JP2013064786A - Developing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which can achieve a good image formation by preventing the occurrence of stripes on a toner layer carried on a developer carrier in a developing device and to provide an image forming apparatus using the same.SOLUTION: A developing device 6 comprises a developing roller 62 for supplying a developer to a photoreceptor drum 32 to develop an electrostatic latent image formed on the photoreceptor drum 32 and a doctor blade 68 for regulating the layer thickness of the developer carried on the surface of the developing roller, wherein the surface of the developing roller 62 is unevenly formed, a first blast-processed area 62B and a second blast-processed area 62C, which are different in average roughness Ra in the surface roughness, are formed adjacently along a circumferential direction of the developing roller 62 on the uneven surface over the axial direction of the developing roller 62 respectively, and uneven part with different average roughness in a mixed state is formed in the boundary part of these areas.

Description

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

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

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

  As a conventional technique, in a developing device using a non-magnetic one-component developing method, as an example of a conventional developer carrying member provided in the developing device, the surface of the developer carrying member is roughened, and unevenness of the surface is developed. The thing which prescribed | regulated pitch and average roughness is proposed (refer patent document 1).

  In addition, as another example of a developer carrier, there has been proposed a method in which the surface of the developer carrier is provided with irregularities, and the height of the irregularities on the surface and the interval between the peaks are defined (patent) Reference 2).

JP 58-57165 A JP 59-189374 A

  As described above, it is generally known that unevenness is formed on the surface of the developer carrying member to stably convey the developer, and the surface is designed in consideration of the above parameters in order to define the unevenness.

  However, in the above-described conventional method, since the entire surface of the developer carrying member is processed to have unevenness under certain conditions, the state of the toner layer formed by the inflow of toner to the pressing portion of the developer amount regulating blade is Since the toner is always constant, the toner is easily welded to the surface of the developer amount regulating blade, and as a result, streaks are generated on the toner layer, resulting in an image defect.

  The present invention has been made in view of the above-described conventional problems, and suppresses the generation of streaks on the toner layer carried on the developer carrying member in the developing device, thereby realizing good image formation. An object of the present invention is to provide a developing device that can be used and an image forming apparatus using the same.

  The developing device and the image forming apparatus using the same according to the present invention for solving the above-described problems are as follows.

  The present invention is provided in an electrophotographic image forming apparatus, and a developer (particularly, a non-magnetic one-component developer, for example, toner) is supplied to a photoconductor provided in the image forming apparatus so that the photoconductor is provided on the photoconductor. A developing device comprising: a developing roller for developing the electrostatic latent image formed on the surface; and a developer regulating member (for example, a doctor blade) that regulates the layer thickness of the developer carried on the surface of the developing roller. In the configuration of the developing roller, the surface of the developing roller is formed in a concavo-convex shape, and the surface of the concavo-convex surface is provided with two regions having different surface roughnesses in the average roughness Ra in the circumferential direction of the developing roller. And adjacent to each other along the axial direction of the developing roller, and at the boundary between the two regions having different average roughness Ra, unevenness having different average roughness Ra is mixedly formed. With features Is shall.

  In the present invention, two regions having different average roughness Ra occupy a region having a small average roughness Ra in a ratio of a region having a large average roughness Ra in a direction along the circumferential direction of the developing roller. It is preferable that the ratio is small but good.

  In the present invention, it is preferable that a region having a large average roughness Ra is formed such that a circumferential width thereof is wider at both end portions in the axial direction of the developing roller than a central portion.

  In the present invention, it is preferable that the developing roller is formed of an aluminum cylindrical member.

  In the present invention, the uneven surface is preferably blasted by glass bead blasting.

  In the present invention, the uneven surface is preferably blasted by sand blasting.

  Further, in the present invention, the average roughness Ra of the uneven surface is set such that the average roughness Ra of one region is 0.3 to 0.5 μm, and the average roughness Ra of the other region is 0.5 μm or more. It is preferable to do.

  In the present invention, it is preferable that the blasting process is performed after a base surface of an aluminum cylindrical member constituting the developing roller is mirror-finished with an average roughness Ra of 0.05 μm or less.

  In addition, the present invention includes a photoconductor on which an electrostatic latent image is formed, and a developing roller for supplying a developer to the photoconductor to develop the electrostatic latent image formed on the photoconductor. In the image forming apparatus for forming an image by an electrophotographic method, the developing device includes a developer regulating member that regulates a layer thickness of the developer carried on the surface of the developing roller. A developing device according to any one of claims 1 to 8 is provided.

  According to the developing device of the present invention, a developer is supplied to a photoconductor provided in an electrophotographic image forming apparatus to develop an electrostatic latent image formed on the photoconductor. And a developer regulating member that regulates the layer thickness of the developer carried on the surface of the developing roller. As a configuration of the developing roller, the surface of the developing roller is formed in an uneven shape. On the uneven surface, two regions having different surface roughness Ra in average roughness Ra are formed adjacent to each other along the circumferential direction of the developing roller, and each region is formed along the axial direction of the developing roller. In addition, the developer transport amount increases or decreases (a small amount) by forming unevenness having different average roughness Ra at the boundary between the two regions having different average roughness Ra. Developer just below the regulating member Not to the flow is always constant, the effect of destroying the retention layer of the developer. Further, the developer transport amount changes gradually without causing abrupt changes. Accordingly, it is difficult to cause the developer to be welded to the surface of the developer regulating member without affecting the development area, and it is difficult to cause streaks on the toner layer, so that a stable image can be obtained.

  Further, according to the present invention, two regions having different average roughness Ra are regions in which the ratio of the region having a large average roughness Ra in the direction along the circumferential direction of the developing roller is small in the average roughness Ra. Since the developer conveyance amount is instantaneously changed during a part of one rotation of the developing roller, the developer flow just below the developer regulating member is not always constant. In addition, there is an effect of breaking the staying layer of the developer. As a result, the developer hardly adheres to the surface of the developer regulating member, and the streaks are hardly generated on the toner layer, so that a stable image can be obtained.

  Further, according to the present invention, by forming the region having a large average roughness Ra in the circumferential width at both ends in the axial direction of the developing roller wider than the central portion, the axial line of the developing roller is formed. In the direction (longitudinal direction), it is possible to partially increase the developer conveyance amount at both ends of the center portion.

  Specifically, the width of a developer regulating member, for example, a fixed sheet metal of a doctor blade, is conventionally formed in a so-called crown shape with the central portion set slightly wider than both ends, and the support portion of the developer regulating member Although the free length of the sheet metal is artificially shortened only at the central portion, the pressure applied to the central portion is raised above both end portions to optimize the balance of the developer transport amount in the entire longitudinal direction. This eliminates the need to change the width of the fixed sheet metal.

  In addition, since both ends of the developing roller have a relatively small influence on the increase or decrease in the developer transport amount compared to the central portion, the surface roughness is higher than that of the central portion in order to increase the effect of breaking the developer retention layer. By providing regions with large Ra at both ends, the flow of the developer immediately below the developer regulating member is not always constant, and it is difficult for the developer to adhere to the surface of the developer regulating member. Since streaks are less likely to occur on the top, a stable image can be obtained.

According to the present invention, the developing roller is formed of an aluminum cylindrical member.
Since the unevenness can be formed in the range of the average roughness Ra = 0.3 to 0.5 μm by the blasting process, it becomes easy to obtain the optimum developer transport amount and the uniformity of the developer layer. A stable image free from unevenness caused by poor developer conveyance above can be obtained.

  In addition, according to the present invention, uniform unevenness can be formed by blasting the uneven surface with glass bead blasting, so the optimal developer transport amount and developer layer uniformity can be achieved. It becomes easy to obtain, and a stable image without unevenness due to poor developer conveyance on the developing roller can be obtained.

  In addition, according to the present invention, uniform unevenness can be formed by blasting the uneven surface by sand blasting, so that an optimal developer conveyance amount and developer layer uniformity can be obtained. And a stable image free from unevenness due to poor developer conveyance on the developing roller can be obtained.

  According to the present invention, the average roughness Ra of the uneven surface is set such that the average roughness Ra of one region is 0.3 to 0.5 μm, and the average roughness Ra of the other region is 0.5 μm. By setting it as the above, an optimal image development characteristic is acquired and there exists an effect which destroys the retention layer of a developer. As a result, the developer hardly adheres to the surface of the developer regulating member, and the streaks are hardly generated on the toner layer, so that a stable image can be obtained.

  Further, according to the present invention, the blasting is performed after mirror-finishing the base surface of the cylindrical member made of aluminum constituting the developing roller with an average roughness Ra of 0.05 μm or less. Unevenness can be formed in the range of Ra = 0.3 to 0.5 μm, and it becomes easy to obtain the optimal developer transport amount and uniformity of the developer layer, and developer transport on the developer carrier. A stable image without unevenness due to defects can be obtained.

  In addition, according to the image forming apparatus of the present invention, a photosensitive member on which an electrostatic latent image is formed is provided, and a developer is supplied to the photosensitive member to develop the electrostatic latent image formed on the photosensitive member. In an image forming apparatus, comprising: a developing roller including: a developing roller; and a developer regulating member that regulates a layer thickness of the developer carried on the surface of the developing roller. The development device according to any one of claims 1 to 8 is provided as the development device, so that the developer regulating member of the developer is not affected without affecting the development area of the development roller. Since it is difficult to cause welding on the surface and streaks are hardly generated on the toner layer, a stable image can be obtained.

1 is an explanatory diagram illustrating a schematic configuration of an image forming apparatus including a developing device according to an embodiment of the present invention. It is explanatory drawing which shows schematic structure of the developing device which concerns on this embodiment. It is explanatory drawing which shows the structure of the doctor blade which comprises the said developing device. It is explanatory drawing which shows the structure of the developing roller which comprises the said developing device. FIG. 5 is an enlarged image of a portion A in FIG. 4 and is an explanatory diagram illustrating an example of a surface state of the developing roller. It is the graph which showed the measured value of the surface roughness of the 1st blasting area | region which carried out the blasting process of the said developing roller. 3 is a graph showing a toner adhesion amount according to a surface roughness of the developing roller. (A) is explanatory drawing which shows the structure of the surface of the said developing roller, (b) is a side view which shows the structure of the surface of the said developing roller. It is the graph which showed the measured value of the surface roughness of the 2nd blasting area | region which carried out the blasting process of the said developing roller. (A) is explanatory drawing which shows an example of the shape of the groove | channel formed in the conventional developing roller, (b) is explanatory drawing which shows the relationship of the toner conveyance amount according to the shape of the said groove | channel. (A) is explanatory drawing which shows an example of the shape of the uneven | corrugated | grooved part formed in the developing roller of this embodiment, (b) is explanatory drawing which shows the relationship of the toner conveyance amount according to the shape of the said uneven | corrugated | grooved part. It is explanatory drawing which shows the outline when performing a blast process to the developing roller in this embodiment. It is explanatory drawing which shows the structure of the modification of the developing roller which comprises the developing device of this embodiment. (A) is explanatory drawing which shows the structure of the doctor blade vicinity which comprises the conventional image development apparatus, (b) is B arrow figure of (a), and is explanatory drawing which shows the structure of the fixed sheet metal which hold | maintains the said doctor blade. It is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments for carrying out a developing device of the present invention and an image forming apparatus including the developing device will be described below with reference to the drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is an example of an embodiment of the invention, and is an explanatory diagram illustrating a schematic configuration of an image forming apparatus including a developing device according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes a photosensitive drum (photosensitive member) 32 on which an electrostatic latent image is formed, and supplies a developer to the photosensitive drum 32 to perform photosensitive. A developing roller 62 for developing the electrostatic latent image formed on the body drum 32 and a doctor blade (developer regulating member) 68 for regulating the layer thickness of the developer carried on the surface of the developing roller (FIG. 2). In the image forming apparatus 1 that forms an image by an electrophotographic method, the developing device 6 adopts the characteristic fixing device configuration according to the present invention. .

  First, the overall configuration of an image forming apparatus 1 including a developing device 6 according to an embodiment of the present invention will be described with reference to FIG.

  The image forming apparatus 1 according to the present embodiment has a copier mode (copying mode), a printer mode, and a FAX mode as print modes, an operation input from an operation unit (not shown), and an external host device such as a personal computer. A print mode corresponding to the reception of the print job from is selected by the control unit described later.

  As shown in FIG. 1, the image forming apparatus 1 is roughly divided into a document reading unit 10, a paper feeding unit 20, a printing unit 30, and a paper discharge unit 40, and the document reading unit 10 is disposed above the paper feeding unit 20. The paper discharge unit 40 is disposed at an intermediate position between the document reading unit 10 and the paper supply unit 20.

Hereinafter, the copier mode will be described from the above processing modes.
After the user places an original on the platen glass 11 of the original reading unit (scanner unit) 10, the paper (recording paper) is placed on the paper supply cassette 21 of the paper supply unit 20 or the manual feed tray 23 provided on the side of the apparatus. The copy operation is started when the start key on the operation panel is operated after the condition input key (number of prints / printing magnification, etc.) is input on the operation panel (not shown) which is mounted and further disposed on the front surface of the apparatus. The

  When the start key is operated, a main drive motor (not shown) starts and each drive gear rotates. Thereafter, the paper feed roller 22 or 22a rotates to feed (feed) the paper into the apparatus, and the fed paper reaches the registration roller 31 (roller pair) and is captured.

  The registration roller 31 temporarily stops the paper so as to synchronize with the leading edge (image formation start portion) of the image formed on the photosensitive drum 32, and the leading edge of the paper is uniformly pressed against the registration roller 31. Thus, the leading edge position of the paper is corrected.

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

  The image information read in this way is converted into an electrical signal by a CCD circuit (not shown), and the image information signal is subjected to image processing under a set condition, and the laser scanner unit. 33 as print data.

  On the other hand, a part of the peripheral surface of the photosensitive drum 32 is charged to a predetermined charging potential over the entire axial direction by the charging unit (charging means) 34, and the entire peripheral surface is predetermined by rotating the photosensitive drum 32. The negative charging potential is charged. The surface of the charged photoconductive drum 32 moves to the next process as the photoconductive drum 32 rotates.

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

  Thereafter, toner (an example of a developer) in the developing tank 61 is supplied onto the surface of the rotating photosensitive drum 32 by the developing roller 62 applied with a negative DC potential in the developing tank 61 provided in the developing device 6. The electrostatic latent image is visualized (developed) by this toner in accordance with the potential gap on the photosensitive drum 32.

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

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

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

  In addition, when it is detected by a predetermined sensor that a document is placed on the document tray 19 provided in the document reading unit 10, the paper feed roller 51 rotates when a predetermined start key operation is performed. Then, the document placed on the document tray 19 is sent into the document reading unit 10 and is transported through a predetermined transport path Rt1.

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

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

Next, the characteristic developing device 6 according to the present embodiment will be described with reference to the drawings.
FIG. 2 is an explanatory diagram showing a schematic configuration of the developing device according to the present embodiment.

  The developing device 6 generally includes a developing roller 62 that carries the developer, a developing tank 61 that contains the developer, and stirring transport members 63, 64, and 65 that stir and transport the developer 60 in the developing tank 61. . Each rotates counterclockwise as indicated by an arrow.

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

  As the developer carried on the developing roller 62, toner that is a non-magnetic one-component developer is used.

  In the developing tank 61, a toner supply roller 66 provided upstream of the developing roller 62 in the toner transport direction attracts the toner to the surface and supplies a certain amount of toner onto the developing roller.

  Above the developing roller 62, a developer regulating member for forming a certain amount of toner layer on the developing roller 62, a so-called doctor blade 68 is provided. The front end of the doctor blade 68 is provided with a restricting portion 67 made of urethane rubber integrated with the blade, and the other end side is sandwiched between the fixed metal plates 71 and 72, and the developing tank 61 main body is fixed by a screw 73. It is fixed to.

  The doctor blade 68 is a thin metal plate having a spring property, and this spring property presses the restricting portion 67 to the position of the contact point p on the developing roller 62 with a constant pressure. As a result, a toner layer having a constant charge is carried on the developing roller 62.

  The toner having these charges is supplied from the developing roller 62 to the photosensitive drum 32 according to the potential difference between the developing roller 62 and the photosensitive drum 32 to develop the electrostatic latent image to form a toner image.

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

  In addition, a third agitation transport member 64 is disposed between the first agitation transport member 65 and the second agitation transport member 63. The third stirring and conveying member 64 is a screw-like rotating member made of, for example, a hard synthetic resin, and mainly has a role of stirring and conveying toner in the axial direction.

An intermediate wall member 80 is provided between the second stirring and conveying member 63 and the toner supply roller 66. The intermediate wall member 80 is a flat plate member made of, for example, synthetic resin, and is provided so as to extend in the longitudinal direction of the developing tank 61 and rise from the bottom of the developing tank 61.
An opening hole 81 is formed in the central portion of the intermediate wall member 80, and a developer flow from the second stirring / conveying member 63 toward the toner supply roller 66 is formed in the developing tank 61.

  The toner supply roller 66 is provided with a cylindrical porous elastic member such as foamed urethane around a cored bar. The toner supply roller 66 rubs the developing roller 62 while adsorbing toner in the hole. It also serves to supply toner to the developing roller 62 and to clean the excess toner layer remaining on the developing roller 62 after development.

Next, the doctor blade 68 will be described with reference to the drawings.
FIG. 3 is an explanatory diagram showing a configuration of a doctor blade constituting the developing device of the present embodiment.

  As shown in FIG. 3, the doctor blade 68 is provided with a restricting portion 67 at a tip portion facing the developing roller 62. The restricting portion 67 has a substantially rectangular cross section, and is formed with substantially the same width as the developing roller 62 in the longitudinal direction, that is, the direction along the axial direction of the developing roller 62.

  The doctor blade 68 is fixed to the developing tank 61 side with screws or the like with the other end side sandwiched between the fixed metal plates 71 and 72.

  In addition, the restricting portion 67 is pressed against the developing roller 62 with a load (pressing force) P at the position of the contact point p by the material elastic force of the main body of the doctor blade 68 that is a support portion.

  The developing roller 62 rotates in the direction of arrow N (counterclockwise direction), and the toner in the developing tank 61 is attracted to the surface by the toner supply roller 66, and a certain amount of toner is put on the developing roller 62. Supply.

  The toner flowing into the contact point p is charged by receiving a frictional force from the developing roller 62 and the restricting portion 67. The toner that has passed through the contact point p is supplied to the developing position facing the photosensitive drum 32 and then supplied to develop the electrostatic latent image formed on the photosensitive drum 32.

The method for setting the force for pressing the regulating portion 67 against the developing roller 62 is as follows. The pressing force mainly uses the material elastic force of the doctor blade 68.
That is, the pressing force is adjusted depending on how much the doctor blade 68 is brought into contact with the developing roller 62 in the bent state (Y direction). Theoretically, it is expressed by the following cantilever formula (1).

Force: P (kgf) = 3EIδ / L3 (1)

Here, E is the Young's modulus of the blade indicator material, I is the moment of inertia of the cross section, δ is the amount of deflection, and L is the free length.

In an actual experiment, one end of a PET member cut into a strip shape is sandwiched between the restricting portion 67 and the developing roller 62, and the other end is connected to a tension gauge so that the PET member is moved at a constant speed. Evaluation is based on the pulling force when pulling out. “RX-5” manufactured by Aiko Engineering Co., Ltd. is used for the tension gauge.
In this experiment, the drawing force was adjusted to be about 0.03 to 0.05 (kgf / cm).

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

  As described above, it is known that the toner layer can be stabilized by making the surface of the developing roller 62 uneven as described above. Therefore, in this embodiment, a specified amount of toner conveyance can be obtained by blasting the aluminum developing roller 62.

Next, a characteristic configuration of the developing roller 62 of the present embodiment will be described with reference to the drawings.
FIG. 4 is an explanatory view showing the structure of the developing roller constituting the developing device of the present embodiment, FIG. 5 is an enlarged view of a portion A of FIG. 4, and an explanatory view showing an example of the surface state of the developing roller, Is a graph showing the measured value of the surface roughness of the first blasted region of the developing roller blasted, FIG. 7 is a graph showing the toner adhesion amount according to the surface roughness of the developing roller, FIG. Is an explanatory view showing the configuration of the surface of the developing roller, (b) is a side view showing the configuration of the surface of the developing roller, and FIG. 9 is a measurement of the surface roughness of the second blasting region of the developing roller subjected to blasting. It is the graph which showed the value.

  As shown in FIG. 4, the developing roller 62 is subjected to a blasting process in an area 62B in contact with the restricting portion 67 of the doctor blade 68 (hereinafter referred to as “first blasting process area 62B”). Regions 62A that are not in contact with the restricting portions 67 of the doctor blade 68 at both ends of the developing roller 62 are used aluminum substrates (hereinafter referred to as “aluminum substrate regions 62A”).

  In this embodiment, aluminum members A5052, A5056, A6061 and the like are used as the constituent members of the developing roller 62.

The blast treatment is generally sand blasting using sand as abrasive grains, but spherical glass beads or steel balls which are regular shapes are often used.
In this embodiment, glass beads or sand is used as the abrasive grains.

  As shown in FIG. 5, the surface of the developing roller 62 is in a different surface state from the aluminum base region 62A and the first blasting region 62B. In the figure, the symbol d indicates a state where the glass beads are deformed into a concave portion by one grain.

Here, the blast process will be described.
In general, the blasting process is performed by causing an abrasive particle having a certain size and hardness to be injected and collided from the injection nozzle to the object at a constant pressure and speed while rotating the object around the central axis. This is performed while adjusting the distance to the object, the number of repeated injections for the object, and the like.

  Depending on how smoothly the surface of the object is finished before blasting, there is a difference in the roughness after processing. In the present embodiment, the blasting process is performed after mirror-polishing the base surface of the aluminum cylindrical member, which is the developing roller 62, with an average roughness Ra = 0.05 μm or less, so that the average roughness Ra = 0.3. Irregularities could be stably formed in the range of ˜0.5 μm.

  Below, the relationship of the average roughness Ra after blasting by the average finishing roughness Ra of the base material of an aluminum material is shown.

  Further, the measured value of the surface roughness of the first blasting region 62B is as shown in FIG. The average roughness in this case is Ra = 0.43 (μm).

In the present embodiment, as described above, the average roughness Ra of the surface of the first blasting region 62B of the developing roller 62 is set to 0.3 to 0.5 μm. With this configuration, the toner adhesion amount of the developing roller 62 is 0.7 to 0.9 (mg / cm ² ), as shown in FIG. The above required concentration was obtained.

  Further, the developing roller 62 according to the present embodiment has a characteristic configuration in which a second roughness that is rougher than the surface roughness of the region 62B in the first blasting region 62B, as shown in FIGS. 8A and 8B. A blasting region 62C is formed.

  Specifically, on the surface of the developing roller 62, as shown in FIG. 8A, the first blasting region 62B and the second blasting region 62C having different average roughness Ra in surface roughness are provided on the developing roller. 62 are formed adjacent to each other along the circumferential direction of 62, and are formed in areas where the doctor blade 68 contacts along the axial direction of the developing roller 62.

  The first blast processing area 62B and the second blast processing area 62C are, as shown in FIG. 8B, a second blast processing area having a large average roughness Ra in the direction along the circumferential direction of the developing roller 62. The proportion occupied by the first blasting region 62B having a small average roughness Ra is smaller than the proportion occupied by the 62C region.

  The measured value of the surface roughness of the second blasting region 62C is as shown in FIG. In this case, the average roughness Ra = 0.65 (μm).

  And the unevenness | corrugation from which average roughness Ra differs is mixedly formed in the boundary part of the 1st blasting area | region 62B and the 2nd blasting area | region 62C.

Here, an example of a processing method when the surface of the developing roller 62 is processed will be described.
When processing the surface of the developing roller 62, for example, a portion (range) corresponding to the second blasting region 62C on the surface of the developing roller 62 is previously masked with an adhesive tape or the like, and then the second blasting region. It is preferable that the entire surface of the developing roller 62 is blasted with a roughness smaller than the surface roughness of 62C, and then the masked tape is peeled off, and then only the second blasting region 62C is blasted again with a predetermined roughness.

  By doing in this way, the unevenness | corrugation from which average roughness Ra differs is mixedly formed in the boundary part of the 1st blast process area | region 62B and the 2nd blast process area | region 62C.

  As described above, the toner conveyance capability of the developing roller 62, which varies depending on the surface roughness, is changed to the first blasting region 62B only when the second blasting region 62C passes under the restricting portion 67 of the doctor blade 68. It will increase in comparison.

  In the case of the conventional method, since the surface roughness of the developing roller is constant over the entire surface, a constant amount of toner is always supplied under the doctor blade, so that the toner is not smoothly conveyed to the developing area in a certain part. The toner sometimes stays under the doctor blade and does not move. Thereby, the toner is easily welded to the surface of the doctor blade by the operation of the apparatus for a long time. As a result, since the toner is not conveyed downstream in the toner welded portion, it appears on the developing roller and appears as an image defect.

  According to the developing roller 62 of the present embodiment, once the developing roller 62 rotates once, the toner conveyance capability increases in the second blast processing area 62C, so that the changing pressure is applied to the toner that has stayed. The toner that has started to harden can be broken down instantaneously. As a result, the toner can be smoothly conveyed downstream.

Here, the configuration and operational effects of the developing roller 62 of the present embodiment and the conventional developing roller will be compared.
FIG. 10A is an explanatory view showing an example of the shape of a groove formed on a conventional developing roller, FIG. 10B is an explanatory view showing the relationship of the toner conveyance amount according to the shape of the groove, and FIG. Is an explanatory view showing an example of the shape of the concavo-convex portion formed on the developing roller of this embodiment, (b) is an explanatory view showing the relationship of the toner conveyance amount according to the shape of the concavo-convex portion, and FIG. It is explanatory drawing which shows the outline when performing a blast process to the developing roller in.

In order to partially increase the developer conveying ability of the developing roller, as a known method, it is known that a groove is provided on the surface of the developing roller by, for example, machining or die molding.
For example, as shown in FIG. 10A, a groove portion having a width k (mm) deep from the surface by h (mm) is provided. With this configuration, the developer is trapped in the groove portion. Therefore, the toner conveyance amount (mg / cm ² ) by the developing roller, that is, the toner conveyance capability is as shown in FIG. It is higher than the other places in the place corresponding to.

  However, in such groove processing, as shown in FIG. 10B, the toner conveyance amount rises sharply and increases as compared with a portion having no groove. As a result, more toner than is required is supplied in a strip shape in the longitudinal direction to the development region, so that the image density increases in a strip shape at the circumferential pitch.

  On the other hand, in the blasting process of the surface of the developing roller 62 in the present embodiment, the abrasive grains are sprayed on the developing roller 62 as described above. As shown to a), the uneven | corrugated process in which the boundary of an adjacent area | region has a gentle change is attained.

  That is, for example, as shown in FIG. 12, on the center line CL1 in the circumferential direction of the belt region of the second blast processing region 62C of the developing roller 62, the blast strength of the grinding stone particles from the blast nozzle 100 is increased, What is necessary is just to weaken a blast intensity | strength toward the direction which remove | deviates from centerline CL1, ie, the boundary vicinity with the 1st blast processing area | region 62B. By doing so, large and small irregularities are mixed in the boundary region between the first blast processing region 62B and the second blast processing region 62C.

  As a result, the toner conveyance amount by the developing roller 62 changes gently as shown in FIG. 11B, so that it is difficult to cause an excessive change in toner conveyance as in the prior art.

  The difference in surface roughness between the first blasting region 62B and the second blasting region 62C and the area ratio depend on the developing device, developer, and development conditions to be used, but are not particularly defined. Optimize according to the conditions used.

  For example, as the surface roughness of the second blasting region 62C is increased, and as the area is increased, the effect of eliminating toner streaks is higher. However, the toner conveyance amount increases and the image density changes accordingly. Therefore, it is necessary to find a combination that does not cause image defects while shaking the above parameters.

  Hereinafter, the average roughness Ra of the first blasting region 62B is set to 0.3 to 0.5 (μm), and the average roughness Ra of the second blasting region 62C is set to 0.5 to 1.0 (μm) or more. In addition, the angle θ that the second blast processing area 62C occupies on the circumference is changed by 15 to 30 ° or more, and the presence or absence of image defects due to the generation of streaks on the toner layer was evaluated. Results are shown.

  Here, the “angle θ” is an angle θ of a portion occupied on the circumference by the second blast processing region 62C from the rotation center O of the developing roller 62 in the side view of FIG. 8B.

  As shown in Table 1, when the average roughness Ra of the second blast treatment region 62C is 0.5 to 0.7 (μm), the angle θ occupied by the second blast treatment region 62C is 15 to 30 (°). Thus, no streak was generated on the toner layer and the image was good.

  As shown in Table 2, when the average roughness Ra of the second blast treatment region 62C is 0.5 to 1.0 (μm), the angle θ occupied by the second blast treatment region 62C is 15 (°) or less. The image was Δ, the angle θ was 15 to 30 (°), no streak was generated on the toner layer, and the image was good.

  As shown in Table 3, when the average roughness Ra of the second blast treatment region 62C is 1.0 (μm) or more, the angle θ occupied by the second blast treatment region 62C is 15 (°) or less and 15 to 30 The image was Δ at (°).

  As described above, according to the results of Tables 1 to 3, according to the developing roller 62 of the present embodiment, the average roughness Ra of the first blasting region 62B is 0.3 to 0.5 (μm), and the second blasting region. When the average roughness Ra of 62C is in the range of 0.5 to 1.0 (μm) and the angle θ occupied by the second blasting region 62C is in the range of 15 to 30 (°), there is no generation of streaks on the toner layer. An image can be formed.

  With the configuration as described above, according to the present embodiment, as the configuration of the developing device 6, the surface of the developing roller 62 is formed into a concavo-convex shape by blasting, and an average roughness in the surface roughness is formed on the concavo-convex surface. A first blasting region 62B and a second blasting region 62C having different thickness Ra are formed adjacent to each other along the circumferential direction of the developing roller 62 and in a range where the doctor blade 68 contacts along the axial direction of the developing roller 62. In addition, since the uneven portion having different average roughness Ra is mixed at the boundary between the first blast processing region 62B and the second blast processing region 62C, the toner is transported without causing a sudden change in the toner transport amount. As a result, it is difficult to cause the toner to adhere to the surface of the doctor blade 68 without affecting the development area. And suppress the raw, it is possible to obtain a stable image.

  In the present embodiment, the second blasting region 62C formed in a concavo-convex shape on the surface of the developing roller 62 is formed substantially parallel along the axial direction of the developing roller 62 as shown in FIG. However, the present invention is not limited to the shape of the region formed to be uneven, and may not be formed in parallel.

(Modification)
Next, a modified example of the developing roller 62 of the present embodiment will be described with reference to the drawings.
FIG. 13 is an explanatory view showing a configuration of a modified example of the developing roller constituting the developing device of the present embodiment, FIG. 14A is an explanatory view showing a configuration in the vicinity of a doctor blade constituting the conventional developing device, and FIG. FIG. 4B is an explanatory view showing a configuration of a fixed sheet metal that holds the doctor blade, as viewed from arrow B in FIG.

In the modification, the configuration of the uneven surface of the developing roller 62 constituting the developing device 6 of the above-described embodiment is changed.
In the developing device according to the modified example, components other than the developing roller and components having different configurations are provided with the same configuration as the developing device 6 of the above-described embodiment. Moreover, the description which abbreviate | omits what has the same structure by attaching | subjecting the same code | symbol.

  As shown in FIG. 13, in the modified developing roller 162, a second blasting region 162C that is rougher than the surface roughness of the first blasting region 162B is formed in the first blasting region 162B.

  The second blasting region 162C is formed such that the circumferential width thereof is wider at both ends 162d2 and 162d3 in the axial direction of the developing roller 162 than at the central portion 162d1.

  By the way, in the conventional developing device, due to the structure of the pressure contact mechanism (not shown) with respect to the developing roller, the toner conveyance amount tends to be larger at the central portion in the longitudinal direction (axial direction) of the developing roller than at both end portions.

  Therefore, as shown in FIGS. 14A and 14B, the shape of the fixed metal plate 271 that holds the doctor blade 68 is set so that the central portion 271w1 in the axial direction of the developing roller 262 is slightly wider than both end portions 271w2 and 271w3. Thus, the free length of the doctor blade 68 is artificially shortened only at the central portion, so that the pressure P applied to the central portion 271w1 is raised above both end portions 271w2 and 271w3, and the longitudinal direction (axial direction). The balance of the total toner conveyance amount was optimized.

  In the modification, the configuration of the developing roller 162 is as shown in FIG. 13, so that the toner conveyance amount at both end portions 162d2 and 162d3 can be increased from the central portion 162d1 in the longitudinal direction (axial direction) of the developing roller 162. It becomes. This eliminates the need to change the width shape along the axial direction of the developing roller as in the conventional fixed metal plate 271 described above.

  Further, both end portions 162d2 and 162d3 of the developing roller 162 have a relatively small influence on the increase / decrease of the toner conveyance amount according to the present invention as compared with the central portion 162d1. The reason is as follows.

  That is, the developing roller 162 is installed with a certain gap with respect to the photosensitive drum 32, but the developing roller 162 has a structure in which a cylindrical portion contributing to development is rotated by drive shafts 162e at both ends. It has become. The shafts 162e at both ends rotate with respect to the developing tank 61 via bearings. In general, when this type of cylindrical member is manufactured with a lathe or the like, the rotational runout at the center of the cylinder is the largest, and the runout becomes smaller as it approaches the both ends.

  Therefore, when the developing roller 162 having such a configuration rotates opposite to the photosensitive drum 32, the gap between them, that is, the developing gap repeatedly repeats a large or small value, that is, moves away or approaches.

  As the development gap becomes wider, the amount of toner adhering to the photosensitive drum 32 inevitably decreases, and as a result, the image density on the paper decreases. On the other hand, when the development gap is small, the image density is high. This becomes more prominent at the center, and has less influence as it approaches both ends. At the time of normal commercialization, various conditions are determined in consideration of the amount of fluctuation, so the influence is offset by another parameter.

  For the above reasons, even if the toner conveyance amount at both ends of the developing roller 162 is slightly increased compared to the central portion, if the increase is about the same as the influence due to the shake of the central portion described above, the influence on the output image is increased. There is no.

  With the above-described configuration, according to the modification, the configuration of the developing roller 162 is configured such that the second blast processing region 162C having a large surface roughness is disposed at both ends of the center portion 162d1 in order to increase the effect of breaking the toner retention layer. By providing the portions 162d2 and 162d3 in a wide range, a difference occurs in the amount of toner movement in the longitudinal direction (axial direction) of the developing roller 162. Therefore, the toner flow directly under the doctor blade 68 is not always constant. Stable image can be obtained by making it difficult for toner to adhere to the surface of the doctor blade 68 and suppressing the generation of streaks on the toner layer.

In the embodiment described above, the main specifications of the developing device 6 are as follows.
Developing roller: 16mm outer diameter
Photoconductor (OPC); outer diameter 30 mm
Toner supply roller; outer diameter 16mm
Process speed: 145 mm / sec
Regulator thickness: 1 mm
Here, the image density on the output paper can be measured using a portable spectrocolorimetric densitometer (trade name: X-Rite 939, manufactured by X-Rite).
The toner charge amount can be measured by using Model “210HS-2A” manufactured by TReK.

  As described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope not departing from the gist of the present invention are also included in the technical scope of the present invention.

1 Image forming apparatus 32 Photosensitive drum (photosensitive member)
60 Developer 62, 162 Developing roller 62A Aluminum base region 62B, 162B First blasting region (one of two regions having different average roughness Ra)
62C, 162C Second blasting region (the other of the two regions having different average roughness Ra)
67 Restriction part 68 Doctor blade 100 Blast nozzle 162d1 Center part 162d2, 162d3 End part

Claims (9)

A developing roller provided in an electrophotographic image forming apparatus for supplying a developer to a photoconductor provided in the image forming apparatus to develop an electrostatic latent image formed on the photoconductor; In a developing device comprising a developer regulating member that regulates the layer thickness of the developer carried on the surface,
The surface of the developing roller is formed in an uneven shape,
Two regions having different surface roughness Ra in the surface roughness are formed adjacent to each other along the circumferential direction of the developing roller and are formed along the axial direction of the developing roller, respectively. And
A developing device, wherein unevenness having different average roughness Ra is mixedly formed at a boundary portion between two regions having different average roughness Ra.   The two regions having different average roughness Ra are configured so that the proportion of the region having a large average roughness Ra in the direction along the circumferential direction of the developing roller is less than the proportion of the region having a small average roughness Ra. The developing device according to claim 1, wherein:   3. The development according to claim 1, wherein the region having a large average roughness Ra has a circumferential width formed so that both end portions in the axial direction of the developing roller are wider than a central portion. apparatus.   The developing device according to claim 1, wherein the developing roller is formed of an aluminum cylindrical member.   The developing device according to claim 1, wherein the uneven surface is blasted by glass bead blasting.   The developing device according to claim 1, wherein the uneven surface is blasted by sandblasting.   The average roughness Ra of the uneven surface is characterized in that the average roughness Ra of one region is 0.3 to 0.5 μm and the average roughness Ra of the other region is 0.5 μm or more. The developing device according to any one of claims 1 to 6.   8. The blasting process is performed after mirror-finishing the base surface of an aluminum cylindrical member constituting the developing roller with an average roughness Ra of 0.05 [mu] m or less. The developing device according to claim 1. A developing roller for developing an electrostatic latent image formed on the photosensitive member by supplying a developer to the photosensitive member, and a surface of the developing roller. In an image forming apparatus that includes a developing device that includes a developer regulating member that regulates the layer thickness of the developer carried on the image forming apparatus and performs image formation by an electrophotographic method.
An image forming apparatus comprising the developing device according to claim 1 as the developing device.