JP5543708B2 - Developing device, imaging unit, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device, an imaging unit, and an image forming apparatus.

  An image forming apparatus using an electrophotographic system is an apparatus that forms an electrostatic latent image on the outer peripheral surface of a uniformly charged photoreceptor drum, and forms the image by visualizing the electrostatic latent image with toner. Used in digital printers and copiers. In the image forming apparatus, for example, a two-component developer composed of toner and a carrier is used, and the electrostatic latent toner formed on the outer peripheral surface of the photosensitive drum is charged with frictionally charged toner by a stirring unit provided in the developing apparatus. A toner image is formed by adhering to the image.

  The developing device of such an image forming apparatus is often provided with a plurality of developer conveying members that convey the developer composed of toner and carrier while stirring in a developing container to which toner is supplied. The developer transport member includes a spiral blade-shaped member on the rotation shaft, and transports the developer while stirring. Further, both end portions of the rotation shaft of the developer conveying member are normally supported by the developing container so as to be rotatable via a bearing portion.

  Here, when the developer is circulated by the developer conveying member in the developing container, if the developer enters the bearing portion, a problem arises that the torque of the bearing portion increases and the bearing portion is overheated. As a result, toner is fused to the bearing portion, or toner granules are generated around the bearing portion. As a result, the bearing part may eventually lock up and image formation will not be possible, or the generated granules may be clogged with the layer regulating part, causing vertical streaks in the image, or spotted defects in the image. There is a problem that the reliability / durability of the developing device is lacking. As a technique for solving such a problem, for example, Patent Document 1 discloses a development in which a reflux unit is provided at the end of the rotating shaft of the developer conveying member to return the developer toward the central portion of the rotating shaft. An apparatus is disclosed.

  The developing device described in Patent Document 1 includes two developer conveying members having different developer conveying directions. Further, the developing device includes a partition plate between the developer transport members in order to circulate the developer in the developer container. In addition, two communicating portions are formed in the partition plate so that the developer is circulated between the developer transport members. Further, the developing device includes a return unit of a spiral blade-shaped member for returning the developer to the upstream side in the transport direction on the downstream side of the developer transport direction of each developer transport member. With this configuration, the developing device can return the developer heading to the bearing portion of the developer transport member to the upstream side in the transport direction. As described above, the developing device described in Patent Document 1 attempts to solve the above problem by providing a reflux unit to prevent the developer from entering the bearing portion.

JP 2003-114576 A

  However, in the developing device described in Patent Document 1, a reflux unit is provided at a position where a communication portion formed on the partition plate, that is, a developer circulation path that connects the transport paths of the developer transport members is formed. ing. Accordingly, since the developer is not transported to the vicinity of the downstream side of the communication portion, the developer cannot be supplied to the end portion of the developing roller (developer carrier) provided adjacent to any developer transport member. A problem occurs. In order to solve this, it is necessary to enlarge the developing device itself, which is not preferable in terms of design.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to maintain the durability of the bearing portion and to add the developer to the developing roller (without increasing the size of the apparatus). It is an object of the present invention to provide a new and improved developing device, imaging unit, and image forming apparatus that can be supplied over the entire axial direction of a developer carrying member.

  In order to solve the above problems, according to one aspect of the present invention, a developer agitation tank in which a developer circulation path in which a developer composed of toner and a carrier is circulated while being agitated is formed, and the developer circulation A developer carrying member for carrying the developer stirred in a path, wherein the developer stirring tank includes a rotation shaft extending in the same direction as a rotation axis direction of the developer carrying member. A spiral blade-shaped stirring and conveying member formed in a predetermined section on the rotating shaft so as to convey the developer while stirring the developer in one of the longitudinal directions of the rotating shaft; and on the downstream side of the developer in the conveying direction A spiral blade-shaped circulation auxiliary member formed in a predetermined section on the rotary shaft so as to convey the developer toward the central portion of the rotary shaft, and supply the developer to the developer carrier. First rotating member and front A rotating shaft extending in the same direction as the rotating shaft direction of the first rotating member and arranged alongside the first rotating member; and the developer in a direction opposite to the developer conveying direction by the first rotating member A spiral blade-shaped stirring and conveying member formed in a predetermined section on the rotating shaft so as to be conveyed, and the rotating shaft so as to convey the developer toward the central portion of the rotating shaft on the downstream side in the conveying direction of the developer. Between the first rotating member and the second rotating member, and from the inner wall of the developer agitation tank, Between the two end partition walls formed to extend a predetermined distance along the circulation assisting member, and between the first rotating member and the second rotating member, the position is separated from the end partition wall by a predetermined distance. A predetermined section is formed along the stirring and conveying member. A central partition wall is formed, the spiral pitch of the circulation assisting member is ¼ or more and ½ or less of the outer diameter of the circulation assisting member, and the section in which the circulation assisting member is formed is: The end part partition wall and the center part partition wall are formed apart by 1 to 1.5 times the spiral pitch of the stirring and conveying member. As a result, a communicating portion for circulating the developer is formed, and the agitating and conveying member formed on the first rotating member and the second rotating member is at least more than the center of the communicating portion. A developing device is provided that extends to the downstream side in the transport direction.

    With this configuration, the developing device can circulate the developer while stirring the developer by the stirring and conveying member formed on the first rotating member and the second rotating member. In the developing device, a circulation assisting member for transporting the developer toward the center of the rotating shaft is formed at the end of each rotating shaft on the downstream side in the transport direction of the developer. As a result, the developer entering the bearing portion of the rotating shaft can be recirculated toward the center of the rotating shaft, and the durability of the bearing can be improved. Further, since the developing device includes the end partition wall at the position where the circulation assisting member is formed between the first rotating member and the second rotating member, the developer can enter the bearing portion from the lateral direction. It can also be prevented. Further, the developing device can be formed by extending the agitating and conveying member formed on the first rotating member and the second rotating member to the downstream side in the developer conveying direction from at least the center of the communicating portion. As a result, a gap section between the circulation assisting member and the stirring and conveying member is formed on the downstream side of the developer from the center of the communication portion of the circulation path. As a result, the developer can be efficiently circulated through the entire communication portion, and the developer can be reliably supplied to the end portion of the developer carrier.

  Further, the clearance between the first rotating member and the second rotating member at the position where the end partition wall is formed and the developer agitation tank is set as the first at the position where the central partition wall is formed. The clearance may be smaller than the clearance between the rotating member and the second rotating member and the developer stirring tank.

  With this configuration, the clearance between the circulation auxiliary member and the end partition wall or the developer agitation tank can be reduced. As a result, the efficiency of returning the developer to the center of the rotating shaft by the circulation assisting member can be increased, and the developer can be prevented from entering the bearing portion.

  Further, the circulation auxiliary member may be formed to be separated from the stirring and conveying member by 1 to 2 times the helical pitch of the circulation auxiliary member. The section in which the circulation assisting member is formed may be not less than 2 times and not more than 2.5 times the spiral pitch of the circulation assisting member. Thereby, without increasing the size of the developing device, the efficiency of transporting the developer to the center of the rotating shaft by the circulation assisting member can be increased, and the developer can be prevented from entering the bearing portion.

  As described above, according to the present invention, the durability of the bearing portion can be maintained and the developer can be supplied over the entire axial direction of the developing roller (developer carrier) without increasing the size of the apparatus. It is.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(Overall configuration of image forming apparatus)
First, the overall configuration of the image forming apparatus 10 including the developing device 100 according to one embodiment of the present invention will be described. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a tandem image forming apparatus 10 as an example of an image forming apparatus including a developing device 100 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 10 mainly includes a plurality of imaging units 16 including a developing device 100 and a photosensitive drum 12 according to the present embodiment, a light traveling device 18, an intermediate transfer member 20, A recording medium conveyance device 22 and a fixing device 24 are provided.

  The developing device 100 is provided for each color of magenta, yellow, cyan, and black, for example, and includes a developing roller 104 (also referred to as a developer carrying member 104), a developer stirring tank 102, and a developer stirring tank 102. The developer supply member 106 and the developer stirring / conveying member 108 that are disposed are mainly included. The detailed configuration of the developing device 100 will be described later.

  The imaging unit 16 includes the developing device 100, and includes the photosensitive drum 12, a charger 26 that uniformly charges the outer peripheral surface of the photosensitive drum 12 to a negative charge, and the outer peripheral surface of the photosensitive drum 12. And a cleaning device 14 that removes and cleans the toner adhering to the toner. The light running device 18 scans and exposes the outer peripheral surface of the uniformly charged photosensitive drum 12 while irradiating laser light, and causes the electrostatic latent image on the photosensitive drum 12 according to the image signal of the recorded image. Form an image.

  The intermediate transfer body 20 mainly includes an endless transfer belt 20a that is circulated by a driving roller 20b, a tension roller 20c, and support rollers 20d and 20e disposed on the inner peripheral side, a plurality of primary transfer rollers 20f, And a next transfer roller 20g. The primary transfer roller 20 f is provided on the inner peripheral side of the transfer belt 20 a so as to press the transfer belt 20 a on the outer peripheral surface of each photosensitive drum 12. Further, the secondary transfer roller 20g is provided so as to sandwich the transfer belt 20a together with the support roller 20e. Although not shown in FIG. 1, the intermediate transfer member 20 may further include a belt cleaning device or the like that removes toner adhering to the transfer belt 20a.

  The recording medium conveyance device 22 includes a cassette that accommodates a plurality of recording media 30 and a plurality of conveyance rollers 28 that rotate in synchronization. The recording medium conveyance device 22 takes out the recording medium 30 from the cassette and conveys it, and supplies it between the secondary transfer roller 20g and the transfer belt 20a. The recording medium conveying device 22 conveys the recording medium 30 carrying the toner image by the secondary transfer roller 20g to the fixing device 24, and then further conveys the recording medium 30 on which the toner image is melted and fixed. 10 to the outside.

  The fixing device 24 mainly includes a heating roller 24a and a pressure roller 24b that are provided so that their outer peripheral surfaces come into pressure contact with each other. The heating roller 24a has a substantially cylindrical shape capable of rotating the shaft, and is configured, for example, by winding a heat-resistant elastic layer such as silicon rubber around a metal core, and includes a heat source such as a halogen lamp inside. ing. The pressure roller 24b has a substantially cylindrical shape that can rotate about its axis. For example, the pressure roller 24b is configured by winding a heat-resistant elastic layer such as silicon rubber around a metal core. Such a fixing device 24 melts and fixes the toner image on the recording medium 30 fed between the heating roller 24a and the pressure roller 24b.

  The image forming apparatus 10 configured as described above can form an image on the recording medium 30 by operating as follows.

  First, when the image forming apparatus 10 is operated, an image signal of a recorded image is transmitted to a control unit (not shown). Thereafter, in response to an instruction from the control means, the charger 26 uniformly charges the outer peripheral surface of the photosensitive drum 12 to a negative charge, and the light traveling device 18 emits laser light to the outer peripheral surface of the photosensitive drum 12. Irradiation forms an electrostatic latent image corresponding to the image signal of the recorded image. In the developer agitation tank 102 of the developing device 100, the developer agitated by the developer supply member 106 and the developer agitation transport member 108 is supplied toward the outer peripheral surface of the developing roller 104. Further, in the developer carried on the developing roller 104, a positively charged carrier is held on the developing roller 104, and only the negatively charged toner attached to the carrier forms an electrostatic latent image formed on the outer peripheral surface of the photosensitive drum 12. The supplied toner image is formed. In this way, a toner image is formed on the photosensitive drum 12 of each imaging unit 16 provided for each color.

  Further, the transfer belt 20a of the intermediate transfer member 20 is transported with the driving of the driving roller 20b in accordance with an instruction from the control means. The transferred transfer belt 20a is pressed against the photosensitive drum 12 of the imaging unit 16 corresponding to the magenta toner tank 32M by the primary transfer roller 20f, and the magenta toner image is transferred to the outer peripheral surface of the transfer belt 20a. In this way, by sequentially transferring the transfer belt 20a, magenta, yellow, cyan, and black toner images are superimposed on the transfer belt 20a.

  Then, the recording medium conveying device 22 that has received an operation instruction from the control means conveys the recording medium 30 between the secondary transfer roller 20g and the transfer belt 20a, and the color that the transfer belt 20a carries on the recording medium 30. The toner image is transferred. The recording medium 30 that has been subjected to the secondary transfer is transferred toward the fixing device 24 and passes while being applied with heat and pressure between the heating roller 24a and the pressure roller 24b, so that the color toner image is melted. It is fixed. In this way, the recording medium 30 on which the recording image is formed is further transported and discharged to the outside of the image forming apparatus 10.

  The tandem-type image forming apparatus 10 illustrated in FIG. 1 is an example of an image forming apparatus that uses the developing device 100 according to the present embodiment, and the developing device 100 according to the present embodiment can use various types of image forming apparatuses. The present invention can also be applied to a forming apparatus. For example, an image forming apparatus 10 ′ of a vertical paper conveyance system that forms a monochrome image as shown in FIG. 2 may be used. In the case of the image forming apparatus 10 ′ shown in FIG. 2, the toner image formed on the photosensitive drum 12 is directly transferred to the recording medium 30 transferred between the photosensitive drum 12 and the transfer roller 20h. It becomes.

(Configuration of the developing device 100)
Next, the details of the configuration of the developing device 100 according to the present embodiment incorporated in the image forming apparatus 10 as described above will be described. FIG. 3 is an explanatory diagram illustrating an outline of a configuration example of the developing device 100 according to the present embodiment.

  As shown in FIG. 3, the developing device 100 includes a developer stirring tank 102 for stirring the toner supplied from the toner tank 32 and the carrier, and the developing roller 104 described above. Further, in the developer agitation tank 102, a developer supply member 106 (hereinafter also referred to as a first rotation member 106) for supplying the developer agitated over the entire longitudinal direction of the rotation shaft of the developing roller 104 is disposed. It is installed.

  The first rotating member 106 has a substantially spiral blade-shaped agitating / conveying member 112 formed on a rotating shaft substantially parallel to the axial direction of the developing roller 104 while agitating and conveying the developer with a predetermined section. In addition, although the example of a detail dimension of the spiral blade-shaped stirring conveyance member 112 is mentioned later, the schematic external view of the 1st rotation member 106 with which the stirring conveyance member 112 was provided becomes like FIG. Further, the rotation shaft of the first rotation member 106 is supported so as to be rotatable with respect to the developer stirring tank 102 via a bearing portion 114. In the example shown in FIG. 3, the first rotating member 106 rotates counterclockwise (in the direction of the arrow in the drawing), thereby transporting the developer downward in FIG. 3 while stirring. In addition, on the downstream side in the developer transport direction, a spiral blade-shaped circulation auxiliary member 116 is formed on the rotation shaft of the first rotating member 106 to recirculate the developer in the direction opposite to the developer transport direction. ing. The circulation assisting member 116 causes the developer toward the bearing portion 114 to flow back toward the central portion of the rotating shaft. Therefore, the developing device 100 according to the present embodiment prevents the developer from entering the bearing portion 114. Can do.

  Next, in the developer agitation tank 102, a substantially spiral for conveying the developer while being agitated to a rotation axis substantially parallel to the axial direction of the first rotation member 106 along with the first rotation member 106. A developer stirring and conveying member 108 (hereinafter also referred to as a second rotating member 108) in which a blade-shaped stirring and conveying member 112 is formed in a predetermined section is disposed. In addition, although the example of a detail dimension of the spiral blade-shaped stirring conveyance member 112 etc. is mentioned later, the schematic external view of the 2nd rotation member 108 with which the stirring conveyance member 112 was provided becomes like FIG.

  Further, the rotation shaft of the second rotation member 108 is supported so as to be rotatable with respect to the developer agitation tank 102 via a bearing portion 114. The spiral blade-shaped stirring and conveying member 112 provided in the second rotating member 108 is formed so as to be able to convey the developer in the direction opposite to the developer conveying direction by the first rotating member 106. That is, in the example shown in FIG. 3, the second rotating member 108 rotates counterclockwise (in the direction of the arrow in the figure) to convey the developer upward in FIG. 3 while stirring. Further, similarly to the first rotating member 106, on the downstream side in the developer transport direction, a spiral for causing the developer to flow back in the direction opposite to the developer transport direction on the rotation shaft of the second rotating member 108. A blade-shaped circulation auxiliary member 116 is formed.

  Further, as shown in FIG. 3, a central partition wall 120 is formed in the developer stirring tank 102 with a predetermined section so as to partition the first rotating member 106 and the second rotating member 108. As described above, in the developer agitation tank 102, the developer is transported by the first partition 122, which is a region where the developer is transported by the first rotating member, and by the second rotating member. It is partitioned off from the second transport unit 126.

  Further, as shown in FIG. 3, at the ends of the first rotating member 106 and the second rotating member 108, the inner wall of the developer agitation tank 102 corresponds to the position where the circulation assisting member 116 is formed. An end partition wall 118 extending a predetermined section is formed. As shown in FIG. 3, the end partition wall 118 and the central partition wall 120 are formed apart from each other by a predetermined interval. That is, as shown in FIG. 3, the developer is transported from the first transport unit 122 to the second transport between the end partition wall 118 and the central partition wall 120 formed on the downstream side of the first transport unit 122. A first communication part 124 to be conveyed to the part 126 is formed. Further, the developer is transported from the second transport unit 126 to the first transport unit 122 between the end partition wall 118 and the central partition wall 120 formed on the downstream side of the second transport unit 126. Two communicating portions 128 are formed. As a result, the developer is transported again to the first transport unit 122 via the first transport unit 122, the first communication unit 124, the second transport unit 126, and the second communication unit 128.

  Further, the stirring and conveying member 112 of the first rotating member 106 and the second rotating member 108 is formed to extend to the downstream side in the developer conveying direction from the central portion of each communicating portion. As a result, since the developer is transported to the downstream side of the first communication portion 124 and the second communication portion 128, the developer is reliably supplied also to the end portion of the developing roller 104 by the first rotating member 106. Can do.

  As described above, in the developing device 100 according to the present embodiment, the circulation assisting member 116 is formed at the end portions of the first rotating member 106 and the second rotating member 108, thereby preventing the developer from entering the bearing portion 114. can do. In addition, since the end partition wall 118 is formed at the position where the circulation assisting member 116 is formed, it is possible to prevent the developer from entering the bearing portion 114 from the lateral direction. Reliability can be further increased. Further, since the stirring and conveying member 112 of the first rotating member 106 and the second rotating member 108 is formed to extend to the downstream direction of the developer from the central portion of each communicating portion, the developing roller is not enlarged. The developer can be reliably supplied over the entire 104 axial direction.

  As shown in FIG. 3, a toner supply unit 132 is formed in the developer stirring tank 102 at the end of the second rotating member 108 on the upstream side in the developer transport direction. As shown in FIG. 3, the toner supply unit 132 is formed at the upstream end of the second rotating member 108 in the developer transport direction so as to join the developer circulation path. With such a configuration, toner having a specific gravity smaller than that of the carrier can be joined to the developer circulation path, and the mixing performance of the toner and the carrier can be improved. Of course, the toner supply unit 132 is not necessarily formed at the position shown in FIG.

(Cross sectional shape of the developing device 100)
Next, the configuration of the developing device 100 configured as described above will be described with reference to cross-sectional views shown in FIGS. 5A and 5B. Here, FIG. 5A (a) is an AA cross-sectional view of the developing device 100 shown in FIG. FIG. 5A (b) is a BB cross-sectional view of the developing device 100 shown in FIG. FIG. 5A (c) is a cross-sectional view taken along the line C-C of the developing device 100 shown in FIG. FIG. 5B (d) is a DD cross-sectional view of the developing device 100 shown in FIG. 5B (e) is a cross-sectional view taken along line EE of the developing device 100 shown in FIG. FIG. 5B (f) is a cross-sectional view of the developing device 100 shown in FIG.

  Referring to FIG. 5A (a), it can be seen that an end partition wall 118 is formed between the first rotating member 106 and the second rotating member 108 in the AA cross section. In the developing device 100 according to this embodiment, the end partition wall 118 formed in this way can reliably prevent the developer from entering the bearing portion 114 from the lateral direction.

  Next, referring to FIG. 5A (b), it can be seen that no partition wall is formed between the first rotating member 106 and the second rotating member 108 in the BB cross section. As a result, the developer is conveyed from the second rotating member 108 to the first rotating member 106 via the second communication portion 128.

  Next, referring to FIG. 5A (c), it can be seen that a central partition wall 120 is formed between the first rotating member 106 and the second rotating member. The central partition wall 120 formed in this way forms a first transport unit 122 and a second transport unit 126 that serve as a developer circulation path.

  Next, referring to FIG. 5B (d), in the DD section, a partition wall is not formed between the first rotating member 106 and the second rotating member 108, as in the BB section. I understand that. As a result, the developer is conveyed from the first rotating member 106 to the second rotating member 108 via the first communication portion 124.

  Next, referring to FIG. 5B (e), in the EE cross section, the end partition wall 118 is provided between the first rotating member 106 and the second rotating member 108 in the same manner as the AA cross section. It can be seen that it is formed. In the developing device 100 according to this embodiment, the end partition wall 118 formed in this way can reliably prevent the developer from entering the bearing portion 114 from the lateral direction.

  Next, referring to FIG. 5B (f), in the FF cross section, a toner supply unit 132 is formed in the developer stirring tank 102 above the second rotating member. Toner is appropriately provided to the developer agitation tank 102 through the toner supply part 132 formed in this way.

  As described above, the developing device 100 according to the present embodiment returns the developer toward the central portion of the rotation shaft at the downstream ends of the first rotating member 106 and the second rotating member 108 in the developer transport direction. A circulation assisting member 116 is provided. Thereby, the developing device 100 according to the present embodiment can prevent the developer from entering the bearing portion 114 from the circulation path and maintain the durability of the bearing portion 114.

  In addition, the developing device 100 according to the present embodiment includes end partition walls 118 between both end portions of the first rotating member 106 and the second rotating member 108, so that the first rotating member 106 and the second rotating member 108 can be connected to each other. It is possible to prevent the developer from entering the bearing portion 114 from the lateral direction.

  Further, in the developing device 100 according to this embodiment, the stirring and conveying member 112 of the first rotating member 106 and the second rotating member 108 conveys the developer more than the central portions of the first communicating portion 124 and the second communicating portion 128. It extends to the downstream side in the direction. As a result, since the developer is conveyed to the downstream side of the first communication portion 124 and the second communication portion 128, the developer is reliably supplied over the entire axial direction of the developing roller 104 without increasing the size of the apparatus itself. can do.

  As a result, the developing device 100 according to the present embodiment can maintain the durability of the bearing portion 114 and can supply the developer over the entire axial direction of the developing roller 104 without increasing the size of the device. is there.

(Design example of developing device 100)
Next, a specific design example of the developing device 100 having the above-described features will be described by showing suitable shape dimensions of each component. Note that the shape dimensions shown in the following description are suitable shape dimensions for realizing the developing device 100 according to the above-described embodiment, and the present invention is not necessarily limited to these values. Moreover, the shape of each figure referred in the following description is a conceptual diagram for explaining a suitable shape dimension, and a dimension ratio etc. differ from an actual dimension ratio.

  FIG. 6 is an explanatory diagram showing the dimensions in the longitudinal direction of the rotating members and the helical pitches of the agitating / conveying member 112 and the circulation assisting member 116 with respect to each component of the developing device 100. FIG. 7 is a cross-sectional view of the developing device 100 and corresponds to the AA cross section of FIG. By designing with the shape and dimensions as shown in FIGS. 6 and 7, it is possible to provide the developing device 100 that can effectively realize the above-described features without increasing the size of the device itself.

  For example, in order to increase the developer conveyance efficiency by the circulation assisting member 116, it is better to increase the spiral pitch and lengthen the section where the circulation assisting member 116 is formed. However, in order to prevent an increase in the size of the developing device main body, it is preferable to design the circulation assisting member 116 with a minimum size as long as the developer can be prevented from entering the bearing portion 114. Specifically, the spiral pitch of the circulation assisting member 116 is set to ¼ or more and ½ or less of the outer diameter dimension of the circulation assisting member 116. As shown in FIG. 7, since the outer diameter dimension of the circulation auxiliary member 116 is 18 mm, the helical pitch of the circulation auxiliary member 116 may be 4.5 mm or more and 9 mm or less. In this design example, as shown in FIG. 5 mm (d, h in FIG. 6).

  Further, the agitating and conveying member 112 formed at the end of the first rotating member 106 on the upstream side in the developer conveying direction can also be designed under the same conditions as the circulation assisting member 116. That is, the helical pitch of the stirring and conveying member 112 at the end of the first rotating member 106 is smaller than the helical pitch (25 mm) of the stirring and conveying member 112 at the center and is the same as the helical pitch (5 mm) of the circulation assisting member 116. (A in FIG. 6).

  Also. The section in which the circulation auxiliary member 116 is formed is 1.5 times or more and 3 times or less, preferably 2 times or more and 2.5 times or less the spiral pitch of the circulation auxiliary member 116, and the developing device by forming the circulation auxiliary member 116 Prevents itself from becoming large. In this design example, since the spiral pitch of the circulation assisting member 116 is 5 mm, the section where the circulation assisting member 116 is formed (d and h in FIG. 6) is 10 mm.

  Further, the end partition wall 118 is formed to extend from the inner wall of the developer agitation tank 102 by a length obtained by adding 0.5 to 1 mm to the length of the section where the circulation auxiliary member 116 is formed. This is because the back-up direction of the circulation assisting member 116 is taken into consideration. In this design example, the section in which the circulation auxiliary member 116 is formed is 10 mm, and therefore the end partition wall 118 is formed to extend 11 mm from the inner wall of the developer stirring tank 102 (j, n in FIG. 6). . Thereby, the space required at the end of each rotating member can be minimized.

  Further, the circulation assisting member 116 and the stirring and conveying member 112 are formed apart from each other by 1 to 2 times the spiral pitch of the circulation assisting member 116. In this design example, since the spiral pitch of the circulation auxiliary member 116 is 5 mm, the circulation auxiliary member 116 is formed 8 mm away from the stirring and conveying member 112 (c and g in FIG. 6).

  Further, a gap section (k in FIG. 6) between the central partition wall 120 and the end partition wall 118 forming the second communication portion 128 is set to 1 of the helical pitch at the central portion of the stirring and conveying member 112 of the first rotating member 106. -1.5 times. Similarly, a gap section (m in FIG. 6) between the central partition wall 120 and the end partition wall 118 forming the first communication portion 124 is set to have a helical pitch at the central portion of the stirring and conveying member 112 of the second rotating member 108. 1 to 1.5 times. In the present design example, since the spiral pitch in the central portion of both the first rotating member 106 and the stirring and conveying member 112 of the second rotating member 108 is 25 mm, the section where the first communicating portion 124 and the second communicating portion 128 are formed is It is 30 mm. As described above, the stirring and conveying member 112 is formed so as to extend from the central portion of the section to the downstream side in the developer conveying direction. That is, the sections c and g shown in FIG. 6 are always located downstream of the central portion of the section where the first communication portion 124 and the second communication portion 128 are formed in the developer transport direction. As a result, the developer can be reliably supplied also to the end portion of the developing roller 104 by the first rotating member 106.

  In order to efficiently transport the developer, it is preferable to reduce the clearance between each rotating member and the developer agitation tank 102, but it is necessary to consider the swing of the rotating member. Therefore, in this design example, as shown in FIG. 7, the clearance between each rotating member and the developer agitation tank 102 is set to 1.5 mm.

  Here, in order to prevent the developer from entering the bearing portion 114 more reliably, the clearance is as shown in FIG. 8 in consideration of the fact that the rotation of the rotating member is smaller at the end than at the center. It can also be a value. Referring to FIG. 8, the clearance between the end of each rotating member and the developer stirring tank 102 is 1.0 mm, which is smaller than the clearance (1.5 mm) at the center. This can be realized, for example, by changing the thickness of the developer stirring tank 102 or the end partition wall 118. As a result, the circulation assisting member 116 can return the developer more efficiently toward the central portion of the rotating shaft, and the bearing 114 can be more reliably protected.

  By designing the developing device 100 with the above dimensions, the features of the above-described embodiment can be efficiently realized without increasing the size of the developing device 100 main body.

  Further, the developing device 100 according to the above-described embodiment can be applied to various types of image forming apparatuses as described above, and the above-described embodiments can be appropriately modified according to the applied image forming apparatus. It can have the following characteristics. For example, the developing device 100 incorporated in the image forming apparatus 10 ′ of the vertical paper conveyance system shown in FIG. 2 is configured as shown in FIG. 9. FIG. 9 is an explanatory diagram illustrating an outline of a configuration example of the developing device 100 incorporated in the image forming apparatus 10 ′ of the vertical paper conveyance method illustrated in FIG. 2.

  In the image forming apparatus 10 ′, the rotation direction of the developing roller 104 is opposite to that of the tandem image forming apparatus 10 shown in FIG. 1 as shown in FIG. 2. Therefore, when the developer circulation path in the developer agitation tank 102 is in the same direction as the above example, as shown in FIG. 9, the first rotating member 106 rotates in the reverse direction to the above example (in the arrow direction in FIG. 9). The spiral winding direction of the agitating / conveying member 112 and the circulation assisting member 116 that are rotated and formed on the first rotating member 106 is also opposite to the above example. As described above, the developing device 100 can arbitrarily change the rotation direction of each rotation member, the spiral winding direction of the stirring and conveying member 112 and the circulation auxiliary member 116, the circulation direction of the developer, and the like according to the design specifications. it can.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the preferred design example of the developing device 100 has been described by exemplifying the shape and dimensions. However, the present invention is not limited to the above-described shape and dimensions. For example, the rotating direction of each rotating member and the spiral winding direction of the stirring / conveying member 112 and the circulation auxiliary member 116 are appropriately changed according to the design specifications such as the method of the image forming apparatus to be applied and the developer circulation path. Also good.

1 is an explanatory diagram showing a configuration of a tandem image forming apparatus 10 including a developing device 100 according to one embodiment of the present invention. FIG. 3 is an explanatory diagram illustrating a configuration of a sheet vertical conveyance type image forming apparatus 10 ′ including the developing device 100 according to the embodiment. FIG. 2 is an explanatory diagram illustrating an outline of a configuration example of a developing device 100 according to the embodiment. FIG. 2 is a schematic external view of a first rotating member and a second rotating member of the developing device 100 according to the same embodiment. FIG. 2 is a cross-sectional view of the developing device 100 according to the same embodiment. FIG. 2 is a cross-sectional view of the developing device 100 according to the same embodiment. In the same embodiment, it is explanatory drawing which shows the suitable shape dimension of the image development apparatus 100. FIG. In the same embodiment, it is explanatory drawing which shows the suitable shape dimension of the image development apparatus 100. FIG. In the same embodiment, it is explanatory drawing which shows the suitable shape dimension of the image development apparatus 100. FIG. It is explanatory drawing which shows the outline of another structural example of the image development apparatus 100 which concerns on the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Photosensitive drum (Image carrier)
DESCRIPTION OF SYMBOLS 14 Cleaning apparatus 16 Imaging unit 18 Light running apparatus 20 Intermediate transfer body 20a Transfer belt 20b Drive roller 20c Tension roller 20d, 20e Support roller 20f Primary transfer roller 20g Secondary transfer roller 20h Transfer roller 22 Recording medium conveyance apparatus 24 Fixing apparatus 24a Heating Roller 24b Pressure roller 26 Charger 28 Conveying roller 30 Recording medium 32 Toner tank 100 Developing device 102 Developer stirring tank 104 Developing roller (developer carrier)
106 Developer supply member (first rotating member)
108 Developer stirring and conveying member (second rotating member)
112 Agitating and conveying member 114 Bearing portion 116 Circulation assisting member 118 End partition wall 120 Central partition wall 122 First conveying portion 124 First communicating portion 126 Second conveying portion 128 Second communicating portion 132 Toner supplying portion

Claims (5)

A developer agitation tank in which a developer circulation path in which a developer composed of toner and a carrier is circulated while being agitated; a developer carrier that carries the developer agitated in the developer circulation path; A developing device comprising:
In the developer stirring tank,
A rotation shaft extending in the same direction as the rotation axis direction of the developer carrying member, and a spiral formed in a predetermined section on the rotation shaft so as to convey the developer while stirring in one of the longitudinal directions of the rotation shaft A blade-shaped stirring and conveying member; and a spiral blade-shaped circulation auxiliary member formed in a predetermined section on the rotation shaft so as to convey the developer toward the central portion of the rotation shaft on the downstream side in the conveyance direction of the developer. A first rotating member for supplying the developer to the developer carrier;
A rotating shaft extending in the same direction as the rotating shaft direction of the first rotating member and disposed alongside the first rotating member; and a direction opposite to the developer conveying direction of the developer by the first rotating member A spiral blade shaped agitating and conveying member formed in a predetermined section on the rotating shaft so as to be conveyed to the rotating shaft, and the rotation so as to convey the developer toward the central portion of the rotating shaft on the downstream side in the conveying direction of the developer. A second rotation member provided with a spiral blade-shaped circulation auxiliary member formed in a predetermined section on the shaft;
Two end partition walls formed between the first rotating member and the second rotating member so as to extend from the inner wall of the developer stirring tank by a predetermined distance along the circulation auxiliary member;
A central partition wall formed between the first rotating member and the second rotating member at a predetermined distance along the stirring and conveying member at a position away from the end partition wall by a predetermined distance;
Formed,
The spiral pitch of the circulation assisting member is ¼ or more and ½ or less of the outer diameter of the circulation assisting member,
The section where the circulation assisting member is formed is 1.5 times or more and 3 times or less of the helical pitch of the circulation assisting member,
The end partition wall and the central partition wall are formed apart by 1 to 1.5 times the helical pitch of the stirring and conveying member, thereby forming a communication portion for circulating the developer.
The stirring and conveying member formed on the first rotating member and the second rotating member is formed to extend from the at least center of the communicating portion to the downstream side in the developer conveying direction,
The circulation auxiliary member is formed separated from the stirring and conveying member by 1 to 2 times the helical pitch of the circulation auxiliary member ,
The developing device according to claim 1, wherein a length of the section in which the circulation assisting member is formed is shorter than a length of the end partition wall .   The clearance between the first rotating member and the second rotating member at the position where the end partition wall is formed and the developer stirring tank is the first rotating member at the position where the central partition wall is formed. The developing device according to claim 1, wherein the developing device is smaller than a clearance between the second rotating member and the developer agitation tank.   The developing device according to claim 1, wherein a section in which the circulation assisting member is formed is not less than 2 times and not more than 2.5 times the spiral pitch of the circulation assisting member. An image carrier on which an electrostatic latent image is formed on the peripheral surface;
A developing device for attaching toner to the electrostatic latent image formed on the peripheral surface of the image carrier;
A cleaning device for removing toner remaining on the surface of the image carrier;
An imaging unit comprising:
The imaging unit according to claim 1, wherein the developing device is the developing device according to claim 1. An image forming apparatus that includes a detachable imaging unit and forms an image on a recording medium,
The image forming apparatus according to claim 4, wherein the imaging unit is the imaging unit according to claim 4.

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