JP3313813B2 - Image forming device - Google Patents

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, a facsimile or the like, a plurality of sheet cassettes arranged vertically in an image forming apparatus main body are provided, and sheets in each sheet cassette are sent to an image forming section. 2. Description of the Related Art An image forming apparatus that selectively feeds paper is known.

In this type of image forming apparatus, since a plurality of sheet cassettes containing sheets of different sizes are provided in the main body of the image forming apparatus, it is possible to save time and effort for sheet replacement. Further, since a plurality of paper feed cassettes are arranged vertically in the image forming apparatus main body, there is an advantage that the installation area of the image forming apparatus main body can be reduced.

[0004] Each sheet cassette in the image forming apparatus of the present system is of a front loading type in which the cassette is taken in and out of the image forming apparatus main body from the front side of the image forming apparatus main body.

FIG. 6 shows the overall configuration of a conventional color image forming apparatus (copier) employing this method.

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

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

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

The sheets stacked and stored in each of the paper feed cassettes 5, 6, 7, and 9 are fed out by paper feed rollers (pickup rollers) 46, 47, 49, and 50 that rotate counterclockwise. Passages 51, 52, 53, 5
5, and is fed between the transfer roller 3 and the suction roller 35 via the merged sheet path 56.

The sheets sent from each of the paper feed cassettes 5, 6, 7, 9 are firstly fed to a first pair of registration rollers 57, 5.
9, 60, and 61, where the skew is corrected, and then the first pair of registration rollers 57, 59, 60, and 61 and the pair of transport rollers 62 and 63 start rotating at an 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 rotating at an appropriate timing, and further sent between the photosensitive drum 2 and the transfer drum 3.

Incidentally, in the case of the present 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 paper feed cassettes 5, 6, 7, and 9 is required as compared with a normal single-color image forming apparatus. It is greatly restricted. Therefore, conventionally, when as many sheet cassettes 5, 6, 7, and 9 as possible can be installed in a limited space in the image forming apparatus main body 1, the sheet feeding roller 46 of the uppermost sheet cassette 5 is set. Small diameter,
The curvature of the curved portion of the sheet passage 51 is increased.

As described above, the diameter of the sheet feeding roller 46 of the uppermost sheet feeding cassette 5 and the increase of the curvature of the curved portion of the sheet passage 51 are determined by the arrangement of the sheet feeding roller 46 by the merged sheet passage 56. 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 sheet having a maximum size. For example, when a sheet having a maximum length of 420 mm is used, a diameter of 160 mm is used. Transfer drum 3
Is required. Also, the photosensitive drum 2 must have the same diameter as the transfer drum 3 in order to prevent image shift.

[0014]

However, in the above-described conventional color image forming apparatus, a small-diameter paper feed roller 46 is used for the uppermost paper feed cassette 5 or the sheet path 51 is not used.
Since the curvature of the curved portion is increased, when thick paper or a film having a strong stiffness 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 includes a manual paper feed unit (not shown) having a linear sheet path (straight path) for feeding thick paper, film, and the like. Paper cassettes 6 other than the top row
We had to deal with cases where 7, 9 could not be used.

Such a problem is not limited to the color image forming apparatus. For example, in a case where the number of sheet cassettes installed in the main body of the image forming apparatus is increased in a limited space in a normal single color image forming apparatus. Has occurred in the same way.

Therefore, the present invention has been made in view of the above-described circumstances, and even if a maximum number of paper cassettes can be installed in a limited space of the image forming apparatus main body, the uppermost stage can be used. It is an object of the present invention to provide an image forming apparatus capable of feeding thick paper having a large friction, a film having a strong stiffness, etc. from a paper feed cassette in a stable state without causing a paper feed failure or a jam.

[0018]

According to the present invention, a plurality of sheet supporting means are arranged vertically below an image forming section in an image forming apparatus main body, and the plurality of sheet supporting means are selectively provided. In an image forming apparatus configured to feed a sheet from a supporting unit to the image forming unit provided with a transfer drum, a sheet fed from an uppermost sheet supporting unit of the plurality of supporting units is transferred to the image forming unit. The path for conveying the sheet fed from the lower sheet support means merges with the path for conveying the sheet at the junction, and the uppermost sheet support means is smaller than the lower sheet support means. The transfer drum is arranged so as to be biased to one side in the left-right direction with respect to the merging portion, and the path between the merging portion from the uppermost sheet supporting means is skewed to the opposite side. A curved portion that curves in the same direction as the direction of the transfer drum, a curved portion that curves in a direction opposite to the sheet winding direction of the transfer drum in a path from the lower sheet support means to the merge portion, The apparatus has a curl forming means for forming a curl in the same direction as the sheet winding direction on the sheet.

[0019]

As described above, since the uppermost sheet supporting means is made compact and arranged to be biased to one side, and the sheet passage is provided on the opposite side of the bias, a wide space can be secured. The curvature of the curved portion of the sheet passage can be set small, and a large-diameter paper feed roller can be used. In addition, by arranging a curl forming unit for forming a curl on a sheet in the sheet conveying path, it is possible to always form a curl in the same direction on a sheet fed to the image forming unit. Sheets can be supplied under the same conditions.

[0020]

FIG. 2 shows a color image forming apparatus in which the present invention is effectively used.

This embodiment has a digital color image reader section at the top and a digital color image printer section at the bottom.

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

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

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

At the time of image formation in the printer section, the photosensitive drum 1
By rotating the photosensitive drum 101 in the direction of the arrow, the photosensitive drum 101 after having been neutralized by the pre-exposure lamp 111 is uniformly charged by the charger 102, and a light image E is emitted for each of the separated colors to form a latent image.

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

Further, the toner image on the photosensitive drum 101 is transferred from the sheet feeding cassette 5 to a sheet supplied to a position facing the photosensitive drum 101 via a transfer system and a transfer device 105. In the present embodiment, the transfer device 105 includes a transfer drum 105a, a transfer charger 105b, and an attraction roller 10 that faces an attraction charger 105c for electrostatically adsorbing a sheet.
5g, an inner charger 105d, and an outer charger 105e, and the transfer drum 105 is rotatably supported.
a carrier sheet 105f made of a dielectric material
Are integrally extended in a cylindrical shape. Carrier 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 by the transfer charger 105b to the recording material carrying sheet 10
Transfer onto the sheet carried on 5f.

A desired number of color images are transferred onto the sheet conveyed by suction on the supporting sheet 105f in this manner, forming 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 pushing roller 10a.
The sheet is separated by the action of the separation charger 8b and the separation charger 105h, and is discharged to the tray 110 via the heat roller fixing device 109.

On the other hand, after the transfer, the 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 a sheet,
Immediately after discharging the fixing device 109, the conveyance path switching guide 11
9 through a vertical transport path 120 and a reverse path 121
After the sheet is once fed to the intermediate tray 122, the sheet is retracted in a direction opposite to the direction in which the sheet is fed, with the rear end of the sheet being fed, by the reverse rotation of the reversing roller 121 b, and stored in the intermediate tray 122. Thereafter, an image is formed on the other surface again by the above-described image forming step.

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

In the present embodiment, the eccentric cam 125 is operated at a desired timing, and the cam follower 105i integrated with the transfer drum 105f is operated, so that the gap between the carrier sheet 105a and the photosensitive drum 101 can be arbitrarily set. It has a configuration that can be set. For example, during standby or when the power is off, the interval between the transfer drum and the photosensitive drum is increased.

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 cassette will be described.

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

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

Further, the sheet path 51 of the sheet fed from the first-stage paper feed cassette 5 is fed to the feed side end 5A of the first-stage paper feed cassette 5 and the second-stage paper feed cassette 6 is fed. Side edge 6
A, the combined sheet path 5 for the sheets fed from the second, third, and fourth paper cassettes 6, 7, 9
6 and merged. A second pair of registration rollers 65 is provided at the junction 66.

In this case, the junction 66 between the sheet passage 51 and the merged sheet passage 56 is located below the photosensitive drum 2 and the transfer drum 3 for forming an image.

With such a configuration, the sheet passage 51 of the first-stage paper feed cassette 5 is provided in the second-stage and third-stage
The space for formation is not restricted by the merging sheet passages 56 of the sheet cassettes 6, 7, 9 of the first and fourth stages, so that the curvature of the curved portion can be reduced.

The paper feed roller 46 of the first-stage paper cassette 5 is connected to the second-stage, third-stage, and fourth-stage paper cassettes 6, 7, and 9 by the combined sheet passage 56. The space for the installation is not restricted, so that a large-diameter paper feed roller can be used.

In the case of the present color image forming apparatus, the distance bc including the amount of registration feed from the sheet leading end b of the first sheet feeding cassette 5 to the transfer position c is determined by the image leading end position d of the photosensitive drum 2 and the transfer position. c can be made smaller than the distance dc (dc> bc), so that the first sheet fed from the first-stage paper feed cassette 5 is a 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 reduced, and the sequence can be simplified.

Note that, even when a sheet cassette in which sheets smaller than 1/2 of the maximum size are stacked and stored is used in the first-stage sheet cassette 5 as in the present color image forming apparatus, for example, the maximum size A3 The sheet mainly used in the image forming apparatus using the sheet A is an A4 size sheet,
Further, since sheets of the maximum size A3 can be fed by the second, third, and fourth sheet cassettes 6, 7, and 9, 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 room for feeding the largest size sheet, the second paper feed cassette 6 is the same as the first paper feed cassette 5. It can be configured.

Here, a detailed description will be given of the confluence portion of the paper feed with reference to FIG.

The sheet P ₁ is sent out of the sheet feeding cassette 5 by the pickup roller 46, and further sent by the feed roller 57 a and the retard roller 57 b, passes between the upper guide 213 and the lower guide 214, and passes through the upper guide. 215
And passes between the movable guide 207 and the right guide 205 to abut the stopped registration roller pair 65a, 65b. Furthermore it rotates about 5mm feed rollers 211 and 212, and stops the sheet P ₁ as illustrated by forming an upward loop. The amount of the loop to be formed is a predetermined amount, ie, ι, after detecting the leading edge of the sheet with the sensors S ₁ and S _2.
What is necessary is just to send + 5mm.

Next, in synchronization with a predetermined position of the carrier sheet 105f on the surface of the transfer drum 105a, the pair of registration rollers 65a and 65b are rotated to pass between the guide right 218 and the guide left 219, so that the transfer drum 105a and the suction roller Along the tangent H of 105 g, from slightly outside, the suction roller 1
05g and the suction charger 105c, and electrostatically attracts the carrier sheet 105f. In addition to the electrostatic attraction, the leading end of the sheet may be gripped by a gripper or the like. Next, the transfer charger 10 immediately above the suction roller 105g
Sheet P a toner image on the photosensitive drum 101 by 5b ₁
Transfer to

Next will be described with reference to FIG. 4 for how to send the sheet P _2.

The sheet P ₂ sent between the guides 203 and 204 is curled upward while passing between the sponge roller 201 and the lower roller 202 made of rubber or the like. The fed sheet further passes between the right guide 205 and the movable guide 207 and further passes between the right guide 205 and the upper guide 215 to stop the registration roller pair 6.
It hits 5a and 65b. Further, the feed rollers 201 and 202 are further rotated by about 5 mm, and as shown in the figure, the sheet P ₂ moves the movable guide 207 to the left around the center axis 206 against the force of the spring 208 due to its rigidity, thereby forming a downwardly convex loop. And stop. Subsequent operation is the same as when feeding of the sheet P _1. Since the movable guide 207 when the sheet P ₁ can move to the right, it may be made convex loop below.

[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 a curl in a direction that is difficult to wind around the transfer drum is likely to be generated while passing through the transfer drum 05 and 207. In addition, since the configuration of the present invention the path through the sheet P ₂ is very long compared to the sheet P _2, a pair of registration rollers in the example of FIG. 4 it is easy to provide a roller to attach the curled in the path 65a,
Although the paper feed rollers 201 and 202 one upstream of the roller 65b are curling rollers, they may be rollers further upstream.

[0051] During the other hand sheet P ₁ is Yuku through the guide, in order to get the easy direction of the curl wrapped around the transfer drum, it is not necessary to provide the curl roller in the path. Accordingly, the merging portion of the sheets P ₁ and P ₂ can be provided immediately below the adsorption portions 105 c and 105 g of the transfer drum 105 a, and the sheet feeding cassette 5 can be provided immediately to the left and below the transfer drum. The height of the machine does not increase due to the paper cassette 5. Further, since the sheet is used only for small-sized sheets, it does not conflict with a sheet guide guided downward for double-sided copying, and the width of the machine is not widened due to the sheet cassette 5.

<Embodiment 2> In Embodiment 2 shown in FIG. 5, the configuration of each of the paper feed cassettes 5, 6, 7, 9 (the paper feed cassettes 7, 9 are omitted) of the above-mentioned Embodiment 1 is a normal single-color image. This shows a case where the present invention is applied to a forming apparatus (copier).

In the case of the present monochromatic image forming apparatus, the sheet fed from the paper feed cassettes 5, 6, 7, and 9 is transferred to the photosensitive drum 67 and the transfer charger 6 by the second pair of registration rollers 65.
9 and sent.

[0054]

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

Further, a curl forming means is provided in the sheet conveying path so that the sheet on which the curl is formed in the same direction is supplied to the image forming section, so that the sheet is always supplied to the image forming section under the same conditions. And stable quality image formation.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of an image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating details of an image forming unit of the image forming apparatus illustrated in FIG. 1;

FIG. 3 is a diagram illustrating a state in which a sheet is fed from an uppermost sheet feeding cassette at a junction of sheet paths in the image forming apparatus illustrated in FIG. 2;

FIG. 4 is a diagram illustrating a state in which a sheet is fed from a lower sheet feeding cassette at a junction of sheet paths in the image forming apparatus illustrated in FIG. 2;

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

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

[Explanation of symbols]

 DESCRIPTION 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 Feeding end 51, 56 Sheet passage 101 Photosensitive drum 105 Transfer Device 201, 202 Paper Feed Roller (Curl Forming Means)

Claims (4)

(57) [Claims] A plurality of sheet support means are arranged vertically below an image forming section in an image forming apparatus main body, and sheets are selectively transferred from each of the sheet supporting means to the image forming section provided with a transfer drum. In the image forming apparatus configured to feed the sheet, from a lower sheet supporting unit to a path for conveying a sheet fed from an uppermost sheet supporting unit of the plurality of supporting units to the image forming unit. A passage for conveying the fed sheet merges at the merging portion, and the uppermost sheet supporting means is smaller than the lower sheet supporting means, and is one side in the left-right direction with respect to the merging portion. Displaced, the path from the uppermost sheet support means to the junction has a curved portion that is curved in the same direction as the sheet winding direction of the transfer drum on the side opposite to the bias, and the lower side Sheet In the passage from the holding means to the merging section, there is provided a curving portion curving in a direction opposite to the sheet winding direction of the transfer drum, and a curl forming means for forming a curl in the same direction as the sheet winding direction of the transfer drum on the sheet. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the merging section is located on a side opposite to a side on which the uppermost sheet supporting unit is arranged with respect to a center of the image forming apparatus main body. Image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the uppermost sheet supporting unit is disposed below the image forming unit. 4. The image forming apparatus according to claim 1, wherein the curl forming unit includes a pair of rollers, one of which is made of a soft material. Transport device.