JP2017102261A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of sufficiently suppressing the excessive discharge of a developer.SOLUTION: The developing device includes an admix auger 13 which conveys the developer in a first direction D1, a supply auger which is extended in parallel with the admix auger 13 and conveys the developer in a second direction being opposite to the first direction D1, an opening which is provided at one end of the admix auger 13 and the supply auger and transfers the developer from the admix auger 13 to the supply auger, a reverse helical blade 16 which is provided on the side of the first direction D1 from the opening in the admix auger 13 and reverses the flow of the developer moving in the first direction D1, a discharge part 11 which is provided on the side of the first direction D1 of the reverse helical blade 16 and discharges the developer overflowing the reverse helical blade 16, and a magnet attraction member 21 which is provided in a position facing the reverse helical blade 16 and attracts the developer.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a developing device employing a trickle developing system. The present invention particularly relates to a developing device that performs development by circulating a developer including toner and a carrier in a conveyance path.

  An image forming apparatus using an electrophotographic system forms an electrostatic latent image on the outer peripheral surface of a charged photosensitive drum, and forms the image by visualizing the electrostatic latent image with toner. In an image forming apparatus that performs development using a two-component developer containing toner and carrier, the toner and carrier are mixed and stirred so that the ratio of toner and carrier becomes uniform. Further, a new carrier is mixed at the time of toner replenishment, and the old developer is overflowed and discharged from the developer discharge port.

  Japanese Unexamined Patent Application Publication No. 2009-48139 describes a trickle developing type developing device. The developing device includes two transport chambers that store the developer and transport the developer. A supply auger that conveys the developer in one direction is arranged in one of the two conveyance chambers, and an admix auger that conveys the developer in the opposite direction to the one direction is arranged in the other. Two openings are provided between the two transport chambers, and the developer is transported from the supply auger to the admix auger through one opening and from the admix auger to the supply auger through the other opening. Be transported. In this way, the developer circulates inside the developing device. Further, at one end of the admix auger, a discharge port for discharging the developer from the developing device and a spiral blade for reversely feeding the developer to the opposite side of the discharge port are provided. At a position facing the spiral blade, there is provided a protrusion that suppresses the discharged developer from being discharged from the discharge port. The protruding portion protrudes from the ceiling of the developing device toward the spiral blade.

JP 2009-48139 A

  In the developing device having the above-described protrusion, a part of the scattered developer is blocked by the protrusion, thereby suppressing excessive discharge of the developer from the discharge port. However, the developer is scattered by an air flow generated with an increase in pressure in the developing device during operation. The developer scattered by this pressure rise goes to the discharge port through the gap between the conveying blade and the protruding portion. Therefore, the developer simply provided with the protrusion cannot block the developer that goes to the discharge port through the gap. Therefore, there is a problem that the excessive discharge of the developer cannot be sufficiently suppressed.

  An object of the present invention is to provide a developing device that can sufficiently suppress excessive discharge of a developer.

  The developing device according to the present invention is a developing device, and includes a first auger, a second auger, an opening, a reverse feed portion, a discharge portion, and a magnetic force adsorbing member, and the first auger Transports the developer in a first direction, and the second auger extends in parallel to the first auger and transports the developer in a second direction opposite to the first direction. The opening is provided at one end of the first auger and the second auger to deliver the developer from the first auger to the second auger, and the reverse feed portion is more than the opening in the first auger. The developer provided on the first direction side is caused to flow backward in the developer moving in the first direction, and the discharge portion discharges the developer provided on the first direction side of the reverse feed portion and overcoming the reverse feed portion. The magnetic force adsorbing member is provided at a position facing the reverse feeding portion and adsorbs the developer.

  In this developing device, a discharge unit that discharges the developer that has passed over the reverse feed unit is provided, and a magnetic force adsorbing member that adsorbs the developer is provided at a position facing the reverse feed unit. Therefore, the scattered developer is adsorbed by the magnetic force adsorbing member when it passes the outside of the reverse feed portion. In this way, the developer scattered on the outside of the reverse feed portion can be adsorbed, and therefore, excessive discharge of the developer from the discharge portion can be suppressed. Therefore, the excessive discharge of the developer can be sufficiently suppressed by the magnetic force of the magnetic adsorption member. Further, the developer can be prevented from being excessively discharged only by disposing the magnetic force adsorbing member at the position opposite to the reverse feeding portion. Therefore, suppression of excessive discharge can be realized in a space-saving manner, and enlargement of the developing device can be suppressed.

  Further, if the distance between the magnetic adsorption member and the reverse feeding portion is A (mm) and the maximum thickness of the developer adsorbed on the magnetic adsorption member is B (mm), A−0.5 ≦ B ≦ A + 0. 5 may be satisfied. In this case, since the amount of developer adsorbed on the magnetic force adsorbing member can be made appropriate, the amount of developer discharged from the discharge portion can be made appropriate.

  Further, the reverse feed unit includes a rotating shaft and a conveying blade spirally provided on the outer peripheral surface of the rotating shaft. The conveying blades are provided at a constant interval along the extending direction of the rotating shaft. If this interval is C (mm) and the minimum length in the extending direction of the magnetic force adsorbing member is D (mm), C × 0.7 ≦ D ≦ C × 1.3 may be satisfied. in this way. By adjusting the thickness of the developer adsorbed by the magnetic force adsorbing member, it is possible to suppress the excessive discharge of the developer and to avoid the problem that the developer is hardly discharged.

  Further, the magnetic adsorption member is alternately magnetized with N and S poles, and the magnetization direction of the N and S poles may coincide with the rotation direction of the reverse feed portion. In this case, it is possible to avoid an event in which the normal discharge amount of the developer decreases and the developer is hardly discharged.

  In addition, a cylindrical portion may be further provided, and the cylindrical portion may extend in the first direction from the reverse feed portion, form a discharge portion, and taper toward the first direction. Thus, the excessive discharge | emission of a developer can be suppressed more effectively by setting it as the shape which tapers the cylindrical part which forms a discharge part.

  Further, the number of the conveying blades described above may be 2 or more and 4 or less. In this case, it is possible to suppress excessive discharge of the developer and maintain an appropriate discharge amount of the developer.

  In addition, the conveying blades are provided at a certain interval along the extending direction of the rotating shaft, and the magnetic force adsorbing member is spaced from the end of the conveying blade in the second direction in the first direction. You may arrange | position within the range to the position extended 4 times. In this case, it is possible to shorten the time from when the developing device is operated until the effect of suppressing the excessive discharge of the developer is exhibited.

  Further, at least a part of the magnetic force adsorbing member may be disposed on the upper side in the gravity direction of the reverse feeding portion. In this case, excessive discharge of the developer can be more reliably suppressed, and the developer can be discharged in an appropriate amount.

  According to the present invention, excessive discharge of the developer can be sufficiently suppressed.

1 is a diagram illustrating a developing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the vicinity of a discharge portion of the developing device of FIG. 1. FIG. 2 is a view showing two augers and a magnetic force attracting member of the developing device of FIG. 1. It is sectional drawing which shows the reverse feed part and magnetic force adsorption member of the developing device of FIG. FIG. 5 is a diagram illustrating an example of a method for measuring the thicknesses of the magnetic force adsorption member and the developer in FIG. 4. It is a figure for demonstrating the pitch of a reverse feed part. (A)-(c) is a figure which shows the example of the shape of a magnetic force adsorption member. It is a figure which shows the magnetization direction of the magnetic force adsorption member facing a reverse feed part. (A)-(d) is a figure for demonstrating the shape of the nozzle which forms a discharge part. It is a figure which shows typically the relationship between the position of the blade | wing of a reverse feed part, and the quantity of a developing agent. It is a figure which shows typically the arrangement position of the magnetic force adsorption member with respect to a reverse feed part. (A)-(e) is a figure for demonstrating the arrangement position of the magnetic force adsorption member with respect to a reverse feed part. It is a graph which shows the relationship between the presence or absence of a magnetic force adsorption member and the discharge amount of a developer. It is a graph which shows the relationship between the presence or absence of a magnetic force adsorption member and the discharge amount of a developer. It is a graph which shows the relationship between the distance between a reverse feed part and a magnetic force adsorption member, and the discharge amount of a developer. It is a graph which shows the relationship between the distance between a reverse feed part and a magnetic force adsorption member, and the discharge amount of a developer. It is a graph which shows the relationship between the minimum length of the magnetic force adsorption member in the axial direction of an auger, and the discharge amount of a developer. It is a graph which shows the relationship between the minimum length of the magnetic force adsorption member in the axial direction of an auger, and the discharge amount of a developer. It is a graph which shows the relationship between the magnetization direction of a magnetic adsorption member, and the discharge amount of a developer. It is a graph which shows the relationship between the magnetization direction of a magnetic adsorption member, and the discharge amount of a developer. It is a graph which shows the relationship between the shape of a nozzle and the discharge amount of a developer. It is a graph which shows the relationship between the number (number of windings) of a reverse feed part, and the discharge amount of a developer. It is a graph which shows the relationship between the number (number of windings) of a reverse feed part, and the discharge amount of a developer. It is a graph which shows the relationship between the arrangement position of a magnetic force adsorption member, and the discharge amount of a developer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The developing device 1 according to the present embodiment is provided in, for example, an image forming apparatus that forms a color image. The developing device 1 develops the electrostatic latent image. In the developing device 1, the toner and the carrier are adjusted to have a desired mixing ratio, and the toner is further mixed and stirred to be uniformly dispersed. In the developing device 1, the carrier is replenished when the toner is replenished in order to keep the charge amount of the developer in the interior constant. Within the developing device 1, the deteriorated developer is accommodated in a waste toner collecting device.

  The developing device 1 performs development using a two-component development system. In the developing device 1, a developer composed of toner and a carrier is replenished from a developer replenishing unit. As shown in FIG. 1, the developing device 1 includes a supply auger 12 (second auger) that supplies developer to the developing roller, and extends parallel to the supply auger 12 and is disposed adjacent to the supply auger 12. And an admixed auger 13 (first auger). The discharge unit 11 is provided at one end of the admix auger 13.

  The supply auger 12 includes a rotating shaft 12A and a spiral blade 12B that protrudes spirally from the rotating shaft 12A. The supply auger 12 conveys the developer inside the developing device 1 in the second direction D2. The second direction D2 is a direction opposite to the direction in which the discharge unit 11 is provided when viewed from the spiral blade 12B. In the supply auger 12, when the rotating shaft 12A is rotated, the spiral blade 12B conveys the developer in the second direction D2.

  The admix auger 13 includes a rotating shaft 13A and a spiral blade 13B that protrudes spirally from the rotating shaft 13A. The admix auger 13 conveys the developer inside the developing device 1 in the first direction D1. That is, in the admix auger 13, when the rotary shaft 13A is rotated, the spiral blade 13B conveys the developer in the first direction D1. The first direction D1 is a direction opposite to the second direction D2.

  In the supply auger 12 and the admixing auger 13, an opening 14 for delivering the developer from the admixing auger 13 to the supply auger 12 is provided at the end (one end) on the first direction D1 side. An opening 15 for delivering the developer from the supply auger 12 to the admixing auger 13 is provided at the end (the other end) of the supply auger 12 and the admixing auger 13 on the second direction D2 side.

  A reverse spiral blade 16 (reverse feed portion) that reversely flows the developer moving in the first direction D1 is provided on the side of the admix auger 13 from the opening portion 14 in the first direction D1. A spiral blade 17 that conveys the developer in the first direction D1 is provided on the side of the admix auger 13 in the second direction D2 from the opening 15. The reverse spiral blade 16 causes the developer to flow backward in the second direction D2 when the rotation shaft 13A of the admix auger 13 rotates. Further, the discharge unit 11 is provided on the first direction D1 side with respect to the reverse spiral blade 16.

  The diameter of the reverse spiral blade 16 is substantially the same as the diameter of the spiral blade 13B, but the pitch of the reverse spiral blade 16 is shorter than the pitch of the spiral blade 13B. Here, the pitch indicates the arrangement interval of the spiral blades in the axial direction of each auger. Note that the pitch of the spiral blades 12B of the supply auger 12 is shorter than the pitch of the spiral blades 13B of the admix auger 13. The pitch of the spiral blade 13B is longer than the pitch of the reverse spiral blade 16 and the pitch of the spiral blade 17. Further, the pitch of the reverse spiral blade 16 is shorter than the pitch of the spiral blade 17.

  As shown in FIG. 2, a nozzle 18 that is a cylindrical portion that forms the discharge portion 11 is provided in the first direction D <b> 1 of the reverse spiral blade 16. The nozzle 18 protrudes from the housing 20 of the developing device 1 in the first direction D1. An admixing auger 13 is passed through the nozzle 18. A spiral blade 19 is provided on the reverse spiral blade 16 on the first direction D1 side. The spiral blade 19 is provided inside the nozzle 18. The spiral blade 19 transports the developer that has passed over the reverse spiral blade 16 and entered the nozzle 18 to the discharge unit 11. The pitch of the spiral blade 19 is the same as the pitch of the reverse spiral blade 16, for example.

  As shown in FIGS. 2 and 3, a magnetic force adsorbing member 21 that adsorbs the developer is provided on the outer side in the radial direction of the reverse spiral blade 16. The magnetic force attracting member 21 is, for example, a flexible rubber magnet. The magnetic force adsorbing member 21 is disposed above the reverse spiral blade 16 so as to have a circular cross section, and has a shape along the outer periphery of the reverse spiral blade 16. Thus, by arranging the magnetic force adsorption member 21 along the outer periphery of the reverse spiral blade 16, the width of the gap S formed between the magnetic force adsorption member 21 and the reverse spiral blade 16 is made uniform, and the gap S is formed. It is possible to evenly adsorb the developer passing therethrough.

  The cross section of the magnetic force adsorbing member 21 has an arcuate umbrella shape that covers the upper side in the gravity direction of the reverse spiral blade 16, and the circumferential ends 21 a and 21 b of the magnetic adsorbing member 21 are in contact with the inner wall 20 a of the housing 20, for example. doing. The magnetic force adsorbing member 21 is supported by a plate-like mounting member 22 located on the upper side thereof. The magnetic force adsorption member 21 is disposed by attaching the attachment member 22 to the housing 20. The magnetic force adsorbing member 21 may not be supported by the attachment member 22 and may be directly fixed to the inner wall 20 a of the housing 20.

  4 and 5, the magnetic force of the magnetic force attracting member 21 is attracted to the magnetic force attracting member 21 with the distance (width of the gap S) between the magnetic force attracting member 21 and the reverse spiral blade 16 being A (mm). When the maximum thickness of the developer G is B (mm), the relationship of A−0.5 ≦ B ≦ A + 0.5 is satisfied. Here, as a method of measuring the thickness of the developer G of the magnetic adsorption member 21, the magnetic adsorption member 21 that adsorbs the developer G is disposed on the support base H1 of the height gauge H, and the upper surface of the support base H1 and the development are developed. There is a method in which the distance from the upper end of the agent G is B, and the distance between the upper surface of the support base H1 and the upper end of the magnetic force adsorbing member 21 is E.

  6 and 7, when the pitch of the reverse spiral blade 16 is C (mm) and the minimum length of the magnetic force adsorbing member 21 in the axial direction of the reverse spiral blade 16 is D (mm), C × 0.7 ≦ D ≦ C × 1.3 is satisfied. Moreover, as shown in FIGS. 7A to 7C, the shape when the magnetic force adsorbing member 21 is viewed from the radially outer side of the reverse spiral blade 16 is, for example, rectangular, L-shaped, or A trapezoidal shape or the like can be selected as appropriate.

  As shown in FIG. 8, the magnetization direction of the magnetic force adsorbing member 21 matches the rotation direction of the reverse spiral blade 16. That is, the N pole 21 c and the S pole 21 d of the magnetic force attracting member 21 are alternately arranged along the rotation direction of the reverse spiral blade 16. As described above, the magnetization direction of the magnetic force adsorbing member 21 preferably matches the rotation direction of the reverse spiral blade 16, but may not necessarily match and can be changed as appropriate.

  Further, as shown in FIGS. 9A to 9D, nozzles 18 </ b> A to 18 </ b> D having a shape that decreases in diameter toward the discharge unit 11 (first direction D <b> 1) are employed as the nozzle 18. It is preferable. Specifically, the diameter may be gradually reduced as it goes in the first direction D1 like the nozzle 18A and the nozzle 18B, or the diameter may be reduced stepwise like the nozzle 18C and the nozzle 18D. Further, the diameters of the spiral blades 19 arranged along the first direction D1 as in the nozzle 18A and the nozzle 18C may be the same as each other, and the spiral blades 19 are spiraled toward the first direction D1 as in the nozzle 18B and the nozzle 18D. The diameter of the blade 19 may be gradually reduced.

  FIG. 10 is a conceptual diagram showing the relationship between the position of the reverse spiral blade 16 and the amount of developer. As shown in FIG. 10, the reverse spiral blade 16 includes a rotation shaft 16 </ b> A and a conveying blade 16 </ b> B provided in a spiral shape on the outer peripheral surface of the rotation shaft 16 </ b> A. The conveying blades 16B are arranged at a constant interval C along the extending direction of the rotating shaft 16A. Moreover, it is preferable that the number of the conveyance blades 16B (the number of strips of the reverse spiral blades 16) is 2 or more and 4 or less. However, the number of the conveying blades 16B is not limited to 2 or more and 4 or less, and may be 5, for example.

  In the reverse spiral blade 16, the amount of developer increases toward the opening 14 (second direction D <b> 2) and decreases toward the discharge unit 11 (first direction D <b> 1). Accordingly, as shown in FIG. 11, the magnetic force adsorbing member 21 is disposed at a position facing the conveying blade 16 </ b> B on the opening 14 side. That is, the magnetic force adsorbing member 21 is disposed in a range from the end portion 16c on the opening portion 14 side (second direction D2 side) of the conveying blade 16B to a position extending four times the interval C in the first direction D1. .

  12A to 12E show the arrangement positions of the magnetic force adsorbing members 21 as viewed from the reverse spiral blade 16. As shown in FIG. 12A, the magnetic force adsorbing member 21 is preferably disposed on the upper side of the reverse spiral blade 16. However, as shown in FIGS. 12B to 12D, the magnetic force adsorbing member 21 is provided on the right side of the reverse spiral blade 16, the left side of the reverse spiral blade 16, or the lower side of the reverse spiral blade 16. It may be arranged in either. Further, as shown in FIG. 12 (e), the magnetic force adsorbing member 21 may be disposed so as to cover the entire circumference of the reverse spiral blade 16.

  Next, functions and effects of the developing device 1 configured as described above will be described.

  First, as shown in FIG. 2, in the developing device 1, a discharge unit 11 that discharges the developer that has passed over the reverse spiral blade 16 is provided, and a magnetic force that adsorbs the developer at a position facing the reverse spiral blade 16. An adsorption member 21 is provided. Therefore, the scattered developer is adsorbed by the magnetic force adsorbing member 21 when it passes outside the reverse spiral blade 16. As described above, since the developer scattered on the outside of the reverse spiral blade 16 can be adsorbed, excessive discharge of the developer from the discharge unit 11 can be sufficiently suppressed. Further, the developer can be prevented from being excessively discharged only by disposing the magnetic force adsorbing member 21 at the position facing the reverse spiral blade 16. Therefore, suppression of excessive discharge can be realized in a space-saving manner, and enlargement of the developing device 1 can be suppressed.

  Further, the magnetic force adsorbing member 21 adsorbs the developer scattered on the flow of air generated toward the discharge unit 11 and forms a magnetic seal with the adsorbed developer G. Therefore, the magnetic force adsorbing member 21 can fill the gap S between the reverse spiral blade 16 and the magnetic adsorbing member 21, and the excessive discharge from the discharge unit 11 can be reduced more effectively. Furthermore, since the air pressure in the developing device 1 may become very high as the speed of the image forming apparatus increases, a flow of air is generated from a small gap S and the developer is discharged from the discharge unit 11. . Therefore, the magnetic seal by the developer G of the magnetic force adsorbing member 21 that fills the gap S is very effective in suppressing excessive discharge from the discharge unit 11.

  Incidentally, the target value of the developer discharge amount (hereinafter referred to as excess discharge amount) scattered and discharged from the discharge unit 11 depends on the carrier content ratio relative to the toner, but is, for example, 0.02 g / min or less. . Here, as shown in FIG. 13, the excess discharge amount when the magnetic force adsorption member 21 is not disposed was 0.1929 g / min, whereas the excessive discharge amount when the magnetic force adsorption member 21 is disposed is 0. It was .0093 g / min. It can be seen that the excessive discharge amount can be greatly reduced by arranging the magnetic force adsorbing member 21 in this manner, and the excessive discharge amount is sufficiently lower than the target value.

  Further, the developer inside the developing device 1 tends to be difficult to be discharged under high temperature and high humidity. Here, when the discharge amount becomes smaller than the replenishment amount of the developer into the developing device 1, the amount of the developer in the developing device 1 increases and the amount of the developer in the developing device 1 cannot be kept constant. May arise. Therefore, the amount of developer discharged over the reverse spiral blade 16 (hereinafter referred to as normal discharge amount) needs to be kept at a certain value or higher even under high temperature and high humidity.

  The target value of the normal discharge amount depends on the carrier content ratio relative to the toner, the printing rate, or the number of printed sheets, but is, for example, 0.5 g / min or more. Here, as shown in FIG. 14, when the magnetic force adsorbing member 21 is not disposed, the normal discharge amount of the developer is 1.2 g / min, whereas when the magnetic force adsorbing member 21 is disposed. The normal discharge amount was 0.98 g / min. Therefore, it can be seen that the normal discharge amount sufficiently exceeds the target value even when the magnetic force adsorbing member 21 is arranged.

  Further, as described above, the magnetic force adsorbing member 21 has a magnetic force such that the maximum thickness of the developer adsorbed on the magnetic force adsorbing member 21 is B (mm). And if the distance between the magnetic force adsorbing member and the reverse feed portion is A (mm), A−0.5 ≦ B ≦ A + 0.5 is satisfied. Here, as shown in FIGS. 15 and 16, when the value of AB is 0.5 (mm) or less, the excessive developer discharge amount is below the target value of 0.02 g / min, When the value of AB is -0.5 (mm) or more, the normal discharge amount of the developer exceeds the target value of 0.5 g / min. Therefore, by adjusting the thickness of the developer adsorbed on the magnetic force adsorbing member 21 so that A−0.5 ≦ B ≦ A + 0.5, the amount of the developer discharged from the discharge unit 11 is made appropriate. be able to.

  Further, as described above, the conveying blades 16B of the reverse spiral blade 16 are provided with a constant interval C (mm) along the extending direction of the rotating shaft 16A. When the minimum length in the extending direction of the magnetic force adsorbing member 21 is D (mm), C × 0.7 ≦ D ≦ C × 1.3 is satisfied. Here, the broken lines in the graphs of FIGS. 17 and 18 are the magnetic force attracting member 21 having the shape of FIG. 7A, the solid line is the magnetic force attracting member 21 having the shape of FIG. 7B, and the alternate long and short dash line is the shape of FIG. The discharge amount of each developer in the magnetic force adsorbing member 21 having a shape is shown.

  As shown in FIGS. 17 and 18, when C × 0.7 ≦ D ≦ C × 1.3, the excessive developer discharge amount is equal to or less than the target value 0.02 g / min. In addition, the normal discharge amount of the developer is 0.5 g / min or more. Therefore, when C × 0.7 ≦ D ≦ C × 1.3, it is possible to suppress the excessive discharge of the developer and to avoid the problem that the developer is hardly discharged.

  As described above, the magnetic force attracting member 21 has the N pole 21c and the S pole 21d alternately magnetized, and the magnetization direction of the N pole 21c and the S pole 21d is the same as the rotation direction of the reverse spiral blade 16. Match. As shown in FIG. 19, the developer is used when the magnetization direction is parallel to the rotation direction of the reverse spiral blade 16 and when the magnetization direction intersects the rotation direction of the reverse spiral blade 16. There was no significant difference in excess emissions.

  However, as shown in FIG. 20, the normal developer discharge amount is larger when the magnetization direction is parallel to the rotation direction of the reverse spiral blade 16 than when the magnetization directions intersect. I understood that. In particular, in the case of being parallel, it can be seen that the normal discharge amount of the developer increases when the value of AB is 0 or less. Therefore, when the magnetization direction of the N pole 21c and the S pole 21d coincides with the rotation direction of the reverse spiral blade 16, the normal discharge amount of the developer is reduced and the developer is hardly discharged. It can be avoided.

  FIG. 21 shows a cylindrical nozzle 18, a nozzle 18A shown in FIG. 9A, a nozzle 18B shown in FIG. 9B, a nozzle 18C shown in FIG. 9C, and FIG. 9D. The excessive amount of developer discharged from each nozzle 18D is shown. 21A shows the excess discharge amount of the nozzle 18A, FIG. 21B shows the nozzle 18B, FIG. 21C shows the nozzle 18C, and FIG. 21D shows the nozzle 18D.

  As shown in FIG. 21, the excessive discharge amount of the developer is further reduced in the nozzles 18 </ b> A to 18 </ b> D having a shape that tapers in the first direction D <b> 1 compared to the cylindrical nozzle 18. Further, the excessive discharge amount of the developer is further reduced in the nozzles 18B and 18D in which the diameter of the spiral blade 19 is gradually reduced in the first direction D1, compared to the nozzles 18A and 18C. As described above, excessive discharge of the developer can be more effectively suppressed by making the nozzles 18 </ b> A to 18 </ b> D forming the discharge portion 11 taper.

  FIG. 22 shows the relationship between the number of strips of the reverse spiral blade 16 (Screw winding number) and the excessive discharge amount of the developer, and FIG. 23 shows the number of strips of the reverse spiral blade 16 and the normal discharge amount of the developer. Shows the relationship. As shown in FIG. 22 and FIG. 23, when the number of the reverse spiral blades 16 is 1, the excessive discharge amount increases, and when the number of the reverse spiral blades 16 is 5, the normal discharge amount is high. It is falling. On the other hand, when the number of strips of the reverse spiral blade 16 is 2 or more and 4 or less, the excess discharge amount can be set to a target value of 0.02 g / min or less, and the normal discharge amount is set to a target value of 0.5 g / min. It can be set to min or more. In this way, by setting the number of the reverse spiral blades 16 to 2 or more and 4 or less, it is possible to suppress the excessive discharge of the developer and maintain an appropriate discharge amount of the developer.

  FIG. 24 shows the relationship between the arrangement position of the magnetic force adsorbing member 21 and the excessive discharge amount of the developer. Specifically, for example, in “1 roll” in FIG. 24, the magnetic adsorption member 21 is arranged at the position facing the first conveying blade 16B counted from the opening 14 side, and the developing device 1 is idled for one minute. The amount of excessive discharge later, “Two windings” in FIG. 24, is obtained after the developing device 1 is idled for one minute by disposing the magnetic force adsorbing member 21 at the position facing the second conveying blade 16B counted from the opening 14 side. The excess discharge is shown respectively. Further, (idling 10 min) in FIG. 24 shows an excessive discharge amount after the magnetic adsorption member 21 is disposed at the position facing the fifth conveying blade 16B from the opening 14 side and the developing device 1 is idled for 10 minutes. Is shown.

  As shown in FIG. 24, when the magnetic force adsorbing member 21 is arranged at the position opposed to the first to fourth conveying blades 16B counted from the opening 14 side, the excessive discharge amount is less than the target value 0.02 g / min. . On the other hand, when the magnetic force adsorbing member 21 was disposed at the position opposed to the fifth conveying blade 16B counted from the opening 14 side, it exceeded 0.02 g / min when the idling time of the developing device 1 was 1 minute. However, when the idling time of the developing device 1 is 10 minutes, the target value of 0.02 g / min is obtained even if the magnetic force adsorbing member 21 is arranged at the position facing the fifth conveying blade 16B from the opening 14 side. Below.

  As described above, the first to fourth opposing positions of the first to fourth conveying blades 16B counted from the opening 14 side, that is, the end 16c on the opening 14 side of the conveying blade 16B, as shown in FIG. When the magnetic force adsorbing member 21 is disposed in a range up to a position extending four times the interval C in the direction D1, excessive discharge of the developer is suppressed in 1 minute of the idling time. Accordingly, it is possible to shorten the time from when the developing device 1 is operated until the effect of suppressing the excessive discharge of the developer is exhibited. On the other hand, even if the magnetic force adsorbing member 21 is arranged at the position facing the fifth conveying blade 16B counted from the opening 14 side, excessive discharge of the developer can be sufficiently suppressed if the idling time of the developing device 1 is long. it can.

  Further, as shown in FIG. 12A, the magnetic force adsorbing member 21 is preferably arranged on the upper side in the gravity direction of the reverse spiral blade 16. Here, when the magnetic adsorption member 21 is arranged on the right side, the left side, or the lower side of the reverse spiral blade 16 as shown in FIGS. 12B to 12D, the excessive discharge amount of the developer is respectively 0.0358, 0.0339, and 0.0458 g / min.

  On the other hand, when the magnetic force adsorbing member 21 is disposed on the upper side as shown in FIG. 12A, the excessive developer discharge amount is 0.0089 g / min. From this result, when the magnetic force adsorbing member 21 is disposed on the upper side in the gravity direction of the reverse spiral blade 16, it is possible to more reliably suppress the excessive discharge of the developer. Furthermore, even when the magnetic force adsorbing member 21 was disposed on the upper side, the right side, the left side, or the lower side of the reverse spiral blade 16, the normal discharge amount exceeded 0.5 g / min. Accordingly, even when the magnetic force adsorbing member 21 is arranged on the upper side in the gravity direction or when arranged on the upper side of the gravity direction, it is possible to suppress a decrease in the normal discharge amount, and to discharge the developer in an appropriate amount. Can do.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above, What was changed in the range which does not change the summary described in each claim, or applied to others It may be. That is, the present invention can be variously modified without departing from the gist described in the claims. For example, although the admix auger 13 includes the spiral blade 17 and the spiral blade 19, the configuration of the admix auger 13 such as the position and size of each blade of the admix auger 13 can be changed as appropriate. The configuration of the supply auger 12 or the magnetic force adsorbing member 21 can be changed as appropriate.

DESCRIPTION OF SYMBOLS 1 ... Developing device, 11 ... Discharge part, 12 ... Supply auger (second auger), 12A ... Rotating shaft, 12B ... Spiral blade, 13 ... Admix auger (first auger), 13A ... Rotating shaft, 13B ... Spiral blade, 14, 15 ... opening, 16 ... reverse spiral blade (reverse feed portion), 16A ... rotating shaft, 16B ... conveying blade, 16c ... end, 17 ... spiral blade, 18, 18A, 18B, 18C, 18D ... Nozzle (cylindrical part), 19 ... Spiral blade, 20 ... Housing, 20a ... Inner wall, 21 ... Magnetic adsorption member, 21a, 21b ... End, 21c ... N pole, 21d ... S pole, 22 ... Mounting member, C ... interval, D1 ... first direction, D2 ... second direction, G ... developer, H ... height gauge, H1 ... support base, S ... gap.

Claims (8)

A developing device,
A first auger, a second auger, an opening, a reverse feed unit, a discharge unit, and a magnetic force adsorbing member;
The first auger conveys developer in a first direction;
The second auger extends in parallel to the first auger and conveys the developer in a second direction that is opposite to the first direction;
The opening is provided at one end of the first auger and the second auger and delivers the developer from the first auger to the second auger,
The reverse feeding portion is provided on the first direction side with respect to the opening in the first auger and causes the developer to move in the first direction to flow backward,
The discharge portion is provided on the first direction side of the reverse feed portion and discharges the developer that has overcome the reverse feed portion,
The magnetic force adsorbing member is provided at a position facing the reverse feeding portion and adsorbs the developer;
Development device. The distance between the magnetic force adsorbing member and the reverse feed portion is A (mm),
When the maximum thickness of the developer adsorbed on the magnetic force adsorbing member is B (mm),
A−0.5 ≦ B ≦ A + 0.5,
The developing device according to claim 1, wherein: The reverse feed portion has a rotating shaft and a conveying blade provided spirally on the outer peripheral surface of the rotating shaft,
The conveying blade is provided at a constant interval along the extending direction of the rotating shaft,
When the interval is C (mm) and the minimum length in the extending direction of the magnetic force adsorption member is D (mm),
C × 0.7 ≦ D ≦ C × 1.3,
The developing device according to claim 1 or 2, wherein: The magnetic adsorption member is alternately magnetized with N and S poles,
The magnetization direction of the N pole and the S pole coincides with the rotation direction of the reverse feed portion.
The developing device according to claim 1. It further includes a cylindrical part,
The cylindrical portion extends from the reverse feed portion in the first direction and forms the discharge portion, and has a shape that tapers in the first direction.
The developing device according to claim 1. The reverse feed portion has a rotating shaft and a conveying blade provided spirally on the outer peripheral surface of the rotating shaft,
The number of strips of the conveying blade is 2 or more and 4 or less,
The developing device according to claim 1. The conveying blade is provided at a constant interval along the extending direction of the rotating shaft,
The magnetic force adsorbing member is disposed within a range from an end of the transport blade on the second direction side to a position extending four times the interval in the first direction.
The developing device according to claim 6. At least a part of the magnetic force adsorbing member is disposed on the upper side in the gravity direction of the reverse feed portion.
The developing device according to claim 1.

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