JP2017097170A - Developing device, image forming apparatus, and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress unevenness in image density according to a blade pitch of a conveyance screw.SOLUTION: A developing device includes an inclined surface K that faces a conveyance screw from above and is inclined to have a developer carrier side located at an upper side; the inclined surface extends to the vicinity of a developer regulating member, such as a developer doctor 12d that forms a regulation gap DG with a surface of the developer carrier and regulates the amount of developer passing through the regulation gap, or to be in contact with the developer regulating member, and includes a developer drop promoting part that drops, from the inclined surface, a developer regulated from passing through the regulation gap by the developer regulating member and moving on the inclined surface to an upper part of the conveyance screw.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a developing device, an image forming apparatus, and a process cartridge.

  Conventionally, a two-component developer consisting of a magnetic carrier and toner contained in a developer containing portion is provided on the outer peripheral surface by a magnetic force and has a magnetic field generating portion inside, up to a portion facing the latent image carrier. A developing device having a developer carrier to be conveyed is known.

  For example, Patent Document 1 discloses such a developing device, which is positioned below a developer carrying member and a developer regulating member that regulates the amount of developer carried on the surface of a rotating developer carrying body. A developing device including a conveying screw that stirs and conveys the developer in the developer accommodating portion is described. The conveying screw includes a shaft portion and blades provided in a spiral shape on the outer peripheral surface of the shaft portion. The developer being transported by the transport screw is attracted to the surface of the developer carrier by the attracting magnetic force of the attracting magnetic pole provided in the magnetic field generation unit, and is carried on the surface of the developer carrier.

  In recent years, there has been a demand for reduction of environmental load. Therefore, it has been demanded to reduce the developer filled in the developer accommodating portion. By reducing the amount of developer filled in the developer accommodating portion, it is possible to save energy during transportation by reducing the weight of the apparatus. Further, the rotational load of the conveying screw can be reduced, and energy saving can be achieved when the apparatus is driven.

  However, when the amount of the developer in the developer accommodating portion is reduced, there is a problem that unevenness in image density occurs in the developed image according to the blade pitch of the conveying screw.

  In order to solve the above-described problems, the present invention provides a developer carrier that carries a developer on the surface thereof, a magnetic field generator that includes a plurality of magnetic poles disposed inside the developer carrier, and a developer. In a developing device having a transport screw positioned below the carrier and disposed in the developer accommodating portion, an inclined surface that faces the transport screw from above and is inclined so that the developer carrier side is positioned upward. And the inclined surface forms a regulating gap with the surface of the developer carrying member to the vicinity of the developer regulating member that regulates the amount of developer passing through the regulating gap or the developer regulating member A developer drop accelerating portion that extends from the inclined surface so as to drop the developer that extends so as to come into contact with the developer and moves on the inclined surface to the upper side of the conveying screw by being restricted by the developer restricting member. It is characterized in that to obtain.

  According to the present invention, it is possible to obtain a specific effect that unevenness in image density according to the blade pitch of the conveying screw can be suppressed.

1 is a diagram illustrating an outline of an image forming apparatus. (A) is a perspective view of a process cartridge. FIG. 4B is a sectional view of the process cartridge. The perspective view which shows the external appearance of a developing device. The perspective view which shows the state which decomposed | disassembled the upper casing and the lower casing so that the inside of the developer accommodating part of a developing device can be visually recognized. FIG. 3 is a diagram schematically illustrating a developer circulation path in a developing device. FIG. 2 is a schematic sectional view of a developing device. The figure which showed the speed distribution of the developer of the broken-line part at the moment when the blade | wing of a 2nd conveyance screw is located horizontally. FIG. 3 is a cross-sectional view illustrating the developing device according to the embodiment. FIG. 3 is a cross-sectional view illustrating the developing device according to the present embodiment having a developer dropping promotion unit.

FIG. 1 is a diagram showing an outline of an image forming apparatus according to an embodiment of the present invention.
An image reading apparatus 200 is attached to the upper part of the apparatus main body 100 of the copying machine as an image forming apparatus.

A process cartridge 1 is provided inside the apparatus main body 100.
FIG. 2A is a perspective view of the process cartridge, and FIG. 2B is a cross-sectional view of the process cartridge.
As shown in FIG. 2B, the process cartridge 1 includes a photosensitive member 10 that is a latent image carrier, a charging device 11 that is disposed around the photosensitive member 10 and that acts on the photosensitive member 10, and a developing device. 12 and a cleaning device 14. The process cartridge 1 is detachably attached to the apparatus main body 100. Since the photosensitive member 10, the charging device 11, the developing device 12, and the cleaning device 14 are unitized as the process cartridge 1, replacement and maintenance work is facilitated. Further, it is possible to maintain the positional accuracy between the members with high accuracy, and to improve the quality of the formed image.

  The charging device 11 serving as a charging unit applies a charging bias to apply a charge to the surface of the photoconductor 10 to uniformly charge the photoconductor 10, and an adhering material such as toner attached to the surface of the charging roller 11a. And a removing roller 11b to be removed.

  The developing device 12 as developing means has a first agent containing chamber V1 in which a first conveying screw 12b as developer conveying means is disposed. Further, it also has a second agent storage chamber V2 in which a second conveying screw 12c as a developer conveying means, a developing roller 12a as a developer carrying member, a developing doctor 12d as a developer regulating member, and the like are disposed. .

  In these two agent storage chambers V1 and V2, a developer which is a two-component developer including a magnetic carrier and a negatively chargeable toner is included. The first transport screw 12b is rotationally driven by a driving unit to transport the developer in the first agent storage chamber V1 to the front side in the drawing. Then, the developer transported to the front side end of the first agent storage chamber V1 in the drawing by the first transport screw 12b enters the second agent storage chamber V2.

  The 2nd conveyance screw 12c in the 2nd agent storage chamber V2 is rotated by a drive means, and conveys a developer to the back in the figure. In this manner, a developing roller 12a as a developer carrying member is disposed in a posture parallel to the second conveying screw 12c above the second conveying screw 12c that conveys the developer. The developing roller 12a includes a magnet roller which is a magnetic field generating means fixedly disposed in a developing sleeve made of a nonmagnetic sleeve that is rotationally driven.

  Part of the developer conveyed by the second conveying screw 12c is attracted to the surface of the developing roller 12a by the magnetic force generated by the magnet roller in the developing roller 12a. Then, the layer thickness is regulated by the developing doctor 12d, which is a developer regulating member composed of a round bar disposed so as to maintain a predetermined gap from the surface of the developing roller 12a. Thereafter, the toner is transported to a developing area facing the photoconductor 10 to attach toner to the electrostatic latent image on the photoconductor 10. By this adhesion, a toner image is formed on the photoreceptor 10. The developer that has consumed toner by development is returned to the second conveying screw 12c as the surface of the developing roller 12a moves. Then, the developer transported to the end of the second agent storage chamber V2 by the second transport screw 12c returns to the first agent storage chamber V1. In this way, the developer is circulated and conveyed in the developing device.

  Further, the developing device 12 includes a toner concentration sensor 124 (see FIG. 5) as toner concentration detecting means for detecting the toner concentration of the developer in the first agent storage chamber V1. The toner concentration sensor 124 measures the toner concentration of the developer from the magnetic permeability of the developer. When the toner concentration is lowered, the magnetic carrier is concentrated, so that the magnetic permeability is increased. When the value measured by the toner density sensor 124 exceeds the target value (threshold value), toner is supplied from the toner bottle 20 as the toner container shown in FIG. 1, and the toner density is controlled to a constant density. The target value is determined based on the detection result obtained by detecting the toner adhesion amount of the toner pattern formed on the photoconductor 10 in advance with an optical sensor.

  With such an operation, control is performed so that the reference pattern density on the photosensitive member is kept constant. However, when the toner in the toner bottle 20 runs out, it is impossible to suppress a decrease in the toner density of the developer. In such a situation, although the operation of replenishing toner from the toner bottle 20 is performed for a predetermined period, the subsequent detection result of the toner pattern by the optical sensor is not improved. Accordingly, when the toner pattern detection result by the optical sensor is not improved despite the operation of supplying the toner from the toner bottle 20, it is determined that the toner has run out (toner end) (or estimation determination). To do.

  In addition, after the toner end is determined, the toner bottle 20 is replaced, and when the toner end recovery for supplying the toner in the replaced toner bottle 20 to the developing device 12 is performed, the following operation is performed. That is, the developing roller 12a and the conveying screws 12b and 12c are rotated in order to satisfactorily mix the replenished toner and the developer. At this time, in order to prevent the developer on the developing roller 12a from sliding unevenly, driving is applied so that the photosensitive member 10 having a potential at which no toner adheres to the photosensitive member 10 is also rotated.

  The cleaning device 14 serving as a cleaning unit includes a cleaning blade 14 a that contacts the surface of the photoconductor 10 and scrapes off transfer residual toner attached to the photoconductor 10. In addition, a toner collection coil 14b is provided that conveys the collected toner collected in the collection unit W and collected by the cleaning blade 14a. The collected toner conveyed by the toner collecting coil 14b is conveyed to the developing device 12 or the waste toner bottle 41 by the toner conveying device.

  A transfer device 17 as a transfer unit shown in FIG. 1 includes a transfer roller 16, and the transfer roller 16 is pressed against and brought into contact with the peripheral surface of the photoconductor 10. Further, a thermal fixing device 24 as a fixing unit is provided above the transfer device 17. The thermal fixing device 24 includes a heating roller 25 and a pressure roller 26. Further, the apparatus main body 100 is provided with a laser writing device 21 as latent image forming means. The laser writing device 21 includes a laser light source, a scanning rotary polygon mirror, a polygon motor, an fθ lens, and the like. Further, the apparatus main body is provided with a plurality of sheet cassettes 22 for storing sheets S such as transfer paper and OHP film.

  When copying using the apparatus configured as described above, the user presses the start switch. Then, first, the contents of the original set on the image reading apparatus 200 are read. At the same time, the photosensitive member 10 is rotated by the photosensitive member driving motor, and the surface of the photosensitive member 10 is uniformly charged by the charging device 11 using the charging roller 11a. Next, a writing process is executed using the laser writing device 21 by irradiating laser light according to the content of the original read by the image reading device 200. Then, after forming an electrostatic latent image on the surface of the photoconductor 10, toner is attached using the developing device 12 to visualize (develop) the electrostatic latent image.

  At the same time as the user presses the start switch, the selected sheet S is sent out by the calling roller 27 from the multistage sheet cassette 22. Next, the sheet is separated one by one by the supply roller 28 and the separation roller 29 and sent to the supply path R1. The sheet S sent to the supply path R <b> 1 is conveyed by the sheet conveyance roller 30 and is abutted against the registration roller 23 and stopped. The transfer roller 16 is sent to a transfer nip formed in contact with the photoconductor 10 in accordance with the rotation timing of the toner image that is visualized on the photoconductor 10.

  The toner image on the photoreceptor 10 is transferred to the sheet S fed to the transfer nip by the transfer device 17. The residual toner on the photoconductor 10 after image transfer is removed and cleaned by the cleaning device 14, and the residual potential on the photoconductor 10 from which the residual toner has been removed is removed by the static eliminator. In preparation for the next image formation starting from the charging device 11.

  On the other hand, the sheet S after the image has been transferred is guided to the heat fixing device 24, passed between the heating roller 25 and the pressure roller 26, and conveyed to these rollers while applying heat and pressure to the toner. The image is fixed. Thereafter, the sheet S on which the image has been fixed is discharged onto the discharge stack unit 32 by the discharge roller 31 and stacked.

Next, the configuration and operation of the developing device 12 will be described in more detail.
FIG. 3 is a perspective view showing the appearance of the developing device 12.
FIG. 4 is a perspective view showing a state where the upper casing 1211 and the lower casing 1212 are disassembled so that the inside of the developer accommodating portion of the developing device 12 can be visually recognized. FIG. 5 is a diagram schematically showing a developer circulation path in the developing device 12. The broken arrow in FIG. 5 indicates the flow of the developer, and the solid arrow in FIG. 5 indicates the flow of the toner replenished from the toner replenishing port 12e.

  As shown in FIG. 4, in the developing roller 12a, the developing roller 12a is rotatably supported by the upper casing 1211. Further, a developing doctor 12d made of a round bar is fitted into fitting holes 1211a provided on both side walls of the upper casing 1211.

  Further, the lower casing 1212 forms a developer accommodating portion inside the developing device 12. The developer accommodating portion has a partition wall 122 that partitions the first agent accommodating chamber V1 and the second agent accommodating chamber V2. Conveying screws 12b and 12c are provided in the first agent storage chamber V1 and the second agent storage chamber V2, respectively. Each conveying screw 12b, 12c is rotatably supported by the lower casing 1212. The first agent storage chamber V <b> 1 and the second agent storage chamber V <b> 2 communicate with each other through the transfer openings 122 a and 122 b at the end of the partition wall 122.

  The developer transported to the downstream end of the second agent storage chamber V2 by the second transport screw 12c passes through the transfer opening 122a at the end of the partition wall 122 and moves to the first agent storage chamber V1. The developer in the first agent storage chamber V1 is transported in the opposite direction to the developer in the second agent storage chamber V2 while being stirred by the first transport screw 12b. And when it reaches the downstream end of the first agent storage chamber V1 in the transport direction, it passes through the transfer opening 122b at the end of the partition wall 122 and moves to the second agent storage chamber V2. As described above, the developer circulates in the developer accommodating portion partitioned by the partition wall 122 by the respective transport screws 12b and 12c provided in the first agent accommodating chamber V1 and the second agent accommodating chamber V2.

  A replenishment toner transport path 123 is connected to the upstream end of the developer transport upstream of the first agent storage chamber V1. The replenishing toner transport path 123 is provided with a toner replenishing port 12e, from which new toner and recovered toner collected by the cleaning device 14 are replenished. The first transport screw 12 b provided in the first agent storage chamber V <b> 1 extends to the replenishment toner transport path 123. The toner replenished from the toner replenishing port 12e is transported through the replenishment toner transport path 123 by the first transport screw 12b, and then passes through the communication hole 123a that connects the first agent storage chamber V1 and the replenishment toner transport path 123. To the first agent storage chamber V1. Further, reference numeral 124 in FIG. 5 denotes a density detection sensor that detects the toner density of the developer, and is installed below the first agent storage chamber V1 of the development casing 121.

FIG. 6 is a schematic sectional view of the developing device 12. The dotted line in FIG. 6 shows the developer surface lifted by the second conveying screw 12c.
The developing roller 12a of the present embodiment includes a developing sleeve 12a2 and a magnet roller 12a1 as a magnetic field generation unit fixedly disposed in the developing sleeve 12a2. The magnet roller 12a1 is a cylindrical member formed by mixing magnetic powder in a resin and is magnetized on its peripheral surface to form magnetic poles P1 to P5 that are five normal direction magnetic force peaks. It is. The magnetic pole P1 facing the photoconductor 10 is a developing magnetic pole, the magnetic pole P4 is a attracting magnetic pole that generates a magnetic force that attracts the developer in the second agent storage chamber V2, and the magnetic pole P5 facing the developing doctor 12d is a regulating magnetic pole. It is. The developer in the second agent storage chamber V2 is attracted to an area between the points on the developing roller 12a (hereinafter referred to as an attracting area) where the magnetic flux density in the normal direction by the attracting magnetic pole P4 and the regulating magnetic pole P5 is maximized. It is done. The magnetic pole P2 and the magnetic pole P3 are magnetic poles different from the magnetic pole 4 and have the same polarity adjacent to each other in the rotation direction of the developing roller 12a, and generate a magnetic force for releasing the developer from the developing sleeve 12a2. The agent separation magnetic pole and the second agent separation magnetic pole. From the region between the points on the developing roller 12a where the magnetic flux density in the normal direction by the first agent-separating magnetic pole P2 and the second agent-separating magnetic pole P3 is maximum (hereinafter referred to as the agent-separating region), the developer is removed from the developing sleeve. Leave 12a2.

  In this embodiment, as shown in FIG. 6, a round bar member having a circular cross section is used as the developing doctor 12d. By using a round bar member as the developing doctor 12d, it is possible to use a solid bar cut out and subjected to an end face treatment, which can be constructed at low cost. As shown in FIG. 4A, the developing doctor 12d is press-fitted into the upper casing 1211 that rotatably supports the developing roller 12a, thereby positioning the developing doctor 12d and the developing roller 12a on the same member. be able to. As a result, accumulation of dimensional tolerances can be minimized, and the doctor gap DG, which is the gap between the developing roller 12a and the developing doctor 12d, can be formed with high accuracy.

  The developer carrier continues to stay in the developing device without being consumed, and deteriorates over time and needs to be replaced periodically. When a large amount of developer is filled in the developer container, a large amount of deteriorated carrier is discarded at the time of replacement, and there is a problem that the environmental load is large. Therefore, in this embodiment, in order to reduce such an environmental load, the developer filled in the developer accommodating portion is reduced by 50 [%] compared to the conventional case. Further, by reducing the developer in the developer container, the apparatus can be reduced in weight, and energy can be saved during transportation. Furthermore, energy saving during operation can be achieved by reducing the rotational load on the transport screws 12b and 12c, and an environmental load reduction effect can be obtained.

  However, if the developer in the developer accommodating portion is reduced, the amount of developer attracted to the developing roller 12a is decreased, and problems such as a decrease in image density occur. Therefore, in the present embodiment, as described below, even if the amount of developer in the developer accommodating portion is reduced by 50 [%] compared to the conventional case, a good image can be developed. This will be specifically described below.

  In this embodiment, as shown in FIG. 6, the diameter d of the shaft portion 12c1 of the second transport screw 12c is made larger than the radius (D / 2) of the second transport screw 12c. Thereby, the volume of the 2nd agent storage chamber V2 can be decreased with the axial part 12c1 of the 2nd conveyance screw 12c. As a result, the height of the developer surface of the developer in the second agent storage chamber V2 can be increased, and the developer filled in the developer storage portion is reduced by 50 [%] compared to the conventional case. It is possible to prevent the developer surface height of the developer in the second agent storage chamber V2 from being lowered. As a result, the developer can be lifted to the vicinity of the developing roller 12a by the blades 12c2 of the second conveying screw 12c, and the developer in the second agent storage chamber V2 can be attracted well and captured by the magnetic pole P4. Therefore, even if the amount of developer filled in the developer storage case is reduced by 50% compared to the conventional case, it is possible to suppress a decrease in the amount of developer drawn.

  Further, the amount of developer attracted by the magnetic force of the attracting magnetic pole P4 is reduced by reducing the amount of developer in the second agent containing chamber V2. When the amount of developer in the second agent storage chamber V2 is large and most of the developer in the second agent storage chamber V2 is in a magnetic force range in which the developer of the attracting magnetic pole P4 can be attracted, the inside of the second agent storage chamber V2 The developer is attracted directly by the magnetic force of the attracting magnetic pole. However, as the amount of developer in the second agent storage chamber V2 decreases, the amount of developer in the second agent storage chamber V2 within the magnetic force range in which the developer of the attracting magnetic pole P4 can be attracted decreases, and the amount of developer that is attracted directly. Decreases. In this case, the developer lifted up to the magnetic force range of the attracting magnetic pole P4 mainly by the blades 12c2 of the second transport screw 12c is attracted by the attracting magnetic pole P4. In this way, as a result of the developer lifted by the blades 12c2 of the second conveying screw 12c being attracted, a sufficient amount of developer is present in the vicinity of the developing roller 12a facing the blades of the second conveying screw 12c. Is carried. However, the developer is hardly carried on the portion not facing the blade 12c2. Therefore, unevenness corresponding to the blade pitch of the second conveying screw is generated in the amount of developer carried on the developing roller. This unevenness in the amount of developer carried on the developing roller is somewhat improved when the developer regulated by the developing doctor 12d flows into a portion with a small amount of developer when passing through the developing doctor 12d. Is done. However, since the amount of developer attracted originally is small, it cannot be leveled until the unevenness in the amount of developer is eliminated. As a result, density unevenness corresponding to the blade pitch of the second conveying screw 12c occurs in the developed image.

  Therefore, in the present embodiment, during the conveyance to the vicinity of the developing roller 12a, the developer that has jumped directly up from the blade 12c2 of the second conveyance screw 12c and dropped into the second agent storage chamber V2 as it is is guided. A member 12g is provided and guided to the developing roller 12a. Then, the developer is carried on the developing roller 12a.

  The guide member 12g is a sheet-like member made of a resin material such as PET (polyethylene terephthalate) and has a thickness of 0.2 [mm]. The guide member 12g faces the second conveying screw 12c from above and is attached to the developing case so as to be inclined so that the developing roller side is positioned upward. The guide member 12g extends to the vicinity of the doctor gap DG, which is a gap between the developing doctor 12d and the developing roller 12a, and is in contact with the developing doctor 12d so that one end thereof is bent toward the developing roller 12a. Further, the other end side of the guide member 12g is attached to the inner surface forming the upper wall of the second agent storage chamber V2 of the upper casing 1211. Further, the other end of the guide member 12g is disposed Z [mm] below the apex of the second transport screw 12c. Moreover, the lower end of the guide member 12g and the top part of the shaft part 12c1 of the second conveying screw are substantially the same in the vertical direction. Further, in the vertical direction, there is a slight gap between the lower end of the developing roller 12a and the top of the second conveying screw 12c.

  Further, a part of the guide member 12g is provided so as to fall within the range of the magnetic flux density in the normal direction of the attracting magnetic pole P4. Specifically, as shown by a broken line in FIG. 6, the magnetic flux density is provided so as to fall within the range of the magnetic flux density in the normal direction of the attracting magnetic pole P <b> 4 formed between the regulating magnetic pole P <b> 5. The guide member 12g extends from one end side to the other end side in the developer transport direction of the second transport screw 12c, and has a shape that is long in the developer transport direction of the second transport screw 12c.

  Further, the guide member 12g is longer than the length of the second transport screw 12c of the upper casing 1211 in the developer transport direction (axial direction), and both ends of the guide member 12c in the developer transport direction are on the second transport screw side. It is preferable that the upper casing 1211 is bent and brought into contact with the inner surfaces of both side walls (walls orthogonal to the developer transport direction). With this configuration, the developer is surrounded by the upper casing 1211, the developing doctor 12d, and the guide member 12g shown in FIG. 6 from the gap between the guide member 12g and the inner surface of the side wall of the upper casing 1211. It is possible to prevent the developer from entering the space S1.

In this configuration, both ends of the guide member 12c in the developer transport direction are not fixed to the inner surfaces of both side walls (walls orthogonal to the developer transport direction) of the upper casing 1211, but can be in sliding contact with the inner surfaces. preferable. As will be described later, the developing doctor 12d side of the guide member 12g may bend away from the developing roller due to the pressure from the developer carried on the surface of the developing roller 12a. When the central portion in the developer transport direction (axial direction) is more bent than the end portion, both ends of the guide member 12c in the developer transport direction are fixed to both side walls of the upper casing 1211. The upper casing 1211 may be deformed by being pulled inward. On the other hand, when both ends of the developer conveying direction of the guide member 12c are not fixed to the both side walls of the upper casing 1211, the both side walls are not pulled inward and the upper casing 1211 is not deformed. . Therefore, it is preferable that both ends of the developer conveying direction of the guide member 12c are not fixed to both side walls of the upper casing 1211.

FIG. 7 is a diagram illustrating the developer velocity distribution at the broken line portion at the moment when the blade 12c2 of the second conveying screw 12c is positioned horizontally.
The second transport screw 12c rotates clockwise in FIG. 7, and the developer in the second agent storage chamber V2 is along the left wall surface (the wall surface of the partition wall 122) of the second agent storage chamber V2. The second conveying screw 12c is lifted upward by the blade 12c2. As shown in FIG. 7, the speed of the developer directly receiving the force from the blade 12c2 increases as it approaches the outer diameter of the second conveying screw 12c. Further, the speed between the second conveying screw and the wall surface is reduced.

  Since there is a wall surface along the outer diameter of the second conveying screw in the direction pushed by the developer blades until the blades 12c2 become horizontal, the developer is lifted without detaching from the blades. However, as shown in FIG. 7, when the blade 12c2 is positioned horizontally, there is a wide space in the developer moving direction. Therefore, when the blade 12c2 is positioned horizontally, a part of the developer lifted by the blade 12c2 separates from the blade 12c2 of the second conveying screw 12c and jumps upward as it is. As a result, the developer lifted to the vicinity of the developing roller 12a by the blades 12c2 of the second transport screw 12c decreases, and the developer attracted to the developing roller 12a by the magnetic force of the attracting magnetic pole P4 decreases.

  Further, when there is no guide member 12g, most of the developer that has jumped upward from the blade 12c2 of the second conveying screw 12c does not go to the developing roller 12a, but falls into the second agent storage chamber V2 as it is. . At this time, the developer collides with the developer that has been lifted by the blades 12c2. As a result, the developer lifted by the blades 12c2 may be returned. As a result, the developer lifted to the vicinity of the developing roller 12a by the blade 12c2 is reduced, and the developer attracted to the developing roller 12a by the magnetic force of the attracting magnetic pole P4 is reduced.

  In contrast, in this embodiment, since the guide member 12g is provided as shown in FIG. 6, the developer that jumps upward from the blade 12c2 of the second conveying screw 12c is positioned on the developing roller side of the guide member 12g. It touches the inclined surface K. The developer that has come into contact with the inclined surface K changes its direction of movement and travels toward the developing roller 12a. The developer traveling toward the developing roller 12a moves within the normal magnetic flux density range of the attracting magnetic pole P4, is captured by the magnetic force, and is carried on the surface of the developing roller 12a. As a result, the developing roller 12a is moved to the vicinity of the developing roller 12a by the blade 12c2 of the second conveying screw 12c, and in addition to the developer drawn to the developing roller 12a by the magnetic force of the attracting magnetic pole P4, The developer that has jumped up from the conveying screw 12c can be carried on the developing roller 12a.

  Furthermore, it is possible to suppress the developer that has jumped upward from the blade 12c2 of the second transport screw 12c from falling into the second agent storage chamber V2. Thereby, it is possible to suppress the developer that has been lifted by the blades 12c2 from colliding with the developer that has fallen into the second agent storage chamber V2. As a result, it is possible to suppress a decrease in the amount of developer that is waiting near the developing roller 12a, and it is possible to increase the amount of developer that is attracted to the developing roller 12a by the magnetic force of the attracting magnetic pole P4.

  In this way, the amount of developer carried on the developing roller 12a can be increased compared to the case where the guide member 12g is not provided. As a result, the developer layer thickness on the surface of the developing roller can be increased as a whole. As a result, the layer thickness of the portion where the developer lifted by the blades of the second conveying screw is attracted to the developing roller is not opposed to the blades 12c2 and the amount of developer is smaller than the portion near the blades. And the difference with doctor gap DG can be made small. Further, the amount of the partial developer near the blade 12c2 where the developer is attracted to the developing roller is increased, and the amount of developer regulated by the developing doctor 12d can be increased. As a result, after the developer in this portion is regulated by the developing doctor 12d, the amount of developer flowing in the portion where the amount of developer corresponding to the portion that moves in the axial direction and does not face the blade 12c2 is small is increased. Can do. Thereby, it is possible to suppress the occurrence of unevenness in the amount of developer on the developing roller that has passed through the doctor gap DG, and it is possible to prevent the unevenness in density according to the blade pitch of the second conveying screw 12c from occurring in the developed image. Can be suppressed.

  The guide member 12g is provided to be inclined with respect to the vertical direction so as to rise linearly from the end on the second agent storage chamber V2 side toward the end on the developing roller side, and the developing roller side is on the upper side. An inclined surface K that is positioned is formed. Accordingly, it is possible to guide the developer in contact with the guide member 12g at a speed that the developing roller 12a can carry while suppressing a decrease in the speed of the developer that has jumped upward from the blade 12c2 of the second transport screw 12c.

  Further, the end of the guide member 12g on the second agent storage chamber V2 side is positioned lower than the apex of the second transport screw 12c by Z [mm]. By positioning the second conveying screw 12c below the apex of the second conveying screw 12c, the following advantages are obtained as compared with the case where the end of the guide member 12g on the second agent storage chamber V2 side is located above the apex. That is, there is an advantage that the distance until the developer jumped upward from the blade 12c2 of the second conveying screw 12c reaches the range of the magnetic flux density in the normal direction of the pumping magnetic pole P4 can be shortened.

  The developer that has jumped upward from the blade 12c2 of the second conveying screw 12c starts to decelerate due to its own weight immediately after jumping up from the blade 12c2. Therefore, the longer the distance to reach the range of the magnetic flux density in the normal direction in the pumping magnetic pole P4, the less the momentum before reaching, and the drop to the second agent storage chamber V2. By arranging the end of the guide member 12g on the second agent storage chamber V2 side below the apex of the second conveying screw 12c, the magnetic flux density in the normal direction at the pumping magnetic pole P before the momentum of movement disappears. The developer can be moved to the range of. Thereby, it is possible to suppress the developer jumped from the second transport screw 12c from falling into the second agent storage chamber V2.

  In particular, as shown in FIG. 7, it is preferable to guide the developer that jumps straight up toward the developing roller 12 a by the guide member 12 g. In this state, from the state of FIG. 7, the direction of the developer that jumps up from the blade 12c2 when the second transport screw 12c rotates clockwise in FIG. As shown in FIG. 6, the developing roller 12a is positioned diagonally to the upper right of the second transport screw. Therefore, from the state of FIG. 7, when the second conveying screw 12c rotates clockwise in the drawing, the developer that jumps up from the blade 12c2 goes to the developing roller 12a. As a result, it is supported on the developing roller 12a without being guided by the guide member 12g.

  Thus, by providing the guide member 12g, the amount of developer carried on the developing roller 12a can be increased compared to the case where the guide member 12g is not provided. However, when the upper end of the guide member 12g is brought into contact with the developing doctor 12d, the following problems occur. That is, as shown in FIG. 8, the developer carried on the developing roller 12a is transported to a restricted place by the developing doctor 12d by the rotating developing roller 12a and is restricted from passing by the developing doctor 12d. A part of the developer passes through the doctor gap DG while convection on the regulating side, but most of the developer cannot pass through the doctor gap DG and remains on the regulating side. As shown in FIG. 8, when the upper end of the guide member 12g is in contact with the developing doctor 12d, the regulated developer remaining on the regulating side (the behavior of the regulated developer is indicated by a one-dot chain line in FIG. Is pushed by the developer regulated later, and is moved downward along the inclined surface K while being pressed by the magnetic force of the magnet roller 12a1 and being pressed against the inclined surface K of the guide member 12g. After the regulation, when the developer reaches the inclined surface where the magnetic force of the magnet roller 12a1 is weakened, the developer falls freely from that location.

  If the dropped position is a place deviated from the range covered by the blades 12c2 of the second conveying screw 12c, the post-regulation developer dropped from the inclined surface is lifted without being swept into the second conveying screw 12c, Again, it is carried on the developing roller 12a by the attracting magnetic force of the attracting magnetic pole P4. Thereafter, the developer carried on the developing roller 12a is again controlled to pass by the doctor gap DG and moves to the inclined surface K of the guide member 12g, and the upper surface (agent surface) of the developer lifted by the second transport screw 12c. Falls again (indicated by the dotted line in FIG. 8). When such an event is repeated, the post-regulation developer is repeatedly rubbed by the developing doctor 12d and the developing roller 12a, so that the charge amount is increased. As a result, a difference occurs between the charge amount of the developer mixed and stirred by the second conveying screw 12c and supplied onto the developing roller 12a. Therefore, when a lump of developer having a high charge amount passes through the doctor gap DG and is supplied to the development area, there is a problem that uneven image density unevenness occurs. The above phenomenon was remarkable in a high-temperature and high-humidity environment where the charge amount of the developer tends to decrease.

  Further, as described above, in the present embodiment, as shown in FIG. 8, since the guide member 12g having the inclined surface K is provided, the developer that jumps upward from the blade 12c2 of the second transport screw 12c (this development) The behavior of the agent is indicated by a solid line in FIG. 8) is in contact with the inclined surface K such that the developing roller side of the guide member 12 g is positioned upward. The developer that has contacted the inclined surface K changes its moving direction and moves toward the developing roller 12a, so that the developer that has jumped upward from the blade 12c2 of the second conveying screw 12c falls into the second agent storage chamber V2. Can be suppressed. However, when the inclined surface K extends to the vicinity of the developing doctor 12d or in contact with the developing doctor 12d, the post-regulation developer remaining on the regulating side of the developing doctor 12d extends along the inclined surface K of the guide member 12g. There is a possibility that the developer moves upward from the second conveying screw 12c and hits the developer jumped up from the blade 12c2 of the second conveying screw 12c. As a result, the post-regulation developer is bounced by the developer jumped upward from the blade 12c2 of the second transport screw 12c toward the developing roller 12a together with the developer jumped from the blade 12c2 of the second transport screw 12c. Thus, the toner is carried on the developing roller 12a without being returned to the second agent storage chamber V2. When such an event is repeated, the post-regulation developer is repeatedly rubbed by the developing doctor 12d and the developing roller 12a, so that the charge amount is increased. When the regulated developer passes through the doctor gap DG locally and is supplied to the development area, uneven image density unevenness is likely to occur.

  Therefore, in the present embodiment, as shown in FIG. 9, a developer drop accelerating portion 12g1 having a surface inclined in the direction in which the regulated developer is dropped is provided on the inclined surface K of the guide member 12g. The developer drop accelerating portion 12g1 is located above the portion of the inclined surface K where the developer that jumps upward from the blade 12c2 of the second conveying screw 12c (the behavior of this developer is indicated by a solid line in FIG. 9) contacts. In addition, the magnetic roller 12a1 is disposed at a location that cannot be captured by the magnetic force of the magnet roller 12a1. With such a configuration, the behavior of the regulated developer is not brought into contact with the developer that has jumped upward from the blade 12c2 of the second conveying screw 12c, as indicated by the alternate long and short dash line in FIG. Can be. Therefore, the developer that has jumped upward from the blade 12c2 of the second conveying screw 12c and contacted the inclined surface K can be directed to the developing roller 12a by changing its moving direction.

  The developer drop accelerating portion 12g1 is provided on the upper surface (developer agent) of the developer in the second agent storage chamber V2 in a range where the dropped regulated developer is subjected to the scooping action by the blades 12c2 of the second transport screw 12c. The surface is configured to fall (shown by the dotted line in FIG. 9). Further, as shown in FIG. 9, the developer drop accelerating portion 12g1 is configured by bending the inclined surface K, but the invention is not limited to this, and the post-regulation developer is a blade 12c2 of the second transport screw 12c. An obstacle may be provided on the inclined surface K that prevents the developer that has jumped upward from the position of the inclined surface K from coming into contact with the developer. The obstacle may be, for example, a wall portion that blocks the developer after regulation. Alternatively, the developer that has jumped upward from the blade 12c2 of the second conveying screw 12c is configured to come into contact with the inclined surface K below the portion where the developer drops from the inclined surface K of the regulated developer. For example, the length of the blade 12c2 (the length from the outer peripheral surface of the shaft portion 12c1 to the outermost end of the blade 12c2) is changed, or the rotational speed of the transport screw 12c is adjusted.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect A)
A developer carrying member such as a developing roller 12a carrying the developer on the surface; a magnetic field generating unit such as a magnet roller 12a1 provided with a plurality of magnetic poles disposed inside the developer carrying member; and a developer carrying member. In the developing device 12 having a transport screw such as a second transport screw 12c disposed in a developer storage section such as the second agent storage chamber V2 below and facing the transport screw from above, the developer carrying An inclined surface K that is inclined so that the body side is located above, and the inclined surface forms a regulating gap DG with the surface of the developer carrying member, and the amount of developer passing through the regulating gap is determined. It extends to the vicinity of the developer regulating member such as the regulating developer doctor 12d to be regulated or is in contact with the developer regulating member, and the developer regulating member regulates the passage of the regulating gap on the inclined surface. Developer moved upward of the transport screw and is characterized in that it comprises a developer fall facilitating portion for dropping from the inclined on a slope.
As described above, when the amount of the developer in the developer accommodating portion is reduced, the reason why the developed image has uneven image density according to the blade pitch of the conveying screw is as follows. That is, when the amount of the developer in the developer accommodating portion is reduced, the distance between the developer surface in the developer accommodating portion and the surface of the developer carrying member is increased. As a result, the developer surface of the developer in the developer container becomes out of the range of magnetic force capable of attracting the developer of the attracting magnetic pole, and the developer in the developer container is directly supported by the developer magnetic force. It becomes difficult to be drawn to the body. As a result, most of the developer attracted by the magnetic force of the attracting magnetic pole becomes the developer lifted to the vicinity of the surface of the developer carrying member by the blades of the conveying screw. For this reason, a sufficient amount of developer is carried on the portion of the developer carrying member facing the conveying screw blade, but almost no developer is carried on the portion not facing the conveying screw blade. Therefore, the layer thickness of the developer at the portion not facing the blade of the conveying screw becomes thinner than the regulation gap. When the developer regulated by the developer regulating member moves to the portion where the developer amount is small when passing through the regulating gap between the developer regulating member and the developer carrying member, the amount of the little portion is reduced. Although the amount of developer increases, it may not reach the specified amount. As a result, the developer amount is conveyed to the developing region in a non-uniform state, and image density unevenness corresponding to the blade pitch of the conveying screw occurs.
As a result of earnest research on the behavior of the developer lifted by the blades of the conveying screw, the present applicant has found the following. That is, a part of the developer lifted by the blades of the conveying screw is separated from the blades by the movement of the blades, and there is a developer that jumps upward. The developer that bounces upward vertically does not get caught by the magnetic force of the attracting magnetic pole of the magnetic field generation unit, and falls freely and returns to the developer storage unit again. Further, when returning freely to the developer accommodating portion, it collides with the developer in the middle of being lifted to the vicinity of the surface of the developer carrier by the blades. The developer colliding with the falling developer slides down the slope of the blade. As a result, it was found that the amount of development lifted to the vicinity of the surface of the developer carrier decreased, and the amount of developer attracted by the magnetic force of the attracting magnetic pole was reduced.
Therefore, in this aspect, an inclined surface that is opposed to the conveying screw from above and is inclined so that the developer carrying member side is positioned upward is provided. As a result, the developer that has jumped upward from the blades of the conveying screw comes into contact with the inclined surface, and its moving direction is changed to a direction toward the developer carrier. In this way, the developer that has jumped upward from the blades of the conveying screw is directed to the developer carrier, so that the developer that has jumped up is captured by the magnetic force of the magnetic field generation unit and is carried on the surface of the developer carrier. The As a result, in addition to the developer lifted to the vicinity of the surface of the developer carrier by the blades of the transport screw and attracted to the surface of the developer carrier by the magnetic force of the attracting magnetic pole, The splashed developer can be carried on the surface of the developer carrying member. Therefore, the amount of developer carried on the surface of the developer carrying body can be increased more than before.
Further, in this aspect, the developer that has jumped upward from the blade of the conveying screw contacts the inclined surface and its moving direction is changed to the direction toward the developer carrying member, so that it jumps upward from the blade of the conveying screw. It is possible to prevent the developer from dropping freely and returning to the developer accommodating portion again. Thereby, it is possible to suppress the developer colliding with the developer being lifted to the vicinity of the developer carrying member by the blades of the conveying screw and sliding down the slope of the blades. As a result, the amount of developer that can be lifted to the vicinity of the developer carrier by the blades of the conveying screw can be increased more than before, and the amount of developer that is attracted to the surface of the developer carrier by the magnetic force of the attracting magnetic pole can be increased. Can do.
Thus, in this aspect, the amount of developer carried on the surface of the developer carrying body can be increased compared to the conventional case. By increasing the amount of developer carried on the surface of the developer carrying body, the layer thickness of the carried developer can be increased as a whole, and the difference between the layer thickness of the portion where the developer amount is small and the regulation gap is increased. It can be made smaller. Further, the developer regulated by the developer regulating member increases, and after the regulation by the developer regulating member, it is possible to increase the developer moving to a portion where the developer amount is small. Thereby, it is possible to suppress the uneven state of the developer amount on the developer carrier after passing through the regulation gap, and it is possible to suppress the image density unevenness according to the blade pitch of the conveying screw.
However, even in such a configuration, image density unevenness may occur if the inclined surface extends to the vicinity of the developer regulating member or in contact with the developer regulating member. Specifically, the developer carried on the developer carrying member and restricted from passing through the regulation gap by the developer regulating member (hereinafter referred to as a post-regulation developer) is captured by the magnetic force of the magnetic field generation unit, and the developer. It stays on the regulating side of the regulating member. A part of the regulated developer that stays in this way is moved upward along the inclined surface by the developer regulated later, along the inclined surface. The post-regulation developer that moves along the inclined surface inherently weakens the action of the magnetic force of the magnetic field generation unit as it moves along the inclined surface, so that it falls off the inclined surface near the upper part of the transport screw, and falls. Returned to the developer container. However, when the developer that has jumped upward from the blades of the conveying screw comes into contact with the inclined surface and its moving direction is changed to the direction toward the developer carrier, the developer after the restriction is placed at the contact point with the inclined surface. May exist. In this case, the post-regulation developer on the inclined surface is bounced by the developer that jumps upward from the blade of the conveying screw toward the developer carrying body together with the developer that jumps upward from the blade of the conveying screw. Then, it is carried on the developer carrier without being returned to the developer container. In this way, the post-regulation developer carried on the developer carrying body is again restricted from passing through the regulation gap, moved on the inclined surface, and again with the developer jumped up from the blades of the conveying screw. It is carried on a carrier. By repeating such an event, the post-regulation developer is rubbed repeatedly by the developer regulating member or the developer carrying member, and as a result, the charge amount is increased. When such a regulated developer having a high charge amount locally passes through the regulation gap, patchy image density unevenness occurs.
Therefore, in this embodiment, the post-regulation developer that moves on the inclined surface to above the conveying screw is dropped from the inclined surface by the developer drop accelerating portion. As a result, the post-regulation developer moving on the inclined surface can be dropped before reaching the location on the inclined surface where the developer jumped upward from the blade of the conveying screw contacts. Therefore, it is possible to suppress the occurrence of an event in which the post-regulation developer moves toward the developer carrying body together with the developer that has jumped upward from the blade of the conveying screw. As a result, it is possible to prevent the regulated developer from being repeatedly rubbed by the developer regulating member or the developer carrying member, to suppress an excessive increase in the charge amount of the regulated developer, and to prevent uneven image density unevenness. Occurrence can be suppressed.
As described above, it is possible to suppress image density unevenness according to the blade pitch of the conveying screw and to suppress occurrence of patchy image density unevenness.

(Aspect B)
In (Aspect A), the developer drop accelerating portion is configured such that the inclined surface is bent in a direction in which the developer is dropped when viewed from the conveying screw shaft direction. It is.
According to this aspect, the regulated developer is moved to a place where the attracting magnetic force of the attracting magnetic pole does not reach the part of the inclined surface that is bent in the direction in which the developer is dropped. It is prevented from moving downward along the inclined surface. As a result, the regulated developer is prevented from coming into contact with the developer that has jumped up from the blades of the conveying screw. As a result, the developer that jumps upward from the blades of the conveying screw and contacts the inclined surface can change its moving direction and head toward the developer carrying member.

(Aspect C)
In (Aspect A), the developer drop accelerating portion is an obstacle that dams up the developer moving above the transport screw along the inclined surface.
According to this aspect, the obstructed hinders the post-regulation developer from moving downward along the inclined surface. As a result, the regulated developer is prevented from coming into contact with the developer that has jumped up from the blades of the conveying screw. As a result, the developer that jumps upward from the blades of the conveying screw and contacts the inclined surface can change its moving direction and head toward the developer carrying member.

(Aspect D)
In (Aspects A) to (Aspect C), the developer drop accelerating portion is located above a location where the developer in the developer accommodating portion, which is jumped upward from the blade of the conveying screw, contacts the inclined surface. It is provided in the location of the said inclined surface.
According to this aspect, the regulated developer is prevented from coming into contact with the developer that has jumped upward from the blades of the conveying screw. As a result, the developer that jumps upward from the blades of the conveying screw and contacts the inclined surface can change its moving direction and head toward the developer carrying member.

(Aspect E)
(Aspect A) to (Aspect D) are characterized in that the developer drop accelerating portion is provided vertically above a range in which a scooping action by the blades of the conveying screw reaches.
According to this aspect, the regulated developer dropped from the inclined surface by the developer drop accelerating portion is dropped onto the upper surface of the developer in the developer accommodating portion where the lifting action by the blades of the conveyance screw is applied and is spread on the conveyance screw. The developer is mixed and stirred with the developer in the developer container. Thereby, the charge amount of the developer supplied onto the developer carrying member is almost equalized. By supplying the developer whose charge amount is made uniform to the development region, it is possible to suppress the occurrence of uneven image density unevenness.

(Aspect F)
In the process cartridge 1 that holds at least the latent image carrier and the developing device and can be attached to and detached from the image forming apparatus main body, the developing device according to any one of (Aspect A) to (Aspect E) is used as the developing device. Using.
According to this aspect, it is possible to provide a process cartridge that can suppress the occurrence of uneven image density unevenness due to a developer having an excessively increased charge amount and obtain a good image.

(Aspect G)
In an image forming apparatus including a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, any one of (Aspect A) to (Aspect E) may be used as the developing unit. The developing device was used.
According to this aspect, it is possible to suppress the occurrence of uneven image density unevenness due to the developer having an excessively increased charge amount, and a good image can be obtained.

1 Process Cartridge 10 Photoconductor 12a Developing Roller 12a1 Magnet Roller 12a2 Developing Sleeve 12b First Conveying Screw 12c Second Conveying Screw 12c1 Shaft 12c2 Blade 12d Developing Doctor 12g First Guide Member 12g1 Developer Drop Promoting Section 12h Second Guide Member 121 Developing casing 122 Partition wall 1211 Upper casing 1211a Fitting hole 1212 Lower casing DG Doctor gap K First inclined surface L Second inclined surface P1 Developing magnetic pole P2 First agent separating magnetic pole P3 Second agent separating magnetic pole P4 Attracting magnetic pole P5 Regulating magnetic pole V1 First agent storage chamber V2 Second agent storage chamber

JP 2010-175945 A

Claims (7)

A developer carrying member for carrying the developer on the surface, a magnetic field generating unit having a plurality of magnetic poles arranged inside the developer carrying member, and disposed in the developer containing unit located below the developer carrying member. In a developing device having a transport screw made
It is provided with an inclined surface that faces the conveying screw from above and is inclined so that the developer carrying member side is positioned above,
The inclined surface forms a regulation gap with the surface of the developer carrying member, and contacts the developer regulation member up to the vicinity of the developer regulation member that regulates the amount of developer passing through the regulation gap. Extending,
A developer drop accelerating portion for dropping the developer that is restricted from passing through the regulation gap by the developer regulating member and moves on the inclined surface to the upper side of the conveying screw; Developing device. The developing device according to claim 1,
The developing device, wherein the developer drop accelerating portion is configured so that the inclined surface is bent in a direction in which the developer is dropped when viewed from the conveying screw shaft direction. The developing device according to claim 1,
The developing device according to claim 1, wherein the developer drop accelerating portion is an obstacle that dams up the developer moving above the conveying screw along the inclined surface. The developing device according to any one of claims 1 to 3,
The developer drop accelerating portion is provided at a location on the inclined surface above a location where the developer in the developer accommodating portion, which is splashed upward from the blades of the conveying screw, contacts the inclined surface. A developing device. In the developing device according to any one of claims 1 to 4,
The developing device according to claim 1, wherein the developer drop accelerating portion is provided vertically above a range in which a squeezing action by the blades of the conveying screw reaches. In a process cartridge that holds at least the latent image carrier and the developing device integrally and is detachable from the image forming apparatus main body,
A process cartridge using the developing device according to claim 1 as the developing device. In an image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing unit that develops the latent image on the latent image carrier.
An image forming apparatus using the developing device according to claim 1 as the developing unit.

Images