JP5534487B2 - Developing device, process unit, and image forming apparatus - Google Patents

Description

  According to the present invention, a developer containing a toner and a magnetic carrier is carried by a magnetic force generated by a magnetic pole, and the developer carrying member carried on its surface and a part of the surface of the developer carrying member are passed through the opening. And a developing device having a casing exposed to the outside. Further, the present invention relates to an image forming apparatus such as a process unit using a developing device having such a configuration, a copying machine, or a printer facsimile.

  As this type of developing device, for example, the one shown in FIG. 17 is known. In the drawing, the developing device 910 includes a first agent storage portion 911, a second agent storage portion 913, and a development portion 916 inside a casing 921. The first agent storage portion 911 and the second agent storage portion 913, which are arranged so as to be aligned in the horizontal direction, each store a developer containing a toner magnetic carrier (not shown).

  A first transport screw 912 is disposed in the first agent storage unit 911. The first transport screw 912 is driven to rotate by a driving unit (not shown), thereby transporting the developer in the first agent storage unit 911 from the near side to the far side in the direction orthogonal to the drawing sheet. The developer transported to the end of the first agent storage portion 911 in the back side of the drawing is not shown provided on a partition wall 929 interposed between the first agent storage portion 911 and the second agent storage portion 913. It enters into the 2nd agent accommodating part 913 through a communicating port.

  A second transport screw 915 is disposed in the second agent storage unit 913. The second transport screw 915 is driven to rotate by a driving unit (not shown) to transport the developer from the back side to the front side in the direction orthogonal to the drawing sheet.

  The developing unit 916 is disposed obliquely above the second agent storage unit 913 so as to communicate with the second agent storage unit 913 and takes a posture parallel to the doctor blade 917 and the second transport screw 915. A developing roll 918 arranged in this manner. A developing roll 918 as a developer carrying member includes a developing sleeve 919 formed of a non-magnetic pipe that is driven to rotate counterclockwise in the drawing by a driving unit (not shown), and a magnet roll 920 that is included so as not to rotate. It is equipped with. Then, a part of the developer conveyed by the second conveying screw 915 in the second agent accommodating portion 913 is attracted to the surface of the developing sleeve 919 by the magnetic force generated by the magnet roll 920 and pumped up.

  A developing opening for exposing a part of the peripheral surface of the developing sleeve 919 to the outside is formed at a position of the developing portion 916 in the casing 921 of the developing device 910. The developing sleeve 919 is disposed so that a part of its peripheral surface is exposed to the outside of the casing 921 through the developing opening. In this exposed portion, a photosensitive region 902 as a latent image carrier is opposed to form a development region.

  The developer pumped up by the developing sleeve 919 moves with the developing sleeve 919. Then, the layer thickness is regulated when passing through the position facing the developing sleeve 919 and the doctor blade 917 facing each other with a predetermined gap. Thereafter, along with the rotation of the developing sleeve 919, the developing sleeve 919 exits the casing 921 through the developing opening and is conveyed to the developing region facing the photoreceptor 902. Then, due to the potential difference between the developing sleeve 919 to which the developing bias is applied and the electrostatic latent image on the photoreceptor 902, the toner in the developer is separated from the magnetic carrier and transferred to the electrostatic latent image on the photoreceptor 902. . As a result, the electrostatic latent image on the photoconductor 902 is developed.

  As the developing sleeve 919 rotates, the developer that has consumed toner through the development enters the casing 921 from the outside of the casing 921 through the developing opening, and then reaches a position facing the second conveying screw 913. At this facing position, the magnet roll 920 forms a repulsive magnetic field by the same magnetic poles aligned in the circumferential direction. The developer that has reached the position facing the second conveying screw 913 is separated from the surface of the developing sleeve 919 by the action of the repulsive magnetic field and returned onto the second conveying screw 913. Then, after being transported from the back side to the near side in the direction orthogonal to the drawing sheet by the second transport screw 913, it is returned into the first agent storage portion 911 through a communication port (not shown) provided in the partition wall 929. It is.

  The toner concentration of the developer in the second agent container 913 is detected by the toner concentration sensor 914. When this detection result falls below a predetermined value, a toner replenishing device (not shown) is activated to replenish toner in the first agent storage unit 911.

  In the developing device 910 having the above-described configuration, an air flow from the inside of the casing 21 to the outside of the casing 21 is generated in the vicinity of the downstream end 990 in the sleeve rotation direction in the developing opening provided in the casing 921. The toner may be scattered.

  Patent Document 1 proposes a developing device that has a configuration shown in FIG. 18 as a developing device that can suppress an air flow generated in the vicinity of the downstream end 990. In the drawing, the developing sleeve 919 rotates in the clockwise direction in the drawing. In the vicinity of the downstream end 990 in the sleeve rotation direction at the developing opening of the casing 921, an auxiliary magnetic pole Pa is disposed inside the developing sleeve 919. The developer that has entered the casing 921 from the outside of the casing 921 with the rotation of the developing sleeve 919 is raised by the magnetic force generated by the auxiliary magnetic pole Pa to form a magnetic brush. According to Japanese Patent Laid-Open No. 2004-133260, an air flow that flows from the inside of the casing 921 to the outside of the casing 921 is generated in the vicinity of the downstream end 990 as follows. That is, when the developer rises due to the magnetic force of the auxiliary magnetic pole Pa, the air interposed between the developer and the inner wall of the casing 921 is pushed toward the inner wall of the casing 921. The pushed air hits the inner wall of the casing 921. A part of the air flows from the downstream side in the rotation direction of the developing sleeve 919 toward the upstream side along the inner wall of the casing 921. This flow is assumed to be a cause of generating a jet air flow from the inside of the casing 921 to the outside of the casing 921. Moreover, in the structure shown by the same figure, it is supposed that generation | occurrence | production of an ejection airflow can be suppressed as follows. That is, in the configuration shown in the figure, the concave portion 921a is provided in the casing portion in the region where the developer rises by the magnetic force generated by the auxiliary magnetic pole Pa. The concave portion 921a extends along the rotation axis direction of the developing sleeve 919, and the air inside is formed between the end portion of the developing sleeve 919 and the side plate of the casing 921 (not shown) along the rotation axis direction. It is a pressure relief space to guide. When air intervening between the developer and the casing 921 is pushed toward the inner wall of the casing 921 due to the rising of the developer, the air enters the recess 921a. And it moves toward the side plate of the casing 921 along the sleeve rotation axis direction in the recess 921a. Thereby, generation | occurrence | production of the blowing airflow is suppressed.

  However, in this developing device, as shown in FIG. 4 of Patent Document 1, a part of the air that has entered the recess 921a is moved along the inner wall of the recess in the direction of the short side of the recess to generate an air flow. Yes. The erupting airflow cannot be completely eliminated. A predetermined gap is formed between the tip of the magnetic brush by the developer spiked by the auxiliary magnetic pole Pa and the inner wall of the concave portion 921a, and the above-mentioned uncharged toner floating in the casing 921 is ejected. There is a risk of being caught in the air current and scattered outside the casing 921.

  Further, the present inventors generate toner scattering near the downstream end 990 even when the tip of the magnetic brush formed by the magnetic force generated by the auxiliary magnetic pole Pa and the inner wall of the casing 921 are in contact with each other. This was confirmed by experiments. In the developing device used in this experiment, a concave portion is not formed at a location facing the magnetic brush in the casing 921, but this magnetic brush contacts the inner wall of the casing 921, so that the casing 921 is near the downstream end 990. The inside and outside of the door are separated. Observation of the vicinity of the magnetic brush while driving the developing device having such a configuration reveals that the air in the casing 921 and the floating toner that is poorly charged pass through a minute gap between the magnetic carriers in the contact magnetic brush and are ejected outside the casing 921. I found out. That is, even if the space inside and outside the casing 921 is partitioned by the magnetic brush that contacts the casing inner wall 921, the floating toner in the casing 921 passes through the minute gaps between the magnetic carrier particles of the magnetic brush and is scattered outside the casing 921. It will let you.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device, a process unit, and an image forming device that can suppress the occurrence of toner scattering near the downstream end of the developing opening. Is to provide a device.

In order to achieve the above object, the invention of claim 1 is a development comprising a plurality of magnetic poles and carrying a developer containing toner and a magnetic carrier on its moving surface by a magnetic force generated by the magnetic poles. A developer carrier, a casing that encloses the developer carrier and exposes a part of the surface of the developer carrier to the outside through its own opening, and the opening of the surface of the developer carrier. At a location downstream of the exposed portion exposed to the outside of the casing in the direction of surface movement of the developer carrying member and a location where the developer carried outside the casing continues to be carried as it is. An opposing member facing a certain agent carrying maintenance location through a gap, and the developer carrying the developer in a direction orthogonal to the surface moving direction along the surface of the developer carrying member. the body's In the developing apparatus comprising a supply member for supplying the surface, a first protrusion protruding toward the developer carrying member, a position adjacent the downstream side of the surface moving direction with respect to the first convex portion And a first recess recessed from the first protrusion and a position adjacent to the first recess on the downstream side in the surface movement direction and projecting toward the developer carrying member from the first recess. A second convex portion, a second concave portion that is recessed from the second convex portion at a position adjacent to the second convex portion on the downstream side in the surface movement direction, and the second concave portion. A third protrusion projecting from the second recess toward the developer carrying member at a position adjacent to the downstream side in the surface movement direction is provided on the opposing member, and the first protrusion, the second The length of the convex part in the orthogonal direction is increased in the order of the convex part and the third convex part .
According to a second aspect of the present invention, in the developing device of the first aspect, as part of the plurality of magnetic poles, a magnetic field is formed on the agent-carrying / maintaining portion so as to convey the developer at the agent-carrying / maintaining portion. At least two transporting magnetic poles arranged side by side in the surface movement direction, and the developer in the first gap formed between the first convex portion and the developer carrier is moved to the surface of the developer carrier. Accordingly, when entering the second gap formed between the first recess and the developer carrier, the surface movement direction of the at least two of the transport magnetic poles is more than that of the other transport magnetic poles. The developer is caused to rise in the space of the second gap by the magnetic force generated by the upstream magnetic pole, which is a transport magnetic pole located on the upstream side, and is formed between the second convex portion and the developer carrier. the third developer in the gap, the surface movement of the developer carrying member that With it, the when to enter the fourth gap formed between the second recess and the developer carrying member, the magnetic force than the upstream-side magnetic pole is a conveying pole located on the downstream side of the downstream-side magnetic pole it is characterized in that so as to rise the developer in the space of the fourth gap by.
According to a third aspect of the present invention, in the developing device of the second aspect , the pressure of the developer that is in contact with the facing member in the third gap is brought into contact with the facing member in the first gap. It is characterized in that it is larger than the pressure of the developer.
According to a fourth aspect of the present invention, in the developing device of the second aspect , the density of the developer that is in contact with the opposing member in the third gap is set to be in contact with the opposing member in the first gap. The density of the developer is higher than that of the developer.
According to a fifth aspect of the present invention, in the developing device of the third or fourth aspect, the third gap is made smaller than the first gap.
The invention of claim 6, in any of the developing apparatus of claims 2 to 5, among the entire area of the orthogonal direction in the region opposed to the upper Symbol downstream pole and the opposing member, developing in accordance with at least the feed member While the third gap is formed in the region of the upstream end in the agent transport direction, the region of the downstream end in the developer transport direction out of the entire region is raised by the magnetic force generated by the downstream magnetic pole. A non-contact area where the developer and the opposing member are not brought into contact with each other is characterized in that it is a feature .
Also, the invention of claim 7, in any of the developing apparatus of claims 2 to 6, respectively, for the first protrusion and the second protrusion, the downstream side in the surface movement direction of the at least those of the developer carrying member The end portion is brought into contact with the developer that is spiked on the surface of the developer carrying member.
The invention according to claim 8 is the developing device according to claim 7 , wherein at least one of the first convex portion and the second convex portion is formed on the surface facing the developer carrier. The curved surface is curved along the peripheral surface of the agent carrier.
According to a ninth aspect of the present invention, there is provided the developing device according to any one of the first to eighth aspects, wherein the casing is provided with a ventilation hole that allows ventilation inside and outside the casing, and the ventilation passage through the ventilation hole is provided. And a filter for capturing toner is provided.
According to a tenth aspect of the present invention, in the developing device according to any one of the first to ninth aspects, an inner wall of the casing is used as the facing member.
The invention of claim 11 holds at least a latent image carrier that carries a latent image and a developing means that develops the latent image carried on the latent image carrier as a single unit on a common holder. in the process unit that integrally detachable from the allowed by the image forming apparatus is, as the developing means, is characterized in that using any of the developing apparatus of claims 1 to 1 0.
According to a twelfth aspect of the present invention, there is provided an image forming apparatus including a latent image carrier that carries a latent image and a developing unit that develops the latent image carried on the latent image carrier. it is characterized in that using either of the developing device of claim 1 1 0.
The invention of claim 13 is an image forming apparatus according to claim 1 2, as the developing device, used as a plurality of developing the different color toners to the latent image, and that their developing devices Any one of the developing devices according to any one of claims 1 to 9 is characterized.
The invention of claim 14 is an image forming apparatus according to claim 1 2 or 1 3, characterized by using as the toner, an average circularity of 0.93 or more, not more than 1.00, the It is what.
The invention of claim 15 is a one of the image forming apparatus according to claim 1 2 to 1 4, as the toner, a polyester prepolymer having a functional group containing at least nitrogen atom, a polyester, coloring A toner material liquid in which a tax and a release accelerator are dispersed is obtained by crosslinking and extending in an aqueous medium.
The invention of claim 16 is a one of the image forming apparatus according to claim 1 2 to 1 5, as the toner shape factor SF-1 of 100 or more and 180 or less, and a shape factor SF -2 is 100 or more and 180 or less.

In these inventions, by generating a suction air flow from the outside of the casing to the inside of the casing through the first gap formed between the first convex portion and the developer carrier, on the contrary, from the inside of the casing. Compared to the conventional apparatus that generates a jet airflow toward the outside of the casing, it is possible to suppress the occurrence of toner scattering near the downstream end of the developing opening.

1 is a schematic configuration diagram showing a printer according to a reference form. FIG. 3 is an enlarged configuration diagram illustrating a process unit for Y of the printer. FIG. 3 is an enlarged configuration diagram showing a developing device of the process unit. The elements on larger scale which show the upper wall and the developing roll of the casing of the developing device on an enlarged scale. The expansion perspective view which shows the upper wall in the casing of the developing device for Y of the printer which concerns on a 1st reference example. The longitudinal cross-sectional view which shows a wall same as the above. FIG. 3 is a side view showing the developing device as viewed from the entire longitudinal direction. The longitudinal cross-sectional view which shows the upper wall of the casing in the image development apparatus for Y of the printer which concerns on a 2nd reference example. Enlarged view showing a developing device for Y in a printer according to the embodiment. The elements on larger scale which show the upper wall of the casing of the image development apparatus, and the image development roll. FIG. 3 is a side view showing the developing device as viewed from the entire longitudinal direction. FIG. 9 is an enlarged configuration diagram illustrating a developing device for Y of a printer according to a third reference example. The elements on larger scale which show the upper wall of the casing of the image development apparatus, and the image development roll. The side view which showed from the direction which looks at the developing device in the printer concerning the 3rd reference example in the whole area of a longitudinal direction. The schematic diagram for demonstrating shape factor SF-1. The schematic diagram for demonstrating shape liquid number SF-2. The expanded block diagram which shows the conventional image development apparatus. FIG. 9 is a partially enlarged view showing a casing upper wall and a developing roll in the developing device described in Patent Document 1.

Hereinafter, as an image forming apparatus to which the present invention is applied , before describing an embodiment of an electrophotographic printer (hereinafter simply referred to as a printer), a printer according to a reference embodiment that is helpful in understanding the present invention will be described. Explain .
First, the basic configuration of the printer according to the reference embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a printer according to a reference embodiment. The printer shown in the figure includes four process units 1Y, 1M, 1C, and 1K for yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K) as process units. These use Y, M, C, and K toners of different colors as image forming substances for forming an image, but the other configurations are the same. Taking a process unit 1Y for generating a Y toner image as an example, as shown in FIG. 2, this includes a photoreceptor 2Y, a charging device 3Y, a drum cleaning device 5Y, a developing device 10Y, and the like. Each of these devices and the photoconductor 2Y are held by a common holding body (not shown) and are integrally attached to and detached from the printer main body as one unit.

  The charging device 3Y uniformly charges the surface of the photoreceptor 2Y that is driven to rotate in the clockwise direction in the drawing by a driving unit (not shown). The charging device 3Y includes a charging roller 4Y, a photosensitive member 2Y, and a charging roller 4Y that are driven counterclockwise in the drawing while a charging roller 4Y that is driven counterclockwise in the drawing is brought close to the photosensitive member 2Y. Causes a discharge during As a result, the surface of the photoreceptor 2Y is uniformly charged to a negative polarity. Instead of the charging roller 4Y, a roller that contacts a charging brush may be used. Further, a device that uniformly charges the photosensitive member 2Y by a charger method, such as a scorotron charger, may be used.

  The surface of the photoreceptor 2Y uniformly charged by the charging device 3Y is exposed and scanned by a laser beam emitted from an optical writing unit described later, and carries a Y electrostatic latent image.

  The developing device 10Y as developing means includes a first agent accommodating portion 11Y, a second agent accommodating portion 13Y, and a developing portion 16Y inside the casing 21Y. The first agent storage portion 11Y and the second agent storage portion 13Y arranged so as to be aligned in the horizontal direction store a developer (not shown) containing a negatively chargeable Y toner and a magnetic carrier, respectively. Yes.

  A first transport screw 12Y is disposed in the first agent storage unit 11Y. The first transport screw 12Y is driven to rotate by a driving unit (not shown), so that the developer in the first agent storage unit 11Y is transported from the back side to the front side in the direction perpendicular to the drawing sheet. And it penetrates into the 2nd agent accommodating part 13Y through the communication port which is not illustrated provided in the partition wall 29Y between the 1st agent accommodating part 11Y and the 2nd agent accommodating part 13Y.

  The second agent storage unit 13Y includes a toner concentration sensor (hereinafter referred to as a T sensor) 14Y formed of a magnetic permeability sensor, a second transport screw 15Y, and the like. The second transport screw 15Y is driven to rotate by a driving unit (not shown), thereby transporting the developer from the back side to the front side in the drawing. At this time, the toner density is detected by the T sensor 14Y.

  The developing unit 16Y is disposed so as to communicate with the second agent storage unit 13Y obliquely above the second agent storage unit 13Y, and takes a posture parallel to the doctor blade 17Y and the second transport screw 15Y. The developing roll 18Y and the like are arranged as described above. The developing roll 18Y includes a developing sleeve 19Y made of a non-magnetic pipe that is driven to rotate counterclockwise in the drawing by a driving means (not shown), and a magnet roll 20Y that is included so as not to rotate. Yes. Then, a part of the developer conveyed by the second conveying screw 15Y in the second agent accommodating portion 13Y is attracted to the surface of the developing sleeve 19Y by the magnetic force generated by the magnet roll 20Y.

  A developing opening for exposing a part of the peripheral surface of the developing sleeve 19Y to the outside is formed at a position of the developing portion 16Y in the casing 21Y. The developing sleeve 19Y is disposed so that a part of its peripheral surface passes through the developing opening and is exposed outside the casing 21Y.

  The developer pumped up by the developing sleeve 19Y moves with the developing sleeve 19Y. Then, the layer thickness is regulated when passing the position where the developing sleeve 19Y and the doctor blade 17Y facing each other with a predetermined gap are passed. Thereafter, along with the rotation of the developing sleeve 19Y, the developing sleeve 19Y exits the casing 21Y through the developing opening and is conveyed to the developing area facing the photoreceptor 2Y. In this development area, the Y toner in the developer is separated from the magnetic carrier by a potential difference (development potential) between the development sleeve 19Y to which a development bias is applied by a power source (not shown) and the electrostatic latent image on the photoreceptor 2Y. It leaves and adheres to the electrostatic latent image on the photoreceptor 2Y. Thereby, the electrostatic latent image on the photoreceptor 2Y is developed as a Y toner image.

  The developer that has consumed Y toner by the development enters the casing 21Y from the outside of the casing 21 through the developing opening as the developing sleeve 19Y rotates, and then in the region facing the second conveying screw 13Y in the developing sleeve 19Y. Is removed from the surface and returned onto the second conveying screw 13Y. And it is conveyed by the 2nd conveyance screw 13Y toward the back side from the near side in the direction which intersects perpendicularly in the figure paper surface. Further, the agitation is repeated during the conveyance, and the movement of being pumped up again to the developing sleeve and used for development is repeated. Thereafter, when it reaches the front end in the direction orthogonal to the drawing sheet surface, it returns to the first agent storage portion 11Y through a communication port (not shown) provided in the partition wall 29Y.

  The result of detecting the magnetic permeability of the developer by the T sensor 14Y is sent as a voltage signal to a control unit (not shown). Since the magnetic permeability of the developer has a correlation with the Y toner density of the developer, the T sensor 14Y outputs a voltage having a value corresponding to the Y toner density. A control unit (not shown) of the printer includes data storage means such as a RAM, in which Y Vtref, which is a target value of the output voltage from the T sensor 14Y, and M, mounted on other developing devices. Data of M Vtref, C Vtref, and K Vtref, which are target values of output voltages from the C and K T sensors, are stored. For the Y developing device 10Y, the value of the output voltage from the T sensor 14Y is compared with the Y Vtref, and the Y toner supply device (not shown) is driven for a time corresponding to the comparison result. With this driving, an appropriate amount of Y toner is supplied to the developer whose Y toner density has been reduced by consumption of Y toner accompanying development in the first agent storage portion 11Y. For this reason, the Y toner concentration of the developer in the second agent container 13Y is maintained within a predetermined range. Similar toner supply control is performed for the developers in the developing devices of the process units (1M, C, K) for other colors.

  The Y toner image formed on the photoreceptor 2Y is primarily transferred onto the front surface of a first intermediate transfer belt 31 described later.

  The drum cleaning device 5Y of the process unit 1Y includes a lubricant application brush roller 6Y, a solid lubricant 7Y made of zinc stearate, a cleaning blade 8Y, a recovery screw 9Y, and the like. The solid lubricant 7Y is in contact with the lubricant application brush roller 6Y at a predetermined pressure while being urged toward the lubricant application brush roller 6Y by a spring (not shown). Further, the lubricant application brush roller 6Y rotates between the solid lubricant 7Y and the photoreceptor 2Y while being in contact with both. Then, the lubricant powder scraped from the solid lubricant 7Y is applied to the surface of the photoreceptor 2Y. Thereby, the adhesion amount between the photoreceptor 2Y and the Y toner is weakened.

  While the cleaning blade 9Y is cantilevered by the casing of the drum cleaning device 5Y, the edge on the free end is brought into contact with the surface of the photoreceptor 2Y. Then, untransferred toner remaining on the surface of the photoreceptor 2Y without being primarily transferred from the photoreceptor 2Y to the intermediate transfer belt 31 in the above-described primary transfer step is scraped off from the surface of the photoreceptor 2Y. The transfer residual toner scraped off falls on the collecting screw 9Y, and is then conveyed from the near side to the far side in the direction orthogonal to the drawing surface as the collecting screw 9Y is driven to rotate. Then, the toner is discharged from the developing device 10Y and collected in a waste toner container (not shown).

  In FIG. 1 described above, in the process units 1M, C, and K for other colors, M, C, and K toner images are similarly formed on the photoreceptors 2M, C, and K, and the intermediate transfer belt 31 is formed. Primary transfer is performed on the front surface. As a result, a four-color superimposed toner image is formed on the front surface of the intermediate transfer belt 31.

  An optical writing unit 80 is disposed below the process units 1Y, M, C, and K in the drawing. The optical writing unit 80 serving as a latent image forming unit irradiates the photoconductors 2Y, M, C, and K of the process units 1Y, M, C, and K with laser light L emitted based on the image information. As a result, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 2Y, M, C, and K. The optical writing unit 80 deflects the laser light L emitted from the light source by the polygon mirror 81 that is rotationally driven by a motor, and passes through the photoconductors 2Y, M, C, and K via a plurality of optical lenses and mirrors. Is irradiated. In place of such a configuration, an optical scanning device using an LDE array may be employed.

  A first paper feed cassette 85 and a second paper feed cassette 86 are disposed below the optical writing unit 80 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of recording papers P as recording members are accommodated in a state of a bundle of recording papers. The top recording paper P includes a first paper feed roller 85a, The second paper feed rollers 86a are in contact with each other. When the first paper feed roller 85a is driven to rotate counterclockwise in the figure by a driving means (not shown), the uppermost recording paper P in the first paper feed cassette 85 is vertically oriented on the right side of the cassette in the figure. The paper is discharged toward the paper feed path 33 arranged so as to extend. Further, when the second paper feed roller 86 a is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost recording paper P in the second paper feed cassette 86 is directed toward the paper feed path 87. Discharged. A plurality of conveying roller pairs 88 are disposed in the sheet feeding path 87, and the recording sheet P fed into the sheet feeding path 87 is sandwiched between the rollers of the conveying roller pair 88 while being fed between the sheet feeding paths 87. 87 is conveyed from the lower side to the upper side in the figure.

  A registration roller pair 89 is disposed at the end of the paper feed path 88. The registration roller pair 89 temporarily stops the rotation of both rollers as soon as the recording paper P sent from the conveying roller pair 88 is sandwiched between the rollers. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above each of the process units 1Y, 1M, 1C, and 1K, a transfer unit 30 that is endlessly moved counterclockwise in the drawing while an intermediate transfer belt 31 that is an endless moving body is stretched is disposed. The transfer unit 30 serving as a transfer unit includes a belt cleaning unit 32 in addition to the intermediate transfer belt 31. The four primary transfer rollers 33Y, 33M, 33C, 33K, the secondary transfer upstream roller 34, the driving roller 35, and the cleaning backup roller 36 that stretch the intermediate transfer belt 31 inside the loop of the endless intermediate transfer belt 31 are also provided. And a tension roller 37. Further, a secondary transfer roller that forms a secondary transfer nip by contacting the belt front surface while sandwiching the intermediate transfer belt 31 between the outer side of the intermediate transfer belt 31 and the driving roller 35 inside the loop. 38.

  The intermediate transfer belt 31 is moved endlessly in the counterclockwise direction in the figure by the rotational drive of the drive roller 35. The four primary transfer rollers 33Y, 33M, 33C, and 33K described above sandwich the intermediate transfer belt 31 that is moved endlessly in this manner from the photoreceptors 2Y, 2M, 2C, and 2K, respectively, so that the primary transfer nips are formed. Forming. Then, a primary transfer bias having a polarity (for example, plus) opposite to that of the toner is applied to the back surface (loop inner peripheral surface) of the intermediate transfer belt 31. As the intermediate transfer belt 31 passes through the primary transfer nips for Y, M, C, and K sequentially along with the endless movement, the intermediate transfer belt 31 is placed on the photoreceptor 2Y, M, C, and K on the front surface. The Y, M, C, and K toner images are superimposed and primarily transferred to form a four-color superimposed toner image.

  The registration roller pair 89 described above feeds the recording paper P sandwiched between the rollers toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 31. The four-color superimposed toner image on the intermediate transfer belt 31 is recorded on the recording paper in the secondary transfer nip due to the effect of the secondary transfer electric field formed between the secondary transfer roller 38 and the driving roller 35 and the nip pressure. Secondary transfer is performed to P at once. Then, combined with the white color of the recording paper P, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 31 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 32. The belt cleaning unit 32 has a cleaning blade 32a in contact with the front surface of the intermediate transfer belt 31, thereby scraping off and removing the transfer residual toner on the belt.

  A fixing unit 40 is disposed above the secondary transfer nip in the drawing. The fixing unit 40 includes a pressure heating roller 41 that includes a heat source such as a halogen lamp, and a fixing belt unit 42. The fixing belt unit 42 includes a fixing belt 44, a heating roller 43 containing a heat source such as a halogen lamp, a tension roller 45, a driving roller 46, a temperature sensor (not shown), and the like. Then, the endless fixing belt 44 is moved endlessly in the counterclockwise direction in the drawing while being stretched by the heating roller 43, the tension roller 45 and the driving roller 46. In the process of endless movement, the fixing belt 44 is heated from the back side by the heating roller 43. A pressure heating roller 41 that is driven to rotate in the clockwise direction in the drawing is in contact with the surface of the fixing belt 44 that is heated in this manner from the front side. Thus, a fixing nip where the pressure heating roller 41 and the fixing belt 44 abut is formed.

  Outside the loop of the fixing belt 44, a temperature sensor (not shown) is disposed so as to face the front surface of the fixing belt 44 with a predetermined gap, and the fixing belt 44 just before entering the fixing nip. Detect surface temperature. This detection result is sent to a fixing power supply circuit (not shown). The fixing power supply circuit performs on / off control of power supply to the heat source included in the heating roller 43 and the heat source included in the pressure heating roller 41 based on the detection result of the temperature sensor. As a result, the surface temperature of the fixing belt 44 is maintained at about 140 [°].

  The recording paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 31 and then fed into the fixing unit 40. Then, in the process of being conveyed from the lower side to the upper side in the figure while being sandwiched between the fixing nips in the fixing unit 40, the full-color toner image is fixed by being heated or pressed by the fixing belt 44.

  The recording paper P subjected to the fixing process in this manner is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 50. A stack unit 51 is formed on the top surface of the printer body. The recording paper P discharged to the outside by the discharge roller pair 50 is sequentially stacked on the stack unit 51.

  Above the transfer unit 30, four toner cartridges 52 Y, M, C, and K that store Y, M, C, and K toners are disposed. The Y, M, C, and K toners in the toner cartridges 52Y, 52M, 52C, and 52K are appropriately supplied to the developing devices 10Y, 10M, 10C, and 10K of the process units 1Y, 1M, 1C, and 1K. These toner cartridges 52Y, 52M, 52C, 52K are detachable from the printer main body independently of the process units 1Y, 1M, 1C, and 1K.

Next, a characteristic configuration of the printer will be described.
FIG. 3 is an enlarged configuration diagram illustrating the developing device 10Y for Y. In the figure, the magnet roll 20Y has five magnetic poles P1 to P5. P1 is a developing magnetic pole for causing the developer on the surface of the developing sleeve 19Y to rise in the developing region. The other magnetic poles are arranged in the order of P2, P3, P4, and P5 in the counterclockwise direction from the developing magnetic pole P1. P5 is a pumping magnetic pole for drawing the developer transported by the second transporting screw 15Y and pumping it to the rotating developing sleeve 19Y. As described above, in the illustrated developing device 10y, the developer on the second conveying screw 15Y is supplied to a portion of the peripheral surface of the developing sleeve 19Y facing the pumping magnetic pole P5.

  The agent separation magnetic pole P4 adjacent to the pumping magnetic pole P5 on the upstream side in the sleeve rotation direction has the same polarity as the pumping magnetic pole P5, and forms a repulsive magnetic field with the pumping magnetic pole P5. When the developer on the surface of the developing sleeve 19Y tries to enter the position facing the pumping magnetic pole P5 from the position facing the agent separating magnetic pole P4 by the repulsive magnetic field, the developer is separated from the surface of the sleeve and the second conveying screw 15Y. Returned to the top. As for the movement of the developer on the sleeve, the developer pumped up to the sleeve by the pumping magnetic pole P5 is carried and conveyed to the developing magnetic pole P1 along with the rotation of the sleeve and used for development, and then the magnetic force of P2 and P3. Then, it is constituted by a series of flows in which the agent separating magnetic pole P4 and the pumping magnetic pole P5 are supported up to the region where the repulsive magnetic field is generated by the rotation of the sleeve and then separated from the sleeve by the repelling magnetic field.

  Between the developing magnetic pole P1 and the agent separating magnetic pole P4, an upstream auxiliary magnetic pole P2 that is a transport magnetic pole and a downstream magnetic pole P3 that is a transport magnetic pole are disposed. The upstream magnetic pole P2 is disposed near the downstream end A of the developing opening in the sleeve rotation direction.

  The developer carried on the surface of the developing sleeve 19Y outside the casing 21Y passes through the downstream end A along with the rotation of the sleeve, and then enters the inside of the casing 21Y to reach the inner surface of the upper wall of the casing 21Y. opposite. A first convex portion B, a first concave portion C, a second convex portion D, and a second concave portion E are formed on the inner surface of the upper wall of the casing 21Y in order in the counterclockwise direction. The developer continues to be carried on the developing sleeve 19Y until it enters the casing and passes through the second recess. Therefore, on the surface of the developing sleeve 19Y, the part from the position facing the first convex part B to the position facing the second concave part E is the agent carrying and maintaining part.

  FIG. 4 is a partially enlarged view showing the upper wall of the casing 21Y and the developing roll 19Y in an enlarged manner. When the developer that has entered from the outside of the casing 21 with the rotation of the developing sleeve 19Y enters the first gap G1 formed between the first convex portion B and the developing sleeve 19Y, the upstream magnetic pole P2 Raises on the sleeve surface by the generated magnetic force. However, the first gap G1 is sized such that the developer due to the magnetic force generated by the upstream magnetic pole P2 can come into contact with the surface of the first convex portion facing the sleeve surface. For this reason, the developer that has risen in the first gap G <b> 1 is conveyed toward the downstream side in the sleeve rotation direction while being in contact with the first convex portion B.

  The first recess C is adjacent to the first protrusion B on the downstream side in the sleeve rotation direction. The second gap between the first recess C and the developing sleeve 19Y is larger than the height of the developer spike due to the upstream magnetic pole P2. For this reason, a space is formed between the developer on the developing sleeve 19Y and the first recess C in the second gap.

  The second convex portion D is adjacent to the first concave portion C on the downstream side in the sleeve rotation direction. The developer that has entered the third gap G3 between the second convex portion D and the developing sleeve 19Y rises due to the magnetic force generated by the downstream magnetic pole P3, but the third gap G3 is filled with the raised developer. The size of the second convex portion D is such that it can contact the surface facing the sleeve. For this reason, the developer that has risen in the third gap G3 is conveyed downstream in the sleeve rotation direction while being in contact with the second convex portion D.

  The second recess E is adjacent to the second protrusion D on the downstream side in the sleeve rotation direction. The fourth gap between the second recess E and the developing sleeve 19Y is larger than the height of the developer spike due to the downstream magnetic pole P3. Therefore, a space is formed between the developer on the developing sleeve 19Y and the second recess E in the fourth gap. The first convex portion B and the second convex portion D are provided at opposing casing locations while the developer continues to be carried after the developer enters the casing. The casing 21 is configured as follows. That is, on the peripheral surface of the developing sleeve 19Y, the agent carrying maintenance position described above in the region from the entry position from the outside to the inside of the casing 21 to the agent separation position for releasing the developer from the sleeve surface. It is configured so that its inner surface is opposed via a gap smaller than the surface portion at the distant position. In addition, when adopting a configuration in which the developer is not separated from the sleeve surface in the casing 21, a developer supply location may be employed instead of the “agent separation position” in the previous sentence.

  In the region where the developing sleeve 19Y and the first convex portion B face each other, the air held in the minute gap between the magnetic carriers in the developer present in the first gap is separated from the developing sleeve 19Y and the first concave portion. In the region facing C, the space in the second gap is opened. The air is again taken in between the magnetic carriers of the developer in the third gap in the region where the developing sleeve 19Y and the second convex portion D face each other. Further, in a region where the developing sleeve 19Y and the second recess E face each other, the developing sleeve 19Y is opened to a space in the fourth gap. The presence of the two concave portions, the first concave portion B and the second concave portion E, allows air to escape between the first convex portion B and the second convex portion D and on the downstream side of the second convex portion. As a result, air is smoothly taken into and released from the developer. That is, when the developer that has taken in air at the first convex portion B releases the air, if the first concave portion C exists, the pressure between the first convex portion B and the second convex portion D increases. Suppress the backflow of air to the opening side. The same applies to the second recess E.

  More specifically, the developer in the first gap G1 enters the second gap as the developing sleeve 19Y rotates while being in contact with the first convex portion B. At this time, the developer that has been limited in earing by the first recess B, which is the opposing member, does not come into contact with the first recess B and rises in the space of the second gap. At the time of this rise, the air held in the minute gaps between the carrier particles in the developer in the first gap G1 is drawn toward the second gap. Thereby, an air flow is generated from the first gap toward the second gap.

  The developer in the second gap passes through the boundary between the upstream magnetic pole P2 and the downstream magnetic pole P3 in the process of being conveyed downstream in the rotational direction as the developing sleeve 19Y rotates. In the process of being transported toward this boundary, the height of the heading is gradually reduced, and the body gradually falls. Further, in the process of transporting toward the third gap G3 from the above-mentioned border, it gradually rises due to the magnetic force generated by the downstream magnetic pole P3.

  The developer that has entered the third gap G3 is conveyed toward the downstream side in the sleeve rotation direction while contacting the second convex portion D, and then enters the fourth gap. Then, the developer that has been limited in earing by the second convex portion D, which is the opposing member, does not come into contact with the second convex portion D, and rises higher than before in the space of the fourth gap. At the time of this rise, the air held in the minute gaps between the carrier particles in the developer in the third gap G3 is drawn toward the fourth gap. Accordingly, an air flow is generated from the third gap toward the fourth gap in the vicinity of the downstream end in the sleeve rotation direction in the third gap G3. Due to the synergistic action of the airflow and the airflow from the first gap to the second gap, an airflow from the first gap to the third gap G3 is generated in the second gap. Then, in the vicinity of the first gap, a suction airflow is generated from the outside of the casing to the inside of the casing via the first gap.

  In this way, by generating a suction airflow from the outside of the casing 21Y to the inside of the casing 21Y through the first gap, on the contrary, compared to the conventional apparatus that generates a blown airflow from the inside of the casing to the outside of the casing. Thus, the occurrence of toner scattering near the downstream end of the development opening can be suppressed.

  In this printer, the magnetic forces of the upstream magnetic pole P2 and the downstream magnetic pole P3 are approximately the same. The third gap G3 is smaller than the first gap G1. The first gap G1 has such a size that the tip of the magnetic brush formed by the developer spiked by the magnetic force generated by the upstream magnetic pole P2 is in close contact with the first convex portion B. On the other hand, the third gap G3 has such a size as to strongly press the developer that is raised by the magnetic force generated by the downstream magnetic pole P3 toward the sleeve. For this reason, the pressure of the developer in the third gap G3 is larger than the pressure of the developer in the first gap G1. Then, the strength of the airflow from the third gap G3 toward the fourth gap is made larger than the strength of the airflow from the first gap G1 toward the second gap, and the first gap G1 side in the second gap. The air flow toward the third gap G3 can be reliably generated. Further, the magnetic brush is crushed more strongly in the third gap G3 than in the first gap G1, and the density of the developer is larger in the magnetic brush in the third gap G3.

  In the first gap G1 between the first convex portion B and the developing sleeve 19Y, as shown in FIG. 4, at least the downstream of the surface facing the developing sleeve 19Y in the first convex portion B in the sleeve rotating direction. The developer that is raised by the magnetic force of the upstream magnetic pole P2 is brought into contact with the side end portion. In such a configuration, in the first gap G1, immediately after entering the second gap while bringing the developer just before entering the second gap with the rotation of the developing sleeve 19Y into contact with the first protrusion B. The developer is allowed to rise in the second gap. The air existing between the magnetic carrier particles in the developer in the first gap G1 can be reliably drawn into the second gap by the rising of the developer in the second gap.

  Also in the third gap G3 between the second convex portion D and the developing sleeve 19Y, at least in the sleeve rotation direction of the surface facing the developing sleeve 19Y in the second convex portion D, as in the first gap. The developer on the downstream side is brought into contact with the developer that has risen by the magnetic force of the downstream magnetic pole P3. In such a configuration, in the third gap G3, the developer immediately before entering the fourth gap with the rotation of the developing sleeve 19Y is brought into contact with the second convex portion D and immediately after entering the fourth gap. The developer is allowed to rise in the fourth gap. The air existing between the magnetic carrier particles in the developer in the third gap G3 can be reliably drawn into the fourth gap by the rising of the developer in the fourth gap.

  The surface of the first convex portion B facing the developing sleeve 19Y and the surface of the second convex portion D facing the developing sleeve 19Y both rotate the sleeve with a constant curvature around the rotation axis of the developing sleeve 19Y. The curved surface is curved in the direction. In such a configuration, both the first gap G1 and the third gap G3 can be made constant in the sleeve rotation direction.

  As shown in FIG. 3 above, a vent 23Y that allows ventilation inside and outside the casing 21Y is provided at the boundary between the second agent accommodating portion 13Y and the developing portion 16Y. The ventilation port 23Y is provided with a filter 22Y that captures toner in the ventilation path through the ventilation port. In such a configuration, the air in the casing 21Y is allowed to escape to the outside through the filter 22Y, thereby avoiding an excessive increase in the atmospheric pressure in the casing 21Y, and the generation of a blown air current near the downstream end A of the developing opening. Can be suppressed more reliably.

  Note that toner scattering hardly occurs near the upstream end of the development opening. This is considered to be due to the reason described below. That is, in the vicinity of the upstream end, the doctor blade 17Y inside the casing faces the sleeve surface via a predetermined doctor gap. In the vicinity of this doctor gap, the developer is spiked by the magnetic force generated by the magnetic pole of the magnet roller to form a magnetic brush, but the doctor gap is much smaller than the height of the magnetic brush rising by the magnetic force of the magnetic pole. ing. In such a doctor gap, the developer is strongly compressed between the doctor blade 17Y and the developing sleeve, and the minute gaps between the particles of the magnetic carrier become very narrow.

  Although the configuration of the Y developing device 10Y has been described in detail, the multicolor developing device has the same configuration as the Y developing device 10Y.

Next, printers of reference examples obtained by adding further configurations to the printer according to the reference embodiment will be described. Unless otherwise specified below, the configuration of the printer according to each reference example is the same as the reference embodiment.
[First Reference Example]
In the printer according to the reference embodiment, the air pressure in the second gap between the first concave portion C and the developing sleeve 19Y is excessively increased, and a slight amount of toner scattering may occur due to the blowing airflow. This toner scattering occurred remarkably on the upstream side in the developer conveying direction of the second conveying screw 15Y shown in FIG. 3, that is, on the front side in the direction perpendicular to the plane shown in FIG. This is because a lot of toner floating due to charging failure occurs on the upstream side in the developer transport direction.

  FIG. 5 is an enlarged perspective view showing the upper wall of the casing 21Y of the developing device 10Y. FIG. 6 is a longitudinal sectional view showing the upper wall of the casing 21Y. FIG. 7 is a side view of the developing device 10Y as viewed from the entire longitudinal direction (opening side where the developing sleeve is exposed). In FIG. 5, an arrow X indicates a developer conveyance direction of a second conveyance screw (not shown). The 1st convex part B is formed over the whole area of the longitudinal direction of the upstream magnetic pole which is not shown in figure at least. On the other hand, the 2nd convex part D is formed only in the area | region of the upstream edge part among the whole areas of the developer conveyance direction X in the area | region facing the downstream magnetic pole which is not shown in figure. In the region of the downstream end portion in the developer transport direction X, the second convex portion D is not formed. Here, the developer on the sleeve raised by the magnetic force generated by the downstream magnetic pole and the upper wall of the casing 21Y. This is a non-contact area where no contact is made.

  In the fourth gap, floating toner due to poor charging is generated in the upstream end region in the developer transport direction X. Therefore, in the region of the upstream end in the developer transport direction X, the developer protruding from the magnetic force generated by the downstream magnetic pole in the third gap G3 is brought into contact with the second convex portion D, whereby the fourth gap And the second gap. Thereby, the movement of the floating toner from the fourth gap to the second gap is suppressed. On the other hand, in the region of the downstream end portion in the developer transport direction X where the amount of floating toner is relatively small, the developer and the second convex portion D that are spiked by the magnetic force generated by the downstream magnetic pole in the third gap G3. By making non-contact, the fourth gap and the second gap are communicated. Accordingly, the air flow from the second gap to the fourth gap is promoted to avoid an excessive increase in the atmospheric pressure in the second gap. Therefore, it is possible to avoid the generation of a blown airflow due to an excessive increase in atmospheric pressure in the second gap.

  In FIG. 7, L3 indicates the length of the second convex portion D. L1 indicates the length of the first convex portion B.

[Second Reference Example]
FIG. 8 is a longitudinal sectional view showing the upper wall of the casing 21Y in the developing device 10Y for Y of the printer according to the second reference example. As illustrated, the height of the second convex portion D gradually decreases from the upstream side to the downstream side in the developer transport direction X. Accordingly, the third gap (G3) gradually increases from the upstream side to the downstream side in the developer transport direction X. In such a configuration, the pressure of the developer in the third gap is gradually reduced from the upstream side to the downstream side in the developer transport direction X. By increasing the developer pressure on the upstream side in the developer transport direction X where floating toner is generated due to poor charging, the movement of the floating toner from the fourth gap to the second gap is further suppressed. On the other hand, on the downstream side in the developer transport direction X where the amount of floating toner is relatively small, the flow of airflow from the second gap to the fourth gap is promoted by reducing the pressure of the developer in the third gap. . Thus, by avoiding an excessive increase in the atmospheric pressure in the second gap, it is possible to avoid the generation of a blown airflow due to an excessive increase in the atmospheric pressure in the second gap.

So far, the example in which the magnet roll 20Y is provided with five magnetic poles P1 to P5 has been described, but the number of magnetic poles is not limited to five. Printers and according to the embodiment described below, the printer according to the third reference example, the number of magnetic poles are I different from the printer according to the reference embodiment and the reference example. Unless otherwise specified below, the configurations of the printer according to the embodiment and the printer according to the third reference example are the same as those of the first reference example.

[ Embodiment ]
FIG. 9 is an enlarged configuration diagram illustrating the developing device 10Y for Y of the printer according to the embodiment . FIG. 10 is an enlarged partial view showing the upper wall of the casing 21Y of the developing device 10Y and the developing roll 18Y in the printer according to the embodiment . FIG. 11 is a side view showing the developing device 10Y in the printer according to the embodiment as viewed from the whole area in the longitudinal direction.

  In FIG. 9, the magnet roll 20Y of the developing device 10Y has seven magnetic poles P1 to P7. P1 is a developing magnetic pole for causing the developer on the developing sleeve 19Y to rise in the developing region. Further, in this developing device 10Y, P6 is the agent separating magnetic pole and P7 is the pumping magnetic pole. Further, all of P2, P3, P4, and P5 are transport magnetic poles. Hereinafter, P2, P3, P4, and P5 are referred to as a first magnetic pole between development and supply, a second magnetic pole between development and supply, a third magnetic pole between development and supply, and a fourth magnetic pole between development and supply.

As shown in FIG. 10, the first convex portion B, the first concave portion C, the second convex portion D, the second concave portion E, the third convex portion F, and the third concave portion H are developed on the upper wall of the casing 21Y. The sleeves 19Y are formed so as to be sequentially arranged in the rotation direction. The structure of the 1st convex part B, the 1st recessed part C, the 2nd convex part D, and the 2nd recessed part E is the same as that of a 1st reference example. The roles of the first magnetic pole P2 between development and supply and the second magnetic pole P3 between development and supply are the same as the roles of the upstream magnetic pole P2 and the downstream magnetic pole P3 in the printer according to the first reference example.

  The developer in the fourth gap between the second concave portion E and the developing sleeve 19Y enters the fifth gap G5 between the third convex portion F and the developing sleeve 19Y as the developing sleeve 19Y rotates. To do. Then, the head is raised on the developing sleeve 19Y by the magnetic force generated by the developing-supplying third magnetic pole P4. The fifth gap G5 is smaller than the height of the developer spike due to the magnetic force generated by the development-supply third magnetic pole P4. For this reason, the developer in the fifth gap G5 is conveyed toward the downstream side in the sleeve rotation direction while contacting the third convex portion F.

  The sixth gap is adjacent to the fifth gap G5 on the downstream side in the developing sleeve rotation direction. The sixth gap is a gap formed between the third recess H and the developing sleeve 19Y, and is larger than the thickness of the developer inside. For this reason, a space is formed between the developer in the sixth gap and the third recess H.

  When the developer in the fifth gap G5 enters the sixth gap as the developing sleeve 19Y rotates, the developer rises larger in the sixth gap than before. At the time of this rise, the air held between the magnetic carrier particles of the developer in the fifth gap G5 is drawn into the sixth gap. Then, an air flow from the third gap G3 to the fifth gap G5 is generated in the fourth gap by a synergistic action with the airflow from the third gap G3 toward the fourth gap. The magnetic force of the second magnetic pole P3 between development and supply is substantially the same as that of the third magnetic pole P4 between development and supply. The fifth gap G5 is smaller than the third gap G3 (G1> G3> G5). Accordingly, the developer pressure in the fifth gap G5 is larger than the developer pressure in the third gap G3.

  L3 in FIG. 11 indicates the length in the developer transport direction X of the second convex portion D (not shown) that forms the third gap. L5 indicates the length in the developer transport direction X of a third protrusion F (not shown) that forms the fifth gap. Similarly to the second convex portion D, the third convex portion F is provided only at the downstream end in the developer transport direction X, but its length L5 is longer than the length L3 of the second convex portion D. Shorter (L3> L5). When the length L1 of the first convex portion B is 1, L3 = L1 / 2 and L5 = L1 / 5.

[ Third reference example]
FIG. 12 is an enlarged configuration diagram illustrating the developing device 10Y for Y of the printer according to the third reference example. FIG. 13 is an enlarged partial view showing the upper wall of the casing 21Y of the developing device 10Y and the developing roll 18Y in the printer according to the third reference example. FIG. 14 is a side view showing the developing device 10Y in the printer according to the third reference example as viewed from the whole area in the longitudinal direction.

  In FIG. 12, the magnet roll 20Y of the developing device 10Y has nine magnetic poles P1 to P9. P1 is a developing magnetic pole for causing the developer on the developing sleeve 19Y to rise in the developing region. Further, in this developing device 10Y, P8 is the agent separating magnetic pole and P9 is the pumping magnetic pole. Further, P2, P3, P4, P5, P6, and P7 are all transport magnetic poles. Hereinafter, P2, P3, P4, P5, P6, and P7 are defined as a first magnetic pole between development and supply, a second magnetic pole between development and supply, a third magnetic pole between development and supply, a fourth magnetic pole between development and supply, and a development and supply. The fifth magnetic pole is called the fifth magnetic pole and the sixth magnetic pole between development and supply.

As shown in FIG. 13, on the upper wall of the casing 21Y, the first convex portion B, the first concave portion C, the second convex portion D, the second concave portion E, the third convex portion F, the third concave portion H, the fourth convex portion. The portion I and the fourth recess J are formed so as to be sequentially arranged in the rotation direction of the developing sleeve 19Y. The configurations of the first convex portion B, the first concave portion C, the second convex portion D, the second concave portion E, the third convex portion F, and the third concave portion H are the same as in the first reference example. The roles of the first magnetic pole P2 between development and supply, the second magnetic pole P3 between development and supply, and the fourth magnetic pole P4 between development and supply are the same as those of the printer according to the first reference example.

  The developer in the sixth gap between the third concave portion H and the developing sleeve 19Y enters the seventh gap G5 between the fourth convex portion I and the developing sleeve 19Y as the developing sleeve 19Y rotates. To do. Then, the head is raised on the developing sleeve 19Y by the magnetic force generated by the developing-supplying fourth magnetic pole P5. The seventh gap G7 is smaller than the height of the developer spike due to the magnetic force generated by the development-supply fourth magnetic pole P5. Therefore, the developer in the seventh gap G7 is conveyed toward the downstream side in the sleeve rotation direction while contacting the fourth convex portion I.

  The eighth gap is adjacent to the seventh gap G7 on the downstream side in the developing sleeve rotation direction. The eighth gap is a gap formed between the fourth recess J and the developing sleeve 19Y, and is larger than the thickness of the developer inside. For this reason, a space is formed between the developer in the seventh gap and the fourth recess J.

  When the developer in the seventh gap G7 enters the eighth gap as the developing sleeve 19Y rotates, the developer rises larger in the eighth gap than before. At the time of this rise, the air held between the magnetic carrier particles of the developer in the seventh gap G7 is drawn into the eighth gap. Then, an air flow from the fifth gap G5 to the seventh gap G7 is generated in the sixth gap by a synergistic action with the airflow from the fifth gap G5 toward the sixth gap. The magnetic force of the third magnetic pole P4 between development and supply is substantially the same as that of the fourth magnetic pole P5 between development and supply. The seventh gap G7 is smaller than the fifth gap G5 (G1> G3> G5)> G7). Thus, the developer pressure in the seventh gap G7 is larger than the developer pressure in the fifth gap G5.

  L7 in FIG. 14 indicates the length in the developer transport direction X of a fourth protrusion I (not shown) that forms the seventh gap. Similar to the second and third convex portions D and F, the fourth convex portion I is provided only at the downstream end in the developer transport direction X, but the length L7 is the second convex portion D. Or shorter than the third protrusion F (L3> L5> L7). When the length L1 of the first convex portion B is 1, the length L7 = L1 / 10.

The toner used in the reference form, each reference example, and the printer according to the embodiment has an average circularity adjusted to 0.93 to 1.00. The average circularity is an index indicating the degree of unevenness of the toner particles, and is 1.00 when the toner is a perfect sphere. As the surface shape becomes more complex, the circularity becomes smaller. It is obtained by the relational expression “circularity a = L0 / L”. In this relational expression, L0 indicates the circumference of a circle having the same projected area as the particle image. L represents the perimeter of the projected image of the particle.

  When the average circularity is in the range of 0.93 to 1.00, the surface of the toner particles is smooth, and the contact area between the toner particles and between the toner particles and the photosensitive member is small, so that the transferability is excellent. Since the toner particles have no corners, the developer agitation torque in the developing device is small, and the agitation drive is stabilized, so that no abnormal image is generated. Since there are no angular toner particles in the toner that forms the dots, when the pressure is brought into contact with the transfer medium during the transfer, the pressure is uniformly applied to the entire toner that forms the dots, and the transfer is not easily lost. Since the toner particles are not angular, the abrasive power of the toner particles themselves is small, and the surfaces of the photoreceptor, the charging member and the like are not damaged or worn.

  In addition, the toner is obtained by crosslinking and / or extending a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is dispersed in an organic solvent in an aqueous solvent. It is a toner obtained by reaction. By this method, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

The toner has a toner shape factor SF-1 adjusted to a range of 100 to 180, and a shape factor SF-2 adjusted to a range of 100 to 180. FIG. 15 is a schematic diagram for explaining the shape factor SF-1. FIG. 16 is a schematic diagram for explaining the shape liquid number SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is obtained by the relational expression “SF-1 = {(MXLNG) ² / AREA} × (100π / 4)” (π = circle). Frequency). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4. When the value of the shape factor SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the shape of the toner, and is obtained by the relational expression “SF-2 = {(PERI) ² / AREA} × (100 / 4π)”. A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.

  When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent. Specifically, the shape factor is measured by taking a photograph of the toner at a magnification of 1000 times with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), reading it with a scanner, and converting it into image data. This was measured by binarizing the image data using an image analysis apparatus (LUSEX3: manufactured by Nireco) and analyzing at least 500 toner particles. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factor SF-1 or the shape factor SF-2 exceeds 180, the transfer rate decreases, which is not preferable.

As described above, in the printer according to the reference embodiment, the developer pressure in the third gap G3 is set larger than the developer pressure in the first gap G1. In such a configuration, as already described, an air flow from the first gap G1 to the third gap G3 can be reliably generated in the second gap.

In the printer according to the reference embodiment, the third gap G3 is smaller than the first gap G1. In such a configuration, a magnetic pole (downstream magnetic pole P3) for causing the developer to rise in the third gap G3 and a magnetic pole (upstream magnetic pole P1) for raising the developer in the first gap G1. The developer pressure in the third gap G3 can be made larger than the developer pressure in the first gap G1 without greatly changing the magnetic force.

In the printer according to the first reference example, as a supply member, the developer is supplied to the developing sleeve 19Y while being conveyed in an orthogonal direction that is orthogonal to the endless moving direction (rotating direction) on the surface of the developing sleeve 19Y. Using the second transport screw 15, development is performed by at least the second transport screw 15Y in the entire region in the same orthogonal direction in the region facing the development-supply second magnetic pole P3 that is the downstream magnetic pole and the casing upper wall that is the opposing member. While the third gap G3 is formed in the upstream end region in the developer transport direction X, the second magnetic pole P3 between the developer and the supply in the downstream end region in the developer transport direction X out of the entire region. A non-contact area is formed in which the developer that has risen due to the generated magnetic force and the upper wall of the casing are not in contact with each other. In such a configuration, as already described, an excessive increase in atmospheric pressure in the second gap is avoided by encouraging the flow of airflow from the second gap to the fourth gap in the non-contact region. Thereby, generation | occurrence | production of the blowing airflow by the excessive raise of the atmospheric | air pressure in a 2nd clearance gap can be avoided.

In the printer according to the second reference example, the third gap G3 is gradually increased from the upstream side to the downstream side in the developer transport direction X in the orthogonal direction. In this configuration, as described above, the developer pressure in the third gap G3 is gradually decreased from the upstream side to the downstream side in the developer transport direction X, so that the second gap is changed to the fourth gap. Gradually encourage the flow of air. Thus, by avoiding an excessive increase in the atmospheric pressure in the second gap, it is possible to avoid the generation of a blown airflow due to an excessive increase in the atmospheric pressure in the second gap.

Further, in the printer according to the reference embodiment or each reference example, the facing portion of the developing sleeve 19Y facing the first gap G1 and the facing portion of the third gap G3 on the casing upper wall facing the non-exposed portion in the casing 21Y. Are the first convex portion B that is the upstream convex portion and the third convex portion D that is the downstream convex portion that protrude toward the developing sleeve 19Y, respectively, and the portion facing the second gap is the first concave portion C. It is said. In such a configuration, the developer in the first gap G1 is brought into contact with the first convex portion B and the developer in the third gap G3 is brought into contact with the third convex portion D only by molding the upper wall of the casing 21Y. A configuration for contact can be realized.

Further, in the printers according to the reference form and each reference example, the first convex portion B and the second convex portion D each stand on the surface of the developing sleeve 19Y at least at the downstream end in the sleeve rotation direction. The developed developer is brought into contact. In this configuration, as already described, the air existing between the magnetic carrier particles in the developer in the first gap G1 is reliably drawn into the second gap by the rising of the developer in the second gap. Can do. Furthermore, the air existing between the magnetic carrier particles in the developer in the third gap G3 can be reliably drawn into the fourth gap by the rising of the developer in the fourth gap.

In the printer according to the reference embodiment and each reference example, the first convex portion B and the second convex portion D are both curved surfaces that curve the surface facing the developing sleeve 19Y along the peripheral surface of the developing sleeve 21Y. It is said. In such a configuration, the size of the first gap G1 and the third gap G3 can be made constant in the sleeve rotation direction.

Further, in the printer according to the reference embodiment and each reference example, a vent 22Y that allows ventilation inside and outside the casing 21Y is provided in the casing 21Y, and a filter 22Y that traps toner in the ventilation path through the ventilation port 21Y. Is provided. In such a configuration, the air in the casing 21Y is allowed to escape to the outside through the filter 22Y, thereby avoiding an excessive increase in the atmospheric pressure in the casing 21Y, and the generation of a blown air current near the downstream end A of the developing opening. Can be suppressed more reliably.

Further, in the printer according to the reference form and each reference example, the inner wall of the casing 21Y is used as a facing member that faces the non-exposed portion in the casing 21Y of the developing sleeve 19Y. In such a configuration, the member can be opposed to the non-exposed portion without adding a dedicated member for functioning as a facing member in the casing 21Y.

1Y, M, C, K: Process unit 2Y, M, C, K: Photoconductor (latent image carrier)
10Y: Developing device 13Y: Second agent container (developer container)
15Y: Second conveying screw (supply member)
17Y: Doctor blade (regulating member)
18Y: Development roll (developer carrier)
19Y: Development sleeve (peripheral surface of developer carrier)
20Y: Magnet roll 21Y: Casing P1: Developing magnetic pole P2: Upstream magnetic pole (conveying magnetic pole)
P3: Downstream magnetic pole (conveying magnetic pole)
G1: 1st gap G3: 3rd gap G5: 5th gap G7: 7th gap B: 1st convex part (opposing member)
C: 1st recessed part (opposing member)
D: 2nd convex part (opposing member)
E: Second recess (opposing member)
F: 3rd convex part (opposing member)
H: Third recess (opposing member)
I: 4th convex part (opposing member)
J: Fourth recess (opposing member)
X: Developer transport direction

JP 2004-20772 A

Claims (16)

A plurality of magnetic poles, and a developer carrier that carries a developer containing toner and a magnetic carrier on its moving surface by a magnetic force generated by the magnetic poles, and enclosing the developer carrier, A casing that exposes a part of the surface of the developer carrier to the outside through its own opening, and the exposed portion of the surface of the developer carrier that is exposed to the outside of the casing through the opening. Opposing member that faces a developer-carrying maintenance location that is a location downstream of the developer carrying member in the surface movement direction and that continues to carry the developer carried outside the casing as it is, with a gap interposed therebetween. When, in the developing apparatus comprising a supply member for supplying the surface of the developer carrying member while transporting the orthogonal direction orthogonal to the surface movement direction while along the surface of the developer carrying member to the developer Stomach,
A first convex portion projecting toward the developer carrying member, and a first concave portion that is recessed from the first convex portion at a position adjacent to the first convex portion on the downstream side in the surface movement direction. A second protrusion projecting toward the developer carrying member from the first recess at a position adjacent to the first recess on the downstream side in the surface movement direction, and the second protrusion On the other hand, a second concave portion that is recessed from the second convex portion at a position adjacent to the downstream side in the surface movement direction, and the second concave portion that is adjacent to the second concave portion on the downstream side in the surface movement direction. A third convex portion projecting toward the developer carrying member than the two concave portions is provided on the facing member;
A developing device characterized in that the length of the convex portion in the orthogonal direction is increased in the order of the first convex portion, the second convex portion, and the third convex portion . The developing device according to claim 1.
As part of the plurality of magnetic poles, in order to transport the developer at the agent carrying and maintaining portion, at least two conveying magnetic poles that form a magnetic field on the agent carrying and maintaining portion are provided side by side in the surface movement direction,
The developer in the first gap formed between the first convex portion and the developer carrying member is transferred to the first concave portion and the developer carrying member along with the surface movement of the developer carrying member. when to enter the second gap formed between, the at least two conveying pole, magnetic force of the upstream pole is the conveyance pole than other transport magnetic pole positioned on the upstream side of the surface moving direction Causing the developer to rise in the space of the second gap,
In addition , the developer in the third gap formed between the second convex portion and the developer carrying member is transferred to the second concave portion and the developer carrying member along with the surface movement of the developer carrying member. when to enter the fourth gap formed between the body and the fourth gap space the developer by the magnetic force than the upstream-side magnetic pole is a conveying pole located on the downstream side of the downstream-side magnetic pole A developing device characterized in that it is made to stand up. The developing device according to claim 2 .
A developing device characterized in that the pressure of the developer in contact with the counter member in the third gap is larger than the pressure of the developer in contact with the counter member in the first gap. The developing device according to claim 2 .
A developing device characterized in that the density of the developer in contact with the counter member in the third gap is higher than the density of the developer in contact with the counter member in the first gap. . The developing device according to claim 3 or 4,
A developing device characterized in that the third gap is smaller than the first gap. The developing device according to any one of claims 2 to 5 ,
Among the entire area of the orthogonal direction in the region opposed to the upper Symbol downstream pole and the opposing member, while forming the third gap region of the upstream end of the developer transport direction of at least the feed member, the In the entire region, the region at the downstream end in the developer transport direction is a non-contact region in which the developer that rises due to the magnetic force generated by the downstream magnetic pole is not brought into contact with the opposing member. Equipment . The developing device according to any one of claims 2 to 6 ,
About each of the first and second convex portions, at least the downstream end portion in the surface movement direction of the developer carrying member is brought into contact with the developer spiked on the surface of the developer carrying member. A developing device characterized by that. The developing device according to claim 7 .
At least one of the first convex portion and the second convex portion is characterized in that the surface facing the developer carrier is a curved surface that curves along the peripheral surface of the developer carrier. A developing device. The developing device according to any one of claims 1 to 8 ,
A developing device characterized in that a vent for allowing ventilation inside and outside the casing is provided in the casing, and a filter for capturing toner in a vent passage through the vent is provided. The developing device according to any one of claims 1 to 9 ,
A developing device using an inner wall of the casing as the counter member. At least a latent image carrier that carries a latent image and a developing unit that develops the latent image carried on the latent image carrier are held as a single unit on a common holder and integrated with the image forming apparatus. In a process unit that is detachable automatically,
As the developing means, a process unit, characterized in that it uses one of the developing apparatus of claims 1 to 1 0. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image carried on the latent image carrier.
As the developing means, the image forming apparatus characterized by using any of the developing apparatus of claims 1 to 1 0. An image forming apparatus according to claim 1 2,
A plurality of developing devices for developing the latent image with different color toners are used, and the developing devices are any of the developing devices according to any one of claims 1 to 9. Image forming apparatus. An image forming apparatus according to claim 1 2 or 1 3,
An image forming apparatus using the toner having an average circularity of 0.93 or more and 1.00 or less. Be any of the image forming apparatus according to claim 1 2 to 1 4,
As the toner, a toner material liquid in which a polyester prepolymer having a functional group containing at least a nitrogen atom, polyester, a coloring tax, and a release accelerator is dispersed is subjected to a crosslinking reaction and an extension reaction in an aqueous medium. An image forming apparatus using the product obtained by the method described above. Be any of the image forming apparatus according to claim 1 2 to 1 5,
An image forming apparatus using a toner having a shape factor SF-1 of 100 or more and 180 or less and a shape factor SF-2 of 100 or more and 180 or less.

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