JP2013145307A - Development device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a carrying amount of developer to a development roller uniform.SOLUTION: A development device is equipped with a development roller for supplying developer to a photoreceptor, and a developer regulating member for regulating a supply amount of the developer. The developer regulating member is equipped with a band-shaped slender regulating plate, and a supporting member for supporting the regulating plate. The supporting member supports the regulating plate so as to make a longitudinal direction of the regulating plate match with an axial direction of the development roller and pushes that on a surface of the development roller. The regulating plate has a curved side on an upstream side of a flow of the developer, and a linear side on a downstream side, and the width of the regulating plate is formed so as to be gradually wider from both ends in the longitudinal direction of the regulating plate toward a center.

Description

  The present invention relates to a developing device, and more particularly to a developing device mounted on an electrophotographic image forming apparatus.

  In an image forming apparatus that employs an electrophotographic system, a latent image formed on the surface of a photoconductor is developed by supplying toner as a developer component from a developing device and developing it. A toner image is formed, the toner image is further transferred onto a recording paper as a transfer medium, and the toner image transferred onto the recording paper is fixed to form a robust recording image.

In recent years, with the widespread use of color inkjet image forming apparatuses, image forming apparatuses using an electrophotographic system are also required to be reduced in size and price.
Under such circumstances, a non-magnetic one-component developing system that has a simple structure and can be miniaturized is often used as an electrophotographic developing apparatus.

By the way, in the conventional non-magnetic one-component developing type developing device, a developer amount regulating member formed of a polyurethane rubber composition is known (for example, see Patent Document 1).
In addition, there is also known a developing device provided with an adjustment mechanism for adjusting the pressing force of a regulating member in order to prevent unevenness in image density (see, for example, Patent Document 2).
Further, there is also known a developer carrying member, that is, a member that applies a warp in the longitudinal direction to a regulating member for uniformly applying the developer to the entire longitudinal direction of the developing roller (see, for example, Patent Document 3).

JP-A-7-181803 JP-A-2005-241925 JP-A-8-328380

However, although it is considered that the regulating member formed of the polyurethane rubber composition aims to improve the water resistance, it is not intended to improve the unevenness of the developer conveyance amount.
Further, a mechanism provided with an adjustment mechanism for the pressing force of the regulating member has a complicated configuration and a complicated adjustment operation.
In addition, the regulation member having a warp in the longitudinal direction is required to have a relatively high accuracy in its production.

  The present invention has been made in view of such circumstances, and by providing an arc portion on the rubbing surface of the regulating member, the pressing force in the longitudinal direction of the developing roller is averaged to develop on the surface of the developing roller. It is an object of the present invention to provide a developing device in which the transport amount of the developer is made uniform and the transport amount of the developer can be efficiently regulated with a simple structure.

  The present invention includes a developing roller that supplies a developer to a photosensitive member, and a developer regulating member that regulates the supply amount of the developer. The developer regulating member includes a strip-like elongated regulating plate and a support that supports the regulating plate. A support member that supports and presses against the surface of the developing roller so that the longitudinal direction of the restricting plate coincides with the axial direction of the developing roller. Provided is a developing device that is curved and has a downstream side that is linear, and the width of the restricting plate is gradually increased from both longitudinal ends of the restricting plate toward the center. .

  According to the present invention, the strip-shaped elongated regulating plate is curved at the upstream side of the developer flow and is straight at the downstream side, and the width of the regulating plate is the both ends in the longitudinal direction of the regulating plate. Therefore, the flow of the developer to the restriction plate is controlled from the center to both ends of the restriction plate, so that the developer conveyance amount can be made uniform.

1 is a configuration explanatory diagram of an image forming apparatus according to the present invention. FIG. FIG. 2 is a diagram illustrating a configuration of a developing device according to the present invention. FIG. 3 is a side view of a developer regulating member according to the first embodiment of the present invention. FIG. 4 is a top view of the regulating member shown in FIG. 3. It is AA arrow sectional drawing of FIG. FIG. 6 is a side view of a developer regulating member according to a second embodiment of the present invention. It is BB arrow sectional drawing of FIG. It is CC sectional view taken on the line of FIG.

  The developing device of the present invention includes a developing roller that supplies a developer to the photosensitive member, and a developer regulating member that regulates the supply amount of the developer, and the developer regulating member includes a strip-like elongated regulating plate and a regulating plate. A supporting member that supports the restricting plate so that the longitudinal direction of the restricting plate coincides with the axial direction of the developing roller and presses it against the surface of the developing roller, and the restricting plate is located upstream of the developer flow. The side is curved and the downstream side is straight, and the width of the restricting plate is formed so as to gradually increase from both longitudinal ends of the restricting plate toward the center. .

  It is preferable that the upstream side of the flow of the developer in the restriction plate has an arcuate shape, and the end of the upstream side at the end of the restriction plate is separated from the contact area between the developing drum and the restriction plate.

  The present invention further includes a developing roller for supplying the developer to the photosensitive member and a developer regulating member for regulating the supply amount of the developer. The developer regulating member supports the strip-shaped elongated regulating plate and the regulating plate. A supporting member that supports the restricting plate so that the longitudinal direction of the restricting plate coincides with the axial direction of the developing roller and presses it against the surface of the developing roller. The first layer closer to the developing drum has a structure in which the upstream side of the developer flow is curved and the downstream side is linear, and the width of the first layer is the length of the regulating plate. The width of the second layer, which is formed so as to gradually increase from both ends in the direction toward the center, is constant, and is the same as the maximum width of the first layer.

The restriction plate is made of urethane rubber, and may be bonded to the support member with an adhesive or integrally formed with the support member.
The support member may be made of phosphor bronze or stainless steel.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is an explanatory view of the configuration of an image forming apparatus according to the present invention.
As shown in the figure, the image forming apparatus 100 has a copier mode (copying mode), a printer mode, and a FAX mode as print modes. An operation input from an operation panel (not shown) or an external host such as a personal computer is provided. A print mode corresponding to reception of a print job from the apparatus is selected by the control unit.

The image forming apparatus 100 is roughly divided into a document reading unit 10, a paper feeding unit 20, a printing unit 30, and a paper discharge unit 40. The document reading unit 10 is disposed above the paper supply unit 20, and the paper discharge unit 40 is provided. It is disposed at an intermediate portion between the document reading unit 10 and the paper feeding unit 20.
Hereinafter, the copier mode will be described from the above processing modes.

  After the user places a document on the platen glass 11 of the document reading unit 10 (scanner unit), the sheet (recording paper) is placed on the sheet feeding cassette 21 of the sheet feeding unit 20 or the manual feed tray 23 provided on the side of the apparatus. Installing. Further, after inputting a condition input key (number of printed sheets / printing magnification, etc.) on an operation panel arranged on the front surface of the apparatus, a copy operation is started by operating the start key on the operation panel.

  When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22a rotates to feed the paper, and the fed paper reaches the registration roller 31 (roller pair) and is captured. The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image forming start part) of the image formed on the photosensitive drum (image carrier) 32, so that the leading edge of the paper is uniform. The front end position of the paper is corrected by being pressed against the registration roller 31.

  On the other hand, in the document reading section 10, the copy lamp 12a (light source) is turned on, and the exposure starts when the copy lamp unit 12 moves in the direction of arrow C. Irradiation light applied to the original by the copy lamp 12a becomes reflected light (reflected light from the original) including image information of the original, and the reflected light is transmitted from the first mirror 12b provided in the copy lamp unit 12 to the second light. Reading is performed by inputting to the CCD 16 from the mirror 13, the third mirror 14, and the optical lens 15.

  The image information read in this way is converted into an electrical signal, and the image information signal is subjected to image processing under a set condition and transmitted to the laser scanner unit 33 as print data.

  On the other hand, a part of the peripheral surface of the photosensitive drum 32 is charged to a predetermined charging potential over the entire axial direction by the charging unit 34, and the entire peripheral surface is negatively charged by rotating the photosensitive drum 32. Charged to potential.

  Next, in the laser scanner unit 33, the laser beam emitted from the semiconductor laser is irradiated to the photosensitive drum 32 while being deflected by a polygon mirror (rotating polygon mirror) having a plurality of reflecting surfaces in the rotation direction and various optical systems. Is done. The laser beam is scanned on the photosensitive drum 32 charged by the charging unit 34 to form an electrostatic latent image on the photosensitive drum 32.

  Thereafter, the toner (developer) in the developing tank 61 is supplied onto the surface of the rotating photosensitive drum 32 by the developing roller 62 applied with a negative DC potential in the developing tank 61 provided in the developing device 200, and statically. The electrostatic latent image is visualized (developed) by this toner in accordance with the potential gap on the photosensitive drum 32.

  In addition, paper (recording paper) to be imaged is conveyed in the direction of the photosensitive drum 32 by the registration roller 31 in time, and the toner on the photosensitive drum 32 is transferred to the paper by the transfer unit 36. The toner remaining on the photosensitive drum 32 is scraped off by the cleaning blade 37 a of the drum unit and collected by the cleaner unit 37.

  The surface of the photosensitive drum 32 from which the toner has been removed by the cleaning blade 37a is neutralized as necessary by the neutralization device 39 while moving to the charging unit 34.

  On the other hand, the sheet on which the toner has been transferred passes between the heating roller 38a and the pressure roller 38b of the fixing device 38, and heat and pressure are applied to melt and fix the unfixed toner on the sheet to the sheet. Then, the paper is discharged onto the paper discharge tray 42 by the paper discharge roller 41. The heating roller 38a is heated by a heater 38c provided therein.

  In addition, when it is detected by a predetermined sensor that a document is placed on the document tray 19 provided in the document reading unit 10, the feed rollers 51 and 52 rotate when a start key operation is performed. Then, the document placed on the document tray 19 is sent into the document reading unit 10 and conveyed through the conveyance path Rt1.

  A registration roller 53 is provided on the conveyance path Rt1, and the document is captured by the registration roller 53, and the leading end of the document is positioned, and then conveyed to the document reading position at a predetermined timing.

Then, the document being conveyed is exposed while the copy lamp unit 12 is stopped at a predetermined stop position (document reading position). The original image is read as described above by the reflected light from the original obtained by this exposure.
The document whose image has been read in this manner is discharged to the document discharge unit 18.

FIG. 2 is an explanatory diagram of the configuration of the developing device 200 shown in FIG.
The developing device 200 includes a developing roller (developer carrying member) 62 that carries a developer, a developing tank 61 that contains the developer, and first, second, and second members that stir and convey the developer 60 in the developing tank 61. 3rd stirring conveyance members 63, 64, and 65 are included. Each rotates counterclockwise as indicated by an arrow.

  The developing roller 62 is an aluminum developing roller that is rotatably provided in the developing tank. The developing roller 62 faces the photoconductor 32, is arranged so that its axis is parallel to the rotation axis of the photoconductor 32, and is supported by the frame portion of the main body of the developing tank 61.

  As the developer carried on the developing roller 62, a non-magnetic one-component developer is used. A toner supply roller 66 provided upstream of the developing roller 62 attracts toner to the surface thereof and supplies a certain amount of toner onto the developing roller 62.

  Above the developing roller 62, a developer regulating member 70 for forming a certain amount of toner layer is provided. The developer regulating member 70 includes a support plate 68. At the tip of the support plate 68, there is a strip-shaped elongated urethane rubber regulating plate 67 extending in the axial direction of the developing roller 62, and the other end is a metal plate for fixing. It is sandwiched between 71 and 72 and fixed to the developing tank 61 with a screw 73.

The support plate 68 is a thin metal plate having a spring property, and the spring plate presses the developing roller 62 at a contact position with a certain pressure.
As a result, the charged toner layer is carried on the developing roller 62. The charged toner is supplied from the developing roller 62 to the photosensitive drum 32 according to the potential difference between the developing roller 62 and the photosensitive drum 32 to develop the electrostatic latent image to form a toner image.

The developing tank 61 is a container member made of, for example, hard synthetic resin and having an approximately rectangular parallelepiped appearance.
In the developing tank 61, the third stirring and conveying member 65 and the first stirring and conveying member 63 mainly have a role of stirring and conveying the toner in the rotation direction. Both members have wings made of thin resin, for example, PET, provided around the rotation shaft.
The second agitating / conveying member 64 is a screw-like rotating member made of, for example, a hard synthetic resin, and mainly has a role of agitating and conveying toner in the axial direction.

  A wall member 80 is provided between the second stirring and conveying member 64 and the toner supply roller 66. The wall member 80 is a plate-like member made of, for example, a synthetic resin, and is provided so as to rise from the bottom of the developing tank 61. However, an opening 81 is provided at the center of the wall member 80 to restrict the flow of the developer from the first stirring / conveying member 63 toward the toner supply roller 66 in the developing tank 61.

  The toner supply roller 66 is provided with a cylindrical porous elastic member such as foamed urethane around a cored bar. The toner is rubbed against the developing roller 62 while adsorbing the toner on the surface thereof, thereby the toner. Is supplied to the developing roller 62, and also has a role of cleaning an excess toner layer remaining on the developing roller 62 after development.

  The developer regulating member 70 will be described in detail with reference to FIGS. 3 and 4. The restriction plate 67 at the tip of the support plate 68 has a strip shape and has the same length as the developing roller 62 in the longitudinal direction. The support member 68 is fixed by screws 73 so as to be sandwiched between the metal plates 71 and 72.

  Further, the regulation plate 67 is pressed against the developing roller 62 in the contact region X by the elastic force of the support member 68. The developing roller 62 rotates counterclockwise, and the developer 60 in the developing tank 61 shown in FIG. 2 is attracted to the surface of the developing roller 61 by a toner supply roller 66, and a certain amount is supplied onto the developing roller 62.

  The toner that has flowed into the contact region X of the regulating plate 67 is charged by receiving a frictional force from the developing roller 62 and the regulating plate 67. Then, a certain amount of toner that has passed through the contact area X is conveyed to a developing position facing the photosensitive drum 32 (FIG. 2), and then developed.

The method for setting the pressing force P for pressing the regulating plate 67 against the developing roller 62 is as follows. The pressing force P is mainly applied using the elastic force of the support plate 68. That is, the pressing force P is adjusted depending on how much the support plate 68 is bent against the developing roller 62. The pressing force P is theoretically expressed by the cantilever formula as follows.
P = 3EIδ / L ³

Here, E is the Young's modulus of the support plate 68, I is the secondary moment of section, δ is the amount of deflection, and L is the free length of the support plate 68.
The actual value of P is determined at a constant speed by placing one end of a PET thin plate cut in a strip shape between the regulating plate 67 and the developing roller 62 and connecting the other end to a tension gauge. It is measured by the pulling force when the PET member is pulled out. For this tension gauge, RX-5 manufactured by Aiko Engineering Co., Ltd. is used.
In this embodiment, the pressing force P is adjusted so that the drawing force is about 0.03 to 0.10 kgf.

The characteristics required for the regulation plate 67 are the above-described function for keeping the toner conveyance amount and the charge amount constant, and the durability that does not deteriorate until the toner life or the developer container life.
On the other hand, the characteristics required for the support plate 68 are rigidity for applying the pressing force P and flexibility.

The material of the support plate 68 is preferably phosphor bronze such as C5210. The plate thickness is about 0.1 to 0.16 mm. Phosphor bronze has an appropriate spring property, is not easily corroded, and is generally well distributed, and thus has an advantage of being easily available.
Other than phosphor bronze, stainless steel SUS303 or 304 is suitable. Since various materials and plate thicknesses having different characteristics are commercially available, it is easy to adjust a desired pressing force.

  Next, the hardness of the restriction plate 67 made of urethane rubber will be described. When the value of the load P is constant, the width (so-called nip width) W of the contact region X when the restriction plate 67 and the developing roller 62 are in contact differs depending on whether the hardness is soft or hard. The nip width W is measured by, for example, uniformly applying an identification agent such as vermilion on the surface of the regulation plate 67 and incorporating it into the apparatus, and then removing it from the apparatus and examining the contact traces.

  In the above pulling force, when the rubber hardness is soft 65 degrees (± 3 degrees), it is about W = 1.2 mm, and when the hardness is 75 degrees (± 3 degrees), W is about 0.5 mm. . That is, as the hardness increases, the nip width W becomes narrower.

  The toner adhesion amount (conveyance amount) on the developing roller 62 must always be constant. At that time, not only the toner weight per unit area is constant, but also the thickness of the toner layer needs to be uniform. Otherwise, the image density varies or streaks occur in the image.

  The above-mentioned defects are made uniform by the crushing action of the toner layer by increasing the pulling force, so that the image defect is improved. However, if the pulling force is increased too much, the toner conveyance is hindered. As a result, the amount of toner adhering on the developing roller 62 necessary for outputting an image becomes insufficient. Therefore, it is necessary to obtain an appropriate value according to the process. is there.

Further, the above-described problem can be improved by increasing the load per unit area by increasing the rubber hardness described above.
Regarding the regulation plate 68, as described above, it is preferable that the rubber hardness is high for image defects, and it is also desirable that the control plate 68 is hard from the viewpoint of durability. This is because if it is soft, the rubber surface is gradually worn away by friction with the developing roller 62 and the nip width W is widened.

  FIG. 5 is a cross-sectional view taken along the line AA in FIG. 3 and shows the top surface shape of the regulating plate 67. As shown in FIG. 3, the regulating plate 67 has a curved upstream side and a downstream side linear in the developer flow, and the regulating plate has a width from the both ends in the longitudinal direction of the regulating plate to the center. It gradually becomes wider toward. That is, the upstream side has an arc shape that swells in the developer inflow direction a. Therefore, the developer flow moves in the direction of arrow a in the sliding area between the developer that moves in the direction of arrow b along the outer periphery of the arc when it collides with the regulation plate 67, and the developing plate 62 and the developing roller 62. It will change to the developer flow.

  Originally, in the developing device 200, due to the structure of the pressure contact mechanism with respect to the developer regulating member 70, the toner conveyance amount tends to be larger at the central portion in the longitudinal direction of the developing roller 62 than at both end portions.

  Therefore, as shown in FIG. 4, the metal plate 71 is configured such that the central portion of the lateral width is set slightly wider than the both end portions (so-called crown shape), and the free length L of the support plate 68 is shortened in the vicinity of the central portion. The pressure P applied to the central portion 67 is made larger than both end portions to optimize the balance of the toner conveyance amount in the entire longitudinal direction.

On the other hand, by making the regulating plate 67 as shown in FIG. 5 as described above, the developer is more likely to flow in both end directions in the longitudinal direction of the developing roller 62 than in the central portion.
In the present invention, the amount of developer transport can be uniformly controlled by making the shape of the metal plate 71 as shown in FIG. 4 and the restriction plate 67 as shown in FIG. Has been confirmed experimentally.

  As shown in FIG. 5, in the restricting plate 67, the end G of the arc-shaped side is separated from the contact region X by a certain distance H. The reason for this is to prevent the developer transport amount from being increased due to the nip width W not being properly secured and being smaller than the set value when there is a variation in parts and mounting. Since the value of H depends on the development conditions used, it is optimized as appropriate. The arc size S is also optimized as appropriate.

FIG. 6 is a view corresponding to FIG. 3 showing a modified example of the developer regulating member 70 shown in FIG.
7 is a cross-sectional view taken along the line B-B in FIG. 6, and FIG. 8 is a cross-sectional view taken along the line C-C in FIG.
As shown in these drawings, the development restricting member 70a in this modification is obtained by replacing the restricting plate 67 in FIG. 3 with a restricting plate 67a, and other configurations are the same as those in FIG. In the developer regulating member 70a, the regulating plate 67a has a two-layer structure integrally laminated, and the first layer closer to the developing drum 62 is the upstream side of the developer flow as shown in FIG. Is curved, the downstream side is linear, and the width of the first layer gradually increases from both longitudinal ends of the restricting plate 67a toward the center, that is, in an arc shape. ing. This corresponds to the form of the restriction plate 67 in FIG.

Further, as shown in FIG. 7, the second layer far from the developing drum 62 has a constant width and the same as the maximum width of the first layer, that is, a rectangular shape.
In addition, both the first layer and the second layer have a certain thickness. The restriction plate 67a is made of urethane rubber like the restriction plate 67, and the first layer and the second layer are integrally formed.

  In the regulating plate 67 of the developer regulating member 70 shown in FIGS. 3 to 5, all of the developer flow collides with the arc-shaped side of the regulating plate 67, whereas the developer regulating member shown in FIGS. 6 to 8. The restricting plate 67a of 70a collides with an arcuate side (FIG. 8) and a linear side (FIG. 7).

By doing so, the amount of the developer conveyed to both ends in the longitudinal direction of the developing roller 62 can be reduced as compared with the case of FIG.
As described above, since the developer transport amount depends on various conditions, the developer transport amount can be made uniform in the longitudinal direction by optimizing the thicknesses of the first and second layers.

By the way, examples of the method for joining the support plate 68 and the regulating plate 67 or 67a include an adhesion method using a double-sided tape or an adhesive, or a method in which both are integrally molded with a mold.
Since the regulating plate 67 or 67a is in close contact with the support plate 68 and adhered without any gap, a uniform and stable pressing force is applied to the developing roller 62, and an optimum developer conveyance amount is obtained. No stable image is obtained.
Further, if the regulating plate 67 or 67a and the support plate 68 are integrally molded, they do not require a mutual coupling step, so that there is less manufacturing variation and a stable image with less developer conveyance failure. can get.

32 Photosensitive drum 60 Developer 61 Developing tank 62 Developing roller 63 First agitating and conveying unit 64 Second agitating and conveying unit 65 Third agitating and conveying unit 66 Toner supply roller 67, 67a Restricting plate 68 Support plate 70, 70a Developer regulating member 71 Metal plate 72 Metal plate 73 Screw 80 Wall member 81 Opening 100 Image forming apparatus 200 Developing device X Contact area W Nip width

Claims (5)

  A developing roller that supplies developer to the photosensitive member, and a developer regulating member that regulates the supply amount of the developer. The developer regulating member includes a strip-like elongated regulating plate and a support member that supports the regulating plate. The support member supports the restricting plate so that the longitudinal direction of the restricting plate coincides with the axial direction of the developing roller and presses the restricting plate against the surface of the developing roller. The restricting plate has a curved upstream side on the upstream side of the developer flow. A developing device in which the side is linear and the width of the regulating plate is gradually increased from both ends in the longitudinal direction of the regulating plate toward the center.   The upstream side of the flow of the developer is arcuate in the regulating plate, and the end of the upstream side at the end of the regulating plate is separated from the contact area between the developing drum and the regulating plate. The developing device according to 1.   A developing roller that supplies developer to the photosensitive member, and a developer regulating member that regulates the supply amount of the developer. The developer regulating member includes a strip-like elongated regulating plate and a support member that supports the regulating plate. The support member supports the restricting plate so that the longitudinal direction of the restricting plate coincides with the axial direction of the developing roller and presses the restricting plate against the surface of the developing roller. The restricting plate has a two-layer structure integrally laminated. The first layer closer to the drum has a curved upstream side in the developer flow and a straight side on the downstream side, and the width of the first layer extends from both longitudinal ends of the regulating plate to the center. The developing device is formed so as to gradually become wider, and the width of the second layer far from the developing drum is constant and the same as the maximum width of the first layer.   The developing device according to claim 1, wherein the regulating plate is made of urethane rubber, and is bonded to the support member with an adhesive or integrally formed with the support member.   The developing device according to claim 1, wherein the support member is made of phosphor bronze or stainless steel.