JP6540210B2 - Image forming system, image forming method, and charge adjustment device - Google Patents

Description

  The present invention relates to an image forming system, an image forming method, and a charge control apparatus.

  When the sheets on which the image is formed by the image forming apparatus are stacked in the post-processing apparatus or the stacker apparatus, the sheets may stick to each other due to the electrostatic force between the sheets.

  Related to this, Patent Document 1 below discloses a technique for discharging paper by performing corona discharge on the paper on which an image is formed. Further, Patent Document 2 below discloses a technique in which a plurality of charge removal brushes are disposed on a sheet conveyance path to repeat charge removal of a sheet.

  However, the techniques of Patent Documents 1 and 2 do not have a sufficient charge removal effect and can not sufficiently remove the charge on the paper surface. Therefore, even if the techniques of Patent Documents 1 and 2 are applied to perform static elimination, sticking between sheets can not be reliably prevented.

JP 10-181969 JP, 2004-10240, A

  The present invention has been made in view of the problems described above. Therefore, an object of the present invention is to provide an image forming system, an image forming method, and a charge adjusting device capable of reliably preventing recording sheets from sticking to each other by electrostatic force.

  The above object of the present invention is achieved by the following means.

  (1) An image forming system having an image forming apparatus and a charge adjusting apparatus, wherein the image forming apparatus is formed on a recording sheet by an image forming section that forms a toner image on the recording sheet, and the image forming section And fixing the toner image on the recording sheet by heating the charged toner image, the charge adjusting device includes a power source capable of output adjustment, and the toner image is fixed by the fixing unit. A first output value for reducing the absolute value of the surface potential of the recording sheet while maintaining the polarity of the surface potential of the recording sheet; When the recording sheet discharged from the charge adjustment device is stacked by switching the output value of the power supply with the second output value having the same polarity as one output value and reversing the polarity of the surface potential, Wherein such opposing surfaces of the recording sheet have the same polarity, imparts a charge to the recording sheet, the image forming system adjacent to the layer direction.

  (2) The image forming system according to (1), wherein the charge applying unit switches between the first output value and the second output value each time one recording sheet passes through the charge applying unit.

  (3) The sum of the first output value and the second output value is based on the sum of surface potentials of two recording sheets continuously conveyed to the charge applying unit. Image formation system as described.

  (4) The charge adjustment device further includes a potential detection unit for detecting the surface potential of the recording sheet on which the toner image is fixed by the fixing unit, and the first and second output values are determined by the potential detection unit. The image forming system according to any one of the above (1) to (3), which is determined according to the detected surface potential.

  (5) The magnitude of the repulsive force acting between the recording sheets adjacent in the stacking direction is designated by the user, and the first and second output values are the magnitudes of the repulsive force designated by the user. The image forming system according to any one of the above (1) to (4), which is determined accordingly.

  (6) forming a toner image on the recording sheet (a), and heating the toner image formed on the recording sheet in the step (a) to fix the toner image on the recording sheet b) When the recording sheets on which the toner image is fixed in the step (b) are stacked, the surface of the recording sheet is such that opposite surfaces of the recording sheets adjacent in the stacking direction have the same polarity. A power supply between a first output value for reducing the absolute value of the surface potential while maintaining the polarity of the potential and a second output value having the same polarity as the first output value and reversing the polarity of the surface potential And (c) applying an electric charge to the recording sheet by switching the output value of the image forming apparatus.

  (7) A charge adjusting device including a power supply capable of output adjustment and having a charge giving unit for giving a charge to a recording sheet on which a toner image is fixed, wherein the charge giving unit has a polarity of surface potential of the recording sheet. Between the first output value for reducing the absolute value of the surface potential and the second output value having the same polarity as the first output value and reversing the polarity of the surface potential while maintaining the When the recording sheets discharged from the charge adjusting device are stacked by switching the value, charge is applied to the recording sheet so that the mutually facing surfaces of the recording sheets adjacent in the stacking direction have the same polarity. , Charge adjustment device.

  According to the present invention, the electrostatic force in the direction of repulsion acts between the recording sheets, so that the recording sheets can be reliably prevented from sticking to each other by the electrostatic force.

FIG. 1 is a diagram showing a schematic configuration of an image forming system according to a first embodiment of the present invention. It is the elements on larger scale of FIG. It is a figure for demonstrating the operation | movement of a charge adjustment apparatus. FIG. 6 is a diagram showing the relationship between the output value of the charge giving unit and the surface potential of the sheet after passing through the charge giving unit. FIG. 6 is a diagram showing the charged state of the sheets stacked in the stacker device. FIG. 6 is a diagram showing the charged state of the sheets stacked in the stacker device. FIG. 6 is a diagram showing the relationship between first and second output values and the surface potential of the sheet. It is a figure for demonstrating the operation | movement of the charge provision part which concerns on a modification. It is a figure which shows schematic structure of the image forming system which concerns on 2nd Embodiment of this invention. It is the elements on larger scale of FIG. FIG. 6 is a diagram showing an example of a conversion table for correlating the surface potential of the sheet and the output value of the charge application unit. It is a figure for demonstrating the operation | movement of a charge adjustment apparatus. It is a figure which shows an example of the conversion table which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment
FIG. 1 is a view showing a schematic configuration of an image forming system 1 according to a first embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG.

  As shown in FIG. 1, the image forming system 1 according to the present embodiment includes an image forming apparatus 2 that forms an image on a sheet, and a charge adjusting apparatus that adjusts the charge state of the sheet on which the image is formed by the image forming apparatus 2. And a stacker device 4 for storing the sheet whose charge state has been adjusted by the charge adjustment device 3. The image forming device 2, the charge adjustment device 3, and the stacker device 4 are sequentially connected from the upstream side to the downstream side of sheet conveyance. Hereinafter, the image forming apparatus 2, the charge adjustment apparatus 3, and the stacker apparatus 4 will be described in order.

<Image forming apparatus>
The image forming apparatus 2 includes a control unit 10, an operation 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 a central processing unit (CPU) and various memories, and performs control of the respective units and various arithmetic processing in accordance with a program.

  The operation panel unit 20 includes a touch panel, a ten key, a start button, a stop button, and the like, and is used to display various information and input 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 data on a sheet using an electrophotographic image forming process. A transfer belt 41 is disposed at the central portion of the image forming unit 40. The transfer belt 41 is rotationally driven in the direction of 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 on the transfer belt 41, which has been primarily transferred, is secondarily transferred to the sheet.

  On the side surface of the transfer belt 41, four imaging units 42Y, 42M, 42C, 42K (hereinafter referred to as “signs” in the order of yellow (Y), magenta (M), cyan (C), black (K)) from the top A simplification is shown at 42). Each imaging unit 42 has a photosensitive drum. Around each photosensitive drum, a charger for uniformly charging the photosensitive drum surface, an exposure device for forming an electrostatic latent image according to image data on the uniformly charged photosensitive drum surface, a toner image for the electrostatic latent image A developing device for developing the image.

  Further, primary transfer rollers 43Y, 43M, 43C and 43K (hereinafter, the reference numerals are simplified and indicated by 43) are disposed at positions facing the respective photosensitive drums with the transfer belt 41 interposed therebetween. 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 disposed. The secondary transfer roller 44 secondarily transfers the toner image formed on the transfer belt 41 onto the conveyed sheet. When performing secondary transfer, by applying a high positive transfer voltage to the secondary transfer roller 44, a negatively charged toner image is electrostatically attracted to the sheet. The sheet on which the toner image has been transferred is supplied to the fixing unit 50.

  The fixing unit 50 heats and presses the toner image transferred onto the sheet by the fixing roller to fix the toner image on the sheet. The sheet on which the toner image is fixed by the fixing unit 50 is supplied to the charge adjusting device 3.

  The sheet feeding unit 60 accommodates the sheet 100 as a recording sheet used for printing. In the sheet feeding unit 60, sheet feeding cassettes 61 and 62 having a two-stage configuration are detachably disposed.

  A sheet conveyance path 74 is provided which extends from the sheet feeding cassettes 61 and 62 through the intermediate conveyance roller 71, the registration roller 72, the secondary transfer roller 44, the fixing unit 50, and the sheet discharge roller 73.

  Further, on the upper side of the sheet feeding cassettes 61 and 62, the registration roller 72 is branched from the conveyance path 74 on the downstream side of the fixing unit 50 via the switching gate 75 and positioned on the upstream side of the image forming unit 40 in the sheet conveyance direction. A reverse conveying path 76 which joins the conveying path 74 immediately before An ADU (Automatic Double-sided Unit) reversing roller 77 and an ADU intermediate transport roller 78 are provided downstream of the reversing transport path 76 to transport the sheet to the downstream side of the reversing transport path 76 by reversing the front and back of the sheet. There is.

  In the reverse conveyance path 76 located immediately below the conveyance path 74 from the fixing unit 50 to the discharge roller 73, the sheet conveyed from the fixing unit 50 is inverted and conveyed to the discharge roller 73. A reversing roller 79 is disposed.

<Charge adjustment device>
The charge adjusting device 3 includes a charge applying unit 80 that applies an electric charge to the sheet on which an image is formed by the image forming device 2. As shown in FIG. 2, the charge applying unit 80 applies a voltage between the first and second conductive rubber rollers 81 and 82 which sandwich and convey the sheet 100 and the first and second conductive rubber rollers 81 and 82. A power supply 83 is provided. The first conductive rubber roller 81 is connected to the power supply 83, and the second conductive rubber roller 82 is grounded. The power supply 83 is configured to be adjustable in output. The charge applying unit 80 of the present embodiment is controlled at constant current, switches the output value (current value) of the power source 83 for each sheet 100, and outputs the first output value between the first and second conductive rubber rollers 81 and 82. Or apply a current of the second output value.

<Stacker device>
The stacker device 4 includes a storage unit 90 for stacking sheets. The sheets 100 on which an image is formed by the image forming apparatus 2 are sequentially supplied and stacked in the storage unit 90.

  The image forming apparatus 2, the charge adjusting device 3, and the stacker device 4 may include components other than the components described above, or some of the components described above are not included. May be

  In the image forming system 1 configured as described above, the sheet on which an image is formed by the image forming apparatus 2 is accumulated in the stacker device 4 through the charge adjusting device 3. At this time, in order to prevent sticking of the sheets stacked in the stacker device 4, the charge adjusting device 3 adjusts the charged state of the sheets. Specifically, when the sheets are stacked in the stacker device 4, the charge adjustment device 3 adjusts the charged state of the sheets so that the opposite surfaces of the sheets adjacent in the stacking direction have the same polarity. Hereinafter, the operation of the charge adjustment device 3 will be described with reference to FIGS. 3 to 7.

  FIG. 3 is a diagram for explaining the operation of the charge adjustment device 3. When the sheet 100 is continuously conveyed from the image forming device 2 to the charge adjusting device 3, the charge applying unit 80 of the charge adjusting device 3 operates the power supply 83 every time a sheet of paper passes the charge applying unit 80. The output value is switched between the first output value and the second output value. Here, the first output value is a current value that reduces the absolute value of the surface potential of the sheet 100 without changing the polarity of the surface potential of the sheet 100, and is, for example, 30 μA. The second output value is a current value having the same polarity as the first output value and reversing the polarity of the surface potential of the sheet 100, and is, for example, 50 μA.

  Specifically, as shown in FIG. 3A, first, the charge application unit 80 adjusts the output value of the power supply 83 to form a sheet of paper between the first and second conductive rubber rollers 81 and 82. While 100 passes, a current of a first output value (30 μA) is passed between the first and second conductive rubber rollers 81, 82. Next, as shown in FIG. 3B, the charge application unit 80 adjusts the output value of the power supply 83 and while the next sheet 100 passes between the first and second conductive rubber rollers 81 and 82. A current of a second output value (50 μA) is passed between the first and second conductive rubber rollers 81, 82. Likewise, similarly, each time one sheet of paper 100 passes between the first and second conductive rubber rollers 81 and 82, the charge application unit 80 adjusts the output value of the power supply 83 to make the first and The current of the first output value or the second output value is caused to flow between the conductive rubber rollers 81 and 82.

  When the sheet 100 negatively charged on the upper surface 101 is continuously conveyed to the charge adjustment device 3, if the sheet 100 passes between the first and second conductive rubber rollers 81 and 82, the first conductivity is obtained. A positive charge is applied from rubber roller 81 to upper surface 101 of sheet 100. As a result, the positive charge applied from the first conductive rubber roller 81 cancels the negative charge on the upper surface 101 of the sheet 100. On the other hand, the same amount of negative charge induced on the second conductive rubber roller 82 also cancels out the positive charge on the lower surface 102 of the sheet 100. Therefore, when the sheet conveyed to the charge adjusting device 3 passes through the charge applying unit 80, the amount of charges present on the surface of the sheet 100 changes, and the surface potential of the sheet 100 changes.

  FIG. 4 is a view showing the relationship between the output value of the charge applying unit 80 and the surface potential of the sheet after passing through the charge applying unit 80. The vertical axis in FIG. 4 is the surface potential of the sheet after passing through the charge application unit 80, and the horizontal axis is the output value of the charge application unit 80. FIG. 4 shows the case where the sheet 100 with the surface potential of the upper surface 101 of −40 V passes through the charge application unit 80.

  As shown in FIG. 4, when the output value of the power source 83 is the first output value (30 μA), if the sheet 100 passes the charge applying unit 80, the positive charge applied from the power source 83 causes the upper surface 101 of the sheet 100 to be charged. The negative charge is partially canceled, and the surface potential of the upper surface 101 of the sheet 100 rises to -10V. On the other hand, when the output value of the power source 83 is the second output value (50 μA), if the sheet 100 passes the charge applying unit 80, the negative charge of the upper surface 101 of the sheet 100 is generated After being canceled, positive charge is further accumulated, and the surface potential of the upper surface 101 of the sheet 100 rises to + 10V.

  As described above, the charge applying unit 80 sets the output value of the power source 83 between the first output value (30 μA) and the second output value (50 μA) each time a sheet of paper passes through the charge applying unit 80. Switch. Therefore, the sheet 100 having a surface potential of −10 V on the upper surface 101 and the sheet 100 having a surface potential of +10 V on the upper surface 101 are alternately discharged from the charge applying portion 80. The sheets 100 discharged from the charge application unit 80 are stacked in order in the stacker device 4.

  FIG. 5 is a view showing the charged state of the sheets 100 stacked in the stacker device 4. As shown in FIG. 5, in the stacker device 4, the facing surfaces of the sheets 100 adjacent in the stacking direction have the same polarity. Specifically, when the upper surface 101 of the sheet 100 is positively charged, the lower surface 102 of the sheet 100 adjacent to the upper side of the sheet 100 is also positively charged. Similarly, when the upper surface 101 of the sheet 100 is negatively charged, the lower surface 102 of the sheet 100 adjacent to the upper side of the sheet 100 is also negatively charged.

According to such a configuration, at work electrostatic force F ₁ the direction to repel each other between the sheet 100 adjacent in the stacking direction, the sheet 100 with each other is away positively. Therefore, sticking between the sheets 100 can be reliably prevented.

FIG. 6 is a view showing a charged state of a sheet in a general image forming system including an image forming apparatus and a stacker device as a comparative example. For example, the upper surface 101 of the sheet 100 on which an image is formed by the image forming apparatus is negatively charged, and the lower surface 102 is positively charged. For this reason, as shown in FIG. 6, when the sheets 100 are stacked in the stacker device, the facing surfaces of the sheets 100 adjacent in the stacking direction have different polarities. Thus, in a general image forming systems, at work electrostatic force F ₂ of the direction attract each other between the sheet 100, the sheet to each other will stick.

Incidentally, the electrostatic force F ₂ of the direction attract each other, as the number of sheets to be stacked in the stacker apparatus is large, the stronger the gap between the sheets is decreased by its own weight. Further, sticking between the sheets by the electrostatic force F ₂ is especially after humidity is low environment or fixing processing becomes remarkable with an increase of the sheet resistance. Sticking between sheets by the electrostatic force F ₂ are cause inviting deterioration of the handling characteristics of the sheet in the subsequent step, which is not preferable.

  As described above, according to the present embodiment, each time a sheet of paper passes the charge applying unit 80, the first output value for reducing the absolute value of the surface potential while maintaining the polarity of the surface potential of the sheet; The output value of the power source 83 is switched between a second output value having the same polarity as the first output value and reversing the polarity of the surface potential of the sheet, and charge is applied to the sheet. According to such a configuration, when the sheets discharged from the charge adjustment device 3 are stacked, the facing surfaces of the sheets adjacent in the stacking direction have the same polarity. Therefore, electrostatic force in the direction of repulsion mutually acts between the sheets adjacent in the stacking direction, and the sheets can be reliably prevented from sticking to each other. As a result, good handling characteristics in the post process can be obtained.

  Note that, unlike the present embodiment, even when one sheet of paper passes through the charge application unit, the power is switched ON / OFF or the positive voltage and the negative voltage are forcibly applied to the paper. The opposite sides of the sheets adjacent in the stacking direction can have the same polarity. However, when switching on / off the power supply, a large capacity power supply is required. Also, in the case of forcibly applying a positive voltage and a negative voltage, a bipolar power supply is required, which increases the size and cost of the power supply. On the other hand, according to the present embodiment, since the magnitude of the output value of the same polarity is switched to adjust the charged state of the sheet, sticking between the sheets can be reliably prevented by the power source having small capacity, size and cost. .

  Next, the first and second output values will be described in more detail with reference to FIG. FIG. 7 is a diagram showing the relationship between the first and second output values and the surface potential of the sheet.

  As shown in FIG. 7, it is assumed that four negative charges (“charge −4”) exist on the top surface of the sheet 100 conveyed to the charge applying unit 80. In this case, in the present embodiment, the amount of charge applied to the sheet 100 by the power supply 83 of the first output value is “charge + 3”, and the amount of charge applied to the sheet 100 by the power supply 83 of the second output value is The first and second output values are determined to be "charge + 5". According to such a configuration, the sum of the charge applied to the sheet by the power supply 83 of the first output value (for example, 30 μA) and the charge applied to the sheet by the power supply 83 of the second output value (for example, 50 μA) Becomes “charge + 8”, which is equal to the charge that cancels the sum “charge − 8” of the surface potentials of the two sheets of paper. As a result, the plurality of sheets of paper 100 discharged from the charge adjustment device 3 can be equally charged.

  As described above, the first and second output values of this embodiment are the sum of the charges applied to the sheet by the power supply 83 of the first and second output values and the sum of the charges present on the surfaces of the two sheets of paper. It is decided to match. However, the first output value is an output value that reduces the absolute value of the surface potential while maintaining the polarity of the surface potential of the sheet, and the second output value has the same polarity as the first output value. If the output value reverses the polarity of the potential, sheet sticking is prevented. Therefore, the sum of the charges applied to the sheet by the power supply 83 of the first and second output values may not necessarily coincide with the sum of the charges present on the surfaces of the two sheets.

(Modification)
In the embodiment described above, a constant first output value or second output value is applied to one sheet of paper. However, different levels of the first output value or the second output value may be applied to one sheet of paper.

  FIG. 8 is a diagram for explaining the operation of the charge applying unit 80 according to the modification. As shown in FIG. 8, in the present modification, the toner image 200 is formed only in a partial region, whereby the sheet 100 having a variation in surface potential in the plane is conveyed to the charge applying unit 80.

  When such a sheet 100 is conveyed, for example, the charge applying unit 80 applies a current of 30 μA to the high coverage area of the sheet 100 as the first output value, and 10 μA to the low coverage area. Pass a current. Further, the charge imparting unit 80 applies a current of 50 μA to the high coverage area of the sheet 100 as the second output value, and applies a current of 30 μA to the low coverage area.

  According to such a configuration, even in the case where the surface potential varies within the surface of one sheet of paper 100, the charged state of the sheet 100 can be made uniform.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIGS. 9 to 12. The present embodiment is an embodiment in which the surface potential of the sheet is detected to change the amount of charge applied to the sheet.

  FIG. 9 is a view showing a schematic configuration of an image forming system 1 according to a second embodiment of the present invention, and FIG. 10 is a partially enlarged view of FIG.

  As shown in FIG. 9, the image forming system 1 according to the present embodiment includes an image forming apparatus 2 that forms an image on a sheet, and a charge adjusting apparatus that adjusts the charge state of the sheet on which the image is formed by the image forming apparatus 2. And a stacker device 4 for storing the sheet whose charge state has been adjusted by the charge adjustment device 3. The image forming device 2, the charge adjustment device 3, and the stacker device 4 are sequentially connected from the upstream side to the downstream side of sheet conveyance.

  The charge adjusting device 3 includes a charge applying unit 80 for applying charges to the sheet on which the image is formed by the image forming device 2 and a surface voltmeter 85 for detecting the surface potential of the sheet on which the image is formed by the image forming device 2. Prepare. The configuration of the image forming system 1 according to the present embodiment is the same as the configuration of the image forming system 1 according to the first embodiment except that the charge adjustment device 3 includes the surface voltmeter 85. , Detailed description is omitted.

  As shown in FIG. 10, the surface potentiometer 85 is provided on the upstream side of the charge applying unit 80, and detects the surface potential of the upper surface of the sheet 100 conveyed from the image forming apparatus 2. The charge applying unit 80 refers to the conversion table 300 (see FIG. 11) which correlates the surface potential of the sheet with the first and second output values, and the surface potential of the sheet 100 detected by the surface voltmeter 85. The first output value or the second output value is determined for each sheet 100.

  FIG. 11 is a diagram showing an example of the conversion table 300 which correlates the surface potential of the sheet and the output value of the charge application unit 80 with each other. In FIG. 11, the surface potential detected by the surface voltmeter 85 and the first and second output values are correlated with each other so that the surface potential of the sheet after passing through the charge imparting unit 80 becomes ± 20V. The charge applying unit 80 refers to the conversion table 300 to determine the first output value or the second output value from the surface potential of the sheet detected by the surface potentiometer 85. For example, when the surface potential of the sheet detected by the surface potentiometer 85 is −40 V, the charge applying unit 80 determines the first output value to be 20 μA and determines the second output value to be 60 μA. The electrification state of the sheet conveyed from the image forming apparatus 2 may be different depending on the type of the sheet, the sheet discharge speed, the coverage of the toner image, the environment around the image forming system 1 and the like.

  FIG. 12 is a diagram for explaining the operation of the charge adjustment device 3. FIG. 12 shows a case where five sheets of paper pass continuously through the charge application unit 80 of the charge adjustment device 3.

  As shown in FIG. 12, for example, when the surface potential of the first sheet of paper 100 detected by the surface voltmeter 85 is −30 V, the charge application unit 80 refers to the conversion table 300 and uses it as a first output value. Determine 10 μA. Then, the charge applying unit 80 applies a current of 10 μA between the first and second conductive rubber rollers 81 and 82 to apply a positive charge to the upper surface of the first sheet of paper 100. As a result, the negative charge on the upper surface is partially canceled, and the surface potential of the first sheet of paper 100 rises to -20V.

  Subsequently, when the surface potential of the second sheet of paper 100 detected by the surface potentiometer 85 is −70 V, the charge application unit 80 refers to the conversion table 300 and determines 90 μA as a second output value. Then, the charge applying unit 80 applies a current of 90 μA between the first and second conductive rubber rollers 81 and 82 to apply a positive charge to the upper surface of the second sheet 100. As a result, after the negative charge on the upper surface is canceled, the positive charge is further accumulated, and the surface potential of the second sheet of paper 100 rises to + 20V.

  Subsequently, when the surface potential of the third sheet of paper 100 detected by the surface voltmeter 85 is −70 V, the charge applying unit 80 refers to the conversion table 300 and determines 50 μA as the first output value. Then, the charge applying unit 80 applies a current of 50 μA between the first and second conductive rubber rollers 81 and 82 to apply a positive charge to the upper surface of the third sheet 100. As a result, the negative charge on the upper surface is partially canceled, and the surface potential of the third sheet 100 rises to -20V.

  Subsequently, when the surface potential of the fourth sheet 100 detected by the surface voltmeter 85 is −30 V, the charge application unit 80 refers to the conversion table 300 and determines 50 μA as the second output value. Then, the charge applying unit 80 applies a current of 50 μA between the first and second conductive rubber rollers 81 and 82 to apply a positive charge to the upper surface of the fourth sheet 100. As a result, after the negative charge on the upper surface is canceled, the positive charge is further accumulated, and the surface potential of the fourth sheet 100 rises to + 20V.

  Subsequently, when the surface potential of the fifth sheet 100 detected by the surface potentiometer 85 is −20 V, the charge applying unit 80 refers to the conversion table 300 and determines 0 μA as a first output value. Then, for example, a small current of about 0 μA flows between the first and second conductive rubber rollers 81 and 82, and the charge applying unit 80 slightly applies a positive charge to the upper surface of the fifth sheet 100. . As a result, the surface potential of the fifth sheet 100 is maintained at -20V.

  As described above, according to the present embodiment, the surface potential of the sheet 100 conveyed from the image forming apparatus 2 is detected, and a current having an output value according to the surface potential of the sheet flows up and down the sheet 100. According to such a configuration, the five sheets discharged from the charge adjustment device 3 and stacked in the stacker device 4 have the same polarity on opposite sides and have the same degree (surface potential +20 V or −20 V) To be charged. As a result, the force acting between the sheets can be made constant.

  In the present embodiment, the surface potential meter as the potential detection unit detects the surface potential on the upper surface of the sheet. However, unlike the present embodiment, the surface potentiometer may detect the surface potential of the lower surface of the sheet.

Third Embodiment
Next, a third embodiment of the present invention will be described with reference to FIG. The present embodiment is an embodiment in which the user of the image forming system 1 designates the magnitude of the repulsive force acting between sheets.

  FIG. 13 is a view showing an example of the conversion table 400 according to the third embodiment of the present invention. As shown in FIG. 13, in the conversion table 400 of this embodiment, the surface potential detected by the surface voltmeter 85, the first and second output values, and the surface potential of the sheet after passing through the charge imparting unit 80 are mutually associated. It is done.

  More specifically, in the conversion table 400, four target values of the surface potential of the sheet after passing through the charge applying unit 80 (± 5 V, ± 10 V, ± 15 V, and ± 20 V) are set, and each target value is set. In addition, the first and second output values and the surface potential of the sheet detected by the surface potentiometer 85 are correlated with each other. The configuration of the image forming system 1 according to the present embodiment is the same as the configuration of the image forming system 1 according to the second embodiment except that the first and second output values are associated with the target value. Therefore, detailed description is omitted.

  When the user of the image forming system 1 designates one target value out of four target values, the charge imparting unit 80 sets the first and second output values corresponding to the target values of the conversion table 400 on the sheet. It is determined according to the surface potential and a current of the determined output value is applied. For example, when the user designates ± 5 V as the target value of the surface potential, the charge application unit 80 refers to the conversion table 400, and the surface potential of the sheet detected by the surface potentiometer 85 is -30 V. , Determine 25 μA and 35 μA as the first and second output values. Then, the charge applying unit 80 applies a current of 25 μA or 35 μA to the sheet.

  As described above, according to the present embodiment, the magnitude of the repulsive force acting between the sheets is designated by the user, and the first and second output values correspond to the magnitude of the repulsive force designated by the user. It is determined. According to such a configuration, depending on the application of the sheets (such as distributing a plurality of sheets one by one, treating a plurality of sheets as one booklet, etc.) Can be specified, and the convenience of the user is improved.

  The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the claims.

  For example, in the first to third embodiments described above, the charge application unit is controlled at constant current, and the current value is switched as the output value of the power supply. However, the charge application unit may be controlled at constant voltage, and the voltage value may be switched as the output value of the power supply.

  In the second and third embodiments described above, the surface potential of the sheet is detected by the surface potentiometer, and the first and second output values are determined. However, the first and second output values may be determined without detecting the surface potential of the sheet. In this case, for example, an optimal output value is estimated for each sheet from information such as the environment around the image forming system, the type of sheet, and the coverage of the toner image.

  Further, in the first to third embodiments described above, the case where the negatively charged toner image is fixed on the sheet is described as an example. However, the toner image fixed on the sheet does not necessarily have to be negatively charged, and may be positively charged. In this case, for example, the first conductive rubber roller is grounded and the second conductive rubber roller is connected to the power supply so that a negative charge is applied to the top surface of the sheet.

  In the first to third embodiments described above, charge is applied to the sheet by passing an electric current between the first and second conductive rubber rollers that sandwich and convey the sheet. However, the charge applying unit for applying the charge to the sheet is not limited to the first and second conductive rubber rollers, and may be a sawtooth electrode or a charger.

  Further, in the first to third embodiments described above, the image forming system having the image forming apparatus and the charge adjusting device has been described as an example. However, the charge adjustment device may be incorporated in the image forming apparatus.

  The means and method for performing various processes in the image forming system according to the first to third embodiments described above can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer readable recording medium such as a flexible disk and a compact disc read only memory (CD-ROM), or may be provided online via a network such as the Internet. In this case, the program recorded on the computer readable recording medium is usually transferred to and stored in a storage unit such as a hard disk. Also, the program may be provided as a single application software or may be incorporated into the software of the apparatus as a function of the image forming system.

1 Imaging system,
2 Image forming device,
3 charge regulator,
4 Stacker device,
10 control units,
20 operation panel section,
30 image reading units,
40 image forming units,
50 fixing parts,
60 sheet feeders,
80 charge application unit,
81, 82 conductive rubber roller,
83 power supply,
85 surface voltmeter,
90 storage units,
100 sheets of paper,
200 toner images,
300,400 conversion tables.

Claims (7)

An image forming system comprising an image forming device and a charge control device, comprising:
The image forming apparatus is
An image forming unit for forming a toner image on a recording sheet;
A fixing unit configured to heat the toner image formed on the recording sheet by the image forming unit to fix the toner image on the recording sheet;
The charge adjustment device
The image forming apparatus further includes a power supply capable of output adjustment, and a charge application unit that applies an electric charge to the recording sheet on which the toner image is fixed by the fixing unit.
The charge application unit has a first output value for reducing the absolute value of the surface potential while maintaining the polarity of the surface potential of the recording sheet, and the same polarity as the first output value and the polarity of the surface potential. When recording sheets discharged from the charge adjusting device are stacked by switching the output value of the power supply between the second output value to be reversed and the recording sheets discharged in the stacking direction, the facing surfaces of the recording sheets adjacent in the stacking direction are the same. An image forming system, wherein the recording sheet is charged so as to have polarity.   The image forming system according to claim 1, wherein the charge applying unit switches between the first output value and the second output value each time one recording sheet passes through the charge applying unit.   3. The image formation according to claim 2, wherein the sum of the first output value and the second output value is based on the sum of surface potentials of two recording sheets continuously conveyed to the charge applying unit. system. The charge adjustment device
The image forming apparatus further includes a potential detection unit that detects the surface potential of the recording sheet on which the toner image is fixed by the fixing unit.
The image forming system according to any one of claims 1 to 3, wherein the first and second output values are determined according to the surface potential detected by the potential detection unit. The magnitude of the repulsive force acting between the recording sheets adjacent in the stacking direction is specified by the user,
The image forming system according to any one of claims 1 to 4, wherein the first and second output values are determined according to the magnitude of the repulsive force designated by the user. Forming a toner image on a recording sheet (a);
And (b) fixing the toner image on the recording sheet by heating the toner image formed on the recording sheet in the step (a).
When the recording sheets on which the toner image is fixed in the step (b) are stacked, the polarity of the surface potential of the recording sheet is set so that the opposing surfaces of the recording sheets adjacent in the stacking direction have the same polarity. The output value of the power supply is between the first output value for reducing the absolute value of the surface potential while maintaining it, and the second output value having the same polarity as the first output value and reversing the polarity of the surface potential. Switching (c) to charge the recording sheet;
An image forming method comprising: A charge adjustment device comprising a power supply capable of output adjustment and having a charge giving unit for giving a charge to a recording sheet on which a toner image is fixed, comprising:
The charge application unit has a first output value for reducing the absolute value of the surface potential while maintaining the polarity of the surface potential of the recording sheet, and the same polarity as the first output value and the polarity of the surface potential. When recording sheets discharged from the charge adjusting device are stacked by switching the output value of the power supply between the second output value to be reversed and the recording sheets discharged in the stacking direction, the facing surfaces of the recording sheets adjacent in the stacking direction are the same. A charge control device, which applies charge to the recording sheet so as to have polarity.