JP5059356B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  The present invention includes a developing device that develops a latent image on a latent image carrier using a two-component developer composed of toner and a carrier, a process cartridge including the developing device, and the developing device or the process cartridge. The present invention relates to an image forming apparatus such as a copying machine, a printer, a plotter, a facsimile, or a complex machine that performs image formation using an electrophotographic system. The present invention further relates to an image forming apparatus including a plurality of the developing devices or the process cartridges and capable of color image formation.

2. Description of the Related Art Conventionally, various developing devices that are equipped in an electrophotographic image forming apparatus and perform development using a two-component developer have been proposed.
FIG. 4 shows a developing apparatus of a biaxial conveyance type as an example, and this developing apparatus 400 is a developing roller (sleeve) 401 (rotating) that is a developer carrying body for supplying a developer to an image carrying body (not shown). A cylindrical sleeve and a magnet or a magnet roll fixedly arranged in the sleeve (only the sleeve is shown in the figure), and a developer regulating member (doctor) for regulating the amount of developer on the sleeve 405 and a supply / recovery screw 402 that is a developer conveying member that supplies the developer to the developing roller 401 while conveying the developer and collects the developer from the developing roller 401. Further, the agitation and conveyance, which is a developer conveying member that conveys the developer conveyed to the downstream end of the supply and recovery screw 402 and the supplied toner as necessary, in a direction opposite to the supply and recovery screw 402. A screw 403 is provided. The supply / recovery screw 402 and the agitating / conveying screw 403 are arranged in the horizontal direction, and the supply / recovery conveying path 406 including the supply / recovering screw 402 and the agitating / conveying path 407 including the agitating / conveying screw 403 are separated by a partition plate 404. It has been. The two conveyance paths communicate with each other through openings provided at the transfer portions at both ends in the axial direction of the partition plate 404, and circulate by conveying the developer in the reverse direction between the stirring conveyance path 407 and the supply / recovery conveyance path 406. Being transported.

  In the biaxial transport type developing device 400 shown in FIG. 4, the supply of the developer to the developing roller 401 and the recovery of the developed developer are performed by the supply / recovery screw 402 and the supply / recovery transport path 406. The developed developer is in a state where the toner is consumed by development and the toner density is lower than that before development. Since the developer supply screw and the recovery screw are the same, and the supply conveyance path and the recovery conveyance path are the same, the developed recovered developer and the developer before development are agitated. The As a result, the toner concentration of the developer supplied to the developing roller 401 decreases toward the downstream side of the supply / recovery screw 402 in the developer transport direction. In particular, in a high printing rate image, a decrease in toner density after development is larger than that before development, and a decrease in toner density on the downstream side in the developer transport direction is large, causing a problem that image quality cannot be maintained. In order to reduce such a decrease in toner density, it is possible to cope with the method by increasing the amount of developer to be conveyed or by increasing the conveyance speed of the developer. Increasing the number increases the stress on the developer and contributes to a decrease in the developer life.

Therefore, in order to solve such a problem, a triaxial conveyance type development that solves the problem by providing a screw for supplying the developer to the developing roller and a screw for collecting the developed developer in different developer conveying paths. A device has been proposed.
FIG. 5 shows an example thereof, which is a three-axis conveyance type developing device disclosed in Patent Document 1. The developing device 410 is disposed opposite to the latent image carrier 1 that carries the electrostatic latent image, and is disposed inside the developer carrier 411 and a developer carrier (sleeve) 411 that is rotatably supported. Magnetic field generating means (magnet body) having a plurality of magnetic poles, stripping means for stripping off the developer on the developer carrier, and a rotatable supply transport member for supplying the developer to the developer carrier 411 (Supply screw) 414, a rotatable recovery conveyance member (recovery screw) 415 that collects and conveys the developer peeled off from the developer carrier 411 that is arranged in parallel above the supply conveyance member 414, An agitating / conveying member (expansion screw) 416 that is disposed adjacent to the supplying / conveying member 414 and agitates and conveys the developer to the supplying / conveying member 414, a developer supply chamber 421 that accommodates the supplying / conveying member 414, and a recovery conveying A developer recovery chamber 422 for storing the material 415, a developer stirring chamber 423 for storing the stirring and conveying member 416, a first partition 417 that partitions the developer supply chamber 421 and the developer recovery chamber 422, and a developer supply chamber. The second partition 418 that partitions the developer 421 and the developer agitation chamber 423, and the first partition 417 is formed to communicate the developer transport downstream side of the developer recovery chamber 422 and the developer transport downstream side of the developer supply chamber 421. A second partition 418 is formed to communicate the first opening (not shown) provided with the developer transport downstream side of the developer supply chamber 421 and the developer transport upstream side of the developer stirring chamber 423. In addition, a second opening (not shown) and a second partition 418 formed in the second partition 418 for communicating the developer transport downstream side of the developer stirring chamber 423 with the developer transport upstream side of the developer supply chamber 421. 3 openings (not shown) The developer peeled off from the developer carrier 411 by the peeling means is collected in the developer collection chamber, and the collected developer is conveyed to the downstream side of the developer conveyance while being agitated by the collection conveyance member 415, and the first partition 417. The developer is returned to the developer supply chamber 421 from the first opening formed in the container, and the recovered developer and the unused developer are conveyed by the supply / conveyance member 414 while being mixed and agitated, thereby developing the developer in the developer supply chamber. The developer is transported into the developer stirring chamber 423 from the second opening formed in the second partition 418 by the supply transporting member 414, and the third opening formed in the second partition 418 by the stirring transporting member 416. Then, the developer is returned to the developer supply chamber 421, mixed with the developer by the supply and transport member 414, discharged with stirring, and supplied to the developer carrier 411.
In this developing device, after being used for development, after the collected recovered developer and the unused developer are mixed, the toner concentration is detected by a toner concentration sensor, and the development in which the toner concentration is detected based on the detection result. By replenishing the toner with the toner, the toner density in the developing device can be kept uniform, and the image density can be obtained uniformly.

By the way, with the increase in the process linear velocity of the image forming apparatus, in the biaxial transport type developing apparatus and the triaxial transport type developing apparatus as described above, the speed of the agent circulation in the developing apparatus is also required to be increased. Yes.
However, it is considered that the developer speed on the screw as the developer conveying member can be increased by increasing the screw pitch. In practice, however, the developer transfer portion at the end of the screw is associated with it. If the developer speed is not increased, it will be rate limiting, and the flow of the developer will stagnate. In order to prevent the stagnation of the developer at the transfer section, the rotational speed of the entire screw must be increased, resulting in an excessive burden on the developer, resulting in a problem that the life of the developer is shortened. is there.

  Therefore, for the purpose of providing a developing device that can smoothly circulate the developer, Patent Document 2 discloses a developer supply unit that supplies the developer to the developer carrier, the developer supply unit, and the partition wall. The developer agitation unit that supplies the developer to the developer supply unit, and is provided in each of the developer supply unit and the developer agitation unit. Due to the rotation of the conveying means, conveying means for conveying the developer in the axial direction, a delivery section in which the developer supplying section and the developer agitating section are communicated with each other at both ends, and There has been proposed a developing device including a backflow prevention unit provided at a portion where the developer backflow occurs in the delivery unit.

More specifically, in this developing device, as shown in FIGS. 6A and 6B, the developer supply unit 615 that supplies the developer to the developing carrier (not shown) has a positive screw direction. A conveying screw 607 that has a spiral blade and rotates to convey the developer in the axial direction is provided. The developer agitating unit 614 that is separated from the developer supply unit 615 by a first partition wall (not shown) and supplies the developer to the developer supply unit 615 has spiral blades in a reverse screw direction, A stirring screw 608 is provided that rotates in the same direction as the transport screw 607 to transport the developer in the axial direction thereof. The first delivery unit 618 a and the second delivery unit 618 b that deliver the developer between the developer agitation unit 614 and the developer supply unit 615 flow back to the first delivery unit 618 a and the second delivery unit 618 b due to the rotation of the transport screw 607 and the agitation screw 608. The first backflow prevention unit 619a and the second backflow prevention unit 619b are provided at a site where the water is generated.
In this way, the developer supply unit 615 and the developer agitation unit 614 are developed in the developer delivery unit formed by connecting the developer supply unit 615 and the developer agitation unit 614 arranged in parallel at both ends. By providing the backflow prevention units 619a and 619b that prevent the backflow caused by the rotation of the transport means (screws) 607 and 608 for transporting the agent, it is possible to prevent the backflow of the developer in the delivery unit. Further, by preventing the backflow of the developer, it is possible to prevent the developer from staying or the developer packing due to the backflow.

Further, as another example, there is a problem that the developer circulation property is improved by adjusting the opening width at the transfer section in order to provide a developing device that can smoothly circulate the developer and toner. It has been.
For example, Patent Document 3 discloses that the first stirring shaft and the second stirring shaft are formed with a multi-thread screw up to both ends, whereby the developer is circulated well, unevenness due to poor pumping of the developer, insufficient density, etc. For the purpose of providing a two-component developing device capable of preventing the above and obtaining a high-quality image, a developing sleeve for developing a latent image on the photosensitive member, and a two-component developer are conveyed and supplied to the developing sleeve. In the two-component developing device having the conveying device, the conveying device is arranged in parallel with the developing sleeve in the axial direction, and a first conveying path and a second conveying path that form a circulation path for the two-component developer. A first agitation shaft and a second agitation shaft that are arranged in a conveyance path, the first conveyance path, and the second conveyance path, respectively, and convey the two-component developer while mixing and stirring, and the first conveyance path. And the second transport path And a first opening that delivers the two-component developer from the first conveyance path to the second conveyance path, and a second opening that delivers the two-component developer from the second conveyance path to the first conveyance path. A partition plate that forms two openings, and of the first opening and the second opening, the two-component developer flows from the lower side between the first stirring shaft and the second stirring shaft. A developing device has been proposed in which the width of the opening is wider than the width of the other opening, and the first stirring shaft and the second stirring shaft are formed of multiple threads to both ends. .

  In the developing device, of the first opening and the second opening, the width of the opening on the side where the two-component developer flows from the lower portion between the first stirring shaft and the second stirring shaft is the other opening. Therefore, it is possible to smoothly transfer the developer from the first stirring shaft to the second stirring shaft and from the second stirring shaft to the first stirring shaft. Insufficient density and unevenness can be prevented, a good quality image can be obtained, and leakage of the developer can be prevented. In addition, since the first stirring shaft and the second stirring shaft are formed with multi-threaded screws up to both ends, the developer is circulated satisfactorily to prevent unevenness and insufficient density due to poor pumping of the developer. , You can get good quality images.

Further, in Patent Document 4, powder is transferred from one end to the other end for the purpose of providing a powder transfer device capable of smoothly delivering powder from the forward transfer shaft to the return transfer shaft. In the powder conveyance device configured to form a circulation conveyance path that is conveyed, folded back at the other end, and returned to the one end, and configured to freely drop part of the powder in the middle of the circulation conveyance path, the circulation A partition plate disposed along the transport direction of the circulating transport path to form a forward path and a return path of the transport path, and a helical powder transport means disposed on the forward path and the return path partitioned by the partition plate, respectively. An opening portion of the partition plate for communicating the forward path and the return path at least while reducing the conveying force by the spiral conveying means arranged at least in the outward path ,in front Powder transfer apparatus is proposed which is characterized in that it is partially extended in the conveying direction of the return path beyond a small range of conveying force.
In this powder conveyance device, the powder conveyed through the forward path is circulated by being transferred from the partition plate opening part at the folding point to the return path, and at this time, the powder is within a range where the conveying force of the folding part is small. Receives a compressive force, and moves by being pushed from the forward path to the return path side by this compressive force. Here, the powder that has received the compressive force in the range where the conveying force of the folding part is small is pushed out from the open part that partially extends in the conveying direction of the return path, that is, the return direction, beyond the range where the conveying force is small. Smooth circulation.

JP 2001-290369 A JP 2002-278271 A Japanese Patent No. 3379678 Japanese Patent Laid-Open No. 8-95381

As described above, with the increase in the process linear velocity of the image forming apparatus, the developer circulation in the developing apparatus is also required to be accelerated. It is thought that the developer speed on the screw can be increased by increasing the screw pitch. However, in practice, if the developer speed at the transfer part at the end of the screw is not increased, it becomes the rate-limiting factor. As a result, the developer flow is delayed. In order to prevent the stagnation of the developer at the transfer section, the number of revolutions of the entire screw must be increased eventually, and an excessive burden is placed on the developer, resulting in a problem that the life of the developer is shortened. .
In order to solve this problem, in the relationship between the developer speed on the screw and the developer speed of the transfer section,
“Developer speed on screw [kg / s] ≦ developer speed at delivery section [kg / s]”
Must hold.

  Therefore, the present invention can satisfy the above relationship, the developer is not stagnated at the transfer section, and as a result, the rotation speed of the entire developer conveying member (screw) can be reduced, and the developer stress can be reduced. It is an object to provide a developing device having a configuration that can be reduced.

Here, the problems of the prior art described in Patent Documents 2 to 3 are similar to those of the present invention. For example, the prior art described in Patent Document 2 attempts to smoothly convey the transfer section by making the case shape uneven. However, if the case of the transfer section is uneven, the developer backflow is prevented, but the developer transport at the transfer section is hindered, causing the developer flow to stagnate. Therefore, the concept is opposite to the present invention in which the unevenness of the transfer portion that causes the developer to stagnate should be eliminated.
The prior arts described in Patent Documents 3 and 4 are intended to increase the conveying speed by increasing the opening width of the transfer section, and are similar to the present invention. However, in the present invention, the opening width of the transfer portion is defined as compared with the conveying speed on the screw, whereas in these conventional techniques, the size of the opening width is not defined.

  The present invention has been made in view of the above circumstances, and by setting the opening width and the number of rotations of the transfer section, the transfer section can have a transport speed equal to or higher than that on the developer transport member, and the transfer section It is an object of the present invention to provide a developing device having a configuration in which the developer does not stagnate at the portion, the rotation speed of the entire developer conveying member can be reduced, and the stress of the developer can be reduced. It is an object of the present invention to provide a process cartridge and an image forming apparatus provided with a developing device.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention includes a developer carrying member for carrying a developer and rotating to develop a latent image on the latent image carrying member, and a developer arranged in parallel to the developer carrying member in different directions. At least two developer conveying members (hereinafter referred to as first and second developer conveying members) and a partition plate disposed between the first and second developer conveying members. The first and second developer transport members are formed of screw-shaped members that transport the developer in the axial direction by rotating with a spiral blade on the rotating shaft portion, and the first developer transport member. The developer is transported from one end to the other end in the axial direction, and the developer is delivered from the other end to the second developer transport member through the opening of the partition plate in a direction perpendicular to the rotation axis. The partition is outside the delivery area. By the plate, the developer between the first and second developer conveying members In the developing device having the configuration as prevent movement, there in the first of the screw-like member and the same center line with the screw-like member from one axial end by the transfer unit before the developer conveying member is formed The developer is delivered to the second developer conveying member by the member provided in the delivery portion provided so as to be relatively rotatable,
The number of rotations of the first developer conveying member, the opening width of the partition plate at the developer delivery part, and the number of revolutions of the member provided at the delivery part are the conditions of the following formula (1): It is characterized by satisfying.
α · R · l ≦ α '· R' · L (1)
here,
α: Transport efficiency of developer transport member R: Number of rotations of developer transport member [rpm]
l: pitch length of developer conveying member [m]
α ′: Conveying efficiency of the transfer unit R ′: Number of rotations of members of the transfer unit [rpm]
L: Opening width of the transfer part [m]
And

Note that the transport efficiency α of the developer transport member indicates what percentage of the agent in the space through which the spiral wing (screw) has advanced when the developer transport member rotates once, The definition is as follows.
α = u / (V · d)
Further, the conveyance efficiency α ′ of the delivery unit represents the percentage of developer in the space through which the paddle passes when a member (for example, paddle) of the delivery unit rotates once, and its definition Is as follows.
α ′ = u ′ / (V ′ · d)
here,
Developer speed on developer conveying member (screw) (actual measurement): u [kg / s]
Screw passing volume: V = R / 60 · π ((r 1/2) 2 - (r 2/2) 2) · l [m 3 / s]
Developer speed at delivery section (actual measurement): u ′ [kg / s]
Paddle passage volume: V '= R' / 60 · dπ ((r 1/2) 2 - (r 2/2) 2) · L [m 3 / s]
External form of screw: r ₁ [m]
Screw shaft diameter: r ₂ [m]
Bulk density of developer: d [kg / m ³ ]
It is.

  By setting the opening width and the number of rotations of the transfer section as in the above formula (1), the transfer section can have a transport speed equivalent to or higher than that on the developer transport member (screw). With this, the developer does not stagnate.

By making the rotation speeds of the transfer section and the developer transport member independent as described above, the developer speeds on the developer transport member and the transfer section can be easily matched, and the developer may stagnate in the transfer section. However, the cost increases when the delivery unit and the developer conveying member are separate parts.
However, in order to prevent the stagnation of the developer at the transfer portion caused by the integration of the transfer portion and the developer conveying member, the number of rotations of the entire developer conveying member must eventually be increased, and an excessive burden is imposed on the developer. As a result, the life of the developer may be shortened.

According to a second means of the present invention, in the developing device of the first means, when the two developer transport members are viewed from the axial direction, the first developer transport member is on the left side, and the second developer When the conveying member is disposed on the right side and the first and second developer conveying members are arranged substantially horizontally, the rotation direction of the first developer conveying member is counterclockwise. Features.
By transferring the developer in the rotational direction (downward feed) as described above, the transfer efficiency of the transfer unit is increased. This is considered to be because the developer filling rate into the space between the members is higher in the lower part of the developer conveying member, and the developer in the state where the filling rate is high can be conveyed in the lower feed. Accordingly, the opening width necessary to satisfy the condition of the second means is reduced.

In order to reduce the opening width of the transfer unit as described above, it is necessary to increase the transfer efficiency of the transfer unit.
Accordingly, a third means of the present invention is the developing device according to any one of the first and second means, wherein the delivery portion is perpendicular to the rotation axis and is equivalent to the wing of the developer conveying member. The paddle which consists of a plane which can connect the line | wire of the length of continuously is attached, The number of the paddles is 2 sheets, It is characterized by the above-mentioned.
Thus, it has been experimentally found that the use of two paddles maximizes the conveyance efficiency. This is considered to be because there is the least useless space in which the developer is not clogged between the paddles of the transfer section when there are two paddles. Accordingly, the opening width necessary to satisfy the condition of the second means is reduced.

According to a fourth means of the present invention, in the developing device of the third means, the paddle of the transfer section is a plane within a range of a lead angle of 50 ° ≦ θ ≦ 80 °.
Experiments have shown that setting the paddle angle as described above increases the transport efficiency. This is considered to be because the entire paddle surface is effectively utilized by sending the developer while compressing it to the back of the paddle. Accordingly, the opening width necessary to satisfy the condition of the second means is reduced.

Meanwhile, if the first developing goods conveying member located below the second developer conveying member, resulting in lowered transport efficiency by the rotation direction of the developer conveying member.
Accordingly, a fifth means of the present invention provides the developing device of the first or second means, wherein when the two developer conveying members are viewed from the axial direction, the first developer conveying member is on the left side, When the second developer conveying member is disposed on the right side and the first developer conveying member is positioned below the second developer conveying member, the rotation direction of the first developer conveying member Is clockwise.
When the first developer conveying member is at a certain level lower than the second developer conveying member, the rotational direction (upward feed) of the seventh means is higher than the rotational direction (downward feed) of the third means. This improves the conveyance efficiency at the transfer section.

According to a sixth means of the present invention, in the developing device of any one of the first to fifth means, the first developer conveying member (referred to as screw A) and the second developer conveying member (screw). B)), there is no unevenness of the case inside the two tangent lines (see FIG. 16).
In order to reduce the opening width of the transfer part, it is necessary to increase the transfer efficiency of the transfer part, but it has been experimentally found that the transfer efficiency is the highest when there is no unevenness within the range of the tangent line as described above. . This is because it is possible to prevent the developer from returning from the screw B to the screw A by providing the unevenness, but this is thought to be because the conveyance from the screw A to the screw B is further inhibited.

According to a seventh means of the present invention, in the developing device of any one of the first to ninth means, the first and second developer transport members are substantially horizontally below the developer carrier. It is a biaxial transport type arranged, and one of the first and second developer transport members is a developer transport member for supplying and collecting developer to the developer carrier, and the other is A developer conveying member for conveying and agitating after toner replenishment, wherein at least one of the transfer locations between the developer conveying members satisfies the above-described condition.
In the biaxial transport type developing device, a toner density deviation occurs in the axial direction on the developer carrying member. In order to reduce this deviation, it is necessary to speed up the circulation of the developer. By satisfying the condition described in any one of the first to ninth means, the developer speed on the developer conveying member can be reduced. However, the developer can be smoothly circulated without delaying at the transfer portion even if the speed is increased, and as a result, the toner density deviation in the axial direction on the developer carrying member can be reduced.

According to an eighth means of the present invention, in the developing device of any one of the first to sixth means, a triaxial shaft having a third developer conveying member in addition to the first and second developer conveying members. Among the first to third developer conveying members, one is a supply developer conveying member (for example, a supply conveying screw) for supplying the developer to the developer carrying member, One of them is to collect the developer after completion of development from the developer carrying member and to collect the collected developer in parallel and in the same direction as the supply developer transport member (for example, the recovery developer). And the other one is an excess developer that has not been supplied from the supply developer transport member to the developer carrier and the developer transported from the recovery developer transport member. And agitating and conveying the developer in the direction opposite to the developer conveying member for supply拌用 a developer conveying member (e.g. agitation conveying screw), at least one of the transfer points between the three developer conveying member is characterized in that it satisfies the above conditions.
In the three-axis conveyance type developing device, there are problems such as the depletion of the developer in the downstream portion of the supply conveyance screw and the overflow of the developer upstream of the collection conveyance screw. Although it is necessary to increase the developer speed in each screw, even if the developer speed on the screw is increased by satisfying the condition described in any one of the first to ninth means, the developer at the transfer section As a result, the developer can be well balanced.

According to a ninth means of the present invention, in the developing device of the eighth means, the first developer transport member is the recovery developer transport member (for example, a recovery transport screw), and the recovery developer transport member The transfer section from the developer to the other developer conveying member satisfies the above conditions.
The overflow of the developer in the downstream part of the collection and conveyance screw is a particularly big problem of the three-axis conveyance type developing device, and this is covered by increasing the number of rotations of the collection and conveyance screw. The developer has been stressed a lot. So as in the ninth means 12, by the conveying speed of the transfer unit from the collection conveyance screw for, or better than, the recovery conveying screw, in particular the rotational speed of the high rotational speed tends recovery conveying screw Can be lowered.

According to a tenth means of the present invention, in the developing device of the eighth means, the three developer conveying members are arranged in a substantially horizontal direction.
Further, according to an eleventh means of the present invention, in the developing device of the tenth means, a paddle is provided in a delivery portion of the supply developer conveying member, and the number of the paddles is 3 to 5. It is characterized by that.
In a three-axis transport type developing device in which three axes are arranged in a horizontal direction, a place where the transfer is continuously performed in two stages, from a recovery transport screw to a supply transport screw and from a supply transport screw to an agitation transport screw. Can do. In such a place, the paddle shape with high transport efficiency is different from the case of one-stage delivery. Thus, it has been confirmed by experiments (experimental result: see FIG. 19) that the transfer efficiency becomes the highest when the number of paddles of the supply transfer screw is determined as in the fourteenth means. For example, when the number of paddles of the supply and conveyance screw is three or more, the conveyance efficiency is saturated. On the other hand, if the number is 6 or more, the developer of the volume of the wing cannot be transported, and transport efficiency is lowered.

In a twelfth aspect of the present invention, at least a latent image carrier on which an electrostatic latent image is formed and a developing device that develops and visualizes the electrostatic latent image on the latent image carrier are integrated. The process cartridge provided in the above item is characterized in that a developing device of any one of the first to eleventh means is provided as the developing device.
In the twelfth means, by using the developing device of any one of the first to eleventh means, a high process linear velocity is realized and the load on the developer is reduced, so that the toner that is always stable over a long period of time. Since the adhesion amount can be obtained, it is possible to provide a process cartridge having high image density stability.

The thirteenth means of the present invention comprises at least a latent image carrier on which an electrostatic latent image is formed on a surface, and a developing device that develops and visualizes the electrostatic latent image on the latent image carrier. The image forming apparatus includes a developing device of any one of the first to eleventh means or a process cartridge of the twelfth means.
In the thirteenth means, by using the developing device of any one of the first to eleventh means or the process cartridge of the twelfth means, a high process linear velocity is realized, and the load on the developer is also reduced. Therefore, a stable toner adhesion amount can be obtained for a long period of time, so that it is possible to provide an image forming apparatus with high image density stability.

A fourteenth means of the present invention is the image forming apparatus of the thirteenth means, comprising a plurality of developing devices or process cartridges having different developing colors, and forming a color image on a recording material.
In the fourteenth means, a developing device of any one of the first to eleventh means or a process cartridge of the twelfth means is used for a plurality of developing devices or process cartridges having different development colors, so that a high process. Since the linear speed is achieved and the load on the developer is reduced, a stable toner adhesion amount can be obtained over a long period of time, so the image density is highly stable, and the color reproducibility and color balance are excellent. It is possible to provide an image forming apparatus capable of obtaining a quality image.

According to a fifteenth means of the present invention, in the image forming apparatus of the thirteenth means, an image forming unit comprising at least a latent image carrier and a developing device for developing an electrostatic latent image formed on the latent image carrier. With multiple process cartridges, each image forming unit or process cartridge forms an image with a different development color and transfers it directly to the recording material or via an intermediate transfer member to form a color image on the recording material. Features.
In the fifteenth means, by using the developing device of any one of the first to eleventh means as the developing device of each image forming unit or process cartridge, a high process linear velocity is realized, and the load on the developer is also increased. Therefore, an image forming apparatus capable of obtaining a high-quality color image with high image density stability and excellent color reproducibility and color balance because a stable toner adhesion amount can be always obtained over a long period of time. It becomes possible to provide.

According to a sixteenth means of the present invention, in the image forming apparatus of the thirteenth means, “a plurality of image forming units having at least an image carrier and a developing device for developing an electrostatic latent image formed on the image carrier” are provided. “A first image forming station comprising a first image forming unit group arranged side by side and a first intermediate transfer member to which a first toner image formed by the first image forming unit group is transferred and carried”; A second image forming unit group in which a plurality of image forming units having at least an image bearing member and a developing device for developing an electrostatic latent image formed on the image bearing member are arranged side by side; and the second image forming unit group A second image forming station including a second intermediate transfer member on which the formed second toner image is transferred and carried, and the first toner image transferred to the first surface of the recording material is Shaped by one image forming station The second toner image transferred to the second surface of the recording material is formed by the second image forming station, and before the fixing, the first toner image and the second toner image are transferred to the recording material simultaneously or sequentially. It is characterized by being.
In the sixteenth means, by using the developing device of any one of the first to eleventh means as the developing device of each image forming unit, a high process linear velocity is realized, and the load on the developer is also reduced. To provide an image forming apparatus capable of obtaining a high-quality color image with high image density stability and excellent color reproducibility and color balance since a stable toner adhesion amount can be obtained constantly over a long period of time. Is possible. Further, by using the developing device of the present invention in a one-pass double-side transfer type image forming apparatus, it is possible to obtain a color image excellent in density stability over a long period of time with extremely high productivity. As a result, there is no difference in image quality between the front and back sides, and a color double-sided image with always stable image quality can be obtained.

As described above, according to the present invention, by setting the rotation speed of the screw-like member of the first developer conveying member, the opening width of the transfer section, and the rotation speed of the member provided in the transfer section, the transfer section The developer conveying member can have a conveying speed equal to or higher than that on the screw-like member , the developer can be prevented from stagnation at the transfer portion, and the rotation speed of the entire developer conveying member can be reduced. Thus, it is possible to realize a developing device having a configuration capable of reducing the stress.
Further, by using the developing device of the present invention, a high process linear velocity is realized and the load on the developer is reduced, so that a stable toner adhesion amount can be always obtained over a long period of time. A process cartridge with high performance can be realized.
Furthermore, by using the developing device or the process cartridge of the present invention, it is possible to realize an image forming apparatus with high image density stability, and furthermore, high image density stability, high color reproducibility and excellent color balance. An image forming apparatus capable of obtaining a color image with high image quality can be realized.

  Hereinafter, specific configurations, operations, and effects of the present invention will be described in detail with reference to the drawings.

[Detailed Description of Entire Image Forming Apparatus]
First, a configuration example of an image forming apparatus using the developing device of the present invention will be described in detail.
FIG. 1 is a schematic central sectional view showing the internal configuration of the entire image forming apparatus according to the present invention. In the image forming apparatus main body 100 shown in FIG. 1, image forming stations are provided above and below the recording material conveyance path 43A, and the upper first image forming station moves endlessly in the direction of the arrow. A first image carrier unit 20 having a first image carrier belt 21 which is a first intermediate transfer member is moved to the lower second image forming station as a second intermediate transfer member which moves endlessly in the direction of the arrow. A second image carrier unit 30 including an image carrier belt 31 is provided. A first image forming unit group (four first image forming units 80Y, 80C, 80M, and 80K) is inclined on the upper stretched surface of the first image carrying belt 21 so that the second image carrying belt 31 is inclined. A second image forming unit group (four second image forming units 81Y, 81C, 81M, 81K) is provided on the surface. Y, C, M, and K attached to the numbers of the first and second image forming units correspond to the colors of the toners to be handled. Y is yellow, C is cyan, M is magenta, and K is black. Means. Y, C, and Y for each photosensitive member (latent image carrier) 1 provided in the first and second image forming units and rotating together with the first image carrier belt 21 and the second image carrier belt 31. M and K are attached. The photoreceptors 1Y to 1K are arranged at the same interval, and at least at the time of image formation, are in contact with a part of the stretched portion between the first and second image carrying belts 21 and 31.

  Each of the four first image forming units 80Y, 80C, 80M, and 80K and the second image forming units 81Y, 81C, 81M, and 81K have the same configuration, and FIG. 2 shows a configuration example of one image forming unit. Yes. In FIG. 2, when the image forming apparatus 100 is operated, a charging device 3 is arranged around a cylindrical photosensitive member 1 rotatably supported by a driving source (not shown) so as to rotate in the direction of an arrow according to an electrostatic photographic process. An image forming member such as a scorotron charger, an exposure device 4, a developing device 5, a cleaning device 2 and a photostatic device Q, a potential sensor S1, and an image sensor S2 are disposed.

The photoreceptor 1 as a latent image carrier is obtained by forming an organic photosensitive layer (OPC) as a photoconductive substance on an aluminum cylinder surface having a diameter of about 30 to 120 mm, for example. In addition, a photoreceptor on which an amorphous silicon (a-Si) layer is formed can be used. In addition to the cylindrical shape, a belt-shaped photosensitive member can also be employed.
As the charging device 3, in addition to a non-contact type charger, for example, a charging roller, a charging brush, or the like that is brought into contact with the surface of the photoreceptor 1 can be employed.
The cleaning device 2 includes a cleaning brush 2a, a cleaning blade 2b, and a recovery member 2c, and removes and recovers foreign matters such as toner remaining on the surface of the photoreceptor 1.

  The exposure device 4 scans the light corresponding to the image data for each color on the surface of each photoreceptor 1 that has been uniformly charged by the charging means, and forms an electrostatic latent image. The exposure apparatus 4 in the illustrated example is a line-shaped exposure apparatus that uses an LED (light emitting diode) array as a light emitting element and is combined with an imaging element array, but uses a laser light source, a polygon mirror, a scanning imaging optical system, and the like. It is also possible to employ a laser scanning type exposure apparatus that irradiates a photosensitive member with a laser beam modulated according to image data to be formed.

The developing device 5 is a developing system that employs a two-component developer composed of toner and carrier. The electrostatic latent image for each color formed on the surface of each photosensitive member 1 by exposure to the negatively charged photosensitive member 1 is developed with toner of a predetermined color having the same polarity (negative polarity) as the charged polarity of the photosensitive member 1. Then, so-called reversal development is performed, which becomes a visible image.
In the illustrated example, the configuration of the developing device 5 is a developing roller 5a which is a developer carrier (only the sleeve is illustrated in the figure, but a plurality of magnets or a plurality of magnetic poles are magnetized inside the sleeve. A magnet roller or the like), a doctor 5b as a developer regulating member, a supply and conveyance screw 5c as a developer supply and conveyance member, and an agitation and conveyance screw 5d as a developer agitation and conveyance member The configuration is a triaxial conveying type provided with the collecting and conveying screw 5e and the partition plates 5f and 5g, but is not limited thereto. That is, although a detailed description of the developing device will be described later, for example, a biaxial transport type developing device as shown in FIG. 4 or a triaxial transport type developing device as shown in FIG. Can be used.

  A first image carrying belt 21 as a first intermediate transfer member, which is supported by a plurality of rollers 23, 24, 25, 26 (two), 27, 28, 29 and runs in the direction of the arrow, forms a first image. The units 80Y to 80K are provided below the photoreceptors 1Y, 1C, 1M, and 1K. The first image carrying belt 21 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. In addition, a primary transfer roller 22 is provided on the inner peripheral portion of the first image carrying belt 21 so as to face the respective photoreceptors 1Y, 1C, 1M, and 1K.

A cleaning device 20 </ b> A is provided on the outer periphery of the first image carrying belt 21 at a position facing the roller 23. The cleaning device 20 </ b> A wipes off unnecessary toner remaining on the surface of the first image carrying belt 21 and foreign matters such as paper dust.
The members related to the first image carrier belt 21 are integrally configured as the first image carrier unit 20 and can be attached to and detached from the image forming apparatus 100.

  A second image carrier belt 31 as a second intermediate transfer member supported by a plurality of rollers 33, 34, 35, 36 (two), 37, 38 and running in the direction of the arrow is a second image forming unit 81Y. Are provided in contact with the photoreceptors 1Y, 1C, 1M, and 1K at ˜81K. The second image bearing belt 31 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. A primary transfer roller 32 is provided on the inner peripheral portion of the second image bearing belt 31 so as to face the photoreceptors 1Y, 1C, 1M, and 1K.

A cleaning device 30 </ b> A is provided on the outer periphery of the second image carrying belt 31 at a position facing the roller 33. The cleaning device 30 </ b> A wipes off unnecessary toner remaining on the surface of the second image carrying belt 31 and foreign matters such as paper dust.
The members related to the second image carrier belt 31 are integrally configured as the second image carrier unit 30 and can be attached to and detached from the image forming apparatus 100.

  Further, a first secondary transfer roller 46 is provided in the vicinity of the support roller 28 on the outer periphery of the first image carrying belt 21. A bias is applied to the first secondary transfer roller 46 while a recording material (hereinafter referred to as paper P) is passed between the first image carrying belt 21 and the secondary transfer roller 46, so that the first image carrying belt 21 carries the recording material. The toner image is transferred onto the paper P.

  A transfer charger 47 serving as a second secondary transfer unit is provided on the outer periphery of the second image bearing belt 31 and in the vicinity of the support roller 34. The transfer charger 47 is a known type, and a thin wire of tungsten or gold is used as a discharge electrode, held by a casing, and a transfer current is applied to the discharge electrode from a power source (not shown). By applying a transfer current while passing the paper P between the image carrying belt 31 and the transfer charger 47, an image by the toner carried by the second image carrying belt 31 is transferred to the paper P. The polarity of the transfer current applied to the transfer roller 46 and the transfer charger 47 is a positive polarity opposite to the polarity of the toner.

  On the right side of the image forming apparatus 100, a paper feeding device 40 that accommodates sheets of various sizes is provided. In the paper feeding device 40, a large-capacity paper feeding tray 40 a and a plurality of paper feeding cassettes are provided. 40b to 40d are mounted. Then, only one sheet P is reliably fed by the sheet feeding / separating means 41A to 41D from the selected one of the sheet feeding tray 40a and the plurality of sheet feeding cassettes 40b to 40d, and a plurality of conveying rollers. The pair 42B is sent to the recording material conveyance path 43B and the recording material conveyance path 43A.

  On the extension of the recording material conveyance path 43A, the sheet that has passed through the second image forming station is conveyed in a flat state to the fixing nip in the fixing device 60 provided downstream in the recording material conveyance direction. The recording material transfer means 50 is provided. The recording material transfer means 50 has rollers 52, 53, 54, 55, and 56 that support the conveyor belt 51 that moves endlessly in the direction of the arrow, and the cleaning device 50A faces the roller 55 outside the conveyor belt 51. , An adsorption charger 57 for adsorbing the recording material P facing the roller 56, and a charge eliminating / separating charger 58 facing the roller 54.

  The conveyance belt 51 that moves together with the recording material P while being in contact with the unfixed toner image is negatively charged by the suction charger 57 with the same polarity as the polarity of the toner. As the conveyance belt 51, a metal belt, a polyimide belt, a polyamide belt, or the like can be employed. The surface is provided with releasability from the toner and has a chargeable resistance value. The traveling speed of the belt conveyance 51 is matched with the traveling speed of the recording material in the fixing device 60.

  A fixing device 60 having a heating unit is provided on the downstream side of the recording material conveyance unit 50 in the sheet conveyance direction. As the fixing device 60, a roller fixing device of a type provided with a heater inside the roller, a belt fixing device that runs a heated belt, a fixing device that employs electromagnetic induction heating as a heating method, or the like can be used. In order to make the color and glossiness of the images on both sides of the paper the same, the material, hardness, surface properties, etc. of the fixing roller and fixing belt are made equal. Further, the fixing condition is controlled by a full-color and monochrome image, or single-sided or double-sided, or is controlled by a control unit (not shown) so as to obtain an optimal fixing condition according to the type of paper. A cooling roller pair 70 having a cooling function is provided in the conveyance path after fixing in order to cool the sheet after fixing and stabilize the unstable toner state at an early stage. As the cooling roller pair 70, a heat pipe structure roller having a heat radiating portion can be adopted. The cooled sheet is discharged and stacked by a discharge roller pair 71 on a discharge stack unit 75 provided on the left side of the image forming apparatus 100. The discharge stacking unit employs a mechanism in which a receiving member moves up and down according to a stack level by an elevator mechanism (not shown) so that a large amount of sheets can be stacked. Note that it is also possible to transport the sheet toward another post-processing apparatus through the sheet discharge stack unit 75. Another post-processing apparatus is an apparatus for bookbinding such as punching, cutting, folding, and binding.

  Each color cartridge 86Y, 86C, 86M, 86K in which developer containing an unused carrier is stored is detachably stored in the storage space 85. A developer is supplied to the developing device of each image forming unit as necessary by a developer conveying means (not shown). In the configuration of the present embodiment, the cartridges 86Y, 86C, 86M, and 86K of the respective colors are common to the four image forming units 80Y to 80K and 81Y to 81K arranged on the upper and lower sides. You can also. Further, the black toner cartridge 86K, which is highly consumed, can have a particularly large capacity. The storage space 85 is on the back side when viewed from the operation direction on the upper surface of the image forming apparatus, and a plane portion is secured on the front side of the upper surface of the image forming apparatus, so that it can be used as a work table.

The operation of the image forming apparatus shown in FIG. 1 will be described below.
[Single-sided recording operation]
An operation during single-sided recording in which a full-color image is formed on one side of the recording material (paper) P in the above configuration will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method in which an image carried on the first image carrying belt 21 is directly transferred to one side of the paper P, and another method is carried on the second image carrying belt 31. In this method, an image is directly transferred to one side of a sheet. In this embodiment, due to the configuration of the image forming apparatus 100, when the image carried on the first image carrying belt 21 is directly transferred to one side of the paper P, the image is formed on the upper surface of the paper P, and the second When the image carried on the image carrying belt 31 is directly transferred to one side of the paper P, the image is formed on the lower surface of the paper P. In the case where the data to be recorded is a plurality of pages, it is convenient to control the image forming order so that the pages are aligned on the paper discharge stack unit 75. Therefore, here, a method will be described in which an image is carried on the first image carrying belt 21 and then transferred onto the paper P so that the image order of the last page is recorded in order and the page order is aligned.

  When the image forming apparatus 100 is operated, the photoreceptors 1Y, 1C, 1M, and 1K in the first image carrying belt 21 and the first image forming units 80Y to 80K rotate. At the same time, the second image carrier belt 31 rotates, but the photoreceptors 1Y, 1C, 1M, and 1K in the second image forming units 81Y to 81K are separated from the second image carrier belt 31 and are not rotated. Is done. First, image formation by the yellow image forming unit 80Y is started. The photosensitive device 1Y is uniformly charged by the charging device 3, and the light corresponding to the image data for yellow emitted from the LED is charged by the operation of the exposure device 4 including an LED (light emitting diode) array and an imaging element. The surface of the photoreceptor 1Y is irradiated to form an electrostatic latent image.

The electrostatic latent image is developed with yellow toner by the developing roller 5a of the developing device 5 and becomes a visible image on the first image carrying belt 21 that moves in synchronization with the photoreceptor 1Y by the transfer action of the primary transfer roller 22. Primary transfer is electrostatically performed. Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner at the timings of the photoreceptors 1C, 1M, and 1K of the cyan, magenta, and black image forming units 80C, 80M, and 80K.
As a result, yellow, cyan, magenta, and black toner images are carried on the first image carrying belt 21 as sequentially overlapping full-color toner images, and are moved in the direction of the arrow together with the first image carrying belt 21. .

  Simultaneously with the above image forming operation, the paper P used for recording from the paper feed tray 40a or the paper feed cassettes 40b to 40d in the paper feed device 40 is one of the paper feed / separation means 41A to 41D for its supply. And is conveyed to the recording material conveyance path 43C by the conveyance roller pairs 42B and 42C. Before the leading edge of the paper P is picked up by the registration roller pair 45, the jogger 44 operates so as to push both sides of the paper P from both lateral directions with respect to the conveyance direction of the paper P. Matching is achieved. The registration roller pair 45 is stationary, and the leading edge of the sheet P is stationary while entering the nip of the registration roller pair 45, but the position with the image on the first image carrier belt 21 is normal. The pair of registration rollers 45 is rotated at the timing to transport the paper P to the transfer area.

  The full-color toner image on the first image carrying belt 21 is transferred to the upper surface of the paper P conveyed in synchronization with the first image carrying belt 21 by receiving a transfer action by the secondary transfer roller 46. The bias applied to the secondary transfer roller 46 has a positive polarity opposite to the charging polarity of the toner.

  Thereafter, the surface of the first image carrying belt 21 is cleaned by the belt cleaning device 20A. Further, foreign matters such as toner remaining on the surfaces of the photoreceptors 1Y, 1C, 1M, and 1K in the first image forming units 80Y to 80K that have finished the primary transfer are removed by the cleaning brush 2a and the cleaning blade 2b of the cleaning device 2. It is removed from the surface of each photoconductor. The surface of each photoconductor is subjected to a discharging operation of residual potential by the discharging device Q to prepare for the next image formation / transfer process. The removed foreign matter such as toner is sent to the collecting unit 87 by the collecting unit 2c. Sensors S1 and S2 detect whether the surface potential after exposure on the surface of the photoconductor and the density of the toner adhering to the surface of the photoconductor after the development process are appropriate, and appropriately set the image forming conditions. Information is output to control means (not shown) for setting and control.

  The sheet P onto which the toner image that has been superposed and carried on the first image carrying belt 21 is secondarily transferred is transferred toward the fixing device 60 by the carrying belt 51 of the carrying device 50. The surface of the transfer belt 51 is charged in advance by a sheet suction charger 57 so that the sheet P can be reliably transferred together with the transport belt 51. The neutralization / separation charger 58 operates so that the paper P is separated from the transport belt 51 and is reliably sent to the fixing device 60.

  The toners of the respective colors superimposed on the paper P are subjected to the fixing action by the heat of the fixing device 60, and are melted and mixed to completely form a color image. In the case of single-sided recording, since the toner image is provided only on one side (upper surface) of the paper P, less heat energy is required for fixing as compared with double-sided recording having a toner image on both sides. Therefore, the control means (not shown) optimally controls the power used by the fixing device according to the image. Until the fixed toner image is completely fixed on the paper, it is rubbed against the guide member or the like in the conveyance path, and the image is lost or distorted. In order to prevent this problem, the cooling roller pair 70 as a cooling unit is operated to cool the toner and the paper P. Thereafter, the paper is discharged by the paper discharge roller 71 onto the paper discharge stack 75 with the image surface facing upward. In the paper discharge stack section 75, the image forming order is programmed so that the recorded matter of the young pages is stacked so as to be sequentially stacked on top, so the page order is aligned. Further, since the paper discharge stack unit 75 is lowered as the number of papers to be discharged increases, the papers can be stacked in an orderly and reliable manner, and the page order is not disturbed. Further, instead of directly stacking the recorded paper on the paper discharge stack section 75, it is possible to carry out a punching process or to transport it to a post-processing device such as a sorter, a collator, a binding device or a folding device.

  In another method for forming an image on one side of the paper P (recording on the lower surface side), images are formed by the second image forming units 81Y to 81K and overlaid on the second image carrying belt 31 for primary transfer. The difference is that the image forming is performed in order from the image data of the younger pages for page alignment, but the process is performed and image formation in the first image forming units 80Y to 80K is not performed. Is the same as the single-sided recording process described above, and a detailed description thereof will be omitted.

[Operation during double-sided recording]
Next, the operation at the time of double-sided recording in which images are formed on both sides of the paper P will be described. When a start signal is input to the image forming apparatus, an image for each color sequentially formed by the first image forming units 80Y, 80C, 80M, and 80K described in the single-side recording operation is applied to the first image carrier belt 21. The image for each color sequentially formed by the second image forming units 81Y, 81C, 81M, and 81K is sequentially applied to the second image carrier belt 31 substantially in parallel with the step of carrying out the primary transfer sequentially and carrying it as the first image. A step of primary transfer and carrying as a second image is performed. Since the arrangement of the first and second image forming stations is the configuration shown in FIG. 1, in order for the first image and the second image to coincide with each other at the front end in the transport direction of the paper P, the first image forming station is arranged as follows. The second image formation is started after the start of the image formation. Further, since the sheet P is stopped and retransmitted by the registration roller pair 45, the sheet P is fed in consideration of the time and aligned by the jogger 44. The registration roller pair 45 transports the sheet P to a first transfer station constituted by a transfer roller 46 that is a first secondary transfer unit and a first image carrying belt 21 at a timing. A positive transfer current is applied to the transfer roller 46, and the image is transferred from the first image carrying belt 21 to one side (upper surface in the drawing) of the paper P.

  Thus, the sheet P having an image on one side is continuously sent to the second transfer station having the transfer charger 47 as the second secondary transfer means by the transfer action of the transfer roller 46. Then, by applying a positive polarity transfer current to the charger, the full-color second image previously carried on the second image carrying belt 31 is transferred to the lower surface of the paper P at a time.

  The sheet P on which the full color toner images are transferred on both sides in this way is transferred to the fixing device 60 by the transport belt 51 of the transport device 50. At this time, the surface of the transport belt 51 is charged with the same negative polarity as the polarity of the toner by the suction charger 57 so that unfixed toner on the lower surface of the sheet does not move to the transport belt 51. An alternating current is applied to the charge removal / separation charger 58, and the paper P is separated from the transport belt 51 and transferred to the fixing device 60. The toner images on both sides of the paper P are melted and mixed by the fixing process by heat of the fixing device 60. The paper P subsequently passes through the cooling roller pair 70 and is discharged onto the paper discharge stack portion 75 by the paper discharge roller 71.

  When double-sided recording is performed on a plurality of pages of paper, the image formation order is controlled so that the image of a young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. The order of the pages is 1 page in order from the top, 2 pages on the back, 3 pages on the second sheet, and 4 pages on the back. Such control of image forming sequence and control such as increasing the power input to the fixing device compared to the one-side recording are executed by a control means (not shown).

  The above-described single-side recording operation and double-side recording operation have been described with reference to an example in which full-color recording is executed. However, the image forming apparatus shown in FIG. 1 can perform monochrome recording using only black toner and multi-color recording such as two colors and three colors. Is possible.

[Description of Another Configuration of Image Forming Apparatus]
Next, another configuration example of the image forming apparatus according to the present invention is shown in FIG.
This image forming apparatus is a so-called tandem image forming apparatus that is a color system that forms an image on only one side at a time with respect to FIG. A schematic configuration is shown below.
The color image forming apparatus shown in FIG. 3 is a so-called tandem system, and process cartridges 10Y, 10C, 10M, and 10K for each color of yellow (Y), cyan (C), magenta (M), and black (K) are intermediately transferred. The intermediate transfer belt 12 as a body is arranged in series. The process cartridges 10Y to 10K for the respective colors have the same configuration, and are composed of a charging device 3, a developing device 5, a cleaning device 2, and the like centering on the photoreceptors 1Y to 1K that are latent image carriers. Further, an exposure device 4 and an intermediate transfer device 11 are arranged for the photoreceptors 1Y to 1K of the process cartridges 10Y to 10K. In addition, a paper feeding device and a paper transport unit (not shown), a registration roller 15, and a paper transfer device are provided. A device 16, a transport device 17, a fixing device 18 and the like are provided.

As the charging device 3, for example, a contact-type charging roller or a charging brush is used, but a non-contact charger can also be used.
The cleaning device 2 includes a cleaning blade, a cleaning brush, and the like, and removes and collects foreign matters such as toner remaining on the surface of the photoreceptor 1.
The exposure device 4 scans the light corresponding to the image data for each color on the surface of each photoreceptor 1 that has been uniformly charged by the charging means, and forms an electrostatic latent image. The exposure apparatus 4 in the illustrated example uses four laser light sources, polygon mirrors, four scanning imaging optical systems, and the like, and laser scanning that irradiates each photoconductor with laser beam light modulated according to image data to be formed. Although an exposure apparatus of the type, an exposure apparatus comprising an LED (light emitting diode) array and an imaging element array can also be employed.

In this embodiment, a plurality of components such as the photosensitive member 1, the charging device 3, the developing device 5, and the cleaning device 2 described above are integrally connected as a process cartridge, and the process cartridges 10Y to 10Y are formed. 10K is configured to be detachable from the image forming apparatus main body.
Further, the configuration and detailed description of the developing device 5 used in each of the process cartridges 10Y to 10K will be described later. For example, a biaxial transport type developing device as shown in FIG. 4 or 3 as shown in FIG. 2 or FIG. An axial conveyance type developing apparatus to which the present invention is applied can be used.

The intermediate transfer device 11 includes an intermediate transfer belt 12 that is stretched around a plurality of rollers 13a, 13b, and 13c and rotates in the direction of the arrow in the drawing, a primary transfer roller 14 that is a primary transfer unit, and a belt cleaning (not shown). The toner images of the respective colors formed on the photosensitive members 1Y to 1K of the process cartridges 10Y to 10K are sequentially superimposed and primarily transferred. The toner image transferred onto the intermediate transfer belt 12 is secondarily transferred to the recording material (paper) P by the paper transfer device 16. The transferred paper P is transported to the fixing device 18 by the transport device 17 and the toner image is fixed on the paper P.
The image forming operation of the image forming apparatus shown in FIG. 3 is the same as the one-side recording operation in which the image forming of the back surface (second surface) is not performed in the image forming apparatus shown in FIG. Detailed description of the operation is omitted.

[Explanation of developing device configuration]
Next, the configuration of the developing device used in the image forming apparatus according to the present invention as described above will be described.
The developing device used in the image forming apparatus of FIG. 1 is, for example, a triaxial conveying type developing device as shown in FIG. 2 described above, a biaxial conveying type developing device configured as shown in FIG. There is a three-axis conveyance type developing device configured as shown in FIG.

  A biaxial transport type developing device 400 shown in FIG. 4 is an example of a developing roller (sleeve) 401 (a rotating cylindrical sleeve and a rotating developer sleeve) that supplies a developer to a latent image carrier (not shown). , Composed of a magnet or a magnet roll fixedly disposed in the sleeve (only the sleeve is shown in the figure), a developer regulating member (doctor) 405 for regulating the amount of developer on the sleeve, and developer Is supplied to the developing roller 401 while being conveyed, and a supply / recovery screw 402 is provided as a developer conveying member that collects the developer from the developing roller 401. Further, the agitation and conveyance, which is a developer conveying member that conveys the developer conveyed to the downstream end of the supply and recovery screw 402 and the supplied toner as necessary, in a direction opposite to the supply and recovery screw 402. A screw 403 is provided. The supply / recovery screw 402 and the agitating / conveying screw 403 are arranged in the horizontal direction, and the supply / recovery conveying path 406 including the supply / recovering screw 402 and the agitating / conveying path 407 including the agitating / conveying screw 403 are separated by a partition plate 404. It has been. The two conveyance paths communicate with each other through openings provided at the transfer portions at both ends in the axial direction of the partition plate 404, and circulate by conveying the developer in the reverse direction between the stirring conveyance path 407 and the supply / recovery conveyance path 406. Being transported.

Next, FIG. 7A is a schematic cross-sectional view of a three-axis conveyance type developing device, and FIG. 7B is a schematic plan view schematically showing the developer flow on a plane.
The developing device 504 having the configuration shown in FIG. 7A serves as a developer carrier that supplies toner to the latent image on the surface of the photosensitive drum 501 as a latent image carrier and develops it while moving the surface counterclockwise. A developing roller 505 (consisting of a rotating cylindrical sleeve and a magnet or magnet roll fixedly disposed in the sleeve) is provided. Further, a supply / conveying screw 508 is provided as a developer supply / conveying member that conveys the developer in the depth direction of FIG. 7 while supplying the developer to the developing roller 505.
A doctor 516 serving as a developer regulating member that regulates the developer supplied to the developing roller 505 to a thickness suitable for development is provided downstream of the surface of the developing roller 505 facing the supply and conveyance screw 508 in the surface movement direction. I have.

  The developed developer that has passed through the developing unit is collected downstream from the developing unit, which is the portion of the developing roller 505 facing the photosensitive drum 501, in the surface movement direction, and the collected collected developer is supplied and transported to the screw 508. And a collecting and conveying screw 506 for conveying in the same direction. A supply conveyance path 509 that is a developer supply conveyance path provided with a supply conveyance screw 508 and a collection conveyance path 507 that is a developer collection conveyance path provided with a collection conveyance screw 506 are arranged in parallel below the developing roller 505. ing. The two conveyance paths of the supply conveyance path 509 and the collection conveyance path 507 are partitioned by a partition plate 534 as a partition member.

  The developing device 504 is provided with an agitation conveyance path 510 that is a developer agitation conveyance path in parallel with the supply conveyance path 509 opposite to the collection conveyance path 507. The agitating / conveying path 510 includes an agitating / conveying screw 511 as a developer agitating / conveying member that conveys the developer to the front side in the figure, which is in the opposite direction to the supply / conveying screw 508 while agitating the developer. The supply conveyance path 509 and the agitation conveyance path 510 are partitioned by a partition plate 533 as a partition member. Both ends of the front side and the back side of the partition plate 533 in the figure are openings, and the supply conveyance path 509 and the agitation conveyance path 510 communicate with each other. The excess developer supplied into the supply conveyance path 509 and not used for development and conveyed to the downstream end in the conveyance direction of the supply conveyance path 509 and the collection conveyance screw 506 were conveyed to the downstream end in the conveyance direction of the collection conveyance path 507. The collected developer is supplied to the agitation conveyance path 510. The agitating / conveying path 510 agitates the supplied excess developer and the collected developer, and conveys them to the downstream side in the conveying direction of the agitating / conveying screw 511 and to the upstream side in the conveying direction of the supplying / conveying screw 508.

The partition plate 534 has an opening at the end in the drawing, which is the most downstream side in the conveyance direction of the collection and conveyance screw 506, and the supply conveyance path 509 and the collection conveyance path 507 communicate with each other. The three conveyance paths are communicated with each other in the conveyance direction downstream end of the collection conveyance screw 506, the conveyance direction downstream end of the supply conveyance screw 508, and the conveyance direction upstream end of the stirring conveyance screw 511.
Then, the recovered developer transported to the downstream end in the transport direction of the recovery transport path 507 is transferred to the supply transport path 509. Further, the recovered developer and the developer that has not been supplied to the developing roller 505 conveyed by the supply and conveyance screw 508 are transferred to the communicating agitation conveyance path 510.

  In the agitating and conveying path 510, the collected developer, the surplus developer, and the toner replenished as necessary in the transfer unit by the agitating and conveying screw 511 are agitated in the opposite direction to the developer in the collecting and conveying path 507 and the supply and conveying path 509. Transport. Then, the agitated developer is transferred to the upstream side in the conveyance direction of the supply conveyance path 509 communicating with the downstream side in the conveyance direction. A toner concentration sensor 527 is provided below the stirring and conveying path 510, and toner is supplied to the transfer unit by a toner supply control device (not shown) based on the sensor output.

  The casing of the developing device 504 includes an integrally formed lower casing 512 and upper casing 513 that are divided into upper and lower portions at the shaft portions of three conveying screws. The partition plate 533 is a part of the lower casing 512, and the partition plate 534 is held by the upper casing 513 and mated with the lower casing 512.

As shown in FIG. 7A, the apex 14 of the supply / conveying screw 508 which is the uppermost part of the developer supply member is disposed below the rotation center 515 of the developing roller 505. In the developing device 504 shown in FIG. 7A, an angle θ ₁ between a straight line connecting the rotation center 515 of the developing roller 505 and the screw vertex 514 and a horizontal straight line passing through the rotation center 515 is set to 30 °. . This angle θ ₁ depends on the diameter of the supply / conveying screw 508, but is preferably 10 ° to 40 ° in view of the layout because the developing device 504 is downsized.
The developer is supplied to the sleeve of the developing roller 505 by attracting the magnetic carrier in the developer by the magnet provided in the developing roller 505 or the magnetic pole of the magnet roll. As described above, by arranging the screw apex 514 to be lower than the rotation center 515 of the developing roller 505, the self-weight of the developer does not affect the amount of developer supplied to the developing roller 505, and the magnetic force The size contributes to the developer supply amount. As a result, since the developer transported in the supply transport path 509 is reliably supplied from above, the development can be performed even if the developer in the supply transport path 509 is not uniform in the transport direction of the supply transport screw 508. An appropriate amount of developer can be supplied to the roller 505.

The configuration examples of the image forming apparatus, the developing apparatus, and the process cartridge of FIG. 1 have been described above . However, the biaxial conveyance type developing apparatus having the configuration shown in FIG. 4 or the configuration shown in FIG. 2 or FIG. The conditions described in the above solution are applied to a three-axis conveyance type developing device. Specific examples will be described below.

The present invention provides a developer carrying member for carrying a developer and rotating to develop a latent image on the latent image carrying member, and at least two for conveying the developer in different directions arranged in parallel with the developer carrying member. At least one developer conveying member (first and second developer conveying members) and a partition plate disposed between the first and second developer conveying members, the first and second The developer transport member is formed of a screw-shaped member that transports the developer in the axial direction by rotating with a spiral wing provided on the rotation shaft portion, and from one end of the first developer transport member in the axial direction to the other end. The developer is transported, and the developer is delivered from the other end through the opening of the partition plate to the second developer transport member in a direction perpendicular to the rotation axis. The partition plate separates the first and second portions outside the delivery region. It has a configuration that prevents the developer from moving between other developer transport members. The developing device that, even on the screw-like member and the same center line relatively rotatably provided on together with the first screw-like member from one axial end by the transfer unit before the developer conveying member is formed The developer is delivered to the second developer transport member by a member provided in the delivery section, and the rotation speed of the first developer transport member and the opening width of the partition plate at the developer delivery section The opening width of the partition plate at the developer delivery section and the rotational speed of the member provided at the delivery section are configured to satisfy the following expression (1).
α · R · l ≦ α '· R' · L (1)
here,
α: transport efficiency of developer transport member (screw) R: rotation speed of developer transport member (screw) [rpm]
l: Pitch length [m] of developer conveying member (screw)
α ′: Transport efficiency of the transfer section R ′: Rotation speed [rpm] of the member (for example, paddle) of the transfer section
L: Opening width of the transfer part [m]
And

Note that the transport efficiency α of the developer transport member indicates what percentage of the agent in the space through which the spiral blade (screw blade) has passed when the developer transport member rotates once. The definition is as follows.
α = u / (V · d)
Further, the conveyance efficiency α ′ of the delivery unit represents the percentage of developer in the space through which the paddle passes when a member (for example, paddle) of the delivery unit rotates once, and its definition Is as follows.
α ′ = u ′ / (V ′ · d)
here,
Developer speed on developer conveying member (screw) (actual measurement): u [kg / s]
Screw passing volume: V = R / 60 · π ((r 1/2) 2 - (r 2/2) 2) · l [m 3 / s]
Developer speed at delivery section (actual measurement): u ′ [kg / s]
Paddle passage volume: V '= R' / 60 · dπ ((r 1/2) 2 - (r 2/2) 2) · L [m 3 / s]
External form of screw: r ₁ [m]
Screw shaft diameter: r ₂ [m]
Bulk density of developer: d [kg / m ³ ]
It is.

  In the present invention, of the two developer conveying members arranged in parallel with the partition plate in between, the developer conveying member on the upstream side (delivering side) in the developer conveying direction at the developer delivering portion is the first. One developer conveying member and the developer conveying member on the downstream side (receiving side) in the developer conveying direction are used as the second developer conveying member. Therefore, in a configuration in which there are transfer portions at both ends of the developing device and the developer circulates, one of the transfer portions is positioned on the upstream side (transfer side) in the developer transport direction, and the first developer transport member and Since this is located on the downstream side (receiving side) in the developer transport direction in the other delivery section, it becomes the second developer transport member. That is, the first and second developer transport members are defined for convenience in one delivery unit.

(Measurement method of developer speed)
Here, a method for actually measuring the developer speed required to obtain the developer transport efficiency is described below, assuming that the first developer transport member is the screw A and the second developer transport member is the screw B.

(1) Measuring method of developer speed on screw As shown in FIG. 8, a developer supply bottle is provided at the upper part of the screw casing where the screw is arranged, and an opening and a developer recovery bottle are provided at the lower part of the screw casing. Provide. The collection port facing the bottle port of the screw casing is made sufficiently large so as not to affect the developer speed. Also, the supply port of the developer supply bottle is made sufficiently large so that a constant developer surface can always be secured.
After setting in this way, the motor is rotated at a certain rotation speed R and waits until the developer surface reaches a steady state.
Thereafter, the motor speed is rotated again, and the developer speed is measured by measuring the weight Δw [kg] of the developer falling into the bottle for Δt seconds (that is, conveyed by the screw),
u [m / s] (= Δw / Δt)
Ask for.

(2) Measure method of developer speed of transfer unit As shown in FIG. 9 (view of the developing device from above), in order to achieve only the transfer speed of the transfer unit, the developer supply bottle and the developer recovery bottle are It is brought close to a place 10 mm from the delivery area.
Then, in the same procedure as (1), the developer speed is measured by measuring the weight Δw [kg] of the developer falling into the bottle for Δt seconds (that is, conveyed by the screw),
u [m / s] (= Δw / Δt)
Ask for.
At this time, the rotational speed of the motor is set to the same rotational speed as when the developer speed on the screw is obtained.

(Derivation of Formula (1) and Formula (2))
The screw conveyance efficiency α represents the percentage of the developer that has advanced in the space where the wings have passed when the screw makes one revolution, and the conveyance efficiency α ′ of the delivery unit is When the paddle, which is a member provided in the transfer section, makes one rotation, it indicates what percentage of the developer contained in the space through which the paddle has passed is transferred.
α and α ′ are substantially constant values regardless of the number of rotations of the screw and the paddle and the opening width of the transfer portion.
Accordingly, the developer weights W and W ′ transported by the screw and the paddle per second can be obtained using the transport efficiencies α and α ′. That is, the developer weights W and W ′ are
W = α · (space volume through which the screw blades passed in 1 second) · d
= Α · (R / 60 · π ((r1 / 2) 2− (r2 / 2) 2) · l) · d
W ′ = α ′ · (space volume through which the paddle passed in 1 second) · d
= Α ′ · (R ′ / 60 · π ((r1 / 2) 2− (r2 / 2) 2) · L) · d
Can be calculated.

In order that the developer does not stagnate at the transfer section, it is necessary to satisfy W ≦ W ′.
α · R · l ≦ α '· R' · L (1)
Can guide.
Further, since the screw and the paddle portion are usually integrated, R = R ′. From this, equation (2),
α · l ≦ α '· L (2)
Can guide.
That is, once the transport efficiencies α and α ′ are obtained by an experiment, the width (opening width) L of the transfer portion necessary for preventing the developer from being stagnated in the transfer portion is obtained by calculation.

[Examples corresponding to each means]
(Example 1: Example of the first means)
FIG. 10 shows a configuration in which the screw and the delivery portion are driven independently.
In FIG. 10, the screw (screw A) that is the first developer conveying member and the members (paddle and screw) of the transfer section are driven to rotate independently of each other. On the other hand, the member of the transfer part is pivotally supported via a bearing (for example, a bearing). The gear attached to the rotating shaft of the screw and the gear attached to the member of the transfer section can be driven by the same motor (not shown) via the drive gear by adjusting the gear ratio, And since each rotation speed can be adjusted independently, above-mentioned Formula (1) can be satisfy | filled.

( Reference example )
FIG. 11 shows the result of measuring the change in the conveyance efficiency of the transfer section when the rotation direction of the screw A and the arrangement angle of the screw A and the screw B are changed. 11D, when the screw A and the screw B are arranged substantially horizontally as shown in FIGS. 11A and 11B, the bottom feed ( As described in the third means, it can be seen that the rotation direction of the screw A is counterclockwise) is advantageous for increasing the conveyance efficiency, but the screw A is below the screw B as shown in FIG. Therefore, when the developer embedment ratio of the screw A is increased, it is understood that the upward feed (the rotation direction of the screw A is clockwise as described in the seventh means) is more advantageous. Therefore, these two rotational directions need to be used properly depending on the positional relationship between the screw A and the screw B.

(Example 4: Example of the fourth means)
FIG. 12 shows the result of measuring the change in the transfer efficiency of the transfer section when the number of the paddles of the screw A is changed. (1) to (4) in FIG. 12A illustrate an example in which the number of paddles is 1 to 4. As can be seen from the result of FIG. 12B, it can be seen that when the number of paddles is two, the transfer efficiency α ′ of the transfer section is the most efficient.

( Reference example )
FIG. 13 shows the result of measuring the change in conveying efficiency when the paddle of the delivery part of the screw A is continuous with the end of the screw blade and when it is discontinuous. It can be seen that the transfer efficiency α ′ of the delivery part is higher when the paddle of the delivery part of the screw A is made continuous with the end of the screw blade.

(Example 6: Example of sixth means)
FIG. 14 shows the result of measuring the change in the transfer efficiency of the delivery section when the lead angle θ of the paddle of the delivery section of the screw A is changed.
Lead angle θ is
50 ° ≦ θ ≦ 80 °
It can be seen that the transfer efficiency of the transfer section is increased within the range of.

  From the results shown in FIGS. 12, 13, and 14, the most suitable paddle shape in the case of downward feeding is such that the paddle of the delivery part of the screw A is made continuous with the end of the screw blade, and the paddle is continuous with the screw blade. 2 and the lead angle is 33 °.

( Reference example )
FIG. 15 shows the result of measuring the change in the transfer efficiency of the transfer section when the number of the paddles of the screw A is changed during the upward feed as shown in FIGS. 11B and 11C. (0) to (4) in FIG. 15A illustrate an example in which the number of paddles is 0 to 4. In the case of top feed, it can be seen that the conveyance efficiency is highest when the number of sheets is 0, that is, when there is no paddle and the screw continues to the end of the delivery section.

(Embodiment 8: Embodiment of ninth means)
The condition of the number of paddles at the transfer section varies depending on whether the screw A is an upper feed or a lower feed, but the hatched lines are added as shown in FIG. 16A regardless of whether the screw A is an upper feed or a lower feed. Experiments have confirmed that the region a is not provided with the case irregularities b as shown in FIGS. 16B and 16C so that the transfer efficiency at the transfer section is good.

(Example 9: Example of the tenth means)
As an example, a description will be given of the case of a biaxial transport type developing device in which the rotation direction of each screw is as shown in FIG. Delivery from the screw I (402) to the screw II (403) is an upward feed, and delivery from the screw II (403) to the screw I (402) is a downward feed.
Therefore, without passing the paddle at the transfer part from the screw I to the upper transfer screw I to the screw II, the screw wing is extended to the transfer part as it is. Is devised to have two. However, since the screw I and the screw II are installed horizontally, there is still a difference in the transfer efficiency of both the transfer parts (for example, α ₁ ′ = 0.7, α ₂ '= 0.74). Therefore, the minimum required opening widths L ₁ and L ₂ of the transfer section are also different on both sides.
Here, when the screw pitch length: l = 20 mm and the screw conveyance efficiency: α = 0.5, from the above formula (2),
L ₁ ≧ 20 × 0.5 / 0.7 = 14.3
L ₂ ≧ 20 × 0.5 / 0.74 = 13.5
It becomes.
Therefore, the opening widths L ₁ and L ₂ on both sides can be set to 15 mm, but the development device can be miniaturized under the conditions of L ₁ = 14.5 mm and L ₂ = 13.5 mm. it can.

(Example 10: Examples of the 11th to 14th means)
In the three-axis conveyance type developing device having the configuration shown in FIG. 2 or FIG. 7, the transfer part from the collection to the supply / stirring was the biggest problem. For example, even though the developer transport screw 5e (506) can sufficiently transport the developer, the developer whose toner density has been lowered due to the developer stagnation at the transfer portion is reduced again to the developing roller (sleeve) 5a ( 505), the rotational speed of the collecting and conveying screw 5e (506) had to be increased more than necessary.

Therefore, the number of rotations of the recovery / conveying screw can be reduced by using the recovery / conveying screw 5e (506) as the first developer conveying member and changing the transfer portion into a shape that satisfies the conditions of the second means. The developing device can cope with a high process linear velocity. FIG. 18 shows the experimental results before and after improvement.
At this time, the number of paddles in the downstream portion of the supply / conveying screw 5c (508) is four (lead angle 90 °). This is because it has been confirmed from experiments that the conveyance efficiency is highest when the number of paddles downstream of the supply conveyance screw 5c (508) is four (see the experimental results in FIG. 19). In this way, the appropriate number of paddles is different only in the supply / conveying screw 5c (508) because the paddles have three-axis side-by-side functions specific to the conveying type (from the supplying / conveying screw 5c (508)). This is because not only the developer that has been released but also the developer that has been carried from the paddle of the collecting and conveying screw 5e (506) must be carried).

(Example 11: Example of the twelfth means)
By using the developing device that satisfies the conditions described in the first to tenth examples for the developing device 5 of the process cartridges 10Y, 10C, 10M, and 10K of the image forming apparatus having the configuration shown in FIG. In addition, since the load on the developer is reduced, a stable toner adhesion amount can be always obtained over a long period of time, so that a process cartridge with high image density stability can be realized.

(Example 12: Examples of the thirteenth to sixteenth means)
By using a developing device that satisfies the conditions described in the first to tenth embodiments in the image forming apparatus having the configuration shown in FIG. 1 or the developing device (or process cartridge) of the image forming apparatus having the configuration shown in FIG. Since the process linear velocity is realized and the load on the developer is reduced, a stable toner adhesion amount can be obtained over a long period of time, so the image density is highly stable, and color reproducibility and color balance are excellent. An image forming apparatus capable of obtaining a high-quality color image can be realized. Further, by using the developing device of the present invention in the one-pass double-side transfer type image forming apparatus shown in FIG. 1, it is possible to obtain a color image excellent in density stability over a long period of time with very high productivity. As a result, there is no difference in image quality between the front and back sides, and a color double-sided image with always stable image quality can be obtained.

1 is a diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied, and is a schematic central sectional view illustrating an internal configuration of the entire image forming apparatus. It is a schematic block diagram which shows the structural example of the image forming unit used for the image forming apparatus shown in FIG. It is a figure which shows another example of a structure of the image forming apparatus with which this invention is applied, Comprising: It is a general | schematic center sectional view which showed the internal structure of the image forming apparatus. It is a schematic sectional drawing which shows the structural example of the developing device of a biaxial conveyance type. FIG. 10 is a schematic cross-sectional view illustrating a configuration example of a conventional triaxial conveyance type developing device described in Patent Document 1. FIG. 10 is an explanatory diagram of the operation of a conventional developing device described in Patent Document 2. 1A and 1B are diagrams illustrating a configuration example of a three-axis conveyance type developing device to which the present invention is applied, in which FIG. 1A is a schematic cross-sectional view of the developing device, and FIG. FIG. It is explanatory drawing of the measuring method of the developer speed on a screw. It is explanatory drawing of the measurement method of the developer speed of a delivery part. It is a figure which shows an example of the structure which a screw and a delivery part drive independently. It is explanatory drawing which shows the result of having measured the change of the conveyance efficiency of the delivery part when changing the rotation direction of the screw A, and the arrangement angle of the screw A and the screw B. It is explanatory drawing which shows the result of having measured the change of the conveyance efficiency of the delivery part when changing the number of paddles of the screw A. FIG. It is explanatory drawing which shows the result of having measured the change of conveyance efficiency by the case where the paddle of the delivery part of the screw A is made continuous with the edge part of a screw blade, and the case where it is made discontinuous. It is explanatory drawing which shows the result of having measured the change of the conveyance efficiency of a delivery part when changing the lead angle (theta) of the paddle of the delivery part of the screw A. FIG. FIG. 12 is an explanatory diagram illustrating a result of measuring a change in conveyance efficiency of the transfer unit when the number of the paddles of the screw A is changed during the upward feeding as illustrated in FIGS. It is explanatory drawing which shows the example which conveyance efficiency reduces when an unevenness | corrugation is given to a case. It is explanatory drawing of the relationship between the opening width in the developer delivery part of a biaxial conveyance type developing device, and conveyance efficiency. FIG. 8 is a diagram showing experimental results of screw rotation speeds with respect to sleeve linear speeds before and after improvement when the transfer part of the recovery conveyance screw of the developing device shown in FIG. 7 is improved to a shape that satisfies the condition of the second means. is there. It is a figure which shows the experimental result of the relationship between the number of paddles of the delivery part of the supply conveyance screw and collection | recovery conveyance screw of a developing device shown in FIG. 7, and conveyance efficiency.

Explanation of symbols

1 (1Y, 1C, 1M, 1K), 501: photoconductor (latent image carrier)
2: Cleaning device 3: Charging device 4: Exposure device 5, 400, 504: Developing device 5a, 401, 505: Developer carrier (developing roller or sleeve)
5c, 5d, 5e, 402, 403, 506, 508, 511: Developer conveying member (screw)
10Y, 10C, 10M, 10K: Process cartridge 11: Intermediate transfer device 12: Intermediate transfer belt (intermediate transfer member)
16: Paper transfer device (secondary transfer means)
17: conveying device 18: fixing device 20: first image carrier unit 21: first image carrier belt (first intermediate transfer member)
22, 32: primary transfer roller (primary transfer means)
40: paper feeding device 46: secondary transfer roller (secondary transfer means)
47: Transfer charger (secondary transfer means)
50: Recording material conveying device (recording material conveying means)
60: fixing device 80Y, 80C, 80M, 80K: first image forming unit 81Y, 81C, 81M, 81K: second image forming unit

Claims (16)

A developer carrying member that carries the developer and rotates to develop the latent image on the latent image carrying member, and at least two developer carrying members arranged in parallel to the developer carrying member and carrying the developer in different directions. At least a member (hereinafter referred to as first and second developer conveying members) and a partition plate disposed between the first and second developer conveying members. The developer transport member is formed of a screw-shaped member that transports the developer in the axial direction by rotating with a spiral wing provided on the rotation shaft portion, and from one end of the first developer transport member in the axial direction to the other end. The developer is transported, and the developer is delivered from the other end through the opening of the partition plate to the second developer transport member in a direction perpendicular to the rotation axis. The partition plate separates the first and second portions outside the delivery region. To prevent the developer from moving between other developer transport members In the developing apparatus,
A screw-like member is formed from one end in the axial direction of the first developer conveying member to the front of the delivery portion, and is provided on the delivery portion provided on the same center line as the screw-like member and relatively rotatable. Deliver the developer to the second developer conveying member by the provided member,
The number of rotations of the first developer conveying member, the opening width of the partition plate at the developer delivery part, and the number of revolutions of the member provided at the delivery part are the conditions of the following formula (1): A developing device characterized by satisfying the above.
α · R · l ≦ α '· R' · L (1)
here,
α: Transport efficiency of developer transport member R: Number of rotations of developer transport member [rpm]
l: pitch length of developer conveying member [m]
α ′: Conveying efficiency of the transfer unit R ′: Number of rotations of members of the transfer unit [rpm]
L: Opening width of the transfer part [m]
And The developing device according to claim 1 ,
When the two developer conveying members are viewed from the axial direction, the first developer conveying member is disposed on the left side, the second developer conveying member is disposed on the right side, and the first and second developer conveying units are disposed. When the members are arranged substantially horizontally, the developing device is characterized in that the rotation direction of the first developer conveying member is counterclockwise. The developing device according to any one of claims 1 or 2,
A paddle made of a plane that can be connected continuously to a line perpendicular to the rotation axis and having the same length as the wings of the developer conveying member is attached as a member provided in the transfer section. The number of sheets of the developing device is two. The developing device according to claim 3 .
The developing device according to claim 1, wherein the paddle of the transfer section is a flat surface within a range of a lead angle of 50 ° ≦ θ ≦ 80 °. The developing device according to claim 1 or 2,
When the two developer conveying members are viewed from the axial direction, the first developer conveying member is disposed on the left side, the second developer conveying member is disposed on the right side, and the first developer conveying member is disposed on the right side. located below the second developer conveying member, the rotation direction of the first developer conveying member, a developing device which is a clockwise direction. In the developing device according to any one of claims 1 to 5 ,
2. A developing device according to claim 1, wherein there is no unevenness of the case inside two tangent lines passing through both the first developer conveying member and the second developer conveying member. In the developing device according to any one of claims 1 to 6 ,
The first and second developer transport members are of a biaxial transport type arranged substantially horizontally below the developer carrier, and one of the first and second developer transport members Is a developer conveying member for supplying and collecting the developer to the developer carrying member, and the other is a developer conveying member for conveying and stirring after toner replenishment. One developing device satisfies the above-mentioned conditions. In the developing device according to any one of claims 1 to 6 ,
In addition to the first and second developer conveying members, the triaxial conveying type has a third developer conveying member, and one of the first to third developer conveying members is the developer. A developer transport member for supplying the developer to the carrier, and the other one collects the developer after completion of development from the developer carrier and supplies the collected developer to the developer transport member. And a recovery developer transport member that is transported in parallel and in the same direction, and the other is a surplus developer that has not been supplied from the supply developer transport member to the developer carrier and the recovery developer A developer transport member for stirring that stirs and transports the developer transported from the developer transport member in a direction opposite to the developer transport member for supply, and at least one of the delivery points between the three developer transport members is The present condition characterized by satisfying the above conditions Apparatus. The developing device according to claim 8 , wherein
The first developer conveying member is the collecting developer conveying member, and a transfer portion from the collecting developer conveying member to another developer conveying member satisfies the above condition. Development device. The developing device according to claim 8 , wherein
The developing device, wherein the three developer conveying members are arranged in a substantially horizontal direction. The developing device according to claim 10 .
2. A developing device according to claim 1, wherein a paddle is provided at a delivery portion of the supply developer conveying member, and the number of the paddles is 3 to 5. In a process cartridge integrally including at least a latent image carrier on which an electrostatic latent image is formed on a surface and a developing device that develops and visualizes the electrostatic latent image on the latent image carrier,
As the developing device, a process cartridge comprising the developing device according to any one of claims 1 to 11. In an image forming apparatus comprising at least a latent image carrier on which an electrostatic latent image is formed on a surface, and a developing device that develops and visualizes the electrostatic latent image on the latent image carrier,
An image forming apparatus comprising the process car ridges according to the developing apparatus, or claim 12 according to any one of claims 1 to 11. The image forming apparatus according to claim 13 .
An image forming apparatus comprising a plurality of developing devices or process cartridges having different developing colors and forming a color image on a recording material. The image forming apparatus according to claim 13 .
A plurality of image forming units or process cartridges each having at least a latent image carrier and a developing device for developing an electrostatic latent image formed on the latent image carrier. An image forming apparatus, wherein a different image is formed and transferred directly to a recording material or via an intermediate transfer member to form a color image on the recording material. The image forming apparatus according to claim 13 .
A first image forming unit group in which a plurality of image forming units each having at least an image bearing member and a developing device for developing an electrostatic latent image formed on the image bearing member are arranged side by side; and the first image forming unit group A first image forming station comprising a first intermediate transfer body on which the formed first toner image is transferred and carried;
A second image forming unit group in which a plurality of image forming units having at least an image bearing member and a developing device for developing an electrostatic latent image formed on the image bearing member are arranged side by side; and the second image forming unit group A second image forming station comprising a second intermediate transfer body on which the formed second toner image is transferred and carried,
The first toner image transferred to the first surface of the recording material is formed by the first image forming station, and the second toner image transferred to the second surface of the recording material is formed by the second image forming station. An image forming apparatus wherein the first toner image and the second toner image are transferred to a recording material simultaneously or sequentially before fixing.

Images