JPH07191554A - Image forming device - Google Patents

Abstract

PURPOSE:To reduce wear of a photoreceptor drum and peeling claw. CONSTITUTION:A copying device 2 contains: an automatic exposure sensor 40 for detecting the density of the image of an original D placed on an original platen 10; the peeling claw 50b which is selectively brought into contact with the photoreceptor drum 42; and a peeling-claw-actuation-deciding circuit 90. Only when the circuit 90 decides that the output of the automatic exposure sensor 40 corresponding to the image density of the original D has a prescribed value or below, the peeling claw 50b is brought into contact with the photoreceptor drum 42. Thus, because undesired wear of the photoreceptive layer 42a of the photoreceptor drum 42 and peeling claw 50b is prevented, durability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention forms a latent image on a photosensitive drum by using light and dark information of light from an original and develops the latent image formed on the photosensitive drum onto an image. The present invention relates to an image forming apparatus that copies an image of a document by transferring it.

[0002]

2. Description of the Related Art In an image forming apparatus, for example, an electrostatic copying apparatus, a photosensitive drum which has been charged to a predetermined polarity in advance has a latent image generated by irradiating an original with light reflected by the surface of the original. An image is formed. The latent image formed on the photoconductor drum is developed by supplying toner from the developing device, and is transferred as a copy image onto a transfer sheet attracted to the photoconductor drum by electrostatic force.

The copy image or toner image transferred to the transfer paper is released from the peeling device which provides an AC charge for releasing the transfer paper from electrostatic attraction with the photosensitive drum to separate it from the photosensitive drum. By peeling and charging, it is peeled off from the photosensitive drum together with the transfer paper, and is fixed on the transfer paper via the fixing device. By the way, in a high-speed copying apparatus in which the moving speed of the photosensitive layer of the photosensitive drum exceeds 400 mm / sec, there is a problem that the peeling charge (AC charge) is not surely peeled off.

Therefore, in many high speed copying machines, in addition to a peeling device for peeling and charging, a nail peeling mechanism in which a nail-shaped peeling member is arranged on the surface of the photosensitive drum, that is, the photosensitive layer is added. . As the nail peeling mechanism of this type, a fixed type in which a nail-shaped peeling member is constantly brought into contact with the photosensitive layer of the photoconductor drum and a nail-shaped peeling member are used when the transfer sheet is conveyed to a predetermined position. A movable type in which the photosensitive layer of the photosensitive drum is brought into contact with the photosensitive layer has been proposed.

[0005]

However, in a high-speed copying apparatus provided with a nail peeling mechanism, since the nail-shaped peeling member is continuously or periodically contacted with the photosensitive layer of the photosensitive drum, There is a problem that the photoconductor drum and / or the claw-shaped peeling member or both are worn by a copying operation for a long period of time, resulting in unwanted scratches.

Even when the movable nail peeling mechanism is used, for example, in the case of continuous copying, there is little space between the sheets, and the leading edge of the sheet is a nail-shaped peeling member. The claw-shaped peeling member and the photosensitive drum are in contact with each other for the reason that the claw-shaped peeling member must be brought into contact with the photosensitive layer of the photosensitive drum before reaching the position where Since the time is relatively long, there arises a problem that the nail-shaped peeling member and / or the photosensitive drum must be frequently replaced within a period shorter than the life of the photosensitive drum.

On the other hand, when the photoconductor drum and / or the claw-shaped peeling member are worn, a gap is created between the photoconductor drum and the claw-shaped peeling member, and there is a problem that the transfer paper is caught. Further, when the movable nail peeling mechanism is used and the nail-shaped peeling member is worn,
Since the nail-shaped peeling member is not brought into close contact with the photosensitive layer due to the vibration when the nail-shaped peeling member is brought into contact with the photosensitive layer of the photosensitive drum, the transfer is performed despite the arrangement of the nail-shaped peeling member. There is a problem that the paper is easily caught.

The present invention prevents the copying paper from being caught in the photoconductor drum due to the peeling failure caused by the image density of the original or the condition of the copying paper, and improves the durability of the photoconductor drum and the peeling device. With the goal.

[0009]

The present invention has been made based on the above problems, and an image carrier on which an image corresponding to the image of an original is formed, and an image formed on the image carrier are covered. The transfer means for transferring to the transfer material and the transfer means, which is arranged so as to be selectively contactable with the surface of the image carrier, and is brought into contact with the surface of the image carrier to transfer the image by the transfer means. Peeling means for peeling the material from the image carrier, density detecting means for detecting the density of the image of the document and outputting a value corresponding to the detected density, and the above-mentioned based on the value output by the density detecting means An image forming apparatus comprising: a peeling unit driving unit that selectively biases the peeling unit.

Further, according to the present invention, an image carrier on which an image corresponding to an image on a document is formed, a transfer means for transferring the image formed on the image carrier to a transfer material, and the transfer target. Information for determining whether or not the material includes a state change, holding means for holding the material to be transferred so that it can be fed toward the image carrier, and the surface of the image carrier And a peeling means for peeling the transferred material to which the image is transferred by the transfer means from the image carrier by being arranged so as to be selectively contactable with the surface of the image carrier,
The density detection means for detecting the density of the image of the original and outputting a value corresponding to the detected density, and the case where the value output by the density detection means is a predetermined value or less An image forming apparatus comprising: a peeling unit driving unit that biases the peeling unit when it is notified that a state change is included.

Further, according to the present invention, an image carrier on which an image corresponding to the image of the original is formed, a holding means for holding the transfer material fed toward the image carrier, and the image carrier. A transfer target material that is fed toward the body and that holds the transfer target material whose state has been changed by heating or the like, and is fed from the holding means and the second holding means. A transfer means for transferring the image formed on the image carrier to the material to be transferred, and a transfer means arranged so as to be selectively contactable with the surface of the image carrier and contacting with the surface of the image carrier. Peeling means for peeling the transferred material to which the image has been transferred by the transfer means from the image carrier, density detecting means for detecting the density of the image of the original, and outputting a value corresponding to the detected density, The above peeling based on the value output by the density detection means A step of selectively urging the step, and a peeling means driving means for continuously urging the peeling means when the transferred material is supplied from the second holding means. Image forming apparatus. Will be provided.

Further, according to the present invention, the reading means for illuminating the original and taking out the reflected light from the original, and the light quantity of the reflected light taken out by the reading means are detected and correspond to the detected light quantity. A detection unit that outputs a value, an image carrier on which an image corresponding to the reflected light extracted by the reading unit is formed, a developing unit that develops the image formed on the image carrier, and the developing unit. And a transfer unit for transferring the developer image developed on the image bearing member onto a sheet adhered to the image bearing member by electrostatic attraction, and arranged so as to be selectively contactable with the surface of the image bearing member. , A peeling means for peeling the paper having the developer image transferred by the transfer means from the image carrier by being brought into contact with the surface of the image carrier, and a value output from the detecting means is a predetermined value. If: Image forming apparatus is provided, characterized in that a control means for operating the serial stripping means.

Further, according to the present invention, the reading means for illuminating the original and extracting the reflected light from the original, and the light quantity of the reflected light taken out by the reading means are detected, and the value corresponding to the detected light quantity is detected. Detecting means for outputting, an image carrier on which an image corresponding to the reflected light extracted by the reading means is formed, a developing means for developing the image formed on the image carrier, and a developing means for developing the image. Transfer means for transferring the developed developer image on the image bearing member onto a sheet which is closely adhered to the image bearing member by electrostatic attraction, and alternating current to the sheet on which the developer image is transferred by the transferring means. By providing an electric field, the separation means for releasing the paper from electrostatic attraction with the image carrier and the surface of the image carrier, which is arranged so as to be selectively contactable with the surface of the image carrier. Transfer above by contact If the value output from the detection means is less than or equal to a predetermined value, the output of the separation means is within a predetermined range. An image forming apparatus comprising: a first control means for suppressing the internal control; and a second control means for operating the peeling means when the value output from the detection means is a predetermined value or less. Will be provided.

[0014]

According to the image forming apparatus of the present invention, the transfer material to which the image formed on the image carrier is transferred through the transfer means is attached according to the image density of the original detected by the density detecting means. It is peeled from the image carrier by the peeling means which is urged. Further, when the transfer material to which the image formed on the image carrier via the transfer means is transferred is a transfer material whose state has already been thermally changed, the transfer material including the state change via the holding means. When the peeling unit is urged by the notification that the above condition is given, the peeling unit peels the image carrier.

[0015]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 to 3 show an electrostatic copying machine in which an embodiment of the present invention is incorporated.

According to FIG. 1, the copying apparatus 2 has an image reading section 4 which optically reads an image recorded on a document D as light and dark information of light, and light and dark information supplied from the image reading section 4. After the electrostatic latent image is formed by the developer, the image is visualized by the developer, and the image forming unit 6 outputs the image to the transfer material, that is, the copy sheet P. The copy sheet P is supplied to the image forming section 6, and the image forming section 6 is used. It is composed of a paper feeding unit 8 and the like that conveys (copied) paper P on which an image is output to the outside of the apparatus 2.

The image reading section 4 is a document table for holding a document D.
10, a document holder 12 that is formed so as to be in close contact with and openable to the document table 10 and that closely adheres the document D placed on the document table 10 to the document table 10, and substantially parallel to and moves with respect to the document table 10. The first carriage 20, which is arranged so that it can optically read the image information of the document D as light / dark information of light, is driven by the first carriage 20, and transmits the information read by the carriage 20 to an information recording medium described later. The second carriage 30 is included.

The first carriage 20 has an illumination lamp 22 for illuminating the original document D, a reflector 24 for efficiently condensing light from the illumination lamp 22 onto the original document D, and increasing the illumination efficiency, and the original document D. A first mirror 26 that reflects the reflected light from toward the second carriage 30 is arranged. On the second carriage 30, the reflected light reflected from the first mirror 26 is turned back by 90 °, and the reflected light from the document D turned back through the second mirror 32 is turned back by 90 °. Three mirrors 34 are arranged.

Below the first carriage 20, in the plane including the optical axis of the third mirror 34 of the second carriage 30, the first
And the document D guided by the second carriages 20 and 30
Lens unit 3 that provides a predetermined magnification for reflected light from
6 and a folding mirror 38 that bends the reflected light that has passed through the lens unit 36 toward a photosensitive drum 40 (described later) of the image forming unit 6 and the like. In addition, in the same plane as the plane in which the lens unit 36 is arranged, that is, in the third plane
The image density of the copy obtained by the copying operation is maintained at a constant level in a region where the light transmitted from the mirror 34 to the folding mirror 38 passes and does not block the light traveling to the folding mirror 38. In order to do so, an automatic exposure sensor (AES) 40 (Fig.
(See) is fixed via a fixing member (not shown).

The image forming section 6 is a photosensitive drum on which an electrostatic latent image corresponding to the image information recorded on the document D is formed based on the reflected light from the document D transmitted through the folding mirror 38. 42, a charging device 44 that supplies a predetermined potential to the photosensitive drum 42, a developing device 46 that supplies a developer, that is, toner to the electrostatic latent image formed on the photosensitive drum 42, a developing device 46
The electrostatic latent image, that is, the toner image developed by
To the paper P supplied by the transfer device 48, the paper peeling device 50 for peeling the paper P having the toner image transferred by the transfer device 48 from the photosensitive drum 42, and the paper P having the toner image transferred thereto. It is composed of a fixing device 52 for fixing the toner image. The charging device 44, the developing device 46, the transfer device 48, and the claw peeling device 50 are sequentially arranged around the photosensitive drum 42 along the direction in which the photosensitive drum 42 rotates. A cleaning device that removes residual toner remaining on the photoconductor drum 42 after the toner image is transferred to the paper P along the direction in which the photoconductor drum 42 is rotated and on the downstream side of the claw peeling device 50. 54 and a static eliminator 56 for erasing the charges on the photoconductor drum 42 are further arranged.

The photosensitive drum 42 is arranged in the approximate center of the apparatus 2 so as to be rotatable in the direction of arrow y via a drive motor (not shown). The photoconductor drum 42 is formed by forming a thin layer of a photoconductor (a material showing photoconductivity) such as amorphous silicon or selenium, that is, a photoconductive layer 42a on the outer periphery of a cylinder formed of aluminum or the like. A charge distribution pattern, that is, an electrostatic latent image can be provided by irradiating light with a given potential applied to the layer.

The charging device 44 extends along the axis of the photoconductor drum 42 and supplies a predetermined charge to the photoconductor drum 42. The corona wire 44a and the charge directed toward the photoconductor drum 42 from the corona wire 44a. It has a grid screen 44b for controlling the quantity. The charging device 44 is continuously or intermittently energized by a charging control device (not shown) according to the input copying conditions (the number of copies).

The developing device 46 includes a developing roller 46a arranged substantially parallel to the axis of the photosensitive drum 42, and a toner containing portion 46b containing a visualization agent, that is, toner. The light (that is, image information) from the document D transmitted by the mirrors 26, 32, and 34 and the folding mirror 38 is applied to the photosensitive layer of the photosensitive drum 42, so that the charge distribution pattern formed on the photosensitive layer, that is, The electrostatic latent image is developed by supplying toner to the electrostatic latent image.

The transfer device 48 copies the image, that is, the toner image developed by the developing device 46, onto the copy paper P fed by the paper feeding portion 8. In the transfer device 48, the paper P is electrostatically attracted to the surface (photosensitive layer) of the photosensitive drum 42 when the toner image is transferred, and the paper P is electrostatically attracted to the surface of the photosensitive drum 42. In order to release P, a separate charging device 48a for generating an AC electric field is provided integrally or separately.

The nail peeling device 50, as shown in FIG.
Shaft 50a arranged parallel to the axis of photoconductor drum 42
, Four, for example, are arranged on the photosensitive layer 42 of the photosensitive drum 42.
Peeling claw 50 formed so as to be in close contact with (contact with) a or retractable
b and the end of the shaft 50a, the peeling claw 50b
Lever 50c for selectively contacting the photosensitive layer 42a with the photosensitive layer 42a.
It is composed of The lever 50c is rotated by the lever 50d and the lever 50e, and at the timing described later, the peeling claw.
50b is brought into contact with the photosensitive layer 42a of the photosensitive drum 42. still,
When the plunger 50g of the solenoid 50f is displaced in the direction of the arrow B, the lever 50d and the lever 50e move the peeling claw 50.
It is rotated in a direction of bringing b into contact with the photosensitive layer 42a. Also,
Undesired movement of the lever 50d is restricted via the spring 50h, while the plunger 50g is turned off.
While (resting in the direction of arrow A), the lever 50c is biased in a predetermined direction so that the peeling claw 50b is held at a position where it does not contact the photosensitive layer 42a, that is, a retracted position.

The fixing device 52 has a heating roller 52a having a heater (not shown) and a pressure roller 52b in pressure contact with the heating roller 52a, and heats the toner held on the paper P to melt the toner image. Toner image and paper P
By pressing and, the toner image is fixed on the paper P.
The cleaning device 54 is formed so as to be capable of being pressed against the photosensitive layer 42a of the photosensitive drum 42 at a predetermined angle, and has a scraper 54a for writing off the toner remaining on the photosensitive layer 42a.
When the toner image is transferred onto the paper P via the photosensitive layer 42,
It is used to remove the untransferred toner remaining on the photosensitive layer 42a from the photosensitive layer 42a.

The static eliminator 56 is a lamp extending along the axis of the photosensitive drum 42, and is used to remove the charge distribution pattern remaining on the photosensitive layer 42a. Development device
Between the 46 and the transfer device 48, first and second slots 58a and 58b into which first and second sheet cassettes of the sheet supply unit 8 which will be described later are inserted are formed. Slot 58a
Paper cassettes 60a and 60b for supplying the copy paper P toward the transfer area defined between the photoconductor drum 42 and the transfer device 48 are inserted in the printers 58 and 58b. A manual bypass (SFB) 60c capable of supplying the paper P independently of the paper P supplied from the paper cassettes 60a and 60b is arranged above the paper cassette 60a.

Photoreceptor drum 42 and slots 58a and 58b
Between the (paper cassettes 60a and 60b), the cassette 60
a or 60b or first and second paper feed rollers 62a and 62 for pulling out the paper P one by one from the SFB 60c
b, the paper P pulled out from the respective cassettes by the first and second paper feed rollers 62a and 62b.
The first and second conveying rollers 64a for sending toward
The rotation speed of the photoconductor drum 42 is corrected by correcting the inclination of the paper P conveyed through the rollers 64b and the respective rollers and aligning the tip of the toner image formed on the photoconductor drum 42 with the tip of the paper. Timing rollers 66 for feeding the sheet P at the same speed as are sequentially arranged.

Between the transfer device 48 and the fixing device 52, there is arranged a conveyor belt 68 for sending out the paper P having the toner image transferred (transferred) by the transfer device 48 toward the fixing device 52. There is. The branching direction in which the paper P having the toner image fixed by the fixing device 52 is conveyed, and the direction in which the paper P passed through the fixing device 52 is conveyed is selectively changed from the outside of the device 2. Gate 70 and branch gate 70
A discharge roller 79 that discharges the paper P that has passed through the apparatus 2 to the outside of the apparatus 2 is arranged.

In the direction in which the sheet P is returned into the apparatus 2 by the branch gate 70, following the branch gate 70, a reversing guide 71 for guiding the sheet P having information already copied on one side to a storage area 72 described later, and A storage area 72 for evacuating the paper P in order to reverse the direction of the paper P is arranged.
It should be noted that the storage area 72 has a length capable of accommodating a sheet P which is a copyable sheet and has a maximum length.

The storage area 72 also includes a reversing roller 75 for pulling out the paper P taken into the storage area 72 in the reverse direction, and the storage area 72.
A switching gate 73 that directs the sheet P toward the timing roller 66 when the sheet P taken in is pulled out, and a sheet sensor (not shown) that detects the presence of the sheet P are arranged.

The switching gate 73 is arranged between the reverse guide 76 for guiding the paper P to the timing roller 66 again, and between the reverse guide 76 and the timing roller 66, and the copied paper P is transferred to the transfer device 48 again. A double-sided paper feed guide 78 that guides to a transfer area between the photoconductor 42 is incorporated. still,
The reverse guide 76 incorporates a plurality of transport rollers 77 that feed the paper P toward the timing roller 66. Further, the reverse guide 76 incorporates a sheet sensor (not shown) that detects the presence of the sheet P.

According to FIG. 4, the copying machine 2 has a main control circuit 80 including a CPU 82 as a main control device. C
The PU 82 has a separation control device 84 that controls the separation output supplied to the separation charging device 48a, a memory 86 that stores a separation current value corresponding to the output from the separation control device 84, and
An input circuit (A / D converter) 88 for converting a document density signal from the automatic exposure sensor (AES) 40 into a digital signal and inputting it to the CPU 82 is connected.
Further, the CPU 82 compares the original density signal input from the AES 40 with the reference value stored in the memory 86, and detects the peeling claw 50b of the nail peeling device 50 from the photosensitive layer 42a of the photosensitive drum 42.
Peeling claw operation determination circuit (comparator) 90 that determines whether or not to adhere to the peeling claw 50
A peeling claw driving circuit 92 for urging the solenoid 50f when an instruction to bring b into close contact with the photosensitive layer 42a of the photosensitive drum 42 is output is connected.

Next, the output of the AES 40 and the operation of the peeling claw 50b will be described. As shown in FIG. 5, AES
The reference numeral 40 outputs an output voltage of a predetermined value according to the amount of light reflected from the document D generated by the image information of the document D placed on the document table 10 being illuminated by the illumination lamp 22 and the reflector 24. To do. Here, if the output voltage range of the AES 40 is set to, for example, 0 V to 5 V, a voltage within the range indicated by “H” is output according to the amount of light reflected from the document D. Therefore, if the image density of the original document D is low, that is, if it is a white original document, a voltage close to 5 volts is obtained, and if the image density of the original document D is high, that is, if it is a black original document or an original document containing many solid black images. , A voltage close to 0 volts
Each is output.

By the way, the copying apparatus 2 includes a separate charging device 48.
In addition to “a”, it has a nail peeling mechanism 50, but many copy sheets P are substantially released from electrostatic attraction with the photoconductor drum 42 only by the separation charging by the separation charging device 48a. Here, a case where the separation charging from the photosensitive drum 42 cannot be performed only by the separation charging by the separation charging device 48a will be considered.

In general, the separation charging output from the separation charging device 48a is fixed to a constant value (reference value).
In many cases, the reference value of the separation charge output is provided to the photosensitive layer 42a of the photoconductor drum 42, which is an original with a large number of white areas (white original) that is relatively difficult to peel off, that is, an original with low image density. The copy paper on which the copy image corresponding to the original with a small amount of toner is formed is set as a strong (high) setting.

However, when the separation charging output set based on the white original is provided, the original has a large black area (solid black original) which is relatively easy to peel off, that is, the original has a high image density. The copy paper on which the copy image corresponding to the original having a large amount of toner provided on the photosensitive layer 42a of the photoconductor drum 42 is formed is reversely charged by the toner due to the separate charging output. Since it is difficult to separate the 42 from the photosensitive layer 42a, it is necessary to use the nail peeling mechanism 50 in combination for reliable separation.

Separately from this, for example, in the double-sided copying mode or the multiplex copying mode, or the SFB44
When a sheet that has already passed through a heating mechanism (heat fixing mechanism) such as a copying machine or a printer via c is fed again as a transfer sheet, the sheet P is generated by passing through the heat fixing mechanism. The curl (curvature, see FIG. 6) and the curvature of the photosensitive drum 42 may be in the same direction. In this case, since the curl cannot be removed only by the separation charging by the separation charging device 48a, reliable separation by using the nail peeling mechanism 50 together is necessary.

Next, the operation of the copying apparatus 2 will be described with reference to FIG. According to FIG. 7, after a power switch (not shown) of the copying apparatus 2 is turned on, a predetermined initial (initial)
By turning on a copy start key (not shown) of the device 2 which is on standby in a copy ready state by operation, the illumination lamp 22 of the first carriage 20 is turned on, and reflection from the document D placed on the document table 10 is performed. The image density of the document D is detected by the AES 40 from the light. In this case, as described above with reference to FIG. 5, the output voltage from the AES 40 is in the range “H” between the output voltage corresponding to the maximum density image and the output voltage corresponding to the minimum density image. Is the value of (STP 1)
. Generally, the AES 40 detects the image density of all areas of the document D, but the peeling claw control of the present invention only needs to be able to determine the image density of about 20 mm from the front end of the document D.

Next, the output voltage V of the AES 40 detected by STP 1 is converted into a digital signal by the input circuit (A / D converter) 88, and then input to the comparator 90 via the CPU 82, and the comparator 90 stores it in the memory. It is determined whether or not the reference value V1 stored in 86 is larger than, for example, 2 volts (STP 2). When it is determined by STP 2 that the image density of the document D is high, that is, the output voltage of the AES 40 is 2 V or less, the CPU 82 outputs an instruction to bring the peeling claw 50b into close contact with the photosensitive layer 42a of the photosensitive drum 42. At the same time, the CPU 82 operates the peeling pawl drive circuit 92 at a predetermined timing based on, for example, the aligning signal supplied to the timing roller 66, and energizes the solenoid 50f. When the solenoid 50f is turned on, the lever 50e is displaced in the direction of arrow B,
When the lever 50d is rotated about the fulcrum C as a fulcrum, the lever 50c and the shaft 50a are rotated, and the peeling claw 50b is rotated.
Is brought into contact with the photosensitive layer 42a (STP 3). When it is determined by the output of the AES 40 and the output of the comparator 90 that the original has a high image density, the separation charging output applied to the separation charging device 48a by the separation control device 84 is lowered within a predetermined range. Good.

Subsequently, the operation time of the peeling claw 50b which is predetermined according to the length of the paper P detected by the paper size sensor or the paper rear end sensor (not shown) is read from the memory 86 by the CPU 82, and the memory 86 is read. The solenoid 50f is turned off and the lever 50e is displaced in the direction of the arrow A at the timing when the allowance is added to the operation time stored in. Therefore, the lever 50d is rotated in the direction opposite to the ON direction of the solenoid 50f, the lever 50c and the shaft 50a are returned to their original positions, and the peeling claw 50b is released from the contact with the photosensitive layer 42a (STP 4). . Incidentally, since the lever 50d is biased in one direction by the spring 50h, it goes without saying that the peeling claw 50b is reliably separated from the photosensitive layer 42a.

FIG. 8 shows a modification of the operation of the peeling claw shown in FIG. According to FIG. 8, the supply source of the paper P is checked by turning on the copy start key (not shown) of the copying apparatus 2 which is on standby in the copy ready state. That is, the SFB44c of the SFB44c of the paper supply unit 8 is controlled by the SFB open detection switch (not shown) or the paper sensor.
Whether the printer is in the paper supply standby state (STP
11).

According to STP 11, the supply source of the paper P is SFB44.
When it is detected that the value other than c is detected (STP 11-N), it is determined whether the double-sided copy mode or the multiplex copy mode is selected by the operation panel (not shown), and the paper P.
It is detected that the supply source is other than the storage area 72 and the reverse guide 76. (STP 12). After it is determined by STP 11 and STP 12 that the supply source of the paper P is one of the cassettes 60a and 60b (STP 12-N), the copy start key (not shown) is turned on, and the first carriage is turned on. The illumination lamp 22 of 20 is turned on, and the image density of the document D placed on the document table 10 is detected by the AES 40 (STP
13) .

Thereafter, similarly to the example shown in FIG. 7, the AE
It is determined whether the output voltage V of S40 is larger than the reference value V1 or 2 volts (STP 14). When the STP 14 determines that the image density of the document D is high, that is, the output voltage of the AES 40 is 2 V or less, the CPU 82 outputs an instruction to bring the peeling claw 50b into close contact with the photosensitive layer 42a of the photosensitive drum 42. As a result, a predetermined drive signal is generated from the peeling pawl drive circuit 92, the solenoid 50f is energized, and the peeling pawl is driven.
50b is brought into contact with the photosensitive layer 42a (STP 15).

Subsequently, the solenoid 50f is turned off at the timing when the margin is added to the peeling claw operating time determined based on the length of the paper P, the lever 50c and the shaft are rotated.
50a is returned to its original position, and the peeling claw 50b is released from the contact with the photosensitive layer 42a (STP16).

In the above embodiment, the copying apparatus for copying the image of the original placed on the original table of the copying apparatus by moving the illuminating device and the reading device has been described. However, the original placed on the original is described. It can also be applied to a copying machine in which a table is moved. Further, a copying machine having the automatic exposure (original density) sensor for detecting the density of the image of the original can be applied to the following types of copying machines regardless of the peeling mechanism or the image forming method.

[0047]

As described above, according to the image forming apparatus of the present invention, the claw peeling device for peeling the copy sheet attracted to the photosensitive drum by the electrostatic force from the photosensitive drum is an automatic exposure sensor. It is operated or stopped based on the image density of the document detected by. For example, if a copy image is transferred to a copy sheet that can be easily peeled without using a nail peeling device, the copy sheet is separated from the photosensitive drum only by the AC electric field provided by the separating device. On the other hand, when an image of an original including a solid black image is copied on the leading edge of the transfer sheet, or when the transfer sheet cannot be determined to have a constant property, it has been manually fed or has already passed through a heat fixing device. When paper is used, the nail of the nail peeling device is brought into contact with the photosensitive layer of the photoconductor drum in accordance with the AC electric field from the separating device,
The paper can be reliably separated (separated) from the photoconductor drum.

Therefore, the abrasion of both the photosensitive layer of the photoconductor drum and the peeling claw of the claw peeling device is reduced, while the copy paper is peeled from the photoconductor drum regardless of the image density of the document or the state of the copy paper. It is prevented to be caught without being caught.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus in which an embodiment of the present invention is used.

FIG. 2 is a schematic diagram showing the position of an automatic exposure sensor incorporated in the image forming apparatus shown in FIG.

FIG. 3 is a partially enlarged view showing the nail peeling device shown in FIG. 1 in detail.

FIG. 4 is a block diagram schematically showing the image forming apparatus shown in FIG.

5 is a graph showing the relationship between the output voltage of the automatic exposure sensor shown in FIG. 2 and the density of the image of the original.

FIG. 6 is a schematic diagram illustrating a state of copy paper that is easily rolled up on a photosensitive drum in the image forming apparatus illustrated in FIG.

FIG. 7 is a flowchart showing an example of the operation of the image forming apparatus shown in FIGS. 1 to 4.

FIG. 8 is a flowchart showing a modification of the operation shown in FIG.

[Explanation of symbols]

2 ... Copying device, 4 ... Image reading unit, 6 ... Image forming unit, 8 ...
Paper feeder, 10 ... Original platen, 12 ... Original pressing, 20 ... First carriage, 22 ... Illumination lamp, 24 ... Reflector, 26 ... First
Mirror, 30 ... Second carriage, 32 ... Second mirror, 34 ... Third mirror, 36 ... Lens unit, 38 ... Folding mirror, 40
... automatic exposure sensor, 42 ... photosensitive drum, 42a ... photosensitive layer,
44 ... Charging device, 46 ... Developing device, 48 ... Transfer device, 48a ... Separation charging device, 50 ... Nail stripping device, 50a ... Shaft, 50b ...
Peeling claws, 50c, 50d, 50e ... Lever, 50f ... Solenoid, 50g ... Plunger, 50h ... Spring, 52 ... Fixing device, 54 ... Cleaning device, 56 ... Eliminating device, 58a, 58b
… Slots, 60a, 60b… Paper cassettes, 62a, 62b…
Paper feed rollers, 64a, 64b ... Conveying rollers, 66 ... Timing rollers, 68 ... Conveying belts, 70 ... Branch gates, 71 ... Reversing guides, 72 ... Storage areas, 73 ... Switching gates, 75 ... Reversing rollers, 76 ... Reverse guides , 77 ... Conveying rollers, 78 ... Double-sided paper feeding guide, 79 ... Discharging rollers, 80 ... Main control circuit, 82 ... CP
U, 84 ... Separation control device, 86 ... Memory, 88 ... Input circuit, 90
… Stripping claw actuation determination circuit, 92… Stripping claw driving circuit.

Claims (5)

[Claims] 1. An image carrier on which an image corresponding to an image of an original is formed, a transfer means for transferring the image formed on the image carrier to a transfer material, and a surface of the image carrier selectively. And a peeling means for peeling the transferred material on which the image has been transferred by the transfer means from the image carrier by being placed in contact with the surface of the image carrier, and the density of the image of the original. And a peeling means driving means for selectively urging the peeling means based on the value output by the density detecting means. An image forming apparatus characterized by. 2. An image carrier on which an image corresponding to an image of an original is formed, a transfer means for transferring the image formed on the image carrier to a transfer material, and the transfer material includes a state change. Information for determining whether or not it is possible to selectively contact the surface of the image carrier with a holding unit that holds the transfer target material toward the image carrier And a peeling means for peeling the transfer-receiving material, on which the image is transferred by the transfer means by being brought into contact with the surface of the image carrier, from the image carrier, and detecting the density of the image on the document. A density detecting means for outputting a value corresponding to the detected density, and when the value output by the density detecting means is less than or equal to a predetermined value and the holding means informs that the transfer target material includes a state change. Peeling means for urging the peeling means An image forming apparatus comprising: the moving means. 3. An image carrier on which an image corresponding to the image of an original is formed, a holding means for holding a transfer material fed toward the image carrier, and a carrier for the image carrier. The transferred material to be sent,
Second holding means for holding the transferred material whose state has been changed by heating, and the image formed on the image carrier on the transferred material fed from the holding means and the second holding means. The transfer means for transferring and the surface of the image carrier are arranged so as to be selectively contactable with the surface of the image carrier, and the transferred material to which the image is transferred by the transfer means is transferred to the surface of the image carrier. The peeling means for peeling from the image carrier, the density detecting means for detecting the density of the image of the original and outputting the value corresponding to the detected density, and the peeling means for the peeling means based on the value output by the density detecting means. Peeling means driving means for selectively urging and for continuously urging the peeling means when the transferred material is supplied from the second holding means. Image forming apparatus. 4. A reading means for illuminating an original and extracting reflected light from the original, and a detecting means for detecting the light quantity of the reflected light taken out by the reading means and outputting a value corresponding to the detected light quantity. An image carrier on which an image corresponding to the reflected light extracted by the reading unit is formed, a developing unit for developing the image formed on the image carrier, and the image carrier developed by the developing unit. Transfer means for transferring the developer image on the body onto a sheet that is brought into close contact with the image carrier by electrostatic attraction; and a transfer unit arranged so as to be selectively contactable with the surface of the image carrier. When the paper having the developer image transferred by the transfer means by being brought into contact with the surface is peeled off from the image carrier, and the value output from the detection means is equal to or less than a predetermined value, Operate the peeling means An image forming apparatus; and a control means. 5. A reading means for illuminating an original and extracting reflected light from the original, and a detecting means for detecting the light quantity of the reflected light taken out by the reading means and outputting a value corresponding to the detected light quantity. An image carrier on which an image corresponding to the reflected light extracted by the reading unit is formed, a developing unit for developing the image formed on the image carrier, and the image carrier developed by the developing unit. Transfer means for transferring the developer image on the body onto a sheet of paper that is in close contact with the image carrier by electrostatic attraction, and providing an AC electric field to the sheet of paper on which the developer image is transferred by the transfer means. The separating means for releasing the paper from electrostatic attraction with the image carrier and the surface of the image carrier are arranged so as to be selectively contactable with each other, and by contacting with the surface of the image carrier. The developer image is formed by the transfer unit. A peeling means for peeling the transferred sheet from the image carrier, and a first means for suppressing the output of the separating means within a predetermined range when the value output from the detecting means is a predetermined value or less. An image forming apparatus comprising: a control unit; and a second control unit that operates the peeling unit when the value output from the detection unit is equal to or less than a predetermined value.