JP2006044835A - Sheet carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict deterioration of service life of a fixing rotor, in regard to a sheet carrying device for a copying machine, a printer and a facsimile for forming images by an electrophotographic method and an electrostatic recording method. <P>SOLUTION: Abutment area abutting on a fixing roller is increased in response to strength of the pressure to be applied to an abutting member abutting on the fixing roller to disperse the pressure to be concentrically applied to the roller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet conveying apparatus such as a copying machine, a printer, or a facsimile machine that forms an image by an electrophotographic system or an electrostatic recording system.

  FIG. 16 shows a sectional view of a conventional laser beam printer as a representative example. FIG. 17 is a sectional view of a conventional fixing device. An overall configuration and function of the laser beam printer and a fixing device which is one of sheet conveying devices will be described.

  In FIG. 16, a paper feed cassette 20 for loading and storing sheets 19 is mounted at the lower part of the main body of the laser beam printer. The paper feed cassette 20 is configured to be detachable from the main body of the laser beam printer. Reference numeral 21 denotes a paper feed roller that feeds the sheets 19 stacked in the paper feed cassette 20 one by one from the uppermost side. A guide member 22 guides the sheet 19 fed by the paper feed roller 21. The sheet 19 is formed by a pair of conveying rollers 23 and 24 including a pre-registration roller 23 that is a driving conveyance roller and a pre-registration roller 24 that is a driven roller, and a registration roller pair 1 and a registration roller pair 1 and a registration roller 2 It is conveyed to 2. The skew feeding is corrected by the registration roller pair 1 and 2, and the registration roller pair 1 and 2 starts rotating operation at a predetermined timing, and conveys the sheet 19 to the image forming unit.

  A process cartridge 26 is detachably attached to the apparatus main body. The process cartridge 26 is provided with image forming means such as a photosensitive drum 27 and a primary charger 38 and a developing device 39 around the photosensitive drum 27. Reference numeral 28 denotes a laser scanner that scans laser light in accordance with image information, and performs writing (latent image formation) on the photosensitive drum 27. A transfer roller 29 is in pressure contact with the photosensitive drum 27, and a toner image is transferred from the photosensitive drum 27 when the sheet 19 passes between the photosensitive drum 27 and the transfer roller 29.

  A conveyance guide 30 guides the sheet 19 after image transfer to the fixing device 46. The fixing device 46 fixes the toner image transferred to the sheet 19, and includes a fixing roller 31, a pressure roller 32, a fixing discharge upper roller 33, a fixing discharge lower roller 34, and the like. The sheet 19 is sent to the paper discharge roller pair 36 by the conveyance roller pair 35, and is discharged out of the apparatus with the image forming surface of the sheet 19 after image fixing facing down. A sheet discharge tray 37 is formed on the upper surface of the apparatus main body, and stacks and holds sheets 19 discharged outside the apparatus after image fixing.

Next, the fixing device 46 will be described in detail with reference to FIG. The sheet 19 on which the toner image has been transferred by the pair of rotating members including the photosensitive drum 27 and the transfer roller 29 passes through the conveyance guide 30 and is guided to the fixing device 46. The fixing device 46 is provided with an entrance guide 40 on the transfer material carrying side. The sheet 19 guided from the inlet guide 40 is nipped and conveyed by a fixing nip formed between the fixing roller 31 and the pressure roller 32 and heated by a heating body (halogen heater) 41 provided in the fixing roller 31. Then, the unfixed toner image is melt-fixed as a permanently fixed image on the sheet 19 by pressing at the fixing nip. The sheet 19 on which the toner image has been fixed is separated from the fixing roller 31 by a separation claw 43 that comes into contact with the surface of the fixing roller 31 with a predetermined pressing force by a spring 42. The sheet passes through the pair of fixing paper discharge rollers 33 and 34 and is discharged out of the fixing device 46 through the separation upper guide 44 and the separation lower guide 45.
JP 2000-47515

  However, the above conventional configuration has the following problems.

  In a fixing device in which an unfixed toner image is fixed on a sheet by heating and pressing, the sheet is wound around a fixing roller or a pressure roller (hereinafter generally referred to as a fixing roller in [Problems to be Solved by the Invention]). May be caused. The toner image transferred onto the sheet is fixed on the sheet by melting and pressurizing the toner heated by the fixing device. However, the melted toner has viscosity, and when the sheet is nipped and conveyed while being heated and pressed by a pair of fixing rollers, it acts like a glue for attaching the sheet to the fixing roller. When the sheet sticks to the fixing roller, it is wound around the fixing roller as it is, and a jam occurs. The higher the printing rate as in the case of a solid image, the more toner serving as glue is transferred onto the sheet, and the sticking force of the sheet to the fixing roller becomes stronger. As a result, separation is more difficult than a print with a low print rate, and the probability of occurrence of a jam increases.

  In order to prevent such a sheet from being wound around the fixing roller, the fixing device is generally provided with a sheet separating member in many cases. There are various sheet separation configurations, such as those in which the sheet separation member is always in contact with the roller and those with a separation mechanism, but the sheet is reliably separated from the fixing roller without being affected by the type of sheet or sticking strength. Therefore, the roller contact portion of the sheet separating member is processed very sharply.

  Therefore, if excessive stress is applied to the sheet separating member, a sharp contact portion may be stuck in the fixing roller or cause a dent. In particular, when a jam occurs and the sheet breaks into a bellows in the fixing device, or when the user performs an unnatural jam processing operation, an excessive stress is applied to the sheet separating member, and the fixing roller There is a high possibility that a dent will occur.

  In recent years, laser beam printers have been improved in image quality and color, and the opportunity to print not only simple text but also high-printing rates such as photographic images and graphics has increased rapidly. In addition, according to the various usages of users, laser beam printers must handle various media such as thin paper and cardboard, OHT sheets, envelopes, postcards, and glossy paper as quality assurance paper. It's getting on. Thin paper is weak in paper, so when printing at a high printing rate, it is easy to wrap around the fixing roller and difficult to separate.On the other hand, because thick paper is strong in paper, it becomes a sheet separating member when jammed. The applied stress is very large, and it is easy to generate dents on the fixing roller.

  In other words, laser beam printers must be able to withstand even the harsh usage conditions, while users demand various high-spec specifications such as high image quality, high speed, and high durability. When a dent is generated on the surface of the fixing roller, the printed image is disturbed. Furthermore, the effect on the image appears more markedly with high-quality prints such as 600 dpi and 1200 dpi.

  Accordingly, in order to solve the above-described conventional problems, the present invention provides the second and third contact portions for fixing so as not to cause a dent on the fixing roller when excessive stress is applied to the sheet separating member. It is an object of the present invention to provide a fixing device including a sheet separating member that disperses stress applied to the roller and reduces the occurrence of dents on the fixing roller.

  In addition to the fixing device, the sheet includes all sheet conveying devices having the above-described problems and nipping and conveying the sheet and provided with contact members.

  In order to achieve the above object, a sheet conveying apparatus according to the present invention includes a sheet conveying unit that sandwiches and conveys a sheet by a conveying nip composed of two rotating bodies, an abutting member that abuts at least one of the rotating bodies, In the sheet conveying apparatus having an elastic member that causes the contact member to contact the rotating body, the contact member is arranged to contact the rotating body with a predetermined contact pressure by the elastic member. When a pressure equal to or higher than a predetermined contact pressure is applied to the contact member, the contact area of the contact portion increases as the strength of the pressure increases.

  A first contact portion that contacts the rotating body at the predetermined contact pressure; and the first contact that contacts the rotating body when a pressure equal to or higher than the predetermined contact pressure is applied. It has the another contact part different from a part, It is characterized by the above-mentioned.

  In addition, there are a plurality of the contact portions.

  Further, the sheet conveying means is a rotating body pair composed of a fixing roller and a pressure roller for fixing the unfixed toner image formed on the sheet by overheating and pressing.

  Further, the sheet conveying means is a rotating body pair composed of a photosensitive drum for transferring a toner image onto a sheet and a transfer means.

  The contact member may be a sheet separating member that separates the sheet from the rotating body.

  Further, the contact member is a foreign matter removing member that removes foreign matter attached to the surface of the rotating body.

  Further, the contact member is a charge removal member that removes the charge on the surface of the rotating body.

  As described above, according to the present invention, the contact area that contacts the roller can be increased according to the strength of the pressure applied to the contact member, and the pressure applied to the roller can be dispersed. By dispersing the pressure, it is possible to greatly reduce or eliminate the possibility that the contact member will make a dent on the roller or the contact member may be stuck in the worst roller.

  In addition, since the roller can be protected only with a simple shape of the abutting member, there is also a relationship such as considering the space to incorporate special configurations such as increased costs and changes in the shape and arrangement of other parts. Absent.

When the roller is deformed, the image is greatly adversely affected. However, since the deformation of the roller can be greatly reduced or eliminated, a stable and high image can be provided at all times.
Further, since it is possible to prevent a situation in which the roller is deformed due to a sudden impact on the roller and the fixing device must be replaced, it is possible to perform a sufficient function until the fixing device reaches the end of its life.

  Further, although the description has been given using the fixing device as a specific example, the effects described above can be obtained not only in the fixing device but also in all sheet conveying devices including a rotating body having a contact member.

  Exemplary embodiments of the present invention will be described below in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. However, the present invention is not intended to be limited to the following embodiments.

  Further, in the following drawings, the same reference numerals are given to the members described in the drawings used in the description of the prior art and the members similar to the members described in the above-described drawings.

  Examples described below will be described in detail by using a fixing device having a typical configuration of a sheet conveying device according to the present invention.

  First, a first embodiment of a fixing device according to the present invention will be described in detail. FIG. 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 46 denotes a fixing device. The fixing device 46 includes various components such as a sheet conveying unit, a sheet separating unit, and an image fixing unit. Inside the fixing roller 31 and the pressure roller 32, two halogen heaters 41 as heating elements are incorporated in the fixing roller 31 and one in the pressure roller 32, and the fixing roller pair 31 and 32 are heated. It is tuned. Reference numeral 50 denotes a pressure roller stay that rotatably supports the pressure roller 32, and reference numeral 51 denotes a pressure roller stay support shaft that rotatably supports the pressure roller stay. The pressure roller stay 50 is rotatably engaged with the pressure roller stay support shaft 51 by an engaging portion 50a. 55 is a pressure spring that is a compression spring, and 56 is a pressure spring base. The pressure spring 55 is locked to the pressure spring base 56 and presses the pressure portion 50b of the pressure roller stay 50 upward. When the pressure spring 55 pushes the pressure roller stay 50 upward, the pressure roller 32 supported by the pressure roller stay 50 is also pushed upward and pressed against the fixing roller 31. A pair of fixing rollers 31 and 32 and a fixing nip are formed.

  The sheet 19 on which the toner image is transferred by a not-shown photosensitive drum and transfer roller is guided by the entrance guide 40 and guided to the fixing roller pair 31 and 32. The toner image transferred onto the sheet 19 is heated and pressurized as it passes through the fixing nip, and is fixed on the sheet 19. Thereafter, the sheet 19 passes through the pair of fixing discharge rollers 33 and 34, is guided by the separation upper guide 44 and the separation lower guide 45, is sent out of the fixing device 46, and is conveyed to the next process.

  54 is a pressure release lever, and 57 is a rotation support shaft of the pressure release lever. The pressure release lever 54 is rotatably mounted on the rotation support shaft 57, and serves as a switching lever for switching the pressure applied by the pressure roller 32. When printing on media such as envelopes, postcards, and OHT sheets, if the pressure is too strong, the media heated and pressed at the fixing nip may be wrinkled or the media may be severely curled. May occur. In the case of OHT sheets, it is common to change throughput settings on the user's PC or to reduce throughput when printing OHT sheets by means of printer detection. In this case, it is general that the user operates the pressure release lever to reduce the pressure applied at the fixing nip and print. When the user lifts the handle portion 54a upward, the pressure release portion 54b is pushed downward about the rotation support shaft 57 as the rotation center. When the pressure releasing unit 54b pushes down the pressing unit 50b against the pressing force of the pressing spring 55, the space between the fixing roller 31 and the pressing roller 32 spreads, and the pressing force in the fixing nip is reduced. The pressure release lever 54 is locked at a position where the pressure is released by a lock mechanism (not shown). Further, when printing plain paper or thin paper, it is possible to return to a predetermined pressure by pushing down the handle 54a.

  Next, the sheet separation mechanism of the fixing device according to the first embodiment of the present invention will be described in detail. 2 is a detailed view of the sheet separating mechanism of the fixing device according to the first embodiment of the present invention, and FIG. 3 is a side view of the sheet separating mechanism of the fixing device according to the present invention.

  2 and 3, reference numeral 43 denotes a separation claw as a sheet separation member. The separation claw 43 has a contact portion 43a that is in contact with the fixing roller 31, a shaft portion 43b, a hook portion 43c, and a back surface 43d. . 42 is a separation claw spring, and 52 is a hook member. One end of the separation claw spring 42 is hooked on the hook member 52, and the other end is hooked on the hook portion 43c of the separation claw 43. The contact portion 43a is brought into contact with the fixing roller 31 with a predetermined contact pressure. ing. 59 is a separation claw stay, and the separation claw stay 59 has a bend 59a, and the bend 59a is provided with a locking portion 59b and a slope 59c. The separation claw 43 is engaged with the separation claw stay 59 so as to be rotatable about the shaft portion 43b and is in contact with the fixing roller 31 by the shaft portion 43b being seated on the engagement portion 59b.

  In many cases, the sheet 19 on which an image is fixed by being pressed and heated in the fixing nip is wound around the fixing roller 31 as described above. The sheet 19 wound around the fixing roller 31 is peeled off from the fixing roller 31 when the leading end abuts against the contact portion 43a. The sheet 19 separated from the fixing roller 31 is conveyed downstream along the back surface 53b.

  Next, the contact of the sheet separating member of the fixing device according to the first embodiment of the present invention will be described in detail. 4 is a contact view of the sheet separating member of the sheet fixing device according to the first embodiment of the present invention, and FIG. 5 is an enlarged view of the contact of the sheet separating member of the fixing device according to the first embodiment of the present invention. .

  4 and 5, the contact portion 43a is always in contact with the fixing roller 31 with a predetermined contact pressure, and both end portions have end surfaces with curved surfaces. Reference numeral 43e denotes a second contact portion, which is provided at a position where the both ends of the contact portion 43a are lowered by one step, and this also has an end surface with a curved surface.

  Next, a state when a jam occurs in the fixing device according to the first embodiment of the present invention will be described in detail. Here, a case where a bellows jam has occurred in the fixing device 46 will be described. FIG. 6 is a cross-sectional view of the fixing device according to the first embodiment of the present invention when a jam occurs. FIG. 7 is a cross-sectional view of the fixing device according to the first embodiment of the present invention when a jam occurs.

  6 and 7, the sheet 19 that has passed through the fixing roller pair 31 and 32 is not conveyed to the downstream side due to the fixing discharge roller pair 33 and 34, and the sheet 19 is still conveyed by the fixing roller pair 31 and 32. If this is continued, bellows jam will occur in the space between the fixing roller pair 31, 32 and the fixing paper discharge roller pair 33, 34. When the bellows jam occurs, a force is generated by which the sheet 19 presses the separation claw 43 in the upward direction in FIG. 7 or in the fixing roller direction (all in the arrow direction in FIG. 7). When these forces are applied, the separation claw 43 retreats upward along the slope 59c against the pressure applied by the separation claw spring 42.

  Finally, the configuration for increasing the contact pressure of the separation claw of the fixing device according to the first embodiment of the present invention will be described in detail. FIG. 8 is a contact view of the sheet separating member when a jam occurs in the fixing device according to the first embodiment of the present invention, and FIG. 9 is a sheet separating member when a jam occurs in the fixing device according to the first embodiment of the present invention. FIG.

  In FIGS. 8 and 9, the contact portion 43 a bites into the fixing roller 31 when a pressure equal to or higher than a predetermined contact pressure applied to the separation claw 43 by the separation claw spring 42 is applied to the separation claw 43. As the pressure increases, the contact portion 43a deeply bites into the fixing roller 31 to cause a dent. Based on the data accumulated in the examination, the second abutting portion 43e has a certain abutting pressure before the separation claw 43 bites into the fixing roller 31. Contact the fixing roller 31. When the second contact member 43e contacts the fixing roller 31, the load applied concentrated on the fixing roller 31 from the contact portion 43a is dispersed.

  In the first embodiment, the detailed description has been given using the fixing device including the typical configuration requirements of the sheet conveying device according to the present invention. However, the fixing device is not limited to the cleaning blade that contacts the photosensitive drum, and the transfer roller. A neutralizing member that abuts, and a Mylar sheet and a driven roller that abut each roller are also suitable.

  Next, a second embodiment of the fixing device according to the present invention will be described in detail. FIG. 10 is a contact view of the sheet separating member of the fixing device according to the second embodiment of the present invention, and FIG. 11 is an enlarged view of the contact of the sheet separating member of the fixing device according to the second embodiment of the present invention.

  10 and 11, the separation claw 43 is provided with a second contact portion 43e at a position where the contact portion 43a and the contact portion 43a are lowered by one step, and further lower by one step than the second contact portion 43e. The third contact portion 43f is provided at the above-mentioned place. And the end surface process is made | formed at the edge part of each contact part. The separation claw 43 abuts the abutting portion 43a on the fixing roller 31 with a predetermined abutting pressure by a spring member (not shown). Only the contact portion 43a is in contact with the fixing roller 31 during normal operation or normal standby.

  FIG. 12 is a contact view of the second contact portion of the sheet separating member of the fixing device according to the second embodiment of the present invention, and FIG. 13 is a view of the sheet separating member of the fixing device according to the second embodiment of the present invention. FIG. 14 is a contact enlarged view of the third contact portion of the sheet separating member of the fixing device according to the second embodiment of the present invention, and FIG. 15 is a second embodiment of the present invention. FIG. 10 is an enlarged contact view of a third contact portion of the sheet separating member of the fixing device according to the embodiment.

  12, 13, 14, and 15, various stresses may be applied to the separation claw 43 in addition to a predetermined contact pressure. The contact portion of the fixing roller 31, that is, the contact area increases in accordance with the strength of the stress. When a jamming, a user operation, or an unexpected event causes a pressure higher than the predetermined contact pressure to be applied to the separation claw 43, the contact portion 43a bites into the fixing roller 31, and the second contact portion 43e becomes the fixing roller. Increase contact area by contacting 31. Further, when a great amount of pressure is applied to the separation claw 43, the contact portion 43a bites into the fixing roller 31 and the second contact portion 43e also bites into the fixing roller 31. Then, the third contact portion 43f contacts the fixing roller 31.

1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention. FIG. 3 is a detailed view of a sheet separation mechanism of the fixing device according to the first embodiment of the present invention. FIG. 3 is a side view of the sheet separating mechanism of the fixing device according to the first embodiment of the present invention. FIG. 3 is a contact view of a sheet separating member of the fixing device according to the first embodiment of the present invention. FIG. 3 is an enlarged view of contact of a sheet separation member of the fixing device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the fixing device according to the first embodiment when a jam occurs. FIG. 3 is a side view of a sheet separating mechanism when a jam occurs in the fixing device according to the first embodiment of the present invention. FIG. 3 is a contact view of a sheet separating member when a jam occurs in the fixing device according to the first embodiment of the present invention. FIG. 3 is an enlarged view of contact of a sheet separating member when a jam occurs in the fixing device according to the first embodiment of the present invention. FIG. 9 is a contact view of a sheet separating member of a fixing device according to a second embodiment of the present invention. The contact enlarged view of the sheet separation member of the fixing device according to the second embodiment of the present invention. FIG. 9 is a contact view of a second contact portion of a sheet separating member of a fixing device according to a second embodiment of the present invention. The contact enlarged view of the 2nd contact part of the sheet separation member of the fixing device which concerns on 2nd Embodiment of this invention. FIG. 9 is a contact view of a third contact portion of a sheet separating member of a fixing device according to a second embodiment of the present invention. The contact enlarged view of the 3rd contact part of the sheet separation member of the fixing device which concerns on 2nd Embodiment of this invention. Sectional drawing of the conventional laser beam printer as a representative example. Sectional drawing of the conventional fixing device.

Explanation of symbols

19 seats
31 Fixing roller
32 Pressure roller
42 Pressure spring
43 Separating nails
43a Contact part
43b Shaft
43c Hook
43d rear
43e 2nd contact part
43f 3rd contact part
59 Separating claw stay
59a Bending
59b Locking part
59c slope

Claims (9)

A sheet conveying unit configured to nipping and conveying a sheet by a conveyance nip including two rotating bodies; an abutting member that abuts at least one of the rotating bodies; and an elastic member that abuts the abutting member against the rotating body. In the sheet conveying device,
The abutting member is arranged to abut against the rotating body with a predetermined abutting pressure by the elastic member, and when a pressure higher than a predetermined abutting pressure is applied to the abutting member, the strength of the pressure The sheet conveying apparatus is characterized in that the abutting area of the abutting portion increases as the thickness increases.   A first abutting portion that abuts on the rotating body with the predetermined abutting pressure; and a first abutting portion that abuts on the rotating body when a pressure equal to or higher than the predetermined abutting pressure is applied. The sheet conveying apparatus according to claim 1, further comprising different contact portions.   The sheet conveying apparatus according to claim 1, wherein there are a plurality of the contact portions.   4. A rotating body pair comprising a fixing roller and a pressure roller for fixing the unfixed toner image formed on the sheet by overheating and pressing the sheet conveying means. The sheet conveying apparatus according to 1.   4. The sheet conveying apparatus according to claim 1, wherein the sheet conveying unit is a pair of rotating members including a photosensitive drum that transfers a toner image onto the sheet and a transfer unit.   The sheet conveying apparatus according to claim 1, wherein the contact member is a sheet separating member that separates a sheet from the rotating body.   The sheet conveying apparatus according to claim 1, wherein the contact member is a foreign matter removing member that removes foreign matter attached to the surface of the rotating body.   The sheet conveying apparatus according to claim 1, wherein the contact member is a charge eliminating member that removes charge on a surface of the rotating body.   The sheet conveying apparatus according to any one of claims 1 to 8.

Images