JP2009258516A - Fixing apparatus, and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt-fixing type fixing apparatus that can prevent a fixing failure from occurring while preventing a fixing temperature from varying, and to provide an image forming apparatus having the same. <P>SOLUTION: A heating means 20 heats a fixing belt 25 by coming into contact with the fixing belt 25. In the heating means 20, a plurality of heating members 21 and 31, which have a planar heating element formed on an inner surface of a curved base material, are formed substantially in a semicircular shape as a whole. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium by heat and pressure, and an image forming apparatus including the fixing device.

  As a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a heat roller fixing type fixing device is frequently used. A heat roller fixing type fixing device includes a roller pair (fixing roller and pressure roller) that are in pressure contact with each other, and is heated by a heating unit including a halogen heater or the like disposed inside or both of the roller pair. After the pair is heated to a predetermined temperature (fixing temperature), a recording medium such as a recording sheet on which a fixed toner image is formed is fed to the pressure contact portion (fixing nip portion) of the roller pair and passed through the pressure contact portion. The toner image is fixed on the recording paper by heat and pressure.

  By the way, in a fixing device provided in a color image forming apparatus, it is common to use an elastic roller provided with an elastic layer made of silicon rubber or the like on the surface of the fixing roller. By using an elastic roller as the fixing roller, the surface of the fixing roller is elastically deformed corresponding to the unevenness of the unfixed toner image, and comes into contact so as to cover the toner image surface. It is possible to perform heat fixing on an unfixed toner image satisfactorily. In addition, due to the strain relief effect of the elastic layer at the fixing nip, it is possible to improve the releasability for color toners that are more likely to be offset than in monochrome. Further, since the nip shape of the fixing nip is convex upward (on the fixing roller side) (so-called reverse nip shape), it is possible to improve the recording paper peeling performance without using a peeling means such as a peeling claw. The recording paper can be peeled off (self-stripping), and image defects caused by the peeling means can be eliminated.

  Incidentally, in the fixing device provided in such a color image forming apparatus, it is necessary to widen the nip width of the fixing nip portion in order to cope with the high speed. As a method for widening the nip width, there are methods such as increasing the thickness of the elastic layer of the fixing roller and increasing the diameter of the fixing roller. However, in a fixing roller having an elastic layer, since the thermal conductivity of the elastic layer is very low, there is a problem that the temperature of the fixing roller does not follow when the process speed is increased when there is a heating means inside the fixing roller. is there. On the other hand, when the diameter of the fixing roller is increased, there are problems that the warm-up time becomes longer and the power consumption increases.

  As a fixing device provided in a color image forming apparatus that solves such a problem, Patent Document 1 discloses that a fixing belt is stretched between a fixing roller and a heating roller, and the fixing roller and the pressure roller are interposed via the fixing belt. A belt-fixing type fixing device having a configuration in which the two are in pressure contact with each other is disclosed. In this belt fixing type fixing device, since the fixing belt having a small heat capacity is heated, the warm-up time is short, and it is not necessary to incorporate a heat source such as a halogen lamp in the fixing roller. A thick elastic layer can be provided, and a wide nip width can be secured.

  Further, Patent Document 2 discloses a fixing device using a sheet heating belt fixing method in which a heating unit is a sheet heating element in a belt fixing method fixing device. In this surface heating belt fixing type fixing device, the heat capacity of the heating means is reduced, and at the same time, the surface heating element as the heating means directly generates heat, so the heating roller is indirectly heated using a halogen lamp or the like. Compared with the method, the thermal response speed is improved, and the warm-up time can be further shortened and further energy saving can be achieved.

JP-A-10-30796 2002-333788

  Here, in a fixing device that obtains a predetermined fixing temperature via a fixing belt, such as the fixing device disclosed in Patent Document 2, a sheet heating element that heats the fixing belt is large in order to prevent fixing failure. It must have heat generation capacity. A planar heating element having a large heat generation capacity can be achieved by increasing the length extending in the circumferential direction to increase the area of the planar heating element itself.

  When the length extending in the circumferential direction of the semicircular arc-shaped substrate is increased, the opening is narrowed. In this way, when forming a planar heating element on the inner surface of the base material with the opening narrowed by painting, screen printing method, etc., it will be formed facing the inner side from the narrowed opening side, It becomes difficult to form a planar heating element having a uniform film thickness. For this reason, the temperature distribution on the surface of the sheet heating element becomes non-uniform, the fixing temperature varies, and high print quality cannot be maintained.

  Accordingly, an object of the present invention is to provide a fixing device capable of preventing a fixing failure from occurring while preventing a fixing temperature from varying in a belt fixing type fixing device. Another object of the present invention is to provide an image forming apparatus including the fixing device.

The present invention includes an endless fixing belt stretched between a fixing roller and a heating unit, and a pressure member facing the fixing roller via the endless fixing belt, and the heating unit includes the fixing unit. Fixing by heating the fixing belt in contact with the belt and fixing the toner image carried on the recording medium by heating and pressing on the recording medium at a fixing nip formed by the fixing belt and the pressure member. A device,
The heating unit is a fixing device in which a plurality of heating members each having a planar heating element formed on the inner surface of a curved substrate are formed in a substantially semicircular arc shape as a whole.

  Moreover, this invention is provided with the press member which presses each of these heating members which the said heating means has from the inner side toward the outward.

  Moreover, this invention is provided with the tension | pulling member which pulls each of these heating members which the said heating means has from the outer side.

  In the invention, it is preferable that the pressing member and the tension member are spring members having elasticity.

  According to the present invention, each of the plurality of heating members is formed with a bent portion that is bent inward at both ends in the circumferential direction.

  In the invention, it is preferable that the bent corner portion of the bent portion has a curved shape having a predetermined radius of curvature.

In addition, the present invention has a stopper member that sandwiches and joins the bent portions formed on one circumferential end of each of the plurality of heating members,
The pressing member is configured to press the locking hand member outward.

In the present invention, a notch is formed in the bent portion formed on one end side in the circumferential direction of each of the plurality of heating members,
The anchoring hand member has a claw portion,
The claw part engages with the notch part, and the plurality of heating members are joined.

  According to the present invention, when the fixing belt is stretched between the heating unit and the fixing roller, a heating unit in which a region in contact with the heating unit is formed in a substantially semicircular arc shape as a whole. The circumferential length of the fixing roller is configured to be 50% or more, or the region in contact with the fixing roller is 50% or more of the circumferential length of the fixing roller.

  Further, in the present invention, the planar heating element included in each of the plurality of heating members includes a resistance heating layer and an insulating layer, and the insulating layer is a layer in contact with the substrate. It is formed on the inner surface of the substrate.

According to the present invention, in the base member included in each of the plurality of heating members, a coat layer capable of reducing a frictional force with the fixing belt is formed on an outer surface in contact with the fixing belt. Features.
According to another aspect of the present invention, there is provided an image forming apparatus including the fixing device.

  According to the present invention, the heating unit that heats the fixing belt in contact with the fixing belt has a plurality of heating members each having a planar heating element formed on the inner surface of the curved base material in a substantially semicircular arc shape as a whole. Is formed. Here, in each heating member, a planar heating element is individually formed on the inner surface of each base material in a state where the opening is widely secured. Therefore, a planar heating element with a uniform film thickness can be formed on the inner surface of each substrate, and the temperature distribution on the surface of the planar heating element is not uniform, thereby preventing the fixing temperature from varying. Can do.

  Furthermore, since the heating means is formed in a substantially semicircular arc shape as a whole with a plurality of heating members on which the planar heating element having a uniform film thickness is formed, the circumferential length of the entire planar heating element is increased. Thus, the area of the entire sheet heating element can be increased. Therefore, a sufficient heat generation capacity can be achieved as the whole heating means, and the fixing belt can be heated to a desired fixing temperature. Therefore, it is possible to prevent a fixing failure from occurring.

  Moreover, according to this invention, the pressing member which presses each of the several heating member which a heating means has from the inside toward outward is provided. This makes it possible to apply a predetermined tension to the fixing belt that slides in contact with the plurality of heating members of the heating means. Therefore, the adhesion between the heating unit and the fixing belt can be improved, and the heating efficiency of the heating unit with respect to the fixing belt can be improved.

  Moreover, according to this invention, the tension member which pulls each of the some heating member which a heating means has from the outer side is provided. This makes it possible to apply a predetermined tension to the fixing belt that slides in contact with the plurality of heating members of the heating means. Therefore, the adhesion between the heating unit and the fixing belt can be improved, and the heating efficiency of the heating unit with respect to the fixing belt can be improved.

  According to the invention, the pressing member and the tension member are spring members having elasticity. The spring member can apply a predetermined tension to the fixing belt that slides in contact with the plurality of heating members included in the heating means by the elastic force thereof.

  According to the present invention, each of the plurality of heating members is formed with a bent portion that is bent inward at both ends in the circumferential direction. As a result, the rigidity of the heating member itself can be increased, and the durability can be improved.

  Moreover, according to this invention, the bending angle part of the bending part formed in the circumferential direction both ends of a heating member is a curved-surface shape with a predetermined curvature radius. As a result, the fixing belt in contact with the heating member can be prevented from receiving excessive stress in the vicinity of the bent corner portion of the heating member, and can be prevented from being worn.

  Moreover, according to this invention, it has a securing hand member which pinches | interposes and joins the bending parts formed in each circumferential direction one end side of a heating member, and a press member turns the said securing hand member outward. It is comprised so that it may press. In this way, a plurality of heating members can be joined to each other by the stopper member by utilizing a bent portion having an effect of improving the rigidity of the heating member itself. Further, since the locking hand member is configured to be pressed outward, a predetermined tension can be applied to the fixing belt that slides in contact with the plurality of heating members of the heating unit at the joint portion. It becomes possible. Therefore, the adhesion between the heating unit and the fixing belt can be improved, and the heating efficiency of the heating unit with respect to the fixing belt can be improved.

  Moreover, according to this invention, a notch part is formed in the bending part formed in the circumferential direction one end side of each of a some heating member, and a nail | claw part is formed in a securing hand member. And a nail | claw part engages with a notch part and a some heating member is joined. In this way, by simply engaging the claw portion with the notch portion, a plurality of heating members can be easily joined to each other, and the securing hand member can be prevented from easily falling off. Can do.

  Further, according to the present invention, when the fixing belt is stretched between the heating unit and the fixing roller, the region of the heating unit in which the winding contact is formed in a substantially semicircular arc shape as a whole is formed. It is configured to be 50% or more with respect to the circumferential length. Accordingly, since the heating unit can take a wide contact area with the fixing belt, the fixing belt can be heated with excellent thermal efficiency and low power consumption. In addition, the fixing belt is configured such that the region in contact with the fixing roller is 50% or more with respect to the circumferential length of the fixing roller. As a result, the contact area between the fixing roller and the fixing belt can be increased, so that it is excellent in thermal followability and can be applied to a fixing device of a high-speed machine.

  According to the invention, the planar heating element included in each of the plurality of heating members includes the resistance heating layer and the insulating layer. The planar heating element is formed on the inner surface of the base material so that the insulating layer is a layer on the side in contact with the base material. Thus, since the insulating layer is interposed between the base material and the resistance heating layer, insulation between the base material and the resistance heating layer can be ensured, and a safer heating means can be obtained. In addition, the selection range of materials that can be used as a base material can be expanded. For example, even if a metal material having a low heat capacity such as aluminum or stainless steel is used as a base material, insulation between the base material and the resistance heating layer is possible. Can be secured.

  According to the invention, in the base material of each of the plurality of heating members, the coat layer capable of reducing the frictional force with the fixing belt is formed on the outer surface in contact with the fixing belt. This prevents wear of the fixing belt that slides in contact with the base material, and ensures high durability of the fixing belt. In addition, since the frictional force with the fixing belt can be reduced, the load on the fixing roller that drives the fixing belt can be reduced, the durability of the fixing roller is ensured, and the driving is performed with low power. Is possible.

  Further, according to the present invention, the image forming apparatus includes the fixing device that can prevent the fixing temperature from being varied and also prevent the fixing failure from occurring, so that an image with high print quality can be formed. be able to.

  FIG. 1 is a diagram illustrating a configuration of a fixing device 15 according to an embodiment of the present invention. The fixing device 15 includes a fixing roller 15a, a pressure roller 15b, a fixing belt 25, and a heating unit 20. In the fixing device 15, the fixing belt 25 is stretched between the fixing roller 15 a and the heating unit 20, and the pressure roller 15 b is disposed so as to face the fixing roller 15 a through the fixing belt 25. The fixing roller 15a and the heating unit 20 are arranged so as to be substantially parallel in the axial direction of the fixing roller 15a. Therefore, when the fixing belt 25 stretched between the fixing roller 15a and the heating unit 20 slides, it can be prevented from meandering and the durability of the fixing belt 25 can be maintained high.

  In the fixing device 15, the heating unit 20 contacts the fixing belt 25 to heat the fixing belt 25, and the fixing nip portion 15 c formed by the fixing belt 25 and the pressure roller 15 b is recorded at a predetermined fixing speed and copying speed. This is an apparatus for fixing an unfixed toner image 31 carried on the recording paper 32 by heating and pressing the recording paper 32 when the recording paper 32 as a medium passes.

  The unfixed toner image 31 is a developer (such as a non-magnetic one-component developer (non-magnetic toner), a non-magnetic two-component developer (non-magnetic toner and carrier), or a magnetic developer (magnetic toner). Toner). The fixing speed is a so-called process speed, and the copying speed is the number of copies per minute. When the recording paper 32 passes through the fixing nip portion 15c, the fixing belt 25 comes into contact with the surface of the recording paper 32 opposite to the toner image carrying surface.

  The fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 25 to form the fixing nip portion 15c, and at the same time, is driven to rotate about the rotation axis in the direction of rotation A by a driving motor (driving means) (not shown). As a result, the fixing belt 25 is conveyed. The fixing roller 15a has a diameter of 30 mm and has a two-layer structure in which a core metal and an elastic layer are formed in order from the inside. The core metal includes, for example, a metal such as iron, stainless steel, aluminum, copper, or the like. An alloy or the like is used. For the elastic layer, a heat-resistant rubber material such as silicon rubber or fluorine rubber is suitable. In the present embodiment, the force when the fixing roller 15a is pressed against the pressure roller 15b via the fixing belt 25 is about 216N.

  The pressure roller 15b is opposed to and pressed against the fixing roller 15a via the fixing belt 25, and is provided to be rotatable about the rotation axis. The pressure roller 15b rotates in the rotation direction B following the rotation of the fixing roller 15a. The pressure roller 15b has a three-layer structure in which a metal core, an elastic layer, and a release layer are formed in this order from the inside. For the metal core, for example, a metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used. For the elastic layer, a rubber material having heat resistance such as silicon rubber and fluorine rubber is suitable, and for the release layer, PFA (copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable. A fluororesin such as fluoroethylene) is suitable. The pressure roller 15b has, for example, a roller diameter of 30 mm, a core (STKM) pipe with a diameter of 24 mm (wall thickness 2 mm), a silicon solid rubber with a thickness of 3 mm as an elastic layer, and a thickness of 30 μm as a release layer. A roller made of a PFA tube can be used.

  A heater lamp 27 (for example, rated power 400 W) for heating the pressure roller 15b is disposed inside the pressure roller 15b. When a control circuit (not shown) supplies (energizes) power to the heater lamp 27 from a power supply circuit (not shown), the heater lamp 27 emits light, and infrared rays are emitted from the heater lamp 27. As a result, the inner peripheral surface of the pressure roller 15b is heated by absorbing infrared rays, and the entire pressure roller 15b is heated.

  The fixing belt 25 is heated to a predetermined temperature by the heating unit 20 and heats the recording paper 32 on which the unfixed toner image 31 that passes through the fixing nip portion 15c is formed. The fixing belt 25 is an endless belt, is suspended by the heating unit 20 and the fixing roller 15a, and is wound around the fixing roller 15a at a predetermined angle. When the fixing roller 15a rotates, the fixing belt 25 follows the fixing roller 15a and rotates in the rotation direction A. The fixing belt 25 is formed of an elastomer material (for example, silicon rubber) excellent in heat resistance and elasticity as an elastic layer on the surface of a hollow cylindrical base material made of a heat resistant resin such as polyimide or a metal material such as stainless steel or nickel. Furthermore, a three-layer structure in which a synthetic resin material (for example, a fluororesin such as PFA or PTFE) having excellent heat resistance and releasability is formed on the surface as a release layer. Moreover, you may add a fluororesin internally to the polyimide of a base material. Thereby, the sliding load with the heating means 20 can be reduced.

  The heating unit 20 is for contacting the fixing belt 25 and heating the fixing belt 25 to a predetermined temperature. The heating means 20 includes a plurality of heating members 21 and 31. In the heating means 20, a plurality of heating members 21 and 31 are joined and formed in a semicircular arc shape in a joined state. Each of the plurality of heating members 21 and 31 includes a base material and a planar heating element, and is similarly configured. The configuration of the heating member 21 will be described below by taking one heating member 21 as an example among the plurality of heating members 21 and 31.

  FIG. 2 is a diagram illustrating a configuration of the heating member 21 included in the heating unit 20. The heating member 21 includes a base material 211 and a planar heating element 212. The base material 211 extends in the width direction of the fixing belt 25 (the axial direction of the fixing roller 15 a), is disposed in contact with the fixing belt 25, and conducts heat generated by the planar heating element 212 to the fixing belt 25. Although the material which comprises the base material 211 is not specifically limited, It is preferable that it is a metal material which has high heat conductivity, and iron, aluminum, etc. can be mentioned as the metal material. A coating layer 211 e is formed on the outer surface of the base material 211 that contacts the fixing belt 25.

  The coat layer 211e needs to be formed of a material that has thermal conductivity for conducting heat generated by the planar heating element 212 to the fixing belt 25 and that can reduce frictional force with the fixing belt 25. is there. By forming such a coat layer 211e, heat can be conducted to the fixing belt 25, and wear of the fixing belt 25 that slides in contact with the base material 211 can be prevented to ensure high durability. it can. Further, since the frictional force with the fixing belt 25 can be reduced, the load on the fixing roller 15a and the pressure roller 15b for driving the fixing belt 25 can be reduced, and the durability of the rollers 15a and 15b is also improved. It can be ensured and driven with low power. Examples of the material constituting the coat layer 211e include fluorine resins such as PFA and PTFE. In the present embodiment, the coat layer 211e is a layer made of PTFE and having a thickness of 20 μm.

  The sheet heating element 212 includes a resistance heating layer 212a and an insulating layer 212b, and the longitudinal direction of the base material 211 (the fixing belt 25) so that the insulating layer 212b is a layer in contact with the base material 212. In the width direction) and formed on the inner surface of the substrate 211. In addition, feed terminal portions (not shown) are formed at both ends in the circumferential direction of the planar heating element 212.

  The insulating layer 212b is a layer formed of a material having both heat resistance and electrical insulation, and is interposed between the resistance heating layer 212a and the base material 211 as described above. By forming such an insulating layer 212b, insulation between the resistance heating layer 212a and the base material 211 can be secured, and the heating means 20 can be made safer. Examples of the material forming the insulating layer 212b include a heat-resistant polymer material such as polyimide resin, and a ceramic material such as alumina. In the present embodiment, the insulating layer 212b is a layer made of polyimide and having a thickness of 30 μm.

  The resistance heating layer 212a is a layer that generates heat when a voltage is applied to the power supply terminal portion, and is formed on the surface of the insulating layer 212b. In the present embodiment, the resistance heating layer 212a is a layer having a thickness of 15 μm made of a metal material mainly composed of nickel chromium.

  The heating means 20 of the present invention is formed by joining a plurality of heating members configured similarly to the heating member 21 described above.

  FIG. 3 is a diagram for explaining a procedure for producing the heating means 20 composed of a plurality of heating members. The case where the heating means 20 is composed of two heating members 21 and 31 will be described as an example. First, as shown in FIG. 3A, a metal thin plate made of a metal material such as iron or aluminum having a desired area and a thickness of about 0.4 to 1.0 mm is curved by pressing or the like, Base materials 211 and 311 are produced. Here, the desired area of each of the base materials 211 and 311 is a desired fixing temperature via the fixing belt 25 in a state where the two heating members 21 and 31 manufactured using the respective base materials 211 and 311 are joined. Set to be able to get.

  In order to obtain a desired fixing temperature via the fixing belt 25, it is necessary to achieve a sufficient heat generation capacity as the entire heating unit 20. For this purpose, it is necessary to lengthen the length extending in the circumferential direction of the base material itself as a base on which the planar heating element is formed so that a large area of the planar heating element itself can be secured. As shown in FIG. 3B, when the desired area is ensured by increasing the circumferential length with one base material 611, the opening of the base material 611 becomes narrow. For example, when the opening angle θ of the opening of the base material 611 is 180 ° or less, when a planar heating element is formed on the inner surface of the base material 611 by thermal spraying or painting, the nozzle for thermal spraying or painting is used. It is difficult to enter the inside of the opening, and it is difficult to form a planar heating element having a uniform film thickness. Even when the planar heating element is formed by the screen printing method, the same problem as described above occurs if the opening of the base 611 is narrow.

  In the present invention, since the desired area is secured in a state where the two heating members 21 and 31 manufactured using the two base materials 211 and 311 are joined, the openings of the base materials 211 and 311 are widened. can do.

  Next, as shown in FIG. 3C, a planar heating element 212 is formed on the inner surface of the base material 211 in a state where the opening is widely secured by spraying, painting, screen printing, etc. 21 is produced. Further, in the same manner as described above, the heating element 31 is manufactured by forming the planar heating element 312 on the inner surface of the base material 311. As described above, the planar heating elements 212 and 312 are formed on the base materials 211 and 311 in a state where the opening is widely secured, so that a planar heating element having a uniform film thickness can be formed.

  Next, as shown in FIG. 3 (d), both end portions in the circumferential direction of the heating member 21 are bent inward to form bent portions 211a and 211b. Similarly, both end portions in the circumferential direction of the heating member 31 are bent inward to form bent portions 311a and 311b. And the one bending part 211a, 311a of each heating member 21 and 31 is joined, and the heating means 20 is produced. In addition, bending the circumferential direction both ends of the heating members 21 and 31 also has an effect of increasing the rigidity of the members. In order to reduce the weight of the fixing device and to efficiently conduct the heat generated by the planar heating elements 212 and 312 to the fixing belt 25, it is necessary to reduce the thickness of the base materials 211 and 311. Since the rigidity can be increased by bending both end portions as described above, the rigidity of the member can be ensured.

  Further, the bent corners of the bent portions 211a, 211b, 311a, 311b of the heating members 21, 31 are preferably curved surfaces having a predetermined radius of curvature r, as shown in FIG. Accordingly, it is possible to prevent the fixing belt 25 in contact with the heating members 21 and 31 from being excessively stressed in the vicinity of the bent corners of the heating members 21 and 31 and to be prevented from being worn. Further, by forming the bent corners of the heating members 21 and 31 into a curved shape, when the fixing belt 25 slides in contact with the heating members 21 and 31, the fixing belt 25 is bent to correspond to the bent corners. It is possible to prevent it from being followed. Therefore, it is possible to prevent occurrence of fixing failure and to prevent the fixing belt 25 from slipping when sliding. In addition, as an example of the curved surface shape of the bent corner portion, FIG. 3D shows only the bent corner portion of the bent portion 211b of the heating member 21, but the other bent portions 211a, 311a, and 311b are similarly bent angles. The part has a curved surface shape. Further, the radius of curvature r when the bent corners of the heating members 21 and 31 are curved may be set so that the stress on the fixing belt 25 can be reduced and the wear can be reduced. In this form, it is set to 1 mm or more.

  As described above, the heating means 20 of the present invention is configured by joining the heating members 21 and 31 on which the planar heating elements 212 and 312 having a uniform film thickness are formed. Therefore, the planar heating elements 212 and 312 are formed. It is possible to prevent the temperature distribution on the surface from becoming uneven and the fixing temperature from varying. Furthermore, since the heating means 20 has a plurality of heating members 21 and 31 joined together to increase the circumferential length of the entire sheet heating element and increase the area of the entire sheet heating element, low consumption. The heating unit 20 as a whole can achieve a sufficient heat generation capacity while maintaining electric power, and the fixing belt 25 in contact with the heating unit 20 can be heated to a desired fixing temperature with excellent thermal efficiency. Therefore, it is possible to prevent the occurrence of fixing failure.

  Note that the number of heating members to be joined is not limited to two. As shown in FIG. 3E, three heating members 21, 31, 41 may be joined, or four or more. These heating members may be joined to constitute the heating means 20.

  FIG. 4 is a diagram illustrating a configuration of a first example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. The bent portions 211a and 311a at one end in the circumferential direction of the heating members 21 and 31 can be joined to each other via a welding member 511 by a welding method commonly used in this field. At this time, the lengths of the bent portions 211a and 311a of the heating members 21 and 31 may be set so as to facilitate welding.

  FIG. 5 is a diagram illustrating a configuration of a second example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. The bent portions 211a and 311a at one end in the circumferential direction of the heating members 21 and 31 are joined so as to be sandwiched by a joint member 515 having elasticity. At this time, the joint member 515 is configured so that its claw portion engages with the notches 211c and 311c formed in the bent portions 211a and 311a, respectively, and the joint member 515 is dropped. Is prevented. In this way, by simply using the bent portions 211a and 311a to engage the notch portions 211c and 311c with the claw portions of the joint member 515, the plurality of heating members 21 and 31 can be easily joined. can do.

  FIG. 6 is a diagram illustrating a configuration of a third example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. The bent portions 211 a and 311 a at one end in the circumferential direction of the heating members 21 and 31 are connected and joined by a concave joining hand member 512. The locking hand member 512 is disposed so as to sandwich the bent portions 211a and 311a. The stopper member 512 is connected by a compression spring 513 to a reinforcing frame 514 that is attached to a fixing frame that is a frame material of the fixing device 100 and reinforces the fixing frame.

  The anchoring hand member 512 may be configured to anchor the bent portions 211a and 311a over the entire length in the longitudinal direction of the heating members 21 and 31 with one member, and a plurality of members are arranged at predetermined intervals. And may be configured to be tethered. In addition, as a material which comprises the stopper hand member 512, metal materials with intensity | strength, such as a pressed sheet metal and aluminum die-casting, are preferable.

  The compression spring 513 is a spring member that elastically presses the locking hand member 512 outward, and holds the joint where the bent portions 211a and 311a of the heating members 21 and 31 are joined together. It is elastically pressed outward through the hand member 512.

  As a result, a predetermined tension (about 0.5 to 1 kgf) can be applied to the fixing belt 25 that slides in contact with the heating unit 20 having the heating members 21 and 31 at the joint. Adhesion with the fixing belt 25 can be improved, and the heating efficiency of the heating unit 20 with respect to the fixing belt 25 can be improved.

  FIG. 7 is a diagram showing a configuration of a fourth example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. Both end portions in the longitudinal direction of the heating member 21 are bent inward to form bent portions 211d. Further, bent portions 311d are formed at both ends in the longitudinal direction of the heating member 31 by bending inward. And in the bending part 211d and 311d of the longitudinal direction both ends, the through-hole is formed corresponding to the joining position where the heating members 21 and 31 are joined in the circumferential direction one end part of the heating members 21 and 31. . A shaft 516 is inserted into the through hole, and the heating members 21 and 31 are joined so as to be angularly displaceable with the shaft 516 as an axis. At this time, a bent portion is not necessarily formed at one end in the circumferential direction of the heating members 21 and 31.

  Further, a kick spring 517 having elasticity is attached to the shaft 516, and the kick spring 517 is connected to the other circumferential end of the heating members 21 and 31 (a circumferential portion not involved in joining of the heating members). The heating members 21 and 31 are angularly displaced by the elastic force so that the bent portions 211b and 311b at the direction ends are directed in the outward direction D.

  As a result, a predetermined tension (about 0.5 to 1 kgf) can be applied to the fixing belt 25 that slides in contact with the heating means 20 having the heating members 21 and 31 at the other circumferential end. The adhesion between the means 20 and the fixing belt 25 can be improved, and the heating efficiency of the heating means 20 with respect to the fixing belt 25 can be improved.

  FIG. 8 is a diagram illustrating a configuration of a fifth example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. Bending portions 211d and 311d are formed by bending inwardly at portions corresponding to one end side in the circumferential direction at both longitudinal ends of the heating members 21 and 31, respectively. And the through-hole is formed in the bending parts 211d and 311d of the circumferential direction one end side of the longitudinal direction both ends corresponding to the joining position where the heating members 21 and 31 are joined. A shaft 516 is inserted into the through hole, and the heating members 21 and 31 are joined so as to be angularly displaceable with the shaft 516 as an axis. At this time, a bent portion is not necessarily formed at one end in the circumferential direction of the heating members 21 and 31.

  Further, bent portions 211f and 311f are formed by bending inwardly at portions corresponding to the other end in the circumferential direction at both longitudinal ends of the heating members 21 and 31, respectively. A compression spring 518 is disposed at the bent portions 211f and 311f. The compression spring 518 is a spring member that elastically presses the bent portions 211f and 311f corresponding to the other circumferential ends of the heating members 21 and 31 in the outward direction D, respectively.

  As a result, a predetermined tension (about 0.5 to 1 kgf) can be applied to the fixing belt 25 that slides in contact with the heating means 20 having the heating members 21 and 31 at the other circumferential end. The adhesion between the means 20 and the fixing belt 25 can be improved, and the heating efficiency of the heating means 20 with respect to the fixing belt 25 can be improved.

  FIG. 9 is a diagram illustrating a configuration of a sixth example of joining in which bent portions at one end in the circumferential direction of the heating members 21 and 31 are joined. Bending portions 211d and 311d are formed by bending inwardly at portions corresponding to one end side in the circumferential direction at both ends in the longitudinal direction of the heating members 21 and 31, and both ends of portions corresponding to the other end in the circumferential direction are formed. Bent portions 211f and 311f are formed on the portion by bending outward. Note that the fixing belt 25 is configured not to contact at both longitudinal ends of the heating members 21 and 31 where the bent portions 211f and 311f are formed.

  Then, the bending portions 211d and 311d at both ends in the longitudinal direction on the side corresponding to the one end in the circumferential direction correspond to the joining positions where the heating members 21 and 31 are joined at one circumferential end of the heating members 21 and 31. Thus, a through hole is formed. A shaft 516 is inserted into the through hole, and the heating members 21 and 31 are joined so as to be angularly displaceable with the shaft 516 as an axis. At this time, a bent portion is not necessarily formed at one end in the circumferential direction of the heating members 21 and 31.

  Further, bent portions 211f and 311f at both ends in the longitudinal direction on the side corresponding to the other circumferential end of the heating members 21 and 31 are respectively connected to a fixing frame 520 and a tension spring 519 which are outer frames of the fixing device 100. It is connected. The tension spring 519 is a spring member that elastically pulls the bent portions 211f and 311f corresponding to the other circumferential ends of the heating members 21 and 31 in the outward direction D, respectively.

  As a result, a predetermined tension (about 0.5 to 1 kgf) can be applied to the fixing belt 25 that slides in contact with the heating means 20 having the heating members 21 and 31 at the other circumferential end. The adhesion between the means 20 and the fixing belt 25 can be improved, and the heating efficiency of the heating means 20 with respect to the fixing belt 25 can be improved.

  FIG. 10 is a diagram illustrating a state where the fixing belt 25 is stretched between the heating unit 20 and the fixing roller 15a. When the fixing belt 25 is stretched between the heating unit 20 and the fixing roller 15a, the entire circumference of the heating unit 20 is formed in a semicircular arc shape in which the region wound around the heating unit 20 is in a semicircular arc shape. On the other hand, it is preferable that 50% or more, or the region that is wound around the fixing roller 15a is 50% or more with respect to the circumferential length of the fixing roller 15a.

  For example, as shown in FIG. 10A, the heating means 20 as a whole is formed such that the diameter of the heating means 20 formed by joining a plurality of heating members into a semicircular arc shape is 40 mm and the diameter of the fixing roller 15a is 30 mm. Is larger than the circumferential length of the fixing roller 15a, the fixing belt 25 has a region where the fixing belt 25 is wound around the heating unit 20 in an area larger than 50% of the circumferential length of the heating unit 20 as a whole. Configured as follows. Accordingly, since the heating unit 20 can take a wide contact area with the fixing belt 25, the fixing belt 25 can be heated with excellent thermal efficiency and low power consumption.

  Further, as shown in FIG. 10B, the circumferential length of the entire heating unit 20 and the circumferential length of the fixing roller 15a such that the diameter of the entire heating unit 20 is 30 mm and the diameter of the fixing roller 15a is 30 mm. Are equal to each other, the fixing belt 25 is 50% of the area wound around the heating means 20 with respect to the circumferential length of the entire heating means 20, and the area wound around the fixing roller 15a is fixed. It is configured to be 50% with respect to the circumferential length of the roller 15a. Accordingly, since the heating unit 20 can take a wide contact area with the fixing belt 25, the fixing belt 25 can be heated with excellent thermal efficiency and low power consumption. Furthermore, since the fixing roller 15a can take a wide contact area with the fixing belt 25, it is excellent in thermal followability and can be applied to a fixing device of a high-speed machine.

  Further, as shown in FIG. 10C, the circumferential length of the fixing roller 15a is larger than the circumferential length of the entire heating unit 20 such that the diameter of the entire heating unit is 20 mm and the diameter of the fixing roller 15a is 30 mm. Is larger than 50% of the circumferential length of the fixing roller 15a. As a result, the contact area between the fixing roller 15a and the fixing belt 25 can be widened, so that it is excellent in thermal followability and can be applied to a fixing device of a high-speed machine.

  FIG. 11 is a diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is an apparatus that forms multi-color and single-color images on the recording paper 32 based on image data of a read original or image data transmitted via a network or the like. The image forming apparatus 100 includes an exposure unit 10, a photosensitive drum 101 (101a to 101d), a developing device 102 (102a to 102d), a charging roller 103 (103a to 103d), a cleaning unit 104 (104a to 104d), and an intermediate transfer belt. 11, a primary transfer roller 13 (13a to 13d), a secondary transfer roller 14, a fixing device 15, paper transport paths P1, P2, and P3, a paper feed cassette 16, a manual paper feed tray 17, and a paper discharge tray 18. .

  The image forming apparatus 100 corresponds to the hues of four colors of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Using the image data, image formation is performed in the image forming units Pa to Pd corresponding to each hue. Each of the image forming portions Pa to Pd has the same configuration. For example, the black (K) image forming portion Pa includes a photosensitive drum 101a, a developing device 102a, a charging roller 103a, a transfer roller 13a, a cleaning unit 104a, and the like. Composed. The image forming portions Pa to Pd are arranged in a line in the moving direction (sub-scanning direction) of the intermediate transfer belt 11.

  The charging roller 103 is a contact-type charger that uniformly charges the surface of the photosensitive drum 101 to a predetermined potential. Instead of the charging roller 103, a contact type charger using a charging brush or a non-contact type charger using a charging wire may be used.

  The exposure unit 10 includes a semiconductor laser (not shown), a polygon mirror 4, a first reflection mirror 7, a second reflection mirror 8, and the like. Black (K), cyan (C), magenta (M), and yellow (Y). Each of the photosensitive drums 101a to 101d is irradiated with a light beam such as a laser beam modulated by the image data of each hue. Each of the photosensitive drums 101a to 101d forms an electrostatic latent image based on image data of each hue of black (K), cyan (C), magenta (M), and yellow (Y).

  The developing device 102 supplies toner as a developer to the surface of the photosensitive drum 101 on which the electrostatic latent image is formed, and develops the electrostatic latent image into a toner image. Each of the developing devices 102a to 102d contains toner of each hue of black (K), cyan (C), magenta (M), and yellow (Y), and is formed on each of the photosensitive drums 101a to 101d. The electrostatic latent image of each hue is visualized into a toner image of each hue. The cleaning unit 104 removes and collects toner remaining on the surface of the photosensitive drum 101 after development and image transfer.

  The intermediate transfer belt 11 is disposed above the photosensitive drum 101, and is stretched between the driving roller 11a and the driven roller 11b to form a loop-shaped moving path. The outer peripheral surface of the intermediate transfer belt 11 faces the photosensitive drum 101d, the photosensitive drum 101c, the photosensitive drum 101b, and the photosensitive drum 101a in this order. Primary transfer rollers 13a to 13d are arranged at positions facing the respective photosensitive drums 101a to 101d with the intermediate transfer belt 11 interposed therebetween. Each of the positions where the intermediate transfer belt 11 faces the photosensitive drums 101a to 101d is a primary transfer position. The intermediate transfer belt 11 is formed of a film having a thickness of about 100 to 150 μm.

  The primary transfer rollers 13a to 13d have constant voltage control of a primary transfer bias opposite to the charging polarity of the toner in order to transfer the toner images carried on the surfaces of the photosensitive drums 101a to 101d onto the intermediate transfer belt 11. Applied. As a result, the toner images of the respective colors formed on the photosensitive drums 101a to 101d are sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 11, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 11. .

  However, when image data of only a part of the hues of yellow (Y), magenta (M), cyan (C), and black (K) is input, input is performed among the four photosensitive drums 101a to 101d. The electrostatic latent image and the toner image are formed only on a part of the photoconductors 101 corresponding to the hue of the image data. For example, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the photosensitive drum 101a corresponding to the black hue, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 11. Is done.

  Each of the primary transfer rollers 13a to 13d is configured by covering the surface of a shaft whose base is a metal such as stainless steel having a diameter of 8 to 10 mm with a conductive elastic material (for example, EPDM, urethane foam, etc.). A high voltage is uniformly applied to the intermediate transfer belt 11 by the elastic material.

  The toner image transferred to the outer peripheral surface of the intermediate transfer belt 11 at each primary transfer position is conveyed to a secondary transfer position that is a position facing the secondary transfer roller 14 by the rotation of the intermediate transfer belt 11. The secondary transfer roller 14 is pressed against the outer peripheral surface of the intermediate transfer belt 11 whose inner peripheral surface is in contact with the peripheral surface of the driving roller 11a at a predetermined nip pressure during image formation. When the recording paper 32 fed from the paper feed cassette 16 or the manual paper feed tray 17 passes between the secondary transfer roller 14 and the intermediate transfer belt 11, the secondary transfer roller 14 is charged with the charged polarity of toner. Is applied with a high voltage of reverse polarity. As a result, the toner image is transferred from the outer peripheral surface of the intermediate transfer belt 11 to the surface of the recording paper 32.

  Of the toner adhering to the intermediate transfer belt 11 from the photosensitive drum 101, the toner remaining on the intermediate transfer belt 11 without being transferred onto the recording paper 32 is transferred in order to prevent color mixing in the next process. Collected by the cleaning unit 12.

  The recording paper 32 onto which the toner image has been transferred is guided to the fixing device 15 of the present invention described above, and between the fixing belt 25 stretched between the fixing roller 15a and the heating means 20, and the pressure roller 15b. It passes through the formed fixing nip 15c and receives heat and pressure. As a result, the toner image is firmly fixed on the surface of the recording paper 32. The recording paper 32 on which the toner image is fixed is discharged onto the paper discharge tray 18 by the paper discharge roller 18a.

  In the image forming apparatus 100, the recording paper 32 stored in the paper cassette 16 is sent to the paper discharge tray 18 between the secondary transfer roller 14 and the intermediate transfer belt 11 and via the fixing device 15. For this purpose, a sheet conveyance path P1 extending in a substantially vertical direction is provided. A pickup roller 16a that feeds the recording paper 32 in the paper cassette 16 one by one into the paper transport path P1 and a transport roller 16b that transports the fed recording paper 32 upward are transported to the paper transport path P1. A registration roller 19 that guides the recording sheet 32 between the secondary transfer roller 14 and the intermediate transfer belt 11 at a predetermined timing, and a discharge roller 18 a that discharges the recording sheet 32 to the discharge tray 18 are disposed.

  Further, inside the image forming apparatus 100, a paper conveyance path P2 in which a pickup roller 17a and a conveyance roller 16b are arranged is formed between the manual paper feed tray 17 and the registration rollers 19. Further, a paper transport path P3 is formed between the paper discharge roller 18a and the upstream side of the registration roller 19 in the paper transport path P1.

  The paper discharge roller 18a is rotatable in both forward and reverse directions, and is used for the second time in forming a single-sided image for forming an image on one side of the recording paper 32 and in forming a double-sided image for forming images on both sides of the recording paper 32. When the surface image is formed, the recording paper 32 is driven in the forward rotation direction and discharged to the paper discharge tray 18. On the other hand, when the first side image is formed in the double-sided image formation, the discharge roller 18a is driven in the forward direction until the rear end of the paper passes through the fixing device 15, and then the rear end of the recording paper 32 is sandwiched. Then, the recording paper 32 is driven in the reverse direction to guide the recording paper 32 into the paper transport path P3. As a result, the recording paper 32 on which an image is formed only on one side at the time of double-sided image formation is guided to the paper transport path P1 with the front and back sides and front and rear ends reversed.

  The registration roller 19 receives the recording paper 32 fed from the paper cassette 16 or the manual paper feed tray 17 or transported via the paper transport path P3 at the timing synchronized with the rotation of the intermediate transfer belt 11. Guided between the transfer roller 14 and the intermediate transfer belt 11. For this reason, the registration roller 19 stops rotating when the operation of the photosensitive drum 101 and the intermediate transfer belt 11 is started, and the recording paper 32 fed or conveyed prior to the rotation of the intermediate transfer belt 11 has a leading edge. The movement in the paper transport path P1 is stopped in a state where it is in contact with the registration roller 19. Thereafter, the registration roller 19 is located at a position where the secondary transfer roller 14 and the intermediate transfer belt 11 are pressed against each other, and the front end portion of the recording paper 32 and the front end portion of the toner image formed on the intermediate transfer belt 11 face each other. Start rotation at the timing.

  At the time of full color image formation in which image formation is performed in all of the image forming portions Pa to Pd, the primary transfer rollers 13a to 13d press the intermediate transfer belt 11 against all of the photosensitive drums 101a to 101d. On the other hand, at the time of monochrome image formation in which image formation is performed only in the image forming portion Pa, only the primary transfer roller 13a is brought into pressure contact with the photosensitive drum 101a.

  As described above, in the image forming apparatus 100, the fixing is performed by the fixing device 15 of the present invention. Therefore, the fixing nip portion in which the recording paper 32 is heated with high heating efficiency while preventing the fixing temperature from being varied. 15c can be passed, and a high-quality image can be formed in which fixing failure is prevented.

1 is a diagram illustrating a configuration of a fixing device 15 according to an embodiment of the present invention. It is a figure which shows the structure of the heating member 21 which the heating means 20 has. It is a figure explaining the procedure which produces the heating means 20 comprised with a some heating member. It is a figure which shows the structure of the 1st example of joining to which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. It is a figure which shows the structure of the 2nd example of joining to which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. It is a figure which shows the structure of the 3rd example of joining to which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. It is a figure which shows the structure of the 4th example of joining to which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. It is a figure which shows the structure of the 5th example of joining in which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. It is a figure which shows the structure of the 6th example of joining to which the bending parts of the circumferential direction one end part of the heating members 21 and 31 are joined. FIG. 3 is a diagram showing a tension state of a fixing belt 25 stretched between a heating unit 20 and a fixing roller 15a. 1 is a diagram illustrating a configuration of an image forming apparatus 100 according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 Fixing device 15a Fixing roller 15b Pressure roller 20 Heating means 21, 31 Heating member 25 Fixing belt 100 Image forming device 211, 311 Base material 212, 312 Planar heating element

Claims (12)

An endless fixing belt stretched between the fixing roller and the heating unit, and a pressure member facing the fixing roller via the endless fixing belt, the heating unit contacting the fixing belt A fixing device that heats and fixes a toner image carried on a recording medium on a recording medium at a fixing nip portion formed by the fixing belt and the pressure member by heating the fixing belt. ,
The fixing device according to claim 1, wherein the heating means includes a plurality of heating members each having a planar heating element formed on an inner surface of a curved base material and having a substantially semicircular arc shape as a whole.   The fixing device according to claim 1, further comprising a pressing member that presses each of the plurality of heating members included in the heating unit from the inside toward the outside.   The fixing device according to claim 1, further comprising a tension member that pulls each of the plurality of heating members of the heating unit from the outside.   The fixing device according to claim 2, wherein the pressing member and the tension member are spring members having elasticity.   5. The fixing device according to claim 1, wherein each of the plurality of heating members is formed with a bent portion bent inward at both circumferential end portions.   The fixing device according to claim 5, wherein the bending angle portion of the bending portion is a curved surface having a predetermined radius of curvature. A holding member that sandwiches and joins the bent portions formed on one circumferential end of each of the plurality of heating members;
The fixing device according to claim 5, wherein the pressing member is configured to press the locking hand member outward. A notch is formed in the bent portion formed on one circumferential end of each of the plurality of heating members,
The anchoring hand member has a claw portion,
The fixing device according to claim 7, wherein the claw portion is engaged with the notch portion, and the plurality of heating members are joined.   When the fixing belt is stretched between the heating unit and the fixing roller, an area in which the fixing belt is wound around the heating unit has a substantially semicircular arc shape as a whole. 9. The structure according to claim 1, wherein the region is 50% or more, or the region in contact with the fixing roller is 50% or more with respect to the circumferential length of the fixing roller. The fixing device according to 1.   The planar heating element included in each of the plurality of heating members includes a resistance heating layer and an insulating layer, and the inner surface of the base material is such that the insulating layer is a layer in contact with the base material. The fixing device according to claim 1, wherein the fixing device is formed as follows.   The base material of each of the plurality of heating members, wherein a coat layer capable of reducing a frictional force with the fixing belt is formed on an outer surface in contact with the fixing belt. The fixing device according to any one of 1 to 10.   An image forming apparatus comprising the fixing device according to claim 1.

Images