Image formation apparatus, method for controlling image formation apparatus, and control program

Abstract

To provide: an image formation apparatus capable of improving the measurement accuracy of surface potential; a method for controlling the image formation apparatus; and a control program.SOLUTION: An image formation apparatus includes an image formation part and a potential measurement processing part. The image formation part applies bias voltage (development bias Vb1) between a first carrier (a developing roller 343A) and a second carrier (a photoreceptor drum 341) to move toner from the first carrier to the second carrier and form an image on the second carrier; the potential measurement processing part measures the surface potential of the first carrier or the second carrier on the basis of a target current (a development current Ib1) flowing between the first and second carriers and measures the surface potential on the basis of a premeasured leakage current between the first and second carriers.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a control method for an image forming apparatus, and a control program. [Background technology]

[0002] As a related technique, a technique is known in which the surface potential on a photoconductor is determined and fed back to control the charging of the photoconductor in an image forming apparatus (see, for example, Patent Document 1). That is, in an electrophotographic image forming apparatus (electrophotographic apparatus), a charged photoconductor is exposed to light based on image data, and an electrostatic latent image is formed on the photoconductor. Then, the image forming apparatus applies a bias voltage to a developing roller and supplies charged toner to the photoconductor in accordance with the electric field between the photoconductor and the developing roller, thereby causing the toner to adhere to the exposed portion of the photoconductor, developing the electrostatic latent image on the photoconductor and forming an image.

[0003] In this type of image forming apparatus, fluctuations in the surface potential (charge potential) of the photoconductor affect image quality, so in an image forming apparatus according to related technology, the surface potential of the photoconductor is determined and the charging of the photoconductor is controlled to obtain a constant surface potential. One method involves detecting the development current that flows from the development roller to the photoconductor when a bias voltage is applied to the development roller, and estimating the surface potential based on this development current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-295540 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method of estimating the surface potential based on the development current, for example, in a high-temperature and high-humidity environment, when a bias voltage is applied, leakage current occurs in the substrate, etc., making it impossible to accurately detect the development current, which may result in a decrease in the accuracy of estimating the surface potential.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus, a control method for an image forming apparatus, and a control program that can improve the accuracy of measuring the surface potential. [Means for solving the problem]

[0007] According to one aspect of the present invention, an image forming apparatus includes an image forming unit and a potential measurement processing unit. The image forming unit applies a bias voltage between a first support and a second support, and transfers toner from the first support to the second support to form an image on the second support. The potential measurement processing unit measures the surface potential of the first support or the second support based on a target current flowing between the first support and the second support. The potential measurement processing unit measures the surface potential based on a leakage current between the first support and the second support that has been measured in advance.

[0008] A control method for an image forming apparatus according to another aspect of the present invention is used in an image forming apparatus including an image forming unit that applies a bias voltage between a first support and a second support, and moves toner from the first support to the second support to form an image on the second support. The control method for the image forming apparatus includes measuring a surface potential of the first support or the second support based on a leakage current between the first support and the second support that is measured in advance and a target current flowing between the first support and the second support.

[0009] According to another aspect of the present invention, there is provided a control program for use in an image forming apparatus including an image forming unit that applies a bias voltage between a first support and a second support, and moves toner from the first support to the second support to form an image on the second support. The control method for the image forming apparatus is a program that causes one or more processors to execute the following: measuring a surface potential of the first support or the second support based on a leakage current between the first support and the second support that is measured in advance, and a target current that flows between the first support and the second support. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image forming apparatus, a control method for an image forming apparatus, and a control program that can improve the accuracy of measuring the surface potential. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the image forming apparatus according to the first embodiment. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of the image forming unit of the image forming apparatus according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a configuration for measuring the surface potential of the image forming apparatus according to the first embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of the operation of the image forming apparatus according to the first embodiment. [Figure 6] FIG. 6 is a block diagram showing the configuration of an image forming apparatus according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description will discuss preferred embodiments of the present invention with reference to the accompanying drawings. The preferred embodiments are merely examples of the present invention and are not intended to limit the technical scope of the present invention.

[0013] (Embodiment 1) [1] Overall configuration of image forming device First, the overall configuration of an image forming apparatus 10 according to this embodiment will be described with reference to FIGS.

[0014] For ease of explanation, the vertical direction in the installed state (as shown in FIG. 2) in which the image forming apparatus 10 can be used is defined as the up-down direction D1. Also, the left side of the image forming apparatus 10 in FIG. 2 is defined as the front (front face) and the front-to-back direction D2 is defined. Also, the left-to-right direction D3 is defined based on the front face of the image forming apparatus 10 in the installed state.

[0015] The image forming apparatus 10 according to the present embodiment is, for example, a multifunction peripheral having multiple functions, such as a scanning function for reading image data from an original, a printing function for forming an image based on the image data, a facsimile function, and a copy function. The image forming apparatus 10 may be a printer, a facsimile machine, a copy machine, or the like, as long as it has the function of forming an image.

[0016] 1, the image forming apparatus 10 includes an automatic document feeder 1, an image reading unit 2, an image forming unit 3, a paper feeder 4, a control unit 5, a storage unit 6, and an operation display unit 7. The automatic document feeder 1 is an ADF (Auto Document Feeder), and is therefore represented as "ADF" in FIG. 1, and will also be referred to as "ADF1" in the following description.

[0017] The ADF 1 transports an original document whose image is to be read by the image reading unit 2. The ADF 1 includes an original document setting unit, a plurality of transport rollers, an original document holder, and a paper discharge unit.

[0018] The image reading unit 2 reads an image from a document and outputs image data corresponding to the read image. The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, a CCD (Charge Coupled Device), and the like.

[0019] The image forming unit 3 realizes a printing function by forming a color or monochrome image on a sheet using an electrophotographic method. The image forming unit 3 forms an image on a sheet based on image data output from the image reading unit 2. The image forming unit 3 also forms an image on a sheet based on image data input from an information processing device external to the image forming apparatus 10, such as a personal computer.

[0020] The paper feed unit 4 supplies sheets to the image forming unit 3. The paper feed unit 4 includes a paper feed cassette, a manual feed tray, a sheet transport path, and a plurality of transport rollers. The image forming unit 3 forms an image on the sheet supplied from the paper feed unit 4.

[0021] The control unit 5 performs overall control of the image forming apparatus 10. The control unit 5 is primarily configured as a computer system having one or more processors and one or more memories. In the image forming apparatus 10, the functions of the control unit 5 are realized by the one or more processors executing programs. The programs may be pre-recorded in memory (storage unit 6), provided via a telecommunications line such as the Internet, or provided by being recorded on a non-transitory recording medium readable by a computer system, such as a memory card or optical disk. The one or more processors are composed of one or more electronic circuits including semiconductor integrated circuits. Furthermore, the computer system referred to here includes a microcontroller having one or more processors and one or more memories. The control unit 5 may be a control unit provided separately from the main control unit that performs overall control of the image forming apparatus 10.

[0022] The storage unit 6 includes one or more non-volatile memories, and stores in advance information such as control programs for causing the control unit 5 to execute various processes. Furthermore, the storage unit 6 is used as a temporary storage memory (work area) for the various processes executed by the control unit 5.

[0023] The operation display unit 7 is a user interface in the image forming apparatus 10. The operation display unit 7 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control unit 5, and an operation unit such as a switch or a touch panel that inputs various information to the control unit 5 in response to user operations.

[0024] [2] Image forming unit configuration Next, the configuration of the image forming unit 3 will be described in more detail with reference to FIGS.

[0025] 2, the image forming section 3 has four image forming units 31 to 34, an optical scanning device 35, an intermediate transfer device 36, a secondary transfer roller 37, a fixing device 38, and a paper discharge tray 39. In FIG. 3, an enlarged view is shown in a speech bubble to schematically show the configuration of image forming unit 34, which is one of the four image forming units 31 to 34.

[0026] Image forming unit 31 forms a Y (yellow) toner image. As shown in Fig. 3, image forming unit 31 includes photosensitive drum 311, charging roller 312, developing device 313 including developing roller 313A, primary transfer roller 314, and drum cleaning unit 315. Image forming unit 31 further includes toner container 316 (see Fig. 2).

[0027] Image forming unit 32 forms a C (cyan) toner image. As shown in Fig. 3, image forming unit 32 includes a photosensitive drum 321, a charging roller 322, a developing device 323 including a developing roller 323A, a primary transfer roller 324, and a drum cleaning unit 325. Image forming unit 32 further includes a toner container 326 (see Fig. 2).

[0028] Image forming unit 33 forms a magenta (M) toner image. As shown in Fig. 3, image forming unit 33 includes a photosensitive drum 331, a charging roller 332, a developing device 333 including a developing roller 333A, a primary transfer roller 334, and a drum cleaning unit 335. Image forming unit 33 further includes a toner container 336 (see Fig. 2).

[0029] The image forming unit 34 forms a K (black) toner image. As shown in Fig. 3, the image forming unit 34 includes a photosensitive drum 341, a charging roller 342, a developing device 343 including a developing roller 343A, a primary transfer roller 344, and a drum cleaning unit 345. The image forming unit 34 further includes a toner container 346 (see Fig. 2).

[0030] 1, in addition to the above configuration, each of the image forming units 31 to 34 further includes a power supply circuit 301 and a current detection circuit 302. That is, the power supply circuit 301 and the current detection circuit 302 are provided in each of the image forming units 31 to 34. Each power supply circuit 301 includes a development power supply circuit 301A and a charging power supply circuit 301B.

[0031] As described above, the multiple (four in this example) image forming units 31-34 correspond to four colors, Y (yellow), C (cyan), M (magenta), and K (black), respectively, and basically share a common configuration. Therefore, unless otherwise noted, the configuration described below for image forming unit 34 also applies to the other image forming units 31-33. In the balloons in Figures 1 and 3, only the photosensitive drum 341, developing roller 343A, power supply circuit 301, current detection circuit 302, etc., for image forming unit 34 are illustrated.

[0032] An electrostatic latent image is formed on the photosensitive drum 341. The photosensitive drum 341 is rotatably supported about a rotation axis extending in the left-right direction D3 by a unit housing that houses the photosensitive drum 341, charging roller 342, and drum cleaning unit 345. The photosensitive drum 341 receives a driving force supplied from a motor, for example, and rotates in a rotation direction D5 shown in FIG.

[0033] Charging roller 342 positively charges the surface (outer circumferential surface) of photosensitive drum 341. Specifically, charging roller 342 is electrically connected to charging power supply circuit 301B of power supply circuit 301, and charges the surface of photosensitive drum 341 by receiving a high voltage from charging power supply circuit 301B. However, charging roller 342 is not limited to a configuration that charges the surface of photosensitive drum 341 positively, and may also charge the surface of photosensitive drum 341 negatively.

[0034] The surface of the photosensitive drum 341, which has been charged by the charging roller 342, is irradiated with light based on image data from the optical scanning device 35. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 341. In other words, the portion of the surface of the photosensitive drum 341 that is irradiated with light from the optical scanning device 35 becomes the "image portion."

[0035] The developing device 343 performs a developing process to develop the electrostatic latent image formed on the surface of the photosensitive drum 341. In this embodiment, the developing device 343 performs development using a two-component developer containing toner and carrier. For example, the developing device 343 includes a case, a pair of stirring members, a magnet roller, and the developing roller 343A. The case rotatably supports the pair of stirring members, the magnet roller, and the developing roller 343A around a rotation axis extending in the left-right direction D3. The case also contains K (black) toner and carrier. The pair of stirring members stir the toner and carrier contained in the case to charge the toner. In this embodiment, the toner is positively charged. However, the charged polarity of the toner is not limited to positive and may be negative. The magnet roller picks up the toner and carrier stirred by the pair of stirring members and supplies the toner to the surface (outer circumferential surface) of the developing roller 343A.

[0036] Developing roller 343A uses charged toner to develop the electrostatic latent image formed on photosensitive drum 341. Specifically, developing roller 343A is electrically connected to developing power supply circuit 301A of power supply circuit 301, and receives developing bias Vb1 (see FIG. 4) from developing power supply circuit 301A, thereby supplying toner to the surface of photosensitive drum 341. That is, a developing electric field is formed between developing roller 343A and photosensitive drum 341 by developing power supply circuit 301A applying high-voltage developing bias Vb1, and charged toner moves from developing roller 343A to photosensitive drum 341. As a result, a toner image corresponding to the electrostatic latent image is formed on the surface of photosensitive drum 341.

[0037] In this embodiment, the developing roller 343A is an example of a "first support," and the photosensitive drum 341 is an example of a "second support." That is, the image forming unit 3 uses a development electric field to move charged toner from the developing roller 343A, which is the first support, to the photosensitive drum 341, which is the second support, and forms a toner image (image) corresponding to the electrostatic latent image on the photosensitive drum 341 (second support). That is, the image forming unit 3 moves charged toner from the first support to the second support in the development process to form an image on the second support. Here, because the photosensitive drum 341, which is the second support, rotates in the rotation direction D5, the portion of the surface of the photosensitive drum 341 facing the developing roller 343A changes over time. In other words, the portion of the surface of the photosensitive drum 341 facing the developing roller 343A moves in the rotation direction D5 of the photosensitive drum 341.

[0038] In this embodiment, the first support is the developing roller 343A and the second support is the photosensitive drum 341, so the developing bias Vb1 is an example of a "bias voltage" applied between the first support and the second support. Furthermore, the developing current flowing between the developing roller 343A and the photosensitive drum 341 due to the application of the bias voltage (developing bias Vb1) is an example of a "target current" flowing between the first support and the second support. The developing current includes a toner current that flows with the movement of toner. In other words, the developing current flows as a "target current" between the first support and the second support. In this disclosure, the target current (developing current) flowing from the first support (developing roller 343A) to the second support (photosensitive drum 341) is defined as "positive" (plus), and the target current flowing conversely from the second support to the first support is defined as "negative" (minus).

[0039] Here, a magnet is disposed inside the developing roller 343A, and the developing roller 343A rotates around the stationary magnet. One of the magnetic poles of the magnet faces the photosensitive drum 341 via the developing roller 343A and the development gap. The developer carried by the developing roller 343A forms a magnetic brush in the development gap. The magnetic brush is a magnetic carrier to which toner adheres. Therefore, the developing current, which is an example of a target current, includes not only a toner current that flows as the toner moves, but also a magnetic brush current that flows through the magnetic brush in the image area and a reverse magnetic brush current that flows through the magnetic brush in the non-image area in the opposite direction to the image area.

[0040] The primary transfer roller 344 transfers the toner image formed on the surface of the photosensitive drum 341 by the developing device 343 onto the outer circumferential surface of the intermediate transfer belt 361 (see FIG. 3). Specifically, the primary transfer roller 344 is electrically connected to the power supply circuit 301, and receives a high voltage from the power supply circuit 301 to transfer the toner image formed on the surface of the photosensitive drum 341 onto the outer circumferential surface of the intermediate transfer belt 361. In other words, a high-voltage transfer bias is applied by the power supply circuit 301 between the photosensitive drum 341 and the primary transfer roller 344, forming a transfer electric field, and the charged toner moves from the photosensitive drum 341 to the intermediate transfer belt 361. As a result, the toner image is formed (transferred) onto the outer circumferential surface of the intermediate transfer belt 361.

[0041] Drum cleaning unit 345 cleans the surface of photosensitive drum 341 after the toner image has been transferred by primary transfer roller 344. For example, drum cleaning unit 345 has a blade-shaped cleaning member and a transport member. The cleaning member comes into contact with the surface of photosensitive drum 341 to remove toner adhering to the surface. The transport member transports the toner removed by the cleaning member to a toner storage container.

[0042] The toner container 346 supplies toner to the case of the developing device 343. In the image forming unit 34 that forms a K (black) toner image, the toner container 346 supplies K (black) toner.

[0043] Current detection circuit 302 detects a development current (an example of a target current) flowing between photosensitive drum 341 and development roller 343A. Current detection circuit 302 is, for example, a circuit including a current sensor such as a shunt resistor or a current transformer, and is provided on a current path from power supply circuit 301 to development roller 343A. Current detection circuit 302 outputs to control unit 5 a detection signal Si4 (see FIG. 4) corresponding to the magnitude of the development current flowing from development roller 343A (first support) to photosensitive drum 341 (second support).

[0044] The optical scanning device 35 forms an electrostatic latent image on each of the photosensitive drums 311, 321, 331, and 341 of the four image forming units 31 to 34. In this embodiment, the optical scanning device 35 includes two optical scanning units 351 and 352. The optical scanning unit 351 irradiates the photosensitive drum 311 with light based on image data in response to input of Y (yellow) image data, thereby forming an electrostatic latent image. The optical scanning unit 351 irradiates the photosensitive drum 321 with light based on image data in response to input of C (cyan) image data, thereby forming an electrostatic latent image. The optical scanning unit 352 irradiates the photosensitive drum 331 with light based on image data in response to input of M (magenta) image data, thereby forming an electrostatic latent image. Furthermore, the optical scanning unit 352 irradiates the photosensitive drum 341 with light based on image data in response to input of K (black) image data, thereby forming an electrostatic latent image.

[0045] The toner images of each color formed by each of the multiple (four in this example) image forming units 31 to 34 are transferred in layers onto the outer circumferential surface of the intermediate transfer belt 361. As a result, a color image (toner image) is formed on the outer circumferential surface of the intermediate transfer belt 361.

[0046] 3, the intermediate transfer device 36 includes an intermediate transfer belt 361, a drive roller 362, a tension roller 363, a belt cleaning unit 364, and a density detection unit 365. The intermediate transfer device 36 uses the intermediate transfer belt 361 to transport the toner images formed by the image forming units 31 to 34 to a transfer position P1 (see FIG. 3) where the toner images are transferred by a secondary transfer roller 37.

[0047] The intermediate transfer belt 361 is an endless belt onto which the toner images of each color are transferred from the photosensitive drums 311, 321, 331, and 341. As shown in FIG. 3, the intermediate transfer belt 361 is looped around a drive roller 362 and a tension roller 363, which are spaced apart from each other in the front-to-rear direction D2 of the image forming apparatus 10. The drive roller 362 rotates by receiving a driving force supplied from a motor. This causes the intermediate transfer belt 361 to rotate in a rotation direction D4 shown in FIG. 3. The toner images transferred onto the outer peripheral surface of the intermediate transfer belt 361 are transported to a transfer position P1 by the secondary transfer roller 37 as the intermediate transfer belt 361 rotates. A belt cleaning unit 364 cleans the outer peripheral surface of the intermediate transfer belt 361 after the toner images have been transferred at the transfer position P1.

[0048] The density detection unit 365 detects the density of the image (toner image) transferred onto the outer peripheral surface of the photosensitive drum 341 or the intermediate transfer belt 361. For example, the density detection unit 365 includes a reflective optical sensor having a light-emitting unit that emits light toward the outer peripheral surface of the intermediate transfer belt 361 and a light-receiving unit that receives light output from the light-emitting unit and reflected by the outer peripheral surface of the intermediate transfer belt 361. As shown in FIG. 3 , the density detection unit 365 is disposed downstream of the image forming unit 34 and upstream of the secondary transfer roller 37 in the rotation direction D4 of the intermediate transfer belt 361. The density detection unit 365 is disposed opposite one end of the outer peripheral surface of the intermediate transfer belt 361 in the width direction (left-right direction D3) of the intermediate transfer belt 361. The density detection unit 365 may also be disposed opposite both ends of the outer peripheral surface of the intermediate transfer belt 361 in the width direction of the intermediate transfer belt 361.

[0049] The secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet supplied by the paper feed unit 4. As shown in FIG. 3, the secondary transfer roller 37 is disposed opposite the tension roller 363 across the intermediate transfer belt 361, so as to be in contact with the outer peripheral surface of the intermediate transfer belt 361. The secondary transfer roller 37 is pressed toward the tension roller 363 by a biasing member. The secondary transfer roller 37 is electrically connected to a power supply circuit, and when a high voltage is applied from the power supply circuit, the secondary transfer roller 37 transfers the toner image formed on the outer peripheral surface of the intermediate transfer belt 361 onto a sheet passing through a transfer position P1 (see FIG. 3) where the secondary transfer roller 37 and the intermediate transfer belt 361 come into contact.

[0050] The length of the secondary transfer roller 37 in its axial direction (left-right direction D3) is shorter than the width of the intermediate transfer belt 361. As a result, a contact area that contacts the secondary transfer roller 37 and a non-contact area (blank area) that does not contact the secondary transfer roller 37 are generated on the outer circumferential surface of the intermediate transfer belt 361. The non-contact areas are areas on both sides of the contact area on the outer circumferential surface of the intermediate transfer belt 361. The density detection unit 365 is disposed facing one of the non-contact areas. Of the images formed on the outer circumferential surface of the intermediate transfer belt 361, the secondary transfer roller 37 transfers an image formed in the contact area onto the sheet, and does not transfer an image formed in the non-contact area onto the sheet. The length of the secondary transfer roller 37 in its axial direction may be the same as the width of the intermediate transfer belt 361.

[0051] The fixing device 38 fuses and fixes the toner image transferred to the sheet by the secondary transfer roller 37 to the sheet. For example, the fixing device 38 includes a fixing roller and a pressure roller. The fixing roller is arranged to be in contact with the pressure roller, and heats the toner image transferred to the sheet to fix it to the sheet. The pressure roller applies pressure to the sheet passing through the contact area formed between the fixing roller and the pressure roller.

[0052] The sheet on which the image has been formed is discharged to the discharge tray 39.

[0053] A related technique is known for an image forming apparatus in which the surface potential of a photoconductor is determined and fed back to control the charging of the photoconductor. Specifically, in an electrophotographic image forming apparatus (electrophotographic device), a charged photoconductor is exposed to light based on image data, forming an electrostatic latent image on the photoconductor. The image forming apparatus then applies a bias voltage to a developing roller and supplies charged toner to the photoconductor in accordance with the electric field between the photoconductor and the developing roller, thereby causing the toner to adhere to the exposed portion of the photoconductor, developing the electrostatic latent image on the photoconductor and forming an image.

[0054] In this type of image forming apparatus, fluctuations in the surface potential (charge potential) of the photoconductor affect image quality, so in an image forming apparatus according to related technology, the surface potential of the photoconductor is determined and the charging of the photoconductor is controlled to obtain a constant surface potential. One method involves detecting the development current that flows from the development roller to the photoconductor when a bias voltage is applied to the development roller, and estimating the surface potential based on this development current.

[0055] However, in the method of estimating the surface potential based on the development current, for example, in a high-temperature and high-humidity environment, when a bias voltage is applied, leakage current occurs in the substrate, etc., making it impossible to accurately detect the development current, which may result in a decrease in the accuracy of estimating the surface potential.

[0056] In contrast to this, in the image forming apparatus 10 according to this embodiment, the measurement accuracy of the surface potential can be improved by using the configuration described below.

[0057] That is, as shown in FIG. 1, the image forming apparatus 10 according to this embodiment includes an image forming unit 3 and a potential measurement processor 51. The image forming unit 3 applies a bias voltage (development bias Vb1) between a first support (development roller 343A) and a second support (photosensitive drum 341), and transfers toner from the first support to the second support to form an image on the second support. The potential measurement processor 51 measures the surface potential of the first support or the second support based on a target current (development current Ib1) flowing between the first support and the second support. Here, the potential measurement processor 51 measures the surface potential based on a leakage current between the first support and the second support that has been measured in advance. In this embodiment, as an example, the potential measurement processor 51 and a potential adjustment processor 52 and a current measurement processor 53, which will be described later, are provided in the control unit 5 as functions of the control unit 5.

[0058] In this embodiment, the first support is the developing roller 343A and the second support is the photosensitive drum 341, so the developing bias Vb1 is an example of a "bias voltage" and the developing current Ib1 (see FIG. 4) is an example of a "target current." The potential measurement processing unit 51 measures (calculates) the surface potential of the photosensitive drum 341, which is the second support, of the first support (developing roller 343A) and the second support (photosensitive drum 341).

[0059] According to the above-described configuration, the image forming apparatus 10 measures the surface potential based on the target current (developing current Ib1 in this embodiment), while also measuring the surface potential based on the leakage current between the first and second support members that has been measured in advance. That is, for example, even if a leakage current occurs in the substrate or the like when a bias voltage (developing bias Vb1) is applied in a high-temperature, high-humidity environment, the leakage current is reflected in the measurement of the surface potential, so that the developing current Ib1 can be measured with high accuracy, and a decrease in the accuracy of estimating (measuring) the surface potential can be suppressed. As a result, this image forming apparatus 10 can improve the accuracy of measuring the surface potential.

[0060] [3] Configuration related to measurement of surface potential Next, the configuration for measuring the surface potential will be described in more detail with reference to Figures 1 and 4. In Figure 4, only the photosensitive drum 341, developing roller 343A, power supply circuit 301, current detection circuit 302, etc., of the image forming unit 34 are shown.

[0061] 1, the control unit 5 has a potential measurement processing unit 51, a potential adjustment processing unit 52, and a current measurement processing unit 53. That is, the image forming apparatus 10 has the potential measurement processing unit 51, the potential adjustment processing unit 52, and the current measurement processing unit 53 as functions of the control unit 5.

[0062] The potential measurement processing unit 51 measures the surface potential of the photosensitive drum 341 based on the target current (developing current Ib1) flowing between the first support (developing roller 343A) and the second support (photosensitive drum 341). That is, the potential measurement processing unit 51 measures the surface potential based on the developing current Ib1 detected by the current detection circuit 302. Essentially, the potential measurement processing unit 51 utilizes the fact that when the surface potential matches the bias voltage (developing bias Vb1), the DC component of the developing current becomes 0 (zero). That is, the potential measurement processing unit 51 identifies the DC component Vdc of the bias voltage (developing bias Vb1) when the DC component of the developing current is 0 as the surface potential.

[0063] The potential adjustment processing unit 52 adjusts the surface potential based on the surface potential measured by the potential measurement processing unit 51. Specifically, the potential adjustment processing unit 52 sets the magnitude of the charging voltage Vb3 (see FIG. 4) that the charging power supply circuit 301B applies to the charging roller 342 based on the surface potential measured by the potential measurement processing unit 51. This allows the image forming apparatus 10 to maintain the surface potential in an appropriate state and suppress deterioration of image quality due to fluctuations or unevenness in the surface potential.

[0064] The current measurement processing unit 53 measures the leakage current. In the present disclosure, the "leakage current" refers to a current that flows through a path other than the normal path, for example, through the surface of the control board 50 (see FIG. 4), and leakage current tends to increase in, for example, a high-temperature, high-humidity environment. The current measurement processing unit 53 measures the leakage current based on the current detected by the current detection circuit 302 (or the detection signal Si4 corresponding to the current). By providing the current measurement processing unit 53, it becomes possible to measure (estimate) the surface potential using the leakage current that is actually measured, further improving the measurement accuracy of the surface potential.

[0065] 4, the image forming apparatus 10 according to this embodiment further includes a switching unit Ry1. The switching unit Ry1 switches the electrical connection of the photosensitive drum 341, which serves as a second support, between the circuit ground and the high voltage Vb2. The switching unit Ry1 is, for example, a relay (electromagnetic relay) controlled by the current measurement processing unit 53 of the control unit 5. In this embodiment, the state of the switching unit Ry1 when the photosensitive drum 341 is connected to the circuit ground, which is the reference potential (zero potential), is referred to as a first state, and the state of the switching unit Ry1 when the photosensitive drum 341 is connected to the high voltage Vb2 is referred to as a second state.

[0066] Here, the high voltage Vb2 is one output of the developing power supply circuit 301A in the power supply circuit 301, and its magnitude is controlled, for example, by a control signal Si2 from the current measurement processing unit 53 of the control unit 5. Similarly, the developing bias Vb1 is one output of the developing power supply circuit 301A in the power supply circuit 301, and its magnitude is controlled, for example, by a control signal Si1 from the potential measurement processing unit 51 of the control unit 5. In other words, the developing power supply circuit 301A is configured to be able to output the developing bias Vb1 and the high voltage Vb2.

[0067] On the other hand, the charging voltage Vb3 is one output of the charging power supply circuit 301B in the power supply circuit 301, and its magnitude is controlled, for example, by a control signal Si3 from the potential adjustment processing unit 52 of the control unit 5. In other words, the charging power supply circuit 301B is configured to be able to output the charging voltage Vb3.

[0068] Here, the developing bias Vb1 is applied to the developing roller 343A, which is the first support, via the current detection circuit 302. The high voltage Vb2 is applied to the photosensitive drum 341, which is the second support, when the switching unit Ry1 is in the second state. The charging voltage Vb3 is applied to the charging roller 342.

[0069] 4, in this embodiment, one or more processors constituting the control unit 5 are mounted on a control board 50 made of a printed wiring board. That is, the control signals Si1, Si2, and Si3 are applied to the developing power supply circuit 301A or the charging power supply circuit 301B through conductive paths included in the control board 50.

[0070] [4] Method for controlling an image forming apparatus 5, a series of processes relating to the measurement of the surface potential, among the control method of the image forming apparatus 10 executed by the control unit 5 in the image forming apparatus 10, will be described below. Here, steps S1, S2, etc. represent the numbers of the processing procedures (steps) executed by the control unit 5. Also, while a control method for K (black) toner is exemplified here, the control unit 5 executes similar processes for Y (yellow), C (cyan), and M (magenta).

[0071] <Step S1> First, in step S1, the current measurement processing unit 53 of the control unit 5 switches the state of the switching unit Ry1 from the first state to the second state, thereby connecting the photosensitive drum 341 as the second support to the high voltage Vb2.

[0072] <Step S2> In the next step S2, the current measurement processing unit 53 of the control unit 5 controls the magnitude of the high voltage Vb2 to the first value Vx1 using the control signal Si2. Furthermore, the potential measurement processing unit 51 of the control unit 5 controls the magnitude of the developing bias Vb1 to the first value Vx1 using the control signal Si1. As a result, the same voltage of the first value Vx1 is applied to both the developing roller 343A, which is the first support, and the photosensitive drum 341, which is the second support.

[0073] <Step S3> In step S3, current measurement processing unit 53 of control unit 5 measures and stores development current Ib1 detected by current detection circuit 302 at this time as current Ix1. At this time, the same voltage (first value Vx1) is applied to development roller 343A, which is the first support, and photosensitive drum 341, which is the second support, so current Ix1 corresponds to leakage current. If no leakage current is occurring, current Ix1 will be 0 (zero).

[0074] <Steps S4, S5, S6> In step S4, the control unit 5 controls the development power supply circuit 301A to turn off the development bias Vb1 and the high voltage Vb2. Then, in step S5, the current measurement processing unit 53 of the control unit 5 switches the state of the switching unit Ry1 from the second state to the first state, thereby connecting the photosensitive drum 341, which serves as the second support, to the circuit ground. Furthermore, in step S6, the potential adjustment processing unit 52 of the control unit 5 applies the charging voltage Vb3 to the charging roller 342 in response to the control signal Si3.

[0075] <Step S7> In the next step S7, the potential measurement processing unit 51 of the control unit 5 controls the magnitude of the development bias Vb1 to the second value Vy1 using the control signal Si1. As a result, a voltage of the second value Vy1 is applied to the development roller 343A, which is the first support. Furthermore, the current measurement processing unit 53 of the control unit 5 measures the development current Ib1 detected by the current detection circuit 302 at this time as the current Iy1.

[0076] <Step S8> In step S8, it is determined whether the currents Ix1 and Iy1 match. If the voltage (second value Vy1) applied to the developing roller 343A, which is the first supporting member, matches the surface potential of the photosensitive drum 341, which is the second supporting member, then the developing current Ib1 at this time is only a leakage current, and therefore the currents Ix1 and Iy1 match (S8: Yes), and the process proceeds to step S10. On the other hand, if the voltage (second value Vy1) applied to the developing roller 343A, which is the first supporting member, does not match the surface potential of the photosensitive drum 341, which is the second supporting member, then the currents Ix1 and Iy1 do not match (S8: No), and the process proceeds to step S9.

[0077] <Step S9> In step S9, the potential measurement processing unit 51 of the control unit 5 changes the second value Vy1, which is the magnitude of the development bias Vb1. Here, if the current Iy1 is larger than the current Ix1, it is estimated that the second value Vy1 is higher than the surface potential of the photosensitive drum 341, and therefore the second value Vy1 is changed to be smaller.

[0078] <Step S10> In step S10, the potential measurement processing unit 51 of the control unit 5 estimates the second value Vy1, which is the magnitude of the developing bias Vb1 at this time, as the surface potential of the photosensitive drum 341.

[0079] The procedure of the current detection method described above is merely an example, and the order of the processes shown in the flowchart of FIG. 5 may be changed as appropriate, and processes may be added or omitted as appropriate.

[0080] In this manner, in this embodiment, the current measurement processing unit 53 measures the current (Ix1) that flows between the first support and the second support when the same voltage is applied to both the first support and the second support (S2) as the leakage current. This makes it possible to measure the leakage current from the current (Ix1) that actually flows between the first support and the second support.

[0081] Furthermore, the image forming apparatus 10 according to this embodiment can be switched between a first state in which the second support is connected to a reference potential (circuit ground) and a second state in which the same voltage as that applied to the first support is applied to the second support. The current measurement processor 53 measures the leakage current in the second state (S3). The potential measurement processor 51 measures the surface potential in the first state (S10). In other words, by switching the switching unit Ry1 between the first state and the second state, it is possible to measure both the leakage current and the surface potential based on the development current Ib1 using the same current detection circuit 302.

[0082] [5] Variation The multiple components included in the image forming apparatus 10 may be distributed across multiple housings. For example, at least one of the potential measurement processing unit 51, the potential adjustment processing unit 52, and the current measurement processing unit 53 is not limited to being realized as a function of the control unit 5, and may be provided in a housing separate from the control unit 5.

[0083] (Embodiment 2) 6, the image forming apparatus 10A according to this embodiment differs from the image forming apparatus 10 according to the first embodiment in that the current detection circuit 302 detects the current flowing between the primary transfer roller 344 and the photosensitive drum 341. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted as appropriate.

[0084] In this embodiment, the photosensitive drum 341 is an example of a "first support," and the primary transfer roller 344 is an example of a "second support." That is, the image forming unit 3 applies a high-voltage transfer bias between the photosensitive drum 341 and the primary transfer roller 344 by the transfer power supply circuit 301C of the power supply circuit 301. As a result, the image forming unit 3 transfers charged toner from the photosensitive drum 341, which is the first support, to the primary transfer roller 344, which is the second support, by a transfer electric field, and forms a toner image (image) on the primary transfer roller 344 (second support). That is, in the primary transfer process, the image forming unit 3 transfers charged toner from the first support to the second support, and forms an image on the second support. The current detection circuit 302 outputs a detection signal corresponding to the magnitude of the transfer current flowing between the primary transfer roller 344 (second support) and the photosensitive drum 341 (first support) to the control unit 5.

[0085] In this embodiment, the first support is the photosensitive drum 341 and the second support is the primary transfer roller 344, so the transfer bias is an example of a "bias voltage" and the transfer current is an example of a "target current." The potential measurement processing unit 51 measures (calculates) the surface potential of the photosensitive drum 341, which is the first support, of the first support (photosensitive drum 341) and the second support (primary transfer roller 344). [Explanation of symbols]

[0086] 3 Image forming unit 10, 10A Image forming device 51 Potential measurement processing section 53 Current measurement processing section 311, 321, 331, 341 Photosensitive drum (second support, first support) 313A, 323A, 333A, 343A Developing roller (first carrier) 314, 324, 334, 344 Primary transfer roller (second carrier) Vb1 Development bias (bias voltage) Ib1 Development current (target current)

Claims

1. an image forming section that applies a bias voltage between a first carrier and a second carrier to transfer toner from the first carrier to the second carrier, thereby forming an image on the second carrier; a potential measurement processing unit that measures a surface potential of the first support or the second support based on a target current flowing between the first support and the second support, the potential measurement processing unit measures the surface potential based on a leakage current between the first support and the second support that has been measured in advance. Image forming device.

2. further comprising a current measurement processing unit that measures the leakage current; The image forming apparatus according to claim 1 .

3. the current measurement processing unit measures, as the leakage current, a current flowing between the first support and the second support when the same voltage is applied to both the first support and the second support; The image forming apparatus according to claim 2 .

4. a first state in which the second support is connected to a reference potential and a second state in which the same voltage as that applied to the first support is applied to the second support, the current measurement processing unit measures the leakage current in the second state; the potential measurement processing unit measures the surface potential in the first state. The image forming apparatus according to claim 3 .

5. The image forming apparatus is provided with an image forming unit that applies a bias voltage between a first carrier and a second carrier, and moves toner from the first carrier to the second carrier to form an image on the second carrier, measuring a surface potential of the first support or the second support based on a leakage current between the first support and the second support that has been measured in advance and a target current that flows between the first support and the second support; A control method for an image forming apparatus.

6. The image forming apparatus is provided with an image forming unit that applies a bias voltage between a first carrier and a second carrier, and moves toner from the first carrier to the second carrier to form an image on the second carrier, measuring a surface potential of the first support or the second support based on a leakage current between the first support and the second support that has been measured in advance and a target current that flows between the first support and the second support; A control program for causing one or more processors to execute the above.

Images