Image forming apparatus

Abstract

To improve usability by reducing the number of times of replacement of a chart to a reader.SOLUTION: An image forming device 1 includes an image carrier 51, an intermediate transfer body 44b, a transfer member 45b, an application unit 76, a discharge unit 48, an image reading device 80, and a control unit 30 capable of executing an adjustment mode for adjusting a secondary transfer voltage by discharging, from the discharge unit 48, a recording material on which a chart is formed by applying a plurality of test voltages and sequentially transferring a plurality of test images. In the adjustment mode, the control unit 30 is configured to be able to discharge a first recording material on which a first chart is formed and a second recording material on which a second chart is formed from the discharge unit 48, read, by the image reading device 80, density information of test images on the first and second recording materials S simultaneously set in the image reading device 80 by an operator, and output information about an adjustment amount of a secondary transfer voltage based on the density information of the test images of the first and second charts acquired from a reading result of the image reading device 80.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine that uses an electrophotographic or electrostatic recording method. [Background technology]

[0002] Conventionally, image forming apparatuses using electrophotography or the like employ an intermediate transfer system in which a toner image formed on an image carrier such as a photosensitive drum is primarily transferred onto an intermediate transfer member such as an intermediate transfer belt, and then the toner image is secondarily transferred from the intermediate transfer member onto a recording material. The primary transfer is performed by applying a primary transfer voltage to a primary transfer section where the image carrier and the intermediate transfer member come into contact, and the secondary transfer is performed by applying a secondary transfer voltage to the secondary transfer section when the recording material passes through a secondary transfer section where the intermediate transfer member and a secondary transfer member come into contact.

[0003] To obtain high-quality images, it is necessary to appropriately adjust the secondary transfer voltage when electrostatically transferring a toner image from an intermediate transfer member to a recording material. If the secondary transfer voltage is insufficient relative to the charge of the toner on the intermediate transfer member, the toner may not be transferred sufficiently to the recording material, resulting in a failure to obtain the desired image density. Furthermore, if the secondary transfer voltage is too high, discharge may occur at the secondary transfer section, which may reverse the charge polarity of the toner on the intermediate transfer member, resulting in "whiteouts" where the toner image on the intermediate transfer member cannot be partially transferred.

[0004] The amount of charge required for the secondary transfer of toner from the intermediate transfer member onto the recording material varies depending on factors such as the size of the recording material and the area ratio of the toner image. Therefore, the secondary transfer voltage supplied to the secondary transfer unit is often applied as a constant voltage that outputs a constant voltage corresponding to a predetermined current density. In this case, a transfer current corresponding to a predetermined voltage can be ensured in the crucial area where the toner image is to be transferred, regardless of the current flowing outside the recording material or in areas on the recording material where there is no toner image.

[0005] The secondary transfer voltage can be determined based on a transfer portion voltage corresponding to the electrical resistance of the secondary transfer section, detected during a pre-rotation process before image formation, and a recording material distribution voltage corresponding to a preset recording material type. This allows an appropriate secondary transfer voltage to be set depending on environmental fluctuations, the usage history of the transfer member, the type of recording material, and other factors. However, because the types and conditions of recording materials used in image formation vary, the preset default recording material distribution voltage may result in an excessive or insufficient secondary transfer voltage. Therefore, it has been proposed to provide an image forming apparatus with an adjustment mode that allows the set transfer voltage to be adjusted depending on the recording material actually used in image formation.

[0006] Patent Document 1 proposes an image forming apparatus equipped with an adjustment mode for adjusting the set voltage of the secondary transfer voltage. In this adjustment mode, a chart in which multiple patches (test images) are formed on a single sheet of recording material is output with the secondary transfer voltage switched for each patch. This chart is read by a reading device provided in the image forming apparatus, and the density of each patch is detected. Then, the optimal secondary transfer voltage conditions are selected based on the detection results. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-37185 Summary of the Invention [Problem to be solved by the invention]

[0008] When using the chart described above, the size of the chart that is desired to be formed with one adjustment may be large, taking into consideration the formation of a sufficient number of patches, the detection accuracy of the density of each patch, ease of judgment by the operator, etc. Furthermore, when using large-size paper such as A3 size, one chart may be sufficient, but when using small-size recording material such as A4 size or LTR size, two charts may be required.

[0009] Conventionally, when a chart spans two pages, the operator must replace the chart with the reader for each page. For example, with a pressure plate-type reader, the operator must replace the chart with the reader twice. Also, when a double-sided adjustment chart that forms patches on both sides of the recording material is output, the operator must replace the chart with the reader four times. In this way, increasing the operator's actions of replacing the chart with the reader can reduce usability.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that can reduce the number of times the chart needs to be replaced with a reading device, thereby improving usability. [Means for solving the problem]

[0011] The above object is achieved by the image forming apparatus according to the present invention. In summary, a typical configuration of the present invention includes an image carrier that carries a toner image, an intermediate transfer member to which the toner image is primarily transferred from the image carrier, a transfer member forming a transfer section that performs secondary transfer of the toner image from the intermediate transfer member to a recording material, an application section that applies a voltage to the transfer member, a discharge section that discharges the recording material on which the toner image transferred in the transfer section is fixed and an image is formed, a reading device that can read density information of the image on the recording material set by an operator, and a recording material on which a chart is formed by sequentially transferring a plurality of test images by applying a plurality of test voltages to the transfer member and discharging the recording material from the discharge section, and a control unit capable of executing an adjustment mode in which the secondary transfer voltage to be applied to the transfer member is adjusted by a control unit configured to: in the adjustment mode, discharge a first recording material on which a first chart is formed and a second recording material on which a second chart is formed from the discharge unit; read, by the reading device, density information of the test images on the first and second recording materials which are set in the reading device simultaneously by an operator; and output information regarding the adjustment amount of the secondary transfer voltage based on the density information of the test images of the first and second charts obtained from the reading result of the reading device. [Effects of the Invention]

[0012] According to the present invention, the number of times the chart needs to be replaced with a reading device can be reduced, thereby improving usability. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Figure 2] FIG. 2 is a block diagram showing a control system of the image forming apparatus. [Figure 3] FIG. 10 is a flowchart illustrating an outline of a procedure for controlling a secondary transfer voltage. [Figure 4] FIG. 10 is a graph showing voltage-current characteristics obtained by controlling a secondary transfer voltage. [Figure 5]FIG. 10 is a schematic diagram showing an example of a table of recording material distribution voltages. [Figure 6] FIG. 1 is a schematic diagram of a chart for large size. [Figure 7] FIG. 1 is a schematic diagram of a chart for small size. [Figure 8] FIG. 4 is a flowchart showing the procedure of an adjustment mode in the first embodiment. [Figure 9] FIG. 10 is a schematic diagram of a setting screen for an adjustment mode. [Figure 10] FIG. 10 is a flowchart illustrating the procedure of a process for determining an adjustment value according to the first embodiment. [Figure 11] FIG. 10 is a graph showing an example of the relationship between the average luminance of the patch and the test voltage. [Figure 12] FIG. 10 is a graph showing an example of the relationship between the average luminance of the patch and the test voltage. [Figure 13] FIG. 10 is a flowchart illustrating the procedure of a process for determining an adjustment value according to the second embodiment. [Figure 14] FIG. 10 is a schematic diagram of another example of a large size chart. [Figure 15] FIG. 10 is a schematic diagram of another example of a chart for small size. [Figure 16] FIG. 10 is a diagram showing the correspondence between the color of the page determination patch and the page number. [Figure 17] FIG. 11 is a flowchart of a process for optimizing the arrangement and order of scanned images in the third embodiment. [Figure 18] FIG. 10 is a diagram showing the effect of Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0014] The image forming apparatus according to the present invention will be described in more detail below with reference to the drawings.

[0015] [Example 1] 1. Configuration and operation of image forming apparatus 1 is a schematic cross-sectional view of an image forming apparatus 1 of this embodiment. The image forming apparatus 1 of this embodiment is a tandem multifunction machine (having the functions of a copier, printer, and facsimile machine) that employs an intermediate transfer system and is capable of forming full-color images using an electrophotographic system.

[0016] As shown in FIG. 1, the image forming apparatus 1 includes a main body 10, a reading device 80, a feed unit 90, an image forming unit 40, a discharge unit 48, a control unit 30, an operation unit 70, and the like. The main body 10 also includes a temperature sensor 71 (FIG. 2) capable of detecting the internal temperature and a humidity sensor 72 (FIG. 2) capable of detecting the internal humidity. The image forming apparatus 1 forms a four-color full-color image on a recording material (sheet, transfer material, recording medium) S in response to image information (image signals) from the reading device 80 or an external device (external device) 200 (FIG. 2). Examples of the external device 200 include a host device such as a personal computer, a digital camera, and a smartphone. The recording material S is a material on which a toner image is formed. Specific examples include plain paper, a synthetic resin sheet (a substitute for plain paper), cardboard, and overhead projector sheet.

[0017] Image forming section 40 is capable of forming an image based on image information on recording material S fed from feeding section (feeding device) 90. Image forming section 40 includes image forming units 50y, 50m, 50c, and 50k, toner bottles 41y, 41m, 41c, and 41k, exposure devices 42y, 42m, 42c, and 42k, an intermediate transfer unit 44, a secondary transfer device 45, and a fixing section 46. Image forming units 50y, 50m, 50c, and 50k form images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Elements having the same or corresponding functions or configurations and provided for these four image forming units 50y, 50m, 50c, and 50k may be generally described by omitting the suffixes y, m, c, and k, which indicate that the elements are for a particular color. The image forming apparatus 1 can also form a monochrome image, such as a black monochrome image, or a multicolor image using a desired single or several image forming units 50.

[0018] The image forming unit 50 has the following means. First, it has a photosensitive drum 51, which is a drum-type (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as an image carrier. It also has a charging roller 52, which is a roller-type charging member serving as charging means. It also has a developing device 20 serving as developing means. It also has a pre-exposure device 54 serving as discharging means. It also has a drum cleaning device 55 serving as photosensitive member cleaning means. The image forming unit 50 forms a toner image on an intermediate transfer belt 44b, which will be described later. The image forming unit 50 is integrated into a process cartridge, which is detachable from the apparatus main body 10.

[0019] The photosensitive drum 51 is movable (rotatable) and carries an electrostatic image (electrostatic latent image) or a toner image. In this embodiment, the photosensitive drum 51 is a negatively charged organic photoconductor (OPC) with an outer diameter of 30 mm. The photosensitive drum 51 has an aluminum cylinder as a base and a surface layer formed on its surface. In this embodiment, the surface layer has three layers: an undercoat layer, a photocharge generation layer, and a charge transport layer, which are coated and stacked on the base in the following order. When an image formation operation starts, the photosensitive drum 51 is rotated in the direction of the arrow in the figure (counterclockwise direction) at a predetermined process speed (circumferential speed) by a motor (not shown) as a driving means.

[0020] The surface of the rotating photosensitive drum 51 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 52. In this embodiment, the charging roller 52 is a rubber roller that comes into contact with the surface of the photosensitive drum 51 and rotates in accordance with the rotation of the photosensitive drum 51. A charging power supply 73 (FIG. 2) is connected to the charging roller 52. The charging power supply 73 applies a predetermined charging voltage (charging bias) to the charging roller 52 during the charging process.

[0021] The surface of the charged photosensitive drum 51 is scanned and exposed by the exposure device 42 based on image information, and an electrostatic image is formed on the photosensitive drum 51. In this embodiment, the exposure device 42 is a laser scanner. The exposure device 42 emits laser light in accordance with image information of separated colors output from the control unit 30, and scans and exposes the surface (outer peripheral surface) of the photosensitive drum 51.

[0022] The electrostatic image formed on the photosensitive drum 51 is developed (visualized) by the developing device 20 by supplying toner, thereby forming a toner image on the photosensitive drum 51. In this embodiment, the developing device 20 contains a two-component developer containing non-magnetic toner particles (toner) and magnetic carrier particles (carrier). Toner is supplied to the developing device 20 from a toner bottle 41. The developing device 20 has a developing sleeve 24. The developing sleeve 24 is made of a non-magnetic material such as aluminum or non-magnetic stainless steel (aluminum in this embodiment). A roller-shaped magnet roller is fixed inside the developing sleeve 24 so as not to rotate relative to the main body (developer container) of the developing device 20. The developing sleeve 24 carries the developer and transports it to a development area facing the photosensitive drum 51. A developing power supply 74 (FIG. 2) is connected to the developing sleeve 24. The developing power supply 74 applies a predetermined developing voltage (developing bias) to the developing sleeve 24 during the development process. In this embodiment, toner charged with the same polarity (negative in this embodiment) as the charge polarity of the photosensitive drum 51 adheres to the exposed portion (image portion) on the photosensitive drum 51, which has been uniformly charged and then exposed to light to reduce the absolute value of the potential (reverse development). In this embodiment, the normal charge polarity of the toner, which is the charge polarity of the toner during development, is negative.

[0023] The intermediate transfer unit 44 is disposed opposite the four photosensitive drums 51y, 51m, 51c, and 51k. The intermediate transfer unit 44 has an intermediate transfer belt 44b, which is an endless belt serving as an intermediate transfer body. The intermediate transfer belt 44b is wound around a plurality of tension rollers (support rollers), including a drive roller 44a, a driven roller 44d, and a secondary transfer inner roller 45a, and is tensioned with a predetermined tension. The intermediate transfer belt 44b is movable (rotatable) while carrying a toner image. The drive roller 44a is driven to rotate by a motor (not shown) serving as a driving means. The driven roller 44d is a tension roller that controls the tension of the intermediate transfer belt 44b to a constant level. A tension spring (not shown), which is a biasing member serving as a biasing means, applies a force to the driven roller 44d to push the intermediate transfer belt 44b from its inner peripheral surface toward its outer peripheral surface. This force applies a tension of approximately 2 to 5 kg to the intermediate transfer belt 44b in the transport direction. The inner secondary transfer roller 45a constitutes a secondary transfer device 45, as will be described later. The intermediate transfer belt 44b receives a driving force as the drive roller 44a is driven to rotate, and rotates (circumferentially moves) in the direction of the arrow (clockwise) in the figure at a predetermined peripheral speed corresponding to the peripheral speed of the photosensitive drum 51. Furthermore, primary transfer rollers 47y, 47m, 47c, and 47k, which are roller-type primary transfer members serving as primary transfer means, are arranged on the inner peripheral surface of the intermediate transfer belt 44b, corresponding to the photosensitive drums 51y, 51m, 51c, and 51k, respectively. The primary transfer rollers 47 sandwich the intermediate transfer belt 44b between themselves and the photosensitive drum 51. As a result, the primary transfer roller 47 comes into contact with the photosensitive drum 51 via the intermediate transfer belt 44b, forming a primary transfer portion (primary transfer nip) N1 where the photosensitive drum 51 and the intermediate transfer belt 44b come into contact with each other.

[0024] The toner image formed on the photosensitive drum 51 is primarily transferred onto the rotating intermediate transfer belt 44b at the primary transfer portion N1. A primary transfer power supply 75 (FIG. 2) is connected to the primary transfer roller 47. During the primary transfer process, the primary transfer power supply 75 applies a primary transfer voltage (primary transfer bias), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, to the primary transfer roller 47. For example, when forming a full-color image, the toner images of yellow, magenta, cyan, and black formed on the photosensitive drums 51y, 51m, 51c, and 51k are sequentially primarily transferred onto the intermediate transfer belt 44b so as to be superimposed on each other. A voltage detection sensor 75a that detects the output voltage and a current detection sensor 75b that detects the output current are connected to the primary transfer power supply 75 (FIG. 2). In this embodiment, primary transfer power supplies 75y, 75m, 75c, and 75k are provided for the primary transfer rollers 47y, 47m, 47c, and 47k, respectively, and the primary transfer voltages applied to the primary transfer rollers 47y, 47m, 47c, and 47k can be individually controlled.

[0025] In this embodiment, the primary transfer roller 47 has an elastic layer of ion-conductive foam rubber (NBR rubber) and a core metal. The outer diameter of the primary transfer roller 47 is, for example, 15 to 20 mm. The primary transfer roller 47 has an electrical resistance of 1×10 5 ~1×10 8A roller with a resistance of Ω (N / N (measured at 23°C, 50% RH, 2 kV applied) can be suitably used. In this embodiment, the intermediate transfer belt 44b is an endless belt having a three-layer structure, including, from the inner circumferential surface to the outer circumferential surface, a base layer, an elastic layer, and a surface layer, in the following order. The base layer can be made of a resin such as polyimide or polycarbonate, or various rubbers containing an appropriate amount of carbon black as an antistatic agent. The thickness of the base layer is, for example, 0.05 to 0.15 mm. The elastic layer can be made of an elastic material such as urethane rubber or silicone rubber containing an appropriate amount of an ion conductive agent. The thickness of the elastic layer is, for example, 0.1 to 0.500 mm. The surface layer can be made of a resin such as fluororesin. The surface layer reduces the adhesion of toner to the surface of the intermediate transfer belt 44b, facilitating the transfer of toner to the recording material S at the secondary transfer section N2 (described later). The thickness of the surface layer is, for example, 0.0002 to 0.020 mm. In this embodiment, the surface layer uses, as its base material, one type of resin material such as polyurethane, polyester, or epoxy resin, or two or more types of elastic materials such as elastic rubber, elastomer, or butyl rubber. The surface layer is then formed by dispersing one or more types of powder or particles, such as fluororesin, or particles of different particle sizes, as a material that reduces surface energy and increases lubricity into this base material. In this embodiment, the intermediate transfer belt 44b has a volume resistivity of 5×10 8 ~1×10 14 The resistance is Ω·cm (23°C, 50% RH), and the hardness is 60 to 85° (MD1 hardness) (23°C, 50% RH). In this embodiment, the static friction coefficient of the intermediate transfer belt 44b is 0.15 to 0.6 (23°C, 50% RH, HEIDON type 94i). Although the intermediate transfer belt 44b has a three-layer structure in this embodiment, it may also have a single layer structure made of a material equivalent to the above-mentioned base layer.

[0026] On the outer peripheral surface of the intermediate transfer belt 44b, there is disposed a secondary transfer outer roller 45b, which is a roller-type secondary transfer member serving as a secondary transfer means and which, together with the inner secondary transfer roller 44a, constitutes the secondary transfer device 45. The outer secondary transfer roller 45b sandwiches the intermediate transfer belt 44b between itself and the inner secondary transfer roller 45a. This causes the outer secondary transfer roller 45b to contact the inner secondary transfer roller 45a via the intermediate transfer belt 44b, forming a secondary transfer portion (secondary transfer nip) N2 where the intermediate transfer belt 44b and the outer secondary transfer roller 45b come into contact. The toner image formed on the intermediate transfer belt 44b is secondarily transferred onto the recording material S, which is being conveyed while being sandwiched between the intermediate transfer belt 44b and the outer secondary transfer roller 45b, at the secondary transfer portion N2. In this embodiment, a secondary transfer voltage (secondary transfer bias) is applied to the outer secondary transfer roller 45b during the secondary transfer process.

[0027] As described above, in this embodiment, the secondary transfer device 45 includes an inner secondary transfer roller 45a as an opposing member and an outer secondary transfer roller 45b as a secondary transfer member. The inner secondary transfer roller 45a is disposed opposite the outer secondary transfer roller 45b across the intermediate transfer belt 44b. A secondary transfer power supply 76 (FIG. 2) serving as a voltage application unit (application unit) is connected to the outer secondary transfer roller 45b. During the secondary transfer process, the secondary transfer power supply 76 applies a secondary transfer voltage (secondary transfer bias), which is a DC voltage of opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner, to the outer secondary transfer roller 45b. A voltage detection sensor 76a that detects the output voltage and a current detection sensor 76b that detects the output current are connected to the secondary transfer power supply 76 (FIG. 2). Furthermore, in this embodiment, the core of the inner secondary transfer roller 45a is connected to ground potential. That is, in this embodiment, the inner secondary transfer roller 45a is electrically grounded (connected to ground). When the recording material S is supplied to the secondary transfer portion N2, a constant-voltage controlled secondary transfer voltage of a polarity opposite to the normal charging polarity of the toner is applied to the outer secondary transfer roller 45b. In this embodiment, for example, a secondary transfer voltage of 1 to 7 kV is applied, and a current of 40 to 120 μA flows, thereby secondarily transferring the toner image on the intermediate transfer belt 44b to the recording material S. Note that in this embodiment, the secondary transfer power supply 76 applies a DC voltage to the outer secondary transfer roller 45b to apply the secondary transfer voltage to the secondary transfer portion N2, but the present invention is not limited to this configuration. For example, the secondary transfer power supply 76 may apply a DC voltage to the inner secondary transfer roller 45a to apply the secondary transfer voltage to the secondary transfer portion N2. In this case, a DC voltage of the same polarity as the normal charging polarity of the toner is applied to the inner secondary transfer roller 45a as the secondary transfer member, and the outer secondary transfer roller 45b as the opposing member is electrically grounded. In this embodiment, the outer secondary transfer roller 45b has an elastic layer of ion-conductive foam rubber (NBR rubber) and a core metal. The outer diameter of the outer secondary transfer roller 45b is, for example, 20 to 25 mm. The outer secondary transfer roller 45b has an electrical resistance of 1×10 5 ~1×10 8 A roller of Ω (measured at N / N (23° C., 50% RH), applied voltage of 2 kV) can be suitably used.

[0028] The recording material S is fed from a feeding unit 90 in parallel with the above-described toner image formation operation. That is, the recording material S is stacked and stored in a recording material cassette 91 serving as a recording material storage unit. The recording material S stored in the recording material cassette 91 is sent to a conveying path 93 by a feeding roller 92 serving as a feeding member. The recording material S sent to the conveying path 93 is conveyed to a registration roller pair 43 serving as a conveying member by a conveying roller pair 94 serving as a conveying member. The registration roller pair 43 corrects skew of the recording material S and synchronizes the timing with the toner image on the intermediate transfer belt 44b before supplying it to the secondary transfer unit N2. The recording material cassette 91, the feeding roller 92, the conveying path 93, the conveying roller pair 94, and the like constitute the feeding unit 90.

[0029] The recording material S onto which the toner image has been transferred is transported to a fixing section (fixing device) 46 serving as a fixing means. The fixing section 46 has a fixing roller 46a and a pressure roller 46b. The fixing roller 46a incorporates a heater serving as a heating means. The recording material S carrying the unfixed toner image is heated and pressurized as it is sandwiched and transported between the fixing roller 46a and the pressure roller 46b. This causes the toner image to be fixed (melted and adhered) to the recording material S. The temperature (fixing temperature) of the fixing roller 46a is detected by a fixing temperature sensor 77 (FIG. 2).

[0030] The recording material S with the fixed toner image is conveyed along a discharge path 48a by a pair of discharge rollers 48b and other conveying members, and is discharged (output) from a discharge outlet 48c and stacked on a discharge tray 48d provided outside the apparatus main body 10. The discharge path 48a, the pair of discharge rollers 48b, the discharge outlet 48c, the discharge tray 48d, and other components form a discharge section (discharge device) 48. In this embodiment, the image forming apparatus 1 is capable of double-sided image formation (double-sided printing, automatic double-sided printing) in which images are formed on both sides of the recording material S. A reversing conveying path 12 is provided between the fixing section 46 and the discharge outlet 48c to turn over the recording material S after the toner image has been fixed on its first side and supply it again to the secondary transfer section N2. During double-sided image formation, the recording material S after the toner image has been fixed on its first side is guided to the reversing conveying path 12. The recording material S has its conveying direction reversed by a switchback roller pair 13 provided in the reversing conveying path 12 and is guided to a duplex conveying path 14. The recording material S is then sent to a conveying path 93 by a re-conveying roller pair 15 provided in the duplex conveying path 14, conveyed to a registration roller pair 43, and supplied to a secondary transfer unit N2 by the registration roller pair 43. Thereafter, a toner image is secondarily transferred to the second side of the recording material S in the same manner as when the image was formed on the first side, and after the toner image is fixed, the recording material S is discharged to an output tray 48d. The reversing conveying path 12, the switchback roller pair 13, the duplex conveying path 14, the re-conveying roller pair 15, etc. form a duplex conveying unit (duplex conveying device) 11. By operating the duplex conveying unit 11, images can be formed on both sides of a single sheet of recording material S.

[0031] After the primary transfer, the surface of the photosensitive drum 51 is neutralized by a pre-exposure device 54. Furthermore, deposits such as toner (primary transfer residual toner) remaining on the photosensitive drum 51 without being transferred to the intermediate transfer belt 44b during the primary transfer process are removed from the photosensitive drum 51 and collected by a drum cleaning device 55. The drum cleaning device 55 uses a cleaning blade as a cleaning member that contacts the surface of the photosensitive drum 51 to scrape off deposits from the surface of the rotating photosensitive drum 51 and collect the scraped deposits in a cleaning container. The cleaning blade is contacted with the surface of the photosensitive drum 51 with a predetermined pressure so that the tip of its free end faces upstream in the counter direction of the rotation direction of the photosensitive drum 51. The intermediate transfer unit 44 also has a belt cleaning device 60 as an intermediate transfer body cleaning means. Deposits such as toner (secondary transfer residual toner) remaining on the intermediate transfer belt 44b without being transferred to the recording material S during the secondary transfer process are removed from the intermediate transfer belt 44b and collected by the belt cleaning device 60.

[0032] A reading device 80 serving as a reading means (reading unit) is disposed on the upper part of the apparatus main body 10. The reading device 80 has an automatic document transport device (automatic document feeder (ADF)) 81 serving as a document transport means (document transport unit), a platen glass 82, a light source 83, an optical system 84 including a group of mirrors 84a and an imaging lens 84b, and a reading element 85 such as a CCD.

[0033] In this embodiment, the reading device 80 can sequentially read an image of an original (recording material S on which an image is formed) placed on a platen glass 82 using a reading element 85 via an optical system 84 while scanning and exposing the original using a movable light source 82. In this case, the reading device 80 sequentially illuminates the original placed on the platen glass 82 using a moving light source 83, and sequentially forms an image of light reflected from the original on the reading element 85 via the optical system 84. This allows the reading element 85 to read the image of the original at a predetermined dot density. The platen glass 82 forms a reading surface that supports the recording material S so that the reading device 80 can read it.

[0034] In this embodiment, the reading device 80 sequentially exposes images of documents conveyed by the automatic document feeder 81 using a light source 82 as the documents are conveyed, and sequentially reads the images using a reading element 85 via an optical system 84. In this case, the reading device 80 sequentially illuminates documents passing a predetermined reading position on the platen glass 82 using a light source 83, and sequentially forms light images reflected from the documents on the reading element 85 via the optical system 84. This allows the reading element 85 to read the images of the documents at a predetermined dot density. The automatic document feeder 81 automatically conveys the documents so that they pass the reading position of the reading device 80 while being separated one by one. The automatic document feeder 81 constitutes a conveying device that sequentially conveys the recording material S so that the reading device 80 can read the documents.

[0035] In this way, the reading device 80 optically reads an image on the recording material S placed on the platen glass 82 or transported by the automatic document feeder 81 and converts it into an electrical signal. In this embodiment, the reading device 80 can arrange one large-size recording material S, such as A3 size, or two small-size recording materials S, such as A4 size, side by side on the platen glass 82. In this embodiment, the reading device 80 can also transport a plurality of recording materials S, for example, A3 size or A4 size, loaded on the document loading section of the automatic document feeder 81 to the above-mentioned reading position in succession. The automatic document feeder 81 can also automatically read images on both sides of the recording material S.

[0036] For example, when the image forming apparatus 1 operates as a copier, the document image scanned by the scanning device 80 is sent to the image processing unit of the control unit 30 as image data for three colors, e.g., red (R), green (G), and blue (B) (8 bits each). The image processing unit performs predetermined image processing on the document image data as needed, converting it into image data for four colors, e.g., yellow, magenta, cyan, and black. Examples of the image processing include shading correction, misalignment correction, brightness / color space conversion, gamma correction, border removal, and color / movement editing. The image data for the four colors, yellow, magenta, cyan, and black, are sequentially sent to the exposure devices 42y, 42m, 42c, and 42k, respectively, where the aforementioned image exposure is performed in accordance with this image data. As will be described in detail later, the scanning device 80 is also used to scan the chart patches (acquire density information (brightness information)) in the adjustment mode.

[0037] FIG. 2 is a block diagram showing the schematic configuration of the control system of the image forming apparatus 1 of this embodiment. As shown in FIG. 2, the control unit 30 is configured by a computer. The control unit 30 includes, for example, a CPU 31 as a calculation control unit, a ROM 32 as a storage unit for storing programs that control each unit, a RAM 33 as a storage unit for temporarily storing data, and an input / output circuit (I / F) 34 for inputting and outputting signals to and from the outside. The CPU 31 is a microprocessor that controls the overall control of the image forming apparatus 1 and is the main system controller. The CPU 31 is connected to the feed unit 90, image forming unit 40, discharge unit 48, and operation unit 70 via the I / F circuit 34, and exchanges signals with these units and controls their operation. The ROM 32 stores an image formation control sequence for forming an image on the recording material S. A charging power supply 73, a developing power supply 74, a primary transfer power supply 75, and a secondary transfer power supply 76 are connected to the control unit 30, and each of these is controlled by a signal from the control unit 30. Also connected to the control unit 30 are a temperature sensor 71, a humidity sensor 72, a voltage detection sensor 75a and a current detection sensor 75b of a primary transfer power supply 75, a voltage detection sensor 76a and a current detection sensor 76b of a secondary transfer power supply 76, and a fixing temperature sensor 77. Signals detected by each sensor are input to the control unit 30.

[0038] The operation unit 70 has an input unit such as operation buttons as input means, and a display unit 70a consisting of a liquid crystal panel or the like as display means. In this embodiment, the display unit 70a is configured as a touch panel and also functions as input means. An operator such as a user or a service representative can execute a job (described below) by operating the operation unit 70. The control unit 30 receives signals from the operation unit 70 and operates various devices of the image forming apparatus 1. The image forming apparatus 1 can also execute a job based on image formation signals (image data, control commands) from an external device 200 such as a personal computer.

[0039] In this embodiment, the control unit 30 includes an image formation preparation processor 31a, an ATVC control processor 31b, an image formation processor 31c, and an adjustment processor 31d. The control unit 30 also includes a primary transfer voltage storage / calculation unit 31e and a secondary transfer voltage storage / calculation unit 31f. These processing units and storage / calculation units may be provided as part of the CPU 31 or RAM 33. For example, the control unit 30 (more specifically, the image formation processor 31c) can execute jobs as described above. The control unit 30 (more specifically, the ATVC control processor 31b) can execute ATVC control (setting mode) of the primary transfer unit and the secondary transfer unit. ATVC control will be described in detail later. The control unit 30 (more specifically, the adjustment processor 31d) can execute an adjustment mode that adjusts the set voltage of the secondary transfer voltage. The adjustment mode will be described in detail later.

[0040] Here, the image forming apparatus 1 executes a job (image output operation, print job) that is a series of operations that starts with a single start command and forms and outputs an image on one or multiple recording materials S. The job generally includes an image formation process, a pre-rotation process, a sheet-to-sheet process when forming images on multiple recording materials S, and a post-rotation process. The image formation process is a period during which electrostatic image formation, toner image formation, primary transfer of the toner image, and secondary transfer of the toner image are performed for the image that is actually formed and output on the recording materials S. This period is referred to as the image formation period. More specifically, the timing of the image formation process differs depending on the positions where the electrostatic image formation, toner image formation, primary transfer of the toner image, and secondary transfer are performed. The pre-rotation process is a period from when a start command is input until the actual start of image formation, during which preparatory operations are performed before the image formation process. The sheet-to-sheet process is a period corresponding to the interval between recording materials S when image formation is performed continuously on multiple recording materials S (continuous image formation). The post-rotation process is a period during which tidying up operations (preparatory operations) are performed after the image formation process. Non-image formation time (non-image formation period) refers to a period other than image formation time, and includes the above-mentioned pre-rotation process, paper interval process, post-rotation process, and also the pre-multi-rotation process, which is a preparatory operation when the image forming device 1 is turned on or when it returns from a sleep state.

[0041] 2. Secondary transfer voltage control Next, the control of the secondary transfer voltage will be described. Fig. 3 is a flowchart showing an outline of the procedure for controlling the secondary transfer voltage in this embodiment. Generally, the control of the secondary transfer voltage is performed using constant voltage control or constant current control, but this embodiment uses constant voltage control.

[0042] First, when the control unit 30 (pre-image formation preparation process unit 31a) acquires job information from the operation unit 70 or the external device 200, it starts the job operation (S101). This job information includes image information specified by the operator and information about the recording material S. This information about the recording material S may include the size (width, length) of the recording material S on which the image is to be formed, information related to the thickness of the recording material S (thickness, basis weight, etc.), and information related to the surface properties of the recording material S, such as whether the recording material S is coated paper. In particular, in this embodiment, the information about the recording material S includes information about the size of the recording material S and information about the category of the recording material S (so-called paper type category), such as "thin paper, plain paper, thick paper, etc.", which is related to the thickness of the recording material S. The information about the recording material S (recording material information) includes any information that can distinguish the recording material S, such as attributes based on general characteristics (so-called paper type categories) such as plain paper, high-quality paper, glossy paper, coated paper, embossed paper, thick paper, and thin paper; numerical values ​​or numerical ranges for basis weight, thickness, size, and rigidity; or brand (including manufacturer, product name, and product number). Each recording material S distinguished by the information about the recording material S can be considered to constitute a type of recording material S. Furthermore, the information about the recording material S may be included in print mode information, such as "plain paper mode" or "thick paper mode," that specifies the operational settings of the image forming apparatus 1, or may be replaced by the print mode information. The control unit 30 (image formation preparation process unit 31a) writes this job information to RAM 33 (S102).

[0043] Next, the control unit 30 (image formation preparation process unit 31a) acquires environmental information detected by the temperature sensor 71 and humidity sensor 72 (S103). The ROM 32 stores information indicating the correlation between the environmental information and the target current Itarget for transferring the toner image on the intermediate transfer belt 44b onto the recording material S. The control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) calculates the target current Itarget corresponding to the environment from the information indicating the relationship between the environmental information and the target current Itarget based on the environmental information read in S103. The control unit 30 then writes this target current Itarget to the RAM 33 (or the secondary transfer voltage storage unit / calculation unit 31f) (S104). The reason the target current Itarget is changed according to the environmental information is because the amount of charge on the toner varies depending on the environment. The information indicating the relationship between the environmental information and the target current Itarget is calculated in advance through experiments or the like.

[0044] Next, before the toner image on the intermediate transfer belt 44b and the recording material S onto which the toner image is transferred reach the secondary transfer portion N2, the control unit 30 (ATVC control processor 31b) acquires information about the electrical resistance of the secondary transfer portion N2 using ATVC (Active Transfer Voltage Control) control (S105). That is, while the outer secondary transfer roller 45b and the intermediate transfer belt 44b are in contact with each other, the secondary transfer power supply 76 supplies a predetermined voltage at multiple levels to the outer secondary transfer roller 45b. The current value while the predetermined voltage is being supplied is detected by the current detection sensor 76b, and the relationship between the voltage and the current (voltage-current characteristics) as shown in FIG. 4 is acquired. The control unit 30 writes the information about the relationship between the voltage and the current to the RAM 33 (or the secondary transfer voltage storage unit / calculator 31f). This relationship between the voltage and the current changes depending on the electrical resistance of the secondary transfer portion N2. In the configuration of this embodiment, the relationship between the voltage and the current is not one in which the current changes linearly (proportional) to the voltage, but rather one in which the current changes in a manner that is expressed by a polynomial of the voltage that is quadratic or higher (a quadratic equation in this embodiment). Therefore, in this embodiment, the predetermined voltage or current supplied when acquiring information about the electrical resistance of the secondary transfer portion N2 is multi-staged at three or more points so that the relationship between the voltage and the current can be expressed by a polynomial.

[0045] Next, the control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) calculates the voltage value to be applied from the secondary transfer power supply 76 to the outer secondary transfer roller 45b (S106). That is, based on the target current Itarget written to the RAM 33 in S104 and the voltage-current relationship calculated in S105, the control unit 30 calculates the voltage value Vb required to apply the target current Itarget when no recording material S is present at the secondary transfer portion N2. This voltage value Vb corresponds to the secondary transfer partial voltage (transfer voltage corresponding to the electrical resistance of the secondary transfer portion N2). Also, the ROM 32 stores information for calculating the recording material partial voltage Vp (transfer voltage corresponding to the electrical resistance of the recording material S), as shown in FIG. 5. In this embodiment, this information is set as table data indicating the relationship between the moisture content of the atmosphere and the recording material partial voltage Vp for each basis weight category (corresponding to a paper type category) of the recording material S. The control unit 30 (image formation preparation process unit 31a) can determine the moisture content of the atmosphere based on environmental information (temperature and humidity) detected by the temperature sensor 71 and humidity sensor 72. The control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) determines the recording material distribution voltage Vp from the table data based on the job information acquired in S101 and the environmental information acquired in S103. Furthermore, when an adjustment value is set in an adjustment mode that adjusts the set voltage of the secondary transfer voltage, which will be described later, the control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) determines an adjustment amount ΔV corresponding to the adjustment value. As will be described later, when this adjustment amount ΔV is set in the adjustment mode, it is stored in the RAM 33 (or the secondary transfer voltage storage unit / calculation unit 31f). The control unit 30 calculates the secondary transfer voltage Vtr to be applied from the secondary transfer power supply 76 to the outer secondary transfer roller 45b when the recording material S passes through the secondary transfer unit N2 by adding together the Vb, Vp, and ΔV, to obtain Vb+Vp+ΔV. The control unit 30 then writes this Vtr (=Vb+Vp+ΔV) to the RAM 33 (or the secondary transfer voltage storage unit / calculation unit 31f). The table data for calculating the recording material shared voltage Vp shown in FIG. 5 is obtained in advance by experiment or the like.

[0046] Here, the recording material voltage Vp may change depending on the surface properties of the recording material S in addition to information related to the thickness of the recording material S (thickness, basis weight, etc.). Therefore, the table data may be set so that the recording material voltage Vp also changes depending on information related to the surface properties of the recording material S. In this embodiment, information related to the thickness of the recording material S (and further information related to the surface properties of the recording material S) is included in the job information acquired in S101. However, it is also possible to provide a measuring means for detecting the thickness and surface properties of the recording material S in the image forming apparatus 1, and to determine the recording material voltage Vp based on the information obtained by this measuring means.

[0047] Next, the control unit 30 (image forming process unit 31c) executes image formation, sends the recording material S to the secondary transfer unit N2, and applies the secondary transfer voltage Vtr determined as described above to perform secondary transfer (S107). Thereafter, the control unit 30 (image forming process unit 31c) repeats the process of S107 until all images of the job have been transferred onto the recording material S and output (S108).

[0048] Regarding the primary transfer portion N1, the same ATVC control as above is performed from the time the job is started until the toner image is transported to the primary transfer portion N1, but a detailed description thereof will be omitted here.

[0049] 3. Adjustment Mode Overview Next, an adjustment mode (simple adjustment mode) for adjusting the set voltage of the secondary transfer voltage will be described.

[0050] Depending on the type and condition of the recording material S used for image formation, the moisture content and electrical resistance of the recording material S may differ significantly from those of a standard recording material S. In this case, optimal transfer may not be achieved by setting the secondary transfer voltage using the default recording material voltage Vp, as previously set. In other words, the secondary transfer voltage must first be a voltage necessary for transferring the toner on the intermediate transfer belt 44b to the recording material S. Furthermore, the secondary transfer voltage must be limited to a voltage that does not cause abnormal discharge. However, depending on the type and condition of the recording material S actually used for image formation, the electrical resistance may be higher than the standard value. In this case, the secondary transfer voltage set using the default recording material voltage Vp may not be sufficient to transfer the toner on the intermediate transfer belt 44b to the recording material S. In this case, it is desirable to increase the secondary transfer voltage, for example by increasing the recording material voltage Vp. Conversely, depending on the type and condition of the recording material S actually used for image formation, the moisture content of the recording material S may be increased, resulting in a lower electrical resistance than the standard value, making discharge more likely to occur. In this case, if the secondary transfer voltage is set using the preset default recording material voltage Vp, image defects may occur due to abnormal discharge. Therefore, in this case, it is desirable to lower the set voltage of the secondary transfer voltage by, for example, lowering the recording material voltage Vp.

[0051] For this reason, it may be desirable for an operator, such as a user or a service technician, to adjust (change) the set voltage of the secondary transfer voltage to an optimal value during job execution, for example by adjusting (changing) the recording material assigned voltage Vp depending on the recording material S actually used for image formation. In other words, it may be desirable to select an optimal recording material assigned voltage Vp+ΔV (adjustment amount) depending on the recording material S actually used for image formation. This adjustment can be performed using the following method. For example, the operator may output the desired image while switching the secondary transfer voltage for each sheet of recording material S, check the output image, and then determine the optimal set voltage of the secondary transfer voltage (more specifically, the recording material assigned voltage Vp+ΔV). However, this method may result in more recording material S being wasted or require a longer adjustment time because the image output and the adjustment of the set voltage of the secondary transfer voltage are repeated.

[0052] Therefore, in this embodiment, the image forming apparatus 1 is provided with an adjustment mode for adjusting the set voltage of the secondary transfer voltage. In this adjustment mode, a chart in which multiple patches (test images) of representative colors are formed on the recording material S actually used for image formation is output while the set voltage of the secondary transfer voltage is changed for each patch. Then, based on the results of reading the output chart by the reading device 80, the optimal set voltage of the secondary transfer voltage (more specifically, the recording material distribution voltage Vp+ΔV) can be determined. In this embodiment, the adjustment mode presents information on the recommended adjustment amount ΔV of the set voltage of the secondary transfer voltage based on density information (luminance information) of the patches on the chart (typically solid image patches). This reduces the need for the operator to visually check the image on the chart, thereby reducing the operator's operational burden and enabling more appropriate adjustment of the set voltage of the secondary transfer voltage.

[0053] 4. Charts Next, the chart (adjustment image, test page) output in the adjustment mode of this embodiment will be described. FIGS. 6 and 7 are schematic diagrams of a chart 100 in this embodiment. In this embodiment, two types of charts 100 are output in the adjustment mode, roughly classified according to the size of the recording material S used, as shown in FIGS. 6 and 7. FIG. 6 shows a chart 100 output when the length of the recording material S in the conveying direction is 420 to 487 mm. FIG. 7 shows a chart 100 output when the length of the recording material S in the conveying direction is 210 to 419 mm. Note that in this embodiment, charts can be output on both sides of the recording material S even in the adjustment mode so that the secondary transfer voltages during secondary transfer to the front side (first side) and back side (second side) in double-sided image formation can be adjusted, respectively. FIGS. 6 and 7 show charts when a chart is formed on one side of the recording material S (hereinafter also referred to as a "single-sided chart") and when a chart is formed on both sides of the recording material S (hereinafter also referred to as a "double-sided chart"), respectively. The double-sided chart is formed by double-sided image formation using the double-sided conveying unit 11 described above.

[0054] Here, the size of the recording material S is expressed as recording material width (length in the main scanning direction) x recording material length (length in the sub-scanning direction). The recording material width is the length in the direction (width direction) substantially perpendicular to the conveyance direction of the recording material S when passing through the secondary transfer portion N2. The recording material length is the length in the direction substantially parallel to the conveyance direction of the recording material S when passing through the secondary transfer portion N2.

[0055] Figure 6 shows a large-size chart (hereinafter also referred to as "large chart") 100L (100La, 100Lb) that is output when using a large-size recording material S such as A3 (297mm x 420mm) or ledger (approximately 280mm x 432mm). Figure 6(a) shows the large chart 100La on the first side when outputting a single-sided chart or a double-sided chart. Figure 6(b) shows the large chart 100Lb on the second side when outputting a double-sided chart.

[0056] Figure 7 shows a small-size chart (hereinafter also referred to as "small chart") 100S (100Sa, 100Sb) that is output when using a small-size recording material S such as A4 landscape (297 mm x 210 mm) or letter landscape (approximately 280 mm x 216 mm). Figures 7(a) and (b) show the first and second small charts 100Sa on the first side when outputting a single-sided chart or a double-sided chart, respectively. Figures 7(c) and (d) show the first and second small charts 100Sb on the second side when outputting a double-sided chart, respectively.

[0057] Considering the operator's visual confirmation, the larger the patch size of the chart output in the adjustment mode, the easier it is to check for image defects. However, larger patches result in fewer patches being able to be formed on one sheet of recording material S. Patch shapes can be square, for example. The patch color can be determined based on the type of image defect to be checked and how easily it can be checked. For example, when the secondary transfer voltage is increased from a low value, the lower limit of the secondary transfer voltage can be determined from the voltage value at which patches of secondary colors such as red, green, and blue can be properly transferred. Furthermore, when the operator visually checks, the upper limit of the secondary transfer voltage can be determined from the voltage value at which image defects occur in halftone patches due to high secondary transfer voltage when the secondary transfer voltage is further increased.

[0058] The chart 100 has a patch set in which one blue solid patch 101, one black solid patch 102, and two halftone patches 103 are arranged in the width direction. The large chart 100L in FIG. 6 has 11 width direction patch sets 101-103 arranged in the transport direction. The small chart 100S in FIG. 7 has 10 width direction patch sets 101-103 arranged in the transport direction. In this embodiment, the halftone patch 103 is a gray (black halftone) patch. Here, the solid image is an image with the maximum density level. In this embodiment, the blue solid is a combination of 100% magenta (M) toner and 100% cyan (C) toner, and the toner coverage of the blue solid is 200%. The black solid is an image with 100% black (K) toner. Furthermore, a halftone image is an image with a toner application amount of 10 to 80%, for example, when the toner application amount of a solid image is 100%. In this embodiment, the chart 100 is provided with patch identification information 104 associated with each of the patch sets 101 to 103, for identifying the secondary transfer voltage setting applied to each patch set. This patch identification information 104 may be a value corresponding to the secondary transfer voltage adjustment value described below. The large chart 100L in FIG. 6 has 11 pieces of patch identification information 104 (11 pieces from -5 to 0 to +5 in this embodiment) corresponding to 11 levels of secondary transfer voltage settings. The small chart 100S in FIG. 7 has 10 pieces of patch identification information 104 (five pieces from -4 to 0 on the first sheet and five pieces from +1 to +5 on the second sheet) corresponding to 10 levels of secondary transfer voltage settings. In addition, the chart 100 may have front / back identification information 105 provided on at least one of the front side (first side) or back side (second side) of the recording material S, which indicates that the recording material S is the front side (first side) or back side (second side).

[0059] The patch size is required to be large enough to allow an operator to easily determine whether or not there is an image defect. Because it is difficult to determine the transferability of the blue solid patch 101 and the black solid patch 102 when the patch size is small, the patch size is preferably 10 mm square or larger, and more preferably 25 mm square or larger. Image defects caused by discharges that occur when the secondary transfer voltage is increased in the halftone patch 103 often appear as white dots. Compared to the transferability of solid images, these image defects tend to be easier to determine even with small images. However, because images are easier to see when they are not too small, in this embodiment, the width of the halftone patch 103 in the transport direction is set to the same as the width of the blue solid patch 101 and the black solid patch 102 in the transport direction. Furthermore, the spacing between the patch sets 101 to 103 in the transport direction may be set to allow for switching of the secondary transfer voltage. In this embodiment, the blue solid patch 101 and the black solid patch 102 are each a 25.7 mm × 25.7 mm square (one side is approximately parallel to the width direction). In this embodiment, the halftone patches 103 at both ends in the width direction each have a width of 25.7 mm in the transport direction and extend to the very edge of the chart 100 in the width direction. In this embodiment, the spacing between the patch sets 101 to 103 in the transport direction is 9.5 mm. The secondary transfer voltage is switched when the portion of the chart 100 corresponding to this spacing passes through the secondary transfer portion N2. In this embodiment, the patch sets 101 to 103 of the chart 100 are sequentially transferred from the upstream side to the downstream side in the transport direction of the recording material S when the chart 100 is formed using a plurality of secondary transfer voltages (test voltages) whose absolute values ​​are sequentially increased. However, the present invention is not limited to this embodiment. Each patch set 101 to 103 of the chart 100 may be transferred sequentially from the upstream side to the downstream side in the conveying direction of the recording material S when the chart 100 is formed, using a plurality of secondary transfer voltages (test voltages) whose absolute values ​​are sequentially decreased.

[0060] It is preferable that patches are not formed near the leading and trailing ends of the recording material S in the conveying direction (for example, within a range of about 20 to 30 mm inward from the edge). This is for the following reason: Among the ends of the recording material S in the conveying direction, there may be an image defect that occurs only at the leading or trailing end in the conveying direction, but not at the end in the width direction. In this case, it may be difficult to determine whether the image defect is caused by fluctuating the secondary transfer voltage.

[0061] The maximum size of the recording material S that can be used with the image forming apparatus 1 in this embodiment is 13 inches (approximately 330 mm) × 19.2 inches (approximately 487 mm), and the large chart 100L in FIG. 6 corresponds to this size of recording material S. When the size of the recording material S is 13 inches × 19.2 inches or less and A3 (297 mm × 420 mm) or larger, a chart corresponding to image data that is cropped from the image data of the large chart 100L shown in FIG. 6 according to the size of the recording material S is output. At this time, in this embodiment, the image data is cropped to fit the size of the recording material S based on the center of the leading edge. That is, the leading edge of the recording material S in the transport direction and the leading edge of the large chart 100L in the transport direction (the top edge in the figure) are aligned, and the center of the width of the recording material S and the center of the large chart 100L in the width direction are aligned, and the image data is cropped. Furthermore, in this embodiment, the image data is cropped so that a margin of 2.5 mm is provided at the ends (both ends in the width direction and the transport direction in this embodiment). For example, when a large chart 100L is output onto an A3 (297 mm x 420 mm) recording material S, image data within a 292 mm x 415 mm range is cropped, leaving 2.5 mm margins at each end. The large chart 100L corresponding to this image data is then output onto an A3 (297 mm x 420 mm) recording material S, with the leading edge centered as the reference. When a recording material S with a width smaller than 13 inches is used, the widthwise size of the halftone patches 103 at the widthwise ends becomes smaller. Furthermore, when a recording material S with a width smaller than 13 inches is used, the margin at the trailing edge in the transport direction becomes smaller. As described above, 11 patch sets ranging from -5 to 0 to +5 are arranged on the large chart 100L. The 11 patch sets 101 to 103 of the large chart 100L are arranged within a range of 387 mm in length in the conveying direction so that they fit within a length of 415 mm in the conveying direction when the size of the recording material S is A3.

[0062] In this embodiment, when a recording material S smaller than A3 (297 mm × 420 mm) is used, the small chart 100S shown in FIG. 7 is output. The small chart 100S shown in FIG. 7 corresponds to sizes smaller than A5 (portrait feed) and A3 (297 mm × 420 mm) (i.e., lengths in the transport direction of 210 to 419 mm). As described above, the small chart 100S has a total of 10 patch sets: five sets of -4 to 0 on the first sheet and +1 to +5 on the second sheet. The size of the image data for the small chart 100S is 13 inches × 210 mm. In the width direction, the halftone patches 103 are smaller to match the size of the recording material S. In the transport direction, the five patch sets fit within a length of 167 mm in the transport direction, and the trailing margin is longer to match the length of the recording material S in the transport direction of 210 to 419 mm. For recording material S with a length in the transport direction of 210 to 419 mm, only five patch sets can be formed in the transport direction on one sheet. Therefore, to increase the number of patches, the chart is divided into two sheets, and five sets from -4 to 0 and five sets from +1 to +5 are formed, for a total of 10 patch sets. Note that the small chart 100S omits the -5 patch set from the large chart 100L.

[0063] Furthermore, regardless of the size of the recording material S, the blue solid patch 101 and the black solid patch 102 are arranged on the front side (first side) and back side (second side) of the double-sided chart so that they do not overlap on the front and back sides of the recording material S. In this embodiment, the patch spacing in the width direction is set to 5.4 mm. This is to suppress variations in the detection results of the patch density on the second side due to the influence of the patch density on the first side, and to more accurately adjust the secondary transfer voltage for the second side.

[0064] In addition, in this embodiment, in addition to standard sizes, the chart 100 can also be output using recording material S of any size (free size) by the operator specifying it through input from the operation unit 70 or external device 200, for example.

[0065] 5. Adjustment mode operation Next, the operation of the adjustment mode in this embodiment will be described. Fig. 8 is a flowchart outlining the procedure of the adjustment mode in this embodiment. Fig. 9 is a schematic diagram showing an example of a setting screen for the adjustment mode. Here, an example is taken of a case where an operator executes the adjustment mode by inputting an instruction from the operation unit 70 of the image forming apparatus 1. Also, an example is taken of a case where the operator reads the density information (brightness information) of the patch by placing a recording material S on which a chart 100 has been formed on the platen glass 82 of the reading device 80. For simplicity, the recording material on which a chart has been formed may sometimes be simply referred to as a "chart."

[0066] The setting screen for the adjustment mode will now be described. In this embodiment, the control unit 30 (adjustment processing unit 31d) displays an adjustment mode setting screen 300, such as that shown in FIG. 9A, on the display unit 70a of the operation unit 70. The setting screen 300 has a voltage setting unit 301 for setting adjustment values ​​for the secondary transfer voltage for the front side (first side) and back side (second side) of the recording material S. The setting screen 300 also has an output side selection unit 302 for selecting whether the chart 100 is to be output on one side or both sides of the recording material S. The setting screen 300 also has an output instruction unit (chart output button) 303 for instructing the output of the chart 100. The setting screen 300 also has a confirmation unit (OK button) 304 for confirming the settings and a cancel button 305 for canceling the setting changes. The setting screen 300 also has a message display unit 306 for displaying various messages related to the adjustment mode. In this embodiment, the start button 307 provided on the operation unit 70 adjacent to the display unit 70a functions as an input unit for inputting an instruction to the reading device 80 to start reading the chart 100. However, a display (button) functioning as the input unit may be provided on the setting screen 300 or the like displayed on the display unit 70a.

[0067] When the adjustment value "0" is selected in the voltage setting unit 301, the secondary transfer voltage (more specifically, the recording material assigned voltage Vp) is set to a predetermined value (table value) that is preset for the currently selected recording material S. In this case, the secondary transfer voltage (more specifically, the recording material assigned voltage Vp) may be set to the value currently set for the currently selected recording material S. In this case, the center voltage value (the value corresponding to the patch set of 0 on the chart 100) of the secondary transfer voltage (more specifically, the recording material assigned voltage Vp) when the chart 100 is output is set to that value. In addition, when an adjustment value other than "0" is selected, in this embodiment, the secondary transfer voltage (more specifically, the recording material assigned voltage Vp) is adjusted by an adjustment amount ΔV of 150 V for each level of the adjustment value. In this case, the center voltage value of the secondary transfer voltage (more specifically, the recording material assigned voltage Vp) when the chart 100 is output is set to that value. After the adjustment value is selected, the chart 100 is output at the selected center voltage value by operating the chart output button 303. Furthermore, after the adjustment value is selected, the adjustment value of the secondary transfer voltage is confirmed by operating the OK button 104. The control unit 30 (adjustment processing unit 31d) acquires information related to settings such as the center voltage value input via the setting screen 300 on the operation unit 70, and stores the information in a storage unit (RAM 33, secondary transfer voltage storage unit / calculation unit 31f, etc.) as necessary.

[0068] The procedure for the adjustment mode will be described. First, when the operator inputs information about the recording material S to be used in the adjustment mode (such as paper type category and size), the control unit 30 (adjustment processor 31d) causes the display unit 70a to display the adjustment mode setting screen 300 (S201). At this time, the control unit 30 (adjustment processor 31d) causes the display unit 70a to display the setting screen 300 in response to the operation of a button or the like provided on the input screen for the recording material S information displayed on the display unit 70a to call up the adjustment mode setting screen 300. The control unit 30 (adjustment processor 31d) acquires the information about the recording material S input by the operator on the input screen and adjusts the secondary transfer voltage in association with the information about the recording material S. Note that the information about the recording material S may be acquired from information previously set in association with the recording material cassette 91, by selecting the recording material cassette 91 containing the recording material S to be used in the adjustment mode.

[0069] Next, the control unit 30 (adjustment processor 31d) acquires the setting of the center voltage value of the secondary transfer voltage when outputting the chart 100 and the setting of whether to output a single-sided chart or a double-sided chart, which have been input by the operator on the setting screen 300 (S202). Next, the control unit 30 (adjustment processor 31d) acquires a signal indicating that the operator has operated the chart output button 303 on the setting screen 300 (S203). Then, prior to outputting the chart 100, the control unit 30 (adjustment processor 31d) acquires a polynomial of degree 2 or higher (a quadratic equation in this embodiment) of the relationship between voltage and current according to the electrical low resistance of the secondary transfer unit N2, through an operation similar to the ATVC control described above (S204). Then, the control unit 30 (adjustment processor 31d) sets the secondary transfer voltage (test voltage) based on the acquired information on the relationship between voltage and current and the information on the center voltage value set on the setting screen 300, and controls the chart 100 to be output (S205). At this time, the control unit 30 (adjustment processing unit 31d) adjusts the image data of the chart 100 as described above, and controls the output of a predetermined chart 100 according to the size of the recording material S while changing the secondary transfer voltage in 150V increments. As described above, when a recording material S corresponding to the large chart 100L is used, one large chart 100L is output, in which 11 patch sets are transferred and fixed onto the recording material S while changing the secondary transfer voltage. Also, as described above, when a recording material S corresponding to the small chart 100S is used, two small charts 100S are output, in which five patch sets are transferred and fixed onto the recording material S while changing the secondary transfer voltage, respectively.

[0070] Next, the control unit 30 (adjustment processor 31d) determines whether the chart 100 can be read by the reading device 80 based on whether the size of the recording material S used to output the chart 100 is a size that can be read by the reading device 80 (step S206). If the control unit 30 (adjustment processor 31d) determines in S206 that reading is not possible, the control unit 30 (adjustment processor 31d) proceeds to the process of S220. At this time, as shown in FIG. 9B, for example, the control unit 30 (adjustment processor 31d) can display a message in the message display section 306 (FIG. 9A) of the setting screen 300 urging the operator to manually adjust the secondary transfer voltage. If the size of the recording material S used to output the chart 100 is not a size that can be read by the reading device 80, the operator can manually adjust the secondary transfer voltage by inputting an adjustment value in the voltage setting section 301 (FIG. 9A) of the setting screen 300 (S220). If the control unit 30 (adjustment processor 31d) determines in S206 that reading can be performed, it proceeds to the process of S207. Then, the control unit 30 (adjustment processor 31d) waits for the operator to operate the start button 307 on the operation unit 70 to input an instruction to start reading the chart 100 (S207). At this time, the control unit 30 (adjustment processor 31d) can display a message in the message display area 306 (FIG. 9A) of the setting screen 300, as shown in FIG. 9C, for example, to prompt the operator to set the chart 100 in the reading device 80. Note that FIG. 9C shows an example in which a small chart 100S is output. If the size of the recording material S is a size that can be read by the reading device 80, the control unit 30 (adjustment processor 31d) can present preferable setting candidates for the secondary transfer voltage based on the reading result of the chart 100 by the reading device 80 (S219). Furthermore, if the adjustment value of the secondary transfer voltage is manually changed on the setting screen 300 while waiting for an instruction to start reading the chart 100 to be input, the control unit 30 (adjustment processor 31d) proceeds to the process of S220.

[0071] Next, when the control unit 30 (adjustment processor 31d) receives a reading start signal from the operation unit 70 instructing the start of reading the chart 100 (S207), it determines whether the recording material S used to output the chart 100 is large size (S208). If the control unit 30 (adjustment processor 31d) determines in S208 that the size of the recording material S is large, such as A3 (297 mm × 420 mm) or ledger (approximately 280 mm × 432 mm), it proceeds to the processing of S209. Then, the control unit 30 (adjustment processor 31d) determines whether a single-sided chart or a double-sided chart has been output (S209). If the control unit 30 (adjustment processor 31d) determines in S209 that a single-sided chart has been output, it causes the reading device 80 to read only one side of the recording material S (S210). Furthermore, when the control unit 30 (adjustment processor 31d) determines in S209 that a double-sided chart has been output, it first causes the reading device 80 to read the front side (first side) of the recording material S (S211). After that, when the control unit 30 (adjustment processor 31d) receives a reading start signal from the operation unit 70 again, it causes the reading device 80 to read the back side (second side) of the recording material S (S212). In this way, when a large-size recording material S is used, one large chart 100L on which eleven patch sets from -5 to 0 to +5 are formed and which are set at one time in the reading device 80 is read in response to one reading start signal.

[0072] On the other hand, if the control unit 30 (adjustment processor 31d) determines in S208 that the size of the recording material S is a small size such as A4 landscape (297 mm × 210 mm) or letter landscape (approximately 280 mm × 216 mm), the process proceeds to S213. Then, the control unit 30 (adjustment processor 31d) determines whether a single-sided chart or a double-sided chart has been output (S213). If the control unit 30 (adjustment processor 31d) determines in S213 that a single-sided chart has been output, the control unit 30 (adjustment processor 31d) reads only one side of each of the two sheets of recording material S at the same time using the reading device 80 (S214). If the control unit 30 (adjustment processor 31d) determines in S213 that a double-sided chart has been output, the control unit 30 (adjustment processor 31d) first reads the front sides (first sides) of each of the two sheets of recording material S at the same time using the reading device 80 (S215). Thereafter, when the control unit 30 (adjustment processing unit 31d) receives a reading start signal from the operation unit 70 again, it simultaneously reads the back sides (second sides) of the two sheets of recording material S (S216). In this way, when small-sized recording material S is used, the first small chart 100S on which five patch sets from -4 to 0 are formed and the second small chart 100S on which five patch sets from +1 to +5 are formed are simultaneously read in response to a single reading start signal. In this embodiment, the single reading start signal is input to the control unit 30 by the operator operating the start button 307 as an input unit. However, the present invention is not limited to this embodiment. For example, the reading unit 80 may have a sensor that detects that a document has been placed on the reading surface or that a document has been placed on the document placement section of the automatic document feeder 81, and the reading of the document may automatically start in response to the sensor's detection result. In such a configuration, the one reading start signal may be input to the control unit 30 from the sensor serving as the input unit.

[0073] Next, the control unit 30 (adjustment processor 31d) performs a read error determination to determine whether the reading device 80 has read the chart 100 correctly (S217). Here, an example is shown in which the chart 100 is placed on the platen glass 82 and read; however, a read error can also be determined, for example, if a problem occurs in the conveyance of the chart 100 by the automatic document feeder 81. If the control unit 30 (adjustment processor 31d) determines in S117 that there is no read error, it performs a process to determine an adjustment value for the secondary transfer voltage (S218). This process of determining the adjustment value for the secondary transfer voltage will be described later. On the other hand, if the control unit 30 (adjustment processor 31d) determines in S117 that there is a read error, it returns to the process of S207 and determines whether to use the reading device 80 again.

[0074] Next, the control unit 30 (adjustment processor 31d) displays the adjustment value determined in S218 in the voltage setting section 301 of the setting screen 300 (S219). This adjustment value indicates a preferable setting candidate for the secondary transfer voltage. The operator can visually check the chart 100 or the like to determine whether the adjustment value displayed on the setting screen 300 is acceptable. If the operator does not want to change the adjustment value displayed on the setting screen 300, he or she simply presses the OK button 304 on the setting screen 300. On the other hand, if the operator wants to change (manually adjust) the adjustment value displayed on the setting screen 300, he or she inputs the adjustment value he or she wants to set in the voltage setting section 301 of the setting screen 300 and presses the OK button 304 on the setting screen 300. The control unit 30 (adjustment processor 31d) determines whether the adjustment value has been changed (S220). Then, when the control unit 30 (adjustment processor 31d) receives a signal indicating that the OK button 304 has been operated without changing the adjustment value, it stores the adjustment value determined in S218 in RAM 33 (or secondary transfer voltage storage unit / calculation unit 31f) (S221). On the other hand, when the control unit 30 (adjustment processor 31d) receives a signal indicating that the adjustment value has been changed and the OK button 304 has been operated, it stores the adjustment value input by the operator in RAM 33 (or secondary transfer voltage storage unit / calculation unit 31f) (S222). This ends the adjustment mode.

[0075] When a subsequent job is executed using the recording material S for which the secondary transfer voltage was set in the adjustment mode, the control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) sets the secondary transfer voltage according to the adjustment value stored as described above until the next time the adjustment mode is executed. That is, the control unit 30 (secondary transfer voltage storage unit / calculation unit 31f) calculates the adjustment amount ΔV using the adjustment value stored as described above as ΔV = adjustment value × 150V, and calculates the adjusted recording material assigned voltage Vp + ΔV using the calculated adjustment amount ΔV. Then, the adjusted recording material assigned voltage Vp + ΔV is used to calculate the secondary transfer voltage Vtr (= Vb + Vp + ΔV).

[0076] Next, the process of determining the adjustment value of the secondary transfer voltage in S218 of Fig. 8 will be described. Fig. 10 is a flowchart outlining an example of the procedure of this process. Here, an example is taken in which two small charts 100S, which are single-sided charts, are read by the reading device 80. Also, an example is taken in which the luminance data of a solid blue patch 101 is used as the patch density information (luminance information) for determining the adjustment value of the secondary transfer voltage. Also, for convenience, the above-mentioned adjustment values ​​-4 to 0 to +5 will be described as corresponding to patch numbers 1 to 10, respectively.

[0077] The control unit 30 (adjustment processor 31d) acquires RGB luminance data (8 bits) of each solid blue patch that has been read by the operator from two small charts 100S set in the reading device 80 and stored in the RAM 33 (S301). Next, the control unit 30 (adjustment processor 31d) calculates the average luminance value Lave_B(N) (N=1 to 10) of each patch using the luminance data acquired in S301 (S302). By the process of S302, information indicating the relationship between the patch number (voltage level, adjustment value) and the average luminance value of the patch, as shown in FIG. 11, for example, is acquired. Next, the control unit 30 (adjustment processor 31d) calculates the standard deviation Lave_stdev(n) (n=1 to 7) of the average luminance values ​​for every four patch numbers (N to N+3) in order from the smallest patch number to the largest patch number (S303). Next, the control unit 30 (adjustment processor 31d) extracts patch numbers N to N+3 (stable brightness region) for which the standard deviation Lave_stdev(n) of the brightness average value is minimum (S304). Next, the control unit 30 (adjustment processor 31d) selects the maximum patch number from among the patch numbers for which the recording material distribution voltage Vp+ΔV (absolute value) determined from the adjustment values ​​corresponding to the patch numbers extracted in S304 is equal to or less than a predetermined upper limit (S305). In other words, the adjustment value for which the brightness average value of the solid blue patch 101 is minimum (maximum density) is selected within a range in which the recording material distribution voltage Vp+ΔV does not exceed the upper limit. Note that the upper limit is preset, for example, according to the paper type category of the recording material S, from the perspective of suppressing image defects caused by an excessively high secondary transfer voltage. The control unit 30 (adjustment processor 31d) then determines the adjustment value corresponding to the patch number selected in S305 as a candidate for a preferred secondary transfer voltage setting, and stores the adjustment value in RAM 33 (S306). By this process, in FIG. 11, a patch number where the decrease in the average brightness value (increase in density) is saturated, for example, an adjustment value corresponding to patch number -1, is determined as a candidate.

[0078] The process for determining adjustment values ​​for the first and second sides of the recording material S based on the results of reading the first and second sides of two small charts 100S, which are double-sided charts, is similar to the process described above. The process for determining adjustment values ​​based on the results of reading one large chart 100L (a single-sided chart, or both sides of a double-sided chart) is also similar to the process described above, except that the number of patch sets is different.

[0079] The color of the patch from which luminance data is acquired is not limited to blue, but may be red or green, or a single solid color of YMCK. Halftone luminance data may also be acquired.

[0080] In this embodiment, the adjustment amount of the secondary transfer voltage is determined by sequentially calculating the standard deviation of the luminance data of the patches for each of a plurality of patch numbers and extracting patches in the luminance stable region. However, the method for determining the adjustment amount of the secondary transfer voltage is not limited to this method. For example, the adjustment amount of the secondary transfer voltage may be determined by sequentially calculating the luminance difference between patches of adjacent patch numbers and extracting patches in the luminance stable region where the luminance difference is equal to or less than a predetermined value.

[0081] 6.Effects As described above, the image forming apparatus 1 of this embodiment includes an image carrier 51 that carries a toner image, an intermediate transfer body 44b onto which the toner image is primarily transferred from the image carrier 51, a transfer member 45b that forms a transfer section N2 that performs secondary transfer of the toner image from the intermediate transfer body 44b to the recording material S, an application section 76 that applies a voltage to the transfer member 45b, a discharge section 48 that discharges the recording material S on which the toner image transferred at the transfer section N2 has been fixed and an image has been formed, a reading device 80 that can read density information of the image on the recording material set by the operator, and a control section 30 that can execute an adjustment mode in which the application section 76 applies multiple test voltages to the transfer member 45b to discharge the recording material S from the discharge section 48 on which a chart has been formed by sequentially transferring multiple test images, and adjusts the secondary transfer voltage to be applied to the transfer member 45b by the application section 76 during secondary transfer. In this embodiment, in the adjustment mode, the control unit 30 discharges from the discharge unit 48 a first recording material on which a first chart is formed and a second recording material on which a second chart is formed, reads density information of test images on the first and second recording materials set simultaneously in the reading device 80 by an operator, and outputs information regarding the adjustment amount of the secondary transfer voltage based on the density information of the test images of the first and second charts obtained from the reading results of the reading device 80. Here, the reading device 80 may have a reading surface 82 that supports the first and second recording materials set simultaneously so that the reading device 80 can read them. The reading device 80 may also have a conveying device 81 that sequentially conveys the first and second recording materials set simultaneously so that the reading device 80 can read them.

[0082] The image forming apparatus 1 may have a duplex conveying unit 11 that conveys the recording material S to the transfer unit N2 in order to transfer a toner image to the second side of the recording material S, on which a toner image has been fixed on the first side, when forming images on both sides of the recording material S. In this case, in the adjustment mode, a first recording material on which a first chart has been formed on its first side and a third chart has been formed on its second side, and a second recording material on which a second chart has been formed on its first side and a fourth chart has been formed on its second side, can be discharged from the discharge unit 48. When the reading surface 82 of the reading device 80 is used, the reading device 80 can read density information of test images on one side of the first and second recording materials simultaneously set in the reading device 80 by the operator, and can also read density information of test images on the other side of the first and second recording materials simultaneously set in the reading device 80 by the operator. Alternatively, when the conveying device 81 of the reading device 80 is used, the reading device 80 can read density information of the test images on one side and the other side of each of the first and second recording materials that have been simultaneously set in the reading device 80 by an operator. Then, the control unit 30 can output information regarding the adjustment amount of the secondary transfer voltage when forming an image on the first side of the recording material S based on the density information of the test images of the first and second charts obtained from the reading results of the reading device 80, and can output information regarding the adjustment amount of the secondary transfer voltage when forming an image on the second side of the recording material S based on the density information of the test images of the third and fourth charts obtained from the reading results of the reading device 80.

[0083] The first chart may have a plurality of test images sequentially transferred from the upstream side to the downstream side in the transport direction of the first recording material when the first chart is formed using a plurality of test voltages whose absolute values ​​vary sequentially so as to increase, and the second chart may have a plurality of test images sequentially transferred from the upstream side to the downstream side in the transport direction of the second recording material when the second chart is formed using a plurality of test voltages whose absolute values ​​vary sequentially so as to increase from a value larger than the largest absolute value of the plurality of test voltages when the first chart is formed. Alternatively, the first chart may have a plurality of test images sequentially transferred from the upstream side to the downstream side in the transport direction of the first recording material when the first chart is formed using a plurality of test voltages whose absolute values ​​vary sequentially so as to decrease, and the second chart may have a plurality of test images sequentially transferred from the upstream side to the downstream side in the transport direction of the second recording material when the second chart is formed using a plurality of test voltages whose absolute values ​​vary sequentially so as to decrease from a value smaller than the smallest absolute value of the plurality of test voltages when the first chart is formed. Furthermore, the control unit 30 can output information regarding the adjustment amount to the display unit 70a provided in the image forming apparatus 1 or to the display unit of the external device 200 connected to the image forming apparatus 1, and cause the display unit to display the information regarding the adjustment amount. The control unit 30 can also output information regarding the adjustment amount to the memory unit 33 provided in the image forming apparatus 1, and cause the memory unit 33 to store the information regarding the adjustment amount. Furthermore, in this embodiment, in the adjustment mode, the control unit 30 can discharge from the discharge unit 48 a single sheet of recording material having a size larger than each of the first and second recording materials, and having a chart with a plurality of transferred test images formed thereon, and adjust the secondary transfer voltage based on the result of reading, by the reading device 80, density information of the test images on the single sheet of recording material.

[0084] Furthermore, according to this embodiment, even when the adjustment mode is executed using a small-sized recording material S such as A4 or LTR, the number of times the chart 100 is replaced with the reading device 80 can be reduced, thereby improving usability.

[0085] [Example 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted.

[0086] In the adjustment mode, considering the reduction of adjustment time and stability, it is preferable to output a chart 100 on which patches are transferred while sequentially switching the secondary transfer voltage (test voltage) from a small absolute value to a large value, or vice versa. Then, assuming that the patches are arranged in a predetermined order, for example, from the leading edge to the trailing edge of the chart 100 in the scanning direction, the density information of the patches read in that order is associated with the secondary transfer voltage (test voltage) information to determine the adjustment amount of the secondary transfer voltage. Specifically, as described in the first embodiment, for example, the standard deviation of the average luminance values ​​corresponding to each patch number is calculated, assuming that the patches were acquired in a predetermined switching order of the secondary transfer voltage (test voltage). Therefore, if the order in which multiple charts 100 (two small charts 100S in this embodiment) are placed on the reading device 80 or the order in which the charts 100 are transported (read) by the automatic document feeder 81 differs from the predetermined order, the processing results will be inappropriate.

[0087] Therefore, in this embodiment, the association between the density information of each patch and the information on the secondary transfer voltage (test voltage) corresponding to each patch is optimized based on the density information of at least one patch on each of the two small charts 100S read by the reading device 80. This will be explained in more detail below.

[0088] 12(a) shows the relationship between the patch number (voltage level, adjustment value) of a solid blue patch 101 and the average patch brightness value when two small charts 100S, which are single-sided charts, are read by the reading device 80, similar to that of FIG. 11. For convenience, the adjustment values ​​-4 to 0 to +5 mentioned above correspond to patch numbers 1 to 10, respectively.

[0089] If the size of the recording material S used to output the chart 100 is a small size such as A4 landscape (297 mm x 210 mm) or letter landscape (approximately 280 mm x 216 mm), patches with patch numbers 1 to 5 will be formed on the first sheet, and patches with patch numbers 6 to 10 will be formed on the second sheet.

[0090] When the operator sets two small charts 100S in the reading device 80 in a predetermined manner, the control unit 30 (adjustment processor 31d) can acquire information on the relationship between patch numbers and average luminance values, as shown in FIG. 12(a). Here, the predetermined manner is, for example, a predetermined arrangement order of the two small charts 100S on the platen glass 82 of the reading device 80 (for example, arranging the first chart on the left and the second chart on the right so that multiple patches are lined up in the same way as in the case of the large chart 100L). Alternatively, the predetermined manner is, for example, the stacking order of the two small charts 100S on the document placing section of the automatic document feeder 81 (for example, stacking the first chart on top and the second chart on bottom). In other words, it is the transport order of the two small charts 100S by the automatic document feeder 81 (for example, transporting the first chart first and the second chart last).

[0091] On the other hand, if the operator does not correctly set the two small charts 100S in the reading device 80 using the above-mentioned predetermined method, the following occurs. For example, if the arrangement order of the two small charts 100S on the platen glass 82 of the reading device 80 is reversed from that of the above-mentioned predetermined method, or if the order in which the two small charts 100S are transported by the automatic document feeder 81 is reversed from that of the above-mentioned predetermined method, the control unit 30 (adjustment processing unit 31d) acquires information on the relationship between patch numbers and average luminance values ​​as shown in FIG. 12(b). In this case, a luminance difference that should not actually occur occurs between the average luminance values ​​of patches with patch numbers 5 and 6. As a result, it becomes impossible to correctly determine a desirable adjustment value using the method for determining the adjustment value of the secondary transfer voltage as described in the first embodiment (FIG. 10).

[0092] Therefore, in this embodiment, if the difference in luminance (difference in average luminance values) between the patch with patch number 5 and the patch with patch number 6 is equal to or greater than a predetermined threshold, the control unit 30 (adjustment processor 31d) determines that the method of setting the two small charts 100S on the reading device 80 is incorrect. Then, the control unit 30 (adjustment processor 31d) performs processing to swap the group of luminance data of patch numbers 1 to 5, which has been acquired from the reading device 80 and stored in RAM 33, with the group of luminance data of patch numbers 6 to 10.

[0093] Next, a process for determining the adjustment value of the secondary transfer voltage in this embodiment will be described. FIG. 13 is a flowchart outlining an example of the procedure for this process. The process shown in FIG. 13 is executed as the process of S218 in the adjustment mode procedure shown in FIG. 8 described in the first embodiment. Here, a case where a single-sided chart is read is taken as an example. Also, as an example of a case where the chart 100 is not correctly set in the reading device 80 using the predetermined method, a case where two small charts 100S, which are single-sided charts, are arranged in the wrong order on the reading device 80 or are conveyed in the wrong order by the automatic document feeder 81 is taken as an example. Also, a case where the luminance data of a solid blue patch 101 is used as the density information (luminance information) of the patch for determining the adjustment value of the secondary transfer voltage is taken as an example.

[0094] The control unit 30 (adjustment processor 31d) acquires RGB luminance data (8 bits) of each solid blue patch that has been read by the operator from two small charts 100S set in the reading device 80 and stored in the RAM 33 (S401). At this time, the control unit 30 (adjustment processor 31d) acquires the luminance data of each patch, assuming that the patches are arranged in a predetermined order from the leading edge to the trailing edge in the scanning direction of the reading device 80. Then, the control unit 30 (adjustment processor 31d) uses the luminance data acquired in S401 to calculate the average luminance value Lave_B(N) (N=1 to 10) of each patch, and stores it in the RAM 33 (S402).

[0095] Next, the control unit 30 (adjustment processor 31d) calculates the luminance difference (difference in average luminance values) between patches of adjacent patch numbers based on the average luminance values ​​stored in RAM 33 in S402 (S403). Next, the control unit 30 (adjustment processor 31d) determines whether the recording material S used to output the chart 100 is small size (S404). If the control unit 30 (adjustment processor 31d) determines in S404 that the size of the recording material S used to output the chart 100 is small size, such as A4 landscape (297 mm x 210 mm) or letter landscape (approximately 280 mm x 216 mm), the control unit 30 proceeds to the process of S405.

[0096] The control unit 30 (adjustment processor 31d) then determines whether the luminance difference between the patch with patch number 5 and the patch with patch number 6 calculated in S403 is less than a predetermined threshold (S405). This predetermined threshold is set in advance as, for example, a value corresponding to the luminance measurement variation value by the reading device 80 when two small charts 100S are correctly set in the reading device 80 in a predetermined manner, and is stored in ROM 32. If the control unit 30 (adjustment processor 31d) determines in S405 that the luminance difference is less than the predetermined threshold, it determines an adjustment value for the secondary transfer voltage using the average luminance value of each patch stored in RAM 33 in S402 (S406). The processing in S406 may be the same as the processing in S303 to S306 in FIG. 10 described in the first embodiment, for example.

[0097] On the other hand, if the control unit 30 (adjustment processor 31d) determines in S405 that the luminance difference is not less than the predetermined threshold (i.e., is equal to or greater than the predetermined threshold), it proceeds to the process of S407. In this case, it can be determined that the arrangement order or transport order (reading order) of the first and second small charts 100S is incorrect. In this case, the control unit 30 (adjustment processor 31d) swaps the data of the average luminance values ​​of each patch stored in RAM 33 in S402 between the data of patch numbers 1 to 5 for the first sheet and the data of patch numbers 6 to 10 for the second sheet (S407). Note that at this time, the association between the luminance data and patch numbers acquired in S401 may be optimized, and the average luminance value may be calculated using the optimized luminance data. In other words, the order of the luminance data is corrected so that each patch number correctly corresponds to the secondary transfer voltage (test voltage), and the association between the patch numbers and the luminance data is optimized. Thereafter, the control unit 30 (adjustment processing unit 31d) determines an adjustment value for the secondary transfer voltage using the average luminance value of each patch whose association with the patch number has been optimized in S407 (S406). As described above, the process in S406 may be the same as the processes in S303 to S306 in FIG. 10 described in the first embodiment, for example.

[0098] Furthermore, if the control unit 30 (adjustment processing unit 31d) determines in S404 that the size of the recording material S used to output the chart 100 is a large size such as A3 (297 mm x 420 mm) or ledger (approximately 280 mm x 432 mm), it proceeds to processing of S406.

[0099] The color of the patch from which luminance data is acquired is not limited to blue, and other colors such as red or green may be used, or a single solid color such as YMCK may be used. Also, halftone luminance data may be acquired.

[0100] In addition, here, an example of a case where the charts 100 are not set correctly in the reading device 80 using the predetermined method is when the arrangement order or transport order of two small charts 100S, which are single-sided charts, is reversed. However, this is not limiting, and examples of a case where the charts 100 are not set correctly in the reading device 80 using the predetermined method include the following: when the arrangement order or reading order of at least one of the multiple charts 100 is incorrect, when the arrangement orientation of at least one of the multiple charts 100 is incorrect, when the front and back sides of at least one of the multiple charts 100 are incorrect, or combinations of these. Furthermore, typical examples include the following: when the arrangement order or reading order of the first and second charts 100 is reversed (corresponding to the above example), when the arrangement orientation of at least one of the first or second charts 100 is reversed, when the front and back sides of at least one of the first or second charts 100 (the arrangement order or reading order of the first and second sides) are reversed, or combinations of these. By presetting threshold values ​​corresponding to each of these cases as the above-mentioned predetermined threshold values, the order of the brightness data can be corrected in either case, thereby optimizing the association between patch numbers and brightness data.

[0101] Furthermore, here, the density information of the patch located most downstream in the conveyance direction of the first chart 100 and the patch located most upstream in the conveyance direction of the second chart 100 was used to determine whether the setting method of the chart 100 in the reading device 80 was correct. However, this is not limited to this. It is also possible to determine whether the setting method of the chart 100 in the reading device 80 is correct based on the density information of at least one arbitrary patch of each of the multiple charts 100. For example, it is also possible to determine whether the setting method is correct using the density information of the patch located most upstream in the conveyance direction of the first chart 100 and the patch located most downstream in the conveyance direction of the second chart 100. That is, referring to FIG. 12(b), in the above example, if the difference between the density information of the most downstream patch of the first chart 100 and the density information of the most upstream patch of the second chart 100 is equal to or greater than a predetermined threshold, it is determined that the setting method is incorrect. In contrast, referring to FIG. 12(b), it is also possible to determine that the setting method is incorrect if the difference between the density information of the most upstream patch of the first chart 100 and the density information of the most downstream patch of the second chart 100 is less than a predetermined threshold. For each of the above-described incorrect setting methods, it is sufficient to use density information of the patches, which makes it easy to determine whether the setting method is correct. Furthermore, the determination is not limited to being based on the difference in density information between patches, and any comparison method can be used, such as the difference in density information, including a comparison of which is larger, or the ratio of density information. Density information of multiple patches on each of multiple charts 100 may also be used.

[0102] Furthermore, whether the setting method of each chart 100 is correct, such as whether the orientation of at least one of the multiple charts 100 is reversed, may be determined based on the density information of at least one patch in each chart 100. For example, referring to FIG. 12(a), if the orientation of the first chart is reversed, the average luminance value increases as the patch number increases, inversely to the increase / decrease pattern shown in the figure. Such an increase / decrease pattern of the average luminance value can be obtained, for example, from the density information of multiple patches in each chart 100 (for example, by sequentially calculating the standard deviation or difference of the density information, or by calculating the difference in density information between the most upstream and most upstream patches). Then, based on the results, it can be determined whether the orientation of each chart 100 is correct.

[0103] As described above, in this embodiment, the control unit 30 determines whether the results read by the reading device 80 correspond to the first chart or the second chart based on the reading result of the reading device 80, and outputs information regarding the adjustment amount of the secondary transfer voltage based on the reading result of the reading device 80 and the determination result. In this embodiment, the control unit 30 associates the density information of the multiple test images acquired from the reading device 80 with information indicating the multiple test voltages so that the density information of each test image corresponds to the test voltage during transfer of each test image, and performs processing to output information regarding the adjustment amount of the secondary transfer voltage. In this embodiment, the control unit 30 is capable of performing a process to optimize the association between the density information of the multiple test images obtained from the reading device 80 and the multiple test voltages when the operator does not set the first and second recording materials in the reading device 80 in a predetermined manner, based on the density information of at least one test image among the multiple test images read from one of the first and second recording materials S and the density information of at least one test image among the multiple test images read from the other of the first and second recording materials S, so that the density information of each test image corresponds to the test voltage at the time of transfer of each test image. In particular, in this embodiment, the control unit 30 performs the optimization process based on first density information acquired from the reading device 80, which is taken as density information of the test image furthest downstream in the transport direction of the first recording material when the first chart is formed if the operator has set the first and second recording materials in the reading device 80 in the predetermined manner, and second density information acquired from the reading device 80, which is taken as density information of the test image furthest upstream in the transport direction of the second recording material when the operator has set the first and second recording materials in the reading device 80 in the predetermined manner. Also, in this embodiment, the control unit 30 performs the optimization process when the difference between the density indicated by the first density information and the density indicated by the second density information is equal to or greater than a predetermined threshold.Here, the optimization process may include a process of interchanging the density information acquired from the reading device 80 as the density information of the test image of the first chart with the density information acquired from the reading device 80 as the density information of the test image of the second chart. Note that identification information indicating at least one of the first and second sides may be formed on each of the first and second recording materials, and the control unit 30 may be configured to determine, based on the identification information read by the reading device 80, whether the density information of the test image acquired from the reading device 80 is density information of the test image of the first side of the recording material or density information of the test image of the second side of the recording material.

[0104] Furthermore, according to this embodiment, the same effects as in the first embodiment can be obtained, and problems caused by incorrect placement order or reading order of the chart 100 when performing the adjustment mode using a small-sized recording material S can be suppressed.

[0105] [Example 3] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are assigned the same reference numerals as those of embodiment 1, and detailed descriptions thereof will be omitted.

[0106] In the second embodiment, the chart reading order (page) and chart placement (orientation) were determined based on patch density information. However, if the change in patch density is small, the processing results may be inappropriate. Furthermore, since it is difficult to determine the first and second sides of a double-sided chart based solely on patch density information, the processing results may be inappropriate or instructions to the user may become complicated.

[0107] Therefore, in this embodiment, the arrangement of the charts and the order in which the charts are read are optimized based on the identification information of the charts read by the reading device 80. This will be explained in more detail below.

[0108] 14 and 15 are schematic diagrams of the chart 100 in this embodiment. In this embodiment, the chart 100 is formed with a trailing edge identification patch 501 for determining the placement of the chart 100 and a page determination patch 502 for determining the reading order of the chart 100.

[0109] FIG. 14 shows a large chart 100L on which a trailing edge identification patch 501 and a page determination patch 502 are formed. FIG. 14(a) shows a large chart 100La on the first side when a single-sided chart or a double-sided chart is output, and FIG. 14(b) shows a large chart 100Lb on the second side when a double-sided chart is output. Meanwhile, FIG. 15 shows a small chart 100S on which a trailing edge identification patch 501 and a page determination patch 502 are formed. FIG. 15(a) shows a first small chart 100Sb on the first side when a single-sided chart is output, or a first small chart 100Sb on the first side when a double-sided chart is output. FIG. 15(b) shows a second small chart 100Sa on the second side when a single-sided chart is output, or a second small chart 100Sa on the first side when a double-sided chart is output. FIG. 15(c) shows a first small chart 100Sb on the second side when a double-sided chart is output. FIG. 15(d) shows the second small chart 100Sb on the second side when a double-sided chart is output.

[0110] In each of the charts 100, a black band, which is a strip-shaped image formed with black toner and extending along the main scanning direction, is formed as a trailing end identification patch 501 at the trailing end of the recording material S in the conveyance direction when the chart 100 is formed. This makes it possible to correct the orientation (position) of the chart 100 based on the position of the trailing end identification patch 501 in the image read by the reading device 80. Also, in each of the charts 100, a page determination patch 502 is formed, which is arranged next to the trailing end identification patch 501 in the main scanning direction. In this embodiment, the page (reading order) of the chart 100 is identified by the color of the page determination patch 502, and page determination patches 502 of different colors are formed on each page of the charts shown in FIGS. 14 and 15. FIG. 16 shows the correspondence between the colors of the page determination patch 502 and each page (page number) of the chart 100 in this embodiment.

[0111] Next, we will explain the process of optimizing the arrangement of the chart 100 and the reading order of the chart 100 in this embodiment. This process is executed when one double-sided large chart, two single-sided small charts, or two double-sided small charts are output, after the reading process of the chart 100 by the reading device 80 and before the process of determining the recommended adjustment value for the secondary transfer voltage.

[0112] The control unit 30 stores in the RAM 33 an input image read from the chart 100 simultaneously set in the reading device 80 by the operator (S601). The control unit 30 determines whether or not a trailing edge identification patch 501 is present at the bottom of the read input image (S602). The bottom of the input image is a position corresponding to the trailing edge of the recording material S in the conveying direction when the chart 100 is formed when the chart 100 is simultaneously set in the reading device 80 in the correct orientation. If the trailing edge identification patch 501 is present at the bottom of the input image, the control unit 30 proceeds to S605. On the other hand, if the trailing edge identification patch 501 is not present at the bottom of the input image, the control unit 30 determines whether or not the trailing edge identification patch 501 is present at the top of the input image (S603). The top of the input image is a position corresponding to the trailing edge of the recording material S in the conveying direction when the chart 100 is formed when the chart 100 is simultaneously set in the reading device 80 in the opposite orientation to the correct orientation. If the trailing end identification patch 501 is present at the top of the input image, the control unit 30 rotates the input image 180 degrees, stores the rotated image in the RAM 33 (S604), and proceeds to S605. That is, the control unit 30 adjusts the orientation of the input image stored in the RAM 33 to match the orientation of the chart 100 when read in the correct orientation. On the other hand, if the trailing end identification patch 501 is not present at the top of the input image, the control unit 30 determines that the chart 100 set in the reading device 80 is not the chart 100 for adjusting the secondary transfer voltage, displays information indicating that an error has occurred on the display unit of the operation unit 70 or the external device 200, and ends the adjustment mode (S608).

[0113] The control unit 30 scans pixels in the image stored in RAM 33, with the trailing end identification patch 501 at the bottom, from the detection position of the trailing end identification patch 501, to detect the page determination patch 502 (S605). The control unit 30 determines the page of the input image based on the luminance information of the detected page determination patch 502 (i.e., the color determination result), and corrects the order of the input images as necessary (S606). In other words, the association between each input image and the reading order stored in RAM 33 is adjusted to match the relationship between each chart 100 and the reading order when read in the correct order. If the order of the input images is correct, no correction is necessary. Thereafter, the control unit 30 proceeds to the process of determining the recommended adjustment value of the secondary transfer voltage (see FIG. 10), which was described in the first embodiment (S607).

[0114] FIG. 18 is an explanatory diagram illustrating the effects of this embodiment. Here, an example is shown in which two double-sided small charts are output and read by the reading device 80. (a) in FIG. 18 is an input image obtained by reading the chart 100 with the arrangement (orientation) and reading order (page) of the chart 100 changed from the normal ones. (b) in FIG. 18 is an input image in which the arrangement and reading order of the chart 100 have been corrected according to this embodiment. As shown in FIG. 18, the orientation of the chart 100 and the reading order of the chart 100 can be optimized based on the rear end identification patch 501 and page determination patch 502, which serve as identification information formed on the chart 100.

[0115] In this embodiment, the identification information 501 indicating the correct layout (orientation) of the chart 100 is formed at the trailing edge of the recording material S in the transport direction when the chart 100 is formed. However, the present invention is not limited to this embodiment. The identification information 501 indicating the correct layout (orientation) of the chart 100 may be formed, for example, at the leading edge of the recording material S in the transport direction when the chart 100 is formed, or at the edge in a direction intersecting the transport direction. Furthermore, in this embodiment, the identification information 502 indicating the correct reading order (page) of the chart 100 is formed at a position different from the identification information 501 indicating the correct layout (orientation) of the chart 100 in the main scanning direction and at a position at least partially overlapping in the sub-scanning direction. In other words, in this embodiment, the page determination patch 502 and the trailing edge identification patch 501 are formed side by side in the main scanning direction. This allows the space on the surface of the recording material S on which the chart 100 is formed to be more effectively used for forming test images for density detection. However, the present invention is not limited to this embodiment. The identification information 502 indicating the correct reading order (page) of the chart 100 may be formed, for example, at a different position in the sub-scanning direction from the identification information 501 indicating the correct arrangement (orientation) of the chart 100 (at a position that overlaps at least partially in the main scanning direction or at a different position).

[0116] In this embodiment, the identification information 501 indicating the correct layout (orientation) of the chart 100 and the identification information 502 indicating the correct reading order (page) of the chart 100 are provided separately. However, the present invention is not limited to this configuration. The identification information 501 indicating the correct layout (orientation) of the chart 100 and the identification information 502 indicating the correct reading order (page) of the chart 100 may be integrated. For example, a band-shaped image similar to the trailing edge identification patch 501 in this embodiment can be formed in a different color for each chart, similar to the page determination patch 502 in this embodiment. It is also possible to provide either the identification information 501 indicating the correct layout (orientation) of the chart 100 or the identification information 502 indicating the correct reading order (page) of the chart 100. In this case, it is possible to determine at least one of the correct layout (orientation) of the chart 100 and the correct reading order (page) of the chart 100, thereby achieving a corresponding effect.

[0117] As described above, in this embodiment, in the adjustment mode, the control unit 30 can form the chart 100 on both sides of a single recording material S as the multiple sides of the recording material S and discharge the recording material S from the discharge unit 48, or form the chart 100 on one or both sides of multiple recording materials S as the multiple sides of the recording material S and discharge the multiple recording materials S from the discharge unit 48, read density information of the test image of the chart 100 on the multiple sides of the recording material S set in the reading device 80 by the operator at once, using the reading device 80, and output information related to the adjustment amount of the secondary transfer voltage based on the reading result of the reading device 80. Furthermore, in this embodiment, identification information 501, 502 is formed on each of the multiple sides, indicating at least one of the correct orientation of the chart 100 on each of the multiple sides and the correct reading order by the reading device 80 of the charts 100 formed on the multiple sides. Then, the control unit 30 outputs information regarding the adjustment amount of the secondary transfer voltage based on the results of reading the density information of the test image of the chart 100 on the multiple sides by the reading device 80 and the results of reading the identification information 501, 502 on the multiple sides by the reading device 80.

[0118] According to this embodiment, the same effects as those of the first embodiment can be obtained, and problems due to mistakes in the arrangement of the chart 100 or the order in which the charts 100 are read can be suppressed.

[0119] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the above-described embodiments.

[0120] In the above-described embodiment, the secondary transfer voltage is adjusted using an adjustment value corresponding to a predetermined adjustment amount, but the adjustment amount may be directly set on a setting screen, for example.

[0121] Furthermore, in the above-described embodiment, a configuration in which the secondary transfer voltage is constant voltage controlled has been described, but the secondary transfer voltage may also be constant current controlled. In the above-described embodiment, in a configuration in which the secondary transfer voltage is constant voltage controlled, the secondary transfer voltage is adjusted by adjusting the target voltage when the secondary transfer voltage is applied using the adjustment mode. In a configuration in which the secondary transfer voltage is constant current controlled, the secondary transfer voltage can be adjusted by adjusting the target current when the secondary transfer voltage is applied using the adjustment mode.

[0122] In the above embodiment, a case where a chart is formed on two sheets of small-sized recording material and outputted has been described, but the present invention can also be applied to a case where a chart is formed on three or more sheets of recording material and outputted. The first chart and second chart in the present invention include charts formed on any two sheets of recording material (first and second recording material) when charts are formed on three or more sheets of recording material and outputted.

[0123] Furthermore, the present invention is not limited to tandem-type image forming apparatuses, but can also be applied to other types of image forming apparatuses. Furthermore, the image forming apparatus is not limited to full-color image forming apparatuses, but may also be monochrome or mono-color image forming apparatuses. Furthermore, the present invention can be implemented in a variety of applications, such as printers, various printing machines, copiers, fax machines, and multifunction machines. [Explanation of symbols]

[0124] 30 Control Unit 44b Intermediate transfer belt 45a Secondary transfer inner roller 45b Secondary transfer outer roller 46 Fixing section 80 Reading device 100 Charts N2 Secondary transfer unit S recording material

Claims

1. an image carrier that carries a toner image; an intermediate transfer member onto which a toner image is primarily transferred from the image carrier; a transfer member forming a transfer section for performing secondary transfer of a toner image from the intermediate transfer body to a recording material; an application unit that applies a voltage to the transfer member; a discharge section that discharges the recording material on which the toner image transferred by the transfer section has been fixed and formed; a reading device capable of reading density information of an image on a recording material set by an operator; a control unit that is capable of executing an adjustment mode in which a recording material on which a chart is formed by sequentially transferring a plurality of test images by applying a plurality of test voltages to the transfer member by the application unit is discharged from the discharge unit, and a secondary transfer voltage that is applied to the transfer member by the application unit during the secondary transfer is adjusted; and The image forming apparatus is characterized in that, in the adjustment mode, the control unit discharges a first recording material on which a first chart is formed and a second recording material on which a second chart is formed from the discharge unit, reads density information of the test images on the first and second recording materials that are set in the reading device at the same time by an operator using the reading device, and outputs information regarding the adjustment amount of the secondary transfer voltage based on the density information of the test images of the first and second charts obtained from the reading results of the reading device.

2. The image forming apparatus according to claim 1, characterized in that the control unit determines whether the result read by the reading device corresponds to the first chart or the second chart based on the reading result of the reading device, and outputs information regarding the adjustment amount of the secondary transfer voltage based on the reading result of the reading device and the determination result.

3. 3. The image forming apparatus according to claim 1, wherein the reading device has a reading surface that supports the first recording material and the second recording material set at the same time so that the reading device can read the first recording material and the second recording material.

4. 3. The image forming apparatus according to claim 1, wherein the reading device includes a conveying device that sequentially conveys the first recording material and the second recording material set at the same time so that the reading device can read them.

5. The image forming apparatus of any one of claims 1 to 4, characterized in that the control unit performs processing to output information regarding the adjustment amount by associating the density information of the multiple test images obtained from the reading device with information indicating the multiple test voltages so that the density information of each test image corresponds to the test voltage at the time of transfer of each test image.

6. The image forming apparatus of claim 5, wherein the control unit is capable of performing a process to optimize the association between the density information of the plurality of test images obtained from the reading device and the plurality of test voltages when the first and second recording materials are not set in the reading device by an operator in a predetermined manner, based on density information of at least one of the plurality of test images read from one of the first and second recording materials and density information of at least one of the plurality of test images read from the other of the first and second recording materials, so that the density information of each of the test images corresponds to the test voltage when each of the test images is transferred.

7. 7. The image forming apparatus according to claim 6, wherein the control unit performs the optimization process based on first density information acquired from the reading device, which is set to be density information of the test image furthest downstream in the transport direction of the first recording material when the first chart is formed if the first and second recording materials are set in the reading device by the operator using the specified method, and second density information acquired from the reading device, which is set to be density information of the test image furthest upstream in the transport direction of the second recording material when the second chart is formed if the first and second recording materials are set in the reading device by the operator using the specified method.

8. The image forming apparatus according to claim 7, characterized in that the control unit performs the optimization process when the difference between the density indicated by the first density information and the density indicated by the second density information is equal to or greater than a predetermined threshold value.

9. 9. The image forming apparatus according to claim 6, wherein the optimization process includes a process of interchanging density information acquired from the reading device as density information of the test image of the first chart with density information acquired from the reading device as density information of the test image of the second chart.

10. 10. The image forming apparatus according to claim 1, wherein the first chart has a plurality of test images that are sequentially transferred from the upstream side to the downstream side in the transport direction of the first recording material when the first chart is formed using a plurality of test voltages that differ so that their absolute values ​​successively increase, and the second chart has a plurality of test images that are sequentially transferred from the upstream side to the downstream side in the transport direction of the second recording material when the second chart is formed using a plurality of test voltages that differ so that their absolute values ​​successively increase from an absolute value that is greater than the largest absolute value of the plurality of test voltages when the first chart is formed.

11. 10. The image forming apparatus according to claim 1, wherein the first chart has a plurality of test images that are sequentially transferred from the upstream side to the downstream side in the transport direction of the first recording material when the first chart is formed using a plurality of test voltages whose absolute values ​​are sequentially decreased, and the second chart has a plurality of test images that are sequentially transferred from the upstream side to the downstream side in the transport direction of the second recording material when the second chart is formed using a plurality of test voltages whose absolute values ​​are sequentially decreased from a value smaller than the smallest absolute value of the plurality of test voltages whose absolute values ​​are sequentially decreased.

12. An image forming apparatus according to any one of claims 1 to 11, characterized in that the control unit outputs information regarding the adjustment amount to a display unit provided in the image forming apparatus or a display unit of an external device connected to the image forming apparatus, and causes the display unit to display the information regarding the adjustment amount.

13. 13. The image forming apparatus according to claim 1, wherein the control unit outputs information relating to the adjustment amount to a storage unit provided in the image forming apparatus, and stores the information relating to the adjustment amount in the storage unit.

14. The image forming apparatus of any one of claims 1 to 13, characterized in that in the adjustment mode, the control unit is capable of discharging from the discharge unit a single sheet of recording material having a size larger than each of the first and second recording materials and having a chart formed thereon onto which a plurality of the test images have been transferred, and adjusting the secondary transfer voltage based on the results of reading the density information of the test images on the single sheet of recording material by the reading device.

15. identification information indicating at least one of a normal orientation of the chart on each of the first and second recording materials and a normal reading order of the charts formed on the first and second recording materials by the reading device is formed on each of the first and second recording materials, The image forming apparatus of claim 1, characterized in that the control unit outputs information regarding the adjustment amount of the secondary transfer voltage based on the reading result of the density information of the test image of the first chart by the reading device, the reading result of the density information of the test image of the second chart by the reading device, the reading result of the identification information of the first recording material by the reading device, and the reading result of the identification information of the second recording material by the reading device.

16. an image carrier that carries a toner image; an intermediate transfer member onto which a toner image is primarily transferred from the image carrier; a transfer member forming a transfer section for performing secondary transfer of a toner image from the intermediate transfer body to a recording material; an application unit that applies a voltage to the transfer member; a discharge section that discharges the recording material on which the toner image transferred by the transfer section has been fixed and formed; a reading device capable of reading density information of an image on a recording material set by an operator; a control unit that is capable of executing an adjustment mode in which a recording material on which a chart is formed by sequentially transferring a plurality of test images by applying a plurality of test voltages to the transfer member by the application unit is discharged from the discharge unit, and a secondary transfer voltage that is applied to the transfer member by the application unit during the secondary transfer is adjusted; and In the adjustment mode, the control unit is capable of forming the chart on both sides of a single recording material as the multiple sides of the recording material and discharging the recording material from the discharge unit, or forming the chart on one or both sides of multiple recording materials as the multiple sides of the recording material and discharging the multiple recording materials from the discharge unit, reading density information of the test image of the chart on the multiple sides of the recording material set in the reading device by an operator at one time, using the reading device, and outputting information regarding the adjustment amount of the secondary transfer voltage based on the reading result of the reading device, identification information indicating at least one of a normal orientation of the chart on each of the plurality of surfaces and a normal reading order of the charts formed on the plurality of surfaces by the reading device is formed on each of the plurality of surfaces, The control unit outputs information regarding the adjustment amount of the secondary transfer voltage based on the results of reading density information of the test image of the chart on the multiple sides by the reading device and the results of reading identification information on the multiple sides by the reading device.

Images