JPH06305591A - Image forming device - Google Patents

Abstract

PURPOSE:To stably supply sheets to an image forming part, in an image forming device in which a plurality of paper feed cassettes are built in above and below. CONSTITUTION:Since a paper feed cassette 5 in the uppermost position is formed in small size and arranged to deflect to one side in a lateral direction so as to provide conveying passages 51, 56 of sheets in an opposite side, curvature of a curved part of the conveying passage can be largely set, and even thick paper and a stiff sheet can be supplied from the paper feed cassette. Further, since a direction of a curl of the sheet, supplied to an image forming part 105, is fixed by curl forming means 201, 202, stable image forming is performed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile, a plurality of sheet feeding cassettes arranged vertically are provided in a main body of the image forming apparatus, and sheets in each sheet feeding cassette are fed to an image forming section. An image forming apparatus that selectively feeds paper is known.

In the image forming apparatus of this system, since a plurality of paper feed cassettes accommodating sheets of different sizes are loaded and housed in the main body of the image forming apparatus, it is possible to save the trouble of exchanging the sheets. Further, since a plurality of paper feed cassettes are arranged vertically in the image forming apparatus body, there is an advantage that the installation area of the image forming apparatus body can be reduced.

Incidentally, each paper feed cassette in the image forming apparatus of this system is of a front loading type in which it is taken in and out from the front side of the image forming apparatus main body.

FIG. 6 shows the overall structure of a conventional color image forming apparatus (copying machine) which employs this method.

In this color image forming apparatus, the photosensitive drum 2 and the transfer drum 3 are provided in the upper portion of the main body 1 of the image forming apparatus.
And the like, and a plurality of sheet feeding cassettes 5 in which sheets of different sizes are stacked and stored in the lower portion of the image forming apparatus main body 1.
6, 7, 9 etc. are arranged.

The paper feed cassettes 5, 6, 7, and 9 are all paper feed cassettes capable of stacking and storing sheets of the maximum size, and are arranged at predetermined intervals in the vertical direction. In this case, the paper feed side end 5 of each paper feed cassette 5, 6, 7, 9
A, 6A, 7A and 9A are located on the same side.

The paper feed cassettes 5, 6, 7 and 9 are slidably fitted to the left and right rails 43A and 43B of the image forming apparatus main body 1 so that the left and right guides 45A and 45B are slidably fitted. The image forming apparatus main body 1 can be put in and taken out from the front side. That is, the paper feed cassettes 5, 6, 7, 9 are slidable in the direction perpendicular to the paper surface.

The sheets stacked and stored in the sheet feeding cassettes 5, 6, 7 and 9 are fed out by the sheet feeding rollers (pickup rollers) 46, 47, 49 and 50 which rotate in the counterclockwise direction. Passages 51, 52, 53, 5
The sheet is fed between the transfer roller 3 and the suction roller 35 via the junction sheet passage 5 and the merged sheet passage 56.

The sheets sent out from the paper feed cassettes 5, 6, 7, and 9 are first paired with the first registration rollers 57 and 5.
The first registration roller pair 57, 59, 60, 61 and the conveyance roller pair 62, 63, which are fed to 9, 60, 61 and straightened there, and then start rotating at appropriate timing.
Is sent to the second pair of registration rollers 65, where the skew is finally corrected. Next, the sheet is sent between the transfer roller 3 and the suction roller 35 by the second registration roller pair 65 which starts to rotate at an appropriate timing, and is further sent between the photosensitive drum 2 and the transfer drum 3.

By the way, in the case of this color image forming apparatus,
Since the large-diameter photosensitive drum 2 and the transfer drum 3 are installed in the image forming apparatus main body 1, a space for installing a plurality of sheet feeding cassettes 5, 6, 7, 9 is provided as compared with a normal single-color image forming apparatus. It is greatly restricted. Therefore, conventionally, when as many paper feed cassettes 5, 6, 7, 9 as possible are installed in a limited space in the image forming apparatus main body 1, the paper feed roller 46 of the uppermost paper feed cassette 5 is installed. Small diameter,
The curvature of the curved portion of the seat passage 51 is reduced.

As described above, the reason why the sheet feeding roller 46 of the uppermost sheet feeding cassette 5 is made small in diameter and the curvature of the curved portion of the sheet passage 51 is made small is that the sheet feeding roller 46 is installed by the merging sheet passage 56. This is because the space for forming the sheet passage 51 is limited and the space for forming the sheet passage 51 is limited.

The transfer drum 3 used in the color image forming apparatus must be capable of winding a maximum size sheet. For example, when using a maximum size sheet of 420 mm in length, a diameter of 160 mm is used. Transfer drum 3
Will be required. Further, the photosensitive drum 2 must also have the same diameter as the transfer drum 3 in order to prevent the image displacement.

[0014]

However, in the above-described conventional color image forming apparatus, a small-diameter paper feed roller 46 is used in the uppermost paper feed cassette 5, or a sheet passage 51 is used.
Since the curvature of the curved portion is small, when a thick paper having a large friction, a strong film, or the like is fed from the uppermost sheet feeding cassette 5, there is a possibility that a feeding failure or a jam may occur. .

For this reason, the conventional color image forming apparatus is provided with a manual sheet feeding section (not shown) having a linear sheet path (straight path) for feeding thick paper or film. Paper cassettes other than the top 6,
I had to deal with cases where 7, 9 could not be used.

Further, such a problem is not limited to the color image forming apparatus, and, for example, in the case of increasing the number of paper feed cassettes installed in the main body of the image forming apparatus in a limited space in an ordinary single color image forming apparatus. Occurs similarly to.

Therefore, the present invention has been made in view of the above-described circumstances, and even when as many sheet feeding cassettes as possible are installed in the limited space of the main body of the image forming apparatus, the uppermost stage is provided. It is an object of the present invention to provide an image forming apparatus capable of stably feeding thick paper having a large amount of friction, a strong film, and the like from a paper feeding cassette in a stable state without a paper feeding failure or a jam.

[0018]

SUMMARY OF THE INVENTION According to the present invention, a plurality of sheet supporting means are arranged vertically in an image forming apparatus main body, and a sheet is selectively fed from each of the sheet supporting means to an image forming section. In the image forming apparatus described above, the uppermost sheet supporting means among the plurality of sheet supporting means is arranged as a small one, and is arranged so as to be biased to one side in the left-right direction with respect to the center of the image forming apparatus main body. A merging portion of a passage for conveying the sheet fed from the sheet supporting means and a passage for conveying the sheet fed from the lower sheet supporting means is provided at the uppermost position with respect to the center of the image forming apparatus main body. Positioned on the side opposite to the side where the seat support means is arranged,
It is characterized in that the curl forming means is provided so that the curl directions of the sheets fed from the respective sheet supporting means are all in the same direction.

[0019]

As described above, since the uppermost sheet supporting means is made small and is arranged so as to be biased to one side, and the seat passage is provided on the opposite side to which the bias is applied, a wide space can be secured. The curvature of the curved portion of the sheet path can be set to a large value, and the paper feed roller or the like can also have a large diameter. Further, by disposing the curl forming means for forming the curl in the sheet conveying passage, it is possible to always form the curl in the same direction on the sheet fed to the image forming section. Sheets can be supplied under the same conditions.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus in which the present invention is effectively used will be described with reference to FIG.

This example has a digital color image reader section in the upper part and a digital color image printer section in the lower part.

In the reader unit, the original 130 is placed on the original table glass 131 and exposed and scanned by the exposure lamp 132, so that the reflected light image from the original 130 is condensed on the full color sensor 134 by the lens 133, and the color color is obtained. Obtain a decomposed image signal. The color-separated image signal passes through an amplifier circuit (not shown), is processed by a video processing unit (not shown), and is sent to the printer section.

In the printer section, a photosensitive drum 101, which is an image carrier, is rotatably supported in the direction of the arrow, and a pre-exposure lamp 111, a corona charger 102, a laser exposure optical system 103, and a potential sensor 112 are provided around the photosensitive drum 101. ,
Four developing devices 104y, 104c, 104 of different colors
m, 104Bk, the on-drum light amount detection means 113, the transfer device 105, and the cleaning device 106 are arranged.

In the laser exposure optical system 103, an image signal from the reader section is converted into an optical signal by a laser output section (not shown), and the converted laser light is converted into a polygon mirror 1.
Reflected by 03a, lens 103b and mirror 103c
And is projected onto the surface of the photosensitive drum 101.

When forming an image on the printer section, the photosensitive drum 1
01 is rotated in the direction of the arrow, the photosensitive drum 101 after the charge is removed by the pre-exposure lamp 111 is uniformly charged by the charger 102, and the light image E is emitted for each separated color to form a latent image.

Next, a predetermined developing device is operated to develop the latent image on the photosensitive drum 101, and a toner image based on resin is formed on the photosensitive drum 101. The developing device selectively approaches the photosensitive drum 101 in accordance with each separated color by the operation of the eccentric cams 124y, 124c, 124m, and 124Bk.

Further, the toner image on the photosensitive drum 101 is transferred to the sheet supplied from the paper feed cassette 5 via the conveying system and the transfer device 105 to the position opposed to the photosensitive drum 101. In this example, the transfer device 105 includes a transfer roller 105a, a transfer charging device 105b, and a suction roller 10 facing a suction charging device 105c for electrostatically sucking a sheet.
5 g, an inner charger 105 d, an outer charger 105 e, and a transfer drum 105 that is rotatably supported and is axially supported.
A supporting sheet 105f made of a dielectric material is provided in the peripheral opening area of a.
Is integrally stretched in a cylindrical shape. Carrying sheet 105f
Uses a dielectric sheet such as a polycarbonate film.

As the drum-shaped transfer device, that is, the transfer drum 105a is rotated, the photosensitive drum-shaped toner image is transferred to the recording material carrying sheet 10 by the transfer charger 105b.
Transfer to the sheet carried on 5f.

A desired number of color images are transferred to the sheet thus sucked and conveyed by the carrying sheet 105f to form a full-color image.

In the case of forming a full-color image, when the transfer of the four color toner images is completed in this way, the sheet is separated from the transfer drum 105a by the separation claw 108a and the separation push-up roller 10.
8b and the separation charger 105h separate the sheets, and the sheets are discharged to the tray 110 via the heat roller fixing unit 109.

On the other hand, the post-transfer photosensitive drum 101 is subjected to the image forming process again after the residual toner on the surface is cleaned by the cleaning device 106.

When images are formed on both sides of the sheet,
Immediately after ejecting the fixing device 109, the conveyance path switching guide 11
9 is driven, and after the conveyance vertical path 120, the reverse path 121
After being guided to a, the reversing roller 121b reversely moves the sheet, with the trailing end of the sheet being fed in at the beginning, and withdraws in the direction opposite to the feeding direction, and is stored in the intermediate tray 122. After that, an image is formed on the other surface by the above-described image forming step.

Further, the carrying sheet 1 of the transfer drum 105a
The fur brush 114 and the carrying sheet 1 are provided to prevent the powder from scattering on the 05f and the oil from adhering to the sheet.
Cleaning is performed by the action of the backup brush 115 facing the brush 114 via 05f and the backup brush 117 facing the roller 116 via the oil removing roller 116 and the carrying sheet 105f. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Further, in this embodiment, the eccentric cam 125 is operated at a desired timing and the cam follower 105i integrated with the transfer drum 105f is operated to arbitrarily set the gap between the carrying sheet 105a and the photosensitive drum 101. It has a configurable configuration. For example, during standby or when the power is off, the transfer drum and the photosensitive drum are separated from each other.

FIG. 1 is a schematic diagram of the image forming apparatus shown in FIG. 2. Based on this, a configuration for feeding sheets from a sheet feeding cassette will be described.

In the image forming apparatus, the paper feed cassettes 6, 7, 9 installed in the second, third and fourth stages
Is a paper feed cassette (normal paper feed cassette) capable of stacking and storing sheets of the maximum size, and the paper feed cassette 5 installed in the first stage (top stage) is loaded with 1/2 or less sheets of the maximum size. It is used as a paper feed cassette (small paper feed cassette). The paper feeding cassette 6 is a reversing unit having a reversing path for forming images on both sides.

Then, the first-stage paper feed cassette 5 is
The sheet feeding cassettes 6, 7, 9 of the second, third, and fourth stages are installed in a state retracted from the feeding-side ends 6A, 7A, 9A. Here, the non-feeding side end 5B of the first-stage paper feeding cassette 5 is the anti-feeding side end 6B of the second-stage, third-stage, and fourth-stage paper feeding cassettes 6, 7, and 9. , 7B, 9B.

Further, the sheet passage 51 for the sheets fed from the first-stage sheet feeding cassette 5 is fed through the sheet feeding side end 5A of the sheet feeding cassette 5 and the sheet feeding cassette 6 of the second stage. Side edge 6
Between A, the merging sheet passage 5 of the sheets fed from the sheet feeding cassettes 6, 7, and 9 of the second, third, and fourth stages
Joined with 6. A second pair of registration rollers 65 is installed at this junction 66.

In this case, the joining portion 66 of the sheet passage 51 and the joining sheet passage 56 is located below the photosensitive drum 2 and the transfer drum 3 for image formation.

With this configuration, the sheet passage 51 of the first-stage sheet feeding cassette 5 has the second and third sheet passages.
The joining sheet passages 56 of the sheet feeding cassettes 6, 7, 9 of the fourth and fourth stages do not restrict the space for formation, and therefore the curvature of the curved portion can be increased.

Further, the sheet feeding roller 46 of the first sheet feeding cassette 5 is formed by the confluent sheet passage 56 of the second, third and fourth sheet feeding cassettes 6, 7 and 9. The space for installation is not restricted, and thus a large diameter feed roller can be used.

In the case of this color image forming apparatus, the distance bc including the resist feed amount from the sheet front end b of the first sheet feeding cassette 5 to the transfer position c is set to the image front end position d of the photosensitive drum 2 and the transfer position. Since the distance can be made smaller than the distance dc to c (dc> bc), the first sheet fed from the first-stage sheet feeding cassette 5 is the photosensitive drum after the photosensitive drum 2 starts rotating. Even if the paper is fed at the same speed as the peripheral speed of 2, the transfer position c can be sufficiently reached. Therefore, the copying time of the first sheet fed from the first-stage sheet feeding cassette 5 can be shortened and the sequence becomes simple.

Even in the case where a sheet feeding cassette for accommodating sheets of 1/2 or less of the maximum size is used in the first stage sheet feeding cassette 5 as in the present color image forming apparatus, for example, the maximum size A3 is used. The sheet that is mainly used in the image forming apparatus that uses the above sheet is an A4 size sheet,
Moreover, since the sheets of the maximum size A3 can be fed by the sheet feeding cassettes 6, 7, 9 of the second, third, and fourth stages, there is no problem in feeding the sheets of the maximum size. .

Therefore, when the number of paper feed cassettes is large and there is a margin for feeding the maximum size sheet, the second paper feed cassette 6 is also the same as the first paper feed cassette 5. Can be configured.

Here, a detailed description of the sheet merging portion will be given with reference to FIG.

The sheet P ₁ is sent out from the paper feed cassette 5 by the pickup roller 46, and then further sent by the feed roller 57a and the retard roller 57b, passes between the upper guide 213 and the lower guide 214, and passes through the upper guide. 215
Then, it passes between the movable guide 207 and the right guide 205 and hits the stopped registration roller pair 65a, 65b. Further, the feed rollers 211 and 212 are rotated by about 5 mm to form an upward loop on the sheet P _{1 as} shown in the figure and stop. The amount of loop to be formed is a predetermined amount after detecting the leading edge of the sheet by the sensors S ₁ and S ₂ , that is, ι
Send by +5 mm.

Then, the pair of registration rollers 65a and 65b are rotated in synchronization with a predetermined position of the carrying sheet 105f on the surface of the transfer drum 105a to pass between the guide right 218 and the guide left 219, and the transfer drum 105a and the suction roller. Along the tangent line H of 105 g, from the outside slightly, the suction roller 1
It is introduced between 05g and the adsorption charger 105c and electrostatically adsorbed on the carrying sheet 105f. In addition to electrostatically adsorbing, the leading edge of the paper may be gripped by a gripper or the like. Next, the transfer charger 10 immediately above the suction roller 105g.
5b to transfer the toner image on the photosensitive drum 101 to the paper P ₁
Transfer to.

Next, a method of feeding the sheet P ₂ will be described with reference to FIG.

The sheet P ₂ fed through between the guides 203 and 204 is curled upward while passing between the sponge roller 201 and the lower roller 202 made of a rubber material. Further, the fed sheet passes between the right guide 205 and the movable guide 207, further passes between the right guide 205 and the upper guide 215, and is stopped.
It hits 5a and 65b. The feed rollers 201 and 202 are further rotated by about 5 mm, and the rigidity of the sheet P ₂ causes the movable guide 207 to move to the left centering on the central shaft 206 against the force of the spring 208 as shown in the figure. And then stop. The subsequent operation is the same as that when the sheet P ₁ is fed. Since the movable guide 207 can move to the right even when the sheet P ₁ is used, a downward convex loop may be formed.

[0050] In this case, the wearing the curl only on the sheet P ₂ are those as of the sheet, guide 203,204,2
This is because curls tend to be hard to wind around the transfer drum while passing through 05 and 207. Further, in the structure of the present invention, since the path through which the sheet P ₂ passes is extremely long compared to the sheet P ₂ , it is easy to provide a roller for curling in the path, and in the example of FIG. 4, the registration roller pair 65a,
Although the paper feed rollers 201 and 202 upstream of 65b are curl rollers, they may be further upstream.

On the other hand, since the sheet P ₁ is curled in such a direction that it easily winds around the transfer drum while passing through the guide, it is not necessary to provide a curl roller in the path. Therefore, since the confluence portion of the sheets P ₁ and P ₂ can be provided immediately below the suction portions 105c and 105g of the transfer drum 105a, the sheet feeding cassette 5 can be provided below the transfer drum immediately to the left thereof. The paper cassette 5 does not increase the height of the machine. Further, since it is exclusively used for a small sheet, it does not collide with a guide of a sheet guided downward for double-sided copying, and the width of the machine does not become wide because of the sheet feeding cassette 5.

<Embodiment 2> In Embodiment 2 shown in FIG. 5, the construction of each of the paper feed cassettes 5, 6, 7 and 9 (paper feed cassettes 7 and 9 are omitted) of Embodiment 1 is a normal monochromatic image. The case where it is applied to a forming apparatus (copier) is shown.

In the case of this monochromatic image forming apparatus, the sheets fed from the sheet feeding cassettes 5, 6, 7 and 9 are transferred to the photosensitive drum 67 and the transfer charger 6 by the second pair of registration rollers 65.
It is sent between 9 and.

[0054]

As described above, according to the present invention, the uppermost sheet support means is made smaller than the other sheet support means, and the sheet support means is disposed so as to be biased in one of the left and right directions of the image forming apparatus main body. By arranging the passage of the seat on the opposite side, the curvature of the curved part of the passage of the seat can be set large,
Further, a paper feed roller or the like having a large diameter can be used. Therefore, it is possible to stably feed thick paper or a strong film from the sheet supporting means.

Further, since the curl forming means is provided in the sheet conveying passage to supply the curled sheet in the same direction to the image forming section, the sheet is always supplied to the image forming section under the same condition. Therefore, image formation with stable quality can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus of the present invention.

FIG. 2 is a diagram showing details of an image forming unit of the image forming apparatus shown in FIG.

FIG. 3 is a diagram showing a state in which a sheet is sent out from the uppermost sheet feeding cassette at a merging portion of a sheet passage in the image forming apparatus shown in FIG.

FIG. 4 is a diagram showing a state in which a sheet is sent out from a lower sheet feeding cassette at a merging portion of a sheet path in the image forming apparatus shown in FIG.

FIG. 5 is a schematic view of a main part showing another embodiment of the present invention.

FIG. 6 is a schematic diagram showing an example of a conventional image forming apparatus.

[Explanation of symbols]

 1 Image Forming Apparatus Main Body 5 Small Paper Feed Cassette (Small Sheet Support Means) 6,7,9 Paper Feed Cassette (Sheet Support Means) 5A, 6A, 7A, 9A Feed Side End 51,56 Sheet Passage 101 Photosensitive Drum 105 transfer device 201, 202 paper feed roller (curl forming means)

Claims (5)

[Claims] 1. An image forming apparatus in which a plurality of sheet supporting means are arranged vertically in an image forming apparatus body, and a sheet is selectively fed from each of the sheet supporting means to an image forming section, Among the plurality of sheet supporting means, the uppermost sheet supporting means is arranged as a small one, and is arranged so as to be biased to one side in the left-right direction with respect to the center of the image forming apparatus main body, and is fed from the uppermost sheet supporting means. The uppermost sheet supporting unit is arranged with respect to the center of the main body of the image forming apparatus at the confluence of the sheet conveying path and the sheet conveying path fed from the lower sheet supporting unit. An image forming apparatus, wherein the curl forming means is provided on the side opposite to the side so that the curl directions of the sheets fed from the respective sheet supporting means are all in the same direction. 2. The curl forming means is arranged in a passage for conveying a sheet fed from a sheet supporting means arranged on the lower side, and the curl forming means feeds from the uppermost sheet supporting means. The image forming apparatus according to claim 1, wherein a curl is formed in the same direction as a curl formed by a path for conveying the sheet. 3. The image forming apparatus according to claim 2, wherein the curl forming unit forms a curl in the same direction as a sheet winding direction of a transfer drum provided in the image forming unit. 4. The image forming apparatus according to claim 1, wherein the uppermost sheet supporting unit is arranged below the image forming unit. 5. The image forming apparatus according to claim 1, wherein the curl forming unit includes a roller pair in which one roller is made of a soft material.