JP4742656B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device for developing an electrostatic latent image on an image carrier, and an image forming device including the developing device, which are used in a copying machine, a printer, a facsimile, and an image forming apparatus having a composite function. Is.

  In a conventional developing device, a rotating developer carrier (developing sleeve) is disposed in the vicinity of the rotating image carrier. The developer carrying member is formed in a hollow cylindrical body and is housed in a developing device main body having an opening on the side facing the image carrying member. The developer carrying member has a magnet inside thereof, and carries a two-component developer in which toner particles and magnetic particles (carriers) are mixed on the outer peripheral surface of the developer carrying member.

  The developing device includes a developing device main body that contains a two-component developer composed of toner and a carrier, a developer carrier having a magnetic field generating means composed of a magnet, and a developer conveyed to the developer carrier. A developer supply member, a developer layer thickness regulating member that regulates the developer layer thickness on the developer carrying member to a predetermined amount, and a developer stirring member that stirs the developer and transports it to the developer transport member. .

  The toner replenished from the toner cartridge into the developing device main body through the toner replenishing port portion, which is an opening provided in the upper portion of the developing device main body, is stored in the developing device main body by the rotating developer agitating and conveying member. The toner is uniformly mixed by stirring and mixing, and is supplied onto the outer peripheral surface of the developer carrying member by the rotating developer carrying member, and only the toner of the developer on the developer carrying member is imaged in the developing region. It adheres on the carrier.

  In the developing device having a configuration in which the developer carrying member and the developer supplying member are opposed to each other, a repelling magnetic field is formed across the opposing proximity point between the developer carrying member and the developer supplying member, thereby developing the developer after development. Is removed from the developer carrier, and a developer to be developed is supplied to the developer carrier.

  In the developing device having such a configuration, when the gap between the developer carrier and the developer supply member is small, uneven density due to the spiral rib of the developer supply member, so-called uneven screw pitch, occurs. That is, the developer supply member formed by a screw or the like disposed in the vicinity of the developer carrying member becomes rough due to the crests and troughs of the screw when the developer is sucked up by the developer carrying member, and the developer carrying member. There is a density difference in the upper developer, and this becomes the density of the magnetic brush at the point opposite to the image carrier, resulting in image unevenness.

  The developing device disclosed in Patent Document 1 includes a developer storage unit that guides the developer to the developing roller, a transport mechanism that transports the developer to the developer storage unit, and the height of the developer on the outer peripheral surface of the developing roller. A doctor blade which regulates and forms a part of a member constituting the developer storage section.

  The developing device disclosed in Patent Document 2 has an opening at a portion facing the developing roller, and has a developer hopper for storing the developed developer removed from the developing roller.

  The developing device disclosed in Patent Document 3 includes a pair of auger shafts installed via a partition plate at the bottom of a developer tank that stores the developer, a first magnet roller installed on the upper part of the partition plate, And a second magnet roller facing the developing roller.

  The developing device disclosed in Patent Document 4 is provided with a developer retaining portion that retains the developer upstream of the developer layer regulating blade, and a toner supply roller provided upstream of the developer retaining portion. .

The developing device disclosed in Patent Document 5 is provided with a developing housing having a developer supply chamber and a developing return chamber partitioned by a partition wall.
Japanese Patent Laid-Open No. 57-211178 Japanese Patent Laid-Open No. 58-34468 JP-A-62-183480 Japanese Patent Laid-Open No. 5-165312 Japanese Patent Laid-Open No. 10-319697

  In recent years, the particle size of toner and carrier has been reduced to improve the image quality of the image, but with this, the fluidization of the developer has decreased, so that the developer used for development is surely removed from the developing roller. Therefore, it is very difficult to supply a sufficiently stirred developer to the developing roller.

  Furthermore, when a color image is continuously formed by the color image forming apparatus, the amount of toner consumed per recording sheet is large, so that the consumed toner is uniformly replenished and sufficiently stirred and mixed. In the case of supplying to the developing roller, it has become difficult to ensure the uniformity of the image within a page or between pages.

  To solve the above problem, by increasing the screw diameter and screw pitch of the developer agitating and conveying member and setting the screw rotation speed higher, the toner replenished in a large amount can be dispersed in an early time, and mixed and agitated. However, along with the downsizing of the developing device, the developer is supplied directly from the screw to the developing roller without using the cross-shaped paddle used for the function of transferring the developer from the screw to the developing roller. Due to the construction, it became difficult to supply the developer to the developing roller, and the problem of uneven image quality density occurred.

  In the developing device of Patent Document 1, since there is a transport mechanism that transports the developer on the guide plate of the developer storage unit, it causes image spots.

  In the developing device of Patent Document 2, there is a developer dropping portion on the guide plate of the developer hopper, the developer hopper does not maintain a constant pressure in the developer hopper, and a partial developer in the developer hopper Image unevenness is likely to occur due to the bias.

  In the developing device of Patent Document 3, the developer peeled off from the developer supply roller attracts the developer peeled off from the developing roller, and slips through the supply roller as it is.

  In the developing device of Patent Document 4, there is a possibility that the developer is excessively supplied or insufficiently supplied in the developer retaining portion provided on the upstream side of the developer layer regulating blade.

  In the developing device of Patent Document 5, since a screw exists between the developing roller and the supply roller, screw pitch spots are likely to occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent screw pitch unevenness and to prevent development density defects due to insufficient supply of developer to the developing roller. Accordingly, an object of the present invention is to provide a developing device and an image forming apparatus that can improve the uniformity of image density and can form a high-quality image.

According to the first aspect of the present invention, there is provided a developing roller that is disposed facing the image carrier and carries the developer and conveys the developer to the developing region, and a developer amount regulating member that regulates the developer carrying amount on the developing roller. And a developer stirring and conveying member that conveys the developer while stirring,
Wherein the developer supply roller disposed above side of the developer stirring and conveying member is bridged between the developing roller and developer feed roller, the developing roller of the developer conveyed by the developer supply roller A developer guide member for guiding, and an upper lid member disposed above the developer guide member;
Forming a developer rectifying space surrounded by the developing roller, the developer supply roller, the developer guide member, the developer amount regulating member, and the upper lid member;
When the developer conveyance amount X supplied by the developer supply roller and the developer conveyance amount Y that passes through the developer guide member and is conveyed from the developer rectifying space onto the development roller, X> have a Y in the relationship,
A first gap is provided between the developer supply roller and the developer guide member, and a second gap is provided between the developer roller and the developer guide member, and passes through the first gap and the second gap. When the developer transport amount Z flows out from the developer rectifying space, and has a relationship of X> Y + Z,
After the developer rectifying space is filled with the developer, the developer supplied excessively from the developer supply roller is returned to the developer agitating and conveying member from the inlet portion of the developer rectifying space. This is a developing device.

According to the second aspect of the present invention, the electrostatic latent image formed on the image carrier by the optical writing means is visualized as a toner image by the developing device according to the first aspect, and the toner image is converted into a visible image. An image forming apparatus that transfers to a recording medium.

According to a third aspect of the present invention, there is provided an optical writing means for forming a plurality of electrostatic latent images on an image carrier, and a plurality of developing devices according to the first aspect of the present invention respectively containing developers of different colors. The image forming apparatus is characterized in that toner images of a plurality of colors are formed by the method and the color image is transferred to a recording medium.

According to the first aspect of the present invention, a large amount of developer conveyed by the developer supply roller is accumulated on the development roller by the developer rectifying space formed between the developer supply roller and the development roller. Since the agent can be supplied, screw pitch spots are prevented. Further, the developer conveyance amount X (g / sec) supplied by the developer supply roller is set to be the developer conveyance amount Y (g / g) that passes through the developer guide member and is conveyed from the developer rectifying space onto the development roller. When a large amount of development processing is performed continuously at a high speed, the development density defect due to insufficient supply of developer to the developing roller is prevented and the uniformity of the image density is improved. Images are obtained.
In the developer rectifying space, the developer conveyance amount X (g / sec) supplied by the developer supply roller, the developer conveyance amount Y (g / sec) conveyed on the development roller, and the developer guide By making it larger than the sum of the developer transport amount Z (g / sec) flowing out from the gaps at both ends of the member, development density defects due to insufficient supply of developer to the developing roller can be prevented, and image density uniformity As a result, a high-quality image can be obtained.
Further, after the developer rectifying space is filled with the developer, the developer rectified space is so returned that the developer supplied excessively from the developer supply roller is returned to the developer agitating and conveying member from the inlet portion of the developer rectifying space. And the developer supply roller, the developer rectifying space is not filled with excessive developer, and stable development processing is performed.

According to the second aspect of the present invention, an electrostatic latent image is formed on the image carrier by the optical writing means, the electrostatic latent image is visualized as a toner image by the developing device, and the toner image is formed. In an image forming apparatus that transfers images to a recording medium, problems such as a decrease in image density that occurs during continuous mass printing or high-speed printing can be solved, and a high-quality print image can be output.

According to the third aspect of the present invention, it is possible to uniformly maintain the image density of each color in the color image forming apparatus and obtain a high-quality color image.

  Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms.

[Image forming apparatus]
FIG. 1 is a configuration diagram of an image forming apparatus according to the present invention.

  The image forming apparatus A is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding device 20, and a fixing device 30. It is composed of

  Above the image forming apparatus A, an image reading device SC is installed. The document placed on the document table is scanned and exposed by the optical system of the document image scanning exposure device of the image reading device SC and read by the line image sensor. The analog signal photoelectrically converted by the line image sensor is subjected to analog processing, A / D conversion, shading correction, image compression processing and the like in the image processing unit, and then input to the optical writing means 3Y, 3M, 3C, 3K. Is done.

  An image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a cleaning unit 5Y disposed around the image carrier 1Y. An image forming unit 10M that forms a magenta (M) color image includes an image carrier 1M, a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a cleaning unit 5M. An image forming unit 10C for forming a cyan (C) color image includes an image carrier 1C, a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a cleaning unit 5C. An image forming unit 10K that forms a black (K) image includes an image carrier 1K, a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a cleaning unit 5K.

  The charging unit 2Y and the optical writing unit 3Y, the charging unit 2M and the optical writing unit 3M, the charging unit 2C and the optical writing unit 3C, and the charging unit 2K and the optical writing unit 3K constitute a latent image forming unit.

  4Y, 4M, 4C, and 4K are developing devices that contain a two-component developer composed of a small particle size toner of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming means 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating intermediate transfer body 6 by the primary transfer means 7Y, 7M, 7C, and 7K, and a combined color image is obtained. It is formed.

  The recording paper P stored in the paper feeding cassette 21 of the paper feeding device 20 is fed by a paper feeding means (first paper feeding unit) 22, and is fed with paper feeding rollers 23, 24, 25, 26 and registration rollers (first rollers). (Second paper feed unit) 27 and the like, and is conveyed to the secondary transfer means 9, and the color image is transferred onto the recording paper P.

  Note that the three-stage sheet feeding cassettes 21 arranged vertically in the vertical direction below the image forming apparatus A have substantially the same configuration. The three-stage sheet feeding means 22 has almost the same configuration. The sheet feeding cassette 21 and the sheet feeding means 22 are collectively referred to as a sheet feeding device 20.

  The recording paper P onto which the color image has been transferred is sandwiched by the fixing device 30 and the color toner image (or toner image) on the recording paper P is fixed by applying heat and pressure to the recording paper P. The sheet is fixed on the upper side, sandwiched between the sheet discharge rollers 28 and placed on a sheet discharge tray 29 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the secondary transfer means 9, the residual toner is removed by the cleaning means 8 from the intermediate transfer body 6 from which the recording paper P is separated by curvature.

  In the description of the image forming apparatus A, the color image formation has been described. However, the present invention includes a case of forming a monochrome image.

  Hereinafter, the image carriers 1Y, 1M, 1C, and 1K are referred to as the image carrier 1, the charging units 2Y, 2M, 2C, and 2K are referred to as the charging unit 2, and the optical writing units 3Y, 3M, 3C, and 3K are optically written. The developing devices 4Y, 4M, 4C, and 4K are referred to as developing devices 4.

[Developer configuration]
FIG. 2 is a sectional view showing an embodiment of the developing device according to the present invention.

The housing of the developing device 4 has a two-part configuration including a lower lower casing 40 and an upper upper casing 50, and can be opened and closed.

  In the lower casing 40 of the developing device 4, a developing roller 41, a first developer stirring and conveying member (hereinafter referred to as a first stirring member) 43, and a second developer stirring and conveying member (hereinafter referred to as a second stirring member). ) 44, a developer supply roller (hereinafter referred to as a supply roller) 45, a developer guide member (hereinafter referred to as a guide member) 46, and the like.

  The lower casing 40 includes a developer supply chamber 401 that houses the first stirring member 43 and a developer stirring chamber 402 that houses the second stirring member 44. The developer supply chamber 401 and the developer agitation chamber 402 are formed on both sides of a partition wall 403 that stands upright from the bottom of the lower casing 40.

  The developing roller 41 includes a rotatable developing sleeve 41A and a fixed magnetic field generating means (magnet roll) 41B.

  At the opposing proximity point between the developing sleeve 41A and the first stirring member 43, the developing sleeve 41A rotates from below to above, and the first stirring member 43 rotates from above to below.

  An upper lid member 52 that holds the developer amount regulating member 51 is fixed to the ceiling portion inside the upper casing 50. A wide space is formed between the upper surface of the guide member 46 and the upper lid member 52 fixed to the ceiling inside the upper casing 50, and a large amount of developer can be accommodated.

  The developing roller 41 is disposed to face the image carrier 1 that carries an electrostatic latent image, and is driven and rotated by a driving source (not shown). On the developing sleeve 41A, an AC voltage from the AC power source E1 and a DC voltage from the DC power source E2 are superimposed as a developing bias.

  The magnetic field generating means 41B is disposed inside the developing sleeve 41A and has seven magnetic poles N1, N2, N3, S1, S2, S3, and S4. The magnetic pole N1 is a main magnetic pole, the magnetic pole S1 is a stripped magnetic pole, and the magnetic pole S2 is a raised magnetic pole. The developer amount regulating member 51 is disposed in the vicinity of the magnetic pole N2 of the magnetic field generating means 41B.

  Two magnetic poles S1 and S2 adjacent to each other among the plurality of magnetic poles of the magnetic field generating means 41B are arranged in the same polarity to form a repulsive magnetic field. The stripping magnetic pole S1 for stripping off the developer strips off and disperses the developer on the developing sleeve 41A. The developer receiving scooping magnetic pole S2 draws up the developer supplied by the first stirring member 43 and attaches it to the developing sleeve 41A.

  The first agitating member 43 agitates and conveys the developer conveyed from the second agitating member 44 and supplies it uniformly to the developing roller 41. Both the first stirring member 43 and the second stirring member 44 are helical screw members.

  The second agitating member 44 is arranged in parallel to the first agitating member 43, and mixes and agitates the new toner replenished from the toner replenishing means 47 and the developer recirculated from the developing sleeve 41A to the upstream side of the first agitating member 43. To the part.

  The first stirring member 43 transports the developer in the direction of the rotation axis and releases the developer in a direction substantially perpendicular to the rotation axis.

  The developing device 4 includes magnetic field generating means 41B having a 7-pole fixed magnet. The developer amount regulating member 51 is made of a magnetic material and regulates the layer thickness of the developer on the developing sleeve 41A. The supply roller 45 is composed of 5-pole fixed magnets N1, N2,. N3. A magnetic field generating unit having S1 and S2 is provided, and the developer conveyed from the first stirring member 43 is held and supplied to the developing sleeve 41A.

  In the vicinity of the opposing proximity point between the developing sleeve 41A and the first stirring member 43, the developer is peeled off from the developing sleeve 41A and conveyed in the direction of the white arrow shown in FIG. 2, and supplied to the developing sleeve 41A. The guide member 46 is disposed in an inclined manner so as to separate the developer from the upper side and deposit the developer conveyed by the supply roller 45 and guide it to the developing roller 41.

  The guide member 46 is made of a nonmagnetic material, for example, a synthetic resin such as ABS resin, nonmagnetic stainless steel, aluminum alloy, copper alloy, ceramics, or the like.

[Developer supply]
A wide developer rectifying space W surrounded by the developing roller 41, the supply roller 45, the guide member 46, the developer amount regulating member 51, and the upper lid member 52 is formed in the upper part of the developing device 4.

  A first gap G1 is formed at a portion where one end portion of the guide member 46 and the outer peripheral surface of the supply roller 45 face each other, and a portion where the other end portion of the guide member 46 and the outer peripheral surface of the developing roller 41 face each other. Is formed with a second gap G2.

  The developer scraped up by the rotation of the first stirring member 43 is transported by the rotation of the supply roller 45 incorporating the magnetic pole, moves on the guide member 46, and is transported by the rotating developing roller 41, thereby developing the developer. The developer height is regulated by the amount regulating member 51, and the developer height is conveyed to the development area facing the image carrier 1.

  Since a large amount of developer can be accommodated in the developer rectifying space W, even when a solid image is continuously developed in large quantities at high speed, the development density is poor due to insufficient supply of the developer to the developing roller. Is prevented and the uniformity of the image density is improved, so that a high-quality image can be obtained.

  The developer conveyance amount X supplied by the supply roller 45 and the developer conveyance amount Y that passes through the guide member 46 and is conveyed from the developer rectifying space W onto the development roller 41 are set such that X> Y. By setting the developer transport amount, a large amount of developer is always deposited in the wide developer rectifying space W on the guide member 46, and there is no shortage of developer supply to the developing roller.

  Further, when the first gap G1 is provided between the supply roller 45 and the guide member 46, and the second gap G2 is provided between the developing roller 41 and the guide member 46, when excessive developer is deposited on the guide member 46, Part of the developer passes through the first gap G <b> 1 and the second gap G <b> 2, flows out of the developer rectifying space W, and is returned to the first stirring member 43. At this time, when the developer transport amount Z passing through the first gap G1 and the second gap G2, the relationship X> Y + Z is established. That is, the developer transport amount XY transported from the supply roller 45 to the developing roller 41 is larger than the developer transport amount Z flowing out of the developer rectifying space W through the first gap G1 and the second gap G2. The amount of developer in the developer rectifying space W tends to increase and does not decrease.

  Further, when the developer rectifying space W is filled with the developer, the developer supplied excessively from the supply roller 45 overflows from the supply roller 45 at the inlet of the developer rectifying space W and enters the first stirring member 43. Returned.

[Circulating developer transport]
FIG. 3 is a schematic diagram showing the circulation of the developer in the developing device 4. Hereinafter, the circulation of the developer will be described.

  (1) On the upstream side of the developer stirring chamber 402, the developer refluxed from the developer supply chamber 401 and the new toner replenished from the toner replenishing means 47 are carried in and stirred and mixed by the second stirring member 44. Then, the developer is conveyed in the developer moving direction indicated by an arrow V1.

  (2) The mixed developer passes through the first opening 404 on the downstream side of the developer agitating chamber 402, is conveyed as indicated by the arrow V2, and is introduced upstream of the developer supply chamber 401. . In the developer supply chamber 401, the developer is conveyed as indicated by an arrow V <b> 3 while being conveyed in the developer moving direction by the first stirring member 43.

  (3) The first stirring member 43 discharges the developer to the supply roller 45 as indicated by an arrow V4 while conveying the developer in the direction of the rotation axis.

  (4) The developer carried on the supply roller 45 is deposited on the inclined surface of the guide member 46.

  (5) The developer deposited on the guide member 46 is carried by the rotating developing sleeve 41A, passes the developer layer thickness regulated by the developer amount regulating member 51, and is conveyed as indicated by an arrow V5. Is done.

  (6) The developer carried on the developing sleeve 41 </ b> A is developed in the developer region facing the image carrier 1. The developer whose toner density has decreased after the development processing is peeled off from the developing roller 41 by the peeling magnetic pole S1.

  (7) The developer thus peeled off is carried into the developer supply chamber 401 as indicated by an arrow V6.

  (8) The developer conveyed into the developer supply chamber 401 is conveyed by the first agitating member 43 as indicated by an arrow V7, passes through the second opening 405, and as indicated by an arrow V8. It is introduced upstream of the stirring chamber 402.

  (9) In the developer stirring chamber 402, the toner supply by the toner supply means 47 is performed by a toner concentration detection signal of a toner concentration sensor (not shown), and the developer merges in the arrow V1.

  The developer is conveyed in the circulation system as described above, but a part of the developer is indicated by arrows V1, V2, V3, V6, V7, and V8 between the developer supply chamber 401 and the developer stirring chamber 402. Circulate.

  [Definition of development ghost]

[Image formation conditions]
Image forming apparatus: A4 size paper, full color, 51 sheets per minute output, tandem full color copier (Konica Minolta 8050 (registered trademark), see FIG. 1)
[Image carrier]
VH potential: -250 to -900V
VL potential: -40 to -150V
[Development conditions]
Developing sleeve 41A: Diameter φ30 mm, rotation speed 382 rpm
Supply roller 45: diameter 16 mm, rotation speed 200 rpm
Magnetic pole arrangement of magnetic field generating means 41B: 7 poles (see FIG. 2)
First stirring member 43, second stirring member 44: outer diameter φ30 mm, rotating shaft diameter φ8 mm, rotation speed: 600 rpm
Spiral blade height H: 11mm
First gap G1 between the supply roller 45 and the guide member 46: 1 mm
Second gap G2 between the developing roller 41 and the guide member 46: 1 mm
Developer transport amount X ′ on the supply roller 45: 3000 g / m ²
Developer transport amount X per unit time of the supply roller 45: 160.8 g / sec
Developer transport amount Y ′ on the developing roller 41: 200 g / m ²
Developer transport amount Y per unit time of the developing roller 41: 38.4 g / sec
Developer transport amount Z flowing out of the developer rectifying space W through the first gap G1 and the second gap G2: 15.0 g / sec
Therefore, the developer transport amount XY transported from the supply roller 45 to the developing roller 41 is larger than the developer transport amount Z flowing out of the developer rectifying space W through the first gap G1 and the second gap G2. The amount of developer in the developer rectifying space W tends to increase and does not decrease.

[Development bias application means]
DC bias (E2): -200 to -700V,
AC bias (E1): 0.5 to -2.0 kvpp, 2 to 7 kHz
Magnetic force of the developing roller 41 and the supply roller 45 facing the guide member 46: 5 mT
[Developer]
Average particle diameter of carrier: 20-60 μm
Average particle diameter of polymerized toner: 3 to 7 μm
Developer amount: 600-1100 g
Developer bulk density: 1.4 to 1.9 g / cm ³
[Experimental result 1]

  Table 1 shows the results of an experiment on the occurrence of image density unevenness with respect to the developer conveyance amount of the developing roller 41 and the supply roller 45. In this experiment, the developing roller 41 is removed from the developing device 4 and the opening of the developing device 4 is sealed with a shielding member 48, and the first gap G1 is further removed from the PET, as shown in the experimental modification device of the developing device in FIG. The developer transport amount X on the supply roller 45 was measured with the sheet 49A shielded and the second gap G2 shielded by the PET sheet 49B.

  That is, the linear velocity of the developing roller 41 and the developer conveyance amounts Y and Y ′ are made constant, the linear velocity of the supply roller 45 is changed to five types, and the developer conveyance amounts X and X per unit time of the supply roller 45 are changed. X ′ was variably formed and the presence or absence of image density unevenness was visually confirmed.

  As a result of the confirmation, image density unevenness occurred under the condition of Y ≧ X (Comparative Examples No. 1 to 3). Under the condition of Y <X, image density unevenness did not occur (Example Nos. 4 and 5).

  [Experimental result 2]

  Table 2 shows the results of an experiment on the occurrence of image density unevenness with respect to the developer conveyance amount of the developing roller 41 and the supply roller 45. In this experiment, the PET sheet 49B in contact with the supply roller 45 was removed so that the developer can flow out from the first gap G1.

  Further, the linear velocity of the developing roller 41 and the developer conveyance amounts Y and Y ′ are made constant as in Table 1, the linear velocity of the supply roller 45 is changed to five types, and the development per unit time of the supply roller 45 is changed. The agent conveyance amounts X and X ′ were variably formed and the presence or absence of occurrence of image density unevenness was visually confirmed.

  As a result of confirmation, image density unevenness occurred under the condition of Y ≧ X (Comparative Example No. 1). Under the condition of Y <X, image density unevenness did not occur (Example Nos. 3 to 5). However, no. In FIG. 2, since image density unevenness occurred, further examination was performed.

  [Experimental result 3]

  Table 3 shows the results of an experiment on the occurrence of image density unevenness with respect to the developer conveyance amount of the developing roller 41 and the supply roller 45. In this experiment, as shown in FIG. 4, the developing roller 41 is removed from the developing device 4, the opening of the developing device 4 is sealed with a shielding member 48, and the first gap G1 is further shielded with a PET sheet 49A. The sheet 49B was removed, and the supply roller regulating plate 53 was installed in the vicinity of the outer peripheral surface of the supply roller 45.

  In this state, the developer conveyance amount X on the supply roller 45 was measured while changing the linear speed of the supply roller 45 in five stages. The developer transport amount Z flowing out through the gap between the supply roller 45 and the supply roller regulating plate 53 was 15 g / sec.

  As shown in Table 3, image density unevenness occurred under the condition of Y> X (Comparative Examples Nos. 1 and 2). Under the condition of Y <X, image density unevenness did not occur (Example Nos. 4 and 5).

  As a result of the above examination, the developer conveyance amount X (g / sec) supplied by the supply roller 45 is passed through the guide member 46 and conveyed from the developer rectifying space W onto the development roller 41. By making the value larger than Y (g / sec), a development density defect due to insufficient supply of developer to the developing roller 41 is prevented when a large amount of development processing is continuously performed at high speed.

  Further, in the developer rectifying space W, the developer transport amount X (g / sec) supplied by the supply roller 45, the developer transport amount Y (g / sec) transported onto the developing roller 41, and the guide member By making it larger than the sum of the developer transport amount Z (g / sec) flowing out from the gaps at both ends of 46, development density failure due to insufficient supply of developer to the developing roller 41 is prevented.

1 is a configuration diagram of an image forming apparatus according to the present invention. 1 is a cross-sectional view showing an embodiment of a developing device according to the present invention. FIG. 4 is a schematic diagram showing circulation of a developer in the developing device. A sectional view of a development machine remodeling experimental machine.

Explanation of symbols

4,4Y, 4M, 4C, 4K Developing device 40 Lower casing 401 Developer supply chamber 402 Developer stirring chamber 41 Developing roller 43 First developer stirring and conveying member (first stirring member)
44 Second developer stirring and conveying member (second stirring member)
45 Developer supply roller (supply roller)
46 Developer guide member (guide member)
48 shielding member 49A, 49B PET sheet 50 upper casing 51 developer amount regulating member 52 upper lid member 53 supply roller regulating plate A image forming apparatus G1 first gap G2 second gap W developer rectifying space

Claims (3)

A developing roller that is disposed opposite to the image carrier and carries the developer and conveys it to the developing area, a developer amount regulating member that regulates the developer carrying amount on the developing roller, and conveys the developer while stirring A developer agitating and conveying member that
Wherein the developer supply roller disposed above side of the developer stirring and conveying member is bridged between the developing roller and developer feed roller, the developing roller of the developer conveyed by the developer supply roller A developer guide member for guiding, and an upper lid member disposed above the developer guide member;
Forming a developer rectifying space surrounded by the developing roller, the developer supply roller, the developer guide member, the developer amount regulating member, and the upper lid member;
When the developer conveyance amount X supplied by the developer supply roller and the developer conveyance amount Y that passes through the developer guide member and is conveyed from the developer rectifying space onto the development roller, X> have a Y in the relationship,
A first gap is provided between the developer supply roller and the developer guide member, and a second gap is provided between the developer roller and the developer guide member, and passes through the first gap and the second gap. When the developer transport amount Z flows out from the developer rectifying space, and has a relationship of X> Y + Z,
After the developer rectifying space is filled with the developer, the developer supplied excessively from the developer supply roller is returned to the developer agitating and conveying member from the inlet portion of the developer rectifying space. A developing device. The electrostatic latent image formed on the image carrier by the optical writing means is visualized as a toner image by the developing device according to claim 1, and the toner image is transferred to a recording medium. Image forming apparatus. A toner image of a plurality of colors is formed by an optical writing unit that forms a plurality of electrostatic latent images on the image carrier and a plurality of developing devices according to claim 1 that respectively store developers of different colors. An image forming apparatus for transferring a color image to a recording medium.

Images