JP4359494B2 - Development method in image forming apparatus - Google Patents

Description

  The present invention relates to a developing method used in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and particularly uses a two-component developer composed of a carrier and a toner. The present invention relates to a developing method for developing an electrostatic latent image by holding only toner on a developing roller.

  Development methods in image forming apparatuses such as copiers, printers, facsimiles, and composite machines using electrophotography are two-component development methods using toner and carrier, one-component development methods that do not use carriers, and carriers. There is a so-called hybrid development system in which a two-component developer that charges toner is used and only the charged toner is held on the developing roller to develop the electrostatic latent image.

  The two-component development method is excellent in the chargeability of the toner by the carrier and can have a long life, but has a drawback that the developing device is greatly complicated and the image quality changes depending on the durability of the carrier. In addition, the one-component development system has a compact developing device and excellent dot reproducibility, but the durability of the developing roller and the replenishing roller is generally low, and the cost of consumables increases because the developing device is periodically replaced. Become.

  Taking advantage of the features of both development methods, a two-component developer composed of toner and carrier is used, and only the toner is held on the developing roller for developing the electrostatic latent image formed on the photoreceptor. In particular, this hybrid development method is used as a development method capable of forming a high-speed image, and for a one-drum color superposition method for sequentially forming a plurality of color images on a photoreceptor. As a tandem developing device, a plurality of electrophotographic process members are arranged side by side, a color image is formed in synchronization with the feeding of the transfer member, and color is superimposed on the transfer member.

  In particular, in the case of the tandem method, since a plurality of electrophotographic process members are arranged side by side, if the developing roller and the supply roller (magnetic roller) are arranged laterally with respect to the photosensitive member, the width of the electrophotographic process member itself is increased. This hinders downsizing. Therefore, it is preferable to arrange the developing roller and magnetic roller constituting the electrophotographic process member above the photosensitive member so that the developing device is a vertical type so that the depth of the image forming apparatus can be reduced.

However, in general, when a two-component developer is used, when sufficient stirring is not performed, or when the charging ability of the developer is reduced due to a high temperature and high humidity environment, a desired toner charge amount Cannot be obtained, and toner scattering and carrier pulling may be caused.
That is, when the toner charge amount decreases, the developer carrier and the toner suction force change, and the amount of developer passing through the regulating blade increases. Then, it becomes difficult for the developer to return to the developer tank provided on the supply roller (magnetic roller) from between the supply roller (magnetic roller) and the developing device wall surface, and between the supply roller (magnetic roller) and the development roller. In combination with the low toner charge amount, the toner layer thickness on the developing roller increases and the carrier is carried by the developing roller, leaking from the opening of the portion facing the photoreceptor in the developing device. Toner scattering and carrier pulling will occur.

Such a shortage in the charge amount of the toner, for example, even though the toner and the carrier constituting the two-component developer are deteriorated and the charging ability is lowered, and it takes time to reach a normal charge amount. When image formation is performed without sufficient stirring time, that is, immediately after turning on the power of the image forming apparatus or when the power is on but the developing device is not used for a long time. Cheap.
Such a problem is a technical problem to be particularly considered in the case of a vertical developing device having a compact stirring mechanism.

  In order to deal with such problems caused by stopping the developing device for a certain period of time, for example, Patent Documents 1 to 3 disclose a method for keeping the toner concentration in the developing tank constant. During the initial check at the start-up of the forming device, the toner conveying member and the developing roller in the developing device are idled (aged) for a time corresponding to the temperature so that the fluidity of the toner is equivalent to the normal use state. When the developing device is stopped for a certain period of time, the developer stirring means is periodically operated, or the toner density when the developing device is stopped is stored and the developing device is operated. It is shown that the density control is performed at the stored density.

JP 2000-47487 A Japanese Patent Laid-Open No. 8-248763 Japanese Patent Publication No. 6-48410

  However, all of the methods disclosed in Patent Documents 1 to 3 are methods for keeping the toner concentration in the developing tank constant, and are not for increasing the charge amount of the toner as described above. That is, in order to obtain a predetermined charge amount when the developer is deteriorated even if idling (aging) is performed as in the methods disclosed in Patent Documents 1 to 3, It is necessary to stir for a longer time than when there is no deterioration, and if the time is not sufficient, development will be performed with insufficient charge amount, causing leakage as described above, toner scattering and carrier pulling. Will occur.

  For this reason, if it is set to always perform idling (aging) for the required time when the developer deteriorates, it takes too much time and this causes an increase in startup time, and the developer is not deteriorated. If excessive idling (aging) is performed, the toner is charged up and developability is impaired.

In view of the above circumstances, the present invention uses a two-component developer that charges a toner using a carrier, holds only the charged toner on the developing roller, and flies to the electrostatic latent image to develop the latent image. An object of the present invention is to provide a developing method capable of coping with insufficient charging of toner associated with deterioration of a developer in an image forming apparatus having such a developing apparatus.
In particular, it is an object to provide a developing method that can cope with insufficient charging even when the developing device itself is arranged vertically, which is employed in a tandem system for forming a color image.

In order to solve the above problems, the present invention
A magnetic brush is formed around a supply roller having a magnetic pole member inside by a two-component developer composed of a toner and a carrier that are stirred and charged by a stirring member, and the magnetic brush is rubbed against the developing roller. using a bias that is applied between the roller only the toner is transferred to the developing roller, the developing method in an image forming apparatus that develops the latent image on the latent image bearing member with toner which has moved said transfer,
At the time of image formation, a developing bias in which an alternating current component is superimposed on a direct current component is applied to the developing roller, and a conveying bias including a direct current component is applied to the supply roller, and a toner is transferred onto the developing roller by a potential difference between the supplying roller and the developing roller. Only form a thin layer,
On the other hand, before the image forming, and less than at or image forming eliminate DC potential difference between the bias between the transfer bias of the supply roller and the developing bias of the developing roller, the conveying bias of the developing bias and the supply roller of the developing roller An aging time for operating the agitating member, the supply roller, and the developing roller by applying an alternating electric field or an alternating electric field to at least one is provided.

  The aging time is provided immediately after the power is turned on or after image formation is not performed for a predetermined time.

In addition, when the DC potential difference between the supply roller conveyance bias and the development roller development bias during the aging is made smaller than that during image formation , the toner moves from the supply roller to the development roller. It is characterized by a range not to be used.

  In the image forming apparatus in which the two-component developer is stirred and charged by the stirring member, and the toner image is transferred to the developing roller by the magnetic brush formed around the supply roller to develop the latent image in a non-contact manner. Before the formation, the DC potential difference between the supply roller and the development roller is eliminated or reduced, and the stirring member, the supply roller, and the development roller are operated by applying an AC electric field or an alternating electric field to at least one of the development roller and the supply roller. By providing the aging time, it is possible to shorten the time until the toner movement in the magnetic brush becomes active and the required charge amount is reached due to the alternating electric field or the alternating electric field. Therefore, even if the charging ability of the carrier decreases due to the deterioration of the developer, the required amount of toner can be charged in a short time, and the charging time when the image forming apparatus is started up or when image formation is not performed for a long time is possible. The developing method in the image forming apparatus can reduce the preparation time and can prevent toner scattering and carrier pulling due to developer leakage.

  By providing the aging time immediately after the power is turned on or after the image formation is not performed for a predetermined time, when the developer is deteriorated, the image formation is performed immediately after the power is turned on, or for a predetermined time. Thus, it is possible to provide a developing method in an image forming apparatus that can reliably set the toner charge amount to a necessary value after the occurrence of the toner leakage and prevent toner scattering and carrier pulling due to leakage.

Further, when the direct current potential difference between the supply roller and the developing roller at the time of aging is made smaller than that at the time of image formation , the potential difference is set to a range in which the toner does not move from the supply roller to the developing roller. Charging can be increased.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a schematic diagram of an embodiment of a developing apparatus for performing a developing method in an image forming apparatus according to the present invention, and FIG. 2 shows a change in toner charge amount of aging by a conventional method and aging by a developing method of the present invention. FIG. 3 is a table showing numerical values of the relationship between the toner charge amount and developer leakage, and FIG. 4 is a schematic diagram of an embodiment of an image forming apparatus having a developing device according to the present invention.

  In the figure, reference numeral 1 denotes a photosensitive member (latent image carrier) drum, 2 denotes an exposure device using an LED, 3 denotes a charger for charging the photosensitive drum 1, 4 denotes a developing roller, and 5 denotes a magnet assembly inside. A supply roller (magnetic roller) consisting of a sleeve that rotates with a magnetic brush 10 made of carrier and toner on the surface, 7 is a regulation that regulates the thickness of the magnetic brush 10 on the supply roller 5 The blades 8a and 8b mix the toner supplied from the toner container 9 with the carrier and stir and stir and charge the mixer, 11 is the recording paper, 12 is the recording paper, 12 is the developing device, and 15 is the AC to the developing roller 4. An AC power source for applying a bias, 16 is a DC power source for applying a DC bias, 17 is a DC power source for applying a DC bias to the supply roller 5, and 20 in FIG. Forming apparatus, 53 paper feed cassette, endless belts 54, 58 transfer device, 59 denotes a fixing device. In the following description, a case where the present invention is applied to a tandem type color image forming apparatus will be described as an example, and a case where the photosensitive drum 1 is used as a photosensitive member will be described as an example. Needless to say, the present invention may be applied to an apparatus or other types of color image forming apparatuses, and the photosensitive member may be a belt-shaped photosensitive belt.

  Among these, as a material of the photoreceptor (electrostatic latent image carrier) 1, an amorphous silicon (a-Si) photoreceptor, an organic photoreceptor (OPC), or the like can be used. Positively charged organic photoconductors (positive OPCs) generate less ozone and have stable charging. In particular, positively charged organic photoconductors with a single-layer structure can be used even when the film thickness changes due to long-term use. Since there is little change in characteristics and the image quality is stable, it is suitable for a long-life system. When the positively charged organic photoconductor is used in a long-life system, the film thickness is preferably set to about 20 μm to 40 μm. In the case of 20 μm or less, black spots are noticeably generated due to dielectric breakdown when the film thickness is reduced to about 10 μm. On the other hand, when the thickness is 40 μm or more, the sensitivity is lowered, which causes a reduction in image density.

  The exposure apparatus 2 can use a semiconductor laser or an LED. When a positively charged organic photoconductor is used, a wavelength around 770 nm is effective, and when an amorphous silicon photoconductor is used, a wavelength around 685 nm is effective. Hereinafter, in the present invention, a case where a positively charged organic photoreceptor is used as the photoreceptor drum 1 and an LED is used as the light source of the exposure apparatus 2 will be described as an example.

  The outermost surface of the developing roller 4 is composed of a sleeve made of uniform conductive aluminum, SUS, conductive resin coating, and the like, and is arranged with a space of about 250 μm with respect to the photosensitive drum 1. No electrodes are used. Connected to the shaft portion is a DC bias power supply 16 of 100 V, for example, preferably an AC bias power supply 15 having a rectangular wave Vpp of 1.6 kV, a frequency of 2.7 kHz and a duty ratio of 50% or less, for example 27%. Then, a bias in which the direct current and the alternating current are superposed acts between the rotating developing roller 4, the photosensitive drum 1, and the supply roller 5. By applying a bias in which a direct current and an alternating current are applied to the conductive sleeve in this way, the toner recoverability with respect to the supply roller 5 is improved as well as good developability with respect to the latent image on the photoreceptor 1, and continuous. Stability during printing is improved.

  The supply roller 5 is supplied with a DC bias of, for example, 400 V from a DC bias power source 17 and has a magnet disposed therein as a developer transport body. Then, the two-component developer composed of the toner and the carrier charged by stirring is magnetically held, the magnetic brush 10 is generated, and the thickness of the magnetic brush 10 is regulated by the regulating blade 7 while developing with the supply roller 5. A thin layer of only toner is formed on the developing roller 4 by the potential difference with the roller 4.

The saturated toner amount of the toner thin layer on the developing roller 4 is basically determined by the potential difference between the DC bias power supplies 16 and 17, and as described above, the DC bias power supply 16 is set to 100V and the DC bias power supply 17 is set to 400V. When the developing roller 4 rotates ^twice, a toner layer of 1.0 mg / cm ² is obtained. This toner layer may also contribute to factors such as the toner charge amount and the magnetic pole strength of the supply roller 5. Yes, if the potential of the DC bias power supply 17 is changed according to the image data, an image having a uniform density can be obtained.

If the toner layer is too thin at 0.5 mg / cm ² or less, the follow-up of the density in the case of continuous high-density images is reduced, and image unevenness is likely to occur, and the toner layer exceeds 1.5 mg / cm ^2. If it is too thick, the development ghost is noticeable and the toner scattering tends to be noticeable. The toner layer thickness also depends on the charge amount of the toner. When the charge amount is as low as 5 μC / g or less, the toner layer thickness increases and scattering increases. On the other hand, when the toner charge amount is 20 μC / g or more, the thickness of the toner layer is reduced, the charge is increased, the toner is difficult to fly to the photosensitive drum 1, and the developability is lowered.

  It is important to define the particle size distribution of the toner in order to avoid selective developability. Generally, the particle size distribution of the toner is measured by a Coulter counter and expressed by the ratio of the volume distribution average particle size to the number distribution average particle size. In order to prevent selective development, it is important to reduce the ratio. When the distribution is wide, toner having a relatively small particle diameter is deposited on the developing roller 4 in continuous printing, and developability is lowered.

As the carrier, magnetite carrier, Mn-based ferrite, Mn-Mg-based ferrite or the like can be used. These carriers may be used as they are, but they may be used after being surface-treated within a range not increasing an appropriate resistance value. Is possible. In the present invention, as an example, a ferrite carrier having a volume resistivity of 10 ⁸ Ωcm ³ and a saturation magnetization of 40 emu / g and an average particle size of 35 μm was used. When the average particle size exceeds 50 μm, the stress of the carrier increases and the toner density cannot be increased, and the amount of toner supplied to the developing roller 4 decreases.

  In order to stabilize the image density in continuous printing, it is necessary to periodically remove the toner from the developing roller 4 according to the print data and refresh it. This is to collect the toner on the developing roller 4 in the magnetic brush 10 by changing the DC bias 16 and 17 while the AC bias 15 is applied at the end of development. When the toner is peeled off from the developing roller 4 at the end of development, the toner is always refreshed. However, it takes time to form a stable toner layer again, and a sufficient printing speed cannot be achieved. In order to maintain a good printing speed, it is only necessary to adjust the sheet interval and adjust the time for putting toner on and off the developing roller 4 in a certain period. In order to supply sufficient toner to the latent image on the photosensitive drum 1 without increasing the paper interval, the peripheral speed of the developing roller 4 is set to 1.5 times or more with respect to the photosensitive drum 1 for a short time. The toner can be taken in and out. Further, when the supply roller 5 is set to a speed of 1 to 2 times that of the developing roller 4, toner replacement is promoted. At this time, the rotation direction of the supply roller 5 is preferably opposite to the developing roller 4.

  The developing device 12 of the present invention is a vertical developing device because the positional relationship between the supply roller 5 and the nearest mixer 8a is the upper portion of the mixer 8a. Under the mixer 8a and the mixer 8b, the photosensitive member 1 and the exposure device are exposed. Since the apparatus 2 can be placed so as to be arranged, the depth of the image forming apparatus 20 can be reduced by arranging the four developing devices 12 as shown in FIG. Further, the toner container 9 can be freely dropped from the toner replenishing port via a motor by disposing it at the upper part of the developing device 12, and at the time of replacement, it can be removed from the top and mounted again from above. Similarly to the toner container 9, it can be removed at the top, and it is easy to remove even when the developing device 12 is abnormal, and the structure is simplified.

  First, the operation of an embodiment of the image forming apparatus 20 to which the developing method by the developing device 12 configured as described above is applied will be described with reference to the schematic diagram of FIG. In the image forming apparatus 20, an endless belt 54 is disposed so as to be able to convey the recording paper from the paper feed cassette 53 toward the fixing device 59, and a black belt is disposed above the belt 54 that conveys the recording paper. Developing device 12A, yellow developing device 12B, cyan developing device 12C, and magenta developing device 12D. These developing devices 12 (A, B, C, D) are respectively developed in close proximity to the supply roller 5 (A, B, C, D) and the supply roller 5 (A, B, C, D). Rollers 4 (A, B, C, D) are arranged, and the photosensitive drum 1 (A, B, C, D) faces the developing roller 4, and further around the photosensitive drum 1, A charger 3 (A, B, C, D) and an exposure device 2 (A, B, C, D) are arranged.

  In the tandem image forming apparatus configured as described above, the two-component developer composed of toner and carrier corresponding to each color such as yellow, cyan, magenta, and black is supplied from the toner container 9 to each developing device 12. The magnetic brush 10 is formed on the supply roller 5 by being stirred and charged by the mixers 8a and 8b shown in FIG. The magnetic brush 10 on the supply roller 5 is layer-regulated by the regulation blade 7, and developed by the potential difference between the DC bias 17 applied to the supply roller 5 and the DC bias 16 applied to the developing roller 4, and the AC bias 15. A thin layer of toner only is formed on the roller 4.

  When a print start signal is received from a control circuit (not shown), first, the photosensitive drum 1 composed of a positively charged organic photoreceptor (positive OPC) is charged by the charger 3 to 400 V, for example, and then, for example, 770 nm. As a result of exposure by the exposure apparatus 2 using LEDs having a wavelength of, the post-exposure potential of the photosensitive drum 1 becomes about 70 V, and a latent image is formed. The latent image is developed with the toner flying from the toner thin layer on the developing roller 4 to the photosensitive drum 1 by a DC bias 16 and an AC bias 15 applied to the developing roller 4 to form a toner image. Then, when the recording paper is fed from the paper feed cassette 53 and sent by the belt 54 to reach the photosensitive drum 1, a transfer bias by the transfer device 58 (A, B, C, D) is applied to the recording paper. The toner image is transferred to the toner image, fixed by the fixing device 59, and discharged. Thereafter, as described above, a thin toner layer on the developing roller 4 is collected by the supply roller 5 by changing the direct current (DC) bias 17 while applying the alternating current (AC) bias 15 periodically according to the print data.

  In the image forming apparatus configured as described above, the toner power is increased by performing predetermined aging before image formation. Here, the meaning of the term “before image formation” in the present invention means that when a large amount of printing is continuously performed as described above, or when the charging ability of the developer is reduced due to a high temperature and high humidity environment, after the power is turned on. The timing prior to the image formation performed during the stabilization operation of the apparatus or after the image formation is not performed for a predetermined time. Before this image formation, the DC potential difference between the supply roller 5 and the developing roller 4 is eliminated or the supply roller 5 In the range where the toner does not move from the developing roller 4 to the developing roller 4, the mixing roller 8 a, 8 b, the supply roller 5, and the developing roller 4 are aged to operate. An alternating electric field oscillated positively or negatively is applied to the toner, and the movement of toner in the magnetic brush 10 is activated to improve the electric power. The range in which the toner does not move from the supply roller 5 to the development roller 4 is as follows. For example, in the case of the development method using positively charged toner, if the potential of the supply roller 5 is higher than that of the development roller 4, If the toner moves and the potential of the developing roller 4 is too high compared to the supply roller 5, the toner is easily held by the supply roller 5, and the movement of the toner is hindered. Therefore, the absolute value of the difference of (developing roller potential) − (supply roller potential) is preferably about 0 to 20V.

  That is, by providing an aging time for applying an alternating electric field or an alternating electric field to the developing roller 4, the movement of the toner in the magnetic brush 10 becomes active due to the alternating electric field or the alternating electric field until the required charge amount is obtained. The time can be shortened, and the required amount of toner can be charged in a short time even if the charging ability of the carrier decreases as the developer deteriorates. Therefore, it is possible to provide a developing method in the image forming apparatus that can shorten the start-up time of the image forming apparatus and the charging time when image formation is not performed for a long time, and can prevent toner scattering and carrier pulling due to leakage.

  FIG. 3 shows the relationship between the toner charge amount and developer leakage as a numerical value. When the gap between the supply roller 5 and the regulating blade 7 is 550 μm, the toner charge amount is 8.0 μC / g or less. In this case, developer leakage occurs between the developing roller 4 and the supply roller 5, but does not occur at 8.5 μC / g or more. That is, it indicates that the developer leaks if the toner is not charged to 8.5 μC / g or more immediately after the power is turned on or when image formation is not performed for a predetermined time, and the charging is performed to 8.5 μC / g or more. If the time until the image formation is long, for example, it takes time until image formation becomes possible immediately after the power is turned on in the morning or after image formation is not performed for a predetermined time.

  In FIG. 2, the DC potential difference between the supply roller 5 and the developing roller 4 is eliminated or reduced immediately after the power is turned on or before image formation is not performed for a predetermined time, and the mixers 8a and 8b and the supply are reduced. In addition to performing aging to operate the roller 5 and the developing roller 4, an AC electric field or an alternating electric field oscillated in a pulsed manner is applied to the developing roller 4 to activate toner movement in the magnetic brush 10 to increase the electric power. When the improved developing method of the present invention is implemented (“●”), the DC potential difference between the supply roller 6 and the developing roller 4 is eliminated or reduced without applying an alternating electric field as in the prior art, and the mixer 8a, 8B is a graph comparing toner charge amount transitions when aging is performed to operate 8b, the supply roller 5, and the developing roller 4 (“◯”).

  In the graph of FIG. 2, the horizontal axis represents time, the vertical axis represents the toner charge amount, and after leaving the developer deteriorated by continuous printing at 32 ° C. and 85% humidity for one day, “●” Then, an alternating current having a rectangular wave Vpp of 1.6 kV, a frequency of 2.7 kHz and a duty ratio of 27% is applied from the alternating current power supply 15 of the developing roller 4, the direct current power supply 16 is 0 V, the direct current power supply 17 of the supply roller 5 is A is set to 0 V, and aging is performed, and “◯” is a case where an alternating electric field is not applied as in the conventional case.

  As is apparent from this graph, when an AC electric field or an alternating electric field is applied (“●”), the charge amount reaches 8.5 μC / g which does not cause developer leakage in about 12 seconds. When not applied (“◯”), the charge amount of 8.0 μC / g was not reached even after 50 seconds. If the aging is performed for a long time, the charge amount of the toner becomes 8.5 μC / g or more. However, as predicted from the graph of FIG. 2, it is necessary to perform the aging for a very long time. Absent.

  As described above, according to the present invention, the two-component developer is stirred and charged by the stirring members (mixers 8a and 8b), and the toner is applied to the developing roller 4 by the magnetic brush 10 formed around the supply roller 5. In an image forming apparatus in which a latent image is developed in a non-contact manner by forming a thin layer, immediately after power-on or before image formation after image formation has not been performed for a predetermined time, between the supply roller 5 and the development roller 4 The aging time for applying an AC electric field or an alternating electric field to the developing roller 4 is provided, and the movement of the toner in the magnetic brush 10 becomes active due to the AC electric field or the alternating electric field. It is possible to shorten the time until a proper charge amount is obtained. Therefore, even if the charging ability of the carrier decreases due to the deterioration of the developer, the required amount of toner can be charged in a short time, and the charging time when the image forming apparatus is started up or when image formation is not performed for a long time is possible. The developing method in the image forming apparatus can be provided in which the toner can be prevented from scattering and carrier pulling due to developer leakage.

  By providing the aging time immediately after the power is turned on or after the image formation is not performed for a predetermined time, when the developer is deteriorated, the image formation is performed immediately after the power is turned on, or for a predetermined time. Thus, it is possible to provide a developing method in an image forming apparatus that can reliably set the toner charge amount to a necessary value after the occurrence of the toner leakage and prevent toner scattering and carrier pulling due to leakage.

Further, when the DC potential difference between the supply roller 5 and the developing roller 4 at the time of aging is made smaller than that at the time of image formation , the potential difference is set within a range in which the toner does not move from the supply roller to the developing roller. The toner charge can be increased by the above.

  According to the present invention, the DC potential difference between the supply roller 5 and the developing roller 4 is eliminated or reduced immediately after the power is turned on or before the image formation is not performed for a predetermined time. Alternatively, by providing an aging time during which an alternating electric field is applied, the time until the toner in the magnetic brush 10 becomes active and reaches the required charge amount can be shortened. It is possible to provide a developing method in an image forming apparatus that can shorten the time until the image forming apparatus is started up while preventing pulling.

1 is a schematic diagram of an embodiment of a developing device that performs a developing method in an image forming apparatus according to the present invention. 6 is a graph showing transition of toner charge amount of aging by a conventional method and aging by a developing method of the present invention. 3 is a table showing the relationship between the toner charge amount and developer leakage in numerical values. 1 is a schematic diagram of an embodiment of an image forming apparatus having a developing device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive body (latent image carrier) drum 2 Exposure apparatus 3 Charger 4 Developing roller 5 Supply roller (magnetic roller)
7 Regulating blade 8a, 8b Mixer 9 Toner container 10 Magnetic brush 11 Recording paper 12 Developing device 15 AC power source 16 DC power source 17 DC power source

Claims (4)

A magnetic brush is formed around a supply roller having a magnetic pole member inside by a two-component developer composed of a toner and a carrier that are stirred and charged by a stirring member, and the magnetic brush is rubbed against the developing roller. using a bias that is applied between the roller only the toner is transferred to the developing roller, the developing method in an image forming apparatus that develops the latent image on the latent image bearing member with toner which has moved said transfer,
At the time of image formation, a developing bias in which an alternating current component is superimposed on a direct current component is applied to the developing roller, and a conveying bias including a direct current component is applied to the supply roller, and a toner is transferred onto the developing roller by a potential difference between the supplying roller and the developing roller. Only form a thin layer,
On the other hand, before the image forming, and less than at or image forming eliminate DC potential difference between the bias between the transfer bias of the supply roller and the developing bias of the developing roller, the conveying bias of the developing bias and the supply roller of the developing roller A developing method in an image forming apparatus, wherein an aging time for operating the stirring member, the supply roller, and the developing roller by applying an alternating electric field or an alternating electric field to at least one of them is provided.   2. The developing method for an image forming apparatus according to claim 1, wherein the aging time is provided immediately after power-on.   2. The developing method for an image forming apparatus according to claim 1, wherein the aging time is provided after image formation is not performed for a predetermined time. If smaller than when a DC potential difference imaging between the bias between the developing bias of the transfer bias and the developing roller in the supply roller at the time of the aging, the potential difference, the range in which the toner does not move from the supply roller to the developing roller The developing method in the image forming apparatus according to claim 1, wherein:

Images