Patent Grant
9738468
Field of the Invention
The present invention relates to a sheet feeding apparatus configured to feed sheets, and to an image forming apparatus including the sheet feeding apparatus.
Description of the Related Art
Hitherto, in image forming apparatus such as a printer or a copying machine configured to form an image on a sheet, sheets stacked in a cassette are fed through use of a sheet feeding apparatus to form images on the fed sheets. In this case, in response to conveyance of the sheet to a predetermined position in a conveyance path, the sheet feeding apparatus separates pickup rollers from the sheet and switches a feed motor to a high speed mode to convey the sheet at higher speed with a roller located downstream of the pickup rollers, thus allowing intervals between the sheets to be reduced while increasing the printing speed (Japanese Patent Application Laid-Open No. 2008-110835).
In the related-art configuration, however, it is necessary to separate the pickup rollers from the sheet at a timing at which the sheet conveying speed is increased, thus causing a problem in that the apparatus configuration is complicated.
The present invention provides a sheet feeding apparatus which increases a sheet feed rate with a simple configuration, and also provides an image forming apparatus including the sheet feeding apparatus.
According to one embodiment of the present invention, there is provided a sheet feeding apparatus, comprising:
According to one embodiment of the present invention, there is provided 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.
A sheet feeding apparatus according to embodiments of the present invention and an image forming apparatus according to embodiments of the present invention including the sheet feeding apparatus will be described below with reference to the attached drawings.
(Image Forming Apparatus)
In the image reading apparatus 901, an original pressing plate 904 is opened by a user, and an original D is placed on an original glass plate 906 with an image side facing downward. Then, the original pressing plate 904 is closed by the user. The original pressing plate 904 presses the original D against the original glass plate 906. When an operation button on an operation panel (not shown) is pressed by the user, an image reading portion 908 is moved to the right direction in
The signals transmitted to the laser scanner 910 are converted to laser light, which is emitted to a photosensitive drum 912 via a scanner mirror 910a rotating at high speed and a reflection mirror 910b. The photosensitive drum 912 is uniformly charged by a charger 914 and an electrostatic latent image is formed on a portion irradiated with the laser light. The electrostatic latent image is developed into a visualized toner image with a toner developer supplied from a developing roller 916.
On the other hand, a sheet is fed from a sheet feed cassette 40 by semicircular pickup rollers 41 in a direction of the arrow E (sheet feed direction) and conveyed to the position between the photosensitive drum 912 and a transfer roller 924 by a separation-and-conveyance roller pair 8 and a registration roller pair 9. The transfer roller 924 transfers the toner image, which is formed on the photosensitive drum 912, onto the sheet being conveyed. The sheet having the toner image transferred thereonto is conveyed to a fixing unit 928 by a conveyance apparatus 926. The fixing unit 928 heats and pressurizes the sheet with a fixing roller 928a and a pressure roller 928b to fix the toner image onto the sheet. The sheet having the toner image fixed thereonto is delivered to a sheet delivery tray 932 with a sheet delivery roller pair 930.
In the above-mentioned configuration, the charger 914 and the photosensitive drum 912 are removably mounted in the apparatus main body 900A in the form of a process cartridge 138. The process cartridge 138 and the transfer roller 924 construct an image forming portion 939 configured to form an image on a sheet.
The above-mentioned image forming apparatus 900 is configured to operate under the control of a CPU 50 illustrated in
(Sheet Feeding Apparatus 1 According to First Embodiment)
The sheet feeding apparatus 1 includes the sheet feed cassette 40, the semicircular pickup rollers 41, the separation-and-conveyance roller pair 8, and a drive portion 23. The sheet feed direction refers to a direction of the arrow E in
The sheet feed cassette 40 in the shape of a box for use as a stacking unit configured to stack sheets thereon includes a loading plate 2 configured to load sheets P by the user. The loading plate 2 is rotatably mounted on a fulcrum 2a of rotation formed upstream of the sheet feed cassette 40 in the sheet feed direction E so that a distal end portion 2b of the loading plate 2 on the downstream side in the sheet feed direction is moved up and down. A loading plate pressing spring 3 is arranged between a bottom plate 40a of the sheet feed cassette 40 and the distal end portion 2b of the loading plate 2. The loading plate pressing spring 3 is configured to press up the distal end portion 2b of the loading plate 2. A compression coil spring is used for the loading plate pressing spring 3 but a leaf spring or rubber may be used instead. A trailing edge regulating plate 4 is removably mounted on the loading plate 2. The mounting position of the trailing edge regulating plate 4 can be changed in accordance with the size of the sheet P by selecting suitable ones of a plurality of holes 2c formed in the loading plate 2 and inserting the trailing edge regulating plate 4 therein. Separation claws 5 configured to regulate the upper surface of the stacked sheet P are arranged at both upper corners of a downstream end portion of the sheet feed cassette 40, respectively. The separation claws 5 are arranged to allow sheets to be fed from the sheet feed cassette 40 one by one.
The semicircular pickup rollers 41 serving as a feed unit, that is, rotary members are rotatably arranged in the apparatus main body 900A so as to face the downstream end portion of the sheet feed cassette 40 in the sheet feed direction. Each pickup roller 41 includes, on an outer periphery in a rotation direction thereof, a semicircular contact portion 41a which is brought into contact with a sheet stacked on the sheet feed cassette 40 and a flat noncontact portion 41b which is not brought into contact with the sheet. The pickup rollers 41 are constructed so that the contact portion 41a is brought into contact with the uppermost sheet among the sheets stacked on the loading plate 2 to feed the uppermost sheet.
The separation-and-conveyance roller pair 8 serving as a conveyance unit, that is, a conveyance roller pair is arranged downstream of the pickup rollers 41 in the sheet feed direction. The separation-and-conveyance roller pair 8 includes a conveyance roller 6 and a separation roller 7, which are brought into press contact with each other. The conveyance roller 6 and the separation roller 7 are configured to convey a sheet by rotating while nipping the sheet therebetween. In the separation-and-conveyance roller pair 8, when sheets fed from the sheet feed cassette 40 by the pickup rollers 41 are stacked on one another, the lower separation roller 7 is configured to apply a load to resist conveyance of the lower sheet of the sheets stacked on one another, and the upper conveyance roller 6 is configured to convey one upper sheet. The sheets can be also separated by the separation claws 5 arranged on the sheet feed cassette 40 so as to be fed one by one, and hence a roller pair configured to convey the sheet may be simply arranged instead of the separation-and-conveyance roller pair 8.
Next, the drive portion 23 configured to increase the sheet feed rate of the sheet feeding apparatus 1 will be described.
The drive portion 23 includes the feed motor M1 serving as a drive source configured to rotate the pickup rollers 41 and the conveyance roller 6, and a rotation transmission mechanism 24 arranged between the feed motor M1 and the conveyance roller 6 so that the rotational driving force of the feed motor M1 is transmitted (transmittable) to the conveyance roller 6. The drive portion 23 further includes a gear train 25 configured to transmit the rotation of the feed motor M1 to the pickup rollers 41, and a solenoid SL1.
The gear train 25 includes a driving gear 26 arranged at the feed motor M1, a first intermediate gear 27, a second intermediate gear 28, a third intermediate gear 29, and a driven gear 30 arranged at a rotary shaft 42 of the pickup rollers 41. The first intermediate gear 27 is meshed with the driving gear 26 and the second intermediate gear 28. The second intermediate gear 28 and the third intermediate gear 29 are arranged integrally with a shared rotary shaft 31. The rotary shaft 31 is rotatably arranged in the apparatus main body 900A. Therefore, the gear train 25 is configured to transmit the rotational force of the feed motor M1 to the rotary shaft 42 via the driving gear 26, the first intermediate gear 27, the second intermediate gear 28, the rotary shaft 31, the third intermediate gear 29, and the driven gear 30, to thereby rotate the pickup rollers 41.
The rotation transmission mechanism 24 includes the driving gear 26 arranged at the feed motor M1, the first intermediate gear 27, the second intermediate gear 28, a small diameter sector gear 14, a large diameter sector gear 15, a large diameter gear 11, and a small diameter gear 12. The second intermediate gear 28 as well as the small diameter sector gear 14 and the large diameter sector gear 15 serving as conveyance control gears 13 is arranged integrally with the shared rotary shaft 31. The large diameter gear 11 and the small diameter gear 12 serving as conveyance driving stepped gears 10 are arranged integrally with a rotary shaft 21 of the conveyance roller 6. The small diameter sector gear 14 is configured to mesh with the large diameter gear 11. The large diameter sector gear 15 is configured to mesh with the small diameter gear 12.
In
The solenoid SL1 is configured to operate the second intermediate gear 28 so that the rotation of the feed motor M1 rotating at a constant speed causes the small diameter sector gear 14 and the large diameter sector gear 15 to make only one revolution.
Next, an operation of the sheet feeding apparatus 1 will be described based on the above-mentioned configuration with reference to
The CPU 50 is configured to rotate the feed motor M1. However, the CPU 50 does not turn on the solenoid SL1 of
In this state, the CPU 50 turns on the solenoid SL1 for a time period of T1 seconds (
On the other hand, the rotation of the rotary shaft 31 causes the small diameter sector gear 14 and the large diameter sector gear 15 to integrally rotate from the state of
The conveyance roller 6 does not rotate as described above but the pickup rollers 41 rotate. Then, as illustrated in
The feed motor M1 continues to rotate, and hence the pickup rollers 41 still apply the feed force to the uppermost sheet. The sheet which is bent to some extent in a convex shape is separated from the separation claws 5 to return to the straight state. The uppermost sheet is separated from a sheet immediately under the uppermost sheet and starts to be fed from the sheet feed cassette 40. In
Before the leading edge of the sheet fed from the sheet feed cassette 40 by the pickup rollers 41 reaches the separation-and-conveyance roller pair 8 (
Then, as illustrated in
However, when the sheet conveying speed of the separation-and-conveyance roller pair 8 is increased from V1 to V2 (V2>V1) in a state in which the sheet is conveyed while being held in contact with the pickup rollers 41 and the separation-and-conveyance roller pair 8, the pickup rollers 41 and the separation-and-conveyance roller pair 8 may pull the sheet from both sides. Then, when the small diameter sector gear 14 is separated from the large diameter gear 11 and the large diameter sector gear 15 meshes with the small diameter gear 12 in
In addition, at the beginning of conveyance of the sheet by the separation-and-conveyance roller pair 8 as illustrated in
The feed motor M1 continues to rotate. Therefore, the pickup rollers 41 rotate from the state of
As described above, in the sheet feeding apparatus 1 according to the first embodiment, the sheet conveying speed of the separation-and-conveyance roller pair 8 can be increased by the rotation transmission mechanism 24 while the noncontact portions 41b of the pickup rollers 41 face the sheet. Therefore, even when the sheet conveying speed of the separation-and-conveyance roller pair 8 is increased from V1 to V2, the sheet feeding apparatus 1 can prevent the pickup rollers 41 and the separation-and-conveyance roller pair 8 from being damaged while sheets neither have conveyance failure nor are pulled from both sides. The sheet feed rate can be prevented from being reduced due to damage to the pickup rollers 41 and the separation-and-conveyance roller pair 8.
Except during the sheet feed, the sheet feeding apparatus 1 can keep the state in which the noncontact portions 41b of the pickup rollers 41 are not in contact with the sheet, and hence it is not necessary to separately arrange a mechanism configured to separate the pickup rollers 41 when the sheet feed cassette 40 is pulled out from the apparatus main body. Moreover, the loading plate 2 configured to place sheets thereon is pressed up by the loading plate pressing spring 3 so that the pickup rollers 41 only rotate during sheet feed to bring the contact portions 41a into contact with the sheet, and hence this configuration is less expensive than the configuration in which the loading plate 2 is elevated to bring the sheet loaded on the loading plate 2 into contact with the pickup rollers 41.
In addition, each of the pickup rollers 41 in the sheet feeding apparatus 1 according to the first embodiment has the shape of a roller having the contact portion 41a and the noncontact portion 41b in the rotational direction, and can switch the mode between contact and noncontact with the sheet on the loading plate 2 by making one revolution. Therefore, this configuration is less expensive than the configuration in which the mode is switched between contact and noncontact by moving the pickup rollers up and down without the noncontact portions.
The sheet feeding apparatus 1 increases the sheet conveying speed of the separation-and-conveyance roller pair 8 from the first conveying speed V1 to the second conveying speed V2 to allow sheet feeding intervals by the pickup rollers 41 to be shortened, thereby increasing the sheet feed rate.
The sheet feeding apparatus 1 according to the embodiment can increase the sheet feed rate without damaging the sheet or reducing the conveyance performance.
Moreover, the image forming apparatus 900 according to the embodiment includes the sheet feeding apparatus 1 having an increased sheet feed rate, thereby forming images on sheets with improved productivity.
(Sheet Feeding Apparatus 101 According to Second Embodiment)
Although the above-mentioned sheet feeding apparatus 1 according to the first embodiment is configured to rotate the pickup rollers 41 and the separation-and-conveyance roller pair 8 with the shared feed motor M1, a sheet feeding apparatus 101 according to a second embodiment is configured to rotate the pickup rollers 41 and the separation-and-conveyance roller pair 8 with separate motors, that is, a pickup motor M2 and a conveyance motor M3.
In
In
An operation of the sheet feeding apparatus 101 according to the second embodiment will be described. In
In this state, the CPU 130 turns on the solenoid SL2 for a time period of T1 seconds (Step S202). Then, the rotational force of the pickup motor M2 is transmitted to the pickup rollers 41 by the pair of the intermediate gears 102 and 103 to rotate the pickup rollers 41. The pickup rollers 41 feed the sheet from the sheet feed cassette. Then, the CPU 130 causes the conveyance motor M3 to rotate so that the conveyance roller 6 of the separation-and-conveyance roller pair 8 rotates (Step S203). In this step, the CPU 130 controls the rotation of the pickup motor M2 and the conveyance rollers M3 so that the sheet conveying speed of the pickup motors 41 and the sheet conveying speed of the conveyance roller 6 become the same sheet conveying speed V1.
The CPU 130 causes the counter 133 to count the rotation time of the pickup rollers 41 and determines that the noncontact portions 41b of the pickup rollers 41 face the sheet when a predetermined rotation time has elapsed (YES in Step S204). Then, the CPU 130 increases the rotation speed of the conveyance motor M3 so that the separation-and-conveyance roller pair 8 has the sheet conveying speed V2 (Step S205). The pickup rollers 41 are brought into a state of conveying no sheet, and the conveyance roller 6 conveys the sheet at the sheet conveying speed V2 (V2>V1) that is higher than the sheet conveying speed V1. When the conveyance roller 6 conveys the sheet at the sheet conveying speed V2 for a predetermined time period, the CPU 130 determines that the sheet has been conveyed adequately, to thereby stop the rotation of the conveyance motor M3 (Step S206). When there is a sheet to be fed in succession (YES in Step S207), the CPU 30 operates the solenoid SL2 again for the time period of T1 seconds to transmit the rotation of the pickup motor M2 to the pickup rollers 41. When there is no sheet to be fed in succession (NO in Step S207), the rotation of the pickup motor M2 is stopped (Step S208). Then, the pickup rollers 41 stop under a state in which the noncontact portions 41b face the sheet.
As described above, also in the sheet feeding apparatus 101 according to the second embodiment, the sheet conveying speed of the separation-and-conveyance roller pair 8 can be increased by the conveyance motor M3 while the noncontact portions 41b of the pickup rollers 41 face the sheet. Therefore, even when the sheet conveying speed of the separation-and-conveyance roller pair 8 is increased from V1 to V2, the sheet feeding apparatus 101 can prevent the pickup rollers 41 and the separation-and-conveyance roller pair 8 from being damaged while sheets neither have conveyance failure nor are pulled from both sides. The sheet feed rate can be prevented from being reduced due to damage to the pickup rollers 41 and the separation-and-conveyance roller pair 8. Moreover, the sheet feeding apparatus 101 can increase the sheet conveying speed of the separation-and-conveyance roller pair 8 from V1 to V2 to allow the sheet feeding intervals by the pickup rollers 41 to be shortened, thereby increasing the sheet feed rate.
Moreover, the sheet feeding apparatus 101 according to the second embodiment is configured to rotate the pickup rollers 41 and the separation-and-conveyance roller pair 8 through use of the separate motors M2 and M3, respectively. Therefore, when the noncontact portions 41b of the pickup rollers 41 face the sheet and the conveyance roller 6 conveys the sheet at the sheet conveying speed V2, the sheet feeding apparatus 101 can rotate the conveyance roller 6 at a higher rotation speed than that at the sheet conveying speed V1. Immediately after the trailing edge of the sheet being conveyed by the conveyance roller 6 at the sheet conveying speed V2 passes below the pickup rollers 41, the pickup rollers 41 can be thus turned into standby at a rotational position in which the next sheet can be conveyed with the contact portions 41a of the pickup rollers 41. Therefore, the intervals between the sheets can be reduced to further increase the sheet feed rate.
In addition, the sheet feeding apparatus 101 according to the second embodiment can feed sheets of various lengths by controlling the angle of rotation and the number of revolutions of the conveyance motor M3 in a state in which the pickup motor M2 is stopped.
The sheet feeding apparatus 101 according to the embodiment can increase the sheet feed rate without damaging the sheet or reducing the conveyance performance.
Moreover, the image forming apparatus 900 according to the embodiment includes the sheet feeding apparatus 101 having an increased sheet feed rate, thereby forming images on sheets with improved productivity.
In the above-mentioned embodiments, the pickup rollers 41 have the semicircular shape. However, the shape is not limited to the shape as long as the pickup rollers 41 are not always in contact with the sheet loaded on the loading plate 2.
The separation-and-conveyance roller pair 8 may not necessarily have the sheet conveying speed V1 equal to that of the pickup rollers 41 as long as the sheets and the separation-and-conveyance roller pair 8 are not damaged when the sheet conveying speed of the separation-and-conveyance roller pair 8 is set higher than that of the pickup rollers 41. Assuming that the sheet conveying speed of the pickup rollers 41 and the sheet conveying speed of the separation-and-conveyance roller pair 8 are represented by V1a and V1b (V1b>V1a), respectively, the sheet conveying speed of the separation-and-conveyance roller pair 8 is set to V2 which is higher than V1b when the pickup rollers 41 are not in contact with the sheet on the loading plate 2. Also in such a case, the sheet feed rate can be further increased to improve the productivity.
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. 2015-030576, filed Feb. 19, 2015, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-030576 | Feb 2015 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 8033541 | Akiyama | Oct 2011 | B2 |
| 8328180 | Kwak | Dec 2012 | B2 |
| 8783676 | Yamamoto | Jul 2014 | B2 |
| Number | Date | Country |
|---|---|---|
| 06-009079 | Jan 1994 | JP |
| 2001-097601 | Apr 2001 | JP |
| 2003-104573 | Apr 2003 | JP |
| 2006-036439 | Feb 2006 | JP |
| 2008-110835 | May 2008 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20160244283 A1 | Aug 2016 | US |
