JPH11316488A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To erase an image having little deviation in an erasing area set by a user by turning on or off a light source at an erasing area and so that a difference between the coordinates of a real erasion area and specified erasion coordinates is a minimum. SOLUTION: The erasure of a latent image in a specified existent area is designated. Next, the reference erasion coordinates (erY1, erY2) of an eraser are calculated from the positional relation of the designated original area, transfer paper size, transfer paper and the eraser. Then, the real erasion area is calculated from the range of the light source of the eraser to be turned on. The difference between the coordinates of the real erasion area at the turning on of the light source of the eraser positioned on the reference erasion coordinates of the eraser and the reference erasion coordinates of the eraser is compared with the difference between the coordinates of the real erasion area at the turning off of the light source thereof and the reference erasion coordinates of the eraser, and an erasure pattern where the light source of the eraser positioned on the reference erasing coordinates of the eraser is turned on or off is formed according to the difference being the smaller one. Then, the eraser is turned on in accordance with the erasing pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for exposing a charged image bearing member to form an electrostatic latent image on the image bearing member, and more particularly to partially removing a charged area of the image bearing member. The present invention relates to control of an eraser region of an eraser. This image forming apparatus can be used in, for example, a copying machine, a printer, and a facsimile (hereinafter, referred to as a copying machine).

[0002]

2. Description of the Related Art In a copying machine or the like, an electrostatic latent image is formed on an image carrier and developed with a developer to form a visible image. In this type of image forming, there is an image forming apparatus equipped with an eraser for erasing a charge or a latent image in an area unnecessary for image forming on an image carrier. The eraser has the effect of erasing the latent image outside the transfer paper, reducing wasteful consumption of toner, and the burden of cleaning for scraping off the toner remaining without being transferred.

This eraser can accommodate various sizes of transfer papers and originals by arranging a plurality of light sources (light emitting elements such as light emitting diodes) and switching the lighting pattern of the light sources according to timing.

Further, an arbitrary area on a document is designated, and the inside of the original is erased (inside erase) or the outside thereof is erased (outside erase). Conventionally, when an area to be erased is designated, when a rectangular area is designated, four-point coordinates are inputted based on the document edge. Then, the erase coordinates on the transfer paper (image carrier) are calculated from the inner erase area and the transfer paper area based on the original, an eraser lighting pattern is generated from the erase coordinates, and the light source of the eraser corresponding to the erase coordinates is turned on. And erase the latent image for that portion.

[0005]

The eraser lighting pattern is determined by the coordinates in the direction perpendicular to the rotation direction of the photoreceptor (hereinafter referred to as Y direction) from the erasing coordinates. There is a gap between the specified area and the result of erasing. If the width per light source is reduced, the deviation can be reduced, but the number of light sources and drivers for driving the light sources increases, which is problematic in terms of cost.

In Japanese Patent Application Laid-Open No. Hei 5-204231,
There has been proposed an image forming apparatus in which the erasing width of an image can be arbitrarily set by adjusting the light amount of a light source and changing the diffusion width of the light. However, the driver of the light source needs to output an arbitrary voltage value, resulting in high cost. Is concerned.

Conventionally, whether to turn on or off the light source of the eraser located on the erase coordinates based on the eraser reference is determined as follows.
Since the control is uniformly performed in one of them, there is a case where the control is not performed so that the difference between the designated area in the Y direction and the erase result is minimized.

It is a first object of the present invention to reduce the deviation of an actually erased region from a designated region, and to reduce the deviation due to an image recording density setting value. A third object is to reduce the variation of the deviation due to the image recording density setting value.

[0009]

(1) In order to achieve the first object, according to the present invention, an eraser reference erase coordinate representing an erase area boundary corresponding to an erase designated area is calculated, and the erase coordinate is calculated on the erase coordinate. An actual erasure area 1 when a certain light source is turned on and an actual erasure area 2 when the light source is turned off are obtained, and the respective deviations 1 between the obtained boundaries 1 and 2 of the actual erasure areas 1 and 2 and the eraser reference erasure coordinates are obtained. , The deviation 2 is calculated, and when the deviation 1 is smaller, the light pattern that turns off the light source on the erasure coordinates is turned off. When the deviation 2 is smaller, the light source on the erasure coordinates is turned on. Generate an erase pattern,
The erase pattern turns on the light source of the eraser. That is, the present invention provides an eraser (11, 30) having a plurality of light sources (11) arranged in a direction (Y) intersecting with the direction of movement of the charged image carrier (3) and removing the charge of the image carrier (3). (32), means (33, 331, 335) for designating an arbitrary area of a document, means (337) for designating erasure of a latent image in the designated document area, and a designated document area ( X1, Y1 /
X2, Y2), the transfer paper size, and the means (24) for calculating the eraser reference erase coordinates (erY1, erY2) from the positional relationship between the transfer paper and the eraser, and the actual erase area from the range of the light source of the eraser to be turned on. Means for calculating (24), the difference between the actual erasure area when the light source of the eraser located on the eraser reference erasure coordinate is turned on and the eraser reference erasure coordinate, and the actual erasure area and eraser reference erasure coordinate when the light is turned off. (57, 5 in FIG. 7)
9) means (24) for generating an erase pattern in which the light source of the eraser located on the eraser reference erasure coordinates with the smaller difference is turned on or off (58, 60 in FIG. 7); And erase control means (24) for lighting the eraser according to the pattern. In addition, in order to facilitate understanding, in the parentheses, elements or items corresponding to the embodiment shown in the drawings and described below are additionally provided for reference.

[0010] According to this, the position difference between the actually erased area and the actually erased area is small.

[0011]

(2) Further, since the light from the light source of the eraser is diffused before reaching the surface of the photoreceptor, the charge is removed more than the lighting range of the light source at the boundary edge of the erase area. Therefore, in an embodiment to be described later, a value obtained by adding the charge removal width (diffusion width) due to light diffusion to the lighting range of the light source is calculated as the actual erasure area. That is, the means for calculating the actual erasure area (24) calculates a range obtained by adding a diffusion width to be erased by diffusion of light from the light source at the end of the illuminating range to a lighting range of the light source of the eraser. Is calculated. As a result, an area erasure that more accurately matches the designated erasure area is performed.

(3) Further, the charge elimination width (diffusion width) due to light diffusion is small when the image recording density is set to be high, and is large when the image recording density is set to be low. Therefore, in the embodiment described later, the diffusion width due to the diffusion of light is obtained from the set image recording density. That is, the diffusion width erased by the diffusion of the light from the light source is a value corresponding to the density adjustment value of the formed image. As a result, irrespective of the image recording density setting value, the area erasure that exactly matches the designated erasure area is performed.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0014]

FIG. 1 shows an outline of a mechanism section of an embodiment of the present invention. This embodiment is an electrophotographic copying machine. In FIG. 1, a document placed on a contact glass 1 is pressed against the contact glass 1 by a pressure plate 1a having a white lower surface. An optical scanning system 2 including an exposure lamp 41 and the like is provided below the contact glass 1. The present embodiment is of a fixed document type, in which a document supply device 23 is mounted,
When the original is closed (at a position where the original can be fed to the contact glass 1) and the original is placed on the original, the original feeder 23 moves the original to the contact glass 1.
When the copy of the original is completed, the original is discharged and the next original is fed to the contact glass 1. In the case of manual document placement, the operator opens the document supply device 23 upward and places the document on the contact glass 1.

An optical scanning system is mechanically driven to scan an original on the contact glass 1. An image formed by reflected light from a document illuminated by the exposure lamp 41 is transmitted to the optical scanning system 2.
The image is formed on the photosensitive surface of the photosensitive drum 3 via. In FIG. 1, the photosensitive drum 3 rotates clockwise.

The paper feed system has two stages, and the recording paper is fed by a paper feed roller 6 or 7 from a paper feed tray 4 or a paper feed cassette 5 which is selected. The fed-out transfer paper is guided to the photosensitive drum 3 (feed) by passing between the registration roller 8 and the tip bending roller 9.

Around the photosensitive drum 3, a charger 10, an eraser 11, a developing unit 12, a pre-transfer neutralizing lamp 13, a transferring unit 14, a separating unit 15, a separating claw 16, and a cleaning unit 17 are provided.
And a static elimination lamp 18 and the like.

Next, a schematic copy process will be described.
The copy process includes a start cycle, a copy cycle, and an end cycle.

When the print key is depressed by the operator, in the start cycle, the photosensitive surface of the photosensitive drum 3 is cleaned and neutralized by a grounded conductive brush and a cleaning blade provided in the cleaning unit 17, and further a neutralization lamp 18 is provided. To eliminate the charge.
After the completion of cleaning and static elimination, the process exits the start cycle and becomes a copy cycle.

In the copy cycle, the photosensitive surface of the photosensitive drum 3 uniformly charged by the charger 10 is illuminated with the reflected light of the original on the contact glass 1 illuminated and scanned by the exposure lamp 41, and the surface potential of the original is reflected. Changes according to the intensity of the original reflected light. As a result, an electrostatic latent image is formed on the photosensitive drum 3. While passing through the developing device 12, this electrostatic latent image
The toner adheres and is visualized (hereinafter, referred to as a toner image). By changing the light intensity of the exposure lamp 41, the density of the image to be formed can be changed.

The transfer paper fed to the registration roller 8 before the start of the exposure is transferred by the registration roller 8 at a predetermined timing corresponding to the rotation of the photosensitive drum 3.
The paper is fed toward. At this time, the leading edge of the transfer paper is slightly folded by the leading edge folding roller 9 in order to facilitate later separation.

When the transfer paper passes just above the transfer unit 14 to which a predetermined voltage is applied, the transfer paper comes into contact with (transfers) the toner image formed on the photosensitive surface of the photosensitive drum 3. Thereafter, the transfer paper is separated from the photosensitive surface of the photosensitive drum 3 by the separator 15 and the separation claw 16 and is sent to the transport belt 19. The transport belt 19 sends the transfer paper to the fixing device 20. The fixing device 20 is a roller having a built-in heater, where the toner image is fixed on the transfer paper, and is discharged to a copy tray 22 via a discharge roller 21.

After repeating the above-described copy cycle for the set number of sheets, the photosensitive drum 3 is further rotated about one turn to execute an end cycle for cleaning the photosensitive surface and removing electricity. If there is a copy start instruction during the execution of the end cycle, the process skips the start cycle and proceeds to the copy cycle.

FIG. 2 shows a part of the electric control system of the copying machine shown in FIG. As shown in FIG. 3, on the operation panel 33,
Touch panel 335 also serving as display device, hard key 331
334, 338 and an indicator light. FIG.
The power pack 28 generates a high-voltage power supply such as a bias applied to the charging charger 10 and the developing device 12 around the drum and a bias applied to the transfer conveyance belt at the request of the CPU 24. The DF 23 is a document supply device placed on the contact glass 1. The DF can detect the size of the document, and can notify the CPU 24 of this. Reference numeral 30 denotes a shift register for registering erase data transmitted from the CPU 24 by serial communication. The erase data is read serially in synchronization with the clock signal from the CPU 24. Reference numeral 31 denotes a latch circuit which latches a parallel output (erase data) of the shift register 30 in response to a latch command from the CPU 24 and outputs the latched output to the driver 32.

The voltage instruction data given by the CPU 24 is D
The / A converter 43 converts the voltage into a voltage instruction signal (analog) and supplies it to the lamp driver 42. The lamp driver 42 applies the specified voltage to the exposure lamp 41. Thus, the exposure lamp 41 is turned on. The intensity of exposure to the drum 3 can be changed by the voltage value applied to the exposure lamp 41.

The CPU 24 serially transmits all erase data to the shift register 30 and stores the data in the shift register, and then causes the latch circuit 31 to store the data. By this erase data output process, new erase data is output to the driver 32. The driver 32 turns on and off the LED 11 as the light source of the eraser 11. In addition, the CPU 24 controls an optical system such as a scanner and a paper transport system.

331 to 331 on the operation panel 33 shown in FIG.
34 and 338 are hard keys, and the touch panel 3
Reference numeral 35 denotes a two-dimensional display for both input and output. The ten keys 331 are used to input the number of copies and erasure coordinates.
Reference numeral 332 denotes an enter key for confirming the erasure coordinate input. Reference numeral 333 denotes a clear key for erasing the value input by the ten keys 331. A start key 334 is pressed after setting the number of copies and various modes to start copying.

The four keys displayed on the touch panel 335
Block 336 is a paper key. An arbitrary transfer paper (size) can be selected by touching this. A key block 337 is an inner erase key. By touching this, the mode shifts to the coordinate input mode for the area to be erased.

Reference numeral 339 denotes an image density setting key. In this example, five levels of densities 1 to 5 can be set.
By setting this key, the voltage value of the exposure lamp voltage can be varied and the image density can be adjusted.

FIG. 10A shows the output value of the exposure lamp voltage that can be changed by the image density setting key 339 in FIG. By strongly shining light when the set density is low in this way, even if the original is a black portion, the reflected light is strong and hits the drum 3 and the image density is low. In the present image forming apparatus, the density adjustment is performed by adjusting the voltage applied to the exposure lamp 41. However, the adjustment can be performed by another method, for example, by changing the voltage of the developing bias. It is also possible to combine these methods. Also, in the method of reading the background density of the original as in the automatic density setting and determining the image density adjustment value based on the density, the only difference is whether the density adjustment value is manually set or automatically set. This is possible.

FIG. 4 shows an outline of the sequence control (copy process control) executed by the CPU 24. When the power is turned on by turning on the power key, the CPU 24 clears the output port, initializes the RAM 26, etc., displays "Please wait!" On the message display, and lights the red lamp of the print key (steps 1 & 2).
2). Hereinafter, the word “step” is omitted in parentheses, and step No. Write only numbers. Next, the CPU 24
Reads the state of each part of the device and detects an abnormality. If there is an abnormality in the device, sets an abnormality display and activates a protection relay or the like (3 to 6). When the abnormality is eliminated and the process exits the preparation loop, the abnormality display is reset (7).

Next, as the initial conditions of the copy processing in the standard mode, the number of copies: 1, density: center, paper feed cassette: upper, and scaling ratio: 1 are set (8). Then, "Copy is possible" is displayed on the message display, the green lamp is turned on in place of the red lamp of the start key, and the copy ready state is set (9). Then, at "operation board reading" (10), the operator waits for an operator input.

Here, if there is a copy condition input, it is read and a process corresponding to the input (setting of copy conditions) is performed (P
RP).

When the start key is pressed, the CPU 24
"Start cycle" (13) and "1 copy processing"
(14) is executed, and the copy number counter (register) C
The content of the NC is incremented by one (15), and it is checked whether the number of copies CNC has reached the set number GN (standard set value 1 or the number set by the operator) (16). If not, "1 copy processing" (14) is executed. When the "1 copy process" (14) for the set number GN is executed, an end cycle is set (17), and the operation returns to "read operation board" (10).

FIG. 5 shows the above-mentioned "operation board reading" (1).
0) shows the contents of "other key reading process" (PRP) executed when a key other than the start key is operated. By this processing, the operator operates the touch panel 33
When the paper key 336 (one of the four) on the button 5 is pressed, the transfer paper is set (22). Image density setting key 3
When the user presses the button 39, an image density setting process is performed (23, 2).
4). The image density set here is stored in the RAM 26,
The exposure lamp lighting voltage corresponding to the set image density is set according to the relationship shown in FIG.

When the inner erase key 337 is depressed, an inner erase area input process is performed (25, 26).
Is displayed.

FIG. 6 shows "internal erasure area input processing" (26).
Indicates the contents of Here, the operator first selects X1 as the first input coordinate (31, 32). After that, it checks whether the numeric keypad is pressed, and if pressed, calculates the coordinate value to be updated after checking the number of input digits and reflects it on the display (33 to 3).
6). After that, the press of the enter key is checked.
uf is determined, and the input waiting coordinates (X1, X2, Y1, Y
2 is substituted for buf (37-4)
1). Thereafter, it is checked whether or not all the coordinates X1, X2, Y1, and Y2 have been input. If all of the coordinates have not been input, the non-input coordinates are set as the next input waiting coordinates (31), and buf is cleared (32). Then, in steps 33 to 41, the uninput coordinates are read.

When the input of all the coordinates X1, X2, Y1, Y2 is completed, the coordinates are corrected. In this case, when the coordinates exceed the size of the document permitted by the image forming apparatus, an allowable value is set to guarantee the magnitude relation of the coordinates. More specifically, the erasing mode is reset when Y1 = Y2, the values are replaced so that Y1 <Y2 when Y1> Y2, and Y1 = 3 when Y1> 300 mm.
00 mm, Y2> 300 mm if Y2> 300 mm
mm (300 mm is the maximum document width in the Y direction in the present image forming apparatus). After that, the area setting routine (26) ends. It checks whether the clear key 333 is pressed, and if pressed, initializes buf and reflects it on the display 42-44).

FIG. 7 shows "setting of inner erase erase pattern" executed at the beginning of "1 copy process" (14) when CNC = 0 (first copy of one original). PD
T). FIG. 11 is a diagram showing the positional relationship between the eraser 11 and the transfer paper. With reference to FIG. 11, variables used in "setting of internal erase erase pattern" (PDT) will be described.

Since the original is placed with reference to the upper left of the contact glass, the image on the upper end of the original is exposed to the lower end (front side) of the transfer paper on the drum. In FIG. 11, the light source number 0 side is the near side of the image forming apparatus, and the coordinates (Y value) follow from the near side.

DocY: Document width (detected when a document is sent to the contact glass by DF) erY1: Erase coordinates Y1 (the initial value in the processing of FIG. 7 is FIG. 6,
ErY2: Erase coordinate Y2 (In the process of FIG. 7, the initial value is
ImY1: Image coordinates Y1 (indicating transfer paper edge) imY2: Image coordinates Y2 (indicating transfer paper edge) erY1num: Erase coordinates Y1 Light source number (light source unit counted from light source number 0) ErY2num: Erase coordinate Y2 light source number (coordinate value of light source unit counted from light source number 0) imY1num: Image coordinate Y1 light source number (coordinate value of light source unit counted from light source number 0) imY2num: image coordinate Y2 light source Number (coordinate value of light source unit counted from light source number 0) ed: Length in Y direction of one light source (illumination width) EC: Distance from eraser end (exposure start end) of light source number 0 to center of transfer paper. In FIG. 11, the one with a white circle means the light source (LED) to be turned on. Light source number 0 or more imY1num
Hereinafter, the light source LEDs of the eraser 11, which are not less than erY1num and not more than erY2num and not less than imY2num and not more than the light source number n, are turned on.

Referring to FIG. 7, first, when the erasure coordinates Y2 exist outside the original, the CPU 24 corrects the erasure coordinates Y2 to the original end. If the erasure coordinates Y1 are also outside the original, the erasure is not performed (51-54).

Next, since the center in the width direction of the transfer sheet passes through a position separated by EC from the front end of the eraser (light source number 0), erasure coordinate correction is performed and image coordinates are also set (55). ). Then, fraction processing is performed (56). In the arithmetic expression of the fraction processing (56), INT (X) means a function for rounding down X below the decimal point. erY1
num + 1 is the light source No. on the start end of the erasure area. , ErY
2num + 1 is the light source No. on the end of the erasure area. It is.

Next, the light source erY1n on the beginning of the erasure area
Erase reference erase coordinates when um + 1 is turned off
The difference between erY1 and the start of the actual erase area is calculated. That is, the absolute difference between the value obtained by subtracting the diffusion width ERASE (notch) corresponding to the image density setting value from the actual erasure coordinates ed × erY1num of each light source [ed × erY1num−ERASE (notch)], and the eraser reference erasure coordinates erY1. The value ABS [ed × erY1num−ERASE (notch) −erY1] is calculated. Then, the light source erY on the beginning of the erase area
The difference between the eraser reference erase coordinate erY1 and the actual erase area start end when 1num + 1 is turned on is calculated. That is, the actual erasure coordinates ed × erY1num of the light source unit
The diffusion width ERASE corresponding to the image density setting value from the value obtained by adding 1 to
Value obtained by subtracting (notch) [(ed × erY1num + 1) −ERASE
(notch)] and the absolute value ABS [(ed × erY1num + 1) −ERASE (notch) −erY
1] is calculated.

Next, the light source erY1n on the beginning of the erasure area
The absolute value of the difference between when um + 1 is turned off (the former) and when it is turned on (the latter) is compared (57), and the former A
If BS [ed × erY1num−ERASE (notch) −erY1] is smaller, the start end of the erase area is set to erY1num. That is, the light source erY1num + 1 on the start end of the erasing area is set to be turned off. If it is larger, the actual erasure coordinates erY1 in light source units
num is corrected (rewritten) to erY1num + 1 (58).
That is, the light source erY1num + 1 on the start end of the erasing area is set to be turned on. ABS (X) is a function that takes the absolute value of X,
notch is a variable indicating the stage of the set image density, ERASE (n
otch), according to the relationship shown in FIG.
This is a function indicating the amount of erasure (diffusion width) due to the diffusion of light from the light source of the eraser 11 at the time of image density (notch).

In the process of step 57, the coordinate Y1 of the actual erase area when the light source of the eraser on the target erase coordinate (erY1) is turned on is smaller than the erY1 when the light is turned off. Is turned off. By taking into account Erase (notch), more accurate erase area setting is realized.

Next, the light source erY2n on the end of the erasure area
Erase reference erase coordinates when um + 1 is turned off
The difference between erY2 and the end of the actual erase area is calculated. That is, the value [ed × erY2num + ERASE (notch)] obtained by adding the diffusion width ERASE (notch) corresponding to the image density setting value to the actual erase coordinates ed × erY2num of the light source unit, that is, the light source unit coordinates of the erase end in the Y direction; Erase reference erasure coordinates er
The absolute value ABS [ed × erY2num + ERASE (notch) −erY2] of the difference from Y2 is calculated. Then, the light source erY on the end of the erase area
A difference between the eraser reference erase coordinate erY2 and the end of the actual erase area when 2num + 1 is turned on is calculated. That is, the actual erasure coordinates ed × erY2num of the light source unit
Plus a diffusion width ERASE (n
otch) [[ed x erY2num + 1) + ERASE (not
ch)] and the absolute value of the difference between the eraser reference erasure coordinate erY2 ABS [(ed × erY2num + 1) + ERASE (notch) −erY
2] is calculated.

Next, the light source erY2n on the end of the erase area
The absolute value of the difference between when um + 1 is turned off (the former) and when it is turned on (the latter) is compared (59), and the former A
When BS [ed × erY2num + ERASE (notch) −erY2] is smaller, the actual erasure coordinate erY2num of each light source is used as a calculated value. That is, the light source erY2num + 1 on the end of the erase area is set to be turned off. When it is larger, the actual erasure coordinates erY2num of the light source unit are calculated as erY2num +
It is corrected (rewritten) to 1 (60). That is, the light source erY2num + 1 on the end of the erasing area is set to be turned on.

In the process of step 60, the coordinates Y2 of the actual erase area when the light source of the eraser on the target erase coordinates (erY2) is turned on and off are determined by erY2
In the case where the difference is smaller when the light is turned off as compared with, the condition judgment for erasing one light source is performed. Again, Eras
By taking into account e (notch), more accurate erase area setting is realized.

FIG. 10B shows the erase width based on the set image density and the amount of light diffusion. The lower the concentration, the more easily the charge is removed by the eraser. Therefore, the erase width due to light diffusion, that is, the diffusion width Erase (notch) increases.

FIG. 8 shows data transfer to the eraser and latch timing. This process is performed in "1 copy process" (14 in FIG. 4). In response to the start key being pressed, the DF 23 is instructed to convey the original to the contact glass. When a signal indicating the end of the original conveyance arrives from the DF 23, the photosensitive drum MT is rotated, and the exposure lamp 41 is turned on. A voltage value is applied according to the relationship shown in FIG. Note that the exposure lamp 41 is turned off after Min (original length, transfer paper length) after receiving the LE signal indicating that scanning of the leading end of the original has started from the scanner.
Min (A, B) means that the smaller of A and B is selected. Although not shown, the exposure lamp and the attached mirror move to scan the original from when the LE signal is received until the exposure lamp is turned off.

The document size information is received from the DF 23 at the same time as the document transport end signal, and the side erase pattern (side erase data) and the inside erase pattern (data) are created (FIG. 7). Perform After creating these erase patterns, the first erase data (full width erase data before the leading edge of the transfer paper: all lighting erase data) is serially transmitted to the shift register 30, and after the transmission is completed, the latch signal is latched. Transmit to the circuit 31. As a result, all the lighting data is given to the driver 32, and all the light emitting diode LEDs, which are the light sources of the eraser 11, are turned on (tip erase).

Thereafter, the sensor generates a timing signal (LE signal) indicating that the scanning of the scanner has reached the leading end of the document. In response to the LE signal, the CPU 24 serially outputs side erase data to the shift register 30. . Switching from the leading edge erase to the side erase occurs when the data of the shift register 30 is set (latched) in the latch 31.

After receiving the LE signal, the photosensitive drum 3
After waiting for rotation by LE2ERS (layout distance from the image exposure point by the scanner to the eraser 11), a latch signal is output to the latch circuit 31, and the LED of the eraser 11 outside the transfer paper area is turned on by side erase. . After that, the CPU 24 transmits the next erase data, that is, erase erase data, to the shift register 30. After receiving the LE signal, the CPU waits for the rotation of the drum 3 by LE2ERS + the erasure coordinate X1, and then applies a latch signal to the latch circuit 31 to light up with the inner erase data. The erase data is serially transferred to the shift register 30. After receiving the LE signal and waiting for the drum to rotate by LE2ERS + the erasure coordinate X2, the latch signal is applied to the latch circuit 31 to turn on the side erase data. After that, the next erase data, that is, all lighting erase data for the trailing edge erase, is serially transmitted to the shift register 30. Then, after the LE signal is equal to LE2ERS + Min (document length, transfer paper length), a latch signal is sent to the latch circuit 31, and full lighting (rear end erase) is performed. Min is the shorter value of the document length and the transfer paper length. Then the light source LE of erase 11
D is all turned off, and the rotation drive of the drum 3 is stopped. With such a control operation of the CPU 24, the inner erase by the eraser 11 is realized.

According to the embodiment described above, when erasing (inside erasing) the inside of the designated area with the erase device, the actual erasing area is obtained, and the difference between the coordinates of the actual erasing area and the designated erasing coordinates is minimized. The light source at the end of the erasing area is turned on or off so that the image is erased with a small deviation from the erasing area set by the user.

The eraser neutralizes the photosensitive drum more widely than the lighting range of the light source at the end of the area, due to diffusion of light from the light source. In the above embodiment, when the actual erase area is obtained, the actual erase area is obtained by adding the diffusion width E (notch) due to the diffusion of light in addition to the lighting range of the light source of the eraser. , An image with less deviation is erased.

The diffusion width E (notch) due to light diffusion is small when the image forming density is set high, and large when the image forming density is low. In the above embodiment, the amount of erase due to light diffusion, that is, the diffusion width E (notc
h) is determined in accordance with the relationship shown in FIG. 10B in accordance with the set image forming density, so that even if the set value of the image forming density changes, it is shifted with respect to the erase area set by the user. Less image erasure is performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a mechanism outline of an embodiment of the present invention.

FIG. 2 shows an example of an erasing device in the electric system of the copying machine shown in FIG.
FIG. 3 is a block diagram illustrating a portion related to the satellite control.

FIG. 3 is an enlarged plan view showing a part of an operation panel of the copying machine shown in FIG.

FIG. 4 is a flowchart showing an outline of a copy mechanism control operation of a CPU 24 shown in FIG. 2;

FIG. 5 is a flowchart showing the contents of a “reading process of another key” PRP shown in FIG. 4;

FIG. 6 is a flowchart showing the contents of an "inside erasure area input process" 26 shown in FIG.

FIG. 7 shows a CP in “1 copy processing” 14 shown in FIG.
"Setting of erase erase pattern" performed by U24 PD
This is a flowchart showing the contents of T.

FIG. 8 shows a CP in “1 copy processing” 14 shown in FIG.
This is a time chart showing the erase data transfer timing in the erase control performed by U24.

9 is an enlarged plan view showing a display on a touch panel 335 when an internal erasure area is set in the copying machine shown in FIG.

10A is a graph showing the relationship between the image density setting value of the copying machine shown in FIG. 1 and the voltage applied to the exposure lamp 41, and FIG. 10B is a graph showing the relationship between the image density setting value and the eraser 11; 6 is a graph showing the relationship between the light source and the diffusion width E (notch) of the light source.

11 is a plan view showing an arrangement of light sources of an eraser 11 of the copying machine shown in FIG. 1 and a positional relationship between transfer sheets.

[Explanation of symbols]

 1: Contact glass 2: Optical scanning system 3: Photoreceptor drum 4: Manual paper feed tray 5: Paper feed cassette 6, 7: Paper feed roller 8: Registration roller 9: Tip bending roller 10: Charger 11 : Eraser 12: developing device 13: static elimination lamp before transfer 14: transfer device 15: separator 16: separation claw 17: cleaning device 18: static elimination lamp 19: transport belt 20: fixing device 21: discharge roller A 22: Copy tray 23: Document feeder 41: Exposure lamp

Claims (3)

[Claims] 1. An image forming apparatus comprising: a plurality of light sources arranged in a direction intersecting a moving direction of a charged image carrier and an eraser for eliminating charge of the image carrier; Means for designating erasure of a latent image in the designated document area, means for calculating eraser reference erase coordinates from the designated document area, transfer paper size, and positional relationship between the transfer paper and the eraser, Means for calculating the actual erasure area from the range of the light source of the eraser to be lit, and the difference between the actual erasure area when the light source of the eraser located on the eraser reference erasure coordinate is turned on and the eraser reference erasure coordinate, and The difference between the actual erasure area and the eraser reference erasure coordinates is compared, and an erase pattern in which the light source of the eraser positioned on the eraser reference erasure coordinates is turned on or off with a smaller difference is generated. And means, the erasure - Spata - erasure accordance emissions - performing lighting Sa erasure - An image forming apparatus comprising: a scan control means. 2. The real erasure area calculating means calculates the actual erasure area by adding a diffusion width that is erased by diffusion of light from a light source at an end of the illuminating range to a lighting area of the light source of the eraser. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 2, wherein the diffusion width erased by diffusion of light from the light source is a value corresponding to a density adjustment value of a formed image.