JPH03282558A - Image forming device - Google Patents

Abstract

PURPOSE:To erase an image appearing around an original image by forcibly removing an unnecessary charge on a peripheral part which corresponds to a non-image area on a photosensitive body in the case of detecting that an original cover means is in an open state. CONSTITUTION:A lamp 4 is turned on by the control of a group of processors 71 through a lamp regulator 81, and a motor 33 is driven by the control of the group of processors 72 through a pulse motor driver 79, and then, a 1st carriage is moved from a scanning starting position to a direction separating from a 2nd carriage, and the original is scanned so as form the image. And also, a motor 36 is driven by the control of the group of processors 73 through a pulse motor driver 80 so as to actuate the photosensitive drum, and an erasing array 150 is driven by an array driving part 160, and then, a light emitting element is controlled to be turned on in accordance with data form a memory 140. Thus, the surface charge on the photosensitive drum which is electrostatically charged by an electrostatic charger can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus applied to, for example, an electronic copying machine.

(Prior Art) Generally, an electrostatic image forming device illuminates an image of a document,
an image scanning section that guides the reflected light to a photoconductor; an image forming section that includes the photoconductor that forms an electrostatic latent image with the light from the image scanning section and reproduces the image of the original document; Replenish the transfer material, such as paper, to the
A supply/discharge section is provided to output the image obtained by the image forming section.

The above-described image scanning section includes a document table on which a document or an object to be read is placed, an illumination device that illuminates the document, and an optical device that transmits reflected light from the document.

The image forming section also includes a photoconductor that is movably (rotatably) formed and that sequentially generates electrostatic latent images corresponding to the light transmitted by the scanning section, and a charging device that charges the photoconductor. , a developing device that visualizes the latent image formed on the photoreceptor, a transfer device that transfers the developed image to a transfer material, a fixing device that fixes the transferred image to the transfer material, and It is equipped with a cleaning device that returns the photoreceptor to its initial state.

On the other hand, the supply/discharge section includes a paper cassette that accommodates the transfer material;
The image forming apparatus includes a paper feeding device that supplies paper to the image forming section, and a discharge section that discharges the paper onto which the image has been transferred.

In the electrostatic image forming apparatus described above, the photoreceptor having photoconductivity is charged with a predetermined charge via a charging device. The light reflected from the original, that is, the light beam, is imaged on the surface of the photoreceptor through optical members such as a plurality of folding mirrors and an imaging lens. This light beam generates an electrostatic latent image on the surface of the photoreceptor, and a developer such as toner is supplied to the image through a developing device to visualize the image. That is, the image of the original is copied. This image is created using transfer agent supplied from a paper feeder.
For example, the toner is transferred onto paper, fixed via a fixing device (generally, since toner is heat-fusible, it is heated or pressurized at the same time as heating), and then discharged.

In an image forming apparatus, such as an electronic copying machine that uses an electrophotographic process, a document placed on a document table is covered with a document cover from above, and the document cover also exposes the light from an exposure lamp that is irradiated onto other than the document. By guiding the photoreceptor to the photoreceptor drum, unnecessary charges remaining on the surface of the photoreceptor drum are removed.

However, if the document is scanned with the document cover left open, for example, the light from the exposure lamp that illuminates areas other than the document will not form an image on the photoreceptor drum. Then, unnecessary charges around the original image are not removed, and
Later development will cause toner to adhere to areas other than the original image. Therefore, if the original size is smaller than the paper size (transfer material), or if the original size and paper size are equal but the copy size due to reduction is smaller than the paper size, the formed image size will be smaller than the paper size. If it is smaller, the periphery of the original image of the output image (copy image) becomes black with toner. Further, in the case of a thick document such as a book, the document cover does not completely contact the document table, so that unnecessary black images due to shadows are generated around the document image in the output image.

In this way, if an unnecessary black image (solid black image) appears around the original image due to wasted toner, the output image will be of poor quality and not aesthetically pleasing. The problem was that the consumption of In addition, since the peripheral portion of the paper becomes black, there is a problem in that the toner is fused to the fixing roller and the paper tends to become jammed. Furthermore, if the document cover is opened during copying, there is another problem in that a black image is formed around the document from the moment it is opened.

(Problem to be Solved by the Invention) When the original holding means is in an open state, if the original size or copy size is smaller than the paper size, unnecessary black images will be generated in areas other than the original image, and the resulting output image will be However, there is a problem in that the quality of the developer is poor and that a lot of developer is wasted. This invention makes it possible to erase unnecessary black images that appear on the outer periphery of the transfer material even when the image size is smaller than the transfer material, improving the quality of the output image and improving the developer material. An object of the present invention is to provide an image forming apparatus that can prevent wasteful consumption.

[Structure of the Invention] (Means for Solving the Problems) In the image forming apparatus of the present invention, an optical system optically reads a document placed on a translucent document table;
In an image forming apparatus that forms an image corresponding to the image of the original on an image carrier, a document holding means for holding the original in cooperation with a former document table and a release of the holding operation by the document holding means are detected. and a detection means for detecting the release of the clamping operation of the original holding means during the image forming operation of the image forming apparatus, an image corresponding to the non-original placement area is formed on the image carrier. and an image erasing means for preventing this.

(Operation) When the open state of the document holding means is detected, the present invention erases the image appearing around the document image by forcibly removing unnecessary charges on the photoreceptor corresponding to the non-image area at the periphery. It was designed to do so.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 schematically show an image forming apparatus of the present invention, such as a copying machine. A document table (transparent glass) 2 that supports the document G is fixed to the top surface of the copying machine body 1, and a cover detection switch 3 is provided near the document table 2 to detect whether the document cover 18 is open or closed. ing.

The document table 2 is provided with a fixed scale 2a that serves as a reference for setting the document G.

The original G placed on the original table 2 is exposed by an optical system consisting of an exposure lamp 4, a mirror 5, and 6.7 being reciprocated in the direction of arrow A along the lower surface of the original table 2. It is meant to be scanned. In this case, mirror 6.7
is moved at half the speed of the mirror 5 so as to maintain the optical path length.

The light reflected from the original G by the scanning of the optical system, that is, the light reflected from the original G by the light irradiation of the exposure lamp 4, is reflected by the mirrors 5, 6.7, and then passes through the variable magnification lens block 8. Further, the image of the document G is reflected by the mirror 9 and guided to the photoreceptor drum 10.
The image is formed on the surface of 0.

The photosensitive drum 10 is rotated in the direction of the arrow C shown in the figure, and the surface thereof is first charged by the charging device 11 . Thereafter, the image is subjected to slit exposure in the exposure section ph, thereby forming an electrostatic latent image on the surface. This electrostatic latent image is made visible by applying toner by the developing device 12.

On the other hand, the paper (transfer material) P is taken out one by one from the selected upper paper feed cassette 13 or lower paper feed cassette 14 by the delivery roller 15 or 16, and the taken out paper P is transferred to the paper guide path. 17 or 18, and is guided to a pair of registration rollers 19, and sent to a transfer section by this pair of registration rollers 19.

Here, the paper feed cassette 1314 is detachably provided at the lower right end of the main body 1, and one of them can be selected on the operation panel described later. Note that the cassette size of each of the paper feed cassettes 13 and 14 is detected by cassette size detection switches 60a and 60b, respectively. This allows the paper size to be detected. This cassette size detection switch 60a
, 60b are composed of a plurality of microswitches that are turned on/off in accordance with the insertion of cassettes of different sizes.

The paper P sent to the transfer section is brought into close contact with the surface of the photoreceptor drum 10 at the transfer charger 20, and
The toner image on the photoreceptor drum 10 is transferred by the action of 0. The transferred paper P is electrostatically peeled off from the photoreceptor drum 10 by the action of the peeling charger 21, and transferred to a pair of fixing rollers 23g and 23b as a fixing device provided at the end of the conveyor belt 22. Sent. The pair of fixing rollers 23a and 23b are provided with peeling claws 31a and 31b, respectively, to prevent the paper P from being wrapped around them. The transferred image is fixed by passing through this, and the fixed paper P is discharged to a tray 25 outside the main body 1 by a pair of paper discharge rollers 24 .

Further, the photoreceptor drum 10 after the transfer is transferred to a charger 26 for removing static electricity.
After the charge is removed by the cleaner 27, residual toner on the surface is removed, and the afterimage is erased by the charge removal lamp 28, so that the initial state is restored. Note that 29 is a cooling fan for preventing the temperature inside the main body 1 from rising.

FIG. 3 shows an operation panel 30 provided on the main body 1. 30a is a copy key for commanding the start of copying; 30b
30c is a numeric keypad used to set the number of copies, etc. 30c is a display unit that displays the operating status of each part and paper jams, etc. 30d
30e is a count command key for displaying the total number of copies. 30f is a density setting section for setting the copy density. 30f is for when the ID copy mode is set, which allows copying only when the identification codes (ID codes) match. , ID for displaying the number of copies corresponding to each ID code
It is a count key.

In addition, 30g is an edit key that is operated when performing multiple copying, etc. 30h is a magnification setting key that is operated when setting the copy magnification, 30i is an upper paper feed cassette, and a lower paper feed cassette) 13.14
For example, if the edit key 30g is operated and copy conditions etc. are set in this state, the set copy conditions etc. can be stored or the previously stored copy A mode memory key 301 is operated to read out conditions, etc., and is an information key that is operated to obtain information corresponding to each mode. Display device 30
Information for clearing the jam is displayed at 0.

Furthermore, 30m is a function check key,
When you operate this function check key 30m,
What functions are set can be displayed on the display 300. 30n is a dial for adjusting the contrast of the display 30o. Reference numeral 300 denotes a display device consisting of, for example, a liquid crystal dot matrix panel, and this display device 30o displays the setting status of the copying machine, etc. in characters, and the various cows 30e, 30
f, 30g, 30h, 30i, 30j, 30k.

When 301.30m is operated, the corresponding characters are displayed. On both sides of the display 30o are operation keys 30p, 30q, 30r, 30 for selecting various functions displayed on the display 300.
s, 30t, 30u.

30v and 30w are installed. The operation panel 30 is also provided with an erase mode release switch 30x that cancels the erase mode for erasing the peripheral portion of the paper, which is normally turned on when the document cover 1a is open.

FIG. 4 shows an example of the drive source configuration of each drive unit of the copying machine configured as described above, and is composed of the following motors. That is, 31 is a lens motor, which is a motor for moving the position of the lens block 8 in the direction indicated by the arrow in the figure for performing magnification change. 32 is a mirror motor, which is a motor for changing the distance (optical path length) between the mirror 5 and the mirror 6.7 for changing the magnification. A scanning motor 33 is a motor for moving the exposure lamp 4, the mirror 5, and the mirror 6.degree.7 for scanning the original. A shutter motor 34 is a motor for moving a shutter (not shown) for adjusting the charging width of the photosensitive drum 10 by the charger 11 during zooming. A developing motor 35 is a motor for driving the developing roller of the developing device 12 and the like. 36 is a drum motor, which is a motor for driving the photosensitive drum 10. 37 is a fixing motor, which connects the paper conveyance path 22.
, a motor for driving the pair of fixing rollers 23 and the pair of paper ejection rollers 24. 38 is a paper feed motor, which is a motor for driving the delivery rollers 15 and 16.

39 is a paper feed motor, and the registration roller pair 1
This is a motor for driving 9. A fan motor 40 is a motor for driving the cooling fan 29.

FIG. 5 shows a drive mechanism for reciprocating the optical system. That is, the mirror 5 and the exposure lamp 4 are supported by a first carriage 41a, and the mirror 6.7 is supported by a second carriage 41b, respectively, and these carriages 41a, 41b are guided by guide rails 42a, 42b in the direction of arrow a. It is said to be able to move in parallel. Also,
The four-phase pulse motor 33 drives a pulley 43. An endless belt 45 is stretched between the pulley 43 and the idle pulley 44.
One end of a first carriage 41a that supports the mirror 5 is fixed in the middle.

On the other hand, two pulleys 47.47 are rotatably provided in the guide portion 46 of the second carriage 41b that supports the mirror 6.7, spaced apart in the axial direction of the rail 42b. A wire 48 is strung around.

One end of this wire 48 is fixed to a fixed part 49, and the other end is fixed to the fixed part 49 via a coil spring 50. Further, one end of the first carriage 41a is fixed to the middle part of the wire 48. Therefore, by rotating the pulse motor 33, the belt 45 rotates, the first carriage 41a is moved, and the second carriage 41b is also moved accordingly. At this time,
Since the pulleys 47, 47 serve as movable pulleys, the second carriage 41b is moved in the same direction at half the speed of the first carriage 41a. In addition, 1. The moving direction of the second carriages 41a and 41b is determined by the pulse motor 33.
It is controlled by switching the direction of rotation.

Further, on the document table 2, a copyable range corresponding to the specified paper is displayed. In other words, cassette selection key 3
The paper size specified by 0i is (P x, P
y) and the copy magnification specified by the magnification setting key 30h is K, the copyable range (x, y) is rx-
Px/Kl, ry-Py/Kl. Of this copyable range (x, y), the
The direction is indicated by the distance between the scale 53 provided on the upper surface of the first carriage 41a and the fixed scale 2a.

The above-mentioned pointers 51 and 52 are connected to the pulley 54
, 55 via a spring 56. The pulley 55 is a motor 58
This motor 58
is driven in accordance with the submerged copyable range in the X direction, thereby changing the distance between the hands 51 and 52.

Further, the first carriage 41a is moved to a predetermined position (home position according to the magnification) by driving the motor 33 according to the paper size and the copy magnification. Then, when the copy key 30a is operated, the first cartridge 41a is transferred to the second cartridge 41b.
The exposure lamp 4 is moved to the scanning start position in the direction.
is turned on and moved in the direction away from the second carriage 41b. When scanning of the original G is completed in this way, the lamp 4 is turned off and the first carriage 41a is returned to the home position.

Incidentally, when scanning the document G, the size of the document G is detected in advance as the first carriage 41a moves. That is, as shown in FIG. 5, the first carriage 41a is provided with a document detector 63 which is constituted by a light receiving element 61 which is, for example, an image line sensor and a light emitting element 62 which is a light emitting diode.
a and 63b are provided. These original detectors 63a
.

63b is the first carriage 41, as shown in FIG.
The teeth 1j are arranged at positions such that they move (scan) along the illustrated teeth 1j [A-A, BB] with respect to the document table 2 as the number a moves. Therefore, copy key 30a
When is operated, the first carriage 41a is moved from the home position to the scanning start position in the direction of the second carriage 41b.

Then, the document detectors 63a and 63b are operated and moved in a direction away from the second carriage 41b, whereby scanning for detecting the size of the document G is performed. When scanning for document size detection is completed, the document detector 63a
63b is stopped, and the first carriage 41a is moved to the scanning start position. After that, exposure lamp 4
is turned on and moved in the direction away from the second carriage 41b. When the scanning for image formation of the original G is completed in this way, the lamp 4 is turned off and the first carriage 41a is returned to the home position.

In this manner, by moving the first carriage 41a away from the second carriage 41b before scanning the original, the original G and the original cover 18 are irradiated with light by the light emitting element 62, as shown in FIG. The reflected light is received by the light receiving element 61 via the document table 2, and is converted into an electric signal according to the reflectance of the document G and the document cover 1a. This electrical signal is supplied to the arithmetic processing unit via a main processor group, which will be described later, and in this arithmetic processing unit, the size of the document G is automatically adjusted according to the level fluctuation of the reflected light with respect to the moving distance of the first carriage 41a. It is now being detected.

In this case, the presence or absence of the original G is determined based on a change in the spectrum of the reflected light, and the size of the original G is detected using the determination result for the scanning direction of the original G. In this type of document, if the document cover la and the document table 2 are not in close contact with each other, the level fluctuation of the reflected light becomes extremely large. Therefore, for example, if the document cover 1a is left open or cannot be completely closed due to a thick document G such as a book, the presence or absence of the document G can be determined very easily. . Therefore, as shown in FIG.
-B) is scanned by the respective document detectors 63a and 63b, and each detection position T is scanned.

U, V, W, X, Y, Z! : The size of the original G can be easily detected by determining the presence or absence of the original G in the holder.

Note that on the document table 2, documents G ranging in size from "A5" to "83" can be placed, for example. (shown) is used as a reference.

FIG. 9 shows the overall control circuit.

The main processor group 71 includes a high-voltage transformer 76 that detects inputs from the operation panel 30 and input devices 75 such as various switches and sensors, such as the cassette size detection switches 60a and 60b, and drives the various chargers;
the static elimination lamp 28, the blade solenoid 27a1 of the cleaner 27, the heater 23a of the fixing roller pair 23,
The exposure lamp 4 and each of the motors 31 to 40.5
8, etc. to perform the above-described copying operation, as well as document detectors 63a, 63b, memory 140, erasing array 15.
0. The array drive unit 60, arithmetic processing unit 170, etc. are controlled in accordance with the input from the input device 75 such as the cover detection switch 3, and unnecessary black images appearing around the original image of the copy image (output image) are erased. It is something that performs an action.

Among the above motors 31 to 40.58, motor 35.37
．． A toner motor 77 that supplies toner to 40 and the developing device 12 is controlled by the main processor group 71 via a motor driver 78 , and the motors 31 to 34 are controlled by the first sub-processor group 72 via a pulse motor driver 79 . The motors 36, 39, 38, and 58 are controlled by the second sub-processor group 73 via a pulse motor driver 80. Further, the exposure lamp 4 is controlled by the main processor group 71 via the lamp regulator 81, and the heater 23a is controlled by the main processor group 71 via the heater control section 82. And main processor group 71
From 1st. Drive/stop commands for each motor are sent to the second sub-processor group 72, 73, and the first. Status signals and the like indicating the drive/stop state of each motor are sent from the second sub-processor group 72 to 73 to the main processor group 71. The first sub-processor group 72 also includes a motor 31
Position information from a position sensor 83 that detects each of the initial positions of 34 to 34 is input. These first. The second sub-processor group 72.73 is, for example, a microcomputer,
It also includes a programmable interval timer that counts reference clock pulses in accordance with the set value supplied from this microcomputer and controls the phase switching interval time of the pulse motor.

The outputs (electrical signals) of the document detectors 63a, 63b (light receiving elements 61) are sent to the arithmetic processing section 11 by the main processor group 71 via an amplifier 66 and a comparison circuit 68.
70. In the comparison circuit 68, the amplifier 66
The output of the light receiving element 61 is compared with a reference voltage (Vref) for correcting fluctuations in the output level of the light receiving element 61 due to variations in sensitivity of the light receiving element 61, temperature changes, and the like.

The arithmetic processing section 170 determines the position of the first carriage 41a (detection position T-) based on the number of pulses supplied to the motor 33.
2), and each document detector 5 at each detection position T-Z found from the position data of 2).
Identification data for identifying the original size according to the combination of the output levels of 3a and 63b (presence or absence of original), the original size identified by this identification data and specified by the magnification setting key 30h of the operation panel 30. It includes setting data for setting an erasing range based on a document image area (image size) corresponding to a copying magnification. Note that the memory 140, erase array 150, and array driver 160 will be described later.

Next, the erase range is set using the paper size detection results. Referring to FIGS. 10 and 11, for example, when it is detected that the document cover 18 is not completely closed, the arithmetic processing unit 170 calculates the size of the document G determined from the identification data and the operation panel Based on the formation area (image size) of the original image in accordance with the copying magnification specified by the magnification setting key 30h of 30, an erasing range is set in which areas other than this original image area are to be erased. This erasing range is selected from the erasing area map setting data according to the image size, and is stored in the memory 140 via the main processor group 71. As a result, in the memory 140, a low level signal "0°" is stored in the document image area and a high level signal "1" is stored in the other part (non-image area).
40 has a capacity slightly larger than the maximum original size that can be copied, and the magnification is 100% (100% magnification).
In this case, for the original G shown in FIG.
As shown in FIG. 1, a low level signal is stored at the address corresponding to the image area of the document G, and a high level signal is stored at the other addresses.

On the other hand, as shown in FIG. 12, an erasing array 150 is provided adjacently between the charger 11 of the photosensitive drum 10 and the exposure section ph. As shown in FIGS. 13 and 14, this erasing array 150 includes a plurality of light-shielding cells 151 arranged in a direction perpendicular to the rotational direction of the photoreceptor drum 10, and each light-shielding cell 151 has a Figure 15(a).

A light emitting element 152 made of, for example, a light emitting diode is provided as shown in FIG. In addition, each cell 151
A light emitting element 1 is placed in the opening facing the photoreceptor drum 10.
A lens 1 that focuses 52 lights onto the surface of the photoreceptor drum 10
53 are provided.

The number of light emitting elements 152 arranged in this erasing array 150 matches, for example, the capacity of the memory 140 in the column direction. Here, the distance between the light emitting elements 152 is Pl
If the number is N, the total length of the erase array 150 is Q.
-NXPl.

The erase array 150 is driven by the array driver 160 described above. This array driving section 160 is the 16th
As shown in the figure, a shift register 161 having the same number of bits as the number of bits in the column direction of the memory 140, and a store register 1 in which the contents of this shift register 161 are held.
62, it is constituted by a switch circuit 164 consisting of a plurality of switch elements 163 that are controlled on/off by each output signal of this store register 162, the movable contacts 163a of these switch elements 163 are grounded, and the fixed contacts 163b are grounded. They are connected to each cathode of the light emitting elements 152 constituting the erase array 150, respectively.

The anode of each of these light emitting elements 152 is a current limiting resistor R
are connected to the power supply Vcc through the respective terminals.

However, after setting the erasure range as described above, the first
As the carriage 41a, photosensitive drum 10, etc. are operated, one column of data is sequentially read out from the memory 140 in the row direction (as shown in FIG. 11). This read data D1 is transferred to the shift register 161 of the array driving section 160 in response to the clock signal CLK. After one column of data has been transferred to the shift register 161,
The charged portion of the photoreceptor drum 10 forms an erase array 150.
When reaching , the main processor group 71 outputs a relatch signal LTH, and the data stored in the shift register 161 is supplied to the store register 162 in response to this signal LTH. That is, since the erase array 150 is disposed between the charger 11 and the exposure section ph, the memory 14
For example, if the angle between the erasing array 150 and the exposure section ph is θ□, and the photosensitive drum 10 is rotating at an angular velocity ω, the data for one column output by 0 is θ1/ω.
The output timing of the latch signal LTH is controlled so that it is supplied to the store register 162 earlier.

Each switch element 163 of the switch circuit 164 is controlled by the output signal of the store register 162. That is, when the output level of the store register 162 is high level, it is turned on, and when it is low level, it is turned off. As a result, the light emitting elements 152 connected to each switch element 163 are turned on when the switch element 163 is on, and are turned off when the switch element 163 is off. Therefore, among the charged parts of the photoreceptor drum 10, the part where the light emitting element 152 is turned on is charge-free, and even if this charge-free part is exposed to light afterwards, no electrostatic latent image is formed and the image is erased. It turns out. In this manner, the light emitting elements 152 of the erasing array 150 are controlled to turn on in response to areas other than the original image area.Similarly, the data of the memory 140 is read out one column at a time to control the original image. Unnecessary black images appearing around the image are erased.

Next, the operation of the above configuration will be explained with reference to the flowchart shown in FIG. 17. For example, now, a document G is placed on the document table 2, and the copy key 30a of the operation panel 30 is pressed.
Suppose that the following is input (ST1). Thereafter, it is determined based on the input from the cover detection switch 3 whether or not the document cover 1a is completely closed (ST2). If it is determined that the document cover 1a is not completely closed, the process moves to step 3, and in the subsequent steps, along with the image forming operation (copying operation),
Unnecessary black images appearing around the original image are erased. In this step 3, an erasing range is set according to the paper size, and a high level signal is stored in the address corresponding to the erasing range of the memory 140 (ST3).
.

Once the erasing range is set in this way, an image forming operation accompanied by an erasing operation is started (ST4).

That is, the exposure lamp 4 is turned on under the control of the main processor group 71 via the lamp regulator 81, and the motor 33 is driven under the control of the first sub-processor group 72 via the pulse motor driver 79, causing the first carriage 41a to scan. By moving from the starting position in a direction away from the second carriage 41b, document scanning for image formation is performed. In addition, the pulse motor driver 80
Under the control of the second sub-processor group 73 via
0 is driven, and lighting of the light emitting element 152 is controlled according to data from the memory 140 as described above. This corresponds to the erased range in which the light emitting element 152 is turned on.
The surface charge on the photoreceptor drum 10 charged by the charger 11 is removed. Of the charged portions of the photosensitive drum 10, the portions whose charges have been removed by the erasing array 150 are as follows:
Thereafter, no electrostatic latent image is formed even if exposed to light. Therefore, when the document cover 13 is not completely closed, depending on the paper size, the copied image formed on the paper P may include unnecessary black images (
A beautiful hard-copy image can always be obtained without the appearance of the peripheral black area shown by diagonal lines in FIG. 18(a).

Furthermore, even when the original cover 18 does not completely contact the original platen 2 due to thick originals such as books, etc., as well as the originals G in the form of a sheet, it is possible to erase unnecessary black images that appear around the original image. It is possible to obtain a beautiful duplicate image as a hard copy.

On the other hand, if it is determined in step 2 that the document cover 18 is not opened, the process proceeds to step 5, where the above-described erasing operation is omitted and a normal copying operation is performed. That is, when the document cover 18 is completely closed, no unnecessary black image will appear around the document image.

Therefore, an erase operation is not necessary. Therefore, if opening/closing of the document cover 1a is detected and it is detected that the document cover 1a is completely closed, the erasing operation can be omitted.

After the copy images are formed in accordance with the set number of copies in this manner, the series of operations is completed and the copying machine is placed in a standby state.

As mentioned above, when the document cover is not completely closed, unnecessary charges on the photoreceptor drum are forcibly removed depending on the paper size, thereby erasing unnecessary images that appear around the document image. I have to.

In other words, even if the document cover is not closed or cannot be closed due to thick documents, etc., it is possible to prevent unnecessary black images from being created around the document image due to wasted toner. becomes. Therefore, it is possible to obtain a copy image that is visually beautiful and of high quality, and it is also possible to prevent wasteful consumption of developer in areas other than the original image. Furthermore, since toner is not placed on the peripheral portion of the transfer paper, the transfer paper is prevented from being caught by the fixing roller.

In addition, it is possible to obtain beautiful copied images without unnecessary black images even when the document cover is left open, so it is expected to have effects such as eliminating the need to close the document cover every time a copy is made. .

Note that this invention is not limited to the above embodiments. For example, the erasing operation is performed when the document cover 1a is not completely closed, but if the erasing operation is always performed, if there is dirt on the back side of the cover 1a, this will be removed as an unnecessary black image. You can prevent this from occurring.

In addition, the opening of the document cover 1a is detected by input from the cover detection switch 3. For example, by detecting the level of reflected light or the brightness, if the brightness of documents other than document G is below a certain level, the document The opening of the cover 1a may be detected.

Further, it is also possible to allow the mode to be specified by inputting from the operation panel 30, and to perform the erasing operation only when the mode is specified.

Furthermore, the arrangement position of the erasing array 150 is not limited to the position shown in FIG. 12, but as shown in FIG. It is also possible to configure erasing according to the erasing range.

Next, a second embodiment will be described with reference to the drawings.

The second embodiment is similar to the first embodiment except for the structure around the photosensitive drum. In the first embodiment, an erasing array was arranged to erase unnecessary charges on the photoreceptor drum.
In place of this, in the second embodiment, a charging shutter is provided. FIG. 20 shows an image forming apparatus according to a second embodiment. Descriptions of the same members denoted by the same reference numerals as in the first embodiment will be omitted. The erasing array 150 of the first embodiment is not provided, but instead a charging shutter 200 is provided.

The operation panel 30 provided on the main body 1, the drive source configuration of each drive section of the copying machine, and the drive mechanism for reciprocating the optical system are all the same as in the first embodiment.

As shown in FIG. 21, a charging shutter 40 is provided closely between the photosensitive drum 10 and the charger 11.

This charging shutter 40 has two shutters 201 and 202 in a direction parallel to the rotation axis of the photoreceptor drum 10, and these shutters 201 and 202 are movable near both ends of the photoreceptor drum 10. Charge cutoff portions 20IA and 202A are arranged, and racks 201B and 202B are provided which are opposed to and meshed with one gear 203, respectively. Gear 203 is rotated by charging shutter motor 204 . When the charging shutter motor 204 rotates, the gear 203 rotates, and force is applied to the racks 201B and 202B, thereby blocking the charging cutoff section 201 of the shutter 201.202.
The position of A, 202A changes. As a result, the length W of the opening of the charged portion of the photoreceptor drum 10 is changed, and an uncharged portion is formed in the peripheral portion.

FIG. 22 shows the overall control circuit of the second embodiment. The main processor group 71 detects inputs from the operation panel 30 and input devices 75 such as various switches and sensors, for example, the cassette size detection switches 60a and 60b, and drives the various chargers, a high voltage transformer 76, and the static eliminator lamp. 28, blade solenoid 27a1 of the cleaner 27; heater 2 of the fixing roller pair 23;
3a, the exposure lamp 4, and each of the motors 31 to 4
0.58, etc. to perform the above-mentioned copying operation, and also control the document detectors 63a, 63b, memory 140, charging shutter motor 204, shutter driver 206, arithmetic processing section 170, etc. by controlling the inputs of the cover detection switch 3, etc. It is controlled in accordance with input from the device 75, and performs an operation to erase unnecessary black images appearing around the original image of the copied image (output image).

Among the above motors 31 to 40.58, motor 35.37
．． A toner motor 77 that supplies toner to 40 and the developing device 12 is controlled by the main processor group 71 via a motor driver 78 , and the motors 31 to 34 are controlled by the first sub-processor group 72 via a pulse motor driver 79 . The motors 36, 39, 38, and 58 are controlled by the second sub-processor group 73 via a pulse motor driver 80. Further, the exposure lamp 4 is controlled by the main processor group 71 via the lamp reginulator 81, and the heater 23a is controlled by the main processor group 71 via the heater control section 82. And main processor group 71
From 1st. Drive/stop commands for each motor are sent to the second sub-processor group 72, 73, and the first. Status signals and the like indicating the drive/stop state of each motor are sent from the second sub-processor group 72 to 73 to the main processor group 71. The first sub-processor group 72 also includes a motor 31
Position information from a position sensor 83 that detects each of the initial positions of 34 to 34 is input. These first. The second sub-processor group 72, 73 is, for example, a microcomputer,
It also includes a programmable interval timer that counts reference clock pulses in accordance with the set value supplied from this microcomputer and controls the phase switching interval time of the pulse motor.

The outputs (electrical signals) of the document detectors 63a, 63b (light receiving elements 61) are sent to the arithmetic processing section 11 by the main processor group 71 via an amplifier 66 and a comparison circuit 68.
70. In the comparison circuit 68, the amplifier 66
The output of the light receiving element 61 is compared with a reference voltage (Vref) for correcting fluctuations in the output level of the light receiving element 61 due to variations in sensitivity of the light receiving element 61, temperature changes, and the like.

The arithmetic processing unit 170 determines the position of the first carriage 41g (detection position T-) based on the number of pulses supplied to the motor 33.
position data for calculating position data (Z), and each document detector 6 at each detection position T-Z determined from this position data.
Identification data for identifying the original size according to the combination of the output levels of 3a and 63b (presence or absence of original), the original size identified by this identification data and specified by the magnification setting key 30h of the operation panel 30. It includes setting data for setting an erasing range based on a document image area (image size) corresponding to a copying magnification. Note that the memory 140, shutter driver 206, and charging shutter motor 204 will be described later.

Next, the erase range is set using the paper size detection results. This method is similar to the first embodiment. For example, when it is detected that the document cover 18 is not completely closed, the arithmetic processing unit 170 uses the size of the document G determined from the identification data and the size specified by the magnification setting key 3゜h of the operation panel 30. Based on the forming area (image size) of the original image according to the copying magnification
An erasing range to be erased in the peripheral area of the paper is set. This erasure range is selected from the erasure area map setting data according to the image size, and is selected from the erasure area map setting data according to the image size.
1 in the memory 140. As a result, in the memory 140, a low level signal “
A high level signal "1" is stored in the other part (non-image area). That is, this memory 140 has a capacity slightly larger than, for example, the maximum original size that can be copied, and when the magnification is the same (100%), it can copy the original G shown in FIG. As shown in FIG. 11, a low level signal is stored at an address corresponding to the image area of the document G, and a high level signal is stored at other addresses.

As shown in FIG. 21, the charging shutter motor 2
04 is driven by the shutter motor driver 206 mentioned above. When the size of the paper is detected, the shutter motor driver 206 drives the memory 14 corresponding to the size of the paper.
Charge cutoff parts 201A and 202A according to data from 0
change the position of Therefore, among the charged portions of the photoreceptor drum 10, the portions blocked by the charge cutoff sections 201A and 202A are not charged, and even if these uncharged portions are subsequently exposed, no electrostatic latent image is formed and the image is not formed. It will be deleted. In this way, the shutters 201 and 202 are controlled corresponding to the area other than the document image area,
Unnecessary black images appearing around the sides of the original image are erased.

Further, the charging device 11 is connected to a high voltage transformer 76, and a charging driver 208 is provided to drive the charging device 11. The charging driver 208 is connected to the main processor group 71
The main processor group 71 controls the operation timing of the charging driver 208 . When the size of the paper is detected, the on/off timing of the charging device 11 is controlled according to data from the memory 140 corresponding to the size. 1, which is the axial direction of the photoreceptor drum 10;
Erasing the upper and lower peripheral areas of the paper is achieved by controlling the timing of charging the photosensitive drum 10. In other words, when copying is started, the position of the photosensitive drum 10 corresponding to the leading edge of the paper is not charged by the charging device 11.
Charging starts from a predetermined position. Then, the charging device 1
Charging at step 1 is terminated. As a result, the photoreceptor drum 1
Since the charging device 11 does not charge the upper and lower leading edge and trailing edge of the 0 sheet, unnecessary black images appearing around the upper and lower portions of the original image are erased. Therefore,
The black image on the periphery of the paper is erased by the charging shutter and turning the charging device on and off.

Furthermore, this second embodiment is operated according to a flowchart similar to that of the first embodiment shown in FIG. For example, now, a document G is placed on the document table 2, and the operation panel 30
It is assumed that the copy key 30a of 1 is inserted (S T 1).

Thereafter, it is determined whether the document cover 1a is completely closed based on the input from the cover detection switch 3° (Sr1).

If it is determined that the document cover 1a is not completely closed, the process moves to step 3, and in the subsequent steps, along with the image forming operation (copying operation), unnecessary unnecessary objects appearing around the document image are removed. The black image is erased. In this step 3, an erasing range is set according to the paper size, and a high level signal is stored in the address corresponding to the erasing range of the memory 140 (
Sr1).

Once the erasing range is set in this way, an image forming operation accompanied by an erasing operation is started (Sr4).

That is, the exposure lamp 4 is turned on under the control of the main processor group 71 via the lamp regulator 81, the motor 33 is driven under the control of the first sub-processor group 72 via the pulse motor driver 79, and the first carriage 41a is scanned. By moving from the starting position in a direction away from the second carriage 41b, document scanning for image formation is performed. In addition, the pulse motor driver 80
Under the control of the second sub-processor group 73 via the second sub-processor group 73, the motor 36 and the like are driven to operate the photoreceptor drum 10 and the like, and the charging shutter motor 2.4 drives the charging shutter 200, and as described above, the memory 140 is driven. The movement of the charge cutoff sections 201A and 202B is controlled according to data from the charge cutoff sections 201A and 202B. Further, the timing of generating the high voltage applied to the charging device 11 is controlled, so that the photosensitive drum 1
The leading edge and trailing edge of the 0 paper are not charged. This prevents the peripheral portion from being charged by the charging device 11, and the surface of the photosensitive drum 1o corresponding to the peripheral portion of the paper is not charged. Charge blocking section 2 of the photosensitive drum 10
01A, 202B and the control of the voltage application timing of the charging device 11, the portions where charging is prevented are free of charge, and therefore no electrostatic latent image is formed. Therefore, no visible image is formed due to toner. Therefore, when the document cover 18 is not completely closed, depending on the paper size, the copied image formed on the paper P may include unnecessary black images (black images) around the periphery, as shown in FIG. 18(b). A beautiful hard copy image can always be obtained without the appearance of the peripheral black area shown by diagonal lines in FIG. 18(a).

Furthermore, even when the document cover 1a does not completely contact the document table 2 due to not only a sheet-like document G but also a thick document such as a book, unnecessary black images that appear around the document image can be erased. It is possible to obtain a beautiful duplicate image as a hard copy.

On the other hand, if it is determined in step 2 that the document cover 18 is not opened, the process proceeds to step 5, where the above-described erasing operation is omitted and a normal copying operation is performed. That is, when the document cover 1a is completely closed, no unnecessary black image will appear around the document image.

Therefore, an erase operation is not necessary. Therefore, if it is detected that the document cover 18 is completely closed by detecting the opening/closing of the document cover 1a, the erasing operation can be omitted.

After the copy images are formed in accordance with the set number of copies in this manner, the series of operations is completed and the copying machine is placed in a standby state.

As mentioned above, when the document cover is not completely closed, unnecessary charges on the photoreceptor drum are forcibly removed depending on the paper size, thereby erasing unnecessary images that appear around the document image. I have to.

In other words, even if the document cover is not closed or cannot be closed due to thick documents, it is possible to prevent unnecessary black images from being created around the document image due to wasted toner. becomes. Therefore, it is possible to obtain a copy image that is visually beautiful and of high quality, and it is also possible to prevent wasteful consumption of developer in areas other than the original image. Furthermore, since toner is not placed on the peripheral portion of the transfer paper, the transfer paper is prevented from being caught by the fixing roller.

In addition, it is possible to obtain beautiful copied images without unnecessary black images even when the document cover is left open, so it is expected to have effects such as eliminating the need to close the document cover every time a copy is made. .

Note that this invention is not limited to the above embodiments. For example, the erase operation is performed when the document cover 18 is not completely closed, but if the erase operation is always performed, if there is dirt on the back side of the cover 18, it will be removed as an unnecessary black image. You can prevent this from occurring.

In addition, the opening of the document cover 1a is detected by input from the cover detection switch 3. For example, by detecting the level of reflected light or the brightness, if the brightness of documents other than document G is below a certain level, the document The opening of the cover 1a may be detected.

Further, it is also possible to allow the mode to be specified by inputting from the operation panel 30, and to perform the erasing operation only when the mode is specified.

In the above-mentioned two embodiments, the arrangement position of the cover detection switch 3 is not limited to the position shown in FIGS. 1 and 22,
It is also possible to arrange it near the tip moving part of the document cover 1a. Furthermore, the cover detection switch 3 is not limited to the above-mentioned switch, for example, the switch 60 shown in FIG.
a, 60b, or a combination of a magnet and a reed switch.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, even when the document cover is open, unnecessary black images appearing around the transfer material can be erased, and the output It is possible to provide an image forming apparatus in which image quality is improved and wasteful consumption of developer can be prevented.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a side sectional view showing the configuration of a copying machine according to the first embodiment, FIG. 2 is an external perspective view of the copying machine according to the first embodiment, and FIG. Figure 3 is a plan view showing the configuration of the operation panel, Figure 4 is a perspective view showing the configuration of the drive section, Figure 5 is a perspective view schematically showing the drive mechanism of the optical system, and Figure 6 is the drive mechanism of the pointer. FIG. 7 is a diagram for explaining the document size detection operation, FIG. 8 is a cross-sectional view for explaining the document detector, and FIG.
The figure is a block diagram showing the overall control circuit of the first embodiment.
Figure 0 is a diagram shown to explain the method of setting the erasure range, Figure 11 is a diagram shown to explain the contents of the memory,
FIG. 12 is a side sectional view of the main parts showing the arrangement of the erasing array, FIGS. 13 and 14 respectively show the relationship between the erasing array and the photosensitive drum, and FIG. 13 shows only the main parts. A perspective view, Figure 14 is a front view showing only the main parts, and Figure 15 is a front view showing only the main parts.
The figures show the configuration of the erasing array, where (a) is a side sectional view, (b) is a partially cutaway front view, and Figure 16 is a circuit showing the configuration of the array drive section. 17 is a flowchart shown to explain the operation, FIG. 18 is a flowchart shown to explain the operation using a sheet-like original as an example, and FIG. FIG. 19 is a diagram showing the case where an unnecessary black image appears from the copied image. FIG. FIG. 20 is a side sectional view showing the configuration of the copying machine of the second embodiment, FIG. 21 is a diagram for explaining the relationship between the photosensitive drum and the electrostatic shutter of the second embodiment, and FIG. 22 is a diagram showing the structure of the second embodiment. FIG. 23 is a block diagram showing the overall control circuit of the example, and is a diagram showing another modification of the cover detection switch. 1...Main body, la,...Document cover 2...Document table, 3...Cover detection switch, 4...Exposure lamp,
8... Lens block for variable magnification, 10... Photoconductor drum (photoconductor), 30... Operation panel, 41... First carriage, 61... Light receiving element, 62... Light emitting element , 63a. 63b... Original detector, 71... Main brochure/fusa group, 140... Memory, 150... Erase array,
160...Array drive unit, 170...Arithmetic processing unit,
201... Charged shutter, 201A, 202A...
・Charge cutoff section, 201B, 202B...Rack.

Claims (1)

[Scope of Claims] An image forming apparatus that optically reads a document placed on a translucent document table using an optical system and forms an image corresponding to the image of the document on an image carrier, comprising: a document holding means for holding the document in cooperation with the document table; a detection means for detecting release of the holding operation by the document holding means; An image forming apparatus comprising: an image erasing means that prevents an image corresponding to a non-document placement area from being formed on an image carrier when the release of the clamping operation of the means is detected.