Patent Grant
9206002
The present invention relates to a sheet feeding apparatus and an image forming apparatus, and particularly, to a configuration for reducing the noise when a sheet abuts against a feeding roller during sheet feeding.
In the related art, image forming apparatuses, such as copying machines and printers, includes a sheet feeding apparatus that feeds out a sheet toward an image forming unit. Such a sheet feeding apparatus includes a liftable intermediate plate, and a feeding roller, and is adapted to lift the intermediate plate by the rotation of the feeding roller to press a sheet on the intermediate plate against the feeding roller, and feed out the sheet as the feeding roller rotates in this state.
Here, as a configuration for lifting the intermediate plate by the rotation of the feeding roller in this way, for example, there are those adapted to fix a cam to a rotating shaft of the feeding roller and to bring this cam into pressure contact with a pressure-contact portion provided at the intermediate plate biased by a spring (refer to Japanese Patent Application Laid-Open No. H3-102019 and Japanese Patent Application Laid-Open No. H10-153247). If a feeding operation starts, the intermediate plate is lifted by the rotation of the cam while opening the spring pressure of a spring that biases the intermediate plate, and a sheet on the intermediate plate is the pressed against the feeding roller.
Incidentally, in such a sheet feeding apparatus of the related art, the ascending speed when the intermediate plate ascends by the rotation of the cam is determined depending on the force of the spring that biases the intermediate plate and the outer peripheral shape (profile) of the cam. Additionally, the ascending speed of the intermediate plate, in other words, the speed at which the top sheet of the stacked sheets abuts against the feeding roller varies depending on the stack amount of the sheets on the intermediate plate, and the speed in a case where the stack amount is small increases more than the speed in a case where the stack amount is large. In a case where the speed at which the top sheet abuts against the feeding roller in this way has increased, an abutment sound (collision sound) is generated when the sheet abuts against the feeding roller.
Here, in order to reduce this abutment sound (collision sound), the rotating speed of the cam, in other words, the rotating speed of the feeding roller may be made slow to make the ascending speed of the intermediate plate slow. In addition, in a case where the rotating speed of the feeding roller is made slow, there is a concern that an image cannot be suitably formed on a sheet. After this, however, if the rotating speed of the feeding roller is increased to the printing speed (process speed) of the image forming apparatus, an image can be suitably formed on a sheet.
However, in order to allow such speed control, it is necessary to drive the feeding roller by a dedicated driving source. However, generally, a driving source often serves also as other driving sources of an image forming system and a conveyance system. In this case, the feeding roller cannot be rotated only at a constant speed. For this reason, only the rotating speed of the feeding roller cannot be made slow, and if the printing speed increases, the rotating speed of the feeding roller increases and the ascending speed of the intermediate plate also increases correspondingly.
That is, in the sheet feeding apparatus of the related art, the driving source of the feeding roller serves as other driving sources. Thus, it is not possible to arbitrarily change the rotating speed of the rotating shaft to abate the abutment sound. For this reason, although the elevating speed of the intermediate plate depends on the profile of the cam, there is a limit of sufficiently securing the reduction region of the ascending speed of the intermediate plate only by the outer peripheral shape of the cam.
Thus, the invention has been made in view of these circumstances, and an object thereof is to provide a sheet feeding apparatus and an image forming apparatus that can reduce the collision sound when a sheet abuts against a feeding roller and suitably form an image on the sheet.
A sheet feeding apparatus of the invention includes a liftable sheet stacking plate that supports a sheet; a feeding roller that is provided above the sheet stacking plate and feeds the sheet supported by the sheet stacking plate; a biasing unit that biases the sheet stacking plate in a direction of the feeding roller and presses the sheet stacked on the sheet stacking plate against the feeding roller; a drive unit that generates a driving force in order to rotate a shaft of the feeding roller; a lifting and lowering unit that has a cam provided on the shaft of the feeding roller and a pressure-contact portion that is provided at the sheet stacking plate and is brought into pressure contact with the cam that lifts and lowers the sheet stacking plate biased by the biasing unit with the rotation of the shaft of the feeding roller while bringing the pressure-contact portion into pressure contact with the cam; and a variable speed unit that changes the rotating speed of the shaft of the feeding roller that rotates under the driving of the drive unit. The variable speed unit rotates the shaft of the feeding roller at a first speed to lift the sheet stacking plate, and rotates the shaft of the feeding roller at a second speed faster than the first speed if the sheet stacked on the sheet stacking plate abuts against the feeding roller.
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 described in detail with reference to the drawings.
Here, the image forming unit 5 includes a laser exposure device 5b, a photoconductive drum 5a that forms a toner image, and a transfer roller 5d that transfers the toner image formed on the photoconductive drum 5a to a sheet S. In addition, reference numeral 5A represents a process cartridge including the photoconductive drum 5a, a developing unit 5c, or the like, and the process cartridge 5A is detachably mounted on the printer body 1A.
The sheet feeding apparatus 1B includes a feeding roller 3, a sheet feed tray 2 that is a sheet storage unit, and an intermediate plate 9 that is a sheet stacking plate that is liftably provided at the sheet feed tray 2 and presses sheets S stored in the sheet feed tray 2 to the feeding roller 3. Additionally, a separation pad 10 brought into pressure contact with the feeding roller 3 is provided on the downstream side of the sheet feed tray 2 in a sheet feeding direction.
In such a sheet feeding apparatus 1B, when an image is formed, sheets S are fed out from the sheet feed tray 2 by the feeding roller 3, and then, the sheets S are separated one by one by the separation pad 10 brought into pressure contact with the feeding roller 3. In addition, the separation pad 10 is held at a turning end of a separation pad holder 10c that has a turning fulcrum 10b below the intermediate plate 9, and is biased toward the feeding roller 3 by a coil spring 10a.
Next, an image forming operation in the printer 1 of such a configuration will be described. If the image forming operation is started, first, the feeding roller 3 rotates and the intermediate plate 9 ascends with the rotation of the feeding roller 3. Then, sheets S stacked on the intermediate plate 9 are pressed against the feeding roller 3, and the sheets S are then fed out by the rotation of the feeding roller 3. Next, the sheets S are separated one by one by the separation pad 10 and conveyed by a conveying roller pair 4. Thereafter, if the tip of a sheet S is detected by a sensor T1, a laser beam according to an image signal is irradiated from the laser exposure device 5b to the photoconductive drum 5a that has a surface subjected to a charging treatment and that is rotationally driven in the direction of an arrow.
Then, as the light according to such an image signal is irradiated, a latent image is formed on the photoconductive drum, and the latent image on the photoconductive drum is developed with toner supplied by the developing unit 5c, and is visualized as a toner image. Thereafter, if the sheet S is conveyed to a transfer unit formed by the transfer roller 5d and the photoconductive drum 5a, the visualized toner image is transferred to the sheet S by applying a voltage, which has polarity reverse to the toner image formed on the photoconductive drum 5a, to the transfer roller 5d.
Next, the sheet S on which the toner image has been transferred is conveyed to a fixing unit 5e arranged at an upper part of the printer body. Then, when passing through the fixing unit Se, the transferred toner image is fixed on the sheet as heat and pressure is applied to the sheet S. Thereafter, the sheet S on which the toner image has been fixed is conveyed by a discharge roller pair 7 and discharged to a discharge unit 8 formed on the top face of the printer body 1A. In addition, in
Here, in the present exemplary embodiment, the feeding roller 3 of the sheet feeding apparatus 1B, as illustrated in
Cams 11 are fixed to both ends of the rotating shaft 6 in the width direction, and pressure-contact portions 9b that abut against the right and left cams 11, respectively, are formed on the top faces of the side wall portions 9A of the intermediate plate 9 on the downstream side in the sheet feeding direction. Then, as the rotating shaft 6 rotates and the cams 11 rotate, the intermediate plate 9 ascends and descends. That is, in the present exemplary embodiment, a lifting and lowering unit 11A that lifts and lowers the intermediate plate 9 biased by the coil springs 9a together with the rotation of the rotating shaft 6 of the feeding roller 3 is constituted by the cams 11 and the pressure-contact portions 9b of the intermediate plate 9.
Additionally, a sheet feed tooth-missing stage gear 12 that is a tooth-missing gear having a tooth-missing portion is fixed to the outside of one cam 11 of the rotating shaft 6. In addition, the sheet feed tooth-missing stage gear 12 is regulated in rotation by the solenoid 14, and meshes with an input stage gear 13 fixed to an input shaft 13a to which a rotational driving force is transmitted via the driving transmission unit from the main motor M if the regulation by the solenoid 14 released.
Here, the input stage gear 13 that is a driving gear, as illustrated in
In addition, in
In addition, although a rotative force in the direction of R1 illustrated by a broken line is applied to the sheet feed tooth-missing stage gear 12 by the tension of the sheet feed gear spring 15, as illustrated in
Additionally,
Next, if the sheet feeding operation is started, the control unit 50 turns on the solenoid 14, and as illustrated in
Then, as the tooth-missing large gear 12a of the sheet feed tooth-missing stage gear 12 meshes with the small gear 13c of the input stage gear 13 in this way, as illustrated in
In addition, at this time, as illustrated in
Next, if the intermediate plate 9 ascends, as illustrated in
Here, at this time, since the sheet feed gear spring 15 exerts tension still in an extended state, then, the sheet feed tooth-missing stage gear 12 continues being rotated by the sheet feed gear spring 15, and the tooth-missing small gear 12c of the sheet feed tooth-missing stage gear 12 meshes with the large gear 13b of the input stage gear 13 eventually. Thereby, as illustrated in
Here, in a case where the tooth-missing small gear 12c of the sheet feed tooth-missing stage gear 12 meshes with the large gear 13b of the input stage gear 13 in this way, the sheet feed tooth-missing stage gear 12 rotates fast with respect to the rotating speed of the input stage gear 13. Namely, the rotating shaft 6 and the feeding roller 3 rotate at the second speed faster than the first speed. In addition, in the present exemplary embodiment, the rotating speed of the sheet feed tooth-missing stage gear 12 at this time is equal to the process speed of the printer body 1A. Then, after only one top sheet fed out by the feeding roller 3 that rotates at such a rotating speed is separated by the separation pad 10 and the feeding roller 3 that are illustrated in
Next, if the separation work of the sheet S by the feeding roller 3 and the separation pad 10 ends and the sheet S is passed to the conveying roller pair 4 after the fed-out sheet has reached the conveying roller pair 4, as illustrated in
Thereafter, if the sheet feed tooth-missing stage gear 12, as illustrated in
However, even in a case where the rotational driving force of the sheet feed tooth-missing stage gear 12 is lost in this way, the sheet feed gear spring 15 is still in an extended state. For this reason, thereafter, the sheet feed tooth-missing stage gear 12 rotates in the direction of R1 by the tension of the sheet feed gear spring 15, and the small gear 13c of the input stage gear 13 and the tooth-missing large gear 12a of the sheet feed tooth-missing stage gear 12 meshes with each other. Thereby, the sheet feed tooth-missing stage gear 12 rotates, and eventually returns to the same initial position as
Incidentally, when a continuous printing job of a plurality of sheets is received, the sheet-to-sheet setting between a preceding sheet and a subsequent sheet may become short. In this case, as illustrated in
In addition,
If the schematic view of
Next, if the pressure contact between the cams 11 and the pressure-contact portions 9b of the intermediate plate 9 is released and the intermediate plate 9 that has ascended reaches a sheet feed separation position where the feeding of a sheet by the feeding roller 3 is allowed, the meshing of the tooth-missing large gear 12a of the sheet feed tooth-missing stage gear 12 with the small gear 13c of the input stage gear 13 is completed. Thereby, the rotation of the cams 11 stops and, the ascent of the intermediate plate 9 is completed correspondingly. Thereafter, switching to the meshing between the tooth-missing small gear 12c of the sheet feed tooth-missing stage gear 12 and the large gear 13b of the input stage gear 13 is made. Thereby, the cams 11 starts rotating, and the cams 11 and the rotating shaft 6 are quickly turned.
Thereby, the feeding roller 3 separates the top sheet at a predetermined process speed and feeds out the sheet to the conveying roller pair 4, and the intermediate plate 9 descends. Moreover, if the cams 11 rotate to depress the intermediate plate 9, the sheet feed tooth-missing stage gear 12 reaches a tooth-missing position to end the meshing, the driving from the input stage gear 13 is cut off, and the cams 11 and the intermediate plate 9 return to their initial positions. In addition,
As described above, in the present exemplary embodiment, if the sheet feeding operation is started, first, the sheet feed tooth-missing stage gear 12 and the input stage gear 13 are made to mesh with each other so as to be a reduction ratio in which the rotating speed of the cams 11 becomes slow. Additionally, during the separation of a sheet by the feeding roller 3 and the feeding-out of the sheet to the conveying roller pair 4, the sheet feed tooth-missing stage gear 12 and the input stage gear 13 are made to mesh with each other in a reduction ratio such that the feeding roller 3 is rotated at a predetermined process speed.
By setting the rotating speed of the rotating shaft 6 and the cams 11 during the ascent of the intermediate plate to the relatively slow first speed in this way, the ascending speed of the intermediate plate 9 can be slowed down, and as a result, the collision sound when the sheet on the intermediate plate abuts against the feeding roller 3 can be reduced. Additionally, during the separation feeding operation of a sheet, the feeding roller 3 can be rotated at a predetermined process speed by increasing the rotating speed of the rotating shaft 6 and the feeding roller 3 to the second speed faster than the first speed.
That is, in the present exemplary embodiment, the ascending speed of the intermediate plate 9 that ascends by one rotational driving of the cams 11 (input stage gear 13) can be slowed down by making the sheet feed tooth-missing stage gear 12 to mesh with the input stage gear 13 that rotates at a constant speed. Thereby, even in a case where an independent driving source is not provided or a driving source that can supply only constant-speed rotational driving is provided, the collision sound when a sheet on the intermediate plate abuts against the feeding roller 3 can be reduced, and a sheet feeding apparatus having excellent silence can be provided.
Next, a second exemplary embodiment of the invention will be described.
In
Here, in the present exemplary embodiment, the input stage gear 13 has such a relationship that the phase of the meshing end of the small gear 13c and the phase of the meshing start of the large gear 13b coincide with each other. For example, in a case where the module of a gear is 1, the switching phase of the meshing of the large gear 13b and the small gear 13c with the sheet feed tooth-missing stage gear 16 is set after the number of teeth of the large gear 13b is set so as to become an integral multiple of the number of teeth of the small gear 13c.
On the other hand, the tooth-missing large gear 16a and tooth-missing small gear 16c of the sheet feed tooth-missing gear 16 that mesh with the input stage gear 13 also have the same relationship. Moreover, the sheet feed tooth-missing gear 16 is arranged so that the phase of the meshing end of the tooth-missing large gear 16a the phase of the meshing start of the tooth-missing small gear 16c match each other, and switches meshing from the tooth-missing large gear 16a to the tooth-missing small gear 16c.
In this way, in the present exemplary embodiment, the phases and mutual meshing phases of each large gear and each small gear are matched when the meshing between the input stage gear 13 and the sheet feed tooth-missing stage gear 16 is switched. Thereby, if the meshing between the small gear 13c of the input stage gear 13 and the tooth-missing large gear 16a of the sheet feed tooth-missing stage gear 16 ends, the tooth-missing small gear 16c of the sheet feed tooth-missing stage gear 16 can be made to mesh with the large gear 13b of the input stage gear 13. By adopting such a configuration, the switching of meshing between the tooth-missing gear 16a or 16c of the sheet feed tooth-missing stage gear 16 and the gear 13b or 13c of the input stage gear 13 is allowed without using a sheet feed gear spring that has a large spring force.
Next, a third exemplary embodiment of the invention will be described.
In
Here, the cam 21, as illustrated in
Then, if the rotating shaft 6 rotates and the cam 21 rotate, first, as illustrated in
Next, if the cam 21 rotates further, the cam pressing member 25 passes through the deflection point of the second cam face 21b. In this case, the compressive force of the spring 26 is opened, and thereby, the cam 21 is pressed in a direction in which the cam further continues its rotation via the second cam face 21b, and urges the rotation of the rotating shaft 6. Here, the meshing state between the input stage gear 13 and the sheet feed tooth-missing gear 12 at this time is the same as
In addition, in the present exemplary embodiment, when the tooth-missing large gear 12a of the sheet feed tooth-missing stage gear 12 that meshes with the small gear 13c of the input stage gear 13 has ended its meshing, as illustrated in
However, in the present exemplary embodiment, as illustrated in
In this way, in the present exemplary embodiment, after the intermediate plate 9 has ascended, the cams 20 and 21 are rotated by the cam pressing members 25, and the tooth-missing small gear 16c of the sheet feed tooth-missing stage gear 16 is made to mesh with the large gear 13b of the input stage gear 13. Thereby, the tooth-missing small gear 16c of the sheet feed tooth-missing stage gear 16 can be made to mesh with the large gear 13b of the input stage gear 13.
In this way, in the present exemplary embodiment, the cams 20 and 21 are rotated by the cam pressing members 25 after the intermediate plate 9 has ascended. Thereby, if the meshing between the small gear 13c of the input stage gear 13 and the tooth-missing large gear 16a of the sheet feed tooth-missing stage gear 16 ends, the tooth-missing small gear 16c of the sheet feed tooth-missing stage gear 16 can be made to mesh with the large gear 13b of the input stage gear 13. By adopting such a configuration, the switching of meshing between the tooth-missing gear 16a or 16c of the sheet feed tooth-missing stage gear 16 and the gear 13b or 13c of the input stage gear 13 is allowed without using a sheet feed gear spring that has a large spring force.
The present invention is also realized by execution of the following process. That is a process in which software (program) for realizing the functions of the embodiment is supplied to a system or an apparatus through a network or various storage media, and a computer (or CPU or MPU) of the system or the apparatus reads and executes the program.
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. 2012-086032, filed Apr. 5, 2012, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-086032 | Apr 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/060417 | 3/29/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/151149 | 10/10/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4717139 | Sootome et al. | Jan 1988 | A |
| 5358230 | Ikemori et al. | Oct 1994 | A |
| 5621451 | Sugiura et al. | Apr 1997 | A |
| 5907745 | Azuma et al. | May 1999 | A |
| 6070867 | Tsurumi et al. | Jun 2000 | A |
| 6308947 | Kojima et al. | Oct 2001 | B1 |
| 6502816 | Inoue et al. | Jan 2003 | B2 |
| 8210528 | Yamaguchi | Jul 2012 | B2 |
| 8439349 | Matsumoto et al. | May 2013 | B2 |
| 8550455 | Yamaguchi | Oct 2013 | B2 |
| 8684346 | Yamazaki et al. | Apr 2014 | B2 |
| 8720886 | Kuroda et al. | May 2014 | B2 |
| 8870182 | Ogata et al. | Oct 2014 | B2 |
| 20080169599 | Lam et al. | Jul 2008 | A1 |
| 20090008868 | Kuroda | Jan 2009 | A1 |
| 20130216291 | Fukusaka et al. | Aug 2013 | A1 |
| 20140047935 | Gaarder et al. | Feb 2014 | A1 |
| Number | Date | Country |
|---|---|---|
| 03102019 | Apr 1991 | JP |
| 10153247 | Jun 1998 | JP |
| 2000118768 | Apr 2000 | JP |
| 2001097579 | Apr 2001 | JP |
| 2002167062 | Jun 2002 | JP |
| 2004083167 | Mar 2004 | JP |
| Entry |
|---|
| International Search Report issued in International Application No. PCT/JP2013/060417 dated Jul. 9, 2013. |
| International Search Report issued in counterpart International Application No. PCT/JP2013/060417, dated Oct. 16, 2014. |
| Number | Date | Country | |
|---|---|---|---|
| 20150042033 A1 | Feb 2015 | US |
