JP2012063619A - Development device, process unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leakage of toner from between a rotary shaft and an inner ring of a ball bearing stably over a long period of time while suppressing cost.SOLUTION: The development device comprises a rotary member which has a rotary shaft 23a and moves toner stored in a housing by rotation of the rotary shaft 23a; and a ball bearing 24 for rotatably holding the rotary shaft 23a against the housing. The development device develops an electrostatic latent image formed on an outer peripheral surface of a photoreceptor using the toner. A first part (a part near a contact point R) which is a part of the rotary shaft 23a facing an inner ring 24a of the ball bearing 24 and a second part (a part near a contact point P) which is a part of the inner ring 24a of the ball bearing 24, corresponding to the first part, form a particle holding part 70 for holding carrier particles 61 having particle diameters larger than an average particle diameter of the toner at a gap between the first and second parts, over a whole circumference in a circumferential direction of the rotary shaft 23a.

Description

  The present invention relates to a developing device that develops an electrostatic latent image on a photoreceptor, a process unit that includes the developing device and the photoreceptor, and an image forming apparatus that includes the process unit.

  For image forming apparatuses such as printers and copiers that form a full-color image with toner of each color of yellow (Y), magenta (M), cyan (C), and black (K) by an electrophotographic method, Y, M, C A process unit for forming toner images with toners of the respective colors K and K is provided. Each color toner image formed by each process unit is usually transferred onto an intermediate transfer belt and then transferred to a recording sheet and fixed.

  Each process unit includes a rotatable photosensitive drum, a charger for charging the photosensitive drum to form an electrostatic latent image on the photosensitive drum, and an electrostatic latent image formed on the photosensitive drum. A developing device for developing the toner with a predetermined color toner is provided. In the developing device, there are a case where a one-component developer constituted only by toners of respective colors Y, M, C, and K is used, and a case where a two-component developer including toner and a magnetic carrier is used. .

  In the developing device of each process unit, a developing roller that is opposed to the photosensitive drum in a state parallel to the photosensitive drum and a conveying screw that is provided in parallel to the developing roller are usually provided in the housing. The toner supplied into the housing is conveyed from one end of the housing to the other end by the conveying screw, supplied to the photosensitive drum by the developing roller, and adheres to the electrostatic latent image on the photosensitive drum. . Thereby, the electrostatic latent image on the photosensitive drum is developed (visualized) with the toner.

  The conveying screw is provided with a conveying blade spirally around a linearly extending rotary shaft, and each end of the rotary shaft can be rotated by bearings on both sides of the housing. It is supported by. In addition, the developing sleeves constituting the developing roller also have rotational shafts provided on both sides thereof rotatably supported by bearings on both side surfaces of the housing.

Since the toner contained in the housing of the developing device is a fine powder, there is a risk of leakage to the outside of the housing from between the bearing that supports the end of the rotating shaft of the conveying screw or the developing sleeve and the rotating shaft. There is.
If the toner in the housing leaks to the outside, the toner is wasted and the economy is impaired. Further, since the periphery of the developing device is contaminated by the leaked toner, there is a possibility that a high-quality image cannot be formed when the image forming operation is executed.

  Here, it is conceivable that the rotary shaft is press-fitted into the bearing so that no gap is generated between the bearing and the rotary shaft, and the bearing is pressed against the outer peripheral surface of the rotary shaft by an interference fit. In this case, there is a problem that assembly is not easy. Therefore, conventionally, a slight gap is provided between the opening into which the rotating shaft of the bearing is inserted and the outer peripheral surface of the rotating shaft for the purpose of facilitating assembly. However, in order to facilitate the assembly, the size of the gap inevitably has to be larger than the average particle diameter of the toner. For this reason, there is a possibility that the toner may leak from there, and in order to solve the problem of toner leakage, a configuration has been conventionally employed in which the gap is sealed.

  In Patent Document 1, in a developing device using a two-component developer, a magnetic plate fitted to a rotating shaft supported by a bearing, and a magnet provided on a side surface in a housing facing the magnetic plate. In the meantime, a configuration is disclosed in which toner is prevented from flowing toward a bearing provided on a side surface of the housing by holding the carrier accommodated in the housing.

  Further, in Patent Document 2, in a sliding bearing (bearing for the other end side supply roller) that rotatably holds a rotating shaft, an inner diameter is larger than an opening at a housing inner peripheral edge of the opening through which the rotating shaft is inserted. A cylindrical small-diameter portion is integrally provided coaxially with the opening, and a ring-shaped seal member (second bearing seal) is fitted into the cylinder by press-fitting. The ring-shaped seal member and the sliding bearing A configuration is disclosed in which a rotating shaft is inserted through the opening. The ring-shaped seal member is brought into pressure contact with the outer peripheral surface of the rotary shaft by an interference fit with the rotary shaft, thereby sealing between the rotary shaft and the bearing.

JP 05-134540 A JP 2006-154431 A

In the configuration disclosed in Patent Document 1, the toner is directed toward the bearing along the rotation axis by the carrier held between the magnetic plate fitted to the rotation shaft and the magnet facing the magnetic plate. It can be prevented from flowing.
However, since another member such as a magnet or a magnetic plate is used, it causes a cost increase.

In the configuration disclosed in Patent Document 2, the sliding bearing that rotatably holds the rotating shaft is fixed to the side surface of the housing, and a ring-shaped seal member is provided with respect to the fixed sliding bearing. It is fixedly attached by press fitting. Therefore, the rotating shaft supported by the sliding bearing rotates with respect to the ring-shaped seal member in a fixed state.
In such a configuration, a ring-shaped seal member, which is a separate member, is used, which again increases costs. Furthermore, since the rotating shaft slides relative to the ring-shaped seal member, the ring-shaped seal member and the rotating shaft may be worn. As a result, the sealing performance between the ring-shaped sealing member and the rotating shaft is deteriorated, and there is a possibility that toner leakage cannot be prevented stably over a long period of time.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a developing device that can stably secure a sealing property between a bearing and a rotating shaft over a long period of time while suppressing cost. Is to provide. Another object of the present invention is to provide a process unit and an image forming apparatus having such a developing device.

  In order to achieve the above object, a developing device according to the present invention has a rotating shaft, and a rotating member that moves toner accommodated in the housing by rotation of the rotating shaft; and the rotating shaft with respect to the housing. A developing device that develops an electrostatic latent image formed on the outer peripheral surface of the photosensitive member using the toner, and the rolling bearing portion of the rotating shaft. And a second portion corresponding to the first portion of the inner ring of the rolling bearing portion over the entire circumference in the circumferential direction of the rotating shaft, with a gap between them. It is characterized in that a particle holding part for holding seal particles having an average particle size larger than the average particle size of the toner is formed.

In addition, a process unit according to the present invention includes the developing device.
Furthermore, the image forming apparatus according to the present invention is characterized in that the process unit is provided.

With the above configuration, in the developing device of the present invention, the seal particles are held in the gap between the rotation shaft and the inner ring of the rolling bearing portion by the particle holding portion over the entire circumference in the circumferential direction of the rotation shaft, thereby closing the gap. Therefore, the toner can be prevented from leaking out of the housing through the gap by the held seal particles.
Further, since the particles held in the particle holding portion rotate together with the rotating shaft and the inner ring while being held, it is suppressed that both wear and the gap is widened, and the rotating shaft and the rolling bearing portion The sealing performance between the inner ring and the inner ring can be ensured stably over a long period of time.

Furthermore, since a separate sealing member is not used, the number of parts can be reduced and the cost can be reduced.
Further, in a state where the seal particles are held in the particle holding part, the contact point between the seal particles and the second part is P, the center point of the seal particles is Q, the seal particles and the first part are The angle PQR may be an obtuse angle, where R is the contact point.

As a result, the seal particles are stably held by the particle holding portion, and there is an effect that the stability of the sealing property is improved.
Furthermore, the size of the gap in the radial direction of the rotating shaft may be smaller than the average particle size of the seal particles and larger than half of the average particle size.
This also has the effect that the sealing particles are stably held by the particle holding part, and the stability of the sealing property is improved.

Here, the seal particles may have a property of being charged to a polarity opposite to that of the toner.
As a result, the toner present around the seal particles adheres to the surface of the seal particles by electrostatic force, and fills and closes the gaps between the seal particles and the gaps between the seal particles and the inner ring and the rotating shaft. The toner can be prevented from leaking out of the housing through the gap.

Here, the seal particles may be made of metal.
As a result, when the toner made of resin and the seal particles made of metal come into contact with each other, the toner is charged by contact charging. It can be surely prevented.
Here, the metal may be iron.

Thereby, since seal particles can be created using iron having high versatility and excellent durability, leakage of toner to the outside of the housing can be prevented stably for a long period of time while suppressing cost.
Here, the housing may contain a two-component developer including toner and a carrier therein, and the seal particles may be the carrier.

Thereby, since the carrier in the developer accommodated in the housing is also used as the seal particles, it is not necessary to prepare the seal particles separately, which can further contribute to cost reduction.
Furthermore, here, the rotational axis may have a surface roughness Rmax of the outer peripheral surface of the particle holding portion of 6.3 s or more and 25 s or less.

As a result, the sealing particles are more stably held in the particle holding portion by fitting the sealing particles in the concave and convex portions present on the surface of the rotating shaft in the particle holding portion.
Further, the rotating shaft may be provided with a groove over the entire circumference along the circumferential direction on the outer peripheral surface inside the housing including the particle holding portion.
As a result, a plurality of seal particles accumulated in the groove are supported from the inside of the housing so as to back up the seal particles held in the particle holding portion, and the effect that the seal particles are held in the particle holding portion more stably is obtained. is there.

Furthermore, at least the outer peripheral surface of the particle holding portion of the rotation shaft may be formed of a resin.
As a result, the surface of the rotating shaft in the particle holding portion is made of a softer resin than the seal particles. There is an effect that the concave portion is formed and the sealing particles are more easily held stably.

Here, the rolling bearing portion is held on a side surface of the housing via a bearing holding portion, the rotating shaft passes through a through hole provided in the bearing holding portion, and the through hole is The diameter decreases toward the outside of the housing, and the outer diameter of the inner ring of the rolling bearing portion may be larger than the minimum value of the diameter of the through hole.
As a result, the wall surface of the through hole has a tapered shape that becomes closer to the rotating shaft toward the outside of the housing, so that the inside of the through hole is outside the housing by the pressure of the developer when moved by the rotating member. The developer carrier pushed out to the edge is guided to the particle holding portion by the taper shape, and the carrier is easily held by the particle holding portion.

Furthermore, since the outer diameter of the inner ring of the bearing portion is larger than the minimum value of the diameter of the through hole, the inner ring can be stably held without entering the inside of the through hole.
Here, the bearing holder may be detachable from a side surface of the housing.
Thus, when the rotating member is assembled to the housing, the bearing holding portion is attached to the side surface of the housing in a state where the rolling bearing portion attached to the end of the rotating shaft of the rotating member is held by the bearing holding portion. Therefore, the rotating member can be easily assembled to the housing.

Here, the bearing holding portion may be formed integrally with a side surface of the housing.
Thereby, the number of parts can be reduced and it can contribute to cost control.
Here, the end surface inside the housing of the inner ring is in contact with the peripheral edge of the through hole in the bearing holding portion over the entire periphery, so that the space between the inner ring and the peripheral edge is sealed. May be.

Thereby, it is possible to prevent leakage of toner from between the peripheral edge portion of the through hole in the bearing holding portion and the inner ring of the rolling bearing portion.
Further, a side seal member may be provided between the inner ring of the rolling bearing portion and the peripheral edge portion of the through hole in the bearing holding portion so as to seal the entire circumference therebetween.

Thereby, the leakage of toner from between the peripheral edge portion of the through hole in the bearing holding portion and the inner ring of the rolling bearing portion can be more reliably prevented.
Furthermore, a fluid sealing material may be filled between the inner ring and the outer ring of the rolling bearing portion.
Thus, even when toner flows out from between the inner ring of the rolling bearing part and the peripheral part of the through hole in the bearing holding part, the toner can be prevented from leaking to the outside through the space between the inner ring and the outer ring. it can.

Here, the rolling bearing portion may include a bearing seal member that seals a side portion facing the peripheral edge portion of the through hole between the inner ring and the outer ring over the entire circumference.
This also prevents the toner from leaking outside between the inner ring and the outer ring even when the toner flows out from between the inner ring of the rolling bearing part and the peripheral part of the through hole in the bearing holding part. Can do.

Here, the bearing seal member may seal the entire circumference between the inner ring of the rolling bearing portion and the peripheral portion.
As a result, the toner leaks to the outside from between the peripheral edge of the through hole and the inner ring of the bearing holder facing the inner ring without contacting the inner ring of the rolling bearing and the peripheral edge of the through hole of the bearing holder. Can be prevented.

  In addition, the present invention can provide the same effects as a process unit including the above-described developing device and an image forming apparatus including the process unit.

1 is a schematic diagram illustrating a configuration of a tandem color digital printer which is an image forming apparatus provided with a developing device according to an embodiment of the present invention. FIG. 2 is a perspective view of a developing device provided in a process unit of the printer shown in FIG. 1. FIG. 3 is a longitudinal sectional view of the developing device shown in FIG. 2. FIG. 4 is an enlarged view showing a schematic configuration of a bearing portion surrounded by a circle F in the longitudinal sectional view of the developing device shown in FIG. 3. FIG. 4 is an enlarged view showing a schematic configuration of a bearing portion surrounded by a circle G in the longitudinal sectional view of the developing device shown in FIG. 3. It is sectional drawing which shows typically the structure of a rotating shaft holding | maintenance mechanism, Comprising: (a) is an enlarged view which shows typically schematic structure of the part enclosed by the circle H in FIG. 4, (b), It is a figure which further expands and shows the part enclosed by the circle K in (a). FIG. 7 is a partially enlarged cross-sectional view schematically showing the configuration of the rotary shaft holding mechanism when the size of the gap between the rotary shaft and the inner ring of the ball bearing is larger than that in FIG. 6. 6 (a) is an enlarged view similar to FIG. 6 (b), and FIG. 6 (b) is a view further enlarging a portion surrounded by a circle J in FIG. It is sectional drawing which shows typically three different cases in the state where the carrier particle is contacting two virtual planes, Comprising: (a) shows the case where angle PQR is an obtuse angle, (b) shows angle PQR. (C) is sectional drawing which shows the case where angle PQR is an acute angle. FIG. 7 is a partially enlarged cross-sectional view schematically showing the configuration of the rotating shaft holding mechanism when round edge processing is applied to the inner peripheral surface side edge of the inner ring of the ball bearing, and FIG. It is an enlarged view similar to a), and (b) is a cross-sectional view showing a portion corresponding to the portion surrounded by the circle J in FIG. It is sectional drawing which shows typically the state by which the carrier is hold | maintained at the particle | grain holding part in the modification 1 of this invention. It is sectional drawing which shows typically the state by which the carrier is hold | maintained at the particle holding part in the modification 2 of this invention. It is sectional drawing which shows typically the state by which the carrier is hold | maintained at the particle | grain holding part in the modification 3 of this invention, Comprising: (a) is a figure which shows the case where a projection part is provided in the rotating shaft side. (B) is a figure which shows the case where a projection part is provided in the inner ring | wheel side. It is sectional drawing which shows typically the state by which the carrier is hold | maintained at the particle holding part in the modification 4 of this invention. It is sectional drawing which shows typically schematic structure of the rotating shaft support mechanism in the modification 5 of this invention. It is sectional drawing which shows typically schematic structure of the rotating shaft support mechanism in the modification 6 of this invention. It is sectional drawing which shows typically schematic structure of the rotating shaft support mechanism in the modification 7 of this invention. It is sectional drawing which shows typically schematic structure of the rotating shaft support mechanism in the modification 8 of this invention. It is sectional drawing which shows typically schematic structure of the rotating shaft support mechanism in the modification 9 of this invention.

Hereinafter, a developing device according to an embodiment of the present invention will be described with reference to the drawings, taking as an example a case where the developing device is applied to a tandem digital color printer (hereinafter simply referred to as “printer”). In addition, the aspect of each structural member which comprises the printer and developing device which concern on embodiment of this invention and each modification shown by drawing is typical, Comprising: Relative in the magnitude | size, position, etc. of each structural member These relationships are not necessarily exactly as shown in the drawings.
<Embodiment>
<Overall configuration of printer>
FIG. 1 is a schematic diagram illustrating a configuration of a printer which is an image forming apparatus provided with a developing device according to an embodiment of the present invention. When the printer receives an instruction to execute a print job, the printer forms a full-color or monochrome image on a recording sheet such as a recording sheet or an OHP sheet by a known electrophotographic method based on the instruction.

The printer includes an image forming unit A that forms toner images of toners of yellow (Y), magenta (M), cyan (C), and black (K) on a recording sheet, and a lower part of the image forming unit A. And a paper feed unit B having a plurality of paper feed cassettes in which recording sheets supplied to the image forming unit A are accommodated.
The image forming unit A includes an intermediate transfer belt 41 that is wound around a driving roller 42 and a driven roller 43 in a horizontal state at a substantially central portion of the printer so as to be able to move around. The intermediate transfer belt 41 is moved in a direction indicated by an arrow X by a motor (not shown).

Below the intermediate transfer belt 41, a process unit 10Y for sequentially forming toner images on the intermediate transfer belt 41 with toners of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). 10M, 10C, and 10K are arranged in this order from the upstream side in the circumferential movement direction of the intermediate transfer belt 41.
Each of the process units 10Y, 10M, 10C, and 10K is configured to be detachable from the image forming unit A, and enters the image forming unit A from the front side to the inner back side (back side) of the printer. By being inserted, the image forming unit A is mounted. Each of the process units 10Y, 10M, 10C, and 10K is replaced with a new process unit 10Y, 10M, 10C, and 10K when the lifetime is reached.

  The three process units 10Y, 10M, and 10C have the same configuration, and the process unit 10K that forms a toner image with K-color toner is larger in size than the other process units 10Y, 10M, and 10C. It has become. Since all the process units 10Y, 10M, 10C, and 10K have the same function except that the color of the toner to be used is different, the configuration of the process unit 10Y will be mainly described below. .

  The process unit 10Y is provided with a photosensitive drum 11 disposed to face the intermediate transfer belt 41. The photosensitive drum 11 has an axial direction along the width direction of the intermediate transfer belt 41, and is linearly arranged from the front end to the inner back end of the printer. Each photosensitive drum 11 is rotated in a direction indicated by an arrow E.

  Below each photoconductor drum 11, an exposure device 13Y that irradiates the surface of the photoconductor drum 11 with laser light to form an electrostatic latent image is provided. The exposure device 13Y is attached to the image forming unit A. Exposure apparatuses 13M, 13C, and 13K that expose the photosensitive drum 11 in the other process units 10M, 10C, and 10K are also attached to the image forming unit A, respectively.

  The process unit 10Y includes a charging device 12 that uniformly charges the surface of the photosensitive drum 11 upstream of the surface position of the photosensitive drum 11 irradiated with laser light from the exposure device 13Y. The developing device 20 is disposed on the downstream side in the rotation direction. The surface of the rotating photosensitive drum 11 is charged by the charging device 12 and then an electrostatic latent image is formed by the laser light emitted from the exposure device 13Y. The formed electrostatic latent image is visualized with toner by the developing device 20.

Above the photosensitive drum 11, a primary transfer roller 15 </ b> Y disposed opposite to the intermediate transfer belt 41 is provided. The toner image on the photosensitive drum 11 developed by the developing device 20 is transferred onto the outer peripheral surface of the intermediate transfer belt 41 by the primary transfer roller 15Y. The primary transfer roller 15Y is attached to the image forming unit A.
Primary transfer rollers 15M, 15C, and 15K that transfer images formed on the respective photosensitive drums 11 to the intermediate transfer belt 41 on the photosensitive drums 11 in the other process units 10M, 10C, and 10K, respectively. The toner images attached to the image forming unit A and formed on the respective photosensitive drums 11 are respectively placed on the same area on the intermediate transfer belt 41 by the primary transfer rollers 15Y, 15M, 15C, and 15K. Transcribed.

  The process unit 10Y includes a cleaning device 16 that removes and cleans toner remaining on the surface of the photosensitive drum 11 after the toner image is transferred onto the intermediate transfer belt 41, and the photosensitive drum 11 that has been cleaned by the cleaning device 16. A neutralization device 17 is provided for neutralizing the surface. The other process units 10M, 10C, and 10K are also provided with a cleaning device 16 and a charge removal device 17 for the photosensitive drum 11, respectively.

  The intermediate transfer belt 41 conveys the toner images transferred by the primary transfer rollers 15Y, 15M, 15C, and 15K to a drive roller 42 that is disposed close to the process unit 10K. A secondary transfer roller 44 is disposed opposite to the drive roller 42 with an intermediate transfer belt 41 interposed therebetween. The secondary transfer roller 44 is in pressure contact with the intermediate transfer belt 41, and a transfer nip for transferring the toner image to the recording sheet is formed in the pressure contact portion.

  To the transfer nip, recording sheets stored in a paper feed cassette provided in the paper feed unit B are conveyed one by one. The recording sheet is conveyed by the timing roller pair 45 in synchronization with the timing at which the toner image formed on the intermediate transfer belt 41 is conveyed to the transfer nip. When the toner image formed on the intermediate transfer belt 41 is pressed against the recording sheet passing through the transfer nip, the toner image is collectively transferred onto the recording sheet by the electrostatic force of the electric field formed by the secondary transfer roller 44. .

  The toner that forms the toner image on the intermediate transfer belt 41 may not be completely transferred onto the recording sheet by the electrostatic force of the secondary transfer roller 44, and a part of the toner may remain on the intermediate transfer belt 41. However, the residual toner is electrically and mechanically removed by the residual toner removing device 46 disposed opposite to the driven roller 43 disposed in the vicinity of the process unit 10Y via the intermediate transfer belt 41. It is like that.

  The recording sheet that has passed through the transfer nip is conveyed to a fixing unit 50 provided in the upper part of the image forming unit A. The fixing unit 50 includes a heating roller 51 and a pressure roller 52 that are in pressure contact with each other, and a fixing nip is formed between the heating roller 51 and the pressure roller 52 by being in pressure contact with each other. ing. A heater lamp (not shown) is arranged at the axial center of the heating roller 51, and the heating roller 51 is heated by the heater lamp.

  The unfixed toner image on the recording sheet that has passed through the transfer nip and is conveyed to the fixing unit 50 is fixed on the recording sheet by being heated and pressurized while the recording sheet passes through the fixing nip. The recording sheet on which the toner image has been fixed in the fixing unit 50 is discharged onto a paper discharge tray 48 provided at the top of the printer by a paper discharge roller pair 49 with the surface on which the toner image is formed facing downward. Is done.

The developing device 20 provided in each of the process units 10Y, 10M, 10C, and 10K develops the electrostatic latent images on the photosensitive drums 11Y, 11M, 11C, and 11K with a two-component developer (carrier and toner). The toners of the respective colors Y, M, C, and K are supplied from the toner hoppers 47Y, 47M, 47C, and 47K provided above the intermediate transfer belt 41 to the developing devices 20. The developing devices 20 provided in each of the three process units 10Y, 10M, and 10C other than the process unit 10K have the same configuration.
<Configuration of developing device>
FIG. 2 is a perspective view of the developing device 20, and FIG. 3 is a longitudinal sectional view of the developing device 20. In addition, the longitudinal cross-sectional view of FIG. 3 is shown in the state which reversed the left-right direction with respect to the perspective view of FIG.

The developing device 20 has a housing 21 that extends long along the axial direction of the photosensitive drum 11. A toner supply port 21 a is provided on the upper surface of one end of the housing 21.
When the process units 10Y, 10M, and 10C are attached to the image forming unit A, they are inserted into the image forming unit A from the end opposite to the end provided with the toner replenishing port 21a. It has come to be. When the process units 10Y, 10M, and 10C are mounted on the image forming unit A, the toners of the toner hoppers 47Y, 47M, and 47C provided in the image forming unit A are transferred to the process units 10Y. The 10M and 10C developing devices 20 can be supplied into the housing 21 through the toner supply port 21a.

  As shown in FIGS. 1 and 3, a first toner conveying screw 22 extending along the longitudinal direction of the housing 21 is provided in the lower part in the housing 21, and the first toner conveying screw 22 extending in the longitudinal direction of the housing 21 is provided in the upper part in the housing 21. A second toner conveying screw 23 parallel to the one toner conveying screw 22 is provided. As shown in FIG. 3, a partition wall 21 b is provided between the first toner conveying screw 22 and the second toner conveying screw 23.

  The first toner conveying screw 22 and the second toner conveying screw 23 respectively have conveying blades 22b and 23b provided in a spiral shape around the rotation shafts 22a and 23a except for the ends on both sides. . The first toner conveying screw 22 and the second toner conveying screw 23 are configured so that the end portions on both sides of the rotating shafts 22a and 23a have the same configuration so that the conveying blades 22b and 23b are located inside the housing 21. It is attached to each side surface 21x on both sides of the housing 21 by a support mechanism 21A.

  The rotary shafts 22a and 23a of the first toner conveying screw 22 and the second toner conveying screw 23 pass through the side surface 21x of the housing 21 at the end opposite to the end where the toner supply port 21a is provided. Gears 28 and 29 are attached to the respective ends. The gears 28 and 29 are meshed with each other, and one gear 28 is meshed with a gear (not shown) provided in the image forming unit A when the process unit is mounted on the image forming unit A. Become.

  As a result, the rotation shaft 22a of the first toner conveying screw 22 is rotated by the power of the motor that drives the image forming unit A being transmitted. Further, the power transmitted to the rotation shaft 22a of the first toner transport screw 22 is transmitted to the rotation shaft 23a of the second toner transport screw 23 through the gears 28 and 29, and the rotation shaft 23a is transmitted to the first toner. The conveying screw 22 is rotated in the opposite direction to the rotating shaft 22a. The first toner conveying screw 22 and the second toner conveying screw 23 function as rotating members that convey toner and carrier by being rotated about their respective rotation axes.

  As shown in FIGS. 1 and 2, a developing roller 25 is disposed in the upper part of the housing 21 so as to face the second toner conveying screw 23 and face the surface of the photosensitive drum 11. . The developing roller 25 includes a magnetic roller fixed to the housing 21 and a developing sleeve externally attached to the magnetic roller, as in the developing roller used in a conventional developing device using a two-component developer. The rotating sleeves 25a (see FIG. 2) that protrude outward in the axial direction are provided at both ends of the developing sleeve.

The developing roller 25 has a length that is approximately the same as the axial length of the photosensitive drum 11, and is disposed in parallel with the second toner conveying screw 23.
As shown in FIG. 3, the toner supplied into the housing 21 through the toner replenishing port 21a passes through the first developer passage hole 21m provided at one end of the partition wall 21b, and is then shown in FIG. As shown by the arrow D1, it falls to the lower part of the housing 21, and by the rotation of the first toner conveying screw 22, toward the end opposite to the toner supply port 21a as shown by the arrow D2 in FIG. Be transported. The toner conveyed by the first toner conveying screw 22 is agitated with the magnetic carrier housed in the housing 21 during the conveyance.

The magnetic carrier is a spherical particle made of iron. Here, the iron includes iron oxide such as hematite and magnetite, ferrite, and the like. Further, the iron surface may be coated with a resin or a surface treatment, and the iron fine particles are collectively fixed using a binder resin or the like and subjected to a spheroidization treatment. There may be.
The toner conveyed to the end opposite to the toner supply port 21a passes through the second developer passage hole 21n provided in the partition wall 21b together with the carrier, and as shown by an arrow D3 in FIG. It is conveyed to the upper part where the second toner conveying screw 23 is provided.

  Since the second toner conveying screw 23 is rotated in the opposite direction to the first toner conveying screw 22, the developing roller 25 is opposite to the first toner conveying screw 22 as indicated by an arrow D 4 in FIG. The toner and the carrier are conveyed along the axial direction. The toner and a part of the carrier conveyed by the second toner conveying screw 23 are supplied to the developing roller 25 during the conveyance.

  The carrier and toner in the housing 21 are transported on the outer peripheral surface of the developing sleeve by the rotation of the developing sleeve that is externally attached to the magnetic roller that is in a fixed state. The carrier conveyed on the outer peripheral surface of the developing sleeve forms a magnetic brush by the magnetic pole of the magnet roller, and the toner attached to the magnetic brush adheres to the electrostatic latent image on the photosensitive drum 11. As a result, the electrostatic latent image on the photosensitive drum 11 is developed with toner.

In the developing device 20 provided in the process unit 10K that forms a toner image with K-color toner, as shown in FIG. 1, a first toner conveying screw 22 and a second toner conveying screw 23 are provided below the housing 21. Are arranged side by side in the horizontal direction, and a developing roller 25 is disposed above the second toner conveying screw 23. Further, the developing roller 25 is in a state of facing the photosensitive drum 11 through an opening 21c provided in the upper portion of the housing 21. Other configurations are the same as those of the developing device 20 provided in each of the other three process units 10Y, 10M, and 10C.
<Configuration of rotating shaft support mechanism>
4 and 5 are enlarged views of a portion surrounded by a circle F and a circle G in FIG. 3, respectively.

  As shown in FIGS. 4 and 5, a cylindrical bearing holding portion (bearing holding portion) 27 is provided on each side surface 21 x located at each end portion on both sides in the longitudinal direction of the housing 21. Each bearing holding portion 27 is detachably fitted in an opening 21w provided on each side surface 21x of the housing 21. In each bearing holding portion 27, a ball bearing 24 is held as a rolling bearing portion that holds the end portions of the rotating shaft 22 a of the first toner conveying screw 22 and the rotating shaft 23 a of the second toner conveying screw 23. Yes.

  Each cylindrical bearing holding portion 27 is concentric with the opening 21w, and an end surface located on the inner side of the housing 21 has a through hole 27b through which each end of each of the rotation shafts 22a and 23a passes. The side wall 27a is provided. Each through hole 27b has a diameter slightly larger than the diameters of the rotating shafts 22a and 23a passing therethrough (the minimum value of the diameter of the through hole 27b indicated by “d1” in FIG. 5, which will be described in detail later). Yes.

  The ball bearings 24 fitted into the respective bearing holding portions 27 have the same configuration as that of generally used ball bearings, and are circumferentially arranged between the inner ring 24a, the outer ring 24b, and the inner ring 24a and the outer ring 24b. And a plurality of balls 24c arranged at regular intervals. Each ball 24c is held by a ball holding member (not shown) at regular intervals in the circumferential direction. ing.

  The ball bearing 24 is fitted into the bearing holding portion 27 so that the outer peripheral surface of the outer ring 24 b is pressed against the inner peripheral surface of the bearing holding portion 27, and the outer ring 24 b is fixed to the bearing holding portion 27. It is attached. The diameter d1 (see FIG. 5) of the through hole 27b is set to be smaller than the outer diameter d2 of the inner ring 24a (d1 <d2), and the inner ring 24a is formed on the peripheral portion of the side wall 27a provided with the through hole 27b. It is in contact all around. Thereby, it is possible to prevent the toner from leaking outside through the space between the inner ring 24a and the side wall portion 27a.

The inner ring 24a and the peripheral edge are in close contact with each other to such an extent that toner does not leak from between them, but the rotation of the inner ring 24a is not hindered.
The rotating shafts 22a and 23a are made of a resin such as a PC / AS material (a composite material of polycarbonate and acrylonitrile / styrene), and specifically, the outer diameter thereof is, for example, 5.985 ± 0.010 [mm]. ]. The rotating shafts 22a and 23a may be formed using a metal such as iron or aluminum. Specifically, the inner diameter and the outer diameter (d2) of the inner ring 24a of the ball bearing 24 are, for example, 6.04 ± 0.004 [mm] and 7.1 ± 0.1 [mm], respectively. The diameter (d1) of the portion with the smallest diameter of the through hole 27b is specifically, for example, 6.5 ± 0.2 [mm].

  Furthermore, in the present embodiment, each bearing holding portion 27 that holds the ball bearing 24 is detachably fitted in each opening 21 w that passes through each side surface 21 x of the housing 21. Therefore, when the first toner conveying screw 22 and the second toner conveying screw 23 are assembled to the housing 21, the ball bearings 24 attached to the respective ends of the rotating shaft 22 a or 23 a are held by the bearing holding portions 27. In this state, each bearing holding portion 27 may be mounted in each opening 21 w provided on each side surface 21 x of the housing 21. Thus, the first toner conveying screw 22 and the second toner conveying screw 23 can be easily assembled to the housing 21.

Further, the diameter of the opening 21w shown in FIG. 5 is larger than that of the opening 21w shown in FIG. In other words, in FIG. 3, the opening portion into which the bearing holding portion 27 that supports the left end portion (the portion surrounded by the circle F) of the first toner conveyance screw 22 and the second toner conveyance screw 23 is fitted. The diameter of the opening 21w into which the bearing holding part 27 that supports the end on the right side of the paper (the part surrounded by the circle G) is fitted is larger than the diameter of 21w. The diameter of the opening 21w on the right side of the paper surface is set larger than the ridge lines (outer peripheral portions) of the conveying blades 22b and 23b of the first toner conveying screw 22 and the second toner conveying screw 23, respectively. The first toner conveying screw 22 and the second toner conveying screw 23 can be easily inserted into the housing 21 from the opening 21w on the right side of the paper, and the assembling work is simplified.
<Configuration of particle holding unit>
FIG. 6A schematically shows a configuration of a portion (corresponding to a portion surrounded by a circle H in FIG. 4) in which the rotation shaft is held by a ball bearing and a bearing holding portion similar to the rotation shaft support mechanism 21A. It is an expanded sectional view shown. FIG. 6B is an enlarged view of a portion surrounded by a circle K in FIG.

FIGS. 7A and 7B are the same as FIGS. 6A and 6B, respectively, but the size d3 of the gap between the rotating shaft 23a and the inner ring 24a is larger than that in FIG. Is set. FIG. 7B is an enlarged view of a portion surrounded by a circle J in FIG. 6 and 7, the right side of the drawing is the inside of the housing 21, and the left side of the drawing is the outside of the housing 21.
In FIG. 6B and FIG. 7B, the illustration of the toner 62 is omitted.

  In addition, a spherical carrier is used as the carrier particle 61. This is because a carrier closer to a sphere has higher fluidity as a developer and better development characteristics can be obtained, so that generally a spheronization process is performed in the carrier manufacturing process. As a method for spheroidizing the carrier, for example, a liquid crystal polymer is used as a binder resin (binder resin), and the binder resin and magnetic substance (for example, iron) fine particles are mixed in a desired quantity ratio. Alternatively, kneading is carried out at an appropriate temperature using a heating / melting mixing apparatus such as an extruder, and the magnetic fine particles are oriented mechanically, magnetically or in combination during injection molding, and the kneaded product is cooled and then pulverized. JP-A-7-175270 discloses a method in which particles obtained after classification are collided with a plate at high speed, and the surface is thermally melted with the energy to perform spheroidization. For details, see the above-mentioned patent document.

  The developer accommodated in the housing 21 is conveyed so as to circulate in the housing 21 by the first conveying screw 22 and the second conveying screw 23. Here, in the portion surrounded by the circle F in FIG. 3, the developer flows from the lower portion of the housing 21 where the first toner conveying screw 22 is provided to the second developer passage hole 21n provided in the partition wall 21b. As shown by an arrow D3 in the figure, the toner is transported to the upper portion of the housing 21 where the second toner transport screw 23 is provided, and further from there to the direction of the arrow D4 by the second toner transport screw 23. Be transported. However, at this time, in the vicinity of the end of the second toner conveying screw 23 on the upstream side in the developer conveying direction (left side in FIG. 3), a part of the developer is caused by the conveying blade 23b of the second toner conveying screw 23. A force that is not conveyed in the direction of the arrow D4 but is pushed in the direction opposite to the arrow D4, that is, the direction toward the outside of the housing 21 due to the pressure of the developer conveyed from the lower part of the housing to the upper part is also received. Then, a part of the developer is carried in the direction opposite to the arrow D4, and as shown in FIGS. 6 (a) and 6 (b) and FIGS. The ball bearing 24 is pressed against the side surface of the inner ring 24a on the inner side of the housing 21 (the right side of the drawing in both figures).

At this time, as shown in FIGS. 6B and 7B, the size d3 of the gap between the rotating shaft 23a and the inner ring 24a is smaller than the diameter d5 of the carrier particles 61. , It does not leak out of the housing 21 through the gap.
Here, conventionally, in order to facilitate the assembly of the rotating shaft 23a and the inner ring 24a, a slight gap is provided between the rotating shaft 23a and the inner ring 24a. However, the toner leaks from the gap. In order to minimize the gap, the size d3 of the gap is set to be as small as possible within a range that does not impair the ease of assembly, as shown in FIG. In the figure, the size d3 of the gap is not more than the radius d4 of the carrier particles 61.

However, even in this case, the size of the gap has to be larger than the average particle size of the toner.
Although not shown, there are a plurality of other carrier particles carried together, which are pressed against the periphery of the carrier particles 61 pressed against the inner side surface of the inner ring 24a on the housing 21 side. Thus, the carrier particles 61 are merely brought into contact with the side surface by receiving a pressing force backing up in the direction of pressing against the side surface of the inner ring 24a from the inside of the housing. Accordingly, when the rotation of the rotating shaft 23a or the flow of new developer changes, the arrangement of the surrounding carrier particles changes, and the backup pressing force from these other carrier particles no longer acts or weakens. The pressed carrier particles 61 are easily separated from the side surface of the inner ring 24a. Then, the toner flows into the toner and leaks out of the housing through the gap unless a seal member that seals the gap between the rotating shaft 23a and the inner ring 24a is used.

Therefore, in the present invention, as shown in FIG. 7B, the size d3 of the gap between the rotating shaft 23a and the inner ring 24a is set larger than that in FIG. 6B. In FIG. 7B, d3 is larger than the radius d4 of the carrier particle 61 and smaller than the diameter d5.
If it does in this way, as shown to the figure, when the carrier particle 61 is pressed between the rotating shaft 23a and the inner ring | wheel 24a, it can be pinched | interposed into the said clearance gap, and, thereby, is hold | maintained at the said clearance gap. At this time, the particle holding portion 70 is configured by the portion (first portion) in contact with the carrier particles 61 of the rotating shaft 23a and the portion (second portion) in contact with the carrier particles 61 of the inner ring 24a. The

At this time, since the rotation shaft 23 a is made of a softer resin than the carrier particles 61, the surface of the rotation shaft 23 a is pressed by the carrier particles 61 when the carrier particles 61 are held by the particle holding unit 70. A concave portion is formed in the shape of the carrier particles 61, and the carrier particles 61 may be more easily held.
Then, the carrier particles 61 are stably held by the particle holding unit 70 by the carrier particles 61 being sandwiched between the gaps, and even if backup pressing force from surrounding carrier particles (not shown) does not act, the carrier particles 61 61 becomes difficult to detach easily from the gap.

Similarly, the carrier particles 61 are held in an annular shape in the gap over the entire circumferential surface of the rotating shaft 23a, and the gap is roughly blocked by the carrier particles 61 in the circumferential direction.
At this time, since the carrier particles 61 are charged with a polarity opposite to that of the toner 62, the toner existing around the carrier particles 61 is electrostatically applied to the surface of the carrier particles 61 as shown in FIG. It is attached by force. Therefore, the gap between the carrier particles 61 held in the circumferential direction of the rotating shaft 23a by the particle holding unit 70 is filled with the electrostatically adhered toner 62, and the seal is completed.

  Further, as shown in the figure, the diameter of the through hole 27b provided in the side wall portion 27a of the bearing holding portion 27 becomes smaller toward the outside of the housing 21, that is, the through hole toward the outside of the housing 21. The taper shape is such that the distance between the peripheral surface of 27b and the rotation shaft 23a is short. The tapered shape works like a funnel, and the developer carrier accommodated in the housing 21 is guided to the gap between the rotating shaft 23 a and the inner ring 24 a and is easily held by the particle holding unit 70. effective. Specifically, the taper angle (the angle formed by the peripheral surface of the through hole 27b and the rotation shaft 23a) is, for example, 15 degrees. In addition, the average particle diameter of the carrier that is generally widely used is, for example, about 0.030 to 0.060 [mm]. Here, the average particle diameter (diameter) of the carrier particles 61 is specific. For example, it is about 0.033 [mm]. The average particle diameter of the toner is, for example, 0.005 to 0.010 [mm]. The values of the average particle diameter of the carrier particles 61 and the average particle diameter of the toner are values obtained by observing the carrier particles 61 and the toner with an electron microscope, measuring these particle diameters, and obtaining the average value for each. is there.

The method for measuring the average particle diameter of the carrier particles and the toner is not limited to the measurement using an electron microscope, and for example, a measurement method such as a Coulter counter method or a laser diffraction / scattering method may be used. In this case, a value of an average particle diameter different from the measurement by the electron microscope may be obtained.
Note that, as described above, the particle size of the carrier particles 61 is, for example, about 0.033 [mm], which is a very small size. Therefore, the first part and the second part are different from each other. Can be considered substantially opposite each other.
<Retention stability of carrier particles>
As shown in FIGS. 6 and 7, when the carrier particles 61 are in contact with the rotation shaft 23 a and the inner ring 24 a, or are sandwiched in a gap between them, this state is that the carrier particles 61 and the inner ring 24 a. Where P is the contact point between the carrier particle 61 and R is the contact point between the carrier particle 61 and the rotating shaft 23a, and the carrier particle 61 is sandwiched by virtual planes S1 and S2 that are in contact with the carrier particle 61 at point P and point R, respectively (here Then, “the state of being sandwiched” includes a state of simply being in contact.)

Here, when the center point of the carrier particle 61 is Q, a cross-sectional view of a plane passing through the three points P, Q, and R in a state where the carrier particle 61 is sandwiched between the virtual planes S1 and S2 is shown in FIG. . 8A shows a case where the angle PQR is an obtuse angle, FIG. 8B shows a case where the angle PQR is a right angle, and FIG. 8C shows a case where the angle PQR is an acute angle.
The angle PRQ here means the smaller one of the two corners formed by the line segment connecting the point P and the point Q and the line segment connecting the point Q and the point R.

  As shown in FIG. 8A, when the angle PQR is an obtuse angle, when the carrier particles 61 are sandwiched between the virtual planes S1 and S2 as shown in FIG. The reaction force F1 is received from S1, and the reaction force F2 is received from the virtual plane S2 at the point R. At this time, the reaction force F1 can be decomposed into component forces F1a and F1b. The carrier particles 61 receive a force in the direction in which the carrier particles 61 are pressed against the virtual plane S2 by the component force F1b. The reaction force F2 can be decomposed into component forces F2a and F2b. The carrier particles 61 receive a force in the direction in which the carrier particles 61 are pressed against the virtual plane S1 by the component force F2b. Thus, when the angle PQR is an obtuse angle, the component force of the reaction force received from the virtual planes S1 and S2 acts in the direction of pressing the carrier particles 61 against the other virtual plane, and the carrier particles 61 and the virtual plane S1. Since the contact with S2 reinforces each other, the holding stability of the carrier particles 61 by the particle holding portion 70 is increased.

  On the other hand, as shown in FIG. 8B, when the angle PQR is a right angle, the virtual planes S1 and S2 cross each other at a right angle, so that the reaction forces F3 and F4 received by the carrier particles 61 from the respective virtual planes. , There is no component force in the direction in which the carrier particles are pressed against each other, and the carrier particles 61 are simply in contact with the virtual planes S1 and S2, and therefore are stably held by the particle holding unit 70. I can't say that.

  Further, as shown in FIG. 8C, when the angle PQR is an acute angle, the component forces F5b and F6b of the reaction forces F5 and F6 that the carrier particles 61 receive from the virtual planes S1 and S2, respectively, are the virtual plane S2, It acts in the direction away from S1. Therefore, the component force acts in a direction that weakens the contact between the carrier particle 61 and the virtual planes S1 and S2, and as a result, the holding stability of the carrier particle 61 by the particle holding unit 70 is the angle PQR shown in FIG. Will be further reduced than when the angle is right.

  When the virtual planes S1 and S2 and the angle PQR are applied to FIGS. 6B and 7B, the angle PQR is a right angle in the state shown in FIG. Although the carrier particles 61 are not stably held by the particle holding unit 70, in the state shown in FIG. 7B, the angle PQR is an obtuse angle, and the carrier particles 61 are stably held by the particle holding unit 70.

Thus, by increasing the size d3 of the gap between the rotating shaft 23a and the inner ring 24a so as not to be larger than the diameter d5 of the carrier particles 61, the carrier particles 61 are more stably held in the gap. be able to.
The angle PQR is a value smaller than 180 degrees. This is because the angle PQR is 180 degrees when the size d3 of the gap between the rotating shaft 23a and the inner ring 24a is equal to the particle diameter (diameter) d5 of the carrier particles 61. The particles 61 leak out of the housing through the gap.

Here, FIG. 6 and FIG. 7 are diagrams schematically showing the configuration of the rotating shaft support mechanism 21A, and the edge on the inner peripheral surface side of the inner ring 24a is represented as a substantially right-angled shape. However, the edge of the actual inner ring 24a is often rounded or chamfered.
9 (a) and 9 (b) are views similar to FIGS. 7 (a) and 7 (b), respectively, but in each drawing of FIG. 9, the edge on the inner peripheral surface side of the inner ring 24a is rounded. Is given. Also in this case, as shown in FIG. 9B, the angle PQR is an obtuse angle, and the carrier particles 61 are stably held by the particle holding unit 70 by being sandwiched in the gap between the rotating shaft 23a and the inner ring 24a. Retained.

As shown in the figure, when the edge on the inner peripheral surface side of the inner ring 24a is rounded or chamfered, the rotation shaft 23a and the inner ring 24a and p between Even if the size of the gap is smaller than the state shown in the figure, the carrier particles 61 may be stably held by the particle holding portion.
<Toner leakage prevention by carrier particles>
As described above, in the developing device of the present invention, the carrier particles 61 are held in the gap between the inner ring 24a of the ball bearing 24 and the rotating shaft 23a. And this is repeated and the carrier particle 61 is hold | maintained cyclically | annularly by the said clearance gap over the perimeter of the surrounding surface of the rotating shaft 23a, and the said clearance gap is roughly obstruct | occluded by the carrier particle. As the developer is transported inside the housing 21, more carrier particles 61 are conveyed so as to be pressed against the annular carrier particle layer, and the carrier particle annular layer housing 21. An annular layer of further carrier particles is formed on the inside so as to overlap several times.

  The toner 62 flows into the gap between the carrier particles 61 in the annular layer of the carrier particles formed in this way and the gap between the carrier particles 61 and the inner ring 24a and the rotating shaft 23a. Since the toner 62 adheres to the surface of the carrier particles 61 by electrostatic force, the toner 62 does not leak through the gaps to the outside of the housing 21, but rather functions to fill these gaps and improve the sealing performance. To do.

  6, 7, and 9, the carrier particles 61 that are held by the particle holding unit 70 (the carrier particles 61 that are in contact with the inner ring 24 a in FIG. 6) are also disposed inside the housing 21. Although the developer (carrier particles 61 and toner 62) exists, the illustration is omitted except for the carrier particles 61 held by the particle holding unit 70 and the toner 62 adhering to the surface of the carrier particles 61. ing. Also in FIG. 9B, the illustration of the toner is omitted as in FIGS. 6B and 7B.

Further, in FIG. 9, the edge of the outer peripheral surface side end portion of the inner ring 24 a and the edge of the inner peripheral surface side end portion of the outer ring 24 b are not subjected to round edge processing. It may be given. Furthermore, it is not limited to round edge processing, and chamfering processing may be used. Hereinafter, the same applies to each modification.
Here, in the above description, the rotating shaft support mechanism 21A at the end of the second toner conveying screw 23 on the side shown in FIG. 4 has been described, but the present invention is not limited to this, and the side of the second toner conveying screw 23 shown in FIG. The same applies to the rotating shaft support mechanism 21A at the end of each of the first and second rotating shaft support mechanisms 21A at both ends of the first toner conveying screw 22. Hereinafter, the same applies to each modification.

In the above description, the rotation shafts 22a and 23a of the first toner conveyance screw 22 and the second toner conveyance screw 23 have been described so as to be rotatably supported with respect to the housing 21 by the rotation shaft support mechanism 21A. However, the rotation shaft of the developing sleeve in the developing roller 25 may be supported so as to be rotatable with respect to the housing 21 by the rotation shaft support mechanism 21A having the same configuration. It is possible to prevent the toner contained in the housing 21 from leaking out of the housing 21 through the gap between the rotation shaft of the developing sleeve and the inner ring 24a of the ball bearing 24. In this case, the rotating member also includes a developing sleeve.
<Summary>
2. Description of the Related Art Conventionally, in a developing device, when a toner conveying screw for conveying a developer is assembled to a housing of the developing device, a rotating shaft that is rotatably held by a ball bearing and an inner ring of the ball bearing in order to facilitate assembly. A slight gap is provided between the two. The size of the gap is inevitably larger than the average flow diameter of the toner. However, in order to minimize the leakage of toner from the gap, the ease of assembly is not impaired. The gap was set to be as small as possible within the range. Therefore, since the carrier particles are not stably held in the gap, the gap cannot be blocked by the carrier particles, and in order to prevent toner leakage, a seal member for closing the gap must be used separately. There wasn't.

However, in the developing device of the present invention, by intentionally expanding the gap, carrier particles can be stably held in the gap, thereby preventing toner leakage. Thereby, waste of the toner in the housing 21 can be suppressed, and the economy can be improved. Further, since the leakage of the toner can be prevented without using a separate sealing member such as a magnet seal or an elastic member, the economy can be further improved. In addition, since a problem such as wear of the seal member does not occur unlike when a separate seal member is used, toner leakage can be stably prevented over a long period of time. Thereby, there is no possibility that the periphery of the developing device in the image forming unit A of the printer is contaminated by the toner leaking from the developing device. Therefore, the image formed in the image forming unit A is not contaminated by the toner. A high-quality image can be obtained stably over a long period of time.
<Modification>
As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above-described embodiment, and the following modifications can be considered.

  (1) The surface roughness of the surface of the rotating shaft 23a facing the inner ring 24a may be rougher than the surface roughness of the processing accuracy on the rotating shaft of the toner conveying screw of a general developing device. For example, as shown in FIG. 10, on the outer peripheral surface of the portion of the rotating shaft 23a facing the inner ring 24a, the surface roughness of the processing accuracy on the rotating shaft of the toner conveying screw of a general developing device is applied over the entire circumference in the circumferential direction. Also, a rough surface portion 23c may be provided. In this case, at the beginning of use of the developing device 20, since a slight gap is provided between the rotating shaft 23a and the inner ring 24a, the rotating shaft 23a is slightly shaken in the inner ring 24a when rotating. The size of the gap rotates slightly, and when the gap widens due to this fluctuation, the carrier particles 61 enter the gap, and when the gap narrows, as shown in FIG. The carrier particles 61 are held in such a manner as to be fitted therein.

As the developing device 20 is used, the carrier particles 61 are held one after another as described above, and when the carrier particles 61 are held over the entire circumference in the circumferential direction of the rotating shaft 23a, the size of the gap varies. Is fixed and has a substantially uniform size over the entire circumference of the rotating shaft 23a.
Specifically, the surface roughness of the rough surface portion 23c is preferably, for example, Rmax of 6.3 s or more and 25 s or less.

  Further, the rough surface portion 23c may be provided over the entire area in the axial direction of the rotating shaft 23a of the portion facing the inner ring 24a of the rotating shaft 23a, and as shown in FIG. It may be provided only in the part. Moreover, it is preferable that the outer peripheral surface of the rotating shaft 23a is continuously provided in a ring shape over the entire circumference in the circumferential direction. By providing continuously, it is possible to prevent the toner from leaking from the portion where the ring is interrupted.

The rough surface portion 23c may be formed, for example, by forming scratches or grooves on the outer peripheral surface of the rotating shaft 23a, or by forming the rotating shaft 23a by forming grooves in a mold in advance. However, the method for forming the rough surface portion 23c is not limited to this, and any other suitable method may be used.
When the rotary shaft 23a is made of resin, even if the outer peripheral surface of the rotary shaft 23a is a smooth surface (Rmax is smaller than 6.3 s) at the beginning of use of the developing device 20, the rotary shaft 23a is used. Accordingly, when the carrier particles 61 are held as described above, the outer peripheral surface of the rotating shaft 23a is pressed down by the carrier particles 61 to form concave portions in the shape of the carrier particles 61, and the locations where the concave portions are formed are the result. In some cases, the same function as the rough surface portion 23c may be performed.

(2) As shown in FIG. 11, a groove 23d may be provided on the outer peripheral surface of the rotating shaft 23a over the entire circumference in the circumferential direction. By adopting a configuration in which the carrier particles 61 are accumulated in the groove 23d, the carrier particles 61 are more easily held in the particle holding unit 70.
Moreover, it is preferable that the groove part 23d is provided in the housing 21 inner side rather than including the particle | grain holding | maintenance part 70 on the outer peripheral surface of the rotating shaft 23a, or adjoining it. Accordingly, the plurality of carrier particles 61 accumulated in the groove 23d are supported from the inside of the housing 21 so as to back up the carrier particles 61 held in the particle holding unit 70, and the carrier particles 61 are more stably supported by the particle holding unit. 70 is effective.

Specifically, the depth and width of the groove 23d are desirably 0.5 to 1 [mm] in depth and 0.5 to 1 [mm] in width.
In the figure, the illustration of the toner 62 is omitted. Hereinafter, the same applies to FIGS. 12 to 18.
(3) In the above-described embodiment, the example in which the end portion on the inner side of the housing 21 of the inner ring 24a of the ball bearing 24 constitutes the particle holding unit 70 has been described. For example, as shown in FIG. 12A, a protrusion 23e is provided over the entire circumference in the circumferential direction at any position in the axial direction of the rotation shaft 23a of the portion of the inner ring 24a facing the rotation shaft 23a. The protrusion 23e may constitute the particle holding unit 70. In this case, if the size of the narrowest part of the gap between the protrusion 23e and the inner ring 24a is smaller than the diameter of the carrier particle 61, the carrier particle 61 is held by the part, so the protrusion of the rotating shaft 23a The size of the gap between the portion other than the portion 23 e and the inner ring 24 a may be larger than the diameter of the carrier particle 61.

  Further, as shown in FIG. 12B, the protrusion may be provided as a protrusion 24d on the inner ring 24a side instead of being provided on the rotating shaft 23a side. In this case as well, if the size of the narrowest part of the gap between the protrusion 24d and the rotating shaft 23a is smaller than the diameter of the carrier particle 61, the carrier particle 61 is held by that part. The size of the gap between the portion of the inner ring 24 a other than the protrusion 24 d and the rotating shaft 23 a may be larger than the diameter of the carrier particle 61.

  (4) In the above-described embodiment and modifications, when the developer is transported inside the housing 21, a part of the developer is transported in the vicinity of the end of the second toner transport screw 23. The screw 23 is pushed out in the direction opposite to the conveying direction and is carried in the direction of the rotating shaft support mechanism 21A, and is held in the gap between the rotating shaft 23a and the inner ring 24a. Absent.

  For example, when assembling the second toner conveying screw 23 to the housing 21, the carrier particles 61 may be preliminarily sprinkled on the surface of the portion of the rotating shaft 23 a facing the inner ring 24 a and attached by electrostatic force. Alternatively, the carrier particles 61 may be dispersed in a volatile solvent or the like and applied to the surface of the portion facing the inner ring 24a of the rotating shaft 23a, and the assembly may be performed after the solvent is volatilized.

  In this case, since the rotating shaft 23a is made of a resin such as a PC / AS material that is softer than the carrier particles 61, when the second toner conveying screw 23 is assembled to the housing 21, as shown in FIG. The surface of the rotating shaft 23a to which the carrier particles 61 are attached is pressed down by the carrier particles 61 to form concave portions in the shape of the carrier particles 61, and the carrier particles 61 are more easily held stably.

  As described above, when the carrier particles 61 are attached to the surface of the rotating shaft 23a in advance during assembly, the carrier particles 61 for sealing held in the gap between the rotating shaft 23a and the inner ring 24a are: Since it rotates integrally with the rotary shaft 23a and the inner ring 24a while being held, it does not flow out into the housing and mix with the developer. Therefore, in this case, the sealing particles (seal particles) are not limited to the carrier particles 61, and other seal particles 63 having a particle diameter larger than the average particle diameter of the toner may be used.

  Here, it is possible to prevent leakage of toner and carrier even if the particle size of the seal particles 63 is larger than the average particle size of the carrier particles 61. However, if the particle size is too large, the gap between the seal particles 63 and the seal particles 63 may be prevented. And the clearance between the rotary shaft 23a and the clearance between the seal particles 63 and the inner ring 24a are increased, and the sealing performance is deteriorated. Therefore, it is desirable that the particle size of the seal particles 63 is approximately the same as that of the carrier particles 61.

  The seal particle 63 is made of, for example, a metal such as iron or a resin. When a resin is used for the seal particles 63, the rotating shaft 23a is preferably made of resin instead of metal, and more preferably a resin having a lower hardness than the resin used for the seal particles 63. In this case, when the second toner conveying screw 23 is assembled to the housing 21, the surface of the rotating shaft 23 a is pressed by the seal particles 63 to form recesses in the shape of the seal particles 63, and the seal particles are formed in the recesses. By fitting 63, the seal particles 63 are more easily held stably.

  When the rotating shaft 23a is made of metal, as shown in the figure, the outer peripheral surface of the portion facing the inner ring 24a may be provided with a resin surface portion 23f made of resin over the entire circumference in the circumferential direction. . As resin which comprises the said resin surface part 23f, a PC / AS material etc. are used, for example, and may be formed in the outer peripheral surface of the rotating shaft 23a by insert molding. Accordingly, since the resin surface portion 23f is made of a softer material than the seal particles 63, as described above, when the second toner conveying screw 23 is assembled to the housing 21, the resin surface portion 23f becomes the seal particles. It is pressed down by 63 and a recessed part is formed in the shape of the seal particle 63, and the seal particle 63 is more easily held.

Further, as the material of the seal particle 63, for example, a material having a property of being charged to a polarity (usually plus) opposite to that of toner such as iron is desirable. In this case, the toner adheres to the surface of the seal particles and functions to further improve the sealing performance.
Here, when the seal particles are dispersed in a volatile solvent or the like and applied to the surface of the portion facing the inner ring 24a of the rotating shaft 23a, when the resin is used for the seal particles 63, the resin that does not melt into the solvent to be dispersed. And a combination of solvents must be selected.

Note that when the seal particles 63 are used instead of the carrier, the present invention can be applied not only to a developing device using a two-component developer but also to a developing device using a one-component developer.
(5) In the above embodiment, the configuration in which the cylindrical bearing holding portion 27 is detachably fitted to the opening portion 21w provided on the side surface 21x of the housing 21 has been described. However, the present invention is not limited to this, and the bearing holding portion may be configured integrally with the housing 21 as shown in FIG.

  In the present modification, the cylindrical bearing holding portion 27 is formed integrally with the housing 21, and the side wall portion 27 a of the bearing holding portion 27 constitutes the side surface of the housing 21. The through hole 27 b provided in the side wall 27 a of the bearing holding part 27 is provided coaxially with the bearing holding part 27. Inside the bearing holding portion 27, a ball bearing 24 that rotatably holds the end portion of the rotating shaft 22a is mounted. And the inner ring | wheel 24a and the side wall part 27a of the bearing holding | maintenance part 27 are contacting over the perimeter. Other configurations are the same as those in the above embodiment.

Also in this case, the inner ring 24a and the side wall portion 27a are in close contact with each other to such an extent that toner does not leak from each other, but the rotation of the inner ring 24a is not hindered.
The rotating shaft 22a of the first toner conveying screw 22 and the rotating shaft of the developing sleeve in the developing roller 25 are also rotatably supported by the housing 21 by the rotating shaft support mechanism 21A having the same configuration.

Even with such a configuration, it is possible to reliably prevent the toner in the housing 21 from leaking to the outside.
(6) Further, instead of the configuration in which the side wall portion 27a facing the inner ring 24a of the ball bearing 24 and the inner ring 24a are pressed against each other, the side wall portion facing the inner ring 24a of the ball bearing 24 as shown in FIG. It is good also as a structure which provides the ring-shaped side surface sealing member 24e which seals the peripheral part of the through-hole 27b over the perimeter between 27a and the inner ring | wheel 24a. The side seal member 24e is formed in a flat plate shape by an elastic body such as urethane foam or malt plain in order to make sliding contact with the inner ring 24a of the ball bearing 24.

Even with such a configuration, it is possible to more reliably prevent the toner from flowing out to the outer peripheral side of the inner ring 24a through the space between the inner ring 24a and the side wall portion 27a.
In the figure, an example in which the configuration of this modification is applied to the configuration of the modification 5 shown in FIG. 14 in which the bearing holding portion 27 is formed integrally with the housing 21 is shown. This configuration may be applied to the configuration of the embodiment in which the bearing holding portion 27 is detachably provided to the housing 21. Hereinafter, the same applies to FIGS. 16 to 18.

  (7) Moreover, as shown in FIG. 16, it is good also as a structure which seals between the inner ring | wheel 24a and the outer ring | wheel 24b of the ball bearing 24 with the fluid sealing material 24f. In this case, in order to prevent the fluid sealing material 24f from flowing out between the inner ring 24a and the outer ring 24b, flat shields are provided on both sides of the ball 24c between the inner ring 24a and the outer ring 24b. Each member 24g may be provided. As the fluid sealant 24f, for example, a lubricant such as grease can be used. When a highly viscous gel lubricant is used as the fluid sealing material 24f, the fluid sealing material 24f is not likely to flow out between the inner ring 24a and the outer ring 24b, and therefore the shield member 24g is omitted. be able to.

With such a configuration, even when toner flows out between the inner ring 24a of the ball bearing 24 and the side wall 27a of the bearing holding portion 27, the toner leaks to the outside through the space between the inner ring 24a and the outer ring 24b. Can be prevented.
(8) Further, as shown in FIG. 17, a flat bearing seal member 24h is provided that seals the side of the ball bearing 24 that faces the side wall 27a between the inner ring 24a and the outer ring 24b over the entire circumference. It is good.

The bearing seal member 24h is formed of, for example, an elastic body such as urethane rubber, metal, or the like, and the entire portion adjacent to the side wall portion 27a of the bearing holding portion 27 on the mutually opposing surfaces of the inner ring 24a and the outer ring 24b. It covers all around.
Such a configuration can also prevent the toner from leaking from between the inner ring 24a and the outer ring 24b of the ball bearing 24.

  (9) Furthermore, as shown in FIG. 18, a bearing seal member 24h that seals between the inner ring 24a and the outer ring 24b, and a second seal that seals between the side wall 27a facing the inner ring 24a and the inner ring 24a. It is good also as a structure which provides the part 24i. In this case, there is no need to press the side wall portion 27a facing the inner ring 24a and the inner ring 24a together, and the tip of the second seal portion 24i is abutted against the side wall portion 27a. Thereby, between the side wall part 27a and the inner ring | wheel 24a which opposes the inner ring | wheel 24a can be sealed by the 2nd seal | sticker part 24i. In this case, the bearing seal member 24h is formed of an elastic body such as urethane rubber.

  (10) Although the carrier particles 61 are made of iron in the above embodiment and each modification (except for the case where the carrier particles 61 are made of resin in the modification 4), the present invention is not limited to this. As the material of the carrier particles 61, any metal other than iron may be used. However, in this case, a metal having a property of being charged with a polarity opposite to that of the toner is desirable. Further, it is desirable to use a metal whose hardness is higher than that of the toner. This is because if the carrier particle hardness is too low, the carrier particle is deformed by the pressure received from the surrounding toner and other carrier particles when the developer is conveyed, and as a result, the rotation shaft and the inner ring of the ball bearing This is because there is a risk of leaking out of the housing through the gap between them.

(11) Specific numerical values in the above-described embodiment and modifications are given as an example, and of course are not limited thereto.
(12) In the above embodiment and each modified example, the example using the ball bearing 24 as the rolling bearing portion has been described, but the present invention is not limited to this. For example, a roller bearing such as a cylindrical roller, a conical roller, a self-aligning roller, or a roller bearing may be used.

(13) The rotating shaft support mechanism in the present invention can be applied to at least one rotating shaft provided in the developing device.
(14) The image forming apparatus according to the present invention is not limited to a tandem color digital printer, but may be a printer that forms a monochrome image, and is not limited to a printer, and can form a color or monochrome image. The present invention can also be applied to a copying machine, FAX, MFP (Multiple Function Peripheral), and the like.

  Further, the contents of the above embodiments and the above modifications may be combined.

  The present invention is useful as a technique for preventing leakage of toner from a developing device in a developing device that develops an electrostatic latent image formed on the outer peripheral surface of a photosensitive drum.

A Image forming unit B Paper feeding unit 10Y, 10M, 10C, 10K Process unit 11 Photosensitive drum 12 Charging device 13Y, 13M, 13C, 13K Exposure device 20 Developing device 21 Housing 21A Rotating shaft support mechanism 21x Side surface 22 First toner transport Screw 22a Rotating shaft 22b Conveying blade 23 Second toner conveying screw 23a Rotating shaft 23b Conveying blade 23e, 24d Protrusion 23f Resin surface 24 Ball bearing 24a Inner ring 24b Outer ring 24c Ball 24e Side seal member 24f Fluid sealant 24g Shield member 24h Bearing seal member 24i Second seal portion 25 Developing roller 27 Bearing holding portion 27a Side wall portion 27b Through hole 61 Carrier particle 62 Toner 63 Seal particle 70 Particle holding portion

Claims (20)

A rotating member that has a rotating shaft, and moves the toner contained in the housing by rotation of the rotating shaft; and a rolling bearing portion that rotatably holds the rotating shaft with respect to the housing, A developing device for developing an electrostatic latent image formed on an outer peripheral surface of a photoreceptor using toner,
The first part in the part of the rotating shaft facing the rolling bearing part and the second part corresponding to the first part of the inner ring of the rolling bearing part are all around the circumference of the rotating shaft. A developing device comprising: a particle holding unit configured to hold seal particles having an average particle size larger than the average particle size of the toner in a gap therebetween. In a state where the seal particles are held in the particle holding portion, the contact between the seal particles and the second part is P, the center point of the seal particles is Q, and the contact between the seal particles and the first part. The developing device according to claim 1, wherein the angle PQR is an obtuse angle, where R is R. 3. The developing device according to claim 1, wherein a size of the gap in a radial direction of the rotation shaft is smaller than an average particle size of the seal particles and larger than a half of the average particle size. The developing device according to claim 1, wherein the seal particles have a property of being charged to a polarity opposite to that of the toner. The developing device according to claim 1, wherein the seal particles are made of metal. The developing device according to claim 5, wherein the metal is iron. The housing contains a two-component developer containing toner and a carrier therein,
The developing device according to claim 1, wherein the seal particles are the carrier. 8. The developing device according to claim 1, wherein the rotation shaft has a surface roughness Rmax of an outer peripheral surface of the particle holding portion of 6.3 s or more and 25 s or less. 9. The groove according to claim 1, wherein the rotation shaft is provided with a groove over the entire circumference along a circumferential direction on an outer peripheral surface of the housing including the particle holding portion. Development device. The developing device according to claim 1, wherein at least the outer peripheral surface of the particle holding unit is formed of a resin. The rolling bearing portion is held on a side surface of the housing via a bearing holding portion,
The rotating shaft passes through a through hole provided in the bearing holding portion,
The diameter of the through hole decreases toward the outside of the housing,
11. The developing device according to claim 1, wherein an outer diameter of the inner ring of the rolling bearing portion is larger than a minimum value of the diameter of the through hole. The developing device according to claim 11, wherein the bearing holding portion is detachable from a side surface of the housing. The developing device according to claim 11, wherein the bearing holding portion is integrally formed on a side surface of the housing. The inner ring housing has an inner end surface that is in contact with the peripheral edge of the through hole in the bearing holding portion over the entire circumference, thereby sealing between the inner ring and the peripheral edge. The developing device according to any one of claims 11 to 13. The side seal member which seals between the inner ring | wheel of the said rolling bearing part and the peripheral part of the said through-hole in the said bearing holding | maintenance part over the perimeter is provided. The developing device according to any one of the above. The developing device according to claim 11, wherein a fluid sealing material is filled between an inner ring and an outer ring of the rolling bearing portion. The rolling bearing portion has a bearing seal member that seals a side portion facing the peripheral edge portion of the through hole between the inner ring and the outer ring over the entire circumference. The developing device according to item. The developing device according to claim 17, wherein the bearing seal member seals between an inner ring of the rolling bearing portion and the peripheral portion over the entire circumference. A process unit comprising the developing device according to claim 1. An image forming apparatus comprising the process unit according to claim 19.

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