JP2018146818A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can reduce occurrence of image defects and the like by determining electrification output precisely at the low-temperature and low-humidity time and that can also solve a problem of keeping a user waiting a long time by determining electrification output in a shorter time than the time required to determine the electrification output at the high-temperature and high-humidity time.SOLUTION: An image forming apparatus comprises: a current detection part 13 that detects a current value flowing to an electrification device 6 during application of an electrification voltage; a temperature and humidity detection part 12 that acquires humidity; and a control part 11 that, in a first environment condition, applies multiple voltages to the electrification device 6 for the purpose of actual measurement and on the basis of each detection result obtained by the current detection part 13, executes first electrification output determination processing of determining an electrification voltage value or an electrification current value as electrification output to be applied to the electrification device 6, and that, in a second environment condition of higher temperature and/or higher humidity than in the first environment condition, executes second electrification output determination processing of determining the electrification voltage value or the electrification current value in a shorter time than the time for the first electrification output determination processing.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus including a charging device that charges an image carrier in proximity to or in contact with the image carrier. In particular, the present invention is characterized in that the time required for the process of determining the charging voltage and charging current for charging the image carrier can be shortened.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a process for determining a charging voltage is performed so that an appropriate charging voltage is applied to the surface of the photoreceptor in a printing process. In such a process for determining the charging voltage, a plurality of AC voltages are test-applied from the charging device, and an actual measurement for deriving an appropriate charging voltage value from the relationship between the obtained AC current value and AC voltage value is performed. However, in this actual measurement, an appropriate charging voltage is derived by applying a plurality of voltages to the test, so that the derivation takes time, and the user is caused to wait unnecessarily when using the image forming apparatus. On the other hand, in order to avoid such a long charging time determination process based on actual measurement, a correction process is performed in which the charging voltage value is corrected according to environmental information and usage conditions. However, this correction processing has a problem that the accuracy of the determined charging voltage value is lower than that of derivation of the charging voltage value by actual measurement.

  In Patent Document 1, attention is paid to the fact that, in a predetermined low temperature and low humidity environment, the resistance of the charging roller is increased and the power consumption in the actual measurement is increased. That is, when performing actual measurement, it is necessary to apply a test with a voltage larger than the required charging voltage, and the power consumption by actual measurement increases at low temperature and low humidity. It has been proposed to derive the charging voltage by actual measurement in an environment exceeding the predetermined low temperature and low humidity. However, with this technique, the accuracy of the charging voltage at low temperatures and low humidity is lowered, and there is a risk of causing image defects and unnecessary wear of the photoreceptor film thickness at low temperatures and low humidity.

  Also, in Patent Document 2, an appropriate charging voltage is derived by actual measurement when the temperature changes by a predetermined threshold value or more, and when the temperature changes within the predetermined threshold value, it is corrected by the correction process based on the environmental information and the usage status of the photoconductor. A large charging voltage. In this technology, measurement is performed in any environment from low temperature and low humidity to high temperature and high humidity.

JP 2011-150309 A Japanese Patent Laying-Open No. 2006-157062

  As described above, in the prior art, the charging output such as the charging voltage cannot be accurately derived at low temperature and low humidity, and the charging output is determined by actual measurement from low temperature and low humidity to high temperature and high humidity. In some cases, there is a problem of making the user wait for a long time.

  The present invention can accurately determine the charging output at low temperature and low humidity to reduce the occurrence of image defects and the like, and at high temperature and high humidity, the charging output can be performed in a shorter time than the time required for the determination of the charging output. It is possible to provide an image forming apparatus capable of solving the problem of making a user wait for a long time by determining the above.

  In order to solve the above problems, an image forming apparatus according to the present invention includes an image carrier, a charging device that approaches or contacts the image carrier to apply a charging voltage and a charging current to the image carrier, A current / voltage detection unit for detecting a current value flowing in the charging device during application of a voltage or detecting a voltage value applied to the charging device during application of a charging current, and at least humidity and temperature as environmental conditions; In the environment information detection unit that acquires one and the first environmental condition, a plurality of voltages or currents for actual measurement are applied to the charging device, and based on the respective detection results detected by the current / voltage detection unit. The first charging output determination process for determining a charging voltage value or a charging current value as a charging output to be applied to the charging device is performed at a higher humidity and / or higher temperature than the first environmental condition. A control unit that executes a second charging output determination process that determines a charging voltage value or a charging current value in a shorter time than the first charging output determination process. And

  With this configuration, in the first environmental condition where the humidity and / or temperature is lower than the second environmental condition, a charging voltage value or a plurality of voltages or currents for actual measurement are applied to the charging device. Since the first charging output determination process for determining the charging current value is executed, the charging output can be determined with high accuracy and the occurrence of image defects and the like can be reduced. In addition, in the second environmental condition where the humidity and / or temperature is high, the charging output can be determined in a shorter time than the time required for the first charging output determination process, thus eliminating the problem of waiting for the user for a long time. it can.

  The first environmental condition may be when the absolute humidity in the image forming apparatus is equal to or less than a predetermined value, and the second environmental condition may be when the absolute humidity exceeds a predetermined value.

  When the absolute humidity fluctuates by a predetermined threshold value or more in the first environmental condition, the first charging output determination process may be performed again. In this case, the predetermined threshold value may be varied according to the absolute humidity value.

  Regardless of the environmental conditions, the first charging output determination process may be performed when the power is turned on.

  In the second charging output determination process, the corrected charging output value is determined by correcting the charging output value determined by the first charging output determination process before the second charging output determination process is performed. You may do it.

  A correction amount for obtaining the corrected charging output value may be determined according to the number of rotations of the image carrier.

  In the second charge output determination process, a charge output value is determined in a shorter time than the first charge output determination process by performing an actual measurement with a smaller number than the actual number in the first charge output determination process. You may do it.

  Even in the second environmental condition, when the environmental condition changes by a predetermined range or more, the first charging output determination process may be executed to determine the charging output value.

  When continuous printing is performed, the charging output value may be determined by executing the first charging output determination process every predetermined number of sheets.

  When it is detected that the developing unit set in the image forming apparatus is new, the first charging output determination process may be executed to determine the charging output value regardless of the environmental conditions. .

  According to the present invention, it is possible to determine a charging output such as an appropriate charging voltage at a low temperature and a low humidity, and to determine a charging output in a shorter time than the time required for the determination at a high temperature and a high humidity. There are various effects such as being able to.

1 is a schematic explanatory view showing an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic explanatory diagram illustrating a power supply unit, a control unit, and the like in the image forming apparatus of FIG. 1. It is the graph which showed the example of a change of the charging roller resistance value with respect to absolute humidity. 3 is a flowchart illustrating an example of switching control between first charging output determination processing and second charging output determination processing executed by the image forming apparatus in FIG. 1. 5 is a graph showing a relationship between an AC current value actually measured in the first charging output determination process in FIG. 4 and a peak voltage. 6 is a flowchart showing an example of processing for determining a charging voltage from two approximate lines shown in the graph of FIG. 5. 3 is a graph showing a first charging output determination process based on actual measurement executed by the image forming apparatus of FIG. 1 and a second charging output determination process in which the number of actual measurements is reduced to shorten the time. It is the graph which showed the example of a change of the charging roller resistance value with respect to temperature.

  Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. Note that the image forming apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  As shown in FIG. 1, an image forming apparatus 100 according to this embodiment is provided with four developing devices 8 each containing a developer corresponding to four photoreceptors 5 on which toner images are formed. In the apparatus 8, the color of the toner in each developer is made different so that black, yellow, magenta, and cyan toners are used.

  Here, in the image forming apparatus 100, the respective photosensitive members 5 are rotated, and the surface of each photosensitive member 5 is charged by the charging device 6. Each of the latent image forming devices 7 performs exposure according to the image formation information to form an electrostatic latent image on the surface of each photoconductor 5.

  Then, with respect to each photoconductor 5 on which the electrostatic latent image is formed in this way, toner of a predetermined color is supplied from the corresponding developing device 8 to the electrostatic latent image on each photoconductor 5 for development. A toner image of each color is formed on the surface of each photoconductor 5.

  Next, each color toner image formed on each photoconductor 5 as described above is placed on the surface of the intermediate transfer belt 14 in the form of an endless belt that is stretched over a rotation roller 14a and rotated. The primary transfer rollers 15 provided so as to face the body 5 are sequentially primary transferred in order to form a full-color toner image on the surface of the intermediate transfer belt 14.

  Further, the toner remaining on the surface of each photoconductor 5 without being transferred to the intermediate transfer belt 14 is removed from the surface of each photoconductor 5 by the first cleaning device 30.

  The full-color toner image formed on the surface of the intermediate transfer belt 14 as described above is guided to a position facing the secondary transfer roller 16 by the intermediate transfer belt 14.

  Further, the sheet S stacked on the sheet feeding device 4 provided in the image forming apparatus 100 is fed by the sheet feeding roller 41 and sent to the timing roller 18, and the sheet S is transferred by the timing roller 18 to the intermediate transfer belt 14. And the secondary transfer roller 16, and the toner image formed on the surface of the intermediate transfer belt 14 is transferred onto the paper S by the secondary transfer roller 16. Further, the toner remaining on the surface of the intermediate transfer belt 14 without being transferred onto the paper S is removed from the surface of the intermediate transfer belt 14 by the second cleaning device 31.

  Then, the sheet S on which the toner image is transferred as described above is guided to the fixing device 19, and after the transferred toner image is fixed on the sheet S by the fixing device 19, the toner image is fixed in this way. The discharged paper S is discharged by the paper discharge roller 20.

  Next, the charging device 6 will be further described with reference to FIG. Each color charging device 6 includes, for example, a charging roller extending in a direction orthogonal to the paper conveyance direction, and is arranged in contact or non-contact with the peripheral surface of the drum-shaped photoconductor 5. In addition, each charging device 6 uniformly charges the peripheral surface of the photosensitive member 5 by rotation with each charging voltage Vg from the power supply unit 10.

  The power supply unit 10 includes a DC power supply circuit 101 and an AC power supply circuit 102 for each color. Each DC power supply circuit 101 outputs a predetermined DC voltage Vdc under the control of the control unit 11. Each AC power supply circuit 102 is composed of, for example, an AC transformer, and outputs an AC voltage Vac having a variable peak-to-peak voltage value Vpp under the control of the control unit 11. The output terminal of each AC power supply circuit 102 is connected to each output terminal of the corresponding color DC power supply circuit 101, whereby a charging voltage Vg in which the AC voltage Vac is superimposed on the DC voltage Vdc is generated. Applied to the charging device 6.

  The control unit 11 includes, for example, a ROM 111, a CPU 112, an SRAM 113, and an NVRAM 114. The CPU 112 executes a control program stored in advance in the ROM 111 while using the SRAM 113 as a work area, and executes various processes (for example, four processes of printing, image stabilization, forced toner supply, and TCR adjustment). Also in the four processes exemplified above, the photosensitive member 5 needs to be charged, and therefore the charging voltage 6 is applied to the charging device 6. In the four processes, “printing” is to print an image on a printing medium, and “image stabilization” is to control the toner density to a target value based on the density of a known pattern image, “Forced toner replenishment” is to forcibly replenish toner to the developing means, and “TCR adjustment” is to control the ratio of toner and carrier to a target value.

  The CPU 112 further performs a first charging output determination process and a second charging output determination process, which will be described later, to determine the peak-to-peak voltage value Vpp of the AC voltage Vac that is actually superimposed in the process. Further, the CPU 112 stores the current total number of printed sheets in the image forming apparatus 100 in the NVRAM 114.

  The environmental information detection unit 12 includes a temperature sensor 121 and a humidity sensor 122. The temperature sensor 121 detects the temperature (in-machine temperature) St in the image forming apparatus 100 and outputs it to the CPU 112. The humidity sensor 122 detects the relative humidity Sh in the image forming apparatus 100 and outputs it to the CPU 112. The absolute humidity RH can be calculated based on the in-machine temperature St, the relative humidity, and Sh.

  Further, the current detection unit 13 detects the alternating current value Iac flowing through the corresponding photosensitive member 5 and outputs it to the CPU 112 when the charging voltage Vg is applied to each charging device 6.

  Next, processing relating to charging voltage determination performed in the control unit 11 of the image forming apparatus 100 will be described. In this process, the CPU 112 determines a first charging output determination process (a process for deriving an appropriate charging voltage or charging current even if it takes time by actual measurement control) and a second charging output determination according to the current environmental conditions. Switching to processing (for example, processing for deriving a charging voltage or charging current in a short time by correction control) is performed. Hereinafter, the derivation of the charging voltage will be described. However, the present invention is not limited to this, and the charging current may be derived.

  FIG. 3 shows changes in the charging roller resistance value with respect to absolute humidity. Table 1 is shown below.

  At absolute humidity RH ≦ 6 (this is the first environmental condition), the electrical resistance of the charging roller increases as the absolute humidity decreases. At this time, in order to determine the charging voltage, it is necessary to take into account a plurality of factors such as a change in the electrical resistance of the charging roller due to absolute humidity and the usage status of the image carrier (photosensitive member). Since it is difficult to accurately derive the charging voltage by the second charging output determination process, the first charging output determination process is performed under the first environmental condition.

  On the other hand, at the absolute humidity RH> 6 (this is the second environmental condition), the change in the electrical resistance of the charging roller is very small. Under this second environmental condition, the charging voltage can be derived with relatively high accuracy by the second charging output determination process taking into consideration the use situation and the like.

  In the processing of the control unit 11 exemplified below, as shown in Table 1 above, when the absolute humidity RH is the first environmental condition of 6 or less, the first charging output determination processing by actual measurement is selected and absolute When the humidity RH is the second environmental condition larger than 6, the second charging output determination process by correction or the like is selected.

  The control unit 11 executes processing related to charging voltage derivation, for example, when the image forming apparatus 100 is first activated for a day. When this process is executed, for example, as shown in the flowchart of FIG. 4, the humidity in the image forming apparatus 100 is detected (S1), and the absolute humidity RH is calculated (S2). Then, it is determined whether or not the absolute humidity RH is 6 or less (S3). When the absolute humidity RH is 6 or less, it is the first environmental condition, so an appropriate charging voltage is derived by the first charging output determination process, that is, by actual measurement (S4). On the other hand, when the absolute humidity RH exceeds 6, since it is the second environmental condition, a second charging output determination process, for example, a process for deriving a charging voltage in a short time by correction is performed (S5).

  Next, a processing example for deriving the charging voltage by actual measurement will be briefly described below. The process itself for deriving the charging voltage by this actual measurement is a conventional process disclosed in Patent Document 1. In the process of deriving the charging voltage for printing by this actual measurement control, the CPU 112 sets eight AC voltages for actual measurement selected based on environmental conditions such as the relative humidity Sh in the machine. As shown in FIG. 5, the eight AC voltages include four AC voltages for each of the positive discharge region and the reverse discharge region. Here, the region of the peak-to-peak voltage value Vpp where charge transfer in only one direction from the charging device 6 to the photoconductor 5 occurs when the charging voltage Vg is applied to the charging device 6 is called a positive discharge region. Conversely, a region where charge transfer in both directions between the photoconductor 5 and the charging device 6 occurs alternately is referred to as a reverse discharge region. As the AC voltage Vac to be output from the AC power supply circuit 102 for each color, for example, 600V, 700V, 800V and 900V are set on the positive discharge region side, and 1850V, 1950V, 2050V and 2150V are set on the reverse discharge region side.

  The CPU 112 sets the AC voltage Vac to be output from the AC power supply circuit 102 for each color, and sets the DC voltage Vdc to be output from the DC power supply circuit 101 for each color to a predetermined value. As a result, the charging voltage Vg for actual measurement (for testing) is applied from the power supply unit 10 to the charging device 6 for each color. The CPU 112 acquires the alternating current value Iac from the current detection unit 13 for each color, and stores the acquired alternating current value Iac in the SRAM 113 for each color. The SRAM 113 can obtain a total of eight alternating current values Iac flowing through the charging devices 6 when four charging voltages Vg included in each of the positive discharge region and the reverse discharge region are sequentially applied. The CPU 112 holds, in the SRAM 113, the combination of the sequentially applied charging voltages Vg and the alternating current value (average value) Iac for each color.

  The CPU 112 selects four (Vac, Iac) belonging to the positive discharge area for each color, linearly approximates these four data by the least square method, and performs positive discharge as shown in the flowchart of FIG. A characteristic straight line L1 (Iac = a × Vac + b) of the alternating current value Iac in the region is obtained (S11). Similarly, the CPU 112 linearly approximates four (Vac, Iac) belonging to the reverse discharge region for each color to obtain a characteristic line L2 (Iac = c × Vac + d) of the alternating current value Iac in the reverse discharge region. (S12).

  Here, a to d are constants, and in particular, c and a are inclinations, and b and d are intercepts. Thereafter, the CPU 112 derives the AC voltage Vac at the intersection (ie, (db) / (ac)) of the characteristic lines L1 and L2 as the peak-to-peak voltage value Vpp and stores it in the NVRAM 114 (S13). In this way, in the first charging output determination process, since a plurality of actually measured charging voltages are applied to the charging device, the charging output determination process takes time. Although the time required for the charging output determination process varies depending on the productivity of the image forming apparatus and the system speed, if the system speed is 290 mm / sec and the number of measurement points is 8, it takes about 8 seconds for the charging output determination process.

(Second Charging Output Determination Processing Example 1)
The second charge output determination process is, for example, a charge output derivation process using a correction table, and can be performed in a shorter time than the first charge output determination process. Specifically, in the second charging output determination process, the control unit 11 uses the charging voltage determined by the first charging output determination process that was determined before the second charging output determination process. Then, a new charging voltage is derived by correcting the charging voltage according to the current environmental information and the usage state of the image carrier (photosensitive member).

  Table 2 below shows the voltage value (correction amount) for correcting the charging voltage in accordance with the absolute humidity and the usage state of the image carrier (photosensitive member). When the predetermined rotation speed of the photosensitive member is reached, the corrected charging voltage is derived by adding the voltage values shown in Table 2 to the charging voltage derived by the first charging output determination process before that time. The voltage values in Table 2 are values calculated from the durability test. Since the second charging output determination process using the correction table does not involve actual measurement, the correction charging voltage can be derived in a shorter time than the first charging output determination process.

(Second charging output determination processing example 2)
The control unit 11 employs the same measurement as the first charge output determination process as the second charge output determination process, and reduces the number of actually measured points from 8 to 6, for example, in the AC discharge region. The charging output value may be determined in a short time. FIG. 7 shows the relationship between the AC voltage value and the AC current value obtained by actual measurement in the first charging output determination process and the second charging output determination process.

  In the AC discharge region, since the AC discharge component is added to the image carrier (photosensitive member) from the charging device in addition to the DC discharge, it exhibits a nonlinear rise. Since the rise of the graph is larger in the second environmental condition than in the first environmental condition, the influence of the voltage error is smaller than in the first environmental condition. Therefore, as shown in FIG. 7, the charging voltage can be derived with the same accuracy even if the number of applied voltages is reduced in the second environmental condition than in the first environmental condition.

(Charging output determination example 1)
The control unit 11 performs a first charging output determination process when the absolute humidity fluctuates more than a predetermined threshold value when the current environment is in the first environmental condition, and sets the predetermined threshold value based on the absolute humidity value. It can also be changed.

  For example, when the current environment is the first environmental condition and the humidity is higher than the predetermined absolute humidity RH, the threshold value for executing the first charging output determination process is increased. As an example, when 0 <RH ≦ 1, when the difference between the absolute humidity RH and the current absolute humidity RH at the time of the previous determination of the charging output is 0.5 or more, and 1 <RH ≦ In the case of 6, when the difference from the previous absolute humidity RH is 2 or more, the first charging output determination process is executed. As a result, even when the absolute humidity fluctuates by a predetermined threshold value or more, the first charging output determination process can be performed to change the charging voltage to an appropriate charging voltage. It is possible to reduce the frequency of execution and reduce the waiting time of the user.

(Charging output determination example 2)
The controller 11 can also perform the first charge output determination process regardless of the environmental conditions when the image forming apparatus 100 is started for the first time in a day. As a result, even when the first image forming apparatus 100 is started up in the day, the charging voltage is derived by the first charging output determination process to reset the usage state of the image carrier even if the second environmental condition is satisfied. To do. For example, when the power is turned on after the power-off period exists for a long time such as 6 hours, or when the power is turned on for the first time after midnight, the first image forming apparatus 100 is started up for the first day. It can be determined that it is (so-called morning). Of course, the first charge output determination process may be simply performed when the power is turned on without considering such a power-off time.

(Charging output determination example 3)
The controller 11 may execute the first charging output determination process to determine the charging output value when the environmental information changes a predetermined amount even if the second environmental condition is satisfied. For example, when the absolute humidity changes from 6 <RH ≦ 14 to 14 <RH in Table 1 or vice versa, the first charging output determination process is executed to determine the charging voltage. However, as described above, the first charge output determination process is not performed when the fluctuation range of the absolute humidity when crossing the area again after crossing the area is within 5 for example. By performing such a restriction, it is possible to suppress frequent occurrence of crossing the region and frequent execution of the first charge output determination process.

(Charging output determination example 4)
The controller 11 may determine the charge output value by the first charge output determination process when the rotation speed of the photoconductor reaches a predetermined rotation speed during continuous printing. In Table 3 below, the number of rotations of each photoconductor is shown as an example. When continuous printing is performed, ions on the charging roller tend to be unevenly distributed as compared to the initial state. As a result, the electrical resistance of the charging roller varies and the charging voltage changes. Therefore, since the charging output value changes with the electric resistance fluctuation of the charging roller, the first charging output determination process is performed when the rotation speed of the photosensitive member reaches a predetermined rotation speed during continuous printing. Note that the first charging output determination process may also be performed when the number of rotations of the photoreceptor again reaches a predetermined number of rotations by further continuous printing.

(Charging output determination example 5)
For example, when the control unit 11 detects that the developing unit is new by the replacement process, the control unit 11 may determine the charging voltage by executing the first charging output determination process regardless of the environment. When the developing unit is replaced by a serviceman or the like, the electric resistance of the charging roller, the electric resistance of the photosensitive member, and the like change, and the current charging voltage is derived again.

(Charging output determination example 6)
In the above example, the first charging output determination process and the second charging output determination process are switched based on the absolute humidity. However, the control unit 11 may switch the first / second charging output determination process depending on the temperature T. . FIG. 8 shows changes in the charging roller resistance value with respect to temperature. At a temperature T ≦ 15 (the first environmental condition), the electrical resistance of the charging roller increases significantly as the temperature decreases. On the other hand, at a temperature T> 15 (the second environmental condition), the change in electrical resistance of the charging roller is very small. This behavior approximates the change in electrical resistance of the charging roller due to the change in absolute humidity. Therefore, as in the case of absolute humidity, the user's waiting time can be reduced by switching between the first charge output determination process and the second charge output determination process under the first / second environmental conditions of temperature.

(Charging output determination example 7)
In the above example, the first charging output determination process and the second charging output determination process are switched according to either absolute humidity or temperature. However, as shown in Table 4 below, the control unit 11 combines the temperature and humidity. You may make it switch a 1st charge output determination process and a 2nd charge output determination process by (matrix).

  In the setting example shown in Table 4 above, the first charging output determination process is performed under the first environmental condition where the temperature is 15 ° C. or less and the humidity is 45% or less, and the temperature is higher than 15 ° C. and the humidity is 45%. When the second environmental condition is exceeded, the charging voltage is derived by the second charging output determination process. As in the case of absolute humidity or temperature, the user's waiting time can be reduced by switching between the first charge output determination process and the second charge output determination process in the first / second environmental conditions of temperature.

4: Paper feeding device 5: Photoconductor 6: Charging device 7: Latent image forming device 8: Developing device 10: Power supply unit 11: Control unit 12: Environmental information detection unit 13: Current detection unit (current / voltage detection unit)
14: Intermediate transfer belt 14a: Rotating roller 15: Primary transfer roller 16: Secondary transfer roller 18: Timing roller 19: Fixing device 20: Paper discharge roller 30: First cleaning device 31: Second cleaning device 41: Feeding Paper roller 100: Image forming apparatus 101: DC power supply circuit 102: AC power supply circuit 111: ROM
112: CPU
113: SRAM
114: NVRAM
121: Temperature sensor 122: Humidity sensor Iac: AC current value L1: Characteristic straight line L2: Characteristic straight line RH: Absolute humidity S: Paper Sh: Relative humidity St: In-machine temperature T: Temperature Vac: AC voltage Vdc: DC voltage Vg: Charging Voltage Vpp: Voltage value between peaks

Claims (11)

An image carrier;
A charging device in proximity to or in contact with the image carrier for applying a charging voltage and a charging current to the image carrier;
A current / voltage detector that detects a current value flowing through the charging device during application of a charging voltage or detects a voltage value applied to the charging device during application of a charging current;
An environmental information detector that acquires at least one of humidity and temperature as environmental conditions;
In the first environmental condition, a plurality of voltages or currents for actual measurement are applied to the charging device, and the charging to be applied to the charging device based on the respective detection results detected by the current / voltage detection unit. While performing a first charging output determination process for determining a charging voltage value or a charging current value as an output, the second environmental condition is higher in humidity and / or higher temperature than the first environmental condition. An image forming apparatus comprising: a control unit that executes a second charging output determination process that determines a charging voltage value or a charging current value in a shorter time than the one charging output determination process.   2. The image forming apparatus according to claim 1, wherein the first environmental condition is when the absolute humidity in the image forming apparatus is a predetermined numerical value or less, and the second environmental condition is when the absolute humidity exceeds a predetermined numerical value. An image forming apparatus.   3. The image forming apparatus according to claim 2, wherein when the absolute humidity fluctuates by a predetermined threshold or more under the first environmental condition, the first charging output determination process is performed again. 4.   4. The image forming apparatus according to claim 3, wherein the predetermined threshold value is varied according to the absolute humidity value.   5. The image forming apparatus according to claim 1, wherein the first charging output determination process is performed when the power is turned on regardless of environmental conditions. 6.   6. The image forming apparatus according to claim 1, wherein the second charging output determination processing is performed before the second charging output determination processing is performed. An image forming apparatus, wherein a corrected charging output value is determined by correcting the charging output value determined by step (a).   7. The image forming apparatus according to claim 6, wherein a correction amount for obtaining the corrected charging output value is determined according to the number of rotations of the image carrier.   6. The image forming apparatus according to claim 1, wherein the second charging output determination process performs an actual measurement with a number reduced from an actual number in the first charging output determination process. Thus, the image forming apparatus determines the charge output value in a shorter time than the first charge output determination process.   9. The image forming apparatus according to claim 1, wherein the first charging output determination process is performed when the environmental condition changes beyond a predetermined range even under the second environmental condition. To determine the charging output value.   10. The image forming apparatus according to claim 1, wherein when continuous printing is performed, the first charge output determination process is executed for each predetermined number of sheets to determine a charge output value. An image forming apparatus. 11. The image forming apparatus according to claim 1, wherein when it is detected that a developing unit set in the image forming apparatus is new, the first unit does not depend on environmental conditions. The charge output value is determined by executing the charge output determination process of the image forming apparatus.

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