JP2004133188A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus dispensing with the installation of a special circuit for detecting the disconnection of a discharging means. <P>SOLUTION: A point of time going backward as long as a time until a position corresponding to a charger 2 on the image carrier 1 reaches a transfer position after the point when the leading end of a paper reaches the transfer position is regarded as a reference point A, and the operation of the charger 2 is stopped for a prescribed time after the reference point A, and a printing processing is performed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic method, and more particularly, to an image forming apparatus having a function of determining whether a static eliminator is operating normally. provide. The image forming apparatus of the present invention includes a copying machine, a printer (eg, an LED printer, a laser beam printer, a printer), a facsimile, and a color device thereof.
[0002]
[Prior art]
2. Description of the Related Art An image forming apparatus using a conventional electrophotographic method includes an electrophotographic photosensitive member serving as an image carrier and process means (charging, exposure, development, transfer , Static elimination, fixing, etc.), and the printing process is performed by repeating the transfer from the electrophotographic photosensitive member to the paper using these process means.
[0003]
[Patent Document 1]
Japanese Patent No. 3261027
In such a series of process means, if one of them has an abnormality such as a failure or a defect, of course, a sufficient print quality cannot be obtained. Methods are known. For example, there is a conventional method of detecting an abnormality of the static elimination unit by detecting a current value flowing into the static elimination unit and determining a disconnection when the current value is small.
[0005]
[Problems to be solved by the invention]
However, when a current value flowing into the static elimination means is detected as in the related art, a dedicated circuit for detecting the current value is required, and there is a problem that the number of parts increases and the cost increases.
[0006]
[Means for Solving the Problems]
The present invention has been made in view of the above problems, and has an image carrier, a charging unit for uniformly charging the surface of the image carrier, a developing unit for developing a toner image on the image carrier, and an image carrier. Transfer means for transferring the toner image developed on the paper to the paper, discharging means for removing the charge of the image carrier, transport means for transporting the paper to the transfer position, and transport of the paper transported by the transport means A control unit for controlling the operations of the charging unit, the developing unit, the transferring unit, and the discharging unit according to the position, and performing a printing process. Image formation in which a time corresponding to the time until the position corresponding to the charging means on the body reaches the transfer position is set as a base point, and after the base point, the operation of the charging means is stopped for a predetermined time to perform a printing process. Device
[0007]
With such a configuration, by performing the above-described printing process as test printing, it is possible to check the operation of the static elimination unit by visually observing the test-printed paper.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an embodiment of an image forming apparatus to which the present invention is applied. A charging device 2 is provided around an image carrier (photosensitive drum) 1 rotating clockwise in FIG. A developing device 4, a transfer roller 5, a cleaning device 6, and a static eliminator 7 are provided.
[0009]
A developing roller 41 is provided in the developing device 4, and the surface of the developing roller 41 is separated from the surface of the image carrier 1 by a predetermined distance. The developing device 4 is configured to be able to appropriately supply a predetermined amount of toner from a toner container (not shown).
[0010]
An optical transmission mechanism 3 for forming image dots on the surface of the image carrier 1 is provided above the image carrier 1, and the optical transmission mechanism 3 transmits laser light from a laser light source (not shown) via a polygon mirror and a reflection mirror. Thus, the optical system is configured to form image dots on the surface of the image carrier 1 between the charger 2 and the developing roller 41.
[0011]
Similarly to Patent Document 2, a base for storing a control circuit for controlling the entire apparatus described below is provided at a lower portion of the image forming apparatus, and a paper cassette is detachably mounted on the upper side of the image forming apparatus from the outside. The sheet before transfer is placed on the sheet cassette, and the sheet properly placed according to a command from the control circuit can be transported to the sheet leading edge detecting means 8 and the registration roller 9. A fixing unit is provided downstream of the transfer roller 5 in the transport direction, and the sheet P passing between the image carrier 1 and the transfer roller 5 is fixed by the fixing unit. Then, the sheet after fixing is discharged out of the apparatus by the conveying roller.
[0012]
[Patent Document 2]
JP-A-10-254231
Next, the specific configuration and process conditions will be described. In the image carrier 1, a photosensitive layer in which a charge generating material, an electron transporting material, and a hole transporting material are dispersed in a resin binder is applied to an aluminum tube of approximately φ30. This is a dispersion type single-layer photoreceptor drum, which is rotated clockwise in the drawing at a linear velocity of about 93 mm / s. The charger 2 is a scorotron charger, and is uniformly charged to 440V. The optical transmission mechanism 3 is a laser light unit, and irradiates a laser beam having a wavelength of 780 nm and a light amount of 1.0 μJ / cm ² to form an electrostatic latent image.
[0014]
Further, the developing roller 41 is an aluminum sleeve containing a magnet body, and a developing bias in which a rectangular wave having an amplitude of 1.65 kV, a frequency of 2.4 kHz and a duty ratio of 50% is superimposed on DC 330 V is applied onto the aluminum sleeve, and an electrostatic latent is applied. Develop into an image. At this time, the gap between the drum and the aluminum sleeve was 0.3 mm.
[0015]
The toner developed on the image carrier 1 is transferred to a sheet by a transfer roller 5 to which -800 V to 1200 VDC is applied. At this time, the residual toner remaining on the image carrier 1 without being transferred is cleaned by the rubber blade 61 of the cleaning device 6 which is pressed against the image carrier 1. The rubber blade 61 is made of urethane rubber having a hardness of 65 °, and the thickness, the free end and the amount of indentation are adjusted so that the pressing force against the image carrier 1 is adjusted to 17 g / cm.
[0016]
Next, the configuration of the control circuit will be described.
FIG. 2 shows a control circuit for determining the process timing. When the engine control device 11 receives a print signal from the controller 10, it starts driving and paper feeding via the driving / paper feeding means 12. At this time, at the same time, a predetermined voltage is applied to the charger 2 via the high voltage generator 14 and the neutralizer 7 is turned on. Next, when the sheet leading edge detecting unit 8 detects the leading edge of the sheet, a predetermined time is measured, and a predetermined voltage is applied to the image forming unit 15 via the high voltage generating unit 14 as needed. Note that the image forming unit 15 is a unit that operates when performing a printing process, such as the image carrier 1 and a process unit. In this embodiment, the leading edge of the sheet is detected by the leading edge detecting means 8, but the arrival of the leading edge of the sheet may be determined by software based on the elapsed time count from the sheet feeding operation.
[0017]
FIG. 3 shows respective timings in the image forming means 15 of the image forming apparatus of the present invention. During normal printing, image formation is performed at the timing indicated by the solid line. That is, the static eliminator 7 is operated at the start of driving (main motor ON), and after a predetermined time, the charger 2 is operated. Next, when the sheet leading edge detecting means 8 detects the leading edge of the sheet, the developing bias to the developing roller 41 and the transfer bias to the transfer roller 5 are sequentially operated at a predetermined timing. At this time, the operation of the developing bias and the transfer bias is started from the leading end of the sheet. Therefore, the drive timing of the developing bias is determined based on the linear velocity of the image carrier 1 and the positional relationship between the transfer position and the developing position. In the present embodiment, the time required for the image carrier 1 to reach the transfer position from the development position, that is, the time required for the region corresponding to the leading edge of the sheet, which is the region where the image carrier 1 is first developed by the developing device 1, to reach the transfer position. The operation is started at the time when the time is 260 msec.
[0018]
On the other hand, the present invention is characterized in that when test pattern printing for detecting abnormality of the static eliminator 7 is performed, image formation is performed at the timing indicated by the broken line in FIG. In other words, the base point is a time point which is the time from when the leading edge of the sheet reaches the transfer position to when the position corresponding to the charger 2 on the image carrier 1 reaches the transfer position. The printing operation is performed after the operation is stopped for a predetermined time. In this embodiment, the point A is 500 msec before the leading edge of the sheet reaches the transfer position. The point A is the base point. The charger 2 is stopped from an arbitrary time thereafter, and from the base point A to the point B where the image carrier 1 makes one rotation. During this time, the charger 2 is turned on again. In the present embodiment, the stop of the charger 2 is restored up to the point B. This is to avoid disturbance of the black band due to the transfer memory, that is, to avoid the history of the transfer roller 5 of the image carrier 1.
[0019]
At the time of printing this test pattern, if the static eliminator 7 is operating normally, the drum surface potential before charging is substantially 0 V. Therefore, while the charging by the charger 2 was stopped, the exposure was performed by the optical transmission mechanism 3. And the black belt is developed.
[0020]
On the other hand, if the static eliminator 7 is not operating normally, the surface potential of the image carrier 1 before the electrification cannot be eliminated. Therefore, while the charger 2 is stopped, it is not exposed by the optical transmission mechanism 3. This is the same state, and the black belt cannot be developed.
[0021]
Thus, when the test pattern is printed and a black band is present, it indicates that the static eliminator 7 is operating normally. Otherwise, it can be determined that the static eliminator 7 is not operating normally.
[0022]
【The invention's effect】
As is apparent from the above description, according to the present invention, the time from the time when the leading edge of the sheet reaches the transfer position to the time when the position corresponding to the charging unit on the image carrier reaches the transfer position goes back. By using this as the base point and stopping the operation of the charging unit for a predetermined time after the base point to perform the printing process, an image forming apparatus that does not require a special circuit to detect disconnection of the charge removing unit is provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing an image forming apparatus of the present invention.
FIG. 2 is a configuration block diagram showing the inside of a control circuit of the present invention.
FIG. 3 shows the operation timing of each unit of the image forming apparatus of the present invention.
[Explanation of symbols]
1: Image carrier 2: Charging device 3: Optical transmission mechanism 4: Developing device 5: Transfer roller 6: Cleaning device 7: Static eliminator 8: Sheet leading edge detecting means 9: Registration roller 10: Controller 11: Engine control device 12: Driving / paper feeding unit 14: high pressure generating unit 15: image forming unit

Claims (2)

Image carrier, charging means for uniformly charging the surface of the image carrier, developing means for developing a toner image on the image carrier, and transfer means for transferring the toner image developed on the image carrier to paper And a discharging unit for discharging the charge of the image carrier, a transporting unit for transporting the sheet to a transfer position, and a charging unit, a developing unit, a transfer unit, and a discharging unit depending on the transport position of the sheet transported by the transporting unit. Control means for controlling the operation and performing a printing process, in an image forming apparatus comprising:
The base point is defined as a point in time from when the leading edge of the sheet reaches the transfer position to when the position corresponding to the charging unit on the image carrier reaches the transfer position. An image forming apparatus in which an operation is stopped for a predetermined time to perform a printing process. The image forming apparatus according to claim 1, wherein a time from any time after the base point to a time when the image carrier makes one rotation from the base point is a predetermined time.

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