JP2010156907A - Development device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To gain a development device which prevents the inside of the device body from dirty with a developer without uselessly spending the developer, and also gain an image forming device. <P>SOLUTION: The circuit of a power source device 98 is closed, and a bias voltage is applied between a layer thickness-controlling roll 87 and a development roll 86 to generate a potential difference. A negatively chargeable developer is used, and the potential of the layer thickness-controlling roll 87 is higher than that of the development roll 86. Then, an electric field is generated, and a developer T is drawn toward the layer thickness-controlling roll 87 side. Consequently, the developer T hardly comes out from the housing 80 of a development device 44, and the amount of the developer T on the development roller 86 decreases (processing for decreasing the amount of the developer). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus.

  The surface of the photosensitive drum provided in the image forming apparatus is charged by a charging device and then irradiated by laser light from an exposure device. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum. Further, the electrostatic latent image is developed by a developing device to form a toner image on the surface of the photosensitive drum, and the toner image is transferred to a sheet material by a transfer device.

  In such an image forming apparatus, as means for preventing contamination by toner, for example, in Patent Document 1, the end of a magnetic member facing the developer carrier is directed upstream in the direction of movement of the developer carrier. An extending portion that extends is provided to prevent the developer chain formed at the end of the magnetic member from being exposed to the outside of the developing device and spilling off the developer.

  Further, in Patent Document 2, when the developer concentration stored in the developing device falls below a specified amount, the developer is forcibly attached to the electrostatic carrier and discharged from the developing device. The developer that has been adhered and transported is collected by a cleaning means for cleaning the residual toner on the electrostatic carrier, so that a constant amount of developer with a predetermined concentration is always accommodated in the developing device. I am doing so.

JP 2005-189249 A JP-A-8-95383

  An object of the present invention is to obtain a developing device and an image forming apparatus that suppress contamination of the image forming apparatus due to the developer without wasteful consumption of the developer.

  According to the first aspect of the present invention, in the developing device, the developer holding member that holds the developer and develops the electrostatic latent image on the image holding member, and the developer before the operation of the image forming apparatus is stopped. Developer reducing means for reducing the amount of developer held by the holding body.

  According to a second aspect of the present invention, in the developing device according to the first aspect, a layer thickness regulating member that regulates a layer thickness of the developer on the surface of the developer holding member is provided, and the developer reducing unit includes: A potential difference generating means for providing a potential difference between the layer thickness regulating member and the developer holder;

  According to a third aspect of the present invention, in the developing device according to the second aspect, when the operation of the image forming apparatus is stopped and then restarted, the portion of the developer holder that faces the layer thickness regulating member While moving to a position facing the image carrier, at least an image forming operation is not performed.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: an exposure unit that emits a light beam; an image holder that is exposed by the exposure unit to form an electrostatic latent image on a surface; and a developer. A developer holder for developing the electrostatic latent image on the image carrier, a transfer means for transferring the developer image on the image carrier to a transfer member, and before stopping the operation of the image forming apparatus, Developer reducing means for reducing the amount of developer held by the developer holder.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, a layer thickness regulating member for regulating a layer thickness of the developer on the surface of the developer holding member is provided, and the developer reducing means is And a potential difference generating means for providing a potential difference between the layer thickness regulating member and the developer holding member.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, when the operation of the image forming apparatus is stopped and then restarted, the developer holding member faces the layer thickness regulating member. While the portion moves to a position facing the image carrier, at least an image forming operation is not performed.

  According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, the operation stop of the image forming apparatus is a power saving state of the image forming apparatus.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the fourth to sixth aspects, whether or not the developer reducing means is operated by an operation display unit through which a user inputs an operation mode. Can be selected.

  According to the first and fourth aspects of the present invention, it is possible to suppress contamination of the image forming apparatus due to the developer without wasteful consumption of the developer.

  According to the second and fifth aspects of the present invention, it is difficult for the developer to come out from the developing device, and the amount of developer in the developer holding member can be reduced.

  In the third and sixth aspects of the invention, a developer image is formed on the image carrier by the developer carrier in a state where the layer thickness of the developer is regulated.

  According to the seventh aspect of the present invention, the developer amount of the developer holder is reduced before the image forming apparatus enters the power saving state.

  According to the eighth aspect of the present invention, it is possible to spontaneously reduce the developer amount of the developer holder when the image forming apparatus is moved.

1 is a schematic overall configuration diagram of an image forming apparatus according to an exemplary embodiment. 1 is a schematic configuration diagram of a developing device according to the present embodiment. (A)-(C) is explanatory drawing explaining the effect | action of the developing device which concerns on this Embodiment, and has shown the process in which the developer amount on a developing roller reduces. 6 shows a timing chart of the power supply device and the like when the developer reduction processing of the developing device according to the present embodiment is performed. 6 is a graph showing a relationship between a voltage of a power supply device that performs developer reduction processing of the developing device according to the present embodiment and an amount of developer on a developing roller. FIG. 10 is an explanatory diagram for explaining the operation of the developing device according to the present embodiment when the image forming apparatus main body is operated again after the operation of the image forming apparatus main body is stopped.

An image forming apparatus 10 according to an embodiment of the present invention will be described.
<Outline of image forming apparatus>
FIG. 1 shows an image forming apparatus 10 according to the present embodiment as an example. First, the configuration and operation of the image forming apparatus 10 will be described.
(Configuration of image forming apparatus)
The image forming apparatus 10 includes an image forming apparatus main body 12, and a photoconductor unit 14, an optical writing device 16, and a transfer unit 18 are disposed in the image forming apparatus main body 12. In addition, a recording paper discharge unit 20 is formed in the upper part of the image forming apparatus main body 12, and a recording paper feeding part 22 is arranged in the lower part of the image forming apparatus main body 12.

  The recording paper feeding unit 22 has a paper feeding cassette 24 in which a large number of recording papers (recording media) are stacked and accommodated, and the paper feeding cassette 24 is detachably provided to the image forming apparatus main body 12. It has been. A feeding roll 26 is disposed at an upper end on one end side of the paper feed cassette 24, and a separation roll 28 is provided to face the feeding roll 26.

  The recording paper at the top of the paper feed cassette 24 can be taken out by the delivery roll 26, and the recording paper can be turned and conveyed by the cooperation of the delivery roll 26 and the separation roll 28. An alignment roll 30 is disposed on the downstream side of the recording paper conveyance direction (hereinafter simply referred to as “downstream side”). The conveyed recording paper is temporarily stopped by the alignment roll 30 and set in advance. It can be conveyed to the transfer unit 18 side at the timing.

  On the other hand, an opening / closing cover 31 is provided on the front surface of the image forming apparatus main body 12, and the opening / closing cover 31 is located with respect to the image forming apparatus main body 12 around a pivot 64 provided at the lower front of the image forming apparatus main body 12. And can be rotated (openable and closable).

  The image forming apparatus main body 12 houses a photoconductor unit 14 to be described later. A shaft (not shown) is provided below the lowermost photoconductor unit 14 to rotate the transfer unit 18. I support it as possible. When the opening / closing cover 31 is opened / closed, the transfer unit 18 is moved to contact / separate from the photoreceptor unit 14, and the opening / closing cover 31 is closed, the transfer unit 18 faces the photoreceptor unit 14, and The opening / closing cover 31 urges and positions the photosensitive member unit 14.

  Here, as shown in FIGS. 1 and 2, in the transfer unit 18, a conveying belt 36 is wound around a driving roll 32 and a driven roll 34 provided in the vertical direction, and recording paper is fed by the conveying belt 36. It can be transported. Further, a transfer roll 35 for transferring a toner image on the surface of each photoreceptor 40 (image holding body), which will be described later, onto a recording sheet on the conveyance belt 36 is predetermined for each color between the drive roll 32 and the driven roll 34. It is arrange | positioned at intervals.

  Since the transfer roll 35 is configured to come into pressure contact with each photosensitive member 40 with a predetermined pressure between the transfer belts 36 when the opening / closing cover 31 is closed, the transfer roll 35 follows the running of the transfer belts 36. Rotate.

  By the way, a charging roll 38 is disposed opposite to the driving roll 32 with the conveying belt 36 interposed therebetween, and a predetermined voltage is applied to the charging roll 38 from a bias power source (not shown). . For this reason, when the charging roll 38 comes into contact with the conveyance belt 36, the conveyance belt 36 is charged, a potential difference is provided between the conveyance belt 36 and the recording paper, and the recording paper is attracted to the conveyance belt 36 and conveyed. .

  On the other hand, the photosensitive unit 14 holds the transfer belt 36 or an image to be transferred onto the recording paper conveyed by the conveyance belt 36. Here, yellow (Y), magenta (M), cyan (C), black Four photoconductors 40 of (K) are supported rotatably.

  Around each photoconductor 40, a charging roll 42 for charging the photoconductor 40, and a developing device 44 (described later) for developing the latent image written on each photoconductor 40 with a two-component developer composed of toner and a magnetic carrier. ), And a neutralizing device 46 for neutralizing the photoconductor 40 after the transfer, and a cleaning device 48 for removing the developer remaining on the surface of the photoconductor 40 after the transfer.

  The photoconductor unit 14 includes the four photoconductors 40, the charging roll 42, the developing device 44, the charge eliminating device 46, and the cleaning device 48, and is detachable from the image forming apparatus main body 12 together with the transfer unit 18. It has become.

  Further, a toner box 50 containing yellow, magenta, cyan and black toners supplied to the developing device 44 is connected to the back side of the photoreceptor unit 14. In each toner box 50, a toner supply unit 52 and a toner collection unit 54 are integrated, and the toner supply unit 52 is connected to the developing device 44 to supply toner of each color to the developing device 44. The toner collecting unit 54 is connected to the cleaning device 48 and collects toner of each color.

  Further, an optical writing device 16 is arranged at a position corresponding to each photoconductor 40 on the back side of the photoconductor unit 14 and is composed of a laser exposure device, and each photoconductor 40 is irradiated with a laser to be sensitized. A latent image is formed on the surface of the body 40.

  Further, a fixing device 56 is disposed on the downstream side of the photosensitive unit 14, and an unfixed toner image on the recording paper is heated and pressurized to be fixed on the recording paper. A discharge roll 58 is disposed on the downstream side of the fixing device 56, and the recording paper on which the toner image is fixed can be discharged onto the recording paper discharge unit 20.

  By the way, the developing device 44 is disposed so as to face the photoreceptor 40 as shown in FIG. The developing device 44 includes a housing 80, and an opening 82 that opens toward the photoreceptor 40 is formed. A developing roll 86 as a developer holding body is provided in the housing 80 so as to be partially exposed from the opening 82, and the developing roll 86 is disposed to face the photoconductor 40. ing.

  Further, a developer storage chamber 96 is provided in the back of the casing 80 (opposite the opening 82), and stirring transport members 88 and 89 for stirring and transporting the developer are provided in the developer storage chamber 96. Is arranged. Although not shown, the stirring and conveying members 88 and 89 are spirally wound with a spiral blade at a predetermined pitch around the rotation axis. The supplied toner is conveyed while being stirred together with the magnetic carrier in the developer accommodating chamber 96 and supplied to the developing roll 86.

  The developing roll 86 includes a thin cylindrical sleeve 86A rotatably supported by a conductive bearing (not shown), and a fixed columnar magnet roll 86B. A gear (not shown) is fixed to the end portion of the developing roll 86, and the rotational force from the motor is transmitted to the gear so that the developing roll 86 is rotated via the gear.

  A predetermined developing bias voltage is applied to the sleeve 80A of the developing roll 86 from a power supply device (not shown), whereby a developing electric field is formed between the developing roll 80 and the photoreceptor 40. Is done.

A cylindrical conductive layer thickness regulating roll (layer thickness regulating member) 87 is fixed on the surface of the sleeve 86 </ b> A of the developing roll 86 with a predetermined gap, and the developer on the developing roll 86 is fixed. Regulate the amount of The developing roll 86 adsorbs the magnetic carrier contained in the developer with a magnetic force to form a magnetic brush of the developer on the surface. The layer thickness regulating roll 87 regulates the amount of the developer on the developing roll 86. The The electrostatic latent image formed on the photoreceptor 40 is visualized as a toner image by the developer on the developing roll 86.
(Operation of image forming apparatus)
Next, the operation of the image forming apparatus 10 having the above configuration will be described.

  First, the recording paper at the top of the paper feed cassette 24 shown in FIG. 1 is taken out by the delivery roll 26, and the recording paper is rolled by the cooperation of the delivery roll 26 and the separation roll 28, and the alignment roll 30. Thus, the sheet is conveyed to the transfer unit 18 side at a predetermined timing.

  On the other hand, in the photoreceptor unit 14, first, the surface of the photoreceptor 40 is charged by the charging roll 42. Then, a laser is irradiated from the optical writing device 16 to scan the surface of the photoconductor 40, and a latent image based on the image data is formed on the surface of the photoconductor 40.

  The developer agitated and conveyed by the agitating and conveying auger 88 is adsorbed to the sleeve 86A of the developing roller 86 of the developing device 44 shown in FIG. 2 by the magnetic force of the magnet roll 86B. Further, the developer adsorbed on the sleeve 86A passes through the gap between the layer thickness regulating roll 87 and the developing roll 86, so that the surplus portion is scraped off and the developer layer thickness becomes uniform.

  Further, a developing bias voltage determined in advance for each color is applied to the developing roll 86, and when the electrostatic latent image on the photoreceptor 40 passes through the developing roll 86, a developer is applied to the electrostatic latent image by the developing electric field. The toner is adhered, and the electrostatic latent image is visualized as a toner image.

  This toner image is printed on the recording paper conveyed by the conveying belt 36 by a transfer roll 35 in the order of yellow (Y), magenta (M), cyan (C), and black (K) in the order of a full color toner image (unfixed image). ) Is transferred to the fixing device 56 by the conveyor belt 36.

The recording paper conveyed to the fixing device 56 is discharged onto the recording paper discharge unit 20 by a discharge roll 58 after an unfixed toner image is heated and pressurized to be fixed on the recording paper. After the transfer of the toner image onto the recording paper, the surface of the photoconductor 40 is cleaned by the cleaning device 48 to prepare for the next image forming process.
(Main part of this embodiment)
By the way, as described above, the layer thickness regulating roll 87 shown in FIG. 2 is formed of a conductive member, and the layer thickness regulating roll is interposed via the conductive bearing portion that rotatably supports the layer thickness regulating roll 87. A bias voltage can be applied to the surface 87. Then, as shown in FIG. 3B, a potential difference can be generated by closing the circuit of the power supply device 98 and applying a bias voltage between the layer thickness regulating roll 87 and the developing roll 86 ( Potential difference generating means).

  Here, in the present embodiment, a negatively chargeable developer is used, and the potential of the layer thickness regulating roll 87 is made higher than the potential of the developer roll 86 (in the case where a positively chargeable developer is used). The potential of the developing roll 86 is made higher than the potential of the layer thickness regulating roll 87).

  As a result, an electric field is generated and the developer T is drawn toward the layer thickness regulating roll 87 side. For this reason, it becomes difficult for the developer T to come out of the housing 80 of the developing device 44, and the amount of the developer T on the developing roll 86 is reduced as shown in the order of FIGS. 3A and 3B. (Developer reduction processing). Here, in order to make it easy to understand the decrease in the developer T, the developer layer is expressed as being thick. Then, as shown in FIG. 3C, when the amount of the developer T on the developing roll 86 decreases, the circuit of the power supply device 98 is opened.

  Here, the developer reduction process is performed before the operation of the image forming apparatus main body 12 is stopped. The operation stop of the image forming apparatus main body 12 means a state in which the image forming apparatus main body 12 is not operated. Here, the main power of the image forming apparatus main body 12 is turned off, the image forming apparatus main body 12 is set in a power saving state, etc. In addition to the case where the image forming apparatus main body 12 is not operated for a long time, the case after the end of the image forming operation is included.

  As described above, the developer reduction processing may be automatically performed by a control device (not shown) of the image forming apparatus main body 12, or an operation panel (operation display unit) provided in the image forming apparatus main body 12. This operation may be selected by 90 (see FIG. 1). In this case, for example, when the operation panel 90 is provided with a developer reduction processing mode and the image forming apparatus main body 12 is moved, the developer reduction processing is performed spontaneously by selecting this mode. To be

  As shown in FIG. 3A, when the image forming apparatus body 12 of the image forming apparatus 10 is transported or reinstalled in a state where the developer T necessary for image formation exists on the developing roll 86, There is a case where the developer T on the developing roll 86 is scattered by the vibration received by the image forming apparatus main body 12 and the inside of the image forming apparatus main body 12 is contaminated.

  For this reason, before the image forming apparatus main body 12 stops operating, the amount of the developer T on the developing roll 86 is reduced, so that the scattering of the developer T on the developing roll 86 is suppressed. That is, the developer T is not wasted, and contamination in the image forming apparatus main body 12 due to vibration received by the image forming apparatus main body 12 is suppressed when the image forming apparatus main body 12 is transported or reinstalled.

  As described above, the developer reduction process is performed before the operation of the image forming apparatus main body 12 is stopped. Specifically, as shown in FIGS. 2 and 4 (FIG. 4 shows the developer reduction process). In this developer reduction process, first, the photoconductor 40 and the charging roll 42 are driven, and the photoconductor 40 is charged by the charging roll 42.

  Here, after the image formation is completed, when the photosensitive member 40 and the charging roll 42 are driven, the photosensitive member 40 and the developing roller 86 are moved from the opposing position P of the photosensitive member 40 and the charging roller 42 along the rotation direction of the photosensitive member 40. No potential is generated on the surface of the photoreceptor 40 until the facing position Q.

  Therefore, the time for driving the photoconductor 40 and the charging roll 42 and the developing roll 86 for the time (t) required to move from the position P facing the charging roll 42 of the photoconductor 40 to the position Q facing the layer thickness regulating roll 87. A difference is provided between the time of driving and. Then, the photosensitive member 40 and the charging roll 42 are driven, and after the elapse of time t, the developing roll 86 is driven, and a voltage is applied between the developing roll 86 and the layer thickness regulating roll 87 to generate a potential difference.

  FIG. 5 shows the relationship between the voltage of the power supply device 98 and the developer amount. Here, the voltage applied between the layer thickness regulating roll 87 and the developing roll 86 is changed between 0 and 1.0 kV, and the result of measuring the amount of the developer remaining on the surface of the developing roll 86 is as follows. It is shown.

  According to this, as the voltage is increased between 1.0 kV, the amount of developer gradually decreases, and about 1/3 of the developer decreases at a voltage of about 0.8 kV. Note that if the potential difference is too large, the leakage current increases and no voltage is applied, so the applied voltage is preferably up to about 1.0 kV.

  By the way, when the image forming apparatus main body 12 is restarted after the operation of the image forming apparatus main body 12 is stopped, as shown in FIG. 6, as shown in FIG. At least the image forming operation is not performed for the time required to move to the facing position S (angle θ).

  By providing a potential difference between the layer thickness regulating roll 87 and the developing roll 86 before the operation of the image forming apparatus main body 12 is stopped, the amount of the developer T on the developing roll 86 is reduced (see FIG. 3C). . Therefore, the development roll 86 in a state where the amount of the developer T is reduced to the development roll 86 having a developer amount necessary for a normal image forming operation (see FIG. 3A) is used as the development time. It takes time for the roll 86 to move from the position R facing the layer thickness regulating roll 87 to the position S facing the photoconductor 40.

  Here, the layer thickness regulating roll 87 is used as the layer thickness regulating member. However, the layer thickness of the developer on the developing roll 86 may be regulated, and therefore the shape is not limited to the roll shape. For example, a plate member may be used. Further, the developer reduction process does not necessarily have to be performed simultaneously for the four colors. For example, only the developing device 44 corresponding to the color that needs to be replaced when the developer is replaced may be subjected to the developer reduction process.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image forming apparatus main body 16 Optical writing apparatus (exposure means)
18 Transfer unit (transfer means)
35 Transfer roll (transfer means)
36 Conveyor belt (transfer means)
40 photoconductor (image carrier)
44 Developing device 86 Developing roll (Developer holder, potential difference generating means, developer reducing means)
87 Layer thickness regulating roll (layer thickness regulating member, potential difference generating means, developer reducing means)
90 Operation panel (operation display section)
98 Power supply (potential difference generating means, developer reducing means)

Claims (8)

A developer holding body that holds the developer and develops the electrostatic latent image on the image holding body;
Developer reduction means for reducing the amount of developer held by the developer holder before the operation of the image forming apparatus is stopped;
A developing device. A layer thickness regulating member for regulating the layer thickness of the developer on the surface of the developer holder is provided;
The developing device according to claim 1, wherein the developer reducing means is a potential difference generating means for providing a potential difference between the layer thickness regulating member and the developer holding member.   When the operation of the image forming apparatus is stopped and then restarted, at least an image forming operation is performed while a portion of the developer holder facing the layer thickness regulating member moves to a position facing the image holder. The developing device according to claim 2, which is not performed. Exposure means for emitting a light beam;
An image carrier that is exposed by the exposure means to form an electrostatic latent image on the surface;
A developer holding body that holds the developer and develops the electrostatic latent image on the image holding body;
Transfer means for transferring a developer image on the image carrier to a transfer member;
Developer reduction means for reducing the amount of developer held by the developer holder before the operation of the image forming apparatus is stopped;
An image forming apparatus. A layer thickness regulating member for regulating the layer thickness of the developer on the surface of the developer holder is provided;
5. The image forming apparatus according to claim 4, wherein the developer reducing means is a potential difference generating means for providing a potential difference between the layer thickness regulating member and the developer holding member.   When the operation of the image forming apparatus is stopped and then restarted, at least an image forming operation is performed while a portion of the developer holder facing the layer thickness regulating member moves to a position facing the image holder. The image forming apparatus according to claim 5, which is not performed.   The image forming apparatus according to claim 4, wherein the operation stop of the image forming apparatus is a power saving state of the image forming apparatus.   The image forming apparatus according to any one of claims 4 to 6, wherein a user can select whether or not to operate the developer reducing means by an operation display unit for inputting an operation mode.

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