Patent Application
20210011399
The present disclosure relates to a sheet-member guide structure and an image forming apparatus.
Japanese Unexamined Patent Application Publication No. 2006-003404 describes an image forming apparatus including a fixing unit and a negative-pressure transport belt. The fixing unit fixes a toner image formed on a paper sheet to the paper sheet by heating the toner image. The negative-pressure transport belt, which is disposed downstream of the fixing unit along a sheet transport path, transports the paper sheet further downstream while the toner image that has been heated and fixed by the fixing unit does not come into contact with a certain member.
For example, a guide member for guiding the recording medium from the fixing unit to a transport roller unit, which discharges the recording medium to the outside of the apparatus, is provided between the fixing unit and the transport roller unit. According to the related art, the guide member is made of a resin material, and guides the recording medium to the transport roller unit by coming into contact with the recording medium to which an image has been fixed by the fixing unit.
The recording medium is heated to a high temperature in the region where the image has been fixed thereto by the fixing unit. When the recording medium comes into contact with the transport roller unit while the temperature thereof is high, contact marks, or “roller marks”, are formed on the image on the recording medium due to contact with the transport roller unit.
Aspects of non-limiting embodiments of the present disclosure relate to a technology for making the occurrence of contact marks on an image formed on a sheet member due to contact with a transport roller unit less than that in the case where guide members that guide the sheet member from a fixing unit to the transport roller unit are made of materials having similar thermal conductivities over the entirety thereof.
Aspects of certain non-limiting embodiments of the present disclosure overcome the above disadvantages and/or other disadvantages not described above. However, aspects of the non-limiting embodiments are not required to overcome the disadvantages described above, and aspects of the non-limiting embodiments of the present disclosure may not overcome any of the disadvantages described above.
According to an aspect of the present disclosure, there is provided a sheet-member guide structure including a first guide member that guides a sheet member from a fixing unit to a transport roller unit, the fixing unit fixing an image formed on the sheet member to the sheet member by heating the sheet member that is transported, the transport roller unit transporting the sheet member; and a second guide member that comes into contact with the sheet member to which the image has been fixed by the fixing unit and guides the sheet member to the transport roller unit, the second guide member being disposed downstream of the first guide member in a transporting direction in which the sheet member is transported and being made of a material having a thermal conductivity higher than a thermal conductivity of a material of the first guide member.
Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein:
An example of a sheet-member guide structure and an image forming apparatus according to a first exemplary embodiment of the present disclosure will be described with reference to
As illustrated in
The storage unit 14 includes a storage member 26 that may be pulled forward from an apparatus body 10a of the image forming apparatus 10 in the apparatus depth direction. The sheet members P are stacked on the storage member 26. The storage unit 14 also includes a feed roller 30 that feeds the top sheet member P of the stack on the storage member 26 to a transport path 28, which is included in the transport unit 16.
The transport unit 16 includes plural transport roller units 32 that transport the sheet member P along the transport path 28, and a discharge roller unit 48 that discharges the sheet member P to the outside of the apparatus body 10a along the transport path 28 after a toner image is formed on the sheet member P. The discharge roller unit 48 is an example of a transport roller unit.
The transport unit 16 also includes a guide structure 60 that guides the sheet member P to which the toner image has been fixed by a fixing unit 34, which will be described below, toward the discharge roller unit 48. The discharge roller unit 48 and the guide structure 60 will be described in detail below.
The image forming section 20 includes four image forming units 18Y, 18M, 18C, and 18K, which are yellow (Y), magenta (M), cyan (C), and black (K) image forming units, respectively. In the following description, the characters Y, M, C, and K may be omitted when it is not necessary to distinguish between Y, M, C, and K.
As illustrated in
As illustrated in
The image forming apparatus 10 forms an image in the following manner.
First, the charging rollers 38 of the respective colors, to which a voltage is applied, come into contact with the peripheral surfaces of the image carriers 36 of the respective colors and uniformly charge the peripheral surfaces of the image carriers 36 to a predetermined negative potential. Subsequently, the exposure devices 42 of the respective colors form electrostatic latent images by irradiating the charged peripheral surfaces of the image carriers 36 of the respective colors with exposure light based on data input from the outside.
Thus, the electrostatic latent images corresponding to the image data are formed on the peripheral surfaces of the image carriers 36. The developing devices 40 of the respective colors develop and visualize the electrostatic latent images into toner images. The first transfer rollers 24 transfer the toner images formed on the peripheral surfaces of the image carriers 36 of the respective colors onto the transfer belt 22.
The feed roller 30 feeds the top sheet member P of the stack on the storage member 26 toward a transfer position T, at which the transfer belt 22 and the second transfer roller 46 are in contact with each other, along the transport path 28. The second transfer roller 46 and the transfer belt 22 transport the sheet member P while nipping the sheet member P therebetween at the transfer position T, so that the toner image on the peripheral surface of the transfer belt 22 is transferred to the sheet member P.
The fixing unit 34 fixes the toner image that has been transferred to the sheet member P to the sheet member P. The sheet member P to which the toner image is fixed is discharged to the outside of the apparatus body 10a by the discharge roller unit 48.
The discharge roller unit 48, the fixing unit 34, and the guide structure 60 according to the present exemplary embodiment will now be described.
As illustrated in
The first roller 52 includes a shaft 52a that extends in the apparatus depth direction and plural roller portions 52b that are cylindrical and through which the shaft 52a extends. The roller portions 52b are arranged with similar gaps therebetween, and both end portions of the shaft 52a are supported by support members (not shown) so that the first roller 52 is rotatable.
The second roller 54 faces the first roller 52 with the transport path 28, along which the sheet member P is transported, disposed therebetween. More specifically, the second roller 54 is disposed below the first roller 52 and faces the first roller 52 with the transport path 28, along which the sheet member P is transported, disposed therebetween. Thus, a portion of the transport path 28 along which the sheet member P is transported by the first roller 52 and the second roller 54 extends in the apparatus width direction when viewed in the apparatus depth direction.
The second roller 54 includes a shaft 54a that extends in the apparatus depth direction and plural roller portions 54b that are cylindrical and through which the shaft 54a extends. The roller portions 54b are arranged with similar gaps therebetween, and are in contact with the roller portions 52b. A rotational force is transmitted to the shaft 54a from a driving member (not shown), so that the second roller 54 is rotated in the direction of arrow F1 and the first roller 52 is rotated by the second roller 54 in the direction of arrow F2.
According to the present exemplary embodiment, the transport speed at which the discharge roller unit 48 transports the sheet member P is lower than the transport speed at which the fixing unit 34 transports the sheet member P. The transport speed at which the discharge roller unit 48 transports the sheet member P is, for example, 99% of the transport speed at which the fixing unit 34 transports the sheet member P.
As illustrated in
The pressing roller 56 is disposed on the same side of the transport path 28, along which the sheet member P is transported, as the side on which the second transfer roller 46 is disposed (see
The shaft 56a extends through the rubber portion 56b, and both end portions of the shaft 56a project from the rubber portion 56b. The end portions of the shaft 56a are supported by support members (not shown) so that the pressing roller 56 is rotatable, and the support members are urged by urging members so that the pressing roller 56 is urged against the heating roller 58. Accordingly, the pressing roller 56 presses the sheet member P that is transported against the heating roller 58. More specifically, the pressing roller 56 comes into contact with a non-image surface (surface on which no toner image is formed) of the sheet member P that is transported and presses the sheet member P against the heating roller 58.
As illustrated in
The portion of the transport path 28 between the fixing unit 34 and the discharge roller unit 48 is curved such that the side thereof facing the pressing roller 56 is convex when viewed in the apparatus depth direction.
The heating roller 58 includes a cylindrical shaft 58a that extends in the apparatus depth direction, a coating (not shown) that covers the shaft 58a, and a heating portion 58b disposed in the shaft 58a. In this configuration, the surface temperature of the heating roller 58 is, for example, 190° C.
A rotational force is transmitted to the heating roller 58 from a driving member (not shown), so that the heating roller 58 is rotated in the direction of arrow E1 and the pressing roller 56 is rotated by the heating roller 58 in the direction of arrow E2.
In the present exemplary embodiment, the transport speed at which the fixing unit 34 transports the sheet member P is, for example, 60 mm/s, and the transport speed at which the above-described discharge roller unit 48 transports the sheet member P is, for example, 59.4 mm/s.
As illustrated in
The first guide member 62 is disposed adjacent to the fixing unit 34, and the second guide member 72 is disposed adjacent to the discharge roller unit 48. In other words, the first guide member 62 and the second guide member 72 are arranged in that order in the transporting direction of the sheet member P from the upstream side toward the downstream side.
As illustrated in
When viewed in the apparatus depth direction, the plate portion 64 is inclined upward in the up-down direction and toward the discharge roller unit 48 along the transport path 28. In addition, when viewed in the thickness direction of the plate portion 64, the plate portion 64 has a rectangular shape that extends in the apparatus depth direction (width direction of the sheet member P) to cover the transported sheet member P in the apparatus depth direction (see
The plate portion 64 has a front surface 64a that faces the transport path 28 and a back surface 64b that is opposite to the front surface 64a and that faces away from the sheet member P that is transported. The ribs 66 are formed on the front surface 64a of the plate portion 64.
The ribs 66 project from the front surface 64a of the plate portion 64 toward the sheet member P that is transported, and extend in the transporting direction of the sheet member P (see
In this configuration, the leading end of the sheet member P that is transported while being nipped between the pressing roller 56 and the heating roller 58 may be curved (curled) toward the first guide member 62. In such a case, as illustrated in
As illustrated in
Accordingly, heat more easily transfers in the second guide member 72 than in the first guide member 62. More specifically, the second guide member 72 more easily receives heat from the outside and dissipates heat to the outside than does the first guide member 62. In other words, the material of the second guide member 72 has higher thermal emissivity and absorptivity than those of the material of the first guide member 62. The heat dissipation plates 76 are an example of a heat dissipating unit.
The plate portion 74 extends in the apparatus width direction when viewed in the apparatus depth direction. When viewed in the thickness direction of the plate portion 74, the plate portion 74 has a rectangular shape that extends in the apparatus depth direction (width direction of the sheet member P) to cover the transported sheet member P in the apparatus depth direction (see
The plate portion 74 includes a contact surface 74a that faces the transport path 28 and comes into contact with the sheet member P that is transported and a non-contact surface 74b that is opposite to the contact surface 74a and that does not come into contact with the sheet member P that is transported. The position of the contact surface 74a in the up-down direction is similar to the position of the contact portion between the first roller 52 and the second roller 54 of the discharge roller unit 48 in the up-down direction. The heat dissipation plates 76 are formed on the non-contact surface 74b (see
The heat dissipation plates 76 have plate surfaces that face in the transporting direction of the sheet member P. The heat dissipation plates 76 extend in the width direction of the sheet member P that is transported (apparatus depth direction). The heat dissipation plates 76 are arranged in the transporting direction of the sheet member P (see
In this configuration, the leading end of the sheet member P guided toward the discharge roller unit 48 by the first guide member 62 comes into contact with the contact surface 74a of the plate portion 74 of the second guide member 72, as illustrated in
The second guide member 72 receives heat from the sheet member P, and the heat dissipation plates 76 dissipate heat from the second guide member 72.
The sheet member P that is transported while being nipped between the pressing roller 56 and the heating roller 58 may have a leading end that is not curled. In such a case, according to the present exemplary embodiment, when viewed in the apparatus depth direction, the angle (01 in
As illustrated in
In this configuration, the leading end of the sheet member P that is transported while being nipped between the pressing roller 56 and the heating roller 58 may be curved (curled) toward the third guide member 82. In such a case, as illustrated in
The leading end of the sheet member P guided toward the discharge roller unit 48 by the third guide member 82 comes into contact with the contact surface 74a of the plate portion 74 of the second guide member 72, as illustrated in
The operation of the relevant structure according to the present exemplary embodiment will now be described.
After the toner image is transferred to the image surface of the sheet member P, the sheet member P is transported to the fixing unit 34, as illustrated in
The leading end of the sheet member P that is transported while being nipped between the pressing roller 56 and the heating roller 58 may be curved (curled) toward the first guide member 62. In such a case, as illustrated in
The leading end of the sheet member P that is transported while being nipped between the pressing roller 56 and the heating roller 58 may instead be curved (curled) toward the third guide member 82. In such a case, as illustrated in
The sheet member P that has been guided toward the discharge roller unit 48 by the first guide member 62 or the third guide member 82, or that has been guided toward the discharge roller unit 48 without coming into contact with the first guide member 62 or the third guide member 82, moves further downstream.
As illustrated in
As described above, the transport speed at which the discharge roller unit 48 transports the sheet member P is lower than the transport speed at which the fixing unit 34 transports the sheet member P. Therefore, as illustrated in
Since the sheet member P is bent toward the second guide member 72, the contact area between the sheet member P and the second guide member 72 is greater than that in the case where the transport speed at which the discharge roller unit 48 transports the sheet member P is similar to the transport speed at which the fixing unit 34 transports the sheet member P.
The second guide member 72 receives heat of the sheet member P from a portion of the sheet member P that is in contact with the second guide member 72, and the heat dissipation plates 76 of the second guide member 72 dissipate heat from the second guide member 72. The discharge roller unit 48 discharges the sheet member P to the outside of the apparatus body 10a by transporting the sheet member P while the sheet member P is continuously in contact with the second guide member 72.
As described above, the guide structure 60 is configured such that the thermal conductivity of the material of the second guide member 72 adjacent to the discharge roller unit 48 is higher than that of the material of the first guide member 62 adjacent to the fixing unit 34. In other words, the thermal conductivity of the material of the first guide member 62 adjacent to the fixing unit 34 is lower than that of the material of the second guide member 72 adjacent to the discharge roller unit 48.
Therefore, the amount of heat generated by the fixing unit 34 and transferred to the second guide member 72 through the first guide member 62 is less than that in the case where the thermal conductivity of the material of the first guide member 62 adjacent to the fixing unit 34 is similar to that of the material of the second guide member 72. Also, the amount of heat which the second guide member 72 receives from the sheet member P is greater than that in the case where the thermal conductivity of the material of the second guide member 72 adjacent to the discharge roller unit 48 is similar to that of the material of the first guide member 62.
Thus, according to the guide structure 60, the temperature of the sheet member P transported toward the discharge roller unit 48 is lower than that in the case where the thermal conductivity of the material of the first guide member 62 is similar to that of the material of the second guide member 72. When the temperature of the sheet member P is reduced, the toner image formed on the sheet member P are solidified, so that contact marks (so-called “roller marks”) due to contact with the discharge roller unit 48 are not easily formed on the toner image on the sheet member P.
To summarize, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is less than that in the case where guide members that guide the sheet member P from the fixing unit 34 to the discharge roller unit 48 are made of materials having similar thermal conductivities over the entirety thereof.
In addition, the guide structure 60 is configured such that the first guide member 62 is made of a resin material and the second guide member 72 is made of a metal material. Therefore, the amount of heat generated by the fixing unit 34 and transferred to the second guide member 72 through the first guide member 62 is less than that in the case where the first guide member 62 and the second guide member 72 are both made of a metal material. Also, the amount of heat which the second guide member 72 receives from the sheet member P is greater than that in the case where the first guide member 62 and the second guide member 72 are both made of a resin material.
To summarize, the temperature of the sheet member P is lower than that in the case where the first guide member 62 and the second guide member 72 are both made of a metal material or that in the case where the first guide member 62 and the second guide member 72 are both made of a resin material. Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced.
In addition, the guide structure 60 is configured such that the heat dissipation plates 76 dissipate heat from the second guide member 72. Therefore, the temperature of the sheet member P that is in contact with the second guide member 72 is lower than that in the case where the heat of the second guide member 72 is accumulated in the second guide member 72 (in the case where the second guide member 72 includes only the plate portion). Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced.
In addition, the guide structure 60 is configured such that the plate surfaces of the heat dissipation plates 76 face in the transporting direction of the sheet member P and that the heat dissipation plates 76 extend in the width direction of the sheet member P that is transported (apparatus depth direction). Therefore, the amount by which the plate portion 74 of the second guide member 72 is bent when viewed in the transporting direction of the sheet member P is less than that in the case where the plate surfaces of the heat dissipation plates face in the width direction of the sheet member P.
In addition, the guide structure 60 is configured such that the first guide member 62 and the second guide member 72 are spaced from each other. Therefore, the amount of heat transferred to the second guide member 72 through the first guide member 62 is less than that in the case where the first guide member 62 and the second guide member 72 are in contact with each other. Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced.
In addition, the guide structure 60 is configured such that the first guide member 62 and the second guide member 72 are spaced from each other in a direction along the plate surface of the plate portion 64 of the first guide member 62 when viewed in the apparatus depth direction. Therefore, the amount of heat transferred to the second guide member 72 through the first guide member 62 is less than that in the case where the first guide member and the second guide member overlap in the thickness direction of the plate portion of the first guide member. Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced.
In addition, the guide structure 60 is configured such that the ribs 66 are formed on the front surface 64a of the plate portion 64 of the first guide member 62. Therefore, the contact area between the sheet member P and the first guide member 62 is less than that in the case where the first guide member includes only the plate portion. Thus, the amount of heat which the sheet member P receives from the first guide member 62 is reduced. Accordingly, an increase in the temperature of the sheet member P is suppressed, so that the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced.
In addition, the guide structure 60 is configured such that the ribs 66 extend in the transporting direction of the sheet member P. Therefore, unlike the case in which the ribs extend in the width direction of the sheet member P that is transported, the movement of the sheet member P is not hindered.
According to the image forming apparatus 10, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is less than that in the case where the materials of all of the guide members have similar thermal conductivities. Accordingly, reduction in quality of the output image is suppressed.
In addition, according to the image forming apparatus 10, the transport speed at which the discharge roller unit 48 transports the sheet member P is lower than the transport speed at which the fixing unit 34 transports the sheet member P. Accordingly, the sheet member P is transported while being bent toward the second guide member 72, so that the contact area between the sheet member P and the second guide member 72 is increased. As a result, the temperature of the sheet member P is reduced. Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced, and reduction in quality of the output image is suppressed.
In addition, according to the image forming apparatus 10, the portion of the transport path 28 between the fixing unit 34 and the discharge roller unit 48 is curved such that the side thereof facing the pressing roller 56 is convex when viewed in the apparatus depth direction. The second guide member 72 is disposed on the convex side.
Accordingly, the sheet member P that is transported more easily comes into contact with the second guide member 72 than in the case where the second guide member is disposed on the concave side.
An example of a guide structure and an image forming apparatus according to a second exemplary embodiment of the present disclosure will now be described with reference to
Referring to
The projections 166 are hemispherical, and plural projections 166 are provided in the transporting direction of the sheet member P and in the width direction of the sheet member P. In the present exemplary embodiment, the projections 166 are arranged in the transporting direction of the sheet member P and in the width direction of the sheet member P.
Referring to
As described above, the projections 166 are formed on the front surface 64a of the plate portion 64 of the first guide member 162. Therefore, the amount by which the first guide member is bent is less than that in the case where the contact area between the sheet member P and the first guide member is reduced by forming plural recesses in the front surface.
In addition, the guide structure 160 includes the fans 180 that blow air toward the non-contact surface 74b of the plate portion 74 of the second guide member 172. Therefore, unlike the case in which the surface area of the second guide member is increased to dissipate heat from the second guide member, heat is actively dissipated from the second guide member.
Although specific exemplary embodiments of the present disclosure are described in detail above, the present disclosure is not limited to the above-described exemplary embodiments. It is obvious to those skilled in the art that various other exemplary embodiments are possible within the scope of the present disclosure. For example, although not described in the above exemplary embodiments, the length of the second guide member 72, 172 may be longer than that of the first guide member 62, 162 when viewed in the width direction of the sheet member P that is transported. In this case, the contact area between the sheet member P and the second guide member 72, 172 is greater than that in the case where the length of the second guide member is shorter than that of the first guide member. Therefore, the temperature of the sheet member P is effectively reduced. Accordingly, the occurrence of contact marks on the toner image formed on the sheet member P due to contact with the discharge roller unit 48 is reduced. In this case, the above-described length is the length of a portion that directly faces the transport path 28. When one of the guide members overlaps the other, the length of the overlapping portion that does not directly face the transport path 28 is not included.
In addition, in the above-described exemplary embodiments, the discharge roller unit 48 is the roller unit disposed downstream of the fixing unit 34 in the transporting direction of the sheet member P. However, the roller unit may instead be any other roller unit that transports the sheet member P.
In the above-described exemplary embodiments, the second guide member 72, 172 comes into contact with the non-image surface of the sheet member P on which no toner image is formed. However, the second guide member may instead come into contact with the image surface of the sheet member P on which the toner image is formed. In this case, however, the effect of suppressing a reduction in quality of the toner image by bringing the second guide member 72, 172 into contact with the non-image surface of the sheet member P cannot be obtained.
In addition, in the above-described exemplary embodiments, the first guide member 62, 162 is made of a resin material and the second guide member 72, 172 is made of a metal material so that the thermal conductivity of the material of the first guide member 62, 162 differs from that of the material of the second guide member 72, 172. However, the first guide member and the second guide member may be made of different resin materials so that the thermal conductivities thereof differ from each other. In this case, however, the effect obtained when the second guide member 72, 172 is made of a metal material cannot be obtained.
Although not described in the above exemplary embodiments, heat may be dissipated from the second guide member by using both the heat dissipation plates and the fans.
In addition, although the guide structures according to the above-described exemplary embodiments of the present disclosure are, for example, each disposed downstream of a fixing device of an image forming apparatus that employs an electrophotographic system, the guide structures are not limited to this. For example, a conductive sheet, such as a metal sheet, may be used as a sheet member P, and the guide structures according to the above-described exemplary embodiments may each be disposed downstream of a fixing device in an electrostatic powder coating apparatus that forms a solid image on a surface of the conductive sheet by coating the surface.
More specifically, the developing device 40 according to the above-described exemplary embodiments may be used as a powder coating head for an electrostatic powder coating process. The conductive sheet is transported through a region close to the powder coating head. A bias voltage is applied between the powder coating head and the conductive sheet so that charged coating powder is applied to (recorded on) the sheet-shaped medium. After that, the sheet-shaped medium is heated by the fixing device so that the surface of the sheet member P is coated. The coating powder may be, for example, thermoplastic toner or thermosetting toner. The fixing device may include a roller that applies heat and pressure, or a non-contact heater that heats the sheet member P without coming into direct contact with the sheet member P.
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 |
|---|---|---|---|
| 2018-137962 | Jul 2018 | JP | national |
This application is a continuation-in-part application of and claims priority benefit of U.S. application Ser. No. 16/255,843, filed on Jan. 14, 2019, which claims priority under 35 USC 119 from Japanese Patent Application No. 2018-137962 filed Jul. 23, 2018. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16255843 | Jan 2019 | US |
| Child | 17037565 | US |
