Image forming apparatus, image forming method, and program

Abstract

To provide an image forming apparatus, an image forming method, and a program that, in adjustment of a transfer bias, can reduce a burden on a user, a time for the adjustment, and a waste recording material generated in the adjustment.SOLUTION: An image forming apparatus comprises: a first control unit that, for a transfer bias applied from a power supply device to a transfer nip that is formed between an image carrier carrying a toner image and a transfer member, generates a plurality of transfer conditions different from each other for a combination including, of a DC component and an AC component, at least the DC component, and causes the power supply device to apply the transfer bias to the transfer nip while switching between the plurality of transfer conditions; and a second control unit that, according to a preset adjustment mode, of a plurality of adjustment modes for adjusting the transfer bias corresponding to a recording material, transfers the image from the image carrier to the recording material for every transfer condition applied by the first control unit.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In an electrophotographic image forming apparatus, a toner image is electrostatically transferred from a photoreceptor, an intermediate transfer member, and an image carrier to a recording material such as paper. When the toner image is transferred, a transfer bias is applied to a transfer member such as a transfer roller that transfers in contact with the image carrier. And in order to improve the transferability to the concave portions of uneven paper and rough paper, a technique of applying a superimposed bias of a DC voltage and an AC voltage to the transfer member for secondary transfer is known. Although it is necessary to set the DC component and the AC component to be applied as this superimposed bias, there is a problem that the optimum superimposed bias shifts due to factors such as deterioration of the developer, change in resistance of each member, and environment.

[0003] As a technique for applying such a superimposed bias, a technique is disclosed in which, in a test transfer mode, among a DC voltage and an AC voltage, only the DC voltage is output from a power source, and there is control means for controlling the superimposed voltage, and the printing speed is increased (for example, Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, when the optimum transfer bias shifts, it is necessary to adjust the DC component and the AC component of the transfer bias each time, so the burden on the user is high, it takes a lot of time to adjust the transfer bias, and there is a problem that a large amount of waste paper of the recording material required for adjustment is generated.

[0005] The present invention has been made in view of the above, and an object thereof is to provide an image forming apparatus, an image forming method, and a program capable of reducing the burden on the user, the time for adjustment, and the waste paper of the recording material generated during adjustment in the adjustment of the transfer bias.

Means for Solving the Problem

[0006] In order to solve the above-described problems and achieve the object, the present invention generates a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component with respect to a transfer bias applied from a power supply device to a transfer nip formed between an image carrier carrying a toner image and a transfer member, and switches the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip. A first control unit; and a second control unit that transfers an image from the image carrier to the recording material for each of the transfer conditions applied by the first control unit according to a set adjustment mode among a plurality of adjustment modes for adjusting the transfer bias corresponding to the recording material. It is characterized by having.

Advantages of the Invention

[0007] According to the present invention, in adjusting the transfer bias, it is possible to reduce the burden on the user, the time for adjustment, and the waste paper of the recording material generated during adjustment.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the image forming apparatus, the image forming method, and the program according to the present invention will be described in detail with reference to the drawings. Further, the present invention is not limited by the following embodiments, and the constituent elements in the following embodiments include those that can be easily conceived by those skilled in the art, substantially the same ones, and those within the so-called equivalent range. Furthermore, various omissions, substitutions, changes, and combinations of the constituent elements can be made without departing from the gist of the following embodiments.

[0010] (Overall Configuration of Image Forming Apparatus) FIG. 1 is a diagram showing an example of the overall configuration of the image forming apparatus according to the embodiment. FIG. 2 is a diagram showing an example of the configuration of the image forming unit of the image forming apparatus according to the embodiment. With reference to FIGS. 1 and 2, the overall configuration of the image forming apparatus 1 according to the present embodiment will be described.

[0011] The image forming apparatus 1 shown in FIG. 1 is an electrophotographic image forming apparatus that transfers a toner image developed based on an electrostatic latent image formed on a photoreceptor drum to a recording sheet (recording material). The image forming apparatus 1 includes image forming units 10C, 10K, 10M, 10Y, an optical writing unit 80, a transfer unit 50, a fixing device 90, a paper feed cassette 100, a registration roller pair 102, a paper discharge roller pair 103, a switching claw 104, and a reverse refeeding device 105.

[0012] The image forming units 10C, 10K, 10M, 10Y are units for forming cyan (C), black (K), magenta (M), and yellow (Y) toner images, respectively. For example, they are arranged in parallel in the order of the image forming unit 10Y, the image forming unit 10M, the image forming unit 10C, and the image forming unit 10K along the upper running side of the intermediate transfer belt 51 described later, and are configured as a tandem image forming unit. Further, the image forming units 10C, 10K, 10M, 10Y are detachably provided with respect to the main body of the image forming apparatus 1. The image forming units 10C, 10K, 10M, 10Y each have a photoreceptor drum 11C, 11K, 11M, 11Y. Note that when indicating an arbitrary image forming unit or when collectively referring to the image forming units 10C, 10K, 10M, 10Y, they are simply referred to as "image forming unit 10". Also, when indicating an arbitrary photoreceptor drum or when collectively referring to the photoreceptor drums 11C, 11K, 11M, 11Y, they are simply referred to as "photoreceptor drum 11".

[0013] As shown in FIG. 2, the image forming unit 10 includes a photoreceptor drum 11, a charging device 21, a developing device 31, and a cleaning device 41.

[0014] The photoreceptor drum 11 is a drum-shaped latent image carrier having an organic photosensitive layer formed on the surface of a drum substrate. The photoreceptor drum 11 is rotationally driven in the clockwise direction in the view of the paper surface of FIG. 2 by a driving means.

[0015] The charging device 21 is a device that uniformly charges the surface of the photoreceptor drum 11 by generating a discharge between the charging roller to which a charging bias is applied and the photoreceptor drum 11 while bringing the charging roller into contact with or close to the photoreceptor drum 11. For example, the charging device 21 uniformly charges the surface of the photoreceptor drum 11 to the same negative polarity as the normal charging polarity of the toner. As the charging bias, a superimposition of an AC voltage on a DC voltage is adopted. Note that instead of the method using a charging roller, a method using a charge roller may be adopted.

[0016] The developing device 31 is a device that develops and visualizes a latent image on the photoreceptor drum 11 with a developer containing toner. As shown in FIG. 2, the developing device 31 includes a developing sleeve 31a as a developer carrier and two screw members 31b and 31c as stirring members that convey the developer while stirring it in a storage container that stores a two-component developer containing toner and carrier. Note that as the developing device 31, it is also possible to adopt a developing device that uses a one-component developer containing toner.

[0017] The cleaning device 41 is a device that cleans the surface of the photoreceptor drum 11. As shown in FIG. 2, the cleaning device 41 includes a cleaning blade 41a and a cleaning brush roller 41b.

[0018] The cleaning blade 41a is in contact with the surface of the photoreceptor drum from the counter direction with respect to the rotation direction of the photoreceptor drum 11. The cleaning brush roller 41b is in contact with the surface of the photoreceptor drum 11 while rotating in a direction opposite to the rotation direction of the photoreceptor drum 11. Then, the cleaning blade 41a and the cleaning brush roller 41b clean the surface of the photoreceptor drum 11.

[0019] The optical writing unit 80 is provided above the image forming units 10C, 10K, 10M, and 10Y, and is a unit that writes a latent image on the surface of the photosensitive drum 11 charged by the charging device 21. The optical writing unit 80 optically scans the surfaces of the photosensitive drums 11C, 11K, 11M, and 11Y with laser light emitted from a laser diode based on image data received from an external device such as a PC (Personal Computer). Specifically, the optical writing unit 80 polarizes the laser light L emitted from the light source in the main scanning direction with a polygon mirror rotationally driven by a polygon motor, and irradiates the surface of the photosensitive drum 11 through a plurality of optical lenses and mirrors. By this optical scanning by the optical writing unit 80, electrostatic latent images for C, K, M, and Y are formed on the surfaces of the photosensitive drums 11C, 11K, 11M, and 11Y. Specifically, among the entire uniformly charged surface of the photosensitive drum 11, the potential of the portion irradiated with laser light from the optical writing unit 80 decays. As a result, the potential of the portion irradiated with the laser light becomes smaller than the potential of the other portions (the background portion), and an electrostatic latent image is thus formed. Note that the optical writing unit 80 may perform optical writing with LED light emitted from a plurality of LEDs of an LED (Light Emitting Diode) array.

[0020] The transfer unit 50 is a unit that secondarily transfers the toner image primarily transferred from the photosensitive drum 11 to the recording sheet P by the intermediate transfer belt 51, which is an endless belt member that is an image carrier and an intermediate transfer member. As shown in FIG. 1, the transfer unit 50 includes an intermediate transfer belt 51, a driving roller 52, a secondary transfer opposing roller 53, a cleaning backup roller 54, primary transfer rollers 55C, 55K, 55M, and 55Y, a secondary transfer roller 56, and a cleaning device 57.

[0021] The intermediate transfer belt 51 is a belt member that is stretched by a driving roller 52 disposed inside, a secondary transfer opposing roller 53, a cleaning backup roller 54, and primary transfer rollers 55C, 55K, 55M, 55Y, and that moves endlessly counterclockwise in the view of the paper surface of FIG. 1 by the rotational driving of the driving roller 52. The intermediate transfer belt 51 secondarily transfers the toner image primarily transferred from the photoreceptor drum 11 to the recording sheet P.

[0022] The driving roller 52 is a roller that is disposed inside the intermediate transfer belt 51 and that moves the intermediate transfer belt 51 endlessly by rotational driving.

[0023] The secondary transfer opposing roller 53 is a roller that is disposed inside the intermediate transfer belt 51 and that sandwiches the intermediate transfer belt 51 between itself and the opposing secondary transfer roller 56. The secondary transfer opposing roller 53 has a secondary transfer bias power source 200 connected thereto, and a secondary transfer bias is applied by the secondary transfer bias power source 200. That is, a secondary transfer bias is applied to a secondary transfer nip, which will be described later, by the secondary transfer bias power source 200. Thereby, a secondary transfer electric field in which toner moves from the secondary transfer opposing roller 53 side toward the secondary transfer roller 56 side is formed between the secondary transfer opposing roller 53 and the secondary transfer roller 56. Note that the secondary transfer bias corresponds to the "transfer bias" of the present invention.

[0024] The cleaning backup roller 54 is a roller that is disposed inside the intermediate transfer belt 51 and that, together with the cleaning device 57, cleans the toner remaining on the intermediate transfer belt 51 after secondary transfer.

[0025] The primary transfer rollers 55C, 55K, 55M, and 55Y are rollers that sandwich the endlessly moving intermediate transfer belt 51 between the photosensitive drums 11C, 11K, 11M, and 11Y, respectively. As a result, primary transfer nips for C, K, M, and Y are formed where the front surface of the intermediate transfer belt 51 contacts the photosensitive drums 11C, 11K, 11M, and 11Y. For the primary transfer rollers 55C, 55K, 55M, and 55Y, when indicating an arbitrary primary transfer roller or referring to them generically, they shall simply be referred to as "primary transfer roller 55".

[0026] A primary transfer bias is applied to each of the primary transfer rollers 55C, 55K, 55M, and 55Y by a primary transfer bias power source (not shown). As a result, a transfer electric field is formed between the toner images of each color on the photosensitive drums 11C, 11K, 11M, and 11Y and the respective primary transfer rollers 55. Due to the action of the transfer electric field and the nip pressure of the primary transfer nip, the toner images are primarily transferred from each photosensitive drum 11 onto the intermediate transfer belt 51. Then, the toner image of Y, the toner image of M, the toner image of C, and the toner image of K are sequentially superimposed and primarily transferred on the intermediate transfer belt 51, thereby forming a color toner image in which four colors are superimposed on the intermediate transfer belt 51. Note that instead of the primary transfer roller 55, primary transfer may be performed using a transfer charger, a transfer brush, or the like.

[0027] Also, when forming a monochrome toner image, a support plate (not shown) that supports the primary transfer rollers 55Y, 55M, and 55C for Y, M, and C in the transfer unit 50 is moved to move the primary transfer rollers 55Y, 55M, and 55C away from the photosensitive drums 11Y, 11M, and 11C, respectively. As a result, the front surface of the intermediate transfer belt 51 is separated from the photosensitive drums 11Y, M, and C, and the intermediate transfer belt 51 is brought into contact with only the photosensitive drum 11K. In this state, only the image forming unit 10K among the four image forming units 10Y, 10M, 10C, and 10K is driven to form a K toner image (monochrome toner image) on the photosensitive drum 11K.

[0028] The secondary transfer roller 56 is disposed outside the intermediate transfer belt 51, and is a transfer member that sandwiches the intermediate transfer belt 51 between itself and the secondary transfer opposing roller 53 inside the intermediate transfer belt 51. Thereby, a secondary transfer nip is formed where the front surface of the intermediate transfer belt 51 contacts the secondary transfer roller 56. The secondary transfer roller 56 is electrically grounded. Note that the secondary transfer bias power supply 200 may be connected to the secondary transfer roller 56 and the secondary transfer opposing roller 53 may be electrically grounded. Also, the secondary transfer nip corresponds to the "transfer nip" of the present invention.

[0029] The toner image on the intermediate transfer belt 51 that is in close contact with the recording sheet P at the secondary transfer nip is secondarily transferred onto the recording sheet P by the action of the secondary transfer electric field and the nip pressure of the secondary transfer nip. In this way, when the recording sheet P with a full-color toner image or a monochrome toner image formed on its front surface passes through the secondary transfer nip, it separates from the secondary transfer roller 56 and the intermediate transfer belt 51 by the amount of curvature.

[0030] The cleaning device 57, together with the cleaning backup roller 54, is a device that cleans the toner remaining on the intermediate transfer belt 51 after secondary transfer.

[0031] The fixing device 90 is a device that fixes the toner image to the recording sheet P by heating and pressing the recording sheet P onto which the toner image has been secondarily transferred at the secondary transfer nip. As shown in FIG. 1, the fixing device 90 includes a fixing roller 91 and a pressure roller 92.

[0032] The fixing roller 91 is a roller that incorporates a heat source such as a halogen lamp. The pressure roller 92 is a roller that contacts the fixing roller 91 with a predetermined pressure. A fixing nip is formed by the fixing roller 91 and the pressure roller 92.

[0033] The recording sheet P fed into the fixing device 90 is sandwiched between the fixing nips in a posture where the surface on which the unfixed toner image has been secondarily transferred is in close contact with the fixing roller 91. Then, due to the heating and pressure applied by the fixing roller 91 and the pressure roller 92, the toner in the toner image softens, and the toner image is fixed.

[0034] The paper feed cassette 100 is disposed below the transfer unit 50 and is a cassette that houses a stack of a plurality of recording sheets P as a transfer member. The paper feed cassette 100 includes a paper feed roller 101.

[0035] The paper feed roller 101 abuts against the topmost recording sheet P of the stack of sheets housed in the paper feed cassette 100 and rotates at a predetermined timing, thereby feeding out the recording sheet P toward the registration roller pair 102 on the paper feed path.

[0036] The registration roller pair 102 is a roller pair disposed near the end of the paper feed path of the recording sheet P. When the registration roller pair 102 sandwiches the recording sheet P fed out from the paper feed cassette 100 by the paper feed roller 101, it immediately stops rotating. Then, the registration roller pair 102 resumes rotational driving at a timing that can synchronize the sandwiched recording sheet P with the toner image formed on the intermediate transfer belt 51 within the secondary transfer nip, and feeds out the recording sheet P toward the secondary transfer nip.

[0037] The paper discharge roller pair 103 is a roller pair that discharges the recording sheet P that has passed through the fixing device 90 and is conveyed to the discharge path by the switching claw 104 outside the image forming apparatus 1.

[0038] The switching claw 104 is a claw member that switches whether to convey the recording sheet P that has passed through the fixing device 90 to the discharge path leading to the paper discharge roller pair 103 or the return path leading to the reverse refeed device 105.

[0039] When double-sided printing is performed on the recording sheet P, the reversing and refeeding device 105 is a device that reverses and refeeds the recording sheet P that has passed through the fixing device 90 and is conveyed back to the return path. As shown in FIG. 1, the reversing and refeeding device 105 includes a switchback unit 105a and a refeeding unit 105b.

[0040] The switchback unit 105a is a part that switchbacks the entered recording sheet P and conveys it to the refeeding unit 105b. The refeeding unit 105b is a conveyance path for conveying the recording sheet P switchbacked by the switchback unit 105a back to the paper feed path again.

[0041] In the case of single-sided printing, the recording sheet P that has passed through the fixing device 90 is guided by the switching claw 104 toward the discharge path. As a result, the recording sheet P is discharged out of the image forming apparatus 1 via the discharge roller pair 103.

[0042] On the other hand, in the case of double-sided printing, the recording sheet P that has passed through the fixing device 90 is guided by the switching claw 104 toward the return path. The recording sheet P guided to the return path is conveyed to the switchback unit 105a of the reversing and refeeding device 105. The recording sheet P that has entered the switchback unit 105a is switchbacked by the switchback unit 105a. As a result, the recording sheet P enters the refeeding unit 105b while being turned upside down with the rear end facing forward. Then, the recording sheet P is conveyed from the refeeding unit 105b toward the paper feed path again. After that, the recording sheet P passes through the registration roller pair 102 and the secondary transfer nip, and after the toner image is transferred to the back surface as well, the toner image is fixed in the fixing device 90. Then, the recording sheet P is discharged out of the image forming apparatus 1 via the discharge roller pair 103.

[0043] (Hardware Configuration of Main Parts of Image Forming Apparatus) FIG. 3 is a diagram showing an example of the hardware configuration of main parts of the image forming apparatus according to the embodiment. The hardware configuration of main parts of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. 3.

[0044] As shown in FIG. 3, the image forming apparatus 1 includes a secondary transfer bias power supply 200 (power supply device), a controller 300, a memory 301 (storage unit), an operation panel 302 (operation unit), and a current detection unit 303.

[0045] The secondary transfer bias power supply 200 includes a DC power supply 201 that outputs a DC voltage, and an AC power supply 202 that outputs a voltage obtained by superimposing an AC voltage on the DC voltage output by the DC power supply 201. The secondary transfer bias power supply 200 can switch and output the application of only a DC component (hereinafter, may be referred to as a DC bias) or a superimposed bias obtained by superimposing an AC component on the DC component as the above-described secondary transfer bias applied to the secondary transfer opposing roller 53.

[0046] The controller 300 is a controller that controls the application operation of the secondary transfer bias to the secondary transfer opposing roller 53 by the secondary transfer bias power supply 200. The controller 300 incorporates, for example, a CPU (Central Processing Unit) that controls the image forming apparatus 1. When applying a superimposed bias to the secondary transfer opposing roller 53, the controller 300 outputs a control signal to the DC power supply 201 and the AC power supply 202, and causes the AC power supply 202 to apply the superimposed bias to the secondary transfer opposing roller 53. Further, when applying a DC bias to the secondary transfer opposing roller 53, the controller 300 outputs a control signal to the DC power supply 201, and causes the AC power supply 202 to apply the DC bias to the secondary transfer opposing roller 53.

[0047] Further, the controller 300 performs PWM (Pulse Width Modulation) constant voltage control on the AC component output from the AC power supply 202 and PWM constant current control on the DC component output from the DC power supply 201 based on the current flowing through the secondary transfer nip detected by the current detection unit 303. By performing constant current control on the DC component, even if the electrical resistance of the intermediate transfer belt 51, the secondary transfer roller 56, etc. varies due to the temperature and humidity environment, etc., the applied voltage changes accordingly, so that the transfer electric field at the secondary transfer nip is stabilized and stable secondary transfer performance can be obtained.

[0048] The memory 301 is a non-volatile storage device that stores a secondary transfer bias table associating secondary transfer biases for each type of recording sheet to be described later. The memory 301 is connected to the controller 300.

[0049] The operation panel 302 is a panel including buttons and a touch panel for receiving operation inputs by the user, and a liquid crystal display device for displaying various screens and setting information, etc. The operation panel 302 is connected to the controller 300.

[0050] The current detection unit 303 is a sensor that detects the current flowing through the secondary transfer nip. The current detection unit 303 is connected to the controller 300 and outputs the detected current value to the controller 300.

[0051] (Configuration and Operation of Function Blocks of Controller of Image Forming Apparatus) FIG. 4 is a diagram showing an example of the configuration of function blocks of the controller of the image forming apparatus according to the embodiment. FIG. 5 is a diagram showing an example of the secondary transfer bias table of the image forming apparatus according to the embodiment. With reference to FIGS. 4 and 5, the configuration and operation of the function blocks of the controller 300 of the image forming apparatus 1 according to the present embodiment will be described.

[0052] As shown in FIG. 4, the controller 300 includes a power control unit 401 (first control unit), a mode switching unit 402, a print control unit 403 (second control unit), a setting unit 404, and a display control unit 405.

[0053] The power control unit 401 is a functional unit that controls the operation of applying the secondary transfer bias to the secondary transfer nip by the secondary transfer bias power supply 200. Specifically, the power control unit 401 controls the secondary transfer bias applied from the secondary transfer bias power supply 200 to the secondary transfer opposing roller 53. When a print job for forming a desired image on the recording sheet is being performed, the power control unit 401 reads out from the memory 301 information on the type of the recording sheet set in the paper feed cassette 100. Also, the power control unit 401 determines whether the image data to be printed is a monochrome image or a full-color image. Then, based on the read information on the type of the recording sheet and the information on whether the image data to be printed is a monochrome image or a color image, the power control unit 401 reads out the corresponding secondary transfer bias from the secondary transfer bias table shown in FIG. 5 stored in the memory 301.

[0054] The power control unit 401 adjusts the secondary transfer bias output from the AC power supply 202 based on the current value detected by the current detection unit 303 during printing. Specifically, for example, when a superimposed bias is applied as the secondary transfer bias because the target recording sheet is uneven paper or the like, the power control unit 401 first acquires the current value detected by the current detection unit 303. Then, based on the current value detected by the current detection unit 303, the power control unit 401 calculates the DC current value and the AC current value (peak-to-peak current) applied to the secondary transfer opposing roller 53. And the power control unit 401 adjusts the DC component of the superimposed bias output from the secondary transfer bias power supply 200 by PWM constant current control so that the calculated DC current value becomes the DC current value of the superimposed bias corresponding to the current recording sheet set by the setting unit 404 in the secondary transfer bias table stored in the memory 301.

[0055] Further, due to the electrical resistance value of the secondary transfer counter roller 53 and the electrical resistance value of the secondary transfer roller 56, the AC voltage output from the AC power supply 202 is different from the AC voltage actually applied to the secondary transfer nip. Therefore, the power control unit 401 calculates the actual AC voltage value (peak-to-peak voltage) applied to the secondary transfer nip based on the calculated AC current value. Then, the power control unit 401 adjusts the AC component of the superimposed bias output from the secondary transfer bias power supply 200 by PWM constant voltage control so that the calculated AC voltage value becomes the AC voltage value of the superimposed bias corresponding to the current recording sheet set by the setting unit 404 in the secondary transfer table stored in the memory 301.

[0056] In this way, when secondarily transferring the toner image onto uneven paper or the like, by applying a superimposed bias in which an AC component is superimposed on the DC component to the secondary transfer counter roller 53, a sufficient amount of toner can be transferred to the concave portions of the uneven surface of the uneven paper. Thereby, it is possible to suppress the occurrence of a density pattern following the unevenness of the surface.

[0057] Also, for example, when applying a DC bias as the secondary transfer bias because the target recording sheet is plain paper or the like, similarly, the power control unit 401 acquires the current value detected by the current detection unit 303. Then, the power control unit 401 calculates the DC current value applied to the secondary transfer counter roller 53 based on the current value detected by the current detection unit 303. Then, the power control unit 401 adjusts the DC bias output from the secondary transfer bias power supply 200 by PWM constant current control so that the calculated DC current value becomes the DC current value of the DC bias corresponding to the current recording sheet set by the setting unit 404 in the secondary transfer bias table stored in the memory 301.

[0058] In this way, when secondarily transferring the toner image onto plain paper or the like, by eliminating the AC component that causes transfer skew and making the secondary transfer bias only a DC component, the occurrence of transfer skew can be suppressed.

[0059] The mode switching unit 402 is a functional unit that switches the operation mode of the image forming apparatus 1 according to an operation on the operation panel 302. The operation modes include a normal mode in which the secondary transfer bias of the secondary transfer bias table shown in FIG. 5 stored in the memory 301 is applied to the secondary transfer opposing roller 53 to perform a normal printing operation, and an adjustment mode for printing an adjustment chart on a target recording sheet to determine the optimum secondary transfer bias of the recording sheet and update the secondary transfer bias table. The adjustment mode includes a simple adjustment mode in which the adjustment chart is printed on both sides while changing the secondary transfer bias within the same page of the recording sheet, and a detailed adjustment mode in which the secondary transfer bias is not changed within the same page of the recording sheet, and the adjustment chart is printed on both sides while changing the secondary transfer bias for each page. The details of the operation of the adjustment mode will be described later.

[0060] Note that the simple adjustment mode corresponds to the "first adjustment mode" of the present invention, and the detailed adjustment mode corresponds to the "second adjustment mode" of the present invention.

[0061] The print control unit 403 is a functional unit that controls the operations of the image forming unit 10, the optical writing unit 80, the transfer unit 50, etc. to print an image on a recording sheet.

[0062] The setting unit 404 is a functional unit that sets various setting information according to an operation on the operation panel 302. For example, the user selects the type of the recording sheet set in the paper feed cassette 100 via the operation panel 302, and the setting unit 404 sets the selected type of the recording sheet and stores it in the memory 301. For example, as will be described later, in the adjustment mode, the setting unit 404 sets the secondary transfer condition of the optimum adjustment chart number selected and input by the user among the adjustment charts printed under a plurality of different secondary transfer conditions as the new secondary transfer bias for the recording sheet, and updates the secondary transfer bias table stored in the memory 301 with the secondary transfer bias. Note that the secondary transfer condition corresponds to the "transfer condition" of the present invention.

[0063] In the adjustment mode, the user is not limited to selecting and inputting the number of the optimal secondary transfer condition based on the adjustment charts printed under a plurality of different secondary transfer conditions. Instead, the user may select and input other identification information for identifying the secondary transfer condition. In this case, the print control unit 403 may transfer identification information near the corresponding adjustment chart so that it can identify which adjustment chart was printed under which secondary transfer condition on the recording sheet.

[0064] The AC component and the DC component of the secondary transfer bias may shift their optimal values due to toner deterioration, changes in the electrical resistance of members forming the secondary transfer nip such as the intermediate transfer belt 51 and the secondary transfer roller 56, and the environment. Therefore, as described above, the image forming apparatus 1 can execute the adjustment mode and change the secondary transfer bias to an optimal DC current value or a combination of an optimal DC current value and an AC voltage value.

[0065] Here, an example of the secondary transfer bias table stored in the memory 301 is shown in FIG. 5. As shown in FIG. 5, when the type of the recording sheet is plain paper, a DC bias is stored as the secondary transfer bias in the secondary transfer bias table. In the present embodiment, as described above, since the DC power supply 201 is controlled to have a constant current by the power supply control unit 401, a DC current value is stored as the DC bias. When the recording sheet has irregularities on its surface such as embossed paper (hereinafter sometimes referred to as irregular paper), a superimposed bias is stored as the secondary transfer bias in the secondary transfer bias table. In the present embodiment, as described above, since the DC power supply 201 is controlled to have a constant current by the power supply control unit 401 and the AC power supply 202 is controlled to have a constant voltage by the power supply control unit 401, a DC current value and an AC voltage value (peak-to-peak voltage value) are stored as the superimposed bias.

[0066] When transferring a full-color toner image onto a recording sheet and when transferring a monochrome toner image onto a recording sheet, the electrical resistance value of the toner image, the thickness of the toner image, etc. are different. Therefore, the optimal secondary transfer conditions are different when secondarily transferring a full-color toner image onto a recording sheet and when secondarily transferring a monochrome toner image onto a recording sheet. Furthermore, when the recording sheet onto which the toner image has been transferred is heated by the fixing device 90 and the contained moisture evaporates, the electrical resistance of the recording sheet may be different when transferring the toner image onto the front surface of the recording sheet and when transferring the toner image onto the back surface of the recording sheet. Therefore, the optimal secondary transfer conditions are different when transferring the toner image onto the front surface of the recording sheet and when transferring the toner image onto the back surface of the recording sheet.

[0067] Therefore, in the present embodiment, as shown in FIG. 5, four secondary transfer biases are associated with and stored in one type of recording sheet. Specifically, as shown in FIG. 5, in the secondary transfer bias table, the secondary transfer bias used when secondarily transferring a monochrome toner image onto the front surface of the recording sheet, the secondary transfer bias used when secondarily transferring a monochrome toner image onto the back surface of the recording sheet, the secondary transfer bias used when secondarily transferring a full-color toner image onto the front surface of the recording sheet, and the secondary transfer bias used when secondarily transferring a full-color toner image onto the back surface of the recording sheet are associated with and stored in the recording sheet.

[0068] Thus, in the present embodiment, in the secondary transfer bias table, the secondary transfer bias is set for all combinations of monochrome / full-color where the optimal secondary transfer conditions are different from each other and the front surface / back surface of the recording sheet. As a result, good images can be obtained for all combinations of monochrome / full-color and the front surface / back surface of the recording sheet.

[0069] In the initial stage of use of the image forming apparatus 1, a default secondary transfer bias is associated with the recording sheet, and each secondary transfer bias stored in association with this recording sheet is rewritten to the secondary transfer bias determined by the adjustment mode described later. Further, as shown in FIG. 5, the secondary transfer bias table in the memory 301 also stores information indicating the type of the recording sheet (for example, plain paper, embossed paper, etc.) set in the paper feed cassette 100.

[0070] The display control unit 405 is a functional unit that controls the display operation of the operation panel 302. The display control unit 405 causes the operation panel 302 to display, for example, a screen for selecting the type of the recording sheet set in the paper feed cassette 100, and a screen for inputting the number of the optimum adjustment chart in the adjustment mode (for example, the screen shown in FIG. 11 described later).

[0071] The above-described power control unit 401, mode switching unit 402, print control unit 403, setting unit 404, and display control unit 405 are realized, for example, by a program being executed by the CPU of the controller 300 shown in FIG. 3. Note that at least a part of the power control unit 401, mode switching unit 402, print control unit 403, setting unit 404, and display control unit 405 may be realized by a hardware circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0072] Note that each functional part of the controller 300 shown in FIG. 4 conceptually shows the functions and is not limited to such a configuration. That is, each functional part of the controller 300 does not necessarily need to be configured as a clear software module as a block shown in FIG. 4, and the functions of each functional part may be realized as a whole by executing a program on the CPU of the controller 300. For example, a plurality of functional parts illustrated as independent functional parts in the controller 300 shown in FIG. 4 may be configured as one functional part. On the other hand, the functions of one functional part in the controller 300 shown in FIG. 4 may be divided into a plurality of functions and configured as a plurality of functional parts.

[0073] (Operation in adjustment mode) FIG. 6 is a diagram showing an example of secondary transfer conditions of the image forming apparatus according to the embodiment. FIG. 7 is a timing chart showing an example of the switching operation of the secondary transfer bias in the simple adjustment mode of the image forming apparatus according to the embodiment. FIG. 8 is a diagram showing an example of an adjustment chart in the simple adjustment mode of the image forming apparatus according to the embodiment. FIG. 9 is a diagram showing an example of an adjustment chart in the detailed adjustment mode of the image forming apparatus according to the embodiment. The details of the operation in the adjustment mode of the image forming apparatus 1 according to the present embodiment will be described with reference to FIGS. 6 to 9.

[0074] First, the controller 300 starts the operation in the adjustment mode for the secondary transfer bias. For example, the controller 300 starts the operation in the adjustment mode in response to an operation on the operation panel 302 by the user. In this case, the user selects either the simple adjustment mode or the detailed adjustment mode in the adjustment mode.

[0075] In addition, when the user inputs information about the type of recording sheet set in the paper feed cassette 100 from the screen displayed on the operation panel 302 and the information of the recording sheet is set by the setting unit 404, the controller 300 may start the operation in the adjustment mode. Further, when the user inputs information about the type of recording sheet set in the paper feed cassette 100 from the screen displayed on the operation panel 302, a screen for inquiring whether to execute the adjustment mode may be displayed on the operation panel 302. Then, when the user selects the execution of the adjustment mode on the screen, the controller 300 may start the operation in the adjustment mode. On the other hand, when the user does not select the execution of the adjustment mode on the screen, the controller 300 may use the secondary transfer bias corresponding to the recording sheet in the secondary transfer bias table stored in the memory 301.

[0076] In addition, when the power of the image forming apparatus 1 is turned on, for each printing of a predetermined number of sheets, or when a predetermined amount of environmental change (for example, the amount of change in temperature and humidity) is detected, the display control unit 405 may display a prompt to execute the operation in the adjustment mode on the operation panel 302 at a timing when the optimum value of the secondary transfer bias may change.

[0077] When the operation in the adjustment mode is started, the power control unit 401 reads out the secondary transfer bias corresponding to the recording sheet for transferring the adjustment chart from the secondary transfer bias table in the memory 301. Next, the power control unit 401 changes the secondary transfer bias within a predetermined range based on the read secondary transfer bias, and transfers the adjustment chart to the recording sheet under different secondary transfer conditions. That is, the power control unit 401 transfers the adjustment chart to the recording sheet for each generated secondary transfer condition. Here, the adjustment chart is an image, character, or other chart image for selecting the optimum secondary transfer condition, which is printed (transferred) on the recording sheet under different secondary transfer conditions as described above.

[0078] Here, FIG. 6(a) shows an example of different secondary transfer conditions when a superimposed bias is applied to the adjustment chart on the embossed paper and secondarily transferred to the secondary transfer counter roller 53. As shown in FIG. 6(a), for the DC current of the superimposed bias, the power supply control unit 401 varies it within a range of ±10 [μA] with respect to the reference DC current value (the DC current value of the target secondary transfer bias set in the secondary transfer bias table at that time). Specifically, the power supply control unit 401 changes to three DC current values: the reference DC current value (def), the DC current value of +10 [μA] with respect to the reference DC current value (def + 10), and the DC current value of -10 [μA] with respect to the reference DC set value (def - 10), and applies a superimposed bias to the secondary transfer counter roller 53. Then, while the superimposed bias is applied to the secondary transfer counter roller 53 by being changed by the power supply control unit 401 respectively, the printing control unit 403 secondarily transfers the adjustment chart to the recording sheet. In the above example, the change amount of the DC current value is 10 [μA], and the range of change is ±10 [μA]. However, the change amount of the DC current value and the range of change may be freely set by the setting unit 404 according to the operation on the operation panel 302 by the user.

[0079] On the one hand, for the AC voltage of the superimposed bias (peak-to-peak voltage Vpp), the power control unit 401 varies it within a range of ±2.0 [kV] with respect to the reference AC voltage value (the AC voltage value of the target secondary transfer bias set in the secondary transfer bias table at that time). Specifically, the power control unit 401 varies the AC voltage values among the reference AC voltage value (def), the AC voltage value +1.0 [kV] with respect to the reference AC voltage value (def+1), the AC voltage value -1.0 [kV] with respect to the reference AC voltage value (def-1), the AC voltage value -2.0 [kV] with respect to the reference AC voltage value (def-2), and the AC voltage value +2.0 [kV] with respect to the reference AC voltage value (def+2), and applies the superimposed bias to the secondary transfer opposing roller 53. Then, while the superimposed bias is applied to the secondary transfer opposing roller 53 by varying it respectively by the power control unit 401, the print control unit 403 secondary-transfers the adjustment chart onto the recording sheet. In the above example, the change amount of the AC voltage value is 1.0 [kV], and the varying range is ±2.0 [kV]. However, the change amount of the AC voltage value and the varying range may be freely set by the setting unit 404 according to the operation on the operation panel 302 by the user.

[0080] That is, when adjusting the secondary transfer bias (superimposed bias) corresponding to the embossed paper, the power control unit 401 varies both the DC current and the AC voltage, and transfers the adjustment chart onto the recording sheet of the embossed paper under the 15 secondary transfer conditions shown in Fig. 6(a). Therefore, when adjusting the secondary transfer bias (superimposed bias) corresponding to the embossed paper, a total of 15 adjustment charts are formed. The numbers shown in Fig. 6(a) are the numbers of the adjustment charts transferred under different secondary transfer conditions corresponding to the embossed paper. For example, the secondary transfer conditions of the first adjustment chart formed first correspond to "(1)" in Fig. 6(a), and are the secondary transfer conditions of the combination of the DC current value -10 [μA] with respect to the DC current value of the reference secondary transfer bias and the AC voltage value -2 [kV] with respect to the AC voltage value of the reference secondary transfer bias.

[0081] Next, FIG. 7 shows a timing chart indicating changes in the AC voltage (AC bias in the figure) and DC current (DC bias in the figure) in the simple adjustment mode when adjusting the secondary transfer bias corresponding to the embossed paper. FIG. 7 shows an example in which a total of 15 adjustment charts to be transferred to the embossed paper under different secondary transfer conditions are transferred to a total of 3 recording sheets. As shown in FIG. 7, for example, 5 adjustment charts are formed on one recording sheet. The first to fifth adjustment charts are transferred to the first recording sheet P1, the sixth to tenth adjustment charts are transferred to the second recording sheet P2, and the eleventh to fifteenth adjustment charts are transferred to the third recording sheet P3. That is, as shown in FIG. 7, the power control unit 401 changes the DC current of the secondary transfer bias for each recording sheet and changes the AC voltage of the secondary transfer bias into 5 levels within each recording sheet, and transfers the adjustment charts to the recording sheets P1 to P3 under the 15 secondary transfer conditions shown in FIG. 6(a). Note that the method of changing the DC current and AC voltage of the secondary transfer bias is not limited to the timing chart shown in FIG. 7.

[0082] FIG. 8 shows an example of an adjustment chart transferred to the recording sheet P1 to adjust the secondary transfer bias used when transferring a full-color toner image to the front surface of the embossed paper in the simple adjustment mode. In the present embodiment, as shown in FIG. 8, the print control unit 403 changes the adjustment chart to be transferred according to the size of the recording sheet. For example, the adjustment chart shown in FIG. 8(a) is for the case where the size of the recording sheet is large, and the adjustment chart shown in FIG. 8(b) is for the case where the size of the recording sheet is small. As shown in FIG. 8, the print control unit 403 changes the lengths in the main scanning direction and the sub-scanning direction of the adjustment chart according to the size of the recording sheet, and transfers the adjustment chart so that it is arranged near the end of the recording sheet. In addition, the print control unit 403 transfers a number indicating any one of the above 15 secondary transfer conditions near the corresponding adjustment chart so that it can identify which adjustment chart transferred under which secondary transfer condition to the recording sheet.

[0083] In this embodiment, first, the power control unit 401 reads out the superimposed bias (DC current value, AC voltage value) of the monochrome front side associated with the embossed paper from the secondary transfer bias table in the memory 301. Then, based on the superimposed bias (DC current value, AC voltage value) read by the power control unit 401, the print control unit 403 transfers the 1st to 5th monochrome adjustment charts to the front side of the recording sheet, which is the first embossed paper. At this time, the print control unit 403 transfers "monochrome front side" to the front side of the recording sheet as an item of the secondary transfer bias for adjustment. Then, this recording sheet, which is embossed paper, is inverted by the inversion and refeeding device 105 and conveyed to the secondary transfer nip again. Then, the power control unit 401 reads out the superimposed bias (DC current value, AC voltage value) of the monochrome back side associated with the embossed paper from the secondary transfer bias table in the memory 301. Then, based on the superimposed bias (DC current value, AC voltage value) read by the power control unit 401, the print control unit 403 transfers the 1st to 5th monochrome adjustment charts to the back side of the recording sheet, which is the first embossed paper. At this time, the print control unit 403 transfers "monochrome back side" to the back side of the recording sheet as an item of the secondary transfer bias for adjustment.

[0084] Next, the recording sheet, which is the second corrugated paper, is conveyed, and the print control unit 403 transfers the 6th to 10th monochrome adjustment charts to the front surface of the recording sheet, which is the second corrugated paper, based on the superimposed bias (DC current value, AC voltage value) read by the power control unit 401. At this time, the print control unit 403 transfers "monochrome front surface" to the front surface of the recording sheet as an item of the secondary transfer bias for adjustment. Similarly, the print control unit 403 transfers the 6th to 10th monochrome adjustment charts to the back surface of the recording sheet, which is the second corrugated paper, based on the superimposed bias (DC current value, AC voltage value) read by the power control unit 401. At this time, the print control unit 403 transfers "monochrome back surface" to the back surface of the recording sheet as an item of the secondary transfer bias for adjustment. Similarly, the print control unit 403 transfers the 11th to 15th monochrome adjustment charts to the front surface and the back surface of the recording sheet, which is the third corrugated paper, respectively.

[0085] Next, the power control unit 401 reads out the superimposition bias (DC current value, AC voltage value) of the full-color front surface associated with the embossed paper from the secondary transfer bias table in the memory 301. Then, based on the superimposition bias (DC current value, AC voltage value) read by the power control unit 401, the print control unit 403 transfers the adjustment charts for the 1st to 5th full-colors to the front surface of the recording sheet, which is the 4th embossed paper. At this time, the print control unit 403 transfers "full-color front surface" to the front surface of the recording sheet as an item of the secondary transfer bias for adjustment. Then, this recording sheet, which is embossed paper, is reversed by the reverse re-feed device 105 and conveyed to the secondary transfer nip again. Then, the power control unit 401 reads out the superimposition bias (DC current value, AC voltage value) of the full-color back surface associated with the embossed paper from the secondary transfer bias table in the memory 301. Then, based on the superimposition bias (DC current value, AC voltage value) read by the power control unit 401, the print control unit 403 transfers the adjustment charts for the 1st to 5th full-colors to the back surface of the recording sheet, which is the 4th embossed paper. At this time, the print control unit 403 transfers "full-color back surface" to the back surface of the recording sheet as an item of the secondary transfer bias for adjustment.

[0086] Similarly, the print control unit 403 transfers the adjustment charts for the 6th to 10th full-colors to the front and back surfaces of the recording sheet, which is the 5th embossed paper, and transfers the adjustment charts for the 11th to 15th full-colors to the front and back surfaces of the recording sheet, which is the 6th embossed paper.

[0087] Note that in the above example, after the transfer of the monochrome adjustment chart, the transfer of the full-color adjustment chart is performed, but it is not limited to this, and it may be possible that the transfer of the monochrome adjustment chart is performed after the transfer of the full-color adjustment chart.

[0088] In this way, in the simple adjustment mode, since the adjustment charts are transferred by switching a plurality of secondary transfer conditions within the same recording sheet, the number of recording sheets required for the adjustment of the secondary transfer bias can be suppressed.

[0089] On the other hand, when adjusting the secondary transfer bias corresponding to the embossed paper in the detailed adjustment mode, the power control unit 401 switches 15 secondary transfer conditions for each recording sheet, and the print control unit 403 transfers the adjustment chart under the secondary transfer conditions switched for each recording sheet by the power control unit 401. In this case, 15 recording sheets, which is the number of secondary transfer conditions, are required.

[0090] FIG. 9 shows an example of an adjustment chart transferred to a recording sheet P for adjusting the secondary transfer bias used when transferring a full-color toner image to the front surface of the embossed paper in the detailed adjustment mode. The recording sheet P shown in FIG. 9 shows an example in which the adjustment chart is transferred under the first secondary transfer condition. For example, the adjustment chart shown in FIG. 9(a) is for the case where the size of the recording sheet is large, and the adjustment chart shown in FIG. 9(b) is for the case where the size of the recording sheet is small. As shown in FIG. 9, the print control unit 403 changes the lengths in the main scanning direction and the sub-scanning direction of the adjustment chart according to the size of the recording sheet, and transfers the adjustment chart so that it is arranged near the end of the recording sheet. Further, the print control unit 403 transfers a number indicating any one of the above 15 secondary transfer conditions so that it can identify which secondary transfer condition the adjustment chart transferred to the recording sheet is. As shown in FIG. 9, in the detailed adjustment mode, since the adjustment chart is transferred to the recording sheet under the same secondary transfer condition, it is possible to transfer a large-size adjustment patch covering the entire main scanning direction, as well as a plurality of color adjustment patches and character strings within the page, etc., and there is an advantage that the judgment information when the user selects a preferred secondary transfer condition can be increased. On the other hand, since the number of recording sheets required for adjusting the secondary transfer bias increases, when there is no problem with less judgment information, the secondary transfer bias can be adjusted with a small number of recording sheets by using the simple adjustment mode.

[0091] Further, FIG. 6(b) shows an example of different secondary transfer conditions when a secondary transfer chart is secondarily transferred onto plain paper while applying a DC bias to the secondary transfer counter roller 53. As shown in FIG. 6(b), the power control unit 401 changes the DC bias within a range of -2 [μA] to +6 [μA] with respect to the reference DC current value (the DC current value of the target secondary transfer bias set in the secondary transfer bias table at that time). Specifically, the power control unit 401 has a reference DC current value (def), a DC current value of -2 [μA] with respect to the reference DC current value (def-2), a DC current value of -1 [μA] with respect to the reference DC current value (def-1), a DC current value of +1 [μA] with respect to the reference DC current value (def+1), a DC current value of +2 [μA] with respect to the reference DC current value (def+2), a DC current value of +3 [μA] with respect to the reference DC current value (def+3), a DC current value of +4 [μA] with respect to the reference DC current value (def+4), a DC current value of +5 [μA] with respect to the reference DC current value (def+5), and a DC current value of +6 [μA] with respect to the reference DC current value (def+6). The power control unit 401 changes to these nine DC current values and applies a DC bias to the secondary transfer counter roller 53. Then, the print control unit 403 causes the adjustment chart to be secondarily transferred onto the recording sheet while the DC bias is applied to the secondary transfer counter roller 53 by the power control unit 401 while being changed respectively. In the above example, the change amount of the DC current value is set to 1 [μA], and the change range is set to -2 [μA] to +6 [μA]. However, the change amount of the DC current value and the change range may be freely set by the setting unit 404 according to the operation on the operation panel 302 by the user.

[0092] That is, when adjusting the secondary transfer bias (DC bias) corresponding to plain paper, the power control unit 401 changes the DC current and transfers the adjustment chart to the recording sheet of plain paper under the nine secondary transfer conditions shown in Fig. 6(b). Therefore, when adjusting the secondary transfer bias (DC bias) corresponding to plain paper, a total of nine adjustment charts are formed. The numbers shown in Fig. 6(b) are the numbers of the adjustment charts transferred under different secondary transfer conditions corresponding to plain paper. For example, the secondary transfer condition of the first adjustment chart formed first corresponds to "(16)" in Fig. 6(b), and it is the secondary transfer condition with a DC current value (def-2) of -2 [μA] with respect to the DC current value of the reference secondary transfer bias.

[0093] Note that the operation of the simple adjustment mode for the recording sheet of plain paper is the same as the operation of the simple adjustment mode for the recording sheet of embossed paper described above. Also, the operation of the detailed adjustment mode for the recording sheet of plain paper is the same as the operation of the simple adjustment mode for the recording sheet of embossed paper described above.

[0094] Also, in the secondary transfer bias table shown in Fig. 5, an example is shown in which a DC bias is applied as the secondary transfer bias for plain paper and a superimposed bias is applied as the secondary transfer bias for embossed paper in the adjustment mode, but it is not limited to this. For example, for plain paper, when creating a plurality of different secondary transfer conditions by the power control unit 401 in the adjustment mode, instead of the secondary transfer condition of the DC bias, a secondary transfer condition of the superimposed bias, or a secondary transfer condition in which the DC bias and the superimposed bias are mixed may be created. Similarly, for embossed paper, when creating a plurality of different secondary transfer conditions by the power control unit 401 in the adjustment mode, instead of the secondary transfer condition of the superimposed bias, a secondary transfer condition of the DC bias, or a secondary transfer condition in which the DC bias and the superimposed bias are mixed may be created.

[0095] Also, when different secondary transfer conditions are created by the power control unit 401 in the adjustment mode, they are created based on the target secondary transfer bias set in the secondary transfer bias table at that time. However, the present invention is not limited to this, and they may be created based on a predetermined default secondary transfer bias.

[0096] In the present embodiment, two adjustment modes, namely, the simple adjustment mode and the detailed adjustment mode, are described as the adjustment modes. However, the present invention is not limited to the case where there are two adjustment modes, and there may be three or more adjustment modes. For example, as shown in FIG. 5, for each of the secondary transfer biases corresponding to "monochrome front side", "monochrome back side", "full color front side", and "full color back side", some of the secondary transfer biases may be operated in the simple adjustment mode, and the remaining secondary transfer biases may be operated in the detailed adjustment mode. That is, it may have a mixed adjustment mode or the like.

[0097] (Flow of operations in the adjustment mode of the image forming apparatus) FIG. 10 is a flowchart showing an example of the flow of operations in the adjustment mode of the image forming apparatus according to the embodiment. FIG. 11 is a diagram showing an example of a screen for inputting the number of the adjustment chart displayed on the operation panel of the image forming apparatus according to the embodiment. An example of the flow of operations in the adjustment mode of the image forming apparatus 1 according to the present embodiment will be described with reference to FIGS. 10 and 11.

[0098] <Step S11> First, the controller 300 starts the operation of the adjustment mode for the secondary transfer bias. For example, the controller 300 starts the operation of the adjustment mode in response to an operation by the user on the operation panel 302. In this case, the user selects either the simple adjustment mode or the detailed adjustment mode among the adjustment modes. Then, the process proceeds to step S12.

[0099] <Step S12> When the adjustment mode selected by the user is the simple adjustment mode (step S12: simple adjustment mode), the process proceeds to step S13. When it is the detailed adjustment mode (step S12: detailed adjustment mode), the process proceeds to step S18.

[0100] <Step S13> The controller 300 executes the operation of the simple adjustment mode. The controller 300 determines whether the length (paper width) in the main scanning direction is greater than or equal to a predetermined value A and the length (paper length) in the sub-scanning direction is greater than or equal to a predetermined value B for the size of the recording sheet preset by the setting unit 404. When the length (paper width) in the main scanning direction is greater than or equal to the predetermined value A and the length (paper length) in the sub-scanning direction is greater than or equal to the predetermined value B for the size of the recording sheet (step S13: Yes), the process proceeds to step S15. When the length (paper width) in the main scanning direction is less than the predetermined value A or the length (paper length) in the sub-scanning direction is less than the predetermined value B (step S13: No), the process proceeds to step S14.

[0101] <Step S14> When the recording sheet has a length (paper width) in the main scanning direction less than the predetermined value A or a length (paper length) in the sub-scanning direction less than the predetermined value B, it is difficult to transfer the adjustment chart in the simple adjustment mode to the recording sheet. Therefore, the controller 300 determines that it is not supported and proceeds to step S22.

[0102] <Step S15> Furthermore, the controller 300 determines whether the length (paper length) in the sub-scanning direction is greater than or equal to a predetermined value C for the size of the recording sheet preset by the setting unit 404. When the length (paper length) in the sub-scanning direction is greater than or equal to the predetermined value C for the size of the recording sheet (step S15: Yes), the process proceeds to step S17. When it is less than the predetermined value C (step S15: No), the process proceeds to step S16.

[0103] <Step S16> In this case, since the recording sheet is small, the controller 300 determines to print the monochrome adjustment chart on both sides of pages 1 to 3 of the recording sheet and the full-color adjustment chart on both sides of pages 4 to 6. Then, it proceeds to step S19.

[0104] <Step S17> In this case, since the recording sheet is large, the controller 300 determines to print the monochrome adjustment chart on both sides of pages 1 and 2 of the recording sheet and the full-color adjustment chart on both sides of pages 3 and 4. Then, it proceeds to step S19.

[0105] <Step S18> The controller 300 executes the operation in the detailed adjustment mode. The controller 300 determines the size of the adjustment chart to be transferred to the recording sheet based on the size of the recording sheet preset by the setting unit 404. Then, it proceeds to step S19.

[0106] <Step S19> The power control unit 401 refers to the memory 301 and reads out the secondary transfer bias (superimposed bias or DC bias) corresponding to the type of the recording sheet preset by the setting unit 404, and the variation amount for generating different secondary transfer conditions based on the secondary transfer bias. Then, it proceeds to step S20.

[0107] <Step S20> The power control unit 401 changes the secondary transfer bias within a predetermined range by the read variation amount with reference to the read secondary transfer bias, generates different secondary transfer conditions, and applies the secondary transfer bias to the secondary transfer opposing roller 53 while switching the secondary transfer conditions. The print control unit 403 causes the adjustment chart to be printed on both sides of the recording sheet while the secondary transfer bias is applied to the secondary transfer opposing roller 53 by being changed by the power control unit 401 respectively. Then, it proceeds to step S21.

[0108] <Step S21> The user inputs, to the operation panel 302, the number of the adjustment chart that is determined to be in the best printing state among the adjustment charts transferred to the recording sheet, that is, the number of the secondary transfer conditions used for printing the adjustment chart. Here, FIG. 11 shows an example of a screen for inputting the numbers of the adjustment charts displayed on the operation panel 302. The operation panel 302 includes a touch panel 302a having an input function and a display function, and a key operation unit 302b that accepts operation inputs. In the example shown in FIG. 11, the touch panel 302a displays a screen that enables the input of the best numbers for each of the adjustment charts of "monochrome front side", "monochrome back side", "full color front side", and "full color back side". In the example shown in FIG. 11, the user operates the key operation unit 302b to input each number. Then, the process proceeds to step S22.

[0109] <Step S22> The setting unit 404 sets, as a new secondary transfer bias for the recording sheet, the secondary transfer conditions of the number of the optimal adjustment chart input by the user among the adjustment charts printed under different secondary transfer conditions, and updates the secondary transfer bias table stored in the memory 301 with the secondary transfer bias. Note that, if step S14 is not applicable, step S22 may be skipped. Then, the controller 300 ends the operation in the adjustment mode.

[0110] As described above, in the image forming apparatus 1 according to the present embodiment, the power control unit 401 generates a plurality of different secondary transfer conditions for a combination including at least a DC component among a DC component and an AC component with respect to the secondary transfer bias applied from the secondary transfer bias power supply 200 to the secondary transfer nip formed between the intermediate transfer belt 51 that carries the toner image and the secondary transfer roller 56, switches the plurality of secondary transfer conditions, and applies the secondary transfer bias from the secondary transfer bias power supply 200 to the transfer nip. The print control unit 403 transfers an adjustment chart from the intermediate transfer belt 51 to the recording sheet for each of the secondary transfer conditions applied by the power control unit 401 according to the set adjustment mode among the plurality of adjustment modes for adjusting the secondary transfer bias corresponding to the recording sheet. As a result, in the adjustment of the secondary transfer bias, it is possible to reduce the burden on the user, the time for adjustment, and the waste of the recording sheet generated during the adjustment.

[0111] In the above-described embodiments, when at least any one of the functional units of the controller 300 of the image forming apparatus 1 is realized by executing a program, the program is provided by being pre-embedded in a ROM or the like. Also, in the above-described embodiments, the program executed in the image forming apparatus 1 may be configured to be recorded and provided on a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), a flexible disk (FD), a CD-R (Compact Disk-Recordable), or a DVD (Digital Versatile Disc) in an installable format or an executable format file. Further, in the above-described embodiments, the program executed in the image forming apparatus 1 may be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Moreover, in the above-described embodiments, the program executed in the image forming apparatus 1 may be configured to be provided or distributed via a network such as the Internet. Also, in the above-described embodiments, the program executed in the image forming apparatus 1 has a module configuration including at least any one of the above-described functional units, and as actual hardware, the CPU reads the program from the above-described storage device (for example, the memory 301) and executes it, so that the above-described functional units are loaded and generated on the main storage device.

[0112] Aspects of the present invention are as follows. <1> A first control unit that generates a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component with respect to a transfer bias applied from a power supply device to a transfer nip formed between an image carrier that carries a toner image and a transfer member, and switches the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip; A second control unit that transfers an image from the image carrier to the recording material for each of the transfer conditions applied by the first control unit according to the set adjustment mode among a plurality of adjustment modes for adjusting the transfer bias corresponding to the recording material; An image forming apparatus comprising the same. <2>The image forming apparatus according to <1>, further comprising a setting unit that sets, as a new transfer bias corresponding to the recording material, the transfer condition corresponding to the identification information for identifying the transfer condition input from the operation unit based on the recording material on which the image has been transferred, in a storage unit. <3>The plurality of adjustment modes are A first adjustment mode in which the first control unit switches a plurality of the transfer conditions within each of the recording materials and causes the power supply device to apply the transfer bias; A second adjustment mode in which the first control unit switches the transfer conditions for each of the recording materials and causes the power supply device to apply the transfer bias. The image forming apparatus according to <1> or <2> including the same. <4>The power supply device includes a DC power supply and an AC power supply, further includes a current detection unit that detects a current flowing through the transfer nip, The first control unit performs constant current control on the DC component output from the DC power supply and constant voltage control on the AC component output from the AC power supply based on the current detected by the current detection unit. The image forming apparatus according to any one of <1> to <3>. <5>The first control unit applies, as the transfer bias, a DC bias that applies only a DC component, or a superimposed bias in which an AC component is superimposed on the DC component, according to the recording material. The image forming apparatus according to any one of <1> to <4>. <6>The second control unit transfers an adjustment chart as the image to the recording material in the adjustment mode. The image forming apparatus according to any one of <1> to <5>. <7>The second control unit is the image forming apparatus according to <6>, which changes the adjustment chart to be transferred to the recording material according to the size of the recording material in the adjustment mode. <8>The setting unit is the image forming apparatus according to <2>, which sets a change amount used to generate the plurality of transfer conditions by the first control unit according to an input to the operation unit. <9>A first control step of generating a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component for a transfer bias applied from a power supply device to a transfer nip formed between an image carrier carrying a toner image and a transfer member, and switching the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip; A second control step of transferring an image from the image carrier to the recording material for each of the transfer conditions to be applied according to a set adjustment mode among a plurality of adjustment modes for adjusting a transfer bias corresponding to the recording material; It is an image forming method having. <10>On a computer, A first control step of generating a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component for a transfer bias applied from a power supply device to a transfer nip formed between an image carrier carrying a toner image and a transfer member, and switching the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip; A second control step of transferring an image from the image carrier to the recording material for each of the transfer conditions to be applied according to a set adjustment mode among a plurality of adjustment modes for adjusting a transfer bias corresponding to the recording material; It is a program for causing to execute.

Explanation of Signs

[0113] 1 Image forming apparatus 10, 10C, 10K, 10M, 10Y Image forming unit 11, 11C, 11K, 11M, 11Y Photoconductor drum 21 Charging device 31 Developing device 31a Developing sleeve 31b, 31c Screw members 41 Cleaning device 41a Cleaning blade 41b Cleaning brush roller 50 Transfer unit 51 Intermediate transfer belt 52 Driving roller 53 Secondary transfer opposing roller 54 Cleaning backup roller 55, 55C, 55K, 55M, 55Y Primary transfer roller 56 Secondary transfer roller 57 Cleaning device 80 Optical writing unit 90 Fixing device 91 Fixing roller 92 Pressing roller 100 Paper feed cassette 101 Paper feed roller 102 Registration roller pair 103 Discharge roller pair 104 Switching claw 105 Reversing and refeeding device 105a Switchback part 105b Refeeding part 200 Secondary transfer bias power supply 201 DC power supply 202 AC power supply 300 Controller 301 Memory 302 Operation panel 302a Touch panel 302b Key operation part 303 Current detection part 401 Power supply control part 402 Mode switching part 403 Printing control part 404 Setting part 405 Display control part L Laser beam P, P1~P3 Recording sheets

Prior Art Documents

Patent Documents

[0114]

Patent Document 1

Claims

1. Regarding the transfer bias applied from a power supply device to a transfer nip formed between an image carrier that carries a toner image and a transfer member, a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component are generated, and a first control unit that switches the plurality of transfer conditions and applies the transfer bias from the power supply device to the transfer nip; A second control unit that transfers an image from the image carrier to the recording material for each of the transfer conditions applied by the first control unit according to a set adjustment mode among a plurality of adjustment modes for adjusting the transfer bias corresponding to the recording material; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1, further comprising a setting unit that sets, in a storage unit, as a new transfer bias corresponding to the recording material, the transfer condition corresponding to identification information for identifying the transfer condition input from an operation unit based on the recording material on which the image has been transferred.

3. The plurality of adjustment modes are: A first adjustment mode in which the first control unit switches a plurality of the transfer conditions within each of the recording materials and applies the transfer bias from the power supply device; A second adjustment mode in which the first control unit switches the transfer conditions for each recording material and applies the transfer bias from the power supply device. The image forming apparatus according to claim 1 or 2, including:

4. The power supply device includes a DC power supply and an AC power supply, The image forming apparatus according to claim 1 or 2, further comprising a current detection unit that detects a current flowing through the transfer nip, The first control unit performs constant current control on the DC component output from the DC power supply and constant voltage control on the AC component output from the AC power supply based on the current detected by the current detection unit.

5. The first control unit applies, as the transfer bias according to the recording material, a DC bias that applies only a DC component, or a superimposed bias in which an AC component is superimposed on the DC component.

6. The second control unit transfers an adjustment chart as the image to the recording material in the adjustment mode.

7. The second control unit changes the adjustment chart transferred to the recording material according to the size of the recording material in the adjustment mode.

8. The image forming apparatus according to claim 2, wherein the setting unit sets a variation amount used for generating the plurality of transfer conditions by the first control unit in response to an input to the operation unit.

9. A first control step of generating a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component of a transfer bias applied from a power supply device to a transfer nip formed between an image carrier carrying a toner image and a transfer member, and switching the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip; A second control step of transferring an image from the image carrier to the recording material for each of the transfer conditions to be applied according to a set adjustment mode among a plurality of adjustment modes for adjusting the transfer bias corresponding to the recording material; An image forming method comprising the steps of:

10. A computer, A first control step of generating a plurality of different transfer conditions for a combination including at least a DC component among a DC component and an AC component of a transfer bias applied from a power supply device to a transfer nip formed between an image carrier carrying a toner image and a transfer member, and switching the plurality of transfer conditions to apply the transfer bias from the power supply device to the transfer nip; A second control step of transferring an image from the image carrier to the recording material for each of the transfer conditions to be applied according to a set adjustment mode among a plurality of adjustment modes for adjusting the transfer bias corresponding to the recording material; A program for causing the computer to execute the steps.

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