JP4611145B2 - Developing device, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to a developing device used in a copying machine, a printer, a facsimile, and the like, and more particularly to a developing device using a two-component developer composed of toner and a magnetic carrier, an image forming apparatus provided with the developing device, and a process cartridge. .

Conventionally, as a developing device using a two-component developer composed of a toner and a magnetic carrier, a developing device described in Patent Document 1 is known.
18A to 18D are explanatory views showing the developing device described in Patent Document 1. FIG. Note that the various arrows in the figure indicate the movement direction of the developer, and the thicker the arrow, the greater the developer movement amount.
As shown in FIG. 18A, the developing device 304 mainly includes a developing roller 5 as a developer carrying member, a collecting screw 6 as a collecting and conveying member, and a first stirring screw 11A as a stirring and conveying member. And a second agitating screw 11B, a supply screw 8 as a supply conveying member, and a developing doctor 16 as a developer regulating member. The developing device 304 is provided with a recovery conveyance path 7 in which the recovery screw 6 is incorporated so as to be obliquely adjacent to the developing roller 5. In addition, a first agitation conveyance path 10 </ b> A containing the first agitation screw 11 </ b> A is provided so as to be adjacent on the same horizontal plane as the collection conveyance path 7. Furthermore, a second stirring and conveying path 10B that houses a second stirring screw 11B is provided above the first stirring and conveying path 10A. Further, a supply conveyance path 9 containing a supply screw 8 is provided so as to be adjacent to the same horizontal plane as the second agitation conveyance path 10 </ b> B and above the collection conveyance path 7. The supply conveyance path 9 is adjacent to the upper side of the developing roller 5 obliquely.

The developer transport in the developing device 304 will be described.
First, when the developer in the supply conveyance path 9 is supplied to the developing roller 5 by the supply screw 8, the supplied developer is regulated by the developing doctor 16 as the developing roller 5 rotates, and thereafter, a latent image (not shown). It is conveyed to the developing area facing the carrier. In this development area, the toner in the supplied developer adheres to the latent image on the latent image carrier and development is performed. The supplied developer that has consumed the toner in the development area in this manner is then removed from the developing roller 5 and collected in the collection conveyance path 7. The recovered developer is conveyed by the recovery screw 6 as shown in FIG. Then, the recovered developer transported to the downstream end in the developer transport direction in the recovery transport path 7 moves to the first stirring transport path 10A. Thereafter, the recovered developer that has moved to the first agitating and conveying path 10A is conveyed to the downstream end in the developer conveying direction in the first agitating and conveying path 10A while being agitated by the first agitating screw 11A. At the downstream end of the first stirring and conveying path 10A, the developer stays and rises upward, so that the developer in the first stirring and conveying path 10A is adjacent to the second stirring and conveying path 10 above the second stirring and conveying path 10A. Move to 10B. As shown in FIG. 18 (d), the developer that has moved to the second agitation conveyance path 10B is conveyed to the downstream end in the developer conveyance direction in the second agitation conveyance path 10B while being agitated by the second agitation screw 11B. The Thereafter, the developer moves into the supply conveyance path 9. As described above, the developing device 304 circulates and conveys the developer in one direction.

Further, as shown in FIG. 18B, the developing device 304 of Patent Document 1 has a toner replenishing port 361A that opens at a location 143 where the developer is transferred from the collection conveyance path 7 to the first stirring conveyance path 10A. And a carrier supply port 361B. The toner supply port 361A communicates with a toner storage portion 386A that stores unused toner HT. The carrier replenishment port 361B communicates with a carrier accommodating portion 386B that accommodates unused carriers HC. In the developing device 304, unused toner and carrier are supplied from the supply ports 361A and 361B. Therefore, the recovered developer recovered into the recovery conveyance path 7 after development is supplied to the first agitation conveyance path 10A after receiving replenishment from these supply ports 361A and 361B.
Further, as shown in FIG. 18A, the supply transport path 9 is provided with a developer discharge port 381 for discharging the developer in the supply transport path 9 to the outside of the developing device. The developer discharge port 381 develops the excess amount of developer when the amount of developer in the supply conveyance path 9 exceeds a predetermined amount due to replenishment of unused developer from the replenishment ports 361A and 361B. It is for discharging outside the device. Thereby, the amount of the developer in the developing device is always kept constant.
In the developing device 304 described in Patent Document 1, the unused carrier HC is periodically supplied into the developing device, and the carrier used for repeated image formation is discharged out of the developing device. It is possible to suppress a decrease in the charge amount of the toner due to deterioration, and to realize frictional charging of the toner with a stable carrier at all times.

JP 2004-77587 A

  However, in the developing device 304 described in Patent Document 1, since the developer discharge port 381 is provided in the supply conveyance path 9, the developer in the supply conveyance path 9 is discharged outside the development apparatus. . The developer in the supply conveyance path 9 is a developer supplied to the developing roller 5 and has a sufficiently high toner density. For this reason, the developing device 304 has a problem in that a lot of toner that can still be sufficiently used is discharged together with the deteriorated carrier to the outside of the developing device.

  The present invention has been made in view of the above problems, and the object of the present invention is to supply a developer to a developer carrier and to develop from the developer carrier as in the developing device described in Patent Document 1. In the configuration in which the agent recovery is separated, when replenishing unused developer and discharging used developer, it is possible to reduce the amount of toner that can still be used at the time of discharging. A developing device, and an image forming apparatus and a process cartridge including the developing device are provided.

In order to achieve the above object, the invention of claim 1 is a portion where a developer composed of a magnetic carrier and toner is carried on the surface by a plurality of magnetic poles provided inside and rotated to face the latent image carrier. The developer carrying member for supplying toner to the latent image on the surface of the latent image carrying member, the developer is conveyed along the axial direction of the developer carrying member, and the developer is supplied to the developer carrying member. A supply conveyance path provided with a supply conveyance member, a developer regulating member for regulating the thickness of the developer on the developer carrying body supplied from the supply conveyance path, and a portion facing the latent image carrying body A recovery transport path provided with a recovery transport member for transporting the developer recovered from the developer carrier after passing through the developer in the axial direction of the developer carrier, and the supply without being used for development Excess developer transported to the most downstream side in the transport direction of the transport path, and the developer from the developer carrier. And the recovered developer transported to the most downstream side in the transport direction of the recovery transport path and transported while stirring the excess developer and the recovered developer in the axial direction of the developer carrier A developer conveying path, comprising: a stirring conveyance path that delivers the surplus developer and the recovered developer to the supply conveyance path; and three collection paths, the collection conveyance path, the supply conveyance path, and the stirring conveyance path. In the developing device having partitioning members that are separated from each other except for receiving and delivering the toner, unused developer including unused toner and unused magnetic carrier is transferred from the developer replenishing port to the above three transport paths. Developer replenishing means for replenishing at least one of the transport paths, and developer corresponding to a part of the total amount of the developer present in the developing device, from the developer discharge port. Discharging developer It is characterized in that it has a stage.
According to a second aspect of the present invention, in the developing device according to the first aspect, the developer discharge port is provided in the vicinity of the downstream end of the recovery conveyance path in the developer conveyance direction.
The invention according to claim 3 is the developing device according to claim 1 or 2, wherein the developer replenishing port is located downstream of the developer discharge port in the recovery transport path in the developer transport direction or the stirring transport path. It is provided inside.
According to a fourth aspect of the present invention, in the developing device according to the first or second aspect, the developer replenishment port is provided with a place where the developer is transferred from the recovery conveyance path and the supply conveyance path to the stirring conveyance path. It is characterized in that it is provided.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, the developer discharging means exceeds the specified amount when the amount of the developer present in the developing device exceeds a specified amount. It is characterized by discharging a sufficient amount of developer.
According to a sixth aspect of the present invention, in the developing device of the first, second, third, fourth, or fifth aspect, the developer replenishing means is a uniaxial eccentricity for transferring the unused developer to the developer replenishing port. Having a screw pump, the developer replenishment passage for feeding the unused developer to the uniaxial eccentric screw pump is negatively pressured, and the unused developer in the uniaxial eccentric screw pump is sent out from the developer replenishing port. It has the structure.
According to a seventh aspect of the present invention, in the developing device of the first, second, third, fourth, fifth or sixth aspect, the recovery conveyance path is provided below the developer carrying member, and the three conveyance paths are substantially arranged. They are arranged at the same height.
The invention of claim 8 is the developing device according to claim 7, wherein the uppermost position of the supply transport member is positioned below the rotation center axis of the developer carrying member, and the supply transport member The supply / conveyance member is arranged so that an angle formed by a virtual plane passing through the uppermost position and the rotation center axis and a horizontal plane passing through the rotation center axis is within a range of 10 ° to 40 °. It is characterized by this.
According to a ninth aspect of the present invention, in the developing device of the first, second, third, fourth, fifth or sixth aspect, the collection conveyance path is provided above the stirring conveyance path. .
According to a tenth aspect of the present invention, there is provided a latent image carrier, a latent image forming unit that forms a latent image on the surface of the latent image carrier, and a developing unit that attaches toner to the latent image and develops the latent image. In the image forming apparatus for forming an image by finally transferring the toner image formed on the surface of the latent image carrier onto a recording material, the developing unit is defined by claim 1, 2, 3, 4, The present invention is characterized in that a developing device of 5, 6, 7, 8 or 9 is used.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect of the present invention, the image forming apparatus further includes a developer container that accommodates an unused developer in a state where the toner and the magnetic carrier are mixed in advance. The developer replenishing means replenishes unused developer in the developer container to the at least one transport path from the developer replenishing port.
According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, the toner concentration detecting means for detecting the toner concentration of the developer present in the developing device, and the detection result of the toner concentration detecting means. Accordingly, a replenishment amount control means for controlling the replenishment amount of the unused developer by the developer replenishment means of the developing device is provided.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to the tenth, eleventh or twelfth aspect, each of the toner formed on each latent image carrier has a plurality of the latent image carriers and the developing devices. The image forming apparatus is characterized in that an image in which images overlap each other is finally formed on a recording material.
According to a fourteenth aspect of the present invention, in the image forming apparatus according to the tenth, eleventh, twelfth or thirteenth aspect, the latent image carrier and the developing device are provided, and a toner image on the latent image carrier is recorded on the recording material. There are two image forming portions to be transferred onto the surface, and the transfer of the toner image onto one surface of the recording material by one image forming portion and the other surface of the recording material by the other image forming portion And a fixing means for fixing the toner images to the recording material after the toner images are transferred onto both surfaces of the recording material simultaneously or sequentially. It is.
The invention according to claim 15 is the image forming apparatus according to claim 10, 11, 12, 13 or 14, wherein the magnetic carrier has a volume average particle diameter in the range of 20 [μm] to 60 [μm]. It is characterized by using what is.
The invention according to claim 16 is the image forming apparatus according to claim 10, 11, 12, 13, 14 or 15, wherein the toner has a volume average particle size in the range of 3 [μm] to 8 [μm]. And the ratio of the volume average particle diameter to the number average particle diameter is in the range of 1.00 to 1.40.
The invention according to claim 17 is the image forming apparatus according to claim 10, 11, 12, 13, 14, 15 or 16, wherein the toner has a shape factor SF-1 in the range of 100 to 180, And what uses shape factor SF-2 in the range of 100-180 is used.
The invention according to claim 18 is the image forming apparatus according to claim 10, 11, 12, 13, 14, 15, 16, or 17, wherein the toner has an average primary particle size of 50 nm to 500 nm. In the following range, an external additive having a bulk density of 0.3 [g / cm ³ ] or more added to the surface of the toner base particles is used.
According to the nineteenth aspect of the invention, at least the latent image carrier and the developing means for developing the latent image on the latent image carrier are integrally supported, and are configured to be detachable from the image forming apparatus main body. In the process cartridge, the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 is used as the developing means.

In the present invention, the supply of the developer in the supply conveyance path to the developer carrying member and the recovery of the developer after development into the collection conveyance path are performed separately from each other. Then, the developer replenishing means replenishes the unused developer from the developer replenishing port to at least one of the three transport paths, and the developer discharging means uses the used developer existing in the developing device. The developer is discharged from the developer discharge port by an amount corresponding to a part of the total amount. As a result, the magnetic carrier is replenished at the time of toner replenishment, and the used developer including the magnetic carrier that has been deteriorated by being used for repeated image formation is discharged. Can be stably suppressed with time, and stable triboelectric charging of the toner by the magnetic carrier can be realized with time.
In the present invention, since the developer discharge port is provided in the collection conveyance path, the used developer discharged from the developer discharge port is the developer in the collection conveyance path. The developer in the collection conveyance path is a developed developer that consumes toner by development, and has a low toner concentration. Therefore, according to the present invention, the amount of toner in the used developer discharged from the developer discharge port can be suppressed as compared with the developing device described in Patent Document 1.

  According to the present invention, when the developer supply to the developer carrying member and the developer recovery from the developer carrying member are separated, when the unused developer is replenished and the used developer is discharged, An excellent effect is achieved in that the amount of toner that can still be used at the time of discharge can be reduced.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic color copier (hereinafter simply referred to as “copier”) as an image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram showing the copying machine according to the present embodiment.
The copying machine includes a printer unit 100, an operation / display unit 90, a paper feeding device 40, an automatic image reading device 200, a paper supply device 300, and the like.

  The printer unit 100 includes a first image forming unit (one image forming unit) disposed above and a second image forming unit (the other image forming unit) disposed below the paper conveyance path 43A. Image portion). The first image forming unit includes a first transfer unit 20 having a first intermediate transfer belt 21 that is an intermediate transfer body that moves endlessly in the direction of the arrow in the drawing. Further, the second image forming unit includes a second transfer unit 30 having a second intermediate transfer belt 31 which is an intermediate transfer body that moves endlessly in the direction of the arrow in the drawing. Four first process units 80Y, 80M, 80C, and 80K are arranged above the upper stretched surface of the first intermediate transfer belt 21. On the other hand, four second process units 81Y, 81M, 81C, 81K are disposed on the side of the inclined tension surface on the side of the second intermediate transfer belt 31. The subscripts (color subscripts) Y, M, C, and K attached to the numbers of the first process unit and the second process unit correspond to the colors of the toners to be handled, respectively. Y is yellow, C is cyan, M means magenta and K means black. The same color-coded subscript is attached to each device in the process unit as necessary.

  The first process units 80Y, 80M, 80C, and 80K have photoreceptors 1Y, 1M, 1C, and 1K as latent image carriers, respectively. Similarly, the second process units 81Y, 81M, 81C, 81K also have photoreceptors 1Y, 1M, 1C, 1K as latent image carriers, respectively. The photoreceptors 1Y, 1M, 1C, and 1K of the first process units 80Y, 80M, 80C, and 80K are arranged at equal intervals, and at least at the time of image formation, contact the upper stretched surface of the first intermediate transfer belt 21, respectively. Hereinafter, the belt surface that contacts in this way is referred to as a first image receiving surface. Similarly, the photoreceptors 1Y, 1M, 1C, and 1K of the second process units 81Y, 81M, 81C, and 81K are also arranged at equal intervals, and at least during the image formation, respectively, on the side stretched surface of the second intermediate transfer belt 31. Contact. Hereinafter, the belt surface that contacts in this way is referred to as a second image receiving surface.

The first intermediate transfer belt 21 is stretched around a plurality of rollers so as to have a horizontally long posture that takes a space in a horizontal direction rather than a vertical direction and a posture in which the first image receiving surface extends substantially horizontally. Yes. The first process units 80Y, 80M, 80C, and 80K are arranged in parallel so as to be in contact with such a substantially horizontal first image receiving surface.
On the other hand, the second intermediate transfer belt 31 has a vertically long posture with a space in the vertical direction rather than the horizontal direction, and a plurality of rollers so that the second image receiving surface is inclined from the upper left to the lower right in the drawing. It is stretched around. The second process units 81Y, 81M, 81C, 81K are arranged on the left side of the second intermediate transfer belt 31 from the upper left to the lower right in the drawing so as to contact the inclined second image receiving surface. It is arrange | positioned so that it may become a diagonal arrangement | sequence.

FIG. 3 is an enlarged configuration diagram showing one of the four first process units 80Y, 80M, 80C, and 80K.
The first process units 80Y, 80M, 80C, and 80K have substantially the same configuration except that the colors of the toners handled are different from each other. Therefore, in FIG. 3, the color-coded subscripts attached to the reference numerals are omitted.
In FIG. 3, the photosensitive member 1 is driven to rotate counterclockwise in the drawing by a driving unit (not shown) during operation of the printer unit 100. Around the photoconductor 1, a scorotron charger 3 as a charging unit, a developing device 4 as a developing unit, a photoconductor cleaning device 2, a photostatic device Q, a potential sensor S1, an image sensor S2, and the like are arranged. Yes. The photosensitive member 1 forms an electrostatic latent image on its surface by a laser beam L emitted from an exposure device (not shown) which is a latent image forming unit. As the photoreceptor 1 of this embodiment, for example, a drum-shaped member in which an organic cylindrical layer (OPC) that is a photoconductive substance is coated on the surface of an aluminum cylinder having a diameter of about 30 to 120 [mm] is used. The photoreceptor 1 may be one that is coated with an amorphous silicon (a-Si) layer. Further, it may be a belt shape instead of a drum shape.

The photoconductor cleaning device 2 includes a cleaning brush 2a, a cleaning blade 2b, a recovery member 2c, and the like, and removes foreign matters such as transfer residual toner remaining on the surface of the photoconductor 1 after passing through a primary transfer nip described later. ,to recover.
The scorotron charger 3 is for uniformly charging the surface of the photoconductor 1 that is rotationally driven to, for example, a negative polarity. As a charging means for performing uniform charging, a charging roller may be used instead of the scorotron charger. Alternatively, a charging bias member to which a charging bias is applied may be in contact with the surface of the photoreceptor 1.
An exposure apparatus (not shown) scans light corresponding to image data for each color on the surface of each photoreceptor 1 that is uniformly charged by a scorotron charger 3 to form an electrostatic latent image. As an exposure apparatus, a laser scanning system that uses an LED (light emitting diode) array as a light emitting element and a crystal element, or scans laser light modulated in accordance with image data using a laser light source, a polygon mirror, or the like. Can be adopted.

  The development system of this embodiment employs a two-component development system in which development is performed using a two-component developer (hereinafter simply referred to as “developer”) composed of toner and a magnetic carrier. In the present embodiment, the electrostatic latent image for each color formed on the surface of each photoconductor 1 is developed with each color toner charged to the same polarity (negative polarity) as the charged polarity of the photoconductor 1. A so-called reversal development method is employed. The developing device 4 of the present embodiment is provided with a magnetic toner density sensor (not shown) as a toner density detection unit. Further, as shown in FIG. 2, developer bottles 86Y, 86M, 86C, and 86K as developer containers are attached inside the printer unit 100, and development described later is performed according to the detection result of the toner density sensor. Each color developer is supplied to each developing device 4 by a developer supplying device as a agent supplying means. A detailed description of the configuration of the developing device 4 will be given later.

FIG. 4 is an enlarged configuration diagram showing one of the four second process units 81Y, 81M, 81C, 81K.
Each of the second process units 81Y, 81M, 81C, and 81K has substantially the same configuration except that each of the handled toner colors is different, and therefore, the color-coded subscripts attached to the reference numerals are omitted in FIG. The configuration of the second process units 81Y, 81M, 81C, 81K is the same as that of the first process units 80Y, 80M, 80C, 80K. However, in the second process units 81Y, 81M, 81C, and 81K, since the rotational direction of the photosensitive member 1 is different in the drawing, the first process unit 81Y is shown in FIG. The process unit 80 is axially symmetric. Such an axially symmetric configuration is an important point related to the arrangement of members provided around the photoreceptor 1. This is because the first process unit can be obtained by considering the coupling portion with the printer unit 100, specifically, the coupling portion with the driving means, the electrical connection portion, the developer supply device, the developer discharge device, and the like. This is because compatibility can be provided between the 80Y, 80M, 80C, and 80K and the second process units 81Y, 81M, 81C, and 81K. That is, it is not necessary to manufacture members such as a dedicated developing device and a cleaning device for each of the first process unit and the second process unit. As a result, the efficiency in component manufacturing and component management is high, and the overall cost can be reduced.

  In FIG. 2 described above, the first image forming unit includes a plurality of first process units 80Y, 80M, 80C, and 80K, and the first transfer unit 20. The second image forming unit includes a plurality of second process units 81Y, 81M, 81C, 81K and a second transfer unit 30. In the printer unit 100, the first transfer unit 20 and the second transfer unit 30 constitute a double-side transfer device.

  As shown in FIG. 2, the first transfer unit 20 stretches the first intermediate transfer belt 21 with a plurality of rollers 23, 24, 25, 26 (two), 27, 28, 29, and performs the first process. The units 80Y, 80M, 80C, and 80K are in contact with the photoreceptors 1Y, 1M, 1C, and 1K. A primary transfer roller 22 is provided at a position facing the photoreceptors 1Y, 1M, 1C, and 1K on the inner periphery of the first intermediate transfer belt 21. By this contact, the first transfer unit 20 transfers the color toner images (hereinafter referred to as “first toner images”) on the photoreceptors 1Y, 1M, 1C, and 1K on the first intermediate transfer belt 21 in a superimposed manner. A primary transfer nip is formed. The first intermediate transfer belt 21 moves endlessly clockwise in the figure while forming these four primary transfer nips. In each primary transfer nip, four primary transfer rollers 22 to which a primary transfer bias is applied by a power source (not shown) sandwich the first intermediate transfer belt 21 between the photoreceptors 1Y, 1M, 1C, and 1K. Yes. Due to the influence of the primary transfer bias and the nip pressure, the first toner images of the respective colors are superimposed on the first intermediate transfer belt 21 and are primarily transferred at each primary transfer nip. By this superposition, a first toner image of a plurality of colors is formed on the first intermediate transfer belt 21.

  A belt cleaning device 20 </ b> A is provided on the outer periphery of the first intermediate transfer belt 21 at a position facing the roller 23. This belt cleaning device 20A wipes off transfer residual toner remaining on the surface of the first intermediate transfer belt 21 after passing through each primary transfer nip and foreign matters such as paper dust. Members related to the first intermediate transfer belt 21 are integrally formed as the first transfer unit 20 and can be attached to and detached from the printer unit 100.

  On the other hand, in the second transfer unit 30, the second intermediate transfer belt 31 is stretched by a plurality of rollers 32 (four), 33, 34, 35, and 36 (two), and the photoreceptors 1Y, 1M, 1C, and 1K. Is in contact with By this contact, the second transfer unit 30 transfers the respective color toner images (hereinafter referred to as “second toner images”) on the photoreceptors 1Y, 1M, 1C, and 1K on the second intermediate transfer belt 31 in a superimposed manner. A primary transfer nip is formed. The second intermediate transfer belt 31 moves endlessly in the counterclockwise direction in the figure while forming these four primary transfer nips. In each primary transfer nip, four primary transfer rollers 32 to which a primary transfer bias is applied by a power source (not shown) sandwich the second intermediate transfer belt 31 between the photoreceptors 1Y, 1M, 1C, and 1K. Yes. Due to the influence of the primary transfer bias and the nip pressure, the second toner image of each color is superimposed on the second intermediate transfer belt 31 and is primarily transferred at each primary transfer nip. By this superposition, a second toner image having a plurality of colors is formed on the second intermediate transfer belt 31.

  A belt cleaning device 30 </ b> A is provided on the outer periphery of the second intermediate transfer belt 31 at a position facing the roller 33. The belt cleaning device 30A wipes off unnecessary toner remaining on the surface of the second intermediate transfer belt 31 after passing through each primary transfer nip and foreign matters such as paper dust. Members related to the second intermediate transfer belt 31 are also integrally formed as the second transfer unit 30 and can be attached to and detached from the printer unit 100.

As the two intermediate transfer belts 21 and 31, for example, belts having a base of a resin film or rubber having a thickness of 50 to 600 [μm], for example, are used. The belt exhibits an electric resistance value at which a toner image, which is a visible image carried on the photoreceptor 1, can be electrostatically transferred to the belt surface by a primary transfer bias applied to the primary transfer rollers 22 and 32. To be configured. As an example of such an intermediate transfer belt, there can be mentioned one in which carbon is dispersed in polyamide and its volume resistance value is adjusted to about 10 ⁶ to 10 ¹² [Ω · cm]. Each of the two intermediate transfer belts 21 and 31 is provided with a belt detent rib for stabilizing the belt running at one end or both end portions of the belt. The belt circumferences of these belts 21 and 31 are about 1500 [mm].

The four primary transfer rollers 22 as the primary transfer means in the first transfer unit 20 and the four primary transfer rollers 32 as the primary transfer means in the second transfer unit 30 have, for example, the following configurations. Things can be used. That is, it is possible to employ a configuration in which a conductive rubber material is coated on the surface of a metal roller serving as a metal core, and a bias is applied to the metal core part from a power source (not shown). In the present embodiment, a conductive rubber material obtained by dispersing carbon in urethane rubber is used, and its volume resistance value is adjusted to about 10 ⁵ [Ω · cm].

  The printer unit 100 can also output a monochrome image using only K toner. When outputting a monochrome image, the Y, M, and C process units 80Y, 80M, and 80C in the first transfer unit 20 are not used. Specifically, the process units 80Y, 80M, and 80C are not operated, and the process units 80Y, 80M, and 80C and the first intermediate unit are not operated by a mechanism for keeping the process unit 80Y, 80M, and 80C in a non-contact state. The transfer belt 21 is separated from each other. As this mechanism, for example, an internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, and a mechanism that supports the roller 26 so as to be rotatable around a certain point can be adopted. If this mechanism is used, the mechanism is rotated in a direction away from the photosensitive member, so that only the first photosensitive member 1K is moved in a state where the process units 80Y, 80M, and 80C and the first intermediate transfer belt 21 are separated from each other. It is possible to execute a monochrome image forming process using black toner by bringing it into contact with the intermediate transfer belt 21. Such a configuration is advantageous in terms of improving the life of the photoreceptor. Similarly, the second transfer unit 30 also separates the process units 81Y, 81M, 81C from the second intermediate transfer belt 31 when outputting a monochrome image.

A secondary transfer roller 46 sandwiches the first intermediate transfer belt 21 between the outer periphery of the first intermediate transfer belt 21 and a support roller 28 that supports the first intermediate transfer belt 21 while supporting it on the back surface. It is arranged. Thereby, in the first transfer unit 20, a secondary transfer nip in which the first intermediate transfer belt 21 and the secondary transfer roller 46 come into contact with each other is formed. A region from the support roller 28 through the secondary transfer nip to the secondary transfer roller 46 is a first transfer portion in the double-side transfer device. The secondary transfer roller 46 is obtained by coating the surface of a metal roller serving as a core metal with a conductive rubber, and a secondary transfer bias is applied to the core metal portion from a secondary transfer bias power source (not shown). The volume resistance value of the conductive rubber is adjusted to about 10 ⁷ [Ω · cm] by the dispersion of carbon.

  A registration roller pair 45 is disposed on the right side of the above-described secondary transfer nip in FIG. The registration roller pair 45 temporarily rotates the rollers after sandwiching a transfer sheet P as a recording material fed from a sheet feeding device 40 disposed on the right side of the printer unit 100 in the drawing. Interrupt. Then, the transfer paper P is sent out toward the secondary transfer nip at a timing that can be synchronized with the multi-color first toner image that is the superimposed toner image on the first intermediate transfer belt 21. The transferred transfer paper P is brought into close contact with the first toner image of a plurality of colors on the first surface (the surface facing the upper side in the figure) which is one surface of the transfer paper P at the secondary transfer nip. Then, due to the influence of the secondary transfer bias and the nip pressure, the multi-color first toner image on the first intermediate transfer belt 21 is secondarily transferred to the first surface. The transfer paper P that has passed through the secondary transfer nip is separated from the first intermediate transfer belt 21 and the secondary transfer roller 46 and transferred to the second intermediate transfer belt 31.

  In the second transfer unit 30, a belt-wrapped portion by the upper stretching roller 34 that stretches the second intermediate transfer belt 31 is an upper stretched surface of the second intermediate transfer belt 31. Above this upper stretch surface, a transfer charger 47 serving as a charge applying means is disposed so as to face the upper stretch surface with a predetermined gap. A region from the transfer charger 47 to the upper tension roller 34 via this predetermined gap is a second transfer portion of the second transfer unit 30.

  A known transfer charger 47 can be used. A thin wire such as tungsten or gold is used as a discharge electrode, which is held by a casing, and a transfer current is applied to the discharge electrode from a power source (not shown). While the transfer paper P is passed between the second intermediate transfer belt 31 and the transfer charger 47, the first surface is provided with charges generated from the transfer charger 47, so that a plurality of colors on the second intermediate transfer belt 31 are provided. The two toner images are secondarily transferred onto the second surface of the transfer paper P. Both the secondary transfer bias and the charge applied by the transfer charger 47 have a positive polarity opposite to the polarity of the toner.

  On the right side of the printer unit 100 in the drawing, a paper feeding device 40 that accommodates the transfer paper P is provided. The paper feeding device includes a plurality of paper storage means. Specifically, the uppermost sheet feed tray 40a, the first sheet feed cassette 40b disposed below the sheet feed tray 40a, the second sheet feed cassette 40c disposed below the first sheet feed cassette 40b, and the lower section thereof Is provided with a third paper feed cassette 40d. Each of these paper storage means is disposed so as to be able to be drawn out to the near right side (operation surface side) with respect to the paper surface. In addition, transfer sheets P of different sizes are accommodated. In each paper storage means, the uppermost transfer paper P is selectively separated and fed by the corresponding paper feed / separation means 41A, 41B, 41C, 41D, and only one sheet is reliably fed by the plurality of transport roller pairs 42B. It is sent to the paper transport path 43B or 43A.

  The pair of registration rollers 45 is provided in the paper transport path 43A in order to take a feeding timing for feeding the transfer paper P to the first transfer unit and the second transfer unit of the double-side transfer device. Further, a lateral registration correction mechanism 44 for setting the position in the direction orthogonal to the conveyance direction of the transfer paper P to a normal position is provided in the paper conveyance path 43A. Examples of the lateral registration correcting mechanism 44 include the following. That is, the transfer paper P is slid and conveyed so as to be composed of a horizontal reference guide (not shown) and a pair of skew rollers, and the horizontal end of the transfer paper is pressed against the reference guide. Then, the transfer paper is aligned with a predetermined position. The reference guide is moved and arranged at a predetermined position according to the size of the transfer paper P. The lateral registration correcting mechanism 44 presses both sides of the transfer paper P for a short time and a plurality of times from both lateral directions of the transfer paper P with respect to the transport direction of the transfer paper P to align the transfer paper P at a predetermined position. A jogger system composed of a regulating member may be used.

  The transfer paper P is conveyed from the registration roller pair 45 toward the first transfer portion where the secondary transfer nip is formed by the contact between the first intermediate transfer belt 21 and the secondary transfer roller 46. Thereafter, the second intermediate transfer belt 31 and the transfer charger 47 are sent toward the second transfer portion facing each other.

  In the paper feeding device 40, the transfer paper P fed from the uppermost paper feeding tray 40 a among the plurality of paper feeding trays is bent with respect to the paper conveyance path 43 A of the printer unit 100. It is designed to be transported almost horizontally and straight. For this reason, even if the thick transfer paper P or the highly rigid paperboard is accommodated in the paper feed tray 40a, the paper can be stably fed to the paper transport path 43A of the printer unit 100. In addition, it is preferable to employ an air sheet feeding composed of a vacuum mechanism so that the sheet feeding tray 40a can reliably feed a sheet of paper having various characteristics. Although not shown, a sensor for detecting the transfer paper P is provided at a key point of the paper transport path 43A, and serves as a trigger for various signals based on the presence of the transfer paper P.

  A second paper feed path 43C is provided above the paper feed tray 40a. The transfer paper P is fed to the second paper feed path 43C from the paper supply device 300 installed on the right side of the paper feed device 40 in the drawing.

On the left side of the second transfer unit 30 in the drawing, paper transport for transporting the transfer paper P that has passed through the second transfer section to the fixing nip in the fixing device 60 downstream in the transport paper transport direction while maintaining a flat state. A unit 50 is arranged. The paper transport unit 50 endlessly moves the paper transport belt 51 counterclockwise in the drawing while stretching the paper transport belt 51 by a plurality of stretching rollers 52, 53, 54, 55, and 56. On the outside of the paper conveying belt 51, the conveying cleaning device 50A is opposed to the stretching roller 55, the adsorption charger 57 for adsorbing the transfer paper P is opposed to the roller 56, and the separating roller 54 is opposed to the conveying roller P. A separation charger 58 for separating the transfer paper P is provided.
The paper transport unit 50 is configured to feed the transfer paper P discharged from the second transfer unit of the second transfer unit 30 at a belt winding position by a receiving roller 52 that is one of a plurality of stretching rollers. Receive on. At a timing earlier than this reception, a negative charge having the same polarity as the polarity of the toner is applied to the surface of the paper transport belt 51 by the suction charger 57. By applying this charge, the paper transport unit 50 can electrostatically attract the transfer paper P discharged from the second transfer unit to the surface of the paper transport belt 51.

The paper conveyance belt 51 having the transfer paper P electrostatically adsorbed on the surface conveys the transfer paper P from the right side to the left side in the drawing along with its endless movement. Then, the transfer paper P is fed toward a fixing device 60 as fixing means disposed on the left side of the paper transport unit 50 in the drawing. Charge is applied to the transfer paper P electrostatically attracted to the surface of the paper transport belt 51 by the separation charger 58 at a timing earlier than this feeding. By applying this electric charge, the transfer paper P that has been electrostatically attracted to the surface of the paper conveyance belt 51 until then can be easily separated from the paper conveyance belt 51. Then, among the plurality of stretching rollers, a paper whose moving direction is suddenly changed in accordance with the curvature of the separation roller 54 at a belt winding position by the separation roller 54 disposed closest to the fixing device 60. The transfer paper P is separated from the conveyance belt 51 by its strength, and the transfer paper P is fed into the fixing device 60.
As the paper conveying belt 51, a metal belt, a polyimide belt, a polyamide belt, or the like can be employed. The paper transport belt 51 has a releasability from the toner on its surface and has a resistance value that allows charging for electrostatic adsorption. The moving speed of the paper conveying belt 51 is matched with the moving speed of the transfer paper P in the fixing device 60.

A fixing device 60 having a heating unit is provided on the downstream side of the paper transport unit 50 in the recording paper transport direction.
As the fixing device 60, a system having a heater inside the fixing roller, a system in which a belt to be heated is run, a system using induction heating, or the like can be used. A system in which a plurality of color first toner images and a plurality of color second toner images are respectively fixed on the transfer paper P by heating the transfer paper P from both sides at a fixing nip formed by contacting two fixing rollers. Is adopted. In order to make the color tone and glossiness of the images on both sides of the transfer paper P the same, the belt material, hardness, surface property, etc. of the two fixing rollers are made to be the same up and down. Further, various parameters of the fixing device 60 are controlled so as to create an optimal fixing condition for each surface depending on whether it is a full-color image and a monochrome image, or one surface or both surfaces.

The transfer paper P that has been subjected to the fixing process by the fixing device 60 is sent out toward the discharge path. In this discharge path, a pair of cooling rollers 70 having a cooling function is disposed for the purpose of cooling the transfer paper P after the fixing process and stabilizing the unstable toner state at an early stage. As the cooling roller pair 70, a heat pipe structure roller having a heat radiating portion can be adopted.
The transfer paper P cooled by the cooling roller pair 70 is discharged and stacked on a discharge stack unit 75 provided on the left side of the printer unit 100 by a discharge roller pair 71. This discharge stacking unit employs a mechanism in which a receiving member moves up and down according to a stack level by an elevator mechanism (not shown) so that a large amount of transfer paper can be stacked. Note that the transfer paper can also be conveyed to another post-processing apparatus after passing through the paper discharge stack unit 75. As another post-processing apparatus, an apparatus for bookbinding such as punching, cutting, folding, and binding can be provided.

  On the upper surface of the printer unit 100, developer bottles 86Y, 86M, 86C, and 86K that contain unused developer in which unused toner and unused magnetic carrier are mixed in advance are detachable for each color. It is stored in the bottle storage portion 85. The unused developer in each developer bottle 86Y, 86M, 86C, 86K is replenished to the corresponding color developing device 4 as necessary by a developer replenishing device described later. In this embodiment, the unused developer to be replenished is one in which toner and magnetic carrier are mixed in advance. However, the replenishing toner and the magnetic carrier are stored in separate containers and replenished. You may comprise so that these may be supplied simultaneously or separately. The unused developer in the present embodiment is one in which the toner weight ratio (toner concentration) with respect to the developer is adjusted to about 85 wt%. The value of the toner density is not limited, and is appropriately set according to the capacity of the developing device 4 and the developer bottles 86Y, 86M, 86C, 86K, the set lifetime, and the like. In the present embodiment, the first image forming unit and the second image forming unit arranged above and below supply toner from a common developer bottle to a developing device that handles toner of the same color. However, it can be separated. The K developer bottle 86K, which consumes a large amount, can have a larger capacity than the other bottles 86Y, 86M, 86C. The bottle housing portion 85 is provided on the back side of the upper surface of the printer unit 100 when viewed from the front surface where the user is located, and a flat surface portion is secured on the front surface side of the upper surface of the printer portion 100, and this flat surface portion is used as a work table for the user. It can be used.

  The operation / display unit 90 provided on the upper surface of the printer unit 100 is provided with an input operation unit (not shown) including a touch panel and the like, thereby inputting conditions for image formation. In addition, various information can be displayed on a display unit (not shown) such as a display, and information exchange between the operator and the printer unit 100 is facilitated.

  A used developer container 87 is provided inside the printer unit 100. The used developer container 87 is connected to the photoconductor cleaning device 2, the belt cleaning devices 20A and 30A for the intermediate transfer belt, the transport cleaning device 50A for the paper transport belt, and the like. Then, foreign substances such as toner and paper powder sent from these are collected and stored in a lump. Further, the used developer container 87 is also connected to a developer discharging means of the developing device 4 as described later, and also stores the used developer discharged from the developing device 4. Since these cleaning devices 2, 20A, 30A, 50A and the developing device 4 are not equipped with a large-capacity used developer container, these devices can be miniaturized, and the operability of discarding the used developer and the like can be reduced. It is good. A full sensor (not shown) is used to issue warnings such as disposal of used developer in the used developer container 87 and container replacement.

  In addition, various power supplies, control boards, and the like are protected and stored in a sheet metal frame in a control unit 95 provided in the printer unit 100. The inside of the image forming apparatus becomes hot due to heat from the fixing device 60 or heat generated from the electrical device. However, as a countermeasure against this, a fan 96 is provided to prevent deterioration of the function due to heat of the internal members. Further, the fan 96 is coupled to the heat radiating portion of the cooling roller pair 70 to enhance the effectiveness of the cooling effect of the cooling roller pair 70.

  An automatic image reading device (ADF) 200 that reads an image of a document while automatically conveying the document by a well-known technique is provided on the upper portion of the paper feeding device 40, and reading information obtained by this is sent to the control unit 95. . Based on the sent read information, the printer unit 100 is driven and controlled, and an image corresponding to the document image is output. Further, image information from a personal computer (not shown) or the like can be sent to the printer unit 100 and an image corresponding to the image information can be output. Furthermore, it is also possible to send image information sent from a telephone line (not shown) and output an image corresponding to the image information. As described above, the paper supply device 300 for supplying the transfer paper P to the paper supply device 40 is disposed on the right side of the paper supply device 40 in the drawing.

Next, an operation at the time of single-sided recording in which the printer unit 100 forms a full-color image on one side of the transfer paper P will be described.
There are two types of single-sided recording methods, which can be selected. One of the two types is a method in which the first toner image transferred onto the first intermediate transfer belt 21 is secondarily transferred onto the first surface of the transfer paper P. In this case, a full-color image based on the first toner image of the plurality of colors is formed on the upper surface of the transfer paper P on the paper discharge stack unit 75. The other is a method in which the second toner image transferred onto the second intermediate transfer belt 31 is secondarily transferred onto the second surface of the transfer paper P. In this case, a full color image based on the second toner image is formed on the lower surface of the transfer paper P on the paper discharge stack portion 75. In the case where the image to be formed covers a plurality of pages, it is preferable to control the image forming order so that the pages are aligned on the paper discharge stack unit 75.
Hereinafter, as an example, a method in which a first toner image of a plurality of colors is carried on the first intermediate transfer belt 21 and then transferred to the transfer paper P so that the pages are formed in order from the last page image and aligned. I will explain.

  When the printer unit 100 is operated, the photoreceptors 1Y, 1M, 1C, and 1K and the first intermediate transfer belt 21 in the first process units 80Y, 80M, 80C, and 80K rotate. At the same time, the second intermediate transfer belt 31 also moves endlessly. At this time, the photoreceptors 1Y, 1M, 1C, and 1K in the second process units 81Y, 81M, 81C, and 81K are separated from the second intermediate transfer belt 31 and are not rotated. When image formation by the first process unit 80Y is started, the light corresponding to the Y image data emitted from the LED is scanned by the operation of an exposure device (not shown) composed of the LED array and the imaging element. The surface of the photoreceptor 1Y uniformly charged by the rotron charger 3 is irradiated to form an electrostatic latent image for Y.

  The electrostatic latent image for Y is developed into a Y toner image by the developing device of the first process unit 81Y for Y, and electrostatically 1 on the first intermediate transfer belt 21 at the primary transfer nip for Y. Next transferred. Such latent image formation, development, and primary transfer operation are sequentially performed in the same manner at the timings on the photosensitive members 1M, 1C, and 1K. Then, the Y toner image on the first intermediate transfer belt 21 is primarily transferred at the M, C, and K primary transfer nips so that the M toner image, the C toner image, and the K toner image sequentially overlap each other. The By these primary transfers, a multi-color first toner image in which the toner images of the respective colors overlap is carried on the first intermediate transfer belt 21. The multi-color first toner image is moved together with the first intermediate transfer belt 21 in the direction of the arrow in the figure.

  On the other hand, the paper feeding device 40 feeds the transfer paper P corresponding to the image data from the internal paper feeding tray 40a or the paper feeding cassettes 40b, 40c, 40d to any one of the paper feeding / separating means 41A, 41B, 41C, 41D. Send out by one. And it conveys toward the paper conveyance path 43C of the printer part 100 by conveyance roller pair 42B, 42C. Then, it is sent to the lateral registration correction mechanism 44. The lateral registration correction mechanism 44 is an inclination correction unit that corrects the inclination of the posture of the transfer sheet P that is being conveyed from the paper feeding device 40 toward the double-side transfer device from the conveyance direction. The lateral registration correction mechanism 44 abuts the pair of guide plates arranged in the paper surface direction orthogonal to the transport direction upstream of the registration roller pair 45 to both ends orthogonal to the transport direction of the transfer paper P. Thus, the inclination of the posture of the transfer paper P is corrected. The two guide plates of the pair of guide plates are movable in the direction of the paper surface orthogonal to the transport direction. By moving according to the width of the fed transfer paper P, the distance between the plates can be reduced. Can be adjusted to the width.

The transfer paper P whose posture inclination is corrected by the lateral registration correction mechanism 44 reaches between the rollers of the registration roller pair 45. At this time, the registration roller pair 45 is stationary, and the leading edge of the transfer paper P is stationary while entering the nip of the registration roller pair 45. Then, the registration roller pair 45 rotates at a timing such that the position of the first color toner image on the first intermediate transfer belt 21 becomes normal, and the transfer paper P is conveyed to the transfer area.
The multi-color first toner images on the first intermediate transfer belt 21 are subjected to a transfer action by the secondary transfer roller 46 on the first surface of the transfer paper P conveyed in synchronization with the first intermediate transfer belt 21, and 2 Next transferred. The bias applied to the secondary transfer roller 46 has a positive polarity opposite to the charging polarity of the toner. The surface of the first intermediate transfer belt 21 that has passed through the secondary transfer nip is cleaned of transfer residual toner by the belt cleaning device 20A.

  Further, in each of the first process units 80Y, 80M, 80C, and 80K, the transfer residual toner remaining on the photoreceptors 1Y, 1M, 1C, and 1K after passing through the primary transfer nip is removed from the photoreceptor cleaning device 2. Cleaned by. As shown in FIG. 2, the photoconductor cleaning device 2 removes transfer residual toner from the surfaces of the photoconductors 1Y, 1M, 1C, and 1K using a cleaning brush 2a and a cleaning blade 2b. The removed foreign matter such as toner is sent to the waste toner container 87 by the collecting member 2c. The sensors S1 and S2 described above detect the surface potential after exposure on the surface of the photoconductor and the density of the toner image adhering to the surface of the photoconductor after the development process, and use the detection results as the detection results. Output to the control unit 95 for appropriately setting and controlling the image forming conditions. Further, the surface of the photoreceptor 1 after the cleaning is initialized by removing the residual charges by the static eliminating device Q.

  After the transfer paper P on which the first toner image of the plurality of colors is secondarily transferred to the first surface at the secondary transfer nip of the first transfer portion is transferred to the second intermediate transfer belt 31 of the second transfer unit 30, It is sent to the paper transport unit 50. Then, the paper is transported from the paper transport unit 50 to the fixing device 60. Prior to this transport, the transfer paper P is charged by the separation charger 58. With this application, the transfer paper P that has been electrostatically attracted to the second intermediate transfer belt 31 can be easily separated from the paper transport belt 51.

  In the fixing device 60, the color toners constituting the first toner image of the plurality of colors carried on the first surface of the transfer paper P are softened or melted by heating and mixed with each other to form a complete color image. Here, since the transfer paper P carries toner only on its first side, less heat energy is required for fixing compared to double-sided recording where toner is carried on both sides. The control unit 95 optimally controls the power used by the fixing device 60 according to the document image. Even after the fixing process is performed, until the first toner image of multiple colors is completely fixed on the transfer paper P, the first toner image of multiple colors is rubbed against a guide member or the like of the conveyance path. May disturb the image. In order to prevent this problem, the transfer paper that has passed through the fixing device 60 is immediately cooled by the cooling roller pair 70 that is a cooling means.

  The transfer paper P that has passed through the cooling roller pair 70 is discharged by the paper discharge roller pair 71 onto the paper discharge stack portion 75 with its image surface facing upward. In this example, since the image forming order is programmed so that the transfer sheets of the young pages are sequentially stacked on the discharge stack unit 75, the page order is aligned in the discharge stack unit 75. Further, since the paper discharge stack unit 75 descends as the number of transfer sheets P to be discharged increases, the transfer sheets can be reliably stacked and the page order is not disturbed. Instead of directly stacking the image-recorded transfer paper P on the paper discharge stack section 75, the transfer paper P may be conveyed to a post-processing device such as a punching device, a sorter, a collator, a binding device, or a folding device.

  Even when an image is formed on the second surface of the transfer paper P using the second process units 81Y, 81M, 81C, and 81K, the transfer paper P using the first process units 80Y, 80M, 80C, and 80K described above. Since this is almost the same as the case where an image is formed on the first surface, description thereof is omitted. However, in this case, it should be noted that the first process units 80Y, 80M, 80C, and 80K are not operated, and the point that images are formed in order from a young page for page alignment is different.

Next, the operation at the time of duplex recording in which the printer unit 100 forms images on both sides of the transfer paper P will be described.
When an image signal is input to the printer unit 100, a first toner image of each color is formed on the photoreceptors 1Y, 1M, 1C, and 1K of the first process units 80Y, 80M, 80C, and 80K described in the single-sided recording operation. To do. These are primary-transferred by sequentially superimposing on the first intermediate transfer belt 21 at the primary transfer nips for Y, M, C, and K. Almost in parallel with this step, second toner images of the respective colors are formed on the photoreceptors 1Y, 1M, 1C, and 1K of the second process units 81Y, 81M, 81C, and 81K, and these are formed as Y, M, C, and K. Primary transfer is performed by sequentially superimposing on the second intermediate transfer belt 31 at the primary transfer nip. In this way, the first toner image and the second color toner image are formed on the first intermediate transfer belt 21 and the second intermediate transfer belt 31, respectively.

  As shown in FIG. 2, in this embodiment, the unit intervals of the second process units 81Y, 81M, 81C, 81K are smaller than the unit intervals of the first process units 80Y, 80M, 80C, 80K. Thereby, the first transfer is completed faster in the second transfer unit 30 than in the first transfer unit 20. In addition, in order for the first toner image of the plurality of colors and the second toner image of the plurality of colors to coincide with each other at the leading edge in the conveyance direction of the transfer paper P, the formation of the second toner image is delayed from the start of the formation of the first toner image. To start. Further, since the transfer paper P is transported after being temporarily stopped by the registration roller pair 45, the transfer paper P is fed in consideration of the time.

  The registration roller pair 45 transports the transfer paper P to the secondary transfer nip of the first transfer portion constituted by the secondary transfer roller 46 and the first intermediate transfer belt 21 at a timing. A positive polarity transfer current flows into the secondary transfer nip through the secondary transfer roller 46, whereby the first toner image of a plurality of colors on the first intermediate transfer belt 21 is transferred onto the first surface of the transfer paper P. The transfer sheet P on which the first color toner image is transferred onto the first surface in this manner is continuously sent to the second transfer section having the transfer charger 47 by the conveying action of the secondary transfer roller 46. Then, a positive polarity transfer current is applied to the transfer charger 47, so that a plurality of color second toner images previously carried on the second intermediate transfer belt 31 are transferred to the second surface of the transfer paper P by 2. Next transferred.

  The transfer paper P on which the multi-color toner images are transferred on both sides in this way is transported to the fixing device 60 by the paper transport belt 51 of the paper transport unit 50. At this time, the surface of the paper transport belt 51 is charged by the suction charger 57 to the same negative polarity as the polarity of the toner. Therefore, unfixed toner adhering to the second surface of the transfer paper P facing the surface of the paper transport belt 51 does not move to the paper transport belt 51 side. Thereafter, alternating current is applied to the charge removal / separation charger 58, and the transfer paper P is separated from the paper transport belt 51 and sent to the fixing device 60. When the fixing process by heating or pressurization is performed in the fixing device 60, the respective color toners constituting the first toner image and the second toner image are softened or melted and mixed with each other. The toner image is fixed on the transfer paper P. Thereafter, the transfer paper P is cooled through the cooling roller pair 70 and the paper discharge roller pair 71 and then discharged onto the paper discharge stack 75.

  When double-sided recording images of a plurality of pages on the transfer paper P, the image forming order is controlled so that the image of the young page is stacked on the paper discharge stack unit 75 as the bottom surface. As a result, when the paper is taken out from the paper discharge stack 75 and the top and bottom surfaces are reversed, the page order is set so that the first page is the top, the second page is the second, the third page is the third, and the back is the fourth page. It's aligned. Such control of the image forming order and control such as increasing the power input to the fixing device 60 from that during single-sided recording are executed by the control unit 95.

In the above description, the single-sided recording operation and the double-sided recording operation are described as an example in which a full-color image is formed. However, the same applies to the case of forming a monochrome image using only K toner.
Further, when the necessity for maintenance or replacement of parts arises, the maintenance is performed by opening an unillustrated exterior cover or the like.

  In the printer unit 100 having the above configuration, a first toner image is formed on the surface of the first intermediate transfer belt 21 that is the first toner image carrier by the combination of the first image forming unit and the control unit 95 described above. A first toner image forming unit is configured. Further, a combination of the second image forming unit and the control unit 95 constitutes a second toner image forming unit that forms a second toner image on the surface of the second intermediate transfer belt 31 that is a second toner image carrier. Yes. A toner image forming unit is configured by a combination of the first image forming unit, the second image forming unit, and the control unit 95.

Next, the configuration of the developing device 4 which is a characteristic part of the present invention will be described.
FIG. 1 is a schematic configuration diagram showing a developing device 4 in the present embodiment. The configuration of the developing device provided in each process unit 80Y, 80M, 80C, 80K, 81Y, 81M, 81C, 81K is substantially the same except that the color of the handled toner is different. Therefore, in FIG. 1, the color-coded subscripts attached to the reference numerals are omitted.
In FIG. 1, the surface of the photoreceptor 1 is charged by the scorotron charger 3 while rotating in the direction of arrow G in the figure. An electrostatic latent image is formed on the surface of the charged photoreceptor 1 by a laser beam L irradiated from an exposure device (not shown), and a toner image is attached to the electrostatic latent image by a developing device 4. And

  The developing device 4 has a developing roller 5 as a developer carrying member whose surface moves in the direction of arrow I in the drawing. The developing roller 5 carries a developer on the surface thereof, and causes the developer to contact the electrostatic latent image on the surface of the photosensitive member, thereby attaching toner to the electrostatic latent image. Further, the developing device 4 has a supply screw 8 as a supply and conveyance member that conveys the developer toward the back side of the sheet of FIG. 1 while supplying the developer to the developing roller 5. Further, the developing device 4 develops as a developer regulating member that regulates the developer supplied to the developing roller 5 to a thickness suitable for development on the downstream side of the developing roller surface moving direction of the portion facing the supply screw 8. A doctor 16 is provided. Further, the developing device 4 collects the developed developer that has passed through the developing area on the downstream side in the developing roller surface movement direction of the developing area, which is a facing portion between the developing roller 5 and the photosensitive member 1, and collects the collected developer. A recovery screw 6 is provided as a recovery transport member that transports the agent in the same direction as the supply screw 8. A supply conveyance path 9 provided with a supply screw 8 and a collection conveyance path 7 provided with a collection screw 6 are juxtaposed below the developing roller 5.

The two conveyance paths of the supply conveyance path 9 and the collection conveyance path 7 are separated from each other by a partition plate 134 as a partition member. However, the partition plate 134 has an opening at the back end in the drawing, which is the most downstream side in the conveyance direction of the collection screw 6, and the supply conveyance path 9 and the collection conveyance path 7 are connected through the opening. Communicate with each other. Further, when the upper end portion of the partition plate 134 is brought into contact with the developing roller 5, the rotational load of the developing roller 5 increases. Therefore, in this embodiment, the distance between the partition plate 134 and the developing roller 5 is preferably 1 [mm] or less. Is provided.
Further, the developing device 4 includes an agitation conveyance path 10 on the opposite side of the collection conveyance path 7 with respect to the supply conveyance path 9. The agitating and conveying path 10 is provided with an agitating screw 11 as an agitating and conveying member that conveys the developer to the front side of the drawing sheet in the drawing, which is the direction opposite to the supply screw 8 while agitating the developer. The supply conveyance path 9 and the stirring conveyance path 10 are partitioned from each other by a partition wall 133 as a partition member. However, both ends of the partition wall 133 on the front side and the back side in the drawing are openings, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other through the opening.

With such a configuration, the excess developer in the supply conveyance path 9 that is not used for development and conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 and the collection screw 6 conveys to the downstream end in the conveyance direction of the collection conveyance path 7. The collected developer that has been collected is delivered to the stirring and conveying path 10. The agitation conveyance path 10 conveys the received excess developer and the collected developer while being agitated by the agitation screw 11 in the opposite direction to the developer in the collection conveyance path 7 and the supply conveyance path 9. Then, the developer is transferred to the upstream side in the transport direction of the supply transport path 9 communicating with the downstream side in the transport direction. A toner concentration sensor 127 serving as a toner concentration detecting unit is provided below the agitation conveyance path 10, and a developer replenishing device 160 serving as a developer replenishing unit is operated by the sensor output, so that the developer bottle 86 Replenish unused developer.
The partition wall 133 is a part of the casing, and the partition plate 134 is held by the casing.

  The developer replenishing device 160 passes unused developer including unused toner and unused magnetic carrier from the developer replenishing port 161 to at least one of the three transport paths 7, 9, and 10 described above. To replenish. In the present embodiment, the developer supply port 161 is provided at a location where the developer is transferred from the collection conveyance path 7 and the supply conveyance path 9 to the stirring conveyance path 10. Since this portion is a place where the stirring action with respect to the developer is intense, if unused developer is replenished to this portion, the toner is vigorously stirred immediately after the replenishment to promote frictional charging of the toner. As a result, it is possible to effectively prevent the toner charge amount from becoming insufficient when the replenished unused developer is conveyed to the supply conveyance path 9 and supplied to the developing roller 5. The same applies to the case where the unused developer is replenished at another location where the developer is delivered.

FIGS. 5A and 5B are explanatory views showing the structure of a Mono pump that is a uniaxial eccentric screw pump constituting the developer supply device 160. FIG.
The developer replenishing device 160 serves as a means for transferring the unused developer in the developer bottle 86 to the developer replenishing port 161. The mono pump 162 as a uniaxial eccentric screw pump and a flexible transport tube as a developer replenishing path. 163. As shown in FIG. 5 (b), the MONO pump 162 includes a screw-shaped roller 162a that is eccentric using a rigid member such as metal or resin, and a stator 162b that is formed into a screw shape with two inner sides made of a rubber material. , And a holder 162c including both of these members. One end of the transport tube 163 is attached to one end of the MONO pump 162, and the other end of the transport tube 163 is connected to the developer bottle 86. When the roller 162a is rotated by the replenishing drive motor 162d, a suction pressure is generated in the holder 162c, and the inside of the transport tube 163 is reduced to a suction negative pressure. As a result, unused developer in the developer bottle 86 is received by the suction force into the holder 162 c via the transport tube 163, and is supplied to the developing device 4 from the developer supply port 161. Further, the rotation operation (time) of the roller 162a can be controlled by the replenishment clutch 162e connected to the replenishment drive motor 162d. Therefore, the replenishment amount of the unused developer can be finely adjusted by controlling the clutch operation of the replenishment clutch 162e.
If this MONO pump 162 is used, the conveyance path connecting the developer bottle 86 and the developing device 4 can be freely bent. Therefore, the positional relationship between the developer bottle 86 and the developing device 4 is less restricted than in a configuration in which a linear conveying path is limited as in the case where a conveying screw or the like is used, and the layout in the copying machine is free. The degree is improved. Further, as a result of the developer bottle 86 containing the unused developer being disposed away from the developing device 4, the developing device itself can be reduced in size.

Further, as shown in FIG. 1, the supply screw 8 of the present embodiment is disposed such that the screw apex 14 indicating the uppermost position is below the rotation center shaft 15 of the developing roller 5. Further, an angle θ ₁ formed by a straight line connecting the rotation center shaft 15 of the developing roller 5 and the screw apex 14 and a horizontal straight line passing through the rotation center shaft 15 is set to 30 [°]. This angle θ ₁ depends on the diameter of the supply screw 8, but is preferably in the range of 10 ° to 40 ° from the viewpoint of downsizing the developing device 4.

  The developer is supplied to the developing roller 5 by a magnetic pole provided in the developing roller 5 attracting a magnetic carrier in the developer. As described above, when the screw apex 14 is disposed below the rotation center axis 15 of the developing roller 5, the developer's own weight does not affect the amount of developer supplied to the developing roller 5, and the magnitude of the magnetic force is large. Will contribute to the amount of developer supplied. As a result, the developer supply to the developing roller 5 is reliably performed from the upper part of the developer in the supply conveyance path 9, so that the volume of the developer in the supply conveyance path 9 in the conveyance direction of the supply screw 8 is increased. Even if it is not uniform, an appropriate amount of developer can be supplied to the developing roller 5 along the axial direction of the developing roller 5.

Next, the magnetic pole arrangement of the developing roller 5 will be described.
FIG. 6 is a schematic explanatory diagram of the magnetic pole arrangement of the developing roller 5.
Inside the developing roller 5, a developing downstream end side S pole 218 is arranged at the most downstream position in the developing region in the surface movement direction of the developing roller 5, and the developer is pumped up to a position facing the supply screw 8. An S pole 219 for use is arranged. The region between the development downstream end side S pole 218 and the developer pumping S pole 219 has no magnetic pole. The area where the magnetic pole does not exist is a developer recovery area for recovering the developed developer to the recovery transport path 7, and the recovery transport path 7 is disposed at a position directly below the developing roller 5 facing the developer recovery area. Yes. The developer after development that has passed through the development area is not affected by the magnetic force when conveyed to the developer collection area, and is dropped into the collection conveyance path 7 due to the centrifugal force and its own weight due to the rotation of the developing roller 5, and collected. Is done.

  It is also conceivable to collect the developed developer above the developing roller 5. However, in this case, the developer after development remains on the surface of the developing roller due to its own weight even in the developer recovery area that is not affected by the magnetic force. Therefore, the developer after development rotates along with the developing roller 5 as the surface of the developing roller 5 moves, passes through the developer recovery area, and is conveyed to the supply conveyance path 9. Since the developer after development has a low toner concentration, if it is transported to the supply transport path 9, it may be used for development as it is. As a result, the toner concentration in the developer on the developing roller 5 sent to the developing area is lowered or non-uniform. In the developing device 4 of the present embodiment, as described above, the surface below the developing roller 5 is used as a developer recovery region, and the recovery conveyance path 7 is provided below the developer recovery region. Therefore, the developer's own weight contributes to recovery, and it is possible to prevent the developer after development from passing around the developer roller 5 and passing through the developer recovery area. Therefore, there is no possibility that the developed developer having a low toner density is conveyed to the supply conveyance path 9 and used as it is for development.

  Further, the developing device 4 of the present embodiment has a configuration in which the recovery conveyance path 7 and the recovery screw 6 are provided almost directly below the developing roller 5, and the supply conveyance path 9 and the supply screw 8 are provided obliquely below the developing roller 5. is there. With such a configuration, the distance between the development downstream end side S pole 218 and the pumping S pole 219 can be set wide. In a conventional developing device (conventional triaxial developing device) in which the developer supply to the developing roller and the developer recovery from the developing roller are separated, the developed developer is separated from the developing sleeve by the influence of the magnetic pole on the pumping side. In some cases, it was sometimes carried around. Therefore, in the same manner as described above, the developed developer having a low toner concentration may be used for development as it is. On the other hand, in the developing device 4 of the present embodiment, the distance between the development downstream end side S pole 218 and the pumping S pole 219 is set wide, so that the developer after development is affected by the pumping S pole 219. It is hard to receive. Therefore, it is possible to prevent the developed developer having a low toner concentration from being used for development as it is.

  Further, in the conventional triaxial developing device, the angle between the drawing-up magnetic pole of the developing roller and the magnetic pole on the upstream side is about 90 [°] even if the angle is large, and is 20 [° with respect to the conventional developing roller. ] The angle becomes a wider interval (increased by about 25 [%]). If the gap between the pumping magnetic pole and the upstream magnetic pole is widened, the developer that has passed through the upstream magnetic pole is less affected by the magnetic force from the pumping magnetic pole, and the accompanying phenomenon described above is less likely to occur. In the developing device 4 of the present embodiment, the angle between the pumping S pole 219 and the development downstream end side S pole 218 is 113 [°]. This angle is not limited to this, and if the angle is larger than that of the conventional triaxial developing device, for example, 100 [°] or more, it is possible to more reliably prevent the toner density defect caused by the accompanying rotation.

  The developer supplied to the surface of the developing roller 5 from the supply conveyance path 9 has an optimum layer thickness for development by regulating the layer thickness by the developing doctor 16. In order to obtain an optimum layer thickness for development, the developer needs to be regulated by the developing doctor 16, and therefore the amount of developer supplied to the developing roller 5 is larger than the amount of developer passing through the developing doctor 16. There must be many states. That is, in the doctor region 17 on the upstream side of the developing doctor 16, it is necessary to always keep the developer regulated. For this reason, the regulated developer that is regulated accumulates in the doctor area 17 as it is operated. The regulated developer is lifted up by the developer that reaches the doctor area 17 later, and then drops, and returns to the doctor area 17 again. In the developing device 4 of this embodiment, when the amount of the regulated developer exceeds a certain amount so that the regulated developer accumulates in the doctor region 17 and does not repeat convection, the doctor region 17 is bypassed. The regulated developer collecting member 18 is installed so as to return into the supply conveyance path 9. The position of the regulated developer recovery member 18 is appropriately set so that the regulated developer that attempts to return to the supply conveyance path 9 due to the magnetic force of the developing roller 5 does not stay on the regulated developer collection member 18. Has been.

  The developing doctor 16 is fixed in close contact with a heat radiating member 19 fixed to the casing of the developing device 4. Therefore, the development doctor 16 has a function of transmitting heat from the developer to the heat radiating member 19. Fins 120 are formed inside the heat dissipating member 19, and heat is dissipated by the air flow during operation. With such a configuration, the temperature rise of the developer present in the developing device 4 is reduced. Further, the heat radiating member 19 includes a guide portion 121 that is used as a guide when the developing device 4 is detached from the printer portion 100. The casing of the developing device 4 is also provided with heat radiating fins 128, and the temperature rise of the entire developing device is reduced by cooling air sent from the front side to the rear side of the printer unit 100.

  A developer catching roller 122 is installed on the downstream side of the developing roller 5 to catch the magnetic carrier attached to the photosensitive member 1 and the developer dropped from the developing roller 5. Then, the magnetic carrier or developer is rotated in the reverse direction with respect to the developing roller 5, and the supplemented magnetic carrier or developer is returned to the developing roller 5 or is collected in the collecting conveyance path 7 by the scraper 123.

Next, the circulation of the developer in the three transport paths 7, 9, and 10 will be described.
FIG. 7 shows a photosensitive member in which the conveying paths 7, 9, and 10 formed by the lower part of the casing and the screws 6, 8, and 11 provided in these conveying paths are removed in the state where the upper part of the casing of the developing device 4 is removed. It is a perspective view when it sees from 1 side.
In the lower part of the casing, a recovery screw 6, a supply screw 8, and a stirring screw 11 are installed in this order from the front side in the figure, and each conveyance path is divided so as to divide a conveyance area by each screw 6, 8, and 11. 7, 9, and 10 are formed. However, the supply conveyance path 9 and the collection conveyance path 7 are separated by a partition plate 134. The developer is conveyed in the directions of arrows 135 and 136 by the collection screw 6 and the supply screw 8, respectively, and is conveyed in the direction of the arrow 137 in the opposite direction by the stirring screw 11. At this time, the arrows 135 and 136 indicating the transport direction of the recovery screw 6 and the supply screw 8 are transport directions from the front side to the back side in FIG. 1, while the arrow 137 indicating the transport direction of the stirring screw 11 is FIG. This is the conveyance direction from the middle back side to the near side.

Here, the configuration of the screw will be described using the stirring screw 11 as an example.
The agitating screw 11 is used for agitating and conveying wings 138 which are wings for agitating and conveying the developer toward the agitation rotating shaft 170 in the developer conveying direction, and for agitating lateral transfer for transferring the developer to the adjacent supply screw 8 side. And a paddle 139. Further, the agitating / conveying blade portion that applies a conveying force in the direction opposite to the conveying direction to the developer at the downstream end portion in the conveying direction of the agitating / conveying path 10 so that the developer is not fed into the bearing portion on the downstream end side in the developer conveying direction A reverse stirring blade 140 in a winding direction opposite to that of 138 is attached. The recovery screw 6 and the supply screw 8 have the same configuration as that of the stirring screw 11. The specific configuration of the stirring screw 11 in the present embodiment is a single screw having an outer diameter of 30 [mm] and a pitch of 36 [mm]. The specific configuration of the supply screw 8 in the present embodiment is a single screw having an outer diameter of 27 [mm] and a pitch of 36 [mm]. The specific configuration of the recovery screw 6 in the present embodiment is a two-threaded screw having an outer diameter of 25 [mm] and a pitch of 34 [mm]. However, the configuration of these screws 6, 8, and 11 is not limited to this configuration.

As described above, the partition wall 133 is provided with an opening on the downstream side in the developer conveyance direction in the agitation conveyance path 10, and the developer conveyance direction downstream end of the agitation conveyance path 10 and the supply conveyance path 9 are developed. The upstream end in the agent transport direction communicates with the end. The developer conveyed to the downstream end portion in the conveying direction of the agitating conveyance path 10 is transferred to the upstream end portion in the conveying direction of the supply conveying path 9 on the supply screw 8 side by the stirring lateral transfer paddle 139 of the agitating screw 11. The
On the other hand, at the opposite end, as described above, openings are provided in the partition wall 133 and the partition plate 134, and the downstream end of the collection transport path 7 and the supply transport path 9 in the developer transport direction and the stir transport The upstream end of the path 10 in the developer conveyance direction is in communication. The collected developer collected in the collection conveyance path 7 is delivered to the supply conveyance path 9 on the supply screw 8 side by the collection lateral transfer paddle 141 of the collection screw 6. The recovered developer delivered to the supply conveyance path 9 in this way is mixed with the excess developer that is not used for development and is conveyed to the downstream end of the supply conveyance path 9 in the conveyance direction. The surplus developer and the collected developer thus mixed are delivered to the stirring conveyance path 10 on the stirring screw 11 side by the feed lateral transfer paddle 142 of the supply screw 8.

Here, the developer at the position where the three conveyance paths of the collection conveyance path 7 and the supply conveyance path 9 on the downstream side in the developer conveyance direction and the agitation conveyance path 10 on the upstream side in the developer conveyance direction communicate with each other. The horizontal transfer will be described.
FIG. 8 is a cross-sectional view showing a location where the three transport paths 7, 9, and 10 communicate with each other.
Openings are provided in portions of the partition wall 133 and the partition plate 134 corresponding to the locations where the developer is transferred. In this location, the recovery conveyance path 7, the supply conveyance path 9 and the agitation conveyance path 10 are laterally transferred by the rotating paddles. Therefore, if the bottom surface portion of this location is simply flat, the dead point is relative to the rotating paddle. Will occur. When such a dead point occurs, the developer cannot be delivered successfully. Therefore, in the present embodiment, a collection / supply convex portion 131 and a supply / stirring convex portion 132 are provided between the transport paths 7, 9, and 10, respectively, so that the developer over the respective convex portions does not flow backward. It is composed. Further, the collection lateral transfer paddle 141 that delivers the developer slightly upward is configured to have an angle on the developer pushing surface 144 that pushes out the developer and pushes the developer outward. The number of paddles is not limited to two, and the number of blades may be increased according to the carry amount as indicated by a dotted line 141b.
The supply lateral transfer paddle 142 of the supply conveyance path 9 located in the middle of the three conveyance paths 7, 9, 10 draws the received collected developer into the supply conveyance path 9, and the supply conveyance path In order to push the developer in 9 to the agitation transport path 10, the developer does not have an angle like the collection lateral transfer paddle 141, and is almost flat.

As described above, in the developing device 4, the recovery screw 6, the supply screw 8, the agitation screw 11, the recovery conveyance path 7, the supply conveyance path 9 and the agitation conveyance path 10 are arranged laterally below the developing roller 5, The developer is circulated. In this embodiment, the developer is transferred between the conveyance paths in a substantially horizontal direction. Therefore, there is no place where the developer is pushed upward in the circulation of the developer. As a result, it is possible to reduce the stress on the developer when circulating the developer in the developing device 4 and to extend the life of the developer, compared to a configuration in which there is a place where the developer is pushed upward. Can be achieved.
In addition, three conveyance paths communicate with the downstream end in the conveyance direction of the collection screw 6 and the supply screw 8 and the upstream end in the conveyance direction of the stirring screw 11. As a result, the recovered developer and excess developer can be transferred to the agitation transport path 10 with a simple configuration.

  Conventionally, in a configuration in which the developer is transferred in a substantially horizontal direction between adjacent conveyance paths, only the conveyance force in the direction parallel to the axial direction is applied to the developer and collected at the downstream end even near the downstream end in the conveyance direction. In some cases, the developer is transferred to the adjacent conveyance path so as to overflow from the opening. In such a configuration in which the conveying force only in the axial direction is applied to the developer, a large pressure is applied to the developer when the developer overflows from the opening, and excessive stress is applied to the developer. For this reason, the life of the developer is reduced. On the other hand, in the developing device 4 of the present embodiment, a paddle-shaped member that applies a lateral conveyance force is provided at the downstream end portion in the conveyance direction of the conveyance path. The pressure applied to the developer during delivery is small, and the stress on the developer can be reduced.

FIG. 9 is a perspective view of the developing device 4 as viewed obliquely from above.
In the present embodiment, the developer supply port 161 is provided on the outer side in the axial direction than the development region. The unused developer replenished by the developer replenishing device 160 is replenished through the developer replenishing port 161 to the developer delivery portion 143 shown in FIG. As shown in FIG. 9, a roller rotating shaft 5a of the developing roller 5 extends above the developer delivery portion between the collection conveying path 7 and the supply conveying path 9, and the roller rotating shaft 5a is attached to this portion. A drive unit for driving is provided. For this reason, in the developing device 4 of the present embodiment, the developer supply port 161 cannot be provided above the developer delivery portion between the collection conveyance path 7 and the supply conveyance path 9. In this regard, if there is no restriction by the drive unit, a developer supply port 161 may be provided above the developer delivery point between the collection conveyance path 7 and the supply conveyance path 9. By replenishing unused developer at a developer delivery point between the recovery conveyance path 7 and the supply conveyance path 9, an unused developer (high toner concentration developer) is added to the recovery developer whose toner concentration is lowered. ) Can be supplied, the toner concentration of the developer present in the developing device 4 can be efficiently maintained constant.

  As shown in FIGS. 7 and 8, the partition wall 133 that divides the agitation conveyance path 10 and the supply conveyance path 9 has a developer bulk on the downstream side in the developer conveyance direction after the center of the development range of the supply screw 8. An adjustment opening 145 is provided. When the developing roller 5 is stopped or depending on the setting of the developing doctor 16, the developer used for development may decrease, and the volume of the developer in the supply conveyance path 9 may become higher than a desired height. If the volume of the developer becomes higher than the desired height, the state of the developer transported by the supply screw 8 changes, and the transport efficiency is extremely lowered or normal developer circulation cannot be maintained. May cause deterioration of the developer. In the present embodiment, when the volume of the developer reaches or exceeds a desired height after the center of the development range in the supply conveyance path 9, the developer overflows from the developer volume adjustment opening 145 to the agitation conveyance path 10. Therefore, it is possible to prevent the height of the developer beyond the central portion of the development range in the supply conveyance path 9 from exceeding a certain height. The developer overflowing from the developer bulk adjusting opening 145 to the agitation transport path 10 is the developer in the supply transport path 9, so that the toner density is in a state suitable for development. Therefore, even if the overflowed developer is transferred in the middle of the agitation transport path 10, the toner concentration in the agitation transport path 10 does not decrease or the toner density does not become non-uniform.

  As shown in FIG. 7, the developer bulk adjusting opening 145 may be divided into a plurality of locations, or may be provided as a single opening from the center of the development range. The above-described configuration in which an excess portion of the developer in the supply conveyance path 9 is overflowed and delivered to the stirring conveyance path by providing an opening in a portion higher than a predetermined height in the partition wall 133 is the same as the supply conveyance path 9. This is possible because the stirring and conveying path 10 is arranged in parallel at substantially the same height. For example, when the supply conveyance path and the agitation conveyance path are arranged side by side, since the agitation conveyance path is above, even if the developer in the supply conveyance path overflows, it cannot be delivered to the agitation conveyance path. . When the supply conveyance path is on the upper side, a dropping path for dropping the developer once overflowed to the lower agitation conveyance path is required, and the configuration of the developing device becomes complicated. When the supply conveyance path 9 and the agitation conveyance path 10 are arranged at substantially the same height as in the present embodiment, the supply conveyance path 9 has a simple configuration in which an opening is provided at a predetermined height of the partition wall 133. The excess developer inside can be transferred to the stirring conveyance path 10.

Next, the relationship of the developer conveyance amount between the conveyance paths will be described.
FIG. 10 is an explanatory diagram for explaining the developer conveyance amount per unit time and the moving direction of the developer in each of the conveyance paths 7, 9, and 10.
The left-right direction in the figure corresponds to the depth direction of the printer unit 100, that is, the axial direction of the developing roller 5. Developer transport amount (hereinafter referred to as “stir transport amount”) 146 in the stirring transport path 10, developer transport amount (hereinafter referred to as “supply transport amount”) 147 in the supply transport path 9, and recovery transport path 7 development. The agent transport amount (hereinafter referred to as “recovered transport amount”) 148 is indicated by diagonal lines. These transport amounts 146, 147, and 148 indicate that the transport amount at that point is larger as the length in the vertical direction in the figure is longer. The developer transport direction is indicated by arrows 135, 136, and 137 in the drawing.

  The developer in the agitation transport path 10 is transferred to the supply transport path 9 on the downstream side in the transport direction (arrow 152). The developer in the supply conveyance path 9 is sequentially transferred to the collection conveyance path 7 (arrow 153) via the developing roller 5 (passing the development area) in the development range. Accordingly, in the developing range, the developer in the supply conveyance path 9 decreases sequentially as it advances in the conveyance direction, and the developer in the collection conveyance path 7 increases on the contrary by substantially the same amount according to the direction. Further, the developer in the collection conveyance path 7 is transferred to the supply conveyance path 9 at the downstream end portion in the conveyance direction (arrow 154), and further stirred together with the developer present at the downstream end of the supply conveyance path 9 in the conveyance direction. It is delivered to the conveyance path 10 (arrow 155). Further, the delivery of the developer from the downstream end in the transport direction of the collection transport path 7 to the upstream end in the transport direction of the agitation transport path 10 described in FIG. 7 is performed in the region K in FIG.

  In order for the developer to circulate smoothly in the developing device 4, the conveying capacity of each of the conveying paths 7, 9, 10 and each of the screws 6, 8, 11 is the output conveying amount of the collection screw 6, and the supply screw When the output conveyance amount of 8 is e and the input conveyance amount of the stirring screw 11 is E, it is necessary to satisfy E = e + f. Further, the output conveyance amount of the agitation conveyance screw = the input conveyance amount of the supply conveyance screw = the input conveyance amount of the agitation conveyance screw = E. When considering stable supply of the developer, the developer in the supply conveyance path 9 conveyed by the supply screw 8 needs to have some margin. At this time, the degree of filling (height) of the developer in the supply conveyance path 9 and the conveyance efficiency of the supply screw 8 are important. The height of the developer is not constant, it will be inclined depending on the stirring direction, and the conveyance efficiency will vary greatly depending on the blade lead, material, thickness, and number of strips, so it should be set as an amount with some margin There is. The error is set to ± 10 [%], a certain overflow amount is set to 10 [%], and e> is greater than 20 [%] of the amount of developer E delivered from the stirring and conveying path 10. (E / 5) is desirable.

  Further, e → E (e approaches E) means that the developer is sent unnecessarily, and extra stress is applied to the developer. This is because the developing doctor 16 determines the supply amount of the developing roller 5 to the developing region and also determines the recovery amount. That is, f is determined by the passing amount of the developing doctor 16. Therefore, e → E means that the surplus developer simply increases with respect to the supply amount, and the developer is agitated and transported unnecessarily, and the developer is excessively stressed. In addition, if the amount of excess developer is large, the ratio of the collected developer after development decreases, so the sensitivity of the toner density sensor 127 becomes insensitive to changes in toner density, and toner density control becomes difficult.

The developing device 4 of this embodiment is designed to satisfy the following expression (1).
(E / 3)>e> (E / 4) (1)
The reason is as follows. From the viewpoint of developer transport efficiency, e → 0 is ideal for the surplus developer. However, the first reason is that a certain amount of surplus is necessary to reliably supply a certain amount of developer onto the developing roller. Further, when the ratio of the collected developer is large, a high stirring performance is required to make the toner concentration uniform by receiving the replenishment toner. If the ratio of the surplus developer is increased, a large amount of toner from the surplus developer can be added to the recovered developer in addition to the replenishment toner, so that large toner density unevenness can be suppressed. This is the second reason. For the above reasons, in the present embodiment, the transport amount is expressed by the above formula (1) from the viewpoints of securing developer transport efficiency (developing developer low stress) and controlling toner density (sensitivity of toner density sensor and uniform toner density). ) Range.

Next, the operation of the developer supply device 160 in the present embodiment will be described.
FIG. 11 is a block diagram showing a control system for controlling the unused developer replenishing operation by the developer replenishing device 160.
The replenishment method in this embodiment is a so-called trickle development method, and replenishes a magnetic carrier together with the timing of a known toner replenishment operation. The control unit 95 is connected to the replenishment drive motor 162d and the replenishment clutch 162e of the developer replenishment device 160 provided in each developing device 4, and controls the replenishment amount to control the replenishment amount of the unused developer. It functions as a quantity control means. The control unit 95 is also connected to a toner density sensor 127 provided in each developing device 4. The control unit 95 is also connected to the pixel count unit 97. The pixel counting unit 97 counts the number of pixels of the output image based on the image data.

FIG. 12 is a flowchart showing a flow of replenishment operation control by the control unit 95.
The control unit 95 causes the toner concentration sensor 127 to detect the toner concentration of the developer in the developing device 4 at a predetermined timing, and acquires the detection result (S1). Then, from the change in the toner density detected by the toner density sensor 127, the replenishment amount of the unused developer for setting the toner density of the developer in the developing device 4 to the target toner density is calculated (S4). When the toner density sensor 127 detects the toner density and the printing operation is in progress (printing) (S2), the control unit 95 acquires the number of pixels of the image data related to the printing operation from the pixel counting unit 97 (S3). ). In this case, the image area ratio of the output image is calculated from the number of pixels of the currently printed image acquired from the pixel counting unit 97, and the consumed toner amount consumed by the printing is obtained from the calculation result. Thereafter, the control unit 95 calculates the replenishment amount of the unused developer from the change in the toner concentration detected by the toner concentration sensor 127 and the calculated consumed toner amount (S4).

  After calculating the replenishment amount of the unused developer in this way, the control unit 95 determines the replenishment operation amount from the calculation result (S5). In the present embodiment, as described above, the replenishment amount can be finely adjusted by controlling the clutch operating time of the replenishment clutch 162e after the replenishment drive motor 162d is driven. Therefore, the control unit 95 issues a drive start command to the replenishment drive motor 162d to drive it, and then issues a command to the replenishment clutch 162e to operate the clutch for the clutch operation time corresponding to the determined replenishment operation amount. Make it work. As a result, unused developer is supplied to the developing device 4 in such an amount that the toner concentration of the developer in the developing device 4 is the target toner concentration (S6).

Next, the configuration and operation for discharging the used developer from the developing device 4 will be described.
As shown in FIG. 1, the developing device 4 is provided with a developer discharging portion 180 as a developer discharging means for discharging the developer present in the developing device 4 from the developer discharging port 181. The developer discharge port 181 of the developer discharge unit 180 communicates with the used developer container 87 via the discharge conveyance path 182. In this embodiment, the magnetic carrier is supplied together with the toner by the developer supply device 160. Therefore, although the toner concentration of the developer in the developing device 4 can be set to the target toner concentration by the replenishment operation by the developer replenishing device 160, the total amount of the developer in the developing device 4 is equal to the replenishment amount of the magnetic carrier. It increases by the corresponding amount. Therefore, in the present embodiment, the developer discharging unit 180 gradually discharges the developer in the developing device 4 by an amount corresponding to a part of the total amount of the developer in the developing device 4, The total amount of developer is made constant.

  Specifically, the developer discharge port 181 of the developer discharge unit 180 is open to a side surface portion that is a predetermined height above the bottom surface in the collection conveyance path 7. Specifically, the developer discharge port 181 has a height at which the upper portion of the developer present in the collection conveyance path 7 is positioned when the total amount of the developer present in the developing device 4 is a specified amount. The developer discharge port 181 is opened so that the lower part is located. As a result, the amount of the developer present in the developing device 4 exceeds the specified amount by the replenishment operation by the developer replenishing device 160, the volume of the developer present in the collection conveyance path 7 increases, and the upper portion of the developer Is raised to the position of the developer discharge port 181, the developer overflows and is discharged from the developer discharge port 181. That is, the developer exceeding the specified amount by the replenishment operation by the developer replenishing device 160 is discharged from the developer discharge port 181. Then, the developer discharged from the developer discharge port 181 is sent to and stored in the used developer container 87 via the discharge conveyance path 182. The discharge conveyance path 182 may be a hollow tube having a spiral screw member inside to convey the developer to the used developer container 87, or by dropping the developer by gravity. It may be conveyed to the used developer container 87.

  Here, in the present embodiment, the developer discharge port 181 is provided in the collection conveyance path 7 so that the developer in the collection conveyance path 7 is discharged. The developer in the collection conveyance path 7 discharged from the developer discharge port is a developed developer (used developer) that has passed through the developing area and consumed the toner. For this reason, the toner concentration of the developer is much lower than that of the developer present elsewhere in the developing device 4. Originally, it is desirable to discharge only the magnetic carrier when discharging the developer. This is because the toner in the developing device 4 is consumed by development and is replaced with new toner one after another by the replenishment operation, so that most of the toner existing in the developing device 4 is sufficiently usable over time. belongs to. Therefore, if the toner is discharged together with the magnetic carrier when discharging the developer, the toner that is still sufficiently usable is discharged wastefully, which is uneconomical. Is desirable. However, it is very difficult to separate and discharge the magnetic carrier mixed with the toner from the toner, and if this is attempted, the apparatus configuration becomes very complicated. In the present embodiment, since the developer in the collection conveyance path 7 having the lowest toner concentration in the developing device 4 is discharged, compared to the case of discharging the developer in other places in the developing device 4, The amount of toner discharged together with the magnetic carrier can be reduced. As a result, it is possible to reduce the amount of wasteful discharge of toner that can still be used sufficiently.

  In particular, in the present embodiment, the developer discharge port 181 is provided in the vicinity of the downstream end of the collection transport path 7 in the developer transport direction, specifically, at the position shown in FIG. The collected developer is transferred to the supply conveyance path 9 at the downstream end in the developer conveyance direction in the collection conveyance path 7, but under the situation where the developer is collected one after another from the developing roller 5 as in the case of continuous printer. Then, the amount of the recovered developer conveyed to the downstream end by the recovery screw 6 may exceed the amount of developer delivered from the downstream end to the supply conveyance path 9 side. In this case, if the collected developer stays at the downstream end of the collection conveyance path 7 and the amount of the retained developer increases excessively, the collected developer may come into contact with the surface of the developing roller 5. When the collected developer comes into contact with the surface of the developing roller 5, the collected developer with a low toner density is transported to the supply transport path 9 along with the developing roller 5 and may be used for development as it is. In this case, there is a possibility that the toner concentration in the developer on the developing roller 5 sent to the developing area may be lowered or non-uniform. In the present embodiment, as shown in FIG. 7, a developer discharge port 181 is provided in the vicinity of the downstream end of the collection conveyance path 7, and the collected developer is placed on the surface of the developing roller 5 at the downstream end of the collection conveyance path 7. The collected developer is discharged from the developer discharge port 181 before it stays so as to come into contact with the developer. Accordingly, the collected developer having a low toner concentration is not transported to the supply transport path 9 along with the developing roller 5.

  In this embodiment, when the developer discharge port 181 is provided on the side surface of the collection conveyance path 7 and the amount of the developer present in the developing device 4 exceeds the specified amount, the developer exceeding that amount is discharged. However, the present invention is not limited to this. For example, a developer discharge port may be provided on the bottom surface of the collection conveyance path 7, a shutter that can be opened and closed is provided, and the operation of this shutter may be controlled to discharge the developer. In this case, for example, the operating time of the shutter is determined according to the amount of unused developer supplied by the developer supply device 160. According to this, the replenishment amount of the unused developer and the discharge amount of the used developer can be made substantially the same amount.

  In the present embodiment, as described above, the developer replenishment port 161 is in the developer transport direction of the agitation transport path 10 located on the upstream side in the developer circulation direction from the downstream end of the recovery transport path 7 in the developer transport direction. Opened at the developer delivery point 143 located at the upstream end. Since the developer replenishment port 161 is located upstream of the developer discharge port 181 in the developer circulation direction in this way, the developer discharged from the developer discharge port 181 is unused immediately after replenishment. No developer is included. In other words, the unused developer replenished from the developer replenishing port 161 must be passed through the agitation transport path 10 to the supply transport path 9 and then supplied to the developing roller 5 and passed through the development area. In this case, it is not delivered into the collection conveyance path 7. Therefore, the developer discharged from the developer discharge port 181 is a developer that has been developed at least once. Therefore, according to the present embodiment, it is possible to prevent the unused developer immediately after replenishment from being discharged from the developer discharge port 181 without contributing to development and being wasted.

Next, the characteristics of the developer used in this embodiment will be described.
As the magnetic carrier contained in the developer used in the present copying machine, a carrier whose volume average particle diameter is in the range of 20 [μm] to 60 [μm] is used. By using a small particle size carrier having a volume average particle size of 60 [μm] or less, it is not necessary to reduce the developing ability even if the amount of developer present in the developing region is small. It is possible to reduce the total amount of the developer present in. In addition, since the amount of developer passing through the stressed development doctor 16 is reduced, the life of the developer can be extended. Further, as a result of realizing a reduction in the capacity of the carrier, the developer bottle 86 can be reduced in size. Furthermore, since the magnetic brush in the development area becomes denser, high image quality and stability of image quality are achieved. When the volume average particle diameter of the magnetic carrier is larger than 60 [μm], overflow tends to occur in the developer circulation portion, and there is a possibility that stable agent circulation cannot be performed. On the other hand, when the volume average particle size of the magnetic carrier is smaller than 20 [μm], there are problems that the carrier adheres to the photoreceptor 1 or the carrier is likely to be scattered outside the developing device 4.
The volume average particle diameter of the carrier was measured by using an SRA type of a Microtrac particle size analyzer (Nikkiso Co., Ltd.) and setting a range of 0.7 [μm] or more and 125 [μm] or less.

  The toner contained in the developer used in the present copying machine has a volume average particle diameter in the range of 3 [μm] to 8 [μm] and a volume average particle diameter D4 with respect to the number average particle diameter D1. The ratio (D4 / D1) is in the range of 1.00 to 1.40. By using a toner having a small volume average particle size and a sharp particle size distribution, the gap between the toner particles is reduced, so that the necessary amount of toner can be reduced without impairing the color reproducibility. Therefore, density fluctuation in development can be reduced. Further, the stable reproducibility of a minute dot image of 600 [dpi] or more is improved, and a stable high image quality can be obtained for a long time. When the volume average particle diameter is less than 3 [μm], phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur. On the other hand, if the volume average particle diameter exceeds 8 [μm], the pile height of the image becomes large, and it is difficult to suppress scattering of characters and lines. The ratio (D4 / D1) is closer to 1.00, indicating that the particle size distribution is sharper. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

The method for measuring the particle size distribution of the toner particles is as follows.
A Coulter Counter TA-II or Coulter Multisizer II (both manufactured by Coulter, Inc.) can be used as an apparatus for measuring the particle size distribution of toner particles by the Coulter Counter method. First, 0.1 to 5 [ml] of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 [ml] of the electrolytic aqueous solution. Here, the electrolytic solution is prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 [mg] of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion process for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of toner particles or toner are measured with the above measuring apparatus using a 100 [μm] aperture. Then, the volume distribution and the number distribution are calculated. From the obtained distribution, the volume average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained. The channels are as follows: 2.00 to less than 2.52 [μm]; 2.52 to less than 3.17 [μm]; 3.17 to less than 4.00 [μm]; 4.00 to 5.04 [μm] less than [mu] m; 5.04 to less than 6.35 [[mu] m]; 6.35 to less than 8.00 [[mu] m]; 8.00 to less than 10.08 [[mu] m]; 10.08 to 12.70 [[mu] m]. Less than 12.70 to less than 16.00 [μm]; less than 16.00 to less than 20.20 [μm]; less than 20.20 to less than 25.40 [μm]; less than 25.40 to less than 32.00 [μm]; Using 13 channels of 32.00 to less than 40.30 [μm], particles having a particle size of 2.00 [μm] or more and less than 40.30 [μm] are targeted.

The toner contained in the developer used in this copying machine has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. Is used.
FIG. 13 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-1.
FIG. 14 is a diagram schematically showing the shape of the toner in order to explain the shape factor SF-2.
The shape factor SF-1 represents the ratio of the roundness of the toner shape and is represented by the following formula (2). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4. When the value of the shape factor SF-1 is 100, the shape of the toner is a true sphere, and the toner becomes indefinite as the value of the shape factor SF-1 increases.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (2)
On the other hand, the shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (3). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π. When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (3)

Specifically, each shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.) and introducing it into an image analyzer (LUSEX3: manufactured by Nireco) for analysis. Calculated.
When the shape of the toner is close to a sphere, the contact state between the toners is close to a point contact, so that the attractive force between the toners is weakened and the fluidity is increased. Therefore, since the circulatory property of the agent is improved, the stress is reduced, and it becomes possible to perform a stable unidirectional circulation for a long time. In addition, since the contact state between the toner and the photoconductor is close to a point contact, the attractive force between the toner and the photoconductor is also weakened, and the transfer rate is increased, which contributes to high image quality. In addition, when any of the shape factor SF-1 and the shape factor SF-2 exceeds 180, the fluidity is deteriorated and the agent circulation property is not preferable. Further, the transfer rate is not preferable.

The developer toner used in this copying machine has an average primary particle size in the range of 50 [nm] to 500 [nm] and a bulk density of 0.3 [g / cm ³ ] or more. A fine particle (external additive) added to the surface of the toner base particle is used. Examples of the fine particles include silica as a fluidity improver. When silica is used as the fine particles, the average primary particle of silica is usually 10 to 30 [nm], and the bulk density thereof is 0.1 to 0.2 [mg / cm ³ ].

  In the present embodiment, the presence of fine particles having appropriate characteristics on the surface of the toner forms an appropriate gap between the toner particles and the object. Further, the fine particles have a very small contact area with the toner particles, the photoconductor, and the charge imparting member and are evenly contacted with each other. Moreover, since the fluidity of the developer is increased, it has an effect of reducing stress and contributes to a longer life. Furthermore, since it plays the role of a roller, it is difficult to be buried in toner particles even during cleaning under high stress (high load, high speed, etc.) between the cleaning blade and the photoconductor without wearing or damaging the photoconductor. Or, even if it is buried a little, it can be detached and returned, so that stable characteristics can be obtained over a long period of time. Further, the toner is moderately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing a phenomenon that the toner passes from the blade. Since these characteristics have an effect of reducing the share received by the toner particles, the filming effect of the toner itself due to the low rheological component contained in the toner is exhibited for high-speed fixing (low energy fixing). Moreover, if the average primary particle size is in the range of 50 [μm] or more and 500 [μm] or less as the fine particles, the excellent cleaning performance can be fully utilized, and the particle size is extremely small. The powder fluidity of the toner is not reduced. Further, although the details are not clear, even if the surface-treated fine particles are externally added to the toner or the carrier is contaminated, the degree of developer deterioration is small. Accordingly, since the change in toner fluidity and chargeability with time is small, the developer can be circulated stably over a long period of time. Also, the stability of image quality is increased.

As described above, the average primary particle size of the fine particles is 50 [μm] or more and 500 [nm] or less, and is particularly preferably in the range of 100 [μm] or more and 400 [nm] or less. If the average primary particle size is less than 50 [nm], the fine particles may be buried in the concave and convex portions of the irregularities on the toner surface, reducing the role of the rollers. On the other hand, when the average primary particle size is larger than 500 [nm], when the fine particles are located between the blade and the surface of the photoreceptor, the toner particles are in the order of the same level as the contact area of the toner itself and are to be cleaned. Pass, i.e., a cleaning failure is likely to occur.
When the bulk density is less than 0.3 [mg / cm ³ ], although there is a contribution to the improvement of fluidity, the scattering property and adhesion of the toner and fine particles are increased. In other words, the so-called dam effect that prevents toner cleaning failure is reduced.

The fine particles that can be employed in the present embodiment include inorganic compounds such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, and K ₂ O. Na ₂ O, ZrO ₂ , CaO.SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _3, etc. can preferably _{include SiO 2, TiO 2, Al 2} O 3. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like. The organic compound may be a thermoplastic resin or a thermosetting resin, for example, vinyl resin, polyurethane resin, epoxy resin, polyester resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin. Aniline resin, ionomer resin, polycarbonate resin and the like. As the resin fine particles, two or more of the above resins may be used in combination. Among these, a vinyl resin, a polyurethane resin, an epoxy resin, a polyester resin, and a combination thereof are preferable because an aqueous dispersion of fine spherical resin particles is easily obtained.
Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

The method for measuring the bulk density of the fine particles is as follows. First, fine particles are gradually added to 100 [ml] using a 100 [ml] measuring cylinder. At that time, no vibration was applied. And the bulk density was measured by the weight difference before and after putting the fine particles of this measuring cylinder. The bulk density is calculated by the following formula (4).
Bulk density (g / cm ³ ) = Amount of fine particles (g / 100 ml) ÷ 100 (4)

  As a method for externally adding and adhering fine particles to the toner surface, a method of adhering the toner base particles and the fine particles mechanically using various known mixing devices, or a method of adhering the toner base particles in the liquid phase Examples include a method in which fine particles are uniformly dispersed with a surfactant and the like, and after the adhesion treatment, dried.

[Modification 1]
Next, a modification of the developing device of the copying machine according to the above-described embodiment (hereinafter, this modification is referred to as “modification 1”) will be described.
In the developing device 4 of the above embodiment, the three transport paths 7, 9, and 10 are arranged at substantially the same height as shown in FIG. 9 and the agitation conveyance path 10 are arranged at substantially the same height, but the recovery conveyance path 7 is arranged above the agitation conveyance path 10. In addition, except the points demonstrated below, it is the same as that of the case of the said embodiment.

FIG. 15 is a schematic configuration diagram showing the developing device 204 in the first modification.
In the developing device 204, below the developing roller 5, the agitation conveyance path 10 including the agitation screw 11 and the supply conveyance path 9 including the supply screw 8 are disposed at substantially the same height. A recovery conveyance path 7 including a recovery screw 6 is disposed above the stirring conveyance path 10. A developer replenishing port 161 for replenishing unused developer from the developer replenishing device 160 opens at the upper part of the downstream end in the developer transport direction of the collection transport path 7. An opening 143 is provided at the bottom of the downstream end of the recovery transport path 7 in the developer transport direction, and the downstream end of the recovery transport path 7 is connected to the developer transport path 10 via the opening 143. It communicates with the upstream end in the direction. Further, the developer discharge port 181 of the developer discharge portion 180 is open to the side surface portion of the collection conveyance path 7 in the vicinity of the downstream end of the collection conveyance path 7 in the developer conveyance direction.

Next, the circulation of the developer in Modification 1 will be described.
FIG. 16 is an explanatory diagram for explaining the moving direction of the developer circulating through the transport paths 7, 9, 10. This figure shows the developing device 204 as viewed from directly above.
In FIG. 16, the part surrounded by the broken line indicated by reference numeral A is the same as that of the developing device 4 shown in FIG. 15, the upper part A (the part including the collection conveyance path 7 and the developing roller 5) and the lower part B (supply conveyance). The portion surrounded by the broken line indicated by the symbol B corresponds to the lower portion B. Further, various arrows in FIG. 16 indicate the moving direction of the developer, and the size of the arrow schematically represents the moving amount of the developer per unit time.

In the upper stage A, the developer after development that has passed through the development area is separated from the development roller by the magnetic pole inside the development roller 5, passes through the collection space 12 positioned above the supply conveyance path 9, and is collected in the collection conveyance path 7. To be recovered. In the collection conveyance path 7, as in the case of the above-described embodiment, the closer to the downstream end, the greater the amount of developer movement. The collected developer in the collection conveyance path 7 is provided with an opening 143 provided on the bottom surface of the collection conveyance path 7 together with the unused developer replenished from the developer supply port 161 at the downstream end in the developer conveyance direction. It passes through to the stirring conveyance path 10 through.
On the other hand, in the lower stage B, the developer delivered from the collection conveyance path 7 through the opening 143 falls to the upstream end of the stirring conveyance path 10 in the developer conveyance direction. In addition, surplus developer in the supply conveyance path 9 that is not used for development and is conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 is also delivered to the upstream end of the stirring conveyance path 10 in the developer conveyance direction. The agitation conveyance path 10 conveys the supplied surplus developer and the recovered developer while agitating.

  As described above, the developer circulation path of the first modification is substantially the same except that the developer is transferred from the collection transport path 7 to the stirring transport path 10 by dropping due to gravity. Since the developer delivery from the collection conveyance path 7 to the stirring conveyance path 10 falls due to gravity, the stress applied to the developer during the delivery is reduced as compared to the case of the above embodiment. That is, in the above-described embodiment, the developer is transferred from the collection conveyance path 7 to the stirring conveyance path 10 by the paddle 139 for agitating lateral transfer provided in the collection screw 6. The configuration of dropping as in Example 1 has less stress applied to the developer. Therefore, the life of the developer can be extended.

[Modification 2]
Next, a modification of the copying machine according to the above-described embodiment (hereinafter, this modification is referred to as “modification 2”) will be described.
FIG. 17 is a schematic configuration diagram showing a copying machine according to the second modification.
This copier is a so-called general tandem type image forming apparatus provided with only one image forming unit in the copier of the above-described embodiment which is the so-called double-sided simultaneous printing method shown in FIG. The printer unit 100 of this copier has a configuration in which process cartridges 220 for each color are arranged in series. The process cartridge 220 for each color includes a charging roller 223 that is a charging unit, a developing device 4 that is a developing unit, a photosensitive member cleaning device 2 that is a cleaning unit, and the like with the photosensitive member 1 at the center. Further, an exposure device 224 as a latent image forming unit is disposed above the four process cartridges 220, and an intermediate transfer device 221 is disposed below. In addition, a paper transport unit 50, a paper transfer device 228, a fixing device 60, and the like are provided. In the printer unit 100, a plurality of components such as the photosensitive member 1, the charging roller 223, the developing device 4, and the photosensitive member cleaning device 2 are integrally combined as a process cartridge 220, and this process cartridge is formed. 220 is configured to be detachable from the printer unit 100 main body. The image forming operation of the printer unit 100 shown in FIG. 17 is not described because only the back surface (first surface) is not formed in FIG. 2 described above.

As described above, the copying machine according to the above-described embodiment (including each modified example; the same applies hereinafter) includes the photoreceptors 1Y, 1M, 1C, and 1K as the latent image carrier and the latent image forming the latent image on the surface of the photoreceptor. An exposure device as an image forming unit, and developing devices 4 and 204 as a developing unit for developing the toner by attaching the toner to the latent image, and finally the toner image formed on the surface of the photosensitive member is recorded on the recording material The image is formed on the transfer paper P as a transfer image. The developing devices 4 and 204 provided in the copying machine rotate by carrying a developer composed of a magnetic carrier and toner on the surface by a plurality of magnetic poles provided inside, and the photoreceptors 1Y, 1M, 1C, A developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photosensitive member at a position (developing region) facing 1K, and the developer is conveyed along the axial direction of the developing roller 5, and this developing roller And a developer regulating member that regulates the thickness of the developer on the developing roller 5 supplied from the supply conveying path 9. And a recovery conveyance path 7 provided with a recovery screw 6 as a recovery conveyance member that conveys the developer recovered from the development roller 5 after passing through the development area in the axial direction of the development roller 5. When The excess developer transported to the most downstream side in the transport direction of the supply transport path 9 without being used for development, and the recovered development recovered from the developing roller 5 and transported to the most downstream side in the transport direction of the recovery transport path 7 And an agitation screw 11 as an agitating and conveying member that conveys the excess developer and the collected developer in the axial direction of the developing roller 5 while agitating them, and supplies the excess developer and the collected developer. An agitation conveyance path 10 that delivers to the conveyance path 9; a partition wall 133 and a partition plate 134 that serve as partition members for partitioning these three conveyance paths 7, 9, and 10 except for a place where the developer is received and delivered; Have Further, the developing devices 4 and 204 transport at least one of the three transport paths 7, 9, and 10 from the developer supply port 161 to use an unused developer containing unused toner and an unused magnetic carrier. A developer replenishing device 160 serving as a developer replenishing unit that replenishes the collection transporting path 7 that is a path, and an amount corresponding to a part of the total amount of the developer present in the developing device 4 in the recovery transporting path 7. A developer discharging unit 180 as developer discharging means for discharging the developer from the developer discharging port 181; As described above, in the developing devices 4 and 204, the developer in the collection conveyance path, which is a developer having a low toner density after consumption of the toner by the development, is discharged. It is possible to reduce the amount of being done.
In the above-described embodiment, the developer discharge port 181 is provided in the vicinity of the downstream end of the recovery transport path 7 in the developer transport direction, so that the recovered developer is supplied to the developing roller 5 at the downstream end of the recovery transport path 7. The collected developer can be discharged from the developer discharge port 181 before it remains so as to come into contact with the surface of the developer. Therefore, the collected developer having a low toner concentration is not transported to the supply transport path 9 along with the developing roller 5. In addition, if the amount of developer in the supply conveyance path 9 decreases, the amount of developer supplied to the developing roller 5 decreases, which affects development. However, even if the amount of developer in the collection conveyance path 7 decreases, development is possible. There is no impact. Therefore, according to the above embodiment, the developer can be discharged without affecting the development.
In the above embodiment, the developer replenishment port 161 is provided on the downstream side in the developer transport direction with respect to the developer discharge port 181 in the collection transport path 7, so the developer discharged from the developer discharge port 181. Is a developer that has been developed at least once. Therefore, it is possible to prevent the unused developer immediately after replenishment from being discharged from the developer discharge port 181 without contributing to the development and being wasted. This effect can be similarly obtained when the developer supply port 161 is provided in the stirring conveyance path 10.
Further, in the above-described embodiment, the developer supply port 161 is provided in the portion 143 where the developer is transferred from the collection conveyance path 7 and the supply conveyance path 9 to the stirring conveyance path 10. Since this portion is a place where the stirring action with respect to the developer is intense, if unused developer is replenished to this portion, the toner is vigorously stirred immediately after the replenishment to promote frictional charging of the toner. As a result, it is possible to effectively avoid a situation where the charged amount of toner becomes insufficient when the replenished unused developer is transported to the supply transport path 9 and supplied to the developing roller 5.
In the above-described embodiment, when the amount of the developer present in the developing devices 4 and 204 exceeds a specified amount, the developer discharge unit 180 discharges the excess developer. Yes. As a result, the total amount of developer in the developing device 4 can be maintained substantially constant, and stable development can be performed.
In the above-described embodiment, the developer replenishing device 160 includes the Mono pump 162 that is a uniaxial eccentric screw pump for transferring the unused developer to the developer replenishing port 161, and unused developer is supplied to the Mono pump 162. There is a configuration in which the inside of the transport tube 163 which is a developer supply path for feeding in is negatively pressured, and unused developer in the Mono pump 162 is sent out from the developer supply port 161. According to this configuration, the conveyance path connecting the developer bottle 86 and the developing device 4 can be freely bent. Therefore, the positional relationship between the developer bottle 86 and the developing device 4 is less restricted than in a configuration in which a linear conveying path is limited as in the case where a conveying screw or the like is used, and the layout in the copying machine is free. The degree is improved. Further, as a result of the developer bottle 86 containing the unused developer being disposed away from the developing device 4, the developing device itself can be reduced in size.
In the above-described embodiment (excluding Modification 1), the collection conveyance path 7 is provided below the developing roller 5, and the three conveyance paths 7, 9, and 10 are arranged at substantially the same height. This eliminates the need to lift the developer upward when circulating the developer in the developing devices 4 and 204. Therefore, it is possible to prevent the developer from being excessively stressed, and to reduce the stress on the developer. As a result, the life of the developer can be extended.
In the above-described embodiment (excluding Modification 1), the uppermost position 14 of the supply screw 8 is positioned below the rotation center shaft 15 of the developing roller 5 and the uppermost position 14 of the supply screw 8. The supply screw 8 is arranged such that an angle formed by a virtual plane passing through the rotation center axis 15 and a horizontal plane passing through the rotation center axis 15 falls within a range of 10 [°] to 40 [°]. . As a result, the weight of the developer does not affect the amount of developer supplied to the developing roller 5. As a result, an appropriate amount of developer can be supplied to the developing roller 5 even if the volume of the developer is not uniform in the developer transport direction in the supply transport path 9.
In the first modification, the collection conveyance path 7 is provided above the stirring conveyance path 10. As a result, it is possible to adopt a configuration in which the developer delivery from the collection conveyance path 7 to the stirring conveyance path 10 falls due to gravity, so the developer delivery direction from the collection conveyance path 7 to the stirring conveyance path 10 is more than the horizontal direction. Compared with the case of the upper side, the stress applied to the developer at the time of delivery can be reduced. Therefore, the life of the developer can be extended.
Further, the copying machine according to the above embodiment includes developer bottles 86Y, 86M, 86C, and 86K as developer containers for storing unused developer in a state where toner and magnetic carrier are mixed in advance. The developer supply device 160 of the developing devices 4 and 204 supplies unused developer in the developer bottle from the developer supply port 161. Accordingly, the configuration can be simplified as compared with the case where the replenishment toner and the magnetic carrier are stored in separate containers.
Further, the copying machine according to the above-described embodiment has a toner concentration sensor 127 as a toner concentration detection unit that detects the toner concentration of the developer present in the developing devices 4 and 204, and the detection result of the toner concentration sensor 127. And a control unit 95 as supply amount control means for controlling the supply amount of unused developer by the developer supply device 160 of the developing device. As a result, the toner concentration of the developer present in the developing devices 4 and 204 can be stably maintained at the target toner concentration.
The copying machine according to the above embodiment includes a plurality of photoreceptors 1Y, 1M, 1C, and 1K and developing devices 4 and 204, and images obtained by superimposing toner images formed on the photoreceptors. A configuration is finally formed on the transfer paper P. This copier is called a so-called tandem image forming apparatus, and is advantageous in terms of increasing the printing speed of color images.
The copying machine according to the above-described embodiment (excluding Modification 1) includes the photoreceptors 1Y, 1M, 1C, and 1K and the developing devices 4 and 204, and the photoreceptors 1Y, 1M, 1C, and 1K. Two image forming portions are provided as image forming portions for transferring the upper toner image onto the transfer paper P. Then, the transfer of the toner image to one surface (first surface) of the transfer paper P by the first image forming unit which is one image forming unit, and this by the second image forming unit which is the other image forming unit. The toner image is transferred to the other surface (second surface) of the transfer paper P simultaneously or sequentially. After the toner images are transferred to both surfaces of the transfer paper P, the toner images are transferred to the transfer paper P. A fixing device 60 is provided as fixing means for fixing. This copying machine is called an image forming apparatus of a so-called double-sided simultaneous printing method, and can form images on both sides of one transfer paper P by one printing operation.
The magnetic carrier of the developer used in the copying machine according to the above embodiment has a volume average particle size in the range of 20 [μm] to 60 [μm]. Thereby, the various effects mentioned above are acquired.
The developer toner used in the copying machine according to the above embodiment has a volume average particle size in the range of 3 [μm] to 8 [μm], and a volume average particle size with respect to the number average particle size. Is a range of 1.00 to 1.40. Thereby, the various effects mentioned above are acquired.
The developer toner used in the copying machine according to the above embodiment has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. . Thereby, the various effects mentioned above are acquired.
The developer toner used in the copying machine according to the above embodiment has an average primary particle size in the range of 50 nm to 500 nm and a bulk density of 0.3 g / cm ^3. The above-mentioned external additive added to the toner base particle surface is used. Thereby, the various effects mentioned above are acquired.
Further, as described in the second modification, at least the photosensitive member 1 and the developing means for developing the latent image on the photosensitive member are integrally supported, and the process is configured to be detachable from the copying machine main body. The cartridge 220 is employed, and the developing devices 4 and 204 described above are used as developing means. By mounting the above-described developing devices 4 and 204 in the process cartridge together with the photosensitive member 1, the consumables provided in the copying machine can be easily replaced.

1 is a schematic configuration diagram showing a developing device of a copying machine according to an embodiment. 1 is a schematic configuration diagram of the copier. FIG. 3 is an enlarged configuration diagram showing one of four first process units in the printer unit of the copier. FIG. 3 is an enlarged configuration diagram showing one of four second process units in the printer unit of the copier. (A) And (b) is explanatory drawing which shows the structure of the Mono pump which comprises the developer supply apparatus provided in the developing device. FIG. 3 is a schematic configuration diagram of a magnetic pole arrangement of a developing roller provided in the developing device. FIG. 3 is a perspective view of the conveying paths formed by the lower part of the casing and the screws provided in the conveying paths when viewed from the photosensitive member side in a state where the upper part of the casing of the developing device is removed. Sectional drawing which shows the location where the three conveyance paths of the developing device are connected. FIG. 3 is a perspective view when the developing device is viewed obliquely from above. FIG. 4 is an explanatory diagram for explaining a developer conveyance amount per unit time and a developer moving direction in the three conveyance paths. FIG. 3 is a block diagram showing a control system for controlling an unused developer supply operation by the developer supply device. The flowchart which shows the flow of control of replenishment operation | movement by a control part. The figure which represented the shape of the toner typically in order to demonstrate shape factor SF-1. The figure which represented the shape of the toner typically in order to demonstrate shape factor SF-2. FIG. 10 is a schematic configuration diagram illustrating a developing device according to Modification 1. FIG. 3 is an explanatory diagram for explaining a moving direction of a developer circulating in each conveyance path of the developing device. FIG. 10 is a schematic configuration diagram illustrating a copying machine according to a second modification. (A) thru | or (d) is a schematic block diagram of the image development apparatus of patent document 1. FIG.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive member 4, 204, 304 Developing device 5 Developing roller 5a Roller rotating shaft 6 Recovery screw 7 Recovery conveyance path 8 Supply screw 9 Supply conveyance path 10, 10A, 10B Agitation conveyance path 11, 11A, 11B Stirring screw 12 Collection space 14 Screw apex 15 Rotation center shaft 16 Developing doctor 20 First transfer unit 21 First intermediate transfer belt 22, 32 Primary transfer roller 30 Second transfer unit 31 Second intermediate transfer belt 50 Paper transport unit 51 Paper Conveying belt 60 Fixing device 75 Discharge stack unit 80Y, 80M, 80C, 80K First process unit 81Y, 81M, 81C, 81K Second process unit 86Y, 86M, 86C, 86K Developer bottle 87 Used developer container 95 Control unit 100 Printer unit 1 27 Toner concentration sensor 133 Partition wall 134 Partition plate 160 Developer supply device 161 Developer supply port 162 Mono pump 162 d Replenishment drive motor 162 e Supply clutch 163 Transport tube 180 Developer discharge unit 181, 381 Developer discharge port 182 Discharge transport path 220 Process cartridge 361A Toner supply port 361B Carrier supply port 386A Toner storage unit 386B Carrier storage unit

Claims (19)

A developer composed of a magnetic carrier and toner is carried on the surface by a plurality of magnetic poles provided inside, and rotated to supply toner to the latent image on the surface of the latent image carrier at a location facing the latent image carrier. A developer carrying member,
A supply conveyance path provided with a supply conveyance member for conveying the developer along the axial direction of the developer carrying member and supplying the developer to the developer carrying member;
A developer regulating member that regulates the thickness of the developer on the developer carrier supplied from the supply conveyance path;
A recovery transport path including a recovery transport member for transporting the developer recovered from the developer carrier after passing through a portion facing the latent image carrier in the axial direction of the developer carrier; ,
The excess developer that was not used for development and was transported to the most downstream side in the transport direction of the supply transport path, and was recovered from the developer carrier and transported to the most downstream side in the transport direction of the recovery transport path An agitation conveying member that receives the collected developer and conveys the excess developer and the collected developer in the axial direction of the developer carrying member, and supplies the excess developer and the collected developer; An agitation conveyance path to be transferred to the conveyance path;
In the developing device having a partition member that partitions the three transport paths of the recovery transport path, the supply transport path, and the agitation transport path from each other except for a place where the developer is received and delivered,
Developer replenishing means for replenishing an unused developer containing unused toner and an unused magnetic carrier from a developer replenishing port to at least one of the three transport paths;
And a developer discharging means for discharging the developer in the collection transport path from the developer discharge port by an amount corresponding to a part of the total amount of the developer present in the developing device. apparatus. The developing device according to claim 1.
The developing device according to claim 1, wherein the developer discharge port is provided in the vicinity of the downstream end of the recovery transport path in the developer transport direction. The developing device according to claim 1 or 2,
The developing device, wherein the developer replenishing port is provided on the downstream side in the developer transport direction from the developer discharge port in the recovery transport path or in the stirring transport path. The developing device according to claim 1 or 2,
The developing device, wherein the developer replenishing port is provided at a location where the developer is transferred from the recovery conveyance path and the supply conveyance path to the agitation conveyance path. The developing device according to claim 1, 2, 3 or 4,
The developer discharging means is characterized in that when the amount of the developer present in the developing device exceeds a specified amount, the developer is discharged in excess. The developing device according to claim 1, 2, 3, 4 or 5.
The developer replenishing means has a uniaxial eccentric screw pump for transferring the unused developer to the developer replenishing port, and in the developer replenishment path for feeding the unused developer to the uniaxial eccentric screw pump. A developing device comprising: a negative pressure of the developer and feeding the unused developer in the uniaxial eccentric screw pump from the developer supply port. The developing device according to claim 1, 2, 3, 4, 5 or 6.
2. A developing apparatus according to claim 1, wherein the recovery conveyance path is provided below the developer carrying member, and the three conveyance paths are arranged at substantially the same height. The developing device according to claim 7.
An imaginary plane passing through the uppermost position of the supply transport member and the rotation center axis so that the uppermost position of the supply transport member is positioned below the rotation center axis of the developer carrier, and the rotation center axis A developing device in which the supply / conveyance member is arranged so that an angle formed with a horizontal plane passing through the nozzle is within a range of 10 [°] to 40 [°]. The developing device according to claim 1, 2, 3, 4, 5 or 6.
A developing device, wherein the recovery conveyance path is provided above the agitation conveyance path. A latent image carrier;
Latent image forming means for forming a latent image on the surface of the latent image carrier;
Developing means for developing toner by attaching toner to the latent image;
In an image forming apparatus for forming an image by finally transferring a toner image formed on the surface of the latent image carrier onto a recording material,
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9 as the developing means. The image forming apparatus according to claim 10.
A developer container for accommodating an unused developer in which toner and a magnetic carrier are mixed in advance;
The image forming apparatus, wherein the developer replenishing means of the developing device replenishes unused developer in the developer container to the at least one transport path from the developer replenishing port. The image forming apparatus according to claim 10 or 11,
Toner density detecting means for detecting the toner density of the developer present in the developing device;
An image forming apparatus comprising: a replenishment amount control unit configured to control a replenishment amount of unused developer by the developer replenishment unit of the developing device in accordance with a detection result of the toner density detection unit. The image forming apparatus according to claim 10, 11 or 12.
Each having a plurality of latent image carriers and developing devices;
An image forming apparatus comprising: a configuration in which an image in which toner images formed on each latent image carrier are overlapped with each other is finally formed on a recording material. The image forming apparatus according to claim 10, 11, 12 or 13.
Including the latent image carrier and the developing device, and having two image forming portions for transferring a toner image on the latent image carrier onto a recording material,
Transfer of the toner image to one side of the recording material by one image forming unit and transfer of the toner image to the other side of the recording material by the other image forming unit are performed simultaneously or sequentially,
An image forming apparatus comprising: fixing means for fixing each toner image to the recording material after the toner images are transferred to both surfaces of the recording material. The image forming apparatus according to claim 10, 11, 12, 13 or 14.
An image forming apparatus, wherein the magnetic carrier has a volume average particle diameter in a range of 20 [μm] to 60 [μm]. The image forming apparatus according to claim 10, 11, 12, 13, 14 or 15.
The toner has a volume average particle diameter in the range of 3 [μm] to 8 [μm], and a ratio of the volume average particle diameter to the number average particle diameter in the range of 1.00 to 1.40. What is used is an image forming apparatus. The image forming apparatus according to claim 10, 11, 12, 13, 14, 15, or 16.
An image forming apparatus using the toner having a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. The image forming apparatus according to claim 10, 11, 12, 13, 14, 15, 16, or 17.
As the toner, an external additive having an average primary particle size in the range of 50 [nm] or more and 500 [nm] or less and a bulk density of 0.3 [g / cm ³ ] or more is formed on the surface of the toner base particles. An image forming apparatus using the added one. In a process cartridge in which at least a latent image carrier and a developing unit for developing a latent image on the latent image carrier are integrally supported and configured to be detachable from the image forming apparatus main body.
A process cartridge using the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9 as the developing means.