JP2003021992A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of realizing non-downtime and non-jamming by predicting the life of a pre-transfer exposure device in an early stage. SOLUTION: This electrophotographic image forming device is equipped with a primary electrifier (electrifying means) 2, an image exposure device (image, exposure means) 15, a surface potentiometer (surface potential measuring means) 6, a pre-transfer electrifier (pre-transfer electrifying means) 9, a pre- transfer exposure device (pre-transfer exposure means) 10, a transfer electrifier (transfer electrifying means) 12, a separation electrifier (separation electrifying means) 13, a cleaning device (cleaner means) 14 and a pre-exposure device (pre-exposure means) 2. The device is provided with a CPU (potential control means) 16 for controlling the surface potential of a photoreceptor drum (image carrier) 1 to a fixed value, and provided with a sequence to perform exposure by the device 10 after performing electrification so that the surface potential of the drum 1 becomes a desired value and measure the surface potential of an area where pre-transfer exposure is performed and a means to hold the value of the measured potential, then the output value of the device 10 is measured and controlled based on the held data.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer. 2. Description of the Related Art A recent image forming apparatus such as a copying machine and a printer using an electrophotographic system is connected to a network environment and is used not only as a device for outputting a document from a computer but also as a reader of a copying machine. There are various uses such as reading an image from a computer and inputting it to a computer. Features of the image forming apparatus used in such a network environment include multi-function, high image quality, high speed, high durability,
Although high reliability and the like can be mentioned, it is important to minimize downtime especially in reliability. On the other hand, on the other hand, it is required to support various types of paper (recycled paper or special paper) as a transfer material because of its high functionality and environmental friendliness. Therefore, image quality is required. [0004] For this reason, an amorphous silicon drum (hereinafter referred to as an a-Si drum) having characteristics of high durability and long life has been used as a photoreceptor which is the heart of an electrophotographic process. FIG. 10 shows an a-Si photosensitive drum 101.
FIG. 3 is a sectional view of a main part of a high-speed digital image forming apparatus using a drum. The illustrated image forming apparatus includes a pre-exposure device 10 including a photosensitive drum 101 as an image carrier and an LED.
2. a primary charger 103 having a grid, an image exposure device 104 using a laser as a light emitting element, a surface voltmeter 105 for detecting a drum surface potential, and a latent image having a positively charged toner on the photosensitive drum 101 with a reduced potential. The developing device 106 attached to the portion, the pre-transfer charger 107 for applying charge to the toner image formed on the photosensitive drum 101 to assist the transfer of the toner to the transfer material, and lowering the potential of the photosensitive drum 101 Pre-transfer exposure device 108 for assisting separation of transfer material from photosensitive drum 101
9, a separation charger 110, and a cleaning device 111. Next, the operation of the image forming apparatus will be described. When the start button is pressed after the image mode is selected, the photosensitive drum 101 starts rotating in the direction of the arrow shown by the motor (not shown), and
04 is driven so as to have a set light amount, and irradiates the photosensitive drum 101. The primary charger 103 starts operating at the same time as the start or after a certain time. That is, the set grid potential is supplied to the wire grid by the grid potential high voltage power supply, and the discharge electrode high voltage power supply is driven so that a predetermined current flows through the discharge line. An image input device (not shown) captures image information, and the image exposure device 104 turns on / off the laser beam to the photosensitive drum 101 so that light emission is turned off in portions where no image information is present and image data portions are turned on. Form a latent image. The electrostatic latent image formed on the photosensitive drum 101 is
The toner image is developed by the developing device 106 and visualized as a toner image. A charge is applied to the toner image by a transfer charger 109, and thereafter, a white background potential is reduced by a pre-transfer exposure device 108. On the other hand, recording paper is fed from a paper feed cassette (not shown), and the visualized toner image is transferred to the recording paper by the transfer charger 109. After the transfer, the recording paper is separated from the photosensitive drum 110 by the separation charger 110, sent to a fixing device (not shown), pressed and heated to fix the toner image, and then discharged out of the main body. During that time, the residual toner on the photosensitive drum 101 is cleaned by the cleaning device 111, and the residual charge is erased by the pre-exposure device 108. Conventionally, in such an image forming apparatus,
The service life of each module is determined by the number of output sheets and the operating time.The service engineer replaces parts with the specified number of operation hours, or at the time of periodic inspection, the service engineer ticks the output image to determine which parts need to be replaced. If the parts had been replaced. However, in a network environment, downtime must be reduced as much as possible, and it is necessary to predict the life of a component at an early stage and to prevent failure or performance degradation. They need to be replaced or modified. In particular, the frequent occurrence of jams on the transfer material greatly reduces productivity, and it is necessary to predict the cause of the jam before taking such a situation and deal with the situation at an early stage. As one type of jam, there is a jam in which a transfer material is not separated from a photosensitive member. As described above, on the one hand, high speed, high durability and multi-functionality are required, and the speed of image formation and paper conveyance is increased, and on the other hand, a transfer paper having a low rigidity such as recycled paper is used. Is becoming severer. Therefore, there is a pre-transfer exposure as a means for assisting the separation. However, if the exposure amount is reduced, the effect of the assisting separation is reduced and the probability of the separation failure increases. One of the causes of the separation failure is a decrease in the amount of light of the pre-transfer exposure apparatus. Due to the decrease in the amount of exposure light before transfer, the amount of reduction in the potential (high potential portion) of the white background portion of the photoconductor is insufficient, and the charge applied to the transfer material by the transfer charger cannot be sufficiently removed by the separation charger. It becomes difficult to separate from the photoconductor. As a light source used in the pre-transfer exposure apparatus, a small and inexpensive LED light emitting element is generally used.
As shown in FIG. 11, the ED has a characteristic that the light emission intensity decreases depending on the operation time and the temperature used. Therefore, if the light amount is predicted to be low and the light amount is set high in advance, the amount of decrease in the potential of the white background becomes large, and the toner scatters outside the latent image area, thereby deteriorating the image quality. For this reason, in general, the pre-transfer exposure apparatus must be driven to obtain a sufficient amount of light to lower the white background potential to a predetermined potential, and the amount of light decreases for various reasons, and the frequency of occurrence of separation jam increases. It was difficult to predict the life of the LED until a certain point. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an image forming apparatus capable of predicting the life of a pre-transfer exposure device at an early stage and realizing down timeless and jamless. Is to do. In order to achieve the above object, the present invention provides a charging means for charging an image carrier, and an electrostatic latent image by exposing the image carrier charged by the charging means. Image exposing means for forming an image, surface potential measuring means for measuring the surface potential of the image carrier, and applying a charge on the image carrier before transferring the toner image formed on the image carrier to a recording material Pre-transfer charging means, pre-transfer exposure means for exposing the surface of the image carrier, transfer charging means for transferring a toner image to a recording material, separation charging means for separating the recording material from the image carrier, and residual toner In an electrophotographic image forming apparatus including a cleaner unit for removing an image carrier and a pre-exposure unit for removing a residual charge on the image carrier, a potential control unit for controlling a surface potential of the image carrier to a constant value is provided. , The surface voltage of the image carrier After the position is charged to a desired value, exposure is performed by the pre-transfer exposure means, a sequence for measuring the surface potential of the pre-transfer exposed area, and means for holding the measured potential value are provided. There is provided a means for measuring and controlling the output value of the pre-transfer exposure means based on the held data, and transferring the control value to a service base via a general public communication line or a network. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a main part of an image forming apparatus according to the present invention.
It has a copying function for forming a binary image by FF and a printer function. In FIG. 1, reference numeral 1 denotes a photosensitive drum having a diameter of 108 mm using a-Si for the photosensitive layer, which is 400 mm / sec to 600 m by a drum motor (not shown).
It is driven to rotate at a peripheral speed of m / sec. Reference numeral 2 denotes 64 LED light emitting elements having a wavelength of about 660 nm for removing residual charges.
The pre-exposure devices 3 arranged in a row are primary chargers. The primary charger 3 uses a tungsten wire having a diameter of approximately 60 μm and an oxidized surface as a discharge electrode 3-1, a metal shield and a metal shield. And a metal wire grid 3-2 electrically connected to the metal wire grid 3-2. Reference numeral 4 denotes a high-voltage power supply for a discharge electrode for applying a positive DC high voltage to the discharge electrode 3-1;
-2 and a grid high-voltage power supply for supplying a high voltage to the shield; 6 a surface voltmeter for measuring the surface potential of the photosensitive drum 1; 7 a digital signal converting an output signal from the surface voltmeter 6; , A drum surface potential measuring circuit for outputting the signal to the CPU 16, and a developing device 8. The developing device 8 is provided with a six-pole magnet roller inside, and carries a one-component magnetic positive toner having an average particle diameter of 6.5 μm to 10 μm on a developing sleeve having a diameter of approximately φ32 mm whose surface is metal-plated. This is to develop a latent image by causing toner to fly on the image information portion of No. 1. Reference numeral 9 denotes a pre-transfer charger for adding a positive charge to the toner on the photosensitive drum 1 so that the toner easily adheres to the transfer material, and has a frequency of 700 to 1500 Hz and an amplitude of about 8 k.
It is driven by a high voltage power supply of V. Reference numeral 10 denotes a pre-transfer exposure apparatus having an LED having the same emission wavelength (660 nm) as the pre-exposure apparatus 2, and 11 denotes a pre-transfer exposure drive power supply. Here, the pre-transfer exposure driving power source 11 is
As shown in FIG. 5, the dark portion potential (Vd
p) is approximately 300 V or less, and the difference potential (ΔV) between the dark portion potential Vdp and the toner layer potential (Vt) is approximately 100 to 200 at the same position.
A DC voltage is supplied from a power supply so that a light amount of V, more preferably 130 to 170 V is emitted. Reference numeral 12 denotes a transfer charger for transferring toner to recording paper, to which a positive voltage is applied from a power supply (not shown). Reference numeral 13 denotes a separation charger for separating the recording paper from the photosensitive drum 1, which has a rectangular waveform having a frequency of 700 to 1500 Hz and an amplitude of 9 to 9 Hz.
A voltage of 12 kVpp is applied to the charging line. 14 is a cleaning device for removing residual toner, 15 is an image exposure device using a laser as a light emitting element, 16 is a CPU for controlling the whole device, and a CPU for calculating and processing a grid voltage value described later, and 17 is a magnetic memory. A storage device for storing data of the measured surface potential of the photosensitive drum 1 which is constituted by a device or a semiconductor memory; 18 is used for setting the number of copies, switching the mode of an input image, selecting a paper feed stage, and starting copying; An operation panel for displaying ON / OFF and a warning described later. The main operation of the present invention will be described below. First, a potential control sequence will be described with reference to FIG. The potential control sequence is a sequence for setting a desired dark potential (Vd) for forming a latent image. Immediately after the power of the main body is turned on, at the start of the first printing operation after the end of a predetermined number of sheets, or after the elapse of a predetermined time after printing. And the drum surface potential (VD) at the developing position is always controlled to a constant value (for example, 400 V ± 10 V). That is, while rotating the photosensitive drum 1,
The pre-exposure device 2 emits a predetermined amount of light to the photosensitive drum 1 using an LED.
, And the total current Ip (for example, 1000 μA) supplied to the discharge electrode 3-1 of the primary charger 3 is kept constant.
The voltage supplied to the wire grid 3-2 is Vg1 = 500
V, Vg2 = 600V, Vg3 = 700V, and three drum potentials Vd1, Vd2, Vd3 (measured values of each surface voltmeter) are obtained, and a Vg-Vd straight line (approximate to a straight line) is estimated from those points. (FIG. 3). Then, the obtained Vg-V
First, Vg0 for obtaining the target drum potential Vdt corresponding to VD is determined from the d straight line. Here, Vdt is VVVD at the development position.
Is determined in consideration of the dark decay of the photosensitive drum 1 such that Further, a slope coefficient α of the straight line is obtained. Here again V
The drum potential at g0 is measured, and if it is within Vdt ± 10V, the control is terminated, and if not, the correction control operation is repeated until it converges to Vdt ± 10V using the correction formula shown below. Vg (i) = Vg (i−1) + α (Vdt−Vd (i−
1)) i = 1, 2, 3,... Vg (i): grid potential Vd (i) after i-times correction: drum potential Vg (0) = Vg0 after i-times correction Data is sampled by one rotation of the photosensitive drum With one Vg setting, for example, six points are measured in one round, and the average is obtained. A sequence for collecting data for measuring and controlling the amount of light of the pre-transfer exposure LED (hereinafter, referred to as a pre-transfer exposure LED sequence) is, for example, immediately after the power is turned on, the fixing temperature of a fixing device (not shown) is set to a predetermined temperature. Perform in the following cases. In this sequence, as in normal image formation, first, except for image exposure, from a predetermined pre-exposure to pre-transfer charging to form a dark portion potential, the photosensitive drum is irradiated with a predetermined amount of pre-transfer exposure, and thereafter, Only the rotation of the photosensitive drum is performed, and the potential of the portion exposed before transfer is monitored by a surface voltmeter (potential sensor) in the second rotation, and the operation is repeated several times (about three times) by changing the exposure amount before transfer. Then, the optimum exposure before transfer is determined from those values. The details will be described below. FIG. 4 is a timing chart of this sequence, and FIG. 5 is a diagram schematically showing the drum potential after passing through each image forming means. After the rotation of the photosensitive drum is started, when the rotation is stabilized, first, the pre-exposure device, the primary charger,
The pre-transfer charger and the pre-transfer exposure device are driven. At this time, the set grid potential Vg of the primary charger and the primary current Ip
Is a value (VD = 400 V at the developing position) obtained in the above-described image forming potential control sequence. In this manner, a potential state corresponding to the dark portion (white background) potential in the normal image forming mode is formed immediately before the pre-transfer exposure, and the pre-transfer exposure means is illuminated with this potential to irradiate the pre-transfer exposure. To VLED1.
The portion subjected to the pre-transfer exposure rotates with the rotation of the photosensitive drum, and in the second rotation, the pre-exposure, the grid of the primary charger and the output of the primary current do not de-electrify the irradiated area of the pre-transfer exposure again. In this case, it is turned off just before the second rotation. At the second rotation of the photosensitive drum, the surface potential of the area where the potential was reduced by the pre-transfer exposure was measured by the surface voltmeter 6,
The value (VP1) is stored in the recording device 17. Similarly, the voltages applied to the LEDs of the pre-transfer exposure means were determined as VLED2 and VLED3, respectively.
The surface potentials Vp2 and VP3 of the rotation are measured and stored in the storage device 1
7 is stored. FIG. 6 shows an appropriate light amount (light amount at which the difference between the dark portion potential VD and the toner layer potential VT at the transfer portion becomes 100 to 200 V) as the exposure amount before transfer and the voltage VLED applied to the LED at that time. Is determined experimentally, and the optimal VLED VLED0 is 13 to 14V. FIG. 7 shows the relationship between the VLED and the second potential in this sequence.
When 13 to 14 V is applied as D, the second potential is 2
Since it is 40 to 300 V, VLED0 may be set so that the second rotation potential VP becomes 240 to 300 V in this LED sequence. This relationship is input to the storage device 17, and VLED is set to 10V, 12.5V, 15V and 3V in the pre-transfer exposure LED sequence.
Potentials VP1 and V at three points obtained by changing the degrees
VP is 240 from P2 and VP3 in the same way as potential control.
VLED0 is calculated to be V to 300V and output. FIG. 8 is a diagram showing the relationship between the amount of exposure light before transfer and the drum surface potential (second rotation potential) after exposure before transfer. As can be seen from FIG. 8, when the light quantity of the LED decreases due to the influence of the accumulated light emission time (temporal change), VLED0 increases in an attempt to compensate for the decrease. That is, VLED0 that optimizes the second rotation potential VP
Of the LED light amount, the optimum LED applied voltage VLED in the LED sequence for the light amount (Pth) at the time of 30% down from the initial light amount.
If 0 is obtained in advance, VL can be calculated from the transition of the value of VLED0.
It is possible to predict when the EDth will occur, and to cope before the life of the LED. The value of VLED0 is expected to vary due to environmental conditions, poor charging, etc.
The change in the value of 0 varies as shown by the solid line in FIG. Therefore, for example, the average value of N data (VLED0
(I)) is obtained, and the life of the LED is estimated based on the obtained value. N
Is, for example, several tens to several hundreds, and the capacity of the storage device 17 is a capacity that can hold at least N data. The value of VLED0 (i) is compared with a preset warning limit value Vs. Here, Vs is an LED in advance.
The light amount Pth determined to be the life of the lens (separation jam frequently occurs)
Is smaller than the LED drive voltage VLEDth corresponding to. When VLED (i) becomes equal to or higher than Vs (VLED (m) in the figure), it is determined that the life of the LED is near and a warning is displayed on the operation panel 18. Further, N VLEDs 0 are stored in a storage device 17 in the image forming apparatus, and thereafter, an averaging process and a comparison process with Vs are performed by the CPU 16, and a warning is displayed on the operation panel 18 according to the result. It is displayed as shown in FIG.
As shown in the figure, a host computer 22 at a service base via an external interface circuit 21 without a storage device
, The value of the VLED may be sequentially transferred, and the host computer at the base may predict the life of the LED. In this case, in the host computer, for example, the operating time of the LED as shown in FIG. 9, or the relationship between the number of prints (copies) and the decrease in the amount of light, and the relationship between the VLEDs at that time are stored in advance as data. The life time may be predicted using a diagnostic program, and the result of the calculation may be reported to a service person, or a life time or life warning may be displayed on the operation panel 18 of the main body. In this embodiment, VLEDs are obtained by averaging N pieces. However, the smoothing method is not limited to this. For example, a maximum value or a minimum value among a certain number is set as a representative value. Is also good. Exposure LE before transfer
The D check sequence may be performed for each regular number of sheets, not when the power is turned on. The image forming apparatus having the pre-transfer exposure LED sequence as described above has been used for a long time.
Defects such as separation failure did not occur, and there was no image scattering due to excessive light amount, and stable transfer material transportability and image quality could be maintained. The pre-transfer exposure LED sequence is a power supply O
This may be performed not only after N, but also at the time of post-rotation after a JOB that exceeds a predetermined time, such as at a regular number of sheets or an integrated LED emission time, at the time of pre-rotation of the next JOB, or at the time of LED replacement. The light source for the pre-transfer exposure does not need to be an LED, and a general light source can be used. Further, the light amount control can be applied not only by changing the DC voltage but also by time division (variable pulse width) at a constant voltage. As is apparent from the above description, according to the present invention, the charging means for charging the image carrier, and the image carrier charged by the charging means are exposed to the electrostatic latent image. Image exposing means for forming an image, surface potential measuring means for measuring the surface potential of the image carrier, and applying a charge on the image carrier before transferring the toner image formed on the image carrier to a recording material Pre-transfer charging means, pre-transfer exposure means for exposing the surface of the image carrier, transfer charging means for transferring a toner image to a recording material, and separation charging means for separating the recording material from the image carrier,
In an electrophotographic image forming apparatus having a cleaner for removing residual toner and a pre-exposure unit for removing residual charges on the image carrier, a potential controller for controlling a surface potential of the image carrier to a constant value. Is provided so that the surface potential of the image carrier is charged to a desired value, and then the exposure is performed by the pre-transfer exposure means, and a sequence for measuring the surface potential of the pre-transfer exposed area is provided. A means for holding the value is provided, the output value of the pre-transfer exposure means is measured and controlled based on the held data, and a means for transferring the control value to a service base via a general public communication line or a network is provided. There is a sign that it is possible to predict the life of the pre-exposure device at an early stage and realize downtimeless and jamless.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating a change in surface potential of a photosensitive drum due to pre-transfer exposure. FIG. 3 is a diagram for explaining a potential control sequence. FIG. 4 is a timing chart for explaining the operation of the image forming apparatus according to the present invention. FIG. 5 is a diagram illustrating a change in drum surface potential during operation of the image forming apparatus according to the present invention. FIG. 6 is a diagram illustrating a relationship between an LED voltage and a transfer unit potential. FIG. 7 is a diagram illustrating a relationship between an LED sequence and a second rotation potential. FIG. 8 is a diagram showing a relationship between an operation time, a pre-transfer exposure amount, and a control voltage of a pre-transfer exposure unit. FIG. 9 is a diagram showing a relationship between a control voltage measurement count of a pre-transfer exposure unit and a warning value. FIG. 10 is a cross-sectional view of a main part of a conventional image forming apparatus. FIG. 11 is a diagram illustrating a relationship between a pre-transfer exposure operation time and a light amount. [Description of Signs] 1 photosensitive drum (image carrier) 2 pre-exposure device (pre-exposure means) 3 primary charger (charging means) 6 surface voltmeter (surface potential measuring means) 9 pre-transfer charger (pre-transfer charging means) 10) Pre-transfer exposure device (pre-transfer exposure device) 12 Transfer charger (transfer charging device) 13 Separator charger (separation charging device) 14 Cleaning device (cleaner device) 15 Image exposure device (image exposure device) 16 CPU (potential) Control means) 17 storage device

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Claims (1)

Claims: 1. A charging device for charging an image carrier, an image exposure device for exposing the image carrier charged by the charging device to form an electrostatic latent image, and an image carrier. Surface potential measuring means for measuring the surface potential of the image carrier, pre-transfer charging means for applying a charge on the image carrier before transferring the toner image formed on the image carrier to a recording material, and a surface of the image carrier surface Pre-transfer exposure means for exposing the toner, transfer charging means for transferring the toner image to the recording material, separation charging means for separating the recording material from the image carrier, cleaner means for removing residual toner, In an electrophotographic image forming apparatus including a pre-exposure unit for removing residual charges, a potential control unit for controlling a surface potential of the image carrier to a constant value is provided, and the surface potential of the image carrier is set to a desired value. After being charged so that A sequence for performing exposure by the pre-exposure means and measuring the surface potential of the pre-transfer exposed area, and a means for holding the value of the measured potential, and measuring the output value of the pre-transfer exposure means based on the held data An image forming apparatus comprising means for controlling and transferring the control value to a service base via a general public communication line or a network;