JP2001194965A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device by which the problem of adhesion of carrier at the time of an emergency shut down is solved, and which can promptly detect a carrier adhesion. SOLUTION: When terminating the operation of the electrophotographic device, the termination of the electrophotographic device is normal or an emergency shut down is stored in a storage means. When the electrophotographic device is started and when the last stop was an emergency shut down, the device is started with a prescribed startup method. The reflectivity on the surface of a photoreceptor drum is measured by using a patch densitometer which detects toner densities at the time other than the time for detecting toner density, and when the reflectivity is a prescribed value or less, it is judged that a carrier adhesion has been generated. Thereby, the carrier adhesion can be detected in its early stages, and the problem arising from carrier adhesion can be suppressed to the minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electrophotographic apparatus. In particular, the present invention relates to an electrophotographic apparatus in which a carrier is prevented from adhering to the surface of a photosensitive drum when being started after an abnormal stop. In addition, the present invention relates to an electrophotographic apparatus capable of detecting carrier adhesion to the surface of a photosensitive drum in a normal state and quickly stopping the operation.

[0002]

2. Description of the Related Art An electrophotographic apparatus is provided around a photosensitive drum.
A charging device for charging the photosensitive drum with a predetermined potential; an exposure device for exposing an image on the surface of the photosensitive drum; a developing device for developing a latent image with toner; a transfer device for transferring toner to transfer paper; and separating the transfer paper from the photosensitive drum A separation device, a fixing device for fixing toner, and the like are provided.

[0003] In the electrophotographic apparatus for digital electrophotography, a reversal development system is often employed.
The charging potential of the photosensitive drum is usually -500 to -900 volts, and the charging potential of the developing sleeve (hereinafter referred to as "developing bias").
And ) Is set to -300 to -800 volts, and the toner from the developing unit adheres to the portion shown in FIG.

In an electrophotographic apparatus, usually, a charger is installed at a predetermined angle upstream of a developing unit in a rotating direction of a photosensitive drum, and a portion where the charging is performed by the charger and the potential of the photosensitive drum is not reduced. When passing through the front surface of the developing unit where the application of the developing bias is stopped, the carrier is attracted to the photosensitive drum in the portion shown in FIG. 3B. Therefore, in an electrophotographic apparatus using the reversal developing method, particularly, when the electrophotographic apparatus is terminated, the charging device and other high-voltage units are sequentially stopped in a predetermined sequence, and the carrier is attracted to the photosensitive drum. There is no.

[0005] Further, the electrophotographic apparatus usually has a toner density detecting means for inspecting whether or not the toner density satisfies a predetermined condition for a predetermined photosensitive operation. In the toner density inspection by the toner density detecting means (patch densitometer), first, a predetermined portion (patch) of the photosensitive drum is irradiated with light (laser light) of a predetermined intensity to be exposed, and the portion is exposed to the toner in a normal state. Irradiates the toner portion with the inspection light by an irradiation mechanism, and detects the intensity of the inspection light reflected and returned on the surface of the photosensitive drum to detect the toner adhesion state. And had

[0006]

However, when an electrophotographic apparatus is stopped immediately due to an internal jam or when the power supply is suddenly disconnected, the voltage applied to each unit such as the charger and the developing sleeve is reduced. It was shut off when the operation of the electrophotographic device was stopped. Then, in the state where the electrophotographic apparatus is urgently stopped, since the stop of the application of each part is not completed according to the predetermined sequence, for example, the portion between the charger and the developing unit is charged potential by the charger. Remains. If the start is performed immediately after the emergency stop, the portion charged by the charger passes through the front surface of the developing unit where no bias is applied due to the rotation of the photosensitive drum, and the carrier is discharged from the developing unit. In some cases, the carrier was attached to the surface of the photosensitive drum due to the suction.

Further, when the potential difference between the charged potential of the photosensitive drum and the developing bias cannot maintain a predetermined condition due to a failure of the high voltage power supply, a connection error of the connector, a contact failure, etc., the carrier adheres to the entire surface of the photosensitive drum. May be done. The adhesion of such a carrier to the photosensitive drum is as follows.
This has been a serious hindrance to the electrophotographic apparatus.

An object of the present invention is to solve the above problems. That is, even if the operation of the electrophotographic apparatus does not end normally due to an emergency stop or the like, the present invention provides an electrophotographic apparatus that can be normally started without causing carrier adhesion or the like at the next start-up. Another object of the present invention is to provide an electrophotographic apparatus capable of immediately and reliably detecting and responding to occurrence of carrier adhesion to a photosensitive drum.

[0009]

According to the present invention, in order to solve the above-mentioned problems, an electrophotographic apparatus is constituted as follows.

[0010] That is, when the operation of the electrophotographic apparatus is completed, there is provided storage means for storing at least until the next start-up whether the end of the operation is normal end or emergency stop. When it was confirmed that the previous operation was terminated by an emergency stop, the electrophotographic apparatus was started by a predetermined operation. The storage unit is a non-volatile storage unit that retains the stored contents even after the power is turned off.

As an operation at the time of startup after an emergency stop, for example, a developing bias is applied simultaneously with the rotation driving of the photosensitive drum. Thereby, even if the charged portion by the charger remains on the surface of the photosensitive drum and the charged portion passes through the front surface of the developing unit when the photosensitive drum rotates, the carrier is attracted to the surface of the photosensitive drum. Nothing.

In addition, not only when the operation is terminated due to an emergency stop, but also when an abnormality is detected in the drive of the photosensitive drum during the operation of the electrophotographic apparatus, for example, a delay or excessive rotation of the rotation speed or a speed fluctuation is detected. In such a case, it is determined that the bias control is not normally performed, and the predetermined control is performed.

Further, a toner density detecting means (a patch densitometer or the like) for detecting the toner density detects the reflection state (reflectance) of the photosensitive drum surface when the toner density detecting operation is not performed. Carrier adhesion on the surface of the photosensitive drum was detected. As described above, by measuring the reflection state at the portion where no toner is attached by the patch density sensor, it can be immediately detected that the carrier has adhered to the surface of the photosensitive drum, and the trouble can be minimized by stopping the operation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the electrophotographic apparatus of the present invention will be described.

FIG. 4 schematically shows a digital copying machine as an electrophotographic apparatus.

As shown in FIG. 4, the digital copying machine 2 includes a scanner section 20 for reading an original, a control section 22, an image forming section 24 for printing an image on paper (transfer paper), and a paper , A fixing device 28 for fixing the toner, a sorter unit 30 for discharging the sheet on which the image is formed, and the like.

The scanner section 20 has a glass plate on the upper surface. When an operation switch is turned on with a document placed on the glass plate, a reading lamp or the like moves to read the document. The original is read as a digital signal, and the read image signal is sent to the control unit 22. In the case of copying, an image signal is sent from the control unit 22 to the image forming unit 24, and printing is immediately performed.

As shown in FIG. 1, the image forming section 24 includes a corona charger 41, a photosensitive drum 42, an exposure section 44 having a laser, a developing section 46, a transfer charger 43, and a separation charger 45. And a cleaning unit 48 and the like, forms an image from the sent image signal, and prints it on a sheet from the sheet feeding unit 26. The paper supply unit 26 stores paper of various sizes and supplies a predetermined size to the image forming unit 24 according to an instruction from the control unit 22. In the cleaning unit 48, a patch densitometer 8 is provided as a toner density detecting means for detecting the density of the toner, as shown in FIG.

The corona charger 41 is, for example, a scoroton charger, and the photosensitive drum 4 is charged before the latent image forming process.
2 is uniformly charged to a predetermined voltage, for example, -600 V.

Further, in the image forming section 24, the photosensitive drum 42 is formed by coating a photosensitive layer on the surface of a cylindrical substrate made of, for example, aluminum having a diameter of 80 mm, and a driving motor for driving the photosensitive drum 42; Drum 42
Encoder for detecting the rotational phase of the motor (neither shown)
It has. The photosensitive layer has a thickness of 15 to 30 μm and a dielectric constant of 2.0 to 5.0, and the substrate is grounded. The photosensitive drum 42 rotates at a speed of, for example, 280 mm / sec, and the rotational phase of the photosensitive drum 42 is measured and controlled by an encoder. The photosensitive drum 42 is uniformly charged by the corona charger 41 while rotating, and is then exposed by the exposure unit 44 to form an electrostatic latent image on the surface.

In the exposure section 44, the laser beam emitted from the laser is reflected by a polygon mirror and is irradiated on the surface of the photosensitive drum 42 via an optical system such as an f-θ lens. The polygon mirror rotates at a constant rotation speed, and the main scanning of the laser beam is performed by the rotation, and the sub-scanning is performed by the rotation of the photosensitive drum 42. The formed electrostatic latent image is visualized by the toner in the developing unit 46.

The developing unit 46 includes the magnet roller 14 and
It has a developing sleeve 16 and the like, has a developer inside, and forms a magnetic brush. The developer comprises a toner of a polyester material having an average particle size of 8.5 μm and a ferrite coating carrier having an average particle size of 60 μm, and the toner concentration is controlled to 4 to 6%. Further, the toner to which a predetermined bias voltage (approximately −600 V) is applied to the developing sleeve 16 is transferred from the photosensitive drum 42 onto the transfer paper by the transfer charger 43, and the transfer paper on which the toner is transferred is separated and charged. The photosensitive drum 42 is separated from the photosensitive drum 42 by the device 45 and sent to the fixing device 28 to be fixed.

The transfer charger 43 is installed to face the photosensitive drum 42, and discharges electric charges from the back side of the transfer paper stacked on the photosensitive drum 42 electrostatically carrying the toner image, thereby transferring the toner image. Transfer toner to paper. Transfer charger 4
3 is preferably a scotron discharger, but may be a corotron charger, a charging roller or the like.

The separation charger 45 includes a scotron discharger, a corotron charger, a charging roller, and the like, and removes the charge of the transfer paper adsorbed on the photosensitive drum 42 to separate the transfer paper from the photosensitive drum 42.

The toner remaining on the surface of the photosensitive drum 42 without being transferred is collected by the cleaning unit 48. The cleaning unit 48 includes a blade that comes into contact with the photosensitive drum 42, and scrapes off toner, dust, and the like adhering to the surface of the photosensitive drum 42, and stores it in the toner box.

Further, the electric history of the photosensitive drum is erased by the pre-exposure lamp, and the next print cycle is started. The fixing device 28 applies pressure and heat to the transfer paper to which the toner image has adhered, and fixes and fuses the toner on the transfer paper.

The patch densitometer 8 includes an irradiation lamp (not shown) for irradiating a predetermined portion of the photosensitive drum 42 with light of a predetermined intensity, and a light radiated from the irradiation lamp to the photosensitive drum 42.
A light receiving unit for receiving the light reflected by the surface of the photosensitive drum 42 and detecting the intensity of the reflected light, exposing a part of the photosensitive drum 42 under predetermined conditions by the exposure unit 44, and detecting a portion where the toner adheres. The state of toner adhesion is detected from the reflectance of the surface of the photosensitive drum 42.

The sorter unit 30 is a discharge mechanism for discharging the printed transfer paper in a predetermined state. Further, a switch unit (not shown) is provided on the upper surface of the digital copying machine 2, and can be used for inputting enlargement / reduction of a print image, designation of print paper, designation of the number of prints, and the like.

The control unit 22 includes a storage unit (not shown) as storage means. The storage unit is non-volatile so that the contents of the storage are not erased even when the power of the digital copying machine 2 is cut off. When the operation of the digital copying machine 2 ends, whether the operation ends normally or due to an emergency stop is stored.

For example, when the main switch is turned off and the operation of the digital copying machine 2 is ended, the end is stored in the storage unit as a normal end, while the transfer paper is wound around the rollers, or in the middle of the conveyance path. When the power supply is clogged or the power supply is suddenly cut off, the control unit 22 issues an emergency stop signal to stop all operations, and the fact that the operation has been terminated by the emergency stop is stored in the storage unit. Therefore, at this time, the bias voltage (approximately −60) applied to the corona charger 41 and the developing sleeve 16 of the developing section 46.
0V) is suddenly shut off.

Further, when the digital copying machine 2 is started up, the control unit 22 confirms from the storage unit whether the immediately preceding operation termination of the digital copying machine 2 is a normal end or an emergency stop, and if the operation ends normally, When it is confirmed that the digital copying machine 2 has been operated, the operation is terminated by an emergency stop. Part 46
A predetermined bias voltage is applied to the developing sleeve 16 to start it.

Thus, when the digital copying machine 2 is started, even when the surface of the photosensitive drum 42 is charged by the corona charger 41 due to an emergency stop, the application of the developing bias is started together with the rotation of the photosensitive drum 42. Therefore, the carrier is not attracted to the surface of the photosensitive drum 42 from the developing unit 46.

When the rotation of the photosensitive drum 42 is modulated during the operation of the digital copying machine 2, it is assumed that the charging of the corona charger 41 and the application of the developing bias of the developing unit 46 are not synchronized. , To suspend operation until it temporarily stops or normal rotation, and then resume operation,
As in the above example, the developing bias is applied simultaneously with the rotation of the photosensitive drum 42.

As a result, rotation of the photosensitive drum 42 is modulated, so that the operation of the digital copying machine 2 is stopped, and thereafter, when the operation is restarted, carrier adhesion to the photosensitive drum 42 can be prevented.

Next, another example of the digital copying machine 2 will be described.

As described above, the patch densitometer 8 includes an irradiation lamp for irradiating a predetermined portion of the photosensitive drum 42 with light of a predetermined intensity, and a light radiated from the irradiation lamp for the photosensitive drum 4.
2 is provided with a light receiving portion (neither is shown) or the like for receiving the light reflected back from the surface of No. 2 and detecting the intensity of the reflected light. The state of adhesion of the toner is detected from the reflectance of the portion, and when the toner density is not detected, the photosensitive drum 42 is irradiated with light from an irradiation lamp, and the reflectance of the light is measured. And the obtained photosensitive drum 4
If the reflectivity of No. 2 is determined to be equal to or less than a predetermined value by a comparing unit (not shown) as a determining means, it is determined that the carrier is attached to the surface of the photosensitive drum 42.

As described above, the presence of the carrier adhered to the surface of the photosensitive drum 42 for some reason can be confirmed by the patch densitometer 8, and the trouble due to the carrier adhesion does not increase by stopping the operation of the digital copying machine 2. We can deal with it.

When carrier adhesion is detected, the carrier concentration is again inspected by the patch densitometer 8, and if carrier adhesion is continuously confirmed, it is determined that carrier adhesion has occurred. Is also good. Thereby, it is possible to prevent an error in the inspection.

Further, after the operation is stopped due to the carrier adhesion, the operation may be temporarily activated and the inspection for the carrier adhesion may be performed again. Then, if carrier adhesion is detected by such a second inspection, it can be determined that carrier adhesion has occurred. When the carrier is not detected in the re-test, the test may be performed again.

The carrier inspection by the patch densitometer 8 may be performed continuously during the operation of the digital copying machine 2, or may be set to be performed at a predetermined time, for example, at the time of start-up or at predetermined time intervals. . Further, another carrier inspection device may be provided separately from the patch densitometer so that the carrier inspection is performed on the position of the photosensitive drum 42 where the toner does not adhere.

[0041]

According to the electrophotographic apparatus of the present invention, when the operation of the electrophotographic apparatus is completed, whether the termination is normal or due to an emergency stop is stored in the storage means. In this case, the photosensitive drum is started by a predetermined starting method such as applying a developing bias simultaneously with the rotation driving of the photosensitive drum.

Thus, it is possible to prevent the carrier from adhering to the photosensitive drum at the time of starting after the emergency stop.

Further, the reflectance of the photosensitive drum surface is detected by a toner density detecting means such as a patch density sensor for detecting the toner density on the surface of the photosensitive drum except when the toner density is detected.

Thus, if the reflectance is equal to or less than the predetermined value, it can be determined that carrier adhesion has occurred, and predetermined processing such as stopping operation can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming unit according to the present invention.

FIG. 2 is a diagram showing a cleaning unit according to the present invention.

FIG. 3 is a diagram showing a charged state.

FIG. 4 is a block diagram showing an outline of a digital copying machine according to the present invention.

[Explanation of symbols]

 2 Digital Copier 8 Patch Densitometer 14 Magnet Roller 16 Developing Sleeve 20 Scanner 22 Control 24 Image Forming 26 Feeder 28 Fixer 30 Sorter 41 Corona Charger 42 Photosensitive Drum 43 Transfer Charger 44 Exposure 46 Development Part 48 cleaning unit 45 separation charger

Claims (8)

[Claims] 1. A latent image formed on a surface of a photosensitive drum is visualized by a toner in a developing unit, the visualized toner image is transferred from the photosensitive drum to a transfer paper, and the toner on the transfer paper is removed. A reversal developing type electrophotographic apparatus for fixing a fixing unit to form a recorded image, comprising: a storage unit for storing whether or not the end operation is normally completed when the operation of the electrophotographic apparatus ends; When the photographic device is activated, based on the information in the storage unit,
An electrophotographic apparatus characterized by performing start-up control. 2. The electrophotographic apparatus according to claim 1, wherein, when the termination operation is not normally terminated, the activation control controls a developing bias. 3. The electrophotographic apparatus according to claim 2, wherein the activation control activates the operation of applying the developing bias simultaneously with driving of the photosensitive drum. 4. An electrophotographic apparatus characterized in that when the rotation drive control of the photosensitive drum is determined to be abnormal and the operation thereof is stopped, the photosensitive drum is started by performing the start control according to claim 2 or 3. 5. A latent image formed on the surface of the photosensitive drum is visualized by a toner in a developing unit, the visualized toner image is transferred from the photosensitive drum to transfer paper, and the toner on the transfer paper is removed. In a reversal development type electrophotographic apparatus that forms a recording image by fixing in a fixing device, a predetermined photosensitive operation is performed on the photosensitive drum, and a toner is applied based on a reflection state of a toner portion attached by the photosensitive operation on the surface of the photosensitive drum. A reflection state of the photosensitive drum surface is obtained when the toner concentration is not detected by the toner concentration detection means, and when the reflection state is equal to or less than a predetermined range, An electrophotographic apparatus comprising: a determination unit configured to determine that carrier adhesion has occurred on the photosensitive drum. 6. The electrophotographic apparatus according to claim 5, wherein the operation of the electrophotographic apparatus is stopped when the judgment means judges that the carrier adheres to the photosensitive drum. 7. When the judging means judges that carrier adhesion has occurred on the photosensitive drum, the reflection state of the photosensitive drum surface is detected again. 7. The electrophotographic apparatus according to claim 5, wherein it is determined that carrier adhesion has occurred on the drum. 8. The electrophotographic apparatus according to claim 6, wherein the operation is stopped after the carrier is attached to the photosensitive drum, and then the photosensitive drum is started and the inspection of the carrier is performed again.