JP5051614B2 - Developing device and image forming apparatus - Google Patents

Description

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

  Patent Document 1 discloses a two-component developing device provided with a developer supplying / separating rotating member that rotates in the same direction as the rotation direction of the developer holding member in a state of being opposed to and in contact with the developer holding member. Is disclosed. Further, in Patent Document 2, a developer stripping area is provided on the outer surface of a non-magnetic cylindrical body that encloses the magnet roller between the developing magnetic pole provided on the magnet roller and the developer pumping magnetic pole. Disclosed is a developing device in which a rotating member that rotates about an axis parallel to the center of rotation of the body is provided to face the developer stripping area. Further, Patent Document 3 provides a non-magnetic pole portion that makes the magnetic flux density substantially zero in a part of the magnet body corresponding to the position where the developed developer falls on its surface on the developer carrier, and also corresponds to the non-magnetic pole portion. A developing device is disclosed in which a non-magnetic peeling member having elasticity that peels and drops the developed developer by lightly pressing the surface of the developer carrying member is disposed above the developer stirring member.

Japanese Patent Laid-Open No. 08-062983 JP 2006-227116 A Japanese Patent Laid-Open No. 04-343376

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus that can reduce the size of a developer without reducing the magnetic force generated by magnetic poles that form a magnetic field toward an image carrier.

In order to achieve the above object, the present invention according to claim 1 is directed to a developer containing portion that contains a developer containing non-magnetic toner and a magnetic carrier, and an image holding means for the developer contained in the developer containing portion. A developer conveyed toward the body, a developer supplying means for supplying the developer accommodated in the developer accommodating portion toward the developer, and the developer conveyed by the developer is peeled from the developer. A developer peeling means, 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, and the magnet member includes: A first magnetic pole that forms a magnetic field in the normal direction of the rotating member toward the image carrier, and the first magnetic pole has a different polarity, and is upstream of the rotating direction of the rotating member with respect to the first magnetic pole. The second magnetic pole disposed on the first magnetic pole is different in polarity from the first magnetic pole, Only the three magnetic poles including the third magnetic pole disposed on the downstream side in the rotation direction of the rotating member with respect to the first magnetic pole are provided on the outer surface side, and the second magnetic pole and the third magnetic pole are The direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized is less than 180 degrees with the first magnetic pole interposed therebetween, and the developer peeling means is less than the third magnetic pole. The rotating member faces the rotating member downstream in the rotating direction of the rotating member and upstream of the rotating member in the rotating direction of the rotating member, and the developer supplying means rotates the rotating member more than the developer peeling means. The developing device is provided to face the rotating member on the downstream side in the rotation direction of the member and on the upstream side in the rotation direction of the rotating member with respect to the second magnetic pole.
According to the first aspect of the present invention, even with only three magnetic poles, the magnetic force of the first magnetic pole can be increased compared to the case where the above-described angle is 180 degrees or more, and toward the image carrier. The developer can be reduced in size (reduced diameter) without reducing the magnetic force generated by the magnetic poles forming the magnetic field.

The present invention according to claim 2 is the developing device according to claim 1, wherein the developer supply means and the developer peeling means are formed by a developer peeling supply member that rotates while being in contact with the rotating member. .
According to the second aspect of the present invention, the developer can be peeled off and supplied in a narrow region.

According to a third aspect of the present invention, the second magnetic pole and the third magnetic pole are located downstream of the third magnetic pole in the rotation direction of the rotating member and more than the second magnetic pole. The developing device according to claim 2, wherein a magnetic field having the same polarity as the magnetic field formed by the first magnetic pole is formed on the upstream side in the rotation direction.
According to the third aspect of the present invention, since a magnetic field having the same polarity as the magnetic field formed by the first magnetic pole is formed, the developer supplied by the developer supply means is attracted to the rotating member and conveyed. Can do.

The present invention according to claim 4 is characterized in that the third magnetic pole has a direction in which the strength of the magnetic field in the normal direction of the rotating member by the third magnetic pole is maximized, and the rotating member by the first magnetic pole. The developing device according to claim 2, wherein the developing device is arranged so that an angle formed by a direction in which the magnetic field strength in the normal direction is maximum is 90 degrees or less.
According to the fourth aspect of the present invention, the strength in the tangential direction on the downstream side in the rotational direction of the rotating member can be increased with respect to the position where the strength of the magnetic field in the normal direction of the first magnetic pole is maximized. Therefore, it is possible to reduce the adhesion of the magnetic carrier to the image carrier.

According to a fifth aspect of the present invention, the second magnetic pole has 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 the rotating member by the first magnetic pole. The developing device according to claim 2, wherein the developing device is arranged so that an angle formed by a direction in which the magnetic field strength in the normal direction is maximum is 90 degrees or less.
According to the fifth aspect of the present invention, the strength in the tangential direction on the upstream side in the rotational direction of the rotating member can be increased with respect to the position where the strength of the magnetic field in the normal direction of the first magnetic pole is maximized. Therefore, it is possible to avoid the developer transported by the developer from staying without being transported well toward the first magnetic pole.

According to a sixth aspect of the present invention, the strength of the magnetic field having a polarity different from that of the first magnetic pole in the normal direction of the rotating member by the second magnetic pole is approximately zero. The developer is supplied from the upstream side in the rotational direction of the rotating member relative to the upstream side in the rotational direction of the rotating member, and is different from the first magnetic pole in the normal direction of the rotating member by the third magnetic pole. 6. The developing device according to claim 2, wherein the developer is peeled off from the downstream side in the rotational direction of the rotating member rather than the downstream side in the rotational direction of the rotating member where the intensity of the magnetic field of polarity is substantially zero. is there.
According to the sixth aspect of the present invention, since the peeling is performed at a position where the magnetic force is different from the three magnetic poles, the stress applied to the developer can be reduced even if the developer peeling supply member is in contact.

According to a seventh aspect of the present invention, the developer peeling supply member has a magnetic field having the same polarity as the magnetic field formed by the first magnetic pole in the tangential direction of the rotating member by the second magnetic pole and the third magnetic pole. The developing device according to claim 2, wherein the developer is supplied in a region where the strength of the toner is substantially 0 and the developer is peeled off.
According to the seventh aspect of the present invention, since the peeling is performed at a position where the magnetic force is weaker, the stress applied to the developer can be reduced even when the developer peeling supply member is in contact with the developer, and the developer can be developed in the magnetic field. Therefore, the developer can be conveyed by being adsorbed to the rotating member.

The present invention according to claim 8 is the developing device according to any one of claims 2 to 7, wherein the developer peeling supply member has a rotating shaft made of a magnetic material.
According to the eighth aspect of the present invention, since the magnetic field is formed between the developer and the developer peeling supply member and the developer stands, the developer can be further easily peeled off.

The present invention according to claim 9 is the developing device according to any one of claims 2 to 8, wherein the developer peeling supply member rotates while an elastic foamable member is in contact with the rotating member.
According to the ninth aspect of the present invention, the contact area between the developer and the developer peeling supply member can be easily widened, the developer can be easily peeled off, and the developer is worn over time. Can be reduced.

The present invention according to claim 10 is the developing device according to any one of claims 2 to 9, wherein the developer peeling supply member rotates in the same direction as the rotating member.
According to the tenth aspect of the present invention, the developer is more easily peeled off because the rotating member and the developer peeling supply member move in opposite directions.

  According to an eleventh 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 device contains a developer including a non-magnetic toner and a magnetic carrier. A developer accommodating portion, a developer conveying the developer accommodated in the developer accommodating portion toward the image carrier, and a developer supplying the developer accommodated in the developer accommodating portion toward the developer. And a developer peeling means for peeling the developer conveyed by the developer from the developer. The developer is a non-magnetic rotating member that rotates to face the image holding member. A magnet member disposed in the rotating member, The recording magnet member has a first magnetic pole that forms a magnetic field in the normal direction of the rotating member toward the image carrier, and the first magnetic pole has a different polarity, and the rotating member is more than the first magnetic pole. The second magnetic pole disposed upstream in the rotation direction of the first magnetic pole is different in polarity from the first magnetic pole, and the third magnetic pole disposed downstream in the rotation direction of the rotating member from the first magnetic pole. And the second magnetic pole and the third magnetic pole are each in the direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized. And the developer peeling means is located downstream of the third magnetic pole in the rotational direction of the rotary member and in the rotational direction of the rotary member relative to the second magnetic pole. Opposite to the rotating member on the upstream side, the developer supplying means is the developer The downstream side in the rotational direction of the rotary member than away means is and the image forming apparatus is provided so as to face the rotary member at the upstream side in the rotational direction of the rotating member than the second pole.

  According to the present invention, the developing body can be reduced in size without reducing the magnetic force due to the magnetic poles that form a magnetic field toward the image carrier.

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 photoconductor 22Y, and the optical writing device 26M corresponds to a magenta image on the photoconductor 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 configuration 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 stirring / conveying member 74, a second stirring / conveying member 76, a developer peeling supply member 78, and a developing roller disposed on the photosensitive member 22Y side of the developing device main body 70. As described above, the two-component developer composed of the non-magnetic toner and the magnetic carrier is conveyed toward the photosensitive member 22Y by the developing roller 72, and written on the photosensitive member 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 84 and supplies the developer to the developing chamber 88.

  The developer peeling supply member 78 has a rotating shaft 79 made of a magnetic material and a foamable member 80 having elasticity such as foamed urethane that covers the rotating shaft 79, and faces the second agitating and conveying member 76. Are arranged as follows. The foamable member 80 rotates clockwise around the rotation shaft 79 (in the clockwise direction in FIG. 2) while being in contact with the developing roll 72, and supplies the developer supplied to the developing chamber 88 to the developing roll 72. At the same time, after the developing roller 72 develops the latent image, the developer that remains on the surface of the developing roller 72 and is conveyed is peeled off from the developing roller 72. Moreover, since the rotating shaft 79 is a magnetic body, it forms a magnetic field with the magnet roll 94. The layer thickness regulating member 82 is disposed above the developer peeling 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 having an outer diameter of 12 mm or less, and is rotated clockwise (clockwise in FIG. 2) at a predetermined interval from the photoreceptor 22Y. ing.

The magnet roll 94 is, for example, a ferrite magnet or a plastic resin magnet fixed to a metal shaft 95, and has, for example, a magnetic pole 96 that is one S pole (main pole) on the outer surface side and two N poles. Magnetic poles 98 and 100 are disposed. The magnetic pole 96 and the magnetic poles 98 and 100 each form a magnetic field in a direction including the normal direction of the sleeve 92 and also affect 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 (first magnetic pole) is disposed so as to face the photoconductor 22Y with the sleeve 92 interposed therebetween, and the direction in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized toward the photoconductor 22Y. The magnetic flux density in the normal direction on the surface of the sleeve 92 at s1 is set to a predetermined value (for example, 100 mT).

  The magnetic pole 98 (second magnetic pole) is disposed between the photoreceptor 22Y and the layer thickness regulating member 82, and in the direction n1 in which the strength of the magnetic field in the normal direction of the sleeve 92 is maximized upward. The magnetic flux density in the normal direction on the surface of the sleeve 92 is set to a predetermined value (for example, 40 mT).

The magnetic pole 100 (third magnetic pole) is disposed downstream of the magnetic pole 96 in the rotation direction of the sleeve 92, and in the direction n2 where the strength of the magnetic field in the normal direction of the sleeve 92 is maximized downward. The magnetic flux density in the normal direction on the surface of the sleeve 92 is set to a predetermined value (for example, 40 mT).
Hereinafter, the thick broken line on the side of the magnetic pole 96 surrounding the direction s1 is abbreviated as the thick broken line S1, the thick broken line on the side of the magnetic pole 98 surrounding the direction n1 is abbreviated as the thick broken line N1, and the thick broken line on the magnetic pole 100 side surrounding the direction n2 is abbreviated as the thick broken line N2. To do.

FIG. 3 is an enlarged view of FIG. 2 showing the positional relationship between the developing roll 72 and the developer supply member 78 and the magnitude of the magnetic flux density in the normal direction and tangential direction of the sleeve 92.
Here, the angle θ1 formed by the direction n1 and the direction n2 described above is set to be less than 180 degrees with the magnetic pole 96 interposed therebetween. Furthermore, the angle θ2 formed by the direction n1 and the direction s1 is 90 degrees or less (90 degrees at the maximum), and the angle θ3 formed by the direction s1 and the direction n2 is also 90 degrees or less (the maximum is 90 degrees). Has been.
In FIG. 3, a thick broken line indicates that the distance in the normal direction from the surface of the sleeve 92 indicates the magnitude of the magnetic flux density in the normal direction on the surface of the sleeve 92. A thin broken line extending outward from the sleeve 92 between them indicates that the distance in the normal direction from the surface of the sleeve 92 indicates the magnitude of the magnetic flux density in the tangential direction on the surface of the sleeve 92.

  The magnetic pole 98 and the magnetic pole 100 are formed with the magnetic pole 96 on the downstream side in the rotation direction of the sleeve 92 relative to the magnetic pole 100 and on the upstream side in the rotation direction of the sleeve 92 relative to the magnetic pole 98 (the direction facing the rotary shaft 79 made of magnetic material) The magnetic field has the same polarity as the magnetic field to be generated, and forms a region where the magnitude of the magnetic flux density in the normal direction of the sleeve 92 is indicated by the thick broken line S2. That is, even if the S pole is not provided between the magnetic pole 98 and the magnetic pole 100 (even if the space A is provided), the magnitude of the magnetic flux density in the normal direction of the sleeve 92 is increased by the thick broken line S2. There is a magnetic field shown.

  And between the direction n1 mentioned above and the direction s1, the magnetic field by which the magnitude | size of the magnetic flux density of the tangential direction of the sleeve 92 is shown by the thin broken line H1 exists. Further, a magnetic field whose magnitude of the magnetic flux density in the tangential direction of the sleeve 92 is indicated by the thin broken line H2 exists between the direction s1 and the direction n2. Further, between the thick broken line N2 and the thick broken line S2, and between the thick broken line S2 and the thick broken line N1, a magnetic field in which the magnitude of the magnetic flux density in the tangential direction of the sleeve 92 is indicated by the thin broken lines H3 and H4. Exists.

FIG. 4 is an enlarged view of FIG. 2 showing the positional relationship between the distribution of magnetic flux density in the normal direction of the sleeve 92 and the developer supply member 78. In addition, the same code | symbol is attached | subjected to the same thing as the component part shown in FIG. 3, a direction, a thick broken line, and a thin broken line.
Between the thick broken line N2 and the thick broken line S2, there is a point B at which the magnetic flux density in the normal direction of the sleeve 92 is substantially zero, and between the thick broken line N1 and the thick broken line S2, the method of the sleeve 92 is present. There is a point C where the magnetic flux density in the linear direction is substantially zero. That is, the point B indicates the position on the upstream side in the rotation direction of the sleeve 92 where the strength of the magnetic field in the normal direction of the sleeve 92 by the magnetic pole 98 becomes substantially zero. A point C indicates a position on the downstream side in the rotation direction of the sleeve 92 where the strength of the magnetic field in the normal direction of the sleeve 92 by the magnetic pole 100 becomes substantially zero.

  The developer supply member 78 is disposed downstream of the point B in the rotation direction of the sleeve 92, and the normal line segment b 1 of the sleeve 92 passing through the point B and the normal direction of the sleeve 92 passing through the point C. Is in contact with the sleeve 92 within a region indicated by a thick line D sandwiched between the line segment c1.

FIG. 5 is an enlarged view of FIG. 2 showing details of a region where the sleeve 92 and the developer supply member 78 are in contact with each other. In addition, the same code | symbol is attached | subjected to the same thing as the component shown in FIG. 4, the thick broken line, the thin broken line, and the point (position).
The developer supply member 78 forms a predetermined contact width (nip width) with respect to the sleeve 92 on the downstream side in the rotational direction of the sleeve 92 from the point B and on the upstream side in the rotational direction of the sleeve 92 from the point C. It is in pressure contact. Further, the developer supply member 78 is in contact with the sleeve 92 at a thin broken line (a region of a thick broken line E where the magnetic flux density in the tangential direction of the sleeve 92 is substantially 0) that is deviated from the thin broken line H3 and the thin broken line H4. Yes. As described above, the sleeve 92 and the developer supply member 78 rotate in the same direction, and the developer supply member 78 supplies the developer on the downstream end (point F) side of the contact portion with respect to the rotation direction of the sleeve 92. The developer is supplied to the developing roll 72, and the developer is peeled off from the developing roll 72 on the upstream end (point G) side of the contact portion.

Next, the action of the magnetic pole 98 and the magnetic pole 100 on the magnetic field formed by the magnetic pole 96 will be described.
In the developing device 28Y shown in FIG. 2, the magnetic pole 96 is the S pole, the other magnetic pole 98 and the magnetic pole 100 are the N pole, and the angle θ1 formed by the direction n1 and the direction n2 is less than 180 degrees across the magnetic pole 96. Therefore, the magnetic field strength of the magnetic pole 96 is stronger than when the angle θ1 is 180 degrees or more.

  The developer transported via the developer transport path 84 and the developer transport path 86 is supplied to the developing roll 72 by the developer peeling supply member 78 that is also a developer supply means, and adheres to the surface of the sleeve 92. The developer adhering to the sleeve 92 and transported is regulated by the layer thickness regulating member 82, transported toward the photoreceptor 22Y with a predetermined layer thickness, and the electrostatic latent written on the photoreceptor 22Y. The image is developed with toner. The developer remaining on the sleeve 92 after development is peeled off from the sleeve 92 by the developer supply member 78 which is also a developer peeling means.

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 configuration of a developing device according to an embodiment of the present invention. FIG. 3 is an enlarged view of FIG. 2 showing a positional relationship between the developing roll and the developer supply member and the magnitude of magnetic flux density in the normal direction and tangential direction of the sleeve. FIG. 3 is an enlarged view of FIG. 2 showing the positional relationship between the distribution of magnetic flux density in the normal direction of the sleeve and the developer supply member. FIG. 3 is an enlarged view of FIG. 2 showing details of a region where a sleeve and a developer supply member are in contact with each other.

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 peeling supply member 79 Rotating shaft 80 Foamable member 82 Layer thickness regulating members 84 and 86 Developer conveying path 88 Developing chamber 92 Sleeve 94 Magnet roll 95 Shaft 96 Magnetic pole (S pole)
98,100 Magnetic pole (N pole)

Claims (9)

A developer containing portion for containing a developer containing a non-magnetic toner and a magnetic carrier;
A developer that conveys the developer contained in the developer container toward the image carrier;
Developer supply means for supplying the developer stored in the developer storage section toward the developer;
A developer peeling means for peeling the developer conveyed by the developer from the developer;
The developer is
A non-magnetic rotating member that rotates to face the image carrier;
A magnet member disposed in the rotating member,
The magnet member has a first magnetic pole that forms a magnetic field in a normal direction of the rotating member toward the image carrier, and the first magnetic pole has a different polarity, and the rotating member is more than the first magnetic pole. The second magnetic pole disposed upstream in the rotation direction of the first magnetic pole is different in polarity from the first magnetic pole, and the third magnetic pole disposed downstream in the rotation direction of the rotating member from the first magnetic pole. Only three magnetic poles consisting of
Each of the second magnetic pole and the third magnetic pole has an angle formed by sandwiching the first magnetic pole in a direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized is less than 180 degrees,
The developer peeling means opposes the rotating member on the downstream side in the rotational direction of the rotating member with respect to the third magnetic pole and on the upstream side in the rotational direction of the rotating member with respect to the second magnetic pole. The supply unit is provided to face the rotating member on the downstream side in the rotation direction of the rotating member with respect to the developer peeling unit and on the upstream side in the rotation direction of the rotating member with respect to the second magnetic pole .
The developer supply means and the developer peeling means are formed by a developer peeling supply member that rotates while in contact with the rotating member,
The developer peeling supply member is a region where the strength of the magnetic field having the same polarity as the magnetic field formed by the first magnetic pole in the tangential direction of the rotating member by the second magnetic pole and the third magnetic pole is substantially zero. A developing device that supplies the developer and removes the developer. The second magnetic pole and the third magnetic pole are located on the downstream side in the rotational direction of the rotating member with respect to the third magnetic pole and on the upstream side in the rotational direction of the rotating member with respect to the second magnetic pole. a developing device of a magnetic field and according to claim 1, wherein forming the same polarity magnetic field of the magnetic poles of the form. The third magnetic pole has a direction in which the strength of the magnetic field in the normal direction of the rotating member by the third magnetic pole is maximized, and the strength of the magnetic field in the normal direction of the rotating member by the first magnetic pole. The developing device according to claim 1 , wherein the developing device is disposed so that an angle formed by a direction in which the angle is maximum is 90 degrees or less. The second magnetic pole has 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 the strength of the magnetic field in the normal direction of the rotating member by the first magnetic pole. The developing device according to claim 1 , wherein the developing device is disposed so that an angle formed by a direction in which the angle is maximum is 90 degrees or less. The developer peeling supply member is located upstream of the rotating member in the rotational direction where the strength of the magnetic field having a polarity different from that of the first magnetic pole in the normal direction of the rotating member by the second magnetic pole is substantially zero. The developer is supplied from the upstream side in the rotation direction of the rotating member with respect to the position, and the strength of the magnetic field having a polarity different from that of the first magnetic pole in the normal direction of the rotating member by the third magnetic pole is substantially 0. and also the position of the downstream side in the rotational direction of said rotary member comprising, a developing device according to any one of claims 1 to 4 for separating the developer from the downstream side in the rotating direction of said rotary member. The developer peeling supply member, rotating shaft developing device according to any one of claims 1 to 5 made of a magnetic material. The developer peeling supply member, a developing device according to any one of claims 1 to 6 effervescent member having elasticity to rotate while in contact with the rotary member. The developer peeling supply member, a developing device according to any one of claims 1 to 7 rotates in the rotating member in the same direction. An image carrier,
A developing device for developing the latent image formed on the image carrier with a developer;
Transfer means for transferring a developer image developed by the developing device to a recording medium;
A fixing device for fixing the developer image transferred to the recording medium by the transfer means to the recording medium,
The developing device includes:
A developer containing portion for containing a developer containing a non-magnetic toner and a magnetic carrier;
A developer that conveys the developer contained in the developer container toward the image carrier;
Developer supply means for supplying the developer stored in the developer storage section toward the developer;
A developer peeling means for peeling the developer conveyed by the developer from the developer;
The developer is
A non-magnetic rotating member that rotates to face the image carrier;
A magnet member disposed in the rotating member,
The magnet member has a first magnetic pole that forms a magnetic field in a normal direction of the rotating member toward the image carrier, and the first magnetic pole has a different polarity, and the rotating member is more than the first magnetic pole. The second magnetic pole disposed upstream in the rotation direction of the first magnetic pole is different in polarity from the first magnetic pole, and the third magnetic pole disposed downstream in the rotation direction of the rotating member from the first magnetic pole. Only three magnetic poles consisting of
Each of the second magnetic pole and the third magnetic pole has an angle formed by sandwiching the first magnetic pole in a direction in which the strength of the magnetic field in the normal direction of the rotating member is maximized is less than 180 degrees,
The developer peeling means opposes the rotating member on the downstream side in the rotational direction of the rotating member with respect to the third magnetic pole and on the upstream side in the rotational direction of the rotating member with respect to the second magnetic pole. The supply unit is provided to face the rotating member on the downstream side in the rotation direction of the rotating member with respect to the developer peeling unit and on the upstream side in the rotation direction of the rotating member with respect to the second magnetic pole .
The developer supply means and the developer peeling means are formed by a developer peeling supply member that rotates while in contact with the rotating member,
The developer peeling supply member is a region where the strength of the magnetic field having the same polarity as the magnetic field formed by the first magnetic pole in the tangential direction of the rotating member by the second magnetic pole and the third magnetic pole is substantially zero. An image forming apparatus that supplies the developer and removes the developer .

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