JP2001100516A - Developing device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing the deterioration of toner by avoiding continuous and repeated application of stress to the same toner by a regulating blade, and obtain an excellent image without void at the time of forming a high-density image. SOLUTION: This developing device 10 is equipped with a container 16 having an aperture part 12 and a toner storage part 14, a developing roller 18 arranged at the aperture part 12 and rotating so that its surface on the storage part 14 side moves from top to down downside in a vertical direction, a recovery roller 26 rotating while coming in contact with the surface of the roller 18 moving from the upside to the downside in the vertical direction, a supply roller 32 rotating while coming in contact with the surface of the roller 18 moving from the upside to the downside in the vertical direction at the lower side in the vertical direction with respect to the roller 18, and a regulating blade 38 arranged to come in contact with the surface of the roller 18 on a downstream side in the rotating direction of the roller 18 with respect to the roller 32.

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 or a printer.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. Hei 9-236979 discloses a developing device 70 shown in FIG. The developing device 70 includes an opening 72 facing the image carrier 2 and a toner storage 74 for storing toner as a developer.
And a container 76 having: Opening 7 of container 76
2, a developing roller 78 is disposed so as to face the image carrier 2 in a non-contact state or a contact state, and is driven to rotate in the arrow 80 direction.

In the container 76, a buffer 82 is formed between the developing roller 78 and the toner storage 74.
In the buffer unit 82, a supply roller 84 and a collection roller 86 are arranged. The supply roller 84 contacts the developing roller 78 in the direction of arrow 88, that is, the developing roller 78.
It is driven to rotate in the opposite direction. on the other hand,
The collection roller 86 is disposed below the supply roller 84 in the vertical direction.
The developing roller 78 is driven to rotate in the same direction as the developing roller 78.

A regulating blade 92 is provided downstream of the supply roller 84 in the rotation direction of the developing roller 78.
8 is provided in contact with the surface. Also, the collection roller 86
On the upstream side in the rotation direction of the developing roller 78, a seal member 94 is provided in contact with the surface of the developing roller 78. Further, in the toner storage section 74, a toner conveying member 96 having a conveying blade 96a is provided so as to be rotatable in the direction of arrow 98.

In the developing device 70 having the above configuration, the toner fed from the toner storage 74 to the buffer 82 by the rotation of the toner conveying member 98 is supplied to the supply roller 84.
Are sequentially supplied to the surface of the developing roller 78 by the rotation of.
The toner supplied to the surface of the developing roller 78 moves in accordance with the rotation of the developing roller 78, and is frictionally charged to a predetermined polarity by the regulating blade 92, and becomes a thin layer having a predetermined thickness. Thereafter, the toner held by the developing roller 78 in a thin layer state is conveyed to a position facing the image carrier 2 according to the rotation of the developing roller 78, where the toner of the electrostatic latent image formed on the surface of the image carrier 2 is formed. Provided for development.

The toner remaining on the developing roller 78 without being subjected to the development is conveyed in accordance with the rotation of the developing roller 78, and after passing through the contact portion with the seal member 94,
The toner is scraped off from the developing roller 78 by the collecting roller 86 and collected from the buffer 82 to the toner storage 74.

[0007]

In the developing device 70, when the amount of toner contained in the toner storage 74 is small and the powder pressure of the toner in the buffer 82 is low, the collecting roller 86 scrapes off the developing roller 78. The removed toner is separated from the collecting roller 86 and is transferred to the buffer 82.
From the toner storage 74.

However, when a large amount of toner is stored in the toner storage section 74, the gravity action causes the toner in the buffer section 82 around the collection roller 86 disposed below the supply roller 84 in the vertical direction. Powder pressure increases. Then, the toner that has moved from the developing roller 78 to the surface of the collection roller 86 cannot separate from the collection roller 86 due to the pushing force of the surrounding toner,
It is transported while remaining on the surface of the collection roller 86, and adheres again to the developing roller 78. In other words, when the collection failure by the collection roller 86 occurs and the image is close to the white background of the sheet, that is, the B / W ratio (the ratio of the area of the image to the area of the sheet,
(The same applies to the following), the toner on the developing roller 78 is not consumed much, and the same toner circulates between the surface of the developing roller 78 and the surface of the collecting roller 86.

As a result, the toner is repeatedly subjected to the stress by the regulating blade 92, and the toner is deteriorated (such as burying or detaching of the post-processing material), thereby decreasing the fluidity of the toner. The toner stagnates at the contact portion between the developing roller 78 and the developing roller 78, and eventually the toner adheres to the regulating blade 92, so that a uniform thin toner layer cannot be formed on the surface of the developing roller 78, resulting in deterioration of image quality. Will be.

On the other hand, in order to reduce the toner powder pressure applied to the collection roller 86, the toner storage 74 supplies
Although it is possible to reduce the amount of toner transported to No. 2, if the amount of toner transported is too small, the supply of toner cannot catch up with a high-density image, that is, when the B / W ratio is high, causing white spots in the image.

Accordingly, an object of the present invention is to prevent the same toner from being continuously and repeatedly subjected to stress by the regulating blade, thereby preventing the deterioration of the toner, and preventing the toner from deteriorating even when a high-density image is formed. An object of the present invention is to provide a developing device capable of obtaining an image.

[0012]

According to a first aspect of the present invention, there is provided a developing device having an opening facing an image carrier and a developer storing portion provided at a distance from the opening. A container, a developer carrier disposed in the opening and rotated so that a surface on the side of the developer storage unit moves vertically downward from above, and to which a developing bias is applied; A developer recovery member that rotates while contacting the surface of the developer carrier that moves downward from above, and a developer that moves downward from above in the vertical direction on the lower side in the vertical direction with respect to the developer recovery member. A developer supply member that rotates while being in contact with the surface of the developer carrier; and a developer supply member that is arranged so as to contact the surface of the developer carrier on the downstream side in the rotation direction of the developer carrier with respect to the developer supply member. And a regulating member. Than it is.

In the developing device according to the present invention, it is preferable that the developer recovery member rotates in the same direction as the developer carrier, and the developer supply member rotates in a direction opposite to the developer carrier.

Further, in the developing device of the present invention, a recovery bias voltage biased to the opposite side of the developer charging polarity with respect to the development bias is applied to the developer recovery member, and the developer bias is applied to the developer bias. A supply bias voltage biased to the same polarity as the charging polarity may be applied to the developer supply member.

Further, in the developing device of the present invention, it is preferable to provide a charge removing member which comes into contact with the developer on the developer carrier at a position upstream of the developer recovery member in the rotation direction of the developer carrier. . In this case, a discharging bias voltage may be applied to the discharging member.

Furthermore, in the developing device of the present invention, during non-image formation, the supply bias voltage may be a voltage biased to the opposite polarity to the developer charging polarity with respect to the developing bias.

In the developing device according to the present invention, the developer storage unit and the developer supply member are arranged so as to be separated from each other, and the developer in the developer storage unit is fed toward the developer supply member. May be provided with a partition member having an opening.

Further, in the developing device of the present invention, a scraper for scraping off the developer collected from the developer carrier and transferred to the surface of the developer collecting member may be provided.

[0019]

According to the developing device of the present invention, the surface of the developer carrier on the side of the developer storage portion rotates so as to move vertically from the upper side to the lower side, and the developer rotates while contacting the surface. The collection member and the developer supply member are disposed vertically on the upper side and the lower side. As a result, regardless of the amount of developer stored in the developing device, the developer collecting member disposed on the upper side in the direction of gravity is little or no affected by the powder pressure of the developer, and the lower side in the direction of gravity. The developer powder is sufficiently applied to the developer supply member disposed at the position. Therefore, the developer scraped from the developer carrier by the rotating developer recovery member is easily separated from the developer recovery member and collected in the developer storage section, while the developer supply member is supplied to the developer carrier. Thus, sufficient developer supply can be performed. As a result, the same developer is not continuously and repeatedly subjected to stress by the regulating member, so that deterioration of the developer can be prevented, and a satisfactory image without white spots can be obtained because the developer is sufficiently supplied. Can be.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a developing device 10 according to one embodiment of the present invention. The developing device 10 includes a container 16 having an opening 12 facing the image carrier 2 and a toner storage unit 14 provided at a distance from the opening 12. Toner storage unit 1
4 stores and stores a toner (not shown) as a developer. In this embodiment, for example, a polyester-based negatively chargeable toner having an average particle size of 8.5 μm is used as the toner.

At the opening 12 of the container 16, a developing roller 18, which is a developer carrier, is disposed so as to face the image carrier 2 in a non-contact or contact state. The developing roller 18 is driven to rotate in the direction of the arrow 20, whereby the surface of the developing roller 18 on the toner storage unit 14 side moves vertically downward from above. Further, a developing bias Vb is applied to the developing roller 18 by a power supply 22.

In the container 16, a buffer section 24 is formed between the developing roller 18 and the toner storage section 14.
A collection roller (developer collection member) 26 is disposed in the buffer section 24 at the upper side in the vertical direction. Collection roller 26
Is a developing roller 18 that moves vertically downward from above.
While contacting the surface of the developing roller 1
8 is driven to rotate in the same direction. Also, the collection roller 30
Is made of a conductive or semiconductive material, and a recovery bias voltage Vre biased to the opposite polarity (positive side in this embodiment) to the toner charging polarity with respect to the developing bias Vb is applied by the power supply 30. .

In the buffer section 24, a supply roller (developer supply member) 32 is disposed vertically below the recovery roller 26. The supply roller 32 is driven to rotate in a direction indicated by an arrow 34, that is, in a direction opposite to the direction of the developing roller 18, while being in contact with the surface of the developing roller 18 that moves downward from above in the vertical direction. The supply roller 32 is made of a conductive or semiconductive material, and has the same polarity as the toner charging polarity with respect to the developing bias Vb (the negative polarity side in this embodiment).
The supply bias voltage Vsup is biased by the power supply 36.

A regulating blade (regulating member) 38 is disposed downstream of the supply roller 32 in the rotation direction of the developing roller 18 so as to contact the surface of the developing roller 18.

An electricity removing member 40 is provided upstream of the collection roller 26 in the rotation direction of the developing roller 18. The charge removing member 40 is pressed against the surface of the developing roller 18 by a seal member 42 made of an elastic foam, felt, or the like for preventing toner leakage from the developing device 10. Further, the charge removing member 40 is made of a material that is biased to the same polarity side in the charging series with respect to the toner and has conductivity, and a charge removing bias voltage Vs is applied by the power supply 44. In the present embodiment, for example, a sheet-shaped member obtained by kneading carbon with a Teflon material that is biased toward the negative electrode side in the charging series with respect to the toner is used as the charge removing member 40.

In the toner storage section 14, a toner conveying member 46 having a conveying blade 46a is provided so as to be rotatable in the direction of arrow 48.

Next, the operation of the developing device 10 having the above configuration will be described. The toner fed from the toner storage unit 14 to the buffer unit 24 by the rotation of the toner conveying member 46 is supplied to the developing roller 18 by the rotation of the supply roller 32.
Are sequentially supplied to the surface. At this time, since the supply roller 32 is disposed on the lower side in the vertical direction, the supply roller 32 receives a large powder pressure of the toner from the periphery thereof due to the gravitational action, so that the toner can be sufficiently and reliably supplied to the developing roller 18. . The supply roller 32 and the developing roller 18 rotate in opposite directions to each other, and since the surfaces of the rollers 32 and 28 move in the same direction at the contact portions, the toner is effectively applied to the developing roller 18. Can be adhered to. Further, the supply roller 32 has a supply bias voltage Vsup biased to the negative polarity side with respect to the developing bias Vb.
Is applied, the supply roller 32 and the developing roller 1
The toner frictionally charged to the negative polarity in the nip portion between the toner particles 8 is electrostatically attracted to the developing roller 18 on the relatively positive side, thereby achieving efficient toner supply.

The toner supplied to the surface of the developing roller 18 is conveyed by the rotation of the developing roller 18 and passes through the contact portion with the regulating blade 38. At this time, the toner is further triboelectrically charged to the negative polarity by the regulating blade 38, and the amount thereof is regulated to a thin layer state having a predetermined thickness.

The toner held on the surface of the developing roller 18 in a thin layer state is conveyed to a position facing the image carrier 2 according to the rotation of the developing roller 18, where the toner formed on the surface of the image carrier 2 is formed. Provided for latent image development.

The toner remaining on the developing roller 18 without being used for development is conveyed as the developing roller 18 rotates and comes into contact with the charge removing member 40. At this time, since the charge removing member 40 is made of a material higher in the charging series than the toner in the same polarity as described above, the charge removing member 4
Due to the friction with 0, the charge amount of the toner on the developing roller 18 decreases. Further, the charge removing member 40 has a charge removing bias voltage Vs.
Is applied to the developing roller 18.
The lowering of the charge amount of the above toner is promoted. The toner having the reduced charge amount has a weak electrostatic adhesion to the developing roller 18 and is easily separated.

The toner that has passed through the contact portion with the charge removing member 40 is conveyed by the rotation of the developing roller 18 and reaches the nip between the collecting roller 26 and the developing roller 18. In the nip portion, the toner on the developing roller 18 is scraped off by the rotating collecting roller 26. At this time, the toner whose adhesive force to the developing roller 18 is weakened due to a decrease in the charge amount by the charge removing member 40 is easily scraped off. Further, the collection roller 26 and the developing roller 18 rotate in the same direction with each other.
Because each surface of 6, 18 is moving in the opposite direction,
The collection roller 26 can effectively scrape off the toner on the developing roller 18. Further, since the collecting bias voltage Vre biased to the positive polarity side with respect to the developing bias Vb is applied to the collecting roller 26, the negative toner on the developing roller is relatively positive. The toner is electrostatically attracted, so that efficient toner collection can be realized.

The relationship between the supply bias voltage Vsup and the recovery bias voltage Vre is as follows: Vsup> Vr in the toner charging polarity direction (negative direction in this embodiment).
It is preferable to set e. Further, the static elimination bias voltage Vs is Vsup> in the charging polarity direction of the toner.
It may be set to a value that satisfies Vre> Vs.

The toner scraped off from the developing roller 18 and moved onto the collecting roller 26 separates from the collecting roller 26 while being transported as the collecting roller 26 rotates. At this time, since the collecting roller 26 is disposed on the upper side in the vertical direction, the powder pressure of the toner from the surroundings due to the gravitational action is small or no, and the collecting roller 26
The separation of the toner from the toner is not hindered by the surrounding toner powder pressure.

The toner separated from the collection roller 26 is collected by the buffer unit 24 and the toner storage unit 14 and mixed with the toner there, and then supplied to the supply roller 32 again.

As described above, according to the developing device 10 of the present embodiment, the surface of the developing roller 18 on the side of the toner storage section 14 rotates so as to move vertically from the upper side to the lower side. The collection roller 26 and the supply roller 32 that rotate while contacting each other are arranged vertically on the upper side and the lower side. Thus, regardless of the amount of toner stored in the developing device 10, the recovery roller 26 disposed on the upper side in the direction of gravity has little or no effect due to the powder pressure of the toner, and is disposed on the lower side in the direction of gravity. The supplied roller 32 is sufficiently subjected to the powder pressure of the toner.
Therefore, the toner scraped off from the developing roller 18 by the rotating collecting roller 26 is easily separated from the collecting roller 26 and collected in the toner storage unit 14, while the developing roller 18 is supplied with sufficient toner by the supply roller 32. It can be carried out. As a result, the same toner is not continuously and repeatedly subjected to the stress by the regulating blade 38, so that the deterioration of the toner can be prevented. Further, since the toner is sufficiently supplied, a good image without white spots can be obtained. .

In the developing device 10 described above,
The collection and supply of toner can be performed more efficiently by frictional charging of the collection roller 26 and the supply roller 32.
In this case, the collection roller 26 is preferably made of a material that removes the charge of the toner in order to weaken the adhesive force with the developing roller 18.
8 is preferably formed of a material that charges the toner to a predetermined polarity (negative polarity in the present embodiment) in the nip portion between them. That is, when the charging series of the collection roller 26 and the supply roller 32 is compared, it is preferable that the charging series of the collection roller 26 be higher than the charging series of the supply roller 32 in the toner charging direction.

When an image having a low B / W ratio is formed, the toner is hardly peeled off from the developing roller 18. However, the tendency depends on the particle size of the toner. It easily adheres to the developing roller 18.
In other words, when an image with a small amount of toner consumption is formed, the toner on the developing roller 18 having a small particle diameter tends to accumulate. However, according to the developing device 10 of the present embodiment, such accumulation of the small particle size toner can be prevented. Here, the experimental results obtained by the developing device 10 are shown in Table 1 below. Table 1 shows the volume average particle diameter of the toner on the developing roller 18 and the ratio of the toner having a particle diameter of 5 μm or less. In the table, “in blank paper” means that the toner is not consumed at a B / W ratio of 0%, and “solid” means that the B / W ratio is 100%.
% Toner consumption. As shown in Table 1, it can be seen that the toner particle size and the ratio of the toner having a particle size of 5 μm or less hardly change due to the difference in the toner consumption, and thus the small particle size toner is replaced without being accumulated.

[0038]

[Table 1]

Further, when printing was performed with the developing device 10, a good image without white spots could be obtained until the life of the developing device 10.

In the above description, the case where the supply and the collection of the toner to the developing roller 18 are performed at the same time is described. Can be completely recovered, whereby the developing roller 18
The above-mentioned accumulation of toner can be more reliably prevented. When only toner collection is performed as described above, the supply bias voltage Vsup applied to the supply roller 32 is changed to the developing bias Vb.
Is switched to a voltage on the opposite polarity side of the toner charging polarity, that is, on the positive polarity side. As a result, the toner is supplied to the supply roller 3
2, the toner supply to the developing roller 18 is stopped.

Next, with reference to FIGS. 2 and 3, a description will be given of developing devices 10a and 10b which are modifications of the above embodiment. As shown in FIG. 2, in the developing device 10 a, a scraper 50 made of, for example, a resin film is provided in a state in which a tip portion thereof is in contact with the surface of the collection roller 26. By providing the scraper 50, the toner transferred from the developing roller 18 to the surface of the collection roller 26 can be completely scraped off, whereby the toner supplied to the developing roller 18 is replaced, so that the same toner can reduce stress. Repeated reception can be more reliably prevented.

The toner storage unit 14 and the supply roller 32
The partition member 52 is provided so as to separate the toner from the collection roller 26 by the scraper 50, so that the toner is more reliably collected in the toner storage unit 14. The partition member 52 has an opening 54, and the toner in the toner storage unit 14 is fed toward the supply roller 32 through the opening 54.

Further, as in the developing device 10b shown in FIG. 3, a partition member 52 to which a scraper 50 is attached is disposed so as to separate the toner storage unit 14 and the supply roller 32, and the toner in the storage unit 14 is removed. It may be provided between the collection roller 26 and the supply roller 32 so as to have an opening 54 for feeding the paper toward the supply roller 32. This also ensures that the toner completely scraped off from the collection roller 26 by the scraper 50 is collected in the toner storage unit 14 more reliably. Note that the scraper 50 and the partition member 52 do not necessarily have to be used together, and may be provided independently.

In the above-described embodiment, the toner recovery member 26 and the toner supply member 32 are formed in a roller shape, but may be a rotating body having another shape such as a brush or a belt.

Each bias voltage used in the developing device is not limited to a DC voltage, but may be an oscillating voltage such as an AC voltage.

Further, the image carrier on which an image is formed by development is not limited to the one on which an electrostatic latent image is formed, and may be, for example, an intermediate transfer member or a sheet in the case of a direct recording system.

Further, the developing device of the present invention can be applied not only to a monochrome image forming apparatus but also to a color image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a developing device according to the present invention.

FIG. 2 is a schematic configuration diagram showing a modified example of the developing device of FIG.

FIG. 3 is a schematic configuration diagram showing a modification of the developing device of FIG. 1;

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

[Explanation of symbols]

2 ... image carrier, 10 ... developing device, 12 ... opening, 14 ...
Toner storage unit (developer storage unit), 16: container, 18: developing roller (developer carrier), 26: collection roller (developer collection member), 32: supply roller (developer supply member), 3
8 ... regulating blade (regulating member).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshitaka Naritaka 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Takashi Akazawa Azuchi, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd. 2-13-13, Tachibana Sakuraba 2-73-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term (in reference) 2H073 BA04 BA11 CA02 2H077 AC04 AC05 AD02 AD06 AD13 AD17 AD31 AD32 AD35 AD36 AE03 CA12 EA14 EA15 EA16 FA22 FA25

Claims (9)

[Claims] A container having an opening facing the image bearing member and a developer storage portion provided at a distance from the opening; The surface rotates vertically from top to bottom, and
A developer carrier to which a developing bias has been applied; a developer recovery member that rotates while contacting the surface of the developer carrier that moves downward from above in the vertical direction; and a direction perpendicular to the developer recovery member. A developer supply member that rotates while being in contact with the surface of the developer carrier that moves downward from above in the vertical direction on the lower side of the developer supply member; and a downstream side in the rotation direction of the developer carrier relative to the developer supply member. And a regulating member arranged to be in contact with the surface of the developer carrier. 2. The developing device according to claim 1, wherein said developer recovery member rotates in the same direction as said developer carrier, and said developer supply member rotates in a direction opposite to said developer carrier. apparatus. 3. A recovery bias voltage biased to the opposite polarity to the developer charging polarity with respect to the developing bias is applied to the developer recovery member, and the recovery bias voltage is applied to the same polarity as the developer charging polarity with respect to the developing bias. 3. The method according to claim 1, wherein a biased supply bias voltage is applied to the developer supply member.
Developing device. 4. A static elimination member provided in contact with the developer on the developer carrier at a position upstream of the developer carrier in the rotation direction of the developer carrier with respect to the developer collection member.
The developing device according to any one of items 1 to 3. 5. The developing device according to claim 4, wherein a static elimination bias voltage is applied to said static elimination member. 6. The developing method according to claim 3, wherein, during non-image formation, the supply bias voltage is a voltage biased to a polarity opposite to a polarity of a developer charged with respect to the developing bias. apparatus. 7. A partition disposed so as to separate the developer storage section and the developer supply member, and having an opening through which the developer in the developer storage section is fed toward the developer supply member. 7. The developing device according to claim 1, further comprising a member. 8. The developing device according to claim 1, further comprising a scraper for scraping off the developer collected from the developer carrier and transferred to the surface of the developer collecting member. 9. An image forming apparatus using the developing device according to claim 1.