JP2007033218A - Electric potential measuring device, imaging forming system and electric potential measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric potential measuring device capable of accurately measuring surface electric potential of charged body without using eccentricity of the charged body and a lead current. <P>SOLUTION: The electric potential measuring device has an electrode 9 arranged close to a rotationally driven photo conductor 2, and a voltage detector 7 detecting the surface potential data around the photo conductor 2 which is induced to the electrode 9 when a voltage over an impressing voltage or a current over an impressing current for saturating the photo conductor 2, in the photo conductor 2, as a calibration data. In this manner, the calibration data is taken around the photo conductor 2 so that the charging potential of the photo conductor 2 sufficiently stabilizes in setting. Even if the measured data includes errors due to the eccentricity of the photo conductor 2, the errors can be eliminated and exact surface potential can be measured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a potential measuring device, an image forming apparatus, and a potential measuring method for measuring and detecting a surface potential on a charged body.

  2. Description of the Related Art Conventionally, as a method for measuring the surface potential of a photoconductor as a member to be charged, a method of measuring an induced current or an induced voltage induced on this electrode using an electrode or the like is known. An electrode is disposed close to the photoreceptor, and the electrode is moved relative to the photoreceptor by rotation of the photoreceptor. As a result, the electric charge detected by the electrode changes with time, and the induced current and induced voltage at that time are detected to measure the surface potential of the photoreceptor.

However, the method of measuring the induced current and induced voltage induced in this electrode has two problems described below.
First, the first problem is that the values of the induced current and induced voltage induced in the electrode vary greatly depending on the distance to the charged body. Since the photosensitive member as the member to be charged has an eccentricity on the outer peripheral surface, it is difficult to always keep the distance between the photosensitive member and the electrode constant, and the measurement data also varies depending on the distance.

  The second problem is that the detection circuit that detects the voltage value or current value induced in the electrode cannot accurately detect the current or voltage induced in the electrode due to a leak current or an offset factor. There are challenges.

  Patent Document 1 discloses an electrostatic recording apparatus equipped with a distance sensor for keeping the distance from the measurement electrode to the surface of the photoreceptor constant.

  In Patent Document 2, a ground plate having a reference potential for correcting an offset amount is provided, and the distance between the photosensitive member and the potential measuring unit when the ground plate is disposed between the photosensitive member and the potential measuring unit. And a technique for displacing the potential measuring means so that the distance between the photosensitive member and the potential measuring means when a ground plate is arranged between the photosensitive member and the potential measuring means coincides.

Japanese Patent No. 3009179 Japanese Patent Laid-Open No. 3-107959

  However, when the distance sensor as disclosed in Patent Document 1 is mounted, there arises a problem that the apparatus becomes large and the cost becomes high. In addition, the technique disclosed in Patent Document 2 cannot cope with the eccentricity caused by the rotation of the photosensitive member.

  The present invention has been made in view of the above circumstances, and is a potential measuring device, an image forming apparatus, and a potential measuring device that can accurately measure the surface potential of a charged body regardless of the eccentricity or leakage current of the charged body. It aims to provide a method.

  In order to achieve such an object, the potential measuring apparatus of the present invention includes a measuring electrode disposed in the vicinity of a member to be rotated and a voltage or an applied current that is equal to or higher than the applied voltage when the charged member is saturated. Detection in which the above current is applied to the member to be charged, and at this time, the surface potential data of the member to be charged guided to the measurement electrode is detected as the first calibration data over one turn of the member to be charged. Part. Thus, in the present invention, the first calibration data is measured over one turn of the charged body by setting the charged potential of the charged body to be sufficiently stable. Even if an error is included due to the eccentricity of, the error can be removed and the surface potential of the charged object can be accurately measured.

  In the potential measuring device having the above-described configuration, a predetermined voltage or current is applied to the object to be charged, the surface potential of the object to be charged is measured by the detection unit, and the measured surface potential data is the first calibration data. It is preferable to have a control unit that performs correction according to the above. Accurate data can be obtained by removing the offset and leak of the measurement circuit.

  In the potential measuring apparatus having the above configuration, the detection unit may detect a potential or current induced in the measurement electrode.

  In the potential measuring device having the above configuration, the detection unit may include an operational amplifier, a capacitor, and a switch for resetting the electric charge accumulated in the capacitor. Therefore, the surface potential of the member to be charged can be measured with a simple configuration.

  In the potential measuring apparatus having the above-described configuration, the control unit switches on and off of the switch in synchronization with a detection timing of a mark provided on the charged body, and measures data for one round of the charged body. Good. Therefore, the first calibration data corresponding to each position on the photoconductor can be obtained. For this reason, the measurement data of the surface potential can be corrected with higher accuracy.

  In the potential measuring device having the above-described configuration, the detection unit is configured to second calibration data obtained by measuring the surface potential of the charged body over one circumference of the charged body after neutralizing the surface potential of the charged body. Should be output. In addition, the control unit corrects the measurement data obtained by measuring the surface potential of the charged body over one circumference of the charged body after the charged charged body is exposed by the second calibration data. Good.

  An image forming apparatus according to the present invention includes the potential measuring device according to any one of claims 1 to 7, and corrects measurement data with the first calibration data to measure a surface potential of the object to be charged. A desired image is formed by adjusting a voltage or a current applied to the member to be charged.

  In the potential measuring method of the present invention, a measuring electrode is arranged in the vicinity of a rotationally driven member to be charged, and a voltage higher than an applied voltage or a current higher than an applied current when the charged member is saturated. In this case, the surface potential data of the charged body guided to the measurement electrode at this time is detected as the first calibration data over one round of the charged body. Thus, in the present invention, the first calibration data is measured over one turn of the charged body by setting the charged potential of the charged body to be sufficiently stable. Even if an error is included due to the eccentricity of, the error can be removed and the surface potential of the charged object can be accurately measured.

  The present invention can accurately measure the surface potential of a member to be charged without depending on the eccentricity or leakage current of the member to be charged.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the present embodiment will be described with reference to FIG. The photoconductor 2 as an image carrier is a cylindrical OPC photoconductor, and is driven to rotate at a predetermined process speed (circumferential speed) in the clockwise direction indicated by an arrow about a central axis perpendicular to the paper surface.

  A charging roll 3 serving as a charging member is disposed around the photoreceptor 2. The charging roll 3 rotates following the rotation of the photosensitive member 2, and a predetermined voltage is applied from a power source (not shown), and the peripheral surface of the rotating photosensitive member 2 is uniformly charged to a predetermined polarity and potential. (In this example, it is negatively charged).

  Next, an image-modulated laser beam output from an exposure device (not shown) is irradiated (scanning exposure) on the charging surface of the rotating photoconductor 2, and the potential of the exposed portion is attenuated to form an electrostatic latent image. Is done.

  When the latent image arrives at the development site facing the developing roll 5 as the photosensitive member 2 rotates, negatively charged toner is supplied from the developing device 4 and a toner image is formed by reversal development.

  An electroconductive transfer roll 5 is disposed in pressure contact with the photoconductor 2 on the downstream side of the developing device 4 when viewed in the rotation direction of the photoconductor 2, and a nip portion between the photoconductor 2 and the transfer roll 5 serves as a transfer site. Forming.

  When the toner image formed on the surface of the photoconductor 2 reaches the transfer site as the photoconductor 2 rotates, the paper is supplied to the transfer position in synchronization with this, and a predetermined voltage is applied to the transfer roll 5 at the same time. As a result, the toner image is transferred from the surface of the photoreceptor 2 to the paper.

  The sheet that has received the toner image transfer at the transfer position is conveyed to the fixing device 6 where the toner image is fixed and discharged out of the apparatus.

  On the other hand, the untransferred toner remaining on the surface of the photosensitive member 2 is scraped off by the cleaning blade 10, whereby the surface of the photosensitive member 2 is cleaned and prepared for the next image formation. Further, the electrostatic latent image on the photosensitive member 2 is erased by the charge eliminating lamp 11.

  In addition, the image forming apparatus 1 includes an electrode 9 disposed opposite to the photoconductor 2 in the vicinity of the photoconductor 2, a voltage detection unit 7 that measures an induced voltage or an induced current induced in the electrode 9, and a control unit 8. As an electric potential measuring device. The voltage detection unit 7 includes an operational amplifier 71, a detection capacitor 72, and a reset switch 73 as shown in FIG. The operational amplifier 71 and the detection capacitor 72 constitute an integrator. The photoconductor 2 and the electrode 9 adjacent to the photoconductor 2 form a capacitor, and a change in the surface potential of the photoconductor 2 when the applied voltage of the charging roll 3 is changed is detected as an induced potential. The surface potential of the photosensitive member 2 is measured by integrating the current flowing through the electrode 9 with an integrator composed of an operational amplifier 71 and a detection capacitor 72. The reset switch 73 discharges the electric charge accumulated in the detection capacitor 72 and resets it. The voltage detector 7 shown in FIG. 1 changes its output according to the amount of change only when the surface potential of the photoreceptor 2 changes and the input changes. Conversely, when the input does not change, the output of the voltage detector 7 also does not change (reset level is output). Thus, the voltage detection unit 7 does not require a high voltage circuit and can be configured with a simple circuit, and thus can be realized at low cost.

  The control unit 8 controls each unit described above, and controls the AC + DC voltage applied to the charging roll 3 to an optimum value based on the photoreceptor surface potential detected by the voltage detection unit 7. A detailed configuration of the control unit 8 shown in FIG. 1 is shown in FIG. As shown in FIG. 2, the control unit 8 includes a ROM 31 that records a program, a CPU 30 that reads a program recorded in the ROM 31 and executes an operation, a RAM 32 that is used as a work area of the CPU 30, and an I that inputs and outputs data. / O33 is connected on the bus. The first calibration data measured by the voltage detection unit 7 (hereinafter referred to as calibration data for simplicity) is recorded in the RAM 32 and used when correcting the measurement data.

  In such a circuit configuration, two problems occur. The first is that the distance between the photosensitive member 2 and the electrode 9 varies depending on the rotational position due to the eccentricity generated when the photosensitive member 2 rotates. Since this detection method is a method in which the detection is performed by the capacitor formed between the photosensitive member 2 and the electrode 9 as described above, a change in distance causes a change in capacitance value and consequently a change in detection signal. The broken line part of FIG. 3 shows the state. Even if the surface potential of the photosensitive member 2 is constant, the output signal follows a curve due to eccentricity shown in FIG.

  The other is output fluctuation due to leakage of the detection capacitor 72. FIG. 4 shows this state, and the detection output fluctuates almost linearly.

  In this embodiment, calibration data is created by capturing a known potential in synchronism with the rotation of the photoconductor 2, and correction is performed using the obtained calibration data.

The operation procedure of the present embodiment will be described with reference to the flowchart shown in FIG.
When measuring calibration data (step S1 / YES), charging is performed by setting the applied voltage Vpp applied to the photosensitive member 2 so that the surface potential of the photosensitive member 2 is sufficiently stabilized. For example, as shown in FIG. 5, when the photosensitive member 2 is saturated with the applied voltage Va, the surface potential of the photosensitive member 2 is sufficiently stabilized by applying a voltage Vb larger than the applied voltage Va (step S2). ). At this time, the surface potential of the photosensitive member is, for example, a stable potential (Vh shown in FIG. 5) of about −750V. Next, when the control unit 8 detects a predetermined mark formed on the photoreceptor 2 by the sensor, the control unit 8 turns on the reset switch 73 to start calibration (step S3). In the calibration, the photoconductor 2 rotates once from the home position (mark position), and the induced current induced in the electrode 9 is integrated by an integrator until the mark is detected again and returned to the home position. The charge accumulated in the detection capacitor 72 is output to the control unit 8 as calibration data (step S4).

  The rotation speed of the photoconductor 2 is obtained, and the output of the voltage detector 7 is made to correspond to the position from the home position, so that the data captured after the reset release of the reset switch 73 corresponds to the position of the photoconductor 2. This data (calibration data) includes both eccentricity and circuit leakage. This variation Vc is Vc (t), where t is the elapsed time from reset release.

  Next, the surface potential of the photoreceptor 2 is measured (step S5). The controller 8 turns on the reset switch 73 and starts measuring the surface potential (step S6). When measuring the surface potential, it is not necessary to capture data for one rotation of the photoconductor 2, and V = V (T) −Vc (T) if the measurement timing is T time from reset release. Here, since V (T) is the surface potential taken in at time T and Vc (T) is the output fluctuation at time T, it is possible to detect an accurate surface potential excluding eccentricity and circuit leakage.

  In addition, according to the configuration of the present embodiment, it is possible to accurately measure the exposure level. That is, after neutralizing the photosensitive member 2 using the neutralizing lamp 11 or the like, the surface potential for one rotation of the photosensitive member is measured from the home position. Alternatively, after charging the photosensitive member 2, the reference pattern is exposed, and the fluctuation of the surface potential is measured by the exposure. The second calibration data obtained by the measurement is written in the RAM 32. At this time, if the movement distance from the home position of the photosensitive member and the position of the reference pattern are grasped, it is possible to remove the eccentricity and the circuit leak as described above, and the exposure level can be accurately obtained. it can.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. In the embodiment described above, the method of controlling by the applied voltage Vpp of the charging roll 3 has been described in particular. However, in order to obtain the shoulder, the applied AC current value may be changed. It is possible to set an optimum applied current value based on the above.

1 is a diagram illustrating a configuration of an image forming apparatus. It is a figure which shows the structure of a control part. This is the output of the voltage detector, and shows a case where there is a variation due to eccentricity. This is an output of the voltage detector, and shows a case where there is a fluctuation due to leakage. It is a figure which shows the relationship between the surface potential of a photoconductor, and the voltage applied to a photoconductor. It is a flowchart which shows an operation | movement procedure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Charging roll 4 Developing device 5 Transfer roll 6 Fixing device 7 Voltage detection part 8 Control part 9 Electrode 10 Cleaning blade 11 Static elimination lamp

Claims (9)

A measurement electrode arranged in proximity to the object to be rotated,
A voltage equal to or higher than an applied voltage when the charged body is saturated or a current equal to or higher than an applied current is applied to the charged body. A detection unit that detects the calibration data over one turn of the object to be charged;
A potential measuring device comprising:   A controller that applies a predetermined voltage or current to the member to be charged, measures the surface potential of the member to be charged by the detection unit, and corrects the measured surface potential data by the first calibration data; The potential measuring device according to claim 1.   The potential measuring device according to claim 1, wherein the detection unit detects a potential or a current induced in the measurement electrode.   The potential measuring apparatus according to claim 2, wherein the detection unit includes an operational amplifier, a capacitor, and a switch that resets the electric charge accumulated in the capacitor.   5. The control unit switches on and off of the switch in synchronization with a detection timing of a mark provided on the member to be charged, and measures data for one turn of the member to be charged. The potential measuring apparatus described.   The detection unit outputs second calibration data obtained by measuring the surface potential of the member to be charged over one round of the member to be charged after neutralizing the surface potential of the member to be charged. The potential measuring device according to any one of claims 2 to 5.   The control unit corrects measurement data obtained by measuring the surface potential of the charged body over one circumference of the charged body after the charged charged body is exposed by the second calibration data. The electric potential measuring apparatus according to claim 6.   A voltage applied to the object to be charged, comprising the potential measuring device according to any one of claims 1 to 7, wherein the surface potential of the object to be charged is measured by correcting measurement data with the first calibration data. An image forming apparatus, wherein a desired image is formed by adjusting Place the measurement electrode close to the object to be rotated,
A voltage equal to or higher than an applied voltage when the charged body is saturated or a current equal to or higher than an applied current is applied to the charged body. A potential measuring method, wherein calibration data is detected over one round of the charged body.

Images