JP2009042258A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for maintaining desirable charging characteristic of toner as a whole by selecting and collecting deteriorated toner, in an image forming apparatus using a developing device of a non-contact developing type to which developing bias voltage including an AC component is applied. <P>SOLUTION: The image forming apparatus 1 has a developing roller 21 facing a photoreceptor 11 through a gap and receiving the developing bias voltage including the AC component so as to apply toner to a latent image to develop the latent image, and has an electrode 31 facing the developing roller at a more downstream side in a rotating direction than the position where the photoreceptor 11 faces the surface of the developing roller 21 via a gap, a toner collecting part 32 arranged apart from the surface of the developing roller 21 at a more downstream side in the rotating direction of the developing roller 21 than the electrode 31, and an electrode voltage applying part 42 applying forcibly consumed bias voltage closer to the voltage of a part to be developed than the voltage of a background part on the surface of the photoreceptor 11 after passing through a latent image forming part to the electrode 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus that forms an image by developing a latent image on an image carrier with toner. More specifically, the present invention relates to an image forming apparatus in which an image carrier and a developing roller face each other through a gap, and a developing bias voltage including an AC component is applied to the developing roller to perform development without contact. .

  Some developing devices of the one-component developing system charge a developer by using friction or the like. Then, it is regulated to a predetermined thickness by a regulating plate or the like and is carried on the surface of the developer carrying member. At the time of development, the image carrier is charged to a predetermined potential, and a part of the image carrier is changed in potential by exposure. The exposed portion is an image portion, and the unexposed portion is a background portion. The electrostatic latent image thus formed is then developed by a developing device. At that time, a developing bias voltage which is a superimposed voltage of a DC voltage and an AC voltage is generally applied to the developer carrying member of the developing device.

  In such a developing device, it is known that the toner deteriorates after a long period of use. In particular, when a large number of images with a low image portion ratio are printed, this deterioration is noticeable. This is due to the deterioration of the charging characteristics of the toner due to the fact that the toner is not used while being repeatedly rubbed. Therefore, in order to prevent such deterioration in image quality due to deteriorated toner, an image forming apparatus is disclosed that forcibly consumes a developer in a non-image area when an image with a low printing ratio is formed (for example, Patent Document 1). reference). As a result, the deteriorated toner is discarded and the developer is refreshed.

  However, if toner is forcibly consumed as described above, undegraded toner that is normally charged is also discarded. Further, simply developing a solid image or the like has a problem that development sorting occurs, and deteriorated toner having low developability is rather difficult to collect. On the other hand, Patent Document 2 discloses an image forming apparatus having a developing blade that is a blade-shaped regulating member, and a regulating member voltage applying unit that applies the same DC blade bias as the developing bias to the developing blade. Yes.

In the apparatus of this document, the blade bias applied to the developing blade is shifted to the charging polarity side of the toner during the operation in the forced toner consumption mode. Thus, a toner having a high charge amount is coated on the developing roller side, that is, a lower layer, and a deteriorated toner having a low charge amount is coated on the upper layer by an electric field between the blade and the developing roller. Since the upper layer toner comes into contact with the photosensitive drum first, the deteriorated toner is easily developed.
JP 2001-75438 A JP 2004-170651 A

  However, the image forming apparatus described in Patent Document 2 is a contact development type, and the applied bias is a DC bias. Therefore, it cannot be applied as it is to a device having a non-contact developing type developing device to which a developing bias voltage including an AC component is applied.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, the problem is that, in an image forming apparatus using a non-contact developing type developing device to which a developing bias voltage containing an AC component is applied, the deteriorated toner is selected and collected, whereby the charging characteristics of the entire toner are collected. It is an object of the present invention to provide an image forming apparatus capable of maintaining a good state.

  The image forming apparatus of the present invention, which has been made for the purpose of solving this problem, includes a rotating image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, and a latent image forming on the surface of the image carrier. A developing roller that faces the position downstream of the position where the latent image is formed by the section through a gap and develops the toner by applying toner while rotating, and the developing roller includes an AC component. An image forming apparatus that performs development by applying a bias voltage, an electrode facing the image bearing member on the surface of the developing roller in a rotational direction downstream from the facing position with a gap, and developing from the electrode The floating toner collecting unit disposed at a position downstream of the developing roller surface in the rotational direction of the roller, and the background voltage on the surface of the image carrier after passing through the latent image forming unit on the electrode Is closer to the voltage of the developed part than Those having an electrode voltage applying unit for applying a braking consumption bias voltage.

  In the image forming apparatus of the present invention, a latent image formed on the surface of an image carrier is developed by a developing roller that faces the image carrier via a gap and is applied with a developing bias voltage including an AC component. Is. Here, the present invention includes an electrode and a floating toner recovery unit, and a forced consumption bias voltage is applied to the electrode by the electrode voltage application unit. Accordingly, the toner is forcibly reciprocated between the electrode and the developing roller and is attached to the electrode. Here, the deteriorated toner having deteriorated charging characteristics has a weak adhesion to the electrode and tends to float between the electrode and the developing roller. The floating toner is collected in the floating toner collection unit. Thereby, since the deteriorated toner can be selected and collected, the charging characteristics of the entire toner can be maintained in a good state.

  Furthermore, in the present invention, it is desirable that the electrode faces only the non-development region at the axial end of the developing roller. In this way, even if the forced consumption bias voltage is applied to the electrode, the development process by the developing roller is hardly affected. Therefore, the deteriorated toner can be collected at any time.

  Further, in the present invention, the electrode voltage application unit applies a normal bias voltage closer to the voltage of the background portion than the voltage of the developed portion on the surface of the image carrier after passing through the latent image forming portion during image formation. It is desirable to apply a forced consumption bias voltage during non-image formation. In this way, at the time of image formation, the electrode is set to a voltage close to the background portion of the image carrier, so that the toner hardly adheres. On the other hand, during non-image formation, since the voltage is close to the voltage of the developed part, the normally charged toner is attracted to the electrode. Therefore, the toner is reciprocated between the electrode and the developing roller, and the deteriorated toner can be collected.

  Furthermore, in the present invention, it is desirable that the amplitude of the alternating current component of the developing bias voltage be larger during non-image formation than during image formation. By doing so, the reciprocation of the toner between the electrode and the developing roller becomes more active during non-image formation. Accordingly, the degree to which the deteriorated toner is floated is increased, and the deteriorated toner can be recovered more efficiently.

  Further, in the present invention, it is desirable to shift the DC component of the developing bias voltage to the normal charging characteristic side of the toner during image non-image formation. Even in this case, during the non-image formation, the reciprocation of the toner between the electrode and the developing roller becomes more active. Accordingly, the degree to which the deteriorated toner is floated is increased, and the deteriorated toner can be recovered more efficiently.

  Further, in the present invention, it is desirable that the frequency of the AC component of the developing bias voltage is larger during non-image formation than during image formation. Even in this case, during the non-image formation, the reciprocation of the toner between the electrode and the developing roller becomes more active. Accordingly, the degree to which the deteriorated toner is floated is increased, and the deteriorated toner can be recovered more efficiently.

  Further, in the present invention, it is desirable that the surface of the electrode that faces the developing roller has a concave curved surface shape along the surface of the developing roller. In this way, the gap between the electrode and the developing roller can be set to a substantially uniform interval. Therefore, the entire surface of the electrode that faces the developing roller contributes to the reciprocation of the toner.

  Further, according to the present invention, the second electrode is disposed between the floating toner collecting portion and the developing roller, and the second electrode is applied with a voltage on the normal charging characteristic side of the toner with respect to the voltage of the electrode. It is desirable that In this way, even if the toner charged on the normal charging characteristic side floats from the developing roller side toward the floating toner collecting portion, it is returned to the developing roller side by the second electrode. Therefore, it is possible to prevent the toner that has not deteriorated from being collected.

  According to the image forming apparatus of the present invention, the image forming apparatus uses a non-contact developing type developing device to which a developing bias voltage including an AC component is applied, and the toner is collected by selecting and recovering deteriorated toner. The overall charging characteristics can be kept in a good state.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to an electrophotographic image forming apparatus having a one-component developing type developing device.

  The image forming apparatus 1 according to this embodiment includes a photoconductor 11 and a developing device 12 as shown in FIG. Further, around the photoconductor 11, a charging device 14 for charging the surface of the photoconductor 11 to a predetermined potential, and an exposure device for irradiating the surface of the photoconductor 11 with a laser beam to form a latent image. 15, thereby forming a latent image on the surface of the photoconductor 11. Further, a transfer device 16 for transferring a toner image formed by developing the latent image onto a sheet or the like, and a cleaner 17 for collecting residual toner remaining on the photoconductor 11 after transfer are provided.

  As shown in FIG. 1, the developing device 12 includes a developing roller 21, a supply roller 22, a downstream screw 23, an upstream screw 24, a regulation blade 25, and a static elimination seal 26. Toner is accommodated in a housing 27 for housing these. In this embodiment, negatively charged nonmagnetic one-component toner is used. In this embodiment, the developing roller 21 and the photoconductor 11 are not in contact with each other, and are arranged in parallel with a slight gap. A location where these are close to each other is a development region D.

  At the time of image formation, the photoconductor 11 and the developing roller 21 are rotated as indicated by arrows in FIG. In this embodiment, the electrode 31 is provided at a position downstream of the developing region D in the rotation direction of the developing roller 21. The electrode 31 is a metal plate disposed in parallel to the axial direction of the developing roller 21 with a slight gap between the electrode 31 and the outer surface of the developing roller 21. The electrode 31 is preferably arranged in parallel to the circumscribed surface of the developing roller 21. Further, the gap between the electrode 31 and the developing roller 21 is approximately the same as the gap between the photoconductor 11 and the developing roller 21. The electrode 31 has a length that covers not only the image area but also the non-image areas at both ends in the axial direction of the developing roller 21 (the depth direction in the drawing). Here, the image area refers to a portion facing the developing area of the photoconductor 11.

  Further, a toner collection unit 32 is provided at a position downstream of the electrode 31 with respect to the rotation direction of the developing roller 21 and spaced from the surface of the developing roller 21. The toner collecting unit 32 is for collecting properly the toner that is scattered and floating in the air. For example, as shown in FIG. 2, a fan 33 having a suction port between the static elimination seal 26 and the electrode 31 may be used. If a filter 34 is provided at the outlet of the fan 33, the toner can be collected here. In addition, the broken line arrow in a figure has shown the main flow directions of air.

  Further, in the present embodiment, a developing bias voltage applying unit 41 for applying a developing bias voltage to the developing roller 21 and an electrode voltage applying unit 42 for applying a voltage to the electrode 31 are provided. A control unit 43 that controls the developing bias voltage application unit 41 and the electrode voltage application unit 42 is provided. The development bias voltage application unit 41 is a power source that applies a superimposed voltage of a DC voltage and an AC voltage, and the electrode voltage application unit 42 is a DC power source.

  At the time of image formation, as indicated by arrows in FIG. 1, the photoconductor 11, the supply roller 22, and the developing roller 21 are rotated. Then, toner is supplied to the surface of the developing roller 21 by the supply roller 22. As the developing roller 21 rotates, the supplied toner is regulated by the regulating member 25 and charged. On the other hand, the surface of the photoconductor 11 is uniformly negatively charged by the charging device 14 and is partially exposed by the exposure device 15 to form an electrostatic latent image on the surface. The portion of the photoconductor 11 on which the electrostatic latent image is formed is further rotated and then faces the developing device 12. At this time, a developing bias voltage is applied to the developing roller 21 by a developing bias voltage applying unit 41.

  In the image forming apparatus 1 of the present embodiment, the development bias voltage at the time of image formation uses a rectangular waveform as shown in FIG. For example, the DC component Vdc = −320 V and the AC component peak-to-peak voltage Vpp = 1400 V is a superimposed voltage. Further, for example, the minus side duty is 30% and the frequency is 2 kHz. On the surface of the photoconductor 11 on which the electrostatic latent image is formed, there are an exposed portion (latent image portion) and an unexposed portion (background portion). The voltage of the latent image portion is about 0V as indicated by * 1 in the figure. The background voltage is about -450 V as indicated by * 2 in the figure.

  Thus, the toner carried on the developing roller 21 reciprocates between the developing roller 21 and the photosensitive member 11 across the gap by the developing bias voltage. Among them, the toner having normal charging characteristics is negatively charged, so that it adheres mainly to the portion of the surface of the photoreceptor 11 where the potential is higher. That is, the toner mainly adheres to the latent image portion, and the electrostatic latent image is developed to form a toner image. Therefore, the latent image portion corresponds to the developed portion. The toner image formed in this way is transferred to a sheet or the like by the transfer device 16 and fixed in a subsequent process to form an image.

  At this time, as shown in FIG. 3, the electrode voltage Ve = −450 V is applied to the electrode 31 by the electrode voltage application unit 42. That is, the electrode 31 has substantially the same potential as the potential of the background portion of the photoreceptor 11 (* 2 in the figure). Since the potential of the background portion of the photoconductor 11 and the electrode 31 is on the negative side with respect to Vdc, that is, the central potential of the developing bias voltage, the negatively charged toner hardly adheres. For this reason, the electrode 31 does not have a special action during image formation. The electrode voltage Ve in this state corresponds to a normal bias voltage.

  Here, the image forming apparatus 1 of the present embodiment executes the toner forced consumption mode at an appropriate timing other than the time of image formation. This mode is a mode for selecting and collecting the deteriorated toner, and is executed at a timing when the developing process between the sheets is not performed. In this mode, the relationship between the potentials of each part is set as shown in FIG. In the toner forced consumption mode, the photoconductor 11 is charged but not exposed. That is, the entire surface is the background portion. The potential is substantially the same as the background potential at the time of image formation, and Vpc = −450 V as indicated by * 2 in the figure. In this state, the photosensitive member 11 has no latent image portion, and therefore there is no developed portion.

  On the other hand, in the forced toner consumption mode, the electrode voltage Ve = 0 V is applied to the electrode 31. This is substantially the same voltage as that of the developed portion of the photoreceptor 11 during image formation. That is, if it is assumed that the photosensitive member 11 has a developed portion, the voltage is about 0 V as in the case of image formation, and is indicated by * 1 in the drawing. In this mode, a voltage closer to the development target at the time of image formation is applied to the electrode 31 than the background portion of the photoconductor 11. In other words, the entire surface of the photoreceptor 11 is a background portion, and only the electrode 31 is a developed portion. Therefore, the toner hardly adheres to the photoconductor 11 and mainly adheres to the electrode 31. The electrode voltage Ve at this time corresponds to a forced consumption bias voltage. The developing bias voltage in this mode may be the same as that at the time of image formation.

  When this is done, the toner reciprocates between the electrode 31 and the developing roller 21 by the developing bias voltage. In particular, a toner with good developability has a good reactivity with an electric field, and therefore actively reciprocates during image formation and in the forced toner consumption mode. Then, as shown in FIG. 5, the toner adheres to the electrode 31 having a relatively high potential in the toner forced consumption mode. By the reciprocating motion of the toner having good developability, the toner adhering to the developing roller 21 or the electrode 31 is ejected, and the amount of the reciprocating toner increases in an avalanche manner.

  When the amount of toner that reciprocates in this way increases, toner with poor developability that does not readily reciprocate alone is ejected. However, toners with poor developability are less responsive to an electric field, so that even if they are ejected, they cannot reciprocate and often float due to an air current. Here, the airflow in this portion forms a laminar flow due to the rotation of the developing roller 21. That is, it is the air flow along the rotation direction of the developing roller 21, and here, as shown by the white arrow in FIG. If the developing roller 21 is rotated at a high speed, this laminar flow is also relatively strong.

  Here, in this embodiment, since the toner collecting unit 32 is provided on the downstream side of the electrode 31 (see FIG. 2), the toner drifting on this laminar flow is collected by the toner collecting unit 32. That is, it is sucked up by the fan 33 and attached to the filter 34 and collected. As described above, a lot of toner drifting in a laminar flow has poor developability, and if this toner forced consumption mode is executed, toner with poor developability is selectively collected. Here, since the toner collecting unit 32 is located immediately downstream of the electrode 31 in the rotation direction of the developing roller 21, the toner that has left the vicinity of the electrode 31 due to the laminar flow is collected immediately. Therefore, the toner is prevented from being scattered inside the image forming apparatus and contaminating the inside.

  The toner having good developability continues to vigorously reciprocate as long as an electric field is present, and adheres to the developing roller 21 or the electrode 31 when the influence of the electric field is reduced. Also, in the forced toner consumption mode, the toner reciprocates somewhat between the photoconductor 11 and the developing roller 21, but since the photoconductor 11 is in a non-exposed state, almost no good toner is applied to the photoconductor 11. Does not adhere. The toner with good developability attached to the electrode 31 is returned to the developing roller 21 side by returning the electrode voltage to the developing bias voltage at the time of image formation after the toner forced consumption mode is completed, and is used again. .

  Therefore, in this embodiment, by executing the toner forced consumption mode at an appropriate timing, toner with poor developability is selectively collected, and the development characteristics of the toner can be recovered. The execution timing of this mode may be performed according to the state of image formation, for example, when a predetermined number of prints are performed, or when an image with a low print ratio is developed. Alternatively, it may be always performed during non-image formation. Since even good toner is not discarded as in the case of conventional forced disposal, the amount of good toner that is wasted even if it is performed relatively frequently is negligible.

Next, variations of each setting in the toner forced consumption mode of this embodiment will be described. For example, in the toner forced consumption mode, the electrode voltage Ve is set to Ve = 0 V in the above embodiment, but may be a positive voltage. For example, Ve = 50V may be set as shown in FIG. Since negatively chargeable toner is used in this embodiment, the force that normal chargeable toner receives from the electric field is increased by doing so. Here, if the maximum developing bias voltage is Vm,
Vpc <Ve <Vm
The electrode voltage Ve may be set on the relatively positive side within a range that satisfies the above. Here, Vpc is the potential of the photoconductor 11 when this mode is executed.

  As another method, in the toner forced consumption mode, in addition to the setting of the electrode 31 as described above, a developing bias voltage slightly different from that at the time of image formation may be applied. That is, the reciprocating motion of the toner is more active between the electrode 31 and the developing roller 21 and between the photoconductor 11 and the developing roller 21 than the normal developing bias voltage. In this way, more toner with poor developability is ejected, and more efficient recovery is possible.

  As an example of changing the development bias voltage, in the forced toner consumption mode, the peak-to-peak voltage of the development bias voltage may be larger than that during image formation. For example, as shown in FIG. 7, the development bias voltage in the toner forced consumption mode is set to Vpp = 1800 V, which is larger than that at the time of image formation. Alternatively, Vpp at the time of image formation may be 1600 V, Vpp in the toner forced consumption mode may be 1900 V, or the like. In this way, toner with poor developability can be collected more efficiently.

  Alternatively, in the toner forced consumption mode, a developing bias voltage may be offset to the negative side from the time of image formation using a Zener diode or the like. For example, as shown in FIG. 8, the DC component Vdc of the developing bias voltage is shifted to the negative side by about 200 V from the time of image formation. Even in this case, the reciprocating motion of the toner becomes active, and the toner having poor developability can be collected more efficiently.

  Alternatively, the frequency of the developing bias voltage may be increased in the toner forced consumption mode. For example, as shown in FIG. 9, a bias voltage having a frequency of 3 kHz is applied. Even in this case, the reciprocating motion of the toner becomes active, and the toner having poor developability can be collected more efficiently.

  Alternatively, in the toner forced consumption mode, the rotation speed of the developing roller 21 may be increased from the time of image formation. For example, the peripheral speed due to the rotation of the developing roller 21 during image formation is 228 mm / sec, and the peripheral speed due to the rotation of the developing roller 21 in the toner forced consumption mode is 324 mm / sec. In this way, the centrifugal force applied to the toner adhering to the surface of the developing roller 21 increases, and more toner flies. Further, since the laminar flow generated around the developing roller 21 becomes strong, the toner with poor developability that is ejected easily gets on the laminar flow. Note that the same effect can be obtained because the laminar flow increases by increasing the rotational speed of the photoconductor 11.

  Alternatively, a curved electrode 51 may be used instead of the plate electrode 31. For example, as shown in FIG. 10, the curved surface is concentric with the outer peripheral surface of the developing roller 21. In this way, the distance between the electrode 51 and the developing roller 21 is substantially constant, so that the entire electrode 51 is effectively used. Therefore, toner with poor developability can be collected more efficiently. Further, in this case, the roller member and the photosensitive member 11 can be positioned by providing a roller member at the end of the developing roller 21 in the axial direction. Therefore, positioning of the electrode 51 is easy.

  Alternatively, as shown in FIG. 11, the electrodes 52 may be provided so as to face only non-image areas at both ends in the axial direction on the developing roller 21. In this way, since the influence on the image is small, it can be executed even when non-image formation is not performed. Therefore, in such a case, the toner forced consumption mode may always be executed, not only during non-image formation. Since the toner is agitated in the axial direction by the downstream screw 23 and the upstream screw 24 inside the developing device 12, the charging characteristics of the entire toner are gradually improved even when only the axial end portion is recovered. . Even in such a case, it is desirable to change the voltage of the electrode to the negative side occasionally in order to return the adhered toner in a good state to the developing roller.

  Alternatively, the electrode 31 may be provided very close to the developing roller 21. That is, the gap between them is made smaller than the gap between the photoconductor 11 and the developing roller 21. For example, when the distance between the photoconductor 11 and the developing roller 21 is 135 μm, the distance between the electrode 31 and the developing roller 21 is about 100 μm. By doing so, the flying distance of the toner during this period is shortened, so that more toner flies between the electrode 31 and the developing roller 21 than between the photosensitive member 11 and the developing roller 21. Therefore, the reciprocating motion of the toner becomes active, and the toner having poor developability can be collected more efficiently.

  Alternatively, another electrode 53 may be provided at the suction port of the toner recovery unit 32 on the downstream side of the electrode 31 to apply a negative voltage. For example, as shown in FIG. 12, the electrode 53 is arranged and a DC voltage of −100 V is applied. In this way, it is possible to attract to the electrode 53 toner having a negative polarity (positive polarity) among toners having poor developability. Further, as shown in this figure, the toner collection unit 32 may be used as a fan 33 without a filter, and the sucked toner may be discarded outside the apparatus.

  As described above in detail, according to the image forming apparatus 1 of the present embodiment, since the electrode 31 and the recovery member 32 are included, the toner 31 is placed between the electrode 31 and the developing roller 21 when the forced toner consumption mode is executed. The toner can be reciprocated actively, and the deteriorated toner can be ejected. Furthermore, since the ejected toner is recovered by the recovery member 32, the toner having poor developability is selectively recovered, and the development characteristics of the toner can be recovered. Therefore, even in the image forming apparatus 1 using the non-contact developing type developing device 12 to which a developing bias voltage including an alternating current component is applied, the deteriorated toner is selected and collected, whereby the charging characteristics of the entire toner can be improved. It can be kept in a good state.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the internal configuration of the developing device 12 is an example, and is not limited thereto. The arrangement of each screw, the presence / absence of the static elimination sheet 26, and the like can be changed. In this embodiment, the negatively chargeable toner is used. However, the present invention can be similarly applied to an apparatus using a positively chargeable toner. In this case, all bias voltages may be reversed in polarity. The present invention can also be applied to electrophotographic image forming apparatuses such as color or monochrome copying machines, printers, and fax machines.

1 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment. FIG. 3 is a schematic configuration diagram illustrating a toner recovery unit. FIG. 6 is a voltage waveform diagram showing a developing bias voltage during image formation. FIG. 6 is a waveform diagram illustrating a relationship between a developing bias voltage and an electrode voltage in a toner forced consumption mode. FIG. 6 is an explanatory diagram illustrating the behavior of toner in a toner forced consumption mode. FIG. 6 is a waveform diagram illustrating a relationship between a developing bias voltage and an electrode voltage in a toner forced consumption mode. FIG. 6 is a waveform diagram illustrating a relationship between a developing bias voltage and an electrode voltage in a toner forced consumption mode. FIG. 6 is a waveform diagram illustrating a relationship between a developing bias voltage and an electrode voltage in a toner forced consumption mode. FIG. 6 is a waveform diagram illustrating a relationship between a developing bias voltage and an electrode voltage in a toner forced consumption mode. It is explanatory drawing which shows a curved-surface-shaped electrode. It is explanatory drawing which shows another example of arrangement | positioning of an electrode. FIG. 6 is a schematic configuration diagram illustrating another example of a toner recovery unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11 Photoconductor 12 Developing apparatus 14 Charging apparatus 15 Exposure apparatus 21 Developing roller 31, 51 Electrode 32 Toner collection | recovery part 41 Developing bias voltage application part 42 Electrode voltage application part 53 Electrode

Claims (8)

A rotating image carrier, a latent image forming part for forming a latent image on the surface of the image carrier, and a position downstream of the position where the latent image is formed by the latent image forming part on the surface of the image carrier in the rotational direction. An image forming apparatus that has a developing roller that faces a position on the side through a gap and that develops by applying toner while rotating, and applies a developing bias voltage including an AC component to the developing roller to perform development In
An electrode facing through a gap at a position downstream in the rotational direction from the facing position with the image carrier on the surface of the developing roller;
A floating toner collecting portion disposed at a position downstream of the electrode in the rotation direction of the developing roller and spaced from the surface of the developing roller;
An electrode voltage applying unit that applies a forced consumption bias voltage closer to the voltage of the developed portion than the voltage of the background portion on the surface of the image carrier after passing through the latent image forming portion to the electrode; An image forming apparatus. The image forming apparatus according to claim 1, wherein the electrode includes:
An image forming apparatus, wherein the image forming apparatus faces only a non-development region at an axial end portion of the developing roller. The image forming apparatus according to claim 1, wherein the electrode voltage application unit is connected to the electrode.
At the time of image formation, a normal bias voltage closer to the voltage of the background portion than the voltage of the developed portion on the surface of the image carrier after passing through the latent image forming portion is applied,
An image forming apparatus, wherein the forced consumption bias voltage is applied during non-image formation. The image forming apparatus according to claim 3,
An image forming apparatus, wherein an amplitude of an alternating current component of the developing bias voltage is made larger during non-image formation than during image formation. The image forming apparatus according to claim 3,
An image forming apparatus that shifts the direct current component of the developing bias voltage toward the normal charging characteristic side of the toner at the time of non-image formation. The image forming apparatus according to claim 3,
An image forming apparatus characterized in that during non-image formation, the frequency of the AC component of the developing bias voltage is made larger than during image formation. In the image forming apparatus according to any one of claims 1 to 6,
The image forming apparatus according to claim 1, wherein a surface of the electrode facing the developing roller has a concave curved surface shape along a surface of the developing roller. In the image forming apparatus according to any one of claims 1 to 7,
A second electrode disposed between the floating toner collecting part and the developing roller;
2. The image forming apparatus according to claim 1, wherein the second electrode is applied with a voltage on the normal charging characteristic side of the toner with respect to the voltage of the electrode.

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