JP6680232B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method.

  In an electrophotographic image forming apparatus, after an electrostatic latent image is formed on a charged photoconductor, the toner image on the photoconductor developed with toner is transferred to a sheet, and the charge remaining on the photoconductor is reduced. Removed by static eliminator. As an example of the static eliminator, a configuration is known in which a grounded static eliminator is brought into contact with a photoconductor to remove charges from the photoconductor (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 01-154186

  By the way, in the structure in which the charge eliminating member is in contact with the photoconductor, the external additive contained in the toner may adhere to the charge eliminating member. Here, when the amount of the external additive attached to the charge eliminating member increases, the contact resistance between the photoconductor and the charge eliminating member increases, and the charge eliminating performance of the charge eliminating member decreases.

  An object of the present invention is to provide an image forming apparatus and an image forming method capable of suppressing deterioration of the charge removal performance of a charge removing member.

  An image forming apparatus according to one aspect of the present invention includes a photoconductor, a charge eliminating member, and a speed changing unit. The charge removing member is electrically grounded and is rotatably arranged in contact with the surface of the photoconductor. The speed changing unit increases the difference between the linear speed of the photoconductor and the linear speed of the charge eliminating member in accordance with an increase in the cumulative value of the consumption amount of the developer acquired based on a preset acquisition condition. Let

  An image forming method according to another aspect of the present invention is performed by an image forming apparatus including a photoconductor and a charge removing member that is electrically grounded and is rotatably arranged in contact with the surface of the photoconductor. The following acquisition step and speed change step are included. In the acquisition step, the cumulative value of the consumption amount of the developer is acquired based on the acquisition condition set in advance. In the speed changing step, the difference between the linear speed of the photoconductor and the linear speed of the charge eliminating member increases in accordance with the increase in the cumulative value of the consumption amount of the developer acquired in the acquiring step.

  According to the present invention, there are provided an image forming apparatus and an image forming method capable of suppressing the deterioration of the charge removing performance of the charge removing member.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention. FIG. 3 is a diagram for explaining a main part of an image forming unit of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram showing an equivalent circuit for explaining electrical characteristics between a photoconductor and a charge eliminating member of an image forming unit of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 6 is a diagram showing an example of a result of Cole-Cole plot of the charge eliminating member of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a diagram showing an example of an experimental device used to obtain the result of Cole-Cole plot of the charge eliminating member of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a diagram showing an example of an experimental device used to obtain the result of Cole-Cole plot of the charge eliminating member of the image forming apparatus according to the first exemplary embodiment of the present invention. It is a figure which shows an Example and a comparative example. FIG. 3 is a diagram showing the relationship between the ratio of the linear velocity of the static elimination member to the linear velocity of the photoconductor of the image forming apparatus according to the first exemplary embodiment of the present invention and the potential after static elimination. It is a figure which shows the structure of the brush bristles of the static elimination member of the image forming apparatus which concerns on 1st Embodiment of this invention. FIG. 1 is a block diagram showing a system configuration of an image forming apparatus according to a first exemplary embodiment of the present invention. 6 is a flowchart showing an example of a first speed changing process executed by the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the ratio of the linear velocity of the static elimination member to the linear velocity of the photoconductor of the image forming apparatus according to the first exemplary embodiment of the present invention and the potential after static elimination. FIG. 6 is a diagram for explaining a main part of an image forming unit of an image forming apparatus according to a second embodiment of the present invention. It is a block diagram showing a system configuration of an image forming apparatus according to a second embodiment of the present invention. 9 is a flowchart showing an example of a contact pressure changing process executed by the image forming apparatus according to the second embodiment of the present invention. It is a block diagram showing a system configuration of an image forming apparatus according to a third embodiment of the present invention. 9 is a flowchart showing an example of second speed changing processing executed by the image forming apparatus according to the third embodiment of the present invention. It is a figure which shows the relationship between the cumulative printing rate of the image forming apparatus which concerns on 3rd Embodiment of this invention, and the contact resistance component in the contact impedance of a static elimination member. FIG. 11 is a diagram for explaining a main part of an image forming unit of an image forming apparatus according to a modified example of the third embodiment of the present invention. It is a block diagram showing a system configuration of an image forming apparatus according to a fourth embodiment of the present invention. 11 is a flowchart showing an example of a third speed changing process executed by the image forming apparatus according to the fourth embodiment of the present invention. It is a figure which shows the relationship between the cumulative print number of the image forming apparatus and the outer diameter of the static elimination member which concern on 4th Embodiment of this invention. It is a block diagram which shows the system configuration of the image forming apparatus which concerns on the modification of 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example in which the present invention is embodied and does not limit the technical scope of the present invention.

[First Embodiment]
As shown in FIG. 1, an image forming apparatus 10 according to the first exemplary embodiment of the present invention includes an electrophotographic monochrome including a control unit 1, an image forming unit 2, a paper feeding unit 3, a paper ejecting unit 4, and the like. It is a printer. Other examples of the image forming apparatus according to the present invention include a fax machine, a copy machine, and a multifunction machine. Further, the image forming apparatus according to the present invention is not limited to the monochrome image forming apparatus 10 as described in the first embodiment, but a tandem system or other color printable electronic photograph including an image forming unit corresponding to each color. A system image forming apparatus may be used.

  The control unit 1 includes a CPU, a RAM, a ROM, an EEPROM (registered trademark), and the like, and controls the image forming apparatus 10 by executing various processes by the CPU according to a control program stored in the ROM.

  The image forming unit 2 includes an electrophotographic image forming unit including a photoconductor drum 21, a charging device 22, an optical scanning device 23, a developing device 24, a transfer roller 25, a cleaning member 26, a charge removing member 27, and a fixing device 28. Is. The photoconductor drum 21 is an example of the photoconductor, and a photoconductor belt may be used as the photoconductor instead of the photoconductor drum 21, for example.

  In the image forming apparatus 10, the image forming unit 2 is controlled by the control unit 1 so that an image is formed on a sheet such as a paper sheet supplied from the sheet feeding cassette 31 of the sheet feeding unit 3 ( (Printing process) is executed, and the sheet after the image forming process is discharged to the discharge unit 4.

  Specifically, in the printing process, an electrostatic latent image based on image data is formed on the surface of the photoconductor drum 21 charged by the charging device 22 by scanning the light beam by the optical scanning device 23. Then, the electrostatic latent image formed on the surface of the photoconductor drum 21 is developed with toner by the developing device 24, and then transferred onto the sheet by the transfer roller 25.

  Then, the toner transferred to the sheet is fused and fixed on the sheet by the fixing device 28. The toner remaining on the surface of the photosensitive drum 21 is cleaned by the cleaning member 26. Further, the electric charge remaining on the photoconductor drum 21 is removed by the charge removing member 27 arranged on the downstream side of the cleaning member 26.

  The photoconductor drum 21 is, for example, an organic photoconductor (OPC) having a single layer structure in which a photoconductive layer containing a charge generation material and a charge transport material is formed around an aluminum tube. For example, the charge generating material is a perylene pigment, a tarocyanine pigment, and the like, and the charge transport material is a hydrazone compound, a fluorenone compound, an arylamine compound, and the like.

  In particular, the photoconductor drum 21 is a positively charged single layer organic photoconductor (PSLP: Positive-charged Single Layer Photoconductor) drum having a single-layer structure that is positively charged. It should be noted that the photoconductor drum 21 may be an organic photoconductor having a multilayer structure as another embodiment.

  As shown in FIG. 2, the charging device 22 includes a charging roller 220 (an example of a charging member) that contacts the photosensitive drum 21. A positive DC voltage is applied to the charging roller 220 from the power source 221. As a result, a positive DC voltage is applied from the charging roller 220 to the photoconductor drum 21, and the photoconductor drum 21 is charged to a predetermined charging potential. That is, the charging device 22 according to the present embodiment is not an AC superposition type charging device that superimposes an AC voltage on a DC voltage, but also a non-contact type that charges the photoconductor drum 21 in a non-contact manner like scorotron charging. It is not a charging device. As another embodiment, the charging device 22 may be an AC superposition type charging device or a non-contact type charging device.

  The charge removing member 27 is electrically grounded to the ground. The charge removing member 27 is rotatably supported while being in contact with the surface of the photosensitive drum 21. Specifically, the static elimination member 27 is a brush-shaped roller member formed of a conductive metal material or resin material. As shown in FIG. 2, the static elimination member 27 has a cylindrical base portion 270 and brush bristles 271 having one end fixed to the base portion 270 and the other end in contact with the surface of the photosensitive drum 21. The static elimination member 27 is not limited to the brush shape, and may be a cylindrical (roll-shaped) roller member formed of a conductive metal material or resin material. The resin material is, for example, rubber or sponge.

  By the way, in the configuration in which the charge removing member 27 is in contact with the photoconductor drum 21 as in the image forming apparatus 10, the electrical characteristics such as the internal capacitance of the charge removing member 27 have potential stability and memory image in the photoconductor drum 21. May affect the presence or absence of. However, not only the internal capacitance of the static elimination member 27 but also the contact capacitance of the static elimination member 27 may affect the potential stability and the presence or absence of the memory image.

  Further, in the image forming apparatus 10, the electrical characteristics such as the internal resistance of the static elimination member 27 may affect the static elimination performance. However, not only the internal resistance of the static elimination member 27 but also the contact resistance of the static elimination member 27 may affect the static elimination performance. Specifically, since the photoconductor drum 21 has a high surface resistance value, a lateral charge flow does not occur on the surface of the photoconductor drum 21. Therefore, even if the internal resistance of the charge removing member 27 is small, if the contact resistance with the photoconductor drum 21 is large, the charge on the photoconductor drum 21 cannot be effectively removed.

  In particular, when the contact-type charging device 22 that contacts the photosensitive drum 21 is used as in the first embodiment, compared to a non-contact charging device such as scorotron charging, a VOC (Voltage Organic) is used. Compounds) and the like are suppressed. However, the contact type charging device 22 may be inferior in charging performance to the non-contact type charging device. In addition, the fact that the charging device 22 is a DC voltage application type charging device may also be a factor that hinders the charging performance.

  On the other hand, in the image forming apparatus 10, as described below, the electrostatic characteristics of the charge removing member 27 are configured to satisfy the preset first specific condition, so that the contact capacitance is also taken into consideration. It is possible to improve the potential stability and suppress the occurrence of a memory image. In addition, as described below, since the electric characteristics of the static elimination member 27 are configured to satisfy the preset second specific condition, the static elimination performance is improved in consideration of the contact resistance of the static elimination member 27. It is possible.

  First, as shown in FIG. 3, in the equivalent circuit 5 showing the electric characteristics between the photoconductor drum 21 and the charge removing member 27 of the image forming unit 2, the resistor 51 corresponding to the DC resistance value R1 of the photoconductor drum 21 is used. A capacitor 52 corresponding to the electrostatic capacity C1 of the photosensitive drum 21 and a resistor 53 corresponding to the DC resistance value R2 of the charge removing member 27 are connected in parallel.

  Generally, in the equivalent circuit 5, it is considered that the lower the DC resistance value R2 of the static elimination member 27, the higher the static elimination performance of the photosensitive drum 21 by the static elimination member 27. However, in practice, it was found that not only the DC resistance value R2 of the static elimination member 27, but also the contact resistance of the static elimination member 27 with the photoconductor drum 21 influences the static elimination performance.

  On the other hand, as shown in FIG. 4, with respect to the static elimination member 27, the internal impedance Z1 and the contact impedance Z2 of the static elimination member 27 are measured by the AC impedance method for a preset frequency range such as 0.05 Hz or more and 100 kHz or less. Is measured, a Cole-Cole plot is obtained. Thereby, the internal resistance component Ra and the internal capacitance component Ca in the internal impedance Z1 and the contact resistance component Rb and the contact capacitance component Cb in the contact impedance Z2 can be calculated. Here, as shown in FIG. 4, in the Cole-Cole plot, the plots corresponding to the internal impedance Z1 and the contact impedance Z2 each draw a semi-circle, but they may have an arc shape such as a semi-elliptical shape. .

  In the first embodiment, the resistance between the cored bar of the photosensitive drum 21 and the photosensitive layer is negligible. Further, the DC resistance value R1 of the photoconductor drum 21 is much larger than the DC resistance value R2 of the charge eliminating member 27. Therefore, it can be considered that the combined resistance R3 of the photosensitive drum 21 and the static elimination member 27 is the same as the DC resistance value R2 of the static elimination member 27.

  Here, a static elimination time in which each region of the photoconductor drum 21 is in contact with the static elimination member 27 is t, and a post-static elimination potential that is predetermined as a target value of the surface potential of the photoconductor drum 21 after the static elimination time t has elapsed. Let V1 be V0, the pre-charge removal potential of the photoconductor drum 21 at the start of charge removal by the charge removal member 27, and C be the electrostatic capacitance of the photoconductor drum 21. In this case, the value of the DC resistance value R2 of the theoretical static elimination member 27 capable of eliminating the surface potential of the photosensitive drum 21 from the pre-elimination potential V0 to the post-elimination potential V1 at the static elimination time t (hereinafter, "calculated resistance"). The value R21 ”is calculated based on the following equation (1). When the linear velocity (surface velocity) of the photoconductor drum 21 is S and the contact width between the photoconductor drum 21 and the static elimination member 27 in the rotation direction of the photoconductor drum 21 is L, the static elimination time t is L / S. It can be calculated.

  However, as described above, the static elimination performance of the static elimination member 27 is also affected by the contact impedance of the static elimination member 27 with the photoconductor drum 21. Therefore, in the image forming apparatus 10, the charge removing member 27 is configured so that the conditions of the following formulas (2) and (3) (the second specific condition) are satisfied.

  That is, in the image forming apparatus 10, the internal resistance component Ra of the static elimination member 27 is calculated by the formula (2), and the calculated resistance value R21 of the static elimination member 27 is changed to the static elimination member 27 corresponding to the linear velocity of the photosensitive drum 21. Is less than or equal to the value obtained by multiplying by the first specific value calculated based on the linear velocity ratio Sr. Further, in the image forming apparatus 10, the contact resistance component Rb of the static eliminating member 27 is the second specified value calculated based on the ratio Sr to the calculated resistance value R21 of the static eliminating member 27, as shown in the equation (3). It is less than or equal to the value multiplied by the value.

  As described above, in the image forming apparatus 10, since the electric characteristics of the static elimination member 27 are determined in consideration of not only the DC resistance value R2 of the static elimination member 27 but also the internal resistance component Ra and the contact resistance component Rb, static elimination is performed. The charge removal performance of the member 27 can be improved. On the other hand, the actual DC resistance value R2 of the static elimination member 27 may be a value equal to or less than the calculated resistance value R21 or a value larger than the calculated resistance value R21.

  Specifically, the internal resistance component Ra and the contact resistance component Rb of the static elimination member 27 are calculated resistance value R21 capable of static elimination to the potential V1 after static elimination at the static elimination time t and the line of the static elimination member 27 with respect to the linear velocity of the photosensitive drum 21. When the values are equal to or less than the values specified based on the speed ratio Sr, the static elimination performance of the static elimination member 27 is improved. Note that the first specific value and the second specific value are not limited to the above-described values as long as the same effect is produced.

  For example, in the image forming apparatus 10, as shown in FIG. 9, the brush bristles 271 of the charge removing member 27 have a core portion 271A and a surface layer portion 271B. Here, FIG. 9 is a cross-sectional view of one brush bristle 271. The core portion 271A is made of resin. The surface layer portion 271B is made of carbon and covers the surface of the core portion 271A. For example, the surface layer portion 271B is formed together with the core portion 271A when manufacturing the brush bristles 271. The surface layer portion 271B may be formed by spraying carbon on the surface of the core portion 271A after the core portion 271A is formed. As a result, the internal resistance component Ra and the contact resistance component Rb of the static elimination member 27 can be reduced while maintaining the strength of the brush bristles 271 as compared with a configuration in which the brush bristles 271 are formed only of a resin layer containing carbon. Is possible. The surface layer portion 271B may include a component other than carbon within a range in which the static elimination member 27 satisfies the above formulas (2) and (3). Further, the core portion 271A may include carbon. Further, the brush bristles 271 may be formed only by the resin layer containing carbon.

  Further, in the image forming apparatus 10, the charge removing member 27 rotates by receiving the rotation driving force supplied from the first driving unit 272 (see FIG. 10) such as a motor. For example, the charge removing member 27 rotates at a higher linear velocity than the photoconductor drum 21. The charge removing member 27 may rotate at the same linear velocity as the photosensitive drum 21 or at a linear velocity slower than that of the photosensitive drum 21. Further, the charge removing member 27 may be driven and rotated by the photoconductor drum 21 at a speed obtained by multiplying the linear velocity of the photoconductor drum 21 by a predetermined ratio.

  As described above, the contact impedance of the charge removing member 27 with the photosensitive drum 21 also affects the potential stability of the photosensitive drum 21 and the presence or absence of the image memory. In the image forming apparatus 10, the charge removing member 27 is configured so that the conditions (the first specific condition) of the following formulas (4) and (5) are also satisfied.

  Ca ≦ 1.0E + 05 (4)

  0 ≦ Cb / Ca ≦ 0.4 (5)

  That is, in the image forming apparatus 10, the internal capacitance component Ca of the charge removing member 27 is 1.0E + 05 or less, which is an example of the fourth predetermined value, which is determined in advance, as shown in the expression (4). Further, in the image forming apparatus 10, as shown in the above formula (5), the electrostatic capacitance ratio (Cb / Ca) which is a value obtained by dividing the contact electrostatic capacitance component Cb of the charge removing member 27 by the internal electrostatic capacitance component Ca. ) Is 0.4 or less, which is an example of a predetermined third specific value.

  As described above, in the image forming apparatus 10, since the electric characteristics of the charge removing member 27 are determined in consideration of the internal capacitance component Ca and the contact capacitance component Cb of the charge removing member 27, the photoconductor drum 21. It is possible to improve the potential stability of and to suppress the generation of image memory. Specifically, the internal capacitance component Ca is determined so that the charges accumulated in the static elimination member 27 are reduced, and the ratio of the contact capacitance component Cb to the internal capacitance component Ca is small, so that the static elimination member is Since the electric charge is easily discharged from 27, the potential stability is improved and the generation of the image memory is suppressed. Note that the third specific value and the fourth specific value are not limited to the values described above as long as the same effect is produced.

[Example]
Hereinafter, the measurement results of the image forming apparatus 10 will be described with reference to FIGS. 5 to 8.

  5 and 6 are diagrams showing an experimental apparatus 90 for measuring the internal resistance component Ra, the contact resistance component Rb, the internal capacitance component Ca, and the contact capacitance component Cb of the static elimination member 27. The experimental apparatus 90 is provided with two stainless steel SUS rollers 91 and 92 each having a diameter of 18 mm and arranged horizontally at a distance of 4 mm. An aluminum film electrode 93 (horizontal length 150 mm) is suspended between the SUS roller 91 and the SUS roller 92. Then, the static eliminating members 27 according to the comparative examples 1 to 15 and the examples 1 to 5 which are the experimental objects are arranged so as to contact the upper surface of the film electrode 93.

  Further, the experimental device 90 includes a SUS roller 95 having a diameter of 30 mm, which is arranged above the charge removing member 27. A weight of 1 kg is applied to the SUS roller 95 downward, and the load is applied to the static elimination member 27 via the SUS roller 95. The static eliminating member 27 and the SUS rollers 91, 92, and 95 are tested in a state where they are not rotated. The two SUS rollers 91 and 92 are connected to one electrode of an impedance measuring instrument 97 (LCR high tester 3522 manufactured by Hioki Electric Co., Ltd.), and the base portion 270 of the static eliminating member 27 is the other of the impedance measuring instrument 97. Is connected to the electrode of, and impedance measurement is performed by the impedance measuring device 97 in this state. In this experiment, a sinusoidal AC voltage having a voltage value of 5.0 V is applied across the electrodes of the impedance measuring instrument 97. Then, while changing the frequency of the applied AC voltage in the range of 0.05 Hz to 100 kHz, the internal resistance component Ra, the contact resistance component Rb, the internal capacitance component Ca, and the contact capacitance component of the static elimination member 27. Measure Cb. The measurement was performed a plurality of times (2 to 16 times), and the experimental results are shown in the table of FIG. 7 based on the average value of the measured values.

  Further, in FIG. 7, the printing process is executed by the image forming apparatus 10 equipped with the static elimination member 27 of each example shown in FIG. 7, and the static elimination performance of the photosensitive drum 21 by the static elimination member 27, the potential stability, and the image. The evaluation results of the presence / absence of memory are shown.

  Here, with respect to the charge removal performance, it was evaluated whether or not the potential of the photoconductor drum 21 was removed to a desired post-charge removal potential V1 after the charge removal member 27 in the image forming apparatus 10 was removed. . In FIG. 7, “O” is shown as the evaluation result of the charge removal performance when the charge is removed up to the desired post-charge removal potential V1, and “X” is shown when the charge is not removed below the desired post-charge removal potential V1.

  Regarding the potential stability, as a result of measuring the surface potential of the photosensitive drum 21 after being charged by the charging device 22 after performing continuous printing for 60 minutes in the image forming apparatus 10, before starting the continuous printing. It was evaluated whether the initial surface potential after being charged by the charging device 22 decreased by 10% or more. In FIG. 7, when the initial surface potential is not reduced by 10% or more, “◯” is shown, and when the initial surface potential is reduced by 10% or more, “x” is shown as the potential stability evaluation result. If the initial surface potential is reduced by 10% or more, problems such as fog may occur. Therefore, the value of 10% is used here.

  Regarding the presence / absence of the image memory, the image forming apparatus 10 forms a black patch of a predetermined shape on the front end of the printing paper by the printing process and prints a half image (gray image) on the other area after that. The presence or absence of image memory was visually evaluated. Specifically, it is determined that the image memory is generated when the shape of the black patch appears in the half image area. In FIG. 7, when the image memory is not generated, “◯” is shown, and when the image memory is generated, “x” is shown as the evaluation result of the presence or absence of the image memory.

  More specifically, the image forming apparatus 10 used in the experiment is a modified machine of the printer “FS-1320DN” manufactured by Kyocera Document Solutions Co., Ltd. Further, in the image forming apparatus 10, the pre-electrification potential V0 of the photoconductor drum 21 is 500 [V], the surface velocity (linear velocity) S of the photoconductor drum 21 is 0.15 [m / s], and the contact width L is 0. It is 0.005 [m]. Further, the dielectric constant ε0 of vacuum is 8.9E-12 [F / m], the relative dielectric constant εr of the photosensitive drum 21 is 3.5, and the film thickness d of the photosensitive drum 21 is 3.5E-05 [m]. Is. In this case, the electrostatic capacitance value C of the photoconductor drum 21 is 8.85E-07 [F] from “ε0 × εr / d”.

  Then, the post-electrification potential V1 which is a desired potential after the static elimination of the photoconductor drum 21 by the static elimination member 27 is set to 100V. In this case, the calculated resistance value R21 of the static elimination member 27 is calculated as 2.34E + 04 [Ω] by the above equation (1). The post-static charge potential V1 may be a value calculated by an arithmetic expression such as V1 = V0 × 0.2, or an arithmetic expression such as V1 = V0 × 0.22 + 80 in order to provide a margin. It may be a value calculated by a formula.

  Here, in Comparative Examples 1 to 13 and Examples 1 to 3, the surface velocity (linear velocity) of the charge removing member 27 was set to 0.15 [m / s], which is the same as the linear velocity S of the photosensitive drum 21. Therefore, in Comparative Examples 1 to 13 and Examples 1 to 3, when the internal resistance component Ra of the static elimination member 27 is 7.02E + 04 [Ω] or less, which is three times the calculated resistance value R21, the above formula (2) is used. Will be met. Further, when the contact resistance component Rb of the static elimination member 27 is equal to or less than 2.81E + 04 [Ω] which is 1.2 times the calculated resistance value R21, the above formula (3) is satisfied.

  On the other hand, in Comparative Examples 14 to 15 and Examples 4 to 5, the linear velocity of the charge removing member 27 was set to be higher than the linear velocity S of the photosensitive drum 21.

  Specifically, in Comparative Example 14, the linear velocity of the charge removing member 27 was set to 0.24 [m / s], which is 1.6 times the linear velocity S of the photosensitive drum 21. Therefore, in Comparative Example 14, the above expression (2) is satisfied when the internal resistance component Ra of the static elimination member 27 is not more than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21. When the contact resistance component Rb of the static elimination member 27 is equal to or less than 6.01E + 04 [Ω], which is 2.57 times the calculated resistance value R21, the above formula (3) is satisfied.

  Further, in Comparative Example 15, the linear velocity of the charge removing member 27 was set to 0.165 [m / s], which is 1.1 times the linear velocity S of the photosensitive drum 21. Therefore, in Comparative Example 15, the above expression (2) is satisfied when the internal resistance component Ra of the static elimination member 27 is not more than 8.35E + 04 [Ω], which is 3.57 times the calculated resistance value R21. Further, when the contact resistance component Rb of the static elimination member 27 is equal to or less than 3.35E + 04 [Ω] which is 1.43 times the calculated resistance value R21, the above expression (3) is satisfied.

  In Example 4, the linear velocity of the charge removing member 27 was set to 0.24 [m / s], which was 1.6 times the linear velocity S of the photosensitive drum 21. Therefore, in the fourth embodiment, the above expression (2) is satisfied when the internal resistance component Ra of the static elimination member 27 is not more than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21. When the contact resistance component Rb of the static elimination member 27 is equal to or less than 6.01E + 04 [Ω], which is 2.57 times the calculated resistance value R21, the above formula (3) is satisfied.

  Further, in the fifth embodiment, the linear velocity of the charge eliminating member 27 is set to 0.255 [m / s], which is 1.7 times the linear velocity S of the photosensitive drum 21. Therefore, in the fifth embodiment, the formula (2) is satisfied when the internal resistance component Ra of the static elimination member 27 is equal to or less than 1.64E + 05 [Ω], which is 6.99 times the calculated resistance value R21. Further, when the contact resistance component Rb of the static elimination member 27 is equal to or less than 6.55E + 04 [Ω], which is 2.80 times the calculated resistance value R21, the above expression (3) is satisfied.

In Comparative Example 1, the static eliminating member 27 was used, in which the brush bristles 271 were raw yarns obtained by subjecting conductive acrylic fibers of SA7 manufactured by Toray Industries, Inc. to cleavage treatment. In the static elimination member 27 according to Comparative Example 1, the yarn resistance is 1.00E + 07 [Ω], the brush fineness is 30 [μm] and high (fiber is thick), and the brush density is 100 [kF / inch ² ]. And has a low density. Comparative Examples 1 to 9 are total dispersion systems in which the carbon state of the fibers is dispersed throughout the raw yarn. That is, in the static elimination member 27 according to Comparative Examples 1 to 9, the brush bristles 271 are formed only of the resin layer containing carbon.

In Comparative Example 2, as in Comparative Example 1, the static elimination member 27, in which the brush bristles 271 were the raw yarn obtained by subjecting the conductive acrylic fiber of SA7 manufactured by Toray Industries, Inc. to the cleavage treatment, was used. The static elimination member 27 according to Comparative Example 2 has a raw yarn resistance of 1.00E + 06 [Ω], a brush fineness of 7 [μm] and low (fine fibers), and a brush density of 500 [kF / inch ² ]. And it is dense.

In Comparative Example 3, the static eliminating member 27 in which the brush bristles 271 are UUN conductive nylon raw yarns manufactured by Unitika Ltd. was used. The static elimination member 27 according to Comparative Example 3 has a raw yarn resistance of 1.00E + 06 [Ω], a brush fineness of 7 [μm] and low (fine fibers), and a brush density of 500 [kF / inch ² ]. And it is dense. The static elimination members 27 according to Comparative Examples 3 to 13 and Examples 1 to 3 have a circular fiber cross-sectional shape.

In Comparative Examples 4 to 6, similarly to Comparative Example 3, the static elimination member 27 in which the brush bristles 271 are the original yarns of UUN conductive nylon made by Unitika Ltd. was used. In the static elimination members 27 according to Comparative Examples 4 to 6, the raw yarn resistances are 1.00E + 05 [Ω], 1.04E + 05 [Ω], and 1.00E + 05 [Ω], respectively. Further, in the static elimination members 27 according to Comparative Examples 4 to 6, the fineness is 7 [μm], 6 [μm], and 6 [μm], respectively. Furthermore, in the static elimination members 27 according to Comparative Examples 4 to 6, the densities are 500 [kF / inch ² ], 550 [kF / inch ² ] and 500 [kF / inch ² ], respectively.

In Comparative Examples 7 to 9, similarly to Comparative Example 3, the static eliminating member 27 in which the brush bristles 271 were UUN conductive nylon raw yarns manufactured by Unitika Ltd. was used. On the other hand, in the static eliminator 27 according to Comparative Examples 7 to 9, the carbon content of the fiber is increased as compared with Comparative Example 3 so that the values of the internal resistance component Ra and the contact resistance component Rb become smaller. In the static elimination members 27 according to Comparative Examples 7 to 9, the raw yarn resistances are 1.00E + 05 [Ω], 1.00E + 04 [Ω], and 1.00E + 05 [Ω], and the brush fineness is 6 [μm] and 7 [μm]. ], 6 [μm] and low (fibers are thin), and the brush density is 550 [kF / inch ² ], 500 [kF / inch ² ], 580 [kF / inch ² ] and high density.

In Example 1, the static elimination member 27 in which the brush bristles 271 are the raw yarns of GBN fiber manufactured by KB Seiren Co., Ltd. was used. In the static elimination member 27 according to Example 1, the yarn resistance is 1.00E + 04 [Ω], the brush fineness is 7 [μm] and low (fine fibers), and the brush density is 500 [kF / inch ² ]. And it is dense. In addition, in the static elimination members 27 according to Examples 1 to 3 and Comparative Examples 10 to 13, the carbon state of the fiber is not a total dispersion system but a two-layer structure in which carbon is present outside the fiber, and the contact resistance component is Rb is decreasing. That is, in the static elimination members 27 according to Examples 1 to 3 and Comparative Examples 10 to 13, the brush bristles 271 have the core portion 271A and the surface layer portion 271B.

  In Comparative Example 10, as in Example 1, the static elimination member 27 in which the brush bristle 271 is the raw yarn of GBN fiber manufactured by KB Seiren Co., Ltd. was used, but the raw yarn resistance was two orders of magnitude higher.

  In Comparative Examples 11 to 13, the static eliminating member 27 in which the brush bristles 271 were yarns in which carbon was sprayed on polyester raw yarns was used. In the static eliminator 27 according to Comparative Examples 11 to 13, carbon is sprayed on the polyester raw yarn so that the values of the internal resistance component Ra and the contact resistance component Rb become small. The amount of carbon sprayed in Comparative Examples 11 to 13 is the same as in Example 3, and the fineness and density of the polyester raw yarn are different from those in Example 3.

In the second embodiment, the static elimination member 27 in which the brush bristles 271 are the polyester yarns is used. In the static elimination member 27 according to Example 2, the yarn resistance is 5.80E + 03 [Ω], the brush fineness is 7 [μm] and low (fibers are thin), and the brush density is 300 [kF / inch ² ]. And it is dense. Further, the static elimination member 27 according to Example 2 has a two-layer structure in which carbon exists on the outside of the fiber as in Example 1, but the carbon particles are directly sprayed on the outside of the fiber. As a result, the electrical characteristics at the same level as in Example 1 are realized with a brush density lower than that in Example 1.

In Example 3, the static eliminating member 27 in which the brush bristles 271 are polyester yarns was used. In the static eliminator 27 according to Example 3, the yarn resistance is 6.40E + 03 [Ω], the brush fineness is 7 [μm] and is low (fine fibers), and the brush density is 300 [kF / inch ² ]. And it is dense. Further, the static elimination member 27 according to Example 3 has a two-layer structure in which carbon exists on the outside of the fiber as in Example 1, but the carbon particles are directly sprayed on the outside of the fiber. The amount of carbon sprayed in Example 3 is smaller than that in Example 2.

  In Comparative Example 14, the same static eliminating member 27 as in Comparative Example 10 was used. Further, in Comparative Example 15, the same static eliminating member 27 as in Comparative Example 13 was used. Moreover, in Example 4, the same static elimination member 27 as that of Comparative Example 5 was used. Moreover, in Example 5, the same static elimination member 27 as that of Comparative Example 6 was used.

  As shown in FIG. 7, in Comparative Examples 1 to 6 and Comparative Example 10, the internal resistance component Ra exceeds 7.02E + 04 [Ω], which is three times the calculated resistance value R21. Is not satisfied. On the other hand, in Comparative Examples 7 to 9 and Comparative Examples 11 to 13, since the internal resistance component Ra is 7.02E + 04 [Ω] or less, which is three times the calculated resistance value R21, the condition of the above formula (2) is satisfied. ing. Further, in Comparative Example 14, the internal resistance component Ra is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, and therefore the condition of the above formula (2) is satisfied. In Comparative Example 15, the internal resistance component Ra is equal to or less than 8.35E + 04 [Ω], which is 3.57 times the calculated resistance value R21, and therefore the condition of the above formula (2) is satisfied. However, in Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 13, since the contact resistance component Rb exceeds 2.81E + 04 [Ω], which is 1.2 times the calculated resistance value R21, the above (3) The condition of the expression is not satisfied. Then, in Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 13, the evaluation result of the static elimination performance was “x”.

  On the other hand, in Examples 1 to 3, the condition of the above formula (2) that the internal resistance component Ra of the static elimination member 27 is 7.02E + 04 [Ω] or less, which is three times the calculated resistance value R21, is satisfied, Further, the condition of the above formula (3) that the contact resistance component Rb is equal to or less than 2.81E + 04 [Ω] which is 1.2 times the calculated resistance value R21 is satisfied. Further, in Example 4, the condition of the above formula (2) that the internal resistance component Ra of the static elimination member 27 is 1.502E + 05 [Ω] or less, which is 6.42 times the calculated resistance value R21, is satisfied, In addition, the condition of the above formula (3) that the contact resistance component Rb is equal to or less than 6.01E + 04 [Ω], which is 2.57 times the calculated resistance value R21, is satisfied. Further, in the fifth embodiment, the condition of the above formula (2) that the internal resistance component Ra of the static elimination member 27 is equal to or less than 1.64E + 05 [Ω] which is 6.99 times the calculated resistance value R21 is satisfied, Further, the condition of the above formula (3) that the contact resistance component Rb is not more than 6.55E + 04 [Ω], which is 2.80 times the calculated resistance value R21, is satisfied. Then, in Examples 1 to 5, the evaluation result of the static elimination performance was “◯”.

  Here, in Comparative Example 5, the evaluation result of the static elimination performance is “x”, whereas in Example 4 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is improved to “◯”. . Further, in Comparative Example 6, the evaluation result of the static elimination performance is “x”, whereas in Example 5 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is improved to “◯”. Similarly, in Comparative Example 10 and Comparative Example 13, the evaluation result of the static elimination performance is “x”, whereas in Comparative Examples 14 and 15 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is It has been improved to "○". From these results, it can be understood that the static elimination performance can be improved by setting the linear velocity of the static elimination member 27 to be higher than the linear velocity S of the photoconductor drum 21. FIG. 8 shows the relationship between the linear velocity of the static elimination member 27 and the post-static elimination potential V1 in the image forming apparatus 10 equipped with the static elimination member 27 according to Comparative Examples 5 to 6, Comparative Example 10, and Comparative Example 13.

  As described above, in the image forming apparatus 10, it has been found that it is possible to obtain a desired static elimination performance by considering not only the DC resistance value R2 of the static elimination member 27 but also the internal impedance Z1 and the contact impedance Z2. . More specifically, when the conditions of the above formulas (2) and (3) are satisfied, the desired static elimination performance was obtained.

  Moreover, as shown in FIG. 7, the internal static electricity of the contact electrostatic capacitance component Cb in the Cole-Cole plot measured using the experimental apparatus 90 about the static elimination member 27 which concerns on the comparative examples 1-15 and Examples 1-5. The capacitance ratio (Cb / Ca) to the capacitance component Ca was calculated. Here, in Comparative Examples 1 to 4, Comparative Examples 8 to 9, Comparative Examples 12 to 13, and Comparative Example 15, since the capacitance ratio (Cb / Ca) exceeds 0.4, the capacitance ratio. The condition of the above formula (5) that (Cb / Ca) is 0 or more and 0.4 or less is not satisfied. On the other hand, in Comparative Examples 5 to 7, Comparative Examples 10 to 11, and Comparative Example 14, since the capacitance ratio (Cb / Ca) is 0.4 or less, the capacitance ratio (Cb / Ca) is 0 or more. The condition of the above formula (5) that it is 0.4 or less is satisfied. However, in Comparative Examples 1 to 3, Comparative Examples 7 to 8 and Comparative Examples 10 to 15, since the internal capacitance component Ca of the static elimination member 27 exceeds 1.0E + 5.0, the internal capacitance component Ca. Is 1.0E + 5.0 or less, the condition of the above formula (4) is not satisfied. Then, with respect to the potential stability and the presence or absence of the image memory, only the evaluation result of the static elimination performance was evaluated as “◯”. Specifically, in Comparative Examples 7 to 9, Comparative Examples 11 to 12, and Comparative Examples 14 to 15 in which the evaluation result of the static elimination performance was “◯”, the evaluation results of the potential stability and the presence or absence of the image memory were “×”. "Met.

  On the other hand, in Examples 1 to 5, the condition of the above formula (4) that the internal capacitance component Ca of the static elimination member 27 is 1.0E + 5.0 or less is satisfied, and the capacitance ratio (Cb The condition of the above formula (5) that / Ca) is 0 or more and 0.4 or less is satisfied. Then, in Examples 1 to 5, the evaluation results of the potential stability and the presence or absence of the image memory were “◯”.

  As described above, in the image forming apparatus 10, by considering not only the DC resistance of the charge removing member 27 but also the internal impedance Z1 and the contact impedance Z2, the potential stability is improved and the occurrence of the image memory is suppressed. all right. More specifically, when the conditions of the expressions (4) and (5) are satisfied, the potential stability is improved and the occurrence of image memory is suppressed.

  By the way, in the image forming apparatus 10, the applied voltage applied to the charging roller 220 that charges the photosensitive drum 21 is changed. Here, in the configuration in which the charge removing member 27 contacts the photoconductor drum 21, when the charge removing performance of the charge removing member 27 is set in accordance with the maximum value of the applied voltage, the wear of the photoconductor drum 21 is promoted. The life of the photosensitive drum 21 may be shortened. On the other hand, in the image forming apparatus 10 according to the first exemplary embodiment of the present invention, as described below, it is possible to suppress the abrasion of the photoconductor drum 21 while ensuring the necessary charge removal performance.

  Specifically, the ROM of the control unit 1 stores in advance a first speed changing program for causing the CPU to execute a later-described first speed changing process (see the flowchart of FIG. 11). The first speed changing program is recorded on a computer-readable recording medium such as a CD, a DVD, or a flash memory, and is read from the recording medium and installed in a storage unit such as the EEPROM of the control unit 1. It may be one.

  And the control part 1 contains the density | concentration detection part 11, the voltage change part 12, and 13 A of 1st speed change parts, as shown in FIG. Specifically, the control unit 1 uses the CPU to execute the first speed changing program stored in the ROM. Thereby, the control unit 1 functions as the concentration detecting unit 11, the voltage changing unit 12, and the first speed changing unit 13A.

  The density detection unit 11 executes a density detection process for detecting the density of a patch image based on predetermined image data formed on the surface of the photoconductor drum 21.

  Specifically, in the image forming apparatus 10, as shown in FIG. 2, on the downstream side of the developing device 24 in the rotation direction of the photosensitive drum 21, and on the upstream side of the transfer roller 25 in the rotation direction, A density sensor 29 is provided. For example, the density sensor 29 is an optical sensor having a light emitting unit and a light receiving unit. In the density sensor 29, the light emitted from the light emitting unit and reflected on the surface of the photosensitive drum 21 is received by the light receiving unit. Then, an electric signal corresponding to the amount of received light is output from the light receiving unit.

  For example, the density detecting unit 11 controls the operation of each unit of the image forming unit 2 to form the patch image on the surface of the photoconductor drum 21 when a predetermined first timing arrives. Then, the density detecting unit 11 detects the density of the patch image using the density sensor 29. For example, the first timing is when the power of the image forming apparatus 10 is turned on, when the sleep state in which some functions of the image forming apparatus 10 are stopped is returned to the normal state, and when the print process is executed.

  The voltage changing unit 12 changes the applied voltage applied from the power source 221 to the charging roller 220.

  Specifically, the voltage changing unit 12 changes the applied voltage based on the density of the patch image detected by the density detecting unit 11. The voltage changing unit 12 changes the developing bias voltage applied to the developing roller provided in the developing device 24 together with the applied voltage.

  For example, in the image forming apparatus 10, the initial setting value of the applied voltage is set to 500V. The voltage changing unit 12 changes the applied voltage from 500V to 800V when the density of the patch image detected by the density detecting unit 11 exceeds a predetermined range and is low. Further, the voltage changing unit 12 changes the applied voltage from 500V to 300V when the density of the patch image exceeds the specific range and is high.

  The image forming apparatus 10 may be provided with a temperature / humidity sensor that detects the temperature and humidity inside the machine. In this case, the voltage changing unit 12 may change the applied voltage based on the detection result of the temperature and humidity inside the machine by the temperature and humidity sensor.

  The first speed changing unit 13A increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge eliminating member 27 as the applied voltage applied to the charging roller 220 is higher.

  Specifically, when the calculated resistance value after changing the applied voltage by the voltage changing unit 12 calculated based on the above formula (1) is R22, the first speed changing unit 13A determines the linear velocity of the static eliminating member 27. , The ratio Sr satisfies the following equations (6) and (7), and is changed to the first specific speed at which the difference from the linear velocity of the photoconductor drum 21 is minimized. The pre-electrification potential V0 in the above equation (1) is acquired by being the same as the applied voltage after being changed by the voltage changing unit 12 or by multiplying the changed applied voltage by a predetermined coefficient.

  For example, in the image forming apparatus 10, the charge removing member 27 rotates at a higher linear velocity than the photoconductor drum 21 as described above. Therefore, the first speed changing unit 13A increases the linear velocity of the static elimination member 27 to increase the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27. When the static elimination member 27 rotates at a linear velocity lower than that of the photoconductor drum 21, the first speed changing unit 13A reduces the linear velocity of the static elimination member 27 to reduce the linear velocity of the photosensitive drum 21 and the static elimination member 27. The difference from the linear velocity may be increased.

  For example, in the image forming apparatus 10, the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R22 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 are stored in advance in the ROM of the control unit 1. There is. The first speed changing unit 13A uses the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R22 stored in the ROM, when the applied voltage is changed by the voltage changing unit 12, and the above-described values are obtained. The linear velocity of the static elimination member 27 satisfying the condition of is calculated. Then, the first speed changing unit 13A changes the linear speed of the static elimination member 27 based on the calculation result.

  The first speed changing unit 13A may change the linear speed of the static eliminator 27 to a speed at which the difference from the first specific speed is equal to or lower than a preset allowable value. The first speed changing unit 13A may change the linear speed of the static eliminator 27 to a speed at which the ratio Sr satisfies the above formula (6) and the above formula (7).

  Further, in the image forming apparatus 10, the first table data indicating the linear velocity of the charge removing member 27 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 may be stored in advance in the ROM of the control unit 1. . In this case, when the voltage changing unit 12 changes the applied voltage, the first speed changing unit 13A may change the linear velocity of the static eliminator 27 using the first table data. For example, the first table data is created based on experimental data obtained by an experiment for investigating the relationship between the ratio Sr corresponding to each pre-elimination potential V0 and the post-elimination potential V1 using the image forming apparatus 10. Here, FIG. 12 shows an example of experimental data obtained by the above experiment.

  Further, the first speed changing unit 13A may change the linear speed of the photosensitive drum 21 to increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removing member 27.

[First speed change process]
Hereinafter, with reference to FIG. 11, an example of a procedure of the first speed changing process executed by the control unit 1 in the image forming apparatus 10 will be described. Here, steps S11, S12, ... Represent numbers of processing procedures (steps) executed by the control unit 1.

<Step S11>
First, in step S11, the control unit 1 determines whether or not the first timing has arrived.

  Here, when the control unit 1 determines that the first timing has arrived (Yes in S11), the control unit 1 shifts the processing to step S12. If the first timing has not arrived (No side of S11), the control unit 1 waits for the arrival of the first timing in step S11.

<Step S12>
In step S12, the control unit 1 executes the density detection process. Here, the processing of step S11 and step S12 is executed by the density detection unit 11 of the control unit 1.

  For example, the control unit 1 controls the operation of each unit of the image forming unit 2 to form the patch image on the surface of the photoconductor drum 21. Then, the control unit 1 uses the density sensor 29 to detect the density of the patch image. In step S12, the controller 1 may detect the temperature and humidity inside the image forming apparatus 10.

<Step S13>
In step S13, the control unit 1 changes the applied voltage based on the density of the patch image detected in step S12. Here, the process of step S13 is executed by the voltage changing unit 12 of the control unit 1.

  For example, when the density of the patch image detected in step S12 is lower than the specific range, the control unit 1 sets the applied voltage stored in the predetermined first storage area of the RAM. The applied voltage is changed to 800V by rewriting the data indicating the value. Further, when the density of the patch image is higher than the specific range, the control unit 1 rewrites the data in the first storage area and changes the applied voltage to 300V. Further, when the density of the patch image is within the specific range, the control unit 1 rewrites the data in the first storage area and changes the applied voltage to 500V.

<Step S14>
In step S14, the control unit 1 changes the linear velocity of the static elimination member 27 according to the applied voltage changed in step S13. Here, the process of step S14 is executed by the first speed changing unit 13A of the control unit 1.

  Specifically, the control unit 1 sets the linear velocity of the charge eliminating member 27 such that the ratio Sr satisfies the above equations (6) and (7) and minimizes the difference from the linear velocity of the photosensitive drum 21. Change to the first specific speed. For example, the control unit 1 changes the linear velocity of the static eliminating member 27 by rewriting the data indicating the set value of the linear velocity of the static eliminating member 27 stored in the predetermined second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the first embodiment, the higher the applied voltage applied to the charging roller 220, the greater the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27. . As a result, it is possible to suppress the abrasion of the photoconductor drum 21 while ensuring the required static elimination performance, as compared with the configuration in which the linear velocity of the static elimination member 27 is set according to the maximum value of the applied voltage. .

  In the image forming apparatus 10 according to the first embodiment, the linear velocity of the charge removing member 27 is different from the linear velocity of the photoconductor drum 21 when the ratio Sr satisfies the equations (6) and (7). Is changed to the first specific speed that minimizes. As a result, the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27 is minimized within a range in which the required static elimination performance can be secured. Therefore, it is possible to more effectively suppress the abrasion of the photoconductor drum 21.

  The first speed changing unit 13A reduces the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge eliminating member 27 in accordance with the decrease in the surface potential of the photosensitive drum 21 due to deterioration over time. It can be considered as a modification of one embodiment. For example, a configuration is conceivable in which the first speed changing unit 13A reduces the linear speed of the charge removing member 27 every time a predetermined period elapses. With this configuration, it is possible to more effectively suppress the abrasion of the photoconductor drum 21.

[Second Embodiment]
Hereinafter, the image forming apparatus 10 according to the second exemplary embodiment of the present invention will be described with reference to FIGS. 13 to 15. In the image forming apparatus 10 according to the second embodiment, the configurations of the charge removing member 27 and the control unit 1 are different from those in the first embodiment. The other configurations are common to the first embodiment and the second embodiment.

  Specifically, in the image forming apparatus 10 according to the second embodiment, as shown in FIG. 13, the charge removing member 27 has a first direction D1 approaching the photosensitive drum 21 and a first direction D1 opposite to the first direction D1. It can move in two directions D2. For example, in the image forming apparatus 10 according to the second exemplary embodiment, the bearing that supports the rotation shaft of the charge removing member 27 is supported by the housing of the image forming apparatus 10 so as to be movable in the first direction D1 and the second direction D2. There is.

  Moreover, as shown in FIG. 14, the control unit 1 includes a movement processing unit 14 instead of the first speed changing unit 13A.

  Specifically, the ROM of the control unit 1 stores in advance a contact pressure change program for causing the CPU to execute a contact pressure change process (see the flowchart of FIG. 15) described later. Then, the control unit 1 functions as the concentration detecting unit 11, the voltage changing unit 12, and the movement processing unit 14 by executing the contact pressure changing program stored in the ROM using the CPU. Note that the concentration detection unit 11 and the voltage change unit 12 are the same as those in the first embodiment, so description thereof will be omitted.

  The movement processing unit 14 reduces the distance between the photosensitive drum 21 and the charge removing member 27 as the applied voltage applied to the charging roller 220 is higher. That is, the movement processing unit 14 increases the contact pressure between the photosensitive drum 21 and the charge removing member 27 as the applied voltage applied to the charging roller 220 is higher. As a result, the contact resistance component Rb between the photoconductor drum 21 and the charge removing member 27 is reduced.

  Specifically, when the voltage changing unit 12 increases the applied voltage, the movement processing unit 14 moves the charge eliminating member 27 in the first direction D1 to reduce the separation distance between the photosensitive drum 21 and the charge eliminating member 27. . Further, when the applied voltage is reduced by the voltage changing unit 12, the movement processing unit 14 moves the charge eliminating member 27 in the second direction D2 to increase the separation distance between the photosensitive drum 21 and the charge eliminating member 27.

  For example, in the image forming apparatus 10, as shown in FIG. 14, a second drive unit 273 such as a motor for moving the charge removing member 27 is provided. Further, in the image forming apparatus 10, the second table data indicating the position within the movable range of the charge removing member 27 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 is stored in advance in the ROM of the control unit 1. There is. The movement processing unit 14 moves the static elimination member 27 using the second table data when the applied voltage is changed by the voltage changing unit 12.

[Contact pressure change processing]
Hereinafter, with reference to FIG. 15, an example of a procedure of the contact pressure changing process executed by the controller 1 in the image forming apparatus 10 will be described. Among the steps included in the contact pressure changing process, steps having the same processing contents as those included in the first speed changing process are denoted by the same reference numerals as those in the first speed changing process. Therefore, the description is omitted.

<Step S15>
In step S15, the control unit 1 moves the charge eliminating member 27 in the first direction D1 or the second direction D2 according to the changed applied voltage in step S13 to separate the photosensitive drum 21 and the charge eliminating member 27 from each other. Increase or decrease. Here, the process of step S15 is executed by the movement processing unit 14 of the control unit 1.

  For example, when the applied voltage increases, the control unit 1 moves the charge eliminating member 27 in the first direction D1 based on the second table data to reduce the distance between the photosensitive drum 21 and the charge eliminating member 27. . Further, when the applied voltage decreases, the control unit 1 moves the charge eliminating member 27 in the second direction D2 based on the second table data to increase the distance between the photosensitive drum 21 and the charge eliminating member 27. .

  As described above, in the image forming apparatus 10 according to the second embodiment, the higher the applied voltage applied to the charging roller 220, the smaller the distance between the photosensitive drum 21 and the charge removing member 27. As a result, as compared with the configuration in which the separation distance between the photoconductor drum 21 and the static elimination member 27 is set in accordance with the maximum value of the applied voltage, abrasion of the photoconductor drum 21 is suppressed while ensuring the required static elimination performance. It is possible.

  The control unit 1 of the image forming apparatus 10 according to the second embodiment may include the first speed changing unit 13A. Specifically, in the image forming apparatus 10 according to the second embodiment, the higher the applied voltage applied to the charging roller 220, the smaller the distance between the photoconductor drum 21 and the charge removing member 27, and the photoconductor drum 21. The difference between the linear velocity of No. 1 and the linear velocity of the static eliminating member 27 may increase.

  By the way, in the configuration in which the charge eliminating member 27 contacts the photoconductor drum 21, an external additive such as silica contained in the toner may adhere to the charge eliminating member 27. Here, when the amount of the external additive adhered to the charge removing member 27 increases, the contact resistance between the photoconductor drum 21 and the charge removing member 27 increases, and the charge removing performance of the charge removing member 27 decreases.

[Third Embodiment]
Hereinafter, the image forming apparatus 10 according to the third exemplary embodiment of the present invention will be described with reference to FIGS. 16 to 19. In the image forming apparatus 10 according to the third embodiment, the configurations of the control unit 1 and the image forming unit 2 are different from those of the first embodiment. Note that the other configurations are common to the first and third embodiments.

  Specifically, in the image forming apparatus 10 according to the third embodiment, the density sensor 29 is not provided in the image forming section 2.

  Further, as shown in FIG. 16, the control unit 1 replaces the concentration detecting unit 11, the voltage changing unit 12, and the first speed changing unit 13A with a first acquisition processing unit 15A and a first change amount acquisition unit 16A. , And a second speed changing unit 13B.

  Specifically, the ROM of the control unit 1 stores in advance a second speed change program for causing the CPU to execute a second speed change process (see the flowchart of FIG. 17) described later. Then, the control unit 1 uses the CPU to execute the second speed change program stored in the ROM to thereby obtain the first acquisition processing unit 15A, the first change amount acquisition unit 16A, and the second speed. It functions as the changing unit 13B.

  The first acquisition processing unit 15A acquires the cumulative value of the consumption amount of toner (developer) based on a preset first acquisition condition (an example of the acquisition condition of the present invention).

  For example, the first acquisition processing unit 15A acquires the cumulative value of the toner consumption amount when the second predetermined timing arrives. For example, the second timing is similar to the first timing when the image forming apparatus 10 is powered on, when returning from a sleep state where some functions of the image forming apparatus 10 are stopped to a normal state, and the printing. For example, when executing a process.

  For example, in the image forming apparatus 10, the cumulative print rate, which is the cumulative value of the print rates of the printed materials output from the image forming apparatus 10, is stored in a predetermined third storage area of the EEPROM. For example, when the printing process is executed, the control unit 1 calculates the coverage ratio of each printed matter output by the printing process based on the image data printed by the printing process. Further, when the size of the sheet on which the image is printed in the printing process is different from the predetermined reference size, the control unit 1 converts each of the calculated print ratios into the print ratio of the reference size sheet. To do. Then, the control unit 1 updates the cumulative printing rate stored in the third storage area based on the total value of the calculated or converted printing rates.

  Then, the first acquisition processing unit 15A acquires the cumulative value of the toner consumption amount based on the cumulative printing rate (an example of the first acquisition condition) stored in the third storage area. For example, the first acquisition processing unit 15A acquires the cumulative value of the toner consumption amount by multiplying the cumulative printing rate read from the third storage area by a predetermined coefficient.

  The first acquisition processing unit 15A accumulates the toner consumption amount based on the cumulative number of prints (another example of the first acquisition condition), which is the cumulative value of the number of prints output from the image forming apparatus 10. You may get the value.

  The first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb of the contact impedance Z2 of the charge removing member 27 based on the cumulative value of the toner consumption amount acquired by the first acquisition processing unit 15A. Here, the first change amount acquisition unit 16A is an example of the change amount acquisition unit in the present invention.

  For example, in the image forming apparatus 10, the third table data indicating the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 corresponding to each predetermined cumulative value of the toner consumption amount is stored in the ROM of the control unit 1 in advance. It is stored. The first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the cumulative value of the toner consumption amount acquired by the first acquisition processing unit 15A and the third table data. To do. For example, the third table data is created based on experimental data obtained by an experiment for investigating the relationship between the cumulative value of toner consumption and the contact resistance component Rb in the image forming apparatus 10 using the image forming apparatus 10. It Here, FIG. 18 shows an example of experimental data obtained by the above experiment. Note that FIG. 18 shows the relationship between the cumulative printing rate P and the contact resistance component Rb used to calculate the cumulative value of toner consumption.

  The following equation (8) showing the relationship between the cumulative printing rate P and the variation ΔRb of the contact resistance component Rb derived from the experimental data shown in FIG. 18 may be stored in advance in the ROM of the control unit 1. . In this case, the first change amount acquisition unit 16A may acquire the change amount ΔRb of the contact resistance component Rb based on the cumulative printing rate P read from the third storage area and the following equation (8). In addition, the control unit 1 may not include the first acquisition processing unit 15A. In the formula (8) below, F, G, and H are constants derived from the experimental data shown in FIG.

  The second speed changing unit 13B determines the difference between the linear speed of the photoconductor drum 21 and the linear speed of the charge removing member 27 according to the increase in the cumulative value of the toner consumption amount acquired based on the first acquisition condition. increase. The second speed changing unit 13B is an example of the speed changing unit in the present invention.

  Specifically, the second speed changing unit 13B sets the linear velocity of the static eliminator 27 such that the ratio Sr satisfies the above equation (2) and the following equation (9), and has a minimum difference from the linear velocity of the photosensitive drum 21. To a second specific speed (an example of the specific speed of the present invention).

  For example, in the image forming apparatus 10, the charge removing member 27 rotates at a higher linear velocity than the photoconductor drum 21 as described above. Therefore, the second speed changing unit 13B increases the linear velocity of the static elimination member 27 to increase the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27. When the charge removing member 27 rotates at a linear velocity slower than that of the photoconductor drum 21, the second speed changing unit 13B reduces the linear velocity of the charge eliminating member 27 to reduce the linear velocity of the photoconductor drum 21 and the charge eliminating member 27. The difference from the linear velocity may be increased.

  For example, in the image forming apparatus 10, the internal resistance component Ra, the contact resistance component Rb, and the calculated resistance value R21 are stored in the ROM of the control unit 1 in advance. The second speed changing unit 13B, when the change amount ΔRb of the contact resistance component Rb is acquired by the first change amount acquiring unit 16A, the internal resistance component Ra, the contact resistance component Rb, and the calculation stored in the ROM. Using the resistance value R21, the linear velocity of the static elimination member 27 satisfying the above-described conditions is calculated. Then, the second speed changing unit 13B changes the linear speed of the static elimination member 27 based on the calculation result.

  The second speed changing unit 13B may change the linear speed of the charge removing member 27 to a speed at which the difference from the second specific speed is equal to or lower than the allowable value. The second speed changing unit 13B may change the linear speed of the static eliminator 27 to a speed at which the ratio Sr satisfies the above formula (2) and the above formula (9).

  Further, in the image forming apparatus 10, fourth table data indicating the linear velocity of the charge removing member 27 corresponding to each predetermined cumulative value of the toner consumption amount may be stored in advance in the ROM of the control unit 1. . In this case, the second speed changing unit 13B may change the linear speed of the charge removing member 27 using the cumulative value of the toner consumption amount acquired by the first acquisition processing unit 15A and the fourth table data. Further, in this case, the control unit 1 may not include the first change amount acquisition unit 16A. For example, the fourth table data is the experimental data obtained by an experiment for investigating the relationship between the cumulative value of the toner consumption amount using the image forming apparatus 10 and the post-elimination potential V1, and the ratio using the image forming apparatus 10. It is created based on experimental data obtained by an experiment investigating the relationship between Sr and the potential V1 after static elimination.

  The second speed changing unit 13B may change the linear velocity of the photosensitive drum 21 to increase the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27. The second speed changing unit 13B may increase the difference between the linear speed of the photoconductor drum 21 and the linear speed of the charge removing member 27 within a range equal to or less than the preset upper limit value.

[Second speed change process]
Hereinafter, with reference to FIG. 17, an example of a procedure of the second speed changing process executed by the control unit 1 in the image forming apparatus 10 will be described.

<Step S21>
First, in step S21, the control unit 1 determines whether or not the second timing has arrived.

  Here, when the control unit 1 determines that the second timing has arrived (Yes in S21), the control unit 1 shifts the processing to step S22. If the second timing has not arrived (No side of S21), the control unit 1 waits for the arrival of the second timing in step S21.

<Step S22>
In step S22, the control unit 1 acquires the cumulative value of the toner consumption amount in the image forming apparatus 10. Here, the processing of step S21 and step S22 is an example of the acquisition step in the present invention, and is executed by the first acquisition processing unit 15A of the control unit 1.

  Specifically, the control unit 1 acquires the cumulative value of the toner consumption amount by multiplying the cumulative printing rate read from the third storage area by the coefficient.

<Step S23>
In step S23, the control unit 1 acquires the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the cumulative value of the toner consumption amount acquired in step S22. Here, the process of step S23 is executed by the first change amount acquisition unit 16A of the control unit 1. The process of step S23 may be omitted.

  Specifically, the control unit 1 acquires the change amount ΔRb of the contact resistance component Rb of the charge removing member 27 based on the cumulative value of the toner consumption amount acquired in step S22 and the third table data.

<Step S24>
In step S24, the control unit 1 changes the linear velocity of the static elimination member 27 based on the amount of change ΔRb of the contact resistance component Rb of the static elimination member 27 acquired in step S23. Here, the process of step S24 is an example of the speed changing step in the present invention, and is executed by the second speed changing unit 13B of the control unit 1.

  Specifically, the control unit 1 sets the linear velocity of the charge removing member 27 such that the ratio Sr satisfies the above equations (2) and (9) and minimizes the difference from the linear velocity of the photosensitive drum 21. Change to the second specific speed. For example, the control unit 1 changes the linear velocity of the static elimination member 27 by rewriting the data indicating the set value of the linear velocity of the static elimination member 27 stored in the second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the third embodiment, the linear velocity of the photoconductor drum 21 and the charge removing member are increased in accordance with the increase of the cumulative value of the toner consumption amount acquired based on the first acquisition condition. The difference from the linear velocity of 27 increases. As a result, it is possible to suppress a decrease in the static elimination performance of the static elimination member 27 due to an increase in the amount of the external additive attached to the static elimination member 27.

  Further, in the image forming apparatus 10 according to the third exemplary embodiment, the linear velocity of the charge removing member 27 is different from the linear velocity of the photoconductor drum 21 when the ratio Sr satisfies the equations (2) and (9). Is changed to the second specific speed that minimizes. As a result, the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27 is minimized within a range in which the required static elimination performance can be secured. Therefore, it is possible to suppress the abrasion of the photoconductor drum 21.

  It should be noted that the second speed changing unit 13B specifies that the cumulative print ratio acquired for each of the divided areas is the largest among the predetermined divided areas in the main scanning direction orthogonal to the sheet conveyance direction on which the image is formed. There is a configuration in which the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the charge eliminating member 27 is increased according to the increase of the cumulative value of the toner consumption amount acquired based on the cumulative printing rate corresponding to the divided area. It can be considered as a modification of the third embodiment. For example, it is conceivable that the EEPROM of the control unit 1 is provided with a plurality of storage areas for storing the cumulative printing rate for each of the divided areas. Further, it is considered that the first acquisition processing unit 15A acquires the cumulative value of the toner consumption amount by multiplying the cumulative printing rate corresponding to the specific divided area by the number of the divided areas and the coefficient. To be According to this configuration, it is possible to set the linear velocity of the charge removing member 27 with reference to a position on the charge removing member 27 in the main scanning direction where the amount of the external additive adheres most.

  Further, a configuration in which the image forming apparatus 10 includes a cleaning member 274 for cleaning the surface of the charge removing member 27 as shown in FIG. 19 is considered as another modification of the third embodiment. For example, the cleaning member 274 is a blade-shaped member that is long in the axial direction of the rotation shaft of the photosensitive drum 21, and is provided in contact with the brush bristles 271 of the charge removing member 27. For example, the cleaning member 274 is provided at a position that bites into the outer diameter of the static elimination member 27 by 0.1 mm to 1.1 mm. According to this configuration, it is possible to suppress the adhesion of the external additive on the charge removing member 27. When the cleaning member 274 is provided in the image forming apparatus 10, the contents of the third table data, the equation (8), and the fourth table data may be modified.

  By the way, in the configuration in which the static elimination member 27 is in contact with the photoconductor drum 21, the tip of the brush bristles 271 in contact with the photoconductor drum 21 is curved according to the increase in the number of executions of the printing process, and the outer diameter of the static elimination member 27 May decrease. Here, when the outer diameter of the static elimination member 27 decreases, the contact area between the photoconductor drum 21 and the static elimination member 27 decreases, and the contact resistance between the photoconductor drum 21 and the static elimination member 27 increases, so that the static elimination member 27 The static elimination performance is reduced.

[Fourth Embodiment]
Hereinafter, the image forming apparatus 10 according to the fourth exemplary embodiment of the present invention will be described with reference to FIGS. In the image forming apparatus 10 according to the fourth embodiment, the configurations of the control unit 1 and the image forming unit 2 are different from those of the first embodiment. The other configurations are common to the first embodiment and the fourth embodiment.

  Specifically, in the image forming apparatus 10 according to the fourth embodiment, the density sensor 29 is not provided in the image forming section 2.

  Further, as shown in FIG. 20, the control unit 1 replaces the concentration detecting unit 11, the voltage changing unit 12, and the first speed changing unit 13A with a second acquisition processing unit 15B and a second change amount acquisition unit 16B. , And a third speed changing unit 13C.

  Specifically, the ROM of the control unit 1 stores in advance a third speed changing program for causing the CPU to execute a third speed changing process (see the flowchart of FIG. 21) described later. Then, the control unit 1 uses the CPU to execute the third speed changing program stored in the ROM to thereby obtain the second acquisition processing unit 15B, the second change amount acquisition unit 16B, and the third speed. It functions as the changing unit 13C.

  The second acquisition processing unit 15B acquires the outer diameter of the static eliminator 27 based on the preset second acquisition condition.

  For example, the second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 when the predetermined third timing arrives. For example, the third timing is the same as the first timing when the image forming apparatus 10 is powered on, when returning from a sleep state where some functions of the image forming apparatus 10 are stopped to a normal state, and the printing. For example, when executing a process.

  For example, the second acquisition processing unit 15B acquires the outer diameter of the charge removing member 27 based on the cumulative number of printed sheets in the image forming apparatus 10 (an example of the second acquisition condition).

  For example, in the image forming apparatus 10, the cumulative number of printed sheets in the image forming apparatus 10 is stored in a predetermined fourth storage area of the EEPROM. For example, the control unit 1 updates the cumulative print number stored in the fourth storage area every time the printing process is executed.

  Further, in the image forming apparatus 10, the fifth table data indicating the outer diameter of the charge removing member 27 corresponding to each of the predetermined cumulative print numbers is stored in the ROM of the control unit 1 in advance. The second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 based on the cumulative number of printed sheets and the fifth table data read from the fourth storage area. For example, the fifth table data is created based on experimental data obtained by an experiment for investigating the relationship between the cumulative number of printed sheets and the outer diameter of the static elimination member 27 in the image forming apparatus 10 using the image forming apparatus 10. . Here, FIG. 22 shows an example of experimental data obtained by the above experiment.

  The second acquisition processing unit 15B may acquire the outer diameter of the static elimination member 27 based on the cumulative number of rotations of the static elimination member 27 (another example of the second acquisition condition). The second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 based on the value of the current flowing through the first drive unit 272 that drives the static elimination member 27 (another example of the second acquisition condition). Good. The second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 based on any one of the cumulative number of printed sheets, the cumulative number of rotations, and the value of the current flowing through the first driving unit 272. Good. For example, the second acquisition processing unit 15B calculates an average value of the outer diameter of the static elimination member 27 acquired based on the cumulative number of printed sheets and the outer diameter of the static elimination member 27 acquired based on the cumulative number of rotations. You may acquire as an outer diameter of the static elimination member 27.

  The second change amount acquisition unit 16B acquires the change amount ΔRb of the contact resistance component Rb of the contact impedance Z2 of the static elimination member 27 based on the decrease amount of the outer diameter of the static elimination member 27 acquired by the second acquisition processing unit 15B. To do.

  For example, in the image forming apparatus 10, the sixth table data indicating the change amount ΔRb of the contact resistance component Rb of the static eliminating member 27 corresponding to each predetermined reduction amount of the outer diameter of the static eliminating member 27 is previously stored in the controller 1. It is stored in ROM. The second variation amount acquisition unit 16B is based on the outer diameter of the static elimination member 27 acquired by the second acquisition processing unit 15B and the outer diameter of the static elimination member 27 stored in the ROM in advance when the image forming apparatus 10 is manufactured. Then, the reduction amount of the outer diameter of the static elimination member 27 is calculated. Then, the second variation amount acquisition unit 16B acquires the variation amount ΔRb of the contact resistance component Rb of the static elimination member 27 based on the calculated reduction amount of the outer diameter of the static elimination member 27 and the sixth table data. For example, the sixth table data is created based on experimental data obtained by an experiment for investigating the relationship between the reduction amount of the outer diameter of the charge removing member 27 and the contact resistance component Rb using the image forming apparatus 10.

  The third speed changing unit 13C increases the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the charge eliminating member 27 in accordance with the decrease in the outer diameter of the charge eliminating member 27 acquired based on the second obtaining condition. Let

  Specifically, the third speed changing unit 13C sets the linear velocity of the static elimination member 27 such that the ratio Sr satisfies the above equations (2) and (9) and has a minimum difference from the linear velocity of the photosensitive drum 21. It changes to the 3rd specific speed.

  For example, in the image forming apparatus 10, the charge removing member 27 rotates at a higher linear velocity than the photoconductor drum 21 as described above. Therefore, the third speed changing unit 13C increases the linear velocity of the static elimination member 27 to increase the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27. When the charge eliminating member 27 rotates at a linear velocity lower than that of the photoconductor drum 21, the third speed changing unit 13C reduces the linear velocity of the charge eliminating member 27 to reduce the linear velocity of the photoconductor drum 21 and the charge eliminating member 27. The difference from the linear velocity may be increased.

  For example, when the second change amount acquisition unit 16B acquires the change amount ΔRb of the contact resistance component Rb, the third speed changing unit 13C stores the internal resistance component Ra and the contact resistance component Rb stored in the ROM, And the calculated resistance value R21 are used to calculate the linear velocity of the static elimination member 27 that satisfies the above condition. Then, the third speed changing unit 13C changes the linear speed of the static elimination member 27 based on the calculation result.

  Note that the third speed changing unit 13C may change the linear speed of the static eliminator 27 to a speed at which the difference from the third specific speed is equal to or lower than the allowable value. In addition, the third speed changing unit 13C may change the linear speed of the static eliminator 27 to a speed at which the ratio Sr satisfies the expressions (2) and (9).

  Further, in the image forming apparatus 10, the seventh table data indicating the linear velocity of the static elimination member 27 corresponding to each predetermined reduction amount of the outer diameter of the static elimination member 27 is stored in the ROM of the control unit 1 in advance. Good. In this case, the third speed changing unit 13C changes the linear velocity of the static elimination member 27 using the reduction amount of the outer diameter of the static elimination member 27 acquired by the second acquisition processing unit 15B and the seventh table data. Good. Further, in this case, the control unit 1 may not include the second change amount acquisition unit 16B. For example, the seventh table data uses experimental data obtained by an experiment for investigating the relationship between the reduced amount of the outer diameter of the charge eliminating member 27 and the post-elimination potential V1 using the image forming apparatus 10 and the image forming apparatus 10. It is created based on experimental data obtained by an experiment investigating the relationship between the ratio Sr and the potential V1 after static elimination.

  Further, the third speed changing unit 13C may change the linear velocity of the photosensitive drum 21 to increase the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removing member 27. The third speed changing unit 13C may increase the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the charge removing member 27 within a range equal to or less than the preset upper limit value.

[Third speed change process]
Hereinafter, with reference to FIG. 21, an example of a procedure of the third speed changing process executed by the control unit 1 in the image forming apparatus 10 will be described.

<Step S31>
First, in step S31, the control unit 1 determines whether or not the third timing has come.

  Here, when the control unit 1 determines that the third timing has arrived (Yes in S31), the process proceeds to step S32. If the third timing has not arrived (No side of S31), the control unit 1 waits for the arrival of the third timing in step S31.

<Step S32>
In step S32, the control unit 1 acquires the outer diameter of the static elimination member 27. Here, the processing of step S31 and step S32 is executed by the second acquisition processing unit 15B of the control unit 1.

  Specifically, the control unit 1 acquires the outer diameter of the charge removing member 27 based on the cumulative number of printed sheets and the fifth table data read from the fourth storage area.

<Step S33>
In step S33, the control unit 1 acquires the change amount ΔRb of the contact resistance component Rb of the static eliminating member 27 based on the amount of decrease in the outer diameter of the static eliminating member 27 acquired in step S32. Here, the process of step S33 is executed by the second change amount acquisition unit 16B of the control unit 1. The process of step S33 may be omitted.

  Specifically, the control unit 1 determines the charge removing member based on the outer diameter of the charge removing member 27 acquired in step S32 and the outer diameter of the charge removing member 27 stored in the ROM in advance when the image forming apparatus 10 is manufactured. The decrease amount of the outer diameter of 27 is calculated. Then, the control unit 1 acquires the change amount ΔRb of the contact resistance component Rb of the static elimination member 27 based on the calculated reduction amount of the outer diameter of the static elimination member 27 and the sixth table data.

<Step S34>
In step S34, the control unit 1 changes the linear velocity of the static elimination member 27 based on the change amount ΔRb of the contact resistance component Rb of the static elimination member 27 acquired in step S33. Here, the process of step S34 is executed by the third speed changing unit 13C of the control unit 1.

  Specifically, the control unit 1 sets the linear velocity of the charge removing member 27 such that the ratio Sr satisfies the above equations (2) and (9) and minimizes the difference from the linear velocity of the photosensitive drum 21. Change to the third specific speed. For example, the control unit 1 changes the linear velocity of the static elimination member 27 by rewriting the data indicating the set value of the linear velocity of the static elimination member 27 stored in the second storage area of the RAM.

  As described above, in the image forming apparatus 10 according to the fourth exemplary embodiment, the linear velocity of the photoconductor drum 21 and the static elimination member 27 are reduced in accordance with the decrease in the outer diameter of the static elimination member 27 acquired based on the second acquisition condition. The difference with the linear velocity of increases. As a result, it is possible to suppress a decrease in the static elimination performance of the static elimination member 27 due to a decrease in the outer diameter of the static elimination member 27.

  Further, in the image forming apparatus 10 according to the fourth embodiment, the linear velocity of the charge removing member 27 is different from the linear velocity of the photoconductor drum 21 when the ratio Sr satisfies the equations (2) and (9). Is changed to the third specific speed that minimizes. As a result, the difference between the linear velocity of the photoconductor drum 21 and the linear velocity of the static elimination member 27 is minimized within a range in which the required static elimination performance can be secured. Therefore, it is possible to suppress the abrasion of the photoconductor drum 21.

  A configuration in which the image forming apparatus 10 includes the rotation control unit 17 as shown in FIG. 23 can be considered as a modified example of the fourth embodiment. Specifically, the rotation control unit 17, at every predetermined fourth timing different from the time of executing the printing process, each time the cumulative number of printed sheets or the cumulative number of rotations is increased by a predetermined reference value, The charge removing member 27 is rotated in a direction opposite to the rotation direction when the printing process is executed. For example, the rotation control unit 17 rotates the charge removal member 27 in a direction opposite to the rotation direction at the time of executing the printing process for a predetermined time or the number of rotations. According to this configuration, since the curvature of the tip of the brush bristles 271 is regularly corrected, it is possible to suppress a decrease in the outer diameter of the static elimination member 27. When the image forming apparatus 10 is provided with the rotation control unit 17, it is possible to correct the contents of the fifth table data.

1 Control Section 2 Image Forming Section 3 Paper Feeding Section 4 Paper Discharging Section 10 Image Forming Apparatus 11 Density Detection Section 12 Voltage Changing Section 13A First Speed Changing Section 13B Second Speed Changing Section 13C Third Speed Changing Section 14 Movement Processing Section 15A First acquisition processing unit 15B Second acquisition processing unit 16A First variation amount acquisition unit 16B Second variation amount acquisition unit 17 Rotation control unit 21 Photoconductor drum 22 Charging device 23 Optical scanning device 24 Developing device 25 Transfer roller 26 Cleaning member 27 Static eliminator 270 Base part 271 Brush bristles 272 First drive part 273 Second drive part 274 Cleaning member 28 Fixing device 29 Density sensor

Claims (12)

A photoconductor,
A static eliminator that is electrically grounded and is rotatably arranged in contact with the surface of the photoconductor;
A speed changing unit that increases the difference between the linear speed of the photoconductor and the linear speed of the charge eliminating member in accordance with an increase in the cumulative value of the consumption amount of the developer that is acquired based on a preset acquisition condition,
A change amount acquisition unit that acquires a change amount of the resistance component of the contact impedance of the static elimination member obtained from a Cole-Cole plot in a predetermined frequency range by an AC impedance method based on the cumulative value of the consumption amount of the developer. When,
Equipped with
The speed change unit is Ra, the resistance component of the internal impedance of the static elimination member obtained from the Cole-Cole plot of the frequency range by the AC impedance method is Ra, the resistance component of the contact impedance is Rb, and is acquired by the change amount acquisition unit. The charge removal time obtained by dividing the amount of change by ΔRb, the ratio of the linear velocity of the static elimination member to the linear velocity of the photoconductor by Sr, and the contact width of the photoconductor and the static elimination member by the linear velocity of the photoconductor. R21 is a calculated resistance value calculated based on a predetermined arithmetic expression as a DC resistance value of the static elimination member necessary for decreasing the pre-static elimination potential of the photoconductor to a predetermined post-static potential during when a, the linear velocity of the charge removing member, an image forming apparatus wherein the ratio Sr is to change the speed at which satisfies the following formula (1) and the following equation (2).
The acquisition condition is one of the cumulative number of printed sheets and the cumulative printing rate,
The image forming apparatus according to claim 1. A specific speed at which the speed changing unit sets the linear velocity of the static elimination member such that the ratio Sr satisfies the equations (1) and (2) and has a minimum difference from the linear velocity of the photoconductor, or Changing to a speed equal to or less than a preset allowable value with a difference from the specific speed,
The image forming apparatus according to claim 1 . When the electrostatic capacity of the photoconductor is C, the static elimination time is t, the pre-static elimination potential is V0, and the post-static elimination potential is V1, the calculated resistance value R21 is calculated based on the following equation (3). ,
The image forming apparatus according to claim 1.
The speed changing unit corresponds to a specific divided area having the largest cumulative print ratio acquired for each divided area among predetermined divided areas in the main scanning direction orthogonal to the sheet conveyance direction on which an image is formed. Increasing the difference between the linear velocity of the photoconductor and the linear velocity of the charge eliminating member in accordance with an increase in the cumulative value of the consumption amount of the developer acquired based on the cumulative printing rate.
The image forming apparatus according to claim 2. A cleaning member for cleaning the surface of the charge removing member,
The image forming apparatus according to claim 1. The speed changing unit increases the linear velocity of the static eliminating member to increase the difference between the linear velocity of the photoconductor and the linear velocity of the static eliminating member.
The image forming apparatus according to claim 1. The speed changing unit reduces the linear velocity of the static eliminating member to increase the difference between the linear velocity of the photoconductor and the linear velocity of the static eliminating member.
The image forming apparatus according to claim 1. The photoconductor is charged by a contact type charging member,
The image forming apparatus according to claim 1. The photoreceptor is charged by applying a DC voltage,
The image forming apparatus according to any one of claims 1 to 9. The charge removing member has a cylindrical base portion and brush bristles having one end fixed to the base portion and the other end in contact with the surface of the photoreceptor.
The brush bristles have a resin core, and a carbon surface layer that covers the surface of the core,
The image forming apparatus according to any one of claims 1 to 10. An image forming method executed by an image forming apparatus, comprising: a photoconductor; and a charge removing member that is electrically grounded and rotatably arranged in contact with a surface of the photoconductor,
An acquisition step of acquiring a cumulative value of the consumption amount of the developer based on the acquisition condition set in advance,
A speed changing step of increasing the difference between the linear speed of the photoconductor and the linear speed of the charge eliminating member according to an increase in the cumulative value of the consumption amount of the developer acquired in the acquisition step,
A change amount acquisition step of acquiring a change amount of the resistance component of the contact impedance of the static eliminator obtained from a Cole-Cole plot of a predetermined frequency range based on the AC impedance method, based on the cumulative value of the consumption amount of the developer. When,
Only including,
In the speed changing step, the resistance component of the internal impedance of the static elimination member obtained from the Cole-Cole plot of the frequency range by the AC impedance method is Ra, the resistance component of the contact impedance is Rb, and the change amount acquisition unit acquires the resistance component. The charge removal time obtained by dividing the amount of change by ΔRb, the ratio of the linear velocity of the static elimination member to the linear velocity of the photoconductor by Sr, and the contact width of the photoconductor and the static elimination member by the linear velocity of the photoconductor. R21 is a calculated resistance value calculated based on a predetermined arithmetic expression as a direct current resistance value of the static elimination member necessary for lowering the pre-static elimination potential of the photoconductor to a predetermined post-elimination potential. Then, the image forming method in which the linear velocity of the charge eliminating member is changed to a velocity at which the ratio Sr satisfies the following equations (4) and (5) .