JP2015108665A - Developing device, process unit, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can prevent scattering of developer without causing an increase in the consumption of power and developer and a reduction in the quality of images to be formed.SOLUTION: A developing device includes a latent image carrier 20, a developing roller 15 that is provided opposite to the latent image carrier 20, a developing device lower cover 16 that is provided at the lower side of the developing roller 15 and has a part opposite to the developing roller 15 formed into an R-shape substantially concentric with the developing roller 15, and a suction unit 30 that is provided on the lower side of the developing device lower cover 16 to perform the suction of developer; and further includes an open channel 31 provided between the developing device lower cover 16 and suction unit 30, where the inside of the open channel 31 is kept under atmospheric pressure.

Description

  The present invention relates to a developing device, a process unit, and an image forming apparatus, and more particularly to a developing device, a process unit, and an image forming apparatus having a mechanism for preventing toner scattering.

  2. Description of the Related Art Conventionally, a developing device used in an image forming apparatus such as an electrophotographic printing apparatus uses a two-component developer in which a magnetic carrier and a magnetic or nonmagnetic toner are mixed.

  In such a developing device, a developer that has been agitated and mixed and has been subjected to frictional charging of opposite polarities is supplied toward the developing roller. The developer supplied to the developing roller forms a magnetic brush on the surface of the developing roller provided with a developing main pole magnet and a developer conveying magnet inside. The developer forming the magnetic brush is carried on a developing roller, conveyed to an electrostatic latent image formed on a photosensitive member, and used for visible image processing of the latent image.

  In recent years, with the trend of increasing the speed of electrophotographic printing apparatuses, recycling of toner, and extending the life of developers, there has been an increasing demand for improvement in prevention performance against toner scattering from the developing apparatus.

  For example, in order to increase the speed of an electrophotographic printing apparatus, it is necessary to increase the linear velocity of the photosensitive member. In this case, the airflow along the photosensitive member also increases, so that the toner floating in the developing device is caused by the airflow. It is easily carried and scattered outside the developing device.

  In addition, when the photosensitive member linear speed is increased, the developer supply amount for the electrostatic latent image on the photosensitive member is insufficient, and the image density is lowered. Therefore, the developer roller linear speed is increased to increase the developer supply amount. It is necessary to prevent a decrease in image density. However, when the linear velocity of the developing roller is increased, the centrifugal force acting on the developer on the developing roller increases, so that the toner is easily scattered from the developer. In order to increase the developer supply amount without increasing the linear velocity of the developing roller, it has been proposed to arrange two developing rollers side by side along the moving direction of the photoreceptor. However, even in this case, the distance that the developer is transported on the developing roller becomes long, and the developer is transferred between the developing rollers, so that the toner is easily scattered from the developer.

  Further, when toner is recycled in order to reduce toner consumption, the generation of reversely charged toner and weakly charged toner increases, so that toner scattering is likely to occur.

  Furthermore, since the maintenance interval becomes longer as the life of the developer becomes longer, there is an increasing demand for reducing trouble due to toner scattering.

  The following are disclosed as techniques for solving these problems.

  In Patent Document 1, in order to prevent toner scattering, in the developing device in which the developing sleeve facing position of the developing device lower case has an R shape that is substantially concentric with the developing sleeve, the pole facing the developing device lower case is formed in an R shape. It has been proposed to be in the middle. For example, as shown in FIG. 7, the developer attached to the magnetic pole P22 of the developing roller 15 seals between the developing device lower case 16 and the developing sleeve 15a. As a result, if this sealing property is sufficient, an air flow along the rotation direction of the developing sleeve 15a is generated, so that it is possible to prevent toner scattering near the lower case 16 of the developing device. This is called a pumping effect. In this example, the position of the magnetic pole P22 of the developing roller 15 is at a position that is more efficient for enhancing the pumping effect of the developing roller 15, that is, the center of the R shape of the lower case 16 of the developing device.

  Patent Document 2 describes a method of reducing toner scattering by forming a suction duct at a position close to the lower surface of the lower case of the developing device and sucking it with a blower.

  Usually, the developing device itself also forms a suction airflow and sucks toner into the developing device. As described above, when a suction slit, for example, a suction duct is brought close to the lower part of the developing roller of the developing device, the air current formed by the developing device itself is sucked into the suction duct, and the suction efficiency is deteriorated. . The filter of the suction duct must be replaced periodically, otherwise the suction effect will be reduced. In the case of this example, the frequency of replacement of the filter increases, so that maintenance work increases.

  In Patent Document 2, in order to improve the above problem, it is further proposed to form a slit portion in the upper plate of the upper plate and the lower plate forming the suction slit to communicate with the inside of the developing device. Yes.

  In Patent Document 3, the problem that Patent Document 2 has a strong suction force that attracts even toner for image formation is to make the air volume variable so that the air volume is lowered during the developing operation and the air volume is increased during the non-developing operation. It is solved with.

  Patent Document 4 discloses a technique for solving the problem that the toner is scattered when the developing operation of Patent Document 3 continues for a long time. In the developing device of Patent Document 4, a suction slit, a filter connected to the suction slit, and a blower are provided below the lower case of the developing device that accommodates toner. The suction opening of the suction slit is connected to a slit substantially parallel to the axis of the developing roller formed at the bottom of the lower case of the developing device, and the slit has a large number of holes through which the developer particles do not pass but allow air to pass. It is suggested to install sex sheets. In the suction device for a developing device configured as described above, the cloud toner is sucked into the developing device by using the suction air flow of the developing device, and at that time, the air is passed through the slit hole provided in the developing device and through the filter. Is sucked out of the developing device. Thus, the suction force by the suction airflow is increased, and the cloud toner is prevented from scattering into the main body of the image forming apparatus.

  In the developing device of Patent Document 1, the developer transport speed is low at the pole facing the lower case of the developing device. Therefore, the airflow speed along the rotation direction of the developing sleeve is low, and the pumping effect is small. Therefore, the toner scattering prevention performance is not sufficient, and there are problems that the inside and outside of the printing apparatus are stained with toner, and the toner adhered inside and outside the printing apparatus contaminates the printed matter.

  In the developing device of Patent Document 2, since the suction slit sucks air through the opening and the slit portion that opens on the lower side of the developing device, a high air suction force is required, the suction motor becomes large, and power consumption increases. There is a problem. In addition, since the developer falls through the slit and the developer is sucked, there is a problem that toner consumption increases. In addition, since the gap between the photosensitive drum and the developing device is smaller than other places, if the suction by the suction device provided near the developing device is too strong, the flow velocity in the gap between the photosensitive drum and the developing device increases. The scattered toner adheres to the photosensitive member to cause scumming or fogging, and the image quality deteriorates. Further, the toner other than the floating toner is sucked, and particularly the toner for image formation on the photosensitive drum is sucked, and there is a problem that the image quality is deteriorated and the toner consumption is increased.

  In the developing device of Patent Document 3, when the developing operation is continued for a long time, the toner scattering prevention performance is not sufficient, and there is a problem that the toner adhered inside and outside the printing apparatus and inside and outside the printing apparatus is soiled.

  In the developing device of Patent Document 4, since toner adheres to the air permeable sheet, the air permeability of the air permeable sheet decreases with time, and the suction force decreases. When the suction force is reduced, the toner scattering prevention performance is lowered, and there is a problem that the toner adhered inside and outside the printing apparatus and inside and outside the printing apparatus is soiled.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device capable of preventing scattering of a developer without causing an increase in power consumption and developer consumption and a reduction in image quality of a formed image. is there.

  The developing device of the present invention includes a latent image carrier, a developing roller provided to face the latent image carrier, a lower side of the developing roller, and a portion facing the developing roller is the developing roller. A developer storage member having a substantially concentric R shape, and a suction means for suctioning the developer provided below the developer storage member, wherein the developer storage member And an open path provided between the suction section and the inside of the open path is maintained at atmospheric pressure.

  According to the present invention, it is possible to provide a developing device capable of preventing the scattering of the developer without causing an increase in power consumption and a consumption amount of the developer and a deterioration in image quality of the formed image. it can.

1 is an overall view of a developing device according to a first embodiment of the present invention. It is a perspective view of Embodiment 1 of a development device of the present invention. It is a perspective view of Embodiment 1 of a development device of the present invention. It is a perspective view of Embodiment 1 of a development device of the present invention. FIG. 3 is a side view of the periphery of the suction slit of the developing device according to the first embodiment of the present invention. It is a perspective view of Embodiment 2 of the developing device of the present invention. It is a side view of the conventional developing device. It is a side view of the conventional developing device.

<Configuration of Embodiment 1>
Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the first embodiment, for example, a two-component developer in which a carrier and a toner are mixed is used, and two developing rollers are provided. This is one example of the embodiment. In practice, a one-component developer may be used, or three or more developing rollers may be used.

  As shown in FIG. 1, the developing device 1 includes a developer tank 2 for storing a developer 3, a toner hopper 4 for storing toner 5, a supply roller 6 for supplying toner 5, a toner concentration sensor 7, an elliptical plate 8, A fin 10 and a paddle 11 are provided. Further, as a mechanism for performing development and toner recycling, a screw 9, a separator 12, a doctor blade 13, a developing roller 14, a developing roller 15, a developing device lower case 16 as a developer storage member, a photosensitive member 20 as a latent image carrier, A suction unit 30 is provided as suction means.

  The developing rollers 14 and 15 are provided to face the photoconductor 20, the developing roller 14 has magnetic poles P11, P12, P13, P14, and P15, and the developing roller 15 has magnetic poles P21, P22, and P23. Around the developing rollers 14 and 15, developing sleeves 14a and 15a made of a fixed magnetic pole and a rotating aluminum sleeve are provided.

  As shown in FIG. 1, the developing roller 15 is provided below the developing roller 14. A developing device lower case 16 is provided on the lower side of the developing roller 15, and a portion facing the developing roller 15 has an R shape substantially concentric with the developing roller 15, and the magnetic pole P <b> 12 is a central portion of the R shape. Is facing. The distance between the developing device lower case 16 and the developing sleeve 15a is, for example, 0.5 to 3 mm. Here, the normal direction magnetic flux density of the magnetic poles P21 and P22 is, for example, 110 to 140 mT.

  An open path 31 connected to the outside of the developing device at atmospheric pressure is formed below the lower case 16 of the developing device. Further, below the open path 31, a suction path 33 connected to the suction fan 32 and a suction slit 35 connected to the suction path 33 are installed so as to face the photoconductor 20.

  As shown in FIGS. 2 and 3, both ends of the open path 31 may be open and connected to the outside, or only one end may be open and connected to the outside as shown in FIG. It may be configured.

<Operation of Embodiment 1>
The operation of the first embodiment will be described. The toner 5 is supplied from the supply roller 6 of the toner hopper 4 to the developer 3 contained in the developer tank 2 of the developing device 1 shown in FIG. An appropriate amount of toner supply is determined from the output value of the toner density sensor 7 and the like. The replenished toner 5 is agitated with the developer 3 by the elliptical plate 8 and is thrown off to the developing roller 14 by the paddle 11 rotating in the arrow A direction.

  The magnetic pole P13 pole of the developing roller 14 is a developer pumping pole, and the thrown away developer 3 is held by this magnetic pole. The developing sleeves 14a and 15a rotate in the arrow B direction. The developer 3 held on the magnetic pole P13 of the developing roller 14 is conveyed in the direction of the magnetic pole P15 from the magnetic pole P14 of the developing roller 14, and the layer thickness, which is the height of the spike, is regulated by the doctor blade 13 between them. Thereafter, the latent image is developed on the photosensitive member 20 rotating in the direction of arrow C by the magnetic pole P11 which is the main pole of the developing roller 14.

  The magnetic pole P12 of the developing roller 14 and the magnetic pole P23 of the developing roller 15 are transfer poles, and the developer 3 is transferred from the developing roller 14 to the developing roller 15 between them. The developed developer 3 is transported as it is, passes through the magnetic poles P23, P21, and P22 of the developing roller 15 and then dissociates from the developing roller 15, and is transported again to the position of the elliptical plate 8 by the paddle 11, and newly replenished The toner 5 is stirred.

  After the layer thickness is regulated by the doctor blade 13, the developer 3 naturally falls on the diagonal plate portion of the separator 12, and a part thereof is slightly skewed by the fin 10 and then returns to the position of the elliptical plate 8. In addition, a part is conveyed by the screw 9 in the direction opposite to the skew by the fin 10, and then returns to the position of the elliptical plate 8. As described above, the developer in the horizontal direction in the developing device is stirred.

  As shown in FIG. 2, since the fixed magnetic poles are not provided at both ends of the developing roller 14 and the developing roller 15, the developer 3 is not conveyed, but the toner and the developer are prevented from scattering from this region. Therefore, side shields 21 are installed at both ends.

  The developer 3 adhered to the magnetic pole P22 of the developing roller 15 seals between the developing device lower case 16 and the developing sleeve 15a. If this sealing property is sufficient, an air flow is generated along the rotation direction of the developing sleeve 15a, so that the toner floating above the developing device lower case 16 is sucked between the developing sleeve 15a and the developing device lower case 16. It is. This is called a pumping effect.

  Since the suction fan 32 is operated so as to suck the air inside the suction slit 35 and out of the suction path 33, when the toner 5 scattered from the developing device 1 comes near the suction slit 35, the suction path 33 is sucked into 33. The air suction amount of the suction fan 32 is, for example, 20 to 100 L / min.

<Operation / Effect of Embodiment 1>
An arrow 100 in FIG. 5 indicates the flow of air. Between the suction slit 35 and the developing device lower case 16, an open path 31 connected to the outside of the developing machine at atmospheric pressure is formed. Therefore, as shown in FIG. 5, when air is sucked by the suction slit 35, the air below the open path 31 and the suction slit 35 is sucked, but the air between the developing device lower case 16 and the developing sleeve 15a is Not sucked. Therefore, the pumping effect between the developing device lower case 16 and the developing sleeve 15a is not lowered, and most of the toner floating on the upper side of the developing device lower case 16 is separated from the developing sleeve 15a by the pumping effect. Sucked between cases 16. Then, the toner scattered to the lower side of a part of the lower case 16 of the developing device is sucked by the suction slit 35.

  In the case of a conventional developing device not provided with the open path 31, air between the developing device lower case 16 and the developing sleeve 15a is sucked as shown in FIG. An arrow 101 indicates the air flow. As a result, the pumping effect between the developing device lower case 16 and the developing sleeve 15a is reduced, or the toner floating above the developing device lower case 16 is sucked. As a result, the amount of toner scattered downward from the developing device lower case 16 along the photosensitive member 20 increases, and the toner adheres to the lower case 16 and the suction slit 35. In this case, toner accumulates in the vicinity of the lower case 16 and the suction slit 35 over time, and when the toner accumulation amount exceeds the limit, the toner falls, and the inside and outside of the printing apparatus and the printed matter are soiled with toner.

<Configuration of Embodiment 2>
As shown in FIG. 6, in the second embodiment, in addition to the configuration of the first embodiment, a blower 34 is provided at the right end of the open path 31. The air blowing amount of the blower 34 is, for example, about 0.5 to 2 times the air suction amount of the suction fan 32.

<Operation of Embodiment 2>
In the second embodiment, air is blown to the open path 31 by the blower 34 simultaneously with the rotation of the developing roller 15 and the suction by the suction fan 32.

<Operation and Effect of Embodiment 2>
In this case, even if the air suction amount of the suction slit 35 is increased, the air below the open path 31 and the suction path 33 is sucked, and the air between the lower case 16 and the developing sleeve 15a is not sucked. . Therefore, the pumping effect between the lower case 16 and the developing sleeve 15a is not lowered, and the amount of air sucked by the suction slit 35 can be increased. Therefore, compared to the first embodiment, the toner accumulation amount in the vicinity of the lower case 16 and the suction slit 35 can be further reduced.

  Further, the developing device 1 can be considered as an example in which the developing device 1 is used by being provided in an image forming apparatus or a process unit for mounting on the image forming apparatus.

  The above-described embodiment is a preferred embodiment of the present invention, and the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

DESCRIPTION OF SYMBOLS 1 Developing device 2 Developer tank 3 Developer 4 Toner hopper 5 Toner 6 Supply roller 7 Toner density sensor 8 Elliptical plate 9 Screw 10 Fin 11 Paddle 12 Separator 13 Doctor blade 14, 15 Developing roller 14a, 15a Developing sleeve 16 Below developing device Case 20 Photoconductor 21 Side shield 30 Suction part 31 Open path 32 Suction fan 33 Suction path 34 Blower 35 Suction slit

JP 2002-189349 A Japanese Examined Patent Publication No. 2-61755 Japanese Patent Application Laid-Open No. 1-1276 JP-A-5-53425

Claims (6)

A latent image carrier;
A developing roller provided facing the latent image carrier,
A developer storage member provided on the lower side of the developing roller, the portion facing the developing roller having an R shape substantially concentrically with the developing roller;
A suction means provided on the lower side of the developer storage member for sucking the developer;
A developing device comprising:
An open path provided between the developer storage member and the suction means;
A developing device characterized in that the inside of the open path is maintained at atmospheric pressure.   2. The developing device according to claim 1, wherein at least one end portion of the open path is open and connected to the outside of the developing device.   3. The developing device according to claim 1, further comprising: a blower that blows outside air toward the inside of the open path at at least one of the both ends of the open path.   A process unit comprising the developing device according to claim 1.   An image forming apparatus comprising the developing device according to claim 1.   An image forming apparatus comprising the process unit according to claim 4.

Images