JP2008256830A - Developing body, developing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase magnetic force of one magnetic pole that a magnetic member has, and to increase magnetic force acting between the one magnetic pole and the other magnetic poles that the magnetic member has. <P>SOLUTION: The developing roll 72 has a sleeve 92 which is the non-magnetic cylindrical member rotated oppositely to a rotating photoreceptor 22Y; and a magnet roll 94 fixedly arranged in the sleeve 92. The sleeve 92 is formed of, for example, aluminum or stainless steel and is made rotatable clockwise (rotating to the right in FIG. 2) with a predetermined gap between the photoreceptor 22Y and the sleeve 92. The magnet roll 94 is formed of a ferrite magnet or plastic resin magnet with a roll diameter of, for example, 14 mm or less. In the external face of the magnet roll 94, the magnetic pole, which is the one S-pole (main pole), and the three magnetic poles 98, 100, and 102, which are three N-poles, are arranged. The magnetic pole 96 and the magnetic poles 98, 100, and 102 each generate magnetic fields in directions including the normal direction of the sleeve 92 and mutually affect their magnetic fields. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developer, a developing device, and an image forming apparatus.

  Patent Document 1 has a three-pole configuration in which a magnetic pole of a fixed magnet roller included in a rotating sleeve is composed of a developing pole N1 disposed near the developing position and two magnetic poles S1 and S2 having a polarity different from the developing pole N1. A horizontal magnetic field having a polarity opposite to that of the magnetic poles S1 and S2 is formed on the rotating sleeve sandwiched between the two magnetic poles S1 and S2, and the angle between the two magnetic poles S1 and S2 is in a range of approximately 120 ° to 170 °. And a developing device in which the magnetic pole S2 is deviated from the layer thickness regulating member by 6 to 15 degrees upstream in the rotational direction of the rotary sleeve.

Japanese Patent No. 3410329

  An object of the present invention is to provide a developer, a developing device, and an image forming apparatus capable of increasing the magnetic force of one magnetic pole of a magnet member and the magnetic force acting between one magnetic pole of the magnet member. To do.

  In order to achieve the above object, the present invention according to claim 1 comprises a nonmagnetic rotating member that rotates to face an image carrier, and a magnet member disposed in the rotating member, and the magnet member Has a first magnetic pole that forms a magnetic field in the normal direction of the rotating member, and the first magnetic pole has a different polarity, and the first magnetic pole is at a position different in the circumferential direction of the rotating member. And a developer having at least three second magnetic poles that form a magnetic field in the normal direction of the rotating member.

  The present invention according to claim 2 is the developer according to claim 1, wherein the magnet member has three second magnetic poles.

  According to a third aspect of the present invention, at least two of the second magnetic poles have an angle formed by each of the directions in which the strength in the normal direction of the rotating member of the magnetic field by the second magnetic pole is maximum. 3. The developing member according to claim 1, wherein the developing member is disposed so as to be less than 180 degrees across one magnetic pole.

  According to a fourth aspect of the present invention, at least one of the second magnetic poles depends on the direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximum and the first magnetic pole. 4. The device according to claim 1, wherein an angle formed by a direction in which the strength of the magnetic field in the normal direction of the rotating member is maximum is greater than 90 degrees and less than 270 degrees. 5. It is a developing body.

  The present invention according to claim 5 includes a non-magnetic rotating member that rotates to face the image carrier and a magnet member disposed in the rotating member, and the magnet member is a method of the rotating member. One first magnetic pole that forms a magnetic field in the linear direction is different in polarity from the first magnetic pole, and is different from the first magnetic pole in the circumferential direction of the rotating member. A plurality of second magnetic poles that form a magnetic field in the linear direction, and at least two of the second magnetic poles have a maximum strength of the magnetic field in the normal direction of the rotating member by the second magnetic poles. The developing members are arranged so that an angle formed by each of the directions becomes less than 180 degrees across the first magnetic pole.

  According to a sixth aspect of the present invention, there is provided a developer containing portion for containing a developer containing non-magnetic toner and a magnetic carrier, and development for conveying the developer contained in the developer containing portion toward the image carrier. And the developer includes a non-magnetic rotating member that rotates to face the image holding member, and a magnet member disposed in the rotating member, and the magnet member includes the rotating member. The first magnetic pole that forms a magnetic field in the normal direction of the first magnetic pole is different in polarity from the first magnetic pole, and the first magnetic pole is located at a different position in the circumferential direction of the rotating member. And a developing device having at least three second magnetic poles that form a magnetic field in the normal direction.

  The present invention according to claim 7 is the developing device according to claim 6, wherein the magnet member has three second magnetic poles.

  The present invention according to claim 8 is characterized in that at least two of the second magnetic poles have an angle formed by each of directions in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximum. The developing device according to claim 6 or 7, wherein the developing device is disposed so as to be less than 180 degrees across one magnetic pole.

  The present invention according to claim 9 is characterized in that at least one of the second magnetic poles is formed by a direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic poles is maximum, and by the first magnetic poles. The arrangement according to any one of claims 6 to 8, wherein an angle formed by a direction in which the strength of the magnetic field in the normal direction of the rotating member is maximum is greater than 90 degrees and less than 270 degrees. It is a developing device.

  According to a tenth aspect of the present invention, at least two of the second magnetic poles are arranged in the normal direction of the rotating member on the downstream side in the rotation direction of the rotating member with respect to the position where the rotating member faces the image carrier. The developing device according to claim 6, wherein a region having a magnetic flux density of 5 mT or less is formed.

  According to the eleventh aspect of the present invention, at least two of the second magnetic poles rotate the rotating member more than a position where a region in which the magnetic flux density in the normal direction of the rotating member is 5 mT or less is formed. The development according to claim 10, wherein a region having the same polarity as the magnetic field formed by the first magnetic pole and having a magnetic flux density in the normal direction of the rotating member of 5 mT or more is formed on the downstream side in the direction. Device.

  According to a twelfth aspect of the present invention, at least two of the second magnetic poles have a tangential direction of the rotating member and a position tangential to the rotating member upstream of the position of the rotating member facing the image carrier. 12. The developing device according to claim 6, wherein the developing device forms a region in which the magnitude of the magnetic flux density in the normal direction is 5 mT or less.

  According to a thirteenth aspect of the present invention, at least two of the second magnetic poles are arranged on the downstream side in the rotation direction of the rotating member from the position where the rotating member faces the image carrier, and the tangential direction of the rotating member and 12. The developing device according to claim 6, wherein the developing device forms a region in which the magnitude of the magnetic flux density in the normal direction is 5 mT or less.

  According to the fourteenth aspect of the present invention, there is provided a developer containing portion for containing a developer containing non-magnetic toner and a magnetic carrier, and development for conveying the developer contained in the developer containing portion toward the image carrier. And the developer includes a non-magnetic rotating member that rotates to face the image holding member, and a magnet member disposed in the rotating member, and the magnet member includes the rotating member. The first magnetic pole that forms a magnetic field in the normal direction of the first magnetic pole is different in polarity from the first magnetic pole, and the first magnetic pole is located at a different position in the circumferential direction of the rotating member. A plurality of second magnetic poles that form a magnetic field in the normal direction, and at least two of the second magnetic poles have a strength of the magnetic field in the normal direction of the rotating member by the second magnetic poles. The angle formed by each of the maximum directions is less than 180 degrees across the first magnetic pole. So that a developing device is disposed.

  According to a fifteenth aspect of the present invention, an image holding member, a developing device that develops a latent image formed on the image holding member with a developer, and a developer image developed by the developing device are transferred to a recording medium. A transfer unit; and a fixing device that fixes the developer image transferred to the recording medium by the transfer unit to the recording medium. The developing unit includes a developer storage unit that stores the developer, and the developer storage unit. A developer that conveys the developer contained in the unit toward the image carrier, and the developer is disposed in the rotary member and a nonmagnetic rotating member that rotates to face the image carrier. A first magnetic pole that forms a magnetic field in the normal direction of the rotating member, and the first magnetic pole has a different polarity, and the first magnetic pole Are at different positions in the circumferential direction of the rotating member and are normal to the rotating member At least three second magnetic pole forming a magnetic field in the direction, which is an image forming apparatus having a.

  The present invention according to claim 16 is the image forming apparatus according to claim 15, wherein the magnet member has three second magnetic poles.

  According to a seventeenth aspect of the present invention, at least two of the second magnetic poles have an angle formed by each of the directions in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximum. The image forming apparatus according to claim 15 or 16, wherein the image forming apparatus is disposed so as to be less than 180 degrees across one magnetic pole.

  According to the eighteenth aspect of the present invention, at least one of the second magnetic poles has a direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized by the second magnetic poles, and the first magnetic poles. 18. The device according to claim 15, wherein the rotation member is arranged so that an angle formed by a direction in which a magnetic field strength in a normal direction of the rotating member is maximum is greater than 90 degrees and less than 270 degrees. An image forming apparatus.

  According to the nineteenth aspect of the present invention, at least two of the second magnetic poles are arranged in the normal direction of the rotating member on the downstream side in the rotating direction of the rotating member from the position where the rotating member faces the image carrier. The image forming apparatus according to any one of claims 15 to 18, wherein a region having a magnetic flux density of 5 mT or less is formed.

  According to the twentieth aspect of the present invention, at least two of the second magnetic poles rotate the rotating member more than a position where a region in which the magnetic flux density in the normal direction of the rotating member is 5 mT or less is formed. The image according to claim 19, wherein a region having the same polarity as the magnetic field formed by the first magnetic pole and having a magnetic flux density in the normal direction of the rotating member of 5 mT or more is formed on the downstream side in the direction. Forming device.

  According to a twenty-first aspect of the present invention, at least two of the second magnetic poles are arranged on the downstream side in the rotational direction of the rotating member from the position where the rotating member faces the image carrier, and the tangential direction of the rotating member and 21. The image forming apparatus according to any one of claims 15 to 20, wherein a region in which the magnitude of the magnetic flux density in the normal direction is 5 mT or less is formed.

  According to a twenty-second aspect of the present invention, an image carrier, a developing device that develops a latent image formed on the image carrier with a developer, and a developer image developed by the developing device are transferred to a recording medium. A transfer unit; and a fixing device that fixes the developer image transferred to the recording medium by the transfer unit to the recording medium. The developing unit includes a developer storage unit that stores the developer, and the developer storage unit. A developer that conveys the developer contained in the unit toward the image carrier, and the developer is disposed in the rotary member and a nonmagnetic rotating member that rotates to face the image carrier. A first magnetic pole that forms a magnetic field in the normal direction of the rotating member, and the first magnetic pole has a different polarity, and the first magnetic pole Are at different positions in the circumferential direction of the rotating member and are normal to the rotating member A plurality of second magnetic poles forming a magnetic field in the direction, and at least two of the second magnetic poles have a maximum magnetic field strength in the normal direction of the rotating member by the second magnetic poles. The image forming apparatus is arranged such that an angle formed by each direction is less than 180 degrees across the first magnetic pole.

  According to the first aspect of the present invention, the magnetic force of the first magnetic pole of the magnet member can be increased compared to the case where the present configuration is not provided.

  According to the second aspect of the present invention, in addition to the effect of the present invention according to the first aspect, the size of the developer can be reduced as compared with the case where the number of the second magnetic poles is four or more. it can.

  According to the third aspect of the present invention, in addition to the effect of the first or second aspect of the present invention, the angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized is the first angle. Compared with the case where there is no at least two second magnetic poles arranged to be less than 180 degrees across the magnetic pole, the magnetic force acting on one magnetic pole of the magnet member can be increased.

  According to the fourth aspect of the present invention, in addition to the effect of the present invention according to any one of the first to third aspects, the magnetic member has one magnetic pole as compared with the case where the present configuration is not provided. Magnetic force can be increased.

  According to the fifth aspect of the present invention, the magnetic force acting on one magnetic pole of the magnet member can be increased as compared with the case where the present configuration is not provided.

  According to the sixth aspect of the present invention, the magnetic force acting between one magnetic pole of the magnet member can be increased as compared with the case where the present configuration is not provided.

  According to the seventh aspect of the present invention, in addition to the effect of the present invention according to the sixth aspect, the developing device can be downsized as compared with the case where the number of the second magnetic poles is four or more. it can.

  According to the eighth aspect of the present invention, in addition to the effect of the present invention according to the sixth or seventh aspect, the angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member is maximum is the first angle. Compared with the case where there is no at least two second magnetic poles arranged so as to be less than 180 degrees across the magnetic pole, the magnetic force acting between one magnetic pole of the magnet member can be increased.

  According to the ninth aspect of the present invention, in addition to the effect of the present invention according to any one of the sixth to eighth aspects, the magnetic member has one magnetic pole as compared with the case where the present configuration is not provided. The magnetic force acting between them can be strengthened.

  According to the tenth aspect of the present invention, in addition to the effect of the present invention according to any one of the sixth to ninth aspects, the sheet is conveyed toward the image carrier as compared with the case where the present configuration is not provided. It is possible to easily peel off the developer attached to the rotating member later.

  According to the eleventh aspect of the present invention, in addition to the effect of the present invention according to the tenth aspect, the developer is newly conveyed toward the image carrier as compared with the case where the present configuration is not provided. It can be made easier.

  According to the twelfth aspect of the present invention, in addition to the effect of the present invention according to any one of the sixth to eleventh aspects, a developer is newly added to the image carrier as compared with the case where the present structure is not provided. It can be made easier to transport toward.

  According to the thirteenth aspect of the present invention, in addition to the effect of the present invention according to any one of the sixth to eleventh aspects, the image is conveyed toward the image carrier as compared with the case where the present configuration is not provided. It is possible to easily peel off the developer attached to the rotating member later.

  According to the fourteenth aspect of the present invention, the magnetic force acting between one magnetic pole of the magnet member can be increased as compared with the case where the present configuration is not provided.

  According to the fifteenth aspect of the present invention, the magnetic force acting between one magnetic pole of the magnet member can be increased as compared with the case where the present configuration is not provided.

  According to the sixteenth aspect of the present invention, in addition to the effect of the present invention according to the fifteenth aspect, the developing device can be downsized as compared with the case where the number of the second magnetic poles is four or more. it can.

  According to the seventeenth aspect of the present invention, in addition to the effect of the present invention according to the fifteenth or sixteenth aspect, the angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized is the first angle. Compared with the case where there is no at least two second magnetic poles arranged so as to be less than 180 degrees across the magnetic pole, the magnetic force acting between one magnetic pole of the magnet member can be increased.

  According to the 18th aspect of the present invention, in addition to the effect of the present invention according to any of the 15th to 17th aspects, compared with the case where the present structure is not provided, the magnetic member has one magnetic pole. The magnetic force acting between them can be strengthened.

  According to the nineteenth aspect of the present invention, in addition to the effect of the present invention according to any one of the fifteenth to eighteenth aspects, the sheet is conveyed toward the image carrier as compared with the case where the present configuration is not provided. It is possible to easily peel off the developer attached to the rotating member later.

  According to the 20th aspect of the present invention, in addition to the effect of the present invention according to the 19th aspect, the developer is newly conveyed toward the image carrier as compared with the case where the present structure is not provided. It can be made easier.

  According to the twenty-first aspect of the present invention, in addition to the effect of the present invention according to any one of the fifteenth to twentieth aspects, the sheet is conveyed toward the image carrier as compared with the case where the present configuration is not provided. It is possible to easily peel off the developer attached to the rotating member later.

  According to the twenty-second aspect of the present invention, the magnetic force acting between one magnetic pole of the magnet member can be increased as compared with the case where the present configuration is not provided.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, an image forming unit 14 in the image forming apparatus main body 12, a recording medium supply device 54 that supplies a recording medium such as a sheet to the image forming unit 14, A power supply unit 16 and a control unit 68 having a CPU (not shown) are arranged. In addition, a recording medium discharge unit 15 for discharging a recording medium on which an image has been formed is provided on the upper part of the image forming apparatus main body 12.

  The image forming unit 14 is of an electrophotographic system for forming a color image, and drum-shaped photoconductors 22Y, 22M, 22C, and 22B as image holding bodies for holding toner images, and the photoconductors 22Y, 22M, Charging devices 24Y, 24M, 24C, and 24B as charging means equipped with charging rolls that uniformly charge 22C and 22B, and latent images for writing electrostatic latent images on the respective photoconductors 22Y, 22M, 22C, and 22B by light Optical writing devices 26Y, 26M, 26C, and 26B as forming means, and a two-component developer composed of a non-magnetic toner and a magnetic carrier for converting latent images written on the photosensitive members 22Y, 22M, 22C, and 22B. Developing devices 28Y, 28M, 28C, and 28B, and toner images formed on the photosensitive members 22Y, 22M, 22C, and 22B, and transferring the toner images to a recording medium. A transfer unit 42 used as a means, and cleaning devices 30Y, 30M, 30C for cleaning off, for example, scraping waste toner remaining on the photoreceptors 22Y, 22M, 22C, 22B after the transfer of the toner image by the transfer unit 42 30B.

  Each of the optical writing devices 26Y, 26M, 26C, and 26B includes a laser exposure device. The optical writing device 26Y corresponds to a laser beam corresponding to a yellow image on the photosensitive member 22Y, and the optical writing device 26M corresponds to a magenta image on the photosensitive member 22M. The optical writing device 26C emits a laser beam corresponding to a cyan image to the photoconductor 22C, and the optical writing device 26B emits a laser beam corresponding to a black image to the photoconductor 22B, and the photoconductors 22Y, 22M, and 22C. , 22B are written with electrostatic latent images, respectively.

  Among the members of the image forming unit 14, the photosensitive members 22Y, 22M, 22C, and 22B, the charging devices 24Y, 24M, 24C, and 24B, the developing devices 28Y, 28M, 28C, and 28B, and the cleaning devices 30Y, 30M, 30C, and 30B are The image forming unit 32 used as an exchange unit is integrated and is detachably attached to the image forming apparatus main body 12 from the front side (right side in FIG. 1).

  Further, the photoreceptor 22Y, the charging device 24Y, and the cleaning device 30Y are integrated to form an image holding unit. Similarly, the photoconductors 22M, 22C, and 22B are integrated with the charging devices 24M, 24C, and 24B and the cleaning devices 30M, 30C, and 30B for each corresponding image color to form an image carrier unit. The developing devices 28Y, 28M, 28C, and 28B are detachably attached to the image forming unit 32, respectively.

Further, in the image forming unit 32, toner cartridges 34Y, 34M, 34C, and 34B as replacement units that respectively store toner supplied to the developing devices 28Y, 28M, 28C, and 28B are provided to the image forming apparatus main body 12. It is detachably mounted from the side.
The toner cartridges 34Y, 34M, 34C, and 34B have toner storage chambers 36Y, 36M, 36C, and 36B for storing toner, and waste toner storage chambers 38Y, 38M, 38C, and 38B, respectively, inside the image forming apparatus main body. The toner is supplied to the developing devices 28Y, 28M, 28C, and 28B through a toner supply path (not shown) provided in 12, respectively. For example, the toner cartridge 34Y is filled (contained) with yellow toner, the toner cartridge 34M with magenta toner, the toner cartridge 34C with cyan toner, and the toner cartridge 34B with black toner.

  The transfer unit 42 is disposed so as to contact the photoreceptors 22Y, 22M, 22C, and 22B of the image forming unit 32. The transfer unit 42 is integrated as a unit, and includes two support rolls 44a and 44b, a conveyance belt 46 as a conveyance unit for conveying a recording medium or an image, and an adsorption unit that adsorbs the recording medium to the conveyance belt 46. And a transfer roll 50Y, 50M, 50C, and 50B for transferring the toner images formed on the photoreceptors 22Y, 22M, 22C, and 22B to a recording medium that is being conveyed by the conveyance belt 46, respectively. Being done.

  The suction roll 48 is provided in pressure contact with the support roll 44 a via the transport belt 46, and a voltage is applied from the power supply unit 16 to electrostatically attract the recording medium to the transport belt 46.

  The transfer rolls 50Y, 50M, 50C, and 50B are each applied with a transfer bias, and sequentially transfer the toner images formed on the photoreceptors 22Y, 22M, 22C, and 22B to the recording medium being conveyed by the conveyance belt 46. A color toner image is formed by superimposing four color toner images of yellow, magenta, black, and cyan on a recording medium.

  Further, a fixing device 52 for fixing the toner image transferred to the recording medium by the transfer unit 42 to the recording medium is provided in the upper part in the image forming apparatus main body 12. The fixing device 52 includes a heating roll 52a and a pressure roll 52b. The fixing device 52 heats and pressurizes the toner image transferred to the recording medium passing between the heating roll 52a and the pressure roll 52b. The toner image is fixed.

  Further, the image forming apparatus main body 12 is provided with a conveyance path 60 for conveying the recording medium supplied from the recording medium supply device 54 to the recording medium discharge unit 15, and along the conveyance path 60, the recording medium is provided. A resist roll 62, a transfer unit 42, a fixing device 52, and a discharge roll 64 are arranged in this order from the upstream side in the transport direction. The discharge roll 64 discharges the recording medium conveyed from the fixing device 52 to the recording medium discharge unit 15.

FIG. 2 is a cross-sectional view showing the first embodiment of the developing device 28Y. The developing devices 28Y, 28M, 28C, and 28B have substantially the same configuration except that the color of the image to be developed is different. The developing device 28Y will be described in detail below.
The developing device 28Y includes a developing roll 72, a first agitating / conveying member 74, a second agitating / conveying member 76, a developer supplying member 78, and a layer as a developing member disposed on the photosensitive member 22Y side of the developing device main body 70. As described above, the two-component developer comprising the non-magnetic toner and the magnetic carrier is transported toward the photoreceptor 22Y by the developing roller 72 and written on the photoreceptor 22Y. Develop the latent image.

  The developing device main body 70 receives a toner from the toner storage chamber 36Y via a toner supply path (not shown) provided in the image forming apparatus main body 12, and transports the toner and the carrier with stirring. It has paths 84 and 86 and a developing chamber 88 in which the developing roll 72 is accommodated. Further, a partition plate 90 is provided between the developer transport path 84 and the developer transport path 86, and the developer transport path 84 and the developer transport path 86 are connected to both ends of the partition plate 90. A passage (not shown) is provided. That is, the developer conveying paths 84 and 86 constitute a developer accommodating portion that accommodates the developer in advance, and the first agitating and conveying member 74 and the second agitating and conveying member 76 convey the developer in alternate directions. As a result, the toner is frictionally charged to a predetermined polarity by the carrier and circulated in the developing device main body 70. The second agitating and conveying member 76 agitates and conveys the developer conveyed via the developer conveying path 86 and supplies the developer to the developing chamber 88.

  The developer supply member 78 is disposed so as to face the second stirring and conveying member 76 and is rotated clockwise (clockwise in FIG. 2). The developer supply member 78 supplies the developer supplied to the developing chamber 88. Supplied to the developing roll 72. The layer thickness regulating member 80 is disposed above the developer supply member 78 and regulates the layer thickness of the developer conveyed by the developing roll 72 toward the photoreceptor 22Y to a predetermined value.

  The developing roll 72 includes a sleeve 92 that is a non-magnetic rotating member that rotates in a counterclockwise direction (counterclockwise in FIG. 2) and a magnet member that is fixedly disposed in the sleeve 92. And a certain magnet roll 94. The sleeve 92 is made of, for example, cylindrical aluminum or stainless steel, and is configured to rotate clockwise (clockwise in FIG. 2) at a predetermined interval from the photoreceptor 22Y.

The magnet roll 94 is, for example, a ferrite magnet or a plastic resin magnet having a roll diameter of 14 mm or less. For example, a magnetic pole 96 that is one S pole (main pole) and three magnetic poles 98 and 100 that are N poles on the outer surface. , 102 are arranged. The magnetic pole 96 and the magnetic poles 98, 100, 102 each form a magnetic field in a direction including the normal direction of the sleeve 92, and influence the magnetic field with each other.
A thick broken line in FIG. 2 indicates that the distance in the normal direction from the surface of the sleeve 92 indicates the strength of the magnetic field or the magnetic flux density in the normal direction on the surface of the sleeve 92. On the surface of the sleeve 92, the maximum value of the magnetic flux density is 100 mT or more.
The magnet roll 94 may be configured by arranging magnets so that the magnetic poles are positioned on the outer surface of the roll, or may be configured by a magnetized member.

  The magnetic pole 96 is disposed so as to face the photoconductor 22Y with the sleeve 92 in between, and is on the surface of the sleeve 92 in the direction s1 in which the magnetic field strength in the normal direction of the sleeve 92 is maximum toward the photoconductor 22Y. The magnetic flux density in the normal direction is set to a predetermined value (for example, 100 mT).

  The magnetic pole 98 is disposed between the photoreceptor 22Y and the layer thickness regulating member 80, and the normal magnetic flux on the surface of the sleeve 92 in the direction n1 in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized. The density is set to a predetermined value (for example, 40 mT).

  The magnetic pole 100 is arranged so as to face the magnetic pole 96 with the center of the magnet roll 94 interposed therebetween, and the magnetic field in the normal direction of the sleeve 92 is directed in a direction substantially opposite to the direction in which the magnetic pole 96 forms s1. The magnetic flux density in the normal direction on the surface of the sleeve 92 in the direction n2 in which the strength of the magnetic field becomes the maximum is set to a predetermined value (for example, 40 mT).

  The magnetic pole 102 is disposed downstream of the magnetic pole 96 in the rotation direction of the sleeve 92, and the normal magnetic flux on the surface of the sleeve 92 in the direction n3 in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized. The density is set to a predetermined value (for example, 40 mT).

Here, the angle formed by the above-described direction n1 and direction n3 is set to be less than 180 degrees across the magnetic pole 96. The angle formed by the direction n2 and the direction s1 is greater than 90 degrees and less than 270 degrees. Furthermore, the angle formed by the direction n1 and the direction n2 is larger than the angle formed by the direction n2 and the direction n3.
Hereinafter, the thick broken line on the magnetic pole 96 side surrounding the direction s1 is the thick broken line S1, the thick broken line on the magnetic pole 98 side surrounding the direction n1 is the thick broken line N1, and the thick broken line on the magnetic pole 100 side surrounding the direction n2 is the thick broken line N2. A thick broken line on the side of the magnetic pole 102 surrounding the direction n3 is abbreviated as a thick broken line N3.

  The magnetic flux in the normal direction of the sleeve 92 between the thick broken line N3 and the thick broken line N2 by the magnetic pole 102 and the magnetic pole 100 on the downstream side in the rotation direction of the sleeve 92 from the position where the sleeve 92 faces the photoreceptor 22Y. A region P1 having a density of a predetermined value (for example, 5 mT) or less is formed. A region where the magnitude of the magnetic flux density in the tangential direction and the normal direction of the sleeve 92 is not more than a predetermined value (for example, 5 mT) is formed around the region P1. That is, the region P1 and its surroundings are regions that prompt the developer to be peeled off from the sleeve 92. Further, a developer supply member 80 is disposed in the vicinity of the region P1 (slightly downstream in the rotation direction of the sleeve 92). Since the developer supply member 80 is rotated in the same direction as the sleeve 92, the developer supply member 80 and the sleeve 92 are moved in opposite directions at a position where the developer supply member 80 and the sleeve 92 are opposed to each other. ing. As a result of the rotation of the developer supply member 80, the developer peeled from the sleeve 92 in and around the region P1 is urged to be sent back to the second stirring and conveying member 76 side, and the second A new developer is supplied from the agitating and conveying member 76 side to the downstream side in the rotation direction of the sleeve 92 from the position where the developer supply member 80 and the sleeve 92 are opposed, and the developer is efficiently circulated.

Further, since the magnetic pole 100 and the magnetic pole 98 are arranged apart from the region P1 in the rotation direction of the sleeve 92, the sleeve 92 is disposed between the thick broken line N2 and the thick broken line N1 with respect to the sleeve 92. A thick broken line S2 is formed in which the magnetic field formed by the magnetic pole 100 and the magnetic pole 98 is opposite to the magnetic field, and the maximum magnetic flux density in the normal direction of the sleeve 92 is a predetermined value (for example, 5 mT). ing. That is, the thick broken line S2 is a so-called ghost pole in which the magnitude of the magnetic flux density in the normal direction of the sleeve 92 is equal to or greater than a predetermined value even if the S pole is not provided between the magnetic pole 98 and the pole 100. Is formed. And the layer thickness control member 80 is arrange | positioned so that this thick broken line S2 may be opposed. Accordingly, a magnetic force having a magnitude greater than or equal to a predetermined value acts in the normal direction on the sleeve 92 at the thick broken line S2, and the developer at the thick broken line S2 stands in the normal direction. The layer thickness of the passed developer on the sleeve 92 is stabilized. Thus, even if the number of magnetic poles is reduced, the developer layer thickness can be regulated stably.
As described above, even if the number of magnetic poles is reduced, the developer can be efficiently circulated and the layer thickness can be regulated stably, which is advantageous for reducing the cost and diameter of the developing roll 72. Further, when the diameter of the developing roll 72 is reduced, if the number of magnetic poles is large, the width of the magnetic pole 96 which is the main pole becomes narrow, and it is difficult to generate a desired magnetic force necessary for developing the developer on the photosensitive member 22Y. Therefore, it is easy to use a magnet made of an expensive material in order to generate a desired magnetic force. However, if the number of magnetic poles can be reduced as in this embodiment, the main pole can be obtained even when the diameter of the developing roll 72 is reduced. The magnetic pole 96 can be widened, and a desired magnetic force required to develop the developer on the photoconductor 22Y can be easily generated.

Next, the action of the magnetic pole 98, the magnetic pole 100, and the magnetic pole 102 on the magnetic field formed by the magnetic pole 96 will be described.
In the developing device 28Y shown in FIG. 2, since the magnetic pole 96 is the S pole and the other magnetic pole 98, the magnetic pole 100, and the magnetic pole 102 are the N pole, the magnetic pole 96 that is the S pole is the N pole. 102 is sandwiched at an angle of less than 180 degrees. The magnetic pole 96 sandwiched at an angle of less than 180 degrees suppresses the spread of the magnetic field lines in the circumferential direction of the sleeve 92 by the magnetic pole 98 and the pole 102 which are opposite polarities, and the magnetic flux density in the normal direction of the sleeve 92 at the magnetic pole 96 is reduced. The value at which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized increases. Further, the magnetic pole 96 that is the S pole is greater than 90 degrees and less than 270 degrees (substantially opposite in FIG. 2) with the magnetic pole 100 that is the N pole. The magnetic pole 96 disposed in a direction substantially opposite to the magnetic pole 100 that is the reverse pole can efficiently increase the magnetic flux density in the normal direction of the sleeve 92 at the magnetic pole 96 by the action of the magnetic pole 100 that is the reverse pole. The value at which the strength of the magnetic field in the direction is maximum increases. Therefore, compared with the case where any of the magnetic pole 98, the magnetic pole 100, and the magnetic pole 102 is the S pole, the magnetic field strength by the magnetic pole 96 is increased.

FIG. 3 is a diagram showing the relationship between the magnetic pole 96, the magnetic pole 98, and the magnetic pole 102 in the developing roll 72, and the magnetic flux density. FIG. (B) is a schematic diagram showing a state (variation example) in which the angle formed by the direction n1 and the direction n3 sandwiching the magnetic pole 96 exceeds 180 degrees.
FIG. 4 is a graph showing an experimental example of the magnetic flux density ratio in the direction s1 in the state shown in FIG.
As shown in FIGS. 3 and 4, the angle formed by the direction n1 of the thick broken line N1 formed by the magnetic pole 98 and the direction n3 of the thick broken line N3 formed by the magnetic pole 102 with the magnetic pole 96 interposed therebetween is less than 180 degrees. The magnetic flux density in the direction s1 at which the strength of the magnetic field in the normal direction of the sleeve 92 by the magnetic pole 96 is maximized is larger than when the angle formed by the direction n1 and the direction n3 sandwiching the magnetic pole 96 exceeds 180 degrees ( For example, increase by 4%).

Therefore, the developer transported via the developer transport path 84 and the developer transport path 86 is transported toward the developing roll 72 by the developer supply member 78 and adheres to the surface of the sleeve 92. The developer that adheres to the sleeve 92 and is conveyed is conveyed in the magnetic field of the thick broken line S2, the layer thickness is regulated by the layer thickness regulating member 80, and conveyed toward the photoreceptor 22Y with a predetermined layer thickness. The electrostatic latent image written on the photoreceptor 22Y is developed with toner. The developer remaining on the sleeve 92 after development is peeled off from the sleeve 92 around the region P1.
As described above, the value that maximizes the strength of the magnetic field in the normal direction of the sleeve 92 in the magnetic pole 96 that is the main pole can be increased, which is advantageous in reducing the diameter of the developing roll 72. When the diameter of the developing roll 72 is reduced, the width of the magnetic pole 96, which is the main pole, is narrowed, and it becomes difficult to generate a desired magnetic force necessary for developing the developer on the photoconductor 22Y. However, if the polarity and arrangement of the magnetic poles are devised as in this embodiment, the magnetic field of the magnetic pole 96, which is the main pole, even when the developing roll 72 is reduced in diameter, is apt to be used. The value at which the strength of the toner is maximized is increased, and a desired magnetic force necessary for developing the developer on the photosensitive member 22Y is easily generated.

Next, a second embodiment of the developing device 28Y will be described.
FIG. 5 is a cross-sectional view showing a second embodiment of the developing device 28Y. Note that, in the second embodiment of the developing device 28Y, substantially the same parts as those constituting the first embodiment shown in FIG.
The developing device 28Y includes, for example, a magnet roll 94 in which one magnetic pole 96 that is an S pole (main pole) and four magnetic poles 104, 106, 108, and 110 that are N poles are arranged on the outer surface.
A thick broken line in FIG. 5 indicates that the distance in the normal direction from the surface of the sleeve 92 indicates the strength of the magnetic field or the magnetic flux density in the normal direction on the surface of the sleeve 92. On the surface of the sleeve 92, the maximum value of the magnetic flux density is 100 mT or more.

  The magnetic pole 104 is disposed between the photoconductor 22Y and the layer thickness regulating member 80, and the normal magnetic flux on the surface of the sleeve 92 in the direction n21 in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized. The density is set to a predetermined value (for example, 40 mT).

  The magnetic pole 106 is disposed upstream of the magnetic pole 104 in the rotation direction of the sleeve 92, and the magnetic field strength in the normal direction of the sleeve 92 is maximized toward the direction in which the layer thickness regulating member 80 is provided. The magnetic flux density in the normal direction on the surface of the sleeve 92 in the direction n22 becomes a predetermined value (for example, 40 mT).

  The magnetic pole 108 is disposed upstream of the magnetic pole 106 in the rotation direction of the sleeve 92, and the magnetic field strength in the normal direction of the sleeve 92 is maximized toward the direction in which the developer supply member 78 is provided. The magnetic flux density in the normal direction on the surface of the sleeve 92 in the direction n23 becomes a predetermined value (for example, 40 mT).

  The magnetic pole 110 is disposed upstream of the magnetic pole 108 in the rotation direction of the sleeve 92, and the normal magnetic flux on the surface of the sleeve 92 in the direction n24 in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized. The density is set to a predetermined value (for example, 40 mT).

Here, the angle formed by the above-described direction n21 and direction n24 is set to be less than 180 degrees across the magnetic pole 96. Further, the angles formed by the direction n22 and the direction n23 with the direction s1 are greater than 90 degrees and less than 270 degrees. Furthermore, the angle formed by the direction n21 and the direction n22 and the angle formed by the direction n23 and the direction n24 are larger than the angle formed by the direction n22 and the direction n23, respectively.
Hereinafter, the thick broken line on the magnetic pole 96 side surrounding the direction s1 is the thick broken line S1, the thick broken line on the magnetic pole 104 side surrounding the direction n21 is the thick broken line N21, the thick broken line on the magnetic pole 106 side surrounding the direction n22 is the thick broken line N22, A thick broken line on the magnetic pole 108 side surrounding the direction n23 is abbreviated as a thick broken line N23, and a thick broken line on the magnetic pole 110 side surrounding the direction n24 is abbreviated as a thick broken line N24.

  Since the magnetic pole 110 and the magnetic pole 108 are spaced apart from the position where the sleeve 92 faces the photoconductor 22Y, the sleeve 92 is disposed between the thick broken line N24 and the thick broken line N23 on the downstream side in the rotation direction. In addition, the magnetic field in the direction opposite to the magnetic field formed by the magnetic pole 110 and the magnetic pole 108 with respect to the sleeve 92 and the magnetic flux density in the normal direction of the sleeve 92 is a predetermined value (for example, 5 mT) or more. A broken line S30 is formed. That is, in the thick broken line S30, the magnetic flux density in the normal direction of the sleeve 92 is equal to or larger than a predetermined value even when the S magnetic pole is not provided between the magnetic pole 110 and the magnetic pole 108.

  Further, the magnetic flux density in the normal direction of the sleeve 92 has a predetermined value (for example, the upstream side of the sleeve 92 in the rotation direction) from the position where the developer supply member 78 conveys the developer toward the developing roll 72. A region P2 that is 5 mT or less is formed. A region where the magnitude of the magnetic flux density in the tangential direction and the normal direction of the sleeve 92 is not more than a predetermined value (for example, 5 mT) is formed around the region P2. That is, the region P2 and its surroundings are regions that prompt the developer to be peeled off from the sleeve 92.

  Further, since the magnetic pole 106 and the magnetic pole 104 are arranged apart from the region P2 in the rotation direction of the sleeve 92, the sleeve 92 is disposed between the thick broken line N22 and the thick broken line N21. A thick broken line S32 is formed which is a magnetic field in the opposite direction to the magnetic field formed by the magnetic pole 106 and the magnetic pole 104, and the magnitude of the magnetic flux density in the normal direction of the sleeve 92 is a predetermined value (for example, 5 mT) or more. . That is, in the thick broken line S32, the magnitude of the magnetic flux density in the normal direction of the sleeve 92 is equal to or greater than a predetermined value even when the south pole is not provided between the pole 106 and the pole 104.

  Therefore, the developer transported via the developer transport path 84 and the developer transport path 86 is transported toward the developing roll 72 by the developer supply member 78 and adheres to the surface of the sleeve 92. The developer adhered and conveyed to the sleeve 92 is regulated in layer thickness by the layer thickness regulating member 80, conveyed in the magnetic field of the thick broken line S32, conveyed toward the photoreceptor 22Y with a predetermined layer thickness, and photosensitive. The electrostatic latent image written on the body 22Y is developed with toner. The developer remaining on the sleeve 92 after the development is transported in the magnetic field indicated by the thick broken line S30 and is peeled off from the sleeve 92 around the region P2.

1 is a side view illustrating an outline of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a first embodiment of a developing device according to an embodiment of the present invention. It is a figure which shows the relationship between the magnetic pole in a developing roll, and magnetic flux density, Comprising: (A) is a schematic diagram which shows the state which the angle which the direction n1 and direction n3 make | form across an S pole is less than 180 degree | times, (B ) Is a schematic diagram showing a state where the angle formed by the direction n1 and the direction n3 across the south pole exceeds 180 degrees. It is a graph which shows the experimental example of the magnetic flux density ratio of the direction s1 in the state shown in FIG. It is sectional drawing which shows 2nd Embodiment of the developing device which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 14 Image forming part 22Y, 22M, 22C, 22B Photoconductor 28Y, 28M, 28C, 28B Developing device 36Y, 36M, 36C, 36B Toner storage chamber 42 Transfer unit 52 Fixing device 70 Developing device main body 72 Developing roll 74 First stirring and conveying member 76 Second stirring and conveying member 78 Developer supply member 80 Layer thickness regulating members 84 and 86 Developer conveying path 88 Developing chamber 92 Sleeve 94 Magnet roll 96 Magnetic pole (S pole)
98, 100, 102, 104, 106, 108, 110 Magnetic pole (N pole)

Claims (22)

  A non-magnetic rotating member that rotates to face the image carrier, and a magnet member disposed in the rotating member, the magnet member forming one magnetic field in a normal direction of the rotating member The first magnetic pole is different in polarity from the first magnetic pole, and is at a position different from the first magnetic pole in the circumferential direction of the rotating member and forms a magnetic field in the normal direction of the rotating member. And a second magnetic pole.   The developing member according to claim 1, wherein the magnet member has three second magnetic poles.   In at least two of the second magnetic poles, an angle formed by each of the directions in which the strength of the rotating member in the normal direction of the magnetic field by the second magnetic pole is maximum is 180 degrees across the first magnetic pole. The developing member according to claim 1, wherein the developing member is disposed so as to be less than a predetermined value.   At least one of the second magnetic poles includes a direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximized, and a normal direction of the rotating member by the first magnetic pole. The developer according to any one of claims 1 to 3, wherein an angle formed by a direction in which the strength of the magnetic field is maximum is greater than 90 degrees and less than 270 degrees.   A non-magnetic rotating member that rotates to face the image carrier, and a magnet member disposed in the rotating member, the magnet member forming one magnetic field in a normal direction of the rotating member The first magnetic pole and the first magnetic pole have different polarities, and the first magnetic pole is located at different positions in the circumferential direction of the rotating member and forms a plurality of magnetic fields in the normal direction of the rotating member. And at least two of the second magnetic poles have an angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximum. A developing member disposed so as to be less than 180 degrees across the first magnetic pole.   A developer containing portion that contains a developer containing non-magnetic toner and a magnetic carrier; and a developer that conveys the developer contained in the developer containing portion toward an image carrier. Comprises a non-magnetic rotating member that rotates to face the image carrier and a magnet member disposed in the rotating member, and the magnet member forms a magnetic field in the normal direction of the rotating member. One first magnetic pole is different in polarity from the first magnetic pole, and forms a magnetic field in the normal direction of the rotating member at a position different from the first magnetic pole in the circumferential direction of the rotating member. A developing device having at least three second magnetic poles;   The developing device according to claim 6, wherein the magnet member has three second magnetic poles.   In at least two of the second magnetic poles, an angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximized is 180 degrees across the first magnetic pole. The developing device according to claim 6, wherein the developing device is disposed so as to be less than a predetermined value.   At least one of the second magnetic poles includes a direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximized, and a normal direction of the rotating member by the first magnetic pole. The developing device according to claim 6, wherein the developing device is disposed such that an angle formed by a direction in which the strength of the magnetic field is maximum is greater than 90 degrees and less than 270 degrees.   At least two of the second magnetic poles have a magnetic flux density of 5 mT or less in the normal direction of the rotating member on the downstream side in the rotating direction of the rotating member from the position where the rotating member faces the image carrier. The developing device according to claim 6, wherein the developing region is formed.   At least two of the second magnetic poles are located on the downstream side in the rotational direction of the rotating member from a position where a region where the magnetic flux density in the normal direction of the rotating member is 5 mT or less is formed. The developing device according to claim 10, wherein a region having the same polarity as a magnetic field formed by the magnetic poles and having a magnetic flux density in the normal direction of the rotating member of 5 mT or more is formed.   At least two of the second magnetic poles have higher magnetic flux densities in the tangential and normal directions of the rotating member upstream of the rotating member in the rotating direction than the position where the rotating member faces the image carrier. The developing device according to any one of claims 6 to 11, wherein an area having a length of 5 mT or less is formed.   At least two of the second magnetic poles have a larger magnetic flux density in the tangential and normal directions of the rotating member on the downstream side in the rotating direction of the rotating member than the position where the rotating member faces the image carrier. The developing device according to any one of claims 6 to 11, wherein an area having a length of 5 mT or less is formed.   A developer containing portion that contains a developer containing non-magnetic toner and a magnetic carrier; and a developer that conveys the developer contained in the developer containing portion toward an image carrier. Comprises a non-magnetic rotating member that rotates to face the image carrier and a magnet member disposed in the rotating member, and the magnet member forms a magnetic field in the normal direction of the rotating member. One first magnetic pole is different in polarity from the first magnetic pole, and forms a magnetic field in the normal direction of the rotating member at a position different from the first magnetic pole in the circumferential direction of the rotating member. A plurality of second magnetic poles, and at least two of the second magnetic poles are formed by respective directions in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic poles is maximum. Is arranged to be less than 180 degrees across the first magnetic pole. The developing device.   An image holding member, a developing device that develops the latent image formed on the image holding member with a developer, a transfer unit that transfers the developer image developed by the developing device to a recording medium, and a recording unit that records the image. A fixing device that fixes the developer image transferred onto the recording medium to the recording medium. The developing device holds a developer containing portion that contains the developer and an image that holds the developer contained in the developer containing portion. A developer that is conveyed toward the body, and the developer includes a nonmagnetic rotating member that rotates to face the image holding member, and a magnet member disposed in the rotating member, The magnet member has one first magnetic pole that forms a magnetic field in the normal direction of the rotating member, and the first magnetic pole has a different polarity, and the first magnetic pole differs in the circumferential direction of the rotating member. A magnetic field in the normal direction of the rotating member Also an image forming apparatus having a three second pole, the.   The image forming apparatus according to claim 15, wherein the magnet member has three second magnetic poles.   In at least two of the second magnetic poles, an angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximized is 180 degrees across the first magnetic pole. The image forming apparatus according to claim 15, wherein the image forming apparatus is arranged so as to be less than the number.   At least one of the second magnetic poles includes a direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximized, and a normal direction of the rotating member by the first magnetic pole. The image forming apparatus according to claim 15, wherein the image forming apparatus is arranged such that an angle formed by a direction in which the strength of the magnetic field is maximum is greater than 90 degrees and less than 270 degrees.   At least two of the second magnetic poles have a magnetic flux density of 5 mT or less in the normal direction of the rotating member on the downstream side in the rotating direction of the rotating member from the position where the rotating member faces the image carrier. The image forming apparatus according to claim 15, wherein the image forming apparatus forms a region that is   At least two of the second magnetic poles are located on the downstream side in the rotational direction of the rotating member from a position where a region where the magnetic flux density in the normal direction of the rotating member is 5 mT or less is formed. The image forming apparatus according to claim 19, wherein a region having the same polarity as the magnetic field formed by the magnetic poles and having a magnetic flux density in the normal direction of the rotating member of 5 mT or more is formed.   At least two of the second magnetic poles have a larger magnetic flux density in the tangential and normal directions of the rotating member on the downstream side in the rotating direction of the rotating member than the position where the rotating member faces the image carrier. 21. The image forming apparatus according to claim 15, wherein the image forming apparatus forms regions having a length of 5 mT or less.   An image holding member, a developing device that develops the latent image formed on the image holding member with a developer, a transfer unit that transfers the developer image developed by the developing device to a recording medium, and a recording unit that records the image. A fixing device that fixes the developer image transferred onto the recording medium to the recording medium. The developing device holds a developer containing portion that contains the developer and an image that holds the developer contained in the developer containing portion. A developer that is conveyed toward the body, and the developer includes a nonmagnetic rotating member that rotates to face the image holding member, and a magnet member disposed in the rotating member, The magnet member has one first magnetic pole that forms a magnetic field in the normal direction of the rotating member, and the first magnetic pole has a different polarity, and the first magnetic pole differs in the circumferential direction of the rotating member. A plurality of magnetic fields in the normal direction of the rotating member And at least two of the second magnetic poles have an angle formed by each direction in which the strength of the magnetic field in the normal direction of the rotating member by the second magnetic pole is maximum. An image forming apparatus arranged to be less than 180 degrees across one magnetic pole.

Images