JP2019056890A - Developing device and image forming apparatus - Google Patents

Abstract

To provide a developing device that reduces the possibility of deterioration associated with wear, can prevent the likelihood of the occurrence of a malfunction along with the running time, and can accurately detect the density of a developer, and an image forming apparatus.SOLUTION: A developing device comprises: developer storage means that stores a developer; stirring means that is built in and pivotally supported by the developer storage means; and a developer density detection sensor (60) that detects the density of the developer stirred by the stirring means with a developer density detection unit (56) of the developer storage means. The developing device uses the developer storage means as a casing (50) and the stirring means as a screw (57) for conveying developer, forms a control projection part (61) in non-contact with and in proximity to the screw (57) and having a substantially reverse U-shaped cross section in a projecting manner on the periphery of the developer density detection unit (56) of the casing (50), arranges the developer density detection sensor (60) inside the control projection part (61), and controls the density of the developer with the control projection part (61).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a developing device and an image forming apparatus using a two-component developer containing toner and a magnetic carrier.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines, printers, and facsimiles are known (see Patent Document 1). In the developing device of this image forming apparatus, a two-component developer that is agitated and mixed and frictionally charged in a developer container, specifically, a two-component developer containing a non-magnetic toner and a magnetic carrier is used. The toner is carried on a developer carrying member, and toner is selectively adhered from the developer to the electrostatic latent image on the image carrying member to obtain a toner image.

  However, when the developer is consumed by the development and the toner concentration in the developer is lowered, it is difficult to obtain a high density image. On the other hand, when the toner concentration in the developer is too high, the occurrence of background stains or the like is caused. In order to obtain a high-quality image in this way, it is necessary to control the toner concentration of the developer in the developer accommodating portion carried on the developer carrying member within a certain range.

In view of this point, conventionally, a toner concentration detection device as a detection unit that detects the toner concentration in the developer storage portion on the detection surface, and a developer supply amount control device that controls the amount of developer supply to the developer storage portion. And a developing device that controls the replenishment of the developer into the developer accommodating portion has been proposed.
However, in the developer concentration detection device of this developing device, if the developer stays on the detection surface, it becomes impossible to detect the accurate toner concentration, which causes a malfunction of the developer supply amount control device.

  In view of this point, conventionally, the flat plate member is fixed parallel to the shaft portion at a position facing the detection surface of the shaft portion of the conveying screw that conveys the developer in the developer accommodating portion while stirring. In addition, the elastic sheet is fixed to the flat plate member so as to be parallel, the flat plate member and the elastic sheet are rotated together with the conveying screw, and the elastic sheet is rubbed against the detection surface to thereby detect the detection surface. A technique has been proposed in which the developer is agitated to prevent erroneous detection due to the developer staying on the detection surface of the toner density sensor (see Patent Document 2).

  However, in the case of this technique, the detection value of the toner density sensor changes periodically in accordance with the period in which the elastic sheet during the stirring operation rubs the detection surface. This is because the developer density of the developer on the detection surface changes before and after the elastic sheet slides on the detection surface. In this way, if the developer density of the developer on the detection surface changes and the difference in the agent density on the detection surface during the stirring operation is large, the detection accuracy of the toner density sensor decreases. It is required to reduce the difference.

  Therefore, a developer carrier containing toner and a magnetic carrier-containing developer, and a developer carrier used for development, a casing forming a developer accommodating portion for accommodating the developer supplied to the developer carrier, and a spiral on the shaft portion A conveying screw that conveys the developer in the casing in the axial direction while agitating the developer in the casing by rotating the shaft portion around the shaft portion, and an inner portion of the casing parallel to the shaft portion of the conveying screw. Part of the wall surface becomes a detection surface, and is fixed at a position facing the detection surface of the toner density detecting means for detecting the toner concentration in the developer and the conveyance screw, and the development on the detection surface is performed by rotating the conveyance screw. A detection surface stirring member that stirs the agent, and the detection surface stirring member is an elastic sheet that stirs the developer on the detection surface while being elastically deformed. Wings A developing device arranged to have the same direction of slope and the slope has been proposed (see Patent Document 3).

JP 2008-209592 A JP 05-150650 A JP 2009-205116 A

  As described above, in the conventional developing device, the detection surface agitating member is an elastic sheet, and this elastic sheet is simply arranged with respect to the shaft portion so as to have the same inclination as the inclination of the wing portion with respect to the shaft portion. Therefore, there is a possibility that the elastic sheet comes into contact with the casing and may be deteriorated due to friction, so that a problem is likely to occur with the running time.

  The present invention has been made in view of the above, and can reduce the risk of deterioration due to friction, suppress the occurrence of problems with running time, and can detect the density of the developer with high accuracy. An object is to provide an apparatus and an image forming apparatus.

In the present invention, in order to solve the above problems, a developer containing means for containing the developer, a stirring means built in the developer containing means for rotating and stirring the developer, and the stirring means A developer concentration detecting means for detecting the density of the developer by a developer concentration detecting portion of the developer containing means,
The developer containing means is a casing, the stirring means is a screw for conveying the developer, and a control projection that approaches the screw in a non-contact manner is provided around the developer concentration detection portion of the casing. It is characterized in that the density of the developer is controlled.

The casing can be provided with an opposing control protrusion that faces the developer concentration detector via a screw.
In addition, a control rib for controlling the density of the developer can be provided in a portion of the screw shaft facing the developer concentration detecting portion.
In addition, a control protrusion including a developer concentration detector can be formed larger on the upstream side of the casing where the developer is supplied.

Further, it is possible to form the control projection part in a substantially inverted U-shaped cross section including the developer concentration detection part, and to arrange the developer concentration detection means in this control projection part.
Moreover, it is preferable that the gap dimension L between the developer concentration detecting portion of the casing and the screw is 0.2 mm <L <1.0 mm.

  In order to solve the above problems, the present invention is characterized in that the image forming apparatus includes the developing device according to any one of claims 1 to 6.

  Here, the casing according to the claims is formed in a substantially box shape, and a partition wall that divides the inside of the casing into an upstream space and a downstream space for developer flow is provided at the bottom of the casing, and the upstream space The developer density detector can be formed at the bottom of at least one of the upstream portion, the midstream portion, and the downstream portion of the upstream space. The vicinity of the developer concentration detecting portion of the casing includes at least the vicinity and the periphery including the developer concentration detecting portion of the casing and the developer concentration detecting portion.

  Further, the opposed control protrusion may be opposed to the entire developer concentration detection unit via a screw, or may be opposed to a part of the developer concentration detection unit via a screw. Further, the image forming apparatus includes at least a copying machine, a printer, a facsimile, and the like.

  According to the present invention, a control projection is formed around the developer concentration detection portion of the casing and is opposed to the screw in a non-contact manner, and this control projection narrows the developer distribution space in the vicinity of the developer concentration detection portion. The density of the developer is controlled by restricting the flow of the developer by the control projection.

  According to the present invention, the developer containing means is a casing, the stirring means is a screw for conveying the developer, and a control projection that approaches the screw in a non-contact manner is provided around the developer concentration detecting portion of the casing. Since the density of the developer is controlled with high accuracy by the control protrusions, there is an effect that the possibility of deterioration due to friction can be reduced and the occurrence of problems with running time can be prevented.

1 is an overall explanatory view schematically showing an embodiment of an image forming apparatus according to the present invention. FIG. 3 is an explanatory plan view schematically showing an embodiment of a developing device according to the present invention. It is principal part explanatory drawing which shows typically the relationship between the screw and control projection part in embodiment of the image development apparatus concerning this invention. It is an end surface explanatory drawing which shows typically the relation between a screw and a control projection part in an embodiment of a developing device concerning the present invention. FIG. 6 is a main part explanatory view schematically showing a relationship between a developer concentration detection sensor and a control protrusion in an embodiment of the developing device according to the present invention. In the embodiment of the developing device according to the present invention, a control projection is formed in the vicinity of the developer concentration detection portion in the midstream portion of the upstream space, and the gap dimension L between the developer concentration detection portion of the control projection and the screw blade is set to 0. FIG. 6 is a graph compared with a case where a control protrusion is not formed in the vicinity of the developer concentration detecting portion in the upstream midstream portion after setting to 60 mm. In the embodiment of the developing device according to the present invention, a control projection is formed near the upstream side of the developer concentration detection unit in the midstream portion of the upstream space, and the gap size between the developer concentration detection unit of this control projection and the screw blades When L is set to 0.60 mm, a control projection is formed near the downstream side of the developer concentration detection unit in the midstream portion of the upstream space, and the gap between the developer concentration detection unit of this control projection and the blade of the screw It is the graph which compared with the case where the dimension L is set to 0.60 mm. It is principal part explanatory drawing which shows typically the relationship between the screw and control projection part in 2nd Embodiment of the developing device which concerns on this invention. It is principal part explanatory drawing which shows typically the relationship between the screw in the 3rd Embodiment of the developing device which concerns on this invention, a control projection part, and a control rib. In the embodiment of the developing device according to the present invention, a control projection is formed in the vicinity of the developer concentration detection section in the middle portion of the upstream space, and the gap dimension L between the surface of the developer concentration detection section of this control projection and the blade of the screw is set. After setting to 0.54 mm, a graph comparing the case where the control rib facing the developer concentration detecting portion is mounted on the rotating shaft of the screw and the case where the control rib facing the developer concentration detecting portion is not mounted. is there.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, an image forming apparatus 1 according to the present embodiment includes a photosensitive drum 2 on which an electrostatic latent image is formed. The charger 3 as a charging device for charging the surface of the photosensitive drum 2, the exposure unit 4 as an exposure device for forming an electrostatic latent image on the surface of the photosensitive drum 2, and the surface of the photosensitive drum 2. A developing device 5 for supplying a two-component developer containing toner to an electrostatic latent image to form a toner image, a developer replenishing device 6 for replenishing the developing device 5 with a developer, and a photosensitive drum 2 An intermediate transfer belt unit 9 that is a transfer device that transfers a toner image on the surface to a recording medium, a cleaner unit 16 that removes excess developer remaining on the surface of the photosensitive drum 2, and a toner image is fixed to the recording medium. Fixing unit is a fixing device , And an image forming apparatus using a developer by an electrophotographic method, and a predetermined sheet (recording paper, recording medium, etc.) as a recording medium according to image data output from the outside. A multicolor or single color image is formed.

  The image forming apparatus 1 handles image data for each color component of black (K), cyan (C), magenta (M), and yellow (Y), and forms a black image, a cyan image, a magenta image, and a yellow image. A color image is formed by superimposing the images of the respective color components. Therefore, in the image forming apparatus 1, four each of the photosensitive drum 2, the charger 3, the developing device 5, and the cleaner unit 16 are installed so as to form an image of each color component.

  That is, the image forming apparatus 1 is provided with four image forming stations (image forming units) each including the photosensitive drum 2, the charger 3, the developing device 5, and the cleaner unit 16. In addition to the above, the image forming apparatus 1 is provided with a paper feed tray 20, a sheet conveyance path 21, and a paper discharge tray 28.

  The photosensitive drum 2 is formed in a cylindrical shape, and an intermediate transfer belt unit 9 is disposed above the photosensitive drum 2, and excess developer remaining on the surface after the development and image transfer processes is removed by the cleaner unit 16. Removed and recovered. The charger 3 functions to uniformly charge the surface of the photosensitive drum 2 to a predetermined potential. As the charger 3, a contact brush type, a non-contact charger type, or the like is appropriately used in addition to the contact roller type shown in FIG.

  As shown in FIG. 1, the exposure unit 4 uses a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror. However, in addition to the laser scanning unit, the exposure unit 4 may be an EL (electroluminescence) in which light emitting elements are arranged in an array or an LED writing head. Such an exposure unit 4 functions to form an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 2 by exposing the charged photosensitive drum 2 according to the input image data. To do.

  The developing device 5 functions to visualize (develop) the electrostatic latent image formed on the photosensitive drum 2 with any one of the developer toners K, C, M, and Y. Above the developing device 5, a developer replenishing device 6, a developer transfer mechanism 7, and a developing tank (developer container) 8 are disposed. The developer supply device 6 stores unused developer (powder-like developer) and is disposed above the developing tank 8. The developer supply device 6 supplies the developer to the developing tank 8 via the developer transfer mechanism 7.

  The intermediate transfer belt unit 9 includes an intermediate transfer roller 10, an intermediate transfer belt 11, an intermediate transfer belt drive roller 12, an intermediate transfer belt driven roller 13, an intermediate transfer belt tension mechanism 14, and an intermediate transfer belt cleaning unit 15. Arranged above the drum 2. The intermediate transfer roller 10, the intermediate transfer belt drive roller 12, the intermediate transfer belt driven roller 13, and the intermediate transfer belt tension mechanism 14 stretch the intermediate transfer belt 11 and rotate the intermediate transfer belt 11.

  The intermediate transfer roller 10 is rotatably supported by an intermediate transfer roller mounting portion in the intermediate transfer belt tension mechanism 14 of the intermediate transfer belt unit 9. A transfer bias for transferring the toner image on the photosensitive drum 2 onto the intermediate transfer belt 11 is applied to the intermediate transfer roller 10.

  The intermediate transfer belt 11 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm, and is provided so as to be in contact with each photosensitive drum 2. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 11 by sequentially superimposing and transferring the toner images of the respective color components formed on the photosensitive drum 2.

  Transfer of the toner image from the photosensitive drum 2 to the intermediate transfer belt 11 is performed by the intermediate transfer roller 10 that contacts the back side of the intermediate transfer belt 11. In order to transfer the toner image, a high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 10.

  The intermediate transfer roller 10 is formed based on a metal (for example, stainless steel) shaft having a diameter of, for example, 8 to 10 mm, and the surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, the intermediate transfer roller 10 functions to apply a high voltage uniformly to the intermediate transfer belt 11. In this embodiment, a roller type (intermediate transfer roller type) is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic latent image on each photosensitive drum 2 is visualized by a developer corresponding to each color component to become a toner image, and these toner images are superimposed on the intermediate transfer belt 11 and stacked. Is done. The toner images stacked in this manner are moved to a contact position (transfer portion) between the conveyed sheet and the intermediate transfer belt 11 by the rotation of the intermediate transfer belt 11, and are transferred by a transfer roller disposed at this position. Transferred onto the sheet.

  In this case, the intermediate transfer belt 11 and the transfer roller are pressed against each other at a predetermined nip, and a voltage for transferring the toner image onto the sheet is applied to the transfer roller. This voltage is a high voltage having a polarity (+) opposite to the charging polarity (−) of the toner of the developer. In order to constantly obtain a predetermined nip, either the transfer roller or the intermediate transfer belt drive roller 12 is formed of a hard material such as metal, and the other is a soft material such as an elastic roller (an elastic rubber roller or a foaming resin). Roller).

  Due to the contact between the intermediate transfer belt 11 and the photosensitive drum 2, the developer adhering to the intermediate transfer belt 11 and the toner image remaining on the intermediate transfer belt 11 are not transferred when transferring the toner image from the intermediate transfer belt 11 to the sheet. Since the developer causes toner color mixing in the next step, the developer is removed and collected by the intermediate transfer belt cleaning unit 15.

  The intermediate transfer belt cleaning unit 15 includes a cleaning blade (cleaning member) that contacts the intermediate transfer belt 11. The portion of the intermediate transfer belt 11 that is in contact with the cleaning blade is supported by the intermediate transfer belt driven roller 13 from the back side.

  The fixing unit 17 includes a heat roller 18 and a pressure roller 19 that face each other, and the heat roller 18 and the pressure roller 19 rotate while sandwiching the sheet. The heat roller 18 is controlled by a control unit (not shown) so as to have a predetermined fixing temperature. This control unit controls the temperature of the heat roller 18 based on a detection signal from a temperature detector (not shown). The heat roller 18 functions so as to heat and press the sheet together with the pressure roller 19 to melt, mix, and press the color toner images transferred to the sheet, and to thermally fix the sheet.

  The sheet on which the multicolor toner image (each color toner image) is fixed is conveyed to the reverse discharge path of the sheet conveyance path 21 by the plurality of conveyance rollers 26 of the sheet conveyance path 21 and is reversed (multicolor). The toner image is discharged onto the paper discharge tray 28 in a state where the toner image faces downward.

  The paper feed tray 20 is a tray for accumulating sheets (for example, recording paper) used for image formation, and is installed below the image forming unit and the exposure unit 4. The sheet conveyance path 21 is a conveyance path for guiding the sheet on the paper feed tray 20 and the sheet on the manual feed tray 22 to the paper discharge tray 28 via the transfer unit and the fixing unit 17. In the sheet conveyance path 21, a plurality of pickup rollers 27, a registration roller 24, a transfer unit, a fixing unit 17, a plurality of conveyance rollers 26, and the like are disposed.

  Of the plurality of pickup rollers 27, one pickup roller 27 is provided at the end of the sheet feeding tray 20, and functions as a calling roller that supplies sheets one by one from the sheet feeding tray 20 to the sheet conveyance path 21. The other pickup roller 27 is provided in the vicinity of the manual feed tray 22 and functions as a drawing roller that supplies sheets one by one from the manual feed tray 22 to the sheet conveyance path 21.

  The registration roller 24 is a roller that temporarily holds the sheet conveyed through the sheet conveyance path 21 and conveys the sheet to the transfer unit at a timing when the leading edge of the toner image on the intermediate transfer belt 11 and the leading edge of the sheet are aligned. . The transfer unit is located between the intermediate transfer belt drive roller 12 and the transfer roller. The plurality of conveyance rollers 26 are small rollers for promoting and assisting conveyance of the sheet, and are pivotally supported along the sheet conveyance path 21. The paper discharge tray 28 is a tray provided on the upper part of the image forming apparatus 1 and functions to load printed sheets face down.

  Next, the developing device 5 will be described in detail. As shown in FIGS. 2 to 5, the developing device 5 in the present embodiment is for containing a two-component developer containing a non-magnetic toner and a magnetic carrier. The casing 50, a plurality of screws 57, 57 </ b> A incorporated in the casing 50 for stirring and conveying the developer, and the developer density detecting unit 56 of the casing 50 detects the density of the developer stirred by the screw 57. And a control projection 61 that restricts the flow of the developer by approaching the screw 57 around the developer concentration detection portion 56 of the casing 50. The density of the developer is controlled by this control projection 61.

  As shown in FIGS. 2 to 4, the casing 50 is injection-molded into a substantially rectangular box shape with a predetermined resin-containing molding material, and in the longitudinal direction (right and left in FIG. A partition wall 51 extending in the direction) is erected, and the partition wall 51 forms an internal width direction (vertical direction in FIG. 2) into an upstream space 52 and a downstream space 53 in which the developer flows. The upstream portion of the upstream space 52 is supplied with developer from above.

  At both ends of the partition wall 51, communication ports that connect the upstream space 52 and the downstream space 53 are respectively formed. One of the pair of communication ports allows the developer to flow downstream from the upstream space 52. From the downstream space 53 to the upstream portion of the upstream space 52, and the other communication port is formed in the outflow passage 55 for flowing the developer from the downstream portion of the downstream space 53 to the upstream portion of the upstream space 52. Is done. A part of the upstream portion, the midstream portion, or the bottom portion of the downstream portion of the upstream space 52 is formed in a developer concentration detection unit 56 that detects the concentration and density of the developer. Among these, it is preferable that a part of the middle portion of the upstream space 52 in which the density of the developer can be stabilized and a part of the bottom portion of the downstream portion are partially formed in the developer concentration detecting portion 56.

  Of the bottom portion of the casing 50 and the developer concentration detection unit 56 thereof, at least the thickness of the developer concentration detection unit 56 is the thickness of the wall of the casing 50 from the viewpoint of improving the detection sensitivity of the developer concentration detection sensor 60. It is preferable to be formed thinner. For example, when the wall thickness of the casing 50 is 2 mm, it is formed to 1.8 mm or less, and when the wall thickness of the casing 50 is 1.5 mm, it is formed to 1.2 mm or less. .

  As shown in FIGS. 2 to 4, the plurality of screws 57 and 57 </ b> A are horizontally incorporated and supported in the upstream space 52 and the downstream space 53 of the casing 50, respectively, and rotate to rotate a nonmagnetic toner as a developer. The magnetic carrier is stirred and mixed to be charged, and the developer is transported. Each of the screws 57 and 57A includes a rotary shaft 58 that is pivoted between both end walls of the casing 50 via a bearing, and a spiral blade 59 that is integrally formed on the peripheral surface of the rotary shaft 58 and pushes out the developer. The rotary shaft 58 is rotated via a gear by driving of the motor.

  From the viewpoint of avoiding collision between the blade 59 and the inner bottom surface of the casing 50, the wall, and the partition wall 51, the peripheral portion of the blade 59 forms a small gap. At the peripheral edge of the blade 59, the gap dimension L with respect to the developer concentration detecting unit 56 is set in a range of 0.2 mm <L <1.0 mm, preferably 0.3 mm <L <0.6 mm. This is because the detection sensitivity of the developer concentration detection sensor 60 can be improved if the gap dimension L with respect to the developer concentration detection unit 56 is within the range of 0.2 mm <L <1.0 mm.

  Of the pair of screws 57 and 57A, the upstream screw 57 rotates to stir and mix the developer toner and the magnetic carrier in the upstream space 52 to charge the developer in the upstream space 52 in the downstream portion. Is conveyed to the downstream space 53 via the inflow channel 54. In contrast, the downstream screw 57A rotates to stir and mix the developer toner and the magnetic carrier in the downstream space 53, and charges the developer in the downstream space 53 via the outflow passage 55 in the downstream portion. Then, it is conveyed to the upstream space 52.

  The developer concentration detection sensor 60 includes, for example, a magnetic permeability sensor that detects the concentration and density of the developer by changing the magnetic permeability of the developer. As shown in FIGS. 3 and 5, the developer concentration detection sensor 60 is installed in the developer concentration detection unit 56 of the casing 50 from below.

  As shown in FIGS. 3 to 5, the control protrusion 61 is bent and formed in a substantially inverted U-shaped cross section in the vicinity of the developer concentration detecting portion 56 in the upstream space 52 of the casing 50 and larger than the developer concentration detecting portion 56. At the same time, the upstream space 52 is narrowed close to the blades 59 of the screw 57 in a non-contact manner from below, and the developer concentration detection sensor 60 is built in the hollow inside, so that the density of the developer in the upstream space 52 is set. It functions to control with high precision. The control protrusion 61 is formed in a substantially U-shaped cross section, a substantially convex cross section, a substantially dish-shaped cross section, or the like as necessary.

  The control protrusion 61 may be approximately the same size as the developer concentration detection unit 56, but partially narrows the upstream space 52 in the vicinity of the developer concentration detection unit 56, thereby reducing the flow of the developer and increasing its flow rate. From a viewpoint, it is preferable that the developer concentration detector 56 is formed large so as to surround and include the front, rear, left and right in a plan view. The wall thickness of the control protrusion 61 is formed thinner than the wall thickness of the casing 50 in order to improve the detection sensitivity of the developer concentration detection sensor 60. For example, when the wall thickness of the casing 50 is 2 mm, it is formed to be 1.8 mm or less, and when the wall thickness is 1.5 mm, it is 1.2 mm or less.

  The flat surface of the developer concentration detector 56 that is a part of the control protrusion 61 has a gap dimension L with the blade peripheral edge of the screw 57 of 0.2 mm <L <1.0 mm, preferably 0.3 mm <L. <0.6 mm is adjusted. This is because an improvement in the detection sensitivity of the developer concentration detection sensor 60 can be expected if the gap dimension L with the peripheral edge of the blade 59 is in the range of 0.2 mm <L <1.0 mm.

  According to the above configuration, the elastic sheet is not disposed on the shafts of the screws 57 and 57 </ b> A so as to have the same inclination as the blade 59, but is thin around the developer concentration detector 56 of the casing 50. The control projection 61 is formed to project and face the blade peripheral portion of the screw 57 in a non-contact manner. Since the developer concentration detection sensor 60 is built in the control projection 61, the elastic sheet and the control projection 61 are attached to the casing. The possibility of contact with 50 and deterioration due to friction can be eliminated.

  Further, since it is possible to effectively prevent the occurrence of problems with the running time, the density of the developer flowing around the developer concentration detecting unit 56 in the upstream space 52 can be controlled with high accuracy. Further, a control projection 61 is formed in the middle of the upstream space 52 in the vicinity of the developer concentration detection unit 56, and the surface of the developer concentration detection unit 56 that is a part of the control projection 61 and the blade periphery of the screw 57. As compared with the case where the control protrusion 61 is not formed in the vicinity of the developer concentration detecting portion 56 in the midstream portion of the upstream space 52 after setting the gap dimension L to the portion to 0.60 mm, the developer concentration detecting sensor 60 is compared. It has been found that the detection sensitivity characteristics can be greatly improved (see FIG. 6).

  Further, a control projection 61 is formed to protrude in the vicinity of the upstream side of the developer concentration detection unit 56 in the middle portion of the upstream space 52, and the surface of the developer concentration detection unit 56 that is a part of the control projection 61 and the screw 57. When the gap dimension L with respect to the peripheral edge of the blade is set to 0.60 mm, a control projection 61 is formed to project in the vicinity of the downstream side of the developer concentration detection unit 56 in the midstream portion of the upstream space 52, and this control projection Compared with the case where the gap dimension L between the surface of the developer concentration detecting portion 56 which is a part of 61 and the blade peripheral edge portion of the screw 57 is set to 0.60 mm, the detection sensitivity characteristic of the developer concentration detecting sensor 60 is high and excellent. The correlation (R2 value) was found to be obtained (see FIG. 7).

  Next, FIG. 8 shows a second embodiment of the present invention. In this case, the developer concentration detecting portion 56 of the control projection 61 is opposed to the upper portion of the casing 50 from above via a screw 57. The opposing control protrusion 62 is attached.

The opposing control projection 62 is formed, for example, as a flat plate, and comes close to the peripheral edge of the blade 59 of the screw 57 from the upper side in a non-contact manner, and functions to narrow the upstream space 52 and narrow the developer flow. The opposing control projection 62 is formed in a substantially inverted U-shaped section, a generally convex section, a substantially dish-shaped section, or the like as necessary. The other parts are the same as those in the above embodiment, and the description thereof is omitted.
In this embodiment, the same effect as that of the above embodiment can be expected, and the density of the developer flowing around the developer concentration detecting unit 56 in the upstream space 52 can be controlled with high accuracy. .

  Next, FIG. 9 shows a third embodiment of the present invention. In this case, development is performed on the circumferential surface of the rotating shaft 58 of the screw 57 facing the developer concentration detecting portion 56 and the control projection 61. A control rib 63 for controlling the density of the agent is attached.

The control rib 63 is formed in, for example, a small block shape having a rectangular cross section, and functions to narrow the flow of the developer by partially narrowing the upstream space 52. The gap dimension L2 between the control rib 63 and the surface of the developer concentration detecting unit 56 is set to satisfy the relationship of L2 ≦ L1 with the relationship of the gap dimension L1 between the surface of the developer concentration detecting unit 56 and the blade peripheral edge of the screw 57. The The other parts are the same as those in the above embodiment, and the description thereof is omitted.
In this embodiment, the same effect as the above embodiment can be expected, and the density of the developer flowing around the developer concentration detecting unit 56 in the upstream space 52 can be controlled with high accuracy.

  Further, a control projection 61 is formed in the middle of the upstream space 52 in the vicinity of the developer concentration detection unit 56, and the surface of the developer concentration detection unit 56 that is a part of the control projection 61 and the blade periphery of the screw 57. The gap L between the first and second portions is set to 0.54 mm, and then the control rib 63 facing the developer concentration detecting unit 56 is mounted on the circumferential surface of the rotating shaft 58 of the screw 57, and the developer concentration detecting unit 56 When the control rib 63 facing the developer concentration detecting unit 56 is mounted, the detection sensitivity of the developer concentration detecting sensor 60 can be greatly improved. Was found (see Figure 10)

  Note that a scanner or the like may be provided above the image forming apparatus 1 in the embodiment. Further, the control protrusion 61 may be integrally formed around the developer concentration detection part 56 of the casing 50, or a separate control protrusion 61 may be formed to protrude. In addition, the opposing opposing walls of the control protrusion 61 having a substantially inverted U-shaped cross section are inclined, thereby making the control protrusion 61 a substantially dish-shaped cross section and preventing the developer from staying near the upright opposing wall. You may make it do. Further, the opposing control protrusion 62 and the control rib 63 may be single or plural. Further, the image forming apparatus 1 may be a device that forms a color image, or may be a device that forms a monochrome image.

  The developing device and the image forming apparatus according to the present invention are used in the field of manufacturing copiers, printers, facsimiles and the like.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photosensitive drum 3 Charger 4 Exposure unit 5 Developing apparatus 6 Developer supply apparatus 9 Intermediate transfer belt unit 16 Cleaner unit 17 Fixing unit 50 Casing 51 Partition wall 52 Upstream space (upstream side)
53 Downstream space 56 Developer concentration detector 57 Screw 57A Screw 58 Rotating shaft (shaft)
59 Blade 60 Developer concentration detection sensor (Developer concentration detection means)
61 Control protrusion 62 Opposite control protrusion 63 Control rib

Claims (7)

Developer containing means for containing the developer, stirring means incorporated in the developer containing means for rotating and stirring the developer, and the density of the developer stirred in the stirring means is developed by the developer containing means. A developer concentration detection means for detection by the agent concentration detection unit,
The developer containing means is a casing, the stirring means is a screw for conveying the developer, and a control projection that approaches the screw in a non-contact manner is provided around the developer concentration detection portion of the casing. A developing device characterized in that the density of the developer is controlled.   The developing device according to claim 1, wherein the casing is provided with an opposing control protrusion that opposes the developer concentration detecting portion via a screw.   The developing device according to claim 1, wherein a control rib for controlling the density of the developer is provided at a portion of the shaft portion of the screw facing the developer concentration detecting portion.   4. The developing device according to claim 1, wherein a control protrusion including a developer concentration detecting portion is formed largely on an upstream side of a casing to which developer is supplied.   5. The developing device according to claim 4, wherein the control protrusion is formed in a substantially inverted U-shaped cross section including the developer concentration detection portion, and developer concentration detection means is disposed in the control protrusion.   The developing device according to claim 1, wherein a gap dimension L between the developer concentration detecting portion of the casing and the screw is 0.2 mm <L <1.0 mm.   An image forming apparatus comprising the developing device according to claim 1.

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