DE19622093A1 - Magnetic roll manufacturing process for electrophotographic equipment - Google Patents

Abstract

In a process for mfg. a magnetic roll, a resin bonded magnetic cpd. comprising a magnetic powder and binder is injected into a cavity (4) of a metal tool (20) to which a magnetic field is applied and the cavity vol. is simultaneously enlarged. In a more specific process tool cavity enlargement is effected by moving part (3) of the cavity wall as injection progresses. Also claimed are: (a) the magnetic roll which has a surface roughness of 20 mu m or less according to the LTIS 10 Point Roughness Scale, a test in which magnetic force is measured in a direction parallel to the axial direction at 1 mm intervals and the difference in magnetic force between adjacent points is 10 Gauss or less; (b) a developing roll for applying a developer onto a picture-carrying element which comprises the claimed magnetic roll, enclosed by a non-magnetic collar; (c) a developing unit including the claimed developing roll, opt. with a developer feed roll; and (d) a cleaning unit with a magnetic roll for removing the developer.

Description

The present invention relates to a magnetic roller, which in a development role, a cleaning role, a toner Carrier roll or the like is built in for one electrophotographic copier, a laser beam printer Fax machine or the like is used, and a method for their manufacture, as well as a developing device and a cleaning device that accommodate the magnetic roller.

An electrophotographic device or an electrostatic Recording device such as a copier or a Laser beam printer, is designed to ensure that a magnetic developing agent, namely a toner, that is supported by a development role electrostatic stored image that is pinned on an image bearing member such as a photosensitive member Drum, is formed, whereby the image is developed. The Development role includes a magnetic role that under Using a resin bonded magnet is formed and that in a rotating, non-magnetic sleeve is arranged; it carries the magnetic toner on them Way near the surface of the photosensitive Drum that the magnetic toner on the surface of the Sleeve spiky or how a thin layer is formed, then it develops an image by the toner in that  he brought into contact with the photosensitive drum is, or is caused by skip development, itself attach to the electrostatic stored image.

So far, the aforementioned magnetic roller has been manufactured by that a pelletized resin-magnet composition made from a thermoplastic resin binder such as nylon or Polypropylene, with a magnetic mixed in Powder such as ferrite Injection molding or extrusion using a Metal mold with a magnetic field generator, which around the Metal mold is arranged around, is shaped, whereby the Roll on a desired magnetic characteristic is magnetized. In this case the role is normal provided with waves at both ends; a single wave can be passed through the roller in the axial direction to create the waves at both ends, it can separate shafts can be provided at both ends, or the There are waves at both ends or a wave at one end integrally with a roller body using the Composition for the magnet glued with resin poured.

The manufacturing process for the magnetic roller, in which the Provide the metal mold with the magnetic field generator on the outside is used for injection molding as a magnetic field injection molding process designated. According to the magnetic field injection molding process, a melted resin-bonded magnetic material that in the first Line composed of resin powder and a binder is in the cavity of a two-piece metal mold injected, then a magnetic field around the outside Cavity of the magnetic mold is created around this magnetize, thereby producing the resin magnet. Then the metal mold is cooled to get out of the resin magnet manufactured magnetic roller to harden, and the shape will disassembled to the completed magnetic roll to take out.  

The manufacturing method for a magnetic roller based on the conventional magnetic field injection molding method will now be described with reference to FIG. 14. Has been Fig. 14 is a cross-sectional view of a resin-bonded material in a magnetic field-injection molding metal mold 100 is formed from Abdeckformhälften 101 and 102, injected, wherein a holding pressure has been applied thereto. A cavity 104 for the magnetic roller is formed by the cover mold halves 101 and 102 , approximately half of which lies in each of the two cover mold halves. The mold temperature is maintained at a fixed level by a cooling line (not shown). One of the cover mold halves 101 and 102 is fixedly attached to the injection molding machine for resin-bonded magnetic material (not shown), and the other cover mold half is mounted as a movable mold. A magnetic field generator 106 is provided adjacent to the metal mold 100 . The injection molding machine is equipped with a nozzle 105 .

As shown in FIG. 14, in order to cast the magnetic roller by the magnetic field injection molding method, the metal mold 100 is formed by clamping the fixed mold half and the movable mold half together with a parting plane 107 as a boundary, and a melted resin-bonded magnetic material 10 is injected through an injection port 102 A while a magnetic field is applied from the magnetic field generator 106 to the cavity 104 of the metal mold 100 , and thereby the resin-bonded material 10 is magnetized to cast the resin magnet. After the cooling time has elapsed, the metal mold 100 is opened and the magnetic roller manufactured from the resin magnet is removed.

The according to the conventional magnetic field injection molding process However, magnetic rolls manufactured from time to time  Defects, such as flow marks on their surfaces or Inflate in their central sections.

Fig. 15 is a typical explanatory diagram showing the flow marks and bubbles that occur in injection molding. These errors are likely to occur when a high viscosity molten resin is used for injection molding. When the viscosity of the molten resin is high, the molten resin 111 is shaped like a tape at the early stage of filling when injected into a metal mold 110 from the opening as illustrated in FIG. 15 (A). Finally, as schematically shown in Fig. 15 (B), the molten resin that has been injected in a ribbon shape is forced into the cavity in a compressed state. The molten resin 112, as the complicated bands has been formed is compressed and fused, resulting in the formation of a fusion mark 113, which is known as flow mark. Further, as schematically illustrated in Fig. 15 (A), when the ribbon-shaped molten resin is injected into the metal mold, air is sometimes trapped in the cavity at a point 115 between the entangled molten resin ribbons. The result is a bubble 116 in the finished casting, as shown in the cross section of Figure 15 (C). This is the bug known as the inner bubble.

Even if magnetic rollers are free from such errors, they tend to be more or in the longitudinal direction are less curved while in the axial direction should be straight. If a magnetic roller is curved, varies between the surface of the roller and the sleeve gap formed when a non-magnetic sleeve is put on will, according to the longitudinal position of the roll. Consequently the development role in which the curved magnet roll is installed, have a magnetic force characteristic that varies in the axial direction of the roll, resulting in a leads to unstable toner carrier function. The magnetic pole  The curved magnetic roll is often in the longitudinal direction twisted.

Thus, the magnetic rollers, which according to the conventional Procedures are made, many mistakes are made and more or less curved, which results in each magnet roll in the manufacturing process in terms of their curvature must be checked. This requires test equipment and Testing hours; those magnetic rollers whose curvature exceeds a tolerance are considered defective products discarded.

The present invention has been made to accomplish the above Solve problems in the prior art and it is one Object of the present invention, a manufacturing method to create the surface defects and / or noticeably decrease within the magnetic rollers and to reliably get magnetic rolls whose Such curvature has been kept under control is that it doesn't cause functional problems.

Another object of the present invention is to provide a Magnetic role and a development role to create that free are of curvature and which are a uniform magnetic Have characteristic in the axial direction.

The inventors have repeatedly carried out numerous experiments carried out to the cause of the bubbles in the core of a Magnetic roller, such mistakes as a flow mark on yours Surface or like its curvature for a magnetic roll find out which one using the conventional Magnetic field injection molding has been produced. The Inventors have found that these problems occur because the melted resin-bonded magnetic material that is in the mold is injected freely in the cavity of the metal mold can flow and first in an area where the magnetic force is strongest, starts to sit down and pile up.  

More specifically, begins when the melted resin-bonded Magnetic material under high pressure in the cavity of the Metal mold to which the magnetic field is applied is injected, the melted resin-bonded Magnetic material that has flowed through the injection port moving around in the cavity of the mold; however caused the magnetic field the melted resin-bonded Magnetic material, first on the cavity wall surface, which has a stronger magnetic force to pin and accumulate. At that time it changes as the strength of the Magnetic field in the cavity changes in the circumferential direction, that Pin and the accumulation of the resin-glued Magnetic material on the cavity wall surface also in the Circumferential direction.

Continuation of injection of the molten resin bonded magnetic material causes the melted resin-bonded magnetic material partially piles up, and also leads to part of it on the Cavity wall surface due to the cooling effect of the mold stiffens. This causes the resin-bonded Magnetic material starting at the outer peripheral surface and then deposited and shaped towards the axis of the magnetic roller becomes. This means that the resin-bonded magnetic material not uniform in weight in the magnetic roller cavity is filled in and the molecular orientation of the Binder is non-uniform. Hence such occur Defects such as bubbles in the central surface of the magnetic roller or will such errors as flow marks on the External surface created.

The filling process of the resin-bonded magnetic material, the previously described is also responsible for one in the circumferential direction uneven heat development of the resin glued magnetic material on the outer surface of the Magnetic roller, which in turn leads to a circumferential direction  uneven shrinkage of the outer surface of the magnetic roller leads. The uneven shrinkage is partly responsible for the curvature of the magnetic roller in the longitudinal direction.

The problem with the conventional magnetic injection molding process can be attributed to the fact that the melted resin-bonded magnetic material that is in the cavity of the mold has been injected under the influence of the magnetic forces can move freely. It was because of that considered the possibility of errors occurring in the central section as well as on the surface of the Magnetic roller and also to control the curvature in that the cavity of the metal mold with the resin-glued Magnetic material is filled uniformly and tightly.

The present invention has been achieved through this knowledge of Problems with the conventional manufacturing process for Magnetic rollers and likewise through efforts to cause determine made; and their goals are achieved by the volume of the mold cavity is made variable and the free movement of the resin-bonded magnetic material in the Cavity is restricted, creating a uniform and tight filling of the resin-bonded magnetic material into the Cavity is enabled.

In particular, the manufacturing process for a Magnetic roller according to the present invention, the resin glued magnetic material filled while the volume of the Cavity is enlarged, whereby a molten resin glued magnetic material that primarily consists of magnetic powder and a binder is injected into the cavity of a metal mold, while a magnetic field is applied to it.

The volume of the cavity can be increased in that at least part of the wall surface of the cavity is movable is designed. More specifically, after the start of  Injection of the resin-bonded magnetic material that moving surface towards enlarging the Volume of the cavity moves while the injection of the resin-bonded magnetic material is continued.

Then with the injection of the resin-bonded magnetic material to begin when the volume of the mold cavity is at smallest prevents the first flow of resin glued magnetic material scattered in the cavity, and allows the resin-bonded magnetic material to do so is filled in that the cross section of the cavity from the Side of the injection port is completely filled.

The movable surface is from the injection port of the Metal mold moved away while the resin-glued one Magnetic material is filled. The moving surface is bonded by the flow pressure of the injected resin Magnetic material moves. At that time prevented one Press the movable surface towards one Reduce the void volume using a Pressure device, such as an air cylinder or one Coil spring that the volume the injection amount of resin bonded magnetic material exceeds. Also allows if the moving shape is under the flow pressure of the resin glued magnetic material along the mold wall surface moved, a support of the movable form by the Pressing device while the magnetic resin material is injected that a suitable balance between the injection quantity of resin-bonded magnetic material and the Increase in void volume is maintained.

According to the present invention, the volume of the Mold cavity only by the volume corresponding to the increase the amount of resin-bonded magnetic material injected elevated; therefore the resin-bonded magnetic material uniform and dense all the way to the center of the Mold cavity are injected. This prevents the  Core of the completed magnetic roll bubbles or others Contains imperfections and also prevents their Surface has flow marks or other imperfections.

Furthermore, the heat development of the resin-bonded Magnetic material on the outer surface of the magnetic roller in Circumferential direction uniform, resulting in a uniform Shrinkage leads in the circumferential direction. This minimizes the Possibility that the magnetic roller in its longitudinal direction is curved.

The surface roughness of the magnetic roller according to the present invention is 20 µm or less according to one JIS 10-point average roughness scale Rz (JIS B0601- 1982). If the magnetic force of the magnetic roller in Intervals of 1 mm in the direction parallel to their axis is measured, the difference in magnetic Force between neighboring points 10 gauss or less. The magnetic roller, such a minor Surface roughness value and such a uniform one has magnetic property along its axis not manufactured using the conventional manufacturing process will; it is only with the present invention that it becomes possible a magnetic roller with the above desired To provide characteristic.

The term "surface roughness Rz" used here denotes a 10-point average surface roughness according to JIS B0601-1982. The terms "surface roughness, profile, reference length of the profile, roughness curve, cut value, profile center line, profile mountain and profile valley" are used as defined in the standard. In Fig. 16, the 10-point mean roughness is the difference value, expressed in micrometers (µm), between the mean of the heights of the peaks from the highest to the fifth highest peak, measured in the direction of the vertical height from a straight line a, which is parallel runs to the center line and does not intersect the profile, and the mean of the heights of the valleys from the deepest to the fifth deepest valley, within a sample section whose length corresponds to the reference length, for the profile. The profile can e.g. B. be represented by means of a test measuring device.

The 10 point mean roughness Rz is due to the following Given equation:

Rz = [(R₁ + R₃ + R₅ + R₇ + R₉) - (R₂ + R₄ + R₆ + R₈ + R₁₀)] / 5

where R₁, R₃, R₅, R₇ and R₉ are the heights of the peaks from the highest up to the fifth highest peak for the rehearsal section corresponding to the reference length L, and R₂, R₄, R₆, R₈ and R₁₀ the heights of the valleys from the deepest to the fifth deepest Valley for the sample section corresponding to the reference length L are. The reference length L varies with the range of the 10-point medium roughness Rz and also corresponds to the standard. For example, L = 0.25 mm if Rz <0.8 µm, L = 0.8 µm, if 0.8 µm <Rz 6.3 µm, L = 2.5 mm, if 6.3 µm <Rz 25 µm etc.

The gastric roll is able to be uniform to generate magnetic force in their axial direction without that it is required the external dimensions of the Magnetic roller by grinding, cutting or another type to rework the processing. Therefore, the Use of the magnetic roller as a development role for a Development device the training of good pictures.

The magnetic roller according to the present invention is ideally as the magnetic role that is the development role the cleaning roller or the toner supply roller Copier, printer, or other electrophotographic device or electrostatic Forms recording device used.  

For example, the magnetic roller is according to the present Invention best for the development role or the Development agent feed roll in one Suitable development device that is an electrostatic stored image on an image carrier element has been trained using a Developed developing agent so as to make the image visible do. The developer feed roll is along with the development role in the developing device arranged and it supplies toner to the development roller.

The magnetic roller of the present invention can conveniently as a magnetic roller for use in a Cleaning device for removing developing agents used, which remains on an image carrier, after a formed on the image carrier electrostatic image from the developing agent transferred to a transfer material as a visible image has been. In the cleaning device Cleaning roller that includes a magnetic roller used to collect toners with magnetic force, after the one on the image carrier, such as one photosensitive drum, remaining toner with a Cleaning blade has been scraped. In this case the magnetic roller on one for collecting the toner appropriate position, the toner is at the magnetic role adsorbed by magnetic force and the Toner is removed from the magnetic roller at a predetermined Position scraped by the blade so that the toner from a predetermined toner collecting unit is collected. The Cleaning roller is also used as a roller for removing toner remaining on an image carrier is used by a magnetic force is applied to or around the toner Remove the toner with a cleaning blade facilitate.

Brief description of the figures

Fig. 1 is a cross-sectional view illustrating an example of a metal mold for injection molding magnetic field, which is used in the method according to the present invention;

Fig. 2 is a cross-sectional view of the metal mold for magnetic field injection molding during the application of a holding pressure;

Fig. 3 is a cross-sectional view of a magnetic roller made in one piece with a shaft;

FIG. 4 (A) to (C) is a cross-sectional view to illustrate the structure of the magnet roller;

Fig. 5 is a schematic cross-sectional view of a development roller;

Fig. 6 is a cross-sectional view illustrating another example of a metal mold for injection molding magnetic field, which is used in the method according to the present invention;

Fig. 7 is a cross-sectional view illustrating still another example of a metal mold for injection molding magnetic field, which is used in the method according to the present invention;

Fig. 8 is a cross-sectional view illustrating further another example of a metal mold for injection molding magnetic field, which is used in the method according to the present invention;

Fig. 9 is a cross sectional view illustrating the metal mold for magnetic field injection molding while the magnetic roller is being molded;

Fig. 10 is another cross-sectional view illustrating the metal mold for injection molding magnetic field, while the magnetic roller is poured;

Fig. 11 is a schematic diagram of a copier;

Fig. 12 is a schematic explanatory diagram of a developing device;

Fig. 13 is a schematic explanatory diagram of a cleaning device;

Fig. 14 is a cross sectional view of a metal mold in which a conventional magnetic roller is cast;

Fig. 15 (A) to (C) is an explanatory diagram for a flow mark and a bladder;

Fig. 16 is a roughness profile for explaining a 10-point average roughness Rz illustrated in accordance with JIS B-0601.

The preferred embodiments of the present invention are described below with reference to the accompanying drawings explained.

Fig. 11 is a schematic diagram for explaining an exemplary copier having an electrophotographic system incorporating the developing device of the present invention and a cleaning device. This copier comprises a cylindrical photosensitive drum 61 which rotates in the direction shown by an arrow, and a primary charger 62 , a light source 63 for image exposure, a developing device 65 , a transfer device 66 and a cleaning device 67 , all around the photosensitive drum 61 are arranged around. The photosensitive drum 61 is charged by the charger 62 with several hundred volts, and an image of an original illuminated by the light source 63 is formed on an image exposure section. Due to this image exposure, a surface charge selectively disappears and an electrostatic image is formed on the photosensitive drum 61 . The developing device 65 attaches toner to the electrostatic stored image formed on the photosensitive drum 61 to make it visible. The visible image formed from the toner is transferred from the transfer device 66, which electrically charges the transfer paper 68 from its rear side on the transfer paper 68th A toner image transferred to the transfer paper 68 in this way is fixed on the transfer paper 68 by a fixing device 69 . The toner remaining on the photosensitive drum after the image transfer by the transfer device 66 is removed from the cleaning device 67 , and the photosensitive drum having a clean surface is in turn charged by the primary charger 62 with a predetermined voltage. So exposure and development are repeated.

Fig. 12 is a schematic diagram illustrating an example of a developing device 65. In a housing 75 of the developing device 65 are a toner carrier roller 71 for conveying magnetic toner from a toner chamber, a developing roller 72 for conveying the toner which has been conveyed out of the toner carrier roller 71 to the surface of a photosensitive drum 61 around it attached to an electrostatic stored image and a doctor blade 73 to keep the thickness of a layer of magnetic toner on the developing roller 72 constant. The toner carrier roller 71 is a shellless magnetic roller; and the developing roller 72 is a magnetic roller provided with a non-magnetic sleeve on the outside. The developing roller 72 , the photosensitive drum 61 and the toner carrying roller 71 each rotate in the directions indicated by arrows in the drawing to convey the magnetic toner from the toner carrying roller 71 to the surface of the developing roller 72 . The toner is formed into a thin layer of uniform thickness by the doctor blade 73 , and the thin layer of toner is conveyed onto the surface of the photosensitive drum 71 to which the toner adheres to the electrostatically stored image.

Fig. 13 is a schematic diagram showing an example of the cleaning device 67. A cleaning blade 92 made of an elastic material such as urethane rubber, a cleaning roller 93 made of a magnetic roller, and a doctor blade 94 to keep the thickness of a layer 95 of magnetic toner on the cleaning roller 93 constant hold, are arranged in the housing 91 of the cleaning device 67 . The toner remaining on the photosensitive drum 61 is removed by the interaction between the toner and the layer 95 of magnetic toner on the cleaning roller 93 , or its adhesion to the surface of the photosensitive drum is weakened. The photosensitive drum 61 is covered with a layer of magnetic toner by contact with the layer 95 of magnetic toner. The layer of magnetic toner covering the photosensitive drum 61 is removed from the cleaning blade 92 along with the remaining toner. The toner thus removed is discharged into a collecting device (not shown).

Figs. 1 and 2 are cross-sectional views to be used in the manufacture of the magnet roller of an exemplary form of the magnetic field-injection molding. Fig. 1 shows the injection operating state of a molding cycle, and Fig. 2 shows the pressure-holding mode.

The mold 20 for magnetic field injection molding consists of a fixed mold 1 for forming a cavity 4 , a fixed mold 2 and a movable mold 3 . The movable mold 3 is made as a cylindrical body made of a metal or a resin and on the outer surface at least one O-ring is 3 E is provided which is made of rubber or the like to the discharge of molten magnetic to prevent resin material. The fixed molds 1 and 2 are each provided on the outside with a magnetic field generating device 6 in order to apply a magnetic field to the entire cavity 4 or to a part thereof. With a parting plane 7 , which serves as a boundary line between the movable and fixed sections of an injection molding machine (not shown), the fixed mold 1 is attached to the movable section of the injection molding machine and the fixed mold 2 is attached to the fixed section of the injection molding machine. A cooling line (not shown) for controlling the temperatures of the molds is built into the injection molding machine, so that the temperatures of the mold 1 and the mold 2 are preferably kept at 100 ° C to 110 ° C. An injection port for injecting a 2 A magnetic resin material, which communicates with the nozzle 5 in the injection molding compound is provided above the molds 1 and 2. FIG.

. With reference to Figure 1, 3 forms a movable mold part of the wall surface of a cavity 4; it has cavity wall surface sections 4 B, 4 C and 4 D for the magnetic roller. The movable mold 3 can slide freely in the vertical direction along a mold wall surface section 4 E, which is formed by the cover mold halves 1 and 2 . The rear end of the movable mold 3 is connected to a slide rod 3 A, which is pressed by an air cylinder 21 to the injection opening 2 A. The pressing force output from the air cylinder 21 is set to approximately 5 kgf when the injection pressure of a resin-bonded magnetic material is 500 kgf, for example.

The resin-bonded magnetic material is prepared by mixing and kneading a binder and magnetic powder and molding the mixture into pieces. The following can be used as binders: Nylon 6 , polystyrene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), PPS, EVA, EEA, EVOH, polypropylene, polyethylene, polyethylene copolymer or another polyolefin or a modified polyolefin, which is introduced by introducing a reactive functional group, such as a maleic anhydride group, a carboxyl group, a hydroxyl group or a glycidyl group, in the structure of the polyolefin.

The mixing quantity of the binder is not limited, however, binder will usually be from about 8% by weight to about 40 wt .-% used (in particular 10 to 20 wt .-%).

Can be used as a magnetic powder in this embodiment Magnetic commonly used for resin magnets Powders are used; Examples include barium ferrite, Strontium ferrite or other ferrites, an alloy of sm Co type, an Nd-Fe-B type alloy or others "Rare earth" type alloys. There are no special ones Limitations on the mixing quantity of the Magnetic powder; it will suitably correspond to the magnetic property required for the magnetic roller fixed, but usually ranges from 60% by weight to 92 % By weight of the total resin-magnet composition, in particular from about 80% to about 90% by weight.  

If necessary, a filler with a large reinforcing effect, such as mica, whisker crystal, Talc, carbon fiber or glass fiber, the resin magnet Composition in addition to the binder and magnetic powder can be added. More specifically, if required a relatively low magnetic force of the cast and the amount of magnetic powder, such as Ferrite, is low, then the strength of the resulting cast be small; therefore such Fillers such as mica or whisker crystal are added to increase the strength of the cast.

In this case, mica or whisker is conveniently called Filler used. For whiskers, the following may be preferred become: a whisker on an oxide-free basis that is made of Silicon carbide, silicon nitride etc. is composed, or a whisker based on metal oxide consisting of ZnO, MgO, TiO₂, SnO₂, Al₂O₃ etc. is composed, or a whisker a complex oxide base made from potassium titanate, Aluminum borate, chlorinated magnesium sulfate etc. is composed. Among these, whisker is on one complex oxide base particularly suitable for the objective, because it has good compatibility with plastics.

There are no particular restrictions on the Mixing ratio for the filler, but it is enough typically from 2% to 32% by weight of the total resin Magnetic composition, most typically from about 5% by weight to about 20% by weight.

The method of filling the cavity 4 with the molten resin-bonded magnetic material while the movable die 3 is moving will now be explained.

When a metal mold is clamped 20 to the magnetic field-injection molding, the movable mold 3 is disposed along the mold wall surface portion 4 E to the injection opening 2 A way such that they by the pressing force applied by the air cylinder 21 via the slide bar 3 A, in protrudes into a cavity 14 of the metal mold; the cavity wall surface portion 4 B of the movable die 3 is almost in contact or is in contact with the cavity wall surface portion 4 B of the die halves 1 and 2 . Therefore, the volume of the cavity 4 in the state in which the slide rod 3 A is acted upon by the air cylinder 21 is equal to the volume of the cavity that of the cavity wall surface portion 4 C of the solid mold halves 1 and 2 and the cavity wall surface portions 4 C and 4 D of the movable form 3 is formed. This volume is essentially the smallest.

As shown in Fig. 1, from the state described above, the magnetic field generator 6 is operated to apply a predetermined magnetic field, and the molten resin-bonded magnetic material 10 is injected into the nozzle 5 through a nozzle 5 as indicated by an arrow A. Injected cavity, which is formed by the cavity wall surface sections 4 B, 4 C and 4 D of the form 3 . The flow pressure F of the molten resin magnetic material 10 is received by the cavity wall surface portions 4 B, 4 C and 4 D of the movable die 3 .

The continued injection of the molten resin-bonded magnetic material 10 further increases the flow pressure; in response to the increase in flow pressure, ie the increase in molten material, the movable die 3 begins to move backwards as it moves over the through the increase in the volume of the molten material in the opposite direction to the direction of the pressing force, ie in FIG Slide rod 3 A is in balance with the pressing force of the air cylinder 21 . Thus, the area of the cavity wall surface portion 4 A gradually increases. The continuation of the injection of the molten resin and the simultaneous backward movement of the movable mold enables the resin-bonded magnetic material 10 to be filled uniformly and tightly into the cavity of the mold, as shown in FIG .

During the molding process, the resin-bonded magnetic material 10 is magnetized into a resin magnet by the applied magnetic field. By cooling the mold halves 1 and 2 at a constant rate, a magnetic roller 12 is cast, which is composed of the resin magnet. After a predetermined period of time, the metal mold 20 is divided to take out the one-piece shaft magnet roll 12 which has been cast as shown in FIG. 3. The magnet roller 12 shown in FIG. 3 includes shafts 26 A and 26 B at both ends of a magnetic body 25, the magnet composition resin have been integrally molded with the magnetic body 25 by using the.

The shaft section of the magnetic roller can be a metal core which passes through the roller magnetic body 25 in the axial direction, or it can be formed from metal shafts 28 A and 28 B which do not pass through the magnetic body 25 but are embedded in such a way that they As shown in Fig. 4 (B), protrude from both ends of the magnetic body 25 in the axial direction. As a further alternative, as illustrated in FIG. 4 (C), one shaft 29 A can be cast integrally with the magnetic body 25 , while the other shaft 29 B can be a metal shaft that is embedded in the magnetic body 25 . These shafts 26 A, 26 B, 27 , 28 A, 28 B, 29 A and 29 B can be provided with drive gears to rotate the roller.

The inventors compared the performance of the magnetic roller made using the metal mold 20 for magnetic field injection molding shown in FIGS. 1 and 2 and using the method according to the present invention with the performance of the magnetic roller using the 14, the metal mold 100 shown in Fig. 14 for magnetic field injection molding and manufactured using the conventional method.

12% by weight of nylon 6 was used as binder; and 88 wt% of Sr ferrite was used as the magnetic powder in the resin-bonded magnetic material. The nylon 6 and the resin-bonded magnetic material were melted and mixed by a kneader, and the mixture was molded into preforms by extrusion molding.

The preform was injected into the metal mold 20 shown in FIGS. 1 and 2 around which a magnetic field generator was provided to be magnetized in a 4-pole magnetic force scheme composed of S1, N1, S2 and N2. A magnetic roller measuring 17.5 mm in diameter of the magnetic body and 304 mm in length was produced. The injection conditions were as follows: the cylinder temperature was 280 ° C, the casting temperature was 100 ° C and the injection pressure was 700 kg / cm².

Another preform, as described above, was injected into the conventional metal mold 100 shown in FIG. 14 around which the magnetic field generator was provided to be used in the four-pole magnetic field scheme composed of S1, N1, S2 and N2. to magnetize. So a magnetic roller was made for comparison; it measured 17.5 mm in diameter of the magnetic body and 304 mm in length. The same casting conditions were used.

The results of the measurement of the properties according to the Present invention manufactured magnetic roller and Properties of according to the conventional method Magnetic rolls produced are shown in Table 1. Of the Ripple value in the table shows the maximum difference  in the magnetic force between neighboring points when the magnetic force of the pole S1 of the magnetic roller is in Intervals of 1 mm measured along the axis of the roll becomes. The curvature is based on the difference between that Maximum value and the minimum value that was measured when the Roll was rotated with a dial gauge on the central section of the magnetic body and the shafts on both Ends of the magnetic roller were stored. The Standard deviation values of ripple and curvature given in the table are from the Standard deviation values of ripples and curvatures, which have been observed in batches of 50 magnetic rolls, where each of the batches are made according to the particular process has been. Rz (µm) denotes the 10 point Average roughness measured according to the JIS standard, namely JIS B0601-1982. Out of roundness describes the Difference between the maximum radius and the minimum Radius in a cross section perpendicular to the axis of the Magnetic body has been observed. The runout is zero in the case of an ideal cylindrical shape; the stronger the Shape deviates, the greater the value of the out-of-roundness.

The surface roughness Rz of the inner surface of the mold was 1.0 µm. The surface roughness of the magnetic roller of the Comparative example could not be found because a Flow mark was formed on the surface.

Table 1

As shown in Table 1, the ripple value is that Curvature, the surface roughness Rz and the out-of-roundness of the Magnetic roller manufactured according to the present invention remarkably smaller than the magnetic roll of the Comparative example. It also goes from the Standard deviation values of ripple and curvature shows that the method of the invention, the production of magnetic rollers enables more homogeneous characteristics have than the magnetic rollers using the conventional method have been produced.

Using the magnetic roller manufactured in accordance with the present invention, a developing roller was manufactured which is used for the developing section in an electrophotographic copier or a laser beam printer. A developing roller 50 has a structure shown in the cross-sectional view in FIG. 5, wherein an aluminum cylinder or a sleeve 51 is arranged with a small space provided between the sleeve and the magnetic roller 25 , and side plates 52 A and 52 B, which are made of a non-magnetic material, are attached via fastening portions 54 A and 54 B at their ends. The sleeve 51 is rotatably mounted on the shafts 26 A and 26 B of the magnetic roller 25 via bearings 53 A and 53 B. The shaft 26 A of the magnetic roller runs through the side window 52 B. The side window 52 A is provided with a shaft 55 .

The developing roller 50 is mounted on the developing portion of a copier or a laser beam printer by fixing the shaft 26 B of the magnetic roller 25 and by rotating the shaft 55 of the side plate. The sleeve 51 rotates relative to the attached magnetic roller 25 to convey the magnetic toner held on the surface of the sleeve and to adhere it to an electrostatically stored image on a photosensitive drum.

Used as this development role for development a good image was created that was free of Vertical stripe is the variation of magnetic force are attributed in the axial direction.

In the metal mold for magnetic field injection molding shown in FIGS. 1 and 2, a helical spring 8 , as shown in FIG. 6, can be used instead of the air cylinder as a device for pressing on the movable mold. In this case, the slide rod 3 A, which is connected to the rear end of the movable mold 3 , is slidably supported in a sleeve 9 which is built into the mold half 2 , and the end of the slide rod 3 A is held by the coil spring 8 , which acts on the movable mold 3 .

Fig. 7 is a cross-sectional diagram for illustrating another example of the metal mold for injection molding magnetic field, which is used in the inventive method. In this example, a metal mold 30 is provided with a plurality (two in Fig. 7) of movable mold counterparts made of columnar objects made of metal, resin, etc.; it is designed so that movable mold counterparts 3 B, 3 C move mirror-symmetrically with respect to the injection opening 2 A, in an equidistant manner forward or backward. The rear ends of the movable mold counterparts 3 B and 3 C are connected to the slide rods 3 A and the ends of the slide rods 3 A are held by coil springs 8 .

When the metal mold 30 composed of the fixed mold counterparts 1 and 2 is clamped together, the movable mold counterparts 3 B and 3 C are pressed by the coil springs 8 in the direction in which they approach each other and the volume of the cavity 4 is minimal. Under this condition, the magnetic field generator 6 is operated to apply a predetermined magnetic field, and a molten resin-bonded magnetic material is injected into the cavity 4 of the metal mold 30 through the nozzle 5 . The flow pressure of the molten resin-bonded magnetic material is taken up by the cavity wall surfaces of the movable mold counterparts 3 B and 3 C. Continued injection of the molten resin-bonded magnetic material further increases the flow pressure; in response to the increase in flow pressure, that is, the increase in molten resin-bonded magnetic material, the movable mold counterparts 3 B and 3 C move in the opposite direction to the pressing force, that is, in the lateral direction, by the increase in volume of the molten resin-bonded magnetic material in Fig. 7, back while they are on the slide rod 3 A in balance with the pressing force of the coil spring 8 .

Thus, the continuation of the injection of the molten resin-bonded magnetic material and the simultaneous backward movement of the movable mold counterparts 3 B and 3 C enables the resin-bonded magnetic material to be filled uniformly and tightly into the cavity. During the casting process, the resin-bonded magnetic material is magnetized into a resin magnet by the applied magnetic field. By cooling the mold counterparts 1 and 2 at a constant rate, a magnetic roller consisting of the resin magnet is cast. After a predetermined time, the metal mold 30 is divided to take out the one-piece shaft magnet roll 12 which has been cast as shown in Fig. 3.

In Fig. 7, coil springs 8 are used as means for pressing the movable mold counterparts 3 B and 3 C; however, other pressing devices, such as an air cylinder, can be used in place of the coil springs.

Figs. 8, 9 and 10 are cross-sectional views showing another example of the metal mold for injection molding magnetic field illustrate, which is used for the inventive method. A metal mold 40 is used in this example to manufacture a magnetic roll that is made in one piece with a shaft by the roll-shaped magnetic body 25 made of a resin-bonded magnetic material and the metallic core 27 as in FIG. 4 (A) shown as a piece being cast. Fig. 8 shows the cross section of the metal mold for magnetic field injection molding, the metal mold being clamped together; FIGS. 9 and 10 show the cross section of the metal mold while watching the magnet roller is poured.

The metal mold 40 for magnetic field injection molding is constructed from the fixed mold half 1 , the fixed mold half 2 and the movable mold 3 , which form the cavity 4 . At the time of clamping, the fixed mold half 1 and the fixed mold half 2 can be fixed, the metal core 27 being held in the center of the cavity 14 of the metal mold. The movable mold 3 consists of a columnar object made of metal, resin, etc., which has a through hole 3 D into which the core 27 is inserted; at least one O-ring 3 E of rubber or the like is provided on the outer peripheral surface to flow out of the molten resin-bonded magnet material to prevent. The movable die 3 is guided by the core 27 attached to the fixed die halves 1 and 2 , and can move freely between the two ends of the cavity wall surface portion 4 B of the fixed die halves 1 and 2 by moving along the die Wall surface section 4 E slides.

The magnetic field generator 6 for applying the magnetic field to the entire cavity 4 or a part thereof is provided around the fixed mold halves 1 and 2 . With a parting plane 7 as a boundary, the fixed mold half 1 is attached to the movable section of an injection molding machine (not shown), and the fixed mold half 2 is attached to the fixed section of the injection molding machine. Although not shown, the fixed mold halves 1 and 2 include cooling lines for controlling the temperature of the metal mold. The uppermost portion of the mold half 2, the injection hole 2 A, in which the nozzle 5 is fitted to the injection molding machine, passing to inject therein the resin-bonded magnet material.

As shown in Fig. 8, the movable die 3 when the metal mold is clamped 40 4 B brought close to the cavity wall surface portion on the side of the injection hole 2 A, so that the cavity 4 has the minimum volume. Under this condition, the magnetic field generator 6 is operated to apply a predetermined magnetic field to the cavity 14 of the metal mold, and the molten resin-bonded material 10 is, as shown by arrow A, through the nozzle 5 into the interior of the cavity wall surface portion 4 B of mold 3 is injected, as shown in Fig. 9. The flow pressure F of the molten magnetic resin material 10 is received by the cavity wall surface portions 4 B of the movable die 3 .

The continued injection of the molten resin-bonded magnetic material 10 further increases the flow pressure due to the injection; in response to the increase of the flow pressure, the increase that is glued Magentmaterial of molten resin, moves the movable mold 3 by the increased volume of molten resin-glued magnetic material 10 to the injection opening 2 A opposite end of the metal mold cavity 14 back towards, ie. in Figure 9 downwards, while it is 3 e of the mold halves 1 and 2 in balance with the frictional force between the O-ring 3 e and the wall surface portion, and thus the area increases the cavity of the cavity wall surface portion 4 A to.

The continuation of the injection of the molten resin-bonded magnetic material and the simultaneous backward movement of the movable mold 3 enables the resin-bonded magnetic material to be filled uniformly and tightly into the cavity 4 of the metal mold, as shown in FIG. 10. During the molding process, the resin-bonded magnetic material 10 is magnetized into a resin magnet by the applied magnetic field. By cooling the solid mold halves 1 and 2 at a constant rate, a magnetic roller is cast, which consists of the resin magnet. After a predetermined time, the metal mold 40 is divided to take out the one-piece shaft-made magnetic roller which has been cast as shown in Fig. 4A.

According to the present invention, the possibilities of Defects on the surface and / or within the by the Magnetic field injection molding process produced magnetic rollers be remarkably reduced and the occurrence of a Curvature in the magnetic rollers can also be controlled. It also allows the use of the magnetic roller, according to the method according to the invention has been produced in a developing device or one Cleaning device that the devices good pictures produce.

Claims (10)

1. Magnetic roller manufacturing method for injecting a molten resin-bonded magnetic material ( 10 ) composed primarily of magnetic powder and a binder into the cavity ( 4 ) of a metal mold ( 20 ; 30 ; 40 ) while applying a magnetic field is applied so as to cast the magnetic roller, the resin-bonded magnetic material ( 10 ) being injected while the volume of the cavity ( 4 ) is increased. 2. Magnetic roller manufacturing method for injecting a molten resin-bonded magnetic material ( 10 ) composed primarily of magnetic powder and a binder into the cavity ( 4 ) of a metal mold ( 20 ; 30 ; 40 ) while applying a magnetic field is applied so as to cast the magnetic roller, at least a part of the wall surface of the cavity ( 4 ) being designed to be movable so that once the injection of the resin-bonded magnetic material ( 10 ) has started, the injection is continued while, as more resin-bonded magnetic material ( 10 ) is injected, the movable surface is moved in a direction to increase the volume of the cavity ( 4 ). 3. Magnetic roller manufacturing method according to claim 1 or 2, wherein the injection of the resin-bonded magnetic material ( 10 ) is started when the volume of the cavity ( 4 ) of the metal mold ( 20 ; 30 ; 40 ) is small. 4. Magnetic roller manufacturing method according to claim 2 or 3, wherein the resin-bonded magnet material (10) is injected, while the movable surface of an injection hole (2 A) of the metal mold is moved away (20; 40; 30). 5. Magnetic roll manufacturing method according to one of claims 2 to 4, wherein the movable surface is moved by the flow pressure (F) of the injected resin-bonded magnetic material ( 10 ). 6. Magnetic roll manufacturing process according to one of the Claims 1 to 5, wherein the surface roughness of the Magnetic roll 20 µm or less according to the JIS 10 point Average roughness scale is Rz, and where, when the magnetic force is parallel in one direction to the axial direction measured at intervals of 1 mm is the difference in magnetic force between adjacent points is 10 Gauss or less. 7. Magnetic roller, the surface roughness being 20 µm or less according to the LTIS 10 point Average roughness scale is Rz and where if the magnetic force in a direction parallel to axial direction is measured at intervals of 1 mm, the difference in magnetic force between adjacent points is 10 Gauss or less. 8. A developing roller which includes a magnetic roller ( 25 ) and a non-magnetic sleeve ( 51 ) which is rotatably disposed around the magnetic roller ( 25 ) and which visualizes an electrostatic stored image by placing a developing agent on its surface Brings into contact with or in the vicinity of an image bearing member ( 61 ) on which the electrostatic stored image is formed so as to adhere the developing agent to the electrostatic stored image using a magnetic roller whose surface roughness is 20 µm or less according to JIS 10- Point is the average roughness scale Rz, and when the magnetic force thereof is measured in a direction parallel to the axial direction at intervals of 1 mm, the difference in magnetic force between adjacent points is 10 gauss or less. 9. A developing device comprising a developing roller (72) or a developing roller (72) and a developing agent supply roller (71), and an electrostatic stored image which has been formed on an image bearing member (61), visible using a developing agent a magnetic roller is used as the developing roller ( 72 ) or the developing agent supply roller ( 71 ), the surface roughness of which is 20 µm or less according to the JIS 10-point average roughness scale Rz, and wherein if the magnetic force thereof is in a direction parallel to the axial direction is measured at 1 mm intervals, the difference in magnetic force between adjacent points is 10 Gauss or less. 10. A cleaning device which includes a magnetic roller and which removes a developing agent left on an image forming member ( 61 ) after an electrostatic stored image formed on the image bearing member ( 61 ) using the developing agent as a visible image Transfer material ( 68 ) has been transferred using a magnetic roller whose surface roughness is 20 µm or less according to the JIS 10-point average roughness scale Rz and wherein when its magnetic force is measured in a direction parallel to the axial direction at intervals of 1 mm , the difference in magnetic force between adjacent points is 10 gauss or less.