JP2012234031A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of more accurately correcting a position of image formation by use of a registration roller and capable of always forming an image at an accurate position.SOLUTION: The image forming apparatus comprises: a registration roller 23 that conveys a recording medium and is movable in a width direction orthogonal to the conveyance direction of the recording medium S; and a fixing device 30 that pressurizes and heats an unfixed toner image to fix the toner image which has been transferred onto a recording medium S by an image forming unit disposed downstream the registration roller 23 along the conveyance direction, the fixing device 30 being movable in the width direction. The recording medium S passing through the registration roller 23 and the fixing device 30 moves in the width direction with the movement of the registration roller 23 and the fixing device 30 in the width direction. The distance where the registration roller 23 can move in the width direction is configured to be larger than the distance where the fixing device 30 can move in the width direction.

Description

  The present invention relates to an image forming apparatus.

  In recent image forming apparatuses such as printers and copiers using an electrophotographic system, a registration roller and a fixing device are provided. The registration roller conveys the recording medium to the transfer unit in the image forming apparatus. The toner is transferred to the conveyed recording medium by the transfer unit. The fixing device passes the recording medium onto which the toner has been transferred between the heating roller and the pressure roller of the fixing device, thereby fixing the unfixed toner on the recording medium to form an image.

  As a technique related to the registration roller, there is a technique including a correction unit that moves the registration roller in the width direction (for example, Patent Document 1). By moving the registration roller in the width direction, it is possible to correct the positional deviation in the width direction of the recording medium. As a result, the registration roller can convey the recording medium so that the toner image transferred by the transfer unit is transferred to an accurate image forming position on the recording medium.

  Further, as a technique related to the fixing device, there is a technology including a moving unit that moves the fixing device in the width direction (for example, Patent Document 2). By moving the fixing device in the width direction, it is possible to prevent the recording medium from always passing through a certain place on the heating roller and the pressure roller, or to reduce the temperature difference gradient in the width direction of the roller. As a result, it is possible to prevent the abrasion from progressing only at a specific portion of the roller, to reduce the gloss difference of the fixed toner generated by the temperature gradient, and to prevent the image quality from deteriorating.

  However, in the image forming apparatus including the registration roller that can move and the fixing device as described above, the position of the recording medium may not be completely corrected by the registration roller. For example, there is a case where the toner is fixed on one surface of the recording medium and then the toner is fixed on the other surface (that is, when duplex printing is performed). In this case, the fixing device is driven in the width direction even while the toner is fixed on one surface of the recording medium. Therefore, the recording medium passing through the fixing device is also moved in the width direction while fixing the toner. If the distance moved in the width direction of the recording medium is larger than the movable range of the registration roller in the width direction, the width direction cannot be corrected by the registration roller when toner is fixed on the other surface. As a result, the image forming position on the recording medium is different between one side and the other side of the recording medium, and the printing accuracy is lowered.

JP 2007-22680 A JP 2004-287317 A

  The present invention has been made based on the above problems, and provides an image forming apparatus capable of reliably correcting an image forming position by a registration roller and always forming an image at an accurate position.

  The above object of the present invention is achieved by the following means.

  (1) The recording medium is conveyed onto the recording medium by a registration roller that is movable in the width direction orthogonal to the conveyance direction of the recording medium and an image forming unit disposed downstream in the conveyance direction of the registration roller. A fixing device capable of fixing the transferred unfixed toner image by applying pressure and heat, and moving in the width direction, and the recording medium passing through the fixing roller and the fixing device includes the resist An image forming apparatus that moves in the width direction along with the movement of the roller and the fixing device in the width direction, and the distance that the resist roller can move in the width direction is movable in the width direction of the fixing device An image forming apparatus configured to be larger than a certain distance.

  (2) The distance that the registration roller can move in the width direction is larger than the distance that the recording medium moves in the width direction while the recording medium passes through the fixing device. Image forming apparatus.

  (3) After an image is formed on one surface of the recording medium by the fixing device, the recording medium is reversed and re-conveyed to the registration roller in order to form an image on the other surface of the recording medium. The image forming apparatus according to (1) or (2), further including a double-sided path.

  (4) The image forming apparatus according to any one of (1) to (3), wherein a speed of the registration roller moving in the width direction is higher than a speed of the fixing device moving in the width direction.

  (5) The image forming apparatus according to (4), wherein the moving speed of the fixing device in the width direction is variable.

  According to the present invention, the distance that the registration roller can move in the width direction is larger than the distance that the fixing device can move in the width direction, so that the position in the width direction of the recording medium moved by the fixing device can be increased. The deviation can be reliably corrected by the registration roller.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to an embodiment. FIG. 3 is a top view schematically illustrating a state in which a registration roller of the image forming apparatus according to the present embodiment is transporting a recording medium. FIG. 6 is a top view illustrating a state in which a recording medium S that has been transported with a positional deviation in the width direction is corrected by a registration roller pair. FIG. 10 is a perspective view illustrating a state in which a skew of a conveyed recording medium is eliminated by a registration roller. FIG. 3 is a top view schematically illustrating a state in which the fixing device according to the present embodiment is driven in a width direction. FIG. 3 is a perspective view schematically illustrating a state in which a recording medium passes through a fixing device. FIG. 4 is a top view schematically illustrating a state in which a recording medium conveyed from a registration roller is conveyed through a fixing device that moves in a width direction.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the following description does not limit the technical scope and terminology described in the claims. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus according to the present embodiment.

  The image forming apparatus A shown in FIG. 1 is also called a tandem color image forming apparatus, and performs color image formation by four sets of image forming units. The image forming apparatus A prints image data on a recording medium such as printing paper using an electrophotographic image forming process.

  The image forming apparatus A performs color image formation by four sets of image forming units. The four image forming units include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and an image forming unit that forms a cyan (C) color image. The unit 10C is an image forming unit 10K that forms a black (K) color image.

  The image forming unit 10Y includes a photosensitive drum 1Y, and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y arranged around the photosensitive drum 1Y. Similarly, the image forming unit 10M includes a photosensitive drum 1M, and a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a drum cleaner 5M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a drum cleaner 5C arranged around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, and a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a drum cleaner 5K disposed around the photosensitive drum 1K. The photosensitive drums 1Y, 1M, 1C and 1K of the image forming units 10Y, 10M, 10C and 10K, charging units 2Y, 2M, 2C and 2K, writing units 3Y, 3M, 3C and 3K, and a drum cleaner Each of 5Y, 5M, 5C, and 5K has a similar function. Therefore, hereinafter, unless otherwise specified, the symbols Y, M, C, and K are used without description.

  Next, an electrophotographic process for printing an image on a recording medium by the image forming apparatus A will be described.

  First, a document is placed on a document table having a slit SL, and the placed document is scanned and exposed by an optical system of a scanning exposure device of the image reading device SC, and reflected light from the document is passed through a mirror. It is read and photoelectrically converted by the line image sensor. The image information signal for each color generated by photoelectric conversion is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like by an image processing unit (not shown), and then image formation of the corresponding color is performed. Input to the optical writing unit 3 of the unit 10.

  The optical writing unit 3 of the image forming unit 10 writes an image information signal to the photosensitive drum 1 and forms a latent image on the photosensitive drum 1 based on the image information signal. Specifically, the photosensitive drum 1 has a photosensitive layer made of a resin such as polycarbonate including an organic photoconductor (OPC) on a metal substrate. The surface of the photosensitive drum 1 is charged by ions generated by a charging unit 2 composed of a corona discharge electrode such as a scorotron type, and the optical writing unit 3 scans and exposes the photosensitive drum 1 on the basis of an image information signal. To do. The exposed portion of the charged photosensitive drum 1 has a reduced potential, and a charge pattern (electrostatic latent image) corresponding to the image information signal is formed on the photosensitive drum 1. The developing device 4 attaches toner to the electrostatic latent image formed on the photosensitive drum 1 using electrostatic force, and forms a toner image corresponding to each color.

  The intermediate transfer belt 6 is an endless belt, is wound around a plurality of rollers, and is supported so as to be able to run. The toner images of the respective colors formed on the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the intermediate transfer belt 6 traveling by the primary transfer units 7Y, 7M, 7C, and 7K, and each color (Y, M, C , K) is formed on the intermediate transfer belt 6 by superimposing a color image (toner image). Although depending on the size of the image forming unit 10 for each color, image formation information, and the like, generally, a color image is formed after the optical writing unit 3 starts to form an electrostatic latent image on the photosensitive drum 1. Takes at least a few seconds.

  The paper transport unit 20 transports a recording medium S such as printing paper. The recording medium S is accommodated in the paper feed trays 291, 292 and 293, fed by the first paper feed unit 21, and conveyed to the secondary transfer unit 7 A through the loop forming roller pair 22 and the registration roller pair 23. Is done. In the secondary transfer unit 7A, the color image formed on the intermediate transfer belt 6 is transferred onto the recording medium S. The recording medium S to which the color image has been transferred is heated and pressurized at the nip portion N of the fixing device 30, whereby the toner image on the recording medium S is melted and fixed. Then, the recording medium S is discharged out of the apparatus by the paper discharge roller 25.

  Further, the image forming apparatus A has a duplex conveying path 24 for printing on both sides of the recording medium S. After the toner image is fixed on one surface of the recording medium S by the fixing device 30, the recording medium S is conveyed from the fixing device 30 to the lower double-side conveying path and switched back, and then re-conveyed to the loop forming roller pair 22. Is done.

  The above-described units of the image forming apparatus A are connected to the control unit 90 via wiring (not shown) and the like, and are appropriately controlled by the control unit 90. In addition, the image forming apparatus A may include components other than the components described above, or may not include some of the components described above.

  Next, with reference to FIG. 2 and FIG. 3, a process for conveying the recording medium by the registration rollers according to the present embodiment will be described in detail.

  FIG. 2 is a top view schematically showing a state where the registration rollers of the image forming apparatus according to the present embodiment are transporting the recording medium, and FIG. 3 is a diagram illustrating that the skew of the transported recording medium is eliminated by the registration rollers. It is a perspective view which shows a mode. As shown in FIG. 2, the image forming apparatus according to this embodiment includes a registration roller pair 23, a stepping motor M1, and a sensor 23 '. In FIG. 2, only the upper roller of the registration roller pair 23 is shown for convenience of explanation. In FIG. 3, the loop forming roller 22 is indicated by a dotted line.

  As shown in FIG. 1, the registration roller pair 23 is composed of a pair of rollers pressed against each other, and conveys the recording medium S in the direction of the arrow in FIG. 2 through the pair of rollers. The registration roller pair 23 conveys the recording medium S, for example, when one of the pair of rollers is rotationally driven. The other roller can be driven by a rotationally driven roller. The registration roller pair 23 conveys the recording medium S at, for example, about 300 mm / sec.

  The registration roller pair 23 is connected to the stepping motor M1 and can be driven in the width direction. A movable range ΔR in which the registration roller pair 23 is driven in the width direction is, for example, about 5 mm from the center reference position Q to the left and right. That is, the total movable range in which the registration roller pair 23 can be driven in the width direction is 2 × ΔR = 10 mm. As will be described later, the total movable range of the registration roller pair 23 is larger than the total movable range in which the fixing device 30 can be driven.

  The stepping motor M1 drives the registration roller pair 23 in the width direction based on an instruction from the control unit 90. Specifically, the stepping motor M1 has, for example, a worm wheel (not shown) that meshes with a worm formed at the end of the core of the registration roller pair 23, and drives the worm wheel. Thus, the rotational driving force is transmitted to the core metal of the registration roller pair 23 to drive the registration roller pair 23 in the width direction. Further, the stepping motor M1 is configured to drive the registration roller pair 23 in the width direction at a speed higher than the speed at which the below-described fixing device 30 is driven in the width direction. In this way, even if the recording medium S is moved in the width direction by the fixing device 30, the position in the width direction of the recording medium S can be reliably corrected by the registration roller pair 23.

  The sensor 23 ′ detects the position on one side in the width direction of the recording medium S and transmits it to the control unit 90. The control unit 90 calculates a deviation amount of the position of the recording medium S from the center reference position Q based on the measurement value. The registration roller pair 23 is driven based on the calculated deviation amount. The manner in which the recording medium S conveyed while being displaced in the width direction is corrected by the registration roller pair 23 is as shown in FIG. As shown in FIG. 3, even when the recording medium S is transported to the right with respect to the center reference line Q, the sensor 23 ′ remains while the recording medium S passes between the registration roller pair 23. The shift amount Z is detected, and the control unit instructs the registration roller pair 23 to correct the shift amount Z by moving it to the left side. Based on an instruction from the control unit, the registration roller pair 23 is driven by the shift amount Z (to the left in the example shown in FIG. 3). As a result, the recording medium S can be transported to the subsequent transfer process in a state where the positional deviation in the width direction of the recording medium S is corrected. The center reference line Q indicates the center reference position in the width direction, and is also the center position in the width direction of the intermediate transfer belt 6 and the secondary transfer portion 7A.

  Further, the registration roller according to the present embodiment has a function of eliminating the skew of the recording medium being conveyed. The mechanism in which the registration roller pair 23 cancels the skew in the transport direction of the recording medium S transported from the loop forming roller pair 22 is as shown in FIG. As shown in FIG. 4, when the recording medium S is conveyed from the loop forming roller pair 22, first, the rotational driving of the registration roller pair 23 is stopped. The loop forming roller pair 22 conveys the recording medium S only for a predetermined period after the one side of the recording medium S conveyed from the loop forming roller pair 22 reaches the nip portion Nr of the registration roller pair 23. continue. As a result, a loop as shown in FIG. 4 is formed on the recording medium S. As a result, regardless of the skew of the recording medium S, one side of the leading end side of the recording medium S is positioned along the nip portion Nr of the registration roller pair 23 as shown in FIG. While the rear end region of the recording medium S is held by the loop forming roller pair 22, the recording medium S in which the loop is formed is subjected to a reaction force that the recording medium S itself tries to return to its original shape. Therefore, the tip does not leave the nip portion Nr. Thereafter, after the registration roller pair 23 is driven to rotate and the recording medium S begins to be conveyed, the loop forming roller pair 22 releases the rear end side of the recording medium S. In this way, the registration roller pair 23 can transport the recording medium S from which the skew is eliminated to the subsequent process.

  Next, a mechanism for driving the fixing device according to the present embodiment in the width direction will be described in detail with reference to FIGS. 5 and 6.

  FIG. 5 is a top view schematically showing how the fixing device according to the present embodiment is driven in the width direction, and FIG. 6 is a perspective view showing how the recording medium passes through the fixing device. As shown in FIG. 5, the image forming apparatus according to the present embodiment includes a fixing device 30, a spring member 31, a moving unit 40, and a fixed portion F. The moving means 40 includes a cam 41 and a stepping motor M2.

  The fixing device 30 fixes the unfixed toner transferred onto the recording medium. Specifically, as shown in FIG. 1, the fixing device 30 includes unfixed toner between a pair of heating roller 31 and pressure roller 32 that are configured inside the fixing device 30 and are pressed against each other. By passing the transferred recording medium S, the toner is fixed on the recording medium S. The distance that the fixing device 30 is driven in the width direction is, for example, about 5 mm on both sides in the width direction from the center reference position Q, and is configured to be narrower than the movable range in the width direction of the registration roller (details will be described later). In addition to the pair of rollers, a belt may be further used.

  The spring member 31 is disposed between the fixing portion F and the fixing device 30 and biases one end of the fixing device 30 from the fixing portion F. That is, the spring member 31 acts so that the other end of the fixing device 30 is always in pressure contact with the cam 41. The fixing part F is, for example, an inner side wall of the fixing device 30.

  The moving means 40 drives the fixing device 30 in the width direction by the cam 41 and the stepping motor M2. As shown in FIG. 5, the cam 41 is formed in a cylindrical shape, for example, and is pivotally supported by the drive shaft of the stepping motor M <b> 2 at a position eccentric from the center of the cylindrical shaft. When the stepping motor M2 rotates the drive shaft in the direction of the arrow shown in FIG. 5A, the contact point between the cam 41 and the fixing device 30 (hereinafter simply referred to as a contact point) moves in the width direction. The fixing device 30 brought into pressure contact therewith can move in the width direction. The manner in which the fixing device 30 is driven and moved in the width direction by the stepping motor M2 is as shown in FIGS. As shown in FIG. 5A, the stepping motor M2 is driven counterclockwise, and the displacement in the width direction of the contact from the center of the drive shaft of the stepping motor M2 is changed. While the stepping motor M2 continues to rotate, the fixing device 30 is moved in the left direction in FIG. 5 from the position shown in FIG. 5A to the position shown in FIG. 5B. In FIG. 5B, the distance in the width direction from the drive shaft center of the stepping motor M2 to the contact is the shortest, and this position is one of the movable limits of the fixing device 30. While the stepping motor M2 continues to rotate, the fixing device 30 is moved to the right in FIG. 5 from the position shown in FIG. 5B to the position shown in FIG. 5C. In FIG. 5C, the distance in the width direction from the drive shaft center of the stepping motor M2 to the contact is the longest, and this position is the other movable limit of the fixing device 30. The stepping motor M2 further continues to rotate, and the fixing device 30 is moved in the left direction in FIG. 5 from the position shown in FIG. 5C to the position shown in FIG. By repeating the operations shown in FIGS. 5A to 5C, the fixing device 30 moves in the width direction.

  Further, the speed at which the moving unit 40 moves the fixing device in the width direction may be 1 mm / print (about 1 mm / sec) as described in Patent Document 2, for example, or less or more. The speed at which the fixing device 30 moves in the width direction can be set in consideration of the type of toner used, fixing conditions, control accuracy, cost of the moving mechanism, and the like. The moving unit 40 can appropriately change the speed at which the fixing device 30 moves in the width direction.

  Further, the state in which the recording medium S passes through the fixing device 30 is as shown in FIG. For convenience of explanation, FIG. 6 does not show the configuration around the fixing device 30 such as the cam 41 and the stepping motor M2. As shown in FIG. 6A, the fixing device 30 is indicated by an arrow in FIG. 6A while the recording medium S positioned in accordance with the center reference position Q is discharged from the front side to the back side. It is moving in the width direction. Accordingly, the recording medium S discharged from the fixing device 30 is also moved in the width direction at the same time, and the recording medium S moves by ΔT in the width direction while passing through the fixing device 30. Further, as shown in FIG. 6B, while the fixing device 30 is moving in the direction indicated by the arrow in FIG. 6B, the recording medium S discharged from the fixing device 30 is simultaneously in the width direction. The recording medium S is moved by ΔT in the width direction. Thus, the recording medium S moves in the same width direction as the direction in which the fixing device 30 moves.

  Next, an embodiment of a configuration for conveying a recording medium by combining a registration roller and a fixing device according to the present embodiment will be described with reference to FIG.

  FIG. 7 is a top view schematically illustrating a state in which the recording medium conveyed from the registration roller is conveyed through a fixing device that moves in the width direction. In FIG. 7, for convenience of explanation, the image forming unit 10 and the like are omitted, and the secondary transfer unit 7 </ b> A is indicated by a dotted line.

  The recording medium S is conveyed from the registration roller pair 23 to the fixing device 30 via the intermediate transfer belt 6 and the secondary transfer portion 7A. At this time, if the speed (process speed) at which the recording medium S is conveyed in the conveying direction is Vp, the time for which the recording medium S passes the nip portion N of the fixing device 30 is the length of the recording medium S in the conveying direction. L can be expressed as t = L / Vp. In addition, since the fixing device 30 moves in the width direction at the speed Vt while the recording medium S is being conveyed, the fixing device 30 is moved in the width direction until the recording medium S is conveyed to the nip portion of the fixing device 30 and finishes passing. The distance ΔT to move to is expressed by the following Equation 1.

  In the present embodiment, the moving distance (ΔT) of the fixing device 30 in the width direction is configured not to exceed the movable range (ΔR) in which the registration roller pair 23 moves in the width direction with respect to the center reference position Q. In this way, when the recording medium S which has been printed on one side of the recording medium S and then reversed through the double-sided conveyance path 24 is printed again on the other side, the fixing device The moving distance (ΔT) of 30 in the width direction does not become larger than the movable range in the width direction of the registration roller pair 23. Since the registration roller pair 23 can move by a movement distance (ΔR) larger than the distance (ΔT) moved by the fixing device 30, the center of the recording medium S can always be corrected to the center reference position Q. In other words, since the total movable range (2ΔR) in which the registration roller pair 23 can move is larger than the total movable range in which the fixing device 30 can move, the registration roller pair 23 can reliably correct the distance that the fixing device 30 has moved.

  As described above, in this embodiment, the distance that the registration roller pair 23 moves in the width direction is greater than the distance that the fixing device 30 moves in the width direction. Further, the total movable range in which the registration roller pair 23 can move in the width direction is configured to be larger than the total movable range in which the fixing device 30 can move in the width direction, and the movable range of the fixing device 30 is within the movable range of the registration roller pair 23. Composed. Therefore, the registration roller pair 23 can reliably correct the positional deviation in the width direction of the recording medium moved by the fixing device 30. Further, since the speed of movement of the registration roller pair 23 in the width direction is faster than the speed of movement of the fixing device 30 in the width direction, the registration roller pair 23 reliably corrects the distance that the fixing device 30 has moved in the width direction. it can. Further, according to the present embodiment, the distance traveled by the fixing device 30 is more than corrected by changing the position of the electrostatic latent image on the photosensitive drum 1 by the optical writing unit 3, and the registration roller pair 23. Can be corrected at a much higher speed by moving in the width direction and changing the transfer position with respect to the recording medium S, thereby improving printing productivity.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims.

  For example, in the above embodiment, it has been described that the moving speed of the fixing device in the width direction is variable. For example, the speed may be set by the operation display unit 80 or may be set by a printer driver installed in a PC (Personal Computer) via a network (not shown).

  In the above-described embodiment, the mode in which the skew in the transport direction of the recording medium transported using the loop forming roller pair has been described, but the present invention is not limited to this. Any method may be used.

  In the above-described embodiment, the entire fixing device is moved in the width direction. However, it is not limited to this. You may comprise so that only the heating roller and pressure roller pair which comprise a fixing device may move.

  The image forming apparatus has been described as a digital color copying machine, but may be configured as a monochrome copying machine or a printer. The image forming apparatus can also be configured as an MFP (Multi-Function Peripheral), and image data transmitted via a network may be used as an image information signal.

A image forming apparatus,
N, Nr nip,
Q center reference position,
S recording medium,
SC image reader SL slit,
1Y, 1M, 1C, 1K photosensitive drum,
2Y, 2M, 2C, 2K charging unit,
3Y, 3M, 3C, 3K optical writing unit,
4Y, 4M, 4C, 4K developing device,
5Y, 5M, 5C, 5K drum cleaner,
6 Intermediate transfer belt,
7A Secondary transfer part,
7Y, 7M, 7C, 7K primary transfer part,
10Y, 10M, 10C, 10K image forming unit,
20 Paper transport section,
21 Paper feed unit,
22 Loop forming roller pair,
23 Registration roller pair,
24 Double-sided conveyance path,
25 Paper discharge roller,
30 fixing device,
80 operation display section,
90 control unit,
291, 292, 293 Paper feed trays.

Claims (5)

A registration roller that conveys the recording medium and is movable in a width direction orthogonal to the conveyance direction of the recording medium;
A fixing device capable of fixing the unfixed toner image transferred onto the recording medium by pressurizing and heating the image forming unit disposed downstream in the conveyance direction of the registration roller and movable in the width direction; With
The recording medium passing through the registration roller and the fixing device is an image forming apparatus that moves in the width direction together with the movement of the registration roller and the fixing device in the width direction,
An image forming apparatus configured such that the distance that the registration roller can move in the width direction is larger than the distance that the fixing device can move in the width direction.   The image forming apparatus according to claim 1, wherein a distance that the registration roller can move in the width direction is larger than a distance that the recording medium moves in the width direction while the recording medium passes through the fixing apparatus. .   After an image is formed on one surface of the recording medium by the fixing device, a double-sided path for reversing the recording medium and re-conveying it to the registration rollers is formed in order to form an image on the other surface of the recording medium. The image forming apparatus according to claim 1, further comprising:   The image forming apparatus according to claim 1, wherein a speed of the registration roller moving in the width direction is faster than a speed of the fixing apparatus moving in the width direction.   The image forming apparatus according to claim 4, wherein the moving speed of the fixing device in the width direction is variable.