Patent Grant
10093497
Field of the Invention
The present invention relates to a feeding device and an image forming apparatus.
Description of the Related Art
There have hitherto been image forming apparatuses, such as a copying machine, a printer, and a facsimile, including a sheet feeding device that supplies sheets to an image forming section. The sheet feeding device includes a sheet container unit that contains sheets to be fed. An example of such a sheet container unit is a feeding cassette detachably mounted in an image forming apparatus.
As the market needs, there has recently been a strong demand to shorten the first print output time (FPOT) of the image forming apparatus. Further, from the viewpoint of usability, it is particularly effective to shorten the FPOT of the image forming apparatus. To shorten the FPOT under such circumstances, one problem is how to shorten the time required to convey a sheet to the image forming section after a print command is received from a personal computer or the like. For this reason, the image forming apparatus is preferably on standby with the pickup roller and the sheet being in contact with each other at the time when the print command is received.
On the other hand, in the market, there is a demand for an image forming apparatus that can use various types of sheets including thin paper having a basis weight of about 50 g/m2 and glossy paper for obtaining a high-quality print.
Among various types of sheets, there is a sheet that locally deforms or a sheet that changes in surface property in a portion in contact with the pickup roller when the standby state in which the pickup roller and the sheet are in contact continues for a long time (for example, one day or more). As a result, these may cause image defects.
The present invention provides a feeding device and an image forming apparatus that can shorten the FPOT, use various types of sheets, and obtain good images.
A feeding device according to an aspect of the present invention feeds a sheet and includes a stack member on which the sheet is stacked, a driving unit configured to generate a driving force of forward rotation and a driving force of reverse rotation, a feeding member configured to feed the sheet stacked on the stack member by rotating in contact with the sheet and provided rotatably by the driving force of forward rotation from the driving unit, and a moving unit configured to move the feeding member located at a contact position in contact with the sheet stacked on the stack member to a retracted position retracted upward from the contact position by the driving force of reverse rotation from the driving unit and to move the feeding member located at the retracted position to the contact position by the driving force of forward rotation from the driving unit. The moving unit includes a one-way clutch configured to move the feeding member from the contact position to the retracted position by the driving force of reverse rotation from the driving unit.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, and relative arrangements of the constituent components adopted in the following embodiments should be appropriately changed according to the configuration and various conditions of the apparatus to which the present invention is applied. Therefore, the present invention should not be limited to the following embodiments, unless otherwise specified.
An image forming apparatus according to a first embodiment will be described with reference to
First, the overall configuration of the image forming apparatus will be described with reference to
The electrophotographic photosensitive drums (hereinafter referred to as “photosensitive drums”) 1 are rotated by a driving member (not illustrated) in the clockwise direction (direction of arrow Q) in
The intermediate transfer belt 5 is stretched by a driving roller 10, a tension roller 11, and an opposing roller 33 for secondary transfer. On an inner side of the intermediate transfer belt 5, primary transfer rollers 12 (12a to 12d) are provided to be opposed to the photosensitive drums 1 (1a to 1d), respectively. To the primary transfer rollers 12, transfer bias is applied by a bias application unit (not illustrated).
Toner images of four colors formed on the photosensitive drums 1 are sequentially primary-transferred onto the intermediate transfer belt 5 as the photosensitive drums 1 rotate in the direction of arrow Q, the intermediate transfer belt 5 rotates in a direction of arrow R, and a bias of positive polarity is applied to the primary transfer rollers 12. The toner images of four colors primary-transferred on the intermediate transfer belt 5 are conveyed to a secondary transfer portion 15 while being superimposed on the intermediate transfer belt 5.
On the other hand, toner remaining on the surfaces of the photosensitive drums 1 is removed by the cleaning members 6. The removed toner is collected into removed-toner chambers provided in photosensitive member units 26 (26a to 26d).
In synchronization with the above-described image forming operation, sheets serving as recording media are conveyed by a feeding device 13, a registration roller pair 17, etc. The feeding device 13 includes a feeding cassette 24 that contains sheets S, a pickup roller 8 that feeds the sheets S, a feed roller 16 that conveys the fed sheets S to the registration roller pair 17, and a separation roller 9 opposed to the feed roller 16. When a plurality of sheets S are fed by the pickup roller 8, they are frictionally separated one by one by a set torque of a torque limiter incorporated in the separation roller 9.
Above the feeding cassette 24, an above-cassette stay 35 serving as a part of a structure is provided to separate the feeding cassette 24 and the image forming section. The feeding cassette 24 can be drawn out to the front side of the apparatus in
Next, a sheet S conveyed from the feeding device 13 is conveyed to the secondary transfer portion 15 by the registration roller pair 17. At the secondary transfer portion 15, toner images of four colors on the intermediate transfer belt 5 are secondary-transferred onto the conveyed sheet S by applying a bias of positive polarity to a secondary transfer roller 18.
Toner remaining on the intermediate transfer belt 5 after secondary transfer on the sheet S is removed by a transfer-belt cleaning device 23. The removed toner passes through a waste-toner conveying path (not illustrated), and is collected into a waste-toner collecting container 34 disposed in the left side part of the apparatus.
On the other hand, a fixing device 14 serving as a fixing unit fixes the transferred toner images on the sheet S by applying heat and pressure to the toner images. A fixing belt 14a is cylindrical, and is guided by a belt guide member (not illustrated) to which a heating unit, such as a heater, is stuck. The fixing belt 14a and a pressure roller 14b form a fixing nip with a predetermined pressing force.
The sheet S on which an unfixed toner image is formed and which is conveyed from the secondary transfer portion 15 is heated and pressed at the fixing nip between the fixing belt 14a and the pressure roller 14b, and the unfixed toner image is fixed on the sheet S. After that, the fixed sheet S is discharged onto a discharge tray 20 by a discharge roller pair 19.
Outline of Feeding Device
As illustrated in
The feeding device 13 includes a pickup roller (feeding member) 8 that feeds out the sheets S stacked on the stack plate 21 from the uppermost sheet. The pickup roller 8 feeds the sheets S stacked on the stack plate 21 by rotating in contact with the sheets S. The feeding device 13 further includes a feed roller 16 that rotates in a sheet conveying direction to convey the sheets S fed by the pickup roller 8, and a separation roller 9 that is in pressure contact with the feed roller 16. At a separation nip portion formed by the feed roller 16 and the separation roller 9, the sheets S are separated and conveyed one by one. Between the separation roller 9 and a shaft of the separation roller 9, an unillustrated torque limiter is provided. The torque of the torque limiter is set so that, when one sheet is fed by the pickup roller 8, the separation roller 9 rotates to follow the sheet S conveyed by the feed roller 16. The torque of the torque limiter is set so that, when two sheets are fed by the pickup roller 8, the separation roller 9 does not rotate to prevent feeding of a lower sheet S (second sheet S) of the sheets S in contact with the pickup roller 8.
A description will be given of a lift operation of the stack plate 21 for lifting the sheets S to a position that allows feeding. As illustrated in
A lifting plate 22 is provided below the stack plate 21, and lifts up the stack plate 21. The lifting plate 22 has a fan-shaped gear 25 at one end. The fan-shaped gear 25 is meshed with a pinion 27 provided in the feeding cassette 24 to be rotated by driving force of a feeding motor M (driving unit) illustrated in
The feeding motor M can generate a driving force of forward rotation and a driving force of reverse rotation. As illustrated in
Side regulation members 30 regulate the positions of the sheets S stacked on the stack plate 21 in a direction (widthwise direction) intersecting the feeding direction at right angles. The side regulation members 30 are provided in the feeding cassette 24 to be movable in the widthwise direction. Further, the side regulation members 30 are movable independently of the stack plate 21, and can regulate the sheets S in the widthwise direction while maintaining the fixed state even during movement (upward movement) of the stack plate 21. A trailing-edge regulation member 31 regulates the positions of the sheets S stacked on the stack plate 21 at an upstream end (trailing edge) in the feeding direction. The trailing-edge regulation member 31 is provided in the feeding cassette 24 to be movable in the feeding direction.
A feeding frame unit 32 will be described with reference to
Holding of the pickup roller 8 and the feed roller 16 will be described. The pickup roller 8 is held by a roller holder (holding member) 47, and the roller holder 47 can pivot on the feed-roller shafts 41a and 41b.
The feed roller 16 is attached to the feed-roller shafts 41a and 41b. The feed-roller shaft 41a is held by the bearing 43 to be rotatable relative to the feeding frame 36. The feed-roller shaft 41b rotatably supports the other side of the feed roller 16. The feed-roller shaft 41b is held to be slidable relative to the feeding frame 36 in the axial direction. The torsion coil spring 42 is provided between the feed-roller shaft 41b and the feeding frame 36. The user can replace the roller holder 47 holding the feed roller 16 and the pickup roller 8 by sliding the feed-roller shaft 41b as necessary.
A description will be given of the structure and operation for pressing the pickup roller 8 against the sheets S. The press lever 40 attached to the feeding frame 36 is held to turn on a shaft portion 48 at about the center thereof relative to the feeding frame 36. The compression spring 38 works on one end of the press lever 40 so that the other end of the press lever 40 is in contact with the roller holder 47. This ensures a desired feeding pressure of the pickup roller 8 against the sheets S. That is, the compression spring 38 functions as an elastic member that generates elastic force for contact of the pickup roller 8 with the sheets S. The press lever 40 functions as a connecting member that connects the compression spring 38 and the roller holder 47.
The paper presence flag 46 and the paper presence sensor 45 constitute a sheet presence detection unit that detects the presence or absence of sheets S on the stack plate 21. When the sheets S are stacked on the stack plate 21, the paper presence flag 46 shields the paper presence sensor 45 from light during upward movement of the stack plate 21. In contrast, when the sheets S are not stacked on the stack plate 21, the paper presence flag 46 falls into a hole provided in the stack plate 21. Therefore, the paper presence flag 46 does not shield the paper presence sensor 45 from light (transmits light).
When the feeding cassette 24 is drawn out of the feeding device 13, the position detection lever 37 and the press lever 40 are pushed downward in
During a process in which the feeding cassette 24 is inserted in the feeding device 13, a rib 50b of the release lever 50 runs on a side wall 24a of the feeding cassette 24. Thus, the position detection lever 37 and the press lever 40 turn in the clockwise direction, and retraction of the pickup roller 8 is released. Then, in a state in which the feeding cassette 24 is loaded in the feeding device 13, the position detection lever 37 and the press lever 40 can operate within the range required for the feeding operation.
The gear 54ab is coupled to the feed-roller shaft 41a. When the feeding motor M rotates and the gear 54ab rotates, the feed roller 16 (feed-roller shaft 41a) also rotates. The electromagnetic clutch 54b controls the driving transmission from a gear 53c to the pinion 27 for pivoting the lifting plate 22. A worm gear 53d and a worm wheel 53e are interposed in a drive train from the electromagnetic clutch 54b to the pinion 27. Therefore, even when transmission of the electromagnetic clutch 54b is interrupted, the gears are not reversed by the weight of the sheets S, and the stack plate 21 is not lowered.
A gear 16a is attached to the shaft of the feed roller 16 with an unillustrated one-way clutch being disposed therebetween. The gear 16a transmits driving to a gear 8a provided on the rotating shaft of the pickup roller 8. A one-way clutch is also incorporated in the shaft of the pickup roller 8. According to this structure, back tension to the registration roller pair 17 can be kept down when the velocity ratio of the rollers is such that the velocity decreases in the order of the registration roller pair 17, the feed roller 16, and the pickup roller 8. Further according to this structure, the contact state between the pickup roller 8 and the sheets S can also be maintained in the period from when the pickup roller 8 feeds a preceding sheet to when the pickup roller 8 feeds a succeeding sheet. Therefore, according to this structure, it is possible to decrease the feeding interval (interval between the preceding sheet and the succeeding sheet) and to shorten the time from when a feeding operation start command is given to when the sheet S is actually fed. As a result, the FPOT can be shortened.
Next, the structure and operation for detecting the position of the paper surface of the sheets S on the stack plate 21 will be described with reference to
As the sheets S are sequentially fed according to a feeding signal, the height of the upper surface of the sheets S stacked on the stack plate 21 decreases. Correspondingly, the roller holder 47 pivots on the feed-roller shafts 41a and 41b, and moves down together with the pickup roller 8. Further, the press lever 40 and the position detection lever 37 also pivot to follow the downward movement of the paper surface. As a result, light shielding by the contact portion 37b is released, and the position detection sensor 55 is brought into a non-detection state. When the position detection sensor 55 is thus brought into the non-detection state, a control section (to be described later) controls the driving of the electromagnetic clutch 54b, and lifts up the stack plate 21 so that the sheets S on the stack plate 21 reach the predetermined position. That is, the control unit lifts up the stack plate 21 until the sheets S on the stack plate 21 turn the position detection lever 37 and the position detection sensor 55 is shielded by the flag-shaped portion 37a. By repeating this control, the position of the upper surface of the sheets S can be kept substantially fixed at the predetermined position that allows feeding until the sheets S on the stack plate 21 run out. Thus, the pickup roller 8 can reliably feed the sheets S.
The CPU circuit part 201 is connected to a feeding-cassette presence sensor 49 and a timer 202, and can obtain detection results of the sensors and the measurement time of the timer 202. The CPU circuit part 201 is also connected to the electromagnetic clutch 54a and the electromagnetic clutch 54b. The CPU circuit part 201 is also connected to the feeding motor M via a driver, and controls driving of the feeding motor M.
Next, a description will be given of the structure and control for moving the pickup roller 8 into contact with and away from the sheets S on the stack plate 21 with reference to
A driving frame 56 holding the feeding motor M holds gears 57a and 57b to be meshed with a gear 53b illustrated in
The operation of the one-way clutch 59 will be described. When the feeding motor M rotates in reverse (in a direction opposite from a direction for the feeding operation), the gear 57a rotates in the clockwise direction (direction of solid arrow) in
In contrast, when the feeding motor M rotates forward (feeding operation), the gear 57a rotates in the counterclockwise direction (direction opposite from the solid arrow) in
Next, the operation of the separation member 58 will be described.
The image forming apparatus A includes the timer 202 that measures the time elapsed from a final job. From the viewpoint of energy saving, when the timer 202 counts (detects) a predetermined time elapsed from the final job, the image forming apparatus A enters a sleep mode in which it stands by with the minimum power consumption.
In contrast, when a state in which the pickup roller 8 is in contact with the sheets S continues from several hours to one day or more, there is sometimes a local influence on the shape and surface property of the sheets S according to the environment of the image forming apparatus A and the surface material of the sheets S. For this reason, in the first embodiment, the CPU circuit part 201 separates the pickup roller 8 from the sheets S by rotating the feeding motor M in reverse by using the elapsed time of the timer 202 as a trigger. That is, the CPU circuit part 201 separates the pickup roller 8 from the sheets S when a feeding operation of the next sheet S is not performed even if a predetermined time elapsed from the end of the feeding operation of the final sheet S by the pickup roller 8. After the pickup roller 8 is separated from the sheets S, the image forming apparatus A enters the sleep mode.
When the feeding motor M rotates in reverse, the separation member 58 receives driving force from the gear 57b, and moves to a lower side in
The moving amount of the separation member 58 is set on the basis of the reverse rotation time (reverse rotation amount) of the feeding motor M so that the pickup roller 8 is located at the position sufficiently apart from the uppermost sheet S. That is, when the CPU circuit part 201 rotates the feeding motor M in reverse by a first predetermined amount, the separation member 58 located at the first position moves to the second position against the elastic force of the tension spring 60. Thus, the pickup roller 8 located at the contact position in contact with the sheets S moves to a retracted position retracted upward from the contact position.
In the first embodiment, the tension spring 60 is provided to prevent a phenomenon in which the separation member 58 does not return to the first position, for example, because of friction loss after the gear 57b and the separation member 58 are disengaged. In this case, even if the apparatus stops during the contact and separating operation owing to, for example, power failure, the CPU circuit part 201 can reliably return the separation member 58 to the first position by rotating the feeding motor M forward by a second predetermined amount. That is, the CPU circuit part 201 can move the separation member 58 from the second position to the first position by rotating the feeding motor M by the second predetermined amount. Thus, the pickup roller 8 located at the retracted position moves to the contact position. That is, in the first embodiment, the separation member 58, the tension spring 60, and the one-way clutch 59 constitute a moving unit that moves the pickup roller 8 between the contact position and the retracted position. The second predetermined amount may be equal to the first predetermined amount.
According to the above-described first embodiment, there is no need for a detector (sensor) that detects the position of the pickup roller 8. Further, since the separation member 58 is not in contact with the press lever 40 at the first position, it does not have any influence on the feeding pressure. In the first embodiment, as illustrated in
In this way, in the first embodiment, the contact and separating operations of the pickup roller 8 are achieved at energy saving, with small size, and at low cost by utilizing the forward and reverse rotations of the feeding motor M while using the one-way clutch 59.
In the state in which the pickup roller 8 is separate from the sheets S, the force of the compression spring 38 for generating the feeding pressure acts on the feeding motor M. The speed reduction ratio between the feeding motor M and the separation member 58 is set so that the force of the compression spring 38 does not exceed the detent torque of the feeding motor M. That is, the state in which the separation member 58 is located at the second position is maintained by the detent torque of the feeding motor M. While the moving amount of the separation member 58 is controlled by the reverse rotation time of the feeding motor M in the above first embodiment, it is clear that advantages similar to those of a structure in which the step number of a stepping motor is managed can be expected.
When separating the pickup roller 8 from the sheets S, the CPU circuit part 201 interrupts transmission of driving of the electromagnetic clutches 54a and 54b in the drive train illustrated in
A case in which the separation member 58 is further moved downward from the second position, for example, owing to control fluctuation or malfunction of the apparatus (excessive separation state) is assumed (
As described above, since the pickup roller 8 is separated when the feeding cassette 24 is drawn out of the feeding device 13, the operating force of the user can be reduced.
As illustrated in
While the above-described control is such that the pickup roller 8 is separated on the basis of the count of the timer 202, the present invention is not limited thereto. As will be described later, in the first embodiment, control for separating the pickup roller 8 is executed on the basis of an OFF signal from a power switch 203 provided in the main body of the apparatus.
The power switch 203 is an input unit of a soft switch. More specifically, when the user operates the power switch 203 and the power switch 203 outputs an OFF signal, the CPU circuit part 201 rotates the feeding motor M in reverse by the first predetermined amount to separate the pickup roller 8 from the sheets S. After that, the apparatus is brought into a stop state.
As described above, in the present invention, even if the feeding device 13 does not include the timer, the pickup roller 8 may be separated in response to the OFF signal from the power switch 203.
Next, a second embodiment will be described. In the following description of the second embodiment, descriptions of structures and operations common to the first embodiment are skipped appropriately. A feeding device according to the second embodiment is different from the first embodiment in the structure of a moving unit that moves a pickup roller 8 between a contact position (contact operation) and a retracted position (separating operation).
A gear holder 64 is held in a driving frame 56. The gear holder 64 holds a cam gear 63. The cam gear 63 includes a cam portion 63a, a gear portion 63b, and a boss 63c. When driving force is transmitted from a gear 57b to the gear portion 63b, the cam gear 63 turns relative to the gear holder 64.
Similarly to the first embodiment, the pickup roller 8 can be returned from the retracted position to the contact position (returned from the state of
As illustrated in
While the driving unit includes the feeding motor M capable of rotating forward and in reverse in the above-described embodiments, the present invention should not be limited thereto. For example, the driving unit may include a motor that rotates in one direction and a clutch that changes the direction of rotation output from the motor.
While the present invention is applied to the laser printer A in the above-described embodiments, it should not be limited thereto, and may be applied to other image forming apparatuses such as a copying machine and a multifunction apparatus. Further, while the electrophotographic image forming process is given as an example of the image forming section for forming an image on a sheet in the above-described embodiments, the present invention should not be limited to the image forming section using the electrophotographic image forming process. For example, the present invention may be applied to an apparatus in which an image forming section for forming an image on a sheet uses an inkjet image forming process for forming an image on a sheet by discharging ink liquid from a nozzle.
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. 2014-115305, filed Jun. 3, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-115305 | Jun 2014 | JP | national |
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| 20080128973 | Hirose | Jun 2008 | A1 |
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| 20160159590 | Zensai | Jun 2016 | A1 |
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| Number | Date | Country | |
|---|---|---|---|
| 20150344246 A1 | Dec 2015 | US |
