JP2014088241A - Sheet transport device,image forming device,sheet transport method,charging control program,and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet transport device,an image forming device, a sheet transport method,a charging control program,and a recording medium capable of improving traveling speed of a transport belt transporting a sheet with performing electrostatic attraction.SOLUTION: An electric charge pattern which alternates on a mounting surface 51A is formed by applying a voltage having same polarity on a same area of the mounting surface 51A by plural charging rollers 571 and 572 contacting to the mounting surface 51A of a transport belt 51 at a different position on a traveling direction R2 of the transport belt 51 having the mounting surface 51A on which a sheet is mounted.

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet by electrostatically attracting the sheet to a conveying belt.

In general, an ink jet recording apparatus (an example of an image forming apparatus) is known that ejects ink from a recording head onto a sheet (recording medium) and records an image on the sheet. As one type of ink jet recording apparatus, there is a so-called line head type ink jet recording apparatus including a recording head of each color fixed along a paper conveyance path. In this type of ink jet recording apparatus, a sheet is transported by a transport belt in a state of facing the ink ejection surface of each recording head, and ink is ejected from each recording head onto the sheet being transported.
In such an ink jet recording apparatus, the distance between the ink ejection surface of the recording head and the paper on the conveying belt is very small (for example, about 1 mm to 2 mm). For this reason, if the paper transported by the transport belt is lifted, the paper may rub against the ink discharge surface of the recording head and damage the ink discharge surface. When the ink discharge surface is damaged, the ink discharge port (nozzle) is clogged, resulting in a decrease in print quality. Specifically, a water repellent film is provided on the ink ejection surface so that ink droplets are ejected vertically. The water-repellent film has a function of preventing ink droplets from being deposited near the ejection port on the ink ejection surface and preventing the ink droplets from drying and sticking. For this reason, when the raised portion of the paper comes into contact with the ink ejection surface and the water-repellent film is damaged, the original function of the water-repellent film is not exhibited, and problems such as defective ejection of ink droplets or clogging of ejection ports occur.
In addition, when ink is attached to the vicinity of the ejection port when the paper comes into contact with the ejection port of the ink, there is a possibility that the ink may not fly from the ejection port in the vertical direction and the image quality may be deteriorated. Further, if the interval between the paper on the transport belt and the recording head is not uniform, the arrival time of the ink from the recording head to the paper changes, which causes color misregistration and image quality degradation.
On the other hand, an electrostatic adsorption type that conveys a sheet by electrostatically adsorbing the sheet to the conveying belt by forming a charge pattern alternating with the loading surface of the conveying belt by bringing the charging member into contact with the conveying surface of the conveying belt Are known (see, for example, Patent Document 1 and Patent Document 2).

JP-A-3-256945 JP 2004-131242 A

Incidentally, in order to increase the printing speed by the ink jet recording apparatus, it is necessary to increase the paper conveyance speed by the conveyance belt. However, in the electrostatic adsorption type paper conveyance device, if the traveling speed of the conveyance belt is increased, the time for the charging member to contact each area of the conveyance belt is shortened, and the conveyance belt cannot be sufficiently charged. Decreases. For this reason, there is a problem that the traveling speed of the conveyance belt cannot be increased in the electrostatic adsorption type paper conveyance device. In the ink jet recording apparatus provided with the electrostatic adsorption type paper conveyance device, the increase in the printing speed is hindered.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus capable of increasing the traveling speed of a conveying belt that electrostatically attracts and conveys a sheet. And a sheet conveying method, a charge control program, and a recording medium.

A sheet conveying apparatus according to the present invention includes a conveying belt and a charging unit. The conveyance belt has a placement surface on which a sheet is placed. The charging unit applies the voltage of the same polarity to the same region of the mounting surface by a plurality of charging members that contact the mounting surface of the transport belt at different positions in the traveling direction of the transport belt. An alternating charge pattern is formed on the surface.
In such a configuration, even when the traveling speed of the transport belt is increased, the placement surface of the transport belt can be sufficiently charged using the plurality of charging members, and the sheet is attracted to the transport belt. Can be made.
The image forming apparatus according to the present invention includes the sheet conveying device and an image forming unit that forms an image on the sheet conveyed by the sheet conveying device.
Further, in the sheet conveying method according to the present invention, a plurality of charging members are brought into contact with the placement surface of the conveyance belt at different positions in the traveling direction of the conveyance belt having a placement surface on which the sheet is placed. This is a method of forming a charge pattern alternating on the placement surface by applying a voltage having the same polarity to the same region of the placement surface.
In addition, the charging control program according to the present invention sets a number of the charging members that apply a voltage to the placement surface among the plurality of charging members to a computer that controls the sheet conveying apparatus, according to a preset charging condition. It is a charging control program for executing a step to be changed accordingly.
Furthermore, the recording medium according to the present invention is a computer-readable recording medium on which the charging control program is recorded.

  According to the present invention, it is possible to increase the traveling speed of a conveyance belt that conveys a sheet by electrostatic adsorption.

1 is a schematic cross-sectional view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a schematic configuration of a sheet conveying apparatus according to an embodiment of the present invention. The figure explaining the charging state in a conveyance belt. The flowchart which shows an example of the procedure of a charging control process. The principal part schematic diagram explaining an example of a moving mechanism. The figure explaining the experimental result of Examples 1-3 of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

First, an ink jet recording apparatus 10 according to an embodiment of the present invention (hereinafter abbreviated as “recording apparatus 10”) will be described with reference to FIG.
As shown in FIG. 1, the recording apparatus 10 includes a paper feed cassette 1, a paper feed unit 2, an image forming unit 3, an ink tank unit 4, a sheet conveying device 5, a control unit 6, a paper discharge unit 7, and a main body frame. 8 is an example of an image forming apparatus including 8 and the like.
The recording device 10 is a printer device that executes print processing based on image data input from an information processing device such as a personal computer. The image forming apparatus according to the present invention can be applied not only to a printer device but also to a copying machine, a facsimile machine, a multifunction machine, and the like.
Further, the present invention is not limited to the ink jet recording apparatus 10 but is also applied to an electrophotographic image forming apparatus including a photosensitive drum, a charging unit, an exposure device, a developing device, a transfer device, a fixing device, and a toner container. Is possible. Furthermore, the sheet conveying apparatus according to the present invention is also applicable to a sheet conveying apparatus that automatically conveys the original in an image reading apparatus that reads image data from the original, for example.

  The paper feed cassette 1 contains paper P that is a dielectric. The sheet P is an example of a sheet conveyed by the sheet conveying apparatus 5 and is a printing target by the recording apparatus 10. The sheet is not limited to paper, but may be another recording medium that is a dielectric such as an OHP film.

  The paper feed unit 2 includes a pickup roller 21, a transport roller 22, a transport path 23, a registration roller 24, a manual feeder 25, and a paper feed roller 26. The pickup roller 21 takes out the sheets P from the sheet feeding cassette 1 one by one. The transport roller 22 and the transport path 23 transport the paper P taken out by the pickup roller 21 to the registration roller 24. The registration roller 24 conveys the paper P to the image forming unit 3 at a predetermined conveyance timing (image writing timing). The manual feeder 25 and the paper feed roller 26 are used for supplying the paper P from the outside.

The image forming unit 3 includes a recording head 31 corresponding to K (black), a recording head 32 corresponding to C (cyan), a recording head 33 corresponding to M (magenta), and a recording head corresponding to Y (yellow). 34 is an ink jet recording unit. In the present embodiment, a configuration having four recording heads 31 to 34 corresponding to four colors of KCMY will be described as an example, but the number of recording heads is not limited to this.
Each of the recording heads 31 to 34 has a long shape in a direction perpendicular to the transport direction of the paper P (paper width direction), and is arranged at predetermined intervals along the transport direction of the paper P. ing. In addition, ink discharge surfaces 31 </ b> A to 34 </ b> A each having a large number of nozzles (discharge ports) for discharging ink are provided at the lower ends of the recording heads 31 to 34.
The image forming unit 3 forms an image on the paper P by ejecting ink from the ink ejection surfaces 31 </ b> A to 34 </ b> A onto the paper P conveyed by the sheet conveying device 5. That is, the recording apparatus 10 is a so-called line head type inkjet recording apparatus. As the ink ejection method of the recording heads 31 to 34, for example, a piezo method that ejects ink using a piezo element or a thermal method that ejects ink by generating bubbles by heating is employed.

  The ink tank unit 4 includes an ink tank 41 corresponding to K (black), an ink tank 42 corresponding to C (cyan), an ink tank 43 corresponding to M (magenta), and an ink corresponding to Y (yellow). A tank 44 is provided. The ink tanks 41 to 44 are connected to the recording heads 31 to 34 of the same color by ink tubes (not shown), and replenish the recording heads 31 to 34 with ink of each color.

The sheet conveying device 5 is disposed below the recording heads 31 to 34. The sheet conveying device 5 conveys the paper P supplied from the paper feeding unit 2 to the paper discharge unit 7 while facing the ink ejection surfaces 31A to 34A.
Specifically, the sheet conveying device 5 includes a conveying belt 51, a driving roller 52, stretching rollers 53, 54, and 55, a pressing roller 56, a charging device 57 (an example of a charging unit), a temperature / humidity sensor 58, and the like. ing. The gap between the transport belt 51 and the ink ejection surfaces 31A to 34A is such that the interval between the paper P transported by the transport belt 51 and the ink ejection surfaces 31A to 34A is, for example, about 1 mm to 2 mm. It is prescribed as follows.

The transport belt 51 has a placement surface (front surface) 51A on which the paper P is placed, and is an endless belt formed of a dielectric, and includes the driving roller 52 and the stretching roller. It is stretched with a predetermined tension by 53-55.
The conveyor belt 51 is formed of a dielectric material such as urethane rubber, PET (polyethylene terephthalate) resin, ETFE (tetrafluoroethylene / ethylene copolymer) resin, PI (polyimide) resin, PAI (polyamideimide) resin, or the like. ing. For example, the transport belt 51 has an inner layer having an electric resistance value of 5 [logΩ] to 7 [logΩ] and an outer layer provided on the outer periphery thereof having an electric resistance value of 14 [logΩ] to 17 [logΩ]. It is a multilayer belt.

The drive roller 52 is connected to the rotation shaft of the drive motor 52A. When the drive roller 52 is rotated counterclockwise (in the direction of arrow R1 in FIG. 1) by the drive motor 52A, the transport belt 51 travels in the travel direction R2 shown in FIG. At this time, the stretching rollers 53 to 55 are rotated by the driving force transmitted through the transport belt 51 by the driving of the driving roller 52.
Here, each of the stretching rollers 53 to 55 is a conductive metal roller or the like, and is connected to a ground common to a power supply device 573 provided in the charging device 57 described later. As a result, the tension roller 54 acts as one electrode during the charging operation of the transport belt 51 by the charging device 57.

  The pressing roller 56 is provided at a paper feeding position of the paper P from the paper feeding unit 2 to the sheet conveying device 5. The pressing roller 56 is disposed at a position opposite to the stretching roller 55, and the transport belt 51 is sandwiched between the stretching roller 55 and the pressing roller 56. The pressing roller 56 presses the paper P supplied from the paper feeding unit 2 against the transport belt 51 to bring the entire paper P into close contact with the transport belt 51.

  The charging device 57 is disposed on the upstream side of the pressing roller 56 in the traveling direction R <b> 2 of the transport belt 51, that is, on the upstream side of the paper feeding position of the paper P from the paper feeding unit 2. The charging device 57 forms a belt-like charge pattern with alternating positive and negative on the placement surface 51A of the conveyor belt 51 by applying an alternating voltage to the conveyor belt 51. Accordingly, the paper P supplied from the paper feeding unit 2 to the transport belt 51 is electrostatically attracted to the transport belt 51 and transported. Therefore, in the recording apparatus 10, the interval between the ink ejection surfaces 31A to 34A of the recording heads 31 to 34 and the sheet P conveyed by the conveying belt 51 is kept constant, and the sheet P is ejected from the ink. There is no contact with surfaces 31A-34A. The details of the charging device 57 will be described later.

  The temperature / humidity sensor 58 is a sensor that is disposed in the vicinity of the sheet conveying device 5 and detects the environmental temperature and environmental humidity of the sheet conveying device 5, and the environmental temperature detected by the temperature / humidity sensor 58 The environmental humidity is input to the control unit 6. Note that the temperature / humidity sensor 58 is not limited to the temperature and humidity of the sheet conveying device 5 as long as the temperature and humidity can be detected. It may be used also as a temperature / humidity sensor.

  The control unit 6 includes control devices such as a CPU as an arithmetic unit, a RAM used as a temporary storage area, an EEPROM, and a ROM in which various control programs are stored in advance. Then, the control unit 6 comprehensively controls each component of the recording device 10 based on image data input from the outside, so that an image corresponding to the image data is generated by the image forming unit 3. An image forming process to be recorded on the paper P is executed.

  The paper discharge unit 7 is provided downstream of the image forming unit 3 in the paper conveyance direction, and includes a drying device 71, a conveyance path 72, a paper discharge roller 73, a paper discharge tray 74, and the like. The drying device 71 dries the ink attached to the paper P by blowing air onto the paper P, for example. Then, the paper P dried by the drying device 71 is discharged to the paper discharge tray 74 by the paper discharge roller 73 through the transport path 72.

[Charging device 57]
Hereinafter, the charging device 57 provided in the sheet conveying device 5 will be described in detail with reference to FIGS. 2 and 3.
As shown in FIG. 2, the charging device 57 includes a charging roller 571, a charging roller 572, a power supply device 573, and the like. Each of the charging roller 571 and the charging roller 572 is electrically connected to the power supply device 573. The charging roller 571 and the charging roller 572 are merely examples of a charging member that applies a voltage to the transport belt 51, and a configuration in which a blade or the like is used as the charging member is also conceivable as another embodiment.

The power supply device 573 is a constant voltage power source that applies a predetermined constant voltage to each of the charging roller 571 and the charging roller 572. That is, the power supply device 573 is a common power supply device provided corresponding to the plurality of charging rollers 571 and the charging roller 572.
Specifically, as shown in FIG. 3 (A), the power supply device 573 supplies +2.5 kV and −2.K to the charging roller 571 and the charging roller 572, respectively, as shown in FIG. A voltage of 5 k [Vp-p] where 5 kV alternates is applied. For example, the power supply device 573 alternately switches the polarity of the constant voltage (2.5 kV) output from the charging roller 571 and the output terminal connected to the charging roller 572 at the alternating cycle T1 [s].
Here, in the sheet conveying apparatus 5, the alternating cycle T1 [s], the traveling speed V1 [mm / s] of the conveying belt 51, and the total length L0 [mm] of the conveying belt 51 are L0 / ( The relationship T1 × V1) = N (N is an integer) is established. As a result, each region of the transport belt 51 is always charged with the same polarity of charge, and the life of the transport belt 51 can be extended.

The charging roller 571 and the charging roller 572 are formed in a long shape in a direction (width direction of the paper P) perpendicular to the traveling direction R2 on the placement surface 51A of the transport belt 51. Further, the charging roller 571 and the charging roller 572 are conductive or semiconductive, and are rollers having an electrical resistance value of 3 [logΩ] to 9 [logΩ]. For example, the charging roller 571 and the charging roller 572 may be made of urethane resin, thermoplastic elastomer, epichlorohydrin rubber, ethylene-propylene-diene copolymer rubber (EPDM), silicon rubber, acrylonitrile-butadiene copolymer rubber, linole. It is formed of a mixture of one or more resin materials such as Bonnen rubber.
Specifically, when the EPDM is used as the material of the charging roller 571 and the charging roller 572, the charging roller 571 and the charging roller 572 can be reduced in order to reduce the electric resistance value of the charging roller 571 and the charging roller 572. The hardness will be high. However, if the hardness of the charging roller 571 and the charging roller 572 increases, the nip between the charging roller 571 and the charging roller 572 and the stretching roller 54 may not be stable. On the other hand, if the electrical resistance value is too high, the charging performance by the charging roller 571 and the charging roller 572 is lowered. Therefore, it is preferable that the electric resistance value of the charging roller 571 and the charging roller 572 is 3 [logΩ] or more and 9 [logΩ] or less. If the range is 3 [logΩ] or more and 9 [logΩ] or less, the hardness of the charging roller 571 and the charging roller 572 does not become too high, and high charging performance of the charging roller 571 and the charging roller 572 can be obtained. it can.
Further, when the traveling speed of the transport belt 51 is as high as about 800 [mm / s], the contact time between the charging roller 571 and the charging roller 572 and each region of the placement surface 51A is shortened. Charging performance is required. Therefore, the electrical resistance values of the charging roller 571 and the charging roller 572 are particularly preferably 5 [logΩ] or more and 7 [logΩ] or less. Since the charging roller 571 and the charging roller 572 having an electric resistance value of 5 [logΩ] or higher have high charging performance, it is suitable when the traveling speed of the conveyor belt 51 is high.
For example, when the traveling speed of the transport belt 51 is about 500 [mm / s], the electrical resistance value of the charging roller 571 and the charging roller 572 is about 3 [logΩ] to 9 [logΩ]. There may be. That is, the electrical resistance values of the charging roller 571 and the charging roller 572 may be set in advance according to the relationship between the hardness required for the charging roller 571 and the charging roller 572 and the charging performance.
By the way, the electrical characteristics of the charging roller 571 and the charging roller 572 may be the same or different. However, as shown in Example 3 described later, from the viewpoint of extending the life of the transport belt 51, it is desirable that the electrical resistance value of the charging roller 571 is higher than the electrical resistance value of the charging roller 572.

As shown in FIG. 2, the charging roller 571 and the charging roller 572 are arranged at different positions in the traveling direction R <b> 2 of the transport belt 51 and in contact with the placement surface 51 </ b> A of the transport belt 51. Yes. Further, the charging roller 571 and the charging roller 572 are disposed at positions facing the stretching roller 54 with the conveyance belt 51 interposed therebetween. The charging roller 571 and the charging roller 572 rotate in the clockwise direction following the traveling of the transport belt 51 in the traveling direction R2.
Here, the charging roller 571 is provided upstream of the charging roller 572 in the traveling direction R2 of the transport belt 51. That is, the contact position 57A between the charging roller 571 and the placement surface 51A is located on the upstream side of the traveling direction R2 of the transport belt 51 with respect to the contact position 57B between the charge roller 572 and the placement surface 51A. To do.
Further, in the sheet conveying apparatus 5, the charging roller 571 and the charging roller 572 press the conveying belt 51 between the one stretching roller 54. In particular, the charging roller 571 is arranged such that a straight line connecting the centers of the charging roller 571 and the stretching roller 54 is orthogonal to the placement surface 51 </ b> A of the transport belt 51. Similarly, the charging roller 572 is arranged such that a straight line connecting the centers of the charging roller 572 and the stretching roller 54 is orthogonal to the placement surface 51 </ b> A of the transport belt 51. That is, in the traveling direction R2 of the transport belt 51, the end of the contact range between the stretching roller 54 and the transport belt 51 is the same as the contact position 57B or downstream of the contact position 57B. As a result, the charge on the placement surface 51A of the transport belt 51 is prevented from moving to the back surface of the transport belt 51 and the charge amount on the placement surface 51A is reduced. In addition, the charging roller 571 and the charging roller 572 can suppress the occurrence of an undulation in the travel path of the conveyor belt 51 and an unnecessary load acting on the conveyor belt 51.

When alternating voltages are applied to the charging roller 571 and the charging roller 572 by the charging device 57, an alternating belt-like charge pattern is formed on the placement surface 51A of the transport belt 51.
Here, in the sheet conveying apparatus 5, the separation distance L1 that is the distance between the contact position 57A and the contact position 57B on the conveyance belt 51 is charged on the placement surface 51A corresponding to one cycle of the charge pattern. The charging roller 571 and the charging roller 572 are arranged at a position that is an integral multiple of the distance L2. That is, in the sheet conveying device 5, a relationship of L1 = L2 × N (N: integer) is established. Accordingly, the charging roller 572 applies a voltage having the same polarity as the polarity of the charge pattern formed on the placement surface 51A by the charging roller 571 to the placement surface 51A.
Specifically, for example, as shown in FIG. 3B, the placement surface 51A is elongated in the width direction of the transport belt 51 (direction perpendicular to the traveling direction R2) and the traveling direction R2 The positively charged regions 51B and the negatively charged regions 51C whose length is half the charging distance L2 are alternately formed along the traveling direction R2. Here, the charging distance L2 is a value determined by the alternating cycle T1 [s] and the traveling speed V1 [mm / s] of the conveyor belt 51, and can be calculated by a calculation formula of L2 = T1 × V1. is there. For example, when the alternating cycle T1 is 0.02 [s] and the traveling speed V1 of the transport belt 51 is 500 [mm / s], the charging distance L2 is 10 [mm].

As described above, in the sheet conveying device 5, the charging device 57 applies a voltage having the same polarity to the same region of the placement surface 51A by the plurality of charging rollers 571 and the charging roller 572. An alternating charge pattern is formed on the placement surface 51A.
Accordingly, in the sheet conveying device 5, the placement surface 51 </ b> A of the conveying belt 51 can be sufficiently charged using the plurality of charging rollers 571 and the charging rollers 572, and the sheet P is conveyed to the conveying belt 51. Can be absorbed. Therefore, in the sheet conveying apparatus 5, the traveling speed of the conveying belt 51 can be increased as compared with the conventional one. Furthermore, since the same voltage is applied to the plurality of charging rollers 571 and the charging rollers 572 from the power supply device 573, the sheet conveying device 5 does not need to include a power supply circuit of a plurality of channels, and the configuration is simplified. Can do.
In the present invention, a plurality of the charging rollers are provided on the placement surface 51A of the transport belt 51 at different positions in the traveling direction R2 of the transport belt 51 having the placement surface 51A on which the paper P is placed. The sheet conveying method may include a step of bringing 571 and 572 into contact with each other and a step of applying a voltage having the same polarity to the same region of the placement surface 51A to form an alternating charge pattern on the placement surface 51A. Good.

By the way, in the present embodiment, the sheet conveying device 5 has been described by taking as an example a configuration including the two charging rollers 571 and the charging roller 572, but it is also possible to have three or more charging rollers. It can be considered as an embodiment. In this case, each of the charging rollers may be arranged so that the interval between the contact positions of the three or more charging rollers and the transport belt 51 is an integral multiple of the charging distance L2.
Further, the charging roller 571 and the charging roller 572 are not limited to the positions where the conveying belt 51 is sandwiched between the charging roller 571 and the stretching roller 54. Specifically, the charging roller 571 and the charging roller 572 are disposed at least at a position upstream of the feeding direction of the transport belt 51 from the feeding position of the paper P from the paper feeding unit 2. That's fine.
Furthermore, if the recording apparatus 10 is configured to change the traveling speed of the transport belt 51 according to, for example, the type of the paper P, the charging distance L2 changes with the change. Therefore, the control unit 6 controls the charging roller 571 and the charging roller 572 by the power supply device 57 so that the separation distance L1 is an integral multiple of the charging distance L2 according to the traveling speed of the transport belt 51. It is conceivable to change the alternating cycle T1 of the applied voltage.

[Other Embodiments]
In the sheet conveying device 5, it is conceivable that both the charging roller 571 and the charging roller 572 are always used in the charging operation of the placement surface 51 </ b> A of the conveying belt 51 by the charging device 57.
On the other hand, the charge amount of the placement surface 51A of the conveyance belt 51 suitable for the adsorption of the paper P in the sheet conveyance device 5 is, for example, the type of the paper P, the environmental temperature of the sheet conveyance device 5, and the environmental humidity. It depends on various conditions such as. Therefore, the recording apparatus 10 may be configured to control the charge amount of the placement surface 51 </ b> A of the transport belt 51 by the charging device 57 by executing the below-described charging control processing by the control unit 6.
Specifically, in the control unit 6, the CPU executes the charge control process according to a charge control program stored in the ROM. Here, the control unit 6 when executing the charge control process corresponds to a charge control means. In this case, the control unit 6 and the sheet conveying device 5 are examples of the sheet conveying device according to the present invention. Further, the present invention may be understood as a charge control program for causing a computer such as the control unit 6 to execute the charge control process or a computer-readable recording medium on which the charge control program is recorded.

  Hereinafter, an example of the procedure of the charging control process will be described with reference to the flowchart of FIG. Here, the processing procedure executed by the control unit 6 is referred to as steps S1, S2,.

<Step S1>
First, in step S <b> 1, the control unit 6 determines whether a print request has been made to the recording apparatus 10. Specifically, the control unit 6 determines that the print request has been made when image data is input from an information processing apparatus such as a personal computer.
Here, when the control unit 6 determines that the print request has been made (Yes side of S1), the process proceeds to Step S2 and until the print request is made (No side of S1), The process waits at step S1.

<Step S2>
In step S <b> 2, the control unit 6 determines whether or not the type of the paper P satisfies a preset first charging condition.
For example, at the time of the print request to the recording apparatus 10 in the information processing apparatus, the type of the paper P stored in the paper feed cassette 1 is designated. Therefore, the control unit 6 can determine the type of the paper P according to the content of the print request. Of course, in the recording apparatus 10, the type of the paper P stored in the paper feed cassette 1 is selected by an operation display unit such as a touch panel (not shown), and the information is stored in the EEPROM of the control unit 6. It is also possible.
The first charging condition determines whether the charge amount of the transport belt 51 suitable for the type of the paper P requires charging by both the charging roller 571 and the charging roller 572. This is a condition set in advance as an index to perform. Specifically, it can be considered as an example of the first charging condition that the type of the paper P is set in advance as a type that can be attracted to the transport belt 51 with a small charge amount like an OHP film.
Further, as the thickness of the paper P increases, the paper P is less likely to be attracted to the transport belt 51. On the other hand, when the thickness of the paper P is small and the charge amount of the transport belt 51 is too large, there arises a problem of flying bending in which ink is not ejected from the recording heads 31 to 34 toward the paper P in the vertical direction. That is, it is desirable that the charge amount of the transport belt 51 increases as the thickness of the paper P increases and decreases as the thickness of the paper P decreases. Therefore, it is conceivable as an example of the first charging condition that the thickness of the paper P is a thickness that requires a charge amount equal to or greater than a threshold value set in advance as the charge amount of the transport belt 51.
Here, when it is determined that the first charging condition is satisfied (Yes side of S2), the control unit 6 shifts the process to step S5 and determines that the first charging condition is not satisfied ( The process proceeds to step S3.

<Step S3>
Next, in step S <b> 3, the control unit 6 determines whether the environmental temperature and the environmental humidity of the sheet conveying device 5 detected by the temperature / humidity sensor 58 satisfy a preset second charging condition. Determine whether.
Whether the charging amount of the transport belt 51 suitable for the environmental temperature and environmental humidity of the sheet transport device 5 requires charging by both the charging roller 571 and the charging roller 572 is the second charging condition. This is a condition set in advance as an index for determining whether or not.
Specifically, the electrical resistance value of the sheet P decreases as the environmental temperature and environmental humidity of the sheet conveying device 5 increase, and the electrical resistance value of the sheet P increases as the environmental temperature and environmental humidity decrease. Therefore, it is desirable that the charge amount of the transport belt 51 is smaller as the environmental temperature is higher and larger as the environmental temperature is lower. Further, it is desirable that the charge amount of the transport belt 51 is smaller as the environmental humidity is higher and is larger as the environmental humidity is lower.
Therefore, it can be considered as an example of the second charging condition that each of the environmental temperature and the environmental humidity is equal to or higher than a threshold temperature and a threshold humidity preset as the charge amount of the transport belt 51. Note that since there is usually a correlation between the environmental temperature and the environmental humidity, the use of either the environmental temperature or the environmental humidity as a determination index in Step S3 can be considered as another embodiment.
Here, when it is determined that the second charging condition is satisfied (Yes side of S3), the control unit 6 shifts the process to Step S5 and determines that the second charging condition is not satisfied ( (No side of S5), the process proceeds to step S4.

<Step S4>
In step S <b> 4, the control unit 6 uses the charging roller 571 and only one of the charging rollers 572 to the power supply device 573 to use the placement surface 51 </ b> A of the transport belt 51. Is given a control instruction to apply a voltage.
Accordingly, the power supply device 573 applies a voltage only to the charging roller 572 and charges the placement surface 51 </ b> A of the transport belt 51 using only the charging roller 572. In this case, the charge amount of the placement surface 51A of the transport belt 51 is reduced as compared with the case where both the charging roller 571 and the charging roller 572 are used. Accordingly, the charge amount of the transport belt 51 that is suitable when it is determined in Step S2 and Step S3 that the first charging condition and the second charging condition are not satisfied is obtained.

  By the way, in the step S4, it is conceivable to charge the mounting surface 51A using only the charging roller 571 disposed on the upstream side of the charging roller 571 and the charging roller 572. However, when a voltage is applied to the charging roller 571 in a state where the charging roller 572 is in contact with the placement surface 51A, the voltage wraps around the charging roller 572 via the placement surface 51A, and the placement surface 51A. There is a possibility that the charged state of becomes unstable. In this regard, in the step S4, the charging roller 572 on the downstream side of the charging roller 571 and the charging roller 572 is used. Therefore, even if a voltage wraps around the charging roller 571 on the upstream side, the charging state of the mounting surface 51A is overwritten by the charging roller 572 on the downstream side. Can be charged.

In addition, a configuration in which the sheet conveying device 5 includes a moving mechanism that causes one or both of the charging roller 571 and the charging roller 572 to contact and separate from the placement surface 51A of the conveying belt 51 is also conceivable. . Accordingly, the control unit 6 controls the moving mechanism to separate the charging roller 571 from the placement surface 51A of the conveying belt 51, thereby using only the charging roller 572 of the conveying belt 51. The placement surface 51A can be charged. Of course, the control unit 6 controls the moving mechanism so that the charging roller 572 is separated from the placement surface 51A of the conveying belt 51, so that only the charging roller 571 is used in front of the conveying belt 51. It is also possible to charge the placement surface 51A.
FIG. 5 is a schematic diagram of a main part showing a moving mechanism 51 which is an example of the moving mechanism. As shown in FIG. 5, the moving mechanism 51 is a rack and pinion mechanism having a frame 591, a rail 592, a pinion gear 593, and a drive motor 594.
The frame 591 rotatably supports the charging roller 571 by a rotation shaft 571A of the charging roller 571. A rack that meshes with the pinion gear 593 is formed on the end surface 591A of the frame 591. The rail 592 is provided in the casing of the sheet conveying device 5 and supports the frame 591 so as to be slidable in a direction approaching and separating from the placement surface 51A. The pinion gear 593 is meshed with a rack formed on the side surface 591A of the frame 591 and is connected to the drive motor 594. In the moving mechanism 51 configured as described above, when the pinion gear 593 is driven by the drive motor 594, the frame 591 slides in a direction approaching and separating from the mounting surface 51A.
Therefore, the control unit 6 can bring the charging roller 571 into contact with and away from the placement surface 51A by controlling the drive motor 594. The moving mechanism 51 is merely an example of a moving mechanism, and the moving mechanism is a mechanism for bringing the charging roller 571 into contact with and away from the placement surface 51A using other driving means such as a solenoid. There may be.

<Step S5>
On the other hand, in step S5, the control unit 6 applies a voltage to the placement surface 51A of the transport belt 51 using the charging roller 571 and the charging roller 572 to the power supply device 573. Give control instructions.
As a result, the power supply device 573 applies a voltage to both the charging roller 571 and the charging roller 572, and uses the both charging roller 571 and the charging roller 572 to place the placement surface 51 </ b> A of the transport belt 51. Is charged. In this case, the charging amount of the placement surface 51A of the transport belt 51 is increased as compared with the case where only one of the charging roller 571 and the charging roller 572 is used. Therefore, the charge amount of the transport belt 51 that is suitable when it is determined in the step S2 or the step S3 that the first charging condition or the second charging condition is satisfied.

As described above, in the recording apparatus 10, the number of charging rollers that apply a voltage to the placement surface 51 </ b> A of the transport belt 51 among the charging rollers 571 and the charging rollers 572 by the control unit 6. Is changed according to the first charging condition and the second charging condition. Therefore, according to the recording apparatus 10, the suction performance required for the transport belt 51 can be exhibited according to the use conditions of the recording apparatus 10. Further, according to the recording apparatus 10, waste of power consumption required for charging the transport belt 51 is suppressed, and flying bending caused by an excessive charge amount is also suppressed.
Further, in the recording apparatus 10, the charge amount of the transport belt 51 is changed by changing the number of charging rollers used when the controller 6 applies a voltage to the placement surface 51 </ b> A of the transport belt 51. Adjusted. Therefore, the power supply device 573 does not need to have a variable constant voltage circuit, and may be any device as long as it always outputs a constant voltage. Therefore, a highly accurate rectangular wave voltage can be applied to the conveyor belt 51. it can. Accordingly, the boundary between the positive charge region 51B and the negative charge region 51C in the charge pattern formed on the placement surface 51A is clarified, and high adsorption performance can be obtained. However, the power supply device 573 has a variable constant voltage circuit, and voltage values applied from the power supply device 573 to the charging roller 571 and the charging roller 572 are changed in steps S4 and S5. This is also conceivable as another embodiment.
In the charging control process, the conveyance belt 51 is placed on the basis of one or more of the type of the paper P, the environmental temperature of the sheet conveying device 5 and the environmental humidity of the sheet conveying device 5. The number of charging rollers for applying a voltage to the surface 51A may be changed.

  In Comparative Examples 1 and 2 and Examples 1 to 3 shown in FIG. 6, the voltage applied by the power supply device 573 is 5 k [Vp-p], and the traveling speed of the conveyor belt 51 is 800 [mm / s]. This is a result of charging the transport belt 51 by the charging device 57. In order to bring the paper P into close contact with the transport belt 51, it is desirable that the potential of the placement surface 51A is 300 [V] or more.

<Comparative Example 1>
First, Comparative Example 1 is a configuration in which the charging device 57 includes only the charging roller 572, and the power supply device 573 charges the transport belt 51 using only the charging roller 572. Here, the electric resistance value of the charging roller 572 is 7 [logΩ].
In the first comparative example, the potential of the placement surface 51A of the charging belt 51 after passing through the charging roller 572 is 270 [V], and the charge amount is smaller than those in Examples 1 to 3 described later. It can be seen that the performance of attracting the paper P to the transport belt 51 is low.

<Comparative example 2>
In Comparative Example 2, the charging device 57 includes the charging roller 571 and the charging roller 572, and the power supply device 573 charges the transport belt 51 using the charging roller 571 and the charging roller 572. It is the result of having gone.
The electric resistance value of each of the charging roller 571 and the charging roller 572 is 7 [logΩ]. The charging distance L2 corresponding to the one-cycle charge pattern formed on the transport belt 51 is 10 [mm].
However, the charging roller 571 and the charging roller 572 are arranged at a position where the separation distance L1 is 55 [mm], which is a half integer multiple of 10 [mm] which is the charging distance L2. ing. In such a configuration, the charging roller 571 and the charging roller 572 do not apply the same polarity voltage to the same region of the placement surface 51 </ b> A of the transport belt 51. Therefore, the charge pattern formed on the placement surface 51 </ b> A of the transport belt 51 by the charging roller 571 is partially canceled during charging by the charging roller 572.
Thereby, in this comparative example 2, the electric potential of the placement surface 51A of the conveyance belt 51 after passing through the charging roller 571 and the charging roller 572 is 224 [V] lower than that of the comparative example 1, It can be seen that the suction performance of the paper P by the transport belt 51 is low.

<Example 1>
Embodiment 1 is a configuration in which the charging device 57 includes the charging roller 571 and the charging roller 572 in the sheet conveying device 5, and the power supply device 573 uses the charging roller 571 and the charging roller 572 to perform the above-described operation. This is a result of charging the conveyor belt 51.
The electric resistance value of each of the charging roller 571 and the charging roller 572 is 7 [logΩ]. The charging distance L2 corresponding to the one-cycle charge pattern formed on the transport belt 51 is 10 [mm].
In the first embodiment, unlike the comparative example 2, the charging roller 571 and the position at which the separation distance L1 is 50 [mm] which is an integral multiple of 10 [mm] which is the charging distance L2 is 5 times. A charging roller 572 is disposed. In such a configuration, the charging roller 571 and the charging roller 572 apply the same polarity voltage to the same region of the placement surface 51 </ b> A of the transport belt 51. Therefore, the charge pattern formed on the transport belt 51 by the charging roller 571 is not canceled when charging by the charging roller 572.
Thereby, in the first embodiment, the potential of the placement surface 51A of the transport belt 51 after passing through the charging roller 571 and the charging roller 572 is 346 [V] higher than those of the first and second comparative examples. It can be seen that the suction performance of the paper P by the transport belt 51 is high. Therefore, according to the configuration of the first embodiment, the traveling speed of the conveyor belt 51 can be increased to 800 [mm / s].

<Example 2>
In the second embodiment, the feeding roller 571 and the charging roller 572 are transported by the power supply device 573 using the charging roller 571 and the charging roller 572 under the condition that the electric resistance values of the charging roller 571 and the charging roller 572 are different from the conditions of the first embodiment. This is a result of charging the belt 51. Specifically, the electrical resistance value of the charging roller 571 is 7 [logΩ], and the electrical resistance value of the charging roller 572 is 7.5 [logΩ]. That is, the electrical resistance value of the charging roller 572 on the downstream side in the traveling direction R2 of the transport belt 51 is higher than the electrical resistance value of the charging roller 571 on the upstream side.
In the second embodiment, the potential of the placement surface 51A of the transport belt 51 after passing through the charging roller 571 and the charging roller 572 is 346 [V] higher than those of the first and second comparative examples, and the transport. It can be seen that the adsorption performance of the paper P by the belt 51 is high. Therefore, even with the configuration of the second embodiment, the traveling speed of the conveyor belt 51 can be increased to 800 [mm / s].

<Example 3>
In the third embodiment, the feeding roller 571 and the charging roller 572 are transported by the power supply device 573 using the charging roller 571 and the charging roller 572 under the conditions in which the charging roller 571 and the charging roller 572 have different electric resistance values. This is a result of charging the belt 51. Specifically, the electrical resistance value of the charging roller 571 is 7.5 [logΩ], and the electrical resistance value of the charging roller 572 is 7 [logΩ]. That is, the electrical resistance value of the upstream charging roller 571 in the traveling direction R2 of the transport belt 51 is higher than the electrical resistance value of the downstream charging roller 572.
Also in the third embodiment, the potential of the placement surface 51A of the transport belt 51 after passing through the charging roller 571 and the charging roller 572 is 342 [V] higher than those of the first and second comparative examples, It can be seen that the suction performance of the paper P by the transport belt 51 is high. Therefore, even with the configuration of the third embodiment, the traveling speed of the conveyor belt 51 can be increased to 800 [mm / s].
Further, in the third embodiment, the electric potential of the placement surface 51A of the transport belt 51 after passing through the charging roller 571 is 220 [V], which is lower than those in the first and second embodiments, and the charging roller 571. The amount of charge of the conveyor belt 51 due to is suppressed. Thereby, in the configuration of the third embodiment, since the rapid charging of the placement surface 51A of the transport belt 51 is suppressed, the deterioration of the transport belt 51 can be suppressed and the life can be extended.
Note that the electrical resistance values of the charging roller 571 and the charging roller 572 can be changed according to the type and mixing ratio of conductive materials included in the charging roller 571 and the charging roller 572, respectively. In addition, by changing the diameters of the charging roller 571 and the charging roller 572, the electric resistance values of the charging roller 571 and the charging roller 572 can be arbitrarily changed.

1: paper feed cassette 2: paper feed unit 3: image forming units 31 to 34: recording heads 31 A to 34 A: ink ejection surface 4: ink tank units 41 A to 44 A: ink tank 5: transport unit 51: transport belt 52: drive Rollers 53 to 55: Stretching roller 56: Pressing roller 57: Charging device (an example of charging means)
58: temperature / humidity sensor 59: moving mechanism 591: frame 592: rail 593: pinion gear 594: drive motor 6: control unit 7: paper discharge unit 8: main body frame 10: inkjet recording apparatus (an example of an image forming apparatus)

Claims (12)

A conveyor belt having a placement surface on which a sheet is placed;
Charges that alternate on the mounting surface by applying a voltage of the same polarity to the same region of the mounting surface by a plurality of charging members that contact the mounting surface of the transport belt at different positions in the traveling direction of the transport belt. Charging means for forming a pattern;
A sheet conveying apparatus.   Each charging member is disposed at a position where an interval between contact positions of the charging member and the placement surface on the conveyor belt is an integral multiple of a distance on the placement surface corresponding to one cycle of the charge pattern. The sheet conveying apparatus according to claim 1.   The sheet conveying apparatus according to claim 1, wherein the charging unit includes one power supply device that applies a predetermined voltage to the plurality of charging members.   The electrical resistance value of the charging member disposed on the upstream side in the traveling direction of the transport belt is higher than the electrical resistance value of the charging member disposed on the downstream side in the traveling direction of the transport belt. The sheet conveying apparatus according to the description.   5. The apparatus according to claim 1, further comprising a charge control unit configured to change a number of the charging members that apply a voltage to the mounting surface among the plurality of charging members according to a preset charging condition. Sheet transport device. A moving mechanism for contacting and separating any one or more of the plurality of charging members from the mounting surface;
The sheet conveying apparatus according to claim 5, wherein the charging control unit changes the number of the charging members in contact with the placement surface by the moving mechanism according to the charging condition.   7. The charging condition according to claim 5, wherein the charging condition is that one or more of a type of the sheet, an environmental temperature of the sheet conveying device, and an environmental humidity of the sheet conveying device satisfy a preset condition. The sheet conveying apparatus according to the description. A sheet conveying device according to any one of claims 1 to 7,
Image forming means for forming an image on the sheet conveyed by the sheet conveying device;
An image forming apparatus comprising:   The image forming apparatus according to claim 8, wherein the image forming unit is an ink jet type recording unit having a recording head that forms an image on the sheet by ejecting ink onto the sheet conveyed by the sheet conveying apparatus. A plurality of charging members are brought into contact with the placement surface of the transport belt at different positions in the traveling direction of the transport belt having a placement surface on which the sheet is placed,
A sheet conveying method for forming a charge pattern alternating on the placement surface by applying a voltage having the same polarity to the same region of the placement surface. Same as the same area of the mounting surface by the transport belt having the mounting surface on which the sheet is mounted and a plurality of charging members that contact the mounting surface of the transport belt at different positions in the traveling direction of the transport belt A computer that controls a sheet conveying apparatus, which includes a charging unit that forms a charge pattern that alternates on the placement surface by applying a voltage of polarity,
The charge control program for performing the step which changes the number of the said charging members which apply a voltage to the mounting surface among the said several charging members according to the preset charging conditions.   A computer-readable recording medium on which the charge control program according to claim 11 is recorded.

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