Patent Application
20230418223
The present invention relates to an image forming apparatus that forms an image on a sheet.
JP 2007-062850 A proposes an image forming apparatus that transfers a toner image to a sheet and fixes the transferred toner image to the sheet by heating and pressurizing the toner image in a fixing unit. The image forming apparatus includes a conveyance roller pair disposed downstream of the fixing unit in the sheet conveyance direction, and an air blowing device that blows air to a pinch roller of the conveyance roller pair to cool the pinch roller. The air blowing device includes a fan and a duct that guides air sent from the fan to the pinch roller. The duct is provided with an upstream opening, air is also sent from the upstream opening to a conveyance path, and the sheet conveyed through the conveyance path is also cooled. By cooling the pinch roller and the sheet with air in this manner, gloss unevenness is suppressed from being formed on the sheet.
However, as described in JP 2007-062850 A, when air is also sent into the conveyance path, ultra fine particles (UFP) generated from the toner image on the fixing unit or the sheet are discharged to the outside of the apparatus via the conveyance path. It is known that the ultra fine particles are generated by applying heat to a toner wax, silicone rubber of a heating roller used in the fixing unit, or the like.
According to one feature of the present invention, an image forming apparatus includes an image forming unit configured to form a toner image on a sheet, a heating unit including a heating element, and a heating rotary member configured to incorporate the heating element and to be rotatable, a pressurizing rotary member configured to form, together with the heating unit, a fixing nip that fixes the toner image formed by the image forming unit to the sheet, a sheet discharge unit including a rotary member disposed downstream of the fixing nip in a sheet conveyance direction and configured to abut on the sheet, the sheet discharge unit discharging the sheet to an outside of the image forming apparatus, a stacking unit configured to stack the sheet discharged by the sheet discharge unit, a fan configured to blow air, and a duct configured to discharge the air sent by the fan toward the stacking unit. The rotary member is disposed such that at least a part of the rotary member enters an inside of the duct.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
A printer 100 serving as an image forming apparatus according to a first embodiment is a laser beam printer of an electrophotographic system that forms a monochrome toner image. As illustrated in
When an image forming command is output to the printer 100, an image forming process by the image forming unit 60 is started based on image information input from an external computer or the like connected to the printer 100. The image forming unit 60 includes a process cartridge 61, a laser scanner 8, and a transfer roller 6.
The process cartridge 61 includes a rotatable photosensitive drum 5, a charge roller 7, a developing roller 9, and an exposure member 10 disposed along the photosensitive drum 5, a supply roller 16, and a developer container 17. The developer container 17 serving as a storage unit stores a toner, and rotatably supports a stirring device 18 that stirs the toner in the developer container 17. The stirring device 18 is driven by a driving source (not illustrated) and rotates to supply the toner to the supply roller 16. Then, the supply roller 16 supplies the toner to the developing roller 9.
In addition, a replenishing port 19 for replenishing a toner from the outside is formed in the developer container 17. A user can expose the replenishing port 19 by opening a sheet discharge tray 15 or a lid (not illustrated) provided on the sheet discharge tray 15. Then, the user can refill the developer container 17 with the toner by inserting a toner container containing the toner into the replenishing port 19.
The transfer roller 6 forms a transfer nip Ti together with the photosensitive drum 5. In the present embodiment, the printer 100 is a monochrome laser beam printer, but is not limited thereto. For example, the printer 100 may be a full color laser beam printer.
The laser scanner 8 irradiates the photosensitive drum 5 with laser light based on input image information. At this time, the photosensitive drum 5 is charged in advance by the charge roller 7, and an electrostatic latent image is formed on the photosensitive drum 5 by being irradiated with laser light. Thereafter, the electrostatic latent image is developed by the developing roller 9, and a monochrome toner image is formed on the photosensitive drum 5.
In parallel with the above-described image forming process, a sheet is fed from the sheet feeding unit 50. The sheet feeding unit 50 includes a feeding tray 1 on which a sheet S is stacked, a pickup roller 3, and a separation roller pair 51. The feeding tray 1 is supported so as to be openable and closable with respect to a casing 100A of the printer 100, forms a part of the exterior of the front surface of the printer 100 in the closed state, and becomes in the open state so that the user can access a sheet storage space inside the casing 100A. Note that the feeding tray 1 may not be configured to rotate, but may be configured to slide to be stored in and pulled out of the casing 100A. The casing 100A detachably supports the process cartridge 61.
The pickup roller 3 rotates in response to an image forming command, and the sheets S supported by the feeding tray 1 are fed by the pickup roller 3. The sheets S fed by the pickup roller 3 are separated one by one by the separation roller pair 51. Instead of the pickup roller 3, the sheet S may be fed by a belt or the like.
The sheets S separated one by one are conveyed to a registration roller pair 4, and skew feeding is corrected by the registration roller pair 4. The toner image on the photosensitive drum 5 is transferred to the sheet S conveyed at a predetermined conveyance timing by the registration roller pair 4 at the transfer nip Ti by an electrostatic load bias applied to the transfer roller 6. Since a potential of the photosensitive drum 5 after transfer varies, the potential is set to a predetermined value by the exposure member 10, and charge for an image to be formed on the next sheet is prepared.
Predetermined heat and pressure are applied to the sheet S to which the toner image has been transferred in a fixing nip F formed by a heating unit 11 and a pressurizing roller 12 of the fixing unit 70, and the toner is fused and fixed. The sheet having passed through the fixing unit 70 is discharged to the sheet discharge tray 15 serving as a stacking unit by the sheet discharge unit 80.
The sheet discharge unit 80 includes a driving roller 13 driven by a driving motor (not illustrated) serving as a driving source, and two driven rollers 14a and 14b that are driven to rotate by the driving roller 13. Since the two driven rollers 14a and 14b form a nip with respect to the driving roller 13, the sheet discharge unit 80 has a function of correcting the sheet S curled in the fixing unit 70. In the present embodiment, the sheet discharge unit 80 includes the two driven rollers 14a and 14b, but is not limited thereto, and may include, for example, only one driven roller.
Next, a configuration of the fixing unit 70 will be described with reference to
The fixing film 20 is made of, for example, a thin cylindrical plastic film having high heat resistance and high thermal conductivity. The heater 21 is, for example, a heating element that generates heat by energization by a power source (not illustrated) by applying a conductor on a ceramic base material. The heater 21 is supported in a state of being fitted and fixed to a groove portion of the holder 22. The fixing film 20 is attached so as to cover the outer peripheries of the heater 21, the holder 22, and the stay 23, and can perform rotational motion. That is, the fixing film 20 serving as a heating rotary member is configured to incorporate the heater 21 and to be rotatable.
The heating unit 11 is configured to pressure contact the pressurizing roller 12 by receiving a force of a pressurizing spring (not illustrated). The pressurizing roller 12 serving as a pressurizing rotary member includes a core metal 12a and an elastic layer 12b formed in a roller shape on the outer periphery of the core metal 12a. Since the outer peripheral surface of the pressurizing roller 12 formed by the elastic layer 12b has elasticity, the fixing nip F having a predetermined width is formed by the heating unit 11 and the pressurizing roller 12 by allowing the heating unit 11 and the pressurizing roller 12 to contact each other at a predetermined pressure. Further, the pressurizing roller 12 is rotationally driven at a predetermined peripheral speed by driving force received from a driving train (not illustrated). Frictional force is generated between the fixing film 20 and the pressurizing roller 12 by rotation of the pressurizing roller 12, and the fixing film 20 is rotated following the pressurizing roller 12.
In a state where the pressurizing roller 12 and the fixing film 20 are rotated and the heater 21 is energized and heated, the sheet S carrying an unfixed toner image is introduced into the fixing nip F, and the same is nipped and conveyed. In the process in which the sheet S is conveyed by the fixing nip F, the heat of the heater 21 is applied to the sheet S via the fixing film and the unfixed toner image is heated and pressurized to be fused and fixed to the sheet S.
The sheet S conveyed in a sheet conveyance direction CD by the fixing nip F is guided to the sheet discharge unit 80 through a conveyance path CP by a guide member 24 and a pre-discharge roller 25. The pre-discharge roller 25 is rotatably supported by the guide member 24, and reduces frictional force between the guide member 24 and the sheet S by contacting the sheet S and rotating following the sheet S. For example, when the conveyance speed of the sheet S by the sheet discharge unit 80 is faster than the conveyance speed of the sheet S by the fixing unit the image surface of the sheet S on which the toner image is formed is strongly rubbed against the guide member 24. In this case, since an image defect such as a loss of the toner image on the image surface may occur, the sheet S is smoothly guided by the guide member 24.
Next, an air blowing configuration of the printer 100 will be described with reference to
The casing 100A supports the fan holder 91, and the fan holder 91 rotatably supports a fan shaft 92. The four impellers 26a, 26b, 26c, and 26d forming the fan 26 are disposed side by side in the width direction W, and are fixed to the fan shaft 92. The fan shaft 92 is driven by a driving motor for driving the driving roller 13. By adopting a common driving motor, it is possible to contribute to miniaturization. When the fan shaft 92 rotates, the impeller 26a, 26b, 26c, and 26d rotates, and the air taken in from the air intake port 27 is sent into the fan holder 91.
As illustrated in
Air sent from the air blow port 28 of the fan holder 91 to the air intake port 30 of the duct 29 passes through the duct 29, and is guided toward an exhaust port 31 of the duct 29. Then, the air is discharged toward the sheet discharge tray 15 through the exhaust port 31. In the present embodiment, four driving rollers 13 and four driven rollers 14a and 14b are provided, and these rollers are disposed side by side in the width direction W orthogonal to the sheet conveyance direction CD (refer to
As illustrated in
As illustrated in
As described above, the air sent by the fan 26 is slightly diffused in the width direction W by the fan holder 91. Then, the air sent from the air blow port 28 of the fan holder 91 enters the air intake port 30 of the duct 29 and is further diffused in the width direction W toward the driven rollers 14a and 14b. The driven rollers 14a and 14b disposed so as to enter the inside of the duct 29 are cooled by air passing through the duct 29. The toner image formed on the sheet by the image forming unit 60 and heated by the heating unit 11 of the fixing unit 70 abuts on the upper surfaces of the driven rollers 14a and 14b. Since the driven rollers 14a and 14b are sufficiently cooled by the air sent from the fan 26, it is possible to reduce formation of image defects such as gloss unevenness in the toner image.
Further, the air is sent to the exhaust port 31 of the duct 29 and discharged from the exhaust port 31 toward the sheet discharge tray 15. Since there is almost no gap between the opening portion 29a of the duct 29 that the driven rollers 14a and 14b enter and the driven rollers 14a and 14b, the air passing through the duct 29 is hardly discharged from the opening portion 29a to the conveyance path CP.
Incidentally, it is known that extremely fine particles are generated by heating the toner wax or the fixing unit 70. The ultra fine particles (UFP) refer to particles having a diameter of 100 nm or less among suspended particulate matter (SPM). It has been found out that the ultra fine particles are mainly generated from silicone rubber used as an elastic layer of a pressurizing roller or the like. That is, when the silicone rubber is heated, a low molecular weight siloxane is generated, and this low molecular weight siloxane is emanated as ultra fine particles.
When the air sent by the fan 26 passes through the fixing nip F, the generated extremely fine particles are discharged to the outside of the printer 100 through the conveyance path CP. However, in the present embodiment, there is almost no gap between the driven rollers 14a and 14b and the opening portion 29a, and the duct 29 is provided with the exhaust port 31 communicating with the outside of the printer 100. Therefore, most of the air sent from the fan 26 is discharged from the exhaust port 31 to the outside of the printer 100 through the duct 29 without passing through the fixing nip F, thereby making it possible to reduce the amount of the extremely fine particles generated from the toner wax and the fixing unit 70 diffused to the outside of the printer 100.
Most of the air sent from the fan 26 is discharged from the exhaust port 31 toward the sheet discharge tray 15. Although four exhaust ports 31 of the present embodiment are provided in the duct 29 corresponding to the four driving rollers 13 and the four driven rollers 14a and 14b, respectively, the technology is not limited thereto. For example, the exhaust port 31 may be formed from one opening portion widened in the width direction W, or may be provided by being divided into two or three or four or more.
As illustrated in
As described above, the area AR1 in which the fan 26 is disposed is narrower than the area AR2 in which the driven rollers 14a and 14b are disposed. This is because the replenishing port 19 of the developer container 17 is disposed upstream of the fan 26 and the duct 29 in a removal direction DD of the process cartridge 61 (refer to
More specifically, the replenishing port 19 is disposed so as not to overlap the first area AR1 and at least a part thereof is disposed so as to overlap the second area AR2 in the width direction W. By configuring the replenishing port 19, the fan 26, and the duct 29 in this manner, the process cartridge 61 can be smoothly attached and detached, and the printer 100 can be formed to be compact.
On the other hand, the air sent from the fan 26 is diffused in the width direction W by the fan holder 91 and the duct 29, and is guided to an entire area of the driven rollers 14a and 14b. That is, the air is diffused in the width direction W by the fan holder 91 and the duct 29 and guided to an entirety of the second area AR2. Thus, the driven rollers 14a and 14b can be sufficiently cooled. As described above, it is possible to improve maintainability of the process cartridge 61, downsize the printer 100, reduce the amount of extremely fine particles diffused from the printer 100, and reduce image defects such as gloss unevenness.
Next, a second embodiment of the present invention will be described. The second embodiment is a modification of the air blowing configuration of the first embodiment. Therefore, configurations similar to those of the first embodiment will be described by omitting illustration or attaching the same reference numerals to the drawings.
As illustrated in
The fan holder 104 is provided with an air intake port 34 through which the fan 33 takes in air and an air blow port 35 through which air sent by the fan 33 is discharged. A duct 129 is provided adjacent to the air blow port 35 of the fan holder 104. As illustrated in
The second duct 37 is disposed directly below driven rollers 14a and 14b, and has an air intake port 39 facing an exhaust port 38 of the first duct 36. The air blow port 35 of the fan holder 104 and the first duct 36 may be directly connected to each other, or may be connected to each other by a connecting member made of rubber or the like. The air blow port 28 and the air intake port 30 may be separated from each other with a slight gap therebetween. Similarly, the exhaust port 38 of the first duct 36 and the air intake port 39 of the second duct 37 may be directly connected to each other, or may be connected by a connecting member made of rubber or the like. In addition, the exhaust port 38 and the air intake port 39 may be separated from each other with a slight gap therebetween.
The air sent from the air blow port 35 of the fan holder 104 to the first duct 36 advances in the width direction W by the first duct 36. The air in the first duct 36 is sent from the exhaust port 38 to the air intake port 39 of the second duct 37. The air sent to the second duct 37 through the air intake port 39 passes through the second duct 37, and is guided toward an exhaust port 40 formed in the second duct 37. Then, as illustrated in
As illustrated in
As illustrated in
The air entering the second duct 37 from the air intake port 39 is diffused in the width direction W toward the driven rollers 14a and 14b. The driven rollers 14a and 14b disposed to enter the second duct 37 are cooled by the air passing through the second duct 37. The toner image formed on the sheet by an image forming unit 60 and heated by a heating unit 11 of a fixing unit 70 abuts on the upper surfaces of the driven rollers 14a and 14b. Since the driven rollers 14a and 14b are sufficiently cooled by the air sent from the fan 33, it is possible to reduce formation of image defects such as gloss unevenness in the toner image.
Further, the air is sent to the exhaust port 40 of the second duct 37 and discharged from the exhaust port 40 toward the sheet discharge tray 15. Since there is almost no gap between the opening portion 29a of the second duct 37 that the driven rollers 14a and 14b enter and the driven rollers 14a and 14b, the air passing through the second duct 37 is hardly discharged from the opening portion 29a to the conveyance path CP (refer to
When the air sent by the fan 33 passes through a fixing nip F, the generated extremely fine particles are discharged to the outside of the printer 100 through the conveyance path CP. However, in the present embodiment, there is almost no gap between the driven rollers 14a and 14b and the opening portion 29a, and the second duct 37 is provided with the exhaust port 40 communicating with the outside of the printer 100. Therefore, most of the air sent from the fan 33 is discharged from the second duct 37 to the outside of the printer 100 through the duct 129 without passing through the fixing nip F, thereby making it possible to reduce the amount of the extremely fine particles generated from the toner wax and the fixing unit 70 diffused to the outside of the printer 100.
Most of the air sent from the fan 33 is discharged from the exhaust port 40 toward the sheet discharge tray 15. Although four exhaust ports 40 of the present embodiment are provided in the second duct 37 corresponding to four driving rollers 13 and four driven rollers 14a and 14b, respectively, the technology is not limited thereto. For example, the exhaust port 40 may be formed from one opening portion widened in the width direction W, or may be provided by being divided into two or three or four or more.
As illustrated in
As described above, the fan 33 is disposed outside the area AR2 in which the driven rollers 14a and 14b are disposed. The area AR3 in which the exhaust port 38 of the first duct 36 is disposed is narrower than the area AR2 in which the driven rollers 14a and 14b are disposed. This is because the replenishing port 19 of the developer container 17 is disposed upstream of the duct 129 in the removal direction DD of the process cartridge 61 (refer to
More specifically, the replenishing port 19 is disposed so as not to overlap the third area AR3 and at least a part thereof is disposed so as to overlap the second area AR2 in the width direction W. In addition, the fan 33 is smaller than the fan 26 of the first embodiment in the width direction W, and has, for example, one impeller. By configuring the replenishing port 19, the fan 33, and the duct 129 in this manner, the process cartridge 61 can be smoothly attached and detached, and the printer 100 can be formed to be compact.
On the other hand, the air sent from the fan 33 is diffused in the width direction W by the fan holder 104 and the duct 129, and is guided to an entire area of the driven rollers 14a and 14b. That is, the air is diffused in the width direction W by the fan holder 104 and the duct 129 and guided to an entirety of the second area AR2. Thus, the driven rollers 14a and 14b can be sufficiently cooled. As described above, it is possible to improve maintainability of the process cartridge 61, downsize the printer 100, reduce the amount of extremely fine particles diffused from the printer 100, and reduce image defects such as gloss unevenness.
In any of the embodiments described above, the heater 21 is in direct contact with the fixing film 20, but the technology is not limited thereto. For example, the heater 21 may be in contact with the fixing film 20 via a sheet material having high thermal conductivity such as iron alloy or aluminum.
In any of the embodiments described above, the heating unit 11 is configured to be brought into pressure contact with the pressurizing roller 12 by a pressurizing spring (not illustrated), but the technology is not limited thereto. For example, the heating unit 11 may be fixed to the casing, and the pressurizing roller 12 may be movably supported with respect to the casing and may be brought into pressure contact with the heating unit 11 by the pressurizing spring.
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. 2022-100482, filed Jun. 22, 2022, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-100482 | Jun 2022 | JP | national |
