JP2006098601A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of image density deterioration at the edge of a developer carrier by properly adjusting a gap between a second regulation member and the developer carrier in a developing device using self-toner concentration control. <P>SOLUTION: The second regulation member 23 is fixed to a long hole 32 provided to the developer housing member 16a of a support case 14 so that its position variably fixed with a screw 31 which is a gap adjustment member. The position of the screw 31 to the long hole 32 is made variable. When deviation of developer arises in the axial direction of a development sleeve 15 and difference in toner concentration arises, the second regulation member 23 is moved and adjusted so that a gap Gpd with thinner image density is wide and a gap Gpd with thicker image density is narrow. When scumming arises at the edge of the development sleeve 15, the toner concentration is lowered by narrowing the gap Gpd on the side where the scumming arises and thereby, the scumming is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser printer, or a plain paper fax machine using a direct or indirect electrophotographic developing system, in order to develop an electrostatic image by electrophotography, electrostatic recording, electrostatic printing or the like. More particularly, the present invention relates to a process cartridge and an image forming apparatus using the same.

  The electrophotographic method generally uses a photoconductive material, forms an electric latent image on the electrostatic latent image carrier by various means, and then develops the latent image with toner, and if necessary, paper The toner is transferred to a recording medium such as a toner image, and then the toner image is fixed on the recording medium by heating or solvent vapor to obtain a copy image or a printed image. As a means for developing the electrostatic latent image formed on the electrostatic latent image carrier such as a photoconductor, a method using a liquid developer (wet development method) and a colorant dispersed in a binder resin are used. Or a method using a one-component or two-component dry developer obtained by mixing this toner with a carrier (dry development method). Each of these methods has advantages and disadvantages, but at present, the dry development method is widely used.

  Among these methods, the two-component development method in which the toner concentration is self-controlled by two developer regulating members and a developer carrier is relatively faster and has a longer life than the one-component development method. Since it is possible, it is widespread mainly in medium to high speed copying machines and printers. In addition, a sensor, a toner supply control device, and the like are not required, so that low cost can be realized and downsizing as a developing device can be realized.

  That is, conventionally, as this type of developing device, the amount of the two-component developer carried and transported by a developer carrying member having a magnetic field generating means therein is regulated by a regulating member, and the development contained in the developer containing chamber There is known a developing device in which toner is supplied from a toner container to a developer container by increasing or decreasing the volume of the agent. In this developing device, a developer moving layer carried by a developer carrying member and a developer circulating layer that can be circulated in the developer containing chamber are generated, and toner is taken in by movement of the developer. Yes. Such a developing device does not require a toner concentration detecting means, but the developer is located in a portion where the developer is active and inactive, or a portion where there is a lot of developer and a portion where there is a lot of developer. However, the toner concentration may be partially unstable due to different amounts of toner.

  For this reason, a second regulating member is provided on the upstream side in the transport direction of the developer on the developer carrying member relative to the regulating member that regulates the amount of developer, and the toner concentration of the developer on the developer carrying member increases. When the developer layer thickness increases, a developing device in which a gap with the developer carrying member is set is proposed in order for the second restricting member to restrict the passage of the increased amount of developer. Yes (see, for example, Patent Document 1).

  In this developing device, the second restricting member restricts the passage of the increased developer, and the regulated developer controls the toner uptake so that the toner supply can be constantly controlled at a constant level. Adjustments can be made. However, the toner supply control is a structure in which toner supply control cannot be forcibly performed. The toner density control is performed by the gap between the regulating member and the developer carrier, the gap between the developer carrier and the developer carrier, and the magnetic field generation means of the developer carrier. It depends on the magnetic flux density, the peak magnetic flux density of the developer carrier, the position (angle) of the half width, and the like.

  Then, deviations in the developer regulation amount occur due to assembly deviations of the regulation gaps of the first and second regulation members, manufacturing component accuracy tolerances, magnetic flux density distribution deviation of the magnetic field generating means of the developer holder, and the like. Thus, the developer is biased with respect to the longitudinal direction of the developer holder.

  For this reason, the developer tends to be displaced to the end portion in the axial direction of the developer carrying member, and the toner supply failure occurs at the end portion where the developer amount increases, and the image density is lowered at that portion. On the other hand, toner is excessively supplied at the end portion where the developer amount is reduced, and background stains may be caused in the formed image.

  As described above, since the two-component developing device that self-controls the toner density can be downsized, it is mainly used in a small printer. However, the small printer is often placed on a desk and placed on the floor. It is easier to use with the device tilted than a large printer. That is, the above-described deviation of the developer and the problems caused by it tend to occur due to the inclination of the apparatus.

  Therefore, in this method, high component accuracy and assembly accuracy are required, and it is essential to use the apparatus in a horizontal state. If these conditions are not satisfied, abnormal images such as uneven image density and background stains are caused.

Accordingly, a developing device is provided that can optimize the gap between the first and second regulating members and the developer carrier and the fluidity of the developer, and uniformize the toner concentration of the developer in the longitudinal direction of the developer carrier. Therefore, the flowability of the developer is set to 10 seconds or more and 30 seconds or less, the values of the first gap and the second gap are defined, and the product value of both gaps is set within a predetermined range. Even if gravity and a magnetic field act on the developer, the developer circulation state is not partially changed, the developer movement unevenness is eliminated, and the difference in the amount of toner taken in is eliminated. There has been proposed a technique for preventing unevenness from occurring (see, for example, Patent Document 2).
JP-A-9-197833 JP 2000-250308 A

  However, in the developing device disclosed in Patent Document 2, the second regulating member is fixed, and there is a problem that image adjustment at the time of manufacturing the developing unit and image adjustment at the time of repair at the user cannot or are difficult. there were.

  The present invention solves the disadvantages of the conventional toner density self-control type two-component developing device, makes it easy to adjust the position of the second regulating member, and does not easily cause a decrease in image density at the end of the developer carrying member. An object of the present invention is to provide a developing device capable of forming a stable image with little or no density unevenness, and a developing unit and an image forming apparatus using the developing device.

  Among the developing devices according to the present invention, the one according to claim 1 is a developer carrying member that carries and conveys a two-component developer composed of toner and a magnetic carrier, and a development that is carried and carried by the developer carrying member. A first regulating member that regulates the amount of the developer, and a toner container that supplies toner to the developer carrier adjacent to the developer container, and the developer toner concentration on the developer carrier A developing device that changes a toner intake state of the developer on the developer carrier in accordance with a change in the developer, wherein the developer containing portion is more developed on the surface of the developer carrier than the first regulating member. A second restricting member is provided on the upstream side in the transport direction of the agent, and a gap between the second restricting member and the developer carrier is variable.

  According to the second aspect of the present invention, there is provided a developer carrying body having a magnetic field generating means therein and carrying and transporting a two-component developer composed of toner and a magnetic carrier, and carried and carried by the developer carrying body. A first regulating member that regulates the amount of developer to be developed, a developer containing portion that contains the developer scraped off by the first regulating member, and the developer carrying member adjacent to the developer containing portion A toner container for supplying toner to the body, and by changing the developer toner density on the developer carrier, the contact state between the developer and the toner is changed to change the developer on the developer carrier. A developing device that changes a toner taking-in state, wherein the developer containing portion is disposed on the upstream side in the transport direction of the developer on the developer carrying member with respect to the first regulating member. In the developing device having a member, the second restricting member and the front The gap between the developer carrying member, characterized in that the variable.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the second restricting members are provided at both axial ends of the developer carrier.

  According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the gap between the second restricting member and the developer carrying member is set to each of both axial ends of the developer carrying member. It is characterized by being variable.

  According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, the gap of the thinner image density is widened and the gap of the darker image density is narrowed to adjust the axis of the developer carrier. The toner density difference in the direction is reduced, and the image density difference can be eliminated.

  According to a sixth aspect of the present invention, in the developing device according to the fourth or fifth aspect, when the background stain occurs at one end portion on the axial direction side of the developer carrier, the gap on the end portion side is reduced. It is characterized in that the toner density can be reduced by making it narrower to prevent scumming.

  The process cartridge according to claim 7 of the present invention integrally supports an image carrier such as a photosensitive member and at least one means selected from a charging means, a developing means, and a cleaning means, and is detachable from the main body of the image forming apparatus. In a certain process cartridge, the developing means is the developing device according to any one of claims 1 to 6.

  An image forming apparatus according to an eighth aspect of the present invention includes the developing device according to any one of the first to sixth aspects.

  According to a ninth aspect of the present invention, the process cartridge according to the seventh aspect is provided.

  According to the present invention, in a developing device using self-toner density control, by appropriately adjusting the gap between the second regulating member and the developer carrier, image density lowering at the end of the developer carrier is eliminated, and density unevenness is eliminated. Even if there is no, a stable image with a small amount can be obtained, and an excellent effect of improving the tilt margin in the axial direction of the developer carrying member is obtained.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a developing device according to the present invention. In the figure, 1 is a photosensitive drum as a latent image carrier, 2 is a charging means, 3 is a laser writing unit, 4 is a developing device, 5 is a transfer roller, and 6 is a cleaning device. In the figure, reference numeral 7 denotes a paper feed unit, 8 denotes a paper feed roller, 9 denotes a registration roller pair, 10 denotes a fixing device, 11 denotes a paper discharge unit, and 12 denotes an image forming apparatus main body.

  The photosensitive drum 1 is rotationally driven in a direction indicated by an arrow in the drawing by a driving unit (not shown), the surface of the photosensitive drum 1 is uniformly charged by the charging unit 2, and then a latent image is formed on the surface by exposure from the laser writing unit 3. The latent image is visualized by the developing device 4 and the toner image is transferred by the transfer device 5 to a transfer material P such as paper supplied from the paper supply unit 7 via the paper supply roller 8 and the registration roller pair 9. . The toner remaining on the surface of the photosensitive drum 1 after the toner image transfer is removed by the cleaning device 6. Further, the surface of the photosensitive drum 1 is repeatedly used for image formation after being neutralized.

  Then, the transfer material P to which the image has been transferred is introduced into the fixing device 10, the toner image is fixed to the transfer material P by heating and pressurization, and then discharged to the paper discharge unit 11. Of course, the present invention is not limited to the illustrated image apparatus, and can be applied to various types.

  Although the detailed illustration and description are omitted, the present invention is configured by integrally connecting the developing device 4 and the like as a process cartridge, and the process cartridge can be attached to and detached from an image forming apparatus main body such as a copying machine or a printer. It can also be applied to those configured as follows.

  FIG. 2 is a schematic sectional view showing an embodiment of the developing device according to the present invention. The developing device 4 disposed on the right side in the drawing in the axial direction of the photosensitive drum 1 as a latent image carrier has a support case 14, a developing sleeve 15 as a developer carrier, a developer containing member 16a, a developer regulation. It is mainly composed of a first restricting member 17 and a second restricting member 23 as members.

  A support case 14 having an opening on the side of the photosensitive drum 1 forms a toner hopper 19 as a toner storage portion that stores toner 18 therein. A developer accommodating member 16 a that forms a developer accommodating portion 16 that accommodates a developer 22 composed of toner 18 and a carrier that is magnetic particles is provided in a portion of the toner hopper 19 near the photosensitive drum 1. The developer accommodating member 16a is provided integrally with the support case 14, and the support case 14 positioned below the developer accommodating portion 16 is formed with a protruding portion 14a having a facing surface 14b. A toner supply opening 20 for supplying the toner 18 is formed by a space between the lower portion of the agent containing portion 16 and the facing surface 14b.

  Inside the toner hopper 19, a toner agitator 21 is disposed as toner supply means that is rotated by a drive means (not shown). The toner agitator 21 sends out the toner 18 in the toner hopper 19 toward the toner supply opening 20 while stirring.

  A developing sleeve 15 is disposed in a space between the photosensitive drum 1 and the toner hopper 19. The developing sleeve 15 that is rotationally driven by a driving means (not shown) has a magnet (not shown) as a magnetic field generating means in which the relative position of the magnetic pole is fixed with respect to the developing device 4.

  A first regulating member 17 is integrally attached to the side of the developer accommodating portion 16 that faces the side attached to the support case 14. The first restricting member 17 is disposed in a state where a certain gap is maintained between the tip of the first restricting member 17 and the outer peripheral surface of the developing sleeve 15.

  A second restricting member 23 as a restricting member is disposed in a portion of the developer accommodating portion 16 located in the vicinity of the toner supply opening 20. The second restricting member 23 is configured so that the front end, which is a free end, is positioned with a desired gap with respect to the outer peripheral surface of the developing sleeve 15, so that the developer 22 formed on the surface of the developing sleeve 15 is formed. The base end is attached to the developer accommodating member 16a in a variable manner in the direction that obstructs the flow of the layers, that is, the front end is directed to the axial center of the developing sleeve 15. Details of the mounting mode will be described later.

  A cylindrical developer peeling member (developer transport body) 30 is located upstream of the first restricting member 17 and downstream of the second restricting member 23 in the toner moving direction in the developer accommodating portion 16. It is arranged. The developer peeling member 30 is rotated in the same direction as the developing sleeve 15 by driving means (not shown). Further, the developer peeling member 30 is disposed with a certain gap between it and the developing sleeve 15. The developer accommodating portion 16 is configured to have a sufficient space for circulating and moving the developer 22 within a range that the magnetic force of the developing sleeve 15 reaches.

  The opposing surface 14b of the support case 14 is formed over a predetermined length so as to incline downward from the toner hopper 19 side toward the developing sleeve 15 side. As a result, when vibration, uneven magnetic distribution of a magnet (not shown) provided in the developing sleeve 15, partial increase in toner concentration in the developer 22, or the like occurs, the second regulating member 23 and the developing sleeve 15. Even if the carrier in the developer accommodating portion 16 falls from between the peripheral surface of the toner, the dropped carrier is received by the facing surface 14b and moves toward the developing sleeve 15 and is magnetically attached to the developing sleeve 15 by magnetic force. The toner is again supplied into the developer accommodating portion 16. As a result, it is possible to prevent a decrease in the amount of carrier in the developer accommodating portion 16 and to prevent occurrence of uneven image density in the axial direction of the developing sleeve 15 during image formation. The inclination angle α of the facing surface 14b is, for example, about 5 °, and the length is preferably 2 to 20 mm, more preferably about 3 to 10 mm.

  With the above-described configuration, the toner 18 delivered from the inside of the toner hopper 19 by the toner agitator 21 is supplied to the developer 22 carried on the developing sleeve 15 through the toner supply opening 20 and is supplied to the developer accommodating portion 16. Carried. The developer 22 in the developer accommodating portion 16 is conveyed by the developing sleeve 15 and the developer conveying body 30 to a position facing the outer peripheral surface of the photosensitive drum 1, and only the toner 18 is conveyed to the photosensitive drum 1. A toner image is formed on the photosensitive drum 1 by electrostatic coupling with the electrostatic latent image formed thereon.

  FIG. 3 is a perspective view showing a structure in an embodiment of the present invention in which the position of the second regulating member 23 is variable, and FIG. 4 is a side sectional view. The second restricting member 23 is fixed to the support case 14 with screws 31 that are gap adjusting members. Specifically, an elongated hole 32 is provided in the developer accommodating member 16 a, and a screw 31 that is a gap adjusting member is passed through the elongated hole 32 and screwed into the upper end edge of the second restricting member 23. Therefore, if the fixing position of the screw 31 with respect to the long hole 32 is changed, the gap Gpd between the developing sleeve 15 and the tip of the second restricting member 23 can be adjusted as appropriate according to the density of the image and the occurrence of background stains. Although not shown, since this configuration is provided at both ends of the developing sleeve 15 in the axial direction, the gap Gpd can be adjusted independently at each of the axial ends of the developing sleeve 15. In addition, even if it is not the long hole 32, if the fixing position of the screw 31 can be changed inside the round hole, it can be used as the adjusting means for the gap Gpd. Various other means can also be employed, and are not limited to the illustrated example.

  FIG. 5 shows the relationship between the gap Gpd, the image density, and the background contamination on the photosensitive drum 1. Since the standard value of the image density is 1.3 or more and the standard value of the background contamination of the photoconductive drum 1 is 0.01 or less, the rectangular frame portion OK shown in the drawing shows a gap Gpd that satisfies both standards. It turns out that. Therefore, when the image density is low or high due to the installation state of the apparatus or the tolerance of components, the desired image can be formed by adjusting the gap Gpd within the range of 1 to 1.4 mm. obtain. The same applies to background dirt.

  Further, when the gap Gpd is changed, the amount of developer passing between the gaps changes, and when the amount of developer passing therethrough increases, the toner density increases, so that the image becomes darker. Conversely, if the gap Gpd is narrowed and the amount of developer passing therethrough is reduced, the toner concentration becomes lower and the image becomes thinner.

  That is, the development due to the assembly deviation of the regulation gap between the first regulating member 17 and the second regulating member 23, the tolerance of the parts accuracy in manufacturing, the magnetic flux density distribution deviation of the magnetic field generating means of the developing sleeve 15 as the developer carrier, etc. When a deviation occurs in the agent regulation amount and the developer is biased with respect to the axial direction of the development sleeve 15, resulting in a difference in toner density, the second regulation member 23 is used as the gap adjustment member 31. The position of the developing sleeve 15 in the axial direction is reduced by adjusting the gap Gpd having the lower image density and adjusting the gap Gpd having the higher image density to be narrow. The difference in image density can also be eliminated, and when the background stain occurs at the end of the developing sleeve 15, the toner density is lowered by narrowing the gap Gpd on the generated side. It is possible to prevent more stains.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus including a developing device according to the present invention. 1 is a schematic sectional view showing an embodiment of a developing device according to the present invention. The perspective view which shows the structure in the Example of this invention which makes the position of a 2nd control member variable. Same side sectional view The figure which shows the relationship between the clearance gap Gpd, an image density, and the background stain | pollution | contamination on a photosensitive drum.

Explanation of symbols

1: Photosensitive drum 2 Charging means 3 Laser writing unit 4 Developing device 5 Transfer roller 6 Cleaning device 7 Paper feed unit 8 Paper feed roller 9 Registration roller pair 10 Fixing device 11 Paper discharge unit 12 Image forming apparatus main body 14 Support case 14b Support Opposing surface of the case 15 developing sleeve 16 developer accommodating portion 16a developer accommodating member 17 first regulating member 18 toner 19 toner hopper 20 toner supply opening 21 toner agitator 22 developer 23 second regulating member 30 developer separating member (developing) Agent carrier)
31 Screw (gap adjustment member)
32 Slot P Transfer material Gpd Gap between the developing sleeve and the tip of the second regulating member

Claims (9)

A developer carrying member that carries and conveys a two-component developer composed of toner and a magnetic carrier; a first regulating member that regulates the amount of developer carried and carried by the developer carrying member; and the developer A toner container for supplying toner to the developer carrier adjacent to the container, and a developer toner on the developer carrier according to a change in developer toner concentration on the developer carrier A developing device that changes an intake state, the developer container having a second regulating member on the developer carrying surface upstream of the first regulating member on the upstream side in the transport direction of the developer, A developing device characterized in that a gap between the second regulating member and the developer carrying member is variable. A developer carrier having a magnetic field generating means therein and carrying and transporting a two-component developer composed of toner and a magnetic carrier, and the amount of developer carried and carried by the developer carrier is regulated. A first restricting member; a developer accommodating portion that accommodates the developer scraped off by the first restricting member; and a toner accommodating portion that supplies toner to the developer carrying member adjacent to the developer accommodating portion. And a developing device that changes the contact state between the developer and the toner by changing the developer toner density on the developer carrying member to change the toner intake state of the developer on the developer carrying member. In the developing device, the developer accommodating portion includes a second restricting member disposed on the upstream side in the transport direction of the developer on the developer carrier relative to the first restricting member. 2 between the regulating member and the developer carrier. Developing apparatus is characterized in that a variable. 3. The developing device according to claim 1, wherein the second regulating member is provided on each of both end sides in the axial direction of the developer carrier. 4. 4. The developing device according to claim 1, wherein the gap between the second restricting member and the developer carrier is variable on both axial ends of the developer carrier. Development device. 5. The developing device according to claim 4, wherein the gap at the lower image density is widened, and the gap at the higher image density is adjusted to be narrowed to reduce a difference in toner density in the axial direction of the developer carrier. A developing device characterized in that an image density difference can be eliminated. In the developing device according to claim 4 or 5, when a background stain occurs at an end portion on one side in the axial direction of the developer carrier, the toner density is reduced by narrowing the gap on the end portion side, A developing device characterized by being able to prevent background contamination. An image carrier such as a photosensitive member and at least one unit selected from a charging unit, a developing unit, and a cleaning unit are integrally supported, and the developing unit is a process cartridge that is detachable from the main body of the image forming apparatus. 7. A process cartridge which is the developing device according to any one of 1 to 6. An image forming apparatus comprising the developing device according to claim 1. An image forming apparatus comprising the process cartridge according to claim 7.