JP2010186095A - Charge removing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charge removing device for reducing a factor affecting the short lifetime of a photoreceptor. <P>SOLUTION: A surface potential sensor movable linearly is arranged along a light source for charge removal where a plurality of LEDs allowing light quantity control are arranged in an array shape, the photoreceptor charged by a charger rotates, and the surface potential sensor measures the photoreceptor surface potential after light quantity smaller than a required light quantity for keeping a stable print quality, namely a predetermined light quantity for calculating the light quantity distribution, is radiated. As a result of the measurement, the light quantity of the light source for charge removal is determined to be smallest at the position having the highest potential, and the light quantity of the light source for charge removal is variably controlled so that the potential after charge removal of that part is a reference potential required for the stable print quality or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a static eliminator that lowers the surface potential by exposing the surface of a photoreceptor in an electrophotographic printing apparatus.

  As shown in FIG. 2, the electrophotographic printing apparatus is cylindrical and rotates around its center line as an axis to apply a charge to the surface of the photoconductor 3 around the photoconductor 3 having photoconductivity. Printing the charger 1, the exposure unit 2 that irradiates the photosensitive member 3 with laser light corresponding to the image data, the developing unit 4 for attaching the toner on the photosensitive member 3, and the toner attached on the photosensitive member 3 A transfer unit 6 for transferring to the paper 5 and a cleaning unit 10 for removing toner remaining on the photoreceptor 3 after transfer are provided.

  The cleaning unit 10 irradiates the entire area of the photosensitive member 3 in the axial direction, lowers the potential remaining on the photosensitive member 3 after transfer to near 0 V, and improves the cleanability. It comprises a photoconductor 3 by means of corona discharge, a static eliminator 7 for removing the residual toner on the photoconductor 3 and a cleaning brush 9 for removing residual toner on the photoconductor by a rotating brush.

  In order for the electrophotographic printing apparatus having the above configuration to obtain a stable print quality, in the static elimination light source 8, the potential on the photosensitive member 3 after the light irradiation can be made constant or less without unevenness. Required. For this purpose, it is necessary to irradiate the entire area in the axial direction of the photosensitive member 3 with the necessary light amount. However, the static elimination light source 8 in which a plurality of LEDs are arranged in an array must take into account variations in the light amount generated between the elements. In other words, the required light amount of the entire photoconductor 3 is secured by irradiating the photoconductor 3 with a light amount several times the minimum required light amount.

  The photoconductor 3 is repeatedly charged and exposed to light, causing fatigue due to charge and light, and thus the residual potential accumulation and the stability of the charge potential are degraded. It is desirable to set it to the minimum necessary.

  Therefore, in order to ensure a uniform amount of light over the entire area of the photoreceptor 3, a surface potential sensor 12 corresponding to each LED of the light removal light source 8 is provided, and the potential on the photoreceptor 3 is determined based on the output value of the surface potential sensor 12. There has been proposed a method for making the light quantity distribution of the static elimination light source 8 uniform by performing feedback control of the light quantity of each LED so as to be equal to or less than the value (see, for example, Patent Document 1).

  Also proposed is a method of detecting the potential distribution in the direction of the rotation axis when the photosensitive member 3 is charged in the next process after the photosensitive member 3 is discharged by moving one surface potential sensor and correcting the unevenness of the amount of static electricity removed from the uneven charging. (For example, refer to Patent Document 2).

  The method of providing the same number of surface potential sensors for a large number of LEDs in order to detect the above-described variation in the amount of light has the problems of increasing the cost of the device and complicating the control circuit.

  Further, in the method of detecting the potential distribution during charging of the photosensitive member 3 by moving one surface potential sensor, it may not be possible to determine whether the cause of the potential unevenness is in the charger or the light source for charge removal.

  An object of the present invention is to calculate a light amount distribution of a light source for static elimination with an inexpensive configuration, and to determine a minimum light amount to be irradiated on a photoconductor based on a calculation result, thereby to influence factors that affect a short life of the photoconductor. The object is to provide a static eliminator that can be reduced.

  In the present invention, a surface potential sensor capable of linear movement is disposed along a static elimination light source in which a plurality of LEDs capable of controlling the amount of light are arranged in an array, and a photosensitive member charged by a charger rotates, As a result of measurement by the surface potential sensor with respect to the surface potential of the photoreceptor after irradiation with a light amount that is weaker than a necessary light amount for maintaining stable print quality, that is, a predetermined light amount for light amount distribution calculation, the potential is the highest. Achieved by variably controlling the light quantity of the light source for static elimination so that the light quantity of the light source for static elimination is determined to be the weakest at the position and the post-static potential of that part is below the reference potential required for stable print quality Is done.

  According to the first aspect of the present invention, since the surface potential after neutralization over the entire rotation axis direction of the photosensitive member is detected, it is possible to grasp the effectiveness of the static elimination light source, that is, the intensity distribution of the amount of light emitted from the light source. Moreover, since it can be calculated by one surface potential sensor, it can be realized at low cost.

  According to the configuration of the second aspect, since the variation in the amount of light emitted from the light source for charge removal appears significantly as the variation in the surface potential after the charge removal from the photosensitive member, it is possible to grasp the position where the amount of light emitted from the light source is the weakest. it can.

  According to the third aspect of the present invention, the static elimination light source is controlled so as to irradiate the entire area of the photoconductor with the minimum amount of light based on the calculated light quantity distribution, so that the factor of shortening the life of the photoconductor can be reduced. .

  According to the configuration of the fourth aspect, by controlling the light amount of the light source for static elimination, when the potential after the static elimination is not improved, it is possible to detect an abnormality (dirt or failure of the light source) of the light source.

It is a characteristic view which shows an example of the electric potential distribution after static elimination in the electrophotographic printing apparatus to which this invention is applied. 1 is a schematic configuration diagram of an electrophotographic printing apparatus. 1 is a configuration diagram of an electrophotographic printing apparatus to which the present invention is applied. FIG. 6 is a characteristic diagram illustrating an example of a post-static potential with respect to the amount of light applied to the photoconductor. It is a flowchart which shows the measurement process which estimates the light quantity distribution of the light source for static elimination. It is a flowchart which shows the process of the light quantity setting minimum required for the light source for static elimination, and the abnormality detection of a light source.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 3 shows a configuration example of an electrophotographic printing apparatus to which the present invention is applied. A surface potential sensor 12 is disposed between the charger 1 disposed around the cylindrical photosensitive member 3 and the light source 8 for static elimination. The surface potential sensor 12 is supported by the slider 11 and is configured to be linearly movable along the static elimination light source 8 by a drive source (not shown).

  When a high voltage is applied to the charger 1 while rotating the photosensitive member 3 in the direction of the arrow, the surface of the photosensitive member that passes immediately below the charger 1 is charged. After passing through the charger 1, the charged portion on the surface of the photoreceptor reaches the cleaning unit 10 through the exposure unit 2, the development unit 4, and the transfer unit 6. When the cleaning unit 10 is reached, the surface of the photoconductor 3 is irradiated with light by the static elimination light source 8, and the surface potential of the photoconductor surface that has passed directly under the static elimination light source 8 is lowered.

  Here, FIG. 4 shows a characteristic example of the post-static potential with respect to the light amount of the static elimination light source 8. When the light quantity of the light source 8 for static elimination is 0, the potential after static elimination is almost the same as the potential after charging. Further, as the light quantity of the static elimination light source 8 is increased, the potential after static elimination gradually decreases. When the light quantity exceeds B, the reduction of the potential after static elimination almost stops. Further, even if the amount of light applied to the photosensitive member 3 is increased, the amount of change in potential after static elimination becomes minute.

  A method for calculating the light amount distribution of the static elimination light source 8 based on the above-described potential characteristics will be described with reference to FIGS. 3, 4, and 5.

  First, the surface potential sensor 12 moves to the end of the photoconductor, and the output is, for example, a light amount that is a half of the post-charging potential (a light amount that is weaker than the light amount necessary to maintain stable print quality). In Example), the light quantity of the static elimination light source 8 is set (set to a constant current circuit (not shown) for driving the LED). The amount of light at this time corresponds to A in FIG.

  Next, while rotating the photosensitive member 3 uniformly charged by the charger 1 (S11 in FIG. 5), light is emitted from the light source 8 for static elimination whose light quantity is fixed to A (S12 in FIG. 5). . Then, the surface potential sensor 12 measures the surface potential of the photosensitive member 3 after static elimination while moving linearly (S13 in FIG. 5).

  As shown in FIG. 4, in the vicinity of the light amount A, even if the light amount changes slightly, the amount of change in the surface potential is large. Therefore, the variation in the light amount of the light removal light source 8 appears as a difference in the surface potential distribution. That is, it can be determined that the portion of the photoconductor having a high surface potential has a low light amount from the light source for charge removal, and the portion having a low surface potential can be determined to have a high amount of light.

  FIG. 1 shows an example of a potential distribution after static elimination in an electrophotographic printing apparatus to which the present invention is applied. The purpose of this measurement is to grasp the position where the post-static potential shown in FIG. 1 is the highest (the position where the light quantity of the static elimination light source is the weakest), and the potential peak is detected in S14 of FIG. 5, the peak potential and the position of the surface potential sensor 12 are stored in a storage device (not shown). Thereafter, the measurement of the potential distribution over the entire rotation axis direction of the photosensitive member is performed in S16 of FIG. After the measurement is completed, the photosensitive member 3 is neutralized with the neutralization light amount during the normal printing operation that is currently set, and the surface potential measurement process is terminated.

  Next, based on the above-described results, the minimum light amount setting required for the static elimination light source 8 and abnormality detection of the light source will be described with reference to FIGS. 3, 4, and 6.

  In S21 of FIG. 6, the surface potential sensor 12 is moved to a position where the light amount is determined to be the weakest from the above result.

  Next, while rotating the photosensitive member 3 uniformly charged by the charger 1 (S22 in FIG. 6), the static elimination light source 8 emits light with the currently set static elimination light amount (S23 in FIG. 6). Then, the surface potential after static elimination is measured (S24 in FIG. 6).

  Since the current position of the surface potential sensor 12 is the position where the amount of light is the weakest, the position of the surface potential sensor 12 becomes the highest potential when it does not fall to the potential that serves as the charge removal reference over the entire area of the photoreceptor 3. appear. In this case, it is determined in S25 of FIG. 6 that the amount of static elimination light is insufficient, and the amount of light of the static elimination light source 8 is changed to a setting that increases one rank according to a predetermined amount of increase in the amount of light (a constant not shown for driving the LED). The set current of the current circuit is increased) (S26 in FIG. 6).

  If the potential of the entire area of the photoconductor 3 is equal to or less than the charge removal reference, it is determined that the current light amount setting is sufficient, and the light amount setting process ends. This corresponds to the position B in FIG.

  Returning to the description of the case where it is determined that the light amount is insufficient in S25 of FIG. 6, if the light amount setting is changed in S26 of FIG. 6, it is determined whether the drive current upper limit of the LEDs constituting the static elimination light source 8 is reached. If it is determined (S27 in FIG. 6) and the upper limit has not been reached, the process returns to S21 in FIG. 6 and the process is repeated until it is determined in S27 in FIG. 6 that the amount of light is sufficient.

  In addition, when the upper limit is reached in S27 of FIG. 6, a sufficient amount of light cannot be secured due to contamination of the LED light emitting surface or a failure in which the LED is not lit, and an abnormality of the light removal light source 8 is caused. A report is made (S28 in FIG. 6), and the light quantity setting process is terminated.

  Note that the light amount distribution of the static elimination light source 8 may be measured at the time of initialization or after completion of a preset printing amount. In addition, immediately after replacing the static elimination light source 8, it is necessary to re-measure the light amount distribution.

  1 is a charger, 2 is a light source, 3 is a photoreceptor, 4 is a developing unit, 5 is printing paper, 6 is a transfer unit, 7 is a static eliminator, 8 is a light source for static elimination, 9 is a cleaner brush, 10 is a cleaning unit, 11 is a slider, and 12 is a surface potential sensor.

JP-A-5-241491 JP 2007-79168 A

Claims (4)

A static elimination light source in which a plurality of LEDs are arranged in an array in the direction of the rotation axis of the photoconductor around a photoconductor having a photoconductivity and rotating, and a surface potential sensor that is also capable of linear movement in the direction of the rotation axis In an electrophotographic printing apparatus provided with a charger for charging a photoreceptor,
A neutralization apparatus configured to calculate a light amount distribution of a static elimination light source by moving the surface potential sensor linearly and measuring a surface potential distribution after neutralization.   The light quantity of the light source for static elimination when measuring the surface potential distribution should be set to be weaker than the light quantity required for the static elimination function in order to maintain stable print quality in order to grasp the position where the light quantity is the weakest. The static eliminator according to claim 1.   In the surface potential distribution after static elimination obtained from the calculated value of the light quantity distribution, the light quantity of the static elimination light source is variably controlled so that the potential after static elimination of the portion having the highest surface potential is kept below a predetermined value. The static eliminator according to claim 1.   The surface potential distribution after static elimination obtained from the calculated value of the light amount distribution detects an abnormality as a contamination or failure of the static elimination light source when there is a portion where the surface potential exceeds a predetermined value. 1. The static eliminator according to 1.

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