JP2007079489A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device having a developing device with a supply conveyance path, a stirring conveyance path and a collection conveyance path and capable of forming an image with stable image density and to provide an image forming apparatus having the same. <P>SOLUTION: In the developing device 4 whose three developer conveyance paths comprised of the collection conveyance path 7, the supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a partition board 134 and a partition wall 133 which are partition members, respectively and the developer conveyance paths is replenished with toner, the length of the stirring conveyance path 10 is considered as stirring length L[m], a period in which the toner is replenished is considered as a replenishment period T[s], a value indicating diffusion performance by performing stirring by a stirring screw 11 which is a stirring conveyance member is considered as a diffusion coefficient D[m<SP>2</SP>/s] and (1) formula: (L×D)/(T<SP>2</SP>×U<SB>1</SB><SP>3</SP>)≥0.075 is established. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, a developing device using a two-component developer composed of toner and a magnetic carrier has a structure shown in FIG. A developing device 4 shown in FIG. 26 supplies a developing roller 5 that is a developer carrying member for supplying a developer to a latent image carrier (not shown), and supplies the developer to the developing roller 5 while conveying the developer. A supply / recovery screw 401 for recovering the developer is provided. Furthermore, a stirring screw 11 is provided as a stirring and transporting member that transports the developer transported to the downstream end of the supply / recovery screw 401 and the toner supplied as necessary, in a direction opposite to the supply / recovery screw 401. ing. The supply / recovery screw 401 and the agitation screw 11 are arranged in the horizontal direction, and the supply / recovery conveyance path 402 provided with the supply / recovery screw 401 and the agitation conveyance path 10 provided with the agitation screw 11 are partitioned by a partition wall 403 that is a partition member. . The two conveyance paths communicate with each other through openings at both end portions in the axial direction of the partition wall 403, and the agitation conveyance path 10 and the supply / recovery conveyance path 402 are circulated and conveyed by conveying the developer in the opposite direction. .

  In the conventional developing device 4 shown in FIG. 26, the supply of the developer to the developing roller 5 and the recovery of the developed developer are performed by the supply / recovery screw 401 and the supply / recovery conveyance path 402. The developed developer is in a state where the toner is consumed by development and the toner density is lower than that before development. Since the developer supply screw and the recovery screw are the same, and the supply conveyance path and the recovery conveyance path are the same, the developed recovered developer and the developer before development are agitated. The As a result, the toner concentration of the developer supplied to the developing roller 5 decreases toward the downstream side of the supply recovery screw 401 in the developer transport direction. In particular, in a high printing rate image, a decrease in toner density after development is larger than that before development, and a decrease in toner density on the downstream side in the developer transport direction is large, causing a problem that image quality cannot be maintained. In order to reduce such a decrease in toner density, it is possible to cope with the method by increasing the amount of developer to be conveyed. However, increasing the amount of developer to be conveyed increases stress on the developer, and the developer This contributes to a reduction in life.

  Such a problem can be solved by providing the developer supply screw for the developer to the developing roller and the developer collecting screw for the developed developer in different developer transport paths as in the developing device described in Patent Document 1. can do. The configuration of the developing device described in Patent Document 1 will be described below.

FIG. 27 shows a developing device described in Patent Document 1.
A developing device 4 shown in FIG. 27 includes a developing roller 5 and a supply screw 8 that supplies the developer to the developing roller 5 while conveying the developer. Furthermore, a recovery agitation screw 110 that passes through the development location on the developing roller 5 and conveys the recovered developer collected in a direction opposite to the supply screw 8 is provided.
The supply screw 8 is disposed above the recovery stirring screw 110, and the supply transport path 9 including the supply screw 8 and the recovery stirring transport path 210 including the recovery stirring screw 110 are partitioned by a partition wall 403 that is a partition member. . The two conveyance paths communicate with each other through openings at both ends in the axial direction of the partition wall 403, and excess developer conveyed to the downstream end of the supply conveyance path 9 without being used for development is downstream of the supply conveyance path 9. It drops at the opening on the end side and is supplied to the recovery agitation transport path 210.
The recovery agitation transport path 210 transports the excess developer and the recovered developer while stirring, pushes the developer by the transport force of the recovery agitation screw 110 at the downstream end, and rises to the supply transport path 9 from the opening. Supply. The recovery stirring and conveying path 210 is provided with an excessive deposition preventing screw 209 that conveys excess developer to the upstream side in order to prevent excessive developer from accumulating at the downstream end.
In the developing device 4 shown in FIG. 27, the developed developer is collected in the collection agitation transport path 210, and the developed developer is not mixed into the supply transport path 9. Thereby, the toner concentration of the developer supplied to the developing roller 5 is constant without changing the toner concentration of the developer in the supply conveyance path 9.

  However, the developing device of Patent Document 1 performs recovery and stirring in the recovery stirring and conveying path 210, and the recovered developer that has passed through the development site also falls in the middle of stirring. Therefore, development in a state where stirring is not sufficiently performed. There is a possibility that the agent goes to the supply conveyance path 9. When the developer with insufficient stirring is supplied to the supply conveyance path 9, there arises a problem that the toner concentration of the entire developer in the supply conveyance path 9 is lowered. Such a problem becomes more conspicuous as an image having a high printing rate in which the toner concentration of the collected developer is lowered.

Japanese Patent No. 3127594

  The problem like the developing device 4 shown in FIG. 27 can be solved by the developing device proposed by the present applicant in Japanese Patent Application No. 2005-068659. In the developing device described in Japanese Patent Application No. 2005-068659, a developer supply screw to the developing roller, a developed developer collecting screw, and a stirring screw for stirring the developer are provided in different developer transport paths. Yes.

The developing device described in Japanese Patent Application No. 2005-068659 is shown in FIG.
The developing device 4 shown in FIG. 4 includes a developing roller 5, a supply screw 8, and a collection screw 6 that passes through a development location on the development roller 5 and conveys the collected developer collected in the same direction as the supply screw 8. ing. Further, the agitation screw 11 that conveys the surplus developer conveyed to the most downstream side of the supply screw 8 and the recovered developer conveyed to the most downstream portion of the recovery screw 6 while conveying in the opposite direction to the supply screw 8. It has.
The supply conveyance path 9 provided with the supply screw 8 and the stirring conveyance path 10 provided with the stirring screw 11 are arranged in a substantially horizontal direction and are partitioned by a partition wall 133 which is a partition member. The two conveyance paths communicate with each other through openings at both ends in the axial direction of the partition wall 133, and excess developer conveyed to the downstream end of the supply conveyance path 9 without being used for the development is supplied to the supply conveyance path 9. It is supplied to the stirring and conveying path 10 from the opening on the downstream end side.
The collection conveyance path 7 including the collection screw 6 is provided in the horizontal direction of the supply conveyance path 9, and the collection conveyance path 7 and the supply conveyance path 9 are partitioned by a partition plate 134 that is a partition member. The two conveying paths communicate with each other through an opening provided in the partition plate 134 on the downstream end side of the recovery screw 6. The recovered developer transported to the downstream end of the recovery transport path 7 is transported in the horizontal direction and supplied to the agitation transport path 10 via the supply transport path 9.
The surplus developer and the recovered developer supplied to the agitation conveyance path 10 are agitated in the agitation conveyance path 10 and supplied to the supply conveyance path 9 from the opening of the partition wall 133.
In the developing device 4 shown in FIG. 4, the developed developer is collected in the collection conveyance path 7, and the developed developer is not mixed into the supply conveyance path 9. Therefore, the toner concentration of the developer supplied to the developing roller 5 is constant without changing the toner concentration of the developer in the supply conveyance path 9.
Further, a recovery conveyance path 7 and an agitation conveyance path 10 are provided, and developer recovery and agitation are performed separately for the recovery conveyance path 7 and the agitation conveyance path 10. As a result, it is possible to prevent a problem that the toner concentration of the entire developer in the supply conveyance path 9 due to the insufficiently agitated developer being supplied to the supply conveyance path 9 is reduced.

However, even in the developing device of FIG. 4, at the toner replenishment position, there is a difference in toner density between the timing when the toner is replenished and the timing when the toner is not replenished. For this reason, the difference in temporal toner density at the toner replenishment position is large, but the developer is agitated in the developer conveyance path, and the difference in temporal toner density of the developer decreases from the toner replenishment position to the downstream side in the conveyance direction. However, if the agitation is not sufficiently performed before reaching the most downstream side of the agitation conveyance path 10 and the toner density difference in time is not sufficiently reduced, the developer is supplied from the agitation conveyance path 10 to the supply conveyance path 9. In this case, the toner density unevenness in the conveyance direction in the supply conveyance path 9 is caused. If there is toner density unevenness in the transport direction in the supply transport path 9, the toner on the developing roller 5 also appears as toner density unevenness in the rotation axis direction of the developing roller 5. Further, if the temporal toner density difference is not sufficiently reduced before being supplied to the supply conveyance path 9, a temporal toner density difference will occur at an arbitrary location on the supply conveyance path 9. A temporal toner density difference at an arbitrary position in the supply conveyance path 9 appears in the developer on the developing roller 5 as toner density unevenness in the surface movement direction of the developing roller 5.
As described above, when the toner density unevenness occurs in the rotation axis direction and the surface movement direction on the developing roller 5, there arises a problem that the image density becomes non-uniform.

The present invention has been made in view of the above problems, and an object of the present invention is to have a developing device including a feeding conveyance path, an agitation conveyance path, and a collection conveyance path, and to form an image with stable image density. A developing device capable of performing the above and an image forming apparatus including the same.
Is to provide.

In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that a two-component developer comprising a magnetic carrier and a toner is carried on the surface and rotated, and the latent image carrier is located at a position facing the latent image carrier. A developer carrying member that supplies toner to the latent image on the surface of the developer for development, and a developer supply that conveys the developer along the axial direction of the developer carrying member and supplies the developer to the developer carrying member The developer recovered from the developer carrying body after passing through the developer supply carrying path provided with the carrying member and the portion facing the latent image carrying body along the axial direction of the developer carrying body. And a developer recovery transport path including a developer recovery transport member that transports in the same direction as the developer supply transport member, and to the most downstream side in the transport direction of the developer supply transport path without being used for development. Excess developer transported and how to transport the developer recovery transport path recovered from the developer carrier The developer supplied and transported to the most downstream side of the developer is supplied and transported along the axial direction of the developer carrying member and while stirring the excess developer and the recovered developer. A developer agitating and conveying member that conveys the developer in a direction opposite to the member, and having a developer agitating and conveying path for supplying the developer to the developer supply and conveying path, the developer collecting and conveying path, and the developer supply The three developer transport paths comprising the transport path and the developer agitation transport path are each partitioned by a partition member, and move in the developer agitation transport path in a developing device in which toner is supplied to the developer transport path. The developer conveying speed is U ₁ [m / s], the developer agitating and conveying path length is L [m], the toner replenishment cycle is T [s], and the agitating and conveying member is agitated. a value indicating diffusion performance by performing a D ^[m 2 / s], the following (1) It is characterized in that the hold. (L · D) / (T ² · U ₁ ³ ) ≧ 0.075 (1)
Further, the invention of claim 2 is the developing device according to claim 1, wherein the transport speed of the developer moving in the developer supply transport path is U ₂ [m / s], and in the developer recovery transport path. The transport speed of the developer that moves is U ₃ [m / s], and U ₂ > U ₁ and U ₃ > U ₁ are satisfied.
According to a third aspect of the present invention, in the developing device according to the first or second aspect, the three developer transport members, the developer supply transport member, the developer recovery transport member, and the developer agitation transport member, have a rotating shaft. The developer transport screw is provided with a spiral wing portion, and transports the developer by rotating. The three developer transport members are a developer supply screw, a developer recovery screw, and a developer stirring screw, respectively. It is characterized by being.
According to a fourth aspect of the present invention, in the developing device of the third aspect, the pitch width of the developer stirring screw is narrower than the pitch width of the supply screw and the recovery screw.
Further, the invention of claim 5 is the developing device according to claim 1, wherein the developer transport speed in at least a part of the developer stirring transport path is such that the developer supply transport path and the developer recovery transport are as follows. It is characterized by being slower than the transport speed of the developer on the path.
According to a sixth aspect of the present invention, in the developing device of the fifth aspect, the three developer transport members, the developer supply transport member, the developer recovery transport member, and the developer agitation transport member, are arranged on the rotating shaft portion. It is a developer transport screw that includes a spiral blade and transports the developer by rotating, and the three developer transport members are a developer supply screw, a developer recovery screw, and a developer stirring screw, respectively. It is characterized by.
The invention of claim 7 is the developing device of claim 6, wherein a part of the pitch width of the developer agitating screw is narrower than the pitch width of the supply screw and the recovery screw. is there.
According to an eighth aspect of the present invention, in the developing device according to the fifth, sixth, or seventh aspect, the toner replenishing position for replenishing toner to the developing device is set at the supply conveying path and the recovery conveying path among the developer stirring and conveying paths. It is provided at a portion where the developer conveyance speed is slower than the path, or at the upstream side of the developer conveyance direction.
According to a ninth aspect of the present invention, in the developing device according to the first, second, third, fourth, sixth, or seventh aspect, a toner replenishing position for replenishing toner to the developing device is provided in the developer collecting conveyance path. It is characterized by this.
According to a tenth aspect of the present invention, in the developing device according to the first, second, third, fourth, sixth, or seventh aspect, a toner replenishing position for replenishing toner to the developing device is located on the most downstream side of the developer collecting conveyance path. It is provided in a developer delivery portion from the first portion to the uppermost stream portion of the developer stirring and conveying path.
The invention of claim 11 is the developing device of claim 3, 4, 6, 7, 8, 9 or 11, wherein the rotational speed of the developer stirring screw is based on the rotational speed of the supply screw and the recovery screw. Is also small.
The invention according to claim 12 is the developing device according to claim 3, 4, 6, 7, 8, 9, 10 or 11, wherein the developer stirring screw is provided with a radial direction of the blade portion and an axial direction of the stirring screw. A fin having a plane composed of sides is attached.
The invention according to claim 13 is the developing device according to claim 3, 4, 6, 7, 8, 9, 10, 11 or 12, wherein the number of blades of the stirring and conveying screw is plural. It is what.
The invention according to claim 14 is the developing device according to claim 3, 4, 6, 7, 8, 9, 10, 11, 12 or 13, wherein the diameter of the blade portion of the agitating and conveying screw is set to the blade of the supply screw. It is characterized by being larger than the diameter of the part.
The invention of claim 15 is the developing device of claim 3, 4, 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein the number of rotations of the stirring and conveying screw can be changed. It is characterized by.
The invention of claim 16 is the developer agitating and conveying apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15. The magnetic field generating means is attached so that a magnetic field is formed on the road.
The invention of claim 17 is the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. A toner concentration detection unit that detects the toner concentration of the developer in the agitation conveyance path is provided, and the developer conveyance speed in the developer agitation conveyance path is controlled based on the detection result of the toner concentration detection unit. It is what.
The invention of claim 18 is characterized in that, in the developing device of claim 17, when the toner density detecting means detects a decrease in toner density, the developer conveying speed of the developer stirring and conveying path is increased. It is what.
According to a nineteenth aspect of the present invention, there is provided the developing device according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelve, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, or eighteenth. And a developer agitation time measuring means for counting the integrated value of the developer agitation time in the developing device, and based on the measured value of the developer agitating and conveying time measuring means, The conveyance speed is controlled.
According to a twentieth aspect of the present invention, in the developing device of the nineteenth aspect, the developer conveying speed of the developer agitating / conveying path is decreased in accordance with the increase in the integrated value. .
The invention of claim 21 is the image of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, or 20. In the forming apparatus, the developer collection conveyance path is provided below the developer carrier, and the three developer conveyance paths are provided at substantially the same height.
According to a twenty-second aspect of the present invention, in the image forming apparatus of the twenty-first aspect, the uppermost part of the developer supply / conveying member is located below the rotation center axis of the developer carrier, and the rotation center of the developer carrier is An angle formed by a plane passing through the shaft and the uppermost portion of the developer supply / conveying member and a horizontal plane passing through the rotation center axis of the developer carrying member is within a range of 10 [°] to 40 [°]. It is a feature.
The invention of claim 23 provides at least a latent image carrier, charging means for charging the surface of the latent image carrier, and formation of a latent image for forming an electrostatic latent image on the latent image carrier. And a developing unit for developing the electrostatic latent image into a toner image, wherein the developing unit is defined as claim 1, 2, 3, 4, 5, 6, 7, 8 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 is used.

In the developing device according to any one of claims 1 to 23, the developer conveying speed in the agitating and conveying path is U ₁ [m / s], the length of the agitating and conveying path is L [m], and the period of toner replenishment is set. When T [s] and the value indicating the diffusion performance due to the stirring / conveying member stirring are D [m ² / s], the relationship of the following expression (1) is established.
(L · D) / (T ² · U ₁ ³ ) ≧ 0.075 (1)
As a result, with respect to the temporal toner concentration difference between the highest toner concentration timing at the most upstream part of the developer stirring conveyance path and the lowest toner concentration timing, The temporal difference in toner density between the timing with the highest toner density and the timing with the lowest toner density can be reduced to 1/20 or less. Note that the maximum value of the toner concentration at the most upstream portion of the developer stirring and conveying path does not exceed the toner concentration of 20% within a practical range even if an extreme value is taken into consideration. Further, the minimum value of the toner density is the state of only the carrier, that is, the toner density of 0 [%]. In such a state, the temporal difference in toner density between the timing when the toner density is highest in the most upstream portion of the developer agitation transport path and the timing when the toner density is lowest is 20 [%]. As described above, even when the difference between the maximum value and the minimum value of the toner density is extremely wide, by satisfying the expression (1) in the developer stirring / conveying unit, it is the most in the most downstream portion of the developer stirring / conveying path. The difference in temporal toner density between the timing when the toner density is high and the timing when the toner density is the lowest can be made 1.0 [%] or less, and toner density unevenness on the developer carrying member can be suppressed. it can.

  According to the first to twenty third aspects of the invention, there is an excellent effect that image formation with a stable image density can be performed by suppressing toner density unevenness on the developer carrying member.

[Embodiment 1]
Hereinafter, an embodiment (hereinafter referred to as Embodiment 1) in which the present invention is applied to an electrophotographic color copying machine (hereinafter simply referred to as a copying machine) as an image forming apparatus will be described.
FIG. 1 is a schematic configuration diagram illustrating a copying machine according to the first embodiment. In this figure, the copier has 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 disposed above and a second image forming unit disposed below the paper conveyance path 43A. The first image forming unit includes a first transfer unit 20 having a first intermediate transfer belt 21 as a first intermediate transfer belt 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 as a first intermediate transfer belt that moves endlessly in the direction of the arrow in the drawing. Four first process units 80 (Y, M, C, K) are arranged above the upper stretched surface of the first intermediate transfer belt 21. On the other hand, four second process units 81 (Y, M, C, K) are arranged on the side of the inclined tension surface on the side of the second intermediate transfer belt 31. The subscripts Y, M, C, and K attached to the numbers of the first and second process units correspond to the entry of toner to be handled. Y is yellow, C is cyan, M is magenta, and K is Means black. The same subscript is attached to each device in the process unit.

  Each process unit (80 (Y, M, C, K), 81 (Y, M, C, K)) has a photoreceptor (1 (Y, M, C, K)) as a latent image carrier. is doing. The photoreceptors 1 (Y, M, C, K) of the first process unit 80 (Y, M, C, K) are arranged at equal intervals, and at least during image formation, the upper stretch of the first intermediate transfer belt 21 is stretched. Touch the surface. Hereinafter, the belt surface that contacts in this way is referred to as a first image receiving surface.

  On the other hand, the photoreceptors 1 (Y, M, C, K) of the second process unit 81 (Y, M, C, K) are also arranged at equal intervals, and at the time of image formation, at the side of the second intermediate transfer belt 31 respectively. Contact the tension surface. 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 by a plurality of rollers in a horizontally long posture that takes a space in the horizontal direction rather than in the vertical direction, and in a posture in which the first image receiving surface extends substantially horizontally. The first process units 80 (Y, M, C, K) are arranged in parallel in a substantially horizontal state 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 is in a vertically long posture with a plurality of rollers to take a space in the vertical direction rather than in the horizontal direction, and the second image receiving surface is slanted from the upper left to the lower right in the drawing. It is built. The second process unit 81 (Y, M, C, K) is on the left side of the second intermediate transfer belt 31 in the drawing so as to contact the inclined second image receiving surface, from the upper left in the drawing. It arrange | positions so that it may become the diagonal arrangement | sequence toward the lower right.

  FIG. 2 is an enlarged configuration diagram showing one of the four first process units 80 (Y, M, C, K). The four first process units 80 (Y, M, C, K) have substantially the same configuration except that the colors of the toners to be handled are different from each other. , C, K are omitted. In the figure, the photosensitive member 1 is driven to rotate counterclockwise in the drawing by a driving means (not shown) during operation of the printer unit 100. Around the photoconductor 1, image forming members such as a scorotron charger 3, a developing device 4, a photoconductor cleaning device 2, and a photostatic device Q, which are charging means, a potential sensor S1, an image sensor S2, and the like are disposed. Has been. The photosensitive member 1 forms an electrostatic latent image on the surface thereof by laser light L emitted from an exposure device (not shown) serving as a latent image forming unit.

  The drum-shaped photoreceptor 1 is formed by coating an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylinder surface having a diameter of about 30 to 120 [mm], for example. An amorphous silicon (a-Si) layer may be coated. 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 and recovers 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 do.

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 such 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 onto the surface of each photoreceptor 1 that has been uniformly charged by a charging means, thereby forming a latent image. As an exposure apparatus, a light emitting element composed of an LED (light emitting diode) array and a crystal element, a laser light source, a polygon mirror, etc., and a laser scanning method using a laser beam modulated according to image data to be formed are used. Can be adopted.

The development of the printer unit 100 is a development system that employs a two-component developer composed of toner and carrier. The electrostatic latent image for each color formed on the surface of each photosensitive member 1 by a laser beam with respect to the negatively charged photosensitive member 1 is developed with toner of a predetermined color having the same polarity (negative polarity) as the charged polarity of the photosensitive member. Then, so-called reversal development is performed, which becomes a visible image. Details of the configuration of the developing device 4 will be described later.
Further, when the Y, M, C, and K color toners are consumed by the developing device 4 that handles each color, the toners are detected by the magnetic permeability toner density sensor 127 and are provided in the bottle accommodating portion 85 inside the printer unit 100. The toner of each color is supplied from the bottle 86 to each developing device 4 by a toner supply control device (not shown).

  FIG. 3 is an enlarged configuration diagram showing one of the four second process units 81 (Y, M, C, K). Since the four second process units 81 (Y, M, C, and K) have substantially the same configuration except that the colors of the handled toners are different from each other, the second process unit 81 is the first process unit. Although the constituent members are the same as 80, the rotation direction of the photosensitive member 1 is different. However, they are mutually shaped with respect to the y-axis passing through the rotation axis 1a of the photoreceptor 1. Although this shape is related to the arrangement of members provided around the photoreceptor 1, it is an important matter. Specifically, consideration is given to a method of connecting a connecting portion with the main body of the printer unit 100, for example, a connecting portion with a driving means, an electrical connecting portion, a toner supplying portion, and a toner discharging portion. Thereby, compatibility can be motored between the first process unit 80 (Y, M, C, K) and the second process unit 81 (Y, M, C, K). Therefore, it is not necessary to separately manufacture the developing device, the cleaning device, and the parts for the first process unit and the second process unit, and the efficiency in manufacturing parts and managing parts is high, and the overall cost can be reduced. it can.

  In FIG. 1 described above, the first image forming unit includes a plurality of first process units 80 (Y, M, C, K) and a first transfer unit 20. Further, the second image forming unit includes a plurality of second process units 81 (Y, M, C, K) and a second transfer unit 30. Further, in the printer unit 100, the first transfer unit 20 and the second transfer unit 30 constitute a double-side transfer device.

  In the first transfer unit 20, the first intermediate transfer belt 21 is stretched by a plurality of rollers 23, 24, 25, 26 (two), 27, 28, 29, and the first process unit 80 (Y, M, C, K) of the photosensitive member 1 (Y, M, C, K). A primary transfer roller 22 is provided at a position facing the respective photoreceptors 1 (Y, M, C, K) on the inner peripheral portion of the first intermediate transfer belt 21. Due to this contact, the first transfer unit 20 causes the Y, M, C, and K toner images (hereinafter also referred to as single-color first toner images) on the photoreceptor 1 (Y, M, C, and K) to be transferred to the first intermediate unit. A primary transfer nip for Y, M, C, and K to be transferred on the transfer belt 21 is formed. The first intermediate transfer belt 21 is endlessly moved clockwise in the figure while forming these four primary transfer nips. In each primary transfer nip, the first intermediate transfer belt 21 is in contact with any one of the four primary transfer rollers 22 to which a primary transfer bias is applied by a power source (not shown) between the photosensitive member 1 (Y, M, C, K). Is sandwiched. Due to the influence of the primary transfer bias and the nip pressure, a monochrome single-color toner image is primary-transferred on the first intermediate transfer belt 21 at each primary transfer nip. By this superposition, a multicolor first toner image is formed on the first intermediate transfer belt 21 as an image carrier.

  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 configured 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 photoreceptor 1 (Y, M, and C). , K). By this contact, the second transfer unit 30 causes the second toner image (hereinafter also referred to as a single-color second toner image) on the photoreceptor 1 (Y, M, C, K) A primary transfer nip for Y, M, C, and K to be transferred onto the second intermediate transfer belt 31 is formed. The second intermediate transfer belt 31 is moved endlessly in the counterclockwise direction in the figure while forming these four primary transfer nips. In each primary transfer nip, any one of the four primary transfer rollers 32 to which a primary transfer bias is applied by a power source (not shown) is between the second intermediate transfer belt 31 and the photoreceptor 1 (Y, M, C, K). Is sandwiched. Due to the influence of the primary transfer bias and the nip pressure, the Y, M, C, K second toner images are primarily transferred onto the second intermediate transfer belt 31 at each primary transfer nip. By this superposition, a multicolor second toner image is formed on the second intermediate transfer belt 31 as an image carrier.

  A belt cleaning device 30 </ b> A is provided on the outer peripheral portion 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.

Each of the two intermediate transfer belts (21, 31) is a belt having a base made of a resin film or rubber having a base thickness of 50 to 600 [μm], for example. The toner image, which is a visible image carried on the photoreceptor 1, exhibits an electrical resistance value that enables electrostatic transfer to the belt surface by a primary transfer bias applied to the primary transfer rollers (22, 32). . As an example of such an intermediate transfer belt, a material in which carbon is dispersed in polyamide and the volume resistance value is adjusted to about 10 ⁶ to 10 ¹² [Ωcm] can be exemplified. Belt detent ribs for stabilizing the running of the belt are provided on one side or both ends of the belt. The circumference of the belt is about 1500 [mm].

As the four primary transfer rollers 22 as the primary transfer means of the first transfer unit 20 and the four primary transfer rollers 32 as the primary transfer means of the second transfer unit 30, for example, those having the following configurations can be used. . That is, the surface of a metal roller as a core metal is coated with a conductive rubber material, and a bias is applied to the core metal part from a power source (not shown). In the first embodiment, as the conductive rubber material, urethane rubber in which carbon is dispersed is used, and the volume resistance is adjusted to about 10 ⁵ [Ωcm].

  The printer unit 100 can also output a monochrome image using only K toner. When outputting a monochrome image, the Y, M, C process units 80Y, 80M, 80C in the first transfer unit 20 are not used. In addition to not operating the process units 80Y, 80M, 80C, a mechanism for keeping these and the first intermediate transfer belt 21 in a non-contact state is provided. An internal frame (not shown) that supports the roller 26 and the primary transfer roller 22 is provided, and is supported so as to be rotatable around a certain point. Then, by rotating in a direction away from the photoconductor, only the photoconductor 1K is brought into contact with the first intermediate transfer belt 21, and an image forming process is executed to create a monochrome image using black toner. Such a configuration is advantageous in terms of improving the life of the photoreceptor. Similarly, the second transfer unit 30 is configured to retract the process units 81Y, 81M, and 81C from the second intermediate transfer belt 31 when outputting a monochrome image.

  On the outer periphery of the first intermediate transfer belt 21, the secondary transfer roller 46 sandwiches the first intermediate transfer belt 21 between the support roller 28 that stretches while supporting the first intermediate transfer belt 21 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 formed by coating a metal roller as a core metal with a conductive rubber, and a secondary transfer bias is applied to a core metal part from a secondary transfer bias power source (not shown). The conductive rubber has a volume resistance adjusted to about 10 ⁷ [Ωcm] by the dispersion of carbon.

  A registration roller pair 45 is disposed on the right side of the secondary transfer nip in the drawing. The registration roller pair 45 temporarily suspends the rotation of both rollers after the transfer paper P sent from the paper feeding device 40 disposed on the right side of the printer unit 100 in the drawing is sandwiched between the rollers. Then, the transfer paper P is sent out toward the secondary transfer nip at a timing that can be synchronized with the four-color toner image that is the superimposed toner image on the first intermediate transfer belt 21. The transferred transfer paper P has a four-color toner image in close contact with the first surface (the surface facing the upper side in the drawing) which is one surface of the transfer paper P at the secondary transfer nip. Then, the four-color toner image on the first intermediate transfer belt 21 is secondarily transferred onto the first surface by the influence of the secondary transfer bias and the nip pressure. 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, the belt-wrapped portion of the second intermediate transfer belt 31 by the upper stretch roller 34 that stretches the second intermediate transfer belt 31 is the upper stretch 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 through the predetermined gap to the upper stretching roller 34 is a second transfer portion of the second transfer unit 30.

  The transfer charger 47 is a known type, and a thin wire of tungsten or gold is used as a discharge electrode, held by a casing, and a transfer current is applied to the discharge electrode from a power source (not shown). While passing the transfer paper P between the second intermediate transfer belt 31 and the transfer charger 47, the four-color toner on the second intermediate transfer belt 31 is applied to the first surface with the charge generated from the transfer charger 47. The image is secondarily transferred collectively 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 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 sheet feed tray 40a, 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 fed and separated by the corresponding paper feeding / separating means 41A to 41D, and only one sheet is reliably fed by the plurality of conveying roller pairs 42B to the paper conveying path 43B. And sent to 43A.

  In the paper transport path 43A, a pair of registration rollers 45 are provided 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 a position perpendicular 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 include a horizontal reference guide (not shown) and a pair of skew rollers, and press the lateral end of the transfer paper 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 correction mechanism 44 regulates the transfer paper P to be aligned at a predetermined position by pressing both sides of the transfer paper P for a short time and a plurality of times from both sides of the transfer paper P with respect to the transport direction of the transfer paper P. A jogger system composed of members may be used.

  The transfer sheet P is conveyed from the registration roller pair 45 toward the first transfer portion where the secondary transfer nip is formed by the contact of the first intermediate transfer belt 21 and the secondary transfer roller 46. Thereafter, the sheet is fed toward the second transfer portion where the second intermediate transfer belt 31 and the transfer charger 47 face each other.

  In the paper feeding device 40, the transfer paper P discharged 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 </ b> A of the printer unit 100. It is transported almost horizontally and straight. Therefore, even thick transfer paper P or highly rigid paperboard can be reliably fed to the paper transport path 43A of the printer unit 100 if it is accommodated in the paper feed tray 40a. In addition, it is convenient to adopt an air sheet feeding composed of a vacuum mechanism so that the sheet feeding tray 40a can reliably feed a transfer sheet 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 uppermost paper feed tray 40a. Transfer paper P can be supplied to the second paper feed path 43C from a 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, the paper transport for transporting the transfer paper P that has passed through the second transfer section to the fixing nip of the fixing device 60 downstream in the transfer paper transport direction while maintaining a flat state. A unit 50 is arranged. The paper transport unit 50 is configured to endlessly move counterclockwise in the figure 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 conveyance belt 51, the transfer 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 separation roller 54 is opposed to and opposed to the transfer roller P. A separation charger 58 for separating the 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 front surface of the paper transport belt 51 by the electrostatic adsorption 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 front surface of the paper transport belt 51.

The paper conveyance belt 51 having the transfer paper P electrostatically attracted to the front 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 delivered to the fixing device 60 as fixing means disposed on the left side of the paper transport unit 50 in the drawing. Charges are applied by the separation charger 58 to the transfer paper P that is electrostatically attracted to the front surface of the paper transport belt 51 at a timing earlier than this delivery. By applying this electric charge, the transfer paper P that has been electrostatically attracted to the front surface of the paper transport belt 51 until then is easily separated from the belt. Of the plurality of stretching rollers, a belt that changes its moving direction abruptly according to 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 paper and transferred to 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 a chargeable resistance value. 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. In the drawing, a fixing nip formed by abutting two fixing rollers is used to fix the multicolor first toner image and the multicolor second toner image by heating the transfer paper P from both sides, respectively. Adopted. In order to make the hue 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 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 cooling roller pair 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 transported to another post-processing apparatus through the paper discharge stack section 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, toner bottles 86Y, 86M, 86C, and 86K of each color in which unused toner is stored are detachably stored in the bottle storage unit 85. Toner is supplied to each developing device as required by a supply means (not shown). To the developing devices that handle toner of the same color in the first image forming unit and the second image forming unit arranged above and below, toner is supplied from a common toner bottle. You can also The toner bottle 86K for black toner that is highly consumed can have a particularly large capacity. The bottle housing portion 85 is on the back side when viewed from the operation direction on the upper surface of the printer unit 100, and a plane portion is secured on the front side of the upper surface of the printer unit 100, so that it can be used as a work table.

  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 keyboard 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 waste toner storage unit 87 provided in the printer unit 100 is connected to the photoreceptor cleaning device 2, the belt cleaning devices 20A and 30A for the intermediate transfer belt, and the like. Then, foreign substances such as waste toner and paper dust sent from these are collected and stored in a lump. Since these cleaning devices (2, 20A, 30A, and 50A) do not include a large-capacity waste toner storage unit, the cleaning device can be reduced in size, and the waste toner disposal operability is good. A full sensor (not shown) is used to issue a warning such as toner disposal in the waste toner storage unit 87 or container replacement.

  Various power supplies, control boards, and the like are protected and housed 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. The fan 96 is coupled to the heat radiating portion of the cooling roller pair 70 to ensure 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 the same image as the original 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, the 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 will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method in which the four-color toner image transferred to the first intermediate transfer belt 21 is collectively transferred onto the first surface of the transfer paper P. The other method is a method in which the four-color toner image transferred to the second intermediate transfer belt 31 is secondarily transferred collectively to the second surface of the transfer paper P. When the image carried on the first intermediate transfer belt 21 is directly transferred to one side of the paper from the configuration of the printer unit 100, the image carried on the second intermediate transfer belt 31 is placed on the upper surface of the paper. In the case of direct transfer on one side, an image is formed on the lower surface of the paper. In the case where the data to be recorded is a plurality of pages, it is convenient to control the image forming order so that the pages are aligned on the paper discharge stack unit 75.
Hereinafter, a method of carrying an image on the first intermediate transfer belt 21 and then transferring it to a sheet so as to sequentially record the image data from the last page and align the page order will be described.

  When the printer unit 100 is operated, the first intermediate transfer belt 21 and the photosensitive member 1 (Y, M, C, K) in the first process unit 80 (Y, M, C, K) rotate. At the same time, the second intermediate transfer belt 31 moves endlessly, but the photoreceptor 1 (Y, M, C, K) in the second process unit 81 (Y, M, C, K) is separated from the second intermediate transfer belt 31. And non-rotating. Then, image formation by the first process unit 80Y is started. The light corresponding to the image data for yellow emitted from the LED is uniformly charged by the scorotron charger 3 by the operation of an exposure apparatus (not shown) composed of an LED (light emitting diode) array and an imaging element. The surface is irradiated to form an electrostatic latent image.

  This electrostatic latent image is developed into a Y toner image by the developing device of the first process unit 81Y for Y, and is electrostatically primarily transferred onto the first intermediate transfer belt 21 at the primary transfer nip for Y. Such latent image formation, development, and primary transfer operations are sequentially performed in a similar manner at the timing of the photoconductors 1M, 1C, and 1K. Then, the M, C, and K toner images are sequentially superimposed and primary-transferred on the Y toner image on the first intermediate transfer belt 21 at the primary transfer nip for M, C, and K. By this primary transfer of superposition, yellow, cyan, magenta, and black toner images are carried on the first intermediate transfer belt 21 as a full color toner image. The full color toner image is moved in the direction of the arrow in the drawing together with the first intermediate transfer belt 21.

  On the other hand, the paper feeding device 40 transfers the transfer paper corresponding to the image data from the internal paper feeding tray 40a or the paper feeding cassettes 40b, c, d to any one of the paper feeding / separating means 41A, B, C, D. So send it out. 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 determines the inclination of the posture of the transfer paper P in the middle of being conveyed from the paper feeding device 40 serving as the recording medium supply unit toward the double-sided transfer device (first and second transfer units) from the conveyance direction. It is an inclination correction means for correcting. A pair of guide plates arranged in the paper surface direction orthogonal to the transport direction on the upstream side of the registration roller pair 45 is abutted against both ends orthogonal to the transport direction of the transfer paper P, so that the posture of the transfer paper P is adjusted. Correct the tilt. 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 sheet P whose posture inclination is corrected by the lateral registration correction mechanism 44 reaches between the rollers of the registration roller pair 45. 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 is rotated at a timing so that the position of the image on the first intermediate transfer belt 21 is normal, and the sheet is conveyed to the transfer area.
This full-color toner image on the first intermediate transfer belt 21 undergoes a transfer action by the secondary transfer roller 46 on the first surface of the paper P that is conveyed in synchronization with the first intermediate transfer belt 21, and is subjected to batch secondary transfer. Is done. 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 the transfer residual toner by the belt cleaning device 20A.

  Further, in each first process unit 80 (Y, M, C, K), transfer residual toner remaining on the photosensitive member 1 (Y, M, C, K) after passing through the primary transfer nip, Cleaning is performed by the photoconductor cleaning device 2. As shown in FIG. 2, the photosensitive member cleaning device 2 removes transfer residual toner from the surface of the photosensitive member 1 (Y, M, C, K) by using a cleaning brush 2a and a cleaning blade 2b. The removed foreign matter such as toner is sent to the collecting unit 87 by the collecting unit 2c. Sensors S1 and S2 detect whether the surface potential after exposure on the surface of the photoconductor and the concentration of toner attached to the surface of the photoconductor after the development process are appropriate, and appropriately set image forming conditions. Information is sent to a control means (not shown) for control. Further, the surface of the photoreceptor 1 after cleaning is initialized by removing the residual charges by the static eliminating device Q.

  The transfer paper P on which the four-color toner image is secondarily transferred on 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 and then transported to the paper. Sent to unit 50. Then, the paper is transferred from the paper transport unit 50 to the fixing device 60. Prior to this transfer, the transfer paper P is charged by the separation charger 58. By this application, the transfer paper that has been electrostatically attracted to the second intermediate transfer belt 31 is easily separated from the belt.

  In the fixing device 60, each color toner in the full-color image carried on the first surface of the transfer paper P is melted and mixed by heating to form a complete color image. Since the transfer paper P has toner only on its first side, less heat energy is required for fixing compared to double-sided recording with toner on both sides. The control unit 95 optimally controls the power used by the fixing device 60 according to the image. Even after the fixing process is performed, until the toner image is completely fixed on the transfer paper P, the toner image is rubbed against a guide member or the like in the conveyance path, and the image is lost or distorted. In order to prevent this problem, the transfer paper that has passed through the fixing device 60 is provided with a pair of cooling rollers 70 as 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 75 with the image surface facing upward. In this copying machine, since the image forming order is programmed so that the transfer sheets of the young pages are sequentially stacked on the paper discharge stack unit 75, the page order is aligned in the paper discharge stack unit 75.
Since the discharge stacking unit 75 is lowered as the number of transfer sheets P to be discharged increases, the transfer sheets can be stacked in an orderly and reliable manner, and the page order is not disturbed. Instead of directly stacking the recorded transfer paper on the paper discharge stack section 75, a punching process can be performed, or the transfer paper can be conveyed to a post-processing device such as a sorter, a collator, a binding device, or a folding device.

  In another method of forming an image on one side of the transfer paper P, an image is not formed in the first process unit 80 (Y, M, C, K), and a young page is used for page alignment. The difference is that images are formed in order from the image data. However, the description is omitted because it is basically the same as the one-side recording process described above.

Next, the operation during double-sided recording in which images are formed on both sides of the transfer paper will be described.
When an image signal is input to the printer unit 100, Y, M, C, K in the first process unit 80 (Y, M, C, K) described in the single-sided recording operation are transferred to Y, M, C, K toner images are formed. These are primarily transferred onto the first intermediate transfer belt 21 in sequence at the primary transfer nips for Y, M, C, and K. Almost in parallel with this step, Y, M, C, and K toner images are formed on the photoreceptor 1 (Y, M, C, K) of the second process unit 81 (Y, M, C, K). . These are primarily transferred onto the second intermediate transfer belt 31 sequentially at the primary transfer nips for Y, M, C, and K. In this way, four-color toner images are formed on the first intermediate transfer belt 21 and the second intermediate transfer belt 31, respectively.

As shown in FIG. 1, the unit interval of the second process unit 81 (Y, M, C, K) is smaller than the unit interval of the first process unit 80 (Y, M, C, K). Thus, the primary transfer is completed in the second transfer unit 30 faster than the first transfer unit 20. In addition, in order for the first image and the second image to coincide with each other at the leading end in the conveyance direction of the transfer paper P, the formation of the second image is started after the start of the formation of the first image. The
Since the sheet is stopped and retransmitted by the registration roller pair 45, the sheet is fed in consideration of the time and aligned by the lateral registration correction mechanism 44.
The registration roller pair 45 transports the sheet to the secondary transfer nip of the first transfer portion constituted by the secondary transfer roller 46 as the first secondary transfer unit and the first intermediate transfer belt 21 at a timing.

  The transfer paper P, which is timed and sent from the registration roller pair 45 to the secondary transfer nip of the first transfer portion, is applied with a positive transfer current to the secondary transfer roller 46, and the first side is applied to the first surface. A full color image is transferred from the intermediate transfer belt 21. The sheet P having an image on one side in this way is continuously sent to the second transfer portion having the transfer charger 47 as the second secondary transfer means 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 the full-color second image previously carried on the second intermediate transfer belt 31 is secondary to the second surface of the transfer paper P in a lump. Transcribed.

The transfer paper P on which the full-color images are formed on both sides in this manner is transferred to the fixing device 60 by the paper transport belt 51 of the paper transport unit 50. The suction charger 57 charges the surface of the paper transport belt 51 with the same negative polarity as the polarity of the toner. This prevents unfixed toner on the second surface of the transfer paper P from moving to the paper transport belt 51. An alternating current is applied to the charge removal / separation charger 58, and the paper is separated from the paper transport belt 51 and delivered to the fixing device 60.
Then, a fixing process by heating or pressurization is performed in the fixing device 60, and the toner images on both sides are respectively melted and mixed. Further, after passing through the cooling roller pair 70 and the paper discharge roller pair 71, the paper is discharged onto the paper discharge stack 75.

  When double-sided recording is performed on a plurality of pages of transfer paper, the image forming order is controlled so that the image of the young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. As a result, when the paper is taken out from the paper discharge stack 75 and the top and bottom surfaces are reversed, the recorded matter is one page in order from the top, the second page on the back, the third page on the second sheet, and the fourth page on the back. 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.

Although an example in which full-color recording is performed regarding the single-sided recording operation and the double-sided recording operation has been described, monochrome recording using only black toner is also possible.
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 configured as described above, a combination of the first image forming unit and the control unit 95 described above allows a multicolor first image as a first toner image on the surface of the first intermediate transfer belt 21 as a first toner image carrier. A first toner image forming unit for forming a toner image is configured. A second toner image that forms a multicolor second toner image as a second toner image on the surface of the second intermediate transfer belt 31 as a second toner image carrier by a combination of the second image forming unit and the control unit 95. A forming part is configured. 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. The first toner image is a multi-color first toner image obtained by superimposing a plurality of single-color first toner images, and a toner image composed of only a single-color first toner image of Y, M, C, or K. It is a generic name. The second toner image is a multi-color second toner image formed by superimposing a plurality of single-color second toner images, and a toner image including only a single-color second toner image of any one of Y, M, C, and K. It is a generic name.

Next, the developing device 4 will be described.
As shown in FIG. 4, the surface of the photoreceptor 1 is charged by the scorotron charger 3 while rotating in the direction of arrow G in the figure. The charged surface of the photosensitive member 1 is supplied with toner from the developing device 4 to a latent image on which an electrostatic latent image is formed by a laser beam L irradiated from an exposure device (not shown) to form a toner image.

The developing device 4 has a developing roller 5 as a developer carrying member for supplying toner to the latent image on the surface of the photoreceptor 1 while moving the surface in the direction of arrow I in the drawing. Further, a supply screw 8 is provided as a developer supply / conveying member that conveys the developer in the depth direction of FIG. 4 while supplying the developer to the developing roller 5.
A developing doctor 16 as a developer regulating member for regulating the developer supplied to the developing roller 5 to a thickness suitable for development is provided on the downstream side of the surface moving direction from the portion facing the supply screw 8 of the developing roller 5. ing.
The developed developer that has passed through the developing unit is collected downstream from the developing unit, which is the part of the developing roller 5 facing the photoconductor 1, and the collected developer is collected in the same direction as the supply screw 8. A recovery screw 6 is provided as a developer recovery / conveying member. A supply conveyance path 9, which is a developer supply conveyance path provided with a supply screw 8, and a collection conveyance path 7, which is a developer collection conveyance path 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 partitioned by a partition plate 134 as a partition member.

  The developing device 4 is provided with an agitation conveyance path 10 that is a developer agitation conveyance path in parallel with the supply conveyance path 9 opposite to the collection conveyance path 7. The agitating and conveying path 10 includes an agitating screw 11 as a developer agitating and conveying member that conveys the developer to the front side in the figure, which is in the opposite direction to the supply screw 8 while agitating the developer. The supply conveyance path 9 and the stirring conveyance path 10 are partitioned by a partition wall 133 as a partition member. Both ends of the front and rear sides of the partition wall 133 in the figure are openings, and the supply conveyance path 9 and the agitation conveyance path 10 communicate with each other. The excess developer that is supplied into the supply conveyance path 9 and is not used for development and is conveyed to the downstream end in the conveyance direction of the supply conveyance path 9 and the collected development conveyed to the downstream end in the conveyance direction of the collection conveyance path 7 by the collection screw 6 The agent is supplied to the stirring conveyance path 10. The agitating and conveying path 10 agitates the supplied excess developer and the recovered developer, and conveys them to the downstream side in the conveying direction of the agitating screw 11 and to the upstream side in the conveying direction of the supplying screw 8.

The partition plate 134 has an opening at the end in the rearward direction in the drawing, which is the most downstream side in the transport direction of the recovery screw 6, and the supply transport path 9 and the recovery transport path 7 communicate with each other. Three conveyance paths are communicated with each other at the downstream end in the conveyance direction of the collection screw 6, the downstream end in the conveyance direction of the supply screw 8, and the upstream end in the conveyance direction of the stirring screw 11.
Then, the recovered developer transported to the downstream end in the transport direction of the recovery transport path 7 is transferred to the supply transport path 9. Further, the collected developer and the developer that has not been supplied to the developing roller 5 conveyed by the supply screw 8 are transferred to the stirring and conveying path 10 that is in communication.
In the agitating and conveying path 10, the agitating screw 11 agitates and conveys the collected developer, the surplus developer, and the toner replenished as needed in the transfer unit in the direction opposite to the developer in the collecting and conveying path 7 and the supply conveying path 9. . Then, the agitated developer is transferred to the upstream side in the conveyance direction of the supply conveyance path 9 communicating with the downstream side in the conveyance direction. A toner concentration sensor 127 is provided below the agitating and conveying path 10, and a toner replenishment control device (not shown) is operated by the sensor output to replenish toner from the toner bottle 86 to the transfer unit.
The casing of the developing device 4 includes an integrally formed lower casing 12 and upper casing 13 which are divided into upper and lower portions at the shaft portions of three conveying screws. The partition wall 133 is a part of the lower casing 12, and the partition plate 134 is held by the upper casing 13 and mated with the lower casing 12.
As the above-described toner replenishment control device, a system using a known MONO pump can be adopted. According to this method, there are few restrictions on the installation location of the toner cartridge, which is advantageous for space allocation in the image forming apparatus. Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device 4, and the developing device 4 can be downsized.

As shown in FIG. 4, the screw apex 14 of the supply screw 8 that is the uppermost part of the developer supply member is disposed below the rotation center 15 of the developing roller 5. In the developing device 4, an angle θ1 between a straight line connecting the rotation center 15 of the developing roller 5 and the screw apex 14 and a horizontal straight line passing through the rotation center 15 is set to 30 [°]. This angle θ1 depends on the diameter of the supply screw 8, but is preferably 10 [°] to 40 [°] in view of the layout because the developing device 4 is downsized.
The developer is supplied to the developing roller 5 by the magnetic pole provided in the developing roller 5 attracting the magnetic carrier in the developer. As described above, by arranging the screw apex 14 so as to be below the rotation center 15 of the developing roller 5, the self-weight of the developer does not affect the supply amount of the developer to the developing roller 5, and the magnetic force The size contributes to the developer supply amount. Accordingly, since the developer is reliably supplied from the upper part of the developer conveyed in the supply conveyance path 9, the developing roller 5 can be used even if the bulk of the developer in the supply conveyance path 9 is not uniform in the conveyance direction of the supply screw 8. An appropriate amount of developer can be supplied.

Next, the magnetic pole arrangement of the developing roller 5 will be described.
FIG. 5 is a schematic explanatory diagram of the magnetic pole arrangement of the developing roller 5. In the developing region facing the photoreceptor 1, a developing downstream end side S pole 218 is disposed at the most downstream position in the surface movement direction of the developing roller 5, and a developer pumping S pole 219 is disposed at a position facing the supply screw 8. is doing. A region between the development downstream end side S pole 218 and the developer pumping S pole 219 has a magnetic pole arrangement without a magnetic pole.
The area without the magnetic pole is a developer collection area for collecting the developed developer, and the collection conveyance path 7 is provided at a position directly below the developing roller 5 facing the developer collection area. The developed developer that has passed through the development area is not affected by the magnetic force when conveyed to the developer collection area, and falls to the collection conveyance path 7 due to the centrifugal force generated by the rotation of the developing roller 5 and the weight of the developer. Is collected and conveyed as a collected developer.
When trying to collect the developed developer above the developing roller 5, even if the developer is not affected by the magnetic force, it remains on the surface of the developing roller due to its own weight, and is transported downstream along with the surface movement. Of the developed developer may occur. When the developed developer rotates, the developer whose toner density has changed is transported to the supply position and used again for development, and the toner density on the developing roller decreases or becomes non-uniform. There is a risk of
In the developing device 4, the surface below the developing roller 5 is used as a developer recovery region, and a recovery conveyance path 7 is provided below the developer recovery region. As a result, since the developer's own weight contributes to the recovery, the developer can be recovered more reliably, the developed developer can be prevented from being accompanied, and the toner density can be made constant. it can.

Further, the developing device 4 has a configuration in which the collection conveyance path 7 and the collection 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 side. 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 the conventional three-axis developing device, the developed developer is not separated from the developing sleeve due to the influence of the magnetic pole on the pumping side, and is rotated as it is and is held on the developing roller 5. was there. When the developed developer is still carried on the developing roller 5, there is a problem that a stable image cannot be obtained with a low toner density developer or a non-uniform density developer.
In the developing device 4, the interval between the development downstream end side S pole 218 and the pumping S pole 219 is set wide, and the developed developer is not easily affected by the pumping S pole 219, thus preventing the above-described problems. Great effect.
In the system in which the supply and recovery are arranged vertically, the developer after development is brought to the horizontal direction, so a conveying magnetic pole is required, and the gap between the pumping magnetic pole and the upstream magnetic pole is narrow. For this reason, troubles due to rotation are likely to occur. In the developing roller 5 of the developing device 4 of the printer unit 100, the angle θ2 between the pumping S pole 219 that is the pumping magnetic pole and the developing downstream end side S pole 218 that is the upstream magnetic pole is 113 [°]. .

In the conventional three-axis developing device, the angle between the pumping 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 [°] relative to the conventional developing roller. The angle is a wider interval (increased by about 25 [%]). If the distance 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, so that the spinning phenomenon does not easily occur. In the developing device 4, the angle θ2 between the pumping S pole 219 and the development downstream end side S pole 218 is set to 113 [°]. The value of θ2 is not limited to this, and if the angle θ2 is larger than that of the conventional developing device, for example, the angle θ2 is 100 [°] or more, it is possible to more reliably prevent the toner density defect due to the accompanying rotation. .
In the developing device 4, since the developing magnetic poles are three, the most downstream developing magnetic pole also serves as the conveying magnetic pole, so that it is considered that a dedicated conveying magnetic pole is unnecessary.

The developer supplied to the surface of the developing roller 5 has an optimum layer thickness for development by regulating the layer thickness by the developing doctor 16. Since it is necessary to be regulated by the developing doctor 16 in order to obtain an optimum layer thickness for development, the amount of developer supplied to the developing roller 5 is larger than the amount of developer passing through the developing doctor 16. is there. The developer supplied to the developing roller 5 is more than the developer passing through the developing doctor 16, and the developer is always regulated in the developing doctor 16. As a result, the regulated developer regulated in the doctor region 17 on the upstream side of the developing doctor 16 is accumulated as the operation is continued.
The regulated developer is supplied to the developing roller 5 later, is lifted by the developer that reaches the doctor region 17, falls to the developing roller 5, and is supplied to the doctor region 17. In this way, the behavior of convection in the doctor region 17 is shown.
In the developing device 4, the regulated developer collecting member that detours and recirculates to the supply conveyance path 9 when the regulated developer stays in the doctor region 17 and exceeds a certain amount so as not to cause circulation convection. 18 is installed. Further, the position of the regulated developer collecting member 18 is set so that the developer that flows back is not affected by the magnetic force of the developing roller 5 and stays.

The developing doctor 16 is firmly fixed to a heat radiating member 19 fixed to the upper casing 13. The developing doctor 16 transmits heat from the developer to the heat radiating member 19, and fins 120 are formed inside the heat radiating member to radiate heat by the air flow during operation, so as to reduce the temperature rise of the developer. Yes. Further, the heat radiating member 19 includes a guide portion 121 that is used as a guide when the developing device or the image forming unit 111 is attached to or detached from the printer portion 100.
Further, the lower casing 12 is provided with heat radiating fins 128 so that the temperature rise of the entire developing device 4 can be reduced and cooled by cooling air sent from the front part of the printer unit 100 to the rear part.

A developer catching roller 122 is installed on the downstream side of the developing roller 5 and catches the developer attached to the photoreceptor 1 and the developer dropped from the developing roller 5. Then, it is rotated reversely to the developing roller 5 and returned to the developing roller 5 or is collected in the collecting and conveying path 7 by the scraper 123.
The upper casing 13 above the stirring screw 11 and the stirring conveyance path 10 is provided with an opening 124 so as to hold the developer cartridge 125. At the time of product delivery or when the developer is replaced, the developer cartridge 125 is set and the developer cartridge seal portion 126 is peeled off, so that the developer is refilled into the developing device 4 from the opening 124. The Since the developer can be replenished as a cartridge, it can be easily replaced.

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 6 shows a state in which the upper casing 13 of the developing device 4 is removed, and is a perspective view of each conveying path constituted by the lower casing 12 and each screw as viewed from the photosensitive member 1 side.
The lower casing 12 is provided with a collection screw 6, a supply screw 8, and a stirring screw 11 from the front side in the figure, and each conveyance path is formed so as to divide a conveyance area by each screw. However, the supply conveyance path 9 and the collection conveyance path 7 are held by the upper casing 13 and are separated by a partition plate 134 that engages with the lower casing 12. The developer is conveyed in the directions of arrows 135 and 136 in the recovery screw 6 and the supply screw 8, and in the direction of the arrow 137 in the reverse direction in the stirring screw 11. At this time, the arrows 135 and 136 of the recovery screw 6 and the supply screw 8 are transport directions from the front side to the back side in FIG. 4, while the arrow 137 of the stirring screw 11 is a transport direction from the back side to the front side.

  Here, the configuration of the screw will be described with the stirring screw 11 as an example. The agitating screw 11 is for agitating and conveying blades 138 which are wings for agitating and conveying the developer toward the agitating rotation shaft 170 in the developer conveying direction, and for agitating lateral transfer for transferring the developer to the adjacent supply screw 8 side. A paddle 139 is attached. 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 stirring reverse blade section 140 in the winding direction opposite to that of 138 is attached. The recovery screw 6 and the supply screw 8 have the same configuration as the stirring screw 11.

On the downstream side in the developer conveyance direction in the stirring conveyance path 10, an opening is provided in the partition wall 133, the downstream end in the developer conveyance direction of the stirring conveyance path 10 and the upstream in the developer conveyance direction in the supply conveyance path 9. The end is in communication. The developer transported to the downstream end portion in the transport direction of the stirring transport path 10 is transported to the upstream end portion in the transport direction of the supply transport path 9 on the supply screw 8 side by the stirring lateral transfer paddle 139 of the stirring screw 11. .
On the other hand, openings are provided in the partition wall 133 and the partition plate 134 on the opposite side, and the downstream ends of the recovery transport path 7 and the supply transport path 9 in the developer transport direction and the upstream of the stirring transport path 10 in the developer transport direction. The side end portion communicates with each other to form a communication portion 150. The collected developer collected in the collection conveyance path 7 is transferred 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 surplus developer transported to the downstream end in the transport direction of the supply transport path 9 without being used for development and the recovered developer transferred from the recovery transport path 7 are mixed in the supply transport path 9. The surplus developer and the collected developer are transferred to the stirring conveyance path 10 on the stirring screw 11 side by the supply lateral transfer paddle 142 of the supply screw 8.

Here, development is performed at a position where the three developer conveyance paths of the collection conveyance path 7 and the supply conveyance path 9 and the downstream end portion in the developer conveyance direction of the agitation conveyance path 10 communicate with each other. The horizontal transfer of the agent will be described.
FIG. 7 is a schematic cross-sectional view of a lateral transfer unit in which three developer conveyance paths are in communication.
Openings are provided in the partition wall 133 and the partition plate 134 of the developer delivery section. Since it is laterally transferred by the rotating paddles of the recovery conveying path 7, the supply conveying path 9, and the stirring conveying path 10, if it is simply a plane where the bottoms are connected, a dead point is generated for the rotating paddle. It may not be delivered successfully. Therefore, a collection / supply convex portion 131 and a supply / stirring convex portion 132 are provided between the conveyance paths, respectively, so that the developer over the respective convex portions does not flow backward.
Further, the collection lateral transfer paddle 141 that needs to be delivered relatively upward is configured such that the developer push-out surface 144 that pushes out the developer is motored at an angle and pushed outward. Further, 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 developer conveyance paths draws in the collected developer that has been fed in and pushes it out to the stirring conveyance path. It is configured to be almost flat.

  The lower casing 12 below the stirring screw 11 is provided with a toner concentration sensor 127. In accordance with an output signal from the toner concentration sensor 127, toner is replenished from above to a transfer portion position 143 between the supply screw 8 and the stirring screw 11 by a toner replenishing means (not shown) including a control system. Since the feeding position 143 is a position where the feed lateral transfer paddle 142 for laterally transporting the developer scoops up the developer, the stirring action is large. In this way, by supplying toner to a place where the stirring action is large, the supplied toner is stirred and mixed with the developer in a short time. The location for replenishing the toner is not limited to between the supply screw 8 and the stirring screw 11, but may be a transfer portion between the recovery screw 6 and the supply screw 8.

As described above, in the developing device 4, the collection screw 6, the supply screw 8, the stirring screw 11, the collection conveyance path 7, the supply conveyance path 9, and the stirring conveyance path 10 are disposed laterally below the developing roller 5 and developed. The agent is circulating. The developer is transported in the lateral direction between the developer transport paths, and there is no need to push the developer upward in the developer circulation. As a result, when the developer is circulated and conveyed in the apparatus, stress on the developer can be reduced, and the life of the developer can be extended.
Further, three conveyance paths are communicated with each other at 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, as a configuration for transferring the developer to the adjacent developer transport path, only the transport force in the direction parallel to the axial direction is applied to the developer even in the vicinity of the downstream end in the transport direction from the opening so as to extrude. Some transfer to the next transport path. As described above, in the configuration in which the conveying force only in the axial direction is applied to the developer, pressure is applied to the developer in order to extrude it from the opening, and the developer is excessively stressed. May decrease. On the other hand, the developing device 4 is provided with a paddle-shaped member that applies a lateral conveying force at the downstream end portion in the conveying direction of the developer conveying path, and can be transported without applying pressure to the developer as in an extruding configuration. The stress applied to the developer can be reduced.

FIG. 8 is a perspective view of the upper casing 13 with the developing roller 5 of the developing device 4 attached.
As shown in the figure, a toner replenishing port 130 for replenishing toner from a toner replenishing means (not shown) is provided outside the developing area in the axial direction. The toner from the toner replenishing means (not shown) is replenished to the transfer portion position 143 shown in FIG.
As shown in FIG. 8, a roller rotation shaft 5 a of the developing roller 5 extends above the transfer portion between the collection conveyance path 7 and the supply conveyance path 9. Since the driving unit for the roller rotation shaft 5 a is provided, the developing device 4 cannot provide the toner supply port 130 above the transfer unit between the collection conveyance path 7 and the supply conveyance path 9. In this regard, if there is no restriction by the driving unit of the developing roller 5, a toner replenishing port 130 may be provided above the transfer unit between the collection conveyance path 7 and the supply conveyance path 9. By replenishing the toner between the recovery conveyance path 7 and the supply conveyance path 9, the toner can be supplied to the recovery developer whose toner concentration is lowered, so that stirring can be performed more efficiently. .

With reference to FIG. 4 described above, the agitation conveyance path 10 and the supply conveyance path 9 are partitioned, and the partition wall 133 formed in the lower casing 12 is downstream in the developer conveyance direction after the center of the development range of the supply screw 8. On the side, a developer bulk adjusting opening 145 is provided.
When the developing roller 5 is stopped or when the developing doctor 16 is set, the developer used for development decreases, the developer stays, and the volume of the developer in the supply conveyance path 9 is larger than the desired height. Can be expensive. When the bulk of the developer is higher than the desired height, the conveyance status by the supply screw 8 is different, and the conveyance efficiency may be extremely lowered, normal developer circulation may not be maintained, and partial developer deterioration may occur. There is.
When the volume of the developer exceeds a desired height after the central portion of the development range, the developer overflows from the developer volume adjusting opening 145 to the stirring conveyance path 10, and the developer height in the supply conveyance path 9 is increased. Is controlling.

The developer in the supply conveyance path 9 is a developer that is not used for development, and its toner density is in a state suitable for development. There is no non-uniform density.
The developer bulk adjusting opening 145 may be provided at a plurality of locations as shown in FIG. 4 or may be provided as a single opening from the center of the developing range.
By providing an opening in a partition member at a position higher than a predetermined height, excess developer in the supply conveyance path is overflowed and supplied to the agitation conveyance path. This is possible because it is arranged at the same height. For example, when the supply conveyance path and the agitation conveyance path are arranged side by side, if the agitation conveyance path is above, even if the developer in the supply conveyance path overflows, it cannot be supplied to the agitation conveyance path . When the supply conveyance path is on the upper side, a dropping path for dropping the overflowed developer to the lower agitation conveyance path is required, and the configuration of the developing device becomes complicated. As in this case, when the supply conveyance path and the agitation conveyance path are arranged side by side at substantially the same height, an excess developer in the supply conveyance path can be removed with a simple configuration in which an opening is provided at a certain height of the partition member. It can be supplied to the stirring conveyance path.

Next, the relationship of the developer conveyance amount between the developer conveyance paths will be described. FIG. 9 is a schematic diagram illustrating the developer conveyance amount (per unit time) and the flow in each developer conveyance path. The horizontal direction in the drawing represents the depth direction of the printer unit 100, that is, the developer transport direction in the developer transport path in the developing device 4.
The developer conveyance state in the agitation conveyance path 10 is 146 (hereinafter referred to as agitation conveyance amount 146), the developer conveyance state in the supply conveyance path 9 is 147 (hereinafter referred to as supply conveyance amount 147), and the recovery conveyance path 7 development. This is expressed as an agent transport state 148 (hereinafter referred to as a recovered transport amount 148). The amount of conveyance at each position in the depth direction at this time is indicated by the size of the width in the drawing. The developer transport direction is indicated by arrows 135, 136 and 137.

  The developer in the agitation conveyance path 10 is transferred to the supply conveyance path 9 on the downstream side in the conveyance direction (arrow 152). In the developing range, the developer in the supply conveyance path 9 is sequentially transferred to the collection conveyance path 7 via the developing roller 5 (arrow 153). Therefore, in the developing range, the developer in the supply conveyance path 9 decreases sequentially, and the developer in the recovery conveyance path 7 increases on the contrary by the same amount. Further, the developer in the recovery conveyance path 7 is transferred to the supply conveyance path 9 downstream in the conveyance direction (arrow 154), and further transferred to the stirring conveyance path 10 together with the developer in the supply conveyance path 9 (arrow 155). It will be. Further, as described with reference to FIG. 6, this is performed in the process of transferring in the lateral direction by the communication portion 150 from the downstream end in the transport direction of the collection transport path 7 to the upstream end in the transport direction of the stirring transport path 10. It is done in the range.

In order for the developer to circulate smoothly, the conveyance capacity of each conveyance path and each screw is as follows. The output conveyance amount of the collection screw 6 is f and the output conveyance amount of the supply screw 8 is e. When the amount is E, it is necessary to satisfy E = e + f.
Further, the output conveyance amount of the agitating and conveying screw = the input conveying amount of the supplying and conveying screw = the input conveying amount of the agitating and conveying screw = E.
When considering the 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 filling degree (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 is inclined depending on the stirring direction, and the conveyance efficiency varies greatly depending on the blade lead, material, thickness, and number of strips, so it must be set to a certain amount of margin. There is. The error is set to ± 10 [%], a certain overflow amount of 10 [%] is set, and e> () so that it is 20 [%] or more 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 developed developer that has been developed decreases, so that the sensitivity of the toner concentration sensor 127 becomes insensitive to changes in the toner concentration, making it difficult to control the toner concentration.

The developing device 4 as an example was designed so as to satisfy the following expression (2).
(E / 3)>e> (E / 4) (2)
This is ideal from the standpoint of developer transport efficiency, and e → 0 of the surplus developer is ideal. However, a certain amount of surplus is required in order to reliably supply a certain amount of developer onto the developing roller. On the other hand, the sensitivity of the toner density sensor generally located on the upstream side of the agitating / conveying path is greatly influenced by the ratio of the excess developer and the collected developer. That is, when the ratio of the collected developer is large, the sensitivity is large, while the variation is large, and when the ratio is small, the sensitivity is small. Further, when the ratio of the collected developer is large, the toner replenishment is performed and the toner density is made uniform, so that it depends on the stirring performance. Therefore, by increasing the ratio of the excess developer, the recovered developer is added with the replenished toner and the toner from the excess developer, and it becomes possible to suppress large toner density unevenness.
In view of the above, the transport amount is set in the range of the formula (2) from the viewpoint of securing developer transport efficiency (developing developer low stress) and controlling toner density (sensitivity of toner density sensor and uniform toner density).

  In the developing device as described above, since the developer that has passed through the developing region and consumed the toner does not return to the supply conveyance path, the axial direction of the developing roller as compared with the biaxial developing device as shown in FIG. Toner density unevenness is less likely to occur. However, even in such a developing device, the toner at a certain time in the developing unit at a timing with the highest toner concentration at the most downstream portion and a timing with the lowest toner concentration at any location in the developing device due to toner consumption / replenishment. A difference in density (hereinafter referred to as toner density deviation) occurs. If the toner density deviation is not sufficiently contracted before reaching the developing roller, a slight change in toner density appears on the developing roller. In particular, in the case of an apparatus with a high process linear velocity, the amount of toner replenishment per hour and the amount of toner consumption increase, so that the amplitude of density fluctuation increases.

Next, with respect to the agitation transport path 10 that is the developer agitation transport path, the agitation part agent speed U ₁ [m / s] that is the transport speed of the developer moving in the agitation transport path 10 and the length of the agitation transport path 10 The stirring length L [m], the replenishment cycle T [s] that is the cycle in which the toner is replenished, and the diffusion coefficient D [m ² / s] will be described.
FIG. 10 is an explanatory diagram of the relationship between the stirring member agent speed U ₁ [m / s] and the diffusion effect.
Toner replenishment cycle of the replenishment (or consumption) T [s], when stirred length L [m] is common, in the case when the stirring unit dosage rate U ₁ is fast and slow, travel time from upstream to downstream t ' , And the wavelength λ of the toner concentration deviation formed on the screw are different.
When U ₁ = U _H [m / s] when the stirrer agent speed U ₁ is high, the movement time t ′ = t _H = L / U _{H and} the wavelength λ = λ _H = U _{H of the} toner density deviation.・ T On the other hand, when U ₁ = _UL [m / s] ( _UL <U _H ) when the stirrer agent speed U ₁ is high, the moving time t ′ = t _L = L / _UL , and the toner density deviation. Λ = λ _L = U _L · T.

The wave of toner density deviation on this screw is defined as a sin wave.
Wt (x) = A (t) sin (2π · x / λ) (3)
And approximate with
Diffusion equation ^{∂W / ∂t = D (∂ 2} W / ∂x 2) ··· (4)
(Here, D is called the diffusion coefficient and represents the diffusion capacity of the screw.)
Substituting into, the time variation of amplitude A is
A (t) = A ₀ exp {− (2π / λ) ² D · t} (5)
And can be calculated.
Therefore, the amplitude A (t ′) of the toner density deviation after moving from the most upstream portion to the most downstream portion of the stirring conveyance path 10 is
A (t ′) = A ₀ exp (− (2π / λ) ² · D · t ′)
= A ₀ exp {− (2π / T) ² · D · L · 1 / U ³ }] (6)
And can be calculated.
That is, it can be seen that the attenuation of the amplitude of the toner density deviation greatly affects the stirring member agent speed U ₁ by the stirring screw 11. From this equation, when the advection speed of the stirring screw is slower, U = U _L [m / s], the toner density amplitude A0 on the most downstream side from the toner density amplitude A0 on the most downstream side of the stirring conveyance path 10 ( The attenuation width obtained by subtracting t ′) can be increased. Therefore, it can be seen that the slower conveyance speed is very advantageous for increasing the diffusion effect.
In order to suppress toner density unevenness on the developing roller 5, it is necessary to sufficiently diffuse the toner density deviation in the developing device caused by toner replenishment and consumption. Decreasing the agent speed in the stirring section leads to the following two effects.
・ Movement time (diffusion time) from the upstream to the downstream of the stirring screw becomes longer.
・ The wavelength of the toner density deviation on the stirring screw becomes small.
Due to these two effects, the diffusion effect on the stirring screw (attenuation width of the toner density deviation during the movement from the stirring screw upstream to the stirring screw downstream) can be increased.

It is considered that the diffusion effect can be improved by lowering the supply part agent speed U ₂ and the recovery part agent speed U _{3, which} are developer transport speeds in the supply transport path 9 and the recovery transport path 7. However, slowing the supply unit dosage rate U ₂ and the recovery unit dosage rate U ₃ leads to the following problems.
Slower feed unit dosage rate U _2, the time in which the developer to the most downstream portion is conveyed becomes longer from the most upstream portion of the supply conveyance path 9. Since the amount of developer to be supplied to the developing roller 5 per unit time is constant, if the time from the most upstream portion to the most downstream portion of the supply conveyance path 9 becomes longer, more developer can be taken by the developing roller 5 accordingly. As a result, there is not much developer remaining around the most downstream portion. When the developer does not remain so much at the most downstream portion, that is, when the developer is exhausted, the developer on the developing roller 5 becomes insufficient and the image density becomes insufficient.
In addition, when slow recovery unit dosage rate U _3, the time in which the developer to the most downstream portion is conveyed becomes longer from the most upstream portion of the collection transport path 7. The amount of developer collected from the developing roller 5 per unit time is somewhat constant depending on the amount of toner consumed, but is substantially constant. Therefore, when the time from the most upstream portion to the most downstream portion of the collection conveyance path 7 becomes long, Accordingly, the amount of developer collected from the developing roller 5 and in the collection conveyance path 7 increases. If the amount of the developer in the collection conveyance path 7 becomes too large, the developer may overflow in the downstream portion of the collection conveyance path 7 beyond the capacity of the collection conveyance path 7.
Therefore, it is preferable to slow the only stirring unit conveying rate U _1.
FIG. 11 shows the time variation of the toner concentration at the central portion of the developing roller when U ₁ = U ₂ and when U ₁ <U ₂ with respect to the agitation unit conveyance speed U ₁ and the supply unit agent speed U ₂ . A graph is shown. As shown in FIG. 11, it can be seen that when U ₁ <U ₂ , the width of the temporal fluctuation of the toner density is smaller.

Next, a method for measuring the developer conveyance speed in the agitation conveyance path 10 will be described.
FIG. 12 is a schematic diagram of a developer speed detecting means using a magnetic permeability sensor. It is assumed that two magnetic permeability sensors are attached to the points A and B below the stirring screw 11 in the stirring conveyance path 10. Point A is the toner replenishment position, and the developer is conveyed in the direction of arrow β in the figure. The X-TC graphs shown above the point A and below the point B show the change in toner density at each point. It can be seen from this graph that toner is replenished at point A and diffused at point B.
A peak is observed with the movement of the replenishing toner. By measuring the time difference between the peaks A and B, the distance of A to B is divided by the time difference to thereby adjust the moving speed of the developer in the stirring conveyance path 10. Can be measured.
The moving speed of the developer in the supply conveyance path 9 can be measured with the same configuration.
As the magnetic permeability sensor, the toner concentration sensor 127 used for toner replenishment control may be shared, but a magnetic permeability sensor for detecting the toner concentration distribution may be provided separately from the toner concentration sensor 127. .
In FIG. 12, the point A is described as the toner replenishment position. However, the new toner immediately after replenishment is above the developer, and if the agitation is not performed, the transparent toner provided at the bottom of the agitation transport path 10 is provided. It is difficult to detect a change in toner density with a magnetic sensor. Therefore, as the position where the reply rate sensor is installed, the point A is the central part of the agitation transport path 10 and the point B is the downstream part of the agitation transport path 10, so that the change in toner density is observed at both the points A and B. It becomes possible to detect.

Further, the value of the diffusion coefficient D of the stirring conveyance path 10 can be obtained by the same measurement. The toner concentration distribution in the upstream portion of the stirring screw is as shown by an X-TC graph shown in FIG. Further, when it comes downstream, it spreads in a normal distribution as shown by an X-TC graph shown in FIG. These toner density distributions are measured, and this measurement result is compared with a calculation result by a one-dimensional diffusion equation expressed by the above equation (4) to obtain a diffusion coefficient D.
In comparing the concentration distribution profile by measurement with the concentration distribution profile calculated by equation (4), the measurement result and the calculation result coincide with each other in terms of the concentration peak value matching condition and the full width at half maximum for the concentration peak value. Using these as error bars, the diffusion coefficient is obtained.

[Experiment 1]
Next, Experiment 1 will be described in which the same screw was used and the developer conveyance speed was varied to compare the diffusibility.
FIG. 13 is an explanatory diagram of Experiment 1 in which the diffusibility was compared. FIG. 13A is an explanatory diagram of a screw with a higher conveying speed, and FIG. 13B is an explanatory diagram of a screw with a lower conveying speed.
Each value of the screw in FIG. 13 is screw length: 337 [mm], screw diameter: 23.5 [mm], shaft diameter: 10 [mm], and pitch length: 20 [mm].
The conditions of the experiment in which the conveyance speed shown in FIG. . The screw 324 is rotated at [rpm], and at the same time as the developer starts to flow in the direction of the arrow in the figure, the output voltage of the T sensor is measured. After measuring for 2 minutes, finish the measurement and stop the screw rotation.
The diffusion coefficient at this time was determined to be D = 0.007 [m ² / s].

The following points were taken into consideration as the conditions for the experiment in which the conveyance speed was slow. That is, if the developer conveyance speed of the stirring unit of the developing device is decreased, the wavelength of the toner density distribution is shortened. Therefore, in this experiment, a short wavelength distribution was created in advance, and a situation where periodic toner replenishment was made was simulated.
Then, as shown in FIG. 13B, a carrier 125 [g] is put on the T sensor side of the screw B, and a developer having a toner concentration of 5 [%] is put on the opposite side, and the carrier and development are similarly performed on the screw A side. Add 125 [g] of agent and flatten. The screw is rotated at 162 [rpm], and at the same time as the developer starts to flow in the direction of the arrow in the figure, the output voltage of the T sensor is measured. After measuring for 2 minutes, finish the measurement and stop the screw rotation.
Further, when the diffusion coefficient at this time was determined, it was D = 0.00015 [m ² / s].
FIG. 14 is a graph showing the results of Experiment 1.
FIG. 14 shows that when the same screw is used, the diffusibility when stirring at the same distance is better when the screw rotation speed is slower, that is, when the developer transport speed is slower. In addition, although the stirring coefficient becomes smaller by slowing the rotation speed, as shown in the equation (6), D is the first power, but U is effective by the third power. Diffusivity is improved.

Next, the stirrer speed U ₁ [m / s], the stirring length L [m], the replenishment cycle T [s], and the diffusion coefficient D [m ² / s], which enable stable image formation, are performed. The conditions will be described.
The toner density deviation at the most upstream portion of the agitation transport path 10 is 20% or less even when an extreme value is considered. The toner density deviation at the most downstream portion of the developer agitating and conveying path is 1.0 [%] or less by setting the toner density deviation to 1/20 during the agitating and conveying in the agitating and conveying path 10. It can be.
Here, the equation (5), since the 'A in (t' time t to reach to the most downstream of the stirring conveyance path 10) may if less 1/20 of _{A 0,}
From equation (5)
A (t ′) = A ₀ exp {− (2π / λ) ² D · t}
A (t ′) = A ₀ exp (− (2π / T) ² D · L · 1 / U ₁ ³ )
Here, from A (t ′) / A ₀ ≦ 20,
exp (− (2π / T) ² D · L · 1 / U ³ ) ≦ 1/20
(2π / T) ² D · L · 1 / U ³ ≧ ln20
L · D / (T ² · U ³ ) ≧ ln20 / (4π ² )
From ln20 / (4π ² ) ≈0.075
L · D / (T ² · U ³ ) ≧ 0.075 (1)
By setting the stirring agent speed U ₁ [m / s], the stirring length L [m], the replenishment cycle T [s], and the diffusion coefficient D [m ² / s] to satisfy the formula (1). The amplitude of the toner density fluctuation can be attenuated by 1/20 or more from the most upstream portion to the most downstream portion of the agitation transport path 10. Therefore, even if there is an amplitude of the toner concentration fluctuation of about 20 [% · wt] in the extreme upstream portion of the agitating / conveying path 10, it is 1 [% · wt] in the most downstream portion of the agitating / conveying path 10. Become. Further, since it is diffused by the supply screw sleeve, it is considered that the toner density fluctuation on the developing roller 5 can be cleared from the target 0.5 [% · wt].
By suppressing the toner density fluctuation on the developing roller 5 as a developer carrying member, it is possible to form an image with a stable image density.

[Example 1]
Next, as Example 1, conditions of the agitation transport path 10 that satisfy the relationship of the above-described formula (1) are given.
First, the expression (1), is modified for _{U 1,} as follows in equation (7).
Stirring screw length: L = 320 [mm], replenishment interval: T = 1.0 [s], diffusion coefficient: D = 0.0001 [m ² / s] When using a screw, stirring that satisfies formula (7) The part velocity is U ₁ = 75 [mm / s].
Then, the stirring unit dosage rate _{U 1} To 75 [mm / s], for example stirring screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], the pitch length: 30 What is necessary is just to design with [mm] and rotation speed 300 [rpm].
It can be approximated by a developer speed U [mm / s] ≈1 / 2 · 1/60 · (pitch length [mm]) · (rotation speed [rpm]) by a screw.

[Experiment 2]
Next, a simulation was performed to compare changes in toner density between a screw satisfying the expression (7) and a screw not satisfying the condition.
The simulation conditions were a screw diffusion coefficient: D = 0.00025 [m ² / s], a screw length: L = 0.35 [m], and a toner supply period T = 2 [s].
In this condition, the stirring conveyance speed U ₁ in order to satisfy the above equation (7), should be in the range of the following equation (8).
U ₁ ≦ 0.0663 [m / s] (8)
Here, without changing the conditions other than U ₁ , the stirring and conveying speed U ₁ was changed to 60 [mm / s] within the range of the equation (8) and 120 [mm / s] outside the range of the equation (8). And changed.
The experimental results at this time are shown in FIG. From FIG. 15, by setting the stirring and conveying speed U ₁ = 60 [mm / s] within the range of the equation (8), the toner on the developing roller is compared with the stirring and conveying speed U ₁ = 120 [mm / s]. It can be seen that the density deviation can be greatly suppressed.

[Example 2]
Next, as Example 2, stirring is performed so that the relationship of U ₂ > U ₁ and U ₃ > U ₁ is established with respect to the stirring part agent speed U ₁ , the supply part agent speed U ₂ , and the recovery part agent speed U _3. The pitch width of the screw 11 was made shorter than the pitch width of the supply screw 8 and the recovery screw 6.
・ Agitating screw Screw length: 320 [mm], screw diameter: 30 [mm], shaft diameter: 5 [mm], pitch width: 20 [mm], rotation speed: 300 [rpm]
Supply screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 30 [mm], rotation speed: 300 [rpm]
・ Recovered screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 30 [mm], rotation speed: 300 [rpm]

In order to perform sufficient diffusion stirring conveyance path 10, it is necessary to slow the stirring unit dosage rate U _1.
Therefore, by reducing the pitch width of the stirring screw 11 to be shorter than the pitch width of the supply screw 8 as in the above-described screw, the rotational speed of the stirring screw 11 is not decreased (in some cases, the rotational speed is increased). Also, the stirring member agent speed U ₁ can be made slower than the supply member agent speed U ₂ . As a result, the effect of increasing the diffusion time and reducing the wavelength of the toner density deviation can be added without reducing the diffusion capability depending on the screw rotation speed (in some cases, increasing the diffusion capability) A dramatic improvement is expected.

[Example 3]
In Example 2, the pitch width of the entire stirring screw is set short. Hereinafter, as Example 3, a screw in which the pitch width of the central portion of the stirring screw 11 is shorter than the pitch width of the supply screw 8 and the recovery screw 6 will be described.
・ Agitating screw Screw length: 320 [mm], screw diameter: 30 [mm], shaft diameter: 5 [mm], pitch width (within 200 [mm] in the central part): 20 [mm], pitch width (in the central part) Other than 200 [mm]): Number of revolutions: 300 [rpm]
Supply screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 30 [mm], rotation speed: 300 [rpm]
・ Recovered screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 30 [mm], rotation speed: 300 [rpm]

  By reducing the speed of the developer only in a part of the region of the agitation transport path 10, the diffusion time at that part is increased, the wavelength of the toner density deviation is reduced, and the diffusion effect is increased. Further, by partially changing the developer speed, the height of the developer surface is higher where the developer speed is lower than where the developer speed is higher. Due to the change in the height of the agent surface, the downstream side is lifted with respect to the conveyance direction, and the developer falls to the upstream side where the height of the agent is low due to the difference in the height of the agent. And since it goes downstream again, a partial convection arises. Partial convection will increase the diffusion capacity.

[Example 4]
Next, as Example 4, the stirring part agent speed U ₁ , the supply part agent speed U ₂ , and the recovery part agent speed U ₃ are stirred so that the relations U ₂ > U ₁ and U ₃ > U ₁ are satisfied. The number of rotations of the screw was set to be smaller than the number of rotations of the supply screw and the recovery screw.
・ Agitating screw Screw length: 320 [mm], screw diameter: 30 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 200 [rpm]
Supply screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 300 [rpm]
・ Recovered screw Screw length: 320 [mm], screw diameter: 25 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 300 [rpm]

It is made smaller than the speed of the stirring screw 11 rotation speed of the supply screw 8 and the recovery screw 6, than the supply unit dosage rate U ₂ and the recovery unit dosage rate U _3, reducing the stirring unit dosage rate U ₁ Can do. Further, the design of the screw can be unified between the supply screw 8 and the stirring screw 11, and the production cost can be reduced. Further, by lowering the rotational speed, the stress on the bearing and the agent of the stirring screw 11 can be reduced, and the life of the bearing / agent can be extended.

Since the agent speed is substantially proportional to the pitch length and the number of rotations, the supply agent speed: stirring agent speed = 3: 2 under the conditions of Example 2, Example 3, and Example 4. Since the developer weight in each developer conveyance path is inversely proportional to the speed, the supply part upstream agent weight: stirring part agent weight = 1/3: 1/2. Thus, although the diffusion effect is improved by slowing the agent speed of the stirring screw, there arises a problem that a large amount of agent is accumulated in the stirring portion. Therefore, in order to make the agent screw embedment ratio equal in the supply section upstream and the stirring section, the stirring screw diameter should be larger than the supply screw diameter as shown in the following equation (9).
By increasing the diameter of the agitating screw 11, the developer burying rate of the developer in the agitating and conveying path 10 can be suppressed within an allowable range (less than about 0.9). Therefore, the diffusion effect is improved. Further, by making a difference from the diameter of the supply screw 8, it is possible to use the space efficiently without creating a useless space in the supply conveyance path 9 with a small amount of developer.

[Example 5]
Next, a description will be given of a fifth embodiment in which a stirring fin having a plane composed of sides of a radial direction of the blade portion and an axial direction of the stirring screw 11 is attached to the stirring screw 11.
FIG. 16A is an explanatory diagram of the stirring screw 11 according to the fifth embodiment. As shown in FIG. 16A, the stirring fin 113 is provided on the shaft portion of the stirring screw 11. In addition, the dimension of the other stirring screw 11 and the dimension of the supply screw 8 and the collection | recovery screw 6 are as follows.
Screw length: 320 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 200 [rpm]
As shown in FIG. 16 (a), the flow of the developer is inhibited by mounting the stirring fins 113, is slow stirring unit dosage rate U _1. In addition, by attaching the fins, the diffusion capability with respect to the toner density deviation can be improved compared to before the attachment, and the replenishment toner can be prevented from slipping up.
Moreover, even if the fins were partially attached as shown in FIG. 16B, a sufficient effect was obtained.

In addition, in order to perform sufficient diffusion in the stirring unit, it is necessary to slow down the agent speed in the stirring unit as in Examples 2, 3, and 4. However, reducing the rotational speed of the stirring screw 11 to reduce the agent speed lowers the diffusing capacity, and thus may cancel the improvement of the diffusing effect.
Accordingly, by attaching the stirring fins 113 to the stirring screw 11, the diffusion capacity is improved. At the same time, the attachment of the fin will lead to the effect of reducing the stirring unit dosage rate U _1. Without decreasing the diffusion capacity (in some cases, increasing the diffusion capacity), it is possible to add the action of increasing the diffusion time and reducing the wavelength of the toner density deviation, and a dramatic improvement in the diffusion effect is expected. .

[Example 6]
In Example 5, the stirring fins 113 were provided in order to increase the diffusibility in the stirring conveyance path 10. Next, as another configuration for improving the diffusibility, a sixth embodiment in which a magnet 112 is attached as a magnetic field generating means to the side surface of the case of the stirring and conveying path 10 will be described.
FIG. 17 is an explanatory diagram of the developing device 4 according to the sixth embodiment. As shown in FIG. 17, a magnet 112 is provided on the side surface of the case of the stirring and conveying path 10. In addition, the dimension of the stirring screw 11, the supply screw 8, and the collection | recovery screw 6 is as follows.
Screw length: 320 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 200 [rpm]
As shown in FIG. 17, the flow of the developer is inhibited by the attachment of the magnet 112, it is possible to slow the stirring unit dosage rate U _1. Further, the attachment of the magnet 112 increases the diffusion capability with respect to the deviation of the toner density from before the attachment, and prevents the replenishment toner from slipping up.

In addition, in order to perform sufficient diffusion in the stirring unit, it is necessary to slow down the agent speed in the stirring unit as in Examples 2, 3, and 4. However, reducing the rotational speed of the stirring screw 11 to reduce the agent speed lowers the diffusing capacity, and thus may cancel the improvement of the diffusing effect.
Therefore, the diffusion capacity is improved by attaching the magnet 112 to the stirring conveyance path 10. At the same time, the mounting of the magnet 112 leads to the effect of reducing the stirring unit dosage rate U _1. Without decreasing the diffusion capacity (in some cases, increasing the diffusion capacity), it is possible to add the action of increasing the diffusion time and reducing the wavelength of the toner density deviation, and a dramatic improvement in the diffusion effect is expected. .

[Example 7]
Next, a description will be given of a seventh embodiment in which two stirring conveyance blade portions 138 that are the blade portions of the stirring screw 11 are provided.
FIG. 18 is an explanatory diagram of the stirring screw 11 according to the seventh embodiment. As shown in FIG. 18, two agitation transport wings 138 as a plurality of wings are provided on the agitation rotating shaft 170 that is the axis of the agitation screw 11. In addition, the dimension of the stirring screw 11, the supply screw 8, and the collection | recovery screw 6 is as follows.
Screw length: 320 [mm], shaft diameter: 5 [mm], pitch width: 25 [mm], rotation speed: 200 [rpm]
As shown in FIG. 18, by providing two agitating / conveying wings 138, the diffusion ability with respect to the toner density deviation is improved as compared with the case where only one agitating / conveying wing 138 is provided, and it is possible to prevent the replenishment toner from slipping upward. it can.

In addition, in order to perform sufficient diffusion in the stirring unit, it is necessary to slow down the agent speed in the stirring unit as in Examples 2, 3, and 4. However, reducing the rotational speed of the stirring screw 11 to reduce the agent speed lowers the diffusing capacity, and thus may cancel the improvement of the diffusing effect.
Therefore, the diffusion capacity is improved by providing two stirring and conveying blades 138. At the same time, the mounting of the magnet 112 leads to the effect of reducing the stirring unit dosage rate U _1. In some cases, the pitch can be reduced to increase the number of screw rotations, or by combining with the stirring fin 113 of the fifth embodiment or the magnet 112 of the sixth embodiment, thereby greatly increasing the diffusing capacity and dramatically increasing the diffusion effect. Improvement is expected.

For the deviation of the toner density, the diffusibility by the stirring screw 11 is important, but the toner replenishment position in the developing device 4 is also important.
Next, the toner replenishment position will be described. FIG. 19 is a schematic diagram illustrating the toner supply position.
FIG. 19A is a schematic diagram for explaining the case where the agent is replenished at the portion where the agent is transferred from the collection unit to the stirring unit of the developing device in which stirring, supply, and collection are substantially horizontal as in the developing device 4 used in the above description. FIG.
As shown in FIG. 19A, by supplying the delivery part, since the paddle is attached at the delivery part, the supplementary toner does not slide up and is sufficiently mixed with the developer. Then, the developer is more easily diffused by replenishing the agent delivery section that moves up and down greatly. Further, since it is the end of the developing unit, the degree of freedom in layout is high in creating the toner supply position. Furthermore, by providing the toner replenishment position on the upstream side as viewed from the agitation unit, the high diffusion effect of the agitation screw can be fully utilized from upstream to downstream.

FIG. 19B is a schematic diagram for explaining a case where a toner replenishment position is provided in the collection conveyance path 7.
From the most upstream side of the collection conveyance path 7 to the vicinity of the center portion, the screw agent burying rate is small, so that the replenishment toner does not slide up and can be sufficiently mixed with the developer. Further, since the toner is replenished to the developer having a low toner concentration in the collection conveyance path 7, it is more easily diffused. Further, since it is located farthest from the replenishment position to the developing roller 5, it is easy to diffuse. Furthermore, by providing the toner replenishment position on the upstream side as viewed from the stirring conveyance path 10, the high diffusion effect in the stirring screw 11 can be fully utilized from the upstream to the downstream.
However, in the case of the developing device 4 configured side by side as shown in FIG. 4, it is difficult because there is no space above. Accordingly, it is necessary to devise a mechanism for replenishing from under the recovery unit case. Further, in a configuration in which the sleeve rotation direction is opposite to that in FIG. 4 and the collection unit is above the supply unit, it can be said that this replenishment method is suitable because toner can be replenished from the normal upper part.

FIG. 19C is a schematic diagram for explaining a case where a toner replenishment position is provided on the upstream side of a portion where the developer conveyance speed in the agitation conveyance path 10 is slow.
As shown in FIG. 19 (c), there is a difference in the height of the agent surface so that the agent surface is higher on the downstream side in the conveying direction where the agitating / conveying speed is slow between the slow part and the fast part where the agitating part agent speed is low. Therefore, the replenished toner does not slide up with respect to the developer and slips downstream. Further, by supplying toner on the upstream side of the portion where the agent speed of the stirring portion is slow, it is possible to make use of the high diffusion effect in the portion where the agent is slow.

Next, description will be given of a configuration for controlling the agitating unit dosage rate U ₁ on the basis of the detection result of the toner density sensor 127 is a toner density detecting means for detecting the toner density of the developer stirring and conveying path 10.
Figure 20 is an explanatory view of a configuration for controlling the agitating unit dosage rate U ₁ on the basis of the detection result of the toner density sensor 127, FIG. 20 (a) block diagram, FIG. 20 (b) is a flow chart. From the output value of the toner density sensor 127, the average value of the toner density in a certain time range is obtained, and the volume of the agent in the developing device is calculated from the average value of the toner density.
If the volume is known, the weight V of the agent at the downstream portion of the supply screw can also be calculated. When the minimum agent weight Vmin + α (margin) ≧ V necessary for pumping properly from the supply screw to the sleeve, the agent speed of the stirring screw is increased and control is performed to increase the agent in the supply unit. Thus, the stirring unit can be used as a buffer for coping with the concentration variation of the agent.
Due to the decrease in the toner concentration of the developer, the developer volume in the developing device is reduced, and the agent is easily depleted in the downstream portion of the supply unit. Therefore, when it is detected that the toner concentration has decreased, the developer in the supply conveyance path 9 can be increased by increasing the number of rotations of the stirring screw to such an extent that the diffusion effect is not impaired, thereby preventing depletion of the agent in the supply conveyance path. be able to.

The volume is calculated by the following method.
Set each value as follows.
m ₁ : Average weight of developer per unit length of the agitating conveyance path m ₂ : Developer weight per unit length on the most upstream side of the supply conveyance path m: Unit length on the most downstream side of the supply conveyance path Developer weight per unit U ₁ : Stirrer part speed U ₂ : Feed part part speed Developer weight (m ₁ · U ₁ , m ₂ · U moving per unit length in the agitation transport path and supply transport path) ₂ ) is compared, the following equation (10) holds.
m ₁ · U ₁ = m ₂ · U ₂ (= E (see FIG. 9)) (10)
Further, if the weight of the developer in the recovery conveyance path is constant, the total weight of the developer contained in the agitation conveyance path and the supply conveyance path is preserved, so that the following equation (11) is established.
m ₂ −G / U ₂ + m ₁ = M (11)
Note that M can be estimated by measuring the toner density with a toner density sensor.
here,
G = ρvL / 2. At this time, ρ = pumping amount, v: sleeve linear velocity, and L: screw length. M is the total amount of developer in the supply conveyance path and the agitation conveyance path divided by L.
(10), (11) From the threshold
m ₁ = (M · U ₂ + G) / (U ₁ + U ₂ )
m ₂ = (M · U ₁ + G · U ₂ / U ₁ ) / (U ₁ + U ₂ )
Therefore, the developer weight per unit length in the most downstream portion of the supply conveyance path where the developer surface is the lowest is obtained as in the following equation (12).
By dividing this m by the bulk density [g / cc] (this bulk density is also obtained by measuring the density with a toner density sensor), the volume V downstream of the supply unit is obtained.
Vmin is a value (constant) determined by the magnitude of the magnetic force, the distance between the screw and the sleeve, and the like.

Next, a developer agitation time measuring unit that counts the integrated value of the developer agitation time in the developing device 4 is provided, and the agitation unit speed U ₁ is controlled based on the measured value of the developer agitation transport time measuring unit. The structure to perform is demonstrated.
Figure 21 is an explanatory view of a configuration for controlling the agitating unit dosage rate U ₁ based on the measurement values of the developer stirring and conveying time measuring means, FIG. 21 (a) block diagram, FIG. 21 (b) in the flow chart is there.
From FIG. 21, when the stirring time is long, and small stirring unit dosage rate U _1. Accordingly, it is possible to cope with the control of slowing the rotational speed of the stirring screw 11 even when the developer deteriorates with time and the diffusibility of the developer decreases.
In addition, by slowing down the stirring screw rotation speed little by little, it is possible to always maintain a constant stirring ability and increase the life of the developing device and the developer.
The diffusibility of the developer changes with time. When the diffusion capacity is lowered due to carrier deterioration, it is necessary to cover the capacity on the developing device side. The developer diffusibility can be sufficiently maintained by slowing the agent speed in the agitating and conveying path and increasing the diffusing effect on the agitating screw in accordance with the decrease in the diffusing ability at the time of diameter due to carrier deterioration.

Next, the characteristics of the developer used in the present invention will be described.
The magnetic carrier in the developer preferably has a volume average particle size in the range of 20 to 60 [μm]. By using a carrier having a small particle diameter having an average particle diameter of 60 [μm] or less, the pumping amount can be reduced without lowering the developing ability.
In the developing device 4 shown in FIG. 4, due to the environment and changes over time, a sufficient amount of agent cannot be supplied to the developing roller 5 due to a shortage of agent downstream of the supply conveyance path 9, and the image density may become unstable. is there.
By using a carrier having a small particle diameter, the gap between the carriers is reduced, the magnetic brush in the development region becomes denser, and sufficient development can be performed with a small pumping amount. Therefore, since the amount of developer circulating can be reduced, the supply unit can supply a developer amount that can be stably pumped without depletion of the developer, and the recovery unit contains developer. It becomes possible to transport the agent stably without overflowing.
Further, as the particle size of the carrier is reduced, the magnetic brush in the development region is further densified, and in the development, the toner supply efficiency to the latent image dots is increased, and an image having excellent dot reproducibility can be obtained. Therefore, the stability of image quality is improved over a long period.
If the average particle diameter of the carrier is larger than 60 [μm], an overflow tends to occur in the recovery part, and stable agent circulation cannot be performed. On the other hand, if it is smaller than 20 [μm], there is a problem that the carrier adheres to the photosensitive member or the carrier is easily scattered from the developing unit.
The average particle size of the carrier can be measured using a SRA type of a Microtrac particle size analyzer (Nikkiso Co., Ltd.) with a range setting of 0.7 [μm] or more and 125 [μm] or less.

Next, the characteristics of the toner will be described.
First, regarding the particle diameter, the volume average particle diameter of the toner is preferably in the range of 3 to 8 [μm]. A small particle diameter toner having an average particle diameter of 8 [μm] or less is used.
In the case of a high process linear velocity, the toner consumption / replenishment speed increases, and the toner density fluctuation on the stirring screw and the developing roller tends to increase.
By using a toner having a small particle size, the amount of toner required to obtain the same photoconductor M / A is smaller in the case of a small particle size toner when comparing the case of a large particle size toner and a small particle size toner. Accordingly, both the consumption and replenishment speed can be reduced, and the toner density fluctuation is reduced.
In addition, even when the flowability of the developer changes, the supply unit can supply a developer amount that can be stably pumped up without being depleted, and the recovery unit It becomes possible to transport the agent stably without overflowing. In addition, since the particle size distribution is sharp, the developer has good fluidity, and it becomes possible to perform a long-term stable agent circulation.
On the other hand, since the gap between the toners becomes smaller and the toner is more satisfactorily contained in the image, the required toner adhesion amount and the height (pile height) of the toner image can be reduced. Further, regarding the reproducibility of minute dots of 600 [dpi] or more, in this range, since the toner particles have a sufficiently small particle diameter with respect to the minute latent image dots, the dot reproducibility is excellent and the image Increased stability. Therefore, the stability of image quality is improved over a long period.
On the other hand, when the volume average particle diameter (D1) is less than 3 [μm], phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur. Furthermore, when the volume average particle diameter (D1) exceeds 8 [μm], the pile height of the image increases, the fluidity of the developer deteriorates, and it is difficult to suppress the scattering of characters and lines and to stabilize the image quality for a long period of time. It becomes difficult to maintain.
At the same time, the ratio (D1 / D2) of the volume average particle diameter (D1) to the number average particle diameter (D2) is preferably in the range of 1.00 to 1.40.
The closer (D1 / D2) is to 1.00, the sharper the particle size distribution. 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.

Next, a method for measuring the particle size distribution of toner particles will be described.
Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter).
The measurement method is described below.
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, and 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 treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measuring device is used to measure the volume and number of toner particles or toner using a 100 [μm] aperture. Then, the volume distribution and the number distribution are calculated.
From the obtained distribution, the weight average particle diameter (D1) and the number average particle diameter (D2) of the toner can be obtained.
As a channel, it is less than 2.00-2.52 [micrometer]; 2.52-less than 3.17 [micrometer]; 3.17-less than 4.00 [micrometer]; 4.00-5.04 [micrometer] Less than 5.04 to 6.35 [μm]; 6.35 to less than 8.00 [μm]; 8.00 to less than 10.08 [μm]; 10.08 to less than 12.70 [μm]; 12.70 to less than 16.00 [μm]; 16.00 to less than 20.20 [μm]; 20.20 to less than 25.40 [μm]; 25.40 to less than 32.00 [μm]; Using 13 channels of 00 to less than 40.30 [μm], particles having a particle size of 2.00 [μm] or more to less than 40.30 [μm] are targeted.

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. 21 and 22 are diagrams schematically showing the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is represented by the following equation (13). 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 100p / 4.
SF-1 = {(MXLNG) 2 / AREA} × (100p / 4) (13)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following expression (14). 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 / 4p.
SF-2 = {(PERI) 2 / AREA} × (100 / 4p) (14)
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.

Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a sphere, the contact state between the toners becomes a point contact, so that the attractive force between the toners is weakened and the fluidity is increased. Therefore, the circulatory property of the agent is improved, and stable one-way circulation can be performed in the long term. In addition, since the contact state between the toner and the photoconductor is a point contact, the attractive force between the toner and the photoconductor is weakened, and the transfer rate is increased, contributing to the improvement in image quality.
Further, since the toner becomes nearly spherical, the bulk density of the developer can be reduced, and the increase or decrease in the volume of the developer conveyed is reduced even when the fluidity changes. Therefore, the supply unit can supply a developer amount that can be pumped stably without depletion of the developer, and the recovery unit can stably transport the agent without overflowing the developer. Become. Therefore, since fluctuations are reduced with changes in the environment and time, it is possible to perform a stable developer circulation over a long period of time, and it is possible to obtain an image with excellent image density stability.
On the other hand, if any of the shape factors SF-1 and SF-2 exceeds 180, the fluidity is deteriorated and the agent circulation property is poor. Further, the transfer rate is lowered, which is not preferable.
In addition, since the contact between the toner and the photoconductor is closer to a point contact and the transfer efficiency can be improved, the dot reproducibility is improved, and the stability of the image quality is improved over a long period of time.

The toner used in this copying machine has fine particles having an average primary particle size of 50 to 500 [nm] and a bulk density of 0.3 [mg / cm ³ ] or more (hereinafter simply referred to as fine particles) attached to the toner particle surface. It has been made. In addition, although silica etc. are often used for a normal fluid improvement agent, for example, the average primary particle diameter of this silica is 10-30 [nm] normally, and the bulk density is 0.1-0.2 [mg / cm < ³ >. ].
By using such a toner, the external additive is less buried and the change in the fluidity of the developer is reduced with time. Therefore, the supply unit can supply a developer amount that can be pumped stably without depletion of the developer, and the recovery unit can stably transport the agent without overflowing the developer. Become. Therefore, since fluctuations are reduced with changes in the environment and time, it is possible to perform a stable developer circulation over a long period of time, and it is possible to obtain an image with excellent image density stability.
In the developer used in the present copying machine, an appropriate gap is formed between the toner particles and the target object due to the presence of fine particles having appropriate characteristics on the surface of the toner. In addition, fine particles have a very small contact area with toner particles, a photoconductor, a conveyance belt, etc., and are evenly contacted. There is little disturbance of the image because it is difficult. In addition, since the development / transfer efficiency is improved and the dot reproducibility is improved, the image is stabilized and a margin is increased against disturbance during conveyance. Further, since the toner acts as a roller, the photoreceptor is not worn or damaged. Even during cleaning under high stress (high load, high speed, etc.) between the cleaning blade and the photosensitive member, it is difficult to embed in the toner particles, or it can be detached and restored even if it is slightly buried. Stable characteristics can be obtained over a 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). In addition, when fine particles having an average primary particle size in the range of 50 to 500 [μm] are used, the excellent cleaning performance can be fully utilized and the particle size of the toner is extremely small. Does not reduce fluidity. 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.
The average primary particle size (hereinafter referred to as the average particle size) of the fine particles is 50 to 500 [nm], and particularly preferably 100 to 400 [nm]. If it is less than 50 [nm], the fine particles may be buried in the concave and convex portions of the unevenness of the toner surface, reducing the role of the rollers. On the other hand, when the particle size is larger than 500 [nm], when the fine particles are positioned between the blade and the surface of the photoreceptor, the toner particles are in the same order as the contact area of the toner itself, and the toner particles to be cleaned are allowed to pass through. It becomes easy to generate.

When the bulk density is less than 0.3 [mg / cm ³ ], although there is a contribution to improving the fluidity, the scattering property and adhesion of the toner and fine particles are increased, so that the effect as a toner and a roller can be improved. In other words, the so-called dam effect that prevents toner cleaning failure is reduced.

In the fine particles of the developer used in this copying machine, as an inorganic compound,
SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ Examples include O (TiO ₂ ) n, Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3 and the} like.
Also, _{preferably, SiO 2, TiO 2, Al} 2 O 3 and the like. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like.

The organic compound fine particles 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, Examples include urea resins, aniline resins, ionomer resins, and polycarbonate resins. As the resin fine particles, two or more of the above resins may be used in combination.
Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred 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 bulk density of the fine particles was measured by the following method. Using a 100 [ml] graduated cylinder, fine particles were gradually added to 100 [ml].
At that time, no vibration was applied. The bulk density was measured by the difference in weight before and after placing the fine particles of the graduated cylinder.
Bulk density [g / cm ³ ] = fine particle amount [g / 100 ml] ÷ 100

  As a method of adding and adhering the fine particles of the developer of the present copying machine to the toner surface, a method of adhering the toner base particles and the fine particles mechanically by using various known mixing devices, There is a method in which toner base particles and fine particles are uniformly dispersed with a surfactant or the like in the phase, and are dried after the adhesion treatment.

As described above, according to the first embodiment, the three developer transport paths including the recovery transport path 7, the supply transport path 9, and the stirring transport path 10 are partitioned by the partition plate 134 and the partition wall 133, which are partition members, respectively. In the developing device 4 in which toner is supplied to the conveyance path, the conveyance speed of the developer moving in the agitation conveyance path 10 is U ₁ [m / s], the length of the agitation conveyance path 10 is L [m], and the toner Assuming that T [s] is the period during which the replenishment is performed, and D [m ² / s] is the value indicating the diffusion performance when the stirring screw 11 that is the stirring and conveying member performs stirring, the above equation (1) seems to hold. I have to. As a result, the toner density deviation at the most downstream portion of the agitating / conveying path 10 can be diffused to 1/20 or less of the toner density deviation at the most upstream area of the agitating / conveying path 10. Therefore, it is possible to form an image with a stable image density by suppressing the toner density fluctuation on the developing roller 5 which is a developer carrying member.
Further, the transport speed of the developer in the supply transport path 9 is U ₂ [m / s], the transport speed of the developer moving in the recovery transport path 7 is U ₃ [m / s], and U ₂ > U _1, and _U 3> so that the relationship of _{U 1} is true. Therefore, even if the agitation property in the agitation conveyance path 10 is improved, it is possible to prevent the overflow of the developer in the recovery conveyance path 7 and the depletion of the developer in the supply conveyance path 9.
Moreover, by making the pitch width of the stirring screw 11 shorter than the pitch width of the supply screw 8 and the recovery screw 6, the rotational speed of the stirring screw 11 is not decreased (in some cases, the rotational speed is increased). it can slow the stirring unit dosage rate U ₁ than the feed portions agents speed U _2. Accordingly, it is possible to add the effects of increasing the diffusion time and reducing the wavelength of the toner density deviation without decreasing the diffusion capability depending on the screw rotation speed (in some cases, increasing the diffusion capability).
In addition, the pitch width of the central region of the stirring screw 11 is made shorter than the pitch width of the supply screw 8 and the recovery screw 6, and the developer speed is reduced only in part in a partial region of the stirring conveyance path 10. As a result, the diffusion time at that location is large, the wavelength of toner density deviation is small, and the diffusion effect is large. Further, by providing a toner replenishment position upstream of the portion where the developer conveyance speed of the agitating / conveying path 10 is slow, the agitating / conveying speed is low in the portion where the agitating agent speed is low and in the portion where the stirring agent is slow. Since the height of the surface of the agent is different so that the surface of the toner is higher on the side, the replenished toner does not slide up with respect to the developer and slips downstream. Then, by supplying toner on the upstream side of the portion where the agent speed of the stirring portion is slow, it is possible to take advantage of the high diffusion effect in the portion where the agent is slow.
Further, by providing the toner replenishment position in the developer delivery portion from the most downstream portion of the collecting and conveying path 7 of the developing device 4 to the most upstream portion of the developer stirring and conveying path 10, the developer moves up and down greatly. It is easier to spread by replenishing the delivery part.
Further, by providing the toner replenishment position in the collection conveyance path 7 of the developing device 4, the toner is replenished to the developer having a low toner concentration in the collection conveyance path 7, so that the toner is easily diffused. It is easy to diffuse because it is farthest from the replenishment position. Furthermore, by providing the toner replenishment position on the upstream side as viewed from the stirring conveyance path 10, the high diffusion effect in the stirring screw 11 can be fully utilized from the upstream to the downstream.
Further, the stirring member agent speed U ₁ is made smaller than the supply member agent speed U ₂ and the recovery member agent speed U ₃ by making the rotation number of the stirring screw 11 smaller than that of the supply screw 8 and the recovery screw 6. can do. Furthermore, by lowering the rotational speed, the stress on the bearing and the agent of the stirring screw 11 can be reduced, and the life of the bearing / agent can be extended.
Also, the flow of the developer is inhibited by mounting the stirring fins 113 on stirring screw 11, is slow stirring unit dosage rate U _1. Furthermore, by attaching the agitation fin 113, the diffusion ability with respect to the toner density deviation can be improved from before the attachment, and the replenishment toner can be prevented from slipping.
Further, the stirring conveyance path 10 is inhibited the flow of the developer by the mounting of the magnet 112, it is possible to slow stirring unit dosage rate U _1. Further, the attachment of the magnet 112 also increases the diffusion capability with respect to the deviation in toner density than before the attachment, and prevents the replenishment toner from sliding up.
Further, by providing two agitating / conveying wings 138, the ability to diffuse the toner density deviation can be improved as compared with the case where only one agitating / conveying wing 138 is provided, and further, the replenishment toner can be prevented from slipping upward.
Further, by increasing the diameter of the agitating screw 11, the screw embedding rate of the developer in the agitating and conveying path 10 can be suppressed to an allowable range (less than about 0.9), and the diffusion effect is improved.
Further, by controlling the stirring unit dosage rate U ₁ on the basis of the detection result of the toner density sensor 127, if it is detected that lowered toner density, by increasing the agitation screw rotation speed to the extent that the diffusion effect is not impaired, the supply conveyance The developer in the path 9 can be increased, and the depletion of the agent in the supply conveyance path can be prevented.
Further, by controlling the stirring member agent speed U ₁ based on the measured value of the image agent stirring / conveying time measuring means and reducing the stirring member agent speed U ₁ when the stirring time is long, the developer deteriorates over time. Even when the diffusibility of the developer is lowered, it is possible to cope with the control for reducing the rotation speed of the stirring screw 11.

[Modification 1]
In the first embodiment, with the developing device 4 in which the three developer conveyance paths shown in FIG. 4 are substantially the same height, the agitation unit speed U ₁ and the supply unit agent speed U ₂ satisfy U ₁ <U _2. Is set. A preferable configuration satisfying U ₁ <U ₂ is not limited to the developing device in which the three developer transport paths shown in FIG. If the recovery conveyance path and the supply conveyance path are provided separately, the developer amount decreases on the downstream side of the supply conveyance path. Therefore, the agitation unit speed U ₁ and the supply unit agent speed U ₂ are set as U ₁ <preferably satisfies the _{U 2.}
Hereinafter, Modification 1 in which the developing device 4 illustrated in FIG. 24 is set to satisfy U ₁ <U ₂ will be described.

In the developing device 4 of FIG. 24, the developer is supplied to the developing roller 5 adjacent to the supply screw 8 arranged in the supply conveyance path 9, and the developed developer is a collection conveyance path arranged below the development roller 5. 7 is moved. The collection screw 6 disposed in the collection conveyance path 7 conveys the developer in the same direction as the supply screw 8, and further to the stirring conveyance path 10 provided at substantially the same height on the downstream side in the conveyance direction of the collection conveyance path 7. Developer is being transported. Further, the developer that has not been supplied to the developing roller 5 in the supply conveyance path 9 moves (drops) to the lower agitation conveyance path 10 on the downstream side in the conveyance direction of the supply conveyance path 9. The agitation screw 11 disposed in the agitation conveyance path 10 agitates the developed developer from the recovery conveyance path 7, the undeveloped developer from the supply conveyance path 9, and the replenishment toner, and moves to the upstream side of the supply conveyance path 9. And move diagonally upward. During the lifting of the developer obliquely upward in the stirring conveyance path 10, and the stirring unit speed U ₁ smaller than the feed unit dosage rate U _2.

As shown in FIG. 24, when the supply conveyance path 9 is above the agitation conveyance path 10, a toner replenishment position may be provided at the falling portion where the developer falls from the supply conveyance path 9 to the agitation conveyance path 10. good. FIG. 25 is a schematic diagram illustrating the toner replenishment position of the developing device 4 according to the first modification.
In addition, the supply conveyance path 9 is not limited to the one above the stirring conveyance path 10, and when the developer conveyance path in which either the collection unit or the supply unit is above the other screw unit has a two-stage configuration, from above Particularly effective replenishment can be achieved by placing the toner replenishment portion in the downward drop portion.

1 is a schematic configuration diagram of a copier according to a first embodiment. 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. FIG. 2 is a schematic configuration diagram of a developing device of the copier. FIG. 3 is a schematic configuration diagram of a magnetic pole arrangement of a developing roller. The perspective view of the lower casing of a developing device. FIG. 3 is a schematic cross-sectional view of a communication portion of a developer conveyance path. The perspective view of the upper casing of a developing device. Schematic explaining the developer conveyance amount and flow in each developer conveyance path. Explanatory drawing of the relationship between a stirring part agent speed and a diffusion effect. 6 is a graph showing a change in toner concentration with time when the stirring unit speed is the same as the supply unit speed and when the stirring unit speed is slower than the supply unit speed. FIG. 3 is a schematic diagram of a developer speed detecting unit using a magnetic permeability sensor. Explanatory drawing of the experiment 1 which performed the comparison of diffusivity, (a) is explanatory drawing of the screw which set the conveyance speed fast, (b) is explanatory drawing of the screw which set the conveyance speed late. Graph showing the results of Experiment 1 The graph which shows the result of Experiment 2. Explanatory drawing of the stirring screw concerning Example 5, (a) is the figure which provided the fin in the whole screw, (b) is the figure which provided the fin in a part of screw. FIG. 10 is an explanatory diagram of a developing device according to a sixth embodiment. Explanatory drawing of the stirring screw concerning Example 7. FIG. Schematic diagram illustrating the toner replenishment position, (a) is a case where a toner replenishment position is provided in the agent delivery portion, (b) is a case where a toner replenishment position is provided in the collection conveyance path, and (c) is a stirring conveyance path. When a toner replenishment position is provided on the upstream side of the portion where the developer transport speed is slow. FIG. 4 is an explanatory diagram of a configuration for controlling the stirring member agent speed based on the detection result of the toner concentration sensor 127, (a) is a block diagram, and (b) is a flowchart. It is explanatory drawing of the structure which controls a stirring part agent speed based on the measured value of a developer stirring conveyance time measurement means, (a) is a block diagram, (b) is a flowchart. The schematic diagram for demonstrating shape factor SF-1. The schematic diagram for demonstrating shape factor SF-2. FIG. 9 is a schematic configuration diagram of a developing device according to Modification Example 1. FIG. 9 is a schematic diagram illustrating a toner replenishment position according to a first modification. 1 is a schematic configuration diagram of a developing device that has been widely used conventionally. FIG. 2 is a schematic configuration diagram of a developing device described in Patent Document 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Photoconductor cleaning apparatus 3 Scorotron charger 4 Developing apparatus 5 Developing roller 6 Collection screw 7 Collection conveyance path 8 Supply screw 9 Supply conveyance path 10 Agitation conveyance path 11 Agitation screw 12 Lower casing 13 Upper casing 14 Screw vertex 15 Rotation Center 16 Developing doctor 17 Doctor area 18 Restricted developer collecting member 19 Heat radiating member 20 First transfer unit 21 First intermediate transfer belt 30 Second transfer unit 31 Second intermediate transfer belt 40 Paper feeder 44 Horizontal registration correction mechanism 45 Registration roller pair 46 Secondary transfer roller 47 Transfer charger 50 Paper transport unit 50A Transport cleaning device 51 Paper transport belt 54 Separation roller 57 Adsorption charger 58 Separation charger 60 Fixing device 70 Cooling roller pair 71 Discharge roller pair 7 Discharge stack unit 80 First process unit 81 Second process unit 85 Bottle storage unit 90 Operation / display unit 95 Control unit 100 Printer unit 110 Collecting stirring screw 111 Image forming unit 112 Magnet 113 Stirring fin 120 Fin 121 Guide unit 122 Developer Trapping roller 123 Scraper 127 Toner concentration sensor 128 Radiation fin 130 Toner replenishment port 131 Collecting / supplying convex part 132 Supplying / stirring convex part 133 Partition wall 134 Partition plate 138 Stirring transport wing part 139 Stirring lateral transfer paddle 140 Stirring reverse feeding part 141 Recovery lateral transfer paddle 142 Supply lateral transfer paddle 143 Transfer portion position 144 Developer push-out surface 145 Image material bulk adjustment opening 200 Automatic image reading device 210 Recovery stirring conveyance path 300 Paper supply device 401 Supply recovery Cru 402 supply collection conveyance path 403 bulkhead

Claims (23)

A developer that rotates by supporting a two-component developer composed of a magnetic carrier and a toner on the surface and supplying the toner to the latent image on the surface of the latent image carrier at a location facing the latent image carrier. A carrier,
A developer supply transport path including a developer supply transport member that transports the developer along the axial direction of the developer support and supplies the developer to the developer support;
The developer recovered from the developer carrier after passing through the portion facing the latent image carrier is along the axial direction of the developer carrier and in the same direction as the developer supply / conveying member. A developer recovery transport path including a developer recovery transport member for transporting
Excess developer transported to the most downstream side in the transport direction of the developer supply transport path without being used for development, and to the most downstream side in the transport direction of the developer collection transport path recovered from the developer carrier Receiving supply of the collected developer that has been conveyed, along the axial direction of the developer carrier, and in the direction opposite to the developer supply and conveying member while stirring the excess developer and the collected developer A developer agitating and conveying member that conveys the developer to the developer supplying and conveying path, and a developer agitating and conveying path that supplies the developer to the developer supplying and conveying path,
The three developer transport paths including the developer recovery transport path, the developer supply transport path, and the developer agitation transport path are each partitioned by a partition member, and a developing device in which toner is supplied to the developer transport path In
The transport speed of the developer moving in the developer stirring and transporting path is U ₁ [m / s], the length of the developer stirring and transporting path is L [m], and the period of toner replenishment is T [ s], and the value indicating the diffusion performance due to stirring by the stirring and conveying member is D [m ² / s],
A developing device characterized in that the following equation (1) holds:
The developing device according to claim 1.
The transport speed of the developer moving in the developer supply transport path is U ₂ [m / s], and the transport speed of the developer moving in the developer recovery transport path is U ₃ [m / s]. age,
U ₂ > U ₁ and U ₃ > U ₁
A developing device characterized by the following relationship: The developing device according to claim 1 or 2,
The three developer transport members, the developer supply transport member, the developer recovery transport member, and the developer agitation transport member, have a spiral blade on the rotating shaft, and transport the developer by rotating. A developing device, comprising: a developer conveying screw, wherein the three developer conveying members are a developer supply screw, a developer recovery screw, and a developer stirring screw, respectively. The developing device according to claim 3.
The developing device, wherein a pitch width of the developer agitating screw is narrower than a pitch width of the supply screw and the recovery screw. The developing device according to claim 1.
A developing device characterized in that a developer conveying speed in at least a part of the developer agitating / conveying path is slower than a developer conveying speed of the developer supplying / conveying path and the developer collecting / conveying path. . The developing device according to claim 5.
The three developer transport members, the developer supply transport member, the developer recovery transport member, and the developer agitation transport member, have a spiral blade on the rotating shaft, and transport the developer by rotating. A developing device, comprising: a developer conveying screw, wherein the three developer conveying members are a developer supply screw, a developer recovery screw, and a developer stirring screw, respectively. The developing device according to claim 6.
Part of the pitch width of the developer stirring screw is narrower than the pitch width of the supply screw and the recovery screw. The developing device according to claim 5, 6 or 7,
The toner replenishment position for replenishing toner to the developing device is a portion of the developer agitation transport path where the developer transport speed is slower than the supply transport path and the recovery transport path, or the developer transport than that part. A developing device provided on the upstream side in the direction. The developing device according to claim 1, 2, 3, 4, 5, 6 or 7.
A developing device characterized in that a toner supply position for supplying toner to the developing device is provided in the developer collection transport path. The developing device according to claim 1, 2, 3, 4, 5, 6 or 7.
A developing device, wherein a toner replenishing position for replenishing toner to the developing device is provided in a developer delivery portion from the most downstream portion of the developer collecting and conveying path to the most upstream portion of the developer stirring and conveying path. The developing device according to claim 3, 4, 6, 7, 8, 9 or 11,
The developing device according to claim 1, wherein the rotation speed of the developer stirring screw is smaller than the rotation speeds of the supply screw and the recovery screw. The developing device according to claim 3, 4, 6, 7, 8, 9, 10 or 11.
2. A developing device according to claim 1, wherein a fin having a plane composed of sides of a radial direction of the blade and an axial direction of the stirring screw is attached to the developer stirring screw. The developing device according to claim 3, 4, 6, 7, 8, 9, 10, 11 or 12.
A developing device characterized in that the number of wings of the stirring and conveying screw is plural. The developing device according to claim 3, 4, 6, 7, 8, 9, 10, 11, 12 or 13.
A developing device characterized in that the diameter of the blade portion of the agitating and conveying screw is larger than the diameter of the blade portion of the supply screw. The developing device according to claim 3, 4, 6, 7, 8, 9, 10, 11, 12, 13 or 14.
A developing device characterized in that the number of rotations of the stirring and conveying screw can be changed. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15.
A developing device comprising a magnetic field generating means attached so as to form a magnetic field in the developer stirring and conveying path. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.
A toner concentration detection unit that detects the toner concentration of the developer in the developer stirring conveyance path is provided, and the developer conveyance speed in the developer stirring conveyance path is controlled based on the detection result of the toner concentration detection unit. A developing device. The developing device according to claim 17,
A developing device characterized in that when a decrease in toner concentration is detected by the toner concentration detecting means, the developer conveying speed in the developer agitating / conveying path is increased. The developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18.
A developer agitation time measuring means for counting the integrated value of the developer agitation time in the developing device, and the developer conveying speed in the developer agitating and conveying path based on the measured value of the developer agitating time measuring means; And a developing device. The developing device according to claim 19,
A developing device characterized in that the developer conveying speed in the developer agitating / conveying path is decreased in accordance with the increase in the integrated value. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19 or 20.
An image forming apparatus, wherein the developer collection conveyance path is provided below the developer carrier, and the three developer conveyance paths are provided at substantially the same height. The image forming apparatus according to claim 21, wherein
The uppermost portion of the developer supply / conveyance member is below the rotation center axis of the developer carrier, and a plane passing through the rotation center axis of the developer carrier and the uppermost portion of the developer supply / conveyance member; An image forming apparatus, wherein an angle formed by a horizontal plane passing through a rotation center axis of a developer carrying member is within a range of 10 [°] to 40 [°]. At least a latent image carrier;
Charging means for charging the surface of the latent image carrier;
Latent image forming means for forming an electrostatic latent image on the latent image carrier;
In an image forming apparatus having developing means for developing the electrostatic latent image into a toner image,
As the developing means, claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 An image forming apparatus using the developing device described in 1.