Patent Grant
8068772
1. Field of the Invention
The present invention relates to a development device installed in a printer or a photocopier employing an electrophotographic method, and relates to an image forming apparatus including the development device.
2. Description of Related Art
A development device of an image forming apparatus such as an electrophotographic printer, a photocopier, a facsimile and a multifunctional device includes a developer carrier carrying a developer thereon and develops an electrostatic latent image formed on an electrostatic latent image carrier with the developer carried on the developer carrier. Here, a surface of the developer carrier is made rough such that an image to be formed on a recording medium has an adequate density. For example, roughness of the developer carrier in a circumferential direction and a mean width of profile elements are defined to obtain the adequate density (See, e.g., Japanese Un-examined Patent Application Publication No. H07-319287).
The image to be formed on the recording medium, however, may not have the adequate density although the roughness of the developer carrier in the circumferential direction and the mean width of profile elements are defined.
According to one aspect of the invention, a development device includes a developer carrier supplying developer to an electrostatic latent image carrier being rotatable, the developer carrier includes: a conductive metal core; and a conductive elastic layer, disposed outside circumference of the conductive metal core, including a surface having roughness formed thereon, and the surface of the conductive elastic layer satisfies a relationship 1.0≦Rz2/Rz1≦1.60, where Rz1 is ten-point mean roughness in a circumference direction and Rz2 is ten-point mean roughness in an axial direction of the developer carrier, and a relationship 0.20≦Sm2/Sm1≦1.00, where Sm1 is a mean width of profile elements of the surface of the conductive elastic layer in the circumference direction of the developer carrier, and Sm2 is a mean width of profile elements of the surface of the conductive elastic layer in the axial direction of the developer carrier.
According to another aspect of the present invention, an image forming apparatus includes: the development device described above; an exposure device exposing a surface of the electrostatic latent image carrier to form an electrostatic latent image based on image information; a transfer unit transferring an developer image formed by development of the electrostatic latent image formed on the surface of the electrostatic latent image carrier by the exposure device with the developer carrier to a recording sheet; and a fixing unit fixing the developer image transferred by the transfer unit to the recording sheet.
Additional features and advantages of the present invention will be more fully apparent from the following detailed description of embodiments, the accompanying drawings and the associated claims.
A more complete appreciation of the aspects of the invention and many of the attendant advantage thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner.
In the following detailed description, reference is made to the accompanying drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views. A description of the present invention is now given below with regard to a particular embodiment, but the present invention is not limited thereto and it must be understood that the invention encompasses all modifications possible not departing from the scope of the invention.
An image forming apparatus 100 according to an embodiment of the present invention includes a development device 10 having a development roller 2 serving as a developer carrier. A description of the image forming apparatus 100 of the present invention is given with reference to
As illustrated in
In addition to the development device 10, the image forming apparatus 100 includes conveyance rollers 45a, 45b and 45c controlled by a sheet conveyance motor 34 to convey a sheet 44 serving as a recording medium, a light emitting diode (LED) head 30 serving as an exposure device exposing a surface of the photosensitive drum 1 of the development device 10 to form the electrostatic latent image thereon, a transfer roller 27 serving as a transfer member transferring a toner image developed on the photosensitive drum 1 by the development device 10 onto the sheet 44, and a fixing device 32 having a heater (not shown) melting the toner 8 of the toner image transferred onto the sheet 44 by the transfer roller 27 and a temperature sensor (not shown) reading a temperature of the fixing device 32 heated by the heater.
As illustrated in
The control unit 19 includes a microprocessor, a read only memory (ROM), a random access memory (RAM), an input port and a timer, and controls the drum counter 20 counting a number of rotations of the photosensitive drum 1 or the dot counter 21 counting print dots. The control unit 19 receives print data or a control command from a higher-level device (not shown) through the I/F control unit 14, controls image formation as a whole, and executes a print operation.
The receiving memory 15 temporarily records the print data or the control command received through the I/F control unit 14. The image data editing memory 16 receives the print data recorded in the receiving memory 15 and records image data formed by editing the print data.
The operation unit 17 includes an LED displaying a state of the image forming apparatus 100 and a switch or a display unit providing an instruction from an operator to the image forming apparatus 100. The sensor group 18 includes a plurality of sensors (not shown), for example, a sheet position detection sensor, a temperature-humidity sensor and a density sensor, each of which is disposed to monitor an operation state of the image forming apparatus 100.
The power source 22 for the charging roller 4 applies a predetermined voltage to the charging roller 4. The power source 24 for the development roller 2 applies a predetermined voltage to the development roller 2. The power source 25 for the supply roller 3 applies a predetermined voltage to the supply roller 3. The power source 26 for the transfer roller 27 applies a predetermined voltage to the transfer roller 27. The power sources 22, 24 and 25 can change the voltage to be applied to the charging roller 4, the development roller 2 and the supply roller 3 respectively in accordance with instructions of the control unit 19.
The power source 28 for the fuse applies a current to a development device old and new distinction fuse 43 that determines whether or not the development device 10 is not used ever. The head drive control unit 29 controls drive of the LED head 30 and transmits the image data stored in the image data editing memory 16 to the LED head 30. The fixing control unit 31 reads an output from an temperature sensor (not shown) of the fixing device 32, and controls a temperature of the fixing device 32 to be a constant level by energizing the heater (not shown) based on the sensor output from the temperature sensor (not shown). The conveyance motor control unit 33 controls the sheet conveyance motor 34 and drives or halts the conveyance rollers 45a, 45b and 45c, so that the sheet 44 is conveyed to directions 46a, 46b, 46c and 46d indicated by respective arrows shown in
The image forming apparatus 100 stores the print data received by the I/F control unit 14 in the receiving memory 15, and the control unit 19 controls a sequence of the image forming apparatus 100 as a whole so as to execute the print operation. After the print data are received, the control unit 19 controls the conveyance motor control unit 33 to drive the conveyance roller 45a by the sheet conveyance motor 34, so that the sheet 44 is rolled at a predetermined timing and is conveyed to the direction indicated by the arrow 46a shown in
Here, the development device 10 forms the toner image. In an image forming process, control data are transmitted from the control unit 19 to the drive control unit 35. Upon receiving the control data, the drive control unit 35 controls the drive motor 36 to rotate the photosensitive drum 1. The power source 22 for the charging roller 4 applies negative voltage to the charging roller 4 rotating with rotation of the photosensitive drum 1, so that the surface of the photosensitive drum 1 is charged.
On the other hand, the print data stored in the receiving memory 15 is converted by the image data editing memory 16. The converted image data are transmitted to the head drive control unit 29 through the control unit 19. The head drive control unit 29 controls the LED head 30 based on the received image data, so that the LED head 30 exposes the surface of the photosensitive drum 1. Therefore, the electrostatic latent image corresponding to the image data are formed on the charged surface of the photosensitive drum 1.
The development roller 2 and the supply roller 3 rotating with rotation of the photosensitive drum 1 are applied with the voltage instructed from the control unit 19, and the toner 8 contained in the toner cartridge 7 is supplied to the development roller 2 through the supply roller 3. The toner 8 supplied to the development roller 2 passes through the development blade 9, so that a thin layer is formed on the development roller 2. The electrostatic latent image formed on the surface of the photosensitive drum 1 is developed by the thin layer of the toner 8 on the development roller 2, and the toner image is formed on the photosensitive drum 1.
Before the sheet 44 passes between the development roller 10 and the transfer roller 27, the transfer roller 27 is applied with the predetermined voltage from the power source 26 for transfer roller 27. Therefore, the toner image is transferred onto the sheet 44 passing between the photosensitive drum 1 and the transfer roller 27 with physical pressure and electrostatic force in a pressure area in which the photosensitive drum 1 and the transfer roller 27 press against each other.
The sheet 44 having the toner image transferred thereon passes through the fixing device 32 controlled by the fixing control unit 31, thereby attaching the toner with heat and pressure and fixing the toner image on the sheet 44. After the toner image is fixed, the sheet 44 is conveyed toward the direction indicated by the arrow 46c shown in
Although the image forming apparatus 100 of the present invention described above includes the development device 10, the present invention is not limited thereto. For example, the image forming apparatus 100 may include four development devices that correspond to respective four colors of the toner such as cyan, magenta, yellow, and black and are disposed parallel along a transfer belt from a sheet-feeding side to a sheet ejection side. In such a case, each of the development devices 10 transfers the toner image of respective color at a timing of the sheet 44 being conveyed based on the control of control unit 19, thereby forming a multi-color image.
Referring to
A length of the elastic layer 2b in a longitudinal direction of the development roller 2 (i.e., a direction indicated by an arrow 2e shown in
The development roller 2 includes a surface layer 2c serving as an outside surface of the elastic layer 2b, and roughness is formed on the surface layer 2c. The roughness to be formed on the surface layer 2c can be provided by a method for forming thereof by molding in a state that particles are mixed with resin material liquid used in the course of forming the elastic layer 2b having the electric conductivity, a method for forming thereof by application of embossment to the surface of the elastic layer 2b, or a method for forming thereof by application of cutting work to the surface of the elastic layer 2b.
After the roughness is formed, a surface treatment and surface coating may be provided to the surface layer 2c as long as the surface of the surface layer 2c has predetermined polishing marks and surface roughness. For example, isocyanate or polyol and amino silane, etc. may be impregnated to or coated on the surface of the surface layer 2c. Moreover, the surface of the surface layer 2c may be coated by polyester resin, urethane resin, acrylic urethane resin, epoxy resin, nylon resin, fluorine resin and silicone resin, etc. In addition, the surface layer 2c may provide and prepare the electric conductivity thereof by adding the electric conductive agent such as carbon black to a surface treatment agent and a coating agent.
As described above, the development device 10 according to the embodiment of the present invention includes the development roller 2 having the surface layer 2c with the roughness.
Now, the development roller 2 according to the embodiment of the present invention capable of providing the adequate image density is examined by a relationship between ten-point mean roughness in the circumference direction (i.e., the direction indicated by the arrow 2d shown in
A description of measurement of the surface roughness indicating the roughness on the surface layer 2 of the development roller 2 is given below. The surface roughness was measured using a surface roughness analyzing system SE3500, a detection device PU-DJ2S, a circumference roughness measuring apparatus ZRM200 (each of which is available from Kosaka Laboratory Ltd, Japan) and an axial direction measuring jig. The surface roughness was measured by two measuring methods depending on a direction to be measured. The first measuring method was a measurement of the surface roughness in the circumference direction by contacting a vertex of the surface layer 2c with a contact pin of the detection device while the development roller 2 was being rotated in the circumference direction indicated by the arrow 2d shown in FIG. 3. The second measuring method was a measurement of the surface roughness in the axial direction by moving the contact pin of the detection device in a longitudinal direction indicated by the arrow 2e shown in
For the metal core 2a of the development roller 2 of the first embodiment, a metal core 2a formed by a metal shaft having an outside diameter of 10.00 mm and made of SUM23L grade steel (JIS steel grade for a free cutting steel material) was plated with the electroless nickel. For the elastic layer 2b having the electric conductivity, a base material having the silicone rubber as the principal component was used and applied with a grinding process using a drum sanding machine after being ground roughly, so that the roughness was formed on the surface layer 2c. For the surface layer 2c, the amino silane as a surface active agent was coated after a surface hardening process by UV irradiation was performed. Eventually, the development roller 2 had the outside diameter of 17.62 mm and a hardness of the surface layer 2c had 42 degrees measured by a micro-durometer MD-1 type A (available from Kobunshi Keiki CO., LTD, Japan).
Here, development roller samples A-1 to A-8, B1 to B-12 and D-1 to D-24 applied with different film abrasion processes including film roughness, film abrasion pressure, a film abrasion speed, a film feed speed, a number of film abrasion and a sample rotation speed were prepared, and the surface roughness of each of the surface layer 2c of the samples was measured. The results are shown in TABLE 1. For example, a surface of the sample B-1 was applied with the abrasion process with the film abrasion pressure of 1.0 kg, the film abrasion speed of 1300 mm/min, the film feed speed of 10 mm/min, the number of film abrasion of one (1), and the sample rotation speed of 2000 rpm using sandpaper having a width of 100 mm and an abrasive grain of 40 μm in such a manner to provide values of Rz1, Sm1, Rz2 and Sm2 listed in TABLE 1.
The values of Rz1, Sm1, Rz2 and Sm2 can be adjusted by following methods. The value of Rz1 can be adjusted by roughness of the sandpaper or the film abrasion pressure. For example, the abrasive grain of the sandpaper is roughened, or the film abrasion pressure is increased, thereby increasing the value of Rz1. The value of Rz2 can be adjusted by the roughness of the sandpaper or the film abrasion speed. For example, the abrasive grain of the sandpaper is roughened, or the film abrasion speed is decreased, thereby increasing the value of Rz2. The value of Sm1 can be adjusted by the film feed speed or the sample rotation speed. For example, the film feed speed is increased, or the sample rotation speed is increased, thereby increasing the value of Sm1. The value of Sm2 can be adjusted by the film abrasion speed or the number of film abrasion. For example, the film abrasion speed is decreased, or the number of film abrasion is increased, thereby increasing the value of Sm2. Each of such conditions interacts one another. Therefore, the samples had desirable values of Rz1, Sm1, Rz2 and Sm2 by combination of the above conditions.
In the first example experiment, each of the samples was evaluated based on print density. Where an area of a solid image across the entire printable region of a sheet as illustrated in
According to the results shown in TABLE 1, although the development rollers have similar values of the ten-point mean roughness Rz1 in the circumference direction, the print densities vary. A comparison between the samples A-8 and B-9, for example, the sample A-8 has the value of the ten-point mean roughness Rz1 in the circumference direction of 9.24 μm, and the sample B-9 has that of 9.29 μm. In other words, the samples A-8 and B-9 have substantially the same values of the ten-point mean roughness Rz1 in the circumference direction. However, the sample A-8 has the print density of 1.14 while the sample B-9 has the print density of 1.31. Thus, the differences in the print densities are recognized. Since each of the samples A-8 and B-9 has a different surface state of the surface layer 2c of the development roller 2, a difference of an absolute value of an adhesion amount of the toner 8 for development simply provides a difference of the print density.
According to the first example experiment, the surface roughness was not only measured in the circumference direction but also in the axial direction of the development roller 2 so that the surface state of the surface layer 2c of the development roller was more accurately converted into a numerical term. As shown in TABLE 1, the roughness of the surface layer 2c of each sample is expressed by an index value of Rz2/Rz1, and the roughness density of the surface layer 2c of each sample is expressed by an index value of Sm2/Sm1.
Referring to
Referring to
Therefore, the surface state of the surface layer 2c cannot be adequately expressed by at least one of the values of the roughness Rz2/Rz1 of the surface layer 2c and the roughness density Sm2/Sm1 of the surface layer 2c. However, since the sample having the values satisfying both the roughness Rz1/Rz1 of the surface layer 2c and the roughness density of Sm2/Sm1 obtains the adequate print density, the surface state of the surface layer 2c is appropriately expressed by both the roughness Rz2/Rz1 of the surface layer 2c and the roughness density Sm2/Sm1 of the surface layer 2c.
Referring to
Referring to
A model illustrated in
A model illustrated in
A model illustrated in
Therefore, where the development roller 2 satisfies the ranges of the formulas 1 and 2 described above, not only the development device 10 including the development roller 2 therein can develop the image with the good print density, but also the image forming apparatus 100 including the development device 10 therein can print the image with the good print density on the sheet. Moreover, the value of the roughness Rz2/Rz1 and the value of the roughness density Sm2/Sm1 of the surface layer 2c of the development roller 2 can be used as control items in a course of manufacturing the development roller 2.
According to the first example experiment described above, where the formulas 1 and 2 are satisfied, the good print density is obtained. However, there raises a problem that the fog slightly deteriorates in the vicinity of the boundary C in the
Particularly, where a glossy sheet of paper having a gloss level of at least 58 (measured by a Gloss Meter Type GM-26D available from Murakami Color Research Laboratory, Japan, with a viewing angle of 75 degrees) is used, the toner of drum fog becomes noticeable on the glossy sheet due to a greater smoothness of a surface of the sheet with an increase in the gloss level, causing deterioration of the image as glossy sheet fog. In the second example experiment, a development roller capable of producing the image having reduced fog by reducing the drum fog to obtain a higher quality image is examined.
A description of the second example experiment is now given. A measurement of the fog was performed with respect to each of the samples of which density was evaluated in the first example experiment. In the fog measurement, the image forming apparatus was stopped in the middle of printing the density of zero percent, and the toner on the photosensitive drum 1 prior to the fixing process was adhered to an adhesive tape (Scotch mending tape available from Sumitomo 3M Ltd., Japan). Such an adhesive tape is referred to as a fog collection tape. The fog collection tape was attached onto a white sheet. Another adhesive tape (Scotch mending tape available from Sumitomo 3M Ltd., Japan) that was not adhered to the photosensitive drum 1 was also attached onto the white sheet as a comparison of the fog collection tape. Such an adhesive tape is referred to as a comparison tape.
A density difference between the fog collection tape and the comparison tape was measured by a spectrophotometer (a spectrophotometer CM-2600d available from Konica Minolta Holdings, Inc., with a measurement diameter of 8 mm), and the density difference ΔY was calculated by subtracting the density of the fog collection tape from the density of the comparison tape. The density difference ΔY calculated for each of the samples is listed in TABLE 1. In the evaluation of the fog toner, the sample having the density difference ΔY ranged between zero and three (0≦ΔY≦3.00) was evaluated as ∘ (circle), the sample having the density difference ΔY ranged between three and five (3.00≦ΔY≦5.00) was evaluated as Δ (triangle), and the sample having the density difference ΔY over 5.00 (5.00≦ΔY) was evaluated as X. Based on the results shown in the TABLE 1, the values of the print density corresponding to the values of the roughness Rx2/Rx1 and the roughness density Sm2/Sm1 of the surface layer 2c are summarized in TABLE 2. Moreover, based on the results shown in the TABLE 1, the evaluation of the fog corresponding to the values of the roughness Rx2/Rx1 and the roughness density Sm2/Sm1 of the surface layer 2c is summarized in TABLE 3.
According to the results shown in TABLE 2, the value of the roughness Rz2/Rz1 of the surface layer 2c ranged between and 6.00 and the value of the roughness density Sm2/Sm1 of the surface layer 2c ranged between 0.20 and 1.00 are relevant to the value of the good print density ranged between 1.20 and 1.40. In other words, where such conditions are satisfied, the good print density is obtained.
According to the results shown in TABLE 3, where the value of the roughness Rz2/Rz1 of the surface layer 2c is greater than 1.40, the fog is deteriorated. Where the value of the roughness density Sm2/Sm1 is smaller than 0.40, the fog is deteriorated. Therefore, a state of the surface layer 2c without occurrence of the fog has the value of the roughness Rz2/Rz1 of the surface layer 2c to be below 1.40 and the value of the roughness density Sm2/Sm1 to be above 0.40. The region surrounded by the boundary lines connecting the points A, E, F and G of
Therefore, where the development roller 2 satisfies the ranges of the formulas 3 and 4 described above, not only the development device 10 including the development roller 2 therein can develop the image with the good print density without occurrence of the fog, but also the image forming apparatus 100 including the development device 10 therein can print the image with the good print density on the sheet without occurrence of the fog. Moreover, the value of the roughness Rz2/Rz1 and the value of the roughness density Sm2/Sm1 of the surface layer 2c of the development roller 2 can be used as control items in a course of manufacturing the development roller 2.
According to the embodiment of the present invention, the printer is described as the image forming apparatus 100, but the present invention is not limited thereto and can be applied to an image forming apparatus such as a multi-functional peripheral (MFP), a facsimile and a photocopier.
As can be appreciated by those skilled in the art, numerous additional modifications and variation of the present invention are possible in light of the above-described teachings. It is therefore to be understood that, within the scope of the appended claims, the disclosure of this patent specification may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-248075 | Sep 2007 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7078143 | Hashimoto et al. | Jul 2006 | B2 |
| 20050226659 | Ebe | Oct 2005 | A1 |
| 20060198664 | Ebe | Sep 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 07-319287 | Dec 1995 | JP |
| 2004341511 | Dec 2004 | JP |
| 2006-243358 | Sep 2006 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20090092421 A1 | Apr 2009 | US |
