JP2014206690A - Electricity removing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electricity removing device for sheets that can stably remove electricity on sheets without excessively increasing the amount of ions to be discharged.SOLUTION: An electricity removing device removes electrification charge on front and rear surfaces of a recording sheet moving on a conveyance path 503 by discharging ions from ion generation units 504 and 505 that are arranged shifted from each other. During the removal of the electrification charge, the electricity removing device acquires image forming information indicating an image forming state when an image is formed on the recording sheet, and estimates a charging state of the recording sheet from the acquired image forming information. The electricity removing device subsequently controls the ion generation units 504 and 505 in response to the estimated charging state to change the amount of ions to be generated.

Description

  The present invention relates to a static eliminator that performs static elimination such as a recording paper, a film, and an OHP (Overhead projector) sheet, and an image forming apparatus that forms an image on the sheet.

Some image forming apparatuses can be connected to a sheet processing apparatus that performs post-processing of a sheet such as a recording paper, a film, and an OHP (Overhead projector) sheet. The post-processing is, for example, a stapling process in which a plurality of sheets on which images are formed are overlapped and bound.
The sheet is charged while being conveyed inside the image forming apparatus or the sheet processing apparatus. When the sheet is charged, there arises a problem that the transportability is deteriorated due to sticking to the transport path or the position of the sheet is shifted with another sheet when the sheets are overlapped in the sheet processing apparatus. Therefore, the sheet needs to be neutralized.

In a conventional image forming apparatus, a static elimination needle, a static elimination roller, an ion generator, and the like are used to neutralize a charged sheet.
The static elimination needle is for neutralizing the sheet by inducing corona discharge around the surface of the sheet. However, since the lower limit value of the voltage when performing static elimination using the static elimination needle is a voltage at which corona discharge occurs, there is a problem that the voltage value becomes high.
The static elimination roller is one that is neutralized by the roller itself, but there is a restriction that the static elimination capability is defined by the ground resistance value.
The ion generator ionizes molecules in the air by corona discharge between electrodes to which a high voltage is applied. In general, positive ions and negative ions are generated, and the generated charges are neutralized by the generated ions such as a sheet to be neutralized.

  As an example in which an ion generator is applied to a sheet processing apparatus or an image forming apparatus, there is a static elimination device for an electrically insulating sheet disclosed in Patent Document 1. In this static eliminator, ion generators having electrode pairs facing each other with a sheet interposed therebetween are arranged in the moving direction of the sheet. Then, a positive voltage is applied to one electrode of the ion generator and a negative voltage is applied to the other electrode to generate ions, whereby the charged sheet is discharged.

Patent Document 2 discloses a static eliminator that neutralizes a sheet by generating an ion cloud by applying a voltage of opposite polarity and equal absolute value to two ion generators arranged symmetrically across the sheet. It is disclosed. An “ion cloud” refers to a group of ions that float in a certain space like a cloud without staying at a specific place.
In the technique disclosed in Patent Document 2, if a new ion cloud is generated after a sheet is neutralized with an ion cloud and the next sheet is conveyed, the sheet is surely neutralized. . Even in the case of continuous sheets, the ions consumed by the charge removal may be replenished between sheets.

JP 2006-236976 A JP 2009-231200 A

In the static eliminator disclosed in Patent Document 1, ions are generated between opposing electrodes. Therefore, ions generated by the electrode pair are fixed to one of positive and negative. However, since the front and back of the sheet are not necessarily charged with one polarity, the charged charge may not be neutralized depending on the charging method.
In addition, since the ions generated by the static eliminator move toward the sheet due to the electric field between the electrodes facing each other, the half of the ions that can be generated with high efficiency may be reversely charged.

In the technique disclosed in Patent Document 2, when a sheet having a charging state biased to either positive or negative is neutralized, only positive or negative ions are consumed by neutralization. As a result, the ion balance in the atmosphere is biased. For this reason, for example, the top portion of the sheet can be normally discharged, but the discharge performance at the rear end portion may be lower than the charge at the leading portion.
In order to suppress the influence of the ion balance collapse due to such charge removal, it is conceivable that the amount of ions released from the ion generator is set to be sufficiently larger than the charged charge amount of the charge removal target. However, the larger the ion emission amount of the ion generator, the shorter the life of the discharge electrode due to electrode consumption. In addition, there is a problem that the performance deterioration due to the formation of an oxide film on the electrode and the adhesion of dust easily proceeds, and the maintenance interval is shortened.

  The present invention makes it possible to stably perform static elimination of a sheet without excessively increasing the amount of ions emitted from the ion generator, and to eliminate static electricity that makes it possible to extend the life of the ion generator and achieve static elimination performance. It is an object of the present invention to provide an image forming apparatus and an image forming apparatus that forms an image using the static eliminator.

  The static eliminator of the present invention acquires generating means for generating ions for neutralizing the front and back surfaces of a sheet moving on a conveyance path, and image formation information representing an image formation status when an image is formed on the sheet. And control means for controlling the amount of ions generated from the generating means in accordance with the acquired image formation information.

  According to the present invention, it is possible to stably perform static elimination without excessively increasing the amount of ions released from the ion generator, and it is possible to achieve both a long life of the ion generator and static elimination performance. The effect is obtained.

Cross section of image forming system Cross section of sheet processing equipment Ion generator layout Configuration block diagram of ion generation unit Control diagram of the amount of ions generated by the ion generator Explanation of electrification of recording paper by electrophotography Configuration block diagram of image forming system Static elimination table for charge estimation Transition diagram of static elimination performance during static elimination on recording paper Initialization flowchart of sheet processing device when power is turned on Ion generation unit output level control flow chart Diagram of other ion generation unit configurations and ion intensity control Control diagram of the amount of ions generated by the ion generator Sectional view of the ion generation unit placed in the image forming apparatus

[First Embodiment]
The image forming system according to the first embodiment of the present invention will be described below.
<Image forming system>
FIG. 1 is a cross-sectional view of the image forming system according to the first embodiment. The image forming system 1000 includes an image forming apparatus 10, a document feeding apparatus 100, a scanner 200, an operation display apparatus 400, and a sheet processing apparatus 500.

<Image forming apparatus>
The image forming apparatus 10 is an apparatus that forms an image on recording paper as an example of a sheet. In other words, the image forming apparatus 10 modulates and outputs a laser beam based on a video signal output by the scanner 200 optically reading the document fed by the document feeding device 100. The laser beam is irradiated onto the photosensitive drum 111 while being scanned by the polygon mirror 110a. An electrostatic latent image corresponding to the scanned laser beam is formed on the photosensitive drum 111. The electrostatic latent image on the photosensitive drum 111 is visualized as a toner image by a color material (developer) supplied from the developing device 113, for example, toner. The recording paper is fed from any of the cassettes 114 and 115 and the manual paper feeding unit 125 at a timing synchronized with the start of laser beam irradiation. This recording sheet is conveyed between the photosensitive drum 111 and the transfer unit 116. The toner image formed on the photosensitive drum 111 is transferred to the recording paper fed by the transfer unit 116.

  The recording paper on which the toner image is transferred is conveyed to the fixing unit 117. The fixing unit 117 fixes the toner image on the recording paper by heating and pressurizing the recording paper. The recording paper that has passed through the fixing unit 117 passes through a conveyance mechanism including a flapper 121 and a discharge roller 118 and is discharged from the image forming apparatus 10 to the outside. The image forming apparatus 10 guides the recording paper that has passed through the fixing unit 117 into the reversing path 122 by the switching operation of the flapper 121 when the recording paper is discharged with its image forming surface facing downward, that is, face-down. . Then, after the trailing edge of the recording paper passes through the flapper 121, the recording paper is switched back and discharged from the image forming apparatus 10 by the discharge roller 118. Such a discharge form is called “reverse discharge”. Reverse paper discharge is performed in order from the first page. If normal, the discharged recording sheets are stacked in the correct page order.

  When recording paper is fed from the manual paper feed unit 125 and an image is formed on the recording paper, the image forming apparatus 10 does not lead the recording paper to the reverse path 122 and the image forming surface is faced up. That is, the paper is discharged by the discharge roller 118 with face-up.

  Further, when double-sided recording is performed to form an image on both sides of the recording paper, the image forming apparatus 10 guides the recording paper to the reverse path 122 by the switching operation of the flapper 121 and then transports the recording paper to the double-sided transport path 124. To do. Then, the recording sheet guided to the duplex conveyance path 124 is fed again between the photosensitive drum 111 and the transfer unit 116 at the timing described above.

<Sheet processing device>
Next, a configuration example of the sheet processing apparatus 500 will be described with reference to FIG. The sheet processing apparatus 500 is connected to the rear side of the image forming apparatus 10, that is, the recording paper discharge side. The recording paper discharged from the image forming apparatus 10 is delivered to the inlet roller pair 502 of the sheet processing apparatus 500. At this time, the entrance sensor 501 detects the delivery timing of the recording paper. The recording paper conveyed by the conveyance mechanism including the inlet roller pair 502 is guided to the conveyance path 504. A pair of ion generation units 504 and 505 are arranged in the conveyance path 503 with the recording paper interposed therebetween. The recording paper is neutralized by these ion generation units 504 and 505. The discharged recording paper is conveyed toward the conveyance roller pair 506 and 510 and the separation roller 511.

  The recording paper that has passed through the separation roller 511 reaches the buffer roller pair 515. Thereafter, when the sheet is discharged to the upper tray 536, the sheet processing apparatus 500 displaces the upper path switching flapper 518 to a position indicated by a broken line in the drawing. As a result, the recording paper is guided to the upper path conveyance path 517 and discharged onto the upper tray 536 by the upper discharge roller 520.

When the sheet is not discharged to the upper tray 536, the recording paper that has reached the buffer roller pair 515 is guided to the bundle conveyance path 521 by the upper path switching flapper 518. Thereafter, the buffer roller pair 522 and the bundle transport roller pair 524 sequentially pass through the transport path. The recording paper that has reached the bundle conveying roller pair 524 is conveyed to the lower path 526.
The recording paper guided to the lower paper discharge roller pair 528 and discharged to the intermediate processing tray 538 is subjected to alignment processing every predetermined number of sheets in the intermediate processing tray 538. Thereafter, the stapler 532 performs a stapling process as necessary, and then the sheet is discharged onto the lower tray 537 by the bundle discharge roller pair 530.

<Control system of image forming system>
Next, a control system of the image forming system 1000 that operates as described above will be described. As shown in the functional configuration diagram of FIG. 3, the image forming system 1000 includes a main control unit 150 that comprehensively controls the operation of the image forming apparatus 10, and the operation of the sheet processing apparatus 500 according to instructions from the main control unit 150. And a finisher control unit 553 that controls the entire system.
The main control unit 150 is mounted on the image forming apparatus 10. Although the finisher control unit 553 is described as being mounted on the sheet processing apparatus 500, the finisher control unit 553 may be mounted on the image forming apparatus 10 when it can communicate with the main control unit 150 by wire or wireless.

The main control unit 150 includes a CPU 150A, a ROM 151, and a RAM 152 as hardware. CPU is an abbreviation for Central Processing Unit (hereinafter the same). ROM is an abbreviation for Read Only Memory (hereinafter the same). RAM is an abbreviation for Random Access Memory (hereinafter the same).
The CPU 150A executes a control program stored in the ROM 151, thereby comprehensively controlling the document feeder control unit 101, the image reader control unit 201, the image signal control unit 202, the printer control unit 301, and the operation unit 401. To do. The RAM 152 is used as a work area for temporarily storing data used by the CPU 150A during operation. The image reader control unit 201 and the image signal control unit 202 are connected by an image bus 203.

  The document feeder control unit 101 controls driving of the document feeder 100. The image reader control unit 201 drives and controls the scanner 200 to optically read the document fed by the document feeding device 100. Then, the image signal obtained thereby is transferred to the image signal control unit 202 via the image bus 203.

  The image signal control unit 202 converts the input image signal into a raster image video signal, and then outputs it to the printer control unit 301. The image signal control unit 202 counts the number of dots for generating a toner image when generating raster image data. This count is calculated independently for each toner color in the case of color printing. The calculated number of dots is notified to the main control unit 150 in units of print images. The main control unit 150 determines the toner adhesion amount by multiplying the number of dots by a predetermined coefficient predetermined for each toner color.

The printer control unit 301 outputs the laser beam based on the video signal input from the image signal control unit 202 to form an electrostatic latent image on the photosensitive drum 111.
The operation unit 401 notifies the main control unit 150 of key signals corresponding to various key operations received through the operation display device 400, and in accordance with instructions from the main control unit 150, a predetermined image is displayed on the display unit of the operation display device 400. Is displayed.

  The finisher control unit 553 includes a CPU 550, a ROM 551, and a RAM 552 as hardware. Based on instructions from the main control unit 150, the CPU 550 executes various programs stored in the ROM 551 to control the sheet processing apparatus 500 in an integrated manner. The finisher control unit 553 also performs state detection of various sensors including the inlet sensor 501, operation control of the ion generation units 504 and 505, and drive control of various motors including the transport motor M701. From the finisher control unit 553, operation control signals mon1, pon1 of the ion generation unit 504 and operation control signals mon2, pon2 of the ion generation unit 504 are output. The output timing of these operation control signals will be described later.

  The finisher control unit 553 includes a CPU 550, a ROM 551, and a RAM 552 as hardware. Based on instructions from the main control unit 150, the CPU 550 executes various programs stored in the ROM 551 to control the sheet processing apparatus 500 in an integrated manner. The finisher control unit 553 also performs state detection of various sensors including the inlet sensor 501, operation control of the ion generation units 504 and 505, and drive control of various motors including the transport motor M701. From the finisher control unit 553, operation control signals mon1, pon1 of the ion generation unit 504 and operation control signals mon2, pon2 of the ion generation unit 504 are output. The output timing of these operation control signals will be described later.

<Charging of recording paper>
Here, the reason why the recording paper is charged in the above-described image forming process will be described.
FIG. 4 shows the transfer process to the recording paper. The unexposed part of the photosensitive drum 111 is positively charged. The negatively charged toner 604 adheres to the electrostatic latent image portion of the photosensitive drum 111 by Coulomb force. The transfer unit 116 described above is disposed on the opposite side of the photosensitive drum 111 via the recording paper 603. That is, the transfer charging roller 601 is in contact with the recording paper 603, and a high voltage is applied to the transfer charging roller 601 from the transfer high voltage power source 602. Therefore, the recording paper 603 is positively charged by the transfer unit 116, and the toner 604 on the photosensitive drum 111 is transferred to the recording paper 603. By this transfer process, the back surface of the recording paper 603 is positively charged and the front surface is negatively charged according to the amount of toner.

Also, the recording paper has different electrical resistivity depending on the paper type. This electrical resistivity varies depending on the environmental humidity.
In addition to the transfer process described above, charging of the recording paper can also occur due to friction or peeling between the recording paper and the recording paper, or friction between the recording paper and a member on the conveyance path, or immediately after image formation by the electrophotographic process. Charging is dominated by charging by the transfer process.

  Further, the transfer process according to FIG. 4 has been described on the premise that the toner is negatively charged and the photosensitive drum 111 is positively charged. However, some electrophotographic processes use different charged states. However, there is no change with respect to transferring the toner image onto the recording paper using the Coulomb force, with the reverse charging of the recording paper and the charging of the toner being oppositely charged.

<Ion generation unit>
As described above, the front and back surfaces of the recording paper are charged when the image forming apparatus 10 moves in the conveyance path or transfers the toner image. The two ion generation units 504 and 505 operate in cooperation with each other at a timing determined by the finisher control unit 553 to neutralize (eliminate) the charged charges on the front and back sides of the recording paper with an ion cloud. “Cooperating operation” means that the other ion generation unit is operated simultaneously with the operation of one ion generation unit or after a certain period of time, rather than operating independently. These ion generation units 504 and 505 are also called “ionizers”.

Hereinafter, configuration examples and operation examples of the ion generation units 504 and 505 will be described.
FIG. 5A is a transparent perspective view illustrating an arrangement example of the ion generation units 504 and 505. For convenience, the upper wall material of the conveyance path 503 and the unevenness of the wall material are omitted. FIG. 5B is a cross-sectional view of the conveyance path 503 formed of a wall material having a size larger than that of the recording paper and its attachment member, and FIG. 5C is a top transparent view thereof.

The ion generation units 504 and 505 are disposed between the entrance roller pair 502 and the transport roller pair 506 as shown in FIGS. 2 and 5A. The ion generation unit 504 emits ions by corona discharge to neutralize charged charges on one surface, for example, the surface of the recording paper, for example, the surface, and generates an ion cloud near the surface. On the other hand, the ion generation unit 505 emits ions by corona discharge in order to neutralize (eliminate) the other surface of the recording paper, that is, the back surface, and generates an ion cloud near the back surface.
The ion generation unit 504 corresponds to a “first ion generation unit”, and the ion generation unit 505 corresponds to a “second ion generation unit”.

  The ion generation units 504 and 505 are arranged apart from each other by a predetermined distance in the moving direction of the recording paper. The “predetermined distance” is, for example, a distance where the spread of ions on the front and back of the recording paper does not overlap.

  The ion generation units 504 and 505 are configured by arranging a plurality of pairs of positive ion generators and negative ion generators in the width direction orthogonal to the conveyance direction of the recording paper, in this example, four pairs. . In FIG.5 (c), the code | symbol 504ap, 504bp, 504cp, 504dp, 505ap, 505bp, 505cp, 505dp represents a positive ion generator. Reference numerals 504am, 504bm, 504cm, 504dm, 505am, 505bm, 505cm, and 505dm denote negative ion generators. A positive ion generator (such as 504ap) generates positive ions (hereinafter referred to as “positive ions”). The negative ion generator (eg, 504am) generates negative ions (hereinafter referred to as “negative ions”). In addition, each ion generator 504ap-504dp and 504am-504dm are components of the same structure.

As shown in FIG. 5B, the ion generation units 504 and 505 generate an ion cloud in a space (residence space) formed by the conveyance path 503, the inlet roller pair 502, and the conveyance roller pair 506. Since the generated ion cloud stays in the staying space, the generated ions are not wasted and the amount of ions generated can be suppressed.
Further, in order to prevent the generated ion cloud from charging the member existing in the staying space, the member, for example, a part or all of the wall material forming the conveyance path 503, the wall member mounting member, etc. are weakly conductive members. The member is grounded. Specifically, the member provided with conductivity is electrically connected to the metal frame of the sheet processing apparatus 500. Thereby, reverse charging by the ion cloud is suppressed.

  A configuration example of the ion generation units 504 and 505 is shown in FIG. FIG. 6A is a configuration diagram of the ion generation unit 504, and FIG. 6B is a configuration diagram of the ion generation unit 505. Since the ion generation units 404 and 405 are composed of the same parts, the ion generation unit 504 shown in FIG. 6A will be described here.

  The ion generation unit 504 includes a high voltage positive power source 5041 and a high voltage negative power source 5042. The positive voltage output from the high-voltage positive power supply 5041 is applied to the high-voltage electrode 5043 of an ion generator (such as 504ap) that generates positive ions. On the other hand, the negative voltage output from the high voltage negative power source 5042 is applied to the high voltage electrode 5044 of an ion generator (eg, 504am) that generates negative ions. The ground terminals of the high-voltage positive power source 5041 and the high-voltage negative power source 5042 and the GND electrode 5044 of each ion generator (504ap, etc.) are grounded.

  When a high voltage is applied to each ion generator (504ap, 504am, etc.), a corona discharge is generated between the high-voltage electrode 5043 and the GND electrode 5044. As a result, ions having a polarity corresponding to the relative potential (including polarity) with respect to the GND electrode 5044 are generated from each ion generator (504ap, 504am, etc.), and an ion cloud is generated.

Here, with reference to FIG. 7, control of the density of the ion cloud, that is, the ion emission intensity by the ion generation units 504 and 505 will be described. 7A to 7D, the horizontal axis represents the flow of time. The finisher control unit 533 controls the ion emission intensity according to an instruction from the main control unit 150.
FIG. 7A shows an example in which the emission intensity of positive ions from the ion generation unit 504 is controlled by changing the ratio of the output time of the voltage generated by the high-voltage positive power supply 5041. The same (b) shows an example in which the emission intensity of negative ions from the ion generation unit 505 is controlled by changing the ratio of the output time of the voltage generated by the high-voltage negative power source 5042. In each figure, the upper side is a voltage output, and the lower side is a control signal.

  In FIGS. 7A and 7B, “Tcycle” is an ion generation cycle. “Ton1” to “Ton3” are times when the voltage output from the high voltage positive power source 5041 and the high voltage negative power source 5042 is on in the ion generation cycle Tcycle. That is, it is the time during which a high voltage is applied to the ion generator (eg, 504ap). The voltage output from the high voltage positive power source 5041 and the high voltage negative power source 5042 is turned on or off according to the control signal pon (mon) output from the finisher control unit 533. That is, the time ratio of on in the ion generation cycle Tcycle is controlled by time-division driving. As the time ratio of on increases, the ion emission intensity substantially increases and the ion concentration of the ion cloud increases.

In (1) of FIG. 7A, the voltage output is on for the entire time of the ion generation cycle Tcycle (Ton1). In (2), the on time is longer than the off time (Ton2). In (3), the on time is shorter than the off time (Ton3). In (4), there is no time for the voltage output on the upper side of the drawing to be on, and the voltage output is turned off for the entire time of the ion generation cycle Tcycle. The time relationship of on is Ton1>Ton2> Ton3. Accordingly, the positive ion emission intensity increases in the order of (1), (2), (3), and (4).
The same applies to FIG. 7B, and the negative ion emission intensity increases in the order of (1), (2), (3), and (4).
When the finisher control unit 533 performs such control, the voltage values output from the high-voltage positive power source 5041 and the high-voltage negative power source 5042 can be made constant. Therefore, there is an advantage that the cost is remarkably reduced as compared with the control mode in which the voltage value is changed. However, in order to suppress fluctuations in the ion density in the ion cloud, it is desirable to switch the ion generation cycle Tcycle as short as possible and to switch at high frequency.

FIGS. 7C and 7D show examples in which the ion emission intensity is changed by changing the applied voltage value. FIG. 7C shows a voltage value output from the high-voltage positive power supply 5041, and FIG. 7D shows a voltage value output from the high-voltage negative power supply 5042. In any case, the ion emission intensity increases in the order of (1), (2), (3), and (4).
In the examples of FIGS. 7C and 7D, since time-division driving is not performed, there is no variation in ion density in the generated ion cloud.

<Initialization process>
FIG. 8 is an explanatory diagram of the procedure of the initialization process of the sheet processing apparatus 500. For example, when the sheet processing apparatus 500 is turned on, the finisher control unit 553 receives an instruction from the main control unit 150 and starts system initialization processing (S1001).
The finisher control unit 553 performs an error check of a circuit or device to be controlled, and if there is no abnormality (S1002: YES), performs an initial communication process (S1103). Specifically, a communication IC (not shown) is activated to establish a communication link with the image forming apparatus 10. When the communication link is established (S1004: YES) and the system data can be received (S1005: YES), the system data is received and stored in the RAM 552 (S1006).
The system data is information on the main body configuration of the image forming apparatus 10 and a charge elimination table described later. Thereafter, the mechanical system is initialized (S1007). The initialization of the mechanism system is a process of driving various motors such as the transport motor M701 to move various mechanisms, for example, the transport mechanism to a predetermined position. At that time, an error check of the mechanical system is performed, and if there is no error, the initialization process is terminated (S1008: YES).

If there is an error in the error check in S1002 (S1002: NO), error processing 2 for putting the driving power source such as a motor power source into a dormant state is performed (S1011). Error processing 2 represents a state in which there is an error in the peripheral circuit of the main control unit 150. This is because there is no point in notifying the image forming apparatus 10 of the error content.
If there is an error in the error check in S1008 (S1008: NO), the error state is notified to the image forming apparatus 10 (S1010), and error processing 1 for stopping the driving power source such as the motor power source is performed (S1011) Finish the conversion process.

<Static elimination table>
Although FIG. 1 shows an example in which the sheet processing apparatus 500 is connected to the output stage of the image forming apparatus 10, the sheet processing apparatus 500 can be connected to a plurality of different types of image forming apparatuses. Since the image forming process depends on the image forming apparatus, the charging state of the recording paper varies depending on the type of the image forming apparatus. The finisher control unit 533 receives system data from the image forming apparatus and stores it in the RAM 552 in the initialization processing (S1004 to S1006 in FIG. 7). This is to do in
Here, the static elimination table included in the system data will be described. The static elimination table is used when the finisher control unit 533 estimates the image formation status on the recording paper. Since the ease of charging and the ease of charge coupling differ depending on the type of recording paper and the front and back of the recording paper, they are defined for each type of recording paper and for the front and back of the recording paper. In addition, since the charging state of the front and back surfaces varies depending on the amount of toner adhering to the recording paper, the amount of transferred toner is also regulated.

FIG. 9 is a diagram illustrating an example of the content of the static elimination table in the present embodiment. In the illustrated example, an OHP sheet, a coated paper, and a plain paper are exemplified as the recording paper type (paper type). Of the “front and back types”, “front surface” means that the ion generation unit 504 is driven, and “back surface” means that the ion generation unit 505 is driven. Among “positive and negative”, “positive” means positive ions and “negative” means that negative ions are released. The numerical values for “preliminary discharge” and “toner amount (inner surface average)” are output intensities of drive outputs of the ion generation units 504 and 505, and the maximum output intensity is set as 100 [%]. This is also called the ion emission intensity.
“Toner amount (inner surface average)” is a value (inner surface average) obtained by averaging the print dots of each color raster image to be printed for each image forming surface of the recording paper. The maximum value when printing all the dots in all four colors is 400 [%].

  The ion generation units 504 and 505 are set in capacity corresponding to the case where the charge amount of the recording paper is maximized. For example, the ion generation unit 504 has a smaller charge amount when the toner amount is 100 [%] than when it is 400 [%], but is negatively charged by the toner, so that positive ions are increased and ions are increased. The emission intensity is set to be weaker than 100 [%]. The ion generation unit 505 determines the positive charge amount mainly depending on the type of recording paper. Therefore, correction according to the toner amount is performed, and the ion emission intensity is set in the same manner as the toner amount on the surface.

  This charge removal table is stored in advance in the ROM 151 in the image forming apparatus 10, read out during the initialization process shown in FIG. 7, and transmitted to the finisher control unit 553 of the sheet processing apparatus 500. The finisher control unit 553 controls the ion emission intensity with reference to the charge removal table as appropriate.

<Control of ion emission intensity>
Next, an example of a procedure for controlling the ion emission intensity will be described with reference to FIG.
The finisher control unit 533 acquires a notification of a job (JOB) accompanied by image formation information from the image forming apparatus 10 (S1101). The image formation information is information representing the image formation status in the image forming apparatus 10 and includes the paper type and the amount of toner attached to the recording paper.

The finisher control unit 533 refers to the charge removal table illustrated in FIG. 8 based on the acquired image formation information, and initially drives the corresponding ionizer (ion generation units 504 and 505) (S1102). For example, when the paper type is plain paper, the ion generation units 504 and 505 are caused to perform preliminary discharge at 50 [%] of the maximum output intensity for both positive ions and negative ions. At this stage, the recording paper has not arrived on the transport path, but the remaining space through which the recording paper passes is preliminarily filled with ions, thereby reducing the amount of ions released during subsequent ion emission. Can do.
At this stage, since the recording paper has not arrived at the conveyance path 503, the positive ions and negative ions in the staying space are balanced. When the ion balance is not achieved, for example, when the ion distributions do not overlap, the output may be adjusted.

  Next, when the inlet sensor 501 detects the leading edge of the recording paper (S1103: YES), the finisher control unit 553 recognizes that the recording paper has arrived at the transport path 503, and adjusts the output of the ionizer (S1104). Specifically, the charging state of the recording paper is estimated based on the image formation information and the charge removal table, and the ion emission intensity by the ion generation unit 504 and the ion generation unit 505 is controlled based on the estimation result. For example, assuming that the paper type is plain paper and the toner amount (inner surface average) is 100 [%], the ion generation unit 504 is configured so that the positive ion is 40 [%] and the negative ion is 20 [%] with respect to the maximum output intensity. Control to be The ion generation unit 505 is controlled so as to be positive ions 30 [%] and negative ions 60 [%]. In this way, the amount of ions in the staying space is changed based on the image formation information.

The finisher control unit 533 recognizes that the recording paper has passed when the entrance sensor 501 detects the trailing edge of the recording paper (S1105: YES). If the next recording sheet is present (1106: YES), the output adjustment of the ionizer (drive adjustment for preliminary discharge based on the charge removal table) is performed according to the image forming status of the next recording sheet (S1111), and the process returns to S1103. .
If there is no next recording sheet (S1106: NO), the drive of the ionizer is stopped (S1107), and the process ends.

<Static elimination effect>
FIGS. 11A to 11D are graphs showing the difference in the static elimination effect when the ion emission intensity is controlled as described above and when it is not performed. These graphs plot the relative charging voltage, the amount of positive ions, and the amount of negative ions for each position of the conveyed recording paper, with the charging voltage due to static elimination at the leading edge of the recording paper being “0”.
In each graph, the horizontal axis represents the transport amount [mm] with the leading edge of the recording paper as the starting point (0 [mm]). The left side of the vertical axis represents an ion relative value and represents the degree of increase or decrease of the ion amount when the ion amount on the recording paper surface at the leading edge of the recording paper is “100”. Further, the right side of the vertical axis is a charging voltage relative value, and represents a relative fluctuation value from the charging voltage after static elimination at the leading edge of the recording paper. In any graph, it is assumed that preliminary discharge is performed before the transport distance is “0”, and positive ions and negative ions are in an equilibrium state.

FIG. 11C shows an example in which the same amount of positive ions and negative ions are released (both “100”) even though the surface of the recording paper is negatively charged. As the recording paper is conveyed, a large amount of positive ions is consumed to neutralize the negative charging of the recording paper. Also, as the trailing edge of the recording paper is reached, the concentration of positive ions in the transport path decreases, so that the negative charge of the recording paper cannot be neutralized. Therefore, the negative charge amount of the recording paper is increased, and the charge removal performance is lowered.
Moreover, the balance of the positive ion and negative ion in the residence space has arisen by the decrease in the amount of positive ions. Since the decrease in the amount of positive ions is accelerated, the amount of negative ions gradually increases with an increase in the conveyance amount of the recording paper.

  On the other hand, FIG. 11A shows the transition when the amount of positive ions is not changed (“100”) and the amount of negative ions is suppressed (“60”). It can be seen that the balance fluctuation of positive and negative ions from the leading edge to the trailing edge of the recording paper is suppressed, and the static elimination effect is maintained.

  FIGS. 11D and 11B are comparisons in the case where the back surface of the recording paper is positively charged, but the description is omitted because the above description is only reversed.

  As described above, in this embodiment, the charging state of the recording paper is estimated based on the paper type, its front / back type, and the toner amount (in-plane average), and the driving state of the ion generation units 504 and 505 is determined based on the estimation result. Changed. Therefore, a stable charge removal effect can be obtained without excessively increasing the ion emission intensity from the ion generation units 504 and 505. As a result, it has become possible to extend the service life of the ion generation units 504 and 505 and extend the maintenance interval.

[Second Embodiment]
In the second embodiment, each of the plurality of ion generators constituting the ion generation units 504 and 505 emits both positive ions and negative ions. These ion generators are arranged in the width direction of the recording paper as in the case of the first embodiment.
FIG. 12 shows a configuration diagram of the ion generation unit 504 in the second embodiment. For convenience, the same members as those shown in the first embodiment (FIG. 6A) are denoted by the same reference numerals.
As shown in FIG. 12, the ion generation unit 504 of the second embodiment uses a high-voltage power source 1201 that can generate a positive voltage and a negative voltage by switching in a time-sharing manner, and the single ion generators 1202a to 1202f have positive and negative ions. Generate both. The ion generation unit 505 has the same configuration.

The control of the ion emission intensity in the second embodiment is realized by changing the voltage generation time (drive duty) in the positive / negative voltage output cycle of the high-voltage power supply 1201. An example of the contents of such control is shown in FIG. In the figure, the horizontal axis indicates the change in time.
FIG. 13 (1) sets the maximum positive voltage output time Ton1 (p) during the positive ion generation cycle Tcycle (p) and the negative voltage output time Ton1 (m) during the negative ion generation cycle Tcycle (m). This is an example. In this case, the ion emission intensity is maximized.

FIG. 13B is an example when the emission intensity of only positive ions is suppressed. That is, the negative voltage output time Ton1 (m) is kept as it is, and only the positive voltage output time is shortened to Ton2 (p). FIG. 13 (3) shows an example in which the emission intensity of only negative ions is suppressed. That is, the positive voltage output time Ton1 (p) is kept as it is, and only the positive voltage output time is shortened to Ton2 (m). FIG. 13 (4) shows an example in which the emission intensity of both positive ions and negative ions is suppressed. That is, the positive voltage output time is shortened to Ton2 (p) and the negative voltage output time is shortened to Ton2 (m).
Note that the ion emission intensity can be controlled by changing the voltage output of the high-voltage power supply 1201 as described in the first embodiment.

[Third Embodiment]
In the third embodiment, the high-voltage power sources 5041 and 5042 in the ion generation unit 504 are not shared in the unit as shown in FIGS. 6A, 6B, or 12, but are provided for each ion generator. It is what I did. With this configuration, it is possible to control each ion generator, not each ion generation unit.
For example, the width direction of the recording paper is obtained by dividing the width direction of the recording paper into a plurality of static elimination areas and acquiring the above-described image formation information and information on the static elimination table from the image forming apparatus 10 as information for each divided area. The control divided for each area becomes possible.

Further, by adding information such as the size of the recording paper and single-sided / double-sided printing to the image formation information, and changing the ion emission intensity according to the added information, the static elimination effect corresponding to the state of the recording paper can be further increased. Improvements can be made.
For example, the ion emission intensity generated between the leading edge and the trailing edge of the recording paper, which was constant in the first embodiment, is changed according to the size of the recording paper and the movement of the recording paper, or the amount of toner on the back surface during double-sided recording is changed. Based on this, it is possible to control the ion emission intensity more optimally, such as changing the ion emission intensity on the back surface.

  In addition, since the electrical resistivity of the recording paper varies greatly depending on the environmental humidity, a humidity sensor may be provided inside the apparatus, and the ion emission intensity may be controlled according to the detected environmental humidity.

<Modification>
In the first to third embodiments, the configuration in which the ion generation units 504 and 505 are provided in the sheet processing apparatus 500 has been described. However, as illustrated in FIG. 14, the ion generation units 504 and 505 may be provided in the conveyance mechanism of the image processing apparatus 10. . In this case, if the main control unit 150 is configured to control the ion generation units 504 and 505, the static elimination table and the paper type, the recording paper type, and the toner amount from the image forming apparatus 10 to the finisher control unit 553 are included. It is not necessary to send image formation information.
In the first to third embodiments, the example using the recording paper on which the image is formed by the image forming apparatus 10 has been described as an example of the sheet. However, other types of sheets such as a film and an OHP sheet are used. Even when it is used, the sheet can be neutralized by the same operation.

  DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 504, 505, 1202 ... Ion generation unit, 504ap-505dp, 504am-505dm, 1202a-1202h ... Ion generator, 503 ... Conveyance path, 5041, 5042, 5051 , 5052, 1201... High voltage (positive / negative) power source, 5043, 5044.

Claims (13)

Generating means for generating ions for neutralizing the front and back surfaces of the sheet moving in the conveyance path;
Control means for acquiring image formation information representing an image formation state when an image is formed on the sheet, and controlling the amount of ions generated from the generation means in accordance with the acquired image formation information. The static eliminator characterized by this. The generating means neutralizes charges charged on the other surface of the sheet, and a first ion generating unit for generating ions for neutralizing charges charged on one surface of the front and back surfaces of the sheet A second ion generating unit for generating ions for
The image formation information includes information on the type of the sheet used for image formation and the amount of color material attached to the sheet,
The control means controls the amount of ions generated from the first ion generation unit and the second ion generation unit according to information on the amount of the color material.
The static eliminator according to claim 1. A power source for supplying a voltage to the first ion generation unit and the second ion generation unit;
The control means generates from the first ion generation unit and the second ion generation unit by controlling a voltage supplied from the power source to the first ion generation unit and the second ion generation unit. The amount of ions to be controlled is controlled,
The static eliminator according to claim 2.   The static eliminator according to claim 3, wherein the control unit controls a voltage value supplied to the first ion generation unit and the second ion generation unit.   The static eliminator according to claim 3, wherein the control unit controls a rate per unit time for supplying a voltage to the first ion generation unit and the second ion generation unit. The second ion generation unit is disposed away from the first ion generation unit by a predetermined distance or more downstream in the moving direction of the sheet,
The static elimination apparatus of any one of Claims 2 thru | or 5.   The control means generates ions from the second ion generation unit simultaneously with the timing of generating ions from the first ion generation unit or after a certain period of time after generating ions from the first ion generation unit. The static eliminator according to claim 6. The first ion generation unit and the second ion generation unit are each configured by arranging a plurality of ion generators that emit ions in the width direction of the sheet,
The static elimination apparatus of any one of Claim 2 thru | or 7. At least one of the ion generators is disposed in a plurality of areas divided in the width direction of the sheet, and is configured to be controlled for each area by the control unit.
The static eliminator according to claim 8. The control means is characterized in that before the sheet arrives at the conveyance path, the ions are released from the first ion generation unit and the ions are retained in the retention space.
The static eliminator according to claim 7. Image forming means for forming an image on a sheet;
11. The static eliminator according to any one of claims 1 to 10, wherein the generating means neutralizes a sheet on which an image is formed by the image forming means.
Image forming apparatus. A retention space for retaining the ions is formed by the conveyance path and a conveyance mechanism for moving the sheet.
The image forming apparatus according to claim 11. A part of the member forming the stay space is composed of a conductive member, and the conductive member is grounded,
The image forming apparatus according to claim 12.