Patent Application
20080038016
Descriptions will be provided hereinafter for embodiments of the present invention with reference to the drawings.
In
The gap G which is accurately formed between the conductive member 10 and the image carrier 61 is required. For this reason, after the electrical resistance adjusting layer 2 and the gap maintaining members 4 are arranged on the conductive supporter 1, a removing process is applied to the external portion of each of the two members, and the stepped portion 6 is thereby formed thereon. During the removing process, burrs are easy to produce, and the external diameter are easy to partly extend, in parts of the external portion at which the cutting process starts and in the stepped portions 6. In a case where the conductive member 10 in which burrs are produced, and in which parts of the external diameter extend in the joint sections, is fitted to the image carrier 61, these burrs and the extended parts of the external diameter intervene between the conductive member 10 and the image carrier 61. This makes it impossible to keep the accuracy with which the gap G has been formed. Particularly in a case where the external portions respectively of the electrical resistance adjusting layer 2 and the gap maintaining members 4 and 4 are cut and ground with a cutting tool for the processing, it is likely that the workpieces change in shape due to the process resistance (elastically deformation), and that the deformed portions return to their original shape, and protrude, after the process. Furthermore, due to the process resistance, chips tend to adhere to, and burrs tend to be produced in, the parts at which the process starts. In addition, while the stepped portion 6 provided in the joint section 5 between the electrical resistance adjusting layer 2 and each of the gap maintaining members 4 and 4 is being processed, the tools are moved axially toward the center portion of the external portion the electrical resistance adjusting layer. This process imposes a heavier load on the workpieces. Accordingly, burrs are easy to produce in the workpieces while chips are easy to adhere thereto. Moreover, if a material of the gap maintaining members 4 and 4 is different from that of the electrical resistance adjusting layer 2, the processing of the junction section 5 between the electrical resistance adjusting layer 2 and each of the gap maintaining members 4 and 4 is apt to produce burrs, and to make chips adhere thereto. Additionally, the processing of the different materials affects the degree of deterioration, and the life, of each of the tools and whetstone.
However, In addition, the stepped portion 6 is formed in the end portion of each of the gap maintaining members 4 and 4 which are adjacent to the electrical resistance adjusting layer 2 with the joint section placed in the middle of the stepped portion 6. In the stepped portion 6, the taper 7 or the chamfer 8 is formed so as to be continuously inclined from the end portion of each of the gap maintaining members 4 and 4 to the outer surface of the electrical resistance adjusting layer 2. The foregoing configuration and formation make it possible to stably maintain the gap G between the image carrier 61 and the conductive member 10, and to evenly charge the surface of the image carrier 61, even though the conductive member 10 is used for a long period of time. This makes it possible to enhance the durability of the conductive member 10. Furthermore, the foregoing configuration and formation make it possible to reduce the amount of burrs which would otherwise be produced in, parts of the external diameter which would otherwise extend in, and the amount of chips which would otherwise adhere to, the stepped portion 6 while the stepped portion 6 is being processed. Moreover, the foregoing configuration and formation make it possible to provide the conductive member 10 capable of suppressing reduction of the life of each tool used for the removing processes.
It is desirable that a resin material used to form the gap maintaining members 4 and 4 should be a material with a lower water absorption property and a lower abrasion resistance property, because the gap G is formed between the conductive member 10 and the image carrier 61 such that the gap G can be stable for a longer period of time. In addition, it is important that the resin material used to form the gap maintaining member 4 and 4 should be a material which makes it less likely that the toner and toner additives to stick thereto, and a material which does not wear down the image carrier 61. Such a resin material is selected depending on various conditions whenever deemed necessary. Preferable examples of such a resin material includes: general-purpose resins such as polyethylene (PE), polypropylene (PP), polymethylmetacrylate (PMMA), polystyrene (PS) and polystyrene copolymers (AS and ABS); polycarbonate (PC); urethane; and fluorine.
The gap maintaining members 4 and 4 are fixed to the conductive supporter 1 with an adhesive by applying the adhesive thereto for the purpose of securing the fixing. It is desirable that the gap maintaining members 4 and 4 should be made of an insulating material, and that the value of resistance thereof should be not less than 1013 Ωcm in specific volume resistance. The reason why the gap maintaining members 4 an 4 need to have the insulating property is to prevent occurrence of a leakage current between the image carrier 61 and each of the gap maintaining members 4 and 4. The gap maintaining members 4 and 4 are formed by molding process.
In the case of the present invention, it is desirable that the specific volume resistance of the electrical resistance adjusting layer 2 should be not smaller than 106, but not larger than 109 Ωcm. If the specific volume resistance of the electrical resistance adjusting layer 2 is larger than 109 Ωcm, the larger resistance makes the charging and transferring capabilities of the electrical resistance adjusting layer 2 smaller than necessary. Furthermore, if the specific volume resistance of the electrical resistance adjusting layer 2 is smaller than 106 Ωcm, the smaller resistance causes electrical discharge from the electrical resistance adjusting layer 2 to the image carrier 61. However, if the specific volume resistance of the electrical resistance adjusting layer 2 is 106 to 109 Ωcm, the resistance makes it possible to secure a sufficient charging and transferring properties. Concurrently, the resistance makes it possible to prevent the occurrence of the discharge from the electrical resistance adjusting layer 2 to the image carrier 61, and to accordingly obtain an even image.
No specific restriction is imposed on the materials used to form the electrical resistance adjusting layer 2. Examples of the material include: resins such as polyethylene (PE), polypropylene (PP), polymethylmetacrylate (PMMA), polystyrene (PS) and polystyrene copolymers (AS and ABS); and thermoplastic resins such as polycarbonate (PC), polyurethane (PU) and a fluororesin. These resins are desirable, because they have better processabilities. It is desirable that a polymeric ion conductive agent to be dispersed in such a resin should be a polymeric compound containing one of polyether ester amides. Polyether ester amides are polymeric materials each with ion conductivity, and are evenly dispersed and fixed in a matrix polymer at the molecular level. For this reason, a composition obtained by dispersing the conductive agent containing a polyether ester amide in the foregoing resin do not vary the electrical resistance value, which would otherwise vary due to an inadequate kneading the mixture of the materials by use of a biaxial kneader, another type of kneader or the like. The electrical resistance adjusting layer 2 is formed on the conductive supporter 1 by coating the conductive supporter 1 with the semiconductor resin composition by use of extrusion molding means, injection molding means or the like. In addition, a needed accuracy of the surface of the electrical resistance adjusting layer 2 is capable of being obtained through a process of cutting or grinding the surface in an arbitrary step.
When the conductive member 10 is configured so as to form only the electrical resistance adjusting layer 2 on the conductive supporter 1, the performance is deteriorated through adherence of the toner or the like to the surface of the electrical resistance adjusting member 2 in some cases. However, the forming of a surface layer 3 on the electrical resistance adjusting layer 2 makes it possible to prevent such a trouble from occurring. In the case of the present invention, it is preferable that the specific volume resistance of the surface layer 3 should be set larger than that of the electrical resistance adjusting layer 2. If the specific volume resistance of the surface layer 3 is set larger than that of the electrical resistance adjusting layer 2 in this manner, this setting makes it possible to prevent abnormal discharge from occurring due to a voltage concentrated on defective parts in the photoconductor. If, however, the specific volume resistance of the surface layer 3 is set too high, this setting makes the charging and transferring capabilities of the electrical resistance adjusting layer 2 smaller than necessary. For this reason, it is desirable that the difference in electric resistance dispersion, unlike a composition obtained by dispersing a conductive agent, such as a metallic oxide and carbon blacks. In addition, bleedout is hard to occur because polyether ester amides are polymeric materials. In order to set the electrical resistance value at a predetermined value, it is desirable that the amount of a thermoplastic resin to be mixed should be 20 to 70% by weight, and that the amount of a polymeric ion conductive agent to be mixed should be 80 to 20% by weight.
An electrolyte (electrolytic salt) may be added thereto for the purpose of adjusting the resistance value. Examples of the electrolytic salt include: alkali metal salts such as sodium perchlorate and lithium perchlorate; quaternary phosphonium salts such as ethyltriphenyl phosphonium-tetrafluoroborate and tetraphenyl phosphonium-bromide. A conductive agent may be used solely, or multiple conductive agents may be used by blending, as long as such a use does not deteriorate the properties. For the purpose of evenly dispersing the conductive agent(s) in the matrix polymer, the conductive agent(s) may be micro-dispersed therein by adding a compatibilizer in the matrix polymer whenever deemed necessary. Examples of the compatibilizer include what contains a glycidyl methacrylate group as a reaction group. Additives such as antioxidants may be used as long as such a use does not deteriorate the properties.
The resin composition constituting the electrical resistance adjusting layer 2 is capable of being easily produced by melting and value between the surface layer 3 and the electrical resistance adjusting layer 2 should be not larger than 103 Ωcm. It is preferable that a material used to form the surface layer 3 should be a resin such as a fluoride-based resin, a silicone-based resin, polyamide resin or polyester resin. Because these resins have a better non-adhesive property, it is desirable that these resins should be used from the viewpoint of preventing the toner from adhering to the surface layer 3. Furthermore, because these resins are electrically insulating, the dispersing of conductive agents in any one of these resins makes it possible to adjust the electrical resistance of the surface layer 3. The surface layer 3 is formed on the electrical resistance adjusting layer 2 in the following manner. First of all, a resin material used to form the surface layer 3 is dissolved in an organic solvent. Thereby, a coating is produced. The electrical resistance adjusting layer 2 is coated with this coating by spray coating, dipping, roll coating or the like. It is desirable that the surface layer 3 should be 10 to 30 μm in thickness.
Any one of a single type or a binary type of liquid coating may be used as a coating used to form the surface layer 3. If a binary type of liquid coating in which a curing agent is used along with a base agent is employed, this employment makes it possible to enhance the environmental resistance, non-adhesive property, and mold release property of the surface layer 3. In a case where the binary type of liquid coating is employed, a general practice is to heat the coated film, thereby crosslinking and hardening the resin constituting the coated film. However, the coated film can not be heated at a high temperature, because the electrical resistance adjusting layer 2 is formed of the thermoplastic resin. For this reason, used is a binary type of liquid coating which is made of a base agent containing a hydroxyl group in its molecule along with an isocyanate-based resin allowing a crosslinking reaction and curing reaction to take place at a relatively low temperature of not higher than 100° C. Examples of such isoyanate-based resin include polyisocyanate resins. Specific examples of the polyisocyanate resins include 2, 4-tolylene diisocyanate, diphenylmethane-4, 4′-diisocyanate, a xylylene diisocyanate, an isophorone diisocyanate, lysine methyl ester diisocyanate, methyl cyclohexyl diisocyanate, trimethyl hexamethylene diisocyanate, a hexamethylene diisocyanate, n-pentane (1), 4-diisocyanate, their trimers, their adducts, their burettes, their polymers having two or more isocyanate groups, and blocked isocyanate. However, polyisocyanate resins to be used are not limited to these examples. With regard to the amounts of ingredients mixed in the curing agent, the equivalent weight ratio of the curing agent to the functional group (—OH group) is within a range of 0.1:1 to 5:1, preferably within a range of 0.5:1 to 1.5:1. In addition, a curing agent made of an amino resin such as a melamine resin or a guanamine resin may be used depending on the heat resisting properties of the base material whenever deemed necessary.
What is an important factor of the conductive member 10 is its electrical characteristic. It is necessary that the surface layer 3 should be conductive. The conductivity of the surface layer 3 is formed by dispersing a conductive agent in the resin material used to form the surface layer 3. No specific restriction is imposed on the conductive agent. Examples of the conductive agent include: conductive carbons such as a Ketjen black EC and an acetylene black; carbons for rubber such as SAF (Super Abrasion Furnace), ISAF (Intermediate SAF), HAF (High Abrasion Furnace), FEF (Fast Extruding Furnace), GPF (General Purpose Furnace), SRF (Semi-Reinforcing Furnace), FT (Fine Thermal), MT (Medium Thermal); carbons for color to which an oxidation treatment or the like has been applied; pyrolytic carbon; tin oxide doped with indium (ITO); metal single bodies such as copper, silver and germanium; metal oxides such as tin oxide, titanium oxide and zinc oxide; and conductive polymers such as polyaniline, polypyrrole and polyacetylene. As the conductivity-imparting agents, there may be used ionic conductive agents. Examples of the ionic conductive agents include: inorganic ionic conductive substances such as sodium pechlorate, lithium perchlorate, calcium perchlorate and lithium chloride; and organic ionic conductive substances such as aliphatic acid-modified dimethylammonium ethosulfate, ammonium stearate acetate, lauryl ammonium acetate. The conductive agents may be used singly or in combination by blending, as long as such a use does not deteriorate the properties. The conductive agents can be dispersed in the resin material by use of a publicly-known method using a dispersing medium such as glass beads or zirconia beads in a ball mill, paint shaker or beads mill.
The taper 7 and the chamfer 8 in each of the stepped portion 6 are formed by the removing process such as the cutting process and the grinding process, as shown in
In the case of the present invention, an external portion starts to be cut in the end surface of a first one of the gap maintaining members 4, as shown in
In the case of this type of cutting process, the smaller the nose R is made, the more accurately the above-described chamfering process can be performed. It is apprehended, however, that the faster the feeding speed of the cutting tool is set, the larger the roughness Rz of the processed surface becomes. For this reason, in a case where the roughness Rz of the processed surface in the electrical resistance adjusting layer 2 needs to be at a level of not larger than 5 μm, it is necessary that the nose R should be not smaller than 2, or that the nose R should be not larger than 1 while the feeding speed should be decreased to 0.1 mm/rev. It is preferable that the cutting process should be performed with a NC (Numeric Control) program. Preferably, conditions for the cutting process are (1) that a cutting tool to be used should be a diamond point tool (sintered diamond/grain size, #1600/nose, R=3/clearance angle, 3°/rake angle, 30°), and (2) that the process should be performed with the process conditions (number of revolutions, 3000 rpm/cutting margin, φ0.8/feeding speed of the cutting tool, 0.2 mm/rev).
It is preferable that the chamfer 8 should be that convex outward or inward. If the chamfer 8 is that convex outward or inward as described above, this makes it possible to relax the stress concentrated on a portion in which the image carrier 61 abuts on each of the outer diameter stepped portions 6, and to accordingly enhance the durability. The curvature radius R of the chamfer is not larger than 50 μm if the step of each of the stepped portions 6 is at a level of 100 μm. If, however, the step of each of the stepped portions 6 is not larger than 50 μm, this makes it impossible to perform the chamfering process due to its processing accuracy (resolution). For this reason, it is desirable that the chamfering process should be applied thereto when the step of each of the stepped portions 6 is larger than that.
In the case of the present invention, the conductive member 10 is a charging roller. If a conductive member is used as the charging roller in this manner, this makes it possible to prevent the charging roll from becoming unclean or the like. Concurrently, the forming of the charging roller of a hard material makes it possible to construct the charging roller with high accuracy, and to accordingly prevent the image carrier 61 from being unevenly charged.
No specific restriction is imposed on the form of the conductive member (charging roller) 10 according to an example of the present invention. The conductive member (charging roller) 10 may be arranged and fixed there in the shape of a belt, blade (plate) or semicircular column. In addition, the conductive member (charging roller) 10 may be formed in the shape of a column, and the two ends thereof may be thus rotatably supported by gears or bearings, respectively. If the conductive agent (charging roller) 10 is formed including curved surfaces which gradually become distant away from the respective portions closest to the image carrier 61 in a direction in which the image carrier 61 rotates, this makes it possible to charge the image carrier 61 evenly. If there exists a pointed portion on the conductive member (charging roller) 10 facing to the image carrier 61, the electrical potential of the pointed portion is higher than any other portion thereon so that an electrical discharge starts at the pointed portion earlier than at any other portion thereon. This discharge makes it difficult to evenly charge the image carrier 61. For this reason, in the case of the present invention, the conductive member (charging roller) 10 is cylindrical. In the case where the conductive member (charging roller) 10 is cylindrical, this makes it possible to cause the conductive member 10 to be driven to rotate, and to accordingly prevent the electrical discharge from continuing in the single portion. This prevention makes it possible to reduce chemical deterioration of the surface which would otherwise take place due to the continuous electrical discharge in the single portion, and to accordingly extend the life (durable period) of the conductive member (charging roller) 10.
Furthermore, the charging device 100 includes a voltage supply (not illustrated) for applying a voltage to the conductive member (charging roller) 10. The applied voltage may be only a DC voltage. It is desirable, however, that the applied voltage should be a voltage obtained by superimposing a DC voltage and an AD voltage on each other (hereinafter referred to as a “superimposed voltage”). If only the DC voltage is applied to the conductive member (charging roller) 10 in a case where the layer formation of the conductive member (charging roller) 10 is partially uneven, the electrical potential of the surface of the image carrier 61 is uneven in some cases. On the other hand, in the case where the superimposed voltage is applied to the conductive member (charging roller) 10, the electrical potential of the surface of the conductive member (charging roller) 10 is even. This stabilizes the electrical discharge, and accordingly makes it possible to charge the image carrier 61 evenly. It is desirable that the interpeak voltage of the AC voltage in the superimposed voltage should be set more than twice as large as a voltage with which the image carrier 61 starts to be charged. In this respect, the voltage with which the image carrier 61 starts to be charged means an absolute value of a voltage which is applied to the image carrier 61 when the image carrier 61 starts to be electrically charged. Once the image carrier 61 is electrically charged, a reverse discharge takes place from the image carrier 61 to the conductive member (charging roller) 10. A smoothing effect of the reverse discharge makes it possible to evenly charge the image carrier 61 in a more stable condition. Moreover, it is desirable that the frequency of the AD voltage should be set more than 7 times as large as the circumferential speed of the image carrier 61. If the frequency of the AD voltage is set more than 7 times as large as the circumferential speed of the image carrier 61, this makes it possible to eliminate an image with moiré interference patterns.
As shown in
The gap G between the conductive member (charging roller) 10 and the image carrier 61 is set to be not more than 100 μm in clearance, particularly within a range of approximately 5 to 70 μm in clearance. This setting makes it possible to check an image from being deteriorated when the charging device 100 operates. In a case where the gap G is more than 100 μm in clearance, the voltage with which the discharge starts in accordance with Paschen's law becomes larger so that corona products such as ozone and NOx are produced in a larger amount when the image carrier 61 is charged to a predetermined extent. These corona products remain in a large amount in the discharge space after an image is formed, and thus adhere to the surface of the image carrier 61, accordingly oxidize the surface of the image carrier 61. This is a cause of accelerating deterioration of the image carrier 61 with time. On the other hand, in a case where the gap G is smaller, the image carrier 61 is capable of being charged by use of a smaller discharged energy. However, in the case where the gap G is smaller, this worsens the air flow so that corona products produced in the discharge space remain in the discharge space after an image is formed. For this reason, the corona products adhere to the surface of the image carrier 61, and are accordingly a cause of accelerating deterioration of the image carrier 61 with time, in common with the case where the gap G is larger. With this taken into consideration, it is preferable that the gap G should have a clearance which makes the discharged energy small enough for the corona products to be produced in a smaller amount, and which concurrently causes the air not to remain there. For instance, it is preferable that the gap G be set not larger than 100 μm in clearance, particularly within a range of 5 to 70 μm in clearance. This setting makes it possible to prevent an image from being deteriorated due to the generation of the corona products.
Part of the toner which remains in the surface of the image carrier 61 after the toner image is transferred to the recording medium is removed by a cleaning device 64 (see
In addition, as shown in
In the case where the process cartridge including the conductive member 10 according to the example of the present invention as described above, this use makes it possible to obtain a stable image quality for a long period of time. In addition, it is easy to replace a used process cartridge with a new one. The process cartridge makes user's maintenance easier.
The exposure device 70 in the image forming apparatus 1 includes a light source (not illustrated). Light L is irradiated on the image carriers 61 charged by the respective charging devices 100, and thus an electrostatic latent image is formed on each of the image carriers 61. The light source may be a lamp such as a fluorescent lamp or a halogen lamp, an LED (light emitting diode), a laser beam from a semiconductor device such as an LD (laser diode), or the like. In this case, the LD is used as the light source. The light L is irradiated in synchronism with the rotational speed of each of the image carriers 61 on a basis of a signal from an image processor, which is not illustrated.
In each of the development devices 63, a toner stored in the development device 63 is transported by supplying rollers to an agitation unit, where the transported toner and a developer are mixed together and agitated. Subsequently, the mixture is transported to an area (development area) opposite to the image carrier 61 above a developer carrier (its illustration is omitted) in the development device 63. The toner, which is charged with a positive or negative polarity, is transferred to the electrostatic latent image on the image carrier 61, followed by a development. The developer may be a developer made of a single magnetic or nonmagnetic ingredient, a developer obtained by using both a magnetic ingredient and a non-magnetic ingredient, or a liquid developer of a wet type.
In each of the primary transfer devices 62, an electric field with a polarity opposite to that of the toner is formed. The developed toner image on each of the image carriers 61 is transferred to the back side of the intermediary transfer body 50. The primary transfer device 62 may be a corona transfer device including a corona charging device such as a corotron or a scorotron, or a transfer device using transfer rollers and transfer brushes, or the like.
Thereafter, in synchronism with a recording medium transported from one of the sheet feeders 21 and 22, each toner image on the back side of the intermediary transfer body 50 is transferred to the recording medium by the secondary transfer device 51. It should be noted that, instead of using the intermediary transfer body 50, the toner image on the surface of each of the image carriers 61 may be directly transferred to the recording medium.
The fixing device 80 fixes each toner image, which is on the recording medium, to the recording medium by heating and pressing. When the recording medium goes between a pair of heating/fixing rollers, the recording medium is heated and pressed, and a binding resin in the toner is fused. Thereby, each toner image is fixed onto the recording medium. The fixing device 80 may be that of a belt type instead of that of the roller type. Otherwise, the fixing device 80 may be that of a type which fixes toner images to a recording medium through thermal irradiation by using a halogen lamp or the like.
The cleaning device 64 for each of the image carriers 61 removes part of the toner which has not been transferred to the recording medium, and which accordingly remains on the image carrier 61. Thereby, the cleaning device 64 enables a new toner image to be formed. The cleaning device 64 may be of a blade type which uses rubber made of urethane or the like, or of fur brush type which uses fibers made of polyester or the like.
Descriptions will be provided for how the image forming apparatus 1 operates according to the example of the present invention. First of all, an operator sets an original on an original table in a reading section 30. Otherwise, the operator opens an original transporting unit 36 in the reading section 30, sets an original on a contact glass 31, closes the original transporting unit 36, and thereby presses down the original. Once the operator pushes the start switch, which is not illustrate, the original is transported to the top of the contact glass 31 in the case where the original has been set in the original transporting unit 36. On the other hand, in the case where the original has been set on the contact glass 31, a first reading carriage 32 and a second reading carriage 33 start to run immediately. A light source provided to the first reading carriage 32 is lit, and light is irradiated on the original. Light reflected off the surface of the original is guided to an image forming lens 34 via the second reading carriage 33. Thereby, an image representing the original is formed on a CCD (Charge-Coupled Device) 35, which is a reading sensor. Information on the image which is read by the CCD 35 is transferred to a control unit, which is not illustrated. On the basis of the information on the image which the control unit receives from the reading section 30, the control unit controls a light source (not illustrated) placed in the exposure device 70 in an image forming section 60, and thereby directs the light source to a corresponding one of the image carriers 61, hence causing the light source to irradiate light L on the image carrier 61 (see
A developer to which the toner adheres due to an electrostatic force is attracted to, and held in, a corresponding one of the development devices 63. Thereby, what is termed as a magnetic brush is formed on the developer carrier 65. A development bias voltage applied to the developer carrier 65 transfers the developer, to which the toner has been adhered, to the image carrier 61. By this, the electrostatic latent image which has been formed on the surface of the image carrier 61 is visualized. Thus, a toner image is formed. The development bias voltage is that obtained by superimposing the AC voltage and the DC voltage.
Subsequently, the intermediary transfer body 50 is transported by a drive motor (not illustrated) and supporting rollers 66. Simultaneously, in the image forming units corresponding respectively to the black, yellow, magenta and cyan colors, the corresponding image carriers 61 are rotated. Thus, black, yellow, magenta and cyan toner images are formed on the respective image carriers 61. Afterward, the resist rollers 23 transport the intermediary transfer body 50 once again. Thereby, the toner images representing the respective colors are sequentially transferred to the intermediary transfer body 50. Accordingly, a superimposed toner image is formed.
On the other hand, in a sheet feeding section 20, recording media are fed one-by-one from one of multiple sheet feeding cassettes 21 by a corresponding set of transportation rollers and separation rollers 22, and the recording media thus fed are sent out to a sheet feeding channel in the image forming section 60. The image forming apparatus 1 is designed in order that sheets can also be fed by what is termed as a manual sheet feeding mechanism instead of by this sheet feeding section 20. A manual sheet feeding tray (not illustrated) for manual sheet feeding as well as transportation rollers and separation rollers (none of the rollers are illustrated) for separating recording media on the manual sheet feeding tray one-by-one and transporting them to a manual sheet feeding channel is also provided to a side surface of the apparatus. A recording medium fed from one of the sheet feeding cassettes 21 is once stopped from being transported, and thus the position of the recording medium is corrected, by the resist rollers 23. Thereafter, the resist rollers 23 rotates to the position of the superimposed toner image on the intermediary transfer body 50 by causing the rotational timing of the resist rollers 23 corresponding to the rotational timing of the intermediary transfer body 50. Thus, the recording medium is sent to a secondary transfer section which is a section where the intermediary transfer body 50 and the secondary transfer device 51 abut on each other. The toner images are transferred to the top of the recording medium by a development bias applied for the secondary transfer and by a pressure produced by the abutment.
The recording medium obtained as a result of the image transfer is transported to the fixing device 80 by a transportation belt in the secondary transfer device 51, and is thus pressed and heated by pressing rollers 81. Thereby, the toner images are fixed to the recording medium. Subsequently, the recording medium is discharged to a copy receiving tray 40 by discharging rollers 41.
The present example has been described focusing mainly on the charging roller embodied by the conductive member 10. The conductive member 10 according to the present invention may be used as development rollers or transfer rollers as long as such use is not against the object of the example of the present invention.
A resin composition was produced by mixing 50% by weight of an ABS resin (DENKA ABS GR-0500 manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) and 50% by weight of polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) together. 5 part by weight of polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (MODIPER CL440-G, NOF Corporation) was mixed into 100 part by weight of the resin composition. Thereafter, a melted and kneaded resin composition was produced by melting and kneading the mixture. This melted and kneaded composition was ejected to a conductive supporter 1 (core shaft) with an external diameter of 10 mm which was made of a nickel-plated sulfur free cutting steel (SUM). Thus, the conductive supporter 1 was coated with the melted and kneaded composition. Thereby, an electrical resistance adjusting layer 2 was formed. Gap maintaining members 4 and 4 each shaped like a ring (having a discontinuous portion in its part), which were made of a high-density polyethylene resin (Novatech PP HY540, manufactured by Japan Polychem Corporation), were arranged in the two end portions of this electrical resistance adjusting layer 2, and thus were fixed to the electrical resistance adjusting layer 2 with an adhesive. Subsequently, as shown in
A resin composition was produced by mixing 50% by weight of an ABS resin (DENKA ABS GR-0500 manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) and 50% by weight of polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) together. 5 part by weight of polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (MODIPER CL440-G, NOF Corporation) was mixed into 100 part by weight of the resin composition. Thereafter, a melted and kneaded resin composition was produced by melting and kneading the mixture. This melted and kneaded composition was ejected to a conductive supporter 1 (core shaft) with an external diameter of 10 mm which was made of a nickel-plated sulfur free cutting steel (SUM). Thus, the conductive supporter 1 was coated with the melted and kneaded composition. Thereby, an electrical-resistance adjusting layer 2 was formed. Gap maintaining members 4 and 4 each shaped like a ring (having a discontinuous portion in its part), which were made of a high-density polyethylene resin (Novatech PP HY540, manufactured by Japan Polychem Corporation), were arranged in the two end portions of this electrical resistance adjusting layer 2, and thus were fixed to the electrical resistance adjusting layer 2 with an adhesive. Subsequently, as shown in
A resin composition was produced by mixing 50% by weight of an ABS resin (DENKA ABS GR-0500 manufactured by Denki Kagaku Kogyo Kabushiki Kaisha) and 50% by weight of polyether ester amide (IRGASTAT P18, manufactured by Ciba Specialty Chemicals) together. 5 part by weight of polycarbonate-glycidyl methacrylate-styrene-acrylonitrile copolymer (MODIPER CL440-G, NOF Corporation) was mixed into 100 part by weight of the resin composition. Thereafter, a melted and kneaded resin composition was produced by melting and kneading the mixture. This melted and kneaded composition was ejected to a conductive supporter 1 (core shaft) with an external diameter of 10 mm which was made of a nickel-plated sulfur free cutting steel (SUM). Thus, the conductive supporter 1 was coated with the melted and kneaded composition. Thereby, an electrical-resistance adjusting layer 2 was formed. Gap maintaining members 4 and 4 each shaped like a ring (having a discontinuous portion in its part), which were made of a high-density polyethylene resin (Novatech PP HY540, manufactured by Japan Polychem Corporation), were arranged in the two end portions of this electrical resistance adjusting layer 2, and thus were fixed to the electrical resistance adjusting layer 2 with an adhesive. Subsequently, as shown in
As a charging roller, each of the conductive members 10 obtained respectively in Example 1, Example 2 and Comparative Example 1 was installed in the image forming apparatus (see
good: not unevenly charged
medium: slightly unevenly charged, but not problematic in practical use
poor: unevenly charged to a large extent
As shown in Table 1, the distance of the gap G was stable, and no uneven discharge was observed, “Before 300K” and “After 300” in each of Examples 1 and 2. In Comparative Example 1, however, even “Before 300K,” damages were observed on the image carrier 61; what looked like burrs were produced in the corner portion in the end portion of each of the gap maintaining members 4; the distance of the gap G between the image carrier 61 and each of the gap maintaining members 4 became uneven and varied to a large extent while the conductive member (charging roller) and the image carrier 61 were rotating; and noise accordingly occurred in an image. In Comparative Example 1, “After 300K,” uneven charge occurred due to an abnormal discharge; and it was observed that the insulating layer came off in the portion in which the image carrier 61 abuts on one of the gap maintaining members 4. One may consider that the phenomena took place because burrs in the corner portion in the end portion of the gap maintaining member 4 damaged the image carrier 61. Furthermore, in Comparative Example 1, there occurred a trouble that, while the stepped portion 6 was being processed, chips entered the interstice between the electrical resistance adjusting layer 2 and each of the gap maintaining members 4 so that the chips adhered around the processed part.
As described above, the conductive member according to the example of the present invention makes it possible to maintain the gap with the certain clearance between the image carrier and the conductive member, to thus charge the surface of the image carrier evenly, and to accordingly enhance the durability, even though used for a long period of time. Furthermore, the conductive member according to the example of the present invention makes it possible to reduce the likelihood that, while the stepped portion is being processed in the joint section between the electrical resistance adjusting layer and each of the gap maintaining members by the removing process, burrs may be produced, parts of the external diameter may extend, and chips may adhere around the processed part. Furthermore, the example of the present invention makes it possible to provide a conductive member capable of suppressing reduction of the life of tools to be used while a removing process is being applied to the conductive member.
In the case of the conductive member according to the example of the present invention, the inclination CL in each of the stepped portions is capable of being formed efficiently with high accuracy because the inclination CL is formed by the removing processes inclusive of the cutting process and the grinding process.
In the case of the conductive member according to the example of the present invention, stress concentration is eased in the section where the image carrier abuts on each of the stepped portions in which the slope is formed because the inclination CL is a taper or a chamfer. This makes it possible to further enhance the durability.
The conductive member according to the example of the present invention is cylindrical so that the conductive member is capable of being driven to rotate. For this reason, the conductive member makes it possible to prevent continuous discharge from a single portion which would otherwise occur, to thus reduce chemical deterioration of the surface of the image carrier which would otherwise occur due to electrification stress, and to accordingly extend the life of the image carrier.
In the case where the conductive member according to the example of the present invention is used as a charging roller, the gap is capable of being maintained with a certain clearance. Thereby, the conductive member makes it possible to prevent an abnormal discharge, to prevent discharging products from being produced, and to prevent a toner from adhering thereto. This makes it possible to prevent the charging roller from being stained and deteriorated.
The process cartridge according to the example of the present invention makes it possible to obtain a stable image quality for a longer period of time, and makes user's maintenance easier. That is because the cartridge includes the conductive member according to the example of the present invention as the charging roller.
The image forming apparatus according to the example of the present invention is more reliable, and makes it possible to obtain a higher image quality. This is because the image forming apparatus uses the process cartridge including the conductive member according to the example of the present invention as the charging roller.
Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-217913 | Aug 2006 | JP | national |
