JP3244086B2 - Electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus applied to a copying apparatus, a printer apparatus, a facsimile apparatus and the like, and more particularly, to an electrophotographic apparatus having a transfer charger capable of improving a transfer rate of a toner image to a recording sheet. About.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram schematically showing an electrophotographic apparatus.

1 is an optical writing unit, 2 is a photoreceptor belt stretched by rollers 3, 4 is a developing unit, 5 is a transfer charger opposed to the photoreceptor belt 2, 6 is a cleaning unit, and 7 is a charge removing unit. The lamp 8 is a charging charger.

With respect to the photosensitive belt 2 which is charged to a uniform charge by the charging charger 8 and moves in the direction of arrow A,
The optical writing unit 1 includes a laser beam L corresponding to image information.
To form an electrostatic latent image. The electrostatic latent image formed on the photosensitive belt 2 is developed into a toner image by the developing unit 4.

On the other hand, the recording paper P is separated one by one by a paper feed roller 9 and a separation and conveyance roller 10, and is conveyed to a transfer position in synchronization with the toner image on the photosensitive belt 2 by a pair of registration rollers 11. At the transfer position, the toner image on the photosensitive belt 2 is transferred onto the recording paper P by the transfer charger 5 that generates corona discharge. The toner image on the recording paper P is pressed or heated by the fixing unit 12 and is fixed on the recording paper P.

After the transfer is completed, the residual toner on the photoreceptor belt 2 is collected by the cleaning unit 6, and the photoreceptor belt 2 from which the residual toner has been removed is neutralized by the charge removing lamp 7 and then charged again. 8 is charged to a uniform charge.

In the above-described conventional electrophotographic apparatus, the transfer charger 5 generates a corona discharge by applying a constant current voltage by a power supply unit (not shown) to transfer the toner image from the photosensitive belt 2 to the recording paper P. Is transferred electrostatically to

[0008]

However, in the conventional electrophotographic apparatus, there is a problem that the transfer rate of the toner image to the recording paper P changes depending on the pattern of the image formed on the photosensitive belt 2.

FIG. 6 is a characteristic diagram showing the relationship between the transfer current value to the transfer charger and the transfer rate of the toner image to the recording paper.

Here, the transfer current value I is supplied from a power supply unit.
Is a conductive <br/> current value corona discharge to the recording paper from the charge wire, usually, the recording sheet P with increasing transcription current value I
Charging voltage also increases. Further, the transfer rate R is a ratio of the toner image formed on the photosensitive belt 2 to the toner mass
Shows the ratio of the mass of the transferred toner. Generally, in order to form a high quality image, it is desirable that the transfer rate R of the toner image is high.

As shown in FIG. 6, the toner image in the thin line area where the image is formed by the thin line has the maximum transfer rate when the transfer current value I is i1, and the black area where the image is painted black by the toner. Has the maximum transfer rate when the transfer current value I is i2 higher than i1. For this reason, when the transfer current value I is set to i1 and the toner image is transferred to the recording paper P, a whiteout phenomenon in which transfer is incomplete in a black region of the toner image may occur, and the transfer current value I When i is set to i2, a phenomenon that a thin line is thinned and unclear in a thin line region may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic apparatus capable of forming a high-quality image by controlling the intensity of corona discharge (corona discharge current) on recording paper in accordance with an image to be transferred.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an image carrier on which a toner image is formed, and a recording paper for electrostatically transferring a toner image from the image carrier to recording paper. In an electrophotographic apparatus provided with a transfer charger that generates corona discharge, a predetermined transfer of a toner image is performed before transfer.
The area is divided into a matrix, and each matrix divided area is
Multiple thin lines consisting of different preset thin line patterns
Comparison with the detection mask
Compared with the fine line detection mask
Judge the ratio of the image formed by the thin line in
Based on this determination result, the transfer rate of the toner image is increased.
Characterized by comprising a control unit for outputting a set signal to control the intensity of the corona discharge to the recording paper at the time of transfer of the predetermined transfer area for.

Further, in order to control the intensity of the corona discharge, a power supply unit is provided which sets a drive current value applied to the transfer charger in accordance with a setting signal of the control unit. Further, in order to control the intensity of the corona discharge, moving means for moving the transfer charger with respect to the recording paper in accordance with a setting signal of the control unit is provided. Further, in order to control the intensity of the corona discharge, a grid for controlling a discharge amount of the transfer charger in accordance with an applied voltage value and a grid voltage value to be applied to the grid in accordance with a setting signal of the control unit are set. And a power supply unit.

[0015]

According to the above-mentioned means, before the transfer, the image
(Toner image) is transferred to a predetermined size and is generated by predetermined transfer
The region is a thin line region where a high ratio is formed by the thin line.
A fine line detection mask to determine whether the region is a non-fine line region.
The control unit that controls the intensity of corona discharge on the recording sheet during the transfer of the predetermined transfer area increases the transfer rate of the toner image transferred from the image carrier to the recording sheet based on the determination result. you.

Further, the intensity of the corona discharge can be controlled in accordance with the setting signal by a power supply unit in which a drive current value applied to the transfer charger is set in accordance with the setting signal of the control unit. Further, the intensity of the corona discharge can be controlled in accordance with the setting signal by a moving means for moving the transfer charger with respect to the recording paper in response to the setting signal of the control unit. Also, a grid that controls the discharge amount of the transfer charger in accordance with the applied voltage, and a power supply unit that sets a grid voltage value to be applied to the grid in accordance with a setting signal of the control unit correspond to the setting signal. Thus, the intensity of the corona discharge can be controlled.

[0017]

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

In the following drawings, members corresponding to those described with reference to FIG. 5 are denoted by the same reference numerals, and description thereof is omitted.

FIG. 4 is a block diagram showing a configuration of a main part of the present invention.

The control section 30 comprises a CPU (central processing unit) 30a, a memory 30b and the like, and controls the entire apparatus. The image information output by the host device 31 or the scanner 32 is stored in the memory 30b.

The control section 30 outputs the image information of the memory 30b to the optical writing unit control circuit 33 and
As a result, an electrostatic latent image based on image information is formed on the photosensitive belt 2, and the electrostatic latent image is developed into a toner image by the developing unit 4.

The control unit 30 outputs the image information to the optical writing unit control circuit 33, reproduces the image information as an image in the control unit 30, divides the image into regions of a predetermined size, Further, it is determined whether each area of the divided image is a thin line area where the ratio of the image formed by the thin line is high or a non-thin line area.

[0023] Here, the control unit 30, co to the recording paper P
By outputting current value switching signals c1 and c2 to the transfer charger control circuit 20 to control the intensity of the Rona discharge , the transfer current value I flowing from the transfer charger 5 to the recording paper by the transfer charger control circuit 20 is set to i1 Or i2
Switch to. Here, the control unit 30 divides the toner image formed on the photoreceptor belt 2 before transfer so as to correspond to the image, and determines whether each area is a fine line area or a non-fine line area. The transfer current value I is set to i1 when transferring the thin line area to the recording paper P at the time of transfer of each area, or the transfer current value I is set to i2 when transferring the non-fine line area.
And let

FIG. 7 is a flowchart when the control unit of this embodiment determines the image type of each divided area of the image.

The control unit 30 further divides the divided area to be determined into a 3 × 3 matrix (S1), sets the number N of thin line matrices as variables to 0 (S2), and sets the matrix constituting the divided area. Select sequentially according to predetermined rules
(S3). Here, the control unit 30 compares the fine line detection mask shown in FIG. 8 with the selected matrix, determines whether or not the image pattern of the matrix matches the fine line detection mask (S4). If so, 1 is added to the number N of fine line matrices (S5), or if they do not match, it is determined whether selection of all the matrices forming the divided area is completed without changing the number N of fine line matrices (S6). . If the selection of all the matrices is not completed, the process returns to S3 to continue the processing until the selection of all the matrices is completed. Then, it is determined whether the difference is equal to or larger than the number TH of the reference matrix or smaller than the number TH of the reference matrix (S7).

When the difference is equal to or larger than the number TH of determination reference matrices, the control unit 30 determines that the divided area is a non-fine line area, and determines the transfer current value I when transferring the corresponding toner image.
Is i2 (S8), or the difference is the number T
If it is smaller than H, the divided area is determined to be a thin line area, and the transfer current value I for transferring the corresponding toner image is set to i.
It is set to 1 (S9).

FIG. 1 is a block diagram showing an example of the transfer charger control circuit of this embodiment.

The transfer charger control circuit 20 includes a power supply section 21 and the like. The control section 30 outputs an on / off signal and current value switching signals c1 and c2 to the power supply section 21. The power supply unit 30 turns on or off the output of the transfer current corresponding to the transfer charger 5 in response to the on / off signal, and further sets the transfer current value i to i1 or i2 in response to the current value switching signals c1 and c2. And

As described above, when the transfer current value I is i1, the transfer rate of the thin line area of the toner image to the recording paper P is maximized, or when the transfer current value I is i2, the black area of the toner image is The transfer rate on the recording paper P is maximized.
When the transfer current value I when transferring a non-thin line area is i2, the transfer rate is not always the maximum, but high image quality can be obtained because the non-thin line area has a higher image density than the thin line area. Transfer rate can be ensured.

When the toner image formed on the photoreceptor belt 2 is transferred onto the recording paper P, the transfer current is determined according to whether the area of a predetermined size to be transferred is a fine line area or a non-fine line area. By setting the value I to i1 or i2,
Since a high transfer rate can be obtained both when transferring a fine line area and when transferring a non-fine line area, the image transferred to the recording paper P can always be made high quality.

FIG. 2 is a block diagram showing another example of the transfer charger control circuit and the actuator of the transfer charger in this embodiment.

The transfer charger control circuit 20 includes a power supply unit 22 and the like. The control unit 30 outputs an on / off signal and an actuator drive signal to the power supply unit 22. The power supply unit 22 turns on or off the output of the transfer current to the transfer charger 5 in response to the on / off signal, and applies a drive voltage to the actuator 23 when the actuator drive signal is being output. .

The actuator 23, which is a means for moving the transfer charger 5, moves the transfer charger 5 from the position shown in the direction of the arrow B when the driving voltage is applied, and moves the transfer charger 5 between the recording paper P and the transfer charger. Increase the separation distance from 5.

At this time, the power supply unit 22 applies the transfer current value I as i2 to the transfer charger 5, but by increasing the separation distance between the recording paper P and the transfer charger 5,
Since the intensity of the corona discharge to the recording paper P decreases, the same effect as when the transfer current value I is set to i1 can be obtained.

The control unit 30 sets the transfer charger 5 to the position shown in FIG. 2 when transferring the non-fine line area to the recording paper P, and sets the distance between the recording paper P and the transfer charger 5 when transferring the fine line area. Is increased, the non-fine line area and the fine line area of the toner image can be transferred onto the recording paper P at a high transfer rate, so that the image transferred on the recording paper P can always be of high quality. .

FIG. 3 is a configuration diagram showing another example of the transfer charger control circuit and the grid of the transfer charger in this embodiment.

The transfer charger control circuit 20 includes a main power supply 24
And a grid power supply unit 25 and the like. Control unit 30
Outputs an on / off signal to the main power supply unit 24, and further outputs a grid voltage switching signal to the grid power supply unit 25.

In response to the on / off signal, the main power supply 24
The output of the transfer current to the transfer charger 5 is turned on or off, and a constant voltage is applied to the grid power supply unit 25 in synchronization with the output of the transfer current.

The grid power supply section 25 is composed of elements such as varistors, and changes the constant voltage of the main power supply section 24 in response to a grid voltage switching signal from the control section 30 to different grid voltage values v1 and v2. Or, it is converted to v2. Grid 26
When the grid voltage applied to the recording paper P changes, the passage of the electron current in the grid 26 is controlled in accordance with the grid voltage, so that the amount of corona discharge to the recording paper P changes and the transfer current I changes. The same effect as the above is obtained. The transfer rate of the thin line area can be maximized by setting the grid voltage value to v1, or the transfer rate of the black area can be maximized by setting the grid voltage value to v2.

The control unit 30 sets the grid voltage value to v2 when transferring the non-fine line area to the recording paper P, and sets the grid voltage value to v1 when transferring the fine line area to the recording paper P.
Since the non-fine line region and the fine line region of the toner image can be transferred to the recording paper P at a high transfer rate, the image transferred to the recording paper P can be made high quality.

[0041]

As described above, according to the present invention, it is possible to more accurately determine the ratio of an image formed by fine lines in a predetermined transfer area of a toner image as compared with the related art.
Therefore, based on the result of the determination , the control unit that controls the intensity of the corona discharge with respect to the predetermined transfer area allows the transfer rate of the toner image transferred from the image carrier to the recording paper to be smaller than that of the related art. it is possible to increase Te, however many fine lines in a predetermined transfer region, less it is possible to form a high-quality image on a recording sheet.

Further, a power supply unit for setting a drive current value to be applied to the transfer charger in accordance with the setting signal of the control unit, and the transfer to a recording sheet in accordance with the setting signal of the control unit. A grid for controlling a discharge amount of the transfer charger in accordance with an applied voltage by a moving means for moving the charger, and a power supply unit for setting a grid voltage value to be applied to the grid in accordance with a setting signal of the control unit Thus, the intensity of the corona discharge can be controlled in accordance with the setting signal, so that the transfer rate of the toner image to the recording paper can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an example of a transfer charger control circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating another example of a transfer charger control circuit and an actuator of the transfer charger in the present embodiment.

FIG. 3 is a configuration diagram illustrating another example of a transfer charger control circuit and a grid of the transfer charger in the present embodiment.

FIG. 4 is a block diagram showing a main part in the embodiment.

FIG. 5 is a configuration diagram schematically showing an electrophotographic apparatus.

FIG. 6 is a characteristic diagram showing a relationship between a transfer current value to a transfer charger and a transfer rate of a toner image to recording paper.

FIG. 7 is a flowchart when the control unit of the present embodiment determines the type of each divided region of an image.

FIG. 8 is a thin line detection mask for determining the type of each divided region.

[Explanation of symbols]

2: photoreceptor belt, 5: transfer charger, 20: transfer charger control circuit, 21, 22: power supply, 23: actuator, 24: main power supply, 25: grid power supply, 26
... grid, 30 ... control unit, P ... recording paper.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-206380 (JP, A) JP-A-3-138677 (JP, A) JP-A-3-122678 (JP, A) JP-A-1-206380 222964 (JP, A) JP-A-4-220080 (JP, A) JP-A-3-29167 (JP, A) JP-A-61-87181 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 G03G 15/16 G03G 21/00 H04N 1/23-1/31 H04N 1/40

Claims (4)

(57) [Claims] 1. An electrophotographic apparatus comprising: an image carrier on which a toner image is formed; and a transfer charger for generating a corona discharge on the recording paper for electrostatically transferring the toner image from the image carrier to a recording paper. In the device, a predetermined rotation of the toner image is performed before transfer.
The image area is divided into a matrix, and each matrix divided area
And a plurality of thin lines consisting of different thin line patterns set in advance.
Compare with the line detection mask and check all matrix
Is compared with the fine line detection mask to determine the predetermined transfer area.
The ratio of the image formed by the thin line in is determined, and the transfer rate of the toner image is increased based on the determination result.
An electrophotographic apparatus, comprising: a control unit for outputting a setting signal for controlling the intensity of the corona discharge on the recording paper at the time of transfer of the predetermined transfer area. 2. In order to control the intensity of the corona discharge,
2. The electrophotographic apparatus according to claim 1, further comprising a power supply unit for setting a drive current value applied to the transfer charger in accordance with a setting signal of the control unit. 3. In order to control the intensity of the corona discharge,
2. An electrophotographic apparatus according to claim 1, further comprising a moving unit for moving said transfer charger with respect to a recording sheet in response to a setting signal of said control unit. 4. In order to control the intensity of the corona discharge,
A grid for controlling a discharge amount of the transfer charger in accordance with an applied voltage value, and a power supply unit for setting a grid voltage value to be applied to the grid in accordance with a setting signal of the control unit. The electrophotographic apparatus according to claim 1, wherein