JP2004029092A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can shorten the time required for the whole work, can adjust the surface potential of a photoreceptor drum according to a change in the environment surrounding the photoreceptor drum, and improves the quality of an image that is formed. <P>SOLUTION: In order to adjust the potential for electrifying the photoreceptor drum 2, the potential used for electrifying the photoreceptor drum 2 is measured with a surface electrometer 3A. According to the result of the measurement of the potential, the electrifying potential is controlled by a process controller (electrification control means). Thus, the electrifying time and the potential controlling time are shortened, and time required for the overall task can also be shortened. Additionally, even in a case where a temperature, as of the surface of the photoreceptor drum 2, changes, the temperature change can be adequately coped with to be able to adjust the potential for electrifying the surface of the photoreceptor drum 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus for forming an image using a photosensitive drum and a method for forming the image.
[0002]
[Background Art]
As an image forming apparatus, for example, the surface of a photoconductor drum on which an image is formed is charged, the surface of the photoconductor drum is exposed after charging to form an electrostatic latent image, and the liquid toner is applied to the surface of the photoconductor drum after exposure. 2. Description of the Related Art An electrophotographic printing machine which supplies an image to develop an electrostatic latent image is known.
In this printing machine, the potential charged on the surface of the photoconductor drum is affected by the temperature of the surface of the photoconductor drum, the ambient temperature, and other environments, thereby changing the sensitivity characteristics of the photoconductor drum.
Conventionally, in order to compensate for a specific change in the sensitivity of the photosensitive drum, a test print is performed once, and the fluctuation of the surface potential is estimated from the result of the test print. Based on this analogy result, the potential charged on the photosensitive drum is adjusted.
[0003]
[Problems to be solved by the invention]
In the conventional example, the variation of the surface potential of the photosensitive drum is estimated from the print result of the test print, and the potential of the photosensitive drum when actually working is adjusted based on the analogy result. The time elapses between the time when the printing operation is performed and the time when the printing operation is actually performed after the potential of the drum surface is adjusted. Therefore, a large work time is required as a whole. In addition, the environment such as temperature may change with the lapse of time between the time of measurement and the time of printing, and it is not always possible to sufficiently adjust the potential charged on the photosensitive drum in response to the environmental change.
Therefore, there is a disadvantage that the developing process becomes unstable and print reproducibility is impaired.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of shortening the entire operation time and adjusting the surface potential of the photosensitive drum in response to environmental changes around the photosensitive drum to improve the quality of an image formed. An object of the present invention is to provide an apparatus and a method for forming the same.
[0005]
[Means for Solving the Problems]
Therefore, the present invention aims to achieve the above object by performing charging in a non-drawing area of the photosensitive drum and controlling the charging potential according to the result of the potential measured in this area.
Specifically, in the present invention according to the image forming apparatus, the surface of the photosensitive drum on which an image is formed on the surface is charged by a charging unit, and after the charging by the charging unit, the surface of the photosensitive drum is exposed by an exposure unit. An image forming apparatus for forming an electrostatic latent image on the surface of the photoconductive drum by developing the electrostatic latent image on the surface of the photoconductive drum by applying liquid toner to the surface of the photoconductive drum after exposure by the exposure unit. A surface voltmeter for measuring the surface potential of the photosensitive drum, and a charging control unit for controlling the potential of the charging unit, wherein the charging unit charges a non-drawing area on the surface of the photosensitive drum. The surface voltmeter measures a surface potential in a non-drawing area charged by the charging unit, and the charging control unit controls the potential of the charging unit according to a measurement result by the surface voltmeter. It is characterized by.
[0006]
Further, the present invention according to the image forming method is developed by using the above-described image forming apparatus as a method, and charges the surface of a photosensitive drum on which an image is formed, and exposes the surface of the photosensitive drum after charging. Forming an electrostatic latent image on the surface of the photoconductor drum after exposure, and supplying a liquid toner to the surface of the photoconductor drum to develop the electrostatic latent image on the surface of the photoconductor drum. In adjusting the potential to be applied, the non-drawing area on the surface of the photosensitive drum is charged, the potential of the charged non-drawing area is measured, and the photosensitive drum is charged according to the measurement result of the potential. It is characterized in that the potential is controlled.
[0007]
In the present invention, before the image forming operation is finally performed, the photosensitive drum is rotated, and the non-drawing area of the image on the photosensitive drum is charged by the charging unit, and the charged non-drawing area is charged. Is measured by a surface voltmeter, and the potential for charging the photosensitive drum is controlled by charging control means in accordance with the measurement result of the potential.
[0008]
After the adjustment of the potential for charging the photoconductor drum is completed, the photoconductor drum is continuously rotated to perform a normal image forming operation, and at least a drawing area on the drum surface is charged by the charging unit.
The surface of the drum charged by the charging unit is exposed by the exposing unit to form an electrostatic latent image, and then the developing unit supplies liquid toner to the drum surface to develop the electrostatic latent image on the drum surface. The developed image is finally transferred to a print sheet to form an image.
[0009]
In the present invention having this configuration, when adjusting the potential charged on the photosensitive drum, the potential charged on the photosensitive drum is measured, and the charging potential is controlled according to the measurement result of the potential. It is possible to reduce the time between the charging and the potential control in the non-drawing area, thereby reducing the working time, and even if the environment such as temperature changes between these points, it is sufficient for the environmental change. Accordingly, the potential charged on the surface of the photosensitive drum can be adjusted. Therefore, the development process is stabilized, and the print reproducibility is not impaired, so that the quality of the formed image is improved.
In addition, since the charging is performed in the non-drawing area, the test portion does not involve the image forming area such as printing, so that the image quality is not degraded from this point. In addition, since there is no need to charge the drawing area, there is no need to provide a special time for a test, and the working time can be reduced.
On the other hand, it is also conceivable to measure the potential of the drum surface by performing test charging on the drawing area. It is necessary to remove electricity by applying light or the like, and after the removal of electricity, an operation of charging again is involved, so that the operation time becomes long.
[0010]
Here, in the present invention according to the image forming apparatus, the image forming apparatus further includes an environment detecting unit that detects an environment around the photoconductor drum, and the charging control unit changes a potential of the charging unit according to a detection result by the environment detecting unit. A controlled configuration is preferred.
In the invention of this configuration, the charging control means is controlled in accordance with the environment around the photosensitive drum detected by the environment detecting means, and the charging potential on the drum surface can be efficiently changed in response to a change in environment. Can be adjusted.
[0011]
Further, it is preferable that the environment detecting means is a thermometer for measuring a temperature on or around the surface of the photosensitive drum and / or a hygrometer for measuring a humidity on or around the surface of the photosensitive drum.
In the present invention of this configuration, temperature and humidity are environmental factors that greatly affect the charging potential of the photosensitive drum, and thermometers and hygrometers that measure these environmental factors are relatively inexpensive and easily available. Since the apparatus is an apparatus, it is possible to provide an inexpensive image forming apparatus that sufficiently responds to changes in the environment around the photosensitive drum.
[0012]
In the present invention according to the image forming apparatus, it is preferable that the charging unit charges a non-drawing area between ends of a drawing area formed along a circumferential direction of the photosensitive drum.
In the present invention having this configuration, after performing the test charging in the non-drawing area and adjusting the potential, the image forming work can be continued in the drawing area formed side by side with the non-drawing area. Can be shortened.
In addition, since the non-drawing area can be secured along the axial direction of the surface of the photosensitive drum, the charged state can be checked along the axial direction, so that the potential control of the surface of the photosensitive drum can be reliably performed. Thus, it is possible to cope with a change in the environment around the photosensitive drum.
[0013]
Further, in the present invention according to the image forming apparatus, the charging unit is preferably a scorotron charger, and the charging control unit is preferably configured to control a bias voltage applied to a grid electrode of the scorotron charger.
In the present invention having this configuration, the potential applied to the surface of the photosensitive drum can be easily controlled by controlling the voltage applied to the grid electrode of the scorotron charger. Therefore, it is possible to accurately cope with environmental changes around the photosensitive drum.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, an image forming apparatus according to the present embodiment is a printing press 1, and the printing press 1 converts drawing data created based on print image data into colors such as yellow, magenta, cyan, and black. It performs printing by image-on-image in which images are sequentially superimposed to form an image, and includes a photosensitive drum 2 on which an image is formed.
[0015]
In the vicinity of the photosensitive drum 2, a charger 3 is provided as a charging unit for imparting photosensitivity by charging the photosensitive drum 2 with an electrostatic charge, and light is applied to the charged photosensitive drum 2 for a certain period of time. An exposing device 4 as an exposing device for forming an electrostatic latent image on the photosensitive drum 2, a surface voltmeter 3A for measuring a surface potential of the photosensitive drum 2, and an environment detecting device for detecting an environment around the photosensitive drum 2 3B.
Further, for example, below the photosensitive drum 2, a developing unit 19 that develops the electrostatic latent image formed on the photosensitive drum 2 with liquid toner is provided. Drying means 13 composed of a blower that blows air onto the surface of the photosensitive drum 2 to dry the liquid toner is provided. Above the photosensitive drum 2, for example, a transfer roller 6 for pressure-transferring a print image on the surface of the photosensitive drum 2, A backup roller 7 that backs up from above the transfer roller 6 to prevent escape of the pressure due to the deflection of the transfer roller 6 and applies a strong printing pressure to the whole is provided. Further, a control means 20 for controlling the entire printing press 1 including the driving of the photosensitive drum 2 and the transfer roller 6 is provided.
[0016]
The photosensitive drum 2 is provided with a first servo motor 8, the transfer roller 6 is provided with a second servo motor 9, and the backup roller 7 is provided with a third servo motor 10. Each of these servo motors 8, 9, 10 The photosensitive drum 2, the transfer roller 6, and the backup roller 7 are configured to be driven synchronously by driving.
The photosensitive drum 2 and the transfer roller 6 have the same diameter, and the backup roller 7 and the photosensitive drum 2 have the same diameter.
The transfer roller 6 can be attached to and detached from the photosensitive drum 2 by a transfer roller attachment / detachment actuator 67 (see FIG. 6), and the backup roller 7 is attached to the transfer roller 6 by a backup roller actuator 68 (see FIG. 6). It is removable.
The transfer roller 6, the backup roller 7, and the photosensitive drum 2 may have different diameters.
[0017]
As shown in FIG. 2, the exposure unit 4 includes a polygon scanner 91 that rotates at a constant rotation, an fθ lens 92 that collects laser light from the polygon scanner 91, and a laser diode 93 that enters the polygon scanner 91. The laser light output from the laser diode 93 is incident on and reflected by the polygon scanner 91, and scans the photosensitive drum 2 via the fθ lens 92.
[0018]
Here, a drawing area H, a non-drawing area I, and the like are formed on the photosensitive drum 2 as shown in FIG.
That is, a drawing area H of a predetermined size is formed in a rectangular shape at the center of the circumferential length G of the photosensitive drum 2, and non-drawing areas I are formed at both ends thereof. The non-drawing area I is formed continuously on the surface of the photosensitive drum 2 adjacent to the drawing area H.
One end of the drawing area H is a drawing start line A, and the other end is a final drawing line B. On the other hand, a scanning width E at which scanning by the polygon scanner 91 is performed is determined with respect to the width F of the photosensitive drum 2, and in the scanning width E, one end of a scanning start line, that is, a drawing start line A is defined as a drawing origin C. The scanning end line, that is, the other end of the final drawing line B is a drawing end point D. Then, the encoder detection angle of the drawing origin C is stored in the phase synchronization control unit 40 (see FIG. 7).
[0019]
When the laser beam output from the laser diode 93 scans on the photosensitive drum 2, as shown in FIG. 4, for synchronization with the drawing position, the dummy signal is first transmitted from the process control unit 35 through the exposure control unit 30. And the drawing synchronizing signal is output from the exposure device 4 in response to the dummy signal. The laser light reflected from the polygon scanner 91 and reflected again by the mirror 95 through the fθ lens 92 is used for synchronizing detection. The detection position detected by the photodetector 94 is output as the drawing synchronization signal. Then, after a predetermined time t has elapsed from the synchronization signal detection position, drawing is started by the drawing signal, and drawing data is created.
The control circuit of the laser diode 93 and the control circuit of the polygon scanner 91 are provided in the exposure control unit 30.
[0020]
In FIG. 1, a charger 3 is a scorotron charger for charging the drawing area H and the non-drawing area I of the photosensitive drum 2, and controls a bias voltage applied to a grid electrode to thereby charge the photosensitive drum 2. The potential charged on the surface of the second 2 is adjusted.
FIG. 5 shows the relationship between the charger 3 and the photosensitive drum 2.
In FIG. 5, when the final drawing line B of the photosensitive drum 2 faces the charger 3, the charger 3 applies a predetermined voltage, for example, a corona wire application voltage Vc of 5 to 6 KV, and further applies a predetermined bias voltage to the grid electrode. That is, the grid voltage Vg is applied, and a corona discharge is performed on the surface of the photosensitive drum 2 to obtain a predetermined photosensitive drum surface potential Vo. The photosensitive drum 2 is provided with a slip ring (not shown) on its shaft core 2A, and the voltage is dropped to the ground.
[0021]
The grid voltage Vg and the photosensitive drum surface potential Vo are in a direct proportional relationship (see FIG. 8).
When the surface temperature of the photosensitive drum 2 is approximately 20 ° C. to 35 ° C., the grid voltage Vg and the photosensitive drum surface potential Vo are linear functions expressed by Vo = α × Vg + β.
When Vs with respect to the target surface potential Vo of the photosensitive drum 2 obtained by the grid voltage Vg, if ΔVo = Vo−Vs, the gradient α of the linear function does not change with temperature. The correction value Vgc of Vg for obtaining the surface potential Vo is Vgc = Vg− (ΔVo / α), and the surface potential of the photosensitive drum 2 is maintained at the target potential by changing the grid voltage from Vg to Vgc. Can be. This control is performed by the process control unit 35.
[0022]
Returning to FIG. 1, an existing electrometer can be used as the surface electrometer 3A. The surface electrometer 3A measures the potential of the charged non-drawing area I on the drum surface, and outputs the measurement result data to the process control unit. 35.
The environment detecting means 3B is a thermometer for measuring the temperature of the surface of the photosensitive drum 2 or its surroundings, and sends data of the measurement result to the process control unit 35.
[0023]
The developing unit 19 includes the developing device main body 5 and the developing roller 15 provided on the developing device main body 5.
The developing machine main body 5 has a base 5A and a plurality of toner storage chambers 5B, 5C, 5D, 5E provided on the base 5A.
In the toner storage chamber 5B, the first of the four process colors, for example, yellow liquid toner, is stored. In the toner storage chamber 5C, the second of the four process colors, for example, red plate, is stored. Liquid toner is stored in the toner storage chamber 5D, and the third color of the four process colors, for example, indigo liquid toner, is stored in the toner storage chamber 5D. The fourth color, for example, black plate liquid toner is stored.
[0024]
The developing roller 15 includes a first developing roller 15B provided in the toner storage chamber 5B, a second developing roller 15C provided in the toner storage chamber 5C, a third developing roller 15D provided in the toner storage chamber 5D, and a toner storage chamber. 5E, a fourth developing roller 15E, which can supply the liquid toner in each of the storage chambers 5B, 5C, 5D, and 5E to the photosensitive drum 2 by the developing roller 15B and the like. ing.
[0025]
These developing rollers 15 </ b> B to 15 </ b> E are selected in accordance with each color electrostatic latent image formed on the photosensitive drum 2. This selection is performed by driving the developing device moving mechanism 12 by the motor 11 based on a command to the developing device moving motor 11 output from the process control unit 35 described later, and moving the developing rollers 15B to 15E to the developing positions. It is realized by positioning. The driving of each of the developing rollers 15B to 15E maintains a predetermined fixed speed ratio with respect to the photosensitive drum 2.
The print paper W is supplied between the backup roller 7 and the transfer roller 6 from the paper transport actuator 49 (see FIG. 6) constituting the print paper transport means, so that the print image on the transfer roller 6 is pressure-transferred. It has become.
[0026]
FIG. 6 shows the control unit 20 of the printing press 1 as described above. The control unit 20 includes a drawing data creation unit 25, an exposure control unit 30, a process control unit 35, and a phase synchronization control unit 40. Have been.
The drawing data creation unit 25 edits and prints the drawing data to be drawn based on the print image data using, for example, a small computer system such as a personal computer or a workstation, and creates a publication. Output of the created drawing data created using a desktop publishing (DTP) system is performed using, for example, a PS file, a Portable Document Format (PDF) file, a Tagged Image File Format (TIFF) file, or the like.
[0027]
The functions corresponding to the respective file formats are possessed by the drawing data creation unit 25, and use the functions to create the drawing data to be used in the printing press 1. The drawing data creation unit 25 performs the four-color separation process, the RIP (Raster Image Processor) process, and the like in accordance with the file format.
The created drawing data is transmitted to the exposure control unit 30, which converts it into a signal (exposure signal) for driving the exposure device 4, and transmits the exposure signal to the exposure device 4. You.
[0028]
Next, the phase synchronization control section 40 will be described with reference to FIG.
The phase synchronization control unit 40 includes a DSP (digital signal processor) unit 41 that operates as an integrated control unit, a servo controller unit 42, and an input / output I / F 53.
The servo controller section 42 includes a first servo controller 43, a second servo controller 44, and a third servo controller 45. Each of the servo controllers 43, 44, 45 includes the first servo motor 8, the second servo motor 9 and the third servomotor 10, and exchanges a drive command signal and a phase signal with the process control unit 35 and the exposure control unit 30 via the input / output I / F 53.
[0029]
The DSP unit 41 simultaneously supplies a single position command (rotation angle) signal to each of the servo controllers 43, 44, and 45 of the servo controller unit 42.
The position command signals output to the servo controllers 43, 44, and 45 are sent to the first servo amplifier 46, the second servo amplifier 47, and the third servo amplifier 48, respectively. A drive signal corresponding to the position command signal is output to the first servomotor 8, the second servomotor 9, and the third servomotor 10, respectively, and the first encoder 50, the second encoder 51, and the third encoder 52 Are input to the servo controllers 43, 44, and 45, respectively.
[0030]
The first, second, and third servo controllers 43, 44, and 45 form position loops 55, 56, and 57 having a fixed period (servo system sampling period), respectively, and perform software servo control for controlling each servo system. Has functions.
The DSP unit 41 maintains a time interval according to the speed command during low-speed operation, and continuously transmits a position command signal to each of the servo controllers 43, 44, and 45. At this time, the synchronization of the photosensitive drum 2, the transfer roller 6, and the backup roller 7 is maintained by software synchronization of the DSP unit 41.
During acceleration and deceleration, a position command signal is continuously transmitted while maintaining a change rate in accordance with a predetermined target angular acceleration according to the acceleration time and the deceleration time. , The transfer roller 6 and the backup roller 7 are kept synchronized.
[0031]
The process control unit 35 also functions as a charge control unit that controls the potential of the charger 3. The process control unit 35 functioning as a charging control unit includes data of the surface potential of the photosensitive drum 2 input from the surface voltmeter 3A, and temperature data of the periphery and the surface of the photosensitive drum 2 input from the environment detecting unit 3B. And the potential of the charger 3 is controlled in accordance with
At this time, the process control unit 35 includes a memory for storing information in which the relationship between the grid voltage Vg and the photosensitive drum surface potential Vo is input in advance for each predetermined temperature data, and the temperature input from the environment detecting unit 3B. The grid voltage Vg is controlled to a predetermined value according to the data.
[0032]
Here, the temperature characteristic of the photosensitive drum 2 is obtained in advance, and the grid voltage Vg is obtained with reference to the characteristic graph. As for the temperature characteristic, if the material of the photosensitive drum 2 to be used is determined, the characteristic graph to be adopted is also determined.
FIG. 8 and FIG. 9 are examples of graphs showing the temperature characteristics of the photosensitive drum 2. For example, FIG. 8 is a graph obtained approximately. In FIG. 8, a grid voltage Vg is obtained from the temperature of the photosensitive drum 2 and the drum surface potential.
Strictly speaking, the graph showing the relationship between the grid voltage Vg and the photoconductor drum surface potential Vo changes in slope depending on the temperature around the drum, as shown in FIG. To perform finer printing, the grid voltage Vg is obtained based on the graph shown in FIG.
[0033]
In FIG. 9, when the surface temperature of the photosensitive drum 2 is 20 ° C., the slope of the graph is a20. Similarly, when the surface temperature is 25 ° C., the slope of the graph is a25, and when the surface temperature is 30 ° C. The slope of the graph at the time is a30, and the slope of the graph when the surface temperature is 35 ° C. is a35. 9, a grid voltage Vg is obtained from the temperature of the photosensitive drum 2 and the drum surface potential as in FIG.
In the present embodiment, the graph is approximated by a straight line. However, a necessary value may be searched using a polynomial approximation or a table.
[0034]
Next, a printing procedure according to the present embodiment will be described with reference to FIGS.
In the flowchart shown in FIG. 10, first, the photosensitive drum 2 is rotated (ST1), and it is determined whether or not the charger 3 faces the final drawing line (ST2). When the charger 3 faces the final drawing line, the charger 3 is turned on to charge the non-drawing area I of the photosensitive drum 2 (ST3), and the non-drawing area of the photosensitive drum 2 is further measured by the surface voltmeter 3A. The surface potential at I is measured (ST4).
Thereafter, a process control unit 35 as a charging control unit controls the data of the surface potential of the photosensitive drum 2 input from the surface voltmeter 3A and the temperature of the periphery and the surface of the photosensitive drum 2 input from the environment detecting unit 3B. The grid voltage Vg of the charger 3 is controlled according to the data (ST5). As a result, the entire drum surface including the non-drawing area I is charged to the predetermined voltage V (see FIG. 11A).
[0035]
Thereafter, the developing roller for the first color is arranged at the developing position (ST6). Further, when the drawing start line reaches the exposure position of the exposure device 4, the exposure control unit 30 maintains the synchronization with the drawing position for the first color. For example, one line for drawing a yellow plate is drawn (ST7). Thus, the charges in the exposed portions P are erased (see FIG. 11B).
The peripheral speed of the photosensitive drum 2 is set in advance so as to move by one dot in one surface scanning time of the polygon scanner 91, and the peripheral speed of the photosensitive drum 2 is set until a predetermined final line is drawn. The drawing is executed while maintaining the two-dimensional synchronization of the circumference and width.
[0036]
When the drawing origin C reaches the developing position, development is performed, and the liquid toner of the first color is transferred from the developing roller 15B for the first color onto the latent image on the surface of the photosensitive drum 2 to form a printed image (ST8). . As a result, the toner T adheres to the portion P where the charge has been erased (see FIG. 11C).
After the development of the final line of the first color is completed, the developing unit 19 is moved for the development of the second color (ST9), and the developing roller of the second color is arranged at the development position (ST10).
In parallel with this, when the drawing origin C reaches the drawing position, the exposure controller 30 starts drawing the second color (ST11). At this time, the synchronization with the rotation of the photosensitive drum 2 is performed in the same manner as in the first color, and thereafter, similarly, the second color development (ST12), the movement of the developing machine (ST13), and the arrangement of the third color development roller at the development position. (ST14) Third-color drawing (ST14), third-color development (ST16), movement of the developing machine (ST17), arrangement of the fourth-color developing roller at the developing position (ST18), fourth-color drawing (ST19), fourth-color Is performed (ST20). After developing the fourth color, the developing unit 19 is moved to the initial position by the developing machine moving mechanism 12.
[0037]
In the above steps, the transfer roller 6 is disengaged from the photosensitive drum 2, and after the development of the fourth color is completed, the transfer roller 6 is attached to the photosensitive drum 2, and the backup roller 7 Is applied to the transfer roller 6 (ST22), the image is transferred from the photosensitive drum 2 to the transfer roller 6 (ST23), the image is transferred from the transfer roller 6 to the printing paper W (ST24), and printing is completed. I do. Note that the charger 3 is turned off after the final line of the fourth color has passed the position of the charger 3.
[0038]
In the embodiment configured as described above, the following effects can be obtained.
(1) In adjusting the potential charged on the photosensitive drum 2, the potential charged on the photosensitive drum 2 is measured by a surface voltmeter 3 </ b> A, and the charging potential is determined in accordance with the measurement result of the potential. , The time between the charging and the potential control is shortened, so that the entire working time is shortened, and even if the temperature of the surface of the photosensitive drum 2 changes, The potential charged on the surface of the photosensitive drum 2 can be adjusted sufficiently in response to the temperature change, so that the developing process is stabilized and print reproducibility is not impaired.
[0039]
(2) An environment detecting unit 3B for detecting the environment around the photosensitive drum 2 is provided, and the process control unit 35 controls the potential of the charger 3 in accordance with the detection result by the environment detecting unit 3B. The process control unit 35 is controlled in accordance with the environment around the photoconductor drum 2 detected by the environment detection unit 3B, so that even if the environment around the photoconductor drum 2 changes, the process change is quickly made. , The charged potential on the drum surface can be adjusted efficiently.
[0040]
(3) Since the environment detecting means 3B is a thermometer for measuring the temperature of the surface of the photosensitive drum 2 or its surroundings, the temperature is an environmental factor which greatly affects the charging potential of the photosensitive drum 2, and this temperature Can be obtained relatively inexpensively, and therefore, it is possible to provide the printing press 1 which can sufficiently cope with environmental changes around the photosensitive drum 2 at low cost.
[0041]
(4) Since the charger 3 is configured to perform test charging on the non-drawing area I formed along the axial direction of the photosensitive drum 2, the non-drawing area I is placed in the axial direction on the surface of the photosensitive drum 2. Therefore, the charged state in the area can be accurately measured. Therefore, the potential control of the surface of the photoconductor drum 2 is reliably performed, and it is possible to cope with a change in the environment around the photoconductor drum 2. In addition, since the drawing area H is formed in the non-drawing area I in the drum circumferential direction, the image forming operation in the drawing area H is performed immediately after the test charging and the potential adjustment are performed in the non-drawing area I. Can be.
In particular, in the present embodiment, since the developing unit 19 is moved to perform four-color printing, the non-drawing area I formed along the axial direction on the surface of the photosensitive drum 2 is indispensable. The charged potential is measured by effectively utilizing the indispensable non-drawing region H.
[0042]
(5) Since the process controller 35 is configured to control the bias voltage applied to the grid electrode of the scorotron charger, the process controller 35 controls the voltage applied to the grid electrode of the scorotron charger 3 so that the surface of the photosensitive drum 2 can be controlled. The potential to be charged can be easily controlled. Therefore, it is possible to cope with a change in the environment around the photosensitive drum 2.
[0043]
The present invention is not limited to the above embodiments, and the following modifications may be made as long as the objects of the present invention can be achieved.
For example, in the above embodiment, the printing press 1 is used for printing, but the printing press 1 can also be used for test printing, that is, for proofreading.
Further, in the above embodiment, the environment detecting means 3B is a thermometer for measuring the temperature of the surface of the photosensitive drum 2 or the surrounding area. However, in the present invention, the environment detecting means is replaced with this thermometer, or In addition to the meter, a hygrometer for measuring the humidity of the surface of the photosensitive drum 2 or its surroundings may be used. Since the humidity greatly affects the potential charged on the surface of the photosensitive drum 2, a thermometer and / or a hygrometer may be used as the environment detecting means 3B to ensure more effective response to environmental changes. Can be.
[0044]
Further, in the present embodiment, the non-drawing area I may be formed to extend in the circumferential direction of the photosensitive drum 2 or may be formed in a predetermined spot shape. For example, when the non-drawing area I is formed along the circumferential direction at the edge of the photosensitive drum 2, the axial dimension of the photosensitive drum and the field dimension of the charger 3 are set smaller than the width dimension of the printing paper. Need to be bigger.
[0045]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, while being able to shorten the whole working time, the quality of the image formed by adjusting the surface potential of a photoconductor drum according to the environmental change surrounding a photoconductor drum improves.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram illustrating an entire image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing an example of an exposure system in the embodiment.
FIG. 3 is a diagram showing a drawing area, a non-drawing area, a drawing origin, and the like on the photosensitive drum in the embodiment.
FIG. 4 is a diagram showing an example of a synchronization detection timing at the time of starting drawing in the embodiment.
FIG. 5 is a schematic diagram illustrating a relationship between a photosensitive drum and a charging unit in the embodiment.
FIG. 6 is a block diagram showing control means in the embodiment.
FIG. 7 is a block diagram showing a phase synchronous drive system in the embodiment.
FIG. 8 is a graph showing a relationship between a grid voltage and a photosensitive drum surface potential.
FIG. 9 is a graph showing a relationship between a grid voltage and a photosensitive drum surface potential.
FIG. 10 is a flowchart for explaining a method of the embodiment.
11A is a schematic diagram illustrating a state where a photosensitive drum is charged, FIG. 11B is a schematic diagram illustrating a state where a charged portion is exposed, and FIG. 11C is a diagram illustrating a state where the exposed portion is developed. FIG.
[Explanation of symbols]
1 printing machine (image forming device)
2 Photoconductor drum
3 Charging means (charging device)
3A surface electrometer
3B Environment detection means
4 Exposure means (exposure device)
19 Developing means
35 Process control unit (charging control means)
I Non-drawing area
H Drawing area

Claims (6)

The surface of the photosensitive drum on which an image is formed is charged by a charging unit, and after charging by the charging unit, the surface of the photosensitive drum is exposed by an exposure unit to form an electrostatic latent image. An image forming apparatus for developing the electrostatic latent image on the surface of the photoconductor drum by supplying a liquid toner to the surface of the photoconductor drum by a developing unit.
A surface potentiometer for measuring the surface potential of the photosensitive drum, and a charging control unit for controlling the potential of the charging unit,
The charging unit charges a non-drawing region on the surface of the photoconductor drum, the surface voltmeter measures a surface potential in the non-drawing region charged by the charging unit, and the charging control unit includes: An image forming apparatus, wherein the potential of the charging unit is controlled in accordance with a measurement result of a surface voltmeter. 2. The image forming apparatus according to claim 1, further comprising: an environment detecting unit configured to detect an environment around the photosensitive drum, wherein the charging control unit controls a potential of the charging unit in accordance with a result of the detection by the environment detecting unit. An image forming apparatus, comprising: 3. The image forming apparatus according to claim 2, wherein the environment detecting unit measures a temperature of a surface of the photosensitive drum or a surrounding thereof and / or a humidity of measuring a humidity of the surface of the photosensitive drum or surrounding thereof. 4. An image forming apparatus, comprising: 4. The image forming apparatus according to claim 1, wherein the charging unit charges a non-drawing region between ends of a drawing region formed along a circumferential direction of the photoconductor drum. 5. Characteristic image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the charging unit is a scorotron charger, and the charging control unit controls a bias voltage applied to a grid electrode of the scorotron charger. Image forming apparatus. The surface of the photosensitive drum on which an image is formed is charged, and after charging, the surface of the photosensitive drum is exposed to create an electrostatic latent image.After the exposure, the liquid toner is supplied to the surface of the photosensitive drum. An image forming method for developing the electrostatic latent image on the surface of the photoconductor drum,
In adjusting the potential charged on the photosensitive drum, charging is performed on a non-drawing area on the surface of the photosensitive drum, the potential of the charged non-drawing area is measured, and the potential is measured in accordance with the measurement result of the potential. An image forming method comprising controlling a potential charged on a photosensitive drum.

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