Patent Application
20150084273
1. Field of the Invention
The present invention relates to a sheet conveying apparatus that conveys a sheet, and an image forming apparatus having the same.
2. Description of the Related Art
Conventionally, in a sheet conveying apparatus used in an electrophotographic system image forming apparatus, a detector that detects a position, a posture or the like of a sheet within a sheet conveying path is provided, and the conveyance control of the sheet is performed depending on the detected information. In the detector that brings a detection element such as a lever (moving portion) into contact with the sheet, there is a configuration that protrudes onto the sheet conveying path, but it is necessary to prevent the detection element from being damaged due to contact of the sheet or the user during jam recovery or the like.
Thus, a configuration for solving the above-described problems has been conventionally suggested. U.S. Patent Application Publication No. 2011/233856 A1 discloses a configuration that brings the components into contact with each other by utilizing a difference in position of a center of rotation of each of an exterior cover, a sheet guide and a detection element that rotate when accessing the conveying path, and retracts the detection element into the sheet guide. Furthermore, Japanese Patent Laid-Open No. 2010-64851 suggests a configuration in which the exterior cover has a center of rotation with respect to the substantially horizontal conveyance path, and the detection element is vertically lowered by its own weight and is retracted within the guide, by rotating the exterior cover up to the substantially vertical direction about the center of rotation of downstream in the conveying direction.
However, an opening angle of the exterior cover are limited, there is a problem that rotation required for retraction of the detection element cannot be achieved.
It is therefore desirable to solve the above-described problems and to prevent damage to the moving portion.
In order to achieve the above-described object, according to the invention, there is provided a sheet conveying apparatus having: a cover that is provided in an apparatus main body in an openable and closable manner to open a sheet conveying path through which a sheet is conveyed, by rotating in an open direction from a closed position; a guide member that is movably provided in the cover and forms the sheet conveying path; and a moving portion that is provided with a contact portion which comes into contact with the sheet conveyed within the sheet conveying path, and is movably provided in the guide member, wherein the guide member moves with respect to the cover by rotating the cover in the open direction from the closed position, and thereby the moving portion moves by its own weight in a direction in which the contact portion of the moving portion is retracted from the sheet conveying path.
According to the invention, it is possible to prevent damage to the moving portion in the jam recovery or the like, by retracting the contact portion of the moving portion into the guide member when opening the cover.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, exemplary embodiments of the invention will be illustratively described in detail referring to the drawings. However, dimensions, materials, and shapes of the components, and relative arrangements thereof described in the following embodiments are to be appropriately changed, depending on the configuration and various conditions of the apparatus to which the invention is applied. Therefore, unless otherwise specified, the scope of the invention is not intended to be limited to only the embodiments.
An overall configuration of an image forming apparatus having a sheet conveying apparatus will be described with reference to
First, in the image forming operation, at each of image forming portions PY, PM, PC, and PB, a toner image is formed on a photosensitive drum by an electrophotographic system. That is, a front side of the rotating photosensitive drum is uniformly charged by a primary charger, and an electrostatic latent image is formed by performing exposure of the photosensitive drum according to an image signal from a laser exposure device. A toner image is formed on the photosensitive drum by performing the toner development of the electrostatic latent image by a developing device to be converted to a visible image. By bias application of the toner image to a transfer roller, the toner image is transferred onto a rotating intermediate transfer belt 8. A full color image is formed by superimposing and transferring the transfer of the toner image onto the intermediate transfer belt 8 in the order of yellow (Y), magenta (M), cyan (C), and black (B).
After the sheet set in a sheet cassette 1 in synchronization with the image forming operation is fed by a feeding roller 2 one by one and is conveyed to a skew feeding correction portion 3 to correct the skew feeding, the sheet is further conveyed to a secondary transfer portion. At the secondary transfer portion, a secondary transfer roller 20 is disposed on an opposite side of a secondary transfer inner roller 7 of an intermediate transfer unit 9, and the toner image on the intermediate transfer belt 8 is secondary transferred onto the conveyed sheet by the bias application to the secondary transfer roller 20. Moreover, the sheet on which the toner image is transferred is conveyed to a fixing device 4 including a fixing roller and a pressure roller through a sheet conveying path formed by a guide member to be described later, and is heated and pressed while passing through a nip portion between both rollers, and the toner image is fixed thereon.
In the sheet conveying path between the secondary transfer roller 20 and the fixing device 4, a loop detection portion 30 that detects a loop amount as an amount of slackening of the sheet is provided. The loop detection portion 30 detects the time when the loop amount of the sheet reaches a predetermined amount or higher. A controller 50 performs a variable speed control of the fixing roller so that the loop amount of the sheet is maintained within a predetermined range, based on a signal from the loop detection portion 30. That is, the controller 50 controls the conveying speed of the sheet by the fixing device as a conveying portion so that the loop amount of the sheet is maintained within a predetermined range. For this reason, the conveying speed of the sheet in the fixing device 4 does not affect the conveying speed of the sheet at the nip portion between the secondary transfer roller 20 as a secondary transfer portion and the secondary transfer inner roller 7.
The sheet on which the toner image is fixed as described above is discharged to a discharge tray 6 by a discharge roller 5 in the case of one-side recording. In the case of duplex image forming, the conveying path of the sheet is switched by a switching member 10, the sheet is conveyed by a reversing roller 11, and immediately after a rear end of the sheet has passed a branch point, the sheet is switching-conveyed and guided to a duplex conveying path. Moreover, after the sheet is conveyed to the secondary transfer portion again by duplex rollers 12 and 13 or the skew feeding correction portion 3 to form the image on the back side, the sheet is finally discharged to the discharge tray 6 through the fixing device 4, thereby finishing the series of image forming operations.
A configuration of the periphery of the loop detection portion in the sheet conveying apparatus according to the first example is illustrated in
Between the secondary transfer portion and the fixing device 4, a secondary transfer guide 33 as a guide member is provided which forms a sheet conveying path through which the sheet is guided. The above-described loop detection portion 30 is provided in the secondary transfer guide 33. The loop detection portion 30 includes a loop sensor flag 31 as a detection element which is rotatably held on the secondary transfer guide 33, and a photo sensor 32 as a detector which is fixedly held on the secondary transfer guide 33. The loop sensor flag 31 forming the moving portion includes a sheet contact portion 31a that is provided to be able to come into contact with the sheet conveyed within the sheet conveying path and can come into contact with the sheet within the sheet conveying path, a detection portion 31b detected by the photo sensor 32, and a rotary shaft 31c serving as the center of rotation. The exterior cover 14 has a center of rotation 14a at the bottom of an apparatus main body 100, and is provided to be able to opened and closed with respect to the apparatus main body 100. The exterior cover 14 is held at a closed position illustrated in
Furthermore, the secondary transfer guide 33 is held to be rotatable (swingable) with respect to the exterior cover 14 so that the bottom thereof rotates in the same direction as the exterior cover 14 toward the inside of the apparatus main body 100 about the center of rotation 33a of the top (see
Furthermore, as described above, the controller 50 provided in the apparatus main body 100 controls the conveying speed of the sheet by the fixing device 4 to maintain the loop amount of the sheet between the secondary transfer roller 20 and the fixing device 4 in a constant range, based on the signal from the loop detection portion 30. Furthermore, here, the controller included in the image forming apparatus is illustrated as an example, but the invention is not limited thereto. For example, a controller included in the sheet conveying apparatus attached in a detachably attachable manner to the image forming apparatus as an option may be used, or a configuration that performs the control by the controller of the sheet conveying apparatus and the controller of the image forming apparatus may be used.
When the exterior cover 14 is held at the closed position, as illustrated in
The diameter of the pressure roller 4a of the fixing device 4 changes by being affected by the temperature of the heated state of the fixing roller (heating roller) 4b and the fixing state to the sheet. Therefore, when rotating at a constant speed, the sheet conveying speed is high when the temperature of the pressure roller 4a is high, and the sheet conveying speed is slow when the temperature is low.
Therefore, the variable control of the fixing roller is performed, based on the detection information of the loop detection portion from just before the leading end of the sheet enters the fixing nip as a nip portion between the pressure roller and the fixing roller until the trailing end of the sheet exits the fixing nip, and the loop amount of the sheet is maintained at a constant amount. The loop control of the sheet performed in this section will be described.
In the loop control of the sheet in the sheet conveying path between the secondary transfer roller 20 and the fixing device 4, the above-described controller 50 changes the rotational speed of the pressure roller 4a at the following three steps, based on the detection signal from the loop detection portion 30.
(1) Just before and just after the leading end of the sheet enters the fixing nip, the rotational speed of the pressure roller 4a rotates at −2% with respect to the speed of the secondary transfer portion.
(2) In the state in which sheet is nipped between both the fixing device and the secondary transfer portion, when the loop detection portion is turned ON, the rotational speed of the pressure roller 4a is switched to the rotation of −1%, the speed becomes higher than the secondary transfer portion, and the loop (slackening) of the sheet is eliminated. When the loop detection portion is turned OFF, the rotational speed of the pressure roller 4a is switched to rotation of −6%, the speed becomes lower than the secondary transfer portion, and the loop (slackening) of the sheet grows. By repeating the switching of the rotational speed, the loop amount of the sheet in the sheet conveying path between the secondary transfer roller 20 and the fixing device 4 is maintained within a constant range.
(3) When the trailing end of the sheet exits the secondary transfer portion, the pressure roller 4a rotates at a rotational speed of 2% to secure the interval between the trailing end and the succeeding sheet.
From a relation of an installation area or the like, at the open position, the exterior cover 14 is often held at an opening angle of about 30° to 50° with respect to the closed position. In this example, the exterior cover 14 is held at the position of 45° (open position) with respect to the closed position. The secondary transfer guide 33 that rotatably holds the loop detection portion 30 is held to be rotatable (swingable) with respect to the exterior cover 14. Moreover, when rotating the exterior cover 14 in the open direction, the bottom of the secondary transfer guide 33 rotates around the center of rotation 33a of the top toward the inside of the apparatus main body 100 in the same direction as the exterior cover 14. In addition, the secondary transfer guide 33 is biased toward the inside of the apparatus main body 100 by the guide biasing spring 34 as an elastic member fixed to the exterior cover 14. Therefore, as illustrated in
In the state illustrated in
The loop sensor flag 31 forming the loop detection portion of this example has a retraction auxiliary portion 31d, in addition to the sheet contact portion 31a, the detection portion 31b, and the rotary shaft 31c.
In addition, in the secondary transfer guide 33 of this example, a flag retraction member 35 as an auxiliary member to assist the rotation of the loop sensor flag 31 is provided to be rotatable by its own weight. The flag retraction member 35 is provided in the vicinity of the loop sensor flag 31. When the exterior cover 14 is located at the closed position, as illustrated in
When the exterior cover 14 is held at the closed position, as illustrated in
In addition, as described above, when the exterior cover 14 is held at the closed position, the flag retraction member 35 held on the secondary transfer guide 33 to be rotatable by its own weight stops at a position that does not interfere with rotation of the loop sensor flag 31.
Furthermore, since the loop control of the fixing device is the same as that described in the aforementioned examples, the description thereof will not be provided here.
Similarly to the above-described examples, at the open position, the exterior cover 14 is held at an opening angle of about 45° with respect to the closed position. The secondary transfer guide 33 that rotatably holds the loop detection portion 30 is held to be rotatable (swingable) with respect to the exterior cover 14. Moreover, when rotating the exterior cover 14 in the open direction, the bottom of the secondary transfer guide 33 rotates around the center of rotation 33a of the top toward the inside of the apparatus main body 100 in the same direction as the exterior cover 14. In addition, the secondary transfer guide 33 is biased toward the inside of the apparatus main body 100 by the guide biasing spring 34 as an elastic member fixed to the exterior cover 14. Therefore, when rotating the exterior cover 14 in the open direction from the closed position, the secondary transfer guide 33 is biased by the biasing force of the guide biasing spring 34 and rotates in the same direction as the exterior cover 14.
Furthermore, at this time, in the course in which the exterior cover 14 is shifted to the open position from the closed position, the flag retraction member 35 rotates by its own weight, and the abutment portion 35a abuts against the retraction auxiliary portion 31d of the loop sensor flag 31 to bias the loop sensor flag 31 in the direction of retracting the sheet contact portion 31a of the loop sensor flag 31 into the secondary transfer guide 33. Biasing force to the loop sensor flag 31 due to rotation of the flag retraction member 35 by its own weight is large enough for the biasing force by which the loop sensor flag 31 rotates to the sheet conveying path side.
For that reason, at the open position of the exterior cover 14, the center of gravity of the loop sensor flag 31 at the retracted position is located outside the apparatus main body 100 on the side opposite to the sheet conveying path side from the vertical line passing through the center of rotation (rotary shaft 31c). Thus, the loop sensor flag 31 stops at the retracted position of the inside of the secondary transfer guide 33 in the open state of the exterior cover 14.
In the state illustrated in
In the above-described examples, the configuration in which the loop sensor flag 31 is retracted to the inside of the secondary transfer guide 33 has been described as an example, but the invention is not limited thereto, and the invention is effective even in other sensor flags and actuators.
In the above-described examples, the configuration in which the exterior cover 14 is held at the open position at an opening angle of about 30° to 50° with respect to the closed position, more specifically, the exterior cover 14 is held at a position (open position) of 45° with respect to the closed position has been described as an example, but the invention is not limited thereto. The opening angle from the closed position to the open position of the exterior cover 14 may be 90° or less.
In the above-described examples, as the conveying portion that controls the loop amount of the sheet to be maintained in a constant range, the fixing device 4 located at downstream in the sheet conveying direction of the loop detection portion 30, but the invention is not limited thereto. As long as any conveying portion detects the loop amount of the sheet by the loop detection portion 30 and is controlled based on the detection signal, other conveying portions may be used, and the conveying portion may be applied to other sheet conveying apparatuses, without being limited to the sheet conveying apparatus leading to the fixing device from the secondary transfer portion.
In the above-described examples, the configuration in which the image forming apparatus has four image forming portions of different colors has been described as an example, but the number of use is not limited and may be appropriately determined as needed.
In the above-described examples, the printer has been described as the image forming apparatus, but the invention is not limited thereto. For example, other image forming apparatuses, such as a copying machine and a facsimile machine, or another image forming apparatus such as a complex machine in which these functions are combined may be used. Alternatively, an image forming apparatus which uses a recording material carrier, and transfers the toner images of respective colors on the recording material supported on the recording material carrier in a sequentially superimposed manner. It is possible to obtain the same effects by applying the invention to the sheet conveying apparatus of such an image forming apparatus.
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. 2013-199276, filed Sep. 26, 2013, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-199276 | Sep 2013 | JP | national |
