JP2002258622A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where irregularities in a toner image are prevented by appropriately setting the discharge value of a separation wire and also where irregularities are not caused in the toner image on a paper sheet by a guiding member for protecting the separation wire. SOLUTION: A plurality of separation wires of the transfer means of the image forming device are provided along in the rotating direction of a photoreceptor drum. A back plate is provided on the side of the separation wire opposite to the photoreceptor drum so that a distance between the back plate and the separation wire can be changed. A guiding member with which the separation wire is covered is provided so as not to come into contact with the paper sheet. Therefore, since the peak of the discharge value is set to be low, the toner is appropriately electrified and the irregularities in the toner image are not caused. Then, the guiding member and the paper sheet do not come into contact with each other, so that the irregularities in the toner in the image due to electrification are prevented.

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 which prevents toner images from being disturbed by a transfer device.

[0002]

2. Description of the Related Art A digital copying machine as an image forming apparatus includes an exposing means for exposing an image on a surface of a photosensitive drum as an image carrier to form a latent image, and a developing means for developing the latent image with toner as a developer. Means, transfer means for transferring toner to the paper and separating the paper from the photosensitive drum, paper feeding means for supplying the paper to the transfer means, fixing means for fixing the toner to the paper, and paper on which an image is formed And an operation display unit for inputting various instructions such as designation of the number of copies and enlargement and reduction on the upper surface.

The transfer means is provided to face the photosensitive drum and transfers a toner image formed on the photosensitive drum to a sheet, and a separation wire for separating the sheet on which the toner image has been transferred from the photosensitive drum. And
The paper is strongly adhered to the surface of the photosensitive drum due to the applied electric charge, and it is necessary to apply a large voltage to the separation wire to separate the paper from the photosensitive drum.

A ladder-shaped guide member is provided on the upper surface of the separation wire for protecting the separation wire so that the sheet conveyed from the photosensitive drum to the fixing means does not enter the transfer means and come into contact with the separation wire. Is provided.

[0005]

However, if the discharge value of the separation wire is increased to ensure the separation of the paper, the toner transferred onto the paper is unnecessarily charged by the discharge from the separation wire, and the toner on the paper is unnecessarily charged. May be disturbed.

In addition, when the sheet separated from the photosensitive drum is conveyed, the sheet comes into contact with the guide member, and the toner image on the sheet may be disturbed by static electricity generated by the friction. Further, the guide member is charged by the discharge from the separation wire, and the paper comes into contact with the charged guide member, so that the toner image on the paper may be disturbed.

An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide an image forming apparatus in which a discharge value of a separation wire is appropriately set and a disturbance of a toner image is prevented.

Another object of the present invention is to provide an image forming apparatus in which a toner image formed on a sheet is not disturbed by a guide member for protecting a separation wire.

[0009]

According to the present invention, in order to solve the above-mentioned problems, an image forming apparatus is configured as follows.

That is, (1) an image carrier, exposure means for exposing the image carrier to form an electrostatic latent image, and developing the electrostatic latent image formed on the image carrier with a developer Transfer means having a developing means, a transfer wire for transferring an image formed on the image carrier onto a sheet, and a separation wire for separating the sheet on which the image is formed from the surface of the image carrier; and the transfer means Paper supply means for storing paper to be sent to
An image forming apparatus comprising: fixing means for fixing a transferred image on the sheet; wherein a plurality of the separation wires are provided along a rotation direction of the image carrier.

(2) an image carrier, and exposing the image carrier,
Exposure means for forming an electrostatic latent image, developing means for visualizing the electrostatic latent image formed on the image carrier with a developer, and transferring the image formed on the image carrier to paper A transfer unit having a transfer wire and a separation wire for separating the sheet on which the image is formed from the surface of the image carrier; a sheet supply unit for storing the sheet to be sent to the transfer unit; An image forming apparatus having a fixing unit for fixing the image forming member, wherein a back plate is provided on a side of the separation wire facing the image carrier, and a distance between the back plate and the separation wire can be changed. Characteristic image forming apparatus.

3. The image forming apparatus according to claim 2, wherein a plurality of the separation wires and the back plate are provided along a rotation direction of the image carrier.

4. The image forming apparatus according to claim 3, wherein the position of the back plate can be changed for each of a plurality of separation wires.

5. The discharge value of any of the separation wires is:
The image forming apparatus according to any one of claims 1, 3, and 4, wherein the discharge value is lower than a peak value of a discharge value required when one separation wire is used.

(6) The distance between at least two of the separation wire positioned closest to the image carrier and the separation wire positioned next to the image carrier is set to 8 mm or more.
The image forming apparatus according to any one of claims 3, 4, and 5.

7: an image carrier, and exposing the image carrier,
Exposure means for forming an electrostatic latent image, developing means for visualizing the electrostatic latent image formed on the image carrier with a developer, and transferring the image formed on the image carrier to paper A transfer unit having a transfer wire and a separation wire for separating the sheet on which the image is formed from the surface of the image carrier; a sheet supply unit for storing the sheet to be sent to the transfer unit; An image forming apparatus comprising: a fixing unit for fixing a sheet to a sheet, wherein a guide member that covers the separation wire is provided at a position that does not intersect with a sheet conveyance path.

8. The image forming apparatus according to claim 7, wherein the guide member is provided at a position that does not intersect a tangent to the surface of the image carrier drawn from a point closest to the image carrier of the transport member that transports the sheet. Image forming apparatus.

9. The guide member is provided at a position that does not intersect a tangent to the surface of the image carrier formed on a line connecting the separation wire closest to the image carrier and the center of the image carrier. 9. The image forming apparatus according to 7 or 8, wherein

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus having a transfer unit according to the present invention will be described below.

FIG. 4 shows the configuration of the digital copying machine 2 as an image forming apparatus.

The digital copying machine 2 includes a scanner 20
An operation including a control unit 22, an image forming unit 24, a sheet feeding unit 26 as a sheet feeding unit, a fixing unit 28 as a fixing unit, a sheet discharging unit 30 as a sheet discharging unit, and various input switches. It comprises a display unit 32 and the like.

The scanner section 20 is installed above the digital copying machine 2 and is a stationary original reading section 34 installed on the right side of FIG. 4 for reading a fixed original.
A moving document reading unit 35 is provided on the left side and reads a document while taking in the document. A reading mechanism 8 common to both is provided movably below.

The reading mechanism 8 includes a lamp 12, a mirror mechanism 14, and a CCD for recognizing light reflected from the mirror mechanism 14.
And the like. In FIG. 4, the lamp 12 and the mirror mechanism 14 are connected to the stationary original reading unit 3.
4 and the moving document reading unit 35,
There is actually one.

The original is read as a digital signal,
The read image signal is sent to the control unit 22. In the case of copying, an image signal is sent from the control unit 22 to the image forming unit 24, and printing is immediately performed on the sheet 5 sent from the sheet feeding unit 26.

The paper supply unit 26 accommodates paper 5 of various sizes, and controls the control unit in accordance with the original read by the scanner unit 20 or according to the size and orientation of the paper 5 input to the operation display unit 32. In accordance with the instruction from 22, predetermined paper 5 is fed to image forming unit 24.

As shown in FIG. 4, the image forming section 24 includes a corona charger 41, a photosensitive drum 42 as an image carrier,
An exposure unit 46, a development unit 48, a transfer unit 49 as a transfer unit, a cleaning unit 50, and the like are formed. An image is formed from the sent image signal, and the image is formed on the sheet 5 sent from the sheet supply unit 26. Form an image.

The corona charger 41 is, for example, a scorotron charger, and uniformly charges the photosensitive drum 42 with a predetermined voltage, for example, -750 V, before the latent image forming process. The photosensitive drum 42 is formed by coating a photosensitive layer on a cylindrical base material surface made of, for example, aluminum having a diameter of 80 mm, and a driving motor for driving the photosensitive drum 42;
An encoder (not shown) for detecting the rotational phase of the photosensitive drum 42 is provided. The photosensitive layer has a thickness of 15 to 3
0 μm, dielectric constant 2.0 to 5.0, and the substrate is grounded. The photosensitive drum 42 rotates at a speed of, for example, 320 mm / sec, and the rotational phase of the photosensitive drum 42 is measured and controlled by an encoder. The photosensitive drum 42 is uniformly charged by the corona charger 41 while rotating,
Upon receiving the exposure by the exposure unit 46, an electrostatic latent image is formed on the surface.

The exposure section 46 is provided with a laser (for example, an output 490).
μW), and the laser beam emitted from the laser is
The light is reflected by a polygon mirror and is irradiated on the surface of the photosensitive drum 42 via an optical system such as an f-θ lens. The polygon mirror rotates at a constant rotation speed, and the main scanning of the laser beam is performed by the rotation, and the sub-scanning is performed by the rotation of the photosensitive drum 42. The formed electrostatic latent image is developed
Is visualized by the toner.

The developing section 48 has a developer inside and forms a magnetic brush. The developer is composed of a polyester-based toner having an average particle size of 8.5 μm and a ferrite-based coating carrier having an average particle size of 60 μm. The toner concentration is controlled to 4 to 6%, and the developing bias is set to −600 V.

The transfer unit 49 transfers the toner on the photosensitive drum 42 to the paper 5 as shown in FIG.
And a separation charger 9 for separating the paper 5 on which the toner has been transferred from the surface of the photosensitive drum 42.

The transfer charger 7 is installed so as to face the photosensitive drum 42, and positively discharges electric charges from the back side of the paper 5 superposed on the photosensitive drum 42. On the surface of the photosensitive drum 42, a toner image is electrostatically carried by a developing unit 48, and the sheet 5 from the paper feeding unit 26 is attracted to the surface, and the toner on the photosensitive drum 42 is discharged by the discharge of the transfer charger 7. Is transferred to the sheet 5. The transfer charger 7 is preferably a scorotron discharger, but may be a corotron charger or the like.

The separation charger 9 comprises a scorotron discharger, a corotron charger, or the like. The separation wire 3 located on the side closer to the photosensitive drum 42 and the separation wire 4 located on the far side are arranged in parallel at an interval of 8 mm. Have. The separation wires 3 and 4 are connected to the power supply circuit 17, respectively, and can apply an arbitrary voltage in accordance with an instruction from the control unit 22. 5 is separated from the photosensitive drum 42 together with the toner.

A back plate 11 is provided below the separation wires 3 and 4. Back plate 11
Is made of a metal plate material such as stainless steel formed to have a length substantially the same as the length of the separation wires 3 and 4, respectively.
A drive mechanism 13 is provided for each of them, and the drive mechanism 13 is operated to individually move up and down so that the separation wires 3 and 4 can be set at an arbitrary distance. Note that the back plate 11 may be integrated. Further, the separation charger 9 may be provided with an LED exposing means so as to assist the separation.

The peak value of the discharge value of the separation wire 3 is set to about 85% of the peak value of the discharge value required for the photosensitive drum 42 when one separation wire is used.
The peak value of the discharge value of the separation wire 4 is
Is about 5% of the peak discharge value. The value of the peak value is not limited to this. FIG. 3 shows a discharge value of the separation charger 9. The shape of the discharge value is preferably a shape having two peaks or a wide lower portion. The voltage applied to the separation wires 3 and 4, the position of the back plate 11, and the like are changed according to the type, temperature, humidity, and the like of the paper 5, and the optimum value is appropriately determined. Set to state.

Next, a method for measuring the discharge value of the separation wire 3 and the like will be described. The discharge value of the separation charger 9 is such that a metal wire having a diameter of about 60 μm is formed on the surface of the photosensitive drum 42.
2 is mounted in parallel with the rotation axis of the photosensitive drum 42 in a state of being insulated from the photosensitive drum 42. When the photosensitive drum 42 is rotated and passes through the front surface of the separation charger 9, a current value generated in the metal wire is measured by an ammeter. And measure.

Further, a guide member 15 is provided on the photosensitive drum 42 side of the separation charger 9 as shown in FIG.
The guide member 15 is made of resin and formed in a ladder shape or a net shape. The guide member 15 is provided at the starting point of the transport belt 18 for feeding the sheet 5 from the photosensitive drum 42 to the fixing unit 28 side.
In other words, a tangent a to the surface of the photosensitive drum 42 that passes through a position closest to the photosensitive drum 42 (a surface extends in the longitudinal direction).
And a separation wire 3
Also, the tangent line b of the photosensitive drum 42 at the intersection of the line connecting the center of the photosensitive drum 42 and the line connecting the center of the photosensitive drum 42 is arranged at a position where it does not contact or cross.

The toner remaining on the surface of the photosensitive drum 42 without being transferred to the sheet 5 by the transfer unit 49 is collected by the cleaning unit 50. Cleaning unit 50
Is provided with a blade that comes into contact with the photosensitive drum 42, and scrapes off toner, dust, and the like adhering to the surface of the photosensitive drum 42, and stores it in the toner box.

Further, the electrical history of the photosensitive drum is erased by the pre-exposure lamp, and the next print cycle is started. The fixing unit 28 applies pressure and heat to the paper 5 on which the toner image has adhered, and fuses and fixes the toner on the paper 5. Sorter unit 30
Is a discharge mechanism for discharging the printed paper 5 in a predetermined state.

The operation display section 32 is provided on the upper surface of the digital copying machine 2 and is a liquid crystal display device having an input mechanism. The operation display section 32 has various functions such as enlargement / reduction of a print image, designation of print paper, designation of the number of prints, and the like. When an operation button is displayed, and a finger or the like is pressed on a portion corresponding to the position of the button, a pressure-sensitive pressure-sensitive sensor made of a transparent electrode (not shown) senses and recognizes that the button is pressed. I do.

The control unit 22 controls the entire system and is connected to a thermometer and a hygrometer (both not shown) in the machine, and can grasp the environment in the machine.

Next, a specific operation of the digital copying machine 2 will be described.

When the operation of the digital copying machine 2 is started, the operation display section 32 displays an initial screen. The initial screen displays a plurality of buttons, such as a copy start button, a copy number setting, a paper 5 selection button, and a button for instructing enlargement or reduction.

An original is placed on the scanner unit 20, and a start button (not shown) of the operation display unit 32 is pressed. Then, the document is pulled in and the document size is read. A signal of the size of the read original is sent to the paper feeding unit 26 and the paper
From 6, a sheet 5 of a predetermined size is sent out. When the size of the paper 5 is specified from the operation display unit 32, the specified paper 5 is sent out from the paper supply unit 26.

Then, the toner image formed on the photosensitive drum 42 is transferred to the sheet 5 by discharging by the transfer charger 7. Next, the paper 5 is separated from the photosensitive drum 42 by the discharge of the separation charger 9 and sent to the fixing unit 28. At that time, since the separation charger 9 has a discharge distribution as shown in FIG. 3 by the two separation wires 3 and 4, a sufficient discharge to the paper 5 is performed and the paper 5 becomes excessive. Is not charged. Further, the control unit 22 controls the temperature, humidity,
The conditions such as the optimum voltage and the position of the back plate 11 are changed depending on the quality of the paper 5 and the operation of the service person. Therefore, the toner image formed on the sheet 5 is separated from the surface of the photosensitive drum 42 without causing disturbance.

Further, since the guide member 15 is arranged at the above-described position, the sheet 5 separated from the surface of the photosensitive drum 42 comes into contact with the guide member 15 when being conveyed from the separation charger 9. The toner image is not disturbed by the contact with the guide member 15. Further, if the sheet 5 is extremely warped or bent and the leading end of the sheet 5 is directed to the separation charger 9, the sheet 5 is guided by the guide member 15.
Can be guided out of the separation charger 9 to protect the separation wires 3 and 4 from contact with the paper 5.

The sheet 5 onto which the image has been transferred is sent to the fixing unit 28, heated and pressed by the fixing unit 53 of the fixing unit 28, and is fixed by being pressed.

In the above example, the image forming apparatus is the digital copying machine 2, but the present invention is not limited to this. Further, the number of separation wires may be more than two. The distance between the separation wires may be at least 8 mm or more between the first and second wires on the photosensitive drum side.

[0048]

According to the image forming apparatus of the present invention, the transfer means has a plurality of separation wires, and the peak value of the discharge value of the separation wires is determined by the discharge value required when one separation wire is used. Is lower than the peak value, it is possible to reliably separate the sheet from the surface of the photosensitive drum without disturbing the toner image on the sheet.

By disposing the guide member provided on the separation wire at a position where the guide member does not come into contact with the sheet at the time of conveyance, it is possible to prevent the image from being disturbed due to the sheet coming into contact with the guide member.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming unit of an image forming apparatus according to the present invention.

FIG. 2 is a view showing a guide member of the image forming apparatus according to the present invention.

FIG. 3 is a view showing a discharge value of a separation charger according to the present invention.

FIG. 4 is a diagram illustrating an embodiment of an image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 Digital copier 3, 4 Separation wire 5 Paper 7 Transfer charger 8 Exposure mechanism 9 Separation charger 11 Back plate 12 Lamp 13 Drive mechanism 14 Mirror mechanism 15 Guide member 16 Photoelectric converter 18 Transport belt 20 Scanner unit 22 Control unit 24 Image forming unit 26 Paper feed unit 28 Fixing unit 30 Paper discharge unit 32 Operation display unit 41 Corona charger 42 Photosensitive drum 48 Developing unit 49 Transfer unit 50 Cleaning unit 53 Fixing unit

Claims (9)

[Claims] 1. An image carrier, an exposure unit that exposes the image carrier to form an electrostatic latent image, and a developing unit that visualizes the electrostatic latent image formed on the image carrier with a developer Means, a transfer wire for transferring an image formed on the image bearing member onto a sheet, and a separating wire for separating the sheet on which the image is formed from the surface of the image bearing member; and An image forming apparatus comprising: a sheet feeding unit for storing a sheet to be sent; and a fixing unit for fixing a transferred image on the sheet, wherein a plurality of the separation wires are provided along a rotation direction of the image carrier. An image forming apparatus comprising: 2. An image carrier, exposure means for exposing the image carrier to form an electrostatic latent image, and developing for developing the electrostatic latent image formed on the image carrier with a developer Means, a transfer wire for transferring an image formed on the image bearing member onto a sheet, and a separating wire for separating the sheet on which the image is formed from the surface of the image bearing member; and An image forming apparatus comprising: a sheet feeding unit for storing a sheet to be sent; and a fixing unit for fixing a transferred image on the sheet, wherein a back plate is provided on a side of the separation wire facing the image carrier. An image forming apparatus capable of changing a distance between the back plate and the separation wire. 3. An image forming apparatus according to claim 2, wherein a plurality of said separation wires and said back plate are provided along a rotation direction of said image carrier. 4. The back plate according to claim 3, wherein the position of the back plate can be changed for each of a plurality of separation wires.
The image forming apparatus as described in the above. 5. The discharge device according to claim 1, wherein a discharge value of each of the separation wires is lower than a peak value of a discharge value required when only one separation wire is used. The image forming apparatus according to claim 1. 6. The separation wire located closest to the image carrier and at least two of the separation wire located next.
The image forming apparatus according to claim 1, wherein an interval between the books is 8 mm or more. 7. An image carrier, exposure means for exposing the image carrier to form an electrostatic latent image, and developing for developing the electrostatic latent image formed on the image carrier with a developer Means, a transfer wire for transferring an image formed on the image bearing member onto a sheet, and a separating wire for separating the sheet on which the image is formed from the surface of the image bearing member; and An image forming apparatus comprising: a sheet feeding unit for storing a sheet to be sent; and a fixing unit for fixing a transferred image on the sheet, wherein a guide member covering the separation wire does not intersect with a sheet conveyance path. An image forming apparatus provided at a position. 8. The image forming apparatus according to claim 1, wherein the guide member is provided at a position that does not intersect a tangent to the surface of the image carrier that is drawn from a point closest to the image carrier of the transport member that transports the sheet. 8. The image forming apparatus according to 7. 9. The guide member is provided at a position that does not intersect a tangent to the surface of the image carrier formed on a line connecting the separation wire closest to the image carrier and the center of the image carrier. 9. The image forming apparatus according to claim 7, wherein: