JP5857587B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Japanese Patent Application Laid-Open No. 2004-133867 describes a technique for turning off the neutralization unit when the transfer bias is equal to or lower than a preset threshold value and not performing neutralization, and turning on the neutralization unit and performing neutralization when the transfer bias exceeds the threshold value. ing.

JP 2003-76076 A

  An object of the present invention is to reduce wear of a charge transport layer of a photoreceptor in an electrophotographic image forming apparatus that performs static elimination.

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member having a charge transport layer for transporting a charge generated by exposure; a charging unit that charges the surface of the photosensitive member; and a charging unit that charges the surface. Exposing the surface to form an electrostatic latent image; supplying toner to the electrostatic latent image formed by the exposing means to develop the electrostatic latent image; A developing unit for forming, a transfer unit for transferring the toner image formed by the developing unit from the surface to the medium, a discharging unit for discharging the surface after the toner image is transferred by the transferring unit, and the discharging unit. For a first static elimination condition in which the means removes the surface with a first intensity, and for a second static elimination condition in which the static elimination means neutralizes the surface with a second intensity that is weaker than the first intensity According to the first static elimination condition Storage means for storing a wear rate representing the amount of wear of the charge transport layer per rotation of the photoconductor, which is determined so that the second static elimination condition is smaller, and the charging means is the surface Measuring means for measuring the number of rotations of the photosensitive member during a charging period for charging the charging member, and specifying means for specifying the thickness of the charge transport layer , wherein the discharging means is the first discharging member during the charging period. In the case of performing charge removal under conditions, the wear rate determined for the first charge removal condition among the wear rates stored in the storage unit is measured by the measurement unit during the charging period. A value obtained by multiplying the number of rotations is calculated as the amount of wear of the charge transport layer during the charging period, and when the charge removal means performs charge removal under the second charge removal condition during the charge period, A value obtained by multiplying the wear rate determined for the second static elimination condition among the wear rates stored by the storage unit by the number of revolutions measured by the measurement unit during the charging period, Calculated as the amount of wear of the charge transport layer during the charging period, and from the thickness of the charge transport layer at a predetermined time to start specifying the thickness of the charge transport layer, the charging period after the time Specifying means for specifying the value obtained by subtracting the total amount of wear calculated in step 1 as the thickness of the charge transport layer, wherein the charge eliminating means has a thickness specified by the specifying means equal to the first thickness. If a small second thickness than, thickness specified by the specifying means than a first thickness, and wherein the you neutralization with a small intensity.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member having a charge transport layer for transporting a charge generated by exposure; a charging unit that charges the surface of the photosensitive member; Exposing the surface to form an electrostatic latent image; supplying toner to the electrostatic latent image formed by the exposing means to develop the electrostatic latent image; A developing means for forming; a transferring means for transferring a toner image formed by the developing means from the surface to a medium; a discharging means for discharging the surface after the toner image is transferred by the transferring means; , A first charge removal condition for removing the surface with a first intensity by the charge removing means, and a second charge removal means for removing the surface with a second intensity that is weaker than the first intensity. Pair with 2 static elimination conditions Storage means for storing a wear rate representing a wear amount of the charge transport layer per one rotation of the photoconductor determined according to the combination, and the photoconductor in a charging period in which the charging means charges the surface. Measuring means for measuring the number of rotations, acquisition means for acquiring environment information representing an environment in which the device is used in the charging period, and specifying means for specifying the thickness of the charge transport layer, In the case where the static elimination unit performs static elimination under the first static elimination condition during the charging period, out of the wear rate stored by the storage unit, the environment represented by the environmental information acquired by the acquisition unit during the charging period A value obtained by multiplying the wear rate determined according to the first static elimination condition by the number of revolutions measured by the measuring means during the charging period is the value before the charging period. Calculated as the amount of wear of the charge transport layer, from the thickness of the charge transport layer at a predetermined time to start specifying the thickness of the charge transport layer, calculated in the charging period after the time A value obtained by subtracting the total amount of wear is specified as the thickness of the charge transport layer, or stored in the storage means when the charge removal means removes charges under the second charge removal condition during the charging period. Among the wear rates, the measurement means measures the wear rate determined according to the environment represented by the environment information acquired by the acquisition means during the charging period and the second charge removal condition during the charging period. A value obtained by multiplying the number of rotations is calculated as the amount of wear of the charge transport layer during the charging period, and from the thickness of the charge transport layer at the time, the charge period after the time Specifying means for specifying, as the thickness of the charge transport layer, a value obtained by subtracting the total amount of wear calculated in step (a), wherein the static elimination means has a thickness specified by the specifying means that is the first thickness. When the second thickness is smaller than the thickness, the static electricity is discharged with a smaller strength than when the thickness specified by the specifying means is the first thickness .

According to the first and second aspects of the present invention, in the electrophotographic image forming apparatus in which the surface of the photosensitive member is neutralized as compared with the case where the surface of the photosensitive member is not configured to be neutralized, Wear of the charge transport layer can be reduced.
According to the first and second aspects of the invention, even when the thickness of the charge transport layer cannot be directly measured, compared to the case where the surface of the photoconductor is not configured to remove electricity as in the present configuration. Thus, in an electrophotographic image forming apparatus that performs static elimination, wear of the charge transport layer of the photoreceptor can be reduced.
According to the first aspect of the present invention, even when the environment in which the apparatus is used fluctuates, the calculated wear is greater than when the configuration for calculating the amount of surface wear as in the present configuration is not provided. The amount accuracy can be increased .
According to the invention of 請 Motomeko 2, self-device environment used varies, or, even if the first period and the second period are mixed, the amount of wear of the surface of the structure Thus, compared with the case where it does not have the structure to calculate, the precision of the calculated wear amount can be made high .

1 is a block diagram illustrating a configuration of an image forming apparatus according to a first embodiment. It is a figure which shows the structure of an image formation part. It is a figure which shows the structure of a photoconductor unit. It is a figure for demonstrating the surface layer and charge generation layer of a photoreceptor. It is a table | surface which shows the relationship between use environment, the presence or absence of static elimination, and a wear rate. It is a graph which shows the relationship between the thickness of a surface layer, and a ghost grade. It is a flowchart which shows the procedure of the process which a control part performs. It is a flowchart which shows the procedure of the process which the control part which concerns on 2nd Embodiment performs.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of an electrophotographic image forming apparatus 10 according to the present embodiment. The image forming apparatus 10 includes a control unit 110, a thermohygrometer 120, a storage unit 130, and an image forming unit 200. The control unit 110 is a computer including an arithmetic device including a CPU (Central Processing Unit) and a memory. The arithmetic unit of the control unit 110 executes a program stored in the memory and controls each unit of the image forming apparatus 10. The thermohygrometer 120 includes a thermometer and a hygrometer, and measures temperature and relative humidity. The thermohygrometer 120 supplies data indicating the measurement result to the control unit 110 as environment information representing an environment in which the image forming apparatus 10 is used. The storage unit 130 includes a storage device such as an HDD (Hard Disk Drive), and stores, for example, image data for forming an image. The storage unit 130 is an example of the “storage unit” according to the present invention.

  The image forming unit 200 forms an image on a recording medium by an electrophotographic process using four color toners of yellow (Y), magenta (M), cyan (C), and black (K). The recording medium is, for example, a recording sheet, but may be a plastic such as an OHP sheet or a sheet of other materials, and may be any medium that can record an image on the surface.

  FIG. 2 is a diagram illustrating a configuration of the image forming unit 200. Among the reference numerals of the image forming unit 200 shown in FIG. 2, the alphabet attached to the end corresponds to the color of toner handled by the image forming apparatus. The configurations having different alphabets at the end of the codes are different in the color of the toner to be handled, but the configurations are common to each other. In the following description, when it is not necessary to distinguish between these components, the description will be made with the alphabet at the end of the reference numerals omitted. The image forming unit 200 includes a photoconductor unit 210, an exposure device 220, a developing device 230, an intermediate transfer belt 240, rotary rolls 241 and 242, a primary transfer roll 250, a secondary transfer roll 261, and a backup roll. 262, a transport roll 270, and a fixing device 280.

  The photoconductor unit 210 has a photoconductor drum 211. The photosensitive drum 211 is a cylindrical member that rotates about an axis, and holds an electrostatic latent image formed on the surface. When the photosensitive drum 211 is in contact with the intermediate transfer belt 240, the photosensitive drum 211 rotates in the direction of the arrow A1 in the drawing with the center of the cylinder as an axis as the intermediate transfer belt 240 rotates. Hereinafter, this direction is referred to as a drum rotation direction A1. The photosensitive drum 211 is an example of the “photosensitive member” according to the present invention. The exposure device 220 exposes the photosensitive drum 211 according to image data to form an electrostatic latent image on the photosensitive drum 211. The developing device 230 contains a developer containing toner of any color of Y, M, C, and K and a magnetic material such as ferrite powder. The developing device 230 performs development by supplying toner to the electrostatic latent image formed on the photosensitive drum 211 using the developer. By this development, a toner image is formed on the surface of the photosensitive drum 211. The exposure apparatus 220 is an example of the “exposure unit” according to the present invention, and the developing device 230 is an example of the “developing unit” according to the present invention.

  The intermediate transfer belt 240 is an endless belt-like member, and rotates in a direction indicated by an arrow A2 in the drawing while being in contact with the rotary rolls 241, 242, the primary transfer roll 250, and the backup roll 262. Hereinafter, this direction is referred to as a belt rotation direction A2. The photosensitive drums 211Y, 211M, 211C, and 211K are arranged in a line from the upstream side to the downstream side in the belt rotation direction A2 along the outer peripheral surface of the intermediate transfer belt 240. The rotary rolls 241 and 242 are cylindrical members that support the intermediate transfer belt 240 and rotate around the center of the cylinder.

  The primary transfer roll 250 is a cylindrical member that faces the photosensitive drum 211 with the intermediate transfer belt 240 interposed therebetween, and transfers the toner image formed on the photosensitive drum 211 to the intermediate transfer belt 240. Specifically, the toner image is transferred from the surface of the photosensitive drum 211 to the surface of the intermediate transfer belt 240 due to a potential difference between the primary transfer roll 250 and the photosensitive drum 211. The secondary transfer roll 261 is a cylindrical member that faces the backup roll 262 with the intermediate transfer belt 240 interposed therebetween, and transfers the toner image transferred to the intermediate transfer belt 240 onto a recording sheet. Specifically, the secondary transfer roll 261 forms an area (referred to as a contact area) that contacts the intermediate transfer belt 240. In this contact area, the toner on the surface of the intermediate transfer belt 240 is transferred to the surface of the recording paper due to the potential difference between the secondary transfer roll 261 and the backup roll 262. The primary transfer roll 250, the secondary transfer roll 261, and the backup roll 262 are examples of the “transfer unit” according to the present invention, and the intermediate transfer belt 240 and the recording paper are examples of the “medium” according to the present invention.

  The transport roll 270 is a cylindrical member that is driven by a drive device (not shown), and transports the recording paper in the direction of the broken arrow A3 shown in FIG. The fixing device 280 performs a fixing process of applying heat and pressure to the recording paper on which the toner image is transferred, and fixes the toner image on the recording paper. With the above configuration, in the image forming unit 200, an image is formed on the recording sheet conveyed in the direction of the broken arrow A3 shown in FIG.

  FIG. 3 is a view showing the structure of the photoreceptor unit 210. The photoconductor unit 210 includes a charging device 214, a cleaning blade 215, a charge removal device 216, and a rotation detection device 217 in addition to the above-described photoconductor drum 211. The photosensitive drum 211 has a cylindrical base 212 formed of aluminum or the like as a material, and a photosensitive layer 213 that covers the outer surface of the base 212. The base body 212 is grounded, and its potential is 0V. In the photosensitive layer 213, when light is applied, an electric charge is generated from the inside, and the electric charge moves to the surface 213 a, whereby the potential of the place where the light is applied changes.

  The charging device 214 is a contact-type charger having a roll-shaped member called a charging roll, and charges the surface 213 a by bringing the charging roll into contact with the surface 213 a of the photosensitive layer 213. The voltage application unit 218 applies a voltage between the charging device 214 and the base body 212. The voltage application unit 218 applies a voltage so that the charging device 214 has a negative potential V0 with respect to the base body 212, whereby the surface 213a is charged to a predetermined potential (hereinafter referred to as “charging potential V1”). . The potentials V0 and V1 have a relationship of 0> V1> V0. The photosensitive layer 213 whose surface 213a is at the charged potential V1 is irradiated (exposed) with the above-described exposure device 220, and the positive charge generated by the light causes the potential to change in the positive direction from the charged potential V1. An area, that is, an electrostatic latent image is formed on the surface 213a. When the potential after the exposure is “post-exposure potential V2”, the relationship is 0> V2> V1. In other words, negative charges are accumulated on the exposed surface 213a of the exposed photosensitive layer 213 at both the exposed location and other locations. These negative charges remain accumulated on the surface 213a side of the photosensitive layer 213 even after the toner image is primarily transferred. The charging device 214 is an example of the “charging unit” according to the present invention.

  The cleaning blade 215 is a long and plate-like member formed of, for example, rubber or resin, and one side extending in the longitudinal direction is in contact with the surface 213a of the photosensitive layer 213, and further on the photosensitive drum 211 side. The adhered matter adhered to the surface 213a is removed by being pressed against the surface 213a.

  The static eliminator 216 has a light source such as a tungsten lamp or LED (Light Emitting Diode), and irradiates the entire surface 213a after the toner image is primarily transferred, and is accumulated on the surface 213a side of the photosensitive layer 213. To remove the negative charge. By this light irradiation, the potential of the entire surface 213a changes to a predetermined potential (hereinafter referred to as “static charge potential V3”). In the present embodiment, it is assumed that the static eliminator 216 neutralizes the surface 213a so that the static elimination potential V3 is 0V. The rotation detection device 217 is an optical sensor and detects a sensor mark provided on the peripheral surface of the photosensitive drum 211. The rotation detection device 217 detects this sensor mark every time the photosensitive drum 211 makes one rotation, and outputs a signal indicating the detection result (hereinafter referred to as “detection signal”) to the control unit 110. The charging device 214, the developing device 230, the rotation detection device 217, the primary transfer roll 250, and the charge removal device 216 are arranged around the photosensitive drum 211 in this order along the drum rotation direction A1.

Next, generation and movement of charges in the photosensitive layer 213 will be described.
FIG. 4 is a view showing the structure of the photosensitive layer 213. FIG. 4 shows a cross section of the photosensitive drum 211. The photosensitive layer 213 includes a charge generation layer 213c and a charge transport layer 213b. The charge generation layer 213c includes a material that generates charges when exposed to light, and covers the base 212. The charge transport layer 213b includes a material that transports charges (for example, charges generated by exposure) inside itself, and is stacked outside the charge generation layer 213c. That is, the charge transport layer 213b is a layer (surface layer) that the photosensitive drum 211 has on the surface. The charge transport layer 213b is charged by the charging device 214, and the surface thereof, that is, the surface 213a of the photosensitive layer 213 is charged so as to have a charging potential V1.

  When the photosensitive layer 213 is exposed, charges are generated in the charge generation layer 213c that has been exposed to the light, and the positive charges move through the charge transport layer 213b to the surface of the charge transport layer 213b (ie, the surface 213a). To do. When this positive charge moves in the charge transport layer 213b, some of the charges are slower than other charges or temporarily stop during the movement. Such charges are still moving when an image is formed by the exposure that generated them, and may reach the surface 213a when the next image is formed. In that case, a so-called ghost phenomenon in which the trace of the previous image appears in the next image due to these charges occurs. The traces appearing here may cause unevenness in the next image, although the degree of shading is smaller (lighter) than the previous image. This phenomenon is more likely to occur as the thickness B of the charge transport layer 213b increases, because the time difference until the charge reaches the surface 213a is likely to increase. This thickness B is the thickness of the charge transport layer 213b in the radial direction of the photosensitive drum 211.

  On the other hand, when the charge removal is performed by the charge removal device 216, the occurrence of the above phenomenon is suppressed even during the period in which the thickness B of the charge transport layer 213b is large. More specifically, this neutralization changes the entire surface 213a to the neutralization potential V3 as described above. As a result, even when the thickness B is large and there is a charge bias on the surface and inside of the charge transport layer 213b, the bias is eliminated and the occurrence of the above phenomenon is suppressed.

  Next, the wear of the charge transport layer 213b will be described. If the charge removal by the charge removal device 216 has already been performed immediately before the charging by the charging device 214, the surface 213a is at the charge removal potential V3. In addition, when the charge removal is not performed, the surface 213a has the post-exposure potential V2 in the exposed portion, and the charged potential V1 in the unexposed portion. The relationship between these potentials and the potential V0 when a voltage is applied to the charging device 214 is V3 (0V)> V2> V1> V0. That is, when the potential difference between the surface 213a and the charging device 214 is compared between the case where the charge is removed and the case where the charge is not removed, the potential difference V3-V0 in the former case is the potential difference V2-V0 or V1- in the latter case. Larger than V0. For this reason, more discharge occurs between the surface 213a and the charging device 214 when neutralization is performed than when neutralization is not performed. As a result, the polymer main chain of the charge transport layer 213b is likely to be broken and the strength of the charge transport layer 213b is reduced as compared with the case where the charge removal is not performed. The charge transport layer 213b wears due to friction with the cleaning blade 215 with which the surface 213a is in contact, for example. However, when the charge is removed and the strength decreases as described above, the charge transport layer 213b is less than the case where the charge is not removed. The amount (hereinafter referred to as “amount of wear”) increases.

  FIG. 5 is a table showing changes in the wear rate depending on the presence or absence of static elimination. In this table, the wear amount (unit: nm: nanometer) of the charge transport layer 213b (that is, the photosensitive layer 213) when the photosensitive drum 211 is rotated 1000 times is measured, and the measured value is shown as a wear rate. It is. In this measurement, the environment in which the image forming apparatus 10 is used is a temperature of 28 ° C. and a humidity of 85% (referred to as “use environment A”), a temperature of 22 ° C. and a humidity of 55% (referred to as “use environment B”), In three cases of the temperature and the humidity of 15% (referred to as “use environment C”), the static electricity was removed (when static electricity was removed) and the static electricity was not removed (when static electricity was not eliminated). In use environment A, it was 9.5 nm / 1000 rotations during static elimination and 5.5 nm / 1000 revolutions during non-static elimination. In use environment B, the speed was 12.1 nm / 1000 rotations during static elimination and 7.8 nm / 1000 revolutions during non-static elimination. In use environment C, it was 14.6 nm / 1000 rotations during static elimination and 9.8 nm / 1000 revolutions during non-static elimination. As described above, the amount of wear increases as the use environment (use environment A) is relatively low compared to the use environment (use environment A) where the temperature and humidity are relatively high. The amount of wear increased at the time compared to the non-static charge. These use environments are examples of the “environment” according to the present invention.

  FIG. 6 is a graph showing the relationship between the thickness of the charge transport layer 213b and the degree of occurrence of the above phenomenon (ghost). This graph shows static elimination when the image forming apparatus 10 installed in the use environment C (temperature 10 ° C., humidity 15%) continues to form an image and the charge transport layer 213b has a thickness of 30 μm, 25 μm, 20 μm, and 15 μm. It shows the result of evaluating the degree of occurrence of ghosts at the time and at the time of non-static elimination. The degree of occurrence of this ghost is represented by a numerical value in increments of 0.5 from 0 to 5 called ghost grade. In this ghost grade, for example, a solid image having a uniform density as a whole is formed, and the density of the portion where the ghost is generated and the portion where the ghost is not generated are measured. Evaluated as a strong occurrence of, and increased the value. For example, if the ghost grade is 2.5 or less, it is assumed that the image is uneven enough to be practically used. As shown in this graph, the ghost grades evaluated at the time of static elimination are 3.0, 2.0, 1.0, and 0.5 in the order of the thicknesses. In addition, the ghost grades evaluated at the time of non-static elimination are 4.0, 3.0, 2.0, and 1.5 in the order of the thicknesses. Thus, in both cases of static elimination and non-neutralization, the ghost grade became smaller as the thickness of the charge transport layer 213b became thinner. Further, at any thickness, the ghost grade was smaller when neutralizing than when non-static.

  In the image forming apparatus 10, while the ghost grade is large, the ghost grade is reduced by performing static elimination, and the ghost grade becomes 2.5 or less even if the charge transport layer 213 b becomes thin due to wear and is not eliminated. After that, do not remove static electricity. Next, a procedure of processing performed by the control unit 110 will be described with reference to FIG.

  FIG. 7 is a flowchart illustrating a processing procedure performed by the control unit 110 of the image forming apparatus 10. FIG. 7 shows a processing procedure in which the control unit 110 stores the use environment, the charge removal condition, and the charged state rotation speed. Here, the use environment is an environment in which the image forming apparatus 10 is used, for example, temperature and humidity in a place where the image forming apparatus 10 is used. The neutralization condition refers to a condition that determines whether the surface 213a of the photosensitive layer 213 is neutralized (with neutralization) or not (without neutralization). The charged state rotational speed refers to the number of rotations (that is, the rotational speed) of the photosensitive drum 211 during a period in which the charging device 214 charges the surface 213a of the photosensitive layer 213 under a certain usage environment and static elimination conditions. . This number of rotations does not include the number of rotations of the photosensitive drum 211 while the surface 213a is not charged. This procedure is started when the image forming apparatus 10 starts an operation in which the charging device 214 charges the surface 213a. In the following, a case where the photosensitive drum 211 attached to the image forming apparatus 10 is used for the first time, that is, when the photosensitive drum 211 is rotated for the first time while the surface 213a is charged by the charging device 214 will be described as an example. .

  First, the control unit 110 of the image forming apparatus 10 determines the usage environment and the charge removal conditions (step S110). Specifically, the control unit 110 determines which of the above-described use environments A, B, and C is the use environment closest to the temperature and humidity values indicated by the data newly supplied from the thermohygrometer 120. . For example, the control unit 110 converts the temperature into a numerical value in which 10 ° C. is 0 and 28 ° C. is 100, and converts the humidity into a numerical value in which 15% is 0 and 85% is 100. By this conversion, for example, 19 ° C. is converted to 50, 37 ° C. is converted to 150, and 1 ° C. is converted to −50. Also, 0% humidity is converted to -21.4, 50% is converted to 50, and 100% is converted to 121.4. By this conversion, the temperature 22 ° C. of the use environment B is converted to 66.7, the humidity 55% is converted to 57.1, and the average is 61.9. In use environments A and C, the averages are 100 and 0, respectively. The control unit 110 converts the supplied temperature and humidity into this numerical value, and calculates an average value thereof. Then, the control unit 110 determines the use environment A, B, or C that has the smallest difference between the average value (100, 61.9, 0) and the calculated average value as the use environment. .

  Further, the control unit 110 stores a flag for determining the charge removal condition in the storage unit 130. The controller 110 stores a flag indicating that the charge removal condition is “with charge removal” before the photosensitive drum 211 is used for the first time as described above. In step S110, the control unit 110 refers to the flag stored in the storage unit 130 and determines that the charge removal condition is “charge removal”.

  Subsequently, the control unit 110 starts an operation of forming an image with or without charge removal depending on the charge removal condition (step S120). Specifically, if the charge removal condition is “with charge removal”, the control unit 110 forms an image while performing charge removal. If the charge removal condition is “no charge removal”, the control unit 110 forms an image without performing charge removal. Next, the control unit 110 starts measuring the above-described charging state rotational speed (step S130). When this measurement is started, the controller 110, for example, when the detection signal is output from the rotation detection device 217 during a period during which the charging device 214 is controlled to be charged (charging period), the charged state rotation speed. 1 is added to (step S140). As described above, the control unit 110 and the rotation detection device 217 cooperate to function as a measurement unit that measures the number of rotations of the photosensitive drum 211 during the charging period.

  Subsequently, the control unit 110 specifies the thickness of the charge transport layer 213b (step S150). In this specification, the thickness of the charge transport layer 213b in the storage unit 130 before the charge transport layer 213b is worn for the first time, that is, at an initial time point when the wear is not worn (hereinafter referred to as “initial time point”). (Hereinafter referred to as “initial thickness”) is stored, and is determined as a combination of the use environment and the presence / absence of static elimination (that is, static elimination conditions) shown in FIG. 5 and the wear rate when static elimination is performed by that combination. It is assumed that a wear rate table is stored in association with the determined wear rate. The control unit 110 refers to the wear rate table stored in the storage unit 130, and sets the charge state rotation speed to a thickness of 1/1000 of the wear rate associated with the use environment and the charge removal conditions determined in step S110. The value multiplied by is calculated. This calculated value represents the amount of wear of the charge transport layer 213b during the period in which the photosensitive drum 211 is rotated by the rotation speed of the charged state at that time. During this period, both the use environment and the charge removal conditions are determined in step S110. The control unit 110 calculates the calculated value as the wear amount in the period. Then, the controller 110 specifies a value obtained by subtracting the calculated wear amount from the initial thickness as the thickness of the charge transport layer 213b.

  Next, the control unit 110 determines a charge removal condition based on whether or not the thickness of the charge transport layer 213b specified in step S150 is less than a threshold value (step S160). In performing this determination, it is assumed that a threshold value is stored in the storage unit 130 in advance. This threshold value is determined to be 22.5 nm, which is a thickness at which the ghost grade becomes 2.5 or less even when the static electricity is not removed, based on the measurement result represented by the graph shown in FIG. If the thickness is equal to or greater than the threshold value, the control unit 110 determines that the charge removal condition is “with charge removal”, and if less than the threshold value, determines that the charge removal condition is “no charge removal”.

  Next, the control unit 110 determines whether or not the charge removal condition has been changed (step S170). In this step, the control unit 110 determines that the charge removal condition has not been changed if the charge removal condition determined in step S160 is the charge removal condition indicated by the flag stored in the storage unit 130 (step S110). S170; NO), if not so, it is determined that the static elimination condition has been changed (step S170; YES). In any case, the control unit 110 overwrites the flag stored in the storage unit 130 with the flag indicating the static elimination condition determined in step S160. Thereby, this flag represents the current static elimination conditions.

  When it is determined that the charge removal condition has not been changed (step S170; NO), the control unit 110 determines whether the use environment has changed (step S180). Here, for example, the control unit 110 performs a process common to the determination of the use environment performed in step S110, and determines that the use environment has not changed unless the result is the same as that in step S110 (step S110). S180; NO). In this case, the control unit 110 determines whether or not the process of forming an image has been completed (step S190), and when it is determined that the process has not been completed (step S190; NO), the process of step S140 is performed again.

  In this way, the control unit 110 determines whether the static elimination conditions have been changed (step S170; YES), determines whether the usage environment has changed (step S180; YES), or determines that the image forming process has ended (step S180; YES). Steps S140 to S190 are repeated until step S190; YES). Thus, the control unit 110 continues to form an image with charge removal until the thickness of the charge transport layer 213b is equal to or less than the threshold value, and after the thickness of the charge transport layer 213b is equal to or less than the threshold value, An image is formed without using any image.

  If YES is determined in steps S170, S180, and S190, the control unit 110 causes the storage unit 130 to store the use environment, the charge removal condition, and the charged state rotation speed in association with each other (step S200). If the usage environment has changed (step S210; YES), the control unit 110 performs the process of step S140 again. Thereby, the thickness of the charge transport layer 213b is specified using a new use environment. Moreover, when there is a change in the charge removal condition (step S220; YES), the control unit 110 performs the process of step S120 again. Thereby, static elimination is performed under new static elimination conditions, and the thickness of the charge transport layer 213b is specified using the static elimination conditions. If there is no change in the use environment and no change in the charge removal conditions (step S210; NO, step S220; NO), the image forming is completed, and the control unit 110 ends the procedure of this processing.

  In the image forming apparatus 10, after the process of step S <b> 140 is performed by the control unit 110, it is necessary until the process of steps S <b> 190, S <b> 210 or S <b> 220, S <b> 120, S <b> 130 described above is performed and the process of step S <b> 140 is performed again. The time is shorter than the time required for one rotation of the photosensitive drum 211. As a result, in step S140, 1 is added to the charging state rotational speed every time the photosensitive drum 211 rotates once. That is, the control unit 110 measures the number of rotations of the photosensitive drum 211 during the period in which the charging device 214 charges the surface 213a of the photosensitive layer 213.

  In the second and subsequent steps S150, the control unit 110 calculates the above-described wear amount from the use environment, the charge removal conditions, and the charged state rotational speed at that time, and the past stored in the storage unit 130 in step S200. From the use environment, the charge removal conditions, and the charged state rotation speed, the wear amount corresponding to them is calculated. If there are a plurality of past use environments, static elimination conditions, and charged state rotational speeds, the controller 110 calculates the wear amount for each. Then, the control unit 110 sums up the calculated wear amounts, the charge transport layer 213b at that time calculates the wear amount, and a value obtained by subtracting the calculated wear amount from the initial thickness of the charge transport layer 213b. Specified as thickness.

  The control unit 110 performs each process according to the above procedure, so that the wear of the current charge transport layer 213b is performed on the premise that the wear progresses at the wear rate associated with the use environment and the charge removal condition in the wear rate table. Specify the thickness. Then, the control unit 110 causes the surface 213a of the photosensitive layer 213 to be neutralized by the static eliminator 216 or not to neutralize depending on the specified thickness.

  According to the first embodiment described above, the surface 213a of the photosensitive layer 213 is neutralized in a period in which the thickness of the charge transport layer 213b is larger than the threshold, that is, in a period in which ghosts are more likely to occur than in subsequent periods. The ghost is suppressed. Further, in the period in which the thickness of the charge transport layer 213b is equal to or less than the threshold value, that is, in the period in which ghosts are less likely to occur compared to the period before the charge transport layer 213b, the surface 213a is not discharged. Wear of the transport layer 213b is reduced. That is, according to the first embodiment, in the electrophotographic image forming apparatus 10 that performs static elimination, wear of the charge transport layer 213b is reduced as compared with the case where static elimination is not performed as described above. Furthermore, compared to the case where the charge removal is not performed as described above, image unevenness (ghost) caused by the toner remaining on the photosensitive drum 211 is suppressed, and the wear of the charge transport layer 213b on the surface of the photosensitive drum 211 is suppressed. Less.

[Second Embodiment]
An image forming apparatus 10 according to a second embodiment of the present invention will be described. Below, about the structure which is common in 1st Embodiment, a common code | symbol is attached | subjected and the description shall be abbreviate | omitted. This embodiment is significantly different from the first embodiment in that the intensity of light emitted by the static eliminator 216 is changed by the control of the control unit 110 and the control unit 110 is only whether or not the static eliminator 216 performs static elimination. Rather, it is to control the strength of static elimination.

  In the present embodiment, the static eliminator 216a is controlled by the control unit 110 to irradiate light with different intensities at a plurality of stages. At that time, the static eliminator 216 emits light with three levels of intensity of levels a, b, and c. It is assumed that the intensity of these lights has a relationship of a> b> c. The static eliminator 216a changes the potential of the entire surface 213a to the static elimination potentials V3a, V3b, and V3c by irradiating light with the intensity of levels a, b, and c, respectively. These potentials have a relationship of V3a> V3b> V3c> V0 when compared with the potential V0 of the charging device 214 when the voltage is applied, and V3a is assumed to be 0V. In this case, the charge removal condition represents the charge removal intensity as levels a, b, c, or 0 (that is, no light is irradiated) that is the intensity of light to be irradiated. In this case, the storage unit 130 stores a wear rate table in which a combination of the use environment and the charge removal condition is associated with a wear rate determined as a wear rate when the combination is used for charge removal.

  FIG. 8 is a flowchart illustrating a procedure of a process in which the control unit 110 controls the static elimination operation. This procedure is different from the procedure of FIG. 7 in steps S120 and S160, and will be described with a focus on these steps. In step S150, the control unit 110 specifies the thickness of the charge transport layer 213b. And the control part 110 determines the static elimination intensity | strength (level a, b, c, or 0) according to the specified thickness as static elimination conditions (step S160a). In this case, the static elimination condition flag represents the static elimination intensity. In step S110, the control unit 110 refers to the flag stored in the storage unit 130 to determine the charge removal condition. Then, the control unit 110 controls the static eliminator 216a to irradiate light with the intensity indicated by the determined static elimination condition, and neutralizes the surface 213a of the photosensitive layer 213 (step S120a). For example, if the specified thickness is 27.5 nm or more, the control unit 110 irradiates light with an intensity of level a, and if the thickness is less than 27.5 nm and 25 nm or more, emits light with an intensity of level b. If the thickness is less than 25 nm and 22.5 nm or more, the light is irradiated with the intensity of level c. In addition, if the specified thickness is less than 22.5 nm, the control unit 110 does not remove the charge from the surface 213a, that is, sets the intensity of the irradiated light to zero. In this case, the static elimination intensity is also zero. As described above, the control unit 110 determines the strength of static elimination according to the thickness of the charge transport layer 213b.

  As described above, image unevenness caused by the toner remaining on the photosensitive drum 211, that is, ghost, is more likely to occur as the thickness of the charge transport layer 213b increases. The control unit 110 performs the process according to the procedure of FIG. 8, and performs static elimination by irradiating with strong light during a period in which a ghost is likely to occur. In this case, the relationship between the static elimination potential (that is, V3a, V3b, V3c) in each period with different static elimination conditions and the potential V0 of the charging device 214 is based on the relationship between the static elimination intensity and the static elimination potential described above, V3a> V3b> V3c. > V0, and when the potential difference between the surface 213a and the charging device 214 is compared, V3a-V0> V3b-V0> V3c-V0. That is, the potential difference gradually decreases from a period in which the thickness of the charge transport layer 213b is large to a period in which the charge transport layer 213b is small, and discharge is less likely to occur. Accordingly, the polymer main chain of the charge transport layer 213b is less likely to be broken, the strength of the charge transport layer 213b is improved, and wear of the surface 213a is reduced. That is, both the degree of ghost suppression and the degree of wear of the charge transport layer 213b change in stages. According to the second embodiment described above, the change in the degree becomes gentler as the level of the charge removal condition is increased.

[Summary of first and second embodiments]
In any of the embodiments described above, the control unit 110 specifies the thickness of the charge transport layer 213b in step S150 of FIG. The control unit 110 is an example of the “specifying unit” according to the present invention.

  In the second embodiment described above, the control unit 110 controls the static eliminator 216, so that the surface 213a of the photosensitive layer 213 is neutralized with the strength corresponding to the specified thickness of the charge transport layer 213b. On the other hand, in the first embodiment described above, when the thickness of the specified charge transport layer 213b is equal to or greater than the threshold value by the control unit 110 controlling the static eliminator 216, the surface 213a has such an intensity that becomes the static elimination potential V3. If neutralization was performed and this thickness was less than the threshold value, neutralization itself was not performed. In the latter case, the static elimination is performed with the static elimination intensity as referred to in the second embodiment being zero. In other words, in any of the embodiments, the control unit 110 and the static eliminator 216 cooperate to function as a static eliminator that neutralizes the surface 213a of the photosensitive layer 213 with the strength corresponding to the thickness specified in step S150. ing. In any of the above-described embodiments, the static eliminator has a specified thickness smaller than the first thickness as compared with a case where the specified thickness is a certain thickness (first thickness). In the case of the thickness (second thickness), static elimination is performed with a small strength.

In the first and second embodiments described above, the storage unit 130 has a wear rate in which a combination of a use environment and a charge removal condition is associated with a wear rate determined as a wear rate in the case where charge removal is performed in the combination. The table was remembered. As described above, the static elimination condition includes the first static elimination condition for eliminating static electricity at a certain intensity (first intensity) when the specified thickness is the first thickness, and the specified thickness. In the case of the second thickness, the second neutralization condition for neutralizing with a weaker strength (second strength) than the first strength is included.
As described above, the charge removal unit removes the charge, and in any of the above embodiments, the wear of the charge transport layer 213b is reduced in the electrophotographic image forming apparatus 10 that performs the charge removal.

[Modification]
The first and second embodiments described above are merely examples of the present invention, and various modifications may be made as follows. Moreover, you may combine each embodiment mentioned above and each following modification as needed.

(Modification 1)
In each of the above-described embodiments, the static eliminator 216 radiates light to eliminate static electricity. However, it may be neutralized by other methods. For example, a so-called scorotron type corona discharger in which a grid electrode is disposed may be applied to perform charge removal by corona discharge, or may be performed by bringing a brush or the like that is a conductor into contact with the surface 213a. Also in this case, it is only necessary to remove the electric charge that reaches the surface 213a when the next image described above is formed by the static elimination of the static eliminator. Desirably, the strength of static elimination changes under the control of the control unit 110.

(Modification 2)
In the second embodiment described above, the above-described static elimination means (the control unit 110 and the static elimination device 216) performed static elimination with the strength corresponding to the thickness of the charge transport layer 213b. In addition to this, You may perform static elimination after changing the intensity | strength of static elimination according to a use environment. For example, in the usage environments A, B, and C shown in FIG. 5, ghosts are likely to occur in the order of the usage environments B, A, and C. In this case, the storage unit 130 stores each usage environment in association with the degree of ghosting in the usage environment. Then, in step S120a in FIG. 8, the control unit 110 refers to the degree of ghosting in the usage environment determined in step S110, and performs static elimination processing by changing the intensity according to the degree.

  For example, when the control unit 110 determines in step S120a that the use environment B is less likely to cause ghosts than other use environments, the control unit 110 increases the intensity of light irradiated to the static eliminator 216 (if level b). If it is determined that the usage environment C is more likely to generate ghosts than other usage environments, the light intensity is reduced by one level (if the level is b, the level is c). In this case, the static elimination means is determined in advance as an environment in which the determined usage environment is less likely to cause ghosting than the first environment, compared to when the determined usage environment is a certain usage environment (first environment). When the environment is a second environment (second environment), the static electricity may be removed at a reduced strength. Thereby, compared with the case where the controller 110 does not perform static elimination as described above, in the first environment in which ghosts are relatively likely to occur, the occurrence of ghosts is suppressed, and ghosts are relatively unlikely to occur. In the environment, wear of the charge transport layer 213b is reduced.

  Note that the charge removal layer 213b is an environment in which the determined use environment is less likely to wear the charge transport layer 213b than the third environment than when the determined use environment is a certain use environment (third environment). When the fourth environment is determined in advance, the static electricity may be removed by increasing the strength. Accordingly, in the third environment in which the charge transport layer 213b is relatively easily worn as compared with the case where the controller 110 does not perform static elimination as described above, the wear of the charge transport layer 213b is reduced and the charge transport layer 213b is reduced. In the fourth environment where the wear is relatively difficult to wear, the occurrence of ghost is suppressed.

(Modification 3)
In each embodiment described above, the control unit 110 calculates the wear amount of the charge transport layer 213b using the use environment, the charge removal condition, and the charged state rotational speed. For example, the control unit 110 uses the use environment and the charged state rotational speed. It may be calculated or may be calculated using the charging condition and the charged state rotation speed. In these cases, the storage unit 130 stores a wear rate table in which the use environment and the wear rate are associated, or a wear rate table in which the charging condition is associated with the wear rate. Then, in step S150 of FIG. 7, the control unit 110 refers to any wear rate table stored in the storage unit 130, and 1000 minutes of the wear rate associated with the use environment or the charge removal condition determined in step S110. A value obtained by multiplying the thickness of 1 by the rotation speed of the charged state is calculated as the wear amount. Subsequently, the control unit 110 specifies a value obtained by subtracting the calculated wear amount from the above-described initial thickness as the thickness of the charge transport layer 213b.

  Further, the control unit 110 may calculate the wear amount from the charged state rotational speed. In this case, the storage unit 130 stores the wear rate on the photosensitive drum 211. Then, in step S150 of FIG. 7, the control unit 110 calculates a value obtained by multiplying the thickness of 1/1000 of the wear rate stored in the storage unit 130 by the charged state rotation speed as the wear amount. Subsequently, the control unit 110 specifies a value obtained by subtracting the calculated wear amount from the initial thickness as the thickness of the charge transport layer 213b.

  As described above, the control unit 110 may calculate the wear amount in the period according to the charge state rotation speed measured in a certain period and specify the thickness of the charge transport layer 213b. At that time, as the number of charged state rotation speeds used for the calculation, or the usage environment and the charge removal conditions are increased, the accuracy of the thickness of the specified charge transport layer 213b increases.

(Modification 4)
In each of the embodiments described above, the controller 110 calculates the wear amount as described above and specifies the thickness of the charge transport layer 213b. However, the control unit 110 specifies the thickness using the measurement result of the measuring device that measures the thickness. Also good. For example, in FIG. 3, the measuring device 219 is indicated by a broken line. The measurement device 219 is an optical sensor, and measures the thickness of the charge transport layer 213b based on the pitch of interference fringes of light reflected by the surface 213a of the photosensitive layer 213. The measuring device 219 supplies data indicating the measurement result to the control unit 110. The control unit 110 specifies the value of the measurement result represented by the supplied data as the thickness of the charge transport layer 213b. The measuring device 219 is not limited to optically measuring this thickness, but may be an electrical measuring device. In this case, the control unit 110 and the measuring device 219 cooperate to function as the “specifying unit” according to the present invention. According to this modification, the accuracy of the specified thickness is higher than when the thickness is specified by calculating the wear amount of the charge transport layer 213b.

  In addition, it is included in specifying thickness if the control part 110 specifies the physical quantity corresponding to this thickness, or the physical quantity which changes according to this thickness. As these physical quantities, for example, the amount of wear of the charge transport layer 213b (the thickness decreases as the amount of wear increases) or the charge state rotational speed of the photosensitive drum 211 (the thickness increases as the charged state rotational speed increases). Less). That is, the controller 110 specifying the wear amount and the charged state rotational speed is also included in specifying the thickness of the charge transport layer 213b.

(Modification 5)
In each embodiment described above, three usage environments A, B, and C are used as usage environments. However, the usage environment is not limited to this, and two or four or more usage environments may be used. Moreover, the value of temperature and the value of humidity may be used as they are as a use environment. In any case, the data supplied from the temperature / humidity meter 120 to the control unit 110, that is, the data acquired by the control unit 110 is environment information indicating the environment (use environment) in which the image forming apparatus 10 is used. Yes. For example, in each of the above-described embodiments, the control unit 110 determines and uses the environment (use environment A, B, C) represented by the data from the temperature value and the humidity value indicated by the data acquired by the control unit 110. ing. Desirably, the control unit 110 may acquire environment information representing the use environment associated with the wear rate from the thermohygrometer 120, and the more the number of use environments associated with the wear rate, the greater the number of use environments. Therefore, the accuracy of the thickness of the charge transport layer 213b increases. Moreover, in the modification 2 mentioned above, the control part 110 is good to acquire the environment information showing the use environment matched with the degree of the ease of generation | occurrence | production of a ghost. As described above, the control unit 110 and the temperature / humidity meter 120 cooperate to function as an “acquisition unit” according to the present invention.

(Modification 6)
In each embodiment described above, the control unit 110 stores the use environment, the charge removal condition, and the charge state rotation speed in the storage unit 130 in association with each other in step S200 of FIG. 7, but at this time, in step S150, The wear amount may be calculated so as to be performed, and the calculated wear amount may be stored in the storage unit 130. In this case, in step S150, the control unit 110 calculates the above-described wear amount from the current use environment, the charge removal condition, and the charged state rotation speed, and the calculated wear amount is stored in the storage unit 130. Add to the total amount of wear. The control unit 110 specifies a value obtained by subtracting the wear amount thus obtained from the initial thickness as the thickness of the charge transport layer 213b. As a result, the amount of calculation performed by the control unit 110 is reduced as compared with the case where the wear amount is calculated from the past use environment, the charge removal conditions, and the charged state rotation speed stored in the storage unit 130 in step S150. Processing time is reduced. Therefore, compared to the above case, the timing at which the static elimination condition is determined in step S160 is earlier, for example, the timing at which the static elimination condition is changed from “with static elimination” to “without static elimination” is earlier. From the above, the power consumption of the control unit 110 and the static eliminator 216 is reduced.

(Modification 7)
In each of the above-described embodiments, the control unit 110 uses the thickness (initial thickness) of the charge transport layer 213b at the initial time, that is, the initial time when the charge transport layer 213b is not worn. Although the thickness of the transport layer 213b is specified, the thickness used in this specification is not limited to that at the initial time point. For example, even for the intermediate transfer belt 300 that has already been used, the thickness of the charge transport layer 213b at that time is first measured, and then the thickness is measured when the thickness of the charge transport layer 213b is specified. For example, the amount obtained by subtracting the amount of wear from the measured thickness and subtracting the measured thickness is specified as the thickness of the charge transport layer 213b. In short, the control unit 110 uses the thickness of the charge transport layer 213b at a predetermined time to start specifying the thickness of the charge transport layer 213b, and determines the thickness of the charge transport layer 213b after that time. What is necessary is just to specify.

(Modification 8)
In each embodiment described above, the charging device 214 is a contact-type charger that makes the charging roll contact the surface 213a. However, the charging device 214 may make a brush or the like contact the surface 213a. The charging device 214 may be a non-contact type charger such as a scorotron or a corotron. Even in these cases, since discharge may occur between the charger and the surface 213a, the strength of the charge transport layer 213b may decrease as described above and the wear amount may increase. That is, in the electrophotographic image forming apparatus that performs charge removal according to the present modification, the charge transport layer 213b has a structure that does not have a structure for charge removal as described in the above embodiments or modifications. Wear will be reduced.

(Modification 9)
The present invention is not limited to an image forming apparatus, but includes a control device (a control unit 110 is an example) and a charge removal device (a control unit 110 and a charge removal device 216 are examples) included in the image forming apparatus, and a method for realizing them. It can also be understood as a program for causing a computer to realize a function executed by a control device. Such a program may be provided in the form of a recording medium such as an optical disk storing the program, or may be provided in the form of being downloaded to a computer via a communication line such as the Internet, and installed and used. Is.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 110 ... Control part, 120 ... Thermohygrometer, 130 ... Memory | storage part, 200 ... Image forming part, 210 ... Image forming unit, 211 ... Photosensitive drum, 212 ... Base | substrate, 213 ... Photosensitive layer, 213a ... surface, 213b ... charge transport layer, 213c ... charge generation layer, 214 ... charging device, 215 ... cleaning blade, 216 ... static discharge device, 217 ... rotation detection device, 218 ... voltage application unit, 219 ... measurement device, 220 ... exposure 230, developing device, 240 ... intermediate transfer belt, 241, 242 ... rotating roll, 250 ... primary transfer roll, 261 ... secondary transfer roll, 262 ... backup roll, 270 ... transport roll, 280 ... fixing device

Claims (2)

A photoreceptor having a charge transport layer on the surface for transporting charges generated by exposure; and
Charging means for charging the surface of the photoreceptor;
Exposure means for exposing the surface charged by the charging means to form an electrostatic latent image;
Developing means for supplying toner to the electrostatic latent image formed by the exposure means to develop the electrostatic latent image, and forming a toner image on the surface;
Transfer means for transferring the toner image formed by the developing means from the surface to a medium;
Neutralizing means for neutralizing the surface after the toner image is transferred by the transfer means;
A first charge removal condition for the charge removal means to remove the surface with a first intensity, and a second charge removal condition for the charge removal means to remove the surface with a second intensity that is weaker than the first intensity. On the other hand, a wear rate representing the amount of wear of the charge transport layer per rotation of the photoreceptor, which is determined so that the second charge removal condition is smaller than the first charge removal condition, is stored. Storage means;
Measuring means for measuring the number of rotations of the photoreceptor during a charging period in which the charging means charges the surface;
A means for identifying the thickness of the charge transport layer , wherein the charge removal means removes charges under the first charge removal condition during the charging period; A value obtained by multiplying the wear rate determined for the first charge removal condition by the number of revolutions measured by the measuring means during the charging period is calculated as the wear amount of the charge transport layer during the charging period. In the case where the charge removal means removes electricity under the second charge removal condition during the charging period, the wear rate stored in the storage means is determined for the second charge removal condition. A value obtained by multiplying the wear rate by the number of revolutions measured by the measuring means during the charging period is calculated as the amount of wear of the charge transport layer during the charge period, and the charge transport layer A value obtained by subtracting the total amount of wear calculated in the charging period after the time point from the thickness of the charge transport layer at a predetermined time point at which the specification of the thickness is started is obtained. Specific means to identify as thickness and
With
When the thickness specified by the specifying means is a second thickness smaller than the first thickness , the charge eliminating means is the first thickness specified by the specifying means. than, you neutralization with a small intensity
An image forming apparatus comprising and this. A photoreceptor having a charge transport layer on the surface for transporting charges generated by exposure; and
Charging means for charging the surface of the photoreceptor;
Exposure means for exposing the surface charged by the charging means to form an electrostatic latent image;
Developing means for supplying toner to the electrostatic latent image formed by the exposure means to develop the electrostatic latent image, and forming a toner image on the surface;
Transfer means for transferring the toner image formed by the developing means from the surface to a medium;
Neutralizing means for neutralizing the surface after the toner image is transferred by the transfer means;
The environment in which the apparatus is used, the first static elimination condition for the static elimination means to neutralize the surface with a first intensity, and the static elimination means to neutralize the surface with a second intensity that is weaker than the first intensity. Storage means for storing a wear rate representing a wear amount of the charge transport layer per one rotation of the photoreceptor, which is determined according to a combination with the second charge removal condition to be performed;
Measuring means for measuring the number of rotations of the photoreceptor during a charging period in which the charging means charges the surface;
Acquisition means for acquiring environment information representing an environment in which the device is used in the charging period;
A means for identifying the thickness of the charge transport layer, wherein the charge removal means removes charges under the first charge removal condition during the charging period; The wear rate determined according to the environment represented by the environmental information acquired by the acquisition unit during the charging period and the first static elimination condition is multiplied by the number of revolutions measured by the measurement unit during the charging period. Value is calculated as the wear amount of the charge transport layer during the charging period, and from the thickness of the charge transport layer at a predetermined time point when the specification of the thickness of the charge transport layer is started, than the time point. A value obtained by subtracting the total amount of wear calculated in the subsequent charging period is specified as the thickness of the charge transport layer, or in the charging period, the charge removal unit performs the second charge removal condition. In the case of neutralizing, the wear determined according to the environment represented by the environmental information acquired by the acquisition unit during the charging period and the second neutralization condition among the wear rates stored in the storage unit. A value obtained by multiplying the rate by the number of rotations measured by the measuring means in the charging period is calculated as the amount of wear of the charge transport layer in the charge period, and from the thickness of the charge transport layer at the time point, Specifying means for specifying a value obtained by subtracting the total amount of wear calculated in the charging period after the time as the thickness of the charge transport layer;
With
When the thickness specified by the specifying means is a second thickness smaller than the first thickness, the charge eliminating means is the first thickness specified by the specifying means. Eliminate static electricity with less strength than usual
An image forming apparatus.

Images