JP2018116117A - Development device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development device and an image forming apparatus capable of performing accurate toner concentration control in a long term.SOLUTION: A development device comprises: a developer storage part for storing developer containing toner and a carrier; an admix auger 23 having a rotary shaft 23A and a stirring blade 23B for stirring and conveying the developer; a development roller for carrying and conveying the developer: a concentration detection sensor 90 disposed at a position facing the admix auger 23, and provided with a detection surface 91 for detecting the concentration of the toner in the developer; and a cleaning member 80 disposed on the stirring blade 23B for cleaning the detection surface 91 in accordance with the rotation of the rotary shaft 23A. The cleaning member 80 comprises a first cleaning member 81 and a second cleaning member 82 each configured of a magnetic body, and the stirring blade 23B, the second cleaning member 82, and the first cleaning member 81 have a laminated-layer structure, and the second cleaning member 82 abuts against the detection surface 91.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a developing device including a developer carrying member that carries a developer, and an image forming apparatus.

  Japanese Patent Application Laid-Open No. 2011-22514 discloses a developing device and an image forming apparatus that include a developer container that stores a developer in which toner and a magnetic carrier are mixed, and a density sensor that detects the concentration of toner in the developer. Have been described. The developing device includes a developing roll that functions as a developer carrying member, and a first stirring and conveying member that conveys the developer while stirring the developer inside the developer container.

  Inside the developer container, the density sensor is disposed at a position opposite to the second stirring and conveying member, and detects the concentration of the toner of the developer stirred and conveyed by the second stirring and conveying member. The density sensor includes a detection unit that faces the second stirring and conveying member, and detects the toner concentration at the timing when the blades of the second stirring and conveying member pass in front of the detection unit.

  The developing device further includes a magnetic plate including a magnetic brush attached to the blades of the second stirring and conveying member. The magnetic plate is a plate-like rubber mixed with a magnet. The magnetic plate passes in front of the detection unit as the second stirring and conveying member rotates, and brushes the detection unit with the magnetic brush. By this brushing, the developer attached on the detection unit is removed.

JP 2011-22514 A

  The developing device and the image forming apparatus are required to stabilize the toner density in order to stably form a good image. In the above-described developing device, the magnetic brush brushes the detection unit to remove the developer on the detection unit, thereby accurately detecting the toner concentration and stabilizing the toner concentration.

  However, for example, due to the use of the developing device in a high-temperature and high-humidity environment, or the deterioration of the developer, the phenomenon that the developer fluidity or changeability is deteriorated in the detection unit and the developer does not move occurs. In this case, the detection of the toner density by the detection unit is not appropriately performed. Therefore, since the toner is not properly replenished, there is a problem that a good image quality cannot be stably formed.

  If the image forming apparatus is continuously used for a long period of time without proper toner replenishment, the toner density becomes abnormal, and there is a concern that the image quality may be abnormal or the apparatus may be contaminated due to toner scattering. Therefore, when the above-described problem occurs and the toner is not properly replenished, it is impossible to provide a stable high-quality image for a long time.

  An object of the present invention is to provide a developing device and an image forming apparatus that can perform accurate toner density control over a long period of time.

  The developing device according to the present invention includes a developer accommodating portion that accommodates a developer including toner and a carrier, a rotating shaft accommodated inside the developer accommodating portion, and stirring the developer by the rotation of the rotating shaft. The developer is provided at a position facing the stirring and conveying member, a stirring and conveying member having a stirring blade to convey, a developer carrying member that carries the developer stirred by the stirring and conveying member, and conveys the developer. A concentration detecting member having a detection surface for detecting the density of the toner therein, and a cleaning member that is provided on the stirring blade and cleans the detection surface of the concentration detection member as the rotation shaft rotates. Has a first cleaning member made of a magnetic material and a flexible second cleaning member, and the stirring blade, the second cleaning member, and the first cleaning member have a laminated structure. The second cleaning member contacts the detection surface.

  This developing device is provided at a position opposed to the agitating and conveying member, provided with a density detecting member on which a detecting surface for detecting the toner density of the developer is formed, and a stirring blade. As the rotating shaft rotates. And a cleaning member for cleaning the detection surface. The cleaning member includes a first cleaning member made of a magnetic material, and a flexible second cleaning member that is sandwiched between the first cleaning member and the stirring blade and that physically contacts the detection surface. In this developing device, the detection surface can be cleaned by removing the developer on the detection surface by the first cleaning member made of a magnetic material. Even when the cleaning capability of the first cleaning member is lowered, the detection surface can be reliably cleaned by the flexible second cleaning member physically contacting the detection surface. Therefore, by providing the first cleaning member and the second cleaning member, the cleaning ability can be maintained in a high state over a long period of time, so that the life can be extended. Further, in a state where the cleaning ability of the first cleaning member is not lowered, the first cleaning member reliably removes the developer on the detection surface and performs cleaning, so that the load on the second cleaning member can be suppressed. it can. As described above, the synergistic effect of the first cleaning member and the second cleaning member contributes to a longer life of the developing device.

  Further, when the distance between the tip of the stirring blade and the detection surface is a and the distance between the first cleaning member and the detection surface is b, a ≦ b ≦ 2.4a may be satisfied. In this case, when the value of b is 2.4a or less, the developer scraping effect on the detection surface can be enhanced, and the retention of the developer on the detection surface can be suppressed, so that detection failure can be avoided. it can. Moreover, the collision of the 1st cleaning member with respect to a detection surface can be avoided because the value of b is more than a.

  Further, the direction of the magnetic force generated by the first cleaning member on the detection surface may be parallel to the detection surface. In this case, the detection surface can be efficiently cleaned by the first cleaning member.

The first cleaning member is disposed so that the direction of the magnetic moment is parallel to the detection surface, and the maximum energy product of the first cleaning member is 11 kj / m ³ or more and 15 kj / m ³ or less. May be. As a result, the magnetic brush that comes into contact with the sensor detection surface becomes a portion where the ears of the developer are lying, and the density of the developer is high. The detection surface can be cleaned by making this portion contact the sensor detection surface. Therefore, the cleaning ability with respect to the detection surface can be enhanced. In addition, since the maximum energy product of the first cleaning member is 11 kj / m ³ or more, it is possible to increase the amount of developer formed in a linear shape. Further, the developer layer can be formed on the first cleaning member, and the distance between the developer layer and the detection surface can be reduced. Therefore, since the cleaning ability with respect to the detection surface can be further enhanced, it contributes to further extending the life. Further, since the maximum energy product of the first cleaning member is 15 kj / m ³ or less, the developer formed on the first cleaning member can be appropriately replaced, and the concentration of the developer flowing at that time can be changed. It can be detected reliably. Moreover, the fluctuation | variation of the output of the density | concentration detection member by a magnetic body can be suppressed because the maximum energy product of a 1st cleaning member is 15 kj / m < ³ > or less.

  The first cleaning member has a thickness in the rotation direction of the rotation shaft, and satisfies 0.8 ≦ c ≦ 2.0 when the thickness of the first cleaning member in the rotation direction is c (mm). May be. Thus, since the value of c is 0.8 mm or more, the detection surface can be reliably cleaned, so that the developer concentration can be detected more accurately. Moreover, when the value of c is 2.0 mm or less, the possibility that the first cleaning member comes into contact with other members can be avoided.

  Further, the Shore A hardness of the second cleaning member may be not less than 80 and not more than 95, and the tensile strength of the second cleaning member may be not less than 80 MPa and not more than 100 MPa. In this case, when the Shore A hardness is 80 or more, the detection surface can be reliably cleaned, so that it is possible to maintain a state where the developer concentration can be detected appropriately. Further, when the Shore A hardness is 95 or less, wear on the detection surface can be suppressed. Furthermore, when the tensile strength of the second cleaning member is 80 MPa or more and 100 MPa or less, it is possible to maintain a state where concentration detection can be appropriately performed, and to suppress deformation of the second cleaning member due to deterioration or the like. .

  Further, when the contact amount of the second cleaning member with the detection surface is d (mm), 0.2 ≦ d ≦ 0.8 may be satisfied. In this case, since the value of d is 0.2 mm or more, the cleaning by the second cleaning member can be reliably performed, so that it is possible to maintain a state where the developer concentration can be appropriately detected. Moreover, when the value of d is 0.8 mm or less, the deformation of the second cleaning member due to deterioration or the like can be suppressed.

  Further, when the distance between the tip of the stirring blade and the detection surface is a (mm), 0.3 ≦ a ≦ 0.6 may be satisfied. In this case, when a is 0.3 mm or more, it is possible to reliably avoid a collision between the stirring blade and the detection surface while maintaining a distance between the stirring blade and the detection surface. Moreover, since the removal performance of the developer on the detection surface by the stirring blade can be improved by a being 0.6 mm or less, the detection sensitivity of the density detection member can be stabilized.

  The average particle diameter of the carrier may be 25 μm or more and 45 μm or less. In this case, when the average particle diameter of the carrier is 45 μm or less, the roughness of the image quality can be suppressed, so that high image quality can be realized. Moreover, when the average particle diameter of the carrier is small, the layer thickness of the developer adsorbed by the first cleaning member may change or the adsorption force of the carrier may be weakened. However, since the second cleaning member reliably cleans the detection surface, the detection sensitivity can be stabilized.

  The density detecting member may detect the mixing ratio of the toner and the carrier based on the magnetic permeability of the developer. In this case, by detecting the mixing ratio of the toner and the carrier from the magnetic permeability, it is possible to detect the change in the toner density during image printing in real time. Therefore, by detecting the change in the toner density in real time, the toner can be replenished in real time when the toner is insufficient. Therefore, it is possible to suppress fluctuations in image quality when images are continuously printed.

  The agitating and conveying member includes a supply auger and an admix auger. The supply auger and the admix auger are arranged along the direction of gravity, and the concentration detection member is positioned opposite the lower admix auger. May be arranged. In this case, the developer tends to stay in the region where the lower admixing auger is arranged due to gravity. By disposing the density detection member in this region, the developer reliably hits the detection surface, so that the density of the developer can be detected with high accuracy. However, if the density detection member is arranged in an area where the developer tends to stay, the developer pressure difference with respect to the detection surface is caused by the difference in the bulk density due to the amount of the developer in the developer accommodating portion or the toner density difference. Problems can occur. However, as described above, the first cleaning member reliably removes the developer on the detection surface, and the second cleaning member physically contacts the detection surface. Therefore, even when the above-described problem occurs, a high cleaning effect on the detection surface and an effect of stabilizing the pressure on the detection surface can be obtained, so that the detection sensitivity can be stabilized.

  Further, the developing device described above may include a supply unit that supplies toner and a carrier to the developer storage unit, and a discharge unit that discharges excess developer from the developer storage unit. In this case, since a new developer is supplied to the developer accommodating portion and the excess developer is discharged from the developer accommodating portion, the deterioration of the developer can be suppressed. Therefore, it is possible to avoid the problem that the image quality deteriorates. In addition, when a new developer is replenished and a surplus developer is discharged, the amount of developer in the developer container may vary. Even in such a case, the first cleaning member and the second cleaning member reliably clean the detection surface, so that the developer concentration can be detected stably.

  An image forming apparatus according to the present invention includes the above-described developing device. Therefore, in this image forming apparatus, the same effect as described above can be obtained.

  According to the developing device and the image forming apparatus of the present invention, accurate toner density control can be performed over a long period of time.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. It is a side view which shows the developing device which concerns on embodiment. It is a figure which shows the developing roller and two augers in the inside of a developing device. It is a figure which shows the cleaning member of a developing device. It is a figure which shows a cleaning member, an auger, and a density | concentration detection sensor. It is a figure which shows typically a cleaning member, an auger, and a density | concentration detection sensor. It is a figure which shows a 1st cleaning member typically. It is a figure which shows the positional relationship of a cleaning member and a density | concentration detection sensor. It is a figure which decomposes | disassembles and shows a cleaning member. 6 is a graph showing the relationship between toner density and sensor output. It is a graph which shows the time-sequential change of the output of a sensor. (A) is a graph which shows the relationship between the density | concentration of a toner and the output of a sensor for every Example and a comparative example. (B) is a graph showing the relationship between toner density and sensor output for each number of printed sheets. (A) is a graph which shows the result of the sensitivity of the sensor in a comparative example. (B) is a graph which shows the result of the sensitivity of the sensor in an Example. (A) is a graph showing the relationship between toner density and sensor output in each example for each developer amount. (B) is a graph showing the relationship between the toner density and the sensor output in the comparative example for each developer amount. It is a graph which shows the relationship between the maximum energy product of a 1st cleaning member, and the layer thickness of a developing agent. 6 is a graph showing the relationship between toner density and sensor output for each value of distance a. (A) is a chart which shows the result of the abrasion of a sensor detection surface, and the sensitivity of a sensor for every hardness. (B) is a graph which shows the result of a deformation | transformation of a 2nd cleaning member, and the sensitivity of a sensor for every tensile strength. (A) is a table | surface which shows the sensitivity of a sensor, and the result of a deformation | transformation of a 2nd cleaning member for every contact amount of a 2nd cleaning member. (B) is a chart which shows the sensitivity of a sensor and the result of collision avoidance for every distance of a stirring blade front-end | tip and a detection surface.

  Hereinafter, a developing device according to an embodiment and an image forming apparatus including the developing device will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

  The image forming apparatus 1 according to the present embodiment forms a color image using each color of magenta, yellow, cyan, and black. As shown in FIG. 1, the image forming apparatus 1 includes a recording medium conveying device 10, four developing devices 20, a transfer device 30, four photosensitive members 40, and a fixing device 50. .

  The recording medium conveyance device 10 conveys a paper P that is a recording medium. The developing device 20 develops the electrostatic latent image. The transfer device 30 secondarily transfers the toner image onto the paper P. The photoreceptor 40 is an electrostatic latent image carrier on which an image is formed on the outer peripheral surface thereof. The fixing device 50 fixes the toner image on the paper P.

  The recording medium transport apparatus 10 includes a paper feed roller 11 that transports the paper P on which an image is formed on the transport path R1. The paper P is stacked and accommodated in the cassette C, and is picked up and conveyed by the paper feed roller 11. The paper feed roller 11 is provided near the exit of the paper P in the cassette C. The recording medium transport device 10 causes the paper P to reach the secondary transfer region R2 via the transport path R1 at the timing when the toner image transferred to the paper P reaches the secondary transfer region R2.

  The developing device 20 is provided for each color. Each developing device 20 includes a developing roller 21 (developer carrying member) that carries the toner on the photoreceptor 40. In the developing device 20, the toner and the carrier are adjusted to have a predetermined mixing ratio, and the toner and the carrier are mixed and stirred to uniformly disperse the toner. As a result, a developer having an optimum charge amount is generated. The developer is carried on the developing roller 21. Then, as the developing roller 21 rotates, the developer is conveyed to a region facing the photoconductor 40. At this time, the toner in the developer carried on the developing roller 21 moves to the electrostatic latent image on the photoconductor 40, whereby the electrostatic latent image is developed. The average particle diameter of the carrier is, for example, 25 μm or more and 45 μm or less, and a specific example is 35 μm.

  The transfer device 30 conveys the toner image formed by the developing device 20 to the secondary transfer region R2. The transfer device 30 includes a transfer belt 31, suspension rollers 32 a, 32 b, 32 c, and 32 d, a primary transfer roller 33, and a secondary transfer roller 34. The transfer belt 31 is suspended by suspension rollers 32a, 32b, 32c, and 32d. Four primary transfer rollers 33 are provided for each color. Each primary transfer roller 33 holds the transfer belt 31 together with each photoconductor 40. The secondary transfer roller 34 holds the transfer belt 31 together with the suspension roller 32d.

  The transfer belt 31 is an endless belt that circulates and moves by suspension rollers 32a, 32b, 32c, and 32d. The primary transfer roller 33 presses the photoconductor 40 from the inner peripheral side of the transfer belt 31. The secondary transfer roller 34 presses the suspension roller 32 d from the outer peripheral side of the transfer belt 31. The photoreceptor 40 is, for example, a photoreceptor drum, and is provided for each color. The four photoconductors 40 are provided side by side along the moving direction of the transfer belt 31. A developing device 20, a charging device 41, an exposure unit 42, and a cleaning device 70 are provided at positions opposed to the outer peripheral surface of each photoconductor 40.

  The image forming apparatus 1 includes a process cartridge 2 that integrally includes a developing device 20, a photoreceptor 40, a charging device 41, and a cleaning device 70, and an apparatus main body 3 to which the process cartridge 2 is attached and detached. The process cartridge 2 is detachable from the apparatus main body 3 by opening the door of the apparatus main body 3 and being inserted into and removed from the apparatus main body 3.

  The charging device 41 is a charging unit that uniformly charges the outer peripheral surface of the photoconductor 40 to a predetermined potential. The charging device 41 is a charging roller that rotates following the rotation of the photoreceptor 40. The exposure unit 42 exposes the outer peripheral surface of the photoconductor 40 charged by the charging device 41 according to an image formed on the paper P. The potential of the portion exposed to the exposure unit 42 on the outer peripheral surface of the photoconductor 40 is changed, thereby forming an electrostatic latent image.

  The four developing devices 20 develop the electrostatic latent image on each photoconductor 40 with the toner supplied from each of the four toner tanks N arranged to face each developing device 20. As a result, the toner image is developed. Each toner tank N is filled with magenta, yellow, cyan and black toners, respectively. The cleaning device 70 removes the toner remaining on the outer peripheral surface of the photoconductor 40 after the toner image formed on the outer peripheral surface of the photoconductor 40 is primarily transferred to the transfer belt 31.

  The fixing device 50 attaches the toner image secondarily transferred from the transfer belt 31 to the paper P to the paper P and fixes the toner image on the paper P. The fixing device 50 includes a fixing belt 51 that heats the paper P and fixes the toner image on the paper P, and a pressure roller 52 that presses the fixing belt 51.

  The fixing belt 51 is formed in a cylindrical shape. A heat source such as a halogen lamp is provided inside the fixing belt 51. The pressure roller 52 is formed in a cylindrical shape. A fixing nip portion that is a contact area is provided between the fixing belt 51 and the pressure roller 52. By passing the paper P through the fixing nip portion, the toner image is melted and fixed on the paper P. Further, the image forming apparatus 1 is provided with discharge rollers 55 and 56 for discharging the paper P on which the toner image is fixed by the fixing device 50 to the outside of the image forming apparatus 1.

  An image forming method by the image forming apparatus 1 configured as described above will be described. First, a printing process by the image forming apparatus 1 will be described. First, when an image signal of an image to be recorded is input to the image forming apparatus 1, the control unit of the image forming apparatus 1 rotates the paper feed roller 11 to pick up the paper P stacked on the cassette C and convey the path R1. Transport to. Based on the received image signal, the charging device 41 uniformly charges the outer peripheral surface of the photoconductor 40 to a predetermined potential (charging process). Thereafter, the exposure unit 42 irradiates the outer peripheral surface of the photoconductor 40 with laser light to form an electrostatic latent image (exposure process).

  Next, a toner image obtained by developing the electrostatic latent image is formed by the developing device 20 (developing step). The toner image is primarily transferred from each photoconductor 40 to the transfer belt 31 in a region where each photoconductor 40 and the transfer belt 31 face each other (transfer process). On the transfer belt 31, toner images formed on each of the four photoreceptors 40 are sequentially stacked, thereby forming one stacked toner image. The laminated toner image is secondarily transferred onto the paper P conveyed from the recording medium conveying device 10 in the secondary transfer region R2 where the suspension roller 32d and the secondary transfer roller 34 face each other.

  The sheet P on which the laminated toner image is secondarily transferred is conveyed from the secondary transfer region R2 to the fixing device 50. The fixing device 50 melts and fixes the laminated toner image on the paper P by passing the fixing nip portion while applying heat and pressure to the paper P (fixing step). Thereafter, the paper P is discharged to the outside of the image forming apparatus 1 by the discharge rollers 55 and 56.

  Here, the developing device 20 will be described in more detail.

  The developing device 20 is a device that performs development using a two-component developing system. As shown in FIG. 2 and FIG. 3, the developing device 20 supplies a developer consisting of a carrier filled with toner into the toner tank N from the supply unit 24, and uses an overflow method to remove excess developer. The toner is discharged from the discharge unit 25 to the outside of the developing device 20.

  In addition to the above-described developing roller 21, the developing device 20 is parallel to the supply auger 22, a developer accommodating portion 20 </ b> A that accommodates the developer, a supply auger 22 (agitating and conveying member) that supplies the developer to the developing roller 21. And an admixing auger 23 (agitating and conveying member) disposed on the lower side in the gravity direction of the supply auger 22.

  The supply auger 22 and the admix auger 23 are arranged along the direction of gravity. Specifically, 45 ° ≦ θ ≦ 90 ° is satisfied, where θ is an angle formed by a straight line L connecting the rotation center O1 of the supply auger 22 and the rotation center O2 of the admixing auger 23 and the horizontal plane H. The supply unit 24 is provided at one end in the longitudinal direction of the admix auger 23, and the discharge unit 25 is provided at one end in the longitudinal direction of the supply auger 22.

  The supply auger 22 includes a rotating shaft 22A and a stirring blade 22B that protrudes spirally from the rotating shaft 22A. The supply auger 22 conveys the developer inside the developing device 20 supplied from the supply unit 24 in the first direction D1. Here, the first direction D1 is an axial direction of the supply auger 22 and is a direction in which the discharge unit 25 is positioned when viewed from the stirring blade 22B. In the supply auger 22, when the rotating shaft 22A is rotated by a driving device (not shown), the stirring blade 22B moves in the first direction D1, so that the developer is conveyed in the first direction D1 by the stirring blade 22B. The

  The admix auger 23 includes a rotating shaft 23A and a stirring blade 23B that protrudes spirally from the rotating shaft 23A. The admix auger 23 conveys the developer supplied from the supply unit 24 in the second direction D2. In the admix auger 23, when the rotating shaft 23A is rotated by the driving device, the stirring blade 23B moves in the second direction D2, and thus the developer is conveyed in the second direction D2 by the stirring blade 23B. Note that the second direction D2 is the opposite direction of the first direction D1.

  A first opening 26 for delivering the developer from the supply auger 22 to the admixing auger 23 is provided at the end of the supply auger 22 and the admixing auger 23 on the first direction D1 side. A second opening 36 for delivering the developer from the admix auger 23 to the supply auger 22 is provided at the end of the supply auger 22 and the admix auger 23 on the second direction D2 side.

  A reverse conveying blade 22 </ b> C that reversely flows the developer is provided on the supply auger 22 on the first direction D <b> 1 side of the first opening 26. The discharge unit 25 is provided on the first direction D1 side with respect to the reverse conveying blade 22C. On the first direction D1 side of the reverse conveying blade 22C, the stirring blades 22D and 22E that move in the first direction D1 when the rotating shaft 22A rotates, and the reverse that moves in the second direction D2 when the rotating shaft 22A rotates. A conveying blade 22F is provided.

  As described above, since the agitating blades 22D and 22E are provided on the first conveying direction D1 side of the reverse conveying blade 22C, the developer over the reverse conveying blade 22C is conveyed to the discharge unit 25 by the agitating blade 22D and 22E. And discharged to the outside of the developing device 20. The reverse conveying blade 22F is located on the opposite side of the stirring blade 22E in the discharge unit 25. Further, on the first direction D1 side of the first opening 26 in the admix auger 23, a stirring blade 23C that moves in the second direction D2 with the rotation of the rotation shaft 23A is provided.

  On the second direction D2 side of the stirring blade 23B of the admix auger 23, a cleaning member 80 and a concentration detection sensor 90 (a concentration detection member) are provided. The concentration detection sensor 90 is provided at a position facing the stirring blade 23B. The cleaning member 80 is provided on the stirring blade 23B, and cleans the concentration detection sensor 90 with the rotation of the rotating shaft 23A.

  FIG. 4 is a view showing the cleaning member 80 attached to the stirring blade 23 </ b> B of the admix auger 23. FIG. 5 is a diagram illustrating the cleaning member 80 and the concentration detection sensor 90. As shown in FIGS. 4 and 5, the cleaning member 80 includes a first cleaning member 81 made of a magnetic material, and a flexible second sandwiched between the first cleaning member 81 and the stirring blade 23B. And a cleaning member 82. The stirring blade 23B, the second cleaning member 82, and the first cleaning member 81 have a laminated structure in this order.

  The first cleaning member 81 and the second cleaning member 82 are trapezoidal. The 1st cleaning member 81 is provided with the acute angle part 81a which makes substantially the same angle as the edge part 23a which makes the acute angle of the stirring blade 23B, and the 2nd cleaning member 82 is also provided with the same acute angle part 82a. For example, the first cleaning member 81 and the second cleaning member 82 have similar shapes.

  The density detection sensor 90 has a detection surface 91 that detects the density of the developer stored in the developer storage section 20A. The density detection sensor 90 is, for example, a magnetic permeability sensor that detects the toner density from the magnetic permeability of the developer. The detection surface 91 is disposed at a position facing the edge portion 23 a of the admix auger 23 and is directed to the rotation shaft 23 </ b> A of the admix auger 23. The density detection sensor 90 detects the density of the toner from the developer that contacts the detection surface 91.

  The cleaning member 80 is provided for cleaning the detection surface 91 of the concentration detection sensor 90. The first cleaning member 81 cleans the developer remaining on the detection surface 91 using magnetic force, and the second cleaning member 82 contacts the detection surface 91 to physically clean the developer. The first cleaning member 81 is, for example, a magnet sheet, and the second cleaning member 82 is a urethane rubber sheet. The Shore A hardness of the second cleaning member 82 is 80 or more and 95 or less. The tensile strength of the second cleaning member 82 is 80 MPa or more and 100 MPa or less.

  6, the distance between the radially outer end 23b of the stirring blade 23B and the detection surface 91 is a (unit mm), the radially outer end of the first cleaning member 81, and the detection surface 91. Where b (unit: mm), a ≦ b ≦ 2.4a is satisfied. The value of the distance a is, for example, not less than 0.3 mm and not more than 0.6 mm. Furthermore, when the thickness of the first cleaning member 81 protruding in the rotation direction Y of the rotating shaft 23A is c (unit mm), the value of c is 0.8 mm or more and 2.0 mm or less.

  FIG. 7 is a diagram showing details of the first cleaning member 81. As shown in FIG. 7, the first cleaning member 81 includes an S pole 81c and an N pole 81d. In the first cleaning member 81, the S pole 81 c and the N pole 81 d are overlapped along the rotational direction Y of the admix auger 23. That is, the first cleaning member 81 is arranged so that the magnetization directions of the S pole 81 c and the N pole 81 d are parallel to the detection surface 91.

For example, in the first cleaning member 81, the S pole 81 c is attached to the second cleaning member 82, and the N pole 81 d is directed to the opposite side of the second cleaning member 82. By arranging the S pole 81c and the N pole 81d as described above, the first cleaning member 81 is formed with a plurality of magnetic brushes B in which the developer is linearly formed like a spike. Further, the maximum energy product (BHmax) of the first cleaning member 81 is 11 kj / m ³ or more and 15 kj / m ³ or less.

  As shown in FIG. 8, the radial length G of the second cleaning member 82 is longer than the distance X between the rotation shaft 23 </ b> A and the detection surface 91. Therefore, the radially outer end portion of the second cleaning member 82 is bent and contacts the detection surface 91. Here, when the difference between the radial length G of the second cleaning member 82 and the distance X is the contact amount d (unit: mm) of the second cleaning member 82 with respect to the detection surface 91, the value of d is 0.2 mm. Above and below 0.8 mm.

  As shown in FIG. 9, the cleaning member 80 includes two double-sided tapes 83 and 84 in addition to the first cleaning member 81 and the second cleaning member 82 described above. The double-sided tape 83 is a double-sided tape that bonds the second cleaning member 82 to the stirring blade 23B. Before being affixed to the agitation blade 23B, a protective paper is affixed to the agitation blade 23B side of the double-sided tape 83 (the right side surface in FIG. 9). The double-sided tape 84 is a double-sided tape that bonds the first cleaning member 81 and the second cleaning member 82, and the first cleaning member 81 and the second cleaning member 82 are previously provided before the cleaning member 80 is bonded to the stirring blade 23B. And are bonded. That is, the first cleaning member 81, the second cleaning member 82, and the double-sided tapes 83, 84 are integrated in advance before being attached to the stirring blade 23B.

  Next, a conventional developing device that does not have the flexible second cleaning member 82 will be described. In this conventional developing device, the first cleaning member made of a magnetic material forms a magnetic brush, so that the magnetic brush cleans the detection surface of the density detection sensor. However, the magnetic brush formed by the first cleaning member has a cleaning capability depending on environmental factors such as the developer amount, toner density change, or developer deterioration, the installation position of the first cleaning member, or the particle size of the carrier. May occur, and it may become impossible to secure sufficient cleaning ability. As shown in FIG. 10, it can be seen that the output value of the density detection sensor 90 is unstable and the output value is unstable, particularly when the amount of developer increases and the toner density is high. This is considered to be due to the fact that the pressure applied to the density detection sensor 90, which has increased as the bulk density of the developer on the detection surface 91 increases, exceeds the cleaning ability of the first cleaning member 81. Note that “developer increase condition 1” in FIGS. 10 and 14 indicates a state in which the amount of developer is larger than “center value”, and “developer increase condition 2” is greater than “developer increase condition 1”. Shows a state where the amount of the developer is larger.

  In contrast to such a conventional developing device, the developing device 20 of the present embodiment applies a constant pressure to the developer on the detection surface 91 by the first cleaning member 81 and the second cleaning member 82, and is shown in FIG. As described above, the peak value of the output of the density detection sensor 90 is stabilized. Even when the cleaning ability of the first cleaning member 81 is lowered, the developer on the detection surface 91 is physically removed by the second cleaning member 82.

  Therefore, as shown in FIG. 6, the developing device 20 of the present embodiment includes a concentration detection sensor 90 in which the detection surface 91 is directed to the stirring blade 23 </ b> B, and a detection surface of the concentration detection sensor 90 provided on the stirring blade 23 </ b> B. And a cleaning member 80 for cleaning 91. The cleaning member 80 is a flexible second cleaning member that is sandwiched between the first cleaning member 81 made of a magnetic material and the first cleaning member 81 and the stirring blade 23B and that physically contacts the detection surface 91. 82. In the developing device 20, the detection surface 91 can be cleaned by removing the developer on the detection surface 91 by the first cleaning member 81 made of a magnetic material.

  Even when the cleaning capability of the first cleaning member 81 is reduced, the detection surface 91 is reliably cleaned by the flexible second cleaning member 82 physically contacting the detection surface 91. be able to. Therefore, as shown in the experimental results of the cleaning member 80 of the embodiment of FIG. 12A and the cleaning member of the comparative example, even when the toner concentration is high, the output of the density detection sensor 90 is suppressed and output is suppressed. Can be stabilized.

  Accordingly, the provision of the first cleaning member 81 and the second cleaning member 82 can maintain the cleaning capability in a high state over a long period of time, and thus the life can be extended. As shown in FIG. 12B, the output of the density detection sensor 90 can be kept stable even at 1000 kpv (when 1000 × 1000 sheets of paper P are printed). Further, in a state where the cleaning capability of the first cleaning member 81 is not lowered, the load applied to the second cleaning member 82 because the first cleaning member 81 reliably removes the developer on the detection surface 91 and performs cleaning. Can be suppressed. As described above, the synergistic effect of the first cleaning member 81 and the second cleaning member 82 contributes to a longer life of the developing device 20.

  Furthermore, in the developing device 20 according to the present embodiment, since the first cleaning member 81 and the second cleaning member 82 reliably clean the detection surface 91 and do not need a configuration for controlling the cleaning member 80, there is no need for special cleaning. It is possible to dispense with unnecessary control or machine operation. Therefore, accurate concentration detection can be performed over a long period of time, the configuration can be simplified, and the cost can be further reduced.

  Further, when the distance between the tip of the stirring blade 23B and the detection surface 91 is a and the distance between the first cleaning member 81 and the detection surface 91 is b, a ≦ b ≦ 2.4a is satisfied. Therefore, when the value of b is 2.4a or less, the developer scraping effect on the detection surface 91 can be enhanced, and the retention of the developer on the detection surface 91 can be suppressed, so that detection failure is avoided. Can do. Moreover, the collision of the 1st cleaning member 81 with respect to the detection surface 91 can be avoided because the value of b is more than a. Furthermore, the direction of the magnetic force generated by the first cleaning member 81 on the detection surface 91 is parallel to the detection surface 91. Therefore, the detection surface 91 can be efficiently cleaned by the first cleaning member 81.

  Further, as shown in FIG. 13A, in the developing device of the comparative example that does not have the second cleaning member 82, the sensitivity of the density detection sensor 90 is deteriorated as the distance b increases. On the other hand, as shown in FIG. 13B, in the developing device 20 having the second cleaning member 82, the sensitivity of the density detection sensor 90 is satisfactorily maintained even when the amount of developer and the distance b vary. be able to.

The first cleaning member 81 is arranged so that the direction of the magnetic moment is parallel to the detection surface 91, and the maximum energy product of the first cleaning member 81 is 11 kj / m ³ or more and 15 kj / m. ³ or less. Therefore, as shown in FIG. 7, the magnetic brush that contacts the detection surface 91 of the density detection sensor 90 becomes a portion where the ears of the developer are lying, and the density of the developer is high. By adopting a configuration in which this portion is brought into contact with the detection surface 91, the detection surface 91 can be cleaned.

  Specifically, as shown in FIG. 10 and FIG. 14B, in the conventional developing device, the developer amount in the developer accommodating portion is increased from the central value to the developer increasing condition 1, and the developer increased. When it fluctuates with condition 2, there is a problem that the output of the density detection sensor becomes unstable or the output value shifts. On the other hand, as shown in FIG. 14A, in the developing device 20 of the present embodiment, the developer amount in the developer accommodating portion 20A is increased from the center value to the developer increasing condition 1, and the developer increased. Even if it fluctuates with condition 2, the output of the density detection sensor 90 can be stabilized. Therefore, it turns out that the cleaning capability with respect to the detection surface 91 is improved.

In addition, since the maximum energy product of the first cleaning member 81 is 11 kj / m ³ or more, the amount of the magnetic brush B can be increased, and the magnetic brush B forming the developer layer on the first cleaning member 81 can be increased. By forming, the distance between the magnetic brush B and the detection surface 91 can be reduced. Further, as shown in FIG. 15, when the maximum energy product is 11 kj / m ³ or more, the layer thickness of the developer can be secured, so that the magnetic brush B can be provided more sufficiently and the cleaning can be performed. Contributes to further improvement of ability.

Therefore, since the cleaning capability with respect to the detection surface 91 can be further enhanced, the life can be further extended. Further, since the maximum energy product of the first cleaning member 81 is 15 kj / m ³ or less, the magnetic brush B formed on the first cleaning member 81 can be appropriately replaced, and the toner flowing at that time can be replaced. The concentration can be detected reliably. Moreover, the fluctuation | variation of the output of the density | concentration detection sensor 90 by a magnetic body can be suppressed because the maximum energy product of the 1st cleaning member 81 is 15 kj / m < ³ > or less.

  The first cleaning member 81 has a thickness in the rotation direction Y of the rotary shaft 23A, and 0.8 ≦ c ≦ when the thickness of the first cleaning member 81 in the rotation direction Y is c (mm). Satisfies 2.0. Thus, since the value of c is 0.8 mm or more, the detection surface 91 can be reliably cleaned, so that the concentration detection of the developer by the concentration detection sensor 90 can be performed more accurately.

  Specifically, as shown in FIG. 16, when the value of c is 0.6 mm, the output of the density detection sensor 90 is slightly higher when the toner density is high (for example, 11% or more). I'm rattling. On the other hand, when the value of c is 0.8 mm or more, the output of the density detection sensor 90 can be stabilized even when the toner density is high. In addition, by setting the value of c to 2.0 mm or less, it is possible to avoid the possibility that the first cleaning member 81 contacts another member.

  The Shore A hardness of the second cleaning member 82 is 80 or more and 95 or less, and the tensile strength of the second cleaning member 82 is 80 MPa or more and 100 MPa or less. Therefore, as shown in FIG. 17A, since the Shore A hardness is 80 or more, the detection surface 91 can be reliably cleaned, so that the sensitivity of the density detection sensor 90 can be made appropriate.

  Further, when the Shore A hardness is 95 or less, wear of the detection surface 91 can be suppressed. Furthermore, as shown in FIG. 17B, the tensile strength of the second cleaning member 82 is 80 MPa or more and 100 MPa or less, so that it is possible to maintain a state in which concentration detection can be performed appropriately, as well as deterioration and the like. The deformation of the second cleaning member 82 due to can be suppressed.

  Further, when the contact amount of the second cleaning member 82 with respect to the detection surface 91 is d (mm), 0.2 ≦ d ≦ 0.8. Thus, when the value of d is 0.2 mm or more, the sensitivity of the density detection sensor 90 can be made appropriate as shown in FIG. Moreover, since the value of d is 0.8 mm or less, the deformation of the second cleaning member 82 due to deterioration or the like can be suppressed.

  Further, the first cleaning member 81 and the second cleaning member 82 are integrated. Therefore, the first cleaning member 81 and the second cleaning member 82 can be managed as one cleaning member 80. Therefore, since the cleaning member 80 can be managed as one part, it contributes to the reduction of the part management man-hours and assembly man-hours of the cleaning member 80.

  Further, when the distance between the end 23b of the stirring blade 23B and the detection surface 91 is a (mm), 0.3 ≦ a ≦ 0.6 is satisfied. When a is 0.3 mm or more, as shown in FIG. 18 (b), the distance between the stirring blade 23B and the detection surface 91 is kept constant, thereby causing the collision between the stirring blade 23B and the detection surface 91. It can be avoided. Further, when a is 0.6 mm or less, the developer removal performance by the stirring blade 23B on the detection surface 91 can be improved, so that the detection sensitivity of the density detection sensor 90 can be stabilized.

  The average particle diameter of the developer carrier is 25 μm or more and 45 μm or less. Therefore, when the average particle diameter of the carrier is 45 μm or less, the roughness of the image quality can be suppressed, and thus high image quality can be realized. Further, when the average particle size of the carrier is small, the layer thickness of the developer adsorbed by the first cleaning member 81 may change or the adsorption force of the carrier may be weakened. However, even in such a case, since the second cleaning member 82 reliably cleans the detection surface 91, the detection sensitivity can be stabilized. In this embodiment, a microtrack is used as a method for measuring the average particle diameter of carriers, and particle diameter information is detected from light scattering information of particles by a semiconductor laser.

  The density detection sensor 90 detects the mixing ratio of toner and carrier based on the magnetic permeability of the developer. Therefore, by detecting the mixing ratio of the toner and the carrier from the magnetic permeability, it is possible to detect the change in the toner density during image printing in real time. Therefore, by detecting the change in toner density in real time, the toner can be replenished in real time when the toner is insufficient. Therefore, it is possible to suppress fluctuations in image quality when images are continuously printed.

  In the developing device 20, a supply auger 22 and an admix auger 23 are arranged along the direction of gravity. Therefore, the developer tends to stay in the region where the lower admixer auger 23 is arranged due to gravity. By disposing the density detection sensor 90 in this region, the developer reliably hits the detection surface 91, so that the density of the developer can be detected with high accuracy. However, when the density detection sensor 90 is arranged in this region, there arises a problem that a developer pressure difference with respect to the detection surface 91 is caused by a difference in bulk density due to a developer amount or a toner density difference in the developer container 20A. Yes. However, as described above, the first cleaning member 81 reliably removes the developer on the detection surface 91 and the second cleaning member 82 physically contacts the detection surface 91. Accordingly, even when the above-described problem occurs, a high cleaning effect on the detection surface 91 can be obtained, so that the detection sensitivity can be stabilized.

  Further, the developing device 20 includes a supply unit 24 that supplies toner and a carrier to the developer storage unit 20A, and a discharge unit 25 that discharges excess developer from the developer storage unit 20A. Therefore, it is possible to supply a new developer to the developer storage unit 20A and discharge the excess developer from the discharge unit 25. Therefore, it is possible to avoid the problem that the image quality deteriorates. In addition, when supplying new developer and discharging excess developer, the amount of developer inside the developer container 20A may vary. Even in such a case, since the first cleaning member 81 and the second cleaning member 82 reliably continue to clean the detection surface 91 of the density detection sensor 90, the toner density can be detected stably. Furthermore, since the image forming apparatus 1 according to the present embodiment includes the developing device 20, the same effects as described above can be obtained.

  The embodiments of the developing device and the image forming apparatus according to the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and may be modified within the scope not changing the gist described in each claim or applied to others. That is, the configurations of the developing device and the image forming apparatus can be variously modified without changing the gist of each claim.

  For example, in the above-described embodiment, the example in which the cleaning member 80 is attached to the admix auger 23 has been described. However, the position at which the cleaning member is attached is not limited to the admix auger 23 and can be changed as appropriate. For example, the cleaning member may be attached to the supply auger 22. Moreover, it may replace with the trapezoidal 1st cleaning member 81 and the 2nd cleaning member 82, and may be provided with the 1st cleaning member and the 2nd cleaning member of shapes other than a trapezoid, and the 1st cleaning member and the 2nd cleaning member The shape, size, number and material are not limited to the above-described embodiments.

  In the above-described embodiment, the density detection sensor 90 that is a magnetic permeability sensor that detects the toner density from the magnetic permeability of the developer has been described. However, the density detection sensor that detects the toner density from parameters other than the magnetic permeability is described. There may be. For example, instead of the density detection sensor 90 that detects the toner density from the magnetic permeability, a density detection sensor that is an optical sensor may be provided.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Process cartridge, 3 ... Apparatus main body, 10 ... Recording medium conveying apparatus, 11 ... Paper feed roller, 20 ... Developing apparatus, 20A ... Developer accommodating part, 21 ... Developing roller (developer carrier) ), 22 ... Supply auger (stirring conveyance member), 22A, 23A ... Rotating shaft, 22B ... Agitating blade, 22C, 22F ... Reverse conveying blade, 22B, 22D, 23B, 23C ... Agitating blade, 23 ... Admix auger (stirring) Conveying member), 23a ... edge portion, 23b ... end portion, 24 ... supply portion, 25 ... discharge portion, 26, 36 ... opening, 30 ... transfer device, 31 ... transfer belt, 32a, 32b, 32c, 32d ... suspension Roller, 33 ... Primary transfer roller, 34 ... Secondary transfer roller, 40 ... Photoconductor, 41 ... Charging device, 42 ... Exposure unit, 50 ... Fixing device, 51 ... Fixing belt, 52 ... Pressure low 55, 56 ... discharge roller, 70 ... cleaning device, 80 ... cleaning member, 81 ... first cleaning member, 81a ... acute angle part, 81b ... end, 81c ... S pole, 81d ... N pole, 82 ... second cleaning Member 82a ... acute angle part 83, 84 double-sided tape 90 ... density detection sensor (density detection member) 91 ... detection surface a, b ... distance, A ... center, B ... magnetic brush, C ... cassette, d Abutment amount, D1, D2 ... direction, H ... horizontal plane, L ... straight line, N ... toner tank, O1, O2 ... center of rotation, P ... paper, R1 ... transport path, R2 ... secondary transfer area, T ... interval , X: distance, Y: rotational direction.

Claims (13)

A developer accommodating portion for accommodating a developer including toner and a carrier;
A rotating shaft accommodated in the developer accommodating portion, and an agitating and conveying member having an agitating blade for conveying the developer while stirring the developer by rotation of the rotating shaft;
A developer carrying member that carries the developer stirred by the stirring and conveying member and conveys the developer; and
A density detection member provided at a position facing the agitation transport member and having a detection surface for detecting the density of the toner in the developer;
A cleaning member that is provided on the stirring blade and that cleans the detection surface of the concentration detection member as the rotation shaft rotates;
With
The cleaning member has a first cleaning member made of a magnetic material, and a flexible second cleaning member,
The stirring blade, the second cleaning member, and the first cleaning member have a laminated structure,
The second cleaning member contacts the detection surface;
Development device. When the distance between the tip of the stirring blade and the detection surface is a, and the distance between the first cleaning member and the detection surface is b, a ≦ b ≦ 2.4a is satisfied.
The developing device according to claim 1. The direction of the magnetic force generated by the first cleaning member on the detection surface is parallel to the detection surface.
The developing device according to claim 1 or 2. The first cleaning member is arranged such that the direction of the magnetic moment is parallel to the detection surface,
The maximum energy product of the first cleaning member is 11 kj / m ³ or more and 15 kj / m ³ or less.
The developing device according to claim 1. The first cleaning member has a thickness in a rotation direction of the rotation shaft,
When the thickness in the rotational direction of the first cleaning member is c (mm), 0.8 ≦ c ≦ 2.0 is satisfied.
The developing device according to claim 1. The Shore A hardness of the second cleaning member is 80 or more and 95 or less, and the tensile strength of the second cleaning member is 80 MPa or more and 100 MPa or less.
The developing device according to claim 1. When the contact amount of the second cleaning member to the detection surface is d (mm), 0.2 ≦ d ≦ 0.8 is satisfied.
The developing device according to claim 1. When the distance between the tip of the stirring blade and the detection surface is a (mm), 0.3 ≦ a ≦ 0.6 is satisfied.
The developing device according to claim 1. The average particle size of the carrier is 25 μm or more and 45 μm or less.
The developing device according to claim 1. The concentration detection member detects a mixing ratio of the toner and the carrier based on a magnetic permeability of the developer;
The developing device according to claim 1. The stirring and conveying member includes a supply auger and an admixing auger,
The supply auger and the admix auger are arranged along the direction of gravity, and the concentration detection member is arranged at a position facing the lower admix auger.
The developing device according to claim 1. A supply unit for supplying the toner and the carrier to the developer storage unit;
A discharge section for discharging the excess developer from the developer storage section;
A developing device according to any one of claims 1 to 11.   An image forming apparatus comprising the developing device according to claim 1.