JPH0679183B2 - Dark potential controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling an electric potential on a photosensitive material in an apparatus for obtaining image recording by using the photosensitive material charged by a charger.

[Background technology]

In this type of equipment, the operator may want to increase or decrease the density of image recording according to his or her preference.In an electrophotographic copying machine, the density of an image to be copied is arbitrarily changed with respect to the density of the original to be copied. There is a background mode selection switch that changes the amount or development bias voltage. When the operator wants the copy density to be higher or lower than the original density according to his or her preference, this mode selection can obtain the desired density by changing the exposure amount or the developing bias potential.

However, when the copy density is changed as desired, the density gradation may be insufficient when this is performed with the exposure amount or the developing bias. When the development curve showing the characteristics of the latent image potential and the copy density has a slope, sufficient density gradation cannot be obtained by the above method alone.

In order to obtain a sufficient gradation, this can be done by changing the dark potential on the photosensitive material. Conventionally, when the copy density is changed according to preference, it is performed by the exposure amount or the development bias as described above, and the method of changing the dark potential is not adopted. Missing.

Even if the slope of the development curve showing the characteristics of the latent image potential and the copy density is raised, it is necessary to cope with this, because the slope of the development curve is raised, the dark potential is increased. It is necessary to change the electric potential control method at this time.In this case, when the photosensitive material used is an organic photosensitive material whose chargeability changes with fatigue, even if the color background mode is selected Potential stabilization control is required. However, in accordance with the selection of the color background mode, as will be described later, only by changing the target potential as a target, a predetermined potential cannot be obtained from the first copy for such a sensitive material,
It takes a long time to set the potential for several cycles every time each mode is selected. In this case, it takes time to obtain the first copy.

[Problems of the Invention]

The present invention has been made in view of the above points, and detects the charging potential of the photosensitive material and controls it so that the charging potential becomes a target value. It is to try to converge to.

[Means and actions for achieving the object]

Therefore, the present invention, therefore, detects the dark potential V _DDP of the photosensitive material and controls the wire applied voltage V _W and the grid applied voltage V _G of the charger so that the dark potential V _DDP becomes the target value. In addition, when the density adjustment mode is selected by the mode selection means for selecting the normal mode and the density adjustment mode, the dark potential according to the selected density mode of the density adjustment modes. target value setting means for setting a target value of V _DDP, the charger as the dark potential V _{DDP-sensitive} material is equal to the target value set by a predetermined target value or the target value setting means in the normal mode the wire and control means for controlling the applied voltage V _W and grid applied voltage V _G, storage means for storing wire applied voltage V _W and grid applied voltage V _G of the charger which is controlled by the control means, the motor When a different mode is selected by the battery selecting means, the wire application voltage V _{W END} and the grid application voltage V _{G END} of the charger after the previous control stored in the storage means are expressed by the following equations. An initial value setting unit that corrects a given voltage value and sets it as an initial value for dark potential control is provided.

V _W = V _{W END} + E * ΔV _DDP V _G = V _{G END} + ΔV _DDP where ΔV _DDP is the difference between the previous dark potential target potential and the dark potential target potential of the selected mode, and E is the sense. The relation E between the dark potential V _{DDP of the} material and the voltages V _W and V _G applied to the charger V _DDP = α * V _W + β * V _G + Const. β) / α.

According to the present invention having such a configuration, in a device for obtaining an image recording using a light-sensitive material, a mode selecting unit for selecting a normal mode and a density adjusting mode, and a case where the density adjusting mode is selected by the selecting unit, Target value setting means for setting the target value of the dark potential according to the selected density mode of the density adjustment modes, and the dark potential of the photosensitive material is set by a predetermined target value in the normal mode or the target value setting means. Since it is configured to include a control unit that controls the voltage applied to the charger so as to be equal to the target value,
The dark potential can be controlled according to the selected density mode of the density adjustment modes, and good image recording can be performed according to the density of the document.

Further, according to the present invention, when different modes are selected by the storage means for storing the voltage applied to the charger controlled by the control means and the mode selection means,
The applied voltage after the previous control stored in the storage means,
The change in the dark potential target value due to the mode change is multiplied by the coefficient determined by the relational expression between the dark potential of the photosensitive material and the applied voltage to the charger to correct the dark potential control. Since the initial value setting means for setting the initial value is also provided, even when a different mode is selected by the mode selecting means, a predetermined correction is applied to the applied voltage after the previous control stored in the storage means. The voltage applied to the charger can be determined by applying the above-mentioned procedure, and it is possible to control the dark potential with higher accuracy by making use of the applied voltage after the previous control. To a new target potential, an applied voltage suitable for quickly converging to a new target potential can be applied to the charger, the dark potential on the photosensitive material can be stably maintained, and a predetermined potential can be obtained from the first image recording. To obtain good image quality It can be.

Further, according to the present invention, a predetermined correction value to be applied to the applied voltage after the previous control stored in the storage means is applied to the dark potential of the photosensitive material and the charger by the change amount of the target value of the dark potential due to the mode change. Since the voltage value is multiplied by the coefficient determined by the relational expression between the applied voltage and the applied voltage, it is possible to properly determine the applied voltage suitable for promptly converging to a new target potential when the mode is switched. It becomes possible to control the target dark potential in a short time.

〔Example〕

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

FIG. 1 shows an embodiment of the present invention, which is applied to an electrophotographic copying machine having a belt-shaped photosensitive material.

In the figure, (1) is an exposure unit, (2) is an exposure unit (1)
A belt-shaped photosensitive material on the surface of which an electrostatic latent image is formed in response to exposure by the exposure device (1) around the photosensitive material (2).
A developing device (3) arranged in the subsequent stage to perform development by adhering toner to the electrostatic latent image, and a potential arranged immediately before the developing device (3) to detect the surface potential of the photosensitive material (2). A sensor (4) and a charger (5) for charging the surface of the photosensitive material (2) prior to the exposure are provided.

In this embodiment, the charger (5) is a screen corotron having a grid electrode, and a wire (6) for applying a high voltage to cause corona discharge and between the wire (6) and the photosensitive material (2). It is composed of the arranged grids (7).

(8) is a high voltage power supply (HVPS) that supplies a predetermined voltage to each member of the charger (5) in a copy cycle,
(9) is a control unit that variably controls the voltage value supplied from the high-voltage power supply unit (8) to the wire (6) and the grid (7) based on the detection output of the potential sensor (4), as will be described later.
This further performs the following control when the mode for increasing or decreasing the copy density is selected. That is, the control unit (9) controls the charging potential of the photosensitive material (2) by the potential sensor (4).
The voltage applied to the charger (5) is controlled according to the output obtained by detecting so that the charging potential becomes a target value. However, when the above mode is selected, the target of the potential to be controlled depends on the selected mode. Based on the voltage applied to the charger (5), which is set to a new value, and which is the optimum voltage to be applied to the charger (5), which is automatically controlled in the previous copy cycle. From the beginning, control is performed so that an optimum voltage can be obtained for a new selection mode.

FIG. 2 shows an example of the detailed configuration of the control unit (9).
A multiplexer (10) to which the dark potential V _DDP at the developing machine installation position output from the potential sensor (4) is added, and A / D conversion that converts an analog signal output from the multiplexer (10) into a digital signal and outputs the digital signal. Device (11) and operation unit (1
2), a RAM (13) that is output to the calculation unit (12) to store the calculation result and data, and a digital control command for setting the corona wire applied voltage V _W output from the calculation unit (12) to analog. The D / A converter (14) for converting and outputting to the high-voltage power supply section (8) and the digital control command for setting the grid applied voltage V _G output from the calculating section (12) are converted into analog and high voltage. D / A converter (1 that outputs to the power supply section (8)
5) consists of and.

The calculation unit (12) calculates the dark potential based on the data output from the A / D converter (11), compares the calculation result with a target value, and applies the wire to the charger (5). In the case of the color background mode which outputs a command corresponding to the applied voltage V _W and the grid applied voltage V _G, and which selectively changes the copy density, when entering the dark potential control of the copy cycle, the color background selection mode is set. Therefore, the charger (5) is obtained as a result of the potential stabilization control of the unnecessary applied voltage in the preceding copying cycle.
It calculates based on the optimum applied voltage to and outputs a control command.

The multiplexer (10) is for selecting from other signals not shown, and when the detection output from the potential sensor (4) is selected, this is input to the A / D converter (11). To be done.

In FIG. 1, a belt-shaped photosensitive material (2) is adapted to be rotated in a direction of an arrow a at a constant peripheral speed. When a document is copied, its surface is charged by a charger (5). After being charged, the content of the original is exposed by the exposure device (1), an electrostatic latent image is formed on the surface of the photosensitive material, and toner is applied to the electrostatic latent image by the developing device (3). Attached,
Development is performed, and the toner image is transferred to a copy sheet by a transfer device (not shown).

Here, between the dark potential V _DDP of the photosensitive material (2), the corona wire applied voltage V _W , and the grid applied voltage V _G , V _DDP = α * V _W + β * V _G + Const. The following relationship holds in the stable discharge region. Further, there is a relationship of β> 2 * α between the coefficients α and β in the above equation. That is, the influence of the grid applied voltage V _{G on} the dark potential V _DDP is more than twice as large as that of V _W.

In the dark potential control device having the above-mentioned configuration, the charging potential of the photosensitive material (2) is controlled so as to reach the target value by using the above relationship. That is, the potential sensor (4) detects the dark potential V _DDP and inputs it to the calculation unit (12) via the A / D converter (11),
The reference potential V _DDPS (for example, _−800V ) is compared. The wire applied voltage V _W and the grid applied voltage V _G of the charger (5) are calculated by the arithmetic unit (12) based on the following equations so that the deviation ΔV _DDP between the two becomes minimum.

However, C and D are correction coefficients corresponding to the potential component of 50 to 70% of the amount required to correct the shift of the dark potential. That is,
The above C and D can be expressed as C = a * 1 / β and D = b * 1 / α, and a and b are a = 0.5 to 0.7, b as described above.
The correction coefficient is 0.5 to 0.7.

Then, the digital signal corresponding to each voltage value is output to the D / A converters (14) and (15), and the analog-converted control commands are applied to the high-voltage power supply unit (8) to obtain the above-mentioned deviation. The wire applied voltage V _W and the grid voltage V _G are supplied to the charger (5) so that ΔV _DDP is minimized. In this way, the charging potential of the photosensitive material (2) is detected, and the voltage applied to the charger (5) is controlled so that the charging potential reaches the target value. In this embodiment, as described above, the wire applied voltage V _{W is}
And the grid applied voltage V _G are controlled. Thus, controlling both V _W and V _G to stabilize the dark potential V _DDP is as follows.
This is because V _DDP is stabilized while maintaining the highest utilization rate without lowering the utilization rate of the sensitive material inflow current that contributes to charging.

The control unit (9) further performs control for promptly converging to a new target potential when the color background mode is selected. This is because, in the case of the color background mode in which the copy density is selectively changed with respect to the original density, if the target potential is changed from -800 V to -600 V in the above potential control method, the target potential can be quickly converged. It depends. Wire applied voltage V _W and grid applied voltage V required for the changed target potential
_{In the} method of providing the routine for performing the potential setting control several times prior to the copy cycle of the first sheet for each _G selection in order to obtain _G , it takes a long time to obtain the first copy. Therefore, in the control section (9), when entering the dark potential control of the copy cycle, V _W and V _G required by the color background selection mode are obtained as a result of the potential stabilization control in the previous copy cycle. Based on the optimum wire applied voltage V _{W END} and grid applied voltage V _{G END} to the device (5), the following equation V _G = V _{G END} −ΔV _DDP (4) (ΔV _DDP = previous target potential ( for example, 800V) - the target potential of the selected mode (for example _{60V)) V W = V W} END - (1-β) / α * ΔV DDP ...... ( by the 5) go-between is calculated, first from the optimization of the color background selection The applied voltage thus applied is applied to the charger (5).

In this case, the reason why all of the target changes are taken into account in the above formula of V _G is that the influence on V _DDP is more than twice that of V _W , as described above, and the sensitive material having the coefficients α and β. This is because there is little error after the change due to fatigue, and by changing V _W as well, the efficiency decrease of the current flowing into the photosensitive material is prevented.

In this way, the charge potential of the photosensitive material (2) is detected, the voltage applied to the charger (5) is controlled so that the charge potential reaches the target value, and the copy density is set according to the original density as desired. When the darker or lighter mode is selected, the target of the voltage to be controlled is set to a new value according to the selected mode, and the voltage to be applied to the required charger (5) is also set in the previous copy cycle. The optimum applied voltage to the charger (5) is automatically controlled and calculated, and the optimum applied voltage to the charger (5) is obtained from the beginning for the new selection mode. When the operator selects the color background mode, the charging voltage (5) can be applied to the charger (5) in a more optimized manner than at the beginning of the color background selection.
A predetermined potential can be obtained from the first sheet. That is, in order to quickly converge to a new target potential when the color background mode is selected, the voltage to be applied based on the voltage applied to the charger (5) obtained as a result of the potential stabilization control in the previous cycle. From the beginning of the color background selection, the applied voltage according to the selection mode can be applied to the charger (5) to charge the photosensitive material (2). Therefore, the target potential is changed according to the selection of the color background mode. Even in this case, it is not necessary to set the potential for several cycles until the convergence for each mode selection, and the predetermined potential can be obtained from the first copy.

Further, as a specific control example below, the standard dark potential is set to −80.
The case where 0 V and the dark potential at the time of selecting a color ground are -600 V will be described with reference to the flow charts of FIGS. 3 and 4. First, the first block shown in FIG. 3 will be described, and then the second block shown in FIG. 4 will be described.

First block: Immediately after the power of the copying machine is turned on, the exposure device (1) is off and the voltage of the charging device (5) does not reach the specified value, but the photosensitive material (2) is rotated. ing.

Immediately after the power is turned on, the time t during which the photosensitive material (2) moves the rising period until the output of the high voltage power supply (HVPS) (8) stabilizes and the distance from the charger (5) to the potential sensor (4). After the passage of time, the potential sensor (4) detects the potential of the surface of the photosensitive material (2) as the dark potential V _DDP .

Then, as described above, the multiplexer (10),
It is input to the calculation unit (13) through the A / D converter (11) and compared with the reference potential V _DDPS (for example, -800 V), and the deviation ΔV between the two.
A wire application voltage V _W and a grid voltage V _G of the charger (5) that minimizes _DDP are calculated by a calculator (12), and a digital signal corresponding to each voltage value is converted into a D / A converter. Output to (14) and (15), and apply the analog-converted control commands to the high-voltage power supply (8) to obtain the above-mentioned deviation ΔV.
_The wire applied voltage V _W and the grid applied voltage V _G are supplied to the charger (5) so that _DDP is minimized. The above control is repeated to optimize the dark potential V _DDP .

After that, V _W600 and V _G600 of the charger (5) with respect to the dark potential −600 V in the color background mode for selecting the copy density are obtained from V _W and V _G , which is −800 V before the above calculation,
Store in RAM (13) in the form shown in Table 1 below.

Second block: This routine is a control routine during normal copying. When the print start button is pressed, whether or not the copy ground mode is selected for the wire applied voltage V _W and the grid applied voltage V _G stored in the RAM (13) when the power was last turned on. The target potential V _DDPS , the wire applied voltage V _W , and the grid voltage V _{G in} Table 1 above are determined according to the determination result obtained, and the V _W and V _G are output from the high-voltage power supply unit (8). . That is, if the copy mode determination step yields a determination result indicating, for example, that the mode is "thin", the target potential is -600V.
As for the wire applied voltage and the grid applied voltage to be applied, the former is -800V as described above.
V stored in RAM (13) calculated from V _{W
The W600} and the latter, similarly, are V _G600 .

When V _W and V _G are output in this way, thereafter, the dark potential V _DDP is detected at the detection timing corresponding to the non-image portion between copies, and the target potential V _DDPS is compared,
The difference is calculated, and the wire applied voltage V _W and the grid applied voltage V _G of the charger (5) are calculated by the above equations and output so as to reduce the difference.

This routine is repeated to correct the decrease in V _DDP caused by fatigue of the photosensitive material until the copying is completed, and maintain a stable V _DDP . That is, even if the photosensitive material (2) is fatigued, the charging potential (5) is maintained so as to maintain a new target potential by compensating for the decrease in the charging potential due to the fatigue of the photosensitive material (2) even during the copying cycle.
The applied voltage can be controlled.

Next, in the step of determining whether or not the multi-copy is performed, when it is determined that the set number of copies has been made and the final copy number has been reached, the final V
_{From the W END} and V _{G END} values, the V required for the first copy start of the next copy
_{W800, V G800, V W600,} V G600 is calculated as shown in the table below 2, rewrites the contents of the data in the RAM (13) storing in the block 1.

As shown in this table, when the previous mode and the next mode are the same, the final V _{W END} and V _{G END} are used as they are, and even when they are different, the final V _{W END} and V _{G END} are calculated. Is used, and in any case, it is obtained based on the voltage applied to the charger (5) obtained as a result of the potential stabilization control in the previous cycle.

When the next copy is first circle, upon the beginning of the selection mode determination block 2 of FIG. 4, since such a new V _W800, V _G800 or V _W600, V _G600 is selected in accordance with the selected mode, sensitive The dark potential on the material (2) can be stably maintained, and a predetermined potential suitable for promptly converging to the new target potential of the selection mode can be obtained from the first sheet.

In the case where there is a fatigue recovery due to suspension of the light-sensitive material (2), it is possible to add a reduction coefficient according to the suspension time to V _W and V _G. Further, because the chargeability is lowered due to fatigue of the photosensitive material, the increased V _W and V _G necessary to obtain the same target potential V _DDPS are _used for calculation, so that the photosensitive material (2) is fatigued. Even if it is an organic photosensitive material that changes its charging property with the same, regardless of the fatigue of the photosensitive material (2), the optimum V _W600 , V in the color background mode from the first sheet
_G600 is obtained, and the target potential of -600V can be obtained. Furthermore, when the method of previously obtaining and storing the applied voltage of the charger that obtains the target potential in accordance with each mode when the power is turned on is not able to follow the chargeability deterioration due to fatigue of the photosensitive material, There is no such inconvenience.

The present invention is not limited to the above embodiment,
For example, setting the color background mode in several steps for the target potential,
Even when 900 to-600V as set to 50V every up, each applied voltage for example V _W to the _charger, the V _G determined accordingly, it is possible to perform the same processing Te cowpea to be stored in the RAM .

〔The invention's effect〕

As described above, according to the present invention, in a device that obtains image recording using a light-sensitive material, mode selecting means for selecting a normal mode and a density adjusting mode, and a case where the density adjusting mode is selected by the selecting means. And a target value setting means for setting a target value of the dark potential according to a selected density mode of the density adjustment modes, and a predetermined target value for the dark potential of the photosensitive material in the normal mode or the target value setting means. The control unit for controlling the voltage applied to the charger so as to be equal to the target value set by the control unit is configured to include the dark potential depending on the selected concentration mode of the concentration adjustment modes. It is possible to control, and it is possible to perform excellent image recording according to the density of the original.

Further, according to the present invention, when different modes are selected by the storage means for storing the voltage applied to the charger controlled by the control means and the mode selection means,
The applied voltage after the previous control stored in the storage means,
The change in the dark potential target value due to the mode change is multiplied by the coefficient determined by the relational expression between the dark potential of the photosensitive material and the applied voltage to the charger to correct the dark potential control. Since the initial value setting means for setting the initial value is also provided, even when a different mode is selected by the mode selecting means, a predetermined correction is applied to the applied voltage after the previous control stored in the storage means. The voltage applied to the charger can be determined by applying the above-mentioned procedure, and it is possible to control the dark potential with higher accuracy by making use of the applied voltage after the previous control. To a new target potential, an applied voltage suitable for quickly converging to a new target potential can be applied to the charger, the dark potential on the photosensitive material can be stably maintained, and a predetermined potential can be obtained from the first image recording. To obtain good image quality It can be.

Further, according to the present invention, a predetermined correction value to be applied to the applied voltage after the previous control stored in the storage means is applied to the dark potential of the photosensitive material and the charger by the change amount of the target value of the dark potential due to the mode change. Since the voltage value is multiplied by the coefficient determined by the relational expression between the applied voltage and the applied voltage, it is possible to properly determine the applied voltage suitable for promptly converging to a new target potential when the mode is switched. It becomes possible to control the target dark potential in a short time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of the control unit of FIG. 1, and FIGS. 3 and 4 show concrete processing of the present invention. It is a flow chart which shows an example. [Explanation of symbols] (2) …… Sensitive material, (4) …… Potential sensor (5) …… Charger, (8) …… High-voltage power supply section (9) …… Control section

Claims (1)

[Claims] [Claim 1] The dark potential V _DDP to become the target value charging unit detects the dark potential V _DDP of sensitive material of the wire applied voltage V _W
And a dark potential control device for controlling the grid applied voltage V _G, which comprises a mode selecting means for selecting a normal mode and a density adjusting mode, and the density adjusting mode when the density adjusting mode is selected by the selecting means. setting a target value setting means for setting a target value of the dark potential V _DDP in accordance with the selected exposure mode, the dark potential V _{DDP-sensitive} material is a predetermined target value or the target value setting means in a normal mode of Control means for controlling the wire applied voltage V _W and the grid applied voltage V _G of the charger so as to be equal to the set target value,
A storage unit that stores the wire applied voltage V _W and the grid applied voltage V _G of the charger controlled by the control unit, and, if a different mode is selected by the mode selection unit, is stored in the storage unit. The initial value setting means for correcting the wire applied voltage V _{W END} and the grid applied voltage V _{G END} of the charger after the previous control by the voltage value given by the following equation to obtain the initial value of the dark potential control. A dark potential control device comprising: V _W = V _{W END} + E * ΔV _DDP V _G = V _{G END} + ΔV _DDP where ΔV _DDP is the difference between the previous dark potential target potential and the dark potential target potential of the selected mode, and E is the sense. The relation E between the dark potential V _{DDP of the} material and the voltages V _W and V _G applied to the charger V _DDP = α * V _W + β * V _G + Const. β) / α.