JPH1138765A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which can reduce the toner splashing and suppress drop of the image quality by removing a developer sucked up to the area between a choking member and a scraper. SOLUTION: A collect magnet 9 is furnished with the first parts 9a embedded in positions near the two ends of a supporting member 4 and deep as specified from the peripheral surface of the supporting member 4, the second parts 9b embedded in positions shallower than the first parts 9a, and a third part 9c embedded as deep as the first parts 9a, wherein the overall length of the magnet 9 is approx. the same as the distance between seal members. Because the second parts 9b lie shallower than the first parts 9a and third part 9c, the intensity of magnetic field at the peripheral surface of the supporting member 4 is higher accordingly. The lengths of the first members 9a are between 15 and 20 mm approximately. The embedded positions of the second parts 9b are decided so that the intensity of the magnetic field of the second parts 9b is approx. 40% or more higher than that of the first parts 9a or the third part 9c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image formed on the surface of a photosensitive drum by using a two-component developer obtained by mixing a magnetic carrier with a non-magnetic toner. The present invention relates to a developing device for developing.

[0002]

2. Description of the Related Art In an electrophotographic apparatus such as a copying machine or an optical printer, an exposure step of exposing a photoreceptor to light scanned on a subject to form an electrostatic latent image on the surface of the photoreceptor, A developing step of adhering toner to the latent image to make it visible, a transfer step of transferring the toner image obtained on the photoreceptor surface by development to paper, and a fixing step of applying heat to the transferred toner image to fix it After that, an image is formed on the sheet.
As the photoreceptor, a cylindrical photosensitive drum having a photosensitive layer provided on an outer peripheral surface is used, and each step of exposure, development and transfer includes an exposure section, a development section, and a development section provided around the photosensitive drum. In the transfer section, the processing is sequentially performed according to the rotation of the photosensitive drum.

In such an electrophotographic apparatus, high-definition images and high image quality such as reproduction of fine lines and realization of a solid portion without unevenness are realized in order to cope with output of a complicated graphic image. Is required. To meet this demand, it is necessary to increase the toner adhesion density in the developing step. Therefore, an apparatus has been developed which uses a two-component developer in which a toner is mixed with a carrier which is a magnetic particle having a particle diameter larger than the particle diameter of the toner and a large number of toners are held around the carrier.

FIG. 7 is a side sectional view showing the structure of a main part of a conventional electrophotographic apparatus using a two-component developer. In FIG. 7, reference numeral 20 denotes a cylindrical photosensitive drum. The photosensitive drum 20 is driven to rotate in the arrow direction, and an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 20 by an exposure device (not shown). Downstream from the position where the electrostatic latent image of the photosensitive drum 20 is formed, a substantially columnar developing device 21 that supplies toner to the peripheral surface of the photosensitive drum 20 to visualize the electrostatic latent image is stored. A certain housing 10 is arranged so that the central axis of the developing device 21 and the central axis of the photosensitive drum 20 are parallel to each other and a predetermined gap is formed between the peripheral surface of the developing device 21 and the peripheral surface of the photosensitive drum 20. I have.

In the housing 10, there is provided a storage section 16 for storing a developer including a magnetic carrier and a toner made of a colored synthetic resin. A part of the developing device 21 is stored in the storage section 16. It comes in contact with the developer. Developer 21
Is formed by inserting a holding member 24 formed of a synthetic resin into a thick cylindrical shape into a thin cylindrical sleeve 22 made of SUS or aluminum, and the holding member 24 supports the holding member 24. The shaft 23 is fitted inside. One end of the shaft 23 is fixed, and the sleeve 22 is rotated in the arrow direction without rotating the shaft 23 and the holding member 24. Both ends of the sleeve 22 are substantially annular seal members 11
(11) is externally fitted to prevent the above-mentioned developer from entering the inside of the developing device 21.

The holding member 24 has substantially the same length as the holding member 24, and has a rod-shaped suction magnet 25 for sucking up the developer onto the surface of the sleeve 22, and the same length and the same polarity as the suction magnet 25, for example. The portion facing the inner peripheral surface of the sleeve 22 is an N-pole, and has a rod-shaped developing magnet 27 for starting up the developer and attaching the toner in the developer to the electrostatic latent image, and has the same length as the developing magnet 27. A rod-shaped recovery magnet 29 which has the same polarity and removes the carrier remaining after development and the developer not used for development from the sleeve 22 is separated from the sleeve 22 by a predetermined distance in the circumferential direction of the holding member 24. It is buried in order.

The length between the suction magnet 25 and the developing magnet 27 of the holding member 24 and the distance between the developing magnet 27 and the collection magnet 29 are the same as the length of the suction magnet 25, and are opposite in polarity. A rod-shaped first transfer magnet 26 for transferring the developer from the suction magnet 25 to the development magnet 27 by a magnetic field generated between the suction magnet 25 and the development magnet 27; and the first transfer magnet 26.
The developing magnet 27 and the collecting magnet 29 have the same length and polarity.
A second transport magnet 28 for transporting the carrier remaining after the development and the developer not subjected to the development from the development magnet 27 to the recovery magnet 29 side is buried by the magnetic field generated between the second transport magnet 28 and the developing magnet 27.
The transfer magnet as described above is not disposed between the recovery magnet 29 and the suction magnet 25, and the recovery magnet 29 and the suction magnet 25 have the same polarity. No carrier and developer are transported.

In the vicinity of the first transfer magnet 26 around the developing device 21, a sharp blade-shaped doctor blade 12 is arranged at a predetermined distance from the surface of the sleeve 22. The thickness of the developer absorbed on the surface of the substrate is made uniform. On the other hand, a scraper 15 having a width substantially equal to the distance between the seal members 11 (11) and a predetermined inclination angle with respect to the tangent line of the sleeve 22 is provided slightly upstream of the collection magnet 29 around the developing device 21. Therefore, the carrier and the developer that are arranged so that a slight gap is formed between the sleeve and the peripheral surface of the sleeve 22 and are conveyed to the collection magnet 29 as described above are:
The toner is scraped off by the scraper 15 and collected in the storage section 16 for further development.

In the storage section 16, two stirring screws 17,
17 is arranged such that the rotation axes of the stirring screws 17 and 17 and the rotation axis of the developing device 21 are parallel to each other, and the carrier 16 collected from the developing device 21 and the developing While the developer is stored, new toner is supplied to keep the toner concentration in the developer stored in the storage unit 16 constant. Then, the carrier and the toner are agitated by the agitating screws 17, 17, and both are charged, so that the developer having the toner electrostatically attached to the periphery of the carrier is sucked up by the magnet 25 to the peripheral surface of the sleeve 22. It has become.

[0010]

However, the conventional developing device has the following problems. FIG. 8 is a rear view of the developing device 21 shown in FIG. As shown in FIG. 8, substantially annular seal members 11, 11 are externally fitted to both ends of the sleeve 22, and a scraper 15 having a width substantially equal to the distance between the seal members 11, 11 is interposed therebetween. However, they are inserted at a predetermined inclination angle with respect to the tangent line of the sleeve 22 so that a slight gap is formed between the sleeve 22 and the peripheral surface. This scraper 15
Between both edges of the seal member 11 and the seal members 11, 11 of the sleeve 22,
There is a gap larger than a carrier having a diameter of about 60 μm. The developer sucked into the gap portion of the sleeve 22 cannot be removed by the scraper 15 and remains on the sleeve 22, so that no new developer is sucked into the portion. On the other hand, in the developer remaining on the sleeve 22, the electrostatic bonding force between the carrier and the toner decreases with time, and the toner eventually scatters. Then, the scattered toner stains the photosensitive drum or the sheet for transfer, and deteriorates the image quality.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a closing member (seal member) in which the length of a recovery magnetic pole is fitted to both ends of a cylindrical member.
Or the length of the recovered magnetic pole is substantially the same as the distance between the blocking members, and a portion of the predetermined region located at the center by a predetermined distance from both ends of the recovered magnetic pole The magnetic field strength of the other part is stronger than the magnetic field strength of other parts, so that the developer sucked up in the part between the blocking member and the scraper is removed, the scattering of toner is reduced, and the deterioration of image quality is suppressed. It is an object of the present invention to provide a developing device capable of performing the following.

[0012]

According to a first aspect of the present invention, there is provided a developing apparatus comprising: a developer containing toner and a carrier adhered to a surface of the developing device and supplying the toner to an electrostatic latent image formed on the surface of the photosensitive drum; , A blocking member fitted to both ends of the cylindrical member to prevent the developer from entering the cylindrical member, and a carrier attached to the surface of the cylindrical member And a collecting magnetic pole provided in the axial direction of the central axis of the cylindrical member at a predetermined position on the downstream side in the rotation direction of the cylindrical member from a position facing the photosensitive drum in the cylindrical member in order to collect the developer. In the developing device provided with, the length dimension of the collecting magnetic pole is substantially the same as the distance between the two closing members, and the magnetic field strength of a portion of a predetermined region located at the center side by a predetermined distance from both ends of the collecting magnetic pole is different. Is characterized in that it is stronger than the magnetic field strength of the portion.

The developer containing the carrier and the toner is sucked up on the surface of the cylindrical member by the sucking magnetic pole provided inside the cylindrical member, and the rotational force of the cylindrical member and the transport magnetic pole provided between the sucking magnetic pole and the developing magnetic pole. To the developing magnetic pole. This developer is started up by a magnetic field formed by a developing magnetic pole, thereby performing toner brush attachment to an electrostatic latent image formed on the surface of the photosensitive drum, so-called magnetic brush development. The carrier remaining on the surface of the cylindrical member due to the development and the developer not used for the development are transported to the recovery magnetic pole by the rotational force of the cylindrical member and the transport magnetic pole provided between the developing magnetic pole and the recovery magnetic pole. In the vicinity of the recovery magnetic pole, a plate-shaped removing member (scraper) having a width substantially equal to the distance between the closing members fitted to both ends of the cylindrical member is disposed close to the surface of the cylindrical member. The carrier and the developer conveyed from the developing magnetic pole to the collecting magnetic pole are scraped off the surface of the cylindrical member by the removing member.

In the first invention, the length of the recovery magnetic pole is substantially the same as the distance between the two closing members, that is, substantially the same as the length of the removing member. The recovery magnetic pole has a magnetic field strength in a predetermined region located at the center side at a predetermined distance from both ends thereof, which is stronger than the magnetic field strength of the other portions. Of these, those near both edges of the cylindrical member are conveyed to a portion where the magnetic field strength of the collected magnetic pole is strong, that is, a portion inside the end of the collected magnetic pole, and removed by the removing member.

A developing device according to a second aspect of the present invention is a rotary driving device for supplying a toner to an electrostatic latent image formed on the surface of a photosensitive drum and developing the toner by applying a developer containing a toner and a carrier to the surface. A cylindrical member, a closing member fitted to both ends of the cylindrical member to prevent the developer from entering the cylindrical member, and a carrier and a developer attached to the surface of the cylindrical member. A collecting magnetic pole provided at a predetermined position on the downstream side in the rotation direction of the cylindrical member from a position facing the photosensitive drum in the cylindrical member, the collection magnetic pole being provided in the axial direction of the central axis of the cylindrical member. The length of the collected magnetic pole is shorter than the distance between the two closing members, and the collected magnetic pole is an area between the two closing members, and a predetermined distance in the axial direction from both the closing members. It is characterized in that it is provided at a separated position.

In the second invention, the length of the collected magnetic pole is shorter than the distance between the two closing members, that is, shorter than the length of the removing member. And at a position separated by a predetermined distance in the axial direction from both blocking members, that is, at a position separated by a predetermined distance from both edges of the removing member. Thereby, the width dimension of the carrier and the developer conveyed from the developing magnetic pole to the recovery magnetic pole is:
The carrier and the developer that are shorter than the width dimension of the removing member and are sucked up in the portion between the blocking member and the removing member are removed by the removing member.

In the developing device according to a third aspect of the present invention, in the second aspect, the length of the recovery magnetic pole is such that a distance from both edges of the recovery magnetic pole to the position of the blocking member in the axial direction is approximately 15 mm. It is characterized in that it is longer and shorter than approximately 20 mm.

According to the third aspect of the present invention, when the distance between both ends of the recovery magnetic pole and the closing member in the axial direction of the central axis of the cylindrical member is smaller than approximately 15 mm, the magnetic pole is transported from the developing magnetic pole to the recovery magnetic pole. The width of the carrier and the developer is not sufficiently short, and the carrier and the developer sucked in the portion between the closing member and the removing member cannot be sufficiently removed by the removing member. On the other hand, if the distance between both edges of the recovery magnetic pole and the closing member in the axial direction is longer than approximately 20 mm, the recovery width is smaller than the width of the carrier and the developer transported from the development magnetic pole to the recovery magnetic pole. Since the length of the magnetic pole is too short, it is not possible to sufficiently transport the carrier and the developer at the edges in the width direction to the collecting magnetic pole, so that they cannot be sufficiently removed by the removing member.

According to a fourth aspect of the present invention, in the developing device according to the second aspect, the magnetic field strength at both ends of the recovery magnetic pole is stronger than the magnetic field strength at other portions.

According to a fifth aspect of the present invention, in the developing device according to the second aspect, the magnetic field intensity of a portion of a predetermined region located at a center side by a predetermined distance from both ends of the recovery magnetic pole is stronger than the magnetic field intensity of other portions. There is a feature.

According to the fourth and fifth aspects of the present invention, since the magnetic field strength of a predetermined region located at the center side by a predetermined distance from both ends of the recovery magnetic pole is made stronger than the magnetic field strength of the other portions, the developing The carrier and developer transported from the magnetic pole to the recovery magnetic pole at the edge in the width direction are reliably transported to the recovery magnetic pole shorter than the width of the removing member, and are removed from the surface of the cylindrical member by the removing member.

According to a sixth aspect of the present invention, in the first, fourth or fifth aspect of the present invention, the portion where the magnetic field strength of the recovery magnetic pole is increased is at least 40% stronger than that of the other portions. It is characterized by.

According to the sixth invention, the magnetic field strength of a portion of a predetermined region located at the center by a predetermined distance from the ends of the recovery magnetic poles or both ends of the recovery magnetic poles is 4 times higher than the magnetic field strengths of the other portions.
By increasing the strength by 0% or more, almost all of the carrier and the developer sucked into the portion between the blocking member and the removing member are conveyed into the width dimension of the removing member and removed by the removing member.

[0024]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 is a side sectional view showing a developing device according to the present invention together with a photosensitive drum. In the drawing, reference numeral 20 denotes a cylindrical photosensitive drum. The photosensitive drum 20 is driven to rotate in the arrow direction, and an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 20 by an exposure device (not shown). Downstream from the position where the electrostatic latent image is formed on the photosensitive drum 20, a substantially columnar developing device 1 that supplies toner to the peripheral surface of the photosensitive drum 20 to visualize the electrostatic latent image is stored. One housing 10 is
The central axis of the developing device 1 and the central axis of the photosensitive drum 20 are parallel,
It is arranged so that a predetermined gap is formed between the peripheral surface of the developing device 1 and the peripheral surface of the photosensitive drum 20.

A housing 16 is provided in the housing 10 for housing a carrier containing a magnetic material and a developer containing a toner made of a colored synthetic resin. A part of the developing device 1 is housed in the housing 16. It comes in contact with the developer. Developing device 1
Comprises a thin cylindrical sleeve (tube member) 2 made of SUS or aluminum, and a holding member 4 formed by molding a synthetic resin into a thick cylindrical shape. The shaft 3 supporting the member 4 is fitted inside. One end of the shaft 3 is fixed, and the shaft 3 and the holding member 4
The sleeve 2 is turned in the direction of the arrow without turning. At both ends of the sleeve 2, substantially annular seal members (blocking members) 11 (11) are externally fitted to prevent the developer from entering the inside of the developing device 1.

The holding member 4 has substantially the same length as the holding member 4, and has a rod-shaped suction magnet 5 for sucking up the developer into the sleeve 2, and has the same length and the same polarity as the suction magnet 5, for example, of the sleeve 2. A portion facing the inner peripheral surface has an N pole, and a rod-shaped developing magnet 7 for starting up the developer and adhering the toner in the developer to the electrostatic latent image, and having the same polarity as the developing magnet 7. The recovery magnet 9 for removing the carrier remaining after the development and the developer not used for the development from the sleeve 2 as described later is provided by the holding member 4.
Are buried in this order at a predetermined distance in the circumferential direction.

The distance between the sucking magnet 5 and the developing magnet 7 of the holding member 4 and the distance between the developing magnet 7 and the collecting magnet 9 are the same as the length of the sucking magnet 5 and have opposite polarities. A first transfer magnet 6 having a rod shape for transferring the developer from the suction magnet 5 to the development magnet 7 by a magnetic field generated between the suction magnet 5 and the development magnet 7;
The developing magnet 7 and the collecting magnet 9 have the same length and polarity.
The second transport magnet 8 that transports the carrier remaining after the development and the developer that has not been subjected to the development from the development magnet 7 to the collection magnet 9 is buried by the magnetic field generated between the magnets. The transfer magnet as described above is not disposed between the recovery magnet 9 and the suction magnet 5, and the recovery magnet 9 and the suction magnet 5 have the same polarity. No carrier and developer are transported.

A sharp blade-shaped doctor blade 12 is arranged at a predetermined distance from the surface of the sleeve 2 near the first transfer magnet 6 around the developing device 1. The thickness of the developer absorbed on the surface of the substrate is made uniform. On the other hand, a scraper 15 having a width substantially equal to the distance between the seal members 11 (11) and a predetermined inclination angle with respect to the tangent line of the sleeve 2 is provided slightly upstream of the collection magnet 9 around the developing device 1. The carrier and the developer which are inserted between the seal members 11 (11) so that a slight gap is formed between the sleeve 2 and the peripheral surface of the sleeve 2 are conveyed to the collection magnet 9 as described above. It is scraped off by 15 and collected in the storage section 16 for further development.

In the storage section 16, two stirring screws 17,
17 is arranged such that the rotation axes of the stirring screws 17 and 17 and the rotation axis of the developing device 1 are parallel to each other, and the carrier 16 collected from the developing device 1 and the developing While the developer is stored, new toner is supplied to keep the toner concentration in the developer stored in the storage unit 16 constant. Then, the carrier and the toner are agitated by the agitating screws 17, 17, so that the toner and the toner are electrostatically attached to the periphery of the carrier. It has become.

FIG. 2 shows II-I of the support member 4 shown in FIG.
It is sectional drawing by the I line, and has shown the structure of the collection | recovery magnet 9. FIG. As shown in FIG. 2, the recovery magnets 9 are buried in the first portions near the opposite ends of the support member 4 externally fitted to the shaft 3 and at respective predetermined depths from the peripheral surface of the support member 4. 9a, 9a, adjacent to both first parts 9a, 9a, first parts 9a, 9a
The second parts 9b, 9b, respectively buried at shallower positions,
And a third portion 9c buried between the second portions 9b, 9b and at the same depth as the first portions 9a, 9a,
The entire length of the recovery magnet 9 is substantially the same as the distance between the sealing members. The second part 9b, 9b is composed of the first part 9a, 9a and the third part
Since it is shallower than 9c, the magnetic field strength on the peripheral surface of the support member 4 is correspondingly high. The length of each of the first portions 9a, 9a is approximately 15
２０20 mm. In addition, the burial positions of the second portions 9b, 9b are as follows.
When the magnetic field strength of the second portion 9b, 9b is less than the first portion 9a, 9a or
The magnetic field strength of the portion 9c is set to be approximately 40% or more stronger.

As a result, the recovered magnet 9 is removed from the developing magnet 7.
Of the carrier and the developer transported to the portion near the edge of the sleeve, the portion is attracted to the second portion 9b, 9b side of the collection magnet 9 and scraped off by the scraper 15, so that the sealing member 11 ( 11) and scraper 15 (both in FIG. 1)
), The amount of the carrier and the developer remaining in the gap with the edge portion can be reduced.

Although the recovery magnet 9 shown in FIG. 2 has the first portion 9a, 9a and the third portion 9c embedded at the same depth in the support member 4, the present invention is not limited to this. , First part 9
a, 9a may be embedded at a position deeper than the third portion 9c. In this case, of the carrier and the developer conveyed from the developing magnet 7 to the collecting magnet 9, the portion near the edge of the sleeve 2 is drawn toward the second portions 9 b and 9 b of the collecting magnet 9, and is scraped by the scraper. 15 ensures that the sleeve 2 is removed from the peripheral surface.

(Embodiment 2) FIG. 3 is a sectional view showing Embodiment 2 and shows a case where the entire length of the recovery magnet 9 is shorter than the distance between the seal members. Note that in FIG.
The same reference numerals are given to the portions corresponding to and the description thereof will be omitted. The total length of the recovery magnet 9 is approximately three times the distance between the sealing members.
The collection magnet 9 is buried at substantially the center in the length direction of the support member 4 as shown in FIG. Therefore, both ends of the collection magnet 9 are separated from the respective sealing members by about 15 to 20 mm.

As a result, the recovered magnet 9 is removed from the developing magnet 7.
The width of the carrier and developer transported to the seal member 11
(11) are shorter than the distance between
It is removed from the peripheral surface of the sleeve 2 (each shown in FIG. 1) by a scraper 15 having a length substantially equal to the distance between 11 (11).

(Embodiment 3) FIG. 4 is a cross-sectional view showing Embodiment 3 and shows a case where the magnetic field strength at the end of the recovery magnetic pole 9 is higher than the magnetic field strength of the other parts. In the figure, portions corresponding to FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 4, the entire length of the recovery magnet 9 is shorter than the distance between the seal members by approximately 30 to 40 mm, and the recovery magnet 9 is buried at substantially the center in the length direction of the support member 4. First portions 9 at both ends of the recovery magnet 9
d and 9d are buried shallower than the second portion 9e which is an intermediate portion, and the embedding position of both is such that the magnetic field strength of the first portions 9d and 9d is about 40% or more stronger than the magnetic field strength of the second portion 9e. It is set as follows.

Thus, the recovered magnet 9 is removed from the developing magnet 7.
Of the carrier and the developer conveyed to the portion near the edge of the sleeve 2, the carrier and the developer are surely drawn to the first portions 9 d and 9 d of the collection magnet 9, and almost all of the peripheral surface of the sleeve 2 is scraped by the scraper 15. Removed from

(Embodiment 4) FIG. 5 is a cross-sectional view showing an embodiment 4 in which the magnetic field strength at a portion slightly closer to the center than the end of the recovery magnetic pole 9 is made stronger than the magnetic field strength at other portions. Is shown. In the figure, portions corresponding to FIG. 3 are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 5, the total length of the collection magnet 9 is shorter than the distance between the seal members by approximately 30 to 40 mm, and the collection magnet 9 is
It is buried approximately in the center in the length direction. First portions 9f, 9f which are both ends of the collection magnet 9 and a third portion 9h which is a central portion.
Is buried in a relatively deep position of the support member 4, and the second portions 9g, 9g between the first portions 9f, 9f and the third portion 9h are
It is buried in the support member 4 at a relatively shallow position. The embedding position is such that the magnetic field strength of the second part 9g, 9g is the first part 9f,
It is set so as to be approximately 40% or more stronger than the magnetic field strength of 9f or the third portion 9h.

Thus, the recovered magnet 9 is removed from the developing magnet 7.
Of the carrier and developer conveyed to the recovery magnet 9, those near the edge of the sleeve 2 are reliably attracted to the first portion 9f, 9f and the second portion 9g, 9g of the collection magnet 9, and the scraper 15
As a result, almost everything is removed from the peripheral surface of the sleeve 2.

In each of the embodiments described above, the magnetic field strength is adjusted by changing the depth at which the recovery magnet is buried. However, the present invention is not limited to this, and magnets having different magnetic field strengths are connected. Needless to say, the recovery magnet may be configured as such. Further, in each of the embodiments, the suction magnet, the developing magnet, the recovery magnet, and the first and second transport magnets are used, but the present invention is not limited to this. For example, the ferrite powder is formed and fired into a substantially roll shape. After the connection, a predetermined position in the circumferential direction may be magnetized to form a suction magnetic pole, a developing magnetic pole, a recovery magnetic pole, and first and second transport magnetic poles. At this time, the length of the recovery magnetic pole is adjusted by providing a notch at the edge of the roll.

[0040]

Next, the results of changing the total length and magnetic field strength of the recovery magnet will be described. FIG. 6 is a graph showing the relationship between the total length and the magnetic field strength of the collected magnet and the weight of the scattered toner. The horizontal axis represents the distance between the end of the collected magnet and the sealing member, and the vertical axis represents the distance of the scattered toner. The weight is indicated respectively.

A recovery magnet (□) with the same magnetic field strength at both ends and the middle part, a recovery magnet (Δ) with the magnetic field strength at both ends 20% stronger than the magnetic field strength at the middle part, Using a collection magnet (ト ナ ー) whose magnetic field strength is 40% stronger than the magnetic field strength of the middle part, the distance between the end of the collection magnet and the sealing member is separated from 0 mm to 5 mm by 40 mm, and the weight of the scattered toner is Was measured respectively.

As is apparent from FIG. 6, the weight of the scattered toner decreased as the magnetic field intensity at both ends of the recovery magnet was increased. Also, regardless of the strength of the magnetic field at both ends, the distance between the end of the collection magnet and the seal member is 15 to
When the thickness was set to 20 mm, the weight of the scattered toner was reduced most. When the distance between the end of the collection magnet and the seal member is 15 to 25 mm and the magnetic field strength at both ends of the collection magnet is 40% stronger than the magnetic field strength at the middle, scattering of toner can be prevented. Was.

[0043]

As described above in detail, in the developing device according to the first aspect, of the carrier and the developer conveyed from the developing magnetic pole to the collecting magnetic pole, those near both edges of the cylindrical member are:
Since it is conveyed to a portion having a high magnetic field strength of the recovery magnetic pole, that is, a portion inside the end of the recovery magnetic pole, and is removed by the removing member, the amount of scattered toner is reduced, and the deterioration of image quality is suppressed.

In the developing device according to the second aspect of the invention, the width of the carrier and the developer conveyed from the developing magnetic pole to the collecting magnetic pole is shorter than the width of the removing member. Since the carrier and the developer sucked up in the portion between them are removed by the removing member, the amount of the scattered toner is further reduced, and the deterioration of the image quality is suppressed.

In the developing device according to the third aspect of the present invention, the length of the collected magnetic pole is adjusted so that the distance between both edges of the collected magnetic pole and the closing member is larger than approximately 15 mm and shorter than approximately 20 mm. As a result, the width of the carrier and the developer conveyed from the developing magnetic pole to the collecting magnetic pole can be made sufficiently small, and the carrier and the widthwise edge of the developer can be sufficiently conveyed to the collecting magnetic pole. The removal rate of the carrier and the developer sucked into the portion between the blocking member and the removing member is improved.

In the developing devices according to the fourth and fifth aspects of the present invention, the magnetic field strength of a part of a predetermined area located on the center side by a predetermined distance from both ends of the recovery magnetic pole is made stronger than the magnetic field strength of the other parts. Therefore, the carrier at the width direction edge of the carrier and the developer conveyed from the developing magnetic pole to the collecting magnetic pole is reliably conveyed to the collecting magnetic pole shorter than the length of the removing member, and the removing member removes the surface of the cylindrical member. Removed from Thereby, scattering of toner is prevented, and deterioration of image quality is avoided.

In the developing device according to the sixth aspect of the present invention, the magnetic field strength of a portion of a predetermined region located at a center by a predetermined distance from the ends of the collected magnetic poles or both ends of the collected magnetic poles, and the magnetic field strengths of other portions are determined. By increasing the strength by 40% or more, almost all of the carrier and the developer sucked into the portion between the blocking member and the removing member are conveyed into the width dimension of the removing member and removed by the removing member. As a result, the present invention has excellent effects, such as preventing scattering of toner and avoiding deterioration of image quality.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a developing device according to the present invention together with a photosensitive drum.

FIG. 2 is a cross-sectional view of the support member shown in FIG. 1 taken along the line II-II.

FIG. 3 is a sectional view showing a second embodiment.

FIG. 4 is a sectional view showing a third embodiment.

FIG. 5 is a sectional view showing a fourth embodiment.

FIG. 6 is a graph showing the relationship between the total length and magnetic field strength of a recovery magnet and the weight of scattered toner.

FIG. 7 is a side sectional view showing a configuration of a main part of a conventional electrophotographic apparatus using a two-component developer.

8 is a rear view of the developing device shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing device 2 sleeve 4 holding member 5 suction magnet 6 first transfer magnet 7 developing magnet 8 second transfer magnet 9 recovery magnet 9a first portion 9b second portion 9c third portion 11 seal member 15 scraper 20 photosensitive drum

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiharu Doi 35th Saho, Kato-gun, Hyogo (No address) Inside Fujitsu Peripheral Machinery Co., Ltd. (72) Inventor Koji Inohara 35th, Saho, Kato-gun, Hyogo ( No address) Inside Fujitsu Peripheral Equipment Co., Ltd.

Claims (6)

[Claims] A cylindrical member having a developer containing a toner and a carrier adhered to the surface thereof, and supplying a toner to an electrostatic latent image formed on the surface of the photosensitive drum and driving the electrostatic latent image to develop the latent image; A blocking member fitted to both ends of the cylindrical member to prevent the developer from entering the cylindrical member, and a carrier and a developer attached to the surface of the cylindrical member to collect the carrier and the developer. In a developing device, provided at a predetermined position on the downstream side in the rotation direction of the cylindrical member from a position facing the photosensitive drum, and a collected magnetic pole provided in the axial direction of the central axis of the cylindrical member, the length dimension of the collected magnetic pole is It is substantially the same as the distance between both blocking members, and the magnetic field strength of a part of a predetermined area located on the center side by a predetermined distance from both ends of the recovery magnetic pole is stronger than the magnetic field strength of the other parts. Developing device. 2. A cylindrical member having a developer containing a toner and a carrier adhered to a surface thereof, and rotationally driven to supply toner to an electrostatic latent image formed on the surface of the photosensitive drum and develop the electrostatic latent image. A blocking member fitted to both ends of the cylindrical member to prevent the developer from entering the cylindrical member, and a carrier and a developer attached to the surface of the cylindrical member to collect the carrier and the developer. In a developing device, provided at a predetermined position on the downstream side in the rotation direction of the cylindrical member from a position facing the photosensitive drum, and a collected magnetic pole provided in the axial direction of the central axis of the cylindrical member, the length dimension of the collected magnetic pole is The collected magnetic pole is provided in a region between the two closing members and at a predetermined distance in the axial direction from the two closing members. A developing device, characterized in that: 3. The length of the recovery magnetic pole is such that the distance from both edges of the recovery magnetic pole to the position of the blocking member in the axial direction is longer than approximately 15 mm and shorter than approximately 20 mm. The developing device according to claim 2. 4. The developing device according to claim 2, wherein the magnetic field intensity at both ends of the recovery magnetic pole is stronger than the magnetic field intensity at other portions. 5. The developing device according to claim 2, wherein the magnetic field intensity of a portion of a predetermined region located at a center side by a predetermined distance from both ends of the recovery magnetic pole is stronger than the magnetic field intensity of other portions. 6. The developing device according to claim 1, wherein a portion where the magnetic field strength of the recovery magnetic pole is increased is 40% or more stronger than a magnetic field intensity of the other portion.