Patent Application
20190384212
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2018-114780 filed Jun. 15, 2018.
The present disclosure relates to an image forming apparatus.
Japanese Unexamined Patent Application Publications Nos. 2006-133377, 2007-178580, and 2011-180230 described below disclose image forming apparatuses according to related art that have a function to reduce deformation such as curling (curving or warping) or cockle that occurs in a sheet of paper after the sheet leaves a fixing unit.
Japanese Unexamined Patent Application Publication No. 2006-133377 describes an image forming apparatus including a fixing device positioned to transport a recording medium upward from a lower position against gravity. The fixing device includes a rotatable heat member such as a fixing roller with a heat source disposed therein, a rotatable pressure member such as a pressure roller disposed in pressure contact with the heat member to define a fixing nip part, and a paper-eject guide member that guides the recording medium to the outside of the image forming apparatus after the recording medium leaves the fixing nip part between the heat member and the pressure member. The paper-eject guide member has a guide surface intersecting a tangent line that is tangent to the heat member at the most downstream point of the fixing nip part. The angle of intersection between the guide surface and the tangent line is an obtuse angle.
Japanese Unexamined Patent Application Publication No. 2007-178580 describes an image forming apparatus including a paper feed device, an image forming unit, a fixing unit, and a discharge unit that discharges a sheet of paper to the outside of the image forming apparatus after the sheet undergoes a fixing process in the fixing unit. A paper-eject guide part of the discharge unit, which is located immediately downstream of a pair of fixing rollers of the fixing unit, is provided with a discharge-direction restriction unit that restricts the direction of discharge of the sheet to thereby correct the orientation of the sheet leaving the pair of fixing rollers.
Japanese Unexamined Patent Application Publication No. 2007-178580 also describes that the discharge-direction restriction unit restricts the direction of sheet discharge to the upward or downward direction with respect to the direction tangential to the nip part of the pair of fixing rollers.
Japanese Unexamined Patent Application Publication No. 2011-180230 describes an image forming apparatus including a fixing device. In the fixing device, a recording sheet carrying a transferred toner image and vertically transported to the fixing device is passed through a nip part formed between a heat rotator and a pressure rotator to fix the toner image to the recording sheet, and then the recording sheet with a fixed image is guided by a pair of guide members toward a discharge roller. With the fixing device viewed in cross-section perpendicular to the axis of the heat member, it is assumed that La denotes a straight line connecting the respective axial centers of the heat member and pressure member, Lb denotes a perpendicular line to the straight line La, P denotes a point on the contour of the guide surface of one of the pair of guide members that is located on the same side as the heat rotator, the point being a point on the contour located closest to the pressure rotator with respect to the direction parallel to the straight line La, Lc denotes a tangent line that, among tangent lines passing the point P and tangent to the outer periphery of the hear rotator, has a tangential point closer to the nip part, and D denotes the distance between the point P and the straight line La. In this case, the distance D is greater than or equal to 1.6 times and less than 2.4 times the diameter of the heat rotator, and the tangent line Lc is inclined toward the heat rotator relative to the perpendicular line Lb, the tangent line Lc forming an angle of greater than 2.2 degrees and less than 6.5 degrees with the perpendicular line Lb.
Aspects of non-limiting embodiments of the present disclosure relate to an image forming apparatus that makes it possible to correct curl occurring at least in the leading end portion of a sheet leaving the nip part of a fixing unit, without provision of a driving source to the image forming apparatus.
Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above.
According to an aspect of the present disclosure, there is provided an image forming apparatus including a fixing unit that transports a sheet of paper carrying an unfixed image through a nip part to fix the unfixed image to the sheet, the nip part applying heat and pressure to the sheet, a pair of transport rollers that first pinches and transports the sheet after the sheet leaves the nip part of the fixing unit, a first guide unit that guides transport of the sheet, the first guide unit coming into contact with a first side of the sheet at a position closer to the fixing unit than is the pair of transport rollers after the sheet leaves the nip part, and a second guide unit that guides transport of the sheet, the second guide unit coming into contact with a second side of the sheet at a position closer to the fixing unit than is the pair of transport rollers after the sheet leaves the nip part, the second side being opposite to the first side. The first guide unit has a recess serving as a guide part, the recess being recessed in a direction away from a transport path of the sheet. The second guide unit has a bending part serving as a guide part, the bending part having a shape of a circular arc in cross-section, the bending part being disposed such that at least a portion of the bending part lies inside the recess.
Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein:
Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
Arrows denoted as X, Y, and Z in each figure respectively represent the width, height, and depth directions of a three-dimensional space assumed for the figure. In figures such as
The image forming apparatus 1 is implemented as, for example, a printer that forms an image on a sheet 9 of paper based on externally input image information.
As illustrated in
Image information refers to information related to an image, such as a character, a geometric figure, a photograph, or a pattern. The housing 10 is a structure constructed of various types of support members, covering materials, or other components formed into a required shape. The housing 10 has, at a portion of its top surface, a paper output receiving part 12 in which each sheet 9 discharged after having an image formed thereon is received in a stacked manner, and a paper eject port 13 through which the sheet 9 is discharged toward the paper output receiving part 12.
In the image forming part 2, for example, the following devices related to an electrophotographic system are disposed around a photoconductor drum 21, which is an example of a photoconductor that rotates as indicated by the arrow.
Examples of the above-mentioned devices include a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, and a cleaning device 26. The charging device 22 electrically charges the outer peripheral surface (surface on which an image can be formed) of the photoconductor drum 21. The exposure device 23 exposes the outer peripheral surface of the photoconductor drum 21 to light based on image information to thereby form an electrostatic latent image on the outer peripheral surface of the photoconductor drum 21. The developing device 24 develops an electrostatic latent image formed on the outer peripheral surface of the photoconductor drum 21 into a visible image by use of developer (toner). The transfer device 25 transfers an unfixed image (toner image) formed on the outer peripheral surface of the photoconductor drum 21 to the sheet 9. The cleaning device 26 cleans away unwanted substances such as toner or paper dust adhering to the outer peripheral surface of the photoconductor drum 21. In the image forming part 2, the area where the photoconductor drum 21 and the transfer device 25 contact or face each other serves as a transfer position TP through which the sheet 9 is passed to transfer an unfixed toner image to the sheet 9.
In the paper feed part 4, for example, devices such as an accommodating cassette 41 and a feeding device 43 are disposed. The paper feed part 4 is disposed at a position inside the housing 10 below the image forming part 2.
Of the above-mentioned devices, the accommodating cassette 41, which has a loading plate 42 to receive a stack of multiple sheets 9 loaded in a required orientation, is an accommodating member that can be drawn out to the outside of the housing 10. The feeding device 43 pays out the stack of sheets 9 loaded on the loading plate 42 of the accommodating cassette 41 one by one, beginning with the uppermost sheet of the stack by means of multiple rollers or other components.
As illustrated in
Of the above-mentioned devices, the heat rotator 51 constitutes a portion of a fixing unit that is in the form of, for example, a roller that rotates as indicated by the arrow. The heat rotator 51 rotates as indicated by the arrow upon receiving rotational power from a driving device (not illustrated). Further, for example, the heat rotator 51 is heated by a heat source 53 disposed inside the heat rotator 51 such that the heat rotator 51 is kept at a required temperature. The pressure rotator 52 constitutes a portion of a fixing unit that is in the form of, for example, a roller that contacts the heat rotator 51 under a required applied pressure so as to rotate following the rotation of the heat rotator 51.
In the fixing part 5, the area where the heat rotator 51 and the pressure rotator 52 contact defines a nip part (fixing processing part) FN. In the nip part FN, the sheet 9 with a transferred unfixed toner image is subjected to heat and pressure for a fixing process.
The fixing part 5 discharges the sheet 9 from the nip part FN after a fixing process, in a substantially upward direction (e.g., in a direction (vertically upward direction) opposite to the direction of gravity and falling within a range of ±45 degrees to the direction of gravity). In the following description, the fixing part 5 that discharges a sheet in this manner will be sometimes also referred to as “upward discharge-type fixing part 5A”.
As illustrated in
Further, a discharge transport path Rt2 is positioned between the fixing part 5 and the paper output receiving part 12 to transport the sheet 9 that has undergone a fixing process so that the sheet 9 is discharged to the paper output receiving part 12. The discharge transport path Rt2 is provided with components such as a pair of discharge rollers 46 and a guide member (not illustrated). The pair of discharge rollers 46 pinches and transports the sheet 9 at a position in front of the paper eject port 13, which is provided in a wall surface constituting a portion of the paper output receiving part 12 of the housing 10. The guide member provides a transport space for the sheet 9 to guide the transport of the sheet 9. The discharge transport path Rt2 defines a transport path that bends and extends upward from the fixing part 5 toward the pair of discharge rollers 46.
The image forming apparatus 1 performs the following basic image forming operation.
First, when a controller (not illustrated) receives a command requesting for an image forming operation from an externally connected device or other devices, required portions of the image forming apparatus 1, such as those in the image forming part 2, the paper feed part 4, the fixing part 5, and other parts, activate at predetermined timing.
As illustrated in
Meanwhile, in the paper feed part 4, the sheet 9 accommodated in the accommodating cassette 41 is fed toward the transfer position TP of the image forming part 2 by the feeding device 43, in synchronization with the timing when an image forming operation is performed in the image forming part 2. At this time, the sheet 9 fed from the accommodating cassette 41 by the feeding device 43 of the paper feed part 4 is sent to the transport rollers 44, which are registration rollers, in the paper feed transport path Rt1. The sheet 9 is subsequently sent to the transfer position TP by the transport rollers 44 at required timing.
Then, at the transfer position TP of the image forming part 2, the transfer device 25 transfers a toner image formed on the photoconductor drum 21 to the sheet 9 fed from the paper feed part 4. Further, in the image forming part 2, the cleaning device 26 cleans away unnecessary substances that remain adhering to the outer peripheral surface of the photoconductor drum 21 after, for example, the transfer process.
Subsequently, the sheet 9 having the toner image transferred thereto in the image forming part 2 is discharged from the transfer position TP toward the fixing part 5. In the fixing part 5, the sheet 9 carrying the toner image is advanced through the nip part FN. Thus, in the nip part FN, the toner image on the sheet 9 is heated under applied pressure to melt, and then fixed to the sheet 9.
Lastly, after the fixing process, the sheet 9 is discharged from the fixing part 5. The sheet 9 is then transported via the discharge transport path Rt2 to the paper output receiving part 12 so that the sheet 9 is received in the paper output receiving part 12. At this time, after undergoing the fixing process and leaving the fixing part 5, the sheet 9 is transported to the discharge rollers 46 via the discharge transport path Rt2. The sheet 9 is then sent by the discharge rollers 46 to the outside of the housing 10 through the paper eject port 13, such that the sheet 9 is dropped to the paper output receiving part 12 and received in the paper output receiving part 12.
Through the series of processes mentioned above, an image of a required color is formed on one side of a single sheet 9, thus completing the basic image forming operation.
If the image forming apparatus 1 receives a command issued to request for an image forming operation on multiple sheets 9, the above-mentioned series of processes is repeated in the same manner for a number of times corresponding to the number of such sheets.
As illustrated in
This curl tends to occur, for example, when the following conditions exist: the fixing part 5 is implemented as a fixing unit having a nip part FN1 where the pressure rotator 52 bites into the surface of the heat rotator 51; and a plain paper sheet is used as the sheet 9.
As illustrated in
The fixing part 5 is the upward discharge-type fixing part 5A and is also the fixing part 5 with type-1 nip. Accordingly, the fixing part 5 will be hereinafter sometimes referred to as upward discharge-type fixing part 5A1 with type-1 nip. The term plain paper sheet as used herein refers to a sheet of paper that is neither thin paper nor heavy paper, with a basis weight in the range of, for example, 60 to 105 g/m2.
If the upward discharge-type fixing part 5A1 with type-1 nip is used to perform a fixing process with a heavy paper sheet (e.g., a sheet of paper with a basis weight of 106 g/m2 or more) used as the sheet 9, the away-from-image curl mentioned above does not occur in the heavy paper sheet. In this case, the heavy paper sheet may sometimes develop a curl (also called, for example, “toward-image curl”) such that the heavy paper sheet is deformed so as to curve toward the side carrying an image formed immediately after fixing of an unfixed image.
In this regard, as illustrated in
As illustrated in
If the upward discharge-type fixing part 5A2 with type-2 nip is used to perform a fixing process with a heavy paper sheet used as the sheet 9, the heavy paper sheet may sometimes develop the toward-image curl mentioned above, although the degree of curvature occurring in the sheet 9 in this case is not as great as the degree of curvature that would occur in a plain paper sheet.
To address the above-mentioned curling, the image forming apparatus 1 includes the decurling part (decurling device) 6 having the configuration described below.
As illustrated in
The front side 9a of the sheet 9 refers to one side of the sheet 9 toward which the sheet 9 is bent for decurling. The back side 9b of the sheet 9 refers to the side opposite to the front side 9a and toward which a curl to be corrected is curved. When viewed from the fixing part 5, with respect to the nip part FN, the first guide unit 61 is disposed to lie on the same side as the heat rotator 51. By contrast, the second guide unit 65 is disposed to lie on the same side as the pressure rotator 52 relative to the first guide unit 61.
As illustrated in
Further, as illustrated in
As illustrated in
The recess 62 serving as a guide part of the first guide unit 61 is located substantially in the middle of the member 611 with respect to the transport direction C of the sheet 9. The recess 62 is in the form of an elongated groove curved along the transport direction C of the sheet 9 and extending in the width direction D1-D2 of the sheet 9.
Features of the recess 62 such as its depth as well as its length and shape with respect to the transport direction C of the sheet 9 are set in accordance with, for example, the amount of bending applied to the sheet 9 to decurl the sheet 9.
As illustrated in
If the guide surface 62c of the recess 62 has intermediate projections in the intermediate area between the upstream end portion 62a and the downstream end portion 62b of the recess 62 as illustrated in
As illustrated in
The directing part 63 has, for example, a surface that extends from the upstream end portion 62a of the recess 62 in a direction substantially normal to the heat rotator 51. The imaginary extension of the surface intersects a portion of the lead-in part 68 located near the bending part 66.
Further, as illustrated in
The tangent line TL may be, for example, a line tangent to a driven discharge roller 46b and to the bending part 66 (a roller 67). The driven discharge roller 46b is one of the pair of discharge rollers 46 located on the opposite side to the bending part 66 across the transport path of the sheet 9.
From the viewpoint of reducing contamination resulting from contact with the sheet 9 (including a fixed image) after a fixing process, the first guide unit 61 may have a release layer made of fluorocarbon resin or other materials disposed on at least the guide surface 62c of the recess 62 and the surface of the directing part 63.
As illustrated in
The second guide unit 65 is disposed such that at least a portion of the bending part 66 lies inside the recess 62 of the first guide unit 61. More specifically, as illustrated in
The bending part 66 is disposed facing the recess 62 of the first guide unit 61, with a required spacing S provided between the bending part 66 and the recess 62 to allow passage of the sheet 9. The spacing S may be adjusted by, for example, changing the amount of entry of the bending part 66 into the recess 62, the shape or depth of the recess 62, or other conditions.
As illustrated in
The bending part 66 according to Exemplary Embodiment 1 is implemented as, for example, the roller 67, which is an example of a rotator disposed in a rotatable manner and having a circular cross-section.
As illustrated in
As illustrated in
As illustrated in
The lead-in part 68 is disposed so as to define, together with the directing part 63 of the first guide unit 61, a receiver opening facing the nip part FN of the fixing part 5 and through which the sheet 9 leaving the nip part FN is led into the decurling part 6. In actuality, the receiver opening is formed as an opening that defines, between the lead-in part 68 and the directing part 63 that face each other, a gap that gradually decreases in width as the gap extends downstream with respect to the transport direction C of the sheet 9.
Further, as illustrated in
Further, as illustrated in
Although the decurling part 6 has been described above as being separate from the fixing part 5, the decurling part 6 may be implemented as a device or mechanism incorporated into the fixing part 5 as a portion of the fixing part 5.
As illustrated in
Each of the discharge guide units 47 and 48 is implemented as a dedicated guide member, or as a guide part that also serves as a portion of another support member.
Of the two discharge guide units, the discharge guide unit 47 is disposed with a lower guide part 47a located between the first guide unit 61 of the decurling part 6 and one (e.g., the driven discharge roller 46b) of the pair of discharge rollers 46. The discharge guide unit 48 is disposed with an upper guide part 48a located between the second guide unit 65 of the decurling part 6 and the other one (e.g., a driving discharge roller 46a) of the pair of discharge rollers 46.
Hereinafter, operation of the decurling part 6 will be described.
Now, the operation of the decurling part 6 when a plain paper sheet 9A is used as the sheet 9 will be described.
In this case, in the fixing process, the plain paper sheet 9A is discharged from the nip part FN of the fixing part 5 as illustrated in
As described above, the fixing part 5 in this case is the upward discharge-type fixing part 5A1 with type-1 nip as illustrated in
As illustrated in
Subsequently, the plain paper sheet 9A having the away-from-image curl continues its travel under the transport force provided by the nip part FN1 of the fixing part 5A1. After the leading end 9c of the plain paper sheet 9A comes into contact with, for example, the directing part 63 of the first guide unit 61 in the decurling part 6, the leading end 9c of the plain paper sheet 9A is directed into contact with the lead-in part 68 of the second guide unit 65 in the decurling part 6 as indicated by the two-dot chain line in
At this time, the leading end 9c of the plain paper sheet 9A may sometimes come into contact with the lead-in part 68 of the second guide unit 65 first before coming into contact with the directing part 63 of the first guide unit 61.
In the decurling part 6, as illustrated in
At this time, as indicated by the solid line in
Subsequently, as indicated by the solid line in
At this time, even at the point when the leading end portion of the plain paper sheet 9A becomes pinched by the pair of discharge rollers 46 during its transport, the trailing portion of the plain paper sheet 9A moving through the decurling part 6 is reliably bent so as to warp toward the front side 9a when passing between the recess 62 of the first guide unit 61 and the roller 67 serving as the bending part 66 of the second guide unit 65. At this time, as illustrated in
Further, as illustrated in
As described above, for the plain paper sheet 9A leaving the nip part FN of the fixing part 5 (5A1) and having away-from-image curl, the decurling part 6 applies the following action to not only the leading end portion but also the trailing portion of the plain paper sheet 9A. That is, as the plain paper sheet 9A is passed through the gap between the recess 62 of the first guide unit 61 and the roller 67 serving as the bending part 66 of the second guide unit 65, the decurling part 6 temporarily bends the plain paper sheet 9A into a curved shape that warps toward the front side 9a. This corrects the away-from-image curl in the plain paper sheet 9A such that the away-from-image curl substantially disappears over the area of the plain paper sheet 9A from its leading end portion to the trailing portion.
At this time, the away-from-image curl is corrected in the decurling part 6 mostly by the recess 62 of the first guide unit 61 and the roller 67 serving as the bending part 66 of the second guide unit 65. Thus, the correction of the away-from-image curl does not require an operation such as adjusting the position of the first guide unit 61 by means of a driving source or rotating the roller 67 by means of a driving source. Therefore, the away-from-image curl is corrected by means of a relatively simple structure without requiring a driving source.
Further, with the image forming apparatus 1, even when the plain paper sheet 9A develops away-from-image curl upon leaving the nip part FN of the fixing part 5, as the plain paper sheet 9A passes through the decurling part 6, the away-from-image curl in the plain paper sheet 9A is corrected. The plain paper sheet 9A is thus substantially flattened. Then, the flattened plain paper sheet 9A is eventually received by the paper output receiving part 12 in substantially proper condition.
In particular, as illustrated in
As illustrated in
For cases where a type of paper sheet other than the plain paper sheet 9A, for example, a heavy paper sheet is used as the sheet 9, the decurling part 6 operates in substantially the same manner as when the plain paper sheet 9A is used.
That is, when a heavy paper sheet used as the sheet 9 passes through the nip part FN1 of the upward discharge-type fixing part 5A1 with type-1 nip, the heavy paper sheet leaving the nip part FN1 is free from the away-from-image curl (91) that would occur in the plain paper sheet 9A.
In this case, the heavy paper sheet is bent to warp toward its front side when passing through the gap between the recess 62 of the first guide unit 61 and the roller 67 serving as the bending part 66 of the second guide unit 65 in the decurling part 6. At this time, since the heavy paper sheet has a higher stiffness (rigidity) than a plain paper sheet, the heavy paper sheet is not kept in this bent state.
After passing through the decurling part 6, the heavy paper sheet is directed into the transport passage defined by the discharge guide units 47 and 48. Subsequently, the heavy paper sheet is transported to eventually reach the pair of discharge rollers 46 that rotates. The heavy paper sheet is then received in the paper output receiving part 12.
Accordingly, although the decurling part 6 acts to bend the sheet 9 toward the front side of the sheet 9 also when a heavy paper sheet passes through the decurling part 6 as the sheet 9, there is no risk of the decurling part 6 giving, for example, toward-image-curl to the heavy paper sheet at this time.
In the decurling part 6, the bending part 66 of the second guide unit 65 is disposed facing the recess 62 of the first guide unit 61 with a spacing S provided between the bending part 66 and the recess 62 to allow passage of the sheet 9. This configuration allows for easy passage and transport of the sheet 9 as compared to when the spacing S is not provided.
In the decurling part 6, the bending part 66 is positioned offset toward the upstream portion of the recess 62 with respect to the transport direction C of the sheet 9. This configuration helps properly correct curl (away-from-image curl) occurring at least in the leading end portion of the sheet 9 (plain paper sheet 9A), as compared to when the bending part 66 is positioned offset toward the downstream portion of the recess 62 with respect to the transport direction C of the sheet 9.
Further, in the decurling part 6, the bending part 66 is implemented as the roller 67, which is a rotator with a circular cross-section. As compared to when the bending part 66 is not formed as a rotator, this configuration allows for easy passage and transport of the sheet 9 and also reduces the load applied to the sheet 9 upon contact of the sheet 9 with the roller 67.
The roller 67 serving as the bending part 66 is disposed such that its center of rotation O1 does not lie inside the recess 62. As compared to disposing the roller 67 with its center of rotation O1 lying inside the recess 62, a relatively smaller portion of the sheet 9 is pushed into the recess 62 when passing the roller 67. This helps minimize poor sheet transport that occurs when the sheet 9 does not readily pass between the roller 67 and the recess 62.
As illustrated in
The semi-perimeter portion of the circular column or circular cylinder forming the stationary bending part 69 of the second guide unit 65B faces the recess 62 of the first guide unit 61. The stationary bending part 69 is substantially identical in configuration to the roller 67 serving as the bending part 66 according to Exemplary Embodiment 1, except that the stationary bending part 69 does not rotate.
With the second guide unit 65B having the stationary bending part 69, the lead-in part 68 may be provided contiguous with the stationary bending part 69.
The first guide unit 61 according to this modification is identical in configuration to the first guide unit 61 according to Exemplary Embodiment 1.
The decurling part 6 including the second guide unit 65B with the stationary bending part 69 according to this modification provides substantially the same operational effect as the decurling part 6 according to Exemplary Embodiment 1.
As illustrated in
Among the above-mentioned components, the image forming part 2B is identical in configuration to the image forming part 2 according to Exemplary Embodiment 1, except that after a transfer process, the image forming part 2B discharges the sheet 9 in substantially the lateral direction from the transfer position TP.
The fixing part 5B is substantially identical in configuration to the fixing part 5 according to Exemplary Embodiment 1, except that after performing a fixing process on the sheet 9, the fixing part 5B discharges the sheet 9 from the nip part FN in substantially the lateral direction (e.g., in a direction falling within a range of ±45 degrees with respect to the horizontal direction of the floor or other surfaces on which the image forming apparatus is placed). In the following description, the fixing part 5B that discharges a sheet in this manner will be sometimes also referred to as “lateral discharge-type fixing part 5B”.
Further, substantially like the fixing part 5 according to Exemplary Embodiment 1, the lateral discharge-type fixing part 5B is also a fixing part with type-1 nip illustrated in
Further, as illustrated in
The image forming apparatus 1B according to Exemplary Embodiment 2 employs, as the decurling part 6B, a decurling part having the configuration described below.
First, substantially like the decurling part 6 according to Exemplary Embodiment 1 (including its modification), the decurling part 6B includes the first guide unit 61 and the second guide unit 65. The only slight difference of the decurling part 6B from the decurling part 6 is that the relative positions of the first guide unit 61 and second guide unit 65 with respect to the vertical direction are reversed from those in the decurling part 6.
As illustrated in
As illustrated in
The decurling part 6B described above provides, for the sheet 9 leaving the nip part FN1 of the lateral discharge-type fixing part 5B1 with type-1 nip, substantially the same operational effect as that of the decurling part 6 according to Exemplary Embodiment 1. In particular, when the plain paper sheet 9A develops away-from-image curl upon leaving the nip part FN1, the away-from-image curl is corrected as the plain paper sheet 9A passes through the decurling part 6B.
The present disclosure is by no means limited to the details set forth in Exemplary Embodiments 1 and 2 above but includes, for example, the following modifications in its scope.
As illustrated in
As illustrated in
However, the decurling part 6C differs from the decurling part 6 according to Exemplary Embodiment 1 in that the first guide unit 61 is disposed to lie mostly on the same side as the pressure rotator 52 with respect to the nip part FN2 of the fixing part 5A2, and that the second guide unit 65 and the bending part 66 are disposed to lie on the same side as the heat rotator 51 of the fixing part 5A2. The fixing part 5A2 is desirably provided with a stripping guide unit (not illustrated) disposed between the nip part FN2 and the second guide unit 65 of the decurling part 6C to strip the leading end 9c of the sheet 9 from the heat rotator 51 after a transfer process and then guide the leading end 9c of the sheet 9 toward the lead-in part 68 of the second guide unit 65.
With the image forming apparatus employing the upward discharge-type fixing part 5A2 with type-2 nip, if the plain paper sheet 9A is used as the sheet 9, the plain paper sheet 9A leaving the nip part FN2 of the fixing part 5A2 may sometimes develop a toward-image curl 93 as indicated by the thick solid line in
At this time, for the plain paper sheet 9A leaving the nip part FN2 of the fixing part 5A2 and having the toward-image curl, the decurling part 6C applies the following action to not only the leading end portion but also the trailing portion of the plain paper sheet 9A. That is, as the plain paper sheet 9A is passed through the gap between the recess 62 of the first guide unit 61 and the roller 67 serving as the bending part 66 of the second guide unit 65, the decurling part 6C temporarily bends the plain paper sheet 9A into a curved shape that warps toward the back side 9b. This corrects the toward-image curl in the plain paper sheet 9A so that the toward-image curl substantially disappears.
If a heavy paper sheet 9B is used as the sheet 9, the decurling part 6C operates in substantially the same manner as the decurling part 6 according to Exemplary Embodiment 1.
The image forming apparatus 1B according to Exemplary Embodiment 2 may employ, instead of the lateral discharge-type fixing part 5B1 with type-1 nip, a lateral discharge-type fixing part (5B2) having the nip part FN2 that is a type-2 nip part.
Further, if necessary, the bending part 66 of the second guide unit 65 in the decurling part 6 (6B or 6C) may be disposed in proximity to or in contact with the recess 62 of the first guide unit 61. In this case, from the viewpoint of allowing easy transport of the sheet 9 passing between the recess 62 and the bending part 66, for example, the bending part 66 may be formed as a rotator such as the roller 67 that is rotatable, or the guide surface 62c of the recess 62 or the surface of the bending part 66 may be provided with a surface layer that is readily capable of elastic deformation.
Further, the decurling part 6 (6B or 6C) may include, instead of the directing part 63 of the first guide unit 61, a stripping guide unit disposed between the first guide unit 61 and the heat rotator 51 (or the pressure rotator 52) to strip the sheet 9 and guide the stripped sheet 9 to areas such as the lead-in part 68 or the bending part 66 of the second guide unit 65.
Further, although the image forming apparatus 1 or 1B according to Exemplary Embodiment 1 or 2 mentioned above includes the image forming part 2 or 2B that forms a monochrome image by use of developer, the image forming apparatus 1 or 1B may be an image forming apparatus including the image forming part 2 or 2B that forms a multi-color image. The above-mentioned image forming part 2 or 2B that forms a multi-color image may be, for example, an image forming part having a body portion that forms unfixed images of various colors, and an intermediate transfer portion used for a first transfer process and a second transfer process, the first transfer process transferring each unfixed image onto the intermediate transfer portion, the second transfer process transferring each transferred unfixed image carried by the intermediate transfer portion to the sheet.
In the foregoing description of Exemplary Embodiments 1 and 2, the fixing part 5 (5A or 5B) includes the heat rotator 51 and the pressure rotator 52 that are of a roller type. Alternatively, the fixing part 5 (5A or 5B) may have a configuration such that one or both of the heat rotator 51 and the pressure rotator 52 are of a belt-support roller type or of a belt-nip type.
The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-114780 | Jun 2018 | JP | national |
