JP2018154474A - Decurler device and image forming apparatus with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decurler device capable of adjusting a correction amount of curl and stably conveying a sheet even in a state of setting the correction amount to zero.SOLUTION: A decurler device 18 comprises a conveying roller 22 having a fixed position and brought into contact with a first surface of a print sheet P, a belt 19 normally circulating while being brought into contact with a second surface of the print sheet P to press it to the conveying roller, a first tension roller 20 at an upstream side brought into contact with an inner surface side of the belt to apply a tensile force and a second tension roller 21 at a downstream side, a pressing roller 23 having a fixed position and preventing the belt from being separated from the conveying roller, and a moving guide member for guiding at least one of the first tension roller and the second tension roller in a direction of changing a winding amount of the belt around the conveying roller, wherein a range in which the winding amount is zero and a range in which the winding amount is positive are included in the moving passage by the moving guide member.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a decurler device that eliminates or reduces curling (warping deformation) of a sheet member. More specifically, the present invention relates to a decurler device that performs curling elimination or relaxation processing while passing a conveyed sheet member. The present invention is also directed to an image forming apparatus using a decurler device.

  As an example of a conventional decurler device, a sheet conveying device described in Patent Document 1 can be given. The sheet conveying apparatus described in FIG. 1 of the same document is configured to pass the “sheet S” between the “conveying belt 11” and the “pressing roll 16”. The “conveying belt 11” is stretched around two rollers, and the “pressing roll 16” is pressed against the middle part between them. The “conveying belt 11” is slightly wound around the “pressing roll 16”. In this sheet conveying apparatus, the “sheet S” curled in the direction opposite to the winding is passed between the “conveying belt 11” and the “pressing roll 16”. As a result, the curl of the “sheet S” is corrected.

  Further, in this sheet conveying apparatus, the “cam 21” can be used to change the pushing amount of the “pressing roll 16” into the “conveying belt 11”. Thereby, the amount of winding of the “conveying belt 11” around the “pressing roll 16” can be increased or decreased. In this way, in this sheet conveying apparatus, the amount of curling correction of “sheet S” can be adjusted.

JP 2013-23292 A

  However, the conventional techniques described above have the following problems. Insufficient response to cases where curl correction is unnecessary. That is, when the sheet member is not curled separately, the pressing of the “pressing roll 16” into the “conveying belt 11” is released. Otherwise, the sheet will be curled by the sheet conveying device. However, if this is done with the sheet conveying apparatus of Patent Document 1, no nip pressure is applied between the “conveying belt 11” and the “pressing roll 16”. For this reason, the conveyance of the paper is unstable and jamming is likely to occur. There is also a difficulty in the configuration of the surrounding paper guides.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a decurler device capable of adjusting a curl correction amount and stably conveying a sheet even when the correction amount is zero, and an image forming apparatus using the decurler device.

  The decurler device according to one aspect of the present invention includes a conveyance member that is in contact with a first surface of a sheet member to be conveyed, a fixed position, and a conveyance member that is in contact with the second surface of the sheet member to be conveyed. A belt that circulates in a forward direction with respect to the conveying direction of the sheet member while being pressed against the belt, and a first tension member that is located upstream of the conveying member in contact with the inner surface of the belt and applies tension to the belt, And a second tension member positioned downstream of the conveying member in the conveying direction, a pressing member positioned on the inner surface side of the belt to prevent separation of the belt from the conveying member, and a first tension member The second tension member is provided for at least one of the second tension member and the first tension member or the second tension member in a direction in which the amount of winding of the belt around the conveying member is changed. A moving guide member that guides the movement, and a moving path guided by the moving guide member includes a range in which the amount of wrapping is zero and a range in which the amount of wrapping is positive. .

  In the decurler device of this aspect, the sheet member is passed through the nip between the belt wound around the first tension member and the second tension member and the conveying member. Here, at least one of the first tension member and the second tension member moves along the movement path guided by the movement guide member, thereby changing the amount of winding of the belt around the conveyance member. Yes. By this movement, the amount of winding can be made zero. However, even when the amount of winding is zero, the pressing member prevents the belt from being separated from the conveying member. For this reason, even if the amount of winding is zero, the conveyance of the sheet member is stable. When a curled sheet member is passed in a direction in which the conveying member is convex, curling is corrected by setting the amount of wrapping to be positive. When passing a sheet member that is not so, the winding amount may be zero.

  In the decurler device of the above aspect, it is desirable that the movement path by the movement guide member has a shape in which the tension applied to the belt is constant even when at least one of the first tension member and the second tension member is moved. If this is the case, the sheet passing resistance of the sheet member is constant regardless of the amount of wrapping of the belt around the conveying member, and therefore jamming and wrinkling are unlikely to occur.

  Alternatively, in the decurler device according to the above aspect, the pressing member may be configured so that at least one of the first tension member and the second tension member is moved to a position where the amount of winding of the belt around the conveying member is maximized. It is desirable that the belt does not contact the belt at a position other than the opposed position. If this is the case, it is easy to configure the apparatus so that the belt tension is constant regardless of the amount of winding of the belt around the conveying member.

  In the decurler device described above, it is also preferable that the movement path by the movement guide member is provided only for the first tension member. Such a configuration is superior in terms of stability in the output direction of the sheet member that has passed through the decurler device.

  The decurler device of the above aspect includes a curl amount detection unit that detects the curl amount of the sheet member, which is provided upstream of the transport member in the transport direction, and the amount of wrapping when the detected curl amount is large. It is also desirable to have a winding angle control unit that moves at least one of the first tension member and the second tension member so that the winding amount is reduced when the detected curl amount is small. By doing in this way, an appropriate curl correction can be performed with respect to the curl degree of each sheet member.

  Alternatively, the decurler device of the above aspect has a movable restricting member that restricts the second surface of the sheet member and moves along the conveying direction, and the movable restricting member has a first tension member and a second member with respect to the conveying member. It is arranged on the side of the two tension members that are moved by the moving guide member so as to be separated from the conveying member when the winding amount is increased, and close to the conveying member when the winding amount is reduced. It is also desirable to move in conjunction with the movement of at least one of the first tension member and the second tension member. With this configuration, the interference between the belt and the movable restricting member can be prevented even when the winding amount is increased, and the transportability of the sheet member before and after the transport member is good even when the winding amount is reduced.

  An image forming apparatus according to another aspect of the present invention includes a sheet supply unit that supplies a sheet member, and an image forming unit that forms an image on the sheet member supplied from the sheet supply unit. The decurler device according to any one of the above aspects is arranged on the conveyance path of the sheet member supplied from the section. Thereby, curling of the sheet member after image formation can be corrected in the image forming apparatus.

  In the image forming apparatus of the above aspect, it is desirable that the decurler device is disposed downstream of the image forming unit and in a direction in which the belt is positioned on the concave surface side of the curl attached to the sheet member in the image forming unit. As a result, the curl generated in the sheet member by the image formation can be corrected in the image forming apparatus.

  The image forming apparatus according to the aspect further includes a fixing device that fixes the toner image provided on the sheet member between the image forming unit and the decurler device by passing between the heating member and the pressure member. It is desirable that the decurler device is disposed in the direction in which the belt is positioned on the pressure member side. Generally, the fixing device has a strong tendency to curl a sheet member. Further, the sheet member tends to curl so that the heating member side is convex. For this reason, with such a configuration, the curl generated in the sheet member by the fixing device can be corrected in the image forming apparatus.

  According to this configuration, a decurler device that can adjust a curl correction amount and can stably convey a sheet even when the correction amount is zero, and an image forming apparatus using the decurler device are provided.

1 is a cross-sectional view illustrating an internal configuration of an image forming apparatus according to an embodiment. It is a front view (the 1) showing composition of a decurler device concerning an embodiment. It is a front view (the 2) showing composition of a decurler device concerning an embodiment. It is a front view which shows the condition which corrects the curl of a printing paper with a decurler apparatus. It is a front view which shows the condition where the printing paper which has not curled passes a decurler apparatus. It is a front view (the 1) which shows the relationship between the movement of a tension roller, and a movement guide member. It is a front view (the 2) which shows the relationship between the movement of a tension roller, and a movement guide member. It is a front view (the 3) which shows the relationship between the movement of a tension roller, and a movement guide member. It is a front view (the 1) showing composition of a decurler device in the state where a belt is wound around a conveyance roller. It is a front view (the 2) which shows the structure of a decurler apparatus in the state which has wound the belt around the conveyance roller. FIG. 6 is a front view (No. 1) illustrating a configuration example in which a sheet regulating member is movable. FIG. 6 is a front view (No. 2) illustrating a configuration example in which a sheet regulating member is movable. It is a front view which shows the structural example provided with the curl sensor. It is a front view which shows the structural example which made only the upstream tension roller movable. It is a front view which shows the structural example which reversed the arrangement | positioning of a belt and a conveyance roller.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to the image forming apparatus shown in FIG. The image forming apparatus 1 shown in FIG. 1 is large and includes a reading unit 2, a main body unit 3, and a paper feeding unit 4. The reading unit 2 is a part that reads a document and acquires image data. The main body 3 is a part that performs image formation based on image data. The paper feed unit 4 is a part that stores printing paper (sheet member) P used for image formation in the main body unit 3.

  The main body 3 will be further described. The main body unit 3 is provided with an image forming unit 5 and a fixing unit 6. The image forming unit 5 further includes a photoreceptor 7, a charger 8, an exposure device 9, a developing device 10, a transfer belt 11, and a transfer roller 12. As a result, a toner image is formed on the printing paper P supplied from the paper supply unit 4. The fixing unit 6 includes a pressure roller 13 and a heating roller 14. As a result, the toner image on the printing paper P is fixed.

  The main body 3 is further provided with a conveyance path 15 for conveying the printing paper P. The conveyance path 15 is provided so as to convey the printing paper P supplied from the paper feeding unit 4 via the transfer roller 12 and the fixing unit 6 of the image forming unit 5. A paper discharge roller 16 is provided at the end of the conveyance path 15. The above-described fixing unit 6 is disposed in a part of the transport path 15 on the downstream side of the image forming unit 5. The main body 3 is also provided with a reversing path 17 for returning the image-formed printing paper P from the downstream side of the fixing unit 6 to the upstream side of the image forming unit 5.

  In the image forming apparatus 1 of this embodiment, a decurler device 18 is provided on the downstream side of the fixing unit 6. The aforementioned reversing path 17 is branched from the transport path 15 on the downstream side of the decurler device 18. The decurler device 18 is a device for correcting curl on the printing paper P that has exited the fixing unit 6. Hereinafter, the decurler device 18 will be described in detail.

  As shown in FIG. 2, the decurler device 18 includes a belt 19, a tension roller 20, and a tension roller 21. The belt 19 is stretched around a tension roller 20 and a tension roller 21. Further, a certain amount of tension is applied to the belt 19. The decurler device 18 is further provided with a conveying roller 22 and a pressing roller 23. The conveying roller 22 is located outside the belt 19, while the pressing roller 23 is located inside the belt 19. There is only a gap about the thickness of the belt 19 between the conveying roller 22 and the pressing roller 23. For this reason, the belt 19 is in contact with both the conveying roller 22 and the pressing roller 23.

  In the decurler device 18 having such a configuration, the printing paper P enters between the belt 19 and the conveying roller 22 from the right in the drawing. That is, of the above-described components of the decurler device 18, the two contact with the printing paper P are the belt 19 and the conveying roller 22, one of which contacts the first surface of the printing paper P and the other the first. Touch two sides. Therefore, when the printing paper P passes through the decurler device 18, the belt 19 circulates and the conveyance roller 22 rotates in the forward direction with respect to the conveyance direction of the printing paper P. Of course, the tension roller 20, the tension roller 21, and the pressing roller 23 also rotate in the forward direction with respect to the circulation of the belt 19.

  Here, among the above-described components of the decurler device 18, the two of the conveyance roller 22 and the pressing roller 23 are fixed in position in the image forming apparatus 1. On the other hand, the tension roller 20 and the tension roller 21 are not fixed in position in the image forming apparatus 1 and are movable. Specifically, the tension roller 20 and the tension roller 21 are movable in the vertical direction in FIG. FIG. 2 shows a state where the tension roller 20 and the tension roller 21 are moved to lower positions within their movable range. In contrast, FIG. 3 shows a state in which it has been moved to an upper position.

  When the state of FIG. 2 is compared with the state of FIG. 3, the winding angle of the belt 19 around the transport roller 22 is different due to the difference in the positions of the tension roller 20 and the tension roller 21. 2, the winding angle refers to a range from a point A where the belt 19 starts to contact the conveyance roller 22 to a point B where the belt 19 is separated from the conveyance roller 22 from the center Q of the conveyance roller 22. The angle θ as seen. On the other hand, the belt 19 in FIG. 3 is not wound around the transport roller 22 but is wound around the pressing roller 23. For this reason, the winding angle θ in the state of FIG. 3 is zero. Even in such a state, the belt 19 is not separated from the conveying roller 22. This is because the pressing roller 23 prevents the belt 19 from being separated from the conveying roller 22 and maintains the nip pressure. For this reason, even in the state of FIG. 3, the transport of the printing paper P in the decurler device 18 is stable.

  By setting the positions of the tension roller 20 and the tension roller 21 to the middle between FIG. 2 and FIG. 3, the value of the wrapping angle θ can be set to a positive value that is smaller than the angle in FIG. . 2 and 3, the decurler device 18 is depicted upside down from that depicted in FIG.

  FIG. 4 shows a situation where the printing paper P passes through the decurler device 18 in the state of FIG. In FIG. 4, a section C in which the belt 19 is wound around the transport roller 22 has a shape that curves upward in the drawing. Therefore, when the printing paper P is curled in a direction that curves downward in the drawing, the curling of the printing paper P is corrected by passing the printing paper P through the decurler device 18 in the state of FIG. be able to. On the other hand, FIG. 5 shows a situation where the printing paper P passes through the decurler device 18 in the state of FIG. In FIG. 5, the belt 19 is not wound around the transport roller 22. For this reason, it is suitable for passing printing paper P that is not curled. This is because if the uncurled printing paper P is passed through the decurler device 18 in the state shown in FIG. 4, the printing paper P may be curled in the opposite direction.

  4 and 5 also show the sheet regulating members 24, 25, 26, and 27 before and after the decurler device 18. Among these, on the upstream side of the decurler device 18, the paper regulating member 24 farther from the printing paper P as viewed from the belt 19 has a shape that draws the printing paper P toward the belt 19 as it approaches the conveyance roller 22. It is desirable. Further, on the downstream side of the decurler device 18, the sheet regulating member 27 closer to the printing sheet P when viewed from the belt 19 has a shape in which the end on the conveying roller 22 side is opened from the sheet regulating member 26. desirable.

  The decurler device 18 of the present embodiment has movement guide members 28 and 29 as shown in FIG. The movement guide members 28 and 29 are members that guide the movement of the tension rollers 20 and 21 shown in FIGS. 2 and 3 (or FIGS. 4 and 5). That is, the moving guide members 28 and 29 are guide rails that define the positions of the shafts 30 and 31 of the tension rollers 20 and 21. The moving guide members 28 and 29 are fixedly arranged with respect to the image forming apparatus 1. FIG. 6 shows a state in which the belt 19 is wound around the transporting roller 22 as in FIG. 2 (or FIG. 4). In this state, the shafts 30 and 31 are located near the lower end of the movement path of the movement guide members 28 and 29.

  FIG. 7 shows a state in which the tension rollers 20 and 21 are moved upward from the state of FIG. 6 and the wrapping of the belt 19 to the transport roller 22 is eliminated. In the state of FIG. 7, the belt 19 is not wound around the transport roller 22 or the pressing roller 23. In the state of FIG. 7, the shafts 30 and 31 are also located in the middle of the movement path of the movement guide members 28 and 29. FIG. 8 shows a state where the tension rollers 20 and 21 are further moved upward from the state of FIG. 7 so that the belt 19 is wound around the pressing roller 23. The decurler device 18 in the state of FIG. 8 is in the same state as shown in FIG. 3 (or FIG. 5). In this state, the shafts 30 and 31 are located near the upper end of the movement path of the movement guide members 28 and 29.

  Here, the shapes of the movement guide members 28 and 29 are determined so that the tension applied to the belt 19 is substantially constant regardless of the position of the movement guide members 28 and 29 in FIGS. is there. More specifically, comparing FIGS. 6 to 8, the distance between the shaft 30 and the shaft 31 is the longest in the state of FIG. 6 and 8, the distance between the shaft 30 and the shaft 31 is slightly shorter than the distance in FIG. This is a measure for making the circumference of the belt 19 constant in the drawing.

  That is, in the state of FIGS. 6 and 8, the range including the portion sandwiched between the conveyance roller 22 and the pressing roller 23 in the belt 19 is curved. On the other hand, in the state of FIG. 7, the range of the belt 19 is linear. Therefore, unless the distance between the shaft 30 and the shaft 31 is set as described above, the belt 19 is extended in the state shown in FIGS. In this case, since the tension of the belt 19 is not constant, the shapes of the movement guide members 28 and 29 are set as described above. For this reason, in the decurler device 18 of this embodiment, the sheet passing resistance of the printing paper P is constant in any state of FIGS.

  In the decurler device 18 of the present embodiment, it is also desirable to make it as shown in FIG. That is, FIG. 9 shows a state in which the amount of winding of the belt 19 around the conveying roller 22 is maximized in the decurler device 18. In this state, the tension rollers 20 and 21 are positioned at the lower limit within the movable range. However, even in this state, the contact between the pressing roller 23 and the belt 19 is only one place where the conveying roller 22 and the pressing roller 23 face each other. That is, the pressing roller 23 and the belt 19 are not in contact with each other at the arrow D in FIG. The effect of this is that the aforementioned moving guide members 28 and 29 for keeping the tension of the belt 19 constant need only have a relatively simple shape.

  On the other hand, as shown in FIG. 10, when the tension rollers 20 and 21 are in the vicinity of the lower limit, the pressing roller 23 and the belt 19 may be in contact with each other at a location E on the side opposite to the conveying roller 22. Conceivable. In this case, in order to make the tension of the belt 19 constant, the shapes of the movement guide members 28 and 29 need to be somewhat complicated. The reason is as follows.

  That is, as shown in FIG. 10, when the belt 19 and the pressing roller 23 come into contact with each other at the location E and the tension rollers 20 and 21 are further lowered, the belt 19 is strongly stretched. This is because both the lower section and the upper section of the pressing roller 23 are curved. In order to make the tension of the belt 19 constant even in such a situation, it is necessary that the movement guide members 28 and 29 have a shape that is strongly refracted inward in the left-right direction in the figure near the lower end thereof.

  This is not the case with the configuration example of FIG. 9, and it is sufficient that the movement guide members 28 and 29 have a simple shape as shown in FIGS. For this reason, it is easy to design the movement guide members 28 and 29. As a means for realizing the configuration example of FIG. 9, it is possible not to use a pressing roller 23 having a large diameter. Alternatively, the movable range of the tension rollers 20 and 21 should not be so wide as downward in the figure.

  The configuration example shown in FIG. 10 is not necessarily inappropriate as an embodiment of the present invention. If the shape of the movement guide members 28 and 29 is considered in consideration of the above, it can be used sufficiently. This is because there is no difference between the surface speed of the pressing roller 23 and the traveling speed of the belt 19 at the location E in FIG.

  In the decurler device 18 of this embodiment, the sheet regulating members 25 and 27 among the sheet regulating members 24 to 27 shown in FIGS. 4 and 5 can be made movable. This will be described with reference to FIGS. The movable paper restricting members 25 and 27 are those on the belt 19 side of the passing print paper P among the paper restricting members 24 to 27. FIG. 11 corresponds to FIG. 4 and shows a state in which the winding amount of the belt 19 around the conveying roller 22 is increased. On the other hand, FIG. 12 corresponds to FIG. 5 and shows a state where the amount of winding is zero.

  Comparing FIG. 11 and FIG. 12, not only the positions of the tension rollers 20 and 21 are different as described above, but also the positions of the paper regulating members 25 and 27 are different. In FIG. 11, compared with the case of FIG. 12, the sheet regulating members 25, 27 are in positions moved in the direction away from the conveyance roller 22 with respect to the left-right direction in the figure (the conveyance direction of the printing paper P). . On the contrary, in FIG. 12, compared to the case of FIG. 11, the sheet regulating members 25 and 27 are located closer to the transport roller 22.

  Accordingly, the configuration examples of FIGS. 11 and 12 have the following advantages. First, in the state shown in FIG. 11, the interference between the belt 19 and the sheet regulating members 25 and 27 is prevented. This is because the sheet regulating members 25 and 27 are retracted from the tension rollers 20 and 21. In the state shown in FIG. 12, the outlets of the upstream sheet regulating members 24 and 25 and the inlets of the downstream sheet regulating members 26 and 27 are not opened excessively. For this reason, particularly on the upstream side, the output direction of the printing paper P from the paper regulating members 24 and 25 to the transport roller 22 is relatively stable, and jamming is unlikely to occur.

  Further, when FIGS. 11 and 12 are compared with FIGS. 4 and 5, the arrangement of the sheet regulating members 24 to 27 is different in the following points. That is, in the configuration examples of FIGS. 11 and 12, the interval between the paper regulation member 24 and the paper regulation member 25 is narrower than the configuration examples of FIGS. The same applies to the interval between the paper restricting member 26 and the paper restricting member 27. This is made possible by making the sheet regulating members 25 and 27 movable. This is because the interference with the belt 19 is prevented and the stability of the conveyance of the printing paper P is also improved. As a result, the transport path of the printing paper P is compact and contributes to the downsizing of the image forming apparatus 1.

  The decurler device 18 according to this embodiment can further include a curl sensor 32 and a control unit 33 as shown in FIG. In the configuration example of FIG. 13, the curl sensor 32 is disposed on the upstream side of the transport roller 22. The curl sensor 32 is a sensor that detects the distance from the printing paper P by irradiating the printing paper P traveling between the paper regulating members 24 and 25 with light or ultrasonic waves. The control unit 33 performs control for operating the positions of the tension rollers 20 and 21 in response to the detection result of the curl sensor 32. Thereby, the amount of winding of the belt 19 around the transport roller 22 is controlled according to the detection result of the curl sensor 32. The control unit 33 may also control the entire image forming apparatus 1.

  In the configuration example of FIG. 13, the curling state of the printing paper P at that time is detected based on the tendency of the change in the detection result of the curling sensor 32 during the period in which one printing paper P passes the location of the curling sensor 32. be able to. That is, if a tendency of “near → far → near” is shown within the passage period of one printing paper P, the printing paper P at that time is curled downwardly. In that case, the positions of the tension rollers 20 and 21 are operated under the control of the control unit 33, and the state shown in FIG. 4 is obtained. Therefore, the printing paper P is discharged after the curl is corrected. On the other hand, when the incoming printing paper P is not curled downward, the state shown in FIG. 5 is obtained. Therefore, the printing paper P is discharged without curl correction.

  Further, in the configuration example of FIG. 13, when the printing paper P is curled downwardly, control according to the degree of curling can be performed. This is because when the difference between “near” and “far” in the tendency of “near → far → near” is large, the degree of curling is strong. The position of the tension rollers 20 and 21 is controlled to increase the winding angle θ in the state of FIG. 4 as the degree of curl detected is stronger. If the degree of curl detected is small, the winding angle θ is reduced. As described above, in the configuration example of FIG. 13, appropriate curl correction can be performed on each printing paper P. This is useful, for example, when the printing paper P after printing on the first side and the printing paper P after printing on the second side enter the decurler device 18 that is replaced during double-sided printing.

  Also, the curl sensor 32 and the control unit 33 can be provided even when the sheet regulating members 25 and 27 shown in FIGS. 11 and 12 are movable. In that case, the positions of the sheet regulating members 25 and 27 are also under the control of the control unit 33. It should be noted that the curl sensor 32 can be arranged not on the paper regulating member 25 side but on the paper regulating member 24 side. In the case of the arrangement, when the detection result is “far → near → far”, it is determined that the printing paper P is curled downwardly.

  In the description so far, both the tension roller 20 and the tension roller 21 are movable in order to make the winding angle θ variable. But this is not a requirement. A configuration may be employed in which only one of the tension rollers 20 and 21 is movable and the other is fixed. FIG. 14 shows a configuration example in which the upstream tension roller 20 is movable and the downstream tension roller 21 is fixed. If the downstream tension roller 21 is fixed in this way, there is an advantage that the output direction of the printing paper P to the outlet side (the paper regulating members 26 and 27 side) is stable regardless of the winding angle θ. .

  In the configuration example of FIG. 14 as well, the sheet regulating member 25 can be made movable as described with reference to FIGS. However, the sheet regulating member 27 has no particular meaning of being movable. Also, of course, in the configuration example of FIG. 14, the curl sensor 32 shown in FIG. 13 can be provided. In contrast to FIG. 14, a configuration example in which the upstream tension roller 20 is fixed and the downstream tension roller 21 is movable can be omitted.

  In addition, the decurler device 18 in the description of FIGS. 2 to 14 so far has an arrangement in which the conveyance roller 22 is positioned on the lower side of the printing paper P, and the tension rollers 20 and 21 and the belt 19 are positioned on the upper side. It was a thing. This is upside down from the decurler device 18 in the image forming apparatus 1 shown in FIG.

  In FIG. 1, the fixing unit 6 is arranged with a pressure roller 13 below and a heating roller 14 above. In general, in the image forming apparatus 1 using toner as a color developing material, the fixing unit 6 has the most influence on the curling of the printing paper P, and the heating roller 14 side of the pressure roller 13 and the heating roller 14 is convex. Thus, the printing paper P tends to curl. Therefore, as shown in FIG. 15, the decurler device 18 is arranged in accordance with the vertical relationship between the pressure roller 13 and the heating roller 14 in FIG. Therefore, in the decurler device 18 of FIGS. 1 and 15, the transport roller 22 is positioned on the upper side (heating roller 14 side), and the tension rollers 20 and 21 and the belt 19 are positioned on the lower side (pressure roller 13 side). Yes.

  That is, the decurler device 18 shown in FIGS. 2 to 14 has an arrangement adapted to the case where the arrangement of the fixing unit 6 is upside down from that shown in FIG. In the case where the two rollers of the fixing unit 6 are both heating rollers, the curling tendency of the printing paper P may be determined by the configuration upstream of the fixing unit 6. In that case, the up and down direction of the decurler device 18 may be determined in accordance with the curl tendency.

  As described above in detail, according to the present embodiment, in the configuration in which the printing paper P is conveyed by passing the printing paper P through the nip portion between the conveying roller 22 and the belt 19, the belt 19 is supplied to the conveyance roller 22. The winding amount is variable. Accordingly, the curl correction state and the non-correction state can be switched according to the curl state of the printing paper P passing through the decurler device 18. In addition, the degree of correction in a state where the curl is corrected can be adjusted. Here, the belt 19 is sandwiched between the conveying roller 22 and the pressing roller 23. For this reason, even when the curl is not corrected, the conveyance of the printing paper P is stable. In this way, the decurler device 18 in which the conveyance of the printing paper P is stable regardless of the degree of curl correction and the decurler device 18 using the decurler device 18 are realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, in the above-described embodiment, the present invention is applied to the image forming apparatus 1 that uses the image forming unit 5 that forms an image with toner. However, the present invention is not limited to this, and the present invention can be applied to an image forming apparatus using a color developing material other than toner. In this case, of course, since the fixing unit 6 does not exist, the decurler device 18 is arranged at a position where the curl is likely to occur in consideration of the direction of the curl that easily occurs, in accordance with the specific configuration of the image forming apparatus. Become.

  Even in the case of an image forming apparatus that forms an image with toner, the position at which the decurler device 18 can be disposed is not limited to the position on the downstream side of the fixing unit 6. Even in other locations, if there is a position where curling is likely to occur, the decurler device 18 can be disposed immediately downstream. Further, not only the printing paper P, but also a document read by the reading unit 2 can be corrected by the decurler device 18. Furthermore, the image forming apparatus to which the present invention is applied may be a printer type that does not have the reading unit 2 or a monochrome image forming apparatus that is not a color. It may be one that can send and receive print jobs to and from other devices. Further, the transport roller 22, the pressing roller 23, and the tension rollers 20 and 21 do not necessarily have to be rotating members as long as they are slippery.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Main body part 5 Image forming part 6 Fixing part 13 Pressure roller 14 Heating roller 15 Conveying path 18 Decurler device 19 Belt 20 Tension roller 21 Tension roller 22 Conveying roller 23 Pressing roller 25 Paper regulating member 27 Paper regulating member 28 Movement guide member 29 Movement guide member 32 Curl sensor 33 Control unit

Claims (9)

A transport member fixed in position that contacts the first surface of the transported sheet member;
A belt that circulates in a forward direction with respect to the conveying direction of the sheet member while contacting the second surface of the conveyed sheet member and pressing the sheet member against the conveying member;
A first tension member that is in contact with the inner surface side of the belt and applies tension to the belt, is located upstream of the transport member in the transport direction, and is positioned downstream of the transport member in the transport direction. A second tension member;
A pressing member having a fixed position which is located on an inner surface side of the belt and prevents separation of the belt from the conveying member;
Movement of the first tension member or the second tension member in a direction to change the amount of wrapping of the belt around the conveying member, provided on at least one of the first tension member and the second tension member A moving guide member for guiding
The decurler device characterized in that the moving path guided by the moving guide member includes a range in which the amount of winding is zero and a range in which the amount of winding is positive. The decurler device according to claim 1,
The decurler device characterized in that the moving path by the moving guide member has a shape in which the tension applied to the belt is constant even when at least one of the first tension member and the second tension member is moved. . A decurler device according to any one of claims 1 to 2,
The pressing member faces the conveying member even when at least one of the first tension member and the second tension member is moved to a position where the amount of winding of the belt around the conveying member is maximized. A decurler device characterized by not contacting the belt at a position other than the position. A decurler device according to any one of claims 1 to 3,
The decurler device characterized in that the movement path by the movement guide member is provided only for the first tension member. A decurler device according to any one of claims 1 to 4,
A curl amount detection unit for detecting a curl amount of a sheet member provided on the upstream side in the transport direction from the transport member;
At least one of the first tension member and the second tension member is configured to increase the amount of wrapping when the detected curl amount is large and decrease the amount of wrapping when the detected curl amount is small. A decurler device comprising a winding angle control unit that moves the wrapping angle. A decurler device according to any one of claims 1 to 5,
The second member has a movable restricting member that restricts the second surface of the sheet member and moves along the conveying direction,
The movable restriction member is
With respect to the transport member, the first tension member and the second tension member are arranged on the side that is moved by the moving guide member,
Movement of at least one of the first tension member and the second tension member moves away from the conveying member when the winding amount is increased and close to the conveying member when the winding amount is decreased. A decurler device, which moves in conjunction with the device. An image forming apparatus comprising: a sheet supply unit that supplies a sheet member; and an image forming unit that forms an image on the sheet member supplied from the sheet supply unit,
An image forming apparatus, wherein the decurler device according to any one of claims 1 to 6 is disposed on a conveyance path of a sheet member supplied from the sheet supply unit. The image forming apparatus according to claim 7, wherein the decurler device includes:
Downstream of the image forming unit,
An image forming apparatus, wherein the belt is disposed in a direction in which the belt is positioned on a concave surface side of a curl attached to a sheet member in the image forming unit. The image forming apparatus according to claim 8, wherein
A fixing device for fixing the toner image applied on the sheet member between the heating member and the pressure member between the image forming unit and the decurler device;
The image forming apparatus, wherein the decurler device is disposed in a direction in which the belt is positioned on the pressure member side.

Images