Patent Grant
11971680
The present invention relates to an image forming apparatus that forms an image on a sheet.
Conventionally, as an image forming apparatus that forms an image on a sheet, a configuration is known in which an image formed on a photoreceptor is transferred to a sheet by a transfer portion, the transferred image is fixed to the sheet by a fixing portion, and the sheet on which the image is fixed is discharged to a discharge tray in an upper portion of the apparatus.
In recent years, it has been required by users that an image forming apparatus copes with various types of sheets such as plain paper, cardboard, and an envelope. In order to cope with such various types of sheets, a configuration is known in which an exterior cover on an apparatus side surface (or an apparatus back surface) is opened, and a sheet on which an image is fixed by a fixing portion is discharged in a horizontal direction from the apparatus side surface.
In addition, a configuration for adjusting a nip pressure between a heating roller and a pressure roller pressed by the heating roller in a fixing portion is disclosed for the purpose of coping with a sheet such as cardboard having a basis weight larger than that of plain paper or an envelope having a size smaller than that of plain paper.
Japanese Patent Application Laid-Open No. 2018-106028 discloses a configuration in which a pressure adjusting lever is operated to switch a nip pressure of a fixing portion between a normal first pressing force (for passing of plain paper) and a second pressing force smaller than the first pressing force for passing cardboard or an envelope. Then, the pressure adjusting lever is operated such that the nip pressure becomes the second pressing force when, for example, an envelope is used, and the posture is held at the position after the operation.
That is, in the above-described conventional technique, when printing is performed on an envelope, printing is performed on the envelope by opening the exterior cover and operating the pressure adjustment lever to switch the nip pressure of the fixing portion to the second pressing force.
However, in the conventional technique, the exterior cover may be closed without switching the nip pressure of the fixing portion to the normal first pressing force after the printing of the envelope is finished. In this case, there is a problem in which an image defect occurs due to an insufficient nip pressure of the fixing portion when printing is performed on plain paper.
An image forming apparatus comprising:
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, embodiments of the present invention will be exemplarily described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention is not intended to be limited only to them.
An image forming apparatus according to the present embodiment will be described with reference to
First, a schematic configuration of the image forming apparatus will be described with reference to
An image forming apparatus 1 includes a fixing portion (fixing unit) 4 that fixes an image on a sheet S. The image forming apparatus 1 is provided with a feeding portion 2 including the sheet S in a lower portion of the apparatus. The sheet S fed from the feeding portion 2 is conveyed to an image forming portion 3, and an image is formed on the sheet S in the image forming portion 3. Thereafter, the sheet S on which the image is formed is conveyed to the fixing portion 4, and the image is fixed to the sheet S by heat and pressure in the fixing portion 4. The sheet S on which the image is fixed is conveyed to a discharge portion 6 and is discharged, by the discharge portion 6, to a discharge tray 5 arranged in an upper portion of the apparatus.
The image forming apparatus 1 is provided with a rear door 7 which is an opening/closing member. The rear door (exterior cover) 7 is provided to be rotatable (openable and closable) around a shaft 7b in a housing of the image forming apparatus 1. The housing here accommodates the fixing portion 4 and is a part of the image forming apparatus 1. The housing accommodating the fixing portion 4 and the rear door 7 are combined to form a main body of the image forming apparatus 1. The rear door 7 can be displaced between a close position (a position illustrated in
Next, the fixing portion 4 in the image forming apparatus 1 will be described with reference to
As illustrated in
Moreover, the fixing portion 4 includes an upper frame 8, a support arm 9, a switching lever (operation lever) 10, a pressing plate 11, and a spring 12. The fixing portion 4 in the image forming apparatus according to the present embodiment will be described with reference to
The upper frame 8 is a first support member that supports the heating roller 13 and the support arm 9. The upper frame 8 is supported by the image forming apparatus 1. Here, a configuration in which the heating roller 13 is supported by the upper frame 8 of the fixing portion 4 is exemplified, but the present invention is not limited thereto, and the heating roller 13 may be supported by the image forming apparatus 1.
The support arm 9 includes a bearing 15 provided at a central portion, a shaft support portion 9a provided at one end, the pressing plate 11 provided at the other end, and a locking portion 9b provided between the bearing 15 and the pressing plate 11. The bearing 15 supports a shaft at each end in a longitudinal direction of the pressure roller 14. Accordingly, the pressure roller 14 is rotatably supported with respect to the support arm 9. In addition, the support arm 9 is swingably supported by the upper frame 8 around the shaft support portion 9a.
The pressing plate 11 is attached to the other end of the support arm 9. The pressing plate 11 is a portion (receiving portion) that engages with the switching lever 10 as described later.
The spring 12 is a biasing member that presses the heating roller 13 and the pressure roller 14 and is provided between the upper frame 8 and the support arm 9. Here, a configuration in which the spring 12 applies a force to the pressure roller 14 toward the heating roller 13 is exemplified as a configuration in which the spring 12 applies a force to one of the pressure roller 14 and the heating roller 13 toward the other.
The spring 12 is, for example, a tension coil spring. One end of the spring 12 is locked to a locking portion 8a provided in the upper frame 8, and the other end is locked to a locking portion 9b provided in the support arm 9 to generate a tensile force between the heating roller 13 and the pressure roller 14. Accordingly, the spring 12 applies a force to (presses) the pressure roller 14 supported by the support arm 9 with respect to the heating roller 13 supported by the upper frame 8.
The switching lever 10 is a switching member for adjusting a pressing force (nip pressure and nip width) between the heating roller 13 and the pressure roller 14. The switching lever 10 includes a shaft support portion 10a, an operation portion 10b, a first cam portion 10c, and a second cam portion 10d. The switching lever 10 is rotatably supported by the upper frame 8 around the shaft support portion 10a. The operation portion 10b is a portion operated by a user. For example, the switching lever 10 is manually operated so as to be located at a first position when plain paper is discharged to the inner side the rear door 7 that is open. In addition, the switching lever 10 is manually operated so as to be located at a second position when an envelope is discharged to the inner side of the rear door 7 that is open.
The first cam portion 10c abuts on the pressing plate 11 which is a receiving portion attached to the other end of the support arm 9. In a state where the first cam portion 10c abuts on the pressing plate 11 as illustrated in
The second cam portion 10d abuts on the pressing plate 11 which is a receiving surface attached to the other end of the support arm 9 in the switching lever 10. In a state where the second cam portion 10d abuts on the pressing plate 11 as illustrated in
Therefore, the switching lever 10 can switch the pressing force between the heating roller 13 and the pressure roller 14 by operating the operation portion 10b so that the switching lever 10 rotates around the shaft support portion 10a and causing the first cam portion 10c or the second cam portion 10d to abut on the pressing plate 11 of the support arm 9.
Moreover, as illustrated in
Specifically, the door cam portion 7a has a contact portion 7d that comes into contact with the operation portion 10b of the switching lever 10 holding the support arm 9 at the second pressing position. The contact portion 7d has an inclination (inclined surface) that generates a force for moving the support arm 9 toward the first pressing position with respect to the switching lever 10 by the movement of the rear door 7 from the open position to the close position. Here, the inclination of the contact portion 7d is not limited to a linear inclination (inclined surface) and may be, for example, an arc-shaped curved surface (curved surface).
Moreover, the inclination of the contact portion 7d is an inclination in which the distance from the center of the shaft 7b, which is the rotation center of the rear door 7, to a contact point K with the operation portion 10b of the switching lever 10 gradually increases according to the movement of the switching lever 10 from the open position to the close position.
Here, an operation for adjusting a nip width (nip pressure and pressing force) of the fixing portion 4 will be described.
By operating the switching lever 10 to cause the first cam portion 10c to abut on the pressing plate 11, the position of the support arm 9 is determined, and the support arm 9 is held at the first pressing position illustrated in
When a sheet to be printed is cardboard having a basis weight larger than that of plain paper or an envelope having a size in the width direction smaller than that of plain paper, the nip width between the heating roller 13 and the pressure roller 14 needs to be smaller than the nip width at the initial position. In other words, the pressing force of the pressure roller 14 to the heating roller 13 needs to be set to the second pressing force smaller than the first pressing force.
In order to reduce the above-described nip width, the rear door 7 is first opened in the direction of an arrow A as illustrated in
By changing the surface that abuts on the pressing plate 11 of the support arm 9 to the second cam portion 10d in this manner, the position of the support arm 9 is switched from the initial position (first pressing position) illustrated in
In this manner, the nip width (nip pressure and pressing force) of the fixing portion 4 is adjusted according to the type of sheet to be printed.
In the image forming apparatus, as illustrated in
Here, the inclination of the contact portion 7d of the door cam portion 7a is an inclination in which the distance from the center of the shaft 7b, which is the rotation center of the rear door 7, to the contact point K with the operation portion 10b of the switching lever 10 gradually increases according to the movement of the switching lever 10 from the open position to the close position. Accordingly, by the operation of closing the rear door 7 in the direction of an arrow C illustrated in
As illustrated in
However, when the rotational moment Fsinθ applied to the contact point G becomes larger than the frictional force H between the switching lever 10 and the pressing plate 11, the switching lever 10 automatically rotates in the direction of the arrow E by the biasing force of the spring 12. Then, the switching lever 10 is separated from the door cam portion 7a and stops at the first pressing position (position illustrated in
Therefore, according to the above-described configuration, even if it is forgotten to return the nip pressure of the fixing portion 4 to the first pressing force after the printing of cardboard or an envelope is finished, the switching lever 10 can be switched from the position illustrated in
In general, a spring is disposed at an end of the pressure roller 14 to press the pressure roller 14 toward the heating roller 13. That is, the spring presses each end of the pressure roller 14 toward the heating roller 13. In such a configuration, a force of pressing the heating roller 13 by the pressure roller 14 is stronger at the ends than at the central portion. Therefore, the diameter of the pressure roller 14 is larger at the central portion than at the ends in a rotational axis direction of the pressure roller 14.
If the rear door 7 can be closed without returning the nip pressure of the fixing portion 4 to the first pressing force, a sheet other than an envelope may be printed with the nip pressure of the fixing portion 4 being the second pressing force. As a result, the sheet cannot be sufficiently pressed by the pressure roller 14 and the heating roller 13, and a fixing failure may occur. In particular, since the pressing force of the pressure roller 14 against the heating roller 13 is weak at the ends of the pressure roller 14, it is considered that a fixing failure at ends of the sheet becomes remarkable.
As illustrated in
The rear door 7 is a resin molded cover and is an exterior cover that forms an exterior of the image forming apparatus 1. When the rib-shaped door cam portion 7a is formed on the rear door 7, the thickness of each of the ribs is determined. Normally, in order to prevent a molding defect such as a sink mark from occurring in the appearance of the rear door 7, the thickness of the rib forming the door cam portion 7a needs to be set to 50% to 70% of the thickness of the rear door 7. Here, assuming that the thickness of the rear door 7 is 2 mm, the thickness of the rib forming the door cam portion 7a is 1 mm to 1.4 mm. The rib forming the door cam portion 7a needs to have strength not overcome by the force D for moving the switching lever 10 acting on the contact point K between the door cam portion 7a and the switching lever 10. Therefore, the door cam portion 7a provided on the rear door 7 is formed of the two ribs 7a1 and 7a2 thinner than the thickness of the rear door 7.
Here, two ribs are used as the plurality of plate-shaped ribs forming the door cam portion 7a, but the present invention is not limited thereto. In a case where the strength is insufficient, three or more plate-shaped ribs may be used accordingly.
In the configuration described above, when the rear door 7 is closed in a state where the switching lever 10 pushes down the support arm 9, the door cam portion 7a as an abutting portion pushes up the switching lever 10. That is, when the rear door 7 is closed, the support arm 9 is automatically pushed up. In a second embodiment described below, when the rear door 7 is closed while the switching lever 10 pushes down the support arm 9, an abutting portion 7e as an abutting portion abuts on the switching lever 10, and the further rotation of the rear door 7 is stopped.
When the switching lever 10 is located at the second position, the abutting portion 7e abuts on the switching lever 10 during the movement of the rear door 7 from the open position to the close position so as not to allow the rear door 7 to be closed. In addition, when the switching lever 10 is located at the first position, the abutting portion 7e does not abut on the switching lever 10 during the movement of the rear door 7 from the open position to the close position so as to allow the rear door 7 to be closed.
As illustrated in
On the other hand, when the switching lever 10 is pushed up, the switching lever 10 is located outside the movement path of the abutting portion 7e that moves with the rotation of the rear door 7. That is, even when the rear door 7 is closed in the direction of the arrow C in
As a result, even if the user forgets to push up the switching lever 10 and closes the rear door 7, the abutting portion 7e abuts on the switching lever 10. Since the user cannot further close the rear door 7, the user can notice that the user has forgotten to push up the switching lever 10.
Note that, in the above-described embodiments, a printer has been exemplified as the image forming apparatus, but the present invention is not limited thereto. For example, another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a complex machine combining these functions may be used. Alternatively, the image forming apparatus may be an image forming apparatus that uses a sheet carrier and sequentially superimposes and transfers toner images of respective colors on a sheet carried on the sheet carrier. Alternatively, the image forming apparatus may be an image forming apparatus that uses an intermediate transfer member, sequentially superimposes and transfers toner images of respective colors on the intermediate transfer member, and collectively transfers the toner images carried on the intermediate transfer member on a sheet. Similar effects can be obtained by applying the present invention to these image forming apparatuses.
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. 2020-206770, filed Dec. 14, 2020, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-206770 | Dec 2020 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7477860 | Hanano | Jan 2009 | B2 |
| 9927750 | Kosaka | Mar 2018 | B2 |
| 10353329 | Ogasawara | Jul 2019 | B2 |
| 10459382 | Iizuka | Oct 2019 | B2 |
| 11520257 | Koyama | Dec 2022 | B2 |
| 20170010574 | Kinoshita | Jan 2017 | A1 |
| 20190049891 | Iikura | Feb 2019 | A1 |
| Number | Date | Country |
|---|---|---|
| 2018-106028 | Jul 2018 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20220187747 A1 | Jun 2022 | US |
