JP3097361B2 - Electrophotographic copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of image stabilization in an electrophotographic digital color copying machine.

[0002]

2. Description of the Related Art In an electrophotographic digital color copying machine which performs color printing using density data of a document image read by an image scanner, it is important to improve the reproducibility of halftone images such as photographs. It has become.

One of the major factors affecting the density of a reproduced image to be printed is the characteristics of the photoconductor and toner. This is a phenomenon in which the amount of toner adhered to the photoconductor changes during development due to environmental changes such as temperature and humidity inside the copying machine. Generally, in a high-temperature and high-humidity environment, the amount of toner adhering to the photoreceptor increases, and the gradient of the γ characteristic from a low-density portion to a medium-density portion increases, and the reproduced image becomes dense. Also,
In a low-temperature and low-humidity environment, the amount of toner adhering to the photoreceptor decreases, and the slope of the γ characteristic from a low-density portion to an intermediate-density portion decreases, resulting in a thin reproduced image.

As described above, in a copying machine, there is a problem that the density of an image reproduced on copy paper changes due to a change in environment. To solve this problem and stabilize the density of a reproduced image, a general copying machine is used. In electrophotographic copying machines,
After the completion of the warm-up at the time of turning on the power, an image stabilizing process for keeping the maximum density level of the image to be printed constant is executed. Image stabilization processing is performed by a digital color copier in 4
Color (C: cyan, M: magenta, Y: yellow, K:
Black) minutes, ie, four runs.

[0005] A general image stabilization process will be briefly described below with reference to FIG. FIG. 3 schematically shows the arrangement of the charging charger 43 around the photosensitive drum 41 and the developing unit 45r. Before the laser exposure, the photosensitive drum 41 has a negative surface voltage V
_O , and a negative bias voltage V _B that satisfies the relationship | V _B | <| V _O | is applied to the roller of the developing unit 45r by the developing bias generation unit 244. By irradiating the photosensitive drum 41 with the laser beam for which the maximum exposure amount is set, the surface voltage V _{O at the} irradiation position transits to the decay voltage V _I of almost zero potential. Here, the absolute value of the damping voltage V _I is,
Becomes lower than the absolute value of the developing bias voltage V _B, the toner that has been carried to the sleeve surface of the developing device 45r (having negative charges) is attached to the photosensitive drum 41. The toner adhesion amount, development voltage ΔV = | V _B -V _I | many becomes the greater. It is desirable that the difference between | V _O | and | V _B | be within a certain range. Therefore, for example, if the surface voltage V _O and the developing device voltage V _B are changed while the difference between V _O and V _B is kept constant, the difference between V _B and V _I changes, so that the toner adhesion amount is changed. Printing density can be controlled. Such image stabilization processing is performed by AI
This operation is called a DC operation and is performed by changing V _O and V _B manually and automatically. Note that the image stabilization processing includes, besides the AIDC operation described above, voltage detection, and image stabilization processing based on both AIDC operation and voltage detection.

[0006] Typically, the concentration data of the document image read by the image scanner, the image and the surface voltage V _O of the photosensitive member is set by the stabilization process, the developing bias voltage V given γ correction data corresponding to the value of _B Is corrected using

[0007]

Conventionally, the image stabilization process has been executed after the power is turned on, a user presses a copy start button, and before the copying operation. For this reason, at the time of the first copy, a considerable time is required until the actual copying operation is started, which is inconvenient for the user. However, if the image stabilization processing is set to be automatically executed at a fixed timing after the completion of the warm-up at the time of turning on the power, for example, it may be performed carelessly during maintenance work by a serviceman. It is a danger.

Accordingly, an object of the present invention is to provide an electrophotographic copying machine that appropriately controls execution of image stabilization processing.

[0009]

According to the present invention, there is provided an electrophotographic copying machine which irradiates a photosensitive member with light based on image data and a charging means which uniformly charges the surface of the photosensitive member. Developing means for applying toner to the electrostatic latent image formed on the photoreceptor surface by the irradiating means; applying means for applying a developing bias voltage to the developing means; the amount of light irradiated by the irradiating means; Image stabilization processing in which the values of the photoreceptor surface voltage charged uniformly by the photoreceptor and the developing bias voltage applied to the developing means by the application means are determined to values at which the image formed on the photoreceptor surface is stabilized. The image stabilization processing is not performed when the copying operation is performed when the elapsed time from the end of the previous image stabilization processing is less than the first predetermined time. Elapsed time is equal to or longer than the first predetermined time In the case where the copying operation is performed when the time is less than the second predetermined time, the image stabilization processing is performed after the completion of the copying operation (where the second predetermined time is longer than the first predetermined time), When the copying operation is performed at the second predetermined time or more, a control unit that controls the image forming condition determining unit is provided so that the image stabilization process is performed before the copying operation.

[0010]

[0011]

According to a second aspect of the present invention, an electrophotographic copying machine according to the first aspect is provided.
The image forming condition determining means reads the density of the reference toner image.
Each value is determined by an IDC operation.

According to a third aspect of the present invention, in the electrophotographic copying machine according to the first aspect,
The image forming condition determining means determines each of the above values by detecting the voltage of the charged photoconductor surface.

An electrophotographic copying machine according to a fourth aspect of the present invention is the electrophotographic copying machine according to the first aspect,
The image forming condition determining means determines the values by detecting the value of the voltage on the charged photoreceptor surface and performing the AIDC operation of reading the density of the reference toner image.

[0015]

[0016]

According to the electrophotographic copying machine described in claim 1,
The image forming condition determining means determines the amount of light applied to the photoreceptor surface, the voltage on the photoreceptor surface, and the development bias voltage to values that stabilize the image formed on the photoreceptor surface. Perform the conversion process. The control means determines the necessity and timing of the image stabilization process accompanying the copying operation according to the elapsed time from the end of the previous image stabilization process.

[0017]

[0018]

According to a second aspect of the present invention, in the electrophotographic copying machine according to the first aspect,
The image forming condition determining means reads the density of the reference toner image.
The above values are determined by the IDC operation.

According to a third aspect of the present invention, in the electrophotographic copying machine according to the first aspect,
The image forming condition determining means determines each of the above values by detecting the value of the voltage on the charged photoreceptor surface.

According to the electrophotographic copying machine described in claim 4, in the electrophotographic copying machine described in claim 1,
The image forming condition determining means determines the above values by detecting the value of the voltage on the charged photoreceptor surface and performing the AIDC operation of reading the density of the reference toner image.

[0022]

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image stabilization process is basically preferably executed immediately before the start of a copying operation, most preferably from the viewpoint of reliability and accuracy of control. However, if the image stabilization process is always executed immediately before the start of a copying operation, The time until the start of the actual copying operation becomes longer.
Therefore, in the present invention, the image stabilization process is started before the warm-up of the copying machine body is completed, and the timing is set such that the completion of the warm-up and the end of the image stabilization process are almost simultaneously performed. It is characterized by the following. The environment in which the main body of the copying machine is placed changes over time.
In consideration of this, in the copying machine of the present invention, after the image stabilization processing is performed, the copying operation performed when the elapsed time is less than 10 minutes is immediately performed, and the copying operation is performed within 10 minutes or more and less than 1 hour. For the copying operation to be performed, the image stabilization process is executed again after the copying operation is completed. If the elapsed time is one hour or longer, the image stabilization process is performed before starting the copying operation, as in the related art. Hereinafter, a copying machine according to the present invention will be described in detail in the following order with reference to the accompanying drawings. (1) Copier configuration (2) Image stabilization processing (3) Control flowchart description (4) Other image stabilization processing

(1) Configuration of Copying Machine FIG. 1 is a diagram showing the overall configuration of a digital color copying machine provided with the processing apparatus of the present invention. The digital color copying machine is roughly divided into an image reader unit 100 for reading a document image and a copying unit 200 for reproducing image data read by the image reader unit 100.

In the image reader section 100, a scanner 10 includes an exposure lamp 12 for irradiating a document, a rod lens array 13 for condensing light reflected from the document, and a contact type for converting the condensed light into an electric signal. CCD color image sensor 14 is provided. The scanner 10 is driven by a motor 11 when reading a document image,
It moves in the direction of the arrow (sub-scanning direction) and scans the original placed on the platen 15. The image on the document surface irradiated by the exposure lamp 12 is photoelectrically converted by the image sensor 14. The multi-valued electrical signals of the three colors R, G, and B obtained by the image sensor 14 are read by the read signal processing unit 20 to be any one of yellow (Y), magenta (M), cyan (C), and black (K). , And stored in the synchronization buffer memory 30.

Next, in the copying section 200, the printer head section 31 performs gradation correction (γ correction) on the inputted gradation data in accordance with the gradation characteristics of the photoconductor, and then performs the correction. The image data is D / A converted to generate a laser diode drive signal, and the semiconductor laser is caused to emit light by the drive signal.

The printer head 3 corresponding to the gradation data
The laser beam generated from 1 exposes the photosensitive drum 41 which is driven to rotate via the reflecting mirror 37. The photoreceptor drum 41 is irradiated with an eraser lamp 42 before receiving exposure for each copy, and is uniformly charged by a charger 43. When exposure is performed in this state, an electrostatic latent image of the document is formed on the photosensitive drum 41. Only one of the cyan, magenta, yellow, and black toner developing units 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. The developed toner image is transferred by a transfer charger 46 onto a copy paper wound around a transfer drum 51.

Here, the rotational position of the transfer drum 51 is detected by a not-shown detector and a detection sensor provided inside. The copying operation is controlled from this point (Time-Base). Further, the photosensitive drum 41 and the transfer drum 5
Reference numeral 1 denotes a drum having an integer ratio of drum diameters, which is connected and driven, so that the same position of the photosensitive drum 41 and the same position of the transfer drum 51 are always in contact. This eliminates misalignment during toner superposition.

The above printing process is repeated for four colors of yellow (Y), magenta (M), cyan (C) and black (K). At this time, the photosensitive drum 41 and
The scanner 10 repeats the scanning operation in synchronization with the operation of the transfer drum 51. Thereafter, the copy paper is separated from the transfer drum 51 by operating the separation claw 7, is fixed through the fixing device 48, and is discharged to the discharge tray 49.
The copy paper is fed from a paper cassette 50, and the leading end thereof is chucked by a chucking mechanism 52 on a transfer drum 51, so that no positional deviation occurs during transfer.

Further, the AIDC sensor 210 according to the present invention
Is about 3 mm with respect to the photosensitive drum 41 at the location shown.
Is set at In addition, when detecting the toner adhesion amount, the pre-transfer Er 55 is turned off to prevent the light of the pre-transfer Er 55 from being incident on the light receiving portion of the AIDC sensor 210.
F.

FIG. 2 is an overall block diagram of a control system of the digital color copying machine according to the embodiment. The image reader unit 100 is controlled by the image reader control unit 101. The image reader control unit 101 includes a platen 15
The exposure lamp 12 is controlled via the drive I / O 103 in accordance with a position signal from the position detection switch 102 indicating the position of the upper document, and the scan motor driver 1 is controlled via the drive I / O 103 and the parallel I / O 104.
05 is controlled. The scan motor 11 is driven by a scan motor driver 105.

On the other hand, the image reader control unit 101 is connected to the image control unit 106 by a bus. The image control unit 106 is connected to each of the CCD color image sensor 14 and the image signal processing unit 20 via a bus.
The image signal from the image sensor 14 is input to the image signal processing unit 20 and processed.

The copying section 200 is provided with a printer control section 201 for controlling general copying operations. A printer control unit 201 having a CPU includes a control ROM 202 storing a control program and various data (AID).
A data ROM 203 in which a C table and a γ correction table are stored is connected. Printer control unit 201
Controls the printing operation based on the data in the ROM.

The printer control unit 201 includes a voltage sensor 44 for detecting the surface voltage of the photosensitive drum 41 and an AIDC sensor 210 for chemically detecting the amount of toner of a reference toner image attached to the surface of the photosensitive drum 41. , Developing unit 45
Analog signals from various sensors such as an ATDC sensor 211, a temperature sensor 212, and a humidity sensor 213 for detecting the toner concentration within a to 45d are input.

The printer control unit 201 includes the sensors 44,
210 to 213, operation panel 221, and data ROM
The data from the control unit 203 controls the copy control unit 231 and the display panel 232 in accordance with the contents of the control ROM 202. Further, during image stabilization processing, the printer control unit 201 performs density control automatically by the AIDC sensor 210 or by input to the operation panel 221 by a user. Thereby, the printer control unit 20
1 is a parallel I / O 241 and a drive I / O 242
V _G generated for high-voltage unit 243 generates a grid voltage V _G of the electric charger 43 via, and developing devices 45a
Controlling the V _B generating high voltage unit 244 for generating a developing bias voltage V _B of ～45D.

The printer control unit 201 is connected to the image signal processing unit 200 of the image reader unit 100 by an image data bus, and stores a γ correction table based on an image density signal transmitted through the image data bus. The semiconductor laser driver 263 is controlled via the drive I / O 261 and the parallel I / O 262 with reference to the data ROM 203 stored in the memory. The light emission of the semiconductor laser 264 is driven by the semiconductor laser driver 263. The gradation expression is executed by modulating the emission intensity of the semiconductor laser 264.

(2) Image Stabilization Processing FIG. 3 shows the charging charger 43 around the photosensitive drum 41.
And the arrangement of the developing device (for example, 45r) is schematically shown. The photosensitive drum 41, a charger 4 of the discharge voltage V _G
3 are installed facing each other. The grid of the main charger 43 negative grid voltage V _G is applied by the grid voltage generating unit 243. The relationship between the grid voltage V _G and the surface voltage V ₀ which the photosensitive drum 41 is V ₀ ≒ V _G, the voltage V ₀ which the photosensitive drum 41 surface is detected by a voltage sensor 44 is a surface voltmeter .

Before the laser exposure, the charger 4
3, the photosensitive drum 41 has a negative surface voltage V
_O is also the rollers of the developing unit 45r by a development bias generation unit _{244, | V B | <|} V O | negative bias voltage V _B which satisfies the relationship is given. Accordingly, the voltage of the sleeve surface of the developing device 45r is V _B.

By the irradiation of the laser beam having the maximum exposure amount, the absolute value of the surface voltage V _O at the irradiation position of the laser beam on the photosensitive drum 41 is attenuated to zero, and the attenuation voltage V _I of the electrostatic latent image is reduced. Transition to. The absolute value of the decay voltage V _I becomes a value close to zero in proportion to the increase in the exposure amount of the irradiated laser light.
The absolute value of the damping voltage V _I becomes lower than the absolute value of the developing bias voltage V _B, the developing unit (negatively charged) toner that has been carried to the sleeve surface of 45r photoreceptor drum 41
Stick on top. The difference between | V _O | and | V _B | may not be too large or too small. Further, the toner adhesion amount, development voltage ΔV = | V _B -V _I | many becomes the greater. On the other hand, the decay voltage V _I changes with a change in the surface voltage V _O even for the same exposure amount. Therefore, while maintaining the difference between V _O and V _B within a certain range, for example, while keeping the difference constant, the surface voltage V
_{If O} and the developing device voltage V _B are changed, V
The difference between _B and V _I is changed, it is possible to vary the amount of toner adhered to the photosensitive drum 41, can control printing density.

More specifically, first, the photosensitive drum 41
A reference toner image serving as a reference for density control is formed thereon, and an AIDC sensor 210 provided near the photosensitive drum 41 detects specular reflection light and scattered reflection light from the reference toner image. Each of the detection signals detected by the AIDC sensor 210 is input to the printer control unit 201, where the toner adhesion amount is obtained from the difference between the two detection signals. By changing the values of V _O and V _{B in accordance} with the detected values, the toner adhesion amount at the maximum density level can be kept constant. Accordingly, the amount of toner attached changes due to changes in the environment such as humidity and temperature inside the copying machine main body. In response to this, by changing the values of V _O and V _B , the toner on the photosensitive drum 41 is changed. , Ie, the maximum density level printed on copy paper, can be kept constant. In the present embodiment, one grid voltage V _G (≒ V _O ) corresponds to one bias voltage V _B , and the difference is kept constant. The printer control unit 201 stores the AIDC stored in the data ROM 203 based on the detection value of the AIDC sensor 210.
From the table (V _G, V _B) to select a value of, selected the (V _G, V _B) to identify a γ correction table No. corresponding to the value of. The printer control unit 201 stores the specified No. gamma correction data in the gamma correction data stored in the data ROM 203.
The data is read from the correction table, and γ correction is executed based on the readout.

The following Table 1 shows an example of the AIDC table stored in the data ROM 203. 0 shown in the leftmost column
The levels of ~ 15 are determined based on the detection values of the AIDC sensor 210. The value of the bias voltage V _B varies with 40V units from -220V to correspond to each level becomes -820V at the maximum. The value of the grid voltage V _G is 1 than V _B
It is kept at a value smaller by 80V. Therefore, the grid voltage V _G
Varies from -400 V to -1000 V in steps of 40 V. Incidentally, the amount of change in the value of (V _G, V _B) is not limited to the case above, it may be determined according to the control accuracy.

[Table 1]

(3) Description of Flowchart of Image Stabilization Processing (3-1) Description of Flowchart of Main Routine FIG. 4 is a flowchart of a main routine relating to the operation of the copying machine according to the present invention. Copy machine power is O
When N is set, the values of the registers and the internal timer in the copying machine are initialized in step S1. Next, an internal timer is started in step S2. After starting the internal timer, the copier performs a main SW input process (step S3), an image stabilization process for determining image forming conditions (step S4), and a time control process (step S5), which will be described in detail later. Is executed, the image reader unit 100 is executed based on the conditions set by the user.
Is driven to execute a copying operation (step S
6), other input processing such as conveyance of copy paper (step S7), and other output processing such as discharge of copy paper on which an image is printed (step S8). After execution of each of the above processes, the process returns to step S2 again after the internal timer has ended. The image forming process (step S6),
The other input processing (step S7) and other output processing (step S8) are the same as well-known processing, and will not be described below.

(3-2) Description of Main SW Input Process FIG. 5 is a flowchart of the main SW input process (step S3) shown in the flowchart of the main routine. First, the printer control device 201 including the CPU checks the value of the state flag in step S101.
When the copier is powered on, the state flag is set to zero. If the value of the state flag is 0 in step S101, the process proceeds to step S102, and it is determined whether the main switch is ON. Main switch is O
If N (YES in step S102),
The temperature of the fixing roller provided in the fixing device 48 shown in FIG. 1 is checked (step S103). Here, when the temperature of the fixing roller is 170 ° C. or higher (step S10).
If the answer is YES in step S4, the condition setting flag is set (step S105). If the temperature of the fixing roller is 175 ° C. or higher (YES in step S106), the heater is turned off (step S107), the value of the state flag is set to 1 (step S108), and the process returns. In step S104, the temperature of the fixing roller becomes 170
If the temperature is lower than 0 ° C. or the temperature of the fixing roller is lower than 175 ° C. in step S106, the heater is turned on (step S109), and the process returns.

Here, the above steps S104 and S10
6, the period in which the condition determination flag is set, that is, the execution period of the image stabilization process is set to a temperature of 170 ° C.
The temperature is set to rise to 175 ° C. because the copier of this embodiment is set so that the image stabilization process is completed during this period. By adjusting the time required for the image stabilization process and the time required for the heater to raise the temperature of the fixing roller from 170 ° C. to 175 ° C., image formation is performed almost at the same time as the completion of the temperature control of the fixing roller. The conditions are determined, and the copy can be made.

Therefore, the temperature of the fixing roller at which the image stabilization process is started is as described above (when the temperature of the fixing roller is 170 ° C.).
The temperature rise rate of the fixing roller by the heater is determined, and the temperature of the fixing roller at which the image stabilization processing is started is determined from the temperature rise rate and the time required for the image stabilization processing. be able to.

On the other hand, when the value of the state flag is 1 in step S101, first, in step S110, the presence or absence of the condition determination flag is checked. This condition determination flag is set with the execution of the image stabilization process in step S105, and is reset when the image stabilization process ends. That is, if the condition determination flag is reset in step S110, it is determined that the image stabilization processing has been completed, and a copy permission flag is set in the next step S111, and the state flag is set in the next step S112. Set the value to 0 and return.
If the value of the condition determination flag is set in step S110 (YES in step S110), the process returns.

(3-3) Description of Image Stabilization Process FIG. 6 is a flowchart of the image stabilization process. Here, the AIDC operation described above is executed as the image stabilization processing, whereby the photosensitive drum 41
The image forming conditions such as the voltage applied to are determined. In the image stabilization processing shown in FIG. 6, first, the condition determination flag is set in the main SW input processing described above (step S3 in FIG. 4) or the time control processing (step S5 in FIG. 4) described later. Is checked (step S201). If the condition determination flag has been set (YES in step S201), a series of image stabilization processing (steps S202 to S207) is executed.

First, the background level of the photoreceptor is detected by the AIDC sensor 210 (step S202), and the output level difference when a fixed density toner (for example, cyan) is applied to the photoreceptor drum 41 (step S202). S20
Execute 3). Here, the sensitivity of the AIDC sensor 210 is checked. Next, the halftone density of each color (C, M, Y, K) is detected using the AIDC sensor 210 (steps S204, S205, S206, and S2).
07). The grid voltage V _G , the development bias voltage V _B, and the γ correction data are read from the data ROM 203 based on the values detected by the AIDC sensor 210 (step S208). Thereafter, a time control flag described later is set (step S209), and the condition determination flag is reset (step S210).

(3-4) Description of Time Control Process FIG. 9 is a flowchart of the time control process (step S5 in FIG. 4). In step S310, the value of the state flag is checked. If the value of the state flag is 0, the process proceeds to step 311 to check whether the time control flag is set. If the time control flag is set (YES in step S311),
The time control flag is reset (step S312), the time counter is started (step S313), and the value of the state flag is set to 1 (step S314).

If the value of the state flag is 1 in step S310, step S315
Then, the started time counter is updated. If the value of the time counter is less than 10 minutes (YES in step S316), the process returns. If the value of the time counter is less than one hour (step S31
In step S318, it is determined whether the copy operation has been completed. If the copy operation has not been completed (NO in step S318), the process returns. If the copy operation has been completed in step S318, the condition determination flag is set (step S319), the value of the state flag is set to 0 (step S320), and the process returns. Time counter value is 1
If the printer SW is turned ON after the time has elapsed (YES in step S321), the condition determination flag is set (step S323), and the image stabilization process is executed before the copy operation.

(4) Other Image Stabilization Process In this embodiment, the image stabilization process in step S4 is performed by the AIDC operation. However, the image stabilization process applied to the present invention is performed by the AIDC operation. Without limitation, image stabilization processing by voltage detection, voltage detection and A
An image stabilization process or the like by both IDC operations can be considered. Hereinafter, the two image stabilization processes will be described.

The image stabilization processing based on the voltage detection is as follows.
The grid voltage generating unit 243 shown in FIG. 3, the initial values of the grid voltage V _G, to the grid of a charger 43, and applies it. Next, the surface voltage (dark portion voltage) V _O on the photosensitive drum 41 is detected, and the surface voltage V _O is detected.
Is determined to be the desired value. The detected surface voltage V
Based on the value of _O is added to the grid voltage V _G corrected voltage V _G1
Determines, the correction voltage V _G1 grid voltage V _G value plus the _{'(= V G + V G1} ) of the grid voltage generating unit 24
Set to 3.

Next, the maximum light amount data of the light emitted from the laser diode is set. This is actually on the photosensitive drum 41 which is applied in grid voltage V _G ', is irradiated with laser light of the set light amount, and detects the attenuation voltage V _I,
The maximum light amount data of the laser diode is set based on this data.

By the above processing, the desired surface voltage V _O , the grid voltage V _G ′ at which the attenuation voltage V _I is obtained, and the amount of light can be set with high accuracy.

FIG. 7 shows a flowchart of the image stabilization processing based on the above voltage detection. In this process, the image forming condition is determined by detecting the voltage of the photoconductor as an image stabilizing process almost simultaneously with the completion of the fixing temperature adjustment. First, in step S211, the main SW input process described above (step S3 in FIG. 4)
Alternatively, a time control process described later (step S in FIG. 4)
In 5), it is checked whether the condition determination flag has been set. Here, if the condition determination flag is set (YES in step S211), the next step S212.
Setting predetermined data of the grid voltage V _G applied to the grid of the charger 43 in the grid voltage generating unit 243. In step S213, the grid voltage V _G of the set predetermined data is applied to the grid of the photosensitive drum 41, and the surface voltage V _O on the photosensitive drum 41 is set.
And the value of the correction voltage V _G1 is determined based on the detected V _O so that the voltage becomes the desired V _O.

[0056] At step S214, the set the correction voltage V _G1 + grid voltage V _G to the grid voltage generating unit 243 as a grid voltage V _G ', which further sets the maximum light quantity data for irradiating a predetermined light amount to the photosensitive member .
At step S215, the by irradiating the predetermined light amount to detect the attenuation voltage V _I on the surface of the photosensitive drum 41 which is charged to a predetermined voltage, determines the maximum light quantity data of the laser by the data.

The grid voltage V _G ′ and the amount of light are determined so that the surface voltage V _O and the attenuation voltage V _I have desired values by the processing of the above steps S 212 to S 215. After the time control flag is set in the next step S216 and the condition determination flag is reset in the next step S217, the process returns.

FIG. 8 shows a flowchart of the image stabilization processing by both the voltage detection and the AIDC operation. In this process, almost simultaneously with the completion of the fixing temperature adjustment, both the image stabilization process by the voltage detection of the photosensitive member described above and the image stabilization process by the AIDC operation are performed to determine the image forming conditions. First, in step S221, the main SW input processing described above (step S3 in FIG. 4) or the time control processing described later (step S3 in FIG. 4)
In 5), it is checked whether the condition determination flag is set. Here, when the condition determination flag is set (YES in step S221), first, in steps S222 to S225, the image stabilization processing by the voltage detection shown in FIG. 7 (steps S212 to S215)
And in the next steps S226 to S230,
The image stabilization process (steps S204 to S208) by the AIDC operation shown in FIG. 6 is executed. Step S22
After the processes from 2 to S230 are completed, step S23
In step S232, the time control flag is set. In step S232, the condition determination flag is reset.

[0059] In the image stabilization process as compared with the image stabilization process by only AIDC operation or voltage detection, the photosensitive member surface potential V _O, can perform finer control of the developing bias voltage V _B and the maximum amount of light Thus, more accurate reproduction of a halftone image such as a photograph can be performed.

[0060]

According to the electrophotographic copying machine of the present invention, the necessity and timing of the image stabilization processing accompanying the copying operation are determined according to the elapsed time from the end of the previous image stabilization processing. Therefore, it is possible to minimize the delay of the copying operation due to the execution of the image stabilization process while coping with the temporal change of the environment around the copying machine.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a digital color copying machine main body.

FIG. 2 is an overall block diagram of a control system of the digital color copying machine.

FIG. 3 shows a charger 43 around a photosensitive drum 41;
FIG. 3 is a diagram schematically showing the arrangement of a developing device (for example, 45r).

FIG. 4 is a flowchart showing a main routine relating to the operation of the copying machine of the present invention.

FIG. 5 is a flowchart of a main SW input process.

FIG. 6 is a diagram showing a flowchart of an image stabilization process by the AIDC operation.

FIG. 7 is a diagram illustrating a flowchart of an image stabilization process based on voltage detection.

FIG. 8 is a diagram showing a flowchart of an image stabilization process by voltage detection and AIDC operation.

FIG. 9 is a flowchart of a time control process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Scanner 41 ... Photoreceptor drum 45a-45d ... Developing machine 48 ... Fixing device 201 ... Printer control part 210 ... AIDC sensor

Continuation of front page (56) References JP-A-57-124363 (JP, A) JP-A-62-168166 (JP, A) JP-A-56-89772 (JP, A) JP-A-60-254061 (JP) JP-A-63-261375 (JP, A) JP-A-6-11928 (JP, A) JP-A-5-45986 (JP, A) JP-A-6-75453 (JP, A) 4-267273 (JP, A) JP-A-4-199070 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 303 G03G 15/36 G03G 21/00 370- 540 G03G 21/02-21/04 G03G 21/14 G03G 21/20

Claims (4)

(57) [Claims] An irradiating means for irradiating the photoconductor with light based on image data; a charging means for uniformly charging the surface of the photoconductor; and a toner on the electrostatic latent image formed on the photoconductor surface by the irradiating means. A developing means for applying a developing bias voltage to the developing means; an amount of light irradiated by the irradiating means; a voltage on the surface of the photoreceptor uniformly charged by the charging means; Image forming condition determining means for performing image stabilization processing for determining each value of the developing bias voltage applied to the means to a value at which an image formed on the photoreceptor surface is stabilized; and image stabilization processing performed last time. When the copying operation is executed when the elapsed time from the end of the processing is less than the first predetermined time, the image stabilization processing is not performed. When the elapsed time is equal to or more than the first predetermined time and less than the second predetermined time, When performing the copy operation, Performs image stabilization processing after the copying operation ends,
Control means for controlling image forming condition determination means so as to perform the image stabilization processing before the copy operation when the copy operation is performed when the elapsed time is equal to or longer than a second predetermined time; An electrophotographic copying machine wherein the second predetermined time is longer than the first predetermined time. 2. An electrophotographic copying machine according to claim 1, wherein said image forming condition determining means determines each of said values by an AIDC operation for reading a density of a reference toner image. Copy machine. 3. An electrophotographic copying machine according to claim 1, wherein said image forming condition determining means determines each of said values by detecting a voltage value of a charged photosensitive member surface. Electrophotographic copier. 4. An electrophotographic copying machine according to claim 1, wherein said image forming condition determining means performs an AIDC operation for detecting a voltage value on a charged photosensitive member surface and reading a density of a reference toner image. An electrophotographic copying machine wherein each value is determined.