Developing device and image forming apparatus equipped with same

Abstract

A developing device (3a to 3d) is provided with a developing container (20), a stirring and conveying member (26), a pair of shaft supporting parts (52), and a pair of bearing parts (28). The developing container (20) stores a developer containing toner. The stirring and conveying member (26) has a rotating shaft (23) and a stirring blade (24a, 24b) formed at an outer peripheral surface of the rotating shaft (23), and stirs and conveys the developer in the developing container (20). The shaft supporting parts (52) are connected to both ends in the axial direction of the rotating shaft (23). The bearing parts (28) rotatably support the respective shaft support parts (52). In the rotating shaft (23), a first through-hole (50) that passes through the whole area in the axial direction of the rotating shaft (23) is formed. The shaft supporting parts (52) are inserted into the first through-hole (50) from both ends in the axial direction of the rotating shaft (23), and a second through-hole (53) that passes through the whole area in the axial direction and communicates with the first through-hole (50) is formed therein.

Description

[Technical field]

[0001] The present invention relates to a developing device and an image forming apparatus equipped with the same. [Background technology]

[0002] Electrophotographic image forming apparatuses such as copiers, printers, facsimiles, and combination machines thereof are equipped with a developing device for developing an electrostatic latent image formed on the outer peripheral surface of an image carrier, that is, for forming a toner image (visible image) by visualizing the electrostatic latent image.

[0003] As such a developing device, Patent Document 1 discloses one that includes a developing container that contains a developer including a toner, an agitating and transporting member that agitates and transports the developer in the developing container, and a developing roller that is partially exposed from an opening formed in the developing container (Patent Document 1). The agitating and transporting member has a rotating shaft that is rotatably supported in the developing container, and an agitating blade formed on the outer circumferential surface of the rotating shaft. The rotating shaft is supported by a bearing portion provided in the developing device and is rotatably supported. As the agitating blade rotates around the rotating shaft, the developer in the developer storage portion is circulated inside the developing container and supplied to the developing roller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-127566 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the developing device as described above, friction occurs between the stirring and transporting member and the bearing, and the temperature of the stirring and transporting member may rise. If the temperature of the stirring and transporting member rises, the stirring and transporting member may deform or deteriorate. In addition, the heat of the stirring and transporting member may spread throughout the developing device, leading to poor development due to deterioration of the developer, poor stirring due to solidification (blocking) of the developer, and an increase in stirring torque.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a developing device capable of suppressing a temperature rise. [Means for solving the problem]

[0007] In order to achieve the above object, a first configuration of the present invention is a developing device including a developing container, an agitating and transporting member, a pair of shaft support portions, and a pair of bearing portions. The developing container contains a developer including a toner. The agitating and transporting member has a rotating shaft and an agitating blade formed on the outer peripheral surface of the rotating shaft, and agitates and transports the developer in the developing container. The shaft support portions are connected to both ends of the rotating shaft in the axial direction. The bearing portions rotatably support each of the shaft support portions. The rotating shaft is formed with a first through hole penetrating the entire axial area of ​​the rotating shaft. The shaft support portions are inserted into the first through hole from both ends of the rotating shaft in the axial direction, and are formed with a second through hole penetrating the entire axial area and communicating with the first through hole. Effect of the Invention

[0008] According to the first configuration of the present invention, the first through hole penetrates the entire axial area of ​​the rotating shaft. Therefore, the heat of the agitating and transporting member is easily dissipated to the air inside the first through hole, and the temperature rise of the agitating and transporting member can be suppressed. In addition, the first through hole and the second through hole communicate with each other, and the second through hole penetrates the entire axial area of ​​the shaft support part. Therefore, the air inside the first through hole is easily replaced with the air outside the agitating and transporting member through the second through hole, and the heat of the agitating and transporting member is more easily dissipated. In addition, by forming the second through hole in the shaft support part, the frictional heat generated between the shaft support part and the bearing part can be efficiently dissipated, and the temperature rise of the shaft support part itself can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an internal structure of an image forming apparatus 100 in which developing devices 3a to 3d according to an embodiment of the present invention are mounted. [Diagram 2] FIG. 3 is a perspective view showing the developing device 3a in a state in which the cover member 61 and the developing roller 31 are removed. [Diagram 3] FIG. 1 is a side cross-sectional view of the developing device 3a with the cover member 61 and the developing roller 31 attached. [Figure 4] FIG. 4 is a plan sectional view showing a cross section of the agitating portion of the developing device 3a, taken along the AA cross-sectional line shown in FIG. [Diagram 5] FIG. 5 is a partial enlarged view of the inside of a circle B shown by a two-dot chain line in FIG. 4 of the developing device 3a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the developing devices 3a to 3d of the present invention and an image forming apparatus 100 including the developing devices 3a to 3d will be described with reference to the drawings. The direction along the rotating shaft 23 provided in the developing devices 3a to 3d of the present invention will be referred to as the "axial direction." Also, the direction along the diameter of the rotating shaft 23 will be referred to as the "radial direction."

[0011] Fig. 1 is a cross-sectional view showing the internal structure of an image forming apparatus 100 equipped with developing devices 3a-3d according to an embodiment of the present invention. Four image forming sections Pa, Pb, Pc, and Pd are arranged in order from the upstream side in the transport direction (the left side in Fig. 1) inside the main body of the image forming apparatus 100 (here, a color printer). These image forming sections Pa-Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and sequentially form images of cyan, magenta, yellow, and black through the processes of charging, exposure, development, and transfer, respectively.

[0012] In these image forming units Pa to Pd, photoconductor drums (image carriers) 1a, 1b, 1c, and 1d that carry visible images (toner images) of each color are disposed, and an intermediate transfer belt 8 that rotates in a counterclockwise direction in FIG. 1 is disposed adjacent to each image forming unit Pa to Pd. The toner images formed on these photoconductor drums 1a to 1d are sequentially primarily transferred and superimposed on the intermediate transfer belt 8 that moves while abutting against each of the photoconductor drums 1a to 1d. Thereafter, the toner images primarily transferred onto the intermediate transfer belt 8 are secondarily transferred onto a transfer paper S, which is an example of a recording medium, by a secondary transfer roller 9. Furthermore, the transfer paper S to which the toner image has been secondarily transferred is discharged from the main body of the image forming apparatus 100 after the toner image is fixed in a fixing unit 13. An image forming process for each of the photoconductor drums 1a to 1d is performed while the photoconductor drums 1a to 1d are rotated in a clockwise direction in FIG. 1 by a main motor (not shown).

[0013] The transfer paper S onto which the toner image is secondarily transferred is stored in a paper cassette 16 arranged at the bottom of the main body of the image forming apparatus 100, and is transported to the nip between the secondary transfer roller 9 and the drive roller 11 of the intermediate transfer belt 8 via a paper feed roller 12a and a pair of registration rollers 12b. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a seamless belt is mainly used. In addition, a blade-shaped belt cleaner 19 is arranged downstream of the secondary transfer roller 9 to remove toner and the like remaining on the surface of the intermediate transfer belt 8.

[0014] Next, the image forming units Pa to Pd will be described. Around and below the rotatably arranged photoconductor drums 1a to 1d, there are provided charging devices 2a, 2b, 2c, and 2d that charge the photoconductor drums 1a to 1d, an exposure device 5 that exposes image information onto each of the photoconductor drums 1a to 1d, developing devices 3a, 3b, 3c, and 3d that form toner images on the photoconductor drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d that remove developer (toner) and the like remaining on the photoconductor drums 1a to 1d.

[0015] When image data is input from a host device such as a personal computer, first, the surfaces of the photoconductor drums 1a-1d are uniformly charged by the charging devices 2a-2d. Next, the exposure device 5 irradiates light according to the image data, and electrostatic latent images corresponding to the image data are formed on the photoconductor drums 1a-1d. The developing devices 3a-3d are filled with a predetermined amount of two-component developer containing toner of each color of cyan, magenta, yellow, and black. When the ratio of toner in the two-component developer filled in each developing device 3a-3d falls below a specified value due to the formation of a toner image described later, toner is replenished from the toner containers 4a-4d to each developing device 3a-3d. The toner in the developer is supplied onto the photoconductor drums 1a-1d by the developing devices 3a-3d, and electrostatically adheres to the toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5.

[0016] Then, an electric field is applied between the primary transfer rollers 6a-6d and the photoconductor drums 1a-1d by the primary transfer rollers 6a-6d at a predetermined transfer voltage, and the cyan, magenta, yellow and black toner images on the photoconductor drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship for forming a predetermined full-color image. After that, in preparation for the subsequent formation of a new electrostatic latent image, the toner and the like remaining on the surfaces of the photoconductor drums 1a-1d after the primary transfer are removed by the cleaning devices 7a-7d.

[0017] The intermediate transfer belt 8 is stretched over a driven roller 10 on the upstream side and a driving roller 11 on the downstream side. When the intermediate transfer belt 8 starts to rotate counterclockwise with the rotation of the driving roller 11 by a belt driving motor (not shown), the transfer paper S is transported from the registration roller pair 12b to a nip portion (secondary transfer nip portion) between the driving roller 11 and the secondary transfer roller 9 at a predetermined timing, and the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the transfer paper S. The transfer paper S to which the toner image has been secondarily transferred is transported to a fixing unit 13.

[0018] The transfer paper S transported to the fixing section 13 is heated and pressurized by the fixing roller pair 13a, so that the toner image is fixed to the surface of the transfer paper S, and a predetermined full-color image is formed. The transfer paper S on which the full-color image has been formed is then transported in a different direction by the branching section 14, which branches into multiple directions, and is discharged directly to the discharge tray 17 by the discharge roller pair 15 (or after being sent to the double-sided transport path 18 and having images formed on both sides).

[0019] Fig. 2 is a perspective view showing the developing device 3a with the cover member 61 and the developing roller 31 removed. Fig. 3 is a side cross-sectional view of the developing device 3a with the cover member 61 and the developing roller 31 attached. Note that in the following description, the developing device 3a arranged in the image forming unit Pa in Fig. 1 is illustrated as an example, but the configurations of the developing devices 3b to 3d arranged in the image forming units Pb to Pd are basically the same, so description thereof will be omitted.

[0020] As shown in FIGS. 2 and 3, the developing device 3a includes a developing container 20 that contains a two-component developer (hereinafter, simply referred to as developer) containing a magnetic carrier and a toner. The developing container 20 has a cover member 61 provided at the top of the developing container 20 and a partition wall 20a provided inside the developing container 20. The cover member 61 closes the top of the developing container 20 and separates the internal space of the developing container 20 from the external space. The partition wall 20a divides the internal space of the developing container 20 into a stirring transport chamber 21 and a supply transport chamber 22.

[0021] A first agitation transport member 25 is provided in the agitation transport chamber 21, and a second agitation transport member 26 is provided in the supply transport chamber 22. Each agitation transport member (first agitation transport member 25 and second agitation transport member 26) mixes toner supplied from a toner container 4a (see FIG. 1) with a magnetic carrier, agitates the toner, and charges the toner. The first agitation transport member 25 and second agitation transport member 26 are rotatably supported by bearings 28 fixed to the developing container 20 via shaft support members 52 provided at both ends in the axial direction (details will be described later).

[0022] As the first agitation transport member 25 and the second agitation transport member 26 rotate, the developer is agitated and transported in the axial direction (the direction perpendicular to the paper surface of FIG. 3), and circulates between the agitation transport chamber 21 and the supply transport chamber 22 via the communication parts 20b and 20c formed at both ends of the partition wall 20a. That is, a circulation path for the developer is formed in the developing container 20 by the agitation transport chamber 21, the supply transport chamber 22, and the communication parts 20b and 20c.

[0023] As shown in Fig. 3, in the developing container 20, a developing roller (developer carrier) 31 is disposed diagonally above and to the right of the second agitating and transporting member 26. A part of the outer circumferential surface of the developing roller 31 is exposed from the opening 20e of the developing container 20 and faces the photosensitive drum 1a. The developing roller 31 rotates in a counterclockwise direction in Fig. 3. The first agitating and transporting member 25, the second agitating and transporting member 26, and the developing roller 31 rotate at a predetermined rotation speed by the driving force from a main motor (not shown).

[0024] The developing roller 31 is composed of a cylindrical developing sleeve (not shown) that rotates counterclockwise in Fig. 3, and a magnet (not shown) having multiple magnetic poles fixed inside the developing sleeve. Note that, although a developing sleeve with a knurled surface is used here, it is also possible to use a developing sleeve with a large number of concave shapes (dimples) formed on the surface, a developing sleeve with a blasted surface, or even a developing sleeve that has been blasted in addition to being knurled or having concave shapes formed, or a developing sleeve that has been plated.

[0025] As shown in Fig. 3, a regulating blade 33 is attached to the developing container 20 along the longitudinal direction of the developing roller 31 (the direction perpendicular to the paper surface of Fig. 3). A small gap is formed between the tip of the regulating blade 33 and the surface of the developing roller 31. The regulating blade 33 uses this small gap to regulate the layer thickness of the toner supplied onto the outer peripheral surface of the developing roller 31 to a predetermined thickness.

[0026] A developing voltage power supply (not shown) is connected to the developing device 3a via a voltage control circuit (not shown). The developing voltage power supply applies a developing voltage, which is a superimposed DC voltage and AC voltage, to the developing roller 31. The developing voltage and the magnetic force of the magnet in the developing roller 31 cause the developer to adhere (be carried) on the surface of the developing roller 31, forming a magnetic brush.

[0027] 3, a toner concentration sensor 27 is disposed on the bottom surface of the stirring and conveying chamber 21 so as to face the first stirring and conveying member 25 in the height direction (the up-down direction in FIG. 3). The toner concentration sensor 27 is connected to a control unit 59 (see FIG. 1) provided at a predetermined position of the image forming apparatus 100. The toner concentration sensor 27 detects the magnetic permeability of the developer in the developing container 20, and transmits the detection result to the control unit 59. Based on the detection result, the control unit 59 determines the toner concentration in the developer (the mixture ratio of toner to carrier in the developer; T / C), and determines whether to replenish toner.

[0028] When replenishing toner, the control unit 59 transmits a control signal to a toner replenishing motor (not shown). This control signal causes the toner replenishing motor to replenishing the toner in the toner containers 4a to 4d into the developing container 20 via the toner replenishing unit 32 (see FIG. 2). At this time, the control unit 59 detects the toner concentration of the developer in the developing container 20 by the toner concentration sensor 27, and replenishing the toner while controlling the toner replenishing motor so that the detected toner concentration becomes a predetermined reference value.

[0029] As shown in FIG. 2, the toner supply unit 32 is provided on the upstream side of the stirring and conveying chamber 21 (the front left side in FIG. 2). The toner supply unit 32 has a supply port 58 that opens to the top of the developing device 3a, and a toner supply path (not shown) that extends downward from the supply port 58 and communicates with the stirring and conveying chamber 21. The supply port 58 is connected to the toner container 4a (see FIG. 1). The toner contained in the toner container 4a is supplied to the stirring and conveying chamber 21 through the supply port 58 and the toner supply path.

[0030] Next, the configuration of the stirring section of the developing device 3a will be described in detail. Fig. 4 is a plan sectional view showing a cross section of the stirring section of the developing device 3a, taken along the AA sectional line shown in Fig. 3. Fig. 5 is a partial enlarged view of the developing device 3a, showing the inside of the circle B shown by the two-dot chain line in Fig. 4.

[0031] 2 to 4, as described above, the developing container 20 is formed with the stirring / transporting chamber 21, the supply / transporting chamber 22, the partition wall 20a, the upstream communication portion 20b, and the downstream communication portion 20c. In addition, the developing container 20 is formed with the toner supply portion 32, and side walls 29a and 29b (opposing walls).

[0032] The partition wall 20a extends in the longitudinal direction of the developing container 20 to partition the stirring transport chamber 21 and the supply transport chamber 22 so as to be arranged in parallel. One end of the partition wall 20a in the longitudinal direction (the right side in FIG. 4) forms an upstream communication portion 20b together with a side wall portion 29b of the developing container 20. The other end of the partition wall 20a in the longitudinal direction (the left side in FIG. 4) forms a downstream communication portion 20c together with the side wall portion 29a of the developing container 20.

[0033] The first agitation and transport member 25 has a rotating shaft 23 and a helical blade 24a. The second agitation and transport member 26 has a rotating shaft 23 and a helical blade 24b (agitation blade). The first agitation and transport member 25 and the second agitation and transport member 26 are different in configuration in that the helical blade 24a and the helical blade 24b are wound in opposite directions, but the other parts are basically the same. Therefore, the first agitation and transport member 25 will be mainly described, and as for the second agitation and transport member 26, only the parts that differ from the first agitation and transport member 25 will be described.

[0034] 2 to 4, the rotating shaft 23 is a cylindrical shaft body extending along the longitudinal direction (the developer transport direction) of the developing container 20. The rotating shaft 23 extends to the vicinity of both ends in the axial direction of the developing container 20. Both ends of the rotating shaft 23 face the side wall portions 29a, 29b in the axial direction.

[0035] The helical blades 24a and 24b are formed on the outer circumferential surface of the rotating shaft 23. The helical blades 24a and 24b are formed integrally with the rotating shaft 23 and are formed in a helical shape with a constant pitch in the axial direction. The helical blades 24a and 24b are formed in opposite windings. The helical blades 24a and 24b extend to both ends of the developing container 20 in the longitudinal direction, and are also provided at the positions of the upstream communicating portion 20b and the downstream communicating portion 20c in the longitudinal direction. The diameter D1 of the helical blade 24b is 1.3 times or more and 1.7 times or less (preferably 1.4 times or more and 1.6 times or less) the outer diameter D2 of the rotating shaft 23.

[0036] As shown in Figures 3 to 5, a first through hole 50 is formed in the radial center of the rotating shaft 23, penetrating from both axial ends of the rotating shaft 23. Support recesses 51 are formed in both axial ends of the first through hole 50. The inner diameter of the support recess 51 is larger than the inner diameter of the first through hole 50. In other words, the first through hole 50 expands in diameter from the axial center toward the support recess 51.

[0037] As shown in FIGS. 4 and 5, the shaft support portion 52 is a cylindrical shaft body that is elongated in the axial direction. The shaft support portion 52 is formed from a metal material (such as brass). The outer diameter of the shaft support portion 52 is equal to or greater than the inner diameter of the support recess 51. The shaft support portion 52 is inserted into the support recess 51 and fixed to the rotating shaft 23. More specifically, the shaft support portion 52 is inserted (press-fitted) into the support recess 51 with a tightening margin, and thereby fixed to the rotating shaft 23. As a result, the shaft support portion 52 and the first stirring and transporting member 25 rotate integrally around the rotating shaft 23.

[0038] A second through hole 53 is formed in the radial center of the shaft support portion 52, penetrating the entire axial area of ​​the shaft support portion 52. The inner diameter of the second through hole 53 is substantially the same as or slightly smaller than the first through hole 50. When the shaft support portion 52 is fixed to the rotating shaft 23, the second through hole 53 communicates with the first through hole 50.

[0039] The shaft support portion 52 extends in the axial direction from the support recess 51, penetrates the side walls 29a and 29b, and protrudes outside the mixing and transporting chamber 21 and the supply and transporting chamber 22.

[0040] 4 and 5, bearings 28 are disposed on the outer sides of the first agitating and conveying member 25 and the second agitating and conveying member 26 (not shown) in the axial direction. Each bearing 28 is fixed to a side wall 29a, 29b. Each bearing 28 is a ball bearing including an outer ring 54, an inner ring 55, and a rolling element 56.

[0041] The outer ring 54 is fixed to the side wall portions 29a and 29b. The inner ring 55 is fixed to the outer peripheral surface of the shaft support portion 52. The outer diameter of the inner ring 55 is smaller than the inner diameter of the outer ring 54. The inner ring 55 is disposed at a position overlapping the outer ring 54 in the axial direction and faces the outer ring 54 in the radial direction. The rolling elements 56 are spherical. The rolling elements 56 are disposed between the outer ring 54 and the inner ring 55. The rolling elements 56 are disposed on the opposing surfaces (raceway surfaces) of the outer ring 54 and the inner ring 55. When the shaft support portion 52 rotates, the outer ring 54 and the inner ring 55 slide against the rolling elements 56, and the outer ring 54 and the inner ring 55 rotate relative to each other.

[0042] As shown in FIGS. 4 and 5, a seal member 57 is provided on the axial outside of the bearing portion 28. The seal member 57 is an annular body made of an elastic member such as an elastomer or rubber. The seal member 57 is fitted onto the shaft support portion 52. The radially inner surface of the seal member 57 is in slidable contact with the outer circumferential surface of the shaft support portion 52. The seal member 57 is disposed between the wall portion of the developing container 20 and the shaft support portion 52. The seal member 57 closes the gap between the wall portion of the developing container 20 and the shaft support portion 52, and prevents the developer in the stirring and conveying chamber 21 and the supply and conveying chamber 22 from flowing out to the outside.

[0043] Of the shaft support parts 52 provided on each rotating shaft 23, the shaft support part 52 located at the end part on one side (here, the side of the side wall part 29a) of the rotating shaft 23 is connected to a drive gear 60. The drive gear 60 is connected to a main motor (not shown) and transmits the rotational driving force of the main motor to the shaft support part 52. When the rotational driving force is transmitted to the shaft support part 52, the first agitating and conveying member 25 (second agitating and conveying member 26) rotates integrally with the shaft support part 52.

[0044] By the rotation of the first agitation transport member 25 and the second agitation transport member 26, the developer in the developing container 20 is agitated while circulating from the agitation transport chamber 21 to the upstream side communication part 20b, the supply transport chamber 22, and the downstream side communication part 20c by the spiral blades 24a and 24b (see FIG. 2). At that time, the developer in the supply transport chamber 22 is supplied to the developing roller 31.

[0045] Generally, the developer refill frequency of a developing device may differ depending on the model of the image forming device to which it is mounted. In such a case, the developer filling amount (the amount of developer filled in the developing container) also differs. For example, in a developing device with a high refill frequency, the developer filling amount is small, and conversely, in a developing device with a low refill frequency, the developer filling amount is large. However, when the developer filling amount is small, if the developer rate (the ratio between the volume of the developing container and the volume of the developer in the developing container) decreases, the developer may not be appropriately supplied to the developing roller. Therefore, some developing devices with a small developer filling amount reduce the developer volume and suppress the decrease in the developer rate by making the developing container smaller or making the diameter of the rotating shaft of the stirring and conveying member relatively large.

[0046] In addition, in general, in a developing device, friction occurs between the driving gear or bearing that transmits the rotational driving force to the stirring and transporting member and the stirring and transporting member, and the temperature of the stirring and transporting member may rise. When the temperature of the stirring and transporting member rises, the stirring and transporting member may be deformed or deteriorated. In particular, in a developing device having a small volume of a developing container and a small amount of developer as described above, the heat of the stirring and transporting member is not easily dissipated through the developer, and the temperature of the stirring and transporting member is easily increased. When the temperature of the stirring and transporting member rises, the stirring and transporting member may be deformed or deteriorated. In addition, when the heat of the stirring and transporting member spreads throughout the developing device and the temperature of the developing device rises, it may have an adverse effect on the development of the developing roller, leading to deterioration of the developing device and the image forming device.

[0047] In contrast, in the developing device 3a of the present invention, as described above, the first through hole 50 is formed in the rotating shaft 23, and the first through hole 50 penetrates the entire axial area of ​​the rotating shaft 23. Therefore, the heat of the first agitation and transport member 25 and the second agitation and transport member 26 is easily dissipated to the air inside the first through hole 50, and the temperature rise of the first agitation and transport member 25 and the second agitation and transport member 26 can be suppressed. In addition, the first through hole 50 and the second through hole 53 communicate with each other, and the second through hole 53 penetrates the entire axial area of ​​the shaft support portion 52. Therefore, the air inside the first through hole 50 is easily exchanged between the inside and outside of the first agitation and transport member 25 and the second agitation and transport member 26 through the second through hole 53, and the heat of the first agitation and transport member 25 and the second agitation and transport member 26 is more easily dissipated.

[0048] Furthermore, by forming the second through hole 53 in the shaft support portion 52, frictional heat generated between the shaft support portion 52 and the bearing portion 28 can be efficiently dissipated, and a temperature rise in the shaft support portion 52 itself can be suppressed. Therefore, a developing device 3a capable of suppressing a temperature rise can be provided.

[0049] As described above, the seal member 57 is located outside the bearing portion 28 in the axial direction. Therefore, the seal member 57 comes into contact with only a small amount of developer that passes through the gap between the bearing portion 28 and the side wall portions 29a, 29b and the side wall portions 29a, 29b and the side wall portions 29b, and the gap between the outer ring 54 and the inner ring 55 and the rolling element 46. Then, when the shaft support portion 52 rotates and the seal member 57 slides against the shaft support portion 52, frictional heat generated between the seal member 57 and the shaft support portion 52 is not easily transmitted to the developer. Therefore, it is possible to suppress a rise in temperature of the developer.

[0050] As described above, the shaft support portion 52 is made of a metal material, and therefore has a relatively high thermal conductivity, so that the heat of the shaft support portion 52 can be dissipated efficiently.

[0051] As described above, the diameter of the spiral blade 24b is 1.3 times or more and 1.7 times or less than the diameter of the rotating shaft 23. That is, the rotating shaft 23 is formed to have a larger diameter than a typical rotating shaft. Therefore, the inner diameter of the first through hole 50 formed in the rotating shaft 23 can be made relatively large, and the volume of the space inside the first through hole 50 can be increased. Therefore, the efficiency of heat dissipation of the first agitating and conveying member 25 and the second agitating and conveying member 26 is improved, and the temperature rise of the first agitating and conveying member 25 and the second agitating and conveying member 26 can be suppressed. Furthermore, by making the diameter 1.4 times or more and 1.6 times or more than the diameter of the rotating shaft 23, the temperature rise of the first agitating and conveying member 25 and the second agitating and conveying member 26 can be suppressed while suppressing the decrease in the amount of developer conveyed by the spiral blade 24b.

[0052] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the present invention is not limited to the tandem color printer shown in Fig. 1, but can be applied to various image forming apparatuses using a two-component development method, such as digital or analog monochrome copiers, monochrome printers, color copiers, and facsimiles.

[0053] In addition, the first agitating and conveying member 25 and the second agitating and conveying member 26 are described as having the spiral blades 24a, 24b wound in opposite directions, but the spiral blades 24a, 24b may be formed in the same direction. In this case, the first agitating and conveying member 25 and the second agitating and conveying member 26 are arranged so that they are inverted relative to each other in the axial direction. In this way, the first agitating and conveying member 25 and the second agitating and conveying member 26 can be made of the same member, and the increase in manufacturing costs can be suppressed by sharing parts.

[0054] Furthermore, although bearing portion 28 is a ball bearing, the present invention is not limited thereto, and may be, for example, a plain bearing in which an inner ring and an outer ring slide in direct contact with each other. Furthermore, inner ring 55 may be configured to be integrally formed with shaft support portion 52. Similarly, outer ring 54 may be configured to be integrally formed with side wall portion 29a.

[0055] As described above, the shaft support portion 52 is configured to be press-fitted and fixed into the support recess 51, but it may be fixed to the support recess 51 by adhesion, or an engaging protrusion may be formed on the outer circumferential surface of the shaft support portion 52 and engaged with an engaging groove in the support recess 51. In this case, the outer diameter of the shaft support portion 52 can be made smaller than the inner diameter of the support recess 51.

[0056] Alternatively, a configuration in which the first through-hole 50 and the second through-hole 53 are formed in only one of the first agitating and transporting member 25 and the second agitating and transporting member 26 may be adopted. [Industrial Applicability]

[0057] The present invention can be used in a developing device having a stirring and transporting member that stirs and transports developer. By using this developing device, it is possible to provide an image forming device that can suppress image formation defects and deterioration of the developing device and image forming device.

Claims

1. a developer container that contains a developer including a toner; a stirring and conveying member having a rotating shaft and a stirring blade formed on an outer circumferential surface of the rotating shaft, the stirring and conveying member stirring and conveying the developer in the developing container; A pair of shaft support parts connected to both axial ends of the rotating shaft; a pair of bearings for rotatably supporting the shaft support portions, The rotating shaft has a first through hole that penetrates the rotating shaft over an entire area in the axial direction, A developing device characterized in that the shaft support portion is inserted into the first through hole from both axial ends of the rotating shaft, a second through hole is formed that penetrates the entire axial direction and communicates with the first through hole, and the inner diameter of the second through hole is smaller than the inner diameter of the first through hole.

2. a seal member provided between the developing container and the shaft support portion and configured to close a gap between the developing container and the shaft support portion; 2. The developing device according to claim 1, wherein the seal member is in contact with an outer circumferential surface of the shaft support portion at a position outside the bearing portion in the axial direction.

3. the developing container has a pair of opposing wall portions opposed to both ends of the rotating shaft in the axial direction, The shaft support portion penetrates the opposing wall portion in the axial direction, The developing device according to claim 1, characterized in that the bearing portion has an outer ring provided on the opposing wall portion and facing the shaft support portion in the radial direction of the rotating shaft, and an inner ring rotatably supported by the outer ring and rotating together with the rotating shaft.

4. the rotating shaft has support recesses recessed inward in the axial direction from both end portions of the rotating shaft and having a diameter larger than that of the first through hole, 2. The developing device according to claim 1, wherein the shaft support portion is inserted into the support recess and fixed to the rotating shaft.

5. 2. The developing device according to claim 1, wherein the shaft support portion is made of a metal material.

6. 2. The developing device according to claim 1, wherein the diameter of said stirring blade is 1.3 times or more and 1.7 times or less the diameter of said rotating shaft.

7. The developing device according to claim 1 ; an image carrier that receives the toner from the developing device and carries the toner on its surface; An image forming apparatus comprising:

8. a developer container that contains a developer including a toner; a stirring and conveying member having a rotating shaft and a stirring blade formed on an outer circumferential surface of the rotating shaft, the stirring and conveying member stirring and conveying the developer in the developing container; A pair of shaft support parts connected to both axial ends of the rotating shaft; a pair of bearings for rotatably supporting the shaft support portions, a seal member provided between the developing container and the shaft support portion and configured to close a gap between the developing container and the shaft support portion; The rotating shaft has a first through hole that penetrates the rotating shaft over an entire area in the axial direction, the shaft support portion is inserted into the first through hole from both ends of the rotating shaft in the axial direction, and a second through hole is formed through the shaft support portion over an entire area in the axial direction and communicating with the first through hole, The developing device, wherein the seal member is disposed at a position outside the bearing portion in the axial direction, spaced apart from the bearing portion in the axial direction, and in contact with an outer peripheral surface of the shaft support portion.

Images