JP2007065293A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of obtaining a high quality image without being affected by an environmental change and variations in the electric resistance value of an intermediate transfer member. <P>SOLUTION: On the basis of the application voltage VT1 of a primary transfer roller 5 performing constant current control, the image forming apparatus 100 controls the grid voltage Vg of a charging device 2. Specifically, a correction expression for obtaining the grid voltage Vg suitable for the electric resistance value of an intermediate transfer belt 7 and matching an environmental change is stored in a data storage section 17. When an image stabilization process is performed, the application voltage VT1 is obtained, and a correction quantity ΔVg for the grid voltage Vg of the charging device 2 is determined on the basis of the application voltage VT1 and the correction expression. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus. More specifically, the present invention relates to an image forming apparatus that primarily transfers a toner image to an intermediate transfer member and then secondarily transfers to a recording medium, and suppresses image defects such as fogging.

  An image forming procedure in a general electrophotographic image forming apparatus will be described with reference to FIG. First, the surface of the photoreceptor is uniformly charged to the surface potential Vo by a charging device to which a negative bias is applied (a). Next, the exposure device irradiates the photosensitive member with laser light, and the surface potential at the irradiation position (exposure position) changes to Vi (b).

  Next, the negative toner carried on the roller of the developing device is transferred onto the photoconductor by the developing device to which the negative bias Vb is applied (c). Here, a bias satisfying | Vb | <| Vo | is applied to the developing device. During development, toner is transferred in a region satisfying | Vb |> | Vi |, that is, in an exposure position. On the other hand, at the non-exposure position, | Vb | <| Vo | is satisfied and the potential difference between | Vo | and | Vb | is kept at 100 V or more. Therefore, the toner is not transferred.

  Next, the back surface of the intermediate transfer member is charged to the positive polarity by the primary transfer device to which the positive bias VT1 is applied. Then, the negative toner image conveyed on the surface of the photosensitive member is transferred onto the intermediate transfer member (d). Thereafter, the toner image on the intermediate transfer member is transferred onto a recording medium by a secondary transfer device and output.

  Conventionally, in such an image forming apparatus, in order to improve the image quality, image forming conditions (application bias to the charging device, exposure light amount of the exposure device, development bias to the development device, application bias to the intermediate transfer member) And the like are appropriately controlled. For example, Patent Document 1 proposes an image forming apparatus that detects a surface potential of a photosensitive member by a potential sensor and applies an appropriate voltage to a charging device according to the surface potential.

  In an electrophotographic image forming apparatus, the amount of toner adhered per unit area on the photosensitive member or intermediate transfer member affects the image density and gradation. For this reason, a test pattern image is created on the image carrier, and the image forming conditions are feedback-controlled so that the toner adhesion amount in each density area in the test pattern image is constant (hereinafter, this control is performed). "AIDC control").

  In AIDC control, image forming conditions such as Vo, Vb, VT1, and exposure amount are automatically changed based on the detection value of the density sensor. For example, the toner adhesion amount increases as | Vb−Vi | increases. That is, the image density can be adjusted by adjusting the potential difference (hereinafter referred to as ΔV (= | Vb−Vo |)) between | Vb | and | Vi |.

  Further, in an image forming apparatus that performs AIDC control, it is necessary to transfer a test pattern image formed on a photosensitive member to an intermediate transfer member at an appropriate density. Therefore, the primary transfer bias VT1 is controlled. Further, in such an image forming apparatus, constant current control of the primary transfer roller is performed, and the charge injection amount when contacting the photoconductor is kept constant.

In addition, in an electrophotographic image forming apparatus, if ΔV is not equal to or greater than a predetermined value, a so-called fog occurs in which toner adheres to a white background portion. Therefore, by changing Vo and Vb while keeping ΔV constant, both suppression of fogging and adjustment of image density are achieved.
Japanese Patent No. 2641050

  However, the conventional image forming apparatus described above has the following problems. That is, the surface potential Vo of the photosensitive member changes due to a change in environment and a difference in electric resistance value of the intermediate transfer member. In other words, the smaller the electrical resistance value, the lower the surface potential Vo of the photosensitive member due to the influence of discharge when the intermediate transfer member charged positively contacts the negatively charged photosensitive member. There is. Therefore, ΔV becomes small and fogging occurs.

  Further, as in the image forming apparatus disclosed in Patent Document 1, the surface potential of the photosensitive member is detected by a potential sensor, and the voltage applied to the charging device is adjusted based on the detected information, thereby stabilizing the image. It is possible. However, the number of parts increases.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus capable of obtaining a high-quality image without being affected by a change in environment or a difference in electric resistance value of an intermediate transfer member.

  An image forming apparatus for solving this problem includes an image carrier that carries a toner image, a charging unit that charges the surface of the image carrier, and an intermediate transfer member that receives the transfer of the toner image on the image carrier. And an intermediate transfer portion that transfers the toner image on the image carrier onto the intermediate transfer member, and a voltage control portion that controls the voltage applied to the charging portion, and constant current control is performed in the intermediate transfer portion In the image forming apparatus, the voltage control unit acquires an applied voltage value to the intermediate transfer unit, and determines a voltage value to be applied to the charging unit based on the applied voltage value.

  The voltage control unit has correction value information for determining a correction amount of the applied voltage value to the charging unit corresponding to the applied voltage value to the intermediate transfer unit, for example, and is obtained from the applied voltage value to the intermediate transfer unit. The applied voltage value to the charging unit is determined based on the correction amount. The voltage control unit defines a range in which the voltage value of the intermediate transfer unit can take, for example, using at least one of temperature and humidity as a parameter, and acquires correction value information about the range. The correction value information includes, for example, a correction formula using a voltage value applied to the intermediate transfer unit as a variable, and a database storing the correction amount for each voltage value applied to the intermediate transfer unit.

  The image forming apparatus of the present invention has an intermediate transfer unit that transfers a toner image on an image carrier to an intermediate transfer member, and constant current control is performed in the intermediate transfer unit. In addition, a voltage control unit that controls an applied voltage value (voltage value Vc) to the charging unit is obtained, and the voltage control unit acquires an applied voltage value (voltage value VT1) to the intermediate transfer unit, and the voltage value The voltage value Vc is determined based on VT1.

  Specifically, in the image forming apparatus of the present invention, the surface potential (surface potential Vo) of the image carrier is estimated from the voltage value VT1 applied to the intermediate transfer portion. That is, the relationship between the voltage value VT1 and the surface potential Vo after transfer can be obtained in advance by experiments or the like. Note that the relationship between the voltage value VT1 and the surface potential Vo differs depending on the electric resistance value of the intermediate transfer member. Therefore, the relationship between the voltage value VT1 and the surface potential Vo when an intermediate transfer member having an electrical resistance value equivalent to that of the intermediate transfer member actually mounted is obtained. Based on the relationship, the surface potential Vo can be estimated from the voltage value VT1. Furthermore, by obtaining the surface potential Vo, the correction amount of the voltage value Vc applied to the charging unit can be defined. Therefore, since the voltage control unit has information (correction value information) regarding the correction amount, the correction amount of the applied voltage to the charging unit can be obtained from the applied voltage value VT1 of the intermediate transfer unit.

  Further, the relationship between the applied voltage value VT1 of the intermediate transfer portion and the surface potential Vo of the image carrier also changes due to changes in the environment such as temperature and humidity. Therefore, the amount of displacement due to temperature and humidity is also obtained in advance by experiments. That is, the voltage control unit has correction value information in which a correction amount is defined for each temperature and humidity state, so that voltage control corresponding to environmental changes can be performed. Further, a range that the voltage value VT1 can take depending on temperature and humidity is obtained by experiments or the like. Therefore, by storing the correction value information about the possible range, the environment is estimated from the voltage value VT1, and the surface potential Vo corresponding to the environment can be accurately determined without using a temperature / humidity sensor or the like. Can be guessed.

  The voltage control unit reflects the acquired correction amount when determining the voltage value Vc of the charging unit. As a result, the voltage value Vc for setting the image carrier to the desired surface potential Vo is determined, and the potential difference ΔV with respect to the developing bias can be set to a desired value. Thereby, the fog is suppressed and a high-quality image is obtained.

  In the image forming apparatus of the present invention, since the surface potential Vo is predicted from the applied voltage value VT1, a sensor for directly measuring the surface potential of the image carrier is not provided. Therefore, there is no increase in the number of parts.

  Further, it is better that the voltage control unit of the image forming apparatus of the present invention acquires a voltage value applied to the intermediate transfer unit when the AIDC control is being performed. That is, it is not always necessary to determine the correction amount of the voltage value Vc applied to the charging unit. For this reason, the applied voltage value VT1 of the intermediate transfer portion is acquired when the test pattern image is formed in the AIDC control, and the applied voltage value Vc of the charging portion is adjusted with the voltage value VT1. This reduces the load on the voltage control unit during image formation and simplifies the control.

  According to the present invention, the surface potential of the image carrier can be maintained at a desired value without being affected by a change in environment or a difference in electrical resistance value of the intermediate transfer member. Therefore, an image forming apparatus that suppresses the generation of fog and obtains a high-quality image is realized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. This embodiment has an intermediate transfer belt, and the present invention is applied to an image forming apparatus that performs image stabilization processing by AIDC control.

  As shown in FIG. 1, the image forming apparatus 100 of this embodiment includes a photosensitive drum 1 that carries a toner image and an intermediate transfer belt 7. The photosensitive drum 1 is an OPC photosensitive member having a negatively charged polarity and rotates at a constant speed in the direction of arrow A in FIG. Further, around the photosensitive drum 1, a charging device 2, a developing device 4, a primary transfer roller 5, and a cleaning member 6 are sequentially arranged along the rotation direction. An electrostatic latent image is formed between the charging device 2 and the developing device 4 by the laser light from the exposure device 3.

  The endless intermediate transfer belt 7 is wound around a roller group including a rotatable primary transfer roller 5 and a driving roller. The intermediate transfer belt 7 is driven in the direction of arrow B in FIG. The primary transfer roller 5 is provided at a position (primary transfer position) facing the photoreceptor 1 with the intermediate transfer belt 7 interposed therebetween. The primary transfer roller 5 is subjected to constant current control.

  Further, the image forming apparatus 100 of the present embodiment includes a main charging voltage generation unit 10 that applies a voltage to the discharge electrode 12 of the charging device 2, a grid voltage generation unit 11 that applies a voltage to the grid electrode 13 of the charging device 2, and A primary transfer voltage generating unit 14 for applying a voltage to the primary transfer roller 5, a developing bias generating unit 15 for applying a voltage to the developing roller, and a controller 9 for controlling these units are provided. The image forming apparatus 100 also includes a density sensor 8 that detects the density of the toner image transferred onto the intermediate transfer belt 7 and a temperature / humidity sensor 16 that detects the temperature and humidity in the image forming apparatus 100. The signals from the sensors are input to the control unit 9. Further, the image forming apparatus 100 includes a data storage unit 17 that stores various types of data, and the control unit 9 can access the data storage unit 17. In addition, the image forming apparatus 100 includes a secondary transfer roller, a cleaning blade for an intermediate transfer belt, and the like.

  The charging device 2 is a non-contact charging device including a corona discharge electrode 12 and a grid electrode 13, and constant current control is performed so that a current of −500 μA flows through the discharge electrode 12. Further, by applying a charging voltage of −4.0 kV to −4.5 kV to the discharge electrode 12 and a grid voltage of −450 V to the grid electrode 13, the surface of the rotating photosensitive drum 1 is applied to about −450 V, respectively. Are uniformly charged.

  The relationship between the grid voltage Vg and the surface potential Vo of the photosensitive drum 1 is Vg = Vo. In practice, Vg = Vo is not always satisfied due to the influence of dark current and the shape of the shield case surrounding the discharge electrode 12, but Vg≈Vo.

  In this embodiment, a rectangular wave voltage obtained by switching a DC voltage is applied to the discharge electrode 12 of the charging device 2. In this embodiment, a rectangular wave voltage is supplied to the charging device 2, but the waveform of the applied bias is not limited to this. That is, the applied bias may have any waveform as long as the surface potential of the photosensitive drum 1 can be set to a predetermined value. For example, it may be a DC voltage or an AC voltage, or may be an oscillating voltage obtained by superimposing the AC voltage on the DC voltage. Also, a pulse voltage or other waveform voltage may be used.

  The developing device 4 applies toner to the latent image. The developing device 4 may be a contact type or a non-contact type. Further, the developing method may be a two-component developing method including toner and a carrier, or a one-component developing method not including a carrier. An oscillating voltage obtained by superimposing a rectangular wave on a −320 V DC voltage is applied to the developing roller of the developing device 4. In this embodiment, negatively charged toner is used, but positively charged toner may be used as long as the toner image can be developed.

  In the image forming apparatus 100 configured as described above, first, the surface of the photosensitive drum 1 is charged to a predetermined potential by the negative polarity bias to the charging device 2. Next, the exposure device 3 emits a laser beam corresponding to a signal input from a host device such as a personal computer to the exposure unit on the photosensitive drum 1, and the surface of the photosensitive drum 1 is scanned and exposed to perform photosensitive exposure. An electrostatic latent image is formed on the body drum 1.

  Next, development with negative polarity toner is performed by the developing device 4 to form a toner image on the photosensitive drum 1. Next, a bias having a polarity opposite to that of the toner (800 V to 1000 V in this embodiment) is applied from the back surface of the transfer material by the primary transfer roller 5, and the visualized toner image is transferred onto the intermediate transfer belt 7. The The toner that has not been transferred to the intermediate transfer belt 7 remains on the photosensitive drum 1 and reaches the cleaning device 6. The cleaning device 6 is located between the transfer device 5 and the charging device 2, is disposed in contact with the photosensitive drum 1, and collects toner remaining on the photosensitive drum 1.

  Next, the toner image on the intermediate transfer belt 7 is conveyed to the secondary transfer position, and transferred to the recording paper that is also conveyed to the secondary transfer position. That is, a secondary transfer voltage (1.5 kV to 3.0 kV in this embodiment) having a polarity opposite to that of the toner image is applied from the back surface of the recording paper, and the visualized toner image is transferred to the recording paper. Thereafter, the recording paper on which the toner image is transferred is conveyed to a fixing device, and the toner image is fixed to the recording paper by heat and pressure when passing through the fixing device. Then, the paper is discharged out of the image forming apparatus 100.

  Next, processing performed by the control unit 9 will be described. In this process, the surface potential Vo of the photosensitive drum 1 is set to a desired value, that is, the bias to the charging device 2 is adjusted to suppress fogging. Specifically, control of the bias applied to the charging device 2, here, the grid voltage Vg applied to the grid electrode 13 will be described.

2 and 3 show the relationship between the primary transfer voltage VT1 and the photoreceptor surface potential Vo. These graphs show the surface potential Vo of the photosensitive drum 1 when the primary transfer voltage VT1 of the primary transfer roller 5 is changed, in an L / L environment (temperature: 10 ° C., relative humidity: 15%), N The results are shown in the / N environment (temperature: 23 ° C., relative humidity: 65%) and H / H environment (temperature: 30 ° C., relative humidity: 85%). 2 shows measured values when an intermediate transfer belt 7 having a high electric resistance (volume resistivity: 1.0 × 10 ¹¹ Ωcm) is used, and FIG. 3 shows a low electric resistance (volume resistivity). : 1.0 × 10 ⁹ Ωcm) is shown for each measured value.

  As shown in FIG. 2, when an intermediate transfer belt having high electrical resistance is used, Vo is within the range of -460V to -470V if VT1 is in the range of 800V to 1200V in any environment. Become. That is, if the intermediate transfer belt has a high electrical resistance, there is almost no influence of discharge with the photosensitive drum 1, and the surface potential Vo of the photosensitive drum 1 is stabilized.

  On the other hand, as shown in FIG. 3, when an intermediate transfer belt having a low electrical resistance is used, Vo is stabilized in an L / L environment. However, in the N / N environment and the H / H environment, the surface potential Vo of the photosensitive drum 1 varies greatly when VT1 is in the range of 800V to 1200V. That is, | Vo | decreases due to the influence of discharge with the photosensitive drum 1. In particular, in the H / H environment, it can be seen that the surface potential | Vo | of the photosensitive drum 1 decreases from −370 V to −470 V, which is nearly 100 V.

  In the control unit 9 of the present embodiment, when the intermediate transfer belt 7 having a low electric resistance as shown in FIG. 3 is used, the Vo characteristic is made to be the same as that when using a high electric resistance. The grid voltage Vg is controlled as follows.

  In the image forming apparatus 100 in which the primary transfer roller 5 performs constant current control, the range that the applied voltage VT1 of the primary transfer roller 5 can take is known for each environment through experiments and the like. For example, in the H / H environment, VT1 does not exceed 1000V. Specifically, the range of VT1 that can be taken in the H / H environment is a range of 800V to 950V (broken line frame H in FIG. 3). Similarly, the range of VT1 that can be taken in the N / N environment is the range of 850V to 1000V (broken line N in FIG. 3), and the range of VT1 that can be taken in the L / L environment is the range of 900V to 1100V ( A broken line frame L) in FIG.

  FIG. 4 is an enlarged view of the broken line frame portion in FIG. 3, and the range of VT1 that can be taken in each environment is indicated by the broken line frame. Further, in FIG. 4, VT1 in each environment and Vo at that time are plotted, and the regression line is indicated by a bold line. This regression line indicates the actual predicted surface potential of the photosensitive drum 1 when the intermediate transfer belt 7 having a low electrical resistance is used. Based on this regression line, the grid voltage Vg is corrected so that the Vo characteristic is the same as when using an intermediate transfer belt having a high electrical resistance.

In this embodiment, a correction formula for calculating the correction amount ΔVg of the grid voltage can be obtained based on the regression line shown in FIG. The correction amount ΔVg (V) of the grid voltage Vg in this embodiment is represented by the following correction formula (1).
ΔVg = −0.3 × VT1 + 315 (1)
FIG. 5 is a graph of Equation (1). Such a relational expression of VT1-Vo (Vg correction expression) is stored in the data storage unit 17.

  Then, the correction amount ΔVg obtained by the correction equation (1) is added to the grid voltage Vg. As a result, Vo (≈Vg + ΔVg) is shifted from −470 V to −480 V in any environment. Therefore, the potential difference ΔV = | Vb−Vo |, which is the target of the image stabilization process, can be obtained.

  That is, the control unit 9 has correction value information (in this embodiment, correction equation (1)) corresponding to the electrical resistance value of the intermediate transfer belt 7. Based on the correction value information, the grid voltage Vg is adjusted according to the value of the primary transfer voltage VT1.

  The flowchart of FIG. 6 shows the control procedure of the grid voltage Vg in the image forming apparatus 100 of this embodiment. First, correction value information of the grid voltage Vg of the charging device 2 is acquired from the data storage unit 17 during an initial operation such as immediately after power-on (S1).

  Next, an image stabilization process (AIDC control in this embodiment) is performed, and an applied voltage value VT1 (1) to the primary transfer roller 5 is acquired (S2). Next, the acquired voltage value VT (1) is substituted into the correction equation (1) described above, and the correction amount ΔVg of the grid voltage Vg of the charging device 2 is determined (S3). Then, image stabilization processing is performed again based on the corrected grid voltage Vg, and the applied voltage value VT1 (2) to the primary transfer roller 5 is acquired again (S4).

  Next, the voltage value VT1 (1) before the grid voltage Vg is corrected is compared with the voltage value VT1 (2) after the correction, and it is determined whether or not the difference is smaller than the threshold ε (S5). ). When the difference is not smaller than ε (S5: NO), the corrected voltage value VT1 (2) is set to the voltage value VT1 (1) (S6), and the grid voltage Vg is corrected again based on the voltage value. The amount ΔVg is determined (S3). Thereafter, the processes from S3 to S6 are repeated until the difference between the voltage value VT1 (1) and the voltage value VT1 (2) becomes smaller than ε. When the difference between the voltage value VT1 (1) and the voltage value VT1 (2) is smaller than ε (S5: YES), the correction amount ΔVg at that time is determined as the optimum correction amount, and the correction amount Δ A grid voltage Vg is determined based on Vg. Thereby, the surface potential Vo of the photosensitive drum 1 can be set to a desired value.

  As described above in detail, the image forming apparatus 100 according to the present embodiment controls the grid voltage Vg of the charging device 2 based on the voltage VT1 applied to the primary transfer roller 5 performing constant current control. . Specifically, a correction formula for the grid voltage Vg suitable for the electrical resistance value of the intermediate transfer belt 7 is stored in the data storage unit 17. When the grid voltage Vg of the charging device 2 is determined, the correction amount ΔVg of the grid voltage Vg is obtained from the voltage value VT1 applied to the primary transfer roller 5 using the correction formula. By reflecting this correction amount ΔVg on the grid voltage Vg, the surface potential Vo of the photosensitive drum 1 can be set to a desired value, and the potential difference ΔV with respect to the developing bias can be set to a desired value. Therefore, an image forming apparatus is realized in which fog is suppressed and a high-quality image can be obtained.

  In addition, this correction formula defines the range that the voltage value VT1 can take for each environment, and is obtained from the data in each range. Therefore, the surface potential Vo of the photosensitive drum 1 can be controlled in consideration of environmental changes such as temperature and humidity without obtaining a signal from the temperature / humidity sensor 16. Therefore, the control is simple, and the surface potential of the image carrier can be maintained at a desired value without being affected by a change in the environment or a difference in the electric resistance value of the intermediate transfer member.

  Further, in the image forming apparatus 100 of this embodiment, no potential sensor that directly measures the surface potential of the photosensitive drum 1 is provided. Therefore, the increase in cost is suppressed without increasing the number of parts.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, in the present embodiment, the grid voltage Vg (that is, the surface potential Vo of the photosensitive drum 1) is controlled based on the primary transfer voltage VT1 during AIDC control. However, the present invention is not limited to this. For example, the surface potential Vo of the photosensitive drum 1 may be controlled based on the applied voltage value of the primary transfer roller 5 that is subjected to constant current control during normal image forming processing.

  In the present embodiment, the application range of the primary transfer voltage VT1 is extracted for each environment, and the correction value information of Vg obtained by the range is stored. However, the present invention is not limited to this. For example, Vg correction value information may be stored for each environment (for example, L / L environment, N / N environment, H / H environment). That is, the correction value of Vg may be determined based on the primary transfer voltage VT1 and environmental information. In this case, environmental information is acquired from the temperature / humidity sensor 16 as needed, and appropriate correction value information is acquired based on the environmental information.

  In this embodiment, the electrical resistance value of the intermediate transfer belt 7 is recognized in advance and correction value information suitable for the electrical resistance value is stored. However, the present invention is not limited to this. For example, Vg correction value information may be stored for each electrical resistance value. That is, the correction amount ΔVg may be determined by the primary transfer voltage VT1 and the electric resistance value.

  Further, the image carrier is not limited to the photosensitive drum, and may be, for example, an intermediate transfer member (belt, drum, roller, etc.) or a paper transport member (belt, etc.). The image forming apparatus of the present embodiment may be an electrophotographic system such as a copying machine, a printer, a FAX, or a complex machine of these.

  In this embodiment, a non-contact charging type charging device is used, but a contact charging type may also be used. Further, although a roller-shaped photosensitive drum is used as the image carrier, a belt-shaped photosensitive belt may be used. The exposure apparatus may be a laser or LED. The transfer device may use a transfer charger in addition to the transfer roller. In addition to the cleaning blade, the cleaning device may be a cleaning brush or a cleaning roller.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. 6 is a graph showing the relationship between the primary transfer voltage VT1 and the photoreceptor surface potential Vo (when using a high resistance intermediate transfer belt). 6 is a graph showing the relationship between the primary transfer voltage VT1 and the photoreceptor surface potential Vo (when using a low resistance intermediate transfer belt). 5 is a graph showing a range that the primary transfer voltage VT1 can take for each environment (when using a low resistance intermediate transfer belt). It is a graph (when using a low resistance intermediate transfer belt) showing a correction amount of the grid voltage Vg with respect to the primary transfer voltage VT1. It is a flowchart which shows the control procedure of the grid voltage Vg concerning this form. It is a figure which shows the outline | summary procedure of an image formation process.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Charging device (charging unit)
3 Exposure device 4 Development device 5 Primary transfer roller (intermediate transfer portion)
6 Cleaning device 7 Intermediate transfer belt (intermediate transfer member)
8 Concentration sensor 9 Control unit (voltage control unit)
16 Temperature / humidity sensor 17 Data storage unit 100 Image forming apparatus

Claims (4)

An image carrier that carries a toner image, a charging unit that charges the surface of the image carrier, an intermediate transfer member that receives a transfer of the toner image on the image carrier, and a toner image on the image carrier. In an image forming apparatus having an intermediate transfer portion to be transferred onto an intermediate transfer member, and a voltage control portion for controlling a voltage applied to the charging portion, wherein constant current control is performed in the intermediate transfer portion,
The image forming apparatus, wherein the voltage control unit obtains an applied voltage value to the intermediate transfer unit and determines a voltage value to be applied to the charging unit based on the applied voltage value. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the voltage control unit has correction value information for determining a correction amount of the applied voltage value to the charging unit corresponding to the applied voltage value to the intermediate transfer unit. The image forming apparatus according to claim 1, wherein:
The voltage control unit defines a range in which the applied voltage value to the intermediate transfer unit can be taken using at least one of temperature and humidity as a parameter, and acquires correction value information within the range. Forming equipment. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the voltage control unit acquires a voltage value to be applied to the intermediate transfer unit when AIDC (Auto Image Density Control) control is performed.

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