JP2001005293A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To specify a lower limit of a minimum value (Frmin) of a magnetic force in a radial direction in a developer carrier acting on a developer in a developer accommodating portion, and to determine a toner density self-contained. Provided is a developing device which has excellent controllability and can obtain a good image without image density unevenness. SOLUTION: Only one magnetic pole is provided in a magnet roller 5 in an area facing a developer accommodating section A, and a change in a magnetic field in the developer accommodating section is continuously and smoothly changed. The minimum value (Frmin) of the magnetic force in the radial direction of the developer carrier acting on the developer in the developer accommodating portion satisfies the following expression. Frmin> 1.5 × 10 ⁻⁷ (N) However, the magnetic force in the radial direction is positive in the direction attracted to the developer carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an image forming apparatus such as a copying machine, a printer, a facsimile, etc., and more particularly, to a developing device using a two-component developer containing toner and magnetic particles. The amount of the developer is regulated by a developer amount regulating member, and the state of taking in the developer is changed based on the change in the toner concentration of the developer on the developer carrier, and the toner is taken in by the movement of the developer. And a developing device for self-controlling the toner density.

[0002]

2. Description of the Related Art Conventionally, a developing device of this type has a magnetic field generating means therein and includes a toner and a magnetic carrier.
A developer carrying member that carries and transports the component developer, a first regulating member that regulates the amount of the developer that is carried and transported by the developer carrying member, and is scraped off by the first regulating member. A developer accommodating section for accommodating the developer, and a toner accommodating section adjacent to the developer accommodating section for supplying toner to the developer carrier, wherein a toner concentration of the developer on the developer carrier is provided. A developing device that changes a state of contact between the developer and the toner according to the change of the developer, thereby changing a state in which the developer on the developer carrier takes in the toner. A second regulating member disposed upstream of the regulating member in the direction of transport of the developer on the developer carrying member, and the second regulating member is provided for the developer on the developer carrying member. When the toner concentration increases and the layer thickness of the developer increases, the In order to regulate the passage of the pressurized component, a developing device, characterized in that the distance between the developer carrying member is set is known (see Japanese Patent Laid-Open No. 9-197833).

The developing device takes in the toner consumed by the circulating movement of the developer in the developer accommodating section, and reduces the charge amount of the toner by stirring the toner of the developer and the magnetic carrier. It is to prevent. As a result, it is possible to eliminate the occurrence of abnormal images such as uneven image density and fogging while reducing the size and cost by reducing the number of components.

[0004]

In order to stabilize the toner density in this type of developing device, it is necessary that the supply of the toner be performed in response to the change in the toner density. That is, the amount of the toner taken in the developer accommodating portion is regulated and conveyed by the first regulating member, whereby the force received by the developer is reflected in the regulation of the toner taking-in by the second regulating member. . For that purpose, it is required that the layer thickness of the developer carried and conveyed on the image material carrier changes in accordance with the change in the toner concentration.

Here, the behavior of the developer in the developing device to which the present invention can be applied will be described with reference to FIGS. 10 (a) to 10 (c). In FIG. 10A, when a starting agent consisting of only the magnetic carrier 3a is set in the developing device, the magnetic carrier 3a is magnetically attached to the surface of the developing sleeve 4 as a developer carrier and the inside of the developer accommodating section A. Divided into those housed in. The magnetic carrier 3a accommodated in the developer accommodating portion A circulates in the direction of arrow b by the magnetic force of the magnet roller 5 as the developing sleeve 4 rotates in the direction of arrow a. Then, an interface X is formed at a boundary between the surface of the magnetic carrier 3a magnetically attached to the surface of the developing sleeve 4 and the surface of the magnetic carrier 3a moving in the developer accommodating portion A.

Next, when the toner 3 b is set in a toner storage section (not shown), the toner 3 b is transferred from the toner supply opening 20 to the magnetic carrier 3 a carried on the developing sleeve 4.
Is supplied. Therefore, the developing sleeve 4 is
And a magnetic carrier 3a.

In the developer accommodating portion A, a force acting to stop the conveyance of the developer 3 conveyed by the developing sleeve 4 is exerted due to the presence of the stored developer 3. Then, when the toner 3b present on the surface of the developer 3 carried on the developing sleeve 4 is conveyed to the interface X, the frictional force between the developers 3 near the interface X decreases, and the developer 3 near the interface X decreases. The transport force of the developer 3 decreases, whereby the transport amount of the developer 3 in the vicinity of the interface X decreases.

On the other hand, the developer 3 on the upstream side in the rotation direction of the developing sleeve 4 from the confluence point Y is compared with the developer 3 conveyed by the developing sleeve 4, such as in the developer accommodating section A described above. Since the force for stopping the conveyance does not act, the balance between the amount of the developer 3 conveyed to the junction Y and the amount of the developer 3 conveyed on the interface X is lost, and the developer 3
3B, and as shown in FIG.
Is raised, and the layer thickness of the developer 3 including the interface X increases.

When the interface X of the developer rises, the interface on the second doctor blade 7 side as a second regulating member also gradually rises. It is similar to the fact that as the so-called mountain peak gets higher, the foot spreads, and the altitude of the originally footed foot gets higher. The developer 3 having the increased layer thickness is moved to the second doctor blade regulating position (hereinafter, referred to as a second doctor blade regulating position).
In G2 (referred to as a second regulating position), the second doctor blade 7 scrapes the wafer.

When the developer 3 which has passed through the first doctor blade 6 reaches a predetermined toner density, FIG.
As shown in FIG. 2, the increased amount of the developer 3 which has been scraped off by the second doctor blade 7 to form a layer is supplied to the toner supply opening 2.
0, and the taking-in of the toner 3b ends in this state. At this time, the bulk of the developer 3 is increased due to the increase in the toner concentration in the developer accommodating section A, and the space in the developer accommodating section A is narrowed. The moving speed of circulating in the direction also decreases.

In the layer of the developer 3 formed so as to cover the toner supply opening 20, the developer 3 scraped off by the second doctor blade 7 as shown by an arrow c in FIG. Although it moves and is received by the opposing surface 10b, the opposing surface 10b is inclined downward at an angle α toward the developing sleeve 4 and has a predetermined length. Since the developer 3 can be prevented from dropping into the toner hopper 8 and the amount of the developer 3 can be kept constant at all times, the toner supply can be constantly controlled to be constant.

The self-control of the toner concentration is performed by the above-described mechanism. However, in practice, a change in the layer thickness of the developer corresponding to the change in the toner concentration cannot be obtained.
It has been found that there is a problem that the toner density becomes unstable and image density unevenness occurs.

The inventors of the present invention have investigated the cause of this problem and found that one of the causes is caused by the developer conveying force of the developer carrying member. If there is a portion where the developer carrying force of the developer carrying member is small, the developer carrying force of the developer carrying member decreases in that portion, and the developer carrying force of the developer carrying member as described above is reduced. It is difficult for a ball-colliding state to occur due to a balance with the developer conveying force near the interface X. As a result, even if the toner concentration increases, the desired layer thickness change cannot be obtained in the developer at the second regulating position G2, the toner concentration cannot be controlled properly, and the toner concentration becomes unstable. is there. Further, in the developing device of the above-described system, since the movement of the developer in the developer accommodating portion relatively affects, the position where the developer conveying force is reduced, which is the cause of the above-described problem, is:
It is conceivable that not only the vicinity of the junction Y where the collision state occurs or the upstream side of the junction Y in the developer transport direction but also the downstream side of the junction Y in the developer transport direction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device which is excellent in self-control of toner density and can obtain a good image without image density unevenness. To provide.

[0015]

According to a first aspect of the present invention, there is provided a magnetic recording medium having a magnetic field generating means therein for carrying and transporting a two-component developer containing a toner and a magnetic carrier. A developer carrying member, a first regulating member that regulates an amount of the developer carried and conveyed by the developer carrying member, and a developer accommodating the developer scraped off by the first regulating member. An accommodating portion, and a toner accommodating portion that is adjacent to the developer accommodating portion and supplies toner to the developer carrying member. The toner concentration of the developer on the developer carrying member varies with the developer accommodating portion. A developing device for changing a state of contact with the toner to change a state of taking in the toner of the developer on the developer carrying member, wherein the developer accommodating portion is provided with the developer more than the first regulating member. A second regulating member disposed on the upstream side in the transport direction of the developer on the carrier; The second regulating member has a function of regulating the passage of the increased amount of the developer when the toner concentration of the developer on the developer carrier increases and the layer thickness of the developer increases. In the developing device in which the gap with the developer carrier is set, the minimum value (Fr) of the radial magnetic force of the developer carrier acting on the developer in the developer accommodating portion in the developer carrier.
min) satisfies the following condition (1).

Frmin> 1.5 × 10 ⁻⁷ (N) where the magnetic force in the radial direction is positive in the direction attracted to the developer carrier.

Here, the layer thickness of the developer 3 at the second regulating position G2 will be described. FIGS. 2A to 2C are diagrams illustrating the layer thickness of the developer 3 at the second restriction position G2. When the toner is consumed and the toner concentration decreases, as shown in FIG. 2A, the layer thickness of the developer 3 at the second regulating position G2 decreases, and the second regulating member and the developer 3 A gap is formed between the gaps, from which toner is taken.
Then, as the toner density increases, the second restriction position G2
2B, the layer thickness of the developer 3 gradually increases, and the amount of toner taken in decreases as shown in FIG. 2B. Then, when the toner concentration further increases, the top of the developer 3 having the increased layer thickness reaches the tip of the second regulating member, and the taking in of the toner is stopped. As described above, the fact that the layer thickness of the developer 3 at the second restriction position G2 changes in accordance with the toner concentration is as follows.
This is important for self-control of toner concentration.

The inventors of the present invention determine how the layer thickness of the developer changes at the second regulating position G2 with respect to the change in the toner density. Was compared with the case where FIG. 3 is a graph showing the relationship between the toner concentration and the layer thickness of the developer 3 at the second restriction position G2 in the above two cases. A in the graph
Indicates a case of a good image state without image density unevenness, and B in the graph indicates a case where image density unevenness occurs. From this graph, the layer thickness of the developer at the second restriction position G2 is:
It has been found that a good image is obtained when the toner density changes linearly as a linear function as shown in A, and that the image density unevenness occurs when the toner density changes as a curve as shown in B. The behavior of the developer layer thickness at the second regulation position with respect to the toner concentration is determined by the force that the developer in the developer accommodating portion receives from the developer carrier, that is, the developer conveying force by the developer carrier. It is determined by

According to the first aspect of the present invention, the minimum value Frmin of the magnetic force in the radial direction on the developer carrier acting on the developer in the developer accommodating portion is set to 1.5 × 10 ⁻⁷ (N).
Make it bigger. The developer conveying force greatly affects the radial magnetic force of the radial magnetic force and the tangential magnetic force. That is, under other conditions, the transport force of the developer by the developer carrier is small if the magnetic force in the radial direction is small, and is large if the magnetic force in the radial direction is large. The minimum value Fr of the magnetic force in the radial direction in the developer container.
If there is a portion where min is too small, the developer conveyance force becomes too small in that portion. In the present invention, Frmin is set to 1.5 × 10
By making the value larger than ⁻⁷ [N], a collision state caused by the balance between the developer carrying force of the developer carrying member and the developer carrying force in the vicinity of the interface X occurs in accordance with a change in toner density. I do. As a result, a behavior of the developer layer thickness that is linear with respect to the change in the toner density can be obtained at the second restriction position as shown in FIG.

According to a second aspect of the present invention, in the developing device according to the first aspect, the magnetic field distribution on the surface of the developer carrier in the entire area of the surface of the developer carrier in the developer accommodating portion is provided. It is characterized by satisfying the condition of the following equation (2).

Hr (dHr / dr) + Hs (dHs / dr)> 1
0 ¹⁰ (A ² · m ^-3 ) Hr: Magnetic field in radial direction Hs: Magnetic field in tangential direction

In the developing device according to the present invention, the magnitude of the magnetic field distribution in the developer accommodating portion, which is one of the factors for determining the magnetic force, is defined. The magnetic force in the developer carrier is
It is determined by the magnetic permeability of the developer and the magnetic field distribution in the developer accommodating portion. The radial magnetic force Fr is expressed by the following equation (3).

## EQU5 ## Fr = μ₀G (μ_s-1) (Hr (dHr / dr)
+ Hs (dHs / dr)) Fr: Magnetic force in radial direction G: Volume of developer μ₀: Magnetic permeability of vacuum = 4π × 10^-7  μ_s: Effective magnetic permeability of the developer r: Radius of the developing sleeve In Formula 3, the volume of the developer is 1 to 10 × 10
^-13(m^-3), The effective permeability of the developer is empirically
It is known that it is about 20. From this,
When the magnetic field distribution in the¹⁰(A²・ M^-3)
By satisfying the relationship of Equation 1,
it can.

The invention according to claim 3 is based on claim 1 or 2
In the developing device, the surface of the developer carrier may be provided with irregularities.

According to the third aspect of the present invention, the surface of the developer carrier is provided with irregularities to increase the friction coefficient of the surface of the developer carrier. Here, the force received by the developer includes a centrifugal force generated by rotation of the developer carrier, gravity, a magnetic force from the developer carrier, and a frictional force between the developer carrier and the developer. And are involved. However, among these, centrifugal force and gravitational force are weaker than magnetic force and therefore can be almost ignored, and the developer is carried on the surface of the developer carrier by the radial magnetic force Fr and frictional force on the developer carrier. Is transported. Then, the developer conveying force can be obtained by Expression 4.

## EQU6 ## Developer conveying force = Fr × friction coefficient Accordingly, by increasing the friction coefficient, the developer conveying force can be further increased.

According to a fourth aspect of the present invention, in the developing device of the third aspect, the unevenness on the surface of the developer carrier is formed by sandblasting.

According to a fourth aspect of the present invention, the unevenness on the surface of the developer carrier is formed by sandblasting.
For example, the number of processing steps is reduced as compared with the etching processing that requires a immersion step in a liquid, a cleaning step, and the like, and an increase in the size of an apparatus for forming unevenness is avoided.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an image forming apparatus such as a copying machine, a facsimile, a printer and the like will be described below.

FIG. 1 is a schematic structural view of a developing device 2 to which the present invention can be applied. In FIG. 1, a developing device 2 disposed on a side of a photosensitive drum 1 as a latent image carrier includes a support case 10, a developing sleeve 4 as a developer carrier, a developer accommodating member 11, a first It comprises a first doctor blade 6 and the like as a developer regulating member.

A support case 10 having an opening on the side of the photosensitive drum 1 forms a toner hopper 8 as a toner storage section for storing the toner 3b therein. Near the photosensitive drum 1 side of the toner hopper 8, a developer accommodating member 11 for forming a developer accommodating portion A for accommodating the developer 3 including the toner 3b and the carrier 3a which is a magnetic particle is provided with a support case 10 and It is provided integrally. Here, in this embodiment, a low-resistance carrier 3a having a particle size of 20 to 50 μm is used as the carrier 3a. The support case 10 located below the developer accommodating member 11 has an opposing surface 1.
0b is formed, and a toner supply opening 20 for supplying the toner 3b is provided by a space between a lower portion of the developer accommodating member 11 and the facing surface 10b.
Are formed.

Inside the toner hopper 8, there is provided a toner agitator 9 as toner supply means which is rotated by a driving means (not shown). The toner agitator 9 sends out the toner 3 b in the toner hopper 8 while stirring it toward the toner supply opening 20. Further, on the side of the toner hopper 8 facing the photosensitive drum 1, there is provided a toner end detecting means 10c for detecting when the amount of the toner 3b in the toner hopper 8 becomes small.

In the space between the photosensitive drum 1 and the toner hopper 8, a developing sleeve 4 is provided. The developing sleeve 4 which is driven to rotate in the direction of the arrow by a driving means (not shown) has a magnet roller 5 as a magnetic field generating means, which is disposed inside the developing sleeve 4 so as to be invariable relative to the developing device 2. I have.

A first doctor blade 6 is integrally attached to the side of the developer accommodating member 11 opposite to the side attached to the support case 10. The first doctor blade 6 is arranged with a certain gap kept between its tip and the outer peripheral surface of the developing sleeve 4.

A second doctor blade 7 as a second regulating member is provided in a portion of the developer accommodating member 11 located near the toner supply opening 20. The second doctor blade 7 has a free end that keeps a constant gap with respect to the outer peripheral surface of the developing sleeve 4 in a direction that obstructs the flow of the layer of the developer 3 formed on the surface of the developing sleeve 4, that is, in a free direction. The base is integrally attached to the developer accommodating member 11 with the end facing the center of the developing sleeve 4.

The developer accommodating portion A is configured to have a sufficient space for circulating the developer 3 within a range where the magnetic force of the developing sleeve 4 can reach.

The facing surface 10b is connected to the toner hopper 8
It is formed over a predetermined length so as to be inclined downward from the side toward the developing sleeve 4 side. Thus, when vibration, uneven magnetic force distribution of the magnet roller 5 provided inside the developing sleeve 4, or a partial increase in toner concentration in the developer 3 occur, the second doctor blade 7 and the developing sleeve 4 Developer accommodating section A
Even if the carrier 3a falls inside, the dropped carrier 3a
Is received by the facing surface 10b, moves toward the developing sleeve 4 side, is magnetically attached to the developing sleeve 4 by magnetic force, and is again supplied into the developer accommodating portion A. As a result, it is possible to prevent the amount of the carrier in the developer accommodating portion A from decreasing, and to prevent the image density unevenness in the axial direction of the developing sleeve 4 during image formation.

With the above configuration, the toner 3 sent out by the toner agitator 9 from the inside of the toner hopper 8
b is supplied to the developer 3 carried on the developing sleeve 4 through the toner supply opening 20, and is carried to the developer accommodating section A. Then, the developer 3 in the developer accommodating portion A is carried by the developing sleeve 4 and transported to a position facing the outer peripheral surface of the photosensitive drum 1, and only the toner 3 b is transferred to the photosensitive drum 1.
The toner image is formed on the photosensitive drum 1 by electrostatically coupling with the electrostatic latent image formed thereon.

Next, a description will be given of a change in the layer thickness of the developer 3 and the self-control mechanism of the toner concentration during the formation of the toner image. FIGS. 2A to 2C show a change in the layer thickness of the developer 3 at the second restriction position G2 by the second doctor blade 7. FIG. FIG. 2A shows a state in which the toner concentration has decreased, and FIG.
2 (b) shows a state intermediate between the two. Toner 3b Immediately after the starter including only the magnetic carrier 3a is set in the developing device 2 or when the toner 3b is consumed and the toner concentration is reduced, as shown in FIG. The layer thickness of the developer 3 carried on the developing sleeve 4 at G2 is reduced, and a gap is generated between the second doctor blade 7 and the developer 3, from which the toner 3b is taken.

When the toner 3b is taken into the developer 3 and the toner concentration increases, the layer thickness of the developer 3 at the second regulating position G2 also gradually increases, and as shown in FIG. The amount of capture decreases.

The toner density further increases, and the layer thickness of the developer 3 increases, so that the top of the developer 3 carried on the developing sleeve 4 reaches the tip of the second doctor blade. As a result, the toner 3b intake port is closed, and the toner 3 b
The loading of b stops. However, even at this time, at a position away from the developing sleeve 4 in the developer accommodating portion A,
The developer 3 keeps circulating. As described above,
The toner concentration of the developer 3 can be automatically controlled.

Next, the features of the present invention will be described. Here, in the developing device 2 having the above configuration, the toner supply opening 2
Whether the toner 3b is taken into the developer 3 depends on the layer thickness of the developer 3 on the developing sleeve 4 near zero. FIG. 3 shows how the layer thickness of the developer 3 changes at the second regulation position G2 with respect to the change in the toner density in the case of a good image state without image density unevenness (A in the figure). This is a result of comparison with the case where the occurrence occurs (B in the figure). From this graph, when the layer thickness of the developer 3 at the second restriction position G2 changes linearly as a linear function with respect to the change in toner density as shown at A, a good image is obtained, and as shown at B. It has been found that when the curve 3 changes in a curve, the toner 3b is not taken in when necessary, or the toner 3b is taken in suddenly, causing image density unevenness.

The behavior of the developer layer thickness at the second regulating position G2 with respect to the toner concentration is based on the force that the developer 3 in the developer accommodating portion A receives from the developing sleeve 4, that is, the developer 3 by the developing sleeve 4. Is determined by the transport force of
The conveying force of the developer 3 greatly affects the radial magnetic force Fr among the radial magnetic force Fr and the tangential magnetic force Fs by the developing sleeve 4.

Here, the radial magnetic force Fr can be expressed by Equation 3 as described above.

## EQU7 ## Fr = μ₀G (μ_s-1) (Hr (dHr / dr)
+ Hs (dHs / dr)) Fr: Magnetic force in radial direction G: Volume of developer μ₀: Magnetic permeability of vacuum = 4π × 10^-7  μ_s: Effective permeability of developer r: Radius of developing sleeve

First of all, developer sleeves were manufactured as comparative examples so that the pattern of the force applied to the developer in the developer accommodating section A was changed, and the second developer sleeve was used for various toner concentrations.
The behavior of the layer thickness of the developer 3 at the regulation position G2 was examined. FIGS. 6, 7, 8, and 9 are Comparative Examples 1, 2, 3, and 4, respectively.
The state of the radial magnetic field Hr, the tangential magnetic field Hs, the radial magnetic force Fr and the tangential magnetic force Fs in the developer accommodating section A, and the developer The minimum value of the magnetic force in the storage section A is obtained, and the behavior of the layer thickness of the developer 3 at the second regulation position G2 with respect to the change in the toner density and the state of the toner density unevenness in the obtained image are shown. is there.

4A, the horizontal axis represents the angle (θ) of the developing sleeve 4 with respect to the rotation axis, and the vertical axis represents the magnetic field intensity (1).
0 ⁻⁴ T), and shows the waveforms of the magnetic flux densities of Hr and Hs in the angle range facing the developer accommodating section A. This angle is defined as 0 degree at a position facing the photoconductor on the surface of the developing sleeve, in a direction opposite to the rotating direction of the developing sleeve,
A right angle is 90 degrees, a toner supply opening side is 180 degrees, and a right angle is 270 degrees. Then, the developer accommodating section A includes the first
The angle is 85 to 180 degrees from the portion facing the doctor blade 6 to the toner supply opening side.

4B, the horizontal axis represents the angle of the developing sleeve 4 with respect to the rotation axis, and the vertical axis represents the magnetic force (N).
FIG. 4 shows a magnetic force distribution of Fr and Fs in an angle range facing the inside of the developer accommodating portion A. FIG. However, in this figure, the direction in which the magnetic force in the radial direction is attracted to the developer sleeve is negative. Also, the radial magnetic force F
The resultant force of r and the tangential magnetic force Fs is shown as Ftotal. Ftotal can be easily obtained from the following equation (5).

Ftotal = (Fr ² + Fs ² ) ^1/2

In (a) and (b) above, the area inside the developer accommodating section A is indicated by a dotted frame C. (C) of each figure shows the toner concentration on the horizontal axis and the layer thickness of the developer 3 at the second restriction position G2 on the vertical axis, and shows the toner concentration and the layer thickness of the developer 3 at the second restriction position G2. It shows the result of examining the relationship with. The line Gp in the figure represents the gap between the tip of the second doctor blade and the developing sleeve 4.

Of these Comparative Examples 1 to 4, Comparative Example 1
5. the minimum value of the magnetic force in the developer accommodating portion A is the smallest;
15 × 10 ⁻⁸ (N), Comparative Example 2 was 1.49 × 10
^-7 (N) and Comparative Examples 3 and 4 had the largest minimum magnetic force, which was 2.08 × 10 ^-7 (N). And
The state of toner density unevenness in the images obtained from these was evaluated as x with image density unevenness, △ with some image density unevenness but no problem as an image, and な し without image density unevenness.

From these results, it can be seen that, as the minimum value of the magnetic force in the developer accommodating portion A is larger, the layer thickness of the developer 3 at the second regulating position G2 is linearly closer to the change in the toner density. It can be seen that the curve changes as the minimum value of the magnetic force decreases. The evaluation results of the image density unevenness of Comparative Examples 1 to 4 were X for Comparative Examples 1 and 2, and Δ for Comparative Examples 2 and 3. From these,
The minimum value of the magnetic force is set to 1.5 × 10
If the value is larger than ^-7 [N], it is possible to obtain a good image with relatively little image density unevenness, and the image evaluation becomes better as the layer thickness of the developer 3 is linearly closer to the change in toner density. It turned out to be prone.

The second regulating position G in the developer accommodating portion A
The developer 3 that has taken in the toner 3 b from the second roller 2 is conveyed to the regulating position G <b> 2 by the first doctor blade 6 while standing on the surface of the developing sleeve on the magnetic pole of the magnet roller 5. At this time, if there are a plurality of magnetic poles in a region facing the developer accommodating portion A of the magnet roller 5, the force received by the developer 3 on the first doctor blade 6 is transmitted as it is to the regulation position G2 by the second doctor blade 7. It is not preferable because it becomes difficult to be performed. Therefore, Comparative Example 1 above
In Nos. 1 to 4, only one magnetic pole is provided in the region of the magnet roller 5 facing the inside of the developer accommodating portion A. When the number of magnetic poles is one, the magnetic field tends to increase as the change of the magnetic field with respect to the angle of the magnet roller 5 with respect to the axis, that is, as the rate of change of the magnetic field with respect to the angle increases. In Comparative Examples 1 to 4, the way of magnetizing the magnet roller 5 was changed in various ways, thereby changing the magnetic field discontinuously, thereby reducing the magnetic force at that position. As a result, it is considered that the minimum value of the magnetic force was reduced, which caused image density unevenness.

Here, the mechanism by which the image density unevenness occurs will be described. If there is a portion where the minimum value of the magnetic force is too small in the developer accommodating portion A, a portion where the conveying force of the developer 3 becomes too small is formed in the developer accommodating portion A, and the developer 3 is transferred to the developing sleeve 4. There is a possibility that the transfer by the surface of the developing sleeve may not be performed well due to separation from the developing sleeve.
If the developer 3 cannot be conveyed by the developing sleeve 4 properly, the force applied to the developer 3 by the first doctor blade 6 is not accurately transmitted to the second regulating position G2 and the second regulating position G2
In this case, an ideal change in the layer thickness of the developer 3 cannot be obtained. From the above, in the developer container A,
It is desirable that the magnetic field be continuous without discontinuous changes.

Next, an embodiment according to the present invention will be described. Embodiment 1 FIG. 4 is an explanatory diagram showing the force applied to the developer 3 in the developer accommodating portion A of the developing device 2 according to the embodiment 1 and the presence or absence of image density unevenness. In the present embodiment, only one magnetic pole is provided in the region of the magnet roller 5 opposed to the inside of the developer accommodating portion A, and the change of the magnetic field in the developer accommodating portion A changes continuously and smoothly. I made it.
At this time, the waveforms of the magnetic flux densities of Hr and Hs and the magnetic force distributions of Fr and Fs in the angle range facing the inside of the developer accommodating portion A are as shown in FIGS. In the first embodiment, the surface of the developing sleeve 4 is provided with irregularities by sandblasting, and the surface roughness Rz is set to 2
It was set to 0 μm. As a result, the minimum value of the magnetic force in the developer accommodating section A is larger than the above-mentioned 1.5 × 10 ⁻⁷ [N].
09 × 10 - in ^{7 (N),} the layer thickness of the developer 3 is linearly changes with respect to the change in the toner concentration, evaluation results of the images could be obtained a good image next ○ No uneven image density .

Second Embodiment FIG. 5 is an explanatory diagram showing the force applied to the developer 3 in the developer accommodating section A of the developing device 2 according to the second embodiment and the presence or absence of image density unevenness. In the present embodiment, as in the first embodiment, only one magnetic pole is provided in the area of the magnet roller 5 opposed to the inside of the developer accommodating section A, and the change in the magnetic field in the developer accommodating section A is continuous. To change smoothly. At this time, the waveforms of the magnetic flux densities of Hr and Hs and the magnetic force distributions of Fr and Fs in the angle range facing the developer accommodating portion A are shown in FIG.
(B). Also in Example 2, the surface of the developing sleeve 4 was provided with irregularities by sandblasting, and the surface roughness Rz was set to 20 μm. As a result, the minimum value of the magnetic force in the developer container A is 1.5
5.09 × 10 ⁻⁷ (N) larger than × 10 ⁻⁷ [N]
As a result, the layer thickness of the developer 3 changed linearly with the change in toner density, and the evaluation result of the image was な し without image density unevenness, and a good image could be obtained.

In this embodiment, Comparative Examples 1 to
4 and the first and second embodiments, the developer container A
In the above, the minimum value of the magnetic force Ftotal is referred to, which substantially coincides with the minimum value of the radial magnetic force Fr.

According to the first and second embodiments, the minimum value of the magnetic force in the developer accommodating section A is made larger than 1.5 × 10 ⁻⁷ [N], and the surface of the developing sleeve 4 is sandblasted. By setting the surface roughness Rz to 20 μm, the behavior of the developer layer thickness at the second regulation position G2 with respect to the toner density can be made linear, and a good image without image density unevenness could be obtained. .

[0053]

According to the first to fourth aspects of the present invention, the behavior of the developer layer thickness at the second regulating position G2 with respect to the toner density can be made linear, so that the self-controllability of the toner density is excellent. And an excellent effect that a good image without image density unevenness can be obtained.

In particular, according to the second aspect of the invention, by controlling the magnetic field distribution in the developer accommodating section A to satisfy the condition of Formula 2, the toner density is excellent in self-control and the image density unevenness is reduced. There is an excellent effect that no good image can be obtained.

According to the third aspect of the present invention, since the developer conveying force is further increased by increasing the friction coefficient of the surface of the developer carrying member, the toner density is more self-controllable and the image density is not uneven. There is an excellent effect that a good image can be obtained.

According to the fourth aspect of the present invention, by performing the sand blasting process, the number of processing steps can be reduced as compared with the etching process, and the apparatus can be prevented from being enlarged. In addition to the reduction in processing cost, there is an excellent effect that a good image having excellent self-controllability of toner density and having no image density unevenness can be easily obtained as compared with the etching process.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device to which the present invention can be applied.

FIGS. 2A to 2C are explanatory diagrams showing a relationship between a toner density and a layer thickness of a developer at a second regulation position.

FIG. 3 is a graph showing a relationship between a toner concentration and a layer thickness of a developer at a second regulation position.

FIGS. 4A to 4C are explanatory diagrams showing a force applied to the developer in a developer accommodating portion of the developing device according to the first embodiment and the presence or absence of image density unevenness.

FIGS. 5A to 5C are explanatory diagrams illustrating a force received by a developer in a developer accommodating portion of the developing device according to the second embodiment and the presence or absence of image density unevenness.

FIGS. 6A to 6C are explanatory diagrams illustrating a force received by a developer in a developer accommodating portion of a developing device according to Comparative Example 1 and the presence or absence of image density unevenness.

FIGS. 7A to 7C are explanatory diagrams showing a force applied to a developer in a developer accommodating portion of a developing device according to Comparative Example 2 and the presence or absence of image density unevenness.

FIGS. 8A to 8C are explanatory diagrams showing a force applied to a developer in a developer accommodating portion of a developing device according to Comparative Example 3 and the presence or absence of image density unevenness.

FIGS. 9A to 9C are explanatory diagrams showing a force applied to a developer in a developer accommodating portion of a developing device according to Comparative Example 4 and the presence or absence of image density unevenness.

FIG. 10 is an explanatory diagram of a behavior of a developer in a developing device to which the present invention can be applied.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 developing device 3 developer 3a magnetic carrier 3b toner 4 developing sleeve 5 magnet roller 6 first doctor blade 7 second doctor blade 8 toner hopper 11 developer accommodating member 20 toner supply opening A developer accommodating portion G2 2 regulation position

Continued on the front page (72) Inventor Shunji Kato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hideo Yoshizawa 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shinji Tamaki 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Junichi Terai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Invention Kazuhisa Sudo 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Shinichi Kawahara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Masayuki Yamane Tokyo 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H031 AA01 AA09 AA12 AC10 AC19 AC20 AC33 AC34 AD01 BA04 BA09 EA03 2H077 AA12 AB04 AB13 AD02 AD06 AD13 AD16 AD18 BA08 DA15 DA36 EA01 FA03 FA19

Claims (4)

[Claims] 1. A developer carrier having a magnetic field generating means therein for carrying and transporting a two-component developer containing a toner and a magnetic carrier, and a developing device carried and transported by the developer carrier. A first regulating member for regulating the amount of the developer, a developer accommodating portion for accommodating the developer scraped off by the first regulating member, and a developer adjoining the developer accommodating portion, A toner container for supplying toner, and the toner concentration of the developer on the developer carrier
A developing device for changing a state of contact between the developer and the toner to change a state of toner taken in by the developer on the developer carrier, wherein the developer accommodating portion is provided by a first regulating member; Also has a second regulating member disposed on the upstream side in the transport direction of the developer on the developer carrying member, and the second regulating member has a toner concentration of the developer on the developer carrying member. In a developing device in which a gap with the developer carrier is set in order to restrict the passage of the increased amount of the developer when the layer thickness of the developer increases, A developing device wherein the minimum value (Frmin) of the magnetic force in the radial direction of the developer carrier acting on the developer satisfies the following condition (1). Frmin> 1.5 × 10 ⁻⁷ (N) where the magnetic force in the radial direction is positive in the direction attracted to the developer carrier. 2. The developing device according to claim 1, wherein the magnetic field distribution on the surface of the developer carrying member is expressed by the following expression (2) in all regions within the developer accommodating portion on the surface of the developer carrying member. A developing device satisfying the conditions. Hr (dHr / dr) + Hs (dHs / dr)> 1
0 ¹⁰ (A ² · m ^-3 ) Hr: Magnetic field in radial direction Hs: Magnetic field in tangential direction 3. The developing device according to claim 1, wherein a surface of said developer carrier is provided with irregularities. 4. The developing device according to claim 3, wherein the unevenness on the surface of the developer carrier is formed by sandblasting.