JP2005173123A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a potential profile measuring apparatus of a new method realizing both high resolution and high speed for measuring absolute potential profile of a photoreceptor. <P>SOLUTION: Accuracy is improved of a sensor obtaining a profile of surface potential of a photoreceptor 2 from induction current generated in a transparent electrode 1 according to a variation in the surface potential of the drum 2 when the photoreceptor 2 is uniformly electrified and exposure scanning is carried out through the transparent electrode 1. 1 indicates the transparent electrode, 2 indicates the photoreceptor drum, 3 indicates a primary high voltage power source, 4 indicates a primary electrifier, 15 indicates detection laser radiation unit, 16 indicates an amplifier, 17 indicates a CPU, 18 indicates an A/D converter and 19 indicates a position sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image using electrophotography, and more particularly to an apparatus for measuring a surface potential profile of a photoreceptor.

  As the surface potential meter for measuring the surface potential profile of a photoconductor of an electrophotographic apparatus in a non-contact manner, a so-called chopper type electrometer, a capacitance variation type electrometer, a so-called potential sensor are mainly known. In particular, a chopper-type potential sensor will be described here. A chopper-type electrometer measures the electric field strength of a measurement object by placing a conductive vibrating object between the measurement object and the measurement electrode, and increasing or decreasing the amount of electric field lines incident on the measurement electrode by the vibration object. The capacitance variation type electrometer measures the electric field strength by physically vibrating the measurement electrode itself and changing the electric field distribution between the measurement object and the measurement electrode. Both types have the same contents regarding signal reception processing.

  FIG. 6 is a diagram showing a schematic configuration of a chopper-type surface electrometer. In the figure, reference numeral 1 is a measurement electrode that receives electric lines of force from the measurement object 8, and 2 is a tuning fork vibrator that vibrates and chops electric lines of force incident on the measurement electrode 1 from the measurement object 8 in the A direction. Reference numeral 3 denotes an amplifying element for amplifying the minute alternating current signal induced in the measurement electrode 1 by impedance conversion, and 4 denotes a piezoelectric element for applying vibration to the tuning fork vibrator 2. In addition, 5 is a circuit board, 6 is a drive signal to the piezoelectric element 4, a received signal from the measurement electrode 1, and a connector for inputting / outputting a power source, and 7 is a measurement object 8 to the measurement electrode 1 in the B direction. An incident electric field line 9 is a shield case for housing the circuit board 5.

  FIG. 7 is a diagram showing an outline of an impedance conversion circuit configured on the circuit board 5. Here, impedance conversion is performed by a source follower circuit in which the input side resistor 11 is set to 100 MΩ, for example, and an FET is used as the amplifying element 3. Further, the resistors 12 and 13 on the output side are, for example, 100Ω and 20KΩ, respectively. These components such as resistors are printed on the circuit board 5 or soldered with discrete chip components.

  FIG. 8 is a perspective view showing the outer shape of the electrometer having the above configuration. As shown in the figure, the circuit board 5 is housed in a shield case 9, a connector 6 is disposed on the side of the case, and a small window (opening) for measurement is provided on the front.

  Next, the operation of the electrometer having the above configuration will be described. First, the piezoelectric element 4 and the tuning fork type vibrator 2 are brought into a resonance state by a piezoelectric element driving signal supplied from the outside, and mechanical vibration is generated. As a result, the amount of electric lines of force that pass from the measurement object 8 through the measurement window of the shield case 9 and enter the measurement electrode 1 increases or decreases in accordance with the vibration of the tuning fork vibrator 2. Thereby, a weak AC induced current is generated in the measurement electrode 1 and the input-side resistor 10 shown in FIG. 3, and this is applied as a voltage signal to the gate of the FET which is the amplifying element 3. At this time, since the FET circuit is a source follower circuit as described above, impedance conversion with an amplification factor of 1 is performed and a voltage signal is output from the source of the FET. Then, this signal is transferred to an external signal processing circuit (not shown) via the connector 6, and the subsequent processing is performed to detect the surface potential of the measurement object 8.

  FIG. 9 schematically shows main elements related to the image forming process with respect to the internal structure of the image forming apparatus using the potential sensor. In FIG. 9, 1 is a potential sensor, 2 is a photosensitive drum, 3 is a primary high voltage power source, 4 is a primary charger, 5 is a laser beam, 6 is a developer, 7 is a copy sheet, 8 is a transfer charger, Reference numeral 9 denotes a transfer high-voltage power source, 10 denotes a separation charger, 11 denotes a separation high-voltage power source, 12 denotes a fixing device, 13 denotes a cleaner, and 14 denotes an exposure unit.

  In the above configuration, a high voltage of several kV is generated by the primary high voltage power source 3 and supplied to the primary charger 4. Therefore, the surface potential of the photosensitive drum 2 is uniformly charged to several hundred volts. Thereafter, the photosensitive drum 2 is irradiated with laser light (not necessarily a laser) 5 corresponding to the original, and an electrostatic latent image is formed on the photosensitive drum 2. Next, the developing device 6 forms a toner image corresponding to the electrostatic latent image (toner development is performed) using the toner stored therein. Next, the transfer high-voltage power supply 9 applies a high voltage to the transfer charger 8 to charge the copy paper 7 from the back surface. Then, the toner image formed on the photosensitive drum 2 is attracted to the copy paper 7 and transferred. Thereafter, a high voltage of AC + DC is applied from the separation high-voltage power supply 11 to the separation charger 10, and the charge charged at the time of transfer is neutralized to separate the copy paper 7 from the photosensitive drum 2. Then, the copy sheet 7 onto which the toner image has been transferred is passed through the fixing device 12 to be thermally fixed and discharged. Residual toner remaining on the photosensitive drum 2 is removed by a cleaner 13.

  Next, potential control performed using a signal from the potential sensor 1 will be described. Control of each image forming process unit based on a signal from the potential sensor 1 is referred to as potential control. This potential control is normally executed through the CPU 17 of the control device before the copy sequence, for example, during warm-up. When executing the potential control, the CPU 17 first supplies a high voltage generated from the primary high-voltage power supply 3 to the primary charger 4 to uniformly apply the surface of the photosensitive drum 2 to several hundred V (for example, 500 V; usually this is a copy). Is read by the potential sensor 1 and the output of the primary high-voltage power supply 3 is controlled by a control line (not shown) so that the potential becomes a predetermined value (500 V in this case). To do. In addition, each image forming process unit is controlled by a signal from the potential sensor 1. The potential control includes exposure control for controlling the amount of laser light 5, development control for controlling a high developing bias voltage applied to a sleeve provided in the developing device 6, transfer control for controlling the output of the transfer full pressure power source 9, and the like. There is.

Next, a signal processing operation from the potential sensor 1 will be described with reference to FIG. FIG. 10 is a schematic connection diagram of a potential sensor signal processing system provided in the image forming apparatus having the above configuration. Reference numeral 14 denotes a sensor control board that amplifies a minute signal from the potential sensor 1 and converts the signal to an analog number V of a normal level signal, and 15 amplifies the signal from the sensor control board 14 in accordance with the signal level of the digital signal processing system. An amplifying means for transmitting the signal, 16 an A / D converter for converting an analog signal from the amplifying means 15 into a digital signal, and 17 a CPU of a control device for controlling the image forming apparatus. As a method of measuring the potential profile of the photoconductor in the main scanning direction, as shown in FIG. 11, a method of measuring by moving the potential sensor in the main scanning direction (see, for example, Patent Document 1) and FIG. As shown, a method of measuring a plurality of potential sensors arranged in the main scanning direction is known. In recent years, as the demand for higher image quality and higher speed of devices has increased, higher resolution of potential profile measurement and higher speed of potential profile measurement have been required.
Japanese Patent Laid-Open No. 5-188837

  However, the conventional surface potential meter as described above has a limit in response speed, and further, there is a limit in increasing the resolution due to structural limitations. It was not always enough.

  The present invention has been made paying attention to the above problems, and provides a new type of potential profile measuring apparatus that realizes both high resolution and high speed when measuring the absolute potential profile of a photoreceptor. The purpose is that.

In order to solve the above problems,
(First means)
A photosensitive member rotatably supported by the apparatus; a charging unit that uniformly charges the photosensitive member; an image exposing unit that exposes the charged photosensitive member to form a latent image; and light irradiation of the image exposing unit Switching means for switching power, developing means for developing an image formed with a latent image by the image exposure means into a visible image with a predetermined developing material, and transferring the visible image developed by the developing means from the photoconductor to the transfer material A transfer means for transferring, a transparent electrode disposed on the optical path of the image exposure means facing the photoconductor, and guided to the transparent electrode when light is irradiated on the photoconductor by the image exposure means A first means including a potential change amount detecting means for detecting a potential change amount by an induced current and a control means for controlling the exposure power of the image exposure means.

(Second means)
In the first means, the image exposure means, the developing means, the transfer means, a mode in which an image is formed, and the image exposure means, the transparent electrode, and the potential change amount detection means. A second means having a mode for measuring the potential profile on the surface.

(Third means)
In the second means, the light irradiation power by the exposure means in the image forming mode and the potential profile measurement mode is set so that the light irradiation power in the potential profile measurement mode is stronger than that in the image formation. Third means for controlling the control means.

(Fourth means)
In the first means, fourth means for measuring a profile in the main scanning direction of the photosensitive member by the potential change amount detecting means.

(Fifth means)
The first means includes fifth means for measuring the profile of the entire surface of the photoconductor by repeating the profile measurement in the main scanning direction a plurality of times by the potential change amount detection means.

  According to the present invention, absolute potential profile measurement can be performed at high speed and with high resolution.

  Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

  FIG. 1 is a diagram showing an outline of the potential profile measuring apparatus according to the first embodiment. In FIG. 1, 1 is a transparent electrode, 2 is a photosensitive drum, 3 is a primary high-voltage power source, 4 is a primary charger, 15 is a detection laser irradiation unit, 16 and 22 are input signals and signal levels of the processing system. An amplifier for amplifying and transmitting in accordance with the signal, 17 is a CPU, 18 and 23 are amplifiers, A / D converters for converting analog signals from 16 and 22 into digital signals, 19 is a position sensor, and 20 is a detection Laser light 24 indicates a potential sensor for measuring the surface potential of the photosensitive drum.

  In the above configuration, a high voltage of several kV is generated by the primary high voltage power source 3 and supplied to the primary charger 4. Therefore, the surface potential of the photosensitive drum 2 is uniformly charged to several hundred volts. Thereafter, a detection laser beam (not limited to a laser but may be an LED or the like) 20 is irradiated onto the photosensitive drum 2 through the transparent electrode 1 in the main scanning direction. At this time, an induced current corresponding to the amount of change in surface potential flows through the transparent electrode 1. This induced current is detected by the amplifier 16 and processed by the CPU 17 via the A / D converter 18 to measure a relative potential profile in the main scanning direction. Further, the absolute surface potential on the photosensitive drum 2 is measured using the potential sensor 24. If the potential sensor 24 is disposed at a location different from the transparent electrode 1, the surface potential changes due to the dark attenuation characteristics of the photosensitive drum 2, and therefore it is preferable to dispose the potential sensor 24 in close proximity. However, if it is difficult to construct, it can be compensated by correcting the change in potential due to the dark decay. Then, by using the position data from the position sensor 19, the relative potential profile in the main scanning direction, and the surface potential at a predetermined position of the photosensitive drum 2, the profile for the entire circumference of the photosensitive member is measured. It is possible to detect the potential profile of the entire area.

  FIG. 2 shows the principle of potential profile measurement of the transparent electrode system. When a transparent electrode is disposed opposite to the photosensitive member charged by the charger, a pseudo capacitance component (capacitor) is formed between the surface of the photosensitive member and the transparent electrode. At this time, by irradiating the photoconductor with detection light, the surface potential of the photoconductor is attenuated, and the electric capacity between the transparent electrode changes. At this time, an induced current corresponding to a change in capacitance, that is, a change amount of the surface potential flows through the transparent electrode. Therefore, this induced current is measured via an operational amplifier. FIG. 3A is a diagram showing the correlation between the surface potential of the photosensitive member and the induced current. By using this correlation, the surface potential can be calculated from the detected induced current.

  FIG. 3B is a diagram showing the correlation between the exposure energy to the photoconductor and the surface potential change amount of the photoconductor. 3A and 3B that the induced current induced in the transparent electrode increases as the exposure energy increases.

  FIG. 3C is a graph showing the position of the photoreceptor and the induced current induced in the transparent electrode. As can be seen from the above description, the amount of change in the induced current increases as the exposure power increases. A single transparent electrode is arranged opposite to the main scanning direction of the photoconductor, and scanning in the main scanning direction with a detection laser makes it possible to measure changes in the induced current flowing in the transparent electrode with respect to time. A relative potential profile can be measured. By repeating this potential profile measurement in the main scanning direction for one rotation of the photoconductor, the potential profile of the entire photoconductor can be measured.

  As described with reference to FIG. 1, this induced current is amplified by a subsequent amplifier, converted into a digital value by A / D, and taken into the CPU. At this time, a larger change in induced current is advantageous for S / N because the gain of the amplifier can be lowered. Needless to say, in terms of A / D resolution, the larger original signal amplitude is advantageous in terms of measurement accuracy.

  Here, the second embodiment of the present invention will be described focusing on the differences from the first embodiment. FIG. 4 is a diagram schematically showing main elements related to the image forming process of the image forming apparatus provided with the potential profile device according to the second embodiment of the present invention. In FIG. 4, 1 is a potential sensor, 2 is a photosensitive drum, 3 is a primary high-voltage power source, 4 is a primary charger, 6 is a developing device, 7 is a copy sheet, 8 is a transfer charger, and 9 is a transfer high-voltage power source. 10 is a separation charger, 11 is a separation high-voltage power supply, 12 is a fixing device, 13 is a cleaner, 15 is an exposure unit, 16 is an amplifier for amplifying and transmitting an input signal in accordance with the signal level of the processing system, Reference numeral 17 denotes a CPU of a control device that controls the image forming apparatus, 18 denotes an A / D converter that converts an analog signal from the amplifier 16 into a digital signal, 19 denotes a position sensor, 20 denotes a laser beam, and 22 denotes a light amount of the exposure unit 15. The exposure control means to control is shown.

  In the above configuration, a high voltage of several kV is generated by the primary high voltage power source 3 and supplied to the primary charger 4. Therefore, the surface potential of the photosensitive drum 2 is uniformly charged to several hundred volts. Thereafter, laser light 20 corresponding to the original is irradiated onto the photosensitive drum 2 through the transparent electrode 1, and an electrostatic latent image is formed on the photosensitive drum 2. Next, the developing device 6 forms a toner image corresponding to the electrostatic latent image (toner development is performed) using the toner stored therein. Next, the transfer high-voltage power supply 9 applies a high voltage to the transfer charger 8 to charge the copy paper 7 from the back surface. Then, the toner image formed on the photosensitive drum 2 is attracted to the copy paper 7 and transferred. Thereafter, a high voltage of AC + DC is applied from the separation high voltage power source 11 to the separation charger 10, and the charge charged at the time of transfer is removed to separate the copy paper 7 from the photosensitive drum 2. Then, the copy sheet 7 onto which the toner image has been transferred is passed through the fixing device 12 to be thermally fixed and discharged. The toner remaining on the photosensitive drum 2 is removed by a cleaner 13.

  Next, potential profile measurement performed using a signal from the transparent electrode 1 will be described. This potential profile measurement is usually executed through the CPU 17 of the control device before the copy sequence, for example, during warm-up. In the above configuration, a high voltage of several kV is generated by the primary high voltage power source 3 and supplied to the primary charger 4. Therefore, the surface potential of the photosensitive drum 2 is uniformly charged to several hundred volts. Thereafter, the laser beam 20 is irradiated on the photosensitive drum 2 through the transparent electrode 1 in the main scanning direction. At this time, an induced current corresponding to the amount of change in surface potential flows through the transparent electrode 1. This induced current is detected by the amplifier 16 and processed by the CPU 17 via the A / D converter 18 to measure the relative potential profile in the main scanning direction.

  Then, by measuring the profile of the entire surface of the photoconductor based on the position data from the position sensor 19 and the potential profile in the main scanning direction, the potential profile of the entire surface of the photoconductor is measured, and the memory of the photoconductor is stored in a memory (not shown). Stores all area profile data.

  Then, based on the obtained potential profile and the position data of the photoconductor from the position sensor 19, the image forming operation is executed by performing exposure control for controlling the light quantity of the laser beam 22 in real time. For example, by changing the amount of laser light in the main scanning direction as shown in FIG. 5 according to the potential profile in the main scanning direction at a certain sub-scanning position of the photosensitive member, the influence of the potential profile on the surface of the photosensitive member is reduced. Correct to erase.

  Further, since the potential profile in the main scanning direction varies depending on the sub-scanning position of the photoconductor, it goes without saying that the laser light quantity is changed for each sub-scanning line based on the potential profile in the main scanning direction.

  By providing the potential profile measuring device using this transparent electrode system, it is possible to increase the speed, resolution, and accuracy of the potential profile measurement, and thus it is possible to provide a high-quality image.

  As described above, in the potential profile measurement device according to each of the above embodiments and the image forming apparatus including the same, the measurement of the potential profile using the transparent electrode method increases the measurement speed, increases the resolution, High accuracy can be achieved.

1 is a schematic diagram of a potential profile device according to a first embodiment of the present invention. The figure shown about the principle of the electric potential profile measurement of a transparent electrode system. The figure which showed the correlation of the surface potential of a photoreceptor, and an induced current. The correlation diagram of exposure energy and surface potential change rate. FIG. 5 is a correlation diagram of the photosensitive drum distance and the induced current. FIG. 6 is a diagram schematically illustrating an image forming apparatus including a potential profile device according to a second embodiment of the present invention. The position of a photosensitive drum and a laser power control diagram. The figure which shows schematic structure of the surface potential meter of a chopper system. The figure which shows the outline of an impedance conversion circuit. The perspective view which shows the external shape of an electrometer. 2 is a diagram showing an internal structure of an image forming apparatus using a potential sensor. FIG. Schematic connection diagram of potential sensor signal processing system. The figure which showed the method of moving and measuring an electric potential sensor in the main scanning direction. A method of measuring a plurality of potential sensors in the main scanning direction.

Claims (5)

A photoconductor rotatably supported by the apparatus;
Charging means for uniformly charging the photoreceptor;
Image exposing means for exposing the charged photoreceptor to form a latent image;
Switching means for switching light irradiation power of the image exposure means,
Developing means for developing the image formed by the image exposure means into a visible image with a predetermined developer;
Transfer means for transferring the developed visible image from the photoreceptor to a transfer material by the developing means;
A transparent electrode facing the photoconductor and disposed on the optical path of the image exposure means;
A potential change amount detecting means for detecting a potential change amount by an induced current induced in the transparent electrode when light is irradiated on the photoconductor by the image exposure means;
Control means for controlling the exposure power of the image exposure means;
An image forming apparatus comprising:   2. The surface of the photosensitive member according to claim 1, wherein the image exposure unit, the developing unit, and the transfer unit form an image, and the image exposure unit, the transparent electrode, and the potential change amount detection unit. An image forming apparatus having a mode for measuring the upper potential profile.   3. The light irradiation power of the exposure unit in the image formation mode and the potential profile measurement mode according to claim 2, wherein the light irradiation power in the potential profile measurement mode is stronger than that in the image formation. An image forming apparatus that controls the control means.   2. The image forming apparatus according to claim 1, wherein a profile measurement in the main scanning direction of the photosensitive member is performed by the potential change amount detection unit.   2. The potential profile measuring apparatus according to claim 1, wherein profile measurement of the entire surface of the photosensitive member is performed by repeating profile measurement in the main scanning direction a plurality of times by the potential change amount detecting means.

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