Conveying screw and image forming apparatus

Abstract

To provide a conveying screw and an image forming apparatus that increase the amount of charge of toner.SOLUTION: A conveying screw 1 comprises a rotation shaft part 10 that is driven to rotate by an actuator, and a spiral blade part 20 that has a conveyance surface 22 inclined relative to the rotation shaft part 10 and has groove parts 30 formed in the conveyance surface 22. The spiral blade part 20 is continuous spirally around the rotation shaft part 10, and a plurality of groove parts 30 are formed in the conveyance surface 22 at respective positions in a radial direction. The image forming apparatus has a screw of a developing unit as the conveying screw 1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conveying screw and an image forming apparatus. [Background technology]

[0002] In image forming devices, a decrease in the amount of charge on toner can cause a decrease in image density and other degradation in image quality. Toner and carrier make up a developer, and the developer can be charged by stirring. For example, Patent Document 1 describes an image forming device equipped with a conveying screw with improved stirring performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-221937 Summary of the Invention [Problem to be solved by the invention]

[0004] The screw in Patent Document 1 has both blades inclined relative to the axis, with the surface behind the transport surface being more gently inclined than the transport surface that pushes the developer in the transport direction. This increases the component of the force that the developer receives from the surface behind the transport surface that is perpendicular to the screw axis, improving agitation performance. However, there is a demand for further improvement in agitation performance and an increase in the amount of charge on the toner. The present invention has been made to solve the above problems, and an object of the present invention is to provide a conveying screw and an image forming apparatus that improve the amount of charge on toner. [Means for solving the problem]

[0005] In order to solve the above problems, the conveying screw and the image forming apparatus according to the present invention have the following configurations (1) to (20). (1) A conveying screw comprising: a rotating shaft portion that is rotationally driven by an actuator; and a spiral blade portion having a conveying surface that is inclined relative to the rotating shaft portion and in which a groove portion is formed on the conveying surface. (2) The conveying screw according to (1), wherein the spiral blade portion continues spirally around the rotating shaft portion.

[0006] (3) The conveying screw according to (1), wherein a plurality of grooves are formed at each radial position on the conveying surface of the spiral blade portion. (4) The conveying screw according to (3), wherein the plurality of grooves have different shapes. (5) The conveying screw according to (4), wherein the grooves are smaller on the outer circumferential side than on the inner circumferential side.

[0007] (6) The conveying screw according to (3), wherein the intervals between the plurality of grooves are different from one another. (7) The conveying screw according to (6), wherein the intervals between the plurality of grooves become smaller from the inner periphery toward the outer periphery. (8) The conveying screw according to (1), wherein the groove is formed at the outer peripheral end of the conveying surface.

[0008] (9) The conveying screw according to any one of (1) to (8), wherein the groove portion is formed in a partial section of the spiral blade portion. (10) The conveying screw according to (9), wherein the partial section is disposed at the end of the spiral blade portion on the conveying surface side. (11) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein either the supply screw or the agitating screw is a transport screw described in any one of (1) to (8).

[0009] (12) The image forming apparatus according to (11), wherein the supply screw is the conveying screw. (13) The image forming apparatus according to (11), wherein the stirring screw is the conveying screw. (14) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein the supply screw is a transport screw described in any one of (1) to (8), and the agitating screw is a transport screw described in any one of (1) to (8).

[0010] (15) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein either the supply screw or the agitating screw is the transport screw described in (9). (16) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein both the supply screw and the agitating screw are transport screws as described in (9).

[0011] (17) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and a stirring screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein the supply screw is the transport screw described in (10). (18) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein the agitating screw is the transport screw described in (10).

[0012] (19) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein both the supply screw and the agitating screw are transport screws as described in (10). (20) An image forming apparatus comprising a supply screw that supplies developer to a developing roller, and an agitating screw that is arranged parallel to the supply screw and transports the developer in the opposite direction to the supply screw, wherein one of the supply screw and the agitating screw is a transport screw described in any one of (1) to (8), and the other is a transport screw described in (10). [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a conveying screw and an image forming apparatus that improve the amount of charge on toner. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a perspective view illustrating an outline of a conveying screw according to the embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3A] 10A and 10B are cross-sectional views illustrating modified examples of the position of the groove portion of the conveying screw. [Figure 3B] 10 is a cross-sectional view illustrating a modified example in which the groove portion of the conveying screw is large. FIG. [Figure 3C] 10 is a cross-sectional view illustrating a modified example in which the surface behind the conveying surface of the conveying screw is an inclined surface. FIG. [Figure 4] 10A and 10B are cross-sectional views illustrating modified examples of the size of the groove portion of the conveying screw. [Figure 5] 10A and 10B are cross-sectional views illustrating modified examples of the intervals between grooves of the conveying screw. [Figure 6A] FIG. 10 is a perspective view illustrating a modified example in which a groove portion is provided in a part of the conveying screw. [Figure 6B] FIG. 10 is a perspective view illustrating a modified example in which a groove portion is provided in a part of the conveying screw. [Figure 7] 1 is a side view illustrating an outline of an image forming apparatus according to an embodiment; [Figure 8] FIG. 2 is a side view illustrating a developing unit of the image forming apparatus according to the embodiment. [Figure 9]FIG. 10 is a side view illustrating a developing unit of an image forming apparatus according to a modified example. [Figure 10A] FIG. 10 is a cross-sectional view of a conveying screw according to a comparative example. [Figure 10B] FIG. 10 is a cross-sectional view of a conveying screw according to a comparative example. [Figure 10C] FIG. 2 is a cross-sectional view of a conveying screw according to an embodiment. [Figure 11] 1 is a graph comparing the stirring performance of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following description will discuss embodiments and modifications of the present invention with reference to the drawings. Note that the present invention is not limited to these embodiments and modifications. In addition, in the drawings, some components may be omitted, and the size, shape, and positional relationship of each component may be exaggerated.

[0016] [Conveyor screw] A conveying screw 1 according to an embodiment will be described with reference to Fig. 1 and Fig. 2. The conveying screw 1 is a screw capable of conveying powder. The conveying screw 1 can be used, for example, to convey developer in an image forming apparatus. As shown in Fig. 1, the conveying screw 1 includes a rotating shaft 10 and a spiral blade 20, and a groove 30 is formed on the conveying surface 22 of the spiral blade 20. Here, the spiral blade 20 continues spirally around the rotating shaft 10. Each component of the conveying screw 1 will be described below.

[0017] (Rotating shaft) The rotating shaft 10 is a rod-shaped member that serves as the rotating shaft of the conveying screw 1. The rotating shaft 10 is driven to rotate by an external actuator powered by electricity or air pressure. The rotating shaft 10 is installed in the conveying direction of the material to be conveyed, such as powder.

[0018] (spiral blade part) The spiral blade portion 20 is a component that contacts the transported object and transports it. The spiral blade portion 20 continues spirally around the rotating shaft portion 10. The spiral blade portion 20 is fixed to the rotating shaft portion 10 and rotates around the rotating shaft portion 10 as the rotation axis. The material of the spiral blade portion 20 may be the same as or different from the material of the rotating shaft portion 10. The spiral blade portion 20 has a conveying surface 22 that conveys the material to be conveyed and a rear surface 24 that is the surface opposite to the conveying surface 22. The conveying surface 22 is the surface on the side facing the direction of travel of the material to be conveyed, i.e., the conveying direction side. The conveying surface 22 is inclined with respect to the rotating shaft portion 10, and is an inclined surface that slopes downward toward the conveying direction 51. The inclination angle θ with respect to the rotating shaft portion 10 can be, for example, 30 degrees or more and 60 degrees or less, and is preferably 40 degrees or more and 50 degrees or less, and is 45 degrees in this example. The rear surface 24 is not inclined with respect to the rotating shaft portion 10.

[0019] A groove 30 is formed in the conveying surface 22. The groove 30 is formed in the circumferential direction. The groove 30 is formed in a continuous spiral shape at a radial position that is a certain distance from the rotating shaft 10. The spirally continuous groove 30 may be one or more. That is, a plurality of grooves 30 may be formed at each radial position on the conveying surface 22 of the spiral blade portion 20. Here, two grooves 31, 32 are formed parallel to each other. When viewed from the extension direction of the rotating shaft portion 10, the grooves 31, 32 are formed concentrically around the central axis 12 of the rotating shaft portion 10.

[0020] Each of the grooves 31 and 32 has two surfaces. Here, these are first surfaces 31A and 32A that are perpendicular to the rotating shaft 10, and second surfaces 31B and 32B that are parallel to the rotating shaft 10. Note that the first surfaces and second surfaces of the multiple grooves 30 may be collectively referred to as first surfaces 30A and second surfaces 30B, respectively. As shown in FIG. 2, the conveyed material is subjected to a force from the conveying surface 22 and the first surface 30A, which includes a component in the conveying direction. Since the conveying surface 22 and the first surface 30A have different surface orientations, the force applied from the spiral blade portion 20 to the conveying surface 22 and the first surface 30A differs in direction. For example, the direction 52 of the normal force from the conveying surface 22 is different from the direction 53 of the normal force applied from the first surface 30A of the groove portion 30. This allows the conveying screw 1 to convey the material while stirring it. Note that the cross section in FIG. 2 is a cross section perpendicular to the ridge line formed by the outer periphery of the spiral blade portion 20. The same applies to other cross sections. The surface orientation may be, for example, the normal direction of the surface.

[0021] In the conveying screw 1 having the above-described configuration, the conveying surface is inclined relative to the rotation shaft, so that the normal force of the conveying surface has a radial component, thereby improving the mixing performance. Furthermore, the grooves formed on the conveying surface cause the conveyed material to move in different directions at positions close to the conveying surface, further improving the mixing performance. Furthermore, a plurality of grooves are formed at each radial position of the conveying screw 1. This allows stirring to occur on both the side closer to the rotating shaft and the side farther from the rotating shaft.

[0022] Note that first surface 30A need only have a larger inclination angle θ than conveying surface 22, and does not have to be perpendicular to rotating shaft 10. First surface 30A may have a curved cross section. Furthermore, first surface 30A may be continuous without a boundary from first surface 30A to second surface 30B, for example, so that the cross section of spiral blade portion 20 has a curved shape such as an arc.

[0023] (Variation) Next, first to fifth modified examples of the groove portion will be described with reference to Fig. 3A to Fig. 5. Since the rotating shaft portion 10 is the same as the conveying screw 1 according to the embodiment, only the spiral blade portion will be described. 3A, the spiral blade portion 20A according to the first modification has a groove 30 formed at the outer peripheral end 26 of the conveying surface 22. As in the embodiment, the first modification has two grooves 31, 32 formed in the circumferential direction. The outer peripheral groove 32 is located at the end 26 of the conveying surface 22. Generally, a conveying screw conveys a larger amount of material on the outer periphery side than on the inner periphery side. In the first modified example, a groove is formed on the outer periphery side end, thereby improving conveying performance.

[0024] 3B, grooves 33 and 34 of spiral blade portion 20B according to the second modification are larger than grooves 31 and 32 of the embodiment. As a result, in the second modification, the ratio of the area of ​​first surface 30A to the area of ​​conveying surface 22 can be increased, thereby prioritizing conveying performance. Furthermore, the grooves may be smaller than the grooves 31 and 32 of the conveying screw 1 according to the embodiment. By adjusting the size of the grooves, the spiral blade portion can adjust the balance between conveying performance and stirring performance.

[0025] The rear surface may or may not be inclined relative to the rotating shaft 10. As shown in Fig. 3C, the spiral blade 20C according to the third modified example has an inclined rear surface. The rear surface 24S of the third modified example is an inclined surface that rises in the conveying direction. In the third modified example, by inclining the rear surface 24S, it is possible to improve the agitation performance of the surface on the opposite side in the conveying direction.

[0026] The grooves may have different shapes. As shown in Fig. 4, a spiral blade portion 20D according to a fourth modification has a plurality of grooves, the outer circumferential side of which is smaller than the inner circumferential side. By making the grooves on the outer periphery smaller than those on the inner periphery, the proportion of the transported material on the outer periphery that is subjected to the normal force of the transport surface 22 increases. The transport screw transports a larger amount of material on the outer periphery than on the inner periphery. Therefore, the fourth modification can efficiently improve mixing performance.

[0027] The spiral blade portion may have three or more grooves. The spacing between the grooves may vary. As shown in FIG. 5, the spiral blade portion 20E according to the fifth modification has three grooves 36, 37, and 38. The spacing between the grooves decreases from the inner periphery to the outer periphery. Here, the spacing Δ2 between the two grooves 37 and 38 on the outer periphery is smaller than the spacing Δ1 between the two grooves 36 and 37 on the inner periphery. In the fifth modified example, the distance between the grooves decreases from the inner periphery toward the outer periphery, thereby improving the conveying performance on the outer periphery and improving the stirring performance on the inner periphery.

[0028] Next, sixth and seventh modified examples in which grooves 30 are formed in a section 25 of the spiral blade portion 20 will be described with reference to FIGS. 6A and 6B. As illustrated in Fig. 6A, in the conveying screw 2A according to the sixth modification, the grooves 30 are formed in a partial section 25 of the spiral blade section 21A. The partial section is a section in the conveying direction 51. Here, the section 25 in which the grooves 30 are formed is a section equivalent to three revolutions of the spiral. In the sixth modification, this section 25 is located at a position other than the end of the spiral blade portion 21A, but it may be located at the end. As shown in Fig. 6B, in a conveying screw 2B according to the seventh modification, a portion of the section 25 in which the groove portion 30 is formed is located at the end 14 of the spiral blade portion 21B on the conveying surface 22 side. The end 14 on the conveying surface 22 side is the end on the conveying direction 51 side, that is, the end on the downstream side of the conveying direction 51.

[0029] Depending on the length of the conveying screw, the type of material being conveyed, and the usage conditions, such as when multiple conveying screws are arranged in parallel, forming grooves in a portion of the spiral blade section may enable efficient conveyance. Furthermore, these portions can be positioned at different positions among the multiple conveying screws. The conveying screws according to the sixth and seventh modifications form grooves in a portion of the spiral blade section, and by combining these grooves, conveyance performance and mixing performance can be balanced. Section 25 may be as short as one full turn of the spiral, or may be longer than three full turns of the spiral, and may be located at the upstream end of the spiral blade. The sixth and seventh modified examples can also be combined with the first to fifth modified examples.

[0030] [Image forming device] Next, an image forming apparatus 100 according to an embodiment will be described with reference to Figs. 7 to 9. The image forming apparatus 100 is an apparatus that forms images using electrophotography, such as a copier or multifunction peripheral. First, an outline of the operation of the image forming apparatus 100 will be described. When image forming apparatus 100 receives a print request or a copy request from scanner unit 114, a recording medium is transported from paper feed cassette 102 or manual feed tray 116 by paper feed roller 103. Then, the transport timing is controlled by timing roller 109, which controls the transport timing of the recording medium, and the recording medium is supplied to recording medium paper transport path 117.

[0031] The imaging units for the four colors of yellow (Y), magenta (M), cyan (C), and black (K) are respectively composed of photoconductor units 106Y, 106M, 106C, and 106K, developing units 150Y, 150M, 150C, and 150K, and toner supply bottles 107Y, 107M, 107C, and 107K. The photosensitive unit has a charging device, a cleaning device, and a static eliminator arranged around a cylindrical photosensitive body having photoconductivity. The charging device charges the photosensitive body as it rotates, and this charging device causes the surface potential of the photosensitive body to reach a predetermined charging potential. The exposure device 104 irradiates the photosensitive body, which has been charged to a predetermined charging potential by the charging device, with an exposure beam based on the image information requested to be printed or copied.

[0032] The surface potential of the photosensitive member at the portion irradiated with the beam decreases to a predetermined level due to the photoconductivity of the photosensitive member. As the surface potential of the photosensitive member changes, an electrostatic latent image based on the image to be printed or copied by the scanner unit 114 is formed on the surface of the photosensitive member exposed by the exposure device 104. The electrostatic latent image formed on the surface of the photosensitive member is developed by developing units 150Y, 150M, 150C, and 150K, and is primarily transferred onto the intermediate transfer belt 108. After that, the four colors Y, M, C, and K are transferred together onto the recording medium that has been conveyed along the recording medium conveying path 117 at the secondary transfer roller 111 that is pressed against the intermediate transfer belt 108.

[0033] The recording medium onto which the toner image has been transferred has the toner image fixed by fixing unit 112 and is then discharged to discharge tray 113. Note that the toner consumed in development by developing units 150Y, 150M, 150C, and 150K is replenished from toner supply bottles 107Y, 107M, 107C, and 107K, so that the amount of toner is kept constant. The image forming apparatus 100 includes conveying screws according to the embodiment or the modified example as the supply screw 131 and the stirring screw 132 of the developing unit 150. In the following description, the developing units 150Y, 150M, 150C, and 150K will be collectively referred to as the developing unit 150.

[0034] The image forming apparatus 100 includes a developing unit 150 that includes a supply screw 131 and an agitating screw 132. The developing unit 150 is a device that develops an electrostatic latent image formed on a cylindrical photosensitive member of a photosensitive member unit with toner. As illustrated in FIG. 8, the developing unit 150 includes a developing roller 120, a supply screw 131, and an agitating screw 132. Here, both the supply screw 131 and the agitating screw 132 are referred to as conveying screws 1 according to the embodiment. The supply screw 131 and the stirring screw 132 are disposed inside the frame 121, and a partition wall 122 separates the supply screw 131 from the stirring screw 132. The frame 121 is a box-shaped member with a portion cut out, and the developing roller 120 is disposed in the cutout portion. The developing roller 120 is a roller that deposits toner onto an adjacent external photosensitive member. A portion of the developing roller 120 is exposed from the frame 121 so as to face the photosensitive member.

[0035] Developer 123 is disposed inside frame 121. Developer 123 is a powder with a diameter of approximately 10 μm, and is composed of toner, a coloring material, and iron powder or the like, which serves as a carrier. The toner becomes charged by friction with the carrier, and adheres to the photosensitive member by electrostatic force. For this reason, developer 123 needs to be conveyed while being stirred inside developing unit 150. Supply screw 131 and stirring screw 132 can convey developer 123 while stirring it. Developer 123 is conveyed while hitting the wall surface of frame 121 and partition wall 122. Note that FIGS. 8 and 9 are side views of the developing unit, and the front wall of frame 121 is not shown.

[0036] (supply screw) The supply screw 131 is a member that supplies the developer 123 to the developing roller 120. The supply screw 131 is disposed parallel to the developing roller 120. The supply screw 131 transports the developer 123 while supplying and collecting the developer 123 to the developing roller 120.

[0037] (mixing screw) The stirring screw 132 is a member that circulates the developer 123. The stirring screw 132 is arranged parallel to the supply screw 131, and transports the developer 123 in the opposite direction to the supply screw 131. The supply screw 131 and the stirring screw 132 are arranged so that their transport surfaces 22 face opposite directions. This causes the developer 123 to be transported so as to circle inside the frame 121. Here, the developer 123 is transported around the partition wall 122 so that the transport direction 51 is clockwise.

[0038] In the image forming apparatus 100 according to the embodiment, the supply screw 131 and the stirring screw 132 are the conveying screw 1 according to the embodiment, so that the charging performance of the toner can be improved. Either or both of the supply screw 131 and the stirring screw 132 may be the conveying screws of Modifications 1 to 5. The supply screw 131 and the stirring screw 132 may be a combination of different conveying screws. In addition, either the supply screw 131 or the stirring screw 132 may be the conveying screw 1 according to this embodiment. In this case, the supply screw may be the conveying screw 1, and the stirring screw 132 may be the conveying screw 1.

[0039] (Variation) Next, a modified example of the image forming apparatus will be described with reference to Fig. 9. The modified example of the image forming apparatus differs from image forming apparatus 100 according to the embodiment in the supply screw 131 and the stirring screw 132, but the rest is the same. 9, the image forming apparatus according to the modified example includes, similarly to the image forming apparatus 100 according to the embodiment, a supply screw 131 that supplies developer 123 to the developing roller 120, and an agitating screw 132 that is arranged parallel to the supply screw 131 and transports the developer 123 in the opposite direction to the supply screw 131. Both the supply screw 131 and the agitating screw 132 are the transport screw 2B according to the seventh modified example.

[0040] In the developing unit 151 of the image forming apparatus according to the modified example, similar to the developing unit 150 of the embodiment, the supply screw 131 and the agitating screw 132 are arranged in parallel with each other with the conveyance surface 22 facing in opposite directions. Meanwhile, the grooves 30 are formed in a partial section 25. The partial section 25 is arranged at the downstream end in the respective conveyance direction 51. That is, in the supply screw 131, the grooves 30 are arranged on one end 126 side inside the frame 121, and in the agitating screw 132, the grooves 30 are arranged on the other end 125 side, which is the opposite side. Note that in this case, the section 25 in which the grooves 30 are formed corresponds to five revolutions of the spiral.

[0041] The powder pressure of the developer 123 tends to be higher on the downstream side of the supply screw 131 and the stirring screw 132. In the image forming apparatus according to the modified example, a groove portion 30 is formed in a part of the section 25 on the downstream side of the supply screw 131 and the stirring screw 132, thereby enabling toner to be charged efficiently.

[0042] Either the supply screw 131 or the stirring screw 132 may be the conveying screw 2B according to the seventh modified example. Furthermore, some sections 25 forming the grooves 30 may be located at the upstream end, or may be located at a position other than the end of the spiral blade portion, as in the conveying screw 2A according to the sixth modified example.

[0043] Furthermore, the supply screw 131 and the stirring screw 132 may be a combination of conveying screws in which some sections 25 forming the grooves 30 are arranged at different positions in the spiral blade section. One of the supply screw 131 and the stirring screw 132 may be the conveying screw according to the embodiment or the first to fifth modifications, and the other may be the conveying screw 2B according to the seventh modification. The other may be a conveying screw in which a part of the section 25 forming the groove portion 30 is arranged at the upstream end or at a position other than the end. [Example]

[0044] A conveying screw was manufactured as an example, and the effect of the present invention was confirmed by comparing it with a comparative example, which is a conventional conveying screw. The example and comparative example have different spiral blades, but the rotating shaft 10 is the same. In conventional example 801 shown in Fig. 10A, conveying surface 822A of spiral blade portion 820A is not inclined with respect to rotating shaft portion 10. In conventional example 802 shown in Fig. 10B, conveying surface 822B of spiral blade portion 820B is inclined with respect to rotating shaft portion 10, and is an inclined surface that slopes downward in the conveying direction. Example 1A shown in Fig. 10C has spiral blade portion 20A according to the first modified example.

[0045] The conveying screws of the example and comparative example were incorporated into developing units of the same configuration, and the same developer components were conveyed at the same rotation speed, and the time until the toner charge amount reached a saturation level was compared. The results of the comparison are shown in Figure 11. Figure 11 is a graph of the toner charge amount versus mixing time, with the vertical axis representing the toner charge amount [-μC / g] and the horizontal axis representing the mixing time [sec]. It took 200 seconds for the toner charge amount to reach saturation level α in Comparative Example 801 and 100 seconds in Comparative Example 802. However, it took 50 seconds for Example 1A to reach saturation level α. These results confirmed the improvement in the charging performance of the toner according to the present invention.

[0046] It is believed that the mixing performance of Comparative Example 801 is low because the conveying surface 822A is not inclined with respect to the rotating shaft portion 10. In Comparative Example 802, the inclination of the conveying surface 822B improves the mixing performance, but does not result in improved charging performance. In contrast, the spiral blade of the present invention has grooves formed on the transport surface, which means that it has surfaces facing in different directions in the transport direction. The developer receives forces in different directions from these surfaces, and is transported while being agitated. This increases collisions between the toner and carrier, providing the toner with enough motion to improve charging. [Explanation of symbols]

[0047] 1 Conveying screw 10 Rotating shaft 12 Center axis 14 End (downstream end) 20 Spiral blade 22 Conveying surface 24 Posterior side 25 sections (sections with grooves) 26 End (end on the outer periphery) 30 Groove 30A front page 30B second side 51 Conveying direction 100 Image forming device 123 Developer 131 Supply screw 132 stirring screw 150 Developer unit

Claims

1. a rotating shaft portion that is rotationally driven by an actuator; a spiral blade portion having a conveying surface inclined with respect to the rotating shaft portion, the conveying surface having a groove formed therein.

2. The conveying screw according to claim 1 , wherein the spiral blade portion continues spirally around the rotation shaft portion.

3. The conveying screw according to claim 1 , wherein a plurality of grooves are formed at respective radial positions on the conveying surface of the spiral blade portion.

4. The conveying screw according to claim 3 , wherein the plurality of grooves have different shapes.

5. The conveying screw according to claim 4 , wherein the grooves are smaller on the outer circumferential side than on the inner circumferential side.

6. The conveying screw according to claim 3 , wherein the intervals between the plurality of grooves are different from one another.

7. The conveying screw according to claim 6 , wherein the intervals between the plurality of grooves become smaller from the inner periphery toward the outer periphery.

8. The conveying screw according to claim 1 , wherein the groove is formed at an end portion on the outer circumferential side of the conveying surface.

9. The conveying screw according to any one of claims 1 to 8, wherein the groove portion is formed in a partial section of the spiral blade portion.

10. The conveying screw according to claim 9 , wherein the partial section is disposed at an end of the spiral blade portion on the conveying surface side.

11. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; 9. An image forming apparatus, wherein either the supply screw or the stirring screw is the conveying screw according to claim 1.

12. The image forming apparatus according to claim 11, wherein the supply screw is the conveying screw.

13. The image forming apparatus according to claim 11, wherein the conveying screw is the stirring screw.

14. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; 9. An image forming apparatus, wherein the supply screw is the conveying screw according to claim 1, and the stirring screw is the conveying screw according to claim 1.

15. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; 10. An image forming apparatus, wherein either the supply screw or the stirring screw is the conveying screw according to claim 9.

16. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; An image forming apparatus in which the conveying screw according to claim 9 is used as both the supply screw and the stirring screw.

17. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; An image forming apparatus, wherein the supply screw is the conveying screw according to claim 10.

18. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; An image forming apparatus in which the conveying screw according to claim 10 is used as the stirring screw.

19. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; An image forming apparatus in which the conveying screw according to claim 10 is used as both the supply screw and the stirring screw.

20. a supply screw for supplying developer to the developing roller; an agitating screw disposed parallel to the supply screw and conveying the developer in a direction opposite to the direction of the supply screw; 11. An image forming apparatus, wherein one of the supply screw and the stirring screw is the conveying screw according to claim 1, and the other is the conveying screw according to claim 10.

Images