JP2012137512A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device for developing an electrostatic latent image by using a developer including magnetic particles, in which leakage of the developer through an end of a developer conveying member used for supplying the developer to a developing region may be suppressed without seriously increasing rotational torque of the developer conveying member.SOLUTION: In developer conveying members (including a developing roller 41 and developer conveying screws 42 and 43), a magnet member 420 (430) is disposed to be spaced, by a gap g1, from an end of a shaft 421 (431) of, for example, the developer conveying screw 42 (43). The magnet member 420 (430) includes an outside portion mg1 and an inside portion mg2, a direction of a magnetic field line of the outside portion mg1 is set to be vertical to a direction of a rotational center line of the developer conveying member, and a direction of a magnetic field line of the inside portion mg2 is set to extend diagonally to the direction of the rotational center line of the developer conveying member.

Description

  The present invention develops an electrostatic latent image formed on an electrostatic latent image carrier by using a developer transport member rotatably supported by the developer housing, which contains magnetic particles contained in the development housing. The present invention relates to a developing device that supplies the developing area to develop the electrostatic latent image.

  The present invention also provides an image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. Also, the present invention relates to an image forming apparatus in which at least one developing device is the type of developing device.

  Generally speaking, a developing device that employs a dry developer is largely divided into a so-called one-component developing device that uses a developer mainly composed of toner and a so-called two-component developing device that uses a developer mainly composed of toner and carrier. Separated. A developing device of the type described at the beginning is often found in so-called two-component developing devices.

  Since the two-component developing device charges the toner by frictional charging by mixing with the carrier, the developer stress just for charging the toner is small and the toner is less likely to deteriorate. It is widely used in image forming apparatuses that can form an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and develop the electrostatic latent image with a developing device to form a toner image.

Specific examples of such an image forming apparatus include an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, and a combination machine combining these.

  In general, an electrophotographic image forming apparatus generally includes an electrostatic latent image carrier (usually a photoreceptor), a charging device that charges the surface of the image forming device, and an electrostatic latent image obtained by performing image exposure on a charging area of the charging device. A developing device that develops an electrostatic latent image to form a visible toner image, a transfer device that transfers the toner image to a recording sheet, a fixing device that fixes the toner image to the recording sheet, and the like.

An electrostatic latent image carrier (usually a photoreceptor), a charging device, a developing device, and the like are often integrated as a process unit.

  In recent years, especially with the increase in full-color output, such process units are required to be more durable (longer life), higher reliability, higher image quality, and lower price as well as smaller and faster. .

By the way, in a developing device that employs a dry developer, whether it is a one-component developing device or a two-component developing device, it relates to the supply of developer to a developing area that is rotatably supported by a developing housing that contains the developer. Generally, a seal portion is provided to prevent the developer from leaking out from the bearing portion of the rotating member.

  However, as described above, today, there is a demand for high speed and high durability of the process unit, and therefore, there is a demand for high speed and high durability of the developing device. There is a problem in that the seal portion with respect to the rotating member involved in the supply is likely to generate heat due to friction, so that toner is welded and fixed on the seal portion, and thus image defects are likely to occur.

  Therefore, among the developing devices that require high speed, high durability, etc., the developing device of the type described above, that is, the developer containing magnetic particles contained in the developing housing can be rotated to the developing housing. In a developing device of a type that develops the electrostatic latent image by supplying the electrostatic latent image formed on the electrostatic latent image carrier to a developing area to be developed by a supported developer conveying member. As for the developer conveying member, a method has been proposed in which a magnet member is disposed as a developer leakage prevention seal portion with respect to a portion to be sealed of the developer conveying member, and a brush composed of the magnetic particles is formed by the magnetic field lines of the magnetic field. ing.

However, in such a sealing method, the direction of the magnetic force line is perpendicular to the direction of the center line of rotation of the developer transport member. Therefore, the developer is separated from the magnet member and the developer by vibration or impact during transportation of the developing device. There is a problem in that if it enters between the part to be sealed of the conveying member, it is held at that position, and the rotational torque for rotating the developer conveying member becomes high.

  To solve this problem, Japanese Patent Laid-Open No. 10-240013 and Japanese Patent Laid-Open No. 2008-76896 disclose that a magnet member is disposed on an end portion that is a seal target portion of a developer conveying member, and the magnet member The magnetic force line of the developer is inclined with respect to the rotation center line direction of the developer conveying member, and the developer entering between the magnet member and the portion to be sealed of the developer conveying member is rotated using the rotating operation of the developer conveying member with respect to the inclined magnetic force line. Then, returning to the inside of the developing housing is described.

Japanese Patent Laid-Open No. 10-240013 JP 2008-76896 A

However, as described in JP-A-10-240013 and JP-A-2008-76896, the developer, particularly the toner, can be obtained only by generating a magnetic force line inclined with respect to the rotation center line direction of the developer conveying member. In addition, when a force is applied in the direction of the rotation center line of the developer conveying member, the toner passes through the magnetic force lines, and thus there is a risk that the prevention of developer leakage is insufficient. In particular, when vibration or impact is applied, there is a high risk of toner leakage.

Accordingly, the present invention provides an electrostatic latent image formed on an electrostatic latent image carrier by a developer conveying member rotatably supported by the developer housing with a magnetic particle contained in the developer housing. A developing device for developing the electrostatic latent image by developing the electrostatic latent image, wherein at least one developer conveying member has a developer leakage from an end of the developer conveying member. In the state where toner melting and welding due to heat generation in the area and its surroundings are suppressed, and without increasing the rotational torque of the developer conveying member as much as to be problematic, it is possible to suppress electrostatic latent image as a whole. It is a first object to provide a developing device capable of image development.

Further, the present invention is an image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. At least one developing device forms an electrostatic latent image formed on the electrostatic latent image carrier by a developer conveying member rotatably supported by the developing housing. The developer includes magnetic particles accommodated in the developing housing. The developing device supplies the latent image to a developing area to develop the electrostatic latent image, and at least one developer conveying member of the developing device is developed from an end of the developer conveying member. A developing device capable of suppressing agent leakage in a state in which toner melting and welding due to heat generation at the end portion and its surroundings are suppressed and without increasing the rotational torque of the developer conveying member as much as possible. And that ’s all As, a second object is to provide an image forming apparatus capable of forming a good image.

In order to solve the first problem, the present invention provides:
A developing area for developing an electrostatic latent image formed on an electrostatic latent image carrier by a developer conveying member rotatably supported by the developing housing with developer containing magnetic particles contained in the developing housing A developing device that develops the electrostatic latent image by supplying to the magnet member with a gap with respect to at least one end of the developer conveying member and along a peripheral surface of the end The magnet member includes an outer portion that is closer to the outside of the developing housing and an inner portion that is closer to the inner side of the developing housing than the outer portion, and the direction of the lines of magnetic force of the outer portion is the developer. The magnetic force line direction of the inner portion is perpendicular to the rotation center line direction of the conveying member, and the developer entering the gap between the inner portion and the end portion causes the developer to enter the gap between the inner portion and the end portion. rotation So as to move more said to developing housing inwardly, to provide a developing device which is inclined relative to the rotational center line direction of the developer conveying member.
Here, “perpendicular” in “the direction of the magnetic field of the outer portion is perpendicular to the direction of the rotation center line of the developer conveying member” means “outside, as described later, even if it is not completely vertical. From the viewpoint of forming a magnetic brush that provides a developer leakage prevention seal by a portion, a direction of magnetic force lines that can be regarded as “perpendicular” is also included.

  According to the developing device of the present invention, the magnet member is disposed along the peripheral surface of the end portion with a gap with respect to at least one end portion of the developer conveying member. Therefore, at the end portion of at least one developer conveying member, the developer outside the developing housing is formed in the gap between the magnet member disposed with respect to the end portion and the magnetic force lines and magnetic particles in the developer. A seal with a magnetic brush that suppresses leakage is formed. With this magnetic seal, developer leakage can be suppressed in a state where toner melting and welding due to heat generation at the end portion and its periphery are suppressed.

In addition, the magnet member includes an outer portion near the outer side of the developing housing and an inner portion closer to the inner side of the developing housing than the outer portion, and the direction of the magnetic force of the outer portion is the rotation of the developer conveying member. Although the direction of the magnetic field of the inner portion is perpendicular to the center line direction, the developer entering the gap between the inner portion and the end portion is caused by the rotation of the end portion with respect to the magnetic force line of the inner portion and the magnetic force line. The developer conveying member is inclined with respect to the rotation center line direction so as to be moved (returned) toward the inside of the developing housing.

Therefore, the developer in the developer housing receives a force in the direction of the rotation center line of the developer transport member in which the magnet member is disposed, or an impact or vibration is applied to the developer, and the magnet member and the developer Even if the developer tries to enter the gap between the end portions of the developer conveying member or enters the developer, the developer rotates the developer conveying member, thereby rotating the rotation center of the developer conveying member at the inner portion of the magnet member. The developer is fed back into the developing housing by the magnetic force lines inclined with respect to the linear direction and the rotation of the end of the developer conveying member.

Accordingly, it is possible to prevent clogging as if the toner or the like is pushed into the gap between the magnet member and the end portion of the developer conveying member where the magnet member is disposed so that the toner cannot be returned later. Developer leakage is suppressed in a state where increase in rotational torque of the member is suppressed.

Further, even if the developer passes through the sealing action by a magnetic brush or the like formed by the inner portion of the magnet member and goes to the outer portion, the amount is limited to a small amount, and the developer that has slipped through the magnet Leakage to the outside of the developing housing is suppressed by a magnetic brush formed by a magnetic force line perpendicular to the rotation center line direction of the developer conveying member in the outer portion of the member.

As a typical example of the developer containing the magnetic particles employed in the developing device according to the present invention, a developer containing toner and a magnetic carrier can be given.

  In order to further smooth the return of the developer by the inner part of the magnet member, the inner diameter of the at least one magnet member is set so that the inner part and the inner part are arranged. The gap with the end of the agent conveying member may be set so as to increase toward the center of the developing housing.

  Further, in order to facilitate the return of the developer by the inner part of the magnet member, at least one of the magnet members includes a part of the outer part of the magnet member and one of the inner parts adjacent thereto. The gap between the end portion of the developer conveying member where the magnet member is disposed and the inner portion may be set larger than the gap between the end portion and the outer portion.

  By overlapping a part of the outer part and a part of the inner part adjacent to the outer part, the magnetic force is also applied to the joint between the outer part and the inner part to suppress the developer from being deposited there. it can.

  In order to facilitate the arrangement of the magnet members and the assembly of the developing device, at least one of the magnet members may be formed with a notch in the circumferential direction of the magnet member or divided in the circumferential direction. For example, a cutout may be formed in each of the outer portion and the inner portion of at least one of the magnet members in the circumferential direction of the portions.

  When the outer portion and the inner portion of at least one of the magnet members are each provided with a notch in the circumferential direction of the portion, the outer portion is used to suppress slipping of toner or the like from the notch. The positions of the notch and the notch of the inner portion may be shifted in the circumferential direction of the magnet member.

  In the developing device according to the present invention, there may be various developer conveying members that dispose the magnet member at the end, but as an example, a developer is carried on the peripheral surface as one of the developer conveying members. A case where a developing roller for supplying to the developing area is provided and the magnet member is disposed with respect to an end of the developing roller can be mentioned.

  In addition, a developer conveying screw having a spiral blade provided around a rotating shaft is provided as at least one of the developer conveying members, and the magnet is disposed at an end of the rotating shaft of at least one developer conveying screw. The case where the member is arrange | positioned can be mentioned.

  In any case, the developer conveying member on which the magnet member is disposed is rotatably supported by the developing housing with a rotating shaft of the developer conveying member, and the magnet member is adjacent to the bearing member. Can be mentioned.

  In order to solve the second problem, the present invention forms an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier, and develops the electrostatic latent image with a developing device to form a toner image. And an image forming apparatus in which at least one developing device is a developing device according to the present invention.

  Since the image forming apparatus according to the present invention employs the developing device according to the present invention as at least one developing device, at least one developer conveying member of the developing device has an end portion of the developer conveying member. The developer leakage from the toner can be suppressed in a state in which toner melting and welding due to heat generation at the end portion and the periphery thereof are suppressed, and without increasing the rotational torque of the developer conveying member to a problem level, As a result, the entire image forming apparatus can form a good image.

As described above, according to the present invention, the developer containing magnetic particles accommodated in the developing housing is formed on the electrostatic latent image carrier by the developer conveying member rotatably supported by the developing housing. A developing device for developing the electrostatic latent image by supplying the electrostatic latent image to a developing area, wherein the developer from the end of the developer conveying member is at least one developer conveying member; Leakage can be suppressed in a state where toner melting and welding due to heat generation at the end portion and its periphery are suppressed, and without increasing the rotational torque of the developer conveying member as much as possible, and as a whole, It is possible to provide a developing device that can perform good electrostatic latent image development.

According to the present invention, there is provided an image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on the electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image. And at least one developing device formed on the electrostatic latent image carrier by a developer conveying member rotatably supported by the developing housing with developer containing magnetic particles accommodated in the developing housing. A developing device that supplies the electrostatic latent image to a developing area to develop the electrostatic latent image, and at least one developer conveying member of the developing device is connected to an end of the developer conveying member; A developing device capable of suppressing developer leakage in a state where toner melting and welding due to heat generation at and around the end portion are suppressed, and without increasing the rotational torque of the developer conveying member to a problem level. Yes, it Overall only, it is possible to provide an image forming apparatus capable of forming a good image.

1 is a diagram schematically showing a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a view showing a developing device in the image forming apparatus of FIG. FIG. 3 is a view showing a magnet member for suppressing developer leakage arranged with respect to a developer conveying screw shaft end portion in the developing device of FIG. 2. It is operation | movement explanatory drawing of the magnet member of FIG. It is a figure which shows the other example of the magnet member which can be arrange | positioned with respect to a developer conveyance screw shaft edge part. It is a figure which shows the further another example of the magnet member which can be arrange | positioned with respect to a developer conveyance screw shaft edge part. It is a figure which shows the further another example of the magnet member which can be arrange | positioned with respect to a developer conveyance screw shaft edge part. It is a figure which shows the further another example of the magnet member which can be arrange | positioned with respect to a developer conveyance screw shaft edge part. FIG. 2 is an enlarged view of a developing device shown in the image forming apparatus of FIG. FIG. 3 is a diagram illustrating a developing roller support structure and a magnet member for suppressing developer leakage at the end of the developing roller in the developing device of FIG. 2.

Hereinafter, an example of an image forming apparatus according to the present invention and a developing device used therein will be described with reference to the drawings.
FIG. 1 shows an outline of the configuration of an example PR of an image forming apparatus. The image forming apparatus PR is a tandem type full color printer.

  This printer PR has a driving roller 82 and an endless intermediate transfer belt 81 wound around a roller 83 facing the driving roller 82. The transfer belt 81 is rotated in the counterclockwise direction (arrow direction in the figure) CCW by a driving roller 82 driven by a belt driving unit (not shown).

  The roller 83 faces a cleaning device 84 that cleans the secondary transfer residual toner and the like on the transfer belt 81, and the drive roller 82 faces the secondary transfer roller 80. The toner or the like collected by the cleaning device 84 is sent to a waste container by a conveying means (not shown).

  The secondary transfer roller 80 is pressed against a portion of the intermediate transfer belt 81 supported by the drive roller 82 by a pressing means (not shown), forms a nip portion with the intermediate transfer belt 81, and rotates the intermediate transfer belt 81. It can be rotated by being driven, or following the movement of the recording sheet S fed into the nip portion, as will be described later, or driven by a drive unit (not shown). A secondary transfer bias can be applied to the secondary transfer roller 80 from a power supply (not shown).

  A fixing device F is disposed above the intermediate transfer belt 81 and the secondary transfer roller 80, a timing roller pair TR is disposed below, and a recording sheet S such as recording paper is accommodated below the fixing device F. The recorded sheet storage cassette 9 is disposed.

The fixing device F includes a fixing heating roller incorporating a heat source such as a halogen lamp heater and a pressure roller pressed against the fixing heating roller.
The recording sheets S stored in the recording sheet storage cassette 9 can be pulled out one by one by the supply roller 91 and supplied to the timing roller pair TR.

  Between the rollers 82 and 83 around which the intermediate transfer belt 81 is wound, the yellow image forming unit Y, the magenta image forming unit M, and the cyan image forming unit C are moved along the transfer belt 81 from the roller 83 to the roller 82. And the black image forming portion K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photosensitive member 1 as an electrostatic latent image carrier, and a charger 2, an exposure device 3, a developing device 4, and the like around the photosensitive member. The cleaning device 5 and the charge eraser 6 are arranged in this order.

  A primary transfer roller 7 is disposed opposite to the photoreceptor 1 of each image forming unit with a belt 81 therebetween. The primary transfer roller 7 is pressed in the direction of the photosensitive member 1 by a pressing unit (not shown), contacts the belt 81 and is driven to rotate, and can bring the belt 81 into contact with the photosensitive member 1.

  A primary transfer bias for primary transfer of the toner image formed on the photoreceptor 1 to the belt 81 can be applied to the primary transfer roller 7 from a power supply (not shown).

  The exposure device 3 can perform image exposure on the photosensitive member 1 by blinking of a laser beam in accordance with image information provided from a personal computer (not shown), an image reading device, or the like.

  The photoconductor 1 in each image forming unit is a negatively chargeable photoconductor here, and can be driven to rotate clockwise in the drawing by a photoconductor drive motor (not shown).

  The charger 2 in each image forming unit is a scorotron charger in this example, and a charging voltage is applied from a power supply (not shown) at a predetermined timing. The charger 2 may be one using a charging roller.

  The developing device 4 in each image forming unit develops an electrostatic latent image formed on the photoreceptor 1 from a power supply (not shown) using a so-called two-component developer mainly composed of a magnetic carrier and a non-magnetic toner. Reversal development can be performed by the developing roller 41 to which a bias is applied. The developing device 4 will be further described later.

According to this printer, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 81 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotated in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the yellow region for the yellow image is transferred from the exposure device 3 to the charged area. Image exposure is performed, and a yellow electrostatic latent image is formed on the photoreceptor 1. This electrostatic latent image is developed by a developing roller 41 to which a developing bias of the developing device 4 having yellow toner is applied, and becomes a visible yellow toner image. The yellow toner image is primarily transferred onto the transfer belt 81 by the primary transfer roller 7. At this time, a primary transfer bias is applied to the primary transfer roller 7 from a power supply (not shown).

Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 81, a cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 81, and the black toner is formed in the black image forming unit K. An image is formed and transferred to the transfer belt 81.

Yellow, magenta, cyan, and black toner images are formed at a timing at which the toner images are transferred onto the intermediate transfer belt 81 in an overlapping manner.
Thus, the multiple toner image formed on the transfer belt 81 moves toward the secondary transfer roller 80 by the rotation of the transfer belt 81.

  On the other hand, the recording sheet S is pulled out from the recording sheet storage cassette 9 by the supply roller 91, supplied to the timing roller pair TR, and is on standby.

  Thus, the recording sheet S waiting at the timing roller pair TR is supplied to the nip portion between the transfer belt 81 and the secondary transfer roller 80 in accordance with the multiple toner image sent by the intermediate transfer belt 81. . The multiple toner image is secondarily transferred onto the recording sheet S by a secondary transfer roller 80 to which a secondary transfer bias is applied from a power source (not shown).

  Thereafter, the recording sheet S is passed through the fixing device F, where the multiple toner images are fixed on the recording sheet S under heat and pressure. The recording sheet S is continuously discharged to the discharge tray T by the discharge roller pair DR.

  In the primary transfer of the toner image to the belt 81, residual toner or the like remaining on the photosensitive member 1 is cleaned by the cleaning device 5, and the residual charge is erased by the eraser 6. Secondary transfer residual toner or the like remaining on the belt 81 by the secondary transfer is cleaned by the cleaning device 84. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  Although the image is formed as described above, the developing device 4 using the two-component developer will be further described. The developing device 4 is shown in FIGS. 2 and 9 and is an example of the developing device according to the present invention. The four developing devices 4 employed in the image forming apparatus PR of FIG. 1 basically have the same structure. Basically, the same reference numerals are given to the same structure and operation parts.

  4 is a diagram showing the developing device 4 as viewed from the photosensitive member 1 side in FIG. FIG. 9 is an enlarged view of the developing device 4 shown in FIG.

The developing device 4 includes a developing housing 40 that contains a two-component developer including toner and a magnetic carrier, a developing roller 41 that is a developer conveying member rotatably supported by the housing 40, and upper and lower developer conveying behind the developing roller. Screws 42 and 43 are included.
FIG. 10 shows a part of the support structure of the developing roller 41 on the developing housing 40.

The developing roller 41 incorporates a magnetic field generator M (hereinafter referred to as “magnet body M”) in a fixed arrangement. Here, the developing roller 41 is in the form of a hollow roller having a circular cross section formed of a nonmagnetic material. Here, the magnet body M is generally formed in a roller shape.

The developing roller 41 is rotatably fitted on the magnet body M. The developing roller shaft 411 protrudes from the left end of the developing roller 41 in FIG. 2, and the developing roller shaft 411 is rotatably supported by the developing housing 40 via a bearing member 41B (see also FIG. 10). A shaft (not shown) protrudes from the right end of the magnet body M built in the developing roller 41 in FIG. 2, and this shaft is fixed to the developing housing 40 via a bearing member 41B ′ shown in FIG. It is supported. It can be said that the shaft of the magnet body M supported by the bearing member 41B 'also serves as the right shaft of the developing roller 41 in FIG.

  The developer conveying screw 42 on the upper side behind the developing roller 41 has a rotating shaft 421 and spiral blades 422 provided around it. As shown in FIG. 2, the left and right shaft end portions of the rotating shaft 421 are bearing members 42B and a developing housing. 40 is rotatably supported.

  The developer conveying screw 43 on the lower side of the screw 42 has a rotating shaft 431 and spiral blades 432 provided around it. As shown in FIG. 2, the left and right shaft end portions of the rotating shaft 431 are bearing members 43B and the developing housing 40. Is rotatably supported.

  A partition wall PW is provided between the developer conveying screws 42 and 43, and a developer passage opening is formed adjacent to both ends of the wall PW.

  A gear is attached to the left end of each of the developing roller 41 and the upper and lower developer conveying screws 42 and 43 that protrudes to the outside of the developing housing 40, and a gear train G formed by these gears is used. Thus, each of the developing roller 41 and the upper and lower developer conveying screws 42 and 43 can be rotationally driven.

The developer accommodated in the developing housing 40 is transported from the left side to the right side in FIG. 2 by the lower screw 43, rises through the developer passing port adjacent to the right end of the partition wall PW, and the upper screw 42. And is circulated so as to descend to the lower screw 43 through the developer passage opening adjacent to the left end of the partition wall PW, and is supplied from each part of the upper screw 42 to the developing roller 41.

  The developer supplied to the developing roller 41 is held on the peripheral surface of the developing roller as a developer spike by the magnetic force of the built-in magnet body M, and to the developing area Dp (see FIG. 9) facing the photoreceptor 1 by the rotation of the developing roller 41. In the middle, the amount of developer is appropriately regulated by a regulating member 44 (see FIGS. 1 and 9), which is used for developing the electrostatic latent image on the photoreceptor 1, and develops the latent image. A toner image can be formed.

  When the toner is reduced by development, new toner can be supplied to the lower screw 43 from the toner supply port 40t.

  As shown in FIGS. 2 and 3, the developing device 4 includes a magnet member 420 for suppressing developer leakage adjacent to the bearing member 42 </ b> B for each of both ends of the shaft 421 of the developer conveying screw 42. Is provided. A magnet member 430 for suppressing developer leakage is provided adjacent to the bearing member 43B for each of both ends of the shaft 431 of the developer conveying screw 43.

  FIG. 3 collectively shows magnet members 420 and 430 provided on the left ends of the shafts 421 and 431 in FIG. Although not shown, the same magnet members as the magnet members 420 and 430 shown in FIG. 3 are provided symmetrically with respect to the right ends of the shafts 421 and 431.

  As shown in FIG. 3, the magnet member 420 (430) includes an outer portion mg1 near the outside of the developing housing 40 and an inner portion mg2 adjacent to the inner side of the developing housing adjacent to the outer portion mg1. The outer portion mg1 and the inner portion mg2 are made of a flexible magnet sheet provided with magnetic poles, and the inner peripheral surface formed integrally with the bearing member 42B (43B) is a cylindrical magnet sheet attaching portion. It is stuck on the inner peripheral surface of b1. The outer part mg1 and the inner part mg2 have the same thickness, and a gap g1 is formed between the outer part mg1 and the inner part mg2 with the rotary shaft 421 (431).

  As shown in FIG. 4, the direction of the magnetic force lines of the outer portion mg1 is perpendicular to the axial thrust (rotation center line CL direction) of the rotating shaft 421 (431) (the outer portion mg1 is not completely perpendicular). From the viewpoint of forming a magnetic brush that provides a developer leakage prevention seal, the direction of magnetic force lines that can be regarded as “perpendicular” is also included.

  On the other hand, the direction of the magnetic lines of force of the inner portion mg2 is inclined with respect to the axial thrust (rotation center line CL direction) of the rotation shaft 421 (431). Such a gradient magnetic field line is obtained by, for example, inclining the magnetic pole arrangement direction of the inner portion mg2 with respect to the axial thrust.

  As an example of the magnetic pole arrangement direction of the inner portion mg2, there is a case where the magnetic pole extends at an inclination with respect to the axial thrust so as to extend inward of the developing housing as it advances downstream in the rotation direction of the shaft 421 (431). be able to.

In any case, the inner portion mg2 causes the developer entering the gap g1 between the inner portion mg2 and the end portion of the shaft 421 (431) adjacent to the bearing member 42B (43B) to move to the magnetic field lines of the inner portion mg2 and the shaft end with respect to the magnetic force lines. It is provided so as to be moved inward of the developing housing by rotation of the part.

  In the example shown in FIG. 4, the gap g1 between the magnet member 420 (430) and the end of the shaft 421 (431) where the magnet member 420 (430) is disposed is moved out of the developing housing 40 by the action of the magnetic lines of force and the magnetic carrier in the developer. A magnetic brush seal that suppresses developer leakage is formed. This magnetic seal can suppress developer leakage in a state where toner melting and welding due to heat generation at and around the end of the shaft 421 (431) are suppressed.

Moreover, the magnet member 420 (430) includes an outer portion mg1 that is closer to the outside of the developing housing 40 and an inner portion mg2 that is closer to the inner side of the developing housing 40 than that, and the magnetic force line direction of the outer portion mg1 is the axis 421 (431). ) Of the inner portion mg2 is perpendicular to the rotation center line direction CL, but the developer entering the gap g1 between the inner portion mg1 and the end of the shaft 421 (431) is separated from the magnetic force lines of the inner portion mg1. The shaft 421 (431) is inclined with respect to the rotation center line direction CL so as to return to the inside of the developing housing by rotation of the shaft end with respect to the magnetic field lines.

Therefore, the developer in the developing housing 40 receives a force in the direction of the rotation center line CL of the conveying screw 42 (43) on which the magnet member 420 (430) is disposed, or the developer is subjected to impact or vibration, and the magnet. Even if an attempt is made to enter or enter the gap g1 between the member 420 (430) and the shaft end, the conveying screw 42 (43) rotates, so that the gradient magnetic field lines of the inner portion mg2 and the conveying screw 42 (43 ) Of the shaft 421 (431) in the direction of the arrow (see FIG. 4), part of the developer entering the gap g1 is returned to the inside of the developing housing while being partly in the state of a magnetic brush. .

Accordingly, it is prevented that the toner or the like is clogged as if it is pushed into the gap g1 between the magnet member 420 (430) and the end portion of the developer conveying screw 42 (43) in which the magnet member 420 (430) is disposed so as not to return. Accordingly, the developer leakage is suppressed in a state where the increase in the rotational torque of the developer conveying screw 42 (43) is suppressed.

Further, even if the developer slips through the sealing action by the inner portion mg2 of the magnet member 420 (430) and enters the outer portion mg1, the amount thereof is limited to a small amount, and the developer that has passed through the outer portion mg1 The magnetic brush formed by the perpendicular magnetic field lines is prevented from leaking out of the developing housing.

  FIG. 5 is a perspective view showing another example of the magnet member. The magnet member in FIG. 5 is a magnet member 420 for the end of the rotating shaft 421 of the developer conveying screw 42, but the same magnet member is also adopted for the end of the rotating shaft 431 of the developer conveying screw 43. Can do.

The magnet member of the type shown in FIG. 5 has a notch formed in the circumferential direction of the magnet member or divided in the circumferential direction in order to facilitate the arrangement of the magnet member and assembly of the developing device. It is based on the idea that it is good.

In the example of FIG. 5, notches c1 are formed at intervals of approximately 180 degrees in the outer portion mg1 constituting the magnet member 420 (430) at two positions in the circumferential direction (one is hidden and cannot be seen). It is divided into parts. The inner part mg2 is also divided into two parts by forming notches c2 at two positions in the circumferential direction at intervals of about 180 degrees. It is also possible to employ such a magnet member.

  The notch c1 of the outer portion mg1 and the notch c2 of the inner portion mg2 are shifted in the circumferential direction to prevent the developer from leaking from the notch.

FIG. 6 shows another example of the magnet member 420 (430). The magnet member of FIG. 6 is the same as the magnet member of FIG. 4 except that the inner portion mg2 has an inner diameter, and the gap between the inner portion mg2 and the shaft 421 (431) of the conveying screw 42 (43) on which the inner portion mg2 is disposed. The gap is gradually set to the expansion gap g2 so as to increase toward the center side. The outer portion mg1 is the same as the outer portion mg1 in FIG.

According to the magnet member of FIG. 6, since the gradually expanding gap g2 is formed by the inner portion mg2, the developer return by the inner portion mg2 can be smoothed accordingly.

  In addition, in magnet member 420 (430) of FIG. 6, inner part mg2 is stuck to the inner peripheral surface truncated cone-shaped part of magnet sheet sticking part b2 formed integrally with bearing member 42B (43B). Has been. The outer portion mg1 and the inner portion mg2 have the same thickness, and a gap g1 is provided between the outer portion mg1 and the rotating shaft 421 (431).

  7 and 8 show still other examples of the magnet member 420 (430). These magnet members overlap a part of the outer part mg1 and a part of the inner part mg2 adjacent thereto with a width w1 (w2), so that the conveying screw 42 (43) on which the magnet member 420 (430) is arranged. The gap g3 (g4) between the end of the shaft 421 (431) and the inner part mg2 is set larger than the gap g1 between the outer part mg1 and the shaft end. The gap g4 is set to a gradually expanding gap g4 similarly to the gap g2 between the inner part mg2 and the shaft end of the magnet member in FIG.

  7 and 8, the gap g3 (g4) is set to be larger than the gap g1, and the gap g4 is set to be gradually expanded, so that the gap g3 (g4) is increased accordingly. ), The developer can be easily moved and the developer can be fed back by the inner portion mg2. Further, by overlapping a part of the outer part mg1 and a part of the inner part mg2 adjacent to it with a width w1 (w2), a magnetic force is also applied to the joint between the outer part mg1 and the inner part mg2. It can suppress that a developer accumulates there.

  The magnet members shown in FIGS. 6, 7, and 8 may be notched in the circumferential direction or may be divided.

  FIG. 10 shows a magnet for suppressing developer leakage arranged along the developing roller end 41 ′ adjacent to the bearing member of the rotating shaft of the developing roller 41 and arranged in an arc shape with a gap g5 from the end. Member 410 is shown. FIG. 9 also shows the magnet member 410. As can be seen from FIG. 9, the magnet member 410 is provided in a portion of the developing housing 40 excluding the opening 400 facing the photoreceptor 1 and the developer regulating member 44. Although only the left magnet member 410 is shown in FIG. 10, the same magnet member 410 is disposed symmetrically with respect to the right end portion of the developing roller.

  The magnet member 410 in FIG. 10 also includes an outer portion mg1 'close to the outside of the developing housing 40 and an inner portion mg2' adjacent to the inner side of the developing housing adjacent thereto. The outer portion mg1 'and the inner portion mg2' are made of a flexible magnet sheet provided with magnetic poles, and are adhered to the inner surface of the developing housing 40. The outer portion mg1 'and the inner portion mg2' have the same thickness, and a gap g5 is provided between the developing roller end portion.

  The direction of the magnetic force line of the outer portion mg1 ′ is perpendicular to the axial thrust (rotation centerline direction) of the developing roller 41 (even if it is not completely perpendicular, the outer portion mg1 ′ provides a developer leakage suppression seal. This includes the direction of magnetic field lines that can be regarded as “perpendicular” from the viewpoint of forming a magnetic brush).

  On the other hand, the direction of the magnetic force lines of the inner portion mg2 'is inclined with respect to the axial thrust (rotation center line direction) of the developing roller 41. The inner portion mg2 ′ is a developer that enters the gap g5 between the inner portion mg2 ′ and the developing roller end 41 ′. The developer enters the inside of the developing housing by the gradient magnetic field lines of the inner portion mg2 ′ and the rotation of the developing roller end 41 ′ with respect to the magnetic lines. It is provided to move to.

  According to the magnet member 410, leakage of the developer can be suppressed as in the case of the magnet member 420 (430). The magnet member 410 is also divided by forming notches in the circumferential direction as shown in FIG. As for the magnet member 410, the same magnet member as shown in each of FIGS.

  Since the image forming apparatus PR adopts the developing device 4 described above, developer leakage from the end portions of the developer conveying screws 42 and 43 of the developing device 4 and the end portion 41 ′ of the developing roller 41 It is possible to suppress the toner melting and welding due to heat generation at these end portions and the periphery thereof, and without increasing the rotational torque of these rotating members as much as a problem, so that the image forming apparatus PR as a whole is good. An image can be formed.

  The image forming apparatus described above is a tandem type color image forming apparatus. However, the present invention can be applied to other types of color image forming apparatuses and developing apparatuses thereof, and monochrome image forming apparatuses and developing apparatuses thereof. .

The present invention relates to a developing device that develops an electrostatic latent image using a developer containing magnetic particles, and at least one developer transport member has developer leakage from the end thereof and the end and To provide a developing device capable of suppressing toner melting and welding due to heat generation in the vicinity thereof and without increasing the rotational torque of the developer conveying member to a problem level, and such a developing device. Can be used to provide an image forming apparatus including

PR printer (an example of an image forming apparatus)
Y Yellow image forming unit M Magenta image forming unit C Cyan image forming unit
K black image forming unit 1 photoconductor 2 charger 3 image exposure device 4 developing device 40 developing housing 400 developing housing opening 41 developing roller 41 ′ developing roller end M magnetic field generator (magnet)
41B, 41B ′ bearing member 410 magnet member mg1 ′ outer portion mg2 ′ inner portion gap g5
42, 43 Developer conveying screws 421, 431 Rotating shafts 422, 432 Spiral blades 42B, 43B Bearing members 420, 430 Magnet member gaps g1, g2, g3, g4
Notches c1, c2
b1, b2 Adhering portion of the inner part of the magnet member

Claims (11)

  A developing area for developing an electrostatic latent image formed on an electrostatic latent image carrier by a developer conveying member rotatably supported by the developing housing with developer containing magnetic particles contained in the developing housing A developing device that develops the electrostatic latent image by supplying to the magnet member with a gap with respect to at least one end of the developer conveying member and along a peripheral surface of the end The magnet member includes an outer portion that is closer to the outside of the developing housing and an inner portion that is closer to the inner side of the developing housing than the outer portion, and the direction of the lines of magnetic force of the outer portion is the developer. The magnetic force line direction of the inner portion is perpendicular to the rotation center line direction of the conveying member, and the developer entering the gap between the inner portion and the end portion causes the developer to enter the gap between the inner portion and the end portion. rotation So as to move more said to developing housing inwardly, developing apparatus is characterized in that is inclined relative to the rotational center line direction of the developer conveying member. The developing device according to claim 1, wherein the developer containing magnetic particles is a developer containing toner and a magnetic carrier.   With respect to at least one of the magnet members, the inner diameter of the inner portion increases so that the gap between the inner portion and the end of the developer conveying member where the inner portion is disposed increases toward the developing housing central side. The developing device according to claim 1 or 2, wherein   For at least one of the magnet members, a part of the outer part of the magnet member overlaps a part of the inner part adjacent to the magnet member, and the developer conveying member in which the magnet member is disposed 3. The developing device according to claim 1, wherein a gap between the end portion and the inner portion is larger than a gap between the end portion and the outer portion.   The developing device according to claim 1, wherein the at least one magnet member has a notch formed in a circumferential direction of the magnet member or is divided in the circumferential direction. The developing device according to claim 1, wherein a cutout is formed in each of the outer portion and the inner portion of at least one of the magnet members in a circumferential direction of the portion.   The developing device according to claim 6, wherein the cutout of the outer portion and the cutout of the inner portion are displaced in the circumferential direction of the magnet member.   As one of the developer conveying members, a developing roller that supports the developer on a peripheral surface and supplies the developer to the developing area is provided, and the magnet member is disposed with respect to an end portion of the developing roller. The developing device according to claim 1.   As at least one of the developer conveying members, a developer conveying screw having a spiral blade around the rotating shaft is provided, and the magnet member is disposed at an end of the rotating shaft of at least one developer conveying screw. The developing device according to claim 1, wherein the developing device is disposed.   The rotating shaft of the developer conveying member on which the magnet member is disposed is rotatably supported by the developing housing by a bearing member, and the magnet member is disposed adjacent to the bearing member. 10. The developing device according to any one of items 9.   An image forming apparatus capable of forming an electrostatic latent image corresponding to a target image on an electrostatic latent image carrier and developing the electrostatic latent image with a developing device to form a toner image, at least one developing device An image forming apparatus comprising: the developing device according to claim 1.

Images