JP5672825B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer and a copying machine, and a developing device used therefor.

  Electrophotographic technology is widely used, and is used in printers connected to facsimiles and personal computers, and multifunction devices equipped with a plurality of these functions. In recent years, digital recording technology has been applied not only to printers but also to ordinary copying machines. Is also being applied to the development of digital copiers, and the demand for these machines is on the rise.

  In an electrophotographic image forming apparatus, an electrostatic latent image obtained by forming optical image information on a latent image carrier that has been uniformly charged in advance is treated with a developer supplied from the developing device. An image is formed by visualizing with the toner to be configured, and transferring and fixing the visible image on a transfer sheet.

  As the developer, there are a two-component system composed of toner and carrier and a one-component system composed of toner alone. In an image forming apparatus adopting a one-component system, a regulating member and a developing roller that contact toner, which is a one-component developer, supplied to a developing roller serving as a developer carrying member provided in the developing device, on the surface of the developing roller By passing between the toner and the surface, the toner is triboelectrically charged and held as a thin toner layer having a constant thickness and conveyed to the development region. As the restricting member, a plate-like elastic blade is often used, but in this case, since the same portion of the plate-like restricting member is always in contact with the developing roller, problems are likely to occur due to long-term use. .

  When using a one-component developer, a significant problem is that toner or its external additive accumulates between the developing roller and the regulating member, and the toner filming takes place at the contact portion of the regulating member with the developing roller. Will occur and will eventually stick.

The fixing of the toner to the contact portion of the plate-shaped regulating member with the developing roller causes various problems. First, the function of imparting normal triboelectric charge to the toner is weakened, and the toner cannot be sufficiently charged, causing problems such as toner scattering and background contamination. The partial fixing of the toner in the longitudinal direction of the developing roller is such that the toner cannot pass through the regulating member only in that portion, so that the toner is not partially supplied and appears as a white streak image. As can be understood from these problems, it is important not to cause toner sticking / filming on the surface of the regulating member in order to allow the toner having a constant layer thickness to always pass therethrough.
Accordingly, the following has been proposed as a measure for improving toner filming on the regulating member.

In Patent Document 1, a fixed toner removing member that is slidable in the width direction of the regulating member is provided between the developer carrying member and the blade-like regulating member, and the stuck toner is removed from the regulating member by sliding this member. It has been proposed that a configuration in which the blade-shaped regulating member is slidable in the vertical direction along the developer carrying member and that the fixed object is removed by sliding the blade up and down.
In Patent Document 2, a regulating member that regulates the amount of toner adhering to the developing roller serving as a developer carrying member is formed in a roller shape, and a cleaning member that removes the toner adhering to the regulating roller is formed in a roller shape or a belt shape. The structure provided in pressure contact with the regulating roller is described.

As in Japanese Patent Application Laid-Open No. H10-133260, the fixing of toner can be improved by rubbing the fixing toner removing member sliding in the width direction and the blade itself serving as the regulating member against the developing roller. However, the members are frequently moved and rubbed together. As a result, scratches or the like may occur, and there is a problem in terms of durability.
In Patent Document 2, since the regulating member is used as a roller shape, it can be easily cleaned. However, since it requires more installation space than the blade member, it is used in a color image forming apparatus using a plurality of developing devices. Therefore, it is difficult to avoid an increase in the size of the apparatus.
SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus that can avoid rubbing due to movement of members as much as possible, add no large parts, and suppress the occurrence of toner filming in a regulating member. .

The present invention includes a developer carrier that holds a one-component developer on the surface thereof and conveys the held one-component developer to a development region by rotating the free developer , and a free end of the developer carrier upstream of the developer carrier. The free end is pressed against the surface of the developer carrying member and charges the one-component developer adhering to the surface and regulates the layer thickness of the one-component developer held by the blade. In the developing device having a developer regulating member in the form of a developer, the contact surface of the developer regulating member that is in pressure contact with the surface of the developer carrying member is separated from the maximum pressure portion where the pressure of the abutting surface is maximized. It has a contact part located on the upstream side in the rotation direction of the carrier and a contact part located on the downstream side, and by displacing the position of the contact surface, the downstream pressure part before displacement is displaced to the maximum pressure part after displacement. Having a cleaning mode located upstream It is a symptom.

  In the developing device according to the present invention, the cleaning mode is characterized in that the developer carrier is idled without consuming the one-component developer held on the surface of the developer carrier.

  In the developing device according to the present invention, it has a displacement means for displacing the maximum pressure portion of the developer regulating member, the displacement means is a cam member disposed on the opposite side of the contact surface with the developer carrier, Drive means for rotationally driving the cam member, and the cam member develops at least in one place during one rotation at the downstream side in the rotation direction of the developer bearing member with respect to the contact portion of the developer regulating member. The developer regulating member is pressed from the opposite side of the developer regulating member and has a portion that does not contact the developer regulating member at least at one position during the same rotation.

In the developing device according to the present invention, the developer regulating member extends in the longitudinal direction of the developer carrier, and a plurality of cam members are arranged in the longitudinal direction of the developer regulating member. Yes.
In the developing device according to the present invention, the downstream contact portion of the maximum pressure portion of the contact surface between the developer regulating member before displacement and the developer carrier is positioned upstream of the maximum pressure portion after displacement. Up to this point, it has a moving means for moving the developer regulating member in contact with the developer carrier.
In the developing device according to the present invention, the downstream contact portion of the maximum pressure portion of the contact surface between the developer regulating member before displacement and the developer carrier is positioned upstream of the maximum pressure portion after displacement. Up to this point, it has a moving means for moving the developer carrier while in contact with the developer carrier.
An image forming apparatus according to the present invention includes any one of the developing devices described above.

  According to the present invention, the toner after the displacement is disposed on the downstream side of the maximum pressure portion at the contact portion between the developer regulating member and the developer carrying member, on which the adhering matter to the blade-like developer regulating member before displacement is likely to accumulate. Since the cleaning mode moves to the upstream side of the maximum pressure part that can remove the deposit with the flowing force of the toner, the effect of removing the deposits can be obtained by the flow of the toner on the upstream side. Therefore, rubbing due to driving between members is avoided as much as possible, and no large parts are added, and toner filming in the developer regulating member can be suppressed.

1 is a perspective view showing an embodiment of an image forming apparatus to which the present invention is applied. 1 is an enlarged cross-sectional view illustrating a configuration of a developing device to which the present invention is applied. FIG. 3 is an enlarged cross-sectional view illustrating a configuration of a developer carrier. (A) is an enlarged view showing the configuration of the contact portion between the developer carrying member and the regulating member, and (b) is an enlarged view showing a state where toner filming has occurred at the contacting portion between the developer carrying member and the regulating member. is there. (A) is an enlarged view of the vicinity of the contact portion when the cam member is not operated, and (b) is an enlarged view of the vicinity of the contact portion when the cam member is operated. (A) is a figure which shows the contact initial state of a developing agent carrier and a control member, (b) is a figure which shows the state which the control member moved to the direction which shifts a contact position. FIG. 6 is an enlarged view showing a state in which toner filming has moved to the upstream side due to displacement of the contact position of the regulating member. (A) is a figure which shows the contact initial state of a developer carrier and a control member, (b) is a figure which shows the state which the developer carrier moved in the direction which shifts a contact position.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the embodiments and modifications, components such as members and components having the same function or shape are given the same reference numerals as much as possible, and redundant description is omitted. In addition, the content described in embodiment is only one form, and the scope of the present invention is not limited to this.

  The overall configuration and operation of the image forming apparatus will be described with reference to FIG. 1, and then the features of the present invention will be described. In FIG. 1, the image forming apparatus is a tandem color copier. In the tandem color copying machine, a document reading unit 4 that reads image information of a document and a document transport unit 3 that transports the document to the document reading unit 4 are disposed above the apparatus main body 1. Below the apparatus main body 1, a paper feeding unit 7 that accommodates a recording medium P such as transfer paper is disposed.

  Inside the apparatus main body 1 are a writing unit 2 that emits laser light based on input image information, a registration roller 9 that adjusts the conveyance timing of the recording medium P, and a process cartridge 10Y corresponding to each color of yellow, magenta, cyan, and black. , 10M, 10C, 10K, and transfer bias roller (primary transfer bias) for transferring the toner images formed on the photosensitive drums 11 included in the process cartridges 10Y, 10M, 10C, 10K on the recording medium P in an overlapping manner. Roller) 14, an intermediate transfer belt 17 serving as an intermediate transfer body onto which toner images of a plurality of colors are transferred, an intermediate transfer belt cleaning unit 16 for cleaning the intermediate transfer belt 17, and a color toner on the intermediate transfer belt 17. Secondary transfer bias roller 18 for transferring the image onto the recording medium P at a time, TBD on the recording medium P Fixing device 20 is arranged for fixing the image on the recording medium P.

  The configuration of the process cartridges 10Y, 10M, 10C, and 10K will be described. Since each process cartridge has the same configuration except that the color of the toner used as the developer is different, here, as shown in FIG. 2, the alphabet (Y, C, M, K) is removed, and 1 One process cartridge 10 will be described as a representative. The process cartridge 10 includes a photosensitive drum 11 that is an image carrier, a charging roller 12 that constitutes a charging unit, a developing device 13 that constitutes a developing unit, and a cleaning unit 15 for the photosensitive drum 11. The apparatus main body 1 is detachably (replaceable).

  Hereinafter, an operation during normal color image formation in the image forming apparatus will be described. The image forming process performed on the photosensitive drums 11 of the process cartridges 10Y, 10M, 10C, and 10K is also referred to FIG.

  In the image forming apparatus, the document is transported from the document table by the transport roller of the document transport unit 3 and placed on the contact glass of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document placed on the contact glass.

  Specifically, the document reading unit 4 scans an image of a document on the contact glass while irradiating light emitted from an illumination lamp. Then, the light reflected from the original is imaged on the color sensor via the mirror group and the lens. The color image information of the original is read for each RGB (red, green, blue) color separation light by a color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information. Image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light L (see FIG. 2) based on the image information of each color toward the corresponding photosensitive drum 11.

  On the other hand, each photosensitive drum 11 is rotated counterclockwise in FIGS. 1 and 2 by a drive motor (not shown). Then, the surface of the photosensitive drum 11 is uniformly charged at the portion facing the charging roller 12 (charging process). Thus, a charged potential is formed on the photosensitive drum 11, and then the surface of the charged photosensitive drum 11 reaches the irradiation position of each laser beam L.

  In the writing unit 2, laser light L corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam L passes through a different optical path for each color component of yellow, magenta, cyan, and black (exposure process).

  The laser beam corresponding to the yellow component is applied to the surface of the photosensitive drum 11Y of the first process cartridge 10Y from the left side of FIG. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11 by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11 after being charged by the charging roller 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated on the surface of the photosensitive drum 11M of the second process cartridge 10M from the left side of the sheet, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the photoconductive drum 11C of the third process cartridge 10C from the left side of the drawing to form an electrostatic latent image of the cyan component. The black component laser light is applied to the surface of the photoconductive drum 11K of the fourth process cartridge 10K from the left side of the drawing to form an electrostatic latent image of the black component.

  Thereafter, the surfaces of the photosensitive drums 11 of the process cartridges 10Y, 10M, 10C, and 10K on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 13, respectively. Then, each color toner is supplied from each developing device 13 onto the photosensitive drum 11, and the latent image on the photosensitive drum 11 is developed (developing step).

  The surface of each photoconductor drum 11 after the development process reaches a portion facing the intermediate transfer belt 17. Here, a transfer bias roller 14 is installed at each of the opposed portions so as to contact the inner peripheral surface of the intermediate transfer belt 17. At the position of the transfer bias roller 14, the toner images of the respective colors formed on the photosensitive drums 11 of the process cartridges 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the intermediate transfer belt 17. (Primary transfer process).

  The surface of each photosensitive drum 11 after the transfer process reaches a position facing the cleaning unit 15. Then, the untransferred toner remaining on each photosensitive drum 11 is collected by the cleaning unit 15 (cleaning process). After cleaning, the surface of each photoconductive drum 1 passes through a neutralization unit (not shown), and a series of image forming processes on each photoconductive drum 11 is completed.

  On the other hand, the intermediate transfer belt 17 onto which the toners of the respective colors on the photosensitive drums 11 of the respective colors are transferred (carried) overlaps with each other and travels clockwise in FIG. 1 to a position facing the secondary transfer bias roller 18. Reach. Then, the color toner images carried on the intermediate transfer belt 17 are collectively transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer process).

  After the transfer, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

  Here, the recording medium P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is conveyed from the paper supply unit 7 via the registration roller 9 and the like. is there.

  Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip in time with the full-color toner image.

  The recording medium P on which the full-color toner image has been transferred at the secondary transfer nip is guided to the fixing device 20 by the transport belt. In the fixing device 20, a color image is fixed on the recording medium P at a fixing nip formed by a fixing belt and a pressure roller. The recording medium P after fixing is discharged as an output image outside the apparatus main body 1 by the paper discharge roller 21, and a series of image forming processes is completed.

  Next, the process cartridge 10 as an image forming unit in the image forming apparatus will be described in detail with reference to FIG. The process cartridge 10 includes a photosensitive drum 11 as an image carrier, a charging roller 12, a developing device 13, a cleaning unit 15, and the like.

  A photoconductive drum 11 as an image carrier is a negatively charged organic photoconductor, and is driven to rotate counterclockwise in FIG. 2 by receiving a driving force from a driving motor (not shown) installed on the apparatus main body 1 side. The

  The charging roller 12 is an elastic roller member in which a medium-resistance foamed urethane layer in which urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape on a core metal. The material of the middle resistance layer of the charging roller 12 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials. In this embodiment, the charging roller 12 is configured to contact the photosensitive drum 11, but the charging roller 12 may be configured not to contact the photosensitive drum 11.

  The cleaning unit 15 is provided with a cleaning blade 15 a whose tip is in sliding contact with the surface of the photosensitive drum 11, and mechanically removes and collects untransferred toner on the surface of the photosensitive drum 11.

  The developing device 13 is disposed such that a developing roller 13a as a developer carrier is in contact with the surface of the photosensitive drum 11, and a developing region (developing nip portion) is formed between both members. In the developing device 13, toner (one-component developer) is accommodated. The developing device 13 develops the electrostatic latent image formed on the surface of the photosensitive drum 11 as a toner image.

  The developing device 13 is a one-component developing type developing device, and includes a developing roller 13a, a supply roller 13b, a regulating blade 13c that is a thinning member and serves as a regulating member, a stirring member 13d, an agitator 13e, a toner supply port 13f, A sealing member 13g and the like are provided. The developing device 13 includes a toner storage unit B1 and a toner supply unit B2.

As shown in FIG. 3, the developing roller 13a is a five-layer roller member in which an elastic layer 13a4, an intermediate layer 13a3, a surface lower layer 13a2, and a surface layer 13a1 are sequentially laminated on a metal core 13a5 made of stainless steel or iron. is there. The elastic layer 13a4 is made of an elastic material such as urethane rubber, silicon rubber, or NBR so that the JIS-A hardness is 50 degrees or less and the electric resistance value is 10 ³ to 10 ¹⁰ Ω. This is for stabilizing the state of the developing roller 13a in contact with the surface of the drum 11. The intermediate layer 13a3 is formed of a conductive resin material, and is for optimizing electrical characteristics such as electrical resistance of the entire developing roller 13a. The surface layer 13a1 is made of a conductive resin material that has wear resistance and is easily charged to a polarity opposite to the polarity of the toner, and has a surface roughness (Ra) of 0.2 to 2.0 μm. In order to carry charged toner (charged toner) on the outer peripheral surface thereof. The surface lower layer 13a2 is laminated so as to be inscribed in the inner peripheral surface of the surface layer 13a1 (laminated between the surface layer 13a1 and the intermediate layer 13a3), and a color former and developer that function as a marker agent. And are contained.

  The developing roller 13a is rotationally driven in a clockwise direction in FIG. 2 by a driving force transmitted from a driving motor (not shown) via a gear train while a predetermined developing bias is applied from a high voltage power source (not shown). The

The supply roller 13b is a roller member in which a foam material having a cell structure is coated on a core metal, and is formed so as to have an electric resistance value of 10 ³ to 10 ¹⁴ Ω, and is in sliding contact with the developing roller 13a. The toner is supplied onto the developing roller 13a while the toner is frictionally charged at the portion.

  The supply roller 13b is rotationally driven in a clockwise direction in FIG. 2 by a driving force transmitted from a drive motor (not shown) through a gear train while a predetermined bias is applied from a high voltage power supply (not shown). . In the present embodiment, the bias applied to the supply roller 13b is a bias having the same polarity as that of the toner, so that the toner is electrostatically transferred from the supply roller 13b to the developing roller 13a.

  The regulating blade 13c is a leaf spring member made of stainless steel (for example, SUS304CSP or SUS301CSP) or phosphor bronze, and extends in the axial direction of the developing roller 13a. The regulating blade 13c is set so that its base end is fixed to the casing of the developing device 13 and its free end abuts against the surface of the developing roller 13a with a pressing force of 10 to 100 N / m. The toner carried on the surface of the developing roller 13a is triboelectrically charged by the regulating blade 13c while being thinned and uniformed, and then conveyed to the position of the developing region. In the present embodiment, a bias having the same polarity as the toner is applied to the regulating blade 13c, thereby electrostatically restricting the movement of the toner from the developing roller 13a side to the regulating blade 13c side, and friction charging of the toner. Will be promoted.

  The stirring member 13d is for preventing aggregation of the toner accommodated in the toner supply unit B2, and rotates in the direction of the arrow in FIG. The agitator 13e is for preventing aggregation of the toner accommodated in the toner accommodating portion B1, and rotates in the direction of the arrow in FIG.

  The toner supply port 13f is for appropriately supplying the toner stored in the toner storage unit B1 toward the toner supply unit B2. By limiting the amount of toner stored in the toner supply unit B2 by the toner supply port 13f, the toner stored in the toner supply unit B2 is less likely to aggregate.

  The seal member 13g is installed so as to contact the developing roller 13a at a position downstream of the developing region in the rotation direction of the developing roller 13a, and prevents toner from leaking from the developing device 13 to the outside of the device. .

  The developing device 13 configured as described above operates as follows.

  Part of the toner supplied and stored in the toner supply unit B2 from the toner storage unit B1 through the toner supply port 13f is carried on the supply roller 13b. The toner carried on the supply roller 13b is frictionally charged at the pressure contact portion with the developing roller 13a, and then moved and carried on the developing roller 13a. The toner carried on the developing roller 13a reaches the developing region where the toner drum 11 is brought into contact with the photosensitive drum 11 after being made thin and uniform at a position facing the regulating blade 13c. The toner reaching the development area is attracted to the latent image formed on the photosensitive drum 11 by an electric field (development electric field) formed in the development area, thereby forming a toner image.

  As described above, in the developing device 13 in the present embodiment, the other members that are in sliding contact with the developing roller 13a (surface layer 13a1) are the three members of the photosensitive drum 11, the supply roller 13b, and the regulating blade 13c. .

Next, a characteristic configuration of the present invention will be described.
FIG. 4A is an enlarged schematic view of the contact portion 60 between the regulating blade 13c and the developing roller 13a during normal operation of the developing device 13. The developing roller 13a having an elastic layer as a surface layer is deformed inwardly by the contact of the regulating blade 13c, and has a maximum pressure portion (center portion) where the pressure of the contact surface receiving the pressure is maximum. The peak pressure portion is P1. In the regulating blade 13c, the upstream region in the developing roller rotation direction with respect to the peak pressure portion P1 is defined as an upstream contact portion P1a, and the downstream region is defined as a downstream contact portion P1b. If the toner in the toner supply part B2 of the upstream contact part P1a is T1, the toner thin layer T2 is formed by the function of the regulating blade 13c at the downstream contact part P1b with the peak pressure part P1 of the contact part as a boundary. .

  FIG. 4B is an enlarged schematic view showing a state where the deposit 17 is generated in the contact portion 60 due to long-term use or the like. Generally, in the upstream contact portion P1a, there is a toner flow from the toner T1 in the toner supply portion B2, and the toner flow is pushed away by this flow, so that it is difficult for deposits and the like to deposit on the regulation blade 13c. On the other hand, since there is no toner flow at the downstream contact portion P1b, the toner, its external additive, and the like are likely to be deposited on the portion where the toner thin layer T2 and the regulating blade 13c are separated, and the adhered matter 17 is likely to be generated.

  In particular, when a solid image or the like is printed and the toner consumption is large, and the toner thin layer T2 on the developing roller 13a is frequently replaced, a lot of external additives and toner pass through the contact portion, so that the deposits 17 tend to accumulate. Become. On the other hand, if the amount of printing is small and the idling is continued without the toner thin layer T2 being replaced, deposits are difficult to deposit.

  In the regulation of one-component development, a toner thin layer on the developing roller 13a is basically formed at the peak pressure portion P1. Since the upstream contact portion P1a is in a state where the toner T1 is moving around in the toner supply portion B2, it is regulated by the peak pressure portion P1 and becomes a thin toner layer on the developing roller 13a at the downstream contact portion P1b. . At this time, a flow toward the regulating portion and a flow returning from the upstream contact portion P1a are generated, and thus a toner flow is generated at the upstream contact portion P1a. In contrast, since the toner is a thin layer on the downstream side of the regulation, which is the downstream side contact portion P1b, the toner does not move violently on the upstream side of the regulation, and the toner flow is extremely small.

  FIG. 5 shows an embodiment of the displacement means 30 for executing the cleaning mode for displacing the position of the contact portion 60. The developing means 30 is provided in each developing device. The displacement means 30 in this embodiment includes a cam member 31 that is supported rotatably about a shaft 31a, and a drive motor 32 that serves as a drive means for rotationally driving the cam member 31, and the maximum pressure of the regulating blade 13c. The position of the peak pressure part P1 which becomes a part is displaced. The cam member 31 is disposed on the back surface 13c2 side opposite to the contact surface 13c1 of the regulating blade 13c with the developing roller 13a. The cam member 31 is in pressure contact with the regulating blade 13c from the back surface 13c2 side at least at one location during one rotation and downstream of the peak pressure portion P1 in the rotation direction of the developing roller 13a. The outer shape has at least one portion that does not contact the regulating blade 13c. The cam member 31 shown in FIG. 5A is in a normal use state before being displaced and shows a state in which it occupies a standby position that is not in contact with the regulating blade 13c.

  In this embodiment, the cleaning mode is executed at regular intervals and is set in a control means (not shown). When the cleaning mode is executed, the developing device 13 displaces the position of the contact portion 60 between the regulating blade 13c and the developing roller 13a, so that the downstream contact portion P1b before displacement is displaced from the peak pressure portion P1 after displacement. The cleaning operation is performed so that the developing roller 13a is rotated for a predetermined time (idle) while the toner held on the surface of the developing roller 13a is not consumed.

  FIG. 5B is a schematic diagram showing the state of the contact portion 60 and the cam member 31 when the developing device 13 is in the cleaning mode. In this state, the cam member 31 is rotated by the drive motor 32, and the regulating blade 13c is pressed from the action surface 13c2 with the cam tip. This state is defined as the operating position of the cam member 31. Since the regulating blade 13c extends in the axial direction of the developing roller 13a, at least one cam member 31 needs to be arranged in the same direction. When the number of the cam members 31 is one, it is desirable that the width is equal to the width in the axial direction of the regulating blade 13c, and the cam members 31 are composed of the same shape member in the axial direction. However, if one cam member 31 is formed long in the axial direction of the regulating blade 13c, it is also assumed that the flow of the toner T1 in the toner supply unit B2 is hindered. A configuration in which the restriction blade 13c is divided into a plurality of parts in the axial direction and a plurality of the restriction blades 13c may be arranged. The cam member 31 is arranged so that the peak position P2 of the contact portion between the regulating blade 13c and the developing roller 13a pressed by rotating the cam member 31 is downstream of the deposit 17 in the developing roller rotation direction.

  Thus, when the cam member 31 rotates, the peak pressure portion P1 before the rotation moves to the regulation pressure peak position P2, and the deposit 17 accumulated on the downstream side of the peak pressure portion P1 due to this movement becomes the peak pressure portion. It moves to the upstream side of P2. When the developing roller 13a is driven to rotate in the clockwise direction in FIG. 6 in this state, the toner flow indicated by the arrow from the toner T1 in the toner supply unit B2 hits the adhering matter 17 and the adhering matter 17 returns to the upstream side. It becomes difficult to deposit because it is diffused and carried away.

  At this time, the toner thin layer T2 is idled with the developing roller 13a reducing the printing amount (preferably blank paper printing), so that the toner thin layer T2 is attached to the upstream side without adhering to the downstream side of the regulation pressure peak portion P2. The kimono 17 can be reduced.

  After the developing roller 13a is idled for a certain time, the drive motor 32 is operated to return the cam member 18 from the operating position shown in FIG. 5B to the standby position shown in FIG. This state is a step of returning from the cleaning mode to the normal use mode.

  By having such a cleaning mode for the developing device 13 and executing this mode, the developing device 13 can be used in a state where the deposits 17 on the contact downstream portion P1b are eliminated. By periodically executing such a cleaning mode, the occurrence of toner filming can be improved in the long term.

  In the cleaning mode, the developing roller 13a is idled without consuming the toner held on the surface of the developing roller 13a. Therefore, by not consuming the toner, accumulation on the downstream contact portion P1b can be avoided, Only the deposit removal effect at the downstream contact portion P1b can be obtained.

By pressing the downstream side of the peak pressure portion P1 during normal use with the cam member 31, the peak pressure portion P1 during normal use is moved to the downstream contact portion P1b. The effect of removing 17 can be obtained. For this reason, rubbing due to the drive between members can be avoided as much as possible, no large parts are added, and toner filming in the regulating blade 13c can be suppressed. That is, the downstream contact portion with respect to the peak pressure portion P1 during normal use By pressing the regulating blade 13c from the back side 13c2 side with the cam member 31 so that P1b is on the upstream side with respect to the peak pressure P1, the effect of removing the adhering matter 17 by the toner flow on the upstream side can be obtained. become able to.

6 and 7 show another form of the contact position changing means.
6 is a means for moving the regulating blade 13c relative to the developing roller 13a. In this embodiment, the regulating blade 13c is moved relative to the developing roller 13a to change the position of the joint between the regulating blade 13c and the developing roller 13a as shown in FIG. It moves to the contact upstream side from P3. In FIG. 6, the contact position is changed by pushing down the regulating blade 13c toward the developing roller 13a, but the contacting position may be changed in a direction in which the regulating blade 13c is pressed against the developing roller 13a.

  When the developing roller 13a is rotated in the clockwise direction in the state shown in FIG. 7, the toner flow caused by the toner T1 in the toner supply unit B2 hits the adhering matter 17 and the adhering matter 17 rides on the toner flow returning to the upstream side. Because it is diffused and carried away, it becomes difficult to deposit. For this reason, adhesion to the contact surface 13c1 of the regulation blade 13c can be reduced.

  FIG. 8 shows another form of the contact position varying means. The contact position varying means 50 shown in FIG. 10 is configured by means for moving the developing roller 13a relative to the regulating blade 13c. As shown in FIG. 8, the contact position between the regulating blade 13c and the developing roller 13a is changed, and the adhering portion 17 to the regulating blade 13c is moved to the contact upstream portion P1a from the regulated peak pressure P3 as shown in FIG. Position. When the developing roller 13a is rotationally driven in the clockwise direction in this state, the toner flow caused by the toner T1 in the toner supply unit B2 hits the adhering matter 17, and the adhering matter 17 rides on the toner flow returning to the upstream side and diffuses. Since it is carried away, it becomes difficult to deposit and adhesion is reduced.

Next, the result of the verification experiment of the present invention will be described.
The toner used in the present invention is as follows.
Carbon black (Cabot Legal 400R): 40 parts, Binder resin: Polyester resin (Sanyo Kasei RS-801, acid value 10, Mw 20,000, Tg 64 ° C.): 60 parts, water: 30 parts are mixed in a Henschel mixer. Thus, a mixture in which water was soaked into the pigment aggregate was obtained. This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 ° C. and pulverized to a size of 1 mm with a pulverizer to obtain [Masterbatch 1].
<Oil phase preparation process>
In a container equipped with a stir bar and a thermometer, 545 parts of [Polyester 1], 181 parts of [paraffin wax (melting point 74 ° C.)] and 1450 parts of ethyl acetate are charged, and the temperature is raised to 80 ° C. with stirring and remains at 80 ° C. After holding for 5 hours, it was cooled to 30 ° C. in 1 hour. Next, 500 parts of [Masterbatch 1] and 100 parts of ethyl acetate were charged in a container and mixed for 1 hour to obtain [Raw material solution 1]. [Raw material solution 1] 1500 parts are transferred to a container, and using a bead mill (Ultra Visco Mill, manufactured by Imex Co., Ltd.), liquid feeding speed is 1 kg / hr, disk peripheral speed is 6 m / sec, and 0.5 mm zirconia beads are 80% by volume. The pigment and WAX were dispersed under the conditions of filling and 3 passes. Next, 655 parts of a 66% ethyl acetate solution of [Polyester 2] was added, followed by one pass with a bead mill under the above conditions to obtain [Pigment / WAX Dispersion 1]. [Pigment / WAX Dispersion 1] 976 parts were mixed for 1 minute at 5,000 rpm with a TK homomixer (manufactured by Tokushu Kika), then 88 parts of [Isocyanate-modified polyester 1] were added, and a TK homomixer (took a special machine) To obtain [Oil Phase 1]. The solid content of [Oil Phase 1] obtained was measured and found to be 52.0% by weight, and the amount of ethyl acetate based on the solid content was 92% by weight.
<Preparation of aqueous phase>
970 parts of ion-exchange water, 40 parts of a 25 wt% aqueous dispersion of organic resin fine particles (styrene-methacrylic acid-butyl acrylate-methacrylic acid ethylene oxide adduct sulfate sodium salt copolymer) for dispersion stabilization, dodecyl diphenyl ether When 95 parts of a 48.5% aqueous solution of sodium disulfonate and 98 parts of ethyl acetate were mixed and stirred, the pH reached 6.2. A 10% aqueous sodium hydroxide solution was added dropwise thereto to adjust the pH to 9.5 to obtain [Aqueous Phase 1].
<Core particle production process>
Add 1200 parts of [Aqueous Phase 1] to the obtained [Oil Phase 1], and cool in a water bath to suppress the temperature rise due to shear heat of the mixer so that the temperature in the liquid is in the range of 20-23 ° C. , Adjusted at a speed of 8,000-15,000 rpm using a TK homomixer and mixed for 2 minutes, then adjusted at a speed of 130-350 rpm with a three-one motor with an anchor blade attached for 10 minutes The mixture was stirred to obtain [core particle slurry 1] in which oil phase droplets serving as core particles were dispersed in an aqueous phase.
<Formation of protrusions>
While the [core particle slurry 1] is stirred by adjusting the number of revolutions between 130 and 350 rpm with a three-one motor equipped with an anchor blade, the resin temperature is 22 ° C. and 106 parts of [resin dispersion 1] and ions What mixed 71 parts of exchange water (solid content concentration 15%) was dripped over 3 minutes. After dropping, the number of rotations was adjusted to 200 to 450 rpm, and stirring was continued for 30 minutes to obtain [Composite Particle Slurry 1]. When 1 ml of [Composite Particle Slurry 1] was taken and diluted to 10 ml and centrifuged, the supernatant was transparent.
<Desolvent>
[Composite particle slurry 1] was put into a container equipped with a stirrer and a thermometer, and the solvent was removed at 30 ° C. for 8 hours while stirring to obtain [Dispersion slurry 1]. When [Dispersion Slurry 1] was placed on a small amount of slide glass and observed with an optical microscope at a magnification of 200 times with a cover glass in between, uniform colored particles were observed. Further, when 1 mL of [Dispersion Slurry 1] was taken and diluted to 10 mL and centrifuged, the supernatant was transparent.
<Washing and drying process>
[Dispersion Slurry 1] After filtering 100 parts under reduced pressure,
(1): 100 parts of ion-exchanged water was added to the filter cake, mixed with a TK homomixer (10 minutes at 12,000 rpm), and then filtered.
(2): 900 parts of ion-exchanged water was added to the filter cake of (1), ultrasonic vibration was applied, and the mixture was mixed with a TK homomixer (30 minutes at 12,000 rpm), and then filtered under reduced pressure. This operation was repeated so that the electric conductivity of the reslurry liquid was 10 μC / cm or less.
(3): 10% hydrochloric acid was added so that the reslurry solution of (2) had a pH of 4, and the mixture was directly filtered with a three-one motor for 30 minutes.
(4): 100 parts of ion-exchanged water was added to the filter cake of (3), mixed with a TK homomixer (10 minutes at 12,000 rpm) and then filtered. This operation was repeated so that the reslurry liquid had an electric conductivity of 10 μC / cm or less to obtain [Filter Cake 1].

  [Filtration cake 1] was dried at 45 ° C. for 48 hours in a circulating drier, and sieved with an opening of 75 μm mesh to obtain [Toner Base 1]. When the obtained [Toner Base 1] was observed with a scanning electron microscope, the vinyl resin was uniformly attached to the surface of the core particles.

  The toner prepared as described above is filled into a color laser printer (Ricoh's Ypsio SPC310) and printed continuously in a high-temperature and high-humidity environment, and when the above cleaning mode is performed every 500 sheets for 1 minute. The number of white streaks and other abnormalities was compared. The results are described below.

  In the case of continuous printing, fine white streaks occurred in the image after printing about 1000 sheets. On the other hand, when the cleaning mode for 1 minute was executed every 500 sheets, the image abnormality did not occur until the filling toner amount was insufficient on 2000 sheets. From this result, it was confirmed that toner filming to the regulating blade 13c can be suppressed by executing the cleaning mode.

DESCRIPTION OF SYMBOLS 13 Developing apparatus 13a Developer carrier 13c Developer control member P1 Maximum pressure part P1a Upstream side contact part P1b Downstream side contact part 30, 40, 50 Displacement means 31 Cam member 32 Drive means

JP 7-168440 A JP 2000-122417 A

Claims (7)

A developer carrier that holds the one-component developer on the surface and conveys the held one-component developer to the development region by rotating;
The free end is arranged toward the upstream side in the rotation direction of the developer carrying member, and the free end is pressed against the surface of the developer carrying member to charge the one-component developer adhering to the surface. A developing device having a blade-shaped developer regulating member that regulates the layer thickness of the one-component developer held together,
The contact surface of the developer regulating member that is in pressure contact with the surface of the developer carrier is upstream of the developer carrier in the rotation direction with a maximum pressure portion where the pressure of the contact surface is maximized as a boundary. Having a contact portion located on the downstream side and a contact portion located on the downstream side;
A developing device having a cleaning mode in which the position of the contact surface is displaced so that the downstream contact portion before displacement is positioned upstream of the maximum pressure portion after displacement. The developing device according to claim 1,
In the cleaning mode, the developer carrier is idled in a state where the one-component developer held on the surface of the developer carrier is not consumed. The developing device according to claim 1 or 2,
Displacement means for displacing the maximum pressure portion of the developer regulating member;
The displacement means includes a cam member disposed on the opposite side of the contact surface with the developer carrier, and a drive means for driving the cam member to rotate.
The cam member is at the same position from the opposite side of the developer regulating member on the downstream side in the rotation direction of the developer carrier relative to the contact portion of the developer regulating member at least at one position during one rotation. A developing device having a portion which is in pressure contact with the developer regulating member and does not contact the developer regulating member at least at one position during the same rotation. The developing device according to claim 3.
The developer regulating member is extended in the longitudinal direction of the developer carrier,
2. A developing device according to claim 1, wherein a plurality of cam members are arranged in a longitudinal direction of the developer regulating member. The developing device according to claim 1,
When the developer is supported until the downstream contact portion of the maximum pressure portion of the contact surface between the developer regulating member before displacement and the developer bearing member is positioned upstream of the maximum pressure portion after displacement. A developing device comprising a moving means for moving the developer regulating member in contact with a body. The developing device according to claim 1,
When the developer is supported until the downstream contact portion of the maximum pressure portion of the contact surface between the developer regulating member before displacement and the developer bearing member is positioned upstream of the maximum pressure portion after displacement. A developing device comprising a moving means for moving the developer carrying body in contact with the body.   An image forming apparatus comprising the developing device according to claim 1.

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