JP2011128403A - Developing device, process unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably prevent toner from being leaked out from space, between a rotary shaft and an inner ring of a ball bearing, over a long term. <P>SOLUTION: The respective ends of the respective rotary shafts 22a and 23a of a first toner conveying screw 22 and a second toner conveying screw 23 for moving the toner stored in a housing 21 are supported by the ball bearings 24 rotatably relative to a side surface 21x of the housing 21. Groove parts 22c and 23c, in which ring-like rotary shaft seal members 26 are fitted, are provided at the respective ends of the rotary shafts 22a and 23a, and the rotary shaft seal members 26 are respectively brought into press-contact with the inner rings 24a of the respective ball bearings 24. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 supplied from one end of the housing to the other end by the conveying screw, and is attached to the electrostatic latent image on the photosensitive drum by the developing roller. Thereby, the electrostatic latent image on the photosensitive drum is developed with 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, it is between the bearing supporting the end of the rotating shaft of the conveying screw or the developing sleeve and the side surface of the housing, or between the bearing and the rotating shaft. There is a risk of leakage to the outside of the housing.
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 leaking toner, there is a possibility that a high-quality image cannot be formed in the image forming operation. For this reason, it is necessary to seal between the bearing that supports the rotating shaft such as a conveying screw and the side surface of the housing, between the rotating shaft and the bearing, and the like.

  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, Patent Document 2 provides a bearing seal that seals between the side surface of the sliding bearing and the side surface of the opposing housing, and includes a second shaft between the rotating shaft that is rotatably supported by the sliding bearing and the sliding bearing. A configuration in which a two-bearing seal is provided is disclosed. The second bearing seal is pressed against the outer peripheral surface of the rotating shaft by an interference fit with the rotating shaft, thereby sealing between the rotating 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, when the rotating shaft vibrates in the axial direction (thrust direction), the carrier cannot be held, and the toner may not be reliably prevented from flowing to the bearing.

In the configuration disclosed in Patent Document 2, the bearing that rotatably holds the rotation shaft is fixed to the side surface of the housing, and the second bearing seal is fixed to the fixed bearing. ing. Therefore, the rotating shaft supported by the bearing rotates relative to the fixed second bearing seal.
In such a configuration, in the case of a developing device using a two-component developer, the carrier may enter between the second bearing seal and the rotating shaft due to vibration of the rotating shaft in the thrust direction. When the carrier that has entered between the second bearing seal and the rotating shaft slides on the rotating shaft by the second bearing seal, there is a risk of promoting wear and cutting of the rotating shaft. As a result, the sealing performance with the rotating shaft by the second bearing seal is lowered, and the leakage of toner by the second bearing seal cannot be stably prevented over a long period of time.

  In an image forming apparatus in which a developing device is provided in each process unit, there is a demand for downsizing and speeding up the entire apparatus. For this reason, each process unit is also downsized. However, each process unit is shortened because the size and speed of the process unit are reduced, so that deterioration and consumption of members constituting the process unit are promoted. Moreover, in the developing device using the two-component developer, if the sealing performance between the bearing and the rotating shaft is lowered in a relatively short time as described above, the life of the process unit is further shortened.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to reliably prevent toner leakage even when vibrations in the thrust direction and the direction perpendicular to the rotation shaft are applied to the rotation shaft. Another object of the present invention is to provide a developing device capable of stably securing a sealing property between a bearing and a rotating shaft over a long period of time. 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, an image forming apparatus according to the present invention is a developing device that develops an electrostatic latent image formed on the outer peripheral surface of a photoconductor using toner accommodated in a housing, and rotates. A rotating member that moves the toner in the housing by rotation of the rotating shaft, a ball bearing that rotatably holds the rotating shaft with respect to the housing, an inner ring of the ball bearing, and the rotating shaft And a rotary shaft seal member interposed between the two and the rotary shaft seal member.

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.

  In the developing device of the present invention, the space between the rotating shaft and the inner ring of the ball bearing is sealed between the rotating shaft and the inner ring of the ball bearing. The toner can be prevented from leaking out of the housing. Since the rotating shaft and the inner ring of the ball bearing rotate together, it is possible to prevent each from being worn and to prevent a gap from being formed between them. Accordingly, it is possible to stably seal between the two over a long period of time.

  In particular, when a two-component developer having a carrier and toner is used, the carrier can be prevented from entering between the rotating shaft and the inner ring of the ball bearing. In addition, since the rotating shaft and the inner ring rotate together, even if the carrier enters between users, the rotating shaft can be prevented from being worn or cut by the carrier. The sealing performance between the inner ring and the inner ring can be ensured stably over a long period of time.

Preferably, a groove is provided on the outer peripheral surface of the rotating shaft along the circumferential direction, and the rotating shaft seal member is fitted in the groove.
Preferably, a side surface of the housing is provided with a bearing holding portion that holds the ball bearing therein, and the bearing holding portion is detachable from the side surface of the housing.

Preferably, the rotating shaft passes through a through hole provided in the bearing holding portion, and a side surface of the inner ring of the ball bearing is pressed against the peripheral portion of the through hole in the bearing holding portion over the entire circumference. By doing so, the pressure contact portion is sealed.
Preferably, the rotating shaft passes through a through hole provided in the bearing holding portion, and the entire space between the inner ring of the ball bearing and the peripheral edge portion of the through hole in the bearing holding portion is interposed therebetween. A side seal member for sealing over the circumference is provided.

Preferably, a space between the inner ring and the outer ring of the ball bearing is sealed with a fluid sealant.
Preferably, the rotating shaft passes through a through hole provided in the bearing holding portion, and the ball bearing has a side portion opposed to the peripheral portion of the through hole between the inner ring and the outer ring. It is characterized by having a bearing seal material that seals around the circumference.

Preferably, the bearing seal material seals between the inner ring of the ball bearing and the peripheral portion over the entire circumference.
Preferably, the housing contains a carrier together with toner.

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. It is a longitudinal cross-sectional view of the developing device. (A) And (b) is an enlarged view of the part shown by F and G in FIG. 3, respectively. It is the further enlarged view of the part shown in FIG.4 (b). FIG. 10 is a schematic cross-sectional view for explaining the configuration of a rotation shaft support mechanism 21A that supports a rotation shaft 22a of a first toner conveying screw 22 in Embodiment 2 of the present invention. It is sectional drawing which shows typically schematic structure of the modification of the rotating shaft support mechanism in Embodiment 2 of this invention. (A) is sectional drawing which shows typically the schematic structure of the further modification of the rotating shaft support mechanism in Embodiment 2 of this invention, (b) is sectional drawing which shows schematic structure in the modification. It is sectional drawing which shows typically schematic structure of the modification of a rotating shaft support mechanism.

<Embodiment 1>
FIG. 1 is a schematic diagram showing a configuration of a tandem color digital printer (hereinafter simply referred to as “printer”) that 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 which is wound around a pair of belt rotation rollers 42 and 43 in a horizontal state and can move around in a substantially central portion of the printer. 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 that 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 is getting bigger. 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 extends linearly 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 developed 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 cleans the surface of the photosensitive drum 11 on which the toner image has been transferred onto the intermediate transfer belt 41, and a static eliminator 17 that neutralizes the surface of the photosensitive drum 11 cleaned by the cleaning device 16. Is provided. 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 one belt rotation roller 42 disposed in the vicinity of the process unit 10K. A secondary transfer roller 44 is disposed opposite to the belt rotation 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.

  A recording sheet in a paper feeding cassette provided in the paper feeding unit B is conveyed to the transfer nip. 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 depending on 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 other belt rotating roller 43 disposed in the vicinity of the process unit 10Y via the intermediate transfer belt 41. It has come to be.

  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 toner image of the recording sheet that passes through the transfer nip and is conveyed to the fixing unit 50 is fixed on the recording sheet by being heated and pressed while the recording sheet passes through the fixing nip. The recording sheet on which the toner image is fixed in the fixing unit 50 is discharged onto a paper discharge tray 48 provided at the top of the printer with the surface on which the toner image is formed facing downward.
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 10Y, 10M, 10C, and 10K 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.

FIG. 2 is a perspective view of the developing device 20 provided in each of the three process units 10Y, 10M, and 10C, 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 includes a housing 21 that extends long along the axial direction of each photosensitive drum 11. A toner supply port 21 a is provided on the upper surface of one end of the housing 21.

  When each of the process units 10Y, 10M, and 10C is attached to the image forming unit A, it is inserted into the image forming unit A from the end opposite to the end provided with the toner replenishing port 21a. It has become. 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 are spirally formed around the rotating shafts 22a and 23a provided in the shaft center portion and the respective ends of both sides of the rotating shafts 22a and 23a. It has the provided conveyance blades 22b and 23b. 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 rotation 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 10 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.

  As shown in FIGS. 1 and 2, a developing roller 25 disposed opposite to the surface of the photosensitive drum 11 is provided adjacent to the second toner conveying screw 23 in the upper part of the housing 21. . The developing roller 25 includes a magnetic roller fixed to the housing 21 and a developing sleeve fitted to the outside of the magnetic roller, similarly to the developing roller used in a conventional developing device using a two-component developer. Rotating shafts 25a (see FIG. 2) projecting outward along the axial direction are respectively 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 arranged in parallel with the second toner conveying screw 23 as shown in FIG. 2. As shown in FIG. 2, the developing roller 25 is shorter than the first toner conveying screw 22 and the second toner conveying screw 23, and is closer to the central portion in the longitudinal direction than the end close to the toner supply port 21a. One end is located at the bottom.

  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 then passes through 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 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, as shown by an arrow D4 in FIG. The toner and the carrier are transported along 25 axial directions. The toner and 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 fitted to the magnet roller 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.

FIGS. 4A and 4B are enlarged views of portions indicated by F and G in FIG. 3, respectively. FIG. 5 is an enlarged view of the rotating shaft support mechanism 21A shown in FIG.
As shown in FIGS. 4A and 4B, a cylindrical 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 that holds the end portions of the rotating shaft 22a of the first toner conveying screw 22 and the rotating shaft 23a of the second toner conveying screw 23 is held.

  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 22b passes. The side wall 27a is provided. Each through-hole 27b has a slightly larger diameter (indicated by “d1” in FIG. 5) than the outer diameter of the rotary shafts 22a and 22b that pass through each through-hole 27b.

  A ball bearing 24 provided inside each bearing holding portion 27 has a configuration similar to that of a generally used ball bearing, and a circumferential direction 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 in 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 with. The outer diameter d2 (see FIG. 5) of the inner ring 24a is larger than the diameter d1 of the through hole 27b (d2> d1), and the inner ring 24a is pressed against the peripheral edge of the side wall part 27a provided with the through hole 27b. Has been.

  Groove portions 22c and 23c along the circumferential direction are respectively formed on the outer peripheral surfaces of the end portions of the rotating shafts 22a and 23a located in each bearing holding portion 27 over the entire circumference. The groove portions 22c and 23c have a rectangular cross section, and a ring-shaped rotary shaft seal member 26 is fitted in each of the groove portions 22c and 23c. The rotating shaft seal member 26 is made of, for example, urethane rubber having elasticity, and the inner peripheral side portion of the rotating shaft seal member 26 is in pressure contact with the bottom surfaces of the groove portions 22c and 23c, respectively.

Further, the outer peripheral side portion of the rotary shaft seal member 26 is in pressure contact with the inner peripheral surface of the inner ring 24a over the entire circumference so that the inner ring 24a and each of the rotary shafts 22a and 23c rotate integrally. It has become.
With such a configuration, even if the toner inside the housing 21 flows out of the through hole 27b, the toner flows out between the inner ring 24a of the ball bearing 24 and the rotary shafts 22a and 23a. And the rotary shaft sealing member 26 that rotates integrally with each of the rotary shafts 22a and 23a can reliably prevent this.

Further, since each of the rotation shafts 22a and 23a and the inner ring 24a does not slide with the rotation shaft seal member 26, the rotation shaft seal member 26, the rotation shaft seal member 26, and the inner ring 24a are prevented from being worn. Is done. Thereby, the sealing performance by the rotating shaft sealing member 26 can be stably maintained over a long period of time.
Further, since each of the rotation shafts 22a and 23a and the rotation shaft seal member 26 rotate integrally, even if each of the rotation shafts 22a and 23a vibrates in the thrust direction, the rotation shaft seal member 26 and The carrier is prevented from entering between each of the rotating shafts 22a and 23a. As a result, it is possible to prevent the rotating shafts 22a and 23a from being worn, cut, and the like by the carrier. This also ensures stable sealing performance between the rotating shafts 22a and 23a by the rotating shaft seal member 26 over a long period of time. can do.

The rotary shaft sealing member 26 is not limited to urethane rubber, and may be silicone rubber. The rotating shaft seal member 26 may be a foamed material such as urethane foam so as not to slide with respect to the inner ring 24a and the rotating shafts 22a and 23a.
Further, the toner inside the housing 21 flows out from the through hole 27b along each of the rotating shafts 22a and 23a. In this case, the pressure of the toner flowing out along the diameter direction of each of the rotating shafts 22a and 23a. Is lower than the pressure of the toner flowing along the axial direction of each of the rotation shafts 22a and 23a. Accordingly, since the inner ring 24a and the side wall 27a of the bearing holding portion 27 are in pressure contact with each other, the toner can be prevented from leaking outside through the space.

  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.

  Note that the rotating shaft of the developing sleeve in the developing roller 25 is also rotatably supported with respect to the housing 21 by the rotating shaft support mechanism 21A having the same configuration. Therefore, the toner accommodated in the housing 21 can be reliably prevented from leaking out of the housing 21 by the rotation shaft seal members 26 provided in the respective rotation shaft support mechanisms 21A.

  Thereby, waste of the toner in the housing 21 can be suppressed, and the economy can be improved. Further, the periphery of the developing device in the image forming portion A of the printer is not likely to be contaminated by the toner leaking from the developing device. Therefore, the image formed in the image forming portion A is not contaminated by the toner. Can be obtained.

  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.

  Also in the developing device 20 of the process unit 10K having such a configuration, as in the other three process units 10Y, 10M, and 10C, the rotation shafts 22a and 23a of the first toner transport screw 22 and the second toner transport screw 23, The rotating shafts of the developing sleeves in the developing roller 25 are rotatably supported with respect to the housing 21 by the rotating shaft support mechanism 21A having the same configuration. Therefore, in all the process units 10Y, 10M, 10C, and 10K, it is possible to reliably and stably prevent the toner from leaking out from the housing 21 of each developing device 20.

<Embodiment 2>
FIG. 6 is a cross-sectional view for explaining the configuration of the rotation shaft support mechanism 21A that supports the rotation shaft 22a of the first toner conveying screw 22 according to the second embodiment of the present invention. In addition, in FIG. 6, in order to make an understanding of the structure of the rotating shaft support mechanism 21A easy, the cross section is shown typically.

  In the present embodiment, 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.

  In such a configuration, as in the first embodiment, a ring-shaped rotary shaft seal member 26 is fitted in a groove 22c provided on the outer peripheral surface of the end portion of the rotary shaft 22a. The member 26 is in pressure contact with the inner ring 24a of the ball bearing 24 in a state where the member 26 is in pressure contact with the bottom surface of the groove 22c. Further, the inner ring 24a and the side wall 27a of the bearing holding portion 27 are in pressure contact with each other. Other configurations are the same as those of the first embodiment.

The rotating shaft 23a of the second toner conveying screw 23 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.

<Modification>
In the embodiment shown in FIG. 6, as shown in FIG. 7, the space between the inner ring 24a and the outer ring 24b of the ball bearing 24 may be sealed with a fluid sealing material 24d. In this case, in order to prevent the fluid sealing material 24d 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 is provided. As the fluid sealant 24d, for example, a lubricant such as grease can be used.

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.
Further, as shown in FIG. 8 (a), a configuration is provided in which a plate-like bearing seal material 24e 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 material 24e 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.

  Further, as shown in FIG. 8B, a bearing seal member 24e 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 24h. In this case, there is no need to press the side wall portion 27a facing the inner ring 24a and the inner ring 24a against each other, and the tip of the second seal portion 24h 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 24h. In this case, the bearing seal material 24e is formed of an elastic body such as urethane rubber.

  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, as shown in FIG. 9, the side wall portion 27a facing the inner ring 24a of the ball bearing 24, It is good also as a structure which provides the ring-shaped side surface sealing material 24f which seals the peripheral part of the through-hole 27b over a perimeter between the inner rings 24a. The side sealing material 24f is formed in a flat plate shape by an elastic body such as urethane foam so as to be in 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 this case, as shown in FIG. 7, the inner ring 24 a and the outer ring 24 b are sealed with a fluid sealant 24 d between the inner ring 24 a and the outer ring 24 b, or as shown in FIG. 8A. A configuration in which a bearing seal member 24e is installed between the two may be applied at the same time.

Moreover, each said modification is applicable also in Embodiment 1. FIG.
Furthermore, 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. Further, the rotation shaft support mechanism can be applied to at least one rotation shaft provided in the developing device.
Furthermore, the present invention can also be applied to the case where only the developing device 20 can be attached to the image forming unit A. Further, the image forming apparatus according to the present invention is not limited to a tandem color digital printer, and may be a printer that forms a monochrome image, and is not limited to a printer, and is a copy that can form a color or monochrome image. It can also be applied to a machine, FAX, MFP (Multiple Function Peripheral), and the like.

  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 22c Groove 23 Second toner conveying screw 23a Rotating shaft 23b Conveying blade 24 Ball bearing 24a Inner ring 24b Outer ring 24c Ball 24e Bearing seal material 24d Fluid sealant 24f Side seal material 25 Developing roller 26 Rotating shaft seal Member 27 Bearing holding portion 27a Side wall portion 27b Through hole

Claims (11)

A developing device that develops an electrostatic latent image formed on the outer peripheral surface of a photoreceptor using toner contained in a housing,
A rotating member having a rotating shaft and moving the toner in the housing by the rotation of the rotating shaft;
A ball bearing for rotatably holding the rotating shaft with respect to the housing;
A rotating shaft seal member interposed between the inner ring of the ball bearing and the rotating shaft;
A developing device comprising: A groove is provided over the entire circumference along the circumferential direction on the outer peripheral surface of the rotating shaft,
The developing device according to claim 1, wherein the rotary shaft sealing member is fitted in the groove. A bearing holding portion that holds the ball bearing inside is provided on a side surface of the housing,
The developing device according to claim 1, wherein the bearing holding portion is detachably attached to a side surface of the housing. The rotating shaft passes through a through hole provided in the bearing holding portion,
The side surface of the inner ring of the ball bearing is in pressure contact with the peripheral edge portion of the through hole in the bearing holding portion over the entire periphery, whereby the pressure contact portion is sealed. Development device. The rotating shaft passes through a through hole provided in the bearing holding portion,
4. The development according to claim 3, wherein a side seal member is provided between an inner ring of the ball bearing and a peripheral portion of the through hole in the bearing holding portion so as to seal the entire circumference therebetween. apparatus.   The developing device according to claim 1, wherein a gap between an inner ring and an outer ring of the ball bearing is sealed with a fluid sealing material. The rotating shaft passes through a through hole provided in the bearing holding portion,
The developing device according to claim 3, wherein the ball bearing includes a bearing seal material that seals a side portion of the through hole between the inner ring and the outer ring that faces the peripheral portion of the through hole over the entire circumference.   The developing device according to claim 7, wherein the bearing seal material seals between an inner ring of the ball bearing and the peripheral portion over the entire circumference.   The developing device according to claim 1, wherein a carrier is accommodated in the housing together with the toner.   A process unit comprising the developing device according to claim 1.   An image forming apparatus comprising the process unit according to claim 10.

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