JP2005193989A - Recording body conveying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording body conveying device that performs stable conveyance without disturbing a visible image on a recording body carrying an unfixed visible image by adding a charge to the recording body conveying body and can suppress the increase of power consumption. <P>SOLUTION: In the recording body conveying device 50, a charge having polarity reverse to the charge of the recording body P is added to a conveying belt 51 of a recording body conveying member, and the stable conveyance is performed to convey the recording body P from a transfer section 301 to a fixing section 601. The charge is added to the conveying belt 51 by an adsorbing roller 52 as a contact charge adding member. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

Conventionally, with regard to a transport unit that transports a recording medium carrying an unfixed toner image on both sides from a transfer device to a fixing device, it has been considered that the image is disturbed by the unfixed toner image coming into contact with the transport member. It was. Patent Documents 1 and 2 disclose configurations in which an unfixed toner image is prevented from coming into contact with a conveying member to prevent the image from being disturbed.
The recording medium conveying means described in Patent Document 1 has a structure in which air blowing members for blowing air are provided on both sides of the recording medium, and the recording medium is guided in the conveying direction by air and guided to the fixing device. Since the recording body is transported from the transfer device to the fixing device by air, the unfixed toner image on the surface of the recording body does not come into contact with the air blowing member, which is a transporting member. Disturbance can be prevented.
In addition, the recording medium conveying means described in Patent Document 2 is configured to guide the leading end portion of the recording body, which is out of the conveying path, to the conveying path by the guide member when the recording body is bent, and to guide to the fixing device. is there. Specifically, a V-shaped guide member having a transfer device side opened up and down and a fixing device side narrowed is provided, and the leading end of the recording body is brought into contact with the guide member and moved along the guide member, thereby recording. The body is guided to the fixing nip portion of the fixing device. In this configuration, since the guide member contacts only the front end portion of the recording body where the toner image is hardly transferred, the unfixed toner image on the surface of the recording body is prevented from coming into contact with the guide member that is the recording body conveying member. be able to. Thereby, it is possible to prevent the image from being distorted due to the unfixed toner image adhering to the conveying member.
However, since the recording medium carrying the unfixed toner is bent by these recording medium conveying means, the surface of the recording body cannot be maintained flat, and the unfixed toner image on the surface of the recording medium may be disturbed. It was.

  Since the recording medium conveying means described in Patent Document 3 can maintain the recording medium in a planar state by using a conveying belt, it can prevent bending due to its own weight. Further, when transporting, a non-contact type charge generation device (hereinafter referred to as a charge charger) discharges a charge to a recording medium, thereby electrostatically adhering to a transport belt to perform stable transport. be able to. Further, by applying a charge having a polarity opposite to that of the toner image to the recording medium and applying a charge having the same polarity as that of the toner image to the conveying belt, the adhesion between the recording medium and the conveying belt can be improved. It is also possible to prevent the image from adhering to the conveyance belt.

JP 2000-250341 A JP 2000-281241 A JP-A-10-258950

  However, the charge charger disclosed in Patent Document 3 requires a large amount of electric power because it charges away from the transport belt. In order to perform stable conveyance, it is preferable to install a plurality of charge chargers. However, installing a plurality of chargers causes an increase in power consumption.

  The present invention has been made in view of the above problems, and the object of the present invention is not to disturb the visible image on the recording medium carrying the unfixed visible image, and to further increase the power consumption. It is an object of the present invention to provide a recording material transport apparatus that can be suppressed.

In order to achieve the above object, the invention according to claim 1 fixes the visible image to the recording body from a transfer means for transferring the visible image to the recording body from the image bearing body that carries and conveys the visible image. The recording material carrying the electrostatic charge is carried on the surface up to the fixing means, and the recording material conveying member conveys the recording material by endless movement, and the recording material is charged on the recording material conveying member. And a charge imparting member that imparts a charge having a polarity opposite to that of the charge, wherein the charge imparting member is a contact-type charge imparting member that contacts the record transport member and imparts a charge. It is characterized by.
According to a second aspect of the present invention, in the recording medium conveying apparatus according to the first aspect, the volume resistivity of the recording medium conveying member is equal to or greater than the volume resistivity of the image carrier in the vicinity of the transfer means. It is characterized by a value.
The invention according to claim 3 is the recording body transporting device according to claim 1 or 2, wherein the recording body transporting member is a recording body transporting belt that is stretched around two or more support members and transports the recording body. The contact-type charge imparting member is characterized in that a charge is imparted by contacting the inside of the recording material transport belt.
According to a fourth aspect of the present invention, in the recording medium conveying apparatus according to the third aspect, the support member has a configuration as the contact-type charge imparting member.
Further, the invention according to claim 5 is the recording body transporting apparatus according to claim 3 or 4, wherein the recording body which is the most downstream side of the recording body transport belt in the recording body transport direction among the two or more support members. And a recording member transport belt, the separation member support member constituting the separation unit is grounded by supporting the recording member transport belt from the inside.
According to a sixth aspect of the present invention, in the recording medium conveying apparatus according to the third, fourth, or fifth aspect, a belt deviation prevention member is provided inside the recording medium conveyance belt, and the belt deviation prevention member includes the recording medium conveyance belt. It has the same volume resistivity.
According to a seventh aspect of the invention, an image carrier that carries a visible image, a visible image forming unit that forms a visible image on the image carrier, and a recording body holding member that holds the recording body are arranged in a predetermined direction. A transfer means for transferring a visible image on the image carrier to a recording medium on the recording medium holding member, and a recording medium after passing through the transfer means. 7. An image forming apparatus having a fixing means for fixing to a recording medium, wherein the recording medium conveying means for conveying the recording medium from the transfer means to the fixing means is a recording according to claim 1, 2, 3, 4, 5, or 6. It is characterized by using a body conveyance device.

  In the recording material transport apparatus according to any one of claims 1 to 6, since the recording material transport member is provided with a charge having a polarity opposite to that of the recording material by the charge applying member, the recording material and the recording material transport member attract each other. Stable conveyance can be performed. Further, since the charge having the opposite polarity to that of the recording medium has the same polarity as the unfixed visible image, the visible image and the recording medium conveying member repel each other, and the visible image is transferred to the recording medium conveying member. It can prevent adhesion. Furthermore, since the charge imparting member that imparts a charge to the recording material transport member is a contact-type charge imparting member, the charge can be efficiently imparted to the recording material transport member.

  According to the first to sixth aspects of the present invention, it is possible to prevent the visible image from adhering to the recording medium and to perform stable conveyance, so that the unfixed visible image can be prevented from being disturbed. . Further, since the charge can be efficiently applied to the recording material conveying member, there is an excellent effect that power consumption can be suppressed.

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 disposed at the upper part and the second image unit 30 is disposed 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 adopted in which at least a part of the horizontal projection surface of the first intermediate transfer belt 21 at the upper portion and the horizontal projection surface of the second intermediate transfer belt at the lower portion overlap each other. That is, the shape is such that the second intermediate transfer belt in the lower part is recessed below the first intermediate transfer belt in 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. 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 photosensitive member is properly secured, and a predetermined line of magnetic force 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. 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 can be secured almost horizontally and linearly above the second image forming unit 81, the conveyance and reliability of the recording medium are excellent, and the entire image forming apparatus is The unity becomes good.
In particular, the first image carrying belt is stretched horizontally and flatly, and the second intermediate transfer belt is stretched long and inclined in the vertical direction. The space in the height direction of the intermediate transfer belt 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 the layout in the height direction is increased, so that the recording medium conveyance 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 feeder having the same height as that occupied by the second intermediate transfer belt can be installed side by side, it is possible to install a sheet feeder capable of storing 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 conveying path can be made substantially the same height, and the sheet feeding and conveying reliability of the recording medium 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.
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.

  On the right side of the image forming apparatus 100, a paper feeding device 40 that stores P so as to be supplied 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. Of 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 fed 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 transported 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 material of the sheet feeding tray 40a is fed and then conveyed straight 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 of 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. The recording material transport device 50 includes rollers 52, 53, 54, 55, and 56 that support a transport belt 51 that moves endlessly in the direction of the arrow. On the outside of the conveyor belt 51, a cleaning device 50A, an adsorption roller 52 for adsorbing the recording medium P, and a grounding charge / separation roller 54 are provided so as to face the roller 55.
The conveyance belt 51 that moves together with the recording medium P in contact with the unfixed toner image is negatively charged by the suction roller 52 with the same polarity as the toner. As the conveyance belt 51, a metal belt, a polyimide belt, a polyamide belt, or the like can be employed. 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.

  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 on a discharge stack portion 75 provided on the left side of the image forming apparatus 100 by a discharge roller pair 71. 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 F is provided to prevent deterioration of the function due to heat of the internal members. The fan F 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 the supply. And it is conveyed by the conveyance roller pair 42B and 42C to the recording medium conveyance path 43C. 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 surface of the conveyance belt 51 is charged in advance by the adsorption roller 52 of the recording medium so that the recording medium P can be reliably conveyed together with the conveyance belt 51. The neutralization / separation roller 54 operates so that the recording material P is separated from the conveyance belt 51 and is reliably sent to the fixing device 60.
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 image forming apparatus, an image for each color that is sequentially formed by the first image forming units 80Y, 80C, 80M, and 80K described in the single-sided recording operation is sequentially applied to the first intermediate transfer belt 21. Next 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. The surface of the conveyor belt 51 is charged by the suction roller 52 with the same negative polarity as the polarity of the toner. The unfixed toner on the lower surface of the recording body is prevented from transferring to the belt. An AC voltage superimposed on the + voltage is applied to the charge removal / separation roller 54, and the recording medium is separated from the belt 51 and transferred to the fixing device 60. The toner image on both sides of the recording medium is melted and mixed in response to 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, the 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 parts replacement arises, an exterior cover (not shown) is opened to perform maintenance. 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, this can be realized by appropriately providing a guide part and a handle for attaching and detaching the image forming apparatus 100.

Next, details of the recording material transport apparatus 50, which is a characteristic part of the present embodiment, will be described. FIG. 5 is a schematic explanatory diagram of the recording material transport apparatus 50.
The recording medium conveying device 50 holds a recording medium P having an unfixed toner image on the surface of a conveying belt 51 that is a recording medium conveying member, and conveys the recording medium P from a transfer unit 301 of a transfer unit to a fixing unit 601 of a fixing unit. It is. As shown in the figure, a positive charge is applied to the recording medium P in the transfer portion 301 by the charge applying means (transfer charger 47 in FIG. 1). At this time, the toner attached on the surface of the recording medium P is charged with a negative polarity.
The surface of the conveyor belt 51 is charged with the same negative polarity as the polarity of the toner from a suction roller 52 which is a contact-type charge imparting member. Then, by grounding the static elimination / separation roller 54 as a separation unit support member, the conveying belt 51 is neutralized in the vicinity of the separation unit 502.

Here, an operation in which the recording medium P is conveyed from the transfer unit 301 to the fixing unit 601 by the recording medium conveyance device 50 will be described.
The recording material P on which the toner image is transferred on both sides by the transfer unit 301 is carried on the recording material conveyance belt 51 from the transfer unit 501. Since the recording body P has a positive charge and the transport belt 51 has a negative charge, the recording body P is adsorbed by the transport belt 51, so that stable transport is possible. Further, since the toner has a negative charge, it repels the fixing belt 51 having a charge of the same polarity, and even if the unfixed toner image and the transport belt 51 are in contact with each other, the unfixed toner remains. The adhesion to the conveyor belt 51 can be prevented.
In the separation unit 502, since the charge eliminating / separation roller 54 is grounded, the charge of the transport belt 51 is lost, and the suction force between the transport belt 51 and the recording material P is lost. The recording medium P is separated from the conveyance belt 51 by the rigidity of the recording medium P, and the recording medium P is conveyed to the fixing unit 601.

  Although the roller-like suction roller 52 is applied as the contact-type charge imparting member, a blade-like or brush-like charge imparting member can be applied as long as it can impart uniform charge to the conveyor belt 51. good. By applying uniform charge to the transport belt 51, the electrostatic adhesion force between the transport belt 51 and the recording material P can be uniformly and efficiently increased. Also, as shown in FIG. 5, by using one of the support rollers of the conveyor belt 51 as a contact-type charge imparting member, the number of members can be reduced.

By using a contact-type charge imparting member such as a roller, blade or brush as the charge imparting member, non-contact charge imparting such as a charge charger between the charge imparting member and the member to which the charge is imparted is provided. There is little loss of electric power compared with members. Further, as shown in FIG. 5, by providing the contact-type charge imparting member inside the transport belt 51, the recording medium transport device 50 saves space compared to the case where the charge imparting member is disposed outside the transport belt 51. Can be achieved.
On the other hand, in the transport device described in Patent Document 1, a plurality of charge chargers are provided in order to perform stable transport using a charge charger, and the number of members is large. In order to provide a plurality of charge chargers outside the area surrounded by the conveyor belt, a space for the conveyor device requires an installation space for the plurality of charge chargers in addition to the installation space for the conveyor belt.
As shown in FIG. 5, by using a contact-type charge imparting member, a plurality of charge imparting members are not required, and the charge imparting member is provided in the region surrounded by the conveyor belt. Space can be saved compared to the one used.

  A cleaning device 50 </ b> A that is a cleaning unit for the transport belt 51 is provided on the transport belt 51 between the separation unit 502 and the transfer unit 501 in the surface movement direction of the transport belt 51. This is intended to remove foreign matter adhering to the conveyor belt 51 because there is a concern about contamination of the belt and deterioration of surface properties due to adhesion of foreign matter on the conveyor belt. By removing the deposits on the conveyance belt, it is possible to remove dirt and maintain the surface property, and to keep the adhesion between the conveyance belt 51 and the recording material P always good.

  By the way, if the conveyor belt 51 keeps a constant charge, there may be a case where the lifetime of the conveyor belt 51 is reduced, leading to problems such as a cleaning failure or separation failure due to electrostatic force. In order to prevent such a problem, the static elimination / separation roller 54 is grounded, and the charge on the conveyance belt 51 is released by the separation portion 502 between the recording medium P and the conveyance belt 51. By releasing the charge when the recording medium P is separated from the transport belt 51, it is possible to obtain a longer life of the transport belt 51, good cleaning performance, and stable separation performance of the recording medium P from the transport belt 51. .

Further, there may be a case where the separation unit 502 does not perform separation due to an electrostatic force due to the residual charge of the transport belt 51 and the charged charge of the recording material P, and a paper jam occurs. In order to prevent such problems, the outer diameter d1 of the static elimination / separation roller 54 is set to 30 mm or less, preferably 20 mm or less. By setting the outer diameter d1 of the static elimination / separation roller 54 forming the separation unit 502 to 30 mm or less, the radius of curvature of the conveyance belt 51 in the separation unit 502 becomes so small that it becomes difficult for the recording medium P to follow the rigidity. can do.
In the separation unit 502, it is difficult for the recording body P to be transported following the transport belt 51, so that the recording body P and the transport belt 51 can be stably separated. Since the recording medium P and the conveyor belt 51 can be stably separated from each other by the rigidity of the recording medium P and the curvature of the conveyance belt 51, the occurrence rate of paper jam in the conveyance device 50 can be reduced.

The volume resistivity value of the conveyance belt 51 is adjusted to be equal to or higher than the volume resistivity value of the intermediate transfer belt 31. In order to hold the recording medium P by the conveying belt 51 by electrostatic force, it is necessary to hold electric charges on the belt surface. Since the volume resistivity of the conveyance belt 51 is equal to or greater than the volume resistivity of the intermediate transfer belt 31, the charge held by the conveyance belt 51 can be equal to or greater than the charge held by the intermediate transfer belt 31. it can. If the charge held by the conveyance belt 51 is equal to or greater than the charge held by the intermediate transfer belt 51, the force for holding the recording material P is equal to or greater than that of the intermediate transfer belt 31 by the conveyance belt 51. Since the conveyance belt 51 is equal to or greater than the intermediate transfer belt 31 in holding force of the recording medium P, the recording medium P is smoothly transferred from the intermediate transfer belt 31 to the conveyance belt 51.
The surface resistivity is also set so that the surface resistivity value of the intermediate transfer belt 31 is equal to or greater than the surface resistivity value of the transport belt 51.

In addition, the charge imparted from the suction roller 52 that is a contact-type charge imparting member diverges from the transport belt 51 to the support member, thereby reducing the charge imparting efficiency and the adhesion between the transport belt 51 and the recording material P. Cases to be detected are detected. In order to suppress the divergence of the electric charge, the conveying belt 51 has a high resistance in which the surface resistivity is adjusted to 10 ⁸ to 10 ¹³ Ω / □ and the volume resistivity is adjusted to 10 ⁶ to 10 ¹² Ω · cm. Yes. By making the resistivity of the conveying belt 51 high, it is possible to suppress the divergence of the electric charge of the conveying belt 51. Therefore, it becomes possible to efficiently apply the electric charge to the conveying belt 51, and to convey the recording material P and the conveying belt 51. High adhesion to the belt 51 can be maintained.

  Since the recording material transport device 50 is close to the fixing device 60, the heat from the fixing device 60 adversely affects (elongates, dissolves, etc.) the transport belt 51, thereby impairing the transport performance of the transport belt 51 and shortening the service life. There are cases where this leads to In order to have durability and stability against heat from the fixing device 60, the material of the conveyor belt 51 should have a heat resistance of 200 degrees or more over time and instantaneously 250 degrees or more (polyimide, polyamide, etc.). Used. Since the conveyance belt 51 has heat resistance, it can withstand the heat of fixing from the fixing device 60, and a long life and stable conveyance performance can be obtained.

  In addition, when the conveyance belt 51 and the unfixed toner existing on the recording medium P come into contact with each other during conveyance of the recording medium, there is a concern that the unfixed toner on the recording medium P is transferred to the conveyance belt 51. In order to make it difficult for the unfixed toner to be transferred onto the conveyance belt 51, the conveyance belt 51 is made of a material having good releasability or the surface is covered with a material having good releasability. Since the surface of the conveyance belt 51 is more releasable than the surface of the recording medium P, unfixed toner on the surface of the recording medium P is prevented from being transferred onto the conveyance belt 51 during conveyance of the recording medium. can do.

  Further, it is desirable that the transport belt 51 is a long-life belt that has durability sufficient to withstand physical stress due to friction with a support member, tension, or the like, and that is less likely to be holed, torn or stretched. Therefore, the transport belt 51 is uniform in a value range of 50 to 600 μm and has a tensile strength of 0.29 MPa or more.

  Next, the length of the conveyance belt 51 in the width direction will be described with reference to FIG. FIG. 6A is a schematic diagram of the conveying device 50, and FIG. 6B is a diagram of the conveying belt 51 as viewed from above. In the drawing, W indicates the width of the conveyor belt 51 (hereinafter referred to as belt width). When the belt width W is smaller than the width of the recording material P to be conveyed, a part of the recording material P is conveyed while protruding in the width direction of the conveying belt 51. Then, slack and fluttering of the recording medium P occurs, and when entering the fixing unit 601, there is a concern about image quality deterioration such as toner dust and generation of wrinkles of the recording medium P during fixing. In order to suppress this deterioration in image quality, the value of the belt width W is the same or larger than the width of the maximum recording body among the recording bodies usable in the image forming apparatus 100. Is set to the width of the conveyor belt 51. Since the width direction of the recording medium P is completely accommodated on the conveying belt 51 by being the same length as the maximum width of the recording medium that can be conveyed or a longer belt width W, the recording medium may be loosened or fluttered. It is possible to prevent degradation of the image quality.

By the way, if it is a conveyance means using a guide member or air, conveyance may become unstable if the space | interval between a transfer part and a fixing part is opened widely. In particular, for the guide member that guides the leading end of the recording body to the fixing device, the leading end of the recording body reaches the fixing position before the trailing end of the recording body passes through the transfer portion, and is not subjected to a pulling force. There is a risk of poor conveyance and poor conveyance.
However, if the distance between the transfer unit and the fixing unit is shorter than the length in the conveyance direction of the recording medium, the image quality caused by the difference between the speed at which the recording medium passes through the transfer section and the speed at which it passes through the fixing section. There is concern about the decline.
The following can be raised as a decrease in image quality due to this difference in speed. When the recording body P is long in the conveyance direction, when fixing of the leading end of the recording body starts with a part of the recording body P being in the transfer position, if the fixing speed is higher than the transfer speed, the recording body The image to which P is pulled and transferred is stretched. In other cases, the transfer may overlap due to an impact when the leading end of the recording medium P is sandwiched between the fixing rollers in the fixing device 60.
In order to prevent such a problem, the recording medium conveyance belt 51 is provided. However, if the length in the conveyance direction, which is the distance between the transfer unit 301 and the fixing unit 601, is not sufficient, the same problem as described above occurs. There is a fear.

Here, the length in the transport direction will be described with reference to FIG. FIG. 7A is a schematic view when a contact type transfer member and a contact type fixing member are used. The transport direction length L1 at this time is the distance of the transport path starting from the nip exit of the contact type transfer member and ending at the nip entrance of the contact type fixing member. On the other hand, FIG. 7B is a schematic view when a non-contact type transfer member and a non-contact type fixing member are used. The conveyance direction length L2 at this time is the distance of the conveyance path starting from the nip exit of the non-contact type transfer member and ending at the nip entrance of the non-contact type fixing member.
The transfer unit, the transport device, and the transport unit distance L1 and L2 are the same or larger than the maximum length of the prints that can be used in the image forming apparatus 100. Set the layout of the fixing unit. When the leading end of the recording body P reaches the fixing unit 601 due to the same length as the maximum length of the recording body that can be transported or longer transport direction distances L 1 and L 2, the trailing end of the recording body P is the transfer section 301. It will be in a state that has been completely removed. After the trailing end of the recording body P has completely passed through the transfer portion 301, the leading end of the recording body P reaches the fixing portion 601. Therefore, due to a difference in conveyance speed between the fixing portion 601 and the transferring portion, or an impact at the fixing portion. A reduction in image quality can be prevented.

Next, the transfer length from the transfer unit to the conveyance device 50 and the transfer length from the conveyance device 50 to the fixing device 60 will be described with reference to FIG. L3 is a transfer length from the transfer unit to the conveyance device 50, and L4 is a transfer length from the conveyance device 50 to the fixing device 60.
The transfer length L3 is determined from the intersection of the perpendicular line from the point closest to the conveyance belt 51 of the transfer member to the conveyance path 43 and the conveyance path 43, and the perpendicular line and conveyance from the point closest to the transfer member to the conveyance path 43 in the conveyance belt 51. This is the distance to the intersection with the route 43.
On the other hand, the transfer length L4 is determined from the intersection of the perpendicular line from the point closest to the fixing device 60 to the conveyance system filter 43 and the conveyance path 43 in the conveyance belt 51 to the conveyance path 43 from the point closest to the conveyance belt in the fixing member. This is the distance to the intersection of the perpendicular and the transport path 43.

If the two delivery lengths L3 and L4 are not appropriate, there is a concern that the delivery of the recording medium P may not be successful and a jam may occur. Furthermore, there is a concern that the impact between the recording medium P and the conveyance belt 51 or the fixing member may lead to a decrease in image quality. Therefore, the transfer length L3 and L4 are set to appropriate distances of 50 mm or less, respectively, so that the recording medium P can be smoothly transferred.
By enabling smooth transfer of the recording medium P, it is possible to suppress the recording medium P from entering and colliding with a member, and it is possible to suppress image quality deterioration due to jamming and impact.

Next, a belt shift prevention rib 57, which is a belt shift prevention member provided on the conveyance belt 51, will be described with reference to FIG. FIG. 9A is a perspective view of only the conveyor belt 51 taken out. FIG. 9B is a development view when the conveyor belt 51 is cut along the dotted line in FIG. FIG. 9C is a cross-sectional view of the conveyor belt 51 in the vicinity of the support roller 53. As shown in FIG. 9B, a slip prevention rib 57 is provided on the back surface of both end portions in the width direction of the conveyor belt 51. As shown in FIG. 9C, the belt slip prevention rib 57 is engaged with each end face of a support roller which is a support member of the transport belt. The belt slip prevention rib 57 can prevent the transport belt 51 from slipping or shifting in the width direction.
By the way, if the volume resistivity values of the belt slip prevention rib 57 and the transport belt 51 are greatly different, the charge non-uniformity on the transport belt 51 is different between the portion where the belt slip prevention rib 57 is present and the portion where the belt slip prevention rib 57 is not present. It is feared that this will occur. Therefore, in order to maintain the same charge in the portion where the belt slip prevention rib 57 of the transport belt 51 exists and the portion where it does not exist, the belt slip prevention rib 57 is made of a material having a volume resistivity equivalent to that of the transport belt 51. Using.
By setting the belt slip prevention rib 57 to a resistance value equivalent to that of the transport belt 51, it is possible to suppress charge nonuniformity such as charge divergence and excessive charge accumulation on the belt slip prevention rib 57. The electrostatic contact force with the recording medium P can be made uniform over the entire surface of the transport belt 51.

Next, the conveyance device 50 used in the present embodiment will be described based on the following examples and comparative examples.
[Example]
. As the transport belt 51, a polyimide belt having good releasability that satisfies the following conditions was adopted.
Belt width: 310 mm (the maximum width of transfer paper that can be used in the image forming apparatus on which the belt is installed is 297 mm)
・ Thickness: 80 μm ・ Tensile strength: 0.36 MPa
・ Heat resistance: 200 degrees over time, 250 degrees instantaneously ・ Resistance value: surface resistivity: 10 ¹¹ Ω / □, volume resistance is 10 ¹⁰ Ω · cm (the resistivity value is two orders of magnitude higher than that of the intermediate transfer belt 31) Adjust to be)

A belt slip prevention rib 57 is fixed to the widthwise end of the back surface of the transport belt 51, and the same material as the transport belt 51 is adopted as the material of the belt slip prevention rib 57.
The conveyance device 50 having the conveyance belt 51 is installed so that the conveyance direction length is 370 mm (the maximum width of the recording material P usable in the image forming apparatus 100 is 297 mm), the delivery length L3 is 30 mm, and L4 is 40 mm. ing. Further, the transfer unit 501 is provided with an adsorption roller 52 as a roller-like contact charge applying member in the belt loop, and a static elimination / separation roller 54 having a diameter of 16 mm and grounded in the separation unit. A cleaning device 50 </ b> A is installed on the conveying belt 51 on the lower surface between the separation unit 502 and the delivery unit 501.
When an image was formed on the A4 size recording medium P under the above-mentioned conditions, smooth conveyance could be performed and a good image could be obtained.

[Comparative Example 1]
An image was formed on the A4 size recording material P without applying a charge from the suction roller 51 as a contact charge applying member under the conditions of the example.
As a result, since no charge is applied to the conveyance belt 51, the electrostatic adhesion between the conveyance belt 51 and the recording medium is low, and the unfixed toner image on the recording medium P is disturbed on the conveyance belt 51. A good image was not obtained.

[Comparative Example 2]
The cleaning device 50A under the conditions of the example was removed, and an image was formed on the A4 size recording medium P.
As a result, since the foreign matter adhering to the conveyance belt 51 is not removed, adhesion of dirt on the recording medium P and a decrease in the adhesion between the recording medium P and the conveyance belt 51 occur, and the output image quality is deteriorated. .

[Comparative Example 3]
An image was formed on an A4 size transfer paper without grounding the charge eliminating / separation roller 54 under the conditions of the example, without the charge removing means.
As a result, the cleaning failure of the conveyor belt 11 and the paper jam occurrence rate in the separation unit 502 increased.

[Comparative Example 4]
The diameter of the static elimination / separation roller 54 in the separation unit 502 under the conditions of the example was set to 36 mm, and an image was formed on A4 size transfer paper.
As a result, the transfer paper and the conveyor belt 50 were not separated successfully, and the jam occurrence rate near the separation unit 502 increased.

[Comparative Example 5]
An image was formed on an A4 size recording medium P with a surface resistivity of 107 Ω / □ and a volume resistivity of 105 Ω · cm of the conveying belt 51 under the conditions of the example.
As a result, the electrostatic adhesion between the conveyance belt 51 and the recording medium P is low, and an unfixed toner image is disturbed on the conveyance belt 51, and a good image cannot be obtained.

[Comparative Example 6]
The heat resistance of the conveyance belt 51 under the conditions of the example was lowered to 170 degrees over time and to 210 degrees instantaneously, and images were continuously formed on the A4 size recording material P.
As a result, it was observed that the feed belt 51 was deteriorated with time due to heat elongation, and among the support rollers, the roller transmitting the driving force to the transport belt 51 and the transport belt 51 caused idle rotation.

[Comparative Example 7]
The releasability on the surface of the conveyor belt 51 under the conditions of the example was greatly deteriorated (measured on the average roughness of the centerline of the conveyor belt surface was 0.21 μm), and an image was formed on the A4 size recording medium P. Formation was performed.
As a result, a part of the unfixed toner image on the recording medium P is transferred onto the transport belt 51, and the unfixed toner image is disturbed on the transport belt 51, so that a good image cannot be obtained.

[Comparative Example 8]
Images were continuously formed on the A4 size recording material P with the thickness of the conveying belt 51 under the conditions of the example being 15 μm and the tensile strength of the material being 0.15 MPa.
As a result, the transport belt 51 is torn and cannot be used.

[Comparative Example 9]
An image was formed on A4 size transfer paper with the belt width W of the conveying belt 51 under the conditions of the example being 250 mm.
As a result, as shown in FIG. 10, slack E occurred at both ends on the belt width side of the transfer paper conveyed on the conveyance belt, and wrinkles occurred on the transfer paper after passing through the fixing portion. In addition, the paper jam occurrence rate at the fixing unit was very high.

[Comparative Example 10]
An image was formed on an A4 size recording medium P with the length in the conveyance direction under the conditions of the example being 280 mm.
As a result, when the recording body P enters the fixing portion 601, a part of the recording body P exists in the transfer nip portion 301, and the impact when the fixing portion 601 enters is transmitted to the recording body P in the transfer nip portion 301, and toner dust Image quality was reduced.

[Comparative Example 11]
Images were formed on A4 size transfer paper with the transfer length of the conditions of the example being 70 mm for both the transfer side L3 and the fixing side L4.
As a result, the recording material P collided with the fixing member and the conveyance belt 51, resulting in a decrease in image quality and an increased paper jam occurrence rate.

[Comparative Example 12]
The volume resistance value of the belt slip prevention rib 57 provided on the back surface of the conveyance belt 51 under the conditions of the embodiment is set to 108 Ω · cm, which is lower than the volume resistance value of the conveyance belt 51, and image formation is performed on the A4 size recording medium P. went.
As a result, the charge on the surface of the conveyance belt 51 is diffused to the support roller via the belt slip prevention rib 57, the adhesion between the recording medium P and the conveyance belt 51 is lowered, and the conveyance performance of the recording medium P is lowered.

As described above, according to the present exemplary embodiment, the conveyance belt 51 serving as the recording medium conveying member is charged with the opposite polarity to the charge of the recording medium P, and the recording medium P is conveyed from the transfer unit 301 to the fixing unit 601. Can be carried out. Further, by applying a charge to the conveying belt 51 by the suction roller 52 that is a contact-type charge applying member, it is possible to apply the charge more efficiently than using a charger that is a non-contact type charge applying member.
Further, by adjusting the volume resistivity of the conveyance belt 51 to a value equal to or higher than the volume resistivity of the intermediate transfer belt 31, the transfer of the recording material P from the transfer unit 301 to the conveyance belt 51 can be made smooth. Can do.
Further, since the contact-type charge imparting member is a roller-like suction roller 52, uniform charge can be imparted to the transport belt 51, and the electrostatic adhesion force between the transport belt 51 and the recording material P can be uniformly and efficiently increased. be able to. Further, since the suction roller 52 is a support member located inside the region surrounded by the conveyance belt 51, it is possible to save space and reduce the number of members, compared to providing a charge imparting member on the outside.
Further, by grounding the static elimination / separation roller 54 constituting the separation unit 502, it is possible to perform good separation at the separation unit 502 between the recording medium P and the conveyance belt 51.
Further, by adjusting the volume resistivity of the belt slip prevention rib 57 to a value equivalent to the volume resistivity of the conveyance belt 51, the charge divergence of the conveyance belt 51 is suppressed, and the recording medium P and the conveyance belt 51 are in close contact with each other. The fall of property can be prevented.

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 a detailed view when the developing unit is used as a first image unit. FIG. 3 is a detailed view when the developing unit is used as a first image unit. Explanatory drawing of the recording material conveyance apparatus which concerns on embodiment. Explanatory drawing of the width direction of the recording material conveyance belt which concerns on embodiment. Explanatory drawing of the conveyance direction length which concerns on embodiment. Explanatory drawing of the delivery length which concerns on embodiment. Explanatory drawing of the belt slip prevention rib which concerns on embodiment. Explanatory drawing of the slack of the recording body which concerns on the comparative example 9. FIG.

Explanation of symbols

1 Photoconductor (Y, C, M, K after the number in the color of the toner to be handled)
2 Cleaning device
2a cleaning blade 2b cleaning brush 2c waste toner collecting means 3 charging charger 4 exposure device 5 developing device 5a developing roller 5b regulating blade 5c, 5d stirring means 5e toner sensor 20 first image unit 20a first intermediate transfer belt cleaning device 21 first 1 Intermediate transfer belt 22 Primary transfer roller
DESCRIPTION OF SYMBOLS 23 Belt support roller 24 Drive roller 26 Image-receiving surface maintenance roller 27 Tension roller 28 Transfer counter roller 29 Bending roller 30 Second image carrier unit 30a Second image carrier belt cleaning device 31 Second intermediate transfer belt 32 Second image carrier Unit primary transfer roller 33 Cleaning backing roller 34 Drive / transfer facing roller 36 Image-receiving surface maintaining roller 37 Tension roller 40 Paper feed device 40a Upper paper feed device 40b, c, d Paper feed cassette 41A, B, C, D Paper feeding / separating means 42A, B, C pair of conveyance rollers 43A, B, C recording medium conveyance path 44 lateral registration correction mechanism 45 registration roller pair 46 secondary transfer roller 47 transfer charger 50 recording medium conveyance device 50a conveyance belt cleaning device 51 Conveying belt 52 Adsorption roller 54 Static neutralization Separation roller 55 cleaning the backing roller 57 belt shift preventing rib 60 fixing device 70 cooling rollers 71 discharge roller pair
75 Discharge stack unit 80 First image forming unit (Y, C, M, K indicating the color to be handled behind)
81 Second image forming unit (attached Y, C, M, K indicating the color to be handled behind)
84 Toner cartridge housing 85 Toner cartridge (Y, C, M, K indicating the color to be handled behind)
87 Waste toner recovery unit 90 Operation / display unit (unit)
DESCRIPTION OF SYMBOLS 95 Electrical equipment / control apparatus 100 Image forming apparatus 200 Image reading apparatus 300 Additional sheet feeding apparatus 301 Image transfer unit to recording medium 601 Fixing unit A1, A2 An arrow indicating a direction in which an intermediate transfer belt can be installed
Y Yellow C Cyan M Magenta K Black Q Static eliminator P Recorder L1, L2 Transport direction length L3, L4 Delivery length W Conveyor belt width length

Claims (7)

From a transfer unit that transfers a visible image to an image carrier from an image carrier that carries and conveys the visible image, to a fixing unit that fixes the visible image to the recording member,
A recording medium conveying member that carries the sheet-like recording medium having an electrostatic charge opposite in polarity to the charge of the visible image on the surface and conveys the recording medium by endless movement;
In a recording material transport apparatus having a charge imparting member that imparts a charge having a polarity opposite to that of the charge on the recording material transport member to the recording material transport member,
The recording material transport apparatus according to claim 1, wherein the charge imparting member is a contact type charge imparting member that contacts the recording material transport member and imparts a charge. In the recording material transport apparatus according to claim 1,
An image forming apparatus characterized in that the volume resistivity of the recording material conveying member is equal to or greater than the volume resistivity of the image carrier in the vicinity of the transfer means. In the recording material transport apparatus according to claim 1 or 2,
The recording body transport member is a recording body transport belt that is stretched over two or more support members and transports the recording body,
The recording material transport apparatus according to claim 1, wherein the contact-type charge applying member contacts the inside of the recording material transport belt to apply a charge. In the recording material transport apparatus according to claim 3,
The recording material transport apparatus, wherein the support member has a configuration as the contact-type charge imparting member. In the recording material transport apparatus according to claim 3 or 4,
Of the two or more support members,
A separation portion between the recording body and the recording body transport belt which is the most downstream side in the recording body transport direction of the recording body transport belt;
A recording medium conveying apparatus characterized in that the recording medium conveying belt is supported from the inside, and a separating portion supporting member constituting the separating portion is grounded. The recording medium conveying apparatus according to claim 3, 4 or 5,
A belt slip prevention member is provided inside the recording material transport belt,
The recording medium conveying apparatus, wherein the belt deviation preventing member has a volume resistivity equivalent to that of the recording medium conveying belt. An image carrier for carrying a visible image;
Visible image forming means for forming a visible image on the image carrier;
Transfer means for transferring the visible image on the image carrier to the recording body on the recording body holding member while moving the recording body holding member for holding the recording body in a predetermined direction;
In an image forming apparatus having fixing means for receiving a recording medium after passing through the transfer means and fixing the visible image on the recording medium,
7. An image forming apparatus using the recording medium conveying apparatus according to claim 1, 2, 3, 4, 5, or 6 as a recording medium conveying means for conveying a recording medium from the transfer means to the fixing means.

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