Patent Application
20240004345
The present invention relates to an image forming apparatus that forms an image on a sheet, such as a copier, a printer, a facsimile machine, or a multifunctional apparatus having functions of a plurality of these.
Conventionally, in an image forming apparatus, after a toner image is transferred onto a sheet and is fixed by melt-fixation in a fixing unit, the sheet is discharged to the outside, or the front surface and back surface thereof are reversed to perform image formation on the back surface. However, there is a possibility that, after the toner image is fixed in the fixing unit, the sheet touches a guide or a roller to be partially cooled, and an image defect such as unevenness in the glossiness occurs. Further, if a large number of sheets having undergone image formation are stacked at high temperature, there is a possibility that a phenomenon in which toner on one sheet sticks to another sheet occurs. To solve this, Japanese Patent Laid-Open No. 2010-266810 proposes an image forming apparatus in which occurrence of an image defect and sticking of sheets is suppressed by disposing a cooling roller pair immediately after the fixing unit to sufficiently cool the sheet and toner heated by the fixing unit.
However, in the configuration described in Japanese Patent Laid-Open No. 2010-266810, in the case where duplex printing is performed successively, since sheets at high temperature constantly pass the cooling roller pair disposed immediately after the fixing unit, there is a possibility that the temperature of the cooling roller pair gradually increases. Further, if the temperature of the cooling roller pair increases, there is a possibility that a sufficient cooling effect cannot be obtained. To solve this, for example, a measure by increasing the size of the cooling roller pair and improving the cooling performance can be considered, but in this case, there is a possibility that this causes increase in the size or cost of the image forming apparatus.
An object of the present invention is to provide an image forming apparatus capable of improving the cooling performance for a sheet after fixation.
According to a first aspect of the present invention, an image forming apparatus includes a fixing portion configured to heat a toner image transferred onto a sheet and fix the toner image to the sheet, a conveyance path in which a sheet conveyed from the fixing portion is conveyed, a roller pair disposed in the conveyance path and including a first roller and a second roller, the first roller and the second roller being configured to nip a sheet conveyed in the conveyance path to cool the sheet, and a duct provided to extend in a width direction orthogonal to a sheet conveyance direction and configured to allow air to pass therethrough. The duct includes a ventilation path forming portion and an opening portion continuous with the ventilation path forming portion and facing the conveyance path, the ventilation path forming portion being disposed to face a side of the roller pair opposite to a nip of the roller pair across a center line of the first roller and configured to form a ventilation path configured to allow air to pass therethrough between the first roller and the ventilation path forming portion.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A first embodiment of the present invention will be described in detail below with reference to
The image forming portion 2 includes image forming units PY, PM, PC, and PK corresponding to respective colors of yellow (Y), magenta (M), cyan (C), and black (Bk). The image forming units PY, PM, PC, and PK have similar configurations, and therefore the image forming unit PY for yellow will be described with a reference sign as a representative. The image forming unit PY includes a photosensitive drum 71 that is a photosensitive member serving as an image bearing member, a charging unit 72, an exposing unit 73 serving as an image drawing portion, and a developing unit 74. In addition, the image forming portion 2 includes an intermediate transfer belt 31, a secondary transfer inner roller 32, a driving roller 33, a tension roller 34, and a primary transfer unit 35.
In the image forming portion 2, the surface of the photosensitive drum 71 is uniformly charged by the charging unit 72 in advance, and the exposing unit 73 is driven on the basis of a signal of image information to form a latent image on the surface of the photosensitive drum 71 that is rotating. The electrostatic latent image formed on the surface of the photosensitive drum 71 is visualized as a toner image through development with toner by the developing unit 74. Then, a predetermined pressurizing force and electrostatic bias are applied by the primary transfer unit 35, and thus the toner image is transferred onto the intermediate transfer belt 31.
The intermediate transfer belt 31 is stretched over rollers such as the driving roller 33, the tension roller 34, and the secondary transfer inner roller 32, and is driven in a direction D1 illustrated in
A sheet S serving as a recording material or a transfer target material is supported and accommodated in or on a first sheet cassette 51, a second sheet cassette 52, a third sheet cassette 53, and a manual feed portion 54. The sheet S is fed by one of feeding portions 51a, 52a, 53a, and 54a, and is then guided by a supply path 5a of the sheet conveyance portion 5 to be conveyed to the image forming portion 2. The supply path 5a is formed by a conveyance roller pair 55, a pre-registration roller pair 56, a registration roller pair 57, and other unillustrated guide members. The sheet S fed by one of the feeding portions 51a, 52a, 53a, and 54a passes through the conveyance roller pair 55 and the pre-registration roller pair 56, and is conveyed to the registration roller pair 57.
The pre-registration roller pair 56 corrects the skew of the sheet S. Specifically, the leading end of the conveyed sheet S is caused to abut a nip portion of the registration roller pair 57 that is in a stationary state. In this manner, the pre-registration roller pair 56 causes the sheet S to form a loop to correct the skew. The registration roller pair 57 conveys the sheet S to the secondary transfer portion 3 at a timing matching the timing at which the toner image on the intermediate transfer belt 31 is transferred onto the sheet S.
The secondary transfer portion 3 includes a toner image transfer nip portion formed by the secondary transfer inner roller 32 and a secondary transfer outer roller 36 that oppose each other, and transfers the toner image onto the conveyed sheet S by applying a predetermined pressurizing force and electrostatic bias. The sheet S after transfer is conveyed to the fixing unit 4 by an air suction conveyance portion 37, and the toner image is melt-fixed to the sheet S by heating and pressurization. That is, the fixing unit 4 is an example of a fixing portion, and heats the toner image transferred onto the sheet S by the secondary transfer portion 3 to fix the toner image to the sheet S.
The controller 6 includes a central processing unit: CPU, and memories such as a read-only memory: ROM and a random access memory: RAM. The CPU obtains various data input by an operation portion, stores the data in a memory, and, for example, by activation operation such as switching the image forming apparatus 1 on by a user, can load a printing program from a memory and execute the printing program. The memory stores various programs and various data such as a printing program and an image formation job.
On the downstream side of the fixing unit 4 in a sheet conveyance direction, the sheet conveyance portion 5 includes a discharge path 5b, a reverse path 5c, a re-feeding path 5d, and a switching portion 60. The discharge path 5b is an example of a first conveyance path, is disposed downstream of the fixing unit 4 in the sheet conveyance direction, and is a path for discharging the sheet S conveyed from the fixing unit 4 to the outside of the apparatus. A conveyance roller pair 61 and a discharge roller pair 58 are provided in the discharge path 5b. The reverse path 5c is an example of a conveyance path and a second conveyance path, is provided to be branched from the discharge path 5b, and is a path for conveying the sheet S conveyed from the fixing unit 4 to a reverse roller pair 59 that reverses the conveyance direction. Here, in the reverse path 5c, not only the conveyance direction but also the front surface and back surface of the sheet S are reversed. A conveyance roller pair 62 and the reverse roller pair 59 are provided in the reverse path 5c. To be noted, the reverse path 5c is curved more than the discharge path 5b. The re-feeding path 5d is a path for conveying the sheet S whose conveyance direction and front and back surfaces are reversed by the reverse roller pair 59 to the secondary transfer portion 3 again, and is connected to the reverse path 5c. The switching portion 60 switches the path to which the sheet S conveyed from the fixing unit 4 between the discharge path 5b and the reverse path 5c. That is, the sheet S conveyed from the fixing unit 4 is selectively conveyed to the discharge path 5b and the reverse path 5c.
If a sheet passing mode of the sheet S is simplex face-up sheet passing, the conveyance path of the sheet S is switched to the discharge path 5b by the switching portion 60, and the sheet S on which a toner image has been melt-fixed by the fixing unit 4 is conveyed to the discharge path 5b. The sheet S is cooled by a first cooling roller pair 10 disposed in the discharge path 5b, and is then discharged to the outside of the apparatus by the discharge roller pair 58.
In the case where the sheet passing mode of the sheet S is duplex sheet passing, the conveyance path of the sheet S is switched to the reverse path 5c by the switching portion 60, and the sheet S to a first surface of which a toner image has been fixed by the fixing unit 4 is conveyed to the reverse path 5c. The sheet S is cooled by a second cooling roller pair 20 disposed in the reverse path 5c. The reverse roller pair 59 is rotated in a reverse direction after the sheet S cooled by the second cooling roller pair 20 is temporarily stopped in a state in which a part of the sheet S of a predetermined length from the trailing end thereof is at the reverse roller pair 59, thus the conveyance direction and front and back surfaces of the sheet S are reversed by the reverse roller pair 59, and the sheet S is conveyed to the re-feeding path 5d. That is, the reverse roller pair 59 is an example of a reverse portion that reverses and conveys the sheet conveyed in the first direction to a second direction opposite to the first direction.
The sheet S is conveyed to the secondary transfer portion 3 through the re-feeding path 5d, a toner image is transferred onto a second surface of the sheet S, and the toner image is fixed by the fixing unit 4. In addition, the conveyance path of the sheet S is switched to the discharge path 5b by the switching portion 60, and the sheet S to the second surface of which a toner image has been melt-fixed by the fixing unit 4 is conveyed to the discharge path 5b. The sheet S is cooled by the second cooling roller pair 70, and is then discharged to the outside of the apparatus by the discharge roller pair 58.
Next, the operation in the case of successively forming images on a plurality of sheets S will be described. In the case of simplex face-up sheet passing, the sheets S are subjected to image formation and discharged to the outside of the apparatus at a sheet passing interval T serving as a predetermined period. In contrast, in the case of duplex sheet passing, whereas the sheets S are subjected to image formation at the sheet passing interval T, since the image formation is alternately performed on the first surface side and the second surface side of the sheets S, the sheets S are discharged to the outside of the apparatus at an interval twice the sheet passing interval T.
Next, the first cooling roller pair 10 and the second cooling roller pair 20 will be described with reference to
Here, in the case where the sheet S has a part that the second cooling roller pair 20 touches and a part that the second cooling roller pair 20 does not touch, glossiness unevenness is likely to occur due to the difference therebetween. Therefore, a wide nipped roller having a nip width approximately equal to the full length thereof in a width direction W (see
Next, the configuration of the air blowing unit 40 will be described with reference to
The air blowing unit 40 includes an air blowing fan 41 and an air supply duct 42, and the air supply duct 42 has an air outlet port 43. The air blowing fan 41 sucks air in from the outside of the apparatus, and air discharged from the air blowing fan 41 is guided by the air supply duct 42 and is blown out from the air outlet port 43. That is, the air outlet port 43 is an example of an opening portion for blowing out air inside the air supply duct 42. In the present embodiment, the air outlet port 43 is divided into three in the width direction W to avoid interference with other members such as sensors, and the total width of the three parts of the air outlet port 43 is approximately equal to the full width in the width direction W of the sheet S. That is, the air supply duct 42 is provided to extend in the width direction W orthogonal to the sheet conveyance direction and allow air to pass therethrough, and thus supplies air outside the apparatus into the apparatus. However, the configuration is not limited to this, and the air outlet port 43 may have a shape that is not divided in the width direction W as long as the air outlet port 43 does not interfere with other members.
As illustrated in
Here, the layout of the air blowing unit 40 and the second cooling roller pair 20 will be described with reference of
Next, the flow of a cooling air in the vicinity of the second cooling roller pair 20 will be described with reference to
The cooling air blown out from the air outlet port 43 is diagonally blown in a direction approximately opposite to the conveyance direction of the sheet S. Then, the cooling air flows in a direction opposite to the conveyance direction of the sheet S. By hitting the sheet S by the cooling air in a direction opposite to the conveyance direction, the wind speed of the cooling air flowing on the surface of the sheet S is (wind speed of cooling air+conveyance speed of sheet S) as viewed from the surface of the sheet S, which is higher than a wind speed in the case of blowing the cooling air in the same direction as the conveyance direction. As a result of this, the sheet S can be more efficiently cooled than in the case of blowing the cooling air in the same direction as the conveyance direction, and the wind speed increases as the conveyance speed increases, which suppresses deterioration of the cooling performance caused by increase in the conveyance speed.
The cooling air having flowed on the surface of the sheet S then hits the second cooling roller pair 20. Since the second cooling roller pair 20 is a roller pair having a nip width approximately equal to the full length thereof in the width direction W, the wind is blocked by the sheet S and the second cooling roller pair 20 and does not pass through. Therefore, the cooling air blows to the outside of the conveyance guide G2 through a gap between the conveyance guide G2 and the second driving roller 21 as indicated by an arrow F1.
Then, the cooling air flows along the outer peripheral portion of the second driving roller 21, and blows out to a space between the second driving roller 21 and the air supply duct 42 along the outer shape of the air supply duct 42. As a result of this, the cooling air flows along the outer periphery of the second driving roller 21, thus the time in which the cooling air is in contact with the second driving roller 21 is long, and thus the second driving roller 21 can be efficiently cooled. Then, the cooling air passes through the conveyance guide G1 through opening portions Gla provided in the conveyance guide G1, and cools the sheet S again.
That is, the air outlet port 43 is disposed downstream of the second driving roller 21 in the sheet conveyance direction to blow out air toward the upstream side, and thus the sheet S conveyed by the second cooling roller pair 20 is cooled. In addition, a ventilation path 45 formed by the second driving roller 21 and the air supply duct 42 ventilates such that the air having been blown out from the air outlet port 43 and having cooled the sheet S reaches a position upstream of the second driving roller 21 while cooling the second driving roller 21.
Here, the air flowing in the air supply duct 42 reaches a temperature close to that of the outside air, and the cooling air flowing outside the air supply duct 42 and flowing in the vicinity of the second cooling roller pair 20 includes heat and moisture emitted from the sheet S, and is thus hotter and more humid than the outside air. At this time, the inner surface of the air supply duct 42 is likely to be hotter than the cooling air, and therefore the temperature of the cooling air having touched the surface of the duct is likely to increase. In addition, on the surface of the side wall 44 of the air supply duct 42, there is a possibility that the hot and humid air is cooled to cause condensation. To address this, in the present embodiment, the air supply duct 42 is formed of resin. Since resin has a heat insulating property, occurrence of such a problem can be avoided.
As described above, according to the image forming apparatus 1 of the present embodiment, the air supply duct 42 includes the air outlet port 43 facing the reverse path 5c, and the side wall 44 serving as a ventilation path forming portion. As a result of this, the cooling performance can be improved by combining cooling by contact with the second cooling roller pair 20 and cooling without contact by blowing air from the air supply duct 42. Further, in addition to this, by cooling the sheet S by blowing air from the air blowing unit 40 and efficiently cooling the second cooling roller pair 20 at the same time by using the side wall 44 serving as the outer shape of the air supply duct 42, the influence of deterioration of the cooling effect corresponding to the conveyance speed can be suppressed. Therefore, the cooling performance of the sheet S after fixation can be improved.
Here, in a method of cooling by blowing air using a fan and a duct, there is a problem that in the case where the conveyance speed of the sheet increases, the time for the sheet to pass through the space for cooling becomes shorter, and the cooling performance is likely to deteriorate. In contrast, according to the image forming apparatus 1 of the present embodiment, the one air blowing unit 40 cools the sheet itself, and also improves the cooling performance of the second cooling roller pair 20 to not cause an image defect caused by the sheet temperature.
In addition, according to the image forming apparatus 1 of the present embodiment, since the entirety of the air supply duct 42 is formed of resin, the heat insulating property of the duct can be secured. Therefore, a situation in which air of a low temperature in the air supply duct 42 is heated or condensation occurs on the surface of the air supply duct 42 can be suppressed.
In addition, according to the image forming apparatus 1 of the present embodiment, the air blowing unit 40 is provided so as to cool the second cooling roller pair 20 provided in the reverse path 5c. Therefore, in the reverse path 5c which is curved more than the discharge path 5b and in which the sheet S is more likely to come into contact with the guide to cause deterioration of the image quality, the deterioration of the image quality can be efficiently suppressed by cooling the second cooling roller pair 20.
Next, a second embodiment of the present invention will be described in detail with reference to
As described in the first embodiment, the air flowing in the air supply duct 42 has a temperature close to that of the outside air, and the cooling air flowing outside the air supply duct 42 and in the vicinity of the second cooling roller pair 20 includes heat and moisture emitted from the sheet S, and is thus hotter and more humid than the outside air. At this time, the inner surface of the air supply duct 42 is likely to have a temperature higher than that of the cooling air, and therefore the temperature of the cooling air having touched the surface of the duct is likely to increase. In addition, there is a possibility that, on the surface of the side wall 44 of the air supply duct 42, the hot and humid air is cooled to cause condensation.
In contrast, in the present embodiment, as illustrated in
To be noted, although the entirety of the air supply duct 42 is formed of resin in each of the embodiments described above, the configuration is not limited to this. For example, the air supply duct 42 may be constituted by a duct body and a side wall including a ventilation forming portion and formed of a material having a higher heat insulating property than the duct body. In this case, for example, the side wall may be formed of resin, and the duct body may be formed of metal.
In addition, although a case where the cooling air blown out from the air outlet port 43 is blown in a direction opposite to the conveyance direction of the sheet S has been described in each of the embodiments described above, the configuration is not limited to this, and for example, the cooling air may be blown in the same direction as the conveyance direction of the sheet S. In this case, the air outlet port 43 is disposed upstream of the second driving roller 21 in the sheet conveyance direction to blow out air toward the downstream side, and thus the sheet S conveyed by the second cooling roller pair 20 is cooled. In addition, the ventilation path 45 formed by the second driving roller 21 and the air supply duct 42 ventilates such that the air having been blown out from the air outlet port 43 and having cooled the sheet S reaches a position downstream of the second driving roller 21 while cooling the second driving roller 21.
In addition, although the air blowing unit 40 is provided so as to cool the second cooling roller pair 20 provided in the reverse path 5c, the configuration is not limited to this. For example, an air blowing unit may be provided so as to cool the first cooling roller pair 10 provided in the discharge path 5b.
In addition, although a case where a duct including a ventilation path forming portion is used as the air supply duct 42 has been described in each of the embodiments described above, the configuration is not limited to this. For example, an exhaustion duct including a ventilation path forming portion may be disposed to face the second driving roller 21 such that after the sheet is cooled by an air blown out from a different air supply duct, the second driving roller 21 is cooled between the exhaustion duct and the sheet and the air is exhausted to the outside through an exhaustion port that is an opening portion of the exhaustion duct.
According to the present invention, the cooling performance of the sheet after fixation can be improved.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2022-107600, filed Jul. 4, 2022 which is hereby incorporated by reference herein in its entirety
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-107600 | Jul 2022 | JP | national |
