Developing apparatus and image forming apparatus equipped therewith

Abstract

To provide a developing device that can effectively prevent occurrence of aggregation of developer near an inclined part on a wall part of a developer tank, and an image forming apparatus including the same.SOLUTION: A developer tank 21 in a developing device 2 is provided with a wall part 212 having an inclined part 211 inclined toward a conveying member 24 from a side of a layer thickness regulation member 21a. A first inclined part 211a of the inclined part 211 is inclined upward toward the side of the layer thickness regulation member 21a at a first inclination angle θ1, and a second inclined part 211b of the inclined part 211 is inclined upward toward a side of the first inclined part 211a at a second inclination angle θ2 larger than the first inclination angle θ1. An end K1 of the second inclined part 211b is located above a first virtual straight line L1 passing through a rotation axis line β of the conveying member 24 and closer to the side of the layer thickness regulation member 21a than a second virtual straight line L2 connecting the rotation axis line β of the conveying member 24 and a rotation axis line α of a developer carrier (22).SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a developing device and an image forming apparatus such as a copying machine, a multifunction peripheral, a printer, and a facsimile apparatus including the same.

Background Art

[0002] In a conventional developing device, generally, in a developing tank in which a developer is stored, a conveying member (conveying screw) is rotated to convey the developer in the axial direction of the rotation axis while stirring the developer, and a developer carrier (developing roller) is rotated to pump up the developer stirred and conveyed by the conveying member and supply it to an image carrier (photoconductor drum), and a layer thickness regulating member regulates the layer thickness of the developer on the developer carrier. The layer thickness regulating member is provided in the developing tank so as to be located on the upstream side of the image carrier and on the downstream side of the conveying member in the rotation direction of the developer carrier. The developing tank may be provided with a wall portion having an inclined portion inclined from the layer thickness regulating member side toward the conveying member (see, for example, Patent Document 1).

[0003] In such a developing device, there is a problem that the stirring property and pumping property of the developer existing in the space between the conveying member and the developer carrier deteriorate.

[0004] Regarding this point, Patent Document 1 describes that, among the wall surfaces forming the developing tank (developer storage chamber) surrounding the conveying member (mixing and stirring member), a convex portion protruding toward the space between the developer carrier and the conveying member is provided at a position on the conveying member side with respect to the layer thickness regulating member and on the conveying member side of the layer thickness regulating member, and the tip of the convex portion is located in a region having a magnetic flux density of 85% or more with respect to the maximum value of the magnetic flux density in the tangential direction between the pickup pole and the layer regulating pole of the developer carrier.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in the configuration described in Patent Document 1, the developer carrier is provided on an inclined portion facing the protruding portion of the developer carrier in a region where the circumferential magnetic flux density of the developer carrier is high. As a result, a large amount of developer pumped up by the developer carrier is sent toward the layer thickness regulating member by the tangential magnetic flux. This presents a problem in that the developer tends to aggregate near the inclined portion. Furthermore, because the inclined portion facing the protruding portion of the developer carrier is inclined toward the conveying member, it is difficult to apply a force to the developer near the inclined portion that moves it toward the conveying member due to its own weight. This presents another problem in that the developer tends to aggregate even more easily near the inclined portion.

[0007] Therefore, the present disclosure aims to provide a developing apparatus and an image forming apparatus equipped therewith that can effectively prevent the aggregation of developer near the inclined portion of the wall of the developing tank. [Means for solving the problem]

[0008] To solve the aforementioned problems, the developing apparatus according to the present disclosure comprises: a developing tank containing a developer; a transport member provided in the developing tank for transporting the developer contained in the developing tank while agitating it by rotation; a developer carrier provided in the developing tank for pumping up the developer transported by the transport member by rotation and supplying it to an image carrier; and a layer thickness regulating member for regulating the layer thickness of the developer on the developer carrier, wherein the layer thickness regulating member is provided in the developing tank so as to be located upstream of the image carrier and downstream of the transport member in the rotation direction of the developer carrier, and the developing tank is inclined from the layer thickness regulating member side toward the transport member A wall portion having an inclined portion is provided, the inclined portion having a first inclined portion on the layer thickness regulating member side and a second inclined portion connected to the transport member side of the first inclined portion, the first inclined portion inclined upward from the second inclined portion side toward the layer thickness regulating member side at a predetermined first inclination angle from a virtual horizontal plane, the second inclined portion inclined upward from the transport member side toward the first inclined portion side at a predetermined second inclination angle from the virtual horizontal plane that is greater than the first inclination angle, the end of the second inclined portion opposite to the first inclined portion is above a horizontal first virtual straight line passing through the rotation axis of the transport member, and is located toward the layer thickness regulating member side of a second virtual straight line connecting the rotation axis of the transport member and the rotation axis of the developer carrier. Furthermore, the first inclined portion is formed such that a fourth virtual straight line, which is in contact with the first inclined surface of the first inclined portion and extends toward the conveying member side along the first inclined surface, is above a third virtual straight line connecting the end of the first inclined portion on the layer thickness regulating member side and the rotation axis of the conveying member, and passes through a region up to the outer circumferential surface of the conveying member. The second inclined portion is formed such that a fifth virtual straight line, which is in contact with the second inclined surface of the second inclined portion and extends toward the conveying member side along the second inclined surface, passes above the rotation axis of the conveying member. It is characterized by the following.

[0009] The image forming apparatus according to this disclosure is characterized by comprising the developing apparatus according to this disclosure. [Effects of the Invention]

[0010] According to this disclosure, it is possible to effectively prevent the aggregation of the developer near the inclined portion of the wall of the developing tank. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view of the image forming apparatus according to this embodiment, viewed from the front. [Figure 2]Figure 1 is a perspective view of the photoreceptor unit and developing apparatus in the image forming apparatus shown, viewed from diagonally above the rear side. [Figure 3] Figure 1 is a perspective view of the developing apparatus in the image forming apparatus, taken from the rear side, diagonally above. [Figure 4] This is a cross-sectional view showing a developing apparatus. [Figure 5] This is an explanatory diagram illustrating the configuration of the inclined section on the wall of the developing apparatus. [Figure 6] This is an explanatory diagram illustrating the configuration of the inclined section on the wall of the developing apparatus. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described below with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0013] [Image forming apparatus] Figure 1 is a schematic cross-sectional view of the image forming apparatus 100 according to this embodiment, viewed from the front. Figure 2 is a perspective view of the photoreceptor unit 80 and developing apparatus 2 in the image forming apparatus 100 shown in Figure 1, viewed from diagonally above the rear side. In the figure, the symbol X represents the left-right direction, the symbol Y represents the depth direction (front-to-back direction), and the symbol Z represents the up-and-down direction (vertical direction).

[0014] The image forming apparatus 100 according to this embodiment is a color image forming apparatus that forms multi-color and monochrome images on a recording sheet P such as paper. The image forming apparatus 100 performs image forming processing according to image data read by the image reading device 90 or image data transmitted from an external source. The image forming apparatus 100 may be a color image forming apparatus of other forms. The image forming apparatus 100 may also be a monochrome image forming apparatus.

[0015] The image forming apparatus 100 comprises an image reading device 90 and an image forming apparatus body 101. The image forming apparatus body 101 is provided with an image forming unit 102 and a sheet transport system 103.

[0016] The image forming unit 102 includes an exposure device 1 (exposure unit), multiple developing devices 2-2 (developing units), multiple photoreceptor drums 3-3 acting as image carriers, multiple photoreceptor cleaning devices 4-4 (cleaning units), multiple charging devices 5-5, an intermediate transfer belt device 6, a belt cleaning device 4T (cleaning unit), multiple toner cartridges 15-15, and a fuser device 7 (fusing unit). The photoreceptor drum 3, photoreceptor cleaning device 4, and charging device 5 constitute a photoreceptor unit 80 (see Figure 2). The sheet transport system 103 includes a paper feed tray 81, an output roller 31, and an output tray 14. The intermediate transfer belt device 6 includes multiple intermediate transfer rollers 65-65 and an intermediate transfer belt 61. The intermediate transfer rollers 65-65 are located inside the intermediate transfer belt 61. The intermediate transfer belt 61 moves circumferentially in a predetermined circumferential movement direction M. The intermediate transfer rollers 65-65 transfer the toner images of each color formed on the surface of the photoreceptor drums 3-3 onto the intermediate transfer belt 61, while rotating in conjunction with the circumferential movement of the intermediate transfer belt 61.

[0017] The photoreceptor cleaning device 4-4 removes toner (waste toner) that remains on the photoreceptor drum 3-3 without being transferred to the intermediate transfer belt 61 using the intermediate transfer rollers 65-65. The belt cleaning device 4T removes toner (waste toner) that remains on the intermediate transfer belt 61 without being transferred to the recording sheet P using the transfer roller 10a of the secondary transfer device 10.

[0018] On the upper part of the image forming apparatus main body 101, an image reading device 90 for reading an image of a document (not shown) is provided. The image reading device 90 reads an image of a document and includes a document conveyance unit 90a and a document reading unit 90b. The image reading device 90 reads an image of a document with the document reading unit 90b while conveying the document with the document conveyance unit 90a, or scans and reads a document placed on the document table of the document reading unit 90b with the document reading unit 90b. The image of the document read by the image reading device 90 is sent to the image forming apparatus main body 101 as image data, and an image is recorded on the recording sheet P.

[0019] A sheet conveyance path W1 is provided in the image forming apparatus main body 101. The sheet supply unit 11a supplies the recording sheet P to the sheet conveyance path W1. The sheet conveyance path W1 guides the recording sheet P to the discharge tray 14 via the transfer roller 10a of the secondary transfer device 10 and the fixing device 7. The fixing device 7 heats and fixes the toner image formed on the recording sheet P to the recording sheet P. Near the sheet conveyance path W1, the sheet supply unit 11a, a plurality of conveyance rollers 12a to 12a, a registration roller 13, a transfer roller 10a, a fixing roller 71 and a pressure roller 72 in the fixing device 7, and a discharge roller 31 are arranged.

[0020] In the image forming apparatus 100, the recording sheet P supplied from the paper feed tray 81 to the sheet supply unit 11a is conveyed to the registration roller 13 through the conveying rollers 12a to 12a. Next, the recording sheet P is conveyed to the transfer roller 10a at a timing when the registration roller 13 aligns the recording sheet P with the toner image on the intermediate transfer belt 61, and the toner image is transferred onto the recording sheet P by the transfer roller 10a. Thereafter, the recording sheet P passes through the fixing roller 71 and the pressure roller 72 in the fixing device 7, and is discharged onto the discharge tray 14 through the conveying rollers 12a, 12a and the discharge roller 31. When forming an image not only on the front surface but also on the back surface of the recording sheet P, the recording sheet P is conveyed in the reverse direction from the discharge roller 31 to the reverse sheet conveyance path W2. The recording sheet P passes through the reverse conveyance rollers 12b to 12b, the front and back surfaces of the recording sheet P are reversed, and the recording sheet P is again guided to the registration roller 13. Then, the recording sheet P is discharged toward the discharge tray 14 after a toner image is formed and fixed on the back surface in the same manner as on the front surface.

[0021] [Developing device] FIG. 3 is a perspective view of the developing device 2 in the image forming apparatus 100 shown in FIG. 1 as viewed obliquely upward from the back side. FIG. 4 is a cross-sectional view showing the developing device 2. FIGS. 5 and 6 are explanatory views for explaining the configuration of the inclined portion 211 in the wall portion 212 of the developing device 2. Since the plurality of developing devices 2 to 2 all have substantially the same configuration, in FIGS. 3 to 5, they are shown represented by one developing device 2.

[0022] The developing device 2 includes a developing tank 21 in which a developer D (see FIG. 4) is accommodated, a first conveying member 23 (first conveying screw) and a second conveying member 24 (an example of a conveying member) (second conveying screw) provided in the developing tank 21, a developing roller 22 (an example of a developer carrier) provided in the developing tank 21, and a layer thickness regulating member 21a (doctor blade). In this example, the layer thickness regulating member 21a is formed of a magnetic material such as iron.

[0023] The first transport member 23 and the second transport member 24 are rotated to transport the developer D contained in the developing tank 21 in the direction of the rotation axis (E1, E2) while stirring it.

[0024] The developing roller 22 rotates to scoop up the developer D that is agitated and transported by the second transport member 24 and supply it to the photoreceptor drum 3. In other words, the developing roller 22 transports the scooped-up developer D to the area facing the photoreceptor drum 3.

[0025] As shown in Figure 4, the layer thickness regulating member 21a regulates the layer thickness of the developer D on the developing roller 22. The layer thickness regulating member 21a is provided in the developing tank 21 so as to be located upstream of the photoreceptor drum 3 and downstream of the second transport member 24 in the rotation direction R3 of the developing roller 22. A predetermined gap d1 (see Figure 5) (doctor gap) is provided between the layer thickness regulating member 21a and the developing roller 22. The developing tank 21 is provided with a wall portion 212 having an inclined portion 211 that slopes from the layer thickness regulating member 21a side toward the second transport member 24.

[0026] More specifically, the developing apparatus 2 includes a developing tank 21 in which the developer D is contained. The developer D contains a magnetic material (magnetic carrier C in this example). In this example, the developer D is a two-component developer mainly composed of magnetic carrier C and non-magnetic toner T. However, it is not limited to this, and the developer D may be a one-component developer mainly composed of magnetic toner.

[0027] The non-magnetic toner T (or magnetic toner if the developer D is a one-component developer) is a low-melting-point toner that is welded to the recording sheet P at a predetermined fixing temperature or below. The fixing temperature is the temperature of the fixing member (for example, a fixing roller 71, fixing belt, pressure roller 72, etc.) when fixing the non-magnetic toner T (or magnetic toner) to the recording sheet P. The predetermined fixing temperature can be, for example, around 140°C to 170°C.

[0028] The developing tank 21 extends in the longitudinal direction (depth direction Y), and the developing tank 21 is provided with an opening OP at a position facing the photoreceptor drum 3. The photoreceptor drum 3 is attached to a mounting portion 21b (see Figures 2 and 3) provided at one end of the developing tank 21 in the longitudinal direction (Y).

[0029] The developing roller 22 is a magnetic roller with a magnet inside and functions as a developer carrier. The developing roller 22 is supported in the developing tank 21 at a position facing the photoreceptor drum 3 and at a predetermined distance from the photoreceptor drum 3. The developing roller 22 is formed in a non-magnetic cylindrical shape and comprises a sleeve portion 22a that is rotatable about a rotation axis α along the longitudinal direction (Y), and multiple magnets (magroll portion) (not shown) arranged inside the sleeve portion 22a around the rotation axis α, which are positioned so as not to rotate around the rotation axis α. Multiple magnetic fluxes, each with a single polarity, are formed on the circumferential surface of the developing roller 22, that is, on the circumferential surface of the sleeve portion 22a, due to the magnetism of the magnets arranged inside the sleeve portion 22a. The developing roller 22 carries the developer D on its surface with the magnetic poles formed on its circumferential surface, and is transported in the rotation direction R3 (counterclockwise in Figure 4) as the sleeve portion 22a rotates in the rotation direction R3.

[0030] The photoreceptor drum 3 rotates in the rotational direction R4 (clockwise in Figure 4) around the rotational axis γ. The developer D supported on the surface of the developing roller 22 is restricted to a predetermined thickness by the layer thickness regulating member 21a provided in the developing tank 21 and is conveyed to the surface of the photoreceptor drum 3 as it rotates in the rotational direction R4. In the developing region AR1 where the photoreceptor drum 3 and the developing roller 22 face each other, the electrostatic latent image formed on the surface of the photoreceptor drum 3 is developed by the non-magnetic toner T in the developer D.

[0031] As shown in Figures 3 and 4, the developing tank 21 is provided with a first chamber 21c and a second chamber 21d as circulation chambers. The first chamber 21c and the second chamber 21d are located on one side X1 and the other side X2 of the developing tank 21 in the left-right direction X, respectively, and contain the developer D.

[0032] As shown in Figure 3, the first chamber 21c and the second chamber 21d form a long space along the longitudinal direction (Y). The first conveying member 23 is installed in the first chamber 21c. The first conveying member 23 conveys the developer D in the first chamber 21c in the first conveying direction E1 (one side Y1) while stirring it. The second conveying member 24 is installed in the second chamber 21d. The second conveying member 24 conveys the developer D in the second chamber 21d in the second conveying direction E2 (the other side Y2), which is opposite to the first conveying direction E1, while stirring it.

[0033] The developing apparatus 2 is equipped with a drive transmission mechanism 26. The drive transmission mechanism 26 comprises a first timing gear 26a, a second timing gear 26b, and a drive gear 26c. The first timing gear 26a and the second timing gear 26b are fixed to the other end Y2 in the longitudinal direction (Y) of the rotation axes 23a and 24a of the first conveying member 23 and the second conveying member 24, respectively. The drive gear 26c is fixed to the outside in the longitudinal direction (Y) of the second timing gear 26b, which is provided on the rotation axis 24a of the second conveying member 24. As a result, when the second conveying member 24 is rotationally driven via the drive gear 26c, the second timing gear 26b transmits rotational force to the first timing gear 26a, causing the first conveying member 23 to rotate in the opposite direction to the second conveying member 24. Then, rotational force is transmitted to the developing roller 22 by a gear and a transmission belt provided at one end Y1, which is the front side in the depth direction Y of the second conveying member 24.

[0034] The developing tank 21 has a first chamber 21c and a second chamber 21d adjacent to each other, and they are connected to each other via connecting passages 2111 and 2121 at both ends in the longitudinal direction (Y). That is, a partition wall 21g is provided inside the developing tank 21 that separates the first chamber 21c and the second chamber 21d, and connecting passages 2111 and 2121 are formed on both sides of the partition wall 21g in the longitudinal direction (Y).

[0035] In the developing apparatus 2 configured in this way, the developer D contained in the first chamber 21c is transported in the first transport direction E1 while being agitated by the first transport member 23, passes through the connecting passage 2111 provided on one side Y1, and reaches the second chamber 21d from the first chamber 21c. The developer D that reaches the second chamber 21d is transported in the second transport direction E2 while being agitated by the second transport member 24, passes through the connecting passage 2121 provided on the other side Y2, and reaches the first chamber 21c. In this way, the developer D is transported in a circulating manner between the first chamber 21c and the second chamber 21d.

[0036] The first transport member 23, located in the first chamber 21c, has a rotating shaft 23a extending in the longitudinal direction (Y) and a blade portion 231. The blade portion 231 is spirally formed around the rotating shaft 23a. The blade portion 231 rotates together with the rotating shaft 24a, stirring the developer D in the first chamber 21c and transporting it in the first transport direction E1.

[0037] The second transport member 24, located in the second chamber 21d, has a rotating shaft 24a extending in the longitudinal direction (Y) and a blade portion 241. The blade portion 241 is spirally formed around the rotating shaft 24a. The blade portion 241 rotates together with the rotating shaft 24a, agitating the developer D in the second chamber 21d and transporting it in the second transport direction E2.

[0038] As shown in Figure 4, the cross-sectional shapes of the blade portions 231 and 241 in the first conveying member 23 and the second conveying member 24, perpendicular to the rotation axes 23a and 24a, are such that the thickness of the blade portions 231 and 241 decreases towards the tip portions 231a and 241a, respectively.

[0039] In the developing device 2, the first transport member 23 and the second transport member 24 are rotated in the rotational direction R1 (R11, R12) when developing the developer D. The developer D transported by the first transport member 23 and the second transport member 24 is then scooped up from the second transport member 24 by the developing roller 22 and transported toward the rotational direction R3. With the layer thickness restricted by the layer thickness restricting member 21a, the electrostatic latent image formed on the surface of the photoreceptor drum 3 in the developing region AR1 is developed by the non-magnetic toner T in the developer D. The second transport member 24 will be referred to simply as the transport member 24 below.

[0040] The developing tank 21 is provided with a wall portion 212. In this example, the wall portion 212 is the inner wall of the developing tank 21 and is provided adjacent to the upstream side of the rotation direction R3 of the developing roller 22 of the layer thickness regulating member 21a. The wall portion 212 has an inclined portion 211 that slopes from the layer thickness regulating member 21a side toward the transport member 24.

[0041] The inclined section 211 has a first inclined section 211a on the layer thickness regulating member 21a side and a second inclined section 211b connected to the transport member 24 side of the first inclined section 211a (upstream of the rotation direction R3 of the developing roller 22). The first inclined section 211a is inclined upward from the second inclined section 211b toward the layer thickness regulating member 21a side at a predetermined first inclination angle θ1 (see Figure 5) from a virtual horizontal plane H (see Figure 5) (approximately 30 degrees in this example). The second inclined section 211b is inclined upward from the transport member 24 side toward the first inclined section 211a at a predetermined second inclination angle θ2 (see Figure 5) from a virtual horizontal plane H that is greater than the first inclination angle θ1 (approximately 45 degrees in this example). In other words, the first inclined portion 211a is inclined downward from the layer thickness regulating member 21a side toward the second inclined portion 211b at a first inclination angle θ1 from the virtual horizontal plane H, and the second inclined portion 211b is inclined downward from the first inclined portion 211a toward the conveying member 24 side at a second inclination angle θ2 from the virtual horizontal plane H.

[0042] The first inclination angle θ1 is the angle between the virtual horizontal plane H and the first inclined surface 211a1 of the first inclined portion 211a. The second inclination angle θ2 is the angle between the virtual horizontal plane H and the second inclined surface 211b1 of the second inclined portion 211b.

[0043] Here, the first tilt angle θ1 can be exemplified as approximately 20 to 40 degrees. The second tilt angle θ2 can be exemplified as approximately 35 to 60 degrees. Furthermore, the second tilt angle θ2 can be approximately 1.5 to 2.5 times the first tilt angle θ1. However, it is not limited to these values.

[0044] As shown in Figure 5, the end K1 of the second inclined portion 211b opposite to the first inclined portion 211a is above the horizontal first virtual straight line L1 passing through the rotation axis β of the conveying member 24, and is located on the layer thickness regulating member 21a side of the second virtual straight line L2 connecting the rotation axis β of the conveying member 24 and the rotation axis α of the developing roller 22. This allows the inclined portion 211 (first inclined portion 211a and second inclined portion 211b) to be formed such that the distance from the developing roller 22 decreases as it approaches the layer thickness regulating member 21a (forming a narrowed portion δ), and the second inclined portion 211b can be formed to cover a part of the upper side of the conveying member 24. Below the second inclined portion 211b, a lower wall portion is provided that has a predetermined gap with the conveying member 24. As a result, the developer in the second chamber 21d, which is transported by the transport member 24, is pushed upward towards the end K1 of the second inclined section 211b while being transported in the E2 direction, thus effectively guiding the developer to the inclined section 211.

[0045] In this embodiment, the developing roller 22 is arranged by magnets placed inside to draw up the developer in the first chamber 21c and transport it in the rotational direction R3, so that the magnetic flux density differs in the circumferential direction. Specifically, as shown in Figure 6, the magnetic flux density formed by the magnets in the direction normal to the surface of the developing roller 22 is formed to increase from a predetermined opposing region AR2 on the surface of the developing roller 22 facing the transport member 24 toward the opposing portion P1 facing the layer thickness regulating member 21a.

[0046] In this embodiment, the developing roller 22 uses a first magnetic force F1 of the first magnetic flux density (pushing magnetic flux density) to push the developer D upstream of a predetermined first region S1 (opposing region AR2). The developing roller 22 uses a second magnetic force F21 (F2) of a portion of the second magnetic flux density (pushing and regulating magnetic flux density) to push the developer D into the first region S1 (AR2). In this state, the developing roller 22 is rotated in the rotational direction R3, thereby feeding the developer D into the space between the second inclined section 211b and the developing roller 22 (narrow section δ). The developing roller 22 also uses a second magnetic force F22 (F2) of a portion of the second magnetic flux density to hold the developer D in a predetermined second region S2 (above the inclined section 211). In this state, the developing roller 22 is further rotated in the rotational direction R3, which feeds the developer D into the gap d1 between the layer thickness regulating member 21a and the developing roller 22, and the thickness of the developer layer is regulated by the layer thickness regulating member 21a.

[0047] Here, the first region S1 and the second region S2 are the upstream and downstream regions, respectively, in the rotational direction R3 of the developing roller 22, with respect to the end K1 of the second inclined portion 211b opposite to the first inclined portion 211a.

[0048] In this example, the first region S1 is the region between the common virtual line L6a and the first virtual line L6b. The common virtual line L6a is a straight line passing through the rotation axis α of the developing roller 22 and the end K1 of the second inclined portion 211b opposite to the first inclined portion 211a. The first virtual line L6b is a straight line passing through the rotation axis α of the developing roller 22 and a point on the outer circumferential surface TR of the conveying member 24 that is further away from the second inclined portion 211b than the rotation axis β of the conveying member 24.

[0049] The second region S2 is the region between the common virtual line L6a and the second region virtual line L6c. The second region virtual line L6c is a straight line passing through the rotation axis α of the developing roller 22 and the end K2 of the first inclined portion 211a on the layer thickness regulating member 21a side.

[0050] The first and second magnetic flux densities are magnetic flux densities in the direction normal to the surface of the developing roller 22, formed by magnets placed inside the developing roller 22.

[0051] The first magnetic flux density is formed upstream of the first region S1 in the rotational direction R3 of the developing roller 22. More specifically, the first magnetic flux density is formed in a predetermined region upstream of the point where the first region virtual straight line L6b intersects the surface of the developing roller 22 in the rotational direction R3.

[0052] The second magnetic flux density is formed to span the inclined portion 211 and the layer thickness regulating member 21a. The maximum magnetic flux density of the second magnetic flux density is located opposite the end 21a1 (see Figure 6) of the layer thickness regulating member 21a that is opposite the developing roller 22. The second magnetic flux density extends from the maximum magnetic flux density to the layer thickness regulating region between the part P1 of the developing roller 22 that faces the layer thickness regulating member 21a and the developing region AR1 of the photoreceptor drum 3. The developing roller 22 uses the first magnetic force F1 of the first magnetic flux density to draw up the developer D and feed it into the first region S1. In the first region S1, it uses the second magnetic force F21(F2) of the second magnetic flux density to draw up the developer D and feed it into the second region S2. In the second region S2, it uses the second magnetic force F22(F2) of the second magnetic flux density to pull the developer D upwards on the inclined portion 211 and feed it into the gap d1 (doctor gap).

[0053] In this case, the second inclined portion 211b is formed to cover a part of the upper side of the transport member 24, making it difficult for the developer D located near the transport member 24 below the second inclined portion 211b to be picked up by the developing roller 22. In this example, the surface of the inclined portion 211 facing the transport member 24 is formed as an arcuate surface centered on the rotation axis β of the transport member 24. The virtual tangent L7 at the end K1 of the second inclined portion 211b on the arcuate surface of the inclined portion 211 does not intersect with the developing roller 22. This makes it even more difficult for the developer D located near the transport member 24 below the second inclined portion 211b to be picked up by the developing roller 22. Furthermore, by appropriately shaping the first magnetic flux region, the appropriate amount of developer D necessary for image formation can be picked up by the developing roller 22.

[0054] Furthermore, the magnetic flux density is formed to increase from a predetermined region on the surface of the developing roller 22 facing the transport member 24 (facing region AR2) toward the position facing the layer thickness regulating member 21a (facing portion P1), and the gap between the inclined portion 211 (first inclined portion 211a and second inclined portion 211b) and the developing roller 22 decreases toward the layer thickness regulating member 21a. As a result, the magnetic flux density acting on the developer D near the surface of the inclined portion 211 can be increased toward the layer thickness regulating member 21a. This ensures that the developer D near the surface of the inclined portion 211 is reliably and sequentially fed by the rotation of the developing roller 22 into the gap d1 between the layer thickness regulating member 21a and the developing roller 22. Therefore, even if an excessive amount of developer D is supplied to the area immediately in front of the layer thickness regulating member 21a (developer reservoir), it is possible to effectively prevent the developer D from accumulating in the developer reservoir, and consequently, to effectively prevent the developer D from being compressed and condensed in the developer reservoir for a long period of time. Here, it is desirable that there is no step at the boundary K3 between the first inclined portion 211a and the second inclined portion 211b.

[0055] Furthermore, the second inclination angle θ2 of the second inclined section 211b is greater than the first inclination angle θ1 of the first inclined section 211a. The distance between the second inclined section 211b and the developing roller 22, and the distance between the first inclined section 211a and the developing roller 22, widens as they move toward the transport member 24. Also, the magnetic flux density of the magnets on the developing roller 22 decreases as it moves away from the developing roller 22. As a result, the density of the developer D pumped onto the inclined section 211 can be reduced as it approaches the transport member 24. Therefore, it is possible to effectively prevent the developer D from agglomerating near the surface of the inclined section 211.

[0056] These measures are particularly effective when the non-magnetic toner T is a low-melting-point toner that fuses to the recording sheet P at a predetermined fixing temperature or below.

[0057] (Second Embodiment) Incidentally, if the length of the first inclined surface 211a1 of the first inclined portion 211a in the direction of inclination is longer than the length of the second inclined surface 211b1 of the second inclined portion 211b in the direction of inclination, the time it takes for the developer D present near the surface of the first inclined portion 211a to pass through the gap d1 (doctor gap) will be longer. Consequently, the likelihood of the developer D condensing increases.

[0058] In this regard, in the second embodiment, in the first embodiment, the length of the second inclined surface 211b1 of the second inclined portion 211b in the inclination direction is longer than the length of the first inclined surface 211a1 of the first inclined portion 211a in the inclination direction.

[0059] By doing so, the time it takes for the developer D present near the surface of the first inclined portion 211a to pass through the gap d1 can be made shorter than when the length of the first inclined surface 211a1 is longer than the length of the second inclined surface 211b1. Therefore, the possibility of the developer D condensing can be reduced.

[0060] (Third embodiment) Incidentally, if the boundary K3 between the first inclined portion 211a and the second inclined portion 211b is located below the third virtual straight line L3 (see Figure 6) that connects the end K2 of the first inclined portion 211a on the layer thickness regulating member 21a side and the rotation axis β of the transport member 24, the first inclination angle θ1 (see Figure 5) becomes too large, which tends to worsen the transportability of the developer D near the surface of the first inclined portion 211a. As a result, there is a risk that the developer D will condense near the surface of the first inclined portion 211a.

[0061] In this regard, in the third embodiment, the boundary K3 between the first inclined portion 211a and the second inclined portion 211b is located above the third virtual straight line L3 that connects the end of the first inclined portion 211a on the layer thickness regulating member 21a side and the rotation axis β of the conveying member 24.

[0062] By doing so, the first inclination angle θ1 does not become too large, and deterioration of the transportability of the developer D near the surface of the first inclined portion 211a can be suppressed, thereby effectively preventing the developer D from condensing near the surface of the first inclined portion 211a.

[0063] (Fourth Embodiment) In the fourth embodiment, in any one of the first to third embodiments, the first inclined portion 211a is formed such that a fourth virtual straight line L4 (see Figure 6), which is in contact with the first inclined surface 211a1 of the first inclined portion 211a and extends toward the transport member 24 side along the first inclined surface 211a1, passes through a region above the third virtual straight line L3, which connects the end of the first inclined portion 211a on the layer thickness regulating member 21a side and the rotation axis β of the transport member 24, up to the outer peripheral surface TR of the transport member 24.

[0064] The second inclined portion 211b is formed such that a fifth virtual straight line L5 (see Figure 6), which is in contact with the second inclined surface 211b1 of the second inclined portion 211b and extends along the second inclined surface 211b1 toward the transport member 24, passes above the rotation axis β of the transport member 24.

[0065] In this way, when the developing roller 22 is stationary, a force can be applied to the developer D (the developer D held by magnetic force) in the space SP (see Figure 6) between the second inclined portion 211b and the developing roller 22, directed toward the transport member 24 by its own weight (a force that tries to move it in the direction that widens the distance between the developing roller 22 and the wall portion 212). This effectively prevents the developer D from excessively agglomerating in the developer reservoir area, which is the region immediately in front of the layer thickness regulating member 21a. In addition, the developer D that falls by its own weight can be reliably dropped onto the transport member 24. Therefore, deterioration of the agitation of the developer D by the transport member 24 can be effectively prevented.

[0066] (Fifth embodiment) In the fifth embodiment, as described above in any one of the first to fourth embodiments, the conveying member 24 has a rotating shaft 24a and a blade portion 241 formed spirally around the rotating shaft 24a. The cross-sectional shape of the blade portion 241 perpendicular to the rotating shaft 24a is such that the thickness of the blade portion 241 becomes thinner towards the tip portion 241a of the blade portion 241.

[0067] Furthermore, the rotation direction R1 (R12) of the conveying member 24 is the direction in which the blade portion 241 rotates upward toward the second inclined portion 211b.

[0068] This makes it easier to move a portion of the developer D on the blade section 241, which has been moved upward by the rotation of the transport member 24, onto the second inclined section 211b. As a result, the developer D that has been scraped up by the transport member 24 can be effectively sent onto the second inclined section 211b.

[0069] (Sixth Embodiment) In the sixth embodiment, in any one of the first to fifth embodiments, the gap d2 (see Figure 5) between the end K2 of the first inclined portion 211a on the layer thickness regulating member 21a side and the developing roller 22 is wider than the gap d1 (doctor gap) between the layer thickness regulating member 21a and the developing roller 22.

[0070] This ensures that the thickness of the developer D on the developing roller 22 can be reliably controlled by the layer thickness regulating member 21a.

[0071] Here, if the gap d2 is too wide, the amount of developer D between the layer thickness regulating member 21a and the developing roller 22 increases, making it easy for the developer D to accumulate in the developer reservoir area, which is the region directly in front of the layer thickness regulating member 21a.

[0072] Therefore, the gap d2 is preferably no more than three times the gap d1. For example, a gap d1 can be approximately 0.6 mm to 0.7 mm.

[0073] This disclosure is not limited to the embodiments described above, and can be implemented in a variety of other ways. Therefore, these embodiments are merely illustrative in all respects and should not be constrained. The scope of this disclosure is defined by the claims and is not restricted by the text of the specification. Furthermore, any variations or modifications falling within the equivalent scope of the claims are all within the scope of this disclosure. [Explanation of Symbols]

[0074] 100 Image forming apparatus 2. Developing device 21 Developer tank 211 Slope 211a 1st slope 211a1 1st slope 211b 2nd slope 211b1 2nd slope 212 Wall section 21a Layer thickness regulating member 22. Developing roller (an example of a developer carrier) 24. Second conveying member (an example of a conveying member) 241 Blade section 241a Tip 24a Rotation axis 3. Photosensitive drum (an example of an image carrier) AR1 development area AR2 opposing area C Magnetic carrier D Developer E1 First conveying direction E2 Second transport direction F1 First magnetic force F2 2nd magnetic force H Virtual horizontal plane K1 end K2 end K3 boundary L1 First virtual line L2 Second virtual line L3 Third virtual line L4 4th virtual line L5 Fifth virtual line L6a Common virtual line in the region L6b First Domain Virtual Line L6c Second Domain Virtual Line L7 Virtual tangent OP opening P Record Sheet P1 Opposite section R1 Rotation direction R3 Rotation direction S1 1st area S2 2nd area SP space T Non-magnetic toner TR outer surface X Left / right direction Y (depth direction) Y1 One side Y2 other side Z vertical direction d1 gap d2 gap α rotation axis β Rotation axis δ Narrow part θ1 1st inclination angle θ2 2nd inclination angle

Claims

1. A developing tank in which the developer is contained, A conveying member provided in the developing tank, which conveys the developer contained in the developing tank while stirring it by rotating, A developer carrier is provided in the developing tank and rotates to pump up the developer, which is agitated and conveyed by the conveying member, and supply it to the image carrier. A developing apparatus comprising a layer thickness regulating member for regulating the layer thickness of the developer on the developer carrier, The layer thickness regulating member is provided in the developing tank such that it is located upstream of the image carrier and downstream of the transport member in the rotational direction of the developer carrier. The developing tank is provided with a wall portion having an inclined portion that slopes from the layer thickness regulating member side toward the transport member, The inclined portion has a first inclined portion on the layer thickness regulating member side and a second inclined portion connected to the conveying member side of the first inclined portion. The first inclined portion is inclined upward from the second inclined portion side toward the layer thickness regulating member side at a predetermined first inclination angle from the virtual horizontal plane. The second inclined portion is inclined upward from the conveying member side toward the first inclined portion side at a predetermined second inclination angle from the virtual horizontal plane that is greater than the first inclination angle. The end of the second inclined portion opposite to the first inclined portion is above a horizontal first virtual straight line passing through the rotation axis of the transport member, and is located on the layer thickness regulating member side of the second virtual straight line connecting the rotation axis of the transport member and the rotation axis of the developer carrier. The first inclined portion is formed such that a fourth virtual straight line, which is in contact with the first inclined surface of the first inclined portion and extends along the first inclined surface toward the conveying member, is above a third virtual straight line connecting the end of the first inclined portion toward the layer thickness regulating member and the rotation axis of the conveying member, and passes through a region up to the outer circumferential surface of the conveying member. The developing apparatus is characterized in that the second inclined portion is formed such that a fifth virtual straight line, which is in contact with the second inclined surface of the second inclined portion and extends along the second inclined surface toward the transport member, passes above the rotation axis of the transport member.

2. A developing apparatus according to claim 1, A developing apparatus characterized in that the length of the second inclined surface of the second inclined portion in the direction of inclination is longer than the length of the first inclined surface of the first inclined portion in the direction of inclination.

3. A developing apparatus according to claim 1, The developing apparatus is characterized in that the boundary between the first inclined portion and the second inclined portion is located above a third virtual straight line connecting the end of the first inclined portion on the layer thickness regulating member side and the rotation axis of the transport member.

4. A developing apparatus according to claim 1, The conveying member has a rotating shaft and a blade portion formed spirally around the rotating shaft. The cross-sectional shape of the blade portion perpendicular to the axis of rotation is such that the thickness of the blade portion decreases towards the tip of the blade portion. The developing apparatus is characterized in that the rotation direction of the transport member is in the direction in which the blade portion rotates upward toward the second inclined portion.

5. A developing apparatus according to claim 1, A developing apparatus characterized in that the gap between the end of the first inclined portion on the layer thickness regulating member side and the developer carrier is wider than the gap between the layer thickness regulating member and the developer carrier.

6. An image forming apparatus characterized by comprising a developing apparatus according to any one of claims 1 to 5.

Images