JP5578421B2 - Developing device, process cartridge having the developing device, and image forming apparatus having the developing device or the process cartridge - Google Patents

Description

  The present invention relates to a developing device used for a copying machine, a facsimile, a printer, and the like, a process cartridge having the developing device, and an image forming apparatus having the developing device or the process cartridge.

  Conventionally, various types of developing devices are known as developing devices that form a toner image on a photoreceptor using a two-component developer. For example, as shown in FIG. 12, in a developing device 500 that forms a toner image on the photoreceptor 1 using a two-component developer, a developing roller 501 that is a developer carrying member as a conveying member that stirs and conveys the developer. A configuration in which two are provided in parallel with each other is known. The developing device 500 mainly includes a case 504, a developing roller 501, a conveying member 503 on the side close to the developing roller 501, a conveying member 502 on the side away from the developing roller 501, and a developer carried on the developing roller. And a developer layer thickness regulating member 505 for regulating the amount.

  The developer accommodating portion is separated from the conveying member 503 on the side close to the developing roller 501 and the conveying member 502 on the side far from the developing roller 501 by a partition wall 504 a provided in the case 504. Openings are provided in the vicinity of both ends of each conveying member of the partition wall 504a, and the developer 320 to be stirred and conveyed is developed from the downstream side in the developer conveying direction of the conveying member 503 near the developing roller 501. The developer is conveyed upstream of the conveying member 502 away from the roller 501 in the developer conveying direction. Further, the developer 320 to be agitated / conveyed from the downstream side in the developer conveying direction of the conveying member 502 on the side away from the developing roller 501 to the upstream side in the developer conveying direction of the conveying member 503 on the side close to the developing roller 501. Be transported. In addition, on the upstream side in the developer transport direction of the developer accommodating portion where the transport member 502 on the side away from the developing roller 501 is provided, a drop opening (hereinafter referred to as replenishment toner) for replenishing newly replenished toner (Not shown) is provided.

  In the developing device 500 configured as described above, the conveying member 503 on the side close to the developing roller 501 supplies the developer 320 to be agitated / conveyed to the developing roller 501 and collects the developer 320 that has not been developed. To do. Then, the collected developer 320 is circulated and agitated in each developer accommodating portion provided with the conveying member 503 on the side close to the developing roller 501 and the conveying member 502 on the side remote from the developing roller 501.・ Conveyed. In such a configuration, the developer 320 collected once after passing through the developing region where the photosensitive member 1 and the developing roller 501 face each other is accommodated on the side away from the developing roller 501 while being stirred and conveyed. The toner is appropriately agitated with the replenishing toner on the upstream side in the developer conveyance direction. It is also known that the image density is stabilized because the developer replenished with the replenished toner is supplied to the development area again after being given a necessary charge amount.

  However, in the above-described example of the conventional developing device, when the developer 320 that has not been used for development is collected in the developer accommodating portion provided with the conveying member 503 on the side close to the developing roller 501, the photoreceptor 1. A part of the foreign matter or the like adhering to the surface is also collected. Furthermore, in recent years, the use of toner having a low melting point has been increased from the viewpoint of energy saving. Low-melting toner tends to aggregate due to heat outside the fixing portion. In particular, since the toner and the carrier are conveyed while being stirred and mixed in the developing device, the toner easily aggregates. As a countermeasure against aggregation, it is important to prevent the temperature of the developer from rising, but heat is generated only by stirring and mixing the developer. When developer aggregation occurs in the developing device or when foreign matter is mixed in, the aggregate or foreign matter is caught by the developer layer thickness regulating member and is a developer carrier. The developer layer on the developing roller is not uniform, and problems such as vertical white stripes occur. In recent years, it has been demanded to solve the problems caused by the aggregation of the toner and the mixing of foreign matters.

  Regarding the above-mentioned problems, Patent Document 1 discloses a separating apparatus used when the developer is reused as follows. As a means for removing foreign matters mixed in the developer, a mesh (mesh filter) is used, and the mesh is made of a material that is frictionally charged to the same polarity as the developer charging polarity by friction with the developer. In this configuration, foreign matters can be removed, but there is no effect of lowering the temperature of the developer, and generation of toner aggregates itself when using a low melting point toner cannot be suppressed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device having a simple configuration capable of removing foreign matters and suppressing the generation of toner aggregates.

In order to solve the above-mentioned problems, the invention of the developing device according to claim 1 includes a developer carrying member carrying a developer for forming a toner image on the image carrying member, and a developer carrying member on the developer carrying member. A developer layer thickness regulating member that regulates the developer layer thickness, a transport path that is arranged side by side and transports the developer, and a first series in which the developer moves from the upper transport path to the lower transport path. A passage and a second communication portion through which the developer moves from the lower conveyance path to the upper conveyance path; and the traveling direction of the developer in the upper conveyance path with respect to a horizontal plane in the first communication portion In contrast, a grounded conductive mesh is arranged so as to be lowered toward the downstream .
The invention according to claim 2, in the developing device according to claim 1, is characterized in that the toner is supplied from above the conductive mesh grounded.
According to a third aspect of the present invention, in the developing device according to the first or second aspect , the maximum width of the grounded conductive mesh hole is smaller than the gap between the developer carrying member and the developer layer regulating member. It is characterized by.
According to a fourth aspect of the present invention, there is provided a process cartridge according to any one of the first to third aspects.
According to a fifth aspect of the present invention, the image forming apparatus includes the developing device according to any one of the first to third aspects or the process cartridge according to the fourth aspect. .
In the present invention, since the mesh is provided in the first continuous portion where the developer moves from the upper conveyance path to the lower conveyance path , foreign matter can be removed. In addition, by using a conductive mesh, that is, a metal mesh having a high thermal conductivity for this mesh, when the developer becomes hot, the heat is released to the outside of the developing device through this mesh to cool the developer. And the generation of developer aggregates can be suppressed. Further, since the conductive mesh is grounded, the heat of the toner can be easily moved even when the electrons move from the charged toner to the conductive mesh where the electrons are grounded. Even when aggregates are generated or foreign substances are mixed in, an object having a size caught by the mesh can be removed. In addition, since the mesh provided in the first continuous portion is provided so as to be inclined downward toward the downstream with respect to the developer traveling direction in the upper conveyance path, the mesh can pass per unit time. The amount of developer can also be increased.

In the present invention, since the grounded conductive mesh is provided in the first continuous portion from the upper conveyance path to the lower conveyance path , foreign matter can be removed, and the developer aggregate is cooled by cooling the developer. It is possible to provide a developing device having a simple configuration capable of suppressing the occurrence. In addition, since the mesh is provided so as to incline toward the downstream with respect to the developer traveling direction in the upper conveyance path, the amount of developer that can pass through the mesh per unit time may be increased. it can.
Therefore, it is possible to suppress problems such as toner aggregation in the developing device and vertical white streaks caused by foreign matters mixed in the developing device.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. It is a schematic block diagram of an image formation part. Explanatory drawing of magnetic flux density distribution formed in the developing roller in a developing device. Explanatory drawing of the structure of the developing roller of a developing device. The internal perspective view of the principal part of a developing device. FIG. 3 is an external perspective view of a main part of the developing device. Explanatory drawing of the communicating port part of a developing device. FIG. 3 is a schematic view of the vicinity of a developer dropping port of a developing device. FIG. 3 is a schematic view of the vicinity of a developer dropping port of a developing device. Graph of developer temperature when the mesh is grounded and when it is not grounded. Explanatory drawing of the flow of the developer in a developing device in a modification. An example of a schematic structure figure of the conventional development device.

Hereinafter, as an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color image forming apparatus (hereinafter, simply referred to as “image forming apparatus”) in which a plurality of photoconductors are arranged in the horizontal direction will be described. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. FIG. 2 is a schematic configuration diagram of the image forming unit.

  This image forming apparatus is provided with a transport belt 15 for transporting the transfer paper 8 at the center thereof. Above the conveyor belt 15, four image forming units 17K, 17M, and 17Y that form black (K), magenta (M), yellow (Y), and cyan (C) color images sequentially from the upstream side in the paper conveyance direction. , 17C are arranged side by side, so-called tandem image forming units are opposed to each other. Note that the order of colors is not limited to this. For example, black (K) may be arranged on the most downstream side, and images may be formed in the order of M, Y, C, and K.

  The conveyor belt 15 is an endless belt that is stretched around support rollers 18 and 19, one of which is a drive roller and the other is a driven roller, and rotates in the counterclockwise direction in the figure by the rotation of the support rollers 18 and 19. To do. Below the transport belt 15, paper feed trays 20, 21, and 22 that store the transfer paper 8 are provided.

  Each of the image forming units 17K, 17M, 17Y, and 17C includes drum-shaped photoreceptors 1K, 1M, 1Y, and 1C as image carriers. Around each of the photoreceptors 1K, 1M, 1Y, and 1C, there are a charging device, an exposure device, a developing device, a cleaning device, and the like, which will be described later.

  In addition, four transfer devices 5K, 5M, 5Y, and 5C are disposed on the inner side of the conveyance belt 15 facing the image forming units 17K, 17M, 17Y, and 17C, respectively. The transfer devices 5K, 5M, 5Y, and 5C are supplied with a transfer bias from a power source (not shown), and the toners formed on the photoreceptors 1K, 1M, 1Y, and 1C by the image forming units 17K, 17M, 17Y, and 17C. The image is transferred onto the transfer paper 8 that is transported to the transport belt 15. A fixing device 24 for fixing the toner image transferred onto the transfer paper 8 is provided on the left side of the transfer conveyance belt 15 in the drawing.

  In this image forming apparatus, at the time of image formation, for example, among the transfer sheets 8 stored in the sheet feed tray 20, the transfer sheet 8 at the uppermost position is sent out and is temporarily put on standby by the registration roller 23. Then, the image forming units 17K, 17M, 17Y, and 17C are sent out in synchronization with the image formation, and are attracted to the transport belt 15 by electrostatic attraction. The transfer paper 8 adsorbed on the conveyance belt 15 is conveyed to the first image forming unit 17K, and the black toner image formed on the photoreceptor 1K is transferred by the transfer device 5K. The transfer paper 8 attracted to the transport belt 15 is transported to the next image forming unit 17M, and a magenta toner image formed on the photoreceptor 1M by the transfer device 5M is already formed on the transfer paper 8. It is transferred onto the black toner image. Further, the transfer paper 8 is conveyed to the next image forming unit 17Y, and the yellow toner image formed on the photoreceptor 1Y by the transfer device 5Y is replaced with a black toner image or magenta toner already formed on the transfer paper 8. It is transferred onto the image. Similarly, in the next image forming unit 17 </ b> C, the cyan toner image is superimposed and transferred, and a full-color superimposed image that is a four-color superimposed toner image is obtained on the transfer paper 8. The transfer paper 8 on which the full-color superimposed image is formed in this way passes through the image forming unit 17C, is peeled off from the conveyance belt 15, and then fixed by the fixing unit 24 while passing between the pair of fixing rollers. The paper is discharged to the paper discharge tray 25.

  Next, the image forming units 17K, 17M, 17Y, and 17C will be described in detail. The four image forming units 17K, 17M, 17Y, and 17C have substantially the same configuration except that they handle different colors of toner. Therefore, the subscripts are omitted and the image forming unit 17 is hereinafter omitted. Will be described.

  FIG. 2 is a schematic configuration diagram of the image forming unit 17. The image forming unit 17 includes a charging device 2, a developing device 3, a cleaning device 6, and the like around the drum-shaped photoconductor 1. In FIG. 2, the charging device 2 includes a rotating body that rotates at the same speed as the photosensitive member 1, but is not limited to the rotating body and may be a corona discharge type. The surface of the photoreceptor 1 is uniformly charged by the charging device 2 and then exposed by the writing exposure L from the exposure device 16 (not shown in FIG. 2) to form an electrostatic latent image. The developing device 3 includes a developing roller 302 that carries a developer 320 made of a magnetic carrier and a toner contained in a developing container 301 as a casing on the surface. An opening is formed in a part of the developing container 301, and a part of the developing roller 302 is exposed and arranged so as to be in close proximity to the photoreceptor 1, and an electrostatic latent image formed on the surface of the photoreceptor 1 is formed. A developing area A where toner is supplied and development is performed is formed. The developing roller 302 transports the developer 320 carried to the developing area A by moving on the surface. A developing bias is applied to the developing sleeve 302 c from a power source (not shown), and a developing potential that is a potential difference is formed between the electrostatic latent image on the photosensitive member 1 and the developing roller 302. The toner from the developer 320 on the developing roller 302 is transferred to the electrostatic latent image on the photosensitive member 1 by this development potential, whereby the electrostatic latent image is developed and a toner image is formed. The toner image formed on the photoreceptor 1 moves to the transfer region B facing the transfer device 5, and the transfer device 5 transfers the toner image onto the transfer paper 8 transported by the transport belt 15. In FIG. 2, the transfer device 5 is composed of a rotating body, but is not limited to a rotating body, and may be a corona discharge type. After the toner image has been transferred, the photosensitive member 1 is not completely transferred onto the transfer paper 8 by the cleaning device 6, and the toner remaining on the surface of the photosensitive member 1 is cleaned to prepare for the next image forming process.

  It is also possible to apply to an intermediate transfer belt system in which the toner image on the photosensitive member 1 is once transferred to an intermediate transfer member (intermediate transfer belt or the like), and then the multicolor toner is collectively transferred to transfer paper. In this case, the toner on the photosensitive member 1 is transferred to the intermediate transfer member (intermediate transfer belt) in the transfer region B.

  In the present embodiment, the image forming unit 17 is in the form of a process cartridge in which the photosensitive member 1, the charging device 2, the developing device 3, and the cleaning device 6 are integrally formed. It is provided so as to be detachable from the apparatus main body.

Next, the basic configuration and operation of the developing device 3 used in the image forming apparatus of the present embodiment will be described with reference to the drawings. A developing device 3, as shown in FIG. 2, the developing inside the developing roller 302 of the container 301, a developer regulating member 303, and the agitation transport member and to supply chamber of the developer conveying member 304 as a developer layer thickness regulating member And a recovery chamber conveyance member 305, and the developer 320 is agitated and conveyed to be circulated. Moreover, the stirring conveyance member of this embodiment uses the screw of a spiral shape, and uses the outer diameter of a screw blade | wing with a diameter of 16 mm or less.

  Further, as shown in FIG. 3, the developing roller 302 has a magnet roller 302d in which a plurality of magnets MG are arranged in the circumferential direction, and a cylindrical developing sleeve 302c is integrated with the rotating shaft 302e around the magnet roller 302d. It is configured to rotate in the direction. The developing sleeve 302c is made of a nonmagnetic metal such as aluminum. The magnet roller 302d is fixed to an immovable member, for example, the developing container 301 so that each magnet MG is directed in a predetermined direction, and the developer sleeve 302c rotates around the periphery of the developer roller 320 to attract the developer 320 attracted by the magnet MG. Carry it. Here, in order to prevent complication of FIG.

  Further, as shown in FIG. 4, the developing roller 302 is mainly composed of the following. A fixed shaft 302a fixed to the developing container 301 as a stationary member, a magnet roller 302d having a columnar shape integral with the fixed shaft 302a, a developing sleeve 302c, a rotating shaft 302e integral with the developing sleeve 302c, and the like. . The developing sleeve 302c and the rotating shaft 302e integrated with the developing sleeve 302c cover the magnet roller 302d around a gap. The rotating shaft 302e is rotatable with respect to the fixed shaft 302a via a bearing 302f, and the rotating shaft 302e is driven to rotate by receiving power from a rotation driving means (not shown).

  In addition, a plurality of magnets MG are fixed to the outer periphery of the magnet roller 302d at a predetermined interval as shown in FIG. The developing sleeve 302c is rotated around these magnets MG. These magnets MG are for forming a magnetic field so that the developer can be spiked on the peripheral surface of the developing sleeve 302c, and can be cut off. A magnetic brush is formed by gathering the magnetic carriers along the normal magnetic field lines emitted from these magnets MG.

  Although there are many configurations of the magnet roller, the configuration of the magnet roller having three magnets MG inside the developing sleeve 302c and generating three magnetic poles (magnetic force distribution) will be described with reference to FIG. The magnetic pole of the portion (area corresponding to the development area A) facing on the line connecting the center O-1 of the developing roller 302 and the center O-2 of the photosensitive member is referred to as a P1 pole (development pole). The magnetic poles are referred to as P2 (casing counter pole) and P3 pole (developer regulating member counter pole) in the order of rotation of the developing roller 302 shown in FIG.

  The polarity is changed from the P1 pole to the N, S, and S poles, but these poles may have opposite polarities. The P1 pole is a development pole and faces the photoreceptor 1. P2 faces the casing, and P3 faces the developer regulating member. As shown in FIGS. 2 and 3, the developing roller 302 and the photosensitive member 1 are not in direct contact with each other in the developing area A, but are opposed to each other while maintaining a developing gap GP at a certain interval suitable for development. Yes. Then, on the developing roller 302, the developer 320 is raised and brought into contact with the photosensitive member 1, whereby toner is attached to the electrostatic latent image on the surface of the photosensitive member 1 to be visualized.

  In the developing device 3, a grounding bias power source is connected to the fixed shaft 302a shown in FIG. 4 (not shown). The voltage of the power source VP connected to the fixed shaft 302a is applied to the developing sleeve 302c via a conductive bearing (not shown) and a conductive rotating shaft 302e. On the other hand, the lowermost conductive support constituting the photoreceptor 1 is also grounded. In this way, an electric field for moving the toner separated from the carrier to the photosensitive member 1 side is formed in the developing region A, and the developing sleeve 302 c and the electrostatic latent image formed on the surface of the photosensitive member 1 are formed. The toner is moved toward the photoreceptor 1 side by the potential difference.

  Here, the developing apparatus of the present embodiment is an example used for an image forming apparatus of a writing method with writing exposure L as shown in FIG. Then, the charging device 2 uniformly applies a negative charge on the photosensitive member 1 and exposes the image portion with the writing exposure L in order to reduce the writing amount. A so-called reversal development method is used in which the electrostatic latent image is developed with negative polarity toner. This is merely an example, and the polarity of the charged charge placed on the photoreceptor 1 is not a major problem in the developing method of the present invention.

  As shown in FIG. 3, after the development, the P2 pole conveys the developed developer 320 carried on the developing roller 302 to the downstream side along with the rotation of the developing roller 302 and draws it into the developing container 301. The P2 and P3 poles have the same polarity, and there is no magnetic force to rise between the P2 and P3 poles, so that the ears fall asleep, and the developer 320 that has been drawn around the developing roller 302 until then is separated from the developing roller 302. The action of "release" works. The portion corresponding to the P2 to P3 poles on the developing roller where the ears are lying down (the region where the peak of the magnetic distribution curve is extremely low compared to other regions) separates the developer 320 from the developing roller 302, the agent separating region ( In FIG. 2, a region indicated by reference numeral 9 is formed.

  The developer 320 having the toner adhered to the photosensitive member 1 has a lower toner concentration in the developer. Therefore, the developer having the lowered toner concentration is conveyed again to the developing area A without leaving the developing roller 302. However, if it is used for development, there is a problem that a target image density cannot be obtained. In order to prevent this, in this embodiment, the developer is separated from the developing roller 302 in the agent separation area 9 after development. Thereafter, the developer separated from the developing roller 302 is sufficiently agitated and mixed in the developing container 301 so that the target toner density and toner charge amount are obtained.

  In this way, the developer 320 having the target toner density and charge amount is supplied to the developer storage space C by the supply chamber conveying member 304. The developer supplied to the storage space C is adjusted to a predetermined thickness by passing through the developer regulating member 303 located immediately downstream of the peak position of the P3 pole, so that the developing region is formed while forming a magnetic brush. It is conveyed to A. In addition, the P3 pole serves as a transport pole for transporting the developer.

  Hereinafter, as needed, referring to FIG. 5 showing the internal configuration of the developing device 3 in an assembled state and FIG. 6 showing a structure of the developing roller 302 shown in an exploded state, etc. The arrangement configuration will be described. As shown in FIGS. 2 and 3, the supply chamber conveying member 304 is arranged around the developing roller 302 and in the direction of 2 o'clock of the clock face in the drawing centering on the developing roller 302. This position is also on the upstream side of the developer regulating member 303. As shown in FIGS. 5 and 6, the supply chamber conveyance member 304 has a screw shape with a spiral around the rotation axis, and is centered on a center line O-304 parallel to the center line O-302 a of the developing roller 302. The developer rotates in the clockwise direction indicated by an arrow, and the developer is conveyed while stirring as indicated by an arrow 11 from the back side in the longitudinal direction of the center line O-304 toward the front side. That is, the supply chamber conveyance member 304 conveys the developer in the axial direction from the near side to the far side by the rotation of the rotation shaft.

  Further, the collection chamber conveying member 305 shown in FIG. 2 is a position around the developing roller 302, and in the drawing centering on the developing roller 302, in the vicinity of the agent separation region 9 on the 4 o'clock direction of the clock face. Is arranged. As shown in FIG. 5, the collection chamber transport member 305 has a screw shape with a spiral around the rotation axis, and an arrow centering on a center line O-305 parallel to the center line O-302a of the developing roller 302 Is rotated counterclockwise, and the developer is conveyed while being stirred as indicated by an arrow 12 from the far side in the longitudinal direction of the center line O-305 toward the near side. That is, the collection chamber transport member 305 transports the developer from the back side to the front side opposite to the transport direction by the supply chamber transport member 304 by the rotation of the rotation shaft.

  As shown in FIGS. 5 and 6, the supply chamber transport member 304 is positioned above the recovery chamber transport member 305, and the space around the supply chamber transport member 304 and the recovery chamber transport in the developing container 301. The space around the member 305 is adjacent. The front side ends of the supply chamber transport member 304 and the collection chamber transport member 305 are set so as to be located slightly in front of the front end of the developing roller 302, and the developer at the front end of the developing roller 302 is set. Is secured. Further, the back end portions of the supply chamber transport member 304 and the collection chamber transport member 305 are located on the back side with respect to the back end portion of the developing roller 302 to secure a space for toner replenishment described later. . Here, the developer regulating member 303 is installed according to the length of the developing roller 302.

  As shown in FIGS. 2 and 3, a partition between the supply chamber transfer member 304 and the recovery chamber transfer member 305 that shields the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305. A plate 306 is supported inside the developing container 301. As shown in FIG. 7, communication ports 307 and 308 are provided at both end portions of the partition plate 306. As shown in FIG. 5, the developer transported in the direction of arrow 12 by the collection chamber transport member 305 is cut off along the side wall of the developing container 301 at the end in the transport direction, and thus rises along this side wall. Then, it is conveyed to the upstream side of the supply chamber conveyance member 304 along the arrow 14 via the communication port 307 described above, and moves in the supply chamber along this supply chamber conveyance member 304. Similarly, the developer transported in the direction of the arrow 11 by the supply chamber transport member 304 is cut off at the end in the transport direction at the side wall of the developer container 301 to the side wall via the communication port 308. Along the collection chamber transporting member 305, it is transported to the upstream side of the recovery chamber transporting member 305 along the arrow 13.

  As described above, the developing device 3 of this embodiment has the developing roller 302 that carries the developer and rotates to visualize the electrostatic latent image formed on the photoreceptor 1. In addition, it has a supply chamber transport member 304 that rotates around a center line O-304 parallel to the center line O-302a of the developing roller 302 and stirs and transports the developer in the longitudinal direction of the center line O-304. ing. Further, the developer is disposed in the vicinity of the agent separation region 9 that separates the developer from the developing roller 302, and rotates around a center line O-305 parallel to the center line O-302 a of the developing roller 302, so A recovery chamber transport member 305 that stirs and transports the developer in a direction opposite to the transport direction is provided. Further, partition plates 306 having openings at both ends between the supply chamber transfer member 304 and the recovery chamber transfer member 305 and shielding the space around the supply chamber transfer member 304 and the space around the recovery chamber transfer member 305 are provided. Have. As described above, in the developing device 3 of the present embodiment, the supply chamber conveyance member 304 and the collection chamber conveyance member 305 in the circulation conveyance path along the arrows 11, 14, 12, and 13 shown in FIG. Two of them are arranged side by side up and down 302. Compared with the prior art shown in FIG. 12 in which two agitating and conveying members are arranged in the direction away from the developing roller (in the horizontal direction) by arranging the two vertically above the developing roller 302. The horizontal (horizontal) size can be reduced.

  Further, in the developing device 3 of the present embodiment that is compact in the horizontal direction, the partition plate 306 partitions the space around the supply chamber transfer member 304 and the space around the collection chamber transfer member 305. Then, only the developer 320 in which the toner and the carrier are sufficiently agitated and mixed is supplied to the developing roller 302 by the supply chamber conveying member 304, and the developer whose toner density has decreased immediately after the development is collected in the collection chamber conveying member. After being stirred and transported by 305, it is transported to the supply chamber side. Therefore, since the toner is not supplied to the developing roller 302 immediately after being collected, only the toner having a target charge amount is used for the developing roller 302, and high image quality can be obtained.

  Further, since the developer 320 in the developing device 3 consumes toner while repeating the developing operation, it is necessary to replenish the toner in the device from the outside of the developing device. In the present embodiment, toner is replenished from the outside from a developer replenishment section provided near the end on the back side of the developing device. In this replenishment, the replenished toner is not immediately used for development, but is supplied to the collection chamber through the communication port 308. The toner supplied to the recovery chamber is agitated by the recovery chamber transport member 305 and is subjected to development at a stable predetermined toner concentration. In the collection chamber provided with the collection chamber conveyance member 305, only the developer 320 separated from the developing roller 302 is collected, and the toner is not supplied to the developing roller 302. Therefore, a developer having a non-uniform toner concentration that is not sufficiently agitated by newly supplied toner from the supply opening 309 is not provided for development. The replenished toner is agitated and mixed in the developer 320 having a lowered toner density away from the developing roller 302, and the toner density is normalized before being conveyed to the front side of the developing device 3. Is lifted up to the supply chamber provided with Then, the toner is supplied to the developing roller 302 while being conveyed to the back side by the supply chamber conveying member 304 and used for development.

In addition, a toner density sensor (not shown) is provided at the lower portion of the inner wall of the developing container 301 shown in FIG. This sensor is a sensor for measuring magnetic permeability, and can detect the carrier concentration (= 100−toner concentration) of the developer. Further, it is determined from the detected carrier concentration whether the toner concentration on the sensor is insufficiently optimized, and the amount of toner to be replenished is determined. This toner concentration sensor is arranged at the downstream end of the collection chamber transport member 305 in the transport direction. Although as described by hand arrows 11,14,12,13 in Figure 5, the front prior to being conveyed by the supply chamber conveyer 304 to the back side, from being used for development, the collection chamber conveyer 305 The developer returned to the side increases, and the developer 320 tends to accumulate on the near side. Therefore, by disposing the toner concentration sensor on the downstream side of the collection chamber transport member 305, the developer is always filled above the sensor, and stable carrier concentration detection is possible.

  Next, the part where the developer falls from the supply chamber of the developing device 3 to the recovery chamber, that is, the part of the communication port 308, which is a characteristic part of the present embodiment, will be described with reference to FIG. FIG. 8 is a schematic view near the communication port 308 where the developer of the developing device 3 falls. The upper side is the supply chamber conveyance member 304 and the lower side is the collection chamber conveyance member 305, and the developer 320 is conveyed in the direction of the arrow. The grounded mesh 310 is disposed at the communication port 308 where the developer falls. When the developer 320 transported by the supply chamber transport member 304 reaches the communication port 308, the developer 320 falls due to gravity. By placing the mesh 310 on the falling part, it passes through the mesh 310 by the force of gravity.

  As shown in FIG. 8, the mesh 310 is disposed obliquely so as to incline downward toward the developer traveling direction of the supply unit. When it takes time for the developer 320 that has fallen before the communication port 308 to pass through the mesh 310, the developer 320 moves in the developer traveling direction of the supply unit along the inclination of the mesh 310, and per unit time. The amount of developer 320 that can pass through is increased. As described above, the inclination direction of the mesh 310 is preferably such that the mesh becomes lower toward the downstream with respect to the developer traveling direction of the supply unit. This is because the developer 320 falls on the mesh 310 as shown in FIG. 8 and can pass through the mesh 310 while flowing along the inclination of the mesh 310.

  If the inclination of the mesh 310 is reversed as shown in FIG. 9, the developer 320 accumulates on the upstream side in the developer traveling direction of the supply portion of the mesh 310, and thus the passing speed of the mesh 310 becomes slow. Furthermore, when the mesh 310 under the portion where the developer 320 is accumulated becomes full of foreign matter, the developer 320 that cannot pass through the mesh 310 is formed, which tends to cause sticking. Therefore, as shown in FIG. 8, the mesh 310 needs to be attached so as to be inclined downward in the developer traveling direction of the supply unit. In the present embodiment, the size of the communication port 308 through which the developer 320 falls is a 20 mm × 15 mm hole.

  The mesh 310 is made of a conductor and is grounded. Being grounded makes it easier for heat to move through the electrons, and thus has the effect of bringing the temperature of the developer 320 closer to the outside temperature (the temperature of the machine sheet metal). Since heat is generated in the conveyance of the developer 320 and the portion of the developer regulating member 303, the heat is transferred to the developer 320. In recent years, since the melting point of the toner has been lowered in order to lower the fixing unit temperature, if the developer 320 is excessively heated in the developing container 301 of the developing device 3, the toner tends to aggregate. Therefore, it is better to lower the temperature of the developer 320. If the developer temperature can be lowered by passing through the mesh 310, the formation of toner aggregates can be suppressed.

  The graph of FIG. 10 shows the results of measuring the temperature of the developer 320 when the mesh 310 is grounded and when it is not grounded. FIG. 10 shows the result of measuring the developer temperature using a thermocouple when the developer is continuously driven with and without grounding of the mesh 310. When the temperature rises at the initial stage of stirring, the temperature of the outside air and the developer 320 are almost the same, so the effect of cooling the temperature of the developer is small. However, as the temperature of the developer 320 rises, the temperature difference from the outside air increases, and heat easily escapes through the mesh 310. For this reason, the temperature at which the mesh finally saturates decreases when the mesh 310 is grounded. In FIG. 10, a difference of about 4 degrees occurs at the saturated temperature.

  Further, a toner replenishing opening 309 is provided in the mesh 310 above. The replenished toner falls on the mesh 310 and the developer 320 falls from above, so that the replenished toner can be mixed with the developer 320 when passing through the mesh 310. If the toner and the carrier in the developer 320 are in contact with each other when the developer passes through the communication port 308, the friction between the toner and the carrier before the recovery chamber transport member 305 transports the recovery chamber. Charging occurs and the toner immediately after replenishment is charged quickly. If the replenished toner is not sufficiently charged by the time it reaches the developing sleeve 302c of the developing roller 302, it becomes a source of fogging and scattering. Therefore, the replenished toner should be sufficiently charged. Further, no screw blade is provided in the most downstream portion of the supply chamber conveying member 304 in FIG. If there are screw blades in this area, the replenished toner will hit the screw blades and be scattered. For this reason, screw blades are not provided immediately below the toner replenishment opening 309 at the most downstream portion of the supply chamber conveying member 304, and only the shaft is configured.

  Usually, the replenished toner is first mixed in the developer 320 and then triboelectrically charged. In this configuration, since the toner becomes finer and mixes with the developer 320 when passing through the mesh 310, the time (movement distance) for triboelectric charging becomes longer. Therefore, the toner just after replenishment is also on the developing sleeve 302c of the developing roller 302. The electrification becomes stable before being carried.

  By the way, the mesh 310 of this embodiment is grounded. Usually, the charged powder tends to adhere electrostatically to the installed metal. However, since the mesh 310 of this embodiment is attached to the portion where the developer falls, even if the toner adheres to the mesh 310 electrostatically, the falling developer 320 peels off the electrostatically attached toner. effective. Therefore, even if a grounded mesh is attached to the communication port 308 from which the developer 320 falls, there is no problem (sticking or the like) due to toner adhesion.

  Next, the size of the mesh holes will be described. One purpose of placing the mesh 310 is to remove foreign matter. A problem that arises when foreign matter is mixed in the developer 320 is that foreign matter is clogged in the developer regulating portion, causing poor pumping and white streaks. This is because, when the foreign matter is clogged, the developer 320 does not rise only at that portion, so that the electrostatic latent image on the photoreceptor 1 cannot be developed with toner. Therefore, in order to prevent the foreign matter from being caught in the developer regulating portion, the size of the hole in the mesh 310 needs to be smaller than the gap (doctor gap) between the developer regulating member 303 and the developing sleeve 302c of the developing roller 302. is there. For example, in a developing device having a doctor gap of 0.45 mm, the mesh hole needs to be smaller than 0.45 mm. In this embodiment, a wire mesh (mesh) having a wire diameter of 0.22 mm (having a hole size of 0.415 mm) is used in order to achieve the purpose of removing foreign matter even at the lower tolerance limit of the doctor gap. Note that if the hole of the mesh 310 is too small, the developer 320 is difficult to pass. Therefore, it is better to use a mesh 310 having a large size as long as foreign matter can be removed.

(Modification)
Next, a modification will be described with reference to FIG. FIG. 11 shows the developing device 3 in a form in which the developer 320 is conveyed from the bottom to the top by the developing sleeve 302 c of the developing roller 302. In this case as well, the mesh 310 installed at the part where the developer 320 falls is disposed, but the position of the toner replenishment opening 309 is disposed not on the mesh 310 but on the upstream side in the developer traveling direction of the collection chamber. Therefore, although the effect of mixing the toner replenished on the mesh 310 with the developer 320 is small, if the lump of replenished toner reaches the position of the mesh 310 without being mixed with the developer 320, the developer 320 is passed when passing through the mesh 310. Can be mixed. In terms of charging stability, it is inferior to the configuration described with reference to FIG. 8 described above. However, since charging is performed even when passing through the developer regulating portion, fogging and scattering are unlikely to occur. Further, in this configuration, the amount of developer passing through the communication port 307 where the developer 320 falls is larger than that in the configuration of FIG. Therefore, it is necessary to make the size of the communication port 307 from which the developer 320 falls larger than the configuration of FIG. The drop port of this modification is 35 mm × 15 mm.

  Further, in the developing device 3 of the present embodiment, by using the above-described configuration, it is possible to cool the developer 320 and remove foreign matter with an inexpensive configuration. In addition, it is possible to suppress problems such as clogging of foreign substances in the developer regulating portion, occurrence of pumping failure, and white streaks.

The image forming apparatus according to the present embodiment forms an electrostatic latent image by arranging a photoconductor in the horizontal direction for each color of yellow, magenta, cyan, and black and providing a charging device, a developing device, and the like on each photoconductor. Then, the image is visualized and then sequentially transferred onto transfer paper to obtain a full color image. In such a tandem-type full-color image forming apparatus, the developing devices 3K, 3M, 3Y, and 3C are provided for the photoconductors 1K, 1M, 1Y, and 1C arranged in the horizontal direction. In order to reduce the size, it is necessary to narrow the interval between the photoconductors 1. And in order to narrow the space | interval of each photoconductor 1, it is necessary to also make each developing device 3 small in the horizontal direction (lateral direction). By using the developing device 3 of this embodiment as the developing device for each color, the lateral dimension of the developing device for each color can be made smaller than that of the conventional one shown in FIG. 12 , so that the image forming apparatus can be downsized. it can. In addition, as described above, these developing devices 3K, 3M, 3Y, and 3C are configured to include the agent separation region, the agent pumping region, the supply chamber conveyance member, the collection chamber conveyance member, the partition plate, and the like. It is possible to obtain a high image quality by developing with toner having a charge amount of. Further, since the deterioration of the toner can be suppressed, it is possible to stably maintain the performance of the developer for a long period of time, and it is possible to provide a developing device having a long life and high durability. Such an effect can be obtained not only in a tandem full-color image forming apparatus but also in a monochromatic image forming apparatus.

As described above, in the developing device 3 according to the present embodiment , the developer 320 moves from the supply chamber (collection chamber in the modified example) that is the upper conveyance path to the collection chamber ( supply chamber in the modification) that is the lower conveyance path. Since the mesh 310 is provided at the communication port 308 that is the first communication portion , foreign matter can be removed. Further, by using a conductive mesh, that is, a metal mesh having high thermal conductivity for the mesh 310, when the developer becomes hot, the heat is released to the outside of the developing device 3 through the mesh 310 and developed. The agent 320 can be cooled, and the generation of aggregates of the developer 320 can be suppressed. Further, since the conductive mesh 310 is grounded, the heat of the toner is easily transferred even when the electrons move from the charged toner to the conductive mesh 310 where the electrons are grounded. Even when aggregates are generated or foreign matters are mixed, those having a size caught by the mesh 310 can be removed. In addition, the mesh 310 provided at the communication port 308 is provided so as to be inclined so as to decrease toward the downstream with respect to the developer traveling direction in the supply chamber (collection chamber in the modified example) which is an upper conveyance path. The amount of developer that can pass through the mesh 310 per unit time can also be increased. Therefore, it is possible to suppress problems such as toner aggregation in the developing device and vertical white streaks caused by foreign matters mixed in the developing device.
Further, in the developing device 3 according to the present embodiment, the dropping port of the developer 320 provided with the mesh 310 is a communication port 308 from the developer supply chamber to the recovery chamber, and the toner is supplied from the supply opening 309 above it. Therefore, the effect of mixing the toner replenished on the mesh 310 and the developer 320 can also be achieved. This is because frictional charging can occur between the toner and the carrier of the developer from the time when the replenishment toner passes over the mesh 310, and the toner immediately after replenishment can be charged quickly. Therefore, it is possible to suppress fogging and toner scattering when the replenished toner is not sufficiently charged before reaching the developing sleeve 302c of the developing roller 302 .
In the developing device 3 according to the present embodiment, the size of the hole of the mesh 310 is smaller than the gap between the developer regulating member 303 and the developing sleeve 302c of the developing roller 302. It is possible to prevent foreign matters that cannot pass through the restricting portion from being carried. Therefore, it is possible to suppress the occurrence of white streaks due to clogging of foreign substances in the developer restricting portion, the occurrence of poor pumping.
In addition, the process cartridge according to the present embodiment includes the developing device 3 according to the present embodiment described above, so that the same operation and effect as the developing device 3 can be achieved.
In addition, the image forming apparatus according to the present embodiment includes the developing device 3 according to the present embodiment described above or the process cartridge according to the present embodiment, and thus can exhibit the same operations and effects as the developing device 3. .

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Developing device 8 Transfer paper 15 Conveying belt 16 Exposure device 17 Image forming unit 18, 19 Conveying belt stretching roller 20, 21, 22 Paper feed tray 23 Registration roller 24 Fixing unit 25 Paper discharge tray 301 Developing container 302 Developing roller 302a Fixed shaft 302c Developing sleeve 302d Magnet roller 302e Rotating shaft 302f Bearing 303 Developer regulating member 304 Supply chamber transport member 305 Collection chamber transport member 306 Partition plate 307 Communication port (collection → supply)
308 Communication port (supply → recovery)
309 Replenishment opening 310 Mesh 320 Developer 500 Developing device 501 Developing rollers 502, 503 Conveying member 504 Case 504a Partition 505 Developer layer thickness regulating member 601 Cleaning blade A Development area B Transfer area C Storage space GP Development gap L Write exposure MG Magnet O Center line

Japanese Patent Application Laid-Open No. 07-077908

Claims (5)

A developer carrier for carrying a developer for forming a toner image on the image carrier;
A developer layer thickness regulating member that regulates the developer layer thickness on the developer carrier;
A transport path that is arranged side by side and transports the developer;
A first passage through which the developer moves from the upper conveyance path to the lower conveyance path;
A second communication part where the developer moves from the lower conveyance path to the upper conveyance path ,
A grounded conductive mesh is disposed in the first continuous portion so as to incline so as to go downstream with respect to a developer traveling direction in the upper conveyance path with respect to a horizontal plane. A developing device . The developing device according to claim 1 ,
A developing device that replenishes toner from above a grounded conductive mesh . The developing device according to claim 1 or 2 ,
A developing device, wherein the maximum width of the grounded conductive mesh hole is smaller than the gap between the developer carrying member and the developer layer regulating member. Process cartridge is characterized in that comprises a developing device according to any one of claims 1 to 3. An image forming apparatus comprising the process cartridge according to the developing apparatus, or claim 4 according to any one of claims 1 to 3.

Images