JP2674002B2 - Image defect evaluation device for electrophotographic photoconductor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an evaluation device for non-contact evaluation of defects such as noise in a ridge image formed by an electrophotographic photosensitive member (referred to as ridge image defect). [Prior Art and Problems Thereof] In the following description of the drawings, the same reference numerals indicate the same or corresponding portions. FIG. 1 shows the structure of a copying machine as a main application of this type of electrophotographic photosensitive member (hereinafter referred to as a drum). In the figure, D is a cylindrical drum, which has a photosensitive surface made of a semiconductor photosensitive layer forming an electrostatic latent image on its outer peripheral surface, and is rotatably supported in a rotation direction AXR indicated by an arrow in the figure. CH1 is a corona discharger that charges the drum D in advance by corona discharge to form the latent image, and EX is an exposure unit having a semiconductor laser light source that exposes the drum D and forms a latent image such as a character pattern. DV is a developing device for developing by attaching a developer such as toner to the latent image, P is a transfer material such as copy paper for transferring the developed ridge image, and CH2 is a transfer corona charge for performing this transfer. A container, CL is a cleaning means for removing the developer remaining on the drum D, and DCH is a static eliminator such as a fluorescent lamp for removing the residual electric charge on the drum D by irradiating with blue light or the like (referred to as optical neutralization). . Conventionally, as a method of evaluating the image defect of the drum D, there is known a method of performing a sensory inspection and an image evaluation by a copying machine without the image. In order to print the image on the copying machine, the drum D is mounted on the copying machine as shown in FIG. 1 and the image is printed. Then, it is necessary to detach the drum D after the ridge image is formed and remove the developer and the like adhering to the drum surface.
Since the transfer material P, the developer, etc. are consumed, there is a defect that a considerable amount of time and cost are spent together. There is also a so-called "noise tester" as an image evaluation device that makes it easy to attach and detach the drum D.
After the ridge image is formed, it is necessary to remove the developer adhering to the surface of the drum. In this way, all the ridge images taken out from these devices have a drawback that humans visually judge pass / fail (sensory test), resulting in measurement error, and it takes time to improve measurement accuracy. There is. [Object of the Invention] Except for the above-mentioned drawbacks, the present invention does not require ridge image formation in a copying machine and complicated work in ridge image formation, and accurately evaluates a defect of an electrostatic latent image caused by a drum in a non-contact manner. The purpose is to provide. [Main points of the invention] The main point of the present invention is to provide a photoreceptor for electrophotography in which a photosensitive layer for an electrostatic image is attached to the outer peripheral surface of a cylindrical or planar metal substrate or on the flat surface to form a photosensitive surface. (A drum, etc.), a means (a corona discharger, etc.) for uniformly charging the photosensitive layer to a predetermined potential, are provided in a row in opposition to the photosensitive surface via a gap and parallel to the surface. An electrode array composed of a plurality of metal electrodes (sensor electrodes) formed in a line, a linear holding means (electrode support) that integrally holds the electrode array, and the photosensitive surface for scanning with the electrode array. , A means for driving the holding means and the photosensitive member (motor or the like), a scanning position detecting means for detecting a scanning position of each electrode in the electrode array on the photosensitive surface, and a potential of each electrode. Electrode potential detection means (voltage divider, amplifier, A /
D multiplexer, CPU, etc.) and means for inputting the detection signals of the scanning position detecting means, the electrode potential detecting means, and creating a potential map on the photosensitive surface (CPU, etc.). A minimum defect (gap) between the electrode and the electrode is an image defect evaluation device for electrophotographic photoconductor, which is characterized by being 1 mm or less. Further, the electrode array composed of the plurality of metal electrodes is provided on the photosensitive surface at a predetermined distance from each other, and the direction of the normal line of the photosensitive surface to which the electrode array is opposed. The maximum outer diameter of the projected image is 1 mm or less, and the distance between the electrodes is in the range of 1 to 100 mm. [Examples of the Invention] The present invention will be described below with reference to FIGS. FIG. 2 is a block diagram showing the principle device of the present invention, FIG. 3 is a diagram showing an example of the measured values obtained in FIG. 2, FIG. 4 is a diagram showing a configuration example of the present invention, and FIG. 4 is a diagram showing an example of the measurement results of the apparatus. In FIG. 2, AXD is a shaft of the drum D (also serves as a rotation shaft), D1 is a photosensitive layer on the drum D, and D2 is a metal cylinder such as aluminum serving as a base of the photosensitive layer. DF is a defective portion in the photosensitive layer D1, and in this case, assuming a circular defective portion, its diameter (called a defect diameter) is 2S. Reference numeral 2 denotes a thin metal columnar sensor electrode having a circular cross section that faces the cylindrical surface of the drum D with a gap g. AX2 is its axis, 2a is its diameter (called the electrode diameter), and axis AX2 is the photosensitive surface of the drum D. It faces in the direction of the normal line. x is a distance between the center of the defect portion DF and the center of the sensor electrode 2 (referred to as a defect distance). Further, 3 is a widening device having a high input impedance for widening the voltage induced in the sensor electrode 2, 4 is a voltage dividing capacitor provided between the sensor electric country 2 and the ground, and SG is a detection taken out from the widening device 3. Voltage. The drum D is a corona charger (not shown) as shown in FIG.
It is almost uniformly charged to a predetermined potential by CH1, and
A static eliminator (not shown) removes static electricity after measuring the detected voltage. Although the drum D is almost uniformly charged, the charge induced on the sensor electrode 2 by this is mainly
It is proportional to the normal component of the surface of the sensor electrode 2 among the electrolytic components forming the photosensitive surface near the electrode including the defective portion DF on the surface of the drum D. Therefore, the charge, and thus the potential of the sensor electrode 2, is affected by the defect portion DF. FIG. 3 shows an example of measurement values measured by the principle device of FIG. 2, and FIG. 3A shows an electrode diameter 2a = 1.00 mm and a gear g = 1.50.
mm, defect distance x = 1.25 mm, defect diameter 2S (m
The rate of change (decrease rate) of the detection voltage SG when the magnitude of m) changes is shown. That is, in the figure, the detection voltage SG when the defect diameter 2S is 0 is set to 1, and the detection voltage SG increases as the defect diameter 2S increases.
The amount of SG reduction is shown as a ratio. As a result, the defect diameters 2S corresponding to the detection voltage SG reduction rates of 10%, 20%, and 50% are 0.62, 1.24, and 2.78 (each mm), and the reduction rate or reduction amount is measured under predetermined conditions. Therefore, it can be seen that the size of the defective portion can be evaluated. The figure (B) shows that when the defect distance x = 0, that is, when there is a defect portion DF directly below the sensor electrode 2, it is effective with the gear gap g when the electrode diameter 2a is set to 2.0, 1.0, 0.5 (each mm), respectively. The relationship with the detectable defect diameter 2S (called defect diameter resolution) is shown. However, in this case, this defect diameter resolution is the defect diameter 2S = 0, that is, the detection voltage when there is no defect.
The size of SG is set to 1, and the value of the defect diameter 2S when this size is reduced by 20% is shown. If the defect diameter 2S of 0.5 is detected from this figure, the following conditions are obtained. 1) Set the drum D, the sensor electrode 2, and the gear g to 1 mm or less. 2) The electrode diameter 2a of the sensor electrode 2 may be 1 mm or less. However, the cross section of the sensor electrode 2 taken along a plane orthogonal to the axis AX2 is not limited to a circle, and may be any shape such as a quadrangle.
It can be considered that the above-mentioned value of the electrode diameter 2a indicates a standard of the maximum outer diameter of the cross section of the sensor electrode 3. Further, the shape of the surface S1 of the sensor electrode 2 facing the drum D does not necessarily have to be a flat surface as shown in FIG. 2, and the capacitance formed between the sensor electrode 2 and the drum D has a predetermined value. As long as it has a spherical surface or a conical surface, it does not matter. At this time, the gear g is the smallest gear. Therefore, the length l1 of the columnar portion of the electrode 2 can be set to a predetermined arbitrary length including 0. Next, FIG. (C) shows the defect distance x and the same defect diameter resolution as in FIG. (B) when the electrode diameter 2a is 1.0 mm and the gear g is 1.5, 1.0, and 0.5 (each mm). Shows the relationship with. From this figure, if the defect diameter 2S of 0.5 mm is effectively detected as in the case of FIG. 3) The defect distance x as the center distance between the defect portion DF and the sensor electrode 2 needs to be 0.5 mm or less. Therefore, as will be described later, when the sensor electrode 2 is translated in the direction of the axis AXD of the drum D while rotating the drum D to detect the defective portion DF on the drum cylindrical peripheral surface, the sensor electrode 2 for one rotation of the drum D The feed pitch must be 0.5 mm or less. On the other hand, as the test time in this case, the drum shaft length L = 30
Assuming 0 mm, such sensor electrodes 2 are arranged in an array of 10 mm.
If 30 pieces are arranged at equal intervals, the time required to scan a feed distance of 0.5 mm for the feed pitch of 10 mm per electrode is 20 rotations of the drum. Therefore, if drum D is rotated at 20 rpm, it will be completed in about 1 minute. become. To this end, in the case of a drum having a diameter of 120 mm, the peripheral speed at 20 rpm is 126 mm / sec, so that the passing time of the defect portion DF of 0.5 mm is about 4 msec. To detect this accurately, the sampling time must be at least 0.4 msec. Also, the time constant of the detection circuit must be at this level.
In addition, since 30 arrays are used for detection, the A / D conversion speed is 10
Must be ~ 20 μsec. At this time, the number of data per sensor is 7.5 kword for one rotation. As described above, various test conditions can be obtained. Next, FIG. 4 will be described.
An image defect evaluation apparatus for detecting an actual defective portion DF on the drum D based on the principle and conditions described in the figure, 1 is a drum drive motor, 2 is an array-shaped sensor electrode, 5 is the above-mentioned Support for many sensor electrodes 2 (referred to as electrode support)
An electrode drive motor that drives 2F back and forth in the direction of the axis AXD of the drum D, 6 is a drum rotational position detection unit that detects the rotational position of the drum D, and 9 is an encoder that also detects rotational position. Further, 7 is a drum rotation display section for inputting an output signal of the drum rotation position detection section 6 and displaying a rotation position of the drum D, and the like.
8 is an A / D multiplexer that A / D converts the output voltage of the amplifier provided for each of the sensor electrodes 2 and inputs it to the CPU, and 10 controls the drum drive motor 1 and the electrode drive motor 5. In addition, the control CPU for determining the position of the defective portion DF by inputting the rotation position signal of the drum D obtained through the drum rotation display unit and the detection voltage of the sensor electrode 2 input from the A / D multiplexer 8. Is. That is, when the drum D is rotated in the rotation direction AXR via the drum driving motor 1, the photosensitive surface of the drum D is charged to a predetermined potential substantially uniformly by the corona charger CH1, while the photosensitive surface of the drum D is below the sensor electrode 2. Then, the detection voltage SG is output from each amplifier 2 through each of the electrodes 2. The drum rotation position detector 6 detects the rotation of the drum D and its position through an encoder 9 attached to the end surface of the drum D, and outputs the output signal to the drum rotation display unit 7 to display the rotation position. , The output signal of the display unit 7 is given to the CPU C
The PU knows the rotation position of the drum D from time to time. On the other hand, each of the sensor electrodes 2 is sent in the direction of the axis AXD by a predetermined feed pitch by the CPU 10 in synchronization with the rotation of the drum D via the electrode drive motor 5 and the electrode support 2F, and scans the circumference of the drum D. . In this way, the detected voltage SG is read by the CPU 10 via the A / D multiplexer 8, and the CPU 10 creates a potential map on the photosensitive surface of the drum D. By inserting the reference image data of the image evaluation into the CPU 10 in advance, it is possible to judge the pass / fail and display the position and size of the defective portion DF. FIG. 5 shows the values obtained by actually making scratches of various sizes on the surface of the drum D by using the image defect evaluation apparatus of FIG. 4 and confirming the same with an optical microscope, and the values measured by the image defect evaluation apparatus. Is a comparison. As is clear from the figure, it can be seen that this apparatus can detect a defective portion with sufficient accuracy in practical use. In the present invention, even if the photoconductor as the object of the defect evaluation has a flat photoconductive surface, it can be considered that the radius of curvature of the photoconductive surface of the drum D is infinite. The defect evaluation according to the present invention is possible. Further, the plurality of sensor electrodes 2 are arranged such that the axes AX2 thereof are arranged in parallel to each other at a predetermined interval. This has the advantage of facilitating the preparation of the potential map, but it is not an essential condition. For example, they may be arranged at predetermined intervals on a spiral curve of predetermined pitch along the photosensitive surface of the drum D. [Effects of the Invention] As is apparent from the above description, according to the present invention, an electrode array including a plurality of thin rod-shaped electrodes facing a cylindrical or planar photosensitive surface with a gap is provided. Since these electrodes are integrally held to scan the photosensitive surface, the defect on the photosensitive surface can be evaluated by detecting the potential distribution on the photosensitive surface in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration example of a normal copying machine, FIG. 2 is a configuration diagram showing a principle device of the present invention, and FIG. 3 is a measured value obtained by the device shown in FIG. FIG. 4 is a diagram showing an example of the configuration of the device of the present invention, and FIG. 5 is a diagram showing an example of the measurement results of the device of FIG. D: Electrophotographic photoconductor (drum), CH1: Corona charger, 1 ... Drum drive motor, 2 ... Sensor electrode, 2F
...... Electrode support, 3 ...... Amplifier, SG ・ ・ ・ Detection voltage, 4 ・ ・ ・
… Voltage dividing capacitor, 5 …… Electrode drive motor, 6 …… Drum rotation position detector, 7 …… Drum rotation indicator, 8 ……
A / D multiplexer, 9 ... Encoder, 10 ... CPU, 2F
…… Electrode support, AXD …… Axis, AXR …… Rotation direction.

Continuation of front page    (56) References JP-A-59-37581 (JP, A)                 JP-A-53-131848 (JP, A)                 JP 58-68651 (JP, A)                 JP 59-49573 (JP, A)                 JP-A-57-116354 (JP, A)                 JP 58-65445 (JP, A)                 JP-A-57-53767 (JP, A)                 Japanese Patent Sho 58-10746 (JP, B2)                 Japanese Patent Publication 2-43134 (JP, B2)                 Special table Sho 61-500690 (JP, A)

Claims (1)

(57) [Claims] A photoconductor for electrophotography having a photosensitive layer for electrostatic images formed on or on the outer peripheral surface of a cylindrical or planar metal substrate, and a predetermined potential on the photosensitive layer. Means for performing charging, and an electrode array composed of a plurality of metal electrodes arranged in a row parallel to the surface and facing the photosensitive surface, and holding the electrode array integrally. A linear holding means, a means for driving the holding means and the photoconductor in order to scan the photosensitive surface with the electrode array, and a scanning position of each electrode in the electrode array on the photosensitive surface Scanning position detecting means for detecting the electric potential of each electrode, the electrode potential detecting means for detecting the electric potential of each electrode, the scanning position detecting means, the detection signal of each means of the electrode electric potential detecting means, and the electric potential on the photosensitive surface. And a means for creating a map, said photosensitive surface and electrodes An image defect evaluation apparatus for an electrophotographic photosensitive member, characterized in that the minimum gap (gap) between the two is 1 mm or less. 2. The ridge image defect evaluation apparatus according to claim 1, wherein the electrode rows composed of the plurality of metal electrodes are provided on the photosensitive surface at predetermined intervals. Image defect evaluation system for electrophotographic photoreceptors. 3. The ridge image defect evaluation apparatus according to claim 1 or 2, wherein the maximum outer diameter of the projection projected in the normal direction of the photosensitive surface facing the electrode row is 1 mm or less. An image photographic defect evaluation apparatus for an electrophotographic photoreceptor. 4. The image defect evaluation apparatus according to claim 2, wherein the distance between the electrodes is in the range of 1 to 100 mm.