Sheet feeding device and image forming apparatus incorporating the sheet feeding device

A sheet feeding device, which is included in an image forming apparatus, includes a sheet container to accommodate a recording medium, a sheet feeding body to press a surface of the recording medium in the sheet container and feed the recording medium in a sheet conveying direction, a pair of sheet position regulators to regulate a position of the recording medium in a sheet width direction perpendicular to the sheet conveying direction, and a load applier to contact the surface of the recording medium and apply a load to the recording medium at the surface. The recording medium is brought to move toward one of the pair of sheet position regulators while the recording medium is being fed. A lower face position in a standby state of the sheet feeding body is lower than a lower face position in a standby state of the load applier.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2015-252625, filed on Dec. 24, 2015, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

BACKGROUND

Technical Field

This disclosure relates to a sheet feeding device and an image forming apparatus incorporating the sheet feeding device.

Related Art

Various types of electrophotographic image forming apparatus are known to include a sheet feeding device to feed a sheet one by one from a sheet container that accommodates multiple sheets therein to an image forming apparatus or to an image forming device.

For example, such a sheet feeding device includes a load applying member disposed between a sheet regulating member and a sheet conveying member in a sheet width direction of a sheet container. The load applying member is pressed against a surface of a sheet that functions as a recording medium to apply a predetermined load to the sheet.

When the sheet is conveyed, the load applying member applies a load such that a moment of rotation exerted by the sheet conveying member to the sheet and a moment of rotation exerted by the load applying member to the sheet are evenly balanced. According to this configuration, the skew of the sheet conveyed from the sheet container is reduced.

For example, conveying forces of the sheet conveying member become uneven affected by installation environment of the sheet conveying device and the image forming apparatus. At that time, the degree of the moment of rotation exerted by the sheet conveying member to the sheet changes. Consequently, the moment of rotation that is exerted by the sheet conveying member to be applied to the sheet and the moment of rotation that is exerted by the load member to be applied to the sheet may not be proportional, in other words, become imbalance. As a result, the skew of the sheet conveyed from the sheet container occurs.

SUMMARY

At least one aspect of this disclosure provides a sheet feeding device including a sheet container, a sheet feeding body, a pair of sheet position regulators, and a load applier. The sheet container accommodates a recording medium. The sheet feeding body presses a surface of the recording medium in the sheet container and feed the recording medium in a sheet conveying direction. The pair of sheet position regulators includes a first sheet position regulator and a second sheet position regulator disposed facing each other across the recording medium in the sheet container in a sheet width direction perpendicular to the sheet conveying direction. The pair of sheet position regulators regulates a position of the recording medium in the sheet width direction. The load applier is disposed between the first sheet position regulator and the sheet feeding body in the sheet width direction. The load applier contacts the surface of the recording medium and apply a load to the recording medium at the surface. The recording medium is brought to move toward the second sheet position regulator while the recording medium is being fed.

Further, at least one aspect of this disclosure provides an image forming apparatus including an image forming device to form an image on a recording medium, and the above-described sheet feeding device to feed recording medium contained in the sheet container toward the image forming device.

Further, at least one aspect of this disclosure provides a sheet feeding device including a sheet container, a sheet feeding body, a pair of sheet position regulators, and a load applier. The sheet container accommodates a recording medium. The sheet feeding body presses a surface of the recording medium in the sheet container and feed the recording medium in a sheet conveying direction. The pair of sheet position regulators includes a first sheet position regulator and a second sheet position regulator disposed facing each other across the recording medium in the sheet container in a sheet width direction perpendicular to the sheet conveying direction. The pair of sheet position regulators regulates a position of the recording medium in the sheet width direction. The load applier is disposed between the first sheet position regulator and the sheet feeding body in the sheet width direction. The load applier contacts the surface of the recording medium and apply a load to the recording medium at the surface. A lower face position in a standby state of the sheet feeding body is lower than a lower face position in a standby state of the load applier.

Further, at least one aspect of this disclosure provides an image forming apparatus including an image forming device to form an image on a recording medium, and the above-described sheet feeding device to feed recording medium contained in the sheet container toward the image forming device.

DETAILED DESCRIPTION

Descriptions are given, with reference to the accompanying drawings, of examples, exemplary embodiments, modification of exemplary embodiments, etc., of an image forming apparatus according to exemplary embodiments of this disclosure. Elements having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted. Elements that do not demand descriptions may be omitted from the drawings as a matter of convenience. Reference numerals of elements extracted from the patent publications are in parentheses so as to be distinguished from those of exemplary embodiments of this disclosure.

This disclosure is applicable to any image forming apparatus, and is implemented in the most effective manner in an electrophotographic image forming apparatus.

In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes any and all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of this disclosure are described.

A description is given of an image forming apparatus100according to an embodiment of this disclosure, configured to form an image on a recording medium that functions as a sheet.

FIG. 1is a schematic diagram illustrating the image forming apparatus100according to the present embodiment of this disclosure.

It is to be noted that identical parts are given identical reference numerals and redundant descriptions are summarized or omitted accordingly.

The image forming apparatus100may be a copier, a facsimile machine, a printer, a multifunction peripheral or a multifunction printer (MFP) having at least one of copying, printing, scanning, facsimile, and plotter functions, or the like. According to the present example, the image forming apparatus100is an electrophotographic copier that forms toner images on recording media by electrophotography.

It is to be noted in the following examples that: the term “image forming apparatus” indicates an apparatus in which an image is formed on a recording medium such as paper, OHP (overhead projector) transparencies, OHP film sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, and/or ceramic by attracting developer or ink thereto; the term “image formation” indicates an action for providing (i.e., printing) not only an image having meanings such as texts and figures on a recording medium but also an image having no meaning such as patterns on a recording medium; and the term “sheet” is not limited to indicate a paper material but also includes the above-described plastic material (e.g., a OHP sheet), a fabric sheet and so forth, and is used to which the developer or ink is attracted. In addition, the “sheet” is not limited to a flexible sheet but is applicable to a rigid plate-shaped sheet and a relatively thick sheet.

Further, size (dimension), material, shape, and relative positions used to describe each of the components and units are examples, and the scope of this disclosure is not limited thereto unless otherwise specified.

Further, it is to be noted in the following examples that: the term “sheet conveying direction” indicates a direction in which a recording medium travels from an upstream side of a sheet conveying path to a downstream side thereof; the term “width direction” indicates a direction basically perpendicular to the sheet conveying direction.

Now, a description is given of an entire configuration and functions of the image forming apparatus100according to an embodiment of this disclosure.

As illustrated inFIG. 1, the image forming apparatus100has printing and copying functions for forming a full color image with four color toners such as yellow (Y), cyan (C), magenta (M), and black (K).

As illustrated inFIG. 1, the image forming apparatus100includes four image forming units101Y,101M,101C, and101K. The image forming units101Y,101M,101C, and101K that form respective single color images are aligned at an upper part of an apparatus body of the image forming apparatus100. The image forming units101Y,101M,101C, and101K have a substantially identical configuration and functions to each other. Therefore, following details of the image forming units101Y,101M,101C, and101K are described with a single image forming unit that corresponds to each of the image forming units101Y,101M,101C, and101K, without the suffixes Y, M, C, and K indicating respective colors. The image forming unit101(i.e., the image forming units101Y,101M,101C, and101K) includes a photoconductor drum102(i.e., photoconductor drums102Y,102M,102C, and102K), a charger103(i.e., chargers103Y,103M,103C, and103K), and a cleaning device105(i.e., cleaning devices105Y,105M,105C, and105K). The charger103, the developing device104, and the cleaning device105are disposed around the photoconductor drum102.

Further, an exposure device107is disposed above the photoconductor drum102.

An intermediate transfer belt108is disposed below the image forming units101Y,101M,101C, and101K. The intermediate transfer belt108is wound around multiple support rollers.

As one of the multiple support rollers is driven by a drive unit, the intermediate transfer belt108is rotated in a direction indicated by arrow A inFIG. 1.

A transfer roller106(i.e., transfer rollers106Y,106M,106C, and106K) that functions as a primary transfer unit is disposed facing the photoconductor drum102of the image forming unit101with the intermediate transfer belt108interposed therebetween. When the transfer roller106and the photoconductor drum102contact with the intermediate transfer belt108interposed therebetween, a primary transfer portion is formed to primarily transfer the toner image onto the photoconductor drum102.

In the image forming unit101, the photoconductor drum102is rotated in a counterclockwise direction inFIG. 1. Then, the charger103uniformly charges a surface of the photoconductor drum102to a predetermined polarity. Then, an optically modulated laser light beam is emitted from the exposure device107, so that an electrostatic latent image is formed on the charged surface of the photoconductor drum102. The electrostatic latent image is developed with toner applied by the developing device104into a visible toner image. The visible toner images of respective single colors formed by the image forming units101Y,101M,101C, and101K are sequentially transferred in layers onto a surface of the intermediate transfer belt108.

By contrast, a sheet feeding device114is disposed below the apparatus body of the image forming apparatus100. The sheet feeding device114includes a tandem sheet tray114aand a sheet tray114band feeds out a sheet. The fed sheet is conveyed to a pair of registration rollers111in a direction indicated by arrow B inFIG. 1.

The sheet contacted and temporarily stopped at the pair of registration rollers111is fed out from the pair of registration rollers111in synchronization with movement of the toner image formed on the surface of the intermediate transfer belt108. Then, the sheet is conveyed to a secondary transfer portion where a secondary transfer roller109contacts the intermediate transfer belt108. A voltage having an opposite polarity to a toner charge polarity is applied to the secondary transfer roller109. By so doing, the composite toner image (the full color image) formed on the surface of the intermediate transfer belt108is transferred onto the sheet.

After the toner image has been transferred thereto, the sheet is conveyed by a sheet conveying belt112to a fixing device113. In the fixing device113, the toner image is fixed to the sheet by application of heat and pressure.

After the toner image is fixed thereto, the sheet is ejected out of the apparatus body of the image forming apparatus100as indicated by arrow C inFIG. 1onto a sheet ejection tray.

It is to be noted that, when the sheet is ejected with the back of the sheet facing up in the single-side printing (a face down ejection), the sides of the sheet are reversed by ejecting the sheet outside the apparatus body of the image forming apparatus100as indicated by arrow C inFIG. 1via a sheet reverse portion115.

Further, in the duplex printing, the sheet after the toner image has been fixed thereto is conveyed via a duplex reverse portion116from a reentry path117to the pair of registration rollers111again. By so doing, a toner image formed on the surface of the intermediate transfer belt108is transferred onto the back of the sheet.

After the toner image has been transferred onto the sheet, the toner image is fixed to the sheet in the fixing device113. Then, similar to the single-side printing, the sheet is ejected out in the direction C inFIG. 1directly from the fixing device115or via the sheet reverse portion115. In addition, switching claws118and119are disposed appropriately to switch a sheet feeding direction.

In a case of a monochrome printing, the image forming apparatus100according to the present embodiment uses the image forming unit101K to form a monochrome toner image and transfers the monochrome toner image onto a sheet via the intermediate transfer belt108. A sheet having a monochrome toner image thereon is handled along the same process as a sheet having a full color toner image after the toner image is fixed to the sheet.

It is to be noted that the image forming apparatus100further includes a toner bottle set120on an upper face of the apparatus body. The toner bottle set120sets respective color toner bottles121(i.e., toner bottles121Y,121M,121C, and121K) that contains toner to be supplied to the developing device104of the image forming unit101.

Further, the image forming apparatus100further includes an operation unit124that includes a display122and a control panel123.

In addition, the image forming apparatus100further includes a bypass tray opening125and a pair of bypass rollers126. A sheet loaded on a bypass tray is guided into the apparatus body of the image forming apparatus100through the bypass tray opening125in a direction indicated by arrow D and fed by the pair of bypass rollers126toward the pair of registration rollers111.

FIG. 2is a cross sectional view illustrating the tandem sheet tray114a.

As illustrated inFIG. 2, the tandem sheet tray114aincludes a sheet feed tray1that functions as a first sheet container and a sheet supply tray2that functions as a second sheet container.

The sheet feed tray1includes a bottom plate3that can be lifted and lowered. The sheet feed tray1further includes a sheet pickup roller4that functions as a sheet feeding unit, a sheet reverse roller5, and a sheet feed roller6. The sheet pickup roller4closely contacts an uppermost sheet placed on top of the bundle of sheets loaded on the bottom plate3, and feeds the sheet toward a sheet separation nip region where the sheet feed roller6and the sheet reverse roller5contact each other. The sheet fed toward the sheet separation nip region is separated from the sheet feed roller6and the sheet reverse roller5. Then, the uppermost sheet is conveyed toward the pair of registration rollers111.

Further, the sheet feed tray1is mounted with a pair of side fences7aand7bto regulate a position in a sheet width position of the bundle of sheets on the bottom plate3. Each two supports are disposed projecting in the sheet width direction from both ends of the bottom plate3in the sheet width direction. The supports go through respective guide openings701. Each two guide openings701extend in a vertical direction and are provided to each of the pair of side fences7aand7b.

The sheet supply tray2that functions as a second sheet container is disposed substantially horizontal along with the sheet feed tray1. The sheet supply tray2is also removably inserted to the apparatus body of the image forming apparatus100in a direction substantially perpendicular to the sheet feeding direction. The sheet supply tray2includes a sheet transfer fence8to shift the bundle of sheets loaded on the sheet supply tray2altogether to the sheet feed tray1.

FIG. 3is a diagram illustrating a sheet feeding state of the tandem sheet tray114aofFIG. 2.

As illustrated inFIG. 3, the sheet feed tray1accommodates a sheet bundle P2and the sheet supply tray2accommodates a sheet bundle P1. In the present embodiment, the sheet feed tray1and the sheet supply tray2can contain approximately 500 sheets such as A4-size sheets, respectively. It is to be noted that, if the tandem sheet tray114ahas a larger capacity, the sheet feed tray1can accommodate approximately 1250 sheets.

In the above-described sheet feeding state, the sheet transfer fence8is located at a home position. As a loader elevation device lifts the bottom plate3, the sheet pickup roller4is brought to contact and press an uppermost sheet placed on top of the sheet bundle P2loaded on the bottom plate3. By driving the sheet pickup roller4, the uppermost sheet of the sheet bundle P2is fed in the direction indicated by arrow E inFIG. 3. Then, the sheet feed roller6and the sheet reverse roller5separate the uppermost sheet from the sheet bundle P2, so that the uppermost sheet is conveyed toward the pair of registration rollers111. Then, when it is detected that no sheet is left on the bottom plate3, the loader elevation device lowers the bottom plate3to the lowest position. Consequently, the sheet transfer fence8that is located at the home position moves toward the sheet feed tray1, so that the sheet transfer fence8shifts the sheet bundle P1loaded on the sheet supply tray2to the sheet feed tray1. Then, the sheet bundle P1is shifted to the sheet feed tray1and the sheet transfer fence8has arrived at a transfer complete position, the sheet transfer fence8shifts backwardly or retreats toward the home position.

When no sheets are left on the sheet feed tray1, the pair of side fences7aand7bof the sheet feed tray1transfers a sheet bundle loaded on the sheet supply tray2to the sheet feed tray1automatically. Therefore, it is difficult to adjust the pair of side fences7aand7bmanually before the sheet bundle is transferred to the sheet feed tray1. In order to address this inconvenience, a motor is caused to move the pair of side fences7aand7bautomatically or the pair of side fences7aand7bis fixed to a predetermined position. A sheet bundle set in the sheet supply tray2may be different in width from another sheet bundles to cutting position error at sheet production. In a case in which a motor is driven to move the pair of side fences7aand7bautomatically, when the sheet bundle P1in the sheet supply tray2is transferred to the sheet feed tray1, the pair of side fences7aand7bis retreated to a retreating position where the side fence7aand the side fence7bseparate from each other to the maximum. Therefore, even if the width of the sheet bundle P2in the sheet feed tray1is different from the width of another sheet bundle P1in the sheet supply tray, the sheet bundle P1can be transferred from the sheet supply tray2to the sheet feed tray1without being caught by the pair of side fences7aand7b. However, in this case, a moving mechanism to move the motor and the pair of side fences7aand7bis provided, and therefore it is likely that an increase in cost of an image forming apparatus due to an increase in the number of parts and an increase in size of the image forming apparatus.

In a comparative sheet feeding device, however, when conveying forces of a sheet feeding member become uneven due to installation environment of the comparative sheet feeding device and an image forming apparatus including the comparative sheet feeding device, the degree of a moment of rotation exerted by the sheet feeding member to the sheet changes. As a result, the moment of rotation exerted by the sheet feeding member to the sheet and the moment of rotation exerted by the load applying member to the sheet become imbalance. Consequently, the skew of the sheet fed from a sheet container cannot be prevented.

For the above-described reasons, the present embodiment provides the pair of side fences7aand7bsecured at a predetermined position. Accordingly, when compared to a configuration in which a motor is driven to move the pair of side fences such as the pair of side fences7aand7b, the configuration of the present embodiment can reduce the number of parts, and therefore can reduce the cost and size of the image forming apparatus100. However, if the side fences7aand7bare secured to respective positions corresponding to a predetermined width of sheet, when the width of the sheet P is greater than the predetermined width, it is likely that the sheet bundle is caught by the side fence7aor the side fence7bto cause the transfer failure of the sheet bundle. Accordingly, a distance between the side fence7aand the side fence7bis set to be greater than the predetermined width. However, in this case, if the width of a set sheet bundle is equal to or smaller than the predetermined width, the pair of side fences7aand7bcannot regulate the sheet P within the sheet width direction, and therefore the position in the width direction of the sheet to be transferred varies. As a result, the image forming position to the sheet also varies.

In the present embodiment, a pressing member is provided to the side fence7ato press the sheet bundle loaded on the sheet feed tray1against the side fence7bso as to regulate the sheet bundle in the width direction.

FIG. 4Ais a plan view illustrating the tandem sheet tray114ain a state in which the bottom plate3is at the lowest position.FIG. 4Bis a side view illustrating the tandem sheet tray114aofFIG. 4A.FIG. 5Ais a plan view illustrating the tandem sheet tray114ain a state in which the bottom plate3is elevated by the loader elevation device.FIG. 5Bis a side view illustrating the tandem sheet tray114aofFIG. 5A.

The sheet supply tray2includes a sheet transfer fence8, a pair of side fences10including side fences10aand10b, and the sheet bundle P1. The bottom plate3that can load the sheet bundle P1on the sheet feed tray1can be elevated and lowered by the loader elevation device. The sheet P elevated by the bottom plate3is conveyed by the sheet pickup roller4, the sheet reverse roller5, and the sheet feed roller6.

A pressing member9is attached to the side fence7a, which is one of the pair of side fences7(that is,7aand7b) that regulates a side end of the sheet P placed in the sheet feed tray1. A pressure point at which the pressing member9presses the sheet P is located higher than a sheet full level of the sheet supply tray2. As illustrated inFIGS. 5A and 5B, as the bottom plate3is elevated, the pressing member9presses the edge of the sheet. By so doing, a gap X between the sheet and the side fence7b, which is the other of the pair of side fences7(that is,7aand7b), can be reduced.

FIG. 6is a diagram illustrating the sheet feed tray1, viewed from the upstream side in the sheet feeding direction.

The pressing member9is biased by a pressure spring99. When the pressing member9presses the sheet bundle P2at an edge face in the sheet width direction perpendicular to the sheet feeding direction, a gap between the side fence7aand the side fence7bcan be reduced. The pressing member9has a sloped face facing the edge of a sheet such as the sheet P, and a lower end portion of the pressing member9is not protruded from the side fence7a. Therefore, the loader elevation device can elevate the bottom plate3without the sheet P being caught by the lower end portion of the pressing member9. Accordingly, in a case in which the bottom plate3is lifted while the sheet bundle P2is sliding along the side fence7a, in other words, in a case in which a sheet bundle is loaded at any position in the sheet feed tray1, the sheet P is not caught by the lower end portion of the pressing member9while the bottom plate3is being lifted and the position of the edge of the sheets in the sheet bundle can be aligned during the sheet feeding of the tandem sheet tray114a.

When compared with a case in which the whole sheet P is pressed by the pressing member9, when an upper end portion of the sheet bundle P2is pressed by the pressing member9, a pressing force to align the sheet P can be reduced. Accordingly, even when the number of sheets loaded on the bottom plate3becomes small, occurrence of buckling of the sheet P caused by an excessively large pressing force applied by the pressing member9can be reduced.

FIG. 7Ais a top view illustrating the sheet feed tray1related to a position and effect of a load applying member11.FIG. 7Bis a top view illustrating the sheet feed tray1related to another position and effect of the load applying member11.

The sheet pickup roller4is disposed to be located such that a center position of the sheet P in the sheet width direction to be at a center of sheet conveyance. In addition, the load applying member11is disposed near the sheet pickup roller4and between the sheet pickup roller4and the side fence7a. The position of the load applying member11is separated from the center of the sheet P by a distance X2.

It is to be noted that the center of sheet conveyance in the sheet P having a width L is at a position by L/2 from an inner side face of the side fence7bin the sheet width direction of the sheet P.

FIG. 8Ais a diagram illustrating operations of the load applying member11and the sheet pickup roller4when the bottom plate3is at the lowest portion.FIG. 8Bis a diagram illustrating operations of the load applying member11and the sheet pickup roller4at elevation of the bottom plate3.

The bottom plate3with the sheet bundle P is loaded thereon elevates in an upward direction ofFIGS. 8A and 8B. As the bottom plate3is lifted, the sheet bundle P comes to contact the load applying member11and the lower face of the sheet pickup roller4at a standby position. Then, the sheet bundle P is pressed in a direction indicated black arrow by the biasing force.

As illustrated inFIG. 8A, the lower face position of the load applying member11at a standby state is lower than a contact face (that is, the lower face position) of the pickup roller4to contact the sheet P in the standby state. The bottom plate3with the sheet bundle P is loaded thereon elevates in an upward direction ofFIGS. 8A and 8B. As the bottom plate3is lifted, the sheet bundle P comes to contact the load applying member11and the lower face of the sheet pickup roller4at the standby position. Then, the sheet bundle P is pressed in a direction indicated black arrow by the biasing force. As illustrated inFIG. 8A, the lower face position of the load applying member11at the standby state is lower than a contact face (that is, the lower face position) of the pickup roller4to contact the sheet P at the standby condition.

FIG. 9Ais a perspective view illustrating the sheet feeding device114, mainly a downstream side in the sheet feeding direction.FIG. 9Bis an enlarged perspective view illustrating the sheet feeding114, mainly the downstream side in the sheet feeding direction.

The pickup roller4is rotatably supported by a pickup arm12. The pickup arm12is disposed to rotate about a sheet feed shaft13that pivotally supports the sheet feed roller6. A position detecting sensor14is attached to the sheet feeding device114. The position detecting sensor14reads a position of a sensing portion17of the pickup arm12, so that the bottom plate3is controlled to be located at a constant height.

A position detecting sensor14is attached to the sheet feeding device114. The position detecting sensor14reads a position of a sensing portion17of the pickup arm12, so that the bottom plate3is controlled to be located at a constant height. As an example of the control, the position detecting sensor14turns off when the sheet pickup roller4is in a standby state. When the bottom plate3is lifted, the pickup arm12contacts the uppermost sheet of the sheet bundle P. Then, when an amount of pressure applied by the pickup arm12reaches a predetermined amount, the position detecting sensor14turns on, and then the bottom plate3is stopped. As the height of the uppermost sheet of the sheet bundle P becomes lower during a serial sheet feeding, the pickup arm12gradually rotates. When the position detecting sensor14turns off, the bottom plate3is lifted again. (When the position detecting sensor14turns on, the bottom plate3is stopped again.) At this time, the position of the sheet pickup roller4is controlled to be higher than the position in the standby state. Therefore, the serial sheet feeding can be performed. Further, the height of the sheet pickup roller4in the standby state is set to be lower than the height of the load applying member11in the standby state. Accordingly, the load applying member11contacts and presses the uppermost sheet of the sheet bundle P reliably without whiffing and failing to contact the uppermost sheet.

As illustrated inFIGS. 7A and 7B, the sheet pickup roller4is disposed between the side fence7aand the load applying member11. At the same time, the side fence7bis disposed facing the side fence7ato substantially align the center of sheet conveyance that is the center of axial direction of the sheet pickup roller4and the sheet center position that is the center in the sheet width direction of the sheet P. It is to be noted that an absolute reference conveyance position in the sheet width direction of the sheet P that is to be fed by the sheet pickup roller4corresponds to the position of the inner side face of the side fence7b.

When the sheet P is conveyed in a direction indicated by black arrow inFIGS. 7A and 7B, a moment of rotation “m” and a moment of rotation “M” are applied to the sheet P along with a distance X1, the distance X2, a pressing force of the sheet pickup roller4, and a pressing force of the load applying member11. The moment of rotation “m” is a force that is exerted by the sheet pickup roller4at the sheet pickup roller4as the center of rotation. The moment of rotation “M” is a force that is exerted by the sheet pickup roller4at the load applying member11as the center of rotation. The distance X1is a distance between the sheet center position and the center of sheet conveyance. The distance X2is a distance between the sheet center position and the center of the load applying member11.

Here, by setting to meet a relation of the moment of rotation “m”<the moment of rotation “M”, the sheet P can be rotated in a direction in which the trailing end of the sheet P is shifted toward the side fence7b. With the rotation of the sheet P, a gap X3is reduced. Consequently, the position of the edge in the sheet width direction of the sheet P can be accurately aligned on the basis of the side fence7b.

It is to be noted that, even when the position of the sheet pickup roller4is shifted from the center of sheet conveyance toward the side fence7adue to installation error, a sufficient amount of moment of rotation “M” is applied to the sheet P. Therefore, the sheet P can be rotated in the direction in which the trailing end of the sheet P is shifted toward the side fence7breliably. In addition, the load applying member11in the sheet feeding direction can be located at any position as long as a load applied from the side fence7ais applied at the center of rotation to rotate the sheet P.

Further, the sheet pickup roller4is disposed at a position substantially the center in the sheet width direction, so as to reduce the moment of rotation “m”. By so doing, even when the moment of rotation “M” is reduced, the above-described relation of the moment of rotation “m” and the moment of rotation “M” (m<M) can be maintained easily. As an example of setting the sheet pickup roller4at a substantially center position in the sheet width direction, the pair of side fences7has a configuration of rack and pinion gears, for example, to open and close in conjunction with each other so as to match the center of sheet conveyance and the sheet center position. In addition, even when stabilized papers or thin papers are used under a high temperature high humidity environment, the moment of rotation “M” is preferably kept small in order to restrain occurrence of damage to the sheet P.

FIG. 10Ais a top view illustrating the sheet feed tray1with the pressing member9to the side fence7aand a regulating member15to the side fence7bwith a gap.FIG. 10Bis a top view illustrating the sheet feed tray1with the pressing member9to the side fence7aand the regulating member15to the side fence7bwith another gap.

As previously illustrated inFIG. 6, the pressing member9presses the upper end of the sheet bundle P2so that the side edge of the sheet P can be aligned to the side fence7b. The regulating member15is attached to the side fence7a. When the sheet P is held between the pressing member9and the regulating member15at the downstream side of the sheet feeding direction, the side edge of the sheet P in the sheet width direction can be aligned along the side fence7bwith a rotational force applied by the load applying member11highly accurately. Consequently, occurrence of a gap X4between the side fence7band the sheet P can be reduced.

The regulating member15includes a material of metal or polyacetal (POM) resin, and therefore provides a good sliding performance. Accordingly, a sheet conveyance load of the sheet P can be reduced. Further, in the present embodiment, the regulating member15is provided as a separate part to be attached to the side fence7b. However, the regulating member15can be replaced to a regulating portion that is a projection formed on a part of the side fence7b. Consequently, the number of parts included in the pair of side fences7can be reduced. In addition, a sheet metal can function as a regulating member to be attached on a side face of the side fence7bfacing the sheet P. By so doing, the whole area of the side face of the side fence7bfacing the sheet P can function as a regulating member. Accordingly, the side face of the side fence7bfacing the sheet P can restrain wear generated due to sliding with the sheet P.

FIG. 11Ais a top view illustrating the sheet feed tray1with the pressing member9and the regulating member15are located at an approximately identical position to each other in the sheet feeding direction.FIG. 11Bis a top view illustrating the sheet feed tray1with the pressing member9and the regulating member15are located at an approximately identical position to each other in the sheet feeding direction, different fromFIG. 11A.

Further, as illustrated inFIG. 11A, the pressing member9and the regulating member15are disposed at a substantially identical position in the sheet feeding direction, as indicated by dotted lines. By so doing, the center of rotation of the sheet P is stabilized, and therefore highly accurate image forming position can be expected.

Further, as illustrated inFIG. 11B, the respective positions of the pressing member9and the regulating member15in the sheet feeding direction may be located to be substantially identical to the sheet pickup roller4and the load applying member11. By so doing, calculation of moments such as the moment of rotation “m” and the moment of rotation “M” can be performed easily.

By contrast, as illustrated inFIG. 11A, it is preferable that the pressing member9and the regulating member15are located at a relatively downstream side of the sheet feeding direction, so that the position of the edge of the sheet P becomes stable at an exit of the sheet feed tray1.

In Embodiment 2, the level of a load applied by the load applying member11to the sheet P is changeable.

FIG. 12is a diagram illustrating a configuration with the load applying member11to apply a load to the sheet P during sheet conveyance, so that the sheet P is aligned to the side fence7bby the moment of rotation “M” applied by the load applying member11.

InFIG. 12, the side fence7bis a reference member in the sheet width direction, which is a direction perpendicular to the sheet feeding direction. By applying a load of a force F by the pressing member9to the end face of the sheet P in the sheet width direction, a gap between the side fence7aand the side fence7bis reduced at the leading end of the sheet P.

Further, as the load applying member11applies the moment of rotation “M” to the sheet P, a gap between the side fence7aand the side fence7bis reduced at the trailing end of the sheet P.

Accordingly, even when the sheet P is set on the sheet feed tray1with a gap relative to the side fence7b, the sheet P can be aligned at the side fence7bthat is a reference member in the sheet width direction. Therefore, the sheet P can be fed without skew.

The load applying member11applies not only the moment of rotation “M” to the sheet P but also a load in a sheet loading direction, which is a vertical direction or a height direction of the sheet bundle P. When the load applied to the sheet loading direction is excessively large, an amount of adhesion between adjacent sheets increases, resulting in misfeeding and generation of creases in sheets due to excess moment.

By contrast, when the load applied to the sheet loading direction is relatively small, the amount of moment becomes short, and therefore the sheet P cannot be aligned to the side fence7b.

The adhesion between adjacent sheets depends on sheet size, sheet thickness, and environment, it is preferable that the load applied by the load applying member11can be changed according to sheet size, sheet thickness, and environment.

Further, when misfeeding due to the adhesion between adjacent sheets is considered, it is preferable that the load applied by the load applying member11is smaller. Therefore, in order to provide a sufficient moment of rotation “M” with a small load, it is preferable that the load applying member11is disposed at a position separated from the center of the sheet P. Specifically, as the sheet size increases, the sufficient moment of rotation “M” also increases. Therefore, it is preferable that a loading position at which the load applying member11applies a load to the sheet P can be changed.

As illustrated inFIG. 12, part of a lower face of the load applying member11is supported by a housing130of the sheet feeding device114. As the bottom plate3elevates, the load applying member11is lifted in an upward direction. According to this operation, a body weight of the load applying member11is added as a load to the sheet P.

The load applying member11is not fixed to the housing130, and therefore can be removed easily. Since multiple load applying members11having different weights are constantly prepared, any one of the multiple load applying members11can be selected and replaced. By so doing, a load can be changed to be applicable to sheet size, sheet thickness, sheet type, and environment.

Further, in an image forming apparatus in which unspecified users use various types of sheets P, the load applying member11may not be installed in the housing130at factory shipping, so that the load applying member11can be added accordingly after the shipping.

It is to be noted that the above-described load applying method by the load applying member11to the sheet P uses the own weight of the load applying member11. However, the load applying method is not limited thereto. Specifically, a spring may be employed to function as a biasing member to bias the load applying member11to the sheet P. That is, by applying a biasing force by the spring to the load applying member11, the load applying member11can apply a load to the sheet P. In such a configuration, multiple springs having different spring constants are prepared. According to the sheet size, sheet thickness, sheet type, and environment, an appropriate spring is selected from the multiple springs. By so doing, the load applied by the load applying member11to the sheet P can be changed.

Further, by changing the compression height of the spring, the load applied by the load applying member11to the sheet P can be changed.

FIG. 13is a diagram illustrating a configuration in which a pressure spring24biases the load applying member11.FIG. 14is a diagram illustrating a state in which the compression height of the pressure spring24is changed from the configuration inFIG. 13.

The pressure spring24is mounted on the load applying member11inFIG. 13to bias the load applying member11to the sheet P. By using the biasing force applied by the pressure spring24, the load applying member11applies a load to the sheet P. While the load applying member11is provided at one end of the pressure spring24, a seat23is provided at the other end of the pressure spring24. The position of the seat23can be changed by a cam21that rotates about a rotation center shaft22. For example, the cam21has a lever shaped portion. When the lever shaped portion of the cam21is rotated, a cam face of the cam21that contacts the seat23is changed, and the position of the seat23is also changed. Along with these changes related to the cam21and the seat23, the compression height of the pressure spring24changes. Consequently, according to the compression height of the pressure spring24, the biasing force of the load applying member11applied by the pressure spring24changes. As a result, the level of load applied by the load applying member11to the sheet P can be changed.

Further, change of the shape of the cam21can adjust the compression height of the pressure spring24to a target load.

Further, instead of the cam21, an attachment opening can be formed on the housing130, so that the seat23can be installed and removed through the attachment opening. With this configuration, a load applied by the load applying member11to the sheet P can be changed.

FIG. 15is a perspective view illustrating the sheet feeding device114provided with the load applying member11.FIG. 16is a diagram illustrating a state in which a weight load of a weight26is not applied to the load applying member11.FIG. 17is a diagram illustrating a state in which the weight load of the weight26is applied to the load applying member11.

In the configurations ofFIGS. 16 and 17, the level of load applied by the load applying member11to the sheet P can be changed with the weight26. The load applying member11illustrated inFIGS. 16 and 17includes a weight.

InFIG. 16, the weight26that is different from the load applying member11is held on a lever25that is slidable along rail grooves provided to the housing130. In the state illustrated inFIG. 16, the weight load of the weight26is not applied to the load applying member11. As the lever25is slid as illustrated inFIG. 17, the lever25is released from holding the weight26. As a result, the weight26is placed on the upper face of the load applying member11, and therefore the weight load of the weight26is applied to the load applying member11. By slidably placing and removing the lever25, application of the weight load of the weight26to the load applying member11is switched. Accordingly, the level of load applied by the load applying member11to the sheet P can be changed.

FIG. 18Ais a diagram illustrating a state in which the pickup arm12is located at a lowered position.FIG. 18Bis a diagram illustrating a state in which the pickup arm12is located at a lifted position.

In Embodiment 3, when the pickup arm12is lifted, the load applying member11is lifted together with the pickup arm12, thereby releasing the load applied by the load applying member11to the sheet P.

A pickup arm link member16is attached to an upper part of the load applying member11. The pickup arm link member16contacts to and separates from the pickup arm12along with lifting and lowering of the pickup arm12. As illustrated inFIG. 18A, when the sheet pickup roller4is in contact with the sheet P, that is, when the pickup arm12is located at the lowered position, the pickup arm12and the pickup arm link member16are separated and are not in contact with each other, and therefore the load applying member11applies a load to the sheet P. By contrast, as illustrated inFIG. 18B, when the sheet pickup roller4is separated from the sheet P, that is, when the pickup arm12is located at the lifted position, the pickup arm link member16moves upwardly together with the movement of the pickup arm12. With this operation, the pickup arm link member16is lifted by the pickup arm12from below. Therefore, the load applying member11to which the pickup arm link member16is attached is separated from the sheet P, thereby not applying a load to the sheet P.

As described above, in the present embodiment, the load applying member11contacts and separates the sheet P along with the lifting and lowering of the pickup arm12. Consequently, as illustrated inFIG. 18A, when the pickup arm12is located at the lowered position and the sheet pickup roller4contacts the sheet P to perform a sheet feeding operation, the load applying member11applies a load to the sheet P, so that the sheet P is aligned to the side fence7bby the moment of rotation “M”. Further, as illustrated inFIG. 18B, when the pickup arm12is located at the lifted position and the sheet pickup roller4stops the sheet feeding operation, the load applying member11does not apply a load to the sheet P, so that the moment of rotation “M” is not applied to the sheet P. Accordingly, by applying a load applied by the load applying member11and the moment of rotation “M” to the sheet P for a relatively long period of time during sheet conveyance, occurrence of wrinkles and gloss streaks in the sheet P can be restrained.

In the present embodiment, as illustrated inFIG. 19, a sheet feed sensor18is disposed in the sheet conveying passage and near and downstream from the sheet reverse roller5and the sheet feed roller6in the sheet feeding direction. Further, a sheet conveyance sensor19is disposed downstream from the sheet feed sensor18in the sheet feeding direction. As illustrated inFIG. 20, the lifting and lowering of the pickup arm12is controlled according to detection timings of the leading end of the sheet P by the sheet feed sensor18and the sheet conveyance sensor19.

FIG. 20is a timing chart of liftings and lowerings of the pickup arm12.

In the timing chart ofFIG. 20, “Pattern1(Separation Enhanced)” indicates a step in which, when the sheet feed sensor18detects the leading end of the sheet P, the pickup arm12located at the lowered position is lifted to the lifted position. This step is indicated as (1) in the timing chart ofFIG. 20.

Then, when the sheet conveyance sensor19detects the leading end of the sheet P, the pickup arm12located at the lifted position is lowered to the lowered position. This step is indicated as (2) in the timing chart ofFIG. 20.

Then, on arrival of the trailing end of the sheet P at a position 15 mm before the sheet pickup roller4in the sheet feeding direction, the pickup arm12located at the lowered position is lifted to the lifted position. This step is indicated as (3) in the timing chart ofFIG. 20.

Then, on arrival of the trailing end of the sheet P at a position 10 mm before the sheet feed roller6in the sheet feeding direction, the pickup arm12located at the lifted position is lowered to the lowered position. This step is indicated as (4) in the timing chart ofFIG. 20.

It is to be noted that the timing of arrival of the trailing end of the sheet P at the position 15 mm before the sheet pickup roller4in the sheet feeding direction and the timing of arrival of the trailing end of the sheet P at the position 10 mm before the sheet feed roller6in the sheet feeding direction can be grasped based on respective elapsed times from the sheet feed start timing.

In “Pattern2(Conveyance of Small Size/Thick Paper)” in the timing chart ofFIG. 20, the pickup arm12is not lifted or lowered at the timing at which either the sheet feed sensor18or the sheet conveyance sensor19detects the leading end of the sheet P. That is, the pickup arm12remains at the lowered position when the leading end of the sheet P is detected in Pattern2.

Then, on arrival of the trailing end of the sheet P at the position 15 mm before the sheet pickup roller4in the sheet feeding direction, the pickup arm12at the lowered position is lifted to the lifted position.

Thereafter, on arrival of the trailing end of the sheet P at the position 10 mm before the sheet feed roller6in the sheet feeding direction, the pickup arm12at the lifted position is lowered to the lowered position.

In “Pattern3(During Silent Conveyance)” in the timing chart ofFIG. 20, the pickup arm12located at the lowered position is lifted to the lifted position when the sheet feed sensor18detects the leading end of the sheet P.

Then, the pickup arm12is not lifted or lowered at the timing at which the sheet conveyance sensor19detects the leading end of the sheet P or at the timing on arrival of the trailing end of the sheet P at the position 15 mm before the sheet pickup roller4in the sheet feeding direction. That is, the pickup arm12remains at the lifted position when the leading end of the sheet P is detected or the trailing end of the sheet P is arrived at the above-described position in Pattern3.

Then, on arrival of the trailing end of the sheet P at the position 10 mm before the sheet feed roller6in the sheet feeding direction, the pickup arm12at the lifted position is lowered to the lowered position.

FIG. 21is a diagram illustrating an electrical grounding passage from the load applying member11.FIG. 22is a diagram illustrating the load applying member11including a sheet contact portion11aand a pressing portion11b.FIG. 23is a diagram illustrating a configuration of a holder130aprovided to the housing130and the load applying member11.

In Embodiment 4, as illustrated inFIG. 21, an electrical grounding passage is defined by the load applying member11, a leaf spring141that is screwed to a stay142, the stay142, a leaf spring143that is screwed to a side plate144, the side plate144, and a frame145. Electrical charge generated by contact of the load applying member11and the sheet P is grounded through the electrical grounding passage from the load applying member11to the frame145in the above-described order.

The load applying member11illustrated inFIG. 22includes a sheet contact portion11aand a pressing portion11b. The sheet contact portion11aincludes a POM resin material having conductive substance. The pressing portion11bincludes a metallic weight. By including the sheet contact portion11aand the pressing portion11b, the load applying member11has electrical conductivity.

As illustrated inFIG. 23, the load applying member11is held by the holder130aincluded in the housing130.

In Embodiment 4, electrical charge generated by contact of the load applying member11and the sheet P can be electrically grounded through the electrical grounding passage from the load applying member11. According to this configuration, charging by friction generated between the load applying member11and the sheet P can be reduced, and therefore occurrence of abnormal image and multi-feeding caused by biased charges on the surface of the sheet P due to the charging by friction can be restrained.

It is to be noted that the load applying member11may include the sheet contact portion11aand the pressing portion11b, both of which are metallic members. However, the load applying member11in the present embodiment includes the sheet contact portion11ahaving a conductive resin material and the pressing portion11bhaving a metal material. By having different types of materials, the pressing portion11bof metallic material can both apply pressure to the sheet P and conduct electrical grounding and the sheet contact portion11acan maintain a good sliding performance.

FIG. 24is a diagram illustrating a case in which the load applying member11ofFIG. 22has a roller11cmounted on the pressing portion11bto contact an inner wall face of a holder130bof the housing130.

As illustrated inFIG. 24, the load applying member11ofFIG. 22further includes the roller11con the pressing portion11b. The roller11crotatably contacts the inner wall face of the holder130bof the housing130. With the roller11crotating along the inner wall face of the holder130b, the load applying member11can move smoothly.

One side of the holder130bis variable in position. A pressure spring40applies a pressure to the holder130btoward a direction (i.e., a horizontal direction) intersecting a moving direction of the load applying member11(i.e., a vertical direction). By so doing, the holder130bcontacts the roller11cof the load applying member11.

Further, both the roller11cand the holder130binclude metallic materials. By so doing, an electrical grounding passage is defined by the sheet contact portion11aof the load applying member11, the pressing portion11bof the load applying member11, the roller11cof the load applying member11, the holder130b, the stay142, the leaf spring143, the side plate144, and the frame145. Electrical charge generated by contact of the load applying member11and the sheet P is grounded through the electrical grounding passage from the load applying member11to the frame145in the above-described order.

According to this configuration, charging by friction generated between the load applying member11and the sheet P can be reduced without greatly changing the level of load to the pressure applied by the pressing portion11bof the load applying member11.

FIG. 25is a diagram illustrating a configuration having a conductive member extending from a contact portion of the roller11cof the load applying member11and a holder130cto the stay142.

As illustrated inFIG. 25, when the holder130bdoes not include a conductive member, a conductive member41such as a destaticizing cloth and a conductive foil may be attached to (put through) an area from the contact portion of the roller11cof the load applying member11and the holder130cto the stay142. By so doing, an electrical grounding passage is defined by the sheet contact portion11aof the load applying member11, the pressing portion11bof the load applying member11, the roller11cof the load applying member11, the conductive member41, the stay142, the leaf spring143, the side plate144, and the frame145. Electrical charge generated by contact of the load applying member11and the sheet P is grounded through the electrical grounding passage from the load applying member11to the frame145in the above-described order.

FIG. 26is a diagram illustrating a configuration in which a pressure spring42is used as a pressing member to directly press the sheet contact portion11a.

As illustrated inFIG. 26, in a case in which the load applying member11does not include the pressing portion11bincluding a metallic weight that functions as a pressing body to press the load applying member11toward the sheet P, a pressure spring42may be employed as a pressing body. The pressure spring42is a member having conductivity such as a metallic body and directly presses the sheet contact portion11aof the load applying member11.

In this case, the pressure spring42can be employed to an electrical grounding passage. Therefore, the electrical grounding passage in this case is defined by the sheet contact portion11aof the load applying member11, the pressure spring42, the stay142, the leaf spring143, the side plate144, and the frame145. Electrical charge generated by contact of the load applying member11and the sheet P is grounded through the electrical grounding passage from the load applying member11to the frame145in the above-described order.

FIG. 27is a perspective view illustrating the sheet feed tray1according to Embodiment 5 of this disclosure.FIG. 28is a diagram illustrating an example configuration in which a position of the load applying member11is changed in a sheet width direction.

As illustrated inFIG. 28, the housing130of the sheet feeding device114includes multiple supporting portions131a,131b, and131cto locate the load applying member11. The multiple supporting portions131a,131b, and131care provided such that the position of the load applying member11is changed according to a sheet size for a print job to be performed. With this configuration, a sufficient amount of the moment of rotation “M” can be applied to the sheet P with a relatively small weight load. When the sheet P having inappropriate sheet size, sheet thickness, and sheet type is used, inconveniences, such as wrinkles and skews generated by an excess load from the load applying member11and non-contact of the sheet P to the side fence7bcaused by an insufficient load from the load applying member11, can occur.

It is to be noted that the housing130includes the multiple supporting portions131a,131b, and131ccorresponding to respective standard sizes of the sheet P, for example, an A4-size sheet, and therefore respective positions of the multiple supporting portions131a,131b, and131ccorresponding to appropriate sheet sizes are clearly indicated to users of the image forming apparatus100.

FIG. 29is a diagram illustrating another example configuration in which the position of the load applying member11is changed in the sheet width direction. In this configuration, the position of the load applying member11in the sheet width direction can be changed automatically.

The configuration inFIG. 29may be employed to a sheet feeder that can remove the sheet feed tray1and the sheet feeding device114together as a single unit from the apparatus body of the image forming apparatus100or a bypass sheet feeding device including a sheet feeder provided with a sheet loader.

The load applying member11is supported by a rail132mounted on the housing130of the sheet feeding device114. The load applying member11is movable in the sheet width direction along the rail132. The rail132can steplessly switch the position of the load applying member11in the sheet width direction. This stepless switching of the position of the load applying member11can be applied to both a standard sized sheet P and a non-standard size sheet P. Part of the load applying member11is joined to the side fence7a. A joined part of the load applying member11and the side fence7ais movable in the sheet loading direction (i.e., the vertical direction) and the load applying member11is movable in the upward direction. According to this configuration, as the side fence7ais moved in the sheet width direction, the load applying member11is also moved in the sheet width direction. Accordingly, the position of the load applying member11in the sheet width direction can be changed to a loading position appropriate to a sheet size of the sheet P automatically.

In addition, a releasing mechanism may be provided to the image forming apparatus100. Specifically, when the sheet feed tray1is pulled out from the apparatus body of the image forming apparatus100, exceeding a predetermined position, the releasing mechanism releases connection of the side fence7aand the load applying member11at the joined part. Therefore, even in another configuration in which the sheet feed tray1is removed from the apparatus body of the image forming apparatus100while the sheet feeding device114remains in the apparatus body, the position of the load applying member11in the sheet width direction can be changed to the loading position appropriate to the sheet size of the sheet P automatically.

FIG. 30is a diagram illustrating a state in which a supporting member31supports the load applying member11in a circumferential direction.FIG. 31is a diagram illustrating the sheet feed tray1, viewed from above, on which the load applying member11is mounted to rotate about an axis thereof.FIG. 32is a diagram illustrating a state in which the sheet P is rotated by the moment of rotation “M” by receiving a load exerted by the load applying member11that is rotatable about the axis thereof.

In Embodiment 6, as illustrated inFIG. 30, the supporting member31supports the load applying member11in the circumferential direction of the load applying member11.

Further, as illustrated inFIG. 30, the load applying member11moves in the vertical direction to the surface of the sheet P, as indicated by vertical arrow illustrated inFIG. 30. In addition, as illustrated inFIGS. 30 and 31, the load applying member11rotates about a center of rotary axis thereof, as indicated by horizontal arrow illustrated inFIGS. 30 and 31. With this configuration, as illustrated inFIG. 32, when the load applying member11applies a load, the sheet P rotates in a direction indicated by arrow inFIG. 32by the moment of rotation “M” by receiving the load from the load applying member11. Since the load applying member11is rotated with the rotation of the sheet P, a load applied by the load applying member11in a direction perpendicular to the sheet feeding direction can be reduced. Accordingly, a sheet shifting performance of the edge of the sheet P in the sheet width direction to the side fence7bcan be more accurate. Further, wear of the load applying member11caused by friction generated between the load applying member11and the sheet P can be reduced, and therefore the service life of the load applying member11can be extended.

Further,FIG. 33is a diagram illustrating a state in which the load applying member11is press-fitted into a bearing32mounted on the supporting member31.

As illustrated inFIG. 33, the bearing32is mounted on the supporting member31into which the load applying member11is pressed. By so doing, the friction between the load applying member11and the supporting member31in the circumferential direction can be reduced, and therefore wear of the load applying member11can be reduced.

In addition,FIG. 34is a diagram illustrating a state in which the load applying member11having a spherical shape is press-fitted into the bearing32mounted on the supporting member31.

As illustrated inFIG. 34, the load applying member11has a spherical shape. Accordingly, the load applying member11can rotate in the (vertical) direction that is perpendicular to the surface of the sheet P and the sheet feeding direction (indicated by black arrow), and therefore the sheet shifting performance of the edge of the sheet P in the sheet width direction to the side fence7bcan be enhanced. Further, the reduction in level of load in the sheet feeding direction and the direction perpendicular to the sheet feeding direction can reduce wear of the load applying member11due to the friction between the load applying member11and the sheet P. Accordingly, the durability of the load applying member11is enhanced.

The configurations according to the above-descried embodiments are not limited thereto. This disclosure can achieve the following aspects effectively.

In Aspect A, a sheet feeding device (for example, the sheet feeding device11) includes a sheet container (for example, the sheet feed tray1), a sheet feeding body (for example, the sheet pickup roller4), a pair of sheet position regulators (for example, the pair of sheet fences7), and a load applier (for example, the load applying member11). The sheet container is configured to accommodate a recording medium (for example, the sheet P). The sheet feeding body is configured to press a surface of the recording medium in the sheet container and feed the recording medium in a sheet feeding direction. The pair of sheet position regulators includes a first sheet position regulator (for example, the side fence7a) and a second sheet position regulator (for example, the side fence7b) disposed facing each other across the recording medium in the sheet container in a sheet width direction perpendicular to the sheet feeding direction. The pair of sheet position regulators is configured to regulate a position of the recording medium in the sheet width direction. The load applier is disposed between the first sheet position regulator and the sheet feeding body in the sheet width direction and is configured to contact the surface of the recording medium and apply a load to the recording medium at the surface. The recording medium is brought to move toward the second sheet position regulator while the recording medium is being fed.

In Aspect A, the recording medium is being fed toward the second sheet position regulator of the pair of sheet position regulators. Therefore, the recording medium can be fed along the second sheet position regulator. Accordingly, since the recording medium is fed on the basis of the second sheet position regulator as a reference member in the sheet width direction, skew of the recording medium fed from the sheet container can be restrained.

In Aspect B, a sheet feeding device (for example, the sheet feeding device11) includes a sheet container (for example, the sheet feed tray1), a sheet feeding body (for example, the sheet pickup roller4), a pair of sheet position regulators (for example, the pair of sheet fences7), and a load applier (for example, the load applying member11). The sheet container is configured to accommodate a recording medium (for example, the sheet P). The sheet feeding body is configured to press a surface of the recording medium in the sheet container and feed the recording medium in a sheet feeding direction. The pair of sheet position regulators includes a first sheet position regulator (for example, the side fence7a) and a second sheet position regulator (for example, the side fence7b) disposed facing each other across the recording medium in the sheet container in a sheet width direction perpendicular to the sheet feeding direction. The pair of sheet position regulators is configured to regulate a position of the recording medium in the sheet width direction. The load applier is disposed between the first sheet position regulator and the sheet feeding body in the sheet width direction and is configured to contact the surface of the recording medium and apply a load to the recording medium at the surface. A lower face position in a standby state of the sheet feeding body is lower than a lower face position in a standby state of the load applier.

According to this configuration, as described in the above-described embodiments, the load applier can be pressed reliably to an uppermost recording medium placed on top of a sheet bundle accommodated in the sheet container.

In Aspect A or Aspect B, the sheet feeding device (for example, the sheet feeding device114) further includes a pressing body (for example, the pressing member9) and a width position regulator (for example, the regulating member15). The pressing body is mounted on the first sheet position regulator and is configured to press the recording medium in the sheet container to the second sheet position regulator. The width position regulator is mounted on the second sheet position regulator and is configured to regulate the position of the recording medium in the sheet width direction while holding the recording medium together with the pressing body.

According to this configuration, as described in the above-described embodiments, the side edge of the recording medium in the sheet width direction can be aligned along the second sheet position regulator highly accurately.

In Aspect C, the pressing body and the width position regulator are disposed downstream from the sheet container in the sheet feeding direction and at an approximately same position.

According to this configuration, as described in the above-described embodiments, calculation of moments can be performed easily. In addition, variation in the position of the edge of the recording medium in the sheet width direction can be reduced due to the rotation.

In any one of Aspect A through Aspect D, the load applier is located at a specified position in the sheet width direction and a level of load applied to the recording medium by the load applier is changeable.

According to this configuration, as described in the above-described embodiments, inconveniences such as occurrence of no sheet feeding, generation of wrinkles, and non-contact of the recording medium to the second sheet position regulator can be reduced.

In Aspect E, the sheet feeding device further includes a biasing body (for example, the compression spring24) configured to bias the load applier toward the recording medium. A height of compression of the biasing body is changeable.

According to this configuration, as described in the above-described embodiments, a space-saving effect can be achieved, and the level of load applied by the load applier to the recording medium can be changed by changing the height of compression of the biasing body.

In Aspect E, the sheet feeding device further includes a weight (for example, the weight26) configured to weight the recording medium by the load applier. The weight includes multiple weights and the number of the multiple weights can be changed.

According to this configuration, as described in the above-described embodiments, a space-saving effect can be achieved, and the level of load applied by the load applier to the recording medium can be changed.

In any one of Aspect A through Aspect D, the sheet feeding device further includes a load releaser (for example, the pickup arm12and the pickup arm link member16) configured to release the load to the recording medium by the load applier.

According to this configuration, as described in the above-described embodiments, occurrence of wrinkles and gloss streaks in the recording medium can be restrained.

In Aspect H, the sheet feeding device further includes a support (for example, the pickup arm12) configured to support and move the sheet feeding body between a lowered position at which the sheet feeding body contacts the recording medium and a lifted position at which the sheet feeding body separates from the recording medium. The load applier and the support are engaged with each other when the support moves from the lowered position to the lifted position, and the load applier and the support are disengaged from each other when the support moves from the lifted position to the lowered position.

According to this configuration, as described in the above-described embodiments, a load applied by the load applier and the moment of rotation to the recording medium for a relatively long period of time during sheet conveyance can be restrained.

In any one of Aspect A through Aspect D, at least a part of the load applier includes a conductive body.

According to this configuration, as described in the above-described embodiments, charging by friction generated between the load applier and the recording medium can be reduced, and therefore occurrence of abnormal image and multi-feeding caused by biased charges on the surface of the recording medium due to the charging by friction can be restrained.

In Aspect J, the load applier includes a sheet contact portion (for example, the sheet contact portion11a) and a pressing portion (for example, the sheet pressing portion11b). The sheet contact portion is configured to contact the recording medium. The sheet pressing portion is configured to press the sheet contact portion to the recording medium.

According to this configuration, as described in the above-described embodiments, both the sheet contact portion and the sheet pressing portion can select respective materials appropriate to respective functions.

In Aspect K, the sheet pressing portion includes a conductive body.

According to this configuration, as described in the above-described embodiments, the conductive body does not directly contact the recording medium. Therefore, the load applier can be electrically grounded without worrying about wear caused by the recording medium.

In Aspect J, the sheet feeding device further includes a grounding body (for example, the holder130b) configured to contact the load applier in a direction perpendicular to a moving direction of the load applier.

According to this configuration, as described in the above-described embodiments, charging by friction generated between the load applier and the recording medium can be reduced without greatly changing the level of load to the pressure applied by the sheet pressing portion of the load applier.

In any one of Aspect A through Aspect D, an amount of rotational moment applied by the load applier to the recording medium is changeable.

According to this configuration, as described in the above-described embodiments, inconveniences, for example, occurrence of wrinkles and skews generated by an excess load from the load applier and non-contact of the recording medium to the second sheet position regulator caused by an insufficient load from the load applier, can be restrained.

In Aspect N, a position of the load applier in the sheet width direction in the sheet container is changeable.

According to this configuration, as described in the above-described embodiments, the position of the load applier can be changed and located to the loading position appropriate to the sheet size of the recording medium.

In Aspect O, the position of the load applier is changeable in conjunction with the position of at least one of the pair of sheet position regulators.

According to this configuration, as described in the above-described embodiments, as the at least one of the pair of sheet position regulators moves in the sheet width direction, the load applier moves in the sheet width direction together with the at least one of the pair of sheet position regulators. Therefore, the position of the load applier in the sheet width direction can be changed to a loading position appropriate to a sheet size of the recording medium automatically.

In any one of Aspect A through Aspect D, the sheet feeding device further includes a support body (for example, the support31) configured to rotatably support the load applier in at least one direction.

According to this configuration, as described in the above-described embodiments, a sheet shifting performance of the edge of the recording medium in the sheet width direction to the second sheet position regulator can be more accurate. Further, wear of the load applier caused by friction generated between the load applier and the recording medium can be reduced, and therefore the service life of the load applier can be extended.

In Aspect Q, the support body supports the load applier such that the load applier rotates axially within a horizontal plane parallel to the surface of the recording medium accommodated in the sheet container.

According to this configuration, as described in the above-described embodiments, a load applied by the load applier in a direction perpendicular to the sheet feeding direction can be reduced, and therefore the sheet shift performance of the edge of the recording medium in the sheet width direction to the second sheet position regulator can be enhanced.

In Aspect R, the support body supports the load applier such that the load applier rotates axially within a horizontal plane parallel to the sheet feeding body in the sheet feeding direction.

According to this configuration, as described in the above-described embodiments, wear of the load applier due to the friction between the load applier and the recording medium is reduced, and therefore the durability of the load applier is enhanced.

In Aspect T, an image forming apparatus (for example, the image forming apparatus100) includes an image forming device (for example, the image forming units101Y,101M,101C, and101K) configured to form an image on a recording medium (for example, the sheet P), and the sheet feeding device (for example, the sheet feeding device114) according to any one of Aspect A through Aspect S to feed the recording medium contained in the sheet container toward the image forming device.

According to this configuration, as described in the above-described embodiments, skew of the recording medium can be restrained and a good image forming operation can be performed.

The above-described embodiments are illustrative and do not limit this disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements at least one of features of different illustrative and exemplary embodiments herein may be combined with each other at least one of substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the embodiments and thus may be preferably set. It is therefore to be understood that within the scope of the appended claims, the disclosure of this disclosure may be practiced otherwise than as specifically described herein.