JP4803962B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device that fixes an unfixed image by heating and pressing, and an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus including the fixing device. Specifically, the present invention relates to a belt-nip type fixing device having a configuration in which a belt-shaped fixing member and a pressure member that faces and abuts against the belt-shaped fixing member are heated and pressed, and an image forming apparatus including the belt nip type fixing device.

In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, printing paper, electrophotographic process, electrostatic recording process, magnetic recording process, etc. As a fixing device that heats and fixes an unfixed image (toner image) of image information formed and supported on a recording paper or the like by a transfer method or a direct method as a permanently fixed image on a recording material surface, a heat roller type device is used. Widely used.
In recent years, belt (film) heating type apparatuses have been put into practical use from the viewpoint of quick start and energy saving. Further, when attention is paid to the principle of generating heat, an electromagnetic induction heating apparatus has also been proposed.

a) Heat roller type fixing device:
The heat roller type fixing device is basically composed of a pressure roller pair consisting of a fixing roller (heating roller) and a pressure roller, and rotates the pressure roller pair to fix a fixing nip portion (heating nip portion) as a mutual pressure contact portion. ) An unfixed image to be fixed on the surface is formed on the surface, and a recording material that carries the unfixed image is introduced and nipped and conveyed (inserted), and it is undecided by the heat of the fixing roller and the pressure applied to the fixing nip. The received image is fixed to the surface of the recording material by heat and pressure.

  In general, the fixing roller has a hollow metal roller made of a material such as aluminum as a base body (core metal), and a halogen lamp as a heat source is inserted into the inner space thereof, and is heated by the heat generated by the halogen lamp. Is controlled to control the temperature of the halogen lamp so that the temperature is maintained at a predetermined fixing temperature.

  In particular, as a fixing device in an image forming apparatus that performs full-color image formation, in which an unfixed image composed of a maximum of four toner image layers is required to be sufficiently heated and melted and mixed, a recording material and Fixing failure occurs if the interface with the toner image layer is not heated sufficiently, so that the core metal of the fixing roller has a high heat capacity, and the toner image is wrapped around the core metal and melted uniformly. An elastic layer is provided, and the toner image is heated through the rubber elastic layer. There is also a configuration in which a heat source is provided in the pressure roller so that the pressure port is heated and temperature-controlled.

b) Belt (film) heating type fixing device:
A belt (film) heating type fixing device is proposed in, for example, Patent Document 1 to Patent Document 4.
That is, a fixing nip is formed by sandwiching a heat-resistant film (fixing film, fixing belt) between a ceramic heater as a heating element and a pressure roller as a pressure member. An unfixed image to be image-fixed is formed between the fixing film and the pressure roller, and a recording material that carries the image is introduced, and is nipped and conveyed (inserted) together with the fixing film. The heat of the ceramic heater is applied to the recording material through the fixing film at the portion, and the unfixed image is fixed to the surface of the recording material by the pressure applied at the fixing nip portion.

  This type of fixing device can be configured as an on-demand type device using a ceramic heater and a member having a low heat capacity as a fixing film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature. The waiting time from power-on of the image forming apparatus to the state where image formation can be executed is short (quick start property), and power consumption during standby is greatly reduced. ) Etc.

c) Electromagnetic induction heating type fixing device:
Patent Document 5 discloses an induction heating fixing device that induces a current in a fixing roller by magnetic flux and generates heat by Joule heat. This can generate heat directly from the fixing roller by using the generation of induced current, and achieves a fixing process more efficient than a conventional heat roller type fixing device using a halogen lamp as a heat source. .

In order to obtain a high density of energy that acts on the fixing, the exciting coil is brought close to the fixing roller, which is a heating element, or the alternating magnetic flux distribution of the exciting coil is concentrated in the vicinity of the fixing nip portion, so that a highly efficient fixing device can be obtained. realizable.
FIG. 6 is a schematic cross-sectional view illustrating a schematic configuration of an example of an electromagnetic induction heating type fixing device. In FIG. 6, reference numeral 110 denotes a fixing belt (fixing film), and an electromagnetic induction heat generating layer (conductor layer, magnetic layer, resistor layer) is disposed on the outer peripheral surface or in the vicinity thereof. The fixing belt 110 is an endless belt-like (endless) and electromagnetic induction heat-generating heating rotator.

  Reference numeral 116 denotes a fixed pad member (film guide member) having a substantially semicircular arc shape in cross section, and the fixing belt 110 is loosely fitted outside the fixed pad member 116. Reference numeral 115 denotes magnetic field generating means disposed inside the fixed pad member 116, which includes an exciting coil 118 and a magnetic core (core material) 117. Reference numeral 130 denotes an elastic pressure roller, and a fixing nip portion N 'having a predetermined width is formed on the lower surface of the fixed pad member 116 with a predetermined pressing force via the fixing belt 110 to be in mutual pressure contact.

  The pressure roller 130 is rotationally driven in the direction of arrow K by the driving hand throw 114. The fixing belt 110 is driven to rotate by the frictional force at the fixing nip portion N ′ due to the rotational driving of the pressure roller 130. The fixing belt 110 has a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 130 while sliding while the inner peripheral surface thereof is in close contact with the lower surface of the fixed pad member 116 at the fixing nip portion N ′. Is rotated in the direction of arrow L (pressure roller driving method).

  The fixed pad member 116 has three roles of pressing the fixing nip portion N ′, supporting the fixing belt 110, and ensuring conveyance stability when the fixing belt 110 rotates. The fixed pad member 116 is an insulating member that does not hinder the passage of magnetic flux, and a material that can withstand a high load is used.

  The excitation coil 118 generates an alternating magnetic flux by an alternating current supplied from an excitation circuit (not shown). The alternating magnetic flux generates an eddy current in the electromagnetic induction heat generating layer of the fixing belt 110 facing the coil by the magnetic core 117 corresponding to the position of the fixing nip portion N. This eddy current generates Joule heat in the electromagnetic induction heating layer due to the specific resistance of the electromagnetic induction heating layer.

Due to the electromagnetic induction of the fixing belt 110, the surface of the fixing belt 110 facing the coil in which the alternating magnetic flux is concentrated or the vicinity thereof is heated with high efficiency.
By controlling the current supply to the exciting coil 118 by a temperature control system including a temperature detection unit (not shown), the temperature of the fixing nip portion N is adjusted to maintain a predetermined temperature.

  First, the pressure roller 130 is rotationally driven in the direction of arrow K, and the fixing belt 110 is rotated in the direction of arrow L around the fixed pad member 116 along with the rotation, and power is supplied from the excitation circuit to the excitation coil 118 as described above. Then, the fixing belt 110 generates heat by electromagnetic induction, rises to a predetermined temperature, and is in a temperature-controlled state. A recording material P ′, on which an unfixed image T is formed by an image forming means (not shown), is in contact with the fixing nip N ′ between the fixing belt 110 and the pressure roller 130, and the image surface is in contact with the fixing belt 110. Is inserted. Then, in the fixing nip portion N ′, the unfixed image T is in close contact with the outer peripheral surface of the fixing belt 110 and is nipped and conveyed together with the fixing belt 110.

  In the process in which the recording material P ′ is nipped and conveyed together with the fixing belt 110 through the fixing nip portion N ′, the unfixed image T on the surface of the recording material P ′ is heated by the electromagnetic induction heat of the fixing belt 110. Heat fixing. Thereafter, when the recording material P ′ passes through the fixing nip portion N ′, it is separated from the outer surface of the rotary fixing belt 110 and is discharged and conveyed (not shown).

  When the endless fixing belt 110 is driven by the pressure roller 130 as in the fixing device of the pressure roller driving method exemplified above, the fixing is performed more than the frictional resistance between the pressure roller 130 and the fixing belt 110. When the sliding resistance between the belt 110 and the fixed pad member 116 increases, or the frictional resistance of the recording material P ′ against the pressure roller 130 causes the sliding resistance between the fixing belt 110 and the fixed pad member 116. In the case where the recording material P becomes smaller, slipping may occur, and the recording material P ′ may not be smoothly conveyed.

  The electromagnetic induction heating type fixing device has been described above as an example. However, the concern of poor conveyance due to the fixing belt side being driven is a belt (film) heating method (belt in which the fixing side is not a pressure side but a belt shape) This can be applied to all nip type fixing devices.

JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 Japanese Utility Model Publication No. 51-109739

  Therefore, the present invention eliminates the concern that the fixing member slips in the belt nip type fixing device having a configuration in which the belt-shaped fixing member and the pressure member that abuts against the belt-shaped fixing member are heated and pressed. It is an object of the present invention to provide a fixing device that hardly causes image misalignment or running failure, and an image forming apparatus using the same.

The above object is achieved by the present invention described below. That is, the fixing device of the present invention includes a flexible and endless fixing belt, a fixing member that is located within the periphery of the fixing belt and that receives sliding friction on the inner peripheral surface of the fixing belt, and the fixing device via the fixing belt. A pressure rotating body that is pressed by a member and rotates together with the fixing belt while sandwiching the fixing belt with the fixing member,
A fixing device that fixes an unfixed image on the surface of the recording material by inserting a recording material carrying an unfixed image on the surface thereof into a nip portion between the fixing belt and the pressure rotator. And
At least one of both end openings in the rotation axis direction of the fixing belt is provided with an end cap member that is fitted and fixed in close contact with the opening, and fixes the shape of the opening in a circular shape, and it characterized in that it comprises a driving device for rotating the direct fixing belt from the end cap member.

According to the present invention, by providing a fixing belt driving means for rotationally driving a fixing belt different from the pressure rotator, the rotational driving force on the fixing belt is increased and the fixing belt is prevented from slipping. Is done.
The driving device is provided with a circular end cap member that is closely fixed to the fixing belt, and a driving device that applies a rotational driving force to the fixing belt via the end cap member. This is a drive device that is different from the device that rotationally drives the pressurizing rotator, and since the drive device is provided, even if sliding resistance increases, the fixing belt rotates without slipping. Can be made.
In addition, among the fixing belts, since the receiving belt is driven by an end portion with little thermal expansion, it is possible to suppress a change in the conveyance speed of the recording material with respect to a temperature change, and the fixing belt is rotated at a stable speed. be able to.

In the present invention, it is preferable that the end cap member is provided at both ends of the fixing belt in the rotation axis direction, and in this case, the driving device is configured to connect one or both of the two end cap members. A rotational driving force is applied to the fixing belt.
In the present invention, the driving stability is improved by adding the driving device for rotating the fixing belt autonomously to the conventional fixing device in which the pressure rotator is rotationally driven by itself. It is good also as a structure to provide. Of course, since the fixing belt rotates autonomously by the drive device, wherein instead of driving the pressure rotating body, the pressure rotating body, there in a manner which is driven to rotate by rotation of the fixing belt It doesn't matter . In any case, it is desirable that the rotation of the fixing belt and the rotation of the pressure rotator are substantially constant as the linear velocity.

As the fixing device of the present invention, a rotation gear having the same axis as the rotation axis of the fixing belt is provided at a portion of the end cap member that is exposed from the end of the fixing belt, and the rotation gear is used as the driving device. It is preferable to be configured to be driven to rotate.
The fixing device of the present invention can employ an electromagnetic induction heating method as its heating principle. That is, the fixing belt can include an electromagnetic induction heat generating member on the outer peripheral surface thereof or in the vicinity thereof, and magnetic field generating means can be disposed in the vicinity of the outer peripheral surface of the fixing belt.

  Here, “in the vicinity of the outer peripheral surface” defined in the present invention means that a layer containing an electromagnetic induction heat-generating member by electromagnetic induction (hereinafter sometimes referred to as a “heat generation layer” if necessary) generates heat. Even when other layers are formed on the outer peripheral surface, the heat is transmitted to the outer peripheral surface, and the temperature of the outer peripheral surface is close enough to be sufficient for fixing. means. Accordingly, the depth from the outer peripheral surface that defines “the vicinity of the outer peripheral surface” varies greatly depending on various conditions, and cannot be specifically shown. In addition, in a state where the base itself constitutes a heat generating layer including an electromagnetic induction heat generating member and another layer is formed on the outer peripheral surface, the heat generating layer is exposed on the inner peripheral surface side. Whether or not it is “near the outer peripheral surface” is determined by paying attention only to the state from the outer peripheral surface.

  On the other hand, the image forming apparatus of the present invention includes at least image forming means for forming an unfixed image on the surface of the recording material, and fixing for fixing the unfixed image formed on the surface of the recording material by heating and pressing. An image forming apparatus comprising: the fixing device according to the present invention.

  According to the present invention, in a belt-nip type fixing device having a configuration in which heating and pressurization are performed by an endless belt-shaped fixing belt and a pressure member that abuts against the fixing belt, the opening of at least one end of the fixing belt is provided. By controlling the shape of the end cap to be circular with the end cap member and rotating it, the concern that the fixing belt slips can be eliminated, and the change in the outer diameter of the pressure rotating body is not affected. The recording material can be conveyed at a substantially constant speed. Therefore, it is possible to provide a fixing device in which image misalignment or running failure is extremely small, and an image forming apparatus using the same.

Hereinafter, the present invention will be described more specifically with reference to preferred embodiments.
< First Embodiment >
First, the first embodiment will be described. The fixing device according to the present embodiment uses an electromagnetic induction heating type endless (cylindrical) fixing belt (fixing film) as a heating member, and drives both the fixing belt and the pressure roller. The fixing device. FIG. 1 shows an overall schematic configuration of the fixing device of this embodiment . Moreover, AA sectional drawing in FIG. 1 is shown in FIG. In FIG. 2, the illustration of the frame 5 is omitted, and recording materials P1 and P2 on which unfixed or fixed toner images are formed are added for the convenience of explanation of the fixing operation described later.

  1 and 2, reference numeral 10 denotes an electromagnetic induction heat generating endless (endless) fixing belt. Reference numerals 50 and 50 'denote cylindrical end cap members, and both end openings of the fixing belt 10 are externally fitted to and closely contact with part of the end cap members 50 and 50' (sleeve portions 50a and 50'a). is doing. Further, in order to ensure the close contact between the fixing belt 10 and the end cap members 50, 50 ′, the fixing is performed by tightening the end cap members 50, 50 ′ from the outside of the fixing belt 10 with the ring-shaped fasteners 51, 51 ′. The belt 10 is fixed. Reference numeral 30 denotes a pressure roller as a pressure rotating body that forms a fixing nip portion with the fixing belt 10 sandwiched between the fixing pad member (fixing member) 16.

  As shown in FIG. 2, a magnetic field generating member 15 as a magnetic field generating unit having a magnetic core 17 and an excitation coil 18 at a position facing the outer peripheral surface of the fixing belt 10 is several from the outer peripheral surface of the fixing belt 10. It is arranged and fixed with a gap of millimeters. In FIG. 2, reference numeral 19 denotes an insulating member for protecting the exciting coil 18 disposed on the surface of the magnetic field generating member 15 facing the fixing belt 10. The insulating member 19 is provided to electrically insulate between the magnetic field generating member 15 and the fixing belt 10.

FIG. 3 is a cross-sectional view of the fixing belt 10 and its peripheral portion taken along the shaft of the fixing belt 10. In FIG. 3, only the fixing belt 10, the end cap members 50 and 50 ′, and the ring-shaped fasteners 51 and 51 ′ are shown, and other components are not shown. Hereinafter, when the end cap members 50 and 50 ′ are described, only the end cap member 50 is mainly taken up, but the end cap member 50 ′ has basically the same configuration.
The ring-shaped end cap member 50 is mainly composed of a sleeve portion (cylindrical portion) 50 a that is fitted into the inner surface from both ends of the fixing belt 10 and a flange portion 50 b that is exposed outward from the end portion of the fixing belt 10. Furthermore, a gear 50c is provided on the outer periphery of the flange portion 50b.

  As materials for the end cap member 50 and the insulating member 19, so-called engineering plastics having excellent mechanical characteristics and insulating properties and high heat resistance are preferable. As specific engineering plastics, for example, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, and LCP resin may be selected.

By inserting the end cap member 50 into the opening portions at both ends of the fixing belt 10 and fixing the end cap member 50 tightly, what was in the state of a flexible belt until then has mechanical characteristics close to a thin roll having a certain degree of rigidity. It becomes like this.
When an external force is applied to the outer peripheral surface of the fixing belt 10 at a position away from the end surface of the sleeve portion 50a of the end cap member 50 (the one-dot chain line portion in FIG. 1) to the center in the longitudinal direction, the outer peripheral surface of the fixing belt 10 is recessed. However, when a torsional torque is applied to the entire fixing belt 10, it is not easily twisted and buckled. In general, the torque acting on the image heating and fixing apparatus using a belt is about 0.1 to 0.5 N · m, and the fixing belt 10 to which the end cap member 50 is attached does not buckle at this level of torque. .

  Further, when a compressive force is applied from both ends of the fixing belt 10 in the axial direction, the fixing belt 10 is easily compressed in the axial direction and does not buckle. The compressive force acting in the axial direction is generated when the fixing belt 10 is moved to one of the axial directions and is further restricted by some restricting means. The magnitude of the compressive force generated in this case is generally about 1 to 5 N. With such a compressive force, the fixing belt 10 to which the end cap member 50 is attached does not buckle.

The pressure roller 30 includes a cored bar 30a, an elastic material layer 30b formed and coated in a roller shape around the cored bar 30a, and a mold release for securing the mold release property coated thereon. The both ends of the cored bar 30a are held by bearings 29 and 29 ′. The bearings 29 and 29 ′ are fixed to the frame 5 via springs 25 and 25 ′, and the pressure roller 30 is placed on the outer peripheral surface of the fixing belt 10 (specifically, due to the resilience of the springs 25 and 25 ′). The fixing pad 10 is urged through a fixing belt 10 with a predetermined load.
The elastic material layer 30b is made of a material having heat resistance and elasticity. Specifically, the elastic material layer 30b is selected from silicone rubber, foamed silicone rubber, fluororubber, fluororesin, and the like. The release layer 30c is made of a material having a good surface releasability. Specifically, a fluororesin or the like can be selected.

31 and 31 'are drive gears as drive rotators. The drive gears 31 and 31 ′ mesh with (engage) the gears 50 c and 50 ′ of the end cap members 50 and 50 ′ respectively attached on both ends of the fixing belt 10, and rotate to the fixing belt 10 through this. Transmits driving force.
Drive gear 31, 31 'rotational driving force of is transmitted to the gear G ₁ via a motor (driving device) driving force transmission system (not shown) by driving the M, further driving gear 31, 31' is the axis of the It is generated by being transmitted to the rotating shaft 31c. In the present embodiment , the rotational driving force of the motor M is also transmitted from the gear G ₁ to the gear G _2, and is transmitted from the core metal 30 a that is the shaft center to the pressure roller 30, and the pressure roller 30 is also rotationally driven. To do. At this time, of course, it is desirable that the fixing belt 10 and the pressure roller 30 driven by the drive gears 31 and 31 ′ have substantially constant linear speeds on the outer surfaces thereof.

  A long rigid stay 22 having both ends fixed to the frame 5 of the fixing device is inserted into the fixing belt 10 and a fixing pad member 16 that forms a nip portion while sliding on the inner peripheral surface of the fixing belt 10 is provided. Is provided. The fixed pad member 16 urges the fixing belt 10 from the inner peripheral surface to the pressure roller 30, and a fixing nip portion N having a predetermined width is formed between the fixing belt 10 and the pressure roller 30.

The pressure roller 30 rotates in the direction of arrow B by the rotational driving force as described above, and the rotational driving force acts on the fixing belt 10 by the frictional force between the pressure roller 30 and the outer peripheral surface of the fixing belt 10. The fixing belt 10 has a linear velocity substantially corresponding to the linear velocity of the outer peripheral surface of the pressure roller 30 while the inner peripheral surface thereof is in close contact with and slides on the lower surface of the fixed pad member 16 in the fixing nip portion N, and in the direction of arrow C. Rotate to. The principle of this rotational drive is the same as that of a conventional belt nip type fixing device. However, in this embodiment , as described above, the rotational driving force from the motor M is directly transmitted to the fixing belt 10 only through the driving gears 31, 31 ′ and the end cap member 50.

  In the fixing nip portion N, a surface corresponding to the fixing nip portion N of the fixed pad member 16 in order to reduce the mutual sliding frictional force between the fixed pad member 16 and the inner peripheral surface of the fixing belt 10 and improve the slidability. A sliding sheet having heat resistance and low friction properties (not shown) is disposed on a portion (a portion in contact with the inner peripheral surface of the fixing belt 10). As this sliding sheet, a sheet having excellent heat resistance, such as a PI (polyimide) film or a fluororesin-coated glass cloth, and having good sliding properties with the inner peripheral surface of the fixing belt 10 is used. Further, in order to improve the slidability, a lubricant such as heat resistant oil may be interposed between the sliding sheet and the fixing belt 10.

The magnetic field generating member 15 is mainly composed of an exciting coil 18 and a magnetic core 17. These are held by the exciting coil holding member 13.
The magnetic core 17 is a member having a high magnetic permeability and is preferably a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite having a low loss even at 100 kHz or higher.

The exciting coil 18 is a conductive wire (electric wire) that constitutes a coil (wire ring) using a bundle (bundle wire) of a plurality of thin copper wires, each of which is covered with an insulation coating, and is wound several times. Is formed. In this embodiment , the exciting coil 18 is formed by winding 11 turns.
The insulating member 19 preferably uses a heat-resistant coating in consideration of heat conduction due to heat generated by the fixing belt 10. Specifically, for example, it is preferable to use a coating such as amideimide or polyimide.

The exciting coil 18 is formed in a shape along the curved surface of the heat generating layer of the fixing belt 10. In the present embodiment , the distance between the surface of the fixing belt 10 and the exciting coil 18 is set to be approximately 2.5 mm.
The magnetic core 17 and the excitation coil 18 and the outer peripheral surface of the fixing belt 10 are as close as possible to increase the magnetic flux absorption efficiency. However, the heat generation layer in the magnetic core 17 and the excitation coil 18 and the fixing belt 10 is high. When the distance to (explained later) exceeds 5 mm, this efficiency is remarkably lowered. If the distance is within 5 mm, the distance between the heat generating layer of the fixing belt 10 and the magnetic core 17 and the exciting coil 18 does not have to be constant.

As for the lead wire from the exciting coil holding member 13 of the exciting coil 18, an insulating coating is applied to the outside of the bundled wire for the portion outside the exciting coil holding member 13.
The excitation coil 18 is connected to a power feeding unit excitation circuit (not shown). This power feeding part excitation circuit can generate a high frequency of 20 kHz to 500 kHz by a switching power supply. An alternating magnetic flux is generated from the exciting coil 18 by the alternating current (high-frequency current) supplied from the power feeding unit excitation circuit.

  The temperature of the fixing nip portion N is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system (not shown) including a temperature detection unit. The temperature detecting means 126 is a temperature sensor such as a thermistor for detecting the temperature of the fixing belt 10. In this example, the temperature of the fixing nip N is controlled based on the temperature information of the fixing belt 10 measured by the temperature detecting means 126. Like to do.

Next, the fixing belt 10 will be described. FIG. 4 is an enlarged cross-sectional view showing the layer configuration of the fixing belt 10 in the present embodiment . The fixing belt 10 has a heat generating layer (a layer including an electromagnetic induction heat generating member) 10c made of copper plating or the like on the surface (one surface) of a base layer 10d made of a polyimide belt which is a base layer of an electromagnetic induction heat generating fixing belt. The composite structure is formed by laminating an elastic layer 10b thereon, and further laminating a release layer 10a on the outer surface thereof. A primer layer (not shown) may be provided between the heat generating layer 10c and the elastic layer 10b or between the elastic layer 10b and the release layer 10a in order to bond the layers.

  In the fixing belt 10 having a substantially cylindrical shape, the base layer 10d is on the inner surface side of the cylinder, and the release layer 10a is on the outer surface side. As described above, when an alternating magnetic flux acts on the heat generating layer 10c, an eddy current is generated in the heat generating layer 10c and the heat generating layer 10c generates heat. The heat generated by induction heat generation in the heat generating layer 10c reaches the elastic layer 10b and the release layer 10a, the entire fixing belt 10 is heated, and the recording material P1 inserted through the fixing nip portion N is heated to be unfixed. The image T1 is heat-fixed.

  The base layer 10d is a material having flexibility, excellent mechanical strength, and heat resistance, such as fluorine resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and FEP resin. Is desirable. The thickness of the base layer 10d is suitably in the range of 30 to 100 μm. If it is less than 30 μm, it is difficult to obtain the strength as a fixing belt, and if it exceeds 100 μm, flexibility is impaired, and the heat capacity increases and the rise time becomes long.

  The heat generating layer 10c is preferably a thin metal layer. The thickness of the heat generating layer 10c is suitably in the range of 1 to 20 μm. If it is less than 1 μm, it may be difficult to obtain sufficient heat generation, and if it exceeds 20 μm, flexibility is impaired, and the heat capacity increases and the rise time becomes long. As the metal material to be used, a metal having low electric resistance such as copper, aluminum, silver or the like is desirable (these are materials referred to as “electromagnetic induction exothermic members” in the present invention).

  The elastic layer 10b is desirably made of a material having good heat resistance and thermal conductivity, such as silicone rubber, fluorine rubber, fluorosilicone rubber or the like. The thickness of the elastic layer 10b is preferably in the range of 10 to 500 μm in order to guarantee the fixed image quality. When forming a color image, particularly in a photographic image, a solid image is formed over a large area on the surface of the recording material P1. In this case, if the heating surface (release layer 10a) cannot follow the unevenness of the recording material P1 or the unevenness of the unfixed image T1, heating unevenness occurs, and the unevenness of glossiness is generated between the portion where the heat transfer amount is large and the portion where the heat transfer amount is small. Occurs. A portion with a large amount of heat transfer has a high glossiness, and a portion with a small amount of heat transfer has a low glossiness.

  If the thickness of the elastic layer 10b is less than 10 μm, there is a possibility that unevenness in image gloss may occur due to not being able to follow the unevenness of the recording material P1 or the unfixed image T1. On the other hand, if the thickness of the elastic layer 10b exceeds 500 μm, the thermal resistance of the elastic layer 10b increases, making it difficult to realize a quick start. The thickness of the elastic layer 10b is more preferably in the range of 50 to 300 μm.

If the hardness of the elastic layer 10b is too high, there is a possibility that unevenness in image gloss may occur because it cannot follow the unevenness of the recording material P1 or the unfixed image T1. Therefore, the hardness of the elastic layer 10b is preferably 50 ° (JIS-A: JIS-KA type tester) or less, and more preferably 35 ° or less.
The thermal conductivity λ of the elastic layer 10b is preferably in the range of 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [cal / cm · sec · deg]. When the thermal conductivity λ is smaller than 6 × 10 ⁻⁴ [cal / cm · sec · deg], the thermal resistance is large, and the temperature rise in the surface layer (release layer 10a) of the fixing belt 10 may be slow. This is not preferable. When the thermal conductivity λ is larger than 2 × 10 ⁻³ [cal / cm · sec · deg], the hardness may be too high or the compression set may be deteriorated. The thermal conductivity λ is more preferably in the range of 8 × 10 ^{−4 to} 1.5 × 10 ⁻³ [cal / cm · sec · deg].

For the release layer 10a, a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, and FEP can be selected.
The thickness of the release layer 10a is preferably in the range of 5 to 50 μm. If the thickness of the release layer 10a is less than 5 μm, there is a concern that problems such as formation of a poorly releasable part due to coating film unevenness during layer formation or insufficient durability may occur. On the other hand, if the thickness of the release layer 10a exceeds 50 μm, there is a possibility that the heat conduction deteriorates. In particular, in the case of a resin release layer, the hardness becomes too high, and the elastic layer 10b. There is a possibility that the effect of will fade.

  Thus, the pressure roller 30 and the drive gears 31 and 31 ′ are rotationally driven, and the fixing belt 10 is rotated accordingly. As described above, power is supplied from the excitation circuit (not shown) to the excitation coil 18. Due to the action of the magnetic field, electromagnetic induction heat is generated in the fixing belt 10 as the heating member, and the fixing nip portion N rises to a predetermined temperature and is in a temperature-controlled state. In this state, the recording material P1 on which the unfixed image T1 is formed by the image forming means (not shown) is fixed on the fixing nip portion N formed between the fixing belt 10 and the pressure roller 30. It is inserted so as to contact the belt 10. Then, in the fixing nip portion N, the unfixed image T1 is brought into close contact with the outer peripheral surface of the fixing belt 10 and is nipped and conveyed together with the fixing belt 10.

  In the process in which the recording material P1 is nipped and conveyed together with the fixing belt 10 through the fixing nip N, the fixing belt 10 is heated by electromagnetic induction heat and the unfixed image T1 on the surface of the recording material P1 is heated and fixed. The When the recording material P1 passes through the fixing nip portion N, it is separated from the outer surface of the fixing belt 10 and discharged and conveyed as a recording material P2 after fixing. The fixed toner image T2 on the surface of the recording material P2 passes through the fixing nip portion N and is then cooled to become a permanently fixed image.

In the fixing device of the present embodiment, the toner containing the low softening substance is used for forming the unfixed image T1, and therefore the fixing device is not provided with an oil application mechanism for preventing offset, but the low softening An oil application mechanism may be provided as necessary, for example, when a toner containing no substance is used. In addition, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

As described above, the drive gears 31, 31 ′ are disposed, and the rotational driving force is transmitted to the fixing belt 10 via the end cap member 50, so that only the driven rotation by the pressure roller 30 is achieved. As a result, the rotational driving force with respect to the fixing belt 10 increases, and slipping of the fixing belt 10 is prevented.
Relative to the frictional resistance between the pressure roller 30 and the outer peripheral surface of the fixing belt 10, the fixing belt 10 and the fixed pad member 16 (or a sliding sheet not shown). And the frictional resistance of the recording material P1 against the pressure roller 130 is the sliding resistance between the fixing belt 10 and the fixed pad member 16. Even when the size is smaller, according to the fixing device of the present embodiment , the recording material P1 can be stably conveyed without causing the fixing belt 10 to slip.

In addition, even if the configuration in which one motor M is a driving source for both the fixing belt 10 and the pressure roller 30 as in the present embodiment , these are not the configuration in which the other is driven by one rotational drive. Therefore, the present invention includes the “driving device that applies a rotational driving force to the fixing belt” according to the present invention, and is also included in the concept of “the pressure rotator is rotationally driven by itself”. Of course, there is no problem to use separate drive systems.

< Second Embodiment>
Next, a second embodiment will be described. The fixing device of this embodiment is that using a fixing belt of the electromagnetic induction exothermic endless (cylindrical) (fixing film) as the heating element is the same as in the first embodiment, drive only fixing belt is, the pressure roller is Fixing device of an electromagnetic induction heating method in the method for the follower. FIG. 5 shows an overall schematic configuration of the fixing device of this embodiment. In addition, since this embodiment contains many parts of the same structure as 1st Embodiment, the same code | symbol is attached | subjected to the part of this same structure, and detailed description is abbreviate | omitted. Further, the entire cross-sectional view and the cross-sectional view of the fixing belt 10 are also similar to those of the first embodiment, and therefore, FIG. 2 and FIG. 3 are used instead.

In the fixing device of the present embodiment, the rotational driving force of the motor M is transmitted only to the driving gears 31 and 31 ′ of the fixing belt 10 in the fixing device of the first embodiment , and the pressure roller 30 is applied to the fixing belt 10. On the other hand, it is configured to rotate by being driven. Except for the difference in the driving force transmission system, everything is the same as in the first embodiment .
When the drive gears 31 and 31 ′ are rotationally driven, the rotational drive force is transmitted to the gears 50c and 50′c of the end cap members 50 and 50 ′ with which the drive gears 31 and 31 ′ are engaged, The fixing belt 10 rotates.

  On the other hand, the pressure roller 30 is opposed to and pressed against the lower surface of the fixed pad member 16 via the fixing belt 10 to form a fixing nip portion N. The pressure roller 30 rotates the fixing belt 10. Followed by rotation. By rotating the pressure roller 30 following the fixing belt 10, the change in the outer diameter due to the thermal expansion of the elastic material layer 30b of the pressure roller 30 does not affect the conveyance speed of the recording material P1.

  Thus, the drive gears 31 and 31 ′ are driven to rotate, the fixing belt 10 rotates, and the pressure roller 30 is driven to rotate accordingly, and is generated by power supply from the excitation circuit (not shown) to the excitation coil 18. Due to the action of the magnetic field, electromagnetic induction heat is generated in the fixing belt 10 as a heating member, and the fixing nip portion N rises to a predetermined temperature and is in a temperature-controlled state. In this state, the recording material P1 on which the unfixed image T1 is formed by the image forming means (not shown) is fixed on the fixing nip portion N formed between the fixing belt 10 and the pressure roller 30. It is inserted so as to contact the belt 10. Then, in the fixing nip portion N, the unfixed image T1 is brought into close contact with the outer peripheral surface of the fixing belt 10 and is nipped and conveyed together with the fixing belt 10.

  In the process in which the recording material P1 is nipped and conveyed together with the fixing belt 10 through the fixing nip N, the fixing belt 10 is heated by electromagnetic induction heat and the unfixed image T1 on the surface of the recording material P1 is heated and fixed. The When the recording material P1 passes through the fixing nip portion N, it is separated from the outer surface of the fixing belt 10 and discharged and conveyed as a recording material P2 after fixing. The fixed toner image T2 on the surface of the recording material P2 passes through the fixing nip portion N and is then cooled to become a permanently fixed image.

As described above, in the fixing device according to the present embodiment, the conveyance speed of the fixing belt 10 can be kept substantially constant without being affected by temperature change, and thus compared with the fixing device according to the first embodiment. The distance between the image transfer portion and the fixing nip portion N in the image forming means can be shortened.

  The fixing device according to the present invention has been described with reference to the preferred embodiment, but the present invention is not limited to the above embodiment. For example, the various conditions such as the shape, material, dimensions, temperature, speed, etc. of each member are merely one example, and on the condition that the configuration of the present invention is provided, a person skilled in the art, based on conventionally known knowledge, Alternatively, any change can be made by studying the condition setting suitable for the present invention.

  In the above-described embodiment, the electromagnetic induction heating type fixing device has been described as an example. However, the concern about the conveyance failure due to the follower of the fixing belt side is a belt heating in which the fixing side is a belt shape instead of the pressure side. This can be applied to all types of fixing devices (belt nip method), and the present invention can be preferably applied to such fixing devices.

  Furthermore, in the above-described embodiment, an example of a configuration in which the end cap members 50 and 50 ′ are provided at both end openings in the rotation axis direction of the fixing belt 10 has been described. However, in the present invention, the end cap member has both ends. If it is provided in at least one of the openings, the shape of the fixing belt is fixed to some extent, and the predetermined effect of the present invention can be realized to some extent. Of course, by providing the end cap members at the openings at both ends, the shape stability of the entire fixing belt is increased, and the effects of the present invention can be realized at a high level.

  The fixing device having the above-described configuration can be used in a conventionally known image forming apparatus using a method such as electrophotography. That is, at least an image forming means for forming an unfixed image on the surface of the recording material by a method such as electrophotography, and a fixing means for fixing the unfixed image formed on the surface of the recording material by heating and pressing By using the fixing device having the above-described configuration according to the present invention as a fixing unit, the concern that the fixing belt slips is eliminated, and an image with extremely little image misalignment or poor running occurs. A forming apparatus can be provided.

Examples of the image forming unit include an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the electrostatic latent image carrier, a developing unit that develops the electrostatic latent image with toner, and an undecided obtained result. And a transfer unit that transfers a toner image to a sheet-like recording material.
Any configuration other than the fixing device known in the art can be used as long as it is not contrary to the object of the present invention.

1 is an overall schematic configuration diagram of a fixing device according to a first embodiment . It is AA sectional drawing in FIG. FIG. 3 is a cross-sectional view of the fixing belt and its peripheral portion cut along the fixing belt shaft in the first embodiment, showing only the fixing belt, the end cap member, and the ring-shaped fastener, and omitting other configurations. Yes. FIG. 2 is an enlarged cross-sectional view illustrating a layer configuration of a fixing belt in the first embodiment. FIG. 6 is an overall schematic configuration diagram of a fixing device according to a second embodiment. It is a schematic sectional drawing which shows schematic structure of an example of the fixing device of the electromagnetic induction heating system of a prior art example.

Explanation of symbols

5: Frame, 10, 110: Fixing belt, 13: Excitation coil holding member, 15: Magnetic field generating member, 16, 116: Fixed pad member (fixing member), 17, 117: Magnetic core, 18, 118: Excitation coil, 19: Insulating member, 22: Rigid stay, 25, 25 ': Spring, 30, 130: Pressure roller (pressure rotating body), 31, 31': Drive gear, 50, 50 ': End cap member, 51, 51 ': ring-shaped fastener, 114: driving hand throw, 126: temperature detecting means 126, M: motor (drive device), P1, P2, P': recording material, T, T1, T2: fixing toner image

Claims (8)

A flexible and endless fixing belt; a fixing member that is located within the periphery of the fixing belt and that is rubbed against the inner peripheral surface of the fixing belt; and is pressed against the fixing member via the fixing belt; A pressure rotator that rotates together with the fixing belt while being sandwiched between the fixing member, and
A fixing device that fixes an unfixed image on the surface of the recording material by inserting a recording material carrying an unfixed image on the surface thereof into a nip portion between the fixing belt and the pressure rotator. And
At least one of both end openings in the rotation axis direction of the fixing belt is provided with an end cap member that is fitted and fixed in close contact with the opening, and fixes the shape of the opening in a circular shape, and A fixing device comprising: a driving device that rotationally drives the fixing belt directly from the end cap member. The end cap members are provided at both ends of the fixing belt in the rotation axis direction, and the driving device applies a rotational driving force to the fixing belt through one or both of the two end cap members. The fixing device according to claim 1. The fixing device according to claim 1, wherein the pressure rotator is rotationally driven by itself. The fixing device according to claim 1, wherein the pressure rotator is driven to rotate by rotation of the fixing belt. A rotation gear having the same axis as the rotation axis of the fixing belt is provided at a portion of the end cap member exposed from the end of the fixing belt, and the rotation gear is rotated by the driving device. The fixing device according to claim 1. The fixing device according to claim 1, wherein the rotation of the fixing belt and the rotation of the pressure rotator are substantially equal as linear speeds. 2. The fixing belt according to claim 1, wherein the fixing belt includes an electromagnetic induction heat generating member on an outer peripheral surface thereof or in the vicinity thereof, and magnetic field generating means is disposed in the vicinity of the outer peripheral surface of the fixing belt. Fixing device. An image forming apparatus comprising at least an image forming unit that forms an unfixed image on the surface of a recording material, and a fixing unit that fixes the unfixed image formed on the surface of the recording material by heating and pressing. And
An image forming apparatus, wherein the fixing unit is the fixing device according to claim 1.

Images