JP2014240924A - Magnet roller, manufacturing method thereof, developing roller, developing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet roller which can be manufactured by injection molding and is available for higher-speed printing in an electrophotographic image forming apparatus, and a developing roller, a developing device, and an image forming apparatus which include the magnet roller.SOLUTION: A magnet roller 10 includes a substantially column-shaped roller body 12. The roller body 12 has a draft taper 125 formed from a first end surface 121 to a second end surface 122. However, the draft taper 125 is not formed in a part including a main magnetic pole in a circumferential direction of the roller body 12. The magnet roller 10 is stored in a sleeve so that a distance between this part and the sleeve is constant, and the sleeve is rotatably supported, whereby the developing roller is constituted. The developing roller is mounted in the developing device and is used in the image forming apparatus.

Description

  The present invention relates to a magnet roller, a method for manufacturing the magnet roller, a developing roller, a developing device, and an image forming apparatus.

  An electrophotographic image forming apparatus supplies toner from a developing device to a photoreceptor on which an electrostatic latent image is formed, and forms a toner image corresponding to the electrostatic latent image. The toner is supplied from the developing device to the photoconductor via the developing roller. The developing roller has a columnar magnet (magnet roller) and a cylindrical sleeve that rotates on the outer peripheral surface of the magnet roller. A magnet roller is comprised by the integral molding of the magnetic body composition containing magnetic body particle | grains and resin, for example.

  The magnet roller can be manufactured by injection molding using a mold having a cylindrical space as a cavity. In this case, in order to take out the obtained magnet roller from the mold, a punch taper having a shape in which the roller radius of the magnet roller gradually decreases from the opening of the cavity toward the bottom is designed on the outer peripheral surface of the magnet roller. There is a need.

  On the other hand, a magnet roller having a taper over the entire circumference in the circumferential direction of the magnet roller from one end to the other end in the axial direction of the magnet roller is known (see, for example, Patent Document 1). In the magnet roller, the magnetic particles in the magnetic composition are prevented from being unevenly distributed in the axial direction of the magnet roller in the process of injecting the magnetic composition into the cavity. Therefore, variation in magnetic force in the axial direction of the magnet roller is suppressed.

Japanese Patent Laid-Open No. 11-144947

  By the way, when the magnetic force of the developing roller is stronger, the developing speed in the image forming apparatus can be increased, and as a result, the printing speed can be further increased. However, the strength of the uniform magnetic force of the magnet roller is determined by the magnetic force of the narrowest part of the tip of the taper. For this reason, it is difficult to make the magnetic force of the developing roller stronger than the magnetic force of the above part. Therefore, although the said magnet roller does not have the said taper, the said printing speed becomes low compared with the magnet roller of the same size.

An object of the present invention is to provide a magnet roller that can be manufactured by injection molding and can be used for higher-speed printing in an electrophotographic image forming apparatus.
Another object of the present invention is to provide a developing roller, a developing device, and an image forming apparatus having the magnet roller.

  The magnet roller according to the present invention is configured as an integrally molded product with a magnetic composition containing magnetic particles and a resin. The magnet roller includes a roller body having a first end surface and a second end surface, and a plurality of magnetic poles formed along the axial direction of the roller body are respectively arranged at different positions in the circumferential direction of the roller body. Yes. The plurality of magnetic poles include a main magnetic pole having a maximum magnetic force, and a portion that does not include the main magnetic pole in the circumferential direction of the roller main body is from the first end surface side to the second end surface side of the roller main body. A draft taper in which the roller radius of the roller body gradually decreases is formed.

  In addition, the method of manufacturing a magnet roller according to the present invention includes a magnetic composition containing magnetic particles and a resin, having a circular opening and a substantially circular bottom of a mold, A first step of injecting from a gate of the mold into a cavity in which a draft is formed in part in the circumferential direction; and a plurality of locations in the circumferential direction of the cavity outside the cavity A second step of arranging a plurality of magnets along the axial direction of the cavity, a third step of solidifying the magnetic composition, and taking out the solidified magnetic composition from the cavity A fourth step. The mold includes a first mold including the cavity, a second mold for closing the opening of the cavity, the first mold or the outside of the second mold, and the cavity. And the gate communicating with the tee. The draft angle is formed in a shape in which the radius of the circle of the shape of the opening gradually decreases according to the depth of the cavity. In the second step, the main magnet having the maximum magnetic force among the plurality of magnets is disposed in a portion other than the draft in the circumferential direction of the cavity, and in the fourth step, the solidified The magnetic composition is pulled out from the opening.

  Further, the developing roller according to the present invention supports the above-mentioned magnet roller, a cylindrical non-magnetic sleeve covering the outer peripheral surface of the roller body of the magnet roller, and the sleeve rotatably at both ends of the sleeve. And a rotation support portion.

  The developing device according to the present invention includes the above-described developing roller, and the image forming apparatus according to the present invention includes the above-described developing device.

  Since the magnet roller according to the present invention has the above-described taper, it can be manufactured by injection molding. In the magnet roller, the radius of the roller at the main magnetic pole can be maximized. Therefore, compared with the conventional magnet roller which has a taper along an axial direction over the perimeter of a circumferential direction, the magnetic force of a main pole becomes larger. In the magnet roller, the roller radius of the main magnetic pole can be made constant in the axial direction of the roller body. Therefore, the magnetic force in the axial direction of the magnet roller becomes uniform. Therefore, the magnet roller can be used in an electrophotographic image forming apparatus having a higher printing speed.

1A is a schematic front view of a magnet roller according to an embodiment of the present invention, FIG. 1B is a schematic side view of the first end surface side of the magnet roller, and FIG. 1C is the magnet roller. It is a schematic side view of the second end face side. 2A is a diagram schematically showing a mold used in the method of manufacturing a magnet roller according to one embodiment of the present invention, and FIG. 2B is a diagram showing a state in which the mold is closed, and FIG. FIG. 2 is a view showing a state where a magnetic composition is injected into the mold, and FIG. 2D is a view showing a state where a magnet roller composed of the magnetic composition is taken out from the mold. is there. FIG. 3 is a schematic front view of the developing roller according to the embodiment of the present invention. FIG. 4 is a diagram schematically showing the configuration of the developing device according to the embodiment of the present invention. FIG. 5 is a diagram schematically showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6A is a diagram schematically illustrating a configuration for measuring the magnetic force in the circumferential direction of the developing roller, and FIG. 6B is a diagram illustrating an example of a measurement result of the magnetic force. FIG. 7A is a diagram schematically illustrating a configuration for measuring the magnetic force of the main magnetic pole in the axial direction of the developing roller, and FIG. 7B is a diagram illustrating an example of a measurement result of the magnetic force. FIG. 8A is a diagram schematically illustrating a configuration for measuring the rotational torque of the sleeve of the developing roller, and FIG. 8B is a diagram illustrating an example of a measurement result of the rotational torque.

[Magnet roller]
The magnet roller according to the present invention is composed of a magnetic material composition as an integrally molded product. The magnetic composition contains magnetic particles and a resin.

  The magnetic composition is composed of, for example, a resin and magnetic particles. One or more resins may be used. Examples of the resin include polyamide (nylon), rigid polyvinyl chloride, polystyrene, polypropylene, styrene acrylonitrile, ABS resin, polyacetal, polycarbonate, polyphenylene and polysulfone.

  One or more magnetic particles may be used. The size and shape of the magnetic particles are not particularly limited as long as the effects of the present invention are obtained. Examples of the material of the magnetic particles include ferrite and rare earth cobalt.

  For example, from the viewpoint of realizing the desired magnetic force and the desired strength of the magnet roller, the magnetic composition is a composition for a bonded magnet made of nylon 6 (for example, TP manufactured by Toda Kogyo Co., Ltd.). -F65K, TP-F66, etc.). The magnetic particles are preferably ferrite particles.

  The said magnetic body composition may further contain other materials other than said resin and magnetic body particle in the range with which the effect of this invention is acquired. Examples of such other materials include iron oxide, strontium oxide and barium oxide. The content of the other material in the magnetic composition is appropriately determined according to the use of the magnet roller and the function of the other material.

  The magnet roller includes a roller body having a first end surface and a second end surface. The shape of the roller body is substantially cylindrical. For example, the shape of the first end surface is circular, the shape of the second end surface is substantially circular, and the edge of the first end surface and the edge of the second end surface are continuous on the circumferential surface. It is a connected solid shape. The shape of the roller body will be further described later.

  In the roller body, a plurality of magnetic poles formed along the axial direction of the roller body are formed at different positions in the circumferential direction of the roller body. The plurality of magnetic poles include a main magnetic pole having the maximum magnetic force.

  The number of main poles is usually one, but may be more. The number of main magnetic poles is appropriately selected according to the application of the magnet roller. The number of magnetic poles (other magnetic poles) other than the main magnetic pole may be one or more. The number of other magnetic poles is also appropriately selected according to the application of the magnet roller. For example, in the case of a magnet roller used as a developing roller of an electrophotographic image forming apparatus, the number of main magnetic poles is 1, and the number of other magnetic poles is 1-6. The arrangement of the other magnetic pole with respect to the position of the main magnetic pole in the circumferential direction of the roller body is arbitrarily determined according to the application of the magnet roller. For example, the main magnetic pole and the other magnetic poles may be arranged at equal intervals in the circumferential direction of the roller body, or may be arranged in a biased manner.

  The magnetic force of the other magnetic poles only needs to be sufficiently lower than the magnetic force of the main magnetic pole, and is, for example, 80% or less of the magnetic force of the main magnetic pole. Each of the magnetic forces of the other magnetic poles may be the same or different. The magnetic force of the main magnetic pole and the magnetic force of the other magnetic poles are magnetic forces at a certain distance from the central axis of the roller body in the circumferential direction of the roller body. The center axis of the roller body is the center axis of the roller body when it is assumed that a later-described taper taper is not formed.For example, when the shape of the first end surface is circular, it passes through the center of the circle. This is a straight line parallel to the peripheral surface of the portion including the main magnetic pole described later (A in FIG. 1A).

  The magnetic force of the main magnetic pole and the magnetic force of other magnetic poles can be measured using a known teslameter. In addition, the magnetic force of the main magnetic pole in a magnet roller or the magnetic force of another magnetic pole can be made into the magnetic force in the center of the axial direction of a roller main body. Alternatively, the magnetic force of the main magnetic pole or the magnetic force of another magnetic pole in the magnet roller may be another statistical value of the magnetic force in the axial direction of the roller body, such as a median value or an average value. The magnetic force of the main magnetic pole and the magnetic force of the other magnetic pole can be adjusted by the magnetic force of the magnetic pole itself or the roller radius of the portion including the magnetic pole in the circumferential direction of the roller body. The magnetic force is also reduced by reducing the roller radius.

  The magnet roller has a taper formed at a portion not including the main magnetic pole in the circumferential direction of the roller body. The draft taper is a shape in which the roller radius of the roller body gradually decreases from the first end face side of the roller body toward the second end face side. By forming the draft taper, the cross-sectional shape of the roller body gradually increases from the second end surface side toward the first opposite surface side. For this reason, it becomes possible to take out the magnet roller by pulling it out of the mold. Since the burr is not formed on the outer peripheral surface of the magnet roller in the magnet roller taken out in this way, the outer peripheral surface does not include burrs or traces of the burr processing.

  The taper angle of the drawing taper may or may not be constant. If the taper angle is too small, it is difficult to pull out the magnet roller from the mold, so that the yield rate of the magnet roller decreases, and if it is too large, the desired magnetic force may not be expressed. From such a viewpoint, the taper angle is preferably 0.1 to 2 °, more preferably 0.1 to 0.5 °, and more preferably 0.1 to 0.2 °. Further preferred. In addition, the taper angle of the drawing taper is an angle formed by the generatrix of the roller body where the drawing taper is formed when the magnet roller is viewed from the front with respect to the central axis of the roller body.

  One or more portions (portions including the main magnetic pole) where the draft taper is not formed in the circumferential direction of the roller body may be used. If the portion including the main magnetic pole is too small in the circumferential direction of the roller body, it may be insufficient to form the main magnetic pole, and if it is too large, the yield rate of the magnet roller may be reduced. From the above viewpoint, the central angle of the portion including the main magnetic pole in the circumferential direction of the roller body is preferably 1 to 75 °, and more preferably 20 to 60 °. When there are a plurality of main magnetic poles, the central angles may be the same or different.

  The draft taper may be formed over the entire length in the axial direction of the roller body, or may be formed in part. If the length of the taper taper in the axial direction of the roller body is too short, the yield rate of the magnet roller may be reduced. From such a viewpoint, the length of the draft taper in the axial direction of the roller body is preferably 50% or more, more preferably 90% or more with respect to the total length of the roller body.

  The thickness of the roller body is appropriately determined according to the use of the magnet roller. For example, in the case of the magnetic roller for the developing roller, the roller diameter of the roller body is preferably 5.5 mm or more, and preferably 10 mm or more from the viewpoint of realizing the mechanical strength required as the developing roller. Is more preferable. In addition, if it is a magnet roller of said use, it is preferable that the roller diameter of a roller main body is 30 mm or less from viewpoints, such as the size of a developing roller. The roller diameter refers to the roller diameter that is the shortest of the roller diameters due to the taper taper.For example, the roller diameter is the center in the axial direction of the roller body and is perpendicular to the central axis of the roller body and includes the main magnetic pole. Of the line segments from the surface to the peripheral surface of the portion where the draft taper is formed, it is represented by the shortest line segment (R in FIGS. 1A and 1C).

  The shape of the main magnetic pole portion on the outer peripheral surface of the roller main body may include an arbitrary shape such as a tapered shape within the range in which the scope of the present invention is obtained. As long as the range covered by the arbitrary shape is a range in which the magnetic force of the main magnetic pole is made substantially constant in the axial direction of the roller main body, it is the circumferential direction of the roller main body or a part of the axial direction in the portion including the main magnetic pole It may be present or the whole. Here, “substantially constant” means that the magnetic force of the main magnetic pole has a fluctuation range of 7% of the magnetic force relative to the magnetic force of the main magnetic pole in the axial center of the roller main body (the center of the roller main body). It is ± 7% of the magnetic force of the main magnetic pole.

  The magnet roller may further have a configuration other than the configuration described above as long as the effect of the present invention is obtained. For example, the magnet roller may further include a protrusion protruding from at least the second end surface of the rotor body. The protrusion may be provided only on the second end face, or may be disposed on both the first end face and the second end face. The protrusion is preferably disposed at the position of the central axis of the roller body on the first end surface or the second end surface from the viewpoint of reliably and easily disposing the magnet roller when configuring the developing roller.

  It is preferable that the projection includes a display unit indicating the position of the main magnetic pole in the circumferential direction of the roller body from the viewpoint of easily and surely arranging a developing roller described later at an appropriate position and orientation in the developing device. The display unit may be a symbol or a character drawn on the protrusion, or may be a three-dimensional structure. Examples of the symbols and characters include diagrams such as arrows and straight lines indicating the position of the main magnetic pole in the circumferential direction of the roller body. Examples of the three-dimensional structure include a notch portion formed corresponding to the position of the main magnetic pole in the circumferential direction of the roller body. The above three-dimensional structure is more preferable because a developing roller can be easily and reliably disposed at an appropriate position and orientation by disposing a positioning structure described later in a housing of the developing device described later.

A magnet roller according to an embodiment of the present invention is shown in FIG.
As shown in FIG. 1A, the magnet roller 10 has a substantially cylindrical roller body 12 having a first end surface 121 and a second end surface 122, a protrusion 14 protruding from the first end surface 121, and a protrusion from the second end surface 122. And a projection 16 to be formed. The roller body 12 and the protrusions 14 and 16 are integrally formed of the magnetic composition described above. The magnetic composition can be obtained, for example, by kneading a resin such as polyamide and magnetic particles such as ferrite or rare earth cobalt. The roller body 12 is formed by, for example, molding and magnetizing using a magnetic field injection molding machine that can form an arbitrary magnetic field around the mold. The content of the magnetic particles in the magnetic composition is determined according to the intended magnetic properties of the roller body 12. For example, if the magnetic property is 700 gauss or more in surface magnetic flux density, the content of the magnetic particles can be 85 to 90% by mass.

  The shape of the first end surface 121 is circular, the shape of the second end surface 122 is substantially circular, and the shape of the roller body 12 is substantially cylindrical. As shown in FIG. 1C, the roller body 12 includes a first portion 123 including a main magnetic pole and a second portion 124 including another magnetic pole in the circumferential direction of the roller body 12.

  The first portion 123 is a portion having an arc having the same size as a part of the circumference of the first end surface 121 in a cross section orthogonal to the central axis A of the roller body 12. The central axis A of the roller body 12 is a straight line that is at a distance of the radius of the first end surface 121 from the arc. The second portion 124 is a portion having an arc having a curvature larger than the circumference of the first end surface 121 in the cross section. The range of the central angle of the first portion 123 in the cross section is, for example, 60 °, and the range of the central angle of the second portion 124 in the cross section is, for example, 300 °.

  In the second portion 124, the roller radius of the roller body 12 gradually decreases from the first end surface 121 to the second end surface 122. In this way, the second portion 124 is formed with a draft taper 125. The taper angle of the extraction taper 125 is, for example, 0.2 °. Here, the taper angle refers to the maximum angle among the angles formed by the generatrix of the second portion 124 with respect to the central axis A of the roller body 12. In FIG. 1, the main magnetic pole is on the center line of the first portion 123 in the vertical cross section of the roller body 12, and the taper angle is set so that the taper angle intersects the center line of the roller body 12 and the roller in the second portion 124. This is an angle formed by the central axis A of the main body 12. That is, in FIG. 1, the draft taper 125 having the taper angle is represented by the upper side of the roller body 12 in FIG. 1A.

  The shape of the protrusion 14 is cylindrical. The central axis of the protrusion 14 is located at the center of the circle of the first end surface 121 and is the same as the central axis A of the roller body 12.

  As shown in FIGS. 1A and 1C, the protrusion 16 has a shape having a notch 161 at the tip of the cylindrical body. The notch 161 is a flat portion that is orthogonal to the center line of the first portion 123 described above. The cross-sectional shape of the portion including the notch 161 in the protrusion 16 is a shape of a portion having a larger arc when the circle is divided into two by a chord smaller than the diameter. The notch portion 161 faces the main magnetic pole side, and indicates that the main magnetic pole is disposed in a direction overlapping the perpendicular of the notch portion 161 in the circumferential direction of the roller body 12. That is, the notch portion 161 corresponds to a display portion including the above-described three-dimensional structure.

  Note that, as described above, the draft taper 125 may not be formed over the entire length of the roller body 12, and the taper angle of the draft taper 125 may not be constant. For example, the taper angle may change continuously or intermittently. Further, the protrusions 14 and 16 may be omitted. In this case, for example, one or more recesses may be provided in one or both of the first end surface 121 and the second end surface 122. Further, the notch 161 may be omitted. In this case, for example, an arrow indicating the position of the main pole may be drawn on the second end face 122, or a line indicating the position of the main pole may be drawn on the outer peripheral face of the protrusion 16.

  Since the magnet roller 10 is composed of the magnetic composition, it is more effective from the viewpoint of weight reduction than a magnet roller composed of magnetized iron or the like.

  Moreover, in the magnet roller 10, the roller main body 12 and the protrusions 14 and 16 are configured as an integrally molded product by injection molding. For this reason, the whole magnet roller 10 can be manufactured at once. Further, the three-dimensional structure of the display part is the notch part 161, and since it has such a simple shape, the structure corresponding to the notch part 161 in the mold is also simple and the cost of the mold is reduced. It can be suppressed. Therefore, it is effective from the viewpoint of manufacturing the magnet roller 10 easily and at low cost.

  By the way, in the developing roller, the magnetic force of the other magnetic pole is usually sufficiently smaller than the magnetic force of the main magnetic pole. It doesn't matter. As described above, the magnet roller 10 is a magnet roller for the developing roller. The magnet roller 10 has a taper 125 in the portion where there is no problem even if the diameter of the roller body 12 is reduced, that is, the second portion 124 of the magnet roller 10. doing.

  The second portion 124 includes magnetic poles other than the main magnetic pole, and the roller radius of the roller body 12 is equal to or less than the radius of the first end surface 121 and changes along the axial direction of the roller body 12. On the other hand, the roller radius in the first portion 123 including the main magnetic pole is the radius of the first end surface 121 and is constant in the axial direction of the roller body 12. Therefore, the magnetic force of the main magnetic pole is larger and constant than the magnetic force of the other magnetic poles. Therefore, the magnetic force of the main magnetic pole can be made uniform and large as compared with the magnet roller in which the main magnetic pole portion is also tapered.

  The magnet roller 10 further has protrusions 14 and 16. The protrusions 14 and 16 are more effective from the viewpoint of easily and reliably determining the position and orientation of the magnet roller 10 with respect to the sleeve when the developing roller is assembled.

  In addition, the magnet roller 10 further includes a notch 161. The notch 161 displays the position of the main magnetic pole in the circumferential direction of the magnet roller 10. Therefore, the magnet roller 10 further having the notch 161 is more effective from the viewpoint of accurately determining the position of the main magnetic pole in the circumferential direction by the protrusion 16 even when the roller body 12 is hidden.

  The notch 161 has a three-dimensional structure. Therefore, if there is a positioning structure corresponding to the notch portion 161 corresponding to the intended arrangement of the main magnetic pole, the magnet roller 10 can be easily arranged as expected without checking the position of the main magnetic pole. be able to. As described above, the notch 161 is more effective from the viewpoint of easily and reliably realizing the intended arrangement of the magnet roller 10.

[Manufacturing method of magnet roller]
The magnet roller can be manufactured by a manufacturing method including the following first to fourth steps.

  The first step is a step of injecting the magnetic composition containing magnetic particles and resin into the cavity from the gate of the mold. In the second step, a plurality of magnets are arranged along the axial direction of the cavity at a plurality of locations in the circumferential direction of the cavity in order to form a plurality of magnetic poles in the magnetic composition injected into the cavity. It is a process to do. The 1st process and the 2nd process should just be performed before the 3rd process mentioned below. The first step may be performed before the second step, may be performed after the second step, or may be performed simultaneously with the second step.

  As the mold, a mold as shown in FIGS. 2A and 2B is used. As shown in FIGS. 2A and 2B, the mold 20 includes a first mold 22 and a second mold 24. The first mold 22 has a cavity 221.

  The cavity 221 has a circular opening and a bottom having a substantially circular diameter, and a draft is formed in a part of the inner peripheral surface in the circumferential direction. The cavity 221 forms a space having the same shape as the roller body 12 described above. A main magnet 222 is disposed in a portion corresponding to the first portion described above. Moreover, the 2nd magnet 223 which has a magnetic force smaller than the magnetic force of the main magnet 222 is arrange | positioned at the part corresponding to the 2nd part mentioned above, for example. As described above, the main magnet 222 having the maximum magnetic force among the plurality of magnets is arranged in a portion other than the draft angle in the cavity 221.

  Magnets such as the main magnet 222 and the second magnet 223 may be permanent magnets or electromagnets. Due to the arrangement of the magnets, the magnetic particles in the magnetic composition are magnetized, and magnetic poles are formed in the magnetic composition. The strength (magnetic force) of the magnetic pole is adjusted by, for example, the magnetic force of a magnet arranged in the mold, such as the main magnet 222 or the second magnet 223, or the distance from the arranged magnet to the cavity 221. It is possible.

  A hole 224 for forming the protrusion 16 is further formed at the bottom of the cavity 221. The hole 224 is formed in a shape corresponding to the protrusion 16 in the magnet roller, that is, a shape forming the notch 161. The hole 224 has, for example, the hole 224 and is formed by fitting the third mold 26 that forms the bottom of the cavity 221 into the bottom of the first mold 22. Alternatively, the hole 224 may be formed by forming a recess or a hole directly in the first mold 22.

  The second mold 24 closes the opening of the cavity 221. The second mold 24 further has a recess 241 and a gate 28 in the center. The shape of the recess 241 is a cylindrical shape and corresponds to the protrusion 14 described above. The gate 28 opens at the bottom of the recess 241 and communicates the outside of the second mold 24 and the cavity 221 via the recess 241. Note that the gate 28 may be disposed in the first mold 22.

  The draft angle is such that the radius of the circle of the opening of the cavity 221 gradually decreases in accordance with the depth of the cavity 221 where the inner peripheral surface of the cavity 221 corresponds to the second part of the magnet roller 10. It is formed to have a shape.

  As shown in FIG. 2B, when the opening of the cavity 221 is closed with the second mold 24, the magnetic composition 29 is injected into the cavity 221 as shown in FIG. 2C. The injection of the magnetic composition 29 is performed according to the properties of the magnetic composition 29. For example, if the resin in the magnetic composition 29 is a thermoplastic resin, an injection molding apparatus is used for the injection. In this case, for example, the cylinder temperature is 265 to 295 ° C., and the injection pressure is 40 to 70 MPa.

  The third step is a step of solidifying the magnetic composition 29 injected into the cavity 221. The solidification condition of the magnetic composition 29 is performed according to the properties of the magnetic composition 29. For example, when the resin of the magnetic composition 29 is a thermoplastic resin, the solidification of the magnetic composition 29 is performed by cooling, and when the resin of the magnetic composition 29 is a thermosetting resin, Solidification of the magnetic composition 29 is performed by heating.

  The fourth step is a step of taking out the solidified magnetic composition 29 from the cavity 221. When the magnetic composition 29 is solidified, the second mold 24 is removed from the first mold 22. In the fourth step, the solidified magnetic composition 29 is pulled out from the opening of the cavity 221 as shown in FIG. 2D. The drawn magnetic composition 29 becomes the magnet roller 10 described above. The magnetic composition remaining on the gate 28 may be taken out integrally with the magnet roller 10 to form the above-described protrusions or discarded.

  In the above manufacturing method, the above-described magnet roller can be manufactured as one part by injection molding. Therefore, it is possible to manufacture the magnet roller at low cost.

  Further, the above manufacturing method uses a mold having a draft angle in a portion corresponding to a magnet other than the main magnet 222 such as the second magnet 223. For this reason, a punch taper is formed in a portion other than the main magnetic pole of the magnet roller, and it is possible to more easily and reliably take out the magnet roller formed by injection molding from the mold.

  For example, when the central angle in the circumferential direction of the first portion 123 including the main magnetic pole in the magnet roller 10 is 75 °, the frictional force between the magnet roller and the mold when the magnet roller is pulled out from the cavity 221 is It becomes 75 ° / 360 ° of the frictional force when pulling out the magnet roller that does not form the drawing taper, and is reduced to about 1/5.

  When the magnet roller 10 is pulled out from the mold, the second portion 124 where the taper taper is formed and the cavity 221 where the draft angle is formed, even if the magnet roller 10 is simply pulled out in the axial direction. The distance from the peripheral wall gradually increases. For this reason, the magnet roller 10 is moved away from the cavity 221 so as to form a slight gap not only between the gap on the second portion 124 side but also between the first portion 123 and the inner peripheral wall of the cavity 221. By pulling out, it is possible to further suppress the frictional force between the magnet roller 10 and the mold. In this case, it becomes possible to ensure the productivity of the magnet roller having a further reduced taper portion of the magnet roller 10 equivalent to the productivity of the magnet roller 10.

  As described above, the above manufacturing method can manufacture a magnet roller that can be used for higher-speed printing in an electrophotographic image forming apparatus with high productivity.

  In the above manufacturing method, the fact that the second mold 24 includes the gate 28 does not require the supply pipe of the magnetic composition 29 reaching the gate 28 around the first mold 22. This is more effective from the viewpoint of increasing the degree of freedom of magnet arrangement around the tee 221.

  In the manufacturing method, the first mold 22 further has a hole 224, and the second mold 24 further has a recess 241. Thus, since the mold 20 has a recess with respect to the cavity 221, it is more effective from the viewpoint of producing the protrusions together with the roller main body at a time.

  Moreover, the hole 224 further has a shape corresponding to the notch 161 as described above. The fact that the first mold 22 further has such a hole 224 is more effective from the viewpoint of manufacturing the above three-dimensional structure indicating the position of the main magnetic pole integrally with the roller body at a time.

[Development roller]
The developing roller according to the present invention has the magnet roller. As the developing roller, a known configuration in the developing roller can be adopted in addition to the magnet roller. A developing roller having the magnet roller 10 is shown in FIG.

  As shown in FIG. 3, the developing roller 30 includes the magnet roller 10 described above, a sleeve 32 that covers the outer peripheral surface of the magnet roller 10, and a first flange 34 that supports the sleeve 32 on the first end surface 123 side of the magnet roller 10. And a second flange 36 that supports the sleeve 32 on the second end surface 124 side of the magnet roller 10.

  The sleeve 32 is a nonmagnetic cylindrical body. The sleeve is, for example, an aluminum cylinder. The central axis of the sleeve 32 is the same as the above-described central axis of the magnet roller 10.

  The first flange 34 is a rotation support portion that rotatably supports the sleeve 32 relative to the magnet roller 10. For example, the first flange 34 is in contact with one end of the sleeve 32 and rotatably supports the protrusion 14 of the magnet roller 10. The first flange 34 protrudes from the flange toward the magnet roller 10, and is fitted into the sleeve 32 so as to be fitted into the sleeve 32. And a rotating shaft that protrudes outward from the flange and is connected to an external rotation driving unit.

  The second flange 36 is also a rotation support portion that rotatably supports the sleeve 32 relative to the magnet roller 10. For example, the second flange 36 abuts the other end of the sleeve 32, the flange through which the projection 16 of the magnet roller 10 passes, and the flange 32 protrudes from the flange toward the magnet roller 10, and is externally fitted to the sleeve 32 to rotate the sleeve 32. A support tube that is freely supported and a fixed tube that protrudes outward from the flange and is to be attached to the developing device. The notch 161 of the protrusion 16 penetrates through the tip of the fixed tube and protrudes further outward to be exposed.

  In the developing roller 30, the sleeve 32 rotates relative to the fixed magnet roller 10 by fixing the second flange 36 and rotating the first flange 34 connected to the rotation drive unit.

  The sleeve 32 is arranged coaxially with the magnet roller 10. For this reason, the sleeve 32 is spaced apart from the first portion 123 including the main magnetic pole in the magnet roller 10 at a constant interval. Therefore, a uniform magnetic field is formed by the main magnetic pole at a portion of the outer peripheral surface of the sleeve 32 facing the main magnetic pole.

  On the other hand, the sleeve 32 is gradually separated from one end toward the other end with respect to the second portion 124 including other magnetic poles in the magnet roller 10. Accordingly, a magnetic field in which the magnetic force gradually decreases from one end of the sleeve 32 toward the other end is formed by the other magnetic pole at a portion of the outer peripheral surface of the sleeve 32 facing the other magnetic pole.

  When the sleeve 32 is rotated relative to the magnet roller 10, an air flow is generated from one end of the sleeve toward the other end in the gap between the magnet roller 10 and the sleeve 32. The gap is narrower at the one end side in the axial direction of the sleeve 32, wider at the other end side, and narrower at the first portion and wider at the second portion in the circumferential direction of the sleeve 32. Therefore, the gap is narrowest at the first portion on the one end side. For this reason, the gap is pressurized by the air accompanying the rotating sleeve 32. As a result, in the gap, the internal pressure on one end side is higher than the internal pressure on the other end side, and the airflow is generated. Conceivable.

  As described above, the developing roller 30 can form a constant and stronger magnetic field on the sleeve 32 by the main magnetic pole.

  Further, since the developing roller 30 rotatably supports the magnet roller 10 on the first end surface 123 side of the magnet roller 10, the developing roller 30 generates an air flow upstream of the bearing portion of the magnet roller 10 in the sleeve 32. Can do.

  Further, when the developing roller 30 exposes the notch as the display portion from the tip of the second flange 36, the position of the main magnetic pole in the circumferential direction of the developing roller 30 is determined from the outside of the developing roller 30. Since it becomes possible, it is more effective.

  Further, the fact that the developing roller 30 includes the cutout portion having a three-dimensional structure means that the developing device in which the developing roller 30 is to be mounted adopts a positioning structure that uses the three-dimensional structure for positioning the developing roller 30. Since the arrangement of the developing roller 30 can be performed more easily and reliably, it is more effective.

[Developer]
The developing device according to the present invention includes the developing roller. In the developing device, a known configuration in the developing device can be adopted in addition to the developing roller. A developing device 40 having the developing roller 30 is shown in FIG.

  As shown in FIG. 4, the developing device 40 is housed in a housing 41, a developing roller 30 disposed in the opening of the housing 41, a transport roller 42 that transports the developer to the developing roller 30, and the housing 41. Agitating rollers 43 and 44 for agitating the developer, and a developing blade 45 for regulating the developer attached to the surface of the developing roller 30 are provided.

  The developing roller 30 is fixed to the housing 41 such that the notch 161 is directed toward the opening of the housing 41. The housing 41 has a substantially semicircular recess having the above-mentioned direction in which the tip of the protrusion 16 including the notch 161 is fitted. The recess may be a through-hole penetrating the housing 41, a recess formed in the wall surface of the housing 41, or may be configured by a peripheral wall surrounding the substantially semicircular portion. Good. By engaging the notch 161 at the tip of the protrusion 16 with the positioning structure such as the recess, the developing roller 30 is easily fixed at the intended position and orientation.

  The magnet roller 10 is disposed so that the main magnetic pole faces the opening. For this reason, the magnetic field 46 formed by the main magnetic pole is formed so as to protrude forward from the opening of the housing 41. When the developing device 40 is attached to the image forming apparatus, a magnetic field 46 is formed so as to enclose the developing area on the photoconductor 48.

  As described above, the developing device 40 forms a magnetic field having a uniform strength along the axial direction of the developing roller 30 because the first taper portion including the main magnetic pole of the magnet roller 10 is not formed with a taper. be able to. For the reasons described above, it is possible to form a stronger magnetic field toward the developing region as compared with the developing roller having a taper in the first portion. Therefore, higher speed development is possible.

  Further, as described above, in the sleeve of the developing roller 30, an air flow is generated from the first end surface side of the roller body, which is the bearing side of the magnet roller 10, toward the second end surface side as the sleeve rotates. . For this reason, it is possible to prevent the developer from entering the sleeve of the developing roller 30. Even when the developer enters the sleeve, it is difficult to stay and accumulate in the bearing portion due to the airflow. Therefore, since the rotational torque of the developing roller 30 (sleeve) is difficult to increase, the developing device 40 can be stably operated for a long time.

  In addition, such suppression of the increase in rotational torque can be achieved without adding new parts to the structure (the flange) that supports the sleeve in rotation. Therefore, the development device 40 having the development sleeve 30 is more effective from the viewpoint of providing the long-life development device 40 at a low cost.

  Further, the developing device 40 has the above-described positioning structure that engages with the protrusion 16 and the notch 161 exposed at the developing roller 30. For this reason, the developing roller 30 can be disposed in the developing device 40 in the intended position and orientation when the developing device 40 is disposed in the image forming apparatus, simply by engaging the tip of the protrusion 16 with the positioning structure. As described above, the developing device 40 having the positioning structure is more effective from the viewpoint of easily and reliably disposing the developing roller 30 at the intended position and orientation.

  The developing device 40 is a developing device for a two-component developer. However, in the present invention, a developing device for a one-component developer can be configured.

[Image forming apparatus]
An image forming apparatus according to the present invention includes the developing device. In the image forming apparatus, a known configuration in the image forming apparatus can be adopted in addition to the developing device. An image forming apparatus 50 having the developing device 40 is shown in FIG.

  The image forming apparatus 50 includes an image forming unit, an intermediate transfer unit, and a fixing device. The image forming apparatus 50 further includes an image reading unit and a recording medium transport unit.

  The image forming unit includes, for example, four image forming units corresponding to yellow, magenta, cyan, and black colors. The image forming unit includes a photosensitive drum 51, a charging device 52 for charging the photosensitive drum 51, an exposure device 53 for irradiating the charged photosensitive drum 51 with light to form an electrostatic latent image, and forming an electrostatic latent image. A developing device 40 that supplies toner to the photosensitive drum 51 and forms a toner image corresponding to the electrostatic latent image; and a cleaning device 54 that removes residual toner from the photosensitive drum 51.

  The photoreceptor drum 51 is, for example, a negatively charged organic photoreceptor having photoconductivity. The charging device 52 is, for example, a corona charger. The charging device 52 may be a contact charging device that contacts a charging member such as a charging roller, a charging brush, or a charging blade with the photosensitive drum 51 for charging. The exposure device 53 is composed of, for example, a semiconductor laser. The developing device 40 corresponds to the developing device according to the present invention described above. “Toner image” refers to a state where toner is gathered in an image form.

  The intermediate transfer unit includes a primary transfer unit and a secondary transfer unit. The primary transfer unit includes an intermediate transfer belt 61, a primary transfer roller 62, a backup roller 63, a plurality of support rollers 64, and a cleaning device 65. The intermediate transfer belt 61 is an endless belt. The intermediate transfer belt 61 is stretched in a loop shape by a backup roller 63 and a support roller 64. When at least one of the backup roller 63 and the support roller 64 is rotationally driven, the intermediate transfer belt 61 travels in one direction on the endless track at a constant speed.

  The secondary transfer unit includes a secondary transfer belt 66, a secondary transfer roller 67, and a plurality of support rollers 68. The secondary transfer belt 66 is also an endless belt. The secondary transfer belt 66 is stretched in a loop by a secondary transfer roller 67 and a support roller 68.

  The fixing device 70 includes a fixing roller 71, a heat generating belt 72, and a pressure roller 73. The heating belt 72 is an endless planar heating element for heating and melting the toner. The heat generating belt 72 is disposed so as to cover the outer peripheral surface of the fixing roller 71. The pressure roller 73 presses the sheet S conveyed to the fixing nip portion toward the fixing roller 71 and the heat generating belt 72. The paper S corresponds to a recording medium.

  The image reading unit includes a paper feeding device 81, a scanner 82, a CCD sensor 83, and an image processing unit 84. The recording medium transport unit includes three paper feed tray units 91 and a plurality of registration roller pairs 92. In the paper feed tray unit 91, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. The registration roller pair 92 is disposed so as to form an intended conveyance path.

Image formation by the image forming apparatus 50 will be described.
The scanner 82 optically scans and reads the document D on the contact glass sent from the paper feeding device 81. Reflected light from the document D is read by the CCD sensor 83 and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 84 and sent to the exposure device 53.

  On the other hand, the photosensitive drum 51 rotates at a constant peripheral speed. The charging device 52 uniformly charges the surface of the photosensitive drum 51 to a negative polarity. The exposure device 53 irradiates the photosensitive drum 51 with laser light corresponding to the input image data of each color component. Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 51. The developing device 40 visualizes the electrostatic latent image by attaching toner to the surface of the photosensitive drum 51. Thus, a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 51. The toner image on the surface of the photosensitive drum 51 is transferred to the intermediate transfer belt 61. The transfer residual toner on the photosensitive drum 51 is removed by the cleaning device 54.

  The toner image on the photosensitive drum 51 is transferred to the intermediate transfer belt 61 by bringing the intermediate transfer belt 61 into pressure contact with the photosensitive drum 51 by the primary transfer roller 62 and applying a transfer voltage to the primary transfer roller 62. To the intermediate transfer belt 61, the toner images of the respective colors formed on the respective photosensitive drums 51 are transferred so as to sequentially overlap.

  On the other hand, the secondary transfer roller 67 presses the secondary transfer belt 66 toward the backup roller 63 and presses against the intermediate transfer belt 61. Thereby, a secondary transfer nip portion is formed. On the other hand, the paper S is conveyed from the paper feed tray unit 91 to the secondary transfer nip portion via the registration roller pair 92. The registration roller pair 92 corrects the inclination of the sheet S and adjusts the conveyance timing.

  When the sheet S is conveyed to the secondary transfer nip, a transfer voltage is applied to the secondary transfer roller 67, and the toner image on the intermediate transfer belt 61 is transferred to the sheet S. The sheet S on which the toner image is transferred is conveyed to the fixing device 70 by the secondary transfer belt 66. The transfer residual toner on the intermediate transfer belt 61 is removed by the cleaning device 65.

  In the fixing device 70, the pressure roller 73 is pressed against the fixing roller 71 and the heat generating belt 72 when the paper S is conveyed, thereby forming a fixing nip portion. The sheet S is heated and pressed at the fixing nip portion. Thus, the toner image on the paper S is fixed on the paper S. The sheet S on which the toner image is formed is discharged out of the apparatus.

  The image forming apparatus 50 includes a developing device 40. Therefore, since a stronger magnetic field is uniformly formed in the axial direction of the developing roller, higher speed development is possible, and higher speed image formation is possible. Further, as described above, an increase in rotational torque in the developing device 40 is suppressed. For this reason, the lifetime of the developing device 40 becomes longer, and it is possible to further reduce the initial cost and running cost of the image forming apparatus that forms a high-quality image at high speed.

  In the following, the invention will be described in more detail with reference to examples. By the description of these examples, the present invention is not construed as being limited.

[Example 1]
A magnetic composition (TP-F66, manufactured by Toda Kogyo Co., Ltd.) is transferred from a gate to a cavity having a die draft as shown in FIG. Injection was performed using an injection molding machine J85AD manufactured by Nippon Steel.

  Next, the main magnets are arranged along the axial direction of the cavity on the outer peripheral side of the portion other than the draft angle of the cavity, and are substantially equidistant from each other including the main magnet in the circumferential direction of the cavity (positions of about 90 °). ), A second magnet, a third magnet, and a fourth magnet were respectively disposed. The magnetic force of the main magnet was 1200 mT (millitesla), the magnetic force of the second magnet was 1000 mT, the magnetic force of the third magnet was 1000 mT, and the magnetic force of the fourth magnet was 600 mT. Thus, the magnetic particles (ferrite) in the magnetic composition were magnetized, and the main magnetic pole, the second magnetic pole, the third magnetic pole, and the fourth magnetic pole were formed in the magnetic composition in the cavity.

Next, the mold was cooled to solidify the magnetic composition in the cavity.
And the solidified magnetic body composition in a cavity was extracted from opening of the 1st metal mold | die, and the magnet roller 1 in which the taper was formed from the 1st end of the roller main body to the 2nd end was obtained. The length of the magnet roller 1 was 220 mm, and the diameter of the circular first end surface of the magnet roller 1 was 10 mm. In the circumferential direction of the magnet roller 1, the central angle of the first portion that faces the main magnet and serves as the main magnetic pole is 20 °, and the other second magnet, the third magnet, and the fourth magnet face each other. The central angle of this part was 340 °. The taper angle of the first part of the magnet roller 1 (the angle formed by the lower generatrix of the roller body 12 with respect to the central axis A of the roller body 12 in FIG. 1A) is 0 °, and the taper angle of the second part (see FIG. The taper angle of the angle formed by the upper generatrix of the roller body 12 with respect to the central axis A of the roller body 12 at 1A was 0.2 °.

  Next, a cylindrical roller sleeve made of aluminum was placed on the magnet roller 1, and flanges serving as rotation support portions were disposed on both ends of the magnet roller 1 to produce a developing roller 1 as shown in FIG. 3. The sleeve had a diameter of 12 mm, and the distance between the first portion of the magnet roller and the inner peripheral surface of the sleeve was 0.4 mm.

[Comparative Example 1]
A magnet roller 2 is obtained in the same manner as in Example 1 except that a die having a 0.2 ° draft is formed from the opening to the bottom over the entire inner peripheral surface of the cavity of the die. It was. The taper angles of the first part and the second part of the magnet roller 2 were both 0.2 °. Next, a developing roller 2 was produced in the same manner as in Example 1. The distance between the first portion of the magnet roller 2 and the inner peripheral surface of the sleeve was 0.4 to 0.78 mm.

[Comparative Example 2]
A magnet roller 3 is obtained in the same manner as in Example 1 except that a mold having a draft of 0.5 ° is formed from the opening to the bottom over the entire inner peripheral surface of the mold cavity. It was. The taper angles of the first part and the second part of the magnet roller 3 were both 0.5 °. Next, a developing roller 3 was produced in the same manner as in Example 1. The distance between the first portion of the magnet roller 3 and the inner peripheral surface of the sleeve was 0.4 to 1.36 mm.

[Comparative Example 3]
The production of the magnet roller 4 was attempted in the same manner as in Example 1 except that a mold having a cylindrical cavity not including a draft was used. However, since no draft angle is formed on the inner peripheral surface of the cavity of the mold, the magnet roller 4 was damaged when pulled out from the mold. For this reason, the magnet roller 4 was not obtained.

[Evaluation]
(1) Measurement of magnetic force (1-1) Measurement of magnetic force in circumferential direction As shown in FIG. 6A, 0.1 mm away from the outer peripheral surface of the sleeve of each of the developing rollers 1 to 3 (reference numeral 30 in FIG. 6A). The magnetic probe 310 was arranged at the center in the axial direction of the sleeve, the developing roller was rotated, and the magnetic force in the circumferential direction of each of the developing rollers 1 to 3 was measured with a teslameter 320. The measurement results are shown in FIG. 6B. Further, the magnetic force (Tm) of the main magnetic pole in the measurement result was determined according to the following criteria. The magnetic force of the main magnetic pole is the maximum value of the magnetic force in the main magnetic pole. Tm is desirably 100 mT or more. Table 1 shows the measurement results and the determination results.
○: Tm is 100 mT or more Δ: Tm is 93 mT or more and less than 100 mT ×: Tm is less than 93 mT

(1-2) Measurement of the magnetic force of the main magnetic pole in the axial direction As shown in FIG. 7A, each of the developing rollers 1 to 3 (reference numeral 30 in FIG. 7A) is positioned 0.1 mm away from the outer peripheral surface. The magnetic probe 310 is moved from the first end side to the second end side of the roller body at the position of the main magnetic pole in the circumferential direction of the developing roller, and the developing roller of each main magnetic pole of the developing rollers 1 to 3 The magnetic force in the axial direction was measured with a Tesla meter 320. The measurement results are shown in FIG. 7B. Further, a value (ΔTm) obtained by subtracting the minimum value from the maximum value in the measurement result was obtained, and this value was determined according to the following criteria. ΔTm is desirably 7 mT or less. Table 1 shows the measurement results and the determination results.
○: ΔTm is 7 mT or less Δ: ΔTm is more than 7 mT and 10 mT or less ×: ΔTm is more than 10 mT

(2) Ease of injection molding (formability)
The above-described mold was set in an injection molding machine, and 100 shots of injection molding were continuously performed under the above-described molding conditions. The yield rate of the obtained magnet roller was obtained, and judged according to the following criteria. Table 1 shows the yield rate and determination results.
○: Good product rate is 99% or more ×: Good product rate is less than 99%

(3) Life of developing roller (durability)
In the sealed container, the sleeve of each of the developing rollers 1 to 3 (reference numeral 30 in FIG. 8A) is fixed, and as shown in FIG. 8A, the protrusion of the magnet roller is connected to the drive motor 340 via the torque sensor 330. Connected. A sufficient amount of developer was accommodated in the sealed container. Then, the drive motor 340 was rotated at 540 rpm for 2000 hours, and the rotational torque during that time was measured by the torque sensor 330. The measurement results are shown in FIG. 8B. Then, the rate of change of torque (torque increase rate) was obtained from the measured value of the rotational torque before and after the rotational drive, and this rate of change was determined according to the following criteria. The increase in rotational torque is desirably 5% or less. Table 1 shows the torque increase rate and the determination result.
○: Torque increase rate is 5% or less △: Torque increase rate is over 5%

  The magnet roller 1 can be obtained with a high productivity of 100% non-defective product because the taper is formed in the second portion including the second to fourth magnetic poles other than the main magnetic pole. Further, the magnet roller 1 has the largest roller radius in the main magnetic pole because the first taper including the main magnetic pole is not formed with a taper. For this reason, the magnetic force of the main pole can be maximized. When the developing roller 1 is used, a large magnetic force of the main magnetic pole is uniformly expressed in the axial direction of the developing roller. Therefore, it can be used for a developing roller for an image forming apparatus that forms an image at a higher speed.

  Furthermore, the developing roller 1 has a very low torque increase rate. As described above, this is because, as the sleeve rotates, an air flow is generated in the sleeve along the outer peripheral surface of the magnet roller from the first end surface side to the second end surface side of the magnet roller 1, and as a result. It is considered that the developer stays and accumulates in the bearing portion of the magnet roller while the developer continues to enter the sleeve.

  On the other hand, the magnet rollers 2 and 3 also have a high yield rate of 100% and high productivity. This is because the draft taper is formed over the entire circumference of the magnet roller. However, since the magnet rollers 2 and 3 are also formed with a taper in the first portion including the main magnetic pole, the roller radius of the main magnetic pole is from the first end surface side to the second end surface side of the magnet roller. The distance between the sleeve and the first portion of the outer peripheral surface of the magnet roller when the developing roller is gradually increased gradually increases. For this reason, the magnetic force difference (ΔTm) of the main magnetic poles in the axial direction of the developing rollers 2 and 3 is larger than the magnetic force difference of the developing roller 1. The difference in the magnetic force difference is more remarkable in the developing roller 3 having a larger taper angle of the drawing taper.

  Further, in the developing rollers 2 and 3, the torque increase rate is clearly higher than that of the developing roller 1. This is because, in the developing rollers 2 and 3, since the gap between the sleeve and the magnet roller is constant in the circumferential direction of the magnet roller, the air accompanying the rotating sleeve flows uniformly in the circumferential direction, As a result, it is considered that the pressure in the sleeve did not increase on the first end face side, and no air flow from the first end face side to the second end face side was generated.

  The magnet roller according to the present invention generates a high magnetic force and a uniform magnetic field in the axial direction of the magnet roller by integral molding. Therefore, the magnet roller can be applied to a developing roller of an image forming apparatus having a higher printing speed, and is expected to contribute to further spread of a high-speed and high-quality image forming apparatus.

DESCRIPTION OF SYMBOLS 10 Magnet roller 12 Roller body 14, 16 Protrusion 20 Mold 22 First mold 24 Second mold 26 Third mold 28 Gate 29 Magnetic body composition 30 Developing roller 32 Sleeve 34 First flange 36 Second Flange 40 Developing device 41 Housing 42 Conveying rollers 43 and 44 Agitation roller 45 Developing blade 46 Magnetic field 48 Photoreceptor 50 Image forming device 51 Photoreceptor drum 52 Charging device 53 Exposure device 54 and 65 Cleaning device 61 Intermediate transfer belt 62 Primary transfer roller 63 Backup roller 64, 68 Support roller 66 Secondary transfer belt 67 Secondary transfer roller 70 Fixing device 71 Fixing roller 72 Heating belt 73 Pressure roller 81 Paper feed device 82 Scanner 83 CCD sensor 84 Image processing unit 91 Paper feed Tray unit 92 Registration roller pair 121 First end surface 122 Second end surface 123 First portion 124 Second portion 125 Draw taper 161 Notch 221 Cavity 222 Main magnet 223 Second magnet 223
224 Hole 241 Recess 310 Magnetic probe 320 Teslameter 330 Torque sensor 340 Drive motor A Center axis of roller body D Document R Roller diameter of roller body S Paper

Claims (14)

A magnet roller configured as an integrally molded product with a magnetic composition containing magnetic particles and resin,
The magnet roller includes a roller body having a first end surface and a second end surface,
A plurality of magnetic poles formed along the axial direction of the roller body are respectively formed at different positions in the circumferential direction of the roller body,
The plurality of magnetic poles includes a main magnetic pole having a maximum magnetic force,
A portion of the roller body that does not include the main magnetic pole in the circumferential direction has a draft taper in which the roller radius of the roller body gradually decreases from the first end surface side to the second end surface side of the roller body. There is a magnet roller.   The magnet roller according to claim 1, further comprising a protrusion protruding from at least the second end surface of the roller body.   The magnet roller according to claim 2, wherein the protrusion includes a display unit that indicates a position of the main magnetic pole in a circumferential direction of the roller body.   The magnet roller according to claim 3, wherein the display unit includes a three-dimensional structure. The magnetic composition containing the magnetic particles and the resin has a circular opening and a substantially circular bottom, and a draft is formed in a part of the inner peripheral wall surface in the circumferential direction. A first step of injecting into the cavity from the gate of the mold;
A second step of disposing a plurality of magnets along the axial direction of the cavity at a plurality of locations in the circumferential direction of the cavity outside the cavity;
A third step of solidifying the magnetic composition;
A fourth step of taking out the solidified magnetic composition from the cavity, and a method for producing a magnet roller,
The mold includes a first mold including the cavity, a second mold for closing the opening of the cavity, the first mold or the outside of the second mold, and the cavity. The gate communicating with the tee,
The draft angle is formed in a shape in which the radius of the circle of the shape of the opening gradually decreases according to the depth of the cavity,
In the second step, the main magnet having the maximum magnetic force among the plurality of magnets is disposed in a portion other than the draft in the circumferential direction of the cavity,
In the fourth step, the solidified magnetic composition is pulled out from the opening,
Manufacturing method of magnet roller.   The method for manufacturing a magnet roller according to claim 5, wherein the second mold includes the gate.   The method for manufacturing a magnet roller according to claim 5 or 6, wherein at least the bottom of the cavity of the first mold further includes a recess.   The method of manufacturing a magnet roller according to claim 7, wherein the recess includes a shape that forms a three-dimensional structure that displays a position of the main magnet in a circumferential direction of the cavity.   The magnet roller according to any one of claims 1 to 4, a cylindrical nonmagnetic sleeve that covers an outer peripheral surface of the roller body of the magnet roller, and the sleeve can be rotated at both ends of the sleeve. A developing roller having a rotation support portion supported on the developing roller. The magnet roller further includes a protrusion protruding from at least the second end surface of the roller body,
The protrusion includes a display unit indicating a position of the main magnetic pole in the circumferential direction of the roller body,
The developing roller according to claim 9, wherein the display unit is exposed through the rotation support unit.   The developing roller according to claim 10, wherein the display unit includes a three-dimensional structure.   The developing device which has a developing roller as described in any one of Claims 9-11. The magnet roller further includes a protrusion protruding from at least the second end surface of the roller body,
The protrusion includes a display unit indicating a position of the main magnetic pole in the circumferential direction of the roller body,
The display unit is exposed through the rotation support unit and includes a three-dimensional structure;
The developing device according to claim 12, further comprising a positioning structure that fixes the developing roller at an intended position in a circumferential direction of the developing roller of the main magnetic pole by engaging with the three-dimensional structure. An image forming apparatus comprising the developing device according to claim 12.

Images