JP2001154494A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image without the scattering of toner a the trace of a discharge brush after transferring a toner image to transfer paper in an image forming device by an electrophotographic processing. SOLUTION: After transferring the toner image on a photoreceptor drum 31 to the transfer paper 15 by a transfer device 35, the discharge brush 39 is brought into contact with the back surface of the paper 15 so as to remove charges with which the paper 15 is electrified. By grounding the brush 39 through a resistor 391, the movement of the charges in the case of removing the charges on the paper 15 is restricted, so that the movement of the toner with the movement of the charges is restrained to be very small, and the trace of the brush caused by the movement of the toner is hardly formed.

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 using an electrophotographic process, such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as a copying machine, a facsimile, and a printer using an electrophotographic process includes a photosensitive drum having a photoconductive substance coated on the surface of a drum, and a photosensitive drum surface. A charging device for applying a predetermined voltage to the surface of the photosensitive drum (to uniformly charge a predetermined charge), and selectively exposing the surface of the photosensitive drum in accordance with a desired image to thereby electrostatically charge the surface of the photosensitive drum. An exposure device for forming a latent image, a developing device for developing an electrostatic latent image formed on the surface of the photosensitive drum by selectively attaching toner to the surface of the photosensitive drum, and a photosensitive drum A transfer device for transferring the developed toner image onto the surface of the transfer paper, a charge removing device for removing charges on the surface of the photosensitive drum, and removing (cleaning) toner remaining on the surface of the photosensitive drum Qu for And over Na, and a fixing device or the like for fixing the toner image transferred onto the transfer sheet.

An exposure apparatus such as a digital copying machine, a facsimile, a laser beam printer, and the like uses a laser oscillator, a polygon mirror, an fθ lens, etc., and responds to image data read by a scanner or image data created by a personal computer. Then, a laser beam is applied to a portion corresponding to, for example, a portion of the surface of the photoreceptor drum which has a low subject luminance (a black portion in the case of binary data of black and white). When light is applied to the uniformly charged surface of the photoreceptor drum, the potential at that portion decreases. next,
By applying an appropriate bias voltage to the photosensitive drum and the developing device, toner having the same polarity as the charged surface potential of the photosensitive drum adheres to the portion where the potential has decreased, and a toner image is formed on the surface of the photosensitive drum. It is formed. This is so-called reversal development. When the transfer paper is brought into contact with the surface of the photosensitive drum on which the toner image has been formed, and a transfer current having a polarity opposite to that of the charge on the surface of the photosensitive drum flows from the back side of the transfer paper, the toner on the surface of the photosensitive drum is transferred. The toner image is transferred onto the sheet, and the toner image is transferred onto the transfer sheet. A desired image can be obtained by fixing the toner image on the transfer paper by applying heat or pressure.

[0006] After a toner image is transferred from a surface of a photosensitive drum onto a transfer sheet, a mechanical separating claw or an electric neutralizing brush is conventionally used to separate the transfer sheet from the photosensitive drum. I have. The separation claw is provided almost in contact with the surface of the photoconductor drum, contacts the leading edge of the transfer paper, and prevents the transfer paper from wrapping around the surface of the photoconductor drum by inhibiting the movement of the transfer paper. I do.
The charge removal brush facilitates separation from the surface of the photoconductor drum by removing the charge on the transfer paper.

[0005]

For example, in a low-temperature and low-humidity environment, the electrical resistance of the transfer paper increases, and a large amount of charge is charged on the surface of the transfer paper during transfer of the toner image. In this state, if an attempt is made to remove the charge on the transfer sheet by the charge elimination brush, the charge on the transfer sheet rapidly flows to the ground via the charge elimination brush, and the toner on the transfer sheet also moves accordingly. As a result, in the image formed through the fixing device, a white streak or a black streak (brush mark) due to the implantation of the neutralization brush remains in the transfer paper transport direction,
This may cause a drop in image quality. On the other hand, it is not possible to unconditionally determine which charge of the same polarity or opposite polarity as the toner is charged on the transfer paper after passing through the transfer device, depending on the transfer conditions, the properties of the paper, and the like. Therefore, assuming that the static elimination brush is insulated under certain conditions, when the transfer paper is charged with the same polarity as the toner, the toner transferred onto the transfer paper scatters and passes through the fixing device onto the transfer paper. The density of the formed image is partially or totally reduced. Further, the scattered toner adheres to the surface of an internal mechanism of the image forming apparatus such as a toner receiving tray of a cleaner. Re-adhesion causes spots and the like, which causes deterioration in image quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus in which there is no deterioration in image quality due to brush traces caused by a discharging brush or scattering of toner.

[0007]

In order to achieve the above object, an image forming apparatus according to the present invention comprises a photosensitive drum having photoconductivity and an electrostatic latent image formed by selectively exposing the surface of the photosensitive drum. An exposure device for forming an image, a developing device for developing an electrostatic latent image on the surface of the photosensitive drum with toner, and an image forming device for transferring a toner image on the surface of the photosensitive drum onto transfer paper. A transfer device, a charge removing brush for removing a charge on the transfer sheet after transferring the toner image on the surface of the photosensitive drum onto the transfer sheet, and a transfer device provided between the charge removing brush and ground. And a fixing device for fixing the toner image transferred onto the transfer sheet.

In the above configuration, it is preferable that the transfer device opposes the surface of the photosensitive drum via a gap larger than the thickness of the transfer sheet.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the image forming apparatus according to the present invention, a digital copying machine will be described with reference to the drawings.

FIG. 1 shows the overall configuration of a digital copying machine according to this embodiment. This digital copier includes a paper feed mechanism 10 disposed at the bottom of the main body of the copier, a paper transport mechanism 20 disposed above the paper feed mechanism 10, and a paper transport mechanism 20 disposed above the paper transport mechanism 20. Image forming mechanism 30 and a fixing device 40 disposed on the discharge side with respect to the image forming mechanism 30.
And an image reading device (scanner) 50 and an exposure device 33 disposed above the image forming mechanism 30 and the fixing device 40, and a control device 60 for controlling the operation of the entire copying machine.
(See FIG. 3).

The paper feed mechanism 10 includes a stack of transfer papers 15
Paper cassette 11 for storing a bundle of
A paper feed roller 12 having an arc-shaped outer peripheral portion provided above the outlet of the paper feed roller, a spring 13 for pushing up the transfer paper bundle 15 to the paper feed roller 12 side, and a paper feed cassette 11 provided at both upper ends in the width direction. It is composed of a judgment claw 16 and the like.

When the paper feed roller 12 is rotated in a predetermined direction, the arc-shaped outer peripheral portion comes into contact with the uppermost transfer sheet 15, and the transfer sheet 15 is fed to the right side in FIG. At this time, the transfer paper bundle 15 is separated by the separating claw 16, and only the transfer paper 15 located at the uppermost position is reliably supplied to the paper transport mechanism 20 one by one.

The paper transport mechanism 20 includes a reversing guide 21 for reversing the transport direction of the transfer paper 15 supplied from the paper feeding mechanism 10 and a transfer paper 15 whose transport direction is reversed by the reversing guide 21 in FIG. A pair of conveying rollers 22 for conveying to the left and a leading edge of the conveyed transfer paper 15 in the width direction are aligned, and a timing for starting transfer of the toner image in accordance with rotation of a photosensitive drum 31 described later is determined. A registration roller pair 23, a conveyance guide 24 for conveying the transfer paper 15 having the toner image transferred to the surface thereof to the fixing device 40, and discharging the transfer paper on which the toner image is fixed by the fixing device 40 and the image is formed. It is composed of a discharge roller pair 25 for discharging onto the tray 26 and the like.

The registration roller pair 23 includes a transport roller pair 2
2, the rotation of the transfer sheet 15 is stopped until the transfer sheet 15 is conveyed, and the tip of the transfer sheet 15 abuts against the pair of registration rollers 23 to correct the distortion at the time of conveyance and align the leading ends in the width direction. Can be The distance between the exposure position on the outer peripheral surface of the photosensitive drum 31 and the transfer position of the toner image and the distance from the registration roller pair 23 to the transfer position are set to be substantially equal. Transfer paper 15
When the leading ends in the width direction are aligned, the registration roller pair 2
Drive 3 and exposure of the surface of the photosensitive drum 31 by the exposure device 33 are started almost simultaneously. Photoconductor drum 31
Top of toner image formed on top and registration roller pair 23
As a result, the toner image is transferred onto the transfer sheet 15 with almost no gap since the leading end of the transfer sheet 15 conveyed by the printer reaches the transfer position almost simultaneously.

The image forming mechanism 30 forms a predetermined toner image on the transfer paper 15 by an electrophotographic process, and is rotatably supported on a photosensitive member having a drum surface coated with a photoconductive substance. Drum 31 and photosensitive drum 3
A photosensitive drum driving device 38 (see FIG. 3) that rotates the photosensitive drum 1 in a predetermined direction at a predetermined speed, and a predetermined potential is applied to the surface of the photosensitive drum 31 (a predetermined charge is uniformly charged).
Device 32 for forming an electrostatic latent image on the surface of the photoconductor drum by selectively exposing the surface of the photoconductor drum in accordance with a desired image, and a photoconductor drum A developing device 34 for developing the electrostatic latent image formed on the surface of the photosensitive drum by selectively attaching toner to the surface of the photosensitive drum 31; Transfer device 35 for transferring to the surface
A cleaner 36 for removing (cleaning) toner remaining on the surface of the photosensitive drum, a charge removing device 37 for removing charge on the surface of the photosensitive drum, and charging the transfer paper after transferring the toner image. It is composed of a charge elimination brush 39 for removing the accumulated electric charge.

The charging device 32 is provided on the upstream side in the rotation direction of the photosensitive drum 31 with respect to an exposure position to be described later, and is opposed to the surface of the photosensitive drum 31 at a predetermined distance. A wire to which a high voltage is applied to generate corona discharge, and a predetermined voltage (for example, +850)
V) is applied, and a predetermined potential is applied to the surface of the photosensitive drum 31 by the wires and the grid.

The exposure device 33 includes a laser oscillator 331,
A polygon mirror 332 which is a rotating polyhedron for reflecting the laser beam output from the laser oscillator 331;
An fθ lens 334 for correcting distortion of the laser beam reflected by the polygon mirror 332, a mirror 333 for re-reflecting the light reflected by the polygon mirror 332 to the exposure position of the photosensitive drum 31, and the like. I have. The laser oscillator 331 is connected to an image reading device 5 described later.
0 outputs a laser beam based on the image data of the document read. The polygon mirror 332 rotates in a predetermined direction at a constant speed, and the angle of the mirror surface that reflects the laser beam output from the laser oscillator 331 changes every moment, so that the laser beam is changed in the width direction of the photosensitive drum 31. Scan.

The photoreceptor drum 31 has an organic photoreceptor (OPC: Organic Photo-Co.
A film of a photoconductive material such as a nductive material is applied. In an unexposed state, a positive charge is charged by the charging device 32 so as to have a constant surface potential (for example, +800 V). In this state, when the surface of the photosensitive drum 31 is selectively exposed by the exposure device 33, the potential of the exposed portion decreases due to the photoelectric effect of the photoconductive material applied to the surface. That is, an electrostatic latent image is formed on the surface of the photosensitive drum 31.

The developing device 34 is provided downstream of the exposure position in the rotation direction of the photosensitive drum 31 so as to face the surface of the photosensitive drum 31 with a predetermined distance therebetween. While holding a certain amount of toner,
The toner is charged to, for example, a positive charge. Photoconductor drum 3
When the electrostatic latent image portion formed on the surface of the photosensitive drum 31 approaches the developing device 34, toner adheres to the surface of the photosensitive drum 31 from the developing device 34, so that a toner image is formed on the surface of the photosensitive drum 31. (Ie, the electrostatic latent image is developed).

The transfer device 35 is located downstream of the developing device 34 in the rotation direction of the photosensitive drum 31 even if the transfer paper 15 is conveyed between the photosensitive drum 31 and the transfer device 35. So that the photosensitive drum 31
Is provided at a predetermined distance from the surface of the photosensitive drum 31, and a transfer current having a polarity opposite to the surface potential of the photosensitive drum 31 is caused to flow between the photosensitive drum 31 and the transfer device 35. The toner adheres to the interposed transfer paper 15. As a result, the toner image on the surface of the photosensitive drum 31 is transferred to the transfer paper 15.

The cleaner 36 is provided on the downstream side in the rotation direction of the photosensitive drum 31 with respect to the transfer device 35 so as to contact the surface of the photosensitive drum 31. Even after the transfer of the toner image to the photosensitive drum 31, the toner remaining on the surface of the photosensitive drum 31 is removed.

The static eliminator 37 is located downstream of the cleaner 36 in the direction of rotation of the photosensitive drum 31, and
And removes the electric charge remaining on the surface of the photosensitive drum 31.

The fixing device 40 is disposed downstream of the image forming mechanism 30 in the sheet conveying direction, and applies a heating roller 41 and a pressure to the transfer sheet 15 on which the toner image has been transferred by the image forming mechanism 30. Heating and pressing are performed by the rollers 42 to fix the toner image on the transfer paper 15.

The image reading device 50 includes a contact glass 51 also serving as a document table, an exposure lamp 52 for illuminating a document placed on the contact glass 51 from the inside, and a CCD line sensor or the like for transferring an image of the document as a subject. An image pickup lens 57 for forming an image on the photoelectric conversion element 56, mirrors 53, 54 and 55 for bending the optical axis of the image pickup lens 57 connecting the original and the photoelectric conversion element 56, and an original on the contact glass 51. In order to scan from the left end to the right end in FIG. 1, the exposure lamp 52, the mirror 53 and the mirror 54 are used.
And 55 are moved by a scanning mechanism (not shown) in the moving space 58 so that the moving speed becomes 2: 1.

An image of an area of a certain width illuminated by the exposure lamp 52 of the original placed on the contact glass 51 is formed on the photoelectric conversion element 56 by the imaging lens 57. Conjugate relationship. When the scanning mechanism starts scanning the exposure lamp 52 and the mirror 53 at the first speed from the left end to the right end in FIG. 1,
In order to keep the optical path length from the original to the photoelectric conversion element 56 constant, the mirrors 54 and 55 are simultaneously scanned together from the left end to the right end in FIG. 1 at a second speed which is の of the first speed. You. As a result, the entire surface of the document placed on the contact glass 51 can be scanned, and the image on the entire surface of the document can be read.

As shown in FIG. 2, the transfer device 35 has a transfer center provided with a fixed gap L with respect to the surface of the rotary drum 31 about a rotation axis about an axis parallel to the rotation axis of the photosensitive drum 31. Transfer roller driving mechanism 360 for rotating roller 350 and transfer roller 350 in a predetermined direction at a predetermined speed
And a transfer current circuit 370 for applying a predetermined transfer current to the transfer roller, a transfer roller-side cleaner 380 for preventing adhesion of paper dust and toner generated from transfer paper, and the like.

The surface of the transfer roller 350 and the photosensitive drum 3
1 is larger than the thickness t of the transfer sheet 15 that can be copied by the digital copying machine, and even if the transfer sheet is interposed between the photosensitive drum and the transfer roller, It is set so that a slight gap is generated between the transfer roller and the back surface of the transfer sheet 15 (L> t). That is, the transfer device 35 of the present embodiment is of a non-contact type.

Between the transfer roller 350 and the conveyance guide 24, the neutralizing brush 3 grounded via a resistor 391
9 are provided. A flocking 392 made of, for example, a conductive resin fiber is provided at the leading end of the charge removing brush 39.
5 are provided at regular intervals in the width direction of the transfer sheet 15 (the direction parallel to the rotation axis of the photosensitive drum 31) so as to contact the back surface of the transfer sheet 5.

The charge removing brush 39 removes the electric charge on the transfer paper 15 during the transfer as described above.
In the present embodiment, the grounding is particularly performed via the resistor 391, so that the movement of the charged electric charge is restricted, and the transfer paper 15
The current flowing through the brush 39 via the flocking 392 becomes smaller. As a result, the movement of the toner accompanying the movement of the electric charge is reduced or almost eliminated. In the image formed via the fixing device 40, almost no white streaks or black streaks (brush marks) due to the flocking 392 of the neutralization brush 39 in the transfer sheet transport direction occur. Even when the transfer paper is charged with the same polarity as the toner at the time of transfer, the charge transferred onto the transfer paper is removed by the discharging brush 39, so that the toner transferred onto the transfer paper scatters. No spots and the like hardly adhere to the transfer paper.
Therefore, according to the present embodiment, there is almost no deterioration in image quality due to the charge on the surface of the transfer paper 15 during transfer, and a good image can be obtained.

Next, the resistance value of the resistor 391 inserted between the neutralization brush 39 and the ground will be discussed. As an example, the diameter of the photosensitive drum 31 is 30 mm (φ30),
The diameter of the transfer roller 350 (the outer diameter of the surface layer 352) is set to 14
mm (φ14), and the thickness t of the transfer paper is 0.1 to 0.15.
mm, the gap L between the surface of the transfer roller 350 and the surface of the photosensitive drum 31 is 0.25 mm, the peripheral speed of the photosensitive drum 31 is 130 mm / s, and the surface potential of the photosensitive drum 31 is +8.
00V, the transfer current flowing through the transfer roller 350 is -26 μ
A.

When the neutralizing brush 39 is directly grounded without passing through the resistor 391, the resistance of the resistor 391 is set to 10K.
For each of the cases of Ω, 100 KΩ, 1 MΩ, 10 MΩ, 100 MΩ and the case where the static elimination brush 39 was insulated, test images were actually created, and brush marks and toner scattering were examined. Table 1 shows the results.

[0032]

[Table 1]

In the above example, it is understood that the resistance value of the resistor 391 should be set to 10 MΩ or more. in this way,
Static elimination brush 39 via resistor 391 having a certain value or more
By grounding, it is possible to prevent both the scattering of toner and the generation of brush marks. The resistance value is determined by the configuration of the transfer device 35 (contact type or non-contact type), the surface potential of the photosensitive drum 31, the photosensitive drum 31
And the value of the transfer current flowing through the transfer roller 350, the properties of the transfer paper 15, the temperature and humidity of the environment, etc., and cannot be determined unequivocally, and are optimally determined by experiments according to the configuration of the image forming apparatus. Determine the value.

Further, when the transfer paper 15 is transported on the transport guide 24, the transfer paper 15 may slide on the guide ribs of the transport guide 24 and may be charged by friction.
Assuming that the transfer paper 15 is conveyed on the conveyance guide 24 in a state in which the electric charge is charged without using the charge removing brush 39, and the electric charge of the opposite polarity is charged by the frictional charge, the electric charge moves on the transfer paper 15, and the electric charge moves accordingly. The toner also moves. As a result, guide rib marks remain on the image formed via the fixing device 40. However, in the present embodiment, the transfer paper 15
Before the toner is conveyed on the conveyance guide 24,
Therefore, even if the transfer sheet 15 is charged by frictional charging between the transfer sheet 15 and the guide rib of the transport guide 24, the amount of charge is small, and the amount of charge is small. There are few traces.

Next, FIG. 3 shows an example of a block configuration of a control circuit in the digital copying machine of the present embodiment. The control circuit includes, in addition to the components described above, a timer 61 for generating a predetermined timing signal, various operation switches 62 provided on an upper part of the main body of the digital copying machine, and the like. A display device 63 such as a liquid crystal panel is provided for displaying various functions, usable paper sizes, and trouble situations such as paper jams.

Next, the operation of this embodiment will be described with reference to the block diagram shown in FIG. 3 and the flowcharts shown in FIGS.

First, when the main switch of the digital copying machine is turned on, the control device 60 energizes the fixing device 40, the developing device 34, and the like, and prepares for image formation (step S1). Next, the control device 60 waits until the copy start switch of the operation switch 62 is turned on (step S).
3). When the copy start switch is turned on (step S3)
YES), the control device 60 controls the image reading device 50 to read the image of the original on the contact glass 51,
Predetermined image processing is performed to create image data used by the exposure device 33 (step S5). In parallel with this image reading operation, the control device 60 drives the sheet feeding mechanism 10 to take out one transfer sheet 15 from the sheet feeding cassette 11 and starts sheet feeding toward the registration roller pair 23 of the sheet conveying mechanism 20. (Step S7).

Next, using a sensor (not shown) provided near the registration roller pair 23, the leading end of the transfer sheet 15 abuts the registration roller pair 23 over the entire width direction to determine whether the transfer paper 15 is aligned. (Step S
9). When the leading ends of the transfer paper 15 are aligned (step S
9 (YES), the control device 60 starts counting the timing signal from the timer 61, and drives the photosensitive drum driving device 38 to rotate the photosensitive drum 31 in a predetermined direction. Further, for example, +850 V is applied to the grid of the charging device 32 to start charging the surface of the photosensitive drum 31 (step S11). Almost simultaneously, the control device 6
0 controls the sheet transport mechanism 20 to control the registration roller pair 23
Then, the transfer of the transfer paper 15 toward the transfer device 35 is started (step S13).

When a predetermined time has elapsed from the start of counting of the timing signal, the leading end portion of the surface of the photosensitive drum 31 charged first by the charging device 32 reaches the exposure position. The exposure device 33 is driven using the image data, and exposure of the surface of the photosensitive drum 31 charged to a predetermined surface potential (for example, +800 V) is started (step S15). As described above, the potential of the exposed portion is reduced due to the photoelectric effect of the photoconductive material applied to the surface of the photosensitive drum 31, and an electrostatic latent image is formed.

After a lapse of a predetermined time, the exposed end of the photosensitive drum 31 reaches the position facing the developing device 34, so that the toner charged from the developing device 34 discharges the electrostatic latent on the surface of the photosensitive drum 31. It adheres to the portion where the image is formed, and development is started (step S17). Due to the adhesion of the toner, a toner image is formed on the surface of the photosensitive drum 31.

After a further elapse of a predetermined time, the front end portion of the surface of the photosensitive drum 31 on which the toner image has been formed reaches a position facing the transfer device 35. At this time, the leading end of the transfer paper 15 transported by the paper transport mechanism 20 also reaches a position facing the transfer device 35. Therefore, the control device 60 controls the transfer device 35 to start supplying a predetermined transfer current (for example, -26 μA), and starts transferring the toner image on the surface of the photosensitive drum 31 onto the transfer sheet 15 ( Step S19).

When the toner image is transferred onto the transfer paper 15, the toner remaining on the surface of the photosensitive drum 31 is removed by the cleaner 36, and the charge on the surface is removed by the charge removing device 37. By reducing the diameter of the photosensitive drum, 1
In order to form a sheet of image on the transfer sheet 15, at least a part of the photosensitive drum 31 is repeatedly subjected to at least two steps of charging, exposure, development, transfer, cleaning, and charge elimination. Therefore, the charging device 32, the exposure device 33,
Developing device 34, transfer device 35, static eliminator 37, photosensitive drum drive device 38, fixing device 40, and paper transport mechanism 20
Are driven simultaneously.

Further, control device 60 determines whether or not all image data has been output by exposure device 33, that is, whether or not exposure has been completed (step S21). When the exposure is completed (YES in step S21), the transfer paper is driven by driving the developing device 34, the transfer device 35, the charge removing device 37, the photosensitive drum driving device 38, the fixing device 40, and the paper transport mechanism 20 for a certain period of time. An image is formed on the entire sheet 15 and is discharged onto a discharge tray 26. In parallel with this, the control device 60 determines whether to continue the image formation (step S23). If an automatic document exchange device (auto feeder) or the like is attached, or if the next copy start switch is turned on within a short time after image formation, the process returns to step S5 and the next image formation is performed.

On the other hand, if image formation is not to be continued (NO in step S23), control device 60 determines whether or not the main switch has been turned off (step S25). When the main switch is not turned off (N in step S25)
O), the control device 60 returns to step S3 to prepare for the next image formation. When the main switch is off (step S
The control device 60 stops supplying power to the fixing device 40, the developing device 34, and the like, cancels the preparation for image formation (step S27), and ends the image forming flow.

In the above embodiment, a digital copying machine has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and analog copying machines, facsimile machines, laser printers, etc. The present invention can be generally applied to those using the electrophotographic process.
Further, it is needless to say that the present invention is not limited to a monochrome image forming apparatus but can be applied to a color image forming apparatus.

In the above-described embodiment, the non-contact type in which the surface of the transfer roller 350 is opposed to the surface of the photosensitive drum 31 with a certain gap as the transfer device 35 is used. However, the same effect can be obtained even in a contact method in which the surface of the transfer roller contacts the surface of the photosensitive drum.

Further, the term "transfer paper" is used throughout the above description, which means not only copy paper using ordinary pulp, but also postcards, tracing paper, OHP (Ove
r Head Projector) is used as a broad concept including a transparent film.

[0048]

As described above, according to the image forming apparatus of the present invention, a photoconductive drum and a surface of the photoconductive drum are selectively exposed to form an electrostatic latent image. An exposure device for developing, a developing device for developing an electrostatic latent image on the surface of the photosensitive drum with toner, and a transfer device for transferring a toner image on the surface of the photosensitive drum onto transfer paper. A charge removing brush for removing a charge on the transfer sheet after transferring the toner image on the surface of the photosensitive drum onto the transfer sheet, and a resistor provided between the charge removing brush and ground. And a fixing device for fixing the toner image transferred onto the transfer sheet.

That is, since the charge removing brush is grounded via the resistor, the charge on the transfer sheet during transfer is grounded and removed via the charge remover brush and the resistor, and is transferred onto the transfer sheet. The toner does not scatter. In addition, when the charge on the transfer paper is grounded, the movement of the charge is restricted by the resistor, so that the possibility that the toner transferred on the transfer paper moves with the movement of the charge is greatly reduced. Almost no brush marks are generated by the neutralizing brush. In addition, depending on the resistance value of the resistor, it is possible to almost completely prevent the occurrence of brush marks. As a result, a good image free of toner scattering and brush marks can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a digital copying machine that is an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a transfer device according to the embodiment.

FIG. 3 is a diagram showing an example of a block configuration of a control circuit in the digital copying machine of the embodiment.

FIG. 4 is a flowchart showing an image forming operation in the digital copying machine of the embodiment.

FIG. 5 is a continuation of the flowchart of FIG. 4;

[Explanation of symbols]

 10: Paper feed mechanism 15: Transfer paper 20: Paper transport mechanism 23: Registration roller pair 30: Image forming mechanism 31: Photoconductor drum 32: Charging device 33: Exposure device 34: Developing device 35: Transfer device 350: Transfer roller 360 : Transfer roller drive mechanism 370: transfer current circuit 380: cleaner 36: cleaner 37: static eliminator 38: photosensitive drum drive 39: static elimination brush 391: resistor 392: flocking 40: fixing device 50: image reading device 60: control Device 61: Timer 62: Operation switch 63: Display device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Matayoshi 1-2-28 Tamatsukuri, Chuo-ku, Osaka City Inside Mita Kogyo Co., Ltd. (72) Inventor Masatake Hayashi 1-2-28 Tamatsukuri, Chuo-ku, Osaka Mita Within Industrial Co., Ltd. (72) Takaki Kamei Inventor 1-2-28 Tamazo, Chuo-ku, Osaka Mita Kogyo Co., Ltd. F-term (reference) 2H032 AA05 BA05 BA12 BA21 BA23 BA29 CA02 CA13 5C072 AA03 BA15 HA02 HA13 HA20 HB20 XA01 XA05

Claims (2)

[Claims] A photosensitive drum having photoconductivity, an exposure device for selectively exposing the surface of the photosensitive drum to form an electrostatic latent image, and an electrostatic latent surface on the surface of the photosensitive drum. A developing device for developing the image with toner, a transfer device for transferring the toner image on the surface of the photosensitive drum onto transfer paper, and a toner image on the surface of the photosensitive drum on transfer paper After the transfer, a static elimination brush for removing the electric charge charged on the transfer paper, a resistor provided between the static elimination brush and the ground, and a fixing unit for fixing the toner image transferred on the transfer paper. An image forming apparatus comprising: a fixing device. 2. The image forming apparatus according to claim 1, wherein the transfer device faces a surface of the photosensitive drum via a gap larger than a thickness of the transfer sheet.