SHEET FEEDING APPARATUS AND IMAGE FORMING APPARATUS

Abstract

The present invention provides a sheet feeding apparatus and an image forming apparatus which can suppress generation of sheet skew feeding by a simple configuration and a pair of side edge regulating portions 30r and 30l is provided opposite each other in a sheet storage portion in order to regulate positions of side edges in a width direction orthogonal to a sheet feeding direction of the stored sheet S. At least one of the side regulating plates 30r and 30l can be moved in the width direction, and abutting portions 301r and 301l are provided opposite each other on inner wall surfaces of the side regulating plates 30r and 30l to abut on side edges of the sheet S.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding apparatus and an image forming apparatus, particularly to a configuration of a side edge regulating portion that regulates a side edge position of a sheet stored in a sheet storage portion detachably attached to an apparatus main body.

2. Description of the Related Art

Currently, in an image forming apparatus such as a copying machine, a printer, and a facsimile machine, one in which a sheet is fed from a sheet feeding apparatus to an image forming portion to form an image becomes widespread. In the sheet feeding apparatus, generally a sheet cassette which is the sheet storage portion is detachably attached to an apparatus main body, and the sheet stored in the sheet cassette is automatically fed to the image forming portion.

In some sheet cassette used in the sheet feeding apparatus, for example, a sheet stacking portion which is pressed against a sheet feeding roller while stacking the sheet thereon is provided in a lifting and lowering manner. In the sheet cassette provided with the sheet stacking portion, a tailing end regulating member is slidably provided. The tailing end regulating member regulates a position of a tailing end in a sheet feeding direction (hereinafter referred to as a tailing end) of the sheet which is stacked on and stored in the sheet stacking portion such that sheets having different sizes can be stored in the sheet cassette. A pair of side edge regulating portions is slidably provided to regulate a side edge position in a direction (hereinafter referred to as a width direction) orthogonal to the sheet feeding direction in delivering the sheet.

In the sheet cassette, the tailing end of the sheet is regulated by the tailing end regulating member while the side edges of the sheet is regulated by the pair of side edge regulating portions, whereby a leading end position of the sheet is always regulated in a predetermined position. Therefore, when the sheet cassette is accommodated in the apparatus main body, the sheet can stably be fed irrespective of the sheet size.

Since the side edge regulating portion is configured to be slid according to the sheet size, an attachment allowance exists due to the configuration, and the side edge regulating portion may be inclined with respect to the sheet feeding direction. Even if the side edge regulating portion is not inclined, slight irregularity may exist in the side edge regulating portion due to a manufacturing tolerance.

When the side edge regulating portion is inclined, or when the slight irregularity exists in the side edge regulating portion, the sheet may be inclined with respect to the sheet feeding direction when the side edge regulating portion abuts on the side edge of the sheet after the sheet is stored in the sheet cassette. The phenomenon will be described with reference to FIGS. 12A and 12B. Side regulating plates 30r and 30l which are the side edge regulating portions has the attachment allowances because the side regulating plates 30r and 30l are configured to be able to be moved in the width direction. In the side regulating plates 30r and 30l, the slight irregularity exists on a regulating surface facing a sheet S when viewed in the whole area in the sheet feeding direction.

Therefore, as illustrated in FIG. 12A, the side regulating plates 30r and 30l have the same inclination of an angle θ with respect to the sheet feeding direction. The case, in which the sheet S is positioned by the side regulating plates 30r and 30l having the inclinations of the angles θ with respect to the sheet feeding direction and lengths X in the sheet feeding direction after a leading end of the sheet S abuts on an abutting surface 3f to stack the sheet S based on the leading end of the sheet S, will be described below.

Conventionally, the lengths X in the sheet feeding direction of the side regulating plates 30r and 30l is increased as much as possible (for example, 60 mm or more) because the sheet S is regulated in a distance as long as possible. However, when the side regulating plates 30r and 30l are inclined with respect to the sheet feeding direction, the sheet S may be inclined by an attaching state or component accuracy if regulated in the long distance.

For example, as illustrated in FIG. 12A, when the side regulating plates 30r and 30l are inclined by the angle θ with respect to the sheet feeding direction, abutting points R1 and L1 between the side regulating plates 30r and 30l and the sheet S are shifted by X cos θ in the sheet feeding direction. The inclination θ generated by the attachment allowances of the side regulating plates 30r and 30l depends on the configuration. However, generally the inclination θ satisfies θ<0.5°. Therefore, approximation of X cos θ≈X holds with no incident. Assuming that Y is a length in the width direction of the sheet S, a distance connecting the abutting points R1 and L1 between the side regulating plates 30r and 30l and the sheet S by a straight line can be expressed by √(X2+Y2).

At this point, the sheet S is subjected to forces F1 at the abutting points R1 and L1 between the sheet S and the side regulating plates 30r and 30l, when the sheet S is positioned such that the side regulating plates 30r and 30l are moved to abut on the sheet S. When the sheet S is subjected to the forces F1 at the abutting points R1 and L1, the abutting points R1 and L1 become power points and also become fulcrums about which the sheet is rotated. Therefore, rotation moment is generated clockwise in the sheet S as illustrated in FIG. 12B, magnitude of the rotation moment is proportional to X cos θ and the forces F1 acting on the abutting points.

As the lengths X of the side regulating plates 30r and 30l are increased, and as the forces F1 of the side regulating plates 30r and 30l are increased, the rotation moment generated in the sheet S is increased to enhance a possibility that the sheet S is rotated as illustrated in FIG. 12B. The inclination of the sheet S cannot completely be corrected even if the tailing end regulating plate 31 abuts on the tailing end of the sheet S. Therefore, the positioning of the sheet S is completed while the sheet S may be inclined with respect to the sheet feeding direction. In such cases, skew feeding of the sheet S is generated when the sheet S is fed by a sheet feeding roller 3c. As described above, when the sheet is inclined while the settings of the side regulating plates 30r and 30l are completed, because the sheet is fed while inclined, the skew feeding of the sheet is generated, which possibly leads to degradation of printing accuracy.

On the other hand, when the side edge regulating portion having the inclination abuts on the sheet, the sheet may not be aligned with the side edge regulating portion. In such cases, a gap is generated between the side edge regulating portion and the side edge of the sheet. At this point, when a force rotating the sheet acts on the sheet due to an unbalance between right and left pressures of the sheet feeding roller, because the sheet is rotated until the side edge abuts on the side edge regulating portion, possibly the skew feeding is generated depending on the position of the gap.

The case, in which the sheet S positioned by the side regulating plates 30r and 30l having the inclinations of the angles θ with respect to the sheet feeding direction is fed by the sheet feeding roller 3c, will be described below with reference to FIG. 13. FIG. illustrates a state immediately after the leading end of the sheet S is fed by the sheet feeding roller 3c. In feeding the sheet S, the sheet S is regulated at the two abutting points R1 and L1 of the side regulating plates 30r and 30l. The sheet S may be subjected to a force F2 illustrated in FIG. 13 depending on a difference between right and left diameters of the sheet feeding roller 3c, a pressure balance between the right and left diameters, and alignment of the sheet feeding roller 3c with respect to the sheet feeding direction. The clockwise (CW) rotation moment is generated in the sheet S by the force F2, and the sheet S is rotated until the gaps between the side edges and the side regulating plates 30r and 30l are filled.

At this point, because the gap can be expressed by √(X2+Y2)−Y, a displacement amount is increased with increasing lengths X of the side regulating plates 30r and 30l, whereby a skew feeding amount is increased. When the side regulating plates 30r and 30l are inclined with respect to the sheet feeding direction, it is disadvantageously found that the skew feeding amount generated in the sheet S in positioning or feeding the sheet S is increased with increasing lengths X of the side regulating plates 30r and 30l.

There is discussed a sheet feeding apparatus including an angle adjusting portion that adjusts an angle of the side edge regulating portion with respect to the sheet feeding direction (for example, see Japanese Patent Laid-Open No. 2005-263458). When the sheet feeding apparatus includes the angle adjusting portion, a service engineer or a user can simply adjust the sheet feeding apparatus to the desired skew feeding accuracy according to a variation in manufacturing tolerance of the sheet feeding apparatus.

Recently, the laser beam printer and the copying machine is widely used in not only offices but also home with low cost and miniaturization, and a demand for improvement of usability is increased. In the conventional sheet feeding apparatus and image forming apparatus in which the angle of the side edge regulating portion is adjusted, it takes a significantly long time for not the service person but the individual user to see a sample to adjust the angle of the side edge regulating portion. As a result, productivity of the sheet feeding apparatus is degraded to decrease the usability. That is, it takes a long time to adjust the angle of the side edge regulating portion in order to prevent the skew feeding in positioning or feeding the sheet. An angle adjusting mechanism is also required to complicate a structure.

The present invention provides a sheet feeding apparatus and an image forming apparatus which can suppress the generation of the sheet skew feeding by a simple configuration.

SUMMARY OF THE INVENTION

According to an aspect of the invention, a sheet feeding apparatus comprising: a sheet storage portion which stores sheets; a sheet feeding roller which feeds the sheet stored in the sheet storage portion; a pair of side edge regulating portions which is provided opposite each other in the sheet storage portion so as to regulate positions of side edges in a width direction orthogonal to a sheet feeding direction of the stored sheet, and at least one of the pair of side edge regulating portions can be moved in the width direction; and projection portions provided opposite each other on inner wall surfaces of the side edge regulating portions so as to abut on the side edges of the sheet, respectively.

According to the invention, the projection portion which abuts on each side edge of the sheet is provided on the inner wall surface of the pair of side edge regulating portions, which allows the generation of the sheet skew feeding to be suppressed by the simple configuration.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic configuration of a printer which is an example of an image forming apparatus provided with a sheet feeding apparatus according to a first embodiment of the invention;

FIG. 2 is a perspective view of the sheet feeding apparatus;

FIG. 3 is a perspective view illustrating a movable portion of a side regulating plate provided in the sheet feeding apparatus;

FIG. 4A illustrates a configuration of the side regulating plate (left member); FIG. 4B illustrates a configuration of the side regulating plate (right member); FIG. 4C is a plan view illustrating the configurations of the side regulating plates;

FIG. 5A illustrates a sheet positioning operation performed by the side regulating plates; FIG. 5B illustrates the sheet positioning operation performed by the side regulating plates;

FIG. 6 illustrates a state immediately after a sheet positioned by the side regulating plates is fed by a sheet feeding roller;

FIG. 7 is a table illustrating a determination result of a length of an abutting portion of the side regulating plate to a tolerance of a skew feeding amount;

FIG. 8A illustrates a side regulating plate (right member) provided in a sheet tray of a sheet feeding apparatus according to a second embodiment of the invention; FIG. 8B illustrates a side regulating plate (left member) provided in the sheet tray of the sheet feeding apparatus of the second embodiment; FIG. 8C is a plan view illustrating the side regulating plates provided in the sheet tray of the sheet feeding apparatus of the second embodiment;

FIG. 9A illustrates a sheet positioning operation performed by the side regulating plates; FIG. 9B illustrates the sheet positioning operation performed by the side regulating plates;

FIG. 10A illustrates a configuration of a movable portion of a side regulating plate provided in a sheet tray of a sheet feeding apparatus according to a third embodiment of the invention; FIG. 10B is an enlarged view illustrating the configuration of the movable portion of the side regulating plate provided in the sheet tray of the sheet feeding apparatus of the third embodiment;

FIG. 11 is a perspective view of the side regulating plate;

FIG. 12A illustrates a sheet positioning operation performed by conventional side regulating plates; FIG. 12B illustrates the sheet positioning operation performed by conventional side regulating plates; and

FIG. 13 illustrates a state immediately after a sheet positioned by the conventional side regulating plates is fed by a sheet feeding roller.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 illustrates a schematic configuration of a printer which is an example of an image forming apparatus provided with a sheet feeding apparatus according to a first embodiment of the invention. In a printer 50 of FIG. 1, an image forming portion 52 is provided in a printer main body 51 which is an apparatus main body, the image forming portion 52 performs image formation by an electrophotographic system, and a sheet feeding apparatus 3 feeds a sheet S to the image forming portion 52.

The image forming portion 52 includes a laser exposure device 1, a photosensitive drum 207 which forms a toner image, and a transfer roller 4 which transfers the toner image formed in the photosensitive drum 207 to the sheet S. A process cartridge B includes the photosensitive drum 207, a charging roller (not illustrated), and a development portion (not illustrated). The process cartridge B is detachably attached to the printer main body 51.

The sheet feeding apparatus 3 includes a sheet feeding roller 3c, a sheet tray 3a which is a sheet storage portion, and a lift-up plate 3b. The lift-up plate 3b is provided in the sheet tray 3a in a lifting and lowering manner, and presses the sheet S stored in the sheet tray 3a against the sheet feeding roller 3c. A separation pad 3d which presses the sheet feeding roller 3c is provided on a downstream side in a sheet feeding direction of the sheet tray 3a. In the sheet feeding apparatus 3, during the image formation, the sheet S is delivered from the sheet tray 3a by the sheet feeding roller 3c, and the sheet S is separated one by one by the separation pad 3d which presses the sheet feeding roller 3c.

An image forming operation in the printer 50 having the above-described configuration will be described below. When the image forming operation is started, the photosensitive drum 207, which is rotated in an arrow direction while a charging treatment is performed to a surface of the photosensitive drum 207, is irradiated with a laser beam L emitted from the laser exposure device 1 according to an image signal. A latent image is formed on the photosensitive drum 207 by the laser irradiation according to the image signal. The latent image on the photosensitive drum 207 is developed and visualized as a toner imager by toner supplied by the development portion.

The lift-up plate 3b is lifted in parallel with the toner image forming operation, the sheet S set in the sheet tray 2a is delivered by friction with the sheet feeding roller 3c, and the sheet S is separated one by one and substantially vertically fed by the separation pad 3d. Then the sheet S is conveyed to a transfer portion by a pair of conveying rollers 3e.

In the transfer portion, a voltage having an opposite polarity to the toner image formed on the photosensitive drum 207 is applied to the transfer roller 4, thereby transferring the visualized toner image on the photosensitive drum 207 to the sheet S. Then the sheet S to which the toner image is transferred is conveyed to a fixing unit 5, which is disposed in an upper portion of the printer main body, by a conveyance guide 3f. The fixing unit 5 includes a driving roller 5a and a heater unit 5c in which a heater 5b is incorporated. In the fixing unit 5, the transferred toner image is fixed by applying heat and pressure to the passing sheet S. Then the sheet S to which the toner image is fixed is conveyed by a pair of discharge rollers 3g and discharged to a discharge portion 6 provided on an upper surface of the printer main body 51.

As illustrated in FIG. 2, a tailing end regulating plate 31 is provided in the sheet tray 3a to regulate a tailing end which is an upstream side edge in the sheet feeding direction on the lift-up plate 3b. The tailing end regulating plate 31 can slidably be moved along the sheet feeding direction and disposed at a position corresponding to a sheet size. The tailing end regulating plate 31 is pressed against the tailing end of the sheet S, and a leading end of the sheet S abuts on an abutting surface 3f, thereby determining the position of the sheet S in the sheet feeding direction based on the leading end of the sheet S.

The sheet tray 3a includes a pair of side regulating plates 30r and 30l. The side regulating plates 30r and 30l abut on both side edges in a width direction orthogonal to the sheet feeding direction of the sheet S stacked on the lift-up plate 3b and regulate side edge positions of the sheet S. The side regulating plates 30r and 30l are supported by a side regulating plate guide 32 while being slidable in the width direction. In not only standard-size sheets such as an A4 size and a letter size but also nonstandard-size sheets such as a postcard and an envelope, the side edge positions of the sheet S can be aligned by the side regulating plates 30r and 30l which are a side edge regulating portion.

The sheet feeding apparatus of the first embodiment performs a center registration type sheet feed. Therefore, as illustrated in FIG. 3, the side regulating plates 30r and 30l include rack members 7r and 7l which are slid in conjunction with each other, and the rack members 7r and 7l engage with a pinion 8 which is journaled at a bottom of the side regulating plate guide 32.

When one of the side regulating plates 30r and 30l is moved in regulating the side edge positions of the sheet S, the rack members 7r and 7l are guided by a lateral guide groove 32a formed in the width direction of the side regulating plate guide 32, thereby also moving the other side regulating plate in conjunction with one of the side regulating plates 30r and 30l. The rack members 7r and 7l are retained at the moved positions by a frictional force with the side regulating plate guide 32.

FIG. 4 illustrates configurations of the side regulating plates 30r and 30l of the first embodiment. As illustrated in FIGS. 4A and 4B, the side regulating plates 30r and 30l include abutting portions 301r and 301l on inner wall surfaces thereof, respectively. The abutting portions 301r and 301l are projection portions whose lengths X′ in the sheet feeding direction are short (for example, 5 mm or less). When the abutting portions 301r and 301l are provided one by one, the side edge of the sheet S and each of the abutting portions 301r and 301l become a state of a substantial point contact.

As described above, the rotation moment applied to the sheet S is proportional to the length X in the sheet feeding direction of each of the side regulating plates 30r and 30l. Therefore, when the side edge of the sheet S and each of the abutting portions 301r and 301l become the state of the substantial point contact like the first embodiment, because the rotation moment applied to the sheet S is decreased even if the side regulating plates 31r and 31l are inclined, the sheet S is hardly influenced by the inclinations of the side regulating plates 30r and 30l.

As illustrated in FIG. 4, the pair of abutting portions 301r and 301l is provided across the sheet S from each other. When the lengths X′ in the sheet feeding direction of the abutting portions 301r and 301l are short (for example, 5 mm or less), directions of forces acting on the sheet S by the abutting portions 301r and 301l become the substantially same straight line orthogonal to the sheet feeding direction. As a result, deviations in the sheet feeding direction of abutting points between the abutting portions 301r and 301l and the sheet S are eliminated, and the generation of the rotation moment by the deviations in the sheet feeding direction at abutting points L1 and R1 can be prevented when the abutting portions 301r and 301l abut on the sheet S.

A positioning operation of the sheet S, which is performed by the side regulating plates 30r and 30l having the above-described configuration, will be described below with reference to FIG. 5. FIG. 5A illustrates a state before the sheet S is positioned, and FIG. 5B illustrates a state after the sheet S is positioned.

When the side regulating plates 31r and 31l are moved from the positions illustrated in FIG. 5A, the side edges of the sheet S and the abutting portions 301r and 301l become the state of the substantial point contact as illustrated in FIG. 5A. Irrespective of an inclination θ with respect to the sheet feeding direction, the abutting portions 301r and 301l abut on the sheet S at the substantially same position in the sheet feeding direction, namely, with no deviation in the sheet feeding direction. As illustrated in FIG. 5B, the sheet S does not rotate, because the rotation moment is not generated in the sheet S even if the sheet S is subjected to forces F4 from the abutting portions 301r and 301l. Therefore, the sheet S is hardly inclined when the sheet S is positioned.

FIG. 6 illustrates a state immediately after the leading end of the sheet S is fed by the sheet feeding roller 3c. The sheet S is subjected to forces F5 at the abutting portions 301r and 301l depending on a difference between right and left diameters of the sheet feeding roller 3c, a pressure balance between the right and left diameters, and alignment of the sheet feeding roller 3c with respect to the sheet feeding direction. On the other hand, in the first embodiment, the abutting portions 301r and 301l of the side regulating plates 31r and 31l abut on the side edges of the sheet S at the same position in the sheet feeding direction to regulate an attitude of the sheet S. Therefore, a gap is eliminated unlike the conventional art, but the sheet S does not rotate. Consequently, in the first embodiment, the skew feeding of the sheet S is not generated during the sheet feed.

In the first embodiment, until the leading end of the sheet S reaches the pair of conveying rollers 3e since the sheet S is fed by the sheet feeding roller 3c, the abutting portions 301r and 301l of the side regulating plates 31r and 31l are set to positions at which the abutting portions 301r and 301l can abut on the side edges of the sheet S. Plural pairs of conveying rollers 3e constituting the sheet conveying portion are provided in the width direction. In the first embodiment, two pairs of conveying rollers 3e are provided, and the two pairs of conveying rollers 3e convey the sheet S while nipping the sheet S, thereby stabilizing the attitude of the sheet S. Therefore, the sheet S is regulated by the abutting portions 301r and 301l such that the attitude of the sheet S does not change until the leading end of the sheet S reaches the pairs of conveying rollers 3e, so that the skew feeding of the sheet S can be prevented from the feed to the conveyance.

In the first embodiment, the lengths X′ in the sheet feeding direction of the abutting portions 301r and 301l of the side regulating plates 31r and 31l are set to 5 mm or less. However, there is no limitation to the lengths X′ in the sheet feeding direction of the abutting portions 301r and 301l. FIG. 7 illustrates a determination result of the lengths X′ of the abutting portions 301r and 301l of the side regulating plates 31r and 31l to a tolerance of a skew feeding amount. In the first embodiment, the tolerance of the skew feeding amount is set to 0.5% of a long side (sheet feeding direction) of the sheet S, and 150 letter-size (215.9 mm×279.4 mm) sheets Shaving a basis weight of 75 g/m² are stacked. The skew feeding amount is determined when the 150 sheets S are positioned.

As illustrated in FIG. 7, the skew feeding amount falls within the tolerance in a range of X′ (lengths of the abutting portions 301r and 301l of the side regulating plates 31r and 31l) 30 (mm). Therefore, the effect of the first embodiment is exerted when the length X′ of each of the abutting portions 301r and 301l of the side regulating plates 31r and 31l is set to the range of X′≦30 (mm). Usually the side regulating plates 31r and 31l are molded by a synthetic resin. In the side regulating plates 31r and 31l, a thickness of at least 0.5 mm is required to cause the synthetic resin to flow to details of a mold. Accordingly, the length X′ of each of the abutting portions 301r and 301l of the side regulating plates 31r and 31l is set to the range of 0.5 (mm)≦X′≦30 (mm).

As described above, in the first embodiment, the abutting portions 301r and 301l of the side regulating plates 31r and 31l abut on the side edges of the sheet S in the state of the substantial point contact and the state in which the deviation in the sheet feeding direction is eliminated. Therefore, when the lengths X′ in the sheet feeding direction of the abutting portions 301r and 301l are short (for example, 5 mm or less), directions of forces acting on the sheet S by the abutting portions 301r and 301l become the substantially same straight line orthogonal to the sheet feeding direction. As a result, the generation of the sheet skew feeding can be suppressed by the simple configuration.

When the lengths X′ in the sheet feeding direction of the abutting portions 301r and 301l are 5 mm or more, sometimes the directions of the forces acting on the sheet do not become the substantially same straight. Even in this case, although accuracy is slightly degraded, the generation of the skew feeding of the sheet can be suppressed better than ever before. In the configurations of the side regulating plates 31r and 31l of the first embodiment, because the regulating portion which regulates the sheet S is restricted compared with the conventional configurations, the size is easily managed on the production.

A second embodiment of the invention will be described below. FIGS. 8A to 8C illustrate a side regulating plate provided in a sheet tray of a sheet feeding apparatus according to a second embodiment of the invention. In FIGS. 8A to 8C, the same or equivalent component is designated by the same numeral as that of FIGS. 4A to 4C.

In FIGS. 8A and 8B, the numerals 32r and 32l designate side regulating plates. Similarly to the side regulating plates 31r and 31l of the first embodiment, the side regulating plates 32r and 32l include abutting portions 302r and 302l having lengths δ (≦30 mm) in the sheet feeding direction, respectively. As illustrated in FIG. 8, the side regulating plates 32r and 32l include regulating portions 322r and 322l, respectively. The regulating portions 322r and 322l are continuously provided from the abutting portions 302r and 302l while recessed by t in the width direction from the abutting portions 302r and 302l.

The regulating portions 322r and 322l are continuously provided for the purpose of backup in the case of the thin sheet having the basis weight of about 50 g. The recess width t of each of the regulating portions 322r and 322l is set such that the abutting portions are in contact with the sheet S even if the side regulating plates 32r and 32l are most inclined on a manufacturing tolerance. In other words, projection amounts of the abutting portions 302r and 302l are set such that the abutting portions 302r and 302l abut on the side edges of the sheet S even if the regulating portions 322r and 322l are most inclined with respect to the sheet feeding direction. In the second embodiment, the recess width t is set to 5 mm. Similarly to the first embodiment, the abutting portions 302r and 302l are provided opposite each other as illustrated in FIG. 8C.

A positioning operation of the sheet S, which is performed by the side regulating plates 32r and 32l having the above-described configuration, will be described below. FIG. 9A illustrates a state in which a thin sheet S′ is positioned by the side regulating plates 32r and 32l having maximum inclinations θ1 on the manufacturing tolerance. FIG. 9B illustrates a state immediately after the thin sheet S′ is fed by the sheet feeding roller 3c while the difference between the right and left diameters of the thin sheet S′, the balance between the right and left diameters, and the alignment with respect to the sheet feeding direction are not adjusted.

The lengths δ and the widths t of the abutting portions 302r and 302l are set to the above-described values in positioning the thin sheet S′, whereby the abutting portions 302r and 302l abut on the side edges of the thin sheet S′ at the substantially same position as illustrated in FIG. 9A similarly to the first embodiment. Part of the regulating portion 322r also abuts on the thin sheet S′.

At this point, it is assumed that a force F7 is applied to the thin sheet S′ during a process in which the thin sheet S′ is fed by the sheet feeding roller 3c. When the side edges of the thin sheet S′ are regulated by the abutting portions 302r and 302l having the lengths δ, the force acting on the side edge per unit length of the thin sheet S′ is increased with decreasing length δ. As a result, sometimes the side edges of the thin sheet S abutting on the abutting portions 302r and 302l are deformed to hardly regulate the rotation of the thin sheet S′ depending on the settings of the lengths 6 of the abutting portions 302r and 302l or a kind of the thin sheet S′. In such cases, the thin sheet S′ rotates.

On the other hand, in the second embodiment, the side edges of the thin sheet S′ are regulated by the backup regulating portions 322r and 322l provided on the upstream side in the sheet feeding direction of the abutting portions 302r and 302l as illustrated in FIG. 9B, so that the excess skew feeding can be prevented. Thus, in the second embodiment, the excess skew feeding can be prevented by providing the backup regulating portions 322r and 322l even if the thin sheet S′ is fed.

A third embodiment of the invention will be described below. FIGS. 10A and 10B illustrate a configuration of a movable portion of the side regulating plates provided in the sheet tray 3a of a sheet feeding apparatus of the third embodiment. In FIGS. 10A and 10B, the same or equivalent component is designated by the same numeral as that of FIG. 3.

In FIG. 10A, a fixing portion 11r is provided on the side regulating plate guide 32 (see FIG. 3) to fix side regulating plates 33r and 33l, and a rack-shaped tooth is provided in the fixing portion 11r. A latching portion 10r is provided in a rack member 7r of the side regulating plate 33r, and a projection which elastically engages with the fixing portion 11r is provided in the latching portion 10r.

When the side regulating plates 33r and 33l are moved in the direction in which the side regulating plates 33r and 33l come close to each other, the latching portion 10r of the side regulating plate 33r is pressed against the rack-shaped tooth of the fixing portion 11r, and the latching portion 10r is subjected to a force in a bending direction by the rack-shaped tooth, whereby the latching portion 10r is moved beyond the rack-shaped tooth. Therefore, the side regulating plates 33r and 33l can be moved in the direction in which the side regulating plates 33r and 33l come close to each other.

On the other hand, when the side regulating plates 33r and 33l are moved in the direction in which the side regulating plates 33r and 33l are separated from each other, the side regulating plates 33r and 33l cannot be moved because the latching portion 10r of the side regulating plate 33r is latched in the rack-shaped tooth of the fixing portion 11r. As illustrated in FIG. 11B, when the side regulating plates 33r and 33l are moved in the direction in which the side regulating plates 33r and 33l are separated from each other, a lever 12r provided in the latching portion 10r is pressed in a direction of an arrow C by a finger to elastically bend the latching portion 10r. Therefore, the latching of the latching portion 10r in the rack-shaped tooth of the fixing portion 11r is released.

When the fixing portion 11r is provided, the positioning is strengthened in the direction in which the side regulating plates 33r and 33l are opened, namely, the direction in which the side regulating plates 33r and 33l are separated from each other. On the other hand, as illustrated in FIG. 10B, the movement in the direction in which the side regulating plates 33r and 33l are closed, namely, the direction in which the side regulating plates 33r and 33l come close to each other can be performed on a pitch p of the rack-shaped tooth of the fixing portion 11r.

Therefore, as illustrated in FIG. 11, one of the sheet regulating portions 303r and 303l is elastically formed so as to abut on the side edge of the sheet S even if the side regulating plates 33r and 33l are opened by the pitch p. In the third embodiment, the sheet regulating portion 303r is elastically formed. The sheet regulating portion 303l is provided across the sheet S from the elastically-formed sheet regulating portion 303r.

As a result, because the sheet regulating portions 303r and 303l abut on the side edges of the sheet S even if the side regulating plates 33r and 33l are opened by the pitch p of the rack-shaped tooth, the effect similar to that of the second embodiment can be obtained. As described above, in the configuration of the third embodiment in which the movements in the width directions of the side regulating plates 33r and 33l are positioned by the rack-shaped tooth, the inexpensive sheet feeding apparatus advantageous to the skew feeding can be provided by the simple configuration.

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. 2010-173729, filed Aug. 2, 2010, which is hereby incorporated by reference herein in its entirety.

Claims

1. A sheet feeding apparatus comprising:

a sheet storage portion which stores sheets;

a sheet feeding roller which feeds the sheet stored in the sheet storage portion;

a pair of side edge regulating portions which is provided opposite each other in the sheet storage portion so as to regulate positions of side edges in a width direction orthogonal to a sheet feeding direction of the stored sheet, and at least one of the pair of side edge regulating portions can be moved in the width direction; and

projection portions provided opposite each other on inner wall surfaces of the side edge regulating portions so as to abut on the side edges of the sheet, respectively.

2. The sheet feeding apparatus according to claim 1, wherein

a projection amount of the projection portion is set such that the projection portion abuts on each side edge of the sheet even if the pair of side edge regulating portions is most inclined with respect to the sheet feeding direction.

3. The sheet feeding apparatus according to claim 1, wherein

a length of the projection portion of the side edge regulating portion is set to a range of 0.5 (mm)≦X′≦30 (mm).

4. The sheet feeding apparatus according to claim 1, comprising

a sheet conveying portion which conveys the sheet fed by the sheet feeding roller while nipping the sheet,

wherein the projection portion is provided at a position at which the projection portion abuts on each side edge of the sheet until the sheet reaches the sheet conveying portion.

5. The sheet feeding apparatus according to claim 4, wherein

the plurality of sheet conveying portions is provided in the width direction.

6. The sheet feeding apparatus according to claim 1, wherein

a regulating portion is provided on the inner wall surface of the side edge regulating portion and on an upstream side in the sheet feeding direction of the projection portion, the regulating portion abutting on the sheet to regulate inclination of the sheet when the sheet is bent by abutting on the projection portion.

7. The sheet feeding apparatus according to claim 1, wherein

at least one of the pair of side edge regulating portions is configured to elastically abut on the side edge of the sheet.

8. An image forming apparatus comprising:

a sheet feeding apparatus in which a sheet stored in a sheet storage portion is fed by a sheet feeding roller;

an image forming portion which forms an image in the sheet fed by the sheet feeding apparatus; and

a pair of side edge regulating portions which is provided opposite each other in the sheet storage portion so as to regulate positions of side edges in a width direction orthogonal to a sheet feeding direction of the stored sheet,

wherein at least one of the pair of side edge regulating portions can be moved in the width direction, and projection portions are provided opposite each other on inner wall surfaces of the side edge regulating portions so as to abut on the side edges of the sheet, respectively.

9. The image forming apparatus according to claim 8, wherein

a projection amount of the projection portion is set such that the projection portion abuts on the side edges of the sheet even if the pair of side edge regulating portions is most inclined with respect to the sheet feeding direction.

10. The image forming apparatus according to claim 8, wherein

a length of the projection portion of the side edge regulating portion is set to a range of 0.5 (mm)≦X′≦30 (mm).

11. The image forming apparatus according to claim 8, comprising

a sheet conveying portion which conveys the sheet fed by the sheet feeding roller while nipping the sheet,

wherein the projection portion is provided at a position at which the projection portion abuts on each side edge of the sheet until the sheet reaches the sheet conveying portion.

12. The image forming apparatus according to claim 11, wherein

the plurality of sheet conveying portions is provided in the width direction.

13. The image forming apparatus according to claim 8, wherein

a regulating portion is provided on the inner wall surface of the side edge regulating portion and on an upstream side in the sheet feeding direction of the projection portion, the regulating portion abutting on the sheet to regulate inclination of the sheet when the sheet is bent by abutting on the projection portion.

14. The image forming apparatus according to claim 8, wherein

at least one of the pair of side edge regulating portions is configured to elastically abut on the side edge of the sheet.