JPH03119373A - Image adjustment control system - Google Patents

Abstract

PURPOSE:To obtain an appropriate image density without spilling toner by controlling the surface potential of a photosensitive body so that a prescribed image density is obtained based on the density of a trial toner image and controlling developing conditions when the control does not ensure the prescribed density. CONSTITUTION:A trial toner image is formed on the surface of the photosensitive body 41, and its density is detected by an IDDC sensor 102, etc. A voltage applied to an electrifying charger 42 is controlled so that the appropriate image density can be obtained based on the detected density, and the surface potential of the photosensitive body 41 is adjusted. When the control of the surface potential does not ensure the prescribed image density because a range of the voltage applied to the electrifying charger 42 reaches the upper limit, control is performed to raise toner concentration (developing conditions). Consequently, an appropriate image density is obtained, and moreover, toner spilling is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image adjustment control method in an image forming apparatus using an electrophotographic process.

[Conventional technology]

Conventionally, electrophotographic processes have been widely used as a method for forming hard copy images in image forming apparatuses such as copying machines, facsimile machines, and optical printers using laser beams, LED arrays, and the like.

The electrophotographic process consists of a charging process that uniformly charges the surface of a photoconductor, an exposure process that forms a latent image by exposing the surface of the photoconductor according to image information, and a toner process that attaches toner to the latent image. It consists of a developing process to form an image, a transfer process to transfer the toner image to recording paper, and a fixing process to fix the toner image transferred to the paper.

In an image forming apparatus using an electrophotographic process, in order to obtain a hard copy image with an appropriate image density (ID),
The surface potential, exposure amount, toner concentration, etc. of the photoreceptor are set in advance, and control is performed so that the set values are maintained.

For example, by forming a test toner image on the surface of a photoreceptor,
Detecting the density of the formed toner image and controlling the toner density so that it becomes a preset toner image density.
The so-called AIDC method is often used (for example, Japanese Patent Laid-Open No. 15185/1985).

[Problem to be solved by the invention]

However, due to long-term use of the image forming apparatus, impurities may adhere to the photoreceptor. The exposure lamp deteriorates, the optical system becomes dirty, and the circuit constants of the control circuit change over time.

Therefore, in the conventional ATDC method described above, during long-term use, the toner concentration directly increases in order to maintain the image density, and as a result, the amount of toner becomes too large and the toner overflows from the developer tank (toner spills).

In addition, if the toner density and the surface potential of the photoreceptor are changed and adjusted at the same time while adjusting the image density, it becomes unclear what history each of these changes followed, which may cause problems in maintenance, etc. This will result in

In view of the above-mentioned problem, it is an object of the present invention to provide an image forming apparatus using an electrophotographic process in which a proper image density can be obtained without toner spillage.

It is an object of the invention as claimed in claim 2 to obtain an appropriate image density and to clarify the history of adjustment control to facilitate maintenance.

[Means to solve the problem]

In order to solve the above-mentioned problem, the invention of claim 1 detects the density of a test toner image formed on the surface of a photoreceptor in an image adjustment control method of an image forming apparatus having an electrophotographic process, controlling the surface potential of the photoreceptor so as to obtain a predetermined image density based on the detected density;
The invention as claimed in claim 2 is characterized in that when a predetermined image density cannot be obtained by controlling the surface potential of the photoreceptor, the developing conditions are controlled. In this method, the surface potential of the photoreceptor is variably adjusted one step at a time to obtain a predetermined image density, and when the variable step of the surface potential of the photoreceptor reaches its limit, the toner density is variably adjusted one step at a time. It is characterized by

[For production]

Test toner image (test pattern) on the surface of the photoconductor
is formed, and its concentration is detected by an AIDC sensor or the like.

Based on the detected density, the voltage applied to the charger is controlled to adjust the surface potential of the photoreceptor so that an appropriate image density is obtained.

When a predetermined image density cannot be obtained by controlling the surface potential because the range of voltage applied to the charger reaches its upper limit, the toner density (development conditions) is controlled to be increased.

Control of the surface potential of the photoreceptor and control of toner density are not performed simultaneously, but are performed one step at a time.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view showing a copying machine A. FIG.

In the figure, copying machine A includes a document feeding section 2, an exposure section 3,
It is composed of an electrophotographic section 4, a paper feed section 6, a paper discharge section 7, and the like.

The document feeding section 2 includes a document tray 11 on which a document is placed, a document feeder 12 that automatically feeds the document, a document glass 13, and the like.

The exposure section 3 includes flash lamps 21, 22, a lens 23, and the like.

The electrophotographic section 4 includes a photoreceptor belt 4 that rotates to the left in the figure.
1, a charging device 42, a developing device 44, a transfer charger 47, a separation charger 48, a cleaning device 50, a main eraser 51, a fixing device 52, and the like.

The paper feed unit 6 includes paper feed trays 61, 62, 63, and 64, paper stacks 61a to 64a1 and paper stacks 61a to 6 stored in these paper feed trays 61 to 64, respectively.
Conveyance bells) 65, 65, etc., and conveyance rollers 66, 66, etc. that selectively convey any of the sheets stored in paper 4a.
, and a swimming roller 67.

The paper discharge section 7 includes a paper discharge tray 71, a sorter 72 having a sorting turbine 73, and a double-sided copy tray 74 in which sheets copied on one side are temporarily stored when performing double-sided copying.
It consists of etc.

The surface of the photoreceptor belt 41 is uniformly charged by passing through the charger 42, and exposed by the exposure section 3 to form a latent image, which is developed by the developer 44 and visualized as a toner image. . In addition, the general operation of each part of the copy ImA is well known, so detailed description thereof will be omitted.

FIG. 2 is a block diagram schematically showing the control system of the copying machine A.

The control unit 80 controls the entire system of the copying machine A.
A memory 82 consisting of a PU 81, a ROM and a RAM, and storing various data such as programs and setting levels; an operation display section 83 for operating the copying machine A and displaying various information;
Communication unit 8 that communicates with an external device through a communication line
4. It consists of an interface section 85 that interfaces with input/output devices such as various sensors, high-voltage transformer circuits, and motors. Although not shown, the memory 82 is backed up by a battery.

FIG. 3 is a block diagram showing the arrangement of input/output equipment used in the copy 411A.

In the figure, a surface electrometer 101 for measuring the surface potential VH of the photoreceptor belt 41 and a sensor for measuring the density of the toner image on the surface of the photoreceptor belt 41 are located close to the surface of the photoreceptor belt 41. AIDC sensors 102 are respectively provided, and a light amount sensor 105 for measuring the light amount of the flash lamps 21 and 22 is provided on the side of the lens 23.
is provided. The light amount sensor 105 is mainly used to detect deterioration of the flash lamps 21 and 22. The developing device 44 also has a toner concentration (
An ATDC sensor (ATDC circuit) 103 is provided to detect the toner weight ratio T/C (wt%) by measuring the magnetic permeability of the developer.

A lamp lighting circuit 212 that can control the light intensity of the flash lamps 21 and 22 in stages, and a charger 42
a high voltage transformer circuit 225 that can control the output of the
A toner replenishment motor 111 is provided for replenishing toner when the toner concentration in the developer tank 112 of the developer 44 decreases.

The interface unit 85 connects each sensor 101 to 103 .
The output signal from 105 is amplified and the A/
D-convert the output signal from the CPU 81 as necessary.
/A Convert.

The developing device 44 uses a developer da made of a mixture of a magnetic carrier and an insulating toner, and uses a well-known magnetic brush method to attach the toner to the latent image passing through the development position.

Inside the developer tank 112, a packet roller 113 for stirring the developer da@, a conveying magnet roller 114 for conveying the developer da, developing rollers 115 to 117 for attaching toner to the photoreceptor belt 41, and the like are installed. There is.

When the toner concentration falls below the set value, or when it is desired to increase the set value, toner is replenished from a toner tank (not shown) by rotating the toner replenishment motor 111.

The replenished toner is stirred and mixed with the developer da already present inside the developer tank 112 and sent to the bucket roller 113 . Frictional charging occurs due to the stirring and mixing, and the magnetic carrier and toner are charged with opposite polarities.

The negative polarity toner is transferred to the photoreceptor belt 41 at the development position.
It adheres to the surface of the photoreceptor belt 41 by electrostatic adsorption with the surface charge. In order to prevent toner from adhering to the surface of the photoreceptor belt 41 (charges remaining even after full exposure), that is, from fogging, a developing bias VB of a predetermined voltage is applied to the developing rollers 115 to 117.

On the other hand, the paper is conveyed by the timing roller 67 in synchronization with the rotation of the photoreceptor belt 41, and the toner image is transferred onto the paper by the transfer charger 47 at the transfer position. The paper onto which the toner image has been transferred is transferred by a separation charger 48 to a device 52 consisting of a photoreceptor belt 41.
sent to.

Thereafter, the cleaning device 50 removes residual toner from the surface of the photoreceptor belt 41, and the main eraser 51 removes residual charges from the surface of the photoreceptor belt 41 in preparation for the next exposure.

In Fig. 4, the photoconductor bell) 41 is charged by the charger 42.
FIG. 3 is a diagram showing the set level of the surface potential Vl (applied to the surface potential Vl).

Note that the setting level of the charger 42 is IrH.
The HV level, referred to as "V level", is set by outputting a control signal (setting data) from the CPU 81 to the high voltage transformer circuit 225.

In FIG. 4, the Hv level is from level rlJ to "5"
When the dark potential vO exceeds 650 volts, overrange occurs. When the range is over, the level is set to "5".

For example, the dark potential ■0 of the photoreceptor belt 41 is 550
To set the HV level to ``3'', set the HV level to ``3'', and use this setting level (level 3) to
A control signal is output from the electrification charger 42 to operate the electrification charger 42. When the flash lamps 21 and 22 are not turned on, the surface potential VH given by the charger 42 is maintained almost unchanged, and the surface potential of the photoreceptor belt 41 becomes the dark potential VO.

The surface potential VH (dark potential VO) of the photoreceptor belt 41 is measured by the surface electrometer 101, but if the measured dark potential VOr is different from the potential planned by the set HV level, H ■Level data is corrected. Note that these data are stored in the memory 82.

FIG. 5 is a diagram showing the setting level of the exposure amount applied to the photoreceptor belt 41 by the exposure section 3. As shown in FIG.

The exposure amount is determined by the flash lamp 2 from the lamp lighting circuit 212.
It is set by controlling the lighting power supplied to 1.22. The setting level of the exposure amount is referred to as "rEXP level", and the exposure amount here is expressed not by the exposure amount itself but by the bright potential VR of the photoreceptor belt 41 due to the exposure.

In FIG. 5, for example, in order to set the bright potential VR to 60 volts, the EXP level is set to "r4", a control signal is output from the CPU 81 according to this setting level (level 4), and the flash lamp 21.22 is outputted from the CPU 81. Exposure by

The surface potential VH (bright potential VR) of the photoreceptor belt 41 is measured by the surface electrometer 101, but if the measured bright potential VRr differs from the potential planned by the set EXP level, EXP Correction of level data is performed. Note that these data are stored in the memory 82 as described above.

The bright potential VR is the potential corresponding to the part that has been neutralized by total exposure (the part corresponding to the white background of the original), and even under the best conditions, it will not reach zero volts due to residual charge.
When the bright potential VR becomes higher than a certain potential VRL, a small amount of toner adheres there, and the background becomes TiIJ! A
<Dirty condition, so-called fogging occurs. Therefore, to prevent the bright potential VR from becoming higher than the potential VRL,
The HV level or EXP level is set within a possible range. Note that the potential VRL varies slightly depending on the developing bias VB, but is approximately constant at about 95 volts.

Although not shown in this embodiment, the developing bias VB can also be controlled in stages by setting a set level (VB level).

Further, the value of the toner weight ratio T/C can also be controlled in stages by setting a setting level (TC level).

The TC level is set in increments of 1 when the toner weight ratio T/C is between 5 and 8.

The control for maintaining the toner weight ratio T/C at the set value is as follows:
This is done at any time during the copying operation, but the toner weight ratio T/
The setting value of C is changed in an image adjustment operation described later.

Generally, as the value of the toner weight ratio T/C increases, the developing ability increases. By increasing , it is possible to obtain a hard copy image with an appropriate image density ID. Therefore, in the image adjustment operation described later, when the output of 42 during charging reaches the upper limit at the standard toner weight ratio T/C, the TC level is changed upward. However, if the toner weight ratio TC exceeds 8 [wt%], excessive driving torque will be applied to the bucket roller 113, etc., and problems such as toner overflowing from the developer tank 112 will occur, so the toner weight ratio T/C The upper limit of 8 [W
It is specified in [%].

In addition, the Hv level, EXP level, or TC level is
For example, it is reset by a program reset that can be operated by a service person, but unless otherwise, it is stored even if the power is turned off, and adjustment is started from each stored level.

Next, the operation of the copying machine A will be explained according to the flowcharts of FIGS. 6 and 7.

FIG. 6 is a main flowchart showing the overall operation of copying machine A.

When the power is turned on, initialization is performed first (step #1).
1) Performs image adjustment (step #12), and then starts a timer T1 to obtain the timing for performing image adjustment (step #13).

Then, it is determined whether or not the print key on the operation display section 83 has been pressed (step #14).During this time, the timer T1 continues to measure time.

If the print key is pressed (YES in step #14), it is determined whether or not the timer T1 has timed up (step #15), and if the timer has timed up, image adjustment is performed (step #16). ), if the time has not expired, image adjustment is not performed and the copying operation is started immediately (step #17).

The copying operation is repeated until a predetermined number of copies are completed (step #18L), after which the timer TI is reset (step #19), and steps #13 and subsequent steps are repeated.

FIG. 6 is a flowchart showing the image adjustment operation.

When performing image adjustment, first save the last data of HV level, EXP level, and TC level to memory 8.
2 and set as their respective levels (step #31).

Photoreceptor belt 41, developer 44, cleaning device 50
, main eraser 51, etc. (step #32
).

The charger 42 is turned on (step #33).

The surface potential VH (dark potential VO) of the photoreceptor belt 41 is measured by the surface potential meter 101 (step #34).

A test toner image (test pattern) is developed on the photoreceptor belt 41 (step #35), thereby creating a solid black image.

The density of the test pattern is detected by the AIDC sensor 102 (step #36).

Based on the output of the AIDC sensor 102, it is determined whether the density of the toner image is appropriate as desired (step #37).

If it is not appropriate, it is determined whether the HV level is at the maximum level (step #51).

If it is the maximum level, it is determined whether the TC level is the maximum (step #52).

If the TC level is not at the maximum level, the TC level is increased by 4.1 (step #57).

Replenish toner and stir developer da in step #
58), proceed to step #35.

If the HV level is not at the ll level in step #51, raise the HV level (step #55),
Proceed to step #33.

Light up the flash lamps 21 and 22 (step #
3B).

The amount of charge on the photoreceptor belt 41 after exposure, that is, the bright potential V
Measure Rr (step #39).

The measured bright potential VRr is stored in the memory 82 (step #40).

It is determined whether the bright potential VRr is smaller than the potential VRL (step #41).

If YES in step #41, the image adjustment ends.

At this time, no fogging occurs in the image.

If NO in step #41, it is determined whether the EXP level is the maximum level (step #61).

If the EXP level is at the maximum level, the EXP level cannot be increased any further, so a warning is displayed that fogging may occur, and the service station is notified of this via communication (step #62). Finish the adjustment.

If the EXP level is not at the maximum level, the EXP level is raised (step #63) and the process proceeds to step #38.

In the image adjustment flowchart described above, in order to ensure a predetermined image density TD, the HV level is first adjusted, and when the HvC level reaches the maximum level and no further adjustment is possible, the TC level is then adjusted. adjust.

If both the HV level and the TC level have reached the maximum level, the EXP level is adjusted to prevent fog from occurring.

That is, in order to obtain a predetermined image density ID, the HV level is first adjusted, and the TC level is adjusted only when the HV level cannot be adjusted completely. As a result, a proper image density ID can be obtained, the TC level can be prevented from increasing rapidly, and toner spillage can be prevented.

When performing image adjustment, first save the last data of HV level, EXP level, and TC level to memory 8.
Since the settings are read from 2, adjustments are made more quickly than when starting from each initial value.
The time required for image adjustment becomes shorter. Furthermore, it is possible to prevent control disturbances due to discrepancies between the TC level output to the developing device 44 and the actual toner density state of the developing device 44.

Also, instead of adjusting each level at the same time, you can adjust one level at a time and store each status in the memory 8.
2, the history of the adjustment control becomes clear and maintenance can be performed easily.

In addition, in the overall flowchart of copying machine A, image adjustment is performed once when the power of copying machine A is turned on, and after that, the copying operation is performed after a certain period of time has elapsed after the copying operation is stopped. Since the image adjustment is performed when the copying machine A is about to be printed, even if the copying machine A is left on and off for a long period of time, the image adjustment is performed efficiently and the best image quality can always be obtained.

According to the embodiment described above, it is possible to set the image density ID to a target as appropriate as possible, and to prevent fog from occurring as much as possible.

According to the embodiments described above, each level, such as the HV level, is
The levels are stored even when the power is turned off, and the next time the power is turned on, adjustment is started from each stored level, so image adjustment can be performed quickly. Additionally, if a certain period of time has passed since no copying operation was performed, image adjustment is performed prior to the next copying operation.
Even if the state of the image changes over time, the image is always adjusted to be appropriate.

In the embodiments described above, the configuration and processing operations of each part of the copying machine A can be modified in various ways other than those described above.

〔Effect of the invention〕

According to the invention of claim 1, in an image forming apparatus using an electrophotographic process, toner spillage does not occur;
Appropriate image density can be obtained.

According to the second aspect of the invention, a proper image density can be obtained, and the history of the adjustment control can be made clear to facilitate maintenance.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing a copying machine, FIG. 2 is a block diagram showing an outline of the control system of the copying machine, and FIG. 3 is a block diagram showing the arrangement of input/output equipment used in the copying machine. Figure 4 shows the setting level of the surface potential applied to the photoreceptor belt by the charger, Figure 5 shows the setting level of the amount of exposure applied to the photoreceptor belt by the exposure section, and Figure 6 shows the entire copying machine. 7 is a main flowchart showing the operation of FIG. 7, and FIG. 7 is a flowchart showing the operation of image adjustment.

Claims (2)

[Claims] (1) In an image adjustment control system for an image forming apparatus having an electrophotographic process, the density of a test toner image formed on the surface of a photoreceptor is detected, and a predetermined image density is determined based on the detected density. An image adjustment control method comprising: controlling the surface potential of the photoreceptor so that a desired image density is obtained; and controlling developing conditions when a predetermined image density cannot be obtained by controlling the surface potential of the photoreceptor. (2) In an image adjustment control method for an image forming apparatus having an electrophotographic process, the surface potential of the photoreceptor is variably adjusted one step at a time so as to obtain a predetermined image density, and the surface potential of the photoreceptor is varied. An image adjustment control method characterized by variably adjusting toner density one step at a time when a step reaches its limit.