JP2003255696A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an irregular layer thickness of developer on a developing sleeve by keeping the developer supply amount to the developing sleeve constant even when the rotating speed of the developing sleeve is changed. <P>SOLUTION: Under the control of a controller 22, the developing sleeve 11 is driven to be rotated by a 1st driving source 20 and developer carrying screws 16 and 17 are driven to be rotated by a 2nd driving source 21, whereby the rotating speed of the screws 16 and 17 is kept constant even in the case of changing the rotating speed of the sleeve 11 in accordance with the change of processing speed. Therefore, a developer surface in a developer container 10 is kept constant even when the rotating speed of a photoreceptor drum 1 is changed, and the developer supply amount to the sleeve 11 can be stably and constantly maintained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing an electrostatic latent image formed on an image bearing member such as a photoconductor to form a developer image, and an electrophotographic system equipped with the developing device. The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile that forms an image by an electrostatic recording method or the like.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an electrophotographic photosensitive member, which is an image carrier, is charged by a charging device and exposed by an exposing device so that the surface of the electrophotographic photosensitive member is electrostatically charged according to image information. A latent image is formed, and the formed electrostatic latent image is developed by a developing device to be visualized as a developer image (toner image). Then, the developer image is transferred to a transfer material such as paper by a transfer device, and the developer image is fixed on the transfer material by a fixing device and discharged.

As a developing device of the above-mentioned image forming apparatus,
For example, there is a developing device as shown in FIG. 4, which performs development using a two-component developer containing a non-magnetic toner and a magnetic carrier.

The developing device 101 includes a developing container 10 containing a two-component developer (hereinafter referred to as developer) T containing a non-magnetic toner (hereinafter referred to as toner) and a magnetic carrier.
2, a developing sleeve 103, which is a developer carrying member, is rotatably installed at a predetermined interval from the photosensitive drum 100, in an opening of a developing container 102 that faces the photosensitive drum 100, which is an image carrying member. . The developing sleeve 103 is made of a cylindrical body made of a non-magnetic material, and is rotated in the direction of arrow b (counterclockwise) in which the facing portion moves in the same direction as the photosensitive drum 100 which rotates in the direction of arrow a (clockwise). It

Inside the developing sleeve 103, a magnet roller 104 as a magnetic field generating means is fixedly arranged. The magnet roller 104 has five magnetic poles (S1,
N1, S2, N2, N3). A developer regulating blade 105 is attached above the developing sleeve 103, and the developer regulating blade 105 is not in contact with the developing sleeve 103 toward the vicinity of the magnetic pole S2 which is substantially located at the maximum point in the vertical direction of the magnet roller 104. Is located close to. Further, developer conveying screws 106 and 107 for stirring and conveying the developer T to the developing sleeve 103 side are installed in the lower portion of the developing container 2.

The developing device 101 is constructed as described above, and the developer T contained in the developing container 102 is
The toner is supplied to the developing sleeve 103 while being circulated in the developing container 102 by stirring and conveying the conveying screws 106 and 107. The developer T supplied to the developing sleeve 103
Is the magnetic pole N2 of the magnet roller 104 (pumping pole)
Is drawn up by the developing sleeve 103 by the developing sleeve 103, and as the developing sleeve 103 rotates, it is conveyed on the outer peripheral surface of the developing sleeve 103 from the magnetic pole S2 to the magnetic pole N1.
And the photosensitive drum 100 reach the developing unit.

During this conveyance, the developer T is magnetically regulated in layer thickness by the developer regulating blade 105 in cooperation with the magnetic pole S2, and the developer T is deposited on the outer peripheral surface of the developing sleeve 103.
A thin layer of is formed.

Magnet roller 10 located in the developing section
The magnetic pole S1 of No. 4 is the main developing pole, and the thin layer of the developer T transported to the developing unit is formed by the magnetic pole S1 and contacts the surface of the photosensitive drum 100, and is formed on the surface of the photosensitive drum 100. Develop the electrostatic latent image. The remaining developer that has not contributed to the development of the electrostatic latent image is the developing sleeve 103.
Is returned to the inside of the developing container 102 by the rotation of the developing roller 102, and is removed from the surface of the developing sleeve 103 by the repulsive magnetic field of the magnetic poles N2 and N3 of the magnet roller 104.
It is collected in the developing container 102.

[0009]

By the way, in the conventional developing device 101 shown in FIG. 4, the developer regulating blade 10 is used.
The developer T, which is not supported as a thin layer on the outer peripheral surface of the developing sleeve 103 due to the regulation of No. 5 and is removed, is removed by the magnetic force generated by the two poles of the magnet roller 104, the S2 pole and the N3 pole. 105 developing sleeve 10
A large amount is retained in the developing container 102 near the upstream side in the rotation direction of No. 3.

Further, since the developer T is conveyed one after another by the rotation of the developing sleeve 103 with respect to the developer T accumulated in the vicinity of the developer regulating blade 105, a great pressure is applied to the accumulated developer T, When the magnetic carrier of the developer T and the toner are pressurized, a phenomenon occurs in which fine particles such as titanium oxide externally added to the toner are embedded in the toner.

Further, due to the friction between the toner and the magnetic carrier, the particle shape of the toner itself becomes rounded and rounded. Further, when it is used for a long time, a so-called spent phenomenon occurs in which toner adheres to the surface of the magnetic carrier and cannot be removed.

When the developer is deteriorated as described above,
The amount of triboelectric charge of toner (so-called tribo) changes with use time, the developability of the toner changes, the image density changes, and the mechanical adhesion of the toner to the magnetic carrier or the photosensitive drum 100 increases, which corresponds to the electric field. It becomes difficult to perform the developed and transferred. For this reason, partial loss (unevenness) of the toner occurs, resulting in an image with an extremely poor impression as compared with the initial image as it is used.

According to the study by the present inventor, it has been found that the above-mentioned deterioration level of the developer has a great relationship with the driving torque of the developing sleeve 103. That is, when the developer regulating blade 105 is removed from the developing device 101 shown in FIG. 4 and the developing sleeve 103 is simply coated with the developer and the developing sleeve 103 is rotated, the deterioration of the developer progresses at all. It wasn't. At this time, the driving torque of the developing sleeve 103 is about 1/10 of that in the above case.
Was falling to.

From the above evaluation experiment, the developing sleeve 103
It has been clarified that the main cause of the increase in the driving torque is due to the amount of the developer remaining in the vicinity of the developer regulating blade 105.

Therefore, in order to reduce the driving torque of the developing sleeve 103, conventionally, as shown in FIG. 5, the developer regulating blade 105 is opposed to the pumping pole (N2) which is the repelling pole of the magnet roller 104. There has been proposed a developing device 110 configured to regulate the layer thickness of the developer T at the same time when the developer T is pumped up. The rest of the configuration is the same as that of the developing device 101 shown in FIG. 4, and duplicate description will be omitted.

In the developing device 110, the developer T regulated and removed near the tip of the developer regulating blade 105 on the upstream side with respect to the rotation direction of the developing sleeve 103 is along the upstream side surface of the developer regulating blade 105. Flows and falls into the developing container 102. Therefore, the developer regulating blade 1
A large amount of developer is not accumulated on the upstream side of 05, and the developer is not subjected to a large pressure. As a result, as compared with the case of the developing device 101 shown in FIG.
The driving torque of 03 was reduced to about 1/4, and the deterioration of the developer could be significantly suppressed.

However, in the developing device 110 having the configuration shown in FIG. 5, the developer carrying screw 106 in the developing container 102 located below the developer regulating blade 105.
Rotates a plurality of screws (not shown) to splash the developer T to the scooping pole (N2) of the magnet roller 104 and supply the developer T to the developing sleeve 103. Therefore, the supply unevenness occurs depending on the screw phase. .

For this reason, in this developing device 110, since there is a very small area serving as a developer accumulating portion on the upstream side of the developer regulating blade 105, this supply unevenness causes unevenness in the layer thickness of the developer to the developing sleeve 103 ( Image defects were likely to occur due to the appearance as screw marks).

Further, since the fixing property of the toner to the paper greatly varies depending on the paper type and the paper thickness of the paper as the transfer material, the fixing speed may be changed according to the paper type and the paper thickness in order to maintain the fixing property. Is being done. At this time, in order to control the paper entry speed into the fixing device, the image forming speed (that is, the peripheral speed of the photosensitive drum 100) has been changed.

However, the peripheral speed (Vd) of the photosensitive drum 100 and the peripheral speed (Vs) of the developing sleeve 103 are
A constant peripheral speed difference (Vs in the past was used to stabilize the development characteristics.
/Vd=1.5 to 2.0).

Therefore, as in the above case, the photosensitive drum 1
00 by changing the peripheral speed of the developing sleeve 103
The peripheral speed of will change. Further, in general, the driving force of the developer carrying screw 106 (107) is transmitted from a drive source (not shown) of the developing sleeve 103 via a gear, so that the rotation speed of the developer carrying screw 106 (107) also changes at the same time. Will end up.

The change in the rotation speed of the developer conveying screw 106 (107) greatly affects the height of the developer surface in the developing container 110. That is, the developer surface gradually rises as the rotation of the developer conveying screw 106 is started from the stopped state.

For example, the developing device 11 having the structure shown in FIG.
0, the peripheral speed of the photosensitive drum 100 in the standard paper mode is 200 mm / s, and the peripheral speed of the photosensitive drum 100 in the thickest paper mode is 25 mm / s (1/8 of the peripheral speed in the standard paper mode (process In the experiment of the present inventor, it has been confirmed that the developer surface in the developing container 110 is lowered by about 30% in the thickest paper mode.

Thus, the developer carrying screw 106
When the height of the developer surface changes due to the change in the rotation speed of (107), the amount of developer supplied to the developing sleeve 103 changes, and thus the change in the amount of developer supplied to the developing sleeve 103 changes. By appearing as uneven layer thickness,
Image defects were likely to occur. This phenomenon is especially shown in FIG.
This was remarkable in the developing device 110 configured so that the driving torque of the developing sleeve 103 as shown in FIG.

Therefore, according to the present invention, even if the rotation speed of the developing sleeve is changed, the amount of developer supplied to the developing sleeve can be kept constant, and uneven layer thickness of the developer on the developing sleeve can be prevented. An object of the present invention is to provide a developing device and an image forming apparatus that can be used.

[0026]

To achieve the above object, the present invention provides a developing container containing a developer containing at least a non-magnetic toner and a magnetic carrier, and a developer carrying the developer on an image carrier. In a developing device having a developer carrying member that conveys the formed electrostatic latent image to a developing unit that develops the electrostatic latent image, and a developer supplying member that supplies the developer in the developing container to the developer carrying member, It has a first driving unit for driving the developer carrying member and a second driving unit for driving the developer supplying member, and the rotation speed of the developer carrying member and the rotation speed of the developer supplying member. Is controlled independently of each other.

Further, there is a changing means for changing the rotation speed of the developer carrying body according to the change of the rotation speed of the image carrying body, and the changing speed of the developer carrying body is changed by the changing means. However, it is characterized in that the rotation speed of the developer supply member is substantially maintained.

The magnetic carrier in the developer has a magnetization amount of 30 to 200e in a magnetic field of 1 kilo Oersted.
It is characterized by being in the range of mu / cm ³ .

Further, it has a magnetic field generating means fixedly arranged inside the developer carrying body, and the magnetic field generating means is located downstream of the developing section in the rotation direction of the developer carrying body and inside the developing container. A first magnetic pole positioned and a second magnetic pole having the same polarity positioned in the developing container on the downstream side of the first magnetic pole in the rotation direction of the developer carrier and adjacent to the first magnetic pole. At least, and between the first magnetic pole and the second magnetic pole, the magnetic flux density B in the vertical direction on the surface of the developer carrier is provided.
r is 50 Gauss or less and the horizontal magnetic flux density Bθ is 5
It is characterized by having a region of 0 Gauss or less.

Further, a developer regulating member for regulating the layer thickness of the developer on the developer carrying member is provided, and the developer regulating member is arranged in the vicinity of the facing position of the second magnetic pole. There is.

An image forming apparatus according to the present invention comprises an image carrier on which an electrostatic latent image is formed, and the developing device according to any one of claims 1 to 5. .

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described based on the illustrated embodiments.

<Embodiment 1> FIG. 1 is a schematic configuration diagram showing a main part of an image forming apparatus having a developing device according to Embodiment 1 of the present invention.

The image forming apparatus is provided with a charging device 2, a developing device 3, a transfer roller 4, and a cleaning device 5 around a drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image bearing member. Therefore, the toner image formed on the photosensitive drum 1 by the electrophotographic image forming process is transferred to a transfer material P such as paper to form an image.

More specifically, image exposure L is given by an exposure device (not shown) onto the photosensitive drum 1 which is charged by the charger 2 and is rotating in the direction of arrow a (clockwise), and the image on the surface of the photosensitive drum 1 is exposed. The potential of the exposed portion is lowered,
An electrostatic latent image corresponding to the input image information is formed. Then, by the developing sleeve 11 as the developer carrying member of the developing device 3 to which the developing bias having the same polarity as the charging polarity of the photosensitive drum 1 is applied to the electrostatic latent image at the developing portion facing the photosensitive drum 1, A developer (toner) charged to the same polarity as the photosensitive drum 1 is attached to form a visible image as a developer image (hereinafter referred to as a toner image) (details of the developing device 3 in the present embodiment). Will be described later).

When the toner image formed on the photosensitive drum 1 reaches the transfer nip portion between the photosensitive drum 1 and the transfer roller 4, the transfer material P such as paper is fed to the transfer nip portion at this timing. Then, the toner image on the photosensitive drum 1 is transferred to the transfer material P by the electrostatic force generated between the photosensitive drum 1 and the transfer roller by the transfer roller 4 to which the transfer bias having the polarity opposite to that of the toner is applied.

Then, the transfer material P on which the toner image is transferred
Is separated from the photosensitive drum 1 and conveyed to the fixing device 6, and the toner image is heated and pressed on the transfer material P at the fixing nip portion between the fixing roller 6a and the pressure roller 6b of the fixing device 6 to fix the toner image to the outside. Output to. Further, the transfer residual toner remaining on the photosensitive drum 1 after the above-mentioned transfer is removed by the cleaning device 5.
Are removed and collected by the cleaning blade 5a.

Next, details of the developing device 3 in the present embodiment will be described.

As shown in FIG. 2, the developing device 3 is provided with a developing container 10 containing a two-component developer T containing a magnetic carrier and a non-magnetic toner, and an opening of the developing container 10 has a developer carrying member. A developing sleeve 11 made of a non-magnetic material such as SUS is rotatably provided facing the photosensitive drum 1.

In the developing sleeve 11, a magnet roller 12 as a magnetic field generating means is fixedly arranged, and the magnet roller 12 has five magnetic poles, that is, a developing main pole arranged to face the photosensitive drum 1. N along the magnetic pole S1 and the rotation direction of the developing sleeve 11 in the direction of arrow b.
It has magnetic poles of 3, N2, S2, and N1.

The N3 pole is located downstream of the developing section facing the photosensitive drum 1 in the rotational direction of the developing sleeve 11 and inside the developing container 10, and the N2 pole is the N3 developing sleeve 1 of the N3 pole.
1 downstream of the rotating direction of 1 and adjacent to the N3 pole
It is located within 0.

The inside of the developing container 10 is divided into a first chamber 14 and a second chamber 15 by a partition wall 13, and the first chamber 14 and the second chamber 1 are separated from each other.
5, developer carrying screws 16 and 17 as developer supplying members are arranged respectively. First chamber 14 and second
The chamber 15 communicates with each other, and the developer conveying screws 16 and 1
By the rotation of 7, the developer T circulates in the first chamber 14 and the second chamber 15.

Above the first chamber 14 of the developing container 10, the tip of the developer regulating blade member 18 as a developer regulating member is located at the N2 pole of the magnet roller 11 with respect to the rotating direction of the developing sleeve 11. ° Downstream developing sleeve 11
And 400 μm apart from each other so that the closest contacts are located. The developer regulating blade member 18 includes a blade 18a made of a non-magnetic material and the developing sleeve 1 thereof.
1. A magnetic plate 18 made of a magnetic material and having a thickness of 0.3 mm, which is adhered to the developer conveying screw 16 side of the tip portion facing 1
and b. That is, the magnetic plate 18b is provided on the upstream side of the blade 18a with respect to the rotation direction of the developing sleeve 11.

The developer T in the developer container 10 is transferred from the second chamber 15 to the first chamber 14 by the rotation of the developer conveying screw 17.
2 is conveyed to the front side with respect to the paper surface of FIG. 2 while being agitated by the developer conveying screw 16. At this time, a part of the developer T is transferred to the magnet roller 1.
Pumped by N2 pole of 1.

The maximum magnetic flux density on the surface of the N2 pole developing sleeve 11 is 600 gauss, and the half-value width of the magnetic flux density is 30 °.
Is. The developer T drawn up by the N2 pole is between the magnetic plate 18b of the developer regulating blade member 18 and the N2 pole,
It is attached to the surface of the developing sleeve 11 while being regulated to a layer thickness of about 30 mg / cm ² .

According to the study by the present inventor, the developer regulating blade member 18 is developed from the position facing the maximum magnetic flux density position of the N2 pole when the half width of the N2 pole of the magnet roller 11 is X °. X ° on the downstream side in the rotating direction of the sleeve 11.
It is preferable to be arranged in a position between / 2.

Then, as the developing sleeve 11 rotates, the developer T whose layer thickness is regulated on the surface of the developing sleeve 11 is used.
Is further conveyed from the S2 pole to the N1 pole, and the electrostatic latent image on the photosensitive drum 1 is developed in the developing portion near the S1 pole which is the developing pole.

The developer remaining without contributing to the development is conveyed to the N3 pole (the magnetic flux density is, for example, 500 to 600 gauss) as the developing sleeve 11 rotates, and the gap between the N3 pole and the N2 pole is reached. The magnetic flux density Br in the vertical direction on the developing sleeve 11 is 50 gauss or less, and the magnetic flux density Bθ in the horizontal direction is 50 gauss or less in the repulsive magnetic field region to drop from the surface of the developing sleeve 11 into the first chamber 14. The magnetic flux densities in the vertical and horizontal directions on the developing sleeve 11 between the N3 pole and the N2 pole are 0 gauss or more, and the N3 pole,
It does not have to be the opposite pole to the N2 pole. The developer that has dropped into the first chamber 14 contributes to the next development.

As described above, according to this embodiment, 2
Of the two magnetic poles N2 and N3 having the same pole, the magnetic plate 18b of the developer regulating blade member 18 nears the facing position of the N2 pole located on the downstream side in the rotational direction of the developing sleeve 11 so that the developer T
By controlling the layer thickness of the developer, of the developer T remaining on the developing sleeve 11 that is not applied, the magnet roller 1
The developer that cannot be held by the N2 pole of No. 1 immediately drops onto the developer conveying screw 16 in the first chamber 14 without accumulating.

Therefore, a large pool of developer does not occur in the vicinity of the upstream side in the rotation direction of the developing sleeve 11 of the developer regulating blade member 18, and compared with the case of the configuration of the developing device in the conventional example of FIG. 4 described above. As a result, the deterioration of the developer T could be reduced to about 1/4.

Further, in the developing device 3 according to the first embodiment of the present invention, as shown in FIG. 1, the developing sleeve 11 is rotationally driven by the first drive source 20, and the developer conveying screw 1
6 and 17 are rotationally driven by the second drive source 21. The first drive source 20 and the second drive source 21 can rotationally drive the developing sleeve 11 and the developer conveying screws 16 and 17 such that the rotational speeds thereof can be changed by the control of the control device 22.

As described above, in order to adjust the transfer material entry speed into the fixing device 6 according to the paper type, paper thickness, etc. of the transfer material P, the image forming speed (the peripheral speed of the photosensitive drum 1 ( When the process speed)) is changed, it is necessary to change the rotation speed of the developing sleeve 11 according to the changed process speed. In such cases, conventionally,
As described above, the surface speed of the developer T accommodated in the first chamber 14 of the developing container 10 is changed by changing the rotation speeds of the developer conveying screws 16 and 17 according to the change of the rotation speed of the developing sleeve 11. Change will occur,
The layer thickness unevenness of the developer attached to the surface of the developing sleeve 11 is likely to occur.

On the other hand, in the embodiment of the present invention, the developing sleeve 11 is rotationally driven by the first drive source 20 and the developer conveying screws 16 and 17 are second driven by the control of the control device 22 as described above. By rotationally driving the source 21, even if the process speed changes and the rotational speed of the developing sleeve 11 changes as described above, the rotational speeds of the developer conveying screws 16 and 17 can be kept constant. .

As described above, in the present embodiment, it is possible to prevent a large amount of developer from being accumulated near the upstream side of the developer regulating blade member 18 in the rotational direction of the developing sleeve 11. Further, even if the rotation speed of the developing sleeve 11 is changed due to the change in the process speed, the rotation speeds of the developer conveying screws 16 and 17 can be kept constant. The developer surface in the first chamber 14 of 10 can be kept constant, and the amount of developer supplied to the developing sleeve 11 can be stably kept constant.

Therefore, it is possible to prevent unevenness of the layer thickness of the developer T on the developing sleeve 11 and perform good development.

<Embodiment 2> In this embodiment also, an image forming apparatus equipped with the developing device according to Embodiment 1 shown in FIGS. 1 and 2 will be described.

In this embodiment, a low magnetization magnetic carrier is used as the magnetic carrier in the developer (two-component developer) T in order to further reduce the driving torque of the developing sleeve 11 and to improve the image quality. . The configurations and operations of the developing device and the image forming apparatus are the same as those in the first embodiment, and the description thereof will be omitted in the present embodiment.

By using a low-magnetization magnetic carrier as the magnetic carrier, not only a good image can be obtained because the magnetic brush density can be increased, but the magnetic shear in the magnetic plate 18b of the developer regulating blade member 18 can be reduced.

According to experiments conducted by the present inventor, the amount of magnetization (the amount of magnetization in a 1 kilo Oersted magnetic field) was 30 emu / c.
By setting the range of m ^{3 to} 200 emu / cm ³ , the driving torque of the developing sleeve 11 could be reduced to about 1/7 as compared with the case where the low magnetization magnetic carrier was not used. Therefore, it is expected that the life of the developer can be significantly improved by using the low magnetization magnetic carrier as the magnetic carrier.

However, as the driving torque of the developing sleeve 11 is made lighter as described above, the tolerance of the layer thickness unevenness of the developer T on the developing sleeve 11 (a screw mark due to the rotation of the developer carrying screw 16) is allowed. Since the range is further reduced, it was difficult to use a low magnetization magnetic carrier as the magnetic carrier. FIG. 3 is an experimental result showing the relationship between the amount of magnetization of the low-magnetization magnetic carrier and the process speed at which a screw trace (uneven layer thickness of the developer T on the developing sleeve 11) is generated.

The value of the screw mark generation process speed (mm / sec) in FIG. 3 indicates the reduction ratio at which the screw mark is generated with respect to the normal process speed (200 mm / sec).

Then, the developer containing the magnetic carrier of ³⁰ emu / cm ³ which is the minimum low magnetization carrier is stored in the developing container 10 of the developing device in the first embodiment of the present invention and developed. When the operation is performed, even when the process speed is changed and the rotation speed of the developing sleeve 11 is changed as described above, the rotation speeds of the developer conveying screws 16 and 17 can be controlled to be constant. The developer surface in the first chamber 14 of the container 10 can always be kept constant.

As a result, even when a low-magnetization carrier, which has been difficult to use as a magnetic carrier in the past, is used, the allowable range of the layer thickness unevenness (screw trace) of the developer T on the developing sleeve 11 is greatly improved. It has become possible.

[0064]

As described above, according to the present invention, the rotation speed of the developer supplying member is kept constant even when the rotation speed of the image carrier changes and the rotation speed of the developer carrier changes. Since it can be held, the developer surface in the developing container can be kept constant even when the rotation speed of the developer carrying member changes in accordance with the change in the rotation speed of the image carrying member. The developer supply amount can be stably maintained constant. Therefore, it is possible to prevent unevenness of the layer thickness of the developer on the developer carrying member and perform good development.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus including a developing device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a developing device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a magnetization amount of a low-magnetization magnetic carrier and a process speed at which a screw trace (uneven layer thickness of the developer T on the developing sleeve 11) is generated.

FIG. 4 is a schematic configuration diagram showing an example of a developing device in a conventional example.

FIG. 5 is a schematic configuration diagram showing an example of a developing device in a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image bearing member) 2 Charging device 3 Developing device 4 Transfer roller 5 Cleaning device 6 Fixing device 10 Developing container 11 Developing sleeve (developer carrying member) 12 Magnet roller (magnetic field generating means) 16, 17 Developer conveying screw (Developer supply member) 18 Developer regulating blade member (Developer regulating member) 18a Blade 18b Magnetic plate 20 First drive source 21 Second drive source 22 Control device (changing means)

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H005 BA02 EA02                 2H031 AB02 AC01 AC15 AC19 AC20                       AC33 AC34 BA05 BA09 EA03                       EA05                 2H077 AB02 AB14 AC02 AD06 AD13                       AD18 AE03 BA01 BA02 BA03                       BA04 BA08 DB14 EA01

Claims (6)

[Claims] 1. A developer container containing a developer containing at least a non-magnetic toner and a magnetic carrier, and a developer carrying the developer and carrying it to a developing section for developing an electrostatic latent image formed on an image carrier. In a developing device having a developer carrying member and a developer supplying member for supplying the developer in the developing container to the developer carrying member, first driving means for driving the developer carrying member; Second driving means for driving the developer supply member, and the rotation speed of the developer carrier and the rotation speed of the developer supply member can be controlled independently of each other. Development device. 2. A changing means for changing the rotation speed of the developer carrying body according to a change in the rotation speed of the image carrying body, wherein the changing speed of the developer carrying body is changed. The developing device according to claim 1, wherein the rotation speed of the developer supply member is substantially maintained. 3. The magnetic carrier in the developer has a magnetization amount of 30 to 200 emu in a magnetic field of 1 kilo Oersted.
It exists in the range of / cm < ³ >, The developing device of Claim 1 or 2 characterized by the above-mentioned. 4. A magnetic field generating means fixedly arranged inside the developer carrying body, wherein the magnetic field generating means is located downstream of the developing section in the rotation direction of the developer carrying body and inside the developing container. A first magnetic pole positioned and a second magnetic pole having the same polarity positioned in the developing container on the downstream side of the first magnetic pole in the rotation direction of the developer carrier and adjacent to the first magnetic pole. A region having at least a magnetic flux density Br of 50 gauss or less in the vertical direction and a magnetic flux density Bθ of 50 gauss or less in the horizontal direction on the surface of the developer carrier between at least the first magnetic pole and the second magnetic pole. The developing device according to any one of claims 1 to 3, further comprising: 5. A developer regulating member for regulating the layer thickness of the developer on the developer carrying member, the developer regulating member being disposed in the vicinity of the facing position of the second magnetic pole. The developing device according to claim 4. 6. An image forming apparatus comprising: an image carrier on which an electrostatic latent image is formed; and the developing device according to claim 1.