JP2014228857A - Fixation device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a small-space, low-cost fixation device having a structure for restraining a fixation belt from leaning to one side.SOLUTION: A heating roller 2 is provided inside a fixation belt 1, and a leaf spring 7 is used as a mechanism for applying tension to the fixation belt 1 in order to form a fixation nip N by bringing a pressure roller and the fixation belt close to each other. The leaf spring is attached to a fixation pad holding member 5 for holding a fixation pad 4, and applies tension from inside the fixation belt 1. A leaning prevention member 8 is held by the leaf spring 7. The leaning prevention member 8 has an inclined surface in which the surface in contact with the fixation belt 1 separates from the leaf spring 7 toward an edge from the center in width direction of the fixation belt 1. Due to that the fixation belt 7 rises onto the inclined surface of the leaning prevention member 8, balance is collapsed, causing a change in the leaning of the fixation belt 1 to occur so that the degree of leaning of the fixation belt 7 is lessened or the direction of leaning is reversed.

Description

  The present invention relates to an FBN type fixing device having a fixing belt, and an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile using the fixing device.

  In the fixing method used for the electrophotographic image forming apparatus, the warm-up time is short such as the FBN fixing (free belt nip fixing) method, the SURF fixing (on-demand fixing) method, and the color QSU (Quick Start-Up) fixing method. A fixing method having an excellent AC-TEC value is already known.

  In these conventionally known fixing device configurations, for fixing the fixing belt, a fixing member is bonded to the entire inner surface of the fixing belt, and a step is provided on a rotating body that runs around the fixing belt, and the fixing belt is brought into contact with the fixing belt. It is known to regulate the shift. In addition, there is also known a method in which the entire circumference of the end surface of the fixing belt is regulated by contacting with a detent member. In these techniques, in order to regulate the deviation of the fixing belt, it is necessary to provide a detent member on the entire circumference of the rotating body that runs around the fixing belt. Therefore, it is necessary that the stopper member has a size corresponding to the entire circumference of the fixing belt, and there is a problem that the size of the member is large and a space is taken up.

  In Patent Document 1, for the purpose of regulating the deviation of the fixing belt, a detent member is provided at a step portion provided so that the outer peripheral side of the end surface of the roller body portion becomes a concave portion, and the deviation fixed to the inner circumference of the belt is provided. A configuration of a fixing device having a stop protrusion and an inclined surface on the protrusion is disclosed. However, the above-mentioned problem caused by providing the detent member on the entire circumference of the end surface of the fixing belt cannot be solved.

  The present invention can provide a fixing device and an image forming apparatus that can be configured such that the detent member is provided only in a part of the circumferential direction of the fixing belt, and the cost is reduced by reducing the cost of components. Objective.

  The fixing device according to the present invention includes a fixing belt made of an endless belt-like member, a fixing member provided inside the fixing belt, a heating roller for transferring heat to the fixing belt, and a heating unit provided inside the heating roller. And a plate spring constituting a belt tension mechanism that applies tension to the fixing belt, and a locking member that regulates a shift in the width direction of the fixing belt. The member is held.

  According to the present invention, the belt tension mechanism of the leaf spring inside the heating belt and the fixing belt detent member at the end of the belt tension mechanism are arranged to regulate the small space and low cost fixing belt. can do.

1 is a cross-sectional view conceptually showing an example of an image forming apparatus such as an electrophotographic copying machine that can be an object of the present invention. FIG. 2 is a cross-sectional view illustrating a main part of an embodiment of a fixing device according to the present invention. FIG. 6 is a perspective view of a state in which a leaf spring constituting the belt tension mechanism is attached to a fixing pad holding member. They are a perspective view (A) which shows the state which attached the detent member to the side edge of a leaf | plate spring, and an expanded sectional view (B) of a line BB part. FIG. 6 is a cross-sectional view showing a state in which the fixing belt rides on an end stop member by approaching the end portion side of the leaf spring.

  The fixing device according to the embodiment of the present invention has a heating roller and a fixing pad inside the fixing belt, has a heat source inside the heating roller, and the heating roller is driven. In this configuration, heat is transferred by bringing the heating roller and the fixing belt into contact with each other, and heat is transmitted to the fixing nip to fix the toner on the paper. In order to efficiently transfer heat, the heating roller and the fixing belt are brought into close contact with each other. For this purpose, a leaf spring is used as a mechanism for applying tension to the fixing belt.

  The leaf spring is attached to a fixing pad holding member that holds the fixing pad, and applies tension across the entire width of the fixing belt. The leaf spring holds a stopper member. The detent member has an inclined surface whose surface that contacts the fixing belt is separated from the leaf spring from the center toward the end in the width direction of the fixing belt.

  By holding the detent member on the leaf spring, the belt runs on the inclined surface of the detent in the process in which the fixing belt approaches one side. When the fixing belt rides on the inclined surface of the detent member, the balance between the left and right rotation centers is lost, and a change occurs in the direction of the fixing belt, so that the degree of deviation of the fixing belt is soft or the direction of the deviation is reversed.

  Furthermore, by attaching the stopper member to the leaf spring, the stopper member pushes the leaf spring against the normal leaf spring position. As a result, a reaction force (spring load) is generated, and by repelling the fixing belt, the fixing belt can be regulated. Since the belt tension is applied by the leaf spring and the offset of the fixing belt is restricted by the offset member held at the end of the leaf spring, it is not necessary to arrange the offset member around the entire end of the fixing belt. For this reason, it is possible to reduce the number of parts that restrict the deviation of the fixing belt. As a result, the fixing device can be reduced in size and cost. In addition, although described as a fixing belt in the above and the following description, not only a so-called belt material but also a film material can be used to constitute the fixing belt.

  Embodiments of the present invention will be described below with reference to the drawings. In the fixing device according to the embodiment of the present invention, a unit that suppresses the deviation of the fixing belt in the fixing belt type device has the following characteristics. In short, the belt tension mechanism in the fixing device of the fixing belt system is a leaf spring, and the leaf spring holds the stopper member and regulates the displacement of the fixing belt.

  FIG. 1 is a cross-sectional view conceptually showing an example of an image forming apparatus such as an electrophotographic copying machine or printer that can be an object of the present invention. The image forming apparatus 200 mainly includes an image reading unit 111 that reads a document, an image forming unit 112 that forms an image, an automatic document feeder (ADF) 113, and a document discharge unit that stacks documents sent from the ADF 113. A paper tray 114, a paper feed unit 119 including paper feed cassettes 115 to 118, and a paper discharge unit (discharge tray 120) for stacking recording paper are configured.

  Then, when the document D is set on the document table 121 of the ADF 113 and an operation unit (not shown) is operated, for example, a press of a print key is performed, the uppermost document D is sent out in the direction of the arrow B 1 by the rotation of the pickup roller 122. Then, by the rotation of the document conveying belt 123, the paper is fed onto the contact glass 124 fixed to the image reading unit 111 and stops there. The image of the document D placed on the contact glass 124 is read by a reading device 125 positioned between the image forming unit 112 and the contact glass 124. The reading device 125 includes a light source 126 that illuminates the document D on the contact glass 124, an optical system 127 that forms an image of the document, a photoelectric conversion element 128 that includes a CCD that forms an image of the document, and the like. After the image reading is completed, the document D is transported in the direction of arrow B2 by the rotation of the document transport belt 123 and discharged onto the document discharge tray 114. In this way, the document D is fed one by one onto the contact glass 124 and the document image is read by the image reading unit 111.

  On the other hand, inside the image forming unit 112, a photoreceptor 130 as an image carrier is disposed. The photoconductor 130 is driven to rotate clockwise in the drawing, and the charging device 131 charges the surface to a predetermined potential. Further, the writing unit 132 emits laser light L that is light-modulated in accordance with image information read by the reading device 125, and the surface of the charged photosensitive member 130 is exposed with the laser light L, whereby the photosensitive member is exposed. An electrostatic latent image is formed on the surface 130. When the electrostatic latent image passes through the developing device 133, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 130 and the transfer device 134 by the opposing transfer device 134. The surface of the photoreceptor 130 after the toner image transfer is cleaned by a cleaning device 135.

  A plurality of paper feed cassettes 115 to 118 disposed below the image forming unit 112 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 115 to 118 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 130 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 100 in the image forming unit 112 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through 136 is conveyed by the discharge roller pair 137, discharged to the discharge tray 120 as shown by an arrow B5, and stacked.

Next, the fixing device will be described.
FIG. 2 is a cross-sectional view showing a main part of one embodiment of the fixing device according to the present invention. This fixing device includes a fixing belt 1 formed of an endless belt-like member as a fixing member. In addition, a heating roller 2 is provided which is provided in the fixing belt 1 and has a function of a holding member that holds the fixing belt 1 and also performs a function of transferring heat to the fixing belt. In the figure, 3 is a halogen heater which is a heating member. Although not shown, a thermistor that is a temperature sensor that detects the surface temperature in contact with the fixing belt 1 is provided. Reference numeral 4 in the figure denotes a fixing pad that contacts the heating roller 2 and holds the fixing belt 1 in the fixing belt 1. In the figure, reference numeral 5 denotes a fixing pad holding member for holding the fixing pad 4. The fixing pad 4 constitutes a pressure roller 6 and a fixing nip N via a lubricating sheet and a fixing belt.

  The pressure roller 6 is configured as a pressure member that forms a fixing nip N in contact with the fixing belt 1. Therefore, the fixing pad 4 is made of an elastic body such as silicone rubber or fluororubber, heat-resistant resin, or metal, and these members are in contact with the inner surface of the sliding sheet or the fixing belt. Although illustration is omitted, it slides indirectly on the inner surface of the fixing belt 1 via a lubricant such as a sliding sheet or grease. The pressure roller 6 and the fixing pad 4 constitute a fixing nip N with a load from the pressure roller 6 via the sliding sheet and the fixing belt 1. The toner is fixed by the pressure and heat of the fixing nip N. can do.

  In the pressure roller 6, for example, a silicone rubber layer is provided on a hollow metal roller, and a release layer (PFA resin layer or PTFE resin layer) is provided on the outer surface in order to obtain releasability. The pressure roller 6 is rotationally driven by a driving force transmitted from a driving source such as a motor provided in the image forming apparatus via a gear train. Further, the pressure roller 6 is pressed against the fixing belt 1 by a spring or the like, and the rubber layer of the pressure roller 6 is crushed and deformed. As a result, a predetermined nip width is formed in the fixing nip N.

  The pressure roller 6 may be formed of a solid roller material, but a hollow heat capacity is preferable because it is less hollow. Further, the pressure roller 6 may be provided with a heating source such as a halogen heater. The silicone rubber layer in the pressure roller 6 may be solid rubber, but if there is no heating source such as a heater inside the pressure roller 6, sponge rubber may be used. Use of sponge rubber is preferable because heat insulation is enhanced and heat of the fixing belt 1 is hardly transmitted to the pressure roller 6.

  The fixing belt 1 can be made of a metal belt such as nickel or stainless steel, or a resin material such as polyimide, polyamide, or fluorine resin, and is an endless belt. This time, polyimide was used. The surface layer of the fixing belt has a release layer such as a PFA resin layer or a PTFE resin, and has a release property so that the toner on the recording medium does not adhere. Further, an elastic layer such as a silicone rubber layer may be formed between the base material of the fixing belt 1 and the PFA resin layer (or PTFE resin). In the absence of a silicone rubber layer, the heat capacity is reduced and the fixability is improved, but the unfixed toner image is crushed, and the subtle irregularities on the surface of the fixing belt are transferred to the image during fixing, and the image There is a problem in that a crusty skin-like mark remains on the solid portion. In order to improve this, it is necessary to provide a silicone rubber layer of 100 μm or more. Due to the deformation of the silicone rubber layer, subtle irregularities are absorbed and the skin image is improved.

  For the hollow heating roller 2, for example, a pipe-shaped metal material such as aluminum, iron, or stainless steel is used. The heating roller 2 is configured, for example, as a circle having a diameter larger than 1 mm than the apparent diameter of the halogen heater 3 which is a heating means. Inside the heating roller 2, black coating is applied to the inner surface in order to easily absorb radiant heat from a heating source such as the halogen heater 3. The pressure applied by the pressure roller 6 to the fixing belt 1 is transmitted to the fixing belt 1, a sliding sheet (not shown), and the fixing pad 4, and is received by the heating roller 2.

  In this embodiment, the heating roller 2 is also rotated. The rotation direction is preferably the same as that of the fixing belt 1 and the rotation speed is preferably substantially the same as that of the fixing belt 1. Further, as the heat source for raising the temperature of the heating roller 2, the halogen heater 3 may be used as in the illustrated embodiment, but an electromagnetic induction heating type heat source may be adopted. Furthermore, a resistance heating element, a carbon heater, or the like can be used. By using a halogen heater, energy in the circumferential direction can be transferred on the inner surface of the heating roller 2 due to the feature of emitting light in the circumferential direction.

  The fixing belt 1 is rotated by the pressure roller 6. The pressure roller 6 is rotated by a driving source (not shown), and the driving force is transmitted to the fixing belt 1 through the fixing nip N, whereby the fixing belt 1 rotates. The fixing belt 1 is rotated by the rotation of the pressure roller 6 by being sandwiched between the fixing pad 4 and the pressure roller 6 in the fixing nip N, but is transported and guided to the fixing pad outside the fixing nip N.

  The toner may be either pulverized toner or polymerized toner. For example, 2 parts of hydrophobic silica AEROSIL (registered trademark) RY50 (manufactured by Nippon Aerosil Co., Ltd.) is added to 100 parts of toner, and the mixture is mixed with a 20 L Henschel mixer at a peripheral speed of 40 m / second for 5 minutes. A toner obtained using a sieve having an opening of 75 microns can be used.

Next, the belt tension mechanism will be described.
As shown in FIG. 2, the plate spring 7 constituting the belt tension mechanism is attached to the fixing pad holding member 5 and applies tension to the fixing belt 1 from the inside. The fixing pad holding member 5 is closer to the heating roller 2 that is a heat source than the fixing pad 4, and a load from the pressure roller 6 is applied through the fixing pad 4. For this reason, the fixing pad holding member 5 is preferably made of a heat-resistant and highly rigid material such as iron, stainless steel, or metal alloy. The fixing pad holding member 5 holds the fixing pad 4 by fixing both ends thereof to a side plate frame (not shown).

  The leaf spring 7 includes an attachment portion 7 a for attachment to the fixing pad holding member 5 and a bent portion 7 b that is brought into contact with the inner peripheral surface of the fixing belt 1. The contact point between the fixing belt 1 and the leaf spring 7 can be set close to the heating roller 2 by bending the leaf spring 7 and arranging it inside the fixing belt 1. For this reason, a small-diameter belt can be adopted as the fixing belt 1, and space can be effectively used. That is, tension can be applied to the fixing belt 1 in a small space. In the belt tension mechanism using the tension roller, the number of components such as a roller, a bearing, and a spring increases, whereas in the configuration using the leaf spring 7, the leaf spring 7 and the leaf spring 7 are attached to the fixing pad holding member 5. Only a screw is needed. Therefore, the cost can be reduced by reducing the number of parts and improving the assemblability.

  By making the tip of the leaf spring 7 into a curved shape, it is possible to prevent the occurrence of damage due to the burrs and edges at the tip of the leaf spring 7 coming into contact with the fixing belt 1 during unit assembly. Further, when used for fixing operation, it contacts the rotating fixing belt 1, and if the tip has a curved shape, damage to the fixing belt 1 due to contact can be prevented.

  Since the fixing belt 1 is rotated together with the heating roller 2, the fixing belt 1 has a tension side and a slack side depending on the rotation direction of the fixing belt 1 (the direction indicated by the white arrow in FIG. 2). The leaf spring 7 is positioned on the slack side of the fixing belt 1 (in FIG. 2, the upper side of the fixing belt 1 in the drawing is the tension side and the lower side is the slack side). By providing the leaf spring 7 below the fixing belt 1, the adhesion between the fixing belt 1 and the heating roller 2 can be improved. Then, heat can be efficiently transferred between the fixing belt 1 and the heating roller 2, and transportability of the fixing belt 1 by the heating roller 2 can be ensured. In the illustrated embodiment, since the opening side of the leaf spring 7 faces the heating roller 2, the length of the curved surface of the bent portion 7b can be ensured to a required value, and the set load of the belt tension of the fixing belt 1 can be secured. It is easy to adjust.

Next, the leaf spring 7 will be described in more detail with reference to FIG.
FIG. 3 is a perspective view of the state in which the leaf spring 7 is attached to the fixing pad holding member 5. The bent portion 7b of the leaf spring 7 is provided with a plurality of holes 7d. The leaf spring 7 load (belt tension force) can be adjusted by changing the number and shape of the holes 7d. For example, by making the hole 7d of the bent portion 7b into a circular or substantially circular shape, the shape of the hole is free from corners. Then, generation of cracks due to processing and stress concentration can be suppressed, and the life of components can be extended. Further, when the leaf spring 7 is attached to the fixing pad holding member 5, the fixing pad holding member 5 is screwed. If there is a hole in the bent portion 7b, the screwdriver used for screwing reaches the attaching portion 7a. Increases sex. In the figure, 7e is a hole through which the tip of the screw passes. The hole 7d is provided in the bent portion 7b toward the heating means, that is, toward the heating roller 2 side. Thereby, it can provide according to the length of a bending part, and it becomes easy to set the load as the leaf | plate spring 7. FIG.

FIG. 4A is a perspective view showing a state in which the detent members 8 are attached to the side edge of the leaf spring 7 which is a belt tension mechanism, and FIG. 4B is a view of FIG. It is an expanded sectional view of line BB.
The detent member 8 is disposed so that the leaf spring 7 is sandwiched between the bent portions 7b of the leaf spring 7, specifically, the both side edges of the portion close to the tip portion 7c. As shown in FIG. 4B, a groove 8a into which the edge of the leaf spring 7 is inserted is formed on the side of the leaf spring 7 of the detent member 8, and the edge portion of the leaf spring 7 is inserted therein. The stopper member 8 sandwiches the leaf spring 7 between both side surfaces of the groove 8a (upper and lower surfaces in FIG. 4B). By attaching the leaf spring 7 in this way, a step is almost eliminated between the leaf spring 7 and the detent member 8. By doing so, damage to the fixing belt 1 can be suppressed even if the fixing belt 1 described later moves. Further, the shape of the plate spring 7 side of the detent member 8 is devised, and a groove 8a into which the plate spring 7 is inserted is provided at two locations on the tip end 7c side of the plate spring 7 and on the opposite side thereof, that is, on the base end side of the bent portion 7b. Assembling is also improved by adding an appropriate retaining.

FIG. 5 is a cross-sectional view showing a state in which the fixing belt 1 is on the detent member 8 near the end of the leaf spring 7. FIG. 4B shows the normal state of the fixing belt 1, the leaf spring 7, and the detent member 8.
The detent member 8 is inclined such that the surface that contacts the fixing belt 1 (the upper surface in FIG. 4B and FIG. 5) is separated from the leaf spring 7 from the center side in the width direction of the fixing belt 1 toward the end side. The surface 8b is formed (see the normal state in FIG. 4B). That is, the inclined surface 8 b of the detent member 8 is inclined so as to rise from the center of the fixing belt 1 toward the end portion.

  That is, by holding the detent member 8 on the leaf spring 7, the fixing belt 1 rides on the inclined surface 8 b of the detent member 8 in the process in which the fixing belt 1 approaches one side. When the fixing belt 1 rides on the inclined surface of the detent member 8, the balance of the rotation center in the width direction of the fixing belt 1 is lost, and the direction of the fixing belt 1 is softened or deviated (direction of movement in the width direction). Is reversed.

  That is, when the fixing belt 1 approaches the end, the fixing belt 1 gradually climbs onto the inclined surface 8 b of the detent member 8 and tries to bend the leaf spring 7. As a result, the reaction force (load) against the force to bend the leaf spring 7 increases, and the fixing belt 1 works to push it back toward the center in the width direction. Further, since the axial center position in the width direction of the fixing belt 1 is shifted, the shifting direction of the fixing belt 1 can be reversed to regulate the shifting.

  Further, since the detent member 8 is attached to the plate spring 7, when the detent member 8 pushes the plate spring 7 beyond the normal position, a reaction force (spring load) is generated. This force is repelled toward the fixing belt 1, thereby restricting the movement of the fixing belt 1.

  In other words, the fixing belt 1 is tensioned by the leaf spring 7 and the offset of the fixing belt 1 is regulated by the offset member 8 at the side end of the leaf spring 7. It does not have to be. Since it is only necessary to partially regulate the shift of the fixing belt 1, it is possible to reduce the size and cost of the fixing device by reducing the component size.

  In the image forming apparatus provided with the above-described fixing device, a halogen heater 3 or the like as a heating unit is arranged inside the small-diameter heating roller 2, thereby constituting a configuration as an image forming apparatus with low cost and good energy efficiency. it can. Further, by using a toner in which oil-containing silica is used as an external additive, it is possible to constitute a configuration as an image forming apparatus that is lower in cost and energy efficient.

  The present invention is not limited to the embodiments described above, and many variations are possible by those having ordinary knowledge in the art within the technical idea of the present invention.

1: Fixing belt 2: Heating roller 3: Halogen heater 4: Fixing pad 5: Fixing pad holding member 6: Pressure roller 7: Leaf spring 7a: Mounting portion 7b: Bending portion 7c: Tip portion 7d: Hole 8: Stopping member 8a: groove 8b: inclined surface 100: fixing device 200: image forming apparatus N: fixing nip

JP 2012-027376 A

Claims (10)

A fixing belt made of an endless belt-like member;
A fixing member provided inside the fixing belt;
A heating roller for transferring heat to the fixing belt;
Heating means provided inside the heating roller;
A leaf spring constituting a belt tension mechanism for applying tension to the fixing belt;
A detent member that regulates a deviation in the width direction of the fixing belt;
In the fixing device provided with
The fixing device, wherein the plate spring holds the stopper member.   2. The slope according to claim 1, wherein a slope of the detent member that is in contact with the fixing belt is provided so as to rise in a width direction of the fixing belt from a center side toward an end portion. Fixing device.   The fixing device according to claim 1, wherein the plate spring has a bent shape at a portion contacting the fixing belt.   The fixing device according to claim 1, wherein a shape of a tip portion of the leaf spring is a curved shape.   5. The fixing device according to claim 3, wherein a hole is provided in a bent portion of the leaf spring.   6. The fixing device according to claim 5, wherein the hole provided in the bent portion of the leaf spring is circular or substantially circular.   The fixing device according to claim 5, wherein a hole of the leaf spring is provided toward the heating unit.   The fixing device according to claim 1, wherein the detent member has a portion sandwiching a leaf spring.   An image forming apparatus comprising the fixing device according to claim 1. The image forming apparatus according to claim 9, wherein a toner using oil-containing silica as an external additive is used.