JP6590563B2 - Heating belt unit - Google Patents

Description

The present invention relates to a pressurized thermal Berutoyuni' bets.

  In recent years, image forming apparatuses such as copiers, printers, and multifunction machines have been required to have high speed, high image quality, color, and energy saving. Further, there is a demand for multimedia compatibility and high productivity (number of printed sheets per unit time) that can support various recording materials such as thick paper, rough paper, embossed paper, and coated paper.

  Here, in a fixing device using a fixing roller, in the case of a recording material (thick paper) having a large amount of weight, a fixing defect occurs because a large amount of heat is taken away from the fixing roller and its surface temperature decreases. For this reason, when fixing thick paper, in order to ensure fixability (adhesive force between the toner and the recording material), the fixing process is performed at a low speed at which the recording material passes through the fixing device. Currently.

  Such a decrease in the surface temperature of the fixing roller is caused by a structure in which a heat-resistant elastic layer such as silicone rubber or fluorine rubber is formed on a metal pipe-shaped core as a fixing roller. One of the causes is low thermal conductivity. That is, the heat of a heating element (for example, a halogen heater) provided in the cored bar of the fixing roller is blocked by the cored bar or the elastic layer, and is not easily transmitted to the surface of the fixing roller.

  There is also a structure in which such an elastic layer is not provided as a fixing roller. In this case, the surface temperature decrease is small due to the absence of the elastic layer. appear. In the absence of this elastic layer, in a recording material having large irregularities, the toner in the recess and the fixing roller are difficult to contact, and the toner in the recess becomes poorly fixed. In particular, in the case of a color image, since the surface of the image cannot be melted uniformly, unevenness of fixing, unevenness of gloss, and unevenness of color occur, resulting in a problem that the image quality deteriorates. Therefore, it is preferable to provide such an elastic layer from the viewpoint of compatibility with various recording materials and image quality.

  Here, in order to prevent the surface temperature of the fixing roller from lowering, if a heating element having a large rated power is provided and the fixing roller is heated rapidly, the temperature of the core metal rises rapidly, and the adhesive layer between the core metal and the elastic layer Is destroyed by thermal degradation. As a result, there arises a problem that the elastic layer is peeled off from the metal core and a problem that the elastic layer is broken due to softening deterioration or hardening deterioration due to heat.

  Therefore, as a technique for fixing without slowing down the speed when the recording material passes through the fixing device, an external heating method is known in which an external heating device is brought into contact with the surface of the fixing roller and the fixing roller is heated from the outside. (Patent Document 1). That is, an external heating belt is suspended on a plurality of heating rollers each having a halogen lamp as a heating element, and the heat of the halogen lamp, which is a heating element, is transmitted through the heating roller in the order of the external heating belt and the fixing roller surface. The fixing roller surface temperature is prevented from decreasing.

  When such an external heating device is used, the external heating device needs to be separated from the fixing roller during standby before passing paper. If the external heating device comes into contact with the fixing roller during standby before passing the paper, the outer surface of the fixing roller is heated by the external heating device, the fixing roller surface layer reaches a predetermined temperature, and the temperature inside the fixing roller decreases. End up. This is because, in such a state, the surface temperature of the fixing roller rapidly decreases in the initial stage of paper feeding, and toner fixing failure may occur.

  Therefore, even in the external heating belt configuration, it is necessary to attach and detach the fixing roller. Here, if the heating roller for suspending the external heating belt is fixed, the external heating belt is loosened by the curvature of the fixing roller when retracted (separated) from the fixing roller. In order to sufficiently retract the belt suspended from the fixing roller to the plurality of heating rollers at the time of separation, the retracting amount of the external heating belt unit needs to be very large. For this reason, the entire configuration of the fixing device becomes large, and there arises a problem that a space for installing the fixing roller must be widened.

  In order to solve this problem, conventionally, compression springs are installed between rotating members that are respectively disposed at both ends of a plurality of heating rollers that suspend an external heating belt and rotatably support the heating rollers. It is known to apply tension. In this case, one of the two heating rollers can be moved to suppress the slack of the belt when the external heating belt unit is retracted, thereby reducing the separation amount of the external heating belt unit. Further, a sufficient adhesion is obtained when the external heating belt unit comes into contact with the fixing roller.

JP 2004-198659 A

  Here, when assembling the external heating belt unit, compression springs are arranged between a plurality of rotating members that are arranged at both longitudinal ends of the plurality of heating rollers that suspend the external heating belt and rotatably support the heating roller. There is a need. As an assembly method, a unit in which a rotating member is attached to both ends in the axial direction (longitudinal direction) of a plurality of heating rollers suspended from an external heating belt is pushed into a place where a compression spring is installed. It becomes.

  In this case, as shown in FIG. 15, the end of the rotating member at the end can be obtained by assembling an external heating belt or the like to the compression spring at a position where the direction of connecting the plurality of rotating members of the arranged compression spring is not fixed. 132 comes into contact with the compression spring 301. Thereby, workability | operativity falls very much and also the problem that a compression spring will be deformed arises.

  As a method for solving this problem, a configuration is proposed in which the wire spring 307 is passed between the compression springs 301 as shown in FIG. 16, thereby restricting the compression springs to a certain range and not obstructing the pressure applied by the compression springs. Has been. However, even in this conventional configuration, the above-mentioned problem cannot be solved ideally because the positional deviation in the direction connecting the plurality of rotating members of the compression spring is not sufficiently suppressed.

An object of the present invention, in the case of the configuration that tensioned by the first and second compression springs between the heating roller for suspending the pressurized heat belt is that the assembly provides easy pressurized heat Berutoyuni' bets.

To achieve the above object, engagement Ru pressurized heat Berutoyuni' preparative the present invention, the belt and the longitudinal opposite ends of the first and the second heating roller, said first and second heating rollers for suspending the belt A compression spring that is compressed to a first compression state by a portion and applies a force in a direction to expand the space between the first and second heating rollers, and heating that heats at least one of the first and second heating rollers Means, a support member for supporting the first and second heating rollers, a compression spring support portion provided on the support member for supporting the compression spring, an opening side of one end of the compression spring, and an end of the other end A holding portion that is provided in contact with the compression spring on the opening side and holds the compression spring in a state where the compression spring can be expanded and contracted, and the holding portion has a maximum length of the compression spring. It will be a predetermined length shorter than the free length Wherein a regulating portion for regulating the maximum length of the compression spring, characterized in that the.

According to the present invention, in the case of the configuration that tensioned by the first and second compression springs between the heating roller for suspending the pressurized heat belt, easy to improve the assembling property of assembling the pressurized heat belt unit It can be in.

1 is a schematic configuration diagram of a fixing device having an external heating belt unit according to an embodiment of the present invention. 1 is a schematic configuration diagram of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. The front view of the external heating belt unit which concerns on the 1st Embodiment of this invention Schematic of the longitudinal direction of the external heating belt unit according to the first embodiment The figure which shows the spring holding member 302 in the assembly apparatus which concerns on 1st Embodiment. Schematic which shows the state which is holding the compression spring 301 which concerns on 1st Embodiment with the spring holding member 302. FIG. The figure which shows the time of the assembly | attachment (assembly) of the external heating belt 105 which concerns on 1st Embodiment. Sectional drawing which shows the state which assembled | attached the external heating belt 105 which concerns on 1st Embodiment. The figure which shows the structure regarding the retraction | saving operation | movement of the external heating belt which concerns on 1st Embodiment. The figure which shows the structure regarding contact | abutting operation | movement of the external heating belt which concerns on 1st Embodiment. The figure which shows the dimension regarding the space | interval of the 1st and 2nd heating roller which concerns on 1st Embodiment, a compression spring, etc. The figure which shows the spring holding members 304 and 305 which concern on 2nd Embodiment. The figure which shows the fixation method of the compression spring 301 which concerns on 2nd Embodiment, and the time of the assembly | attachment (assembly) of the external heating belt 105 The figure which shows the state after the assembly | attachment of the external heating belt 105 which concerns on 2nd Embodiment. The figure which shows the problem at the time of the assembly of the external heating belt in a prior art example The figure which shows the assembly improvement of the external heating belt using the wire spring in a prior art example

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
An image forming apparatus equipped with a fixing device having an external heating belt unit according to an embodiment of the present invention will be described with reference to FIG. In the apparatus shown in FIG. 2, first, second, third, and fourth image forming portions Pa, Pb, Pc, and Pd are provided, and toner images (developer images) of different colors are latent images. , Development and transfer processes.

  Each of the image forming portions Pa, Pb, Pc, and Pd includes a dedicated image carrier, in this example, the electrophotographic photosensitive drums 3a, 3b, 3c, and 3d, and each color is provided on each of the photosensitive drums 3a, 3b, 3c, and 3d. The toner image is formed. An intermediate transfer member 130 is installed adjacent to each of the photosensitive drums 3a, 3b, 3c, and 3d, and the toner images of the respective colors formed on the photosensitive drums 3a, 3b, 3c, and 3d are primary on the intermediate transfer member 130. It is transferred and transferred onto the recording material p at the secondary transfer portion. Further, the recording material p onto which the toner image has been transferred is fixed to the toner image by heating and pressurizing at the fixing unit 9 and then discharged out of the apparatus as a recorded image.

  Drum chargers 2a, 2b, 2c, 2d, developing devices 1a, 1b, 1c, 1d, primary transfer chargers 24a, 24b, 24c, 24d, and cleaners are disposed on the outer periphery of the photosensitive drums 3a, 3b, 3c, 3d, respectively. 4a, 4b, 4c, 4d are provided. A light source device and a polygon mirror (not shown) are further installed in the upper part of the device.

  The laser light emitted from the light source device is scanned by rotating the polygon mirror, the light beam of the scanning light is deflected by the reflection mirror, and condensed on the buses of the photosensitive drums 3a, 3b, 3c, and 3d by the fθ lens. Exposure. As a result, latent images corresponding to the image signals are formed on the photosensitive drums 3a, 3b, 3c, and 3d.

  The developing devices 1a, 1b, 1c, and 1d are filled with a predetermined amount of cyan, magenta, yellow, and black toners, respectively, as developers. The developing devices 1a, 1b, 1c, and 1d develop the latent images on the photosensitive drums 3a, 3b, 3c, and 3d, respectively, and visualize them as cyan toner images, magenta toner images, yellow toner images, and black toner images.

  The intermediate transfer member 130 suspended from the tension roller 13, the secondary transfer inner roller 14, and the driving roller 15 is rotationally driven in the direction of the arrow at the same peripheral speed as the photosensitive drum 3. The yellow toner image of the first color formed and supported on the photosensitive drum 3a is passed through the nip portion between the photosensitive drum 3 and the intermediate transfer body 130 by the primary transfer bias applied to the intermediate transfer body 130. Intermediate transfer is performed on the outer peripheral surface of the intermediate transfer body 130.

  Reference numeral 11 denotes a secondary transfer roller, which corresponds to the intermediate transfer member 130 and is provided in parallel and in contact with the lower surface portion. A desired secondary transfer bias is applied to the secondary transfer roller 11 by a secondary transfer bias source.

  Transfer of the composite color toner image superimposed and transferred onto the intermediate transfer body 130 to the transfer material P is performed as follows. That is, the transfer material P is fed at a predetermined timing to the contact nip between the intermediate transfer body 130 and the secondary transfer roller 11 through the registration roller 12 and the pre-transfer guide from the paper feeding cassette 10, and simultaneously the secondary transfer. A bias is applied from a bias power source. The composite color toner image is transferred from the intermediate transfer body 130 to the recording material P by the secondary transfer bias.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black toner image are sequentially superimposed and transferred onto the intermediate transfer body 130, and a composite color toner image corresponding to the target color image is obtained. Is formed.

  After the primary transfer, the photosensitive drums 3a, 3b, 3c, and 3d are cleaned and removed of the transfer residual toner by the respective cleaners 4a, 4b, 4c, and 4d, and are subsequently prepared for forming the next latent image. The toner and other foreign matters remaining on the transfer belt 130 are wiped off by contacting the surface of the transfer belt 130 with a cleaning web (nonwoven fabric) 20.

  Then, the transfer material P that has received the transfer of the toner image is sequentially introduced into the fixing device 9 and fixed by applying heat and pressure to the transfer material.

  When the recording material P is in the double-sided mode, the recording material P fed from the paper feeding cassette 10 passes through the registration roller 12, the pre-transfer guide, and the contact nip between the intermediate transfer body 130 and the secondary transfer roller 11. After being fixed on one side by the fixing device 9, it is guided to the reverse path by the flapper 16.

  Thereafter, the recording material P is reversed by the reversing roller 17 and guided to the double-sided path 19. Then, the recording material P again passes through the contact roller nip between the registration roller 12, the pre-transfer guide, the intermediate transfer body 130 and the secondary transfer roller 11, the second surface is transferred, and both surfaces are fixed by the fixing device 9. The surface flapper 16 is switched during the double-sided image formation of the recording material, and the recording material P fixed on both sides is discharged out of the apparatus as a recorded image.

(Fixing device)
Next, the configuration of the fixing device using the external heating belt unit assembling apparatus according to the present invention will be described in detail with reference to FIG. In FIG. 1, the fixing device 9 includes a fixing roller 101 as an image heating member, a pressure roller 102 as a pressure member, and an external heating belt unit described below.

  Here, the external heating belt unit is in a first compressed state at both longitudinal ends of the belt 105, the first and second heating rollers 103 and 104 that suspend the belt, and the first and second heating rollers. And an elastic member that applies a force in a direction to expand the space between the heating rollers. Further, the external heating belt unit has a heating means for heating at least one of the first and second heating rollers.

  Then, the recording material P carrying the unfixed toner K is nipped and conveyed to the fixing nip portion N formed by the fixing roller 101 and the pressure roller, and the toner K is fixed on the recording material P.

  The fixing roller 101 is driven to rotate at a predetermined speed in the direction of arrow A by a driving source (not shown). Inside the core of the fixing roller 101, a halogen heater 111 is disposed as a heating element, and is heated from the inside so that the surface temperature of the fixing roller 101 becomes a predetermined temperature.

  The surface temperature of the fixing roller 101 is detected by a thermistor 121 as temperature detecting means that contacts the fixing roller 101. And based on this detected temperature, the control apparatus 140 as a temperature control (adjustment) means turns on / off the halogen heater 111 to control at a predetermined target temperature.

  The pressure roller 102 is pressed to the fixing roller 101 with a predetermined pressure by a pressure unit (not shown) to form the fixing roller 101 and the fixing nip portion N, and is fixed at a predetermined speed in the arrow B direction. The roller 101 is driven to rotate. In addition, a halogen heater 112 is disposed as a heating element inside the metal core of the pressure roller 102 and is heated from the inside so that the surface temperature of the pressure roller 102 becomes a predetermined temperature.

  The surface temperature of the pressure roller 102 is detected by a thermistor 122 as temperature detecting means that contacts the pressure roller 102, and the halogen heater 112 is turned on / off by the heater control means 140 and controlled at a predetermined target temperature. .

(External heating belt unit)
Next, the external heating belt unit will be described in more detail. As shown in FIG. 3, an external heating belt (belt) 105 serving as an external heating member is disposed on the outer peripheral surface of the fixing roller 101. Then, the external heating belt unit including the first and second heating rollers 103 and 104 that stretch the belt 105 is pressed against the outer peripheral surface of the fixing roller 101 with a predetermined pressure by the pressing unit 204. As a result, the outer peripheral surface of the belt 105 is pressed against the outer peripheral surface of the fixing roller 101. At this time, as shown in FIG. 3, the belt 105 forms a contact surface Ne with the fixing roller 101.

  Here, the belt 105 pressed by the fixing roller 101 is rotatably supported by the heating rollers 103 and 104 so as to be rotated by the rotation of the fixing roller 101.

  On the outer peripheral surface of the belt 105, a cleaning roller 108 for cleaning the surface of the belt 105 is provided upstream of the thermistor 123 and the thermistor 124 with respect to the rotation direction of the belt (at a predetermined pressure by a not-shown pressurizing means). Pressed against the belt 105).

  The belt 105 has a layer of a metal base material (stainless steel, nickel, etc.) or a resin base material (PI, etc.), and is used as a heat-resistant sliding layer to prevent adhesion with toner. Covered with resin. The belt 105 is driven and rotated by the fixing roller 101 at a predetermined speed in the direction of arrow C shown in FIG. 1 to heat the surface of the fixing roller 101.

  In addition, a halogen heater 113 is disposed as a heating element inside the core of the first heating roller 103, and is heated from the inside so that the surface temperature of the belt 105 becomes a predetermined temperature. The surface temperature of the belt 105 is detected by a thermistor 123 that is in contact with the contact region D1 between the first heating roller 103 and the belt 105, which is a temperature detecting means. Then, based on the detected temperature, the heater control unit 140 turns the halogen heater 113 on / off (on / off) and controls (temperature adjustment control) so as to reach a predetermined target temperature.

  The second heating roller 104 over which the belt 105 is stretched has substantially the same configuration as the first heating roller 103 and is disposed on the downstream side in the fixing roller rotation direction. The second heating roller 104 also contacts the inner surface of the belt 105 to heat the belt 105. In addition, a halogen heater 114 is disposed as a heating element inside the core of the second heating roller 104, and is heated from the inside so that the surface temperature of the belt 105 becomes a predetermined temperature.

  The surface temperature of the belt 105 is detected by a thermistor 124 that is in contact with the contact region D2 between the second heating roller 104 and the belt 105, which is a temperature detecting means. Then, based on the detected temperature, the heater control means 140 turns the halogen heater 114 on / off (on / off) and controls (temperature adjustment control) so as to reach a predetermined target temperature.

  Since the target temperature of the belt 105 is set to be higher than the target temperature of the fixing roller 101, the belt has good response (heat sensitivity accuracy) with respect to the surface temperature of the fixing roller 101 dropping due to contact with the recording material. Heat is supplied from 105 to the fixing roller 101.

  FIG. 4 is a schematic view of the external heating belt unit of this embodiment in the longitudinal direction (direction perpendicular to the recording material conveyance direction), whereas FIG. 3 is a front view of the external heating belt unit of this embodiment. 3, 4, and FIG. 7, FIG. 8, and FIG. 10 described later, the holding members (second holding members) 206 (206 a, b) are respectively the first heating roller 103 and the second heating roller 104. Rotating members 131 and 132 as bearings that rotatably support both end portions in the longitudinal direction are held. The holding members 206 (206a, b) are rotatably supported by pressure arms 117 (117a, b) shown in FIG.

  Here, the external heating belt unit including the belt 105 is configured to be able to contact / retreat with respect to the fixing roller 101. Specifically, in FIG. 3, the pressure arm 117 rotates around the shaft 203 disposed between the main body side plates 202 (FIG. 4) at both ends in the longitudinal direction, and is pressed by the pressure spring 204 (FIG. 3). Under pressure, it is biased toward the fixing roller 101. Then, when the cam 205 (FIG. 3) rotates, the pressure arm 117 is raised and lowered, and the contact / retraction operation of the belt 105 with respect to the fixing roller 101 is performed.

  9 and 10 show in detail the operation related to the contact / retraction of the belt 105 with respect to the fixing roller 101. FIG.

1) Retraction of Belt from Fixing Roller First, a configuration in which the belt 105 is retracted from the fixing roller 101 will be described.

  FIG. 9A shows a comparative example, and FIG. 9B shows an embodiment of the present invention. In FIG. 9A, unlike FIG. 9B, a force is applied in a direction to widen the space between the first heating roller 103 and the second heating roller 104 that suspends the external heating belt 105 (a tension described later on the external heating belt 105). There is no configuration.

  In FIG. 9A, since the first heating roller 103 and the second heating roller 104 that suspend the external heating belt 105 are fixed and the distance between the two axes is kept constant, the belt 105 is slackened, The belt 105 is bent in a direction approaching the fixing roller 101. Therefore, in order to sufficiently separate the external heating belt 105 from the fixing roller 101, it is necessary to increase the retraction amount of the external heating belt unit, and it is necessary to increase the size of the fixing unit itself.

  On the other hand, in FIG. 9B, when the external heating belt 105 is retracted from the fixing roller 101, the space between the first heating roller 103 and the second heating roller 104 is widened. Therefore, the belt 105 is pulled in the tangential direction of the first heating roller 103 and the second heating roller 104 to apply tension. As a result, the retracting amount of the external heating belt unit for sufficiently separating the external heating belt 105 from the fixing roller 101 can be reduced.

2) Contact of Belt with Fixing Roller Next, a configuration in which the belt 105 contacts the fixing roller 101 will be described. In the present embodiment, a configuration is employed in which tension described later is applied between the heating rollers that suspend the belt 105 to tension the belt.

  As shown in FIG. 10, when the belt 105 is brought into contact with the fixing roller 101, the second heating roller 104 does not move because the position is fixed by the holding member 206. On the other hand, since there is a clearance between the first heating roller 103 and the holding member 206, the first heating roller 103 moves in a direction approaching the second heating roller 104 when contacting the fixing roller 101. A first heating roller is disposed at a position where the belt 105 is in close contact with the fixing roller 101 with a desired nip width. In order to obtain adhesion with such a desired nip width, the external heating belt unit is pressurized by the pressure member 204 (FIG. 3).

  As described above, in this embodiment, the retracting amount of the external heating belt unit when retracting from the fixing roller 101 is reduced, and the adhesion of the belt 105 when contacting the fixing roller 101 is improved. It becomes possible.

(Applying tension to the belt 105)
Next, the application of tension to the belt 105 in this embodiment will be described. In the present embodiment, the compression spring 301 is inserted between the first and second heating rollers 103 and 104 and the rotary members 131 and 132 (FIG. 3) in the longitudinal direction using an assembly device described below. Then, as shown in FIG. 1, a force is applied in the direction of widening the distance between the first heating roller 103 and the second heating roller (tension is applied).

1) External Heating Belt Unit Assembly Device In FIG. 7, the holding member 206 includes a spring holding member (first holding member) 302 that holds the compression spring 301 and both ends in the longitudinal direction of the heating roller (outer region of the belt 105). ) And the spring holding member 302 which shows an outline figure in FIG. 5 is provided with arm parts 303a and 303b, and holds the compression spring 301 in a compressed state. At this time, since the compression spring 301 is contracted from the free length, a force is applied in the direction of expanding the space between the first heating roller 103 and the second heating roller 104 via the surface of the spring holding member 302. Further, the spring holding member 302 prevents the compression spring 301 from moving in the direction perpendicular to the pressing direction.

  Regarding the spring holding member 302, it is necessary to prevent the compression spring 301 from obstructing the application of tension between the first heating roller 103 and the second heating roller 104. In this configuration, the spring holding member 302 formed of a plate-shaped elastic member (plate spring) assists the force in the direction of widening the interval between the first heating roller 103 and the second heating roller 104. The thickness of the leaf spring is reduced. For this reason, the force is very small compared to the tension generated by the compression spring 301. Therefore, it is possible to realize a desired tension between the heating rollers.

  In FIG. 7, the holding member 206 has a clearance between the first heating roller 103 and the first heating roller 103 can be displaced within the clearance range. On the other hand, there is no clearance between the second heating roller 104 and the second heating roller 104 is fixed.

2) Assembling procedure The assembling procedure of the external heating belt unit in this embodiment is shown below. First, a compression spring 301 having a free length L0 (free length G in FIG. 11 to be described later) is passed between spring holding members 302 formed of a leaf spring shown in FIG. The arm portions 303a and 303b are hooked. Thereby, the compression spring 301 can be held between the arm portions 303a and 303b of the spring holding member 302 (FIG. 6). At this time, the compression spring 301 is compressed (second compressed state) by being sandwiched between the spring holding members 302, and is held at the length L1 (FIG. 6).

  On the other hand, in the external heating belt unit without the compression spring 301, the first heating roller 103 and the second heating roller 104 in which the rotating members 131 and 132 are arranged at both ends in the longitudinal direction are passed through the belt 105, and the belt 105 Is suspended.

  Here, as shown in FIG. 7, the rotating members 131 and 132 in the external heating belt unit are pushed in such that the compression spring 301 held by the spring holding member 302 is disposed between the rotating members 131 and 132. Since the spring holding member 302 has a tapered shape, the compression spring 301 is mounted between the first and second heating rollers 103 and 104 while compressing the compression spring 301 from the state of FIG. 7 to the state of FIG. it can. At this time, the compression spring 301 is further compressed between the rotating members 131 and 132, and is held at the length L2 (FIG. 8).

  Then, as shown in FIG. 8, a heating roller fixing member 209 is attached to prevent the heating rollers 103 and 104 from falling. The heating roller fixing member 209 is removed before the external heating belt unit is attached (assembled) to the fixing roller 101.

3) Comparison before and after assembly of the compression spring The length L1 of the compression spring 301 held by the spring holding member 302 shown in this configuration and the tension between the heating members arranged between the rotating members 131 and 132 are applied. The relationship between the length L2 at the time of giving and the free length L0 is as shown in the following equation (a).

L0>L1> L2 (a)
Here, L2 is the length of the first compression state (fixed state after assembly), and L1 is the length of the second compression state (before assembly) whose degree of compression is weaker than that of the first compression state.

4) Effect As shown in FIG. 14, in the conventional example, when the belt 105 is assembled, the rotating members 131 and 132 that rotatably support the first heating roller 103 and the second heating roller 104 are the first and second heating members. It contacts the compression spring 301 whose position in the direction of connecting the rollers is not regulated. Then, there is a possibility that the position of the compression spring 301 is largely displaced and the compression spring 301 may get under the end of the first heating roller 103 or the second heating roller 104. Furthermore, since the compression spring 301 may fall off or deform due to contact, it is very difficult to assemble.

  On the other hand, in this configuration, the spring holding member 302 regulates the position in the direction connecting the first and second heating rollers, and the compression spring 301 is arranged in a state shorter than the free length L0. The rotating members 131 and 132 are pushed into the places. For this reason, it becomes possible to prevent the rotation member arrange | positioned at the both ends of a heating roller from contacting the cylindrical part side surface of the compression spring 301, and can prevent the deformation | transformation of the compression spring 301 at the time of an assembly.

  Further, since the spring holding member 302 is formed of a leaf spring, it can be easily assembled by pushing the rotating members 131 and 132 so as to slide into the flat portion of the leaf spring.

  As described above, in the external heating belt unit assembled as in the present embodiment, a compression spring is provided between the first heating roller 103 and the second heating roller 104 that suspends the belt 105 and pressurizes in a direction in which the distance between the rollers expands. The heating roller is movably arranged. Thus, when the belt 105 is retracted from the fixing roller 101, tension is applied to the belt 105 by the heating rollers 103 and 104, and the belt 105 is prevented from slackening. For this reason, the retraction amount of the external heating belt unit can be reduced.

  Furthermore, in this embodiment, the compression spring 301 for applying tension between the heating rollers 103 and 104 is shorter than the free length, and the length when applying tension between the heating rollers 103 and 104 (L2). It is held in a longer state (length L1). Thereby, it becomes possible to improve assemblability and exchangeability.

  Here, specific dimensions are shown in FIG. 11A and 11B show dimensions relating to the distance between the first and second heating rollers 103 and 104, and the minimum of the rotating members 131 and 132 as the bearings of the first and second heating rollers 103 and 104. The interval is A, and the interval during tension is B. Also, let C be the interval when the first and second heating rollers 103 and 104 are in tension. Further, the minimum roller axis distance between the first and second heating rollers 103 and 104 is H, and the tension roller axis distance is I.

  The free length of the compression spring 301 is G, the fixed length is E, the spring holding frame length is F, and the fixed member head length is D.

Here, specific dimensions are as follows: A is o. 2 mm, B is 11.7 mm, C is 11.5 mm, D is 12 mm, E is 14 mm, F is 6.8 mm, G is 17 mm, H is 32.2 mm, and I is 43.6 mm. The spring constant of the compression spring 301 is 0.6 kgf / mm.
<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIG. 12, FIG. 13, and FIG. In the present embodiment, as a portion different from the portion shown in the first embodiment, a configuration different from the first embodiment in which the compression spring is held in a state shorter than the free length in a state where the heating roller is not disposed. Show.

  In this embodiment, in order to arrange the compression spring 301 in a state shorter than the free length, the compression spring 301 is passed through a spring holding member 304 having a claw shape as shown in FIG. 12, and a holding member having a hole into which the claw shape enters. The holding member 304 is pushed into 305. Then, by inserting the claw of the holding member 304 into the hole of the holding member 305, the compression spring 301 is disposed between the holding member 304 and the holding member 305 in a state shorter than the free length L0 (compression length L1). The length L1 of the compression spring 301 at this time is longer than the length L2 that applies tension when the heating roller is arranged.

  Thus, in this embodiment, the spring holding member (first holding member) is composed of two holding members each having a claw shape on one side and a hole shape into which the claw shape enters the other side. In this way, the compression spring 301 is disposed between the holding members 304 and 305 and the state in which the compression spring 301 is maintained shorter than the free length L0 (compression length L1) is substantially cylindrical formed on the holding member 206 as shown in FIG. It is placed inside the shaped wall 306.

  Further, the substantially cylindrical wall 306 and the elastic member 307 formed on the holding member 206 regulate the position in the direction connecting the compression spring 301 and the rotating members 131 and 132 (FIG. 13) of the holding members 304 and 305. In addition, the compression spring 301 is arranged at a fixed position.

  As described above, in this embodiment, the compression spring 301 is disposed on the substantially cylindrical wall 306 formed on the holding member 206 and is held between the spring holding members 304 and 305 in a state shorter than the free length L0. This avoids the possibility of contacting the compression spring 301 at both ends of the first heating roller 103 and the second heating roller 104 when the belt 105 is assembled, and the belt 105, the first heating roller 103, and the second heating roller. Assembling 104 becomes easy.

(External heating belt unit manufacturing method)
What is described in the above-described embodiment can be expressed as a method for manufacturing an external heating belt unit as follows.

  A step (step) of holding the compression spring 301 in a state (compression length L1) shorter than the free length L0 using a spring holding member. On the other hand, in the external heating belt unit without the compression spring 301, the first heating roller 103 and the second heating roller 104 in which the rotating members 131 and 132 are arranged at both ends in the longitudinal direction are passed through the belt 105, and the belt 105 There is a step (step) of suspending. And it has the step (step) which pushes in the rotation members 131 and 132 in an external heating belt unit so that the compression spring 301 may be arrange | positioned between the rotation members 131 and 132. FIG.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the above-described embodiment, the compression spring 301 is inserted between the rotating members 131 and 132 provided at both ends in the longitudinal direction of the first and second heating rollers, but the rotating members 131 and 132 are not provided. good. In this case, the compression spring 301 is inserted between the first and second heating rollers at both ends in the longitudinal direction of the first and second heating rollers.

103, 104 ... heating roller, 105 ... external heating belt, 113, 114 ... halogen heater, 206 ... holding member (second holding member), 301 ... compression spring, 302 ... spring Holding member (first holding member)

Claims (5)

Belt,
First and second heating rollers for suspending the belt;
A compression spring that is compressed into a first compressed state at both longitudinal ends of the first and second heating rollers and applies a force in a direction that widens the space between the first and second heating rollers;
Heating means for heating at least one of the first and second heating rollers;
A support member for supporting the first and second heating rollers;
A compression spring support provided on the support member and supporting the compression spring;
A holding portion that is provided in contact with the compression spring at an opening side at one end and an opening side at the other end of the compression spring, and holds the compression spring in a state in which the compression spring can expand and contract,
The holding portion has a restricting portion for restricting the maximum length of the compression spring so that the maximum length of the compression spring is a predetermined length shorter than a free length.
A heating belt unit characterized by that. Before Kiho lifting portion is formed of an elastic spring plate shape,
Pressurized heat Berutoyuni' bets according to claim 1, characterized in that. In the restricting portion, one end of the elastic spring is inserted into the compression spring from an opening at one end of the compression spring, and the other end of the elastic spring is inserted into the compression spring from an opening at the other end of the compression spring. Inserted, and one end of the elastic spring and the other end of the elastic spring are connected inside the compression spring to regulate the maximum length of the compression spring,
The heating belt unit according to claim 2. The restricting portion has a claw shape on one side and a hole shape into which the claw shape enters the other side,
Pressurized heat Berutoyuni' bets according to claim 1, characterized in that. An image heating roller for heating an image on a recording material and the belt are brought into contact with each other to heat the image heating roller.
The heating belt unit according to claim 1, wherein the heating belt unit is a heating belt unit.