JP2016030666A - Medium transportation mechanism, fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for suppressing the curved state formed on a medium.SOLUTION: A medium transportation mechanism comprises: a fixation part which fixes developer on a medium to which the developer is transferred; a transportation member which is disposed on the downstream side of the fixation part in the medium transportation direction and transports the medium; and a guide member which is disposed between the fixation part and the transportation member and guides the medium. In the transportation member, a plurality of roller pairs are disposed on a rotational shaft. The guide member is formed so that the width in the rotational shaft direction becomes substantially the same as an interval of the outermost side ends of the roller pairs in the rotational shaft direction, and protrudes from a virtual straight line connecting the fixation part and the roller pairs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a medium transport mechanism, a fixing device, and an image forming apparatus that transport a medium.

  A conventional image forming apparatus conveys a medium to each unit such as an image forming unit and a fixing unit by a pair of conveying rollers provided at a predetermined position on the medium conveying path, and develops the medium by heating and pressing the fixing unit. After fixing the agent, the sheet is discharged to the medium stacking tray by the discharge roller pair, and is transported to a post-processing device provided on the downstream side of the pair of discharge rollers to be subjected to post-processing such as stable, and then to the medium stacking tray. It is made to discharge | emit (for example, refer patent document 1).

JP 2006-213518 A

However, in the conventional technology, the developer is fixed to the medium by heating and pressurizing with the fixing unit. Therefore, in the case of a medium such as thin paper or recycled paper or a medium that has absorbed moisture, the medium passes through the fixing unit. Then, there is a problem that the medium is curved and the curved medium is conveyed.
An object of the present invention is to solve such a problem, and an object thereof is to suppress a curved state formed on a medium.

  Therefore, the present invention provides a fixing unit that fixes the developer on the medium onto which the developer has been transferred, a conveyance member that is disposed downstream of the fixing unit in the medium conveyance direction and conveys the medium, and the fixing unit. A guide member that guides the medium, and the transport member has a plurality of roller pairs disposed on a rotation shaft, and the guide member is arranged in the direction of the rotation shaft. The width is substantially the same as the interval between the outermost ends of the roller pair in the rotation axis direction, and protrudes from an imaginary straight line connecting the fixing unit and the roller pair.

  According to the present invention thus configured, an effect that the curved state formed in the medium can be suppressed is obtained.

Schematic side sectional view showing the structure of the image forming apparatus in the embodiment FIG. 3 is a block diagram showing a control configuration of the image forming apparatus in the embodiment. External perspective view of first discharge roller in the embodiment The perspective view which shows the structure of the 1st discharge roller in an Example. The perspective view which shows the structure of the 1st discharge roller in an Example. Sectional drawing of the medium conveyance guide and the 1st discharge roller in an Example Enlarged sectional view of the medium transport guide and the first discharge roller in the embodiment Top view of medium conveyance guide and first discharge roller in the embodiment The perspective view of the fixing unit in the embodiment The perspective view of the fixing unit in the embodiment The perspective view of the fixing unit of a modification Explanatory drawing of curled state of media Explanatory drawing of curled state of media

  Embodiments of a medium transport mechanism, a fixing device, and an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional side view showing the configuration of the image forming apparatus in the embodiment.
In FIG. 1, an image forming apparatus 1 is a color printer, for example, and includes image forming units 2K, 2Y, 2M, and 2C, transfer rollers 10K, 10Y, 10M, and 10C, a paper cassette 24, and a paper feed roller 11. The first inlet sensor 12L, the second inlet sensor 12U, the writing sensor 13, the first conveying rollers 14R and 14P, the second conveying rollers 15R and 15P, the belt driven roller 16, and the belt driving roller 17, Conveying belt 18, fixing roller 19, fixing backup roller 20, fixing unit 28, discharge sensor 21, first discharge rollers 22, 23, duplex unit 25, medium conveyance guide 40, and second discharge roller 26 and 27 and a discharge tray 31.

  The image forming units 2K, 2Y, 2M, and 2C form toner images with toner as developers of black (K), yellow (Y), magenta (M), and cyan (C), respectively. The surfaces of LED (Light Emitting Diode) heads 3K, 3Y, 3M, and 3C as exposure means, and photosensitive drums 4K, 4Y, 4M, and 4C as image carriers, and photosensitive drums 4K, 4Y, 4M, and 4C The toner is conveyed to the electrostatic latent image formed on the surface of the photosensitive drums 4K, 4Y, 4M, and 4C by the charging rollers 5K, 5Y, 5M, and 5C that are uniformly charged and the LED heads 3K, 3Y, 3M, and 3C. Developing rollers 6K, 6Y, 6M, and 6C for developing toner images, toner tanks 7K, 7Y, 7M, and 7C for storing toner, and developing rollers 6K, 6Y, 6M, and 6 Developing blades 8K, 8Y, 8M, 8C for uniformly thinning the toner on the surface C; and toner supply sponge rollers 9K, 9Y, 9M, 9C for supplying toner to the developing rollers 6K, 6Y, 6M, 6C; It is composed of

The transfer rollers 10K, 10Y, 10M, and 10C are arranged to face the image forming units 2K, 2Y, 2M, and 2C, and transfer the toner images formed on the photosensitive drums 4K, 4Y, 4M, and 4C to a medium. It is.
The paper cassette 24 accommodates a medium, and the paper feed roller 11 separates and takes out the medium contained in the paper cassette 24 one by one using a separation tongue or the like.

The first transport rollers 14R and 14P sandwich and transport the medium taken out by the paper feed roller 11.
The second transport rollers 15R and 15P sandwich and transport the medium transported by the first transport rollers 14R and 14P.
The first inlet sensor 12L is a sensor that detects the medium taken out by the paper feed roller 11, and the second inlet sensor 12U is a sensor that detects the medium conveyed by the first conveying rollers 14R and 14P.

The writing sensor 13 is a sensor that detects the medium transported by the first transport rollers 14R and 14P and generates timing for starting image formation in the image forming units 2K, 2Y, 2M, and 2C.
The conveyor belt 18 is an endless belt that conveys the medium, is stretched between a belt driving roller 17 that is rotated by a driving source and a belt driven roller 16, and rotates by the rotation of the belt driving roller 17. The belt driven roller 16 is rotated by the rotation of the conveyor belt 18 and is supported by a spring in order to keep the tension of the conveyor belt 18 constant.

The fixing unit 28 as a fixing unit fixes the toner to the medium on which the toner has been transferred. The fixing unit 28 includes a heating element such as a halogen lamp inside, and fixes the toner to the medium by heating and pressing the medium. A roller 19 and a fixing backup roller 20 disposed so as to contact the fixing roller 19 are provided.
The discharge sensor 21 is a sensor that detects the medium on which the toner is fixed by the fixing unit 28.
The duplex unit 25 reverses the medium so that the medium on which the toner is fixed by the fixing unit 28 is conveyed again to the image forming units 2K, 2Y, 2M, and 2C, and an image is formed on the opposite surface of the medium. is there.

  The first discharge rollers 22 and 23 as conveying members are arranged on the downstream side of the fixing unit 28 in the medium conveying direction indicated by the arrow A in the figure, and the medium on which the toner is fixed by the fixing unit 28 is removed from the image forming apparatus 1. It conveys to the conveyance path 46 which leads to, or the conveyance path 47 which leads to the post-processing apparatus. The first discharge rollers 22 and 23 are configured such that a plurality of roller pairs are arranged on a rotation shaft.

  The medium conveyance guide 40 as a first guide member is disposed between the fixing unit 28 and the first discharge rollers 22 and 23, and the first discharge roller 22 and the fixing backup roller 20 to the first discharge roller 22 and 23. This guides the medium conveyed through the conveyance path 42 up to 23. The details of the medium transport guide 40 and the first discharge rollers 22 and 23 will be described later.

The second discharge rollers 26 and 27 discharge the medium transported to the transport path 46 by the first discharge rollers 22 and 23 to the outside of the image forming apparatus 1.
The discharge tray 31 is for stacking the medium discharged by the second discharge rollers 26 and 27.
In addition, a plurality of rollers are disposed in the conveyance path for conveying the medium while maintaining a distance equal to or less than the length of the minimum medium, and a motor as a driving source for rotating each roller including the rollers is disposed. ing.

Next, the configuration of the medium conveyance guide 40 and the first discharge rollers 22 and 23 described above will be described.
First, the configuration of the first discharge rollers 22 and 23 will be described with reference to FIGS. 3 is an external perspective view of the first discharge roller in the embodiment, and FIGS. 4 and 5 are perspective views showing the configuration of the first discharge roller in the embodiment.
In FIG. 3, a plurality of first discharge rollers 22 (22a, 22b) are arranged in the axial direction of a rotary shaft 221 provided in a direction orthogonal to the medium transport direction indicated by arrow A in the drawing, and the first discharge rollers A plurality of 23 (23a, 23b) are arranged so as to contact the first discharge roller 22. Each of the first discharge rollers 22 and 23 is disposed so as to maintain a substantially equal distance from the central portion of the medium to be conveyed with respect to the width of the medium in the axial direction orthogonal to the medium conveying direction.

  When the maximum interval between the plurality of first discharge rollers 22 and 23 arranged in the axial direction of the rotating shaft 221 is the first discharge roller width 41, when two pairs of the first discharge rollers 22 and 23 are arranged, As shown in FIG. 4, the interval between the first discharge rollers 22a and 23a and the first discharge rollers 22b and 23b is the first discharge roller width 41a, and three pairs of the first discharge rollers 22 and 23 are arranged. As shown in FIG. 5, the distance between the first discharge rollers 22a and 23a and the first discharge rollers 22c and 23c is the first discharge roller width 41b.

Next, the configuration of the medium transport guide 40 will be described with reference to FIGS. 6, 7, and 8. FIG. 6 is a cross-sectional view of the medium transport guide and the first discharge roller in the embodiment, FIG. 7 is an enlarged cross-sectional view of the medium transport guide and the first discharge roller in the embodiment, and FIG. 8 is a medium transport guide and the first discharge roller in the embodiment. It is a top view of 1 discharge roller.
6 and 7, the conveyance path 42 from the fixing roller 19 and the fixing backup roller 20 of the fixing unit 28 to the first discharge rollers 22 and 23 is a first guide member that guides the medium on which the toner is fixed. The medium transport guide 40 and the medium transport guide 61 as the second guide member are disposed to face each other.

The medium conveyance guide 40 is directed toward the surface opposite to the printing surface (toner fixing surface) on which the toner image fixed on the medium by the fixing roller 19 and the fixing backup roller 20 exists, that is, toward the medium conveyance guide 61. It is formed to protrude. Therefore, the medium conveyance guide 40 is disposed so as to come into contact with the surface opposite to the toner fixing surface of the medium.
Further, the medium transport guide 61 is disposed so as to face the medium transport guide 40 and is formed in a rib shape, and a gap is formed between the medium transport guide 40 and the opposed medium transport guide 40, which is indicated by an arrow A in the figure. A plurality are arranged in a direction orthogonal to the medium conveyance direction.

As shown in FIG. 7, the medium transport guide 40 includes a first discharge roller from a nip position 191 at the most downstream side in the medium transport direction indicated by an arrow A in the nip portion where the fixing roller 19 and the fixing backup roller 20 abut. Inclination as an inclined portion in the protruding portion 43 protruding in the direction toward the medium conveying guide 61 from a virtual line 42a connecting the nip portion where the nip portion 22 is in contact with the first discharge roller 23 to the most upstream nip position 192 in the medium conveying direction. A surface 48 is formed. The inclined surface 48 is formed so as to gradually approach the medium conveyance guide 61 from the upstream side to the downstream side in the medium conveyance direction.
The medium conveyance guide 61 is also formed with an inclined surface 62 so as to gradually approach the medium conveyance guide 40 from the upstream side to the downstream side in the medium conveyance direction.
In this way, by forming the inclined surface 48 in the medium transport guide 40, the occurrence of the jam of the medium due to the leading edge of the transported medium hitting the medium transport guide 40 is suppressed.

Further, a tip portion 43R as an R-shaped curved portion is formed at the tip of the inclined surface 48 of the medium transport guide 40, and the tip portion 43R projects from the virtual line 42a toward the medium transport guide 61 by a projecting amount h. ing. The protrusion h is desirably 5 to 10 mm, and the tip 43R has an arc shape of R = 1 mm to R = 5 mm so as not to damage the reverse printing surface of the medium conveyed by the fixing roller 19 and the fixing backup roller 20. Has been.
Further, as shown in FIG. 8, the medium conveyance guide 40 includes an outermost end portion of the first discharge roller 22 and an outermost end portion of the first discharge roller 23 in the axial direction of the rotation shaft 221 orthogonal to the medium conveyance direction. The first discharge roller width 41 is the same width as that of the first discharge roller.

In other words, when the width of the medium transport guide 40 in the direction orthogonal to the medium transport direction (the axial direction of the rotation shaft 221) is the guide width 40a, the guide width 40a and the first discharge roller width 41 are substantially the same. Here, “substantially coincide” means that the guide width 40a is formed to be in the range of 80% to 120% of the first discharge roller width 41, and is constant by being formed within that range. The effect is obtained.
Further, the ridge line between the inclined surface 48 of the medium transport guide 40 and both side surfaces in the axial direction of the rotary shaft 221 orthogonal to the medium transport direction of the medium transport guide 40 does not damage the anti-printing surface of the transported medium. A ridge line arc shape 49 as a large curved portion of R = 1 mm to R = 5 mm is formed at the tip.

9 and 10 are perspective views of the fixing unit in the embodiment. FIG. 9 is a perspective view seen from the downstream side in the medium conveying direction indicated by an arrow A in FIGS. 6 and 7. FIG. 10 is a perspective view of FIG. It is the perspective view seen from the upstream in the medium conveyance direction which the arrow A in the figure in FIG. 7 shows.
As shown in FIG. 9, the medium transport guide 40 is fixed to or integrally molded with a cover 45 of the fixing unit 28.

FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus in the embodiment.
2, the image forming apparatus 1 includes an image formation control unit 700, an I / F control unit 710, an operation unit 701, various sensors 702, a reception memory 720, an image data editing memory 730, and a charging voltage control. 740, a head control unit 750, a development voltage control unit 760, an image formation drive control unit 780, a fixing control unit 790, a conveyance belt drive control unit 800, and a paper feed / conveyance drive control unit 810. doing.

The image forming control unit 700 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, a timer, and the like, and print data and control commands (commands) from a host device. Is received, the operation of the entire image forming apparatus 1 is controlled, and the printing operation is controlled.
The I / F control unit 710 performs communication control with a host device that is communicably connected via a communication line, and transmits information on the image forming apparatus 1 to the host device and It analyzes and processes received control commands and print data.
The operation unit 701 includes a display for displaying information such as the state of the image forming apparatus 1, LEDs, a switch for accepting an input operation by an operator, a touch panel, and the like.

The various sensors 702 are a plurality of sensors (entrance sensors 12L and 12U, a writing sensor 13, and a discharge sensor 21) that detect the transport position of the medium, and the output of each sensor is input to the image formation control unit 700.
The reception memory 720 is a storage unit that temporarily stores print data input from a host device via the I / F control unit 710.
The image data editing memory 730 is a storage unit that stores image data that has been edited to transmit the print data stored in the reception memory 720 to the print head.

The charging voltage control unit 740 applies a voltage to the charging rollers 5K, 5Y, 5M, and 5C according to instructions from the image formation control unit 700, and each photosensitive drum (photosensitive drums 4K, 4Y, 4M, and 4C shown in FIG. 1). ) To charge the surface.
The head control unit 750 controls the LED heads 3K, 3Y, 3M, and 3C to irradiate and expose the surface of each charged photosensitive drum according to the image data stored in the image data editing memory 730. The electrostatic latent image is formed.

The developing voltage controller 760 applies the developing rollers 6K, 6Y, 6M, and 6C to the toner on the electrostatic latent images formed by the LED heads 3K, 3Y, 3M, and 3C on the surfaces of the respective photosensitive drums. On the other hand, control for applying a voltage is performed.
The image forming drive control unit 780 includes a K motor 781, a Y motor 782, an M motor 783, which rotate the respective photosensitive drums, charging rollers, and developing rollers of the image forming units 2K, 2Y, 2M, and 2C shown in FIG. The C motor 784 is controlled.

  The fixing control unit 790 performs control to apply a voltage to a heater built in the fixing unit 28 according to an instruction from the image forming control unit 700 in order to fix the toner image transferred to the medium. Further, the fixing control unit 790 inputs the detected temperature from the thermistor 792 that measures the temperature of the fixing unit 28, and performs heater on / off control. Further, when the fixing unit 28 rises to a predetermined temperature, the fixing control unit 790 performs the fixing roller 19, the fixing backup roller 20, the first discharge rollers 22, 23, and the second discharge rollers 26, 27 shown in FIG. The fixing motor 793 for rotating the motor is controlled.

The conveyance belt drive control unit 800 rotates and drives the conveyance belt 18 shown in FIG. 1 that conveys the medium. In response to an instruction from the image formation control unit 700, the conveyance belt drive control unit 800 rotates the belt drive roller 17 shown in FIG. Control is performed.
A sheet feeding / conveying drive control unit 810 feeds and conveys a medium to the position of the conveying belt, and in response to an instruction from the image forming control unit 700, a sheet feeding motor 811 for rotating the sheet feeding roller 11 shown in FIG. The conveyance motor 812 that rotates the first conveyance rollers 14R and 14P and the second conveyance rollers 15R and 15P is controlled.

The operation of the above configuration will be described.
First, an outline of the operation of the image forming apparatus will be described with reference to FIGS. 1 and 2.
The image formation control unit 700 of the image forming apparatus 1 receives a control command and print data transmitted from the host device via the I / F control unit 710 as a print instruction.
When receiving an instruction for printing from the host apparatus, the image forming control unit 700 instructs the sheet feeding / conveying drive control unit 810 to specify a predetermined conveying speed and rotates the sheet feeding roller 11 to make one medium from the sheet cassette 24. Send out. The inlet sensor 12L detects whether or not the paper feeding roller 11 has been normally operated. If the paper feeding roller 11 has not been normally operated, the inlet sensor 12L detects the purpose of performing the paper feeding operation again or the leading edge of the medium, and then the first transport roller 14R. , 14P is installed for the purpose of correcting the skew of the medium by abutting the leading edge of the medium against the first transport rollers 14R and 14P by controlling the drive timing of 14P.

The medium sent out from the paper supply roller 11 is sent to the first transport rollers 14R and 14P, and then transported to the image forming unit 2Y by the second transport rollers 15R and 15P.
The image forming units 2K, 2Y, 2M, and 2C start rotation of the rollers substantially simultaneously with the sheet feeding by the image forming drive control unit 780 that has received an instruction from the image forming control unit 700. At this time, a negative voltage (about −1000 V) instructed by the image forming control unit 700 to the charging voltage control unit 740 is applied to the charging rollers 5K, 5Y, 5M, and 5C, and the charging rollers 5K, 5Y, 5M, and 5C are applied. Thus, the surfaces of the photosensitive drums 4K, 4Y, 4M, and 4C are charged. Further, toner used for printing is supplied from the toner tanks 7K, 7Y, 7M, and 7C to the developing rollers 6K, 6Y, 6M, and 6C via the toner supply sponge rollers 9K, 9Y, 9M, and 9C. The toner placed on the developing rollers 6K, 6Y, 6M, and 6C is frictionally charged by the developing blades 8K, 8Y, 8M, and 8C. Further, along with the rotation of the photosensitive drums 4K, 4Y, 4M, and 4C, the transport belt 18 also starts moving at the same speed by the rotation of the belt driving roller 17.

The medium is transported by the second transport rollers 15R and 15P, and the leading edge is detected by the writing sensor 13. After a predetermined time has elapsed since the detection of the tip here, the LED head 3K starts exposure and forms an electrostatic latent image on the photosensitive drum 4K. A toner image is formed on the photosensitive drum 4K by the developing roller 6K according to the formed electrostatic latent image.
The toner image formed on the photosensitive drum 4K is drawn toward the medium side by applying a positive voltage (about + 3000V) to the transfer roller 10K when the medium reaches between the transfer roller 10K and the photosensitive drum 4K. And transferred to the medium.

The image forming units of other colors are sequentially exposed and transferred in the same manner to transfer the toner image onto the medium. When the transfer of the toner image to the medium is completed, the medium is heated and pressurized between the fixing roller 19 and the fixing backup roller 20 to fix the toner on the medium.
The medium on which the toner has been fixed is guided by the medium transport guide 40, the discharge sensor 21 monitors the arrival of the leading edge (monitoring of the medium clogging near the heater), and the discharge sensor 21 determines the length of the medium after fixing. After being detected, it is conveyed to the first discharge rollers 22 and 23.
Thereafter, the medium is transported to the second discharge rollers 26 and 27 and is transported to a transport path 46 that is a discharge route to be discharged to the discharge tray 31 or a transport path 47 that is a post-processing transport route to the post-processing apparatus. .

Next, the operation of the medium transport guide will be described with reference to FIGS. The operation when the medium conveyed between the fixing roller 19 and the fixing backup roller 20 is discharged will be described.
When the medium is conveyed between the fixing roller 19 and the fixing backup roller 20, the medium is conveyed while being heated and pressurized by the fixing roller 19 and the fixing backup roller 20 to fix the toner.

  Here, the medium conveyed while being heated and pressed by the fixing roller 19 and the fixing backup roller 20 to fix the toner is a medium of a type such as thin paper or recycled paper, or a medium in a state of moisture absorption. In this case, the sheet is conveyed while the cylindrical curl (curved) is generated (for example, the medium A in a state where the state discharged to the discharge tray 31 is curled upward (curved state) shown in FIG. 12 or downward shown in FIG. It is discharged as a curled medium B).

The medium conveyed in the curled state is detected by the discharge sensor 21 while the leading end contacts the inclined surface 48 of the medium conveyance guide 40 and then guides the non-printing surface to which the toner is not transferred to the medium conveyance guide 61 side. And conveyed to the first discharge rollers 22 and 23.
When the leading end of the medium is conveyed to the first discharge rollers 22 and 23, the medium is conveyed to the conveyance path 46 or the conveyance path 47 by the fixing roller 19, the fixing backup roller 20, and the first discharge rollers 22 and 23.

  At this time, the medium conveyance guide 40 is configured so that the medium is guided by a virtual line 42a connecting from the nip position 191 where the fixing roller 19 and the fixing backup roller 20 abut to the nip position 192 where the first discharge roller 22 and the first discharge roller 23 abut. Since the protrusion 43 is formed so as to protrude by the protrusion amount h (5 to 10 mm) in the direction toward the conveyance guide 61, the medium to be conveyed is a medium conveyance as in the medium conveyance route 50 shown in FIG. The guide 40 contacts the inclined surface 48 and the tip 43R, and is conveyed while being deformed into a convex shape on the printing surface side. That is, as shown in FIGS. 12 and 13, in order to correct the cylindrical curl whose axial direction is the medium conveyance direction orthogonal to the rotation axis of the second discharge rollers 26 and 27, the medium conveyance is performed on the medium to be conveyed. A convex shape extending in a direction orthogonal to the direction is formed to deform the medium.

Even when the leading edge of the medium to be conveyed contacts the medium conveyance guide 61, the inclined surface 62 ensures that the leading edge of the medium is between the medium conveyance guide 61 and the protrusion 43 of the medium conveyance guide 40. Can be guided to.
Here, as shown in FIG. 7 and FIG. 8, an arc shape from R = 1 mm to R = 5 mm is formed at the distal end portion 43R of the medium transport guide 40, and the inclined surface 48 of the medium transport guide 40 and the medium A large ridgeline arc shape 49 of R = 1 mm to R = 5 mm is formed on each ridgeline with both side surfaces (both end surfaces of the first discharge roller width 41) in the axial direction of the rotation shaft 221 orthogonal to the medium conveyance direction of the conveyance guide 40. Is formed and the anti-printing surface side of the medium is guided to the printing surface side, so that the printing surface does not contact the medium transport guide 40, so that the printing surface is not damaged, and the anti-printing of the medium is further performed. Since the surface is not damaged by the arc shape 43R and the ridgeline arc shape 49, good image formation can be performed.

  Further, since the medium transport guide 40 is formed up to substantially the same position as the first discharge roller width 41 of the first discharge rollers 22 and 23, the width direction of the medium perpendicular to the medium transport direction (the arrow B in FIG. In the direction shown), the medium is transported while being deformed to the first discharge roller width 41, and the entire width in the width direction of the medium is not deformed. The running load due to the deformation of the medium can be minimized without further curling.

Furthermore, since the medium is deformed in the conveyance path immediately after the medium is heated and pressed by the fixing roller 19 and the fixing backup roller 20, curling of the cylindrical medium can be effectively improved.
In this embodiment, the medium transport guide 40 is formed in a surface shape up to substantially the same position as the first discharge roller width 41 of the first discharge rollers 22 and 23. However, as shown in FIG. Even if the ribs 51 having the inclined portions 51a are arranged at substantially the same positions as both ends of the discharge roller width 41, the same effect as described above can be obtained, and the running load due to the deformation of the medium can be minimized. Can be suppressed.

  In an image forming apparatus that does not include the medium conveyance guide 40, curl occurs in a medium such as thin paper or recycled paper, or a medium that has absorbed moisture, and the curl is curled in a cylindrical shape with the direction orthogonal to the medium conveyance direction as the axial direction. In this case, when the subsequent medium collides with the rear end of the lifted up, a stacking failure occurs, and when the medium is curled in a cylindrical shape with the transport direction of the medium as an axial direction, both ends in the transport direction of the medium are directed upward and post-processing is performed. There has been a problem that the post-processing in the apparatus has a problem.

  However, in this embodiment, the medium conveyance guide 40 having the inclined surface 48 is provided downstream of the fixing roller 19 and the fixing backup roller 20 of the fixing unit 28 in the medium conveyance direction, so that the width of the medium orthogonal to the medium conveyance direction is provided. The curl of the cylindrical medium with the medium transport direction as the axial direction can be suppressed without deteriorating the curl of the medium curved in the direction (the direction indicated by the arrow B in FIG. 8). Processing defects can be suppressed. Further, curling of the medium curved in the medium transport direction can be suppressed, and medium stacking failure and post-processing failure can be suppressed.

  In the present embodiment, the first discharge rollers 22 and 23 are described as having two pairs in the axial direction. However, the present invention is not limited to this, and a plurality of three or more pairs may be used. Further, the medium transport guide 40 is fixed to the cover 45 of the fixing unit 28 or is integrally molded. However, the present invention is not limited to this, and another component is provided on the transport path from the fixing unit 28 to the first discharge rollers 22 and 23. You may make it comprise as.

Further, as shown in FIG. 2, the image forming units 2K, 2Y, 2M, and 2C are driven by independent K motor 781, Y motor 782, M motor 783, and C motor 784. However, the driving means of each unit is not limited.
In this embodiment, the image forming apparatus including four color image forming units has been described. However, the present invention is not limited to this, and a single color image forming apparatus such as a black color may be used.

As described above, in the first embodiment, by providing the medium conveyance guide having the inclined surface downstream of the fixing unit in the medium conveyance direction, curling that is a curved state formed on the medium is suppressed. The effect that it can be obtained.
In particular, it is possible to obtain an effect that curling of a cylindrical medium whose axial direction is the medium conveyance direction can be suppressed.
In the present embodiment, the image forming apparatus is described as a printer. However, the present invention is not limited to this, and a copier, a facsimile machine, a multifunction peripheral (MFP), or the like may be used.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming unit 10 Transfer roller 18 Conveying belt 19 Fixing roller 20 Fixing backup roller 22, 23 First discharge roller 40, 61 Medium conveying guide 43 Protruding part 43R Tip part 48, 62 Inclined surface 49 Ridge arc shape 700 Image formation control unit 710 I / F control unit 740 Charge voltage control unit 750 Head control unit 760 Development voltage control unit 780 Image formation drive control unit 790 Fixing control unit 800 Conveyance belt drive control unit 810 Paper feed / conveyance drive control unit

Claims (9)

A fixing unit for fixing the developer on the medium onto which the developer has been transferred;
A conveying member disposed on the downstream side of the fixing unit in the medium conveying direction and conveying the medium;
A guide member that is disposed between the fixing unit and the transport member and guides the medium;
Have
The conveying member has a plurality of roller pairs arranged on a rotating shaft,
The guide member has a width in the rotation axis direction that is substantially the same as a distance between the outermost ends of the roller pair in the rotation axis direction, and protrudes from an imaginary straight line that connects the fixing unit and the roller pair. A medium transport mechanism. The medium transport mechanism according to claim 1,
The guide member is a first guide member,
A second guide member disposed opposite the first guide member;
The medium conveying mechanism according to claim 1, wherein the first guide member is formed with a protruding portion that approaches the second guide member. The medium transport mechanism according to claim 2,
The medium transport mechanism, wherein the protruding portion is formed with an inclined portion that gradually approaches the second guide portion from the upstream side to the downstream side in the medium transport direction. In the medium conveyance mechanism according to claim 2 or 3,
The protruding portion has a curved portion formed at a tip thereof. In the medium conveyance mechanism in any one of Claims 2-4,
The medium transport mechanism according to claim 1, wherein the first guide member has curved portions formed on both side portions in the rotation axis direction. In the medium conveyance mechanism in any one of Claims 2-5,
The medium conveying mechanism, wherein the first guide member is in contact with a surface opposite to a developer fixing surface of the medium. In the medium conveyance mechanism in any one of Claims 2-6,
The medium conveying mechanism, wherein the first guide member has an amount of protrusion from an imaginary straight line connecting the fixing unit and the roller pair of 5 mm to 10 mm.   A fixing device comprising the medium transport mechanism according to claim 1.   An image forming apparatus comprising the medium transport mechanism according to claim 1.

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