JP4326930B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In general, in an electrophotographic image forming apparatus, a recording medium on which a toner image is formed is sandwiched between a fixing belt or a pressure roller facing the fixing roller, and the toner image is formed by applying only heat and pressure or pressure. A fixing device for fixing on a recording medium is provided.

  Conventionally, as described above, the recording medium having the toner image fixed at the fixing belt or the nip portion between the fixing roller and the pressure roller is wound around the fixing belt or the fixing roller by the adhesive force of the toner. In this state, there were many cases in which separation occurred due to discharge from the nip portion. On the other hand, during double-sided printing, there is a case where the pressure roller is wound around and the separation is poor.

  As one of the solutions to these separation failures, the recording medium that has been ejected in a state of being wound by bringing the separation claw into contact with the surface of the fixing member such as the fixing belt, the fixing roller, or the pressure roller immediately after the nip exit is forcibly applied. A method of separation has been proposed.

  However, according to the method for forcibly separating the recording medium using such a separation claw, the surface against which the separation claw abuts due to the rotation of the fixing member during operation of the image forming apparatus is abraded over time by contacting the separation claw. As a result, there arises a new problem that scratches (claw marks) are generated on the surface of the fixing member. Such scratches (nail marks) cause image defects.

  Therefore, Patent Document 1 proposes a method for forcibly separating the recording medium discharged in a state of being wound around the surface of the fixing member by using a separation plate instead of the separation claw. The most different point between the separation plate and the separation claw is that the separation claw abuts a plurality of image passing portions on the surface of the fixing member, whereas the separation plate is not in contact with the fixing member at the image passing portion. That's what it means. Therefore, image defects that cause problems with the separation claw do not occur.

Japanese Utility Model Publication No. 05-20071

  By the way, according to the method of forcibly separating the recording medium discharged in a state of being wound around the surface of the fixing member by using the separation plate, the image defect that becomes a problem when the separation claw is used does not occur, but the surface of the fixing member In order to reliably separate the recording medium that is wound around and conveyed, it is necessary to manage the gap between the surface of the fixing member and the tip of the separation plate in units of 0.1 mm.

  As one of the effective means, there is a method of managing the gap of the image passing portion by bringing both end portions of the separation plate outside the image passing range into contact with the fixing member. This can also follow a slight change in the diameter of the fixing member over time, and can more reliably manage the gap as compared with the case where the separation plate is positioned at another location.

  However, when this contact portion shape is processed with the same member as the separation plate, it is considered that sufficient accuracy cannot be obtained in consideration of workability.

  An object of the present invention is to provide a fixing device and an image forming apparatus capable of managing a gap between a separation plate and a surface of a rotating body with high accuracy.

According to a first aspect of the present invention, there is provided a fixing device comprising: a pair of rotating bodies that fix a toner image on a recording medium that passes through a nip portion; and the image after fixing the image that has been discharged around the rotating body. And a medium separating member for separating the recording medium from the rotating body. The medium separating member includes a separating plate for separating the recording medium from the rotating body, and the separating plate on the nip side. And a base member that is formed as a separate member on the base member and abuts against the surface of the rotating body so as to define a distance between the tip of the separating plate and the surface of the rotating body. The abutting members are provided at both ends of the base member, and the distance between the abutting members and the distance from the surface of the rotating body is greater than the abutting members. Preliminary contact with To install the wood.

Therefore, the gap between the separation plate and the surface of the rotator can be managed with high accuracy by configuring the contact member to be brought into contact with the surface of the rotator and the base member holding the separation plate as separate members. . Further, the spare abutting member does not come into contact with the rotating body when the abutting members at both ends are in contact with the surface of the rotating body. When a problem such as narrowing occurs and the abutting members at both ends stop functioning, the abutting against the rotating body is made for the first time. As a result, even when gap management at the contact members at both ends becomes impossible, gap management can be performed with almost no decrease in accuracy.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the holding surface of the separation plate of the base member serves as a reference surface, and the contact member extends from the reference surface to a contact position with respect to the surface of the rotating body. Manage distance only.

  Accordingly, it is possible to reduce the number of stacked dimensions from the base member to the contact member, and it is possible to determine the tip position of the separation plate with higher accuracy.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect , the attachment position of the auxiliary contact member is a central portion of the separation plate.

  Therefore, it is possible to cope with the case where one of the left and right contact members stops functioning, and it is also effective for a change in the diameter of the rotating body (the diameters at both ends are smaller than the diameter at the center).

According to a fourth aspect of the present invention, in the fixing device according to the first or second aspect , the attachment position of the auxiliary contact member is a place outside the passing range of the recording medium.

  Therefore, it is effective without damaging the abutting member on the rotating body within the passing range of the recording medium.

According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the contact member is formed of a material having excellent heat resistance and workability.

  Therefore, a highly accurate processed shape can be obtained, and a contact member that can be used even at high temperatures can be obtained.

According to a sixth aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the shape of the contact portion of the contact member is a curved surface shape.

  Therefore, the rotating body is not scraped over time by the contact member due to the rotation of the rotating body.

According to a seventh aspect of the present invention, in the fixing device according to any one of the first to fifth aspects, the shape of the contact portion of the contact member is a planar shape.

  Therefore, the rotating body is not scraped over time by the contact member due to the rotation of the rotating body.

According to an eighth aspect of the invention, there is provided the fixing device according to any one of the first to seventh aspects, further comprising means for improving slidability at a contact portion between the contact member and the rotating body.

  Therefore, by further improving the slidability at the contact portion between the contact member and the rotating body, the rotating body can be prevented from being damaged, and the rotating body can also rotate smoothly.

According to a ninth aspect of the present invention, there is provided an image forming apparatus for forming a toner image by an electrophotographic method, transferring the formed toner image onto a recording medium, and fixing the toner image transferred onto the recording medium. And a fixing device according to any one of claims 1 to 8 .

  Therefore, this image forming apparatus has the same operation as that of any one of the first to ninth aspects.

According to the first aspect of the present invention, the abutting member to be brought into contact with the surface of the rotating body and the base member for holding the separating plate are configured as separate members, so that the gap between the separating plate and the surface of the rotating body can be accurately determined. Can be managed. Further, the spare abutting member does not come into contact with the rotating body when the abutting members at both ends are in contact with the surface of the rotating body, and the gap is caused by wear of the abutting member and the rotating body. Even when the abutting members at both ends stop functioning due to problems such as narrowing, it is almost impossible even when the gap management at the abutting members at both ends becomes impossible by contacting the rotating body for the first time. Gap management can be performed without reducing accuracy.

  According to the second aspect of the present invention, the number of stacked dimensions from the base member to the contact member can be reduced, and the tip position of the separation plate can be determined with higher accuracy.

According to the third aspect of the present invention, it is possible to cope with either of the right and left contact members not functioning, and to change the diameter of the rotating body (the diameters at both ends are smaller than the diameter at the center). It is also effective against

According to the fourth aspect of the present invention, it is effective without damaging the abutting member on the rotating body within the passing range of the recording medium.

According to the invention of claim 5 , a highly accurate processed shape can be obtained, and a contact member that can be used even at high temperatures can be obtained.

According to the sixth aspect of the present invention, the rotating body is not scraped over time by the contact member due to the rotation of the rotating body.

According to the seventh aspect of the present invention, the surface of the rotating body is not scraped over time by the contact member due to the rotation of the rotating body.

According to the eighth aspect of the present invention, the slidability at the contact portion between the contact member and the rotating body is further increased to prevent the rotating body from being damaged, and the rotating body can also rotate smoothly.

According to the image forming apparatus of the ninth aspect of the invention, the same effect as the invention of any one of the first to eighth aspects can be obtained.

  An embodiment of the present invention will be described with reference to FIGS. In this embodiment, a copying machine is applied as an image forming apparatus.

  Here, FIG. 1 is a sectional view showing the copying machine of the present embodiment. The copying machine 1 according to the present embodiment includes a printer 2 and an image reading device 3 attached to the upper part of the printer 2.

  An image forming unit 4 is provided at a substantially central portion in the printer 2, and this image forming unit 4 is arranged around a drum-shaped photoconductor 5 as an image carrier and an electrophotographic system around the photoconductor 5. The charging device 6, the developing device 7, the transfer device 8, the cleaning device 9, and the like are formed. A toner replenishing device 10 is connected to the developing device 7. In this image forming unit 4, the outer peripheral surface of the photoconductor 5 is charged to a predetermined potential by the charging device 6, and the outer peripheral surface of the charged photoconductor 5 is exposed by the optical writing device 11. An electrostatic latent image is formed on the outer peripheral surface, and toner is supplied from the developing device 7 to the electrostatic latent image, whereby the electrostatic latent image is visualized as a toner image, and the visualized toner image Is transferred onto the recording medium S by the transfer device 8. The toner remaining on the outer peripheral surface of the photosensitive member 5 without being transferred onto the recording medium S during the transfer is removed by the cleaning device 9.

  Below the image forming unit 4 in the printer 2, an upper and lower two-stage paper feed cassette 12 that stores the recording medium S, a manual feed tray 13 that can manually feed the recording medium S, and the like are provided. In the printer 2, the recording medium S fed from the paper feed cassette 12 or the manual feed tray 13 is conveyed toward a paper discharge tray 14 formed in a gap between the printer 2 and the image reading device 3. A conveyance path 15 is formed, and along the conveyance path 15, a conveyance roller 16, a registration roller 17, an image forming unit 4, a fixing device 18, a paper discharge roller 19, and the like are arranged. Further, a reverse conveyance path 20 branched from the conveyance path 15 is provided on the downstream side of the fixing device 18 along the conveyance direction of the recording medium S. The recording medium S that has passed through the fixing device 18 is sent to the reverse conveyance path 20, and the recording medium S is sent to the upstream side of the image forming unit 4 in the reverse direction through the reverse conveyance path 20. The image can be formed on both sides.

  The image reading device 3 sequentially reflects an ADF (automatic document feeder) 21 that automatically feeds a document to be read, a contact glass 22, a light source 23 that illuminates the document reading surface, and reflected light from the document reading surface. A plurality of mirrors 24, an imaging optical lens 25, an image sensor 26 such as a CCD, and the like are provided.

  Next, the fixing device 18 will be described in detail. Here, FIG. 2 is an enlarged cross-sectional view of the fixing device 18. The fixing device 18 includes a fixing member 33 that is a rotating member around which a fixing belt 32 is wound between a rotatable fixing roller 30 and a rotatable heating roller 31, and a pressure roller 34 that is a rotating member. ing. The heating roller 31 is provided with a heating halogen heater 35. In the fixing member 33, the fixing roller 30 is rotationally driven by a drive source (not shown) such as a motor, and the fixing roller 32 is rotated by the rotation of the fixing roller 30, so that the heating roller 31 is driven to rotate. Further, the pressure roller 34 is also driven to rotate by the rotation of the fixing roller 30. With such a configuration, in the fixing device 18, the recording medium S on which the toner image is transferred by the image forming unit 4 passes through the nip portion 36 between the fixing member 33 and the pressure roller 34, and in the process of passing through the recording medium S. Heat and pressure are applied, and the toner image on the recording medium S is fixed to the recording medium S.

  In addition, a medium separating member 40 is disposed on the fixing member 33 side of the fixing device 18 and on the downstream side of the nip portion 36 along the conveyance direction of the recording medium S. Specifically, the medium separating member 40 makes a contact member 44 (see FIG. 3) described later contact the surface of the fixing belt 32 of the fixing member 33. Although not particularly shown, the medium separating member 40 is pressed against the fixing belt 32 by the biasing force of the spring. In general, the medium separating member 40 is fixed when the recording medium S on which the toner image is fixed at the nip portion 36 is discharged while being wound around the surface of the fixing member 33 by the adhesive force of the toner. The recording medium S wound around the surface of the fixing belt 32 is forcibly separated by a separation plate 43 (see FIG. 3) described later.

  Here, the medium separating member 40 will be described in detail. Here, FIG. 3 is an enlarged side view showing the medium separating member 40, and FIG. 4 is a perspective view partially showing the medium separating member 40. The medium separating member 40 is provided so as to be rotatable about the axis of the support shaft 37 by a base member 42 having a fitting portion 41 that is fitted to the support shaft 37 disposed in parallel with the shaft center of the fixing roller 30. It has been. On such a base member 42, a separation plate 43 formed of another member is disposed so as to extend to the nip portion 36 side with respect to the base member 42. In the medium separating member 40, managing the gap between the separating plate 43 and the fixing member 33 is an important issue. In order to manage the gap between the separation plate 43 and the fixing member 33, the base member 42 is provided with a contact member 44 formed of a separate member. That is, the rotation of the base member 42 stops when the contact member 44 abuts against the fixing belt 32, and the position of the separation plate 43 is determined.

  As described above, the gap between the separation plate 43 and the fixing member 33 can be managed with higher accuracy when the contact member 44 and the base member 42 that are in contact with the fixing member 33 are configured as separate members. . However, unless the contact position of the contact member 44 with respect to the fixing member 33 is not devised, the assembly configuration is complicated, and the position accuracy of the tip of the separation plate 43 is difficult to be obtained due to the accumulation of the dimensions of each part. Therefore, in the present embodiment, as shown in FIG. 3, the upper surface of the base member 42 (the holding surface of the separation plate 43) is used as a reference surface, and the distance X ± a from the reference surface to the contact position with the fixing member 33 Only X is managed (X is a distance on the drawing, and a is a dimensional tolerance), and the number of components from the reference position is reduced to facilitate the accuracy of the mounting position. That is, in the present embodiment, the attachment position of the contact member 44 attached to the base member 42 is determined based on the reference surface of the base member 42. As a result, the number of stacked dimensions from the base member 42 to the contact member 44 can be reduced, and the tip position of the separation plate 43 can be determined with higher accuracy. With this configuration, it is possible to reduce the processing steps of the separation plate 43, the configuration from the contact position of the contact member 44 to the tip of the separation plate 43 is simplified, and dimensional tolerances do not stack. As a result, the accuracy can be increased.

  Further, when considering the shape of the contact member 44, if there is an acute angle portion at the contact position with the fixing member 33, the surface of the fixing member 33 is scraped over time as the fixing member 33 rotates. Eventually break. As a preventive measure, it is desirable that the contact portion of the contact member 44 with the fixing member 33 has a curved surface shape as shown in FIG. Note that the contact portion is not limited to the curved shape as shown in FIG. 3, and may be a planar shape as shown in FIG.

  Further, when the apparatus is in operation, the surface of the fixing member 33 becomes a high temperature of 150 ° C. to 180 ° C. in order to fix the unfixed recording medium S. Therefore, the abutting member 44 that abuts on the fixing member 33 is desirably a material having a heat deformation temperature of 150 ° C. or higher, and must be a material that can be processed with high-precision dimensions. Therefore, as the resin material for forming the contact member 44, PC (polycarbonate), PBT (polybutylene terephthalate), PA (polyamide), PPS (polyphenylene sulfide), PAI (polyamideimide), PI (polyimide), PBI ( And a resin material such as polybenzimidazole. Other than the resin, for example, a member obtained by coating fluororubber or silicone rubber with a resin having high slidability such as fluorine may be used.

  Incidentally, the contact member 44 attached to the base member 42 of the medium separation member 40 with high accuracy can manage the gap between the tip of the separation plate 43 and the fixing member 33 with high accuracy in the initial operation. However, problems such as a gap narrowing due to wear of the contact member 44 and the fixing member 33 over time and a change in the diameter of the fixing roller 30 (the diameters at both ends become smaller than the diameter at the central part) occur. It is difficult to keep the gap constant. Therefore, in the present embodiment, as shown in FIG. 6, in addition to the contact members 44 attached to both ends of the base member 42 of the base member 42 of the medium separating member 40, a spare member is provided. By providing a plurality of contact members 45, the above problem is solved. Note that it is sufficient that one or more spare contact members 45 are provided. More specifically, the spare contact member 45 is slightly higher (about 0.1 to 0.25 mm) than the attachment position of the contact member 44 attached to both ends of the base member 42 (from the fixing member 33). If the contact members 44 at both ends are in contact with the fixing member 33, the fixing member 33 is not in contact with the fixing member 33. When the abutting members 44 at both ends stop functioning, the abutting member 33 abuts on the fixing member 33 for the first time. The auxiliary contact member 45 can be attached to the center portion of the base member 42 (separating plate 43) so that the left and right contact members 44 can function even when the fixing member 33 is not functioning. This is also effective for changes in the diameter of the fixing roller 30 (the diameters at both ends are smaller than the diameter at the center). Further, even when the spare contact member 45 is attached to a place outside the center of the base member 42 (separating plate 43) as shown in FIG. Since the belt 32 is effective without damaging the contact member 45, a plurality of spare contact members 45 may be attached. As a result, even when gap management at the contact members 44 at both ends becomes impossible, gap management can be performed with almost no decrease in accuracy.

  Further, by further improving the slidability at the contact portion between the contact members 44 and 45 and the fixing member 33, the fixing member 33 can be prevented from being damaged, and the fixing member 33 can be rotated smoothly. Specifically, the contact members 44 and 45 may be coated with a resin having high slidability such as fluorine, or oil (for example, silicon oil) as a lubricant on the surface of the fixing member 33 at the contact portion. Etc.) or a surface treatment that smoothly contacts the contact portions of the contact members 44 and 45. As for the shapes of the contact members 44 and 45, in addition to the curved surface / planar shape as described above, rollers (roller-shaped members that rotate when contacting and hardly damage the fixing member) It can also be mentioned.

  Further, the medium separation member 40 of the present embodiment has been described with respect to the case where the recording medium S in a state of being wound around the fixing belt 32 by being brought into contact with the fixing belt 32 of the fixing member 33 that is a rotating body is forcibly separated. However, the present invention is not limited to this, and a fixing roller or a pressure roller may be applied as the rotating body. That is, the medium separating member 40 of the present embodiment can be applied to the case of forcibly separating the recording medium S that has been discharged while being wound around a fixing roller or a pressure roller.

1 is a cross-sectional view showing a copying machine according to an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view illustrating a fixing device. It is a side view which expands and shows a medium separation member. It is a perspective view which shows a medium separation member partially. It is a side view which expands and shows the modification of a medium separation member. It is a perspective view which shows a preliminary | backup contact member. It is explanatory drawing which shows the attachment position of a preliminary | backup contact member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Image forming part 18 Fixing device 33, 34 Rotor 36 Nip part 40 Medium separation member 42 Base member 43 Separation plate 44 Contact member 45 Preliminary contact member S Recording medium

Claims (9)

A pair of rotating bodies that fix the toner image on the recording medium that passes through the nip portion, and a medium separation that separates the recording medium after image fixing that has been discharged around the rotating body from the rotating body. In the fixing device, the medium separating member includes a separation plate for separating the recording medium from the rotating body, and a base member that extends and holds the separation plate toward the nip portion side. comprising a contact member which defines the distance between the base member and the separation plate tip by abutting the surface of the rotating member be formed of a separate member on the rotating surface, wherein the contact member is the It is provided at both ends of the base member, respectively, and a spare contact member is installed between the contact members and at a position farther from the surface of the rotating body than the contact member. Characteristic constant Apparatus.   2. The fixing according to claim 1, wherein a holding surface of the separation plate of the base member is used as a reference surface, and the contact member manages only a distance from the reference surface to a contact position with respect to the surface of the rotating body. apparatus. Mounting position of the spare of the abutment member, said a central portion of the separation plate, the fixing device according to claim 1 or 2, wherein the. Mounting position of the spare of the abutment member, said a passing range to become the location of the recording medium, fixing device according to claim 1 or 2, wherein the. The abutment member is formed by a material excellent in heat resistance and workability, fixing device according to any one of claims 1 to 4, wherein the. Wherein the shape of the contact portion of the contact member is a curved shape, that the fixing device according to any one of claims 1 to 5, characterized in. Wherein the shape of the contact portion of the contact member is a planar shape, fixing device according to any one of claims 1 to 5, characterized in. The contact member and the rotating member and the fixing apparatus as claimed in having a means for improving the sliding property, claims 1, characterized in that 7 in abutting locations. The toner image formed by the electrophotographic method, an image forming unit for transferring a formed toner image onto a recording medium, a fixing according to any one of claims 1 to 8 to fix the toner image transferred onto the recording medium And an image forming apparatus.

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