JP2002099149A - Developing roller and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device whose image quality is improved by making a developer form a developer layer of uniform thickness on the surface of a developing sleeve by passing below a restriction member without any resistance. SOLUTION: The formation of image spots is suppressed by stabilizing and improving developer carrying performance by setting the ratio Ba/Bt of normal- directional magnetic flux density components Ba at a restriction position and normal-directional magnetic flux density components Bt to 0.4 or less. Further, a defect in carrying the developer can be prevented by obtaining proper magnetic flux density by setting the normal-directional magnetic flux density at the restriction position to 35 to 45 mT. Furthermore, the layer thickness can be restricted more effectively by compressing the developer and preventing developer deterioration by a restriction member by setting the angle θ on a photosensitive body side that the tangent of a developing roller at the restriction position and the width-directional line of the restriction member contains to 100 to 120 deg..

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 an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a laser printer, and a developing roller used in the developing device for such an image forming apparatus. More specifically, the present invention relates to a developing roller having improved developer passage property (removal property) through a regulating member (doctor blade).

[0002]

2. Description of the Related Art In an electrophotographic or electrostatic recording type image forming apparatus, in order to visualize an electrostatic latent image formed on a photosensitive member as a toner image on a transfer material, a toner and a carrier are used. A developing device using a two-component developer is often used. The toner in the developing device is charged by friction with the carrier, and is transferred to an electrostatic latent image on a photoconductor by a developing operation.

FIG. 7 is a sectional view showing a part of a conventional developing device 1. As shown in FIG. A developing device 1 that performs development using a two-component developer includes a photosensitive drum 8 that is a photosensitive member, a developing casing 2,
It is configured to include the developing roller 5. The developing roller 5 includes a developing sleeve 10 and a magnet roller 10a. The developing sleeve 10 has a hollow cylindrical shape,
It is rotatably supported. Inside the developing sleeve 10, a magnet roller 10 a having a plurality of fixed magnet bodies 3 as shown in FIGS.
It is provided non-rotating with respect to zero rotation.

[0004] As shown in FIG.
The developing roller 5 is controlled by the internal magnet roller 10a.
A plurality of magnetic poles are formed near the outer periphery of. Specifically, within the developing casing 2, as the developing sleeve 10 advances from the upstream to the downstream in the rotational direction, an N pole is formed at the N ₃ position, an N pole is formed at the N ₂ position, and an S pole is formed at the S ₂ position. externally, as one proceeds downstream from the rotation upstream of the developing sleeve 10, N-pole to the N ₁ position, the S pole to S ₁ position is formed. Wherein S ₁ position is a position where the developing sleeve 10 the photosensitive drum 8 is close.

The developing casing 2 is provided with developer conveying screws 4 and 6 shown in FIG. The developer 9 contained in the developing casing 2 is reciprocated in the casing 2 by the screws 4 and 6 described above. Further, another screw 11 shown in FIG. 9 may be used in addition to the screws 4 and 6 described above.

[0006] As shown in FIG. 7, the developing device 1 is provided with a photosensitive drum 8 that rotates in one direction (arrow a) to develop an electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 8. On the other hand, the developing sleeve 10 rotates in the forward direction (arrow b). As a result, the toner adhered to the outer peripheral surface of the developing sleeve 10 from within the developing casing 2 is transferred to an electrostatic latent image formed on the outer peripheral surface of the photoconductor.

Specifically, the magnetic developer 9 in the casing 2 is pumped by magnetic force onto the surface of the developing sleeve 10 at the N ₂ position and the S ₂ position of the magnet roller 10 a. Developer 9 adhered to developing sleeve 10
Are changed along with the rotation of the developing sleeve 10.
The upper is sequentially conveyed S ₂ position → N ₁ position → S ₁ position.

In the course of transport, the thickness of the developer 9 is regulated by a regulating member 7 which is arranged close to and perpendicular to the developing sleeve 10, and a thin layer of the developer 9 is formed on the surface of the developing sleeve 10. Is done.

The S pole formed at the S ₁ position where the developing sleeve 10 and the photosensitive drum 8 are close to each other is a main developing pole for performing development, and the developer spiked by the S pole at the S ₁ position is formed. 9 develops the electrostatic latent image formed on the photosensitive drum 8. Thereafter, the developer 9 remaining on the developing sleeve 10 moves into the casing 2 and is removed from the developing sleeve 10 by a repelling magnetic field formed between the N ₃ position and the N ₂ position, and the developer 9 is removed from the casing. It is returned in 2.

In the developing device 1 using such a two-component developer, various configurations have been proposed, and at the same time, with the rapid spread of personal computers in recent years, the personalization and miniaturization of the image forming device itself have progressed. And
In a developing device of an image forming apparatus mainly for a personal user, the image density of a solid portion (solid black portion) is particularly important in terms of image quality.

In order to cope with such a demand, an image forming apparatus equipped with a developing device using a "reverse rotation developing roller" in which the developing roller 5 rotates in a direction opposite to the rotation of the photosensitive drum 8 has appeared. In spite of the fact that the leading end of the toner image after the development has been slightly fainted has a defect referred to as "faint fading development", it has been used to some extent with emphasis on image density.

In order to reduce the manufacturing cost of the image forming apparatus, a "forward-rotating developing roller" requires a developing roller having at least five magnetic poles.
If it is a "reverse rotation developing roller", the magnetic pole of the developing roller is 3
It is also adopted because it can be covered by a pole configuration.

In the description of the developing device in this case, for convenience, the expressions "forward rotation developing roller" and "reverse rotation developing roller" are used, but the "forward rotation developing roller" is a photosensitive drum. 8 means the developing roller 5 which rotates counterclockwise when it rotates clockwise.
That is, the forward rotation developing roller has the same moving direction when viewed in the developing area.

On the other hand, the "reverse rotation developing roller"
If the photosensitive drum 8 rotates clockwise, it means the developing roller 5 that rotates clockwise. That is, when viewed in the developing area, the direction of movement of both is opposite to that of the reverse rotation developing roller. In other words, the photosensitive drum rotates in a direction against the rotation of the developing roller.

[0015]

In such a conventional technique, each step from the pumping of the developer 9 to the developing roller 5 to the collection thereof is performed by each magnetic pole provided on the outer peripheral surface of the developing roller 5. Have been done. The regulating member 7 is a regulating member 7
The developer 9 passes just below the developing sleeve 10 so that the developing sleeve 10
This is for forming a developer layer having a uniform thickness on the surface. To form a developer layer having a uniform thickness on the surface of the sleeve 10, the developer 9 passes under the regulating member 7 without resistance. This is important, and is considered as an important issue when designing the magnetic field distribution around the regulating member 7 as a problem of "removal of the developer from the doctor blade".

Since the design and evaluation of the magnetic pattern of each magnetic pole is performed mainly based on the magnetic flux density in the normal direction on the surface of the developing roller 5, that is, the strength of the magnetic field of the normal component, the regulating member 7 is disposed. The magnetic patterns of the portions are also designed only based on the strength of the magnetic field of the normal component. If the strength of the magnetic field of the normal component of the portion facing the regulating member 7 is too strong, it becomes difficult to scrape off the excessively adhered developer, and the doctor blade receives a strong resistance when passing through the gap. Recognition that the "removability" is reduced, the restricting member is designed so that the minimum part of the strength of the magnetic field of the normal component existing between the adjacent magnetic poles is positioned.

The developer 9 adhered on the developing sleeve 10
At the position where the magnetic flux density in the normal direction of the magnet arranged inside becomes large, the ears of the developer 9 stand. At the position where the magnetic flux density in the tangential direction of the magnet becomes large, the ears of the developer 9 are in a lying state. If the regulating member 7 is disposed at a position where the ears of the developer 9 stand on the developing sleeve 10, the density of the developer 9 becomes low, and the developer 9 conveyed to the photosensitive drum 8 side
Is not sufficient.

As described above, it is determined that the regulating member 7 is preferably disposed near the minimum position of the magnetic flux density of the normal component between the adjacent magnetic poles, but more specific magnetic flux density setting (magnetic field distribution). Is unknown. In addition, since the specific magnetic flux density setting (magnetic field distribution) slightly changes depending on the characteristics of the developer 9, a position where the releasability of the developer 9 is the best by the tri-and-error method by changing the pole positions on both sides conventionally. The reality was that they were looking for, and development took a great deal of cost and time.

The present invention has been made in view of such a situation. Therefore, an object of the present invention is to set a magnetic flux density (magnetic field density) which has been found by changing only the normal direction component by a tri-and-error method. Distribution) can be easily determined by considering the tangential component,
A developing roller with improved "removal of the doctor blade";
An object of the present invention is to provide a developing device in which such a developing roller is mounted as a reverse rotation developing roller.

[0020]

According to the present invention, the thickness of the developer adhering to the surface of the developing roller is regulated by a regulating member arranged to face the outer peripheral surface of the rotating developing roller. In a developing roller mounted on an electrophotographic developing device that transfers a developer from a developing roller to a photoreceptor that rotates in an opposite direction to form an image, the developing roller is positioned close to the surface of the developing roller and a regulating member. The magnetic flux density component Ba in the normal direction is substantially minimum, and the ratio Ba / Bt of the magnetic flux density component Ba in the normal direction of the developing roller to the magnetic flux density component Bt in the tangential direction of the developing roller is 0.4.
The developing roller is set to be less than the developing roller.

According to the present invention, the magnetic flux density component Ba in the normal direction at a position close to the developing sleeve and the regulating member,
The ratio Ba / Bt to the tangential magnetic flux density component Bt is set to 0.
By setting the value to less than 4, the developer transportability is stabilized and improved, and the occurrence of image spots is suppressed.

Thus, the gap between the regulating member and the developing sleeve can be smoothly passed, and the amount of the developer attached to the regulating member can be reduced.

According to the present invention, the thickness of the developer adhering to the surface of the developing roller is regulated by a regulating member disposed opposite to the outer peripheral surface of the rotating developing roller, and the photosensitive member rotating in the direction opposite to the rotation of the developing roller is regulated. In a developing roller mounted on an electrophotographic developing device that transfers a developer from a developing roller to a body to form an image, a magnetic flux density component in a tangential direction of the developing roller at a position close to a surface of the developing roller and a regulating member. Bt is set in a range of 35 mT or more and 45 mT or less.

According to the present invention, the magnetic flux density in the tangential direction at a position close to the developing sleeve and the regulating member is 35 mT
As described above, by setting the range to 45 mT or less, it is possible to obtain an appropriate magnetic flux density at a close position, and to prevent a poor conveyance of the developer.

According to the present invention, there is provided a developing device having the above-described developing roller, wherein the regulating member extends in parallel with the axial direction of the developing roller, and adjusts a distance between an edge portion at a developing roller side tip and a surface of the developing roller. Hold at a predetermined interval, regulate the layer thickness of the developer at the edge portion, the tangent line of the developing roller at the regulating position of the outer peripheral surface of the developing roller facing the edge portion, the line extending in the width direction of the regulating member The developing device is characterized in that the angle θ on the photosensitive member side is set to an obtuse angle.

According to the present invention, the angle θ between the tangent of the developing roller at the regulating position and the line in the width direction of the regulating member on the photosensitive member side is set to an obtuse angle, so The developer flow path can be gently narrowed, stress on the developer is reduced, and the developer can be smoothly fed to the photoconductor.

According to the present invention, the angle θ is 100 degrees to 120 degrees.
It is set every time. According to the present invention, by setting the angle θ on the photoconductor side between the tangent line of the developing roller at the regulation position and the line in the width direction of the regulation member to 100 degrees to 120 degrees, the developer is compressed by the regulation member. In addition, the deterioration of the developer property is prevented, and the regulation of the layer thickness is more effectively performed.

The present invention is characterized in that the distance between the outer peripheral surface of the developing roller at the regulating position and the regulating member is set in a range of 0.5 mm or more and 1 mm or less.

According to the present invention, by setting the distance between the developing sleeve and the regulating member at the regulating position in the range of 0.5 mm or more and 1 mm or less, uniform layer thickness regulation can be performed, A good image without image noise due to unevenness can be obtained.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a developing device, an electrostatic latent image formed on a photosensitive drum as a photosensitive member is developed as a toner image on a transfer material as a developing operation. At this time, the developing device moves the toner from the developing roller to which the developer has been attached to the electrostatic latent image on the photosensitive drum. Hereinafter, the present invention will be described based on the embodiments shown in the drawings, but the present invention is not limited thereto.

FIG. 1 shows a developing device 20 according to this embodiment.
FIG. The developing device 20 employs a “reverse rotation developing roller”, and has one side (the right side in FIG. 1) of the photosensitive drum 8.
Is provided with a developing casing 22 for housing a two-component developer composed of a toner and a carrier. Developing casing 2
2 is divided into a developing section 31 and a developer stirring section 41, and a two-component developer obtained by mixing a toner and a carrier is accommodated in the developing section 31.

The developer agitating section 41 includes a toner supply roller 37 for supplying the developer contained in the toner supply tank 39 from the supply port 34 to the development tank 35, a stirring member 38 for supplying toner to the toner supply roller 37, and a stirring member. A seat 36 is provided. Toner supply roller 37 and stirring member 38
Are rotationally driven in conjunction with a motor, and
The developer in the toner replenishing layer 39 is stirred by the rotation of the stirring sheet 37, and the toner is scooped by the stirring sheet 36. The picked-up toner is sent to the upper side of the toner replenishing roller 37, and is attracted and conveyed by the toner replenishing roller 37, and the toner replenishing port 34.
Is supplied to the developing tank 35 via the

In the developing section 31, as shown in FIG.
A developing roller 25 serving as a developer holding member, a screw 24 serving as a developer conveying unit, and a toner concentration sensor 40 for detecting a toner concentration in the developer are provided. The developing roller 25 has a structure similar to the conventional developing roller 5 shown in FIG. 8 and includes a developing sleeve 30 and a magnet roller.

The developing sleeve 30 is formed in a hollow cylindrical shape, and is rotatably supported at a position facing the photosensitive drum 8 at an opening of the developing casing 22. A magnet roller having a fixed magnet body is arranged so as not to rotate with respect to the rotation of the developing sleeve 30 (see FIGS. 7 and 8).

On the fixed magnet body of the magnet roller, there are formed a developing pole used in a developing operation, a transport pole for transporting the developer, and the like. The developer magnetized by the fixed magnet body can be adhered to the outer peripheral surface of the developing sleeve 30, and the developer can be moved by the rotation of the developing sleeve 30 to be brought close to the photosensitive drum 8. The developing sleeve 30 is made of a non-magnetic material such as an aluminum alloy or stainless steel, and rotates in the same direction (arrow c) as the photosensitive drum 8 rotates (arrow d), as shown in FIG. That is, the developing sleeve 30
The photosensitive drum 8 rotates in a direction against the rotation of the photosensitive drum 8.

The average roughness of the surface of the developing sleeve 30 is 2 to 15 μm so that the developer is stably and uniformly conveyed.
Is set between. This is because if the surface of the developing sleeve 30 is smooth, the conveyance is not sufficiently performed, and even if the surface is too rough, uneven development occurs. Sand blasting is used as a method for obtaining the above surface roughness, and in the case of aluminum material, an insulating property and a predetermined surface roughness can be obtained by performing alumite processing. The developing sleeve 30 rotates at a predetermined peripheral speed, and
To supply new developer.

The regulating member 27 is a thin plate made of a non-magnetic material such as aluminum alloy, stainless steel, brass or phosphor bronze, and extends in parallel with the axis of the developing sleeve 30. The regulating member 27 is located on the upstream side in the rotation direction of the developing sleeve 30 with respect to the developing region 26 where the photosensitive drum 8 and the developing sleeve 30 are opposed to each other.
0 and a predetermined gap are provided. Then, the edge portion 2 at the tip of the regulating member 27 on the side of the developing roller 25.
The developer adhered to the outer peripheral surface of the developing sleeve 30 comes into contact with 1, and excess developer adheres to the edge portion 21, and the layer thickness of the developer is regulated to be constant. Further, since the developer is attracted and held by the developing sleeve 30 by the action of the fixed magnet body, it is not separated from the developing sleeve 30 when being transported to the developing area 26, and is transported in a uniform thin layer.

In the present embodiment, the developing roller 25 in which the magnetic flux density is set in consideration of not only the normal component Ba of the magnetic flux density but also the tangential component Bt is used as the above-mentioned "reverse rotation developing roller". The results obtained by studying the developer transportability will be described below. FIG. 1 shows a magnetic pattern appearing around the developing roller 25, and its magnetic flux density is a quadratic curve having a maximum value in both the normal direction and the tangential direction.

As shown in FIG. 1, a quadratic curve indicated by a solid line MY is a magnetic flux density curve in a normal direction, and a quadratic curve indicated by a broken line MX.
The next curve is the tangential magnetic flux density curve. Control member 27
In the vicinity of the opposed portion, that is, in the regulation position 28, the magnetic flux density component Ba in the normal direction is substantially minimum, and the portion having the tangentially flat region in the magnetic flux density component Bt is opposed.

As one method for confirming the developer transportability, the magnetic flux density component Ba / Bt
Table 1 and the graph of Table 1 show the results of confirming the amount of the developer adhered to the regulating member depending on the idling time of the developing roller 25 by changing the ratio of.

[0041]

[Table 1]

FIG. 2 shows the optimum Ba / B at the regulating position 28.
It is a graph which shows a t ratio. The vertical axis indicates the amount of developer attached (m
g), and the horizontal axis is the idling time of the developing sleeve 30 (H
r. ). The amount of the developer attached was obtained by subtracting the weight of the regulating member 27 after the test from the weight of the regulating member 27 to which the developer adhered during the test. The idling time was such that the developing sleeve 30 was idle for a predetermined time. Time. As is clear from FIG. 2, when the ratio Ba / Bt of the normal component Ba and the tangential component Bt of the magnetic flux density is 0.1 to less than 0.4, even if the long-term idle test is performed, Control member 27
The amount of the developer adhered to the substrate is relatively low, but the ratio Ba
When the magnetic flux density component in the normal direction relatively increases with / Bt as a boundary of 0.4, the amount of developer attached to the regulating member 27 increases.

By setting the range (Ba / Bt) of the ratio of the magnetic flux density component Ba in the normal direction to the magnetic flux density component Bt in the tangential direction (Ba / Bt) to less than about 0.4 from FIG. It was confirmed that excellent developer transportability was obtained.

It is relatively preferable to lower the magnetic flux density component in the normal direction and increase the magnetic flux density component in the tangential direction. However, when the magnetic force is set by limiting the range with respect to the ratio of the two. It is possible to make it easy to set a specific target.

As another method for confirming the developer transportability, a tangential magnetic flux density Bt
Table 2 and Table 2 show the results of confirming the amount of the developer adhered to the regulating member by the idling time of the developing roller 25 by changing
3 is shown in FIG.

[0046]

[Table 2]

FIG. 3 is a graph showing the optimum tangential magnetic flux density Bt at the restriction position 28. The vertical axis represents the amount of the applied developer (mg), and the horizontal axis represents the idling time (Hr.) Of the developing sleeve 30. As is clear from FIG. 3, when the magnetic flux density component Bt in the tangential direction at the regulation position 28 is too large, the developer spikes and the developer density becomes excessive, and the Excess developer is supplied to 26.

More specifically, at the regulating position 28 of the regulating member 27, the tangential magnetic flux density component Bt is reduced by 35 mT
As described above, it has been confirmed that by setting the temperature to 45 mT or less, good developer transportability can be obtained. As a result, the method considered only by the normal component Ba of the magnetic force can be obtained. Is not always perfect,
Rather, the tangential component Bt of the magnetic force that was not considered
Has been found to greatly contribute to the control of developer transportability.

In the apparatus according to the present embodiment, the installation position of the regulating member 27 for solving various problems that may occur when the regulating layer 27 regulates the developing layer on the developing sleeve 30 will be described below.

The pressure of the developer during the regulation of the layer thickness is controlled by the regulating member 2.
The result of study on the inclination angle of No. 7 will be described. From many experiments and studies, it has been found that the pressure applied to the developer during the regulation of the layer thickness greatly depends on the intersection angle θ between the tangential direction with the developing sleeve 30 at the regulation position 28 and the width direction of the regulation member 27. did.

FIG. 4 shows the regulating member 27 and the developing sleeve 30.
5 is a schematic view showing a relative positional relationship with the above. Fig. 4 (1)
As shown in FIG. 7, a regulating position 28 at which the layer thickness regulation is started, a developer passage S through which the developer passes between the regulating member 27 and the developing sleeve 30, and a developing sleeve 30 passing through the regulating position 28. The tangent X to the restriction position and the normal Y to the tangent X, the intersection angle θ is defined by the tangent X to the restriction position
7 is an angle on the photoconductor side with respect to a line along the width direction of the photoconductor 7.

In each of FIGS. 4A and 4B, the intersection angle θ is set to (1): 90.
FIG. 4 (4) is a schematic view when the angle is (2): obtuse angle, (3): acute angle, (4): 180 degrees (when the regulating member 27 has the regulating position 28 on the abdomen). Since the developer flow path S is extremely small, effective layer thickness control is not performed. In each of FIGS. 4A and 4B, Table 3 shows the result of confirming the amount of the developer adhering to the regulating member 27 during the idling time of the developing sleeve 30 when the intersection angle θ is changed.
5 is shown in FIG.

[0053]

[Table 3]

When the intersection angle θ changes, the amount of developer retained in the developer flow path S and the developer pressure change, and the regulating member 27 is pressed, so that the amount of developer adhering to the regulating member 27 changes. The vertical axis in FIG. 5 is the amount of the applied developer (mg), and the horizontal axis is the idle time of the developing roller 30 (Hr.).

According to Table 3 and FIG. 5 described above, when the crossing angle θ is 90 degrees or less (FIGS. 4 (1) and 4 (3)), the adhesion of the developer to the regulating member 27 increases. Therefore, a preferable intersection angle θ is, as shown in FIG.
Is an obtuse angle (FIG. 4 (2)). Therefore, the regulating member 27
Is inclined and the intersection angle θ is set at an obtuse angle, so that the amount of developer attached to the regulating member can be reduced.

Table 2 and FIG. 5, which are the results of the above experiments, will be described in more detail with reference to FIG.

When the intersection angle θ is 90 degrees, the regulating member 27
Is opposed to the normal line Y of the developing sleeve 30,
A large amount of developer stays in the developer passage S surrounded by the developing sleeve 30, the regulating member 27, the bottom surface of the developing casing 22, and the like, and is not smoothly delivered to the developing unit. Further, since the developer flow path S is sharply narrowed at the regulation position 28, the developer is continuously stressed during a long-term operation, and the performance deteriorates.

Next, when the intersection angle θ is smaller than 90 degrees, that is, when the intersection angle θ is an acute angle, the amount of the developer adhered to the regulating member 27 after a certain period of time increases, and the uniform layer thickness is obtained. No regulation. This is because the amount of the retained developer in the developer flow path S is increased, so that the developer is not smoothly delivered to the developing unit, and the stress due to the pressure on the developer is also increased.

When the crossing angle θ exceeds 90 degrees and falls in an obtuse angle range, the amount of developer attached decreases. If the crossing angle θ exceeds 120 degrees even in the range of the obtuse angle, the leading edge 21 of the regulating member 27 does not face the regulating position 28 of the developing sleeve 30 and the abdomen of the regulating member 27 faces. Therefore, the layer thickness regulation is not effectively performed. Therefore, by setting the intersection angle θ of the regulating member 27 in the range of 100 to 120 degrees, the layer thickness of the developer can be more reliably regulated.

Next, in the apparatus described in this embodiment, the crossing angle θ of the regulating member 27 is fixed at 100 °, and the regulating position 2
FIG. 6 shows a graph of the developer conveyance amount when the facing distance with the developing sleeve 30 in FIG. 8 is changed. In FIG. 6, the vertical axis represents the amount of developer transported (mg / cm ² ), and the horizontal axis represents the opposing distance (μ) between the regulating member 27 and the developing sleeve 30.
m). As shown in FIG. 6, when the distance between the developing sleeve 30 and the regulating member 27 is less than 0.5 mm, the developer stress is extremely increased due to the shortage of the developer conveyance amount. Further, when the above-mentioned facing distance exceeds 1 mm, even if the facing distance is minutely changed, the developer transport amount changes rapidly, and the transport amount of the developer becomes unstable. Lacks gender.

Therefore, the facing distance between the developing sleeve 30 and the regulating member 27 at the control position 28 should be 0.5 mm or more,
By setting the distance to 1 mm or less, the developer conveyance amount is stabilized, and the developer stress can be relatively suppressed.

[0062]

As described above, according to the present invention, the ratio B of the magnetic flux density component Ba in the normal direction and the magnetic flux density component Bt in the tangential direction at the position close to the developing sleeve and the regulating member is obtained.
By setting a / Bt to less than 0.4, the developer transportability is stably and improved, and the occurrence of image unevenness is suppressed.

As a result, the gap between the regulating member and the developing sleeve can be smoothly passed, and the amount of developer adhered to the regulating member can be reduced.

That is, if the normal component magnetic force of the portion facing the regulating member is too strong, it becomes difficult to scrape off the developer excessively adhering to the surface of the developing sleeve, and at the same time, a strong resistance force is passed when passing through the gap. Since the receiving `` doctor blade removability '' is reduced, adverse effects such as developer stagnation immediately before the regulating member and a rise in temperature due to heat generation occur.However, by smoothly passing the gap between the regulating member and the developing sleeve, The shearing force applied to the developer is reduced, the adhesion of the developer to the regulating member is suppressed, and the torque at the regulating member-facing portion can be reduced.

Also, only the component in the normal direction of the magnetic flux density is considered, and a regulating member (doctor blade) is used in a tri-and-error method as in the case of improving the developer transportability.
There is no need to determine the magnetic force setting (magnetic field distribution) of the adjacent pole in the vicinity, and the cost and time required for designing the developing roller can be greatly reduced.

Further, according to the present invention, the magnetic flux density in the tangential direction at a position close to the developing sleeve and the regulating member is reduced by 35%.
By setting the range of mT or more and 45 mT or less, an appropriate magnetic flux density at a close position can be obtained, and defective conveyance of the developer can be prevented.

Also, only the component in the normal direction of the magnetic flux density is considered, and a regulating member (doctor blade) is used in a tri-and-error method as in the case of improving developer transportability.
There is no need to determine the magnetic force setting (magnetic field distribution) of the neighboring poles in the vicinity, and the cost and time required for designing the developing roller can be greatly reduced.

According to the present invention, the angle θ on the photoconductor side between the tangent line of the developing roller at the regulating position and the line in the width direction of the regulating member is set to an obtuse angle, so that the angle θ along the surface of the developing sleeve can be increased. The developer flow path can be gently narrowed, stress on the developer is reduced, and the developer can be smoothly fed to the photoconductor. As a result, the layer thickness of the developer adhering to the developing roller at the regulation position can be properly regulated, and a decrease in print quality can be suppressed.

According to the present invention, the angle θ between the tangent of the developing roller and the line in the width direction of the regulating member at the regulating position is set at 100 ° to 120 ° on the photosensitive member side. Compression of the developer and deterioration of the developer property are prevented, the regulation of the layer thickness is more effectively performed, and a decrease in print quality can be suppressed.

According to the invention, the distance between the developing sleeve and the regulating member at the regulating position is set to 0.5 mm or more and 1 mm.
By setting the thickness in the following range, uniform layer thickness regulation can be performed, and a good image free from image noise due to uneven conveyance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a developing device 20 according to an embodiment of the present invention.

FIG. 2 shows a magnetic flux density Ba in a normal direction and a magnetic flux density B in a tangential direction.
6 is a graph showing the amount of developer attached when the ratio of t (Ba / Bt) is changed.

FIG. 3 is a graph showing the amount of developer adhesion when the magnetic flux density Bt in the tangential direction is changed.

FIG. 4 is a schematic diagram showing a relative relationship between a developing sleeve 30 and a regulating member 27.

FIG. 5 is a graph showing the amount of developer attached when the crossing angle θ of the regulating member 27 is changed.

FIG. 6 is a graph showing a developer conveyance amount when a facing distance between a regulating member 27 and a developing sleeve 27 is changed.

FIG. 7 is a cross-sectional view illustrating a conventional developing device 1.

FIG. 8 is a view showing a conventional magnet roller 10a.

FIG. 9 is a perspective view showing conventional screws 4, 6, 11;

[Explanation of symbols]

REFERENCE SIGNS LIST 20 developing device 21 edge portion 22 developing casing 24 screw 25 developing roller 27 regulating member 28 regulating position 30 developing sleeve MX tangential magnetic flux density curve MY normal magnetic flux density curve θ tangential line of developing roller at regulated position and regulation The angle (crossing angle) on the photoconductor side between the line in the width direction of the member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Sanada 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Akira Nakakuma 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Jun Yamaguchi 22-22, Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture F-term (reference) 2H031 AB02 AB03 AC01 AC10 AC11 AC14 AC15 AC19 AC20 AC30 AC31 AC34 AD03 BC00

Claims (5)

[Claims] An image forming apparatus according to claim 1, wherein a regulating member disposed opposite to an outer peripheral surface of the rotating developing roller regulates a layer thickness of a developer adhering to the developing roller surface. A developing roller mounted on an electrophotographic developing apparatus for forming an image by transferring a developer from the developing roller, wherein a magnetic flux density component Ba in a normal direction of the developing roller is provided at a position close to the surface of the developing roller and the regulating member. And the ratio Ba / Bt of the magnetic flux density component Ba in the normal direction of the developing roller to the magnetic flux density component Bt in the tangential direction of the developing roller.
Is set to less than 0.4. And a regulating member disposed opposite to an outer peripheral surface of the rotating developing roller to regulate a layer thickness of the developer adhering to the developing roller surface. In a developing roller mounted on an electrophotographic developing device that forms an image by transferring a developer from a developing roller, a magnetic flux density component Bt in a tangential direction of the developing roller is located at a position close to the surface of the developing roller and the regulating member. , 35mT or more, 45
A developer roller, wherein the developer roller is set to a range of mT or less. 3. A developing device equipped with the developing roller according to claim 1, wherein the regulating member extends parallel to an axial direction of the developing roller.
The distance between the edge of the front end of the developing roller and the surface of the developing roller is maintained at a predetermined distance, and the layer thickness of the developer is regulated at the edge. A developing device characterized in that an angle θ between the tangent of the roller and the line extending in the width direction of the regulating member on the photoconductor side is set to an obtuse angle. 4. The developing device according to claim 3, wherein said angle θ is set to 100 degrees to 120 degrees. 5. The developing device according to claim 4, wherein an interval between the outer peripheral surface of the developing roller at the regulating position and the regulating member is set in a range of 0.5 mm or more and 1 mm or less.