Image forming apparatus, fixation alignment control method for image forming apparatus, and fixation alignment control program

Abstract

To provide an image forming apparatus that prevents defects such as wrinkles in and deformation of a recording medium in correspondence with deviation in conveyance during transfer of a toner image.SOLUTION: An image forming apparatus comprises a control unit that, upon detection of deviation in conveyance of a recording medium 9 between an intermediate transfer section 3 and a fixing unit 4, performs a movement in a first direction P1 in which the fixing unit 4 is inclined in a virtual plane 90 connecting respective nips 3N and 4N of the intermediate transfer section 3 and the fixing unit 4, and a movement in a second direction P2 in which the fixing unit is included in a plane perpendicular to the virtual plane 90, while setting the direction and the amount of movement.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a fixing alignment control method for the image forming apparatus, and a fixing alignment control program. [Background technology]

[0002] Electrophotographic image forming devices, such as laser printers and copiers, transfer a toner image onto a recording medium, such as paper, while sandwiching it between an intermediate transfer belt (an image carrier) and rollers and transporting it. The toner image is then fixed to the recording medium by sandwiching it between a pair of rollers (a fixing unit), one of which is heated, and transporting it while applying pressure. In electrophotographic image forming devices, if the recording medium experiences a skew or other misalignment during transport after the toner image has been transferred, the recording medium enters the fixing unit in a state of uneven undulation (single loop) across the width of the recording medium, resulting in wrinkles and creases that are difficult to repair. To address this issue, a known technology includes a means for detecting a single loop between the transfer and fixation of the toner image, and, upon detection, corrects the single loop by changing the recording medium transport speed (roller rotation speed) in the fixing unit. Furthermore, an image forming device has been disclosed that tilts the fixing unit within the recording medium transport plane to match the skew during transfer (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-237779 Summary of the Invention [Problem to be solved by the invention]

[0004] The image forming apparatus described in Patent Document 1 limits the upper limit of the tilt of the fixing unit to a range that can be absorbed by a loop of a predetermined size between transfer and fixation. Therefore, it is difficult to address large conveyance deviations that cannot be corrected by tilting the fixing unit. For example, if the leading edge of the recording medium enters the fixing unit while tilted to match the skew during transfer, and then the leading edge of the recording medium enters, it is difficult to prevent a one-sided loop from occurring. Furthermore, because continuous recording media such as roll paper are stretched evenly without slack, tilting the fixing unit can pull one edge (edge) of the recording medium across the conveyance width, potentially causing tearing. Furthermore, if a recording medium such as a resin film is stretched unevenly across the conveyance width, it may enter the fixing unit under such external force and be deformed by heat. Therefore, there is room for improvement.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent defects such as wrinkles and deformation of the recording medium by dealing with conveyance deviations during toner image transfer. [Means for solving the problem]

[0006] The above-mentioned problems of the present invention can be solved by the following configuration.

[0007] (1) a transfer unit that transfers a toner image onto a recording medium; a fixing unit that fixes the toner image onto the recording medium; An image forming apparatus comprising: a control unit that moves the fixing unit in a first direction, tilting it within one of two planes that intersect with each other and include the transport width direction of the recording medium, and moves it in a second direction, tilting it within the other plane.

[0008] (2) further comprising an image discrimination means for detecting image noise from the toner image fixed by the fixing unit; 2. The image forming apparatus according to claim 1, wherein the control unit sets a direction and an amount of movement of the fixing unit based on a location where the image noise occurs.

[0009] (3) A detection unit is further provided for detecting the recording medium between the transfer unit and the fixing unit, 2. The image forming apparatus according to claim 1, wherein the control unit sets a direction and an amount of movement of the fixing unit based on the detected position of the recording medium.

[0010] (4) The image forming apparatus according to (2) or (3), wherein the control unit sets the movement amount of the fixing unit depending on the thickness and / or density of the recording medium.

[0011] (5) The image forming apparatus according to (1), wherein the movement in the first direction is inclined within an imaginary plane connecting the nips of the fixing unit and the transfer unit.

[0012] (6) The image forming apparatus according to (5), wherein the control unit is capable of switching between a mode in which the fixing unit is permitted to move in the second direction and a mode in which the fixing unit is prohibited from moving in the second direction.

[0013] (7) The image forming apparatus according to (1), wherein the recording medium is transported between the transfer section and the fixing section without slack.

[0014] (8) The image forming apparatus according to (7), wherein the recording medium is a continuous recording medium.

[0015] (9) The image forming apparatus according to (1), wherein the recording medium contains a resin.

[0016] (10) The image forming apparatus according to (1), wherein the fixing unit rotates around one end of the nip of the fixing unit as an axis.

[0017] (11) A fixing alignment control method for an image forming apparatus including a transfer unit that transfers a toner image onto a recording medium and a fixing unit that fixes the toner image onto the recording medium, the method comprising: detecting a tilt of the recording medium between the transfer unit and the fixing unit; A fixing alignment control method that executes a step of moving the fixing unit in a first direction to tilt it within one of two planes that intersect with each other and include the transport width direction of the recording medium, and / or moving it in a second direction to tilt it within the other plane, so as to correct the tilt of the recording medium.

[0018] (12) To the computer, a procedure for detecting the inclination of a recording medium between a transfer unit and a fixing unit of an image forming apparatus; a step of setting a movement direction and a movement amount, in which the fixing unit is moved in a first direction to tilt the fixing unit in one of two planes that include the conveyance width direction of the recording medium and intersect with each other, and / or in which the fixing unit is moved in a second direction to tilt the fixing unit in the other plane, so as to correct the tilt of the recording medium; A fixing alignment control program that executes the above. [Effects of the Invention]

[0019] According to the image forming apparatus of the present invention, defects such as wrinkles in the recording medium can be prevented by dealing with conveyance deviations when a toner image is transferred onto the recording medium. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to the present invention. [Figure 2] 1 is a block diagram illustrating a configuration of an image forming apparatus according to the present invention. [Figure 3] FIG. 2 is a partially enlarged view of an intermediate transfer section and a fixing unit of the image forming apparatus according to the present invention, and is an external view illustrating the direction of movement of the fixing unit and one loop of the recording medium. [Figure 4A] 5A and 5B are schematic diagrams illustrating a fixing alignment control operation performed by the image forming apparatus according to the present invention. [Figure 4B] 5A and 5B are schematic diagrams illustrating a fixing alignment control operation performed by the image forming apparatus according to the present invention. [Figure 5A] 5A and 5B are schematic diagrams illustrating a fixing alignment control operation performed by the image forming apparatus according to the present invention. [Figure 5B]5A and 5B are schematic diagrams illustrating a fixing alignment control operation performed by the image forming apparatus according to the present invention. [Figure 6] 4 is a flowchart showing a fixing alignment control method for an image forming apparatus according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. Note that the size and positional relationship of components shown in the drawings may be exaggerated and the shape may be simplified for clarity. In the following description, identical or similar components are designated by the same reference numerals, and their description will be omitted where appropriate.

[0022] [Image forming apparatus] FIG. 1 is a schematic diagram of an image forming apparatus according to the present invention, seen from the side. The image forming apparatus 10 shown in FIG. 1 is a full-color, four-unit tandem intermediate transfer image forming apparatus. It has an external unwinder 81 and winder 82 and forms a color image on the surface of a continuous recording medium 9. As shown in FIGS. 1 and 2, the image forming apparatus 10 includes a control unit 1, four color image forming units 2y, 2m, 2c, and 2k, an intermediate transfer unit (transfer unit) 3, a fixing unit (fixing unit) 4, a conveying device 5 for conveying the recording medium 9, a media sensor 61, recording medium detectors 62, 63, and 64, an image reading device 65, a toner bottle mounting unit and hopper for supplying toner of each color as a recording agent, a housing (not shown) that houses these components, and an operation panel 7 (operation unit 71, display device 72) installed on the exterior of the housing. The control unit 1 is a printer controller for the image forming apparatus 10. On the other hand, the image forming units 2y, 2m, 2c, 2k, the intermediate transfer unit 3, the fixing unit 4, the conveying device 5, the toner bottle mounting unit and the hopper are the printer engine, which is the mechanical part of the image forming device 10, and perform the image formation (printing) process of adhering toner to the surface of the recording medium 9 while conveying it to form a toner image (image).

[0023] (Recording medium) The recording medium 9, which is the printing substrate of the image forming apparatus 10, is a long sheet-like member. The recording medium 9 has a width corresponding to the image forming apparatus 10, for example, approximately 330 mm or less, similar to that of an image forming apparatus for sheet-fed paper. The recording medium 9 is also supplied in lengths of, for example, several tens to several thousands of meters, and the unprinted area is cut off after printing is completed. The recording medium 9 can be, for example, paper, a plastic film such as polypropylene (PP) or polyethylene terephthalate (PET), or tack paper with an adhesive applied to the backside and releasably attached to release paper. The recording medium 9 is supplied to the image forming apparatus 10 in a form corresponding to the material, and is wound around a spool (not shown), for example. Below, each element constituting the image forming apparatus 10 will be described, starting with the printer engine.

[0024] (Image forming unit) Image forming units 2y, 2m, 2c, and 2k form toner images of the colors Y (yellow), M (magenta), C (cyan), and K (black), respectively, and when no distinction is made between colors, they will be referred to as image forming units 2. Image forming units 2y, 2m, 2c, and 2k each include a photosensitive drum 21, a charging device 22, an exposure device 23, a developing device 24, a drum cleaning device 25, and a motor (not shown) that rotates and drives the rotating elements of these.

[0025] The photosensitive drum 21 is an image carrier on whose surface (periphery) a monochromatic toner image is formed. It rotates around an axis perpendicular to the plane of the drawing in FIG. 1 and faces, in the circumferential direction, a charging device 22, an exposure device 23, a developing device 24, an intermediate transfer belt 31, and a drum cleaning device 25, in that order. The charging device 22 uniformly charges the surface of the photosensitive drum 21. The exposure device 23 irradiates the photosensitive drum 21 with a laser beam or the like based on a signal from the image processing unit 12 of the control unit 1, exposing the image formation area on the surface to form an electrostatic latent image. The developing device 24 includes a housing and, installed therein, a stirring / conveying means, a developing roller, a toner detection means, and the like. The developing device 24 charges the toner supplied from the toner supply port of the housing by stirring it with the carrier, and then supplies the charged toner to the photosensitive drum 21 via a developing roller equipped with a magnet. The electrostatic latent image on the surface of the photosensitive drum 21 is developed by the action of an electric field to form a toner image. The photosensitive drum 21 is pressed against the intermediate transfer belt 31 by a primary transfer roller 32 that faces the photosensitive drum 21 with the intermediate transfer belt 31 in between, and the toner image formed on the surface of the photosensitive drum 21 is transferred to the intermediate transfer belt 31. The drum cleaning device 25 is provided with a roll brush or a blade that is arranged to contact the surface of the photosensitive drum 21, and removes toner remaining on the surface of the photosensitive drum 21 after the toner image has been transferred to the intermediate transfer belt 31.

[0026] (Intermediate transfer unit) The intermediate transfer unit (transfer unit) 3 includes an intermediate transfer belt 31, on whose surface a full-color toner image is formed. The intermediate transfer unit 3 further includes four primary transfer rollers 32, a drive roller 33, a secondary transfer backup roller 34, driven rollers 36 and 37, a cleaning opposing roller 35, a belt cleaning device 38, a secondary transfer roller 39, a motor that rotates and drives the drive roller 33, and a toner adhesion amount detection means (not shown). The intermediate transfer belt 31 is an image carrier, and a full-color toner image is formed on its surface by sequentially transferring toner images from the photosensitive drums 21 of the image forming units 2y, 2m, 2c, and 2k. The intermediate transfer belt 31 is an endless belt, and is stretched around the drive roller 33, the secondary transfer backup roller 34, and driven rollers 36 and 37, with its outer periphery facing outward, and is fed in a fixed direction (clockwise in FIG. 1).

[0027] The primary transfer roller 32, drive roller 33, secondary transfer backup roller 34, cleaning opposing roller 35, driven rollers 36 and 37, and secondary transfer roller 39 are all installed with their rotation axes perpendicular to the plane of FIG. 1 , similar to the photosensitive drum 21 of the image forming unit 2. The primary transfer roller 32 is arranged facing each photosensitive drum 21 of the image forming units 2y, 2m, 2c, and 2k across the intermediate transfer belt 31, and presses the intermediate transfer belt 31 against the photosensitive drum 21. The drive roller 33 and driven rollers 36 and 37 are arranged to feed the intermediate transfer belt 31 along a predetermined trajectory together with the secondary transfer backup roller 34, and of these, the drive roller 33 is driven to rotate and feed the intermediate transfer belt 31 in a fixed direction. The drive roller 33 is preferably arranged at the most downstream position of the image forming units 2y, 2m, 2c, and 2k, i.e., downstream of the primary transfer roller 32 facing the photosensitive drum 21 of the image forming unit 2k. Therefore, the drive roller 33 is disposed between the primary transfer roller 32 and the secondary transfer backup roller 34. Meanwhile, the driven rollers 36 and 37 are disposed between the primary transfer roller 32, which faces the photosensitive drum 21 of the image forming unit 2y, and the secondary transfer backup roller 34. The secondary transfer backup roller 34 is disposed opposite the secondary transfer roller 39 across the intermediate transfer belt 31. The secondary transfer backup roller 34 presses the intermediate transfer belt 31 against the recording medium 9 that has been transported between the intermediate transfer belt 31 and the secondary transfer roller 39, thereby transferring the toner image on the surface of the intermediate transfer belt 31.

[0028] The cleaning counter roller 35 is disposed so as to contact the backside of the intermediate transfer belt 31 at the contact point with the belt cleaning device 38. The belt cleaning device 38 includes a roll brush or blade disposed so as to contact the surface of the intermediate transfer belt 31 and removes toner remaining on the surface of the intermediate transfer belt 31. The toner adhesion amount detection means detects the amount of toner of each color from the full-color toner image formed on the surface of the intermediate transfer belt 31. The toner adhesion amount detection means is, for example, a contact image sensor (CIS) and is composed of a light source such as an LED (Light Emitting Diode) and a photodetector. The toner adhesion amount detection means is disposed so as to face the surface of the intermediate transfer belt 31 between the photosensitive drum 21 of the most downstream image forming unit 2k and the secondary transfer backup roller 34. The secondary transfer roller 39 is disposed so as to face the secondary transfer backup roller 34 across the intermediate transfer belt 31 and forms a transfer nip (nip) 3N (FIG. 3) with the intermediate transfer belt 31. The secondary transfer roller 39 presses against the intermediate transfer belt 31 while transporting the recording medium 9 in cooperation with the intermediate transfer belt 31 , thereby transferring the toner image on the surface of the intermediate transfer belt 31 onto the surface of the recording medium 9 .

[0029] (Fuser unit) The fixing unit (fixing section) 4 fixes the toner image to the recording medium 9 by applying pressure and heat to the recording medium 9 onto which the toner image has been secondarily transferred at a fixing nip (nip) 4N (FIG. 3). The fixing unit 4 includes a pressure roller 41, a fixing belt 42, a heating roller 43, a fixing roller 44, a motor that rotates and drives the fixing roller 44, and a frame (not shown) that supports these components. In the present invention, the fixing unit 4 further includes a movement mechanism 45 that controls the orientation of the fixing unit 4 itself, and a detection means (not shown) such as an optical sensor that detects the tilt (orientation) of the fixing unit 4. The fixing belt 42 is an endless belt that is stretched between the heating roller 43 and the fixing roller 44. The heating roller 43 incorporates a heating means such as a halogen heater and heats the fixing belt 42. The pressure roller 41 is located downstream of the secondary transfer roller 39 in the conveyance direction of the recording medium 9, facing the fixing roller 44 across the fixing belt 42, and forms the fixing nip 4N together with the fixing belt 42. The pressure roller 41 conveys the recording medium 9 while pressing it against the fixing belt 42 supported by the fixing roller 44. The pressure roller 41, the heating roller 43, and the fixing roller 44 are installed with their respective rotation axes parallel to one another, and during normal conveyance, they are oriented perpendicular to the plane of the paper in FIG. 1, just like the secondary transfer roller 39 of the intermediate transfer unit 3. The fixing unit 4 may be any unit that includes two or more members that form a fixing nip. For example, the fixing unit 4 may not include the fixing belt 42 and the heating roller 43, and the fixing roller 44 may incorporate a heating means and form a fixing nip directly with the pressure roller 41.

[0030] The fixing unit 4 is installed so that it can be tilted relative to a reference (fixed position) position where the rotation axes of the pressure roller 41 and other components are in the transport width direction of the recording medium 9 in the image forming apparatus 10 (the direction perpendicular to the plane of the paper in FIG. 1). In this specification, the transport width direction refers to the transport width direction of the recording medium 9 in the fixing unit 4 when it is in its fixed position, and is therefore the same as the intermediate transfer unit 3 and the transport device 5 described below. The fixing unit 4 tilts as a whole while sandwiching and transporting the recording medium 9 between the pressure roller 41 and the fixing roller 44 via the fixing belt 42. To achieve this, the fixing unit 4 is installed such that a frame (not shown) supporting the axes of the pressure roller 41, the heating roller 43, and the fixing roller 44 can be tilted.

[0031] Here, the configuration for tilting the fixing unit 4 will be described with reference to FIG. 3. FIG. 3 is a partially enlarged view of the intermediate transfer section 3 and fixing unit 4, showing a portion of the intermediate transfer belt 31, the secondary transfer backup roller 34, the secondary transfer roller 39, the pressure roller 41, a portion of the fixing belt 42, and the fixing roller 44. In FIG. 3, the fixing unit 4 is in its normal position, and the fixing nip 4N is parallel to the transfer nip 3N of the intermediate transfer section 3. FIG. 3 also shows an imaginary plane 90 connecting the nips 3N and 4N of the intermediate transfer section 3 and the fixing unit 4. The imaginary plane 90 is the transport surface of the recording medium 9, which is sandwiched between the intermediate transfer belt 31 and the secondary transfer roller 39, and the fixing belt 42 and pressure roller 41 of the fixing unit 4 in its normal position, and is stretched flat and tight. Therefore, the imaginary plane 90 will be referred to as the transport surface 90 as appropriate.

[0032] In the present invention, the fixing unit 4 is installed so as to be movable and tiltable within two intersecting planes that include the conveyance width direction. Specifically, the fixing unit 4 is capable of movement in a first direction P1, in which the fixing unit 4 is tilted within the conveyance surface 90, and movement in a second direction P2, in which the fixing unit 4 is tilted within a plane that intersects with the conveyance surface 90. Herein, the plane that intersects with the conveyance surface 90 is a plane perpendicular to the conveyance surface 90, i.e., a plane whose normal is the conveyance direction on the conveyance surface 90. As an example, the fixing unit 4 rotates within the conveyance surface 90 in the first direction P1, using one end of the fixing nip 4N in the conveyance width direction (here, the left end, which is the near side in FIG. 1) as a fulcrum. In other words, the movement in the first direction P1 is performed around an axis S1, which is normal to the conveyance surface 90 and passes through this fulcrum. Hereinafter, in this specification, left and right refer to positions in the conveyance width direction. The fixing unit 4 rotates its left end in a plane perpendicular to the conveying surface 90 in the second direction P2, with the right end of the fixing nip 4N as a fulcrum. That is, the movement in the second direction P2 is performed around an axis S2 in the conveying direction, which passes through the fulcrum. The moving mechanism 45 for moving the fixing unit 4 can be configured with mechanical elements such as gears, cams, and biasing members (springs, etc.), as well as a motor. The tilting operation of the fixing unit 4 will be described later. The pivot points (axes S1 and S2) are provided on the frame of the fixing unit 4, and can therefore be a single point on an extension of the conveying direction center line of the fixing nip 4N (the intersection line with the plane connecting the rotation axes of the pressure roller 41 and the fixing roller 44), as shown in FIG. 3. However, it is preferable that the pivot point is not too far from the fixing nip 4N (fixing belt 42).

[0033] The first direction P1 does not have to completely coincide with the conveying surface 90, and is preferably within a plane at an angle of 45° or less to the conveying surface 90. For example, although this depends on the inclination angle of the conveying surface 90, the first direction P1 may be within a horizontal plane. The second direction P2 is preferably within a plane at an angle of 45° or less to a plane perpendicular to the conveying surface 90. The first direction P1 and the second direction P2 are preferably within two planes that intersect each other at an angle of 45° to 90°.

[0034] The range of movement of the fixing unit 4 depends on the length of the fixing unit 4 in the transport width direction. For example, if the length of the recording medium 9 in the transport width direction is up to 330 mm, the other end of the fixing nip 4N can move up to ±2 mm in both the first and second directions, with one end of the fixing nip 4N as the fulcrum. It is preferable that this movement distance be controllable to 0.1 mm or less. It is also preferable that the movement speed be 0.05 mm / s or less at the other end of the fixing nip 4N, which moves at the highest speed, with one end of the fixing nip 4N or its vicinity as the fulcrum, and that the movement speed can be further reduced. Alternatively, the fixing unit 4 may be configured to move intermittently in short increments.

[0035] (Transportation device) The conveying device 5 conveys the recording medium 9 at a predetermined speed in the direction indicated by the arrow, and passes the recording medium 9 sequentially between the intermediate transfer belt 31 and secondary transfer roller 39 of the intermediate transfer section 3, and between the fixing belt 42 and pressure roller 41 of the fixing unit 4. The conveying device 5 includes conveying rollers 51, 53, and 54, a registration roller 52, seven guide rollers 55, and a motor (not shown) that rotates the conveying rollers 51, 53, and 54 and the registration roller 52. The conveying rollers 51, 53, and 54, the registration roller 52, and the guide roller 55 suspend the recording medium 9 within the image forming apparatus 10 and rotate on a rotation axis that extends in the conveying width direction (the printing width direction, perpendicular to the plane of the paper in FIG. 1).

[0036] The conveying rollers 51, 53, and 54 each consist of two rollers (roller pairs) that rotate cooperatively while sandwiching the recording medium 9 from both sides. The registration roller 52 is disposed upstream of the secondary transfer roller 39 in the conveying direction and corrects the posture of the recording medium 9 entering between the intermediate transfer belt 31 and the secondary transfer roller 39 in the intermediate transfer unit 3. The registration roller 52, like the conveying rollers 51, 53, and 54, is a roller pair and can have a known configuration. In the image forming apparatus 10, one or more conveying rollers 51, 53, and 54 are disposed upstream of the registration roller 52 in the conveying direction and downstream of the fixing unit 4, and are further installed at locations corresponding to the conveying path of the recording medium 9. In this example, the conveying roller 51 is disposed upstream of the secondary transfer roller 39, and the conveying rollers 53 and 54 are disposed downstream of the fixing unit 4. Of these, the conveying roller 54 is disposed downstream of the image reading device 65, which will be described later. In this specification, upstream, downstream, front, and rear refer to those in the transport direction of the recording medium 9. The guide roller 55 is a driven shaft that is rotatably supported and rotates as the recording medium 9 is transported. The guide roller 55 is provided as needed, and is installed at a location according to the transport path of the recording medium 9.

[0037] (Media Sensor) The media sensor 61 detects the physical properties of the recording medium 9 supplied to the image forming apparatus 10. The type of recording medium 9 can be identified by comparing one or more physical properties of the recording medium 9, specifically, thickness, basis weight, and surface texture. In this embodiment, the media sensor 61 includes a thickness sensor, a basis weight sensor, and a surface texture sensor (not shown). These sensors can be any known device capable of detecting the recording medium 9 stretched between rollers (the conveying roller 51 and the upstream guide roller 55) of the conveying device 5. The thickness sensor is, for example, a rotary encoder type sensor. The basis weight sensor is, for example, a transmissive optical sensor equipped with multiple LEDs and photodiodes of different wavelengths, and can determine the basis weight based on the transmittance of light of each wavelength through the recording medium 9. The surface texture sensor is, for example, a reflective optical sensor, and can detect specular and diffuse reflections from the surface of the recording medium 9 to determine the surface roughness and gloss. These sensors output detected optical data (electrical signals converted from light intensity) to the control unit 1. In the image forming apparatus 10, the media sensor 61 is disposed near the upstream side of the most upstream conveying roller 51 of the conveying device 5, but the location is not particularly limited as long as it is upstream of the secondary transfer roller 39. Furthermore, if the media sensor 61 is not built into the image forming apparatus 10, it can be installed between the image forming apparatus 10 and the unwinder 81 as an external device.

[0038] (Recording Media Detector) The recording medium detectors 62 and 63 detect the recording medium 9 to detect slack in the stretched recording medium 9 and any misalignment with the conveying surface (the surface of the recording medium 9 conveyed in an ideal orientation). The recording medium detector 62 is located below the recording medium 9, between the registration roller 52 and the secondary transfer roller 39, and the recording medium detector (detection means) 63 is located below the recording medium 9, between the secondary transfer roller 39 and the fixing unit 4. The recording medium detectors 62 and 63 can be any known mechanical or optical sensor capable of detecting the thickness (height) position of the stretched recording medium 9. For example, a mechanical sensor can be used, which includes a rod-shaped actuator with a fan-shaped plate with multiple slits attached to its base, a light source, and a light-receiving element. This actuator is rotatably attached around its base, and its tip abuts against the back surface of the recording medium 9. When the recording medium 9 presses the actuator, the recording medium detectors 62 and 63 rotate. The light-receiving element detects light passing through the slits and outputs the information to the control unit 1. This makes it possible to detect the height position of the recording medium 9 at the installation location of the recording medium detectors 62, 63 and determine the degree of slack in the recording medium 9 (see, for example, Japanese Patent Application Laid-Open No. 10-59582). It is preferable that such recording medium detectors 62, 63 are each disposed at multiple locations in the transport width direction. If the positions of the recording medium 9 detected in the transport width direction differ or the timing of displacement is different, it is possible to detect a one-sided loop in the recording medium 9.

[0039] The recording medium detector 64 is disposed near the downstream side of the fixing unit 4 in order to detect a paper jam of the recording medium 9. A known mechanical or optical jam detection means can be applied to the recording medium detector 64. The image reading device 65 can also serve as the recording medium detector 64 and detect a jam from a delay in the image conveyance speed.

[0040] (Image reader) The image reading device 65 captures an image formed on the recording medium 9 being conveyed, and acquires image data. A known scanner or the like can be used as the image reading device 65. The scanner is a line image sensor that simultaneously captures the entire width of the recording medium 9 in the conveying width direction (full width), and outputs the acquired image data to the control unit 1. If the image reading device 65 is not built into the image forming device 10, it can also be installed as an external device between the image forming device 10 and the winder 82.

[0041] (Operation panel) The operation panel 7 includes an operation unit 71 such as buttons operated by a user (operator) and a display device (display means) 72 such as a liquid crystal display, and may be a touch panel display that integrates these. The operation unit 71 and the display device 72 may also be an external information terminal (not shown) such as a PC.

[0042] (Toner bottle mounting area, hopper) The toner bottle mounting section holds a toner bottle containing toner of each color. The toner bottle mounting section is equipped with a motor that rotates the toner bottle around its cylindrical axis, discharging an amount of toner from the toner bottle according to the amount of rotation. The toner bottle mounting section is also equipped with a sensor that detects when the toner bottle is empty. The hopper collects and temporarily stores the toner discharged from the toner bottle, and then supplies this toner to the developing device 24 of the image forming unit 2. A toner bottle mounting section and hopper are provided for each color of toner; that is, four of each are provided in the image forming apparatus 10.

[0043] (Control unit) The control unit 1 is a printer controller for the image forming apparatus 10, and as shown in FIG. 2, includes a drive control unit 11, an image processing unit 12, and a communication unit 13. The control unit 1 further includes a recording medium identification unit 14, transport error detection units 15, 16, and 17, and an image determination unit 18. To accommodate these elements, the control unit 1 includes a CPU (Central Processing Unit) and memory for storing software and temporarily storing input job data, and realizes the following processing using software programs. Note that some elements of the control unit 1, such as the image determination unit 18, may be provided in an external information terminal (not shown). The operation of each element of the control unit 1 will be described in detail below.

[0044] The drive control unit 11 drives and controls the printer engine, which is an element of the image forming apparatus 10 other than the control unit 1. That is, the drive control unit 11 drives the transport device 5 to transport the recording medium 9. The drive control unit 11 also drives the image forming unit 2, causes the exposure device 23 to form an electrostatic latent image on the surface of the photosensitive drum 21 based on the bitmap data converted by the image processing unit 12, and causes the developing device 24 to form a toner image of each color. The drive control unit 11 also drives the intermediate transfer unit 3 and the fixing unit 4 to transfer and fix the full-color toner image onto the surface of the recording medium 9 via the surface of the intermediate transfer belt 31. At this time, the drive control unit 11 sets the transport speed of the recording medium 9 by the transport device 5 and the rotation speeds of the photosensitive drum 21, drive roller 33, fixing roller 44, etc., and drives them at those speeds. In particular, in this embodiment, the drive control unit 11 controls the rotation speeds of the drive roller 33 and fixing roller 44 so that the recording medium 9 does not slacken between the intermediate transfer unit 3 and the fixing unit 4. Furthermore, if the transport error detection unit 15 detects a transport deviation of the recording medium 9, the drive control unit 11 adjusts the rotation speed of the registration rollers 52 to correct the transport deviation of the recording medium 9. If the transport error detection unit 16 detects slack in the recording medium 9, the drive control unit 11 adjusts the rotation speed of the fixing roller 44, etc., and if a transport deviation of the recording medium 9 is detected, the drive control unit 11 tilts the attitude of the fixing unit 4 to control the fixing alignment. The fixation alignment control by the drive control unit 11 will be described later. If the transport error detection unit 17 detects a paper jam in the recording medium 9, the drive control unit 11 stops driving the printer engine, such as the conveyance device 5, i.e., stops operation. The drive control unit 11 may also display the status of the image forming apparatus 10, such as the name and content of the job being executed (image, type of recording medium 9, number of copies or printing distance, etc.), printing conditions, machine trouble such as a toner bottle running out of toner, or a paper jam, on the operation panel 7 or a display of an information terminal connected to the image forming apparatus 10 (control unit 1) via the communication unit 13.

[0045] The image processing unit 12 performs digital image processing on image data included in job data input from an external device. Specifically, the image processing unit 12 converts the input image data into data in a print file format (for example, PDL (Page Description Language) data), and then performs rasterization processing to convert it into bitmap data.

[0046] The communication unit 13 is an interface that connects to an external device and transmits and receives job data, etc. Specifically, it receives commands from the operation panel 7 of the image forming apparatus 10, displays notifications, and also transmits and receives data by connecting to an information terminal such as a PC via a wired or wireless connection.

[0047] The recording medium identification unit 14 identifies the type of recording medium 9 supplied to the image forming apparatus 10. To do this, the recording medium identification unit 14 receives signals from various sensors included in the media sensor 61 and calculates the physical properties (thickness, basis weight, surface texture, etc.) of the recording medium 9 from these signals. Furthermore, the recording medium identification unit 14 receives and stores information (database) about various recording media used in the image forming apparatus 10 in advance, and identifies the type of recording medium based on the calculated physical properties of the recording medium 9. For example, it can determine whether the recording medium is paper or PP, and if it is paper, whether it is high-quality paper, recycled paper, gloss-coated paper (glossy paper), matte-coated paper, or special paper such as embossed paper.

[0048] The conveyance error detection unit 15 receives a signal from the recording medium detector 62 and determines whether there is a conveyance deviation of the recording medium 9 stretched between the registration rollers 52 and the intermediate transfer unit 3. The conveyance error detection unit 16 receives a signal from the recording medium detector 63 and determines whether there is a slack or conveyance deviation of the recording medium 9 stretched between the intermediate transfer unit 3 and the fixing unit 4. The conveyance error detection unit 17 receives a signal from the recording medium detector 64 and determines whether there is a paper jam in the recording medium 9.

[0049] The image determination unit 18 determines the quality of the image formed on the recording medium 9. The image determination unit 18, together with the image reading device 65, constitutes an image calibration control unit (ICCU) (image determination means). The image determination unit 18 receives data of the image formed on the recording medium 9 from the image reading device 65 and determines the quality (image quality) of this image. A known method can be applied as the determination method, and for example, the difference from the image data included in the job data is calculated. The image determination unit 18 may further detect image noise (bleed) from the image data and detect conveyance deviation from the positional deviation.

[0050] (Unwinding machine) The unwinder 81 is a device (unwinder, feeder) that supplies the recording medium 9 wound around a spool in a roll to the image forming apparatus 10. It is installed upstream of the conveyance device 5 of the image forming apparatus 10. The unwinder 81 includes a feed roller 83 that supports and rotates the wound recording medium 9, and a guide roller 84. The feed roller 83 is rotatably supported by a rotation shaft in the conveyance width direction. It is a support member that fits over a spool (not shown), which serves as a jig for the recording medium 9, and is a driven shaft that rotates together with the spool when the recording medium 9 is unwound from its wound outer side. The feed roller 83 preferably has a structure, such as a torque limiter, that applies an appropriate load to the rotation to prevent excessive rotation relative to the amount of recording medium 9 being fed by the conveyance device 5 of the image forming apparatus 10, causing the recording medium 9 to slacken. The guide rollers 84 can be configured similarly to the guide rollers 55 of the conveyance device 5. The required number of guide rollers 84 are installed at locations corresponding to the conveyance path of the recording medium 9. A portion of the guide roller 84 may be attached to the tip of a tension arm that is rotatable within a predetermined angular range. By providing the unwinder 81 with a guide roller that is movable within a predetermined range, tension is applied to the recording medium 9 between the unwinder 81 and the image forming device 10, thereby suppressing slack. In addition, the delivery roller 83 may be an active shaft that is rotated by a motor, and the rotation speed can be adjusted to apply tension to the recording medium 9 between the unwinder 81 and the image forming device 10. The unwinder 81 may further include a cutter that cuts the recording medium 9, as necessary.

[0051] (winding machine) The winder 82 is a device (winder) that winds and stores the recording medium 9 on which an image is formed by the image forming apparatus 10, and is installed downstream of the conveying device 5 of the image forming apparatus 10. The winder 82 includes a winding roller 85, a guide roller 86, and a motor (not shown) that rotates the winding roller 85. The winding roller 85 is an active shaft that receives rotational motion from the motor and rotates on a rotation axis in the conveyance width direction, and is also a support member that fits and engages with a spool. The winding roller 85 rotates the fitted spool at an appropriate rotational speed to wind the recording medium 9 onto the spool. The guide rollers 86 can have a configuration similar to the guide rollers 55 of the conveying device 5, and the required number of guide rollers 86 are installed at locations corresponding to the conveyance path of the recording medium 9. Like the unwinder 81, the winder 82 may also include a movable guide roller and a cutter.

[0052] [Fixing Alignment Control Method] The fixing alignment control operation by the image forming apparatus according to the present invention will be described with reference to Figures 3, 4A, 4B, 5A, and 5B. Figures 4A, 4B, 5A, and 5B are schematic diagrams for explaining the fixing alignment control operation by the image forming apparatus according to the present invention, in which the conveying surface 90 is oriented horizontally compared to Figure 3, and fixing belt 42 is omitted. The upper part of Figure 4A corresponds to Figure 3.

[0053] In FIG. 3, the recording medium 9 is tilted obliquely to the right from the intermediate transfer unit 3. Therefore, between the intermediate transfer unit 3 and the fixing unit 4 (unfixed area), the recording medium 9 is curved diagonally with the left side forward, and the left side is curved more than the right side (left half loop). As a result, the left side of the recording medium 9 comes into close proximity with the fixing belt 42 just before entering the fixing unit 4. Then, the portion of the recording medium 9 that comes into close proximity with the fixing belt 42 becomes image noise (bleed) due to heat. Furthermore, if the recording medium 9 enters the fixing unit 4 in this state, it will develop wrinkles, or if the recording medium 9 is made of resin, it will be deformed by the heat, making it difficult to repair.

[0054] 3 and 4A, the transport error detection unit 16 detects a transport deviation (a left-side loop) in the unfixed area of ​​the recording medium 9. Specifically, the recording medium detector 63 detects that the left side (the front in FIG. 4A) of the recording medium 9 is looser than the right side, causing the transport error detection unit 16 to detect a left-side loop. Alternatively, the image determination unit 18 detects that image noise has occurred in the left-side area of ​​the image data of the recording medium 9 captured by the image reading device 65. Furthermore, combined detection may be performed by both the transport error detection unit 16 and the image determination unit 18. When the transport error detection unit 16 detects a transport deviation in the unfixed area of ​​the recording medium 9, the drive control unit 11 sets the movement direction and movement distance of the fixing unit 4 to correct the transport deviation, and moves the fixing unit 4.

[0055] First, a control method for moving the fixing unit 4 in the first direction P1 will be described. As shown in the lower part of FIG. 4A, the drive control unit 11 tilts the fixing unit 4, with the left end (near side in FIG. 4A) as a fulcrum, to move the right end upstream, i.e., to draw it toward the intermediate transfer unit 3. In other words, the fixing unit 4 moves in the negative direction of the first direction P1, with the first axis S1 on the left side as the axis of rotation (FIG. 3). This reduces distortion in the unfixed area of ​​the recording medium 9, making it possible to avoid wrinkles, deformation, and image noise during fixing.

[0056] After the registration rollers 52 correct the skew of the recording medium 9 at the intermediate transfer unit 3, the recording medium 9 now curves obliquely with the right side (the rear in FIG. 4B) forward, as shown in the upper part of FIG. 4B, and the right side curves more than the left side. When the conveyance error detection unit 16 detects this conveyance deviation (single-loop on the right) of the recording medium 9, the drive control unit 11 controls the fixing unit 4 to move the right end downstream, using the left end as a fulcrum, as shown in the lower part of FIG. 4B, thereby tilting the fixing unit 4 so that it pushes the right end toward the conveyance direction. In other words, the fixing unit 4 moves in the positive direction of the first direction P1 with the first axis S1 as the rotation axis (FIG. 3). As a result, the fixing unit 4 returns to its original position, parallel to the conveyance width direction. This causes the slack in the recording medium 9 to become uniform in the conveyance width direction. The drive control unit 11 then adjusts the rotation speed of the fixing roller 44 to correct the slack in the recording medium 9 and flatten it.

[0057] As shown in Figure 4A, movement in the first direction P1 is sufficient as long as it pulls the right end of the fixing unit 4 upstream, but conversely, for the right single loop, the right end of the fixing unit 4 is pushed in the transport direction (downstream), so the recording medium 9 is pulled back and forth at its right edge. As described above, the recording medium 9, which is a continuous recording medium, is stretched tightly between the intermediate transfer section 3 and the fixing unit 4, so it may be pulled and torn, or if it is a resin film, it may be stretched and distorted. Therefore, in the present invention, as described below, control is performed by moving the fixing unit 4 in the second direction P2.

[0058] The upper part of FIG. 5A shows a state in which the recording medium 9 is skewed leftward from the intermediate transfer unit 3, resulting in a right-side loop. Then, as shown in the lower part of FIG. 5A, the drive control unit 11 tilts the fixing unit 4 so that its right end (the rear in FIG. 5A) is used as a fulcrum and its left end moves toward the back side of the recording medium 9 (downward in FIG. 5A). In other words, the fixing unit 4 moves in the negative direction of the second direction P2, with the right-side second axis S2 as the axis of rotation (FIG. 3). This causes the recording medium 9 to twist slightly in the unfixed area, reducing distortion and preventing wrinkles, deformation, and image noise during fixing. After that, the registration rollers 52 correct the skew of the recording medium 9 at the intermediate transfer unit 3. As shown in the upper part of FIG. 5B, the slack bias is reduced, and the recording medium 9 assumes a tilted position due to the tilt of the fixing unit 4. When the transport error detection unit 16 detects such a change in the attitude of the recording medium 9, the drive control unit 11 tilts the fixing unit 4 so that the right end serves as a fulcrum and the left end moves toward the front (printing surface) of the recording medium 9 (up in FIG. 5B), as shown in the lower part of FIG. 5B. In other words, the fixing unit 4 moves in the positive direction of the second direction P2 with the second axis S2 as the rotation axis (FIG. 3). As a result, the fixing unit 4 returns to its home position.

[0059] As shown in FIGS. 5A and 5B, conveyance deviations in the unfixed region of the recording medium 9 can also be corrected by moving the fixing unit 4 in the second direction P2 around the second axis S2. The movement of the fixing unit 4 in the second direction P2 gently twists the recording medium 9 in the unfixed region. This type of recording medium 9 is less subject to strong local tension than movement in the first direction P1 within the conveyance surface 90, making it less likely to deform or tear. Furthermore, proximity of the recording medium 9 to the fixing belt 42 due to a single loop is quickly resolved, reducing or even preventing image noise. Therefore, conveyance deviations can be corrected even when the recording medium 9 is a continuous recording medium that is normally conveyed without slack between the intermediate transfer unit 3 and the fixing unit 4, or a resin film that is easily deformed when pulled.

[0060] The amount of movement of the fixing unit 4 is calculated by the drive control unit 11 based on the degree of conveyance deviation detected by the conveyance error detection unit 16. For example, the amount of movement (movement length) can be set to 1 mm or less at the end of the fixing nip 4N where the amount of movement (movement length) is greatest, 0.6 mm for moderate conveyance deviation or image noise, and 0.2 mm for slight deviation. Furthermore, the fixing unit 4 may be moved in small increments (for example, at a maximum speed of 0.05 mm / s) rather than in a single operation, with the recording medium detector 63 detecting slack in the recording medium 9 each time, and the rotation operation may be terminated when the slack falls within an allowable range (to the extent that there is no risk of wrinkles, deformation, or image noise during fixing).

[0061] Furthermore, the movement amount of the fixing unit 4 may be calculated taking into account the thickness and density of the recording medium 9. Specifically, when the recording medium 9 is made of paper or the like, the thicker it is, the less likely it is to wrinkle or otherwise deform. Therefore, the movement amount is reduced as the recording medium 9 becomes thicker, or if the thickness is equal to or greater than a predetermined threshold. Furthermore, when the recording medium 9 has low rigidity (low density, e.g., thin paper) or is made of a resin film or the like, it is prone to deformation, so the speed is reduced to, for example, 0.03 mm / s or less. The thickness and density of the recording medium 9 may be detected by the media sensor 61 or may be input by the operator before starting operation. The upper limit (maximum tilt angle) of the movement amount of the fixing unit 4 in the first direction P1 and the second direction P2 can be set according to the type (material, thickness) of the recording medium 9. Furthermore, since recording media with low rigidity are highly sensitive to the movement of the fixing unit 4, the movement of the fixing unit 4 is likely to degrade image quality. This can be prevented by reducing the movement amount per movement or reducing the movement speed. On the other hand, since a recording medium with low rigidity is easily deformed when stretched, the upper limit of the movement of the fixing unit 4 is extended to, for example, a maximum of 1.5 mm in order to maintain an appropriate posture.

[0062] If the conveyance deviation of the recording medium 9 is not resolved even when the fixing unit 4 is moved to its upper limit in the second direction P2, it may also be moved in the first direction P1. A fixing alignment control method by the image forming apparatus 10 will be described below with reference to Fig. 6. Fig. 6 is a flowchart showing the fixing alignment control method for the image forming apparatus according to the present invention.

[0063] When the image forming apparatus 10 starts executing a job, it starts driving the printer engine and starts printing (operation). When starting operation, the image forming apparatus 10 preferably starts driving (rotating) the components in order, starting from the downstream side in the conveying direction. That is, the order is the winding roller 85 of the winder 82, the conveying roller 54 of the conveying device 5, the conveying roller 53, the fixing unit 4 (fixing roller 44), the intermediate transfer unit 3 (drive roller 33), the registration roller 52 of the conveying device 5, and the conveying roller 51, with an interval of about 30 ms depending on the arrangement of each component. By this procedure, tension can be applied to the recording medium 9.

[0064] When the transport error detection unit 16 detects a transport deviation in an unfixed area of ​​the recording medium 9 (step S11: Yes), the drive control unit 11 selects whether to move the fixing unit 4 in the first direction P1 or the second direction P2 to correct the transport deviation (step S12). In this embodiment, if the fixing unit 4 is in its normal position (not tilted), movement in the second direction P2 is selected (step S12: Second Direction). Then, the drive control unit 11 sets the orientation (+ / -) and movement amount of the fixing unit 4 in the second direction P2 to correct the transport deviation (step S21). If the fixing unit 4 can be moved in the set movement direction and by the set movement amount (step S22: Yes), the fixing unit 4 is moved (step S23). Then, if the transport error detection unit 16 no longer detects a transport deviation (step S24: No), the fixing unit 4 continues operation in that position. As described above, after the conveyance deviation is eliminated by tilting the fixing unit 4 in the second direction P2, if the skew of the recording medium 9 at the intermediate transfer unit 3 is corrected, the recording medium 9 will assume a tilted posture due to the tilt of the fixing unit 4. This change in posture of the recording medium 9 is detected as a conveyance deviation (step S11: Yes). At this time, the fixing unit 4 is tilted in the second direction P2. In this case, the drive control unit 11 selects movement in the second direction P2 (step S12: Second Direction). Then, the fixing unit 4 is moved in the opposite direction to return to its original position (steps S21, S22: Yes, S23). In other words, the tilted posture of the fixing unit 4 is, in principle, a temporary state. On the other hand, if the conveyance deviation is not eliminated (step S24: Yes) even after tilting the fixing unit 4 (step S23), the drive control unit 11 again sets the orientation and movement amount of the fixing unit 4 in the second direction P2 (step S21).

[0065] However, if the set movement is not possible, such as when the fixing unit 4 is already tilted to its upper limit in the second direction P2 (step S22: No), the fixing unit 4 is moved in the first direction P1. That is, the drive control unit 11 sets the orientation (+ / -) and movement amount of the fixing unit 4 in the first direction P1 so as to correct the conveyance deviation detected immediately before (step S31). If the set movement direction and movement amount for the fixing unit 4 are possible (step S32: Yes), the fixing unit 4 is moved (step S33). Then, if the conveyance error detection unit 16 no longer detects the conveyance deviation (step S34: No), the fixing unit 4 is maintained in that position and operation continues. At this time, the fixing unit 4 is tilted in both the first direction P1 and the second direction P2. If a conveyance deviation is detected again in this state (step S11: Yes), the drive control unit 11 selects movement in the first direction P1 (step S12: First Direction). On the other hand, if the conveyance deviation is not resolved (step S34: Yes), the drive control unit 11 again sets the orientation and movement amount in the first direction P1 of the fixing unit 4 (step S31). If the set movement in the first direction P1 is also impossible (step S32: No), it is determined that a conveyance abnormality has occurred and operation is stopped (step S4). Furthermore, when printing of the number of print copies (printing distance) of the job is completed (step S5: Yes), operation is ended.

[0066] When moving the fixing unit 4, the rotation speed of the fixing roller 44 may be reduced to prevent the recording medium 9 from being pulled. In particular, in a movement in the positive direction of the first direction P1 in which the distance between the nips 3N and 4N is partially widened, the recording medium 9 can be prevented from being pulled. Furthermore, even if the attitude of the fixing unit 4 is not tilted, the fixing unit 4 may be configured to select movement in the first direction P1 depending on the conveyance deviation (step S12: first direction). For example, this may be the case when the conveyance deviation is slight and the amount of movement in the first direction P1 is sufficiently small.

[0067] In FIG. 3, the fixing unit 4 has two fulcrums for movement in the first direction P1 and the second direction P2, each located at one end of the fixing nip 4N (the fulcrum for movement in the first direction P1 is the left end, and the fulcrum for movement in the second direction P2 is the right end). However, a common fulcrum may be used. Furthermore, the fixing unit 4 is fixed to one end of the fixing nip 4N as a fulcrum for movement in each of the first direction P1 and the second direction P2. However, a structure in which either end can be selected as the fulcrum may be used. With this configuration, when tilting the fixing unit 4 in the first direction P1, the fixing unit 4 can always be pulled toward the upstream side, preventing the recording medium 9 from being pulled. Furthermore, when tilting the fixing unit 4 in the second direction P2, the fixing unit 4 can always be raised toward the printing surface of the recording medium 9, allowing the fixing unit 4 to move in accordance with the entry of the side of the recording medium 9 with the greatest deformation. Alternatively, the fixing unit 4 may be configured to rotate about axes S1 and S2 passing through the center of the fixing nip 4N in the conveyance width direction. Since the movement distance at both ends in the conveyance width direction is short relative to the tilt angle of the fixing unit 4, the recording medium 9 is not pulled strongly even if the fixing unit 4 moves in either the positive or negative direction. A known two-axis gimbal mechanism can be used as such a movement mechanism.

[0068] [Modification] The present invention is not limited to the above-described embodiment, and modifications can be made without departing from the spirit of the present invention, for example, the following aspects can be mentioned.

[0069] Image forming apparatus 10 can also be used for sheet-fed printing using cut paper or the like. Instead of being connected to unwinder 81 and winder 82, this type of image forming apparatus 10 includes a paper feed cassette containing printing paper or the like as recording medium 9, and conveyance device 5 includes a pickup roller that picks up a sheet of printing paper from the paper feed cassette. Furthermore, media sensor 61 can also be a device that detects the physical properties of recording medium 9 (printing paper) contained in the paper feed cassette. Recording medium detectors 62 and 63 detect the passage of the leading edge of recording medium 9, and conveyance error detection units 15 and 16 can detect the tilt of the recording medium in the conveyance width direction. Recording medium detector 64 detects the passage of the leading edge of recording medium 9, and conveyance error detection unit 17 can detect a paper jam based on the delay.

[0070] In this modification, if the transport error detection unit 16 detects skew at the intermediate transfer unit 3 before the leading edge of the recording medium 9 enters the fixing unit 4, the fixing unit 4 can be moved in the first direction P1 to align the leading edge of the recording medium 9 before it enters the fixing unit 4. If the recording medium 9 is made of a highly rigid (high-density) material such as cardboard, the amount of movement in the first direction P1 can be reduced relative to the angle of inclination of the skew at the intermediate transfer unit 3, allowing the recording medium 9 to enter the fixing unit 4 at a slight incline. This reduces the impact of the leading edge of the recording medium 9 entering the fixing unit 4 and prevents image noise. Furthermore, since the recording medium 9 is transported with a certain amount of slack (loop) between the intermediate transfer unit 3 and the fixing unit 4 during normal transport, moving the fixing unit 4 in the first direction P1 to correct the one-sided loop will not cause the recording medium 9 to be pulled too hard and tear.

[0071] Here, the operation of moving the fixing unit 4 in the second direction P2, although depending on the orientation of the axes S1 and S2, involves a larger vertical movement and therefore a larger load than the movement in the first direction P1. Furthermore, when printing on stacked sheet-like materials such as envelopes, the movement of the fixing unit 4 in the second direction P2 can cause twisting, resulting in wrinkles, misalignment, and poor image quality. Therefore, as in this modified example, when the printing method is a sheet-fed printing method and the recording medium 9 is not a resin film or thin paper, the fixing alignment control operation generally only moves the fixing unit 4 in the first direction P1. To achieve this, the image forming apparatus 10 may be configured such that an operator switches between operating modes that permit or prohibit movement in the second direction P2, or the control unit 1 switches the mode depending on the type of recording medium 9, so that the fixing unit 4 does not move in the second direction P2. Alternatively, if the recording medium 9 is not properly misaligned even after tilting the fixing unit 4 to its upper limit in the first direction P1, the fixing unit 4 may then be moved in the second direction P2. That is, the movement in the first direction P1 and the movement in the second direction P2 are interchanged in the procedure shown in Fig. 6. Furthermore, in this modification, after the recording medium 9 has completely passed through the tilted fixing unit 4, the fixing unit 4 can be set to return to its original position before the subsequent recording medium 9 enters. [Explanation of symbols]

[0072] 10 Image forming device 1. Control section 11 Drive control unit 12 Image processing section 13 Communications Department 14 Recording medium identification section 15, 16, 17 Transport abnormality detection unit 18 Image judgment unit 2y, 2m, 2c, 2k Image forming units 2 Image forming unit 21 Photosensitive drum 22 Charging device 23 Exposure equipment 24 Developing device 25 Drum cleaning device 3 Intermediate transfer unit (transfer unit) 31 Intermediate transfer belt 32 Primary transfer roller 33 Drive roller 34 Secondary transfer backup roller 35 Cleaning opposing roller 36, 37 Driven roller 38 Belt cleaning device 39 Secondary transfer roller 4 Fusing unit (fusing section) 41 Pressure roller 42 Fixing belt 43 Heating roller 44 Fuser roller 45 Moving mechanism 5. Conveyor equipment 61 Media Sensor 62, 63, 64 Recording medium detector 65 Image reader 7 Operation panel 71 Operation section 72 Display device 81 Unwinding machine 82 Winder 9. Recording Media

Claims

1. a transfer section for transferring a toner image onto a recording medium; a fixing unit that fixes the toner image onto the recording medium; an image forming apparatus comprising: a control unit that moves the fixing unit in a first direction, tilting it within one of two planes that intersect with each other and include the transport width direction of the recording medium, and moves it in a second direction, tilting it within the other plane;

2. further comprising an image discrimination unit that detects image noise from the toner image fixed by the fixing unit, The image forming apparatus according to claim 1 , wherein the control unit sets a direction and an amount of movement of the fixing unit based on a location where the image noise occurs.

3. The recording medium is further provided with a detection unit that detects the recording medium between the transfer unit and the fixing unit, The image forming apparatus according to claim 1 , wherein the control unit sets a direction and amount of movement of the fixing unit based on the detected position of the recording medium.

4. 4. The image forming apparatus according to claim 2, wherein the control unit sets the movement amount of the fixing unit in accordance with the thickness and / or density of the recording medium.

5. The image forming apparatus according to claim 1 , wherein the movement in the first direction is inclined within an imaginary plane connecting the nips of the fixing unit and the transfer unit.

6. The image forming apparatus according to claim 5 , wherein the control unit is capable of switching between a mode in which the fixing unit is permitted to move in the second direction and a mode in which the fixing unit is prohibited from moving in the second direction.

7. 2. The image forming apparatus according to claim 1, wherein the recording medium is transported without slack between the transfer section and the fixing section.

8. 8. The image forming apparatus according to claim 7, wherein the recording medium is a continuous recording medium.

9. The image forming apparatus according to claim 1 , wherein the recording medium comprises a resin.

10. 2. The image forming apparatus according to claim 1, wherein the fixing unit rotates around one end of the nip of the fixing unit as an axis, and the other end of the nip of the fixing unit rotates around the other end as an axis.

11. 1. A fixing alignment control method for an image forming apparatus including a transfer unit that transfers a toner image onto a recording medium and a fixing unit that fixes the toner image onto the recording medium, comprising: detecting a tilt of the recording medium between the transfer unit and the fixing unit; A fixing alignment control method that executes a step of moving the fixing unit in a first direction to tilt it within one of two planes that intersect with each other and include the transport width direction of the recording medium, and / or moving it in a second direction to tilt it within the other plane, so as to correct the inclination of the recording medium.

12. On the computer, a procedure for detecting the inclination of a recording medium between a transfer unit and a fixing unit of an image forming apparatus; a step of setting a moving direction and a moving amount to move the fixing unit in a first direction to tilt the fixing unit in one of two planes that include the conveyance width direction of the recording medium and intersect with each other, and / or to move the fixing unit in a second direction to tilt the fixing unit in the other plane, so as to correct the tilt of the recording medium; A fixing alignment control program that executes the above.

Images