JP2007011004A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which has a developing device equipped with a supply transport path, an stirring transport path, and a recovery transport path, and can form an image of stable image density. <P>SOLUTION: The developing device 4, equipped with the three conveying paths; the recovery conveying path 7, the supply conveying path 9 and the stirring transport path 10, satisfies the relation U<SB>1</SB><U<SB>2</SB>, when the transport speed of a developer in the direction shown by arrow 136 within the supply transport path 9 is defined as a supply section agent speed U<SB>1</SB>[m/s] and the transport speed of the developer in the direction shown by arrow 137 within the agitating conveying path 10 as an agitating section agent speed U<SB>2</SB>[m/s]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a fax machine, and a printer. More specifically, the present invention relates to an image forming apparatus including a developing device that uses a two-component developer composed of toner and a magnetic carrier.

  Conventionally, as a developing device using a two-component developer composed of a toner and a magnetic carrier, the one shown in FIG. 18 is known. A developing device 4 shown in FIG. 18 supplies a developing roller 5 which is a developer carrying member for supplying a developer to a latent image carrying member (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. 18, 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.

The developing device described in Patent Document 1 is shown in FIG.
The developing device 4 shown in FIG. 19 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. 19, the developed developer is collected in the collection stirring and conveying path 210, and the developed developer is not mixed into the supply and conveying 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 density of the whole developer in the supply conveyance path 9 is lowered and the toner density becomes non-uniform. 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.

  The problems of the developing device 4 shown in FIGS. 18 and 19 are caused by the stirring for stirring the developer, the developer supplying screw to the developing roller, the developed developer collecting screw and the developer as in Patent Document 2. This can be solved by providing a screw in a different developer conveyance path. The configuration of the developing device described in Patent Document 2 will be described below.

The developing device described in Patent Document 2 is shown in FIG.
The developing device 4 shown in FIG. 20 includes a developing roller 5, a supply screw 8, and a recovery screw 6 that passes through a development location on the development roller 5 and conveys the recovered 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 screw 8 is disposed above the stirring screw 11, and the supply conveyance path 9 including the supply screw 8 and the stirring conveyance path 10 including the stirring screw 11 are partitioned by a first partition 404 which is a partition member. The two conveyance paths communicate with each other at the openings at both axial ends of the first partition 404, and the excess developer that is not used for development and is conveyed to the downstream end of the supply conveyance path 9 is supplied to the supply conveyance path 9. And is supplied to the agitation transport path 10 by dropping at the opening on the downstream end side. The collection conveyance path 7 including the collection conveyance screw is provided side by side in the horizontal direction of the agitation conveyance path 10, and the collection conveyance path 7 and the agitation conveyance path 10 are partitioned by a second partition 405 that is a partition member. The two conveying paths communicate with each other through an opening provided in the second partition 405 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 stirring transport path 10.
The surplus developer and the recovered developer supplied to the agitation conveyance path 10 are agitated in the agitation conveyance path 10, pushed in by the conveyance force of the agitation screw 11 at the downstream end, and raised to the supply conveyance path 9 from the opening. Supply is made.
In the developing device 4 shown in FIG. 20, 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, there is a problem in that the toner density of the entire developer in the supply conveyance path 9 is reduced or the toner density becomes nonuniform due to the insufficiently stirred developer being supplied to the supply conveyance path 9. Can be prevented.

Further, as in Patent Document 2, the present applicant describes in Japanese Patent Application No. 2005-068659 as a developing device 4 provided with three developer transport paths, that is, a supply transport path 9, a recovery transport path 7 and a stirring transport path 10. A developing device as 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, there is a problem in that the toner density of the entire developer in the supply conveyance path 9 is reduced or the toner density becomes nonuniform due to the insufficiently stirred developer being supplied to the supply conveyance path 9. Can be prevented.

Japanese Patent No. 3127594 (first figure) JP-A-11-167260 (first figure)

  However, unlike the developing device 4 in FIG. 18, the developing device 4 divided into three transport paths as shown in FIGS. 4 and 20 is supplied to the developing roller 5 and the developer used for development is supplied to the supply transport path. Since it does not return to 9, the amount of developer decreases in the supply conveyance path 9 as it goes downstream. When the amount of developer on the downstream side of the supply conveyance path 9 decreases and becomes less depleted than the required amount, the developer amount necessary for development cannot be supplied to the developing roller 5, and the developer in the supply conveyance path There is a possibility that the image density corresponding to the downstream side in the transport direction is lowered.

Here, the agent weight per unit length at the most upstream portion in the developer conveyance direction of the supply conveyance path 9 is the supply unit upstream agent weight m ₁ [kg / m], and the supply weight of the supply conveyance path 9 in the developer conveyance direction is the maximum. The agent weight per unit length in the downstream part is defined as the supply part downstream agent weight _mmin [kg / m]. Furthermore, let the agent weight per unit length of the stirring conveyance path 10 be stirring part agent weight m < ₂ > [kg / m]. Then, the developer transport speed (hereinafter referred to as supply part agent speed) U ₁ that moves in the supply transport path 9, and the developer transport speed (hereinafter referred to as stirrer part speed) that moves in _the stirring transport path 10. Assuming U ₂ , the weight of the agent that moves per unit time in the upstream portion of the supply conveyance path 9 and the downstream portion of the stirring conveyance path 10 is equal, and therefore, the relationship m ₁ U ₁ = m ₂ U ₂ is established. Further, since the appropriate amount of developer supplied to the developing roller 5 is substantially constant, if the supply section upstream agent weight m ₁ is increased, the supply section downstream agent weight _mmin can be increased.
Then, in order to prevent the developer amount from being depleted on the downstream side of the supply conveyance path 9, when the total developer amount in the developing device 4 is simply increased so as to increase the supply unit upstream agent weight m ₁ , the supply unit Although both the upstream agent weight m ₁ and the supply unit downstream agent weight _mmin increase and prevent the developer amount from being depleted on the downstream side of the supply conveyance path 9, the stirring unit agent weight m ₂ also increases. When the stirring member weight m ₂ increases, the amount of the developer in the stirring conveyance path 10 becomes excessive, and the developer is not sufficiently stirred. If the developer with insufficient stirring in the stirring / conveying path 10 is supplied to the supply / conveying path 9, the entire developer in the supplying / conveying path 9 becomes insufficient in charge amount, resulting in a problem that the image density becomes non-uniform.

  The present invention has been made in view of the above problems, and an object thereof is to have a developing device including a supply conveyance path, a stirring conveyance path, and a collection conveyance path, and to form an image with stable image density. An image forming apparatus capable of performing the above is provided.

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 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 supplying and conveying In the image forming apparatus having a developing device, each of the three developer transport paths including the path and the developer stirring transport path is partitioned by a partition member, the transport speed of the developer (hereinafter referred to as the developer supply transport path). The following equation (1) is established for U ₁ , which is referred to as a supply part agent speed), and U ₂ , the transport speed of the developer moving in the developer agitation transport path (hereinafter referred to as a stirrer part speed) U _2. It is what.
U ₁ <U ₂ (1)
According to a second aspect of the present invention, in the image forming apparatus of the _{first aspect} , the following equation (2) is established for the supply part agent speed U ₁ and the agitation part agent speed U _2. It is.
However, D = ρvW / 2, M = Q / W (ρ: pumping amount [kg / m ² ], v: developer carrier linear velocity [m / s], W: length in developing region axial direction [m] , Q: Weight of agent in the developer supply conveyance path + Weight of agent in the developer stirring conveyance path [kg])
The invention of claim 3 is the image forming apparatus according to claim 1 or 2, the feed unit dosage rate U ₁ is characterized by decreases as the developer conveyance direction downstream side of the supply compartment 301S Is.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the developer surface in the developer supply / conveyance path is higher than the horizontal surface so that the developer carrier side is higher. Is also characterized by being inclined.
According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third, or fourth aspect, the three developer transports of the developer supply transport member, the developer recovery transport member, and the developer agitation transport member are provided. The member is a developer transport screw that includes a spiral blade on the rotating shaft and transports the developer by rotating. The three developer transport members are a developer supply screw, a developer recovery screw, and a developer recovery screw, respectively. It is a developer stirring screw.
According to a sixth aspect of the present invention, in the image forming apparatus of the fifth aspect, the pitch width of the developer supply screw is shorter than the pitch width of the developer agitating screw.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fifth or sixth aspect, the rotational speed of the developer supply screw is smaller than the rotational speed of the developer stirring screw.
The invention of claim 8 is the image forming apparatus according to claim 5, 6 or 7, wherein the developer supply screw on the downstream side of the developer supply conveyance path in the developer supply conveyance path has a radial direction of the blade portion and the wing portion. A fin having a plane composed of a side with the axial direction of the supply screw is attached.
According to a ninth aspect of the present invention, in the image forming apparatus according to the fifth, sixth, seventh, or eighth aspect, the developer conveyance path of the developer supply conveyance path is maintained while the radius of the blade portion of the developer supply screw remains constant. The member volume of the developer supply screw is increased toward the downstream side in the direction.
According to a tenth aspect of the present invention, in the image forming apparatus according to the fifth, sixth, seventh, eighth, or ninth aspect, the shaft diameter of the rotating shaft portion of the developer supply screw is determined by the developer in the developer supply conveyance path. It is characterized in that it becomes larger toward the downstream side in the transport direction.
The invention according to claim 11 is the image forming apparatus according to claim 5, 6, 7, 8, 9 or 10, wherein the thickness of the blade portion of the developer supply screw is determined by the development in the developer supply conveyance path. It is characterized in that it becomes larger toward the downstream side in the agent transport direction.
According to a twelfth aspect of the present invention, in the image forming apparatus of the fifth, sixth, seventh, eighth, ninth, tenth, or eleventh aspect, a plurality of the wings on the downstream side in the developer conveyance direction of the developer supply conveyance path are provided in a plurality. In addition, the number of the wings is larger than that on the upstream side in the developer conveyance direction.
The invention according to claim 13 is the image forming apparatus according to claim 5, 6, 7, 8, 9, 10, 11 or 12, wherein the wing portion closer to the developer carrying member than the rotating shaft portion is provided. The developer supply screw is rotated from the lower side to the upper side.
The invention according to claim 14 is the image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the developer collection transport path is provided in the image forming apparatus. It is provided below the developer carrier, and the three developer transport paths are provided at substantially the same height.
The image forming apparatus according to claim 15 is the image forming apparatus according to claim 14, wherein the uppermost portion 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 provided. 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.
According to a sixteenth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, or thirteenth aspect, the developer recovery conveyance path is provided on the developer collection conveyance path. Provided below the developer carrier, the developer supply transport path is provided at a position higher than the developer recovery transport path, and the developer agitation transport path is located on the most upstream side in the developer transport direction. The developer is provided at substantially the same height as the path, and the developer is transported to the height of the developer supply transport path on the most downstream side in the developer transport direction of the developer stirring transport path.
According to a seventeenth aspect of the present invention, in the image forming apparatus of the sixteenth aspect, the lowermost portion of the developer supply / conveying member is located above the lowermost portion of the developer carrying member, and the rotation center axis of the developer carrying member. And an angle formed by a plane passing through the lowermost 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 −20 [°] to 20 [°]. It is a feature.
The invention of claim 18 is the image forming apparatus of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17. A first intermediate transfer belt for carrying a toner image formed by supplying toner to each latent image corresponding to each color formed on the latent image carrier, and a second image carrier belt; The toner image on the intermediate transfer belt is transferred to one surface of the recording member, and the toner image on the second image carrier belt is transferred to the other surface of the recording member.

The image forming apparatus of the claims 1 to 18, a supply unit dosage rate _{U 1} and the stirring conveyance speed _{U 2 is,} U 1 <by a relationship of _{U 2,} the m ₁ U _{1 =} m 2 _{U 2} From the relationship, m ₁ > m ₂ , and the amount of developer in the most upstream portion of the developer supply conveyance path can be increased without increasing the amount of developer in the developer stirring conveyance path. Since the amount of developer at the most upstream part in the developer supply transport path can be increased, the developer amount can also be increased on the downstream side of the developer supply transport path, and the developer can be prevented from being depleted, It is possible to prevent the image density corresponding to the downstream side in the developer transport direction of the developer supply transport path from decreasing. Furthermore, since the amount of developer in the developer agitation transport path is not increased, the developer agitation caused by the excessive amount of developer in the developer agitation transport path is insufficient. It is possible to prevent the image density from becoming non-uniform due to insufficient charging of the developer.

  According to the first to eighteenth aspects of the present invention, it is possible to prevent the image density corresponding to the downstream side in the developer conveyance direction of the developer supply conveyance path from being lowered, and the image density becomes non-uniform due to insufficient charging of the developer. Therefore, there is an excellent effect that an image can be formed with a stable image density.

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 has a vertically long posture that takes a space in the vertical direction rather than the horizontal direction by a plurality of rollers, and the second intermediate transfer belt 31 is inclined in a posture in which the second image receiving surface is inclined 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 formula (3).
(E / 3)>e> (E / 4) (3)
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.
From the above points, the transport amount is set in the range of the formula (3) from the viewpoints of ensuring developer transport efficiency (developing developer low stress) and controlling toner density (sensitivity of toner density sensor and uniform toner density).

Next, the relationship between the transport speed of the developer moving on the supply transport path 9 and the transport speed of the developer moving on the stirring transport path 10 will be described.
Here, the moving speed of the developer in the direction indicated by the arrow 136 in FIG. 6 and FIG. 9 in the supply conveyance path 9 is the supply part agent speed u ₁ [m / s], and FIG. The developer transport speed in the direction indicated by the arrow 137 in FIG. 9 is defined as the stirring member speed u ₂ [m / s]. Further, the agent weight per unit length at the most upstream portion in the developer conveyance direction of the supply conveyance path 9 is the supply unit upstream agent weight m ₁ [kg / m], and the supply conveyance path 9 is most downstream in the developer conveyance direction. The agent weight per unit length in the part is defined as the supply part downstream agent weight _mmin [kg / m]. Furthermore, let the agent weight per unit length of the stirring conveyance path 10 be stirring part agent weight m < ₂ > [kg / m].

In FIG. 9, since the output conveyance amount of the agitating and conveying screw = the input conveying amount of the supply and conveying screw = E, the agent moves per unit time in the upstream portion of the supply and conveying path 9 and the downstream portion of the agitating and conveying path 10. The weight is equal. Here, when the transport amount E is the transport amount E [kg / s] per time, the following equation (4) is established.
E = m ₁ u ₁ = m ₂ u ₂ (4)
From the equation (4), if the relationship of u ₁ <u ₂ is satisfied, m ₁ > m ₂ is satisfied. Thereby, the amount of developer in the supply conveyance path 9 can be increased without increasing the amount of developer in the stirring conveyance path 10.
That is, by setting the speed of the developer in the supply conveyance path 9 and the agitation conveyance path 10 as shown in Expression (1), the speed of the developer is minimized, and the supply conveyance path 9 is effectively obtained. Thus, the developer capacity in the toner can be increased, and the depletion of the developer in the supply conveyance path 9 can be prevented. Therefore, a stable developer amount can always be supplied to the developing roller 5, and an image having a stable image density can be obtained over a long period of time.
On the other hand, since the developer capacity in the agitation conveyance path 10 can be reduced, the screw filling rate of the developer can be lowered without increasing the diameter of the agitation screw 11, and the replenishment toner can be sufficiently agitated. . Further, the number of rotations of the screw can be reduced, and the life of the developer and the screw bearing can be extended.

Further, the pumping amount per unit area of the developing roller 5 is ρ [kg / m ² ], the linear velocity in the rotating direction of the developing roller 5 is v [m / s], and the axial length of the developing region is W [m. ], The following formula (5) is established.
m _min = m ₁ −ρvW / u ₁ (5)

Further, if the moving speed of the developer in the collection conveyance path 7 does not change with time, the total amount of developer in the supply conveyance path 9 and the agitation conveyance path 10 is stored, so the following formula (6 ) Holds.
m ₁ −D / u ₁ + m ₂ = M (6)
Here, D = ρvL / 2, and M [kg / m] is a value obtained by dividing the total amount [kg] contained in the supply conveyance path 9 and the stirring conveyance path 10 by W [m].

From the formulas (4), (5) and (6), the supply part downstream agent weight m _min , the supply part upstream agent weight m ₁ and the stirring part agent weight m ₂ are respectively expressed by the following formulas (7-1) and ( 7-2) and (7-3).

FIG. 10 is a graph of Expression (7-1). (Ρ = 0.4 [kg / m ² ], v = 0.2 [m / s], L = 0.3 [m], M = 0.7 [kg])
Greater than the value m _Z that is z-axis m _min in the graph, allows the supply of developer to the developing roller from the feed screw. Also, smaller than a value m _Z, supply unit downstream the dosage is depleted, the supply of the developer is not sufficiently performed in the developing roller, which means that pumping failure would occur. Note that the value of m _Z placement of strength and feed screw of the magnet of the developing roller, come determined by the shape and rotation direction and the like of the feed screw.

From 10, with respect to the agitating portion agent velocity _{u 2, m min} are seen to monotonically increase. On the other hand, it can be seen that the supply agent speed u ₁ has a peak at a certain value.
From (7-1), the relationship between the supply part agent speed u ₁ and the stirring part agent speed u ₂ at the peak position is obtained as in the following formula (8).
From FIG. 10, when the moving speed of the developer in the supply conveyance path 9 and the movement speed of the developer in the stirring conveyance path 10 are in the relationship of the formula (8), the unit length of the agent in the downstream portion of the supply conveyance path 9 It turns out that the per weight takes a peak.

FIG. 11 is a graph obtained by projecting FIG. 10 by xy. Curve corresponds to intersection line between the plane of the graph and z = m _Z shown in FIG. 10. From this graph, by satisfying (region 1) where u ₁ <u ₂ , further, the agent speed of the supply unit / stirring unit is a value satisfying the relationship of equation (8), that is, the region in FIG. If it is set to 2, the agent supply condition to the developing roller can be satisfied while suppressing the supply / stirring part agent speed.
By setting the area 2 as the range, the weight of the agent in the downstream portion of the supply conveyance path 9 can be increased particularly effectively while minimizing the speed of the developer among the conditions of the formula (1). The supply is stable. Therefore, a stable developer amount can always be supplied to the developing roller 5 at a low rotation speed of the screw, and an image having a stable image density can be obtained over a long period of time. Further, the life of the developer and screw bearing can be extended by reducing the screw rotation speed.

Next, a method for measuring the developer conveyance speed in the supply conveyance path 9 and the stirring 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.

As the developer weight decreases downstream of the supply conveyance path 9, the height of the developer decreases. For this reason, the developer does not exist in the range where the magnetic force of the developing roller 5 reaches downstream of the supply conveyance path 9, and the pumping is likely to be exhausted.
Therefore, the developer surface in the supply conveyance path 9 may be inclined with respect to the horizontal plane so that the developing roller 5 side becomes higher.
FIG. 13 is a diagram illustrating the relationship between the positions of the developing roller 5 and the supply screw 8 and the rotation direction of the supply screw 8. FIG. 13A shows a configuration in which the supply screw 8 rotates such that the wing portion on the developing roller 5 side from the rotation shaft portion of the supply screw 8 is directed downward from above. FIG. 13B shows a configuration in which the supply screw 8 rotates such that the wing portion on the developing roller 5 side from the rotation shaft portion of the supply screw 8 is directed upward from below.

Without changing the other conditions, only the rotation direction of the supply screw 8 was changed from FIG. 13A to FIG. 13B. As a result, the minimum required for pumping from the supply conveyance path 9 to the developing roller 5 It was confirmed by an experiment that the developer weight in the downstream portion of the simple supply conveyance path 9 is reduced by about 70%.
The developer conveyance speed in the supply conveyance path 9 and the agitation conveyance path 10 is set to an appropriate value, and the rotation direction of the supply screw 8 is set so that the blade on the developing roller 5 side is upward from below as shown in FIG. By setting so as to go to, the supply of the developer to the developing roller 5 can be made more stable.

In this way, by inclining the developer surface of the developer closer to the developing roller 5 side than the horizontal plane, the developer is lifted to the range where the magnetic force of the developing roller 5 reaches even in the state where the developer is small in the downstream portion of the supply conveyance path 9. Therefore, the ability to pump up to the developing roller 5 is improved, so that the agent can be pumped up stably.
Further, the ability to pump up even if there is little developer downstream of the supply conveyance path 9 increases, so that it is not necessary to convey excess agent in addition to the supply amount to the developing roller 5, and efficient conveyance can be performed. become able to. Thereby, the rotation speed of the supply screw 8 and the stirring screw 11 can be reduced, and the stress on the developer can be reduced.

[Example 1]
In Example 1, the supply screw 8 and the stirring screw 11 were designed as follows in order to set the stirring part agent speed and the supply part agent speed to the conditions of the plot A in FIG. 11 as an example.
Supply screw Axial length: 320 [mm], wing diameter 25 [mm], shaft diameter 5 [mm], pitch width: 12 [mm], rotation speed: 300 [rpm]
・ Agitating screw Axial length: 320 [mm], wing diameter 25 [mm], shaft diameter 5 [mm], pitch width: 20 [mm], rotation speed: 300 [rpm]

Thus, in Example 1, the pitch width of the supply screw 8 is made narrow by making the pitch width of the screw different between the supply screw 8 and the stirring screw 11.
By making the pitch width of the supply screw 8 narrower than the pitch width of the stirring screw 11, U ₁ <U ₂ can be satisfied for the supply part agent speed U ₁ and the stirring part agent speed U ₂ . Further, by reducing the pitch interval of the supply screws 8, it is possible to reduce the screw pitch unevenness on the developing roller 5.

[Example 2]
As Example 1, the supply screw 8 and the stirring screw 11 were designed as follows in order to set the stirring part agent speed and the supply part agent speed as an example to the conditions of plot A in FIG.
Supply screw Axial length: 320 [mm], wing diameter 25 [mm], shaft diameter 5 [mm], pitch width: 20 [mm], rotation speed: 180 [rpm]
・ Agitating screw Axial length: 320 [mm], wing diameter 25 [mm], shaft diameter 5 [mm], pitch width: 20 [mm], rotation speed: 300 [rpm]

As described above, in the second embodiment, the supply screw 8 and the stirring screw 11 are made different in the rotation speed of the screw, so that the rotation speed of the supply screw 8 is slowed down.
By making the rotation speed of the supply screw 8 smaller than the rotation speed of the stirring screw 11, U ₁ <U ₂ can be satisfied with respect to the supply part agent speed U ₁ and the stirring part agent speed U ₂ . Further, in Example 1, different screws were used for the supply screw and the stirring screw in order to vary the pitch width, but in Example 2, the design of the screw can be unified with the supply screw and the stirring screw, Production costs can be reduced.

As described above, in the printer unit 100 according to the first embodiment, the developing device 4 including the three developer transport paths, that is, the recovery transport path 7, the supply transport path 9, and the agitation transport path 10, and FIG. The developer moving speed in the direction indicated by the arrow 136 in FIG. 9 is the supply agent speed U ₁ [m / s], and the developer in the direction indicated by the arrow 137 in FIG. 6 and FIG. When the conveying speed is set to the stirring part agent speed U ₂ [m / s], the relationship U ₁ <U ₂ is satisfied. From m ₁ u ₁ = m ₂ u ₂ , m ₁ > m ₂ , and the amount of developer in the supply conveyance path 9 can be increased without increasing the amount of developer in the agitation conveyance path 10. Therefore, the developer capacity in the supply conveyance path 9 can be effectively increased, and the developer depletion in the supply conveyance path 9 can be prevented. Thus, a stable developer amount can be always supplied to the developing roller 5, and an image with a stable image density can be obtained over a long period of time. Further, since the developer capacity in the stirring conveyance path 10 can be reduced, the screw filling rate of the developer can be lowered without increasing the diameter of the stirring screw 11, and the replenishment toner can be sufficiently stirred. . Further, the number of rotations of the screw can be reduced, and the life of the developer and the screw bearing can be extended.
Moreover, by making the pitch width of the supply screw 8 narrower than the pitch width of the stirring screw 11, U ₁ <U ₂ can be satisfied with respect to the supply part agent speed U ₁ and the stirring part agent speed U ₂ . In particular, the screw pitch unevenness on the developing roller 5 can be reduced by shortening the pitch interval of the supply screws 8.
Moreover, by making the rotation speed of the supply screw 8 smaller than the rotation speed of the stirring screw 11, U ₁ <U ₂ can be satisfied with respect to the supply part agent speed U ₁ and the stirring part agent speed U ₂ . In particular, since the supply screw 8 and the stirring screw 11 have the same shape and the desired developer conveyance speed can be obtained by adjusting the rotation speed, the design of the screw can be unified with the supply screw and the stirring screw. Production costs can be reduced.
In addition, by setting the supply agent speed u ₁ and the agitation agent speed u ₂ so as to satisfy the expression (8), the developer speed is minimized in the condition of the expression (1). Thus, the developer weight on the downstream side of the supply conveyance path 9 can be increased particularly effectively, and the supply of the developer to the developing roller 5 is stable. Therefore, a stable developer amount can always be supplied to the developing roller 5 at a low rotation speed of the screw, and an image having a stable image density can be obtained over a long period of time. In addition, the life of the developer and the screw bearing can be extended by reducing the screw rotation speed.
Further, the rotation direction of the supply screw 8 is set so that the blade on the developing roller 5 side is directed upward from below, so that the developer surface is inclined closer to the developing roller 5 side than the horizontal plane, and the supply conveyance path 9. Even in a state where there is little developer in the downstream portion, the developer can be lifted to the range where the magnetic force of the developing roller 5 can reach, and the ability to pump to the developing roller 5 is improved, so that the agent can be pumped more stably. Furthermore, the ability to pump up even if there is little developer downstream of the supply conveyance path 9 increases, so that it is not necessary to convey excess agent in addition to the supply amount to the developing roller 5, and efficient conveyance can be performed. become able to. Thereby, the rotation speed of the supply screw 8 and the stirring screw 11 can be reduced, and the stress on the developer can be reduced.
Further, the collection conveyance path 7 is provided below the developing roller 5, and the three developer conveyance paths of the collection conveyance path 7, the supply conveyance path 9, and the stirring conveyance path 10 are provided at substantially the same height, so that the developer circulation Since the height difference can be eliminated, the stress on the developer can be reduced and the life of the developer can be extended. Further, since the collection conveyance path 7 is located immediately below the developing roller 5, the collection efficiency of the developer after development is improved, the image density is stabilized, and an image with a stable image density can be obtained over a long period of time. it can.
Further, by arranging the screw apex 14, which is the uppermost part of the supply screw 8, below the rotation center 15 of the developing roller 5, the developer's own weight affects the amount of developer supplied to the developing roller 5. However, the magnitude of the magnetic force contributes to the developer supply amount. As a result, the developer is reliably supplied from the upper part of the developer conveyed in the supply conveyance path 9, so that even if the developer in the supply conveyance path 9 is not uniform in the conveyance direction of the supply conveyance screw 8, the developing roller 5 can be supplied with an appropriate amount of developer. In particular, an angle formed by a plane passing through the rotation center axis of the developing roller 5 and the uppermost portion of the supply screw 8 and a horizontal plane passing through the rotation center axis of the developing roller 5 is within a range of 10 [°] to 40 [°]. By doing so, a stable developer can be supplied.
In addition, since the printer unit 100 has a double-sided one-pass configuration, it is possible to obtain image quality with a stable image density over a long period of time, so there is no work stoppage time due to a problem such as a decrease in image density, and the productivity is higher. An image forming apparatus can be obtained.

[Modification 1]
In the first embodiment, the supply unit speed U ₁ and the stirring unit speed U ₂ are set to satisfy U ₁ <U ₂ in the developing device 4 in which the three developer transport paths illustrated in FIG. 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, and therefore the supply part agent speed U ₁ and the agitation part 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. 20 is set to satisfy U ₁ <U ₂ will be described.

In the developing device 4 of FIG. 20, the developer is supplied to the developing roller 5 adjacent to the supply screw 8 disposed in the supply conveyance path 9, and the developed developer is a collection conveyance path disposed 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. When the developer is lifted obliquely upward in the agitation transport path 10, the supply part agent speed U ₁ is made smaller than the agitation part agent speed U _2, and a sufficient amount of developer is accommodated in the supply transport path 9 while stirring. When the agent embedding ratio of the screw 11 was adjusted to about 0.6 or less, the stirring ability of the replenishing toner could be sufficiently ensured, and the agent stress was reduced.

In the developing device 4 shown in FIG. 20, since the supply conveyance path is disposed above, the problem that the developer is easily depleted in the downstream portion of the supply conveyance path 9 does not become a big problem. However, there is a problem that developer stress increases in the agitation conveyance path 10 that lifts the developer from the collection conveyance path 7 to the height of the supply conveyance path 9.
By setting U ₁ <U ₂ , the weight of the agent in the stirring and conveying path 10 can be reduced, and the embedding rate of the stirring screw 11 in the stirring and conveying path 10 with respect to the developer can be reduced. Thereby, the stress of the developer in the stirring conveyance path 10 which is a problem of the developing device 4 shown in FIG. 20 can be suppressed. Moreover, since U ₁ <U ₂ makes it possible to secure the agent height in the downstream portion of the supply conveyance path 9, it is possible to simultaneously prevent the supply depletion of the supply conveyance path 9.
In particular, the angle formed by the plane passing through the rotation center 15 and the lowest point 114 of the supply screw 8 and the horizontal plane passing through the rotation center 15 in the developing roller 5 is set in the range of -20 [°] to 20 [°]. Thus, a stable developer can be supplied from the supply conveyance path 9 to the developer.

[Embodiment 2]
In the first embodiment, a case where the moving speed of the developer in the supply conveyance path 9 is uniform in the conveyance direction has been studied. Next, as the second embodiment, a case where the supply agent speed U ₁ decreases toward the downstream side in the developer conveyance direction of the supply conveyance path 9 will be considered.
Note that the configuration other than the supply conveyance path 9, the supply screw 8, the agitation conveyance path 10, and the agitation screw 11 is the same as that of the first embodiment, and thus the description of the common parts is omitted.

If the supply unit dosage rate U ₁ in the supply conveyance path 9 was constant for axially over the upstream of the supply conveyance path 9 to the downstream, the weight of the agent at each location is reduced linearly. Therefore, unless an excess developer exceeding 100% of the screw embedding rate is supplied to the upstream side of the supply conveyance path 9, the developer is exhausted in the downstream portion. Supplying the agent excessively to the upstream side of the supply conveyance path 9 leads to stress on the agent. Therefore, it is desirable to reduce the rate of decrease in the developer weight at each location from upstream to downstream in the supply conveyance path 9.
FIG. 14 is a graph showing the relationship between the transport speeds of the three developer transport members and the developer weight at the supply transport path position. The graph (a) in FIG. 14 is a graph when the agent speed by the supply / stirring / recovery screw is 0.12 [m / s].
On the other hand, in the graph of FIG. 14B, the agent speed by the stirring / recovery screw is 0.12 [m / s], and the agent speed by the supply screw is changed from 0.12 [m / s] in the upstream part to the downstream part. Is the calculation result of the agent weight per unit length in the supply section when linearly decreasing to 0.06 [m / s].
The parameters other than the agent speed are the same in (a) and (b).
From FIG. 14, the weight of the agent per unit length in the downstream portion of the supply conveyance path is increased by reducing the agent speed of the supply screw as it goes downstream in (b) rather than (a). I understand. In addition, it can be seen that the rate of decrease in the developer weight at each location is smaller in (b) than in (a) from upstream to downstream in the supply conveyance path 9.
In addition to the configuration in which the supply part agent speed U ₁ and the stirring part agent speed U ₂ satisfy the relationship of U ₁ <U _{2 as in} the _first embodiment, the agent speed by the supply screw is reduced as it goes downstream. Thereby, the agent weight per unit length in the downstream part of a supply conveyance path can be increased further.

[Example 3]
FIG. 15 is a schematic explanatory diagram of the supply screw 8 applied to the third embodiment.
In Example 3, the supply unit dosage rate U ₁ is so small that the developer conveyance direction downstream side of the supply conveyance path 9, was designed supply screw 8 as follows.
Axial length: 320 [mm], wing diameter 25 [mm], shaft diameter 5 [mm], pitch width: 20 [mm]
Furthermore, six agitation fins 159 that are increased in width toward the downstream side are attached to the downstream side in the developer transport direction.
Image formation was performed using the supply screw 8 shown in FIG. The supply agent speed U ₁ on the upstream side of the supply conveyance path 9 was the same as the stirring part agent speed U ₂ of the agitation conveyance path 10.

By attaching these stirring fins 159, the flow of the developer was hindered, and the supply part agent speed U ₁ was continuously decreased on the downstream side. Further, the ability of the stirring fin 159 to transport the developer perpendicular to the surface increased the ability to lift a small amount of the agent on the downstream side of the supply transport path 9 to the developing roller 5. As a result, even when almost no developer remains on the downstream side of the supply conveyance path 9, the developer can be supplied to the developing roller 5 and there is no need to carry excess agent. Thereby, screw rotation speed can be reduced and agent stress and screw bearing stress can be reduced.

Above, the printer unit 100 of the embodiment 2, by the smaller as it goes the supply unit dosage rate U ₁ is the speed of the developer supply conveyance path 9 downstream of the developer from the supply conveyance path 9 to the developing roller 5 Even if it is sequentially supplied, the decrease in the height of the developer can be reduced, so that a stable developer amount can be supplied to the developing roller 5. In addition, since it is not necessary to supply an excessive amount of agent to the upstream side of the supply conveyance path 9, the agent stress is reduced. Furthermore, the agent speed in the supply conveyance path 9 and the stirring conveyance path 10 is set so that the condition of the formula (1) is simply satisfied, so that sufficient developer is conveyed downstream of the supply conveyance path 9. In this case, the difference between U ₁ and U ₂ becomes large, and the developer flow may be discontinuous at the transfer portion from the stirring conveyance path 10 to the supply conveyance path 9. The supply unit dosage rate U ₁ of the supply conveyance path 9 from upstream to be smaller toward the downstream, while preventing depletion of the developer in the supply conveyance path 9, from the stirring conveyance path 10 to the supply conveyance path 9 The agent speed at the delivery part can be continuously changed, and the stress of the agent can be reduced.
In particular, the supply screw 8 on the downstream side in the developer conveyance direction of the supply conveyance path 9 is provided with a stirring fin 159 as a fin having a plane composed of sides of the radial direction of the blade and the axial direction of the supply screw 8. The speed of the developer in the downstream portion can be reduced, and a stable developer amount can be supplied to the developing roller 5. Further, by attaching the stirring fin 159, the ability to pump the developer to the developing roller 5 is increased even when the amount of developer is small on the downstream side of the supply conveyance path 9. Therefore, it is not necessary to transport extra agent in addition to the supply amount to the developing roller 5, and efficient transport can be performed. Thereby, the rotation speed of the supply screw 8 and the stirring screw 11 can be reduced, and the stress of the developer can be reduced.

[Embodiment 3]
In the second embodiment, the case where the supply part agent speed U ₁ decreases toward the downstream side in the developer transport direction of the supply transport path 9 was examined. Next, as a third embodiment, a case where the member volume of the supply screw 8 is increased as it goes downstream in the developer conveyance direction of the supply conveyance path 9 will be considered.
Since the configuration other than the supply screw 8 is the same as that of the first embodiment, the description of the common parts is omitted.

By increasing the member volume of the supply screw 8 while keeping the radius of the wings constant as going downstream in the developer conveyance direction of the supply conveyance path 9, even when there is little developer on the downstream side of the supply conveyance path 9 Since the height of the apparent developer surface is substantially constant, the developer always exists in a range where the magnetic force of the developing roller 5 reaches, and the developing roller 5 can pump up the agent as usual. Further, the ability to pump up even if there is little developer downstream of the supply conveyance path 9 increases, so that it is not necessary to convey excess agent in addition to the supply amount to the developing roller 5, and efficient conveyance is performed. Therefore, the rotation speed of the supply screw 8 and the stirring screw 11 can be reduced, and the stress on the developer can be reduced.
Then, increases as a supply unit dosage rate U ₁ and the agitation unit dosage rate U ₂ as in the embodiment 1, in addition to the structure satisfying a relation of U 1 _{<U 2,} go to parts agent volume of the supply screw 8 in the downstream By doing so, the agent weight per unit length in the downstream part of a supply conveyance path can be increased further.

Next, a specific shape of the supply screw 8 applicable to the third embodiment will be described. FIG. 16 is a schematic explanatory diagram of a supply screw 8 applicable to the third embodiment. 16A is a schematic explanatory diagram of a supply screw 8 according to a fourth embodiment, FIG. 16B is a fifth embodiment, FIG. 16C is a sixth embodiment, and FIG. 16D is a seventh embodiment.
The supply screw shown in FIG. 16 is based on a screw having an axial length of 320 [mm], a blade diameter of 25 [mm], a shaft diameter of 5 [mm], and a pitch width of 20 [mm]. The part volume of the supply screw 8 was increased by various methods.

[Example 4]
FIG. 16A is a schematic configuration diagram of a supply screw 8 applied to the fourth embodiment. In the fourth embodiment, the member diameter of the supply screw 8 is increased by increasing the shaft diameter of the supply shaft portion 157 that is the rotation shaft portion of the supply screw 8 toward the downstream side in the developer conveyance direction of the supply conveyance path 9. Yes.
Specifically, the shaft diameter of the supply screw 8 increases from 5 [mm] on the upstream side to 15 [mm] on the downstream side as it goes downstream in the developer transport direction. It is.

[Example 5]
FIG. 16B is a schematic configuration diagram of the supply screw 8 applied to the fifth embodiment. In the fifth embodiment, the member volume of the supply screw 8 is increased by increasing the thickness of the supply blade portion 158 that is the blade portion of the supply screw 8 toward the downstream side in the developer conveyance direction of the supply conveyance path 9. .
Specifically, the thickness of the supply blade portion 158 of the supply screw 8 is increased from 1.5 [mm] on the upstream side to 4 [mm] on the downstream side as it goes downstream in the developer conveyance direction. It was what I did.

[Example 6]
FIG. 16C is a schematic configuration diagram of the supply screw 8 applied to the sixth embodiment. In the sixth embodiment, the supply blades 158 of the supply screw 8 have a plurality of strips on the downstream side of the supply conveyance path 9, and the number of strips is larger than that on the upstream side of the supply conveyance path 9, thereby reducing the member volume of the supply screw 8. It is getting bigger.
Specifically, as shown by the broken line B in the drawing of the supply screw 8, from the upstream line 1/2 to the upstream part 1/2, from the upstream between the broken lines B to C, from 1/2 to 3/4, from the double line, the broken line C From the downstream upstream, 3/4 to 4/4 on the most downstream side, the number of strips is increased toward the downstream side.

[Example 7]
FIG. 16D is a schematic configuration diagram of the supply screw 8 applied to the seventh embodiment. In Example d, the member volume of the supply screw 8 is increased by attaching two supply stirring rods 160 having a diameter of 2 [mm] outside the supply blade portion 158 of the supply screw 8.

As described above, in the printer unit 100 according to the third embodiment, the developer volume is reduced in the downstream portion of the supply conveyance path 9 by increasing the member volume of the supply screw 8 toward the downstream side of the supply conveyance path 9 in the developer conveyance direction. Even in this state, the height of the apparent developer surface is almost constant, so that the developer is always present in the range where the magnetic force of the developing roller 5 reaches, and the developing roller 5 can pump up the agent as usual. Furthermore, the ability to pump up even if there is a small amount of developer downstream of the supply conveyance path 9 increases, so that it is not necessary to convey excess agent in addition to the supply amount to the developing roller 5, and efficient conveyance is performed. Therefore, the number of rotations of the supply screw 8 and the stirring screw 11 can be reduced, and the stress on the developer can be reduced.
In particular, by continuously increasing the shaft diameter of the supply shaft portion 157 that is the rotation shaft of the supply screw 8 toward the downstream side in the developer transport direction, the volume of the supply screw 8 also increases continuously, By setting the increase amount of the shaft diameter in accordance with the supply amount of the developer, the height of the developer in the supply conveyance path 9 can be made substantially constant.
Note that it is considered that the possibility of uneven screw pitch is increased on the downstream side of the supply conveyance path 9 with a small amount of developer. In particular, by increasing the number of supply blades 158, which are the blades of the supply screw 8, toward the downstream side in the developer transport direction, the screw pitch unevenness can be reduced.

[Modification 2]
Modification 2 in which the configuration of the printer unit 100 is different will be described.
FIG. 17 is a schematic configuration diagram of the printer unit 100 according to the second modification. This is a so-called tandem configuration, which is a color system that forms an image on only one side at a time with respect to the simultaneous duplex printing shown in FIG. A schematic configuration is shown below.
The printer unit 100 which is the color image forming apparatus of FIG. 17 is called a so-called tandem method, and has a configuration in which process cartridges 220 for each color are arranged in series. The process cartridge 220 for each color is composed of a charging roller 223 that is a charging device, a developing device 4, a photosensitive member cleaning device 2, and the like with the photosensitive member 1 at the center. An exposure device 224 is disposed above the four process cartridges 220, and an intermediate transfer device 221 is disposed below. In addition, a paper transport unit 50, a paper transfer device 228, a fixing device 60, and the like are provided. In the printer unit 100, a plurality of components such as the photosensitive member 1, the charging roller 223, the developing device 4, and the photosensitive member cleaning device 2 are integrally combined as a process cartridge 220. The trough 220 is configured to be detachable from the printer unit 100 main body.
The image forming operation of the printer unit 100 shown in FIG. 17 is merely the absence of image formation on the back surface (first surface) in FIG.

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. The three-dimensional graph which shows the relationship between a supply part agent speed | rate, a stirring part agent speed | rate, and a supply part downstream agent weight. The cross section when cutting the three-dimensional graph of FIG. 10 is an XY plane. FIG. 5 is a schematic diagram of a developer speed measuring method using a magnetic permeability sensor. Explanatory drawing of the relationship between the position of a developing roller and the rotation direction of a supply roller. The graph which shows the relationship between the conveyance speed of three developer conveyance part agents, and the developer weight in a supply conveyance path position. FIG. 6 is a schematic explanatory diagram of a supply screw applied to the third embodiment. FIG. 6 is a schematic explanatory diagram of a supply screw applicable to the third embodiment. (A) is the supply screw of Example 4, (b) is the supply screw of Example 5, (c) is the supply screw of Example 6, (d) is the supply screw of Example 7. FIG. FIG. 9 is a schematic configuration diagram of a printer unit according to a second modification. 1 is a schematic configuration diagram of a developing device that has been widely used conventionally. 1 is a schematic configuration diagram of a developing device described in Patent Document 1. FIG. 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 120 Fin 121 Guide unit 122 Developer catching roller 123 Scraper 127 Toner Concentration Sensor 128 Radiation Fin 130 Toner Supply Port 131 Recovery / Supply Protrusion 132 Supply / Agitation Protrusion 133 Partition Wall 134 Partition Plate 138 Stirring Conveying Feather 139 Stirring Horizontal Transfer Paddle 140 Stirring Reverse Feeding Portion 141 For Collecting Lateral Transfer Paddle 142 Supply lateral transfer paddle 143 Transfer portion position 144 Developer pushing surface 145 Image material bulk adjusting opening 159 Stirring fin 200 Automatic image reading device 210 Recovery stirring transport path 300 Paper supply device 401 Supply recovery screw 40 2 Supply / collection conveyance path 403 Partition 404 First partition 405 Second partition

Claims (18)

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 The supply of the collected developer that has been conveyed is received, along the axial direction of the developer carrier, and in the direction opposite to the developer supply and conveyance 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.
In the image forming apparatus having a developing device, each of the three developer transport paths including the developer recovery transport path, the developer supply transport path, and the developer stirring transport path is partitioned by a partition member.
Transport speed of the developer moving in the developer supply transport path (hereinafter referred to as supply part speed) U ₁ , transport speed of the developer moving in the developer stirring transport path (hereinafter referred to as stirrer part) For U _{2 (} speed)
An image forming apparatus characterized by the following equation (1):
U ₁ <U ₂ (1) The image forming apparatus according to claim 1.
About the supply part agent speed U ₁ and the agitation part agent speed U ₂ ,
An image forming apparatus characterized by the following equation (2):
However, D = ρvW / 2, M = Q / W
(Ρ: pumping amount [kg / m ² ], v: developer carrying member linear velocity [m / s], W: length in developing region axial direction [m], Q: developer weight in developer supply conveyance path + development Agent weight in the agent stirring and conveying path [kg] The image forming apparatus according to claim 1 or 2,
2. The image forming apparatus according to claim _{1, wherein the} supply part agent speed U1 decreases toward the downstream side of the developer supply and conveyance path in the developer conveyance direction. The image forming apparatus according to claim 1, 2 or 3.
The image forming apparatus according to claim 1, wherein the developer surface in the developer supply / conveyance path is inclined with respect to a horizontal plane so that the developer carrier side becomes higher. The image forming apparatus according to claim 1, 2, 3, or 4.
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. An image forming apparatus, 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 image forming apparatus according to claim 5.
An image forming apparatus, wherein a pitch width of the developer supply screw is shorter than a pitch width of the developer stirring screw. The image forming apparatus according to claim 5 or 6,
The image forming apparatus according to claim 1, wherein the rotation speed of the developer supply screw is smaller than the rotation speed of the developer stirring screw. The image forming apparatus according to claim 5, 6 or 7.
A fin having a plane composed of sides of the radial direction of the blade and the axial direction of the supply screw is attached to the developer supply screw on the downstream side in the developer conveyance direction of the developer supply conveyance path. An image forming apparatus. The image forming apparatus according to claim 5, 6, 7, or 8.
An image forming apparatus, wherein the volume of the developer supply screw is increased toward the downstream side of the developer supply conveyance path in the developer conveyance direction while the radius of the blade portion of the developer supply screw remains constant. The image forming apparatus according to claim 5, 6, 7, 8, or 9.
The image forming apparatus according to claim 1, wherein an axial diameter of the rotation shaft portion of the developer supply screw increases toward a downstream side in the developer transport direction of the developer supply transport path. The image forming apparatus according to claim 5, 6, 7, 8, 9 or 10.
The image forming apparatus according to claim 1, wherein the thickness of the wing portion of the developer supply screw increases toward the downstream side in the developer transport direction of the developer supply transport path. The image forming apparatus according to claim 5, 6, 7, 8, 9, 10, or 11.
An image forming apparatus comprising: a plurality of wings on the downstream side in the developer conveyance direction of the developer supply conveyance path, wherein the number of wings is greater than that on the upstream side in the developer conveyance direction. The image forming apparatus according to claim 5, 6, 7, 8, 9, 10, 11 or 12.
The image forming apparatus, wherein the developer supply screw rotates such that the wing portion on the developer carrier side of the rotation shaft portion is directed upward from below. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13.
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 14.
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 [°]. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13.
Providing the developer recovery transport path below the developer carrier, providing the developer supply transport path at a position higher than the developer recovery transport path;
The developer stirring / conveying path is provided on the most upstream side in the developer conveying direction at substantially the same height as the developer collecting / conveying path, and the developer supply / conveying is performed on the most downstream side in the developer conveying direction of the developer stirring / conveying path. An image forming apparatus for conveying a developer to a height of a path. The image forming apparatus according to claim 16.
The lowermost part of the developer supply / conveyance member is above the lowermost part of the developer carrier, a plane passing through the rotation center axis of the developer carrier and the lowermost part of the developer supply / conveyance member, and the development An image forming apparatus, wherein an angle formed by a horizontal plane passing through the rotation center axis of the agent carrier is in a range of −20 [°] to 20 [°]. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17.
A first intermediate transfer belt for supporting a toner image formed by supplying toner to the latent image corresponding to each color formed on the latent image carrier, and a second image carrier belt; An image forming apparatus, wherein a toner image on an intermediate transfer belt is transferred to one surface of a recording member, and a toner image on a second image carrier belt is transferred to the other surface of the recording member.