JP2006106223A - Supply/collection apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supply/collection apparatus capable of simultaneously and efficiently supplying and collecting developer. <P>SOLUTION: The supply/collection apparatus for supplying chargeable developer to a photoreceptor drum 19 and collecting the developer from the photosensitive drum 19 is provided with: a developer carrier constituted to stretch a ring-like belt to be rotated on the outer periphery of a supporting member arranged on a position close to the photoreceptor drum 19 while sticking the developer, including the surface of the rotary body and a gap between a first electrode and a second electrode in a moving route and carry the developer; a voltage application part 17 for applying AC voltage to the first electrode to supply the carrying developer to the rotary body; and a voltage application part 18 for applying AC voltage to the second electrode to collect the developer from the rotary body. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developer supply / recovery device used in an image forming apparatus using an electrophotographic method, an electrostatic recording method, or the like, and an image forming apparatus using the supply / recovery device, and more particularly to efficiently recover the developer. The present invention relates to a supply / recovery device and an image forming apparatus.

In an image forming apparatus using an electrophotographic system or an electrostatic recording system, some toner remains on the surface of the photosensitive drum after transfer.
When toner remaining on the surface of the photosensitive drum (hereinafter referred to as “residual toner”) remains attached, a so-called image memory is generated in which the previously formed image pattern is reflected again on the same or the next sheet. Therefore, it is necessary to quickly remove the residual toner from the surface of the photosensitive drum.

  Methods for removing the residual toner are roughly divided into two. One is a cleaning method in which residual toner removed from the surface of the photosensitive drum is discarded without being reused, and the other is a cleanerless method in which residual toner removed from the surface of the photosensitive drum is reused. It is. In recent years, of the above two methods, the adoption of a cleanerless method is desired from the viewpoint of effective use of resources.

In the cleanerless system, a member such as the above-described photosensitive drum from which toner is collected (hereinafter referred to as “collection source member”) and a member that collects toner (hereinafter referred to as “collection destination member”). It is desirable to move the residual toner to the collection destination member, that is, to collect the toner after making it easy to exchange the toner.
As a method for exchanging toner between two members in a state where the toner can easily move, for example, a photosensitive drum and a developing roller that are driven and rotated in proximity to each other are provided, and the proximity of the developing roller is within a range where the proximity occurs. There is a method in which an electrode is provided and an AC voltage is applied to the electrode to alleviate the influence of the dielectric polarization of the toner adhering to the photosensitive drum and the developing roller so that the toner can easily move, that is, can fly. . (For example, Patent Document 1)
As an apparatus for more efficiently exchanging toner, as shown in FIG. 7, an agitator 512, a supply roller 513, and a developing roller 516 are housed in a casing 511, and among these, the developing roller 516 is the casing 511. The electrode 601 and the electrode 602 are embedded in the developing roller 516, and both electrodes are connected to the AC voltage power supply device 517. There is an image forming apparatus 510. (For example, Patent Document 2)
By applying an AC voltage to the electrode 601 and the electrode 602, the influence of the dielectric polarization of the residual toner existing on the photosensitive drum 519 is reduced, and the residual toner is attracted to the developing roller 516 and attached to the supply roller 513. Finally, it can be recovered in the casing 511.

The residual toner collected in the casing 511 is stirred together with other toners by the agitator 512 and then reused.
This collection can be performed simultaneously with the supply (development) of the toner to the photosensitive drum, and the collection and supply timing can be shifted, but the time loss for the user can be reduced. It is desirable to carry out recovery and supply simultaneously.
Japanese Patent Laid-Open No. 5-127501 Japanese Patent Laid-Open No. 11-352772

  However, in the image forming apparatus described in Patent Document 2, in the case where toner collection and supply are simultaneously performed as described above, if the AC voltage condition is set to an optimum condition for toner collection, the developing roller 516 performs photosensitive operation. There is a problem in that development is not performed sufficiently because the toner flies to the body drum 519 and the toner is supplied to the latent image portion of the photoreceptor drum 519 to deviate from the optimum conditions for development.

  The present invention has been made to solve such a problem, and in the case of collecting while supplying toner, a supply / recovery device capable of efficiently performing supply and recovery simultaneously and an image using the same An object is to provide a forming apparatus.

  In order to achieve the above object, the supply and recovery apparatus of the present invention supplies a chargeable developer to a rotating body that performs development processing or subsequent processing in cooperation, and supplies the developer from the rotating body. A recovery device including a first electrode and a second electrode arranged at positions close to the surface of the rotating body, and a gap between the surface of the rotating body and the first electrode and the second electrode in a moving path; A developer conveying body that conveys the developer; a first voltage applying unit that applies an AC voltage to the first electrode so as to supply the developer being conveyed to the rotating body; and the development from the rotating body. A second voltage applying unit for applying an AC voltage to the second electrode so as to recover the agent;

  In order to achieve the above object, the image forming apparatus of the present invention comprises the above supply / recovery device, an image carrier, an electrostatic image forming means for forming an electrostatic image on the image carrier, and development. And a developing device for developing the electrostatic image on the image carrier with the agent.

  The supply / recovery device of the present invention is a supply / recovery device that supplies charging developer to a rotating body that performs development processing or subsequent processing in cooperation, and collects the developer from the rotating body. A developer that transports the developer by including a first electrode and a second electrode disposed at positions close to the moving body surface, and a gap between the surface of the rotating body and the first electrode and the second electrode in a moving path. A transport body, a first voltage applying unit for applying an AC voltage to the first electrode so as to supply the developer being transported to the rotating body, and a means for recovering the developer from the rotating body. A second voltage applying unit that applies an AC voltage to the second electrode.

The image forming apparatus of the present invention includes the above supply / recovery device, an image carrier, an electrostatic image forming unit for forming an electrostatic image on the image carrier, and a static on the image carrier by a developer. And a developing device for developing the charge image.
As a result, a first voltage application unit that applies a voltage for supplying the developer and a second voltage application unit that applies a voltage for recovering the developer are separately provided, which is suitable for supplying the developer. Therefore, it is possible to set both the voltage setting and the voltage condition suitable for the developer recovery.

Thereby, even if it is a case where supply and collection | recovery of a developer are implemented simultaneously, highly efficient developer supply and collection | recovery are implemented.
The first electrode is disposed upstream of the developer transport body in the moving direction, the second electrode is disposed downstream, and the first voltage application unit is a voltage obtained by superimposing an alternating current voltage on a direct current voltage. A voltage whose average value is the same as the charging polarity of the developer is applied to the first electrode, and the second voltage application unit is a voltage obtained by superimposing an AC voltage on a DC voltage, and the average value It is preferable to apply a voltage having a polarity different from the charging polarity of the developer to the second electrode.

As a result, the first voltage application unit and the second voltage application unit output the voltage within the conditions suitable for the supply of the developer and the recovery of the developer, respectively, so that the supply and recovery of the developer are performed simultaneously. Even in this case, highly efficient developer supply and recovery are performed.
The first voltage application unit and the second voltage application unit may be set so that the frequencies of the voltages output from each other substantially coincide with each other and the phase difference is substantially zero.

According to this, since the first voltage application unit and the second voltage application unit are set so that the phase difference between the output voltages is substantially zero, the first electrode connected to each of the first voltage application unit and the second voltage application unit Even when the potential difference between the second electrodes is small and the distance between the first electrode and the second electrode is short, it is easy to ensure the insulation distance.
The rotating body is a developing roller, the developer conveying body is an endless belt, the belt is in contact with the developing roller, and rotates in a direction in which the relative speed between the contact surfaces increases. It may be moved.

According to this, the first electrode is located upstream in the belt rotation direction when viewed from the supply and recovery device side, and is located downstream in the rotation direction when viewed from the developing roller side, and the second electrode is provided in the supply and recovery device. When viewed from the side, it is downstream in the belt rotation direction and from the development roller side, it is positioned upstream in the rotation direction.
That is, the supply / recovery path is set so that the recovered developer is not supplied immediately or the supplied developer is not recovered immediately, thereby improving the supply and recovery efficiency of the developer.

In addition, the rotating body is a photosensitive drum, the developer transport body is an endless belt, and the belt is in contact with or close to the photoconductive drum, and the surfaces that are in contact with or close to each other are relative to each other. It may be rotated in the direction in which the speed increases.
According to this, the first electrode is located upstream in the belt rotation direction when viewed from the supply and recovery device side, and is located downstream in the rotation direction from the photosensitive drum side, and the second electrode is provided in the supply direction. When viewed from the collection device side, it is located downstream in the belt rotation direction, and from the photosensitive drum side, it is located upstream in the rotation direction.

That is, the supply / recovery path is set so that the collected developer is not developed immediately or the developed developer is not collected immediately, so that the supply and recovery efficiency of the developer can be improved.
In the belt, it is preferable that a foamed elastic layer is formed on the conductor layer.
According to this, even when the belt is in contact with the rotating body, the belt is composed of a flexible foamed elastic layer, so that the rotating body can be avoided from being brazed.

In addition, the first electrode and the second electrode have a configuration in which a substantially cylindrical electrode is divided into two with a single plane passing through the central axis as a boundary surface, and the boundary surface is an insulating support. One of the two boundary portions that are covered with a member and located on the circumferential surface of the cylinder may be close to the rotating body.
According to this, the electrode area can be increased.

1. Embodiment <Configuration>
Hereinafter, the supply and recovery apparatus in the present embodiment will be described.
FIG. 1 is a schematic diagram of an image forming apparatus using a supply / recovery device that simultaneously supplies and recovers a developer to / from a rotating body according to an embodiment of the present invention.

The image forming apparatus 10 is an image output apparatus that employs a so-called electrophotographic system in which toner (as an example of a developer) is electrostatically attached to a drum and transferred to an output material.
In the image forming apparatus 10, a developing roller 16 (as an example of a rotating body or a supply / recovery device) is disposed in the vicinity of the opening in a casing 11 having an opening and containing toner. A supply roller 13 (as an example of a supply / recovery device) is disposed so as to be in contact with the agitator, and an agitator 12 is disposed in the vicinity of the supply roller 13 to block a gap between the outer edge of the opening and the developing roller 16. As described above, the regulation blade 20 and the charge removal member 22 are extended from the wall surface of the casing 11.

  Further, a photosensitive drum 19 (as an example of a rotating body) is disposed outside the casing 11 so as to be close to the developing roller 16, and the proximity occurs on the outer periphery of the photosensitive drum 19. The exposure unit 23 and the charging roller 24 are arranged on the outer periphery of the photosensitive drum 19 in order as going back to the upstream side in the rotation direction of the photosensitive drum 19 with respect to the position where the photosensitive drum 19 is a reference. The transfer roller 27 and the charge removal roller 25 are in contact with the outer periphery of the photosensitive drum 19.

The tangent line between the transfer roller 27 and the photosensitive drum 19 is on the transfer paper transport path, and a pair of transport rollers 26 are disposed on the upstream side in the transfer paper transport path direction with respect to the tangent line. A pair of fixing rollers 28 are disposed on the downstream side in the transfer paper conveyance path direction.
In addition, two electrodes are embedded in the developing roller 16 and the supply roller 13, respectively.

The two electrodes existing in the supply roller are connected to a voltage application unit 14 and a voltage application unit 15 for applying a voltage, respectively.
Similarly, the two electrodes present in the developing roller 16 are connected to a voltage applying unit 17 and a voltage applying unit 18 that apply a voltage, respectively.
These members described above constitute the image forming apparatus 10.

Note that the toner filled in the casing 11 in the present embodiment has a triboelectric charging property that is easily negatively charged by friction.
Hereinafter, each member will be described in detail.
The agitator 12 is a plate-like member, and has a function of rotating the toner contained in the casing 11 and moving the toner to the vicinity of the supply roller 13 by rotating.

Further, the agitated toner is negatively charged by friction as described above.
As shown in FIG. 2, the supply roller 13 has a rotating member 111 provided around the outer periphery of the shaft member 110, and a supply electrode 113 (as an example of a first electrode) and a (first electrode) are provided on the outer periphery of the rotating member 111. A substantially crescent-shaped support member 112 made of an insulating material in which a collecting electrode 114 is embedded (as an example of two electrodes) is disposed, and a developer conveying member is formed on a contoured portion of the support member 112 and the rotating member 111. An annular belt 115 (as an example) is provided around.

The relative positions of the shaft member 110 and the support member 112 are fixed, and the rotating member 111 rotates counterclockwise in FIG. 1 about the shaft member 110, whereby the belt 115 follows the contour. Rotate.
The support member 112 is made of a material that is non-conductive and excellent in wear resistance, and examples thereof include polyacetal and ceramic.

The belt 115 is a conductive seamless belt having a thickness of 50 μm in which ketjen black is dispersed in a polysulfone resin film.
In addition, the belt 115 may form a foamed elastic body made of a silicon foam or urethane foam having a thickness of 2 to 3 mm on a polyester resin film, and the material of these films may be PET, PTFE, PS, PI, etc. may be substituted.

In addition, carbon and other ion conductive materials may be added to these foams.
The belt 115 is in contact with a belt 125 (described later) disposed on the developing roller 16 in the vicinity of the substantially center of the support member 112 in the contour.
The contact position and the boundary position between the supply electrode 113 and the recovery electrode 114 are substantially coincident with each other.

The rotation direction of the belt 115 is a direction in which the belts 115 are opposed to each other at a portion where the belt 115 is in contact with each other, that is, a direction in which the relative speed between the contact surfaces increases.
The supply electrode 113 and the recovery electrode 114 have a strip shape or a column shape, and have a longitudinal direction substantially parallel to the central axis of the shaft member 110.
Since the supply roller 13 is positioned below the casing 11, it receives the toner powder pressure due to gravity, so that the toner can be adhered onto the belt 115.

The supply electrode 113 positioned on the upstream side in the rotation direction of the belt 115 is applied with an AC voltage, and the average value of the applied voltage is on the negative polarity side. Therefore, the belt 115 transported to the vicinity of the supply electrode 113. The negative polarity toner adhering to the toner is separated from the belt 115 due to the reaction force by the electric field, and adheres to the belt 125 described later.
On the other hand, the recovery electrode 114 located on the downstream side in the rotation direction of the belt 115 is applied with an AC voltage, and the average value of the applied voltage is on the positive polarity side. Since the toner of the nature is attracted to the belt 115 by being attracted by the electric fields of different polarities, the toner can be collected well from the developing roller 16.

  The developing roller 16 has the same configuration as that of the supply roller 13 and is larger than the supply roller 13 in terms of size, and the details thereof are shown in FIG. 3 as the outer periphery of the conductive shaft member 120. A conductive rotation member 121 is provided around the rotation member 121, and a supply electrode 123 (as an example of a first electrode) and a recovery electrode 124 (as an example of a second electrode) are embedded on the outer periphery of the rotation member 121. A substantially crescent-shaped support member 122 made of an insulating material is disposed, and an annular belt 125 is provided around the contour portion of the support member 122 and the rotating member 121. The shaft member 120 is grounded. Yes.

The relative positions of the shaft member 120 and the support member 122 are fixed, and the rotation member 121 rotates counterclockwise in FIG. 1 around the shaft member 120, whereby the belt 125 follows the contour. Rotate.
The belt 125 is a conductive seamless belt having a thickness of 50 μm in which ketjen black is dispersed in a polysulfone resin film, and the material can be replaced with the same content as the belt 115.

The belt 125 and the photosensitive drum 19 are close to each other in the vicinity of the center of the support member 122 in the contour.
The adjacent position and the boundary position between the supply electrode 123 and the recovery electrode 124 are substantially coincident with each other.
The rotation direction of the belt 125 is a direction in which the relative speed between the surfaces close to the photosensitive drum 19 increases.

The supply electrode 123 and the recovery electrode 124 have a strip shape or a column shape, and have a longitudinal direction substantially parallel to the central axis of the shaft member 120.
The supply electrode 123 located on the upstream side in the rotation direction of the belt 125 is applied with an AC voltage, and the average value of the applied voltage is on the negative polarity side. Therefore, the belt 125 carried in the vicinity of the supply electrode 123. The negative toner adhering to the toner is developed by being attracted to the electrostatic latent image on the photosensitive drum 19 by receiving a reaction force due to the electric field and flying away from the belt 125.

On the other hand, the recovery electrode 124 located downstream in the rotation direction of the belt 125 is applied with an AC voltage, and the average value of the applied voltage is on the positive polarity side, and therefore exists on the surface of the photosensitive drum 19. The negative-polarity toner flies by being attracted by an electric field and is attracted to the belt 125.
At this time, the flying toner reciprocates in the gap between the photosensitive drum 19 and the developing roller 16 due to the influence of the AC component of the voltage, and also collides with the surface of the photosensitive drum 19 and adheres to the surface of the photosensitive drum 19. Since the toner that has been removed is peeled off, the toner is satisfactorily collected from the photosensitive drum 19.

The photosensitive drum 19 is formed by applying an alumite treatment to the surface of an aluminum substrate having an outer diameter of 30 mm, and subsequently forming UCL (Under Coat Layer), CGL (Carrier Generation Layer), and CTL (Carrier Transport Layer) on the surface. It becomes.
UCL is a 0.5 μm thick film body in which metal oxide (titanium oxide) is dispersed in polyamide resin.

CGL is a 0.3 μm thick film formed by applying a solution in which titanyl phthalocyanine is dispersed in a polypropylene resin.
CTL is a film body having a thickness of 25 μm formed by applying a coating solution in which a diamino compound as a hole transport agent and a hindered amine as an antioxidant are dissolved in a polycarbonate resin.

Note that the materials and film thicknesses of UCL, CGL, and CTL are not limited to those described above, and alternatives to other materials having equivalent functions or other film thicknesses may be employed.
The charging roller 24 is in contact with the surface of the photosensitive drum 19, and a predetermined charging voltage is applied by a power supply unit (not shown), and the surface of the photosensitive drum 19 is charged to a negative potential.

The exposure unit 23 is a laser output device, and the exposure unit 23 forms an electrostatic latent image on the surface of the photosensitive drum 19 charged to a negative potential.
The neutralizing roller 25 is in contact with the surface of the photosensitive drum 19, and the surface is made of a conductive material that is biased to the same polarity side of the charging series as compared with the toner, and remains on the surface of the photosensitive drum 19. It has a function of erasing the existing potential over the entire surface to make it a reference potential.

The conveying roller 26 has an elastic layer formed on the surface of a shaft member serving as a base material, and a polyurethane foam is used as a material constituting the elastic layer from the viewpoint of flexibility, cost, and the like.
The transfer roller 27 has a conductive elastic layer formed on the outer periphery of the cored bar, is in contact with the surface of the photosensitive drum 19, and is fed from a power supply unit (not shown) to the positive electrode so as to attract negative toner. Charging voltage is applied.

The pair of fixing rollers 28 includes a heating roller having a built-in heater therein and a roller pressed against the roller. The toner image is carried on the transfer paper surface by passing between the pair of fixing rollers. Is established.
The voltage application unit 14 and the voltage application unit 15 have a function of independently applying a voltage to the supply electrode 113 and the recovery electrode 114 disposed in the supply roller 13, respectively.

FIG. 4 is a diagram illustrating an example of each voltage application pattern of the voltage application unit 14 and the voltage application unit 15.
The voltage application unit 14 is a voltage obtained by superimposing an AC voltage on a DC voltage, and a voltage whose average value attracts toner, typically a voltage having a polarity opposite to the toner charging polarity (here, positive polarity). May be applied to the downstream electrode.

More specifically, in the case of a negatively chargeable toner as in this example, the peak-to-peak voltage value is 800 (v) with a DC voltage in the range of 50 (v) to 500 (v) with reference to the potential of the developing roller. ) To 2000 (v), a voltage superimposed with an alternating voltage may be applied.
When the belt 115 is a laminate of a conductor layer and a foamed elastic layer, the DC voltage is V _dc (v), the peak-to-peak voltage of the AC voltage superimposed on this is V _pp (v), the belt and the developing roller Assuming that the distance between the conductive layer and the developing roller at the opposite portion of the toner is t μm, the voltage applying unit 14 has a relationship of 0.35 <(V _pp / 2 + V _dc ) / t <0.50 with respect to the potential of the developing roller. You may apply the voltage which satisfy | fills to a downstream electrode.

The voltage application unit 15 is also a voltage obtained by superimposing an AC voltage on a DC voltage, and an average value thereof is a voltage that keeps the toner away, typically the same polarity as the toner charging polarity (here, negative polarity). A voltage may be applied to the upstream electrode.
Specifically, a voltage with a DC voltage of about −50 (v) to −500 (v) and an AC voltage peak-to-peak voltage of about 800 (v) to 2000 (v) is applied based on the potential of the developing roller. do it.

In principle, the voltage application unit 14 and the voltage application unit 15 apply a voltage independently. However, when the frequency of the AC component of the applied voltage is the same, the voltage application unit 14 and the voltage application unit 15 may output in synchronization as follows.
That is, as shown in FIG. 4, the phase difference between the voltages output from the voltage application unit 14 and the voltage application unit 15 is set to be zero.

By doing so, the potential difference between the supply electrode 113 and the recovery electrode 114 is minimized, and a sufficient insulation distance can be secured even when the supply electrode 113 and the recovery electrode 114 are arranged close to each other.
Note that the vibration voltage in the waveform 401 and the waveform 402 may not be a rectangular wave but may be a sine wave or a triangular wave.

Regarding the voltage application unit 17 and the voltage application unit 18, the toner movement is determined by the potential relationship between the photosensitive drum and the developing roller, but basically, according to the voltage application unit 14 and the voltage application unit 15, respectively. What is necessary is just to apply a voltage. That is, the voltage application unit 17 is a voltage obtained by superimposing an AC power interruption on a DC voltage, and the average value is a voltage that attracts toner, and the voltage application unit 18 is a voltage obtained by superimposing the AC voltage on a DC voltage. Each voltage is applied such that the average value keeps the toner away. In particular, the voltage application unit 17 is a voltage obtained by superimposing an alternating current voltage on a direct current voltage. The direct current voltage is V _dc (v), and the peak-to-peak voltage of the alternating current voltage superimposed thereon is V _pp (v). Apply a voltage of 3.5 <(V _pp / 2 + V _dc ) / d <5.0 to the downstream electrode, where d μm is the distance between the conductive layer of the belt and the photosensitive drum in the area facing the body drum. Good.

The regulating blade 20 is made of a plate-like elastic body made of metal, rubber, and a composite thereof, one end is fixed to the casing 11, the other end is a free end, and the free end side is connected to the developing roller 16. It is in contact.
The regulating blade 20 is above the developing roller 16 and has a function of regulating the toner layer thickness to a predetermined thickness and increasing the charge amount of the toner by friction with the toner.

Further, the charge eliminating member 22 is formed by coating the surface of the metal plate with a material that is higher in the same polarity side than the toner in the charging series, and reduces the charge amount of the toner by rubbing against the toner adhering to the belt 125. And has a function of facilitating peeling by weakening the electrostatic adhesive force.
2. Evaluation Test An image forming apparatus equipped with the following four types of test products was prepared, and an evaluation test for the recovery capability was performed for each of them.

In both the product of the example and the comparative example, the supply roller is in the direction in which the relative speed between the two is increased at the facing portion of the developing roller (counter direction), and the developing roller is at the portion facing the photosensitive drum. It was rotated in the direction of increasing relative speed (counter direction).
<Specifications of test product>
The configuration of each test product is the same except for the following differences.

Here, the supply roller without an electrode is the above-described conventional supply roller, and refers to the configuration of the supply roller 513 shown in FIG. 7. The supply roller with an electrode is shown in FIG. 2 in the embodiment. This is the configuration of the supply roller 13.
Further, in the present embodiment, the developing roller having an electrode refers to the configuration of the developing roller 16 shown in FIG. 3, and the developing roller having no electrode is the above-described conventional developing roller. The structure which excluded the support member 112, the supply electrode 113, and the collection | recovery electrode 114 from said structure.
<About others>
All of the test products were manufactured based on a color laser printer (manufactured by Konica Minolta Holdings, Inc .: magicolor2300DL), and the configuration other than the above is the same as the configuration of the printer.

  However, this color laser printer is provided with a cleaning blade that contacts the surface of the photosensitive drum and removes residual toner remaining on the surface of the photosensitive drum after toner transfer. In Example Product 2 and Comparative Product 2, the cleaning blade is removed so that the effect of collecting residual toner can be easily confirmed. Further, in the example product 1 and the comparative example product 1, in order to evaluate the unevenness on the developing roller, the static eliminating member is removed while leaving the cleaning blade.

In other words, in this test, the test product is driven under conditions that are severer than normal use conditions.
In addition, whether or not the transfer voltage is supplied to the intermediate transfer belt back roller is the intermediate transfer belt system in which the above-mentioned color laser printer is used, and the intermediate transfer belt interposed between the photosensitive drum and the transfer paper and the back surface thereof. There is a back roller disposed, and by eliminating the supply of the transfer voltage to the roller on the back surface, transfer of toner to the intermediate transfer belt is suppressed, and residual toner is more easily generated.
1) Content of supply roller improvement effect confirmation test Example product 1 and comparative product 1 are used as test products, and for example product 1, a plurality of voltage waveforms of the collection electrode 114 arranged on the supply roller are as follows. After setting the pattern and forming a 48mm square black pattern in a horizontal row on the first half of A4 size paper, operate it with a print pattern that forms a halftone image to the end of the paper, and determine the degree of occurrence of each image memory confirmed.

The toner is cyan, which is the color laser printer toner, and the voltage application condition to the upstream electrode is that the value of V _dc is −300 (v), and the superimposed AC voltage is the peak-to-peak voltage. It was set to be a rectangular wave with a V _pp value of 1200 (v) and a frequency of 2 (kHz). The belt 115 is a conductive seamless belt provided with a foamed elastic layer having a thickness of 3 (mm), and is in contact with the developing roller so that the pressing amount of the foamed elastic layer is 1 (mm). I let you.
(Evaluation results of supply roller improvement test)

Here, V _pp (v) and V _dc (v) are the peak value of the voltage applied to the collection electrode 114 disposed on the supply roller 13 and the voltage value of the DC component.
In the halftone dot image, a black pattern in the first half that can be confirmed as an image memory is indicated as x, and a black pattern that cannot be confirmed is indicated as ◯.
According to this, the image memory was confirmed in the comparative example product 1 employing the conventional configuration, whereas in the example product 1, V at the voltage applied to the recovery electrode 114 disposed on the supply roller 13. Experiments were conducted by changing the combinations of the values of _pp (v) and V _dc (v) as shown in Table 2, and it was found that no image memory was generated.

In Example Product 1, when the development state of the photosensitive drum was visually confirmed, the toner supply state was good in all voltage patterns of Example Product 2, and no problem was found.
Further, in the comparative example product 1 as well, when the development state of the photosensitive drum was visually confirmed, the toner supply state was good in all the voltage patterns of the example product 2, and no problem was recognized.
2) Contents of development roller improvement effect confirmation test Example product 2 and comparative example product 2 were used as test products, and for example product 2, the waveform of the voltage of the recovery electrode 124 disposed on the development roller 16 is as follows. Multiple patterns were set, and the operation was performed with a print pattern that printed three lines of character patterns in a horizontal row on the first half of A4 (T) size paper, and the occurrence of each image memory was checked.

In the evaluation, when the character pattern developed on the photosensitive drum rotates once and passes through the developing device again, the operation of the printer is stopped, and the character pattern on the photosensitive member is visually confirmed to determine the degree of occurrence of residual toner. evaluated.
The toner is cyan, which is the color laser printer toner, and the voltage application condition to the upstream electrode is that the value of V _dc is ₊₃₀₀ (v). A rectangular wave having a _pp value of 1200 (v) and a frequency of 2 (kHz) was set. In addition, a developing roller having a conductive seamless belt disposed on the outermost surface was used, and the developing roller was disposed so that the distance between the conductive seamless belt and the photosensitive drum was 150 (μm).

Here, V _pp and V _dc are the peak value of the voltage applied to the collection electrode 124 disposed in the developing roller 16 and the voltage value of the DC component.
Rank 3 is the case where no residual toner is generated, rank 1 is the case where the occurrence of residual toner can be clearly confirmed, and rank 2 is the middle.
According to this, in the comparative product 2 adopting the conventional configuration, residual toner is clearly generated, whereas in the practical product 2, the residual toner is applied to the collecting electrode 124 disposed on the developing roller 16. Experiments were conducted by changing the combinations of the V _pp and V _dc values as shown in Table 3, and it was found that no image memory was generated.

In Example Product 2, when the development state of the photosensitive drum was visually confirmed, the toner supply state was good in all voltage patterns of Example Product 2, and no problem was found.
Further, in the comparative example product 2 as well, when the development state of the photosensitive drum was visually confirmed, the toner supply state was good in all the voltage patterns of the example product 2, and no problem was recognized.

As described above, the supply electrode for supplying the toner to the rotating body and the recovery electrode for collecting the remaining toner from the rotating body in the present embodiment are disposed in the supply roller and the developing roller. By applying individual voltage waveforms to the electrodes, the residual toner can be recovered efficiently, and the voltage conditions suitable for supplying the toner are determined independently of the residual toner recovery conditions. Therefore, highly efficient toner supply and recovery can be performed simultaneously.
(Modification)
In the present embodiment, in the developing roller and the supply roller in which the supply electrode and the recovery electrode are disposed, these electrodes are disposed outside the rotating member. However, the present invention is not limited to such a configuration. For example, as shown in FIG. 5, the supply electrode 213 and the recovery electrode 214 are embedded in the shaft member 210, and the rotating member 211 having a thin dielectric property is provided around the outer periphery of the shaft member 210. Alternatively, the supply roller 206 having an elastic dielectric layer 215 such as urethane formed on the surface of the shaft member 210 may be used.

By doing so, it can be formed by simply coating the surface of the rotating member 211 with a material such as urethane without disposing a belt-like belt as a separate member. Space saving is achieved.
Further, in the supply roller 206 shown in FIG. 5, the supply electrode 213 and the recovery electrode 214 are partly cut out of the cylinder, like the supply electrode 113, the recovery electrode 114, the supply electrode 123, and the recovery electrode 124 in this embodiment. However, the shape of the electrode is not limited to such a shape. For example, as shown in FIG. 6, most of the upper portion of the portion corresponding to the shaft member 210 in FIG. 5 is a semicircular supply electrode. The lower part of the portion corresponding to the shaft member 210 may be occupied by the semicircular collection electrode 314.

In this case, the shaft member 310 is constituted by the supply electrode 313, the recovery electrode 314, and the plate-like insulating member positioned between the two. Similar to the supply roller 206, a rotating member 211 is provided around the outer periphery of the shaft member 310.
In the present embodiment, the belt 115 and the belt 125 (described later) arranged on the developing roller 16 are in contact with the belt 115 and the developing roller 16 in the vicinity of the center of the support member 112 in the contour. However, the present invention is not limited to this. It may be close.

In this embodiment, an example is shown in which two electrodes are provided in the supply roller and the developing roller. However, the number of electrodes is not limited to two, and the number of electrodes may be three or more. Good.
For example, a form including a recovery electrode and a plurality of development electrodes, a form including a development electrode and a plurality of recovery electrodes, or a form including a plurality of development electrodes and a plurality of recovery electrodes may be employed.
When providing the development electrode, a larger voltage may be applied to the upstream electrode. When a plurality of recovery electrodes are provided, a large voltage may be applied to the downstream electrode.

In the present embodiment, the supply and recovery device is applied to both the supply roller 13 and the developing roller 16, but may be applied to either one.
In this case, the supply roller 13 or the developing roller 16 not applied is a conventional supply roller (hereinafter referred to as “conventional supply roller”) or a conventional development roller (hereinafter referred to as “conventional development roller”) manufactured by a known technique. The structure of that) may be adopted.

For example, as a conventional developing roller, a base layer made of a conductive material having elasticity is formed on the surface of a cylindrical core made of a metal such as aluminum, and a urethane resin or a polyamide resin is formed on the base layer. A surface layer made of a nitrogen-containing resin film is formed.
Moreover, as a structure of the conventional supply roller, the foaming elastic body which consists of urethane foam is formed in the cylindrical core body surface which consists of electroconductive materials, such as a metal.

  More specifically, the foam has a thickness of about 3 mm and rotates independently of the developing roller while being pushed into the developing roller by about 1 mm, with a rotation speed ratio of about 1.5. It is a set supply roller.

  The supply and recovery apparatus according to the present invention is applicable to an electrophotographic image forming apparatus that develops a developer by electrostatically adhering it to a drum.

1 is a schematic diagram of an image forming apparatus using a supply and recovery device in the present embodiment. It is a schematic sectional drawing of the supply roller in this embodiment. It is a schematic sectional drawing of the developing roller in this embodiment. It is a figure which shows an example of the voltage application pattern of the voltage application part in this embodiment, and a voltage application part. It is a figure explaining the modification regarding the shape of a supply electrode and a collection | recovery electrode in this embodiment. It is a figure explaining the modification regarding the shape of a supply electrode and a collection | recovery electrode in this embodiment. It is a schematic diagram of a conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Casing 12 Agitator 13 Supply roller 14 Voltage application part 15 Voltage application part 16 Developing roller 17 Voltage application part 18 Voltage application part 19 Photosensitive drum 20 Regulation blade 22 Static elimination member 23 Exposure part 24 Charging roller 25 Static elimination roller 26 Conveying roller 27 Transfer roller 28 Fixing roller 110 Shaft member 111 Rotating member 112 Support member 113 Supply electrode 114 Recovery electrode 115 Belt 120 Shaft member 121 Rotating member 122 Support member 123 Supply electrode 124 Recovery electrode 125 Belt 210 Shaft member 211 Rotating member 213 Supply Electrode 214 Recovery electrode 215 Elastic dielectric layer 310 Shaft member 313 Supply electrode 314 Recovery electrode 401 Waveform 402 Waveform 510 Image forming apparatus 511 Casing 512 Agitator 513 Supply row 516 developing roller 517 an alternating voltage power supply 519 photosensitive drum 601 electrode 602 electrode

Claims (8)

A supply and recovery device for supplying a chargeable developer to a rotating body that performs development processing or subsequent processing in cooperation, and recovering the developer from the rotating body;
A first electrode and a second electrode arranged at positions close to the surface of the rotating body;
A developer transport body that includes a gap between the surface of the rotating body and the first electrode and the second electrode in a movement path, and transports the developer;
A first voltage applying unit that applies an AC voltage to the first electrode so as to supply the developer being conveyed to the rotating body;
A supply / recovery device comprising: a second voltage applying unit that applies an AC voltage to the second electrode so as to recover the developer from the rotating body. The first electrode is upstream of the developer transport body in the moving direction.
The second electrodes are respectively disposed downstream,
The first voltage application unit is a voltage obtained by superimposing an alternating current voltage on a direct current voltage, and an average value of the first voltage application unit applies a voltage having the same polarity as the charging polarity of the developer to the first electrode,
The second voltage applying unit applies a voltage, which is a voltage obtained by superimposing an AC voltage on a DC voltage, and an average value of which is different from a charging polarity of the developer, to the second electrode. Item 2. The supply and recovery device according to Item 1.   The first voltage application unit and the second voltage application unit are set so that frequencies of voltages output from the first voltage application unit and the second voltage application unit are substantially the same and a phase difference is substantially zero. Item 3. The supply and recovery device according to Item 2. The rotating body is a developing roller,
The developer carrier is an endless belt,
3. The supply and recovery apparatus according to claim 2, wherein the belt is in contact with the developing roller and rotates in a direction in which a relative speed between the contact surfaces increases. The rotating body is a photosensitive drum,
The developer carrier is an endless belt,
3. The supply / recovery device according to claim 2, wherein the belt is in contact with or close to the photosensitive drum and rotates in a direction in which a relative speed between the surfaces in contact with or close to each other increases.   The supply / recovery device according to claim 1, wherein the belt has a foamed elastic layer formed on a conductive layer. The first electrode and the second electrode have a configuration in which a substantially cylindrical electrode is divided into two with a plane that passes through the central axis as a boundary surface.
The boundary surface is covered with an insulating support member;
The supply and recovery device according to claim 1, wherein one of the two boundary portions located on the circumferential surface of the cylinder is close to the rotating body. 8. The supply / recovery device according to claim 1, an image carrier, an electrostatic image forming means for forming an electrostatic image on the image carrier, and a developer on the image carrier. An image forming apparatus comprising: a developing device for developing an electrostatic charge image.

Images