JP2010231099A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress change in pressure with time at a contact of a pair of rotating bodies even when contact and separation of the pair of rotating bodies are repeated. <P>SOLUTION: A positioning part 110 is provided with: a first lever 111 having a through-hole and rotationally driven by a drive part 130; a hexagon bolt 118 whose head part is exposed on one side and shaft part is exposed on the other side through the through-hole; a coil spring 115 through which the shaft part of the hexagon bolt 118 penetrates; a spring pressure adjustment member screwed into the shaft part of the hexagon bolt 118 so as to interpose the first lever 111 and the coil spring 115 between the head part of the hexagon bolt 118 and the spring pressure adjustment member; and a second lever 113 rotating in contact with a pressure roll 62 according to the power received from the spring pressure adjustment member. The spring pressure adjustment member is formed so as not to bring the outer peripheral part thereof in contact with the second lever 113 when being rotated in a direction to screw into the hexagon bolt 118. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a recording material.

In an image forming apparatus using an electrophotographic method, a toner image is fixed onto a sheet by inserting a sheet on which a toner image is formed between a pair of rotating bodies that rotate while contacting each other.
For example, Patent Document 1 includes a mechanism for moving the other rotating body forward and backward with respect to one rotating body, and using this mechanism, the pair of rotating bodies are brought into contact with each other at a predetermined pressure. A technique for separating the rotating bodies is described.

JP 2008-152247 A

  An object of the present invention is to suppress a change in pressure over time at a contact portion of a pair of rotating bodies even when the contact and separation of the pair of rotating bodies are repeated.

  According to the first aspect of the present invention, there is provided a first rotating body that rotates, and a recording material that rotates in the same direction as the first rotating body at a contact portion that contacts the first rotating body and forms an image. A second rotating body that fixes the image on the recording material by passing through the contact portion, a drive member that is driven from the outside, and a contact member that is disposed in contact with the drive member, and according to driving by the drive member A first moving member that moves, a second moving member that is arranged in contact with the second rotating body and moves according to a force received from the outside, the first moving member, and the second moving member Using the coil spring disposed between the moving member and the bolt and nut, the coil spring is held by the first moving member so that the nut is allowed to rotate as the bolt rotates. From one moving member through the coil spring The received power is an image forming apparatus including a transmitting means for transmitting to said second moving member.

A second aspect of the present invention is the image forming apparatus according to the first aspect, further comprising a resin member disposed between the first moving member and the coil spring.
According to a third aspect of the present invention, the driving member causes the second rotating body to advance toward the first rotating body, and the first rotating body and the second rotating body are preliminarily determined. And a second state in which the second rotating body is retracted from the first rotating body side and the first rotating body and the second rotating body are not in contact with each other. The image forming apparatus according to claim 1, wherein the image forming apparatus is driven to perform the operation.
According to a fourth aspect of the present invention, the driving member causes the second rotating body to contact the first rotating body and the second rotating body with a pressure smaller than the predetermined pressure. 4. The image forming apparatus according to claim 3, wherein driving for setting to the state of 3 is further performed.

  According to a fifth aspect of the present invention, there is provided a first rotating body that rotates and a recording material that rotates in the same direction as the first rotating body at a contact portion that contacts the first rotating body and forms an image. A second rotating body that fixes the image on the recording material by passing through the contact portion and a through-hole penetrating from one surface to the other surface are formed and moved according to the force received from the outside. 1 moving member, a bolt that is attached through the through hole, and is arranged so that the head is exposed on the one surface and the shaft portion is exposed on the other surface, and the other surface side A nut that is screwed into the shaft portion of the bolt so as to sandwich the first moving member and the coil spring between the coil spring through which the shaft portion of the bolt is attached and the head portion of the bolt, From the first moving member to the coil The second rotating body moves in contact with the second rotating body according to the force received through the nut and the nut, and moves the second rotating body closer to or away from the first rotating body. A second moving member, and the nut has an outer shape in which an outer peripheral portion of the nut does not contact the second moving member when the nut is rotated in a direction to be screwed into the bolt. The image forming apparatus is characterized.

A sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, further comprising a resin member disposed between the first moving member and the coil spring.
According to a seventh aspect of the present invention, the first moving member and the second moving member are arranged so as to rotate about the same axis, and the through hole has a diameter larger than that of the shaft portion of the bolt. The image forming apparatus according to claim 5, wherein a large value is set.

According to the first aspect of the present invention, even when the contact and separation of the first rotating body and the second rotating body are repeated, the first configuration is compared with the case where the present configuration is not provided. It is possible to suppress a change in pressure over time at the contact portion between the rotating body and the second rotating body.
According to the second aspect of the present invention, even when the contact and separation between the first rotating body and the second rotating body are repeated, the time at the contact portion of the first rotating body and the second rotating body is increased. Fluctuations in pressure can be further suppressed.
According to invention of Claim 3, compared with the case where it does not have this structure, a deformation | transformation of a 1st rotary body and a 2nd rotary body can be suppressed.
According to the fourth aspect of the present invention, it is possible to suppress the second rotating body from hanging when the image forming apparatus is moved, for example, as compared with the case where the present configuration is not provided.
According to the fifth aspect of the present invention, even when the contact and separation of the first rotating body and the second rotating body are repeated, the first configuration is compared with the case where the present configuration is not provided. It is possible to suppress a change in pressure over time at the contact portion between the rotating body and the second rotating body.
According to the sixth aspect of the present invention, even when the contact and separation of the first rotating body and the second rotating body are repeated, the time at the contact portion of the first rotating body and the second rotating body is increased. Fluctuations in pressure can be further suppressed.
According to the seventh aspect of the present invention, it is possible to suppress a loss from occurring in the force to be applied to the second rotating body as compared with the case where the present configuration is not provided.

1 is a diagram illustrating a configuration example of an image forming apparatus to which the exemplary embodiment is applied. FIG. 3 is a diagram illustrating a configuration of a fixing unit. FIG. 3 is a cross-sectional layer configuration diagram of a fixing belt. It is a figure for demonstrating the structure of an end cap member. It is sectional drawing explaining the structure of an IH heater. FIG. 4 is a diagram for explaining a state of a fixing unit during non-image formation. FIG. 4 is a diagram for explaining a state of a fixing unit when power is turned off. FIG. 4 is a perspective view illustrating a state in which a contact / separation mechanism is attached to the fixing unit. FIG. 4 is a plan view showing a state in which a contact / separation mechanism is attached to the fixing unit. It is a perspective view of the positioning part which comprises an approach / separation mechanism. It is the perspective view which looked at the positioning part which comprises an approach / separation mechanism from the reverse side. It is a perspective view of a spring pressure adjustment member. It is a perspective view of the jig for spring length adjustment. It is a figure for demonstrating the length adjustment of the coil spring using the jig for spring length adjustment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Description of Image Forming Apparatus>
FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus 1 to which the exemplary embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is a so-called tandem color printer, and includes an image forming unit 10 that forms an image based on image data and a control unit 31 that controls the operation of the entire image forming apparatus 1. Further, for example, a communication unit 32 that receives image data by communicating with a personal computer (PC) 3 or an image reading device (scanner) 4, and a predetermined image for the image data received by the communication unit 32. An image processing unit 33 that performs processing is provided.

The image forming unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (also collectively referred to as “image forming unit 11”) arranged in parallel at a predetermined interval. Each image forming unit 11 includes a photosensitive drum 12 as an example of an image carrier that forms an electrostatic latent image and holds a toner image, a charger 13 that charges the surface of the photosensitive drum 12 to a predetermined potential, An LED (Light Emitting Diode) print head 14 that exposes the photosensitive drum 12 charged by the charger 13 based on each color image data, a developing device 15 that develops an electrostatic latent image formed on the photosensitive drum 12, and a transfer A drum cleaner 16 for cleaning the surface of the subsequent photosensitive drum 12 is provided.
Each of the image forming units 11 is configured in substantially the same manner except for the toner stored in the developing device 15, and each forms a toner image of yellow (Y), magenta (M), cyan (C), and black (K). To do.

  The image forming unit 10 also receives the intermediate transfer belt 20 onto which the color toner images formed on the photosensitive drums 12 of the image forming units 11 are transferred, and the color toner images formed on the image forming units 11. A primary transfer roll 21 that sequentially transfers (primary transfer) to the intermediate transfer belt 20 is provided. Further, a secondary transfer roll 22 that batch-transfers (secondary transfer) each color toner image (image) superimposed and transferred onto the intermediate transfer belt 20 onto a sheet P as an example of a recording material, and each color that is secondarily transferred. A fixing unit 60 for fixing the toner image on the paper P is provided.

  In the image forming apparatus 1 of the present embodiment, under the operation control by the control unit 31, image forming processing is performed by the following process. That is, the image data from the PC 3 or the scanner 4 is received by the communication unit 32, subjected to predetermined image processing by the image processing unit 33, and then sent to each image forming unit 11 as image data for each color. It is done. For example, in the image forming unit 11K that forms a black (K) toner image, the photosensitive drum 12 is uniformly charged at a predetermined potential by the charger 13 while rotating in the arrow A direction, and the image processing unit 33 is charged. The LED print head 14 scans and exposes the photosensitive drum 12 based on the K-color image data transmitted from. As a result, an electrostatic latent image relating to the K color image is formed on the photosensitive drum 12. The K-color electrostatic latent image formed on the photosensitive drum 12 is developed by the developing unit 15, and a K-color toner image is formed on the photosensitive drum 12. Similarly, yellow (Y), magenta (M), and cyan (C) toner images are formed in the image forming units 11Y, 11M, and 11C, respectively.

  Each color toner image formed on the photosensitive drum 12 of each image forming unit 11 is sequentially electrostatically transferred (primary transfer) onto the intermediate transfer belt 20 that moves in the direction of arrow B by the primary transfer roll 21, and each color toner is superimposed. A superimposed toner image is formed. The superimposed toner image on the intermediate transfer belt 20 is conveyed to a region (secondary transfer portion T) where the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves. When the superimposed toner image is conveyed to the secondary transfer unit T, the paper P is supplied from the paper holding unit 40 to the secondary transfer unit T in accordance with the timing. The superimposed toner image is collectively electrostatically transferred (secondary transfer) onto the conveyed paper P by the transfer electric field formed by the secondary transfer roll 22 in the secondary transfer portion T.

Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is conveyed to the fixing unit 60. The toner image on the paper P conveyed to the fixing unit 60 receives heat and pressure by the fixing unit 60 and is fixed on the paper P. Then, the paper P on which the fixed image is formed is conveyed to a paper stacking unit 45 provided in the discharge unit of the image forming apparatus 1.
On the other hand, the toner adhering to the photosensitive drum 12 after the primary transfer and the toner adhering to the intermediate transfer belt 20 after the secondary transfer are removed by the drum cleaner 16 and the belt cleaner 25, respectively.
In this way, the image forming process in the image forming apparatus 1 is repeatedly executed for the number of printed sheets.

<Description of fixing unit configuration>
Next, the fixing unit 60 of this embodiment will be described.
FIG. 2 is a diagram illustrating a configuration of the fixing unit 60 of the present embodiment.
The fixing unit 60 includes an IH (Induction Heating) heater 80 that generates an alternating magnetic field, a fixing belt 61 that is electromagnetically heated by the IH heater 80 to fix a toner image, and a pressure that is disposed to face the fixing belt 61. A pressing pad 63 that is pressed from the pressing roll 62 via the roll 62 and the fixing belt 61 is provided.
Further, the fixing unit 60 includes a holder 65 that supports constituent members such as the pressure pad 63, a temperature-sensitive magnetic member 64 that induces an alternating magnetic field generated by the IH heater 80 to form a magnetic path, and a temperature-sensitive magnetic member 64. A guide member 66 that guides the lines of magnetic force that have passed through, and a peeling assisting member 70 that assists in peeling the paper P from the fixing belt 61.
Furthermore, the fixing unit 60 is provided with a contact / separation mechanism 100 that moves the pressure roll 62 to contact and separate the fixing belt 61 and the pressure roll 62. Details of the contact / separation mechanism 100 will be described later.

<Description of fixing belt>
The fixing belt 61 as an example of the first rotating body is constituted by an endless belt member whose original shape is a cylindrical shape, and has a diameter of 30 mm and a length in the width direction of 370 mm when the original shape (cylindrical shape) is used, for example. Further, as shown in FIG. 3 (cross-sectional layer configuration diagram of the fixing belt 61), the fixing belt 61 includes a base layer 611, a conductive heat generating layer 612 laminated on the base layer 611, and a toner image fixability. The belt member has a multilayer structure including an elastic layer 613 for improving the surface and a surface release layer 614 coated on the uppermost layer.

The base material layer 611 is composed of a heat-resistant sheet-like member that supports the thin conductive heat generating layer 612 and forms the mechanical strength of the fixing belt 61 as a whole. In addition, the base material layer 611 is made of a material having a physical property (relative magnetic permeability, specific resistance) that allows the magnetic field to pass therethrough so that the AC magnetic field generated by the IH heater 80 acts to the temperature-sensitive magnetic member 64, and the thickness. Formed with. On the other hand, the base material layer 611 itself is configured not to generate heat or hardly generate heat due to the action of a magnetic field.
Specifically, as the base material layer 611, for example, a nonmagnetic metal such as nonmagnetic stainless steel having a thickness of 30 to 200 μm (preferably 50 to 150 μm), a resin material having a thickness of 60 to 200 μm, or the like is used.

The conductive heating layer 612 is an electromagnetic induction heating element layer that is electromagnetically heated by an alternating magnetic field generated by the IH heater 80. That is, the conductive heat generating layer 612 is a layer that generates an eddy current when the AC magnetic field from the IH heater 80 passes in the thickness direction.
Usually, a general-purpose power source manufactured at low cost is used as a power source for an excitation circuit (described later) for supplying an alternating current to the IH heater 80. Therefore, the frequency of the alternating magnetic field generated by the IH heater 80 is generally 20 k to 100 kHz by a general-purpose power source. Thereby, the conductive heat generating layer 612 is configured such that an alternating magnetic field having a frequency of 20 k to 100 kHz enters and passes therethrough.

The region where the alternating magnetic field can enter the conductive heat generating layer 612 is defined as “skin depth (δ)”, which is a region where the alternating magnetic field attenuates to 1 / e, and is derived from the following equation (1). (1) In the equation, f is the AC magnetic field frequency (e.g., 20 kHz), [rho is resistivity (Omega · m), the mu _r is the relative permeability.
Therefore, the thickness of the conductive heat generating layer 612 is determined by the skin depth (δ) of the conductive heat generating layer 612 defined by the equation (1) such that an alternating magnetic field having a frequency of 20 k to 100 kHz penetrates and passes through the conductive heat generating layer 612. It is configured in a thinner layer. Further, as a material constituting the conductive heat generating layer 612, for example, metals such as Au, Ag, Al, Cu, Zn, Sn, Pb, Bi, Be, and Sb, and metal alloys thereof are used.

Specifically, a nonmagnetic metal such as Cu having a thickness of 2 to 20 μm and a specific resistance of 2.7 × 10 ⁻⁸ Ω · m or less (relative magnetic permeability is approximately 1) is used as the conductive heating layer 612.
Further, from the viewpoint of shortening the time required for the fixing belt 61 to be heated to the fixing set temperature (hereinafter referred to as “warm-up time”), the conductive heat generating layer 612 is preferably formed as a thin layer.

Next, the elastic layer 613 is composed of a heat-resistant elastic body such as silicone rubber. The toner image held on the sheet P to be fixed is formed by laminating each color toner as powder. Therefore, in order to supply heat uniformly to the entire toner image at the nip portion N as an example of a contact portion where the fixing belt 61 and the pressure roll 62 are in contact, the fixing belt follows the unevenness of the toner image on the paper P. 61 It is preferable that the surface is deformed. Therefore, for example, silicone rubber having a thickness of 100 to 600 μm and a hardness of 10 ° to 30 ° (JIS-A) is suitable for the elastic layer 613.
Since the surface release layer 614 is in direct contact with the unfixed toner image held on the paper P, a material having a high release property is used. For example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether polymer), PTFE (polytetrafluoroethylene), silicone copolymer, or a composite layer thereof is used. If the thickness of the surface release layer 614 is too thin, it is not sufficient in terms of wear resistance, and the life of the fixing belt 61 is shortened. On the other hand, if it is too thick, the heat capacity of the fixing belt 61 becomes too large and the warm-up time becomes long. Therefore, the thickness of the surface release layer 614 is preferably 1 to 50 μm in consideration of the balance between wear resistance and heat capacity.

<Description of pressure roll>
The pressure roll 62 as an example of the second rotating body is disposed so as to face the fixing belt 61 and rotates in the direction of arrow D shown in FIG. 2 following the fixing belt 61. Then, a nip portion N is formed in a state where the fixing belt 61 is sandwiched between the pressure roll 62 and the pressing pad 63, and the sheet P holding the unfixed toner image is passed through the nip portion N, so that the heat and pressure To fix the unfixed toner image on the paper P.
The pressure roll 62 includes, for example, a solid aluminum core (cylindrical metal core) 621 having a diameter of 18 mm, and a heat-resistant elastic body layer 622 such as a silicone sponge having a thickness of 5 mm, which is coated on the outer peripheral surface of the core 621. Further, for example, a release layer 623 made of a heat-resistant resin coating such as PFA containing carbon having a thickness of 50 μm or a heat-resistant rubber coating is laminated.

<Description of pressing pad>
The pressing pad 63 is made of an elastic body such as silicone rubber or fluorine rubber, or a heat-resistant engineering plastic such as PPS resin or LCP resin, and is supported by the holder 65 at a position facing the pressure roll 62. Then, it is arranged in a state of being pressed from the pressure roll 62 via the fixing belt 61, and a nip portion N is formed with the pressure roll 62.
The pressing pad 63 includes a pre-nip region 63a on the inlet side of the nip portion N (upstream side in the conveyance direction of the paper P) and a peeling nip region 63b on the outlet side of the nip portion N (downstream side in the conveyance direction of the paper P). Different nip pressures are set. That is, in the pre-nip region 63 a, the surface on the pressure roll 62 side is formed in an arc shape that substantially follows the outer peripheral surface of the pressure roll 62, thereby forming a uniform and wide nip portion N. Further, the peeling nip region 63b is formed so as to be locally pressed from the surface of the pressure roll 62 with a large nip pressure so that the radius of curvature of the fixing belt 61 passing through the peeling nip region 63b becomes small. As a result, a curl (down curl) in a direction away from the surface of the fixing belt 61 is formed on the paper P passing through the peeling nip region 63b to promote the peeling of the paper P from the surface of the fixing belt 61.

  In the present embodiment, the peeling assisting member 70 is disposed on the downstream side of the nip portion N as a peeling assisting means by the pressing pad 63. The peeling auxiliary member 70 is supported by the holder 72 in a state where the peeling baffle 71 is close to the fixing belt 61 in a direction (so-called counter direction) opposite to the rotational movement direction of the fixing belt 61. The curled portion formed on the paper P at the outlet of the pressing pad 63 is supported by the peeling baffle 71, thereby suppressing the paper P from moving toward the fixing belt 61.

<Description of temperature-sensitive magnetic member>
Next, the temperature-sensitive magnetic member 64 is formed in an arc shape that follows the inner peripheral surface of the fixing belt 61, and a predetermined gap (for example, 0.5 to 1.5 mm) from the inner peripheral surface of the fixing belt 61. Are arranged close to each other but in a non-contact manner. The temperature-sensitive magnetic member 64 is disposed close to the fixing belt 61 because the temperature of the temperature-sensitive magnetic member 64 changes corresponding to the temperature of the fixing belt 61, that is, the temperature of the temperature-sensitive magnetic member 64 is changed. This is because the temperature is substantially the same as the temperature 61. Further, the temperature-sensitive magnetic member 64 is disposed in a non-contact manner with the fixing belt 61 because the heat of the fixing belt 61 is increased when the main switch of the image forming apparatus 1 is turned on and the fixing belt 61 is heated to the fixing set temperature. This is to prevent the temperature from flowing into the temperature-sensitive magnetic member 64 and shorten the warm-up time.

Further, the temperature-sensitive magnetic member 64 has a “permeability change start temperature” (see below), which is a temperature at which the magnetic permeability of the magnetic characteristics changes suddenly, equal to or higher than a fixing set temperature at which each color toner image is melted. The elastic layer 613 and the surface release layer 614 are made of a material set in a temperature range lower than the heat resistant temperature. That is, the temperature-sensitive magnetic member 64 is made of a material having a characteristic (“temperature-sensitive magnetism”) that reversibly changes between ferromagnetic and non-magnetic (paramagnetic) in a temperature range including the fixing set temperature. . The temperature-sensitive magnetic member 64 induces magnetic lines of force generated by the IH heater 80 and transmitted through the fixing belt 61 in the temperature range equal to or lower than the magnetic permeability change start temperature exhibiting ferromagnetism, and the temperature-sensitive magnetic member 64. A magnetic path passing through the inside of the is formed. As a result, the temperature-sensitive magnetic member 64 forms a closed magnetic path that encloses the fixing belt 61 and the exciting coil 82 of the IH heater 80 (see FIG. 5 at a later stage). On the other hand, in the temperature range exceeding the permeability change start temperature, the temperature-sensitive magnetic member 64 crosses the magnetic field lines generated by the IH heater 80 and transmitted through the fixing belt 61 in the thickness direction of the temperature-sensitive magnetic member 64. Make it transparent. Thereby, the magnetic lines of force generated by the IH heater 80 and transmitted through the fixing belt 61 form a magnetic path that passes through the temperature-sensitive magnetic member 64, passes through the inside of the guide member 66, and returns to the IH heater 80.
The “permeability change start temperature” here is a temperature at which the magnetic permeability (for example, the magnetic permeability measured by JIS C2531) starts to decrease continuously. For example, a member such as the temperature-sensitive magnetic member 64 This is the temperature point at which the amount of magnetic flux that passes through (the number of lines of magnetic force) starts to change. Therefore, the permeability change start temperature is a temperature close to the Curie point, which is the temperature at which magnetism disappears, but has a concept different from the Curie point.

Examples of the material used for the temperature-sensitive magnetic member 64 include a binary temperature-sensitive magnetic alloy such as an Fe—Ni alloy (permalloy) having a permeability change start temperature set within a range of 140 to 240 ° C., Fe-Ni, and the like. A ternary temperature-sensitive magnetic alloy such as a Cr alloy is used. For example, in a Fe-Ni binary temperature-sensitive magnetic alloy, the magnetic permeability change start temperature is about 225 ° C. by setting the Fe to 64% and Ni to 36% (atomic ratio). Such metal alloys such as permalloy and magnetic shunt steel are suitable for the temperature-sensitive magnetic member 64 because they are excellent in moldability and workability, have high thermal conductivity, and are inexpensive. As other materials, a metal alloy made of Fe, Ni, Si, B, Nb, Cu, Zr, Co, Cr, V, Mn, Mo or the like is used.
Further, the temperature-sensitive magnetic member 64 is formed with a thickness smaller than the skin depth δ (see the above formula (1)) with respect to the AC magnetic field (lines of magnetic force) generated by the IH heater 80. Specifically, for example, when an Fe—Ni alloy is used, the thickness is set to about 50 to 300 μm.

<Description of holder>
The holder 65 that supports the pressing pad 63 is made of a material having high rigidity so that the amount of bending in a state where the pressing pad 63 receives the pressing force from the pressing roll 62 becomes a certain amount or less. Thereby, the uniformity of the pressure (nip pressure) in the longitudinal direction at the nip portion N is maintained. Furthermore, since the fixing unit 60 according to the present embodiment employs a configuration in which the fixing belt 61 is heated using electromagnetic induction, the holder 65 is made of a material that does not affect or hardly gives influence to the induced magnetic field. It is made of a material that is not affected or hardly affected by the induced magnetic field. For example, a heat-resistant resin such as glass-mixed PPS (polyphenylene sulfide) or a nonmagnetic metal material such as Al, Cu, or Ag is used.

<Description of induction member>
The induction member 66 is formed in an arc shape that follows the inner peripheral surface of the temperature-sensitive magnetic member 64, and has a predetermined gap (for example, 1.0 to 5.0 mm) from the inner peripheral surface of the temperature-sensitive magnetic member 64. And arranged in a non-contact manner. The induction member 66 is made of a nonmagnetic metal having a relatively small specific resistance value, such as Ag, Cu, or Al. Then, when the temperature-sensitive magnetic member 64 rises to a temperature equal to or higher than the permeability change start temperature, an alternating magnetic field (line of magnetic force) generated by the IH heater 80 is induced, and the vortex is more vortexed than the conductive heating layer 612 of the fixing belt 61. A state in which the current I is easily generated is formed. Thereby, the thickness of the induction member 66 is formed with a thickness (for example, 1.0 mm) sufficiently thicker than the skin depth δ (see the above formula (1)) so that the eddy current I flows easily. .

<Description of end cap member>
FIG. 4 is a diagram for explaining a configuration of an end cap member 67 that rotationally drives the fixing belt 61 in the circumferential direction while maintaining a circular cross-sectional shape of both ends of the fixing belt 61 at both ends in the axial direction of the holder 65. It is. The fixing belt 61 directly receives a rotational driving force from both ends via the end cap member 67 and rotates together with the end cap member 67 in the direction of arrow C (see FIG. 2) at a process speed of 140 mm / s, for example. It is supposed to be.
Here, FIG. 4A is a side view of the end cap member 67, and FIG. 4B is a plan view of the end cap member 67 viewed from the IVb direction. As shown in FIG. 4, the end cap member 67 has a fixing portion 67 a fitted inside the both ends of the fixing belt 61, and has an outer diameter larger than that of the fixing portion 67 a, and is attached to the fixing belt 61. Rotating through a flange portion 67d formed so as to project radially from the fixing belt 61, a gear portion 67b to which rotational driving force is transmitted, a support portion 65a formed at both ends of the holder 65, and a coupling member 166. A bearing bearing portion 67c that is freely coupled is provided. Then, the support portions 65a provided at both ends of the holder 65 are fixed to both ends of the casing 69 of the fixing unit 60, so that the end cap member 67 has a bearing bearing portion 67c coupled to the support portion 65a. It is supported rotatably via.
As a material constituting the end cap member 67, so-called engineering plastics having high mechanical strength and heat resistance are used. For example, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, LCP resin and the like are suitable.

Here, when the fixing belt 61 rotates by receiving a driving force directly from the end cap members 67 at both ends, a torque of about 0.1 to 0.5 N · m is generally applied. However, in the fixing belt 61 of the present embodiment, the base material layer 611 is made of, for example, nonmagnetic stainless steel having high mechanical strength. For this reason, even when a torsional torque of about 0.1 to 0.5 N · m acts on the entire fixing belt 61, buckling or the like hardly occurs in the fixing belt 61.
Further, the flange portion 67d of the end cap member 67 suppresses the deviation of the fixing belt 61. In general, the fixing belt 61 at that time is generally 1 to 5 in the axial direction from the end portion (flange portion 67d) side. A compressive force of about 5N works. However, even when the fixing belt 61 receives such a compressive force, since the base material layer 611 of the fixing belt 61 is made of nonmagnetic stainless steel or the like, occurrence of buckling or the like is suppressed.
As described above, the fixing belt 61 according to the present embodiment rotates by receiving a driving force directly from both end portions of the fixing belt 61, and thus stable rotation is performed. At that time, the base material layer 611 of the fixing belt 61 is made of, for example, non-magnetic stainless steel having high mechanical strength, thereby realizing a structure in which buckling or the like hardly occurs against torsion torque or compression force. is doing. Furthermore, since the base material layer 611 and the conductive heat generating layer 612 are formed as thin layers to ensure the flexibility and flexibility of the fixing belt 61 as a whole, deformation and shape restoration following the nip portion N are prevented. Done.

<Description of IH heater>
Next, the IH heater 80 that performs electromagnetic induction heating by applying an AC magnetic field to the conductive heat generating layer 612 of the fixing belt 61 will be described.
FIG. 5 is a cross-sectional view illustrating the configuration of the IH heater 80 of the present embodiment. As shown in FIG. 5, the IH heater 80 includes a support 81 made of a nonmagnetic material such as a heat resistant resin, and an exciting coil 82 that generates an alternating magnetic field. Further, an elastic support member 83 made of an elastic body that fixes the excitation coil 82 on the support 81 and a magnetic core 84 that forms a magnetic path of an alternating magnetic field generated by the excitation coil 82 are provided. Furthermore, a shield 85 that shields the magnetic field, a pressure member 86 that pressurizes the magnetic core 84 toward the support 81, and an excitation circuit 88 that supplies an alternating current to the excitation coil 82 are provided.

  The support 81 is formed in a shape whose cross section is curved along the surface shape of the fixing belt 61, and an upper surface (supporting surface) 81 a that supports the exciting coil 82 has a predetermined gap (for example, 0) from the surface of the fixing belt 61. 0.5 to 2 mm). Moreover, as a material which comprises the support body 81, heat resistance, such as heat resistant resins, such as heat resistant glass, a polycarbonate, polyether sulfone, PPS (polyphenylene sulfide), or the glass fiber mixed with these, for example. Some non-magnetic materials are used.

  The exciting coil 82 is configured by winding, for example, 90 litz wires, which are bundled with, for example, 90 copper wires having a diameter of 0.17 mm and wound in a closed loop with a hollow shape such as an ellipse, an ellipse, or a rectangle. . Then, when an alternating current having a predetermined frequency is supplied to the exciting coil 82 from the exciting circuit 88, an alternating magnetic field centered around a litz wire wound in a closed loop is generated around the exciting coil 82. . Generally, the frequency of the alternating current supplied from the excitation circuit 88 to the excitation coil 82 is 20 k to 100 kHz generated by the general-purpose power source.

For the magnetic core 84, for example, a ferromagnetic material made of an oxide or alloy material having a high magnetic permeability such as soft ferrite, ferrite resin, amorphous alloy (amorphous alloy), permalloy, or temperature-sensitive magnetic alloy is used. The magnetic core 84 induces a magnetic force line (magnetic flux) generated by the alternating magnetic field generated by the exciting coil 82, and crosses the fixing belt 61 from the magnetic core 84 toward the temperature-sensitive magnetic member 64. A path of magnetic lines of force (magnetic path) is formed so as to pass through and return to the magnetic core 84. That is, the AC magnetic field generated by the excitation coil 82 is configured to pass through the inside of the magnetic core 84 and the inside of the temperature-sensitive magnetic member 64 so that the magnetic lines of force wrap the fixing belt 61 and the excitation coil 82 inside. A closed magnetic circuit is formed. As a result, the magnetic field lines of the alternating magnetic field generated by the exciting coil 82 are concentrated in a region facing the magnetic core 84 of the fixing belt 61.
Here, the magnetic core 84 is preferably made of a material having a small loss due to magnetic path formation. Specifically, the magnetic core 84 is desirably used in a form that reduces the eddy current loss (current path interruption or division by slits, thin plate bundling, etc.), and is preferably formed of a material having a small hysteresis loss.
Further, the length of the magnetic core 84 along the rotation direction of the fixing belt 61 is configured to be smaller than the length of the temperature-sensitive magnetic member 64 along the rotation direction of the fixing belt 61. Thereby, the leakage of magnetic lines of force to the periphery of the IH heater 80 is reduced, and the power factor is improved. Furthermore, electromagnetic induction to the metal member constituting the fixing unit 60 is suppressed, and the heat generation efficiency of the fixing belt 61 (conductive heat generation layer 612) is increased.

<Description of fixing method of excitation coil>
Next, a method for fixing the exciting coil 82 to the support 81 in the IH heater 80 of the present embodiment will be described.
In the IH heater 80 of the present embodiment, the elastic support member 83 that supports the excitation coil 82 on the support 81 is made of an elastic body such as silicone rubber or fluorine rubber. The elastic support member 83 is elastically deformed while pressing the excitation coil 82 against the support 81, thereby supporting the excitation coil 82 on the support surface of the support 81. That is, the elastic support member 83 is made of a material having a low Young's modulus, and when the elastic support member 83 presses the excitation coil 82 against the support 81, the elastic support member 83 with a low Young's modulus is elastically deformed, The exciting coil 82 is supported on the support body 81.

<Description of contact / separation mechanism>
In the present embodiment, the fixing unit 60 uses the contact / separation mechanism 100 to form a nip portion N when the fixing belt 61 and the pressure roll 62 come into contact with each other at a predetermined pressure ( 2), the second state (see FIG. 6) in which the fixing belt 61 and the pressure roll 62 are not in contact with each other by retracting the pressure roll 62 from the fixing belt 61, and the fixing belt 61 and the pressure. The roll 62 is set to a third state (see FIG. 7) in which the roll 62 comes into contact with a pressure lower than that in the first state.

  Here, the first state shown in FIG. 2 is set at the time of image formation in which a switch (not shown) of the image forming apparatus 1 is set to an on state and a toner image is fixed on the paper P. The second state shown in FIG. 6 is set when non-image formation is performed in which a switch (not shown) of the image forming apparatus 1 is set to an on state and the toner image is not fixed on the paper P. further. The third state shown in FIG. 7 is set when the power is turned off so that the energization is stopped by turning off a switch (not shown) of the image forming apparatus 1.

  Therefore, for example, the fixing unit 60 that is set to the third state by the contact / separation mechanism 100 when the switch of the image forming apparatus 1 is turned off becomes the third state by the contact / separation mechanism 100 as the switch is turned on. The warming-up operation is performed by setting the second state to the second state, and then the second state is set to the first state by the contact / separation mechanism 100 with the start of the image forming operation. Further, for example, the fixing unit 60 set in the first state is set from the first state to the second state by the contact / separation mechanism 100 as the image forming operation is completed, for example, the image forming apparatus 1. When the switch is turned off, the contact / separation mechanism 100 sets the second state to the third state.

  Here, the fixing unit 60 is set to the second state at the time of non-image formation because the partial region of the fixing belt 61 located in the nip portion N is deformed by being fixed for a long time in a state where the rotation is stopped. This is to suppress this. The reason why the fixing unit 60 is set to the third state when the power is turned off is that a part of the fixing belt 61 located in the nip portion N is deformed by being fixed for a long time while the rotation is stopped. This is because, for example, the fixing belt 61 is prevented from hanging when the image forming apparatus 1 is moved or conveyed.

Next, the configuration of the contact / separation mechanism 100 will be described.
FIG. 8 is a perspective view showing a state in which the contact / separation mechanism 100 is attached to the fixing unit 60. FIG. 9 is a plan view showing a state in which the contact / separation mechanism 100 is attached to the fixing unit 60. Further, FIG. 10 is a perspective view of the positioning portion 110 constituting the contact / separation mechanism 100, and FIG. 11 is a perspective view of the positioning portion 110 viewed from the opposite side to FIG. The positioning portions 110 are provided on both ends of the pressure roll 62 in the axial direction. However, in FIGS. 8 to 11, one side, that is, the rear side in the image forming apparatus 1 shown in FIG. Only what is provided is shown. Therefore, FIG. 9 is a view of the contact / separation mechanism 100 provided on the back side in FIG. 1 as viewed from the front side in the drawing.

  The contact / separation mechanism 100 holds a shaft 624 provided at an end portion in the axial direction of the pressure roll 62, and a positioning unit 110 that positions the pressure roll 62 with respect to the fixing belt 61 via the shaft 624. The image forming apparatus 1 includes a driving unit 130 that drives the positioning unit 110 by rotating in response to driving from the main body side.

  Here, the drive unit 130 extends along the axial direction of the pressure roll 62, is held by a frame (not shown) provided in the fixing unit 60, and is driven to rotate, and the axial direction of the pressure roll 62. An eccentric cam 132 attached in a state of being fixed to the rotary shaft 131 is provided at a position outside the both ends. Therefore, two eccentric cams 132 are attached to one rotating shaft 131. In the present embodiment, the rotating shaft 131 and the eccentric cam 132 constitute a drive member.

  On the other hand, the positioning part 110 has a circular first through hole 111a formed through the axial direction of the pressure roll 62, and the first lever 111 that rotates around the first through hole 111a. And a cam follower 112 that is rotatably mounted with the shaft fixed to the first lever 111 so as to come into contact with the cam surface of the eccentric cam 132 provided in the drive unit 130. The positioning unit 110 has a second through hole 113a provided along the axial direction of the pressure roll 62 and coaxially with the first through hole 111a of the first lever 111. The second through hole A second lever 113 that rotates about 113a is further provided. Here, the first lever 111 and the second lever 113 are configured by, for example, processing a metal plate into a sheet metal. The first through hole 111 a provided in the first lever 111 and the second through hole 113 a provided in the second lever 113 have a common shaft (not shown) along the axial direction of the pressure roll 62. They are inserted and are configured to rotate about a common axis. In the present embodiment, the first lever 111 and the cam follower 112 constitute a first moving member, and the second lever 113 constitutes a second moving member.

  Further, the second lever 113 constituting the positioning unit 110 has a notch formed in a portion corresponding to the attachment position of the shaft 624 of the pressure roll 62, and the second lever 113 has a second notch. A wire member 114 for holding the shaft 624 between the notch provided in the lever 113 is attached. 10 and 11, the wire member 114 is not shown.

  Further, of the first lever 111 and the second lever 113, the first lever 111 and the second lever 113 are respectively disposed on the free end side which is the farthest side from the first through hole 111a and the second through hole 113a. A coil spring 115 extending along the direction from the pressure roll 62 toward the fixing belt 61 is disposed between the lever 113 and the lever 113. One end side of the coil spring 115 is configured to press the inner wall surface of the first lever 111 via a spring guide 116 as an example of a resin member made of resin or the like, and the other end side of the coil spring 115 Is pressed against a spring pressure adjusting member 117 made of metal or the like attached to the hexagonal bolt 118, and the inner wall surface of the second lever 113 is pressed via the hexagonal bolt 118. . 10 and 11, the description of the spring guide 116 is omitted.

  A shaft portion of the hexagon bolt 118 is disposed in the hollow portion of the coil spring 115. Here, the head of the hexagon bolt 118 is positioned outside (one surface side) of the first lever 111, and its shaft portion is a through-hole provided in the first lever 111 via a washer 119. The second lever 113 is inserted into the first lever 111 via a spring guide 116, a coil spring 115, and a spring pressure adjusting member 117 which are inserted into the first lever 111 from the through hole (not shown). Is inserted into a through-hole (not shown) provided in. Further, a boss portion 118 a having a smaller outer diameter than the shaft portion of the hexagon bolt 118 is formed at the end of the shaft portion of the hexagon bolt 118, and the boss portion 118 a is a through-hole provided in the second lever 113 ( It protrudes to the outside of the second lever 113 via a not shown). Further, an E-ring 120 that functions as a hexagonal bolt 118 is attached to the outside of the second lever 113 by holding a boss 118a formed at the end of the shaft of the hexagonal bolt 118. Yes. The spring guide 116 is preferably made of a fluororesin having a low friction coefficient, such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether polymer), PTFE (polytetrafluoroethylene), or the like.

  Among these, the through hole provided in the first lever 111 for inserting the shaft portion of the hexagon bolt 118 has a larger diameter than the shaft portion of the hexagon bolt 118, and the first lever described later. The position of the shaft portion is allowed to vary with the rotation operation 111. In addition, the through hole provided in the second lever 113 for inserting the boss portion 118a formed at the end of the shaft portion of the hexagon bolt 118 is smaller than the shaft portion of the hexagon bolt 118 and the hexagon bolt 118 has a through hole. Although it has a slightly larger diameter than the boss portion 118a formed at the end portion of the shaft portion, a screw groove is not formed inside the boss portion 118a. On the other hand, the spring pressure adjusting member 117 is formed with a thread groove for screwing a thread formed on the shaft portion of the hexagon bolt 118 as will be described later. Thus, the spring pressure adjusting member 117 functions as a nut into which the hexagon bolt 118 is screwed. In the present embodiment, the hexagon bolt 118 and the spring pressure adjusting member 117 have a function as a transmission means.

  Therefore, the compression amount, that is, the length of the coil spring 115 in the initial state (third state) is that the head of the hexagon bolt 118 positioned on the first lever 111 via the spring guide 115 and the washer 119, and the hexagon bolt 118. It is determined by the spring pressure adjusting member 117 attached to the shaft portion. That is, the length of the coil spring 115 is adjusted by changing the distance between the head of the hexagon bolt 118 and the spring pressure adjusting member 117 by rotating the hexagon bolt 118.

  Here, the positioning unit 110 attached to the back side of the image forming apparatus 1 shown in FIG. 1 has been described as an example. However, the positioning unit 110 attached to the front side of the image forming apparatus 1 is illustrated in FIGS. 11 is symmetrical with respect to that shown in FIG. 11, that is, symmetrical with respect to the axial direction of the pressure roll 62.

FIG. 12 shows a perspective view of the spring pressure adjusting member 117 constituting the positioning part 110.
The spring pressure adjusting member 117 includes a base 117a having a circular outer shape, and a thread groove that is formed through the base 117a at the center of the base 117a and into which a thread formed on the shaft of the hexagon bolt 118 is screwed. Are formed on the outer peripheral surface of the base portion 117a and rectangular cutout portions 117c formed at four positions at intervals of 90 °. Here, the diameter of the spring pressure adjusting member 117 is selected so that the outer peripheral surface thereof does not contact the second lever 113 when attached to the positioning portion 110 (see FIG. 10).

  Next, the contact / separation operation of the fixing belt 61 and the pressure roll 62 by the contact / separation mechanism 100 will be specifically described. Here, as an example, in the image forming apparatus 1 in which the switch is set to the on state, the fixing unit 60 is repeatedly set to the second state shown in FIG. 6 and the first state shown in FIG. Give an explanation. Note that the fixing unit 60 is initially set to the second state.

  When the fixing unit 60 is in the second state, the eccentric cam 132 is in a state where the second position 132B of the cam surface shown in FIG. 9 is moved to a position facing the cam follower 112 as the rotating shaft 131 rotates. It has stopped. In this example, the second position 132 </ b> B is a portion where the cam surface is closest when viewed from the axis center of the rotating shaft 131.

  In a state where the second position 132B of the cam surface of the eccentric cam 132 has moved to a position facing the cam follower 112, the cam follower 112 stops in a state where it hits the second position 132B of the cam surface of the eccentric cam 132. Thereby, the position of the first lever 111 in the second state is determined. When the first lever 111 rotates counterclockwise, the head of the hexagon bolt 118 contacts the outside of the first lever 111, so that the hexagon bolt 118 also rotates counterclockwise. The second lever 113 also rotates counterclockwise around the second through-hole 113a through an E-ring 120 attached to a boss 118a formed at the end of the shaft portion 118. Then, the pressure roll 62 moves in a direction away from the fixing belt 61 via the shaft 624 held between the second lever 113 and the wire member 114. A state away from 61, that is, the second state shown in FIG.

  Next, when the fixing unit 60 shifts from the second state to the first state, the eccentric cam 132 has the first position 132A of the cam surface shown in FIG. Move to the opposite position. In this example, the first position 132 </ b> A is a portion where the cam surface is farthest from the center of the rotating shaft 131.

  As the first position 132A moves from the second position 132B of the eccentric cam 132 to the position facing the cam follower 112, the first lever 111 to which the cam follower 112 is attached is shown in FIG. It rotates clockwise around the through hole 111a (see FIG. 11). Further, as the first lever 111 rotates clockwise in FIG. 9, the second lever 113 is pushed via the coil spring 115, the spring pressure adjusting member 117, and the hexagon bolt 118, and as a result, the second lever The lever 113 also rotates clockwise around the second through hole 113a in FIG. Then, the pressure roll 62 moves toward the fixing belt 61 via the shaft 624 held between the second lever 113 and the wire member 114, and the pressure roll 62 is moved to the fixing belt 61. Contact.

  Then, as the first position 132A of the eccentric cam 132 approaches the position facing the cam follower 112, the first lever 111 to which the cam follower 112 is attached further rotates clockwise in FIG. Further, as the first lever 111 rotates clockwise in FIG. 9, the second lever 113 is pushed through the coil spring 115, the spring pressure adjusting member 117 and the hexagon bolt 118, and the second lever 113 is also In FIG. 9, it is going to rotate further clockwise. However, at this time, since the pressure roll 62 is already in contact with the fixing belt 61 and the pressure by the pressure roll 62 is applied to the fixing belt 61, the second lever 113 in FIG. Further clockwise rotation becomes difficult. Then, the coil spring 115 provided between the first lever 111 and the second lever 113 cannot be moved to the second lever 113 side by the spring pressure adjusting member 117, while the first lever 111 Since the pressure is further pressed, the pressure is compressed and shortened compared with the second state, and as a result, the pressure applied to the pressure roll 62 via the coil spring 115 and the third lever 113 becomes higher. . Accordingly, a gap is formed between the first lever 111 and the head of the hexagon bolt 118 as shown in FIG. 9, and the shaft portion of the hexagon bolt 118 is formed outside the first lever 111. Exposed. At this time, since the through hole provided in the first lever 111 has a larger diameter than the shaft portion of the hexagon bolt 118, the shaft of the hexagon bolt 118 is moved to the first lever 111 along with such movement. The situation that the part gets caught does not occur. Then, when the first position 132A of the eccentric cam 132 reaches the position facing the cam follower 112 and stops, the pressure roll 62 forms a nip portion N on the fixing belt 61 and contacts with a predetermined pressure. That is, the first state shown in FIG.

  Further, when the fixing unit 60 shifts from the first state to the second state again, the eccentric cam 132 has the second position 132B of the cam surface shown in FIG. Move to the opposite position.

As the second position 132B of the eccentric cam 132 moves from the first position 132A to the position facing the cam follower 112, the first lever 111 to which the cam follower 112 is attached is pushed by the coil spring 115. Accordingly, in FIG. 9, the first through hole 111a is rotated counterclockwise. Further, as the first lever 111 rotates counterclockwise in FIG. 9, the head of the hexagon bolt 118 contacts the first lever 111 and the pressing force of the coil spring 115 against the second lever 113 is weakened. . As the first lever 111 further rotates in the counterclockwise direction in FIG. 9, the E-ring 120 attached to the boss portion 118a formed at the end of the shaft portion of the hexagon bolt 118 is further moved. Thus, the second lever 113 also rotates counterclockwise around the second through hole 113a in FIG. Then, the pressure roll 62 moves in a direction away from the fixing belt 61 via the shaft 624 held between the second lever 113 and the wire member 114, and the second state shown in FIG. It becomes.
Thereafter, by repeating the above-described operation, the first state and the second state are alternately set.

  On the other hand, when the fixing unit 60 shifts from the second state to the third state, the eccentric cam 132 moves to a position where the third position 132C shown in FIG. 9 faces the cam follower 112 as the rotating shaft 131 rotates. Moving. In this example, the third position 132C is a part where the distance from the axis center of the rotating shaft 131 is between the first position 132A and the second position 132B.

  As the third position 132C moves from the second position 132B of the eccentric cam 132 to the position facing the cam follower 112, the first lever 111 to which the cam follower 112 is attached is shown in FIG. It rotates clockwise around the through hole 111a. Further, as the first lever 111 rotates clockwise in FIG. 9, the second lever 113 is pushed via the coil spring 115, the spring pressure adjusting member 117, and the hexagon bolt 118, and as a result, the second lever The lever 113 also rotates clockwise around the second through hole 113a in FIG. Then, the pressure roll 62 moves toward the fixing belt 61 via the shaft 624 held between the second lever 113 and the wire member 114, and the pressure roll 62 is moved to the fixing belt 61. Contact. Then, when the third position 132C of the eccentric cam 132 reaches the position facing the cam follower 112 and stops, the pressure roll 62 is in contact with the fixing belt 61 with a pressure smaller than that in the first state, that is, The third state shown in FIG.

  In the transition from the first state to the second state and the transition from the second state to the first state of the fixing unit 60 described above, the compression force is applied to the coil spring 115 and the compression force is released. It will be repeated. In the present embodiment, since the coil spring 115 is attached to the first lever 111 using the hexagon bolt 118 and the spring pressure adjusting member 117, the hexagonal force is applied to the coil spring 115 whenever the compression force is applied and the compression force is released. Due to the frictional force acting between the bolt 118 and the first lever 111, a moment of force is applied to the hexagonal bolt 118 in the rotational direction. Therefore, the hexagon bolt 118 tries to rotate as the pressure roll 62 is brought into and out of contact with the fixing belt 61.

  Here, in the present embodiment, the surface of the outer peripheral portion of the spring pressure adjusting member 117 is the second lever 113 by devising the shape of the spring pressure adjusting member 117 that sandwiches the coil spring together with the hexagon bolt 118 in the positioning portion 110. It is configured to have an outer shape that does not come into contact with. For this reason, when the hexagonal bolt 118 rotates in accordance with the contact / separation operation of the pressure roll 62 with respect to the fixing belt 61, the rotational movement of the spring pressure adjusting member 117 is not restricted by the second lever 113. Along with 118, the spring pressure adjusting member 117 also rotates in the same direction. Therefore, when the hexagon bolt 118 rotates with the contact / separation operation, the hexagon bolt 118 is less likely to be tightened or loosened with respect to the spring pressure adjusting member 117. For this reason, even if the pressing roll 62 is repeatedly brought into and out of contact with the fixing belt 61, the change in the length of the coil spring 115 in the second state shown in FIG. 6 is suppressed. In the state 1, the occurrence of a situation in which the nip pressure generated in the nip portion N between the fixing belt 61 and the pressure roll 62 fluctuates (increases or decreases) with time is suppressed.

  In the present embodiment, since the resin spring guide 116 is sandwiched between the first lever 111 and the coil spring 115, when the hexagon bolt 118 is about to rotate, the coil spring 115 becomes the spring guide. 116 to slide. This also makes it difficult for the hexagonal bolt 118 to rotate when the hexagonal bolt 118 rotates along with the contact / separation operation, so that the hexagonal bolt 118 is tightened against the spring pressure adjusting member 117, Or, the situation of loosening is less likely to occur.

  Now, in the first state shown in FIG. 2, the magnitude of the nip pressure generated in the nip portion N between the fixing belt 61 and the pressure roll 62 is the same as that in the second state shown in FIG. It depends on the length of the coil spring 115. Here, in order to adjust the length of the coil spring 115, the hexagon bolt 118 may be screwed or loosened with respect to the spring pressure adjusting member 117. However, in the present embodiment, as described above, the hexagon bolt 118 is used. Since the spring pressure adjusting member 117 is also rotated together with the rotation of the coil spring 115, it is difficult to adjust the length of the coil spring 115 as it is. Therefore, in the present embodiment, the length of the coil spring 115 in the positioning unit 110 is adjusted using the method described below.

FIG. 13 is a perspective view of a spring length adjusting jig 200 used for adjusting the length of the coil spring 115.
The spring length adjusting jig 200 integrates a base portion 201 having a rectangular parallelepiped shape and a protruding portion 202 having a rectangular parallelepiped shape and formed by protruding from one end surface on the short side. Configured. Here, the length L in the longitudinal direction of the base 201 is set to be equal to a predetermined length of the coil spring 115. On the other hand, the width W of the protrusion 202 is set to be slightly smaller than the width of the notch 117c provided in the spring pressure adjusting member 117 shown in FIG. The predetermined length of the coil spring 115 means that when the fixing unit 60 is set to the first state shown in FIG. 2, the pressure applied to the nip portion N, that is, the nip pressure is within the range of pressure necessary for fixing. The length of the coil spring 115 necessary for

FIG. 14 is a view for explaining the length adjustment of the coil spring 115 of the positioning unit 110 using the spring length adjusting jig 200 described above. The length adjustment of the coil spring 115 is performed, for example, when the image forming apparatus 1 is shipped or when the image forming apparatus 1 is maintained.
In this adjustment, first, the spring length adjusting jig 200 is mounted on the coil spring 115 between the first lever 111 and the second lever 113 of the positioning unit 110. At this time, any one of the notches 117c provided on the spring pressure adjusting member 117 faces upward, and the protrusion 202 provided on the spring length adjusting jig 200 faces the notch 117c facing upward. Try to get stuck.

  Then, by rotating the hexagon bolt 118 with the spring length adjustment jig 200 mounted on the positioning portion 110, the shaft portion of the hexagon bolt 118 is tightened or loosened with respect to the spring pressure adjustment member 117. At this time, since the spring pressure adjusting member 117 is restricted from moving in the rotational direction by the spring length adjusting jig 200, the rotation of the spring pressure adjusting member 117 is restricted even if the hexagon bolt 118 is rotated. As a result, the distance between the head of the hexagon bolt 118 and the spring pressure adjusting member 117, that is, the length of the coil spring 115 is adjusted. Then, the hexagon bolt 118 is rotated to a position where the end of the spring length adjustment jig 200 is in contact with the inner surface of the first lever 111, and then the spring length adjustment jig 200 is removed from the positioning section 110. Thus, the length of the coil spring 115 in the positioning unit 110 is set to a predetermined length.

  In this embodiment, the endless belt-shaped fixing belt 61 is used as the first rotating body, and the roll-shaped pressure roll 62 is used as the second rotating body. However, the first rotating body and the first rotating body are used as the first rotating body. The configuration of the rotating body 2 may be changed. That is, the roll material and the roll material may be combined, the endless belt and the endless belt may be combined, or the endless belt may be advanced and retracted relative to the roll material.

  In the present embodiment, the case where the head of the hexagon bolt 118 is disposed on the first lever 111 side and the spring pressure adjusting member 117 is disposed on the second lever 113 side has been described as an example. In this case, for example, the head of the hexagon bolt 118 may be disposed on the second lever 113 side, and the spring pressure adjusting member 117 may be disposed on the first lever 111 side.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Image forming unit, 12 ... Photoconductor drum, 20 ... Intermediate transfer belt, 21 ... Primary transfer roll, 22 ... Secondary transfer roll, 31 ... Control part, 60 ... Fixing unit, 61 ... Fixing Belt, 62 ... Pressure roll, 63 ... Pressing pad, 64 ... Temperature sensitive magnetic member, 65 ... Holder, 66 ... Induction member, 80 ... IH heater, 81 ... Support, 82 ... Excitation coil, 83 ... Elastic support member, 84 ... magnetic core, 85 ... shield, 86 ... pressure member, 88 ... excitation circuit, 100 ... contact / separation mechanism, 110 ... positioning unit, 130 ... drive unit

Claims (7)

A first rotating body that rotates;
A first rotating member rotates in the same direction as the first rotating body at a contact portion in contact with the first rotating body, and the recording material on which an image is formed passes through the contacting portion to fix the image on the recording material. Two rotating bodies,
A driving member driven from the outside;
A first moving member that is disposed in contact with the driving member and moves in response to driving by the driving member;
A second moving member arranged in contact with the second rotating body and moving in accordance with a force received from the outside;
A coil spring disposed between the first moving member and the second moving member;
Using the bolt and nut, the coil spring is held by the first moving member so that the rotation of the nut accompanying the rotation of the bolt is allowed, and received from the first moving member via the coil spring An image forming apparatus including: a transmission unit configured to transmit a force to the second moving member;   The image forming apparatus according to claim 1, further comprising a resin member disposed between the first moving member and the coil spring.   The driving member has a first state in which the second rotating body is advanced to the first rotating body side to bring the first rotating body and the second rotating body into contact with each other at a predetermined pressure, And driving for setting the second rotating body to the second state in which the first rotating body and the second rotating body are not brought into contact with each other by retracting the second rotating body from the first rotating body side. The image forming apparatus according to claim 1, wherein:   The drive member is for setting the second rotating body to a third state in which the first rotating body and the second rotating body are brought into contact with each other at a pressure smaller than the predetermined pressure. The image forming apparatus according to claim 3, further driven. A first rotating body that rotates;
A first rotating member rotates in the same direction as the first rotating body at a contact portion in contact with the first rotating body, and the recording material on which an image is formed passes through the contacting portion to fix the image on the recording material. Two rotating bodies,
A through-hole penetrating from one surface to the other surface is formed, and a first moving member that moves according to a force received from the outside;
A bolt that is attached through the through hole, and is arranged so that the head is exposed on the one surface and the shaft portion is exposed on the other surface;
A coil spring to which the shaft portion of the bolt is attached so as to penetrate on the other surface side;
A nut that is screwed into the shaft of the bolt so as to sandwich the first moving member and the coil spring between the head of the bolt;
It moves while contacting the second rotating body according to the force received from the first moving member via the coil spring and the nut, and moves the second rotating body closer to the first rotating body or A second moving member away from the first rotating body,
The image forming apparatus according to claim 1, wherein the nut has an outer shape in which an outer peripheral portion of the nut does not contact the second moving member when the nut is rotated in a direction in which the nut is screwed into the bolt.   The image forming apparatus according to claim 5, further comprising a resin member disposed between the first moving member and the coil spring. The first moving member and the second moving member are arranged to rotate about the same axis,
The image forming apparatus according to claim 5, wherein the through hole is set to have a diameter larger than that of the shaft portion of the bolt.

Images