JP5495099B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer.

Conventionally, as this type of image forming apparatus, an intermediate transfer belt, which is a belt member supported by a plurality of stretching members, and a plurality of photoconductors arranged side by side so as to be in contact with and face the intermediate transfer belt An intermediate transfer type tandem type color image forming apparatus is known (for example, Patent Document 1 and Patent Document 2). In this apparatus, the toner images of the respective colors formed on the respective photoconductors are transferred (primary transfer) while being superimposed on the intermediate transfer belt, and the toner images on the intermediate transfer belt are collectively transferred (secondary transfer) to the transfer material. As a result, a color image can be formed on the transfer material.
In addition, this type of color image forming apparatus forms a color image in which a single color mode using a single photoconductor is used to form an image composed of a single color toner image and a plurality of color toner images superimposed. Some are configured to selectively execute a multi-color mode using a plurality of photoconductors.
In such an apparatus, in the single-color mode using one photoconductor, the other photoconductors are not used and are generally separated from the intermediate transfer belt. This is for the purpose of extending the life by suppressing the consumption of the photosensitive member, the parts around the photosensitive member, and the primary transfer member facing the photosensitive member across the intermediate transfer belt.

An example of an intermediate transfer type tandem color image forming apparatus will be described with reference to the drawings.
FIG. 10 is an explanatory diagram showing a layout of the intermediate transfer belt 10 and the four photosensitive members 40 (Y, C, M, K) of the tandem type color image forming apparatus. In the layout shown in FIG. 10, the four photoconductors 40 (Y, C, M, K) are arranged at equal intervals, and the interphotoconductor distance W is 100 [mm].
In the example shown in FIG. 10, the four primary transfer rollers 12 (Y, C, M, and K) are positioned at positions facing the respective photoreceptors 40 (Y, C, M, and K) with the intermediate transfer belt 10 interposed therebetween. K) is arranged to form four primary transfer portions. The intermediate transfer belt 10 moves on the surface in the direction of arrow A in FIG. 10 during image formation, and among the four photoreceptors 40 (Y, C, M, K), the most downstream side in the surface movement direction of the intermediate transfer belt 10. The photoconductor 40 arranged in the black line is a black photoconductor 40K.
FIG. 11 shows a yellow photoconductor 40Y disposed at a position farthest from the black photoconductor 40K among the three color photoconductors 40 (Y, C, M), a primary transfer roller 12Y for yellow, It is expansion explanatory drawing of the area | region (alpha) in FIG. 10 with which the movable tension roller 102 is arrange | positioned. FIG. 12 shows a magenta photoreceptor 40M and a magenta primary transfer roller that are disposed closest to the black photoreceptor 40K among the three color photoreceptors 40 (Y, C, M). FIG. 11 is an enlarged explanatory view of a region β in FIG. 10 in which 12M is arranged.

In the full color mode in which image formation is performed using the four photoconductors 40 (Y, C, M, K), the primary transfer stretched surface 10f of the intermediate transfer belt 10 and the four photoconductors 40 (Y, C, M, and K). K) contacts. For this reason, the arrangement of the primary transfer roller 12 (Y, C, M) facing the intermediate transfer belt 10, the movable stretching roller 102, and the three photosensitive members 40 (Y, C, M) for color is shown in FIG. The position is indicated by the broken line inside.
In the monochrome mode, which is a monochrome mode using the black photoreceptor 40K, the three color photoreceptors 40 (Y, C, M) are not used. For this reason, in the monochrome mode, the moving tension roller 102 and the three primary transfer rollers 12 (Y, C, M) for color are moved in the direction away from the photoreceptor 40 to the position indicated by the solid line in FIG. As a result, the intermediate transfer belt 10 moves to the position indicated by the solid line in FIG. 10 and is separated from the three color photoconductors 40 (Y, C, M). By separating the three color photoconductors 40 (Y, C, M) and the intermediate transfer belt 10 in the monochrome mode, the three color photoconductors 40 (Y, C, M) and the opposite ones are arranged. Thus, the life of the three primary transfer rollers 12 (Y, C, M) and the like can be extended.

  However, since the primary transfer stretch surface 10f of the intermediate transfer belt 10 is formed so as to connect the movable stretch roller 102 and the primary transfer portion for black in a straight line, the intermediate transfer belt 10 is linearly arranged in the monochrome mode. The primary transfer tensioning surface 10f is inclined with respect to the four photoconductors 40 (Y, C, M, K). For this reason, the amount of separation between each of the three photoconductors 40 (Y, C, M) separated from the intermediate transfer belt 10 and the intermediate transfer belt 10 in the monochrome mode is close to that of the black photoconductor 40K. The photosensitive member 40 arranged at the position becomes narrower. Therefore, the distance D1 (see FIG. 12) between the magenta photoconductor 40M arranged next to the black photoconductor 40K and the intermediate transfer belt 10 is the movement amount T (see FIG. 11) of the movable stretching roller 102. ) Is a small value.

Specifically, when the moving amount T of the moving stretching roller 102 is set to 5 [mm], the distance D1 between the magenta photoreceptor 40M and the primary transfer stretching surface 10f is about 1.6 [mm]. there were.
Further, when the photoreceptors 40 are arranged at equal intervals, as the number of the photoreceptors 40 increases, the distance D1 between the photoreceptor 40 disposed adjacent to the black photoreceptor 40K and the intermediate transfer belt 10 increases. It becomes smaller with respect to the moving amount T of the moving stretching roller 102.

FIG. 13 is an explanatory diagram showing a layout of the intermediate transfer belt 10 and the five photoconductors 40 (Y, C, M, K, and N) of a tandem type color image forming apparatus having five photoconductors. In the layout shown in FIG. 13, the five photoconductors 40 (Y, C, M, K, N) are arranged at equal intervals, and the inter-photoconductor distance W is 190 [mm].
FIG. 14 shows an additional toner photoconductor 40N disposed at a position farthest from the black photoconductor 40K among the four color photoconductors 40 (Y, C, M, N), and the primary for the additional toner. It is expansion explanatory drawing of the area | region (alpha) in FIG. 13 in which the transfer roller 12N and the movable tension roller 102 are arrange | positioned. FIG. 15 shows a magenta photoconductor 40M and a magenta primary arranged at the closest position from the black photoconductor 40K among the four color photoconductors 40 (Y, C, M, N). It is expansion explanatory drawing of the area | region (beta) in FIG. 13 in which the transfer roller 12M is arrange | positioned.
The configuration including five photoconductors 40 shown in FIG. 13 is a configuration in which a fifth color toner can be used to improve color reproducibility and image quality in addition to the four-color toners of CMYK, which have been mainstream in recent years. For example, clear toner or white toner can be used for the fifth color, and some other toners such as light magenta and light cyan can be used for color reproducibility.

  When five photoconductors 40 are arranged as shown in FIG. 13, the distance from the transfer position of the black photoconductor 40K to the transfer position of the magenta photoconductor 40M arranged next to the black photoconductor 40K. On the other hand, the distance from the transfer position of the black photoconductor 40K to the movable stretching roller 102 becomes longer. Therefore, if the distance D1 between the magenta photoreceptor 40M and the intermediate transfer belt 10 is 1.6 [mm], which is the same as the layout of FIGS. 10 to 12, the movement amount T of the movable stretching roller 102 is 6. .6 [mm] is required, and the movement amount T of the photosensitive member 40 must be increased by 1.6 [mm] as compared with the four configurations.

When the moving amount T of the moving stretching roller 102 is increased, the moving range of the moving stretching roller 102 and the intermediate transfer belt 10 stretched around it is widened, so that a space for the space is secured, which causes a problem of enlargement of the apparatus.
Furthermore, when the movement amount T of the movable stretching roller 102 is increased, there arises a problem that the amount of fluctuation in belt tension between the monochrome mode state and the color mode state increases.

Hereinafter, the relationship between the movement amount T of the movable stretching roller 102 and the fluctuation amount of the belt tension will be described.
10 and 13 includes a tension roller 101 that is urged against the surface of the intermediate transfer belt 10 by a tension spring 101 s and applies belt tension to the intermediate transfer belt 10.
When the color mode is changed to the monochrome mode, the track of the intermediate transfer belt 10 on the primary transfer stretch surface 10f moves inward. For this reason, the surface of the intermediate transfer belt 10 is moved downstream in the surface movement direction of the black photoconductor 40K from the first stretching roller 15 on the upstream side in the surface movement direction of the intermediate transfer belt 10 with respect to the moving stretch roller 102. The track of the intermediate transfer belt 10 to the second tension roller 110 on the side becomes shorter. However, the peripheral length L [mm] of the intermediate transfer belt 10 does not change between the monochrome mode and the color mode. For this reason, the tension roller 101 moves to lengthen the trajectory of the intermediate transfer belt 10 from the second tension roller 110 to the first tension roller 15, so that the circumference of the intermediate transfer belt 10 becomes L [mm]. Forming an orbit.
Here, in the layout of FIG. 10, the peripheral length L of the intermediate transfer belt 10 is set to 904.38 [mm], and the movable stretching roller 102 is moved by the movement amount T = 5.0 [mm] as described above. However, the position of the tension roller 101 was displaced by about 0.5 [mm]. On the other hand, in the layout of FIG. 13, if the peripheral length L of the intermediate transfer belt 10 is assumed to be 2200 [mm], the movable stretching roller 102 is moved by the movement amount T = 6.6 [mm] as described above. The position of the tension roller 101 was displaced by about 1.5 [mm].
Thus, the distance that the tension roller 101 moves increases as the moving amount T of the moving tension roller 102 increases.

For example, when the belt tension is set to 1.5 [N / cm], it is necessary to apply a load of about 60 [N] to the tension roller 101 in the layout shown in FIG. When a load is applied to the axial end of the tension roller 101 by two tension springs 101s, a load of 30 [N] is required on one side. In order to obtain such a load, for example, when the natural length of the tension spring 101 s is about 40 [mm], the spring constant is 1 to 5 [N / mm], depending on the configuration.
Assuming that the spring constant of the tension spring 101s is 3 [N / mm], the load applied to the tension roller 101 changes as follows.
In the layout shown in FIG. 10, the color mode state is 60 [N], but the monochrome mode state is 57 [N], and the load applied to the tension roller 101 is 5 [%]. On the other hand, in the layout shown in FIG. 13, the color mode state is 60 [N], but the monochrome mode state is 51 [N], and the load applied to the tension roller 101 is 15 [%]. .
As described above, when the moving amount T of the movable stretching roller 102 is increased, the load applied to the tension roller 101 in the monochrome mode state and the color mode state increases, and the belt tension also increases. If the belt tension is greatly reduced, slip may occur between the intermediate transfer belt 10 and the belt driving roller 14, and the drive may not be accurately transmitted to the intermediate transfer belt 10. Considering that the belt tension is greatly reduced, if the belt tension is set to be higher than necessary in the color mode, the driving load when driving the intermediate transfer belt becomes excessively large. Arise.
Therefore, it is required to secure a separation amount between the intermediate transfer belt 10 and the photosensitive member 40 disposed adjacent to the black photosensitive member 40K without increasing the moving amount T of the movable stretching roller 102.

  Such a problem is not limited to a configuration in which a plurality of photoconductors 40 are opposed to one intermediate transfer belt 10 and a part of the plurality of photoconductors 40 and the intermediate transfer belt 10 are in contact with or separated from each other depending on an image forming mode. Absent. For example, a problem may occur even in a configuration in which a plurality of developing rollers are opposed to one belt-shaped photoconductor and a part of the plurality of developing rollers and the intermediate belt-shaped photoconductor are in contact with or separated from each other depending on an image forming mode It is. That is, it has one endless belt member and a plurality of toner supply members that supply toner onto the belt member in contact with or close to the outer peripheral surface of the endless belt member. This is a problem that can occur if a part and the belt member are in contact with each other.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a belt at a position facing a part of the toner supply members in a configuration in which a part of the plurality of toner supply members is brought into contact with and separated from the belt member. An object of the present invention is to provide an image forming apparatus capable of increasing the amount of movement of a member.

According to a first aspect of the present invention, an endless belt member supported by a plurality of stretch members is juxtaposed so as to be in contact with or in close proximity to the outer peripheral surface of the belt member, and a toner is disposed on the surface of the belt member. A plurality of toner supply members, and a part of the plurality of toner supply members separated from the belt member from a proximity state in which the plurality of toner supply members are in contact with or close to the belt member Belt contact / separation means for moving the belt member so as to be in a separated state, and the belt contact / separation means is in contact with or close to the belt member in the separated state. The inner side of the belt member opposite to the non-separation facing position of the belt member facing the member across the spacing facing position of the belt member facing the part of the toner supply member in the proximity state. Stretch the circumference A movable tension member that is movable, and moves the movable tension member from the proximity state in a direction away from the plurality of toner supply members to separate the belt member from the part of the toner supply members. In the image forming apparatus to be in the separated state, the auxiliary tension that contacts the outer peripheral surface of the belt member between the non-separation facing position and the spacing facing position and stretches the belt member in the separated state. have a bridging member, as the auxiliary tension members, is characterized in Rukoto a brush member having bristles short fibers to the substrate.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a tension applying mechanism that applies belt tension to the belt member, and the auxiliary tension member is separated from the belt member in the close state, A synchronization mechanism that synchronizes the operation of the auxiliary tension member with the contact / separation operation of the belt contacting / separating means so that the auxiliary tension member contacts the belt member when in the separated state, The position of the auxiliary tension member is displaced so as to prevent the belt tension from fluctuating in the separated state.
According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, there is provided auxiliary tension member urging means for urging the auxiliary tension member toward the belt member in the separated state. It is characterized by this.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, when the image forming operation is not performed, the plurality of toner supply members are separated from the belt member. The auxiliary tension member is separated from the belt member.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a member made of a material having a high electrical resistivity is used as the auxiliary stretch member. It is.
The invention of claim 6 is the image forming apparatus according to any one of 請 Motomeko 1 to 5, an intermediate transfer member of the belt member is a belt-like, the plurality of toner supplying member respectively It is an image carrier on which a toner image transferred to the intermediate transfer member is formed.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the belt member is a belt-shaped latent image carrier, and the plurality of toner supply members are respectively It is a developer carrier that develops latent images for images of different colors on the latent image carrier.

  In the conventional image forming apparatus, the trajectory of the belt member between the movable stretch member and the non-separation facing position in the separated state is inclined with respect to the trajectory in the close state. For this reason, the closer to the non-separation facing position from the movable stretching member, the closer the distance to the track in the proximity state, and the closer the distance between the partly separated toner supply member and the belt member. On the other hand, in the image forming apparatus of the present invention, the auxiliary stretching member is stretched from the outer peripheral surface of the belt member between the non-separation facing position and the spacing facing position, so that the proximity state in the conventional image forming apparatus is reached. The belt member track in a separated state inclined with respect to the track can be pushed away from the toner supply member.

  According to the present invention, the movement amount of the belt member at a position facing a part of the toner supply member is increased by pushing the belt member track in the separated state away from the toner supply member by the auxiliary tension member. There is an excellent effect of being able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory diagram of a main configuration of a copying machine according to a reference configuration example 1 to which the present invention is applicable . 1 is a schematic configuration diagram of a copying machine according to a reference configuration example 1. FIG. The figure which represented the shape of the toner typically in order to demonstrate shape factor SF-1. The figure which represented the shape of the toner typically in order to demonstrate shape factor SF-2. 2 is an explanatory diagram of a main configuration of a copying machine according to Reference Configuration Example 1. FIG. 5A and 5B are enlarged explanatory diagrams of the region α, FIG. 5A is an explanatory diagram in the full color mode, and FIG. 5B is an explanatory diagram in the monochrome mode. 5A and 5B are enlarged explanatory diagrams of the region γ, FIG. 5A is an explanatory diagram in the full color mode, and FIG. 5B is an explanatory diagram in the monochrome mode. 5 is an enlarged explanatory view of a region γ in FIG. 5 having a configuration including an auxiliary tension pressing spring, (a) is an explanatory view in the full color mode, and (b) is an explanatory view in the monochrome mode. Expansion explanatory drawing of the area | region (gamma) in FIG. 5 of a structure provided with the auxiliary | assistant tension brush. FIG. 3 is an explanatory diagram showing a layout of an intermediate transfer belt and four photosensitive members of a tandem type color image forming apparatus. Expansive explanatory drawing of the area | region (alpha) in FIG. Expansive explanatory drawing of the area | region (beta) in FIG. 3 is an explanatory diagram showing a layout of an intermediate transfer belt and five photoconductors of a tandem type color image forming apparatus. FIG. Expansive explanatory drawing of the area | region (alpha) in FIG. FIG. 14 is an enlarged explanatory view of a region β in FIG. 13.

[Reference configuration example 1]
A reference configuration example 1 as a first reference configuration example of an intermediate transfer type tandem type color image forming apparatus to which the present invention is applicable will be described below.
FIG. 2 is a schematic configuration diagram of a copying machine (hereinafter referred to as a copying machine 500) as an image forming apparatus according to Reference Configuration Example 1 . The copying machine 500 includes a copying machine main body (hereinafter referred to as the apparatus main body 100), a paper feed unit 200 that houses transfer paper and places the apparatus main body 100 on the upper side, a scanner 300 that is mounted on the apparatus main body 100, and a scanner 300. The automatic document feeder (ADF) 400 mounted on the upper side of the document. A control unit (not shown) that controls the operation of each device in the copying machine 500 is also provided.

  In the center of the apparatus main body 100, four image forming units 18 (Y, C, M, K) of yellow (Y), cyan (C), magenta (M), and black (K) are arranged side by side. Thus, the tandem image forming unit 20 is configured. Each image forming unit 18 of the tandem image forming unit 20 has a photoreceptor 40 (Y, C, M, K) on which toner images of respective colors Y, C, M, and K are formed.

  An exposure device 21 is provided above the tandem image forming unit 20. The exposure device 21 is arranged in four laser diode (LD) light sources prepared for each color, a set of polygon scanners composed of a six-sided polygon mirror and a polygon motor, and an optical path of each light source. It is composed of a lens such as an fθ lens, a long WTL, or a mirror. The laser light emitted from the LD in accordance with the image information of each color is deflected and scanned by the polygon scanner and applied to the photoconductor 40 of each color.

Below the tandem image forming unit 20, an endless belt-like intermediate transfer belt 10 is installed. In the illustrated example, the intermediate transfer belt 10 is wound around three support rollers (14, 15, 16) and can be rotated and conveyed clockwise in the figure. The drive roller 14 of the three support rollers is an intermediate transfer belt. It is a roller that rotates. Further, a primary transfer roller 12 (Y, C, M, K) is provided between the first stretching roller 15 and the driving roller 14 as primary transfer means for transferring the toner image from the photoreceptor 40 of each color to the intermediate transfer belt 10. ) Is provided so as to face each photoconductor 40 with the intermediate transfer belt 10 interposed therebetween. An intermediate transfer belt cleaning device 17 for removing residual toner remaining on the intermediate transfer belt 10 after image transfer is located at a position facing the cleaning counter roller 170 on the downstream side of the secondary transfer counter roller 16 with the intermediate transfer belt 10 interposed therebetween. Is provided.
The primary transfer roller 12 (Y, C, M, K) is obtained by applying a foamed resin agent to a metal core (iron, SUS (stainless steel), AI (aluminum), etc.). The thickness of the foamed resin agent is 2 [mm] to 10 [mm].

  A secondary transfer device 22 is provided below the intermediate transfer belt 10. In the illustrated example, the secondary transfer device 22 includes a secondary transfer belt 24, which is an endless belt, spanned between two secondary transfer stretching rollers 23, and is opposed to the secondary transfer via the intermediate transfer belt 10. The roller 16 is pressed against the roller 16, and the image on the intermediate transfer belt 10 is transferred to the transfer paper. As the secondary transfer belt 24, the same material as that of the intermediate transfer belt 10 can be used.

  A fixing device 25 for fixing the image on the transfer paper is provided on the left side of the secondary transfer device 22 in FIG. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.

  The secondary transfer device 22 described above is also provided with a sheet conveying function for conveying the transfer paper after image transfer to the fixing device 25. Of course, a transfer roller or a transfer charger may be disposed as the secondary transfer device 22, and in such a case, it is necessary to provide this transfer material conveyance function separately.

  In the copying machine 500 shown in FIG. 2, the transfer paper is reversed and discharged below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming unit 20 described above, or images are printed on both sides of the transfer paper. A reversing device 28 is provided for reversing and transferring the transfer paper for forming.

  When performing a copy operation using the copying machine 500, a document is set on the document table 30 of the ADF 400. Alternatively, the ADF 400 is opened and an original is set on the contact glass 32 of the scanner 300, and the ADF 400 is closed and the original is pressed. When a start switch of an operation unit (not shown) is pressed, when a document is set on the ADF 400, the document is transported and moved onto the contact glass 32. On the other hand, when a document is set on the contact glass 32, Immediately, the scanner 300 is driven and the first traveling body 33 and the second traveling body 34 travel. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34 and reflects by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read. Thereafter, when the mode setting is set on the operation unit or the automatic mode selection is set on the operation unit, the image forming operation is started in the full color mode or the monochrome mode according to the reading result of the document.

  Further, when a start switch of an operation unit (not shown) is pressed, along with the above-described operation, the drive roller 14 is rotationally driven by a drive motor (not shown), and the other two support rollers (15, 16) are driven and rotated. The transfer belt 10 is rotated and conveyed. When the full color mode is selected, each photoconductor 40 provided in each image forming unit 18 rotates counterclockwise in FIG. The surface of each photoconductor 40 is uniformly charged by a charging roller as a charging device. Then, each color photoconductor 40 is irradiated with laser light corresponding to the image of each color from the exposure device 21, and a latent image corresponding to the image data of each color is formed. Each latent image is developed into a toner image of each color by each color developing device 60 (Y, C, M, K) as the photoreceptor 40 rotates. The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 10 along with the conveyance of the intermediate transfer belt 10 to form a full color image on the intermediate transfer belt 10. After the transfer, the photoreceptor 40 is subjected to light neutralization by a neutralization lamp, and the residual toner is removed by a cleaning unit.

On the other hand, when a start switch of an operation unit (not shown) is pressed, one of the paper feed rollers 42 of the paper feed unit 200 is selectively rotated together with the above-described operation, and one of the paper feed cassettes 44 provided in the paper feed table 43 in multiple stages. The transfer paper is sent out from. Then, the paper is separated one by one by the separation roller 45, put into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the apparatus main body 100, and abutted against the registration roller 49 and stopped. Alternatively, the transfer paper on the manual feed tray 51 is sent out by rotating the manual feed roller 50, separated one by one by the manual feed separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped.
Then, the registration roller 49 is rotated in synchronization with the full-color image on the intermediate transfer belt 10, the transfer sheet is fed between the intermediate transfer belt 10 and the secondary transfer device 22, and is transferred by the secondary transfer device 22. A color toner image is transferred onto the transfer paper.

The transfer paper on which the toner image has been transferred is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where heat and pressure are applied by the fixing device 25 and the toner image is fixed. The paper is switched and discharged by a discharge roller 56 and stacked on a discharge tray 57. Alternatively, it is switched by the switching claw 55 and conveyed to the reversing device 28, where it is reversed and fed again to the transfer position. After the image is also recorded on the back surface, it is discharged onto the discharge tray 57 by the discharge roller 56. The
On the other hand, the residual toner remaining on the surface of the intermediate transfer belt 10 after the transfer of the toner image onto the transfer paper is removed by the intermediate transfer belt cleaning device 17 to prepare for re-image formation by the tandem image forming unit 20.
Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

  After the predetermined number of images have been formed, the post-image forming process is performed, and then the rotation of the photoconductor 40 is stopped. In the post-image forming process, the photosensitive member 40 is rotated one or more times with the charging bias and transfer bias turned off, and at that time, the charge on the surface of the photosensitive member is discharged by the discharging means, and the photosensitive member 40 is left discharged. This prevents the photoreceptor 40 from deteriorating.

  When the monochrome mode is selected, the first tension roller 15 moves downward to separate the intermediate transfer belt 10 from the photoreceptor 40 (Y, C, M). Only the black photoconductor 40K rotates counterclockwise in FIG. 2, the surface of the black photoconductor 40K is uniformly charged by the charging roller, and the laser beam corresponding to the K image is emitted from the exposure device 21. Irradiated to form a latent image on the black photoreceptor 40K, and the latent image is developed with K toner by the black developing device 60K to form a toner image. This toner image is transferred from the photoreceptor 40 to the intermediate transfer belt 10. At this time, the three-color photoconductors 40 (Y, C, M), the developing devices 60 (Y, C, M) other than the black photoconductor 40K are stopped, and the photoconductors 40 (Y, C) are stopped. , M) and the developer contained in the developing device 60 (Y, C, M) are prevented from being consumed unnecessarily.

  On the other hand, the transfer paper fed from the paper feed cassette 44 is conveyed by the registration roller 49 at a timing that coincides with the toner image formed on the intermediate transfer belt 10. The transfer paper on which the toner image has been transferred is fixed by the fixing device 25 as in the case of a full-color image, and processed through a paper discharge system corresponding to a designated mode. Thereafter, when the formation of two or more images is instructed, the above-described image forming process is repeated.

The intermediate transfer belt 10 is made of PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), or the like in a single layer or a plurality of layers. Then, a conductive material such as carbon black is dispersed, and the volume resistivity is adjusted to be in the range of 10 ⁸ to 10 ¹² [Ωcm], and the surface resistivity is adjusted to be in the range of 10 ⁹ to 10 ¹³ [Ωcm]. If necessary, a release layer may be coated on the surface of the intermediate transfer belt 10. Materials used for the coating include ETFE (ethylene-tetrafluoroethylene copolymer), PTFE (polytetrafluoroethylene), PVDF (vinylidene fluoride), PEA (perfluoroalkoxy fluorocarbon resin), FEP (four-fluorocarbon). Fluorine resin such as ethylene fluoride-propylene hexafluoride copolymer) or PVF (vinyl fluoride) can be used, but is not limited thereto.

The method of manufacturing the intermediate transfer belt 10 includes a casting method, a centrifugal molding method, and the like, and the surface thereof may be polished if necessary.
If the volume resistivity of the intermediate transfer belt 10 exceeds the above-described range, the bias required for transfer increases, which increases the power supply cost. Further, since the charging potential of the intermediate transfer belt 10 becomes high and the self-discharge becomes difficult in the transfer process, the transfer paper peeling process, etc., it is necessary to provide a static eliminating means. Also, if the volume resistivity and surface resistivity are below the above ranges, the charge potential decays quickly, which is advantageous for static elimination by self-discharge, but toner scatter occurs because the current during transfer flows in the surface direction. End up. Therefore, the volume resistivity and surface resistivity of the intermediate transfer belt 10 in the copying machine 500 are preferably within the above ranges.
The volume resistivity and surface resistivity were measured by connecting an HRS probe (inner electrode diameter 5.9 [mm], ring electrode inner diameter 11 [mm]) to a high resistivity meter (manufactured by Mitsubishi Chemical Corporation: Hiresta IP). Then, a voltage of 100 [V] (surface resistivity is 500 [V]) was applied to the front and back of the intermediate transfer belt 10, and the measured value after 10 seconds was used.

Next, a toner suitably used for the copying machine 500 will be described.
The toner suitably used for the copying machine 500 is a polymerized toner produced by a polymerization method, and it is preferable that the toner has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. When the shape factor SF-1 exceeds 150, the transfer rate decreases, which is not preferable.

FIG. 3 is a diagram schematically showing the shape of the toner for explaining the shape factor SF-1.
The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

FIG. 4 is a diagram schematically showing the shape of the toner for explaining the shape factor SF-2.
As shown in FIG. 4, the shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following equation (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × (100π / 4) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered and the cleaning property when attached to the transfer means is also lowered, which is not preferable.

The toner particle size is preferably in the range of 4 to 10 [μm] in terms of volume average particle size. When the particle size is smaller than this, it becomes a cause of background stains at the time of development, fluidity is deteriorated, and further, aggregation tends to occur, so that voids are likely to occur. On the other hand, when the particle size is larger than this, it is impossible to obtain a high-definition image due to toner scattering or resolution deterioration.
In the copying machine 500 of Reference Configuration Example 1 , a toner having a volume average particle diameter of 6.5 [μm] was used.

Next, features of the copying machine 500 of the reference configuration example 1 will be described.
FIG. 1 is a schematic explanatory diagram of the main configuration of the apparatus main body 100 of the copying machine 500. In the overall view of the copying machine 500 shown in FIG. 2, the configuration including the four photoconductors 40 has been described. In the following description, the configuration including the five photoconductors 40 will be described. Note that the characteristic configuration of the reference configuration example 1 is not limited to the five configurations of the photoconductors 40 but can be applied to four configurations, and further, as long as the configuration includes a plurality of photoconductors 40. Applicable.

In the apparatus main body 100 of the reference configuration example 1 shown in FIG. 1, the tension surface stretched between the movable tension roller 102 and the second tension roller 110 is provided on each photoconductor 40 (Y, C, M). , K, N) is a primary transfer stretched surface 10f on which the toner images of the respective colors are primarily transferred. The position of the primary transfer stretched surface 10f of the intermediate transfer belt 10 is different between the full color mode and the monochrome mode. The primary transfer stretched surface 10f is in the position indicated by the broken line in FIG. 1 in the full color mode, and the primary transfer stretched surface in the monochrome mode. The transfer stretch surface 10f is at the position indicated by the solid line in FIG.
As shown in FIG. 1, the copier 500 is in contact with the endless intermediate transfer belt 10 supported by a plurality of stretching rollers (14, 15, 16, 102, 110, etc.) and the outer peripheral surface of the intermediate transfer belt 10. And five photoconductors 40 (Y, C, M, K, and N) that are arranged side by side and transfer the toner image onto the surface of the intermediate transfer belt 10.
Further, four photoconductors 40 (Y, C) out of the five adjacent photoconductors 40 (Y, C, M, K, N) from the proximity state indicated by broken lines in FIG. , M, N) has a belt contacting / separating means for moving the intermediate transfer belt 10 so as to be in a separated state shown by a solid line in FIG. The belt contact / separation means includes a movable movable roller 102 that stretches the inner peripheral surface of the intermediate transfer belt 10 on the opposite side of the color toner transfer position with respect to the black toner transfer position. The belt contacting / separating means moves the moving transfer roller 102 and the four primary transfer rollers 12 (Y, C, M, N) to five photosensitive members from the contact / separation state where the primary transfer stretching surface 10f is indicated by a broken line. Move downwards away from 40 (Y, C, M, K, N). As a result, the four photoconductors 40 (Y, C, M, N) are separated from the intermediate transfer belt 10 as indicated by the solid line on the primary transfer stretch surface 10f.
The black toner transfer position is a position on the intermediate transfer belt 10 where the black photoconductor 40K, which is one photoconductor 40 in contact with the intermediate transfer belt 10 in the separated state, contacts. The color toner transfer position is a position on the intermediate transfer belt 10 where the four color photoconductors 40 (Y, C, M, and N) are in contact with each other in the proximity state.

Further, the apparatus main body 100 of the copying machine 500 of Reference Configuration Example 1 includes a magenta photoconductor disposed next to the black photoconductor 40K among the four photoconductors 40 (Y, C, M, and N). 40M is in contact with the outer peripheral surface of the intermediate transfer belt 10 between the position on the intermediate transfer belt 10 where the toner image is transferred (transfer position of magenta toner) and the transfer position of black toner, and is in an intermediate state. An auxiliary tension roller 150 that stretches the belt 10 is provided. The auxiliary transfer roller 150 pushes down the intermediate transfer belt 10 between the transfer position of the magenta toner and the transfer position of the black toner, thereby lowering the primary transfer stretch in the separated state as compared with the configuration shown in FIG. The surface 10f is almost horizontal. The primary transfer tensioning surface 10f from the position where the intermediate transfer belt 10 is stretched by the movable tensioning roller 102 to the magenta toner transfer position becomes nearly horizontal, so that the magenta photoreceptor 4M and the intermediate transfer belt. The distance from 10 can be the same as the amount of movement of the movable stretching roller 102. Therefore, the distance between the four photosensitive members 40 (Y, C, M, and N) that are separated from the intermediate transfer belt 10 in the monochrome mode and the intermediate transfer belt 10 is smaller than that of the configuration in which the auxiliary stretching roller 150 is not provided. Become bigger.

  In the example shown in FIG. 1, the arrangement of five photoconductors 40 (Y, C, M, K, and N) is the same. In the example shown in FIG. 1, the black photoconductor 40 </ b> K moves the surface of the intermediate transfer belt 10. Although it arrange | positions in the direction most downstream side and the auxiliary | assistant tension roller 150 is made to contact the upstream side, it does not restrict to this. For example, regarding the arrangement of the five photoconductors 40 (Y, C, M, K, N), the black photoconductor 40K may be arranged on the most upstream side in the surface movement direction of the intermediate transfer belt 10. In this case, in the monochrome mode, the auxiliary tension roller 150 is in contact with the outer peripheral surface of the intermediate transfer belt 10 downstream of the black toner transfer position. May adhere to the auxiliary stretching roller 150 and disturb the image. Therefore, in such a case, a voltage having the same polarity as the toner is applied to the auxiliary tension roller 150. Thereby, it is possible to prevent the black toner on the intermediate transfer belt 10 from adhering to the auxiliary stretching roller 150.

In the apparatus main body 100 of the reference configuration example 1 , the auxiliary tension roller 150 is disposed between the magenta photoconductor 40M and the black photoconductor 40K. The auxiliary tension roller 150 may be disposed between the two. Compared to a configuration in which the auxiliary tension roller 150 is not provided at any position, the position of the primary transfer tension surface 10f in the separated state can be lowered, and the four photoconductors 40 (Y, C, M) can be lowered. , N) and the intermediate transfer belt 10 can be separated from each other in comparison with a configuration in which the auxiliary tension roller 150 is not provided.
However, among the four photosensitive members 40 (Y, C, M, and N) that are separated from the intermediate transfer belt 10 in the monochrome mode, as in the apparatus main body 100 of the reference configuration example 1 , they are separated in the monochrome mode. It is optimal to dispose the auxiliary tension roller 150 between the magenta photosensitive member 40M and the black photosensitive member 40K that are disposed closest to the black photosensitive member 40K. This is due to the following reason.
That is, the track of the intermediate transfer belt 10 closer to the black toner transfer position than the position where the auxiliary tension roller 150 abuts is obliquely upward, so that the photosensitive member 40 separated from the intermediate transfer belt 10 faces this position. Then, the distance between the photoreceptor 40 and the intermediate transfer belt 10 becomes smaller as the distance from the black toner transfer position becomes closer. On the other hand, as in Reference Configuration Example 1 , the auxiliary tension roller 150 is interposed between the magenta photoconductor 40M and the black photoconductor 40K that are disposed closest to the black photoconductor 40K. Place. As a result, the transfer positions of the four photosensitive members 40 (Y, C, M, N) that are separated from the intermediate transfer belt 10 in the monochrome mode are intermediate between the auxiliary tension roller 150 and the movable tension roller 102. The position is on the transfer belt 10. Therefore, the height of each transfer position on the intermediate transfer belt 10 is a height between the position where the auxiliary tension roller 150 contacts the intermediate transfer belt 10 and the position where the movable tension roller 102 contacts the intermediate transfer belt 10. It becomes. Thereby, it is possible to secure a sufficient amount of separation from the intermediate transfer belt 10 for all of the four photosensitive members 40 (Y, C, M, N).

Next, the configuration of the main part of the apparatus main body 100 will be described in more detail with reference to FIGS.
FIG. 5 is an explanatory diagram illustrating the configuration of the main part of the apparatus main body 100 in more detail than FIG. 1, and is an explanatory diagram in the full-color mode that is in a contact state. FIG. 6 shows an additional toner photoconductor 40N disposed at a position farthest from the black photoconductor 40K among the four color photoconductors 40 (Y, C, M, N), and the primary for the additional toner. FIG. 6 is an enlarged explanatory view of a region α in FIG. 5 in which a transfer roller 12N and a movable stretching roller 102 are arranged. FIG. 6A is an explanatory diagram in the full color mode (contact state), and FIG. 6B is an explanatory diagram in the monochrome mode (separated state). Further, FIG. 7 shows a magenta photosensitive member 40M and a black photosensitive member 40M, which are arranged closest to the black photosensitive member 40K among the four color photosensitive members 40 (Y, C, M, N). FIG. 6 is an enlarged explanatory view of a region γ in FIG. 5 in which an auxiliary tension roller 150 is disposed between the body 40K. FIG. 7A is an explanatory diagram in the full color mode (contact state), and FIG. 7B is an explanatory diagram in the monochrome mode (separated state).

In the apparatus main body 100, the four primary transfer rollers 12 (Y, C, M, N) for color contact and separate from the photoreceptors 40 (Y, C, M, N), and the movable stretching roller 102 The up / down movement is performed using the contact / separation slider 140.
The four primary transfer rollers 12 (Y, C, M, N) are respectively supported by primary transfer roller brackets 120 (Y, C, M, N), and in the full color mode, primary transfer pressure springs 121 (Y , C, M, N) to the photosensitive member 40 (Y, C, M, N). When the contact / separation slider 140 moves to the left and right, the four primary transfer roller brackets 120 (Y, C, M, N) rotate, and the four primary transfer rollers 12 (Y, C, M, N) rotate. The photoconductors 40 (Y, C, M, N) are in contact with and separated from each other.

The movable tension roller 102 is supported by one end of the movable tension roller bracket 122, and the other end of the movable tension roller bracket 122 is moved up and down depending on the lateral position of the contact / separation slider 140 attached rotatably. The position of the direction is determined. In the full color mode, the contact / separation slider 140 is at the right end of the moving range, and at this time, the moving tension roller 102 is at the upper end of the moving range.
That is, the moving tension roller 102 moves up and down by moving the contact / separation slider 140 to the left and right, and the movable tension roller 102 is moved from the full color mode state shown in FIGS. 5, 6A and 7A. By moving the roller 102 downward, the trajectory of the intermediate transfer belt 10 is changed to separate the intermediate transfer belt 10 from the four photoconductors 40 (Y, C, M, N).

The contact / separation slider 140 is urged rightward in the drawing by a slider spring 141, and a part of the contact / separation slider 140 abuts against the contact / separation cam 142.
When the contact / separation cam 142 rotates in the direction of the arrow E1 in FIG. 7 from the state of the full color mode shown in FIGS. 5, 6A, and 7A, the contact / separation slider 140 moves along the arrow E2 in the drawing. Move to the left side as shown. The primary transfer roller bracket 120 (Y, C, M, N) has a protrusion 146 (Y, C, M) whose lower end is provided on the contact / separation slider 140 when the contact / separation slider 140 moves leftward. , N) and rotate. As a result, the four primary transfer rollers 12 (Y, C, M, N) are released from the urging force by the primary transfer pressure springs 121 (Y, C, M, N) and moved downward, and each photoconductor. 40 (Y, C, M, N). Further, when the contact / separation slider 140 moves leftward in the figure, the movable tension roller 102 moves downward.
As the contact / separation slider 140 moves in the left direction in the figure as described above, the primary transfer roller bracket 120 (Y, C, M, N) and the movable tension roller bracket 122 rotate, and the primary transfer roller 12 (Y , C, M, N) and the movable stretching roller 102 move downward. As a result, the primary transfer rollers 12 (Y, C, M, N) are completely separated from the photoreceptors 40 (Y, C, M, N) and the intermediate transfer belt 10. The intermediate transfer belt 10 that forms the primary transfer stretch surface 10f is a black primary transfer portion upstream stretch roller 130 disposed between the black primary transfer roller 12K and the magenta primary transfer roller 12M. And a movable stretching roller 102, and a track is formed.

In addition, the auxiliary tension roller 150 is positioned at the position of the intermediate transfer belt 10 where the primary transfer roller 12M for magenta contacts in the full color mode and the intermediate transfer belt 10 where the tension roller 130 upstream of the primary transfer section for black contacts. In the monochrome mode, the intermediate transfer belt 10 is contacted. The auxiliary tension roller bracket 160 that supports the auxiliary tension roller 150 is configured to be caught by the contact / separation slider 140, and the contact / separation cam 142 rotates in the direction of arrow E1 in FIG. By moving in the left lateral direction as indicated by an arrow E2 in the drawing, the rotation in the direction of the arrow E3 in FIG. That is, when the four primary transfer rollers 12 (Y, C, M, N) are moved away from the respective photoreceptors 40 (Y, C, M, N), the auxiliary stretching roller 150 performs the intermediate transfer. The belt 10 is moved to a position where it is pushed down. On the other hand, when the four primary transfer rollers 12 (Y, C, M, N) are in contact with the respective photoreceptors 40 (Y, C, M, N) via the intermediate transfer belt 10, auxiliary stretching rollers are used. 150 moves to a position away from the intermediate transfer belt 10.
In the monochrome mode, the auxiliary tension roller 150 pushes down the intermediate transfer belt 10, so that the four photosensitive members 40 (Y, C, M, and N) that are separated from the intermediate transfer belt 10 and the intermediate transfer are in the monochrome mode. The distance from the belt 10 can be made larger than before.

Further, the apparatus main body 100 comes into contact with the outer peripheral surface of the intermediate transfer belt 10 between the cleaning facing roller 170 and the fourth stretching roller 114, and is biased to the surface of the intermediate transfer belt 10 by the tension spring 101s. A tension roller 101 that applies belt tension to the transfer belt 10 is provided. The tension springs 101s are provided at both ends of the rotation shaft of the tension roller 101, respectively.
In the apparatus main body 100 of Reference Configuration Example 1 , the belt tension for preventing slipping between the driving roller 14 and the intermediate transfer belt 10 during driving is 1.0 to 2.5 [N / cm]. preferable. Further, the belt width which is the length in the width direction orthogonal to the surface movement direction of the intermediate transfer belt 10 is determined to some extent by the maximum sheet passing width, but is preferably 300 to 350 [mm] for A3, for example. . In the apparatus main body 100 of the reference configuration example 1 , when the belt width is 330 [mm] as an example, the tension spring 101s is 15 to 35 on one side to obtain a belt tension of 1.0 to 2.5 [N / cm]. Set between [N].
In this case, as described above, the spring constant of the tension spring 101s is about 1 to 5 [N / mm], and the position variation of the tension roller 101 greatly affects the belt tension variation.

As described above, the full-color mode in which all the primary transfer rollers 12 (Y, C, M, K, N) are in contact with the photoreceptors 40 (Y, C, M, K, N) with the intermediate transfer belt 10 interposed therebetween. At this time, as shown in FIGS. 5 and 7A, the auxiliary tension roller 150 is located away from the intermediate transfer belt 10. On the other hand, in the monochrome mode in which only the black primary transfer roller 12K is in contact with the black photoconductor 40K with the intermediate transfer belt 10 in between, the auxiliary tension roller 150 pushes down the intermediate transfer belt 10 to cause the other 4 The two photoconductors 40 (Y, C, M, N) and the intermediate transfer belt 10 are separated from each other.
As described above, when only the other four photosensitive members 40 (Y, C, M, and N) and the intermediate transfer belt 10 are sufficiently separated from each other, the moving amount T of the movable stretching roller 102 is set to be the same. With respect to 6.6 [mm], the amount D2 of pressing down the intermediate transfer belt 10 by the auxiliary tension roller 150 is about 1-2 [mm].

However, in order to suppress fluctuations in the belt tension, the intermediate transfer belt 10 of the auxiliary tension roller 150 is prevented so that the position of the tension roller 101 does not fluctuate due to the change in the trajectory of the intermediate transfer belt 10 in the full color mode and the monochrome mode. It is desirable to set a pressing amount D2 with respect to.
In order to prevent the position of the tension roller 101 from fluctuating, it is necessary to set the trajectory of the intermediate transfer belt 10 from the second stretching roller 110 to the first stretching roller 15 so as not to fluctuate. That is, if the trajectory of the intermediate transfer belt 10 from the second stretching roller 110 to the first stretching roller 15 does not fluctuate, the amount of displacement from the natural length of the tension spring 101s that biases the tension roller 101 does not vary. The position of the tension roller 101 does not fluctuate, and fluctuations in belt tension can be prevented.
In order to prevent the trajectory of the intermediate transfer belt 10 from the second tension roller 110 to the first tension roller 15 from fluctuating, the first tension must be changed between the full color mode and the monochrome mode. The amount D2 of pressing down of the intermediate transfer belt 10 by the auxiliary stretching roller 150 is set so that the length of the track of the intermediate transfer belt 10 from the stretching roller 15 to the second stretching roller 110 is constant in the full color mode and the monochrome mode. Set. In the apparatus main body 100 of Reference Configuration Example 1 , by setting the push-down amount D2 to 3.6 [mm], the position of the tension roller 101 could be set so as not to fluctuate. The value of the push-down amount D2 that can prevent such belt tension fluctuation was 3.6 [mm] in the case of the layout of the reference configuration example 1 shown in FIG. 5, but the value of the push-down amount D2 is Since it differs depending on the layout, it is necessary to calculate an appropriate value depending on the layout.

  As shown in FIG. 7, in the apparatus main body 100, an auxiliary tension positioning spring 151 is fixed to the other end of the auxiliary tension roller bracket 160 that supports the auxiliary tension roller 150 at one end. The other end of the auxiliary tension roller bracket 160 is abutted against the recessed portion of the contact / separation slider 140 by urging in the right direction. With this configuration, when the contact / separation slider 140 moves to the left, the position where the other end of the auxiliary tension roller bracket 160 abuts also moves to the left, and the auxiliary tension roller at a position where the predetermined push-down amount D2 is reached. 150 positions can be fixed.

As described above, the four primary transfer rollers 12 (Y, C, M, and N) for color are linked to the lateral movement of the contact / separation slider 140 and the respective photoreceptors 40 (Y, C, M, and N). ). On the other hand, the black primary transfer roller 12K is supported by the black primary transfer roller bracket 120K, and the black photosensitive member is separated from the other primary transfer rollers 12 (Y, C, M, N) by a contact / separation mechanism. It is possible to contact and separate from 40K.
When the image forming operation is not performed or when the power is turned off, all the primary transfer rollers 12 (Y, C, M, K, N) are moved from the respective photoreceptors 40 (Y, C, M, K, N). Further, the auxiliary tension roller 150 is controlled to be separated from the intermediate transfer belt 10. Thereby, unnecessary wear of the member constituting the image forming means of the black toner image such as the black photoconductor 40 and the auxiliary stretching roller 150 can be prevented, and the life can be extended.

  The auxiliary tension roller 150 is preferably a resin roller. This is because a primary transfer bias is applied to the primary transfer roller 12, so that the position where the conductive roller or member contacts the intermediate transfer belt 10 is close to the position where the primary transfer roller 12 contacts. , Current may leak. For this reason, a resin roller is used as the auxiliary tension roller 150 when the position of the auxiliary tension roller 150 and the black primary transfer roller 12K are close to each other (for example, within 17 [mm]).

  Further, the material of the auxiliary tension roller 150 is preferably the same material as that of the primary transfer roller 12. The metal roller is preferably a roller coated with an elastic foamed resin agent because the intermediate transfer belt 10 is easily damaged when brought into contact with the surface of the intermediate transfer belt 10.

[ Reference configuration example 2 ]
In the apparatus main body 100 of Reference Configuration Example 1 shown in FIG. 7, the position of the auxiliary tension roller 150 is fixed in a state where the auxiliary tension roller 150 is separated from and in contact with the intermediate transfer belt 10. It is a configuration. On the other hand, the auxiliary tension roller 150 may pressurize the intermediate transfer belt 10 in a state where the auxiliary tension roller 150 is in contact with the intermediate transfer belt 10.
FIG. 8 shows a black photoconductor 40K among the four color photoconductors 40 (Y, C, M, and N) in the configuration of the reference configuration example 2 in which the auxiliary tension roller 150 presses the intermediate transfer belt 10. FIG. 6 is an enlarged explanatory view of a region γ in which an auxiliary stretching roller 150 is disposed between a magenta photosensitive member 40M and a black photosensitive member 40K that are disposed closest to each other.
As shown in FIG. 8, the reference configuration example 2 includes an auxiliary tension pressure spring 161 that biases the side of the auxiliary tension roller bracket 160 that supports the auxiliary tension roller 150 downward. . FIG. 8A is an explanatory diagram in the full color mode (contact state), and FIG. 8B is an explanatory diagram in the monochrome mode (separated state).

In the state of the full color mode shown in FIG. 8A, the end of the auxiliary tension roller bracket 160 on the other end abuts against the left side of the dent on the contact / separation slider 140, and the urging force by the auxiliary tension pressure spring 161 works. There is no state. In order to change from this state to the monochrome mode, the contact / separation slider 140 moves in the left lateral direction indicated by the arrow E2 in FIG. The urging force of the auxiliary tensioning pressure spring 161 acts on the auxiliary tension roller bracket 160, and the auxiliary tension roller bracket 160 rotates in the direction of arrow E3 in FIG. ), The auxiliary tension roller 150 comes into contact with the intermediate transfer belt 10. At this time, since the urging force of the auxiliary tension pressing spring 161 works even when the auxiliary tension roller 150 is in contact with the intermediate transfer belt 10, the auxiliary tension roller 150 presses against the intermediate transfer belt 10 and the belt It will be in the state to give tension. In other words, in the full color mode, the auxiliary tension roller 150 is separated from the intermediate transfer belt 10 and the tension member 101 is the only tension member that applies belt tension. However, in the monochrome mode, the auxiliary tension roller 150 is in the intermediate transfer belt. By pressing down 10 to pressurize, the auxiliary tension roller 150 in addition to the tension roller 101 becomes a tension member that applies belt tension. As a result, it is possible to prevent the belt tension from being lowered in the monochrome mode and to prevent the belt tension from fluctuating between the full color mode and the monochrome mode.
Further, even in the configuration in which the auxiliary stretching roller 150 presses the intermediate transfer belt 10 as in the apparatus main body 100 of the reference configuration example 2 , the auxiliary stretching roller 150 pushes down the intermediate transfer belt 10, so that the above-described reference configuration example 1 In the same manner as described above, the distance between the four color photoreceptors 40 (Y, C, M, and N) and the intermediate transfer belt 10 can be increased.

( Example )
In the reference configuration example 1 and the reference configuration example 2 described above, the configuration in which the roller-shaped member is used as the auxiliary stretching member that contacts the intermediate transfer belt 10 in the monochrome mode has been described. It is not limited to the members.
FIG. 9 shows four color photoreceptors 40 (Y, C, M) in the configuration of an embodiment in which an auxiliary tension brush 250 in which a large number of short fibers 251 are planted pressurizes the intermediate transfer belt 10 as an auxiliary tension member. , N), an enlarged explanatory view of the region γ in which the auxiliary stretch member is disposed between the magenta photosensitive member 40M and the black photosensitive member 40K, which are disposed closest to the black photosensitive member 40K. It is.
Unlike the auxiliary tension roller 150 described above, the auxiliary tension brush 250 is not a member that rotates in accordance with the movement of the surface of the intermediate transfer belt 10 that is in contact.
In the case of using a roller member as the auxiliary stretching member, the roller member rotates while being supported at both ends of the shaft, but eccentricity occurs due to molding errors. Due to this eccentricity, the contact state repeatedly changes between a state where the long part from the rotation center to the roller surface is in contact and a state where the short part is in contact. For this reason, as the distance from the center of rotation to the roller surface comes into contact, the moving speed of the belt increases, the speed unevenness occurs at the primary transfer position, and the belt behavior fluctuates, adversely affecting the image. There is a fear.
On the other hand, if the auxiliary tension brush 250 is fixed while being in contact with the intermediate transfer belt 10, it is possible to prevent the belt behavior from fluctuating. Further, when the fixed auxiliary tension member comes into contact with the intermediate transfer belt 10 that moves on the surface, a frictional force acts between them, and there is a concern that the intermediate transfer belt 10 may be worn or increased in driving due to rubbing. By bringing the fibers 251 into contact with the intermediate transfer belt 10, the frictional force can be reduced, and problems caused by the frictional force can be suppressed.

In the reference configuration example 1 , the reference configuration example 2, and the embodiment described above, the configuration including the intermediate transfer belt 10 as an endless belt member and the plurality of photoreceptors 40 as the plurality of toner supply members has been described. The combination of the belt member and the plurality of toner supply members is not limited to this. A photosensitive belt is provided as an endless belt member, and a plurality of developing rollers for developing a latent image formed in a photosensitive belt shape are provided as a plurality of toner supply members. Even if it is the structure which adjoins or leaves | separates with respect to a belt, the structure provided with an auxiliary stretch member is applicable.

Above, copiers 500, as a plurality of stretching members, driving roller 14, the first stretching roller 15, secondary transfer counter roller 16, the second stretching roller 110, a third stretching roller 111, fifth Zhang A gantry roller 113 and a fourth tension roller 114 are provided. Further, the copying machine 500 is arranged side by side so as to be in contact with and opposed to the outer peripheral surface of the intermediate transfer belt 10, which is an endless belt member supported by the plurality of stretching rollers. It has a photoreceptor 40 (Y, C, M, K, N) which is five toner supply members for supplying a toner image to the surface of the intermediate transfer belt 10 by primary transfer. Further, depending on the image mode, in the full color mode, the five photoconductors 40 (Y, C, M, K, and N) are in close proximity to the intermediate transfer belt. In the monochrome mode, four color photoconductors 40 (Y, C, M, N), which are a part of the five photoconductors 40 (Y, C, M, K, N), are intermediately transferred. The separated state is separated from the belt 10. A belt contacting / separating means for moving the intermediate transfer belt 10 so as to switch from the proximity state to the separation state is provided. This belt contact / separation means is a non-separation facing position of the intermediate transfer belt 10 facing the black photoconductor 40K which is another toner supply member that is in contact with the intermediate transfer belt 10 member in the separated state. For the color, which is a position opposite to the intermediate transfer belt 10 where the four color photoreceptors 40 (Y, C, M, N) face each other in the proximity of the transfer position of the black photoreceptor 40K. A movable tension roller 102, which is a movable movable member that stretches the inner peripheral surface of the intermediate transfer belt 10 on the opposite side across the transfer position of the photosensitive member 40 (Y, C, M, N) K, is provided. Prepare. Then, the movable tension roller 102 is moved downward from the proximity state in a direction away from the five photosensitive members 40 (Y, C, M, K, N), and the intermediate transfer belt 10 is moved to the four photosensitive members 40 for color. A separated state is established by separating from (Y, C, M, N). In such a copying machine 500, when the monochrome mode is in the separated state, the transfer position of the black photoconductor 40K and the transfer positions of the four color photoconductors 40 (Y, C, M, N) are different. There is an auxiliary tension roller 150 as an auxiliary tension member that is in contact with the outer peripheral surface of the intermediate transfer belt 10 and stretches the intermediate transfer belt 10. The auxiliary tension roller 150 is stretched from the outer peripheral surface of the intermediate transfer belt 10 between the transfer position of the black photoreceptor 40K and the transfer positions of the four color photoreceptors 40 (Y, C, M, N). Thus, the track of the intermediate transfer belt 10 in the separated state, which is inclined with respect to the track of the contact state in the conventional copying machine, is moved with respect to the four photoconductors 40 (Y, C, M, N) for color. Can be released. Thus, the amount of movement of the intermediate transfer belt 10 at a position facing the four color photoreceptors 40 (Y, C, M, N) can be increased.

  As shown in FIGS. 5 and 7, the intermediate transfer belt 10 is located between the transfer position of the black photoconductor 40K and the transfer positions of the four color photoconductors 40 (Y, C, M, N). In the case where the black primary transfer portion upstream tension roller 130 is in contact with the inner peripheral surface, the transfer positions of the four color photoconductors 40 (Y, C, M, N) and the black primary transfer portion upstream. The auxiliary stretching roller 150 is disposed so as to come into contact with the outer peripheral surface of the intermediate transfer belt 10 between the stretching roller 130. The black primary transfer portion upstream-side stretching roller 130 is disposed at a position where the intermediate transfer belt 10 is not stretched and is in contact with or close to the inner peripheral surface in the full color mode. In the monochrome mode, the intermediate transfer belt 10 is stretched between the intermediate tension belt 102 and the moving tension roller 102 by lowering the left side of the primary transfer tension surface 10 f of the intermediate transfer belt 10. By providing such a black primary transfer portion upstream tension roller 130, the position fluctuation of the intermediate transfer belt 10 near the upstream side in the surface movement direction with respect to the transfer position of the black photoconductor 40 </ b> K is suppressed. This suppresses the change in the shape of the transfer nip at the transfer position of the black photoconductor 40K between the full color mode and the monochrome mode, and performs the primary transfer of the black toner image under the same conditions in the full color mode and the monochrome mode. Can be done.

  Further, the apparatus main body 100 of the copying machine 500 includes a tension spring 101 s and a tension roller 101 which are tension applying mechanisms that apply belt tension to the intermediate transfer belt 10. Further, the auxiliary tension roller 150 is separated from the intermediate transfer belt 10 in the contact state, and assists the contact / separation operation of the belt contact / separation means so that the auxiliary tension roller 150 contacts the intermediate transfer belt 10 in the separation state. As a synchronization mechanism that synchronizes the operation of the tension roller 150, a configuration of catching between the contact / separation slider 140 and the auxiliary tension roller bracket 160 is provided. Then, the auxiliary tension roller 150 is set so that the intermediate transfer belt 10 is pushed down so that the predetermined push-down amount D2 = 3.6 [mm] in the separated state, so that the belt tension is changed between the contact state and the separated state. The position of the auxiliary tension roller 150 can be displaced so as to suppress the fluctuation. Thereby, it is possible to prevent the belt tension from fluctuating due to the contact / separation operation of the intermediate transfer belt 10 with respect to the four color photoconductors 40 (Y, C, M, N).

Further, in the reference configuration example 2 , the auxiliary tension pressing spring 161 which is an auxiliary tension member urging means for urging the auxiliary tension roller 150 toward the intermediate transfer belt 10 in the separated state in the monochrome mode. Is provided. Thus, in the monochrome mode, the auxiliary tension roller 150 presses down the intermediate transfer belt 10 so as to pressurize it, so that the auxiliary tension roller 150 in addition to the tension roller 101 becomes a tension member that applies belt tension. . As a result, it is possible to prevent the belt tension from being lowered in the monochrome mode and to prevent the belt tension from fluctuating between the full color mode and the monochrome mode.

  When the image forming operation is not performed or when the power is turned off, all the primary transfer rollers 12 (Y, C, M, K, N) are moved from the respective photosensitive members 40 (Y, C, M, K, N). The five photosensitive members 40 (Y, C, M, K, and N) are separated from the intermediate transfer belt 10 by being separated from each other, and further, the auxiliary stretching roller 150 is controlled to be separated from the intermediate transfer belt 10. Thereby, unnecessary wear of the member constituting the image forming means of the black toner image such as the black photoconductor 40K and the auxiliary tension roller 150 can be prevented, and the life can be extended.

  In addition, when the auxiliary tension roller 150 is made of a material having a high electrical resistivity, that is, a resin roller having a high insulating property, the distance between the primary transfer roller 12 and the auxiliary tension roller 150 is short. It is possible to prevent the primary transfer bias leak that easily occurs.

  Further, the auxiliary tension roller 150 can be an elastic roller such as a sponge roller or a rubber roller to prevent the surface of the intermediate transfer belt 10 from being damaged.

Further, as in the embodiment, by using an auxiliary stretching brush 250 that is a brush member in which short fibers 251 are planted on the base as an auxiliary stretching member, the flexibility is increased as compared with the configuration using the auxiliary stretching roller 150. There is no belt speed fluctuation. Furthermore, since a bearing or the like is not required, it can be inexpensive and space-saving.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 10f Primary transfer stretch surface 12 Primary transfer roller 12K Black primary transfer roller 14 Drive roller 15 First stretch roller 16 Secondary transfer counter roller 17 Intermediate transfer belt cleaning device 18 Image forming unit 20 Tandem image formation Section 21 Exposure device 22 Secondary transfer device 23 Secondary transfer stretching roller 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Reversing device 30 Document table 32 Contact glass 33 Traveling body 34 Traveling body 35 Imaging lens 36 reading sensor 40 photoconductor 40K black photoconductor 42 paper feed roller 43 paper feed table 44 paper feed cassette 45 separation roller 46 paper feed path 47 transport roller 48 paper feed path 49 registration roller 50 manual paper feed roller 51 manual tray 52 Manual separation roller 53 Manual feed path 55 Switching claw 56 Ejection Discharging roller 57 Discharging tray 60 Developing device 100 Main unit 101 Tension roller 101s Tension spring 102 Moving tension roller 110 Second tension roller 111 Third tension roller 113 Fifth tension roller 114 Fourth tension roller 120 Primary Transfer roller bracket 120K Black primary transfer roller bracket 121 Primary transfer pressure spring 122 Moving stretch roller bracket 130 Black primary transfer portion upstream stretch roller 140 Contact / separation slider 141 Slider spring 142 Contact / separation cam 146 Projection 150 Auxiliary Tension roller 151 Auxiliary tension positioning spring 160 Auxiliary tension roller bracket 161 Auxiliary tension pressure spring 170 Cleaning counter roller 200 Paper feed unit 250 Auxiliary tension brush 251 Short fiber 300 Scanner 400 ADF
500 Copying machine T Movement amount D1 Separation amount D2 Push-down amount

JP 2008-129448 A JP 2009-75350 A

Claims (7)

An endless belt member supported by a plurality of tension members;
A plurality of toner supply members arranged in parallel so as to be in contact with or in close proximity to the outer peripheral surface of the belt member and supplying toner to the surface of the belt member;
The belt member such that a part of the plurality of toner supply members is separated from the belt member from a proximity state in which the plurality of toner supply members are in contact with or close to the belt member. Belt contact / separation means for moving
The belt contact / separation means is in the proximity state with respect to the non-separation facing position of the belt member opposed to the other toner supply member that is in contact with or close to the belt member in the separation state. A movable movable member that stretches the inner circumferential surface of the belt member on the opposite side across the position where the part of the toner supply member opposes the separation facing position of the belt member;
In the image forming apparatus in which the moving tension member is moved in a direction away from the plurality of toner supply members from the proximity state to separate the belt member from the part of the toner supply members.
Contact with the outer peripheral surface of the belt member between said non-spaced facing position and the spaced opposed position when the separated state, possess an auxiliary tension member for stretching the belt member,
As the auxiliary tension members, an image forming apparatus according to claim Rukoto a brush member having bristles short fibers to the substrate. The image forming apparatus according to claim 1.
A tension applying mechanism for applying belt tension to the belt member;
In the contact state, the auxiliary tension member is separated from the belt member, and in the separated state, the auxiliary tension member is in contact with and separated from the belt contacting / separating means so that the auxiliary tension member is in contact with the belt member. A synchronization mechanism for synchronizing the operation of the frame member,
An image forming apparatus characterized in that the position of the auxiliary tension member is displaced so as to suppress fluctuation of the belt tension between the proximity state and the separation state. The image forming apparatus according to claim 1 or 2,
An image forming apparatus, comprising: an auxiliary tension member urging unit that urges the auxiliary tension member toward the belt member in the separated state. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus characterized in that when the image forming operation is not performed, the plurality of toner supply members are separated from the belt member, and the auxiliary stretch member is separated from the belt member. The image forming apparatus according to any one of claims 1 to 4, wherein:
An image forming apparatus using a member made of a material having a high electrical resistivity as the auxiliary stretching member . The image forming apparatus according to any one of 請 Motomeko 1 to 5,
The belt member is a belt-like intermediate transfer member;
An image forming apparatus, wherein each of the plurality of toner supply members is an image carrier on which a toner image to be transferred to the intermediate transfer member is formed. The image forming apparatus according to any one of claims 1 to 6 ,
The belt member is a belt-like latent image carrier;
An image forming apparatus, wherein each of the plurality of toner supply members is a developer carrier that develops latent images for different color images on the latent image carrier.

Images