JP4678795B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof. In particular, the present invention relates to an electrophotographic image forming apparatus that directly or indirectly transfers a toner image formed on an image carrier and records the image on a recording medium such as a sheet / OHP film. In such an image forming apparatus or the like, recording is performed by applying heat and pressure while conveying the fixing member and the pressure member through the recording medium between the fixing member that is heated to the fixing temperature and the pressure member that is pressed against the fixing member. The present invention relates to a fixing device that fixes an unfixed toner image on a medium.

  Conventionally, in a fixing device provided in an electrophotographic image forming apparatus, a fixing member such as a fixing roller and a fixing belt that is heated to a fixing temperature by a heat source, and a pressure member such as a pressure roller and a pressure belt that are pressed against the fixing member. In the meantime, the fixing member and the pressure member are rotated by rotating the fixing member and the pressure member through the recording medium on which the unfixed toner image is placed, and heat and pressure are applied to the toner image to fix the toner image on the recording medium. In general, a halogen heater using a halogen lamp has been used as a heat source.

  Incidentally, in recent years, in an image forming apparatus or the like, a zero energy standby mode (Zero Energy Standby Mode-ZESM) is performed at the time of standby because of a request for energy saving. In the zero energy standby mode, during non-image formation, the power supply to the heat source is cut to reduce energy consumption, and the heat source is turned on when the image forming operation starts, and the fixing member of the fixing device is raised to the fixing temperature. Warm up.

  At this time, energy saving can be achieved by reducing the heat capacity of the fixing member by reducing the wall thickness of the fixing roller to 1 mm or less, and improving the temperature responsiveness and shortening the rise time until fixing is possible to about 10 seconds. At the same time, the convenience of users was improved.

  On the other hand, if the fixing member is formed of a rigid body, it cannot follow the unevenness of the recording medium at the time of fixing, and image quality deterioration such as minute gloss unevenness occurs. Even at a level that is not a problem for monochrome machines in particular, color machines, which are increasing in number in recent years, become a big problem. For color machines, maintaining the elasticity of the fixing surface is essential for improving image quality. It was.

  In view of such a demand, in a conventional image forming apparatus, as shown in FIG. 10, for example, a fixing belt that holds a conveyance shape in a cylindrical shape as shown in the figure by belt conveyance shape holding members (not shown) provided on both sides. 1, a nip forming member 2 disposed inside the fixing belt 1, a pressure roller 3 that presses against the nip forming member 2 across the fixing belt 1 to form a fixing nip, and presses the pressure roller 3. On the opposite side, opposite to the fixing belt 1, an induction heating source 4 that induction heats the fixing belt 1, and an intermediate between the induction heating source 4 and the pressure roller 3 that faces the fixing belt 1, There is a configuration including a temperature detection member 5 that detects the temperature of the fixing belt 1 and a control unit (not shown) that controls the induction heating source 4 based on the temperature detected by the temperature detection member 5.

  The nip forming member 2 includes a heat-resistant elastic member 8 provided on a support member 6 via a heat insulating member 7, and the heat-resistant elastic member 8 is covered with a protective member 9.

  Then, as shown in the drawing, heat and pressure are applied to the fixing nip while running and transporting the fixing belt 1 by rotating the pressure roller 3 through the recording medium p on which the unfixed toner image is placed. The image t was fixed on the recording medium p.

  However, in such a fixing device, when a belt running failure such as the fixing belt 1 slips or stops running of the fixing belt 1 due to an unexpected reason, the induction heating source 4 faces it. The belt surface is heated abnormally. However, depending on the temperature detection member 5 located away from the fixing belt surface facing the induction heating source 4, the abnormal temperature rise cannot be detected, and the fixing belt 1 may be burned out. There was a problem that the fire accident of the belt 1 could not be prevented.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent a fixing belt from firing accidents and ensure safety in a fixing device using a fixing belt or an image forming apparatus including such a fixing device.

To achieve this object, the present invention provides a fixing belt, an induction heating source provided outside the fixing belt for induction heating, and a non-rotating non-rotating contact with the fixing belt inside the fixing belt. In the fixing device, comprising a nip forming member and a pressure roller for forming a fixing nip between the nip forming member via the fixing belt, and fixing an image on a recording medium passing through the fixing nip, A temperature detecting member that is disposed opposite to the induction heating source with the fixing belt interposed therebetween, and that detects the temperature of the fixing belt from the inside; and a belt guide member that is formed of a magnetic material and slides on the fixing belt. The temperature detection member is disposed to face the induction heating source through a notch provided in the belt guide member.

The belt guide member may include an arcuate belt guide surface, and the notch may be provided on the arcuate belt guide surface. The arcuate belt guide surface provided in the belt guide member may be coated with one of fluororesin, silicone oil, zinc stearate, and wax. The temperature detection member may be in contact with the inner periphery of the fixing belt, and may include a control unit that controls the induction heating source based on a temperature detected by the temperature detection member.

The fixing belt is preferably a thin endless loop having a low heat capacity and flexibility, and guides both side edges of the endless loop fixing belt to hold the conveying shape of the fixing belt in a cylindrical shape. It is good to provide a conveyance shape holding member. The nip forming member includes a protective member that contacts the fixing belt, a heat insulating member provided on the other side of the fixing belt with respect to the protective member, and a metal material support member that supports the heat insulating member. Good. In particular, an elastic foam layer may be provided between the protective member and the heat insulating member.

The pressure roller may be a heat insulating roller in which a heat insulating layer having a porous structure is provided around a metal core. The heat insulating roller may be formed of a silicone rubber foam.

  In order to achieve the above-described object, the present invention is characterized in that the image forming apparatus includes the fixing device as described above.

According to the invention described in claim 1, and faces the induction heating source across the fixing belt is disposed, since the temperature of the fixing belt includes a temperature sensing member for detecting the internal, unforeseen events, fixing When a belt running failure occurs, such as when the belt slips or when the fixing belt stops running, the belt surface facing it is abnormally heated by the induction heating source, but it faces the induction heating source. The abnormal temperature rise can be detected by the temperature detecting member at the position, and it is possible to prevent the fixing belt from being ignited and to ensure safety without causing the fixing belt to burn out.

According to the fourth aspect of the invention, since the temperature detection member is in contact with the inner periphery of the fixing belt, temperature detection by the temperature detection member can be stabilized and accurately performed.

According to the first aspect of the invention, in addition, the belt guide member is provided with a notch hole, and the temperature detection member is opposed to the induction heating source through the notch hole. This can be done and can save space.

According to the second aspect of the present invention, since the belt guide member is provided with the arcuate belt guide surface, the belt guide member is guided by the belt guide surface of the belt guide member without providing a separate guide member. The fixing belt can be driven.

According to the invention described in claim 1, further added, the belt guide member, since made in magnetic resistance materials, magnetic field lines from the induction heating source becomes dense concentrated on the belt guide member, is a surface nonmagnetic It is difficult to concentrate on the temperature detection member and is sparse. Therefore, the magnetic shield effect makes it difficult to be affected by the lines of magnetic force, prevents self-heating of the temperature detection member, enables accurate temperature detection, and improves the heating efficiency of the fixing belt.

According to the invention described in claim 6 , since the fixing belt is formed into an endless loop having a thin wall and a low heat capacity and having flexibility, the belt heating efficiency is increased to 30 seconds or less, preferably 10 seconds or less. be able to. In addition, a temperature detection member is arranged inside the endless loop-shaped fixing belt so that the fixing belt is not easily damaged, and even if the fixing belt is damaged, the image is not affected and the durability of the belt is improved. Can do.

According to the seventh aspect of the present invention, since the belt conveying shape holding member for guiding the both side edges of the endless loop-shaped fixing belt and holding the conveying shape of the fixing belt in a cylindrical shape is provided, the fixing device can be downsized. And space saving can be achieved. Further, it is possible to stably detect the temperature of the fixing belt by reducing the fluctuation of the contact pressure of the temperature detecting member.

According to the ninth aspect of the present invention , the nip forming member includes a protective member that contacts the fixing belt, a heat insulating member provided on the other side of the fixing belt with respect to the protective member, and supports the heat insulating member. A support member made of a metallic material, and an elastic foam layer between the protective member and the heat insulating member , ensuring a wide fixing nip at a low pressure, and in combination with the heat insulating effect, Can be raised.

According to the invention of claim 1, because it has a non-rotation of the nip forming member for forming a fixing nip between the pressure roller via the fixing belt, to allow a smooth running of the fixing belt, heat insulating effect In combination with this, it is possible to make an instant start-up at a low temperature.

According to the invention described in claim 10 , since the pressure roller is a heat insulating roller provided with a heat insulating layer having a porous structure around the core metal , heat conduction from the fixing belt is reduced to reduce heat loss. In addition, the belt heating efficiency can be increased. Further, by using a heat-insulating roller hardness is greater than the constant wearing belt, the running of the fixing belt can be stabilized.

According to the twelfth aspect of the present invention, since the image forming apparatus includes the fixing device as described above, an image forming apparatus including the fixing device having the above-described effects can be provided.

1 is an overall schematic configuration diagram of a color electrophotographic image forming apparatus of an indirect transfer quadruple dandem system. FIG. 2 is a schematic configuration diagram illustrating the fixing device as viewed from an axial direction. (A) is a partially enlarged sectional view of a fixing belt used in the fixing device, and (B) is a partially enlarged sectional view of a fixing belt as another example. (A) is a side view of a belt guide member used in the fixing device, and (B) is a partial plan view. FIG. 4 is a configuration diagram of one end of a fixing belt used in the fixing device. It is a figure which shows magnetic force distribution from the induction heating source in the fixing device. FIG. 10 is a schematic configuration diagram illustrating another example of a fixing device as viewed in the axial direction. FIG. 6 is a schematic configuration diagram illustrating another example of the fixing device as viewed in the axial direction. It is a longitudinal cross-sectional view of the other example of the pressure roller which is an opposing member. FIG. 10 is a schematic configuration diagram illustrating a conventional fixing device as viewed from an axial direction.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 shows a color electrophotographic image forming apparatus of indirect transfer quadruple dandem system.

  Reference numerals 10c, 10m, 10y, and 10b in the figure are four image forming apparatuses of cyan, magenta, yellow, and black, respectively, and are arranged in tandem. Each image forming device is provided with a drum-shaped image carrier 11c, 11m, 11y, 11b, respectively, and the surface is uniformly made uniform by each charging device 12c, 12m, 12y, 12b as it rotates clockwise in the figure. Then, writing is performed with the laser beams Lc, Lm, Ly, and Lb from the common writing device 13, and then toner is attached to each of the developing devices 14c, 14m, 14y, and 14b, and the image carriers 11c, 11m, A single color image is formed on each of 11y and 11b.

  Then, the endless belt-like intermediate transfer member 15 is run counterclockwise in the drawing, and the primary transfer devices 16c, 16m, 16y, and 16b transfer the single color images on the image carriers 11c, 11m, 11y, and 11b to the primary transfer device. Then, a full color image is formed on the intermediate transfer member 15.

  On the other hand, the feeding roller 20 is rotated at an appropriate timing to feed out the sheet 22 in the sheet cassette 21, conveyed through the sheet conveying path 23, and abutted between the pair of registration rollers 24 and stopped. Then, the pair of registration rollers 24 are rotated in synchronization with the full color image on the intermediate transfer member 15, and the full color image is secondarily transferred to the sheet 22 by the secondary transfer device 25. After that, the sheet 22 after full color image transfer is conveyed upward as it is through the sheet conveyance path 23, and unfixed transfer toner is fixed on the sheet 22 when passing through the fixing nip of the fixing device 100, and discharged by the discharge roller 26. To be stacked on the sheet stack portion 27 on the image forming apparatus main body.

  The image carriers 11c, 11m, 11y, and 11b after the completion of the primary transfer are cleaned by the primary cleaning devices 17c, 17m, 17y, and 17b to remove residual toner. After the completion of the secondary transfer, the intermediate transfer member 15 is cleaned by the secondary cleaning device 18 to remove residual toner.

  Reference numerals 28c, 28m, 28y, and 28b in the figure denote toner replenishing devices that replenish toner to the color developing devices 14c, 14m, 14y, and 14b, respectively.

FIG. 2 shows a schematic configuration of the fixing device 100 as viewed from the axial direction.
Reference numeral 30 in the drawing is an endless loop fixing belt having flexibility. The fixing belt 30 has a thickness of 50 to 120 μm, preferably 50 to 100 μm, 20 to 80 φ, preferably 30 to 50 φ, and three or more layers.

3A and 3B show partially enlarged cross sections of the fixing belt 30. FIG.
As can be seen from FIG. 3A, the fixing belt 30 is composed of, for example, a base material layer 31, a heat generating layer 32, an intermediate elastic layer 33, and a surface release layer.

  The base material layer 31 is made of a heat-resistant resin material such as polyimide of 100 to 100 μm and a metal material such as nickel and stainless steel of 10 to 50 μm. The heat generating layer 32 is made of a conductive metal material such as nickel, stainless steel, silver, or copper. The intermediate elastic layer 33 is made of a heat-resistant elastic material such as silicon rubber or fluororubber having a thickness of 50 to 300 μm for uniform fixing. The surface release layer 34 is made of a fluororesin material having a thickness of 10 to 30 μm for the purpose of releasing effect and oilless.

  As shown in FIG. 3B, a heat generating base material layer 35 in which the base material layer 31 and the heat generating layer 32 are integrated may be provided to have a three-layer structure.

And (0.019-0.077) J / kcm ² thin and low heat capacity, the belt heating efficiency by induction heating source 66 to be described later can be increased and instantaneous startup (30 seconds or less, preferably 10 seconds or less) is possible. And

  As shown in FIG. 2, a belt guide member 40 and a nip forming member 50 are provided inside such an endless loop-shaped fixing belt 30.

4A and 4B show a side surface and a planar shape of the belt guide member 40. FIG.
As can be seen from the figure, the belt guide member 40 is composed of a flat first strip 41 and a curved second strip 42.

  A temperature detecting member 43 is attached to the first band plate portion 41 in the middle. On the other hand, the second belt plate portion 42 is provided with an arcuate belt guide surface 44 on the outer surface, and a rectangular cutout hole 45 is formed in the middle. The cutout hole 45 faces the induction heating source 66 (to be described later) with the detection surface of the temperature detection member 43 facing outside and sandwiches the fixing belt 30 to detect the temperature of the fixing belt 30. In order to reduce belt sliding resistance, the belt guide surface 44 is made to have low friction by applying a fluororesin, silicone oil, zinc stearate, wax, or the like.

  For example, when the base material layer 31 of the fixing belt 30 is formed of polyimide, the temperature detecting member 43 is provided in contact with the fixing belt 30 so as not to adversely affect the temperature detection by a thermostat or a thermal fuse. . The temperature detection member 43 may be provided so as not to come into contact with the fixing belt 30 only in proximity.

  The nip forming member 50 includes a support member 51, a heat insulating member 52, and a heat resistant elastic member 53, and the heat resistant elastic member 53 is covered with a protective member 54. The support member 51 is generally made of a metal material such as iron, stainless steel, or aluminum. You may make using a carbon fiber reinforced metal. The heat-resistant elastic member 53 is formed in a rectangular shape using an elastic foam, and the surface thereof is equal to or smaller than the surface hardness of a pressure roller described later.

FIG. 5 shows one end of the fixing belt 30.
As can be seen from FIG. 5, both ends of the support member 51 of the nip forming member 50 pass through the belt conveyance shape holding member 60 and are supported by long holes (not shown) of the fixing side plate 61, and a biased member 62 is provided at the tip. Install. The biased member 62 is biased by a pressure spring 63. Accordingly, the nip forming member 50 is formed by pressing and backing the heat-resistant elastic member 53 made of an elastic foam against the fixing belt 30.

  The belt conveyance shape holding member 60 has a circular shape having a flange portion 64 and guides both end edges in the axial direction of the endless loop-shaped fixing belt 30 on the outer periphery to hold the conveyance shape of the fixing belt 30 in a substantially cylindrical shape. Both ends of the belt guide member 40 are also held by the belt conveyance shape holding member 60.

As shown in FIG. 2, an induction heating source 66 is disposed around the fixing belt 30 so as to face the belt guide member 40 across the fixing belt 30 and along the belt surface. The induction heating source 66 is for inductively heating the heat generating layer 32 of the fixing belt 30 and has the following characteristics as compared with the halogen lamp system.

1) High energy conversion efficiency. At 85%, which is 10% higher than that of the halogen lamp method, the rise time is shortened.
2) The output can be varied by changing the frequency.
3) Self-temperature control using the magnetic properties of the heated object is possible. Since the object to be heated is directly heated, there are advantages such as a small time lag for temperature control, and there are few temperature ripples.

  The induction heating source 66 is connected to the temperature detection member 43 via the control means 67 and is turned on / off by the control means 67 based on the temperature detected by the temperature detection member 43.

  Incidentally, as shown in FIG. 6, for example, the belt guide member 40 is made of an insulating heat-resistant material having magnetism, such as a ferrite or a thin layer of ferrite formed on the surface of a heat-resistant resin material, heat-resistant glass, ceramics or the like.

  In this way, the magnetic lines of force M from the induction heating source 66 are concentrated on the belt guide member 40 and become dense, and are hardly concentrated on the temperature detection member that is non-magnetic on the surface. Therefore, the magnetic shield effect makes it difficult to be affected by the lines of magnetic force, prevents self-heating of the temperature detecting member 43, enables accurate temperature detection, and improves the heating efficiency of the fixing belt.

  The belt guide member 40 may be made of a nonmagnetic insulating heat resistant material such as a heat resistant resin material, heat resistant glass, or ceramics. As a result, heat generation of the belt guide member 40 can be prevented and the heating efficiency of the fixing belt 30 can be increased. Moreover, the possibility that accurate temperature detection by the temperature detection member 43 is hindered by noise due to magnetic action can be eliminated.

  Now, as shown in FIG. 2, the pressure roller 70, which is an opposing member, is pressed against the heat-resistant elastic member 53 of the nip forming member 50 via the protection member 54, and fixing is performed between the pressure roller 70. Form a nip.

  The pressure roller 70 has three or more layers and is 20 to 80φ, which is a heat insulating roller. For example, a silicone rubber foam, a silicone layer having a hollow core, a hollow balloon or the like to increase the air content is used. A silicone layer provided with a hollow element, a hollow balloon or the like has a large roller surface hardness and a small compression set, and can be used as a belt driving roller. The pressure roller 70 is rotationally driven by a driving unit (not shown), and conveys the sheet 22 passing through the fixing nip while running on the fixing belt 30.

  In the illustrated example, a heat source 71 is also provided inside the pressure roller 70, and a pressure side temperature detection member 72 is provided on the outer periphery. The pressure side temperature detection member 72 prevents the pressure roller 70 from rising above a certain level.

  In the above-described example, the non-rotating nip forming member 50 is used. However, for example, a rotating roller may be used as the nip forming member 50 as shown in FIG. In the above-described example, the fixing belt 30 is stretched in a substantially cylindrical shape. For example, as illustrated in FIG. 8, the fixing belt 30 is spaced from the rotation roller that is the nip forming member 50 and the belt guide member 40. 30 may be stretched elliptically.

FIG. 9 shows a longitudinal section of another example of the pressure roller 70 which is a facing member.
As can be seen from FIG. 9, the pressure roller 70, which is a facing member, may be provided with a heat insulating layer 75 around the cored bar 74 and a release layer 76 around it. The heat insulating layer 75 has a porous structure, for example.

22 sheet (recording medium)
DESCRIPTION OF SYMBOLS 30 Fixing belt 40 Belt guide member 43 Temperature detection member 44 Belt guide surface 45 Notch hole 50 Nip forming member 53 Heat resistant elastic member (elastic foam layer)
60 Belt conveying shape holding member 66 Induction heating source 67 Control means 70 Pressure roller (opposing member)
100 Fixing device

Japanese Patent Laid-Open No. 2002-148983

Claims (12)

A fixing belt, an induction heating source provided outside the fixing belt for induction heating the fixing belt, a non-rotating nip forming member that contacts the fixing belt inside the fixing belt, and the fixing belt A fixing device that includes a pressure roller that forms a fixing nip with the nip forming member, and fixes an image on a recording medium that passes through the fixing nip;
A temperature detecting member that is disposed opposite to the induction heating source with the fixing belt interposed therebetween, and that detects the temperature of the fixing belt from the inside; and a belt guide member that is formed of a magnetic material and slides on the fixing belt. Prepared,
The fixing device according to claim 1, wherein the temperature detection member is disposed to face the induction heating source through a notch provided in the belt guide member.   The fixing device according to claim 1, wherein the belt guide member includes an arcuate belt guide surface, and the notch is provided on the arcuate belt guide surface. The fixing device according to claim 1, wherein any one of fluororesin, silicone oil, zinc stearate, and wax is applied to an arc-shaped belt guide surface provided in the belt guide member. . The fixing device according to claim 1, wherein the temperature detection member is in contact with an inner periphery of the fixing belt. The temperature based on the detected temperature of the sensing member, characterized in that it comprises control means for controlling the induction heating source, a fixing device according to any one of claims 1 to 4. Wherein the fixing belt, a thin low heat capacity, characterized by an endless loop having a flexible fixing device according to any one of claims 1 to 5. The fixing device according to claim 6 , further comprising a belt conveyance shape holding member that guides both side edges of the endless loop-shaped fixing belt and holds the conveyance shape of the fixing belt in a cylindrical shape. The nip forming member includes a protective member that contacts the fixing belt, a heat insulating member provided on the other side of the fixing belt with respect to the protective member, and a metal material supporting member that supports the heat insulating member. The fixing device according to claim 1, further comprising a fixing device. The fixing device according to claim 8 , wherein the nip forming member includes an elastic foam layer between the protective member and the heat insulating member . The pressure roller is characterized in that a heat-insulating roller having a heat insulation layer of the porous structure around the core metal, a fixing device according to any one of claims 1 to 9. The fixing device according to claim 10, wherein the heat insulating roller is formed of a silicone rubber foam. Characterized in that it comprises a fixing device according to any one of claims 1 to 11, the image forming apparatus.

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