JP2000338774A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an excellent printed image by reducing concentric fogging or developing irregularity in the vicinity of a boundary between an image part and a non-image part in an image forming device using a developing system performing development by making developer particles fly to space between an image carrier and a developing roll. SOLUTION: An area where the developer particles flying by developing electric field are concentrically retained exists on the upstream side and the downstream side of a developing area where the image carrier 1 and the developing roll 13 are opposed. Then, the device is provided with a retained developer particle removing device 20 removing the developer particles in the retained area. The device 20 is equipped with a sheet member 22 circularly moving on the surface of a stainless core material 21 and supporting rollers 23 and 24 for stretching and laying the member 22 and circularly moving the member 22, and a cleaning blade 27 cleaning the surface of the member 22. The developer particles in the retained area adhere to the member 22 and are carried to the outside of the retained area by the circular movement of the member 22.

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 for forming a visible image on an image receiving body by using developer particles, which is used for a copying machine, a printer or the like utilizing an electrophotographic system.
In particular, the present invention relates to an image forming apparatus that visualizes an electrostatic latent image on an image receiving member by flying developer particles between the image receiving member and a developer carrying member.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method has been widely used. In the electrophotographic image forming apparatus, for example, an image carrier composed of a drum-shaped photoreceptor is charged almost uniformly by a charging device, and image light is irradiated on the image carrier by an exposure device, and the surface of the image carrier is An electrostatic latent image is formed on the image. The electrostatic latent image is developed by selectively adhering charged developer particles, and the developed image formed on the image carrier is transferred to a copy sheet as a transfer material. The image transferred onto the copy paper is fixed by heating and pressing by a fixing device. Further, the developer particles remaining on the surface of the image carrier are removed and collected by a cleaning means such as a cleaning blade before forming the next electrostatic latent image, and the image carrier is neutralized by uniform exposure.

The developing method in such an image forming apparatus generally involves developing an electrostatic latent image electrostatically by using charged developer particles as described above. Developer particles are usually charged so that they have a sufficient charge to electrostatically adhere to the electrostatic latent image, but all developer particles have a constant charge. Instead, they are charged with a certain distribution. Some of these developer particles have an insufficient amount of electric charge for developing an electrostatic latent image (hereinafter referred to as low-charged developer particles) or have the same polarity as the polarity of the electrostatic latent image. Charged particles (hereinafter referred to as “reverse polarity developer particles”) are present, and the developer particles adhere to the non-image area and are developed, resulting in fogging, or image quality deterioration such as image unevenness where the density of the developed area is not constant. Can cause.

As a countermeasure for preventing fogging of a non-image area, Japanese Patent Application Laid-Open No. 4-14078 discloses a method for preventing fogging of a printed image which occurs at the time of transfer and fixing, by using a material for both an image carrier and developer particles. A technique has been proposed in which the above-described technique has been improved and reduced. In this technology, during development, the material of both the image carrier and the developer particles is selected in such a combination that the developer particles sandwiched between the image carrier and the developing roller are not charged to the opposite polarity even if they are frictionally charged. are doing. However, even with this technique, reverse polarity developer particles may be generated, and although a small amount of the generated reverse polarity developer particles and low-charged developer particles are not electrostatically attracted to the image receiving member, they may be generated during development. When the particles are rubbed by contact with the developer, a small amount of the low-charged developer particles and the opposite-polarity developer particles adhere to the image carrier. As a result, when transferred by a transfer method such as a transfer fixing method, fog occurs in a printed image. Further, to realize this technique, it is necessary to change the materials of both the image carrier and the developer particles.

Japanese Patent Application Laid-Open No. Hei 8-278701 discloses that a bias voltage is applied between a developing roller for transporting a developer and a developer supply member for supplying developer particles to the developing roller. Fogging is suppressed by preventing low-charged developer particles and reverse-polarity developer particles that are the source of fogging on the supply member from being supplied onto the developing roller.

From the viewpoint of preventing scattering toner,
For example, in Japanese Patent Application Laid-Open No. 2-197883, in a developing device in which a magnetic roller is incorporated inside a developer carrier and the developer is transported by rotation of the magnetic roller, the developer is placed on the developer carrier along a transport direction of the developer. A technique has been disclosed in which a plurality of electrodes are provided, and a bias voltage is applied so that the potential of the electrode on the upstream side in the transport direction of the developer is increased, thereby preventing the toner from scattering without lowering the developing ability. .

In JP-A-8-220882, the balance between the attractive force between the developing roller and the image carrier due to the magnetic force applied to the developing roller and the electrostatic force due to the electric field between the developing roller and the image carrier is unstable. Pointed out that the developer particles in the state scattered below and around the developing area due to the influence of the rotation of the developing roll, etc., fouling the image and the surroundings, and the developer scattered by the suction means installed in the developing device There is disclosed a technique for collecting particles and preventing fogging due to scattered developer particles and contamination of equipment.

In Japanese Patent Application Laid-Open No. Hei 8-254896, in order to prevent developer particles from leaking from a developing unit, a charge opposite to the developer particles is provided between a developing area and a developing tank so as to contact a developing roller. A technique of installing a polar elastic seal member is disclosed. Further, there is disclosed a technique capable of preventing the developer accumulated under the developing roller from leaking and blowing out in an electrophotographic process of a one-component developing method irrespective of whether the developer particles are magnetic or non-magnetic.

As described above, the techniques disclosed in Japanese Patent Application Laid-Open Nos. 4-14078 and 8-278701 disclose a fog image in a non-image portion by low-charged developer particles or reverse-polarity developer particles. This is a technique for reducing the noise, which is disclosed in JP-A-2-197883, JP-A-8-278701, JP-A-8-220882, and JP-A-8-254896.
The technique disclosed in Japanese Patent Application Laid-Open Publication No. H10-209,216 is a technique for collecting scattered developer to prevent developer particles leaking and scattered from a developing device from contaminating an image on a photoreceptor or the inside of an image forming apparatus. . According to these techniques, it is possible to reduce the general fogging phenomenon caused by a low-charge developer, a reverse polarity developer, and a flying developer to some extent.

[0010]

However, the above-described conventional image forming apparatus has the following problems. The development method in which the developer particles fly to perform development has a characteristic image quality deterioration phenomenon that occurs near the boundary between the image area and the non-image area, and this image quality deterioration cannot be solved by the techniques described above. . The characteristic image quality deterioration phenomenon that occurs near the boundary between the image part and the non-image part is, for example, as shown in FIG.
In the case of developing in the direction of 0a, fogging phenomenon 2 in which particles are concentrated and developed as fog in a non-image portion near the boundary.
02 and development unevenness 203 in which the density of the rear end portion is not constant when an image having a constant density is developed. Both of these deteriorations in image quality are caused by the fact that the developer particles flying between the developing roller 220 and the image carrier 210 are not developed in the development area but stay in the area A as shown in FIG. is there.

It is considered that such stagnation of the developer particles occurs when forces applied to the developer particles balance in the developer transport direction. When the force applied to the developer particles at the boundary between the image portion and the non-image portion changes while the developer particles are staying due to such a force balance, the force balance is broken and concentrated. And appears as image quality degradation. Japanese Patent Application Laid-Open No. 8-278701 describes that a force acts on developer particles in a direction perpendicular to the developer transport direction, and the balance of the force becomes partially unstable. No mention is made of the balance of forces in the transport direction.

The balance of the forces in the transport direction of the developer particles and the mechanism in which the image quality is degraded when the balance is broken will be considered with an example of magnetic one-component jumping development in an electrophotographic system. In this example, it is assumed that the developer magnetic particles are negatively charged. The developer particles are attracted to the magnetic roller in the developing roller and conveyed to the developing area. In the developing area, the DC bias voltage and the AC voltage applied between the image carrier and the developing roller cause the image carrier to develop. While reciprocating between the rollers, the toner adheres to the electrostatic latent image, which is a high potential portion of the surface of the image carrier, to make the image visible. At this time, some of the developer particles stay in the developer transport direction. FIG. 16 shows the behavior of the particles between the developing roller and the image carrier visualized by numerical calculation. It can be seen that the developer particles stay in the region 225.

As shown in FIG. 17, the force acting on the developer particles, which balances in the developer transport direction, is received by contacting the developer transport direction component 231 of the magnetic force of the developing roller with the image carrier and the developing roller. Force or a force 232 caused by the flow of air generated by the image carrier and the developing roller, and a centrifugal force 233 applied in an alternating movement along an arc-shaped electric force line.
It is considered to be.

When the non-image portion of the image carrier is passing through the developing area, if the developer particles alternately move on a line of electric force passing through a certain position on the image carrier, the particles move at that position. The speed of moving in the transport direction under the above-mentioned forces 131, 132, 133 can be schematically represented, for example, as shown in FIG. In this figure, the horizontal axis represents the position of the particles on the image carrier with the upstream side in the particle transport direction being positive when the minimum gap between the developing device and the image carrier is 0, and the vertical axis represents the developer. Shows the velocity of the particles. As shown in this figure, assuming that the speed due to the magnetic force is F231, the speed due to the conveyance of the developing roller is F232, and the speed due to the centrifugal force is F233, the speed at which the developer particles receive the above force and move is the image carrier. Each has a different distribution in the upper position.

As shown in FIG. 18 (b), the moving speed 234 based on the sum of all the forces is 0 at a certain position 235, and moves further downstream in the upstream direction in the developer particle transport direction. It has a speed such that it moves upstream in the downstream direction of the developer particles in the transport direction, so that when the non-image portion of the image carrier passes through the development area, the developer particles It can be seen that it stays in the vicinity. When the boundary between the image area and the non-image area enters the development area, the balance of the force is lost, and the retained developer particles flow out of the area A at a stretch. At that time, some of the developer particles are intensively developed in a region near the boundary between the image area and the non-image area, and intensive fog at the boundary between the image area and the non-image area, or deterioration in image quality such as uneven development. Appears. In particular, FIG.
When developing in the direction of arrow 200a as shown in FIG.
Development unevenness 203 due to the normally charged toner occurs behind the boundary between the non-image portion 201 and the image portion 200, and the image density tends to become unstable. Fogging with the opposite polarity toner occurs behind the boundary from the image portion to the non-image portion. 202 is likely to occur.
Whether or not the particles stay depends on the physical property values, and not all the particles cause the stay phenomenon.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a developing system in which developer particles are caused to fly between an image carrier and a developer carrier such as a developing roller. An object of the present invention is to provide an image forming apparatus capable of reducing intensive fogging and development unevenness near a boundary between an image portion and a non-image portion and forming a good print image.

[0017]

Means for Solving the Problems To solve the above problems, the invention according to claim 1 has an endless peripheral surface,
An image receiving member on which an image is formed on the peripheral surface, a developer carrying member disposed to face the image receiving member and transporting the developer particles while carrying the developer particles on the surface; and An image forming apparatus that has a flying force applying unit that flies between the developer carrying member and a visible image by selectively adhering the developer particles that have flown onto the image receiving body;
On the upstream side or downstream side of the developing area where the image receiving body and the developer carrier face each other, a developer particle removing means for removing the developer particles that are concentrated and stay while flying from the stay area is provided. Shall be.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the staying developer particle removing means moves from the staying area of the developer particles to the outside of the staying area, and Has a developer particle transport member that carries out the developer particle from the stagnation area.

In such an image forming apparatus, when the developer flies between the image receiving member and the developer carrying member and is developed on the image receiving member, the developer particles are located upstream or downstream of the developing area. Even if stagnation occurs, these developer particles are conveyed to the outside of the stagnation area by the stagnation developer particle removing means. Further, as described in claim 2, when the developer particle transport member is used, the developer particles adhered to the developer particle transport member in the retention region are moved from the retention region by the movement of the developer particle transport member. It is carried out. For this reason, fogging and uneven development which are caused by adhering to the image receiving body when the balance of the force acting on the staying developer particles is lost are prevented, and a good image without deterioration in image quality can be obtained.

According to a third aspect of the present invention, there is provided an image receiving member having an endless peripheral surface on which an image is formed, and a developer particle disposed on the image receiving member and facing the image receiving member. A developer carrier for carrying while carrying the developer, and a flying force applying unit for causing the developer particles to fly between the image receiver and the developer carrier; An image forming apparatus that selectively adheres to a top surface to form a visible image, wherein the image receiving member and the developer carrier are upstream or downstream of a developing area opposed to each other, and developer particles fly. And a shielding plate provided on the image receiving side of the region where the developer stays concentrated while preventing the staying developer particles from being attracted to the image receiving side.

In such an image forming apparatus, a shield plate is provided on the image receiving side of the area where the developer particles are concentrated and stay while flying, and the developer particles fly upstream or downstream of the developing area. Even when the developer particles stay, the developer particles can be prevented from being adsorbed on the image receiving body side.
For this reason, the occurrence of fogging and uneven development due to the staying developer particles is prevented, and a good image without image quality deterioration is obtained.

According to a fourth aspect of the present invention, there is provided an image receiving body having an endless peripheral surface, on which an image is formed, and a magnetic material disposed on the surface and disposed opposite to the image receiving body. A developer carrier that carries and transports the developer particles; and a flying force applying unit that causes the developer particles to fly between the image receiving body and the developer carrier. Is selectively adhered to the image receiving member to form a visible image, wherein the image receiving member and the developer carrier are on the upstream or downstream side of a developing region facing the developer, A magnetic field generating means is provided for forming a magnetic field in a region where the particles fly and concentrate and stay, and suppresses the behavior of the staying developer particles in the region.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the magnetic field generating means is disposed near the stagnation area between the image receiving member and the developer carrier. It is assumed that the conductive circuit generates a magnet or a magnetic field.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the magnetic field generating means is disposed in the developer carrier and has a magnet having a magnetic pole in a portion near the stagnation region. It is assumed that the member is a magnetic field generating member.

In such an image forming apparatus, a magnetic field is generated by a magnetic field generating means in a region where the developer particles fly and concentrate and stay. For example, the magnetic developer particles are attracted toward the developer carrier. By forming such a magnetic field, the staying developer particles are attracted to the developer carrier and removed from the staying area. For this reason, the occurrence of fogging and uneven development due to the developer staying in the upstream or downstream area of the developing area is prevented, and a good image without image quality deterioration is obtained.

According to a seventh aspect of the present invention, there is provided an image receiving member having an endless peripheral surface on which an image is formed, and a developer which is disposed opposite to the image receiving member and is charged on the surface. A developer carrying member that carries the particles while carrying the particles, and a flying force applying unit that causes the developer particles to fly between the image receiving member and the developer carrying member; In an image forming apparatus that forms a visible image by selectively adhering on a receiver, an upstream or downstream side of a development area where the receiver and the developer carrier face each other, and developer particles are An electric field generating means is provided for forming an electric field in a region where the developer particles are concentrated while flying, and controls the behavior of the developer particles staying due to electrostatic force.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, the flying force applying means applies a developing bias voltage between the image receiving body and the developer carrier. These form an electric field in a developing region opposed to the developing region, and the electric field generating means is disposed inside the developer carrying member, and is located on the upstream side of the developing region or along the peripheral surface of the developer carrying member. Including an electrode provided on the downstream side,
By applying a voltage between the electrode and the image receiving body, an electric field whose strength is adjusted separately from the electric field due to the developing bias voltage is formed.

In the above-described image forming apparatus, an electrode is provided on the upstream or downstream side of the developing area along the peripheral surface of the developer carrier, and a voltage is applied between the electrode and the image receiving body. As a result, an electric field having a strength different from that of the developing electric field is formed in these opposed portions. For example, when a positively charged developer is used as a normally charged developer, a voltage applied between the image receiving member and the developer carrier on the upstream or downstream side of the development region is applied in the development region. By setting the voltage higher than the voltage, it is possible to prevent the developer particles from flying toward the image receiving body when the balance of the force acting on the staying developer particles is lost. That is, the retained developer particles are blown toward the developer carrier by the action of the electric field, adhere to the developer carrier, and are collected. For this reason, it is possible to prevent fogging, uneven development, and the like that occur due to the accumulated developer intensively adhering to the image receiving body, and it is possible to form a good image without deterioration in image quality.

According to a ninth aspect of the present invention, in the image forming apparatus of the seventh aspect, the electric field generating means forms an electric field whose direction alternates periodically.

According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the flying force applying means comprises:
An alternating voltage obtained by superimposing an alternating current on a direct current is applied as a developing bias voltage between the image receiving member and the developer carrying member. It is assumed that an alternating voltage having a smaller amplitude than the alternating voltage applied to the region is applied.

In the above-described image forming apparatus, the alternating voltage having a smaller amplitude than the alternating voltage applied to the developing region is applied to the upstream side of the developing region by the electric field generating means. When the developer particles are developed while alternately moving with the body, the alternating movement caused by the developer particles on the upstream side of the developing area is suppressed, and the centrifugal force acting on the upstream side in the developer transport direction is reduced. Can be weakened. That is,
The effect of the centrifugal force that prevents the developer particles from being transported can be reduced, the developer particles can be promoted to be transported to the development area, and the stagnation of the developer can be prevented. For this reason, the occurrence of fogging and uneven development due to the staying developer is prevented, and a good image without image quality deterioration is obtained.

[0032] According to an eleventh aspect of the present invention, in the image forming apparatus according to the eighth aspect, the flying force applying means comprises:
An alternating voltage obtained by superimposing a direct current and an alternating current as a developing bias voltage is applied between the image receiving member and the developer carrying member. It is assumed that an alternating voltage having a larger amplitude than the alternating voltage applied to the region is applied.

In the above-described image forming apparatus, an alternating voltage having a larger amplitude than the alternating voltage applied to the developing area is applied to the downstream side of the developing area by the electric field generating means. When the developer particles are developed while alternately moving with the body, the alternating movement caused by the developer particles on the downstream side of the developing area is promoted, and the centrifugal force acting on the downstream side in the developer conveying direction is reduced. Can be strengthened. Thus, the developer particles are encouraged to be conveyed from the stagnant area on the downstream side of the developing area to the outside thereof, and the stagnation of the developer can be prevented. For this reason, the occurrence of fogging and uneven development due to the staying developer is prevented, and a good image without image quality deterioration is obtained.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a drum-shaped image carrier 1 having a photoreceptor layer on a surface thereof, and a charging device for charging the surface of the image carrier 1 substantially uniformly around the image carrier 1. 2, an image writing device 3 for irradiating the image carrier 1 with image light to form an electrostatic latent image, and an electric field acting between the image carrier 1 to cause developer particles to fly, Developing device 4 for selectively adhering and visualizing the electrostatic latent image on 1
And a transfer roller 5 for transferring the toner image formed on the image carrier 1 to the recording paper 9.

Further, a fixing device 8 for fixing the toner image transferred onto the recording paper 9 by applying heat and pressure, a cleaning device 6 for removing the toner remaining on the image carrier 1 after the transfer, and an image carrier 1 A static elimination lamp 7 for erasing the upper electrostatic latent image.

The developing device 4 is supplied to a developing roller (developer carrying member) 13 for carrying the developer 11 on the surface thereof in a housing 12 for accommodating the developer 11 and a developing roller 13. A layer forming member 14 that regulates the developer and forms a developer layer having a substantially constant thickness. As shown in FIG. 2, the developing roller 13 includes a sleeve 13a that moves around the surface, and a magnetic roller 13b that generates magnetic force and is fixed and supported inside the sleeve 13a. The magnetic developer 11 is applied to the sleeve 1 by the magnetic roller 13b.
The developer 11 adheres to the surface 3a and conveys the developer 11 to the developing area by the circumferential movement of the sleeve 13a. The layer forming member 14 includes:
The developer 11 is charged to a negative charge while regulating the thickness of the developer layer by frictional charging. The developing roller 13 includes
As shown in FIG. 3, a voltage obtained by superimposing an alternating current on a direct current is applied from a power supply device 15.
Developing roller 1 by the action of an electric field between
The developer particles fly from 3, and these developer particles selectively adhere to the electrostatic latent image on the image carrier 1.

FIG. 3 is a partially enlarged view showing a position where the image carrier 1 and the developing device 4 face each other. Between the image carrier 1 and the developing roller 13, there is a region A where the developer particles fly and concentrate and stay on the upstream and downstream sides of the developing region B,
A staying developer particle removing device 20 for removing these staying developer particles is provided. As shown in FIG. 2, the stagnant developer particle removing device 20 includes a stainless steel core 21 disposed at a position facing the image carrier 1 and the developing roller 13 with its front end facing the stainless steel core 21. An endless sheet member 22 that moves around, a support roller 23 and a drive roller 24 that are arranged inside the sheet member 22 and that stretches around the sheet member 22 so that the sheet member 22 can rotate around the sheet member 22. And a tension applying roller 25 that is pressed on the rear side of the roller 21. Further, a power supply 26 for applying a voltage to the stainless steel core 21,
A cleaning blade 26 for cleaning the surface of the sheet member 22;

In such an image forming apparatus, the image carrier 1
Is 30 mm, the diameter of the developing roller 13 is about 15 mm, and the stainless core material 21 has a thickness of 20 μm.
An annealed conductive stainless steel plate having a length of about m and a length of about 1 mm is used. A voltage is applied to the stainless steel core material 21 from the power supply 26 such that normally charged toner is hardly attracted, but reversely charged toner is easily attracted. For example, when the normally charged toner is negatively charged, the exposed portion is developed, the image carrier is negatively charged, and the bias voltage of the developing roller is set to negative, the voltage applied to the stainless steel core 21 is set to the bias of the developing roller. It is set to a voltage lower than the voltage, that is, a voltage higher in the negative direction. The sheet member 22 is made of a polyimide or aramid sheet having a thickness of about 20 μm, and has a tension of 10 kg.
f / mm ² (to the extent that the sheet member does not loosen).

The distance between the image carrier 1 and the developing roller 13 is maintained at 50 μm or more. As shown in FIG. 3, the stainless steel core material 2 is set such that the distance M between the sheet member and the closest portion between the image carrier 1 and the developing roller 13 is 2 mm.
1 is arranged. At the position of the tip of the stainless steel core 21, the distance N between the image carrier 1 and the developing roller 13 is 0.5 mm.
It has become about. The sheet member 22 is supplied endlessly to the leading end of the stainless steel core member 21 by the rotation of the driving roller 24, and the developer adhered to the surface at a sufficient distance from the developing area is removed by the cleaning blade 27.

Next, the operation of the image forming apparatus will be described. The surface of the image carrier 1 is charged to the same polarity (negative) as the developer particles by the charging device 2, the surface of the image carrier 1 is exposed by the image writing device 3 using a light emitting diode or a laser diode, and the surface is statically charged. An electric latent image is written. The portion where the electrostatic latent image is written has a higher potential than the non-latent image portion, and the negatively charged developer particles tend to adhere to the image area. The electrostatic latent image on the image carrier 1 moves to a position facing the developing device 4, and the alternating voltage applied from the power supply device 15 causes the magnetic developer 11 to reciprocate in the developing region, and the developer particles The electrostatic latent image is adhered to the exposed portion of the image carrier 1 and becomes visible.

The toner image formed on the image carrier 1 is electrostatically transferred to the recording paper 9 by the action of the transfer roller 5 to which the bias voltage is applied, and is fixed on the recording paper 9 by the fixing device 8. You. The developer particles remaining on the image carrier 1 are peeled off by a cleaning blade provided in a cleaning device 6, and an electrostatic latent image on the image carrier 1 is erased by a discharge lamp 7.

In the above-described image forming apparatus, as shown in FIG. 3, the developer 11 reciprocates in the direction of arrow 18a and passes through the development area. However, the developer 11 is charged by frictional charging. Therefore, the charge amount has a distribution, and the size and the applied magnetic force also vary. For this reason, some developers remain in the area A due to the balance of various forces such as magnetic force, electrostatic force, and air flow. At this time, the sheet member 22 provided in the staying developer particle removing device 20 moves on the surface of the stainless steel core member 21 in the direction of the arrow 22a, so that the staying developer adheres to the sheet member 22 and the area A Removed from
At this time, since a voltage is applied to the stainless steel core material 21 so that the oppositely charged toner is easily attracted, the opposite polarity toner that causes image quality deterioration is efficiently removed.
The developer attached to the sheet member 22 is removed and collected by the cleaning blade 27 on the downstream side in the circumferential direction. In such an image forming apparatus, since the developer that flies and stays is removed from the stay area A on the upstream side and the downstream side of the development area, intensive fogging and uneven development caused by the staying developer are caused. Image quality degradation can be prevented.

FIG. 4 is a schematic structural view showing an apparatus for removing staying developer particles used in an image forming apparatus according to another embodiment of the present invention.
4A is a sectional view, and FIG. 4B is a side view. This image forming apparatus includes the same apparatus as the image forming apparatus shown in FIG. 1, but the configuration of the staying developer particle removing apparatus 40 is different. The staying developer particle removing device 40 includes a developing roller 3
3, a plurality of support rollers 43 for stretching the sheet member 42, and a cleaning blade 44 pressed against the peripheral surface of the sheet member 42.
And

The sheet member 42 is an endless sheet made of polyimide or aramid, and the tension of this sheet is set to 20 kgf / mm ² or more (to the extent that it does not loosen). The sheet member 42 moves in the longitudinal direction while maintaining a substantially constant distance from the image carrier 31 due to the rigidity of the sheet. The other configuration of the image forming apparatus is the same as that of the image forming apparatus shown in FIG.

In such an image forming apparatus, the image carrier 3
Even if the developer reciprocates in the direction of arrow 38a between the developing roller 1 and the developing roller 33 and stays in the area A, the developer adheres to the sheet member 42, and the sheet member 42 rotates around the area A Removed from The developer attached to the sheet member 42 is removed and collected by the cleaning blade 44 at a position away from the opposing portion between the image carrier 31 and the developing roller 33. As a result, the developer accumulated on the upstream side and the downstream side of the development area B is efficiently removed from the area A, so that it is possible to prevent the occurrence of intensive fogging and uneven development caused by the accumulated developer. it can.

FIG. 5 is a schematic structural view showing a staying developer particle removing device used in an image forming apparatus according to an embodiment of the present invention. This image forming apparatus includes the same apparatus as the image forming apparatus shown in FIG. 1, but the configuration of the staying developer particle removing apparatus 60 is different. The staying developer particle removing device 60 includes a shield plate 62 disposed in the area A where the developer stays in the vicinity of the image carrier 51, and two support rollers 64 for detachably supporting the shield plate 62. , 65, and a cleaning brush 63 for removing the developer attached to the developing roller 53 side of the shielding plate 62. Further, two projections 67 are provided behind the shielding plate 62, and the stopper 66 prevents the shielding plate 62 from moving more than necessary. The shielding plate 62
Is made of a non-magnetic, insulating material and is very thin and does not affect the electric and magnetic fields in the development area. The other configuration of the image forming apparatus is the same as that of the image forming apparatus shown in FIG.

In such an image forming apparatus, the image carrier 5
The developer staying in the area A where the developing roller 1 and the developing roller 53 face each other is prevented from moving toward the image carrier 51 by the shielding plate 62, and a part of the developer adheres to the shielding plate 62. Therefore, the developer that has flown in the developing area B is
Even if the developer remains, the developer does not adhere to the image carrier 51, thereby preventing the occurrence of image quality deterioration such as intensive fog and uneven development. Developer particles adhere to the shield plate 62 on the side of the developing roller 53, but after development is completed, the shield plate 62 is retracted rearward by rotation of the support rollers 64 and 65, and the developer particles are removed by the cleaning brush 63. You. Then, when the development is started, the shielding plate 62 is again rotated by the rotation of the support rollers 64 and 65 so that the image carrier 51 is rotated.
To prevent the staying developer from adhering to the image carrier 51.

FIG. 6 is a schematic configuration diagram showing an apparatus for removing staying developer particles used in an image forming apparatus according to an embodiment of the present invention. This image forming apparatus has the same apparatus as the image forming apparatus shown in FIG. 1, but instead of the staying developer particle removing apparatus 20 shown in FIG.
The developing roller 73 is disposed on the upstream and downstream sides of the facing portion between the image bearing member 3 and the image carrier 71. During the development, a magnetic field is generated by the electromagnet 80, and the developer remaining in the region A is attached to the electromagnet 80. In addition, until the development is completed and the next development is started, the developing roller 73 is rotated without generating a magnetic field in the electromagnet 80, so that the developer attached to the electromagnet 80 is collected by the magnetic force of the developing roller 73. Is done. With such a configuration, it is possible to collect the stagnant developer that causes fogging or development unevenness, and to form a good image without image quality deterioration.

FIG. 7 is a schematic diagram showing the vicinity of a portion where an image carrier and a developing roller are opposed to each other in an image forming apparatus according to an embodiment of the present invention. In this image forming apparatus, a magnetic roller 93b included in a developing roller 93 is used instead of the electromagnet 80 shown in FIG. The developing roller 93 includes a sleeve 93a that moves around the peripheral surface and a magnetic roller 93b fixed and supported inside the sleeve 93a.
, An N-pole and an S-pole are sequentially arranged from the upstream side at a position facing the region A in which the developer stays. The magnetic roller 93b generates a strong magnetic field in the region A where the developer stays, and the developer acts on the developing roller 93
Adheres to FIG. 6 shows another configuration of the image forming apparatus.
Is the same as the image forming apparatus shown in FIG.

In such an image forming apparatus, since a strong magnetic field is generated in the area A where the developer stays by the developing roller 93b, the staying developer adheres to the developing roller 93 and is caused by the circumferential movement of the sleeve 93a. Conveyed. This makes it possible to collect the stagnant developer that causes intensive fogging and image unevenness, and to form a good image without image quality deterioration. The developing roller 93
Although the magnetic pole is provided at a position facing the area A of the magnetic roller 93b, the same effect can be obtained by using an electromagnet or the like instead of the magnetic pole.

FIG. 8 is a schematic structural view showing the vicinity of a portion where an image carrier and a developing roller of an image forming apparatus according to an embodiment of the present invention are arranged. In this image forming apparatus, the image carrier 1 is provided inside the developing roller 113.
An electrode 122 for forming an electric field is arranged in a developing region B facing the substrate 11 and an upstream and downstream region A of the developing region B, and a power supply for applying a bias voltage having a different strength to the electrode 122 in the circumferential direction of the developer. Devices 123, 124, 125, 1
26 are provided. The electrode 122 is made of a high-resistance material, and has a power supply device 115 and power supply devices 123, 124, and 12.
By applying a bias voltage from 5, 126, the intensity of the electric field formed in the developing region and the upstream and downstream regions A thereof is controlled. FIG. 9 is a graph schematically showing the value of the DC bias component applied to the electrode 122 at a position on the developing roller. In this figure, the horizontal axis represents the position on the developing roller with the closest part between the developing roller and the image carrier as 0, and the upstream side with respect to the developer transport direction is positive, and the vertical axis is provided inside the developing roller. Of the DC bias component applied to the applied electrode 122. As shown in FIG. 9, the potential 1 near the region A where the particles stay is 1
28 is set higher than the potential of the development area. In this image forming apparatus, a positively charged developer is used as a normally charged developer.

When a uniform DC bias voltage is applied to the developing roller, the developer charged to the opposite polarity (negative) stays. However, by applying the DC bias voltage as shown in FIG. It is possible to control so that the developer particles in the area A fly to the developing roller 113 side instead of the image carrier 111 side. As a result, the developer particles in the area A adhere to the developing roller 113 and are transported outside the developing area. Developer particles charged to the opposite polarity (negative) cause concentrated fog to appear on the non-image portion near the boundary between the image portion and the non-image portion. Is removed from the area A by controlling the electric field between the developing roller 113 and the image carrier 11, and it is possible to prevent the occurrence of fog in the non-image portion near the boundary between the image portion and the non-image portion. In the above image forming apparatus, the electrode 1
Although a high-resistance element is used as 22, four electrodes may be arranged in the developer conveyance direction, and different DC bias voltages may be separately applied from the four power supply devices.

In the above-described image forming apparatus, a positively charged developer is used as a normally charged developer. However, the present invention can be applied to a case where a negatively charged developer is used as a normally charged developer. When the negatively charged developer is used as a regular charged developer, the regular charged developer has an effect of attaching to the developing roller by the same effect as described above and removing it from the area A, and the regular charged developer remains. Occasionally, development unevenness can be prevented from occurring at the boundary between the uniform density image and the non-image portion.

The electrode 122 provided inside the developing roller 113 has the same configuration as the image forming apparatus shown in FIG.
By controlling the DC bias voltage applied to the particles, the potential 129 near the region where the particles stay may be set to be low as shown in FIG. When the negatively charged developer is used as a regular charged developer, the developing roller 1
When a uniform DC bias voltage is applied to the developer 13, the developer charged to the opposite polarity (positive) stays.
By applying the DC bias voltage shown in (1), the developer charged to the opposite polarity (positive) adheres to the developing roller 113 and is transported out of the developing area. Further, when the positively charged developer is used as a regular charged developer, there is an effect of removing these regular charged developers from the area A, and when the regular charged developer stays, a non-image portion of a uniform density image is obtained. Developing unevenness can be prevented from being generated at the boundary between.

FIG. 11 is a schematic diagram showing the vicinity of a portion where an image bearing member and a developing roller of an image forming apparatus according to an embodiment of the present invention are arranged. . In this image forming apparatus, a developing area B facing the image carrier 131 and an electrode 142 for forming an electric field in the upstream and downstream areas A are arranged inside the developing roller 133. Power supply devices 143, 144, and 14 for applying voltages of different strengths in the circumferential direction of the developer
5,146 are provided. The electrode 142 is made of a high-resistance material, and includes the power supply 135 and the power supply 143, 144,
145 and 146 are set so as to apply an alternating voltage obtained by superimposing an alternating current on a direct current.

In FIG. 12, the horizontal axis shows the position on the developing roller where the closest part between the developing roller and the image carrier is 0 and the upstream side in the developer transport direction is positive, and the vertical axis is the electrode. 1
42 is a graph showing the amplitude of the alternating voltage applied to 42. As shown in FIG. 12, the amplitude C of the alternating voltage applied to the upstream side in the transport direction of the developer is applied during the normal development at the closest part between the developing roller 133 and the image carrier 131 and at the downstream side thereof. Smaller than the amplitude D of the alternating voltage
On the upstream side with respect to the developer transport direction, the alternating voltage 147 is
An alternating voltage 148 is applied to the nearest part between the developing roller 133 and the image carrier 131 and the downstream side thereof. The developer particles are transferred to the developing roller 133 and the image carrier 1 by the action of the alternating electric field.
31 reciprocates in the direction of arrow 138a. This movement is along the arc-shaped electric force line 136, so that centrifugal force acts outward of the arc. Developing roller 133 and image carrier 13
On the upstream side of the portion closest to the toner cartridge 1, the centrifugal force 137 acts on the upstream side in the developer transport direction, thereby preventing the developer particles from being transported. This force contributes to the stagnation of the developer particles. As shown in FIG.
Since the amplitude of the alternating voltage 147 applied to the electrode 142 is set to be small on the upstream side of the closest part between the image bearing member 33 and the image carrier 131, the speed of the reciprocating movement caused by the developer particles is reduced, thereby The generated centrifugal force is also reduced. For this reason, stagnation of the developer can be prevented, and fogging and uneven development near the boundary between the image area and the non-image area can be prevented.

FIG. 13 is a schematic diagram showing the vicinity of a portion where an image carrier and a developing roller are opposed to each other in an image forming apparatus according to an embodiment of the present invention. . In this image forming apparatus, a developing area facing the image carrier 151 and an electrode 162 for forming an electric field in the upstream and downstream areas A are arranged inside the developing roller 153. Power supplies 163, 16 for applying bias voltages of different strengths in the circumferential direction of the agent
4,165,166. The electrode 162 is made of a high-resistance material, and the power supply 155 and the power supply 163, 16
4, 165, 166 are set so as to apply an alternating voltage obtained by superimposing an alternating current on a direct current.

As shown in FIG. 14, the alternating voltage has an amplitude F of the alternating voltage applied to the downstream side in the developer conveying direction.
Is larger than the amplitude E of the alternating voltage applied at the time of normal development at the closest portion between the developing roller 153 and the image carrier 151 and at the upstream side thereof, and at the downstream side with respect to the developer transport direction. The alternating voltage 168 is the alternating voltage 1 at the closest point between the developing roller 153 and the image carrier 131 and on the upstream side thereof.
67 is applied. The developer particles move between the developing roller 153 and the image carrier 151 by an arrow 158 due to the action of the alternating electric field.
A reciprocating motion is performed in the direction of a, but since this motion is along the arc-shaped electric force line 156, a centrifugal force acts outward of the arc. On the downstream side of the closest portion between the developing roller 153 and the image carrier 151, the centrifugal force 157 acts on the downstream side in the developer transport direction, thereby promoting the transport of the developer particles. At this time, as shown in FIG. 14, the amplitude of the alternating voltage 168 applied to the electrode 162 is set to be larger on the downstream side in the developer transport direction than the nearest part between the developing roller 153 and the image carrier 151. Therefore, the speed of the reciprocating motion generated by the developer particles increases, and the generated centrifugal force increases, thereby facilitating the transport of the developer particles. For this reason, stagnation of the developer on the downstream side of the developing area can be prevented, and fog near the boundary between the image area and the non-image area, development unevenness, and the like can be prevented.

[0059]

As described above, according to the present invention, in an image forming apparatus which performs development by causing developer particles to fly between an image receiving member and a developer carrying member, the image forming apparatus is provided with an image receiving device and a developer carrying member. Paying attention to the fact that the developer particles stay in a certain area between them due to a subtle balance of forces, and focusing on the fact that these developer particles are causing a major image quality defect, they stay upstream or downstream of the development area The developer particles can be removed, or the retention of the developer particles can be suppressed. For this reason, the occurrence of fogging and uneven development near the boundary between the image area and the non-image area due to the retained developer particles is prevented, and a good image without image quality defects can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram showing a staying developer removing device used in the image forming apparatus shown in FIG.

FIG. 3 is a schematic configuration diagram illustrating an opposing portion between an image carrier and a developing roller of the image forming apparatus illustrated in FIG. 1;

FIG. 4 is a schematic configuration diagram showing a staying developer removing device used in an image forming apparatus according to another embodiment of the invention described in claim 1 or 2;

FIG. 5 is a schematic configuration diagram showing a structure near a shielding plate used in an image forming apparatus according to an embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing an opposing portion between an image carrier and a developing roller of the image forming apparatus according to an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing an opposing portion between an image carrier and a developing roller of the image forming apparatus according to an embodiment of the present invention.

FIG. 8 is a schematic configuration diagram illustrating an opposing portion between an image carrier and a developing roller of the image forming apparatus according to an embodiment of the present invention.

9 is a diagram showing a DC bias component of a voltage applied between an image carrier and a developing roller of the image forming apparatus shown in FIG.

10 is a diagram illustrating another example of the DC bias component of the voltage applied between the image carrier and the developing roller of the image forming apparatus illustrated in FIG.

FIG. 11 is a schematic configuration diagram showing an opposing portion between an image carrier and a developing roller of the image forming apparatus according to an embodiment of the invention described in claim 7, 9 or 10;

12 is a diagram illustrating an alternating voltage component of a voltage applied between an image carrier and a developing roller of the image forming apparatus illustrated in FIG. 11;

FIG. 13 is a schematic configuration diagram showing a facing portion between an image carrier and a developing roller of an image forming apparatus according to another embodiment of the present invention.

14 is a diagram illustrating an alternating voltage component of a voltage applied between an image carrier and a developing roller of the image forming apparatus illustrated in FIG. 13;

FIG. 15 is a diagram illustrating an example of an image quality defect that occurs in a conventional image forming apparatus.

FIG. 16 is a diagram visualizing the behavior of developer particles in a development region by numerical calculation.

FIG. 17 is a diagram schematically illustrating a force acting on a developer particle in a developing region in a developer conveying direction.

18 is a graph showing an example of an average speed at which developer particles are conveyed by the force shown in FIG.

[Explanation of symbols]

1, 31, 51, 71, 91, 111, 131, 151
Image carrier 2 Charging device 3 Image writing device 4 Developing device 5 Transfer roller 6 Cleaning device 7 Static elimination lamp 8 Fixing device 9 Recording paper 11, 41, 61, 81, 101, 121, 141, 1
61 developer 12 housing 13, 33, 53, 73, 93, 113, 133, 15
3 Developing roller 14 Layer forming member 15, 115, 135, 155 Power supply device 18a, 38a, 78a, 98a Direction of reciprocating developer 20, 40, 60 Retained developer particle removing device 21 Stainless steel core material 22, 42 Sheet member 23, 43 support roller 24 drive roller 25 tension application roller 26 power supply 27, 44 cleaning blade 62 shielding plate 63 cleaning brush 64, 65 support roller 66 stopper 67 protrusion 80 electromagnet 118a, 138a, 158a direction of developer reciprocating movement 122, 142, 162 electrode 123, 124, 125, 126 power supply device 143, 144, 145, 146 power supply device 163, 164, 165, 166 power supply device A staying area B developing area

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Kawamoto 430 Nakai-cho, Sakaigami-gun, Kanagawa Prefecture Green Tech Nakai Inside Fuji Xerox Co., Ltd. (72) Inventor Yutaka Toyota 3-7-1 Fuchu, Iwatsuki-shi, Saitama Fujize Rocks (72) Inventor Toshiaki Suzuki 3-7-1, Fuuchi, Iwatsuki-shi, Saitama F-term in Fuji Xerox Co., Ltd. (Reference) 2H077 AD36 AE04 CA00 CA02 EA16

Claims (11)

[Claims] 1. An image receiving member having an endless peripheral surface, on which an image is formed, and a developer disposed to face the image receiving member and transporting while carrying developer particles on the surface. A carrier, and a flying force applying means for causing the developer particles to fly between the image receiving body and the developer carrying body, and causing the developer particles to be selectively adhered to the image receiving body. In the image forming apparatus that forms a visible image, the developer particles that fly and concentrate and stay on the upstream or downstream side of the developing area where the image receiving body and the developer carrier face each other are formed by An image forming apparatus comprising a staying developer particle removing means for removing the developer particles from an area. 2. The developer particle removing means according to claim 1, further comprising a developer particle transport member that moves from a stagnation area of the developer particles to a position outside the stagnation area and carries out the developer particles from the stagnation area. The image forming apparatus according to claim 1. 3. An image receiving member having an endless peripheral surface on which an image is formed, and a developer arranged opposite to the image receiving member and transporting while carrying developer particles on the surface. A carrier, and a flying force applying means for causing the developer particles to fly between the image receiving body and the developer carrying body, and causing the developer particles to be selectively adhered to the image receiving body. In the image forming apparatus that forms a visible image by using the image forming apparatus, an area on the upstream or downstream side of the developing area where the image receiving body and the developer carrying body are opposed to each other, where the developer particles are concentrated and stay while flying. An image forming apparatus, comprising: a shielding plate provided on the image receiving member side to prevent retained developer particles from being adsorbed to the image receiving member side. 4. An image-receiving member having an endless peripheral surface on which an image is formed, and a developer particle arranged on the surface opposite to the image-receiving member and carrying a developer particle containing a magnetic material on the surface. A developer carrier to be conveyed; and a flying force applying unit for causing the developer particles to fly between the image receiving body and the developer carrying body. The flying developer particles are selected on the image receiving body. In the image forming apparatus that forms a visible image by adhering the developer particles, the image receiving body and the developer carrier are on the upstream or downstream side of the developing area facing each other, and the developer particles are concentrated while flying. An image forming apparatus comprising: a magnetic field generating unit that forms a magnetic field in an area where the developer stays in the area and suppresses the behavior of the developer particles staying in the area. 5. The magnetic field generating means according to claim 4, wherein the magnetic field generating means is a magnet or a conductive circuit for generating a magnetic field disposed in the vicinity of the stagnation region between the image receiving member and the developer carrier. An image forming apparatus according to claim 1. 6. The magnetic field generating means according to claim 4, wherein the magnetic field generating means is a magnet or a magnetic field generating member disposed in the developer carrier and having a magnetic pole in a portion near the stagnation area.
An image forming apparatus according to claim 1. 7. An image receiving body having an endless peripheral surface, on which an image is formed, and an image receiving body disposed opposite to the image receiving body, and carrying the charged developer particles while carrying the charged developer particles on the surface. A developer carrying member, and a flying force applying means for causing the developer particles to fly between the image receiving member and the developer carrying member, wherein the flying developer particles are selectively placed on the image receiving member. In an image forming apparatus for forming a visible image by adhering, the developer particles are concentrated and fly and stay on an upstream or downstream side of a developing area where the image receiving body and the developer carrier face each other. An image forming apparatus comprising: an electric field generating unit that forms an electric field in a region where the developer particles stay, and controls a behavior of the developer particles staying due to an electrostatic force. 8. The flying force applying unit applies a developing bias voltage between the image receiving body and the developer carrier,
These form an electric field in a developing region opposed to the developing region, and the electric field generating means is disposed inside the developer carrying member, and is located on the upstream side of the developing region or along the peripheral surface of the developer carrying member. It includes an electrode provided on the downstream side, and forms an electric field whose strength is adjusted separately from the electric field by the developing bias voltage by applying a voltage between the electrode and the image receiving body. The image forming apparatus according to claim 7, wherein: 9. The image forming apparatus according to claim 7, wherein said electric field generating means generates an electric field whose direction alternates periodically. 10. The electric field generating means, wherein the flying force applying means applies an alternating voltage obtained by superimposing a direct current to an alternating current as a developing bias voltage between the image receiving member and the developer carrier. 9. The image forming apparatus according to claim 8, wherein an alternating voltage having a smaller amplitude than an alternating voltage applied to the developing region is applied to an upstream side of the developing region. 11. The electric field generating means, wherein the flying force applying means applies an alternating voltage obtained by superimposing a direct current to an alternating current as a developing bias voltage between the image receiving member and the developer carrier. 9. The image forming apparatus according to claim 8, wherein an alternating voltage having a larger amplitude than an alternating voltage applied to the developing region is applied to a downstream side of the developing region.