Intermediate transfer unit, image forming apparatus including the same, and method for manufacturing intermediate transfer unit

Abstract

To provide an intermediate transfer unit that can prevent the occurrence of transfer failure.SOLUTION: An intermediate transfer unit comprises an endless intermediate transfer belt, a plurality of primary transfer members, and a power supply line. Toner images formed on a plurality of image carriers are sequentially laminated on the intermediate transfer belt. The primary transfer members are arranged opposite to the image carriers with the intermediate transfer belt therebetween, and transfer the toner images formed on the image carriers onto the intermediate transfer belt. The power supply line is branched and extends into at least two parts from a transfer voltage power supply that applies primary transfer voltage to the primary transfer members, and causes primary transfer current to flow in the primary transfer members. The power supply line and the primary transfer members are connected to each other via a high-voltage resistance part formed of a plurality of resistors with different resistance values.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an intermediate transfer unit, an image forming apparatus including the same, and a method for manufacturing the intermediate transfer unit. [Background technology]

[0002] A conventional intermediate transfer unit includes an endless intermediate transfer belt, multiple primary transfer members, a power supply line, and a resistor. Toner images formed on multiple image carriers are sequentially stacked on the intermediate transfer belt. The primary transfer members are arranged opposite each image carrier via the intermediate transfer belt and transfer the toner images formed on the image carriers onto the intermediate transfer belt. The power supply line branches out from a transfer voltage power source that applies a primary transfer voltage to the primary transfer members, extending to at least two locations, and passes a primary transfer current to each primary transfer member. The resistor connects the power supply line to the primary transfer members. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-26872 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of the above-mentioned patent document, if there is variation in the resistance of the primary transfer member and the resistor, the transfer current flowing through the primary transfer member may deviate from the target value, which may result in transfer defects.

[0005] In view of the above problems, an object of the present invention is to provide an intermediate transfer unit capable of suppressing the occurrence of transfer defects, an image forming apparatus including the same, and a method for manufacturing the intermediate transfer unit. [Means for solving the problem]

[0006] To achieve the above object, the first aspect of the present invention is an intermediate transfer unit including an endless intermediate transfer belt, multiple primary transfer members, and a power supply line. Toner images formed on multiple image carriers are sequentially stacked on the intermediate transfer belt. Primary transfer members are disposed opposite each image carrier via the intermediate transfer belt, and transfer the toner images formed on the image carriers onto the intermediate transfer belt. The power supply line branches out from a transfer voltage power supply that applies a primary transfer voltage to the primary transfer member, extending to at least two locations, and passes a primary transfer current to each primary transfer member. The power supply line and each primary transfer member are connected via a high-voltage resistor unit composed of multiple resistors with different resistance values.

[0007] To achieve the above object, a second aspect of the present invention is a manufacturing method for an intermediate transfer unit including an endless intermediate transfer belt, multiple primary transfer members, a transfer voltage power supply, a power supply line, and a high-voltage resistor. Toner images formed on multiple image carriers are sequentially stacked on the intermediate transfer belt. The primary transfer members are positioned opposite each image carrier via the intermediate transfer belt and transfer the toner images formed on the image carriers onto the intermediate transfer belt. The power supply line branches from a transfer voltage power supply that applies a primary transfer voltage to the primary transfer member, extending at least two or more times, and passes a primary transfer current to each primary transfer member. The high-voltage resistor connects the power supply line to each primary transfer member. The method includes a current measurement step and a resistor determination step. The current measurement step measures the primary transfer current flowing through each primary transfer member. The resistor determination step determines resistors that constitute the high-voltage resistor based on the primary transfer current measured in the electrical measurement step. The current measurement step and the resistor determination step are repeated in sequence to form the high-voltage resistor using multiple resistors with different resistance values. [Effects of the Invention]

[0008] According to the first aspect of the present invention, it is possible to provide an intermediate transfer unit that can suppress the occurrence of transfer defects and a method for manufacturing the intermediate transfer unit. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus 100 according to an embodiment of the present invention; [Figure 2] Partially enlarged view of the image forming section Pa and its surroundings in FIG. [Figure 3] 1 is a side cross-sectional view of an intermediate transfer unit 30 mounted in an image forming apparatus 100 according to an embodiment of the present invention; [Figure 4] FIG. 1 is a block diagram showing a control path of an image forming apparatus 100 according to an embodiment of the present invention. [Figure 5] 1 is a partial cross-sectional view of the vicinity of a high-voltage resistor 80a of an intermediate transfer unit 30 according to an embodiment of the present invention; [Figure 6] 1 is a flowchart showing a manufacturing process for an intermediate transfer unit 30 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 100 according to an embodiment of the present invention, and Fig. 2 is an enlarged view of the vicinity of image forming section Pa in Fig. 1. Note that image forming sections Pb to Pd have basically the same configuration, so their description will be omitted.

[0011] Image forming apparatus 100 includes image forming units Pa, Pb, Pc, and Pd, and an intermediate transfer unit 30, which will be described later. The four image forming units Pa, Pb, Pc, and Pd are arranged in order from the upstream side in the transport direction (the left side in FIG. 1). Image forming units Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and sequentially form cyan, magenta, yellow, and black images through the processes of charging, exposure, development, and transfer, respectively.

[0012] Each of these image forming stations Pa to Pd is provided with a photosensitive drum 1a, 1b, 1c, and 1d that carries a visible image (toner image) of each color. Furthermore, an intermediate transfer belt 8 that is wound around multiple rollers, including a drive roller 10 and a tension roller 11, and rotates counterclockwise in FIG. 1 is provided adjacent to each of the image forming stations Pa to Pd. As shown in FIG. 2, a charging device 2a, a developing device 3a, a cleaning device 7a, and a static elimination lamp 20 are disposed around the photosensitive drum 1a in the drum rotation direction (clockwise in FIG. 2), and a primary transfer roller 6a is disposed across the intermediate transfer belt 8.

[0013] The photosensitive drums 1a to 1d are each composed of a conductive substrate 19a and a photosensitive layer 19b formed on the surface of the conductive substrate 19a. In this embodiment, an organic photosensitive layer is laminated as the photosensitive layer 19b on the surface of the cylindrical conductive substrate 19a made of aluminum.

[0014] The charging devices 2a to 2d each have a charging roller 21 that contacts the photosensitive drum 1a and applies a charging voltage (DC voltage) to the drum surface, and a charging cleaning roller 24 that cleans the charging roller 21. In the present invention, a charging voltage consisting of only a DC voltage is applied to the charging roller 21 in order to reduce the amount of ozone generated and to reduce the cost of the charging voltage power supply 52 (see FIG. 4).

[0015] Developing devices 3a-3d are two-component development devices each equipped with two stirring / conveying screws 25 and a developing roller 29. Each device is filled with a predetermined amount of two-component developer containing cyan, magenta, yellow, and black toner and magnetic carriers. A magnetic brush is formed on the surface of developing roller 29 using the two-component developer, and a developing voltage of the same polarity as the toner (positive polarity in this case) is applied to developing roller 29. The magnetic brush is then brought into contact with the surface of photosensitive drum 1a, causing the toner to adhere and form a toner image. If the toner content of the two-component developer filled in each developing device 3a-3d falls below a specified value due to the formation of a toner image, toner is replenished from toner containers 4a-4d to each developing device 3a-3d.

[0016] When image data is input from a host device such as a personal computer, first, the main motor 40 (see FIG. 4) starts rotating the photosensitive drums 1a-1d. The belt drive motor 41 (see FIG. 4) also starts rotating the intermediate transfer belt 8. Next, the charging devices 2a-2d uniformly charge the surfaces of the photosensitive drums 1a-1d to the same polarity as the toner (positive polarity in this case). Next, the exposure device 5 irradiates light according to the image data, forming electrostatic latent images on the photosensitive drums 1a-1d with the charge attenuated according to the image data. Finally, the developing devices 3a-3d supply toner onto the photosensitive drums 1a-1d, where it electrostatically adheres to form toner images corresponding to the electrostatic latent images.

[0017] Then, by applying a predetermined primary transfer electric field between the primary transfer rollers 6a-6d and the photosensitive drums 1a-1d by the primary transfer rollers 6a-6d, the yellow, cyan, magenta, and black toner images on the photosensitive drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. Toner and the like remaining on the surfaces of the photosensitive drums 1a-1d after the primary transfer are removed by cleaning devices 7a-7d. Residual charge remaining on the surfaces of the photosensitive drums 1a-1d after the primary transfer is removed by a discharge lamp 20.

[0018] The transfer paper S onto which the toner image is transferred is stored in a paper cassette 16 located at the bottom of the image forming apparatus 100. The transfer paper S is transported at a predetermined timing via a paper feed roller 12a and a pair of registration rollers 12b to a nip portion (secondary transfer nip portion) between the intermediate transfer belt 8 and a secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8. The transfer paper S onto which the toner image on the intermediate transfer belt 8 has been secondarily transferred by the secondary transfer roller 9 is transported to a fixing unit 13.

[0019] The transfer paper S transported to the fixing unit 13 is heated and pressurized by the fixing roller pair 13a, and the toner image is fixed to the surface of the transfer paper S, forming a predetermined full-color image. The transfer paper S on which the full-color image has been formed is discharged to the discharge tray 17 by the discharge roller pair 15 as is (or after being diverted to the reversing conveyance path 18 by the branching unit 14 and images formed on both sides).

[0020] 3 is a side cross-sectional view of the intermediate transfer unit 30 mounted in the image forming apparatus 100. Note that Fig. 3 also shows a power supply line 81 and high-voltage resistors 80a-80d. The intermediate transfer unit 30 includes an intermediate transfer belt 8 stretched across a drive roller 10 and a tension roller 11, primary transfer rollers 6a-6d that contact the photosensitive drums 1a-1d via the intermediate transfer belt 8, and a pressure switching roller 34.

[0021] The drive roller 10 and tension roller 11 are respectively arranged downstream and upstream with respect to the traveling direction (conveying direction) of the conveying surface (lower surface) of the intermediate transfer belt 8. A belt cleaning unit 37 for removing toner remaining on the surface of the intermediate transfer belt 8 is arranged opposite the tension roller 11 (see FIG. 1). A secondary transfer roller 9 is disposed and pressed against the drive roller 10 via the intermediate transfer belt 8, forming a secondary transfer nip N.

[0022] The intermediate transfer unit 30 is equipped with a pair of support members 33 (see FIG. 5) that rotatably support both ends of the rotation shafts of the primary transfer rollers 6a-6d and the pressure switching roller 34 and move perpendicularly to the direction of travel of the intermediate transfer belt 8 (the up-and-down direction in FIG. 3), and a roller contact / separation mechanism 35 that includes drive means (not shown) that reciprocates the primary transfer rollers 6a-6d and the pressure switching roller 34 in the up-and-down direction. The roller contact / separation mechanism 35 is switchable between a color mode in which the four primary transfer rollers 6a-6d are pressed against the photosensitive drums 1a-1d (see FIG. 1) via the intermediate transfer belt 8, a monochrome mode in which only the primary transfer roller 6d is pressed against the photosensitive drum 1d via the intermediate transfer belt 8, and a retraction mode in which all four primary transfer rollers 6a-6d are separated from the photosensitive drums 1a-1d.

[0023] The intermediate transfer unit 30 also includes a power supply line 81 and high-voltage resistors 80a-80d. The power supply line 81 branches out at least two locations from a transfer voltage power supply 54 (described below) that applies a primary transfer voltage to the primary transfer rollers 6a-6d. The power supply line 81 also passes a primary transfer current to each of the primary transfer rollers 6a-6d. The high-voltage resistors 80a-80d connect the power supply line 81 to the primary transfer rollers 6a-6d and adjust the primary transfer current that flows through the primary transfer rollers 6a-6d. The high-voltage resistors 80a-80d will be described in detail later.

[0024] In this embodiment, the power supply line 81 branches into four locations and is connected to each of the primary transfer rollers 6a to 6d. This connects the high-voltage resistor units 80a to 80d in parallel. Although the high-voltage resistor units 80a to 80d are connected in parallel, for example, the high-voltage resistor units 80a to 80c may be connected in parallel to the transfer voltage power supply 54, and the high-voltage resistor unit 80d may be connected independently to the transfer voltage power supply 54.

[0025] Next, the control path of the image forming apparatus 100 of the present invention will be described. Fig. 4 is a block diagram showing an example of the control path used in the image forming apparatus 100 of the present invention. Note that, since various controls are performed on each section of the image forming apparatus 100 when it is used, the control path of the entire image forming apparatus 100 becomes complex. Therefore, the following description will focus on the parts of the control path that are necessary for implementing the present invention.

[0026] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only memory, a RAM (Random Access Memory) 93 as a readable and writable memory, a temporary memory (memory unit) 94 that temporarily stores image data and the like, a counter 95 that accumulates and counts the number of printed sheets, and a plurality of (here, two) I / Fs (interfaces) 96 that transmit control signals to each device in the image forming apparatus 100 and receive input signals from the operation unit 60. The control unit 90 can be placed anywhere inside the main body of the image forming apparatus 100.

[0027] ROM 92 stores data such as a control program for image forming apparatus 100, numerical values ​​necessary for control, and data that will not be changed while image forming apparatus 100 is in use. RAM 93 stores necessary data that is generated during the control of image forming apparatus 100, data that is temporarily necessary for controlling image forming apparatus 100, and the like.

[0028] Furthermore, the control unit 90 transmits control signals from the CPU 91 to each part and device in the image forming apparatus 100 via the I / F 96. Furthermore, signals indicating the state of each part and device and input signals are transmitted from each part and device to the CPU 91 via the I / F 96. Examples of each part and device controlled by the control unit 90 include image forming units Pa to Pd, the exposure device 4, primary transfer rollers 6a to 6d, the secondary transfer roller 9, the main motor 40, the belt drive motor 41, the image input unit 50, the voltage control circuit 51, and the operation unit 60.

[0029] The image input unit 50 is a receiving unit that receives image data transmitted from a personal computer or the like to the image forming apparatus 100. The image signal input from the image input unit 50 is converted into a digital signal, and then sent to the temporary storage unit 94 via the I / F 96.

[0030] The voltage control circuit 51 is connected to the charging voltage power supply 52, the developing voltage power supply 53, and the transfer voltage power supply 54, and operates these power supplies in response to output signals from the control unit 90. In response to control signals from the voltage control circuit 51, the charging voltage power supply 52 applies a charging voltage to the charging rollers 21 in the charging devices 2a to 2d. The developing voltage power supply 53 applies a developing voltage, which is a developing DC voltage superimposed on a developing AC voltage, to the developing rollers 29 in the developing devices 3a to 3d. The transfer voltage power supply 54 applies a primary transfer voltage to the primary transfer rollers 6a to 6d. Furthermore, the transfer voltage power supply 54 applies a secondary transfer voltage to the secondary transfer roller 9.

[0031] The charging voltage applied to the charging roller 21 from the charging voltage power supply 52 is preferably a DC voltage. When the charging voltage is a DC voltage, the amount of discharge from the charging roller 21 to the photosensitive drums 1a to 1d is smaller than when the charging voltage is a superimposed voltage of a DC voltage and an AC voltage, and the amount of wear on the photosensitive layers 19b of the photosensitive drums 1a to 1d can be reduced.

[0032] The operation unit 60 is provided with a liquid crystal display unit 61 and an LED 62 that indicates various states, and the user operates the stop / clear button on the operation unit 60 to stop image formation, and operates the reset button to reset various settings of the image forming apparatus 100 to their default states. The liquid crystal display unit 61 indicates the state of the image forming apparatus 100, as well as the image formation status and the number of copies to be printed. Various settings of the image forming apparatus 100 are made using a printer driver on a personal computer.

[0033] 5 is a partial cross-sectional view of the vicinity of the high-voltage resistor 80a of the intermediate transfer unit 30. Note that the high-voltage resistors 80b, 80c, and 80d have basically the same configuration, so a description thereof will be omitted.

[0034] The high-voltage resistor unit 80a connects the power supply line 81 and the primary transfer roller (primary transfer member) 6a, and is composed of multiple resistors 801a, 802a, and 803a with different resistance values. The resistors 801a, 802a, and 803a each have a resistance value indicated by a color code or a numerical value. The resistors 801a, 802a, and 803a are connected in series.

[0035] Between the power supply line 81 and the primary transfer roller 6a, there are contact springs 47a, 47b, leads 43a, 43b, a bearing 66, and a high-voltage resistor 80a. The bearing 66 rotatably supports the rotation shaft 65 of the primary transfer roller 6a. The contact spring 47a connects the power supply line 81 and the lead 43a. The contact spring 47b connects the lead 43b and the bearing 66. The high-voltage resistor 80a connects the lead 43a and the lead 43b.

[0036] The power supply line 81 branches off and extends from the primary transfer contact terminal portion 37a, which is electrically connected to a high-voltage board (not shown) that constitutes the transfer voltage power supply 54, and supplies a primary transfer current to the primary transfer roller (primary transfer member) 6a.

[0037] This results in an electrical connection from primary transfer contact terminal 37a to rotation shaft 65 of primary transfer roller 6a. Also, high-voltage resistor 80a adjusts the value of the current flowing from transfer voltage power supply 54 to primary transfer roller 6a, so that an appropriate primary transfer voltage is applied to primary transfer roller 6a. A similar configuration is used to apply appropriate primary transfer voltages to primary transfer rollers 6b to 6d.

[0038] High-voltage resistor unit 80a is mounted on, for example, circuit board 84 that electrically connects lead 43a and lead 43b. It is preferable that resistor 801a has a resistance of 100 MΩ or more, and resistors 802a and 803a have a resistance of 1 MΩ or more and 100 MΩ or less. That is, the resistance value of resistor 801a, one of the resistors that constitute high-voltage resistor unit 80a, is 100 MΩ or more, and the resistance values ​​of resistors 802a and 803a are 1 MΩ or more and 100 MΩ or less.

[0039] The resistance value of high-voltage resistor section 80a can be adjusted by combining multiple resistors 801a, 802a, and 803a with different resistance values. For example, in this embodiment, high-voltage resistor section 80a is made up of three resistors 801a, 802a, and 803a, but resistor 803a may be omitted. This allows the resistance value of high-voltage resistor section 80a to be reduced. High-voltage resistor section 80a may also be made up of a combination of four or more resistors. This allows the resistance value of high-voltage resistor section 80a to be freely set. Furthermore, the arrangement of resistors 801a, 802a, and 803a is not particularly limited.

[0040] If the resistor 803a is omitted, a gap (not shown) is formed on the circuit board 84, but for example, by arranging a lead wire, the power supply line 81 and the primary transfer roller 6a can be electrically connected stably.

[0041] The resistance value of the high-voltage resistor 80a can be adjusted while measuring the value of the current flowing through the primary transfer roller 6a.

[0042] In this case, by making one resistor 801a 100 MΩ or more, the resistor 801a with a large resistance value is first installed to pass the target primary transfer current, allowing the resistance value of the high-voltage resistor unit 80a to quickly approach the target value. Then, by installing resistors 802a and 803a with small resistance values ​​of 1 MΩ or more and 100 MΩ or less, the resistance value of the high-voltage resistor unit 80a can be fine-tuned. This allows for efficient adjustment of the resistance value of the high-voltage resistor unit 80a.

[0043] Therefore, it is preferable that the resistance values ​​of the high-voltage resistors 80a-80d connected to the primary transfer rollers 6a-6d aligned in the toner image transport direction decrease in order downstream in the transport direction. Specifically, the resistors are combined and adjusted so that the resistance values ​​decrease in the order of high-voltage resistor 80a, high-voltage resistor 80a, high-voltage resistor 80a, and high-voltage resistor 80a.

[0044] By decreasing the resistance values ​​of the high-voltage resistors 80a to 80d, a larger primary transfer current can be passed through the primary transfer rollers 6a to 6d. By decreasing the resistance values ​​of the high-voltage resistors 80a to 80d sequentially downstream in the toner image transport direction, the primary transfer current that flows increases in the order of the primary transfer rollers 6a to 6d. Because the toner image transported by the intermediate transfer belt 8 is overwritten as it moves downstream, passing a larger primary transfer current through the primary transfer rollers located downstream can reduce the occurrence of transfer defects.

[0045] The resistance values ​​of the high-voltage resistors 80a to 80d are preferably greater than the resistance values ​​of the connected primary transfer rollers 6a to 6d. By arranging high-voltage resistors 80a to 80d with resistance values ​​sufficiently greater than the resistance values ​​of the primary transfer rollers 6a to 6d, it is possible to keep the variation in the resistance values ​​of the primary transfer rollers 6a to 6d relatively small. For example, it is preferable that the resistance value of the primary transfer rollers 6a to 6d is 5.0 (log Ω) or greater when a primary transfer voltage of 1000 V is applied, and that the resistance values ​​of the high-voltage resistors 80a to 80d be 10 times or greater than the resistance value of the primary transfer rollers 6a to 6d.

[0046] Furthermore, the transfer currents flowing through the primary transfer rollers 6a to 6d or the applied primary transfer voltages obtained when adjusting the resistance values ​​of the high-voltage resistors 80a to 80d may be stored in a temporary storage unit (storage unit) 94, and the control unit 90 may perform image formation based on the transfer currents or primary transfer voltages stored in the temporary storage unit 94. This can further reduce the occurrence of transfer defects.

[0047] FIG. 6 is a flowchart showing the manufacturing process of the intermediate transfer unit 30. In step S1, a primary transfer voltage is applied from the transfer voltage power supply 54 to the primary transfer rollers 6a to 6d, and the primary transfer currents flowing through the primary transfer rollers 6a to 6d are measured. In step S2, it is determined whether the measured primary transfer currents have reached their target values. If the primary transfer currents have not reached their target values, the process proceeds to step S3. On the other hand, if the primary transfer currents have reached their target values, it is determined that the resistance values ​​of the high-voltage resistors 80a to 80d are appropriate.

[0048] In step S3, resistor 801a is mounted on circuit board 84 to adjust the resistance values ​​of high-voltage resistor sections 80a-80d, and the process returns to step S1. By repeating steps S1-S3, the resistance value of high-voltage resistor section 80a can be adjusted by combining 802a and 803a. By adjusting high-voltage resistor sections 80a-80d, an optimal primary transfer current can be passed through primary transfer rollers 6a-6d. This makes it possible to manufacture an intermediate transfer unit 30 that can prevent transfer defects from occurring.

[0049] When steps S1 to S3 are repeated, in step S3, a resistor having a resistance value smaller than the resistance value of the resistor added last time is mounted on circuit board 48. This allows the resistance values ​​of high-voltage resistor sections 80a to 80d to be gradually fine-tuned, thereby obtaining optimal resistance values ​​for high-voltage resistor sections 80a to 80d with a small number of adjustments.

[0050] That is, the manufacturing method of the intermediate transfer unit 30 of this embodiment includes a current measurement process (step S1) and a resistor determination process (step S3). The current measurement process measures the primary transfer current flowing through each of the primary transfer rollers 6a to 6d. The resistor determination process determines the resistors 801a, 802a, and 803a that make up the high-voltage resistor sections 80a to 80d based on the primary transfer current measured in the electrical measurement process. The current measurement process and the resistor determination process are repeated in order, and the high-voltage resistor sections 80a to 80d are made up of multiple resistors 801a, 802a, and 803a with different resistance values. By adjusting the high-voltage resistor sections 80a to 80d, an optimal primary transfer current can be passed through the primary transfer rollers 6a to 6d.

[0051] The resistance values ​​of resistors 802a and 803a determined in the next resistor determination step (step S3) are smaller than the resistance value of resistor 801a determined in the previous resistor determination step (step S3). As a result, by gradually fine-tuning the resistance values ​​of high-voltage resistor sections 80a-80d, optimal resistance values ​​of high-voltage resistor sections 80a-80d can be obtained with fewer adjustments. Therefore, intermediate transfer unit 30 can be manufactured efficiently.

[0052] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention.

[0053] In the above embodiment, which is predicted using the following method, a color printer as shown in FIG. 1 is used as an example of image forming apparatus 100, but the image forming apparatus is not limited to a color printer and may be other image forming apparatuses such as monochrome and color copiers, digital multifunction machines, facsimiles, etc. [Industrial Applicability]

[0054] The present invention can be used in an image forming apparatus equipped with a charging roller. [Explanation of symbols]

[0055] 1a to 1d Photosensitive drum 2a~2d Charging device 3a~3d developing device 4 Exposure equipment 4a~4d Toner container 5 Exposure equipment 6a~6d Primary transfer roller 7a~7d Cleaning device 8 Intermediate transfer belt 9 Secondary transfer roller 10 Drive Roller 11 Tension roller 12a Paper feed roller 12b Registration Roller Pair 13 Fixing section 13a Fuser roller pair 14 Branch 15 Discharge Roller Pair 16 Paper cassette 17 Output tray 18 Reversing conveyance path 19a Conductive substrate 19b Photosensitive layer 20. Static elimination lamp 21 Charging roller 24 Electrostatic cleaning roller 25 Mixing and conveying screw 29 Developing roller 30 Intermediate transfer unit 33 Support member 34 Pressure switching roller 35 Roller contact / separation mechanism 37 Belt cleaning unit 37a Primary transfer contact terminal 40 Main motor 41 Belt drive motor 43a Lead 43a, 43b lead 43b Lead 47a, 47b Contact spring 48 Circuit Board 50 Image input unit 51 Voltage control circuit 52 Charge voltage power supply 53 Development voltage power supply 54 Transfer voltage power supply 60 Control section 61 LCD display section 62 LED 80a~80d High voltage resistor section 81 Power supply line 84 Circuit Board 90 Control Unit 91 CPU 92 ROM 93 RAM 94 Temporary storage 95 Counter 100 Image forming device 801a, 802a, 803a resistor N Secondary transfer nip S transfer paper

Claims

1. an endless intermediate transfer belt on which toner images formed on a plurality of image carriers are sequentially stacked; a plurality of primary transfer members disposed opposite the image carriers with the intermediate transfer belt interposed therebetween, and configured to transfer the toner images formed on the image carriers onto the intermediate transfer belt; a power supply line that branches out from the transfer voltage power supply, which applies a primary transfer voltage to the primary transfer member, to at least two or more locations and that passes a primary transfer current to each of the primary transfer members; The power supply line and each of the primary transfer members are connected via a high-voltage resistance unit that is composed of a plurality of resistors with different resistance values.

2. 2. The intermediate transfer unit according to claim 1, wherein the resistance value of one of the resistors constituting the high-voltage resistance section is 100 MΩ or more, and the resistance value of the other resistor is 1 MΩ or more and 100 MΩ or less.

3. 3. The intermediate transfer unit according to claim 1, wherein the resistance values ​​of the high-voltage resistors connected to the primary transfer members arranged in a direction in which the toner image is transported decrease in order toward the downstream side in the transport direction.

4. 3. The intermediate transfer unit according to claim 1, wherein the resistance value of the high-voltage resistor is greater than the resistance value of the primary transfer member connected thereto.

5. 3. The intermediate transfer unit according to claim 1, wherein a lead wire is disposed in a gap in the high-voltage resistance portion where the resistor is not mounted, and connects the power supply line and the primary transfer member.

6. an intermediate transfer unit according to claim 1 or claim 2; an image forming unit including the image carrier and forming an image; a storage unit that stores the transfer current flowing through each of the primary transfer members or the applied primary transfer voltage; a control unit that performs the image formation based on the transfer current or the primary transfer voltage stored in the storage unit.

7. an endless intermediate transfer belt on which toner images formed on a plurality of image carriers are sequentially stacked; a plurality of primary transfer members disposed opposite the image carriers with the intermediate transfer belt interposed therebetween, and configured to transfer the toner images formed on the image carriers onto the intermediate transfer belt; a power supply line extending from the transfer voltage power supply, which applies a primary transfer voltage to the primary transfer member, to at least two or more branches, and which supplies a primary transfer current to each of the primary transfer members; a high-voltage resistor portion connecting the power supply line and each of the primary transfer members, a current measuring step of measuring a primary transfer current flowing through each of the primary transfer members; a resistor determination process for determining resistors that constitute the high-voltage resistor section based on the primary transfer current measured in the electrical measurement process, wherein the current measurement process and the resistor determination process are repeated in sequence to form the high-voltage resistor section using a plurality of resistors with different resistance values.

8. The method for manufacturing an intermediate transfer unit according to claim 7 , wherein the resistance value of the resistor determined in the next resistor determination step is smaller than the resistance value of the resistor determined in the previous resistor determination step.

Images