JP2006251127A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the scattering of toner stuck to the surface on a transport member side of a recording body and irregularities in an image are suppressed by suppressing separating discharge to the surface on the transport member side of the recording body. <P>SOLUTION: The recording body P is self stripped from a second intermediate transfer belt 31, when the recording body P is transported to a first separation region A by the second intermediate transfer belt 31. At this time, the top end of a static elimination brush 110 arranged in the curvature region A comes into contact with the recording body P. When the recording body P comes into contact with the static elimination brush 110, a charge having positive polarity on the recording body P escapes to the static elimination brush 110, so that the charge on the recording body P is removed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile. More specifically, the present invention relates to an image forming apparatus that transfers a visible image onto both sides of a recording sheet such as a transfer sheet and fixes the visible images on both sides at the same time.

  Conventionally, a so-called switchback method and a one-pass method are known as methods for transferring an image onto both surfaces of a recording medium such as transfer paper. In the switchback method, first, a visible image is transferred to one surface of the transfer member that transfers a visible image on an image carrier such as a photosensitive member to the recording member through the recording member. Then, after the recording medium is inverted and switched back to the transfer means, the visible image is transferred to the other surface. On the other hand, the one-pass method forms images on both sides of the recording medium without switching back the recording medium by applying a visible image transfer process to both sides of the recording medium as a transfer means. The one-pass method is superior to the switchback method in the following points. That is, it is possible to avoid an increase in cost by providing a complicated mechanism for switchback and an increase in image formation time due to switchback. As an image forming apparatus that realizes such a one-pass method, for example, the one described in Patent Document 1 is known.

JP-A-1-209470

  FIG. 10 is a diagram illustrating a main part of a one-pass image forming apparatus. As shown in FIG. 10, the toner image carried on the first intermediate transfer belt 221 is transferred onto the upper surface of the recording medium P by the transfer roller 246, and the toner image carried on the second intermediate transfer belt 231 is transferred. The recording material P is transferred to the lower surface, which is the surface on the conveying member side, by the charger 247. The recording material P having the toner images transferred on both sides in this way is conveyed by the second intermediate transfer belt 231 that also serves as a conveying member for the recording material, and is transferred to the conveying belt 251 that is another conveying member. The transferred recording material P is transported to the fixing device 260 by the transport belt 251.

  When the recording medium P moves away from the second intermediate transfer belt 231 to the transport belt 251, there is a problem that the toner adhering to the lower surface of the recording medium P is scattered and the apparatus is soiled. This is because the recording material P is charged with a positive polarity by being charged by the transfer roller 246 and the transfer charger 247. For this reason, a potential difference is generated between the second intermediate transfer belt 231 and the recording material P. With such a potential difference, when the recording medium P is separated from the second intermediate transfer belt 31, the potential difference between the recording medium P and the second intermediate transfer belt 31 becomes large, and peeling discharge occurs. It is considered that the toner adhering electrostatically to the lower surface of the recording medium was scattered by the impact of the peeling discharge. As described above, as a result of the toner adhering to the lower surface of the recording medium P being scattered, there is a problem that the periphery of the delivery area where the recording medium P is transferred from the second intermediate transfer belt 231 to the conveying belt 251 is soiled with toner. Further, there is a problem that the unfixed image on the lower surface of the recording material P is disturbed by the peeling discharge.

  Further, as shown in FIG. 10, such discharge is caused not only by the portion where the recording body P is separated from the second intermediate transfer belt 231 but also the portion where the recording body P is in contact with the transport belt 51 and the recording body P is transported. It also occurs at a part away from the belt 51.

  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 prevent toner from adhering to the surface of the recording medium on the conveying member side while suppressing discharge discharge on the surface of the recording medium on the conveying member side. It is an object to provide an image forming apparatus capable of suppressing the scattering of the image and the disturbance of the image.

In order to achieve the above object, according to the first aspect of the present invention, the first toner image is transferred to one surface of the recording medium in the course of conveying the recording medium, and the second toner image is transferred to the other surface of the recording medium. In the image forming apparatus, the toner image is transferred onto both sides of the recording medium, transferred onto the recording medium, the toner image is transferred to the fixing unit, and the toner image is fixed on the recording medium. Providing a potential difference suppressing means for suppressing an increase in potential difference between the transport member and the recording body when the recording body separates from and close to the transport member that carries and transports the recording body to which the image has been transferred. It is a feature.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the potential difference suppressing unit includes a recording body neutralizing unit that neutralizes the recording body.
According to a third aspect of the present invention, in the image forming apparatus of the second aspect, a plurality of the conveying members are provided, and the recording medium onto which the toner image has been transferred is delivered to the plurality of conveying members until conveyed to the fixing unit. The recording body neutralizing means is provided in an initial separation region where the recording body is separated from the conveying member.
According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the recording member neutralizing means is a neutralizing brush or a neutralizing needle.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the recording member charge eliminating means contacts the recording member and releases charges charged in the recording member to the ground. To do.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the second to fourth aspects, the recording member charge eliminating unit includes a bias applying unit, and a polarity opposite to the charging polarity of the recording member from the bias applying unit. The charge is imparted to the recording medium.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, in the separation region where the recording body separates from the conveying member and / or the proximity region where the recording body is close to the conveying member, The recording medium is charged to the same polarity as the recording medium.
According to an eighth aspect of the present invention, in the image forming apparatus of the seventh aspect, the image forming apparatus further includes a charge applying unit that applies a charge having the same polarity as that of the recording body to the separation region and / or the proximity region on the transport member side. It is characterized by this.

  According to the first to eighth aspects of the present invention, by providing the potential difference suppressing means, it is possible to suppress an increase in the potential difference between the conveying member and the recording body when the recording body separates and approaches. As a result, it is possible to suppress the discharge that occurs due to an increase in the potential difference between the recording medium and the conveying member. As a result, the toner image formed on the surface of the recording member on the conveying member side can be prevented from being directly disturbed by the impact caused by the discharge. In addition, it is possible to suppress the toner adhering to the surface of the recording member on the conveying member side from being directly impacted by the discharge and scattering, thereby suppressing the contamination of the apparatus.

Embodiments in which the present invention is applied to an image forming apparatus will be described below. FIG. 1 illustrates a full-color printer capable of duplex printing by an electrophotographic method as the image forming apparatus 100 according to the first embodiment.
In the image forming apparatus main body 100 shown in FIG. 1, the first image unit 20 is arranged at the upper part and the second image unit 30 is arranged at the lower part with the recording material conveyance path 43A as a boundary. The first image unit 20 includes a first intermediate transfer belt 21 that is a first toner image conveying belt that moves endlessly in the direction of the arrow, and the second image unit 30 is a second toner image conveying belt that moves endlessly in the direction of the arrow. Two intermediate transfer belts 31 are provided. Four first image forming units 80Y, 80C, 80M, and 80K, which are first toner image forming units, are arranged on the upper tension surface of the first intermediate transfer belt 21. On the other hand, four image forming units 81Y, 81C, 81M, 81K, which are four second toner image forming units, are arranged on the upper stretched surface of the second intermediate transfer belt 31. Y, C, M, and K along the numbers of the first and second image forming units correspond to the colors of the toner to be handled. Y is yellow, C is cyan, M is magenta, and K is black. Means. Similarly, Y, C, M, and K are provided along the photosensitive member 1 provided in the first and second image forming units and rotating together with the first intermediate transfer belt 21 and the second intermediate transfer belt 31. The photoreceptors 1Y to 1K are arranged at the same interval in each image forming unit, and at least at the time of image formation, are in contact with a part of the stretched portion between the intermediate transfer belts 21 and 31, respectively. These contacting surfaces are referred to as a first image receiving surface F1 and a second image receiving surface F2, respectively, and their positional relationships are shown in FIG.

As shown in FIG. 2, when the angle of the angle including the first and second image forming units among the angles formed by the first image receiving surface F1 and the second image receiving surface F2 is α, the value of α is 180. It should be larger than 270 ° and smaller than 270 °.
Further, a configuration is employed in which at least a part of the horizontal projection surface of the first intermediate transfer belt 21 in the upper portion and the horizontal projection surface of the second intermediate transfer belt 31 in the lower portion overlap each other. That is, the second intermediate transfer belt 31 at the lower part is shaped so as to be recessed below the first intermediate transfer belt 21 at the upper part. By adopting such a configuration, a more compact layout is possible in the lateral direction.

Although the toner colors to be handled are different, the configurations of the first image forming units 80Y, 80C, 80M, and 80K are the same. Therefore, the configuration of the first image forming unit 80 will be described with reference to FIG.
In FIG. 3, when the image forming apparatus 100 is operated, a cylindrical photosensitive member 1 that is rotatably supported by a drive source (not shown) so as to rotate in the direction of an arrow is disposed. Then, an image forming member such as a scorotron charger 3, an exposure device 4, a developing device 5, a cleaning device 2, and a photostatic device Q, which are charging means according to an electrophotographic process, an electric potential sensor S1, and an image around the photoreceptor 1. A sensor S2 is provided.
The photoreceptor 1 is obtained by forming an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylinder surface having a diameter of about 30 to 120 mm, for example. A photoconductor on which an amorphous silicon (a-Si) layer is formed can also be used. A belt-like photoreceptor can also be employed. The cleaning device 2 includes a cleaning brush 2a, a cleaning blade 2b, and a recovery member 2c, and removes and recovers foreign matters such as toner remaining on the surface of the photoreceptor.

  The exposure device 4 scans the light corresponding to the image data for each color on the surface of each photoreceptor 1 that has been uniformly charged by the charging means, and forms an electrostatic latent image. The exposure apparatus 4 in the illustrated example is an exposure apparatus that includes an LED (light emitting diode) array and an imaging element as light emitting elements, but uses a laser light source, a polygon mirror, etc., and beam light modulated according to image data to be formed. It is also possible to adopt a laser scanning type exposure apparatus. In addition to the charger 3, a type that makes contact with the surface of the photoreceptor 1, such as a charging roller, can be used as the charging means.

The development at this time is a development system that employs a two-component developer composed of toner and carrier. The electrostatic latent image for each color formed on the surface of each photoconductor 1 by the exposure device 4 with respect to the negatively charged photoconductor 1 is a toner of a predetermined color having the same polarity (negative polarity) as the charged polarity of the photoconductor. Developed to become a visible image. So-called reversal development is performed.
The yellow (Y), cyan (C), magenta (M), and black (K) toners are detected by the magnetically permeable toner detecting means 5e when consumed by the developing device that handles each color. Then, toner of each color is supplied to each developing device 5 by a supply unit (not shown) from a toner cartridge 86 provided in the toner cartridge housing portion 85 inside the image forming apparatus 100.
As this supply means, a system using a known MONO pump can be adopted. According to this method, there are few restrictions on the installation location of the toner cartridge, which is advantageous for space allocation in the image forming apparatus. Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device, and the developing device can be downsized.

  The developing device 5 is provided with screws 5c and 5d for stirring and conveying the toner and carrier. When the developing device 5 is mounted on the image forming apparatus 100, one end of the toner replenishing unit is connected to a part of the screw 5d. The toner is supplied to the developing roller 5a rotating in the direction of the arrow by the screw 5c, but the thickness of the toner layer on the surface of the developing roller 5a is regulated to a predetermined thickness by the blade 5b. The developing roller 5a is a cylinder made of stainless steel or aluminum, and is supported by the frame of the developing device 5 so as to be rotatable and a distance from the photoreceptor is properly secured, and a predetermined magnetic force line is formed inside. Has a magnet. As the toner, a spherical or irregular toner obtained by a conventionally known method is used. The volume average particle diameter is 20 μm or less, preferably 10 μm or less and 4 μm or more. A carrier obtained by a conventionally known method is also used. The carrier has a volume average particle size of about 25 μm to 60 μm.

Since the second image forming units 81Y, 81M, 81C, and 81K used in the second image unit 30 have the same configuration, the second image forming unit 81 will be described with reference to FIG.
The second image forming unit 81 shown in FIG. 4 has the same constituent members as the first image forming unit 80, but the rotational direction of the photosensitive member 1 is different from that of FIG. However, they are mutually shaped with respect to the y-axis passing through the rotation axis 1a of the photosensitive member 1 indicated by an arrow in the drawing. This shape is an important matter although it is related to the arrangement of image forming members provided around the photoreceptor 1. In other words, consideration is given to a method of connecting a connecting portion with the image forming apparatus 100, for example, a connecting portion with a driving unit, an electrical connecting portion, a toner supplying portion, and a toner discharging portion. Thereby, the first image forming units 80Y, 80M, 80C, and 80K can be compatible with the second image forming units 81Y, 81M, 81C, 81K. Therefore, it is not necessary to manufacture the developing device, the cleaning device, and the parts individually for the first image forming unit and the second image forming unit, and the efficiency in manufacturing parts and managing parts is high, and the overall cost can be reduced. It is peeled off.
There are the following two conditions that can be used in the first image unit 20 and the second image unit 30 in the form of an axial object with the first and second image forming units as the center of the y-axis. As a first condition, a peripheral surface where no member for image formation is provided around the photosensitive member 1 is secured, that is, a wide range in which the intermediate transfer belt can contact is secured. The second condition is that the arrangement angle between the image receiving surface F1 of the first intermediate transfer belt 21 and the image receiving surface F2 of the second intermediate transfer belt 31 is appropriate.

The first condition and the second condition will be described with reference to FIGS. 3 or 4, the intermediate transfer belt 21 or 31 can be installed between the arrows A1 and A2. That is, the A1 side is the developing device 5, and the A2 side is that the intermediate transfer belt can be installed in a range where the belt does not contact the cleaning device 2. The inclusion of the second image bearing belt 31 in FIG. 3 shows an intermediate transfer belt on which the target image forming unit can be arranged with respect to the y axis including the rotation axis 1 a of the photoreceptor 1.
If the image forming unit 80 is turned upside down with respect to an axis orthogonal to the y axis and used as the image forming unit 81, the toner is stirred at least in the developing device 5 due to the influence of the earth's gravity and the toner on the developing roller 5a. Conditions such as replenishment are different. As a result, the members of the image forming unit 80 must be optimized, and parts cannot be shared.

  As shown in FIG. 2, the angle α is greater than 180 degrees and less than or equal to 270 degrees as a positional relationship between the image receiving surface of the first image carrying belt 21 and the image receiving surface of the second image carrying belt 31. When the angle is preferably from 210 degrees to 255 degrees, the first image carrier belt shown in FIG. 3 and the second image carrier belt shown in FIG. 4 can be used as the image forming unit. That is, it is possible to avoid an image forming unit that makes it impossible to share parts as described above.

Further, as shown in FIG. 2, since the recording medium conveyance path 43 can be secured substantially horizontally and linearly above the second image forming unit 81, the recording medium is excellent in conveyance and reliability, and the entire image forming apparatus. The unity becomes good.
In particular, the first image bearing belt is stretched horizontally and flatly, and the second intermediate transfer belt 31 is stretched long and inclined in the vertical direction. The space in the height direction of the second intermediate transfer belt 31 is increased. However, as shown in FIGS. 3 and 4, the image forming unit has a vertical dimension with respect to the horizontal dimension by ensuring a wide range in which the image forming unit can contact the intermediate transfer belt. Is a short configuration. For this reason, in the second image unit, the image forming unit is disposed obliquely in the vertical direction with respect to the first image unit in which the image forming unit is disposed substantially horizontally. In addition, the interval between the image forming units can be set short, and the space in the height direction of the second image unit can be saved. As a result, the degree of freedom in layout in the height direction is increased, so that the recording material transport path can be set to an ideal height considering operability, a paper feeding device, and a post-processing device (not shown). .

In addition, since the sheet feeders having the same height as that occupied by the second intermediate transfer belt 31 can be installed side by side, it is possible to install a sheet feeder that can accommodate a large number of recording media. In addition, the sheet feeding surface on the upper surface of the sheet feeding device and the recording medium conveyance path can be made substantially the same height, and the recording sheet feeding and conveyance reliability can be ensured.
As described above, the image forming units 80 and 81 have many common points due to the arrangement of the image forming apparatus around the photosensitive member and the arrangement of the intermediate transfer belt, that is, the realization of the second condition. But it is very advantageous.

Next, the intermediate transfer belt will be described. The first intermediate transfer belt 21 as the first toner image conveying belt is supported by a plurality of rollers 23, 24, 25, 26 (two), 27, 28, 29 and travels in the direction of the arrow. The first image forming units 80Y to 80K are provided below the photoreceptors 1Y, 1C, 1M, and 1K. The first intermediate transfer belt 21 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. In addition, a primary transfer roller 22 is provided on the inner peripheral portion of the first intermediate transfer belt 21 so as to face the photoreceptors 1Y, 1C, 1M, and 1K.
A cleaning device 20 </ b> A is provided on the outer periphery of the first intermediate transfer belt 21 at a position facing the roller 23. The cleaning device 20 </ b> A wipes away unnecessary toner remaining on the surface of the first intermediate transfer belt 21 and foreign matters such as paper dust.
Members related to the first intermediate transfer belt 21 are integrally configured as the first image unit 20, and can be attached to and detached from the image forming apparatus 100.

On the other hand, the second intermediate transfer belt 31 as the second toner image conveying belt is supported by a plurality of rollers 33, 34, 35, 36 (two), 37, 38 and travels in the direction of the arrow. The second image forming units 81Y to 81K are provided in contact with the photoreceptors 1Y, 1C, 1M, and 1K. The second intermediate transfer belt 31 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. A primary transfer roller 32 is provided on the inner peripheral portion of the second intermediate transfer belt 31 so as to face the photoreceptors 1Y, 1C, 1M, and 1K. Further, the roller 34 facing the conveyor belt 51 is connected to the ground.
A cleaning device 30 </ b> A is provided on the outer periphery of the second intermediate transfer belt 31 at a position facing the roller 33. The cleaning device 30 </ b> A wipes off unnecessary toner remaining on the surface of the intermediate transfer belt 31 and foreign matters such as paper dust.
Members related to the second intermediate transfer belt 31 are integrally configured as the second image unit 30 and can be attached to and detached from the image forming apparatus 100.

The intermediate transfer belts 21 and 31 are belts having, for example, a resin film or rubber having a base thickness of 50 to 600 μm as a base. The toner image carried by each photoconductor 1 has a resistance value that enables electrostatic transfer onto the belt surface by a bias applied to the primary transfer rollers 22 and 32. As an example of such a belt, carbon is dispersed in polyamide, and the volume resistance value thereof is adjusted to a resistance of about 10 ⁶ to 10 ¹² Ωcm. Belt detent ribs for stabilizing the running of the belt are provided on one side or both ends of the belt.

As the primary transfer rollers 22 and 32, the surface of a metal roller serving as a core metal is coated with a conductive rubber material, and the core metal part to which a bias is applied from a power source (not shown) is raised. Here, as for the conductive rubber material, carbon is dispersed in urethane rubber, and the resistance is adjusted to a volume resistance of about 10 ⁵ Ωcm.

  The image forming apparatus 100 can perform monochrome recording using only black toner. In such a case, there are photosensitive members that are not used. Therefore, not only the unused photoreceptors 1Y, 1C, 1M or the developing device 5 are operated, but also a mechanism for keeping these unused photoreceptors and the image carrying belt 21 or 31 in a non-contact state is provided. An internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, and is supported so as to be rotatable about a certain point. Then, by rotating in a direction away from the photosensitive member, only the photosensitive member 1K comes into contact with the image carrying belt 21 or 31, and an image forming process is executed to create a monochrome image using black toner. This is advantageous in terms of improving the life of the photoreceptor.

Further, a first secondary transfer roller 46 is provided on the outer periphery of the first intermediate transfer belt 21 in the vicinity of the support roller 28. The secondary transfer roller 46 is made of a metal roller serving as a core metal and is coated with conductive rubber, and a bias is applied to the core metal part from a power source (not shown). Carbon is dispersed in the conductive rubber, and the volume resistance is adjusted to about 10 ⁷ Ωcm. By applying a bias to the first secondary transfer roller 46 while passing the recording medium P between the first intermediate transfer belt 21 and the secondary transfer roller 46, an image by toner carried by the first image carrying belt 21 is obtained. Is transferred to the recording medium P.

A transfer charger 47 serving as a second secondary transfer unit is provided on the outer periphery of the second intermediate transfer belt 31 and in the vicinity of the support roller 34. The transfer charger 47 is a known type, and a thin wire of tungsten or gold is used as a discharge electrode, held by a casing, and a transfer current is supplied to the discharge electrode from a power source (not shown). By supplying a transfer current while passing the recording medium P between the second intermediate transfer belt 31 and the transfer charger 47, an image by the toner carried by the second image carrying belt 31 is transferred to the recording medium P. The polarity of the transfer current supplied to the transfer roller 46 and the transfer charger 47 is a positive polarity opposite to the polarity of the toner.
As described above, the toner images are transferred onto both sides of the recording medium P by the double-side transfer means including the first intermediate transfer belt 21, the secondary transfer roller 46, the second intermediate transfer belt 31, the transfer charger 47, and the like. .

  On the right side of the image forming apparatus 100, a paper feeding device 40 that accommodates the recording material P is provided. Paper feed device (tray) 40a containing a large number of recording media in a plurality of stages, for example, the upper stage, and three stages of paper feed cassettes 40b, 40c, and 40d below each are pulled out to the front (operation surface side) perpendicular to the paper surface. It is arranged to be possible. Different types of recording media P are stored in the paper feed tray 40a and the paper feed cassettes 40b, 40c, and 40d, respectively. Among these, the uppermost recording medium is selectively fed and separated by the corresponding paper feeding / separating means 41a to 41d, and only one sheet is reliably transported by the plurality of conveying roller pairs 42B to the recording medium conveying paths 43B and 43A. Sent to.

  A pair of registration rollers 45 is provided in the recording material conveyance path 43A in order to take a feeding timing for sending the recording material P to the secondary transfer position which is the first and second transfer positions. Further, a lateral registration correcting mechanism 44 for setting the position perpendicular to the conveyance direction of the recording medium to a normal position is provided in the recording medium conveyance path 43A. The lateral registration correction mechanism 44 includes the following. The recording medium P is slid and conveyed so as to include a horizontal reference guide (not shown) and a pair of skew rollers, and press the lateral end of the recording body against the reference guide. Then, the recording body is aligned with a predetermined position. The reference guide is moved and arranged at a predetermined position depending on the size of the recording medium. The lateral registration correcting mechanism 44 is composed of a regulating member that presses both sides of the recording body for a short time and a plurality of times from both lateral directions of the recording body with respect to the conveyance direction of the recording body to align the recording body at a predetermined position. The jogger method may be used.

The recording material P is conveyed from the registration roller pair 45 toward a transfer area which is a first transfer position constituted by the first intermediate transfer belt 21 and the secondary transfer roller 46. Thereafter, the sheet is transported toward a transfer area which is a second transfer position constituted by the second intermediate transfer belt 31 and the transfer charger 47.
Note that the recording medium can be supplied to the recording medium conveyance path 43C having the conveyance roller pair 42C from another sheet feeding device 300 that can be installed upstream in the conveyance direction. The upper sheet feeding surface of the sheet feeding tray 40a is arranged so that the uppermost recording medium of the sheet feeding tray 40a is fed and then conveyed substantially horizontally without being bent. Therefore, even thick recording media and highly rigid paperboard can be reliably fed. In addition, it is convenient to adopt an air sheet feeding composed of a vacuum mechanism so that the sheet feeding tray 40a can reliably feed a sheet of paper having various characteristics. Although not shown, a sensor for detecting the recording medium is provided at a key point of the recording medium conveyance path, and serves as a trigger for various signals based on the presence of the recording medium.

  A recording body for transporting the recording body that has passed the second transfer position on the extension of the recording body transporting path 43A to the fixing nip in the fixing device 60 provided downstream in the transporting direction of the recording body while maintaining a planar state. A transport device 50 is provided.

  A fixing device 60 having a heating unit is provided on the downstream side in the recording material conveyance direction of the recording material conveyance device 50. A type having a heater inside the roller, a belt fixing device that runs a heated belt, a fixing device that employs induction heating as a heating method, and the like can be employed. In order to make the color tone and glossiness of the images on both sides of the recording medium the same, the material, hardness, surface properties, etc. of the fixing roller and fixing belt are made equal in the vertical direction. Further, the fixing condition is controlled by a full-color and monochrome image, or single-sided or double-sided, or is controlled by a control unit (not shown) so as to obtain an optimal fixing condition according to the type of the recording medium. A cooling roller pair 70 having a cooling function is provided in the conveyance path after fixing in order to cool the recording medium after fixing and stabilize the unstable toner state at an early stage. As the cooling roller pair 70, a heat pipe structure roller having a heat radiating portion can be adopted. The cooled recording medium is discharged and stacked by a discharge roller pair 71 on a discharge stack portion 75 provided on the left side of the printer main body 100. The discharge stacking unit employs a mechanism in which a receiving member moves up and down according to a stack level by an elevator mechanism (not shown) so that a large number of recording bodies can be stacked. Note that the recording medium can also be transported to another post-processing apparatus through the paper discharge stack unit 75. As another post-processing apparatus, an apparatus for bookbinding such as drilling, cutting, folding, and binding can be connected.

  The toner cartridges 86Y, 86C, 86M, and 86K for each color in which unused toner is stored are detachably stored in the space 85. A toner conveying means (not shown) supplies toner to each developing device as necessary. In the configuration shown in FIG. 1, the toner cartridge is common to the upper and lower image forming units, but may be separated. The toner cartridge 86K for black toner that is highly consumed can have a particularly large capacity. This storage space 85 is on the back side when viewed from the operation direction on the upper surface of the image forming apparatus, and a plane portion is secured on the front side of the upper surface of the image forming apparatus, so that it can be used as a work table.

The operation and display unit 90 provided on the upper surface of the image forming apparatus 100 includes a keyboard and the like. Accordingly, conditions for image formation can be input, the state of the apparatus is displayed on the display unit, and information exchange between the operator and the image forming apparatus 100 is facilitated. The waste toner container 87 provided inside the image forming apparatus 100 is connected to the image forming unit cleaning device 2, the intermediate transfer belt cleaning devices 20 </ b> A and 30 </ b> A, and the conveyance belt 51 cleaning device 50 </ b> A. Then, foreign substances such as waste toner and paper dust sent from these are collected and stored in a lump. Since these cleaning devices (2, 20A, 20B, 50A) are not provided with a large-capacity waste toner storage section, the cleaning device can be reduced in size, and the waste toner disposal operability is also good. A full sensor (not shown) is used to issue a warning such as toner disposal in the waste toner storage unit 87 or container replacement.
Further, in the electrical / control device 95 provided inside the image forming apparatus 100, various power supplies, control boards, and the like are protected and housed in a sheet metal frame.
The inside of the image forming apparatus becomes hot due to heat from the fixing device 60 or heat generated from the electrical device. However, as a countermeasure against this, a fan 96 is provided to prevent deterioration of the function due to heat of the internal members. The fan 96 is coupled to the heat radiating portion of the cooling roller pair 70 to ensure the cooling effect of the cooling roller pair 70.
In FIG. 1, reference numeral 200 denotes a document reading device, and 300 denotes a paper feeding device that can be additionally installed.

Next, an operation at the time of single-sided recording in which the image forming apparatus 100 forms a full-color image on one side of the recording medium P will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method in which an image carried on the first intermediate transfer belt 21 is directly transferred to one side of the recording medium, and the other method is an image carried on the second intermediate transfer belt 31. This is a method of transferring directly to one side of a recording medium. Here, due to the configuration of the image forming apparatus 100, when the image carried on the first intermediate transfer belt 21 is directly transferred to one side of the recording body, the image is formed on the upper surface of the recording body. On the other hand, when the image carried on the second intermediate transfer belt 31 is directly transferred to one side of the recording body, the image is formed on the lower surface of the recording body. In the case where the data to be recorded is a plurality of pages, it is convenient to control the image forming order so that the pages are aligned on the paper discharge stack unit 75. A method will be described in which an image is carried on the first intermediate transfer belt 21 and then transferred to a recording body so that the pages are arranged in order from the image data of the last page.

When the image forming apparatus 100 is operated, the photoreceptors 1Y, 1C, 1M, and 1K in the first intermediate transfer belt 21 and the first image forming units 80Y to 80K rotate. At the same time, the second intermediate transfer belt 31 rotates, but the photoreceptors 1Y, 1C, 1M, and 1K in the second image forming units 81Y to 81K are separated from the second intermediate transfer belt 31 and are not rotated. First, image formation by the image forming unit 80Y is started. By the operation of the exposure device 4 composed of an LED (light emitting diode) array and an imaging element, light corresponding to image data for yellow emitted from the LED is irradiated onto the surface of the photoreceptor 1Y uniformly charged by the charging device 3. Thus, an electrostatic latent image is formed.
This electrostatic latent image is developed with yellow toner by the developing roller 5a, becomes a visible image, and is electrostatically transferred onto the first intermediate transfer belt 21 that moves in synchronization with the photoreceptor 1Y by the transfer action of the primary transfer roller 22. Primary transfer. Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner on the photosensitive members 1C, 1M, and 1K.
Thereafter, yellow, cyan, magenta, and black toner images are carried on the first intermediate transfer belt 21 as sequentially overlapping full-color toner images and are moved in the direction of the arrow together with the first intermediate transfer belt 21. .

  At the same time, the recording material P used for recording is fed out from the paper feed tray 40a or the paper feed cassettes 40b to 40d in the paper feed device 40 by one of the paper feed / separation means 41a to 41d for its supply. Then, it is conveyed to the recording material conveyance path 43A by the conveyance roller pairs 42B and 42C. Further, the surface roughness of the recording material P is measured by the optical sensor unit 140 while passing through the roller 42A. Before the leading edge of the recording body is held by the registration roller pair 45, the lateral registration correction mechanism 44 operates to push both sides of the recording body from both lateral directions with respect to the conveyance direction of the recording body. Can be aligned. The registration roller pair 45 is stationary, and the leading end of the recording body is stationary while entering the nip of the registration roller pair 45. Then, the registration roller pair 45 rotates at a timing so that the position of the image on the first intermediate transfer belt 21 is normal, and the recording medium is conveyed to the transfer area.

  The full color toner image on the first intermediate transfer belt 21 is transferred to the upper surface of the recording material P conveyed in synchronization with the first intermediate transfer belt 21 by receiving a transfer action by the secondary transfer roller 46. The bias applied to the secondary transfer roller 46 has a positive polarity opposite to the charging polarity of the toner. After the transfer, the surface of the first intermediate transfer belt 21 is cleaned by the belt cleaning device 20A. Further, foreign matters such as toner remaining on the surfaces of the photoreceptors 1Y, 1C, 1M, and 1K in the first image forming units 80Y to 80K that have finished the primary transfer are removed by the cleaning brush 2a and the cleaning blade 2b of the cleaning device 2. Made. The surface of each photoconductor is neutralized by a residual potential by the static eliminator Q to prepare for the next image formation / transfer process. The removed foreign matter such as toner is sent to the collecting unit 87 by the collecting unit 2c. Sensors S1 and S2 detect whether the surface potential after exposure on the surface of the photoconductor and the concentration of toner attached to the surface of the photoconductor after the development process are appropriate, and appropriately set image forming conditions. Information is sent to a control means (not shown) for control.

The recording material P onto which the toner image that has been superposed and carried on the first intermediate transfer belt 21 is transferred is transferred toward the fixing device 60 by the conveyance belt 51 of the recording material conveyance device 50.
The toners of the respective colors superimposed on the recording medium P are subjected to a fixing action by the heat of the fixing device 60, and are melted and mixed to form a completely color image. Since the toner is provided on only one side (upper surface) of the recording medium, less heat energy is required for fixing compared to double-sided recording having toner on both sides. A control means (not shown) optimally controls the power used by the fixing device according to the image. Until the fixed toner is completely fixed on the recording medium, it is rubbed against a guide member or the like on the conveyance path, and an image is lost or distorted. In order to prevent this problem, the cooling roller pair 70 which is a cooling unit is operated to cool the toner and the recording medium. Thereafter, the paper is discharged by the paper discharge roller 71 onto the paper discharge stack 75 with the image surface facing upward. In the paper discharge stack section 75, the image forming order is programmed so that the recorded matter of the young pages is stacked so as to be sequentially stacked on top, so the page order is aligned. Since the paper discharge stack unit 75 descends as the number of discharged recording media increases, the recording media can be stacked in an orderly and reliable manner, and the page order is not disturbed. Instead of directly stacking the recorded recording body on the paper discharge stack section 75, it is possible to carry out a punching process or transport it to a post-processing device such as a sorter, a collator, a binding device or a folding device.

  In another method of forming an image on one side of the recording medium P, image formation is not performed in the first image forming units 80Y to 80K, and image formation is performed in order from image data of young pages for page alignment. The difference is that However, since it is basically the same as the single-sided recording process described above, details are omitted.

Next, the operation during double-sided recording in which images are formed on both sides of the recording medium P will be described. When a start signal is input to the printer main body, images for each color sequentially formed by the first image forming units 80Y, 80C, 80M, and 80K described in the single-sided recording operation are sequentially applied to the first intermediate transfer belt 21 in order. Transfer. Substantially in parallel with the step of supporting the first image, the images for the respective colors sequentially formed by the second image forming units 81Y, 81C, 81M, 81K are sequentially primary-transferred to the second intermediate transfer belt 31, and the second The process of carrying as an image is performed. As shown in FIG. 1, the interval between the second image forming units in the belt conveyance direction is set closer than the interval between the first image forming units. Thereby, in order for the first image and the second image to coincide with each other at the front end in the transport direction of the recording medium, the formation of the second image is started after the start of the formation of the first image. . Further, since the recording medium is stopped and retransmitted by the registration roller pair 45, the sheet is fed in consideration of the time, and is aligned by the lateral registration correction mechanism 44. The registration roller pair 45 transports the recording medium to a first transfer station, which is a first transfer position constituted by the transfer roller 46 as the first secondary transfer means and the first intermediate transfer belt 21 at a timing. A transfer current having a positive polarity is supplied to the transfer roller 46, and an image is transferred from the first intermediate transfer belt to one side (the upper surface in the drawing) of the recording medium P.
In this way, the recording material P having an image on one side is continuously sent to the second transfer station, which is the second transfer position where the transfer charger 47 as the second secondary transfer means is located, by the conveying action of the transfer roller 46. . Then, by supplying a positive polarity transfer current to the charger, the full-color second image previously carried on the second intermediate transfer belt 31 is collectively transferred to the lower surface of the recording medium P.

The recording material P having the full color toner image transferred on both sides in this way is transferred to the fixing device 60 by the transport belt 51. Then, the toner image on both sides of the recording medium is melted and mixed by receiving a fixing process by heat of the fixing device 60. The recording body subsequently passes through the cooling roller pair and is discharged onto the discharge stack portion 75 by the discharge roller 71.
When double-sided recording is performed on a recording medium of a plurality of pages, the image forming order is controlled so that an image of a young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. When the image formation is completed, it is taken out from the stack, and when the top and bottom surfaces are reversed, the recorded matter is one page in order from the top, the second page on the back, the third page on the second sheet, and the fourth page on the back. Such control of image forming sequence and control such as increasing the power input to the fixing device compared to the one-side recording are executed by a control means (not shown).

  As for the single-sided recording and the double-sided recording operation, an example in which full-color recording is executed has been described, but monochrome recording using only black toner is also possible. When the need for maintenance or replacement of parts arises, maintenance is performed by opening an unillustrated exterior cover or the like. At this time, it is convenient to unitize the members constituting the image forming units 80 and 81 shown in FIGS. 3 and 4 and replace them as process cartridges. The configuration of the process cartridge is such that the image forming members excluding the intermediate transfer belts 21 and 31 and the primary transfer roller 22 and the exposure device 4 from the configuration shown in FIGS. It is housed and configured. Further, it can be realized by appropriately providing a guide part and a handle for attaching and detaching to the printer main body 100.

  Next, the recording material transport apparatus 50 will be described in detail. FIG. 5 is a schematic diagram of the recording material transport apparatus 50. The recording medium conveyance device 50 conveys the recording medium P delivered from the second intermediate transfer belt 31 to the fixing device 60, and guides the recording medium P conveyed by the conveyance portion 150 to the fixing device 60. And a guide 140. The transport unit 150 includes a transport belt 51 stretched between an entrance roller 53 provided at a position facing the second intermediate transfer belt 31 and an exit roller 54 disposed at a position facing the guide unit 140. Yes. Either the entrance roller 53 or the exit roller 54 is rotationally driven by a driving means (not shown) to move the conveyor belt 51 in the direction of the arrow in the figure. Further, the entrance roller 53 and the exit roller 54 are connected to ground.

  As the conveyor belt 51, a metal belt, a polyimide belt, a polyamide belt, or the like can be used. The surface is provided with releasability from the toner and has a chargeable resistance value. The traveling speed of the belt 51 is matched with the traveling speed of the recording medium in the fixing device 60. Further, the conveyance belt 51 has a length and a width such that one sheet of the maximum size recording material P on which an image can be formed is placed. When the maximum size of the recording medium P is not placed on the conveyance belt 51, particularly when the length of the conveyance belt 51 is insufficient, the leading edge reaches the fixing device 60 before the trailing edge of the recording medium P passes the transfer position. Therefore, it becomes difficult to carry the paper at the fixing speed. In addition, when the width is insufficient, slack occurs at both ends of the recording medium on the belt width side, wrinkles occur on the recording medium after passing the fixing section, and the paper jam occurrence rate at the fixing section becomes very high. To do.

  The guide unit 140 includes a plurality of spurs 141 and guides the recording medium P conveyed by the conveyance belt 51 to the fixing device 60 by the plurality of spurs 141. Moreover, the guide part 140 is connected to earth | ground.

  Next, features of the present embodiment will be described. When the recording medium P moves away from the second intermediate transfer belt 31 and moves to the conveying belt 51, there is a problem that toner that adheres electrostatically to the lower surface of the recording medium P is scattered. This is because the recording material P is charged with a positive polarity by being charged by the transfer roller 46 and the transfer charger 47. On the other hand, the delivery roller 34 provided at a position facing the entrance roller 53 is connected to the ground so that the second intermediate transfer belt 31 is not charged. For this reason, a potential difference is generated between the second intermediate transfer belt 31 and the recording material P. With such a potential difference, when the recording medium P is separated from the second intermediate transfer belt 31, the potential difference between the recording medium P and the second intermediate transfer belt 31 becomes large, and peeling discharge occurs. It is considered that the toner adhering electrostatically to the lower surface of the recording medium was scattered by the impact of the peeling discharge. As described above, as a result of the toner adhering to the lower surface of the recording medium P being scattered, there is a problem that the periphery of the delivery area where the recording medium P is transferred from the second intermediate transfer belt 31 to the conveying belt 51 is stained with toner. Further, there is a problem that the unfixed image on the lower surface of the recording material P is disturbed by the peeling discharge. The larger the potential difference between the recording medium P and the second intermediate transfer belt 31 is, the easier the peeling discharge occurs. Further, as shown in FIG. 5, such discharge is caused not only in the first separation area A where the recording body P is separated from the second intermediate transfer belt 31, but also in the proximity area F where the recording body P is in contact with the conveying belt 51. This also occurs in the second separation region G where the recording material P is separated from the transport belt 51.

  Therefore, in the present embodiment, a second intermediate transfer belt 31 as a conveying member that carries and conveys the recording medium P, or a potential difference suppressing unit that suppresses an increase in potential difference between the recording belt and the recording medium is provided. . Hereinafter, the potential difference suppressing means will be described with reference to FIGS.

  FIG. 6 is a diagram in which the potential difference suppressing unit is a neutralizing brush 110 as a recording body neutralizing unit. As shown in FIG. 6, the static elimination brush 110 is provided in a delivery area D where the recording medium P is passed from the second intermediate transfer belt 31 to the conveyance belt 51. The static eliminating brush 110 is connected to the ground. The neutralizing brush 110 is disposed so that the tip of the neutralizing brush is in sliding contact with the recording material P. The neutralizing brush 110 is arranged so that the tip of the neutralizing brush 110 is in the first separation area A where the recording medium P is separated from the second intermediate transfer belt 31. As shown in FIG. 7, the first separation area A is an area from a point B where the recording medium P is separated from the second intermediate transfer belt 31 to a point C which is advanced by the radial distance of the delivery roller 34. The neutralizing brush 110 is disposed so as to be in sliding contact with an area where the image of the recording body P is not formed, so that the unfixed toner image formed on the lower surface of the recording body by the neutralizing brush 110 is not disturbed.

  When the recording medium P is conveyed to the first separation area A by the second intermediate transfer belt 31, the recording medium P is separated from the second intermediate transfer belt 31 by curvature. At this time, the tip of the static elimination brush 110 arranged in the curvature area A contacts the recording medium P. When the recording material P comes into contact with the charge eliminating brush 110, the positive polarity charge on the recording material P escapes to the charge eliminating brush 110, and the charge on the recording material P is removed. As a result, the charge amount of the recording medium P is reduced, and the potential difference with the second intermediate transfer belt 31 is suppressed from increasing. As a result, the occurrence of peeling discharge between the second intermediate transfer belt 31 and the recording material P is suppressed. Therefore, it is possible to suppress the toner adhering to the lower surface of the recording medium P from being scattered by an impact caused by the peeling discharge. Further, it is possible to suppress the toner adhering to the lower surface of the recording body from being disturbed by an impact caused by the peeling discharge.

  In the above description, the static elimination brush 110 is connected to the ground, but may be connected to a bias applying means for supplying a negative charge. As a result, the recording body P transported to the first separation region A is given a negative polarity charge from the static elimination brush 110 and cancels out with a positive polarity charge on the recording body. As a result, it is possible to suppress an increase in the potential difference between the recording medium and the second intermediate transfer belt due to a decrease in the charge amount of the recording medium.

  FIG. 8 is a diagram in which the potential difference suppressing unit is a neutralizing needle 120 as a recording body neutralizing unit. Similar to the above-described static elimination brush 110, the tip of the static elimination needle 120 is disposed so as to be in the first separation region A described above. In addition, a bias applying unit 121 that applies a negative charge to the static elimination needle 120 is connected to the static elimination needle 120. In the static elimination needle 120, similarly to the static elimination brush 110 described above, a negative charge is applied to the recording material P conveyed to the delivery area D to reduce the charge amount of the recording material P. Thereby, it is possible to suppress an increase in potential difference between the recording medium and the second intermediate transfer belt 31 and suppress peeling discharge. In FIG. 8, bias applying means 121 for applying a negative charge to the static elimination needle 120 is connected. However, by connecting the static elimination needle 120 to the ground and releasing the positive charge on the recording medium, recording is performed. The charge amount of the body P may be decreased.

  As shown in FIGS. 6 and 8, the neutralizing brush 110 and the neutralizing needle 120 may be provided in the first separation area A where the recording body charged at least with a positive polarity is separated from the conveying member for the first time. Because the charge of the recording body is removed in the first separation area A, the potential difference between the recording body and the transport belt 51 in the proximity area F and the second separation area G does not become so large that discharge occurs. Because.

  FIG. 9 is a diagram showing another potential difference suppressing means. The potential difference suppressing means shown in FIG. 9 is obtained by connecting charge applying means 130, 151, 152, 142 for applying positive charges to the delivery roller 34, the entrance roller 53, the exit roller 54, and the guide section 140, respectively. By applying a positive charge to the delivery roller 34 by the charge applying unit 130, the second intermediate transfer belt 31 side is charged positively in the first separation area A with the same polarity as the recording medium. Thereby, it is possible to suppress an increase in potential difference between the second intermediate transfer belt and the recording medium. As a result, the peeling discharge between the second intermediate transfer belt 31 and the recording medium P can be suppressed, and the toner adhering to the lower surface of the recording medium is scattered or the toner image on the lower surface of the recording medium is disturbed. Can be suppressed.

  Further, when a positive polarity charge is applied to the delivery roller 34 to suppress the peeling discharge, the recording body is not neutralized, so the spur 141 between the conveyance belt and the recording body in the proximity area F or the second separation area G. And a recording discharge occurs. In addition, the potential difference between the spur 141 and the recording body is large between the spur 141 and the recording body of the guide section 140, and there is a possibility that electric discharge occurs.

  Therefore, a positive polarity charge is imparted to the entrance roller 53 by the charge imparting means 151. Further, a positive polarity charge is imparted to the exit roller 54 by the charge imparting means. Further, the guide unit 140 is also charged to the plus polarity of the same polarity as the recording medium by the charge applying unit 142.

  Since the entrance roller 53 and the exit roller 54 are charged with the same positive polarity as the recording body, the potential difference between the recording body P and the conveyance belt 51 increases in the proximity area F and the second separation area G. Can be suppressed. Therefore, even if the recording body P charged with a positive polarity is conveyed to the proximity area F or the second separation area G, it is possible to suppress discharge, and to suppress toner scattering and disturbance of the image on the lower surface of the recording body. can do.

  Similarly, the guide unit 140 is charged with a positive polarity by the charge applying unit 142 to be charged with the same positive polarity as the recording medium. As a result, an increase in potential difference between the recording material P and the spur 141 can be suppressed. Therefore, even if the recording material P charged to the positive polarity is conveyed to the guide unit 140, it is possible to suppress the occurrence of discharge and to suppress the scattering of toner and the disturbance of the image on the lower surface of the recording material.

  Further, it is preferable that the potential of each member such as the delivery roller 34, the entrance roller 53, the exit roller 54, and the guide portion 140 is lower than the potential of the recording medium. When the potential of each member is higher than the potential of the recording body, the negative polarity toner electrostatically attached to the lower surface of the recording body is electrostatically moved to the respective member side, and the second intermediate transfer belt 31 is moved. The spur 141 adheres to the conveyor belt 51. As a result, there is a possibility that problems such as a decrease in image density on the lower surface of the recording medium may occur. However, if the potential of each member is made lower than the potential of the recording body, it is possible to suppress the toner adhering to the lower surface of the recording body from electrostatically moving to the respective member side.

  Further, the potential difference suppressing means is not limited to the one shown above. For example, in the first separation region A, a positive charge is applied to the delivery roller 34 to suppress the occurrence of peeling discharge. Then, the neutralization brush 110 is provided in the proximity area F to reduce the charge amount of the recording body and suppress the occurrence of discharge after the proximity area F. Thereby, for example, even if the static elimination brush 110 cannot be arranged in the first separation region A due to the arrangement relationship of the devices, the occurrence of discharge can be suppressed in each region. In addition, a discharge brush may be arranged in each of the first separation area A, the proximity area F, and the second separation area G to suppress peeling discharge. However, if the recording medium is excessively discharged, the electrostatic adhesion between the recording medium and the toner is weakened. Therefore, it is necessary to adjust the material of each discharging brush 110 so as not to discharge too much.

  In addition, the charge eliminating brush 110 is disposed in the first separation area A to reduce the charge amount of the recording material, and a positive polarity charge is applied to the delivery roller 34, the entrance roller 53, the exit roller 54, and the guide portion 140 to perform recording. You may make it reduce the electrical potential difference with a body.

Next, based on the image forming apparatuses of the examples and comparative examples, the effects of the features of the present embodiment will be specifically described.
(Comparative Example 1)

First, the image forming apparatus of Comparative Example 1 will be described. The image forming apparatus of Comparative Example 1 has the basic configuration of the one-pass image forming apparatus shown in FIGS.
The first intermediate transfer belt 21 of Comparative Example 1 was an endless belt made of polyvinylidene fluoride having a thickness of 150 [μm]. The second intermediate transfer belt 31 and the conveyance belt 51 are endless belts made of polyimide having a thickness of 80 [μm]. As the first intermediate transfer belt 21, the one having a volume resistance of 13.1 [log Ωcm] under a measurement condition of an applied voltage of 500 [V] and a measurement time of 10 seconds using a Hiresta IP manufactured by Mitsubishi Oil Industries was used. In addition, the second intermediate transfer belt 31 and the conveyance belt 51 are those having a volume resistance of 7.5 [log Ωcm] under a measurement condition of an applied voltage of 500 [V] for a measurement time of 10 seconds using a Hiresta IP manufactured by Mitsubishi Yuka. used. Further, a transfer bias was applied to the transfer roller 46 so that a transfer current of 70 [μA] flows, and a transfer bias was applied to the transfer charger 47 so that a current of 100 [μA] flows to the second intermediate transfer belt 31.
Example 1

In the image forming apparatus of Example 1, the image forming apparatus of Comparative Example 1 is provided with a neutralizing brush 110 in the first separation area A where the recording medium is separated from the second intermediate transfer belt 31. The neutralizing brush 110 is connected to the ground.
(Example 2)

In the image forming apparatus of Example 2, the image forming apparatus of Comparative Example 1 is provided with a charge eliminating needle 120 in the first separation area A where the recording medium is separated from the second intermediate transfer belt 31. In addition, a bias applying unit 121 is connected to the static elimination needle 120, and a charge having a negative polarity is applied to the static elimination needle 120.
(Comparative Example 2)

Similar to the image forming apparatus of the second embodiment, the image forming apparatus of the second comparative example is different from the image forming apparatus of the first comparative example in the first separation region A where the recording medium is separated from the second intermediate transfer belt 31. Is provided. And the bias application means 121 is connected to the static elimination needle 120, and it becomes the structure by which the electric charge of plus polarity is provided to the static elimination needle 120. FIG.
(Example 3)

  The image forming apparatus according to the second embodiment is different from the image forming apparatus according to the first comparative example in that charge applying units 130, 151, and 152 that apply positive charge to the delivery roller 34, the entrance roller 53, the exit roller 54, and the guide unit 140, respectively. 142 is provided.

Using the image forming apparatuses of Comparative Examples 1 and 2 and Examples 1 to 3, predetermined images were printed on both sides of the recording medium. As a result, in the image forming apparatuses of Comparative Examples 1 and 2, it was confirmed that the image on the recording body was deteriorated. In particular, the deterioration of the image on one side of the recording medium was significant. This is considered to be a result of discharge occurring in the recording medium in the first separation area A, the proximity area F, the second separation area G, and the like, and the unfixed image is disturbed. Further, the image in which the deterioration appears noticeably is an image formed by the second image forming unit. That is, it is an image formed on the surface of the recording medium on the conveying member side. The reason why the image formed on the surface of the recording member on the conveying member side is significantly disturbed is that the surface on the conveying member side is directly subjected to an impact due to electric discharge.
On the other hand, in the image forming apparatuses of Examples 1 to 3, no deterioration of the image on the recording material was confirmed. This is considered to be because the discharge was suppressed in the first separation region A, the proximity region F, the second separation region G, and the like.

  Next, ten continuous double-sided black solid images were formed, and the degree of contamination of the image forming apparatus was examined. In the image forming apparatuses of Comparative Examples 1 and 2, contamination due to toner scattering was confirmed in the vicinity of the first separation area A, the proximity area F, and the second separation area G. In particular, the contamination near the first separation region A was remarkable. On the other hand, in the image forming apparatuses of Examples 1 to 3, no contamination due to toner scattering was confirmed in the vicinity of the first separation area A, the proximity area F, and the second separation area G.

  Thus, it can be seen that the image forming apparatuses of Examples 1 to 3 can perform good double-sided printing without image distortion, and the image forming apparatus can suppress contamination.

(1)
As described above, according to the image forming apparatus of the present embodiment, by providing the potential difference suppression unit, when the recording body is separated from the transport member or when the recording body is close to the transport member, the potential difference between the recording body and the transport member is reduced. It is possible to suppress the increase. As a result, it is possible to suppress the discharge that occurs due to an increase in the potential difference between the recording medium and the conveying member. As a result, it is possible to suppress the toner image formed on the surface of the recording member on the conveying member side from being disturbed by an impact caused by discharge. Further, the toner image formed on the surface of the recording member on the conveying member side can be prevented from being scattered due to the impact caused by the discharge, and the contamination of the apparatus can be suppressed.
(2)
In addition, according to the image forming apparatus of the present embodiment, the potential difference suppressing unit is a recording body neutralizing unit that neutralizes the recording body. By neutralizing the recording body, when the recording body is separated from the transport member or when the recording body is close to the transport member, it is possible to suppress an increase in potential difference between the recording body and the transport member. Occurrence can be suppressed.
(3)
Further, according to the image forming apparatus of the present embodiment, the recording body neutralizing means is the first separation area where the recording body is separated from the second intermediate transfer belt, which is the first separation region where the recording body is separated from the conveying member. It is provided in region A. If neutralization of the recording medium is performed in the first separation area A, the potential difference between the recording medium and the conveyance belt is close to the proximity area where the recording medium is close to the conveyance belt or the second separation area where the recording medium is separated from the conveyance belt. It is possible to suppress the increase. Thereby, it is not necessary to provide a potential suppressing means in the proximity region or the second separation region. Therefore, the number of parts can be reduced.
(4)
Further, according to the image forming apparatus of the present embodiment, the recording member can be effectively discharged by using the discharging member as the discharging brush or the discharging needle.
(5)
In addition, according to the image forming apparatus of the present embodiment, the recording medium can be discharged by discharging the electric charges charged on the recording medium and contacting the recording medium to the ground.
(6)
Further, according to the image forming apparatus of the present embodiment, the charge applied to the recording medium can be erased by applying a charge having a polarity opposite to the charging polarity of the recording medium by the bias applying unit, and the recording medium can be erased. The body can be neutralized.
(7)
Further, according to the image forming apparatus of the present embodiment, the delivery roller that forms the first separation area A, the exit roller that forms the second separation area G, and the entrance roller that forms the proximity area F have the same polarity as the recording medium. It is charged. As a result, the conveying member side is charged to the same polarity as the recording body, and the potential difference between the recording body and the conveying member in each of the above regions is reduced. Thereby, it is possible to suppress an increase in potential difference when the recording body is separated from the conveying member or close to the recording body. As a result, the occurrence of discharge on the recording medium can be suppressed, and toner scattering and image disturbance on the lower surface of the recording medium can be suppressed.
(8)
Further, according to the image forming apparatus of the present embodiment, the delivery roller, the exit roller, and the entrance roller are each provided with a charge imparting unit that imparts a charge having the same polarity as that of the recording medium. As a result, the delivery roller, the exit roller, and the entrance roller can be charged to the same positive polarity as the recording medium.

1 is a schematic diagram of a copying machine according to an embodiment. Explanatory drawing of angle (alpha) which two image receiving surfaces form. FIG. 3 is an enlarged configuration diagram showing one of four first process units in the printer unit of the copier. FIG. 3 is an enlarged configuration diagram showing one of four second process units in the printer unit of the copier. FIG. 3 is a schematic configuration diagram of a recording material transport apparatus. The figure which shows the example which used the electric potential difference suppression means as the static elimination brush. The figure which shows the arrangement position of the front-end | tip of a static elimination brush. The figure which shows the example which used the electric potential difference suppression means as the static elimination needle. The figure which shows the other example of a potential difference suppression means. 1 is a diagram illustrating a main part of a one-pass image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 5 Developing device 20 1st image unit 21 1st intermediate transfer belt 30 2nd image carrier unit 31 2nd intermediate transfer belt 34 Delivery roller 46 Transfer roller 47 Transfer charger 50 Recording material conveyance apparatus 51 Conveyance belt 53 Entrance roller 54 Exit roller 60 Fixing device 80 First image forming unit 81 Second image forming unit 100 Printer main body (image forming device)
110 Static elimination brush 120 Static elimination needle 140 Guide part 141 Spur

Claims (8)

In the course of transporting the recording medium, the first toner image is transferred to one side of the recording body, the second toner image is transferred to the other side of the recording body, and the toner image is transferred to both sides of the recording body. In the image forming apparatus for transporting the recording body onto which the toner image has been transferred to a fixing unit and fixing the toner image on the recording body,
There is provided a potential difference suppressing means for suppressing an increase in potential difference between the transport member and the recording body when the recording body is separated from and close to the transport member that carries and transports the recording body to which the toner image is transferred. An image forming apparatus. The image forming apparatus according to claim 1.
The image forming apparatus according to claim 1, wherein the potential difference suppressing unit includes a recording body discharging unit that discharges the recording body. The image forming apparatus according to claim 2.
The recording medium provided with a plurality of the conveying members and transferred with the toner image is transferred to the plurality of conveying members until conveyed to the fixing unit. An image forming apparatus, wherein the image forming apparatus is provided in a first separation region separated from a conveying member. The image forming apparatus according to claim 2 or 3,
The image forming apparatus, wherein the recording body charge eliminating means is a charge eliminating brush or a charge eliminating needle. The image forming apparatus according to any one of claims 2 to 4,
The image forming apparatus according to claim 1, wherein the recording member charge-eliminating means releases the electric charge charged in the recording member in contact with the recording member to the ground. The image forming apparatus according to any one of claims 2 to 4,
The image forming apparatus according to claim 1, wherein the recording member neutralizing unit includes a bias applying unit, and applies a charge having a polarity opposite to a charging polarity of the recording member from the bias applying unit to the recording member. The image forming apparatus according to claim 1.
Image formation characterized in that the conveying member side is charged to the same polarity as the recording member in a separation region where the recording member separates from the conveying member and / or a proximity region where the recording member is close to the conveying member apparatus. The image forming apparatus according to claim 7.
An image forming apparatus comprising: a charge applying unit configured to apply a charge having the same polarity as that of the recording body to the separation region and / or the proximity region on the transport member side.

Images