JP2002091182A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing irregularities in a toner image by setting a more optimum destaticizing condition for transfer material in accordance with the electrification state of the transfer material changed according to various conditions for the irregularities in the toner image by a carrying guide associated with the electrification of the transfer material separated from a transfer belt. SOLUTION: In this image forming device 1 provided with a photoreceptor 14 on which an electrostatic latent image is formed, a developing device 16 for forming the toner image by developing an electrostatic latent image on the photoreceptor 14, and the transfer belt 22 for transferring the toner image on the photoreceptor 14 to the transfer material P, the guide surface of the belt 22 is composed of material whose surface has electric resistance being >=1010 Ω/square, and at least any one of aperture parts formed on the upstream side and the downstream side of a guide plate 105 and on the guide plate 105 has a destaticizing member 113, and applied voltage to the destaticizing member 113 is set lower at the leading edge or the trailing edge of the transfer material P than that of destaticizing a part other than the leading edge or the trailing edge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as an electrophotographic printer, a facsimile, and a copying machine. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, the size of an image forming apparatus has been reduced, or
In some cases, a transfer belt is used due to the stability of transfer of the transfer material. The transfer belt forms an image by transferring a toner image on a photoconductor to a transfer material via a transfer belt as an intermediate transfer body. In this type of image forming apparatus, for example, an indirect bias application method in which a transfer bias is indirectly applied to a transfer belt is known as a transfer method to an intermediate transfer belt. In this method, a belt transfer bias roller is provided in a contact nip portion between a photosensitive member and a transfer belt, which is a transfer area, and a transfer bias is applied to the belt transfer bias roller, so that the intermediate transfer belt is separated from the photosensitive member. Primary transfer is performed. However, the transfer may be disturbed during the primary transfer from the photoconductor to the transfer belt. This is because, at the time of transfer, the toner image formed on the photoreceptor is scattered around the photoreceptor, and the image is blurred and the sharpness of the image is impaired.

In order to prevent this transfer disturbance, for example, Japanese Unexamined Patent Publication No. Hei 5-333704 discloses that a driving roller, which is a portion where a transfer material is separated from a transfer conveyance belt, is provided with a grounding circuit having a capacitance load. An image forming apparatus is proposed, in which the transfer material is contact-discharged immediately after the transfer material is separated, thereby preventing a discharge generated when the transfer material is peeled off and obtaining a normal image without deterioration in the transfer material. Have been. However, this alone cannot make the charge of the transfer material 0 V, and it has been proposed to provide a charge removing member at a position adjacent to the transfer belt, but does not describe a detailed charge removing method. The above proposal is a means for reducing the charging of the transfer material when separated from the transfer belt, and is a corresponding means closer to the causal system. Conversely, this kind of means involves the transfer material charging after the transfer belt separation. It is also difficult to completely eliminate defects.

In particular, since the transfer material separated from the transfer belt enters the conveyance guide in a charged state, the toner image on the transfer material is likely to be disturbed by the disturbance of the electric field. In order to prevent such disturbance of the toner image, it is effective to provide a charge removing member in the transport path and positively remove the charge of the transfer material.
At the rear end, the discharge from the charge removing member goes around the image surface side of the transfer material, abnormal discharge occurs, and the toner image is likely to be disturbed. If the intensity of static elimination is reduced to avoid this, there may be a shortage of static elimination other than the leading and trailing ends of the transfer material. In this case, the insufficient static elimination may cause a disturbance of the toner image. Becomes

[0005] The charging state of the transfer material is greatly affected by the transfer voltage applied at the transfer portion of the transfer belt. Generally, the transfer voltage of the constant current control applied in the transfer unit is
When the A4 size paper is passed vertically, the area where the transfer belt and the photoconductor are in direct contact increases, and as a result, the applied transfer voltage becomes lower than when the A4 size paper is passed horizontally.
As described above, the applied transfer voltage varies depending on the width of the transfer material that passes through the sheet. As a result, the charge state of the transfer material varies, and the optimal static elimination condition also varies.

Further, in order to prevent the toner image from being disturbed, it is effective to provide a charge removing member in the transport path and positively remove the charge of the transfer material.
Since the transfer material on the back side where the moisture content is extremely low is dry, the electric resistance increases and the state becomes more easily charged, so that the transfer material is used for single-sided paper passing (front side) and two-sided paper passing (back side). Thus, the charging state of the transfer material is different, and as a result, the optimum static elimination condition is also different.

[0007]

Therefore, in the present invention,
Toner image disturbance in the conveyance guide due to transfer material charging after transfer belt separation, toner image disturbance due to more optimal transfer material charge elimination conditions, depending on the transfer material charging state that changes depending on various conditions It is an object of the present invention to provide an image forming apparatus that prevents the occurrence of the image.

[0008]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 comprises a photosensitive member on which an electrostatic latent image is formed, and a method for developing the electrostatic latent image on the photosensitive member. An image forming apparatus comprising: a developing device that forms a toner image; and a transfer belt that transfers a toner image on a photoconductor to a transfer material.
The transfer belt has a guide surface having an electric resistance of 10
¹⁰ Ω □ or more material, upstream of the guide plate,
Downstream, at least one of the openings provided in the guide plate has a static elimination member, and the voltage applied to the static elimination member is higher at the leading or trailing end of the transfer material than at the leading or trailing end. And the applied voltage is reduced. According to a second aspect of the present invention, there is provided a photoreceptor on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image on the photoreceptor to form a toner image, and transferring the toner image on the photoreceptor And a transfer belt for transferring the material to a material.
^At least one of the upstream and downstream of the guide plate and at least one of the openings provided in the guide plate has a static elimination member, and the voltage applied to the static elimination member is equal to or less than the transfer material. An image forming apparatus in which constant current control is performed based on the size of the width in the sheet passing direction.
According to a third aspect of the present invention, there is provided a photoconductor on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image on the photoconductor to form a toner image, and a transfer of the toner image on the photoconductor. And a transfer belt for transferring to a material.
The transfer belt has a guide surface having an electric resistance of 10 ¹⁰ Ω on the surface.
□ At least one of the upstream and downstream of the guide plate, the opening provided in the guide plate has a static elimination member, and the voltage applied to the static elimination member is the passing surface of the transfer material. The image forming apparatus determines the voltage applied to the static elimination member.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment of the present invention from the front side. Although the image forming apparatus shown here has a copying function and a printer function of reading an original and forming an image by an electrophotographic method based on the original image, a function as a facsimile can be added.

As shown in FIG. 1, an original (not shown) is placed on a contact glass 2 fixed on an upper part of an image forming apparatus main body 1, and the original is moved by a light source 3 moving rightward in FIG. The illuminated reflected light image is reflected by the first mirror 4 moving rightward together with the light source 3, and then the second and third mirrors moving rightward at half the speed of the light source 3,
After being reflected at 5 and 6, the light enters the reading device 7. The reading device 7 includes an image sensor (not shown) formed of, for example, a CCD for reading a reflected light image from a document,
It also has an imaging lens (not shown) for forming an optical image on this sensor. The exposure device 8 shown in FIG. 1 reflects a laser beam L that has passed through a scanning image forming lens system 10 including a rotary polygon mirror 9 and an fθ lens that reflect a laser beam emitted from a laser light source (not shown). Mirror 11, 1
2 and 13, and the laser light L is imaged on the photoreceptor 14. The laser light is optically modulated in accordance with the image signal read by the reading device 7, and the laser light L
An electrostatic latent image corresponding to the image document is formed on the surface of the photoconductor 14 irradiated with the image.

When the electrostatic latent image passes through the developing device 16, it is visualized as a toner image. The developing device 16 shown in FIG. 1 has a developer case 18 containing a developer D and a developing roller 17 rotatably supported inside the developer case 18.
The developer is carried and conveyed on the peripheral surface of the developing roller 17 which is driven to rotate, and the photoconductor 14 is conveyed by the conveyed developer.
Is visualized as a toner image. In the developing device 16 of the present embodiment, as the developer D, a powdery two-component developer having a toner and a carrier is used, and a one-component developer not containing a carrier can also be used. Further, a toner supply container 18A is attached to the developer case 18, and the toner T is stored therein. When the toner concentration of the developer D in the developer case 18 decreases, the toner supply roller 19 rotates. Then, the toner T in the toner supply container 18A is supplied into the developer in the developer case 18.

On the other hand, a plurality of sheet cassettes 20, 20A,
20B, which is an example of a transfer material.
The copying material P is fed in the direction of arrow A, and the transfer material P
Matched with the toner image on the photoconductor 14 by the pair of rollers 21
Between the photoreceptor 14 and the transfer belt 22
The sheet is fed to the transfer position S. Electrically medium resistance 10
¹⁰Endless transfer belt made of Ω □ or higher material
22 is wound around a driving roller 23 and a driven roller 24.
And is driven in the direction of arrow B, and
14 is in contact with the surface. By registration roller pair 21
The transfer material P sent out on the transfer belt 22
The transfer belt 22 and the photoreceptor 14
Pass through the transfer position S. At this time, the transfer belt 22
The transfer bias roller 25 disposed on the back side of the
A voltage having a characteristic opposite to the charging characteristic of the toner on the optical body 14 is applied.
The toner image on the photoreceptor 14 is electrostatically charged on the surface of the transfer material P.
Transcribed. The transfer material P on which the toner image has been transferred continues
The transfer belt 22 carries the transfer belt 22 and conveys the transfer belt 22.
After passing through the guide member, the fixing device 3
0, and at this time, the toner image is transferred to the transfer material by the action of heat and pressure.
It is fixed on P. Next, the transfer material P is applied to a paper discharge roller.
The sheet 31 is output to the output tray 32 as
It is.

After the toner image is transferred, the transfer material P
Untransferred toner that has not been transferred onto the photosensitive member is removed by the carrier cleaning device 33, and the surface of the photoconductor is cleaned. The cleaned photoreceptor surface is initialized by being subjected to a static elimination action by a static eliminator 37 composed of a lamp, and furthermore, the photoreceptor 14 is uniformly charged by the charging device 15, and subsequently the above-described operation is executed. The toner image is transferred onto the transfer. The carrier cleaning device 33 includes a cleaning member including a cleaning blade 34, a cleaning case 35, and a toner discharging member 36 disposed at the bottom of the cleaning case 35. The cleaning blade 34 is made of an elastic material such as rubber, and extends in parallel with the photoconductor 14 over the entire image area in the axial direction of the photoconductor 14, that is, the area where the transfer residual toner adheres. It is fixed to the cleaning case 35, and the leading edge opposite to the cleaning case 35 is pressed against the surface of the photoreceptor 14 to scrape off and remove transfer residual toner attached to the surface. In the transfer device, a drive roller 23 around which a transfer belt 22 is wound, a driven roller 24, and a transfer bias roller 25 are rotatably supported by a case 27. Some background toner on the photoreceptor 14 migrates and adheres to the surface of the transfer belt 22, and when left unattended, the toner adheres to the back surface of the transfer material P sent to the transfer belt 22. Since the transfer material is contaminated with toner, the toner adhered to the surface of the transfer belt 22 is removed by the belt cleaning device 26. The belt cleaning device 26 cleans the toner on the transfer belt 22 by a cleaning blade 40 that is in direct contact with the transfer belt 22 in the counter direction.

As described above, the image forming apparatus of the present invention
An image carrier composed of a photoreceptor 14 driven in rotation, a developing device 16 for forming a toner image on the surface of the image carrier, and a transfer material composed of a transfer material P on which a toner image on the surface of the image carrier is transferred. A transfer belt 22 to be conveyed; a carrier cleaning device 33 for controlling the surface of the image carrier after transferring the toner image to the transfer material; and a toner attached to the surface of the transfer belt 22 which is removed from the surface of the transfer belt. It has a belt cleaning device 26 for cleaning the surface of the transfer belt.

(First Embodiment) FIG. 2 is a schematic cross-sectional view showing a configuration around a transfer belt of an image forming apparatus according to an embodiment of the present invention from the front side. FIG. 3 is a schematic diagram showing the configuration of the guide plate. FIG. 4 is a configuration diagram illustrating a state where the transfer material is passing through the guide plate. FIG.
FIG. 5 is a configuration diagram showing the state of FIG. 4 from above. The transfer belt 101 is made of a rubber-based material, and has a surface layer having a medium electrical resistance. The transfer belt 101 is held by a metal driving roller 102 and a driven roller 103 and set in a case 104. When the transfer material P passes through the transfer section S, an electric field having a polarity opposite to the toner charging polarity is applied to the bias roller 108 from the high voltage power supply 107. As a result, the current a also flows through the bias roller 108, and the current a
A current c is applied to the driven roller 103, and further via the transfer material P,
A current d flows through the photoconductor 100. In order to perform the transfer step stably, it is necessary to always stably maintain the transfer electric field. Therefore, the voltage applied to the bias roller is controlled so that the current d flowing through the photoconductor 100 becomes a predetermined value. Actually, it is difficult to directly detect the current d because the photoconductor 100 has a charging process or the like. Therefore, the current e is changed to d = a by using the current detection resistor 109 in the high voltage power supply 107. The control is performed by detecting by-(b + c) = e.

By controlling the transfer voltage in this manner, variations in the electrical resistance of the transfer belt 101 and the transfer material P and fluctuations due to the environment can be absorbed. Since the transfer belt 101 is in direct contact with the photoconductor 100 outside the area (width) of the transfer material P and between papers, background toner on the photoconductor 100 adheres. If the background toner adhered to the transfer belt 101 is not removed, the back surface of the transfer material P will be stained when the transfer material P passes thereafter. Therefore, the transfer belt 1
The cleaning member 106 is in contact with 01.
The cleaning member 106 uses a cleaning method based on a counter blade method. The toner scraped off by the cleaning member 106 is
Cleaning case 104 constituted by a part of
A is discharged by a toner discharge screw 111 arranged at the bottom of A. The transfer material P transferred / conveyed by the transfer bell 101 is separated from the transfer bell 101 at the position of the drive roller 102 by the curvature separation of the drive roller 102. At this time, the transfer material P is charged, and the guide plate 1 which is the next transport path
Proceed to 05. The guide plate 105 includes a charged transfer material P
A high-voltage power supply 110 that supplies a neutralization voltage is connected to the neutralization member, and a predetermined voltage is applied to the neutralization member.

As shown in FIG. 3, the guide plate 105 has a static elimination member 113 disposed on a sheet metal base 112.
Further, a guide 116 to which an electrically insulating PET film 115 is adhered is arranged on the side of the sheet metal 114 on which the transfer material passes, and is fixed by screws 117.
The static elimination member 113 is made of a thin metal material having a thickness of 0.1 mm, and a portion to be neutralized is a needle-like electrode having a sharp tip. The transfer material P is, as shown in FIG.
After the transfer belt 101 is separated, the transfer belt 101 is guided by the guide plate 105 and the fixing guide plate 118, and is guided to the fixing roller 119. By the guide plate 105 and the fixing guide plate 118,
The posture of the transfer material P is stabilized, and the charge of the transfer material P is removed by the charge removing member 113 on the guide plate 105. The transfer material P contacts the guide plate 105 in a charged state, and the guide surface of the guide plate 105 is formed of an insulating PET film 1.
The use of No. 15 prevents the toner image from scattering due to contact discharge. FIG. 5 shows this state as viewed from above.

FIG. 6 is a block diagram showing the control of the static elimination voltage applied to the static elimination member. FIG. 7 is a table for controlling the static elimination voltage. FIG. 8 is a chart showing the timing of applying a static elimination voltage at the position of the static elimination member when performing control. The static elimination voltage is applied to the static elimination member 113 from the high-voltage power supply 105, and the output level is determined by sending an output control signal from the control unit in the image forming apparatus main body as shown in FIG. . As shown in FIG. 7, the output control signal sent from the control unit of the image forming apparatus main body is transferred to a transfer material position (top, middle, rear end, ), Output values are individually determined as shown in FIG.

(Second Embodiment) FIG. 9 is a table for controlling a static elimination voltage. The static elimination voltage is applied to the static elimination member 113 from the high-voltage power supply 105, and the output level is determined by sending an output control signal from the control unit in the image forming apparatus main body as shown in FIG. . As shown in FIG. 9, the output control signal sent from the control unit of the main body of the image forming apparatus is individually determined based on the width of the transfer material in the sheet passing direction by a predetermined output control table. The output value is determined.

(Third Embodiment) FIG. 10 is a table for controlling a static elimination voltage. FIG. 11 is a chart showing a timing at which a static elimination voltage is applied at a static elimination member position when control is performed. The static elimination voltage is applied to the static elimination member 113 from the high-voltage power supply 105, and the output level is determined by the output of an output control signal from the control unit in the image forming apparatus main body as shown in FIG. You. As shown in FIG. 10, the output control signal sent from the control unit of the image forming apparatus main body is determined according to a predetermined output control table for one-sided sheet passing (front side) and for two-sided sheet passing (back side). As shown in (1), output values are individually determined.

[0021]

As described above, in the image forming apparatus according to the first aspect, the charge elimination conditions are individually set at the leading and trailing ends of the transfer material having different optimal charge elimination conditions, and in other ranges. Thereby, the disturbance of the toner image can be prevented.
In the image forming apparatus according to claim 2, the applied transfer voltage is different depending on the lateral width of the transfer material, and the charging state of the transfer material is different. However, the voltage applied to the charge removing member is determined based on the lateral width of the transfer material, By optimizing the static elimination conditions, disturbance of the toner image can be prevented. In the image forming apparatus according to the third aspect, the voltage applied to the charge removing member is changed between the single-sided sheet passing (front side) and the double-sided sheet passing (back side) when the charging state of the transfer material is different, thereby obtaining the optimum charge removing condition. This can prevent the toner image from being disturbed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment of the present invention from the front side.

FIG. 2 is a schematic cross-sectional view showing a configuration around a transfer belt of the image forming apparatus according to the embodiment of the present invention from the front side thereof.

FIG. 3 is a schematic diagram showing a configuration of a guide plate.

FIG. 4 is a configuration diagram illustrating a state where a transfer material is passing through a guide plate.

FIG. 5 is a configuration diagram showing the state of FIG. 4 from above.

FIG. 6 is a block diagram illustrating control of a static elimination voltage applied to the static elimination member.

FIG. 7 is a table for controlling a static elimination voltage;

FIG. 8 is a chart showing timings for applying a static elimination voltage at a static elimination member position when performing control.

FIG. 9 is a table for controlling a static elimination voltage.

FIG. 10 is a table for controlling a static elimination voltage.

FIG. 11 is a chart showing timings for applying a static elimination voltage at a static elimination member position when performing control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Contact glass 3 Light source 4 1st mirror 5 2nd mirror 6 3rd mirror 7 Reading device 8 Exposure device 9 Rotating polygon mirror 10 Lens system 11, 12, 13 Mirror 14, 100 Photoconductor 16 Developing device 17 Development Roller 18 Developer case 18A Toner supply container 20 Paper cassette 20A, 20B Paper cassette 21 Registration roller pair 22, 101 Transfer belt 23 Drive roller 24 Follower roller 25 Transfer bias roller 26 Belt cleaning device 27 Case 30 Fixing device 31 Discharge Paper roller pair 32 Paper discharge tray 33 Cleaning device 34 Cleaning blade 35 Cleaning case 36 Toner discharge member 37 Static eliminator 40 Belt cleaning blade 102 Driving roller 103 Follower roller 104 Case 105 Id plate 106 Cleaning member 107 High voltage power supply 108 Bias roller 109 Current detection resistor 110 High voltage power supply 112 Base 113 Static elimination member 114 Sheet metal 115 PET film 116 Guide portion 117 Screw 118 Fixing guide plate 119 Fixing roller a, b, c, d, e Current D Developer P Transfer material T Toner S Transfer position

Claims (3)

[Claims] 1. A photoconductor on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image on the photoconductor to form a toner image, and transferring the toner image on the photoconductor to a transfer material Transfer belt
The transfer belt has a guide surface made of a material having a surface electrical resistance of 10 ¹⁰ Ω □ or more, and at least one of an opening provided in the guide plate upstream, downstream, or in the guide plate. An image forming apparatus comprising: a charge removing member; and a voltage applied to the charge removing member is such that a voltage to be applied to a leading end or a trailing end of the transfer material is lower than a voltage applied to the charge removing member other than the leading end or the trailing end. . 2. A photoreceptor on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image on the photoreceptor to form a toner image, and transferring the toner image on the photoreceptor to a transfer material Transfer belt
The transfer belt has a guide surface made of a material having a surface electrical resistance of 10 ¹⁰ Ω □ or more, and at least one of an opening provided in the guide plate upstream, downstream, or in the guide plate. An image forming apparatus comprising: a charge removing member; and a voltage applied to the charge removing member is controlled by a constant current based on a size of a width in a sheet passing direction of the transfer material. 3. A photoconductor on which an electrostatic latent image is formed, a developing device for developing the electrostatic latent image on the photoconductor to form a toner image, and transferring the toner image on the photoconductor to a transfer material Transfer belt
The transfer belt has a guide surface made of a material having a surface electrical resistance of 10 ¹⁰ Ω □ or more, and at least one of an opening provided in the guide plate upstream, downstream, or in the guide plate. An image forming apparatus comprising: a charge removing member; and a voltage applied to the charge removing member determines a voltage applied to the charge removing member based on a passage surface of the transfer material.