JP2011158570A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for setting an applied voltage value applied on an electrifying roller by using a correction value obtained by making atmospheric pressure associated with the depletion state of a surface layer of an image carrier. <P>SOLUTION: A voltage setting part 221 sets the applied voltage value V on a voltage applying part 21. The applied voltage value V is derived from the sum of a reference voltage value V1, an atmospheric pressure correction value V2, a depletion correction value V3, an atmospheric pressure depletion correction value V4 and the other correction value V5. The atmospheric pressure depletion correction value V4 is a correction value which acts in an opposite direction with respect to the atmospheric pressure correction value V2 and the depletion correction value V3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus. More specifically, the present invention relates to an image forming apparatus capable of charging the surface of an image carrier to an appropriate charging voltage even if the apparatus is continuously used under a low atmospheric pressure.

  The image forming apparatus exposes the surface of the charged image carrier to form an electrostatic latent image, develops it with a developer, and transfers the resulting toner image onto a sheet to form an image. Is. Such image forming apparatuses include those using a contact type charging device such as a charging roller and those using a non-contact type charging device that charges an image carrier by corona discharge.

In a charging system in which the surface of the photoreceptor is uniformly charged by a charging roller, the following relational expression Vo = Va−Vd
Vo: Potential of the photoreceptor after charging
Va: Applied voltage
Vd: A discharge start voltage is established. That is, the photoreceptor potential Vo is a difference obtained by subtracting the discharge start voltage Vd from the applied voltage Va applied to the charging roller. Here, the discharge start voltage is the minimum voltage required to cause discharge.

In order to form a high-quality and uniform image, it is necessary to make the photoreceptor potential Vo constant. Therefore, it is desirable to set an optimum applied voltage Va. Here, the discharge start voltage Vd changes depending on the atmospheric pressure and the discharge distance. That is, it follows Paschen's law. In Paschen's law, the following relational expression holds.
Vd = f (p · d)
Vd: discharge start voltage
p: atmospheric pressure
d: Discharge distance, that is, the discharge start voltage Vd is expressed as a function of the product of the atmospheric pressure p and the discharge distance d.

  As is apparent from Paschen's law, the discharge start voltage changes according to the change in discharge distance over time due to the difference in atmospheric pressure due to altitude and the deterioration of the photoreceptor surface. Therefore, the surface potential of the photoreceptor changes depending on changes in atmospheric pressure and discharge distance.

  Therefore, an image forming apparatus has been developed that sets a voltage to be applied to the charging roller in accordance with changes in atmospheric pressure and discharge distance. For example, Patent Document 1 discloses an image forming apparatus that performs image formation by setting a discharge voltage in consideration of the influence of atmospheric pressure. On the other hand, Patent Document 2 discloses an image forming apparatus that forms an image by setting a discharge voltage in consideration of depletion of the photoreceptor. Thereby, the applied voltage can be set in accordance with the change in the discharge distance due to the wear of the photosensitive member. As described above, an image forming apparatus that independently corrects atmospheric pressure and wear has been developed.

JP 2009-122245 A JP-A-9-190144

  In contrast, the inventors of the present application have clarified through experiments that the surface potential of the photoconductor is not easily affected by the wear of the surface layer of the image carrier under low pressure. FIG. 9 shows the surface potential of the photoreceptor. The horizontal axis in FIG. 9 is the film thickness of the photoreceptor. Here, the reduction in the film thickness of the photoconductor indicates that the capacitance C increases and the absolute value of the potential on the surface of the photoconductor increases. The vertical axis represents the photoreceptor potential Vo. The solid line in FIG. 9 indicates the photoreceptor potential Vo at 1 atmosphere. The broken line indicates the photoreceptor potential Vo at 0.73 atmospheres.

  If the influence on the photoreceptor potential Vo due to the film thickness of the photoreceptor and the influence on the photoreceptor potential Vo due to the atmospheric pressure are independent, the solid line and the broken line should be almost parallel. However, in reality, when the atmospheric pressure is low (broken line), it is less susceptible to changes in film thickness. In other words, when image formation is performed using a photoconductor whose surface has been depleted, correction is excessively performed at a low atmospheric pressure, that is, at a high altitude. As a result, the photoreceptor potential deviates from the optimum value.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide an image forming apparatus that sets an applied voltage value to be applied to the charging roller using a correction value that relates the atmospheric pressure and the depletion state of the surface layer of the image carrier.

  The image forming apparatus of the present invention, which has been made for the purpose of solving this problem, has an image carrier, a charging roller for uniformly charging the surface of the image carrier, and a voltage application unit for applying a voltage to the charging roller. In the image forming apparatus, an atmospheric pressure correction value deriving unit for deriving an atmospheric pressure correction value for correcting an applied voltage by the atmospheric pressure, and a depletion correction value deriving unit for deriving a depletion correction value for correcting the applied voltage by the amount of wear of the surface layer of the image carrier. An atmospheric pressure depletion correction value deriving unit for deriving an atmospheric pressure depletion correction value for correcting the applied voltage according to the atmospheric pressure and the amount of depletion on the surface of the image carrier, an atmospheric pressure correction value derived by the atmospheric pressure correction value deriving unit, and a depletion correction value A voltage setting unit that sets an applied voltage value corrected by the depletion correction value derived by the deriving unit and the atmospheric pressure depletion correction value derived by the depletion correction value deriving unit to the voltage application unit; correction Is a correction in the opposite direction by the pressure correction value and the depletion correction value are those in a range that does not negate the correction by pressure correction value and the depletion correction value to correct the value of the applied voltage. Such an image forming apparatus is not easily affected by depletion of the surface of the photosensitive member under a low atmospheric pressure. Therefore, even if the image carrier is continuously used under a low pressure, the surface potential of the image carrier is hardly shifted due to the wear of the image carrier.

  In the image forming apparatus described above, the atmospheric pressure depletion correction value is a correction value that increases the absolute value of the applied voltage as the product of the atmospheric pressure and the wear amount of the image carrier increases. The smaller the product of the depletion amount is, the better the correction value is to decrease the absolute value of the applied voltage. This is because the effect of excessive correction by the atmospheric pressure correction value or the depletion correction value can be suppressed, and the charging roller can be charged with the applied voltage with appropriate correction.

In the image forming apparatus described above, the atmospheric pressure depletion correction value deriving unit is expressed by the following equation: V4 = C · P · Δd
V4: Atmospheric pressure depletion correction value C: Predetermined atmospheric pressure depletion coefficient P: Atmospheric pressure Δd: The atmospheric pressure depletion correction value may be calculated from the amount of depletion of the image carrier. This is because a more suitable applied voltage value can be set.

  The image forming apparatus described above includes an atmospheric pressure depletion correction value storage unit that stores a plurality of combinations of atmospheric pressure and an atmospheric pressure depletion correction value corresponding to the atmospheric pressure, and the voltage setting unit is stored in the atmospheric pressure depletion correction value storage unit. The applied voltage value may be set using the atmospheric pressure depletion correction value. This is because the correction can be performed without calculation.

  In the image forming apparatus described above, an image carrier current measuring unit that measures a current flowing through the image carrier, and a film that converts the current measured by the image carrier current measuring unit into a film thickness value of the image carrier The depletion correction value deriving unit derives the depletion correction value using the film thickness value calculated by the film thickness calculating unit, and the atmospheric pressure depletion correction value deriving unit The pressure loss correction value may be derived using the film thickness value calculated by the calculation unit. This is because even in this case, it is still possible to perform suitable correction.

  The image forming apparatus described above may include an image carrier depletion estimation unit that estimates a depletion amount of the surface layer of the image carrier from the rotational speed or travel distance of the image carrier. This is because even in this case, it is still possible to perform suitable correction.

  The image forming apparatus described above may include an input unit that receives input from the user regarding the atmospheric pressure information related to the atmospheric pressure at the installation location of the image forming apparatus. This is because the user can input information on the atmospheric pressure.

  The image forming apparatus described above may include an output unit that displays a selection screen showing options to the user for the atmospheric pressure information. This is because options can be shown to the user.

  The image forming apparatus described above includes an atmospheric pressure conversion unit, the input unit accepts input of altitude information or position information of an installation location of the image forming apparatus, and the atmospheric pressure conversion unit receives the input altitude information. Alternatively, the position information may be converted into atmospheric pressure. This is because even in this case, it is still possible to perform suitable correction.

  The image forming apparatus described above may include a barometric sensor or an altimeter. This is because the atmospheric pressure can still be acquired in this way.

  According to the present invention, there is provided an image forming apparatus for setting an applied voltage value to be applied to a charging roller by using a correction value relating pressure and a depletion state of a surface layer of an image carrier.

1 is a schematic configuration diagram for explaining an image forming apparatus according to the present invention. 6 is a graph for comparing an applied voltage value between an image forming apparatus according to the present invention and a conventional image forming apparatus. 6 is a graph for comparing the image forming apparatus according to the present invention and a conventional image forming apparatus with respect to the surface potential of the photoreceptor after charging. 2 is a block diagram for explaining a control system of the image forming apparatus according to the present invention. FIG. It is a figure (the 1) which shows the display screen which receives the input of the altitude information in this invention. It is FIG. (2) which shows the display screen which receives the input of the altitude information in this invention. It is FIG. (3) which shows the display screen which receives the input of the altitude information in this invention. 6 is a graph for comparing the charging roller and other charging devices with respect to the atmospheric pressure dependency of the surface potential of the photoreceptor. It is a graph for showing the difference by the atmospheric pressure with respect to the film thickness dependence of the surface potential of the photoreceptor.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is embodied in an image forming apparatus.

(First embodiment)
1. Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to this embodiment. As shown in FIG. 1, the image forming apparatus 100 according to the present embodiment includes a photosensitive drum 10, a charging roller 20, a voltage applying unit 21, a charging roller cleaning device 22, an exposure device 30, and a developing device 40. , A transfer device 50 and a cleaning device 60. The developing device 40 has a developing roller 41. The transfer device 50 includes a transfer roller 51 and a transfer belt 52.

  The photosensitive drum 10 is an image carrier for carrying an electrostatic latent image or a toner image on the surface thereof. The charging roller 20 is a charging device for uniformly charging the surface of the photosensitive drum 10. The charging roller 20 is disposed in parallel with the photosensitive drum 10. The charging roller 20 and the photosensitive drum 10 are actually arranged with a certain distance d. The voltage application unit 21 is for applying a voltage for charging the charging roller 20. The charging roller cleaning device 22 is for cleaning the surface of the charging roller 20.

  The exposure device 30 is for drawing an electrostatic latent image on the surface of the photosensitive drum 10 by exposing the surface of the photosensitive drum 10 uniformly charged by the charging roller 20. The developing device 40 is for developing the electrostatic latent image carried on the photosensitive drum 10. The developing roller 41 is a developing member for applying a developer to the photosensitive drum 10. The transfer member 50 is a transfer member for transferring the toner image carried on the photosensitive drum 10 onto a sheet.

  The cleaning device 60 is for collecting development residual toner from the surface of the photosensitive drum 10. The cleaning device 60 includes a cleaning blade 61 and a waste toner box 62. The cleaning blade 61 is a cleaning member for scraping off development residual toner from the surface of the photosensitive drum 10. The waste toner box 62 is a container for collecting the toner scraped off by the cleaning blade 61.

  The photosensitive drum 10 rotates in the direction of arrow A in FIG. The charging roller 20 rotates in the direction indicated by the arrow B in FIG. 1, that is, the direction following the rotation direction of the photosensitive drum 10. The developing roller 41 rotates in the direction indicated by the arrow C in FIG. 1, that is, the direction following the rotation direction of the photosensitive drum 10. However, the developing roller 41 may rotate in the direction opposite to the arrow C. The transfer roller 51 rotates in the direction of arrow D in FIG. The transfer belt 52 travels in the direction of the arrow P. The charging roller cleaning device 22 rotates in the direction of arrow E in FIG.

  Next, the basic operation of the image forming apparatus 100 will be briefly described. As described above, the photosensitive drum 10 rotates in the direction of the arrow A in FIG. And the process shown below is given with the rotation. First, the charging roller 20 uniformly charges the surface of the photosensitive drum 10 while rotating in the direction of arrow B. The charged surface potential of the photosensitive drum 10 is the background potential of the image.

  Downstream of that, the exposure device 30 draws an electrostatic latent image on the surface of the photosensitive drum 10. That is, the potential at the exposed portion becomes the image portion potential. Further downstream, the developing roller 41 rotating in the direction of arrow C in FIG. 1 applies toner to the electrostatic latent image formed on the surface of the photosensitive drum 10. As a result, a toner image is formed on the surface of the photosensitive drum 10. This toner image is transferred to the transfer belt 52 conveyed in the direction of arrow P by the transfer roller 51 of FIG.

2. Configuration of Voltage Control of Charging Roller FIG. 4 is a block diagram showing the configuration of the control system of the charging roller 20. 4 includes a touch panel 210, a control unit 220, a storage unit 230, and a measurement unit 240. The touch panel 210 is an interface that serves as both an output unit that displays various types of information and an input unit that receives input from the user based on the displayed information.

  The control unit 220 includes a voltage setting unit 221, an atmospheric pressure correction value deriving unit 222, an atmospheric pressure depletion correction value deriving unit 223, a depletion correction value deriving unit 224, and other control units 225. The voltage setting unit 221 is for setting a voltage value applied by the voltage application unit 21 to the charging roller 20, that is, an applied voltage value. The atmospheric pressure correction value deriving unit 222 is for deriving an atmospheric pressure correction value that depends only on the atmospheric pressure of the applied voltage value set by the voltage setting unit 221. The wear correction value deriving unit 224 is for deriving a wear correction value that depends only on the degree of wear of the photosensitive drum 10 at the applied voltage value set by the voltage setting unit 221.

  The atmospheric pressure depletion correction value deriving unit 223 is for deriving an atmospheric pressure depletion correction value that corrects the applied voltage value that has been excessively corrected by the atmospheric pressure correction value and the depletion correction value described above to an appropriate value. As will be described later, the atmospheric pressure depletion correction value is a correction value calculated based on the product of the atmospheric pressure and the degree of depletion of the photosensitive drum 10. The feature of the present invention is that this atmospheric pressure depletion correction value is introduced. The other control unit 225 controls each device and performs other controls.

  The storage unit 230 includes a reference voltage value table 231, an atmospheric pressure correction value table 232, an atmospheric pressure depletion correction value table 233, an exhaustion correction value table 234, and other storage units 235. The reference voltage value storage unit 231 stores a reference voltage value of an applied voltage value set by the voltage setting unit 221. The atmospheric pressure correction value table 232 is an atmospheric pressure correction value storage unit in which information for deriving an atmospheric pressure correction value of the applied voltage value set by the voltage setting unit 221 is stored. The wear correction value table 234 is a wear correction value storage unit that stores a wear correction value of an applied voltage value set by the voltage setting unit 221.

  The atmospheric pressure depletion correction value table 233 is an atmospheric pressure depletion correction value storage unit in which information for deriving an atmospheric pressure depletion correction value of the applied voltage value set by the voltage setting unit 221 is stored. As described above, it is possible to correct the excessively corrected applied voltage value to an appropriate value by the atmospheric pressure depletion correction value stored in the atmospheric pressure depletion correction value storage unit. The other storage unit 235 is a storage unit for storing the initial film thickness and other information. Note that the atmospheric pressure correction value table 232, the depletion correction value table 234, and the atmospheric pressure depletion correction value table 233 are used in the second embodiment described later, and are not used in the first embodiment.

  The measurement unit 240 includes an atmospheric pressure sensor 241, a film thickness sensor 242, and a photoconductor current sensor 243. The atmospheric pressure sensor 241 is for measuring atmospheric pressure. The film thickness sensor 242 is for measuring the thickness of the surface layer of the photosensitive drum 10. The photoconductor current sensor 243 is an image carrier current measurement unit for measuring the current flowing through the photoconductor drum 10.

3. Method for Setting Voltage Control of Charging Roller Next, a method for setting an applied voltage value set by the voltage setting unit 221 will be described. The applied voltage value set by the voltage setting unit 221 is expressed by the following equation: V = V1 + V2 + V3 + V4 + V5 (1)
V: Applied voltage value
V1: Reference voltage value
V2: Pressure correction value
V3: Abrasion correction value
V4: Pressure loss correction value
V5: Expressed with other correction values.

  Here, the value stored in the reference voltage value storage unit 231 is used as the reference voltage value V1. The reference voltage value V1 is a reference voltage value. The reference voltage value V1 is a value determined in advance as a reference value. The method for determining the reference value is arbitrary. For example, an applied voltage value at 0 ° C. and 1 atm can be employed.

The atmospheric pressure correction value V2 is calculated by the atmospheric pressure correction value deriving unit 222. The atmospheric pressure correction value V2 is expressed by the following equation: V2 = A · P (2)
A: Predetermined atmospheric pressure correction coefficient
P: Calculated by atmospheric pressure.

  The atmospheric pressure correction value V2 is a correction value that changes depending only on the value of the atmospheric pressure P. As shown in FIG. 8, in the charging roller, generally, the charging performance of the surface of the photoreceptor changes depending on the atmospheric pressure. That is, at a low pressure, the surface of the photoreceptor is easily charged. The atmospheric pressure correction value V2 is opposite in sign to the reference voltage value V1. Some other types of charging chargers (charging CH in FIG. 8) are hardly affected by atmospheric pressure. This is because corona discharge, which is a discharge method of the charging charger (charging CH in FIG. 8), does not follow Paschen's law.

  Actually, as shown in FIG. 2, the absolute value of the applied voltage value V must be decreased as the altitude increases, that is, as the atmospheric pressure decreases. In FIG. 2, all the lines are descending to the right. That is, the atmospheric pressure correction value V2 is a correction value that makes the absolute value of the applied voltage value V smaller as the atmospheric pressure becomes lower.

The wear correction value V3 is calculated by the wear correction value deriving unit 224. The depletion correction value V3 is expressed by the following equation: V3 = B · Δd (3)
B: Preliminary wear correction coefficient
Δd: calculated from the amount of wear of the photosensitive drum.

  The wear correction value V3 is a correction value that changes depending only on the wear amount Δd of the photosensitive drum 10. The surface layer of the photosensitive drum 10 is worn by being repeatedly charged or scraped by the cleaning device 60. Due to this wear, the amount of wear Δd of the photosensitive drum 10 changes. As shown in FIG. 2, the absolute value of the applied voltage value V is small as the surface of the photosensitive drum 10 is worn out. That is, the wear correction value V3 is a correction value that makes the absolute value of the applied voltage value V smaller as the film thickness of the photoconductor drum 10 becomes thinner due to wear of the surface of the photoconductor drum 10.

The atmospheric pressure depletion correction value V4 is calculated by the atmospheric depletion correction value deriving unit 223. The atmospheric pressure depletion correction value V4 is expressed by the following equation: V4 = C · P · Δd (4)
C: Calculated by a predetermined atmospheric pressure depletion correction coefficient.

  This atmospheric pressure depletion correction value V4 is a correction value introduced for the first time by the present invention. The pressure reduction correction value V4 is a correction value that changes depending on only the product of the pressure P and the amount of wear Δd of the photosensitive drum 10. The pressure reduction correction value V4 is a correction value that makes the correction range corrected by the above-described pressure correction value V2 and the wear correction value V3 small. That is, the pressure correction value V2 and the wear correction value V3 are corrected in the opposite directions. However, the atmospheric pressure depletion correction value V4 does not cancel the correction by the atmospheric pressure correction value V2 and the depletion correction value V3, and does not perform a larger correction. As will be described later, by introducing this atmospheric pressure depletion correction value V4, even when the surface layer of the photoconductive drum 10 is depleted under low atmospheric pressure, it can be charged to almost the same potential as in other cases.

  The other correction value V5 is, for example, a temperature / humidity correction value. Alternatively, other correction values may be considered.

  As described above, the setting of the applied voltage value by the voltage setting unit 221 requires the atmospheric pressure P and the amount of wear Δd of the photosensitive drum 10. The atmospheric pressure P is measured by the atmospheric pressure sensor 241. The amount of wear Δd of the photosensitive drum 10 is measured by the film thickness sensor 243.

Next, an outline of a procedure for calculating an applied voltage value by the voltage setting unit 221 will be described. The procedure is as follows.
<1>. Acquisition of atmospheric pressure P and photoconductor drum wear amount Δd <2>. Acquisition of reference voltage value V1 <3>. Calculation of atmospheric pressure correction value V2 <4>. Calculation of wear correction value V3 <5>. Calculation of atmospheric pressure depletion correction value V4 <6>. Calculation of other correction value V5 <7>. Calculation of applied voltage value V

<1> to <2>
First, the controller 220 acquires the atmospheric pressure P from the atmospheric pressure sensor 241 and the film thickness value of the photosensitive drum 10 from the film thickness sensor 242. Then, the control unit 220 compares the measured film thickness value with the initial film thickness stored in the other storage unit 235 to calculate the amount of wear Δd of the photosensitive drum 10. Subsequently, the reference voltage value V1 is read from the reference voltage value storage unit.

<3> to <6>
Next, the atmospheric pressure correction value deriving unit 222 calculates the atmospheric pressure correction value V2 using Equation (2). Next, the depletion correction value deriving unit 224 calculates the depletion correction value V3 using equation (3). Next, the atmospheric pressure depletion correction value deriving unit 223 calculates the atmospheric pressure depletion correction value V4 using equation (4). Next, the other correction value V5 is acquired.

<7>
Next, the applied voltage value V is calculated using Equation (1). The voltage setting unit 221 sets the applied voltage value V thus calculated as a voltage to be applied to the voltage application unit 21.

3. Comparison with Prior Art Next, a comparison between the present invention and the conventional invention will be described. First, the applied voltage value in the conventional image forming apparatus will be described. The conventional applied voltage value is shown in the following equation (2).
Vp = V1 + V2 + V3 + V5 (5)
Vp: Conventional applied voltage value
V1: Reference voltage value
V2: Pressure correction value
V3: Abrasion correction value
V5: Other correction values

  The applied voltage value of the conventional image forming apparatus has no atmospheric pressure depletion correction value V4. For this reason, the correction by the atmospheric pressure depletion correction value V4 does not work. Therefore, if the image forming apparatus is continuously used in a low-pressure environment, the surface potential of the photosensitive drum 10 cannot be kept constant as will be described later.

  A comparison between the image forming apparatus according to the present invention and a conventional image forming apparatus will be described with reference to FIGS. FIG. 2 is a graph showing the set value of the applied voltage. The horizontal axis in FIG. 2 is the altitude of the installation location where the image forming apparatus is installed. The vertical axis represents the voltage value applied to the charging roller by the voltage application unit. The initial use is shown in New. Those at the end of use are marked with Old.

  In FIG. 2, both lines are descending to the right. In FIG. 2, the line indicating the initial use of the present invention (the present invention New) and the line indicating the initial use of the conventional use (conventional New) are almost the same, so the two lines overlap. . As shown in FIG. 2, in the present invention and the related art, the absolute value of the applied voltage value set at the installation site with the low altitude is larger than the absolute value of the applied voltage value set at the installation site with the high altitude. Further, the absolute value of the applied voltage value set at the beginning of use is larger than the applied voltage value set at the end of use.

  At the initial stage of use, the applied voltage value set in the image forming apparatus 100 of the present invention and the applied voltage value set in the conventional image forming apparatus are almost the same regardless of the altitude. At the end of use, the applied voltage value set by the image forming apparatus 100 of the present invention and the applied voltage value set by the conventional image forming apparatus are almost the same at low altitudes. There is a difference at higher locations. This is because, as will be described later, the effect of depletion of the photosensitive drum 10 is small at an installation place with a high altitude, that is, a place with a low atmospheric pressure.

  In FIG. 2, only the line indicating the final stage of the present invention (the present invention Old) is different in inclination from the other three lines. That is, the inclination is small. Therefore, in the final stage of the present invention, the difference between the applied voltage value when the atmospheric pressure is high (for example, at an altitude of 0 m) and the applied voltage value when the atmospheric pressure is low (for example, at an altitude of 3000 m) is small compared to the other cases. Also, the difference between the applied voltage value at the final stage (present invention Old) and the applied voltage value at the initial stage (present invention New) in the present invention is the difference between the conventional applied voltage value at the final stage (conventional Old) and the initial applied voltage value (conventional New). Smaller than the difference in values.

  FIG. 3 shows measured values of the potential on the surface of the photosensitive drum. The legend is the same as in FIG. In FIG. 3, a line indicating the initial one in the image forming apparatus 100 of the present invention (the present New), a line indicating the final one (the present Old), and a line indicating the initial one in the conventional image forming apparatus ( Conventional New) is almost the same, so the lines overlap. Only the line indicating the final stage in the conventional image forming apparatus (conventional Old) is different from the other three lines.

  That is, in the image forming apparatus 100 of the present invention, the initial (the present invention New) photoconductor potential and the final (the present Old) photoconductor potential are almost the same. That is, even if the surface layer of the photosensitive drum 10 is worn out by 10 μm, the thickness does not change. On the other hand, the initial (conventional New) photoconductor potential in the conventional image forming apparatus is different from the final (conventional Old) photoconductor potential. This is due to the difference in the pressure reduction correction value V4 set in FIG.

  Therefore, the correction by the atmospheric pressure depletion correction value V4 derived by the atmospheric pressure depletion correction value deriving unit 223 in the present invention has the following effects. That is, the photosensitive member potential at the end of the image forming apparatus 100 of the present invention (Old of the present invention) can be set to the photosensitive member potential at the end of the conventional image forming apparatus (Conventional Old).

  As can be seen from FIG. 3, the image forming apparatus 100 of the present invention can make the surface potential of the photosensitive drum 10 constant regardless of the pressure at the installation location or the wear of the photosensitive drum 10. As in the conventional image forming apparatus, even if it is continuously used at a location where the atmospheric pressure is low, the photoreceptor potential is not affected. In the conventional image forming apparatus, the absolute value of the photoreceptor potential is lowered, and the background portion potential of the image is lowered. For this reason, fog was likely to occur. On the other hand, in an image forming apparatus in which no correction using the atmospheric pressure correction value V2 or the wear correction value V3 is performed, there is a concern that the absolute value of the photosensitive member potential becomes high. In such an image forming apparatus, there is a possibility that the image density is lowered or discharge is caused during development. In the present invention, these problems do not occur.

4). Modified example 4-1. Altitude input Here, a modified example is described. The modification described here is a modification of the process performed in <1>. In this embodiment, the applied voltage value is corrected using the atmospheric pressure P measured by the atmospheric pressure sensor 241. However, a user, a service person, etc. may input information about atmospheric pressure such as the altitude of the installation location. FIG. 5 illustrates an elevation input screen displayed on the touch panel 210. The user or the like inputs the altitude from the input screen. The input altitude value is stored in the other storage unit 235. The controller 220 calculates the atmospheric pressure P based on the stored altitude value. Thereby, the atmospheric pressure correction value V2 and the atmospheric pressure depletion correction value V3 can be calculated, and the applied voltage value V similar to this embodiment can be set.

  Further, the user or the like may select an altitude close to a location where the image forming apparatus is installed. FIG. 6 is a selection screen for selecting the altitude of the installation location of the image forming apparatus. This selection screen is displayed on the touch panel 210. The user or the like selects the altitude closest to the installation location from the input screen. The selected altitude value is stored in the other storage unit 235. The controller 220 calculates the atmospheric pressure P based on the stored altitude value. Thereby, the atmospheric pressure correction value V2 and the atmospheric pressure depletion correction value V3 can be calculated.

  Further, the user or the like may select a numerical value corresponding to the altitude of the location where the image forming apparatus is installed. FIG. 7 is an input screen for selecting the altitude of the installation location of the image forming apparatus. In FIG. 7, input of numbers 1 to 9 is accepted. Here, the number 0 is set to an altitude of 0 m in FIG. 2, and the number 9 is set to 3,000 m in FIG. The remaining numbers may be set to values that equally divide the altitude from 0 m to 3,000 m.

  Further, position information regarding the installation position of the image forming apparatus may be acquired by means such as GPS, and the acquired position information may be converted into atmospheric pressure. In this case, the other control unit 225 shown in FIG. 4 may convert the position information into atmospheric pressure. In other words, the other control unit 225 also serves as an atmospheric pressure conversion unit. An altimeter may be used instead of the atmospheric pressure sensor 241. This is because the atmospheric pressure information can still be acquired.

4-2. Acquisition of Film Thickness Information In this embodiment, the film thickness of the surface layer of the photosensitive drum 10 is measured by the film thickness sensor 242. However, instead of this, the film thickness may be estimated by using the photoconductor current sensor 243 shown in FIG. The photoconductor current is a current that flows from the photoconductor drum to the ground when the potential is attenuated by exposing the charged photoconductor drum. As the film thickness d of the photosensitive drum as the member to be charged decreases, the capacitance C increases accordingly. As a result, the photoreceptor current also increases. Therefore, information on the film thickness can be obtained by measuring the photoreceptor current. The correction value can be determined based on the film thickness value thus obtained. In this case, the calculation of the film thickness of the photosensitive drum 10 may be performed by the other control unit 225 in FIG. In other words, the other control unit 225 also serves as the film thickness calculation unit.

  Further, the film thickness of the surface layer of the photosensitive drum 10 can be estimated by the amount of the imaging cartridge used. Therefore, the film thickness of the surface layer of the photoconductive drum 10 can be estimated from the usage history after the imaging cartridge including the photoconductive drum 10 is replaced, for example, the rotation speed and the travel distance of the photoconductive drum 10. The usage history may be stored in the other storage unit 235. From this usage history, the other control unit 225 shown in FIG. 4 estimates the degree of wear of the photosensitive drum 10. In other words, the other control unit 225 also serves as an image carrier depletion estimation unit.

5. Summary As described in detail above, the voltage setting unit 221 according to this embodiment sets the applied voltage value V corrected by the atmospheric pressure correction value V2 and the atmospheric pressure depletion correction value V3 to the charging roller 20 by the voltage application unit 21. It is what you do. The atmospheric pressure reduction correction value V3 is a correction value derived based on the atmospheric pressure and the amount of wear of the image carrier. Since the correction using the atmospheric pressure depletion correction value V3 is performed, the potential of the surface of the photosensitive drum 10 can be kept constant even if the image forming apparatus is continuously used in a low atmospheric pressure environment. As a result, an image forming apparatus that does not easily cause fogging even when used continuously in a low-pressure environment is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention is not limited to the type of developer.

(Second Embodiment)
A second embodiment will be described. This embodiment is different from the first embodiment in a method for deriving the atmospheric pressure depletion correction value V3. In the first embodiment, the correction value is calculated by calculation. In this embodiment, a table storing correction values is prepared in advance, and the correction values are derived by appropriately reading from the table.

  The configuration of the charging control unit 200 of this embodiment is the same as that of FIG. However, it differs from that of the first embodiment in the following points. In the first embodiment, the atmospheric pressure correction value deriving unit 222, the depletion correction value deriving unit 224, and the atmospheric depletion correction value deriving unit 223 calculate the atmospheric pressure correction value V2, the depletion correction value V3, and the atmospheric depletion correction value V4, respectively, by calculation. It was used to do.

  In this embodiment, the atmospheric pressure correction value deriving unit 222 derives the atmospheric pressure correction value by reading out the atmospheric pressure correction value from the atmospheric pressure correction value table 232 as shown in Table 1. Table 1 stores the altitude corresponding to the atmospheric pressure and the atmospheric pressure correction value V2 corresponding to the atmospheric pressure. The wear correction value deriving unit 224 derives the wear correction value by reading the wear correction value from the wear correction value table 234.

  Further, the atmospheric pressure depletion correction value deriving unit 223 reads out the depletion correction coefficient from the atmospheric pressure depletion correction value table 233 as shown in Table 2. Here, in Table 2, the altitude corresponding to the atmospheric pressure and the depletion correction coefficient (C · P in the equation (4)) corresponding to the atmospheric pressure are stored. Next, the atmospheric pressure depletion correction value deriving unit 223 reads the depletion amount Δd of the photosensitive drum 10 from the other storage unit 225. Subsequently, the pressure reduction correction value is derived by multiplying the wear correction coefficient by the wear amount Δd of the photosensitive drum 10.

  The application voltage value to be set is determined using the pressure correction value and the pressure depletion correction value derived as described above, as in the first embodiment.

  Here, a modified example will be described. In this embodiment, the depletion correction coefficient is used to derive the atmospheric pressure depletion correction value V4. However, a two-dimensional table including the atmospheric pressure P and the amount of wear Δd of the photosensitive drum 10 may be used.

Further, the atmospheric pressure correction value V2, the depletion correction value V3, and the atmospheric depletion correction value V4 in the formula (1) all depend on the atmospheric pressure P, the depletion amount Δd of the photosensitive drum 10, or both of them. Therefore,
Vx = V2 + V3 + V4
Vx: Sum of correction values A two-dimensional table of the sum Vx of correction values may be created. The applied voltage value V may be derived from the two-dimensional table.

  As described above in detail, the voltage setting unit 221 according to the present embodiment sets the applied voltage value V corrected by the atmospheric pressure correction value V2 and the atmospheric pressure depletion correction value V3 to the charging roller 20 by the voltage application unit 21. It is what I did. The atmospheric pressure reduction correction value V3 is a correction value derived based on the atmospheric pressure and the amount of wear of the image carrier. Since the correction using the atmospheric pressure depletion correction value V3 is performed, the potential of the surface of the photosensitive drum 10 can be kept constant even if the image forming apparatus is continuously used in a low atmospheric pressure environment. As a result, an image forming apparatus that does not easily cause fogging even when used continuously in a low-pressure environment is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention is not limited to the type of developer.

DESCRIPTION OF SYMBOLS 10 ... Photosensitive drum 20 ... Charging roller 21 ... Voltage application part 100 ... Image forming apparatus 200 ... Charge control part 210 ... Touch panel 220 ... Control part 221 ... Voltage setting part 222 ... Atmospheric pressure correction value deriving part 223 ... Derivation pressure correction value of atmospheric pressure Unit 224 ... Depletion correction value deriving unit 225 ... Other control unit 230 ... Storage unit 231 ... Reference voltage value table 232 ... Atmospheric pressure correction value table 233 ... Atmospheric pressure depletion correction value table 234 ... Depletion correction value table 235 ... Other storage unit 240 ... Measurement unit 241 ... Atmospheric pressure sensor 242 ... Thickness sensor 243 ... Photoconductor current sensor

Claims (10)

An image carrier;
A charging roller for uniformly charging the surface of the image carrier;
In an image forming apparatus having a voltage application unit for applying a voltage to the charging roller,
An atmospheric pressure correction value deriving unit for deriving an atmospheric pressure correction value for correcting an applied voltage by atmospheric pressure;
A depletion correction value deriving unit for deriving a depletion correction value for correcting the applied voltage according to the depletion amount of the surface layer of the image carrier;
An atmospheric pressure depletion correction value deriving unit for deriving an atmospheric pressure depletion correction value for correcting the applied voltage according to the atmospheric pressure and the depletion amount of the surface layer of the image carrier;
Corrected by the atmospheric pressure correction value derived by the atmospheric pressure correction value deriving unit, the depletion correction value derived by the depletion correction value deriving unit, and the atmospheric pressure depletion correction value derived by the atmospheric pressure depletion correction value deriving unit A voltage setting unit for setting an applied voltage value in the voltage application unit,
The pressure loss correction value is
An image forming apparatus that corrects the value of an applied voltage within a range that is opposite to the correction by the atmospheric pressure correction value and the depletion correction value and that does not cancel the correction by the atmospheric pressure correction value and the depletion correction value. . The image forming apparatus according to claim 1,
The pressure loss correction value is
A correction value that increases the absolute value of the applied voltage as the product of the atmospheric pressure and the amount of wear of the image carrier increases.
An image forming apparatus, wherein the correction value is such that the smaller the product of the atmospheric pressure and the amount of wear of the image carrier, the smaller the absolute value of the applied voltage. The image forming apparatus according to claim 1, wherein:
The atmospheric pressure depletion correction value deriving unit is
V4 = C · P · Δd
V4: Atmospheric pressure depletion correction value C: Predetermined atmospheric pressure depletion coefficient P: Atmospheric pressure Δd: An atmospheric pressure depletion correction value is calculated from the depletion amount of the image carrier. The image forming apparatus according to claim 1, wherein:
An atmospheric pressure depletion correction value storage unit storing a plurality of combinations of atmospheric pressure and atmospheric pressure depletion correction values corresponding to the atmospheric pressure;
The voltage setting unit is
An image forming apparatus, wherein an applied voltage value is set using a pressure reduction correction value stored in the pressure reduction correction value storage unit. The image forming apparatus according to claim 1, wherein:
An image carrier current measuring unit for measuring a current flowing through the image carrier;
A film thickness calculation unit that converts the current measured by the image carrier current measurement unit into a value of the film thickness of the image carrier;
The depletion correction value deriving unit is:
A depletion correction value is derived using the film thickness value calculated by the film thickness calculation unit,
The atmospheric pressure depletion correction value deriving unit is
An image forming apparatus characterized in that a pressure loss correction value is derived using a film thickness value calculated by the film thickness calculation unit. The image forming apparatus according to claim 1, wherein:
An image forming apparatus comprising: an image carrier depletion estimation unit that estimates a depletion amount of a surface layer of the image carrier from a rotational speed or a travel distance of the image carrier. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, comprising: an input unit that receives an input from a user with respect to atmospheric pressure information relating to an atmospheric pressure at an installation location of the image forming apparatus. The image forming apparatus according to claim 7,
An image forming apparatus, comprising: an output unit configured to display a selection screen showing options to the user for the atmospheric pressure information. The image forming apparatus according to claim 7 or 8, wherein:
Has a pressure conversion part,
The input unit is:
Receiving the altitude information or position information of the installation location of the image forming apparatus;
The atmospheric pressure converter
An image forming apparatus for converting input altitude information or position information into atmospheric pressure. The image forming apparatus according to any one of claims 1 to 9,
An image forming apparatus having an atmospheric pressure sensor or an altimeter.

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