Image forming apparatus and photoreceptor surface potential estimation method

Abstract

To estimate the surface potential of a photoreceptor during image formation while removing the influence of electric charges remaining in the photoreceptor after the image formation without increasing the distance of travel of the photoreceptor and the waiting time for a user.SOLUTION: An image forming apparatus comprises: a rotatable photoreceptor 3 that carries a latent image; an electrifying member 6 that electrifies the photoreceptor 3; a static eliminating member 21 that irradiates the photoreceptor 3 with light to eliminate static electricity; a current detection unit 70 that detects a feedback current generated when an electrification bias is applied to the electrifying member 6; and a control unit 65 that controls the electrifying member 6 and the static eliminating member 21. The electrification bias applied to the electrifying member 6 is switched from an electrification bias V1 during image formation to an electrification bias V2 before static elimination, and the image forming apparatus estimates the surface potential of the photoreceptor during image formation from a DC component of the feedback current flowing in the current detection unit 70 when the electrification bias is switched.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image reading device and a method for estimating a surface potential of a photoconductor. [Background technology]

[0002] In an image forming apparatus, a configuration in which a device such as a surface potential sensor is installed near the photosensitive member to detect the surface potential of the photosensitive member has the problem of increasing costs and machine size. To address this problem, a technology is known that uses a feedback (FB) circuit to detect the current flowing through the charging member when charging the photosensitive member, and estimates the surface potential of the photosensitive member after charging without using a device such as a surface potential sensor.

[0003] For example, Patent Document 1 discloses a technology in which, during printing, a charging AC bias and a charging DC bias are superimposed and applied to a charging member to charge the photosensitive member, and when the printing operation is completed, only the charging AC bias is applied to the charging member to discharge the surface of the photosensitive member, the charging DC current, which is the DC component of the current flowing from a power source to the photosensitive member, is detected and output to a control unit, and the surface potential of the photosensitive member after discharge is estimated based on the amount of charging charge calculated based on the information on the charging DC current.

[0004] Furthermore, Patent Document 2 proposes a technology that can detect the surface potential of a photosensitive element under the same conditions as during image formation, in which the surface potential of the photosensitive element after charging is estimated by using the change in internal current that occurs during AC neutralization. Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology of Patent Document 2 requires the preparation of a dedicated sequence for estimating the surface potential using the internal current, which poses the problem of increasing the travel distance of the photosensitive drum and increasing the waiting time of the user. On the other hand, if only AC static elimination is performed to avoid these problems, the residual charge in the photosensitive layer of the photoreceptor may not be completely removed, which may adversely affect the quality of subsequent image formation.

[0006] To remove the residual charge after AC static elimination, a method of combining it with light irradiating the photoconductor can be considered. As a means for irradiating the photoconductor with light, a light source, which is a writing means for the photoconductor, can also be used. However, simply combining AC de-ionization with de-ionization by light irradiation may result in abnormalities such as carrier adhesion due to the potential difference between the photosensitive element outside the writable area and the developing member, for example, when the development opening width is larger than the writable area.

[0007] Therefore, the present invention aims to estimate the surface potential of a photosensitive element during image formation, while eliminating the influence of electric charges remaining on the photosensitive element after image formation, without increasing the travel distance of the photosensitive element or the waiting time of the user. [Means for solving the problem]

[0008] In order to solve the above problems, an image forming apparatus of the present invention includes a rotatable photosensitive member that carries a latent image, a charging member that charges the photosensitive member, a discharging member that discharges electricity by irradiating the photosensitive member with light, a current detection unit that detects a feedback current that occurs when a charging bias is applied to the charging member, and a control unit that controls the charging member and the discharging member, and before starting discharging by irradiating the discharging member with light, the charging bias applied to the charging member is switched from a charging bias V1 during image formation to a charging bias V2 before discharging. and a DC component of a feedback current I_FB3 that flows through the current detection unit after neutralization by light irradiation of the neutralization member has started and the charging bias has been switched off from the charging bias V2. The present invention is characterized by estimating the surface potential of the photosensitive member during image formation.

[0009] In order to solve the above-mentioned problems, the present invention provides a method for estimating a surface potential of a photoconductor during image formation in an image forming apparatus that includes a rotatable photoconductor carrying a latent image, a charging member that charges the photoconductor, a discharging member that discharges the photoconductor by irradiating light onto the photoconductor, a current detection unit that detects a feedback current generated when a charging bias is applied to the charging member, and a control unit that controls the charging member and the discharging member, the method comprising the steps of: before starting discharging by irradiating light onto the discharging member, switching a charging bias applied to the charging member from a charging bias V1 during image formation to a charging bias V2 before discharging; a step of obtaining a DC component of a feedback current I_FB2 flowing in the current detection unit when the charging bias is switched to V2; and a step of obtaining a DC component of a feedback current I_FB3 flowing in the current detection unit after neutralization by light irradiation of the neutralization member is started and the charging bias is turned off from V2. and estimating the surface potential of the photosensitive member during image formation from the obtained value. [Effects of the Invention]

[0010] According to the present invention, it is possible to estimate the surface potential of a photosensitive element during image formation without increasing the travel distance of the photosensitive element or the waiting time of the user, while eliminating the influence of the charge remaining on the photosensitive element after image formation. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of an image forming unit included in the image forming apparatus of FIG. [Figure 3] FIG. 10 is a schematic diagram showing an example of a configuration for estimating a photosensitive member surface potential. [Figure 4] 4 is a flowchart illustrating a method for estimating a photoconductor surface potential according to an embodiment of the present invention. [Figure 5] FIG. 10 is a timing chart showing a sequence for estimating a surface potential of a photoconductor; [Figure 6] 5 is an explanatory diagram showing the photosensitive member surface potential at each timing shown in FIG. 4. FIG. [Figure 7] 10 is a graph showing the relationship between the neutralization current and the estimated surface potential of the photosensitive member during image formation. DETAILED DESCRIPTION OF THE INVENTION

[0012] The image forming apparatus and the photoconductor surface potential estimation method of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiments, and other modifications, additions, corrections, deletions, and other changes can be made within the scope of what a person skilled in the art can conceive. Any embodiment is within the scope of the present invention as long as it achieves the functions and effects of the present invention.

[0013] 1 is a schematic diagram showing the overall configuration of an image forming apparatus (printer) according to one embodiment of the present invention. The printer includes four image forming units 1Y, 1C, 1M, and 1K for generating toner images of yellow, cyan, magenta, and black (hereinafter referred to as Y, C, M, and K; for simplicity, these abbreviations may be omitted below). These image forming units 1Y, 1C, 1M, and 1K use different colored Y toner, C toner, M toner, and K toner as image-forming materials for forming images, but are otherwise identical in configuration.

[0014] An example of an image forming unit 1Y for Y toner will be described. FIG. 2 is a schematic diagram of an image forming unit according to one embodiment of the present invention. As shown in FIG. 2, the image forming unit 1Y is composed of a photosensitive unit 2Y having a drum-shaped photosensitive member 3Y that is a latent image carrier, and a developing unit 7Y as a developing device that develops the latent image on the photosensitive member 3Y. The image forming unit 1Y is detachable from the printer body as an integral unit, and when removed from the printer body, the developing unit 7Y can be detached from the photosensitive member unit 2Y. That is, in the printer shown in FIG. 1, the image forming unit 1Y is configured as a process cartridge.

[0015] In FIG. 2, the photoreceptor unit 2Y includes a photoreceptor 3Y, a drum cleaning device 4Y, and a charging device 5Y that charges the surface of the photoreceptor 3Y. The charging device 5Y uniformly charges the surface of the photoreceptor 3Y, which is rotated clockwise in the drawing by a driving means. 2 shows a charging device 5Y that applies a charging bias to a charging roller 6Y, which serves as a charging member placed close to the photoreceptor 3Y, to uniformly charge the surface of the photoreceptor 3Y. Instead of the charging roller 6Y, a charging brush or a charger such as a scorotron charger may be used.

[0016] 1, an optical writing unit 20 serving as a latent image forming means is provided below the image forming unit 1. The optical writing unit 20 irradiates the uniformly charged photoconductor 3 of the image forming unit 1 with writing light (laser light) L based on image information. In the example of FIG. 1, the optical writing unit 20 is configured to irradiate the photosensitive member 3 with writing light L emitted from a writing light source 21 via a plurality of optical lenses and mirrors while deflecting the light with a polygon mirror that is driven to rotate by a motor. The optical writing unit 20 is not limited to such a polygon scanning method, and can also perform optical scanning using an LED array. Of the entire area of ​​the photoconductor 3, the area irradiated with the writing light L by optical scanning attenuates the potential and carries an electrostatic latent image. Furthermore, the image forming apparatus of this embodiment does not include a dedicated static elimination light source, and static elimination is performed using light emitted from the writing light source 21 of the optical writing unit 20 as static elimination light.

[0017] The printer also includes a controller 65 as a control section that controls bias during detection, contact and separation of the peripheral module with the photosensitive member 3, and irradiation of static elimination light.

[0018] 2, the surface potential of the photoconductor 3Y drops (to, for example, −50 V) only in the area exposed to the writing light L, and an electrostatic latent image is formed. As the photoconductor 3Y rotates, the electrostatic latent image is transported to a development area facing the development roller 12Y of the development unit 7Y. The developing unit 7Y has a first conveying / agitating means 8Y having a conveying screw and agitating fins, and a first developer circulating / transporting passage 9Y provided with a toner supply port. It also has a second conveying / agitating means 11Y having a conveying screw and agitating fins, a toner concentration sensor 10Y consisting of a magnetic permeability sensor, a developing roller 12Y, and a second developer circulating / transporting passage 14Y provided with a doctor blade 13Y. Hereinafter, the first and second developer circulating / transporting passages 9Y and 14Y will be referred to as the first and second transport passages 9Y and 14Y, respectively.

[0019] The first and second transport paths 9Y and 14Y are connected by communication ports at both ends (the front and rear sides of the paper in FIG. 2) and contain negatively charged Y toner and Y developer having a magnetic carrier.

[0020] The first transporting and stirring means 8Y is rotated by a drive means and transports the Y developer in the first transport passage 9Y from the back side to the front side of the paper in FIG. 2. The Y developer transported to the front side moves to the second transport passage 14Y through a connecting port on the front side of the paper. The second transporting and stirring means 11Y also rotates in the same way and transports the Y developer that has reached the second transport passage 14Y from the front side to the back side of the paper in FIG. 2. The toner concentration of the Y developer during transport is detected by a toner concentration sensor 10Y fixed to the bottom of the second transport passage 14Y.

[0021] Above the second transport passage 14Y, the developing roller 12Y is disposed in parallel with the second transport / agitation means 11Y. The developing roller 12Y is composed of a non-magnetic developing sleeve 15Y that rotates counterclockwise in FIG. 2 and a non-rotating magnetic roller 16Y contained within the developing sleeve 15Y. A portion of the Y developer transported through the second transport passage 14Y is drawn up onto the surface of the developing sleeve 15Y by the magnetic force of the magnetic roller 16Y. A doctor blade 13Y is provided opposite the developing sleeve 15Y with a small gap maintained between them, and the layer thickness (pick-up amount) of the drawn-up Y developer is regulated as it passes through the doctor blade 13Y.

[0022] The Y developer that has passed through the doctor blade 13Y is transported to the development zone facing the photoconductor 3Y. Due to the potential difference between the development bias (e.g., −550 V) applied to the development sleeve 15Y and the surface potential (e.g., −50 V) of the exposed portion of the photoconductor 3Y, only the Y toner in the Y developer transported to the development zone adheres to the exposed portion of the photoconductor 3Y. This forms a Y toner image on the photoconductor 3Y. The Y developer that has consumed the Y toner during development is returned to the second transport path 14Y, transported to the back side of the paper in FIG. 2 by the second transport / mixing means 11Y, and moved to the first transport path 9Y through the connecting port on the back side. The Y developer that has returned to the first transport path 9Y is replenished with new toner at the toner supply port and is again transported to the front side of the paper in FIG. 2 by the first transport / mixing means 8Y.

[0023] The Y toner image formed on the photoreceptor 3Y is intermediately transferred to an intermediate transfer belt 41, which is the intermediate transfer body shown in FIG. 1. Waste toner remaining on the surface of the photoreceptor 3Y after the intermediate transfer is removed by a drum cleaning device 4Y. The surface of the photoreceptor 3Y from which the waste toner has been removed is neutralized by a neutralization member and moves toward a charging device 5Y for the next image formation.

[0024] The image forming temperature sensor to be installed near the developer transport passage is positioned at a location where it can detect a temperature that is highly correlated with the temperature of the developer in the first and second transport passages 9Y and 14Y (for example, inside the development unit 7Y or near the development unit 7Y on the main body side of the image forming apparatus).

[0025] Returning to Figure 1, a first paper feed cassette 31 and a second paper feed cassette 32 are provided below the optical writing unit 20. These paper feed cassettes store a plurality of stacked sheets of recording paper P, and a first paper feed roller 31a and a second paper feed roller 32a respectively come into contact with the topmost sheet of recording paper P. When these paper feed rollers 31a and 32a are driven counterclockwise, the topmost sheet of recording paper P in the paper feed cassettes 31 and 32 is ejected into the paper feed path 33.

[0026] The recording paper P is conveyed upward by a pair of conveying rollers 34 and temporarily stops at the position of a pair of skew correction and timing adjustment rollers (so-called registration rollers) 35. Then, the recording paper P is conveyed to the secondary transfer nip (the contact position between the secondary transfer roller 50 and the secondary transfer opposing roller 46) at a timing that matches the image on the intermediate transfer belt 41.

[0027] An intermediate transfer unit 40 is disposed above the image forming unit 1. The intermediate transfer unit 40 is composed of an intermediate transfer belt 41, a belt cleaning unit 42, primary transfer rollers 45Y, 45C, 45M, and 45C, a secondary transfer opposing roller 46, and a drive roller 47. The intermediate transfer belt 41 is rotated counterclockwise by the drive roller 47. The four primary transfer rollers 45 sandwich the intermediate transfer belt 41 and form a primary transfer nip between themselves and the photoconductors 3 of their corresponding colors. The primary transfer rollers 45 apply a primary transfer bias to the inner periphery of the intermediate transfer belt 41. Due to the potential difference between the primary transfer rollers 45 and the photoconductors 3, the toner image on the photoconductors 3 is transferred to the intermediate transfer belt 41 at the primary transfer nip. At the primary transfer nips for each color, a Y toner image, a C toner image, an M toner image, and a K toner image are sequentially transferred to the intermediate transfer belt 41, and a four-color toner image is formed on the intermediate transfer belt 41 by superimposing the four color toner images. .

[0028] The secondary transfer opposing roller 46 is positioned opposite the secondary transfer roller 50, and they sandwich the intermediate transfer belt 41 between them to form a secondary transfer nip. A skew correction / timing adjustment roller pair 35 transports the recording paper P to the secondary transfer nip in synchronization with the timing of the four-color toner image formed on the intermediate transfer belt 41. A secondary transfer bias is applied between the secondary transfer opposing roller 46 and the secondary transfer roller 50, and this force causes the four-color toner image on the intermediate transfer belt 41 to be secondarily transferred onto the recording paper P. This is then combined with the background color of the recording paper P to form a full-color toner image. Any waste toner remaining on the intermediate transfer belt 41 after passing through the secondary transfer nip is removed by a belt cleaning unit 42.

[0029] A fixing unit 60 is provided above the secondary transfer nip. The fixing unit 60 is made up of a pressure roller 61 containing a heat source such as a halogen lamp, and a fixing belt unit 62. The fixing belt unit 62 is further made up of a fixing belt 64, a heating roller 63 containing a heat source such as a halogen lamp, and a drive roller 66. The fixing belt 64 is rotated counterclockwise in the figure by the drive roller 66, and is heated by the heating roller 63 to be maintained at a constant temperature (for example, 140°C).

[0030] The pressure roller 61 also rotates clockwise, and is heated by an internal heat source and maintained at a constant temperature (for example, 120°C). The fixing belt 64 and the pressure roller 61 come into contact with each other, forming a fixing nip. After passing through the secondary transfer nip, the recording paper P carrying the toner image is transported to the fixing nip inside the fixing unit 60. The toner image is fixed onto the recording paper P by being heated and pressed in the fixing nip. The recording paper P with the fixed toner image passes through a pair of paper discharge rollers 67 and is discharged to a paper discharge stack section 68 outside the machine.

[0031] Four toner cartridges 100Y, 100C, 100M, and 100K, each containing Y toner, C toner, M toner, and K toner, are provided above the intermediate transfer unit 40. The toner of each color in the toner cartridges 100 passes through a supply path and is supplied to the developing unit 7 from a toner supply port. These toner cartridges 100 are detachable from the image forming apparatus main body independently of the image forming unit 1.

[0032] The toner cartridge 100 and the toner bottle are examples of a toner storage container.

[0033] FIG. 3 is a schematic diagram showing an example of a configuration for estimating the photosensitive member surface potential according to the present invention in an image forming apparatus according to one embodiment of the present invention. The image forming apparatus of this embodiment comprises a rotatable photoconductor 3 that carries a latent image, a charging member 6 that charges the photoconductor 3, a discharging member that dissipates electricity by irradiating the photoconductor 3 with light, a current detection unit 70 that detects a feedback current generated when a charging bias is applied to the charging member 6, and a control unit 65 that controls the charging member 6 and the discharging member.The charging bias applied to the charging member 6 is switched from the charging bias V1 during image formation to the charging bias V2 before discharging, and the surface potential of the photoconductor during image formation is estimated from the DC component of the feedback current that flows to the current detection unit 70 when the charging bias applied to the charging member 6 is switched from the charging bias V1 during image formation to the charging bias V2 before discharging.

[0034] In addition, when the charging bias V2 before neutralization is applied to the charging member 6, an internal current is generated, and a current detection unit 70 is provided to detect a feedback current obtained by adding the internal current and the current flowing through the charging member 6, and the current flowing through the charging member 6 is estimated from the amount of change in the internal current.

[0035] The electrophotographic imaging process includes a discharge step in which the photoreceptor 3 is exposed to light to eliminate residual charges in the photosensitive layer 3a of the photoreceptor 3, in preparation for the next charging step. Discharging may be performed using a writing light source. In this embodiment, the discharge member is an optical writing means serving as a latent image forming means for the photoreceptor 3. That is, discharge is performed using the writing light L irradiated from the writing light source 21 as discharging light. Hereinafter, this process will also be referred to as "discharging by writing light." Examples of writing light sources include laser diodes (LDs) and light-emitting diodes (LEDs).

[0036] If the photosensitive surface is at the potential during image creation and then static elimination is performed using the writing light L, and the development opening width is larger than the writable area, the potential difference between the photosensitive material outside the writable area and the development member may cause abnormalities such as carrier adhesion. To prevent this, when discharging by the writing light L, it is preferable to change the charging bias applied to the charging member 6 to a potential (V2) lower than the potential (V1) used for image formation as a pre-process. It is preferable that the charging bias V1 during image formation and the charging bias V2 before static elimination satisfy the relationship V1>V2>0. The surface potential of the photoconductor during image formation can be estimated from the magnitude of the neutralization current generated in the feedback circuit when the potential changes from V1 to V2. The current detection unit 70 shown in Figure 3 constitutes the feedback circuit.

[0037] An oscillating voltage obtained by superimposing a direct current voltage (charging DC bias) and an alternating current voltage (charging AC bias) is applied as a charging bias to the charging member 6 from a charging power source 71. The photosensitive member 3 is charged by the charging bias applied to the charging member 6. In this embodiment, the charging member 6 is configured as a charge-removing member, so that it is possible to eliminate the space required for providing a separate charge-removing member and reduce costs.

[0038] In the image forming apparatus of this embodiment, there is no need to provide a device such as a surface electrometer, and there is no need to provide a separate circuit or charge removing member, so that it is possible to avoid an increase in cost and an increase in the size of the circuit layout.

[0039] In the image forming apparatus of this embodiment, the process of estimating the photosensitive member surface potential during image formation and the process of neutralizing the photosensitive member are carried out in parallel.

[0040] The photoconductor surface potential estimation method of this embodiment is a method for estimating the surface potential of the photoconductor 3 during image formation in an image forming apparatus that includes a rotatable photoconductor 3 that carries a latent image, a charging member 6 that charges the photoconductor 3, a discharging member 21 that discharges the photoconductor 3 by irradiating it with light, a current detection unit 70 that detects the feedback current generated when a charging bias is applied to the charging member 6, and a control unit that controls the charging member 6 and the discharging member 21.The method includes the steps of switching the charging bias applied to the charging member 6 from the charging bias V1 during image formation to the charging bias V2 before discharging, obtaining the DC component of the feedback current that flows to the current detection unit 70 when the bias is switched, and estimating the photoconductor surface potential during image formation from the obtained value.

[0041] FIG. 4 is a flowchart showing the flow of a method for estimating a photoconductor surface potential according to one embodiment of the present invention. During the image formation operation, a charging bias V1 is applied to the charging member to charge the photosensitive member. After the image formation operation is completed (step S1), the charging bias is switched to V2 when the point where the photosensitive member surface potential is to be detected faces the charging member (step S2). This timing will be described later using the timing chart in Figure 5. The charging bias V1 is, for example, 470 to 820V. The charging bias V2 is lower than V1 and is equal to or greater than 0V, for example, 200V.

[0042] Next, the current flowing through the charging member when the charging bias V2 is applied is acquired by a feedback circuit (step S3). The feedback circuit corresponds to the current detection unit 70 in Fig. 3. This current detection unit 70 detects the DC component of the current flowing through the charging member.

[0043] Next, the neutralization current is calculated as the difference between the current value acquired in step S3 and the internal current estimated from the applied charging bias V2 (step S4). The neutralization current is a current generated by neutralizing the charge on the photosensitive member.

[0044] Next, a calculation is performed by a calculation means using the value of the neutralization current obtained in step S4 to estimate the photoconductor surface potential when the charging bias V1 is applied (step S5). That is, the surface potential of the photoconductor before the charging member passes is estimated from the DC component of the current flowing through the current detection unit 70 when the charging bias for charging the photoconductor is switched from V1 to V2. For this estimation, the relationship between the neutralization current and the photoconductor surface potential, which is obtained experimentally or by calculation, as shown in FIG.

[0045] On the other hand, after step S2, static elimination is carried out by writing light in parallel with step S3. First, when the area to be irradiated with the static elimination light reaches the irradiation position, the output of the writing light source is turned on (step S6). Then, static elimination is performed using the writing light L irradiated from the writing light source 21 as static elimination light (step S7).

[0046] In this way, by performing the photosensitive body surface potential estimation operation and the photosensitive body discharge operation in parallel, it is possible to estimate the photosensitive body surface potential without increasing the travel distance of the photosensitive body or the user's waiting time, while eliminating the influence of the charge remaining on the photosensitive body after image formation. Reducing the travel distance of the photoconductor also leads to a longer life for the photoconductor unit.

[0047] The photosensitive body surface potential estimation sequence is not limited to the flow shown in Figure 4, and may be performed consecutively from a sequence in which a bias is applied in another adjustment operation, or a separate adjustment operation may be provided for the photosensitive body surface potential estimation sequence.

[0048] FIG. 5A is a timing chart of the sequence for estimating the photosensitive member surface potential, and FIG. 5B is a diagram for explaining the symbols L, L1, and L2 in FIG. 5A. For simplicity of explanation, it is assumed that the charging DC bias of the charging member 6 and the surface potential of the photosensitive member charged by the bias are equal. Furthermore, when the charging DC bias V1 is applied, the internal current generated in the feedback circuit is designated as I_FB1.

[0049] In this embodiment, the target of estimation is the photosensitive drum surface potential after charging (charged with charging bias V1), so the transfer bias is turned off to avoid external disturbances. The point in time when the transfer bias is turned off is called timing T A Let's say.

[0050] Timing T A The time it takes for the photosensitive member position facing the primary transfer roller 45 to move to a position facing the charging member 6 is represented by "L1 / S." L1 is the distance L1 shown in the central diagram of FIG. 5(B), and S is the process linear velocity. The point at which this L1 / S time has elapsed is called timing T B and timing T B The charging DC bias is switched from V1 to V2.

[0051] Timing T B The time it takes for the photosensitive member position facing the charging member 6 to move to a position where it is irradiated with the writing light L from the writing light source 21 is represented by "L2 / S." L2 is the distance L2 shown in the diagram on the right side of FIG. 5(B), and S is the process linear velocity. The point at which this L2 / S time has elapsed is called timing T C and timing T C At this point, the output of the writing light source 21 is turned on.

[0052] The time for one revolution of the photosensitive member 3 is represented by "L / S." L is the distance L shown in the diagram on the left side of FIG. 5(B), and S is the process linear velocity. The output of the writing light source 21 is turned on for a time (L / S) corresponding to one rotation of the photosensitive member, and after the photosensitive member 3 is discharged by irradiation with the writing light L, the output is turned off.

[0053] When the charging bias V2 is applied, the internal current generated in the feedback circuit is I_FB3. After the charging bias is switched from V1 to V2, the neutralization current flows in the opposite direction to the internal current, canceling out the current. The FB current at this point is I_FB2. The difference between I_FB2 and I_FB3 is the neutralization current D. The value of the neutralization current D is used to estimate the surface potential of the photoconductor during image formation.

[0054] 6 is an explanatory diagram showing the photoconductor surface potential at times T1, T2, and T3 shown in FIG. 5(A). For simplicity, the applied charging bias and the photoconductor surface potential are shown as the same potential. The arrow indicates the rotation direction of the photoconductor 3. In FIG. 6A, the time when the transfer bias is turned off is the timing T A FIG. 6B shows the state at the timing T when the charging DC bias is switched from V1 to V2.B 6C shows the state after the time T 2 has elapsed since the output of the writing light source 21 was turned on. C 10, that is, after the start of static elimination by the writing light. As specific values, for example, V1 can be set to 470 to 820 V, and V2 can be set to 200 V. Note that V0 in FIG.

[0055] At timing T1 in FIG. 6A, the surface of the photosensitive member 3 has a portion that is charged to V1 by the charging member 6 to which the charging bias V1 is applied. At timing T2 in FIG. 6B, the surface of the photosensitive member 3 has a portion charged to V1 and a portion charged to V2 by the charging member 6 to which the charging bias V2 is applied. At timing T3 in Figure 6(C), the surface of the photosensitive member 3 has areas charged to V1 and areas charged to V2, as well as areas where static electricity has been removed by irradiation with the writing light L and where the surface is charged to V0, which is approximately 0V.

[0056] The current detection unit 70 acquires the neutralization current generated in the feedback circuit when the photoconductor surface potential is switched from V1 to V2. Then, based on the neutralization current, the potential of the photoconductor surface during image formation can be estimated using the relationship shown in Figure 7.

[0057] FIG. 7 is a graph showing the relationship between the neutralization current and the estimated photosensitive member surface potential Vd during image formation. The neutralization current was experimentally obtained when the charging bias was switched to V2 (Vs = 200 [-V]) for a photoconductor surface potential charged with multiple charging biases V1. Figure 7 is a calibration curve showing the relationship between the neutralization current obtained and the photoconductor surface potential Vd charged with charging bias V1. As shown in Figure 7, high linearity was obtained.

[0058] From the magnitude of the neutralization current D obtained by the image forming apparatus and the flow described above, calculation is performed using this calibration curve, and the photosensitive member surface potential Vd during image formation can be estimated. The calculation using the calibration curve can be executed by a control unit provided in the image forming apparatus body and including a calculation means (CPU) and storage means (RAM and ROM).

[0059] According to the image forming apparatus and photosensitive body surface potential estimation method of the present invention, the influence of the charge remaining on the photosensitive body after image formation can be eliminated by static elimination using writing light performed after printing is completed, and the photosensitive body surface potential during image formation can be estimated without increasing the travel distance of the photosensitive body or the user's waiting time. [Explanation of symbols]

[0060] 3 Photoreceptor 6. Charging member 21 Antistatic member (writing light source) 45 Primary transfer roller 65 Control means section 70 Current detection unit 71 Charging power supply [Prior art documents] [Patent documents]

[0061] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-154039 [Patent Document 2] Patent Publication No. 2021-71715

Claims

1. a rotatable photoreceptor carrying a latent image; a charging member for charging the photoreceptor; a static elimination member that irradiates the photosensitive member with light to eliminate static electricity; a current detection unit that detects a feedback current generated when a charging bias is applied to the charging member; a control unit that controls the charging member and the neutralizing member, an image forming apparatus characterized in that the surface potential of a photosensitive member during image formation is estimated from the DC component of a feedback current I_FB2 that flows in the current detection unit when the charging bias applied to the charging member is switched from the charging bias V1 during image formation to the charging bias V2 before neutralization by irradiating the neutralization member with light, and the DC component of a feedback current I_FB3 that flows in the current detection unit after neutralization by irradiating the neutralization member with light has started and the charging bias has been switched off from the charging bias V2.

2. 2. The image forming apparatus according to claim 1, wherein the charging bias V1 during image formation and the charging bias V2 before charge removal satisfy the relationship V1>V2>0.

3. 3. The image forming apparatus according to claim 1, further comprising a current detection unit that detects a feedback current obtained by adding an internal current generated when the charging bias V2 before the charge removal is applied to the charging member, and that estimates the current flowing through the charging member from the amount of change in the internal current.

4. 4. The image forming apparatus according to claim 1, wherein the charge removing member is an optical writing means serving as a latent image forming means for the photosensitive member.

5. 5. The image forming apparatus according to claim 1, wherein a process for estimating the surface potential of the photosensitive member during image formation and a process for neutralizing the photosensitive member are performed in parallel.

6. A method for estimating a surface potential of a photoconductor during image formation in an image forming apparatus including: a rotatable photoconductor carrying a latent image; a charging member for charging the photoconductor; a discharging member for discharging the photoconductor by irradiating the photoconductor with light; a current detecting unit for detecting a feedback current generated when a charging bias is applied to the charging member; and a control unit for controlling the charging member and the discharging member, a step of switching the charging bias applied to the charging member from a charging bias V1 during image formation to a charging bias V2 before neutralization by irradiating the neutralization member with light; a step of obtaining a DC component of a feedback current I_FB2 flowing in the current detection unit when the charging bias is switched to V2; a step of obtaining a DC component of a feedback current I_FB3 flowing in the current detection unit after neutralization by irradiating the neutralization member with light is started and the charging bias is switched off from the charging bias V2; and a step of estimating the surface potential of the photosensitive body during image formation from the obtained value.

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