JP2006227292A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents degradation in an image during conveyance and achieves high image quality by keeping the fixed conveyance speed of a recording medium. <P>SOLUTION: The image forming apparatus is equipped with: a first image carrying unit 20 to carry a first image on a first image carrying belt 21; a second image carrying unit 30 to carry a second image on a second image carrying belt 31; a first transfer station including a first transfer means 46 to transfer the first and second images onto the first surface of a recording material P; a second transfer station including a second transfer means 47 to transfer images onto the second surface of the recording material; a recording material conveying path 43A including a conveying means to supply and convey a recording material between the first and second transfer stations; a conveying means 50 to convey a recording material exiting the second image carrying unit 30 to a heating and fixing device 60; and the heating and fixing device 60 to fix images on both surfaces. In the apparatus, the conveyance speed of the first image carrying unit 20 is detected to control the conveyance speed of the second image carrying unit 30, the conveying means 50 and the heating and fixing means 60. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device and an image forming apparatus that transfer a toner image formed on a photoreceptor to a transfer material such as transfer paper and fix the transferred toner image.

  Conventionally, as a method for recording images on both the front and back sides of a transfer paper, a method is generally used in which the transfer paper once passed through the fixing device is reversed and the toner is transferred to another side of the transfer paper and fixed again. Yes.

  However, in this method, the transfer paper is changed in the transport direction, and once the transfer paper is heated and pressurized through the fixing device, the transfer paper is curled. Have.

  As a method for solving such a problem, for example, there is one disclosed in Patent Document 1. In this method, after toner images are formed on both sides of the transfer paper, fixing is performed once.

  Specifically, the first image formed on the photoconductor is transferred to the transfer belt by the first transfer unit, and then the second image formed on the photoconductor is transferred to one side of the transfer paper by the first transfer unit. Transcript to. Thereafter, the first image on the transfer belt is transferred to the other surface of the transfer paper by the second transfer means, whereby the image is transferred and fixed on both sides of the transfer paper.

  However, in the method of Patent Document 1, since the leading edge of the transfer paper is in a free state until the leading edge of the transfer paper having an unfixed image is unloaded from the transfer belt and loaded into the fixing device, it is unfixed. The toner image is disturbed.

  For this reason, in the case where the toner image is transferred to both surfaces of the transfer paper as in Patent Document 2, and the transfer paper is transported to the fixing device, a spur is installed in the transport path to prevent unfixed toner image disturbance. It is possible to do so.

JP-A-1-209470 JP-A-10-142869

  However, when a spur is installed in the conveyance path as in Patent Document 2 to prevent the unfixed toner image from being disturbed, the spur that transports the transfer paper carrying the unfixed toner image to the fixing device over time. The toner becomes dirty, and the toner moves to the image, resulting in a deterioration in image quality. In addition, if vertical conveyance is adopted for the purpose of downsizing, the result is a drop in the conveyance quality from the stiffness of the recording medium.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide an image forming apparatus that achieves high image quality by preventing the image deterioration during conveyance by keeping the conveyance speed of the recording medium constant. It is to provide.

  In order to solve the above-mentioned problem, the invention described in claim 1 is an image forming apparatus, and can carry a first image formed by a first image forming unit on a first image carrying belt. A first image carrying unit; a second image carrying unit capable of carrying a second image formed by the second image forming unit on a second image carrying belt; and the first and second image carrying units carry the second image carrying unit. A first transfer station including first transfer means for transferring the first image and the second image to the first surface of the recording medium; and a second transfer for transferring the first image and the second image to the second surface of the recording medium. A second transfer station including a recording medium, a recording medium conveyance path including a conveyance means for supplying and conveying the recording medium between the first and second transfer stations, and a recording medium exiting the second image carrier unit. Conveying means that conveys up to In the image forming apparatus having a heating fixing device for fixing, to detect the transport speed of the first image bearing unit, the second image bearing unit, characterized in that to control the speed of the conveying means and heat fixing means.

  According to a second aspect of the present invention, in the first aspect of the present invention, the first image carrying unit, the second image carrying unit, the conveying unit, and the heat fixing device are independent drive devices. It is characterized by having.

  According to a third aspect of the present invention, in the first aspect of the present invention, the first image carrying belt and the second image carrying belt are not in contact with each other in the first transfer station and the second transfer station. In addition, among the transfer means provided at each transfer station, a transfer roller to which a bias can be applied is employed as the transfer means provided upstream in the conveyance direction of the recording medium.

  The invention described in claim 4 is characterized in that, in the invention described in claim 1, the conveying means is configured in an endless belt shape.

The invention described in claim 5 is characterized in that, in the invention described in claim 1, the volume resistance value of the conveying means is 10 ⁶ to 10 ¹² Ωcm.

  The invention described in claim 6 is characterized in that, in the invention described in claim 1, the speed is controlled by the type of the recording medium.

Further, in the invention described in claim 7, in the invention described in claim 1, when the recording medium having a basis weight of 90 g / m ² or more is used, the speed of the conveying means and the fixing means is halved. It is characterized by.

  According to an eighth aspect of the present invention, in the first aspect of the present invention, recording is performed from substantially the same sheet supply and supply surface as the recording medium conveyance path upstream of the recording medium conveyance path in the recording medium conveyance path. A sheet feeding device capable of supplying a body is provided.

  The invention described in claim 9 is characterized in that, in the invention described in claim 1, the recording material conveyance path is substantially the same surface from the paper supply surface of the paper supply portion to the nip portion of the fixing device. .

  The invention described in claim 10 is the invention described in claim 1, characterized in that the average circularity of the toner used is 0.90 to 0.99.

  The invention described in claim 11 is the invention described in claim 1, wherein the shape factor SF-1 of the toner used is 120 to 180 and the shape factor SF-2 is 120 to 190. It is characterized by.

  The invention described in claim 12 is the invention described in claim 1, wherein Dv / Dn of the toner to be used (Dv is a volume average particle diameter (μm), Dn is a number average particle diameter (μm)). Is 1.05-1.30.

  According to the present invention, a high-quality image can be obtained without disturbing the unfixed images on both sides by providing a conveying means between the transfer unit and the fixing nip of the fixing device and making all the conveying speeds constant. (Unfixed images on both sides can be conveyed to the fixing unit without image deterioration).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the image forming apparatus main body 100 shown in FIG. 1, the first image carrier unit 20 having the first image carrier belt 21 that moves endlessly in the direction of the arrow at the upper part with the recording material conveyance path 43A as a boundary, A second image carrier unit 30 having a second image carrier belt 31 that moves endlessly in the direction of the arrow is disposed at the bottom. Four first image forming units 80Y, 80C, 80M, and 80K are provided on the upper tension surface of the first image carrier belt 21, and four first image forming units 80Y, 80C, 80M, and 80K are provided on the inclined tension surface of the second image carrier belt 31. Two image forming units 81Y, 81C, 81M and 81K are provided. 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. Y, C, M, and K are also used in the same meaning with respect to the photoreceptor 1 provided in the first and second image forming units and rotating together with the first image carrying belt 21 and the second image carrying belt 31. . The photoreceptors 1Y to 1K are arranged at the same interval, and at least at the time of image formation, are in contact with a part of the stretched portion with the image bearing belts 21 and 31, respectively. This contacting surface is called an image receiving surface, and the mutual positional relationship is shown in FIG.

  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, during the operation of the image forming apparatus 100, charging means is provided around a cylindrical photosensitive member 1 that is rotatably supported by a drive source (not shown) so as to rotate in the direction of the arrow in accordance with an electrophotographic process. 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, a potential sensor S1, and an image sensor S2 are disposed.

  The photoreceptor 1 is obtained by forming an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylindrical 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.

  As the charging means, in addition to the charger 3, a type that is brought into contact with the surface of the photoreceptor 1, for example, a charging roller can be employed.

  The development in this embodiment 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 photosensitive member 1 by a laser beam with respect to the negatively charged photosensitive member 1 is developed with toner of a predetermined color having the same polarity (negative polarity) as the charged polarity of the photosensitive member. And become a visible image. So-called reversal development is performed.

  When each color toner of yellow (Y), cyan (C), magenta (M), and black (K) is consumed by a developing device that handles each color, the toner is detected by the magnetically permeable toner detecting means 5e, and the image forming apparatus The toner of each color is supplied to each developing device 5 from a toner cartridge 86 provided in the toner cartridge housing 85 inside 100 by a supply unit (not shown).

  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 means 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 line of magnetic force is formed inside. Has a magnet. The toner used has an average circularity of 0.90 to 0.99, a shape factor SF-1 of 120 to 180, a shape factor SF-2 of 120 to 190, and Dv / Dn of 1.05 to 1.30. is there. [Dv is the volume average particle diameter (μm), Dn is the number average particle diameter (μm)]
The second image forming units 81Y to 81K used in the second image carrier unit 30 will also be described as the second image forming unit 81 as a representative 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 photoreceptor 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, the first image forming units 80Y to 80K can be combined with a coupling unit with the image forming apparatus 100, for example, a coupling unit with a driving unit, an electrical connection unit, a toner supply unit, and a toner discharge unit. The second image forming units 81Y to 81K can be compatible. 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.

  As a first condition that can be used by the first image carrier unit 20 and the second image carrier unit 30 in the form of an axis object with the first and second image forming units as the center of the y-axis, the photoreceptor 1 A peripheral surface on which no member for image formation is provided is secured around the periphery, that is, a wide range in which the image bearing belt can contact is secured. The second condition is that the arrangement angle of the first image carrier belt 21 and the second image carrier belt 31 is appropriate.

  The above first condition and second condition will be described with reference to FIGS. 3 or 4, the image bearing 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 image carrying belt can be installed in a range where the belt does not contact the cleaning device 2. The inclusion of the second image carrier belt 31 in FIG. 3 shows an image carrier belt on which the target image forming unit can be arranged with respect to the y axis including the rotation shaft 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, there is an influence of earth gravity, and at least in the developing device 5, the toner is agitated and the developing roller 5a is moved. The toner replenishment conditions are different and must be optimized, and it is impossible to share parts.

  As shown in FIG. 2, the 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 is such that the angle α exceeds 180 degrees and is 270 degrees, preferably 210 degrees to 255 degrees. Then, as the image forming unit, the first image carrying belt shown in FIG. 3 and the second image carrying belt shown in FIG. 4 can be adopted. In other words, as described above, it is possible to avoid an image forming unit that makes it impossible to share parts.

  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 bearing belt is stretched horizontally and flatly, and the second image bearing belt is stretched long and inclined in the longitudinal direction. Although the space in the height direction of the two-image carrying belt becomes large, it is possible to install a sheet feeder having a height substantially the same as the height occupied by the second image-carrying belt. As a result, a paper feeding device capable of storing a large amount of paper can be installed, and the paper feeding surface on the upper surface of the paper feeding device and the recording material conveyance path can be made substantially the same height, thereby ensuring the paper feeding / conveying reliability. .

  A first image carrier belt 21 as an image carrier that is supported by a plurality of rollers 23, 24, 25, 26 (two), 27, 28, 29 and runs in the direction of the arrow is a first image forming unit 80Y. It is provided below the photoreceptors 1Y, 1C, 1M, and 1K at -80K. The image bearing belt 21 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. Further, a primary transfer roller 22 is provided on the inner peripheral portion of the first image carrying belt 21 so as to face each of the photoreceptors 1Y, 1C, 1M, and 1K.

  A cleaning device 20 </ b> A is provided on the outer periphery of the first image carrying belt 21 at a position facing the roller 23. The cleaning device 20 </ b> A wipes off unnecessary toner remaining on the surface of the image bearing belt 21 and foreign matters such as paper dust.

  The members related to the image carrier belt 21 are integrally configured as the first image carrier unit 20 and can be attached to and detached from the image forming apparatus 100.

  A second image carrier belt 31 as an image carrier that is supported by a plurality of rollers 33, 34, 35, 36 (two), 37, 38 and runs in the direction of the arrow is a second image forming unit 81 </ b> Y to 81 </ b> K. In contact with the photoconductors 1Y, 1C, 1M, and 1K. The image carrying 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 image carrying 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 image carrying belt 31 at a position facing the roller 33. The cleaning device 30 </ b> A wipes away unnecessary toner remaining on the surface of the image bearing belt 31 and foreign matters such as paper dust.
The members related to the image carrier belt 31 are integrally configured as the second image carrier unit 30 and can be attached to and detached from the image forming apparatus 100.

Here, the configuration and material of the image bearing belt will be described. The image carrying 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, and the toner images carried by the respective photoreceptors 1 are transferred to the primary transfer rollers 22 and 32. Has a resistance value that enables electrostatic transfer to the belt surface. In one embodiment, carbon is dispersed in polyamide, and the volume resistance value 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.

The transport belt 51 is, for example, a belt based on a resin film or rubber having a base thickness of 50 to 600 μm, and has a resistance value that enables the recording medium to be electrostatically adhered to the belt surface by an applied bias. It is what you have. In one embodiment, carbon is dispersed in polyamide, and the volume resistance value 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.

Regarding the configuration of the primary transfer roller, as one embodiment, the primary transfer rollers 22 and 32 are obtained by coating the surface of a metal roller serving as a core metal with a conductive rubber material. A bias is applied from the power supply. In the conductive rubber material, carbon is dispersed in urethane rubber, and the resistance is adjusted to a volume resistance of about 10 ⁵ Ωcm.

  Monochrome recording using only black toner is also possible. 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. In this embodiment, an internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, is supported so as to be rotatable around a certain point, and is rotated in a direction away from the photosensitive member. Thus, only the photosensitive member 1K comes into contact with the image carrier 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 in the vicinity of the support roller 28 on the outer periphery of the first image carrying belt 21. 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 rubber, and the volume resistance is adjusted to about 10 ⁷ Ωcm. The first image carrying belt 21 is carried by applying a bias to the first secondary transfer roller 46 while passing a recording medium (hereinafter referred to as paper P) between the first image carrying belt 21 and the secondary transfer roller 46. The toner image is transferred to the recording material P.

  A transfer charger 47 serving as a second secondary transfer unit is provided on the outer periphery of the second image bearing 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 applied to the discharge electrode from a power source (not shown). By applying a transfer current while passing the recording medium P between the image bearing belt 31 and the transfer charger 47, an image formed by toner carried by the second image bearing belt 31 is transferred to the recording medium P. The polarity of the transfer current applied 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 paper so as to be fed is provided. Paper feed device (tray) 40a storing a large amount of paper in a plurality of stages, for example, the upper stage, and three stages of paper feed cassettes 40b, 40c, and 40d below each can be pulled out to the right side (operation side) with respect to the paper surface. It is arranged. Among the sheets P stored in the sheet feed tray 40a and the sheet cassettes 40b, 40c, and 40d, the uppermost sheet is selectively fed and separated by the corresponding sheet feeding / separating means 41A to 41D. Only one sheet is reliably sent to the recording medium conveyance paths 43B and 43A by the plurality of conveyance roller pairs 42B.

  A pair of registration rollers 45 are provided in the recording medium conveyance path 43A in order to take a feeding timing for feeding the paper P to the secondary transfer position. Further, a jogger 44 for making the position perpendicular to the sheet conveyance direction a normal position is provided in the recording medium conveyance path 43A. The jogger 44 includes guide members that move from both sides toward the edge of the paper in the paper conveyance direction, and the guides press the paper from both sides of the running paper for a moment to align the paper at a predetermined position. .

  The sheet P is transported from the registration roller pair 45 toward a transfer area serving as a first transfer station including the first image carrying belt 21 and the secondary transfer roller 46. Thereafter, the sheet is conveyed toward a transfer area which is a second transfer station including the second image carrier belt 31 and the transfer charger 47.

  Note that the recording medium conveyance path 43C having the conveyance roller pair 42C can be supplied with a sheet from another sheet feeding device 300 that can be installed upstream in the conveyance direction. The upper sheet feed surface of the sheet feed tray 40a is arranged so that the uppermost sheet in the sheet feed tray 40a is fed and then conveyed substantially horizontally without being bent. Therefore, even thick paper and highly rigid paperboard can be reliably fed. In addition, it is advantageous 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 a sheet is provided at a key point of the recording material conveyance path, and serves as a trigger for various signals based on the presence of the sheet.

  In order to convey the sheet that has passed through the second transfer station on the extension of the recording material conveyance path 43A to the fixing nip in the heat fixing device 60 provided downstream in the conveyance direction of the recording material while maintaining a planar state. The recording medium transport means 50 is provided. The recording medium transporting unit 50 has rollers 52, 53, 54, 55, and 56 that support a conveyor belt 51 that moves endlessly in the direction of the arrow, and a cleaning device 50A that faces the roller 55 outside the conveyor belt 51. , An adsorption charger 57 for adsorbing the recording medium P facing the roller 56, and a charge eliminating / separating charger 58 facing the roller 57.

  The conveyance belt 51 that moves together with the recording medium P while being in contact with the unfixed toner image is negatively charged by the suction charger 57 with the same polarity as the polarity of the toner. A polyimide belt can be adopted as the transport belt 51. The surface is provided with releasability from the toner and has a chargeable resistance value.

  A fixing device 60 having a heating unit is provided on the downstream side of the recording material transport unit 50 in the paper transport direction. 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 this embodiment, the belt is run, and heaters H1 and H2 are arranged as heating elements on the belt conveyance roller. In order to make the color and glossiness of the images on both sides of the paper the same, the material, hardness, surface properties, etc. of the fixing roller and fixing belt are made equal. A cooling roller pair 70 having a cooling function is provided in the conveyance path after fixing in order to cool the sheet after fixing and stabilize the unstable toner state at an early stage. A heat pipe structure roller having a heat radiating portion can be employed. The cooled sheet is discharged and stacked by a discharge roller pair 71 on a discharge stack unit 75 provided on the left side of the image forming apparatus 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 amount of sheets can be stacked. It is also possible to pass the paper through the paper discharge stack unit 75 and transport the paper toward another post-processing apparatus. Another post-processing apparatus is an apparatus for bookbinding such as punching, cutting, folding, and binding.

  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 of this embodiment, the toner cartridge is common to the image forming units 80 and 81 arranged above and below, but can be separated. The toner cartridge 86K for black toner, which is highly consumed, can be set to 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 provided on the upper surface of the image forming apparatus 100, the display unit 90 is provided with a keyboard or the like, and conditions for image formation can be input, the state of the apparatus is displayed on the display unit, and the operator and Information exchange with the image forming apparatus is facilitated.

  The waste toner storage portion 87 provided in the image forming apparatus 100 is connected to the image forming unit cleaning device 2, the image carrier belt cleaning devices 20A and 30A, and the conveying belt 51 cleaning device 50A, and is collectively discarded. Collect and store foreign materials such as toner and paper dust. Since the cleaning devices (2, 20A, 20B, 50A) are not provided with a large-capacity waste toner storage unit, each 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.

  In the electrical / control device 95 provided in 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 heat fixing device 60 or heat generated from the electrical equipment. However, as a countermeasure, 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. Reference numeral 200 is a document reading device, and 300 is a paper feeding device that can be additionally installed.

  Next, the conveyance speed will be described. The first image carrier unit 20, the second image carrier unit 30, the conveying means 50, and the heat fixing device 60 each have a drive device (motor) (M), and the first image carrier unit 20 has an encoder (not shown). ) To detect the rotational output.

  Since this apparatus transports a recording medium having an unfixed image on both sides from transfer to fixing, the influence of speed fluctuation during transport has a great influence on the image. In particular, the difference in speed between the heat fixing device and the conveying means has a large influence, and if there is a difference in speed, slippage between the conveying belt 51 and the recording medium occurs and the image is disturbed. In order to solve the above problem, the present apparatus detects the output based on the speed of the first image carrier unit 20, and controls the speed of each unit.

  That is, since the second image carrier unit 30, the conveyance means 50, and the heat fixing device 60 detect the speed of the first image carrier unit 20 and determine the speed, the conveyance speed of the recording medium is always controlled to be constant.

  Next, the operation of the above configuration will be described. First, the operation during single-sided recording in which a full-color image is formed on one side of the paper P in the above configuration 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 of directly transferring an image carried on the first image carrying belt 21 to one side of the paper, and the other method is an image carried on the second image carrying belt 31. Is directly transferred onto one side of the paper.

  In the present embodiment, because of the configuration of the image forming apparatus 100, when an image carried on the first image carrying belt 21 is directly transferred to one side of the paper, the image is placed on the upper surface of the paper and the second image carrying belt. When the image carried on 31 is directly transferred to one side of the paper, the image is formed on the lower surface of the paper. 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. An explanation will be given of a method in which an image is carried on the first image carrying belt 21 and then transferred to a sheet 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 image carrying belt 21 and the first image forming units 80Y to 80K rotate. At the same time, the second image carrier belt 31 rotates. However, the photoreceptors 1Y, 1C, 1M, and 1K in the second image forming units 81Y to 81K are separated from the second image carrier belt 31 and are not rotated. Is done. 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 applied on the first image carrying 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.

  As a result, yellow, cyan, magenta, and black color toner images are carried on the first image carrying belt 21 as sequentially overlapping full color toner images, and are moved in the direction of the arrow together with the first image carrying belt 21. .

  At the same time, the recording medium P used for recording is fed from one of the paper feed trays 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 feeding and transporting. The pair of rollers 42B and 42C are conveyed to the recording material conveyance path 43C. Before the leading end of the recording body is not picked up by the registration roller pair 45, the jogger 44 operates to push both sides of the recording body from both lateral directions with respect to the conveyance direction of the recording body. Position alignment is achieved. The registration roller pair 45 is stationary, and the leading edge of the recording body is stationary in a state where it enters the nip of the registration roller pair 45, but the position with the image on the first image carrier belt 21 is normal. The registration roller pair 45 rotates at the timing to convey the sheet to the transfer area.

  The full-color toner image on the first image carrying belt 21 is transferred to the upper surface of the paper P conveyed in synchronization with the first image carrying 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.

  Thereafter, the surface of the first image carrying 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, respectively. It is removed from the surface of the photoreceptor. The surface of each photoconductor is subjected to a discharging operation of residual potential by the discharging device 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 of the photosensitive member surface after exposure and the density of the toner adhering to the photosensitive member surface 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 to which the toner image that has been superposed and carried on the image carrying belt 21 is transferred is transferred toward the heat fixing device 60 by the carrying belt 51 of the carrying device 50. The surface of the transfer belt 51 is charged in advance by an adsorption charger 57 for the recording medium so that the recording medium P can be reliably transferred together with the conveying belt 51. The neutralization / separation charger 58 operates so that the paper P is separated from the transport belt 51 and is reliably sent to the heat 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 heat fixing device 60, and are melted and mixed to completely form a color image. Until the fixed toner is completely fixed on the paper, it is rubbed by 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 means, operates to cool the toner and the paper. 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 punching processing or to 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 material P, the image formation in the first image forming units 80Y to 80K is not performed, and the image data of the young pages is sequentially formed for page alignment. Although the formation is different, the details are omitted because it is basically the same as the one-side recording process described above.

  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, the first image carrying belt 21 displays an image for each color sequentially formed by the first image forming units 80Y, 80C, 80M, and 80K described in the single-sided recording operation. The image for each color sequentially formed by the second image forming units 81Y, 81C, 81M, 81K is applied to the second image carrier belt 31 substantially in parallel with the step of carrying out the primary transfer sequentially and carrying it as the first image. A step of sequentially performing primary transfer and carrying as a second image is performed. With the configuration shown in FIG. 1, in order for the first image and the second image to coincide with each other at the leading edge in the sheet transport direction, the second image is formed after the start of the first image formation. Is started. Further, since the sheet is stopped and retransmitted by the registration roller pair 45, the sheet is fed in consideration of the time, and the surface roughness of the front and back of the recording medium is measured between the rollers 42 by the measuring machines 150 and 160. Further, the jogger 44 is used for alignment. The registration roller pair 45 transports the sheet to a first transfer station constituted by a transfer roller 46 as a first secondary transfer unit and the first image carrying belt 21 at a timing. A transfer current having a positive polarity is applied to the transfer roller 46, and the image is transferred from the first image carrying belt to one side (upper surface in the drawing) of the paper P.

  Thus, the sheet P having an image on one side is continuously sent to the second transfer station having the transfer charger 47 as the second secondary transfer means by the transfer action of the transfer roller 46. Then, by applying a positive transfer current to the charger, the full-color second image previously carried on the second image carrying belt 31 is transferred onto the lower surface of the paper P at a time.

  The paper P on which the full color toner images are transferred on both sides in this way is transported to the fixing device 60 by the transport belt 51. The surface of the transport belt 51 is charged with the same negative polarity as the polarity of the toner by the suction charger. The unfixed toner on the lower surface of the paper is prevented from transferring to the belt. An alternating current is applied to the charge removal / separation charger 58, and the paper is separated from the belt 51 and transferred to the heat fixing device 60. The toner image on both sides of the paper is melted and mixed by the fixing process by heat of the heat fixing device 60. The sheet subsequently passes through the cooling roller pair and is discharged onto the discharge stack unit 75 by the discharge roller 71.

  When double-sided recording is performed on a plurality of pages of paper, the image formation order is controlled so that the image of a young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. The order of the pages is 1 page in order from the top, 2 pages on the back, 3 pages on the second sheet, and 4 pages 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.

In the case of thick paper printing, in the case of thick paper printing with a grammage exceeding 90 g / m ² , this fixing system will cause insufficient fixing. In the case of thick paper, the system speed is reduced by half to prevent fixing failure. Correspond. In this case, the speed is switched after the recording medium exceeds the second transfer means. At that time, it is a condition that the recording medium does not enter the nip of the fixing unit. Therefore, a distance from the transfer unit 50 to the nip of the fixing device 60 is ensured more than the maximum image length of the recording medium.

  As described above, in the image forming apparatus according to the present embodiment, the first image formed by the first image forming units 80Y, 80C, 80M, 80K can be carried on the first image carrying belt 21. An image carrier unit 20; a second image carrier unit 30 capable of carrying a second image formed by the second image forming units 81Y, 81C, 81M, 81K on the second image carrier belt 31; A first transfer station including first transfer means 46 for transferring the first image carried by the second image carrying unit and the second image onto the first surface of the recording medium P; A recording medium conveyance path including a second transfer station including a second transfer means 47 for transferring to the surface of the recording medium, and conveyance means 42A and 45 for supplying and conveying the recording medium between the first and second transfer stations. 43A and second image carrier unit 3 In the image forming apparatus including the conveyance unit 50 that conveys the recording medium that has come out to the heat fixing device 60 and the heat fixing device 60 that fixes the images on both sides, the conveyance speed of the first image carrier unit 20 is detected, and the second image is detected. It is characterized in that the speeds of the carrying unit 30, the conveying means 50, and the heat fixing device 60 are controlled. For this reason, it is possible to obtain a high-quality print by eliminating image defects due to speed fluctuations by making all the conveyance speeds constant.

  In the present embodiment, the first image carrying unit 20, the second image carrying unit 30, the conveying unit 50, and the heating and fixing unit 60 have a single driving device. Therefore, by providing each with a driving device, speed control becomes possible and the conveyance speed can be made constant.

  In the present embodiment, the first intermediate transfer belt and the second intermediate transfer belt are not in contact with each other in the first transfer station and the second transfer station, and the transfer means disposed in each transfer station A transfer roller 46 to which a bias can be applied is adopted as the transfer means provided upstream in the recording material conveyance direction. Therefore, the transfer means is provided in each of the first and second stations, and the transfer roller is used in the first station, so that the recording medium can be reliably conveyed, and the recording medium is reliably conveyed in the transfer station, and the image is distorted. In addition, it is possible to provide a one-pass double-sided image forming apparatus that realizes reliable image transfer onto a recording medium that does not generate any problems.

  Moreover, in this embodiment, the said conveyance means 50 is comprised by the endless belt shape.

  For this reason, the recording medium can be conveyed to the fixing device in a stacked state without being separated from the second image carrier, and image deterioration before the fixing process can be prevented.

Moreover, in this embodiment, the volume resistance value of the conveyance means 50 is 10 < ⁶ > -10 < ¹² > (omega | ohm) cm. For this reason, the sheet can be electrostatically brought into close contact with the belt surface by the bias applied by giving the conveyance means 50 a resistance value.

In the present embodiment, the speed is controlled by the type of the recording medium. for that reason,
By optimizing the speed of the fixing unit depending on the paper type, it is possible to provide an image forming apparatus that does not deteriorate the image quality (fixing failure).

In this embodiment, the speed of the conveying means 50 and the fixing means 60 is halved when using a recording medium having a basis weight of 90 g / m ² or more. Therefore, in the case of thick paper, a sufficient fixing time can be obtained by reducing the speed of the fixing unit, so that it is possible to provide an image forming apparatus in which the image quality does not deteriorate due to fixing failure.

  In the present embodiment, a sheet feeding device 40a capable of supplying a recording medium from substantially the same sheet feeding surface as the recording medium conveyance path is provided upstream of the recording medium conveyance path 43A in the conveyance direction of the recording medium P. Yes. Therefore, it is possible to provide an image forming apparatus that has a straight conveyance path, can supply and convey a high-rigidity recording medium, and can widely cope with the types and characteristics of the recording medium.

  In this embodiment, the recording material conveyance path is substantially the same surface from the paper feed surface of the paper feed unit to the nip portion of the fixing device. Therefore, it is possible to provide an image forming apparatus that has a straight conveyance path, can supply and convey a high-rigidity recording medium, and can widely cope with the types and characteristics of the recording medium.

  Subsequently, the terms “circularity”, “shape factors SF-1, SF-2”, and “particle size distribution” used throughout the present specification are defined and described in detail below.

(Circularity and circularity distribution)
The circularity is one parameter representing the shape of the toner. It is important that the toner in the present invention has a specific shape and shape distribution. An toner having an average circularity of less than 0.90 and an irregular shape that is too far from a spherical shape exhibits satisfactory transferability and dust. A high-quality image with no image cannot be obtained. As a method for measuring the shape, an optical detection band method is suitable in which a suspension containing particles is passed through an imaging unit detection band on a flat plate, and a particle image is optically detected and analyzed by a CCD camera. Toner having an average circularity of 0.90 to 0.99, which is a value obtained by dividing the perimeter of an equivalent circle having the same projected area obtained by this method by the perimeter of the actual particle, has high reproducibility with an appropriate density reproducibility. It was found to be effective in forming a clear image. More preferably, particles having an average circularity of 0.93 to 0.97 and a circularity of less than 0.94 are 10% or less. When the average circularity exceeds 0.99, in a system that employs blade cleaning or the like, poor cleaning occurs on the photosensitive member and the transfer belt, causing stains on the image. For example, when outputting an image with a low image area ratio, there is little transfer residual toner and there is no problem with poor cleaning. However, when outputting an image with a high image area ratio such as a color photographic image, If an untransferred image remains on the photoreceptor due to a defect or the like, a cleaning defect is likely to occur. If the above-mentioned cleaning failures occur frequently, further, the charging roller that contacts and charges the photoreceptor is contaminated, and the original charging ability cannot be exhibited.

(Measurement method of circularity)
The average circularity can be measured by a flow type particle image analyzer FPIA-2100 (manufactured by Toa Medical Electronics Co., Ltd.). As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance, and further measurement is performed. Add about 0.1-0.5g of sample. The suspension in which the sample is dispersed is obtained by performing dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser and measuring the shape and distribution of the toner with the above apparatus at a dispersion concentration of 3000 to 10,000 / μl. .

(Shape factors SF-1 and SF-2)
SF-1 and SF-2 are parameters representing the shape of the toner, and are familiar parameters in the field of powder engineering. As shown in FIG. 5, the shape factor SF-1 is a value indicating the ratio of the roundness of the shape of the spherical substance, and the maximum length MXLNG of the elliptical figure formed by projecting the spherical substance on a two-dimensional plane. It is expressed by a value obtained by dividing the square by the graphic area AREA and multiplying by 100π / 4.

That is, the shape factor SF-1 is expressed by the following equation:
SF-1 = {(MXLNG) ² / AREA} × (100π / 4)
Is defined by

  When the value of SF-1 is 100, the shape of the substance becomes a true sphere, and as the value of SF-1 increases, the shape of the substance becomes indefinite.

  Further, as shown in FIG. 6, the shape factor SF-2 is a numerical value indicating the ratio of the unevenness of the shape of the substance, and the square of the perimeter PERI of the figure formed by projecting the substance on the two-dimensional plane is the figure area. It is expressed as a value when divided by AREA and multiplied by 100 / 4π.

That is, the shape factor SF-2 is expressed by the following equation:
SF-2 = {(PERI) ² / AREA} × (100 / 4π). When the value of SF-2 is 100, there is no unevenness on the surface of the substance, and as the value of SF-2 increases, the unevenness on the surface of the substance becomes more prominent.

  In the embodiment of the present invention, a toner image is randomly sampled 100 times using an FE-SEM (S-800) manufactured by Hitachi, and the image information is stored in an image analysis apparatus (LUSEX3) manufactured by Nireco. Introduced and analyzed, calculated from the above formula.

  It has been clarified by the present inventors that the transfer efficiency increases when the toner shape approaches the spherical shape as much as possible (both SF-1 and SF-2 approach 100). This is because there is only a point contact between the toner particles and the thing (toner particles, image carrier, etc.) in contact with the toner particles due to the shape effect, so that the toner fluidity is increased or the toner is adsorbed on the image carrier, etc. This is thought to be because the force (mirror power) is weakened and is easily affected by the transfer electric field.

On the other hand, when the shape of the toner approaches a spherical shape, it is disadvantageous for mechanical cleaning (such as blade cleaning). As described above, this is because the toner fluidity is increased and the adsorbing force (mirroring force) on the image carrier is weakened so that the toner can easily pass through the slight gap between the cleaning member and the image carrier. End up. Therefore, from the viewpoint of cleaning properties, the shape of the toner is somewhat irregular (in the direction in which the value of SF-1 is greater than 100) or uneven (in the direction in which the value of SF-2 is greater than 100). It is more preferable.
(Dv / Dn (ratio of volume average particle diameter / number average particle diameter))
Dv / Dn is one of the parameters representing the toner particle size distribution. The toner has a volume average particle diameter (Dv) of 4 to 8 μm and a ratio (Dv / Dn) to the number average particle diameter (Dn) of 1.05 to 1.30, preferably 1.10 to 1.25. According to the dry toner, the particle size distribution of the toner becomes narrow, so that the following merits occur.

  A stable image can be formed at all times because a phenomenon such as selective development on the toner particle size surface (toner particles having a (suitable) toner particle size corresponding to the image pattern are selectively developed) hardly occurs. Can do.

  When a toner recycling system is mounted, a large amount of small-size toner particles that are difficult to transfer are recycled in quantity. However, since the toner particle size distribution is originally narrow, it is difficult to receive the above-mentioned action. Therefore, a stable image can always be formed. In the two-component developer, even if the toner balance for a long time is performed, the fluctuation of the toner particle diameter in the developer is reduced, and good and stable developability can be obtained even in the long-term stirring in the developing device.

  Even when used as a one-component developer, even if the balance of the toner is performed, the fluctuation of the toner particle diameter is reduced, the filming of the toner on the developing roller, and a blade for thinning the toner The toner was not fused to a member such as the above, and good and stable developability and an image were obtained even in the long-term use (stirring) of the developing device.

  In general, it is said that the smaller the particle size of the toner, the more advantageous it is to obtain a high-resolution and high-quality image, but it is disadvantageous for transferability and cleaning properties. is there. Further, when the volume average particle diameter is smaller than the range of the present invention, in the case of the two-component developer, the toner is fused to the surface of the carrier during a long period of stirring in the developing device, and the charging ability of the carrier is reduced, or the one-component development is performed. When used as an agent, toner filming on the developing roller and toner fusion to a member such as a blade for thinning the toner are likely to occur.

  Further, these phenomena are the same for the toner having a fine powder content larger than the range of the present invention.

  On the contrary, when the particle diameter of the toner is larger than the range of the present invention, it becomes difficult to obtain a high resolution and high quality image, and when the balance of the toner in the developer is performed, In many cases, the variation of the particle size becomes large. It was also clarified that the same applies when the volume average particle diameter / number average particle diameter is larger than 1.30.

  Further, when the volume average particle diameter / number average particle diameter is smaller than 1.05, there is a preferable aspect from the viewpoint of stabilizing the behavior of the toner and uniforming the charge amount, but the thin line portion is developed with small size particles. On the other hand, it is difficult to separate the functions depending on the toner particle diameter, such as developing a solid image mainly on large-size particles, which is not preferable.

(Measurement method related to toner particle size)
As an apparatus for measuring the particle size distribution of toner particles by the Coulter counter method, there are Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter). The measurement method is described below.

  First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the volume average particle diameter (Dv) and the number average particle diameter (Dn) of the toner can be obtained.

  As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

1 is a schematic central sectional view showing an internal configuration of an image forming apparatus to which the present invention is applied. FIG. 2 is a simplified diagram showing an arrangement of image carrier belts in FIG. 1. It is an enlarged view which shows one main part for image formation. It is an enlarged view showing the other main part for image formation. It is explanatory drawing regarding a shape factor. It is explanatory drawing regarding a shape factor.

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 Collection Unit 3 Charging Unit (Scorotron Charger)
4 exposure device 5 developing device 5a developing roller 5b regulating blade 5c, 5d stirring means 5e toner sensor 20 first image carrier unit 20a first image carrier belt cleaning device 21 first image carrier belt 22 primary transfer rollers 23 to 29 First image bearing belt support roller 23 Belt support roller (backing of cleaning device)
24 Drive roller 26 Image-receiving surface maintaining roller (2 pieces)
27 Tension roller 28 Transfer counter roller 29 Bending roller 30 Second image carrier unit 30a Second image carrier belt cleaning device 31 Second image carrier belt 32 Primary transfer rollers 33 to 38 for second image carrier unit Second image Supporting belt support roller 33 Cleaning backing roller 34 Driving / transfer facing roller 36 Image-receiving surface maintaining roller (two)
37 Tension roller 40 Paper feeding device 40a Upper paper feeding device (tray)
40b to 40d Paper feed cassettes 41A to 41D Paper feed / separation means 42A to 42C Transport roller pair 43A to 43C Recording medium transport path 44 Jogger 45 Registration roller pair 46 First secondary transfer means (secondary transfer roller)
47 Second secondary transfer means (transfer charger)
50 Recording medium transporting means 50a Conveyor belt cleaning device 51 Conveyor belts 52 to 56 Conveyor belt support roller 52 Receiving roller 54 Separation / charger facing roller 55 Cleaning backing roller 57 Adsorption charger 58 Static elimination / separation charger 60 Fixing device 70 Cooling roller pair 71 Paper discharge roller pair 75 Paper discharge stack section 80 First image forming unit (Y, C, M, and K attached to indicate 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)
95 Electrical Equipment / Control Device 100 Image Forming Device 200 Image Reading Device 300 Additional Sheet Feeder A1, A2 Arrow F Fan Y Yellow C Cyan M Magenta K Black Q Static neutralizer y axis (vertical coordinate axis)
α Angle formed by the image receiving surfaces of the first and second image bearing belts

Claims (12)

A first image carrying unit capable of carrying a first image formed by the first image forming unit on a first image carrying belt;
A second image carrying unit capable of carrying a second image formed by the second image forming unit on a second image carrying belt;
A first transfer station including first transfer means for transferring the first image and the second image carried by the first and second image carrying units to a first surface of a recording medium;
A second transfer station including second transfer means for transferring to the second surface of the recording medium;
A recording medium conveyance path including conveyance means for supplying and conveying the recording medium between the first and second transfer stations, and a conveyance means for conveying the recording medium exiting the second image carrier unit to the heat fixing device;
In an image forming apparatus comprising a heat fixing device for fixing images on both sides,
An image forming apparatus characterized in that the conveyance speed of the first image carrier unit is detected and the speeds of the second image carrier unit, the conveyance means and the heat fixing means are controlled.   The image forming apparatus according to claim 1, wherein the first image carrying unit, the second image carrying unit, the transport unit, and the heat fixing device have a single driving device.   In the first transfer station and the second transfer station, the first image carrying belt and the second image carrying belt are not in contact with each other, and the transfer means disposed in each transfer station is upstream in the recording medium conveyance direction. The image forming apparatus according to claim 1, wherein a transfer roller to which a bias can be applied is adopted as the deployed transfer unit.   The image forming apparatus according to claim 1, wherein the conveying unit is configured in an endless belt shape. The image forming apparatus according to claim 1, wherein a volume resistance value of the conveying unit is 10 ⁶ to 10 ¹² Ωcm.   2. The image forming apparatus according to claim 1, wherein the speed is controlled according to the type of the recording medium. ^2. The image forming apparatus according to claim 1, wherein when a recording medium having a basis weight of 90 g / m ² or more is used, the speed of the conveying unit and the fixing unit is halved.   2. The image according to claim 1, further comprising a sheet feeding device capable of supplying the recording medium from a substantially same sheet feeding and supply surface as the recording medium conveyance path upstream of the recording medium conveyance direction in the recording medium conveyance path. Forming equipment.   The image forming apparatus according to claim 1, wherein the recording medium conveyance path is substantially the same surface from a paper feeding surface of the paper feeding unit to a nip portion of the fixing device.   The image forming apparatus according to claim 1, wherein the toner used has an average circularity of 0.90 to 0.99.   The image forming apparatus according to claim 1, wherein the toner has a shape factor SF-1 of 120 to 180 and a shape factor SF-2 of 120 to 190.   2. The image according to claim 1, wherein the toner used has a Dv / Dn [Dv is a volume average particle diameter (μm) and Dn is a number average particle diameter (μm)] of 1.05 to 1.30. Forming equipment.

Images