JP4747735B2 - Developing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and more particularly, to a developing device using a one-component magnetic toner and an image forming apparatus using the developing device.

As a developing device used in a conventional image forming apparatus such as an electrophotographic system, a system using a one-component magnetic toner is known in order to simplify the apparatus configuration. In such a developing device, a system in which toner supplied to the surface of a magnet roll (sleeve) for carrying and transporting toner is regulated in layer thickness and frictionally charged by a layer thickness regulating member (plate spring or the like) is usually used.
On the other hand, the toner on the sleeve after development differs in the residual toner amount and charge amount after development between the portion consumed by development and the portion not consumed, and when toner newly adheres to the layer, The charge amount distribution is generated in the toner on the sleeve after the thickness regulating member. For this reason, the amount of toner that moves from the sleeve to the photoconductor during the next development varies depending on the location (depending on the history), so-called ghost phenomenon occurs.

In order to prevent such a ghost phenomenon, for example, there is a method in which residual toner adhering to the sleeve after development is once scraped off from the sleeve with a blade or the like. This is not a preferable method because of problems such as deterioration of toner, deterioration of toner scraped off or scattering, and increase in the number of members.
Therefore, the following method is known as a method for suppressing ghost without adding a new member that scrapes off the residual toner on the sleeve.

In Patent Document 1, a molybdenum-based film is formed on the surface of the sleeve, and further, the ghost is suppressed by devising the toner filling density at the entrance portion of the nip region between the sleeve and the layer thickness regulating member. Is described.
Further, in Patent Document 2, an alternating electric field is applied between the layer thickness regulating member and the sleeve, and the toner firmly adhered to the sleeve is peeled off from the sleeve to make the toner on the sleeve uniform, and further peeled off. A system in which the magnetic pole arrangement is devised so as to prevent the scattered toner from being scattered is described.

JP-A-9-114252 (Embodiment of the Invention, FIG. 4) JP-A-8-30093 (Example, FIG. 1)

However, in the method of Patent Document 1, since a sleeve formed with a molybdenum-based coating is used and the toner filling density itself depends on the distance between the layer thickness regulating member and the sleeve, it has been used for a long time. If this is the case, there is a concern that sufficient performance cannot be obtained due to deterioration of the sleeve or change in distance.
Further, the method of Patent Document 2 requires a high-voltage power supply for applying an alternating electric field, leading to an increase in the cost of the apparatus. Further, since an alternating electric field is applied, there is a concern that the stability of the charging characteristics of the toner may be impaired.

  On the other hand, regarding toner charging, it is difficult to uniformly charge each toner particle when a toner having a small particle diameter and a toner having a large particle diameter are mixed. When the charge amount increases, small particle size toner with a large charge amount per unit mass tends to remain on the sleeve, and the particle size is small on the sleeve by repeating the layer thickness regulation (including charging) step and the development step. The toner tends to increase. For this reason, the particle size distribution between the newly supplied toner and the toner remaining on the sleeve is expanded, and it is difficult to uniformly charge the toner on the sleeve. Therefore, the toner having a small particle diameter remaining on the sleeve is reduced, and a toner having a large particle diameter is preferentially adhered to the sleeve as a newly supplied toner, so that the toner particles are applied to the toner particles by the layer thickness regulating member. It is necessary to perform uniform charging.

  The present invention has been made to solve the above technical problem, and prevents toner supplied from the toner supply port from being directly supplied onto the toner carrier, thereby providing stable image quality over the long term. A developing device that can be secured and an image forming apparatus using the same are provided.

That is, as shown in FIG. 1, the present invention provides a rotatable toner carrier that is provided opposite to an image carrier 1 on which an electrostatic latent image is carried and carries a one-component magnetic toner (toner) on its surface. A toner container 3, a toner container 3 that holds the toner carrier 2 and stores toner, and a toner supply member 5 that is provided adjacent to the toner container 3 and supplies toner to the toner container 3. Of the partition that separates the toner supply unit 4, the toner storage unit 3, and the toner supply unit 4, the toner supply port 6 that opens to face the toner carrier 2, and the toner supply port 6 that surrounds the toner carrier 2 And a layer thickness regulating member 7 that regulates the toner on the toner carrier 2 to a predetermined thickness. The toner carrier 2 is disposed below the layer thickness regulating member 7. And over the entire region facing the toner supply port 6 Toner to form a toner pool 8 circulating movement I, the supply toner comprising a magnetic bypass supplying magnetic field can be formed on the toner carrying member 2 along the direction of circulation of the toner reservoir 8, the magnetic poles, the toner A guide magnetic pole M1 set on the upstream side in the rotation direction of the toner carrier 2 with respect to a straight line connecting the central axis of the carrier 2 and the lower edge of the toner supply port 6, and adjacent to the downstream side of the guide magnetic pole M1 A conveying magnetic pole M2 having a polarity different from that of the magnetic pole M1 and set on the downstream side in the rotation direction of the toner carrier 2 from the contact portion between the layer thickness regulating member 7 and the toner carrier 2 It is.

In such technical means, the toner carrier 2 in the present invention is only required to be able to carry a one-component magnetic toner (toner). Usually, a non-magnetic sleeve and one having a plurality of magnetic poles as magnetic field generating means are used. The The number of magnetic poles is not particularly limited, but an embodiment having four magnetic poles is preferable from the viewpoint of cost reduction and ease of manufacture. The guide magnetic pole M1 is a magnetic pole that guides toner to the toner carrier 2 side. In addition, for example, the influence of other adjacent magnetic poles is considered in the guide magnetic pole M1.
Further, the layer thickness regulating member 7 only needs to be able to regulate the amount of toner on the toner carrier 2, and the shape thereof is not limited to a plate shape or a roll shape. In addition, the toner may be charged by the layer thickness regulating member 7, or a charge control member may be separately provided on the downstream side of the layer thickness regulating member 7 to control the toner charging. Note that “above the area facing the toner supply port 6” means that the upper side in the opening area of the toner supply port 6 may be higher.

  In the present invention, by providing the toner reservoir 8, it is possible to further suppress, among the toners supplied from the toner supply unit 4, particularly the toner having a small particle diameter directly supplied to the toner carrier 2. Further, the newly supplied toner is detoured along the outer peripheral flow of the circulating flow by the circulating flow of the toner reservoir 8, and the toner having a small particle diameter is taken to the circulating flow. For this reason, the toner adhering to the toner carrier 2 is easily made uniform.

Further, in constructing the toner reservoir 8 in the present invention, the toner carrying member 2, a straight line connecting the center axis of the lower edge and the toner carrying member 2 of the toner supply port 6, and the layer thickness regulating member 7 and the toner carrying Any magnetic poles built in the toner carrier 2 are disposed within a range facing the toner supply port 6 which is partitioned by a straight line connecting the contact portion with the body 2 and the central axis of the toner carrier 2. No aspect is adopted.

In other words, the toner carrier 2 includes the guide magnetic pole M1 set on the upstream side in the rotation direction of the toner carrier 2 with respect to the straight line connecting the central axis of the toner carrier 2 and the lower edge of the toner supply port 6, and adjacent to the downstream side of the guide pole M1, conveyance poles is set downstream in the rotation direction of the toner carrier 2 from contact sites and and the layer thickness regulating member 7 in polarity differs from the guide pole M1 and the toner carrying member 2 M2 is provided .
As a result, the toner reservoir 8 can be formed in the vicinity of the toner supply port 6, the toner supplied from the toner supply port 6 can be prevented from being guided directly to the toner carrier 2, Further, it becomes difficult to adhere to the toner carrier 2.

In the present invention, the lower edge of the toner supply port 6 is preferably provided below the toner carrier 2 until the toner supplied from the toner supply unit 4 adheres to the toner carrier 2. And the toner is difficult to be directly supplied to the toner carrier 2.
On the other hand, the upper edge of the toner supply port 6 is preferably provided below the contact portion between the toner carrier 2 and the layer thickness regulating member 7, so that the toner scraped off by the layer thickness regulating member 7 can also be removed. The toner can be effectively collected in the toner reservoir 8 and the toner reservoir 8 is easily formed over the entire area so as to cover the toner supply port 6.
Further, it is preferable that the toner supply port 6 is provided within a range where the magnetic force by the magnetic poles of the toner carrier 2 can reach, and this makes it possible to form an effective toner reservoir 8 in the vicinity of the toner supply port 6. Become.

Further, it is preferable that the toner storage unit 3 is set so that a toner amount capable of forming the toner reservoir 8 is secured, and the toner reservoir 8 can be effectively formed by the secured toner amount.
Furthermore, the present invention is also directed to an image forming apparatus including the above-described developing device. In this case, an image carrier 1 on which an electrostatic latent image is carried, and the image carrier 1 on the image carrier 1 are provided. The developing device described above may be used as a developing device for developing the electrostatic latent image.

According to the present invention, in a developing device that uses a one-component magnetic toner (toner), a toner reservoir in which toner circulates on the toner carrying member over the whole region below the layer thickness regulating member and facing the toner supply port. forming a, this field bypass supplying supply toner to the toner carrying member along the direction of circulation of the toner reservoir is provided with a formable pole, among the toner supplied from the toner supply unit to the toner accommodating portion, the small It is possible to prevent the toner having a particle size from adhering to the toner carrier and to homogenize the toner adhering to the toner carrier.
Therefore, it is possible to suppress the occurrence of ghosts with a simple configuration, and it is possible to provide a low-cost developing device that can obtain stable image quality over a long period of time.
Further, by using such a developing device, it is possible to provide an image forming apparatus having stable developing characteristics over a long period of time.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 2 shows an image forming apparatus according to an embodiment to which the present invention is applied.
In the figure, reference numeral 21 denotes a photoconductor provided with a photosensitive layer such as an organic photoconductor on the surface of a metal substrate such as stainless steel rotating in the direction of the arrow. The photoconductor 21 is charged by a charging device 22 such as a charging roll. The electrostatic latent image is written by the exposure device 23 having a laser writing device or an LED array. The written electrostatic latent image is formed as a potential image based on the contrast with the high potential portion not exposed to light because the surface potential of the portion exposed to light on the photoreceptor 21 is lowered.

Further, a developing device 30 for visualizing the electrostatic latent image is provided on the downstream side of the exposure device 23 so as to face the photoconductor 21.
In the developing device 30 in the present embodiment, a one-component magnetic toner (toner) is accommodated in a developing housing 31, and toner is carried on a developing roll 32 as a toner carrying member. Is applied, the developing roll 32 is held at an intermediate potential between the high potential portion and the low potential portion of the electrostatic latent image, and only the image portion of the electrostatic latent image on the photoreceptor 21 side is charged with charged toner. It is intended to be developed.

  Further, the transfer device 24 is provided on the downstream side of the developing device 30 and is constituted by, for example, a transfer roll disposed in contact with the photoconductor 21, and records a toner image on the photoconductor 21 by a transfer bias (not shown). It is made to transfer on the paper 25 as a material. The toner remaining on the photosensitive member 21 is removed by, for example, a doctor blade type cleaning device (not shown).

  In this embodiment, the paper 25 on which the toner image on the photoconductor 21 is transferred is conveyed to the fixing device 60, and the toner image is fixed on the paper 25 by the fixing device 60. The fixing device 60 has, for example, a heat roll method and includes a heating roll 61 and a pressure roll 62, and the toner image is fixed by passing the paper 25 between the heating roll 61 and the pressure roll 62. It has come to be.

Next, details of the developing device 30 in such an image forming apparatus will be described.
As shown in FIG. 3, the developing device 30 according to the present embodiment carries the toner T at a position facing the photosensitive member 21 of the developing housing 31 that is spaced from the photosensitive member 21 in the opening of the developing housing 31. A toner storage chamber 40 that holds the developing roll 32 to be conveyed and stores the toner T is provided, and a toner hopper 50 that supplies the toner T to the toner storage chamber 40 is provided behind the toner storage chamber 40. ing.
An opening window 42 serving as a toner supply port opened in a part of the developing housing 31 is provided between the toner hopper 50 and the toner storage chamber 40, and the toner T in the toner hopper 50 passes through the opening window 42. Thus, the toner is supplied to the toner storage chamber 40 side. Reference numeral 51 denotes an agitator for stirring the toner T in the toner hopper 50 and supplying the toner T to the toner storage chamber 40 side.
Further, a layer thickness regulating member 41 that controls the layer thickness of the toner adhering to the developing roll 32 and at the same time applies a charge to the developing roll 32 is provided above the opening window 42.

The developing roll 32 in the present embodiment includes a rotatable nonmagnetic developing sleeve 33 and a magnet body 34 fixedly disposed inside the developing sleeve 33 and having a plurality of magnetic poles. The photosensitive member 21 and the photoconductor 21 rotate in the With direction (the same direction at opposite portions).
The magnet body 34 includes four magnetic poles (S 2, N 1, S 1, N 2) on the outer periphery thereof, and a developing magnetic pole S 1 is provided at a position substantially opposite to the photoreceptor 21. A transport magnetic pole N1 is provided in the vicinity, a guide magnetic pole S2 is provided in the lowermost vicinity, and a transport magnetic pole N2 is provided on the substantially opposite side of the transport magnetic pole N1. A developing bias (not shown) for developing the electrostatic latent image on the photosensitive member 21 is applied to the developing sleeve 33 with the photosensitive member 21. The number and arrangement of the magnetic poles of the magnet body 34 are not limited to the present embodiment, and may be appropriately selected. The names of the magnetic poles used in the present embodiment indicate convenient names.

  Further, the layer thickness regulating member 41 is set to fix one end side of the urethane rubber sheet to, for example, a bracket or the like extending from the developing housing 31, and to be in contact with the developing roll 32 on the free end side. On the free end side, the developer roll 32 is brought into contact with the inside of the end portion.

In addition, the agitator 51 in the toner hopper 50 fixes the PET film stirring blade to a resin rotating shaft, and the PET film stirring blade is rotated by the rotation of the rotating shaft so that the toner T can be stirred and conveyed. It has become a thing.
In this embodiment, the toner T in the toner hopper 50 is supplied to the toner storage chamber 40 side by the rotation of the agitator 51 through the opening window 42 between the toner hopper 50 and the toner storage chamber 40. It has become.
At this time, the opening window 42 is formed in a part of the developing housing 31, the upper edge position is a position indicated by A in the figure, and the lower edge position is a position indicated by B in the figure. In the present embodiment, the upper edge position A of the opening window 42 is provided at substantially the same height as the vicinity of the free end of the layer thickness regulating member 41, and the lower edge position B is below the lower end of the developing roll 32. Is provided.

Next, the general operation of the developing device 30 in the present embodiment will be described with reference to FIG. In the drawing, the toner T stirred by the agitator 51 in the toner hopper 50 is supplied to the toner storage chamber 40 side through the opening window 42 by the rotation of the agitator 51.
The toner T supplied to the toner storage chamber 40 is attracted to the developing roll 32 by the action of the magnet body 34 fixedly disposed inside the developing roll 32. When the toner T adsorbed on the developing roll 32 reaches the portion facing the layer thickness regulating member 41 as the developing roll 32 rotates, the toner T is regulated to a predetermined layer thickness and a predetermined amount of frictional charging. Amount is given. When the toner T, whose layer thickness and charge amount are controlled, reaches the developing region at a position facing the photoreceptor 21 as the developing roll 32 rotates, the electrostatic latent image on the photoreceptor 21 is developed by a developing bias (not shown). The image is visualized (developed).
Then, the toner T remaining on the developing roll 32 after development moves as it is in accordance with the rotation of the developing roll 32, and the next new toner T is attached thereon.

  Here, the toner accumulation in the toner storage chamber 40, which is a feature of the present invention, will be described in detail with reference to FIGS. The magnet body 34 of the present embodiment includes a straight line L1 that connects the rotation center O of the developing roll 32 to the nip center between the developing roll 32 and the layer thickness regulating member 41, and a lower edge position of the opening window 42 from the rotation center O. None of the magnetic poles are disposed within an angle θ formed by the straight line L2 connecting B, the conveying magnetic pole N1 is disposed downstream of the straight line L1, and the guide magnetic pole S2 is disposed upstream of the straight line L2.

  Therefore, the toner T supplied from the toner hopper 50 through the opening window 42 into the toner storage chamber 40 is guided to the developing roll 32 side. On the other hand, the toner T adsorbed on the developing sleeve 33 of the developing roll 32 is conveyed to the layer thickness regulating member 41 side with the rotation of the developing sleeve 33, and much toner T is scraped off by the layer thickness regulating member 41. It becomes like this. The toner T thus scraped off is returned in a direction away from the surface of the developing sleeve 33. As a result, in the upstream region of the layer thickness regulating member 41, the arrow indicated in the α region (the region indicated by the dotted line) in the figure. It is included in the circulating flow of such toner T. This circulating flow is formed so as to close the opening window 42, and the toner T supplied from the toner hopper 50 to the toner storage chamber 40 has an outer periphery of the α region of the circulating flow as indicated by a thick arrow β in the figure. Or is supplied to the developing roll 32 side while detouring along the line or included in the circulating flow α region.

Here, the generation mechanism of an image defect such as a ghost will be described.
Among the characteristics of the toner on the developing roll 32, the important characteristics are the particle size (particle size), the charge amount and their distribution, and the amount of adhered toner (after layer thickness regulation). These characteristics are related to each other. For example, if the charge amount changes, the particle diameter and the amount of adhered toner also change. Specifically, as the charge amount increases, the mirror image force between the developing roll 32 and the toner (attractive force acting on the metal surface when it approaches the metal surface) increases, so that the small particle having a large charge amount per unit mass. The diameter toner is more likely to adhere to the developing roll 32, and the amount of adhesion increases.

That is, as the charge amount increases, the amount of toner on the developing roll 32 increases and the amount of small particle size toner also increases relatively.
In addition, a relatively small toner having a small particle size in the toner particle size (particle size) distribution is firmly attached to the surface of the developing roll 32, and the newly supplied toner has a small particle size toner. If included, the toner particle size reduction on the surface of the developing roll 32 is further accelerated.

On the other hand, the toner is charged by frictional charging in the nip region between the layer thickness regulating member 41 and the developing roll 32. At this time, the toner charge amount does not saturate by this one charge and is charged several times. It becomes saturated by repeating.
Further, of the toner adhering on the developing roll 32, newly supplied toner adheres to a portion where the toner has moved to the photosensitive member 21 side by development. For this reason, the newly attached toner and the toner attached before that are united and charged by the layer thickness regulating member 41. Thus, the number of passages of the layer thickness regulating member 41 differs between the part where the toner has moved due to the development and the part where the toner has not moved, so that the characteristics of the toner on the developing roll 32 are not uniform. This will cause image defects such as ghosts.

  In order to prevent such a ghost, the present inventors aim to reduce the adhesion of a small particle size toner to the developing roll 32, and a large amount of toner is placed in the vicinity of the opening window 42 in the toner storage chamber 40. A circulation flow was formed, and it was considered to make it difficult for the small-diameter toner of the toner T supplied into the toner storage chamber 40 to adhere to the developing roll 32 by this circulation flow. That is, even if a small particle size toner is supplied, it does not reach the developing roll 32 side directly by this circulating flow, and it takes a long time by bypassing the distance until it reaches the vicinity of the guide magnetic pole S2, and during this time the small particle size is reduced. By trapping the toner on the circulating flow side, the toner T having a uniform particle diameter is adhered on the developing roll 32.

As described above, in the present embodiment, by appropriately setting the magnetic pole arrangement of the developing roll 32, a large toner reservoir that closes the opening window 42 in the vicinity of the opening window 42 in the toner storage chamber 40 is formed. It became possible to make it. Therefore, among the toner T supplied from the toner hopper 50 through the opening window 42 to the toner storage chamber 40, the small particle size toner can be trapped in the toner reservoir, and the small particle of the toner T supplied to the developing roll 32 can be trapped. The diameter can be suppressed.
Therefore, it is possible to suppress the occurrence of ghosts at low cost without adding new members, and in particular without using special toner that has been removed in advance. Thus, stable image quality can be maintained.

In the present embodiment, the circulation flow of the toner pool (generated in the α region) also helps the leveling effect of the toner adhering to the developing roll 32, thereby making it possible to make the toner more uniform and further increase the ghosting. Reduction is possible.
Further, in the present embodiment, the rotation direction of the developing roll 32 and the photosensitive member 21 is the Whit direction, but the rotation direction is not limited to this, and seems to rotate in the Gainst direction (directions opposite to each other at opposite portions). There is no problem.
In the present embodiment, a shape having a space in which substantially triangular toner accumulates is shown below the toner storage chamber 40. However, this portion is a space required only for assembling the developing device 30 in the present embodiment. It goes without saying that the same effects as described above can be obtained even if this space is eliminated. Needless to say, the rotation speed of the developing sleeve 33 has a sufficient toner conveying force to form a toner reservoir.

In the present embodiment, the evaluation of the occurrence of toner accumulation in the toner accommodating chamber when the magnetic pole arrangement and the magnetic flux density of the guide magnetic pole S2 (see, for example, FIG. 4) are changed, particularly in the magnet body of the developing roll. .
The magnetic pole S2 is arranged such that the angle formed on the upstream side in the rotation direction of the developing roll from the straight line L1 (see FIG. 4) connecting the rotation axis center of the developing roll and the nip center between the developing roll and the layer thickness regulating member is 61 °. The strength of the normal component of the magnetic flux density was 85 mT.
For comparison, an evaluation was also made on the arrangement of the guide magnetic pole S2 in the range from the straight line L1 to the straight line L2 (see FIG. 4).
(1) Example: Angle = 61 °, intensity of normal component of magnetic flux density = 85 mT
(2) Comparative Example 1 Angle = 38 °, intensity of normal component of magnetic flux density = 85 mT
(3) Comparative Example 2 ... Angle = 38 °, intensity of normal component of magnetic flux density = 60 mT
(4) Comparative Example 3 ... Angle = 15 °, strength of normal component of magnetic flux density = 60 mT

FIG. 5A shows the toner flow obtained from the result of observation by a high-speed video camera and the analysis result by simulation of the toner flow in the developing chamber at the time of the embodiment, from the guide magnetic pole S2 to the layer thickness regulating member. A large circulating toner flow (indicated by a solid line in the figure) was confirmed.
For this reason, the toner supplied from the opening window (between points A and B in the figure) into the developing chamber is largely changed by this circulation flow, and flows as indicated by the broken arrow in the figure or into the circulation flow. I understood that it was included.
FIG. 5B shows the toner circulation flow in Comparative Example 1 (indicated by solid arrows in the figure), and only a small circulation flow is formed in the upstream region of the layer thickness regulating member. Therefore, the toner supplied from the opening window into the developing chamber is directly guided to the developing sleeve side as indicated by a broken line arrow in the figure.
Further, FIG. 6A shows the toner flow in the comparative example 2. In this comparative example, the magnetic flux density of the comparative example 1 is reduced. It was confirmed that similar results were obtained.
Furthermore, FIG. 6B shows the toner flow in Comparative Example 3, which is the same as in Comparative Examples 1 and 2.

Next, in the above-described examples and comparative examples, image output was performed at an output density of 600 dpi and 1200 dpi, and the occurrence of ghosts was evaluated. A ghost is generated when a pattern image in which a halftone image is formed on a recording paper (plain paper) immediately after a bold character image (within one rotation pitch of a developing roll) is repeatedly formed. A visual evaluation was performed as to whether or not it was, and was evaluated according to the following criteria.
Evaluation point 0: no occurrence, evaluation point 1: a level that can be recognized when viewed in detail, evaluation point 2: a level that is slightly generated but is not worrisome, and a rating point 3 that can be clearly recognized .

As shown in FIG. 7, the generation result of the ghost is not so problematic at an output density of 600 dpi, but it was confirmed that the output density of 1200 dpi was good in the example but inferior in Comparative Examples 1 to 3. It was.
For this reason, the opening window is blocked by a large circulation flow of toner, and the toner supply path to the development roll becomes long or is contained in the circulation flow. It is confirmed that the adhesion of is reduced.

  FIG. 8 shows an example in which, for example, the toner scraping effect by the layer thickness regulating member is slightly different under the conditions shown in the above-described embodiment (see FIG. 5A). There may be a case where a small circulation flow (circulation flow indicated by a solid line arrow on the side of the layer thickness regulation member in the figure) is generated immediately below the regulation member. As described above, even if a small circulating flow is generated, the toner supplied from the opening window to the developing chamber flows as shown by the broken-line arrows in the drawing, and the same effect as in the embodiment can be obtained. become. As described above, it is understood that even if the number of circulation flows is plural, it is sufficient that the toner supplied to the developing chamber is detoured and supplied.

From the above, the relationship between the toner flow and the ghost in the developing chamber when the four types of developing rolls with different magnetic pole positions and strengths of the guide magnetic pole S2 are used is understood.
That is, if the opening window is closed by a toner reservoir formed by a large toner circulation flow from the region immediately below the developing roll to the layer thickness regulating member, adhesion of small-diameter toner to the developing roll is suppressed, and ghosting is prevented. It is understood that it can be improved.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. 1 is an explanatory diagram showing an embodiment of an image forming apparatus to which the present invention is applied. It is explanatory drawing which shows the developing device of embodiment. It is a principal part enlarged view of the image development apparatus of an embodiment. (A) is an explanatory view showing the flow of toner in the embodiment, and (b) is an explanatory view showing the flow of toner in Comparative Example 1. (A) is an explanatory view showing the flow of toner in Comparative Example 2, and (b) is an explanatory view showing the flow of toner in Comparative Example 3. It is explanatory drawing which shows the generation | occurrence | production situation of the ghost of an Example and a comparative example. Is an explanatory view showing the flow of toner in the other embodiments.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Toner carrier, 3 ... Toner accommodating part, 4 ... Toner supply part, 5 ... Toner supply member, 6 ... Toner supply port, 7 ... Layer thickness control member, 8 ... Toner reservoir, M1 ... Guide magnetic pole, M2 ... Conveying magnetic pole

Claims (6)

A rotatable toner carrier provided opposite to an image carrier on which an electrostatic latent image is carried and carrying a one-component magnetic toner on its surface;
A toner container for holding the toner carrier and containing toner;
A toner supply unit provided adjacent to the toner storage unit and supplying toner to the toner storage unit by a toner supply member;
A toner supply port that is opened to face the toner carrier among the partition walls separating the toner storage unit and the toner supply unit;
A layer thickness regulating member that is disposed above the area facing the toner supply port in the periphery of the toner carrying body and regulates the toner on the toner carrying body to a predetermined thickness ;
The toner carrier forms a toner reservoir in which the toner circulates under the layer thickness regulating member and over the entire region facing the toner supply port. The toner is carried along the circulation direction of the toner reservoir. It has magnetic poles that can form a magnetic field that bypasses the body ,
The magnetic pole is a guide magnetic pole set on the upstream side in the rotation direction of the toner carrier from a straight line connecting the central axis of the toner carrier and the lower edge of the toner supply port;
A conveying magnetic pole that is adjacent to the downstream side of the guide magnetic pole and has a polarity different from that of the guide magnetic pole and is set on the downstream side in the rotation direction of the toner carrier from the contact portion between the layer thickness regulating member and the toner carrier. A developing device. The developing device according to claim 1,
A developing device characterized in that the lower edge of the toner supply port is provided below the toner carrier. The developing device according to claim 1,
A developing device, wherein an upper edge of the toner supply port is provided below a contact portion between the toner carrier and the layer thickness regulating member. The developing device according to claim 1,
3. A developing device according to claim 1, wherein the toner supply port is provided within a range to which a magnetic force by a magnetic pole of the toner carrier is applied. The developing device according to claim 1,
The developing device according to claim 1, wherein the toner container is set so as to secure a toner amount capable of forming a toner reservoir. An image carrier on which an electrostatic latent image is carried;
An image forming apparatus, comprising a developing device according to any one of claims 1 to 5 for developing an electrostatic latent image on the image carrier.

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