JP2000284623A - Image forming device and curl removing mechanism for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device equipped with a curl removing mechanism of high durability, which is simply constituted and made compact, and capable of appropriately removing the curl of a paper, irrespective of a paper discharging direction, and to obtain the curl removing mechanism for the image forming device. SOLUTION: The image forming device is provided with a fixing device constituted of a heat roller 52 and a pressure roller 54 arranged in a frame 51 as a fixing unit and the curl removing mechanism 55 of high durability arranged just behind the fixing device, and a paper discharging direction switching mechanism 62 with a guiding part 62a where a guiding path is arranged so as to communicate with the fixing unit. The paper P with the fixed image is curved in a reverse direction by the curl removing mechanism 55, then, the curl is removed by the mechanism 55. In the case of discharging the paper P to a printed paper placing part 69, the paper P is formed to a shape suitable to the printed paper placing part 69 by making the paper P with high temperature/humidity follow the shape of the guiding part 62a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing curl of a sheet after fixing by heating in an image forming apparatus.

[0002]

2. Description of the Related Art In recent years, there has been a demand for space saving in image forming apparatuses such as printers. Therefore, in order to discharge the sheet after forming an image on the sheet in the image forming apparatus from the image forming apparatus, a sheet guide path is provided by providing a sheet guide path instead of discharging the sheet from the side of the image forming apparatus in the same direction. It is possible to reduce the size of the image forming apparatus itself by inverting the top and bottom and discharging it to the upper or lower part of the image forming apparatus,
Since the work area can be reduced, in many cases, the sheet is turned over and discharged after the image formation in a normal discharge direction. In this case, a curl removing mechanism provided in the vicinity of the paper discharge port often removes the curl (warpage) of the paper caused by the heat fixing device after image formation. On the other hand, when an image is formed using paper that is likely to cause a jam (paper jam) because the paper is hard, thick, or small, such as a postcard made by government, the paper is turned over after the image is formed. It is safer to discharge the paper as it is in the side direction of the image forming apparatus. Therefore, besides ejecting the paper upside down,
2. Description of the Related Art There has been an image forming apparatus capable of switching so that a sheet can be discharged in a lateral direction of the image forming apparatus without turning over the sheet. When the paper is discharged to the side of the image forming apparatus as described above, the curl removing mechanism is not provided as an exceptional use.However, even when the paper is discharged without being inverted, the paper is curled by the fixing device. It is not preferable that
It is also desirable to provide a curl removing mechanism here.

[0003]

However, in the conventional curl removing mechanism, a relatively complicated structure occupies a large space. Therefore, providing the curl removing mechanism in two places makes the apparatus complicated and bulky. There has been a problem that the manufacturing cost is high. Here, FIG. 16 is a diagram illustrating an example of a conventional curl removing mechanism. When a curl removing mechanism is provided in the vicinity of a discharge port for discharging the image in the lateral direction of the image forming apparatus, according to the conventional curl removing mechanism 155 shown in FIG. 16, a roller holder 159 for holding driven rollers 156 and 157 is provided. Since the springs 160, 160 for urging the driven rollers 156, 157 to the driving roller 158 via the roller holder 159 are provided, there is a problem that the apparatus becomes large and complicated, and the manufacturing cost is increased. In addition, when the curl is removed immediately after the heat fixing in the fixing device, the guide portion 159a of the roller holder 159 slidably contacts the image on the paper which has been heated to a high temperature by the fixing device and is in an unstable state. And the roller shafts 156a and 157a made of resin and the roller holder 159
There is also a problem that the resins slide with each other and the durability is reduced by heat.

An object of the present invention is to solve the above-mentioned problems, and provide an image forming apparatus which has a highly durable curl removing mechanism with a simple and compact structure, and which can appropriately remove curl of a sheet regardless of a sheet discharging direction. An object of the present invention is to provide a curl removing mechanism of an image forming apparatus.

[0005]

In order to achieve this object, in an image forming apparatus according to the present invention, an image forming means for forming an image on a sheet and an image formed by the image forming means are provided. A fixing unit that heats the sheet to fix the formed image; a curl removing mechanism that removes the curl of the sheet on which the image is fixed by the fixing unit; and a downstream side of the curl removing mechanism in the sheet conveying direction. A first discharge direction for discharging the sheet upside down and a second discharge direction for discharging the sheet without turning upside down, the discharge direction of the sheet being switchable. And a paper direction switching mechanism.

In the image forming apparatus according to this configuration, the curl removing mechanism is provided on the upstream side in the sheet transport direction of the sheet discharging direction switching mechanism. It can be removed regardless of the paper discharge direction. Further, there is no need to provide two curl removing mechanisms, and the image forming apparatus itself can be downsized.

In the image forming apparatus according to the second aspect of the present invention,
In addition to the configuration of the image forming apparatus according to claim 1, the paper ejection direction switching mechanism deforms the paper so as to bend the paper in a direction opposite to a direction in which the paper is curled by the curl removing mechanism. A guide path having a guide wall for guiding the leading end of the sheet in the first sheet discharging direction is provided, and an outside air blocking unit provided in the guide path and preventing an exchange with outside air is provided.

[0008] In the image forming apparatus according to this configuration, an undesired strong curl on the sheet is properly removed by the fixing device by the curl removing mechanism so that the sheet can be discharged in the second sheet discharging direction, and the outside air is blocked to block outside air. While maintaining the temperature and humidity of the paper by the means, while guiding the paper in the first paper discharging direction while the paper is easily plastically deformed, the first wall is used by the guide wall.
The paper can be deformed in a state more suitable for discharging in the first paper discharging direction and discharged in the first paper discharging direction. Therefore, the paper from which the curl has been properly removed can be discharged from any of the paper discharge ports.

In the image forming apparatus according to the third aspect of the present invention,
An image forming unit for forming an image on a sheet, a fixing unit for heating the sheet on which the image is formed by the image forming unit, and fixing the formed image; and And a curl removing mechanism disposed to remove curl of the sheet on which the image is fixed by the fixing unit.

[0010] In the image forming apparatus according to this configuration, an undesired strong curl attached to the sheet by the fixing means can be efficiently removed by the curl removing mechanism while the temperature and humidity of the sheet immediately after fixing are high. .

[0011] In the image forming apparatus according to the fourth aspect of the present invention,
In addition to the configuration of the image forming apparatus according to any one of claims 1 to 3, the fixing unit is disposed opposite to the heat roller and a heat roller that heats the sheet, and the fixing unit applies the sheet to the heat roller. A pressure roller configured to be brought into pressure contact, and a fixing unit frame configured to house and support the heat roller and the pressure roller. The fixing unit frame is disposed downstream of the roller and the pressure roller in the sheet conveyance direction.

In the image forming apparatus according to this configuration, the fixing unit and the curl removing mechanism are formed integrally with the fixing unit frame, so that the curl removing mechanism can be provided immediately after the fixing unit. Therefore, the curl can be efficiently removed while the paper is still hot and wet and easily deformed plastically in the same frame. Further, since these can be configured compactly, the size of the image forming apparatus itself can be reduced. Furthermore, the maintenance of the image forming apparatus is facilitated by unitizing the fixing unit and the curl removing mechanism.

[0013] In the image forming apparatus of the invention according to claim 5,
In addition to the configuration of the image forming apparatus according to any one of claims 1 to 4, the curl removing mechanism includes: a driving roller;
It is composed of a plurality of rollers supported by a coaxial support shaft,
A first driven roller driven by the driving roller, and one or more rollers supported by a coaxial support shaft;
A second driven roller driven by the driving roller,
The support shaft of the first driven roller and the support shaft of the second driven roller are disposed in parallel with the support shaft of the drive roller, and the support shaft of the first driven roller and the second driven shaft The inter-axis distance of the support shaft of the roller is larger than the radius of the roller of the first driven roller and the radius of the roller of the second driven roller, and the radius of the roller of the first driven roller is smaller than the radius of the first driven roller. The second driven roller is disposed at a distance smaller than the sum of the radii of the rollers, and the rollers constituting the first driven roller and the second driven roller are alternately disposed.

In the image forming apparatus according to this configuration, the curl removing mechanism includes the first driven roller and the second driven roller that are driven by the driving roller, so that the curl of the sheet can be efficiently removed. Further, the distance between the first driven roller and the second driven roller can be adjusted within a range where the rollers overlap, and the time for contact with the drive shaft can be increased or decreased to adjust the degree of curl removal. It is possible. Further, since the roller group including the two rollers is interdigitated, the paper can be properly conveyed without paper entering between the first driven roller and the second driven roller. Can be effectively prevented. In addition, this configuration eliminates the need for a fixed guide that guides the paper in the transport direction, and the paper is transported while being held by the rotating body. There is no sliding contact with the fixed guide, and the image formed on the paper is not damaged. Further, the first driven roller and the second driven roller can be arranged close to each other, and the curl removing mechanism can be made compact. In addition, since the driven roller includes a plurality of rollers, heat radiation is improved.

In the image forming apparatus of the invention according to claim 6,
In addition to the configuration of the image forming apparatus according to claim 5, in the curl removing mechanism, both the support shaft of the first driven roller and the support shaft of the second driven roller are formed of an elastic body. The support shaft is configured to urge the first driven roller and the second driven roller against the driving roller by its elastic force.

In the image forming apparatus according to this configuration, since the support shaft itself of the curl removing mechanism is made of an elastic body, there is no need to provide a biasing means with a member separate from the support shaft, and the image forming apparatus is simple and low. It can be a costly mechanism. Also,
Even with a simple configuration, the driven roller can be appropriately biased and pressed against the sheet. Even in the case of sheets having different thicknesses, the respective rollers of the driven rollers can be pressed in accordance with the sheet thickness, and the sheets are not damaged by urging each portion with an appropriate force.

[0017] In the image forming apparatus of the invention according to claim 7,
In addition to the configuration of the image forming apparatus according to claim 6, in the curl removing mechanism, the support shaft of the first driven roller and the support shaft of the second driven roller are formed by a helical spring. It is characterized by.

In the image forming apparatus according to this configuration, since the support shaft of the curl removing mechanism is constituted by a helical spring, it can flexibly cope with a large displacement, and appropriately biases the driven roller to form a sheet. Can be pressed against. In particular, even when the paper has a partially uneven thickness, each roller of the driven roller can flexibly press against the paper according to the thickness of the paper, and the paper may be damaged by urging each part with an appropriate force. Absent. Further, even if the support shaft becomes hot, the helical spring is made of metal, so that there is no sliding between the resins, so that the heat resistance and the heat radiation are high as compared with a resin support shaft or the like.

In the curl removing mechanism for an image forming apparatus according to the present invention, the first driven roller comprises a driving roller and a plurality of rollers supported by a coaxial support shaft, and driven by the driving roller. And one supported by a coaxial support shaft
Or a second driven roller composed of a plurality of rollers and driven by the driving roller, wherein a supporting shaft of the first driven roller and a supporting shaft of the second driven roller are supported by the driving shaft of the driving roller. And the distance between the support shaft of the first driven roller and the support shaft of the second driven roller is equal to the radius of the roller of the first driven roller and the second driven roller. The first driven roller and the second driven roller are disposed at a distance that is larger than the radius of the roller and smaller than the sum of the radius of the roller of the first driven roller and the radius of the roller of the second driven roller. The rollers constituting the two driven rollers are alternately arranged.

In the curl removing mechanism of the image forming apparatus according to this configuration, the curl of the sheet can be efficiently removed by the first driven roller and the second driven roller driven by the driving roller. Further, the distance between the first driven roller and the second driven roller can be adjusted within a range where the rollers overlap, and the time for contact with the drive shaft can be increased or decreased to adjust the degree of curl removal. It is possible. Further, since a roller group consisting of two plural rollers is intertwined with each other,
Sheets do not enter between the first driven roller and the second driven roller, so that the sheet can be properly conveyed and jams can be effectively prevented. In addition, this configuration eliminates the need for a fixed guide that guides the paper in the transport direction, and the paper is transported while being held by the rotating body. There is no sliding contact with the fixed guide, and the image formed on the paper is not damaged. Further, the first driven roller and the second driven roller can be arranged close to each other, and the curl removing mechanism can be made compact. In addition, since the driven roller includes a plurality of rollers, heat radiation is improved.

According to a ninth aspect of the present invention, in addition to the configuration of the curl removing mechanism of the image forming apparatus according to the eighth aspect, in addition to the configuration of the curl removing mechanism of the image forming apparatus, the support shaft of the first driven roller and the second shaft are provided. The support shaft of each of the second driven rollers is formed of an elastic body, and the support shaft attaches the first driven roller and the second driven roller to the drive roller by the elastic force. It is characterized by being constituted so that it may be energized.

In the curl removing mechanism of the image forming apparatus according to this configuration, since the support shaft itself is formed of an elastic body, there is no need to provide an urging means with a member separate from the support shaft, and the structure is simple and low. It can be a costly mechanism. Also,
Even with a simple configuration, the driven roller can be appropriately biased and pressed against the sheet. Even in the case of sheets having different thicknesses, the respective rollers of the driven rollers can be pressed in accordance with the sheet thickness, and the sheets are not damaged by urging each portion with an appropriate force.

According to a tenth aspect of the present invention, in addition to the configuration of the curl removing mechanism of the image forming apparatus according to the ninth aspect, the support shaft of the first driven roller and the second Is characterized in that the support shaft of the driven roller is constituted by a helical spring.

In the curl removing mechanism of the image forming apparatus according to this configuration, since the support shaft is constituted by a helical spring, it can flexibly cope with a large displacement, and can appropriately bias the driven roller to form a sheet. Can be pressed against. In particular, even when the paper has a partially uneven thickness, each roller of the driven roller can flexibly press against the paper according to the thickness of the paper, and the paper may be damaged by urging each part with an appropriate force. Absent. Further, even if the support shaft becomes hot, the helical spring is made of metal, so that there is no sliding between the resins, so that the heat resistance and the heat radiation are high as compared with a resin support shaft or the like.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus and a curl removing mechanism of the image forming apparatus according to the present invention will be described below with reference to the accompanying drawings using an image forming apparatus 1 as a preferred embodiment.

FIG. 1 is a cross-sectional view of the image forming apparatus 1 as viewed from the side perpendicular to the sheet conveying direction. The overall shape of the image forming apparatus 1 is formed in a substantially rectangular parallelepiped by the main body frame 11. 1, the right side is the front surface of the image forming apparatus 1, and the near side is the left side of the image forming apparatus 1. A paper feed unit 19 composed of a paper feed cassette that stores and feeds the paper P is provided below the main body frame 11, and the paper P stored in the paper feed unit 19 is transported from the front of the image forming apparatus 1 to the transport unit 18.
Transported by A developing unit 17 integrally formed as a process unit is disposed above the transport unit 18.
Further, an optical scanning device 12 configured as a laser scanner is disposed above the developing unit 17. As shown in FIG. 3, in the developing section 17, the light scanning device 1 is placed on the photosensitive drum 77, which is uniformly charged by a charger 78 composed of a scorotron.
2 is a laser beam LB modulated by an image signal
Are scanned to form a latent image. The latent image is developed by the developer T conveyed by the developing roller 75 and is made visible to form an image. The exposed image is transferred to the sheet P by the transfer roller 87. Paper P with transferred image
Is the fixing unit 1 on the left side of the developing unit 17 by the transport unit 18.
5.

The fixing unit 15 integrally formed as a fixing unit fixes the developer T by applying pressure while heating the sheet P on which an image is formed. Further, a curl removing mechanism 55 for removing the curl of the sheet P after fixing is arranged in the frame 51 of the fixing unit 15, and corrects and removes the curl of the sheet P after fixing. The paper P from which the curl has been removed is printed by the paper output unit 16 provided with the paper output direction switching mechanism 62 at the rear of the image forming apparatus 1 or at the top of the apparatus.
9 is discharged. The schematic configuration of the image forming apparatus 1 is as described above. Hereinafter, the configuration of each unit will be described in detail.

As shown in FIG. 1, the paper feeding section 19 has a drawer-like configuration in which the whole is a frame 91, a box-like shape having a substantially rectangular parallelepiped opening at the top, and a handle 97 on the front surface. A storage section 92 is provided inside which a number of sheets P can be stacked and stored. Near the center of the bottom of the storage section 92,
A swingable paper press 93 having its base pivotally attached thereto is provided. A coil spring (not shown) is provided below the paper press 93 to urge the paper press 93 upward. Therefore, even when a large number of sheets P are stacked and stored, or when the number of stacked sheets P becomes small and the thickness of the stacked sheets P becomes thin, the top sheet of the stored sheets P is always fed to the paper feed roller. 81 can be brought into contact with an appropriate magnitude of force. A separation pad 94 formed of a material having a large friction coefficient with respect to the sheet P is disposed in front of the sheet press 93 (right side in FIG. 1).
Is a separation pad spring 9 composed of a coil spring disposed below the paper P so as to press the paper P in the direction of the paper feed roller 81.
5 energized. The separation pad 94 holds the paper P other than the paper conveyed by the paper feed roller 81 by its frictional force and feeds only one sheet to the conveyance unit 18.

The paper feeding section 19 is configured to be able to be pulled out forward by pulling the handle 97 forward, so that replenishment of the paper P and processing of paper jam can be easily performed. In that case,
As the paper feed unit 19 is pulled out, the separation pad 94 and the driven roller 96 are separated from the paper feed roller 81, so that the paper P can be processed without being pinched.

Next, the transport section 18 will be described. The sheet P pulled obliquely forward (upper right in FIG. 1) from the sheet feeding unit 19 by the sheet feeding roller 81 and the driven roller 96.
The guide 82 guides the leading end of the sheet upward by the guide 82, and further guides the sheet backward along the guide 82. When the paper P is further conveyed by the paper feed roller 81 and the driven roller 96, the leading end of the paper P pushes down the first paper feed sensor 83 and enters. Then, the leading end of the sheet P comes into contact with the contact portion between the registration roller 84 and the driven roller 85 that rotates with the registration roller 84.

The registration roller 84 and the driven roller 85
Performs skew correction of the sheet P. That is, the registration roller 84 is stopped for a predetermined time after the first paper feed sensor 83 detects the leading end of the paper P. Since the paper P continues to be conveyed by the paper feed roller 81 and the driven roller 96, the leading edge of the paper P comes into contact with the stopped portion of the registration roller 84 and the driven roller 85 without being bitten by the contact portion. However, since the entire sheet P is further conveyed by the sheet feeding roller 81 and the driven roller 96, the middle portion of the sheet P whose leading end is in contact with the registration roller 84 and the driven roller 85 is a space of the guide 82. Is deflected. In the meantime, the sheet P is conveyed by the sheet feeding roller 81 and the driven roller 85, and the leading end of the sheet P is entirely in contact with the contact portion between the registration roller 84 and the driven roller 85. At the time of the contact, the leading end of the sheet P is completely parallel to the rotation axis of the registration roller 84, that is, the skew is corrected. At this stage, if the registration roller 84 is rotated in the paper transport direction by the control unit 20, the skew of the paper P is corrected and the paper P is transported in a correct posture.

When the skew correction is completed by the registration roller 84, the sheet P is further conveyed, and the second sheet feeding sensor 86 is pushed down at the leading end to further move the leading end to the photosensitive drum 77.
And the transfer roller 87. The control unit 20 recognizes the position of the leading end portion of the paper P by the second paper supply sensor 86, and the control unit 20 conveys the paper P including a margin up to a predetermined printing start portion of the paper P. The printing is performed from the printing start portion of the predetermined paper P. Here, the description of the optical scanning device will be simplified first.

FIG. 4 shows the optical scanning device 12 as a cover 22 (FIG. 2).
FIG. 2 is a plan view seen from above (in the direction opposite to Y in FIG. 1) with the reference numeral removed. As shown in FIG. 4, the periphery is surrounded by a side wall 21 d of the support member 21, and the upper surface side (see FIG. 2) of the optical scanning device 12 is provided with a laser diode 41, a laser diode holder 42 supporting the laser diode 41, A light emitting unit 4 including a substrate 43 in which a lead wire is connected to a diode 41;
7, a collimator lens 45 for converting the diffused light of the laser beam LB emitted from the light emitting section 47 into parallel light, and a lens cell 44 having a slit (not shown) for regulating the parallel light to a predetermined width. (Hereinafter, the light emitting unit 47 and the lens cell 44
Are collectively referred to as a parallel light unit. ), The first cylindrical lens 46 for converging the parallel laser beam LB to the mirror surface of the polygon mirror 23, and the converged light are sequentially reflected by six plane mirrors arranged on the hexagonal prism-shaped side surface rotating at high speed. The polygon mirror 23 deflects and scans the light beam, and the laser beam LB deflected at a constant angular velocity by the polygon mirror 23 is scanned at a constant speed on the surface of the photosensitive drum 77 (see FIG. 3) to be scanned. fθ
A lens 31 and an optical element of a first fixed mirror 32 that bends a light beam transmitted through the fθ lens 31 downward are provided.

FIG. 2 is a sectional view taken along the line AA of FIG. As shown in FIG. 2, the optical scanning device 12 is separated on the upper surface side and the lower surface side by the partition wall 21e of the support member 21 which is the frame of the present invention, and each optical element is arranged on both surfaces. The light beam reflected by the polygon mirror 23 and transmitted through the fθ lens 31 while being diffused in the up-down direction (Y-axis direction) and bent downward by the first fixed mirror 32 is further deflected by the second fixed mirror 33 to be deflected by the upper surface. Travels in a direction substantially parallel to the light beam on the side and in the opposite direction. The lower side surface converges the light flux in the vertical direction in order to focus the second fixed mirror 33 and the light flux diffused by the second fixed mirror 33 on the photosensitive drum 77 (see FIG. 3) to be scanned. Each optical element of a second cylindrical lens 34 to be made, and a third fixed mirror 35 that deflects the converged light beam toward the photosensitive drum 77 and reflects the light beam is disposed. Optical scanning device 12
With such a configuration, the latent image is formed by scanning the photosensitive drum 77 provided in the developing unit 17 (see FIG. 3) with the laser beam LB modulated based on the image data.

FIG. 3 is an enlarged view of a part of the optical scanning device 12, the developing unit 17, and the main body frame 11 of the image forming apparatus 1 shown in FIG. As shown in FIG. 3, the developing unit 17 includes a frame 7 that houses and supports the whole as a process unit.
0, where each component is located. Frame 7
0 is largely divided into a developer chamber 71 and a developing chamber 73.
The developer chamber 71 stores a nonmagnetic one-component developer T,
A blade-like stirring member 72 called an agitator is supported on a rotating shaft driven by a motor (not shown).
Therefore, the developer T is always replenished from the developer chamber 71 to the developing chamber 73 by the rotation of the stirring member 72.

In the developing chamber 73, a photosensitive drum 77 and a photosensitive drum 7 disposed in front thereof (right side in FIG. 3) are provided.
7, a developing roller 75 rotated in the opposite direction to the photosensitive drum, and a developing roller 75 further disposed in front of the developing roller 75.
Are provided, a supply roller 74 rotated in the same direction as the above, a paper dust removing unit 79 arranged behind the photosensitive drum 77, a charger 78 arranged above the photosensitive drum 77, and the like.

The supply roller 74 is for rotating the sponge surface to adhere the fine and granular developer T to the developing roller 75 by pressing while rotating. The layer pressure regulating blade 76 is provided with a developer T attached to the developing roller 75 by the supply roller 74.
In order to equalize the amount of the developer T to an appropriate level, the amount of the developer T is adjusted so that the developer T is urged and contacted at a predetermined pressure to scrape off the excess developer T.

The photosensitive drum 77 is moved in the sheet transport direction (FIG. 3).
(Clockwise in FIG. 1), and can convey the paper P in cooperation with the transfer roller 87. First, the paper dust attached to the photosensitive drum 77 is removed from the photosensitive drum 77 by the paper dust removing unit 79. Although not shown in detail, the paper dust removing unit 79 of this embodiment is configured to use a brush or a nonwoven fabric to pass the developer T remaining on the surface of the photosensitive drum 77 and capture the paper dust. Have been. The portion of the photosensitive drum 77 that has passed through the paper dust removing unit 79 is then moved to a position facing the charger 78 by rotation of the photosensitive drum 77.

In the charger 78, a charging wire 78a made of a tungsten wire having a diameter of 50 to 100 μm, called a corona wire, is arranged in parallel at a distance of about 10 mm from the photosensitive drum 77, and the periphery is surrounded by an aluminum shield electrode 78d. A groove-shaped opening is provided along the portion covered with and facing the photosensitive drum 77, and a grid electrode 78b made of several wires or meshes is insulated from the shield electrode 78d in this opening. It is arranged and configured as a scorotron. The shield electrode 78
A cleaning hole 78c, which is a hole for guiding a cleaning member slidably holding the dirty charged wire 78a in a slidable manner, is provided on the opposite side of the surface of the photosensitive drum 77 which faces the photosensitive drum 77. Along the direction, it is opened in a groove shape facing the optical scanning device support portion 11a.

The charging line 78a is connected to a positive pole of a power supply device (not shown), and a high voltage of 5 to 10 kv is applied. Positive ions generated by the charging are moved to the surface of the photosensitive drum 77 to be charged. Further, the charging potential is regulated by applying a bias voltage to the grid electrode 78b, and the charging can be controlled by changing the voltage. The surface of the photosensitive drum 77 is positively charged by the charger 78. The charger 78 may be a corotron having no grid electrode 78b instead of the scorotron shown in the embodiment, and may be of another type as long as it can generate corona discharge such as brush charging.

The portion of the photosensitive drum 77 whose surface is positively charged by the charger 78 moves by rotation.
The laser beam LB is emitted by the optical scanning device 12 described above. Since the photoconductor drum 77 is exchanged as a process unit together with the exchange of the developer T, the durability is relatively low, but the organic OPC (Org) is lightweight and relatively inexpensive.
an ani Photoconductor) photoconductor. When the laser beam LB is applied, the conductivity of the surface of the photosensitive drum 77 hit by the laser beam LB increases, so that the charging potential decreases, and a latent image is formed due to the difference in potential. The photoconductor drum 77 may be made of a selenium-based photoconductor made of aSi (amorphous silicon), Se or a Se-based alloy, or CdS (cadmium sulfide), which has high photosensitivity and a long life photoconductive property. Good.

The portion of the photosensitive drum 77 on which the latent image has been formed by the laser beam LB is brought into contact with the developing roller 75 on which the developer T is adhered by the rotation of the photosensitive drum 77. The developing roller 75 is a rubber roller made of a base material obtained by imparting conductivity in which carbon black is dispersed in silicon rubber or urethane rubber on a roller shaft made of stainless steel, and the roller surface is coated with a fluororesin. . At this time, the developer T attached to the developing roller 75 is supplied to the supply roller 74 and the layer thickness regulating blade 7.
6 and is positively charged by friction.

When the developing roller 75 comes in contact with the photosensitive drum 77, the laser beam LB is irradiated, and the developer T adheres to a portion where the charged potential is lowered. Therefore, the developer T
As a result, the latent image is made visible and visualized, and the development is completed.
At this time, the developer T remaining on the photosensitive drum 77 is collected by the developing roller 75. The image developed here is further conveyed to a position facing the sheet P in a nip portion with the transfer roller 87 by the rotation of the photosensitive drum 77.

The transfer roller 87 is formed as a conductive roller whose surface is covered with a base material in which carbon black is dispersed in silicon rubber or urethane rubber to impart conductivity, and is connected to a negative pole of a power supply (not shown). Is applied, a voltage is applied to the sheet P, and the photosensitive drum 7
The sheet P and the photosensitive drum 77 are brought into contact with each other by the transfer roller 87 urged in the seven directions, and the image formed by the developer T formed on the photosensitive drum 77 is transferred to the sheet P. .

As shown in FIG. 1, an image is formed on the paper P by the developing unit 17 configured as described above,
The paper P is further conveyed by 8 and enters the fixing unit 15.

Next, the fixing unit 15 will be described in detail. FIG. 5 is a diagram schematically illustrating the fixing unit 15 in which a portion below the sheet P is omitted, as viewed from the lower side (opposite Y direction) of FIG. In addition,
In FIG. 5, a part of the drive roller 58 is not shown in order to show the positional relationship of the drive roller 58. FIG. 6 is a cross-sectional view of the fixing unit 15 as viewed in the Z direction from the line CC in FIG. The fixing unit 15 includes components arranged on a frame 51 and is configured to be detachable from the image forming apparatus 1 (see FIG. 1) as an integrated fixing unit. As shown in FIG. 6, the fixing unit 15 is provided on a frame 51, a heat roller 52 having a halogen heater 53, a pressure roller 54 for urging the sheet P against the heat roller 52, and a fixing roller provided downstream of the sheet conveying direction. Curl removing mechanism 5 including a driven roller 58 and a first driven roller 56 and a second driven roller 57 driven by the driven roller 58.
5 and a paper ejection sensor 61 are configured as a fixing unit integrally provided.

The heat roller 52 has a resin bearing at both ends in a direction (Z-axis direction) which is substantially the width of the paper and is orthogonal to the paper transport direction, as shown in a cutaway sectional view with a part thereof omitted in FIG. 52a, 52b, the frame 51e,
The sheet P is fixed to 51f, rotatably disposed, and disposed such that the surface thereof is in close contact with an image formed by the developing unit 17 (see FIG. 1) on the sheet P to be conveyed. The heat roller 52 is formed in a hollow cylindrical shape made of an aluminum alloy, and its outer surface is coated with a fluororesin on a base material of an aluminum alloy so that the developer T or the like does not adhere by heating. As shown in FIG.
A gear in which both ends are rotatably supported by bearings 52a and 52b, and a driving gear driven by a motor through a gear train (not shown) is provided at one end in the Z direction of the heat roller 52 (left side in FIG. 5). The sheet 52 abuts on the section 52 c and rotates in the sheet conveying direction (clockwise in FIG. 6).

The halogen heater 53 includes a heat roller 52
And terminals 53a, 5a provided at both ends thereof.
3b is gripped and fixed by the electrodes 53d and 53e, respectively. The halogen heater 53 is a halogen lamp that includes a tungsten filament (not shown) in a main body 53c formed of a quartz glass tube and is filled with a halogen gas. Then, by the so-called halogen cycle, the tungsten evaporated from the tungsten filament is returned to the filament again without adhering to the inside of the quartz glass tube.
Therefore, the blackening inside the quartz glass tube is prevented, the amount of heat radiated is not reduced, and the filament is not thinned, so that the life is long. When the halogen heater 53 is turned on to generate heat, the heat roller 52 is heated from the inside, and the surface temperature of the heat roller 52 is increased to about 200 ° C. In addition,
The surface temperature is detected by a temperature sensor 59 including a thermistor 59a and a supporting portion 59b made of polyimide for supporting the thermistor 59a, and is controlled by the controller 20 (see FIG. 1).

As shown in FIG.
The pressure roller 54 presses the paper P conveyed to
Is arranged. The pressure roller 54 is formed of a heat-resistant rubber material such as silicon rubber so that the surface thereof can be in close contact with the heat roller 52, and is further coated with a fluorine resin to prevent the adhesion of the developer T and the like. Pressure roller 54
Are configured to rotate with the rotation of the heat roller 52. At this time, both ends of the pressure roller 54 are coil springs (not shown) so that the sheet P is pressed against the nip portion between the heat roller 52 and the pressure roller 54. Heat roller 52
Supported by a bearing that is biased toward.

When the paper P conveyed by the conveyance unit 18 enters the fixing unit 15 thus configured, the image formed by the developer T formed on the paper P is applied to the surface of the heat roller 52 by the pressure roller 54. Is pressed and pressed. At this time, the surface of the heat roller 52 is at a high temperature as described above, so that the developer T is melted and permeated into the fibers of the paper P.

The curl removing mechanism 55 includes a heat roller 52.
The paper P on which the developer T is fixed by being heated and pressed by the pressure roller 54 is deformed so that the paper P is curved along the surface of the heat roller 52 due to the heat and pressure. This causes a so-called curl, and is a mechanism for removing the curl. This curl is not only uncomfortable for the user, but also inconvenient when stacking the discharged sheets P. Therefore, the curl is reversed to the curl. It is to make it flat.

As shown in FIG. 6, the curl removing mechanism 55 is provided within the frame 51 of the fixing unit in which the heat roller 52 and the pressure roller 54 are housed.
2 and the pressure roller 54 are provided integrally as a part of a fixing unit on the downstream side (the left side in the drawing) of the pressure roller 54 in the sheet conveyance direction.
The curl removing mechanism 55 includes a gear portion 52 of the heat roller 52.
A driving roller 58 to which the driving force is transmitted from c through an idle gear (not shown) is disposed. A first driven roller 56 that rotates with the first driven roller 56 is provided, and substantially above the driving roller 58 (counter Y direction) downstream of the first driven roller 56 in the sheet conveyance direction. Two driven rollers 57 are provided and configured. In the present embodiment, the first driven roller and the second driven roller according to the present invention correspond to the first roller group 561 of the first driven roller 56, which removes curl in cooperation with each other. This is a first roller group 571 of the second driven rollers 57. That is, this embodiment is configured by using four sets of the curl removing mechanism of the present invention as an example.

As shown in FIG. 5, the first driven roller 56
Are the respective support shafts 561h and 562 in the order of the anti-Z direction.
h, 563h and 564h are arranged on the same straight line, and the first
Roller group 561, second roller group 562, third roller group 5
63, and a fourth roller group 564.
In these first to fourth roller groups 561 to 564 (hereinafter simply referred to as roller groups), the first roller group 561 and the second roller group have the same configuration, and the third roller group 563 and the fourth roller group 564 are formed. , The first roller group 561 and the second roller group 56
Since the second roller group 561 is substantially symmetrical with respect to the center of the fixing unit in the Z-axis direction, the description of the first roller group 561 will be replaced with the description of the other roller groups, and the description thereof will be omitted.

As shown in FIG. 5, the second driven roller 57 is different from the first driven roller 56 described later in detail in the arrangement of rollers and spacers constituting each of the roller groups 571 to 574. Although the rollers 56 and the second driven roller 57 are different from each other in that they are partially overlapped with each other, the details thereof are substantially the same as those of the first driven roller 56. The description of the roller 56 will be omitted instead of the description of the second driven roller 57.

The driving roller 58 includes a driving shaft 58b, a first roller 581, a second roller 582, a third roller 583, and a fourth roller 584. The drive shaft 58b is composed of a single stainless steel roller having a drive gear (not shown) integrated at one end, and is arranged in the paper width direction. The first roller 581, the second roller 582, the third roller 583, and the fourth roller 584 abut on and drive the first driven roller 56 and the second driven roller 57, respectively, so that the respective roller groups 561 to 561 are driven. 564,57
They are arranged and arranged at positions on the drive shaft 58b corresponding to 1 to 574, respectively. The first roller 581 and the second roller 581
Roller 582, third roller 583, fourth roller 584
Is formed using a heat-resistant rubber such as silicon rubber as a base material.

FIG. 12 shows a first roller group 561 and a first roller group 561 of the first driven roller 56 and the second driven roller 57, respectively.
FIG. 7 is a diagram illustrating a configuration of a first embodiment. According to FIG.
Four roller groups 561 to 56 constituting the driven roller 56
4, the configuration of each roller group will be described in detail by taking the first roller group 571 as an example among the four roller groups 571 to 574 constituting the second driven roller 57. In the figure, the lower side is the X direction which is the paper transport direction, and the left direction is the Z direction.

The first roller group 561 of the first driven roller 56
Are three cylindrical first rollers 56 having a relatively large radius.
1a, a second roller 561b, a third roller 561c, and a first spacer 561 which is a columnar spacer having a relatively small radius inserted between every other roller.
d, a second spacer 561e, a third spacer 561f, and a fourth spacer 561g are provided. In the present embodiment,
These are formed as an integrally molded product of a resin, where the first roller 561a and the second roller 561 are formed.
b, third roller 561c, first spacer 561d, second
The spacer 561e, the third spacer 561f, and the fourth spacer 561g are integrally formed so that their central axes are coaxial. Note that the first roller 561a and the second
Roller 561b, third roller 561c, first spacer 5
61d, second spacer 561e, third spacer 561
f and the fourth spacer 561g may be formed separately.

The first roller group 561 comprises
The members 61a to 561g are formed of POM (polyacetal) having high mechanical strength and excellent wear resistance. Note that POM has heat resistance of about 120 ° C., and therefore has little deterioration even when it comes into contact with high-temperature paper P immediately after fixing. However, sliding between resins at high temperature is not preferable because the surface easily deteriorates. . The first to third rollers 561a, 561b,
561c and the first to fourth spacers 561d, 561e,
A support shaft 561h for rotatably supporting 561f and 561g is provided. This support shaft 561h is made of SUS
And the like, and is formed into a cylindrical tension coil spring in which the wire is in close contact. Therefore, the first roller group 561 slides with the metal support shaft 561h, and there is no sliding between the resins. Therefore, even when the temperature is high, deterioration of the surface is reduced. In particular, a helical spring has a hollow structure so that the heat dissipation effect is high and the sliding part can be prevented from being overheated. In addition, the support shaft 561h itself is a good heat dissipation plate to effectively heat heat. Diverge. Further, since the support shaft 561h itself is supported in an open state (see FIG. 13), the heat dissipation effect is high.

Here, FIG. 13 is a diagram showing a state in which the first roller group 561 of the first driven roller 56 contacts the drive roller 58 and rotates. As shown in FIG. 13, the support shaft 561h is normally contacted by the support shaft support portions 51b and 51d so as to urge the first roller group 561 to the first drive roller 581 in a state where the wire is substantially in close contact. The first roller group 561 of the first driven roller 56 is
In cooperation with the first roller group 571 (see FIG. 5) of the driven roller 57, the sheet P is urged against the drive roller 58 with an appropriate pressure and pressed against the same, as with a fixed support shaft so as to remove curl. To work.

On the other hand, when a predetermined force or more is applied to the first roller group 561, the support shaft 361h formed of a helical spring is easily deformed. The position in the Z-axis direction is regulated by the regulating portion 51c that regulates the position of the first roller group 561, and the position is similarly regulated in the X direction (not shown), but in the Y-axis direction (vertical direction in FIG. 13). Can be moved to some extent.

FIG. 11 is a cross-sectional view of the curl removing mechanism 55 viewed from the direction opposite to the Z direction in FIG. As shown in FIG. 11, these rollers 561a, 571a and spacer 5
First roller group 561, 571 having 61d, 571d
A hole is drilled at the center of rotation of. Similarly, each of the other rollers and spacers (not shown) is provided with this hole through the support shaft 561.
h, 571h. At this time, since the diameters of the support shafts 561h and 571h are smaller than the holes, the first roller groups 561 and 571 are smoothly rotatably supported.

As shown in FIG. 12, the second driven roller 57
The first roller group 571 has substantially the same configuration as the first roller group 561 of the first driven roller 56 described above, but has a configuration in which the direction is reversed in the Z-axis direction. That is, since the thicknesses of the spacers 561d and 561g of the first driven roller 56 are different from those of the spacers 571d and 571g of the second driven roller 57, the rollers 561a and 561 of the first driven roller 56 are different.
b, 561c and spacers 561e, 561f, and the rollers 571a, 571 of the second driven roller 57.
The positions at which the spacers 71b and 571c and the spacers 571e and 571f are arranged are displaced in the Z-axis direction. As a result, the rollers 561a, 561b and 561c and 571a, 571b,
571c are arranged at positions not opposed to each other.

Here, as shown in FIG. 11, a support shaft 5 serving as a support shaft for the first driven roller 56 and the second driven roller 57 is provided.
The distance between the axes of 61h and 571h is larger than the radius of each roller, and smaller than the sum of the radii of these rollers. Roller 5 of first driven roller 56
Since the rollers 61a, 561b, 561c and the rollers 571a, 571b, 571c of the second driven roller 57 are disposed, the rollers 561a, 561b,
561c and 571a, 571b, and 571c are arranged so that they may intertwine with each other. Therefore, the distance between the shafts can be changed as long as the rollers overlap each other. The distance between the shafts is set slightly larger than the sum of the radius of the roller and the radius of the spacer, so that the roller does not interfere with the spacer.

Next, a configuration in which the first driven roller 56 and the second driven roller 57 configured as described above rotate in contact with the driving roller 58 will be described, taking a first roller group 561 of the first driven roller 56 as an example. Will be described.

As shown in FIG. 13, a position approximately one-fourth from both ends of the support shaft 561h is positioned on the support shaft support portion 51 which is a part of the frame 51 of the fixing portion 15 (see FIG. 11).
b, 51d support in the direction of the drive shaft 58b (Y direction).
Further, the first roller group 561 and the end support portions 51a, 51e
Therefore, the support shaft 561h is bent by being pressed by the support shaft support portions 51b and 51d, and the first roller group 561 presses the sheet P against the first roller 581 by the return elastic force.

The movement in the X direction (perpendicular to the plane of FIG. 13) is restricted because it is surrounded by a frame 51 (not shown). The ends of the support shaft 561h are restricted from moving in the Z-axis direction by the end support portions 51a and 51e, and are supported in the opposite Y direction. Then, the movement of the first roller group 561 in the Z-axis direction is regulated by the regulating portion 51c. Therefore, the driving roller 58
, The first roller group 561 is driven to rotate. Further, the paper P is transferred to the first roller group 561 and the driving roller 5.
8 enters a contact portion (nip portion) with the first roller 581, the sheet P is conveyed by being sandwiched between these rollers. The first roller 571 of the second driven roller 57 has the same configuration and has the same function.

As described above, the paper P is transferred to the first driven roller 5
6. Since the second driven roller 57 cooperates and urges the second driven roller 57 to wind around the driving roller 58, the paper P is
And is deformed according to the curvature of the drive roller 58 to remove the curl.

FIG. 14 is a diagram schematically showing a state in which the first roller group 561 of the first driven roller 56 rotates in contact with the drive roller 58 when the thickness of the sheet P is not uniform. In FIG. 14, the gap G is exaggerated. When the thickness of the paper P is uneven, for example, when there is a gap G which is an uneven portion in FIG. 14, or when a conventional iron rod shaft is used, the roller cannot be displaced, In such a case, the driven roller as a whole floats up and cannot press the sheet P, or an image formed by pressing the sheet P with an excessively strong force may be damaged or the sheet P may be damaged. .

In this embodiment, the support shaft 561h is constituted by a helical spring as described above, and thus has the following operation. That is, when the third roller 561c rides on the gap G, the first roller group 561 formed integrally in this case is inclined and displaced to a position corresponding to the gap G, and the support shaft 561h formed by the helical spring is The support shafts 51b and 51d are elastically deformed about the fulcrum. Therefore, the first roller group 561 riding on the gap G presses the sheet P while displacing the gap G so as not to damage the sheet P. for that reason,
Even if there is such a gap G, it is possible to remove the curl by pressing the paper P without damaging it.

In the present embodiment, the first to third rollers 5 forming the first roller group 561 of the first driven roller 56 are used.
61a, 561b, 561c, and first to fourth spacers 5
Although the example in which 61d, 561e, 561f, and 561g are integrally formed of resin has been described as an example, as a modification, the first to third rollers 561a, 561b,
561c, and the first to fourth spacers 561d, 561e,
The configuration in which 561f and 561g are separately formed will be described below.

FIG. 15 is a diagram schematically showing a modified example in which the first roller group 561 of the first driven roller 56 rotates in contact with the driving roller 58 when the thickness of the sheet P is not uniform. . In FIG. 15, the gap G is exaggerated. When the thickness of the paper P is not uniform, for example, FIG.
When there is a gap G which is a non-uniform part in 5,
In the above-described embodiment, the rollers are not individually displaced, and the entire first roller group 561 is inclined to absorb the gap. In this modification, however, the first to third rollers 561a, 56
1b, 561c, and first to fourth spacers 561d, 56
1e, 561f, and 561g are formed separately, so that the respective rollers 561a, 561b, 56
1c is movable in the Y-axis direction, and each can correspond to a displacement. Hereinafter, the operation will be described. If the third roller 561c runs over the gap G, the support shaft 561h is elastically deformed with the support shaft support portions 51b and 51d as fulcrums. In this case, the rollers 561a, 561b, 5
61c and spacers 561d, 561e, 561f, 5
61g and a support shaft 56 penetrated therethrough.
There is a slight gap between 1h and it is possible to displace with the adjacent member. Therefore, the third roller 561c riding on the gap G is displaced and pressed against the gap G to such an extent that the sheet P is not damaged. Therefore, even if there is such a gap G, the rollers 561a, 561b, and 561c can be displaced more flexibly corresponding to the gap G, and the curl can be removed by pressing the sheet P without damaging it. .

Here, the operation of the curl removing mechanism 55 configured as in the embodiment will be described. As shown in FIG.
The sheet P is heated and pressed by the heat roller 52 and the pressure roller 54 to fix the developer T, and is conveyed in the sheet conveying direction (left direction in FIG. 6). Then, the sheet ejection sensor 61 is pushed down, the leading edge of the sheet P further advances, and comes into contact with each roller of the first driven roller 56 or each roller of the driving roller 58 to make contact with these rollers (nip portion).
To enter. Then, the paper P is further conveyed by the driving force of the driving roller 58, and the leading end of the paper P is further conveyed while being sandwiched between the nip portions of the respective rollers of the second driven roller 57 and the respective rollers of the driving roller 58. You.

At this time, the sheet P is pressed against the heat roller 52 heated to about 200 ° C. to complete the fixing, and the sheet P is deformed by the heat roller 52 into a shape along the surface. That is, although the paper P is curled, the paper P has a concave curve on the upper side (the opposite side in the Y direction), and the leading end of the paper P is located between the first driven roller 56 and the second driven roller 57. The first driven roller 5
6 and the second driven roller 57 are intertwined with each other and there is no gap, so that they are not entangled in the first driven roller 56 and enter the space between the second driven roller 57 and
The sheet P can be reliably transferred to the second driven roller 57 and the driving roller 58 without a guide for guiding the leading end of the sheet P.
And transported between the rollers.

Here, immediately after fixing, the sheet P is still at a high temperature. When the paper P once heated and curled is cooled and the humidity is reduced by evaporation,
Once formed, curls cannot be easily corrected. In the present embodiment, since the fixing unit 15 is surrounded by the frame 51 and the entrance of outside air is extremely small, the fixing unit 15 has an atmosphere of high temperature and high humidity, and the plasticity of the paper P is high. As described above, the paper P is
The sheet P is warped in the opposite direction to the curl caused by fixing without being separately heated only by being urged by the driven roller 57 so as to be wound around the driving roller 58, and the curl caused by fixing is prevented. It is corrected efficiently.

Further, since the temperature of the sheet P is still high, the developer T is not completely solidified. In this case, if the image formed by the developer T is rubbed, the image may be damaged. However, in the present embodiment, there is no guide member such that the surface of the sheet P slides as in the above-described conventional example, and all the contacts are made by rolling, so that there is no risk of damaging the image.

Even if the first driven roller 56 and the second driven roller 57 become hot due to contact with the high-temperature paper P immediately after fixing, the support shafts 561h and 571h are made of metal and are damaged. Or not.

As described above, in the fixing unit 15, the developer T is fixed to the sheet P by the heat roller 52 and the pressure roller 54, and the fixing unit 15 is disposed immediately downstream of the heat roller 52 in the sheet conveying direction. After the curl of the sheet P is removed by the curl removing mechanism 55, the sheet P is discharged outside the frame 51 constituting the fixing unit.

As shown in FIG. 1, a paper discharge direction switching mechanism 62 is provided downstream of the fixing unit 15 in the paper transport direction.

FIG. 7 is a view showing a state in which the paper discharge direction switching mechanism 62 reverses the paper and discharges the paper. The discharge direction switching mechanism 62 includes an outside air blocking wall 62c having a guide rib 62a. The guide rib 62a guides the leading end of the sheet P upward (toward the X direction) from the rear side of the apparatus (in the X direction) so as to guide the sheet P to the printed sheet placement section 69, and further forwards. (Right direction in FIG. 7, anti-X direction) A plurality of rib-shaped guides composed of surfaces parallel to the X-axis and Y-axis directions that are curved so as to change directions, and the outside air blocking wall 62c is a rear outer periphery of the guide rib 62a. (Left side in the figure) It consists of a partition which shuts off outside air. Further, a paper guide 64 is provided which is composed of a plurality of ribs projecting substantially semicircularly from the main body frame 11 rearward (leftward in FIG. 7) and having a surface parallel to the X-axis and Y-axis directions. A guide path is formed at a portion sandwiched between the paper guide 64 and the sheet guide 62a.
The shape of the guide path is suitable for sequentially stacking the paper P curled by the curl removing mechanism 55 and the continuous printed paper P in the printed paper mounting portion 69 without refracting the paper P. The shape of the paper P is adjusted so that the upper surface is flat or slightly convex. In other words, in the printed paper placement unit 69, when the rear end of the paper P is positioned above the driven roller 66 when the upper surface of the stacked paper P is concave, the next printed paper is printed. Paper P
May fall under the previously printed paper P and be stacked in the reverse order, or the rear end of the previously printed paper P may be pushed and dropped out of the apparatus. is there. Accordingly, the guide path formed by the guide ribs 62a and the paper guide 64 has a shape that can adjust the shape of the paper P to a flat shape or a slightly convex upper surface.

Further, when the sheet P after fixing is exposed to the outside air, the temperature drops sharply and loses plasticity, making it difficult to correct the curl on the sheet P. Therefore, the fixing unit 1
The outside air blocking wall 62c forms a wall as outside air blocking means for preventing an exchange with the outside air so that the sheet P discharged from the sheet 5 is not exposed to the outside air. Further, the frame 11b, 11c, 11d, which is a part of the main body frame 11, prevents the exchange of outside air and maintains the high-temperature, high-humidity atmosphere generated in the fixing unit 15.

The paper guide 64 projecting in the form of a rib inside the guide rib 62a (in the direction opposite to the X direction) forms a guide path together with the guide rib 62a, thereby forming the paper P.
Prevents the paper P from being bent inward and causing a jam, and guides the paper P to smoothly advance along the guide of the guide rib 62a.

According to the paper discharge direction switching mechanism 62 configured as described above, the fixing unit 1 is controlled by the curl removing mechanism 55.
5 is guided by the guide ribs 62a and enters, and the leading edge of the sheet P discharged from the sheet 5 is heated to a high temperature by the outside air blocking wall 62c and the like.
The paper P is appropriately deformed by the guides of the guide ribs 62a in an atmosphere maintained at a high humidity, and the paper P is formed into a flat or slightly convex shape at the upper part, and is guided by the guide ribs 62a toward the printed paper mounting portion 69 and guided. The sheet P is further conveyed by the second sheet discharge roller 65 and the driven roller 66 and discharged to the printed sheet placement section 69. In addition, a paper discharge extension tray 68 is provided in front of the printed paper placement section 69.
(See FIG. 1) is pivotally mounted to be deployable forward.

FIG. 8 is a diagram showing a state in which the paper discharge direction switching mechanism 62 is switched to a state in which the paper is discharged without turning over the paper. The upper portion of the paper discharge direction switching mechanism 62 is supported by a shaft support 62b. This shaft support 62b is
A biasing portion 62e formed of a wire spring that is regulated by a regulating portion 62d that regulates the shaft supporting portion 62b so as to be movable only in the vertical direction (Y-axis direction), and biases the shaft supporting portion 62b downward (Y direction).
Urged downward. A torsion coil spring formed integrally with the urging portion 62e is disposed on the shaft support portion 62b, and the guide rib 62a and the outside air blocking wall 62c are provided.
Is urged to jump upward and backward (upper left in FIG. 8). The main body frame 11 near the lower end of the outside air blocking wall 62c in a state where the outside air blocking wall 62c is closed is provided with a hooking portion 63 for hooking the outside air blocking wall 62c to hook the lower end of the outside air blocking wall 62c. are doing. Therefore, in order to switch the paper discharge direction switching mechanism 62 to a state in which the paper P is discharged without being inverted, the finger is hooked on the finger hook 62f of the outside air blocking wall 62c and shifted upward. Then 2
From the original position shown by the dashed line, the shaft support 62b is
e, displaced upward along the restricting portion 62d against the bias of e,
The latch by the latch 63 is released. Therefore, the outside air blocking wall 62c is displaced by the torsion coil spring (not shown) in a state of being flipped upward and rearward about the shaft support 62b together with the guide rib 62a. At this time, the shaft supporting portion 62b is again shifted downward along the regulating portion 62d by the urging of the urging portion 62e and returns to the original position.

FIG. 9 is a view showing a state in which the paper discharge direction switching mechanism 62 discharges the paper P without reversing it. In this state, the first driven roller 56 and the second driven roller 57
The sheet P ejected from the fixing unit 15 by the driving roller 58 does not enter the guide path of the sheet formed by the guide rib 62a, and is directly behind the image forming apparatus 1 (X
Direction). In addition, a paper discharge tray (not shown) is mounted behind the image forming apparatus 1, and the discharged paper P can be stacked and placed.

In this state, the paper P is ejected to the rear of the image forming apparatus 1 by the curl removing mechanism 55, and the paper transport path does not bend or there is no gap between a plurality of rollers to be transported. Paper jam does not occur even on hard or small paper. Also, the curl removing mechanism 5
5, the curl generated by the fixing is removed, and when the paper P is stacked, the paper P is formed so that the upper surface is flat or slightly convex, so that the printed paper P is stably stacked. .

FIG. 10 shows a paper discharge direction switching mechanism 62,
FIG. 7 is a diagram illustrating a state where the state is switched to a state where the sheet P is inverted and discharged. When the user wants to discharge the sheet P to the printed sheet placement section 69 again, the leading end of the outside air blocking wall 62c of the sheet discharge direction switching mechanism 62 that has been flipped up (X direction) is hooked by the main body frame 11. Press down in the direction of the stop 63 by hand. Then, the tip of the outside air blocking wall 62c is
3 and is further pushed forward (in the anti-X direction) so that the tip of the outside air blocking wall 62c slides obliquely upward and forward as shown by the arrow in FIG. It moves upward as regulated by the regulation portion 62d,
The tip of the outside air blocking wall 62c passes over the hook 63 and returns to the state shown in FIG.

As shown in FIGS. 1 and 4, a control unit 20 having a CPU, a ROM, and a RAM (not shown) for controlling the image forming apparatus 1 is provided at a rear portion of the main body frame 11. The control unit 20 is a device for inputting and processing image data, controlling the modulation of oscillation of the laser diode 41, controlling the polygon mirror driving motor 24, controlling the transport unit 18, controlling the halogen heater 53, and controlling the power supply. It also performs general control.

The present embodiment is constructed and operated as described above, and has the following effects.

The image forming apparatus 1 can discharge paper in two directions by the paper discharge direction switching mechanism 62, and even if paper is discharged in any discharge direction, the curl at the time of fixing is corrected by the curl removing mechanism 55. Therefore, it is possible to obtain a good state of the paper P with less curl, and it is possible to smoothly stack the printed papers P.

Further, when the paper P whose curl has been corrected by the curl removing mechanism 55 is to be discharged to the printed paper mounting section 69, the paper P is communicated with the fixing section 15 and its surroundings constitute an outside air blocking means. Guide rib 6 in which the exchange of outside air is prevented by the frame 11 and the wall surface of the outside air blocking wall 62c.
Since the sheet P passes through the guide path 2a, the sheet P can be plastically deformed into a more preferable shape in a high-temperature and high-humidity atmosphere and discharged.

The curl removing mechanism 55 has a compact structure, and has a heat roller 52 and a paper discharge direction switching mechanism 62.
And is housed in a frame 51 configured as a fixing unit frame, and is configured as a unit integrally with the fixing device. Therefore, the image is fixed by being heated and pressed by the heat roller 52 and the pressure roller 54, and the curl is removed in the same frame while the paper is still hot and wet. Can be. In addition, the integration contributes to the downsizing of the image forming apparatus 1 and becomes a part of the unit, thereby facilitating maintenance.

The curl removing mechanism 55 itself has a compact structure for the roller diameter as compared with the conventional one and does not have a roller holder as a guide plate, so that the print surface of the printed paper P slides. Therefore, the image is small and simple. Further, since the rollers are configured so as to be intertwined, jamming due to winding around the rollers does not occur.

Since the support shaft 561h and the like are constituted by a helical spring, the paper P is constantly pressed with an appropriate pressure to efficiently remove the curl. Furthermore, even when the paper P has irregularities, it can be pressed flexibly. Further, since a separate pressing spring or the like is not required,
The decurling mechanism 55 can be produced at low cost. Further, even if the paper P comes into contact with the high-temperature paper P immediately after fixing, the curl removing mechanism 5
In addition to the heat resistance of the resin and metal that make up the resin 5, the sliding portion between the resins that are relatively easily affected by heat is eliminated, and the heat resistance is increased.

Although the present invention has been described based on one embodiment, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present invention. It is possible to

For example, in the present embodiment, the first driven roller 56 and the second driven roller 57 are each composed of four roller groups 561 to 564, 571 to 574. The roller may be constituted by a roller group, or may be constituted by a plurality of roller groups other than four. That is, the first driven roller 56
The number of roller groups constituting the second driven roller 57 depends on the size of the image forming apparatus 1, the size of the paper P, or the size of the paper P.
Can be appropriately selected depending on the quality of the material.

The roller groups 561 to 564 and 571 to 574 are each composed of three rollers and four spacers, but the number of rollers and spacers is not limited to this embodiment. For example, the present invention can be realized even if one roller is one and the other roller is two. Conversely, the roller may be configured such that the entire paper width direction is constituted by a number of rollers and spacers, or the roller and the spacer may be integrated. The point is that the rollers of the first driven roller 56 and the second driven roller 57 may be intertwined with each other so that a part overlapping each other is generated. Furthermore, the size of the rollers of the two roller groups that are intertwined may not be the same.

The rollers and the spacers are configured such that one roller group includes a plurality of rollers and is integrally formed of resin as in the present embodiment, and the rollers and the spacers are formed separately. Or a roller provided with spacers on one or both sides of each roller. Further, the roller may be overlapped with each other by thinning the tip of the roller without providing the spacer.

Further, a support shaft 561h for supporting each roller group 561 and the like is arranged for each roller group, but the first driven roller 56 or the second driven roller 57 is entirely supported by one support shaft. You may make it.

The shape of the paper discharge direction switching mechanism 62 can be selected so that the paper P can be corrected into a desired shape.
The curvature can be appropriately changed according to the heating temperature at the time of fixing, the degree of correction by the curl removing mechanism 55, and the like. Needless to say, the guide wall constituting the guide path of the present invention is not limited to a guide formed in a rib shape like the guide rib 62a of the present embodiment, but is constituted by a flat guide wall. In addition, a configuration may be used in which the guide wall and the outside air blocking means are combined.

The switching mechanism for discharging the paper P in two directions is not limited to a method in which the entirety of the outside air blocking wall 62c and the guide rib 62a jumps up, and an opening is formed only in a part of the outside air blocking wall 62c and the guide rib 62a. The sheet P may be ejected rearward, or the sheet P may be ejected by a movable plate that guides the leading end of the sheet P by swinging up and down.

In addition, it can be easily inferred that those skilled in the art can make various improvements and modifications without departing from the spirit of the present invention.

[0102]

As is apparent from the above description, claim 1
According to the image forming apparatus of the present invention, since the curl removing mechanism is provided on the upstream side in the sheet transport direction of the sheet discharging direction switching mechanism, an undesired strong curl on the sheet in the fixing unit is discharged by one curl removing mechanism. There is an effect that it can be removed regardless of the paper direction. Further, there is an effect that it is not necessary to provide two curl removing mechanisms, and the image forming apparatus itself can be downsized.

According to the image forming apparatus of the second aspect of the present invention, in addition to the effect of the image forming apparatus of the first aspect, in addition, the undesired strong curl applied to the sheet by the fixing device can be appropriately removed by the curl removing mechanism. There is an effect that the paper can be removed and discharged in the second paper discharge direction. Also, while the temperature and humidity of the sheet are maintained by the outside air blocking means for blocking the outside air, the sheet is guided in the first sheet discharging direction while the sheet is easily plastically deformed, and the first discharge is performed by the guide wall. There is an effect that the sheet can be deformed in a state more suitable for discharging in the sheet direction and discharged in the first sheet discharging direction. Therefore, there is an effect that the paper from which the curl has been properly removed can be discharged from any of the paper discharge ports.

According to the image forming apparatus of the third aspect of the present invention, an undesired strong curl attached to the sheet by the fixing means is efficiently removed by the curl removing mechanism while the temperature and humidity of the sheet immediately after fixing are high. There is an effect that it can be removed.

In the image forming apparatus according to the fourth aspect of the present invention,
In addition to the effects of the image forming apparatus according to any one of claims 1 to 3, the curl removing mechanism is provided immediately after the fixing means by integrally forming the fixing means and the curl removing mechanism with the fixing unit frame. There is an effect that can be. Therefore, there is an effect that the curl can be efficiently removed while the sheet is still hot and wet and easily plastically deformed in the same frame. Further, since these can be configured compactly, there is also an effect that the size of the image forming apparatus itself can be reduced. Further, there is an effect that the maintenance of the image forming apparatus is facilitated by unitizing the fixing unit and the curl removing mechanism.

In the image forming apparatus according to the fifth aspect,
5. The image forming apparatus according to claim 1, wherein the curl removing mechanism includes a first driven roller and a second driven roller that are driven by the driving roller. This has the effect of removing the curl.
Further, the distance between the first driven roller and the second driven roller can be adjusted within a range where the rollers overlap, and the time for contact with the drive shaft can be increased or decreased to adjust the degree of curl removal. It is possible. Further, since the roller group including the two rollers is interdigitated, the paper can be properly conveyed without paper entering between the first driven roller and the second driven roller. Is also effectively prevented. In addition, this configuration eliminates the need for a fixed guide that guides the paper in the transport direction, and the paper is transported while being held by the rotating body. There is also an effect that the image formed on the sheet is not spoiled without being brought into sliding contact with the fixed type guide. Further, the first driven roller and the second driven roller can be arranged close to each other, and the curl removing mechanism can be made compact. In addition, there is also an effect that heat dissipation is improved by forming the driven roller from a plurality of rollers.

According to the image forming apparatus of the present invention,
In addition to the effects of the image forming apparatus according to claim 5, since the support shaft itself of the curl removing mechanism is formed of an elastic body, there is no need to provide an urging means with a member separate from the support shaft. There is. Therefore, there is an effect that a simple and low-cost mechanism can be provided. In addition, there is an effect that the driven roller can be pressed against the sheet by appropriately urging the driven roller with a simple configuration. Therefore, even in the case of papers having different thicknesses, the respective rollers of the driven rollers can be pressed against each other in accordance with the paper thickness, and there is an effect that the papers are not damaged by urging each part with an appropriate force.

According to the image forming apparatus of the present invention,
In addition to the effect of the image forming apparatus according to claim 6, since the support shaft of the curl removing mechanism is constituted by a helical spring, it can flexibly cope with a large displacement and appropriately biases the driven roller. And presses the sheet against the paper. In particular, even when the paper has a partially uneven thickness, each roller of the driven roller can flexibly press against the paper according to the thickness of the paper, and the paper may be damaged by urging each part with an appropriate force. Absent. Furthermore, even if the support shaft becomes hot, the helical spring is made of metal, so there is no sliding between the resins, and the heat resistance and heat dissipation are higher than those of a resin support shaft. is there.

The curl removing mechanism of the image forming apparatus according to the present invention has the effect that the first driven roller and the second driven roller driven by the driving roller can efficiently remove the curl of the sheet. . Further, the distance between the first driven roller and the second driven roller can be adjusted within a range where the rollers overlap, and the time for contact with the drive shaft can be increased or decreased to adjust the degree of curl removal. It is possible. Further, since the roller group including the two rollers is interdigitated, the paper can be properly conveyed without paper entering between the first driven roller and the second driven roller. Can be effectively prevented. In addition, this configuration eliminates the need for a fixed guide that guides the paper in the transport direction, and the paper is transported while being held by the rotating body. There is also an effect that the image formed on the sheet is not spoiled without being brought into sliding contact with the fixed type guide. Further, the first driven roller and the second driven roller can be arranged close to each other, and the curl removing mechanism can be made compact. In addition, there is also an effect that heat dissipation is improved by forming the driven roller from a plurality of rollers.

In the curl removing mechanism of the image forming apparatus according to the ninth aspect, in addition to the effect of the curl removing mechanism of the image forming apparatus according to the eighth aspect, since the support shaft itself is formed of an elastic body, There is an effect that there is no need to provide an urging means with a member separate from the support shaft. Therefore, there is an effect that a simple and low-cost mechanism can be provided.
In addition, there is an effect that the driven roller can be pressed against the sheet by appropriately urging the driven roller with a simple configuration.
Therefore, even in the case of papers having different thicknesses, the respective rollers of the driven rollers can be pressed against each other in accordance with the paper thickness, and there is an effect that the papers are not damaged by urging each part with an appropriate force.

According to the tenth aspect of the present invention, in addition to the effects of the curl removing mechanism of the image forming apparatus according to the ninth aspect, the support shaft is constituted by a helical spring. It is possible to flexibly cope with a large displacement, and there is an effect that the driven roller can be appropriately biased and pressed against the sheet. In particular, even when the paper has a partially uneven thickness, each roller of the driven roller can flexibly press against the paper according to the thickness of the paper, and the paper may be damaged by urging each part with an appropriate force. There is no effect. Furthermore, even if the support shaft becomes hot, the helical spring is made of metal, so there is no sliding between the resins, and the heat resistance and heat dissipation are higher than those of a resin support shaft. is there.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus 1 as viewed from a side orthogonal to a sheet conveying direction.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 illustrates an optical scanning device 12 of the image forming apparatus 1 illustrated in FIG.
FIG. 2 is an enlarged view of a developing unit 17 and a part of a main body frame 11.

FIG. 4 shows the optical scanning device 12 with the lid 22 removed (FIG. 1
FIG. 3 is a plan view as viewed from the direction opposite to the Y direction.

FIG. 5 is a diagram schematically illustrating the fixing unit 15 in which a portion below a sheet P is omitted when viewed from a lower side (opposite Y direction) of FIG.

FIG. 6 is a view showing a fixing unit 15 viewed in a Z direction from a CC section of FIG. 5;
FIG.

FIG. 7 is a diagram illustrating a state in which the sheet discharge direction switching mechanism 62 inverts and discharges the sheet P.

FIG. 8 is a diagram illustrating a state in which the paper discharge direction switching mechanism 62 is switched to a state in which the paper P is discharged without being inverted.

FIG. 9 is a diagram illustrating a state in which the paper discharge direction switching mechanism 62 discharges the paper P without reversing the paper P.

FIG. 10 is a diagram illustrating a state in which a paper discharge direction switching mechanism is switched to a state where paper P is inverted and discharged.

FIG. 11 is a cross-sectional view of the curl removing mechanism 55 viewed from a direction opposite to the Z direction.

FIG. 12 is a diagram showing a configuration of first roller groups 561 and 571 of a first driven roller 56 and a second driven roller 57, respectively.

FIG. 13 is a diagram illustrating a state in which a first roller group 561 of a first driven roller 56 rotates in contact with a driving roller 58;

FIG. 14 is a diagram schematically illustrating a state in which a first roller group 561 of a first driven roller 56 contacts and rotates with a driving roller 58 when the thickness of a sheet P is not uniform.

FIG. 15 is a diagram schematically illustrating a modified example in which the first roller group 561 of the first driven roller 56 rotates in contact with the drive roller 58 when the thickness of the sheet P is not uniform.

FIG. 16 is a diagram illustrating an example of a conventional curl removing mechanism.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 11 main body frame 12 optical scanning device 15 fixing unit (fixing unit) 16 paper discharge unit 17 developing unit (image forming unit) 18 transport unit 19 paper feed unit 20 control unit 51 frame (fixing unit frame) 51a, 51e End support portions 51b, 51d Support shaft support portion 51c Restriction portion 52 Heat roller 53 Halogen heater 54 Pressure roller 55 Curl removal mechanism 56 First driven roller 561 First roller group 561a First roller 561b Second roller 561c Third roller 561d first spacer 561e second spacer 561f third spacer 561g fourth spacer 561h support shaft 562 second roller group 563 third roller group 564 fourth roller group 57 second driven roller 571 first roller group 571a first roller 571b first 2 roller 571c 3rd b L 571d First spacer 571e Second spacer 571f Third spacer 571g Fourth spacer 571h Support shaft 572 Second roller group 573 Third roller group 574 Fourth roller group 58 Drive roller 62 Discharge direction switching mechanism 62a Guide rib (guide wall) 62b axial support portion 62c outside air blocking wall (outside air blocking means) 62d regulating portion 62e urging portion 62f finger hook portion 63 hook portion 64 paper guide 65 second paper ejection roller 66 driven roller

Claims (10)

[Claims] An image forming unit configured to form an image on a sheet, a fixing unit configured to heat the sheet on which the image is formed by the image forming unit and fix the formed image, and an image formed by the fixing unit. A curl removing mechanism for removing the curl of the sheet on which is fixed, and provided downstream of the curl removing mechanism in the sheet transport direction;
A first paper discharge direction for discharging the paper upside down,
An image forming apparatus comprising: a discharge direction switching mechanism capable of switching a discharge direction of the sheet to a second discharge direction for discharging the sheet without turning over the sheet. 2. The paper ejection direction switching mechanism according to claim 1, wherein the paper ejection direction switching mechanism deforms the paper so as to bend in a direction opposite to a direction in which the paper is curled by the curl removing mechanism. The image forming apparatus according to claim 1, further comprising: a guide path including a guide wall that guides in a paper direction; and an outside air blocking unit that is provided in the guide path and that blocks an exchange with outside air. 3. An image forming unit for forming an image on a sheet, a fixing unit for heating the sheet on which the image is formed by the image forming unit to fix the formed image, and An image forming apparatus, comprising: a curl removing mechanism that is disposed immediately after the sheet transport direction and removes curl of the sheet on which an image is fixed by the fixing unit. 4. A fixing device comprising: a heat roller configured to heat the sheet; a pressure roller disposed to face the heat roller and configured to press the sheet against the heat roller; A fixing unit frame configured to house and support the pressure roller, wherein the curl removing mechanism is configured to perform the fixing on a downstream side of the heat roller and the pressure roller in a sheet conveying direction. The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is arranged on a unit frame. 5. The curl removing mechanism includes a drive roller, and a plurality of rollers supported by a coaxial support shaft.
A first driven roller driven by the driving roller; and a second driven roller configured of one or a plurality of rollers supported by a coaxial support shaft and driven by the driving roller; The support shaft of the driven roller and the support shaft of the second driven roller are disposed in parallel with the support shaft of the drive roller, and the support shaft of the first driven roller and the support shaft of the second driven roller are provided. The distance between the shafts is larger than the radius of the roller of the first driven roller and the radius of the roller of the second driven roller, and the radius of the roller of the first driven roller is equal to the radius of the second driven roller. 4. The roller according to claim 1, wherein the first and second driven rollers are arranged at a distance smaller than the sum of the radii of the first and second driven rollers. 4 described in any of Image forming device. 6. The curl removing mechanism, wherein the support shaft of the first driven roller and the support shaft of the second driven roller are both formed of an elastic body. 6. The apparatus according to claim 5, wherein the first driven roller and the second driven roller are biased against the driving roller by an elastic force.
An image forming apparatus according to claim 1. 7. The curl removing mechanism according to claim 6, wherein the support shaft of the first driven roller and the support shaft of the second driven roller are formed by a helical spring. An image forming apparatus according to claim 1. 8. A driving roller, comprising: a plurality of rollers supported by a coaxial support shaft;
A first driven roller driven by the driving roller; and a second driven roller configured of one or a plurality of rollers supported by a coaxial support shaft and driven by the driving roller; The support shaft of the driven roller and the support shaft of the second driven roller are disposed in parallel with the support shaft of the drive roller, and the support shaft of the first driven roller and the support shaft of the second driven roller are provided. The distance between the shafts is larger than the radius of the roller of the first driven roller and the radius of the roller of the second driven roller, and the radius of the roller of the first driven roller is equal to the radius of the second driven roller. The curl removal of the image forming apparatus, wherein the first driven roller and the second driven roller are arranged alternately at a distance smaller than the sum of the radii of the rollers. mechanism. 9. The support shaft of the first driven roller and the support shaft of the second driven roller are both formed of an elastic body, and the support shaft is configured to move the first driven roller by the elastic force. 9. The apparatus according to claim 8, wherein said driven roller and said second driven roller are urged against said driving roller.
2. The curl removing mechanism of the image forming apparatus according to 1. 10. The image forming apparatus according to claim 9, wherein the support shaft of the first driven roller and the support shaft of the second driven roller are formed by a helical spring. Decurling mechanism.