JP6589899B2 - 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 photoreceptor, the toner image on the photoreceptor developed with toner is transferred to a sheet, and the charge remaining on the photoreceptor is transferred. It is removed by the static eliminator. As an example of the static eliminator, there is known a configuration in which a grounded brush-shaped static eliminator is brought into contact with the photoconductor to remove the charge on the photoconductor (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 01-154186

  By the way, in the configuration in which the brush-shaped charge eliminating member is in contact with the photoconductor, the outer diameter of the charge eliminating member may be reduced by curving the tip of the brush hair that contacts the photoconductor as the number of executions of the printing process increases. is there. Here, when the outer diameter of the charge removal member decreases, the contact area between the photoconductor and the charge removal member decreases, the contact resistance between the photoconductor and the charge removal member increases, and the charge removal performance of the charge removal member decreases.

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

  An image forming apparatus according to one aspect of the present invention includes a photoconductor, a charge removal member, and a speed changing unit. The charge eliminating member is in the form of a brush, is electrically grounded, and is rotatably disposed in contact with the surface of the photoreceptor. The speed changing unit increases the difference between the linear velocity of the photosensitive member and the linear velocity of the charge eliminating member in accordance with a decrease in the outer diameter of the charge eliminating member acquired based on a preset acquisition condition.

  An image forming method according to another aspect of the present invention includes: a photoconductor; and a brush-shaped static eliminating member that is electrically grounded and is rotatably disposed in contact with the surface of the photoconductor. It is executed by the apparatus and includes the following acquisition step and speed change step. In the acquisition step, the outer diameter of the static elimination member is acquired based on a preset acquisition condition. In the speed changing step, the difference between the linear velocity of the photosensitive member and the linear velocity of the neutralizing member increases as the outer diameter of the neutralizing member acquired in the acquiring step decreases.

  ADVANTAGE OF THE INVENTION According to this invention, the image forming apparatus and image forming method which can suppress the fall of the static elimination performance of a static elimination member are provided.

1 is a diagram illustrating a configuration of an image forming apparatus according to a first 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 illustrating an equivalent circuit for explaining electrical characteristics between the photosensitive member and the charge removal member of the image forming unit of the image forming apparatus according to the first embodiment of the present invention. It is a figure which shows an example of the result of the Cole-Cole plot of the static elimination member of the image forming apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows an example of the experimental apparatus used in order to obtain the result of the Cole-Cole plot of the static elimination member of the image forming apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows an example of the experimental apparatus used in order to obtain the result of the Cole-Cole plot of the static elimination member of the image forming apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows an Example and a comparative example. FIG. 3 is a diagram illustrating a relationship between a ratio of a linear speed of a static eliminating member to a linear speed of a photosensitive member of the image forming apparatus according to the first embodiment of the present invention and a post-static potential. It is a figure which shows the structure of the bristle of the static elimination member of the image forming apparatus which concerns on 1st Embodiment of this invention. 1 is a block diagram illustrating a system configuration of an image forming apparatus according to a first embodiment of the present invention. 6 is a flowchart illustrating an example of a first speed change process executed by the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating a relationship between a ratio of a linear speed of a static eliminating member to a linear speed of a photosensitive member of the image forming apparatus according to the first embodiment of the present invention and a post-static potential. FIG. 10 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 which shows the system configuration | structure of the image forming apparatus which concerns on 2nd Embodiment of this invention. 10 is a flowchart illustrating 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 which shows the system configuration | structure of the image forming apparatus which concerns on 3rd Embodiment of this invention. 14 is a flowchart illustrating an example of a second speed change process 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. It is a figure for demonstrating the principal part of the image forming part of the image forming apparatus which concerns on the modification of 3rd Embodiment of this invention. It is a block diagram which shows the system configuration | structure of the image forming apparatus which concerns on 4th Embodiment of this invention. 14 is a flowchart illustrating an example of a third speed change 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 number of printed sheets of the image forming apparatus which concerns on 4th Embodiment of this invention, and the outer diameter of a static elimination member. It is a block diagram which shows the system configuration | structure 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. In addition, the following embodiment is an example which actualized this invention, Comprising: It does not have the character which limits the technical scope of this invention.

[First Embodiment]
As shown in FIG. 1, an image forming apparatus 10 according to the first embodiment of the present invention includes an electrophotographic monochrome that includes a control unit 1, an image forming unit 2, a paper feed unit 3, a paper discharge 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 copier, and a multifunction machine. In addition, 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 is an electrophotographic image capable of color printing such as a tandem method including an image forming unit corresponding to each color. The image forming apparatus may be of a type.

  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 photosensitive 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, a fixing device 28, and the like. It is. Note that the photoconductor drum 21 is an example of a photoconductor, and for example, a photoconductor belt may be used as the photoconductor instead of the photoconductor drum 21.

  In the image forming apparatus 10, the image forming unit 2 is controlled by the control unit 1, whereby an image forming process for forming an image on a sheet such as paper supplied from the paper feed cassette 31 of the paper feed unit 3 ( Print processing) is executed, and the sheet after the image forming process is discharged to the paper discharge unit 4.

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

  Thereafter, the toner transferred to the sheet is melted 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 photosensitive drum 21 is removed by the charge removing member 27 disposed on the downstream side of the cleaning member 26.

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

  In particular, the photoconductor drum 21 is a positively charged single layer organic photoconductor (PSLP) drum that is positively charged. In addition, it is also conceivable as another embodiment that the photosensitive drum 21 is an organic photoreceptor having a multilayer structure.

  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. The charging roller 220 is applied with a positive DC voltage from the power source 221. As a result, a positive DC voltage is applied from the charging roller 220 to the photosensitive drum 21, and the photosensitive drum 21 is charged to a predetermined charging potential. That is, the charging device 22 according to the present embodiment is not an AC superimposing type charging device that superimposes an AC voltage on a DC voltage, and is a non-contact type that charges the photosensitive 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 superposed charging device or a non-contact charging device.

  The static elimination member 27 is electrically grounded to the ground. Further, the static elimination member 27 is rotatably supported while being in contact with the surface of the photosensitive drum 21. Specifically, the charge removal member 27 is a brush-like 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 whose one end is fixed to the base portion 270 and the other end contacts the surface of the photosensitive drum 21. The static elimination member 27 is not limited to a 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 static elimination member 27 is in contact with the photosensitive drum 21 as in the image forming apparatus 10, the electrical characteristics such as the internal capacitance of the static elimination member 27 are related to the potential stability and the memory image in the photosensitive drum 21. May affect the presence or absence of. However, not only the internal capacitance of the charge removal member 27 but also the contact capacitance of the charge removal member 27 may affect the potential stability and the presence or absence of a memory image.

  In the image forming apparatus 10, 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 photosensitive drum 21 has a high surface resistance value, no lateral flow of charges occurs on the surface of the photosensitive drum 21. Therefore, even if the internal resistance of the static elimination member 27 is small, if the contact resistance with the photosensitive drum 21 is large, the charge on the photosensitive drum 21 cannot be effectively removed.

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

  On the other hand, as described below, the image forming apparatus 10 is configured so that the electrical characteristics of the static elimination member 27 satisfy the first specific condition set in advance, so that the contact capacitance is also taken into consideration. Thus, it is possible to improve the potential stability and suppress the generation of a memory image. Further, as will be described below, since the electrical characteristics of the static elimination member 27 are configured so as to satisfy the second specific condition set in advance, 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 electrical characteristics between the photosensitive drum 21 and the charge removal member 27 of the image forming unit 2, a resistor 51 corresponding to the DC resistance value R <b> 1 of the photosensitive drum 21. A capacitor 52 corresponding to the electrostatic capacitance C1 of the photosensitive drum 21 and a resistor 53 corresponding to the DC resistance value R2 of the static elimination member 27 are connected in parallel.

  In general, in the equivalent circuit 5, it is considered that the lower the DC resistance value R <b> 2 of the charge removal member 27, the higher the charge removal performance of the photosensitive drum 21 by the charge removal member 27. However, in practice, it has been found that not only the DC resistance value R2 of the charge removal member 27 but also the contact resistance of the charge removal member 27 with the photosensitive drum 21 affects the charge removal performance.

  On the other hand, as shown in FIG. 4, the internal impedance Z1 and the contact impedance Z2 of the static elimination member 27 with respect to the preset frequency range such as 0.05 Hz to 100 kHz, for example, by the AC impedance method. 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 plot corresponding to each of the internal impedance Z1 and the contact impedance Z2 draws a semicircle, but may be an arc shape such as a semi-elliptical shape. .

  In the first embodiment, the resistance between the core of the photosensitive drum 21 and the photosensitive layer is negligible. Further, the DC resistance value R1 of the photosensitive drum 21 is very large with respect to the DC resistance value R2 of the static elimination member 27. Therefore, the combined resistance R3 of the photosensitive drum 21 and the charge removal member 27 can be considered to be the same as the DC resistance value R2 of the charge removal member 27.

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

  However, as described above, the contact impedance of the charge removal member 27 with the photosensitive drum 21 also affects the charge removal performance of the charge removal member 27. Therefore, in the image forming apparatus 10, the charge removal member 27 is configured so that the conditions (the second specific condition) of the following formula (2) and the following formula (3) are satisfied.

  That is, in the image forming apparatus 10, as shown in the above equation (2), the internal resistance component Ra of the static elimination member 27 is equal to the calculated resistance value R 21 of the static elimination member 27 and the static elimination member 27 with respect to the linear velocity of the photosensitive drum 21. Or less than a value obtained by multiplying the first specific value calculated based on the linear velocity ratio Sr. Further, in the image forming apparatus 10, as shown in the above equation (3), the contact resistance component Rb of the charge removal member 27 is calculated based on the ratio Sr to the calculated resistance value R21 of the charge removal member 27. It is below the value multiplied by the value.

  As described above, in the image forming apparatus 10, the electrical characteristics of the static elimination member 27 are determined in consideration of not only the DC resistance value R 2 of the static elimination member 27 but also the internal resistance component Ra and the contact resistance component Rb. It is possible to improve the static elimination performance by the member 27. On the other hand, the DC resistance value R2 of the actual static elimination member 27 may be a value equal to or less than the calculated resistance value R21 or greater 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 values R21 that can be neutralized to the potential V1 after static elimination in 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. By being below the value prescribed | regulated based on each ratio Sr of speed, the static elimination performance by the static elimination member 27 improves. If the same effect occurs, the first specific value and the second specific value are not limited to the above-described values.

  For example, in the image forming apparatus 10, as shown in FIG. 9, the brush bristles 271 of the charge removal member 27 have a core portion 271 </ b> A and a surface layer portion 271 </ b> B. Here, FIG. 9 is a cross-sectional view of one brush hair 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 the brush bristles 271 are manufactured. Further, the surface layer portion 271B may be formed by spraying carbon onto the surface of the core portion 271A after the core portion 271A is formed. Accordingly, the internal resistance component Ra and the contact resistance component Rb of the static elimination member 27 are reduced while maintaining the strength of the brush bristles 271 as compared with the configuration in which the bristles 271 are formed only by the resin layer containing carbon. Is possible. The surface layer portion 271B may include components other than carbon as long as the static elimination member 27 satisfies the above formulas (2) and (3). The core portion 271A may contain carbon. Further, the brush bristles 271 may be formed of only a resin layer containing carbon.

  In the image forming apparatus 10, the static elimination member 27 rotates in response to a rotational driving force supplied from a first drive unit 272 (see FIG. 10) such as a motor. For example, the static elimination member 27 rotates at a higher linear speed than the photosensitive drum 21. Note that the static elimination member 27 may rotate at the same linear velocity as the photosensitive drum 21 or at a slower linear velocity than the photosensitive drum 21. Further, the static elimination member 27 may be rotated by following the photosensitive drum 21 at a speed obtained by multiplying a linear ratio of the photosensitive drum 21 by a predetermined ratio.

  Further, as described above, the potential stability of the photosensitive drum 21 and the presence / absence of an image memory are also affected by the contact impedance of the charge removal member 27 with the photosensitive drum 21. In the image forming apparatus 10, the charge removal member 27 is configured so as to satisfy the conditions of the following formula (4) and the following formula (5) (the first specific condition).

  Ca ≦ 1.0E + 05 (4)

  0 ≦ Cb / Ca ≦ 0.4 (5)

  That is, in the image forming apparatus 10, as shown in the above equation (4), the internal capacitance component Ca of the static elimination member 27 is 1.0E + 05 or less, which is an example of a predetermined fourth specific value. Further, in the image forming apparatus 10, as shown in the above equation (5), the capacitance ratio (Cb / Ca) which is a value obtained by dividing the contact capacitance component Cb of the charge removal member 27 by the internal 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, the electrical characteristics of the charge removal member 27 are determined in consideration of the internal capacitance component Ca and the contact capacitance component Cb of the charge removal member 27. It is possible to improve the potential stability of the image and suppress the occurrence of image memory. Specifically, the internal capacitance component Ca is determined so that the charge accumulated in the charge removal member 27 is reduced, and the ratio of the contact capacitance component Cb to the internal capacitance component Ca is also small. Since electric charges are easily removed from 27, the potential stability is improved and the generation of image memory is suppressed. If the same effect occurs, the third specific value and the fourth specific value are not limited to the values described above.

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

  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. FIG. The experimental apparatus 90 includes two stainless steel SUS rollers 91 and SUS rollers 92 each having a diameter of 18 mm and arranged at an interval of 4 mm in the horizontal direction. An aluminum film electrode 93 (horizontal length 150 mm) is suspended between the SUS roller 91 and the SUS roller 92. And the static elimination member 27 which concerns on Comparative Examples 1-15 and Examples 1-5 which are test objects is arrange | positioned so that the upper surface of the film electrode 93 may be contacted.

  The experimental apparatus 90 includes a SUS roller 95 having a diameter of 30 mm disposed above the static elimination member 27. A load is applied to the SUS roller 95 downward by a 1 kg weight 96, and the load is applied to the charge removal member 27 via the SUS roller 95. The static elimination 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 the impedance measuring device 97 (LCR high tester 3522 manufactured by Hioki Electric Co., Ltd.), and the base portion 270 of the static elimination member 27 is the other of the impedance measuring device 97. In this state, impedance measurement by the impedance measuring device 97 is performed. In this experiment, an AC voltage having a sinusoidal waveform with a voltage value of 5.0 V is applied across the electrodes of the impedance measuring device 97. Then, 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 are changed while changing the frequency of the applied AC voltage in a range from 0.05 Hz to 100 kHz. Cb is measured. The measurement is 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.

  In FIG. 7, the printing process is executed by the image forming apparatus 10 equipped with the neutralization member 27 of each example shown in FIG. 7, and the neutralization performance, potential stability, and image stability of the photosensitive drum 21 by the neutralization member 27 are illustrated. The evaluation result of evaluating the presence or absence of memory is shown.

  Here, with respect to the static elimination performance, it was evaluated whether or not the photosensitive drum 21 was neutralized by the neutralizing member 27 in the image forming apparatus 10 and then the potential of the photosensitive drum 21 was neutralized to a desired post-static potential V1. . In FIG. 7, “◯” is shown as the evaluation result of the static elimination performance when the static elimination is performed up to the desired post-neutralization potential V1, and “x” is shown when the static elimination is not performed below the desired post-neutralization potential V1.

  Regarding the potential stability, after continuous printing for 60 minutes in the image forming apparatus 10, the surface potential of the photosensitive drum 21 after being charged by the charging device 22 was measured, and as a result, before the start of the continuous printing. It was evaluated whether or not the initial surface potential after being charged by the charging device 22 decreased by 10% or more. In FIG. 7, “◯” is shown as the evaluation result of the potential stability when it is not lowered by 10% or more from the initial surface potential, and “X” is shown when it is lowered by 10% or more from the initial surface potential. Note that a value of 10% was adopted here because a problem such as fogging may occur when the initial surface potential drops by 10% or more.

  As for the presence or absence of the image memory, a black patch having a predetermined shape is formed at the leading edge of the printing paper by the printing process in the image forming apparatus 10, and a half image (gray image) is printed in the other areas thereafter. The presence or absence of image memory was visually evaluated. Specifically, it is determined that the image memory has been generated when the shape of the black patch appears in the half image area. In FIG. 7, “◯” is shown as an evaluation result when there is no image memory, and “X” is shown as an evaluation result when there is an image memory.

  More specifically, the image forming apparatus 10 used in the experiment is a modified machine of a printer “FS-1320DN” manufactured by Kyocera Document Solutions Inc. Further, in the image forming apparatus 10, the potential V0 before neutralization of the photosensitive drum 21 is 500 [V], the surface speed (linear velocity) S of the photosensitive drum 21 is 0.15 [m / s], and the contact width L is 0. 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]. It is. In this case, the electrostatic capacitance value C of the photosensitive drum 21 is 8.85E-07 [F] from “ε0 × εr / d”.

  Then, the post-static potential V1, which is a desired potential after the static elimination of the photosensitive drum 21 by the static eliminating 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). Note that the post-static discharge potential V1 may be a value calculated by an arithmetic expression such as V1 = V0 × 0.2, for example, and an arithmetic operation such as V1 = V0 × 0.22 + 80 in order to provide a margin. It may be a value calculated by an expression.

  Here, in Comparative Examples 1 to 13 and Examples 1 to 3, the surface speed (linear velocity) of the charge removal 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) Will be satisfied. 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 expression (3) is satisfied.

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

  Specifically, in Comparative Example 14, the linear velocity of the static elimination 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 the comparative example 14, when the internal resistance component Ra of the static elimination member 27 is equal to or less than 1.502E + 05 [Ω] which is 6.42 times the calculated resistance value R21, the above expression (2) is satisfied. Further, when the contact resistance component Rb of the charge removal member 27 is equal to or less than 6.01E + 04 [Ω] which is 2.57 times the calculated resistance value R21, the above expression (3) is satisfied.

  In Comparative Example 15, the linear velocity of the static elimination 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 the comparative example 15, when the internal resistance component Ra of the static elimination member 27 is equal to or less than 8.35E + 04 [Ω] which is 3.57 times the calculated resistance value R21, the above expression (2) is satisfied. 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 static elimination 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 Example 4, when the internal resistance component Ra of the static elimination member 27 is equal to or less than 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, the above expression (2) is satisfied. Further, when the contact resistance component Rb of the charge removal member 27 is equal to or less than 6.01E + 04 [Ω] which is 2.57 times the calculated resistance value R21, the above expression (3) is satisfied.

  In Example 5, the linear velocity of the static elimination member 27 was set to 0.255 [m / s], which is 1.7 times the linear velocity S of the photosensitive drum 21. Therefore, in Example 5, 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, the above expression (2) is satisfied. 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 the comparative example 1, the static elimination member 27 which is the raw yarn which the bristle 271 performed the cleavage process to the conductive acrylic fiber of SA7 by Toray Industries, Inc. was used. 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 low density. In addition, Comparative Examples 1 to 9 are all dispersed systems in which the presence state of carbon in the fiber is dispersed throughout the whole yarn. That is, in the static elimination member 27 which concerns on Comparative Examples 1-9, the bristle 271 is formed only with the resin layer containing carbon.

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

In the comparative example 3, the static elimination member 27 whose brush bristles 271 are the raw yarn of the conductive nylon of UUN made by Unitika Ltd. was used. In the static elimination member 27 according to Comparative Example 3, the yarn resistance is 1.00E + 06 [Ω], the brush fineness is 7 [μm] and low (fiber is thin), and the brush density is 500 [kF / inch ² ]. And high density. In addition, the static elimination member 27 which concerns on Comparative Examples 3-13 and Examples 1-3 has a circular fiber cross-sectional shape.

In Comparative Examples 4 to 6, as in Comparative Example 3, the static elimination member 27 in which the brush bristles 271 are the raw yarn of conductive nylon of UUN manufactured by Unitika Ltd. was used. In the static elimination member 27 according to Comparative Examples 4 to 6, the yarn resistances are 1.00E + 05 [Ω], 1.04E + 05 [Ω], and 1.00E + 05 [Ω], respectively. Moreover, in the static elimination member 27 which concerns on Comparative Examples 4-6, the fineness is 7 [micrometers], 6 [micrometers], and 6 [micrometers], respectively. Furthermore, in the static elimination member 27 which concerns on Comparative Examples 4-6, the density is 500 [kF / inch < ² >], 550 [kF / inch < ² >], and 500 [kF / inch < ² >], respectively.

In Comparative Examples 7 to 9, as in Comparative Example 3, the static elimination member 27 in which the brush bristles 271 are the raw yarn of UUN made by Unitika Ltd. UUN was used. On the other hand, the static elimination member 27 according to Comparative Examples 7 to 9 increases the carbon amount of the fiber as compared with Comparative Example 3 so that the values of the internal resistance component Ra and the contact resistance component Rb are small. In the static elimination member 27 according to Comparative Examples 7 to 9, the yarn resistance is 1.00E + 05 [Ω], 1.00E + 04 [Ω], 1.00E + 05 [Ω], and the brush fineness is 6 [μm], 7 [μm]. ], 6 [μm], low (fibers are thin), 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 whose brush bristles 271 are raw yarns of GBN fibers manufactured by KB Seiren Co., Ltd. were 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 (fiber is thin), and the brush density is 500 [kF / inch ² ]. And high density. Moreover, in the static elimination member 27 which concerns on Examples 1-3 and Comparative Examples 10-13, the presence state of the carbon of a fiber is not a total dispersion system, but is a two-layer structure in which carbon exists on the outer side of a fiber, and contact resistance component Rb is decreasing. That is, in the static elimination member 27 which concerns on Examples 1-3 and Comparative Examples 10-13, the bristle 271 has the core part 271A and the surface layer part 271B.

  In Comparative Example 10, as in Example 1, the bristles 271 used the neutralizing member 27 which is a raw yarn of GBN fiber manufactured by KB Seiren Co., Ltd., but differs in that the yarn resistance is two orders of magnitude higher.

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

In Example 2, the static elimination member 27 in which the bristle 271 is a polyester yarn 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 (fiber is thin), and the brush density is 300 [kF / inch ² ]. And high density. Moreover, although the static elimination member 27 according to the second embodiment has a two-layer structure in which carbon is present outside the fiber as in the first embodiment, the carbon particles are directly sprayed on the outer side of the fiber. As a result, the same level of electrical characteristics as in Example 1 is realized with a lower brush density than in Example 1.

In Example 3, the static elimination member 27 in which the bristle 271 is a polyester yarn is used. In the static elimination member 27 according to Example 3, the yarn resistance is 6.40E + 03 [Ω], the brush fineness is 7 [μm] and low (fiber is thin), and the brush density is 300 [kF / inch ² ]. And high density. In addition, 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 is in a state in which carbon particles are directly sprayed on the outside of the fiber. Note that the amount of carbon sprayed in Example 3 is smaller than that in Example 2.

  In Comparative Example 14, the same static elimination member 27 as in Comparative Example 10 was used. In Comparative Example 15, the same static eliminating member 27 as that in Comparative Example 13 was used. In Example 4, the same static eliminating member 27 as that in Comparative Example 5 was used. In Example 5, the same static eliminating member 27 as that in 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. The condition is not met. On the other hand, in Comparative Examples 7 to 9 and Comparative Examples 11 to 13, the internal resistance component Ra is 7.02E + 04 [Ω] or less, which is three times the calculated resistance value R21. Therefore, the condition of the above expression (2) is satisfied. ing. 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. Therefore, the condition of the above expression (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. Therefore, the condition of the above expression (2) is satisfied. However, in Comparative Examples 1 to 6, Comparative Example 10, and Comparative Example 13, the contact resistance component Rb exceeds 2.81E + 04 [Ω], which is 1.2 times the calculated resistance value R21. The condition of the expression is not satisfied. And in the comparative examples 1-6, the comparative example 10, and the comparative example 13, the evaluation result of the static elimination performance was "x".

  On the other hand, in Examples 1 to 3, 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. In addition, the condition of the above formula (3) is satisfied 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. In Example 4, 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 1.502E + 05 [Ω], which is 6.42 times the calculated resistance value R21, is satisfied. In addition, the condition of the above expression (3) is satisfied that the contact resistance component Rb is 6.01E + 04 [Ω] or less which is 2.57 times the calculated resistance value R21. In Example 5, the condition of the above formula (2) that the internal resistance component Ra of the static elimination member 27 is 1.64E + 05 [Ω] or less, which is 6.99 times the calculated resistance value R21, is satisfied. In addition, the condition of the above expression (3) is satisfied that the contact resistance component Rb is 6.55E + 04 [Ω] or less, which is 2.80 times the calculated resistance value R21. And in Examples 1-5, the evaluation result of static elimination performance was "(circle)".

  Here, in Comparative Example 5, the evaluation result of the static elimination performance is “×”, whereas in the Example 4 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is improved to “◯”. . In Comparative Example 6, the evaluation result of the static elimination performance is “×”, 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 Example 14 and Comparative Example 15 in which the same static elimination member 27 is used, the evaluation result of the static elimination performance is It has improved to “○”. From these results, it can be seen that the static elimination performance can be improved by setting the linear velocity of the static elimination member 27 at a speed higher than the linear velocity S of the photosensitive drum 21. FIG. 8 shows the relationship between the linear velocity of the static elimination member 27 and the post-static 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 was found that desired static elimination performance can be obtained 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, the desired static elimination performance was obtained when the conditions of the above formulas (2) and (3) were satisfied.

  In addition, as shown in FIG. 7, the internal capacitance of the contact capacitance component Cb in the Cole-Cole plot measured using the experimental apparatus 90 for the static elimination members 27 according to Comparative Examples 1 to 15 and Examples 1 to 5 is used. The capacitance ratio (Cb / Ca) with respect to the capacitance component Ca was calculated. Here, in Comparative Examples 1-4, Comparative Examples 8-9, Comparative Examples 12-13, 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 5-7, Comparative Examples 10-11, 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) of 0.4 or less is satisfied. However, in Comparative Examples 1-3, Comparative Examples 7-8, and Comparative Examples 10-15, since the internal capacitance component Ca of the charge removal member 27 exceeds 1.0E + 5.0, the internal capacitance component Ca The condition of the above formula (4) that is 1.0E + 5.0 or less is not satisfied. The potential stability and the presence / absence of image memory were evaluated only for the evaluation results of the static elimination performance of “◯”. 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 charge removal member 27 is 1.0E + 5.0 or less is satisfied, and the capacitance ratio (Cb The condition of the above equation (5) that / Ca) is 0 or more and 0.4 or less is satisfied. 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, not only the direct current resistance of the static elimination member 27 but also the internal impedance Z 1 and the contact impedance Z 2 are taken into consideration, whereby the potential stability is improved and the generation of the image memory is suppressed. all right. More specifically, when the conditions of the above equations (4) and (5) are satisfied, the potential stability is improved and the generation of image memory is suppressed.

  Incidentally, 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 static elimination member 27 is in contact with the photosensitive drum 21, when the static elimination performance of the static elimination member 27 is set in accordance with the maximum value of the applied voltage, wear of the photosensitive 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 embodiment of the present invention, as described below, it is possible to suppress wear of the photosensitive drum 21 while ensuring necessary static elimination performance.

  Specifically, the ROM of the control unit 1 stores in advance a first speed change program for causing the CPU to execute a first speed change process described later (see the flowchart of FIG. 11). The first speed change program is recorded on a computer-readable recording medium such as a CD, DVD, or 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 a thing.

  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 FIG. 10 shows. Specifically, the control unit 1 executes the first speed change program stored in the ROM using the CPU. Thereby, the control unit 1 functions as the concentration detection unit 11, the voltage change unit 12, and the first speed change unit 13A.

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

  Specifically, in the image forming apparatus 10, as shown in FIG. 2, on the downstream side in the rotation direction of the photosensitive drum 21 with respect to the developing device 24 and on the upstream side in the rotation direction with respect to the transfer roller 25. 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 by the surface of the photosensitive drum 21 is received by the light receiving unit. Then, an electrical signal corresponding to the amount of received light is output from the light receiving unit.

  For example, the density detection unit 11 controls the operation of each unit of the image forming unit 2 to form the patch image on the surface of the photosensitive drum 21 when a predetermined first timing arrives. The density detector 11 detects the density of the patch image using the density sensor 29. For example, the first timing is when the image forming apparatus 10 is turned on, when returning from a sleep state in which some functions of the image forming apparatus 10 are stopped, and when the printing 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 also 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 is lighter than a predetermined range. In addition, the voltage changing unit 12 changes the applied voltage from 500 V to 300 V when the density of the patch image exceeds the specific range.

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

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

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

  For example, in the image forming apparatus 10, the static elimination member 27 rotates at a higher linear speed than the photosensitive drum 21 as described above. Therefore, the first speed changing unit 13A increases the linear speed of the static elimination member 27 and increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27. When the static elimination member 27 rotates at a slower linear speed than the photosensitive drum 21, the first speed changing unit 13 </ b> A decreases the linear speed of the static elimination member 27 to reduce the linear speed 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. Yes. When the applied voltage is changed by the voltage changing unit 12, 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. The linear velocity of the static elimination member 27 that satisfies the above condition is calculated. Then, the first speed changing unit 13A changes the linear speed of the charge removal member 27 based on the calculation result.

  In addition, 13 A of 1st speed change parts may change the linear speed of the static elimination member 27 to the speed whose difference with the said 1st specific speed is below the preset allowable value. Moreover, 13 A of 1st speed change parts may change the linear speed of the static elimination member 27 into the speed with which ratio Sr satisfy | fills said Formula (6) and said Formula (7).

  In the image forming apparatus 10, first table data indicating the linear velocity of the charge removal member 27 corresponding to each of the applied voltages that can be set in the image forming apparatus 10 may be stored in the ROM of the control unit 1 in advance. . In this case, when the applied voltage is changed by the voltage changing unit 12, the first speed changing unit 13A may change the linear velocity of the charge removal member 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-static potential V0 and the post-static potential V1 using the image forming apparatus 10. Here, FIG. 12 shows an example of experimental data obtained by the experiment.

  The first speed changing unit 13 </ b> A 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 removal member 27.

[First speed change process]
Hereinafter, an example of the procedure of the first speed change process executed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG. Here, steps S11, S12,... Represent the 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, if the control part 1 judges that the said 1st timing has come (Yes side of S11), it will transfer a process 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 concentration detection process. Here, the processing of step S11 and step S12 is executed by the concentration 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 photosensitive drum 21. Then, the control unit 1 uses the density sensor 29 to detect the density of the patch image. In step S12, the control unit 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 S <b> 13 is executed by the voltage changing unit 12 of the control unit 1.

  For example, if the density of the patch image detected in step S12 is lighter than the specific range, the control unit 1 sets the applied voltage stored in the predetermined first storage area of the RAM. The data indicating the value is rewritten to change the applied voltage to 800V. In addition, when the density of the patch image exceeds the specific range, the control unit 1 rewrites the data in the first storage area and changes the applied voltage to 300V. In addition, 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 S <b> 14, the control unit 1 changes the linear velocity of the static elimination member 27 according to the applied voltage after the change in step S <b> 13. 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 static elimination member 27 so that the ratio Sr satisfies the above formulas (6) and (7) and the difference from the linear velocity of the photosensitive drum 21 is minimized. Change to the first specific speed. For example, the control unit 1 rewrites data indicating the set value of the linear velocity of the static elimination member 27 stored in a predetermined second storage area of the RAM, and changes the linear velocity of the static elimination member 27.

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

  Further, in the image forming apparatus 10 according to the first embodiment, the linear velocity of the static elimination member 27 is such that the ratio Sr satisfies the above formulas (6) and (7) and is different from the linear velocity of the photosensitive drum 21. Is changed to the first specific speed. As a result, the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27 is minimized within a range in which the required static elimination performance can be ensured. For this reason, it is possible to more effectively suppress wear of the photosensitive drum 21.

  The first speed changing unit 13A is configured to reduce the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removal member 27 in accordance with a 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 in which the first speed changing unit 13A decreases the linear speed of the static elimination member 27 every time a predetermined period elapses can be considered. According to this configuration, it is possible to more effectively suppress wear of the photosensitive drum 21.

[Second Embodiment]
The image forming apparatus 10 according to the second embodiment of the present invention will be described below with reference to FIGS. In the image forming apparatus 10 according to the second embodiment, the configurations of the charge removal member 27 and the control unit 1 are different from those of the first embodiment. 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 neutralizing member 27 is the first direction D1 approaching the photosensitive drum 21 and the 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 embodiment, the bearing that supports the rotation shaft of the charge removal member 27 is supported by the housing of the image forming apparatus 10 so as to be able to move in the first direction D1 and the second direction D2. Yes.

  Further, 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 changing program for causing the CPU to execute a contact pressure changing process (see the flowchart of FIG. 15) described later. And the control part 1 functions as the density | concentration detection part 11, the voltage change part 12, and the movement process part 14 by running the said contact pressure change program memorize | stored in said ROM using said CPU. Note that the concentration detection unit 11 and the voltage change unit 12 are not different from those in the first embodiment, and thus description thereof is omitted.

  The movement processing unit 14 decreases the separation distance between the photosensitive drum 21 and the charge removal 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 removal member 27 as the applied voltage applied to the charging roller 220 is higher. Thereby, the contact resistance component Rb between the photosensitive drum 21 and the charge removal member 27 is reduced.

  Specifically, when the applied voltage is increased by the voltage changing unit 12, the movement processing unit 14 moves the static elimination member 27 in the first direction D <b> 1 to reduce the separation distance between the photosensitive drum 21 and the static elimination member 27. . Further, when the applied voltage decreases by the voltage changing unit 12, the movement processing unit 14 moves the static elimination member 27 in the second direction D <b> 2 and increases the separation distance between the photosensitive drum 21 and the static elimination member 27.

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

[Contact pressure change processing]
Hereinafter, an example of the procedure of the contact pressure changing process executed by the control unit 1 in the image forming apparatus 10 will be described with reference to FIG. Of the steps included in the contact pressure changing process, steps having the same processing contents as the steps 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 static elimination member 27 in the first direction D1 or the second direction D2 in accordance with the applied voltage after the change in step S13, thereby separating the photosensitive drum 21 and the static elimination member 27 from each other. Increase or decrease. Here, the process of step S <b> 15 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 static elimination member 27 in the first direction D1 based on the second table data to reduce the separation distance between the photosensitive drum 21 and the static elimination member 27. . Further, when the applied voltage decreases, the control unit 1 moves the static elimination member 27 in the second direction D2 based on the second table data to increase the separation distance between the photosensitive drum 21 and the static elimination member 27. .

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

  Note that 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, as the applied voltage applied to the charging roller 220 is higher, the separation distance between the photosensitive drum 21 and the charge removal member 27 is decreased, and the photosensitive drum 21 is also used. The difference between the linear speed and the linear speed of the static elimination member 27 may be increased.

  By the way, in the configuration in which the charge removal member 27 is in contact with the photosensitive drum 21, an external additive such as silica contained in the toner may adhere to the charge removal member 27. Here, when the adhesion amount of the external additive on the charge removal member 27 increases, the contact resistance between the photosensitive drum 21 and the charge removal member 27 increases, and the charge removal performance of the charge removal member 27 decreases.

[Third Embodiment]
The image forming apparatus 10 according to the third embodiment of the present invention will be described below with reference to FIGS. 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. Other configurations are common to the first embodiment and the third embodiment.

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

  In addition, as shown in FIG. 16, the control unit 1 replaces the concentration detection unit 11, the voltage change unit 12, and the first speed change 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 executes the second speed change program stored in the ROM using the CPU, so that 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 a cumulative value of toner (developer) consumption based on a preset first acquisition condition.

  For example, the first acquisition processing unit 15A acquires the cumulative value of the toner consumption amount when a predetermined second timing arrives. For example, the second timing is the same as the first timing, when the image forming apparatus 10 is turned on, when a part of the functions of the image forming apparatus 10 is stopped, when returning from the sleep state to the normal state, and when the printing is performed. For example, when processing is executed.

  For example, in the image forming apparatus 10, a cumulative printing rate that is a cumulative value of the printing rates of each printed matter output from the image forming device 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 a printing rate in each printed matter output by the printing process based on image data printed by the printing process. In addition, when the size of a sheet on which an image is printed by the printing process is different from a predetermined reference size, the control unit 1 converts each calculated printing rate into a printing rate for a sheet of the reference size. To do. Then, the control unit 1 updates the cumulative printing rate stored in the third storage area based on the calculated or converted total values of the printing rates.

  Then, the first acquisition processing unit 15A acquires a cumulative value of toner consumption 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 a cumulative value of toner consumption 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 based on the cumulative number of printed sheets (another example of the first acquisition condition) that is the cumulative value of the number of printed materials output by the image forming apparatus 10. A value may be acquired.

  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 static elimination member 27 based on the cumulative value of the toner consumption acquired by the first acquisition processing unit 15A.

  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 static elimination member 27 corresponding to each predetermined cumulative value of toner consumption is stored in the ROM of the control unit 1 in advance. Stored. The first change amount acquisition unit 16A acquires the change amount ΔRb of the contact resistance component Rb of the charge removal member 27 based on the cumulative amount of toner consumption 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 investigating the relationship between the cumulative value of toner consumption in the image forming apparatus 10 using the image forming apparatus 10 and the contact resistance component Rb. The Here, FIG. 18 shows an example of experimental data obtained by the experiment. FIG. 18 shows the relationship between the cumulative printing rate P used for calculating the cumulative value of the toner consumption and the contact resistance component Rb.

  18 may be stored in advance in the ROM of the control unit 1 to indicate the relationship between the cumulative printing rate P derived from the experimental data shown in FIG. 18 and the change amount ΔRb of the contact resistance component Rb. . 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). Further, the control unit 1 may not include the first acquisition processing unit 15A. In the following equation (8), F, G, and H are constants derived from the experimental data shown in FIG.

  The second speed changing unit 13B calculates the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge eliminating member 27 in accordance with an increase in the cumulative value of the toner consumption acquired based on the first acquisition condition. increase.

  Specifically, the second speed changing unit 13B is configured such that the linear speed of the static elimination member 27 is such that the ratio Sr satisfies the above formula (2) and the following formula (9), and the difference from the linear speed of the photosensitive drum 21 is the smallest. The second specific speed is changed.

  For example, in the image forming apparatus 10, the static elimination member 27 rotates at a higher linear speed than the photosensitive drum 21 as described above. Therefore, the second speed changing unit 13B increases the linear speed of the static elimination member 27 and increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27. When the static elimination member 27 rotates at a slower linear speed than the photosensitive drum 21, the second speed changing unit 13 </ b> B decreases the linear speed of the static elimination member 27 to reduce the linear speed 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 R21 are stored in advance in the ROM of the control unit 1. When the change amount ΔRb of the contact resistance component Rb is acquired by the first change amount acquisition unit 16A, the second speed change unit 13B calculates 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 that satisfies the above-described conditions is calculated. And the 2nd speed change part 13B changes the linear velocity of the static elimination member 27 based on a calculation result.

  Note that the second speed changing unit 13B may change the linear speed of the charge removal member 27 to a speed in which the difference from the second specific speed is equal to or less than the allowable value. Further, the second speed changing unit 13B may change the linear speed of the static elimination member 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 eliminating member 27 corresponding to each predetermined cumulative value of toner consumption may be stored in the ROM of the control unit 1 in advance. . In this case, the second speed changing unit 13B may change the linear speed of the charge removal member 27 using the accumulated value of the toner consumption acquired by the first acquisition processing unit 15A and the fourth table data. In this case, the control unit 1 may not include the first change amount acquisition unit 16A. For example, the fourth table data includes experimental data obtained by an experiment for investigating the relationship between the cumulative value of toner consumption using the image forming apparatus 10 and the post-charge 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 post-static discharge potential V1.

  Further, the second speed changing unit 13 </ b> B 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 removal member 27. Further, the second speed changing unit 13B may increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge removal member 27 within a range equal to or less than a preset upper limit value.

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

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

  Here, if the control part 1 judges that the said 2nd timing has come (Yes side of S21), it will transfer a process to step S22. If the second timing has not arrived (No side in S21), the control unit 1 waits for the arrival of the second timing in step S21.

<Step S22>
In step S <b> 22, the control unit 1 acquires a cumulative value of toner consumption in the image forming apparatus 10. Here, the processing of step S21 and step S22 is executed by the first acquisition processing unit 15A of the control unit 1.

  Specifically, the control unit 1 obtains a cumulative value of toner consumption 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 removal member 27 based on the cumulative value of the toner consumption 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. Note that 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 removal member 27 based on the cumulative value of the toner consumption acquired in step S22 and the third table data.

<Step S24>
In step S24, the control unit 1 changes the linear velocity of the charge removal member 27 based on the change amount ΔRb of the contact resistance component Rb of the charge removal member 27 acquired in step S23. Here, the process of step S24 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 static elimination member 27 so that the ratio Sr satisfies the above formulas (2) and (9) and the difference from the linear velocity of the photosensitive drum 21 is minimized. Change to the second specific speed. For example, the control unit 1 rewrites data indicating the set value of the linear velocity of the static elimination member 27 stored in the second storage area of the RAM, and changes the linear velocity of the static elimination member 27.

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

  Further, in the image forming apparatus 10 according to the third embodiment, the linear velocity of the static elimination member 27 is such that the ratio Sr satisfies the above formulas (2) and (9) and is different from the linear velocity of the photosensitive drum 21. Is changed to the second specific speed that minimizes. As a result, the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27 is minimized within a range in which the required static elimination performance can be ensured. For this reason, it is possible to suppress wear of the photosensitive drum 21.

  The second speed changing unit 13B has the highest cumulative print rate acquired for each of the divided areas among the predetermined divided areas in the main scanning direction orthogonal to the conveyance direction of the sheet on which the image is formed. A configuration in which the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the charge removal member 27 is increased in accordance with an increase in the cumulative value of the toner consumption 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 in which the cumulative printing rate for each of the divided areas is stored. Further, it is considered that the first acquisition processing unit 15A obtains a cumulative value of toner consumption by multiplying the cumulative printing rate corresponding to the specific divided area by the number of the divided areas and the coefficient. It is done. According to this configuration, it is possible to set the linear velocity of the static elimination member 27 with reference to the location where the amount of the external additive attached in the main scanning direction is the largest in the static elimination member 27.

  Further, as shown in FIG. 19, the image forming apparatus 10 may include a cleaning member 274 that cleans the surface of the charge removal member 27 as another modification of the third embodiment. For example, the cleaning member 274 is a blade-like 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 removal member 27. For example, the cleaning member 274 is provided at a position that bites into the outer diameter of the charge removal 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 to the static elimination member 27. When the image forming apparatus 10 is provided with the cleaning member 274, it is conceivable to correct the contents of the third table data, the above equation (8), and the fourth table data.

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

[Fourth Embodiment]
The image forming apparatus 10 according to the fourth embodiment of the present invention will be described below 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. Other configurations are common between 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 unit 2.

  Further, as illustrated in FIG. 20, the control unit 1 replaces the concentration detection unit 11, the voltage change unit 12, and the first speed change 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 change program for causing the CPU to execute a third speed change process (see the flowchart of FIG. 21) described later. Then, the control unit 1 uses the CPU to execute the third speed change program stored in the ROM, thereby obtaining a second acquisition processing unit 15B, a second change amount acquisition unit 16B, and a third speed. It functions as the changing unit 13C.

  The second acquisition processing unit 15B acquires the outer diameter of the static elimination member 27 based on a preset second acquisition condition (an example of the acquisition condition of the present invention).

  For example, the second acquisition processing unit 15B acquires the outer diameter of the charge removal member 27 when a predetermined third timing has arrived. For example, the third timing is similar to the first timing, when the image forming apparatus 10 is turned on, when a part of the functions of the image forming apparatus 10 is stopped, and when returning from the sleep state to the normal state, and when the printing is performed. For example, when processing is executed.

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

  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 number of printed sheets stored in the fourth storage area every time the printing process is executed.

  Further, in the image forming apparatus 10, fifth table data indicating the outer diameter of the charge removal member 27 corresponding to each of the predetermined cumulative number of printed sheets is stored in the ROM of the control unit 1 in advance. The second acquisition processing unit 15B acquires the outer diameter of the charge removal 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 investigating the relationship between the cumulative number of printed sheets and the outer diameter of the charge removal 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 experiment.

  Note that the second acquisition processing unit 15B may acquire the outer diameter of the charge removal member 27 based on the cumulative number of rotations of the charge removal member 27 (another example of the second acquisition condition). Further, 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). Also good. Further, 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 current value flowing through the first driving unit 272. Also 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. FIG.

  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 charge removal member 27 based on the decrease amount of the outer diameter of the charge removal member 27 acquired by the second acquisition processing unit 15B. To do. The second change amount acquisition unit 16B is an example of the change amount acquisition unit in the present invention.

  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 elimination member 27 corresponding to each predetermined reduction amount of the outer diameter of the static elimination member 27 is previously stored in the control unit 1. Stored in ROM. The second change amount acquisition unit 16B is based on the outer diameter of the charge removal member 27 acquired by the second acquisition processing unit 15B and the outer diameter of the charge removal member 27 stored in advance in the ROM when the image forming apparatus 10 is manufactured. Thus, the reduction amount of the outer diameter of the static elimination member 27 is calculated. And the 2nd variation | change_quantity acquisition part 16B acquires variation | change_quantity (DELTA) Rb of the contact resistance component Rb of the static elimination member 27 based on the amount of reduction | decrease in the outer diameter of the static elimination member 27, and the said 6th table data. For example, the sixth table data is created based on experimental data obtained by an experiment investigating the relationship between the reduction amount of the outer diameter of the static elimination member 27 using the image forming apparatus 10 and the contact resistance component Rb.

  The third speed changing unit 13C increases the difference between the linear velocity of the photosensitive drum 21 and the linear velocity of the static elimination member 27 in accordance with the decrease in the outer diameter of the static elimination member 27 acquired based on the second acquisition condition. Let Here, the third speed changing unit 13C is an example of a speed changing unit in the present invention.

  Specifically, the third speed changing unit 13 </ b> C has the linear speed of the static elimination member 27, the ratio Sr satisfies the above formulas (2) and (9), and the difference from the linear speed of the photosensitive drum 21 is the smallest. To the third specific speed (an example of the specific speed of the present invention).

  For example, in the image forming apparatus 10, the static elimination member 27 rotates at a higher linear speed than the photosensitive drum 21 as described above. Therefore, the third speed changing unit 13 </ b> C increases the linear speed of the static elimination member 27 and increases the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27. When the static elimination member 27 rotates at a slower linear speed than the photosensitive drum 21, the third speed changing unit 13 </ b> C decreases the linear speed of the static elimination member 27 to reduce the linear speed of the photosensitive drum 21 and the static elimination member 27. The difference from the linear velocity may be increased.

  For example, when the change amount ΔRb of the contact resistance component Rb is acquired by the second change amount acquisition unit 16B, the third speed change unit 13C has the internal resistance component Ra, the contact resistance component Rb, And the linear velocity of the static elimination member 27 which satisfy | fills the above-mentioned conditions is calculated using calculated resistance value R21. And the 3rd speed change part 13C changes the linear velocity of the static elimination member 27 based on a calculation result.

  Note that the third speed changing unit 13C may change the linear speed of the charge removal member 27 to a speed at which the difference from the third specific speed is equal to or less than the allowable value. Further, the third speed changing unit 13C may change the linear speed of the static elimination member 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, seventh table data indicating the linear velocity of the neutralizing member 27 corresponding to each predetermined reduction amount of the outer diameter of the neutralizing member 27 is stored in the ROM of the control unit 1 in advance. Also good. In this case, even if the third speed changing unit 13C changes the linear velocity of the static eliminating member 27 using the reduction amount of the outer diameter of the static eliminating member 27 acquired by the second acquisition processing unit 15B and the seventh table data. Good. 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 investigating the relationship between the reduction amount of the outer diameter of the static elimination member 27 using the image forming apparatus 10 and the post-static potential V1, and the image forming apparatus 10. It is created on the basis of experimental data obtained by an experiment investigating the relationship between the ratio Sr and the post-static discharge potential V1.

  The third speed changing unit 13 </ b> C 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 removal member 27. Further, the third speed changing unit 13C may increase the difference between the linear speed of the photosensitive drum 21 and the linear speed of the charge eliminating member 27 within a range that is equal to or less than a preset upper limit value.

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

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

  Here, if the control part 1 judges that the said 3rd timing has come (Yes side of S31), it will transfer a process to step S32. If the third timing has not arrived (No side in S31), the control unit 1 waits for the arrival of the third timing in step S31.

<Step S32>
In step S <b> 32, the control unit 1 acquires the outer diameter of the static elimination member 27. Here, the process of step S31 and step S32 is an example of the acquisition step in the present invention, and 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 removal 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 S <b> 33, the control unit 1 acquires the change amount ΔRb of the contact resistance component Rb of the charge removal member 27 based on the decrease amount of the outer diameter of the charge removal member 27 acquired in step S <b> 32. Here, the process of step S33 is executed by the second change amount acquisition unit 16B of the control unit 1. Note that the process of step S33 may be omitted.

  Specifically, the control unit 1 determines whether the static elimination member 27 is based on the outer diameter of the static elimination member 27 acquired in step S32 and the outer diameter of the static elimination member 27 at the time of manufacturing the image forming apparatus 10 stored in advance in the ROM. The amount of decrease in the outer diameter of 27 is calculated. And the control part 1 acquires variation | change_quantity (DELTA) Rb of the contact resistance component Rb of the static elimination member 27 based on the reduction | decrease amount of the outer diameter of the static elimination member 27 and the said 6th table data.

<Step S34>
In step S34, the control unit 1 changes the linear velocity of the charge removal member 27 based on the change amount ΔRb of the contact resistance component Rb of the charge removal member 27 acquired in step S33. Here, the process of step S34 is an example of a speed changing step in the present invention, and 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 static elimination member 27 so that the ratio Sr satisfies the above formulas (2) and (9) and the difference from the linear velocity of the photosensitive drum 21 is minimized. Change to the third specific speed. For example, the control unit 1 rewrites data indicating the set value of the linear velocity of the static elimination member 27 stored in the second storage area of the RAM, and changes the linear velocity of the static elimination member 27.

  As described above, in the image forming apparatus 10 according to the fourth embodiment, the linear velocity of the photosensitive drum 21 and the charge removal member 27 are changed according to the decrease in the outer diameter of the charge removal member 27 acquired based on the second acquisition condition. The difference from the linear speed increases. Thereby, it is possible to suppress a decrease in the charge removal performance of the charge removal member 27 due to a decrease in the outer diameter of the charge removal member 27.

  In the image forming apparatus 10 according to the fourth embodiment, the linear velocity of the static elimination member 27 is such that the ratio Sr satisfies the above formulas (2) and (9) and is different from the linear velocity of the photosensitive drum 21. Is changed to the third specific speed. As a result, the difference between the linear speed of the photosensitive drum 21 and the linear speed of the static elimination member 27 is minimized within a range in which the required static elimination performance can be ensured. For this reason, it is possible to suppress wear of the photosensitive drum 21.

  As shown in FIG. 23, the image forming apparatus 10 includes a rotation control unit 17 as a modification of the fourth embodiment. Specifically, the rotation control unit 17 increases the accumulated number of printed sheets or the accumulated number of rotations by a predetermined reference value at a predetermined fourth timing different from the execution time of the printing process. The neutralizing member 27 is rotated in the direction opposite to the rotation direction when the printing process is executed. For example, the rotation control unit 17 rotates the static elimination 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 periodically corrected, a decrease in the outer diameter of the static elimination member 27 can be suppressed. When the rotation control unit 17 is provided in the image forming apparatus 10, it is conceivable to correct the contents of the fifth table data.

DESCRIPTION OF SYMBOLS 1 Control part 2 Image formation part 3 Paper feed part 4 Paper discharge part 10 Image forming apparatus 11 Density detection part 12 Voltage change part 13A 1st speed change part 13B 2nd speed change part 13C 3rd speed change part 14 Movement process part 15A First acquisition processing unit 15B Second acquisition processing unit 16A First change amount acquisition unit 16B Second change amount acquisition unit 17 Rotation control unit 21 Photoconductor drum 22 Charging device 23 Optical scanning device 24 Development device 25 Transfer roller 26 Cleaning member 27 Static elimination member 270 Base portion 271 Brush bristles 272 First drive portion 273 Second drive portion 274 Cleaning member 28 Fixing device 29 Density sensor

Claims (12)

A photoreceptor,
A brush-like static eliminating member that is electrically grounded and is rotatably disposed in contact with the surface of the photoreceptor;
A speed changing unit that increases a difference between a linear velocity of the photosensitive member and a linear velocity of the static eliminating member in accordance with a decrease in the outer diameter of the static eliminating member acquired based on a preset acquisition condition;
An image forming apparatus comprising: The acquisition condition includes one or more of a cumulative number of printed sheets, a cumulative number of rotations of the static elimination member, and a current value flowing through a drive unit that drives the static elimination member.
The image forming apparatus according to claim 1. A change amount acquisition unit for acquiring a change amount of a resistance component of the contact impedance of the charge removal member obtained from a Cole-Cole plot in a predetermined frequency range by an AC impedance method based on a decrease amount of the outer diameter of the charge removal member. With
The speed change unit is acquired by the change amount acquisition unit by 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, Rb, the resistance component of the contact impedance. The amount of change is ΔRb, the ratio of the linear velocity of the neutralizing member to the linear velocity of the photosensitive member is Sr, and the static elimination time obtained by dividing the contact width of the photosensitive member and the neutralizing member by the linear velocity of the photosensitive member R21 is a calculated resistance value calculated based on a predetermined arithmetic expression as a direct current resistance value of the static eliminating member necessary for lowering the potential before static elimination of the photoconductor to a predetermined potential after static elimination during The linear velocity of the static elimination member is changed to a speed at which the ratio Sr satisfies the following formula (1) and the following formula (2).
The image forming apparatus according to claim 1.

The speed changing unit is a specific speed at which the linear speed of the static elimination member is satisfied, the ratio Sr satisfies the above formulas (1) and (2), and the difference from the linear speed of the photoconductor is minimized, or The difference from the specific speed is changed to a speed equal to or less than a preset allowable value.
The image forming apparatus according to claim 3. When the electrostatic capacity of the photoconductor is C, the static elimination time is t, the potential before static elimination is V0, and the potential after static elimination is V1, the calculated resistance value R21 is calculated based on the following equation (3). ,
The image forming apparatus according to claim 3 or 4.

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 is rotated at a predetermined timing different from the execution time of the printing process. Has a rotation control unit that rotates in the opposite direction,
The image forming apparatus according to claim 2. The speed changing unit increases a linear velocity of the static elimination member to increase a difference between a linear velocity of the photosensitive member and a linear velocity of the static elimination member;
The image forming apparatus according to claim 1. The speed changing unit decreases the linear velocity of the static elimination member and increases the difference between the linear velocity of the photoreceptor and the linear velocity of the static elimination member;
The image forming apparatus according to claim 1. The photoreceptor is charged by a contact-type charging member;
The image forming apparatus according to claim 1. The photoreceptor is charged by application of a DC voltage;
The image forming apparatus according to claim 1. The static eliminating member has a cylindrical base portion, and brush hairs, one end of which is fixed to the base portion and the other end contacts 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 claim 1. An image forming method executed by an image forming apparatus comprising: a photoconductor; and a brush-shaped static elimination member that is electrically grounded and is rotatably disposed in contact with the surface of the photoconductor,
An acquisition step of acquiring the outer diameter of the static elimination member based on a preset acquisition condition;
A speed changing step for increasing a difference between the linear velocity of the photosensitive member and the linear velocity of the static elimination member in accordance with a decrease in the outer diameter of the static elimination member acquired in the acquisition step;
An image forming method comprising:

Images