JP4344202B2 - Developing device and process cartridge provided with the same - Google Patents

Description

  The present invention relates to an electrophotographic developing apparatus using toner used as a developer for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, etc., and more particularly, direct or indirect electrophotographic development. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for a copying machine, a laser printer, a plain paper fax machine, and the like using the system, and a process cartridge provided with the developing device.

  The electrophotographic method generally uses a photoconductive substance, forms an electric latent image on the electrostatic latent image carrier by various means, and then develops the latent image with a toner, and if necessary, After transferring the toner onto paper or the like, it is fixed by heating or solvent vapor to obtain a copy image or a printed image.

  As a means for developing an electrostatic latent image formed on an electrostatic latent image carrier such as a photoconductor, a method using a liquid developer (wet development method) and a method of dispersing a colorant in a binder resin are used. And a method using a one-component or two-component dry developer in which this toner is mixed 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 is relatively widespread mainly in medium to high-speed copiers and printers because it can achieve a relatively high speed and long life compared to the one-component development method. (For example, see Patent Documents 1 to 8).

JP 2001-66897 A JP 2001-56609 A JP 2000-305362 A JP 2000-284484 A JP 2000-250308 A JP 2000-227712 A JP 2001-109202 A JP 2001-117338 A

  Conventionally, in the two-component development method in which the toner density is self-controlled by two developer regulating members and a developer carrier, a sensor and a toner supply control device are unnecessary, so that low cost can be realized and the developing device can be downsized. Can be realized.

  However, because toner supply control cannot be performed forcibly, 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 for the developer carrier. , The peak magnetic flux density of the developer carrier, the position (angle) of the half width, and the like.

  Deviations in the developer regulation amount occur due to deviations in assembly of the regulation gaps of the first regulation member and the second regulation member, tolerances in manufacturing parts accuracy, magnetic flux density distribution deviations in the magnetic field generating means of the developer holder, etc. However, deviation occurs with respect to the longitudinal direction of the developer holder. For this reason, the developer moves closer to the end portion, whereby toner supply failure occurs at the end portion where the developer amount increases, and the density of the image is lowered at that portion. On the other hand, in the case of the end portion where the developer amount is reduced, the toner supply becomes excessive, causing background staining.

  In addition, the two-component developing device that self-controls the toner density can be reduced in size, and thus is mainly used in a small printer. Small printers are often placed on a desk, and are easier to use with the device tilted than large printers installed on the floor. Due to the inclination of the apparatus, the developer moves closer to the end portion, thereby causing a decrease in image density and background staining at the end portion.

  Therefore, in this method, high component accuracy and assembly accuracy are required, and it is essential that the apparatus is used in a horizontal state. When these are not satisfied, abnormal images such as image density unevenness and background stains are caused.

  The present invention has been made paying attention to the above circumstances, and its object is to solve the above-mentioned disadvantages in the two-component developing device of the toner density self-control type, and to reduce the image density at the end. It is an object of the present invention to provide a stable developing device that does not cause image density unevenness and a process cartridge including the same.

The inventions of claim 1, comprising a magnetic field generating means therein, a developer carrying member for carrying and conveying the two-component developer comprising at least magnetic carrier, is supported on the developer carrying member a first regulating member for regulating the amount of developer to be conveyed, a developer accommodating portion for accommodating the developer scraped off by the first regulating member, adjacent to the developer accommodating portion, said developer carrying member A toner supply opening for supplying toner to
Wherein a change in the developer toner concentration on the developer carrying member, by changing the contact state between the developer and the toner, a developing device for varying the toner uptake state of the developer on said developer carrying member, the developer accommodating portion has a second regulating member disposed in the upstream side of the developer on the developer carrying member than the first regulating member, second regulating member, the developer carrying member increases the toner concentration of the developer above, in order to regulate the passage of the increment of the developer when the layer thickness of the developer is increased, the gap between the developer carrying member is set, the second restriction An auxiliary member made of a non-magnetic member is provided at the end portion of the second restricting member except for the central portion in the longitudinal direction of the member so as to protrude into the developer accommodating portion .

  According to a second aspect of the present invention, in the first aspect of the invention, the edge of the auxiliary member facing the developer carrying member is located at the edge of the second regulating member facing the developer carrying member. Alternatively, it is characterized in that it is positioned by being pulled a predetermined amount from the end edge of the second regulating member to the inside of the developer accommodating portion so as to be separated from the developer carrier.

The invention according to claim 3, in the invention described in claim 1, wherein the auxiliary member has a shape that gradually thick toward the center from an axial end portion of the developer carrying member of the second regulating member is reduced It is characterized by doing.

  The invention according to claim 4 is the invention according to claim 3, characterized in that the second regulating member mounting surface of the auxiliary member and the opposing surface have the same shape.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the auxiliary member is an elastic member.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein at least a portion of the auxiliary member facing the developer carrying member is an elastic member and is opposed to the developer carrying member. A portion other than the portion is covered with a protective member.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus main body integrally including a photosensitive member, the developing device according to any one of the first to sixth aspects, and at least one of a charging unit and a cleaning unit. It features a process cartridge that can be freely attached to and detached from.

  According to the first aspect of the present invention, the auxiliary member is attached to the end portion of the second regulating member, and the developer accumulation in the developer accommodating portion is improved in order to remove the area where the developer is accumulated and stagnated. The decrease in image density at the end of the second regulating member is eliminated. That is, a stable image without density unevenness is obtained, and the tilt margin in the left-right direction (developer axis direction) is improved. Further, by using a non-magnetic material for the auxiliary member, a magnetic field is not generated between the auxiliary member and the developer that has passed through the second restricting member is on the downstream side without a flow stagnation. It will be conveyed to.

  According to the invention described in claim 2, since the same effect as that of the invention described in claim 1 is obtained and the developer weight becomes equal to or lower than the saturated state, the image density at the end of the second regulating member is lowered. Does not occur.

  According to the invention described in claim 3, the same effect as that of the invention described in claim 1 can be obtained, and the auxiliary member has a thickness reduced for a while from the axial end to the center of the second restricting member. The step formed between the axial end of the second restricting member and the center can be eliminated, and density unevenness that may be caused by the step can be prevented.

  According to the invention described in claim 4, the same effect as that of the invention described in claim 3 can be obtained, and the two surfaces of the auxiliary member have substantially the same shape. 2 When attaching to the regulating member, there is no need to worry about the attachment surface. Therefore, since the two surfaces of the auxiliary member can be used, it is easy to reduce and assemble the component cost.

  According to the invention described in claim 5, since the same effect as that of the invention described in any one of claims 1 to 4 can be obtained, and the auxiliary member is made of an elastic member, the second Even when attached to the end of the restricting member, the elastic member is deformed by the developer pressure even if it sticks in a state where it protrudes slightly closer to the developer carrying body than the second restricting member. The developer flow is not hindered. Therefore, since the auxiliary member is an elastic member, the accuracy at the time of attachment to the second restricting portion can be relaxed, and workability is improved.

  According to the invention described in claim 6, the same effect as that of the invention described in any one of claims 1 to 5 can be obtained, and the developer pressure except for the portion facing the developer carrier is provided. Since the elastic member can be prevented from being deformed by the protective member, the area where the developer is accumulated and the flow is stagnated can be surely occupied by the auxiliary member, and the image density at the end can be prevented from being lowered.

  According to the invention described in claim 7, by using the process cartridge in which the developing device according to any one of claims 1 to 6 is used, there is no density unevenness by exchanging the cartridge. A stable image can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a developing device portion of an image forming apparatus showing an embodiment of the present invention.

  The developing device 13 disposed on the side 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, and a first member as a developer regulating member. It is mainly composed of a first regulating member 17, a second regulating member 23, and the like.

  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. Near the photosensitive drum 1 side of the toner hopper 19, 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 integrated with the support case 14. Provided. The support case 14 located below the developer accommodating portion 16 is formed with a protruding portion 14a having a facing surface 14b, and the space between the lower portion of the developer accommodating portion 16 and the facing surface 14b A toner supply opening 20 for supplying the toner 18 is formed.

  Inside the toner hopper 19, a toner agitator 21 is disposed as a toner supply unit that is rotated by a driving unit (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 13.

  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 regulating member 17 is disposed in a state where a certain gap is maintained between the tip of the first regulating 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 has a free end in a direction that obstructs the flow of the layer of the developer 22 formed on the surface of the developing sleeve 15 so as to keep a certain gap with respect to the outer peripheral surface of the developing sleeve 15, that is, free The base end is integrally attached to the developer accommodating portion 16 with the end directed toward the center of the developing sleeve 15.

  A cylindrical developer conveyance body 30 is disposed on the upstream side of the first regulating member 17 and the downstream side of the second regulating member 23 in the developer accommodating portion 16. The developer carrier 30 is rotated in the same direction as the developing sleeve 15 by a driving unit (not shown). Further, the developer transport body 30 is disposed with a certain gap between it and the developing sleeve 15.

  The developer accommodating portion 16 is configured to have a space sufficient to circulate and move the developer 22 within the range where the magnetic force of the developing sleeve 15 reaches.

  The facing surface 14b 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 and the peripheral surface, 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 a 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 about 5 °, and the length is preferably 2 to 20 mm, more preferably about 3 to 10 mm.

  With the above configuration, the toner 18 sent out 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 carried to the developer container 16. It is. 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.

  An auxiliary member 40 is disposed on the second restriction member at least at the end of the second restriction member. The auxiliary member 40 restricts the amount of developer in the developer accommodating portion 16 at the end portion from increasing due to a deviation or inclination in the longitudinal direction of the regulating member, and the auxiliary member 40 can prevent a decrease in the image density at the end portion. The margin for the inclination of the device is improved.

  When there is no auxiliary member 40 and there is a left / right (axial direction) deviation of the gap between the first and second restricting members, a region B in which there is no stagnation in the flow of developer as shown in FIG. Thus, a developer flow occurs, and a region A where the developer is stagnated is generated. Region A is a region where the developer is compressed by the flow in the end direction and the density is high. In this area A, the amount of developer conveyed downstream by the developer conveyance body 30 is small. This is because there is a region A where the density of the developer is high and obstructs the flow of the normal developer in the downstream direction, and the friction between the developers is large because the friction coefficient μ of the developer particles is high. This hinders the flow of developer in the downstream direction.

  Since the developer does not sufficiently flow from the second restricting member 23 in the downstream direction, the amount of developer increases before passing through the second restricting member 23, and toner replenishment deteriorates, resulting in a decrease in toner density. Causes a drop.

  Similarly, even when the developing device is installed inclined to the left and right, the developer flows in the direction of lower height, so that the flow of the developer that has passed through the second regulating member 23 is stagnated at the lower end. In this region, the developer is unlikely to flow downstream, so the amount of developer before passing through the second regulating member 23 increases, and toner density failure occurs there, thereby reducing the image density.

  In the present invention, the auxiliary member 40 is attached to the end of the second restricting member 23 so that the developer flow that has passed through the second restricting member 23 is transported downstream without stagnation. The area A is removed. As a result, the state of region B is also obtained at the edge, and the edge image density reduction is eliminated.

  Hereinafter, the present invention will be specifically described by way of examples.

(First embodiment)
In the first embodiment, the auxiliary members 40 are disposed at both ends of the second restricting member 23, and the density of the black solid image at the edge and the center of the sheet after 1000 sheets of A4 paper are passed through is measured. did. For comparison, the same printing was performed without the auxiliary member 40, and the image density was measured. The center of the measurement position was measured at the center of the image forming area, and the end portion was measured 10 mm inside the image forming area. The results are shown in Table 1.

  A perspective view of the auxiliary member 40 attached to the second restricting member 23 is shown in FIG. 3, and a non-magnetic material such as PC or ABS is used. FIG. 3 shows the second regulating member 23 as viewed from the right end, and the developer carrier 15 is present on the right side of the second regulating member 23. If the auxiliary member 40 is made of a magnetic material such as SUS or SECC, a magnetic field is generated between the auxiliary member 40 and the developer carrying member 15, thereby hindering the flow of the developer. By using a non-magnetic material, the above-mentioned problems can be prevented, and the auxiliary member is provided at the end of the second regulating member 23 so that the developer flow that has passed through the second regulating member 23 is conveyed downstream without stagnation. 40 is attached, and the area A (FIG. 2) where the developer is accumulated and stagnated can be removed, so that the state also becomes the state of the area B even at the edge, and the edge image density reduction is eliminated.

  Next, the developer weight before passing through the second regulating member 23 was compared with and without the auxiliary member 40. The developer weight was measured by putting the developer into the developer and driving the developer at a photosensitive member linear velocity of 120 mm / sec for 3 minutes.

  The developer weight measurement results are shown in FIG. For the developer amount measurement, the developer before passing through the second regulating member was collected from the toner replenishment opening 20 by a bar magnet. The developer collecting width was 25 mm from the right end (relative to the paper traveling direction). As shown in FIG. 4, when the auxiliary member 40 is present, the developer amount before passing through the second regulating member is reduced by about 40%.

(Second embodiment)
The auxiliary member 40 is disposed at the right end of the second restricting member 23, the gap C between the auxiliary member 40 and the second restricting member tip 23 is changed, and the developer weight is measured before passing through the second restricting member 23. . The positional relationship between the auxiliary member 40 and the distal end of the second regulating member 23 is shown in FIG.

  The developer weight was measured by putting the developer into the developer and driving the developer for 3 minutes at a photosensitive member linear velocity of 120 mm / sec. The developer collection width was 25 mm from the right end.

  The developer weight measurement results are shown in FIG. When the gap C was 1.0 mm or more, the developer weight before passing through the second regulating member was saturated. Although not shown in FIG. 6, when the auxiliary member 40 is not provided, the developer weight is 1.2 g, which is almost the same as the saturated state of FIG. Accordingly, the auxiliary member 40 is effective when the gap C is 0 to 1.0 mm. In particular, the gap C is more preferably 0.5 mm or less. When the gap C = −0.5 mm, that is, the auxiliary member 40 protrudes from the second regulating member tip 23 toward the developer carrying member, the developer weight becomes equal to or higher than the saturated state, and the edge image density decreases.

(Third embodiment)
The developing means described above is integrally coupled as a process cartridge, and the process cartridge is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer. The configuration is shown in FIG. This comprises a charging means 105, a developing means 106, a photoconductor 107, and a cleaning means 108.

  In the image forming apparatus using the process cartridge using the developing device of the present invention, the photosensitive member is rotationally driven at a predetermined peripheral speed. In the rotation process, the photosensitive member is uniformly charged with a positive or negative predetermined potential on its peripheral surface by the charging unit, and then the image exposure light from the image exposure unit such as slit exposure or laser beam scanning exposure. The electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor, and the formed electrostatic latent images are then toner developed by the developing means, and the developed toner images are exposed from the paper feeding unit. The transfer unit sequentially transfers the image to the transfer material fed in synchronization with the rotation of the photosensitive member between the transfer unit and the transfer unit. The transfer material that has received the image transfer is separated from the surface of the photosensitive member, introduced into the image fixing means, and fixed on the image, and printed out as a copy (copy). The surface of the photoconductor after the image transfer is cleaned by removing the transfer residual toner by a cleaning means, and after being further discharged, it is repeatedly used for image formation.

  As described above, in the developing device of the present invention using self toner density control, the flow in the downstream direction before and after the second regulating member at the end is improved by attaching the auxiliary member to the end of the second regulating member. To do. As a result, the reduction in image density at the edge is eliminated, a stable image without density unevenness is obtained, and the tilt margin in the left-right direction (developer axis direction) is improved.

(Fourth embodiment)
As shown in FIG. 8, the auxiliary member 40 has a substantially isosceles cross section and is provided so that the exposed surface 41 and the mounting surface 43 have substantially the same shape. As described above, since the two surfaces of the auxiliary member 40 have substantially the same shape, there is no need to worry about the mounting surface when the auxiliary member 40 is attached to the second restricting member 23. Therefore, since two surfaces of the auxiliary member 40 can be used, it is easy to reduce and assemble the component cost.

(Fifth embodiment)
In the fifth embodiment, as shown in FIG. 9, the auxiliary member 40 is an elastic member. As shown in FIG. 9, even when the auxiliary member 40 is mounted in a state where the auxiliary member 40 protrudes from the second restricting member 23 toward the developer carrier 15 (FIG. 9C), the developer pressure is received. However, the auxiliary member 40 is deformed by elastic deformation, and the developer flow path (FIG. 9C) is secured. Thus, the precision at the time of sticking auxiliary member 40 to the 2nd regulating member 23 can be loosened, and workability improves. Even when the auxiliary member 40 was attached in a state of protruding from the second restricting member 23 toward the developer carrier 15, substantially the same result as the graph shown in FIG. 4 was obtained.

(Sixth embodiment)
In the sixth embodiment, as shown in FIG. 9, a protective member 43 such as a PET film (thickness 0.1 to 0.2 mm) is attached to the upper surface and the right side surface of the auxiliary member 40. In this case, as described in the fifth embodiment, even if the auxiliary member 40 is deformed by the developer pressure and the portion shown in FIG. 9C is deformed, the other portions are covered with the protective member 43. Therefore, since it has the rigidity that can withstand the developer pressure, it hardly deforms. Even in this case, a result almost similar to the graph shown in FIG. 4 was obtained.

It is sectional drawing which shows the structure of the image development apparatus of this invention. It is sectional drawing which shows the developing agent state after a 2nd control member passage. It is a perspective view which shows an auxiliary member attachment state. It is a graph which shows the relationship between the amount of developer before an auxiliary member and a 2nd control member passage. 3 is a cross-sectional view showing a positional relationship of a gap C. FIG. FIG. 6 is a graph showing a relationship between a gap C and a developer amount before passing through a second regulating member. It is a figure which shows schematic structure of a process cartridge. It is a modification of the auxiliary member of FIG. 3, and is a perspective view showing a fourth embodiment. It is a modification of the auxiliary member of FIG. 3, and is sectional drawing which shows the 5th and 6th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 15 Developer carrier 16 Developer accommodating part 17 1st control member 19 Toner hopper (toner accommodating part)
23 Second regulating member 30 Developer transport body (developer stirring member)
40 Auxiliary members

Claims (7)

It has a magnetic field generating means therein, to regulate at least the developer carrying member made of a magnetic material carrier a two-component developer conveyed carries, the amount of the developer conveyed is supported on the developer carrying member a first regulating member, a developer accommodating portion for accommodating the scraped developer by the first regulating member, and wherein adjacent to the developer accommodating portion, said toner supply opening for supplying the toner to the developer carrying member With
Wherein a change in the developer toner concentration on the developer carrying member, by changing the contact state between the developer and the toner, a developing device for varying the toner uptake state of the developer on said developer carrying member, the developer containing portion, than the first regulating member has a second regulating member disposed in the upstream side of the developer on said developer carrying member, the second regulating member, the developer carrying the toner concentration of the developer increases on the body, in order to regulate the passage of the increment of the developer when the layer thickness of the developer is increased, the gap between the developer carrying member is set, the second A developing device, wherein an auxiliary member made of a non-magnetic member is provided so as to protrude into the developer accommodating portion at an end portion of the second restricting member except for a central portion in the longitudinal direction of the restricting member . Edge of the auxiliary member facing the developer carrying member is located on the edge of the second regulating member facing the developer carrying member, or second regulated so as to be separated from the developer carrier the developing device according to claim 1, characterized in that it is located by drawing a predetermined amount from the edge of the member inside said developer accommodating portion. Said auxiliary member is a developing device according to claim 1, characterized in that a shape that gradually thick toward the center from an axial end portion of the developer carrying member of the second regulating member is reduced. The developing device according to claim 3, wherein the second regulating member mounting surface of the auxiliary member and the opposing surface have the same shape. The developing device according to claim 1, wherein the auxiliary member is an elastic member. 6. The auxiliary member according to claim 1, wherein at least a portion facing the developer carrying member is an elastic member, and a portion other than the portion facing the developer carrying member is covered with a protective member. The developing device according to one item.   A process comprising a photosensitive member, the developing device according to any one of claims 1 to 6, and at least one of a charging unit and a cleaning unit, and is detachable from an image forming apparatus main body. Cartridge.

Images