JP2012189745A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a separating member for separating transfer material from a fixing member, from damaging the fixing member and to perform fixing to the transfer material having free sizes.SOLUTION: The fixing device makes a recording medium P where an unfixed toner image T is formed pass through a nip part N formed by a fixing roller 110 and a pressure roller 120, and performs fixing. The fixing device comprises: a flexible linear member 140 stretched between a surface of the fixing roller 110 and the recording medium P having passed, along an axis line of the fixing roller 110, for separating the recording medium having been ejected from the nip part N, from the surface of the fixing member; and a pair of support members 130a, 130b which are arranged at both ends of the linear member 140 and support the linear member so as to be swingable following behavior of the fixing roller 110 during conveyance of the recording medium.

Description

  The present invention relates to a fixing device and an image forming apparatus. In particular, the recording medium on which an unfixed toner image is formed is passed through a nip formed by two fixing members, and the unfixed toner image is heated and pressurized. The present invention relates to a fixing device that fixes a toner image on a recording medium and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copying machines and printers that employ an electrophotographic system include a fixing device for fixing a toner image formed on an image carrier to a recording medium. This fixing device includes two rollers that rotate in contact with each other, and also uses an endless fixing belt as a heating side rotating body.

  For example, a fixing device using two rollers includes a fixing roller having a heat source therein, and a pressure roller pressed against the fixing roller by a pressure spring, and between the heating roller and the pressure roller. The toner image carried on the recording medium supplied to the fixing nip is heated and pressurized to fix it on the recording medium.

  FIG. 8 is a schematic view showing a conventional fixing device, and FIG. 9 is a plan view showing the fixing device. The fixing device 6 includes a fixing roller 1 having a heater 2 and a pressure roller 3 that is pressed against and contacts the fixing roller 1. A recording medium P such as a recording sheet on which an unfixed toner image T is formed is heated and pressed to be fixed by passing through a nip portion N formed between the fixing roller 1 and the pressure roller 3. Also, the fixing device is provided with a separation claw 4 that is pressed by a spring 5 so that its tip comes into contact with 1.

  At this time, the fixing roller 1 is heated to a temperature suitable for toner fixing by the heater 2. Thereafter, the recording medium P is separated from the fixing roller 1 by the separation claw 4. There are various types of sizes of the recording medium P, such as A4 landscape feed, A4 portrait feed, A5 portrait feed, and B4 portrait feed. In order to correspond to these paper sizes, as shown in FIG. 9, a plurality of separation claws 4 are provided in the paper passing range in the longitudinal direction.

  In Patent Document 1, it is possible to reliably suppress the adhesion of unfixed toner from the separation claw, prevent occurrence of problems such as recording sheet image fouling, paper jams, and premature fixing roller wear. In order to form stably, the separation claw holding member can be displaced between the contact position where the separation claw contacts the surface of the fixing roller and the non-contact position spaced apart from the surface of the fixing roller by rotating the separation claw holding member. The separation claw holding member is driven by a solenoid so as to be displaced between a contact position and a non-contact position. In the non-contact position, the separation claw holding member contacts the rotating member. In this document, the positioning member is rotated and the rotating member is driven to rotate, and thereby the separation claw holding member and the separation claw are vibrated to remove unfixed toner from the separation claw.

  Further, in Patent Document 2, a fixing separation claw that is pressed against the outer peripheral surface of a heating member in a thermal fixing device is provided, and a claw width of a contact portion that contacts the fixing separation claw heating member is set to 1 mm or less. In other words, even if the toner adhering to the heating member adheres and accumulates on the contact portion and a toner lump is generated, a problem that the image on the recording medium is prevented from being soiled is described.

However, the conventional fixing device described above has the following problems.
(1) Since a separation claw is provided in the sheet passing area, and this separation claw is in contact with the fixing roller, a layer of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) such as fluororesin is formed on the surface of the fixing roller. However, the separation claw wears the PFA layer on the surface of the fixing roller to cause scratches, and the toner on the transfer material is lost due to contact with that portion, resulting in an adverse effect on the image.

(2) There is a need for the user to use a transfer material of any size, but since the position of the separation claw is determined in advance, the size of the transfer material that can be passed through is limited, and other sizes When the paper is passed, separation from the fixing member becomes poor, and there is a possibility that the transfer material may be bent or jammed. On the other hand, the fact that only a transfer material of a predetermined size can be used cannot be said to be sufficient in usability of the image forming apparatus.

  Further, in the device described in Patent Document 1, the separation claw holding member and the separation claw are rotated by a solenoid or the like to contact or separate from the fixing roller. However, during separation, the separation claw contacts the fixing roller. Compared to the case where the separation claw is always in contact with the fixing roller, it may be possible to lengthen the time until the fixing roller is damaged by the shorter contact time, but only the contact and separation are repeated. Thus, it is impossible to completely prevent the fixing roller from being damaged.

  Moreover, since the thing of patent document 2 has set the nail | claw width | variety narrowly, there exists a problem described in said (1).

  The present invention solves such problems, prevents a damage to the fixing member by a separating member for separating the transfer material from the fixing member, and fixes a fixing material and an image forming apparatus capable of fixing a transfer material of any size. The purpose is to provide.

  According to the first aspect of the present invention for solving the above-mentioned problems, a recording medium on which an unfixed toner image is formed is passed through a nip portion formed by two fixing members, and the unfixed toner image is heated and pressurized. In the fixing device for fixing a toner image on a recording medium, the fixing member is disposed between the surface of the fixing member and the recording medium that has passed therethrough in order to separate the recording medium discharged from the nip portion from the surface of the fixing member. A flexible linear member stretched along the axis of the linear member, and arranged at both ends of the linear member, the linear member can be swung following the behavior of the fixing member during conveyance of the recording medium. And a pair of support members that support the fixing device.

  Similarly, a second aspect of the present invention is the fixing device according to the first aspect, wherein the linear member is formed of a metal including a steel wire.

  Similarly, the invention of claim 3 is the fixing device according to claim 1 or 2, wherein the linear member has a long side along the moving direction of the recording medium and a short side perpendicular to the moving direction of the recording medium. It is characterized by having a quadrangular cross section along any direction.

  Similarly, the invention of claim 4 is the fixing device according to any one of claims 1 to 3, further comprising a gap adjusting member that sets a dimension of the gap between the linear member member and the fixing member. It is characterized by.

  Similarly, the invention of claim 5 is the fixing device according to any one of claims 1 to 4, wherein the support member is disposed outside an area in which the recording medium is conveyed. .

  Similarly, the invention of claim 6 is the fixing device according to any one of claims 1 to 5, wherein the support member includes a groove for attaching the linear member.

  Similarly, the invention of claim 7 is an image comprising: the fixing device according to any one of claims 1 to 6; and a toner image forming unit that forms an unfixed toner image on the recording medium. Forming device.

  According to the fixing device and the image forming apparatus according to the present invention, it is possible to prevent the fixing member from being damaged by a separation component for separating the transfer material from the fixing member, and to fix a transfer material of a free size. can do.

1 is a cross-sectional view conceptually showing an image forming apparatus according to an embodiment. It is a side view which similarly shows a fixing device. It is a side view which similarly shows the separation apparatus of a fixing device. It is a side view which similarly shows a separation apparatus. It is a perspective view which similarly shows the support member of a separation apparatus. FIG. 6 is a schematic diagram showing a separated state of the transfer material in the fixing device. It is sectional drawing which shows the linear member and fixing roller which concern on an Example. FIG. 10 is a schematic diagram illustrating a conventional fixing device. It is a top view which similarly shows a fixing device.

  In the fixing device according to the embodiment, a recording medium on which an unfixed toner image is formed is passed through a nip formed by two fixing members, and the toner image is recorded by heating and pressing the unfixed toner image. In order to separate the recording medium discharged from the nip portion from the surface of the fixing member, a fixing device that fixes the toner image between the surface of the fixing member and the recording medium that has passed along the axis of the fixing member. A pair of flexible linear members stretched over and a pair of linear members disposed at both ends of the linear member, and supporting the linear member in a swingable manner following the behavior of the fixing member during conveyance of the recording medium. A support member.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present invention (hereinafter simply referred to as an embodiment) will be described. Several examples are described below, but the present invention is not limited to these examples, and numerous improvements, modifications, variations, substitutions and application examples are possible without departing from the true spirit and scope of the present invention. It will be possible for those skilled in the art to conceive.

  First, an image forming apparatus according to an embodiment will be described. FIG. 1 is a sectional view conceptually showing the image forming apparatus according to the embodiment. The image forming apparatus 10 according to this example includes a reading unit 11 that reads a document, an image forming unit 12 that forms an image, an automatic document feeder (ADF) 13, a document discharge tray 14 that stacks documents sent from the ADF 13, A paper feed unit 19 including paper cassettes 15 to 18 and a paper discharge unit (discharge tray 20) for stacking recording paper are provided.

  In this image forming apparatus 10, when the document D is set on the document table 21 of the ADF 13 and an operation on an operation unit (not shown) is performed, for example, a print key is pressed, the uppermost document D is rotated by the pickup roller 22. The paper is fed in the direction of the arrow B1, and is conveyed onto the contact glass 24 fixed to the image reading unit 11 by the rotation of the original conveying belt 23, and stops there.

  The image of the document D placed on the contact glass 24 is read by a reading device 25 located between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light source 26 that illuminates the document D on the contact glass 24, an optical system 27 that forms an image of the document, a photoelectric conversion element 28 that includes a CCD that forms an image of the document, and the like. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is fed one by one onto the contact glass 24 and the document image is read by the image reading unit 11.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the reading device 25, and the surface of the charged photoreceptor 30 is exposed with the laser beam L, whereby the photoreceptor is exposed. An electrostatic latent image is formed on the surface 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to a recording medium P such as a recording sheet fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  A plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 100 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 100 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

  Next, the fixing device according to the embodiment will be described. FIG. 2 is a side view illustrating the fixing device according to the embodiment. The fixing device 100 separates the fixing roller 110 including a heating unit 111 such as a halogen heater, a pressure roller 120 pressed against the fixing roller 110 with a predetermined force, and the fixed recording medium P from the fixing roller 110. A separation device 150 is provided. The separation device 150 is arranged near the surface of the fixing roller 110, and a linear member 140 to be inserted between the recording medium P and the fixing roller 110 is arranged so as to be stretched between two support members 130a and 130b. .

  3 is a perspective view showing a separation device of the fixing device according to the embodiment, FIG. 4 is a side view showing the separation device, and FIG. 5 is a perspective view showing a support member of the separation device. In the fixing device 100 according to the embodiment, the linear member 140 of the separation device 150 is formed of a steel wire having flexibility. Both ends of the linear member 140 are fixed to two support members 130 a and 130 b fixed to the image forming apparatus 10. Here, FIG. 5 shows only the support member 130a, but the support member 130b has a structure symmetrical to the support member 130a.

  Here, the linear member 140 is arranged such that the cross section is a quadrangle, the long side is generally coincident with the moving direction of the paper, and the short side is generally perpendicular to the moving direction of the paper. Thereby, a cross-sectional area can be made large compared with the member of the other shape which is the same thickness dimension, and intensity | strength can be ensured.

  Each of the support members 130a and 130b includes a columnar arm member 131a and 131b, and rod-shaped swinging members 132a and 132b that are integrally joined to one end (the lower end in FIG. 5) of the arm member 131a and 131b at the center. With. The linear member 140 is fitted into groove portions 135a and 135b formed at one end portions of the swinging members 132a and 132b, and is difficult to come off. The end of the linear member 140 is fixed so that a predetermined tension is applied to the swinging members 132a and 132b via the first springs 141a and 141b. The first springs 141 a and 141 b have one end fixed to the end of the linear member 140 and the other end fixed to the pins 137 a and 137 b of the swinging members 132 a and 132 b, and a predetermined tension is applied to the linear member 140. .

  The support members 130a and 130b are rotatably supported by fixing portions of the fixing device 100 (not shown) through shaft holes 134a and 134b formed in hole forming portions 133a and 133b formed at the centers of the arm members 131a and 131b. The linear member 140 is movably disposed on the fixing roller 110 side. Both support members 130 a and 130 b are arranged on both outer sides of the sheet passing range of the fixing device 100.

  The support members 130a and 130b press the linear member 140 toward the fixing roller 110 with the second springs 142a and 142b. The second springs 142 a and 142 b are attached to pins 136 a and 136 b formed at the ends of the arm members 131 a and 131 b and a fixing portion of the fixing device 100. The first springs 141a and 141b and the second springs 142a and 142b are members having different sizes and constants, but may happen to have the same size and the same spring constant.

  The swing members 132a and 132b of the support members 130a and 130b have gap adjusting members 144a and 144b having a predetermined thickness dimension t so as to cover the grooves 135a and 135b to which the linear member 140 is attached. Be placed. The gap adjusting members 144a and 144b come into contact with the surface of the fixing roller 110 when the support members 130a and 130b are pressed against the fixing roller 110 by the second springs 142a and 142b. Is set to t.

  In FIG. 3, the gap adjusting members 144a and 144b are drawn away from the support members 130a and 130b, but in actuality, they are in close contact with the swinging members 132a and 132b. Therefore, the thickness dimension t of the gap adjusting members 144a and 144b in FIG. 3 determines the distance (gap) between the fixing roller 110 and the arm members 131a and 131b of the support members 130a and 130b. Therefore, when the thickness dimension t of the gap adjusting members 144a and 144b in FIG. 3 is changed, the interval is changed.

  If the dimension t is too small, the separation performance of the recording medium P from the fixing roller 110 will be good, but toner, paper dust, etc. will immediately accumulate between the linear member 140 and the fixing roller 110, and the image The device may not be able to be used due to the influence on the printer, or the paper cannot be passed.

  On the other hand, if the thickness dimension t value is too large, the transfer material with a small thickness may not be separated, and jamming may occur, which is also not convenient. Therefore, it is important to set the thickness of the gap adjusting member appropriately. In the examples, the thickness is about 30 to 50 μm. The thickness t of the gap adjusting member 144a is preferably slightly smaller than the thickness of the thinnest paper that can be passed through the image forming apparatus (usually 40 μm to 60 μm).

  Since the supporting members 130a and 130b are disposed outside the range through which the transfer material passes, the gap adjusting member 144a directly contacts outside the sheet passing range of the fixing roller 110, but the linear member 140 contacts the fixing roller 110. do not do. Therefore, unlike the conventional separation claw, the linear member 140 does not damage the fixing roller and can prevent an abnormal image.

  Next, separation of the recording medium P from the fixing roller 110 by the linear member 140 will be described. FIG. 6 is a schematic diagram showing a separated state of the transfer material. Before the separation, as shown in FIG. 6A, the recording medium P that has passed through the nip portion N advances in the direction of the arrow in the drawing by the rotation of the fixing roller 110 and collides with the linear member 140.

  As shown in FIG. 4B, when the distance between the fixing roller 110 and the linear member 140 is sufficiently smaller than the thickness dimension of the recording medium P, the recording medium P is fixed to the fixing roller 110 by the linear member 140. Separated from.

  On the other hand, as shown in FIG. 5C, when the distance between the fixing roller 110 and the linear member 140 is larger than the thickness of the recording medium P, the recording medium P enters between them and the separation fails. .

  In this way, whether the separation is successful or unsuccessful depends on the distance between the fixing roller 110 and the linear member 140 and the size relationship of the paper thickness. Therefore, keeping the distance between the linear member 140 and the fixing roller 110 below a certain value is important for reliable separation, and as described above, the thinnest paper that can be passed through the image forming apparatus. If the thickness is made slightly smaller than the thickness, all sheets including the thinnest sheet can be separated.

  The gap adjusting members 144a and 144b may be made of a material different from that of the linear member 140, but the same material may be used. The same material is preferable because it reduces the types of parts to be procured, reduces labor, and increases the possibility of cost reduction.

  In the embodiment, the linear member 140 is configured as a quadrangular member having a cross-sectional shape made of steel. The linear member may be formed of another member having a strength that does not break even when the recording medium P collides, for example, cotton thread or Teggs (fishing line, generally made of nylon), or a linear member. It is also conceivable that the cross-sectional shape of this is circular.

  Hereinafter, the reason why the linear member is formed of a steel material having a quadrangular cross section, a long side substantially matching the moving direction of the paper, and a short side being generally perpendicular to the moving direction of the paper will be described. FIG. 7 is a cross-sectional view showing the linear member and the fixing roller. In FIG. 7, the linear member 160 having a circular cross-sectional shape, the cross-section is square, and the long side coincides with the paper moving direction, and the short side is generally the paper moving direction. The linear member 140 provided with thickness is shown.

  In such a state, it is the thickness in the direction perpendicular to the paper moving direction that affects the separation performance. If the linear member 160 and the linear member 140 have the same thickness d, similar performance is obtained. have. In order to obtain separation performance, the direction perpendicular to the paper movement direction cannot be more than a certain thickness, but increasing the thickness in the direction parallel to the paper movement direction increases the strength and relatively easy handling of the steel wire. It becomes. Here, a line that is too thin is easily cut and difficult to handle. In addition, as a material, steel wire is harder to cut than natural fiber or synthetic fiber resin, and the life is prolonged.

  In the above-described embodiment, the image forming apparatus is described as performing a monochrome image using a single color toner. However, each fixing apparatus performs color image formation using a plurality of colors of toner. It can be applied to the device.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Reading unit 12 Image forming part 13 Automatic document feeder (ADF)
14 Document discharge trays 15 to 18 Paper feed cassette 19 Paper feed unit 20 Paper discharge tray 21 Document tray 22 Pickup roller 23 Document transport belt 24 Contact glass 25 Device 26 Light source 27 Optical system 28 Photoelectric conversion element 30 Photoconductor 31 Charging device 32 Unit 33 Developing device 34 Transfer device 35 Cleaning device 36 Fixing device 37 Discharge roller pair 100 Fixing device 110 Fixing roller 111 Heating means 120 Pressing roller 130 Separating devices 130a and 130b Support members 131a and 131b Arm members 132a and 132b Oscillating member 133a 133b Hole forming portions 134a, 134b Shaft holes 135a, 135b Groove portions 136a, 136b Pins 137a, 137b Pins 140 Linear members 141a, 142b First springs 142a, 142b Second springs 144a, 14 b gap adjusting member 150 separator 160 linear members

JP 2005-099426 A JP 2004-271760 A

Claims (7)

In a fixing device that passes a recording medium on which an unfixed toner image is formed in a nip formed by two fixing members, and heats and pressurizes the unfixed toner image to fix the toner image on the recording medium.
In order to separate the recording medium discharged from the nip portion from the surface of the fixing member, the flexibility stretched along the axis of the fixing member between the surface of the fixing member and the recording medium that has passed therethrough A linear member comprising:
A fixing device, comprising: a pair of support members disposed at both ends of the linear member and configured to swingably support the linear member following the behavior of the fixing member during conveyance of a recording medium.   The fixing device according to claim 1, wherein the linear member is formed of a metal including a steel wire.   3. The linear member includes a quadrangular cross section having a long side along a moving direction of the recording medium and a short side extending along a direction perpendicular to the moving direction of the recording medium. The fixing device according to 1.   The fixing device according to claim 1, further comprising a gap adjusting member that sets a dimension of a gap between the linear member member and the fixing member.   The fixing device according to claim 1, wherein the support member is disposed outside an area in which the recording medium is conveyed.   The fixing device according to claim 1, wherein the support member includes a groove for attaching the linear member.   An image forming apparatus comprising: the fixing device according to claim 1; and a toner image forming unit that forms an unfixed toner image on the recording medium.