JP2007304202A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device for preventing density insufficiency and irregularity due to inferiority of developer pumping-up of a developer carrier in the developing device by performing circulation of a developer in the developing device well in the developing device using an agitating and conveying member having a plurality of spiral blade members in order to agitate the developer sufficiently, and to provide an image forming apparatus equipped with the developing device. <P>SOLUTION: The developing device improves the inflow of the developer from a taking-in part to an agitating part by continuing any one of the spiral blade members of the agitating part and the spiral blade member of the taking-in part. In addition, the developer can smoothly circulate in the developing device without stagnating in the taking-in part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device including a developer carrier that carries a developer for developing a latent image on an image carrier, and an image forming apparatus including the same.

  In a developing device using a two-component developer composed of a toner and a carrier, in order to always obtain good development, a well-stirred and well-charged developer is uniformly supplied to a developing sleeve as a developing carrier. It is necessary.

  The developing device described in Patent Document 1 includes a first agitation transport member and a second agitation transport member that are arranged so as to be substantially parallel to the axial direction of the development sleeve. These two agitating / conveying members convey the developer in directions opposite to each other in the agitating / conveying member axial direction. Further, the developer is delivered in a substantially vertical direction from the downstream side of the developer transport direction of one stirring transport member to the upstream side of the developer transport direction of the other stirring transport member. Therefore, the developer is circulated in the developing device by transferring the developer between the two agitating and conveying members.

  The first agitating / conveying member faces the developing sleeve and is composed of three or more spiral blade members in the entire region in the agitating / conveying member axial direction. The second agitating and conveying member has three or more spiral blade members on the upstream side in the developer conveying direction in the axial direction of the agitating and conveying member, and has two or less spiral blade members on the downstream side in the developer conveying direction. is doing.

  There is a method for improving the stirring efficiency of a developer and suppressing the occurrence of abnormal images such as background stains by using a stirring and conveying member having a plurality of spiral blade members as in the developing device described in Patent Document 1. Proposed.

JP-A-11-024380

  FIG. 3 shows a case where the developer flows in from a direction perpendicular to the axis of the stirring and conveying member having three or more spiral blade members 31. In this case, when the stirring and conveying member having three or more spiral blade members 31 is viewed from the direction perpendicular to the axis of the stirring and conveying member, the gap between the spiral blade members is narrow. Therefore, in the stirring and conveying member having three or more spiral wing members 31, it is difficult for the developer to flow into the space between the spiral wing members from a direction perpendicular to the axis of the stirring and conveying member.

  In the developing device described in Patent Document 1, since the first stirring / conveying member is a spiral blade member having three or more strips in the entire region of the stirring / conveying member shaft, from the second stirring / conveying member to the first stirring / conveying member Inflow of developer is difficult. Further, since the second agitating / conveying member is provided with three or more spiral blade members on the upstream side in the developer conveying direction, the inflow of the developer from the first agitating / conveying member to the second agitating / conveying member. Is difficult. Therefore, there is a problem that the developer stays in the part where the developer is transferred between the first stirring and conveying member and the second stirring and conveying member.

  As a method of suppressing this problem, two or less spiral blade members are provided on the upstream side in the developer conveying direction in the stirring and conveying member axial direction, and three or less spiral blade members are provided on the downstream side in the developer conveying direction. A method using the agitated and transported member is considered. In this case, since there are two or less spiral blade members on the upstream side in the developer conveying direction, that is, in the developer intake portion, when the stirring and conveying member is viewed from a direction perpendicular to the axis of the stirring and conveying member, two or less spirals are formed. The gap between the blade members is wider than the gap between three or more spiral blade members. Therefore, by providing a stirring and conveying member having two or less spiral blade members in the developer intake portion, the intake of the developer from the direction substantially perpendicular to the axis of the agitating and conveying member at the intake portion can be improved. Can be done.

  However, generally, in the axial direction of the agitating and conveying member, when the developer is conveyed from the smaller number of spiral blade members to the larger number, the number of spiral blade members shown in FIG. 2 changes. At the boundary portion X, the developer hits the end portion W of the spiral blade member having the larger number of stripes. For this reason, it becomes difficult for the developer to flow from the smaller number of lines to the larger number of lines. Therefore, the developer stays at the boundary X where the number of spiral blade members of the agitating and conveying member changes. This makes it difficult to smoothly circulate the developer in the developing device. As described above, if the developer is not circulated satisfactorily, the amount of the developer supplied to the developing sleeve is insufficient, causing problems such as insufficient density and unevenness in the image.

  The present invention has been made in view of the above problems, and an object of the present invention is a developing device using a stirring and conveying member having a plurality of spiral blade members in order to sufficiently stir the developer. Another object of the present invention is to provide a developing device and an image forming apparatus equipped with the developing device that allow good circulation of the developer in the developing device and prevent density deficiency and unevenness due to poor developer pumping of the developer carrying member.

In order to achieve the above object, the invention of claim 1 comprises a developer carrier carrying a two-component developer for developing a latent image on an image carrier, and conveying the two-component developer while stirring. In addition, in the developing device including the agitating / conveying unit that supplies the two-component developer to the developer carrying member, the agitating / conveying unit is disposed at least 2 arranged substantially parallel to the rotation axis of the developer carrying member. There are two or more stirring and conveying members, and the shaft of at least one of the stirring and conveying members among the stirring and conveying members is less than the number of the stirring portions having a plurality of spiral blade members and the number of the stirring portions. A take-up portion upstream of the developer conveying direction having a number of spiral blade members, and the spiral blade member of the take-up portion is continuous with one of the spiral blade members of the stirring portion, Spira of spiral blade member Pitch is characterized in that less than a spiral pitch of the spiral vane member the stirring 拌部.
The invention of claim 2 is characterized in that, in the developing device of claim 1, the number of spiral blade members of the take-in portion is two or less.
The invention of claim 3 is the developing device according to claim 1 or 2, wherein the open end of at least one spiral blade member of the agitating unit that is not continuous with the spiral blade member of the take-in unit is It is characterized in that it is located downstream of the connecting position of the spiral blade member of the take-in portion and the spiral blade member of the stirring portion in the developer transport direction.
According to a fourth aspect of the present invention, in the developing device of the third aspect, the distance in the axial direction of the stirring and conveying member between the open end and the connecting position is half the spiral pitch of the spiral blade member of the stirring unit. It is characterized by the following.
Further, the invention of claim 5 is the developing device of claim 1, 2, 3 or 4, wherein the open end of the spiral blade member of the stirring unit that is not continuous with the spiral blade member of the take-in unit is It has a tapered shape.
According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: a developing unit that develops a latent image on an image carrier; and an image forming unit that forms an image on a recording body. 2, 3, 4 or 5 developing devices are provided.

In the present invention, any one of the spiral blade members of the agitation unit and the spiral blade member of the intake unit are connected so as to be continuous. As a result, the developer is placed on the surface of the spiral blade member and smoothly conveyed from the take-in unit to the stirring unit, so that the inflow of the developer from the take-in unit to the stirring unit is improved.
In the present invention, the spiral pitch of the spiral blade member of the intake portion is shorter than the spiral pitch of the spiral blade member of the stirring portion. As a result, the transport distance of the developer when the stirring and transporting member makes one rotation is longer in the stirring section than in the taking-in section. That is, the amount of developer transported per unit time is larger in the stirring unit than in the taking-in unit. Therefore, in order to supplement the developer conveyed by the agitation unit, the developer easily flows from the intake unit to the agitation unit. Therefore, the developer can smoothly circulate in the developing device without staying in the take-in portion.

  As described above, according to the present invention, the developer in the developing device can be circulated satisfactorily, so that the problem of insufficient developer supplied to the developer carrier can be suppressed. Therefore, there is an excellent effect that a density deficiency and unevenness due to a poor developer pumping of the developer carrying member can be suppressed, and a high-quality image can be obtained.

Hereinafter, a tandem color laser printer (hereinafter referred to as “printer”) 100 in which a plurality of photoconductors are arranged in parallel will be described as an embodiment of an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer 100 will be described.
FIG. 4 is a schematic configuration diagram of the printer 100 according to the present embodiment. The printer 100 includes four sets of image forming devices 10c, 10m, 10y, and 10b for forming images of each color of cyan (c), magenta (m), yellow (y), and black (b). In accordance with the clockwise rotation in the figure, the surface is first uniformly charged by each charging device 12c, 12m, 12y, 12b. Next, writing is performed with the laser beams Lc, Lm, Ly, and Lb from the common writing device 13. After that, toner is attached by the developing devices 14c, 14m, 14y, and 14b to form monochromatic images on the image carriers 11c, 11m, 11y, and 11b.

  Then, the endless belt-shaped intermediate transfer member 15 is run counterclockwise in the drawing, and the primary transfer devices 16c, 16m, 16y, and 16b transfer the single color images on the image carriers 11c, 11m, 11y, and 11b to the primary transfer. Then, a full color image is formed on the intermediate transfer member 15.

  On the other hand, the feeding roller 20 is rotated at an appropriate timing to feed out the recording medium 22 in the recording medium cassette 21, conveyed through the recording medium conveyance path 23, and abutted between a pair of registration rollers 24 and stopped. Then, the pair of registration rollers 24 are rotated in synchronization with the full color image on the intermediate transfer member 15, and the full color image is conveyed upward as it is by the recording member 22 by the secondary transfer device 25, and the fixing device 30. When the toner passes through the fixing nip, the unfixed transfer toner is fixed on the recording member 22, discharged by the discharge roller 26, and stacked on the recording member stack portion 27 on the printer 100 body.

The image carriers 11c, 11m, 11y, and 11b after the completion of the primary transfer are cleaned by the primary cleaning devices 17c, 17m, 17y, and 17b to remove the residual toner on the image carriers 11.
After the completion of the secondary transfer, the intermediate transfer member 15 is cleaned by the secondary cleaning device 18 to remove residual toner on the intermediate transfer member 15.
The toner replenishing devices 28 that replenish the toner to the color developing devices 14c, 14m, 14y, and 14b are 28c, 28m, 28y, and 28b, respectively.

[Configuration example 1]
A configuration example 1 of the developing device according to the present embodiment will be described below with reference to the drawings.
FIG. 5 is a schematic configuration diagram of the developing device according to the present embodiment as viewed from the side. FIG. 1 is a schematic configuration diagram of the developing device as viewed from above.
The developing device 14 includes a developing sleeve 1 as a developer carrying member facing the image carrier 11 (not shown), a first stirring / conveying shaft 42 and a second stirring / conveying shaft 43 arranged in parallel with the developing sleeve 1. The doctor blade 2 that regulates the layer thickness of the developer on the developing sleeve 1, and the partition wall 3 that extends between the first stirring and conveying shaft 42 and the second stirring and conveying shaft 43 are provided. The developing sleeve 1, the first stirring / conveying shaft 42, and the second stirring / conveying shaft 43 rotate in the direction of the arrow shown in FIG. 5, respectively, and the developer circulates in the direction of the arrow in FIG.
The toner density of the circulating developer is detected by the density sensor 60. When the detected value is lower than the reference value, the upstream side end portion of the second agitating / conveying shaft 43 receives the toner by a control unit (not shown) and the toner replenishing device 28. To be supplied.

  The first stirring / conveying shaft 42 includes a stirring portion 42a having a plurality of spiral blade members mounted on the shaft, and a taking-in portion 42b having a number of spiral blade members smaller than the number of the stirring portion 42a. Is done. The taking-in part 42b is located upstream of the stirring part 42a in the developer conveying direction, and the taking-in part 42b and the spiral blade member of the stirring part 42a are continuous. FIG. 6 shows a continuous part of the intake part 42b and the stirring part 42a.

  Similarly, the second agitating and conveying shaft 43 includes a stirring portion 43a having a plurality of spiral blade members mounted on the shaft, and a taking-in portion 43b having spiral blade portions having a number smaller than that of the stirring portion 43a. Consists of. The intake portion 43b is located upstream of the agitating portion 43a in the developer conveying direction, and the spiral blade member of the intake portion 43b and the spiral blade member of the agitating portion 43a are continuous.

  In this configuration example, the agitating portions 42a and 43a are 4-thread screws with a spiral pitch of 60 [mm], and the intake portions 42b and 43b are 1-thread screws with a spiral pitch of 12 [mm]. Further, the outer diameter of the developing sleeve 1 is φ16, and the outer diameters of the first stirring and conveying shaft 42 and the second stirring and conveying shaft 43 are φ20. In addition, there is a toner supply port at the top of the take-in portion 43b.

In the stirring and conveying shaft using a multi-thread screw, the developer flowing in from the axial direction hits the end surface of the spiral blade member of the multi-thread screw, and the transport performance is hindered so that it does not easily flow into the multi-thread screw portion. Therefore, as in this configuration example, when the spiral wing member of the taking-in portion and the spiral wing member of the stirring portion that is a multi-thread screw are continuously arranged, the developer is placed on the surface of the spiral wing member and the stirring portion is removed from the taking-up portion. As a result, the developer can be easily fed into the agitating section.
As a result, the developer is circulated in the developing device satisfactorily, and density deficiency and unevenness due to poor pumping of the developer do not occur, and a high-quality image can be obtained.

  Further, when the spiral pitch of the taking-in portions 42b and 43b is increased to about the spiral pitch of the stirring portions 42a and 43a, the carrying amount of the developer is smaller in the taking-in portions 42b and 43b than the stirring portions 42a and 43a. More than the parts 42a and 43a. As a result, the amount of developer supplied from the intake portions 42b and 43b to the agitator portions 42a and 43a is larger than the developer transport amount of the agitator portions 42a and 43a, so that the intake portions 42b and 43b and the agitator portions 42a and 43a The developer stays at the boundary.

  Therefore, if the spiral pitch of the intake portions 42b and 43b is made smaller than the spiral pitch of the agitating portions 42a and 43a as in this configuration example, the amount of developer transported is greater in the agitating portions 42a and 43a than in the intake portions 42b and 43b. Become. Accordingly, in order to supplement the developer conveyed by the agitating units 42a and 43a, the developer easily flows into the agitating units 42a and 43a from the intake units 42b and 43b. Therefore, the developer can smoothly flow in at the boundary between the intake portions 42b and 43b and the agitating portions 42a and 43a, so that the developer can be circulated well in the developing device.

Next, toner density detection by the density sensor 60 will be described.
If the developer is not circulated well in the developing device, the amount of the developer passing through the second agitating / conveying shaft agitating portion 43a is small, and the volume of the developer near the density sensor 60 becomes small. If the bulk of the developer in the vicinity of the density sensor 60 is small, variations in the output value of the density sensor 60 tend to occur, and an accurate toner density cannot be detected.
However, in the developing device of the present embodiment, the developer in the developing device can be circulated satisfactorily. Therefore, the amount of developer passing through the second agitating / conveying shaft agitating portion 43a is large, and the developer near the density sensor 60 is used. Increases in bulk. As a result, variation in the output value of the density sensor 60 is small, and an accurate toner density can be detected.

[Modification 1]
FIG. 7 shows a first modification of the configuration of the stirring and conveying shaft. In the stirring and conveying shaft 44, the take-in portion 44b is a two-thread screw, and the stirring portion 44a is a four-thread screw. The intake portion 44b is located upstream of the stirring portion 44a in the developer conveying direction, and the two spiral blade members of the intake portion 44b and the stirring portion 44a are continuous. Specifically, every other spiral wing member of the intake portion 44b is continuous with the spiral wing member of the stirring portion 44a. Further, the screw pitch and the outer diameter of the stirring and conveying shaft 44 are the same as those of the stirring and conveying shafts 42 and 43.
When the take-in portion 44b is a two-thread screw, the conveying force in the take-up portion 44b in the direction of the agitating portion 44a increases, so that the amount of developer flowing into the agitating portion 44a increases and the developer can be circulated well. it can. In addition, if the number of screws in the take-in portion 44b is two or less, the gap seen from the axial direction is sufficient to take in the developer, so that the transportability by the end surface of the spiral blade member of the screw can be improved. Inhibition does not occur, and the developer flows into the stirring section 44a well.
If both the first agitation conveyance shaft and the second agitation conveyance shaft are configured as the agitation conveyance shaft 44, it is easy to balance the circulation of the developer, but only one of the first agitation conveyance axis and the second agitation conveyance axis is agitated. It is also possible to adopt a configuration of the transport shaft 44.

[Modification 2]
FIG. 8 shows a second modification of the configuration of the stirring and conveying shaft. In the stirring and conveying shaft 45 shown in FIG. 8, the open end C of the stirring portion 45a is tapered. In this case, since the space near the open end C becomes wider as compared with the case where the end face of the open end C is a plane perpendicular to the agitating and conveying shaft 45, the developer from the axial direction to the stirrer 45a. Inflow becomes easy. As a result, the developer can be circulated more favorably in the developing device.

[Modification 3]
FIG. 9 shows a third modification of the configuration of the stirring and conveying shaft. In the stirring and conveying shaft 46 shown in FIG. 9, the take-in portion 46b is a single screw, and the stirring portion 46a is a four-thread screw. The taking-in part 46b is located upstream of the stirring part 46a in the developer conveying direction, and the taking-in part 46b and one spiral blade member of the stirring part 46a are continuous.
The open end P1 of the spiral wing member D of the agitating portion 46a that is not continuous with the spiral wing member of the intake portion 46b is the connection position P2 between the spiral wing member of the intake portion 46b and the spiral wing member of the agitator portion 46a. It is located more downstream in the developer transport direction. Here, the spiral wing member of the agitating unit 46a whose open end P1 is downstream of the connecting position P2 in the developer conveying direction is at least one spiral wing member that is not continuous with the intake unit 46b. Therefore, since the space near the portion E shown in the figure becomes large, the developer is easily taken into the stirring portion 46a from the taking-in portion 46b. Thereby, the circulation of the developer in the developing device can be performed satisfactorily.
Note that the take-in portion 46b may be a two-thread screw.

Here, if the open end P1 goes too far downstream in the developer transport direction, the axial transport force in the vicinity of the connecting portion decreases, the developer is stagnated in the vicinity of the connecting portion, and the developer is not circulated satisfactorily. End up. Therefore, the position of the open end P1 where the developer is circulated satisfactorily will be described with reference to the stirring and conveying member 47 of FIG.
In the stirring and conveying shaft 47, the take-in portion 47b is a two-thread screw, and the stirring portion 47a is a four-thread screw. The intake portion 47b is located upstream of the agitating portion 47a in the developer conveying direction, and the intake portion 47b and the two spiral blade members of the agitating portion 47a are continuous.

  Next, the transport of the developer in the vicinity of the connecting portion will be described where the distance in the axial direction of the stirring and conveying member between the open end P1 and the connecting position P2 is T and the spiral pitch of the spiral blade member of the stirring portion 47b is L.

In the present embodiment, when a configuration satisfying the relationship of Equation 1 is applied to the agitation transport shaft 47, the transport force in the axial direction in the vicinity of the connecting portion is reduced, and the developer is not circulated satisfactorily.

On the other hand, when the configuration satisfying the relationship of Equation 2 is applied to the stirring and conveying shaft 47 in the present embodiment, the developer is not stagnation in the vicinity of the connecting portion, and the developer is transferred from the take-in portion 47b to the stirring portion 47a. Was successfully incorporated.
Therefore, by applying a configuration that satisfies the relationship of Equation 2 to the stirring and conveying shaft 47, the developer can be circulated in the developing device satisfactorily.

Even if the spiral wing member of the intake section 47b and the open ends P1 of the two spiral wing members of the stirring section 47a that are not continuous are at the same position, the two spiral wing members are within the range of Formula 2. The position of the open end P1 may be different.
In addition, although the taking-in part 47b was made into the 2 thread | sled screw, a 1 thread | sled screw may be sufficient.

  The agitation transport shaft described so far can be used for the first agitation transport shaft and the second agitation transport shaft by changing the length of the screw.

  As described above, since the developing device of the present invention has a stable toner density and a high toner density followability, even in a color image forming apparatus that consumes a large amount of toner, a high-quality image without insufficient density and unevenness. Can be obtained.

[Configuration example 2]
Configuration example 2 of the developing device according to this embodiment will be described with reference to the drawings.
FIG. 11 is a schematic configuration diagram of a developing device according to the present embodiment. Except for the point that the developing sleeve 50 is positioned above the first stirring and conveying shaft 48, the configuration is the same as that of the developing device of Configuration Example 1. Further, the stirring and conveying shafts described in the configuration example 1 are used for the first stirring and conveying shaft 48 and the second stirring and conveying shaft 49. The toner density of the circulating developer is detected by the density sensor 60, and when the detected value is lower than the reference value, the toner is supplied to the upstream end of the second agitating and conveying shaft 49 by a control unit (not shown) and the toner replenishing device 28. Supplied to the department.

In the configuration in which the developing sleeve 50 is positioned above the first stirring and conveying shaft 48 as in this configuration example, the developing sleeve 50 has to pump up the developer from below, so that the developer is circulated well. When it disappears, the developer liquid level is lowered, and insufficient density or unevenness is likely to occur due to poor pumping.
Therefore, by using the agitation and conveyance shaft described in the configuration example 1 for the first agitation and conveyance shaft 48 and the second agitation and conveyance shaft 49, the developer can be circulated satisfactorily, resulting in insufficient density and unevenness due to poor developer pumping. It is possible to prevent and obtain a good quality image. Further, since the amount of developer passing through the second stirring / conveying shaft 49 is large, an accurate toner concentration can be detected.

[Configuration example 3]
Configuration example 3 of the developing device according to this embodiment will be described with reference to the drawings.
FIG. 12 is a schematic configuration diagram of a developing device according to the present embodiment. Except that the developing sleeve 52 is disposed so as to straddle the first stirring / conveying shaft 48 and the second stirring / conveying shaft 49, the developing sleeve 52 has the same configuration as the developing device of Configuration Example 1. The first agitation transport shaft 48 and the second agitation transport shaft 49 are the agitation transport shafts described in the configuration example 1.
The developing sleeve 52 draws up the developer from the first stirring / conveying shaft 48 side as indicated by an arrow F1, and releases the developer toward the second stirring / conveying shaft 49 side as indicated by an arrow F2. Therefore, in the developing device of this configuration example, circulation by the first stirring / conveying shaft 48 and the second stirring / conveying shaft 49 is carried by the developing sleeve 52 from the first stirring / conveying shaft 48 side to the second stirring / conveying shaft 49 side. It has two circulation paths with circulation.
Further, the toner density of the developer that circulates is detected by the density sensor 60, and when the detected value is lower than the reference value, the control unit (not shown) and the toner replenishing device 28 cause the toner to flow upstream of the second agitating and conveying shaft 49. Supplied to the side end.

In the developing device of this configuration example, all the developer after passing through the developing nip on the developing sleeve 52 is separated to the second stirring and conveying shaft 49 side, and all the developer passing through the developing nip is pumped up from the first stirring and conveying shaft 48 side. ing. For this reason, density reduction does not occur even when a black solid image is output or continuously output. Further, the developer on the first stirring / conveying shaft 48 side is sufficiently stirred by the second stirring / conveying shaft 49 and the first stirring / conveying shaft 48, and the developer is stably charged. Toner scattering can be prevented. Further, since the developer on the first stirring and conveying shaft 48 side has a constant toner concentration in the axial direction, there is no difference in toner concentration in the output image.
Therefore, the developing device of this configuration example uses the stirring and transport shaft described in the configuration example 1 for the first stirring and transporting shaft 48 and the second stirring and transporting shaft 49 so that the developer is circulated well, and the developer is pumped up. Insufficient density and unevenness due to defects can be prevented, and a high-quality image free from background contamination and toner density difference can be obtained.
Further, since the amount of developer passing through the second stirring / conveying shaft 49 is large, an accurate toner concentration can be detected.

[Configuration example 4]
Configuration example 4 of the developing device according to the present embodiment will be described with reference to the drawings.
FIG. 13 is a schematic configuration diagram of a developing device according to the present embodiment. FIG. 14 is a schematic configuration diagram of the developing device when FIG. 13 is viewed from above. In FIG. 14, the developing sleeve 53 and the doctor blade 51 are not shown.
In the present configuration example, the developing sleeve 53 is disposed so as to straddle the first stirring / conveying shaft 48 and the recovery screw 54. Furthermore, the stirring and conveying shaft described in the configuration example 1 is used for the first stirring and conveying shaft 48 and the second stirring and conveying shaft 49.
As shown by arrows G1 and G2 in FIG. 13, the developing sleeve 53 pumps up the developer from the first stirring / conveying shaft 48 side and separates it toward the collecting screw 54 side. The collection screw 54 conveys the developer separated from the developing sleeve 53 in the direction indicated by the arrow G3 in FIG. 14, and is delivered to the first stirring and conveying shaft 48 side at the delivery section on the downstream side in the developer conveying direction. The first agitation transport shaft 48 and the second agitation transport shaft 49 circulate in the direction indicated by the arrow H in FIG. The toner density of the circulating developer is detected by the density sensor 60. When the detected value is lower than the reference value, the upstream side end portion of the second agitating / conveying shaft 49 receives the toner by the control unit (not shown) and the toner replenishing device 28. To be supplied.

In the developing device of this configuration example, all the developer that has passed through the developing nip on the developing sleeve 53 is separated to the collection screw 54 side, and all the developer that has passed through the developing nip is pumped up from the first stirring and conveying shaft 48 side. For this reason, density reduction does not occur even when a black solid image or a continuous image is output.
Further, the developer on the first stirring / conveying shaft 48 side is conveyed through a long stirring path formed by the entire length of the second stirring / conveying shaft 49 and the first stirring / conveying shaft 48. As a result, the developer on the first stirring / conveying shaft 48 side is sufficiently agitated and the developer is stably charged, so that background contamination and toner scattering can be reliably prevented. Furthermore, since the developer on the first stirring and conveying shaft 48 side has a constant toner concentration in the axial direction, no difference in toner concentration occurs in the output image.
Therefore, the developing device of this configuration example uses the stirring and transporting shaft of Configuration Example 1 for the first stirring and transporting shaft 48 and the second stirring and transporting shaft 49 so that the developer can be circulated satisfactorily. Insufficient density and unevenness can be prevented, and a high-quality image free from background contamination and toner density difference can be obtained. Further, since the amount of developer passing through the second stirring / conveying shaft 49 is large, an accurate toner concentration can be detected.

As described above, according to the present embodiment, the developing sleeve which is a developer carrying member that carries the developer for developing the latent image on the image carrier, the two-component developer is conveyed while being stirred, and the two-component development is performed. In a developing device including an agitating and conveying unit that supplies the developer to the developing sleeve, the agitating and conveying unit includes an agitating and conveying shaft that is at least two agitating and conveying members disposed substantially parallel to the rotation axis of the developer sleeve. And at least one of the stirring and transporting shafts includes a stirring unit having a plurality of spiral blade members, and a developer transport having a number of spiral blade members smaller than the number of the stirring unit. The spiral blade member of the agitation part and the spiral blade member of the intake part are continuous, and the spiral pitch of the spiral blade member of the intake part is the spy of the agitation part. Shorter than the spiral pitch of the Le-shaped blade member.
As a result, one of the spiral blade members of the stirring unit and the spiral blade member of the taking-in unit are connected so as to be continuous, so that the developer is placed on the surface of the spiral blade member and smoothly flows from the taking-in unit to the stirring unit. It is conveyed to. Therefore, the inflow property of the developer from the taking-in part to the stirring part is improved. Therefore, it is possible to suppress the retention of the developer at the portion where the developer is transferred from the spiral blade member of the take-in portion having a small number of stripes to the spiral blade member of the stirring portion having a large number of stripes.
Further, the spiral pitch of the spiral blade member of the intake portion is made smaller than the spiral pitch of the spiral blade member of the stirring portion. Thereby, the transport distance of the developer when the stirring transport shaft makes one rotation is longer in the stirring section than in the taking-in section. That is, the amount of developer transported per unit time is larger in the stirring unit than in the taking-in unit. Therefore, in order to supplement the developer conveyed by the agitation unit, the developer easily flows from the intake unit to the agitation unit. Therefore, since the developer can smoothly circulate in the developing device without staying in the take-in portion, it is possible to prevent density deficiency and unevenness due to poor developer pumping and to obtain a good image.
Further, according to the present embodiment, the number of spiral blade members of the intake portion is two or less. Thereby, the clearance gap between the spiral blade members of the taking-in part seen from the rotation-axis perpendicular | vertical direction of the stirring conveyance axis | shaft becomes wide. Therefore, by providing the agitating and conveying shaft having two or less spiral blade members in the intake portion, the intake of the developer from the direction substantially perpendicular to the rotation axis of the agitating and conveying shaft in the intake portion can be performed well. Can do.
Further, according to the present embodiment, the open end P1 of the spiral blade member of at least one agitation unit that is not continuous with the spiral blade member of the intake unit includes the spiral blade member of the intake unit and the agitation unit. Is located downstream of the connecting position P2 with the spiral blade member in the developer conveying direction. Thereby, the space between the open end P1 on the stirring and conveying shaft and the connection position P2 becomes wide. Therefore, the developer is easily taken in from the take-in portion to the stirring portion.
Further, according to the present embodiment, the distance T between the open end P1 and the connection position P2 in the rotation axis direction of the stirring conveyance shaft is equal to or less than half the spiral pitch L of the spiral blade member of the stirring unit. As a result, the developer transport force between the open end P1 and the connection position P2 does not decrease, and therefore it is possible to prevent the developer from being delayed between the open end P1 and the connection position P2.
Moreover, according to this embodiment, the open end part C of the spiral blade member of the stirring part which is not continuous with the spiral blade member of the intake part has a tapered shape. Thereby, compared with the case where the end surface of the open end C is a plane perpendicular to the stirring and conveying shaft, the space near the open end C is widened. Therefore, it becomes easy for the developer to flow in from the axial direction from the take-in portion to the stirring portion.

FIG. 2 is a schematic plan sectional view of a developing device that is a characteristic part of the present invention. Explanatory drawing of the boundary part from which the number of strips of a spiral blade member changes. Explanatory drawing when a developer flows in from the orthogonal | vertical direction with respect to the rotating shaft of a multi-thread screw. 1 is an overall configuration diagram of a color laser printer to which a developing device of the present invention is applied. FIG. 3 is a schematic side sectional view of the developing device according to Structural Example 1. FIG. 2 is a schematic configuration diagram of a stirring and conveying shaft used in Configuration Example 1. The schematic block diagram of the stirring conveyance axis | shaft used in the modification 1. FIG. The schematic block diagram of the stirring conveyance axis | shaft used in the modification 2. FIG. The schematic block diagram of the stirring conveyance axis | shaft used in the modification 3. FIG. Explanatory drawing of the distance T in the rotating shaft direction of the stirring conveyance member of the open end P1 and the connection position P2, and the spiral pitch L of the spiral blade member of a stirring part. FIG. 6 is a schematic side sectional view of a developing device according to Structural Example 2. FIG. 10 is a schematic side sectional view of a developing device according to Structural Example 3. FIG. 10 is a schematic side sectional view of a developing device according to Structural Example 4. FIG. 6 is a schematic plan sectional view of a developing device according to Structural Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing sleeve 2 Doctor blade 42 1st stirring conveyance shaft 42a Stirring part 42b taking-in part 43 2nd stirring and carrying shaft 43a Stirring part 43b taking-in part 44 Stirring and conveying shaft 44a Stirring part 44b Taking-in part 45 Stirring and conveying shaft 45a Stirring part 45b Taking-in part 46 agitating and conveying shaft 46a agitating portion 46b taking-in portion 47 agitating and conveying shaft 47a agitating portion 47b taking-in portion 48 first agitating and conveying shaft 49 second agitating and conveying shaft 50 developing sleeve 51 doctor blade 52 developing sleeve 53 developing sleeve 54 recovery screw 60 concentration sensor

Claims (6)

A developer carrier carrying a two-component developer for developing a latent image on the image carrier;
In a developing device including a stirring and conveying unit that conveys the two-component developer while stirring and supplies the two-component developer to the developer carrier,
The agitating / conveying unit has at least two agitating / conveying members arranged substantially parallel to the rotation axis of the developer carrying member, and at least one of the agitating / conveying member shafts among the agitating / conveying members. Is composed of a stirring portion having a plurality of spiral blade members and a take-up portion on the upstream side in the developer transport direction having a spiral blade member having a number smaller than the number of the stirrer portions. The spiral blade member is continuous with one of the spiral blade members of the stirring unit, and the spiral pitch of the spiral blade member of the take-up unit is shorter than the spiral pitch of the spiral blade member of the stirring unit. Development device. The developing device according to claim 1,
2. A developing device according to claim 1, wherein the number of spiral blade members of the intake section is two or less. The developing device according to claim 1 or 2,
The open ends of at least one or more spiral blade members of the agitation unit that are not continuous with the spiral blade members of the intake unit are a spiral blade member of the intake unit, a spiral blade member of the agitation unit, and The developing device is located on the downstream side in the developer conveying direction from the connecting position. The developing device according to claim 3.
The developing device according to claim 1, wherein a distance in the axial direction of the stirring and conveying member between the open end and the connecting position is equal to or less than half of a spiral pitch of the spiral blade member of the stirring unit. The developing device according to claim 1, 2, 3 or 4,
2. A developing device according to claim 1, wherein an open end portion of the spiral blade member of the agitating portion which is not continuous with the spiral blade member of the intake portion has a tapered shape. Developing means for developing a latent image on the image carrier;
In an image forming apparatus including an image forming unit that forms an image on a recording body,
An image forming apparatus comprising the developing device according to claim 1 as the developing means.

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