JP4535077B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus and a developing device used in the image forming apparatus.

  As a developing method employed in an electrophotographic image forming apparatus, a developing method called hybrid development has been proposed in Patent Document 1 and the like. An image forming apparatus adopting hybrid development has a developing device including a magnetic roller and a developing roller, and selects only toner from a developer including nonmagnetic toner and magnetic carrier held on the outer peripheral surface of the magnetic roller. The electrostatic latent image (electrostatic latent image portion) on the photosensitive member is developed by supplying the toner to the outer peripheral surface of the developing roller and using the toner held on the outer peripheral surface of the developing roller.

  Specifically, with reference to FIG. 19, in the hybrid development, the developer held on the outer peripheral surface of the magnetic roller 354 is arranged along the magnetic field lines formed around the magnetic roller 354, and thus arranged. The developer in such a state is called a magnetic brush. In the proximity region (supply / recovery region) 388 between the magnetic roller 354 and the developing roller 348, the tip of the magnetic brush contacts the outer peripheral surface of the developing roller 348, and only the toner of the developer constituting the magnetic brush is the magnetic roller 354. And the developing roller 348 are moved to the outer peripheral surface of the developing roller 348 by an electric field formed between the developing roller 348 and the developing roller 348. A part of the toner held on the outer peripheral surface of the developing roller 348 is part of the photosensitive member 312 by an electric field formed between the developing roller 348 and the photosensitive member 312 in a region (developing region) 396 close to the photosensitive member 312. When the remaining toner on the developing roller 348 moves to the electrostatic latent image portion and is conveyed to the supply / recovery region 388 by the rotation of the developing roller 348, the toner is mechanically scraped off by the tip of the magnetic brush. 348 is removed from the outer peripheral surface.

  In the hybrid development, development is performed in such a manner, so that the stress applied to the toner can be reduced and the charge amount is more uniform as compared with the conventionally known one-component development and two-component development. A toner layer can be formed on the outer peripheral surface of the developing roller. Therefore, the hybrid development has an advantage that a high-quality image can be obtained and toner scattering can be reduced in the supply / recovery area and the development area as compared with the one-component development and the two-component development.

  However, even when hybrid development is adopted as the development method, when a part of the toner carried on the developing roller is not sufficiently charged due to deterioration, it is scattered in the air in the supply and recovery area and the development area. There is a risk of becoming smoke. The toner smoke generated in this manner drifts in the image forming apparatus due to the action of airflow and gravity, and causes contamination in the apparatus. Therefore, regardless of the development method to be employed, development of a technique for preventing in-machine contamination due to toner dust is required.

  In view of such a problem, Patent Document 2 proposes a technique for preventing in-machine contamination due to toner dust.

In the technique of Patent Document 2, a fan is provided in the developing device, and an air flow that draws air around the opening of the housing of the developing device into the housing is formed by this fan. At the same time, suction to the inside of the housing prevents the toner dust from being scattered outside the housing, thereby preventing contamination inside the image forming apparatus.
JP 2006-308687 A JP 2005-84372 A

  However, when the technique of Patent Document 2 is applied to a color image forming apparatus in which four color developing devices of yellow, magenta, cyan, and black are mounted, when each of the four developing devices is provided with a fan, the developing device Increase in size and material cost. On the other hand, even if only one fan is provided corresponding to the four developing devices, a duct for guiding the fan from each developing device to the fan is necessary, so it is necessary to secure a space for installing the duct. In addition to increasing the size of the image forming apparatus, the material cost increases as much as the duct is installed.

  In the technique of Patent Document 2, the toner dust is returned to the inside of the housing of the developing device by suction by a fan. However, since most of the toner returned to the inside of the housing is deteriorated, the housing When it is carried by the developing roller, it tends to be scattered again in the developing area or the supply / recovery area.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reliably prevent contamination in the apparatus due to toner dust while preventing an increase in the size of the developing device and the image forming apparatus and a reduction in material cost.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A belt-shaped member that moves in a predetermined moving direction during image forming operation, a latent electrostatic image bearing member which is contactable disposed on the surface of the belt-shaped member in the vicinity of the upper Symbol belt-shaped member, and, and a developing equipment which will be disposed in the upstream side of the electrostatic latent image bearing member in the moving direction of the belt-shaped member,
The developing device
A first conveying member that faces the electrostatic latent image carrier through the first region and supplies toner to the electrostatic latent image carrier, which is rotatable in a predetermined rotation direction;
A second conveying member that faces the first conveying member via a second region and supplies toner to the first conveying member;
A housing that houses the first transport member and the second transport member;
The housing includes a dust collecting unit for collecting toner dust generated in the first region or the second region,
The dust collection unit
An airflow introduction opening for communicating at least one of the space in the vicinity of the first region or the space in the vicinity of the second region and the internal space of the dust collector,
Plugged with filter to prevent passage of toner, and, e Bei an opening for air flow discharge for communicating the interior space of the space and the Konakemuri recovery portion of the belt-like member near,
The airflow discharge opening is formed in a belt facing portion provided in the dust collecting part so as to face the belt-like member .

  According to the present invention, it occurs in the first region between the first transport member and the electrostatic latent image carrier or in the second region between the first transport member and the second transport member. The toner smoke can be collected in the internal space of the dust collection unit provided in the developing device by utilizing the pressure difference generated around the developing device during the image forming operation. Specifically, as the belt-shaped member moves in a predetermined moving direction during the image forming operation, an air flow is generated in the vicinity of the belt-shaped member, so that the air pressure in the vicinity of the belt-shaped member is reduced. A pressure difference is generated between the space near the region or the second region and the space near the belt-shaped member. The space in the vicinity of the first region or the second region is an airflow introduction opening formed in the powder collection unit, an internal space of the powder collection unit, and an airflow discharge formed in the powder collection unit. Since the air pressure difference is generated during the image forming operation, the space close to the first region or the second region is communicated with the space near the belt-like member through the opening. An airflow that flows toward the space in the vicinity of the belt-like member is generated, and by this airflow, the toner dust generated in the first region or the second region is guided to the internal space of the powder smoke recovery unit, and this internal space To be recovered. Therefore, according to the present invention, it is possible to reliably collect the toner dust in the dust collector using the above-described pressure difference without providing a fan or a duct for sucking the toner dust. In addition, contamination inside the image forming apparatus due to toner dust can be reliably prevented.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms. Further, in the image forming apparatus and the developing apparatus described below, the same reference numerals are used for the same or similar components.

[1. Image forming apparatus]
FIG. 1 shows a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 2 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction machine having a combination of these functions, and more specifically, so-called tandem color image formation. Device.

  The image forming apparatus 1 includes an endless intermediate transfer belt 230 (corresponding to a belt-like member in claims). For the intermediate transfer belt 230, a material excellent in transfer performance is used. Specifically, for example, polyimide is used. Further, as the intermediate transfer belt 230, a belt having a thickness of, for example, 50 μm or more and 150 μm or less is preferably used.

  In the present embodiment, the intermediate transfer belt 230 is wound around a pair of rollers 232 and 234 disposed on the right and left sides of the drawing, respectively. The roller 232 on the right side of the drawing is a driving roller that is drivingly connected to a motor (not shown). The driving roller 232 connected to the motor rotates based on the driving of the motor, and the belt 230 and the other roller 234 in contact with the belt 230. Is rotated counterclockwise in the figure.

  In order to secure a sufficient frictional force between the driving roller 232 and the intermediate transfer belt 230, the intermediate transfer belt 230 is given a predetermined tension by a plurality of rollers 232 and 234. The magnitude of the tension applied to the intermediate transfer belt 230 is preferably 15N or more and 50N or less, for example.

  A secondary transfer roller 240 that clamps the recording medium 36 together with the belt 230 is provided outside the belt portion supported by the driving roller 232 disposed on the right side in the drawing. The secondary transfer roller 240 is disposed so as to be switchable between a position in contact with the outer peripheral surface of the belt 230 and a position separated from the outer peripheral surface of the belt 230 as shown in the figure. In a state where the secondary transfer roller 240 is in contact with the outer peripheral surface of the belt 230, the contact portion (nip portion) forms a secondary transfer region 241. As the secondary transfer roller 240, for example, an ion conductive roller is used, but an electronic conductive roller can also be used.

  A cleaning member 242 for the intermediate transfer belt is provided outside the belt portion supported by the roller 234 arranged on the left side in the drawing. The cleaning member 242 is, for example, a rotary brush type cleaning member, but is not limited to this. For example, a fixed brush type cleaning member or a plate-like cleaning blade may be used.

  Below the belt portion moving from the roller 234 on the left side to the roller 232 on the right side in the drawing, yellow (Y), magenta (M), cyan (C), black ( Four image forming units 3 (3Y, 3M, 3C, and 3K) that generate toner images of corresponding colors using the developer K) are arranged along the intermediate transfer belt 230.

  Each image forming unit 3 includes a cylindrical photosensitive member 12 as an electrostatic latent image carrier. Around the photoconductor 12, a charger 208, an exposure device 210, a developing device 34, a primary transfer roller 214, and a photoconductor cleaning member 216 are arranged in this order along the rotation direction (clockwise direction in the drawing). Yes. The cleaning member 216 is, for example, a rotary brush cleaning member, but is not limited thereto. For example, a fixed brush cleaning member or a plate-shaped cleaning blade can be used.

  The primary transfer roller 214 is disposed inside the endless intermediate transfer belt 230. The primary transfer roller 214 is arranged to be switchable between a position in contact with the intermediate transfer belt 230 and a position away from the intermediate transfer belt 230 as shown in the figure. The primary transfer roller 214 is connected to a high voltage power supply (not shown), and a primary transfer voltage is applied to the primary transfer roller 214 by the high voltage power supply during image formation.

  A control unit 270 that controls various operations related to printing is provided on the upper part of the image forming apparatus 1.

  A paper feeding cassette 244 is detachably disposed as a paper feeding device at the lower part of the image forming apparatus 1. The recording media 236 such as sheets stacked and accommodated in the sheet cassette 244 are sent out one by one from the top to the transport path 250 by the rotation of the sheet feed roller 252 disposed in the vicinity of the sheet cassette 244.

  A registration roller 254 for sending the recording medium 236 to the secondary transfer area 241 at a predetermined timing is provided in the vicinity of the paper feed roller 252.

  The conveyance path 250 passes from the paper feed cassette 244 through the nip portion of the registration roller pair 254, the secondary transfer region 241, the nip portion of the fixing roller pair 256, and the nip portion of the paper discharge roller pair 260 to the image forming apparatus 1. It extends to the paper discharge unit 261 provided on the top of the paper.

  An example of an image forming operation in the color mode will be described.

  First, in each image forming unit 3, the outer peripheral surface of the photoreceptor 12 that is rotationally driven at a predetermined peripheral speed is charged by the charger 208. Next, light is projected from the exposure device 210 that has received the drive signal output from the control unit 70 onto the outer peripheral surface of the charged photoconductor 12 to form an electrostatic latent image. Subsequently, the electrostatic latent image is made visible by the developer toner supplied from the developing device 34. When the toner image of each color formed on the photoconductor 12 in this way reaches the primary transfer area by the rotation of the photoconductor 12, the intermediate transfer belt 230 from the photoconductor 12 in the order of yellow, magenta, cyan, and black. Transferred (primary transfer) and overlaid.

  Untransferred toner remaining on the photosensitive member 12 without being transferred to the intermediate transfer belt 230 reaches the contact portion between the photosensitive member 12 and the cleaning member 216, and is scraped off by the cleaning member 216. It is removed from the outer peripheral surface.

  The four color toner images superimposed on the belt 230 are conveyed to the secondary transfer region 241 by the movement of the intermediate transfer belt 230.

  On the other hand, the recording medium 236 accommodated in the paper feed cassette 244 is sent to the transport path 250 by the rotation of the paper feed roller 252 and is transported to the nip portion of the registration roller pair 254. The recording medium 236 conveyed to the nip portion of the registration roller pair 254 is conveyed to the secondary transfer area 241 in accordance with the timing at which the toner image is conveyed to the secondary transfer area 241 by the intermediate transfer belt 230.

  When the recording medium 236 is conveyed to the secondary transfer area 41, the toner image is transferred (secondary transfer) from the intermediate transfer belt 230 to the recording medium 236. After the secondary transfer, the recording medium 236 is conveyed to the nip portion of the fixing roller pair 256 further downstream of the secondary transfer area 241, and the toner image is fixed by the fixing roller 256 and then discharged by the paper discharge roller 260. It is sent out to the paper portion 261.

  Untransferred toner remaining on the outer peripheral surface of the intermediate transfer belt 230 without being transferred to the recording medium 236 in the secondary transfer region 241 is removed from the intermediate transfer belt 230 by the cleaning member 242.

[2. Development device]
As shown in FIG. 2, the developing device 34 is disposed in the vicinity of the lower side of the intermediate transfer belt 30 and on the upstream side of the corresponding photosensitive member 12 in the moving direction of the belt 30.

  The developing device 34 includes a two-component developer including a non-magnetic toner that is first component particles and a magnetic carrier that is second component particles, and is configured to perform so-called hybrid development.

  The developing device 34 includes a housing 42 that accommodates various members described below. In order to facilitate understanding of the invention by simplifying the drawings, a part of the housing 42 is omitted.

  The housing 42 is provided with an opening 44 opened toward the photosensitive member 12, and a developing roller 48 (corresponding to a first transport member in claims) is provided in the vicinity of the opening 44. The developing roller 48 is a cylindrical member, and is arranged in parallel with the photoconductor 12 and rotatable in a predetermined rotation direction via a predetermined development gap from the outer peripheral surface of the photoconductor 12.

  In the space behind the developing roller 48, a conveying roller (corresponding to a second conveying member in claims) 54 is parallel to the developing roller 48 and through a predetermined supply / recovery gap with the outer peripheral surface of the developing roller 48. Are arranged. The conveyance roller 54 includes a magnet body 58 that is fixed so as not to rotate, and a cylindrical sleeve 60 (corresponding to a rotating cylinder body in claims) that is rotatably supported around the magnet body 58. Below the sleeve 60, a restricting plate 62 fixed to the housing 42 and extending in parallel with the central axis of the sleeve 60 is disposed so as to oppose a predetermined restricting gap.

  The magnet body 58 has a plurality of magnetic poles facing the inner surface of the transport roller 54 and extending in the direction of the central axis of the transport roller 54. In the embodiment, the plurality of magnetic poles oppose the magnetic pole S1 facing the lower inner peripheral surface portion of the transport roller 54 in the vicinity of the regulating plate 62, and the right inner peripheral surface portion of the transport roller 54 in the vicinity of the supply and recovery gap. A magnetic pole N1, a magnetic pole S2 facing the upper inner peripheral surface portion of the transport roller 54, and two adjacent magnetic poles N2 and N3 of the same polarity facing the left inner peripheral surface portion of the transport roller 54 are included.

  A developer stirring chamber 66 is formed behind the transport roller 54. In the developer stirring chamber 66, a screw 72 as a stirring member for stirring the developer is rotatably disposed.

  The housing 42 is a supply / recovery region (corresponding to a second region of the claims) 88 where the developing roller 48 and the conveying roller 54 face each other, or a developing region (the claims of claim) where the photoconductor 12 and the developing roller 48 are opposed. Corresponding to the first region.) A dust collecting unit 220 for collecting the toner dust generated in 96 is provided. A specific configuration of the dust collecting unit 220 will be described later.

  The operation of the developing device 34 configured as described above will be described. During image formation, the developing roller 48 and the sleeve 60 rotate in the directions of arrows 78 and 80, respectively, based on driving of a motor (not shown). The screw 72 rotates in the direction of the arrow 82, whereby the developer 2 stored in the developer stirring chamber 66 is stirred. As a result, the toner and the carrier contained in the developer come into frictional contact with each other and are charged with opposite polarities. In the embodiment, it is assumed that the carrier is positively charged and the toner is negatively charged. As shown in FIG. 3, the carrier 4 is considerably larger than the toner 6. Therefore, as shown in FIG. 4, the negatively charged toner 6 is adhered to the periphery of the positively charged carrier 4 mainly based on the electrical attraction force of both.

  Returning to FIG. 2, the charged developer 2 is supplied to the transport roller 54 in the course of being stirred in the developer stirring chamber 66 by the screw 72. The developer 2 supplied from the screw 72 to the conveying roller 54 is held on the outer peripheral surface of the sleeve 60 by the magnetic force of the magnetic pole N3 in the vicinity of the magnetic pole N3. The developer 2 held by the sleeve 60 constitutes a magnetic brush along the magnetic field lines formed by the magnet body 58, and is conveyed in the counterclockwise direction based on the rotation of the sleeve 60. The amount of developer 2 held by the magnetic pole S1 in the area facing the restriction plate 62 (restriction area 86) is restricted by the restriction plate 62 to a predetermined amount. The developer 2 that has passed through the regulation gap is conveyed to the supply / recovery region 88 that the magnetic pole N1 faces. As will be described in detail later, in the supply / recovery area 88, the upstream area (supply area) mainly in the rotation direction of the sleeve 60 is due to the presence of an electric field formed between the developing roller 48 and the sleeve 60. The toner 6 adhering to the carrier 4 is electrically supplied to the developing roller 48. Further, in the supply / recovery area 88, the development roller fed back to the supply / recovery area 88 without contributing to the development, as will be described later, mainly in the area downstream of the rotation direction of the sleeve 60 (recovery area). The toner on 48 is scraped off by a magnetic brush formed along the magnetic field lines of the magnetic pole N <b> 1 and collected in the sleeve 60. The carrier 4 is held on the outer peripheral surface of the sleeve 60 by the magnetic force of the magnet body 58 and does not move from the sleeve 60 to the developing roller 48. When the developer 2 that has passed through the supply / recovery region 88 is held by the magnetic force of the magnet body 58 and passes through the opposing portion of the magnetic pole S2 along with the rotation of the sleeve 60, the developer 2 reaches the opposing region (discharge region 94) of the magnetic poles N2 and N3. The repulsive magnetic field formed by the magnetic poles N2 and N3 is discharged from the outer peripheral surface of the sleeve 60 to the developer stirring chamber 66 and mixed with the developer 2 stirred in the developer stirring chamber 66.

The toner 6 held on the developing roller 48 in the supply / recovery area 88 is conveyed counterclockwise with the rotation of the developing roller 48, and the electrostatic latent image formed on the outer peripheral surface of the photoconductor 12 in the developing area 96. Adhere to the image area. In the image forming apparatus according to the embodiment, a predetermined negative potential V _H is applied to the outer peripheral surface of the photosensitive member 12 by the charger 208, and the electrostatic latent image image portion onto which the image light is projected by the exposure device 210 is a predetermined portion. decayed to the potential V _L, an electrostatic latent image non-image portion of the image light by the exposure device 210 is not projected maintains almost charging potential V _H. Accordingly, in the developing region 96, the negatively charged toner 6 adheres to the electrostatic latent image portion due to the action of the electric field formed between the photosensitive member 12 and the developing roller 48, and the electrostatic latent image portion. The latent image is visualized as a developer image.

  When the toner 6 is consumed from the developer 2 in this way, it is preferable to supply the developer 2 with an amount of toner corresponding to the consumed amount. For this purpose, the developing device 34 removes the toner from the developer stirring chamber 66 based on the outputs of the means for measuring the mixing ratio of the toner and the carrier accommodated in the housing 42 and the means for measuring the mixing ratio of the toner and the carrier. It is preferable to provide means for replenishing.

[3. Electric field forming means]
In order to efficiently move the toner 6 from the sleeve 60 to the developing roller 48 in the supply / recovery area 88, the developing roller 48 and the sleeve 60 are electrically connected to the electric field forming device 110. Specific examples of the power source are shown in FIGS.

The electric field forming apparatus 110 according to the embodiment shown in FIG. 6A has a first power source 112 (corresponding to the second electric field forming means in the claims) connected to the developing roller 48 and a second power source connected to the sleeve 60. It has a power source 114 (corresponding to the first electric field forming means in the claims). The first power supply 112 includes a DC power supply 118 connected between the developing roller 48 and the ground 116, and a first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the charging polarity of the toner 6. Is applied to the developing roller 48. The second power supply 114 has a DC power supply 120 connected between the sleeve 60 and the ground 116, and has the same polarity as the charging polarity of the toner 6 and a second DC voltage that is higher than the first DC voltage. V _DC2 (eg, −400 volts) is applied to the sleeve 60. As a result, in the supply / recovery region 88, the negatively charged toner 6 is electrically transferred from the sleeve 60 to the developing roller 48 by the action of a DC electric field formed between the developing roller 48 and the sleeve 60. Sucked. At this time, the positively charged carrier 4 is not attracted to the developing roller 48 from the sleeve 60. Further, in the developing area 96, the negative polarity toner held on the developing roller 48 is, as shown in FIG. 6B, the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L :−). It adheres to the electrostatic latent image portion based on the potential difference of 80 volts). At this time, the negative polarity toner adheres to the electrostatic latent image non-image portion due to a potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image non-image portion (V _H : −600 volts). There is nothing.

In the electric field forming apparatus 122 of the embodiment shown in FIG. 7A, the first power supply 124 has a DC power supply 128 connected between the developing roller 48 and the ground 126, like the power supply shown in FIG. A first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the charging polarity of 6 is applied to the developing roller 48. The second power source 130 includes a DC power source 132 and an AC power source 134 between the sleeve 60 and the ground 126. The DC power supply 132 applies a second DC voltage V _DC2 (for example, −400 volts) having the same polarity as the charging polarity of the toner 6 and higher than the first DC voltage to the sleeve 60. As shown in FIG. 7B, the AC power supply 134 applies an _AC voltage VAC having a peak-to-peak voltage V _PP of, for example, 300 volts between the sleeve 60 and the ground 126. As a result, in the supply / recovery region 88, the negatively charged toner 6 is electrically transferred from the sleeve 60 to the developing roller 48 by the action of a pulsating electric field formed between the developing roller 48 and the sleeve 60. Sucked into. At this time, the positively charged carrier 4 is held by the sleeve 60 by the magnetic force of the fixed magnet inside the sleeve 60 and is not supplied to the developing roller 48. In the developing region 96, the negative toner held on the developing roller 48 is caused by a potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L : −80 volts). Based on the electrostatic latent image portion.

In the electric field forming device 136 shown in FIG. 8A, the first power supply 138 includes a DC power supply 142 and an AC power supply 144 between the developing roller 48 and the ground 140. The DC power supply 142 applies a first DC voltage V _DC1 (for example, −200 volts) having the same polarity as the charging polarity of the toner 6 to the developing roller 48. The AC power supply 144 applies an _AC voltage VAC having an amplitude (peak-to-peak voltage) _VP-P of, for example, 1,600 volts between the developing roller 48 and the ground 140. The second power source 146 includes a DC power source 150 connected between the terminal 148 between the developing roller 48 and the AC power source 144 and the sleeve 60. The DC power supply 150 can output a predetermined DC voltage V _DC2 , and the anode is connected to the terminal 148 and the cathode is connected to the sleeve 60, so that the sleeve 60 is biased to the negative polarity with respect to the developing roller 48. (See FIG. 8B). Therefore, in the supply / recovery region 88, the negatively charged toner 6 is electrically transferred from the sleeve 60 to the developing roller 48 due to the action of the pulsating electric field formed between the developing roller 48 and the sleeve 60. Sucked. In the developing region 96, the negative toner on the developing roller 48 is statically charged based on the potential difference between the developing roller 48 (V _DC1 : −200 volts) and the electrostatic latent image portion (V _L : −80 volts). It adheres to the electrostatic latent image portion.

A power source 152 shown in FIG. 9 is obtained by adding AC electric field forming devices 154 and 156 to the first power source 112 and the second power source 114, respectively, in the power source of the embodiment shown in FIG. 5A. The output voltages of the AC electric field forming devices 154 and 156 are V _AC1 and V _AC2 . The voltages V _AC1 and V _AC2 may be the same or different. An electric field forming device 158 shown in FIG. 10 is obtained by adding an AC power source 160 to the first power source 112 in the power source of the embodiment shown in FIG. 6A. The output voltage of the AC power supply 160 is _{V AC.} Similarly to the power sources 110, 122, and 136, the electric field forming devices 152 and 158 of these forms are also subjected to the action of the pulsating electric field formed between the developing roller 48 and the sleeve 60, and the negative electrode in the supply and recovery region 88. The toner 6 charged in the negative direction is supplied from the sleeve 60 to the developing roller 48, and the toner 6 charged in the negative polarity is supplied from the developing roller 48 to the electrostatic latent image portion (V _L : −80 volts) ) To the electrostatic latent image portion.

[4. Developer)
In general, in a two-component developer containing toner and carrier as main components, dirt (spent) is generated by the toner adhering to the surface of the carrier, and this reduces the life of the carrier. In order to solve this problem, charged particles (implant particles) are added as a third component to the two-component developer.

  3 to 5, the image forming apparatus and the developing apparatus according to the present invention make the toner 6 have a normal polarity (the embodiment) by frictional contact with the toner 6 in addition to the toner 6 and the carrier 4. In this case, charged particles 8 having a diameter smaller than that of the toner 6 are included. In the embodiment, the charged particles 8 are detachably held on the outer peripheral surface of the toner 6 and are replenished together with the toner 6 from the toner replenishing unit 98.

  At the time of image formation, the charged particles 8 are transported through the housing 42 together with the toner 6 and the carrier 4, and then are held by the sleeve 60 and move in the regulation region 86, the supply / recovery region 88, and the discharge region 94. In this conveyance process, the charged particles 8 held on the surface of the toner 6 and charged to the positive polarity are placed in the electric field of the supply / recovery region 88, which is opposite to the electric force acting on the toner 6. The toner 6 is detached from the outer peripheral surface of the toner 6 by receiving the electric force in the direction. The separated charged particles 8 are held or driven on the outer peripheral surface of the carrier 4 by stress acting between the separated charged particles 8 and the carrier 4. As shown in FIG. 5, when a part or the whole of the outer peripheral surface of the carrier 4 is covered with the spent 10, the charged particles 8 are driven into the spent 10. The charged particles 8 held or driven on the outer peripheral surface of the carrier 4 are charged to a polarity opposite to that of the toner 6 by frictional contact with the toner 6. In the embodiment, since the toner 6 is charged to a negative polarity, the charged particles 8 are charged to a positive polarity. As a result, the carrier 4 into which the charged particles 8 are implanted maintains the same chargeability as the state without the spent 10 even if at least a part of the outer peripheral surface thereof is covered with the spent 10, and the toner 6 is preliminarily provided. Charged to the polarity.

  As described above, the charged particles 8 are charged with a polarity opposite to that of the toner 6. Therefore, as shown in FIG. 11, in the supply / recovery region 88, the toner 6 moves from the sleeve 60 to the developing roller 48 based on an electric field formed between the developing roller 48 and the sleeve 60. Further, the charged particles 8 separated from the toner 6 are quickly held on the carrier surface of the developer that is relatively carrier-rich by the toner 6 being taken away in the supply region 90 and supplied to the developing roller 48 together with the toner 6. Even if not supplied or supplied to the developing roller 6, the amount is extremely small.

  In the embodiment, the toner 6 is charged to a negative polarity and the carrier 4 is charged to a positive polarity by frictional contact between the toner 6 and the carrier 4. Further, the charged particles 8 are charged negatively by contact with the toner 6, and the charged particles 8 are charged positively. However, the chargeability of the toner, carrier, and charged particles is not limited to such a combination. Specifically, the toner 6 is charged positively by the frictional contact between the toner 6 and the carrier 4, the carrier 4 is charged negatively, and the charged particles 8 are charged positively by the contact with the toner 6. A combination in which the charged particles 8 are negatively charged is also conceivable.

[5. Specific materials)
Specific materials of the toner, carrier, charged particles, and other particles contained in the developer will be described.

[Charged particles]
The charged particles preferably used are appropriately selected according to the charging polarity of the toner. The number average particle diameter of the charged particles is, for example, 100 to 1000 nm. When using toner that is negatively charged by frictional contact with the carrier, charged particles are fine particles that are positively charged by contact with the toner. Such fine particles can be composed of, for example, inorganic fine particles such as strontium titanate, barium titanate, and alumina, and thermoplastic resins or thermosetting resins such as acrylic resins, benzoguanamine resins, nylon resins, polyimide resins, and polyamide resins. . The resin constituting the fine particles may contain a positive charge control agent that is positively charged by contact with the toner. As the positive charge control agent, for example, nigrosine dye, quaternary ammonium salt and the like can be used. The charged particles may be composed of nitrogen-containing monomers. Examples of the material constituting the nitrogen-containing monomer include 2-dimethylaminoethyl acrylate, 2-diethylaminoethyl acrylate, 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, vinylpyridine, N-vinylcarbazole, There is vinylimidazole.

  In the case of a toner that is positively charged by frictional contact with the carrier, fine particles that are negatively charged by contact with the toner are used as the charged particles. Examples of such fine particles include inorganic fine particles such as silica and titanium oxide, and fine particles made of thermoplastic resin or thermosetting resin such as fluororesin, polyolefin resin, silicone resin, and polyester resin. A negative charge control agent that is negatively charged by contact with the toner may be contained in the resin constituting the charged particles. Examples of negative charge control agents include salicylic acid-based and naphthol-based chromium complexes, aluminum complexes, iron complexes, and zinc complexes. The charged particles may be a copolymer of a fluorine-containing acrylic monomer or a fluorine-containing methacrylic monomer.

  In order to control the chargeability and hydrophobicity of the charged particles, the surface of the inorganic fine particles may be surface-treated with a silane coupling agent, a titanium coupling agent, silicone oil, or the like. In particular, when imparting positive electrode chargeability to inorganic fine particles, it is preferable to surface-treat with an amino group-containing coupling agent. When imparting negative chargeability to the fine particles, it is preferable to surface-treat with a fluorine group-containing coupling agent.

〔toner〕
As the toner, a known toner that has been conventionally used in an image forming apparatus can be used. The toner particle size is, for example, about 3 to 15 μm. A toner containing a colorant in a binder resin, a toner containing a charge control agent or a release agent, and a toner holding an additive on the surface can also be used.

  The toner can be produced by a known method such as a pulverization method, an emulsion polymerization method, or a suspension polymerization method.

[Binder resin]
The binder resin used for the toner is not limited. For example, styrene resin (monopolymer or copolymer containing styrene or styrene-substituted product), polyester resin, epoxy resin, vinyl chloride resin, phenol resin. , Polyethylene resin, polypropylene resin, polyurethane resin, silicone resin, or any mixture of these resins. The binder resin preferably has a softening temperature in the range of about 80 to 160 ° C and a glass transition point in the range of about 50 to 75 ° C.

[Colorant]
For the colorant, a known material such as carbon black, aniline black, activated carbon, magnetite, benzine yellow, permanent yellow, naphthol yellow, phthalocyanine blue, first sky blue, ultramarine blue, rose bengal, lake red, etc. should be used. Can do. In general, the addition amount of the colorant is preferably 2 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

[Charge control agent]
As the charge control agent, materials conventionally known as charge control agents can be used. Specifically, for the positively charged toner, for example, nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazole compounds, and polyamine resins can be used as charge control agents. For the negatively charged toner, metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkyl salicylic acid metal compounds, and curixarene compounds can be used as charge control agents. The charge control agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As the release agent, a known release agent conventionally used as a release agent can be used. As the material for the release agent, for example, polyethylene, polypropylene, carnauba wax, sazol wax, or a mixture of them as appropriate is used. The release agent is preferably used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

[Other additives]
In addition, a fluidizing agent that promotes fluidization of the developer may be added. As the fluidizing agent, for example, inorganic fine particles such as silica, titanium oxide, and aluminum oxide, and resin fine particles such as acrylic resin, styrene resin, silicone resin, and fluorine resin can be used. In particular, it is preferable to use a material hydrophobized with a silane coupling agent, a titanium coupling agent, silicon oil or the like. The fluidizing agent is preferably added at a ratio of 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner. The number average primary particle size of these additives is preferably 9 to 100 nm.

[Carrier]
As the carrier, a known carrier that has been generally used can be used. Either a binder type carrier or a coat type carrier may be used. The carrier particle size is not limited, but is preferably about 15 to 100 μm.

  As the binder type carrier, magnetic fine particles are dispersed in a binder resin, and those having fine particles or a coating layer that are positively or negatively charged on the surface can be used. The charging characteristics such as the polarity of the binder type carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer.

  Examples of the binder resin used for the binder-type carrier include thermoplastic resins such as vinyl resins, polyester resins, nylon resins, polyolefin resins, and the like typified by polystyrene resins, and curable resins such as phenol resins. .

  Magnetic fine particles of the binder type carrier include spinel ferrite such as magnetite and gamma iron oxide, and magnets such as spinel ferrite and barium ferrite containing one or more metals other than iron (Mn, Ni, Mg, Cu, etc.). Plumbite type ferrite, iron or alloy particles having an oxide layer on the surface can be used. The shape of the carrier may be granular, spherical, or needle-shaped. In particular, when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. In consideration of chemical stability, it is preferable to use ferromagnetic fine particles of magnetoplumbite type ferrite such as spinel ferrite and barium ferrite containing magnetite and gamma iron oxide. A magnetic resin carrier having a desired magnetization can be obtained by appropriately selecting the type and content of the ferromagnetic fine particles. The magnetic fine particles are suitably added in an amount of 50 to 90% by weight in the magnetic resin carrier.

  Silicone resin, acrylic resin, epoxy resin, fluorine resin, etc. are used as the surface coating material for the binder type carrier. The charge imparting ability of the carrier can be improved by coating and curing these resins on the carrier surface to form a coat layer.

  For example, the charging fine particles or the conductive fine particles can be fixed to the surface of the binder type carrier by, for example, mixing the magnetic resin carrier and the fine particles uniformly and adhering the fine particles to the surface of the magnetic resin carrier. This is done by driving fine particles into the magnetic resin carrier by applying a strong impact force. In this case, the fine particles are not completely embedded in the magnetic resin carrier, but are fixed so that a part thereof protrudes from the surface of the magnetic resin carrier. Organic and inorganic insulating materials are used for the chargeable fine particles. Specifically, organic insulating materials include polystyrene, styrene-based copolymers, acrylic resins, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesin, and cross-linked products thereof such as organic insulating fine particles. is there. The charge imparting ability and the charge polarity can be adjusted to the material of the chargeable fine particles, the polymerization catalyst, the surface treatment and the like. As the inorganic insulating material, negatively charged inorganic fine particles such as silica and titanium dioxide, and positively charged inorganic fine particles such as strontium titanate and alumina are used.

  The coat type carrier is a carrier in which carrier core particles made of a magnetic material are coated with a resin, and like the binder type carrier, chargeable fine particles that are charged positively or negatively can be fixed to the surface of the carrier. The charging characteristics such as the polarity of the coated carrier can be adjusted by selecting the type of the surface coating layer and the electrifying fine particles. As the coating resin, the same resin as the binder resin of the binder type carrier can be used.

  The mixing ratio of the toner and the carrier may be adjusted so as to obtain a desired toner charge amount, and the toner ratio is preferably 3 to 50% by weight, preferably 6 to 30% by weight based on the total amount of the toner and the carrier. .

[6. (Smoke recovery section)
Hereinafter, based on FIGS. 12-18, the structure of the dust collection part of the housing 42 of the developing device 34 is demonstrated concretely.

[First Embodiment]
With reference to FIG. 12, the dust collection unit 220 according to the first embodiment will be described.

  The dust collecting unit 220 is provided at the upper right end of the developing device 34 and is disposed in the vicinity of the intermediate transfer belt 230 and the photoreceptor 12.

  The dust collecting unit 220 includes a belt facing unit 222 that faces the intermediate transfer belt 230, a photoconductor facing unit 224 that faces the photoconductor 12, and a developing roller facing unit that faces the developing roller 48 (first claim of claim). 226 and a transport roller facing portion 228 that faces the transport roller 54.

  The belt facing portion 222 is disposed such that the outer surface thereof is substantially parallel to the lower surface of the intermediate transfer belt 230. An airflow discharge opening 204 is formed in the belt facing portion 222, and a space near the lower side of the intermediate transfer belt 230 and an internal space of the dust collection unit 220 through the airflow discharge opening 204. And communicate with each other. The airflow discharge opening 204 is a through-hole penetrating the belt facing portion 222 in the vertical direction, and a plurality of openings 204 are provided at intervals in the axial direction of the developing roller 48. The airflow discharge opening 204 is closed with a filter 206 for preventing the passage of toner. The airflow discharge opening 204 is not limited to the above-described through hole, and may be a slit-like opening extending in the axial direction of the developing roller 48.

  The photosensitive member facing portion 224 is suspended from the right end portion of the belt facing portion 222, and the lower end portion of the photosensitive member facing portion 224 constitutes the upper peripheral edge portion of the opening 44 of the housing 42.

  The developing roller facing portion 226 has a shape extending from the lower end portion of the photosensitive member facing portion 224 toward the vicinity of the supply / recovery area 88 along a part of the outer peripheral surface of the developing roller 48, and the rotation of the developing roller 48. In the direction 78, it faces the developing roller surface portion downstream of the developing region 96 and upstream of the supply / recovery region 88. A space is secured between the developing roller facing portion 226 and the developing roller 48, whereby an airflow passage 237 is formed between the developing roller facing portion 226 and the developing roller 48. An opening 202 for introducing an air current is formed in the developing roller facing portion 226. As a result, the internal space of the powder smoke recovery unit 220 and the development region 96 communicate with each other via the airflow introduction opening 202 and the airflow passage 237. Further, the internal space of the powder smoke recovery unit 220 and the supply / recovery region 88 communicate with each other via the airflow introduction opening 202 and the airflow passage 237.

  The airflow introduction opening 202 is a through-hole penetrating the developing roller facing portion 226 in the vertical direction, and a plurality of openings 202 are provided at intervals in the axial direction of the developing roller 48. The opening 202 for introducing the airflow is provided corresponding to the opening 204 for discharging the airflow. For example, the opening 202 is provided immediately below the opening 204 for discharging the airflow. The airflow introduction opening 202 is not limited to the above-described through hole, but may be a slit-like opening extending in the axial direction of the developing roller 48.

  The conveyance roller facing portion 228 has a shape that extends obliquely upward from an end near the supply / recovery area 88 of the developing roller facing portion 226 and along a part of the outer peripheral surface of the conveyance roller 54.

  Next, the airflow generated around the dust collection unit 220 during the image forming operation will be described.

  When the image forming operation is performed, the intermediate transfer belt 230 moves in the right direction in the drawing, and accordingly, an air flow that moves in the right direction in the drawing is generated between the intermediate transfer belt 230 and the belt facing portion 222. . When such an air flow is generated, the kinetic energy of the air between the intermediate transfer belt 230 and the belt facing portion 222 increases, so that the pressure decreases according to Bernoulli's theorem.

  The rightward airflow generated between the intermediate transfer belt 230 and the belt facing portion 222 is blocked by the photoconductor 12 and changes its direction, and the space between the photoconductor facing portion 224 and the photoconductor 12 is moved downward. It becomes a moving air flow. This downward airflow is blocked by the nip portion between the photoreceptor 12 and the developing roller 48, and becomes an airflow that advances in the rotation direction 78 of the developing roller 48 along the outer peripheral surface of the developing roller 48. The airflow in the rotation direction 78 of the developing roller 48 enters the airflow passage 237 through the opening 44 and travels toward the airflow introduction opening 202.

  At this time, a magnetic brush is formed on the outer peripheral surface of the conveying roller 54, and the airflow passage 237 is in the vicinity of the supply / recovery region 88 on the downstream side in the rotation direction 78 of the developing roller 48 with respect to the opening 202 for introducing the airflow. The air pressure in the airflow passage 237 is increased because the portion is blocked by the magnetic brush. For this reason, a pressure difference is generated between the air passage 237 having a relatively high pressure and the space between the intermediate transfer belt 230 and the belt facing portion 222 having a relatively constant pressure. From the passage 237, the air flows into the space between the intermediate transfer belt 230 and the belt facing portion 222 through the airflow introduction opening 202, the internal space of the dust collection unit 220, and the airflow discharge opening 204. An upward airflow is generated.

  Since such an air flow is generated during image formation, even if the toner scatters in the developing region 96 to generate dust, the toner dust is generated by the air flow passage 237 and the air flow introduction opening. After being guided to the internal space of the dust collecting unit 220 through 202 and blocked by the filter 206, it stays in the internal space of the dust collecting unit 220. In addition, even if toner dust is generated in the supply and recovery area 88, the toner dust is guided to the internal space of the dust collector 220 from the air flow passage 237 by the above-described air flow, and is similarly recovered. It stays in the internal space of the part 220. As described above, according to the present invention, by utilizing the pressure difference generated in association with the image forming operation, the toner can be placed in the internal space of the dust collecting unit 220 provided in the developing device 34 without using power. The dust can be reliably recovered.

[Second Embodiment]
In the dust collection unit 262 according to the second embodiment illustrated in FIG. 13, the belt facing unit 222 is a streamlined curved unit that bulges toward the intermediate transfer belt 230. The airflow discharge opening 204 is formed in a portion closest to the intermediate transfer belt 230 in the belt facing portion 222.

  In the present embodiment, since the surface of the belt facing portion 222 is streamlined, when an air flow similar to that in the first embodiment is generated during the image forming operation, the space between the belt facing portion 222 and the intermediate transfer belt 230 is generated. The energy loss when air flows through the belt becomes extremely small, and the velocity of the airflow between the belt facing portion 222 and the intermediate transfer belt 230 increases. In particular, the space between the belt 230 and the portion closest to the belt 230 in the belt facing portion 222 and the belt 230 has the smallest cross-sectional area, so that the velocity of the airflow is maximized, thereby minimizing the atmospheric pressure. FIGS. 17 and 18 are diagrams in which the flow of air around the dust collection unit 262 generated during the image forming operation is visualized by numerical analysis. Specifically, FIG. 17 represents the air flow with streamlines, and FIG. 18 represents the flow velocity vector of the airflow shown in FIG.

  During the image forming operation, the space between the belt facing portion 222 and the portion closest to the belt 230 and the belt 230, that is, the portion of the space between the belt facing portion 222 and the belt 230 where the atmospheric pressure is minimum (minimum). The air pressure discharge opening 204 communicates the minimum air pressure portion and the internal space of the powder smoke recovery portion 262 with each other. . Therefore, during the image forming operation, the belt facing portion 222 and the belt 230 pass through the airflow passage opening 237, the airflow introduction opening 202, the internal space of the dust collection unit 262, and the airflow discharge opening 204. The upward flow of air flowing into the space between the two increases the flow velocity due to a larger pressure difference, and the toner dust collection performance is further improved.

  In the second embodiment, the configuration in which the entire belt facing portion 222 is a streamlined curved portion has been described. However, a part of the belt facing portion 222 may be a streamlined curved portion. Further, the airflow discharge opening 204 may be formed not only in the portion closest to the belt 230 in the belt facing portion 222 but also in the peripheral portion of the portion.

[Third Embodiment]
In the dust collection unit 263 according to the third embodiment shown in FIG. 14, a conveying screw (corresponding to a third conveying member in claims) 238 is provided in the internal space. More specifically, the conveying screw 238 is provided in the vicinity of the lower end portion of the developing roller facing portion 226 where the toner is most likely to stay in the internal space of the dust collecting portion 263. The conveyance screw 238 is, for example, a long member extending in parallel with the axial direction of the developing roller 48, and a waste toner box (not shown) provided in the image forming apparatus 1 via another conveyance member. It corresponds to the recovery unit.) When the conveying screw 238 is rotationally driven, the toner staying in the internal space of the dust collecting unit 263 is conveyed to the waste toner box by the conveying screw 238 and collected in the waste toner box.

  As described above, in the present embodiment, since the toner staying in the internal space of the dust collecting unit 263 is appropriately conveyed to the waste toner box, it is possible to prevent the toner from filling the internal space of the dust collecting unit 263. . Therefore, the life of the developing device 34 can be extended, and the dust collecting unit 263 can be downsized, that is, the developing device 34 can be downsized.

[Fourth Embodiment]
In the dust collecting unit 264 according to the fourth embodiment shown in FIG. 15, the toner collected in the internal space of the dust collecting unit 264 is prevented from flowing out through the opening 202 for introducing airflow. Therefore, a protrusion 244 for preventing the recovery toner from flowing out is provided at the peripheral edge of the opening 202 for introducing the airflow. The protruding portion 244 is provided so as to surround the airflow introducing opening 202 and toward the inside of the powder smoke collecting portion 264. Therefore, the toner collected in the internal space of the dust collecting unit 264 is prevented from moving to the opening 202 for introducing the air current by the protrusion 244, so that the toner flows out through the opening 202 for introducing the air current. It can be prevented as much as possible.

[Fifth Embodiment]
In the dust collection part 265 according to the fifth embodiment shown in FIG. 16, an opening 202 for introducing an air current is formed in the photosensitive member facing part 224. Thereby, the internal space of the dust collection part 265 communicates with the space between the photosensitive member facing part 224 and the photosensitive member 12 through the opening 202 for introducing airflow. During the image forming operation, the air pressure in the space between the belt facing portion 222 and the belt 230 decreases with the generation of the airflow in the right direction in the drawing, as in the first to fourth embodiments. The air pressure is lower than the space between the body facing portion 224 and the photoconductor 12. For this reason, during the image forming operation, a pressure difference is generated between the space between the photosensitive member facing portion 224 and the photosensitive member 12 and the space between the belt facing portion 222 and the belt 230. From the space between the body facing portion 224 and the photoreceptor 12, the belt facing portion 222 and the belt pass through the opening 202 for introducing airflow, the internal space of the dust collecting unit 265, and the opening 204 for discharging airflow. An airflow is generated that travels to a space with 230. Therefore, even if the toner is scattered in the developing region 96 during the image forming operation, the toner dust is generated from the space between the photoconductor facing portion 224 and the photoconductor 12 by the above-described air flow. The air is introduced into the internal space of the dust collection unit 265 through the opening 202 for introducing the air current, and is collected in the internal space of the powder collection unit 265. Therefore, the same effect as the first to fourth embodiments can be obtained.

  While the present invention has been described with reference to the above-described embodiment, the present invention is not limited to the above-described embodiment.

  For example, in the above-described embodiment, the case where so-called hybrid development is adopted as the development method has been described. However, the present invention also applies to the case where so-called one-component development or two-component development or other development methods are adopted as the development method. The same applies.

  In the above-described embodiment, the configuration in which the developing device is disposed in the vicinity of the intermediate transfer belt has been described. However, in the present invention, the developing device has a belt shape that moves in a predetermined moving direction during an image forming operation. The belt-shaped member is not limited to the intermediate transfer belt as long as it is configured in the vicinity of the member. Examples of the belt-like member other than the intermediate transfer belt include an endless belt-like conveyance member that conveys a recording medium such as paper.

  Furthermore, in the above-described embodiment, the internal space of the dust collection unit communicates with both the development region (first region) and the supply / collection region (second region) through the opening for introducing the airflow. The configuration (first to fourth embodiments) and the configuration in which the internal space of the dust collection unit communicates only with the development region (first region) via the opening for introducing airflow (fifth embodiment) However, the present invention includes a configuration in which the internal space of the dust collection unit communicates only with the supply and collection region (second region) through the airflow introduction opening.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional view of a developing device according to the present invention. The figure which illustrates the composition of a developer typically. The figure which shows typically the state in which the toner which hold | maintained the charged particle has adhered to the surface of a carrier. The figure which shows typically the state by which the charged particle was bombarded on the surface of the carrier to which the spent adhered. The figure which shows one Embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 6A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 7A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows the relationship between the voltage supplied to the sleeve and the image development sleeve from the electric field formation apparatus shown to FIG. 8A. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows other embodiment of an electric field formation apparatus. The figure which shows typically the motion of the toner and charged particle in a supply collection area | region. The figure which shows the cross section of the dust collection part which concerns on 1st Embodiment. The figure which shows the cross section of the dust collection part which concerns on 2nd Embodiment. The figure which shows the cross section of the dust collection part which concerns on 3rd Embodiment. The figure which shows the cross section of the dust collection part which concerns on 4th Embodiment. The figure which shows the cross section of the dust collection part which concerns on 5th Embodiment. The figure which shows the flow of the air around the dust collection part shown in FIG. The figure which shows the flow velocity vector of the airflow shown in FIG. Sectional drawing which shows the prior art example of a developing device.

Explanation of symbols

1: image forming apparatus, 2: developer, 4: carrier, 6: toner, 8: charged particles, 10: spent, 12: photoconductor, 34: developing apparatus, 36: transfer apparatus, 38: sheet, 40: cleaning Device: 42: Housing, 44: Opening, 48: Developing roller, 54: Conveying roller, 58: Magnet body, 60: Sleeve, 63: Restricting plate, 66: Developer stirring chamber, 72: Screw, 86: Restricting area , 88: supply / recovery region, 94: emission region, 96: development region, 110: electric field forming device, 112: first power source, 114: second power source, 116: ground, 118: DC power source, 120: DC power source 122: electric field forming device, 124: first power supply, 126: ground, 128: DC power supply, 130: second power supply, 132: DC power supply, 134: AC power supply, 136: electric field forming device, 138 1st power supply, 140: Ground, 142: DC power supply, 144: AC power supply, 146: Second power supply, 148: Terminal, 150: DC power supply, 152: Electric field forming device, 154: AC power supply, 156: AC power supply 158: electric field forming device, 160: AC power source, 202: opening for introducing airflow, 204: opening for discharging airflow, 206: filter, 208: charger, 210: exposure device, 220: powder smoke recovery unit 222: belt facing portion, 224: photoconductor facing portion. 226: Developing roller facing portion, 228: Conveying roller facing portion, 230: Intermediate transfer belt, 236: Recording medium, 237: Airflow path, 238: Conveying screw, 244: Protruding portion for preventing recovery toner outflow, 262 to 265 : Powder smoke recovery unit.

Claims (6)

A belt-shaped member that moves in a predetermined moving direction during image forming operation, a latent electrostatic image bearing member which is contactable disposed on the surface of the belt-shaped member in the vicinity of the upper Symbol belt-shaped member, and, an image forming apparatus having a developing equipment which will be disposed in the upstream side of the electrostatic latent image bearing member in the moving direction of the belt-shaped member,
The developing device is
A first conveying member that faces the electrostatic latent image carrier through the first region and supplies toner to the electrostatic latent image carrier, which is rotatable in a predetermined rotation direction;
A second conveying member that faces the first conveying member via a second region and supplies toner to the first conveying member;
A housing that houses the first transport member and the second transport member;
The housing includes a dust collecting unit for collecting toner dust generated in the first region or the second region,
The dust collection unit
An airflow introduction opening for communicating at least one of the space in the vicinity of the first region or the space in the vicinity of the second region and the internal space of the dust collector,
Plugged with filter to prevent passage of toner, and, e Bei an opening for air flow discharge for communicating the interior space of the space and the Konakemuri recovery portion of the belt-like member near,
The image forming apparatus, wherein the airflow discharge opening is formed in a belt facing portion provided in the dust collecting portion so as to face the belt-like member . The belt facing portion has a streamlined curved portion that bulges toward the belt-shaped member, and an opening for discharging the airflow at a portion of the curved portion closest to the belt-shaped member or a peripheral portion of the portion. The image forming apparatus according to claim 1 , wherein a portion is formed. The dust collecting unit is opposed to the surface portion of the first conveying member on the downstream side of the first region and on the upstream side of the second region in the rotation direction of the first conveying member. Having a first conveying member facing portion,
3. The image forming apparatus according to claim 1, wherein an opening for introducing the airflow is formed in the first conveying member facing portion. 4. The powder smoke recovery part has a protruding part for preventing recovery toner outflow, which protrudes toward the inside of the powder smoke recovery part so as to surround the opening for introducing the air flow. The image forming apparatus according to claim 3. A developer including a toner and a carrier, wherein the toner and the carrier are charged to a first polarity by frictional contact with each other and the carrier is charged to a second polarity different from the first polarity; ,
A first electric field is formed between the first conveying member and the second conveying member, and the toner held by the second conveying member is moved to the first conveying member. Electric field forming means,
A second electric field is formed between the first conveying member and the electrostatic latent image carrier, and the toner held by the first conveying member is transferred to the electrostatic latent image carrier. e Bei and second electric field forming means for a visible image to the electrostatic latent image is moved to the latent image,
The second transport member has a magnet body and a rotating cylindrical body that rotates around the magnet body,
The airflow passage formed between the powder smoke recovery unit and the first transport member is rotated on the downstream side of the airflow introduction opening in the rotation direction of the first transport member. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to be blocked by the developer held on the outer peripheral surface of the cylindrical body. The image according to any one of claims 1 to 5, wherein a third conveying member for conveying the toner to a predetermined waste toner collecting unit is provided in the internal space of the dust collecting unit. Forming equipment .