JP2017015942A - Development device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a development device and an image formation apparatus which can suppress toner scattering.SOLUTION: A development device includes: a developer carrier; a development casing which forms a developer storage part storing a developer; and developing bias application means which applies a developing bias to the developer carrier; a gap formation member which is a different body from the development casing, arranged on the downstream side in the rotation direction of the developer carrier with respect to a development region, has a plurality of conductive members so that the adjacent conductive members hold the insulation member in the rotation direction of the developer carrier, is configured so that surfaces facing the developer carrier of the plurality of conductive members and insulation member are flush with each other, and forms a gap between the surface of the developer carrier and itself; and voltage application means which applies the voltage having the same polarity as the normal electrification polarity of toner to the plurality of conductive members so as to form an electric field by which the toner is moved with an electrostatic force toward the developer carrier side from the conductive member side.SELECTED DRAWING: Figure 1

Description

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

  In general, a developing device used in an electrophotographic image forming apparatus includes a casing that contains a developer containing at least toner, and a developer that is contained in the casing on the surface thereof and is opposed to the latent image carrier. It is composed of a developer carrying member or the like that is conveyed to a developing area that is an area.

  In the developing device described in Patent Document 1, two electrodes are arranged in the developing roller rotation direction on the opposite surface of the casing facing the developing roller with a predetermined gap on the downstream side of the developing region in the rotation direction of the developing roller. They are arranged side by side. A voltage having the same polarity as the normal charging polarity of the toner is applied to each electrode, and an electric field is formed between the developing roller and the electrode so that the toner moves in the direction of the developing roller, and is floating in the gap. It is said that toner scattering can be suppressed by returning the toner onto the developing roller.

  However, in the configuration in which the electrode is disposed on the facing surface of the casing facing the developing roller as in the developing device described in Patent Document 1, the portion where the electrode is disposed on the facing surface and the electrode are not disposed. The size of the gap differs depending on the location. Therefore, the gap cannot be set with high accuracy.

  If the gap cannot be set with high accuracy, for example, the following problem may occur. That is, on the downstream side of the developing region in the rotation direction of the developing roller, the surface of the developing roller exposed to the outside of the casing in the developing region moves toward the inside of the casing, so that the air near the surface of the developing roller A suction air flow that is an air flow toward the inside is generated. However, if the gap is too wide, a gap is generated between the tip of the developer magnetic brush carried on the surface of the developing roller and the opposed surface of the casing. When the pressure inside the casing rises due to the suction airflow, a discharge airflow that is an airflow going from the inside of the casing to the outside is generated so that the pressure that has risen from this gap is released, and the above-described toner scattering suppression effect can be sufficiently obtained. There is a risk of being lost. On the contrary, if the gap is too narrow, the entire amount of the developer on the developing roller that has passed through the developing region cannot pass through the gap, and the developer may overflow.

  In order to solve the above-described problems, the present invention provides a developing device that transports a developer to a developing region facing the surface of the latent image carrier by carrying and rotating at least a developer containing toner on the surface. And a developer casing that forms a developer accommodating portion that accommodates the developer. The developer carrier is separate from the developer casing and is located downstream of the developing region in the rotation direction of the developer carrier. A plurality of conductive members arranged in the rotation direction of the developer carrier, with an insulating member sandwiched between adjacent conductive members, and the developer carrier of the plurality of conductive members and the insulating member; The opposing surfaces are configured to be flush with each other, a gap forming member that forms a gap with the surface of the developer carrier, and a space between the plurality of conductive members and the developer carrier. In the conductive member side As the electric field as the toner is moved by the electrostatic force toward the developer bearing member is formed, and having a voltage applying means for applying a voltage to the plurality of conductive members.

  As described above, according to the present invention, there is an excellent effect that toner scattering can be suppressed.

1 is a schematic configuration diagram of a developing device according to Configuration Example 1. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. The schematic block diagram of a liquid cooling device. FIG. 3 is an enlarged configuration diagram illustrating a developing device and a photoreceptor provided in the image forming unit. The perspective view which showed the flow of the developer of the lower stage of a developing device. The perspective view which showed the flow of the developer of the upper stage of a developing device. FIG. 3 is a perspective cross-sectional view of a developing device for explaining the flow of the developer in the developer transport path. FIG. 3 is a schematic diagram of a developer flow in a developing device. The figure which showed the bias | deviation of the developer of the developer conveyance direction downstream vicinity part in the stirring conveyance path. The developer transported by the stirring screw near the downstream end of the developer transport direction of the stirring transport path from the vicinity of the downstream end of the developer transport direction of the stirring transport path to the upstream end of the supply transport path in the developer transport direction The figure which showed the flow of the developer in the part conveyed upwards to the vicinity. The graph which showed the relationship between the time passage of a developing device, and a temperature change. FIG. 3 is an enlarged view of a gap forming member provided in the developing device according to Configuration Example 1. The enlarged view of the square hole opened in the gap formation member. FIG. 4 is an explanatory diagram of an electric field that guides toner floating between the developing roller and the developing roller facing portion to the inside of the developing case. FIG. 4 is an explanatory diagram of an electric field in which toner moves in the direction of the developing roller formed between the developing roller and a conductive layer. FIG. 6 is a schematic configuration diagram of a developing device according to Configuration Example 2. FIG. 10 is a schematic configuration diagram of a developing device according to Configuration Example 3;

  Hereinafter, an embodiment in which the present invention is applied to an image forming apparatus will be described. First, the configuration and operation of the image forming apparatus according to the present embodiment will be described. FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the present embodiment. The image forming apparatus of FIG. 2 includes an image forming unit 1 in which four image forming units 11Y, 11M, 11C, and 11K are arranged in parallel. Each of the image forming units 11Y, 11M, 11C, and 11K is a drum-shaped photoconductor 18Y, M, C, K serving as a latent image carrier, a drum cleaning unit 12Y, M, C, K, and a charging unit 13Y, M, C, K, a two-component developing type developing device 40Y, M, C, K, etc. are housed in a frame. These image forming units 11Y, 11M, 11C, and 11K are detachable from the printer main body, so that consumable parts can be replaced at a time.

  Above the image forming unit 1, an exposure unit 9 is provided as a latent image forming unit. In addition, a reading device 10 that scans and reads a document placed on a contact glass is provided at the top of the device. Below the image forming unit 1, a transfer unit 2 including an intermediate transfer belt 15 as an intermediate transfer member is provided. The intermediate transfer belt 15 is stretched around a plurality of support rollers, and rotates in the clockwise direction in the drawing. A secondary transfer device 4 is provided below the transfer unit 2. The secondary transfer device 4 includes a secondary transfer roller 17, and the secondary transfer roller 17 abuts on the intermediate transfer belt 15 where the intermediate transfer belt 15 is wound around the transfer counter roller 16 from the belt front surface and performs secondary transfer. A nip is formed. A secondary transfer bias is applied to the secondary transfer roller 17 by a power source. The transfer counter roller 16 is electrically grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

  On the left side of the secondary transfer device 4 in the figure, a fixing unit 7 having a heating roller having a heating element therein is provided in order to fix the toner image transferred onto the paper. In addition, a conveyance belt 6 is provided between the secondary transfer device 4 and the fixing unit 7 to convey the sheet after transfer of the toner image to the fixing unit 7. A paper feed unit 3 is provided below the apparatus to feed paper that is separated and fed one by one from the paper feed storage unit to the secondary transfer device 4. In addition, a paper discharge unit 8 that transports the paper that has passed through the fixing unit 7 to the outside of the apparatus or to the duplex unit 5 is provided.

  When making a copy with this image forming apparatus, the reading apparatus 10 reads the document. In parallel with this document reading, the intermediate transfer belt 15 moves in the clockwise direction in the figure. At the same time, in the image forming unit 1, yellow, magenta, cyan, black on the photoreceptors 18 Y, M, C, and K charged by the charging units 13 Y, M, C, and K based on the read document contents. Each of the color-specific information is used for exposure by the exposure unit 9 to form a latent image. Next, the latent images on the photoconductors 18Y, 18M, 18C, and 18K are developed by the developing devices 40Y, 40M, 40C, and 40K to form single-color toner images (developed images). Then, the toner images on the photoconductors 18Y, 18M, 18C, and 18K are sequentially transferred so as to overlap each other on the intermediate transfer belt 15 to form a composite toner image on the intermediate transfer belt 15. The photosensitive members 18Y, 18M, 18C, and 18K after the transfer of the toner image are removed by the drum cleaning units 12Y, 12M, 12C, and 12K to remove residual toner remaining on the photosensitive members 18Y, 18M, 18C, and 18K. Prepare for image formation.

  In parallel with the toner image formation, the paper is fed out from the paper feed storage unit one by one, and abutted against the registration roller 14 and stopped. Then, the registration roller 14 is rotated in synchronization with the formation of the composite toner image on the intermediate transfer belt 15, the sheet is fed between the intermediate transfer belt 15 and the secondary transfer device 4, and is transferred by the secondary transfer device 4. Then, the toner image is transferred onto the paper. The sheet on which the toner image has been transferred is conveyed by the conveying belt 6 and sent to the fixing unit 7. The fixing unit 7 applies heat and pressure to fix the toner image, and then the sheet is sent to the paper discharge unit 8. The paper discharge unit 8 is switched by a switching claw and guided to a paper discharge tray outside the apparatus (on the left side of the apparatus) or the lower duplex unit 5. In the duplex unit 5, the sheet is reversed and guided again to the secondary transfer position (nip position between the secondary transfer device 4 and the intermediate transfer belt 15). Eject onto the output tray. The intermediate transfer belt 15 after image transfer is removed by the intermediate transfer belt cleaning unit 90 to remove the residual toner remaining on the intermediate transfer belt 15 and prepare for image formation again.

  Here, in the image forming apparatus, from the viewpoint of reducing the size of the machine, the arrangement is such that the fixing unit 7 is pulled down to the lower side of the transfer unit 2 together with the higher density inside the machine. In the image forming apparatus of FIG. 2, the intermediate transfer belt 15 is bent so as to cover the upper surface and the right side surface of the fixing unit 7. With this configuration, the height direction and width direction of the apparatus are made compact. However, if the fixing unit 7 is brought close to the intermediate transfer belt 15, the intermediate transfer belt 15 is thermally affected and deformed by the fixing unit 7, which is a heating element, and image defects such as color misregistration may occur. . This has become more prominent due to an increase in the amount of heat generated inside the apparatus as the speed of the apparatus increases. Further, during double-sided printing, the paper heated by the fixing unit 7 passes through the double-sided unit 5 and again contacts the intermediate transfer belt 15 at the secondary transfer position. Therefore, the intermediate transfer belt is further transferred by heat transfer from the paper. The temperature of 15 rises and becomes a more severe condition. Further, heat is also transmitted to the photosensitive members 18Y, 18M, 18C, and 18K that are in contact with the intermediate transfer belt 15, and further to the developing devices 40Y, M, C, and K, and image defects due to belt deformation, solidification of toner, and the like. Problems are more likely to occur.

  Therefore, a heat insulating device 20 is provided between the fixing unit 7 that is a heat source and the intermediate transfer belt 15 that is disposed in the vicinity of the fixing unit 7. Although the heat insulating device 20 is often composed of an air flow by a duct, here, a heat insulating device using a heat pipe will be described. This is mainly composed of a heat receiving plate 21, a heat pipe 22, a heat radiating plate 23, a duct 24 and an exhaust fan. The heat receiving plate 21 that is a heat receiving member is formed of a material that easily absorbs heat, and is disposed between the fixing unit 7 that is a heat generation source and the transfer unit 2 that is a protection target portion to be protected from the influence of the heat. . The heat pipe 22 as a heat transfer means (heat transport means) is attached to the lower surface of the heat receiving plate 21, and one end portion (lower end portion) side thereof is a heat receiving portion. The other end side of the heat pipe 22 is a heat radiating portion, and is mounted on the heat radiating plate 23 at a position higher than the heat receiving portion. The heat radiating plate 23 that is a heat radiating member is formed of a material that easily releases heat, and a heat sink may be provided as necessary.

  In this example, the duct 24 extends from the front surface to the back surface of the image forming apparatus main body, and is provided so that the heat radiating plate 23 is positioned inside the duct. An air inflow port is provided at the front side end of the duct 24, an exhaust port is provided at the back side end, and an exhaust fan is provided at the exhaust port. The heat insulating device 20 configured as described above receives heat from the heat generating portion (the fixing unit 7 in this example) by the heat receiving plate 21, and the heat is transferred to the heat radiating portion (heat radiating plate 23) by the heat pipe 22 serving as heat transfer means. Transported up to. Then, heat is released from the heat radiating plate 23 in the duct 24, and the released heat is discharged to the outside by an exhaust fan. Note that it is possible to perform natural cooling without providing an exhaust fan.

  In this way, the influence of the fixing heat is cut off, and the image forming units 11Y, 11M, 11C, and 11K, and the transfer unit 2 that are the protection targets are effectively protected, thereby preventing color misregistration due to deformation of the intermediate transfer belt 15 and the like. The occurrence of troubles and troubles due to toner solidification is prevented in advance.

  In the developing device, when the developer agitating and conveying member that agitates and conveys the developer accommodated in the developing case which is a developer accommodating container is driven, friction caused by friction between the developer agitating and conveying member and the developer is generated. The temperature in the developing device 40 is increased by heat or frictional heat generated by rubbing between the developers. In addition, the friction heat generated by the friction between the developer regulating member and the developer that regulates the layer thickness of the developer carried on the developer carrying body before the developer is transported to the developing area, and the developer regulating member. The temperature in the developing device 40 is raised by frictional heat due to rubbing between the developers at the time of regulation. When the temperature in the developing device 40 rises, the charge amount of the toner decreases, the toner adhesion amount increases, and a predetermined image density cannot be obtained. Further, the toner may melt due to the temperature rise and adhere to the developer regulating member, the developer carrying member, the photosensitive member, etc., and a streaky abnormal image may be generated in the image. In recent years, when a toner having a low melting temperature is used in order to reduce the fixing energy, an abnormal image or the like is likely to occur due to toner fixation. In addition, the development device 40 is likely to become hot due to the increase in printing speed. Therefore, the developing devices 40Y, M, C, and K are very important cooling parts for achieving high image quality and high reliability.

  Conventionally, an air flow is generated around the developing device 40 by an air cooling fan or the like to cool the developing devices 40Y, 40M, 40C, and 40K, which are the temperature rising points, and the temperatures of the developing devices 40Y, 40M, 40C, and 40K rise excessively. It is restrained to do. However, along with a demand for miniaturization, it is necessary to reduce a duct for forming a flow path around the developing device 40. If the duct becomes small, the flow rate of the gas flowing around the developing device 40 decreases, and the developing device 40 cannot be sufficiently cooled. For this reason, in the image forming apparatus of the present embodiment, the developing devices 40Y, 40M, 40C, and 40K are cooled by the liquid cooling device.

  FIG. 3 is a schematic configuration diagram of the liquid cooling device 30. As shown in FIG. 3, the liquid cooling device 30 is pressed against the wall surfaces of the developing devices 40Y, 40M, 40C, and 40K, where the temperature rises, and the coolant receives heat from the developing devices 40Y, 40M, 40C, and 40K. Four heat receiving portions 32Y, M, C, and K are provided. In addition, three cooling sections 35 for cooling the cooling liquid, a circulation pipe 34 for containing the cooling liquid, a cooling pump 31 as a conveying means for circulating the cooling liquid in the circulation pipe, and a reserve tank 33 for storing excess cooling liquid Etc. Each cooling unit 35 includes a radiator 35b, a cooling fan 35a, and the like serving as heat dissipation means. The heat receiving portion 32 is provided with a flow path 32b inside a case 32a formed of a member having high thermal conductivity. Usually, the case 32a of the heat receiving portion 32 is configured based on copper having a thermal conductivity of about 400 [W / mK] or aluminum of about 200 [W / mK]. Further, a material having higher thermal conductivity (for example, silver or gold) may be used.

  Further, since the side surface of the developing device 40 is also made of a material having high thermal conductivity such as aluminum or copper, when the heat receiving portion 32 is brought into close contact with the side surface of the developing device 40, an air layer is formed. End up. If an air layer is formed, the efficiency of heat exchange falls. Therefore, in the present embodiment, a heat conductive sheet 130 (see FIG. 4) is attached to a surface (hereinafter referred to as a pressure contact surface) facing the developing device 40 of the heat receiving unit 32. The heat conductive sheet 130 is required to have high heat conductivity and at the same time, hardness (easiness to deform) that can crush the surface accuracy between the developing device 40 and the heat receiving unit 32. However, since the heat conductive sheet 130 is hard when it has high heat conductivity and soft when it has low heat conductivity, the heat conductive sheet 130 becomes hard to some extent in order to obtain high heat conductivity. Therefore, in the present embodiment, the heat receiving portion 32 is pressed with a large pressing force so that the heat receiving portion 32 is pressed against the side surface of the developing device 40. Accordingly, even if a heat conductive sheet that is hard to some extent is used, the heat conductive sheet 130 is deformed, and the surface accuracy between the developing device 40 and the heat receiving unit 32 is crushed. Therefore, it is possible to suppress the formation of an air layer between the developing device 40 and the heat receiving unit 32 and to conduct heat of the developing device 40 to the heat receiving unit satisfactorily. Further, the heat conductive sheet 130 may be attached to the side surface of the developing device 40.

  As shown in FIG. 3, in each cooling unit 35, heat dissipation is performed to transfer and dissipate the cooling liquid through a housing (contained of aluminum having a high thermal conductivity) containing the cooling medium from the circulation pipe 34. A radiator 35b as means is provided. Further, forced air cooling or natural air cooling is performed by the cooling fan 35a according to the heat radiation amount. Moreover, the cooling part 35 may be one and may be four or more. Moreover, although the cooling fan is provided for every cooling part, you may comprise so that external air may be supplied to the radiator of each cooling part with one cooling fan. By providing a plurality of cooling units 35, even if the cooling efficiency of each cooling unit is low, it is possible to satisfactorily suppress the temperature rise of all the developing devices 40Y, M, C, and K. As a result, it is possible to use a small radiator that has a small heat radiation area and does not have a very high cooling efficiency as compared with one that suppresses the temperature rise of all the developing devices 40Y, 40M, 40K, and K in one cooling unit. It is possible to reduce the size of the part.

  The cooling pump 31 is a drive source that circulates the cooling liquid between the heat receiving parts 32Y, 32M, 32C, and 32K and the cooling part 35, and circulates the cooling liquid as shown by arrows in FIG. The reserve tank 33 is a tank for storing a coolant. The coolant is a heat transport medium that transports the heat received by the heat receiving portions 32Y, 32M, 32C, 32K to the radiator 35b. The main component is water, and propylene glycol or ethylene glycol is added to lower the freezing temperature, or a rust inhibitor (for example, phosphate-based materials: potassium phosphate, to prevent rusting of metal components) Inorganic potassium salt or the like) is used. When the coolant is water, the constant heat capacity is 3000 times or more that of air, and a large amount of heat can be transferred with a small flow rate, so that cooling can be performed more efficiently than forced air cooling.

  FIG. 4 is an enlarged configuration diagram illustrating the developing device 40 and the photoconductor 18 included in one of the four image forming units 11Y, 11M, 11C, and 11K. The four image forming units 11Y, 11M, 11C, and 11K have substantially the same configuration except that the colors of the toners to be handled are different from each other. Therefore, Y, M, C, and K indicated by “4” in FIG. Subscripts are omitted. As shown in FIG. 4, the surface of the photoconductor 18 is charged by a charging device while rotating in the direction of arrow G in the drawing. The charged surface of the photosensitive member 18 is supplied with toner from the developing device 40 to the latent image on which the electrostatic latent image is formed by the laser light emitted from the exposure device, and forms a toner image.

  The developing device 40 has a developing roller 45 as a developer carrying member for supplying and developing the developer contained in the developing case to the latent image on the surface of the photosensitive member 18 while moving the surface in the direction of arrow I in the drawing. ing. The developing roller 45 includes a rotatable developing sleeve, and a magnetic body including a plurality of magnetic poles is disposed therein. The magnetic material is necessary for holding the developer on the surface of the developing roller 45. Further, a supply screw 48 is provided as a supply conveying member that conveys the developer in the front direction of FIG. 4 along the axial direction of the developing roller 45 while supplying the developer to the developing roller 45. A doctor blade 42 as a developer regulating means for regulating the developer supplied to the developing roller 45 to a thickness suitable for development is provided downstream of the surface of the developing roller 45 facing the supply screw 48 in the direction of surface movement. ing.

  A collection conveyance path 47 that collects the developed developer that has passed through the development region and separated from the surface of the development roller 45 on the downstream side in the surface movement direction from the development region that is the portion of the development roller 45 facing the photoreceptor 18. Faces the developing roller 45. The collection conveyance path 47 is a collection conveyance member that conveys the collected developer collected in the same direction as the supply screw 48 along the axial direction of the developing roller 45, and a spiral collection screw 46 that is arranged in parallel to the axial direction. I have. A supply conveyance path 49 provided with a supply screw 48 is provided in the lateral direction of the developing roller 45, and a collection conveyance path 47 provided with a collection screw 46 is provided in parallel below the development roller 45. Note that the developer can be separated from the developing roller 45 by setting the magnetic body in the developing sleeve described above to a state where there is no magnetic pole only at a position where the developer is desired to be separated. Yes. Further, a magnetic body having a magnetic pole arrangement in which a repulsive magnetic field is formed at a location to be separated may be used.

  The developing device 40 is provided with a stirring conveyance path 44 in parallel with the collection conveyance path 47 below the supply conveyance path 49. The agitating / conveying path 44 includes an agitating screw 43 as an agitating / conveying member that conveys the developer in the direction opposite to the supply screw 48 while stirring the developer along the axial direction of the developing roller 45. The stirring screw 43 has a screw shape in which a spiral stirring blade 43b is fixed to a stirring shaft 43a that is arranged in parallel to the axial direction. The supply conveyance path 49 and the stirring conveyance path 44 are partitioned by a first partition wall 133 as a partition wall. In the first partition wall 133, the supply conveyance path 49 and the agitation conveyance path 44 are partitioned at both ends on the front side and the rear side in the figure, and the supply conveyance path 49 and the agitation conveyance path 44 communicate with each other. doing. The supply conveyance path 49 and the collection conveyance path 47 are also partitioned by the first partition wall 133, but an opening is provided at a location where the supply conveyance path 49 and the collection conveyance path 47 of the first partition wall 133 are partitioned. Absent. In addition, the two developer conveyance paths of the agitation conveyance path 44 and the collection conveyance path 47 are partitioned by a second partition wall 134 as a partition member. The second partition wall 134 has an opening on the front side in the figure, and the stirring conveyance path 44 and the collection conveyance path 47 communicate with each other.

  The supply screw 48, the recovery screw 46, and the stirring screw 43, which are developer conveying members, are made of resin or metal screws. The diameter of each screw is φ22 [mm], the screw pitch is two windings with a supply screw of 50 [mm], the collecting screw 46 and the stirring screw 43 are one winding with 25 [mm], and the number of rotations is about 600. [Rpm] is set. Further, in the developing device 40 of the present embodiment, the total length of the agitation transport path 44 is 410 [mm], and the total length of the supply transport path 49 is 320 [mm]. The developer thinned by the doctor blade 42 made of stainless steel on the developing roller 45 is transported to a developing area which is a portion facing the photoconductor 18 for development. The surface of the developing roller 45 is V-groove or sandblasted and is made of aluminum or stainless steel (SUS) tube with a diameter of 25 mm, and the gap between the doctor blade 42 and the photoreceptor 18 is about 0.3 mm. It has become.

  The developer after development is collected in the collection conveyance path 47, conveyed to the front side of the cross section in FIG. 4, and to the agitation conveyance path 44 through the opening of the second partition wall 134 provided in the non-image area portion. Developer is transferred. The toner is supplied to the stirring and conveying path 44 from the toner supply port provided on the upper side of the stirring and conveying path 44 in the vicinity of the opening of the second partition wall 134 on the upstream side in the developer conveying direction in the stirring and conveying path 44. . The developing case of the developing device 40 is formed of a wall member that forms the agitation conveyance path 44, the recovery conveyance path 47, the supply conveyance path 49, and the like.

  FIG. 5 is a perspective view showing the flow of the developer at the lower stage of the developing device 40. An arrow I indicates the flow of the developer until the developer used by the developing roller 45 is conveyed by the recovery screw 46 and the stirring screw 43 and finally pushed up to the upper stage. A region indicated by an alternate long and short dash line a is a portion for transporting the developer upward. An alternate long and short dash line b is a portion that transports the developer horizontally.

  FIG. 6 is a perspective view showing the flow of the developer on the upper stage of the developing device 40. An arrow II indicates the flow of the developer until the developer pushed up by the stirring screw 43 is conveyed by the supply screw 48 and pumped up to the developing roller 45.

  Next, the circulation of the developer in the three developer conveyance paths will be described. FIG. 7 is a perspective sectional view of the developing device 40 for explaining the flow of the developer in the developer transport path. Each arrow in the figure indicates the moving direction of the developer. FIG. 8 is a schematic diagram of the flow of the developer in the developing device 40, and each arrow in the drawing indicates the moving direction of the developer as in FIG.

  In the supply conveyance path 49 that receives the developer supplied from the agitation conveyance path 44, the developer is conveyed downstream in the developer conveyance direction of the supply screw 48 while supplying the developer to the developing roller 45. The surplus developer that has been transported to the downstream end of the supply transport path 49 without being supplied to the developing roller 45 is supplied to the stirring transport path 44 from the surplus opening 92 of the first partition wall 133. (Arrow E in FIG. 8). On the other hand, the developer supplied to the developing roller 45 is used for development in the developing region, and then separated / separated from the developing roller 45 and transferred to the collection conveyance path 47. The collected developer transferred from the developing roller 45 to the collection conveyance path 47 and conveyed to the downstream end of the collection conveyance path 47 in the developer conveyance direction by the collection screw 46 is agitated from the collection opening 93 of the second partition wall 134. It is supplied to the conveyance path 44 (arrow F in FIG. 8). The agitating and conveying path 44 agitates the supplied surplus developer and the collected developer, conveys the agitating screw 43 downstream in the developer conveying direction, conveys the supplying screw 48 upstream in the developer conveying direction, and It is supplied to the supply conveyance path 49 from the supply opening 91 of the partition wall 133 (arrow D in FIG. 8). In the agitating and conveying path 44, the agitating screw 43 agitates and conveys the collected developer, surplus developer, and toner replenished as necessary in the transfer unit in the direction opposite to the developer in the collecting and conveying path 47 and the supply conveying path 49. . Then, the agitated developer is transferred to the upstream side in the developer conveyance direction of the supply conveyance path 49 communicated by the supply opening 91 on the downstream side in the developer conveyance direction.

  In the developing device 40 shown in FIG. 8, a supply conveyance path 49 and a collection conveyance path 47 are provided, and developer supply and collection are performed in different developer conveyance paths, so that the developed developer is supplied to the supply conveyance path 49. There is no contamination. For this reason, it is possible to prevent the toner concentration of the developer supplied to the developing roller 45 from decreasing toward the downstream side of the supply conveyance path 49 in the developer conveyance direction. In addition, since the recovery conveyance path 47 and the agitation conveyance path 44 are provided, and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer does not fall during the agitation. Thereby, since the sufficiently stirred developer is supplied to the supply conveyance path 49, it is possible to prevent the developer supplied to the supply conveyance path 49 from being insufficiently stirred. In this way, the toner density of the developer in the supply conveyance path 49 can be prevented from decreasing, and the developer in the supply conveyance path 49 can be prevented from being insufficiently stirred, so the image density during development can be reduced. Can be constant.

  As shown in FIG. 8, only the arrow D moves the developer from the lower part to the upper part of the developing device 40. The movement of the developer indicated by an arrow D is to push the developer downstream of the agitation transport path 44 by the rotation of the agitation screw 43, so that the developer is raised and supplied to the supply transport path 49. . A fin member may be provided on the shaft of the stirring screw 43 in the vicinity of the downstream end of the developer transport path of the stirring transport path 44 where the stirring transport path 44 and the supply transport path 49 communicate with each other. This fin member is a plate-like member constituted by a side parallel to the axial direction of the stirring screw 43 and a side perpendicular to the axial direction of the stirring screw 43. By scooping up the developer with this fin member, it is possible to more efficiently deliver the developer from the stirring conveyance path 44 to the supply conveyance path 49. Further, the stirring screw 43 rotates in the clockwise direction when viewed from the front side in FIG. 4, and the developer is lifted and supplied by the stirring screw 43 along the shape of the wall surface of the stirring conveyance path 44. It is transferred to the conveyance path 49. As a result, the developer can be lifted efficiently, and the stress on the developer can be further reduced.

  As shown in FIG. 4, the holder 36 that holds the heat receiving portion 32 against the developing device 40 is attached to the left side surface of the developing device 40 by a claw 203 and a claw 204. The holder 36 holds the heat receiving portion 32 in contact with a contact surface 106 that is provided on the outer wall surface of the developing case of the developing device 40 and contacts the heat receiving portion 32. The position of the contact surface 106 in the longitudinal direction of the developing case is a region indicated by an alternate long and short dash line a shown in FIG. 5, and is in the vicinity of the downstream end portion in the developer transport direction of the stirring transport path 44.

  FIG. 9 shows the bias of the developer 108 in the vicinity of the downstream end portion in the developer transport direction in the stirring transport path 44. The stirring screw 43 rotates in the clockwise direction R in the drawing. As a result, the developer 108 is collected at a position in contact with the contact surface 106 cooled by the heat receiving portion 32. As described above, the developer is collected at a position in contact with the contact surface 106 by the rotating stirring screw 43, so that the developer is easily cooled by the heat receiving portion 32 through the contact surface 106, and the cooling efficiency of the developer is increased. be able to. Further, as described with reference to FIG. 5 and the like, there is a place where the developer is conveyed upward toward the supply conveyance path 49 in the vicinity of the downstream end of the agitation conveyance path 44 in the developer conveyance direction. At this location, the developer stays in the vicinity of the downstream end of the agitating and conveying path 44 in the developer conveying direction, and more developer is collected than the collecting and conveying path 47 and the supply and conveying path 49. As described above, in the developing device 40 of the present embodiment, the developer is collected near the downstream end of the agitating / conveying path 44, which is the portion facing the contact surface 106 in the developing case, in the developer conveying direction. Easy-to-use conditions are created.

  In FIG. 10, the developer conveyed to the vicinity of the downstream end of the agitating / conveying path 44 in the developer conveying direction by the agitating screw 43 is transferred from the vicinity of the downstream end of the agitating / conveying path 44 in the developer conveying direction. The flow of the developer in the portion transported upward to the vicinity of the upstream end portion in the developer transport direction is shown. In the drawing, an arrow III indicates a flow in which the developer is transferred from the stirring conveyance path 44 to the supply conveyance path 49. Since the developer is transported upward in this developer delivery section, a part of the developer returns from the supply transport path 49 side to the stirring transport path 44 due to gravity. This flow is indicated by arrow IV in the figure. In this way, the developer is evenly cooled by stirring the developer at the delivery section.

  FIG. 11 shows the case where the outer wall surface of the developing case in the vicinity of the downstream end of the agitating / conveying path 44 in the developer conveying direction and the portion where the developer is conveyed vertically upward is used as the contact surface 106 that contacts the heat receiving portion 32. (Region of dashed-dotted line a in FIG. 5) and the heat receiving portion 32 are brought into contact with the outer wall surface of the developing case in the vicinity of the upstream side of the developer conveying direction of the stirring conveying path 44 where the developer is conveyed in the horizontal direction. FIG. 5 is a graph showing the relationship between the time lapse of the developing device and the temperature change in the case where the contact surface 106 is set to be the contact surface 106 (region in FIG. . In addition, the area of the contact surface with which the heat receiving part 32 is brought into contact, in other words, the cooling area cooled by the heat receiving part 32 is the same.

  As can be seen from FIG. 11, if the cooling area is the same, the contact surface 106 is provided on the outer wall surface of the developing case near the downstream end of the developer conveying direction of the stirring conveying path 44 where the developer is conveyed vertically upward. When the contact surface 106 is provided on the outer wall surface of the developing case in the vicinity of the upstream side end of the developer conveying direction of the stirring conveying path 44 through which the developer is conveyed in the horizontal direction, the cooling can be performed more efficiently. You can see that Further, the contact surface 106 with which the heat receiving unit 32 of the liquid cooling device 30 is brought into contact is limited to the developing case outer wall surface in the vicinity of the downstream end portion in the developer transport direction in the stirring transport path 44, so that The space occupied by the heat receiving portion 32 of the liquid cooling device 30 in the space around the developing device 40 can be reduced compared to the case where the heat receiving portion 32 is provided over the entire contact surface 106 and the image receiving apparatus 106 occupies the space. It is possible to reduce the size of the main body. Furthermore, the flow path of the coolant can be shortened, and the cooling pump 31 can be reduced in size and energy can be saved.

[Configuration example 1]
FIG. 1 is a schematic configuration diagram of a developing device 40 according to Configuration Example 1. As shown in FIG. 1, the gap forming member 112 facing the developing roller 45 on the downstream side of the developing region in the rotation direction of the developing roller is provided separately from the casing 121. In the gap forming member 112, a developing roller facing portion 112a which is a facing portion facing the developing roller 45 extends in the longitudinal direction. The developing roller facing portion 112 a is formed with a curved surface so as to face the developing roller 45 and have a surface along the developing roller 45.

  Further, by forming the casing 121 of the developing device 40 from metal, the heat of the developer can be efficiently transmitted to the heat receiving portion 32 of the liquid cooling device 30 via the casing 121. It is also possible to cool the developer in 40 efficiently. Here, it is desirable that the metal heat receiving portion 32 provided in the liquid cooling device 30 is electrically grounded by being electrically connected to the image forming apparatus main body. The metal casing 121 that comes into contact with the heat receiving portion 32 that is electrically grounded as described above is inevitably electrically grounded. Since the heat receiving part 32 is electrically grounded, the casing 121 may be electrically grounded by electrically connecting the casing 121 to the image forming apparatus main body without using the heat receiving part 32. The gap forming member 112 is attached to the casing 121 having the same potential as that of the main body of the image forming apparatus via the insulating tape 123. As a result, no current flows from the gap forming member 112 to the casing 121, and the gap forming member 112 is in an electrically floating state with respect to the electrically grounded casing 121. Therefore, even if a conductor such as metal powder is clogged in the gap formed between the developing roller 45 and the gap forming member 112, a current flows rapidly from the developing roller 45 through the conductor into the gap forming member 112. Can be suppressed.

  The gap forming member 112 may be fixed to the casing 121 with screws. In this case, for example, as a screw used to fix the gap forming member 112 and the casing 121, it is desirable to use an insulating resin screw. In the case of using a metal screw, an insulating washer may be sandwiched between the screw seat portion of the gap forming member 112. Thereby, it can prevent that the gap formation member 112 and the casing 121 do not conduct | electrically_connect through a screw | thread.

  FIG. 12 is an enlarged view of the gap forming member 112 provided in the developing device 40 according to Configuration Example 1. The gap forming member 112 is formed by alternately laminating a plurality of conductive layers 112A and a plurality of insulating layers 112B in the rotation direction of the developing roller. That is, as shown in FIG. 12, from the upstream side toward the downstream side in the developing roller rotation direction, the conductive layer 112A1, the insulating layer 112B1, the conductive layer 112A2, the insulating layer 112B2, the conductive layer 112A3, the insulating layer 112B3, the conductive layer 112A4, The insulating layer 112B4 is layered. In this configuration example, a 1 [mm] aluminum plate as the conductive layer 112A and a 1 [mm] acrylic plate as the insulating layer 112B are overlapped and integrated with each other, and then developed by adjusting the outer shape with a milling machine. The roller facing part 112a was manufactured to be flush with each other. The conductive layer 112A1 is exposed outside the developing device 40, and a bias is applied to the conductive layer 112A1 from the power source 142. A part of the gap forming member 112 has a square hole penetrating from the conductive layer 112A1 to the conductive layer 112A4 in the direction of the arrow shown in FIG.

  FIG. 13 is an enlarged view of a square hole opened in the gap forming member 112. The conductive layers adjacent to each other with the insulating layer sandwiched in the square hole are connected by a chip resistor 112C. That is, the conductive layer 112A1 and the conductive layer 112A2 are electrically connected by the chip resistor 112C1 with the insulating layer 112B1 interposed therebetween. Further, the conductive layer 112A2 and the conductive layer 112A3 are electrically connected by the chip resistor 112C2 with the insulating layer 112B2 interposed therebetween. The conductive layer 112A3 and the conductive layer 112A4 are electrically connected by the chip resistor 112C3 with the insulating layer 112B3 interposed therebetween. In this configuration example, the resistance values of the chip resistor 112C1, the chip resistor 112C2, and the chip resistor 112C3 are each 10 [MΩ]. The conductive layer 112A4 and the casing 121 are electrically connected with a resistance of 20 [MΩ].

  In the present configuration example, the normal charging polarity of the toner is a negative polarity, and a voltage that is larger in absolute value than the voltage applied from the power supply 141 to the developing roller 45 is applied from the power supply 142 to the conductive layer 112A1. In this configuration example, the voltage applied from the power source 142 to the conductive layer 112A1 is −1000 [V], which is a voltage having the same polarity as the normal charging polarity of the toner. Then, by applying a voltage of −1000 [V] to the conductive layer 112A1, due to the action of each chip resistor 112C, −800 [V] is applied to the conductive layer 112A2, −600 [V] is applied to the conductive layer 112A3, −400 [V] is applied to the layer 112A4. Thus, in each conductive layer 112A, a potential gradient is created from the upstream side to the downstream side in the rotation direction of the developing roller, and the toner floating between the developing roller 45 and the developing roller facing portion 112a is removed from the inside of the developing case. The electric field that leads to is formed as shown by the arrows in FIG. Further, the potentials of the conductive layers 112A1, 112A2, 112A3, and 112A4 are set to be larger in absolute value than the potential of the developing roller 45. As a result, an electric field for moving the toner in the direction of the developing roller as shown in FIG. 15 can be formed between the developing roller 45 and each conductive layer 112A. Therefore, by this electric field, the toner floating between the developing roller 45 and the developing roller facing portion 112a (gap) is returned to the developing roller 45, so that toner scattering can be suppressed.

[Configuration example 2]
FIG. 16 is a schematic configuration diagram of a developing device 40 according to Configuration Example 2. In the developing device 40 according to this configuration example, as shown in FIG. 16, an insulating coating layer 124 is provided on the developing roller facing portion 112 a of the gap forming member 112 to insulate the developing roller 45 from the gap forming member 112. doing. This is because if the potential difference between each conductive layer of the gap forming member 112 and the developing roller 45 becomes too large, a bias leak may occur in the space between the two and dielectric breakdown may occur. When such dielectric breakdown occurs, the image on the photoconductor 18 developed by the developing roller 45 becomes a horizontal streak-like abnormal image. Therefore, by insulating the developing roller 45 and the gap forming member 112 with the insulating coating layer 124, occurrence of bias leak between the developing roller 45 and the gap forming member 112 can be suppressed, and dielectric breakdown occurs. Can be suppressed. As the insulating coating layer 124, a PET (polyethylene terephthalate) film having a thickness of about 0.1 [mm] can be preferably used.

[Configuration example 3]
FIG. 17 is a schematic configuration diagram of a developing device 40 according to Configuration Example 3. In the developing device 40 according to this configuration example, as illustrated in FIG. 17, two conductive members are provided on the upstream side and the downstream side with the insulating member 112 </ b> E sandwiched in the developing roller rotation direction, and the gap forming member 112 is provided. Is configured. One of the two conductive members is an upstream conductive member 112D1 located upstream of the insulating member 112E in the developing roller rotation direction, and the other is located downstream of the insulating member 112E in the developing roller rotation direction. This is the downstream conductive member 112D2. Further, the surfaces of the upstream conductive member 112D1, the insulating member 112E, and the downstream conductive member 112D2 that face the developing roller 45 are flush with each other to form a developing roller facing portion 112a. This increases the accuracy of the gap formed between the developing roller 45 and the developing roller facing portion 112a.

  A voltage having the same polarity as the normal charging polarity of the toner is applied to the upstream conductive member 112D1 and the downstream conductive member 112D2 by the power supply 142 and the power supply 143, respectively. At this time, when the voltage applied to the developing roller 45 is V1, the voltage applied to the upstream conductive member 112D1 is V2, and the voltage applied to the downstream conductive member 112D2 is V3, | V2 |> | The relationship of V3 |> | V1 | is satisfied. As a result, an electric field that conveys toner from the outside to the inside of the developing device 40 can be generated in the gap region between the developing roller 45 and the gap forming member 112. As a result, not only the effect of making it difficult for toner to adhere to the gap forming member 112 but also the effect of attracting toner outside the developing device 40 into the inside can be added. The problem of dropped images can be solved.

  Further, in the developing device 40 according to the present configuration example, similarly to the developing device 40 according to the configuration example 2, the insulating coating layer 124 is provided on the developing roller facing portion 112a of the gap forming member 112, and the developing roller 45 and the gap are formed. It insulates from the formation member 112. As a result, it is possible to suppress the occurrence of bias leakage between the developing roller 45 and the gap forming member 112 due to an excessive potential difference between the conductive members of the gap forming member 112 and the developing roller 45. It is possible to suppress the occurrence of dielectric breakdown.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect A)
In a developing device such as the developing device 40, a developer such as a developing roller 45 that transports the developer to a developing region facing the surface of the latent image carrier by carrying and rotating a developer containing at least toner on the surface. A developer carrying body, and a developing casing such as a casing 121 that forms a developer containing portion that contains the developer. The developer carrying body is separate from the developing casing, and is downstream of the developer carrying body in the rotation direction with respect to the developing region. A plurality of conductive members such as a plurality of conductive layers 112 </ b> A in the direction of rotation of the developer carrier, with an insulating member such as an insulating layer 112 </ b> B sandwiched between adjacent conductive members, and the plurality of conductive members And a surface of the insulating member that faces the developer carrying member is flush with each other, and a gap forming member 1 that forms a gap with the surface of the developer carrying member. 2 and the like, and an electric field in which the toner moves between the plurality of conductive members and the developer carrying member by an electrostatic force from the conductive member side toward the developer carrying member. Voltage application means such as a power source 142 for applying a voltage to the plurality of conductive members.
In (Aspect A), a voltage is applied to the plurality of conductive members constituting the gap forming member by the voltage applying means, and the developer from the conductive member side between the plurality of electrode members and the developer carrier. An electric field is formed so that the toner moves by electrostatic force toward the carrier side. As a result, the toner floating between the gap forming member and the developer carrier can be returned to the developer carrier by the electric field, and toner scattering can be suppressed. In addition, since the surfaces of the plurality of conductive members and insulating members facing the developer carrier are aligned, the conductive members such as electrodes are placed on the surface of the gap forming member facing the developer carrier. The gap between the gap forming member and the developer carrying member can be set with higher accuracy than in the case of disposing the gap. Therefore, it is possible to prevent the gap from being too wide to obtain a sufficient toner scattering suppressing effect, or the gap from being too narrow to overflow the developer.
(Aspect B)
In (Aspect A), the voltage application means is the conductive member located downstream in the developer carrying member rotation direction than the voltage applied to the conductive member located upstream in the developer carrying member rotation direction. A voltage having the same polarity as the normal charging polarity of the toner is applied to each conductive member so that the voltage applied to is smaller in absolute value. According to this, as described in the above embodiment, an electric field that guides the floating toner between the developer carrying member and the gap forming member to the inside of the developing casing is formed, and the toner scattering is more effective. Can be suppressed.
(Aspect C)
In (Aspect A) or (Aspect B), three or more conductive members are provided. According to this, as described in the above embodiment, the toner floating between the developer carrying member and the gap forming member is removed from the inside of the developing casing rather than the configuration in which the two conductive members are provided. It is possible to more reliably form an electric field that leads to.
(Aspect D)
In (Aspect A) to (Aspect C), an insulating layer such as an insulating coating layer 124 is provided on a portion of the gap forming member facing the developer carrier. According to this, as described in the above embodiment, it is possible to suppress the occurrence of bias leak between the developer carrying member and the gap forming member and to suppress the occurrence of dielectric breakdown.
(Aspect E)
In (Aspect A) to (Aspect D), the developing casing is provided with a contact portion that makes contact with an electrically grounded contact member, and the developing casing has conductivity, and the developing casing An insulating member such as an insulating tape 123 for insulating the developing casing and the gap forming member is provided between the casing and the gap forming member. According to this, as described in the above embodiment, no current flows from the gap forming member to the developing casing, and the gap forming member is in an electrically floating state with respect to the developing casing electrically grounded. Become. Therefore, even if a conductor such as metal powder is clogged in the gap formed between the developer carrier and the gap forming member, the current suddenly flows from the developer carrier to the gap forming member through the conductor. Can be suppressed.
(Aspect F)
In (Aspect E), the contact member is a heat receiving portion such as a heat receiving portion 32 of a cooling device such as the liquid cooling device 30. According to this, as described in the above-described embodiment, according to this, as described in the above-described embodiment, the developer stored in the developing casing is cooled, and the temperature rise in the developing device is suppressed. Can do.
(Aspect G)
(Aspect F) includes a partition member such as a first partition wall 133 that partitions the space in the developing casing and forms a plurality of developer transport paths in which the developer transport members are respectively disposed in the space. As each developer conveying member arranged in a plurality of developer conveying paths, an upper developer conveying member such as a supply screw 48 arranged above and below the partition member and a lower developer conveying member such as a stirring screw 43 A lower developer transport path such as a stirring transport path 44 in which the lower developer transport member is disposed by the partition member, and a supply transport in which the upper developer transport member is disposed in the space in the developing casing. An upper developer conveyance path such as a path 49 is formed, and the lower development is located at a position near the downstream end in the developer conveyance direction in the lower developer conveyance path of the partition member. An opening such as a supply opening 91 that communicates the transport path with the upper developer transport path is provided, and the heat receiving section is brought into contact with the outer surface of the developing casing on the downstream side in the developer transport direction in the lower developer transport path. The contact portion was provided. According to this, as described in the above embodiment, the developer can be efficiently cooled by the heat receiving portion of the cooling device at the place where the developer stays and a lot of developer is collected.
(Aspect H)
In the image forming apparatus including a latent image carrier such as the photosensitive member 18 and a developing unit such as a developing device 40 that develops the latent image formed on the latent image carrier with a developer, The developing device according to any one of Aspect A) to (Aspect G) was used. According to this, as described in the above embodiment, toner scattering can be more effectively suppressed, and problems such as contamination in the image forming apparatus due to the scattered toner and a toner drop image can be solved.

DESCRIPTION OF SYMBOLS 1 Image forming part 2 Transfer unit 3 Paper feed unit 4 Secondary transfer device 5 Duplex unit 6 Conveyor belt 7 Fixing unit 8 Paper discharge unit 9 Exposure unit 10 Reading device 11 Image forming unit 12 Drum cleaning unit 13 Charging unit 14 Registration roller 15 Intermediate transfer belt 16 Transfer counter roller 17 Secondary transfer roller 18 Photoconductor 20 Heat insulating device 21 Heat receiving plate 22 Heat pipe 23 Heat radiating plate 24 Duct 30 Liquid cooling device 31 Cooling pump 32 Heat receiving portion 32a Case 32b Flow path 33 Reserve tank 34 Circulation pipe 35 Cooling section 35a Cooling fan 35b Radiator 36 Holder 40 Developing device 42 Doctor blade 43 Stirring screw 43a Stirring shaft section 43b Stirring blade section 44 Stirring conveyance path 45 Developing roller 46 Recovery screw 47 Recovery Conveying path 48 Supply screw 49 Supply conveying path 90 Intermediate transfer belt cleaning unit 91 Supply opening 92 Excess opening 93 Recovery opening 106 Contact surface 108 Developer 112 Gap forming member 112a Developing roller facing part 112A Conductive layer 112A1 Conductive layer 112A2 Conductive Layer 112A3 conductive layer 112A4 conductive layer 112B insulating layer 112B1 insulating layer 112B2 insulating layer 112B3 insulating layer 112B4 insulating layer 112C chip resistor 112C1 chip resistor 112C2 chip resistor 112C3 chip resistor 112D1 upstream conductive member 112D2 downstream conductive member 112D2 downstream conductive member 112D2 Casing 123 Insulating tape 124 Insulating coating layer 130 Thermal conductive sheet 133 First partition wall 134 Second partition wall 141 Power source 142 Power source 143 203 nails 204 nails

JP-A-8-171282

Claims (8)

A developer carrying member that conveys the developer to a developing region facing the surface of the latent image carrying member by carrying and rotating at least a developer containing toner on the surface;
A developing casing that forms a developer containing portion for containing the developer,
It is a separate body from the developing casing, and is disposed downstream of the developing region with respect to the rotation direction of the developer carrier, and a plurality of conductive members are insulated between adjacent conductive members in the direction of rotation of the developer carrier. The plurality of conductive members and the insulating member are arranged so that the surfaces of the plurality of conductive members and the insulating member facing the developer carrier are flush with each other and between the surfaces of the developer carrier. A gap forming member for forming a gap in
An electric field is formed between the plurality of conductive members and the developer carrier so that the toner moves by an electrostatic force from the conductive member side toward the developer carrier side. A developing device comprising voltage applying means for applying a voltage to a plurality of conductive members. The developing device according to claim 1,
The voltage application means is configured to apply a voltage applied to the conductive member positioned downstream in the developer carrying member rotation direction relative to a voltage applied to the conductive member located upstream in the developer carrying member rotation direction. A developing device, wherein a voltage having the same polarity as the normal charging polarity of the toner is applied to each conductive member such that the absolute value becomes smaller. The developing device according to claim 1 or 2,
A developing device comprising three or more conductive members. The developing device according to any one of claims 1 to 3,
A developing device, wherein an insulating layer is provided on a portion of the gap forming member facing the developer carrying member. In the developing device according to any one of claims 1 to 4,
The developing casing is provided with a contact portion that makes contact with an electrically grounded contact member, and the developing casing has conductivity,
An developing device comprising an insulating member for insulating the developing casing and the gap forming member between the developing casing and the gap forming member. The developing device according to claim 5,
The developing device according to claim 1, wherein the contact member is a heat receiving portion of a cooling device. The developing device according to claim 6,
A partition member for partitioning the space in the developing casing and forming a plurality of developer transport paths in which the developer transport members are respectively disposed in the space;
As each developer conveying member arranged in the plurality of developer conveying paths, an upper developer conveying member and a lower developer conveying member arranged above and below across the partition member,
A lower developer transport path in which the lower developer transport member is disposed by the partition member and an upper developer transport path in which the upper developer transport member is disposed are formed in the space in the developing casing, An opening for communicating the lower developer transport path and the upper developer transport path is provided at a position near the downstream end of the developer transport direction in the lower developer transport path in the partition member, and the lower development The developing device according to claim 1, wherein the contact portion that contacts the heat receiving portion is provided on the outer surface of the developing casing on the downstream side in the developer transport direction in the developer transport path. A latent image carrier;
An image forming apparatus comprising: a developing unit that develops the latent image formed on the latent image carrier with a developer;
An image forming apparatus using the developing device according to claim 1 as the developing unit.

Images