JP2001154548A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming the recording image of high quality and reducing stains inside a machine as well by preventing the phenomenon that a toner image scatters from the surface of an image receiving body such as a recording sheet and an intermediate transfer body belt after the transfer of the toner image to the image receiving body. SOLUTION: In this image formation device provided with a transfer means 17 for electrostatically transferring the toner image formed on an image carrier 11 corresponding to image information to the image receiving body 20, a cleaner 15 for cleaning the surface of the image carrier 1 for which the transfer of the toner image is ended and a pre-cleaning destaticizer 16 provided between the transfer means 17 and the cleaner 15 for destaticizing residual toner stuck to the image carrier 11, while an AC bias voltage is applied to the pre-cleaning destaticizer 16, the pre-cleaning destaticizer 16 is attached so as to discharge a part of electric charges generated in the destaticizer toward the surface of the image receiving body 20 after the toner image transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly, to an image receiving body such as a recording sheet or an intermediate transfer belt from an image carrier such as a photosensitive drum. To improve the transfer of toner images.

[0002]

2. Description of the Related Art In a copying machine or a laser beam printer using an electrophotographic system, a toner image corresponding to image information is formed on an image carrier such as a photosensitive drum and then transferred to a recording sheet. Thus, a recorded image is formed. For example, in a laser beam printer, first, the surface of the photosensitive drum is charged to a predetermined background potential, and then the surface of the photosensitive drum is exposed to a laser beam modulated by image information to form an electrostatic latent image. I have. Next, after developing the electrostatic latent image with toner to form a toner image as a visible image, the toner image is transferred to a recording sheet, and the recording sheet after the transfer of the toner image is heated and fixed by a fixing device. The recording image has been obtained with. Further, the photosensitive drum after the transfer of the toner image is subjected to static elimination of the residual toner by the static eliminator before cleaning, and after the static elimination, the residual toner is removed by the cleaner.

In the process of forming such a recorded image,
As a method of transferring a toner image to a recording sheet, a method of directly transferring a toner image from an image bearing member to a recording sheet, and a method of transferring a toner image A method of transferring an image, a method of first transferring a toner image to an intermediate transfer belt in the form of an endless film, and then secondary transferring the toner image to a recording sheet are also used. Of these, a transfer method using a sheet conveying belt or an intermediate transfer belt is most suitable for forming a full-color image that requires superposition of toner images of a plurality of colors, and is employed in a color copying machine, a color laser printer, and the like. ing.

In either transfer method, a transfer means such as a corona discharger or a bias roll is disposed at a position facing the image carrier with an image receiving member such as a recording sheet or an intermediate transfer belt therebetween. The toner image is electrostatically transferred to the front surface of the image receiving member by applying a charge having a polarity opposite to that of the toner to the back surface of the image receiving member. For example, when the charge polarity of the toner is minus (-), the transfer means provided on the back side of the image receiving member has plus (+)
Is applied to apply a positive (+) charge to the back surface of the image receiving body.

[0005]

Normally, after the transfer of the toner image to the image receiving member, the amount of charge of the toner adhered to the surface of the image receiving member and the amount of the opposite polarity charge applied to the back surface of the image receiving member by the transfer means. Can be said to be balanced. However, due to fluctuations in environmental factors such as temperature and humidity, non-uniformity of the shape and electric resistance of the transfer unit, etc., the charge may not be appropriately applied to the back surface of the image receiving body. In this case, the balance of the charge amount on the front and back surfaces of the image receiving body is lost. When the balance of the charge amount is lost, the electrostatic attraction for holding the toner on the surface of the image receiving member is weakened, so that the toner cannot be reliably held on the surface of the recording sheet. There is a problem that the image is scattered from the surface of the image receiving body, which deteriorates the quality of the recorded image and causes stains inside the image forming apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object the object of transferring a toner image onto an image receiving member such as a recording sheet or an intermediate transfer belt from the surface of the image receiving member. An object of the present invention is to provide an image forming apparatus capable of preventing a phenomenon in which a toner image is scattered, forming a high-quality recorded image, and reducing stains in the apparatus.

[0007]

In order to achieve the above object, an image forming apparatus according to the present invention comprises an image carrier which rotates at a predetermined process speed and has a surface on which a toner image corresponding to image information is formed. A transfer unit that is arranged to face the image carrier and electrostatically transfers the toner image from the image carrier to the image receiver; and a cleaner that cleans the surface of the image carrier after the transfer of the toner image is completed. It is assumed that the image forming apparatus is provided between the transfer means and the cleaner and has a pre-cleaning static eliminator for neutralizing residual toner adhered to the image carrier. An AC bias voltage is applied to the pre-cleaning static eliminator. On the other hand, the cleaning static eliminator is mounted so that a part of the electric charge generated by the static eliminator is released toward the surface of the image receiving body after the transfer of the toner image.

In such a technical means, since an AC bias voltage is applied to the pre-cleaning static eliminator, the pre-cleaning static eliminator generates both positive and negative charges, so that the image bearing member is removed. The residual toner adhering to the surface is neutralized. At this time, since the pre-cleaning static eliminator is disposed adjacent to the toner image transfer portion, if the charge balance of the image receiving body after the transfer of the toner image is lost, the pre-cleaning static eliminator is generated. As a result, one of the two polar charges is attracted to the image receiving member. For example, if the amount of charge given to the back side of the image receiving body by the transfer means exceeds the amount of charge of the toner image on the surface of the image receiving body, the charge having the same polarity as that of the toner image is attracted from the pre-cleaning neutralizer to the surface of the image receiving body. Will be done. Also, when the amount of charge given to the back surface of the image receiving member is smaller than the amount of charge of the toner image on the surface of the image receiving member, the charge of the polarity opposite to the polarity of the toner image is attracted from the pre-cleaning charge eliminator to the surface of the image receiving member. Become.

For this reason, by providing such a pre-cleaning static eliminator such that a part of the electric charge generated by the pre-cleaning static eliminator is released toward the surface of the image receiving member after the toner image transfer, the toner image is removed. The amount of charge on the front and back surfaces of the image receiving body onto which the image has been transferred naturally balances with the charge discharged from the pre-cleaning static eliminator. Therefore, immediately after the transfer of the toner image, even if the charge amount on the front and back surfaces of the image receiving body is imbalanced, the pre-cleaning static eliminator acts to correct this naturally. Can be prevented from scattering.

Here, the configuration of the pre-cleaning static eliminator, such as a brush for rubbing the image carrier or a corona discharger facing the image carrier with a predetermined gap, may be appropriately changed. No problem. However, from the viewpoint that a charge can be more reliably applied to the surface of the image receiving member after the transfer of the toner image, such a transfer unit is a corona discharger including a discharge wire and a shield, The emitted charge is directed toward the image receptor,
It is preferable to regulate the tip position of the shield. By arranging the shield of the corona discharger in this way, the charges radially generated from the discharge wire can directly reach the image receptor, which is compared to the case where the charges are simply carried to the image receptor by ion wind. As a result, it is possible to reliably maintain the balance between the charge amounts on the front and back surfaces of the image receiving body.

As a transfer means for transferring a toner image from the image carrier to the image receiving member, if a predetermined transfer bias voltage is applied, the transfer means may be interposed between the back surface of the image receiving member and a predetermined gap. It may be a corona discharger that is disposed oppositely or a bias roll that is in contact with the back surface of the image receiving body. Here, comparing the case where the corona discharger is used as the transfer unit and the case where the bias roll is used as the transfer unit, as shown in FIG. Discharge occurs in the wedge-shaped space generated before and after, and charge is given to the back surface of the image receiving body by the discharge.
In addition, since such discharge occurs only when the distance between the surface of the bias roll 101 and the image receiving body 100 is equal to or less than a predetermined value (for example, 300 μm), the electric charge is applied to the image receiving body 100 only in an extremely narrow region a. Will be. On the other hand, as shown in FIG.
In 02, the charges are emitted radially from the corona discharge wire 103, so that the charges are given to a wide area b that is equal to or larger than the opening width of the shield 104. Therefore, comparing the two as transfer means, the corona discharger 102
In the case where is used, there is an advantage that the charge generated in the pre-cleaning static eliminator 105 is easily guided to the image receiving body 100, and the above-described effect of the present invention is easily exerted. Reference numeral 106 in the drawing denotes an image carrier that rotates in the direction of the arrow.

On the other hand, when a bias roll is used, the adhesion between the image bearing member and the image receiving member is improved, so that a higher transfer efficiency can be obtained as compared with the case where a corona discharger is used. There is an advantage that the value of the current flowing through the bias roll can be suppressed accordingly.
For this reason, from the viewpoint of improving the image quality of a recorded image and extending the life of components, in recent years, an image forming apparatus using a bias roll as a transfer unit has increased. Therefore, from the viewpoint of facilitating the charge generated by the pre-cleaning static eliminator to the image receiving body while using the bias roll as the transfer unit, such a bias roll is located at a position where the image receiving body and the image carrier abut. It is also preferred that the image receiving member is also displaced downstream in the transport direction of the image receiving member.

Furthermore, the present invention is most suitable for a color image forming apparatus for transferring a plurality of toner images on an image receiving member in a superimposed manner. When a plurality of toner images are successively transferred onto the surface of the image receiving body, the amount of charge on the back side of the image receiving body increases each time the toner image is transferred. This is because the balance of the amounts is easily lost, and scattering of the toner image after transfer is more likely to occur.

On the other hand, in the present invention, when the resistance value of the transfer means increases, the transfer bias voltage applied to the transfer means increases, so that the transfer member is formed between the transfer means and the image carrier. The transfer electric field becomes strong, and the electric charge released from the pre-cleaning charge remover is easily guided to the image receiving body. However, if the amount of charge released from the static eliminator before cleaning to the image receiving member becomes too large, the amount of charge of the toner transferred to the image receiving member decreases excessively. There is a concern that a retransfer phenomenon in which the toner attracted to the image receiving member is transferred to the image bearing member again due to a drastic decrease in the electrostatic attraction force. In an image forming process in which a toner image primary-transferred from an image carrier to an intermediate transfer belt is secondarily transferred to a recording sheet, the charge amount of the toner may be excessively reduced in the primary transfer step. In addition, the secondary transfer efficiency is extremely deteriorated, and the quality of the recorded image is reduced. Therefore, from this viewpoint, a constant current is supplied to the transfer unit prior to the formation of a recorded image, and a voltage measurement unit for measuring a voltage value applied to the transfer unit at that time is provided. It is preferable to control the output of the pre-cleaning static eliminator according to the voltage value obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a configuration of a color laser beam printer to which the present invention is applied. This laser beam printer has four process units 10Y, 10M, 10C, 10C that form toner images for each color of yellow, magenta, cyan and black.
Bk, and an intermediate transfer belt 20 on which a toner image is primarily transferred from each process unit. The toner image multiplex-transferred onto the intermediate transfer belt 20 is secondarily transferred onto a recording sheet P to form a full-color image. It is configured as follows.

The intermediate transfer belt 20 is formed endlessly and is wound around a plurality of belt transport rolls 21 to 25 including a drive roll 21. Each intermediate transfer belt 20 rotates in the direction of an arrow to process each color process unit 10Y, 10M. , 10C, 1
It is configured to receive the primary transfer of the toner image formed at 0Bk. Further, a secondary transfer roll 30 is disposed at a position facing the belt transport roll 24 with the intermediate transfer belt 20 interposed therebetween, and the recording sheet P is placed between the transfer roll 30 and the intermediate transfer belt 20 that are pressed against each other. The intermediate transfer belt 20 is inserted to receive the secondary transfer of the toner image from the intermediate transfer belt 20. That is, the belt transport roll 24 functions as a backup roll of the transfer roll 30. On the other hand, a cleaner 26 of the intermediate transfer belt 30 is provided at a position facing the drive roll 21, and is configured to remove toner remaining on the intermediate transfer belt 20 after the secondary transfer from the intermediate transfer belt 20. ing.

Above the intermediate transfer belt 20, the four process units 10Y, 10M, 10C, 1
0Bk are arranged in parallel so that a toner image formed in accordance with image information of each color is primarily transferred to the intermediate transfer belt 20. These four process units move along the rotation direction of the intermediate transfer belt 20 so that the yellow 10
Y, magenta 10M, cyan 10C and black 10B
The black process units 10K, which will be used most frequently, are arranged in the vicinity of the secondary transfer portion. Each of the process units 10Y, 10M, 10C, and 10Bk includes a raster scanning unit 12 that exposes the photosensitive drum 11 included in each process unit according to image information, and according to image information of each color. The modulated laser beam Bm exposes the photosensitive drum 11 of each of the process units 10Y, 10M, 10C, and 10Bk.

Each of the process units 10Y, 10Y
M, 10C, and 10Bk are formed on the photosensitive drum 11 by the photosensitive drum 11, a charger 13 for charging the photosensitive drum 11 to a uniform background potential, and exposure to the laser beam Bm. A developing device 14 that develops an electrostatic latent image to form a toner image;
The cleaner includes a cleaner 15 for removing residual toner and paper dust from the surface of the photoconductor drum 11 after the transfer to 0, and a pre-cleaning static eliminator 16 for removing the residual toner prior to cleaning by the cleaner. It is configured such that a toner image corresponding to image information of each color can be formed on the drum 11.

Each of the process units 10Y, 10M, 10M
C, 10Bk at a position facing the photosensitive drum 11
The primary transfer roll 1 is held so as to sandwich the intermediate transfer belt 20.
7Y, 17M, 17C, and 17Bk are provided. By applying a predetermined transfer bias voltage to the transfer rolls 17Y, 17M, 17C, and 17Bk, the photosensitive drum 11 and the transfer rolls 17Y, 17M, and 17C are applied. ,
17Bk, an electric field is formed, and a charged toner image on the photosensitive drum 11 is transferred to the intermediate transfer belt 20 by Coulomb force.

Therefore, in forming a full-color image by the color laser beam printer, first, the raster scanning unit 12 causes the photosensitive drum 11 of each of the process units 10Y, 10M, 10C, and 10K to move in a predetermined manner in accordance with image information of each color. Exposure is performed at the timing, whereby a toner image corresponding to image information is formed on the photosensitive drum 11 of each of the process units 10Y, 10M, 10C, and 10K. Each process unit 10Y, 10M, 10C, 10
The toner image formed by K is rotated by the rotating intermediate transfer belt 20.
Are sequentially transferred, and a multi-toner image in which the toner images of the respective colors are overlapped is formed on the intermediate transfer belt 20.

On the other hand, after the recording sheet P is pulled out one by one from the paper feed cassette 40 by the paper feed roll 41, it passes through a predetermined sheet feeding path 46 shown by a broken line in FIG. The sheet is fed to a secondary transfer section where the roller 30 contacts. A registration roll 42 is provided in front of the secondary transfer unit, and the timing at which the recording sheet P enters the secondary transfer unit is controlled by the registration roll 42, and the intermediate transfer belt 20.
The alignment with the toner image primarily transferred thereon is performed. A predetermined transfer bias voltage is applied to the backup roll 24 facing the secondary transfer roll 30 with the intermediate transfer belt 20 interposed therebetween, and the toner image held on the intermediate transfer belt 20 is The image is electrostatically transferred to the recording sheet P by a transfer electric field formed between the backup roll 24 and the recording sheet P.

After the recording sheet P on which the secondary transfer of the toner image has been performed is separated from the intermediate transfer belt 20, the fixing unit 4 is rotated by a double sheet transport belt 43 arranged in series.
4. After the secondary transfer of the toner image to the recording sheet P, since the recording sheet P and the intermediate transfer belt 20 are charged, the charge of the recording sheet P is removed between the secondary transfer roll 30 and the sheet conveyance belt 43. Members (not shown)
The intermediate transfer belt 20 is also provided on the back side of the intermediate transfer belt 20 adjacent to the backup roll 24.
Is provided to prevent the recording sheet P from re-adsorbing to the intermediate transfer belt 20.

After the toner image is fixed on the recording sheet P by the fixing device 3, the recording sheet P is discharged to the paper discharge tray 45, thereby completing the formation of the full-color image on the recording sheet P. Further, in this printer, in order to enable a so-called face-down discharge in which the image surface of the recording sheet P faces downward, an inverter passage 47 for reversing the front and back of the recording sheet P is provided between the fixing device 44 and the discharge tray 45. Are formed. Furthermore, this inverter passage 47
The sheet re-feeding path 48 is used for the sheet feeding path 4 described above.
The recording sheet P, which is connected to the recording sheet P and is turned upside down in the inverter path 47, is sent to the secondary transfer portion again, whereby a recording image can be formed on both the front and back surfaces of the recording sheet P.

FIG. 2 is an enlarged view showing a primary transfer section for transferring the toner image T from the photosensitive drum 11 to the intermediate transfer belt 20 of each process unit. In this embodiment, the intermediate transfer belt 20 is made of a polyimide resin,
The thickness is 60 to 90 μm, and the volume resistivity is 10 ¹¹ to 10
¹³ Ω · cm and the surface resistivity are adjusted to 10 ¹¹ to 10 ¹³ Ω / □. On the other hand, the primary transfer roll 17 is an EPDM
It is a foamed elastic body made of rubber and has a hardness of 25 to 35.
Degree (Asuka C measurement), volume resistivity is 10 ⁷ to 10 ⁹ Ω ·
cm. The primary transfer roll 17 is pressed against the back surface of the intermediate transfer belt 20 by a spring (not shown), and is in contact with the intermediate transfer belt 20 at a linear pressure of 10 to 20 g / cm. In this embodiment, when the diameter of the primary transfer roll 17 is set to 28 mm and the diameter of the photosensitive drum 11 is set to 84 mm, the contact width (nip width) between the intermediate transfer belt 20 and the photosensitive drum 11 is 1 to 3 mm.
It was about.

Since the toner image T formed on the photosensitive drum 11 is charged to a negative polarity (-), a transfer bias voltage of a positive polarity (+) is applied to the primary transfer roll 17, and the intermediate transfer is performed. A charge of brass polarity (+) is applied to the back surface of the belt 20. As a result, the toner image T on the photosensitive drum 11 is transferred onto the intermediate transfer body 20 by the electrostatic attraction. At this time, variations in the resistance of the primary transfer roll 17 and variations in the amount of charge held by the toner itself cause the primary transfer roll 17 and the photosensitive drum 1 to change.
The constant electric current control is easier to control the transfer electric field formed between them than the constant voltage control. In the present embodiment, the toner image T was successfully transferred to the intermediate transfer belt 20 by controlling the transfer current to 25 to 35 μA.

On the other hand, the above-described pre-cleaning static eliminator 16 is disposed at a position facing the photosensitive drum 11 downstream of the primary transfer portion, and the residual toner adhered to the photosensitive drum after the primary transfer. To remove residual toner by a cleaner. The pre-cleaning static eliminator 16 according to the present embodiment is a corona discharger, and includes a corona discharge wire 16a to which an AC bias in which DC is superimposed is applied, and a grounded and corona discharge wire 16
and a shield 16b provided so as to surround a. The DC component of the bias applied to the corona discharge wire 16 a is −80 μA (constant current), and the AC component is 2.3 kV (constant voltage). The AC component mainly contributes to the residual toner and the neutralization of the photosensitive drum 11. ing. Also,
The DC component contributes to reliably eliminate the surface potential of the photosensitive drum 11 to 0 V, and serves to eliminate latent image ghosts and development ghosts in the previous toner image forming process. That is, when a negatively charged organic photosensitive layer is used for the photosensitive drum 11 or the like, it is difficult to completely remove the charge of the photosensitive drum 11 that has been positively charged during the primary transfer. However, when a DC component having a negative polarity (-) is applied to the pre-cleaning static eliminator 16, the surface potential of the photosensitive drum 11 can be uniformly adjusted to the negative polarity, and the cleaner 15 and the charger 13 can be in contact with each other. By providing a static elimination lamp in between, it is possible to reliably eliminate the surface potential of the photosensitive drum 11.

FIG. 3 shows the positional relationship between the pre-cleaning neutralizer 16 and the primary transfer section. Both positive and negative charges discharged from the corona discharge wire of the pre-cleaning static eliminator 16 are transferred to the shield 16 b or the photosensitive drum 1.
1 such that the shield 16 of the pre-cleaning charge remover 16 can reach the intermediate transfer belt 20 without being interrupted by the shield 16.
The position of the tip b is regulated, and a part of the electric charge discharged from the corona discharge wire 16a is directly irradiated on the surface of the intermediate transfer belt 20 that has passed through the primary transfer portion.

As described above, in transferring the negatively charged toner image T to the intermediate transfer belt 20, it is necessary to apply a positive charge to the back surface of the intermediate transfer belt 20. If the charge amounts on the front and back surfaces of the intermediate transfer belt 20 are not balanced after the transfer of the toner image T, a problem occurs such that the toner image T scatters from the surface of the intermediate transfer belt 20. However, a part of the positive / negative bipolar charges generated by the pre-cleaning neutralizer 16 is transferred to the intermediate transfer belt 2.
When configured to irradiate 0, these charges act to restore the balance of the charge amount on the front and back of the intermediate transfer belt 20, and it is possible to prevent the toner image T from scattering. Therefore, if there is an area A (shaded area in FIG. 3) where the charge generated by the pre-cleaning charge remover 16 is irradiated toward the intermediate transfer belt 20 without being blocked by the shield 16b or the photosensitive drum 11, the primary Scattering of the transferred toner image T can be prevented.

In this embodiment, as a means for transferring the toner image T from the photosensitive drum 11 to the intermediate transfer belt 20, a transfer roll 17 to which a transfer bias is applied is used. As described above, the width of the transfer roll 17 applying charges to the back surface of the intermediate transfer belt 20 must be narrower than when the corona discharger is used as the transfer unit. For this reason, the transfer roll 17
Is disposed so as to oppose the contact position between the intermediate transfer belt 20 and the photosensitive drum 11.
Cannot be effectively guided to the intermediate transfer belt 20, and the effect of preventing the scattering of the toner image T after the primary transfer is reduced.

Therefore, in this embodiment, the charge generated by the pre-cleaning charge remover 16 is more effectively used for the intermediate transfer belt 2.
In order to irradiate the primary transfer roll 1 as shown in FIG.
7 is displaced by a distance a (2 to 4 mm) on the downstream side in the transport direction of the intermediate transfer belt 20 from a position where the intermediate transfer belt 20 and the photosensitive drum 11 are in contact with each other. When the primary transfer roll 17 is provided in this manner, the position at which the charge is generated by the primary transfer roll 17 comes close to the pre-cleaning static eliminator 16, and the charge generated by the pre-cleaning static eliminator 16 due to the influence of the charge generation is reduced. It can be positively guided to the intermediate transfer belt 20. Therefore, scattering of the toner image T on the intermediate transfer belt 20 can be more effectively prevented.

On the other hand, if the charge generated by the pre-cleaning charge remover 16 is applied to the intermediate transfer belt 20 too much, the charge amount of the toner itself decreases, and the charge from the intermediate transfer belt 20 to the recording sheet P is reduced. This makes it difficult to secondary transfer the toner image T. Therefore, it is necessary to adjust the amount of electric charge irradiated from the pre-cleaning charge remover 16 toward the intermediate transfer belt 20 while referring to the scattering of the toner image T on the intermediate transfer belt 20, the transfer efficiency of the secondary transfer, and the like. In addition, by adjusting the AC voltage applied to the corona discharge wire 16a and regulating the position of the tip of the shield 16b, it is possible to adjust the irradiation amount of the electric charge to the intermediate transfer belt 20.

Further, since the transfer bias voltage is applied to the primary transfer roll 17 by a constant current control, when the resistance value of the transfer roll 17 increases due to a change in environmental factors such as temperature and humidity or a change with time, the transfer bias is applied. The voltage increases, and the amount of charge applied to the back surface of the intermediate transfer belt 20 increases. Then, the amount of charge attracted to the intermediate transfer belt 20 from the pre-cleaning charge remover 16 increases, and the charge amount of the toner image T itself decreases as described above.

Therefore, in this embodiment, the primary transfer roll 1
When a constant current is applied to the transfer roll 7, the voltage applied to the transfer roll 17 is measured in advance by a voltmeter, and is applied to the corona discharge wire 16a of the pre-cleaning neutralizer 16 based on the measured voltage value. The magnitude of the AC voltage is controlled. FIG. 4 is a graph showing the relationship between the measured voltage value of the transfer roll 17 and the magnitude of the AC voltage applied to the static eliminator 16 before cleaning. As shown in this figure, as the voltage value applied to the transfer roll 17 increases, the AC voltage applied to the pre-cleaning static eliminator 16 is reduced, thereby irradiating the intermediate transfer belt 20 from the pre-cleaning static eliminator 16. Thus, it is possible to prevent the charge amount of the toner image T itself from decreasing.

Although the transfer roll 17 to which the transfer bias voltage is applied is used as the primary transfer means in the above-described embodiment, a corona discharger may be used instead of the transfer roll 17. However, when the corona discharger is used as the transfer means, it is not necessary to displace the disposition position of the corona discharger toward the downstream side of the intermediate transfer belt 20, and the corona discharger is directly opposed to the photosensitive drum 11. Even if there is, the charge generated by the pre-cleaning charge remover 16 can be efficiently guided toward the intermediate transfer belt 20.

[0035]

As described above, according to the image forming apparatus of the present invention, immediately after a toner image is transferred to an image receiving member such as a recording sheet or an intermediate transfer belt, the charge on the front and back surfaces of the image receiving member is obtained. Even if the amount is out of balance, the static eliminator before cleaning acts to correct this naturally, so that the phenomenon that the toner image scatters from the surface of the image receiving body after the transfer of the toner image can be prevented. As a result, a high-quality recorded image can be formed, and dirt in the image forming apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a color laser beam printer to which the present invention has been applied.

FIG. 2 is an enlarged view showing a primary transfer section of the laser beam printer according to the embodiment.

FIG. 3 is an enlarged view showing an arrangement of a pre-cleaning static eliminator for a primary transfer unit.

FIG. 4 is a graph showing a relationship between a transfer bias voltage applied to a transfer roll and an AC voltage applied to an electric device before cleaning.

FIG. 5 is an enlarged view showing a charge application area a when a transfer roll to which a bias voltage is applied is used as a toner image transfer unit.

FIG. 6 is an enlarged view showing a charge application area b when a corona discharge device to which a bias voltage is applied is used as a toner image transfer unit.

[Explanation of symbols]

11 photoreceptor drum (image carrier), 15 cleaner, 1
6: static eliminator before cleaning, 16a: corona discharge wire, 16b: shield, 17: primary transfer roll (transfer means), 20: intermediate transfer belt (image receiving body), P: recording sheet, T: toner image

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoko Miyamoto 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Masaaki Takahashi 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. Ebina Works (72) Inventor Minoru Niwa 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Shuji Iseki 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Takashi Kawabata 2274 Hongo, Ebina-shi, Kanagawa, Fuji Xerox Co., Ltd.Ebina Office (72) Inventor Tatsuya Soga 2274, Hongo, Ebina-shi, Kanagawa Prefecture, F-Term in Fuji Xerox Co., Ltd. ) 2H030 BB42 BB55 2H032 AA02 AA 05 AA15 BA09 BA23 BA29 BA30 2H034 AA06 2H035 AA05 AB02 AC06 AZ11

Claims (5)

[Claims] An image carrier that rotates at a predetermined process speed and has a surface on which a toner image corresponding to image information is formed;
A transfer unit that is disposed opposite to the image carrier and electrostatically transfers the toner image from the image carrier to the image receiving body; a cleaner that cleans the surface of the image carrier on which the toner image has been transferred; And a pre-cleaning static eliminator provided between the cleaner and the cleaner and for neutralizing residual toner attached to the image carrier, wherein an AC bias voltage is applied to the pre-cleaning static eliminator, An image forming apparatus according to claim 1, wherein said cleaning static eliminator is mounted so that a part of the electric charge generated by said cleaning static eliminator is released toward the surface of the image receiving member after the transfer of the toner image. 2. The image forming apparatus according to claim 1, wherein
The pre-cleaning static eliminator includes a corona discharge wire stretched along the axial direction of the image carrier, and a shield provided to surround the corona discharge wire and opened toward the image carrier. An image forming apparatus, wherein the position of the tip of the shield is regulated so that the electric charge discharged from the discharge wire is irradiated toward the image receiving body after the transfer of the toner image. 3. An image forming apparatus according to claim 1, wherein said transfer means is a bias roll which abuts on a back surface of the image receiving body and to which a transfer bias is applied, and said bias roll is an image receiving body and an image carrier. An image forming apparatus, which is disposed so as to be displaced downstream of the image receiving body in the transport direction of the image receiving member from a position where the image receiving member abuts. 4. The image forming apparatus according to claim 1, wherein the image receiving member is an endless intermediate transfer belt wound around a plurality of transport rolls. An image forming apparatus, wherein a plurality of toner images are transferred from an image carrier in a multiplex manner. 5. The image forming apparatus according to claim 1, further comprising: a voltage measuring unit that measures a voltage value applied to the transfer unit when a constant current is applied to the transfer unit. An image forming apparatus which controls an output of the pre-cleaning static eliminator according to a measured voltage value.