JPH09114247A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and efficiently release a developer returned to a device body after development from a developer carrying member. SOLUTION: This device is constituted so that plural fixed magnetic poles N and S are arranged in a peripheral direction on the inner peripheral side of a cylindrical developer carrying member 11, the developer carrying member is rotated to carry the developer to an image carrier 1 and attain the development, and the developer remaining on the developer carrying member after the development is returned to the device main body 10, then released from the developer carrying member. In the device this time, the fixed magnetic poles different from each other in polarity are provided in an adjacent relation on the inner peripheral side of the developer carrying member in the device main body. A vertical magnetic force strength curve Iy by the fixed magnetic pole on the upstream side in the rotational direction of the developer carrying member has two inflection points I1 and I2 or more and a horizontal magnetic force strength curve lx between the adjacent fixed magnetic poles different from each other in the polarity has two inflection points I3 and I4 or more.

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 developing an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly to a developing device having a cylindrical shape. A plurality of fixed magnetic poles are arranged in the circumferential direction on the inner peripheral side of the developer transport member, and the developer transport member is rotated to transport the developer to the image carrier to perform development, and the developer transport after development. Return the developer remaining on the member to the inside of the device,
The present invention relates to a developing device adapted to separate the developer from the developer carrying member.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, there are various types of developing apparatuses for supplying a developer to an electrostatic latent image formed on an image carrier to develop the electrostatic latent image. Had been used.

As one of such developing devices, as shown in FIGS. 1 and 2, a cylindrical developer transport member 11 is arranged so as to face the image carrier 1 with a required gap. A magnet member 1 provided with a plurality of fixed magnetic poles N and S on the inner peripheral side of the developer transport member 11 in the circumferential direction.
2 is arranged and the developer transport member 11 is rotated to fix the developer to the fixed magnetic poles N and S provided on the magnet member 12.
After being transported while being restrained by the magnetic force of, and the amount of the developer transported in this way is regulated by the regulation member 13,
There has been one in which this developer is introduced to a position facing the image carrier 1 to perform development.

In this developing device, after the developer is carried to the position facing the image carrier 1 by the developer carrying member 11 as described above, and is developed, the developer remains on the developer carrying member 11. Returned developer into the device body 10,
The above-described operation was repeated to perform development many times.

However, as described above, the magnet member 12
When the developer is carried by the developer carrying member 11 while being restrained by the magnetic force in the developer carrying member 11, the developer returned to the inside of the apparatus main body 10 after the development as described above is not well separated from the developer carrying member 11. , The same developer is repeatedly guided to the image carrier 1 by the developer transport member 11 and used for development, and the toner concentration in the developer decreases,
It is said that a good image cannot be stably obtained because the density of the formed image is lowered, the density of the image is uneven, and the developer is gradually deteriorated to cause fogging of the formed image. There was a problem.

For this reason, conventionally, as in the developing device shown in FIG. 1, the peeling plate 14 is provided in the main body 10 of the device so as to come into contact with the developer transport member 11 rotating as described above. The peeling plate 14 allows the apparatus body 1
The one in which the developer returned to 0 is removed from the developer transport member 11 or the inside of the developer transport member 11 inside the device body 10 as in the developing device shown in FIG. Fixed magnetic poles N and N having the same polarity are provided adjacent to each other on the magnet member 12 in FIG. 1, and the developer returned to the inside of the apparatus main body 10 by the repulsive magnetic field between the fixed magnetic poles N and N is conveyed by the developer transport member 11. It was developed to be released from.

However, when the peeling plate 14 is brought into contact with the surface of the rotating developer conveying member 11 as described above to separate the developer on the developer conveying member 11,
The developer conveying member 11 is damaged by contact with the peeling plate 14, and the developer is conveyed by the peeling plate 14 to the developer conveying member 11.
There is a problem that the developer is pressed upward and the developer is fixed to the surface of the developer transport member 11, and spotted noise is generated in the formed image.

When the fixed magnetic poles N having the same polarity are provided adjacent to each other on the magnet member 12 on the inner peripheral side of the developer carrying member 11 as in the developing device shown in FIG. When the diameter of this magnet member 12 is made small together with the developer transport member 11 in order to make it difficult to balance the magnetic poles of the entire member 12 and in particular to downsize the developing device, the number of fixed magnetic poles N, S in this magnet member 12 is reduced. However, in order to separate the developer from the developer transport member 11 as described above, if the fixed magnetic poles N and N having the same polarity are provided adjacent to each other, the development and the developer The number of fixed magnetic poles that can be used for transporting is reduced, the position where such fixed magnetic poles are provided, etc. are limited, the transportability of developer is deteriorated, and the degree of freedom in designing in the developing device is reduced. Various problems such as were present.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a developing device used for developing an electrostatic latent image formed on an image bearing member in an image forming apparatus such as a copying machine or a printer, which has a cylindrical shape. A plurality of fixed magnetic poles are arranged in the circumferential direction on the inner peripheral side of the developer carrying member, and the developer carrying member is rotated to carry the developer to the image carrier to perform the development. Return the developer remaining on the transport member to the inside of the device,
It is an object of the present invention to solve the above-mentioned various problems in a developing device which is designed to separate the developer from the developer transport member.

That is, according to the present invention, in the developing device as described above, when the developer returned to the inside of the device body after development is separated from the developer carrying member, the developer carrying member is brought into contact with the developer carrying member as in the conventional case. A release plate on the
Even if the fixed magnetic poles having the same polarity are not provided adjacent to the magnet member on the inner peripheral side of the developer carrying member, the developer returned to the inside of the apparatus main body is easily and efficiently separated from the developer carrying member. The task is to do so.

[0011]

According to the present invention, in order to solve the above problems, a plurality of fixed magnetic poles are arranged in the circumferential direction on the inner peripheral side of a cylindrical developer conveying member. The developer conveying member is rotated to convey the developer to the image carrier to perform development, and the developer remaining on the developer conveying member after the development is returned to the inside of the apparatus main body, and the developer is conveyed from the developer conveying member. In the developing device which is to be detached, fixed magnetic poles of different polarities are provided adjacent to each other on the inner peripheral side of the developer transporting member in the main body of the device, and fixed magnetic poles on the upstream side in the rotation direction of the developer transporting member are perpendicular to each other. The magnetic force intensity curve has two or more inflection points, and the horizontal magnetic force intensity curve between adjacent fixed magnetic poles of different poles has two or more inflection points. The inflection point here is a point at which the second derivative of the magnetic force intensity curve becomes zero.

Here, the magnetic attraction force by which the fixed magnetic pole restrains the developer on the developer carrying member has a stronger vertical magnetic force at this fixed magnetic pole, and becomes stronger as the change of the vertical magnetic force becomes more rapid, and the horizontal magnetic force becomes stronger. While it is strong even when it is weak, the vertical magnetic force is weak, and weak when the change in the vertical magnetic force is small, and weak when the horizontal magnetic force is strong.

When a fixed magnetic pole having a different polarity is provided on the inner peripheral side of the developer conveying member in the main body of the apparatus like the developing device according to the present invention, the fixed magnetic pole on the upstream side in the rotation direction of the developer conveying member is used as a vertical pole. When the magnetic force intensity curve has two or more inflection points and the horizontal magnetic force intensity curve between the adjacent fixed magnetic poles of different poles has two or more inflection points, the first inversion force with high vertical magnetic force intensity is obtained. At the inflection point, the vertical magnetic force rapidly changes in a strong state, and at this first inflection point, a strong magnetic attraction force acts on the developer, and the developer is strongly restrained on the developer conveying member. To be done. On the other hand, in the portion of the second inflection point where the perpendicular magnetic force strength is weak,
Its perpendicular magnetic force is weak and its change is small,
At the inflection point, the magnetic attraction force suddenly decreases and the force for restraining the developer on the developer transport member becomes very weak, and the developer transport member causes the developer to move to the second inflection point. When guided to the portion, this developer comes to be separated from the developer transport member.

Therefore, in the developing device according to the present invention, when the developer returned to the inside of the device body after development is released from the developer transport member, as in the conventional case,
It is not necessary to provide a peeling plate so as to come into contact with the developer carrying member, or to provide adjacent fixed magnetic poles having the same pole on the magnet member on the inner peripheral side of the developer carrying member.

Further, in order to efficiently separate the developer after development, which has been returned into the apparatus main body as described above, from the developer conveying member between the fixed magnetic poles of different polarities adjacent to each other as described above, In the vertical magnetic force strength curve of the fixed magnetic pole on the upstream side in the rotation direction of the developer transport member, the vertical magnetic force at the first inflection point where the vertical magnetic force strength is high is IF ₁ , and the vertical magnetic force at the second inflection point where the vertical magnetic force strength is low is when the IF _2, the ratio of the vertical force IF ₂ at the second inflection point with respect to the vertical force IF ₁ at the first inflection point (IF ₂ / I
F ₁ ) is small, and the angle formed by the first inflection point and the second inflection point with respect to the axis of the developer transport member is φ.
(Degrees), the angle of φ is preferably large, and the condition of IF ₂ / IF ₁ <0.8 IF ₂ / IF ₁ <0.05φ is satisfied, and more preferably IF ₂ / Make sure that the condition of IF ₁ <0.03φ is satisfied.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a developing device according to the present invention will be specifically described below with reference to the accompanying drawings.

Here, as shown in FIG. 3, the developing device in this embodiment also faces the image carrier 1 with a required space therebetween, as in the conventional developing device shown in FIGS. 1 and 2. A cylindrical developer transport member 11 is provided on the inner surface of the developer transport member 11, and a plurality of fixed magnetic poles N and S are provided on the inner peripheral side of the developer transport member 11.
Are arranged in the circumferential direction, and the developer carrying member 11 is rotated to carry the developer while restraining the developer by the magnetic force of the fixed magnetic poles N and S provided on the magnet member 12. After the amount of the developer conveyed in this way is regulated by the regulation member 13, the developer is guided to a position facing the image carrier 1 to perform the development.

Then, after the developer is guided to the image carrier 1 and developed as described above, the developer on the developer transport member 11 is returned into the apparatus main body 10 by the rotation of the developer transport member 11. The developer thus returned is separated from the developer transport member 11.

Here, in the developing device in this embodiment, as shown in FIGS. 3 and 4, the magnet on the inner peripheral side of the developer carrying member 11 in the device main body 10 on the opposite side of the image carrier 1. The member 12 is provided with an N pole and an S pole having different polarities so as to be adjacent to each other, and between the N pole on the upstream side in the rotation direction of the developer transport member 11 and the S pole on the downstream side, the perpendicular magnetic force at the N pole is provided. The intensity curve Iy has two inflection points I ₁ and I ₂ , and the horizontal magnetic force intensity curve Ix between the N pole and the S pole also has two inflection points I ₃ and I _4. I have to.

As described above, in the apparatus main body 10 on the opposite side of the image carrier 1, the magnet member 12 on the inner peripheral side of the developer carrying member 11 is provided with the N pole and the S pole. Between them, the vertical magnetic force intensity curve Iy due to the N pole on the upstream side in the rotation direction of the developer transport member 11 has two inflection points I ₁ and I ₂ , and the horizontal magnetic force intensity curve Ix also changes. By providing the inflection points I ₃ and I ₄ , in the perpendicular magnetic force intensity curve Iy due to the N pole, the first inflection point I ₁ where the perpendicular magnetic force intensity is high on the upstream side in the rotation direction of the developer transport member 11. Is abruptly changed in a state where the vertical magnetic force is strong, a strong magnetic attraction force acts on the developer, and the developer is strongly restrained on the developer transport member 11, while the rotation direction of the developer transport member 11 is increased. Second inflection with weak vertical magnetic strength on the downstream side In the part of I _2, the change weak vertical magnetic force decreases, the magnetic attraction force decreases rapidly with respect to the developing agent, the force for restraining the developer on the developer carrying member 11 is significantly weakened.

Then, as described above, the developer is applied to the image carrier 1.
After conducting the development to perform development, the developer remaining on the developer transport member 11 is returned to the inside of the apparatus main body 10 by the rotation of the developer transport member 11, and this developer has a perpendicular magnetic force intensity curve by the N pole. When guided to the second inflection point I ₂ of Iy,
The magnetic attraction force to the developer sharply decreases, and at the portion of the second inflection point I ₂ , the developer is conveyed to the developer transport member 11
You will be separated from the top.

Next, in the apparatus main body 10 on the opposite side of the image carrier 1 as described above, the magnet member 12 provided on the inner peripheral side of the developer carrying member 11 has an N pole and an S pole having different polarities. When adjacent to each other, the state of the vertical magnetic force intensity curve Iy of the N pole on the upstream side in the rotation direction of the developer transport member 11 is changed to change the developer transport member 11.
Vertical force IF ₁ in the first inflection point I ₁ in the rotation direction upstream side of the first with respect to the axis of the second inflection point vertical force in I ₂ IF ₂ and the developer conveying member 11 on the downstream side Angle φ formed by the inflection point I ₁ and the second inflection point I _2.
Performs development using a developing device which can appropriately change (degrees), the ratio of the vertical force IF ₂ in the second inflection point I ₂ relative to the vertical force IF ₁ in the first inflection point I ₁ (IF ₂ / I
The influence of the angle φ (degree) formed by the first inflection point I ₁ and the second inflection point I ₂ with respect to F ₁ ) and the axis of the developer transport member 11 is examined.

[0023] Then, a vertical force IF ₁ in the first inflection point I ₁ as described above, the vertical force IF ₂ in the second inflection point I _2, first with respect to the axis of the developer conveying member 11 1 When developing using each developing device in which the value of the angle φ (degree) formed by the inflection point I ₁ and the second inflection point I ₂ is changed, a black image is developed on each A3 sheet, The difference in image density between the leading edge and the trailing edge of the developed paper was measured to evaluate the detachability of the developer from the developer transport member 11, and the results are shown in FIG. In this figure, when the image density difference is 0 to 0.1, the rank is A, when the image density difference is 0.1 to 0.2, the rank is B, and the image density difference is 0.2 to 0.3. In the case of C, the image density difference is 0.
The case of 3 or more is shown as x rank.

[0024] with this result, the ratio of the vertical force IF ₂ vertical force IF ₁ in the first inflection point I ₁ of the second inflection point _{I 2 (IF 2 / IF 1} ) is 0.8 or less, IF
The relationship between ₂ / IF ₁ and φ (degree) is IF ₂ / IF ₁ <0.0
In the case of 3φ, there is almost no density difference in the developed image, a good image without density unevenness is obtained, and IF
_In the case of ₂ / IF ₁ <0.05φ, there was a slight density difference in the developed image, but there was no problem in practical use. On the other hand, when IF ₂ / IF ₁ > 0.05φ, the density difference in the developed image was large.

[0025]

As described above in detail, in the developing device of the present invention, the fixed magnetic poles of different polarities are provided adjacent to each other on the inner peripheral side of the developer conveying member in the main body of the device. The vertical magnetic field strength curve of the fixed magnetic pole on the upstream side in the rotation direction has two or more inflection points, and the horizontal magnetic field strength curve between the adjacent fixed magnetic poles of different poles is also 2.
Since the above-mentioned inflection point is provided, the developer returned to the inside of the apparatus main body after the development can be efficiently separated from the developer transport member between the adjacent fixed magnetic poles of different polarities. As described above, it is not necessary to provide the peeling plate so as to contact the developer carrying member or to provide the magnet member on the inner peripheral side of the developer carrying member with the fixed magnetic poles having the same pole adjacent to each other.

As a result, in the developing device according to the present invention, the developer conveying member is damaged due to contact with the peeling plate, or the developer is pressed against the developer conveying member by the peeling plate and is brought to the surface of the developer conveying member. It did not occur that sticking, the number of fixed magnetic poles that can be used for developing or carrying the developer is reduced, the developer carrying property is deteriorated, and the degree of freedom in designing the developing device is not reduced.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a conventional developing device in which a developer returned to the inside of the apparatus main body is removed from a developer transporting member by a peeling plate provided so as to contact the developer transporting member.

FIG. 2 is a conventional structure in which fixed magnetic poles of the same pole are provided adjacent to each other on a magnet member on the inner peripheral side of a developer transport member so that the developer returned to the inside of the apparatus main body can be separated from the developer transport member. 2 is a schematic explanatory view of the developing device of FIG.

FIG. 3 is a schematic explanatory view showing a developing device according to an embodiment of the present invention.

FIG. 4 is a schematic view showing states of a vertical magnetic force intensity curve and a horizontal magnetic force intensity curve between fixed magnetic poles provided on a magnet member on an inner peripheral side of a developer transporting member in the main assembly of the developing device in the above embodiment. FIG.

FIG. 5 is a diagram showing a vertical magnetic force intensity curve of a fixed magnetic pole provided on a magnet member on an inner peripheral side of the developer carrying member in the developing device according to the above-described embodiment by a fixed magnetic pole on the upstream side in the rotation direction of the developer carrying member. Vertical magnetic force I at one inflection point
The influence of F ₁ and the perpendicular magnetic force IF ₂ at the second inflection point and the angle φ formed by the first inflection point and the second inflection point with respect to the axis of the developer transport member on the image is described. It is the figure shown.

[Explanation of symbols]

1 image carrier 10 apparatus main body 11 developer carrying member 12 magnet member N, S fixed magnetic pole Iy vertical force intensity curve I _1, I ₂ inflection point in the vertical force intensity curve Ix horizontal force intensity curve I _3, I ₄ horizontal force Inflection point in intensity curve

Claims (2)

[Claims] 1. A plurality of fixed magnetic poles are arranged in the circumferential direction on the inner peripheral side of a cylindrical developer carrying member, and the developer carrying member is rotated to carry the developer to an image carrier to develop it. In the developing device, the developer remaining on the developer carrying member after development is returned to the inside of the apparatus main body, and the developer is separated from the developer carrying member. The fixed magnetic poles of different polarities are provided adjacent to each other on the inner peripheral side of the magnetic pole, and the perpendicular magnetic force intensity curve by the fixed magnetic poles on the upstream side in the rotation direction of the developer transport member has two or more inflection points, and A developing device, wherein the horizontal magnetic intensity curve between fixed magnetic poles has two or more inflection points. 2. The developing device according to claim 1, wherein
In the vertical magnetic force intensity curve by the above-mentioned fixed magnetic pole on the upstream side in the rotation direction of the developer transport member,
The perpendicular magnetic force at the inflection point is IF ₁ , the perpendicular magnetic force at the second inflection point where the perpendicular magnetic force strength is low is IF ₂ , and the first inflection point and the second inflection point with respect to the axis of the developer transport member described above. When the angle formed by and is φ (degrees), the perpendicular magnetic force IF _{2 at} the second inflection point with respect to the perpendicular magnetic force IF _{1 at} the first inflection point
The ratio of (IF ₂ / IF _{1) is, IF 2 / IF 1 <0.8} IF 2 / IF 1 < satisfy the conditions developing apparatus is characterized in the 0.05Fai.