JP2014186276A - Image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and a program capable of easily suppressing scattering of toner without adding a new member.SOLUTION: An image forming apparatus includes a transfer roll 24 that transfers a toner image held on a photoreceptor 10 to paper P, and a current source 26 that supplies current to the transfer roll 24. The image forming apparatus acquires information indicating the resolution of the toner image, and when the resolution indicated by the acquired information is equal to or more than a predetermined threshold, controls the current source 26 to increase a current to be supplied to the transfer roll 24 larger than that when the resolution is less than the resolution.

Description

  The present invention relates to an image forming apparatus and a program.

  Patent Document 1 discloses a transfer belt that conveys a transfer sheet fed so as to be in contact with the outer peripheral surface of an image carrier toward a fixing device, and a transfer sheet provided between the transfer belt and the fixing device. In the transfer conveyance belt device including a guide mechanism, the transfer paper guide mechanism includes a transfer outlet guide mechanism disposed on an outlet side of the transfer belt, and a fixing inlet guide mechanism disposed on an inlet side of the fixing device. And a transfer conveyance belt device in which a charge removal member is provided on the lower surface of the conveyance surface of the transfer outlet guide mechanism, and the charge removal member faces an opening formed on the conveyance surface.

  Patent Document 2 discloses an image carrier that carries a toner image, an endless transfer belt that carries a sheet and transfers the toner image on the image carrier to the carried sheet, and faces the transfer belt. A first electrode for contacting the transfer belt and applying a transfer bias to the transfer belt; a second electrode for contacting the transfer belt; a power supply for supplying the transfer bias to the first electrode; When I1 is a current value output from the power source and I2 is a current value flowing from the power source through the transfer belt to the second electrode, I1-I2 = Iout is kept constant at a predetermined target current value. Thus, there is described a transfer apparatus including transfer control means for variably controlling the current value I1 and setting means for setting the target current value according to setting conditions.

  Further, Patent Document 3 discloses a transfer transport unit that transfers a toner image on the surface of the photoconductor to the transfer paper while electrostatically attracting and transporting the photoconductor and the transfer paper. In an image forming apparatus having a plate-like electrode member provided at a position where the transfer paper is peeled off, an angle of the plate-like electrode member with respect to the transfer paper peeled off from the transfer conveying unit is set to a volume resistance value of the transfer paper or An image forming apparatus provided with angle adjusting means for adjusting based on a printed pattern to be transferred is described.

Further, Patent Document 4 discloses a transfer material on which a transfer material is conveyed to a transfer portion of an image carrier that carries a toner image, and the toner image is transferred to the transfer portion by receiving an electric field having a polarity opposite to that of the toner image. Further, in the transfer belt that is electrostatically attracted and conveyed toward the downstream side, there is described a transfer belt in which the outer surface resistance in surface contact with the transfer material is set larger than the inner surface resistance.

JP 2002-268301 A JP 07-146594 A JP 2006-267136 A Japanese Patent Laid-Open No. 08-030109

  The present invention eliminates the scattering of toner generated in a toner image on a transfer medium such as a recording medium when the resolution of the toner image is equal to or higher than a threshold without adding a new member or a new member. It is an object to provide an image forming apparatus and a program that can be easily suppressed.

  The image forming apparatus according to claim 1, a transfer unit that transfers the toner image held on the image holding member to the transfer target member by supplying current, a supply unit that supplies current to the transfer unit, An acquisition unit that acquires information indicating the resolution of the toner image, and the supply unit is controlled and supplied to the transfer unit when the resolution indicated by the information acquired by the acquisition unit is equal to or greater than a predetermined threshold. Control means for making the current value to be larger than the current value supplied to the transfer means when the resolution is lower than the resolution.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the acquisition unit further acquires information indicating the type of the transfer target, and the control unit acquires the information acquired by the acquisition unit. The control is performed when the type indicated by is a predetermined type.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus further includes a neutralizing unit that neutralizes the transferred body onto which the toner image is transferred by the transfer unit, and the control unit includes: When the resolution indicated by the information acquired by the acquisition unit is equal to or greater than the threshold value, the static elimination unit is controlled so that the amount of static elimination of the transfer target is less than when the resolution is less than the resolution.

  The image forming apparatus according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the toner image is transferred onto the transfer target by the transfer unit before the toner image is transferred to the transfer target. A charging unit configured to charge the toner image; and the control unit controls the charging unit when the resolution indicated by the information acquired by the acquiring unit is equal to or higher than the threshold, and The charge amount of the toner image is increased as compared with the case where the resolution is less than the resolution.

  A program according to a fifth aspect causes a computer to function as the acquisition unit and the control unit in the image forming apparatus according to any one of the first to fourth aspects.

  According to the first and fifth aspects of the present invention, a toner image on a transfer medium such as a recording medium is used when the resolution of the toner image is equal to or higher than a threshold without adding a new member and without applying the present invention. It is possible to easily suppress the toner scattering that occurs in the toner.

  According to the second aspect of the present invention, as compared with the case where the present invention is not applied, the scattering of toner can be effectively suppressed according to the type of the transfer target.

  According to the third and fourth aspects of the present invention, it is possible to make it difficult for the toner to be peeled off from the transfer medium as compared with the case where the present invention is not applied.

1 is a schematic side view illustrating an overall configuration of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus according to an embodiment. FIG. 6 is a front view illustrating an example of a target image formed on the paper P when toner is scattered and adhered to the paper P when the paper is peeled from the transfer belt. 6 is a graph illustrating an example of a relationship between a value of a current supplied to a transfer roll and a toner scattering grade. It is a graph which shows an example of the relationship between the value of the voltage applied to a static elimination part, and a toner scattering grade. It is a graph which shows an example of the relationship between the value of the voltage applied to a static elimination part, and the charging potential of a paper. It is a schematic side view which shows an example of the state at the time of a cardboard being neutralized by the static elimination part. It is a schematic side view which shows an example of the state at the time of a plain paper being neutralized by the static elimination part. 6 is a graph illustrating an example of a relationship between resolution and toner scattering grade. It is a schematic diagram which shows an example of the condition information which concerns on 1st Embodiment. It is a flowchart which shows the flow of a process of the image formation condition setting process program which concerns on 1st Embodiment. It is a graph which shows an example of the relationship between the resolution which concerns on 1st Embodiment, and the value of the electric current supplied to the pre-transfer charger. It is a graph which shows an example of the relationship between the resolution which concerns on 1st Embodiment, and the value of the electric current supplied to a transfer roll. It is a graph which shows an example of the relationship between the resolution which concerns on 1st Embodiment, and the value of the voltage applied to a static elimination part. It is a schematic diagram which shows an example of the condition information which concerns on 2nd Embodiment. It is a flowchart which shows the flow of a process of the image formation condition setting process program which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[First Embodiment]
First, the image forming apparatus according to the present embodiment will be described.

  As shown in FIG. 1, an image forming apparatus 100 according to this embodiment includes an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) 10 that rotates in the direction of arrow A. The photoreceptor 10 according to the present embodiment includes a base material made of, for example, cylindrical aluminum, and an organic photosensitive layer formed on the outer peripheral surface of the base material.

  A charger 11 that charges the surface of the photoconductor 10 is provided around the photoconductor 10. The charger 11 is disposed in pressure contact with the photosensitive member 10 so as to be rotatable. The charging roller 11 is driven to rotate as the photosensitive member 10 rotates, and a charging bias having a predetermined value (in this embodiment). , Negative polarity).

  A laser exposure device 12 is provided around the photoconductor 10 to form an electrostatic latent image by irradiating the surface of the photoconductor 10 charged by the charger 11 with the exposure beam Bm. The laser exposure device 12 has a laser (for example, a semiconductor laser) that emits an exposure beam Bm to the photosensitive member 10, and responds to image information input from an image processing device 29 (see FIG. 2) described later. Then, the photosensitive member 10 is irradiated with the exposure beam Bm emitted from the laser. The surface of the photoreceptor 10 is scanned and exposed by the laser exposure device 12, whereby an electrostatic latent image is formed on the photoreceptor 10.

  Further, around the photoconductor 10 is provided a developing device 13 that contains toner and develops an electrostatic latent image on the photoconductor 10 with toner to form a toner image. The developing device 13 according to the present embodiment includes a developer holding body 13a that holds a developer containing toner and a carrier. The electrostatic latent image formed on the surface of the photoreceptor 10 is developed as a toner image by the developing device 13. That is, a developing bias consisting of a DC voltage from a power source (not shown) or a developing bias in which a DC voltage is superimposed on an AC voltage is applied to the developer holding body 13a, so that a developing electric field is formed between the developer holding body 13a and the photoreceptor 10. . As a result, the toner on the developer holding member 13a is transferred to a portion corresponding to the electrostatic latent image formed on the photoreceptor 10, and the electrostatic latent image is visualized as a toner image.

  A pre-transfer charger 14 that charges the toner image formed on the photoconductor 10 is provided around the photoconductor 10. The pre-transfer charger 14 according to this embodiment is connected to a current source (not shown) that is a power source capable of adjusting the output current value. Note that charging by the pre-transfer charger 14 is performed prior to electrostatic transfer by a transfer unit 15 described later. The toner image charged by the pre-transfer charger 14 moves to the transfer portion 15 that is transferred to the paper P that is a transfer target as the photosensitive member 10 rotates.

  A transfer unit 20 that transfers the toner image formed on the photoconductor 10 to the paper P in the transfer unit 15 is provided around the photoconductor 10. The transfer unit 20 is bridged with tension by a drive roll 22 and a driven roll 23, and is disposed inside the transfer belt 21 made of an elastic body, and inside the transfer belt 21, and is photosensitive via the transfer belt 21. And a transfer roll 24 pressed against the body 10.

  The transfer roll 24 is configured, for example, by covering the outer periphery of a stainless steel conductive core material with a rubber conductive foam elastic body. In the transfer roll 24, resistance adjustment is performed by mixing a substance having ion conductivity (for example, NBR rubber (nitrile rubber)) into the conductive foamed elastic body. Here, as the transfer roll 24, it is preferable that the volume resistivity in the initial state is set in the range of 105 to 109 Ω · cm and the hardness (Asuka C hardness) is in the range of 30 ° to 50 °. preferable. The transfer roll 24 may be adjusted for resistance by mixing a substance having electron conductivity (for example, carbon black) in addition to the substance having ion conductivity.

  A current source 26 that is a power source capable of adjusting an output current value is connected to the transfer roll 24. On the other hand, the base material of the photoreceptor 10 is grounded. The current source 26 performs constant current control to supply a bias voltage having a polarity (positive polarity) opposite to the toner charging polarity (negative polarity in this embodiment) to the transfer roll 24. A current (hereinafter referred to as “transfer current”) is supplied. Then, when a transfer current is supplied from the current source 26 to the transfer roll 24, a current flows through the transfer roll 24, the transfer belt 21, and the photoconductor 10. As a result, an electric field is formed between the photoconductor 10 and the transfer belt 21, and a charge having a polarity opposite to the charge polarity of the toner on the photoconductor 10 is applied from the transfer roll 24 to the paper P.

  On the other hand, in the transfer unit 15, the sheet P conveyed in time with the movement of the toner image is sandwiched between the photoconductor 10 and the transfer roll 24 via the transfer belt 21 of the transfer unit 20. As a result, the toner image held on the photoconductor 10 is electrostatically transferred onto the paper P in the transfer unit 15 pressed by the photoconductor 10 and the transfer roll 24.

  The sheet P on which the toner image has been electrostatically transferred is peeled off from the photoreceptor 10 by being electrostatically attracted to the transfer belt 21, and is provided by the transfer belt 21 on the downstream side in the transport direction of the sheet P of the transfer unit 20. Further, it is conveyed to the vicinity of a fixing device 60 described later.

  At this time, at the end of the transfer belt 21 on the fixing device 60 side, the paper P is peeled from the transfer belt 21 due to the curvature when the transfer belt 21 is wound around the driving roll 22 and the stiffness of the paper P. Then, the paper P is guided to the fixing inlet guide 56 and conveyed to the fixing device 60.

  Further, the transfer unit 20 is provided with a cleaning blade 25 that scrapes off deposits on the surface of the transfer belt 21 after the paper P has passed the position where the drive roll 22 is disposed.

  In some cases, the paper P is not peeled off from the photoconductor 10 and remains adsorbed on the photoconductor 10. In this case, the paper P is separated from the photoconductor 10 by a separation claw (not shown) disposed in the vicinity of the surface of the photoconductor 10 on the downstream side of the transfer portion 15 in the conveyance direction of the paper P, and the transfer belt 21 is fixed to the transfer belt 21. Electroadsorbed.

  Further, the top of the sheet P side is formed into a saw blade shape when viewed from the direction of arrow D in FIG. A static elimination unit 27 composed of a body is provided. The static elimination unit 27 is sandwiched between blocks so that the top portion is not exposed, and is provided so as not to contact the paper P.

  The neutralization unit 27 is connected to a neutralization power source (not shown) that applies a voltage to the neutralization unit 27. In the present embodiment, the toner image is transferred and the potential difference between the charged paper P and the charge removal unit 27 is adjusted by adjusting the voltage (in this embodiment, negative polarity) applied from the charge removal power source to the charge removal unit 27. Thus, the charge removal amount of the paper P by the charge removal unit 27 (that is, the charge amount of the paper P) is adjusted. The neutralization unit 27 is provided to assist the separation of the paper P from the transfer belt 21.

  Further, the image forming apparatus 100 according to the present embodiment includes a fixing device 60 that fixes the toner image transferred onto the paper P to the paper P. The unfixed toner image on the paper P conveyed to the fixing device 60 is fixed on the paper P by being subjected to fixing processing by heat and pressure in the fixing device 60. The paper P on which the fixed image is formed is conveyed to a discharge unit (not shown) of the image forming apparatus 100.

  On the other hand, a pre-cleaning charger 28 for charging the surface of the photoconductor 10 is provided around the photoconductor 10 in order to remove the positive charge attached to the photoconductor 10 after the transfer of the toner image onto the paper P. ing. Further, on the downstream side of the pre-cleaning charger 28 around the photoconductor 10, a cleaning unit 17 including a cleaning blade 17 a that removes toner remaining on the photoconductor 10 is provided.

  In addition, the image forming apparatus 100 according to the present embodiment has, as a paper transport system, a paper tray 50 that stores the paper P, and a pickup roll that picks up and transports the paper P accumulated in the paper tray 50 at a predetermined timing. 51 is provided. Further, the image forming apparatus 100 includes, as a paper transport system, a transport roll 52 that transports the paper P taken out by the pickup roll 51, and a registration roll 54 that feeds the transported paper P to the transfer unit 15 at a predetermined timing. I have. Further, the image forming apparatus 100 serves as a paper conveyance system, a conveyance guide 55 that guides the paper P sent out from the registration roll 54 to the transfer unit 15, and guides the paper P to which the toner image is transferred and conveyed to the fixing device 60. The fixing entrance guide 56 described above is provided.

  The paper P taken out by the pickup roll 51 is transported in the direction of arrow C by the transport roll 52 and reaches the registration roll 54. The transport roll 52 and the registration roll 54 are temporarily stopped when the paper P reaches the position where the registration roll 54 is disposed, and are rotated again in accordance with the movement timing of the toner image formed on the photoconductor 10. . As a result, the position of the sheet P and the position of the toner image are aligned, and the sheet P is sent out from the transport guide 55 to the transfer unit 15.

  Next, an electrical configuration of the image forming apparatus 100 according to the present embodiment will be described.

  As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a control unit 30 that comprehensively controls the entire apparatus.

  The control unit 30 includes a CPU (Central Processing Unit) that executes various processes including an image forming condition setting process described later, and a RAM (Random Access Memory) that temporarily stores various information as a work area of the CPU. . In addition, the control unit 30 includes storage means such as a ROM (Read Only Memory) and a HDD (Hard Disk Drive) that store various information used for execution of processing by the CPU for a long period of time.

  A user interface 31 is electrically connected to the control unit 30. The user interface 31 includes a display unit such as a display for displaying information and an operation input unit such as an operation button for inputting information according to a user operation. The control unit 30 provides information indicating an execution instruction for image forming processing via the operation input unit, information indicating the resolution when forming an image to be imaged (hereinafter referred to as “target image”), and will be described later. Input of various information such as selected paper information to be received is accepted. The control unit 30 is connected to each unit such as the pre-transfer charger 14, the current source 26, and the charge removal unit 27, and controls the operation of each unit.

  Further, the image forming apparatus 100 according to the present embodiment includes an image processing apparatus 29 that performs various types of image processing on an image to be formed on the paper P. In the image forming apparatus 100 according to the present embodiment, the control unit 30 inputs image information output from an image reading device or a personal computer (not shown) to the image processing device 29. Then, an electrostatic image is formed on the photosensitive member 10 by the laser exposure device 12 based on the image information subjected to the image processing by the image processing device 29.

  By the way, in an image forming apparatus using toner as a color material (hereinafter referred to as “toner printer”), generally, the transfer belt 21 is wound around the driving roll 22 on the paper P on which the toner image is transferred as described above. The sheet is peeled off from the transfer belt 21 due to the curvature of the sheet and the stiffness of the sheet P. However, depending on the image forming conditions such as the value of the transfer current supplied to the transfer roll 24, the value of the voltage applied to the charge removal unit 27, and the value of the current supplied to the pre-transfer charger 14, the paper P is transferred from the transfer belt 21. When peeling off, toner may be scattered. Further, depending on the type of the paper P to be image-formed and the resolution, the toner may be scattered when the paper P is peeled from the transfer belt 21.

  When the toner is thus scattered and attached to the paper P, as shown in FIG. 3 as an example, the toner may be drawn on the paper P in the shape of a bird footprint. At this time, when the drawn image is enlarged, the above-mentioned bird footprint-like image (hereinafter referred to as “toner scattering image”) generated on the paper P due to toner scattering is hardly visible. However, when the entire image is viewed without being enlarged, the toner scattered image is easily visually recognized.

  In the graph shown in FIG. 4, the horizontal axis indicates an example of a transfer current value, and the vertical axis indicates an example of a toner scattering grade indicating the amount of toner scattering. The toner scattering grade represents the high visibility of the toner scattering image by a predetermined number of stages (in this embodiment, 10 stages). In the toner scattering grade according to the present embodiment, the state in which the toner scattering image cannot be visually confirmed is defined as grade G0, and the larger the number from grade G1 to G10, the higher the visibility of the toner scattering image. As shown in FIG. 4, in a toner printer, generally, the smaller the transfer current value, the weaker the adhesion of toner to the paper P and the higher the toner scattering grade.

  In the graph shown in FIG. 5, the horizontal axis indicates an example of the value of voltage (negative polarity) applied to the charge removal unit 27, and the vertical axis indicates an example of the toner scattering grade. FIG. 5 shows a case where the charging potential of the sheet P immediately before the charge removal by the charge removal unit 27 is −10 kV. As shown in FIG. 5, in a toner printer, generally, the toner scattering grade tends to increase as the absolute value of the potential difference between the paper P and the charge removal unit 27 increases by bringing the voltage applied to the charge removal unit 27 close to 0V. There is.

  For example, as shown in FIG. 6, this tendency is generally observed in a toner printer. As the potential difference between the paper P and the charge removal unit 27 increases, the charge removal amount of the paper P increases, that is, the charge amount decreases. This is caused by a decrease in adhesion to the paper P.

  As described above, it is known that the toner scattering grade depends on the transfer current supplied to the transfer roll 24 and the charge removal amount by the charge removal unit 27, but also depends on the type of the paper P. That is, when the paper P is peeled off from the transfer belt 21, if the paper P is caught in the transfer belt 21 and peeled off, the peeling discharge increases and the amount of toner scattering increases. Therefore, as shown in FIG. 7 as an example, compared to the case where the paper P is a thick paper that is not easily caught in the transfer belt 21, as shown in FIG. 8 as an example, plain paper in which the paper P is easily caught in the transfer belt 21. In the case of a thin paper such as the toner, the amount of toner scattering increases.

  Therefore, as described above, the larger the value of the transfer current supplied to the transfer roll 24, the smaller the toner scattering grade. In the image forming apparatus 100 according to the present embodiment, the thinner the sheet P, The value of the transfer current supplied to the transfer roll 24 is increased.

  In addition, as described above, in the image forming apparatus 100 according to the present embodiment, as the potential difference between the paper P and the charge removal unit 27 becomes smaller, the toner scattering grade becomes smaller. The potential difference between the paper P and the charge removal unit 27 is reduced.

  Further, as the current supplied to the pre-transfer charger 14 increases, that is, the amount of charge applied to the toner by the pre-transfer charger 14 increases, the adhesion between the paper P and the toner increases and the toner scattering grade decreases. Tend. In the present embodiment, since the current supplied to the pre-transfer charger 14 is negative, “current increases” means that the current increases to the negative side, for example, −100 μA becomes −300 μA. Based on this tendency, in the image forming apparatus 100 according to this embodiment, the value of the current supplied to the pre-transfer charger 14 is increased as the thickness of the paper P is thinner. At this time, the thickness of the paper P is determined in advance after fixing the value of the current supplied to the pre-transfer charger 14 in consideration of the occurrence of uneven charging due to dust collection by the pre-transfer charger 14. Charging by the pre-transfer charger 14 may be performed only when the thickness is smaller than the thickness.

  On the other hand, in the graph shown in FIG. 9, the horizontal axis indicates an example of the resolution (in this embodiment, the number of screen lines (number of lines) per inch), and the vertical axis indicates an example of the toner scattering grade. . As shown in FIG. 9, in a toner printer, generally, the higher the resolution, the higher the toner scattering grade. Note that the amount of toner scattering does not directly depend on the resolution, but the higher the resolution, the more the toner scattering grade becomes higher, which affects the visibility of the toner scattering image. Therefore, in the image forming apparatus 100 according to the present embodiment, as the resolution increases, the value of the transfer current is increased, the potential difference between the paper P and the charge eliminating unit 27 is decreased, or the pre-transfer charger 14 is supplied. The current value to be increased is increased.

  As described above, when the image forming apparatus 100 according to the present embodiment performs the image forming process, the value of the transfer current to the transfer roll 24 and the voltage applied to the charge removal unit 27 according to the resolution and the type of the paper P. And the value of the current supplied to the pre-transfer charger 14 are determined.

  For this reason, the image forming apparatus 100 according to the present embodiment stores in advance the condition information 40 used when performing the above setting in the ROM of the control unit 30. As shown in FIG. 10, the condition information 40 according to the present embodiment is a state in which sheet type information indicating the type of the selected sheet P, resolution information indicating the resolution, and change amount information indicating the change amount are associated with each other. It consists of

  Further, in the image forming apparatus 100 according to the present embodiment, as the change amount information of the condition information 40, the value of the transfer current for the transfer roll 24 is represented by a difference with respect to the reference value. Further, as the change amount information of the condition information 40, the change amount with respect to each reference value of the potential difference between the charge eliminating unit 27 and the paper P and the current value supplied to the pre-transfer charger 14 is also expressed as a difference with respect to the reference value. Has been. Each of the change amounts d1 to d3, j1 to j3, and t1 to t3 takes a positive value. When the sign is “+”, it indicates an increase amount, and when the sign is “−”. Represents the amount of decrease. When the change amount is 0 (zero), it indicates that the reference value is used as it is without being changed.

  In the condition information 40 shown in FIG. 10, the resolution is stepwise as “high (0 line or more and less than 100 lines)”, “medium (100 lines or more and less than 200 lines)”, and “low (200 lines or more and 300 lines or less)”. It represents. In the condition information 40 shown in FIG. 10, for example, when the type of the paper P is “thick paper A” and the resolution is “high”, a predetermined reference value (hereinafter, referred to as a current supplied to the transfer roll 24). The current value obtained by adding d1 [μA] to the “transfer current reference value”) is the current value supplied to the transfer roll 24. Further, in this case, the absolute value of the potential difference between the static elimination unit 27 and the paper P is obtained by subtracting j1 [kV] from a predetermined reference value of the potential difference (hereinafter referred to as “static elimination voltage reference value”). The value of the voltage applied to the static elimination unit 27 is determined so that the obtained value is obtained, and this value is set as the value of the voltage applied to the static elimination unit 27. Further, in this case, the current obtained by adding t1 [−μA] to a predetermined reference value (hereinafter referred to as “charging current reference value”) of the current supplied to the pre-transfer charger 14. The value is the value of the current supplied to the pre-transfer charger 14.

  Further, in the condition information 40 shown in FIG. 10, d1> d2> d3 is set so that the value of the current supplied to the transfer roll 24 increases as the resolution increases. In the condition information 40, −j1 <−j2 <−j3 is set such that the higher the resolution, the smaller the absolute value of the potential difference between the paper P and the charge removal unit 27. Further, in the condition information 40, t1> t2> t3 is set such that the higher the resolution, the larger the value of the current supplied to the pre-transfer charger 14.

  In the image forming apparatus 100 according to the present embodiment, the change amount information of the condition information 40 is information expressed as a difference with respect to the reference value, but is not limited thereto, and is information indicating a value after change. Also good.

  On the other hand, in the ROM of the control unit 30 according to the present embodiment, the transfer current reference value information indicating the transfer current reference value, the discharge voltage reference value information indicating the discharge voltage reference value, and the charging current reference value indicating the charging current reference value. Is stored in advance. In the image forming apparatus 100 according to the present embodiment, each reference value is a range in which a toner scattering grade is allowed when using a type of paper P (for example, plain paper A) that is frequently used (in this embodiment, It is set to a predetermined value so as to be within the grades G0 to G2).

  Further, as the type of paper P according to the present embodiment, thick paper, plain paper, glossy paper, recycled paper, special paper, colored paper, and the like are applied. This is because characteristics such as whether or not the paper P is difficult to be caught in the transfer belt 21 and whether or not toner easily adheres to the paper P depend on the thickness, surface treatment, hardness, and the like of the paper. Is taken into account.

  By the way, the image forming apparatus 100 according to the present embodiment is configured such that the paper tray 50 can be inserted and removed from the apparatus main body, and the paper P is replenished and the paper P is replaced while the paper tray 50 is pulled out from the apparatus main body. Is done.

  Here, in the image forming apparatus 100 according to the present embodiment, when the paper tray 50 is pulled out from the apparatus main body and inserted again, it is considered that there is a possibility that different types of paper P may be stored in the paper tray 50. All the paper type information is read from the condition information 40. In the image forming apparatus 100 according to the present embodiment, the read paper type information is displayed on the display unit of the user interface 31 in a state where any one of the information can be selected and specified. On the other hand, the user of the image forming apparatus 100 selects information (hereinafter referred to as “selected paper information”) indicating the type of the paper P supplemented or replaced in the paper tray 50 from the displayed paper type information. In response to this, the image forming apparatus 100 stores (registers) the selected selected sheet information in the RAM of the control unit 30. At this time, if the paper tray 50 is inserted / removed after it is detected that the paper P is out of the paper tray 50, it is simply regarded that the same type of paper is stored, and the above paper types are used. It is good also as a form which does not perform re-registration.

  Further, considering that the above characteristics also depend on the size of the paper P, if the size is different even if the type of the paper P is the same, it may be registered as a different type of paper P in the condition information 40. .

  As described above, in the image forming apparatus 100 according to the present embodiment, the user selects and designates the paper type information. However, the present invention is not limited to this, and may be input from an external device such as the personal computer described above.

  Further, the image forming apparatus 100 according to the present embodiment is equipped with a function of reading an image via the above-described image reading apparatus and forming the image on the paper P (hereinafter referred to as “copying function”). . In addition, the image forming apparatus 100 according to the present embodiment is also equipped with a function of inputting image information indicating an image targeted for image formation from the external apparatus and forming an image indicated by the input image information on the paper P. Has been.

  Next, the operation of the image forming apparatus 100 according to the present embodiment when executing the image forming process will be described with reference to FIG. FIG. 11 is a flowchart showing the flow of the image forming process program executed by the control unit 30 of the image forming apparatus 100 at this time, and the program is stored in advance in the ROM of the control unit 30. Here, a case where an image is formed by the copying function will be described.

  When executing the copying function, the user places a sheet to be copied on the image reading unit of the image reading apparatus, designates the resolution via the operation input unit of the user interface 31, and is provided in the apparatus main body. The user presses a copy button (not shown). In response to this, the image forming apparatus 100 stores information indicating the designated resolution in the RAM of the control unit 30, and then starts executing the image forming processing program shown in FIG.

  First, in step S101, the information indicating the resolution is read from the RAM of the control unit 30 to acquire the information.

  In the next step S103, the selected sheet information is read from the RAM of the control unit 30 to acquire the information.

  In the next step S105, the condition information 40 is read from the ROM of the control unit 30, and in the next step S107, the transfer current reference value information, the neutralization voltage reference value information, and the charging current reference value information are read from the control unit 30. Read from ROM.

  In the next step S109, based on the condition information 40 and the reference value information obtained by the above processing, the value of the current supplied to the pre-transfer charger 14, the value of the transfer current supplied to the transfer roll 24, and the static eliminator The value of the voltage applied to 27 is derived.

  At this time, the control unit 30 adds the amount of change in the value of the current supplied to the pre-transfer charger 14 in the condition information 40 to the charging current reference value, whereby the value of the current supplied to the pre-transfer charger 14 is obtained. Is derived.

  The control unit 30 derives the value of the current supplied to the transfer roll 24 by adding the amount of change in the value of the current supplied to the transfer roll 24 in the condition information 40 to the transfer current reference value.

  Further, the control unit 30 derives the value of the voltage to be applied to the static elimination unit 27 based on the potential difference obtained by adding the change amount of the potential difference in the condition information 40 to the reference value of the static elimination potential difference and the charging potential of the paper P. To do.

  As described above, in the image forming apparatus 100 according to the present embodiment, the control unit 30 determines the value of the current supplied to the pre-transfer charger 14 based on the condition information 40, but the determination method is not limited to this. For example, as shown in FIG. 12, as the resolution increases, the value of the current supplied to the pre-transfer charger 14 increases, and a calculation formula representing the relationship between the resolution and the current value is used. The value may be determined. In this case, information indicating the calculation formula is stored in advance in the ROM of the control unit 30. Further, when the resolution is equal to or higher than a predetermined threshold, the value of the current supplied to the pre-transfer charger 14 may be a predetermined fixed value that is larger than the charging current reference value. In this case, information indicating the fixed value is stored in advance in the ROM of the control unit 30.

  In the image forming apparatus 100 according to the present embodiment, the control unit 30 determines the value of the current supplied to the pre-transfer charger 14 based on the condition information 40, but the determination method is not limited to this. For example, as shown in FIG. 13, the value of the current may be determined using a calculation formula representing the relationship between the resolution and the transfer current value at which the transfer current value increases as the resolution increases. . In this case, information indicating the calculation formula is stored in advance in the ROM of the control unit 30. Further, when the resolution is equal to or higher than a predetermined threshold, the value of the transfer current supplied to the transfer roll 24 may be a predetermined fixed value that is larger than the transfer current reference value. In this case, information indicating the fixed value is stored in advance in the ROM of the control unit 30.

  Furthermore, in the image forming apparatus 100 according to the present embodiment, the control unit 30 determines the value of the voltage to be applied to the charge removal unit 27 based on the condition information 40, but the determination method is not limited to this. For example, as shown in FIG. 14, as the resolution increases, the voltage difference is calculated using a calculation formula that represents the relationship between the resolution and the voltage value so that the potential difference between the paper P and the charge removal unit 27 increases. The value may be determined. In this case, information indicating the calculation formula is stored in advance in the ROM of the control unit 30. Further, when the resolution is equal to or higher than a predetermined threshold value, the voltage value applied to the static elimination unit 27 is a voltage value at which the potential difference between the paper P and the static elimination unit 27 is smaller than the static elimination voltage reference value. It is good also as a fixed value defined beforehand.

  In the next step S111, the pre-transfer charger 14, the transfer roll 24, and the charge removal unit corresponding to the pre-transfer charger 14, the transfer roll 24, and the charge removal unit 27 using the values derived by the above processing. The control of the unit 27 is started.

  In the next step S113, an image forming process for forming the image on the paper P is performed after reading the image of the paper placed on the image reading unit of the image reading device. Note that the image forming process executed here is the same as a commonly performed process, and thus detailed description thereof is omitted here.

  In the next step S115, the control of each part of the pre-transfer charger 14, the transfer roll 24, and the charge removal unit 27 started in step S111 is stopped, and then the image forming processing program is ended.

  By executing the image forming processing program described above, the image forming apparatus 100 according to the present embodiment performs the image forming process based on the image forming conditions corresponding to the resolution and the type of the paper P, so that the amount of scattered toner is suppressed. As a result, the visibility of the toner scattered image is reduced.

  The image forming apparatus 100 according to the present embodiment employs a transfer method (so-called direct transfer method) in which an image is directly transferred from the transfer roll 24 to the paper P, but the transfer method is not limited to this. For example, the present invention is also applied to a transfer method (a so-called intermediate transfer method) in which a plurality of toner images are transferred onto a transfer belt in a superimposed manner, and then the toner image transferred to the transfer belt is transferred to a sheet P.

  In recent years, toner printers generally use toners that are less soluble than conventional ones. It has also been found that the higher the toner sphericity, the more easily the toner scatters. In consideration of these, the change amounts, the reference values, and the like may be changed according to the type of toner. For example, when using a toner that hardly melts or a toner with high sphericity, the transfer current reference value may be increased, the charging current reference value may be increased, or the charge removal voltage reference value may be decreased. In addition, the processing of steps S101 to S111 and S115 of the first embodiment and the second embodiment may be performed only when a toner that hardly dissolves or a toner having a high sphericity is used.

  Further, if the value of the transfer current applied to the transfer roll 24 is large and the transfer roll 24 is positively charged, the toner attached to the photoreceptor 10 or the paper P will adhere to the transfer roll 24 ( So-called electrostatic offset). Therefore, in order to prevent the toner from adhering to the transfer roll 24, it is desirable to increase the voltage applied to the charger 11 and the pre-cleaning charger 28 as the transfer current is increased.

Further, it has been found that when the target image has gradation, the amount of toner scattering described above increases. That is, when the target image is an image showing a photograph, the amount of toner scattering is greater than when the target image is an image showing a character or a graph. Therefore, the image forming conditions may be changed according to the type of target image. For example, whether or not the target image has gradation is determined from the image information of the target image, and the condition information 40 is used only when the target image is an image having gradation (for example, an image on which a photograph is drawn). An image forming process may be performed. At this time, for example, information indicating whether or not the target image is an image having a gradation is added to the image information of the target image, and an image having the gradation of the target image is determined from the added information. May be. In this case, when the target image is an image having no gradation (for example, an image in which characters or graphs are drawn), the image forming process is performed using the above reference values as they are without using the condition information 40.
[Second Embodiment]
Since the image forming apparatus 100 according to the second embodiment has the same configuration as the image forming apparatus 100 according to the first embodiment, description of each configuration is omitted.

  The image forming apparatus 100 according to the first embodiment performs the setting based on the resolution and the type of the paper P, while the image forming apparatus 100 according to the second embodiment performs the setting based only on the resolution. Set up.

  In the image forming apparatus 100 according to the present embodiment, the condition information 40 </ b> A used when performing the above setting is stored in advance in the ROM of the control unit 30. As shown in FIG. 15, the condition information 40A according to the present embodiment is configured in a state in which the information indicating the resolution and the information indicating the setting value are associated with each other. The set values in the condition information 40A according to the present embodiment include values of a transfer current supplied to the transfer roll 24, an absolute value of a potential difference between the charge removal unit 27 and the paper P, and a current supplied to the pre-transfer charger 14. It is represented by each of the values. In the condition information 40A shown in FIG. 15, it is assumed that d4> d5> d6, j4 <j5 <j6, t4> t5> t6.

  Next, the operation of the image forming apparatus 100 when performing the image forming condition setting process will be described with reference to FIG. Note that FIG. 16 illustrates the processing of the image forming condition setting processing program executed by the control unit 30 prior to the image forming processing when the input of information indicating the execution instruction of the image forming processing is received via the user interface 31. It is a flowchart which shows the flow. The program is stored in advance in the ROM of the control unit 30.

  First, after performing the process of step S101, without performing the process of step S103, the process proceeds to step S105, and after performing the process of step S105, the process proceeds to step S108.

  In step S108, set values for the pre-transfer charger 14, the transfer roll 24, and the static eliminator 27 are derived based on the condition information 40, and the process proceeds to step S111. In the image forming apparatus 100 according to the present embodiment, for the pre-transfer charger 14 and the transfer roll 24, the set values indicated by the set value information of the condition information 40A are set as the set values. For the charge removal unit 27, a set value for the charge removal unit 27 is derived based on the set value indicated by the set value information of the condition information 40 </ b> A and the charging potential of the paper P.

  As described above, according to the resolution, the image forming apparatus 100 according to the present embodiment has a transfer current value for the transfer roll 24, a voltage value applied to the charge removal unit 27, and a current supplied to the pre-transfer charger 14. Control the value. As a result, in the image forming apparatus 100 according to the present embodiment, the amount of toner scattering is suppressed as a result of performing the image forming process based on the image forming condition corresponding to the resolution.

  In the image forming apparatus 100 according to the present embodiment, the above setting is performed based on the condition information 40A, but the setting method is not limited to this. For example, based on the information indicating the amount of change of each type of paper P in the condition information 40 according to the first embodiment, an average value of the amount of change is derived for each resolution, and each unit is set using the derived amount of change. You may control. Further, for example, based on the information indicating the change amount of the type of paper P (for example, plain paper) having the highest use frequency in the condition information 40 according to the first embodiment, the average value of the change amount is set for each resolution. It may be derived and each part may be controlled using the derived average value.

10 Photoconductor (image carrier)
DESCRIPTION OF SYMBOLS 11 Charger 12 Laser exposure device 13 Developer 14 Charger before transfer (charging means)
15 Transfer section 24 Transfer roll (transfer means)
26 Current source (supply means)
27 Static elimination part (static elimination means)
28 Pre-cleaning charger 30 Control unit (acquisition means, control means)
100 Image forming apparatus P Paper

Claims (5)

A transfer means for transferring the toner image held on the image holding member to the transfer target by supplying an electric current;
Supply means for supplying current to the transfer means;
Obtaining means for obtaining information indicating the resolution of the toner image;
When the resolution indicated by the information acquired by the acquisition unit is greater than or equal to a predetermined threshold value, the supply unit is controlled to determine the current value supplied to the transfer unit when the resolution is less than the threshold value. Control means for making it larger than the current value supplied to the transfer means;
An image forming apparatus. The acquisition unit further acquires information indicating the type of the transfer object,
The image forming apparatus according to claim 1, wherein the control unit performs the control when a type indicated by the information acquired by the acquisition unit is a predetermined type. The image forming apparatus further includes a charge removing unit that removes charge from the transfer body onto which the toner image is transferred by the transfer unit.
The control means controls the static elimination means when the resolution indicated by the information acquired by the acquisition means is equal to or greater than the threshold, and the static elimination amount of the transfer object is less than the resolution. The image forming apparatus according to claim 1, wherein the image forming apparatus is less than the case. Charging means for charging the toner image on the image holding body before the toner image is transferred to the transfer target by the transfer means;
The control unit controls the charging unit when the resolution indicated by the information acquired by the acquiring unit is equal to or greater than the threshold value, and determines the charge amount of the toner image on the image holding member, The image forming apparatus according to any one of claims 1 to 3, wherein the image forming apparatus is set to be larger than a case where the resolution is less than the resolution.   A program for causing a computer to function as the acquisition unit and the control unit in the image forming apparatus according to any one of claims 1 to 4.