JPH08220887A - Developing device - Google Patents

Abstract

PURPOSE: To stably attain excellent image formation without density unevenness and surface fogging by promptly dispersing supplied toner in the whole of a developer in carrying parts and sufficiently stirring/mixing the supplied toner with carriers in the developer, so as to electrify the supplied toner, at the time of supplying toner to the developer in the carrying parts of a developing device. CONSTITUTION: In the developing device constituted in such a manner that stirring/carrying members 15 and 16 provided with blade members 15b and 16b on the outer peripheries of rotary shafts 15a and 16a are arranged in the carrying parts 13 and 14 carrying the developer, so that the rotary shafts of the stirring/carrying members are rotated to carry the developer in the carrying parts, while stirring the developer, by the blade members 15b and 16b, at least in a part of the insides of the carrying parts, the diameters of the rotations of the blade members 15b and 16b in the stirring/carrying members 15 and 16 are made smaller as it goes from the upstream side to the downstream side in the carrying direction of the developer.

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 a latent image formed on an image bearing member in an image forming apparatus such as a copying machine or a printer, and more particularly to conveying a developer. An agitating / conveying member having a blade member provided on the outer periphery of the rotating shaft is disposed in the conveying unit, and the rotating shaft of the agitating / conveying member is rotated so that the developer in the conveying unit is conveyed while being agitated by the blade member. The present invention relates to a developing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing apparatuses have been used as a developing apparatus used for developing a latent image formed on an image carrier.

As one of such developing devices, while a developer containing a toner and a carrier is mixed and stirred in a conveying section, the developer is conveyed along the conveying section and mixed and stirred in this way. It is known that the developing agent is supplied to the image bearing member on which the latent image is formed by the developing sleeve to perform the development.

Here, in carrying the developer along the carrying section while mixing and stirring the developer in the carrying section as described above, in the conventional developing device, a constant rotation diameter is provided on the outer periphery of the rotary shaft. The stirring / conveying member provided with the blade member is arranged inside the conveying unit, the rotating shaft of the stirring / conveying member is rotated, and the developer is mixed in the conveying unit by the above-mentioned blade member provided on the rotating shaft. It was made to convey, stirring.

However, when the developer is conveyed while being mixed and stirred in the conveying section by the agitating and conveying member having the blade member having a constant rotation diameter provided on the outer periphery of the rotating shaft as described above, the developer is Is always conveyed in a constant state, and toner is consumed by development, so if new toner is replenished to the developer in the transport section, the replenished toner will be well dispersed throughout the developer in the transport section. Is not replenished, and especially when a large amount of toner is consumed due to continuous development of an image having a high image density, so when toner is replenished to the developer in the conveyance section at one time, toner is replenished. There is a problem that only the toner density of the developer in the formed portion becomes extremely high, and unevenness in density occurs in the formed image.

Further, in the developer in the portion where the toner density is increased by replenishing the toner as described above,
Since the replenished toner is not sufficiently mixed and agitated with the carrier in the developer, the toner is not properly charged, and background fog occurs in an image formed by a poorly charged toner that is not sufficiently charged. There is also a problem that defectively charged toner is scattered and the inside of the image forming apparatus is soiled with the toner.

[0007]

SUMMARY OF THE INVENTION According to the present invention, an agitating / conveying member having a blade member provided on the outer periphery of a rotating shaft is provided in a conveying unit, and the rotating shaft of the agitating / conveying member is rotated to develop a developer in the conveying unit. It is an object of the present invention to solve the above-mentioned problems in the developing device in which the toner is conveyed while being stirred by the blade member.

That is, according to the present invention, when new toner is replenished to the developer in the conveying section in the developing device as described above, the developer in the toner replenished section is conveyed along the conveying section. On the way
The replenished toner is quickly dispersed throughout the developer in the transport section, and even if a large amount of toner is replenished at one time, uneven toner concentration in the developer in the transport section may occur. A small amount of the replenished toner and the carrier in the developer are sufficiently mixed and stirred so that they are appropriately charged, resulting in uneven density or a background fog in the formed image. It is an object of the present invention to provide good image formation in a stable manner and to prevent toner that is not properly charged from scattering and contaminating the inside of the image forming apparatus with the toner.

[0009]

According to the present invention, in order to solve the above problems, an agitating / conveying member having a blade member provided on the outer periphery of a rotary shaft is arranged in a conveying section for conveying a developer. In a developing device for rotating the rotating shaft of the stirring / transporting member to transport the developer in the transporting section while stirring by the blade member, the blade member in the stirring / transporting member in at least a part of the transporting section. The rotation diameter of the developer is reduced from the upstream side to the downstream side in the developer conveying direction.

[0010]

In the developing device according to the present invention, the rotary shaft of the agitating / conveying member is rotated and the blade member provided with the agitating / conveying member conveys the developer in the conveying unit. At least in part, the rotation diameter of the blade member in the stirring and conveying member is made smaller from the upstream side to the downstream side in the developer conveying direction. In the above, the amount of the developer conveyed is gradually reduced from the portion having a large rotation diameter of the blade member toward the portion having a small rotation diameter.

When new toner is replenished to the developer in the transport section of the developing device, the developer thus replenished with toner is guided to the portion where the rotation diameter of the blade member is changed, When this developer is sent to the portion of the blade member having the smaller rotation diameter by the blade member having the larger rotation diameter, the amount of the developer conveyed in the portion of the blade member having the smaller rotation diameter is larger than the blade member having the large rotation diameter. Since the amount of developer is less than that of the blade member having a large rotation diameter as described above, a portion of the developer sent by the blade member having a large rotation diameter is transferred from the blade member having a small rotation diameter to a blade member having a large rotation diameter. Then, part of the developer passes through the portion of the blade member with a smaller rotation diameter and is sent to the portion of the blade member with a smaller rotation diameter. By such an operation is performed repeatedly in sequence toward the small part from a large portion of the rotation diameter of the blade member, so that the toner supplied is rapidly dispersed in the developer in the transport section.

When the toner thus replenished is quickly dispersed in the developer in the carrying section, unevenness in toner concentration in the developer in the carrying section is less likely to occur, and the replenished toner is The carrier in the developer is sufficiently mixed and stirred to be appropriately charged.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A developing device according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings, and when the developing device in this embodiment is replenished with toner, the replenished toner is stored in a conveying section. It reveals that it is rapidly dispersed in the developer.

In the developing device of this embodiment, as shown in FIGS. 1A and 1B, a partition wall 11 of which both ends are open is provided in an image carrier (not shown) in the main body 10 of the device. (1) is provided so as to be slightly inclined with respect to the axial direction of the developing sleeve 12 that conveys the developer, and the partition wall 11 allows the inside of the apparatus main body 10 to supply the developing sleeve 12 with the developer. Secondly, the developer is supplied to the first transport unit 13 from the supply port 11a at one end of the partition wall 11.
The partition wall 11 and the partition wall 11 are separated from each other.
The first and second transport units 13 and 14 separated by
The volume of each is reduced from the wide portion toward the narrow portion.

Further, each of the first and second transfer sections 1 described above
The first and second stirring / transporting members 15 and 16 provided with blade members 15b and 16b on the outer circumferences of the rotating shafts 15a and 16a are arranged in the cooling rods 3 and 14, respectively. The rotating shafts 15a and 16a are rotated, and the respective blade members 15b and 16b provided on the outer circumferences of the rotating shafts 15a and 16a are used to move the first and second conveying units 1.
While stirring the developer in each of Nos. 3 and 14, the first
The developer is conveyed in the opposite directions in the conveying section 13 and the second conveying section 14, and the developer is supplied to the supply port 11a at one end of the partition wall 11 and the return port 1 at the other end of the partition wall 11.
1b and the first and second transfer sections 13 and 14 are circulated.

In this embodiment, the first and second agitating / conveying members 15 and 16 are used as the first and second agitating / conveying members 15 and 16 from the upstream side to the downstream side in the developer conveying direction in the first and second conveying sections 13 and 14, respectively. The blade members 15 provided on the outer circumferences of the rotary shafts 15a and 16a from the wide side to the narrow side of the transport units 13 and 14, respectively.
The rotating diameters of b and 16b are each smaller.

When developing the latent image formed on the image bearing member by the developing device of this embodiment, the above-mentioned arrangements are provided in the first and second conveying portions 13 and 14 as described above. Rotating shaft 1 in each stirring and conveying member 15, 16
5a and 16a are rotated to rotate the rotating shafts 15a,
By the blade members 15b and 16b provided on the outer periphery of 16a, as described above, the first and second transport units 13 and 14 are provided.
The developer in the inside is conveyed in the opposite direction while being stirred, and the developer is passed through the supply port 11a and the return port 11b at both ends of the partition wall 11 to each of the first and second conveying sections 1.
It is circulated in the inside of 3, 14 and the 1st conveyance part 13
A part of the developer conveyed while being stirred therein is supplied to the developing sleeve 12, and the developing sleeve 12 conveys the developer to the image carrier to perform the development.

When the toner in the developer is consumed as a result of the development in this way and the toner concentration in the developer is lowered, the development is carried out from the first carrying section 13 to the second carrying section 14. The toner is replenished in the vicinity of the return port 11b for returning the agent.

The developer thus replenished with toner is conveyed while being agitated by the second agitating and conveying member 16 provided in the second conveying section 14 as described above, and is passed through the supply port 11a. The developer is supplied to the first carrying unit 13, and the developer is carried while being stirred by the first stirring and carrying member 15 provided in the first carrying unit 13, and a part of the developer is supplied to the developing sleeve 12 for developing. I decided to do it.

Here, as described above, the rotary shafts 15a, 16
The rotation diameters of the blade members 15b and 16b provided on the outer periphery of a are smaller as the diameter of rotation from the upstream side to the downstream side of the developer transport direction is reduced.
Thus, in the case where the developer to which the toner is replenished is conveyed while being stirred in the first and second conveying portions 13 and 14, as described in the section of the above operation, the blade having a large rotation diameter is used. When the toner-supplemented developer is sent to the blade members 15b and 16b having a small rotation diameter by the members 15b and 16b, a part of the developer is returned to the blade members 15b and 16b having a large rotation diameter. With
A part of the developer is a blade member 15 having a smaller rotation diameter.
b, 16b, and such an operation is repeated in order from the portion of the blade members 15b, 16b having a large rotation diameter to the portion having a small rotation diameter, and the replenished toner is supplied to each of the conveying portions. It became quickly dispersed in the developer in the Nos. 13 and 14.

As a result, when developing is performed using the developing device of this embodiment, even when toner is replenished, the replenished toner is quickly dispersed in the developer in each of the transport portions 13 and 14, and It is unlikely that the toner concentration in the developer in the transport units 13 and 14 becomes uneven, and the replenished toner is sufficiently mixed and agitated with the carrier in the developer to be appropriately charged.
There is no density unevenness or background fog on the formed image, good image formation can be performed stably, and there is no scattering of toner to stain the inside of the image forming apparatus. It was

Next, as in this embodiment, an agitating / conveying member in which the rotation diameter of the blade member provided on the outer periphery of the rotating shaft becomes smaller from the upstream side to the downstream side in the developer conveying direction is used. The toner is replenished using a stirring and conveying member that is provided with a blade member having a constant rotation diameter on the outer circumference of the rotating shaft as in the case where the developer whose toner is replenished is conveyed while stirring. An experiment was conducted to examine the state in which the replenished toner was dispersed in the developer when the developer was conveyed while being stirred, and the state in which the replenished toner was dispersed in the developer was compared.

In this experiment, as the stirring / conveying member A of the embodiment, as shown in FIG. 2, the length (l) of the portion where the blade member was provided on the rotating shaft was 300 mm.
The rotation diameter (d _{1 to} d ₂ ) of the blade member is 40 mm to ₂₀ m from the upstream side to the downstream side in the developer conveying direction.
It gradually decreases to m and the pitch (p) of the blade member is 20 mm
On the other hand, as shown in FIG. 3, in the stirring and conveying member B1 of the conventional example 1 to be compared, the length (l) of the portion where the blade member is provided on the rotating shaft and the pitch (p) of the blade member are compared. Is the same as the above stirring and conveying member A, and the blade member has a constant rotation diameter (d ₁ ) of 20 mm. Further, in the stirring and conveying member B2 of Conventional Example 2, as shown in FIG. The length (l) of the portion of the rotary shaft where the blade member is provided and the pitch (p) of the blade member are the same as those of the stirring and conveying member A described above, and the rotation diameter (d ₂ ) of the blade member is constant.
The one with 0 mm was used.

Then, each of the above-mentioned stirring and conveying members A, B1,
B2 is arranged in each of the transport units having a corresponding size, each of the transport units stores the developer to which the toner is not supplied, and 10 g of the toner is loaded in each of the transport units at the upstream side in the transport direction of the developer. The stirring and feeding members A, B1, and B2 described above are rotated to feed the developer to which the toner is fed by the respective blade members while being mixed and stirred in the respective feeding portions. The change over time in the toner concentration in the developer was measured at the end portion on the downstream side of the rotation shaft.

Here, each of the above-mentioned stirring and conveying members A, B1,
FIG. 5 shows the result when B2 was rotated at 200 rpm, and FIG. 6 shows the result when B2 was rotated at 100 rpm. In these figures, the results when the stirring and conveying member A of the embodiment is used are shown by solid lines, and the stirring and conveying member B1 of Conventional Example 1 in which the rotation diameter of the blade member is 20 mm.
The result of using is the broken line, and the rotation diameter of the blade member is 40
The result of using the stirring and conveying member B3 of Conventional Example 2 having a size of mm is shown by a dashed line.

As a result, the rotation speed was 200 rpm and 10
In any case of 0 rpm, the conventional examples 1 and 2
When the agitating and conveying members B1 and B2 of No. 1 are used, the toner concentration in the developer sharply increases locally.
When the agitating and conveying member B1 is used, the toner concentration is 10
% By weight, when the stirring and conveying member B2 of Conventional Example 2 was used, the toner concentration reached 5% by weight, and the replenished toner was conveyed without being sufficiently dispersed, whereas the stirring and conveying of the example was carried out. When the member A is used, the change in the toner concentration in the developer is much gentler than when the agitating and conveying members B1 and B2 of Conventional Examples 1 and 2 are used, and the toner in the developer is changed. The maximum value of the concentration was as low as 3% by weight, and the replenished toner was sufficiently dispersed and conveyed.

When the agitating / conveying member B1 of Conventional Example 1 is used, the time required for a portion having a density of more than half the measured maximum toner density in the developer to pass is
Rotation speed 200 rpm for 10 seconds, 100 rpm for 20
When the stirring and conveying member B2 of Conventional Example 2 was used for 12 seconds, the rotation speed was 200 rpm for 12 seconds and 200 rpm for 23 seconds, whereas when the stirring and conveying member A of the embodiment was used, the rotation speed was 35 seconds at 200 rpm, 100r
The pm was as long as 70 seconds, which also revealed that the replenished toner was sufficiently dispersed and conveyed.

In the developing device of the above embodiment, the blade members 15b and 16b provided on the outer circumferences of the rotating shafts 15a and 16a are provided in the first and second conveying portions 13 and 14 of the apparatus body 10. The agitating and conveying members 15 and 16 each having a rotational diameter that becomes smaller from the upstream side toward the downstream side in the developer conveying direction are provided.
It is not necessary to provide the stirring and conveying members 15 and 16 as described above in the first and second conveying units 13 and 14, respectively.

For example, as shown in FIG. 7, the rotary shaft 1 is provided in the first carrying section 13 for supplying the developer to the developing sleeve 12.
A conventional stirring / conveying member 17 provided with a blade member 17b having a constant rotation diameter is provided around 7a, while only in the second conveying unit 14 for supplying the developer to the first conveying unit 13, As in the case of the above-described embodiment, the stirring and conveying member 16 in which the rotation diameter of the blade member 16b provided on the outer periphery of the rotating shaft 16a becomes smaller from the upstream side to the downstream side in the developer conveying direction. It is also possible to provide.

Here, also in this developing device, the return port 11 for returning the developer from the first carrying section 13 to the second carrying section 14 when the toner concentration in the developer is lowered.
When toner is replenished in the vicinity of b, and the developer thus replenished with toner is conveyed while being mixed and stirred by the blade member 16b of the stirring and conveying member 16 in the second conveying section 14, As in the case of the developing device according to the embodiment, the replenished toner is quickly dispersed in the developer in the second transport unit 14, which causes uneven toner concentration in the developer. In addition, the replenished toner was sufficiently mixed and stirred with the carrier in the developer to be sufficiently charged.

Further, in the developing device in the above embodiment, the first carrying section 13 and the second carrying section 13 in the main body 10 of the apparatus are used.
Although the developer transport direction is opposite to that of the transport unit 14,
Although the developer is conveyed in a fixed direction in each of the transport units 13 and 14, the developer transport direction is also changed in each of the first and second transport units 13 and 14. It is also possible to do so.

For example, as in the developing device shown in FIG. 8, the first carrying section 13 and the second carrying section 14 are provided in the apparatus main body 10.
The partition wall 11 for separating the developing sleeve 12 and the developing sleeve 12 is opened not only at both end portions thereof but also at the central portion thereof.
In the first transport portion 13 that supplies the developer to the blades, the blade member 18b having a constant rotation diameter is provided on the outer periphery of the rotation shaft 18a.
Is provided, and the direction of the blade members 18b on both sides of the center of the rotating shaft 18a is reversed.
In the second carrying section 14 for supplying the developer to the first carrying section 13, while the blades 8 are arranged, the diameter of the rotation blade is reduced from the center to the end on the outer circumference of the rotary shaft 19a. A member 19b may be provided, and the stirring and conveying member 19 may be arranged in which the directions of the blade members 19b on both sides of the center of the rotating shaft 19a are reversed.

In developing the latent image formed on the image bearing member in this developing device, the above-mentioned first
Also, by rotating the stirring and conveying members 18 and 19 provided in the second conveying units 13 and 14, respectively, in the second conveying unit 14, the developer is fed from the central portion toward both end portions. The developer is fed to the first transport unit 13 from the supply ports 11a at both ends of the partition wall 11 while being stirred, while the first transport unit 13 develops the developer from both ends toward the central portion. The developer is conveyed while being stirred, and the developer is circulated in the first and second conveyance units by returning the developer into the second conveyance unit 14 from the return port 11b at the center of the partition wall 11. First
A part of the developer conveyed while being stirred in the conveying section 13 is supplied to the developing sleeve 12, and the developing sleeve 1
2, the developer is conveyed to the image carrier to develop the image.

Further, when the toner in the developer is consumed as a result of the development in this way and the toner concentration in the developer is lowered, the first transport unit 13 is used.
To replenish the toner in the vicinity of the return port 11b in the central portion of the partition wall 11 for returning the developer to the second transport unit 14,
The developer thus replenished with toner is supplied to the second transport unit 14
The second agitating / conveying member 19 provided inside the second agitating / conveying member 19 conveys the second agitating / conveying member 14 from the center to the end portions on both sides while agitating.

Also in this case, the developer whose toner is replenished by the blade member 19b of the agitating and conveying member 19 whose rotation diameter becomes smaller from the upstream side toward the downstream side in the developer conveying direction is removed. As a result of being conveyed while being stirred in the second conveying section 14, the replenished toner is quickly dispersed in the developer in the second conveying section 14 as in the case of the above-described embodiment, and the toner is dispersed in the developer. The unevenness in the toner concentration is less likely to occur, and the replenished toner is sufficiently mixed and stirred with the carrier in the developer to be sufficiently charged.

[0036]

As described above in detail, in the developing device according to the present invention, at least one of the insides of the conveying section is rotated when the stirring and conveying member is rotated to convey the developer in the conveying section while stirring the developer. In this section, since the rotation diameter of the blade member in the stirring / conveying member is made smaller from the upstream side to the downstream side in the developer conveying direction, when replenishing the developer in the conveying unit with new toner, While the toner-supplemented developer is being conveyed while being stirred in the conveying section by the blade member of the stirring and conveying member, the replenished toner is quickly dispersed in the developer in the conveying section. .

As a result, when the developing device according to the present invention is used, even if a new toner is replenished to the developer in the carrying section, the replenished toner is quickly dispersed throughout the developer in the carrying section. Even when a large amount of toner is replenished at one time, unevenness in the toner concentration in the developer in the transport section rarely occurs, and the replenished toner is sufficiently mixed and stirred with the carrier in the developer. The resulting image is appropriately charged, uneven density is not generated in the formed image, and the background fog is not generated, and good image formation can be stably performed, and toner with poor charging is generated. There is no longer any scattering and soiling of the image forming apparatus with toner.

[Brief description of drawings]

FIG. 1 is a schematic view of the inside of a developing device according to an embodiment of the present invention seen from above and a cross-sectional view of the developing device.

FIG. 2 is a schematic view of a stirring and conveying member used as an example in an experiment of the present invention.

FIG. 3 is a schematic view of a stirring and conveying member used as Conventional Example 1 in the above experiment.

FIG. 4 is a schematic diagram of a stirring and conveying member used as Conventional Example 2 in the above experiment.

FIG. 5 is a graph showing a change with time of the toner concentration in the developer when the agitating and conveying members of the above-described embodiment and the conventional examples 1 and 2 are rotated at 200 rpm to convey the toner-supplemented developer while stirring. It is the figure shown.

FIG. 6 shows changes with time in the toner concentration in the developer when the agitating and conveying members of the above-described embodiment and the conventional examples 1 and 2 are rotated at 100 rpm to convey the toner-supplemented developer while stirring. It is the figure shown.

FIG. 7 shows a developing device according to another embodiment of the present invention, in which a stirring and conveying member in which the rotation diameter of the blade member is reduced from the upstream side to the downstream side in the developer conveying direction is provided only in the second conveying section. It is the schematic which looked at the inside from the top.

FIG. 8 is a schematic view of the inside of a developing device according to another embodiment of the present invention in which the carrying direction of the developer in each carrying section is changed, and a cross-sectional view of the developing device.

[Explanation of symbols]

 10 Device Main Body 13 First Conveying Section 14 Second Conveying Section 15, 16, 19 Stirring Conveying Member 15a, 16a, 19a Rotating Shaft of Stirring Conveying Member 15b, 16b, 19b Blade Member of Stirring Conveying Member

Claims (1)

[Claims] 1. An agitating / conveying member having a blade member provided on the outer periphery of a rotating shaft is arranged in a conveying unit for conveying the developer, and the rotating shaft of the agitating / conveying member is rotated to remove the developer in the conveying unit. In the developing device which conveys while stirring by the blade member, the rotation diameter of the blade member in the stirring and conveying member becomes smaller from the upstream side to the downstream side in the developer conveying direction in at least a part of the conveying section. A developing device characterized by the above.