JPS6045426B2 - Photoconductor surface defect detection device - Google Patents

Description

[Detailed description of the invention] -1-Mari 2nn, 13, wo'
“Re↓ゝth” +←Kuzuwa J-day, Tobu I’s.

Photoconductive insulators mainly composed of amorphous selenium, photoconductive insulators formed by dispersing inorganic photoconductive substances such as zinc oxide or cadmium sulfide in resin, or polyvinylcarbazole or polyvinylphenylanthracene. uniformly charging the surface of a photoconductive insulating drum coated with an organic photoconductor such as, exposing a light image by beam exposure to form an electrostatic latent image on the photoconductive insulating drum surface;
A recording apparatus has been proposed in which the latent image thus obtained is visualized using electrostatically dissipated powder, and if necessary, the visible image is transferred to a transfer member such as plain paper. A typical example is to electrically control a laser beam and mechanically deflect it to form an electrostatic latent image on the recording medium, and develop the latent image to create an electrophotographic toner image. This is a laser printer that transfers images onto paper to obtain visible images.

If there is a defect in the photoconductor drum used in such laser printers, etc., the defect will cause important information to be recorded. There must be no defects on the drum. It goes without saying that this defect on the photoconductor drum must not exist on an unused photoconductor drum, and if it does exist, it is necessary to remove the defect by some means when installing the photoconductor drum. Needless to say, it is necessary to prevent a detected defective photosensitive drum from being installed in a recording apparatus. In the case of a laser printer, which is an embodiment of the present invention, the photosensitive drum is used repeatedly. Therefore, even if the drum is carefully checked in advance as described above, it is impossible to avoid the occurrence of defects due to peeling or damage of the photoreceptor as the photoreceptor is repeatedly used. Conventional recording devices do not check for defects in the photosensitive drum during use, so if these defects occur during recording,
Information would be periodically dropped or the recording paper surface would become smudged, and it was only after printing a considerable number of sheets that I noticed these defects and was told that I had to replace the photosensitive drum and print again. There were flaws.

This becomes an extremely serious problem when information stored in software must be printed out, such as with a computer printer.

In other words, the printed information is completely unknown to the person handling it, so even if the defect is just one character... There is a strong possibility that what has been printed out up to that point will end up looking exactly the same. Therefore, it is necessary to store the information to be printed on a magnetic tape or the like for a considerable period of time, and there is a drawback that the buffering factor cannot be easily reduced. Of course, it is possible to stop the operation of the recording device for a certain period of time and inspect the recording drum according to a certain predetermined procedure during that time, but stopping the printer for a certain period of time causes a large financial loss. Furthermore, it is actually difficult to train full-time personnel for the inspection.

Particularly in the case of high-speed printers, it is nearly impossible to repeatedly perform such inspections because the speed of printed information is fast. SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate the above-mentioned drawbacks of the prior art and to provide a device for detecting surface defects on a photoreceptor drum during a period when no signal to be recorded is provided to the recording device. It is in.

According to the present invention, these above-mentioned drawbacks are solved as follows.

A beam recording device comprising a beam light source, a modulating means for modulating a beam light (emitted from the beam light source), a deflection means for deflecting the beam light, and a photoreceptor for receiving the beam light. , (1) means for irradiating the beam light source with a beam light of a saw-like intensity during a period when beam recording is not actually performed, and (2) means for irradiating the beam light with a saw-like intensity during a period when beam recording is not actually performed; (3) means for deflecting the light beam so modulated to scan the surface of the photoreceptor; and (4) means for reflecting the modulated light beam on the surface of the photoreceptor. (5) means for determining that the reflected light is not a predetermined one; A recording device is provided that detects surface defects on a photoreceptor by outputting an output signal indicating the presence of a defect.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a beam recording apparatus showing one embodiment of the present invention. Reference numeral 1 denotes a metal drum on which an electrophotographic photoreceptor 2 is mounted, and the electrophotographic recording drum 3 is configured in this manner.

The electrophotographic photoreceptor 2 is typically formed by depositing sensitized amorphous selenium containing several percent tellurium on a metal drum 1 made of aluminum or the like. Other materials include organic electrophotographic photoreceptors in which an organic photoconductor such as polyvinylcarbazole or polyvinylphenylanthracene is sensitized with a stimulant such as trinitrofluorenone or tetranitrofluorenone, or a binder containing cadmium sulfide, zinc oxide, etc. A material with excellent durability is selected, such as a composite photoreceptor with a two-layer structure, in which an insulating thin film such as polyethylene terephthalate is bonded to a photoreceptor layer dispersed in the photoreceptor.
The electrophotographic recording drum 3 is required to have durability, mainly abrasion resistance on the surface of the photosensitive layer, as will be made clear in the description below. The durability of the electrophotographic recording drum 3 is tens of thousands of times.
Desirably, it is required to withstand repeated use one time or more. The above-mentioned example of the photoreceptor can almost satisfy this durability. The surface of the electrophotographic recording drum 3 is uniformly charged to a predetermined polarity by a corona charging device 4. When using an amorphous selenium photoreceptor that has been subjected to tellurium sensitization as the electrophotographic recording drum 3 (in the following description, this selenium photoreceptor will be used as a specific example), approximately 1 kV is applied to the positive polarity. The structure and specifications of the charger 4 and the voltage applied to the discharge electrode are determined so that the surface potential becomes . This factor varies depending on the rotational speed of the drum 3 and the thickness of the photoreceptor 2. As is well known, the structure of the charger 4 includes a plurality of discharge electrodes made of tungsten wire or the like having a diameter of several tens of microns, the purpose of uniformity of discharge, and the purpose of uniformity of discharge, and the structure of the charger 4 includes a plurality of discharge electrodes made of tungsten wire or the like having a diameter of several tens of microns. It is a well-known fact that a high-voltage DC power source of about +7K is directly connected to the discharge electrode. The uniformly charged surface of the photoreceptor 2 is then exposed to a beam light source, such as a helium-neon laser light source or a helium-cadmium laser light source, which has an emission spectral characteristic at a position approximately corresponding to the peak of the spectral sensitivity curve of the photoreceptor 2. exposed to light from 5.

A light beam 6 having a substantially uniform intensity emitted from the light beam source 5 is modulated by an optical modulator 7, and the modulated light beam 8 is deflected by deflection means 9,10. The deflected beam light is irradiated onto the surface of the photoreceptor 2. Here, it is necessary to determine the optical modulator 7 that can be practically used, taking into consideration various factors such as modulation speed, stability, cost, and ease of handling. Considering the above points, lead molybdate (PbMO) is used for combination and one-ter terminal printers with a clock frequency of several MHz.
A modulator using an acousto-optic effect such as O4) is used. The beam light deflecting means includes a motor 9;
A polyhedral mirror 10 directly connected to the photoreceptor 2 is generally used, rotated at several thousand revolutions per minute, and scans the surface of the photoreceptor 2 with a reflected beam 11 at high speed. An output 14 from the control device 13 is applied to the optical modulator 7, and the light beam 6 is modulated;
That is, it is determined whether the signal passes through the modulator 7 or is blocked at the position of the modulator 7. The deflected light beam 11 hits the surface of the photoreceptor 2 and is reflected,
The reflected light beam 12 enters a photoelectric converter 30. The converter 30 generates an output signal 16 depending on the presence or absence of reflected light, which output signal 16 is the output 1 from the control device 13.
5 is input to the surface defect determination device 17. As will be described in detail later, the determiner 17 determines whether or not there is a defect on the surface of the photoreceptor 2, and if it is determined that there is a defect, a control output signal 18 is output to control various parts of the beam recording device. Movement is controlled. An image is formed in the following manner on the surface of the photoreceptor 2 where no defects exist.

A corona discharge charge is uniformly applied to the surface of the photoreceptor 2, and the modulated and deflected beam light 1 passes thereon.
2, and selectively exposes the surface of the photoreceptor 2 according to a signal from the control device 13. The exposed portion of the photoreceptor 2 dissipates the electrostatic charge carried thereon, and substantially lowers its surface potential to about 300 V or less, while the unexposed portion loses its surface potential, although there is some dark attenuation. almost maintains its charged potential. In this way, an electrostatic latent image is formed on the photoreceptor 2 in the form of information to be recorded. The photoreceptor 2 on which the electrostatic latent image is formed is developed by the developing device 19.

The developing device 19 uses a magnet to attract a developer, which is an electrostatic detection powder and is a mixture of negatively charged toner and iron powder at a weight ratio of about 3:1 (1), and slides it onto the photoreceptor 2. move,
The so-called magnet 7 net brush method is adopted. The developing method is not necessarily limited to the above-mentioned magnetic brush method, and there are other methods such as a method in which the toner itself is magnetic powder is directly attracted to a magnet without using a carrier and the drum slides, or a method in which the toner is applied to glass beads. A cascade development method in which the deposited material 9 is slid onto a photoreceptor and developed is also generally well known. In the electrostatic latent image, the individual surface potentials that should be developed and become black are low, and the surface potentials of the areas to which toner should not be attached are high and hold a positive electrostatic charge. Therefore, it is desirable that the charging polarity of the toner used here is positive. The recording drum 3, which has been developed with toner in this way and carries the toner image on the surface of the photoreceptor 2, reaches the transfer station, where it is synchronized with the rotational speed of the recording drum 3 and is transferred to a transfer member. continuous foam sheet 20.

The continuous foam sheet 20 is driven by pressing rollers 21 and 22 and a driving device 24, and a transfer charger 23 applies ions of negative polarity to the reverse polarity of the toner charge to the back surface of the sheet 20. Through this operation, the sheet 20 is charged to a negative polarity in the transfer station, and the toner image is transferred from the recording drum 3 side to the sheet 20 side by electrostatic attraction. After the toner image is transferred onto the sheet 20 in the transfer station, the sheet 20 is separated from the electrophotographic recording drum 3 and conveyed to the fixing station by the drive device 24. In the fixing section, the toner image is fused to the sheet 2 by the toner fusing device 25.
permanently affixed to 0. The toner fusing device 2
4, a hot plate, a hot roller, an infrared heater, or the like is usually used to raise the temperature of the toner to 150° C. or higher. Toner is typically formed by coating carbon black with a thermoplastic resin, so exposing the toner to these high temperatures will melt the resin and firmly fix the carbon onto the sheet 20, creating a visible permanent image. It becomes possible to form.
Due to the operation of the toner image transfer device, not all of the toner on the electrophotographic recording drum 3 is transferred onto the sheet 20.

Since a portion of the toner remains on the recording drum 3, these residual toners must be removed before the recording drum 3 is used repeatedly for image formation. Therefore, the recording drum 53 carrying the residual toner image is successively subjected to the action of the erasing lamp 27 and the electrostatic charge erasing device 28. The erasing lamp 27 is for erasing the electrostatic latent image remaining on the recording drum 3, and as is clear from the above description, the surface of the photoreceptor 2 to which no toner image is attached is still of positive polarity at this point. It has the effect of lowering the surface potential of a charged surface to substantially the ground level by irradiating it with light. In addition, the static charge erasing device 28 removes the positive charge carried by the remaining toner image to make the toner uncharged, making it easier to peel off from the recording drum 3, and at the same time promotes the static elimination effect of the recording drum 3. do. Normally, in this erasing device 28, an AC high voltage having a frequency of several kilovolts and a frequency higher than the commercial power source is applied to a discharge electrode having a structure similar to that of the charging device 4. The recording drum 3 is then sent to a cleaning department.

In the cleaning department, a rotating cleaning brush housed in the housing, a toner scraping member for wiping off toner from the brush, and an exhaust hole for sucking the scraped toner to the outside are installed as appropriate. The toner image of the previous recording remaining on the recording drum 3 is removed by the residual toner cleaning device 29. The rotating cleaning brush is made of fluororesin, nylon or other synthetic resin fibers, and the scraping member is made of aluminum pieces, iron pieces, or suitable synthetic resin pieces, but these materials are selected. Needless to say, when doing so, it is necessary to take the charging order into account and select a material that will better attract toner from the surface of the drum 3. By going through the steps described above, cycling of the drum to record the desired image is completed, and the surface of the drum 3 is newly subjected to charging, exposure, and development to record the next image. become.

Now, in the present invention, during a period when no recording is actually performed on the recording drum, that is, at the beginning of a computer job,
Alternatively, defects in the photosensitive layer existing on the drum surface are determined by scanning the drum with light of a constant intensity over an area corresponding to at least the entire recording surface of the drum after the power is turned on and before recording starts.

Here, the constant intensity may be light modulated at an appropriate frequency. The principle of this circuit for detecting the surface of the photoreceptor will be explained in detail below. FIG. 2 is a block diagram showing the principle of detecting surface defects on a photosensitive drum.

The terminal 31 receives the output 1 from the control device 13 in FIG.
5 is supplied, and the output signal of the photoelectric converter 30 in FIG. 1 is applied to the terminal 32. The signal input to the terminal 31 is a pulse signal with an adjusted waveform. One terminal 32
The signal input to the photoelectric converter 30 is the output signal of the photoelectric converter 30, and its waveform is a waveform mixed with noise. These signals are passed through a waveform shaping circuit 33 and converted into clean waveforms from which excess noise has been removed. It should be noted here that, as shown in FIG. 1, the output signal 15 is one input of this surface defect determiner and is also an input to the optical modulator 7.

The signal applied to the terminal 31 has, for example, a waveform as shown in FIG. 3a, with a pulse width T of at least a time corresponding to scanning the entire recording surface of the drum. Here, when the signal is at a high level, the optical modulator 7 acts to transmit light,
The optical modulator 7 is designed so that no light is emitted from the optical modulator 7 when the signal is at a low level. Therefore, from the normal recording drum surface, a signal is generated in which a photocurrent flows when the waveform a is at a high level, and no photocurrent flows when the waveform is at a low level, that is, a signal as shown in Fig. 3b. It turns out. That is, in a recording drum 3 whose surface has no defects at all, the signal a and the signal b should have a one-to-one correspondence. 3
7 shows the state of the output signal 16 when there is a defect on the surface of one drum 3.

In this case, even if the drum surface 3 is irradiated with the beam light 6, no reflected light is generated, so the output signal 16 does not appear at the position of the defect, resulting in the state 37. These signal waveforms b pass through a waveform shaping circuit 33 and are shaped into a beautiful rectangular wave c in FIG. The signal waveform c thus obtained is inputted together with the output signal 15 (signal waveform a) from the control device 13 to a comparator 34 typified by an exclusive OR circuit.

As is well known, the comparator (exclusive OR circuit) 34 is a logic circuit that generates an output signal of ゜゛0゛ if the two inputs are at the same level, and an output signal of ``1'' if the two inputs are at different levels. If there are no defects on the surface of
Since the two inputs (signal waveform a and signal waveform b) of the exclusive OR circuit 34 are the same signal, the output of the exclusive OR circuit maintains the O level. As has been made clear from the above explanation, when there is a defect on the surface of the drum 3, the two signals are different, so when the defect is scanned, an output signal having the signal waveform d is generated. Since the pulse width of such a signal waveform d is generally a short pulse of several tens of nanoseconds, it is often too short as a control signal. Signal waveform d is pulse width expansion circuit 3
5, the pulse width is converted to an appropriate time pulse width, and the signal waveform e
is obtained and output to the output terminal 36. The signal waveform e thus obtained indicates the surface defect and is used as a signal to actuate a control mechanism to prevent an image from being recorded on the surface defect.

Generally, measures are taken to notify the operator that there is a defect on the surface of the photoconductor by means such as a lamp, and at the same time stop information coming directly from the magnetic tape device, disk device, or CPU main body to the printer device. . Alternatively, countermeasures can be taken, such as installing an appropriate memory inside the printer and rewriting the line to be recorded at the location where the defect has occurred. Since these operations are a matter of device design and have no direct relation to the content of the present invention, it is deemed beyond the point to discuss them in detail here. As has already been made clear from the above detailed explanation, it is possible to detect surface defects on the photoreceptor drum and effectively prevent typos and omissions by using a very simple means. For implementation, it is desirable to use the following embodiments.

As is clear from the above description, the present invention detects the presence or absence of surface defects by detecting the light beam reflected on the surface of the photoreceptor drum. It goes without saying that it is better to use the one that shows the best sensitivity to the target.

On the other hand, the photoelectric converter should be installed at a position where the light beam reflected on the surface of the photoreceptor drum becomes the strongest. In other words, the beam light is not irradiated perpendicularly to the surface of the photoreceptor drum, but is irradiated from an oblique position.
It is desirable to place the photoelectric converter in the specularly reflective area of the drum. This allows the output signal from the photoelectric converter to show the highest current value, making it possible to significantly reduce malfunctions. Furthermore, as a preferred embodiment, when forming a photoreceptor layer on a metal drum, the surface of the metal drum is matte,
If the surface of the photoreceptor formed thereon is glossy, the signal-to-noise ratio of the output of the photoelectric converter will be significantly improved, especially in the detection of photoreceptor surface defects, and the reliability of the surface defect detector will be improved. I will focus on improving.

As an example of such a photosensitive drum, the following can be implemented. A metal drum is made of aluminum, and a porous film of phosphoric acid bath anodized film is formed on the aluminum.

Furthermore, a selenium photosensitive layer is formed by vacuum-depositing a Se alloy layer to a thickness of about 50 μm thereon. The selenium photosensitive layer obtained in this way is glossy and specularly reflects the beam light, but the beam light is diffusely reflected in areas where the anodic oxide film is exposed, that is, where there are surface defects on the photosensitive layer. As a result, the output of the photoelectric converter that enters the surface defect detector has an excellent signal-to-noise ratio. Another advantage is that when a selenium photoreceptor is deposited on a porous anodic oxide film, the contact area of the substrate increases due to its porous nature, and the adhesion between selenium and aluminum is significantly improved, resulting in less friction due to surface sliding. One example is that the occurrence of photoreceptor falling off is significantly reduced. It has been found that selenium deposited on this porous layer has excellent photosensitivity, chargeability, etc. As described above, a drum in which an anodic oxide film is formed on an aluminum drum and a selenium photosensitive layer is deposited thereon is not only effective for the purpose of the present invention, but also has great overall advantages. In a photoreceptor with a two-layer structure in which polyethylene terephthalate or the like is laminated onto a photoreceptor in which cadmium sulfide or zinc oxide is dispersed in a binder, it is difficult to detect surface defects in the photoreceptor layer. This is equivalent to detecting breakdown of an insulating film such as phthalate.

In these photoreceptors, the photoreceptor itself, in which cadmium sulfide or zinc oxide is dispersed in a binder, is matte, and the insulating film, such as polyethylene terephthalate, has gloss. essentially satisfies the above conditions. As described above, according to the present invention, when the actual beam recording is not being performed, the reflection of the beam light from the surface of the photoreceptor is detected and it is determined whether the reflected light is a predetermined light. Since it is a detection device, it is possible to find surface defects prior to recording, and there is no need for a special light source for detecting surface defects. In addition, there is no need to stop and inspect each drum to find surface defects on the photoreceptor, and typographical errors and omissions caused by surface defects can be significantly reduced or completely eliminated. This brings about the great advantage that the reliability of the printer can be greatly improved by very simple means. Although the present invention has been described using the example of a printer using a light beam, the present invention is not limited to printers. That is, a facsimile machine having a form very similar to that of the embodiment, COM (Compu
tetOltputMicrOfjlming) device,
10M(LaserOutputMjcrOfiImi
ng) It can be applied as is to devices, etc.

These should be considered as not departing from the scope of the present invention in any way. Copying machines also have a similar mechanism, but those skilled in the art can easily implement a mechanism for detecting surface defects and preventing omissions caused by such defects. Also, although this specification states that the photoreceptor should be inspected when the drum is not actually being recorded, it is of course recommended to interrupt the inspection process at any point during recording and perform the inspection. Needless to say, it can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the configuration of a beam recording device according to an embodiment of the present invention, and FIG. 2 is a block diagram illustrating the principle of construction of a photoreceptor surface defect detector according to the present invention. FIG. 3 is a signal waveform diagram. DESCRIPTION OF SYMBOLS 1...Metal drum, 2...Electrophotographic photoreceptor, 5...Beam light source, 7...Optical modulator, 12...Photoreceptor beam of light reflected from,
13... Control device, 17... Surface defect determiner, 30... Photoelectric converter, 33... Waveform shaping circuit, 34... Comparison Vessel, 35...
・Pulse width expansion circuit.

Claims (1)

[Claims] 1. A beam generating means for generating a beam of light, a means for scanning a uniformly charged photoconductive photoreceptor with the beam to form an electrostatic latent image, and a means for scanning this latent image with an electrostatic detection powder. A surface defect detection device for a photoconductor of an electrophotographic recording device that repeatedly uses the photoconductor, comprising a developing device that develops to form a powder image, and a transfer device that transfers the powder image to a transfer member. , means for applying a test signal to the beam generating means so as to generate a test beam having a uniform intensity to scan the recording surface of the photoreceptor during a non-recording period; a detection means for detecting the reflected beam light reflected by the recording surface of the photoreceptor, and a detection signal obtained from the detection means compared with the form of the inspection signal to detect defects on the recording surface of the photoreceptor. What is claimed is: 1. A surface defect detection device for a photoreceptor, comprising: a comparator for determining the presence or absence of a photoreceptor.