JP5999207B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device of an electrophotographic image forming apparatus that is applied to a copying machine, a facsimile, a printer, or the like and forms an image using toner.

  The developed toner image is transferred to a transfer material by a transfer device, the transfer material is sent to a fixing device using pressure, heat, etc., the toner image is fixed, and the fixed transfer material is discharged out of the apparatus. An image forming apparatus is known. The transfer material onto which the toner image has been transferred does not go directly to the fixing device, but is guided to the fixing nip by a guide member provided at the inlet of the fixing device, and the toner image is fixed by being heated and pressurized. . The guide member is required to stably convey the transfer material between the transfer device and the fixing device, and the shape of the guide member and the electrical characteristics of the surface are important.

  When the sliding friction between the guide member and the transfer material becomes strong, the problem of so-called dust phenomenon occurs in which unfixed toner is scattered by disturbing the holding charge of the transfer material due to frictional charging between the guide member and the transfer material. To do. This is particularly likely to occur when a highly resistant paper type (TP paper, my paper, etc .; see FIG. 33) is used in a low humidity environment. That is, particularly when the tip of the guide member is excessively frictionally charged and the charging potential becomes high, the electric field between the guide member and the fixing roller becomes strong, and discharge (leakage) occurs between the guide member and the fixing roller when entering the transfer material. Occurs, and the toner image is scattered to cause conveyance dust. The guide member is easily triboelectrically charged over time (when about 100 sheets are passed). In addition, when the adhesion amount of a 2C image (red, green, blue, etc.) is large, the image is scattered by a potential difference between the potential of the transfer material and the guide member (for example, the surface potential of the guide member is 0 V). There is a problem of 2C dust. This is because, when the guide member is made of sheet metal and is grounded, the voltage is 0 V. Therefore, the image is scattered due to a potential difference between 0 V and the transfer material. In particular, when the attracting force (contact force) with the transfer material is strong, the image is easily disturbed on the guide member.

  In order to eliminate the above-mentioned problems, the composite sheet of metal powder and ceramic powder and a fluororesin film with a controlled volume resistance value are formed on the sheet passing and conveying member, so that the surface of the sheet passing and conveying member is electrically Techniques for creating a stable transfer material conveyance state in a high and low humidity environment in which the electric characteristics of the transfer material change by controlling the characteristics are disclosed in “Patent Document 1” and “Patent Document 2”. In addition, an elastic sheet and a release / high-slip sheet are laminated on the surface of the transfer material guide portion of the guide member to reduce the impact when the transfer material collides with the transfer material guide portion of the guide member, thereby fixing the image. A technique for preventing image quality degradation is disclosed in “Patent Document 3”. Further, a technique for providing a guide member above the transfer material conveyance path is disclosed in “Patent Document 4”.

However, in the above-described technology, when coating the base material of the guide member for the purpose of controlling the electrical characteristics of the sheet passing and conveying member surfaces to prevent toner dust due to frictional charging of the transfer material, Many processes such as base material processing, quenching, heat drying, cooling, painting, and firing are required, and when applying multiple layers of coating, various conditions such as paint type, painting time, painting speed, angle, etc. There is a problem that the desired electrical characteristics and mechanical characteristics cannot be obtained.
SUMMARY An advantage of some aspects of the invention is that it solves the above-described problems and provides a fixing device including a guide member capable of suppressing the occurrence of a dust phenomenon and an image forming apparatus using the same.

According to a first aspect of the present invention, in the fixing device including a fixing unit that fixes the toner image transferred onto the transfer material by the transfer unit, the fixing device includes a guide member that guides the transfer material to the fixing unit. The member has one or more coating layers on a grounded sheet metal substrate, and the coating layer is formed so that the thickness is gradually reduced from the transfer means side toward the fixing means side. Features.

According to a second aspect of the present invention, in the fixing device according to the first aspect , an electric field generated between the guide member and the fixing unit due to frictional charging between the guide member and the transfer material is 2.32 × 10 ^2. It is characterized by being kV / m or less .

According to a third aspect of the invention, in the fixing device according to claim 1, further characterized by potential than 840V occurring at the tip of the guide member by a frictional electrification between the guide member and the transfer material.

According to a fourth aspect of the present invention, in the fixing device according to the first aspect, a charge amount generated on the coating layer by frictional charging between the guide member and the transfer material is further 3.40 × 10 ⁻⁴ C / m ^2. It is characterized as follows.

According to a fifth aspect of the invention, in the fixing device according to claim 1, further thickness of the coating layer in the plane portion of the guide member is characterized in that it is a 20 to 50 m.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the guide member is further formed so that the fixing side end thereof has a convex shape. And

According to a seventh aspect of the present invention, in the fixing device according to any one of the first to sixth aspects, the guide member is made of sheet metal at least at a portion of 1 to 3 mm from the tip .

According to an eighth aspect of the present invention, in the fixing device according to any one of the first to seventh aspects, the coating layer has a layer thickness of 46 μm or less .

A ninth aspect of the invention is an image forming apparatus including the fixing device according to any one of the first to eighth aspects .

  According to the present invention, the tip configuration and tip shape of the guide member, the electric field from the guide member to the fixing means, the potential on the guide member, the material of the guide member, the layer thickness of the coating layer at the tip of the guide member, the guide member By defining the amount of charge above, the layer thickness of the coating layer on the flat surface of the guide member, and the pinhole diameter formed in the coating layer on the guide member, the occurrence of the Chile phenomenon is prevented and good image formation is achieved. Can be done continuously.

1 is a schematic front view of an image forming apparatus employing an embodiment of the present invention. It is the schematic which shows the tip dust in one Embodiment of this invention. It is the schematic explaining the pinhole dust in one Embodiment of this invention. It is the schematic explaining the pinhole dust in one Embodiment of this invention. It is a figure which shows the relationship between the surface roughness of the base material in one Embodiment of this invention, and a Chile phenomenon incidence rate. It is a table | surface explaining the relationship between the pinhole diameter in one embodiment of this invention, the coating layer thickness, and pinhole dust. It is the schematic explaining the guide member used for one Embodiment of this invention. It is the schematic explaining the guide member used for one Embodiment of this invention. It is the schematic explaining the guide member used for one Embodiment of this invention. It is the schematic explaining the guide member used for one Embodiment of this invention. It is the schematic which shows the front-end | tip shape of the guide member used for one Embodiment of this invention. It is the schematic explaining the application | coating method of the fluororesin layer to the guide member used for one Embodiment of this invention. It is a figure which shows the relationship between the electric potential in the edge part of the guide member used for one Embodiment of this invention, and the number of sheets of a transfer material. It is a table | surface which shows the relationship between the electric potential in the edge part of the guide member used for one Embodiment of this invention, an electric field, and a Chile phenomenon generation | occurrence | production. It is a figure which shows the relationship between the arrangement | positioning position of the guide member used for one Embodiment of this invention, the layer thickness of a coating layer, and a Chile phenomenon generation | occurrence | production. It is the schematic explaining the position from the front-end | tip of the guide member used for one Embodiment of this invention, and the layer thickness of a coating layer. It is the schematic explaining the position from the front-end | tip of the guide member used for one Embodiment of this invention, and the layer thickness of a coating layer. It is a figure which shows the relationship between the electric potential in the edge part of the guide member used for one Embodiment of this invention, an electric field, a guide plate position, and a Chile phenomenon generation | occurrence | production. It is a figure which shows the relationship between the arrangement | positioning position of the guide member used for one Embodiment of this invention, the layer thickness of a coating layer, and a Chile phenomenon generation | occurrence | production. It is a table | surface which shows the relationship between the layer thickness of the coating layer of the guide member in one Embodiment of this invention, an electric potential, an electric field, and generation | occurrence | production of the Chile phenomenon. It is a table | surface which shows the image evaluation result of each side at the time of the image at the time of single-sided paper passing when changing the layer thickness and acceleration condition of the coating layer of the guide member in one Embodiment of this invention. It is the schematic explaining the measurement of the tip layer thickness potential of the guide member in one Embodiment of this invention. It is the schematic explaining the measurement of the tip layer thickness potential of the guide member in one Embodiment of this invention. It is the schematic explaining the measurement of the tip layer thickness potential of the guide member in one Embodiment of this invention. It is the schematic explaining the measurement of the tip layer thickness potential of the guide member in one Embodiment of this invention. It is the schematic which shows the fixing means used for one Embodiment of this invention. It is the schematic which shows the fixing means used for the modification of one Embodiment of this invention. It is the schematic explaining the electric field to the fixing means from the guide member in one Embodiment of this invention. It is an enlarged photograph which shows the pinhole which arose in the guide member in one Embodiment of this invention. It is an enlarged photograph which shows the pinhole which arose in the guide member in one Embodiment of this invention. It is a photograph which shows the guide member in the state without a pinhole in one Embodiment of this invention. It is a photograph which shows the pinhole dust in one Embodiment of this invention. It is a graph which shows the relationship between the surface resistivity in each paper type, and generation | occurrence | production of the Chile phenomenon.

  FIG. 1 shows an image forming apparatus capable of forming a full color image to which an embodiment of the present invention is applied. The image forming apparatus 1 includes an image forming apparatus 2Y that forms a yellow (yellow) image, an image forming apparatus 2M that forms a red (magenta) image, and an image forming apparatus that forms a blue (cyan) image. 2C, an image forming device 2K for forming a black image, and each image forming device 2Y, 2M, 2C, 2K is configured to be detachable from an image forming station provided in the apparatus main body 3. Has been. An optical unit 4 for irradiating the image forming devices 2Y, 2M, 2C, and 2K with laser light is disposed below the image forming devices 2Y, 2M, 2C, and 2K.

  Each of the image forming devices 2Y, 2M, 2C, and 2K has the same configuration, and includes a photosensitive drum 5, and a charging device 6, a cleaning device 7, a developing device 8, and the like disposed around the photosensitive drum 5. The photosensitive drum 5 is attached to and detached from the apparatus main body 3 in the axial direction. Above the image forming devices 2Y, 2M, 2C, and 2K, a toner bottle 29Y that stores yellow toner, a toner bottle 29M that stores red toner, a toner bottle 29C that stores blue toner, and a toner bottle that stores black toner 29K is provided, and the color toners in the toner bottles 29Y, 29M, 29C, and 29K are respectively supplied to the corresponding developing devices 8.

  An intermediate transfer unit 9 is disposed above each image forming device 2Y, 2M, 2C, 2K. The intermediate transfer unit 9 includes a transfer belt 10 that is an intermediate transfer member, four rollers 11, 12, 13, and 14 that support the transfer belt 10 so that the transfer belt 10 can run, and toner of each color formed on the surface of each photosensitive drum 5. Four primary transfer rollers 15 provided corresponding to the image forming devices 2Y, 2M, 2C, and 2K that transfer the image to the transfer belt 10 and the toner image transferred on the transfer belt 10 are transferred to a transfer material. A secondary transfer roller 16 is provided. The secondary transfer roller 16 is configured to be able to contact and separate from the transfer belt 10 by a contact / separation mechanism (not shown). Of the above-described configuration, the transfer belt 10, the roller 11, and the secondary transfer roller 16 constitute a transfer unit 17. In addition to the above-described configuration, the transfer unit 17 includes a biaxial transfer unit 9, a configuration using a transfer roller instead of the transfer belt 10, a configuration using a transfer belt instead of the secondary transfer roller 16, etc. A well-known configuration can be employed.

  The transfer belt 10 has a multi-layer structure in which the base layer is made of a material with little elongation, the surface of the base layer is covered with a material having good smoothness, and the coat layer is formed on the base layer. . Examples of the material for the base layer include a fluororesin, a PVD sheet, and a polyimide resin. Examples of the material of the coat layer constituting the surface include a fluorine resin having good smoothness. Although not shown in the drawing, a detent guide that functions as a detent is provided at the edge of the transfer belt 10. The detent guide is disposed in order to prevent the transfer belt 10 from being biased in the width direction of the transfer material when the transfer belt 10 travels, and the material thereof includes various rubbers such as urethane rubber and silicone rubber. Material is used.

  A paper feeding unit 18 is disposed below the optical unit 4. The sheet feeding unit 18 includes a plurality of sheet feeding trays 19, a manual feed tray 20, a registration roller pair 21, and the like. Each sheet feeding tray 19 feeds a transfer material to be stored toward the registration roller pair 21. The manual feed tray 20 has a roller 22 and a paper feed roller 23 that feeds the placed transfer material toward the registration roller pair 21.

  A fixing device 24 is disposed on the upper right side of the intermediate transfer unit 9. The fixing device 24 includes a fixing roller 25 having an internal heat source and a fixing unit 30 having a pressure roller 26 pressed against the fixing roller 25, and the toner image transferred onto the transfer material by the transfer unit 17. Fix by heat and pressure. The fixing device 24 is provided with a guide member to be described later.

  An image forming operation in the image forming apparatus 1 described above will be described. First, after the photosensitive drum 5 is uniformly charged by the charging device 6 in the first color image forming device 2Y, an electrostatic latent image is formed on the surface of the photosensitive drum 5 by the laser light emitted from the optical unit 4. Is done. The formed electrostatic latent image is visualized by the developing device 8, and a yellow toner image is formed on the surface of the photosensitive drum 5. The yellow toner image formed on the surface of the photosensitive drum 5 is primarily transferred to the transfer belt 10 by the primary transfer roller 15. The photosensitive drum 5 after the primary transfer is cleaned by the cleaning device 7 and is prepared for the next image formation. The residual toner collected by the cleaning device 7 is stored in a waste toner collection bottle (not shown) arranged in the take-out direction of the image forming device 2Y. The waste toner collection bottle is configured to be detachable from the apparatus main body 3 so that it can be replaced when it is full.

  An image forming process similar to that of the image forming device 2Y is performed in each of the image forming devices 2M, 2C, and 2K, and each color toner is provided on the surface of each photosensitive drum 5 provided in each of the image forming devices 2M, 2C, and 2K. Each image is formed. The formed toner images are superposed in the order of yellow, red, blue, and black, and are primarily transferred to the same portion of the transfer belt 10.

  On the other hand, one sheet of transfer material is separated and fed from one of the sheet feeding trays 19 or from the manual feed tray 20 from the sheet feeding unit 18, and this transfer material is subjected to a predetermined timing by a pair of registration rollers 21 and then transferred to the transfer belt. 10 is sent to the transfer means 17 at a timing coincident with the primary transfer image on 10. The transfer material sent to the transfer means 17 is subjected to secondary transfer of the primary transfer image on the transfer belt 10 collectively by the secondary transfer roller 16, and a full color toner image is transferred to the surface. The transfer material onto which the full-color toner image has been transferred is sent to the fixing device 24, where the toner image is fixed by the fixing means 30 of the fixing device 24, and then each image forming device 2Y, 2M, 2C, 2K by the discharge roller pair 27. The sheet is discharged onto a sheet discharge tray 28 provided above.

  Here, the guide member which is a characteristic part of the present invention will be described. As shown in FIG. 1, the guide member 31 is between the transfer unit 17 and the fixing device 24, and in order to guide the transfer material onto which the toner image has been transferred by the transfer unit 17, to the fixing unit 30. It is provided on the entrance side. In this embodiment, a configuration in which the transfer paper is vertically conveyed is adopted, but a configuration in which the transfer paper is horizontally conveyed may be employed. In this embodiment, an intermediate transfer system is used, but a direct transfer system may be used. Further, in the present embodiment, as shown in FIG. 1, the transfer guide plate 32 is provided on the upstream side of the guide member 31 in the transfer material conveyance direction. However, the guide member 31 and the transfer guide plate 32 are integrated with one guide member. A configuration may be used in which the transfer exit guide and the fixing entrance guide are combined. In the following description, a convex guide member is described, but a flat guide member having no convex portion may be used.

First, the dust phenomenon shown in the column “Problems to be solved by the invention”, which occurs when the above-described guide member 31 is used, will be described. In this dust phenomenon, as shown in FIG. 2, a phenomenon that occurs when toner is scattered toward the moving direction of the transfer material is the front dust. When the transfer material is strongly applied to the tip of the guide member, the guide member is triboelectrically charged, and the coating layer at the tip of the guide member is thick (for example, about 140 μm at the maximum), the surface potential is expressed by the following formula: Since it is proportional to the thickness, the surface potential is increased.
V = Qd / (εS) (Equation 1)
V: surface potential on the guide member d: guide member coating layer thickness ε: relative dielectric constant Q: charge amount on the guide member When the surface potential increases, an electric field forward from the guide member 31 toward the fixing unit 30 is generated. Due to the influence of the electric field, dust (conveyance dust) occurs before the toner on the transfer material is scattered forward. Here, the surface potential of the fixing roller 25 is 0 V to 400 V, which is lower than the surface potential of the guide member 31, the potential difference between the guide member 31 and the fixing roller 25 is large, and a high electric field is generated. . In this embodiment, the process linear velocity is 230 mm / sec, the secondary transfer current is 34 μA in the monochromatic mode (Bk or the like), and 50 μA in the color mode.

  In addition, as described in the “Background Art” column, when there is a large amount of adhesion such as a 2C image, a trouble phenomenon of 2C dust is likely to occur. This increases the influence of the electric field and contact force when the amount of adhesion increases. It is because it becomes easy to receive. Since the transfer material first comes into contact with the guide member 31 and the planar portion of the guide member 31 (excluding 1 to 3 mm from the tip), the transfer material is likely to be easily affected by an electric field or the like at the time of contact. The 2C dust is in contact with the 2C dust while the previous dust is affected by the rise in potential at the tip of the guide member charged with the transfer material over time (the potential of the guide member rises when the transfer material rubs). Since the dust phenomenon is affected by the contact force and electric field at the moment, 2C dust is generated from the first sheet while the previous dust is generated over time.

  In a state where the guide member 31 is made of stainless steel and is grounded, a transfer material having a potential is in contact with the guide member having a voltage of 0 V, so that a dust phenomenon is likely to occur, particularly when the amount of adhesion is large. This is because a sudden disturbance of the electric field occurs when the transfer material comes into contact with the guide member 31 of 0V. Accordingly, it is necessary to provide a coating layer capable of maintaining a certain level of surface potential instead of a stainless steel + grounding structure on the flat surface portion of the guide member 31 (excluding 1 to 3 mm from the tip portion), and the minimum layer thickness is 20 μm. It needs to be about.

  Next, pinhole dust will be described. FIG. 3 shows a guide member 31 having a thick coating layer, and FIG. 4 shows a guide member 31 having a thin coating layer. When the coating layer is thick, the surface potential of the coating layer becomes high, and pinholes (deficient holes; often penetrating to the substrate) exist in the coating layer in a state where the surface potential is high (FIG. 29, 30; FIG. 31 shows no pinhole), and the electric field between the substrate and the coating layer becomes stronger, resulting in the occurrence of a dust phenomenon (see FIG. 32) at the pinhole portion. In addition, when the potential of the coating layer is high and the surface roughness of the substrate is rough, the rough portion of the substrate surface acts like a lightning rod and plays a role of concentration of charge leakage, and the dust phenomenon occurs. FIG. 5 shows the results of investigating the relationship between the surface roughness of the base material and the occurrence rate of dust phenomenon (pinhole dust, 2C dust, trailing edge dust). As shown in FIG. 5, it was found that the occurrence rate of the Chile phenomenon is 0 when the surface roughness of the substrate is 10-point average roughness Rz 75 μm or less. For this reason, the surface roughness of the substrate needs to be Rz 75 μm or less.

  On the other hand, when the coating layer is thin, the surface potential of the coating layer is lower than when the coating layer is thick, and the electric field between the substrate and the coating layer is weak as shown in FIG. Therefore, even if there is a pinhole penetrating to the base material, the dust phenomenon does not occur. In addition, the relationship between the pinhole diameter and the dust generation rate when the thickness of the coating layer was changed was investigated. As is apparent from FIG. 6 showing the results of the investigation, it has been found that if the pinhole diameter is 170 μm or less and the coating layer thickness is 40 μm or less, the Chile phenomenon does not occur.

  A specific example of the guide member 31 will be described below. As shown in FIG. 7, the guide member 31 is coated with an insulating coating layer 34 for the purpose of adhering the insulating coating layer 35 to the upper surface of a base 33 made of sheet metal such as aluminum, stainless steel, or iron. A surface having different properties from the base material 33, such as properties such as electrical insulation, non-adhesiveness, acid resistance, slidability, and corrosion prevention, which are properties such as fluororesin Can be laminated. In this example, as the base material 33, a chromate-free electrogalvanized steel sheet made of Nippon Steel whose surface was galvanized for the purpose of corrosion protection was used. The coating layer 34 may be coated with an inorganic material in consideration of conductivity, paintability, and adhesion with the coating layer 35.

  As shown in FIGS. 8 and 9, the base material 33 is grounded, and the occurrence of the dust phenomenon can be prevented by satisfying the above-described electric field, potential, and charge amount. The guide member 31 may be configured to be grounded via a resistor 36 (or varistor) or the like as shown in FIG. 10 as long as the above-described electric field, potential, and charge amount can be satisfied.

At least one or more coating layers are required to be formed on the base material 33. In this embodiment, the coating layers 34 and 35, which are two fluororesin layers, are formed using tetrafluoroethylene resin. Yes. Each of the coating layers 34 and 35 is formed so that the thickness of the flat portion excluding the tip portion is about 10 to 20 μm for the coating layer 34 and about 20 to 30 μm for the coating layer 35 so that the total thickness is 50 μm or less. Yes. The resistance of the fluororesin layer is such that the resistance as the guide member 31 is made to be a resistance in the middle resistance to high resistance region by forming a coating layer on the sheet metal with tetrafluoroethylene resin which is an insulating resistance. On the other hand, it is necessary to reduce the layer thickness of the tip. In the present embodiment, a configuration having two layers of the coating layers 34 and 35 is shown. However, a single layer may be used as long as the layer thickness is thin and the potential is lowered to obtain the above-described electric field, potential, and charge amount. However, it is important to make the electric potential of the tip portion lower than that of the flat portion other than the convex portion 31a (see FIG. 11).

  The coating liquid used in the present embodiment is modified (modified) with Teflon (registered trademark) manufactured by Mitsui DuPont Fluorochemicals for both coating layers 34 and 35. In particular, since the coating layer 34 needs to be bonded to the base material 33, an adhesive component is added and modified. However, other fluororesins may be used as long as the predetermined potential and the layer thickness can be maintained.

  Next, functions of the coating layers 33 and 34 will be described. The fluororesin paint is classified into two types according to function: primer (undercoat, coating layer 34 in the present embodiment) and topcoat (topcoat, coating layer 35 in the present embodiment). The primer component includes an adhesive component and a fluororesin, and serves to bond the base material 33 and the top coat. On the other hand, the top coat is made of the fluororesin itself, and imparts excellent properties of the fluororesin to the substrate 33.

  As shown in FIG. 12, the fluororesin layer is applied by a route indicated by an arrow C from an arbitrary writing position, and the writing position x, excess distance y, pitch, and the like can be arbitrarily set. However, it is necessary to apply so as not to cause cracks on the surface of the coating layer. In addition, it is necessary to pay attention to voids generated when the coating layer is dried, and it is also necessary to control the coating speed so that defects such as pinholes do not occur on the surface. For example, the coating speed may be set to 50 mm / sec to 100 mm / sec, the distance between the coating gun and the base material 33 may be set to 30 to 120 mm, and the air pressure may be set to 0.1 to 0, 4 MPa. Further, if there is no generation of cracks or voids and there is no problem in adhesion to the base material 33, a single layer coating may be used. The processing steps of the guide plate 31 are performed in the order of processing of the base material 33, air baking, one-layer coating, drying, two-layer coating, drying, and baking. Although the firing temperature varies depending on the fluororesin used, firing is generally set at 200 to 300 ° C.

  In the guide member 31 shown in this embodiment, coating layers 34 and 35 made of fluororesin are provided on a base 33 made of sheet metal, and the fluororesin is coated on the mold resin disclosed in “Patent Document 2”. However, the configuration disclosed in “Patent Document 2” has a problem that electric charges are accumulated and charged over time (100 sheets or more). In addition, paragraph number “0018” of “Patent Document 2” has a description that “the holding power is strengthened” and further that “the charge on the surface can be relaxed without harmful effects”. In the case of one transfer sheet, for example, when 100 or more transfer sheets are passed, the guide plate is charged due to the mold resin. On the other hand, since the guide member 31 shown in the present embodiment has a configuration of sheet metal + fluororesin, the guide member 31 is not charged even when paper is passed over time (for example, 100 or more), and stable charging is performed. It is possible to control the state. Further, the guide member disclosed in “Patent Document 4” is located on the upper side of the transfer paper conveyance path and is provided on the lower side of the transfer paper conveyance path shown in the present embodiment (the transfer paper is conveyed while being in contact). ) The structure is different from the guide member 31.

  FIG. 13 shows the experimental results of investigating the relationship between the number of passing sheets of transfer material and the potential at the edge portion of the guide member 31. As shown in FIG. 13, the dust phenomenon occurred when the potential at the edge rose to 2 kV. Further, even if about 160 sheets were passed, the Chile phenomenon did not occur as long as the voltage increased only to 600V. From this, it was found that the dust phenomenon does not occur when the potential at the edge portion of the guide member 31 is set to 600 V or less. Further, when the experiment was continued and the range where the dust phenomenon did not occur was narrowed, the result shown in FIG. 14 was obtained. As shown in FIG. 14, it was finally found that the dust phenomenon does not occur by setting the potential at the edge portion of the guide member 31 to 844 V or less.

The distance between the front end of the guide member 31 and the fixing unit 30 in FIG. 14 is 3.64 mm, and the electric field at this time is 844 V / 3.64 mm = 2.32 × 10 ² kV / m, and at least the electric field is 2.32. If it is 10 ² kV / m or less, the dust phenomenon does not occur. On the other hand, the electric field when the potential at the edge portion of the guide member 31 is 951 V is 951 V / 3.64 mm = 2.61 × 10 ² kV / m. When this level of electric field is reached, the Chile phenomenon occurs.

Further, as described in the lowermost stage of FIG. 14, when the position of the guide member 31 is lowered by 3 mm from the above condition and the distance between the tip of the guide member 31 and the fixing unit 30 is 6.04 mm, 3.31 × 10 ^2. Even in an electric field of kV / m, the occurrence of the dust phenomenon was 1 to 2 of 20 dust particles of Δ level (the protrusion from the line was about 1 mm), which was not perfect. Under this condition, the electric field at which no dust is generated must be at least 2.32 × 10 ² kV / m or less as shown in FIG. Further, the retained charge amount of the guide member 31 is as follows: on the coating layer 35 when the potential on the guide member 31 is −840 V, the vacuum dielectric constant is 8.85 × 10 ⁻¹² , the relative dielectric constant of the fluororesin is 2.1, and the layer thickness is 46 μm. From the charge amount Q = εε0 · S · V / d, abnormal discharge does not occur if it is 3.40 × 10 ⁻⁴ C / m ² or less.

  As shown in FIG. 15, the thickness of the coating layer at the edge portion of the guide member 31 is the position “5” at the tip portion of the guide member 31 (the position indicated by the circle 5 in FIG. 12; about 2 to 3 mm from the end portion). The dust phenomenon occurs when the layer thickness at 50 μm or more. As shown in FIG. 15, when the layer thickness at the position “5” is 46 μm or less, the dust phenomenon does not occur. The convex part in FIG. 15 shows the convex part of the guide member 31 in FIG. 12, and the concave part shows the concave part of the guide member 31 in FIG. The range in which the layer thickness of the coating layer is 46 μm or less needs to be in the range of about 1 to 3 mm, which is the range indicated by symbol b in FIG. 16 or the range indicated by symbol x in FIG. In addition, the part indicated by reference sign c in FIG. 16 or the part indicated by reference sign t2 in FIG. 17 may or may not be coated. Did not occur.

  As described above, the thickness of the coating layer at the edge portion of the guide member 31 is preferably 46 μm or less. However, if only the edge portion (fixing means side tip portion of the guide member 31) is used, the coating thickness is 0 μm. It is good also as a structure which does not have a layer. That is, as long as the potential does not increase, a guide member having a configuration in which coating is not performed may be used, and the layer thickness of the coating layer at the edge portion may be 0 to 46 μm. FIG. 19 shows dust data when the layer thickness of the edge portion is 0 μm. At this time, the range in which the layer thickness is 0 μm is about 3 to 4 mm from the tip edge portion (the sample indicated by the symbol b in FIG. 16 or the sample indicated by the symbol x in FIG. 17 is 3 to 4 mm). .

FIG. 20 shows the result of a more detailed experiment than the experiment shown in FIG. In this experiment, the thickness of the coating layer, the potential, the electric field, and the presence or absence of the occurrence of the dust phenomenon are investigated, and the data are obtained after passing 160 sheets for each condition. From the results shown in FIG. 20, it was found that the Chile phenomenon does not occur when the electric field is 2.32 × 10 ² kV / m or less, the surface potential of the guide member 31 is 844 V or less, and the coating layer thickness is 46 μm or less. . At this time, the thickness distribution of the coating layer in the guide member 31 is a flat distribution as shown in FIG. 16, and a distribution that is inclined so as to become thinner as it approaches the tip as shown in FIG. 17. Also good.

  FIG. 21 shows a comparison test result between the case where the thickness of the coating layer of the guide member 31 is 40 μm and 80 μm, and data when the acceleration condition where the dust phenomenon is likely to occur as the machine side condition is shown. In addition, as conditions, an image when one side is passed, and an image evaluation result of one side and two sides when both sides are passed are shown. Nine kinds of charts were passed, and 20 charts were passed. ○ was good, x was about 5 to 10 dusts as shown in FIG. 2, and Δ was as shown in FIG. It is shown that about 1 to 2 dusts with a slight degree of protrusion of about 1 mm from a straight line are generated. As is apparent from the results shown in FIG. 21, in the default condition, only one triangle was seen on both sides of chart A, but there was no problem with other charts (note that each chart was intentionally described) However, Chart A is a chart of line images only, and is an acceleration condition chart for the Chile phenomenon).

  In the above experiment, the thickness of the coating layer is measured using an eddy current film thickness meter (LZ-200 manufactured by Kett Chemical Co., Ltd.). At the time of measurement, the measuring instrument is calibrated taking into account the thickness of the sheet metal guide member. For example, since the thickness of the sheet metal is thin at the front end portion of the guide member and is thick at the flat portion, the measurement is performed with calibration according to each thickness.

  As shown in FIG. 22, FIG. 23, FIG. 24 and FIG. 25, the tip layer thickness potential is measured by installing a 5 mm square probe (measuring instrument) at a position 2 to 3 mm from the tip of the guide member. The potential was measured with a meter. Since a 5 mm square probe is used as a measuring instrument, a minute electric potential at the tip edge portion of the guide member can be measured, and unlike a normal probe, it can measure up to an area near the fixing means.

FIG. 26 shows a fixing unit 30 used in this embodiment, and FIG. 27 shows a fixing unit 37 that is used in place of the fixing unit 30 and uses a fixing belt. In the fixing unit 30, the fixing roller 25 is a non-conductive material, and foamed silicone rubber is used for the surface layer. The pressure roller 26 has a silicone rubber is a non-conductive material in the middle layer of the roller material (rubber layer), the surface layer has a PFA tube is a conductor, surface resistivity 10 ⁶ or fewer It is configured. In the fixing unit 37, the surface material of the fixing belt is PFA, the material of the intermediate layer which is a rubber layer is silicone rubber, and the base material is polyimide.

  Due to the above configuration, the fixing roller 25 is non-conductive and its surface potential is in the range of about 0 to several hundreds (about 400) V. Since the pressure roller 26 is of a conductive type, its surface potential is approximately 0V. Since the potential is as described above, when the potential of the guide member 31 is high as described above, an electric field is generated from the guide member 31 to the fixing roller 25 as shown in FIG.

  With the above-described configuration, according to the present invention, the tip configuration and tip shape of the guide member, the electric field from the guide member to the fixing means, the potential on the guide member, the material of the guide member, and the coating layer at the tip of the guide member By controlling the thickness, the amount of charge on the guide member, the layer thickness of the coating layer on the flat surface of the guide member, and the pinhole diameter formed in the coating layer on the guide member, it is possible to prevent the occurrence of the dust phenomenon. Image formation can be performed continuously.

  In the above-described embodiment, an example in which a color copying apparatus is used as the image forming apparatus has been described. However, the image forming apparatus to which the present invention can be applied is not limited to this, and other printers, plotters, facsimiles, multifunction peripherals thereof, and the like. The present invention can also be applied to other image forming apparatuses.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 24 Fixing apparatus 30, 37 Fixing means 31 Guide member 33 Base material 34, 35 Coating layer 36 Resistor

JP-A-4-16442 JP 2008-152126 A JP 2007-133046 A JP-A-8-152794

Claims (9)

In a fixing device including fixing means for fixing a toner image transferred onto a transfer material by a transfer means,
A guide member for guiding the transfer material to the fixing unit; the guide member has one or more coating layers on a grounded sheet metal base, and the thickness of the coating layer is the transfer unit; The fixing device is characterized in that the fixing device is gradually thinned from the side toward the fixing unit side. The fixing device according to claim 1.
A fixing device, wherein an electric field generated between the guide member and the fixing unit by frictional charging between the guide member and the transfer material is set to 2.32 × 10 ² kV / m or less. The fixing device according to claim 1.
A fixing device in which a potential generated at a tip of the guide member due to frictional charging between the guide member and the transfer material is 840 V or less. The fixing device according to claim 1.
A fixing device, wherein an amount of charge generated on the coating layer by frictional charging between the guide member and the transfer material is 3.40 × 10 ⁻⁴ C / m ² or less. The fixing device according to claim 1.
The fixing device according to claim 1, wherein a thickness of the coating layer in a flat portion of the guide member is 20 to 50 μm. In the fixing device according to any one of claims 1 to 5,
The fixing device is characterized in that the guide member is formed so that the fixing side end thereof has a convex shape. The fixing device according to any one of claims 1 to 6,
The fixing device according to claim 1, wherein at least a portion of 1 to 3 mm from the tip of the guide member is made of sheet metal. In the fixing device according to any one of claims 1 to 7,
The fixing device, wherein the coating layer has a layer thickness of 46 μm or less.   An image forming apparatus comprising the fixing device according to claim 1.

Images