JP2002258631A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of improving transfer performance deteriorated by the moisture absorption of transfer material and the soiling of a transfer wire, and solving the problem on carrying caused by the curl of the transfer material at double-sided image forming time. SOLUTION: This image forming device is provided with a means for forming a toner image on a photoreceptor, a transfer means for transferring the toner image from the photoreceptor to the transfer material, a separation means for discharging and separating the transfer material from the photoreceptor, and a bias voltage applying means for applying bias voltage to the transfer means and the separation means. In the device, the bias voltage applying means for applying the bias voltage to the transfer means is a constant-voltage power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus having improved transferability to a transfer material and transferability of the transfer material.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a copying machine or a printer of the electrophotographic type, a constant current power supply is supplied from a constant current power supply immediately before a transfer material reaches a transfer device (hereinafter referred to as a transfer device) as a transfer means. Is output. A part of the charge of the opposite polarity to the toner image discharged from the transfer device is applied to the back surface of the transfer material, and the transfer material is electrostatically attracted to the photoconductor and the toner image on the photoconductor is transferred to the transfer material at the same time. Is done.
When the transfer material passes over the transfer device and the transfer is completed, the constant current power supply is turned off.

Next, the transfer material is subjected to a static elimination action by a separator as a separating means, and the adsorbing force with the photoreceptor is weakened. Then, the transfer material is separated from the photoreceptor. The toner image is melted and fixed on the transfer material, and the image formation on the transfer material is completed.

In the transfer under a high environmental humidity, the transfer material absorbs moisture and the electric resistance value is lowered, so that the electric charge applied in the transfer process leaks to the separator, the paper feed guide, etc. through the transfer material. However, a desired transfer charge cannot be obtained, resulting in transfer failure. Therefore, in the related art, a humidity sensor is provided to detect environmental humidity, and under a high environmental humidity, the output current of transfer is increased, and the output current is corrected according to the environment.

However, the electric resistance value of the transfer material is not simply determined with respect to the environmental humidity, but varies depending on the standing time in the humidity environment, the leaving state, the quality of the paper as the transfer material, and the like. In, the transfer current is set based on the electrical resistance value of an intermediate condition between the sufficiently conditioned transfer material and the transfer paper immediately after being taken out of the wrapping paper.

Therefore, since an optimum current value corresponding to each transfer material cannot be determined, transfer failure due to insufficient current or transfer repelling due to excessive current tends to occur depending on the degree of moisture absorption of the transfer material.

Concerning the transfer material transfer, in the case of double-sided image formation, the transfer material is once passed through the fixing device to complete the fixing of one surface, and then is reversed and transported by the reversing sheet feeding unit. Then, a problem caused by curling of the transfer material occurs in the process of being transferred to the fixing device again after the process of transferring and separating the other surface. When an image on one surface is fixed by a general heat roll method, both ends of the transfer material curl downward, and then when the transfer material is inverted for image formation on the other surface, the transfer material is turned upward. It will curl. In this state, the transfer material is transferred and separated, passes through a transport belt as a transport unit, and goes to a fixing device. Therefore, the transfer material floats with respect to the transport belt. In the case of a transfer material such as paper or recycled paper, the curl becomes large and hits an upper structure such as a separation claw, and often causes corner breaks, wrinkles, and jams. In addition, since the leading end of the transfer material is curled upward, the transfer material fluctuates due to air resistance or the like,
A similar problem tends to occur. Conventionally, fixing temperature conditions are optimized and decurlers are provided to prevent curling, but it is difficult to cope with various types of transfer materials and changing temperature and humidity environments.

[0008] There is also a configuration in which a belt is conveyed by a fan using a conveyor belt having a hole to adsorb the transfer material by a fan. It is difficult to adsorb.

[0009]

SUMMARY OF THE INVENTION The present invention solves the problems caused by environmental humidity, which are difficult to solve with the prior art, and also solves the problem of transport due to the curl of the transfer material during double-sided image formation. It is an object to provide an image forming apparatus.

[0010]

The above object can be achieved by the following constitution.

(1) means for forming a toner image on a photoreceptor, transfer means for transferring the toner image from the photoreceptor to a transfer material, separation means for removing and separating the transfer material from the photoreceptor, In an image forming apparatus having a bias voltage applying unit for applying a bias voltage to each of a transfer unit and the separation unit, the bias voltage applying unit for the transfer unit is a constant voltage power supply. Invention).

(2) means for forming a toner image on a photoconductor, transfer means for transferring the toner image from the photoconductor to a transfer material, separation means for separating the transfer material from the photoconductor, and the toner An image forming apparatus comprising: a fixing unit for fixing an image to the transfer material; a conveying unit for conveying the transfer material separated from the photoconductor to the fixing unit; and a unit for forming a double-sided image. An image forming apparatus provided with a blowing unit for blowing air toward the transfer material (second invention).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of double-sided image formation according to an embodiment of the present invention will be described below with reference to the drawings.

Note that the description in the present application does not limit the technical scope of the claims and the meaning of terms.

In the description of the embodiments of the present invention, in forming a double-sided image, the first toner image formed on the photoreceptor is called a back side image, and the second toner image is called a front side image.

FIG. 1 is a schematic diagram showing the overall configuration of an image forming apparatus of the electrophotographic type. 2 (a), (b),
3C is a partial view for explaining the transfer route of the transfer material during double-sided image formation.

FIG. 3 is a schematic diagram for explaining a transfer means provided with a bias voltage applying means to the transfer unit and a blowing means.

FIG. 4 is a graph for explaining the difference between the reference integrated amount of the output current of the transfer unit and the actual integrated amount.

FIG. 5 is a schematic diagram for explaining another example of changing the output voltage to the transfer device. In FIG. 1, reference numeral 10 denotes a photoreceptor serving as an image forming body, 11 denotes a scorotron charger,
12 is an exposure optical system as an image writing means, 13 is a developing device,
14 is a cleaning device for cleaning the surface of the photoreceptor 10, 15 is a cleaning blade, 16 is a developing sleeve, 17 is a transfer device, 18 is a transfer material separator for the photoreceptor 10, and 19 is a transfer material photoreceptor 10 The photoreceptor 10, scorotron charger 11, exposure optical system 12, developing device 13, transfer device 17, separator 18, separation claw 19, cleaning device 14, and the like constitute the image forming unit 1.
Is composed.

The photoreceptor 10 is formed by forming a conductive layer, an a-Si layer, or a photosensitive layer such as an organic photoreceptor (OPC) on the outer periphery of a cylindrical metal base formed of, for example, an aluminum material. Is rotated clockwise as indicated by the arrow in FIG.

Reference numeral 20 denotes a paper feed cassette for storing the transfer material P,
21 is a feed roller, 22 is a transfer material transport roller, 23
Is a timing roller, and 24 is a paper feed guide.

Reference numeral 3 denotes a conveying means, which is a conveying belt 30 having a plurality of holes, a driving roller 31 for driving the conveying belt 30, a driven roller 32, and a plurality of pores formed on a sliding surface with the conveying belt 30. The suction box 33 is connected to a suction fan (not shown) via an air duct (not shown).
It is conveyed while being sucked on the surface of "0".

Reference numeral 4 denotes a fixing device, which includes a heat roller 41, a pressure roller 42, a fixing discharge roller 43, and the like. Reference numeral 44 denotes a paper discharge roller for discharging the fixed transfer material to the outside of the apparatus.

Reference numeral 5 denotes a blower, which comprises a blower fan 34 and a louver 35. In the case of double-sided image formation, the transfer material P on which the fixing process of the back side image is completed is circulated through the hinge 57 into the machine again for forming the front surface image or discharged outside the machine. It is a distribution valve. 51 is a distribution valve via a hinge 58, and 52 is a distribution valve via a hinge 59. The selection of opening and closing of these distribution valves is performed by the control unit S. 53, 54, 55 and 56 are conveying rollers.

Reference numeral 6 denotes a reversing sheet feeding unit for reversing the transfer material P on which the back side image is fixed when forming the front side image.

Next, the double-sided image forming process will be described with reference to FIG. When a drive motor (not shown) starts rotating at the start of image formation (recording), the photoconductor 10 rotates clockwise as indicated by an arrow. At the same time, the application of the potential to the photoconductor 10 by the scorotron charger 11 is started.

On the photoreceptor 10 after the potential is applied,
Image writing of an electric signal corresponding to image data from the image reading device 70 is started through the exposure optical system 12,
An electrostatic latent image corresponding to a document image is formed on the surface of the photoconductor 10, and the electrostatic latent image is reversely developed by a developer conveyed by a developing sleeve 16 of a developing device 13, and is a first toner image. It becomes the back side image (visible image).

On the other hand, the transfer material P is sent out from a paper feed cassette 20 by a feed-out roller 21, is transferred to a timing roller 23 via a transfer material transfer roller 22, is sent out by driving the timing roller 23, and is transferred onto the photosensitive member 10. And is fed to the area between the transfer unit 17 and the photoreceptor 10.

The back side image is transferred to the transfer unit 1 to which a bias voltage from a DC constant voltage power supply having a polarity opposite to that of the toner is applied.
7, the image is transferred onto the transfer material P.

Thereafter, the photosensitive member 10 is moved to the cleaning device 1.
4 and is directed to the next image formation.

The transfer material P on which the back side image is placed is separated from the transfer material P by the separator 18
Is separated from the photoreceptor 10, is sent to the conveying unit 3, is sucked by the conveying belt 30 through the suction box 33, and is
Transported to Thereafter, the transfer material P is transferred to the heat fixing roller 41.
By applying heat and pressure while being nipped and conveyed in the nip T between the pressure roller 42 and the pressure roller 42, the back surface image is fused and fixed on the transfer material P.

The transfer material P on which the back side image has been fixed is discharged by a fixing discharge roller 43, distributed by a distribution valve 50, passed through a distribution valve 51, and conveyed to a reversing paper feed unit 6 by a transport roller 53. It is transported (see FIG. 2A).

In the reversing sheet feeding section 6, the rear end of the transfer material P is in a state of being locked to the transport roller 53 (see FIG. 2B).

Next, the transfer material P locked on the transport roller 53 is reversely transported by the reverse rotation of the transport roller 53, and
It is distributed in the direction of internal circulation by the distribution valve 51, passes through the distribution valve 52 via the conveyance rollers 54, 55 and 56, and is conveyed to the timing roller 23. On the other hand, the front surface image which is the second toner image is formed on the photoconductor 10 in the same process as the formation of the back surface image, and the transfer material P having the back surface image on one surface is synchronized with the front surface image, The transfer roller 17 is fed to a region between the transfer device 17 and the photoreceptor 10 by the timing roller 23, and the surface image is transferred to the transfer material P by the transfer device 17 to which a bias voltage is applied by a DC constant voltage power supply having a polarity opposite to that of the toner. (See FIG. 2 (c)).

Further, the transfer material P on which the surface image is placed is blown by the blowing means 5 and is brought close to the transport belt 30.
The air is suctioned by the conveyor belt 30 by the suction box 33 and is sent to the fixing device 4. Here, the air blowing means according to the present invention will be described with reference to FIG.

As described above, after the back surface image as the first toner image is fixed, both ends of the transfer material P curl downward, and when the transfer material P is inverted, the transfer material P becomes curled upward. Since the surface image is transferred and separated in that state, when the wind blowing means 5 blows the transfer material P with a wind of such a degree that the surface image as the second toner image is not disturbed, floating and fluttering can be prevented, and It is brought close to and adhered to the surface of the conveyor belt 30 to enable stable conveyance to the fixing device 4. The louver 35 can adjust the wind direction, and is preferably inclined in the direction A of the transport direction of the transfer material P.

In the fixing device 4, the surface image is fixed on the surface of the transfer material P. The transfer material P on which the double-sided image formation has been completed is discharged by the fixing discharge roller 43 through the distribution valve 50 selected so as to guide the transfer material P out of the machine, and then discharged by the discharge roller 44.

Next, the transfer according to the present invention will be described. In FIG. 3, a transfer unit 17 includes a constant voltage power supply 17c (hereinafter, referred to as a constant voltage power supply) serving as a bias voltage applying unit.
Although a more constant voltage is applied and the transfer material P is discharged, the electric resistance of the transfer material P decreases due to moisture absorption or the like, and even if the electric charge discharged to the transfer material P leaks to the paper feed guide 24 or the separator 18. Since the current is supplied to the transfer unit 17 to compensate for this, the bias voltage is unlikely to decrease. Therefore,
Stable transfer is possible regardless of the electric resistance value of the transfer material P.

However, in the case of transfer using a constant voltage power supply, the output current tends to gradually change due to a change in impedance due to contamination of the transfer wire 17a or the like. In order to improve this, it is necessary to change the output voltage and set the output current to a value when the transfer wire 17a and the like are free from dirt.

That is, the constant voltage power supply 17 to the transfer device 17
Detecting means 17b for detecting the output current of c is provided, and the detecting means 17b detects the output current and integrates the output values.

In FIG. 4, when the ordinate is the integrated amount Q of the detected output current and the abscissa is the copy count C, if the transfer wire 17a (see FIG. 3) is clean, the reference line B The integrated amount follows (provided that the output voltage at that time is V ₀ , the output current is I ₀ , and the impedance is R ₀ ). However, if the impedance changes with time due to contamination of the transfer wire 17a (see FIG. 3), the output current decreases, and the actual integrated amount becomes D. When the difference Δx between the integrated amounts B and D is equal to or greater than a predetermined value, the output voltage is changed so that the output current of the constant voltage power supply 17c (see FIG. 3) becomes I ₀ at the start. When the copy count C of this time N, impedance and R _N, R _N is n
Since it can be approximated to V ₀ / ΣI (where n is an appropriate predetermined number of copies up to the copy count N and is set in advance. ΔI is the integrated amount of the output current from N−n to N). The output voltage to be changed at the time is V = R _{NI 0} =
It is determined by nV ₀ I ₀ / ΣI.

In practice, the difference Δx is monitored for each copy or copy sequence, and when the difference Δx reaches a predetermined value, the constant voltage power supply 17c (FIG. ) Is set to V.

In the present embodiment, the case of the corona transfer method using a wire has been described. However, the same can be said for the roller transfer method because the change is related to the aging of the roller resistance value.

In this embodiment, the constant voltage power supply 17c
However, as shown in FIG. 5, the output current of the constant voltage power supply may be changed so that the current flowing into the photoconductor 10 is maintained at a constant value _ID .

[0045] That is, in FIG., The current I _D flowing into the photosensitive member 10 is a value obtained by subtracting the current I _B flowing to the control plate of the transfer device 17 from the output current I of the constant-voltage power source 17c. Thus, integrated by detecting the current I _B by the detection means 17e, the value to change the output voltage of the constant voltage source 17c reaches the predetermined difference. However, in this case, since only the current flowing into the control plate of the transfer unit 17 is detected, the transfer unit 17 and the separator 18 must be separate.

[0046]

The present invention has the following effects.

(1) Even if the impedance changes due to moisture absorption of the transfer material or contamination of the transfer wire, a constant voltage power supply is used.
By changing the output voltage, stable transfer properties can be obtained.

(2) By providing the air blowing means for blowing air toward the transfer material on the transfer material transporting means, it is possible to solve the transport problem caused by the curl of the transfer material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of an electrophotographic image forming apparatus.

FIGS. 2A, 2B, and 2C are partial views illustrating a transfer route of a transfer material during double-sided image formation.

FIG. 3 is a schematic diagram for explaining a transfer unit provided with a bias voltage applying unit and a blowing unit to a transfer unit.

FIG. 4 is a graph for explaining a difference between a reference integrated amount of the output current of the transfer device and an actual integrated amount.

FIG. 5 is a schematic diagram for explaining another example of changing the output voltage to the transfer device.

[Explanation of symbols]

 Reference Signs List 6 reverse sheet feeding section 10 photoreceptor 13 developing device 17 transfer device 23 timing roller 30 transport belt 33 suction box 34 blower fan 35 louver 50, 51, 52 distribution valve

Claims (4)

[Claims] A means for forming a toner image on a photoreceptor;
Transfer means for transferring the toner image from the photoconductor to a transfer material; separation means for removing and separating the transfer material from the photoconductor; and bias voltage applying means for applying a bias voltage to each of the transfer means and the separation means. Wherein the bias voltage applying means for the transfer means is a constant voltage power supply. 2. A detecting means for detecting an output current of the constant voltage power supply, wherein an integrated value of an output value of the detecting means is
The image forming apparatus according to claim 1, wherein an output voltage of the constant voltage power supply is changed. 3. The image forming apparatus according to claim 2, wherein a change timing of the output voltage of the constant voltage power supply is determined based on a difference between an integrated output value of the detection unit and a predetermined reference value. 4. A means for forming a toner image on a photoreceptor,
Transfer means for transferring the toner image from the photoconductor to a transfer material; separation means for separating the transfer material from the photoconductor; fixing means for fixing the toner image to the transfer material; and separation from the photoconductor. An image forming apparatus comprising: a conveying unit that conveys the transferred transfer material to the fixing unit; and a unit that forms a double-sided image, wherein an image forming apparatus includes a blowing unit that blows air toward the transfer material on the conveying unit. apparatus.