JP2022032390A - Developing device and image forming apparatus including the same - Google Patents

Abstract

To provide a developing device of a non-magnetic one-component system that suppress generation of streaks on an image due to a toner adhered to a regulation blade while stably maintaining a layer thickness regulation function, and an image forming apparatus including the same.SOLUTION: A developing device 33 comprises: a developing roller 331 that is opposite to a photoreceptor drum 31; a supply roller 332; a regulation blade 334; and a pressing mechanism 5. The supply roller 332 is in contact with a peripheral surface of the developing roller 331 to form a supply nip part SN with the developing roller 331, supplies toner to the developing roller 331, and recovers the toner from the developing roller 331. The pressing mechanism 5 changes deflection of the regulation blade 334 to move a contact area of the regulation blade 334 with respect to the developing roller 331.SELECTED DRAWING: Figure 4

Description

The present invention relates to a developing apparatus for developing an electrostatic latent image formed on a photoconductor drum using a non-magnetic one-component developer, and an image forming apparatus provided with the developing apparatus.

Conventionally, a developing device used in an image forming apparatus such as a printer and developing an electrostatic latent image formed on a photoconductor drum by using a non-magnetic one-component developer is known. In such a non-magnetic one-component developing system developing apparatus, a regulating blade as a developer regulating member is arranged so as to come into contact with the surface of a developing roller which is a developer carrier. The toner carried on the developing roller is regulated to a desired thickness by passing through the regulating nip portion where the regulating blade and the developing roller come into contact with each other as the developing roller rotates, and then is supplied to the photoconductor drum. Toner.

In such a developing apparatus, there is a problem that the toner is melted by the frictional heat generated between the regulating blade and the rotating developing roller, and the melted toner is fixed to the regulating blade. When the toner adheres to the regulation blade, the toner adheres further starting from the adhered toner, and the adhered toner grown to a size of about several tens of μm to several hundreds of μm hinders the movement of the toner layer on the developing roller, resulting in a white streak image. May occur.

As a countermeasure against such a problem, for example, in Patent Document 1, a regulation blade including a contact surface in contact with a developing roller, a mechanism for bringing the contact surface of the regulation blade into contact with the development roller, and contact of the regulation blade Disclosed is a technique comprising a removing member that moves along a surface and removes foreign matter from the contact surface. When the regulating blade is separated from the developing roller, the removing member moves while contacting the contact surface of the regulating blade, and removes foreign matter from the contact surface.

Japanese Unexamined Patent Publication No. 9-211972

In a configuration in which the removing member moves while in contact with the contact surface of the regulating blade while the regulating blade is separated from the developing roller as in the technique described in Patent Document 1, the regulating blade is elastic on the side opposite to the removing member. Since it is deformable, sufficient rubbing force is not applied to the regulation blade, and foreign matter cannot be sufficiently removed from the contact surface. In addition, the mechanism for bringing the regulating blade into contact with the developing roller and the mechanism for moving the removing member along the contact surface of the regulating blade become complicated, resulting in an increase in size and cost of the device. In addition, since the regulating blade is separated from the peripheral surface of the developing roller, it is difficult to reproduce the pressing force and posture when the blades come into contact with each other again, and it is difficult to stably maintain the original layer thickness regulating function.

The present invention has been made to solve the above-mentioned problems, and has suppressed the generation of streaks on the image due to the toner adhering to the regulation blade while stably maintaining the layer thickness regulation function. It is an object of the present invention to provide a non-magnetic one-component developing apparatus and an image forming apparatus equipped with the developing apparatus.

The inventor of the present invention diligently analyzed the toner sticking substance on the regulation blade as the cause of the streak on the image as described above. It was confirmed that fine particles of toner having a small particle size adhered on it. Rather than scraping the surface of the regulated blade with a cleaning member made of resin or metal, such deposits can be polished by using the toner itself, which has a high affinity with the toner adherents, as an abrasive. We newly found that it is easier to remove. In particular, the present inventor has found that the above-mentioned toner sticking occurs in the vicinity of the boundary with the contact area in the non-contact area adjacent to the contact area where the regulation blade and the toner layer on the developing roller are in contact with each other. It was further found that it is easy to do. As a result, we have newly conceived a developing device that can quickly and accurately polish the toner adhering to the non-contact region and easily and accurately reproduce the layer forming function required for the regulatory blade during the developing operation.

Based on the above idea, the developing apparatus according to one aspect of the present invention supplies toner to a photoconductor drum having a surface that allows the formation of an electrostatic latent image, thereby supplying the electrostatic latent image. It is a developing device capable of performing a developing operation that manifests the above in a toner image, and is composed of a developing housing for accommodating a non-magnetic one component toner and an elastic body having a cylindrical shape, and is developed on the photoconductor drum. It is rotatably supported by the developing housing so as to be arranged so as to face each other in the nip portion, and is composed of a developing roller having a peripheral surface for carrying the toner and a foam elastic body having a cylindrical shape, and is rotatable on the developing housing. A supply nip portion is formed between the developing roller and the peripheral surface of the developing roller, and the toner is supplied to the developing roller while the toner is recovered from the developing roller. The roller, the fixed end portion fixed to the developing housing, and the peripheral surface of the developing roller are arranged on the side opposite to the fixing portion and on the downstream side in the rotational direction of the developing roller from the supply nip portion. It has a free end in contact and can change the deflection of the restricting blade between the fixed end and the free end of the restricting blade that regulates the thickness of the toner on the developing roller. It is equipped with a flexible bending change mechanism.

According to this configuration, the deflection change mechanism is capable of changing the deflection of the regulatory blade between the fixed end and the free end. Therefore, it is possible to change the contact area of the regulating blade with respect to the developing roller by changing the deflection of the regulating blade without separating it from the developing roller. As a result, the toner adhered near the boundary of the non-contact region adjacent to the contact region can be brought into contact with the toner layer on the developing roller, and the adhered matter can be removed from the regulation blade. Therefore, it is possible to prevent streaks from being generated on the image due to the toner adhering to the regulation blade.

In the above configuration, it is desirable that the deflection change mechanism changes the deflection of the regulation blade by pressing the portion between the fixed end portion and the free end portion of the regulation blade from the opposite side of the developing roller. ..

According to this configuration, the deflection change mechanism can change the deflection of the regulation blade by pressing the portion between the fixed end portion and the free end portion of the regulation blade, so that the fixation end portion of the regulation blade can be moved. It is possible to change the contact area of the regulated blade with the developing roller without causing it to occur, and to stably reproduce the contact state of the regulated blade with the developing roller during the developing operation. Further, since the deflection change mechanism presses the portion between the fixed end portion and the free end portion of the regulation blade from the opposite side of the developing roller, the elastic force of the regulation blade is used to change the contact area of the regulation blade. And can be restored.

In the above configuration, the deflection change mechanism is such that the abutting portion that abuts on the restricting blade, the driving portion that drives the abutting portion, and the abutting portion come into contact with and separate from the restricting blade. The control unit has a control unit that can control the drive unit and rotate the developing roller in a state where the contact unit is in contact with the regulation blade, and the control unit executes the development operation. It is desirable to control the driving unit to press the contacting portion against the regulating blade to rotate the developing roller during non-development operation.

According to this configuration, the control unit presses the contact portion against the regulation blade during the non-development operation, so that the deflection and the contact region of the regulation blade can be changed. Further, by rotating the developing roller in a state where the contact area is changed, the toner adhered matter can be easily polished and removed by the rotational force of the developing roller while the toner layer functions as an abrasive.

In the above configuration, the contact portion is an elliptical cam having an outer peripheral surface capable of contacting the regulation blade, and the drive portion is around a rotation center axis extending the cam in the axial direction of the developing roller. It is desirable to bring the outer peripheral surface of the cam into contact with the regulation blade by rotating it.

According to this configuration, the deflection of the regulation blade can be easily changed according to the rotation of the cam.

In the above configuration, it is desirable that the control unit controls the drive unit so that the outer peripheral surface of the cam comes into contact with the regulation blade from the fixed end side of the regulation blade.

According to this configuration, it is possible to strongly contact the toner layer near the boundary of the non-contact area located on the fixed end side of the contact area toward the free end side, and the toner formed near the boundary. The sticking substance can be easily removed.

In the above configuration, it is desirable that the melt viscosity (Pa · s) of the toner at 95 ° C. is set in the range of 10,000 or more and 330000 or less.

According to this configuration, even when a toner having a relatively low melt viscosity and whose viscosity tends to increase due to the temperature inside the apparatus is used, the toner adhered near the boundary of the non-contact region adjacent to the contact region of the regulation blade. Can be brought into contact with the toner layer on the developing roller to remove deposits from the regulatory blade. Therefore, it is possible to prevent streaks from being generated on the image due to the toner adhering to the regulation blade.

The image forming apparatus according to another aspect of the present invention includes the developing apparatus described above and a photoconductor drum on which an electrostatic latent image is formed on the surface and the toner is supplied from the developing roller.

According to this configuration, it is possible to provide an image forming apparatus that suppresses the generation of streaks on an image due to the toner adhering to the regulation blade.

According to the present invention, a non-magnetic one-component developer that stably maintains the layer thickness regulation function and suppresses the generation of streaks on the image due to the toner adhering to the regulation blade, and an image provided with the same. A forming device is provided.

It is sectional drawing which shows the internal structure of the image forming apparatus which concerns on one Embodiment of this invention. It is sectional drawing around the photoconductor drum of the image forming apparatus which concerns on one Embodiment of this invention. It is an enlarged sectional view of the supply nip part between the developing roller and the supply roller of the developing apparatus which concerns on one Embodiment of this invention. It is a side view which shows the state which the contact part is arranged facing the regulation blade in the developing apparatus which concerns on one Embodiment of this invention. It is a side view which shows the state which the contact part pressed the regulation blade in the developing apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the appearance of the toner sticking substance on the regulation blade in the developing apparatus which concerns on one Embodiment of this invention. It is sectional drawing which shows the state that the toner adhering substance was removed from the regulation blade in the developing apparatus which concerns on one Embodiment of this invention. It is a side view which shows the state which the contact part pressed the regulation blade in the developing apparatus which concerns on the modification of this invention.

<About the image forming device>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view showing an internal structure of an image forming apparatus 1 according to an embodiment of the present invention. Here, a monochrome printer is exemplified as the image forming apparatus 1, but the image forming apparatus may be a copying machine, a facsimile apparatus, or a multifunction device having these functions, and an image forming apparatus for forming a color image. It may be.

The image forming apparatus 1 includes a main body housing 10 having a substantially rectangular parallelepiped housing structure, a paper feeding unit 20 housed in the main body housing 10, an image forming unit 30, and a fixing unit 40.

A front cover 11 is provided on the front side of the main body housing 10, and a rear cover 12 is provided on the rear side. The rear cover 12 is a cover that is opened during seat jam and maintenance. Further, the upper surface of the main body housing 10 is provided with a paper ejection portion 13 from which the sheet P after image formation is discharged. Various devices for performing image formation are installed in the internal space S defined by the front cover 11, the rear cover 12, and the paper ejection unit 13.

The paper feed unit 20 includes a paper feed cassette 21 that houses the sheet P to be subjected to the image forming process. A part of the paper cassette 21 projects further forward from the front surface of the main body housing 10. The upper surface of the portion of the paper cassette 21 housed in the main body housing 10 is covered with the paper cassette top plate 21U. The paper cassette 21 is provided with a sheet storage space for accommodating the bundle of sheets P, a lift plate for lifting up the bundle of sheets P for paper feeding, and the like. A sheet feeding portion 21A is provided on the upper portion of the paper feed cassette 21 on the rear end side. In the sheet feeding section 21A, a paper feeding roller 21B for feeding out the uppermost sheet P of the sheet bundle in the paper feed cassette 21 one by one is arranged.

The image forming unit 30 performs an image forming process of forming a toner image on the sheet P sent out from the paper feeding unit 20. The image forming unit 30 includes a photoconductor drum 31, a charging device 32, an exposure device (not shown in FIG. 2), a developing device 33, and a transfer roller 34 arranged around the photoconductor drum 31. include.

The photoconductor drum 31 includes a rotation axis and a cylindrical surface (surface) that rotates around the rotation axis. The cylindrical surface allows an electrostatic latent image to be formed, and a toner image corresponding to the electrostatic latent image is supported on the cylindrical surface. As the photoconductor drum 31, an OPC photoconductor drum can be used.

The charging device 32 uniformly charges the surface of the photoconductor drum 31, is arranged at a predetermined interval with respect to the photoconductor drum 31, and discharges when a predetermined voltage is applied. Includes Scorotron.

The exposure device has a laser light source and optical system devices such as a mirror and a lens, and irradiates the peripheral surface of the photoconductor drum 31 with light modulated based on image data given from an external device such as a personal computer. To form an electrostatic latent image.

The developing device 33 supplies toner to the peripheral surface of the photoconductor drum 31 to develop the electrostatic latent image on the photoconductor drum 31 and execute a developing operation to make it manifest in the toner image. The developing operation is executed at the time of the image forming operation of forming an image on the sheet in the image forming apparatus 1.

The transfer roller 34 is a roller for transferring the toner image formed on the peripheral surface of the photoconductor drum 31 onto the sheet P. The transfer roller 34 abuts on the cylindrical surface of the photoconductor drum 31 to form a transfer nip portion. A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 34.

The fixing unit 40 performs a fixing process for fixing the transferred toner image on the sheet P. The fixing portion 40 includes a fixing roller 41 having a heating source inside, and a pressure roller 42 that is pressed against the fixing roller 41 to form a fixing nip portion between the fixing roller 41 and the fixing roller 41. When the sheet P on which the toner image is transferred is passed through the fixing nip portion, the toner image is fixed on the sheet P by heating by the fixing roller 41 and pressing by the pressure roller 42. In this embodiment, the melt viscosity (Pa · s) of the non-magnetic one-component toner used in the developing device 33 at 95 ° C. is set in the range of 10,000 or more and 330,000 or less.

The main body housing 10 is provided with a main transport path 22F and an inverted transport path 22B for transporting the seat P. The main transport path 22F is provided as a paper ejection port facing the paper ejection portion 13 on the upper surface of the main body housing 10 from the sheet feeding portion 21A of the paper feeding unit 20 via the image forming portion 30 and the fixing portion 40. It extends to 14. The reverse transfer path 22B is a transfer path for returning the single-sided printed sheet P to the upstream side of the image forming unit 30 in the main transfer path 22F when double-sided printing is performed on the sheet P.

The main transport path 22F is extended so as to pass through the transfer nip portion formed by the photoconductor drum 31 and the transfer roller 34 from the lower side to the upper side. Further, a resist roller pair 23 is arranged on the upstream side of the main transport path 22F with respect to the transfer nip portion. The sheet P is temporarily stopped by the resist roller pair 23, skew correction is performed, and then the sheet P is sent out to the transfer nip portion at a predetermined timing for image transfer. A plurality of transport rollers for transporting the sheet P are arranged at appropriate positions in the main transport path 22F and the reverse transport path 22B, and for example, a paper discharge roller pair 24 is arranged in the vicinity of the paper discharge port 14.

The reversing transport path 22B is formed between the outer surface of the reversing unit 25 and the inner surface of the rear cover 12 of the main body housing 10. One roller of the transfer roller 34 and the resist roller pair 23 is mounted on the inner surface of the reversing unit 25. The rear cover 12 and the reversing unit 25 can each rotate around the axis of the fulcrum portion 121 provided at the lower end thereof. When a seat jam occurs in the reverse transfer path 22B, the rear cover 12 is opened. When a sheet jam occurs in the main transport path 22F, or when the unit of the photoconductor drum 31 or the developing device 33 is taken out to the outside, the reversing unit 25 is opened in addition to the rear cover 12.

<About developing equipment>
FIG. 2 is a cross-sectional view showing the structure around the photoconductor drum 31. In the present embodiment, the transfer roller 34 is arranged behind the photoconductor drum 31 so as to come into contact with the photoconductor drum 31, and the charging device 32 is arranged in front of and above the photoconductor drum 31 at predetermined intervals. It is arranged so as to face 31. A transfer nip portion is formed between the photoconductor drum 31 and the transfer roller 34, and the sheet P passes through the transfer nip portion as shown by an arrow in FIG. At this time, the toner image is transferred from the photoconductor drum 31 to the sheet P.

The developing device 33 is arranged in front of and below the photoconductor drum 31 so as to face the photoconductor drum 31. The developing device 33 includes a developing housing 330, a developing roller 331, a supply roller 332, a stirring paddle 333, a regulation blade 334, a blade holding portion 334S, and a lower seal 336 (seal member).

The developing housing 330 houses a non-magnetic one-component toner inside. The developing housing 330 has a housing main body 330A and a housing lid portion 330B. As shown in FIG. 2, an opening for exposing a part of the developing roller 331 to the photoconductor drum 31 side is formed at the rear end portion of the developing housing 330.

The developing roller 331 is rotatably supported by the developing housing 330 so as to be arranged facing the photoconductor drum 31 in the developing nip portion, and has a peripheral surface for carrying toner. The developing roller 331 abuts on the photoconductor drum 31 and forms a developing nip portion for supplying toner to the photoconductor drum 31 together with the photoconductor drum 31. The developing roller 331 is composed of a shaft made of SUS material or SUM material and a cylindrical rubber layer (elastic body) formed around the shaft. The rubber layer is made of conductive silicon rubber as an example. Further, a urethane coat layer is formed on the surface of the rubber layer. As a result, the surface of the developing roller 331 is imparted with chargeability and toner transferability.

The supply roller 332 is arranged in front of and below the developing roller 331 so as to face the developing roller 331, and is rotatably supported by the developing housing 330. The supply roller 332 comes into contact with the peripheral surface of the developing roller 331, and forms a supply nip portion for supplying toner to the developing roller 331 with the developing roller 331. The supply roller 332 is formed by fixing a cylindrical conductive urethane foam rubber (foamed elastic body) around a predetermined shaft. Further, the supply nip width is set in a range of 0.2 mm or more and 1.5 mm or less in the rotational direction when viewed along the radial direction.

The stirring paddle 333 is rotatably supported by the developing housing 330 in front of the supply roller 332. As shown in FIG. 2, the stirring paddle 333 includes an L-shaped shaft in a cross-sectional view and a PET film arranged so as to extend radially from the shaft.

Note that FIG. 2 shows the rotation directions of the developing roller 331, the supply roller 332, and the stirring paddle 333 when the image forming operation for the sheet P is performed in the image forming apparatus 1. The developing roller 331 rotates so that its surface moves in the same direction as the surface of the photoconductor drum 31 at the developing nip portion. As an example, the peripheral speed ratio of the developing roller 331 to the photoconductor drum 31 is set to 1.5 times. The supply roller 332 rotates so that its surface moves in the direction opposite to the surface of the developing roller 331. The peripheral speed ratio of the developing roller 331 to the supply roller 332 is set to 1.5 times. The stirring paddle 333 rotates so as to supply the toner in the developing housing 330 to the supply roller 332 while scooping up the toner. Further, the stirring paddle 333 rotates in the same direction as each other in the region facing the supply roller 332.

The regulation blade 334 is made of a thin metal plate, and the surface (periphery) of the developing roller 331 is on the downstream side in the rotation direction of the developing roller 331 from the supply nip portion and on the upstream side in the rotation direction of the developing roller 331 from the developing nip portion. It is in contact with the surface). The regulating blade 334 is fixed to the developing housing 330 so as to be inclined toward the upstream side in the rotational direction of the developing roller 331. The regulation blade 334 regulates the layer amount (layer thickness) of the toner on the developing roller 331. In addition, toner non-supporting regions that do not support toner are arranged at both ends of the developing roller 331 in the axial direction. Further, the developing housing 330 is provided with a pair of left and right felt seals (not shown) along the peripheral surface of the developing roller 331. Both ends of the regulation blade 334 are arranged so as to be sandwiched between both ends of the developing roller 331 and the left and right felt seals.

The blade holding portion 334S holds the regulation blade 334 and is fixed to the housing lid portion 330B of the developing housing 330.

The lower seal 335 is supported by the housing body 330A on the opposite side of the regulation blade 334 so as to close the gap between the developing roller 331 and the housing body 330A. The tip of the lower seal 335 is in contact with the surface of the developing roller 331.

In the present embodiment, as shown in FIG. 2, the charging device 32 is arranged on the downstream side in the rotation direction of the photoconductor drum 31 when viewed from the transfer nip portion formed by the photoconductor drum 31 and the transfer roller 34. Therefore, a so-called cleanerless method is adopted, in which a known cleaning device is not provided. That is, when the toner image is transferred from the photoconductor drum 31 to the sheet P at the transfer nip portion, the untransferred toner remains on the photoconductor drum 31. The untransferred toner passes through the charging device 32 and is recovered from the photoconductor drum 31 by the developing roller 331 of the developing device 33. At this time, when an image (toner image) is continuously formed on the sheet P, the developing roller 331 collects the untransferred toner from the photoconductor drum 31, while the electrostatic latent on the photoconductor drum 31. Supply toner to the image.

On the other hand, the supply roller 332 supplies new toner to the developing roller 331 at the supply nip portion, and collects the toner not supplied from the developing roller 331 to the photoconductor drum 31 from the developing roller 331.

FIG. 3 is an enlarged cross-sectional view of the facing portions of the developing roller 331 and the supply roller 332 of the developing device 33 according to the embodiment of the present invention. In the present embodiment, the shafts of the developing roller 331 and the supply roller 332 are supported by the developing housing 330, respectively, so that the surface of the developing roller 331 bites into the surface of the supply roller 332 by the amount H. As a result, a supply nip portion SN having a predetermined width is formed between the developing roller 331 and the supply roller 332 along the mutual rotation direction. Since the hardness of the supply roller 332 is lower than the hardness of the developing roller 331, the supply nip portion SN is formed mainly by deforming the surface of the supply roller 332 as shown in FIG. Therefore, when the developing roller 331 and the supply roller 332 rotate respectively, the toner conveyed by the supply roller 332 stays on the upstream side of the supply nip portion SN, and a toner pool TN is formed. Even when a high-density image is formed on the photoconductor drum 31 by the toner pool TN, the toner can be stably supplied from the supply roller 332 to the developing roller 331.

On the other hand, when the developing roller 331 and the supply roller 332 come into contact with each other by point contact in a cross-sectional view, the toner pool TN as shown in FIG. 3 is not sufficiently formed, so that the toner supply property may be significantly reduced. .. Therefore, it is desirable to set the distance between the shafts (distance between the shafts) of the developing roller 331 and the supply roller 332 and their respective diameters so that the biting amount H is appropriate. The hardness of the developing roller 331 is set in the range of 50 or more and 80 or less in the Asker-C hardness in order to come into contact with a hard member called the photoconductor drum 31. Therefore, in order for the developing roller 331 to be recessed into the supply roller 332 as shown in FIG. 3, it is desirable that the hardness of the supply roller 332 is set lower than the hardness of the developing roller 331.

FIG. 4 is a side view showing a state in which the pressing cam 50 is arranged facing the regulation blade 334 in the developing apparatus 33 according to the present embodiment. FIG. 5 is a side view showing a state in which the pressing cam 50 presses the regulation blade 334. FIG. 6 is a cross-sectional view showing a state in which a toner adhered substance is generated on the regulation blade 334. FIG. 7 is a cross-sectional view showing how the toner adhering substance is removed from the regulation blade 334. In FIGS. 6 and 7, the unevenness of the surface of the developing roller 331 is schematically represented by a plurality of protrusions.

With reference to FIG. 4, the regulatory blade 334 has a fixed end 334J and a free end 334K.

The fixed end portion 334J is fixed to the developing housing 330 via the blade holding portion 334S described above.

The free end portion 334K is arranged on the side opposite to the fixed end portion 334J and on the upstream side in the rotational direction of the developing roller 331 with respect to the fixed end portion 334J. Further, the free end portion 334K abuts on the peripheral surface of the developing roller 331 on the downstream side in the rotation direction of the developing roller 331 from the supply nip portion. The tip of the free end 334K has a guide 334P bent away from the peripheral surface of the developing roller 331. The guide unit 334 guides the toner that could not completely enter between the developing roller 331 and the regulation blade 334 so as to be separated from the developing roller 331 (FIG. 6).

Further, the developing device 33 has a pressing mechanism 5 (FIGS. 4 and 5). The pressing mechanism 5 functions as a bending change mechanism capable of changing the bending of the regulation blade 334 between the fixed end portion 334J and the free end portion 334K. In particular, in the present embodiment, the pressing mechanism 5 presses the portion between the fixed end portion 334J and the free end portion 334K of the regulating blade 334 from the opposite side of the developing roller 331 to change the bending of the regulating blade 334.

The pressing mechanism 5 has a pressing cam 50 (contact portion), a driving unit 51, and a control unit 52.

The pressing cam 50 is a cam having an elliptical cross section having an outer peripheral surface capable of contacting the regulation blade 334. The pressing cam 50 may extend over the entire axial direction of the regulation blade 334, or may be a plurality of cams arranged at intervals along the axial direction. The pressing cam 50 has a short diameter portion and a long diameter portion. When the short diameter portion of the pressing cam 50 faces the regulation blade 334, the outer peripheral surface of the pressing cam 50 does not contact the regulation blade 334. On the other hand, when the major axis portion of the pressing cam 50 faces the regulation blade 334, the outer peripheral surface of the pressing cam 50 presses the regulation blade 334, and the deflection of the regulation blade 334 changes.

The drive unit 51 includes a motor that drives the pressing cam 50 and the like. The drive unit 51 rotates the pressing cam 50 around a rotation center axis extending in the axial direction of the developing roller 331 so that the outer peripheral surface of the pressing cam 50 comes into contact with the regulation blade 334.

The control unit 52 can control the drive unit 51 so that the pressing cam 50 is brought into contact with and separated from the regulation blade 334, and can rotate the developing roller 331 in a state where the pressing cam 50 is in contact with the regulation blade 334. It is said that. Further, the control unit 52 controls the drive unit 51 to press the pressing cam 50 against the regulation blade 334 during the non-development operation in which the development operation in the developing device 33 is not executed, and further rotates the developing roller 331.

With reference to FIG. 4, during the image forming operation in the image forming apparatus 1, that is, during the developing operation in the developing apparatus 33, the control unit 52 controls the driving unit 51 to control the outer peripheral surface (major diameter portion) of the pressing cam 50. Separate from the regulation blade 334. In this case, as an example, the linear pressure (pressing pressure) of the regulating blade 334 with respect to the developing roller 331 is set in the range of 30 to 50 N / m. At this time, the linear pressure of the regulation blade 334 is applied toward the center of the developing roller 331. Then, when the image forming operation is continued in this state, the toner adhering substance TP begins to be formed on the surface of the regulation blade 334 as shown in FIG. In particular, the wax component and the external additive component of the toner adhere to the fine uneven portion of the contact portion where the regulation blade 334 contacts the developing roller 331, and the toner having a smaller particle size adheres to these to form a fixed substance. Will be done. As shown in FIG. 6, the portion of the free end portion 334K of the regulation blade 334 connected to the guide portion 334P is in contact with the peripheral surface of the developing roller 331 and the toner layer supported on the peripheral surface (contact portion C). ). On the other hand, the portion on the fixed end portion 334J side of the contact portion C is not in contact with the toner layer (non-contact portion A), and in particular, the toner fixing portion B in the non-contact portion A near the boundary with the contact portion C. Is formed. If such a toner fixing portion B is gradually and firmly fixed, it leads to the generation of thin layer streaks on the developing roller 331 and white streaks on the image.

In order to solve such a problem, in the present embodiment, the pressing mechanism 5 operates during non-image formation (non-development operation). In particular, the control unit 52 controls the drive unit 51 before the image forming operation (before the developing operation) or after the image forming operation (after the developing operation) in the image forming apparatus 1, and as shown in FIG. 5, the pressing cam 50 The outer peripheral surface (major axis portion) of the above is brought into contact with the regulation blade 334. As a result, the regulation blade 334 is pressed toward the developing roller 331 by the pressing cam 50 (arrow D3), and its deflection changes. At this time, the free end portion 334K of the regulation blade 334 bites into the developing roller 331 side, so that the toner fixing portion B in FIG. 6 comes into contact with the toner layer on the developing roller 331. Then, when the control unit 52 controls the roller drive unit (not shown) to rotate the developing roller 331, the toner fixing portion B is scraped (polished) by the rotation of the developing roller 331 using the toner layer as an abrasive. .. As a result, the toner fixing portion B can be eliminated over the entire axial direction of the developing roller 331, and the generation of thin layer streaks on the developing roller 331 and white streaks on the image can be prevented.

As described above, in the present embodiment, the pressing mechanism 5 is capable of changing the deflection of the regulation blade 334 between the fixed end portion 334J and the free end portion 334K. Therefore, it is possible to change the contact region of the regulating blade 334 with respect to the developing roller 331 by changing the bending of the regulating blade 334 without separating it from the developing roller 331. In particular, as described above, the contact region of the regulating blade 334 changes along the direction in which the regulating blade 334 extends toward the developing roller 331 (rotational direction of the developing roller 331). As a result, the toner (toner fixing portion B) adhered near the boundary of the non-contact region (non-contact portion A) adjacent to the contact region (contact portion C) is brought into contact with the toner layer on the developing roller 331, and the adhered substance is formed. It can be removed from the regulation blade 334. Therefore, it is possible to prevent streaks from being generated on the image due to the toner adhering to the regulation blade 334.

Further, in the present embodiment, the pressing mechanism 5 can change the bending of the regulating blade by pressing the portion between the fixed end portion 334J and the free end portion 334K of the regulating blade 334, so that the bending is changed. It is not necessary to move the fixed end 334J of the regulation blade 334 in order to make it move. Therefore, it is possible to stably reproduce the contact state of the regulation blade 334 with the developing roller 331 during the developing operation. Further, since the pressing mechanism 5 presses the portion between the fixed end portion 334J and the free end portion 334K of the regulation blade 334 from the opposite side of the developing roller 331, the regulation blade uses the elastic force of the regulation blade 334. The contact area of 334 can be altered and restored.

Further, in the present embodiment, the control unit 52 presses the pressing cam 50 against the regulation blade 334 during the non-development operation, so that the deflection and the contact region of the regulation blade 334 can be changed. Further, by rotating the developing roller 331 in a state where the contact region is changed, the toner adhered matter can be easily polished and removed by the rotational force of the developing roller 331 while the toner layer functions as an abrasive.

Further, in the present embodiment, the pressing mechanism 5 has an elliptical pressing cam 50, a driving unit 51, and a control unit 52. Therefore, the deflection of the regulation blade 334 can be easily changed according to the rotation of the pressing cam 50.

In addition, referring to FIG. 4, when the control unit 52 controls the drive unit 51 to rotate the pressing cam 50, it may be rotated in any of the directions of the arrows D1 and D2. However, when the pressing cam 50 rotates in the D1 direction, the control unit 52 controls the driving unit 51 so that the outer peripheral surface of the pressing cam 50 comes into contact with the regulation blade 334 from the fixed end portion 334J side of the regulation blade 334. On the other hand, when the pressing cam 50 rotates in the D2 direction, the control unit 52 controls the driving unit 51 so that the outer peripheral surface of the pressing cam 50 comes into contact with the regulation blade 334 from the free end portion 334K side of the regulation blade 334. In the former case, the vicinity of the boundary of the non-contact region located on the fixed end portion 334J side of the contact region (contact portion C) can be strongly contacted with the toner layer toward the free end portion 334K side, and the vicinity of the boundary is reached. The formed toner fixing portion B can be easily removed.

Further, as shown in FIG. 5, when the pressing cam 50 presses the regulation blade 334 and the deflection of the regulation blade 334 changes, the pressing cam 50 constitutes a pseudo fixed end portion of the regulation blade 334. In this case, the free length of the regulation blade 334 is shorter than that in the case of FIG. The natural frequency of a cantilever is inversely proportional to the square of the free length of the beam. Therefore, in the state of FIG. 5, the natural frequency of the regulation blade 334 shifts to the high frequency region as compared with the state of FIG. Therefore, the control unit 52 may promote the high frequency vibration of the regulation blade 334 by increasing the rotation speed of the developing roller 331 at the time of non-image formation as compared with the time of image formation. In this case, the toner fixing portion B can be more easily removed from the regulation blade 334 by the rotation of the developing roller 331.

Further, the control unit 52 may alternately rotate (reciprocate) the pressing cam 50 in the directions of arrows D1 and D2 in FIG. 4 in a state where the peripheral portion of the major axis portion of the pressing cam 50 is in contact with the regulation blade 334. .. In this case, the deflection of the pressing cam 50 changes from moment to moment, so that the developing roller 331 can be rotated while changing the contact area between the regulating blade 334 and the developing roller 331, and the toner fixing portion B becomes the regulating blade 334. It becomes easy to separate from.

Further, it is desirable that a member having a high coefficient of friction with respect to the surface of the regulation blade 334 is used for the outer peripheral surface of the pressing cam 50. In this case, the pressing cam 50 is prevented from slipping with respect to the regulation blade 334, and the deflection of the regulation blade 334 can be stably changed.

Further, in the present embodiment, a so-called low-temperature fixing toner in which the melt viscosity (Pa · s) of the non-magnetic one-component toner used in the developing device 33 at 95 ° C. is set in the range of 10,000 or more and 330,000 or less is used. Even in this case, it is possible to prevent the toner from sticking to the regulation blade 334. That is, even if the toner has a relatively low melt viscosity and the viscosity tends to increase depending on the temperature inside the apparatus, it is possible to suppress the adhesion of the toner to the regulation blade 334 and its growth. When the melt viscosity (Pa · s) exceeds 330000, the toner does not easily adhere to the regulation blade 334, so that the pressing operation of the regulation blade 334 by the pressing mechanism 5 does not need to be performed frequently. On the other hand, toner having a melt viscosity (Pa · s) of less than 10,000 is particularly prone to sticking, so it is desirable to set it within the above range.

Further, in the present embodiment, in the image forming apparatus 1 including the developing apparatus 33 adopting the non-magnetic one-component developing method as described above, white streaks (images) are formed on the image due to the adhesion of toner to the regulation blade 334. It is possible to prevent the occurrence of defects). Further, by combining such a developing device 33 with a cleanerless method in which the photoconductor drum 31 is not provided with a cleaning device, it is possible to realize miniaturization and cost reduction in the image forming apparatus 1. In particular, in a configuration in which the restricting blade 334 is fixed to the developing housing 330 of the developing device 33 and the developing device 33 needs to be replaced when the quality of the regulating blade 334 deteriorates, the pressing mechanism 5 extends the life of the regulating blade 334. By extending it, the life of the developing device 33 can be extended.

Next, a preferred embodiment of the developing device 33 will be described with reference to examples. In addition, each subsequent Example was carried out under the following experimental conditions.
<Experimental conditions>
-Photoreceptor drum 31: OPC drum-Peripheral speed of the photoconductor drum 31: 118 mm / sec
Circumferential speed of developing roller 331: 182 mm / sec
-Development bias DC component: 350V
・ Supply bias DC component: 450V
-Surface potential of the photoconductor drum 31: 640V
-Diameter of developing roller 331: 13 mm
-Diameter of supply roller 332: 13 mm
-Diameter of photoconductor drum 31: 24 mm
-Average particle size of non-magnetic toner: 8.0 μm (D50)
-Linear pressure (pressing pressure) of the regulating blade 334 with respect to the developing roller 331: 30 to 50 N / m (toward the center of the developing roller 331).

Under the above experimental conditions, as a comparative example, a developing device 33 having no pressing mechanism 5 is attached to the image forming device 1, and a predetermined number of sheets (1000 sheets) are printed with a half image (image density 15%). As a result, thin streaks were generated on the image.

On the other hand, under the above experimental conditions, as an example, under the condition that the toner fixing portion B is removed from the regulation blade 334 by using the pressing mechanism 5 before and after printing, the image forming apparatus 1 has a predetermined number (2000 sheets). ) Was printed, and as a result, thin-layer streaks on the image did not occur.

In addition, the inventor of the present invention observed the toner sticking state of the regulation blade 334 when the thin layer streaks were generated in the above comparative example. Specifically, when observed at a magnification of 50 times using a microscope (KH-8700 manufactured by HIROX), it was confirmed that toner adhered to the regulation blade 334 (toner fixing portion B in FIG. 6).

Further, since a transparent substance other than the toner was attached to the portion to which the toner was attached as described above, it was included in the toner as a result of analysis using infrared spectroscopy (abbreviated as IR). It was found that the wax component was attached to the toner fixing portion B.

Further, when the particle size of the adhered toner was measured with the above-mentioned microscope at a magnification of 2000 times, the toner having a volume average particle size of 8.0 μm was mainly adhered to the toner having a volume average particle size of 2 to 4 μm. Was confirmed. Further, when the adhered toner was removed with an air gun, a recess of wax was observed in the portion of the regulation blade 334 where the toner had adhered. From the above, it was confirmed that in the adhesion of the toner at the free end portion 334K of the regulation blade 334, the wax first adheres, and then the fine particles of the toner having a small particle size adhere to the wax.

On the other hand, in the developing apparatus 33 having the pressing mechanism 5 according to the present embodiment represented by the above embodiment, the toner is fixed by changing the bending of the regulation blade 334 during non-image formation (non-developing operation). The portion B can be easily removed.

As described above, the inventor of the present invention diligently analyzed the adhered substance of the toner on the regulated blade 334 as the cause of the streak on the image. It was found that the toner had adhered and fine particles of toner having a small particle size adhered on it. It is new that such deposits can be removed more easily by using the toner itself, which has a high affinity with the adhered matter, as an abrasive, rather than scraping it off with a cleaning member made of resin or metal. Found in. In particular, the above-mentioned toner sticking is likely to occur in the non-contact region adjacent to the contact region where the regulation blade 334 and the toner layer on the developing roller 331 are in contact with each other, in the vicinity of the boundary with the contact region. Was further found. Therefore, the present inventor has conceived a developing device 33 that can quickly and accurately polish the toner adhering to the non-contact region and easily and accurately reproduce the layer forming function required for the regulation blade 334 during the developing operation. Such an idea is not to separate the regulation blade 334 from the developing roller 331, but to change the deflection of the regulation blade 334. Further, the idea is to remove the toner fixing portion B by rotating the developing roller 331 using the toner as an abrasive without bringing another cleaning member into contact with the surface of the regulation blade 334. Since the regulation blade 334 is not separated from the developing roller 331, it is possible to easily reproduce the contact condition of the regulation blade 334 with the developing roller 331 and form the toner layer, and the toner fixing portion B can be formed. It is possible to immediately shift to the development operation after removing the toner.

Although the developing apparatus 33 and the image forming apparatus 1 provided with the developing apparatus 33 according to the embodiment of the present invention have been described above, the present invention is not limited to this, and for example, the following modified embodiments are adopted. Can be done.

(1) In the above embodiment, the image forming apparatus 1 is provided with one developing apparatus 33, but the image forming apparatus 1 is a color image forming apparatus having development apparatus 33 corresponding to a plurality of colors. It may be.

(2) In the above embodiment, the development housing 330 of the developing apparatus 33 has been described in that the non-magnetic toner is stored inside, but a toner container and a toner cartridge for storing the non-magnetic toner are provided separately from the developing housing 330. It may have.

(3) In the above embodiment, the pressing mechanism 5 has a pressing cam 50, a driving unit 51, and a control unit 52, but the present invention is not limited thereto. FIG. 8 is a side view showing a state in which the pressing portion 57 presses the regulation blade 334 in the developing apparatus 33 according to the modified embodiment of the present invention. In this modified embodiment, the pressing mechanism 5 has a control unit 52 and a pressing unit 55 (driving unit). The pressing unit 55 has a main body portion 56 and a pressing portion 57 (contact portion). The pressing unit 55 has a known electromagnetic solenoid structure. The pressing portion 57 can appear and disappear with respect to the main body portion 56. Upon receiving the command signal from the control unit 52, the pressing unit 57 protrudes from the main body unit 56 as shown by the arrow D5 and comes into contact with the regulation blade 334. As a result, the regulation blade 334 is pressed as shown by the arrow D6, and the deflection of the regulation blade 334 changes. Then, during the developing operation, the control unit 52 controls the pressing unit 55 so that the pressing unit 57 is immersed in the main body 56, so that the deflection of the regulation blade 334 is restored.

As described above, also in this modification, the pressing mechanism 5 changes the deflection of the regulation blade 334 so that the toner fixing portion B formed on the free end portion 334K of the regulation blade 334 is brought into contact with the toner layer and the developing roller is formed. It can be easily removed by rotating 331. The configuration of the contact portion and the drive portion according to the present invention is not limited to the above, and other embodiments may be used.

(4) Further, the image streaks caused by the toner fixing portion B described above become apparent in an image having a predetermined area visible to the user (particularly, a half image or a solid image). In other words, such an image streak does not pose a big problem (difficult to see) in an image (low print rate image) in which characters are printed on the entire surface of the sheet. Therefore, in the job including the continuous pages requested for the image forming apparatus 1, the control unit 52 abuts the pressing cam 50 on the regulation blade 334 at the timing when the pages of the predetermined character image are continuous, and the toner fixing unit B may be removed. In this case, it is possible to prevent image streaks from occurring in advance on a page including a half image or a solid image (high print rate image) to be printed next to the page of the character image.

1 Image forming device 31 Photoconductor drum 33 Developing device 330 Developing housing 330A Housing body 330B Housing lid 331 Developing roller 332 Supply roller 333 Stirring paddle 334 Restriction blade 335 Lower seal 5 Pressing mechanism 50 Pressing cam (contact part)
51 Drive unit 52 Control unit 55 Pressing unit (drive unit)
56 Main body 57 Pressing part (contact part)
A Non-contact part B Toner fixing part (near the boundary of the non-contact area)
C contact part

Claims (7)

A developing device capable of performing a developing operation for manifesting the electrostatic latent image in a toner image by supplying toner to a photoconductor drum having a surface that allows the electrostatic latent image to be formed. There,
A developing housing that houses a non-magnetic one-component toner,
A developing roller made of an elastic body having a cylindrical shape, rotatably supported by the developing housing so as to be arranged opposite to the photosensitive drum in the developing nip portion, and having a peripheral surface for carrying the toner.
It is made of a foam elastic body having a cylindrical shape, is rotatably supported by the developing housing, and abuts on the peripheral surface of the developing roller to form a supply nip portion with the developing roller, and the developing roller has the above-mentioned. A supply roller that collects the toner from the developing roller while supplying the toner, and a supply roller that collects the toner from the developing roller.
A fixed end portion fixed to the developing housing and a free end arranged on the side opposite to the fixed portion and abutting on the peripheral surface of the developing roller on the downstream side in the rotational direction of the developing roller from the supply nip portion. A regulatory blade that has a section and regulates the thickness of the toner on the developing roller.
A deflection change mechanism capable of varying the deflection of the regulatory blade between the fixed end and the free end,
A developing device. The development according to claim 1, wherein the bending change mechanism presses a portion between the fixed end portion and the free end portion of the regulation blade from the opposite side of the developing roller to change the bending of the regulation blade. Device. The bending change mechanism is
The contact portion that abuts on the regulation blade and
The drive unit that drives the contact unit and
A control unit capable of controlling the drive unit so that the contact portion is brought into contact with the regulation blade and rotating the developing roller while the contact portion is in contact with the regulation blade. When,
Have,
The developing apparatus according to claim 2, wherein the control unit controls the driving unit to press the contact portion against the regulating blade to rotate the developing roller during a non-developing operation in which the developing operation is not executed. .. The contact portion is an elliptical cam having an outer peripheral surface capable of contacting the regulation blade.
The developing apparatus according to claim 3, wherein the driving unit rotates the cam around a rotation center axis extending in the axial direction of the developing roller to bring the outer peripheral surface of the cam into contact with the regulating blade. The developing device according to claim 4, wherein the control unit controls the drive unit so that the outer peripheral surface of the cam comes into contact with the regulation blade from the fixed end side of the regulation blade. The developing apparatus according to any one of claims 1 to 5, wherein the melt viscosity (Pa · s) of the toner at 95 ° C. is set in the range of 10,000 or more and 330000 or less. The developing apparatus according to any one of claims 1 to 6.
An image forming apparatus including a photoconductor drum to which the toner is supplied from the developing roller.

Images