JP2005148288A - Developer agitating member, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer agitating member with high mixing efficiency imparting small amount of stress to toner in agitation, a developing device provided with it and an image forming apparatus provided with the developing device. <P>SOLUTION: The image forming apparatus 1 is provided with the developing device 7 and the developing device 7 is provided with the developer agitating member 45. Auxiliary spiral wings 48 and 49 with different twisting directions to each other are provided on both end parts in the axial direction of the developer agitating member 45. The developer agitating member 45 is constituted of six unit members 50a to 50f and apertures 58 are formed in central parts in the axial direction over the whole range of the unit members 50a to 50f. One piece of inner spiral wing 52 and 12 pieces of outer spiral wings 53, in which the twisting directions are in reverse to each other, are formed along the axial direction in the inside and on the outer peripheral surface of each unit member 50a to 50f. The twisting cycles of the inner spiral wings 52 and the outer spiral wings 53 are respectively set to be 1 and 1/12. Each unit member 50a to 50f is connected by engaging a projection 56 and a recession 57. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developer agitating member, a developing device, and an image forming apparatus, and in particular, a developer agitating member provided with an inner spiral blade and an outer spiral blade whose twist directions are opposite to each other on the inner and outer peripheral surfaces, respectively. The present invention relates to a developing device provided, and an image forming apparatus provided with the developing device.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus includes a developing device that develops an electrostatic latent image to form a developer image by supplying the developer to the surface of an image carrier on which the electrostatic latent image is formed. The developing device includes an agitating member for agitating the developer. The developer is charged by being agitated by the agitating member in the developing device and develops the electrostatic latent image formed on the surface of the image carrier. Ready to go.

  In particular, a two-component developer is a mixture of a carrier that is a magnetic powder such as ferrite and a toner made of a non-magnetic material such as resin or carbon. The quality of the captured image is greatly affected. In addition, when a two-component developer is used, as the development is repeated and the toner in the developing device decreases and the toner density decreases, a new toner is added to maintain the toner density in the developing device at a predetermined density. Is supplied. Therefore, when a two-component developer is used, the stirring performance of the developer stirring member is particularly important.

  Conventionally, as a stirring member for stirring the developer, two stirring members each having a spiral blade or a flat blade disposed in a discontinuous manner are configured as one set, and the feeding directions are opposite to each other. Those arranged so as to be oriented were generally used.

More recently, there has been a growing demand for downsizing of developing devices and improvement of stirring performance, and spiral wings whose twist directions are opposite to each other are provided on the inside and the outer peripheral surface of one cylindrical body. A stirring member having a structure in which an opening is provided in a part of the peripheral surface of the shaped body is used (see, for example, Patent Documents 1 to 3). According to this, since the developer can be transported in both directions parallel to the axial direction of the stirring member and also in the direction perpendicular to the shaft, the developer can be efficiently stirred in a short time. It is said that uneven charging of the developer can be reduced.
Japanese Examined Patent Publication No. 6-95244 Japanese Patent Laid-Open No. 4-100074 Japanese Patent Laid-Open No. 2001-42616

  Recently, as the particle size of the toner is reduced and the image forming speed is increased, further improvement in mixing efficiency and stirring operation with less stress on the toner have been required. On the other hand, with the stirring member having a structure as described in Patent Documents 1 to 3, it becomes difficult to stir newly replenished toner in a short time with low stress and uniformly charge the predetermined charge. It is coming.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developer stirring member having high mixing efficiency and low stress on toner during stirring, a developing device including the same, and an image forming apparatus including the developing device. .

  The developer stirring member of the present invention is configured as follows to solve the above-described problems.

  (1) A cylindrical body which is axially supported in a developing device for storing a developer, and has an inner spiral blade and an outer spiral blade formed in the axial direction on the inner and outer peripheral surfaces, the twist directions being opposite to each other. In addition, the present invention is characterized in that an opening that extends over the entire area in the circumferential direction is provided in at least one place in the axial direction of the circumferential surface.

  In this configuration, the developer is conveyed in one axial direction by the inner spiral blade inside the cylindrical developer stirring member, and opposite to the inner portion in the axial direction by the outer spiral blade outside the developer stirring member. Conveyed in the direction. Further, since the opening is provided on the peripheral surface, the developer inside the developer agitating member and the outside developer are efficiently mixed through this opening. Furthermore, since the opening is provided over the entire circumferential direction, the developer can be transported in the direction perpendicular to the axial direction, the developer can be moved freely, and the stress on the developer during stirring is increased. Is reduced.

  (2) Each of the inner spiral wing and the outer spiral wing is characterized by being continuous in the axial direction beyond the opening.

  In this configuration, since each of the inner spiral blade and the outer spiral blade continues in the axial direction beyond the opening, the developer in the axial direction continues even in the vicinity of the opening.

  (3) A plurality of unit members having a single shape are connected in the axial direction.

  In this configuration, the developer stirring member is composed of a plurality of unit members. For example, when the developer stirring member is provided with six inner spiral blades and one outer spiral blade for one cycle, and the developer stirring member is composed of six unit members of the same size. In one unit member, the inner spiral blade is provided for one cycle and the outer spiral blade is provided for 1/6 cycle. Here, rather than forming a developer stirring member having six cycles of inner spiral blades and one cycle of outer spiral blades, one cycle of inner spiral blades and 1/6 cycle of outer spiral blades It is easier to form six unit members. Therefore, the developer stirring member is easily formed by being composed of a plurality of unit members.

  (4) The unit member is characterized by including an opening at the center in the axial direction.

  In this configuration, since the opening is provided in the central portion in the axial direction of the unit member, when the inner spiral wing and the outer spiral wing are provided continuously in the axial direction beyond the opening, the inner spiral wing and A decrease in the strength of each of the outer spiral wings is minimized. In addition, by providing an opening at a predetermined position of each unit member, when the unit member is assembled into a developer stirring member, the openings are arranged at predetermined intervals, so that the developer mixing efficiency is improved. Stabilized in the axial direction.

  Furthermore, the axial dimension of the opening can be set to 40% to 60% of the axial dimension of the unit member, for example. In this case, the mixing efficiency between the developer inside the developer agitating member and the external developer is improved without significantly reducing the strength of the unit member, and the developer inside the developer agitating member and the outside The degree of freedom of movement of the developer is increased, and the stress on the toner during stirring is reduced.

  (5) The torsion period in the axial dimension of each unit member of the inner spiral wing and the outer spiral wing is set to be equal to the reciprocal of the divisor of the number of spirals of the inner spiral wing and the outer spiral wing. It is characterized by that.

  In this configuration, the twist cycle of each unit member of the inner spiral blade is set to be equal to the reciprocal of the divisor of the number of spirals of the inner spiral blade, and the twist cycle of each unit member of the outer spiral blade is the outer spiral. It is set to be equal to the reciprocal of the divisor of the wing spiral. In this case, when unit members having the same shape are connected in the axial direction at the same angle in the circumferential direction, the inner spiral blade and the outer spiral blade are connected without any step.

  (6) The twist period of the inner spiral blade in the axial dimension of the unit member is set to be equal to the reciprocal of the spiral number of the inner spiral blade.

  In this configuration, the twist cycle of each unit member of the inner spiral wing is set to be equal to the reciprocal of the number of spirals of the inner spiral wing. In this case, since the inner spiral wing is formed so as not to overlap in the axial direction in one unit member, the slide core of the mold forming the inside of the unit member is connected from both ends in the axial direction of the unit member. It can be pulled out by sliding in a direction away from each other.

  (7) The unit member includes a projection at one end in the axial direction, and a recess having a shape that can be fitted in the projection and the axial direction at the other end.

  In this configuration, the angle of the circumferential direction of the unit member is positioned by connecting the unit members so as to fit the protrusion and the recess. The axial dimension of the unit member is set so that the torsion period of each unit member of the inner spiral blade and the outer spiral blade is equal to the reciprocal of the divisor of the number of spirals of the inner spiral blade and the outer spiral blade. In addition, when the circumferential angle of the unit member is positioned, the inner spiral wing and the outer spiral wing are connected to each other without a step.

  (8) The projection and the recess are provided one each.

  In this configuration, since each unit member is provided with one protrusion and a recess, the rotational position of each unit member is uniquely determined, and a plurality of protrusions and recesses are provided in a rotationally symmetrical manner. As such, the unit members are prevented from being connected at an incorrect angle.

  (9) A shaft hole having the same cross-sectional shape as the shaft into which the rotational driving force is inserted and having a shaft hole including at least a single straight line in a part of the cross-sectional shape.

  In this configuration, by inserting the shaft into the shaft hole, the shaft is engaged with the developer agitating member without using a separate rotation stop member. As a result, the rotational driving force is transmitted to the developer stirring member. Further, it is easy to form without the need for a keyway or the like.

  (10) Auxiliary spiral wings having different twist directions are further provided at both axial ends.

  The developer agitating member is pivotally supported in the developing device via a bearing, and a gap is provided between the developer agitating member and the side wall of the developing device so that the shaft can rotate with respect to the bearing. . When the developer enters the gap, the rotational load on the developer stirring member becomes extremely large. In order to prevent this, a seal member is used. However, when the developer pressure toward the bearing increases, the developer easily enters the bearing beyond the seal member.

  In this configuration, auxiliary spiral blades that convey the developer in the vicinity of the bearing in a direction away from the bearing are provided at both ends in the axial direction of the developer stirring member. As a result, the pressure of the developer toward the bearing is reduced, the developer is prevented from entering the gap, and the developer agitating member is smoothly rotated.

  (11) The outer spiral wing is a part of a tip portion in the radial direction and is notched at a position facing a density sensor that detects the density of toner contained in the developer stored in the developing device. It has the part.

  The developing device is provided with a density sensor at a position facing the developer agitating member, and the density sensor detects the concentration of toner contained in the developer stored in the developing device. The detection value detected by the density sensor varies depending on the thickness of the developer present at the position facing the density sensor. In this configuration, a notch is provided at a position that is a part of the radial tip of the outer spiral blade and faces the density sensor, and therefore when the outer spiral blade faces the density sensor and when it does not face the density sensor. The difference in developer thickness at the position facing the density sensor is reduced.

  (12) The notch is provided in a portion other than the portion facing the opening in the outer spiral wing.

  If the notch provided at the position facing the density sensor for detecting the toner density in the developer is provided at the position facing the opening, the density sensor faces the opening. The difference in the thickness of the developer facing the density sensor becomes very large when the outer spiral blade faces the density sensor and when it does not face the density sensor.

  In this configuration, the opening is provided at a position that does not face the density sensor, and the notch is provided at a position that is a part other than the part that faces the opening in the outer spiral blade and faces the density sensor. Therefore, the difference in developer thickness at the position facing the density sensor between when the outer spiral blade faces the density sensor and when it does not face the density sensor becomes small. In addition, since the base end portion in the radial direction of the outer spiral blade other than the portion facing the opening is supported by the cylindrical main body, a notch is provided in a portion other than the portion facing the opening. As a result, the strength of the outer spiral blade does not decrease.

The developing device of the present invention is configured as follows.
(13) A developing device for storing a developer, the developer agitating member according to any one of (1) to (12), and a toner replenishing unit arranged on the upstream side of the agitating member in the toner supply direction; And a developing roller disposed in parallel with the stirring member on the downstream side of the stirring member in the toner supply direction.

  In this configuration, the toner replenished from the toner replenishing unit is transported in the axial direction and in the direction perpendicular to the axial direction by the developer agitating member, so that the developer contained in the developing device and Mixes efficiently in a short time. At this time, since the opening is provided over the entire area in the circumferential direction, the newly replenished toner is agitated at low stress with the developer stored in the developing device. Then, development is performed by the developing roller using a developer that is efficiently mixed in a short time and stirred with low stress.

The image forming apparatus of the present invention is configured as follows.
(14) An image forming apparatus that supplies developer from the developing device to the surface of the image carrier on which the electrostatic latent image is formed, and transfers the developer image that visualizes the electrostatic latent image onto a recording medium. A developing device according to (13) is provided.

  In this configuration, the newly supplied toner and the developer stored in the developing device are efficiently mixed in a short time and stirred with low stress. The electrostatic latent image is visualized using a developer that is efficiently mixed in a short time and stirred with low stress, and the developer image is transferred onto a recording medium.

  According to the present invention, the following effects can be obtained.

  (1) The developer can be efficiently stirred and mixed with low stress in a short time, and the developer can be charged uniformly.

  (2) The developer can be mixed and stirred efficiently in a short time.

  (3) The developer stirring member can be easily formed.

  (4) The inner spiral wing and the outer spiral wing can be easily provided continuously in the axial direction beyond the opening.

  (5) A plurality of unit members constituting the developer agitating member can all be made the same shape. Therefore, the manufacturing cost can be reduced.

  (6) The developer stirring member can be produced using a mold such as a mold. Therefore, mass productivity can be improved and manufacturing cost can be reduced.

  (7) The circumferential angle of the unit member can be positioned.

  (8) Since the unit members can be prevented from being connected at an incorrect angle, the inner spiral blade and the outer spiral blade can be accurately connected without any step, and the assembly efficiency of the developer stirring member can be improved. Can do.

  (9) The rotational driving force can be transmitted by easily engaging the shaft with the developer stirring member.

  (10) The developer stirring member can be smoothly rotated. Further, the interval of maintenance time of the developing device can be lengthened.

  (11) The value detected by the concentration sensor can be stabilized without interrupting the outer spiral blade.

  (12) While preventing the strength of the outer spiral wing from being lowered, the detection value by the concentration sensor can be stabilized.

  (13) It is possible to develop with a developer that is stirred with low stress, efficiently mixed in a short time, and charged uniformly. Therefore, a high-quality developer image can be formed.

  (14) A high-quality image can be formed immediately after toner replenishment.

  Hereinafter, an image forming apparatus 1 according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of the image forming apparatus 1. The image forming apparatus 1 includes an electrophotographic image forming unit 2 and a paper feeding unit 3 disposed below the image forming unit 2. The image forming unit 2 includes a photosensitive drum 4 that is an image carrier. The photosensitive drum 4 rotates clockwise in FIG. Around the photosensitive drum 4, a charging unit 5, an optical scanning unit 6, a developing device 7, a transfer unit 8, and a cleaning unit 9 are arranged in this order from the upstream side along the rotation direction of the photosensitive drum 4. The

  The charging unit 5 uniformly charges the surface of the photosensitive drum 4. The optical scanning unit 6 scans the optical image on the uniformly charged photosensitive drum 4 to form an electrostatic latent image. The developing device 7 visualizes the electrostatic latent image formed by the optical scanning unit 6 with a developer T (see FIG. 7) to form a developer image. The transfer unit 8 transfers the developer image formed on the photosensitive drum 4 onto the recording paper. The cleaning unit 9 removes the toner remaining on the photosensitive drum 4 so that a new image can be formed on the photosensitive drum 4. The developing device 7 is provided with an intermediate hopper 95 and a toner supply cartridge 10, and the toner removed by the cleaning unit 9 is collected in a collection container attached to the toner supply cartridge 10 and discarded later.

  The paper feed unit unit 3 includes a plurality of paper feed trays 11 to 14. Each of the paper feed trays 11 to 14 accommodates recording papers of different sizes, for example. The paper feed unit 3 further includes a manual paper feed unit 18. A relatively small amount of recording paper is set in the manual paper feeding unit 18. The recording paper supplied from any one of the paper feed trays 11 to 14 or the manual paper feed unit 18 is conveyed to the image forming unit 2 via the paper conveyance path, and is between the photosensitive drum 4 and the transfer unit 8. The developer image is transferred. The recording sheet to which the developer image has been transferred is conveyed to the fixing unit 15, and the toner is thermocompression bonded to the recording sheet by the fixing unit 15, whereby the developer image is fixed to the recording sheet. The recording paper on which the developer image is fixed is further conveyed and discharged onto the paper discharge tray 16.

  In addition, a paper feed unit 20 as an optional device is connected to the paper feed unit 3 as necessary. The paper supply unit 20 accommodates a larger amount of recording paper than the paper supply trays 11 to 14. The recording paper supplied from the paper supply unit 20 is conveyed to the image forming unit 2 and the developer image is transferred and fixed in the same manner as the recording paper supplied from the paper supply trays 11 to 14, and then the paper output tray. 16 is discharged.

  FIG. 2 is a cross-sectional view illustrating a schematic configuration of the developing device 7, the intermediate hopper 95, and the toner supply cartridge 10. In this embodiment, a two-component developer is used as the developer T. The developing device 7, the intermediate hopper 95, and the toner supply cartridge 10 are disposed adjacent to each other substantially horizontally. The toner supply cartridge 10 is detachably connected to the intermediate hopper 95. New toner to be supplied is supplied to the toner supply cartridge 10 by the user. Then, new toner is supplied from the toner supply cartridge 10 to the intermediate hopper 95 as necessary.

  The intermediate hopper 95 is detachably connected to the developing device 7. The toner accommodated in the intermediate hopper 95 is stirred by the stirring member 82. Then, as necessary, the toner is fed to the toner supply roller 47 side by the stirring member 82 and the toner feed screw 86, and is supplied to the developing device 7 by the toner supply roller 47.

  FIG. 3A is a plan view illustrating a schematic configuration of the developing device 7, and FIG. 3B is a front view illustrating a schematic configuration of the developing device 7. The toner replenished from the intermediate hopper 95 is replenished into the developing device 7 from the portion indicated by the arrow a in FIG. 3B, and gradually supplied to the left in the direction in which the developing roller 44 is arranged, that is, FIG. 3B. The In the developing device 7, the sub stirring member 46, the developer stirring member 45, and the developing roller 44 are arranged in this order from the upstream side in the toner supply direction.

  The sub-stirring member 46 includes a spiral blade on the outer peripheral surface, and the rotation shaft is disposed in a direction orthogonal to the toner supply direction, and both ends are pivotally supported on the side wall of the developing device 7. By rotating the sub agitation member 46, the toner supplied from the intermediate hopper 95 is dispersed in a balanced manner in the vertical direction in FIG. The developer stirring member 45 and the developing roller 44 are each supported on the side wall of the developing device 7 so as to be parallel to the sub stirring member 46. Further, a density sensor 41 for measuring the density of the toner with respect to the developer T in the developing device 7 is disposed at a position facing the developer stirring member 45. In this embodiment, a magnetic permeability sensor is used as the concentration sensor 41, but a differential transformer type concentration sensor may be used. The detailed structure of the developer stirring member 45 will be described later.

  The developing roller 44 includes a hollow cylindrical developing sleeve made of a non-magnetic metal such as aluminum alloy, brass, SUS304 stainless steel, etc., and a magnet roller in which a plurality of magnet bodies for generating a magnetic field are fixed in the developing sleeve Is interpolated. The developing roller 44 conveys the toner to the surface of the photosensitive drum 4 by rotating only the developing sleeve while magnetically attracting the toner to the surface of the developing sleeve.

  The developer stirring member 45 includes six unit members 50 a to 50 f and two auxiliary spiral blades 48 and 49. The auxiliary spiral blades 48 and 49 respectively convey the developer T in the vicinity of the side wall of the developing device 7 to the axially central side when the developer stirring member 45 is rotated at both ends in the axial direction of the developer stirring member 45. As described above, the twisting directions are opposite to each other.

  4 is a perspective view of the unit member 50a as viewed from one end side in the axial direction, and FIG. 5 is a perspective view as viewed from the other end side. In this embodiment, unit members 50a-50f are formed with resin. The six unit members 50a to 50f have the same shape and the same size. Here, the unit member 50a will be described as an example.

  The unit member 50a includes a cylindrical main body 51. In this embodiment, the axial dimension of the main body 51 is set to 50 mm, the outer diameter of the main body 51 is set to 40 mm, and the inner diameter of the main body 51 is set to 36 mm. An opening 58 is provided in the central portion of the main body 51 in the axial direction over the entire circumferential direction. The dimension of the opening 58 in the axial direction of the unit member 50a is set to about 40% to 60% of the dimension in the axial direction of the unit member 50a.

  Twelve outer spiral blades 53 are arranged at equal intervals on the outer peripheral surface of the main body 51. The outer diameter of the unit member 50a including the outer spiral blade 53 is set to 50 mm. That is, the radial dimension of the outer spiral blade 53 is set to 5 mm. The outer spiral blade 53 is provided continuously in the axial direction beyond the opening 58. The torsion period of the outer spiral blade 53 in the unit member 50a is set to 1/12. The gradient angle of one side of the outer spiral blade 53 is set to 15 degrees with respect to the radial direction, and the outer spiral blade 53 is formed so as to become thinner toward the distal end in the radial direction. In addition, notches 59 are provided at both ends of the outer spiral blade 53 in the radial direction and in the axial direction. That is, the notch 59 is provided in a portion other than the portion facing the opening 58 in the outer spiral blade 53.

  Inside the main body 51, a boss 54 having a shaft hole 55 having a square shape with a cross section of 8 mm square is provided. When the developer agitating member 45 is assembled, the shaft 60 having the same cross-sectional shape as the cross-sectional shape of the shaft hole 55 is inserted into the shaft hole 55. By inserting the shaft 60 into the shaft hole 55, the rotational driving force of a driving source (not shown) is transmitted to the developer stirring member 45 via the shaft 60. Note that both end portions of the shaft 60 are formed to have a circular cross-sectional shape so as to be supported by the side wall of the developing device 7.

  One inner spiral blade 52 is provided inside the main body 51 and outside the boss 54. The twist direction of the inner spiral blade 52 is set to be opposite to the twist direction of the outer spiral blade 53. The twist cycle of the inner spiral blade 52 in one unit member 50a is set to 1. One protrusion 56 is provided on one end face of the boss 54 in the axial direction. In addition, the other end face in the axial direction of the boss 54 is provided with one concave portion 57 having a shape that can be fitted in the axial direction with the protrusion 56. The recess 57 is provided at the same angle as the projection 56 with the rotation axis of the unit member 50a as a fulcrum.

  Since the unit members 50a to 50f have the shapes as described above, they are resin-molded using, for example, a mold. Inside the main body 51, a slide core for forming the inner peripheral surface of the main body 51, the shaft hole 55, the boss 54, the inner spiral blade 52, and the like is disposed, and is separated from both ends in the axial direction after molding. Pull out in the direction. In addition, a four-part mold for forming the outer peripheral surface of the main body 51, the outer spiral wing 53, the notch 59, the opening 58, and the like is arranged outside the main body 51, and the radial direction after molding is arranged. Removed.

  FIG. 6 is a cross-sectional view showing a partial configuration of the developer stirring member 45. The six unit members 50a to 50f are respectively passed through the shaft 60 and connected in the axial direction so that the protrusions 56 and the recesses 57 of the adjacent unit members 50a to 50f are fitted to each other. At this time, the outer spiral blade 53 and the inner spiral blade 52 are connected to the outer spiral blade 53 and the inner spiral blade 52 of the adjacent unit members 50a to 50f without any step, and the notch 59 is adjacent to the adjacent unit members 50a to 50f. It connects with the notch part 59 of this. Further, in the developer stirring member 45, the openings 58 are arranged at equal intervals in the axial direction.

  When the developer stirring member 45 is rotated counterclockwise when viewed from the left side in FIG. 6, the developer T inside the developer stirring member 45 is conveyed to the right side by the inner spiral blade 52 and partly. The developer T is discharged from the opening 58 to the outside of the developer stirring member 45. Further, the developer T outside the developer stirring member 45 is conveyed to the left by the outer spiral blade 53, and a part of the developer T enters the developer stirring member 45 from the opening 58.

  FIG. 7 is a schematic partially enlarged view of the developer stirring member for explaining the positional relationship between the developer stirring member and the density sensor. A density sensor 41 for detecting the toner density in the developer T accommodated in the developing device 7 is provided so as to face the developing device 7 from the bottom 71 of the developing device 7. Further, as shown in FIG. 7A, the developer stirring member 45 is designed so that the notch 59 of the outer spiral blade 53 faces the density sensor 41. Therefore, as shown in FIG. 7A, the outer spiral blade 53 and the concentration sensor 41 face each other, and as shown in FIG. 7B, the outer spiral blade 53 and the concentration sensor 41 do not face each other. The difference in the thickness of the developer T at the portion facing the density sensor 41 is smaller than that in the case where the notch 59 is not provided.

  On the other hand, as shown in FIG. 7C, when the developer agitating member 45 is designed so that the opening 58 and the density sensor 41 face each other, as shown in FIG. Development of a portion facing the density sensor 41 between the state where the spiral blade 53 and the density sensor 41 face each other and the state where the outer spiral blade 53 and the density sensor 41 do not face each other as shown in FIG. The difference in the thickness of the agent T becomes very large as compared with the case shown in FIG. However, as described above, in the developer stirring member 45, the opening 58 and the density sensor 41 are not opposed to each other, and the outer spiral blade 53 and the density sensor 41 are formed to face each other. The difference in the thickness of the developer T at the portion facing the density sensor 41 between when the toner is opposed to the density sensor 41 and when it is not opposed is small. Therefore, the detected value of the toner density by the density sensor 41 is stabilized.

  According to the developer stirring member 45, since the opening 58 is provided over the entire region in the circumferential direction, the developer T inside the developer stirring member 45 and the external developer T can be efficiently mixed. Further, the developer T is transported very smoothly in the direction perpendicular to the axial direction, the degree of freedom of movement of the developer T is increased, and the stress on the toner during stirring is reduced. Therefore, the developer T can be agitated with low stress, the developer T can be efficiently mixed in a short time, and the toner can be charged without unevenness.

  Further, since each of the inner spiral blade 52 and the outer spiral blade 53 continues in the axial direction beyond the opening 58, the developer T can be efficiently stirred and mixed in a short time.

  Furthermore, since the notch 59 is provided at the tip of the outer spiral blade 53 in the radial direction, the outer spiral blade 53 is not interrupted even in the portion where the notch 59 is provided, and the developer T is conveyed. Can be stirred. Further, since the notch 59 is provided at a position facing the density sensor 41, the detection value of the density sensor 41 can be stabilized.

  Further, since one projection 56 and one recess 57 are provided for each of the unit members 50a to 50f, the angle in the circumferential direction when the unit members 50a to 50f are connected to each other is uniquely determined. Therefore, the outer spiral blade 53 and the inner spiral blade 52 can be reliably connected without any step.

  Further, the developer stirring member 45 is composed of a plurality of unit members 50a to 50f having the same shape, and each unit member 50a to 50f can be resin-molded using a mold, so that mass productivity is improved. Manufacturing cost can be reduced.

  According to the developing device 7, it is possible to develop with the developer T which is stirred with low stress, efficiently mixed in a short time, and charged uniformly. Therefore, a high-quality developer image can be formed.

  According to the image forming apparatus 1, a high-quality image can be formed immediately even after toner replenishment.

  Note that the number of spirals of each of the outer spiral blade 53 and the inner spiral blade 52 and the torsion period of the single unit members 50a to 50f depend on the stirring ability with respect to the developer T and the inside and outside of the developer stirring member 45. It may be determined appropriately in consideration of the balance of the transport speed of the developer T and the like.

  However, when the respective torsion periods of the inner spiral blade 52 and the outer spiral blade 53 are set to be equal to the reciprocals of the divisors of the respective spiral numbers of the inner spiral blade 52 and the outer spiral blade 53, they have the same shape. When the unit members 50a to 50f are axially connected at the same angle in the circumferential direction, the inner spiral blade 52 and the outer spiral blade 53 can be connected without any step. Further, when the twisting period of the inner spiral blade 52 is set to be equal to the reciprocal of the spiral number of the inner spiral blade 52, the inner spiral blade 52 does not overlap in the axial direction in one unit member 50a to 50f. Since the slide core forming the inside of the unit members 50a to 50f can be slid in the direction away from the both axial ends of the unit members 50a to 50f and pulled out, the unit member 50a ~ 50f can be injection molded.

  Further, the twist angle of every other outer spiral blade 53 can be set large.

  The cross-sectional shape of the shaft hole 55 may be a shape including at least a single straight line in a part, for example, a polygon such as a hexagon or an octagon, or a shape in which a straight part is provided in a part of a circle. It may be.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a schematic configuration of a developing device, an intermediate hopper, and a toner supply cartridge. FIG. 3A is a plan view showing a schematic configuration of the developing device, and FIG. 3B is a front view showing a schematic configuration of the developing device. It is the perspective view seen from the one end part side of the axial direction of a unit member. It is the perspective view seen from the other end part side of the axial direction of a unit member. FIG. 4 is a cross-sectional view illustrating a partial configuration of a developer stirring member. FIG. 7A is a schematic partially enlarged view of the developer stirring member for explaining the positional relationship between the developer stirring member and the density sensor, and FIG. 7A shows a state when the outer spiral blade and the density sensor face each other. 7B shows a state when the outer spiral blade and the concentration sensor are not opposed to each other, and FIG. 7C shows a state when the opening and the concentration sensor are arranged so as to face each other. .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Photosensitive drum 7 Developing apparatus 41 Density sensor 44 Developing roller 45 Developer stirring member 48, 49 Auxiliary spiral blades 50a-50f Unit member 52 Inner spiral blade 53 Outer spiral blade 55 Shaft hole 56 Projection portion 57 Concave portion 58 Opening 59 Notch 60 Shaft T Developer

Claims (14)

  A cylindrical body that is axially supported by an inner helical wing and an outer helical wing that are axially supported in a developing device that contains a developer and that are twisted in opposite directions on the inner and outer circumferential surfaces. A developer stirring member, wherein an opening is provided at least at one location in the axial direction of the surface over the entire circumferential direction.   2. The developer stirring member according to claim 1, wherein each of the inner spiral blade and the outer spiral blade continues in the axial direction beyond the opening.   The developer stirring member according to claim 1, wherein a plurality of unit members having a single shape are connected in the axial direction.   The developer stirring member according to claim 3, wherein the unit member includes the opening at a central portion in an axial direction.   The torsion period in the axial dimension of the unit member of each of the inner spiral wing and the outer spiral wing is set to be equal to the reciprocal of the divisor of the number of spirals of the inner spiral wing and the outer spiral wing. The developer agitating member according to claim 3, wherein the developer agitating member is provided.   5. The twist period of the inner spiral blade in the axial dimension of the unit member is set to be equal to the reciprocal of the spiral number of the inner spiral blade. 6. Developer stirring member.   7. The unit unit according to claim 3, wherein the unit member includes a protrusion at one end in the axial direction, and a recess having a shape that can be fitted to the protrusion in the axial direction at the other end. The developer stirring member according to the description.   The developer stirring member according to claim 7, wherein each of the protrusion and the recess is provided.   2. A shaft hole having the same cross-sectional shape as a shaft into which a rotational driving force is inserted and having a shaft hole including at least a single straight line in a part of the cross-sectional shape. The developer stirring member according to claim 8.   The developer stirring member according to any one of claims 1 to 9, further comprising auxiliary spiral blades having different twisting directions at both ends in the axial direction.   The outer spiral wing has a notch at a position facing a density sensor that detects a density of toner contained in the developer housed in the developing device and is a part of a tip in the radial direction. The developer agitating member according to claim 1, wherein the developer agitating member is provided.   The developer stirring member according to claim 11, wherein the notch is provided in a portion of the outer spiral blade other than the portion facing the opening. A developing device for storing a developer,
The developer stirring member according to any one of claims 1 to 12,
A toner replenishing portion disposed on the upstream side of the stirring member in the toner supply direction;
A developing device comprising: a developing roller disposed in parallel with the stirring member on a downstream side of the stirring member in a toner supply direction. An image forming apparatus that supplies a developer from a developing device to the surface of an image carrier on which an electrostatic latent image is formed, and transfers the developer image that visualizes the electrostatic latent image onto a recording medium,
An image forming apparatus comprising the developing device according to claim 13.

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