JP2666957B2 - Image forming device - Google Patents

Description

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

2. Description of the Related Art In an image forming apparatus, for example, an electronic copying machine using an electrophotographic process, an original placed on an original platen is covered with an original cover from above, and an exposure lamp that irradiates a part other than the original with the original cover. The unnecessary light remaining on the surface of the photosensitive drum is removed by guiding the light to the photosensitive drum.

However, if the original is scanned while the original cover is kept open, for example, the light from the exposure lamp irradiating the portions other than the original is not formed on the photosensitive drum. Then, unnecessary charges around the original image are not removed, and the toner adheres to portions other than the original image by later development. For this reason, when the original size is smaller than the paper size (transfer material), or when the copy size due to reduction is smaller than the paper size even when the original size is equal to the paper size, the formed image size is smaller than the paper size. In this case, the output image (the periphery of the original image of the copy image becomes black with toner. Also, in the case of a thick original such as a book, since the original cover does not completely contact the original platen, the periphery of the original image of the output image Unnecessary black images occur due to shadows.

In this way, if an unnecessary black image (black solid image) appears around the original image due to useless toner, the output image is not good-looking and is of poor quality. There was a problem that the consumption of intense.

(Problems to be Solved by the Invention) According to the present invention, when the original size or the copy size is smaller than the paper size, an unnecessary black image is generated in a portion other than the original image, so that a poor quality output image is obtained. It is intended to eliminate the problem that wasteful consumption of developer is increased. Even when the image size is smaller than the material to be transferred, an unnecessary black image appears in a portion other than the original image. It is an object of the present invention to provide an image forming apparatus capable of improving the quality of an output image and preventing wasteful consumption of a developer.

[Configuration of the Invention] (Means for Solving the Problems) In the image forming apparatus of the present invention, a document table on which a document is placed, a position for covering the document table, and a position for opening the document table are provided. A platen cover that can be opened and closed between the cover, cover open detection means for detecting that the platen cover is open, size detection means for detecting the size of a document placed on the platen, and paper Paper setting means for setting a size, magnification setting means for setting an image forming magnification, calculation means for calculating a copy range from the original size detected by the magnification setting means and the detection means, and this calculation means Comparing means for comparing the copy range calculated by the above with the paper size set by the paper setting means; and copying means provided near the photoreceptor whose surface is uniformly charged and irradiating the photoreceptor with light. Luminous element of Erasing means for erasing the electric charge on the photoreceptor by selectively lighting the light emitting elements, and having the same number of storage regions as the plurality of light emitting elements constituting the erasing means in the column direction. The storage means and the detection result by the cover opening detection means, the comparison result by the comparison means, and the paper size set by the setting means are referred to, and the platen cover is opened and the copy range is the paper size. If it is determined that the first signal is smaller than the first signal, the first signal is stored in a region corresponding to the position corresponding to the copy range in the column direction area of the storage unit, and the first signal is stored in the column direction region of the storage unit. A second signal different from the first signal is stored in an area corresponding to a position other than the copy range, the document plate cover is opened, and the copy range is smaller than the paper size. If it is determined that the first signal is large or if the document cover is determined to be closed, an arithmetic unit that stores the first signal in the entire area in the column direction of the storage unit; The contents of the storage means storing the calculation results are read out one column at a time, the light emitting element of the storage means corresponding to the area where the first signal is stored is turned off, and the content is stored in the area where the second signal is stored. And control means for lighting the corresponding light emitting element of the storage means.

(Operation) The present invention detects the opening of the platen cover that can be freely opened and closed between a position where the platen on which the document is placed and a position where the platen is opened, and is placed on the platen. The size of the original is detected, the paper size is set, the image forming magnification is set, the copy range is calculated from the setting of the image forming magnification and the detected size of the original, and the calculated copy range and By comparing with the set paper size, the light emitting element of the erasing means, which is provided in the vicinity of the photoreceptor having a uniformly charged surface and irradiates the photoreceptor with light, is selectively selected. Erasing the charge on the photoreceptor by turning on the light-emitting element, and providing a storage means having the same number of storage areas in the column direction as the plurality of light-emitting elements constituting the erasing means,
Referring to the detection result of the opening of the platen cover and the set paper size, when it is determined that the platen cover is opened and the copy range is smaller than the paper size, The first signal is stored in an area corresponding to the position corresponding to the copy range in the column direction area, and the first signal is stored in an area corresponding to a position other than the copy range in the column direction area of the storage unit. A second signal different from the first signal is stored, and it is determined that the platen cover is open and the copy range is larger than the paper size or that the document cover is closed. In this case, the first signal is stored in the entire area in the column direction of the storage means, and the stored content of the storage means is read out one column at a time, and stored in the area where the first signal is stored. Equivalent Turns off the light emitting elements of said memory means,
The light emitting element of the storage means corresponding to the area where the second signal is stored is turned on.

Hereinafter, an embodiment 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, for example, a copying machine. A document table (transparent glass) 2 for supporting a document G is fixed to an upper surface of the copying machine body 1. This is the document platen 2 fixed scale 2 ₁ is provided as a set reference of the document G, more in the vicinity of the platen 2 open or closed state of the document cover 1 ₁ by the openable original cover 1 ₁ and the magnet and the reed switch Is provided with a cover detection switch 600 for detecting the state.

The original document G placed on the original table 2 is exposed by the optical system including the exposure lamp 4 and the mirrors 5, 6, 7 being reciprocated in the direction of arrow a along the lower surface of the original table 2. It is to be scanned. In this case, the mirrors 6 and 7 are moved at half the speed of the mirror 5 so as to maintain the optical path length. The reflected light from the original G due to the scanning by the optical system, that is, the reflected light from the original G due to the irradiation of the exposure lamp 4 is reflected by the mirrors 5, 6, and 7 and then passes through the lens block 8 for zooming. Further, the light is reflected by the mirror 9 and guided to the photosensitive drum 10, and the image of the original G is
The image is formed on the surface of the camera.

The photoreceptor drum 10 is rotated in the direction of arrow c in the drawing, and first, the surface is charged by the charging charger 11. Thereafter, the image is subjected to slit exposure in the exposure section Ph, so that an electrostatic latent image is formed on the surface. This electrostatic latent image is
The toner is adhered by the developing device 12 to form a visible image.

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

Here, the paper feed cassettes 13 and 14 are detachably provided at the lower right end portion of the main body 1, and one of them can be selected on an operation panel described later. The cassette sizes of the sheet cassettes 13 and 14 are detected by cassette size detection switches 60 ₁ and 60 ₂ , respectively. This cassette size detection switch 60
Reference numerals ₁ and 602 _each include a plurality of microswitches that are turned on / off in response to insertion of cassettes having different sizes.

The sheet P sent to the transfer section is brought into close contact with the surface of the photosensitive drum 10 at the transfer charger 20, and the toner image on the photosensitive drum 10 is transferred by the action of the charger 20.
The transferred paper P is electrostatically peeled off from the photosensitive drum 10 by the action of the peeling charger 21, and is fixed by a transport belt 22 to a fixing roller 23 provided at the end of the photosensitive drum 10.
Sent to Then, the transferred image is fixed by passing therethrough, and the sheet P after the fixing is discharged to the tray 25 outside the main body 1 by the sheet discharging roller pair 24.

After the transfer, the photoreceptor drum 10 is returned to its initial state by being charged by the charge removing charger 26, and then the residual toner on the surface is removed by the cleaner 27, and the residual image is erased by the charge removing lamp 28. It is supposed to be. Reference numeral 29 denotes 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 instructing the start of copying, 30b is a ten-key for setting the number of copies, 30c is a display section for displaying the operating status of each section and paper jam, 30d is a density setting section for setting the copy density, and 30e Is the count command key for displaying the total number of copies, and 30f is the number of copies corresponding to each ID code when the ID copy mode is set to permit copying only when the identification code (ID code) matches. This is an ID count key for displaying.

Also, 30g is an edit key operated when performing multiple copies, 30h is a magnification setting key operated when setting a copy magnification, and 30i is a cassette selection operated when selecting the upper and lower supply cassettes 13 and 14. The key 30k is operated, for example, when the editing key 30g is operated and copy conditions are set in this state, the set copy conditions and the like are stored or the pre-stored copy conditions and the like are read out. The mode memory key 30l is an information key operated to obtain information according to each mode. For example, when a paper jam occurs, this key 30l is used.
By operating l, information for clearing the jam is displayed on a display 30o described later.

In addition, 30m is a function check key,
By operating the function check key 30m, what kind of function is set can be displayed on the display 30o. 30n is a dial for adjusting the contrast of the display 30o. 30o is a display composed of, for example, a liquid crystal dot matrix panel.
The setting state of the copying machine is displayed on the character 30o by characters or the like, and when the various keys 30e, 30f, 30g to 30m are operated, characters corresponding to the keys are displayed. On both sides of the display unit 30o, operation keys 301 _to 303 for selecting various functions displayed on the display unit 30o
_4, 30 ₅ to 30 ₈ are arranged.

FIG. 4 shows an example of the drive source configuration of each drive unit of the copying machine configured as described above, and is constituted by the following motors. That is, reference numeral 31 denotes a lens motor, which is a motor for moving the position of the lens block 8 for zooming in the direction of arrow b in the figure. Reference numeral 32 denotes a mirror motor, and the mirror 5 for changing the magnification is used.
It is a motor for changing the distance (optical path length) between the mirror and the mirrors 6 and 7. A scanning motor 33 moves the exposure lamp 4, the mirror 5, and the mirrors 6, 7 for scanning the original. Reference numeral 34 denotes a shutter motor for moving a shutter (not shown) for adjusting the charging width of the photoconductor drum 10 by the charger 11 during zooming. Reference numeral 35 denotes a developing motor, which is a motor for driving a developing roller and the like of the developing device 12. 36 is a drum motor, which is a motor for driving the photosensitive drum 10. Reference numeral 37 denotes a fixing motor, which is a motor for driving the paper transport path 22, the fixing roller pair 23, and the paper discharge roller pair 24. Reference numeral 38 denotes a paper feed motor, which is a motor for driving the delivery rollers 15 and 16. Reference numeral 39 denotes a paper feed motor, which is a motor for driving the registration roller pair 19. Reference numeral 40 denotes a fan motor, which 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 is ₁ the first carriage 41, the mirror 6 and 7 are respectively supported in _two second carriage 41, these carriages 4
The guide rails 1 ₁ and 4 _{1 2} are guided by guide rails _{1 2} and 4 ₂ so that they can move in parallel in the direction of arrow a. Also, the 4-phase pulse motor 33
Drives the pulley 43. This pulley 43
Are looped is an endless belt 45, first carriage 41 ₁ at one end for supporting the mirror 5 in the middle portion of the belt 45 is fixed between the idle pulley 44 and.

On the other hand, the the second carriage 41 _{and second} guide portions 46, spaced apart in the axial direction of the rail 42 ₂ two pulleys 4 supporting the mirror 6
7,47 are provided rotatably, these pulleys 47,47
A wire 48 extends between them. One end of the wire 48 is fixed to the fixing portion 49, and the other end is fixed to the fixing portion 49 via a coil spring 50. Also, the wire 48
To the middle portion ₁ of the end the first carriage 41 is fixed. Therefore, by the pulse motor 33 is rotated, the first carriage 41 ₁ is moved by rotating the belt 45, ₂ second carriage 41 with the also moved. In this case, the pulleys 47, 47 to serve the Gado pulley, the first carriage 41 _{1 2} second carriage 41 is 1 /
Moved in the same direction at speed 2. The direction of movement of the first and second carriages 41 ₁ and 41 ₂ is controlled by switching the rotation direction of the pulse motor 33.

Further, a copyable range corresponding to the designated sheet is displayed on the document table 2. That is, the cassette selection key
If the paper size specified by 30i is (Px, Py) and the copy magnification specified by the magnification setting key 30h is K, the copyable range (x, y) is "x = Px / K", "y". = Py /
K ". The copy range (x, y) of, x-direction is displayed by the mutual distance between the platen 2 of the pointer 51, 52 disposed on the rear surface, y-direction to the first upper surface portion of the carriage 41 ₁ and it is displayed as a scale 53 provided by the mutual distance between the fixed scale 2 _1.

As shown in FIG. 6, the pointers 51 and 52 are provided on a wire 57 which extends between the pulleys 54 and 55 via a spring 56. The pulley 55 is adapted to be rotated by a motor 58, and the motor 58
The distance between the hands 51 and 52 can be changed by being driven in accordance with the copyable range in the direction.

The first carriage 41 _1, by the motor 33 in accordance with the magnification of the paper size and copying is driven, and is moved to a predetermined position (home position corresponding to the magnification). Then, when the copy key 30a is operated, the first carriage 41 ₁ is moved to the operation start position in the second carriage 41 ₂ direction, and then the exposure lamp 4 is turned on and moved in the direction away from the second carriage 41 _2. Is done. In this manner, the scanning of the document G is completed, the lamp 4 is turned off, the first carriage 41 ₁ is returned to the home position.

Meanwhile, when the scanning of the document G, the size of the document G with the movement of the first carriage 41 ₁ is adapted to be pre-detected. That is, the first carriage 41 _1, document detector 63a, 63b is provided constituted by, as shown in FIG. 5, for example, a light receiving element 61 consisting of an image line sensor and the light emitting element 62 comprising a light emitting diode . These document detectors 63a, 63b, as shown in FIG. 7, with movement of the first carriage 41 _1, shown respectively platen 2 linear A-A, moves along the B-B (scanning ).
Therefore, when the copying key 30a is operated, the first carriage 41 ₁ is moved to the scanning start position of the second carriage 41 _{in two} directions from the home position. Then, the document detector 63a,
63b is operated by being moved in a direction away from the second carriage 41 _2, the scan for size detection of the document G is performed. When the scanning for the document size detection has finished, the document detection device 63a, the operation of 63b is stopped, the first carriage 41 ₁ is moved to the scanning start position. Thereafter, the exposure lamp 4 is moved away from the ₂ second carriage 41 is lighted. In this manner, when scanning for forming an image on the original G is completed, the lamp 4 is turned off and the first
The carriage 41 ₁ is returned to the home position.

Thus, by moving away the first carriage 41 ₁ from the second carriage 41 ₂ before the original scanning, as shown in FIG. 8, the document G and the document by light irradiation of the light emitting element 62 It reflected light from the cover 1 ₁ is received by the light receiving element 61 through the platen 2, wherein the document G
And document cover 1 ₁ is converted into electric signals corresponding to the respective reflectivity. This electric signal is supplied to the arithmetic processing unit via a main processor group described later, and in this arithmetic processing unit, the size of the document G is automatically adjusted according to the level variation of the reflected light with respect to the moving distance of the first carriage 41 _1. Is detected.

In this case, the presence or absence of the original G is determined based on the change in the spectral 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.
Those of this kind, when the document cover 1 ₁ and platen 2 and is not in close contact, the level variation of the reflected light becomes extremely large. Thus, for example, the document cover 1 ₁ is left open state, or if the thickness was the original G, such as the inability to close the document cover 1 ₁ completely, the original G
Can be determined very easily. Therefore, as shown in FIG. 7, two points (straight lines AA, BB) on the platen 2
Are scanned by the respective document detectors 63a and 63b, and the presence or absence of the document G at each of the detection positions T, Y, V, W, X, Y, and Z can be easily detected. .

Note that, on the document table 2, for example, a document G from an "A5" size to an "A3" size can be placed.
Each original G is placed on the basis of the center of the original table 2 (indicated by a dashed line in the figure).

FIG. 9 shows the overall control circuit. The main processor group 71 includes an operation panel 30 and various switches and sensors, for example, the cassette size detection switch 60 ₁ ,
A high-voltage transformer 76 that detects an input from an input device 75 such as 60 ₂ and drives the various chargers, the charge eliminating lamp 28, the blade solenoid 27a of the cleaner 27, the heater 23a of the fixing roller pair 23, the exposure lamp. 4, and controls the motors 31 to 40, 58, etc. to perform the above-described copying operation, and also detects the original detectors 63a, 63b, the memory 140, and the erase array.
150, the array drive unit 160, the arithmetic processing unit 170, and the like are controlled in accordance with the input from the input device 75 such as the cover detection switch 600, and the unnecessary black image appearing around the original image of the copy image (output image) is erased. Is performed.

Of the motors 31 to 40, 58, the motor 35 for supplying toner to the motors 35, 37, 40 and the developing device 12 is controlled by a main processor group 71 via a motor driver 78. Are controlled by the first sub-processor group 72 via the pulse motor driver 79, and the motors 36, 39, 38, 5
8 is controlled by the second sub-processor group 73 via the pulse motor driver 80. The exposure lamp 4 is controlled by a main processor group 71 via a lamp regulator 81, and the heater 23a is controlled by a main processor group 71 via a heater control unit 82. And the main processor group 71
A drive / stop command for each motor is sent to the first and second sub-processor groups 72 and 73 from the first and second sub-processor groups 72 and 73.
From 3, a status signal indicating the driving / stop state of each motor is sent to the main processor group 71. Also, the first
Position information from a position sensor 83 that detects each initial position of the motors 31 to 34 is input to the sub-processor group 72.
These first and second sub-processor groups 72 and 73 are, for example, a microcomputer and a programmable clock for counting reference clock pulses according to a set value supplied from the microcomputer and controlling a phase switching interval time of the pulse motor. -It is composed of an interval timer and the like.

Outputs (electric signals) of the document detectors 63a and 63b (light receiving element 61) are supplied to an arithmetic processing unit 170 by the main processor group 71 via an amplifier 66 and a comparison circuit 68. In the comparison circuit 68, the output of the amplifier 66 is
Light receiving element due to variation in sensitivity or temperature change of 61
Reference voltage (Vre
f) is to be compared.

The arithmetic processing unit 170, first carriage 41 ₁ position by a number of pulses supplied to the motor 33 (detection position T～Z)
And the original detectors 63a and 63 at the respective detection positions T to Z obtained from the position data.
Identification data for identifying the original size according to the combination of the output level b (the presence or absence of the original), the original size identified by the identification data, and the copy magnification specified by the magnification setting key 30h of the operation panel 30 And data for setting the erasure range based on the original image area (image size) corresponding to the above. The memory 140, the erase array 150, and the array driving section 160 will be described later.

FIG. 10 theoretically shows identification data used for document size detection. In this identification data, first the detection position of the carriage 41 ₁ (position data) T～Z,
Various document sizes are identified by a combination of output levels of the document detectors 63a and 63b (presence or absence of a document) at that time. In this figure, the output levels at the respective detection positions T to Z of the document detector 63a which moves the position of the document table 2 indicated by the straight line AA in FIG.
In FIG. 7, the output levels at the respective detection positions T to Z of the document detector 63b moving at the position of the document table 2 indicated by the straight line BB are indicated by "O" and "X". Here, the level output according to the reflected light from the original G, that is, the presence (presence) of the original G is determined by “◯”, and the reflected light from other than the original G is indicated by “x”. The level output, that is, a case where the absence (absence) of the document G is determined.

Here, an operation for detecting the size of the document G will be described. In the arithmetic processing unit 170, as well as determine the number of pulses and the position data and the first position of the carriage ₄₁₁ from the motor 33, each of the original detectors 63a, 63b each detection position T from the output level of, U, V, The presence or absence of the document G at W, X, Y, and Z is determined, and the size of the document G is detected from these determination results (combinations of the output levels of the document detectors 63a and 63b at the detection positions T to Z) and the identification data. You. That is,
As shown in FIG. 11A, for example, when a document G of “A3” size is placed on the document table 2, the first carriage 41
_In any case where ₁ is located at any of the detection positions T to Z, the document G is determined (（) by the output of the document detectors 63a and 63b. Such a discrimination state occurs only when the original G has the size of “A3” as shown in FIG. 10. In such a case, the arithmetic processing unit 170 identifies the original G as the “A3” size. Is done.

Also, as shown in FIG. 11 (e), for example, when a document G of “A4 vertical” size is placed on the document table 2,
Document detector 63a when the first carriage 41 ₁ is located at the detection position T～V, the document G is discriminated (○) by the output of 63 b, the original detectors 63a when positioned in the detection position W-Z, 63 b Are discriminated (×) except for the document G. Such a discrimination state occurs only when the original G is in the “A4 vertical” size as shown in FIG. 10. In such a case, the arithmetic processing unit 170 determines that the original G is “A4 vertical”. Identified as size.

Further, as shown in FIG.
When the “A5 vertical” document G is placed on the
Original G from the output of the document detection unit 63b when the first carriage 41 ₁ is located at the detection position T is determined (○),
Documents other than the document G are discriminated (×) from the outputs of the document detector 63a when located at the detection position T and the document detectors 63a and 63b when located at the detection positions U to Z. Such a discrimination state occurs only when the original G has the size of “A5 vertical” as shown in FIG. 10. In such a case, the arithmetic processing unit 170 sets the original G to “A5 vertical”. ”Size.

As described above, the size of the document G is identified based on the identification data by determining the presence or absence of the document G at each of the detection positions T to Z by utilizing the level fluctuation of the reflected light from the document surface due to the light irradiation. I have to. In this case, as described above, the presence or absence of the document G is determined based on a change in the spectral spectrum of the reflected light. Thus, for example, when the document cover 1 ₁ is not fully closed, large variations in the level of the reflected light other than the original G and the document G appears. Therefore,
It is easy to determine whether or not the document is a document G based on the output levels of the document detectors 63a and 63b. obtain. FIG. 11 (b),
(C), (d), (e), (f), (g) are "B4" size, "A4 horizontal table" size, "B5 horizontal table" size, "B5 vertical table" size, "A5", respectively. Original G for "Horizontal"
Is shown, and in each case,
As shown in FIG. 10, information indicating the presence or absence of the first carriage 41 _first position data and the document G, that is, the two detectors 63a, the combination of 63b output level at each detection position T～Z, the document G Size is accurately detected.

Next, with reference to FIGS. 12 and 13, a description will be given of a method of setting the erasure range using the detection result of the document size. For example, if the document cover 1 ₁ is not completely closed is detected, the operation processing unit 170, and the size of the document G was determined from the identification data, the operation panel 30
An erasure range in which an area other than the original image area is to be erased is set based on the original image forming area (image size) corresponding to the copy magnification specified by the magnification setting key 30h. This erasing range is selected from the 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,
The low level signal "0" is stored in the original image area portion, and the high level signal "1" is stored in the other portions (non-image area). That is, this memory 140 has, for example, a capacity slightly larger than the maximum manuscript size that can be copied, and if the magnification is the same size (magnification is 100%), the manuscript G shown in FIG. As shown in FIG. 13, a low level signal is stored at an address corresponding to the document G, and a high level signal is stored at other addresses.

On the other hand, as shown in FIG.
An erasing array 150 is provided between and the exposure unit Ph. In this erase array 150, as shown in FIGS. 15 and 16, a plurality of light shielding cells 151 are arranged in a direction orthogonal to the rotation direction of the photosensitive drum 10, and each of the light shielding cells 151 is provided inside the light shielding cells 151. As shown in FIGS. 17 (a) and 17 (b), a light emitting element 152 made of, for example, a light emitting diode is provided. Further, the light of the light emitting element 152 is applied to the photosensitive drum 1 in the opening of each cell 151 facing the photosensitive drum 10.
A lens 153 for converging light on the surface of 0 is provided. The number of light emitting elements 152 arranged in the erase array 150 is equal to, for example, the capacity of the memory 140 in the column direction. Here, assuming that the distance between the light emitting elements 152 is P ₁ and the number is N, the total length of the erase array 150 is Q = N × P ₁ .

The erase array 150 is driven by the array driving unit 160 described above. As shown in FIG. 18, the array driver 160 includes 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 switch circuit 164 composed of a plurality of switch elements 163 that are turned on / off by respective output signals of the store register 162. The movable contact piece 1 of these switch elements 163
63a is grounded, and fixed contacts 163b are connected to respective cathodes of the light emitting elements 152 constituting the erase array 150. The anode of each light emitting element 152 is connected to a power supply Vcc via a current limiting resistor R.

Thus, after setting the deletion range as described above, with such first carriage 41 ₁ and the photosensitive drum 10 is operated, the data for one column in the memory 140 from the row direction (shown in FIG. 13) Are sequentially read. The read data D ₁ by a clock signal CLK, the array driver 160
To the shift register 161. Shift register 161
When the charged portion of the photosensitive drum 10 reaches the erase array 150 after the data of one column is transferred to the erase array 150, the main processor group 71 outputs a latch signal LTH.
The data stored in the shift register 161 is supplied to the store register 162 according to TH. That is, since the erasing array 150 is arranged between the charger 11 and the exposure unit Ph, the data for one column output from the memory 140 is, for example, the angle θ ₁ between the erasing array 150 and the exposure unit Ph. Assuming that the photosensitive drum 10 is rotating at the angular velocity ω, the output timing of the latch signal LTH is controlled so that θ ₁ / ω is supplied to the store register 162 previously.

Each switch element 163 of the switch circuit 164 is controlled by an output signal of the store register 162. That is,
When the output level of the store register 162 is at the high level, it is turned on, and when it is at the low level, it is turned off. As a result, the light emitting element 152 connected to each switch element 163 is turned on when the switch element 163 is on, and is turned off when the switch element 163 is off. Therefore, of the charged portion of the photoconductor drum 10, the portion where the light emitting element 152 is turned on is discharged, and the discharged portion is not formed with an electrostatic latent image even after exposure, and the image is erased. Will be. As described above, the data of the memory 140 is read out one row at a time in a similar manner so that the light emitting elements 152 of the erase array 150 are controlled to be turned on corresponding to portions other than the document image area. The black image appearing around the image is erased.

Next, the operation of the above configuration will be described with reference to the flowchart shown in FIG. For example, it is assumed that a document G is placed on the document table 2 and the copy key 30a of the operation panel 30 is turned on (ST1). Then, the motor 33 is driven by the control of the first sub-processor 72 via the pulse motor driver 79, and the first carriage 41 ₁ moves from the home position corresponding to the magnification of copying to the scanning start position in the second carriage 41 ₂ direction. (ST2).

Thereafter, the document detectors 63a and 63b are operated under the control of the main processor group 71, and the first carriage 41 ₁
There by being moved in a direction away from the second carriage 41 _2, the scan for size detection of the document G is started (ST3). That is, the document detector 63a by the movement of the first carriage 41 _1, 63 b is linearly A against the document table 2, respectively
-A, BB (shown in FIG. 7), and with this movement, the light reflected from the original surface by the light irradiation of the light emitting element 62 is received by the light receiving element 61. This light receiving element 61
The outputs of the (document detectors 63a and 63b) are converted into voltage signals by the amplifier 66, and then the reference voltage (Vr
ef).

The output of the comparison circuit 68 is supplied to the arithmetic processing unit 170 via the main processor group 71, and the detection positions T,
The presence or absence of the original G in U, V, W, X, Y, and Z is used to detect the size of the original G (ST4). That is, the arithmetic processing unit 170, while being determined number of pulses and the position data and the first carriage 41 position ₁ from the motor 33, the document detector 63a, by the 63b output level check, the detection position T~ The presence or absence of the document G in Z is determined. Then, the size of the document G is identified from the determination result and the identification data.

If the document size is detected in step (ST) 4, the image size, that is, the detected document size (at the same magnification), or the copy size (magnification / reduction) based on the document size and the magnification specified by the magnification setting key 30h Is compared with the paper size specified by the cassette selection key 30i (ST5). If the comparison determines that the document size or copy size is smaller than the paper size,
For example by an input from the cover detection switch 600, in a state where the document cover 1 ₁ is not fully closed, whether the copy key 30a is operated is determined (ST6). That is, when the document size or the copy size is smaller than the paper size, and document cover 1 ₁ that is in a state of not completely closed is determined, the process moves to step 7, in the subsequent step, an image of Along with the forming operation (copying operation), unnecessary black images appearing around the document image are erased.

In this step 7, the erasing range is set according to the image size, that is, the original size and the magnification.
A high-level signal is stored at an address corresponding to 140 erase ranges.

When the erasing range is set in this way, an image forming operation with an erasing operation is started (ST8). That is, the exposure lamp 4 by the control of the main processor group 71 via the lamp regulator 81 is turned on, the first carriage 41 ₁ motor 33 is driven by the control of the first sub-processor group 72 through a pulse motor driver 79 by being moved in a direction away from the second carriage 41 ₂ from the scan start position, the original scanning for image formation is performed. Also,
Second sub-processor group via pulse motor driver 80
The motor 36 and the like are driven by the control of 73 and the photosensitive drum
10 and the like are operated, and the erasing array 150 is driven by the array driving unit 160, and the lighting of the light emitting element 152 is controlled in accordance with the data from the memory 140 as described above. As a result, the surface charge on the photoconductor drum 10 charged by the charger 11 corresponding to the erasure range where the light emitting element 152 is turned on is removed. A portion of the charged portion of the photosensitive drum 10 which has been discharged by the erase array 150 does not form an electrostatic latent image even when exposed thereafter. Therefore, when the document cover 1 ₁ is not closed completely, for example if the size of the original G is smaller than the paper size specified by the cassette selection key 30i, or if the equal size and paper size of the original G However, even when the copy size corresponding to the copy magnification set by the magnification setting key 30h is smaller than the paper size, as shown in FIG. 20 (b), the copy image formed on the paper P is surrounded by the original image. Unnecessary black images (black areas indicated by the slant in FIG. 20 (a)) do not appear, and a beautiful copy image can always be obtained as a hard copy.

Further, not only the sheet-like document G, even when the document cover 1 ₁ by the thickness thereof document such as this is not in full contact with the platen 2, to delete unnecessary black image appearing around the original image And a beautiful copied image can be obtained as a hard copy. In the above embodiment, the twentieth
As shown in FIG. 6B, since part of the original image shown by the broken line in the figure is erased (deletion range is shown by a chain double-dashed line) due to diffusion of irradiation light by the light emitting element 152,
Unnecessary black images appearing around the original image can be completely erased from the copy image.

On the other hand, if it is determined in step 5 that the document size or copy size is equal to or larger than the paper size, or in step 6, the document cover ₁₁
Is not released, the process shifts to processing step 9, where the above-described erasing operation is omitted and a normal copying operation is performed. In other words, unnecessary black image is not to appear around the document image if the document cover 1 ₁ is completely closed. Therefore, the erasing operation becomes unnecessary. Therefore, document cover 1 ₁ detects the opening and closing of the document cover 1 ₁
Is detected to be completely closed, the erasing operation can be omitted.

When a copy image is formed in accordance with the set number of sheets in this manner, a series of operations is completed, and the copying machine is set in a standby state.

As described above, the size of the document placed on the document table is read, and the size of the image formed based on the size of the document is compared with the size of the paper, and it is determined that the image size is smaller than the paper. In such a case, an unnecessary charge on the photosensitive drum is forcibly removed to erase an image appearing around the document image.

That is, with the movement of the first carriage, reflected light from the original surface due to light irradiation of the light emitting element is received by the light receiving element, and the presence or absence of the original in the scanning direction of the first carriage is determined based on a change in the output level of the light receiving element. Then, the original size is detected from the result of this determination, and when the original size or the copy size is smaller than the specified paper size, the charges on the surface of the photosensitive drum other than the image format area are removed to appear around the original image. I try to erase the image. Thus, when the original size is smaller than the paper size, or when the copy size is smaller than the paper size, for example, when the original cover is not closed, or when the original cover cannot be closed by a thick original or the like. Even if there is, it is possible to prevent an unnecessary black image from being generated due to useless toner around the document image. Therefore, it is possible to obtain a good-quality copy image that is beautiful in appearance, and to prevent wasteful consumption of the developer in a region other than the document image.

Moreover, since a beautiful copy image without unnecessary black images can be obtained even with the document cover opened, it is possible to expect an action and an effect that it is not necessary to close the document cover each time copying is performed. .

The present invention is not limited to the above embodiment. For example, although to perform the erase operation when the document cover 1 ₁ is not closed completely, if at all times to perform the erase operation, if there is dirt on the rear surface of the cover 1 _1, which is unnecessary black It can be prevented from appearing as an image.

In addition, cover detection switch 600 the opening of the document cover 1 ₁
Was to be detected by an input from, for example, the level of the magnitude or brightness of the reflected light is detected and also as brightness non original G detects the opening of the document cover 1 ₁ at a constant level or less good.

Further, it is also possible to make the mode designation possible by input from the operation panel 30, and to perform the erasing operation only when the mode is designated.

The document cover when the multi-key 30a has been operated 1 ₁
When it is detected that the document G is completely closed, it is possible to omit the scanning for detecting the size of the document G.

Further, the arrangement position of the erase array 150 is not limited to the position shown in FIG. 14, and as shown in FIG. 21, it is arranged between the exposure unit Ph and the developing unit 12, and the formed electrostatic latent image is It is also possible to configure so as to erase according to the erasing range.

Further, the arrangement position of the cover detection switch 600 is not limited to the position shown in FIGS. 1 and 2, as shown in FIG. 22, it is also possible to arrange the base end portion of the document cover 1 _1. Furthermore, the cover detection switch 600 is not limited to the combination of the magnet and the reed switch, for example, as on / off according to opening and closing of the document cover 1 _1, the actuator 601
And a micro switch 602.

Further, it is also applicable to a case where the document G is not placed on the basis of the fixed scale 2 _1. In this case, when the document size is detected, for example, the timing of starting the counting of the number of pulses can be easily changed by changing the timing according to the mounting state of the document G.

Of course, various modifications can be made without departing from the scope of the present invention.

As described above in detail, according to the present invention, even if the image size is smaller than the transfer material, it is possible to erase an unnecessary black image appearing in a portion other than the original image, It is possible to provide an image forming apparatus capable of improving the quality of an output image and preventing wasteful consumption of a developer.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a side sectional view showing the structure of a copying machine, FIG. 2 is a perspective view showing the appearance of the copying machine, and FIG. FIG. 4, FIG. 4 is a perspective view showing a configuration of a driving unit, FIG. 5 is a perspective view schematically showing a driving mechanism of an optical system, FIG. 6 is a perspective view schematically showing a driving mechanism of a pointer, FIG. FIG. 8 is a view for explaining the document size detection operation, FIG. 8 is a cross-sectional view for explaining the document detector, FIG. 9 is a configuration diagram showing an overall control circuit, and FIG. FIG. 11 is a diagram logically showing identification data used for size detection of FIG. 11, FIG. 11 is an operation explanatory diagram showing an example of document size detection, FIG. 12 is a diagram for explaining a method of setting an erasure range, FIG. FIG. 14 is a view for explaining the contents of the memory, FIG. 14 is a side sectional view of a main part showing the arrangement of the erase array, and FIG. 16 and 16 show the relationship between the erasing array and the photosensitive drum, respectively. FIG. 15 is a perspective view showing only the main part, FIG. 16 is a front view showing only the main part, and FIG. 17 is the erasing process. FIG. 1A shows a configuration of an array, FIG. 1A is a side sectional view, FIG. 1B is a partially cutaway front view, and FIG. 18 is a circuit diagram showing the configuration of an array drive unit. 19
The figure is a flow chart for explaining the operation, and FIG. 20 is a flow chart for explaining the operation using a sheet-like document as an example. FIG. 20A shows a case where a black image necessary for a copy image appears. FIG. 21B is a diagram showing a case where an unnecessary black image is erased from a copied image, FIG. 21 is a side sectional view of a main part showing another arrangement example of an erasing array, and FIG. 22 is a cover. It is a figure showing other examples of a detection switch. 1 ... body, 1 ₁ ... document cover, 2 ... platen, 4 ...
Exposure lamp, 8 ... Lens block for zooming, 10 ... Photoconductor drum (photoconductor), 30 ... Operation panel, 41 ₁ ... 1st
Carriage, 61 ... Light receiving element, 62 ... Light emitting element, 63a, 63
b… Document detector, 71… Main processor group, 140…
Memory, 150: Erase array, 160: Array driver, 17
0: arithmetic processing unit, 600: cover detection switch.

Continuation of the front page (56) References JP-A-62-96976 (JP, A) JP-A-57-102667 (JP, A) JP-A-62-206571 (JP, A) JP-A-61-282867 (JP, A) JP-A-60-185942 (JP, A) JP-A-54-94038 (JP, A) JP-A-62-222275 (JP, A) JP-A-62-192766 (JP, A) 60-159446 (JP, U)

Claims (1)

(57) [Claims] An original table on which an original is placed, an original table cover that can be opened and closed between a position covering the original and an open position of the original table, and that the original table cover is open. Cover open detection means for detecting, size detection means for detecting the size of a document placed on the platen, paper setting means for setting a paper size, magnification setting means for setting an image forming magnification, Calculating means for calculating a copy range from the magnification setting means and the size of the document detected by the detecting means; and comparing the copy range calculated by the calculating means with the paper size set by the paper setting means. Means, and a plurality of light emitting elements provided near the photoreceptor having a uniformly charged surface and irradiating the photoreceptor with light. Erasing means for erasing electric charges on the body, storage means having storage areas of the same number as the plurality of light emitting elements forming the erasing means in the column direction, detection results by the cover opening detection means, and the comparison means With reference to the comparison result and the paper size set by the setting unit, if it is determined that the platen cover is open and the copy range is smaller than the paper size, The first signal is stored in an area corresponding to a position corresponding to the copy range in the area of the storage area, and the first signal is stored in an area corresponding to a position other than the copy range in the column direction area of the storage unit. The second signal different from the signal of the above is stored, and when it is determined that the platen cover is open and the copy range is larger than the paper size, or when the document cover is closed. In the case of being cut off, the arithmetic means for storing the first signal in the whole area in the column direction of the memory means, and the contents of the storage means storing the arithmetic result by the arithmetic means are read out one column at a time. Control means for turning off the light emitting element of the storage means corresponding to the area where the first signal is stored, and turning on the light emitting element of the storage means corresponding to the area where the second signal is stored; An image forming apparatus comprising: