JP2012042763A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device of non-contact development system with which uniformity of toner adhesion amount in an axial direction of a developing roller is attained, toner fusion to a layer thickness regulation blade is prevented, and stable developing property can be secured.SOLUTION: A developing device 14 comprises: a developer tank 60 for storing toner; a developing roller 61 for carrying the toner stored in the developer tank 60 and conveying the toner to a photoreceptor 11; and a layer thickness regulation blade 64 which abuts on an outer peripheral surface of the developing roller 61 and regulates layer thickness of the toner. A first inclined groove 611 and a second inclined groove 612 which intersect with each other, each of which is inclined in a circumferential direction, and spirally continues are provided on the outer peripheral surface of the developing roller 61. Regarding the first inclined groove 611 and the second inclined groove 612, the ratio (P1/P2) of a groove interval P1 in a central part 610a of the developing roller 61 in an axial direction against a groove interval P2 in end parts 610b, 610c of the developing roller 61 in the axial direction is 0.2-0.75.

Description

  The present invention relates to a developing device that develops an electrostatic latent image formed on an image carrier using toner, and an image forming apparatus including the developing device.

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

  As a developing device provided in an electrophotographic image forming apparatus, a non-magnetic one-component developing system that has a simple structure and can be reduced in size is useful, and development of an improved technique is still underway. As a developing device of the non-magnetic one-component developing system, a contact developing system in which development is performed by bringing a developing roller as a developer carrying body into contact with an image carrying body, and development arranged with a predetermined gap from the image carrying body. There is a non-contact development system in which development is performed by causing toner of a non-magnetic one-component developer to fly from a roller to an image carrier. In both types, the structure of the developing device itself is similar and has a feature that can be reduced in size, but the material of the developing roller may be different.

  In the contact developing type developing device, the developing roller is composed of an elastic member such as rubber having conductivity in order to obtain uniform contact in the developing region. In particular, when a rigid body such as a photosensitive drum is used as the image bearing member, it is effective from the viewpoint of preventing damage due to a failure in the contact state to constitute the developing roller with an elastic member.

  In a non-contact developing type developing device, since the developing roller needs to accurately maintain a gap with the image carrier, a roller or sleeve made of a rigid body such as metal is often used. This is because it is effective for improving the polishing accuracy of the surface and suppressing the eccentricity of the drive shaft and the surface as compared with the rubber roller. In addition, since there is no contact, there is no fear of damage to the image carrier due to contact.

  In the non-contact developing type developing device, the toner carried on the developing roller is regulated in layer thickness by friction by a layer thickness regulating blade provided in contact with the developing roller, and is triboelectrically charged. Is done. In this case, in order to improve the charge imparting ability for the toner on the developing roller, the outer peripheral surface of the developing roller is subjected to sandblasting so as to have a predetermined surface roughness.

  However, when a developing operation is performed for a long time in the developing device, the outer peripheral surface of the developing roller is scraped, and the surface roughness is reduced. As described above, when the surface roughness of the outer peripheral surface of the developing roller is reduced, the friction charging ability of the developing roller with respect to the toner is lowered.

  As a method for solving such a problem, Patent Document 1 discloses a developing device including a developing roller in which an uneven pattern including regular grooves is formed on an outer peripheral surface. A developing roller having an outer peripheral surface in which such a regular groove is formed has an outer surface such as silica particles externally added to the toner surface than a developing roller having an outer peripheral surface having an irregular surface roughness by sandblasting. It is possible to suppress wear due to the additive, and thereby it is possible to suppress a decrease in frictional charging ability of the developing roller with respect to the toner.

JP 2008-33124 A

  In a non-contact developing type developing device, toner that is triboelectrically carried on the outer peripheral surface of the developing roller is caused to fly to the image bearing member to develop the electrostatic latent image on the image bearing member. In order to achieve this, it is necessary to uniformly and uniformly control the toner adhesion amount on the outer peripheral surface of the developing roller.

  However, the linear pressure on the developing roller of the layer thickness regulating blade that contacts the developing roller is not uniform in the axial direction of the developing roller, and the linear pressure at the central portion in the axial direction is higher than the linear pressure at both ends in the axial direction. Yes. For this reason, the toner adhesion amount on the outer peripheral surface of the developing roller is not uniform in the axial direction, and the toner adhesion amount tends to decrease in the central portion in the axial direction. Such a phenomenon of uneven toner adhesion amount in the axial direction of the developing roller is a phenomenon that occurs also in the developing roller disclosed in Patent Document 1 and having an outer peripheral surface in which regular grooves are formed. .

  When the amount of toner adhering to the central portion in the axial direction of the developing roller is small, the image density of the recorded image formed on the recording paper is reduced corresponding to the central portion in the axial direction of the developing roller. As a result, non-uniform image density occurs.

  Further, since the linear pressure of the contacting layer thickness regulating blade is high at the central portion in the axial direction of the developing roller, toner fusion to the layer thickness regulating blade is likely to occur. White streaks occur in the recorded image to be formed, and the image quality deteriorates.

  Accordingly, an object of the present invention is to achieve a uniform toner adhesion amount in the axial direction of the developing roller in a non-contact developing type developing device, and to prevent toner fusion of the layer thickness regulating blade, thereby achieving stable developability. It is an object of the present invention to provide a developing device that can be secured and an image forming apparatus including the developing device.

The present invention relates to a developing device that forms a toner image by developing an electrostatic latent image formed on the surface of an image carrier with toner that is a non-magnetic one-component developer.
A developer tank containing toner;
A developing roller that faces the image carrier at a predetermined interval, is rotatably provided in the developing tank, and carries the toner contained in the developing tank and transports the toner to the image carrier, the outer periphery of the developing roller A developing roller having a surface formed with a first inclined groove and a second inclined groove that are spirally inclined with respect to a circumferential direction intersecting each other;
A layer thickness regulating blade that is provided in contact with the outer circumferential surface of the developing roller and regulates the layer thickness of the toner carried on the outer circumferential surface of the developing roller that is driven to rotate, and that frictionally charges the toner;
The first inclined groove and the second inclined groove have a groove interval P2 when the groove interval in the axial direction of the developing roller is P1 as the groove interval at the central portion in the axial direction and P2 as the groove interval at both ends in the axial direction. The developing device is characterized in that the ratio (P1 / P2) of the groove interval P1 to the groove is 0.2 or more and 0.75 or less.

  The developing device of the present invention is characterized in that the first inclined groove and the second inclined groove have spiral directions opposite to each other.

  In the developing device of the present invention, the first inclined groove and the second inclined groove have a groove interval of 0.75 to 5 mm in the axial direction of the developing roller, a groove depth of 5 to 50 μm, The inclination angle of the developing roller with respect to the circumferential direction is 10 to 60 degrees.

The present invention also provides an image carrier,
Latent image forming means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image formed on the image carrier using toner which is a non-magnetic one-component developer,
The developing unit is an image forming apparatus according to the present invention.

  According to the present invention, the developing device is a device that forms a toner image by developing the electrostatic latent image formed on the surface of the image carrier with toner that is a non-magnetic one-component developer, and contains the toner. A developing tank, a developing roller, and a layer thickness regulating blade. The developing roller faces the image carrier at a predetermined interval and is rotatably provided in the developing tank. The developing roller carries toner contained in the developing tank and conveys the toner to the image carrier. The layer thickness regulating blade is provided in contact with the outer circumferential surface of the developing roller, regulates the layer thickness of the toner carried on the outer circumferential surface of the rotationally driven developing roller, and frictionally charges the toner. Then, on the outer peripheral surface of the developing roller, there are formed a first inclined groove and a second inclined groove that extend along the axial direction between both ends in the axial direction and are spirally inclined with respect to the circumferential direction intersecting each other. Is done. The first inclined groove and the second inclined groove are grooves with respect to the groove interval P2 when the groove interval in the axial direction of the developing roller is P1 as the groove interval at the central portion in the axial direction and P2 as the groove interval at both ends in the axial direction. The ratio (P1 / P2) of the interval P1 is 0.2 or more and 0.75 or less.

  The first inclined groove and the second inclined groove formed on the outer peripheral surface of the developing roller are provided such that the groove interval P1 at the central portion in the axial direction is smaller than the groove interval P2 at both end portions in the axial direction at a predetermined rate. Therefore, in the central portion in the axial direction where the linear pressure due to the contact of the layer thickness regulating blade is high, the toner carrying ability by the first inclined groove and the second inclined groove, and the removal of the toner fused material fused to the layer thickness regulating blade Ability can be improved. As a result, the developing device can achieve uniform toner adhesion in the axial direction of the developing roller, and can prevent the toner fusion of the layer thickness regulating blade and ensure stable developability.

  According to the invention, the first inclined groove and the second inclined groove provided on the outer peripheral surface of the developing roller have spiral directions opposite to each other. As a result, the toner adhesion amount in the axial direction of the developing roller can be made more uniform, and the toner fusion product removal efficiency of the layer thickness regulating blade can be improved.

  According to the invention, the first inclined groove and the second inclined groove provided on the outer peripheral surface of the developing roller have a groove interval of 0.75 to 5 mm in the axial direction of the developing roller, and a groove depth of 5 respectively. The inclination angle of the developing roller with respect to the circumferential direction is 10 to 60 degrees. As a result, the toner adhesion amount in the axial direction of the developing roller can be made more uniform, and the toner fusion product removal efficiency of the layer thickness regulating blade can be improved.

  According to the invention, the image forming apparatus uses an image carrier, latent image forming means for forming an electrostatic latent image on the image carrier, and the electrostatic latent image formed on the image carrier using toner. Developing means for developing. The image forming apparatus includes, as the developing unit, a developing device in which the toner adhesion amount in the axial direction of the developing roller is made uniform and toner fusion of the layer thickness regulating blade is prevented, so that the image density is made uniform Can be achieved, and a high-quality image can be formed in which the occurrence of image defects such as white streaks is prevented.

1 is a diagram illustrating a configuration of an image forming apparatus 1 according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a developing device 14 according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a configuration of a developing roller 61 provided in the developing device 14.

(Image forming device)
FIG. 1 is a diagram showing a configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is an electrophotographic full-color image forming apparatus, and is applied to a recording sheet 71 that is a recording medium based on image data of a document read by the image reading apparatus and image data transmitted via a network or the like. On the other hand, it is an apparatus for forming a multicolor or single color image.

  The image forming apparatus 1 includes a visible image forming unit 10, a paper feeding unit 20, a recording paper transport unit 30, and a fixing unit 40. The image forming apparatus 1 corresponds to four hues of yellow (Y), magenta (M), and cyan (C), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Image formation is performed using the image data. Therefore, in the image forming apparatus 1, the visible image forming unit 10 includes four visible image forming units 10Y, 10Y corresponding to each of yellow (Y), magenta (M), cyan (C), and black (K). It consists of 10M, 10C, 10K. The visible image forming unit 10Y forms an image using yellow (Y) toner, the visible image forming unit 10M forms an image using magenta (M) toner, and the visible image forming unit 10C is cyan. An image is formed using the toner (C), and the visible image forming unit 10K forms an image using the black (K) toner. Each of the visible image forming units 10Y, 10M, 10C, and 10K includes a visible image forming unit 10Y and a visible image forming unit along a conveyance path along which the recording paper 71 is conveyed from the paper supply unit 20 toward the fixing unit 40. The units 10M, the visible image forming unit 10C, and the visible image forming unit 10K are arranged in this order, and each color toner is multiplex-transferred onto the recording paper 71 transported by the recording paper transport unit 30.

  Each of the visible image forming units 10Y, 10M, 10C, and 10K has the same configuration, and is a photoreceptor 11 that is an image carrier, a charging unit 12, an exposure unit 13, and a developing device 14 that is a developing unit. The transfer unit 15, the cleaner unit 16, and the charge eliminating unit 17 are included. In the image forming apparatus 1 of the present embodiment, the latent image forming unit includes a charging unit 12 and an exposure unit 13. Further, the charging unit 12, the exposure unit 13, the developing device 14, the transfer unit 15, the cleaner unit 16, and the charge eliminating unit 17 are arranged around the photoconductor 11 in this order from the upstream side to the downstream side in the rotation direction of the photoconductor 11. Be placed.

  The photoconductor 11 has a cylindrical drum shape and is driven to rotate around an axis by a driving unit (not shown). The photoreceptor 11 has a cylindrical conductive substrate and a photosensitive layer provided on the surface of the conductive substrate. The photoconductor 11 is driven to rotate around the axis at a peripheral speed of 145 mm / second, for example.

  The charging unit 12 includes a plate-like discharge electrode having a plurality of sawtooth-shaped sharp protrusions, and a screen-like grid electrode for adjusting the charging potential of the surface of the photoreceptor 11, and is configured to be non-contact charging. This is a scorotron charging device. The charging unit 12 corona discharges when a voltage is applied to the discharge electrode to charge the surface of the photoconductor 11, and a charged state of the surface of the photoconductor 11 by applying a predetermined grid voltage to the grid electrode. And the surface of the photoconductor 11 is charged to a predetermined potential and polarity. The charging unit 12 faces the photoconductor 11 and is disposed along the axial direction of the photoconductor 11.

  The exposure unit 13 exposes the surface of the photoconductor 11 charged by the charging unit 12 by irradiating a laser beam corresponding to the image data to form an electrostatic latent image on the surface of the photoconductor 11. Although described in detail later, the developing device 14 develops the electrostatic latent image formed on the surface of the photoreceptor 11 with toner to form a toner image.

  The transfer unit 15 is a roller-like member disposed inside the conveyance belt 33 so as to face the photoconductor 11 via the conveyance belt 33 of the recording paper conveyance unit 30. A bias voltage having a polarity opposite to the charging polarity of the toner is applied to the transfer unit 15, whereby the toner image formed on the surface of the photoreceptor 11 is placed on the transport belt 33 and transported. Transferred to paper 71. The transfer means 15 for transferring the toner image formed on the surface of the photoconductor 11 to the recording paper 71 is not limited to the above-described configuration, and the toner image formed on the surface of the photoconductor 11 is intermediate. A configuration may be adopted in which primary transfer is performed to an intermediate transfer medium such as a transfer belt, and the toner image primarily transferred to the intermediate transfer medium is secondarily transferred to the recording paper 71.

  The cleaner unit 16 includes a cleaning blade 16a. The toner remaining on the surface of the photoconductor 11 after the transfer operation by the transfer unit 15 is scraped off by the cleaning blade 16a to clean the surface of the photoconductor 11. The neutralizing unit 17 neutralizes the surface of the photoconductor 11 after being cleaned by the cleaner unit 16.

  The recording paper transport unit 30 includes a driving roller 31, an idling roller 32, and a transport belt 33, and a toner image is transferred to the recording paper 71 by each of the visible image forming units 10Y, 10M, 10C, and 10K. In this way, the recording paper 71 supplied from the paper supply unit 20 is conveyed. The driving roller 31 and the idling roller 32 stretch an endless conveying belt 33, and the conveying belt 33 rotates when the driving roller 31 is rotationally driven at a predetermined peripheral speed. . Further, the outer surface of the transport belt 33 is charged to a predetermined potential, and transports the recording paper 71 while electrostatically attracting it. The recording paper 71 that has been transported by the recording paper transport unit 30 and passed through the visible image forming units 10Y, 10M, 10C, and 10K and onto which the toner image (unfixed toner image) has been transferred is transported by the curvature of the drive roller 31. It is peeled off from the belt 33 and conveyed to the fixing unit 40.

  The fixing unit 40 applies appropriate heat and pressure to the recording paper 71 to melt the toner transferred onto the recording paper 71 and fix the recording paper 71 on the recording paper 71, and the recording paper 71 is discharged to a discharge tray (not shown). ). The configuration of the fixing unit 40 is not particularly limited, and for example, a configuration in which a heating roller 41 and a pressure roller 42 are provided and the recording paper 71 is conveyed while being sandwiched between these rollers can be used.

  The operation of each unit provided in the image forming apparatus 1 is controlled by a main control unit (such as a control integrated circuit board or a computer).

(Developer)
FIG. 2 is a diagram showing a configuration of the developing device 14 according to the embodiment of the present invention. The developing device 14 includes a developing tank 60, a developing roller 61 that is a developer carrier, a toner supply roller 62, a layer thickness regulating blade 64 that is a layer thickness regulating member, and an agitating and conveying member 69.

  The developing tank 60 is a container member that is made of, for example, hard synthetic resin and accommodates the toner 70 that is a nonmagnetic one-component developer and has a substantially rectangular parallelepiped shape. The toner 70 accommodated in the developing tank 60 has a volume average particle diameter D50 of 8.50 which is mainly composed of a binder resin made of polyester (glass transition temperature Tg: 62.5 ° C., softening temperature Tm: 126 ° C.). The surface of 8 μm toner particles is externally added with 3.0% by weight of silica particles and 0.75% by weight of titanium oxide particles as external additives.

  The developing roller 61 is rotatably provided in the developing tank 60, carries the toner 70 accommodated in the developing tank 60, and conveys it to the photoreceptor 11. The rotation direction of the developing roller 61 is opposite to the rotation direction of the photoconductor 11 and is driven to rotate around the axis at a peripheral speed of 145 mm / second, for example.

  The developing roller 61 is opposed to the photoconductor 11 with a predetermined gap G (development gap G), and its axis is parallel to the rotation axis of the photoconductor 11, and is supported by the frame portion of the developing tank 60. Is done. In the present embodiment, the developing roller 61 is supported by the frame portion of the developing tank 60 so that the developing gap G is 150 ± 20 μm by a gap holding member (not shown).

  The developing roller 61 has a cylindrical outer peripheral member 61b made of metal such as aluminum around a columnar shaft 61a made of metal. In the present embodiment, the developing roller 61 has an axial length of 320 mm, an outer diameter of 16 mm, an outer diameter of the shaft 61a of 7 mm, and a thickness of the outer peripheral member 61b of 1 mm. The developing roller 61 is sandblasted so that the arithmetic average roughness Ra on the surface thereof, that is, the outer surface of the outer peripheral member 61b is 0.3 μm. The developing roller 61 is connected to a developing roller side DC power supply 67, and a voltage is applied from the developing roller side DC power supply 67. Details of the developing roller 61 will be described later.

  The layer thickness regulating blade 64 includes a support portion 65 and an elastic rubber portion 66. The elastic rubber portion 66 is formed in a plate shape and is in surface contact (contact) with the surface of the outer peripheral member 61 b of the developing roller 61, that is, the outer peripheral surface of the developing roller 61, between both axial ends of the developing roller 61. It is provided as follows. In the layer thickness regulating blade 64, the elastic rubber portion 66 is in surface contact with the outer circumferential surface of the developing roller 61, thereby regulating the layer thickness of the toner 70 carried on the outer circumferential surface of the developing roller 61 that is driven to rotate and the toner. 70 is triboelectrically charged. The linear pressure when the elastic rubber portion 66 of the layer thickness regulating blade 64 is in pressure contact with the developing roller 61 is 5 to 50 g / cm (0.049 to 0.49 N /) in consideration of the layer pressure regulating effect and the triboelectric charging effect. cm). In this embodiment, the elastic rubber portion 66 is made of urethane rubber having a JIS-A hardness of 20 to 75 degrees, has a length corresponding to the axial direction of the developing roller 61 315 mm, and is perpendicular to the axial direction of the developing roller 61. The length corresponding to each direction is 10 mm and the thickness is 1 mm.

  The support portion 65 of the layer thickness regulating blade 64 is formed in an elastic plate shape and supports the elastic rubber portion 66. In the present embodiment, the support portion 65 is made of phosphor bronze or aluminum, has a length corresponding to the axial direction of the developing roller 61 of 315 mm, and a length corresponding to a direction perpendicular to the axial direction of the developing roller 61 is 35 mm. The thickness is 0.1 mm. The support portion 65 is fixed to the frame portion of the developing tank 60.

  The toner supply roller 62 is rotatably provided in the developing tank 60, and the rotation direction thereof is the same as that of the developing roller 61. The toner supply roller 62 is driven to rotate around the axis at a peripheral speed of 116 mm / second, for example. The toner supply roller 62 comes into contact with the developing roller 61 to form a nip portion 63, and the amount of biting of the toner supply roller 62 with respect to the developing roller 61 in the nip portion 63 is 0.5 mm. The toner supply roller 62 is provided with a cylindrical porous elastic member 62b (Asuka C hardness: 2 to 15 degrees) made of urethane foam or the like around a columnar shaft 62a made of metal. In this embodiment, the toner supply roller 62 has an axial length of 300 mm, an outer diameter of 16.6 mm, an outer diameter of the shaft 62a of 7 mm, and a thickness of the porous elastic member 62b of 4.8 mm. . Further, a supply roller side DC power source 68 is connected to the toner supply roller 62, and a voltage is applied from the supply roller side DC power source 68. The toner supply roller 62 configured in this manner develops the toner 70 by rubbing the developing roller 61 in the nip portion 63 while carrying the toner 70 conveyed from the agitating and conveying member 69 in the hole in the surface. The excess toner 70 supplied to the roller 61 and remaining on the developing roller 61 after development is removed.

  The agitating / conveying member 69 is rotatably provided in the developing tank 60, and the rotation direction thereof is the same as the developing roller 61. The agitating / conveying member 69 includes a rotation shaft portion 69a and a plurality of blade pieces 69b protruding radially outward from the rotation shaft portion 69a. The blade pieces 69b are thick using a resin such as polyester. It is formed in a thin plate shape with a thickness of 0.1 mm. The agitating and conveying member 69 conveys the toner 70 in the developing tank 60 to the toner supply roller 62 while agitating.

  In the developing device 14 configured as described above, the voltage difference between the voltage applied to the developing roller 61 by the developing roller side DC power source 67 and the voltage applied to the toner supply roller 62 by the supply roller side DC power source 68; The toner 70 conveyed from the agitating and conveying member 69 to the toner supply roller 62 by the pumping force of the rotating developing roller 61 is supplied to the developing roller 61 and carried on the outer peripheral surface of the developing roller 61. Then, when the toner 70 carried on the outer peripheral surface of the developing roller 61 passes through the elastic rubber portion 66 of the layer thickness regulating blade 64, the toner 70 is frictionally charged by the friction from the elastic rubber portion 66 while the layer thickness is regulated. . Thus, the toner 70 on the outer peripheral surface of the developing roller 61 whose layer thickness is regulated and frictionally charged flies to the surface of the photosensitive member 11 according to the potential difference between the photosensitive member 11 and the developing roller 61. As a result, the electrostatic latent image formed on the surface of the photoconductor 11 is developed by the toner 70, and a toner image is formed on the surface of the photoconductor 11. In addition, excess toner 70 remaining on the outer peripheral surface of the developing roller 61 after development is removed by the toner supply roller 62 rubbing the developing roller 61 at the nip portion 63.

  Next, the developing roller 61 having a characteristic configuration in the developing device 14 of the present embodiment will be described in detail with reference to FIG. FIG. 3 is a diagram illustrating a configuration of the developing roller 61 provided in the developing device 14.

  A first inclined groove 611 and a second inclined groove 612 that are recessed inward in the radial direction are formed on the outer peripheral surface (the surface of the outer peripheral member 61b) of the developing roller 61 provided in the developing device 14 of the present embodiment. . The first inclined groove 611 and the second inclined groove 612 are spirally continuous grooves that extend along the axial direction across both ends in the axial direction of the developing roller 61 and intersect with each other, and are inclined with respect to the circumferential direction.

  In the first inclined groove 611 and the second inclined groove 612, the directions of the spirals are opposite to each other. Otherwise, the length of the spiral, the inclination angle θ with respect to the circumferential direction of the developing roller 61, the groove depth, and the development The groove spacing in the axial direction of the roller 61 is the same, and the shape of the island portion surrounded by the intersecting first inclined groove 611 and second inclined groove 612 is a rhombus.

  Such a processing method for forming the first inclined groove 611 and the second inclined groove 612 on the outer peripheral surface of the developing roller 61 is not particularly limited. For example, the developing roller 61 is rotated. A cutting tool such as a cutting tool for metal cutting or a needle-shaped metal can be machined by abutting it from the radially outer side and moving it in the axial direction. An arbitrary groove depth can be obtained by changing the contact pressure of the cutting jig against the developing roller 61, and an arbitrary groove interval can be obtained by changing the moving speed of the cutting jig in the axial direction. it can.

  In the present embodiment, the first inclined groove 611 and the second inclined groove 612 are such that the groove interval in the axial direction of the developing roller 61 is P1, the groove interval of the axial central portion 610a, and the groove interval of the axial end portions 610b and 610c. In the case of P2, the ratio of the groove interval P1 to the groove interval P2 (P1 / P2, hereinafter referred to as “groove interval ratio”) is 0.2 or more and 0.75 or less. Here, the groove interval P1 of the axial center portion 610a and the groove interval P2 of the axial end portions 610b and 610c are the same in the axial center portion 610a and the axial end portions 610b and 610c. Alternatively, the width may be gradually increased from the axial center 610a toward the axial ends 610b and 610c. In the present embodiment, the groove intervals P1 and P2 of the first inclined groove 611 and the second inclined groove 612 are the same in the region of the axial center portion 610a and in the regions of both axial ends 610b and 610c. . With respect to the axial direction of the developing roller 61, the length of the central portion 610a in the axial direction is 120 to 240 mm, whereas the overall length is 320 mm.

  As described above, in the developing device 14 of the present embodiment, the first inclined groove 611 and the second inclined groove 612 formed on the outer peripheral surface of the developing roller 61 have the groove interval P1 in the axial center portion 610a so that both ends in the axial direction. Since it is provided to be smaller than the groove interval P2 in the portions 610b and 610c at a predetermined rate, the first inclined groove 611 and the axially central portion 610a where the linear pressure due to the contact of the layer thickness regulating blade 64 is high The toner carrying ability by the second inclined groove 612 and the ability to remove the toner fused material fused to the layer thickness regulating blade 64 can be improved. As a result, the developing device 14 can achieve a uniform toner adhesion amount in the axial direction of the developing roller 61, and prevent toner fusion of the layer thickness regulating blade 64 to ensure stable developability. Can do.

  Further, the first inclined groove 611 and the second inclined groove 612 formed on the outer peripheral surface of the developing roller 61 have groove intervals (groove intervals P1, P2) in the axial direction of the developing roller 61 of 0.75 to 5 mm, respectively. Preferably, the groove depth is 5 to 50 μm, and the inclination angle θ with respect to the circumferential direction of the developing roller is 10 to 60 degrees. As a result, the toner adhesion amount in the axial direction of the developing roller 61 can be made more uniform, and the toner fusion product removal efficiency of the layer thickness regulating blade 64 can be improved. In addition, the groove width of the 1st inclination groove | channel 611 and the 2nd inclination groove | channel 612 is set to 5-100 micrometers.

  When the groove interval set in the first inclined groove 611 and the second inclined groove 612 exceeds 5 mm, the groove depth is less than 5 μm, and the inclination angle θ exceeds 60 degrees, the first inclined groove 611 and There is a possibility that not only the toner carrying ability by the second inclined groove 612 and the ability to remove the toner fused material fused to the layer thickness regulating blade 64 will be lowered, but also the toner carrying ability of the developing roller 61 to the photoreceptor 11 may be lowered. Further, when the groove interval set in the first inclined groove 611 and the second inclined groove 612 is less than 0.75 mm, the groove depth exceeds 50 μm, and the inclination angle θ is less than 10 degrees, Only the labor and cost are required for processing, and the toner carrying ability, the toner fused removal ability, and the toner carrying ability by the first inclined groove 611 and the second inclined groove 612 are saturated.

  In addition, examples of the cross-sectional shapes of the first inclined groove 611 and the second inclined groove 612 include a V shape, a U shape, and a rectangular shape, and are not particularly limited. To a V shape.

  Hereinafter, the present invention will be described in more detail based on examples and comparative examples. However, the present invention is not limited to such examples.

Example 1
The developing device 14 shown in FIG. 2 is mounted as a developing device in a visible image forming unit corresponding to black (K) of a full-color image forming apparatus (MX2300, manufactured by Sharp Corporation). As the developing roller in this developing device, the developing roller 61 shown in FIGS. 3 and 4 was employed. The developing tank of the developing device has a volume average particle diameter D50 of 8.8 μm, which is mainly composed of a binder resin made of polyester (glass transition temperature Tg: 62.5 ° C., softening temperature Tm: 126 ° C.). The surface of the toner particles was filled with a non-magnetic one-component toner externally added with 3.0% by weight of silica particles and 0.75% by weight of titanium oxide particles as external additives. The configuration and setting conditions of the developing device in Example 1 are shown below.

<Developing roller>
・ Size: 320mm length in the axial direction, 16mm outer diameter, 200mm length in the center in the axial direction
-Outer peripheral member: made of aluminum-Groove depth of the first and second inclined grooves: 25 μm
-Groove interval at the axial center of the first and second inclined grooves: 1.5 mm
-Groove spacing at both axial ends of the first and second inclined grooves: 3 mm
・ Groove spacing ratio: 0.5
Inclination angle with respect to the circumferential direction of the first and second inclined grooves: 35 degrees Groove width of the first and second inclined grooves: 50 μm
・ Applied voltage from DC power supply on developing roller side: DC-800V
・ Peripheral speed during rotation: 145 mm / sec (peripheral speed of photoconductor is 145 mm / sec)
・ Development gap G: 150 ± 20 μm

<Toner supply roller>
-Size: 300mm length in the axial direction, outer diameter 16.6mm
-Porous elastic member: Asuka C made of urethane foam with a hardness of 5 degrees, thickness 4.8 mm
・ Applied voltage from DC power supply on the supply roller side: DC-900V
・ Peripheral speed during rotation: 116 mm / sec

<Agitating and conveying member>
・ Rotation speed during stirring and conveying operation: 157 rpm

<Layer thickness regulating blade>
Elastic rubber part: made of urethane rubber having a JIS-A hardness of 50 degrees, a length of 315 mm corresponding to the axial direction of the developing roller, a length of 10 mm corresponding to the direction perpendicular to the axial direction, and a thickness of 1 mm
-Linear pressure in the axial direction of the developing roller: center portion 35 g / cm, one end portion 38 g / cm, the other end portion 39 g / cm

(Example 2)
Example 1 was the same as Example 1 except that the developing roller of the developing device had the following configuration.

<Developing roller>
・ Size: 320mm length in the axial direction, 16mm outer diameter, 240mm length in the center in the axial direction
-Outer peripheral member: made of aluminum-Groove depth of first and second inclined grooves: 5 μm
・ Groove spacing at the center in the axial direction of the first and second inclined grooves: 1 mm
-Groove spacing at both axial ends of the first and second inclined grooves: 5 mm
・ Groove spacing ratio: 0.2
Inclination angle with respect to the circumferential direction of the first and second inclined grooves: 60 degrees Groove width of the first and second inclined grooves: 5 μm
・ Applied voltage from DC power supply on developing roller side: DC-800V
・ Peripheral speed during rotation: 145 mm / second ・ Development gap G: 150 ± 20 μm

(Example 3)
Example 1 was the same as Example 1 except that the developing roller of the developing device had the following configuration.

<Developing roller>
・ Size: 320mm length in the axial direction, 16mm outer diameter, 120mm length in the center in the axial direction
-Outer peripheral member: made of aluminum-Groove depth of first and second inclined grooves: 50 μm
-Groove interval at the center in the axial direction of the first and second inclined grooves: 0.75 mm
-Groove spacing at both axial ends of the first and second inclined grooves: 1 mm
・ Groove spacing ratio: 0.75
Inclination angle with respect to the circumferential direction of the first and second inclined grooves: 10 degrees Groove width of the first and second inclined grooves: 100 μm
・ Applied voltage from DC power supply on developing roller side: DC-800V
・ Peripheral speed during rotation: 145 mm / second ・ Development gap G: 150 ± 20 μm

(Comparative Example 1)
Example 1 was the same as Example 1 except that the developing roller of the developing device had the following configuration.

<Developing roller>
・ Size: 320mm length in the axial direction, 16mm outer diameter, 200mm length in the center in the axial direction
-Outer peripheral member: made of aluminum-Groove depth of the first and second inclined grooves: 3 μm
-Groove spacing at the center in the axial direction of the first and second inclined grooves: 4.25 mm
-Groove spacing at both axial ends of the first and second inclined grooves: 5 mm
・ Groove spacing ratio: 0.85
Inclination angle with respect to the circumferential direction of the first and second inclined grooves: 70 degrees Groove width of the first and second inclined grooves: 25 μm
・ Applied voltage from DC power supply on developing roller side: DC-800V
・ Peripheral speed during rotation: 145 mm / second ・ Development gap G: 150 ± 20 μm

(Comparative Example 2)
Example 1 was the same as Example 1 except that the developing roller of the developing device had the following configuration.

<Developing roller>
・ Size: 320mm length in the axial direction, 16mm outer diameter, 200mm length in the center in the axial direction
-Outer peripheral member: made of aluminum-Groove depth of first and second inclined grooves: 55 μm
-Groove interval at the center in the axial direction of the first and second inclined grooves: 0.12 mm
-Groove spacing at both axial ends of the first and second inclined grooves: 0.8 mm
・ Groove spacing ratio: 0.15
Inclination angle with respect to the circumferential direction of the first and second inclined grooves: 8 degrees Groove width of the first and second inclined grooves: 50 μm
・ Applied voltage from DC power supply on developing roller side: DC-800V
・ Peripheral speed during rotation: 145 mm / second ・ Development gap G: 150 ± 20 μm

[Evaluation methods]
The following evaluation was performed for Examples 1 to 3 and Comparative Examples 1 and 2.

<Characteristics of toner carried on developing roller>
(Charging characteristics)
The toner carried on the developing roller was sucked and collected, and the charge amount of the collected toner was measured with a suction-type charge amount measuring device (product name: 210HS, manufactured by Trek Japan Co., Ltd.). Then, the specific charge was obtained from the measurement result of the charge amount and the mass of the collected toner, and was defined as the charge amount (μC / g) of the toner.

Further, when the charge amount of the toner carried on the developing roller is too low, toner scattering and background fogging occur, and when the charge amount is too high, the image density is insufficient. Therefore, whether or not the charge amount obtained as described above is within an appropriate range was evaluated according to the following criteria.
○: The charge amount is lower than −8 μC / g and equal to or higher than −12 μC / g.
Δ: Charge amount is −8 μC / g or more and −5 μC / g or less, or lower than −12 μC / g and −15 μC / g or more.
X: Charge amount is higher than −5 μC / g or lower than −15 μC / g.

(Toner adhesion on developing roller surface)
In the above evaluation of charging characteristics, a transparent tape (mending tape manufactured by Sumitomo 3M) is attached to the suction mark on the developing roller after the toner carried on the developing roller is sucked and collected. The film was peeled off and pasted on a white paper, and the area of the suction mark, that is, the area of toner adhesion on the developing roller was determined. Then, the toner adhesion amount (mg / cm ² ) per unit area was determined from the result of the toner adhesion area and the mass of the toner collected by suction.

Further, when the toner adhesion amount on the surface of the developing roller is too small, the image density is insufficient, and when the toner adhesion amount is too large, excessive toner consumption occurs. Therefore, whether or not the toner adhesion amount obtained as described above is within an appropriate range was evaluated according to the following criteria.
○: The toner adhesion amount is 0.50 mg / cm ² or more and 0.70 mg / cm ² or less.
△: toner adhesion amount, 0.40 mg / cm ² or more 0.50 mg / cm less than ^2, or less than 0.75 mg / cm ² beyond the 0.70 mg / cm ^2.
×: the amount of adhered toner is 0.40 mg / cm less than ^2, or 0.75 mg / cm ² or more.

(Toner adhesion uniformity)
In the same manner as the toner adhesion amount calculation method, the maximum toner adhesion amount and the minimum toner adhesion amount in the axial direction of the developing roller were obtained. Specifically, from one end in the axial direction of the developing roller toward the center, the position is 1 to 3 cm (one end in the axial direction), 15 to 17 cm (the center in the axial direction), and 28 to 30 cm ( The toner carried in each 2 cm ² region (at the other end in the axial direction) is sucked and collected, and the toner adhesion amount (mg / cm ² ) per unit area is calculated for the mass of the toner in each collected region did. The calculated toner adhesion amount in each region was compared to determine the maximum toner adhesion amount and the minimum toner adhesion amount. Then, from the results of the maximum toner adhesion amount and the minimum toner adhesion amount, the adhesion difference rate (%) was calculated using the following formula (1).

It can be determined that the smaller the adhesion difference rate, the smaller the difference in toner adhesion amount in the axial direction of the developing roller, and the higher the uniformity of toner adhesion on the surface of the developing roller. The toner adhesion uniformity on the surface of the developing roller was evaluated according to the following criteria.
○: Adhesion difference rate is 10% or less.
Δ: Adhesion difference rate is more than 10% and 15% or less.
X: The adhesion difference rate exceeds 15%.

<Evaluation of printed image>
(Image density)
The density of a solid image portion formed in a 30 mm × 280 mm region in the center of A4 size M paper manufactured by Sharp Corporation was measured at 14 locations at 2 cm intervals with a densitometer (RD-918, manufactured by Macbeth). Went. The average value of the density values at the 14 locations was taken as the image density. Further, whether or not the image density is in an appropriate range was evaluated according to the following criteria.
○: Image density is 1.35 or more.
Δ: Image density is 1.25 or more and less than 1.35.
X: The image density is less than 1.25.

(Image density uniformity)
The maximum image density and the minimum image density were determined using the density values measured at the 14 positions in the evaluation of the image density. Then, the density difference rate (%) was calculated from the results of the maximum image density and the minimum image density using the following formula (2).

It can be determined that the smaller the density difference rate, the higher the uniformity of the image density corresponding to the axial direction of the developing roller. Image density uniformity was evaluated according to the following criteria.
○: The density difference rate is 5% or less.
(Triangle | delta): A density | concentration difference rate is 8% or less exceeding 5%.
X: The density difference rate exceeds 8%.

(Evaluation of white stripes by halftone printing)
The presence or absence of white streaks was visually observed in a halftone image having an image density of 0.3 to 0.4 formed in a 100 mm × 280 mm region in the center of A4 size M paper manufactured by Sharp Corporation.
○: There is no white streak.
Δ: White streaks were generated, but the width of white streaks was 0.5 mm or less, and the number of white streaks was within two.
X: Three or more white stripes having a width dimension of 0.5 mm or less are generated, or one or more white stripes having a width dimension exceeding 0.5 mm are generated.

(Comprehensive evaluation)
In the plurality of evaluations, if there is no “x” in the evaluation result, the comprehensive evaluation result is “◯”, and if there is even one “×” in the evaluation result, the comprehensive evaluation result is “x”.
The evaluation results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

  As is apparent from the results in Table 1, in Examples 1 to 3, the charge amount of the toner carried on the developing roller is in the proper range, and the toner adhesion amount on the surface of the developing roller is in the proper range. High uniformity of toner adhesion on the surface. In Examples 1 to 3, the solid image portion has a high image density in the print image, the uniformity of the image density corresponding to the axial direction of the developing roller is high, and no white streak occurs in the halftone image.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Visible image forming unit 11 Photoconductor 12 Charging means 13 Exposure means 14 Developing apparatus 15 Transfer means 16 Cleaner means 17 Electric discharge means 40 Fixing unit 60 Developing tank 61 Developing roller 62 Toner supply roller 64 Layer thickness regulating blade 69 Agitating and conveying member 611 First inclined groove 612 Second inclined groove

Claims (4)

In a developing device that forms a toner image by developing an electrostatic latent image formed on the surface of an image carrier with toner that is a non-magnetic one-component developer,
A developer tank containing toner;
A developing roller that faces the image carrier at a predetermined interval, is rotatably provided in the developing tank, and carries the toner contained in the developing tank and transports the toner to the image carrier, the outer periphery of the developing roller A developing roller having a surface formed with a first inclined groove and a second inclined groove that are spirally inclined with respect to a circumferential direction intersecting each other;
A layer thickness regulating blade that is provided in contact with the outer circumferential surface of the developing roller and regulates the layer thickness of the toner carried on the outer circumferential surface of the developing roller that is driven to rotate, and that frictionally charges the toner;
The first inclined groove and the second inclined groove have a groove interval P2 when the groove interval in the axial direction of the developing roller is P1 as the groove interval at the central portion in the axial direction and P2 as the groove interval at both ends in the axial direction. The developing device characterized in that the ratio (P1 / P2) of the groove interval P1 to the groove is 0.2 or more and 0.75 or less.   The developing device according to claim 1, wherein the first inclined groove and the second inclined groove have spiral directions opposite to each other.   The first inclined groove and the second inclined groove have a groove interval in the axial direction of the developing roller of 0.75 to 5 mm, a groove depth of 5 to 50 μm, and an inclination angle with respect to the circumferential direction of the developing roller. The developing device according to claim 1, wherein the angle is 10 to 60 degrees. An image carrier;
Latent image forming means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image formed on the image carrier using toner which is a non-magnetic one-component developer,
The image forming apparatus according to claim 1, wherein the developing unit is the developing device according to claim 1.

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