JPS6162073A - Exposure control device for color copying machine - Google Patents

Abstract

PURPOSE:To reduce a color difference generated in continuous copying operation and to improve detecting accuracy by correcting a power supply voltage to be supplied to an exposure lamp in the succeeding process by a surface potential detecting value of a setting part of a developing machine, and when the deviation between a reference value and the surface potential of the succeeding process exceeds an allowable value, compensating the power supply voltage moreover. CONSTITUTION:A surface potential detecting signal at a position of the developing machine 9a is compared with a reference signal obtained from a correcting reference voltage generating circuit 21 by a comparator 22 through a detecting circuit 20. If a difference is generated between both the values, the detected signal is corrected, and when the signal is included in a control objective level, development is executed. The voltage value of an exposing power supply 26 is previously corrected so that the difference between the detecting signal of the surface potential of the position of the developing machine 9b in the succeeding developing process which is formed by a density pattern 31 and a reference signal becomes almost the same as the difference between the detecting signal of the preceding developing process and the reference signal by multiplying the latter difference by a positive correction factor. If the difference between the detecting signal of light potential at the position of the developing machine 9b and the reference signal exceeds the control objective level, the difference is multiplied by the 2nd correction factor to correct the power supply voltage and to control the voltage value of the exposing power supply 26.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is designed to obtain copies with small color differences between copies and continuous copies under predetermined standard setting conditions, and with stable image density over a long period of time. 2 - Relating to an exposure control device for a copying machine.

[Conventional technology]

Conventional exposure control devices for copying machines, for example, those used to expose black-and-white or monochromatic frames, detect the potential (bright potential) of the background area at the position of the shutter and developer, and calculate the deviation from the reference value. However, there are methods that attempt to maintain a stable bright potential over a long period of time by applying the calculated correction value to the exposure in the next copying process. According to such a configuration, within a certain potential level (for example, 1
00V±20V), it is possible to supply copies with stable image density.

[Problem that the invention seeks to solve]

However, according to the conventional exposure device for a copying machine, when the above-mentioned control content is introduced into a color copying machine, the bright potential is kept within a certain level (for example, 100V) in each color separation image forming process.
±20v) Even if it were possible to reduce the amount of electricity, it would result in differences in the colors reproduced on the copies, making it difficult to supply copies with the same color tone over a long period of time.

In addition, if we try to solve this problem by narrowing the allowable fluctuation amount (target potential level) of the bright potential (for example, 100 V ± 5 V), it will be necessary to improve the performance of the potential detection element and prevent detection errors. There are problems that require countermeasures, complicate the configuration, and increase costs.

[Means and operations for solving the problem] The present invention has been made in view of the above, and in order to reduce the color difference that occurs during continuous copying, the following method is used based on the difference between the bright potential detection value and the reference value. The present invention provides an exposure control device for a color copying machine that controls the amount of exposure in a color development process.

[Example] Hereinafter, an exposure control device for a color copying machine according to the present invention will be described in detail.

FIG. 2 shows an example of an electronic copying apparatus to which the present invention is applied, in which a platen 1 is placed with an original and moves back and forth at the same time as copying, and an illumination lamp that irradiates light over a predetermined width of the platen 10 that moves back and forth. a lamp 2, a mirror 3b that reflects the light reflected by the lamp on the document surface in a predetermined direction, and a mirror 3b.
A lens 4 that focuses the light at a predetermined position;
A color separation filter 5 that inserts a filter of a color corresponding to the toner color of the developing machine into the optical path of the other light, a mirror 6 that reflects the light that has passed through the filter 5 in a predetermined direction, and a filter that reflects the light that has passed through the filter 5 in a predetermined direction. A photoreceptor drum 7 is exposed to light, a charger 8 charges the surface of the drum 7 in advance before exposure, and the electrostatic latent image formed on the surface of the photoreceptor drum 70 by the exposure is transferred once the drum rotates. A developing machine 9 that sequentially develops toner each time
a, 9b, 9c, and 9d, and a surface potential sensor 1 that detects the surface potential of the electrostatic latent image near each of the developing machines 98 to 9d.
0 g, 10b.

10c and 10d, a paper tray 11 into which a required number of copies are loaded, a paper feed roll 12 which feeds a sheet of paper from the paper tray 11 at a predetermined timing, and a paper feed roll 12 from which the roll 12 is fed. A transport mechanism 13 that transports the fed paper to the transfer position, a transfer drum 14 that wraps the fed paper and rotates for each transfer, and a high voltage installed inside the drum to perform the transfer. A transfer charger 15 that performs the transfer, a fixing device 16 that fixes the color transferred image on the paper surface after the transfer, an ejection tray 17 that stores the paper after the fixing, and a transfer device corresponding to each of the developing machines 9a to 9d. A cleaner 18 cleans the surface of the drum 7 every time the drum 7 is finished.

The operation of the above configuration will be described. As shown in FIG. 2, an original to be copied is placed on the platen 1, and the illumination lamp 2 illuminates it. Scanning mirror 3 that scans the original
The original is scanned in synchronization with the 0 rotation of the photoreceptor drum 1 along with the illumination lamp 2, and the image of the scanned original is reflected on the mirror 3.
b. The surface of the photoreceptor drum 7 is exposed to light through the optical system lens 4, color separation filter 5, and mirror 6.

Here, the color separation filter 5 is configured to
One of the filter colors green, red, and neutral density (ND) is automatically selected. On the other hand, the photoreceptor drum 7 is uniformly charged by the charger 8 and maintains a uniform surface potential. At the same time, since the light passes through the area where the light reaches by the mirror 6, an electrostatic latent image with a high electrostatic contrast is formed on the surface of the photoreceptor drum 70.Next, for example, cyan, magenta, yellow and black The electrostatic latent image described above is developed by the developing machines 9a to 9d that supply developer for each color.On the other hand, transfer paper for transferring the developed image is transferred to a paper tray by a paper feed roll 12. 11) The paper is fed, passes through the transport mechanism 13, is sent to the transfer drum 14, and is held by the transfer drum 14.

Corona discharge is performed on the transfer paper from the back side by a transfer charger 1s in the transfer drum 14, and the developed image on the photosensitive drum 7 is transferred to the paper. When the development and transfer of a predetermined number of colors is completed by multiple rotations of the photoreceptor drum 7 and transfer drum 14, the transfer paper is separated from the transfer drum 14, sent to the fixing device 16, and then heated. After being compressed, the transferred toner image is fixed on the paper and stored in the ejection tray 17, completing the entire process.

FIG. 1 shows an embodiment of the present invention, and shows a surface potential sensor 1.
Developing machines 9a to 9d based on each output signal of Ga to lOd.
a detection circuit 20 that detects the surface potential of the drum 7 at each installation position; and a reference voltage generation circuit 21 that generates a reference voltage for comparison with the output voltage of the detection circuit 20.
, a comparison circuit 22 that compares the output voltage from the detection circuit 20 and the output voltage from the reference voltage generation circuit 21, and an arithmetic control circuit 23 that performs arithmetic processing based on the output signal of the comparison circuit and outputs a control signal. , a storage circuit 24 connected to the circuit 23 and storing calculation results, data, etc., and a charging power source 25 that controls the voltage applied to the charger 8 based on a control signal from the calculation control circuit 23. Arithmetic control circuit 23
The exposure power source 26 is configured to control the voltage supplied to the lamp 2 based on a different control signal. Incidentally, the concentration pattern for surface potential detection necessary for operating the process control circuit shown in FIG. 1 is as shown in FIG. This pattern is set in the non-developing area of the platen, and the surface potential sensor 10
Detected by a to 10d.

The operation of the above configuration will be explained according to the flowchart shown in FIG. In the following explanation, the exposure control operation will be explained using the case of three-color separation as an example, but the present invention can also be used when performing more color separation or two-color separation, or when performing thin or monochrome color copying. It is possible to apply For convenience, the order of arrangement of the developing machines and the order of the developing steps are cyan, magenta, and yellow, but the present invention is applicable to other cases as well. For black, the fourth developing device 9d is used.

Density patterns 30.degree. 31 shown in FIG. 3 are provided on the non-image area of the document table of the color electrophotographic copying machine shown in FIG. 2, and electrostatic latent images of each pattern are formed on the photosensitive drum 7.

In this case, the voltage value applied to the lamp 2 is determined by the memory circuit 24.
is based on the value stored in Therefore, the initial exposure amount changes depending on the stored voltage value. The details will be described later. Next, surface potential sensors 10a to 1oday electrostatic latent images disposed near the developing machines 98 to 9d are detected. At this time, first, the surface potential detection signal V! of the electrostatic latent image of the cyan developing process formed by the density pattern 31 for exposure control at the position of the cyan developing machine 9m! '
26c is the reference signal U! of the reference voltage generation circuit 21 for correction, which is passed through the detection circuit 20 shown in FIG. . . and comparison circuit 2
Compare within 2. Reference signal U3°. and detection signal vw
When the difference vscrc from oe is outside the control target level (for example, Dsocl > 20 V), the power supply voltage ve in the cyan mode of the illumination lamp 2 is corrected according to equation (1), and the exposure The voltage value v of the power supply 26 for
By controlling the reference signal c; and the detection signal U,. .

The difference with V! . 0 is within the control target level (for example, IV!G
el ≦20v). Therefore, cyan development is the difference between the reference signal 4n and the detection signal IJsoc.

. is executed after entering the control target level. In addition,
The difference between the reference signal and the detection signal UIOC. When C is within the control target level, no correction operation is performed and the process moves to the next operation.

ΔvC:=βs-*V20C-...(1) However,
Vt. ,! The difference between the surface potential detection value IJsec at the position of the cyan developing machine 91 of the electrostatic latent image formed in the density pattern 31 in the cyan developing process and the reference value page term [V first. = U bird. C-Siπ] ΔVcE Correction value of power supply voltage vc of dew source power supply 26 (cyan) β1! Correction coefficient (<0) Next, the correction value Δvc of the power supply voltage of the exposure power supply 26 obtained by the above correction is stored in the storage circuit 24. When this operation is executed, the bright potential in the cyan developing process has already been controlled to within the target level, and this operation is performed to maintain this bright potential at the same level in the next copying process. Therefore, at the beginning of the copying process, the exposure light amount is determined based on the previously stored correction value, so even during long-term copying, the variation in bright potential is maintained at the same level. After completing this process, the magenta development process begins.

First, according to the correction formula of equation (2), the density pattern 31
Detection signal U2 of the surface potential at the position of the magenta developing machine 9b of the electrostatic latent image formed by the magenta developing process
The difference between oM and reference signal UIOM is v, OM(VfiOM
The voltage value VM of the exposure power supply 26 for the illumination lamp 2 is corrected in advance so that "U!OM - U!OM)" is approximately the same as the difference VIOC between the detection signal TJioC and the reference signal in the cyan developing process. .

In the case of
Although the values of V20C and vzoM do not necessarily have to match, the correction coefficient α1 is positive because the signs are corrected so that they always match.

ΔVM = xαt * Vioc...-
(2) However, ΔVBg is the correction value of the power supply voltage VM of the optical power supply 26 (magenta) αl: correction coefficient (>0) Furthermore, the magenta developing machine of the electrostatic latent image in the magenta developing process obtained as a result of correction using the above formula Bright potential detection signal U at position 9b!・M and reference signal Ul! OM On Vz
When oa is outside the control target level (e.g. lV20M
+ > 20 V), the voltage value VM of the exposure power source 26 is controlled by causing the V-zenta mode of the illumination lamp 2 to perform a correction calculation of the off power supply voltage VM according to equation (3). shi, reference signal 020M and detection signal TJ20
The difference between vgoM and M is within the control target level (for example, lV20
M+ ≦20v). Therefore, for magenta development, the difference between the reference signal U20M and the detection signal U20M is V2.
Executed after 0M falls within the control target level.

ΔVM = β2 * VsoM”...(3) However, V
The difference between the surface potential detection value UilOM at the position of the 1-zenta developing machine sb of the electrostatic latent image in the magenta developing process formed by the density pattern 31 and the reference value 6- (VIIOM x UsoM-Us Agency) ] ΔvM: Correction value of the power supply voltage vM of the exposure power supply 26 (magenta) β-quake: Correction coefficient (ku0) Note that the difference between the reference signal U!6M and the detection signal U!6M is V!gIM
is within the control target level, this operation is not performed,
Move on to the next operation. Next, ΔVM is stored in the storage circuit 24. When this operation is executed, the bright potential in the magenta developing process is already controlled within the target level, and ΔVM is used as a correction value to maintain this bright potential at the same level in other copying processes. . Next, according to the correction equation (4), the surface potential detection signal us OY and the reference signal U! at the position of the inil-developing machine 9c of the electrostatic latent image of the yellow developing process formed by the density pattern 31 are determined. 07 difference V*oy (Vl(17= Usoy −Usoy
) are the detection signals U, ·M and the reference signal U in the magenta development process! The potential value V of the exposure power supply 26 for the illumination lamp 2 is set in advance so that the difference in OM is approximately the same as the difference Via@M.
Correct Y. In this case as well, l>σ, as mentioned earlier,
Although the values of vOM and VlOr do not necessarily have to match depending on the photoreceptor material used, the position of the developing machine, etc., the correction coefficient α3 is positive because the signs are corrected so that they always match.

ΔVY−α* * V2gIM ・・・・
...(4) However, ΔVY: Power supply voltage V of the exposure power supply 19
Correction value of y (ye a-) α snow: correction coefficient (〉0) Furthermore, the detection signal of the bright potential at the position of the yellow developing machine 9C of the electrostatic latent image in the yellow developing process obtained as a result of the correction using the above formula Difference between TJzoy and reference signal LJoy VII
When OY is outside the control target level (e.g. ttd 1Vzo
yl > 20 V), the voltage value V of the exposure power source 26 is calculated by correcting the power supply voltage Vy of the illumination lamp 2 in the 4-mode according to the following correction formula (5).
By controlling y] the reference signal plane and the detection signal UIIO
The difference V20Y from Y is made to fall within the control target level (for example, 1v snow◎Y11≦20V). Therefore, the fourth development is the difference between the reference signal 6i and the detection signal tJ*oy vs.
Executed after oy falls within the control target level.

ΔVy-βs * Vgoy control-(s) However, V20Y! Difference between the detected value U26Y of the electrostatic latent image in the yellow developing process at the yellow developing machine 9c and the reference value IdL (V2oy W Usoy - Umoy) Δv = Exposure Correction value for power supply 19 power supply voltage V (yellow) β3 low correction coefficient (<0) As mentioned above, reference signal plane and detection signal U! 07 difference vi
This operation is not performed when oy is within the control target level. The obtained ΔVy is stored in the storage circuit 24.

Here, once the copying process is completed, the correction results ΔVc, ΔVM, and ΔVY are stored in the storage circuit 24 until the next copying process, and are used when controlling the voltage value of the exposure power source 26 in the next copying process. becomes the initial value. If the copying process is not completed, the stored correction result Δ will be used in the next copying process.
The voltage value of the exposure power supply 26 is controlled based on Vc, ΔVM%ΔVd. In the above case, the second developing process is performed based on the detected value of the bright potential at the position of the first developing machine 9a in the first developing process. In this method, the amount of exposure light in the third development step is controlled based on the detected value of the bright potential at the position of the second developing machine 9b in the second further development step. the first of
Based on the detected value of the bright potential at the 9th position of the developing machine, the third
It is okay to control the exposure light amount in the developing process.Differences between the black detection signal and the reference signal for each of cyan, magenta, and yellow can be determined by controlling the exposure light amount in these exposure light amount control steps.
Since V2mM%VIOT is kept at the same sign and level, it is a standard setting that occurs due to fluctuations in bright potential that occur during continuous copying and due to fatigue and deterioration of the photoreceptor material caused by long-term copying. It is possible to reduce the color difference between the copied image and the copied image under the conditions.

In the above example, the monochromatic color, two-color separation image forming process, and black toner image forming process were not described, but if you want to perform the exposure side, you can perform it in the same manner as above. The relationship between the correction coefficients based on the calculation is as described above. In addition, the correction results ΔWe, Δ■M
In order to store 1ΔVY in the memory circuit, 24 as appropriate, there is a change in the bright potential even in 3-color separation, 2-color separation, and monochromatic power 2-5VQoy is maintained at the same sign and level, and the color difference occurring between each separation process is (For example, the color difference that occurs when a document having cyano, magenta, and yellow colors is copied using different color separations) can also be reduced.

Sara K.

When the power is turned on, by accurately correcting the exposure light amount based on the bright potential at the position of the first developing machine 9m in the first developing process, there is no need to carry out negative feedback control of the exposure light amount during copying. Therefore, a decrease in copying speed that may occur during exposure control can be minimized.

Furthermore, if it becomes possible to detect the potential at a certain position by analyzing various properties such as charging and capital reduction of the photoreceptor drum 7, and predict the potential in each device in the subsequent process, the surface potential sensor 10a .about.10d are not necessarily all necessary, and can be installed at least in front of the first developing device 9a.If K is arranged in this way, it is possible to keep the cost low.

The electrostatic latent image forming process itself is not limited to the Carlson process, but other processes such as the NP process can be used, and the present invention can be applied to any of these various image forming process electronic copying machines.

Further, as an embodiment of the present invention, a copying machine equipped with a four-color developing device (I8) and a drum-shaped photoreceptor has been described, but it can be applied to any machine having a developing device of two or more colors. However, it is clear that similar effects can be applied to belt-shaped photoreceptors, which fall within the scope of the present invention.

〔Effect of the invention〕

As explained above, according to the exposure control device for a color copying machine according to the present invention, the amount of exposure light in the next developing process is controlled based on the difference between the detected bright potential and the reference signal. The resulting color difference can be reduced, and detection accuracy can be improved without increasing costs.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram of a color copying machine to which the present invention is applied, FIG. 3 is a density pattern diagram for surface potential detection, and FIG. 70-Chart showing the process of the invention. Explanation of symbols 2... Lamp, 4... Lens, 5... Color separation filter, 7... Photosensitive drum, 8...
Charger, 9 a to 9 d = developing machine, I Q a
-10d □'' surface potential sensor, 14... Transfer drum, 15... Transfer charger, 16... Fixing device, 2o... Detection circuit, 21... Reference voltage generation circuit, 22...・Comparison circuit, 23... Arithmetic control circuit, 24... Memory circuit, 25... Charging power source, 26... Exposure power source. Patent applicant Fuji Zeμ, Kusu Co., Ltd. agent Patent attorney Matsu Shin Hara 2 Patent Attorney Seishun Muraki Patent Attorney
1) Tadaozu Patent Attorney
Jun Ueshima - Patent attorney Hitoshi Suzuki (20)

Claims (1)

[Scope of Claims] A potential sensor detects the potential (bright potential) of a background area formed on the surface of a photoreceptor in each color separation image forming process of a color electrophotographic copying machine equipped with a plurality of developing machines, In an exposure control device for a color copying machine that compares and calibrates a predetermined bright potential reference value and a detected value for each color separation step, and controls the amount of exposure light in the next color separation exposure step based on the result, a first correction means for correcting a power supply voltage supplied to an exposure lamp for exposure in a subsequent process by multiplying a surface potential detection value at a developing machine installation site before a process by a positive correction coefficient; When the deviation from the surface potential detection in the subsequent process exceeds the allowable value, a second value is added to the surface potential detection value.
an exposure control device for a color copying machine, further comprising a second correction means for further correcting the correction made by the first correction means by a value multiplied by a correction coefficient.