to the secondary transfer inner roller 62 by the secondary transfer power source 302 is controlled to be a constant voltage. On the other hand, the secondary transfer outer roller 211 is electrically floated. Furthermore, a conductive roller 213 made of a metal roller is in contact with the outer peripheral surface of the outer secondary transfer roller 211 . The conductive roller 213 is arranged near a position facing the inner secondary transfer roller 62 via the outer secondary transfer roller 211 . The conductive roller 213 is electrically grounded (connected to the ground). During the secondary transfer process, in the secondary transfer part N2, the positive conductive agent was biased toward the outside of the elastic layer 211b in the radial direction of the secondary transfer outer roller 211, and the negative conductive agent was biased toward the inside (core metal side). become a state. On the other hand, at the contact portion N3 where the conductive roller 213 and the secondary transfer outer roller 211 come into contact, the direction is to alleviate the polarization of the conductive agent of the secondary transfer outer roller 211 that occurs in the secondary transfer process (cancel the uneven distribution of the conductive agent). Current flows in the direction of Note that in this example, a constant voltage source is used as the secondary transfer power source 302, but the present invention can also be applied to a configuration that uses a constant current source.

Further, in the above embodiment, the conductive roller bearing member 224 and the conductive roller pressure spring 226 are held by the transfer roller bearing member 221 movably held by the holder 201 . Although the above-mentioned effects can thereby be obtained, the present invention is not limited to this configuration. The transfer roller bearing member 221 and the conductive roller bearing member 224 may be configured to be held independently by a first holding part and a second holding part provided on the holder 201, respectively. In this case, the transfer roller bearing member 221 and the conductive roller bearing member 224 may be configured to be pressurized by a transfer roller pressure spring 225 and a conductive roller pressure spring 226, respectively, which are arranged between them and the holder 201. . In this case, for example, the holder 201 and the transfer roller bearing member 221 may be provided with a transfer roller retaining portion 222 having the same configuration as in the above-described embodiment, and the holder 201 may be provided with a conductive roller bearing having the same configuration as in the above-described embodiment. A stop 223 can be provided. That is, the image forming apparatus 1 includes the above-described transfer roller 211, conductive roller 213, first pressure member 225, first holding section 231, second pressure member 226, second holding section 233, It is sufficient if the first regulating section 222 and the second regulating section 223 are provided. Furthermore, in this case, the bearing-side engagement hole 241 that engages with the spacing member 202 described in the third embodiment may be provided in the transfer roller bearing member 222. Thereby, the spacing member 202 can be engaged with the bearing side engagement hole 241, and the secondary transfer outer roller 211 can be separated from the intermediate transfer belt 61 (secondary transfer inner roller 62). As in the above-described embodiment, the pressing force of the conductive roller 213 against the outer secondary transfer roller 211 can be reduced.

Further, in the above-described embodiments, the present invention is applied to a secondary transfer section in an intermediate transfer type color image forming apparatus, but the present invention may also be applied to, for example, a transfer section in a monochrome image forming apparatus. In this case, for example, the support structure of the transfer roller that comes into contact with the photoreceptor as the image carrier and the conductive roller that comes into contact with the transfer roller can be the same as in the above embodiment. Thereby, effects similar to those of the above embodiment can be obtained.

1 Image forming device 61 Intermediate transfer belt 62 Secondary transfer inner roller 200 Secondary transfer unit 211 Secondary transfer outer roller 213 Conductive roller 221 Transfer roller bearing member 222 Transfer roller retaining portion 223 Conductive roller bearing retaining portion 224 Conductive roller bearing Member 225 Transfer roller pressure spring 226 Conductive roller pressure spring 227 Bearing 301 Secondary transfer power source 302 Secondary transfer power source

Claims (9)

an image carrier that carries a toner image;
an intermediate transfer belt to which a toner image is transferred from the image carrier;
a transfer roller that includes a core metal and an elastic layer provided around the core metal, and that contacts an outer peripheral surface of the intermediate transfer belt to form a transfer portion;
an opposing roller that is disposed opposite to the transfer roller with the intermediate transfer belt in between, and that contacts an inner circumferential surface of the intermediate transfer belt to form the transfer portion together with the transfer roller;
a power source that supplies current to the transfer section;
a conductive roller that comes into contact with the transfer roller and forms a current path between the core metal of the transfer roller and the current supplied from the power source;
first pressure members that are provided at both ends of the transfer roller in the rotational axis direction and press the transfer roller toward the intermediate transfer belt;
first holding portions that are provided at both ends of the transfer roller in the rotational axis direction and hold the transfer roller rotatably and movably along the pressing direction of the first pressure member;
a second pressure member that is provided on both ends of the conductive roller in the rotational axis direction and presses the conductive roller toward the transfer roller;
a second holding part that is provided at both ends of the conductive roller in the rotational axis direction and holds the conductive roller rotatably and movably along the pressing direction of the second pressure member;
a first regulating portion that regulates the movement of the transfer roller in the pressure direction of the first pressure member by contacting the transfer roller or a member that moves together with the transfer roller;
a second regulating portion that regulates movement of the conductive roller in the pressing direction of the second pressure member by contacting the conductive roller or a member that moves together with the conductive roller;
has
When the transfer roller is separated from the intermediate transfer belt, the transfer roller or a member that moves together with the transfer roller is in contact with the first regulating portion, and the conductive roller or the member that moves together with the conductive roller is in contact with the first regulating portion. An image forming apparatus characterized in that a member that moves is in contact with the second regulating portion. an image carrier that carries a toner image;
an intermediate transfer belt to which a toner image is transferred from the image carrier;
a transfer roller that includes a core metal and an elastic layer provided around the core metal, and that contacts an outer peripheral surface of the intermediate transfer belt to form a transfer portion;
an opposing roller that is disposed opposite to the transfer roller with the intermediate transfer belt in between, and that contacts an inner circumferential surface of the intermediate transfer belt to form the transfer portion together with the transfer roller;
a power source that supplies current to the transfer section;
a conductive roller that comes into contact with the transfer roller and forms a current path between the core metal of the transfer roller and the current supplied from the power source;
first pressure members that are provided at both ends of the transfer roller in the rotational axis direction and press the transfer roller toward the intermediate transfer belt;
first holding portions that are provided at both ends of the transfer roller in the rotational axis direction and hold the transfer roller rotatably and movably along the pressing direction of the first pressure member;
a second pressure member that is provided on both ends of the conductive roller in the rotational axis direction and presses the conductive roller toward the transfer roller;
a second holding part that is provided at both ends of the conductive roller in the rotational axis direction and holds the conductive roller rotatably and movably along the pressing direction of the second pressure member;
a first regulating portion that regulates movement of the transfer roller in the pressure direction of the first pressure member by contacting the transfer roller or a member that moves together with the transfer roller;
a second regulating portion that regulates movement of the conductive roller in the pressing direction of the second pressure member by contacting the conductive roller or a member that moves together with the conductive roller;
has
When the transfer roller is separated from the intermediate transfer belt, the conductive roller or a member that moves together with the conductive roller is in contact with the second regulating portion, and the conductive roller or the member that moves together with the conductive roller is in contact with the second regulating portion, and An image forming apparatus characterized in that none of the members that move are in contact with the first regulating section. The amount of penetration of the conductive roller into the transfer roller when the transfer roller is separated from the intermediate transfer belt is the amount of penetration of the conductive roller into the transfer roller when the transfer roller is in contact with the intermediate transfer belt. The image forming apparatus according to claim 1 or 2, wherein the amount of penetration is smaller than the amount of penetration. The amount of penetration of the conductive roller into the transfer roller when the transfer roller is separated from the intermediate transfer belt is the amount of penetration of the conductive roller into the transfer roller when the transfer roller is in contact with the intermediate transfer belt. 4. The image forming apparatus according to claim 3, wherein the amount of penetration is 50% or less. a bearing member including the first holding part, the first regulating part, the second holding part, and the second regulating part;
a conductive roller bearing member that rotatably supports the conductive roller and is movably held by the second holding portion in a pressing direction of the second pressure member;
a holder that holds the bearing member movably along the pressing direction of the first pressing member;
has
The first pressure member is arranged between the bearing member and the holder, and the second pressure member is arranged between the conductive roller bearing member and the bearing member. The image forming apparatus according to claim 1 or 2. a support member rotatably supporting the transfer roller and movably held by the first holding portion in a pressing direction of the first pressure member; 6. The image forming apparatus according to claim 5, wherein movement of the transfer roller is regulated by contacting the transfer roller. The image according to claim 5, wherein the second regulating portion regulates the movement of the conductive roller by contacting the conductive roller bearing member, which is a member that moves together with the conductive roller. Forming device. The transfer roller, the conductive roller, the first pressure member, the first holding part, the second pressure member, the second holding part, the first regulation part, and the second regulation 3. The image forming apparatus according to claim 1, wherein the unit including the unit is removable from the image forming apparatus. 3. The image forming apparatus further comprises a separating member that separates the transfer roller from the intermediate transfer belt when the transfer roller is disposed at a position facing the intermediate transfer belt in the image forming apparatus. The image forming apparatus described in .

Images