JP2009053362A - Development device in image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device in an image forming apparatus where, without increasing the precision and cost of components forming a nap cutting gap between a nap cutting blade regulating a magnetic nap and a magnetic roller, the components equal to the conventional ones are used, the stabilization of the carrying amount of a two-component developer on a magnetic roller and the uniformization of the carrying amount of the developer to the axial direction of the magnetic roller are achieved, and the stabilization of image quality and the uniformization of the image quality in axial direction of the magnetic roller are achieved. <P>SOLUTION: A nap cutting blade is composed of a magnetic substance, a nap cutting pole in a magnetic roller is provided at a position confronted with the nap cutting blade, further, as a carrier, the one having a particle diameter of 30 to 50 μm and a saturation magnetization of 55 to 80 emu/g is used, the magnetism of the nap cutting pole is controlled to 60 to 90 mT, and the nap cutting gap between the magnetic roller and the nap cutting blade is controlled to 150 to 250 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and more particularly, a two-component developer that charges a nonmagnetic toner using a magnetic carrier. The magnetic brush is formed on the magnetic roller, the height of the magnetic brush is regulated by a cutting plate, and the toner is transferred to the non-magnetic roller including the photosensitive member on which the electrostatic latent image is formed or the toner carrier. The present invention relates to a developing device in an image forming apparatus.

  Conventionally, a magnetic brush of a two-component developer consisting of a non-magnetic toner and a magnetic carrier is carried on a magnetic roller having a plurality of magnetic poles inside, and a photosensitive member and a toner are carried while controlling the layer thickness by a cutting plate. The toner is transferred to a non-magnetic roller such as a body to develop the electrostatic latent image formed on the photosensitive member, or the toner is ejected from the toner carrying member on which the toner thin layer is formed to the electrostatic latent image. In the developing device that develops the toner, in order to stabilize the image quality and to make the image quality uniform in the axial direction of the magnetic roller, the developer transport amount on the magnetic roller is stabilized, and the axial direction of the magnetic roller. It is very important to make the developer transport amount uniform with respect to the toner.

  For example, in a developing device that develops toner by transferring toner from a magnetic spike formed on a magnetic roller to a toner carrier to form a thin toner layer, if the developer transport amount of the magnetic roller decreases, the development of the magnetic spike is performed. The ability to form a toner thin layer on the agent carrier is reduced, resulting in a decrease in image density. Deterioration in development ghosting that appears when the toner is used on the developer carrier last time as the afterimage history during the next development. Cause. Conversely, when the developer conveyance amount increases, the developer overflows in the gap between the magnetic roller and the developer carrier.

  One reason for these problems is that the end plate is generally fixed to the developing device with screws at both ends. In other words, by fixing both ends of the cutting plate to the screws, the central portion of the cutting plate is deflected by the pressing force of the developer being conveyed, and the gap with the magnetic roller at the central portion in the axial direction is widened toward the end portion. This makes it difficult to make the image quality uniform in the magnetic roller axial direction.

  Therefore, it has been devised that the front end of the cutting plate is not straight, but the central part is convex with respect to both ends in consideration of the above-mentioned deflection. Further, when the magnetic roller is manufactured with a general manufacturing accuracy, the gap fluctuates by about 30 μm, for example, due to the core blur. Therefore, aiming at high-accuracy hot-cut gap management, improve component accuracy of components, for example, straightness / warp regulation at the tip of the hot-cut plate, magnetic roller outer diameter / run-out tolerance, and ho-cut gap assembly tolerance Various things such as reduction have been performed.

  In addition, in the developing device in which the magnetic roller of the two-component developer is supported on such a magnetic roller and the toner is transferred to the non-magnetic roller while controlling the layer thickness by the cutting plate, the cutting plate is made of a magnetic material. In the magnetic roller, the magnetic head is regulated by generating a vertical magnetic force toward the head cutting pole provided opposite to the head cutting plate in the magnetic roller, but if this vertical magnetic force is too strong, the head cutting plate As a result, the frictional force of the magnetic spikes increases and the quality of the formed image is deteriorated due to the deterioration of the developer. For this reason, it is also practiced that the cutting plate is formed of a non-magnetic plate and a thin magnetic plate is attached so as not to increase the magnetic force.

  As described above, Patent Document 1 discloses that the amount of developer passing through the doctor gap is constant in the axial direction even under the condition that the gap between the developing sleeve and the doctor is not constant in the axial direction. The magnetic member 45b made of a magnetic material is fixed to the doctor blade 45a, the cross-sectional area of the central part of the magnetic member 45b is made larger than the cross-sectional area of the end part, and the magnetic field near the central part is larger than the magnetic field near the end part. Providing a developing device that increases the magnetic field at the center of the doctor to increase the amount of brushing of the magnetic brush compared to the end, and makes the amount of developer passing through the doctor gap constant in the axial direction. Has been.

  Patent Document 2 does not relate to a cutting plate, but prevents toner scattering during development, prevents carrier from adhering to the latent image carrier during development, and is dense and smooth. In order to obtain a high-quality toner image with no toner, the volume average particle diameter of the carrier is set to be equal to or smaller than the volume average particle diameter of the toner, and the toner coating on the carrier surface of the developer supplied on the toner supply roller immediately after being regulated by the doctor blade Development with a control means for controlling the ratio of toner to carrier in the developer so that the rate is 100% or less and the average magnetic susceptibility per unit volume excluding voids of the developer is 50 emu / cc or more The device is shown.

  Further, in Patent Document 3, in order to prevent a development ghost, the toner layer on the developing roller can be removed without complicating the developing device when the toner thin layer on the developing roller is stripped off by the magnetic spike of the magnetic roller. In order to prevent occurrence of layer unevenness at the time of re-formation, the developing roller is rotated by changing the potential difference between the developing roller and the magnetic roller at the non-development interval between any latent image corresponding to the space between the recording papers. After the toner thin layer is peeled off, a toner layer peeling and re-forming step for re-forming the toner thin layer on the developing roller is provided. At least the linear speed of both rollers during the toner layer peeling step is set to 1 A developing method and apparatus in an image forming apparatus is shown in which the other roller is controlled to rotate once in excess or deficiency in the range of ± 2 mm or less in the circumference when rotating.

JP-A-2005-091953 JP 2003-228229 A JP 2005-055840 A

  However, the countermeasure for non-uniformity in the developer conveyance amount due to the deflection of the center part of the cutting plate shown in Patent Document 1 is that the convex shape of the leading edge of the cutting plate or the longitudinal magnetic field strength of the cutting plate at both ends. On the other hand, it is a method accompanied by an increase in cost by providing a magnetic body or magnet so that the central portion is strong. The methods disclosed in Patent Document 2 and Patent Document 3 are used to scatter toner at the time of development and to apply to the latent image carrier. This relates to prevention of carrier adhesion and development ghost prevention, and does not relate to stabilization of the developer conveyance amount on the magnetic roller and equalization of the developer conveyance amount in the axial direction of the magnetic roller.

  Therefore, in the present invention, as in the prior art, a component with the same accuracy as the conventional one without increasing the accuracy and cost of the component that forms the gap between the cutting plate that regulates the magnetic spike and the magnetic roller. Is used to stabilize the developer conveyance amount on the magnetic roller and to make the developer conveyance amount uniform in the magnetic roller axial direction, to stabilize the image quality and to make the image quality in the magnetic roller axial direction uniform. It is an object to provide a developing device in an image forming apparatus that realizes the above.

  In order to solve the above problem, the applicant of the present application manufactured a magnetic roller and a scissor plate using parts having the same accuracy as the conventional one, and still stabilized the developer conveyance amount on the magnetic roller, and the magnetic roller. In order to consider how to make the developer transport amount uniform in the axial direction, first prepare a non-magnetic body cutting plate (blade) and a magnetic body cutting plate (blade). Then, the flow rate of the developer was examined by changing the interval (blade gap) between the cutting plate (blade) and the magnetic roller.

  As a result, when a non-magnetic spike plate (blade) is used, the flow rate of the developer increases almost linearly as the blade gap increases, and the amount of magnetic spikes carried by the core blur of the magnetic roller is restricted. However, when using a magnetic cutting plate (blade), the change in developer flow rate is relatively small when the ear cutting gap is between 150 μm and 250 μm, and the flow rate increases when it exceeds 250 μm. I found out that

  This is because when a magnetic cutting plate (blade) is provided at a position opposite to the panning electrode, a magnetic field is generated between the panning plate and the panning plate so that the developer spikes along the lines of magnetic force. This is considered to be because the amount of cutting is increased and the amount of developer transported is reduced in order to cut it with a cutting plate. On the other hand, in the non-magnetic blade, since the magnetic lines of force at the ear cutting part are inclined in the tangential direction, it is considered that the ear rising is inclined, the amount of ear cutting is reduced, and the developer conveyance amount is increased.

  In addition, the magnetic force of the magnetic roller changes in proportion to the square of the distance. However, since the distance is short between 150 μm and 250 μm, the magnetic force is relatively large and the change in magnetic force is gradual, whereas the change in magnetic force is 250 μm. It is considered that the magnetic force is gradually reduced in proportion to the square of the head gap, and the developer conveyance amount is increased. For this reason, it has been found that when the ear gap exceeds 250 μm, the influence of the core blur of the magnetic roller greatly affects the developer conveyance amount of the magnetic roller.

  Next, it was examined how the flow rate changes due to the core blur of the magnetic roller and how the flow rate is affected by changing the peripheral speed of the magnetic roller. In this investigation, the flow rate caused by the maximum and minimum gaps between the magnetic roller and the chopping board (blade) caused by the core blur was examined as the difference between the maximum and minimum flow rates. As in the case of the head cutting plate, the head cutting gap is relatively small between 150 μm and 250 μm, and the influence of the core blur of the magnetic roller is considered to be small, whereas when the head cutting gap exceeds 250 μm, the maximum flow rate and minimum The difference from the flow rate increased, and at the maximum flow rate, the developer overflowed between the gaps with the non-magnetic rollers such as the toner carrier (developing roller) and the photosensitive member.

  This is because, as described above, when the head gap is between 150 μm and 250 μm, the magnetic force of the magnetic roller is strong and the change is relatively slow, and the difference between the maximum flow rate and the minimum flow rate (that is, the influence of the core blur) is relatively small. On the other hand, it is considered that when the ear cutting gap exceeds 250 μm, the magnetic force is reduced and the developer flow rate is increased (that is, the influence of the core blur is increased). Further, it was found that the peripheral speed of the magnetic roller does not greatly affect the flow rate of the developer.

  Therefore, in the present invention, the cutting plate is made of a magnetic material, and the toner transfer pole is disposed at least at a position facing a non-magnetic roller such as a photoconductor or a developing roller. A head-cutting pole on the side facing the head-cutting plate, and a magnetic pole separation pole on the upstream side of the rotation direction of the rotation sleeve of the head-cutting pole, and on the upstream side. Was set to 60 to 90 mT, and the gap between the magnetic roller and the cutting plate was set to 150 to 250 μm. The reason why the magnetic force of the panicle pole is 60 to 90 mT is that if the magnetic force is less than 60 mT, the magnetic force for forming the magnetic brush is too weak, and if the magnetic force exceeds 90 mT, the magnetic force is too strong. This is because there is a concern about the deterioration of the image quality and the deterioration of the image quality due to this, and if an expensive rare earth element is not used, an ordinary ferrite cannot generate such a magnetic force and becomes expensive.

  As the carrier, a carrier with a relatively small diameter of 30 to 50 μm, which has been used conventionally, was used, and the saturation magnetization was 55 to 80 emu / g. When a carrier having a relatively small diameter of 30 to 50 μm conventionally used as the carrier is used, if the saturation magnetization value is reduced, the restraining force by the magnetic roller is reduced and the carrier is flew to the photoreceptor. Conversely, in order to increase the saturation magnetization, it is necessary to use an expensive material, and in this case, the developer becomes expensive.

Therefore, the developing device in the image forming apparatus according to the present invention is
A magnetic roller carrying a magnetic spike of a two-component developer composed of a non-magnetic toner and a magnetic carrier on a rotating sleeve having a plurality of magnetic poles disposed therein, a spike plate for regulating the layer thickness of the magnetic spike, and the magnetic Image formation comprising a toner carrier that develops an electrostatic latent image formed on a photoreceptor by electrophotography with the thin layer formed by facing the roller and transferring toner from the magnetic ears In the developing device in the apparatus,
The magnetic roller has a toner transfer pole at least at a position facing the toner carrier, and a panning pole at a position upstream of the toner transfer pole in the rotational direction of the rotating sleeve and facing the panning plate, A pumping pole is provided on the upstream side of the rotating sleeve in the rotational direction of the rotating sleeve, the cutting plate is made of a magnetic material, the carrier has a particle size of 30 to 50 μm, and a saturation magnetization of 55 to 80 emu / g. In addition, the magnetic force of the cutting electrode is 60 to 90 mT, and the cutting gap between the magnetic roller and the cutting plate is 150 to 250 μm.

Similarly,
A rotating sleeve having a plurality of magnetic poles disposed therein carries a magnetic spike of a two-component developer composed of a non-magnetic toner and a magnetic carrier, and the electrostatic latent image formed on the photosensitive member by an electrophotographic method is used as the magnetic spike. In the developing device in the image forming apparatus having a magnetic roller for developing in
The magnetic roller has at least a toner transfer pole at a position facing the photoconductor, and a panning pole at a position upstream of the toner transfer pole in the rotational direction of the rotating sleeve and facing the panning plate, A pumping pole is provided on the upstream side of the rotating sleeve rotating direction of the rotating sleeve, the cutting plate is made of a magnetic material, the carrier has a particle size of 30 to 50 μm, and a saturation magnetization of 55 to 80 emu / g. The magnetic force of the ear cutting pole is 60 to 90 mT, and the ear cutting gap between the magnetic roller and the head cutting plate is 150 to 250 μm.

  By doing so, the developing device in the image forming apparatus according to the present invention can increase the accuracy and cost of the components that form the gap between the cutting plate and the magnetic roller that regulate the magnetic spike as in the prior art. The quality of the image is stabilized by stabilizing the developer conveyance amount on the magnetic roller and making the developer conveyance amount uniform in the axial direction of the magnetic roller using parts with the same accuracy as before. In addition, it is possible to provide a developing device in an image forming apparatus capable of forming a high quality image by realizing uniform image quality in the axial direction of the magnetic roller at low cost.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a cross-sectional view of main parts, an arrangement of magnetic poles, and a range covered by a magnetic force in an example of a developing device in an image forming apparatus according to the present invention. As an example, the developing device 10 shown in FIG. 1 is a thin layer of toner only on a toner carrier (developing roller) 15 that is a non-magnetic roller, using magnetic spikes formed by a two-component developer formed on a magnetic roller 11. A so-called touch is formed in which a layer is formed and toner is caused to fly to an electrostatic latent image formed on a photoreceptor (not shown) by a development bias in which direct current and alternating current applied to the developing roller 15 are superimposed. This is a developing device of a down development system. In this type of developing device, the photoconductor is provided facing the developing roller 15. However, in the present invention, not only the touchdown developing type developing device but also a photoconductor as a non-magnetic roller is provided at the position of the developing roller 15. It is obvious that the present invention can also be applied to an installed ordinary two-component developing device.

  In FIG. 1, reference numeral 11 denotes a toner transfer pole of the magnetic pole N1 counterclockwise inside, at a position facing the developing roller 15, on the upstream side in the rotation sleeve rotation direction of the magnetic roller of the toner transfer pole N 1. There is a S2 ear-cutting pole at a position facing the cut plate 12, a N3 pumping pole further upstream of the head-cutting pole S2, and a stationary magnet provided with N2 and S1 poles further upstream. A magnetic roller 12 for forming a magnetic spike of the two-component developer on the sleeve, 12 is a spike plate (blade) for regulating the height of the magnetic spike on the magnetic roller 11, and is L-shaped with a magnetic material such as SUS430. And extends in the axial direction of the magnetic roller 11 and is fixed to the housing 16 of the developing device 10. Reference numerals 13 and 14 denote stirring mixers that charge the developer in the developer chambers 161 and 162, which are partitioned by a partition wall 161 that is shortened so that both ends in the longitudinal direction do not contact the housing 16, while stirring and transporting. Reference numeral 15 denotes a toner carrier (developing roller) in which a thin toner layer is formed by magnetic spikes formed on the magnetic roller 11.

  The housing 16 of the developing device 10 is a vertical developing device in which developer chambers 162 and 163 are provided in the lower portion and a magnetic roller 11 and a toner carrier (developing roller) 15 are provided in the upper portion. The developer in 162 is pumped up by the stirring mixer 13 and the pumping pole N3, and the developer is supplied to the magnetic roller 11 provided in the upper part to form a magnetic spike. Can be configured short.

  In the figure, the ranges covered by the magnetic forces generated by the magnetic poles N1, S1, N2, N3, and S2 are indicated by 17N1, 17S1, 17N2, 17N3, and 17S2, respectively. In the case of the figure, it is provided opposite to the position shifted by 3 to 5 degrees counterclockwise with respect to the head cutting pole S2. Therefore, a magnetic force substantially perpendicular to the cutting plate (blade) 12 is formed from the cutting blade pole S 2, and the magnetic spike formed on the magnetic roller 11 is formed by the magnetic roller 11 and the cutting plate 12. The blade gap is cut by this vertical magnetic force and the developer conveyance amount and the developer conveyance amount in the axial direction of the magnetic roller 11 are made uniform.

  Further, as described above, the toner transfer pole N1 is provided with an angular difference of several degrees with respect to the toner carrier (developing roller) 15 further downstream in the counterclockwise direction of the ear-cut pole S2. Further, a magnetic pole S1 is provided on the downstream side in the counterclockwise direction, and a separation pole N2 and a pumping pole N3 are provided further downstream.

  In the developing device 10 in the image forming apparatus according to the present invention configured as described above, the applicant of the present application can increase the accuracy of the components that form the gap between the cutting plate 12 and the magnetic roller 11 as described above. To stabilize the developer conveyance amount on the magnetic roller 11 and make the developer conveyance amount uniform in the axial direction of the magnetic roller 11 by using parts with the same accuracy as before without increasing the cost. In order to consider what should be done, first, a non-magnetic body cutting board (blade) and a magnetic body cutting board (blade) are prepared. The developer flow rate was examined by changing the interval (blade gap). The result is the graph shown in FIG.

In the graph shown in FIG. 2, the horizontal axis represents the distance between the magnetic roller 11 and the scissor plate (blade) 12 (blade gap: unit mm), and the vertical axis represents the developer flow rate (unit: mg / cm ² ). The solid line plotted with ■ indicates the magnetic blade, and the broken line with ◆ indicates the non-magnetic blade.

  The image forming apparatus used in the experiment is a modified KM-C2520 manufactured by Kyocera Mita, which is a mixture of a Mn-Mg carrier having a saturation magnetization of 69 emu / g and an average particle diameter of 35 μm and a toner having an average particle diameter of 7 μm. The developer weight in the developing container was set to 185 g using the two-component developer. The magnetic roller has a magnetic force of 70 mT at the cutting edge and a peripheral speed of 420 mm / sec. The material of the cutting board is SUS430 as a magnetic cutting board and is 1.5 mm thick. As the cutting plate, SUS304 having a thickness of 1.5 mm was used.

As can be seen from the graph of FIG. 2, when a non-magnetic blade is used, the flow rate of the developer is 7.8 mg / cm ² when the blade gap is 0.15 mm, and the blade gap is 0.2 mm and 0.25 mm. 3.0 mm. As larger and 3.5 mm, the developer flow rate ^{also, 9.6mg / cm 2, 12.7mg /} cm 2, 14.6mg / cm 2, and 17.0 mg / cm ^2, has increased substantially linearly.

On the other hand, when a magnetic blade is used, when the blade gap is 0.15 mm, the developer flow rate is 6.0 mg / cm ² , which is smaller than that of the non-magnetic blade, and when the blade gap is 0.2 mm, 6 .6mg ^/ cm 2, and 7.5mg / cm ² in the case of 0.25mm, blade gap is not increased flow rate is increased to 0.25mm. When the blade gap is 3.0 mm, the developer flow rate is 9.7 mg / cm ^2, which is a larger developer amount than before, and when the blade gap is 3.5 mm, the developer flow rate is 12. 1 mg / cm ² and 3.0mm after is growing almost linearly.

  This is because, as described above, when a magnetic cutting plate (blade) is provided at a position facing the panning pole, the developer spikes along the lines of magnetic force generated between the panning plate and the panning plate. In order to cut it with a blade, the amount of cutting is increased and the amount of developer transported is reduced.On the other hand, with a non-magnetic blade, the magnetic lines of force at the cutting end are inclined in the tangential direction. It is considered that the amount of cutting is reduced and the developer transport amount is increased. Therefore, when a nonmagnetic blade is used, the flow rate of the developer greatly changes with a slight core blur of the magnetic roller 11.

  In addition, since the magnetic force changes in proportion to the square of the distance, when the head gap is between 0.15 mm (150 μm) and 0.25 mm (250 μm), since the distance is short, the magnetic force is relatively large and the magnetic force change is also large. On the other hand, if it exceeds 0.25 mm (250 μm), the magnetic force is gradually decreased in proportion to the square of the ear-cut gap, and the developer conveyance amount is increased. Therefore, in this case, it is considered that the influence of the core blur of the magnetic roller greatly affects the developer conveyance amount of the magnetic roller.

  From the above results, when a magnetic material is used as the material of the trimming plate (blade) 12 and the trimming gap is between 150 μm and 250 μm, there is no significant change in the developer transport amount even if the trimming gap varies somewhat. However, in order to investigate how the developer flow rate changes due to the core blur of the magnetic roller 11, the variation in the distance between the magnetic roller and the blade (blade) due to the core blur is determined by Instead of the distance between the magnetic roller and the magnetic roller (blade gap), the maximum flow rate (variation upper limit) and the minimum flow rate (variation lower limit) of the developer were examined. A graph showing the results is shown in FIG.

In the graph shown in FIG. 3, the horizontal axis is the distance between the magnetic roller 11 and the cutting plate (blade) (blade gap: unit mm), and the vertical axis is the developer flow rate (unit: mg) as in the graph of FIG. / cm ^2), the line obtained by plotting the ■ the solid line (hereinafter, referred to as standard line) is the maximum flow rate (variations in the the same line, the line obtained by plotting the ◆ dotted developer shown in FIG. 2 (Upper limit), and a line in which a dot is plotted on the alternate long and short dash line indicates the minimum flow rate (variation lower limit) of the developer. The image forming apparatus and developer used in this experiment are as described above.

  The upper and lower limits of the variation in the graph of FIG. 3 are as follows. When the magnetic roller 11 is formed with general manufacturing accuracy, for example, a core blur of about 30 μm occurs. It is a thing.

As a result, when the blade gap is 0.15 mm, the upper limit developer flow rate is 6.4 mg / cm ² , the standard line is 6.0 mg / cm ² , and the lower limit developer flow rate is 5.6 mg / cm ^2. There upper limit of developer flow rate 7.0 mg / cm ² in 0.2 mm, the standard line 6.6 mg / cm ^2, the developer flow rate lower limit is 6.0 mg / cm ^2, the blade gap is maximum at 0.25mm The developer flow rate is 8.2 mg / cm ² , the standard line is 7.5 mg / cm ² , and the lower limit developer flow rate is 6.7 mg / cm ² . Even if it increases, the flow rate does not increase greatly, and the difference does not spread so much.

But the blade gap is 3.0 mm, the developer flow rate 11.2 mg / cm ² of the upper limit, the standard line 9.7 mg / cm ^2, the developer flow rate lower limit is ever respectively 7.9 mg / cm ² developer flows greater than increment further and the blade gap is as large as 3.5 mm, the developer flow rate 13.8 mg / cm ² of the upper limit, the standard line 12.1 mg / cm ^2, the developer flow rate lower limit From 10.1 mg / cm ² and after 3.0 mm, it increases almost linearly, the difference between them increases, and the influence of the core blur increases.

  As described with reference to FIG. 2, since the magnetic force changes in proportion to the square of the distance, the magnetic roller 11 has a gap between 0.15 mm (150 μm) and 0.25 mm (250 μm). There is no significant difference in the developer flow rate even if there is core blurring, and the magnetic force suddenly decreases beyond 0.25 mm (250 μm). Is thought to have spread.

Next, FIG. 4 shows the result of examining the flow rate of the developer by using a magnetic cutting plate (blade), changing the spacing (blade gap) between the cutting plate and the magnetic roller, and the peripheral speed of the magnetic roller. It is the shown graph. In the graph shown in FIG. 4, as in the graphs of FIGS. 2 and 3, the horizontal axis is the distance between the magnetic roller and the scissor plate (blade) (blade gap: mm), and the vertical axis is the developer flow rate (unit). : Mg / cm ² ), and a line (hereinafter referred to as a standard line) in which ■ is plotted on a solid line is a case where the peripheral speed of the magnetic roller 11 is 420 mm / sec, which is the same as in FIGS. This is a developer flow line. The line plotted with ◆ on the two-dot chain line is 210 mm / sec, the developer flow line at the lower limit of the peripheral speed, and the line plotted with ◆ on the broken line is the peripheral speed of 500 mm / sec, the upper limit. The developer flow lines are respectively shown. The image forming apparatus and developer used in this experiment are as described above.

  As can be seen from the graph in FIG. 4, the lower limit peripheral speed developer flow line, the standard line, and the upper limit peripheral speed developer flow line show almost the same values in any blade gap, and the magnetic It is considered that the peripheral speed of the roller hardly affects the developer flow rate.

  In this way, a magnetic material is used as the material of the cutting plate (blade), and the distance (blade gap) between the magnetic roller 11 and the cutting plate 12 is set to 150 to 250 μm, so that the magnetic with a core blur of about 30 μm is obtained. Even when the roller 11 is used, it is considered that the developer flow rate does not change greatly. As described above, the above results are obtained by using a two-component developer in which a toner having an average particle diameter of 7 μm and a carrier having an average particle diameter of 35 μm and a Mn—Mg-based saturation magnetization of 69 emu / g are mixed. The results are obtained when the magnetic force of the hogiri pole S2 is set to 70 mT, and the developer flow rate is examined when the average particle diameter, saturation magnetization, and magnetic force of the hogiri pole S2 are changed. .

  The results are shown in the table of FIG. In the table shown in FIG. 5, Example 1 has been described above, the average particle diameter (35 μm) and saturation magnetization (35 μm) of the carrier used for investigating the optimum distance between the magnetic roller 11 and the scissor plate 12. 69 emu / g), which is the magnetic force (70 mT) of the head roller pole S2 of the magnetic roller, whereas in Example 2, the magnetic force (70 mT) of the head roller pole S2 of the magnetic roller is the same as in Example 1, The average particle size was 35 μm, the saturation magnetization was 64 emu / g, and the change in this range had no problem with the developer flow rate, as indicated by the circle in “Developer flow rate stability”.

  Examples 3 and 4 and Comparative Example 1 use the carrier having average particle diameters of 35 μm and 50 μm, which was not problematic in Examples 1 and 2, and the magnetic cutting head S2 of a magnetic roller having a magnetic force of 70 mT, and changing the saturation magnetization of the carrier. In Examples 3 and 4 in which the saturation magnetization was 57 emu / g and 75 emu / g, the “developer flow rate stability” was ○ without causing a problem, but the comparison was made with the saturation magnetization of 39 emu / g. In Example 1, since the saturation magnetization is small, the magnetic brush on the magnetic roller 11 is weak, density unevenness occurs, causing a problem in “developer flow rate stability”, and x.

  In Examples 5 and 6 and Comparative Example 2 in which the magnetic force of the head cutting pole S2 of the magnetic roller 11 was changed using a carrier having an average particle diameter of 35 μm and a saturation magnetization of 69 emu / g, which had no problem in Example 1, In Examples 5 and 6 in which the magnetic force of the hogiri pole S2 was set to 80 mT and 60 mT, “developer flow rate stability” became “O” without causing a problem. The amount of the magnetic brush that passes is too large, and the “developer flow rate stability” is still “x”.

  From the above results, when using a Mn—Mg system as the carrier, it is preferable that the saturation magnetization is 55 to 80 emu / g and the average particle diameter is between 30 and 50 μm. It has been found that the magnetic force of is preferably between 60 and 90 mT.

  Therefore, it is considered that it is preferable based on the experimental results, and is usually mixed with an inexpensive Mn—Mg-based carrier having a saturation magnetization of 69 emu / g and an average particle diameter of 35 μm and a toner having an average particle diameter of 7 μm. When the two-component developer is used, and as described above, the magnetic force of the cutting edge in the magnetic roller 11 is 70 mT, the peripheral speed is 420 mm / sec, and the cutting board 12 having a thickness of 1.5 mm is used, first, FIG. From the results of this graph, the material of the cutting plate (blade) is preferably a magnetic material, and if the distance (blade gap) between the magnetic roller 11 and the cutting plate 12 is 150 to 250 μm, the developer flow rate fluctuates. Is expected to decrease.

  Further, from the result of the graph of FIG. 3, even if a magnetic roller 11 having a core blur of about 30 μm is used with a component made with a normal tolerance, the distance (blade gap) between the magnetic roller 11 and the scissor cutting plate 12 is used. ) Is set to 150 to 250 μm, the developer flow rate does not fluctuate greatly. From the result of the graph of FIG. 4, if the peripheral speed of the magnetic roller 11 is between 210 mm / sec and 500 mm / sec, the developer flow rate It is considered that there will be no difference.

  Therefore, in the present invention, a carrier having a particle diameter of 30 to 50 μm and a relatively small diameter and a saturation magnetization of 55 to 80 emu / g, which has been used conventionally as a carrier, is used, and the cutting plate is made of a magnetic material. Parts with the same precision as before without increasing the precision and cost of the components by setting the gap between the magnetic roller and the cutting plate to 150 to 250 μm and the magnetic force of the cutting roller on the magnetic roller side to 60 to 90 mT. Is used to stabilize the developer conveyance amount on the magnetic roller and to make the developer conveyance amount uniform in the magnetic roller axial direction, to stabilize the image quality and to make the image quality in the magnetic roller axial direction uniform. Is realized at low cost.

  According to the present invention, without increasing the accuracy and cost of the components that form the gap between the cutting plate and the magnetic roller that regulates the magnetic spike, the magnetic roller can be used by using components with the same accuracy as before. An image forming apparatus capable of stabilizing the upper developer conveyance amount and uniforming the developer conveyance amount in the magnetic roller axial direction, and realizing uniform image quality and image quality in the magnetic roller axial direction. Can be provided.

FIG. 2 is a diagram illustrating a cross-sectional view of main parts, a magnetic pole arrangement, and a range of magnetic force, as an example of a developing device in the image forming apparatus according to the present invention. The flow rate of the developer was examined by changing the spacing (blade gap) between the non-magnetic spike plate (blade) and the magnetic spike plate (blade) between the spike plate and the magnetic roller. It is the graph which showed the result. The result of examining the maximum flow rate (variation upper limit) and the minimum flow rate (variation lower limit) of the developer by changing the distance (blade gap) between the blade cutting plate and the magnetic roller, using a magnetic cutting plate (blade). It is a graph. 5 is a graph showing the results of examining the developer flow rate by using a magnetic cutting plate (blade) and changing the spacing (blade gap) between the cutting plate and the magnetic roller and the peripheral speed of the magnetic roller. 6 is a table summarizing the results of investigating the stability of developer flow rate stability by changing the particle size of the carrier, saturation magnetization, and magnetic force of the head cutting pole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Developing device 11 Magnetic roller 12 Bread cutting board (blade)
13 Stirring Mixer 14 Stirring Mixer 15 Toner Carrier (Developing Roller)
16 Case 17 Range of magnetic force in each magnetic pole

Claims (2)

A magnetic roller carrying a magnetic spike of a two-component developer composed of a non-magnetic toner and a magnetic carrier on a rotating sleeve having a plurality of magnetic poles disposed therein, a spike plate for regulating the layer thickness of the magnetic spike, and the magnetic Image formation comprising a toner carrier that develops an electrostatic latent image formed on a photoreceptor by electrophotography with the thin layer formed by facing the roller and transferring toner from the magnetic ears In the developing device in the apparatus,
The magnetic roller has a toner transfer pole at least at a position facing the toner carrier, and a panning pole at a position upstream of the toner transfer pole in the rotational direction of the rotating sleeve and facing the panning plate, Separation poles are provided on the upstream side of the rotation direction of the rotating sleeve of the spiked pole, the spiked plate is made of a magnetic material, the carrier has a particle size of 30 to 50 μm, and a saturation magnetization of 55 to 80 emu / g. A developing device in an image forming apparatus, wherein a magnetic force of the cutting electrode is 60 to 90 mT, and a cutting gap between the magnetic roller and the cutting plate is 150 to 250 μm. A rotating sleeve having a plurality of magnetic poles disposed therein carries a magnetic spike of a two-component developer composed of a non-magnetic toner and a magnetic carrier, and the electrostatic latent image formed on the photosensitive member by an electrophotographic method is used as the magnetic spike. In the developing device in the image forming apparatus having a magnetic roller for developing in
The magnetic roller has at least a toner transfer pole at a position facing the photoconductor, and a panning pole at a position upstream of the toner transfer pole in the rotational direction of the rotating sleeve and facing the panning plate, Separation poles are provided on the upstream side of the rotation direction of the rotating sleeve of the spiked pole, the spiked plate is made of a magnetic material, the carrier has a particle size of 30-50 μm, and a saturation magnetization of 55-80 emu / g. A developing device in an image forming apparatus, wherein a magnetic force of the cutting electrode is 60 to 90 mT and a cutting gap between the magnetic roller and the cutting plate is 150 to 250 μm.

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