JPH0954503A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable sure destaticization without increasing the scale and cost of a device, to reduce a load to a transfer material carrying means and an intermediate transfer body and to prolong the life by destaticizing the front and rear surfaces of the transfer material carrying means and the intermediate transfer body with a contact type destaticization member, that is, destaticizing the inside and outside on the upstream and downstream sides of a cleaning means respectively. SOLUTION: First and second destaticization means are provided on the upstream and downstream sides of a belt cleaner 20 respectively. The first destaticization means is composed of a conductive destaticization brush 21 which is provided inside a transfer belt 5 and comes into contact with the rear surface of the belt 5 and an earth electrode 23 arranged to face the brush 21, without contacting and an AC voltage is applied to the brush 21 from a power source 22. On the other hand, the second destaticization means is composed of a conductive destaticization brush 24 which is provided outside the transfer belt 5 and comes into contact with the front surface of the belt 5 and a grounded electrode 26 arranged to face the brush 24, without contacting and the AC voltage is applied to the brush 24 from a power source 25.

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 such as a copying machine or a printer, and more specifically, it is provided with a transfer material conveying device for carrying and conveying a sheet on which a toner image is transferred. The present invention also relates to an image forming apparatus having an intermediate transfer member that transfers a toner image onto a belt or a film and then retransfers the toner image onto a sheet.

[0002]

2. Description of the Related Art Conventionally, a so-called belt transfer method in which a transfer material such as a sheet or an OHP sheet is held and transferred and conveyed by a belt-shaped transfer material conveying means, or a transfer material is transferred to a cylindrical drum-shaped transfer material conveying means. A so-called transfer drum method for holding, transferring, and conveying has been proposed. In addition, there is a transfer belt or a transfer drum for removing charges on the front and back surfaces of a transfer material conveying unit such as a transfer belt or a transfer drum. It has been proposed to dispose a corona charger for static elimination and a static elimination brush to face each other.

Further, an image forming apparatus has been proposed in which toner images of different colors are sequentially transferred onto a belt-shaped intermediate transfer member, and then these toner images are collectively transferred onto a transfer material.
In this type of apparatus as well, it is necessary to remove the charge on the front and back surfaces of the intermediate transfer member as in the case of the above.

[0004]

However, when a corona charger is provided in order to neutralize the transfer material conveying means and the intermediate transfer member, a large amount of ozone is generated by the corona charger, so that an ozone filter or an ozone filter is used. It is necessary to provide an ozone suction fan or the like, which causes problems such as an increase in size of the device and an increase in cost.

On the other hand, there is also a method of providing a pair of conductive brushes which come into contact with the front and back surfaces of the transfer material conveying means and the intermediate transfer body, and applying a voltage to the brushes to remove the charge. If the brush is contaminated with the toner or the like adhering to the surface of the conveying unit or the intermediate transfer member, the charge removal performance is deteriorated, so the brush must be provided downstream of the cleaning unit. In that case, the toner adhering to the transfer material conveying means and the intermediate transfer body is adsorbed on the surface by the electric charge held by the transfer material conveying means and the intermediate transfer body, and the cleaning means is stronger to completely clean the toner. Therefore, there is a problem that the surface of the transfer material conveying means is easily scratched and its life is shortened. For this reason, a method in which both brushes are rotary brushes and brush cleaning means is provided on the rotary brush is conceivable. However, there is a problem in that a rotating means and a brush cleaning means are required, resulting in an increase in size and an increase in cost.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to remove charge from a transfer material conveying means and an intermediate transfer body without increasing the size of the apparatus and increase the cost, and at the same time, to transfer material conveying means and an intermediate transfer body. An object of the present invention is to provide an image forming apparatus that can reduce the load of the cleaning means on the above and can achieve a longer life.

In order to achieve the above object, the present invention uses a contact charge-eliminating member such as a brush as a charge-eliminating unit for a transfer material conveying unit or an intermediate transfer member, and the charge-eliminating unit for eliminating the charge on the surface of these members is located on the downstream side of the cleaning unit. In addition, the discharging means for discharging the back surface is provided upstream of the cleaning means.

[0008]

According to the structure of the present invention, by removing the charges on the back surface of the transfer material conveying means or the intermediate transfer member before cleaning, the attraction force between the transfer member and the toner can be weakened, and the cleaning load can be reduced. Can be reduced. Further, since the surface is neutralized after cleaning the transfer material conveying means and the intermediate transfer member, the contact neutralizing member on the surface is not contaminated with the toner, and stable static neutralization can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIG. 1 is an overall schematic configuration diagram of a first embodiment to which the present invention is applied. In the figure, a photosensitive drum (1) is rotationally driven in a direction of an arrow a, around which a charging charger is provided. (2), a print head (3), a developing device (4), a transfer belt (5), a cleaner (6), an eraser (7), etc. are arranged.

The transfer belt (5) is rotationally driven in the direction of arrow b in synchronism with the photosensitive drum (1).
(Polyvinylidene fluoride) and PC (Polycarbonate)
It is formed of a dielectric film belt made of, for example, or a rubber belt made of CR rubber, urethane rubber, or the like, and is stretched by a driving roller (18) and a driven roller (19).

A transfer brush (16) is arranged inside the transfer belt (5) so as to face the photosensitive drum (1). The transfer brush (16) is composed of a conductive brush provided in contact with the back surface of the transfer belt (5), and has a power source (1
7), and a DC voltage is applied during transfer. A separation claw (14) for separating the paper from the transfer belt (5) is provided on the downstream side of the transfer brush (16) so as to face the drive roller (18), and a belt cleaner (downstream) is provided on the downstream side of the separation claw (14). 20) is provided. Belt cleaner (20)
Comprises a blade arranged in contact with the surface of the transfer belt (5), and a roller facing the blade via the transfer belt.

A first static eliminator is provided on the upstream side of the belt cleaner (20) and a second static eliminator is provided on the downstream side. The first charge eliminating means is a belt cleaner (2
0) and the driving roller (18), which is provided inside the transfer belt (5) and has a conductive static elimination brush (21) contacting the back surface of the belt (5) and the belt (5). The static elimination brush (21) is constituted by a ground electrode (23) arranged in a non-contact manner so as to face the static elimination brush (21), and an AC voltage is applied to the static elimination brush (21) from a power source (22). On the other hand, the second static eliminator is located between the belt cleaner (20) and the driven roller (19), is provided outside the transfer belt (5), and is a conductive static eliminator brush (contacting the surface of the belt (5)). 24) and the static elimination brush (24) via the belt (5)
And a ground electrode (26) which is arranged in a non-contact manner so as to face the above, and an AC voltage is applied to the static elimination brush (24) from a power source (25). That is, the belt cleaner (2
0) is arranged so that the static elimination brush (21) located on the upstream side is in contact with the back surface of the transfer belt (5), and the static elimination brush (24) located on the downstream side is in contact with the front surface of the transfer belt (5). It is arranged.

In the above structure, the paper tray (10)
The paper P sent from the paper by the paper feed roller (11) is
Guided by the guide (12) to the timing roller (9),
The driven roller (1) connected to the DC power source (28) after being synchronized with the photosensitive drum (1) by the timing roller (9)
9) is fed between the grounded opposing roller (24) and electrostatically attracted to the transfer belt (5) driven by the driving roller (18). Paper P is photoconductor drum (1)
When the transfer position between the transfer belt (5) and the transfer belt (5) is reached, transfer charges are supplied to the transfer belt (5) by the transfer brush (16) inside the transfer belt (5), and the photoconductor drum (1).
The upper toner image is electrostatically transferred onto the paper P.

The sheet P on which the toner image has been transferred is conveyed while being attracted to the transfer belt (5), and the separation claw (14).
Is peeled off from the transfer belt (5). And guide (1
The sheet is guided to the fixing section by 5), is fixed by the fixing roller (8), and is discharged onto the sheet discharge tray (13).

The transfer belt (5) from which the paper P is peeled off is
First, the back surface of the transfer belt (5) is neutralized by the static elimination brush (21) to eliminate the transfer charges provided by the transfer brush (16), and then the front surface of the transfer belt (5) is cleaned by the belt cleaner (20). At this time, the charge on the back surface of the transfer belt (5) has already been removed, and the attraction force of the toner to the transfer belt (5) is weakened, so that the transfer belt (5) can be easily cleaned. Then, the surface of the transfer belt (5) is neutralized by the static elimination brush (24). At this time, the surface of the transfer belt (5) has already been cleaned, and the static elimination brush (24) is not contaminated with toner or the like.

In this embodiment, an AC power source is connected to the static elimination brushes (21) and (24), but an AC power source in which DC is superimposed may be used, or only a DC power source may be applied.

FIG. 2 is an overall schematic configuration diagram of a second embodiment to which the present invention is applied. This apparatus is a so-called transfer drum type color image forming apparatus, which will be described in detail below.

In FIG. 2, reference numeral (30) is a photosensitive drum, which is rotationally driven in the direction of arrow a in the figure, and around which a charger (31) and a print head (3) are provided.
2), a developing device (33) containing a yellow developer, a developing device (34) containing a magenta color developer, a developing device (35) containing a cyan color developer, and a developing device containing a black developer. (36), cleaner (38), eraser (3
9) etc. are arranged.

The transfer drum (37) is a cylindrical drum having a frame body around which a dielectric film such as PVDF (polyvinylidene fluoride) or PC (polycarbonate) is wound and fixed. The transfer drum (37) is synchronized with the photosensitive drum (30) by an arrow b. Driven to rotate.

A transfer brush (46) is arranged inside the transfer drum (37) so as to face the photosensitive drum (30). The transfer brush (46) is a conductive brush provided in contact with the back surface of the transfer drum (37), is connected to a power source (47), and is applied with a DC voltage during transfer.
An adsorption brush (43) for adsorbing the paper to the transfer drum (37) is provided inside the upstream side of the transfer brush (46) in contact with the back surface of the transfer drum (37). A grounding conductive roller (44) is arranged to face the suction brush (43). This suction brush is connected to a power supply 45, and a DC voltage is applied when the paper is sucked. On the other hand, a separation claw (51) for separating the paper from the transfer drum (37) is provided on the downstream side of the transfer brush (46), and a drum for cleaning the surface of the transfer drum (37) on the downstream side of the separation claw (14). A cleaner (53) is provided.

Further, a first static eliminator is provided on the upstream side of the drum cleaner (53), and a second static eliminator is provided on the downstream side. The first static eliminator is located between the separating claw (51) and the transfer brush (46), is provided inside the transfer drum (37), and is a conductive static eliminator brush (48) that contacts the back surface of the drum (37). And a ground electrode (50) arranged in a non-contact manner facing the static elimination brush (48) through the drum (37), and an AC voltage is applied to the static elimination brush (48) from a power source (49). Has been done. On the other hand, the second static eliminator includes the drum cleaner (53) and the suction brush (4
3), which is provided outside the transfer drum (37) and is in contact with the surface of the drum (5), and is a conductive static elimination brush (54), and the static elimination brush (5) via the drum (37).
4) and a ground electrode (56) arranged in a non-contact manner facing each other, and an AC voltage is applied to the static elimination brush (54) from a power source (25). The separation claw (51), the transfer drum cleaner (53) and the static elimination brush (54) are configured to be separated from the surface of the transfer drum (37) by a mechanism (not shown).

In this way, the paper P is sent to the timing roller (41) from the paper tray (not shown), synchronized with the photosensitive drum (30) by the timing roller (41), and then the direct current is fed by the guide (42). A suction brush (43) connected to a power source (45) and an opposing roller (4) grounded
4) and is electrostatically adsorbed to the transfer drum (37). When the paper P reaches the transfer position between the photoconductor drum (30) and the transfer drum (37), the DC power supply (4
Transfer charges are supplied to the inner surface of the transfer drum (37) by the conductive transfer brush (46) connected to 7), and the yellow toner image formed on the photoconductor drum (30) is first transferred onto the paper P. It is electrostatically transferred.

The paper P on which the yellow toner image has been transferred is
It is conveyed while being attracted to the transfer drum (37) and passes through the non-actuated static elimination brush (48), separation claw (51), transfer drum cleaner (53), static elimination brush (54) and suction brush (43). The transfer position between the transfer drum (37) and the photoconductor drum (30) is again reached. During this time, the separation claw (51), the transfer drum cleaner (53), and the static elimination brush (54) are separated from each other and are in non-contact with the transfer drum (37), and the opposing roller (44) of the suction portion is also provided. Originally, the yellow toner image on the paper P is not disturbed because it is originally arranged in non-contact with the transfer drum (37).

The magenta toner image formed on the photosensitive drum (30) is transferred to the paper P, which has reached the transfer position, by the action of the transfer brush (47) as described above. After that, the paper P is conveyed in the same manner as described above while holding the yellow toner image and the magenta toner image transferred thereon, and the cyan toner image is transferred this time.

Similarly, when the black toner image is finally transferred, a voltage is applied to the charge eliminating brush (48) and
The separation claw (51), the transfer drum cleaner (53), and the static elimination brush (54) are switched to a state in which they are in contact with the transfer drum (37), and the paper P is removed by the static elimination brush (48) on the back surface of the transfer drum (37). While removing the charge, separate claw (5
In 1), it is separated from the transfer drum (37). At this time, the separation claw (51) peels off the paper P that has been weakened by the static elimination brush (48) and has a weaker adsorption force. Therefore, the load on the paper P is also reduced, and the toner image on the paper P is disturbed. Absent. Then, the paper P is guided to the fixing portion by the guide (52), fixed by the fixing roller (40), and discharged onto a paper discharge tray (not shown).

Transfer drum (37) from which the paper P has been peeled off
The surface is cleaned by the transfer drum cleaner (53). At this time, the charge on the inner surface of the transfer drum (37) has already been removed by the charge removal brush (48) when the paper is separated, and the attraction force of the toner to the transfer drum (37) is weakened so that the transfer drum (37) can be easily cleaned. Then, the surface of the transfer drum (37) is neutralized by the static elimination brush (54). At this time, the surface of the transfer drum (37) has already been cleaned, and the charge removal brush (54) is not contaminated with toner or the like.

Although an AC power source was connected to the static elimination brushes (48) and (54) in this embodiment, it may be an AC power source in which DC is superposed or a DC power source.

The results of confirmation by the image forming apparatus shown in FIG. 1 are shown below. In FIG. 1, the transfer belt (5) has a surface and volume resistance of 10 14 Ω · cm and a thickness of 15
PVDF (polyvinylidene fluoride) of 0 μm was used.

The static elimination brushes (21) and (24) are obtained by weaving the conductive brush thread (60) into the conductive cloth (61) and then cutting it with a conductive adhesive as shown in FIG. The brush (60) has a brush length L of 5 mm and a width D.
Was 8 mm. The brush (60) has a density of 100,000 F (filler) / inch2 and an electric resistance of 104.
A material was used in which conductive carbon was added to a rayon-based resin so as to be Ω · cm. The details of the transfer brush (16) are omitted, but the same material is used.

Further, the toner used in the image forming apparatus of FIG. 1 has a triboelectrification polarity of (-) polarity, and the transfer brush (16) has a polarity of (+) from the DC power supply (17).
Transfer is performed by applying a voltage of KV.

With the above structure, when an image was formed with the static elimination brushes (21) and (24) in a non-operating state, the static elimination of the transfer belt (5) was not performed, resulting in defective transfer. The linear pressure of the belt cleaner (20) is 2.5g.
If it is not about / mm, cleaning failure of the belt occurs.

At this time, the linear pressure is too high and the belt cleaner (2
0) and the transfer belt (5) were rubbed against each other too much, and many linear scratches were formed on the outer surface of the transfer belt (5), resulting in uneven halftone images. In addition, the linear pressure may be too high and the blade of the belt cleaner (20) may be turned over.

Therefore, the static elimination brushes (21) and (2
When an AC voltage having a peak voltage of 2.5 KV was applied to 4) from the AC power supplies (22) and (25), the transfer belt (5) was sufficiently neutralized and the above-mentioned transfer failure did not occur, and a belt cleaner was used. The linear pressure of (20) is also 1.5g /
The belt could be completely cleaned at a thickness of about mm, and neither the scratches on the transfer belt (5) nor the curl phenomenon of the blade occurred.

Further, the alternating current power supplies (22) and (25) are changed to direct current power supplies, and the static elimination brush (21) has a negative polarity (2).
The same effect was obtained even when a voltage of KV was applied and a voltage of 2 KV of (+) polarity was applied to the static elimination brush (24). Here, the voltage of the (-) polarity is applied to the charge removal brush (21) to remove the charge of the (+) polarity supplied to the inner surface of the transfer belt (5) by the transfer brush (16). Further, the voltage of the (+) polarity is applied to the charge eliminating brush (24) because the discharge of the transfer belt (5) is caused in the vicinity of the transfer portion, which is the facing portion of the transfer belt (5) and the photosensitive drum (1). This is because the (−) charge on the outer surface of () is eliminated.

The same confirmation was performed in the image forming apparatus shown in FIG. 2, but the same effect was obtained.

Further, in the above-mentioned embodiment, the one using the conductive static eliminating brush was explained, but instead of the static eliminating brush in the above-mentioned embodiment, a conductive or semi-conductive roller as shown in FIG. 4 ( The same effect can be obtained by using 63) and (64).

Although the above embodiment describes the image forming apparatus in which the sheet is held on the transfer belt or the transfer drum and the toner image is transferred onto the held sheet, the present invention is not limited to this. However, for example, Japanese Patent Laid-Open No. 1-16
It is also applicable to an image forming apparatus of a so-called intermediate transfer system in which a toner image is once transferred from a photosensitive drum to an intermediate transfer member and then transferred again from the intermediate transfer member to a sheet as described in JP-A-6070.

[0039]

As described above, according to the present invention, the charge removal on the front and back surfaces of the transfer material conveying means and the intermediate transfer member is performed by the contact type charge removing member, and the charge removal on the inner surface is performed on the upstream side of the cleaning means. In addition, since the outer surface is discharged on the downstream side of the cleaning means, it is possible to reliably discharge electricity without increasing the size and cost of the device, and reduce the load on the transfer material conveying means and the intermediate transfer member by the cleaning means. The life of the means and the intermediate transfer member can be extended.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the image forming apparatus according to the present invention.

FIG. 3 is a diagram showing details of a contact static eliminator.

FIG. 4 is a diagram showing another specific example of the contact charge-eliminating member.

[Explanation of symbols]

 1, 30 ... Photoconductor drum 5 ... Transfer belt 37 ... Transfer drum 16, 46 ... Transfer brush 21, 24, 48, 54 ... Static elimination brush 20 ...・ Transfer belt cleaner 53 ・ ・ ・ ・ Transfer drum cleaner 63, 64 ・ ・ Electrification elimination roller

Claims (6)

[Claims] 1. An image including an image carrier on which a toner image is formed, a transfer material carrier that carries and conveys a transfer material, and means for transferring the toner image onto the transfer material on the transfer material carrier. In the forming apparatus, a charge removing member that comes into contact with the transfer material carrying member is provided on the transfer material carrying surface on the downstream side of the cleaning means of the transfer material carrying body, and on the transfer material non-bearing surface, on the upstream side of the cleaning means. An image forming apparatus characterized by. 2. An image carrier on which a toner image is formed, a transfer material carrier that carries and conveys a transfer material on the surface, and the toner image is electrostatically transferred onto a transfer material on the transfer material carrier. Transfer means for cleaning, and a cleaning means for cleaning the surface of the transfer material carrier,
A first charge removing member that is provided on the upstream side of the cleaning unit in the transport direction and contacts the back surface of the transfer material carrier, and a second charge removing member that is provided on the downstream side of the cleaning unit in the transport direction and contacts the surface of the transfer material carrier. An image forming apparatus comprising a charge removing member. 3. The image forming apparatus according to claim 2, further comprising a separating means for separating the transfer material from the transfer material carrier, wherein the first charge removing member is on the upstream side of the separating means in the transfer material conveying direction. An image forming apparatus characterized in that the image forming apparatus is arranged in. 4. The image forming apparatus according to claim 2, further comprising a first ground electrode, which is arranged in non-contact with the first charge removing member so as to face the first charge eliminating member with the transfer material carrier interposed therebetween. An image forming apparatus, comprising: a second ground electrode that is disposed in a non-contact manner so as to face the second charge eliminating member via the intermediate electrode. 5. An image carrier on which a toner image is formed, an intermediate transfer member provided facing the image carrier, and an electrostatic transfer of the toner image from the image carrier to the intermediate transfer member. 1 transfer means, a second transfer means for electrostatically transferring a toner image from an intermediate transfer body to a transfer material, a cleaning means for cleaning the surface of the intermediate transfer body, and a upstream side of the cleaning means in the transport direction. An image forming device comprising: a first static eliminator member that contacts the back surface of the intermediate transfer member; and a second static eliminator member that is provided downstream of the cleaning unit in the transport direction and that contacts the surface of the intermediate transfer member. apparatus. 6. A device for removing toner and charges remaining on a flexible dielectric surface, the cleaner being provided in contact with a moving dielectric surface, and the cleaner upstream in the moving direction of the dielectric. And a second static eliminator member that is provided on the side and contacts the back surface of the dielectric, and a second static eliminator member that is provided on the downstream side of the cleaner in the moving direction of the dielectric and that contacts the surface of the dielectric. A charge and toner removing device.