This application is based on Japanese Patent Application No. 2014-263486 filed on Dec. 25, 2014, the contents of which are incorporated herein by reference.
1. Technical Field
The present invention relates to an image forming system, an image forming method, and a charge adjusting apparatus.
2. Description of Related Arts
When papers with images formed by an image forming apparatus are stacked in a post-processing apparatus or a stacker apparatus, the papers may adhere to one another by electrostatic force among them.
In this regard, Japanese Unexamined Patent Application Publication No. H10-181969 (Patent Literature 1) discloses a technology of performing static elimination of a paper with a formed image by performing corona discharge on the paper. Furthermore, Japanese Unexamined Patent Application Publication No. 2004-10240 (Patent Literature 2) discloses a technology in which a plurality of static eliminating brushes are arranged on a paper conveyance path and static elimination of a paper is repeatedly performed.
However, in the technologies disclosed in Patent Literature 1 and 2, it is not possible to sufficiently eliminate charge accumulated in a toner image on a paper. Accordingly, although static elimination has been performed using the technologies disclosed in Patent Literature 1 and 2, electrostatic force among papers does not disappear and thus the problem that the papers adhere to one another is not still solved.
The present invention has been accomplished in view of the above problem. Accordingly, objectives of the present invention are to provide an image forming system, an image forming method, and a charge adjusting apparatus, by which it is possible to reliably prevent recording sheets such as papers from adhering to one another by electrostatic force.
In order to achieve at least one of the aforementioned objectives, an image forming system, reflecting one aspect of the present invention, is an image forming system having an image forming apparatus and a charge adjusting apparatus, and includes a decision unit configured to decide an amount of charge to be applied to a recording sheet from coverages of toner images of both surfaces of the recording sheet, wherein the image forming apparatus includes a fixing unit configured to heat and press a recording sheet to which a toner image is transferred, thereby fixing the toner image to the recording sheet, and the charge adjusting apparatus includes a voltage applying unit configured to apply a voltage to the recording sheet to which the toner image is fixed by the fixing unit, thereby applying charge with the amount decided by the decision unit to the recording sheet.
In the aforementioned image forming system, preferably, one recording sheet with a fixed toner image overlaps with another recording sheet with a fixed toner image, and the decision unit decides an amount of charge to be applied to the one recording sheet from coverages of both surfaces of the one recording sheet and a coverage of a surface of the another recording sheet, which faces the one recording sheet.
In the aforementioned image forming system, preferably, the decision unit decides the amount of charge to be applied to the one recording sheet from the coverages of both surfaces of the one recording sheet, the coverage of the facing surface of the another recording sheet, and an amount of charge to be applied to the another recording sheet by the voltage applying unit.
In the aforementioned image forming system, preferably, the voltage applying unit applies the voltage subjected to constant-current control to the recording sheet, and the decision unit decides a current value of the constant-current control as the amount of charge to be applied to the recording sheet.
In the aforementioned image forming system, preferably, the recording sheet is conveyed in a horizontal direction, and the voltage applying unit applies the voltage to an upper surface of the recording sheet conveyed in the horizontal direction.
In the aforementioned image forming system, preferably, the amount of charge to be applied to the recording sheet is changed in response to a surrounding environment of a place where the image forming apparatus has been installed.
In the aforementioned image forming system, preferably, the amount of charge to be applied to the recording sheet per unit time is changed in response to a conveyance speed of the recording sheet.
In the aforementioned image forming system, preferably, the amount of charge to be applied to the recording sheet is changed in response to a type of the recording sheet.
In the aforementioned image forming system, preferably, the amount of charge to be applied to the recording sheet is changed in response to at least one of a basis weight and a size of the recording sheet.
The objectives, features, and characteristics of this invention other than those set forth above will become apparent from the description given herein below with reference to preferred embodiments illustrated in the accompanying drawings.
The embodiments of this invention will be described below with reference to the accompanying drawings.
As shown in
<Image Forming Apparatus>
The image forming apparatus 2 includes a control unit 10, an operating panel unit 20, an image reading unit 30, an image forming unit 40, a fixing unit 50, and a paper feeding unit 60.
The control unit 10 includes CPU (Central Processing Unit) and various memories, and performs the control of the aforementioned each unit and various calculation processes according to a program.
The operating panel unit 20 includes a touch panel, a numeric keypad, a start button, a stop button and the like, and is used for the display of various types of information and the input of various instructions. The image reading unit 30 reads an image of a document and generates image data.
The image forming unit 40 forms an image based on various pieces of data on a paper by using a well-known image creating process such as an electrophotographic process. A transfer belt 41 is arranged at a center part of the image forming unit 40. The transfer belt 41 is rotationally driven in a direction indicated by an arrow A, and a toner image formed on the surface of a photosensitive drum (not shown) is primarily transferred onto the transfer belt 41. Then, the toner image primarily transferred onto the transfer belt 41 is secondarily transferred to the paper.
At a lateral side of the transfer belt 41, four image creating units 42Y, 42M, 42C, and 42K (hereinafter, indicated by 42 by simplifying reference numerals) are arranged in sequence of yellow (Y), magenta (M), cyan (C), and black (K) colors from an upper side. Each image creating unit 42 has a photosensitive drum. Around each photosensitive drum, a charging device for uniformly charging the surface of the photosensitive drum, an exposure device for forming an electrostatic latent image corresponding to image data on the uniformly charged surface of the photosensitive drum, and a development device for developing the electrostatic latent image into a toner image are arranged.
Furthermore, primary transfer rollers 43Y, 43M, 43C, and 43K (hereinafter, indicated by 43 by simplifying reference numerals) are arranged at positions facing the photosensitive drums while interposing the transfer belt 41 between the primary transfer rollers 43Y, 43M, 43C, and 43K and the photosensitive drums. The primary transfer roller 43 electrostatically attracts the toner image formed on the surface of the photosensitive drum, and primarily transfers the toner image onto the transfer belt 41.
Below the transfer belt 41, a secondary transfer roller 44 is arranged. The secondary transfer roller 44 secondarily transfers the toner image formed on the transfer belt 41 to a conveyed paper. When the secondary transfer is performed, a high positive transfer voltage is applied to the secondary transfer roller 44, so that the negatively charged toner image is electrostatically attracted to the paper. The paper with the transferred toner image is supplied to the fixing unit 50.
The fixing unit 50 heats and presses the toner image transferred onto the paper by a fixing roller, thereby fixing the toner image to the paper. The paper with the toner image fixed by the fixing unit 50 is supplied to the charge adjusting apparatus 3.
The paper feeding unit 60 accommodates papers 100 as recording sheets to be used in printing. In the paper feeding unit 60, paper feeding cassettes 61 and 62 of a two-stage configuration are detachably arranged. The paper feeding cassettes 61 and 62, for example, accommodate plain papers and coated papers, respectively.
A paper conveyance path 74 from the paper feeding cassettes 61 and 62 to the charge adjusting apparatus 3 is provided via an intermediate conveying roller 71, a resist roller 72, the secondary transfer roller 44, the fixing unit 50, and a paper discharge roller 73.
Furthermore, above the paper feeding cassettes 61 and 62, an inversion conveyance path 76, which is branched from the paper conveyance path 74 via a switching gate 75 at the downstream side of the fixing unit 50 and merged into the paper conveyance path 74 immediately before the resist roller 72 positioned at the upstream side of the image forming unit 40 in the paper conveyance direction, is provided. At the downstream side of the inversion conveyance path 76, an ADU (Automatic Double-sided Unit) inverting roller 77 and an ADU intermediate conveying roller 78 are provided to invert the front and the back of a paper and convey the paper to the downstream side of the inversion conveyance path 76.
Furthermore, on the inversion conveyance path 76 positioned directly under the paper conveyance path 74 from the fixing unit 50 to the paper discharge roller 73, conveying and inverting rollers 79 are arranged to invert the front and the back of the paper conveyed from the fixing unit 50 and convey the paper to the paper discharge roller 73.
<Charge Adjusting Apparatus>
The charge adjusting apparatus 3 includes a voltage applying unit 80 that applies a voltage to the paper with the fixed toner image. As shown in
The first conductive rubber roller 81 is connected to the power source 83 and the second conductive rubber roller 82 is grounded. The power source 83 applies a positive voltage to the first conductive rubber roller 81. If the positive voltage is applied to the first conductive rubber roller 81, positive charge is applied to a second surface (a rear surface) 102 of the paper 100. Furthermore, negative charge with the same amount as that of the positive charge applied from the first conductive rubber roller 81 is induced to the second conductive rubber roller 82, and cancels with positive charge of a first surface (a front surface) 101 of the paper 100. The voltage applying unit 80 is constant-current controlled and applies a voltage subjected to the constant-current control with a predetermined current value to the paper 100.
<Stacker Apparatus>
The stacker apparatus 4 includes an accommodating unit 90 for loading the paper 100. In the accommodating unit 90, papers with the image formed by the image forming apparatus 2 are sequentially supplied and stacked.
In addition, the image forming apparatus 2, the charge adjusting apparatus 3, and the stacker apparatus 4 may also respectively include elements other than the aforementioned elements, or a part of the aforementioned elements may not be included.
In the image forming system 1 configured as described above, the papers with the image formed by the image forming apparatus 2 are accumulated in the stacker apparatus 4 by passing through the charge adjusting apparatus 3. At this time, in order to prevent adhesion of the papers stacked in the stacker apparatus 4, charged states of the papers are adjusted by the charge adjusting apparatus 3. Hereinafter, with reference to
(1) Operation when Coverages of Both Surfaces of Paper are High
The voltage applying unit 80 of the present embodiment applies a positive voltage to the paper 100 immediately after the fixing, thereby applying charge with an amount corresponding to about a half of the positive charge accumulated in the toner image 210 of the first surface 101 to the paper 100. If the positive voltage is applied to the first conductive rubber roller 81 from the power source 83, positive charge is applied to the second surface 102 of the paper 100, so that the positive charge is accumulated in a toner image 220 of the second surface 102. On the other hand, negative charge with the same amount as that of the positive charge applied from the first conductive rubber roller 81 is induced to the second conductive rubber roller 82, and cancels with the positive charge in the toner image 210 of the first surface 101.
Consequently, as shown in
(2) Operation when Coverage of First Surface of Paper is High and Coverage of Second Surface is Low
The voltage applying unit 80 of the present embodiment applies a positive voltage to the paper 100 immediately after the fixing, thereby applying charge with the same amount as that of the positive charge accumulated in the toner image 210 of the first surface 101 to the paper 100. If the positive voltage is applied to the first conductive rubber roller 81 from the power source 83, positive charge is applied to the second surface 102 of the paper 100. However, charge does not almost remain in the second surface 102 in which a toner layer does not almost exist. On the other hand, negative charge with the same amount as that of the positive charge applied from the first conductive rubber roller 81 is induced to the second conductive rubber roller 82, and cancels with the positive charge in the toner image 210 of the first surface 101.
Consequently, as shown in
(3) Operation when Coverage of First Surface of Paper is Low and Coverage of Second Surface is High
(4) Operation when Coverages of Both Surfaces of Paper are Low
For example, when both surfaces of the paper are almost white backgrounds, the paper 100 immediately after the fixing enters an almost non-charged state. Consequently, the voltage applying unit 80 of the present embodiment applies no voltage to the paper 100 and maintains the non-charged state of the paper 100.
As described above, the voltage applying unit 80 of the charge adjusting apparatus 3 applies charge with amounts different in each paper in response to the coverages of both surfaces of the paper 100. According to such a configuration, the charged states of two facing surfaces of papers stacked in the stacker apparatus 4 are adjusted, so that adhesion of papers due to electrostatic force is prevented. Hereinafter, with reference to
As described above, the paper 110 with the low coverage of the first surface and the high coverage of the second surface is maintained in an almost non-charged state after the charge adjustment process. On the other hand, in the paper 120 with the high coverages of both surfaces, the amount of charge accumulated in the toner image 210 of the first surface is reduced to about ½ before and after the charge adjustment process.
Consequently, according to the charge adjustment process of the present embodiment, the amount of the charge accumulated in the toner image 210 of the first surface of the paper 120 is reduced, so that electrostatic force acting between the papers 110 and 120 also becomes small. As a consequence, the papers 110 and 120 are not stuck with each other.
Furthermore, as shown in
Hereinafter, with reference to
As described above, in the image forming apparatus 2, when a toner image is transferred to a paper, a positive transfer voltage is applied from the rear side of the paper, so that the toner image charged to be negative is electrostatically attracted to the paper 100. Then, when the toner image charged to be negative is fixed to a paper, the charge is eliminated by heat applied by the fixing unit 50, so that the negative charge does not almost remain in the toner image fixed to the paper.
However, when duplex printing is performed, the negative charge does not remain in the toner image 210 of the first surface 101 of the paper 100, but positive charge is newly applied at the time of transfer of the toner image 220 of the second surface 102. Then, at the time of fixing of the toner image 220 of the second surface 102, since heat is not sufficiently applied to the toner image 210 of the first surface 101, positive charge remains in the toner image 210 of the first surface 101 as shown in
If the papers 100 with the toner image 210 of the first surface in which the positive charge has remained overlap with one another, since negative induced charge 300 is generated in the papers 100 as shown in
Furthermore, as the number of papers stacked in the stacker apparatus 4 is large, since a gap between the papers becomes small due to their weights, electrostatic force acting between the papers becomes large. Furthermore, if the stacked papers are coated papers with small surface roughness, since a gap between the papers becomes smaller than that of plain papers, electrostatic force becomes large. In particular, adhesion of papers due to electrostatic force frequently occurs under an environment in which temperature and humidity are low.
In the first embodiment, the amount of charge to be applied to a paper has been decided in consideration of the coverages of both surfaces of the paper. However, the amount of charge to be applied to a paper may also be decided further in consideration of the coverage of another paper overlapped and the like.
Firstly, a control unit 10 of an image forming apparatus 2 determines whether the coverage of a second surface of a paper is equal to or more than 0.4 times of the coverage of a first surface (step S101). In more detail, for example, the control unit 10 of the image forming apparatus 2 calculates the coverages of toner images formed on the first surface and the second surface of the paper by analyzing print data, and determines whether the coverage of the second surface is equal to or more than 0.4 times of the coverage of the first surface.
When it is determined that the coverage of the second surface is smaller than 0.4 times of the coverage of the first surface (step S101: NO), the control unit 10 proceeds to a process of step S110.
On the other hand, when it is determined that the coverage of the second surface is equal to or more than 0.4 times of the coverage of the first surface (step S101: YES), the control unit 10 determines whether the coverage of the second surface is equal to or more than 1.67 times of the coverage of the first surface (step S102). When it is determined that the coverage of the second surface is smaller than 1.67 times of the coverage of the first surface (step S102: NO), the control unit 10 proceeds to a process of step S108.
On the other hand, when it is determined that the coverage of the second surface is equal to or more than 1.67 times of the coverage of the first surface (step S102: YES), the control unit 10 determines whether the coverage of the second surface is equal to or more than 2.5 times of the coverage of the first surface (step S103).
When it is determined that the coverage of the second surface is equal to or more than 2.5 times of the coverage of the first surface (step S103: YES), the control unit 10 determines that a ratio of the coverages of the first surface and the second surface is included in a first area (see
On the other hand, in the process shown in step S103, when it is determined that the coverage of the second surface is smaller than 2.5 times of the coverage of the first surface (step S103: NO), the control unit 10 determines that the ratio of the coverages of the first surface and the second surface is included in a second area (see
On the other hand, in the process shown in step S102, when it is determined that the coverage of the second surface is smaller than 1.67 times of the coverage of the first surface (step S102: NO), the control unit 10 determines that the ratio of the coverages of the first surface and the second surface is included in a third area (see
On the other hand, in the process shown in step S101, when it is determined that the coverage of the second surface is smaller than 0.4 times of the coverage of the first surface (step S101: NO), the control unit 10 determines that the ratio of the coverages of the first surface and the second surface is included in a fourth area (see
When it is determined that the coverage of the second surface of the previous paper is within the range of 0% to 100% (step S111: YES), the control unit 10 decides 70 μA, which is a current value assigned in advance, as the output current value (step S112), and ends the procedure.
On the other hand, when it is determined that the coverage of the second surface of the previous paper is not within the range of 0% to 100% (step S111: NO), the control unit 10 decides, as the output current value, a value obtained by subtracting a current value of the previous paper from 80 μA (step S113), and ends the procedure. In more detail, the control unit 10 reads the output current value decided by the current value decision process with respect to the paper passing through the voltage applying unit 80 immediately before the current paper, and decides, as the output current value of the current paper, a value obtained by subtracting the read output current value from 80 μA.
As shown in
In addition, a paper with low coverages of both surfaces is considered to be a conductor, and for example, even though a voltage subjected to constant-current control with 70 μA is applied, no charge is accumulated. Consequently, for papers around the origin of
As described above, according to the procedure of the flowchart shown in
Furthermore, the voltage applying unit 80 applies a voltage subjected to constant-current control with the output current value decided by the control unit 10 to the paper 100. The voltage subjected to constant-current control is applied to the paper, so that charge on the surface of the paper 100 is adjusted and adhesion of papers is prevented. Hereinafter, with reference to
In this case, the control unit 10 of the image forming apparatus 2 performs the aforementioned current value decision process, thereby deciding an output current value 20 μA with respect to the paper 110 with the low coverage of the first surface and the high coverage of the second surface and deciding an output current value 50 μA with respect to the paper 120 with the high coverages of both surfaces.
Furthermore, the voltage applying unit 80 applies a voltage subjected to constant-current control with 20 μA to the paper 110 and applies a voltage subjected to constant-current control with 50 μA to the paper 120. As a consequence, in the paper 110, charge with a very small amount is accumulated in a toner image 220 of a second surface, and in the paper 120, charge with an amount corresponding to about ½ before the charge adjustment process is accumulated in the toner images 210 and 220 of both surfaces.
Consequently, according to the charge adjustment process of the present embodiment, electrostatic force in a direction to repel each other acts between the papers 110 and 120, so that the papers 110 and 120 are actively separated from each other.
Furthermore, as shown in
As described above, according to the charge adjustment process of the present embodiment, the amount of charge existing on two facing surfaces of the two papers 110 and 120 overlapping with each other is appropriately adjusted, so that the papers are reliably prevented from being stuck by electrostatic force.
In addition, in the procedure of the flowchart shown in
Furthermore, in the process shown in step S113 of
Furthermore, the current value decided by the aforementioned current value decision process can be appropriately changed in response to the surrounding environment of the image forming apparatus 2, the conveyance speed of a paper, the type of the paper, the basis weight and/or the size of the paper, and the like. In detail, the current value can be changed to a large value as the ambient temperature and humidity of an installation place of the image forming apparatus 2 are high, and can be changed to a large value as the conveyance speed of the paper is fast. Furthermore, the current value can be changed to a large value as the surface roughness of the paper is fine as with a coated paper, and can be changed to a large value as the basis weight and/or the size of the paper are large. In this case, for example, a conversion table is created by associating the parameters such as the surrounding environment, the conveyance speed of the paper, the type of the paper, and the basis weight and/or the size of the paper with the current values assigned in the aforementioned first to fourth areas, and a current value to be applied to each area is decided from each parameter value.
The present invention is not limited only to the aforementioned embodiments, and can be variously modified within the scope of the appended claims.
For example, in the aforementioned embodiments, the control unit of the image forming apparatus serves as a decision unit that decides the amount of charge to be applied to a paper from the coverages of both surfaces of the paper. However, a control unit may be provided in the charge adjusting apparatus and the control unit of the charge adjusting apparatus may also serve as the aforementioned decision unit. In this case, the control unit of the charge adjusting apparatus communicates with the control unit of the image forming apparatus and acquires information on the coverages of each paper.
Furthermore, in the aforementioned embodiments, the voltage applying unit is subjected to constant-current control. However, the control method of the voltage applying unit is not limited to the constant-current control and the voltage applying unit, for example, may also be subjected to constant-voltage control.
Furthermore, in the aforementioned embodiments, a voltage is applied to a paper by a pair of conductive rubber rollers arranged to face to each other, so that charge is applied to the paper. However, the voltage applying unit that applies charge by applying a voltage to a paper is not limited to the pair of conductive rubber rollers and may also be a sawtooth electrode or a charger.
Furthermore, in the aforementioned embodiments, the image forming system having the image forming apparatus and the charge adjusting apparatus has been described as an example. However, the charge adjusting apparatus may also be integrally formed with the image forming apparatus. In this case, the voltage applying unit is provided in the image forming apparatus.
A units and a method for performing various processes in the image forming system according to the aforementioned embodiments can also be realized by any one of a dedicated hardware circuit and a programmed computer. The aforementioned program, for example, may also be provided by a computer-readable recording medium such as a flexible disk and CD-ROM (Compact Disc Read Only Memory), or may also be provided on-line via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is typically transmitted to and stored in a storage unit such as a hard disk. Furthermore, the aforementioned program may also be provided as single application software, or may also be incorporated in software of the image forming system as one function of the image forming system.
Number | Date | Country | Kind |
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2014-263486 | Dec 2014 | JP | national |