JP2000053266A - Sheet conveyance device and image forming device therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convey sheets smoothly without causing failed conveyance of the sheets by correcting the deformation of the sheets when the front end parts of the sheets stacked on a sheet stacking means are deformed. SOLUTION: This sheet conveyance device is provided with a sheet stacking means 2a which stacks a plurality of sheets and has a sheet receiving surface 7 receiving the front end of the sheet at the downstream end of the sheet in the conveying direction, a sheet feeding roller 2b which comes into contact with the sheet and rotates to bring the sheet into contact with the sheet receiving surface for separation and deliver it from the sheet stacking means, and a sheet pressing means 8 which is positioned between the sheet receiving surface 7 and a sheet feeding roller and presses the front end part of the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus for conveying a sheet, and an image forming apparatus including the apparatus, such as a printer, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art Conventionally, a sheet conveying device provided in an image forming apparatus such as a printer, a copying machine, a facsimile machine, etc. is designed to reliably separate and convey sheets one by one from sheet stacking means on which the sheets are stacked. It has become.

[0003] An image forming apparatus is a general term for an apparatus having a sheet processing unit for performing a predetermined process (for example, forming an image, reading an image, etc.) on sheets conveyed one by one. Say The sheet is a generic term for paper, a thin resin sheet, etc., which is a substitute for paper.

There are various types of sheet conveying apparatuses, and among them, there is a slope separation sheet supply system.

Hereinafter, a sheet conveying apparatus of a slope separation sheet supply type will be described.

In the slope separation sheet feeding system, the sheets stacked on the sheet cassette are stacked in such a manner that the front end of the sheets stacked on the sheet cassette as the sheet stacking means abuts against the inclined surface 7 which is the sheet receiving surface of the sheet cassette at an acute angle. In this method, only the top sheet is bent and separated. For this reason, the slope separation sheet supply method requires a configuration in which the conveyance force given by the sheet supply roller or the rigidity of the sheet is changed according to the movement of the sheet.

FIG. 8 shows the first sheet A loaded
And the second sheet B show the conveying force generated by the vertical load (hereinafter referred to as "sheet pressure") N of the sheet supply roller 2b and the rotation of the sheet supply roller 2b.

In FIG. 8, μp indicates a coefficient of friction between a sheet and a sheet supply roller, and μ and μ ′ indicate a coefficient of friction between sheets. These relationships are set so that μp> μ ≧ μ ′ (μ ′ is the coefficient of friction between the foot or pile).

Therefore, the conveying force N acting on the first sheet A
(Μp-μ) and the conveying force N acting on the second sheet B
(Μ−μ ′) has a relationship of N · (μp−μ)> N · (μ−1μ ′).

The distance (natural length) between the sheet supply roller 2b and the inclined surface 7 in each of the sheets A and B is represented by Ll, L
Let it be 2.

In order to bend only the l-th sheet A, it is roughly divided into the following two methods.

1) Sheet pressure fluctuation method In this method, the sheet pressure N applied to the sheet is gradually increased, and the sheet pressure is attenuated at the same time as the first sheet A is bent.

This will be described with reference to FIG. When the sheet pressure N is gradually (primarily) increased after the rotation of the sheet supply roller 2b, the conveying force for the first and second sheets A and B increases as shown in FIG. The sheet receives a reaction force corresponding to the conveyance force from the inclined surface 7, and the sheet bends when the reaction force exceeds the sheet strength Pr. When the sheet pressure N is increased, the first sheet starts to bend at first. At this time, by reducing the sheet pressure N, the bending of the second sheet is prevented, and only the bent first sheet is used.
It will be handled and transported from the pile.

2) Natural length variation method A method in which L1 and L2 in FIG. 8 are gradually increased while the sheet pressure (N) is constant, and the natural length is attenuated simultaneously with the first sheet A being bent.

This will be described with reference to FIG. L in FIG.
It is assumed that l and L2 are substantially equal. Sheet supply roller 2b
When the sheet supply roller 2b is gradually moved away from the inclined surface 7 of the sheet cassette after the start of rotation of the sheet cassette, the sheet strength Pr gradually decreases in inverse proportion to the square of (Ll). The proof stress Pr of the sheet is the conveyance force N · (μp
−μ), the first sheet A bends. At this time, the sheet supply roller 2b is brought close to the inclined surface 7, and the proof stress P
By not lowering r further, the bending of the second sheet B is prevented, and only the bent first sheet A is separated from the pile and conveyed.

[0016]

In any of the above-described inclined-surface separating sheet supply systems, various rigid sheets can be reliably separated with a simple and inexpensive structure, but the front end of the sheet abutting against the inclined surface 7 can be used. Is deformed,
More specifically, when the first sheet A and the second sheet B have different proof stresses, the following problem occurs.

1) When the yield strength of the second sheet B is small This will be described with reference to FIG. The front end Sa in the transport direction of the second sheet B stacked on the sheet cassette, that is, the portion that abuts the inclined surface 7 of the sheet cassette is the inclined surface 7.
Curved upward in the transport direction along
When the first sheet A is bent, the second sheet B may be bent at the same time. That is, the proof stress of the second sheet B is significantly reduced due to the upper curl, and as a result, the first sheet A and the second sheet B simultaneously overlap without being separated, and It is conveyed from the upper end of the cassette (double feed).

2) When the Strength of the First Sheet is Large The description will be made with reference to FIG. Similarly, when the first sheet A stacked on the sheet cassette is curved downward (hereinafter, referred to as “lower curl”) on the opposite side to the conveyance direction along the inclined surface 7, the first sheet A is bent. At the same time, the second sheet B also bends at the same time. This is because the strength of the first sheet A is significantly increased due to the lower curl compared to the second sheet B, and the sheet pressure or the natural length from the inclined surface 7 must be excessively increased. B
Will bend. Also in this case, similarly to the upper curl, the first sheet A and the second sheet B are simultaneously stacked without being separated and conveyed from the upper end of the sheet cassette.

Further, the image forming apparatus cannot accurately form an image on a sheet if the sheet is double-fed by the upper curl or the lower curl from the sheet conveying apparatus.

(Purpose) According to the present invention, when the leading end of a sheet stacked on a sheet stacking unit is deformed, the deformation of the sheet is corrected, and the sheet is smoothly conveyed without causing a sheet conveyance failure. It is an object of the present invention to provide a sheet conveying apparatus capable of performing the above-described operations and an image forming apparatus including the apparatus.

[0021]

The above-mentioned object is achieved by the following sheet conveying apparatus.

A sheet stacking means on which a plurality of sheets are stacked and which has a sheet receiving surface for receiving the leading end of the sheet at a downstream end in the sheet conveying direction; A sheet supply roller that abuts on a receiving surface and separates and feeds the sheet from the sheet stacking unit; and a sheet pressing unit that is located between the sheet receiving surface and the sheet supply roller and presses a leading end of the sheet. Have.

The sheet receiving surface is an inclined surface which is inclined such that its upper end is located downstream of the lower end in the sheet conveying direction.

The sheet supply roller can move up and down substantially in parallel with the sheet receiving surface.

The sheet pressing means is a pressing piece rotatably provided coaxially with the sheet supply roller.

The sheet supply roller is movable substantially parallel to the upper surface of the sheets stacked on the sheet stacking means.

The sheet supply roller is provided on a movable frame having a pinion that meshes with a rack parallel to the sheet receiving surface so as to be urged downstream in the sheet conveying direction so as to be movable in the sheet conveying direction. .

The sheet pressing means is a pressing piece rotatably provided on the movable frame.

A plurality of the pressing pieces are provided.

The sheet holding means includes an arm rotatably provided on a rotation shaft of the sheet supply roller, and a roller on a support shaft provided at a free end side of the arm in parallel with the rotation shaft. The rollers press the leading end of the sheet.

The sheet holding means includes an arm and a base pulley rotatably provided coaxially with the rotation axis of the sheet supply roller; a free end pulley provided on a free end side of the arm; A belt extending around the end pulley and the free end pulley, wherein the belt presses the leading end of the sheet.

The sheet holding means is a flat sheet holding plate.

The length of the sheet holding plate is substantially the same as the length in the direction perpendicular to the sheet conveying direction.

A part of the sheet holding plate protrudes to a position where the amount of sheets stacked on the sheet stacking means can be checked.

A recess is formed in the sheet receiving surface to allow a part of the sheet pressing means to enter.

The above problem is solved by the following image forming apparatus.

The apparatus includes any one of the above-described sheet conveying apparatuses, and an image forming section that forms an image on a sheet conveyed from the sheet conveying apparatus.

(Operation) The sheet pressing means comes into contact with the top sheet stacked on the sheet stacking means to correct the deformation of the sheet. The sheet is brought into contact with the sheet receiving surface of the sheet stacking unit by the sheet supply roller, is separated, and is discharged from the sheet stacking unit. Since the deformation of the sheets is corrected, the proof stresses of the first sheet and the second sheet are made more uniform, and the above-described double feeding is prevented, and the sheets are reliably separated and carried out one by one.

If the upper end side of the sheet receiving surface is an inclined surface inclined toward the downstream side in the sheet conveying direction, the sheet is smoothly sent out from the sheet stacking means.

When the pressing direction of the sheet supply roller is substantially parallel to the sheet receiving surface, even if the number of sheets is reduced, the sheet supply roller is positioned at a predetermined distance from the sheet receiving surface at the front end of the sheet. By pressing a predetermined position, the sheet is always loosened in an optimal state.

If the sheet supply roller is provided movably on the movable frame, the sheet supply roller moves according to the rigidity of the sheet until the first sheet comes into contact with the sheet receiving surface and bends. The sheet is reliably sent out from the sheet stacking means.

If the sheet pressing means is a pressing plate having substantially the same length in the direction (width direction) orthogonal to the sheet conveying direction, not only deformation in the sheet conveying direction but also deformation in the sheet width direction is corrected. can do.

When the sheet holding means is a holding plate and partially protrudes to a position where the stacked amount of the sheets stacked on the sheet stacking means can be confirmed, the sheet stacked amount can be determined from the outside.

[0044]

Embodiments of the present invention will be described below.

(Configuration of Image Forming Apparatus with Sheet Conveying Apparatus) First, a laser beam printer, which is an image forming apparatus with a sheet conveying apparatus, will be described with reference to FIG.

FIG. 1 is a cross-sectional view showing a schematic configuration of a laser beam printer 1 provided with a sheet conveying device 2.

The laser beam printer 1 includes a sheet conveying device 2, a scanner unit 3, an image forming unit 4, a fixing unit 6, and the like.

The sheet conveying device 2 includes a sheet cassette (sheet stacking means) 2a having an inclined surface 7 whose upper end is inclined downstream of the lower end in the sheet conveying direction and is a sheet receiving surface for receiving the leading end of the sheet. A sheet supply roller 2b for conveying the sheets S in the cassette 2a one by one;
And a number of rollers (2c, 2d) for transporting the sheet S sent from the sheet cassette 2a.

The scanner unit 3 irradiates information light based on image information to the electrophotographic photosensitive member 4a of the image forming section 4.

The image forming section 4 forms an image on the electrophotographic photosensitive member 4a, and includes transfer means 5 for transferring the image formed on the electrophotographic photosensitive member 4a to the sheet S.

The fixing means 6 applies the transferred image to the sheet S
It is settled in.

Normally, the number of output sheets of the laser beam printer 1 is predetermined, and in this embodiment, the conveyance of the sheet S conveyed by the conveying means 2 (2c, 2d), the transfer means 5, and the fixing means 6 The speeds are set to be substantially the same speed P.

The image forming section 4 includes an electrophotographic photosensitive member 4
a) and at least one process unit, and is unitized as a process cartridge detachable from the image forming apparatus 1. Here, as the process means, for example, a charging means for charging the electrophotographic photosensitive member 4a, a developing means for developing a latent image formed on the electrophotographic photosensitive member 4a, and a toner remaining on the surface of the electrophotographic photosensitive member 4a are used. There are cleaning means for cleaning.

(Operation of Image Forming Apparatus with Sheet Conveying Apparatus) Referring to FIG.
The scanner unit 3 irradiates the electrophotographic photosensitive member 4a with information light based on image information to form a latent image on the electrophotographic photosensitive member 4a, and develops the latent image to form a toner image.
In synchronization with the formation of the toner image, the sheet S is transferred from the sheet cassette 2a to the sheet supply roller 2b and the relay roller pair 2
c and the registration roller pair 2d, the image forming unit 4
Transport to Then, the toner image formed on the electrophotographic photosensitive member 4a is transferred to the sheet S by the transfer unit 5.
The sheet S after the image transfer is conveyed to the fixing unit 6, and the transferred toner image is fixed on the sheet S. The fixed sheet S is transferred to the sheet discharge tray 24 by the discharge roller pair 2g.
Is discharged.

(Sheet Conveying Apparatus of First Embodiment) FIG. 2
FIG. 2 is a perspective view of a main part of the sheet conveying apparatus according to the first embodiment.

The sheet cassette 2a is formed with an inclined surface 7 inclined so that its upper end is located downstream of the lower end in the sheet conveying direction and receives the leading end of the sheet, for example, inclined at about 70 degrees.

The surface (so-called tread surface) of the sheet supply roller 2b which comes into contact with the sheet has a large friction coefficient, for example, EP so that the sheet S can be urged without slipping by frictional force.
It is formed of a rubber material such as DM (ethylene propylene rubber). The sheet supply roller-2b is provided integrally at both ends of the rotating shaft 10, and rotates in the direction of arrow B when the rotation of the driving shaft 11 is transmitted to the rotating shaft 10 by a method (for example, a belt) not shown. It has become. Further, since the sheet supply arm 9 is supported so as to be rotatable about the drive shaft 11, the sheet supply roller 2b is inclined by its own weight with respect to the first sheet regardless of the number of sheets loaded in the sheet cassette 2a. The contact can be made at a distance L from the surface 7.

The sheet supply roller 2b is connected to the drive shaft 1
It is located at a position abutting on the sheet on the downstream side in the sheet conveying direction from the position No. 1. That is, the sheet supply roller 2b can increase the vertical load (sheet pressure) on the sheet according to the rigidity of the sheet until the front end of the first sheet hits the inclined surface and bends. When the first sheet starts to bend and is conveyed on the inclined surface 7, the biting of the sheet supply roller 2b is released, so that the sheet pressure on the first sheet rapidly decreases. This makes the second sheet 1
It is prevented that the sheet is bent and double-fed together with the second sheet.

It is not preferable that the distance L greatly fluctuates depending on the number of sheets loaded in the sheet cassette 2a.
Accordingly, the radius of rotation of the sheet supply roller 2b by the sheet supply arm 9 is set to be large so that the fluctuation of L is small. A pair of pressing pieces 8 serving as sheet pressing means are rotatably supported at both ends of the rotating shaft 10. The pressing piece 8 abuts on the first sheet in the sheet cassette, and corrects the deformation of the sheet with respect to the inclined surface 7. The pressing piece 8 is located at a position overlapping the inclined surface 7 in order to reliably correct the leading end of the sheet. Therefore, the inclined surface 7 is formed with two concave portions 7a for avoiding interference.

The number of pressing pieces 8 is not limited to one pair, but may be any number. Also, the number of the concave portions 7a may be formed in a number corresponding to the number of the pressing pieces 8.

The sheet conveying apparatus according to the first embodiment has the following advantages.

By correcting the front end of the sheet by the pressing piece 8, the strength of the sheet in the sheet cassette 2a can be made uniform.

Therefore, it is possible to prevent the double feed due to the proof stress of the sheet as described above.

Further, the sheet has an effect of uniformly increasing the proof stress of the sheet (Pr → Pr ′), and as shown in FIG.
Double feed can be prevented when | and | µ-µ '| That is, in FIG. 13, since the difference between the conveyance force of the second sheet due to the sheet pressure when the first sheet is bent and the proof stress (Pr ′) of the sheet can be sufficiently obtained (D ′> D), The bending of the first sheet and the bending of the second sheet do not occur at the same time. Therefore,
The advantage is that double feed of a bond sheet having a rough surface can be prevented.

Although the pressing piece 8 according to the first embodiment abuts against the sheet by its own weight, the same advantage can be obtained when the pressing piece 8 is urged using an urging member such as a spring.

(Sheet Conveying Apparatus of Second Embodiment) FIG.
FIG. 9 is a perspective view of a main part of the sheet conveying device according to the second embodiment.

The sheet supply roller 2b driven by a drive system (not shown) is supported by a sheet supply frame (movable frame) 12 so as to be able to move in parallel to the surface of the sheets stacked in the sheet cassette 2a. Further, the sheet supply roller 2b is always pulled toward the inclined surface 7 by a tension spring 14 provided between the sheet supply frame 12 and the shaft 13. The shaft 10 is movably supported by long holes 25 (one of which is not shown) formed on both sides of the sheet supply frame 12 in parallel with the sheet surface.

The sheet supply frame 12 is guided by the pinions 16, 16 rotatably supported on both side surfaces of the sheet supply frame 12 and the racks 15, 15 formed parallel to the inclined surface 7 of the sheet cassette 2a. It is configured to be movable between the upper surface of the sheet S and the inclined surface 7. Accordingly, the sheet supply roller 2b is in contact with the first sheet at a position substantially at a constant distance L from the inclined surface 7 due to the weight of the sheet supply roller 2b, the weight of the sheet supply frame 12, and the like.

The sheet supply roller 2b is rotated in the direction of arrow B to move on the sheet in a direction away from the inclined surface 7, and depends on the rigidity of the sheet until the front end of the first sheet hits the inclined surface 7 and bends. Thus, the distance L between the inclined surface 7 and the sheet supply roller 2b is increased. When the sheet is deflected and the sheet is conveyed, the sheet supply roller 2b is pulled by the tension spring 14 and is made to approach the inclined surface 7 almost integrally with the conveyed sheet, thereby reducing the distance L. To prevent the second sheet from being bent and fed again.

At both ends of the shaft 13, a pair of pressing pieces 12a for correcting the deformation of the front end of the sheet abutting on the inclined surface 7 are rotatably provided. This pressing piece 12a is shown in FIG.
Irrespective of the number of loaded sheets,
The sheet comes into contact with the second sheet to correct the deformation of the leading end of the sheet. The pressing piece 12a is located at a position overlapping the inclined surface 7 in order to reliably correct the leading end of the sheet. Therefore, the inclined surface 7 is formed with two concave portions 7a for avoiding interference.

The number of pressing pieces 12a is not limited to one pair, but may be any number. The number of the concave portions 7a may be formed by the number corresponding to the number of the pressing pieces 12a.

The sheet conveying device of the second embodiment has the same advantages as the conveying device of the first embodiment.
Until the front end of the second sheet deflects on the inclined surface 7,
Since the sheet supply roller 2b moves according to the rigidity of the sheet, there is an advantage that the sheet can be surely separated.

(Sheet Conveying Apparatus of Third Embodiment) FIG.
FIG. 9 is a perspective view of a main part of a sheet conveying device according to a third embodiment.

The sheet pressing plate 18 serving as a sheet pressing means
Is mounted on the front end of the sheet over substantially the entire width of the conveyed sheet so that the front end of the sheet can be corrected. The sheet holding plate 18 is located at a position overlapping with the inclined surface 7 in order to reliably correct the leading end of the sheet. Therefore, a pair of projecting pieces 18a, 18a projecting from the sheet holding plate 18 and overlapping the inclined surface 7 are provided,
Two concave portions 7a are formed on the inclined surface 7 to avoid interference. The projecting piece 18a engages with the concave portion 7a and regulates the position so that the sheet pressing plate 18 does not move in the width direction of the sheet S. The sheet holding plate 18 is formed with a notch portion 18b for the sheet supply roller 2b.

The sheet conveying device according to the third embodiment also has the first
In addition to having the same advantages as the embodiment, since the sheet pressing plate 18 can correct not only the deformation of the sheet in the sheet conveying direction but also the deformation of the sheet in the width direction,
It is possible to make the proof strength of the stacked sheets more uniform, and to reliably prevent double feeding of the sheets.

(Sheet Conveying Apparatus of Fourth Embodiment) FIG.
FIG. 9 is a front view of a main part of a sheet conveying device according to a fourth embodiment.

The sheet pressing means 26 includes a pair of arms 20 rotatably supported at both ends of the rotating shaft 10 of the sheet supply roller 2b, and a rotating shaft 1 between the free ends of the pair of arms 20.
The support shaft 21 includes a support shaft 21 provided in parallel with 0 and a pair of rotatable rollers 19 provided near both ends of the support shaft 21. The roller 19 comes into contact with the leading end of the sheet,
The deformation of the leading end of the sheet is corrected by its own weight and the weight of the arm 20.

Note that, since FIG. 5 is a front view, one of the pair of components overlaps the other and is not shown in FIG. The number of the rollers 19 is not limited to one pair, but may be any number.

The sheet conveying device according to the fourth embodiment also has the first
It has the same advantages as the embodiment.

The rollers 19 may be driven in the sheet conveying direction at substantially the same rotation speed as the sheet unloading speed. In this case, there is a similar advantage.

(Sheet Conveying Apparatus of Fifth Embodiment) FIG. 6
FIG. 14 is a front view of a main part of the sheet conveying apparatus according to the fifth embodiment.

The sheet holding means 27 includes a pair of arms 28 and a pair of base pulleys 29 rotatably provided at both ends of the rotary shaft 10 of the sheet supply roller 2b, and each free end of the pair of arms 28. A pair of free end pulleys 30 provided on the side;
A pair of rubber-made belts 22 spanning a base pulley 29 and a free end pulley 30 are provided. The belt 22 presses the leading end of the sheet to correct the deformation of the leading end of the sheet,
When a sheet is conveyed from the sheet cassette 2a, the sheet rotates following the sheet. The pair of free end pulleys 30 may have their rotation centers connected by a common shaft.

Since FIG. 6 is a front view, one of the pair of components overlaps the other and is not shown in FIG.

The number of belts 22 is not limited to one pair, but may be any number. Further, the number of the arms 28 and the number of the pulleys 29 and 30 may be provided corresponding to the number of the belts 22.

The sheet conveying device according to the fifth embodiment is also the same as the first embodiment.
It has the same advantages as the embodiment.

[0086] The belt 22 may be driven in the sheet conveying direction at substantially the same rotation speed as the sheet unloading speed. In this case, there is a similar advantage.

(Sheet Conveying Apparatus of Sixth Embodiment) FIG. 7
FIG. 13 is a perspective view of a main part of a sheet conveying device according to a sixth embodiment.

The sheet conveying device of the sixth embodiment has a structure in which sheet pressing plates 17 are provided at both ends of the rotary shaft 10 as sheet pressing means instead of the pressing pieces 8 in the sheet conveying device of the first embodiment so as to be rotatable. It has become. The sheet holding plate 17 has a pair of projections 1 overlapping the inclined surface 7.
7a and 17a are protruded, and two concave portions 7a are formed on the inclined surface 7 to avoid interference. Further, a relief portion 17b of the sheet supply roller 2b is formed in the sheet holding plate 17 in a cutout shape.

The sheet pressing plate 17 abuts on the first sheet in the entire area in the sheet width direction to correct the deformation of the front end of the sheet. In part of the sheet holding plate 17,
A projecting piece 17c is provided outside the widthwise region of the sheet and protrudes downstream from the inclined surface 7 in the conveying direction. Projection piece 17c
Project from the through hole 2aa of the sheet cassette 2a.

The sheet conveying device according to the sixth embodiment has a first
In addition to having the same advantages as the sheet conveying device of the embodiment, the sheet cassette 2a is in contact with the first sheet supplied so that the sheet cassette 2a In the state assembled in the
7c, the sheet cassette 2
This has the advantage that the remaining number of sheets in a can be checked from the outside. Therefore, the sheet holding plate 17 has a function of indicating the number of remaining sheets.

The arrangement and operation of the sheet supply roller 2b in the third to sixth embodiments described above are the same as the arrangement and operation of the sheet supply roller 2b in the first embodiment.

[0092]

The sheet conveying apparatus of the present invention has the following effects.

In a sheet feeding system of a sheet feeding system for separating sheets by bending the sheets by using the sheet receiving surface of the sheet cassette, a sheet pressing means for correcting the front end of the stacked sheets in the conveying direction is provided with the sheet receiving surface and the sheet feeding. By providing the sheet between the sheet and the roller, double feeding due to deformation of the sheet can be prevented.

When the upper end of the sheet receiving surface is inclined to the downstream side in the sheet conveying direction from the lower end, the sheet can be conveyed smoothly.

When the pressing direction of the sheet supply roller is substantially parallel to the sheet receiving surface, even if the number of sheets is reduced, the sheet supply roller is separated from the sheet receiving surface by a predetermined distance at the front end of the sheet. By pressing a predetermined position, the sheet can always be loosened in an optimal state.

Further, if the sheet pressing means is a plate-shaped sheet pressing plate and a part thereof projects to a position where the sheet stacking amount can be checked, the sheet pressing plate reduces the remaining amount of sheets in the sheet cassette. Can be displayed, and the remaining amount of sheets can be easily managed.

Since the image forming apparatus of the present invention is provided with the above-described sheet conveying device, the sheet is smoothly fed from the sheet conveying device, so that an image can be accurately formed on the sheet.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a laser beam printer which is an image forming apparatus provided with a sheet conveying device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the sheet conveying apparatus according to the first embodiment.

FIG. 3 is a perspective view of a main part of a sheet conveying apparatus according to a second embodiment.

FIG. 4 is a perspective view of a main part of a sheet conveying apparatus according to a third embodiment.

FIG. 5 is a front view of a main part of a sheet conveying apparatus according to a fourth embodiment.

FIG. 6 is a front view of a main part of a sheet conveying apparatus according to a fifth embodiment.

FIG. 7 is a perspective view of a main part of a sheet conveying apparatus according to a sixth embodiment.

FIG. 8 is a diagram illustrating a state of action of each force on a sheet and an inclined surface in a sheet conveying apparatus based on an inclined surface separating sheet supply method using an inclined surface.

FIG. 9 is a diagram illustrating a relationship between a sheet pressure and a conveying force for explaining a slope separation sheet supply method.

FIG. 10 is a diagram illustrating a relationship between a natural length and a sheet proof stress for explaining a slope separation sheet supply system.

FIG. 11 is a diagram illustrating a state where a second sheet is curled upward.

FIG. 12 is a diagram illustrating a state where a first sheet is curled downward.

FIG. 13 is a diagram illustrating a relationship between a sheet pressure and a conveying force for explaining advantages of each embodiment.

[Explanation of symbols]

 S Sheet Sa Leading end of sheet 1 Laser beam printer (image forming apparatus) 2 Sheet transporting apparatus 2a Sheet cassette (sheet stacking means) 2b Sheet feeding roller 4 Image forming section 7 Inclined surface of sheet cassette (sheet receiving surface) 7a Depression 8 Press Piece (sheet holding means) 12 Sheet supply frame (movable frame) 12a Pressing piece (sheet holding means) 15 Rack 16 Pinion 17 Sheet holding plate (sheet holding means) 17a Projection piece 17b Relief portion 17c Projection piece 18 Sheet holding plate (sheet) Pressing means) 19 Roller (sheet pressing means) 20 Roller arm (sheet pressing means) 21 Support shaft (sheet pressing means) 22 Belt (sheet pressing means) 25 Slot 26 Sheet pressing means 27 Sheet pressing means 28 Arm (sheet pressing means) 29) Base Pulley (Sheet Holding Means) 30 Play Pulleys (sheet pressing means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H072 BA03 BA08 BA17 BA19 3F343 FA02 FB02 FB03 FB04 FC01 GA01 GB01 GC01 GD01 HC24 HC30 HE07 HE08 HE09 HE11 JA01 JA16 JA17 JD13 JD22 KA03 KA13 LA04 LA14 LA15 LA16 LC07

Claims (15)

[Claims] 1. A sheet stacking means on which a plurality of sheets are stacked and provided with a sheet receiving surface for receiving a leading end of the sheet at a downstream end of the sheet in a conveying direction; A sheet supply roller that abuts on the sheet receiving surface and separates the sheet from the sheet stacking unit and sends the sheet from the sheet stacking unit; and a sheet pressing unit that is positioned between the sheet receiving surface and the sheet supply roller and presses a leading end of the sheet. A sheet conveying device, comprising: 2. The sheet conveying device according to claim 1, wherein the sheet receiving surface is an inclined surface that is inclined such that an upper end thereof is located on a downstream side in a conveying direction of the sheet than a lower end thereof. apparatus. 3. The sheet conveying device according to claim 1, wherein the sheet supply roller is capable of moving up and down substantially in parallel with the sheet receiving surface. 4. The sheet conveying apparatus according to claim 1, wherein the sheet pressing means is a pressing piece rotatably provided coaxially with the sheet supply roller. 5. The sheet conveyance device according to claim 1, wherein the sheet supply roller is movable substantially in parallel with an upper surface of the sheets stacked on the sheet stacking unit. 6. The sheet supply roller is provided movably in the transport direction by being urged by a movable frame having a pinion meshing with a rack parallel to the sheet receiving surface in a downstream direction in the sheet transport direction. The sheet conveying device according to claim 5, wherein: 7. The sheet conveying device according to claim 6, wherein the sheet pressing means is a pressing piece rotatably provided on the movable frame. 8. The sheet conveying device according to claim 4, wherein a plurality of the pressing pieces are provided. 9. An arm provided rotatably on a rotation shaft of the sheet supply roller, and a roller on a support shaft provided parallel to the rotation shaft on a free end side of the arm. The sheet conveying device according to claim 1, wherein the roller presses a leading end of the sheet. 10. An arm and a base pulley provided so as to be rotatable coaxially with a rotation axis of the sheet supply roller, a free end pulley provided on a free end side of the arm, wherein the sheet pressing means comprises: The sheet conveying device according to claim 1, further comprising: a belt extending around the base pulley and the free end pulley, wherein the belt presses a leading end of the sheet. 11. The sheet conveying apparatus according to claim 1, wherein said sheet pressing means is a flat sheet pressing plate. 12. The sheet holding plate has a length substantially equal to a length in a direction orthogonal to a sheet conveying direction.
2. The sheet conveying device according to 1. 13. The sheet according to claim 11, wherein a part of the sheet pressing plate protrudes to a position where a stacking amount of the sheets stacked on the sheet stacking unit can be checked. Transport device. 14. The sheet conveying device according to claim 1, wherein a concave portion is formed in the sheet receiving surface so that a part of the sheet pressing unit enters. 15. An image, comprising: the sheet conveying device according to claim 1; and an image forming unit that forms an image on a sheet conveyed from the sheet conveying device. Forming equipment.