JP2008033058A - Development apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development apparatus constituted so as to stably supply a developer without entailing complication and upsizing of a mechanism as compared to the conventional development apparatus. <P>SOLUTION: The development apparatus 11 is equipped with a developing roller 14 which carries and conveys the developer, a developing chamber 16 which supplies the developer to the developing roller 14, and a developer stirring chamber 17 which forms a circulation path by communicating with the developing chamber 16 and conveys the developer while stirring the developer. Then, the development apparatus 11 is equipped with a communication section 20b in which the supply of the developer from the developing chamber 16 to the developer stirring chamber 17 is performed and the communication section, in which the supply of the developer from the developer stirring chamber 17 to the developing chamber 16 is performed. Further, the development apparatus 11 is equipped with an inclined plane 20 which receives the developer from the developing roller 14 or the developing chamber 16 and moves the received developer toward the communication section 20b in compliance with gravity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to a developing apparatus that employs a two-component developing system that is used in the image forming apparatus and charges toner by friction with a carrier.

  In recent years, with the practical application of laser printers, facsimiles, digital copiers, full-color digital copiers and laser printers with high recording density, the display quality when printing images with large print areas and high printing rates has been increased. Stabilization is required.

  For this reason, in the developing device used in the image forming apparatus such as the above-described laser printer, uniform and sufficient toner supply is realized even for a high printing rate image in which a large amount of toner is consumed, and a solid image or Those having excellent reproducibility of continuous tone are used. Further, since the toner does not contain a magnetic material, it is possible to cope with a reduction in particle size and it is suitable for colorization, so that a developing device using a two-component developing method including a toner and a carrier is frequently used.

  Among such two-component development type development devices, development is possible in a tandem system that has excellent developer agitation even for images with a high printing rate and a plurality of development devices are mounted in parallel in the horizontal direction. There is a demand for downsizing of the apparatus in the lateral direction. Thus, two agitating and conveying screws having opposite conveying directions are arranged with respect to the upper conveying path and the lower conveying path of the developing device having two conveying paths above and below, and these agitate the developer in the developing device. A vertical developing device that circulates up and down is proposed (see Patent Document 1).

  That is, in the vertical developing device as described above, as shown in FIG. 1, the upper portion of the developing device 1 is a developer chamber 3 for supplying the developer to the developing roller 2, and the lower portion is the developer developer from the developing roller 2. The developer agitating chamber 4 is used for agitation and mixing of the collected developer and the replenishment toner. The agitating and conveying screws 5a and 5b circulate in the direction of arrow R while agitating the two-component developer in the developing chamber 3 and the developer agitating chamber 4, respectively. Then, the developing device supplies the two-component developer to the developing roller 2 in the upper developing chamber 3 while circulating the two-component developer while stirring the electrostatic latent image on the latent image carrier 6. On the other hand, after the development, the developer is recovered from the developing roller 2 in the developer stirring chamber 4 below. Here, the latent image carrier 6 forms a toner image on the electrostatic latent image while rotating in the direction of arrow S.

  However, in the developing device 1 which is a vertical developing device as described above, the developer is stirred and circulated by the developing chamber 3 and the developer stirring chamber 4, but when printing an image with a high printing rate, There has been a problem that the toner density may be partially uneven or reduced.

  With respect to this problem, the flow of the developer in the developing device 1 of FIG. 1 will be described below with reference to a model using the block diagram shown in FIG. Here, the direction of the arrow shown in FIG. 2 indicates the direction of the developer flow (developer flow). Normally, the developer peeled off from the developing roller 2 is collected in the developer stirring chamber 4 (arrow a1), and then passes through the communicating portion 51 to the developing chamber 3 (arrow a2) to the developing chamber 3. It is conveyed (arrow a3). The developer that has moved to the developing chamber 3 is carried on the developing roller 2 and re-supplied (arrow a4), while being regulated by the developer regulating member 52 and being conveyed through the developing chamber 3. It is divided into those that stay (arrow a5). Further, the developer that has not been supplied to the developing roller 2 is returned to the developing chamber 3 from the communicating portion 53 to the developer stirring chamber 4 through the developer stirring chamber 4 (arrows a6 and a7). The new toner is supplied from the toner supply device 54 to the communication unit 53 (arrow a8).

  However, the developer carried on the developing roller 2 on the upstream side in the transport direction in the developing chamber 3 is downstream in the transport direction in the developer stirring chamber 4 as indicated by a dotted line (arrow a9) in FIG. It is collected on the side, that is, in the vicinity of the communicating portion 51 between the developer stirring chamber 4 and the developing chamber 3. Since such a developer is delivered to the developing chamber 3 side without being sufficiently replenished with toner, the developer is carried on the developing roller 2 with a low toner concentration contained in the developer. If such a developer having a low toner density exists partially on the developing roller 2 (particularly the upstream portion in the developer traveling direction), sufficient toner cannot be supplied onto the latent image carrier 6 only as a result. Causes toner density unevenness. Note that the one-dot chain line in the figure falls off when the developer carried on the developing roller 2 is regulated by the developer regulating member 52, but directly to the developing roller 2 again without moving to the developer stirring chamber 4. The flow supplied is shown.

  The following developing device was considered for the problem of uneven toner density. The developing device is of a vertical type, and includes a developing chamber that is a developer conveying path for supplying the developer onto the developing roller, and a developer stirring chamber that is a developer conveying path for mixing the toner and the developer. And a third developer conveying path provided with a developer conveying screw. It has been proposed to collect all the developer carried on the developing roller and contributing to image formation in the third developer conveying path (see Patent Document 2).

  That is, the third developer conveyance path has a function of collecting the developer that has been performed in the developer stirring chamber so far, and functions as a developer collecting chamber for collecting the developer. In the developing device having this configuration, the toner is replenished to the communication portion connecting the developer recovery chamber and the developer stirring chamber, so that a desired amount of toner can be uniformly mixed with the developer. . Then, since the toner after replenishment is sufficiently mixed with the developer before reaching the developing chamber, a partial decrease in toner density, density unevenness, or the like during image formation is extremely unlikely to occur.

  However, when the three conveying paths and the developer agitating and conveying screws are provided as in the developing apparatus in Patent Document 2, the developing apparatus is larger than when the two conveying paths are provided. This is a disadvantageous configuration in terms of “downsizing”, which is the original purpose of the vertical developing device.

  In the vertical developing device, toner density unevenness may occur for the following reasons. That is, the developer stays in the vicinity of the transfer portion (communication portion) from the developer stirring chamber to the developing chamber. Then, in the vicinity of the transfer unit, there is a case in which the developer whose toner density has decreased after passing through the developing region is transported again in the developing region without being collected into the developer stirring chamber ( (Indicated by the dashed line developer flow in FIG. 2).

  As shown in FIG. 1, when the developer accumulates near the surface of the developing roller 2 in the developer stirring chamber 4, the developer collected from the developing region adheres again to the surface of the developing roller 2, and the developing roller It is conveyed to the development area by rotation of 2. Since such a developer has a low toner concentration, a phenomenon occurs in which the toner concentration in the developer on the developing roller becomes non-uniform.

  To solve the above problems, a developer stirring chamber is provided substantially directly below the developing chamber in the vertical developing device. A third developer agitating and conveying screw that conveys the developer in a direction opposite to the agitating and conveying screw is provided above the developer agitating and conveying screw in the developer agitating chamber. (See Patent Document 3).

  In the developing device having such a configuration, when the developer in the developer stirring chamber is carried into the developing chamber by the stirring and conveying screw, the developer staying in the vicinity of the transfer portion from the developer stirring chamber to the developing chamber is the third. Are conveyed in the opposite direction to the developer agitating and conveying screw. For this reason, it becomes possible to keep the developer substantially uniform in the axial direction of the stirring and conveying screw in the developer stirring chamber. Such a developer is carried into the developing chamber by being conveyed again in a predetermined direction by the agitating and conveying screw in the developer agitating chamber. Therefore, the developer collected from the developing roller is not carried again in the form of the developing roller as it is, and is always supplied to the developing roller after passing through the developer stirring chamber.

  However, since the developing device in Patent Document 3 is provided with a device such as a third agitating and conveying screw, the size of the developing device is increased compared to the vertical developing device as shown in FIG. Installation space will be required. In addition, although this developing device removes a factor that causes toner density non-uniformity, it is not a sufficient method for preventing the occurrence of toner density unevenness. When image output is continuously performed, there is still a possibility of causing density unevenness.

Japanese Patent Laid-Open No. 05-333691 Japanese Patent Laid-Open No. 11-167260 Japanese Patent Laid-Open No. 06-051634

  As described above, in the developing device as shown in Patent Document 1, the developer is stirred and circulated by the stirring and conveying screw in the developing chamber and the developer stirring chamber. However, such a conventional developing device still has a problem that the toner density may be partially uneven or the density may be lowered for an image with a high printing rate. It was.

  Further, in the developing devices as shown in Patent Documents 2 and 3, the conveying path and / or the developer stirring and conveying screw are added as compared with the conventional vertical developing device shown in FIG. It has a structure. Accordingly, such a developing device has problems such as an increase in the size of the device and an increase in the number of parts.

  Accordingly, the present invention provides a developing device that is configured so that the developer can be stably supplied without complicating or increasing the size of the mechanism as compared with a conventional developing device, and thereby solving the above-described problems. It is intended to do.

  The present invention comprises a developer carrying member that carries and conveys a developer comprising a toner and a carrier that imparts charge to the toner, and the developer carrying the developer along the longitudinal direction of the developer carrying member, A developing chamber that supplies the developer onto the developer carrying member, and a stirring chamber that communicates with the developing chamber to form a developer circulation path and conveys the developer toward the developing chamber while stirring the developer. A first communication part for supplying the developer from the developing chamber to the stirring chamber, a second communication part for supplying the developer from the stirring chamber to the developing chamber, and the developer carrying And a developer receiving portion that receives the developer from the body or the developing chamber and moves the received developer toward the first communicating portion according to gravity. is there.

  According to the present invention, the developer is agitated and mixed effectively, and unevenness in toner density can be reduced. Further, in the developing device of the present invention, the developer can be effectively stirred without adding a new stirring member or the like as compared with the conventional one. Space saving at the time can be achieved.

  Hereinafter, a developing device 11 according to an embodiment of the present invention will be described with reference to FIGS. 3 to 5, 7, and 10. 3 is a cross-sectional plan view of the developing device 11 of the present embodiment cut away from the top, and FIG. 4 is a rear cross-sectional view of the developing device 11 shown in FIG. 3 viewed from the direction of arrow A in FIG. FIG. 5 is a side cross-sectional view from the left-right width direction, (a) is a side cross-sectional view as seen from the direction of arrow Ba in FIG. 3, and (b) is from the direction of arrow Bb in FIG. It is side sectional drawing shown in the state seen. FIG. 7 is a schematic diagram showing a specific example of the first and second stirring and conveying screws, and FIG. 10 is a schematic perspective view showing the configuration of the developing device 11 in the present embodiment in three dimensions.

  That is, for example, as shown in FIG. 3, the developing device 11 is disposed so as to face an electrostatic latent image carrier (image carrier) 13 that can hold an electrostatic latent image due to a difference in charging potential. The The developing device 11 supplies the developer to the electrostatic latent image carrier 13 by a developing device 12 that contains a two-component developer (hereinafter also referred to as a developer) composed of a non-magnetic toner and a magnetic carrier. I do.

  In the developing device 12, a rotatable developing roller (developer carrying member) 14 that magnetically attracts the developer to form a magnetic brush on the surface, and the amount of developer adsorbed on the developing roller 14 are stored. A developer regulating member 15 for regulating is provided. A developing chamber 16 having a first agitating and conveying screw 18 a that conveys the developer along the axial direction (longitudinal direction) of the developing roller 14 is located on the side of the developing roller 14. They are arranged in parallel along the longitudinal direction. Further, a developer agitating chamber (agitating chamber) having a second agitating and conveying screw 18b divided by a developing chamber 16 and a partition wall 19 on the side opposite to the developing roller 14 on the side of the first agitating and conveying screw 18a. 17 is disposed.

  Each of the first and second agitating and conveying screws 18a and 18b has a shape in which a plurality of spiral pleats 33a are formed around a cylindrical shaft 33 as shown in FIG. 7, for example. The developer can be stirred and transported by rotating around the center. Therefore, the first agitating and conveying screw 18a disposed in the developing chamber 16 conveys the developer onto the developing roller 14 while conveying the developer in the direction of arrow α as shown in FIGS. Supply. The second agitating and conveying screw 18b disposed in the developer agitating chamber 17 conveys the developer in the direction of the arrow β as shown in FIGS. Supply.

  On the other hand, the developing roller 14 includes a magnetic roller 14a containing a plurality of magnets whose positions are fixed, and a cylindrical sleeve 14b covering the outer periphery thereof. The sleeve 14b is rotatably arranged and rotates so that the outer periphery of the magnetic roller 14a is in sliding contact with a drive source (not shown). The developing roller 14 magnetically attracts the developer to form a magnetic brush on the surface of the sleeve 14b, and supplies the developer onto the latent image carrier 13 by the rotation of the sleeve 14b on the cylinder. ing.

  A plurality of magnets are arranged on the magnetic roller 14a so as to be arranged in the circumferential direction, and one of the same poles is arranged adjacent to one another to form a repulsive pole for the developer. (See FIGS. 5A and 5B). The developer adsorbed on the developing roller 14 to form a magnetic brush is dissociated from the developing roller 14 at the repulsion pole.

  The rotation direction of the developing roller 14 is a direction indicated by an arrow x in FIG. From the developing roller 14, development is performed by supplying toner onto the electrostatic latent image of the electrostatic latent image carrier 13 based on the carried developer. This is because a desired electric field is formed by applying a voltage between the developing roller 14 and the electrostatic latent image carrier 13, and the magnetic brush is rubbed against the surface of the electrostatic latent image carrier 13. The non-magnetic toner is attached to the electrostatic latent image. The nonmagnetic toner and the magnetic carrier remaining on the surface of the developing roller 14 after development are dissociated from the surface of the developing roller 14 at the position of the repulsion pole described above due to the rotation of the surface of the developing roller 14, and the arrows in FIG. It is received by the inclined surface (developer receiving part) 20 from the direction of y.

  As shown in FIGS. 4 and 5, the developer agitating chamber 17 has a lower upstream end position in the developer conveying (traveling) direction in the developer agitating chamber 17 than the bottom surface height of the developing chamber 16. Is formed. Further, the bottom surface height at the downstream end portion in the developing direction of the developer is formed substantially the same as the bottom surface height of the developing chamber 16. As a result, the entire bottom surface of the developer stirring chamber 17 is an inclined surface formed by linearly connecting the bottom surface positions at both ends.

  An inclined surface 20 that descends as a whole is formed from the receiving portion 20a located below the developing roller 14 to the communicating portion (first communicating portion) 20b located upstream of the developer stirring chamber 17. . As shown in FIG. 5A, the height of the end of the inclined surface 20 on the back side (the back side of the paper surface in FIG. 5A) is the bottom surface of the upstream end in the developer traveling direction in the developing chamber 16. It is almost the same as the height. Further, in the vicinity of the front side of the inclined surface 20 (the front side of the paper surface in FIG. 5A), the developer progresses in the developer stirring chamber 17 from the bottom surface height at the upstream end in the developer traveling direction of the developing chamber 16. A slope is formed to the height of the bottom surface at the upstream end in the direction. Therefore, a height difference is provided between the receiving portion 20a and the communication portion 20b in the inclined surface 20, and a relatively large gradient is formed over the entire inclined surface 20.

  As shown in FIGS. 3 and 4, the downstream end of the developing chamber 16 in the developer traveling direction is inclined with respect to the developing chamber 16 by a communication portion 21 formed as a gap as if the bottom surface of the developing chamber 16 was removed. Surface 20 communicates. Accordingly, in the developing chamber 16, the developer conveyed to the downstream side by the stirring and conveying screw 18 a without being carried on the developing roller 14 is collected to the inclined surface 20 through the communication portion 21.

  As described above, the inclined surface 20 includes the developer that has been carried on the developing roller 14 and has not contributed to image formation, and the developer that has fallen and recovered from the developing chamber 16 to the inclined surface 20 through the communication portion 21. Accept. Since the inclined surface 20 is provided with the above-described height difference and a relatively steep slope is formed, all of the received developer collects in the communicating portion 20b according to gravity. Then, these developers are moved from the inclined surface 20 to the developer stirring chamber 17 in the communication portion 20b.

  In order to realize the flow operation of the developer in which the developer received from the receiving portion 20a gathers on the inclined surface 20 to the communicating portion 20b due to its own weight based on gravity, dynamic friction between the inclined surface 20 and the developer is achieved. It is required to make the coefficient as small as possible so that the developer can easily slide down. Therefore, as the material of the inclined surface 20, it is desirable to use, for example, a resin material having a smooth surface and a fluororesin-based coating, or a metal material such as stainless steel, aluminum, or copper having a sufficiently smooth surface. The material of the inclined surface 20 is not limited to the above, and may be arbitrarily selected depending on the configuration of the developing device, the type of developer used, and the like. Further, the efficiency of the developer flow operation on the inclined surface 20 may be further improved by providing a mechanism or device for applying vibration to the inclined surface 20 as necessary.

  On the other hand, a toner replenishing port 23 is provided on the wall surface of the developer container in the vicinity of the communication portion 20b, and new toner is appropriately supplied from the toner replenishing port 23 in accordance with the toner consumption during image formation. It is replenished inside. The new toner is replenished so as to be added to the developer already present in the developing device 12 at the communication portion 20 b between the inclined surface 20 and the developer stirring chamber 17. Accordingly, all the developer received from the receiving portion 20a passes through the communicating portion 20b, so that new toner can be reliably supplied to the developer after completion of development where the toner has been consumed. .

  Next, a series of developer flows (flow) in the developing device 11 will be described with reference to FIG. 6 while referring to a developer flow (FIG. 2) in a conventional vertical developing device having a simple configuration. FIG. 6 is a block diagram illustrating the flow of the developer in the developing device 11.

  As shown in FIG. 6, the new toner is replenished from the toner replenishing port 23 to the vicinity of the communication portion 20b that passes through the inclined surface 20 and the developer stirring chamber 17 (arrow b1). The new toner moves to the developer stirring chamber 17 together with the developer circulating in the developing device 12 (arrow b2), and is mixed and stirred by the stirring and conveying screw 18b in the developer stirring chamber 17. When the mixed and stirred developer reaches the communication portion (second communication portion) 24 between the developer stirring chamber 17 and the developing chamber 16 (arrow b3), the new toner is sufficiently uniform in the developer. To be mixed.

  The developer that has reached the communicating portion 24 is conveyed to the developing chamber 16 (arrow b4). The developer conveyed to the developing chamber 16 is carried on the developing roller 14 (arrow b5), and is regulated by the developer regulating member 15 so as to stay while being conveyed in the developing chamber 16. (Arrow b6). Here, the developer carried on the developing roller 14 contributes to the formation of an image (toner image) on the electrostatic latent image on the electrostatic latent image carrier 13. An arrow b9 indicates a flow in which the developer passes through the developing chamber 16 without being carried on the developing roller 14 and is conveyed to the communication unit 20b.

  The carrier on the developing roller 14 and the toner that does not contribute to image formation are dissociated by the action of the repulsive pole generated by the magnetic roller 14a and are received by the inclined surface 20 from the receiving portion 20a (arrow b7). The received developer is collected by the inclination of the inclined surface 20 into the communication portion 20b connecting the inclined surface 20 and the developer stirring chamber 17 under the influence of gravity (arrow b8). Thus, the developer circulation path is formed by the developing chamber 16, the communication portion 20 b, the developer stirring chamber 17, and the communication portion 24.

  Then, new toner is supplied from the toner supply port 23 onto the developer collected in the communication portion 20b between the inclined surface 20 and the developer stirring chamber 17, and is mixed again. As described above, in the developing device 11, all of the developer collected on the inclined surface 20 (that is, the developer whose toner has been consumed on the developing roller 14) passes through the communication portion 20 b, so that the development is performed. It becomes possible to supply new toner to all the agents. In the developing device 11, the developer repeats the circulation as described above in the developing device 12. As a result, the developing device 11 can reduce the occurrence of density unevenness due to poor mixing with the developer as compared with the conventional vertical developing device as shown in FIG.

  As described above, the developing device 11 according to this embodiment includes the developing roller 14 that carries and conveys the developer, the developing chamber 16 that supplies the developer to the developing roller 14, and the developer. And a developer agitating chamber 17 that conveys the toner. The developing device 11 includes a communication unit 20b that supplies the developer from the developing chamber 16 to the developer stirring chamber 17, and a communication unit 24 that supplies the developer from the developer stirring chamber 17 to the developing chamber 16. Is provided. Further, the developing device 11 includes an inclined surface 20 that receives the developer from the developing roller 14 or the developing chamber 16 and moves the received developer toward the communicating portion 20b according to gravity. As a result, the inclined surface 20 can be supplied to the upstream side of the developer stirring chamber 17 where the received developer is stirred to the maximum. Density unevenness can be reduced.

  Further, in the present developing device 11, the developer can be stirred and circulated effectively and effectively with a minimum number of members without adding a new stirring member or the like as compared with the conventional one. Therefore, it is possible to reduce the manufacturing cost and to save space during the design.

  Further, since the inclined surface 20 with a small dynamic friction coefficient is lowered from the vicinity of the developing roller 14 to the upstream end portion in the developer conveying direction in the developer stirring chamber 17, the developer received in the receiving portion 20a. The developer is effectively collected into the developer stirring chamber 17 according to gravity. As a result, the developer collected from the developing roller 14 and the developing chamber 16 is stirred again by the second stirring / conveying screw 18b of the developer stirring chamber 17, so that the toner density unevenness is reliably reduced. It becomes.

  Further, a toner replenishing port 23 for replenishing new toner is provided upstream of the developer stirring chamber 17 in the transport direction. As a result, new toner can be supplied evenly and reliably to all the developers received on the inclined surface 20 including the developer having a low toner content after the image is formed on the developing roller 14. become able to. Accordingly, the developing device 11 can constantly maintain the toner density and uniformity of the developer circulating in the developing device 12, and the level of display quality can be achieved even for an image with a high printing rate. Can be maintained high.

(Example)
Here, an example will be described below as a specific example for implementing the above-described embodiment. In the present embodiment, a specific example of the developing device 11 will be described, and it will be described that density unevenness is reduced as compared with a conventional vertical developing device by forming an image with the developing device 11.

  In this embodiment, the vertical developing apparatus having the configuration shown in FIG. 1 and the developer flow shown in FIG. 2 and the configuration shown in FIGS. 3 to 5, 7, and 10 and the developer shown in FIG. Two types of developing device 11 were prepared so as to produce a flow.

  In the developing device 11, the inclined surface 20 has a layered structure shown in FIG. FIG. 11 is a schematic cross-sectional view showing the cross section of the inclined surface 20 in a layered manner. The surface stainless steel thin plate 30 is polished so that the surface thereof is smooth, and the friction between the developer and the surface of the inclined surface 20 is sufficiently small. Further, an ultrasonic wave generating means 31 is provided at the back side end portion of the stainless steel thin plate 30. By generating minute ultrasonic vibration, the developer smoothly slides down the surface of the inclined surface 20 by its own weight by the action of gravity. To help. Further, vibration absorbing means 32 is provided between the stainless steel thin plate 30 and the ultrasonic wave generating means 31 and the bottom of the inclined surface 20, and the vibration generated by the ultrasonic vibration generating means 31 propagates to the entire developing device 11. To prevent. With the above-described configuration, the developer circulation during development can be performed without any delay.

  As the two-component developer, a spherical polymerized toner manufactured by Canon Inc. was used as the toner, and a spherical / magnetic resin-coated carrier (average particle diameter of 35 μm) was used as the carrier (manufactured by Canon Inc.). In the combination of toner and carrier used in this embodiment, the toner is negatively charged. The developer used in this example has a toner charge amount (specific charge, hereinafter referred to as Q / M) when the toner weight ratio to the total developer weight (hereinafter referred to as T / D) is 8 wt%. An appropriate value is −22 to −25 [μC / g]. The toner Q / M is measured by using E-SPART Analyzer manufactured by Hosokawa Micron Corporation, and the charge amount of 3000 toners is measured and the average value is used as a representative value.

  First, using the two-component developer in which the carrier and the toner are mixed so that T / D = 8 wt% is used in the developing device 11, all solid images are continuously printed on A3 paper by 10 sheets. The T / D at the X, Y, and Z positions shown in FIG. 3 on the developing roller 14 was examined. The result is shown by a solid line in FIG. According to this, in this embodiment, it is possible to maintain a uniform and good toner concentration over the entire length of the developing roller 14 in the developing device 11 despite the rapid consumption of toner during printing. It could be confirmed.

  On the other hand, using the conventional vertical developing device described with reference to FIG. In this case, as shown by the dotted line in FIG. 8, the toner density is lowered due to a delay in toner replenishment, and particularly in the longitudinal direction of the developing roller 14, the toner density is significantly lowered on the upstream side in the developer traveling direction, resulting in density unevenness. .

  Next, with the conventional vertical developing device and the main developing device 11, an image having a high printing rate of 25% was printed continuously on 200,000 sheets on A4 paper, and the change in toner density at that time was examined. It was. The result is shown in FIG. The dotted line in FIG. 9 shows the result of the conventional vertical developing device. From this result, it can be seen that the vertical developing device has a variation in the toner replenishment speed. It turns out that it fluctuates greatly. On the other hand, the solid line in FIG. 9 shows the result of the developing device 11, but it was found that the toner density did not change with the increase in the number of printed sheets, and a good toner density was stably obtained. .

  From the results of the present embodiment described above, in the developing device 11 in the configuration of the present embodiment, the stirring property of the two-component developer and the replenishability of new toner are improved. As a result, it has been proved that it is possible to reduce image density unevenness without enlarging the apparatus as compared with the conventional vertical developing apparatus.

  It should be noted that the developing device 11 in the present embodiment described above is not limited to the above-described form / mode, and it is needless to say that various design changes may be made. For example, the toner, carrier, etc. in the two-component developer are not particularly limited as long as the material or particle size is in a range that is usually used, and the shape and mode of various members such as a stirring and conveying screw Similarly, the same is not limited.

  In addition to the shape of the developing device 11 shown in the above-described embodiment, for example, a structure in which the upstream side of the developer stirring chamber 17 is positioned almost directly below the developing roller 14 may be employed. More specifically, the upstream side of the developer agitating chamber 17 is positioned below the downstream side of the developing chamber 16, and the downstream side of the developer agitating chamber 17 is extended to the same position as in the above embodiment. The developer stirring chamber 17 is structured so as to dive under the developing chamber 16. With such a structure, after the image is formed, the developer dissociated from the vicinity of the front side of the developing roller 14 (the front side of the paper surface in FIG. 5A) is received by the receiving portion 20a and then is almost directly under its own weight. It can be moved to the upstream side of the developer stirring chamber 17 by dropping into the developer stirring chamber 17. Accordingly, the developer received from the vicinity of the front side of the developing roller 14 can be moved directly upstream of the developer stirring chamber 17 by the action of gravity without being brought into contact with the inclined surface 20. . Thereby, although it is a part of the developer received from the developing roller 14, it can be moved upstream of the developer stirring chamber 17 without considering the dynamic friction coefficient with the inclined surface 20.

  As described above, the developing device according to the present invention is useful for stably forming an image (toner image), and in particular, a developing device that continuously requires high display quality of an image. Suitable for

It is a longitudinal cross-sectional view which shows schematic structure in the conventional vertical developing apparatus. FIG. 10 is a block diagram illustrating a developer flow in a conventional vertical developing device. It is a top sectional view cut and showing the upper part in the development device of this embodiment. FIG. 4 is a rear sectional view showing the developing device shown in FIG. 3 as viewed from the direction of arrow A in FIG. 4A and 4B are side cross-sectional views from the left-right width direction, in which FIG. 3A is a side cross-sectional view as viewed from the direction of arrow Ba in FIG. 3, and FIG. FIG. It is a block diagram showing the flow of developer in the developing device of the present embodiment. It is the schematic which shows the specific example of a 1st and 2nd stirring conveyance screw. 6 is a graph showing changes in toner density depending on the position of a developing roller. 6 is a graph showing a change in toner density according to the number of printed sheets. FIG. 2 is a schematic perspective view showing a three-dimensional configuration of a developing device in the present embodiment. It is the schematic sectional drawing which showed the section of the inclined surface in layers.

Explanation of symbols

11 Developing Device 14 Developer Carrier (Developing Roller)
16 Developing chamber 17 Stirring chamber (Developer stirring chamber)
20 Developer receiving part (inclined surface)
20b 1st communication part (communication part)
24 Second communication part (communication part)

Claims (5)

A developer carrying member that carries and conveys a developer comprising a toner and a carrier that imparts a charge to the toner;
A developing chamber for supplying the developer onto the developer carrier while transporting the developer along the longitudinal direction of the developer carrier; and
A stirring chamber that communicates with the developing chamber to form a developer circulation path, and that conveys the developer toward the developing chamber while stirring;
A first communicating portion for supplying the developer from the developing chamber to the stirring chamber;
A second communicating portion for supplying the developer from the stirring chamber to the developing chamber;
A developer receiving portion that receives the developer from the developer carrying member or the developing chamber and moves the received developer toward the first communication portion according to gravity.
A developing device. The developer receiving portion includes an inclined surface that descends from the vicinity of the developer carrier that receives the developer toward the first communication portion.
The developing device according to claim 1. The surface of the inclined surface is formed of a material having a low dynamic friction coefficient.
The developing device according to claim 2. Having vibration imparting means for vibrating the inclined surface;
The developing device according to claim 2, wherein: A toner replenishing portion for replenishing new toner in the vicinity of the first communicating portion;
The developing device according to claim 1, wherein

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