Image forming apparatus

Abstract

To provide an image forming apparatus that can reduce the time to adjust image density unevenness.SOLUTION: An image forming apparatus comprises: an image forming unit that forms an image on a recording medium based on an image forming condition; an input unit 93 that receives input of information to reduce image density unevenness; and a CPU 301 that causes the image forming unit to create charts on which test images for reducing image density unevenness are printed, and sets an image forming condition according to the information input from the input unit 93 based on the charts. The charts are printed with scales indicating the information input to the input unit 93.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to image forming apparatuses such as printers, copiers, facsimiles, and multifunction peripherals.

Background Art

[0002] An image forming apparatus includes a plurality of rotors such as a photosensitive drum, a charging roller, a developer carrier, and a paper transport roller. Among these, the photosensitive drum, the charging roller, and the developer carrier cause uneven image density due to rotational runout, uneven sensitivity, uneven resistance, etc. The photosensitive drum, the charging roller, and the developer carrier have a short rotation period, so periodic uneven image density that is easy to visually recognize occurs within one page of an image.

[0003] For example, when rotational runout occurs in the photosensitive drum, the distance between the photosensitive drum and the developer carrier becomes unstable. The developer carrier forms a toner image on the photosensitive drum by attaching toner to the photosensitive drum using an electric field generated by the potential difference between the photosensitive drum and itself. Since the distance between the photosensitive drum and the developer carrier becomes unstable, the strength of the electric field fluctuates, so the amount of toner adhering to the photosensitive drum fluctuates. Therefore, periodic uneven image density occurs in the image (toner image) formed on the photosensitive drum due to the rotational runout of the photosensitive drum. Even when rotational runout occurs in the developer carrier, uneven image density occurs for the same reason.

[0004] Due to factors such as environmental changes and changes over time, uneven sensitivity occurs in the photosensitive layer on the surface of the photosensitive drum. When uneven sensitivity occurs in the photosensitive drum, even if it is exposed with a certain exposure amount, a difference occurs in the bright potential, which is the potential after exposure. The difference in bright potential also causes uneven image density.

[0005] The charging roller uniformly charges the photosensitive layer of the photosensitive drum by passing a discharge current through it. If there are inconsistencies in the resistance of the charging roller (resistance variations), the amount of discharge current will fluctuate, causing differences in the dark potential, which is the potential of the photosensitive layer of the photosensitive drum after charging. Even if the photosensitive layer of the photosensitive drum, which has differences in dark potential, is exposed with a constant exposure amount, differences will occur in the bright potential, which is the potential after exposure. Differences in bright potential cause inconsistencies in image density.

[0006] To suppress periodic image density unevenness caused by such rotating bodies, Patent Document 1 discloses a technique for forming an image larger than one rotation of a photosensitive drum, detecting periodic image density unevenness based on the reading result of this image, and suppressing the detected image density unevenness. Image density unevenness is suppressed by adjusting the charging bias, development bias, exposure light amount conditions, etc. Patent Document 2 discloses a technique for forming an image for checking image density unevenness on a recording medium, and for the user who has checked this to input adjustment data via an operation unit to fine-tune the image density unevenness. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-139604 [Patent Document 2] Japanese Patent Publication No. 2017-201381 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, when fine-tuning image density unevenness using adjustment data corresponding to an image used for checking image density unevenness, it is not possible to confirm whether the adjustment data is appropriate without printing the image used for checking image density unevenness onto the recording medium again. If the adjustment data is inappropriate, the input of adjustment data and printing of the image used for checking image density unevenness onto the recording medium will be repeated. This causes the adjustment time for image density unevenness to increase.

[0009] In view of the above problems, the present invention aims to provide an image forming apparatus that can shorten the time required to adjust for uneven image density. [Means for solving the problem]

[0010] The present invention provides an image forming apparatus comprising: an image forming means for forming an image on a recording medium based on image forming conditions; an input means for receiving information for suppressing uneven image density; and a control means for causing the image forming means to create a chart on which test images for suppressing uneven image density are printed, and for setting the image forming conditions according to the information input from the input means based on the chart, wherein the chart is printed with a scale indicating the information input to the input means. [Effects of the Invention]

[0011] According to the present invention, the time required to adjust for uneven image density can be reduced by printing scales on the chart. [Brief explanation of the drawing]

[0012] [Figure 1] Diagram showing the configuration of an image forming apparatus. [Figure 2] Diagram showing the configuration of the image forming unit. [Figure 3] An illustrative diagram of a phase detection sensor. [Figure 4] An example diagram of the output values ​​of a photointerrupter. [Figure 5] Hardware configuration diagram of an image forming apparatus. [Figure 6] A flowchart illustrating the image density uniformity correction process. [Figure 7] An example diagram of the input screen. [Figure 8] An example diagram of the input screen. [Figure 9] An example diagram of the input screen. [Figure 10] An example diagram of the input screen. [Figure 11] An example diagram of Chart 1. [Figure 12] An example diagram of the second chart. [Figure 13] Exemplary diagram of Chart 3 [Figure 14] Explanation diagram of bias voltage correction waveform [Figure 15] Configuration diagram of image forming apparatus [Figure 16] Configuration diagram of image forming section [Figure 17] Exemplary diagram of Chart 1 [Figure 18] Exemplary diagram of input screen [Figure 19] Exemplary diagram of Chart 2 [Figure 20] Exemplary diagram of Chart 3 [Figure 21] Flowchart showing image density unevenness correction process [Figure 22] Exemplary diagram of Chart 1 [Figure 23] Exemplary diagram of Chart 1

Mode for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described in detail with reference to the drawings.

[0014] (First Embodiment) FIG. 1 is a configuration diagram of the image forming apparatus of the present embodiment. The image forming apparatus 100 includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a transfer charger 5, a cleaner 6, a pre-exposure device 7, a conveying belt 8, a fixing device 9, and a paper feed cassette 60 inside. An operation unit 200 is provided on the upper part of the housing of the image forming apparatus 100.

[0015] The photosensitive drum 1 is a drum-shaped image carrier having a photosensitive layer on its surface. The photosensitive drum 1 rotates in the direction of arrow Y during the image formation operation. The charging roller 2 uniformly charges the surface of the photosensitive drum 1. The exposure unit 3 exposes the photosensitive body, whose surface has been uniformly charged, based on image information. Exposure forms an electrostatic latent image on the surface of the photosensitive drum 1 based on the image information. The developer unit 4 deposits toner onto the electrostatic latent image formed on the surface of the photosensitive drum 1 to make it visible. This forms a toner image on the surface of the photosensitive drum 1. The developer unit 4 is supplied with toner by the toner supply unit T.

[0016] The transfer charger 5 electrostatically transfers the toner image formed on the photosensitive drum 1 to the surface of the recording medium P. The recording medium P is housed in the paper feed cassette 60 and is fed from the paper feed cassette 60 to the transfer charger 5 according to the timing of the start of toner image formation on the photosensitive drum 1. The recording medium P on which the toner image has been transferred is transported to the fuser 9 by the transport belt 8. The fuser 9 heats and pressurizes the recording medium P on which the toner image has been transferred. As a result, the toner image melts and is pressed onto the recording medium P.

[0017] Furthermore, any residual toner remaining on the photosensitive drum 1 after transfer is removed by the cleaner 6. Residual charge on the photosensitive drum 1 is also removed by the pre-exposure unit 7. After the removal of residual toner and residual charge, the photosensitive drum 1 is used for the next image formation.

[0018] The control unit 200 is a user interface operated by users or service personnel. The control unit 200 includes an input interface and an output interface. The control unit 200 receives various settings and instructions to start image forming operations via the input interface. The control unit 200 displays input screens and screens showing the status of the image forming apparatus 100 via the output interface.

[0019] Figure 2 is a diagram showing the configuration of the image forming section of the image forming apparatus 100, which consists of a photosensitive drum 1, a charging roller 2, an exposure unit 3, a developing unit 4, a transfer charger 5, a cleaner 6, and a pre-exposure unit 7.

[0020] The charging roller 2 is rotatably held at both ends of its core by bearing members (not shown) and is biased toward the photosensitive drum 1 by a compression spring 21. With this configuration, the charging roller 2 is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force and rotates in accordance with the rotation of the photosensitive drum 1.

[0021] A predetermined charging bias voltage is applied to the core metal of the charging roller 2 by a high-voltage power supply 101. The charging roller 2, upon application of the charging bias voltage, contact-charges the surface of the rotating photosensitive drum 1 to a predetermined potential with a predetermined polarity. In this embodiment, the charging bias voltage applied to the charging roller 2 is an oscillating voltage obtained by superimposing a DC voltage of -500[V] and a sinusoidal AC voltage with a frequency of 1.3[kHz] and a peak-to-peak voltage Vpp=1.5[kV]. Due to the charging bias voltage, the surface of the photosensitive drum 1 is uniformly charged to -500[V] (dark potential Vd), the same as the DC voltage applied to the charging roller 2.

[0022] The developing unit 4 has a developing container 40. Inside the developing container 40 is a two-component developer mainly consisting of a non-magnetic toner and a magnetic carrier. The developing container 40 has an opening facing the photosensitive drum 1. A developing sleeve 41, which serves as a developer carrier, is positioned so that a portion of it is exposed from the opening. The developing sleeve 41 is made of a non-magnetic material and has a magnet 42 fixed inside. The magnet 42 generates a magnetic field around the developing sleeve 41.

[0023] The developing container 40 is equipped with first and second stirring screws 44 and 45, which are components for agitating and conveying the developer. The two-component developer inside the developing container 40 is agitated by the first and second stirring screws 44 and 45 and circulated and conveyed within the developing container 40.

[0024] During the developing operation, the developing sleeve 41 rotates in the direction of arrow X (counterclockwise), and the photosensitive drum 1 rotates in the direction of arrow Y (clockwise). The developing sleeve 41 carries a thin layer of two-component developer formed by the regulating member 43, and the rotating sleeve transports the two-component developer it carries. That is, a carrier with triboelectrically charged toner attached to its surface is restrained on the developing sleeve 41 by the magnetic field generated by the magnet 42 and transported therefrom.

[0025] In this embodiment, the photosensitive drum 1 has a diameter of 30 mm, the charging roller 2 has a diameter of 12 mm, and the developing sleeve 41 has a diameter of 16 mm. To improve the development of toner against electrostatic latent images, the linear velocity of the developing sleeve 41 at the opposing position of the photosensitive drum 1 is driven so that the speed of the developing sleeve 41 is 1.7 times that of the photosensitive drum 1.

[0026] For the non-magnetic toner of the two-component developer, particles obtained by grinding and classifying a mixture of pigment and a resin binder, primarily polyester, can be suitably used. The average particle size of the non-magnetic toner in this embodiment is approximately 6 [μm], taking into consideration image quality and handling. Furthermore, if necessary, silica, alumina, titania, or organic resin particles may be added as external additives to ensure the fluidity and charge imparting properties of the toner. The magnetic carrier of the two-component developer is made of a core mainly composed of a magnetic material such as ferrite, coated with a resin such as silicon or acrylic, and particles with a 50% particle size (D50) of about 40 [μm] can be suitably used.

[0027] In this embodiment, the developer in the developing container 40 is a two-component developer in which toner and carrier are mixed in a weight ratio of approximately 8:92, and the toner concentration (ratio of toner weight to total developer weight: TD ratio) is 8%, with 200 g contained in the developing container 40. When toner is consumed during the developing process and the toner concentration decreases, toner is replenished to the developing container 40 from the toner replenishment unit T.

[0028] A predetermined development bias voltage is applied to the developing sleeve 41 from the high-voltage power supply 102. In this embodiment, the development bias voltage is an oscillating voltage obtained by superimposing a DC voltage and an AC voltage. For example, the development bias voltage is an oscillating voltage obtained by superimposing a DC voltage of -350[V] and a square wave AC voltage with a frequency of 8.0[kHz] and a peak-to-peak voltage Vpp=1.8[kV]. Due to the potential difference between the development bias voltage and the electrostatic latent image formed on the surface of the photosensitive drum 1, toner moves from the developing sleeve 41 to the photosensitive drum 1, and the electrostatic latent image is inverted and developed.

[0029] The transfer charger 5 receives a transfer bias voltage under predetermined conditions from the high-voltage power supply 103. In this embodiment, the transfer bias voltage is a DC voltage. For example, the transfer bias voltage is a DC voltage of +800[V]. The transfer bias voltage transfers the toner image formed on the photosensitive drum 1 onto the recording medium P.

[0030] The photosensitive drum 1, charging roller 2, and developing sleeve 41 of this embodiment are equipped with a phase detection mechanism for detecting the rotational phase. As an example of the phase detection mechanism, Figure 3 shows an example of a phase detection sensor for detecting the rotational phase of the photosensitive drum 1. This phase detection sensor 50 includes a photointerrupter 51.

[0031] The photosensitive drum 1 has a drum shaft 53, which is the rotational axis, connected to the output shaft of a drive motor 54 via a coupling (not shown). The photosensitive drum 1 is rotationally driven by the driving force of the drive motor 54. The phase detection sensor 50 of the photosensitive drum 1 has a photointerrupter 51 and a light-shielding member 52 that rotates along with the rotation of the drum shaft 53. When the photosensitive drum 1 rotates and reaches a predetermined phase (rotational position), the light-shielding member 52 blocks the light path of the photointerrupter 51. The photointerrupter 51 detects that the photosensitive drum 1 has reached a predetermined phase (rotational position) because the light path is blocked. In this way, the photointerrupter 51 can detect the rotational position of the photosensitive drum 1. The charging roller 2 and the developing sleeve 41 are also equipped with phase detection devices with substantially the same configuration, and the rotational positions of the charging roller 2 and the developing sleeve 41 can be detected.

[0032] In the example shown in Figure 3, a direct drive system is described in which the photosensitive drum 1 is directly connected to the drive motor 54. However, a reduction mechanism may be provided in the transmission path of the driving force from the drive motor 54. The same applies to the driving of the developing sleeve 41. As described above, the charging roller 2 in this embodiment is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force and rotates in accordance with the rotation of the photosensitive drum 1. For this reason, the charging roller 2 does not have a drive motor.

[0033] Figure 4 is an example diagram of the output value of the photointerrupter 51. When the photointerrupter 51 detects the light-shielding member 52, which rotates in sync with the photosensitive drum 1, the output value of the photointerrupter 51 drops to approximately 0[V]. The change in the output value (edge) of the photointerrupter 51 allows detection of the rotational position (phase) of the photosensitive drum 1. The interval at which the photointerrupter 51 detects the light-shielding member 52 corresponds to the circumference of the photosensitive drum 1. In this embodiment, the timing at which the output value of the photointerrupter 51 becomes 0[V] due to the detection of the light-shielding member 52 is defined as the home position.

[0034] Figure 5 is a hardware configuration diagram of the image forming apparatus 100. The image forming apparatus 100 includes an information processing device having a CPU (Central Processing Unit) 301, RAM (Random Access Memory) 306, and ROM (Read Only Memory) 307. The CPU 301 is connected to an image data generation unit 89, a phase detection sensor drive unit 305, a motor control unit 91, a high-voltage control unit 92, an image processing unit 84, an I / F unit 85, a timer 90, a controller 87, and a paper feed cassette 60.

[0035] The CPU 301 controls the overall operation of the image forming apparatus 100 by executing computer programs stored in the ROM 307. The RAM 306 provides a workspace for the CPU 301 to perform processing. The CPU 301 generates various command signals and performs calculations to operate various sensors, motors, etc., provided in the image forming apparatus 100.

[0036] The image data generation unit 89 is connected to the laser drive unit 303, which drives the exposure unit 3. The image data generation unit 89, under the control of the CPU 301, converts various image data into signals (image information) for laser control and transmits them to the laser drive unit 303. The image data generation unit 89 also includes a function to generate test images, which will be described later. Based on the signals sent from the image data generation unit 89, the laser drive unit 303 drives the laser element of the exposure unit 3 and controls the illumination and light intensity of the laser.

[0037] The phase detection sensor drive unit 305 is connected to the phase detection sensor 50. The phase detection sensor drive unit 305 controls the operation of the phase detection sensor 50 as described above under the control of the CPU 301. The motor control unit 91 is connected to the various motors 910 in the image forming apparatus 100, such as the drive motor 54 described above. The motor control unit 91 controls the drive timing and drive speed of the various motors 910 under the control of the CPU 301. The rotating bodies in the image forming apparatus 100 are driven and controlled by the various motors 910. The high-voltage control unit 920 is connected to the high-voltage power supplies 920, such as the high-voltage power supplies 101, 102, and 103 described above. The high-voltage control unit 920 controls the high-voltage power supplies 920 under the control of the CPU 301 and controls the output of bias voltages necessary for the image forming process, such as the charge bias voltage, development bias voltage, and transfer bias voltage.

[0038] The I / F unit 85 is an interface with the operation unit 200. The operation unit 200 has an input interface and an output interface as described above. Here, the input interface is provided as an input unit 93, which consists of various key buttons or a touch panel. The output interface is provided as a display unit 94, which consists of a display or the like. Various settings and instructions input by the input unit 93 are input to the CPU 301 via the I / F unit 85. The CPU 301 displays the input screen, etc., on the display unit 94 via the I / F unit 85. In addition, the I / F unit 85 may be configured to perform communication control with an external device such as a personal computer instead of the operation unit 200. In this case, various settings and instructions are input from the personal computer, and the input screen, etc., is displayed on the personal computer.

[0039] The CPU 301 controls the operation of the paper feed cassette 60 and controls the feeding of the recording medium P stored in the paper feed cassette 60. The CPU 301 can also determine whether or not the recording medium P is stored in the paper feed cassette 60 and whether or not the paper feed cassette 60 is attached to the image forming apparatus 100 by using various sensors provided in the paper feed cassette 60.

[0040] The controller 87 acquires image information from an image information storage unit 88 located outside the image forming apparatus 100. The controller 87 transmits the acquired image information to the CPU 301. The CPU 301 processes the acquired image information using the image processing unit 84 and uses it for image formation. The image processing unit 84 transmits the processing results of the image information to the image data generation unit 89. The image data generation unit 89 processes the image information as image data based on the processing results.

[0041] (Image density unevenness correction) Figure 6 is a flowchart illustrating the image density unevenness correction process performed by the image forming apparatus 100 with the configuration described above. The image density unevenness corrected here is a periodic image density unevenness caused by the rotation of multiple rotating bodies such as the photosensitive drum 1, the charging roller 2, and the developing sleeve 41. Figures 7 to 10 are illustrative diagrams of the input screen displayed on the display unit 94 during the image density unevenness correction process. Figures 11, 12, and 13 are illustrative diagrams of the chart created during the image density unevenness correction process. The chart is created by printing a test image for image density unevenness correction on the recording medium P.

[0042] Image density uniformity correction processing is initiated when a user or service technician inputs a start command for image density uniformity correction from the input unit 93 of the operation unit 200. The CPU 301 receives this start command from the input unit 93 and activates the adjustment mode (S11), and displays an input screen on the display unit 94 that instructs the output of a chart as illustrated in Figure 7 (S12). If the user or service technician selects the "Cancel" button from this input screen, the image density uniformity correction processing is terminated.

[0043] When the CPU 301 detects that the user or service technician has selected the "Output First Chart" button (S13), the image forming apparatus 100 creates a first chart, as illustrated in Figure 11, under image forming conditions that do not perform image density uniformity correction (S14). The first chart is ejected from the image forming apparatus 100. The first chart has a long, strip-shaped test image in the transport direction of the recording medium P, a scale indicating the period of the rotating body, and instructions for the user or service technician to perform the next operation.

[0044] The scale printed on the first chart of this embodiment shows that "A" represents the period of the photosensitive drum 1, "B" represents the period of the charging roller 2, and "C" represents the period of the developing sleeve 41. As described above, the photosensitive drum 1 of this embodiment has a diameter of 30 [mm], the charging roller 2 has a diameter of 12 [mm], and the developing sleeve 41 has a diameter of 16 [mm]. The linear velocity at the opposing positions of the photosensitive drum 1 and the developing sleeve 41 is such that the developing sleeve 41 is driven at 1.7 times the speed of the photosensitive drum 1. For this purpose, the scale is printed so that the period of A is 94.2 [mm], the period of B is 37.7 [mm], and the period of C is 29.6 [mm].

[0045] The CPU 301, which created the first chart, displays the period input screen shown in Figure 8 on the display unit 94 (S15). The user or service technician checks the first chart and inputs the symbol for the period with noticeable image density unevenness from the input screen in Figure 8 using the input unit 93. The user or service technician also selects the "Output Second Chart" button using the input unit 93. The CPU 301 obtains the symbol for the period with noticeable image density unevenness from the input unit 93 and detects that the "Output Second Chart" button has been selected (S16). In Figure 8, symbol A is input as the period with noticeable image density unevenness.

[0046] The CPU 301 detects the home position of the rotating body corresponding to the selected period symbol using the phase detection sensor 50 (S17). The CPU 301 matches the timing of the detected home position with the position of the image to be formed and creates a second chart as illustrated in Figure 12 (S18). The second chart is ejected from the image forming apparatus 100. The second chart has a strip-shaped test image the length of one period of the rotating body input in the S16 process that extends in the transport direction of the recording medium P, a scale that divides one period of the rotating body into equal parts, and instructions for the user or service technician to perform the next operation. In this embodiment, a scale that divides one period of the rotating body (photosensitive drum 1) into 12 equal parts is printed. A number from 0 to 11 is printed for each scale. The test image and scale are printed so that the position of "0" on the scale coincides with the home position of the rotating body.

[0047] The CPU 301, which created the second chart, displays the phase input screen shown in Figure 9 on the display unit 94 (S19). The user or service technician checks the second chart and inputs the number of the position with the highest image density from the input screen in Figure 9 using the input unit 93. The user or service technician also selects the "Output Third Chart" button using the input unit 93. The CPU 301 obtains the number of the position with the highest image density from the input unit 93 and detects that the "Output Third Chart" button has been selected (S20). In Figure 9, 4 is input as the position with the highest image density.

[0048] The CPU 301 creates a bias voltage correction waveform (S21) based on the period obtained in processing S16 and the position (phase) obtained in processing S20. Figure 14 is an explanatory diagram of the bias voltage correction waveform. The image density unevenness profile y is expressed by the following formula, using the period ω of the image density unevenness obtained in processing S16, the home position detected in processing S17, and the position (phase) with the highest image density obtained in processing S20. Note that φ is the phase difference (position number × π / 12) between the home position and the position (phase) with the highest image density. y = (amplitude) × cos(ωt + φ) (1)

[0049] The bias voltage correction waveform x is obtained by shifting the phase of the image density unevenness profile y by 180° in order to correct the bias voltage to cancel out this image density unevenness. x=(amplitude)×cos(ωt+φ+π) (2)

[0050] If the photosensitive drum 1 or the charging roller 2 is selected for the period of image density unevenness, the voltage of the bias voltage correction waveform x created here is superimposed on the DC voltage applied from the high-voltage power supply 101 connected to the charging roller 2. If the developing sleeve 41 is selected for the period of image density unevenness, the voltage of the bias voltage correction waveform x created here is superimposed on the DC voltage applied from the high-voltage power supply 102 connected to the developing sleeve 41.

[0051] The CPU 301 prints a test image onto the recording medium P while switching the amplitude level of the created bias voltage correction waveform x to create a third chart as illustrated in Figure 13 (S22). The third chart is ejected from the image forming apparatus 100. The third chart has printed strip-shaped test images extending in the transport direction of four recording medium P with different image forming conditions, each with a different amplitude level of the bias voltage correction waveform x in equation (2), along with a number representing the amplitude level and instructions for the user or service technician to perform the next operation. Two test images are printed on each side of the recording medium P. In this embodiment, the test images are printed by switching the voltage of the amplitude of the bias voltage correction waveform x in 10[V] increments. A DC voltage of -500[V] and a sinusoidal AC voltage with a frequency of 1.3[kHz] and a peak voltage Vpp=1.5[kV] are applied to the charging roller 2 from the high-voltage power supply 101. A third chart is created by superimposing a DC voltage (correction voltage) corresponding to the bias voltage correction waveform x onto the initially applied voltage. Multiple test images are printed on the third chart according to multiple correction voltages with varying amplitude levels. If the developing sleeve 41 is selected for the period of image density unevenness, a correction voltage corresponding to the bias voltage correction waveform x is superimposed on the developing bias voltage applied from the high-voltage power supply 102 while switching the amplitude level to create the third chart.

[0052] The CPU 301, which created the third chart, displays the amplitude input screen shown in Figure 10 on the display unit 94 (S23). The user or service technician checks the third chart and, using the input unit 93, enters the number that makes the image density unevenness least visible from the input screen in Figure 10, and selects the "OK" button. The CPU 301 obtains the number that makes the image density unevenness least visible from the input unit 93 (S24). In Figure 10, 3 is entered as the number that makes the image density unevenness least visible.

[0053] The CPU 301 determines the amplitude of the bias voltage correction waveform x in equation (2) to the amplitude corresponding to the number where the image density unevenness is least visible. The CPU 301 stores the bias voltage correction waveform x with the determined amplitude in RAM 306 (S25). With this, the periodically occurring image density unevenness correction process is completed.

[0054] In image formation after the image density uniformity correction process is completed, a bias voltage superimposed with a voltage corresponding to the saved bias voltage correction waveform x is set as the image formation condition. Based on this image formation condition, the CPU 301 performs image formation processing by the image forming apparatus 100.

[0055] The above explanation describes an example of suppressing periodic image density unevenness caused by one of the rotating parts of the photosensitive drum 1, the charging roller 2, and the developing sleeve 41. In the case of periodic image density unevenness caused by two or more rotating parts, it can be suppressed by repeatedly performing the image density unevenness correction process described above. In this case, when forming the band-shaped test image for confirmation of the second image density unevenness correction, the image formation conditions that reflect the bias voltage correction waveform x determined in the first image density unevenness correction process are used.

[0056] As described above, the periodic image density unevenness correction process, performed by users or service technicians while checking printed images (charts), is made easier by displaying periodic and phase scales on the chart used, which facilitate the input of user or service technician confirmation results. This makes it easier for users and service technicians to determine the adjustment level to input. As a result, the number of repetitions of printing adjustment data and confirmation images can be reduced, shortening the image density unevenness adjustment time. In addition to using the operation unit 200, the input work performed by users and service technicians in the image density unevenness correction process can also be performed using a printer driver installed on a personal computer that can communicate with the image forming apparatus 100.

[0057] (Second Embodiment) Figure 15 is a configuration diagram of the image forming apparatus of the second embodiment. The image forming apparatus 100 of the first embodiment is a monochrome printer, but the image forming apparatus 100a of the second embodiment is a color printer. The image forming apparatus 100a of this embodiment is an electrophotographic color copier employing a contact charging method and a two-component development method. The image forming apparatus 100a is equipped with four image forming units Pa to Pd. Figure 16 is a configuration diagram of image forming unit Pa. Image forming units Pb, Pc, and Pd have the same configuration as image forming unit Pa, so their description is omitted. The same reference numerals are used for components that are the same as those in the image forming apparatus 100 of the first embodiment. The description of components that are the same as those in the image forming apparatus 100 of the first embodiment is omitted.

[0058] The image forming units Pa to Pd are arranged in series along the rotation direction (arrow direction) of the intermediate transfer belt 11 and are detachable from the image forming apparatus 100a. The image forming unit Pa includes a photosensitive drum 1a, which is an image carrier, a charging roller 2a, a developer 4a, and a cleaner 6a. The main body of the image forming apparatus 100a is equipped with an exposure unit 3a. A primary transfer charger 5a is provided at a position opposite the photosensitive drum 1a, with the intermediate transfer belt 11 in between. Although not shown in the illustration, the image forming units Pb to Pd also include photosensitive drums 1b to 1d, charging rollers 2b to 2d, developers 4b to 4d, and cleaners 6b to 6d, respectively. The main body of the image forming apparatus 100a is equipped with exposure units 3b to 3d. Primary transfer chargers 5b to 5d are provided at positions opposite the photosensitive drums 1b to 1d, with the intermediate transfer belt 11 in between.

[0059] The charging rollers 2a to 2d, when a charging bias voltage is applied, contact charge the surfaces of the rotating photosensitive drums 1a to 1d to a predetermined potential with a predetermined polarity. For example, the charging roller 2a uniformly charges the surface of the corresponding photosensitive drum 1a when a charging bias voltage is applied by the high-voltage power supply 101a.

[0060] The exposure units 3a to 3d are located below the image forming units Pa to Pd and are equipped with a light source and a polygon mirror. The laser light emitted from the light source moves in one direction due to the rotation of the polygon mirror. The laser beam is deflected by multiple reflective mirrors and focused by an fθ lens onto the generatrix on the surface of the photosensitive drums 1a, 1b, 1c, and 1d for exposure. The laser light scans the generatrix of the photosensitive drums 1a, 1b, 1c, and 1d due to the rotation of the polygon mirror. This scanning with laser light is performed after the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the charging rollers 2b to 2d. As a result, an electrostatic latent image corresponding to the image information is formed on the photosensitive drums 1a, 1b, 1c, and 1d.

[0061] Developer unit 4a is filled with a predetermined amount of a two-component developer, which is a mixture of yellow non-magnetic toner and magnetic carrier in a predetermined mixing ratio. Developer unit 4b is filled with a predetermined amount of a two-component developer, which is a mixture of magenta non-magnetic toner and magnetic carrier in a predetermined mixing ratio. Developer unit 4c is filled with a predetermined amount of a two-component developer, which is a mixture of cyan non-magnetic toner and magnetic carrier in a predetermined mixing ratio. Developer unit 4d is filled with a predetermined amount of a two-component developer, which is a mixture of black non-magnetic toner and magnetic carrier in a predetermined mixing ratio. Toner supply units Ta to Td are provided correspondingly for developers 4a to 4d. When the built-in non-magnetic toner in developers 4a to 4d is consumed during the development process and the toner density decreases, the corresponding color of non-magnetic toner is supplied from the corresponding toner supply unit Ta to Td.

[0062] The developing units 4a to 4s develop the electrostatic latent images formed on the corresponding photosensitive drums 1a to 1d to form toner images of the corresponding colors on each of the photosensitive drums 1a to 1d. For example, developing unit 4a performs the developing process by applying a predetermined developing bias voltage from the high-voltage power supply 102a. Primary transfer chargers 5a to 5d transfer the toner images of each color formed on the photosensitive drums 1a to 1d onto the intermediate transfer belt 11. Primary transfer chargers 5a to 5d perform the toner image transfer by applying a transfer bias voltage under predetermined conditions from the high-voltage power supply 103a. This forms a full-color toner image on the intermediate transfer belt 11. The intermediate transfer belt 11 rotates to transport the carried toner image to the secondary transfer unit 12. Any remaining toner on the photosensitive drums 1a to 1d after transfer is removed by cleaners 6a to 6d.

[0063] The recording medium P stored in the paper feed cassette 60 is fed to the secondary transfer unit 12 in accordance with the timing of the intermediate transfer belt 11 transporting the toner image to the secondary transfer unit 12. The secondary transfer unit 12 transfers the toner image carried on the intermediate transfer belt 11 to the recording medium P. The recording medium P on which the toner image has been transferred is heated and pressurized by the fuser unit 9, thereby fixing the toner image. The printed material thus produced is discharged outside the image forming apparatus 100a.

[0064] The intermediate transfer belt 11 is equipped with a belt cleaner 13 between the position of the secondary transfer section 12 and the position of the primary transfer charger 5a. The belt cleaner 13 cleans off cap toner and residual secondary transfer toner that adheres to the surface of the intermediate transfer belt 11. Also, similar to the first embodiment, the photosensitive drums 1a to 1d, the charging rollers 2a to 2d, and the developing sleeves 41a to 41d of the developing units 4a to 4d are provided with a phase detection mechanism (phase detection sensor) (not shown).

[0065] (Image density unevenness correction) The chart used for periodic image density uniformity correction and the input screen displayed on the display unit 94 of the operation unit 200 will be described. Figure 17 is an example of the first chart. Figure 19 is an example of the second chart, and Figure 20 is an example of the third chart. Figure 18 is an example of the input screen. The image density uniformity correction process of the second embodiment will be described using a flowchart (see Figure 6) similar to that of the first embodiment.

[0066] Image density uniformity correction processing is initiated when a user or service technician inputs a start command for image density uniformity correction from the input unit 93 of the operation unit 200. The CPU 301 receives this start command from the input unit 93 and activates the adjustment mode (S11), and displays an input screen on the display unit 94 that instructs the output of a chart as illustrated in Figure 7 (S12). If the user or service technician selects the "Cancel" button from this input screen, the image density uniformity correction processing is terminated.

[0067] When the CPU 301 detects that the user or service technician has selected the "Output First Chart" button (S13), the image forming apparatus 100 creates a first chart, as illustrated in Figure 17, under image forming conditions that do not perform image density uniformity correction (S14). The first chart is ejected from the image forming apparatus 100. The first chart has printed strip-shaped test images of yellow (Y), magenta (M), cyan (C), and black (K) colors, which are long in the transport direction of the recording medium P, a scale indicating the period of the rotating body, and instructions for the user or service technician to perform the next operation. The scale is the same as that of the first chart in the first embodiment (Figure 11).

[0068] The CPU 301, which created the first chart, displays a period input screen on the display unit 94 as illustrated in Figure 18 (S15). The input screen is provided with input units for the periods of four colors. The user or service technician checks the first chart and uses the input unit 93 to input the symbols for the periods with noticeable image density unevenness from the input screen in Figure 18. The user or service technician also uses the input unit 93 to select the "Output Second Chart" button. The CPU 301 obtains the symbols for the periods with noticeable image density unevenness from the input unit 93 and detects that the "Output Second Chart" button has been selected (S16). In the example in Figure 18, yellow (Y) is not input as the period with noticeable image density unevenness, symbol A is input for magenta (M), symbol B is input for cyan (C), and symbol A is input for black (K).

[0069] The CPU 301 detects the home position of the rotating body corresponding to the selected period symbol using the phase detection sensor 50 (S17). The CPU 301 matches the timing of the detected home position with the position of the image to be formed and creates a second chart as illustrated in Figure 19 (S18). The second chart is ejected from the image forming apparatus 100.

[0070] The second chart prints a strip-shaped test image the length of one cycle of the rotating body input in the S16 process, which extends in the transport direction of the recording medium P, a scale that divides the cycle of the rotating body into equal parts, and instructions for the user or service technician to perform the next operation. In this embodiment, a scale that divides one cycle of the rotating body into 12 equal parts is printed. Period A is printed on the scales corresponding to the photosensitive drums 1b and 1d. Period B is printed on the scale corresponding to the charging roller 2c. A number from 0 to 11 is printed for each division. The test image and scale are printed so that the position of "0" on the scale coincides with the home position of the rotating body. If the user or service technician does not notice any periodic image density unevenness in any of the four test images and does not select a symbol in the S16 process, the test images of the unselected colors will not be printed on the second chart.

[0071] Here, the photosensitive drums 1a-1d, charging rollers 2a-2d, and developing sleeves 41a-41d, which are the components to be adjusted for each color, do not necessarily have the same phase. For this reason, when a test image of the four colors is formed, the position of the number 0 on the scale of the second chart may not be the home position detected by the phase detection sensor. Therefore, in this embodiment, a yellow test image is printed so that the home position of the adjustment target member in the yellow image forming unit Pa, where imaging is performed first, is at the position of the number 0 on the scale. For the home positions of the adjustment target members in the other image forming units Pb to Pd, the number of the closest position is stored. When creating the bias voltage correction waveform x in the S21 process, an offset corresponding to the stored number is applied to the phase of the bias voltage correction waveform.

[0072] Alternatively, a second chart can be created by aligning the four color test images with the home positions of the components to be adjusted in the image forming units Pa to Pd, allowing users and service technicians to perform similar adjustments. Yet another method allows users and service technicians to perform similar adjustments by changing the numbers on the scale of the second chart for each color so that the relationship between the phase of the component to be adjusted and the numbers is the same for all four colors.

[0073] The CPU 301, which created the second chart, displays a phase input screen on the display unit 94 (S19). This input screen is illustrated in Figure 9, and allows input of phase for each color: yellow, magenta, cyan, and black. The user or service technician checks the second chart and uses the input unit 93 to input the number of the position with the highest image density for each color from the input screen. The user or service technician also uses the input unit 93 to select the "Third Chart Output" button. The CPU 301 obtains the number of the position with the highest image density from the input unit 93 and detects that the "Third Chart Output" button has been selected (S20).

[0074] The CPU 301 creates a bias voltage correction waveform x based on the period obtained in the S16 process and the position (phase) obtained in the S20 process (S21). The CPU 301 prints a test image onto the recording medium P while switching the amplitude level of the created bias voltage correction waveform x to create a third chart as illustrated in Figure 20 (S22). The third chart is ejected from the image forming apparatus 100.

[0075] The third chart prints strip-shaped test images extending in the transport direction of four recording media P for each color, each with different image formation conditions, where the amplitude level of the bias voltage correction waveform x is varied. It also prints numbers representing the amplitude level and instructions for the user or service technician to perform the next operation. The test images are printed in two colors on both sides of the recording media P. In this embodiment, the test images are formed by changing the amplitude voltage of each bias voltage correction waveform x in 10[V] increments for the color of the symbol selected in the S16 process. No test images are formed for the color (yellow) for which no symbol was selected in the S16 process. A DC voltage of -500[V] and a sinusoidal AC voltage with a frequency of 1.3[kHz] and a peak voltage Vpp=1.5[kV] are applied to the charging rollers 2a~2d of each color from the high-voltage power supply 101. The third chart is created by superimposing a DC voltage (correction voltage) corresponding to the bias voltage correction waveform onto this originally applied voltage. Multiple test images are printed on the third chart according to multiple correction voltages with varying amplitude levels. When the development sleeve 41 is selected for the period of image density unevenness, a correction voltage corresponding to the bias voltage correction waveform x is superimposed on the development bias voltage applied from the high-voltage power supply 102 while switching the amplitude level, thereby creating a third chart.

[0076] The CPU 301, which created the third chart, displays an amplitude input screen on the display unit 94 (S23). The user or service technician checks the third chart and, using the input unit 93, enters the number that makes the image density unevenness least visible on the input screen and selects the "OK" button. The CPU 301 obtains the number that makes the image density unevenness least visible from the input unit 93 (S24). The CPU 301 determines the amplitude of the bias voltage correction waveform x in equation (2) to be the amplitude corresponding to the number that makes the image density unevenness least visible. The CPU 301 saves the bias voltage correction waveform x with the determined amplitude substituted into the RAM 306 (S25). With this, the periodically occurring image density unevenness correction process is completed.

[0077] In image formation after the image density uniformity correction process is completed, a bias voltage superimposed with a voltage corresponding to the saved bias voltage correction waveform x is set as the image formation condition. Based on this image formation condition, the CPU 301 performs image formation processing by the image forming apparatus 100a.

[0078] Similar to the first embodiment, periodic image density unevenness caused by two or more rotating bodies can be suppressed by repeatedly performing the above image density unevenness correction process. In this case, when forming the band-shaped test image for the second image density unevenness correction, image formation conditions that reflect the bias voltage correction waveform x determined in the first image density unevenness correction process are used.

[0079] As described above, the periodic image density unevenness correction process, performed by users or service technicians while checking printed images (charts), is made easier by displaying periodic and phase scales on the chart used, which facilitate the input of user or service technician confirmation results. This makes it easier for users and service technicians to determine the adjustment level to input. As a result, the number of repetitions of printing adjustment data and confirmation images can be reduced, shortening the image density unevenness adjustment time. In addition to using the operation unit 200, the input work performed by users and service technicians in the image density unevenness correction process can also be performed using a printer driver installed on a personal computer that can communicate with the image forming apparatus 100.

[0080] (Third embodiment) In the second embodiment, a chart containing test images of four colors—yellow, magenta, cyan, and black—is used to perform periodic image density uniformity correction for all four colors simultaneously. In contrast, in the third embodiment, the periodic image density uniformity correction for yellow is adjusted by checking a test image of a secondary color obtained by superimposing yellow and cyan. The configuration of the image forming apparatus in the third embodiment is the same as that of the image forming apparatus 100a in the second embodiment.

[0081] Figure 21 is a flowchart showing the image density uniformity correction process by the image forming apparatus 100a of the third embodiment. Figures 22 and 23 are illustrative diagrams of the first chart.

[0082] Image density uniformity correction processing is initiated when a user or service technician inputs a start command for image density uniformity correction from the input unit 93 of the operation unit 200. The CPU 301 receives this start command from the input unit 93 and activates the adjustment mode (S31), and displays an input screen on the display unit 94 that instructs the output of a chart as illustrated in Figure 7 (S32). If the user or service technician selects the "Cancel" button from this input screen, the image density uniformity correction processing is terminated.

[0083] When the CPU 301 detects that the user or service technician has selected the "Output First Chart" button (S33), the image forming apparatus 100 creates the first chart illustrated in Figure 22 under image forming conditions that do not perform image density uniformity correction (S34). The first chart is ejected from the image forming apparatus 100. The first chart has printed strip-shaped test images of magenta (M), cyan (C), and black (K) colors that are long in the transport direction of the recording medium P, a scale indicating the period of the rotating body, and instructions for the user or service technician to perform the next operation. The scale is the same as in the first embodiment (Figure 11).

[0084] The CPU 301, which created the first chart, displays a period input screen on the display unit 94 as illustrated in Figure 18 (S35). The user or service technician checks the first chart and inputs the symbols for periods with noticeable image density unevenness from the input screen using the input unit 93. The user or service technician also selects the "Output Second Chart" button using the input unit 93. The CPU 301 obtains the symbols for periods with noticeable image density unevenness from the input unit 93 and detects that the "Output Second Chart" button has been selected (S36).

[0085] The CPU 301 detects the home position of the rotating body corresponding to the selected period symbol using the phase detection sensor 50 (S37). This rotating body is involved in the formation of magenta, cyan, and black images. The CPU 301 matches the timing of the detected home position with the position of the image to be formed and creates a second chart (S38). The second chart is ejected from the image forming apparatus 100. The second chart has a strip-shaped test image the length of one cycle of the rotating body input in the S36 process that extends in the transport direction of the recording medium P, a scale that divides one cycle of the rotating body into equal parts, and instructions for the user or service technician to perform the next operation. The test image is printed for magenta, cyan, and black, but not for yellow.

[0086] The CPU 301, which created the second chart, displays a phase input screen on the display unit 94 (S39). This input screen is illustrated in Figure 9, and allows input of phase for each color: magenta, cyan, and black. The user or service technician checks the second chart and uses the input unit 93 to input the number of the position with the highest image density for each color from the input screen. The user or service technician also uses the input unit 93 to select the "Third Chart Output" button. The CPU 301 obtains the number of the position with the highest image density from the input unit 93 and detects that the "Third Chart Output" button has been selected (S40).

[0087] The CPU 301 creates magenta (M), cyan (C), and black (K) bias voltage correction waveforms x based on the period obtained in processing S36 and the position (phase) obtained in processing S40 (S41). The CPU 301 prints test images onto the recording medium P while switching the amplitude level of the created bias voltage correction waveforms x to create a third chart (S42). The third chart is ejected from the image forming apparatus 100. The third chart has printed strip-shaped test images extending in the transport direction of four recording mediums P for each color with different image forming conditions, each with a different amplitude level of the bias voltage correction waveform x, along with numbers representing the amplitude level and instructions for the user or service technician to perform the next operation. The test images are magenta, cyan, and black.

[0088] The CPU 301, which created the third chart, displays an amplitude input screen on the display unit 94 (S43). The user or service technician checks the third chart and, using the input unit 93, enters the number that makes the image density unevenness least visible on the input screen and selects the "OK" button. The CPU 301 obtains the number that makes the image density unevenness least visible from the input unit 93 (S44). The CPU 301 determines the amplitude of the magenta (M), cyan (C), and black (K) bias voltage correction waveform x to the amplitude corresponding to the number that makes the image density unevenness least visible. The CPU 301 saves the magenta (M), cyan (C), and black (K) bias voltage correction waveform x with the determined amplitudes substituted into the RAM 306 (S45). With this, the periodically occurring magenta, cyan, and black image density unevenness correction process is completed.

[0089] Next, periodic image density unevenness correction for yellow is performed. The CPU 301 uses the image forming apparatus 100 to create the first chart exemplified in Figure 23 under image forming conditions that do not perform image density unevenness correction for yellow (S46). The first chart is ejected from the image forming apparatus 100. The cyan is formed under image forming conditions that include bias conditions in which the voltage of the cyan bias voltage correction waveform x saved in the S45 process is superimposed. The first chart has a long, strip-shaped test image of secondary colors, consisting of yellow (Y) and cyan (C), printed on it, along with a scale indicating the period of the rotating body and instructions for the user or service technician to perform the next operation. The period of the scale is the same as in the first embodiment (Figure 11).

[0090] The CPU 301, which created the first chart, displays a period input screen on the display unit 94 (S47). The user or service technician checks the first chart and uses the input unit 93 to input the symbols for periods with noticeable image density unevenness from the input screen. The user or service technician also uses the input unit 93 to select the "Output Second Chart" button. The CPU 301 obtains the symbols for periods with noticeable image density unevenness from the input unit 93 and detects that the "Output Second Chart" button has been selected (S48).

[0091] The CPU 301 detects the home position of the rotating body corresponding to the selected period symbol using the phase detection sensor 50 (S49). This rotating body is the one involved in the formation of the yellow image. The CPU 301 matches the timing of the detected home position with the position of the image to be formed and creates a second chart (S50). The second chart is ejected from the image forming apparatus 100. The second chart has a strip-shaped test image the length of one cycle of the rotating body input in the S48 process that extends in the transport direction of the recording medium P, a scale that divides one cycle of the rotating body into equal parts, and instructions for the user or service technician to perform the next operation. The test image is a secondary color created by superimposing yellow and cyan.

[0092] The CPU 301, which created the second chart, displays a phase input screen on the display unit 94 (S51). The user or service technician checks the second chart and inputs the number of the position with the highest image density from the input screen using the input unit 93. The user or service technician also selects the "Output Third Chart" button using the input unit 93. The CPU 301 obtains the number of the position with the highest image density from the input unit 93 and detects that the "Output Third Chart" button has been selected (S52).

[0093] The CPU 301 creates a yellow bias voltage correction waveform x based on the period obtained in the S48 process and the position (phase) obtained in the S52 process (S53). The CPU 301 prints a test image onto the recording medium P while switching the amplitude level of the created bias voltage correction waveform x to create a third chart (S54). The third chart is ejected from the image forming apparatus 100. The third chart has printed strip-shaped test images extending in the transport direction of four recording mediums P with different image forming conditions, each with a different amplitude level of bias voltage correction waveform x, along with numbers representing the amplitude level and instructions for the user or service technician to perform the next operation. The test image is a secondary color of yellow and cyan.

[0094] The CPU 301, which created the third chart, displays an amplitude input screen on the display unit 94 (S55). The user or service technician checks the third chart and, using the input unit 93, enters the number that makes the image density unevenness least visible on the input screen and selects the "OK" button. The CPU 301 obtains the number that makes the image density unevenness least visible from the input unit 93 (S56). The CPU 301 determines the amplitude of the yellow bias voltage correction waveform x to the amplitude corresponding to the number that makes the image density unevenness least visible. The CPU 301 saves the yellow bias voltage correction waveform x with the determined amplitude substituted into the RAM 306 (S57). With this, the periodically occurring yellow image density unevenness correction process is completed.

[0095] Similar to the first embodiment, periodic image density unevenness caused by two or more rotating bodies can be suppressed by repeatedly performing the above image density unevenness correction process. In this case, when forming the band-shaped test image for the second image density unevenness correction, image formation conditions that reflect the bias voltage correction waveform x determined in the first image density unevenness correction process are used.

[0096] As described above, the periodic image density unevenness correction process, performed by users or service technicians while checking printed images (charts), is made easier by displaying periodic and phase scales on the chart used, which facilitate the input of user or service technician confirmation results. This makes it easier for users and service technicians to determine the adjustment level to input. As a result, the number of repetitions of printing adjustment data and confirmation images can be reduced, shortening the image density unevenness adjustment time. In addition to using the operation unit 200, the input work performed by users and service technicians in the image density unevenness correction process can also be performed using a printer driver installed on a personal computer that can communicate with the image forming apparatus 100.

[0097] Furthermore, by changing the chart used to correct periodic image density unevenness in yellow images from a test image of yellow alone to a test image of a secondary color of yellow and cyan, the visibility of the image density unevenness in yellow images is improved. As a result, image density unevenness correction of yellow images is performed with high precision. In the third embodiment, a secondary color of yellow and cyan was described, but even when a test image of a secondary color of yellow and magenta is used, the visibility of the image density unevenness in yellow images is improved, and image density unevenness correction of yellow images is performed with high precision.

[0098] As described in the first to third embodiments, the output image (chart) that users and service personnel check when correcting periodic image density unevenness is created by adding scales indicating periodic and phase information to the test image used to check image density unevenness. Using such a chart makes the input adjustment level clear. As a result, the number of repetitions of printing adjustment data and confirmation images can be reduced, and the adjustment time for image density unevenness can be shortened.

Claims

1. an image forming means for forming an image on a recording medium based on image forming conditions; an input means for inputting information for suppressing image density unevenness; a control means for causing the image forming means to create a chart on which a test image for suppressing the image density unevenness is printed, and for setting the image forming conditions according to the information input from the input means based on the chart, a scale indicating the information input to the input means is printed on the chart; Image forming device.

2. the control means causes the image forming means to create the chart; The input means inputs the information confirmed by the chart, the scale indicating information for suppressing the image density unevenness is printed on the chart.

2. The image forming apparatus according to claim 1.

3. the control means causes the image forming means to form a test image on a recording medium to determine a period of the image density unevenness and create a first chart, and causes the image forming means to form a test image on a recording medium to determine a position of the image density unevenness and create a second chart; the input means receives input of the period of the image density unevenness and the position of the image density unevenness confirmed by the first chart and the second chart, a scale indicating the period is printed on the first chart, and a scale indicating the position is printed on the second chart.

3. The image forming apparatus according to claim 1.

4. the image forming means forms an image using a plurality of rotating bodies, a scale indicating the period of each of the plurality of rotating bodies is printed on the first chart; a scale indicating the position of image density unevenness caused by a rotating body according to a cycle selected from the first chart is printed on the second chart; 4. The image forming apparatus according to claim 3.

5. the control means causes the image forming means to form a test image on a recording medium to determine an amplitude for suppressing uneven image density, and to create a third chart; a number indicating the amplitude is printed on the third chart; 5. The image forming apparatus according to claim 3.

6. the control means sets the image forming conditions in accordance with the information input from the input means based on the third chart.

6. The image forming apparatus according to claim 5.

7. The image forming means is characterized in that it comprises, as the rotating body, a photosensitive drum having a photosensitive layer on its surface, a charging roller that charges the surface of the photosensitive drum, and a developer carrier that makes a developer adhere to the surface of the photosensitive drum.

5. The image forming apparatus according to claim 4.

8. the control means superimposes a plurality of correction voltages with varying amplitudes on the bias voltage applied to the charging roller, causes the image forming means to form a plurality of test images corresponding to the plurality of correction voltages, and causes the image forming means to form test images on a recording medium to determine the amplitude of the voltage for suppressing image density unevenness, thereby creating a third chart; a number indicating the amplitude is printed on the third chart; 8. The image forming apparatus according to claim 7.

9. the control means superimposes a plurality of correction voltages with varying amplitudes on the bias voltage applied to the developer carrier, causes the image forming means to form a plurality of test images corresponding to the plurality of correction voltages, and causes the image forming means to form test images on a recording medium to determine the amplitude of the voltage for suppressing image density unevenness, thereby creating a third chart; a number indicating the amplitude is printed on the third chart; 8. The image forming apparatus according to claim 7.

10. a plurality of image forming means for forming images of different colors, the control means creates the chart for each of the plurality of image forming means, and sets the image forming conditions according to the information input from the input means based on the chart. The image forming apparatus according to any one of claims 1 to 9.

Images