Image forming apparatus

Abstract

To provide an image forming apparatus that can suppress delay of a first printing time in the first image formation after replacing an intermediate transfer unit.SOLUTION: An image forming apparatus includes: a primary transfer roller as a primary transfer member to which a primary transfer voltage is applied and which performs primary transfer of a toner image on a photoreceptor as an image carrier to an intermediate transfer belt as an intermediate transfer unit in a primary transfer part; an engine control unit as a control unit which performs primary transfer voltage setting control for setting the primary transfer voltage on the basis of a current value flowing in the primary transfer roller as detected by a primary transfer current detection unit; and an operation panel as an operation input unit which receives a user's operation input. The engine control unit performs the primary transfer voltage setting control at a timing when intermediate transfer belt replacement information is input through the operation panel and at a timing after a first image formation after replacing the intermediate transfer belt.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Conventionally, there has been known an image forming apparatus that includes a primary transfer member to which a primary transfer voltage is applied and which performs primary transfer of a toner image on an image carrier to an intermediate transfer member at a primary transfer unit, a control unit that performs primary transfer voltage setting control to set the primary transfer voltage based on the value of the current flowing through the primary transfer member detected by a primary transfer current detection unit, and an operation input unit that accepts user operation input, and the control unit performs primary transfer voltage setting control when intermediate transfer member replacement information is input via the operation input unit.

[0003] Patent Document 1 describes a system that performs primary transfer voltage setting control when the cumulative number of printed sheets since the previous execution of primary transfer voltage setting control reaches 1,000, when the intermediate transfer belt serving as an intermediate transfer body is replaced, and when the image forming apparatus is used for the first time.The system describes that when information that the intermediate transfer belt has been replaced is input as intermediate transfer belt replacement information via an operation display unit serving as an operation input unit, the control unit recognizes that the intermediate transfer belt has been replaced, and that when the first print job is executed after the replacement, the primary transfer voltage setting control is performed before the print job is started. Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a problem in that the first print time is delayed when forming an image for the first time after replacing the intermediate transfer member. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus including a primary transfer member to which a primary transfer voltage is applied and which performs primary transfer of a toner image on an image carrier to an intermediate transfer member at a primary transfer section, a control unit which performs primary transfer voltage setting control to set the primary transfer voltage based on the current value flowing through the primary transfer member detected by a primary transfer current detection unit, and an operation input unit which accepts user operation input, wherein the control unit performs the primary transfer voltage setting control at the timing when intermediate transfer member replacement information is input through the operation input unit and at the timing after the first image formation after the intermediate transfer member is replaced. [Effects of the Invention]

[0006] According to the present invention, delay in the first print time in the first image formation after replacement of the intermediate transfer member can be suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus configured as a printer. [Figure 2] FIG. 2 is a diagram illustrating the hardware configuration of the image forming apparatus. [Figure 3] FIG. 2 is a diagram showing an example of a functional block diagram illustrating the image forming apparatus. [Figure 4] FIG. 10 is a diagram showing another example of functional blocks for explaining the image forming apparatus. [Figure 5] 10 is a graph showing the relationship between the primary transfer voltage and the transfer rate. [Figure 6] 10 is a graph showing the relationship between the surface resistance value of the intermediate transfer belt and the detected current. [Figure 7] FIG. 10 is a diagram showing an example of a bias table for setting a primary transfer voltage based on a detected current. [Figure 8] Graph showing the conversion formula. [Figure 9] Graph showing multiple transformation formulas. [Figure 10] FIG. 10 is a flow diagram of primary transfer voltage setting control. [Figure 11]10 is a flowchart of primary transfer voltage setting control when the intermediate transfer unit is replaced according to the present embodiment. [Figure 12] 10 is a flowchart illustrating a process for performing the primary transfer voltage setting control again after the first process control is performed after the intermediate transfer unit is replaced. DETAILED DESCRIPTION OF THE INVENTION

[0008] The best mode for carrying out the present invention will be described below with reference to the drawings. Note that a person skilled in the art can easily modify or alter the present invention within the scope of the claims to create other embodiments, and these modifications and alterations are included within the scope of the claims. The following description is an example of the best mode for carrying out the present invention and does not limit the scope of the claims.

[0009] FIG. 1 is a schematic diagram showing an example of an image forming apparatus 100 configured as a printer. The image forming apparatus 100 shown in FIG. 1 has a plurality of photoconductors 1a, 1b, 1c, and 1d (hereinafter, referred to as "photoconductors 1" when the colors are not distinguished) arranged in a main body housing as four image carriers. Toner images of different colors are formed on each photoconductor, and a black toner image, a magenta toner image, a cyan toner image, and a yellow toner image are formed on each of the photoconductors 1a, 1b, 1c, and 1d, respectively. Although the photoconductors 1a, 1b, 1c, and 1d shown in FIG. 1 are formed in a drum shape, an endless belt-like photoconductor that is wrapped around multiple rollers and driven to rotate can also be used.

[0010] An intermediate transfer belt 3 serving as an intermediate transfer body is disposed opposite the first to fourth photosensitive bodies 1a, 1b, 1c, and 1d, and each of the photosensitive bodies 1a, 1b, 1c, and 1d contacts the surface of the intermediate transfer belt 3 to form a primary transfer section. The intermediate transfer belt 3 performs a secondary transfer of the toner images that have been primarily transferred onto itself from the photosensitive bodies 1a, 1b, 1c, and 1d onto a transfer material.

[0011] The intermediate transfer belt 3 is wound around a drive roller 4, a tension roller 5, and an inlet roller 7. One of these support rollers, for example, support roller 4, is configured as a drive roller driven by a drive source, and the drive of this drive roller drives the intermediate transfer belt 3 to rotate in the direction of arrow A.

[0012] The intermediate transfer belt 3 may have a multi-layer structure or a single-layer structure, but if it has a multi-layer structure, it is preferable that the base layer is made of, for example, a fluororesin, PVDF sheet, or polyimide resin, which has low elongation, and that the surface is covered with a smooth coating layer of fluororesin or the like.If it is a single layer, it is preferable that it is made of a material such as PVDF, PC, or polyimide.

[0013] Meanwhile, primary transfer rollers 11a, 11b, 11c, and 11d (hereinafter referred to as "primary transfer roller 11" when color is not distinguished) are arranged inside the intermediate transfer belt 3, substantially facing the photosensitive member 1a across the belt. The primary transfer rollers 11 abut against the back surface of the intermediate transfer belt 3, ensuring an appropriate transfer nip between the photosensitive member 1a and the intermediate transfer belt 3. The primary transfer rollers 11 are made of metal.

[0014] The primary transfer roller 11 contacts the inner circumferential surface of the intermediate transfer belt 3 (indirect transfer method) so that the primary transfer portion, which is the contact area between the photosensitive member 1 and the intermediate transfer belt 3, and the contact area between the primary transfer roller 11 and the intermediate transfer belt 3 do not overlap in the direction of movement of the intermediate transfer belt 3. In this embodiment, the belt distance (offset amount) between the photosensitive member 1 and the primary transfer roller 11 where it is not in contact with either is set to 4 to 5 mm.

[0015] In this way, by using an indirect transfer method in which the primary transfer section and the contact area between the primary transfer roller 11 and the intermediate transfer belt 3 do not overlap in the direction of movement of the intermediate transfer belt 3, it is possible to use a metal for the primary transfer roller that has little increase in electrical resistance during repeated use.

[0016] The configuration for forming toner images on photoconductors 1a, 1b, 1c, and 1d and the configuration for transferring each toner image onto intermediate transfer belt 3 are all substantially the same, with only the color of the toner images formed being different. Therefore, we will only explain the configuration and operation for forming a black toner image on first photoconductor 1a and transferring that toner image onto intermediate transfer belt 3. This photoconductor 1a is rotated counterclockwise in Figure 1, and at this time light from a static eliminator is irradiated onto the photoconductor surface, initializing the surface potential of photoconductor 1a.

[0017] The initialized photoreceptor surface is uniformly charged to a predetermined polarity, negative in this example, by a charging device 8. This charged surface is irradiated with an optically modulated laser beam L emitted from an exposure device 9, and an electrostatic latent image corresponding to the written information is formed on the surface of the photoreceptor 1a. The image forming apparatus 100 shown in Figure 1 uses an exposure device 9 consisting of a laser writing device that emits a laser beam, but it is also possible to use an exposure device having an LED array and imaging means.

[0018] The electrostatic latent image formed on photoreceptor 1a is visualized as a black toner image as it passes through developing device 10. A primary transfer voltage of a polarity opposite to the toner charge polarity of the toner image formed on photoreceptor 1a, positive in this example, is applied to primary transfer roller 11, forming a primary transfer electric field between photoreceptor 1a and intermediate transfer belt 3. As a result, at the primary transfer section where photoreceptor 1a and the outer circumferential surface of intermediate transfer belt 3 come into contact, the toner image on photoreceptor 1a is electrostatically transferred onto intermediate transfer belt 3, which is rotated in synchronization with photoreceptor 1a (primary transfer). Residual toner remaining on the surface of photoreceptor 1a after the toner image has been transferred to intermediate transfer belt 3 is removed by cleaning device 12, cleaning the surface of photoreceptor 1a.

[0019] In exactly the same way, a magenta toner image, a cyan toner image, and a yellow toner image are formed on the second to fourth photosensitive drums 1b, 1c, and 1d, respectively, and the toner images of each color are electrostatically transferred in succession onto the intermediate transfer belt 3 on which the black toner image has been transferred.

[0020] There are two modes: a full-color mode in which toner images of each of the four colors are used, and a black monochrome mode in which only black is used. In the full-color mode, the intermediate transfer belt 3 and the photoconductors 1 of the four colors come into contact with each other, and toner for all four colors is transferred onto the intermediate transfer belt 3. On the other hand, in the black monochrome mode, only the black photoconductor 1a comes into contact with the intermediate transfer belt 3, and only black toner is transferred to the intermediate transfer belt 3. In this case, the intermediate transfer belt 3 and the magenta, cyan, and yellow photoconductors 1b, 1c, and 1d are not in contact with each other, and a contact / separation mechanism provided in the image forming apparatus 100 separates the primary transfer rollers 11b, 11c, and 11d from the photoconductors 1b, 1c, and 1d.

[0021] A paper feeder 14 is disposed at the bottom of the apparatus body, and paper feeder 14 feeds a recording medium P, such as transfer paper, in the direction of arrow B by the rotation of paper feed roller 15. The fed recording medium P is then fed by a pair of registration rollers 16 at a predetermined timing between a portion of intermediate transfer belt 3 wrapped around support roller 4 and a secondary transfer roller 17, an example of a transfer device, disposed opposite to the portion. At this time, a predetermined transfer voltage is applied to secondary transfer roller 17, which causes the composite toner image on intermediate transfer belt 3 to be secondarily transferred to recording medium P.

[0022] The recording medium P onto which the composite toner image has been secondarily transferred is transported further upward and passes through a fixing device 18, where the toner image on the recording medium P is fixed by the action of heat and pressure. After passing through the fixing device 18, the recording medium P is discharged outside the image forming apparatus via a pair of paper discharge rollers 19 provided in a paper discharge section.

[0023] Furthermore, residual toner remaining on the intermediate transfer belt 3 after the toner image has been transferred is removed by a belt cleaning device. The belt cleaning device in this embodiment uses a blade-shaped cleaning blade 21 made of urethane or the like, and the cleaning blade 21 is brought into contact with the intermediate transfer belt 3 in the counter direction to the rotation direction. However, as will be apparent to those skilled in the art, various types of belt cleaning devices can be used as appropriate, and for example, the cleaning device may be of a capacitance type.

[0024] The residual toner removed from the intermediate transfer belt 3 by the cleaning blade 21 is sent to the rear longitudinal side by the waste toner coil inside the cleaning case, and is transported to a waste toner container through a waste toner path provided in the device main body.

[0025] In the image forming apparatus 100 of this embodiment, a process control operation, which serves as image density adjustment control, is performed to optimize the image density of each color every time a predetermined number of sheets are printed (every 30 to 200 sheets). The process control operation first forms a gradation pattern for each color on the intermediate transfer belt 3, consisting of multiple toner patches with different adhesion amounts for each color of toner. To create the gradation pattern, the charging bias and developing bias are sequentially switched at appropriate timing to create a gradation pattern consisting of multiple toner patches with different adhesion amounts. As the intermediate transfer belt 3 moves endlessly, the gradation pattern formed on the intermediate transfer belt 3 passes a position facing the optical sensor 22, which serves as an image density detection unit. At this time, the optical sensor 22 receives light in an amount corresponding to the toner adhesion amount per unit area for each toner patch of the gradation pattern.

[0026] Next, the system calculates the amount of toner adhesion in each toner patch of each color toner pattern based on the output voltage of the optical sensor 22 when the toner patch is detected and an adhesion amount conversion algorithm, and adjusts the image formation conditions based on the calculated adhesion amount. Specifically, a linear function (y = ax + b) representing the current development capability is calculated by regression analysis based on the detected toner adhesion amount in the toner patch and the development potential when each toner patch is formed. Then, by substituting the target image density value into this function, an appropriate development bias value is calculated, and the exposure power, charging bias, and development bias for Y, M, C, and Bk are determined as the image formation conditions. Furthermore, if the development device 10 uses a two-component development method using a two-component developer consisting of toner and carrier, the image density may be controlled by changing the toner concentration control target value within the development device 10. Specifically, the maximum target adhesion amount (the amount of adhesion required to achieve the target ID) can be set to a target value by changing the toner concentration control target value within the development device based on the detection results of the optical sensor 22.

[0027] Alternatively, the optical sensors 22 may be provided at positions facing the photosensitive members 1a, 1b, 1c, and 1d, respectively, so that the toner patterns formed on the photosensitive members can be detected by the optical sensors.

[0028] FIG. 1 shows an example of a schematic diagram of an applied power source used in this embodiment. A primary transfer power supply 27BK for black, which applies a voltage to the primary transfer roller 11a, is connected to a detection unit 28, which serves as a primary transfer current detection unit, and an engine control unit 930, which serves as a control unit. The detection unit 28 is connected to the primary transfer power supply 27BK for black, the black primary transfer roller 11a, and the engine control unit 930. The detection unit 28 is a primary transfer current detection unit that detects the amount of current flowing through the primary transfer roller 11a when a bias is applied to the black primary transfer roller 11a. The other primary transfer rollers 11b, 11c, and 11d are energized by a primary transfer power supply 29FC for colors. The primary transfer power supply 29FC for colors is connected to the engine control unit 930.

[0029] The engine control unit 930 sets the primary transfer voltages of all the primary transfer rollers 11a, 11b, 11c, and 11d based on the detection result by the detection unit , that is, the current value detected by the detection unit .

[0030] In this embodiment, the detection unit 28 is connected only to the primary transfer roller 11a corresponding to the Bk (black) photosensitive member 1a, detects the amount of current flowing through this primary transfer roller 11a, and sets the primary transfer voltage for all primary transfer rollers 11a, 11b, 11c, and 11d. This allows the image forming apparatus 100 to have only one detection unit 28, thereby reducing the costs of the intermediate transfer unit configuration and resistance detection configuration.

[0031] As described above, the color primary transfer rollers 11b, 11c, and 11d are moved away from the photoconductors 1b, 1c, and 1d by the contact / separation mechanism in the black monochrome mode. However, the Bk (black) primary transfer roller 11a is always located in the same position, and the contact relationship between the black photoconductor 1a and the intermediate transfer belt 3 and the contact relationship between the primary transfer roller 11a and the intermediate transfer belt 3 are stable. Therefore, the detection unit 28 can stably detect the amount of current by detecting the amount of current flowing through the Bk (black) primary transfer roller 11a among the four primary transfer rollers 11a to 11d.

[0032] Furthermore, by using an indirect transfer system and a metal roller as the primary transfer roller, it is no longer necessary to control the target value of the transfer bias over time or whenever the environment changes, which means there is no need to drive the intermediate transfer belt or photosensitive member each time, thereby extending the life of the intermediate transfer belt 3 and photosensitive member.

[0033] FIG. 2 is a diagram showing the hardware configuration of the image forming apparatus 100. As shown in FIG. As shown in FIG. 2, the image forming apparatus 100 includes a controller 910, a short-range communication circuit 920, an engine control unit 930, an operation panel 940, and a network I / F 950.

[0034] The controller 910 controls the entire image forming apparatus 100, for example, controlling drawing, communication, input from the operation panel 940, and the like. The controller 910 has a CPU 901, which is the main part of the computer, a system memory (MEM-P) 902, a north bridge (NB) 903, a south bridge (SB) 904, an ASIC (Application Specific Integrated Circuit) 906, a local memory (MEM-C) 907, which is a storage unit, an HDD controller 908, and an HD 909, which is also a storage unit. The NB 903 and the ASIC 906 are connected by an AGP (Accelerated Graphics Port) bus 921.

[0035] The CPU 901 is a control unit that performs overall control of the image forming apparatus. The NB 903 is a bridge that connects the CPU 901 with the MEM-P 902, the SB 904, and the AGP bus 921, and includes a memory controller that controls reading and writing to the MEM-P 902, a PCI (Peripheral Component Interconnect) master, and an AGP target.

[0036] The MEM-P 902 comprises a ROM 902a, which is memory for storing programs and data that realize the functions of the controller 910, and a RAM 902b, which is used for expanding the programs and data and as a drawing memory during memory printing. The programs stored in the RAM 902b may be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, CD-R, or DVD.

[0037] The SB 904 is a bridge for connecting the NB 903 with PCI devices and peripheral devices. The ASIC 906 is an integrated circuit (IC) for image processing applications that has hardware elements for image processing and functions as a bridge connecting the AGP bus 921, PCI bus 922, HDD controller 908, and MEM-C 907. The ASIC 906 includes a PCI target and AGP master, an arbiter (ARB) that forms the core of the ASIC 906, a memory controller that controls the MEM-C 907, multiple direct memory access controllers (DMACs) that perform image data rotation using hardware logic, and a PCI unit that transfers data between the printer unit 932 and the ASIC 906 via the PCI bus 922. A Universal Serial Bus (USB) interface or an Institute of Electrical and Electronics Engineers 1394 (IEEE 1394) interface may also be connected to the ASIC 906.

[0038] The MEM-C907 is a local memory used as an image buffer for copying and a code buffer. The HD909 is a storage for storing image data, font data used during printing, and forms. The HD909 controls the reading and writing of data from and to the HD909 under the control of the CPU901. The AGP bus 921 is a bus interface for a graphics accelerator card proposed to speed up graphics processing. By directly accessing the MEM-P902 at high throughput, the graphics accelerator card can be made faster. Further, the short-distance communication circuit 920 includes a short-distance communication circuit 920a. The short-distance communication circuit 920 is a communication circuit such as NFC or Bluetooth (registered trademark).

[0039] The engine control unit 930 controls the image forming operation by controlling the printer unit 932. The printer unit 932 includes various devices for forming an image on the recording medium P, such as a drive unit that rotates the photosensitive member, a drive unit that rotates the intermediate transfer belt, and the developing device 10. The printer unit 932 also includes an image processing unit that performs error diffusion, gamma conversion, etc.

[0040] The operation panel 940, which serves as an operation input unit, includes a panel display unit 940a and an operation unit 940b. The panel display unit 940a displays current setting values, selection screens, etc., and is configured with a touch panel or the like that receives input from the operator. The operation unit 940b includes a numeric keypad that receives setting values ​​for image formation conditions such as density setting conditions, and a start key that receives a copy start instruction.

[0041] Image forming apparatus 100 can sequentially switch among the document box function, printer function, and facsimile function using the application switching key on operation panel 940. When the document box function is selected, the document box mode is selected, when the printer function is selected, the printer mode is selected, and when the facsimile mode is selected, the facsimile mode is selected.

[0042] The network I / F 950 is an interface for performing data communication using a communication network. The short-range communication circuit 920 and the network I / F 950 are electrically connected to the ASIC 906 via a PCI bus 922.

[0043] FIG. 3 is a functional block diagram of the image forming apparatus 100 for realizing a flow shown in FIG. 11, which will be described later. 3, image forming apparatus 100 includes a primary transfer current detection unit 32, an operation input unit 33, a control unit 31, and an intermediate transfer member usage status storage unit 38. Furthermore, control unit 31 includes a primary transfer voltage setting control unit 34 and a primary transfer voltage calculation unit 35.

[0044] The control unit 31 is an engine control unit 930 that controls the printer unit 932 to control the image forming operation. The primary transfer current detection unit 32 is a detection unit 28 that detects the value of a current flowing through a primary transfer member such as a primary transfer roller 11 that performs primary transfer of a toner image on an image carrier such as a photosensitive member 1 onto an intermediate transfer member such as an intermediate transfer belt 3 at a primary transfer unit.

[0045] The operation input unit 33 is an operation panel 940 that accepts operation inputs from the user, etc. The image density detection unit 36 ​​is an optical sensor 22 that detects the image density of a toner image carried on an image carrier or an intermediate transfer body, etc.

[0046] The primary transfer voltage setting control unit 34 sets the primary transfer voltage to be applied to the primary transfer member based on the current value flowing through the primary transfer member, such as the primary transfer roller 11, detected by a primary transfer current detection unit 32, such as the detection unit 28.

[0047] The primary transfer voltage calculation unit 35 calculates the primary transfer voltage to be set using a conversion formula that converts a current value detected by a primary transfer current detection unit such as the detection unit 28 into a primary transfer voltage. The intermediate transfer member usage status storage unit 38 is a storage unit such as HD909 that stores the usage status of the intermediate transfer member such as the intermediate transfer belt 3, including the number of prints made since the start of use of the intermediate transfer member.

[0048] FIG. 4 is a functional block diagram of the image forming apparatus 100 for realizing a flow shown in FIG. 12, which will be described later. 4, image forming apparatus 100 includes a primary transfer current detection unit 32, an operation input unit 33, a control unit 31, an intermediate transfer member usage status storage unit 38, and an image density detection unit 36. Furthermore, control unit 31 includes a primary transfer voltage setting control unit 34, a primary transfer voltage calculation unit 35, and an image density adjustment control unit 37.

[0049] The control unit 31 is an engine control unit 930 that controls the printer unit 932 to control the image forming operation. The primary transfer current detection unit 32 is a detection unit 28 that detects the value of a current flowing through a primary transfer member such as a primary transfer roller 11 that performs primary transfer of a toner image on an image carrier such as a photosensitive member 1 onto an intermediate transfer member such as an intermediate transfer belt 3 at a primary transfer unit.

[0050] The operation input unit 33 is an operation panel 940 that accepts operation inputs from the user, etc. The image density detection unit 36 ​​is an optical sensor 22 that detects the image density of a toner image carried on an image carrier or an intermediate transfer body, etc.

[0051] The primary transfer voltage setting control unit 34 sets the primary transfer voltage to be applied to the primary transfer member based on the current value flowing through the primary transfer member, such as the primary transfer roller 11, detected by a primary transfer current detection unit 32, such as the detection unit 28.

[0052] The primary transfer voltage calculation unit 35 calculates the primary transfer voltage to be set using a conversion formula that converts a current value detected by a primary transfer current detection unit such as the detection unit 28 into a primary transfer voltage. The intermediate transfer member usage status storage unit 38 is a storage unit such as HD909 that stores the usage status of the intermediate transfer member such as the intermediate transfer belt 3, including the number of prints made since the start of use of the intermediate transfer member.

[0053] The image density adjustment control unit 37 detects the image density of a toner image carried on an image carrier such as a photosensitive member 1 or an intermediate transfer member such as an intermediate transfer belt 3 using an image density detection unit 36 ​​such as an optical sensor 22, and performs control such as process control to adjust the image formation conditions of an image forming means (consisting of a charging device 8, an exposure device 9, a developing device 10, etc.) that forms a toner image on the image carrier based on the detection result of the image density detection unit 36.

[0054] FIG. 5 is a graph showing the relationship between the primary transfer voltage and the transfer rate. The relationship between the primary transfer voltage and the transfer rate differs depending on whether the surface resistivity of the intermediate transfer belt 3 is 9.5 Log Ω / □, 9.7 Log Ω / □, 10.0 Log Ω / □, or 10.2 Log Ω / □, and therefore the optimal transfer voltage at which the transfer rate is maximized also changes, as indicated by the four arrows. Therefore, when the primary transfer power supply 27BK for Bk is under constant voltage control, the optimal primary transfer voltage changes depending on the surface resistivity of the intermediate transfer belt 3. For this reason, the primary transfer voltage must be set based on the surface resistivity of the intermediate transfer belt.

[0055] The surface resistivity of the intermediate transfer belt 3 can be estimated based on the average current value detected by the detection unit 28 when a predetermined bias (2000 V) is applied to the intermediate transfer belt for approximately one revolution. This makes it possible to set the primary transfer voltage value to be applied to the primary transfer roller 11a to an optimal value that maximizes the transfer rate, based on the average current value detected by the detection unit 28.

[0056] FIG. 6 is a graph showing the relationship between the surface resistivity of the intermediate transfer belt and the detected current. The detected current value in FIG. 6 is the average current value detected by the detection unit 28 when a predetermined bias (2000 V) is applied over approximately one revolution of the intermediate transfer belt. As shown in FIG. 6, it can be seen that the larger the detection current, the smaller the surface resistivity of the intermediate transfer belt.

[0057] In this embodiment, the primary transfer power supply 27BK for Bk and the detection unit 28 are used to detect the current flowing through the primary transfer roller 11a for Bk, and the primary transfer voltage to be applied to the primary transfer rollers 11a, 11b, 11c, and 11d of the four colors Y, M, C, and Bk is set.

[0058] There are two possible methods for setting the primary transfer voltage based on the average current value detected by the detection unit 28. The first method is to set a fixed value for the primary transfer voltage value Y in accordance with the magnitude of the detected current value X based on the detected current value X (also referred to as the "detected current value X") and the bias table shown in FIG. 7. The bias table shown in FIG. 7 is stored in the HD 909, which is a storage unit.

[0059] 7, the magnitude of the detected current value X is divided into four ranges, and four corresponding primary transfer voltage values ​​Y1, Y2, Y3, and Y4 are defined. By using this method, the engine control unit 930 only needs to select one of four fixed values ​​as the primary transfer voltage value Y depending on the magnitude of the detected current value X, which simplifies the control of setting the primary transfer voltage value Y.

[0060] The second method is to use a conversion formula to find the primary transfer voltage value Y from the detected current value X. Fig. 8 is a graph showing the conversion formula. As shown in FIG. 8, the conversion formula is a quadratic function, and the inventors have verified that the best fit (the optimum transfer voltage for maximizing the transfer rate) is achieved by using this quadratic conversion formula.

[0061] The quadratic function (transformation formula) shown in Figure 8 is Y=A1*X 2 +B1*X+C(A1≠0). That is, the conversion formula is a quadratic function with the detected current value X as the independent variable. Here, A1=0.5, B1=-77, and C=3700. When X=50[uA], Y=1100[V]. However, the optimum conversion formula varies depending on the conditions around the primary transfer section, such as the distance between the photosensitive member 1 and the primary transfer roller 11 and the type of toner used.

[0062] According to this second method, the engine control unit 930 can determine the optimum primary transfer voltage value Y in more detail in response to variations in the surface resistivity of the intermediate transfer belt.

[0063] Also, as shown in FIG. 9, the conversion formula may be changed depending on the range of the detected current value X. In the example shown in Figure 9, two conversion formulas are used: If X<50[μA], Y=A2*X 2 +B2*X+C2(A2≠0), When X≧50[μA], Y=D2*X+E2(D2≠0). That is, the conversion formula for calculating the primary transfer voltage value Y is determined by a plurality of conversion formulas that correspond to the magnitude of the detected current value X and that use the detected current value X as a variable. Here, A2=0.5, B2=-77, C2=3700, D2=-22, and E2=2200. Therefore, when X=60[μA], Y=880[V].

[0064] In this way, by changing the conversion formula in accordance with the detected current value, it is possible to determine the optimum primary transfer voltage value corresponding to the variation in the surface resistance value of the intermediate transfer belt in more detail.

[0065] Furthermore, in the above, the standard primary transfer voltage value Y is calculated using the conversion formula, but depending on the usage environment and belt linear speed (paper type and mode), the primary transfer voltage value Y may be set by further multiplying the detected current value X by a correction coefficient for the usage environment and belt linear speed.

[0066] FIG. 10 is a flow diagram of primary transfer voltage setting control. When the primary transfer voltage setting control operation is started (S1), the intermediate transfer belt 3 is driven (S2). Next, the engine control unit 930 controls the primary transfer power supply 27BK for Bk to apply a constant voltage (2000 V) to the primary transfer roller 11 (S3). Here, in this embodiment, the primary transfer roller to which the voltage is applied is the primary transfer roller 11a, but it may be another primary transfer roller. At this time, the detection unit 28 detects the current flowing through the primary transfer roller 11 (S4).

[0067] Next, the engine control unit 930 detects the current over approximately one revolution of the intermediate transfer belt using the detection unit 28 and calculates the detected current value X (average current value). Then, based on the detected current value X, the engine control unit 930 calculates the primary transfer voltage to be applied during normal printing using one of the methods shown in FIGS. 7 and 8 (S5). Here, the primary transfer voltage is the primary transfer voltage value for the primary transfer rollers 11a, 11b, 11c, and 11d corresponding to all colors. As a result, the primary transfer voltage to be applied during normal printing is determined for all primary transfer rollers 11a, 11b, 11c, and 11d (S6).

[0068] 10 is performed when replacing the intermediate transfer belt 3. This is because replacing the intermediate transfer belt 3 changes the surface resistance value of the intermediate transfer belt 3, which changes the optimal primary transfer voltage at which the transfer rate is highest.

[0069] In this embodiment, primary transfer voltage setting control is performed every predetermined number of prints. This is because the surface resistivity of the intermediate transfer belt 3 changes with continued use, and the optimal primary transfer voltage at which the transfer rate is highest changes. In this embodiment, primary transfer voltage setting control is performed every 10,000 prints. Specifically, as will be described later, the print count counter value of the intermediate transfer unit, which counts the number of prints since the intermediate transfer unit (intermediate transfer belt) began to be used, is stored in a storage unit such as the HD 909. Primary transfer voltage setting control is performed based on this counter value.

[0070] If the surface resistivity of the intermediate transfer belt remains almost constant over time, the primary transfer voltage setting control may be performed only when the intermediate transfer belt is replaced. This minimizes the travel distance of the intermediate transfer belt and photosensitive member, thereby extending the life of other components.

[0071] In this embodiment, the intermediate transfer belt 3 is replaced by replacing an intermediate transfer unit that integrates the intermediate transfer belt 3, primary transfer rollers 11a to 11d, cleaning blade 21, etc. However, the intermediate transfer belt 3 may be replaced by itself.

[0072] Whether the intermediate transfer unit (intermediate transfer belt 3) has been replaced is determined based on intermediate transfer unit replacement information input by the user through the operation panel 940 when replacing the intermediate transfer unit. Specifically, in this embodiment, to understand the usage status of the intermediate transfer unit (intermediate transfer belt), the number of printed pages since the intermediate transfer unit began to be used is counted, and this counter value is stored in a storage unit such as the HD 909. After replacing the intermediate transfer unit (intermediate transfer belt), the user operates the operation panel 940 to press the counter reset button displayed on the panel display unit 940a to reset the printed page count counter value of the intermediate transfer unit. The counter reset information input as intermediate transfer belt replacement information through the operation panel 940 triggers execution of primary transfer voltage setting control when the intermediate transfer unit (intermediate transfer belt) is replaced. In this way, executing primary transfer voltage setting control when counter reset information is input through the operation panel 940 has the advantage of allowing the first print job after the intermediate transfer belt replacement to start without waiting.

[0073] However, some users may mistakenly perform the replacement procedure and press the counter reset button on the operation panel 940 before replacing the intermediate transfer unit (intermediate transfer belt). In this case, the primary transfer voltage setting control may be performed with the old intermediate transfer belt 3 still installed, and then the intermediate transfer unit (intermediate transfer belt) may be replaced. This may result in image formation being performed at an inappropriate primary transfer voltage with a poor transfer rate until the next primary transfer voltage setting control is performed (10,000 sheets printed). As a result, the image density printed on the recording medium may be lighter than the desired image density. Furthermore, much of the toner is not primarily transferred from the photoconductor to the intermediate transfer belt, resulting in residual toner. This results in wasted toner consumption until the next primary transfer voltage setting control is performed.

[0074] For example, a detection mechanism consisting of an IC tag provided in the intermediate transfer unit and a detection unit that detects the IC tag provided in the image forming apparatus can detect replacement of the intermediate transfer unit (intermediate transfer belt) and perform primary transfer voltage setting control, thereby preventing the primary transfer voltage from being set to an inappropriate value. However, providing a detection mechanism may increase the number of parts, which may lead to an increase in the cost of the image forming apparatus.

[0075] Therefore, in this embodiment, the primary transfer voltage setting control is performed again after the first print job (image forming operation) is completed after the intermediate transfer unit (intermediate transfer belt) is replaced.

[0076] FIG. 11 is a flowchart of primary transfer voltage setting control when the intermediate transfer unit is replaced in this embodiment. First, when a counter reset of the intermediate transfer unit is input as intermediate transfer member replacement information through the operation panel 940 (S11), the same primary transfer voltage setting control operation as that shown in FIG. 10 is executed. Specifically, the intermediate transfer belt 3 is driven (S12), a constant voltage (2000 V) is applied to the primary transfer roller 11 (S13), and the current flowing through the primary transfer roller 11 is detected by the detection unit 28 (S14). Next, based on the detected current value X (average current value) detected by the detection unit 28, the primary transfer voltage to be applied during normal printing is calculated using one of the methods shown in FIGS. 7 and 8 (S15). The calculated primary transfer voltage is set as the primary transfer voltage for Y, M, C, and Bk (S16).

[0077] Next, the first print job after the replacement of the intermediate transfer unit (intermediate transfer belt) is started (S17), and when the print job is finished (S18), the primary transfer voltage setting control is executed again (S19-S23). Whether or not this is the first print job can be determined by checking the value of the print count counter of the intermediate transfer unit, which indicates the usage status of the intermediate transfer belt and is stored in a storage unit such as the HD909. Specifically, when the print job starts, the value of the print count counter of the intermediate transfer unit is checked, and if the counter value is 0, it can be determined that this print job is the first print job after the replacement of the intermediate transfer belt.

[0078] In this way, by performing primary transfer voltage setting control again after the first print job (image formation operation) after replacing the intermediate transfer unit (intermediate transfer belt), the primary transfer voltage setting control, triggered by the user's operation of the counter reset button, is performed on the previous intermediate transfer belt. Even if the set primary transfer voltage becomes an inappropriate value, printing at the inappropriate value will only be performed for the first print job. As a result, from the next print job onwards, primary transfer is performed at the optimal primary transfer voltage (the primary transfer voltage that maximizes the transfer rate) according to the surface resistivity of the replaced intermediate transfer belt, preventing image density from becoming low or an increase in residual toner from being transferred. Furthermore, because primary transfer voltage setting control is performed after the print job is completed, a long first print time can be prevented, preventing users from having to wait.

[0079] Furthermore, the first print job after replacing the intermediate transfer unit (intermediate transfer belt) is to print a test pattern, and a screen is displayed on the panel display unit 940a of the operation panel 940 to prompt the user to confirm whether the image density of the test pattern is low. If the user determines that the image density is low after viewing the printed test pattern, the user operates the operation panel 940 to instruct the primary transfer voltage setting control to be executed again. The engine control unit may be configured to execute the primary transfer voltage setting control when instructed to do so.

[0080] In FIG. 11 , primary transfer voltage setting control is performed again after the first print job (image forming operation) after replacing the intermediate transfer unit (intermediate transfer belt). However, primary transfer voltage setting control may also be performed again after the first process control after replacing the intermediate transfer unit. In this embodiment, process control is performed every 30 printed sheets. Some printer models perform process control at intervals longer than 30 sheets, but process control is performed at a maximum of every 200 sheets. In this manner, process control is performed at much shorter intervals than primary transfer voltage setting control, which is performed every 10,000 sheets. Therefore, by performing primary transfer voltage setting control again after the first process control after replacing the intermediate transfer unit, an appropriate primary transfer voltage can be set earlier than the timing of the next primary transfer voltage setting control.

[0081] FIG. 12 is a flowchart showing the process of executing the primary transfer voltage setting control again after the first process control is executed after the intermediate transfer unit (intermediate transfer belt) is replaced. As shown in FIG. 12, primary transfer voltage setting control is performed using the user's operation of the counter reset button as a trigger, and the primary transfer voltages to be applied to the primary transfer rollers 11a to 11d are set (S31 to S36).

[0082] Thereafter, when a predetermined number of sheets have been printed and it is time to execute process control (Yes in S39), the first process control after replacement of the intermediate transfer unit (intermediate transfer belt) is executed (S40). Whether the process control being executed is the first process control after replacement of the intermediate transfer unit (intermediate transfer belt) can be determined, for example, as follows. That is, if the value of the print count counter for the intermediate transfer unit stored in a storage unit such as the HD909 is less than the number of prints during the execution interval of the process control, it can be determined that it is time to execute the first process control. Also, a flag is set when the counter for the print count for the intermediate transfer unit is reset. Then, if the flag is set when the process control is executed, it may be determined that the process control is the first process control after replacement of the intermediate transfer unit (intermediate transfer belt).

[0083] Then, after the first process control is performed after the intermediate transfer unit (intermediate transfer belt) is replaced, the primary transfer voltage setting control is performed again, and the primary transfer voltages are set for the primary transfer rollers 11a to 11d (S41 to S45).

[0084] In the above description, the primary transfer voltage setting control is performed after the process control is performed, but the process control may be performed after the primary transfer voltage setting control is performed. Specifically, when the timing for performing the process control arrives, it is determined whether the process control to be performed is the first process control after the replacement of the intermediate transfer unit (intermediate transfer belt). If it is the first process control after the replacement of the intermediate transfer unit (intermediate transfer belt), the primary transfer voltage setting control is performed before the process control is performed. This allows the process control to be performed with the primary transfer voltage set appropriately, enabling accurate adjustment of the image density.

[0085] In the primary transfer voltage setting control, the photoconductor surface may be uniformly charged by the charging device 8 and current detection may be performed. During primary transfer, the primary transfer current flowing varies depending on the surface potential of the photoconductor, thereby changing the transfer rate. Therefore, by uniformly charging the photoconductor surface by the charging device 8 and detecting the current, and setting the primary transfer voltage based on the detected current value, the primary transfer voltage can be set taking into account the electrical resistance of the intermediate transfer belt 3 and the surface potential of the photoconductor during primary transfer. This allows for a more optimal primary transfer voltage to be set. In the primary transfer voltage setting control in which the photoconductor surface is uniformly charged by the charging device 8 and current detection is performed, it is preferable to perform the primary transfer voltage setting control after the first process control is performed after replacing the intermediate transfer unit (intermediate transfer belt), as shown in the flow chart in Figure 12. In this way, in the primary transfer voltage setting control, the photoconductor surface is uniformly charged with the charging bias optimized by the process control and current detection is performed. This allows for a more optimal primary transfer voltage to be set.

[0086] When current detection for primary transfer voltage setting control is performed by uniformly charging the photosensitive drum surface with charging device 8, it is more preferable to perform primary transfer voltage setting control before the start and after the end of the first process control. This allows for accurate adjustment of image density and a more optimal primary transfer voltage to be set.

[0087] In the above description, the counter value of the number of printed sheets since the start of use of the intermediate transfer unit (intermediate transfer belt) is used as information for understanding the usage status of the intermediate transfer unit (intermediate transfer belt), but this is not limited to this. For example, the cumulative travel distance of the intermediate transfer belt or the cumulative drive time of the drive motor that drives the intermediate transfer belt may also be used as information for understanding the usage status of the intermediate transfer unit (intermediate transfer belt). If the usage status of the intermediate transfer unit (intermediate transfer belt) is understood based on the cumulative travel distance of the intermediate transfer belt, when the intermediate transfer unit (intermediate transfer belt) is replaced, the cumulative travel distance is reset by operating the operation panel. Then, the cumulative travel distance reset information input through the operation panel is acquired as intermediate transfer unit replacement information, and primary transfer voltage setting control is performed.

[0088] In addition, when the usage status of the intermediate transfer unit (intermediate transfer belt) is grasped based on the cumulative drive time of the drive motor that drives the intermediate transfer belt, when the intermediate transfer unit (intermediate transfer belt) is replaced, the cumulative drive time is reset by operating the operation panel. Then, the reset information of the cumulative travel distance input through the operation panel is acquired as intermediate transfer unit replacement information, and primary transfer voltage setting control is performed.

[0089] As described above, the image forming apparatus 100 according to the embodiment is provided with only one detector 28 that detects the value of the current that flows through the primary transfer roller 11a for Bk when a constant voltage is applied to the primary transfer roller 11a for Bk from the primary transfer power supply for Bk. The primary transfer voltage value Y corresponding to all colors is determined based on the detected current result, thereby reducing the cost of the image forming apparatus.

[0090] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise specifically limited in the above description, various modifications and variations are possible within the spirit and scope of the present invention as set forth in the claims.

[0091] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) In an image forming apparatus including a primary transfer member such as a primary transfer roller 11 to which a primary transfer voltage is applied and which primarily transfers a toner image on an image carrier such as a photosensitive member 1 onto an intermediate transfer member such as an intermediate transfer belt 3 at a primary transfer unit, a control unit such as an engine control unit 930 which performs primary transfer voltage setting control to set the primary transfer voltage to be applied to the primary transfer member based on the current value flowing through the primary transfer member detected by a primary transfer current detection unit such as a detection unit 28, and an operation input unit such as an operation panel 940 which accepts user operation input, the control unit performs primary transfer voltage setting control at the timing when intermediate transfer member replacement information is input through the operation input unit and at the timing after the first image formation after the intermediate transfer member is replaced. As described in the aforementioned Patent Document 1, a technique is known in which primary transfer voltage setting control is performed in conjunction with the first image formation after input of intermediate transfer body replacement information. By the time the first image formation is performed after input of the replacement information, the intermediate transfer body replacement operation is usually completed. Therefore, unlike a technique in which primary transfer voltage setting control is performed when the replacement information is input, this technique has the following advantage. Specifically, if the replacement information is input before the actual replacement operation, as opposed to the usual procedure of inputting the replacement information, the primary transfer voltage setting control can be performed using the previous intermediate transfer body, preventing the use of an inappropriate primary transfer voltage for the replaced intermediate transfer body in image formation using the replaced intermediate transfer body. If the interval between primary transfer voltage control operations is long, an inappropriate primary transfer voltage would continue to be used until the next primary transfer setting control operation. This is a significant advantage in avoiding this situation. However, in Patent Document 1, when forming the first image after replacing the intermediate transfer body, the primary transfer voltage setting control is performed before starting image formation, which causes a problem in that the first print is delayed because the primary transfer voltage control operation is inserted between the first image formation instruction and the start of image formation. According to the present invention, primary transfer voltage control is performed in conjunction with the first image formation after replacement of the intermediate transfer body. Therefore, as with Patent Document 1, even if replacement information is input first, which is the opposite of the normal order, image formation can be performed with the optimal primary transfer voltage after the first image formation after replacement. Moreover, since primary transfer voltage setting is performed after the first image formation, delays in the first print of the first image formation can be prevented. Furthermore, since primary transfer voltage setting is also performed when replacement information is input, the present invention allows the first image formation after replacement to be performed with the optimal primary transfer voltage if replacement and input are performed in the normal order. If the exchange input is performed in the reverse order, the first image formation will be performed with an inappropriate primary transfer voltage, but as described above, subsequent image formation will be performed with an appropriate primary transfer voltage, and it is possible to avoid the situation where an inappropriate primary transfer voltage is continued to be used until the next primary transfer voltage setting control.

[0092] (Aspect 2) In an image forming apparatus including a primary transfer member such as a primary transfer roller 11 to which a primary transfer voltage is applied and which primarily transfers a toner image on an image carrier such as a photosensitive member 1 to an intermediate transfer member such as an intermediate transfer belt 3 in a primary transfer unit, a control unit such as an engine control unit 930 which performs primary transfer voltage setting control to set the primary transfer voltage to be applied to the primary transfer member based on a current value flowing through the primary transfer member detected by a primary transfer current detection unit such as a detection unit 28, and an operation input unit such as an operation panel 940 which accepts operation inputs from a user, the control unit such as the engine control unit 930 controls the primary transfer voltage setting control to set the primary transfer voltage to be applied to the primary transfer member based on a current value flowing through the primary transfer member detected by a primary transfer current detection unit such as a detection unit 28, The image density of the toner image held on the image carrier is detected by an image density detection unit such as an optical sensor 22, and image density adjustment control such as process control that adjusts the image formation conditions of the image formation means that forms a toner image on the image carrier based on the detection result of the image density detection unit is executed at intervals shorter than the primary transfer voltage setting control, and the control unit executes the primary transfer voltage setting control at the timing when intermediate transfer body replacement information is input through the operation input unit, the timing when the first image density adjustment control is executed after the intermediate transfer body is replaced, or the timing when the first image density adjustment control is completed after the intermediate transfer body is replaced. According to this, as explained with reference to FIG. 12, primary transfer voltage setting control is performed again during image density adjustment control, such as the first process control, after intermediate transfer body replacement. As a result, even if intermediate transfer body replacement information is erroneously entered before intermediate transfer body replacement and primary transfer voltage setting control is performed before the intermediate transfer body is replaced, printing at an inappropriate primary transfer voltage can be performed by the time of the first image density adjustment control after intermediate transfer body replacement. This makes it possible to set an appropriate primary transfer voltage at a timing earlier than the timing of the next primary transfer voltage setting control or the timing of the next intermediate transfer body replacement, thereby preventing unnecessary toner consumption and printing of images with low image density.

[0093] (Aspect 3) In aspect 1 or 2, there are provided a plurality of image carriers such as photosensitive bodies that carry toner images of different colors, and a plurality of primary transfer members such as primary transfer rollers that are provided corresponding to each image carrier, and a primary transfer current detection unit such as detection unit 28 detects the current flowing through one of the plurality of primary transfer members, and sets the primary transfer voltages of all primary transfer members based on the current value detected by the primary transfer current detection unit. This allows for a reduction in the number of parts and costs compared to providing a primary transfer current detection unit for each primary transfer member and using each primary transfer current detection unit to set the primary transfer voltage for each primary transfer member, as described in the embodiment.

[0094] (Aspect 4) In the third embodiment, the primary transfer member whose current is detected by a primary transfer current detection unit such as detection unit 28 is a black primary transfer member. According to this, primary transfer members such as the primary transfer rollers for the colors Y, M, and C are moved by a contact / separation mechanism in a direction away from the corresponding photosensitive member in black monochrome mode, but primary transfer members such as black primary transfer roller 11a are always located in the same position, and the contact relationship between photosensitive member 1a and the intermediate transfer member and the contact relationship between the primary transfer member and the intermediate transfer belt are stable. Therefore, by detecting the value of the current flowing through the black primary transfer member with a primary transfer current detection unit, the current value can be detected stably.

[0095] (Aspect 5) In any of aspects 1 to 4, a memory unit such as HD909 is provided that stores the usage status of the intermediate transfer body, such as the number of pages printed since the start of use of the intermediate transfer belt, and the intermediate transfer body replacement information is reset information that resets the usage status input through the operation input unit. According to this, when the intermediate transfer body is replaced, reset information for resetting the usage status of the intermediate transfer body is input through the operation input unit. Therefore, by using the reset information as intermediate transfer body replacement information, it is possible to easily grasp that the intermediate transfer body has been replaced.

[0096] (Aspect 6) In the fifth aspect, the usage status is the number of prints made since the intermediate transfer member was first used. This makes it possible to know how much the intermediate transfer member is being used from the number of printed sheets.

[0097] (Aspect 7) In any of the first to sixth aspects, the engine control unit controls the setting of the primary transfer voltage based on the number of printed sheets. As a result, as described in the embodiment, the optimal primary transfer voltage can be set to maximize transfer efficiency in accordance with changes in the electrical resistance of the intermediate transfer body due to repeated use, thereby suppressing reductions in image density and unnecessary toner consumption over time.

[0098] (Aspect 8) In any of the first to seventh aspects, the primary transfer voltage to be set is calculated using a conversion formula that converts a current value detected by a primary transfer current detection unit such as detection unit 28 into a primary transfer voltage. This allows the optimal primary transfer voltage to be set more precisely than when, as described in the embodiment, the detected primary transfer current is divided into multiple ranges and a fixed primary transfer voltage is set for each range. [Explanation of symbols]

[0099] 1: Photoreceptor 3: Intermediate transfer belt 11: Primary transfer roller 22: Optical sensor 27BK: Primary transfer power supply 28:Detection unit 29FC: Primary transfer power supply 100: Image forming device 910: Controller 930: Engine control unit 940: Operation panel 940a: Panel display 940b:Operation unit P: Recording medium X: Detected current value Y: Primary transfer voltage value [Prior art documents] [Patent documents]

[0100] [Patent Document 1] Japanese Patent Application Publication No. 2017-211636

Claims

1. a primary transfer member to which a primary transfer voltage is applied and which primarily transfers the toner image on the image carrier to the intermediate transfer member at a primary transfer portion; a control unit that performs primary transfer voltage setting control to set the primary transfer voltage based on a current value flowing through the primary transfer member detected by a primary transfer current detection unit; An image forming apparatus including an operation input unit that accepts operation input from a user, The image forming apparatus is characterized in that the control unit performs the primary transfer voltage setting control at the timing when intermediate transfer body replacement information is input through the operation input unit and at the timing after the first image formation after the intermediate transfer body is replaced.

2. a primary transfer member to which a primary transfer voltage is applied and which primarily transfers the toner image on the image carrier to the intermediate transfer member at a primary transfer portion; a control unit that performs primary transfer voltage setting control to set the primary transfer voltage based on a current value flowing through the primary transfer member detected by a primary transfer current detection unit; An image forming apparatus including an operation input unit that accepts operation input from a user, an image density detection unit detects the image density of the toner image carried on the image carrier or the intermediate transfer body, and performs image density adjustment control, which adjusts image forming conditions of an image forming unit that forms the toner image on the image carrier based on the detection result of the image density detection unit, at intervals shorter than that of the primary transfer voltage setting control; The control unit executes the primary transfer voltage setting control at the timing when intermediate transfer body replacement information is input through the operation input unit, and at the timing when the first image density adjustment control is performed after the intermediate transfer body is replaced, or at the timing when the first image density adjustment control is completed after the intermediate transfer body is replaced.

3. 3. The image forming apparatus according to claim 1, a plurality of image carriers carrying toner images of different colors; a plurality of primary transfer members provided corresponding to the respective image carriers; the primary transfer current detection unit detects a current flowing through one of the plurality of primary transfer members; an image forming apparatus, wherein the primary transfer voltages of all primary transfer members are set based on the current values ​​detected by the primary transfer current detection unit;

4. 4. The image forming apparatus according to claim 3, 10. An image forming apparatus according to claim 9, wherein the primary transfer member, the current of which is detected by the primary transfer current detection unit, is a black primary transfer member.

5. 3. The image forming apparatus according to claim 1, a storage unit for storing the usage status of the intermediate transfer member; The image forming apparatus is characterized in that the intermediate transfer member replacement information is reset information inputted through the operation input unit to reset the usage status.

6. 6. The image forming apparatus according to claim 5, The image forming apparatus is characterized in that the usage status is the number of prints made since the intermediate transfer member was first used.

7. 3. The image forming apparatus according to claim 1, The image forming apparatus is characterized in that the control unit controls the setting of the primary transfer voltage based on the number of prints.

8. 3. The image forming apparatus according to claim 1, an image forming apparatus, wherein a primary transfer voltage to be set is calculated using a conversion formula for converting a current value detected by the primary transfer current detection unit into the primary transfer voltage;

Images