JP3738626B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and a belt type fixing device used for an image forming apparatus having a composite function, and an image forming apparatus including the fixing device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus has an unfixed toner by a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and being in pressure contact with the heating roller. A heat roller fixing system in which a recording material on which an image is formed is nipped and conveyed while being heated is frequently used.
[0003]
However, in this type of apparatus, the heat capacity of the heating roller is increased, the warm-up time is increased, the temperature inside the elastic layer is increased, and the life of the roller is shortened.
[0004]
Further, many color images have a large solid area, and there are many solid images other than black, and uneven gloss is conspicuous. In the case where a hard roller is used as the heating and pressure roller, there is a problem in that the unevenness of the gloss according to the unevenness of the paper or the toner layer occurs, so that the image quality is deteriorated.
[0005]
[Problems to be solved by the invention]
In order to solve the above problems, a fixing method using a rubber roller or a rubber belt has been proposed.
[0006]
Good image quality can be obtained by using a rubber roller, but it takes time to warm up and there are problems such as a short roller life. This problem becomes more prominent as the speed of copiers and printers increases. It has become to.
[0007]
The fixing device using the fixing belt has the following problems.
Two pressure rollers for pressing and fixing the endless fixing belt that is wound around the outer periphery of a plurality of support rollers and a transfer material carrying a toner image in a stacked state are sandwiched and conveyed. In the conventional fixing belt type fixing device, the conventional support roller that supports the fixing belt takes away an extra heat capacity from the fixing belt and increases the warm-up time. It was.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, exhibit a fixing performance stable over a long period of time, and achieve a power saving by improving the heating efficiency of a heating source, and an image provided with the fixing device An object is to provide a forming apparatus.
[0009]
[Means for Solving the Problems]
The fixing device of the present invention that solves the above problems is a fixing device that heats and fixes a toner image formed on a transfer material with a heated fixing belt, and a plurality of support rollers that rotatably support the fixing belt. Among them, at least one support roller, a rotating shaft, two flange members fixed to both end portions of the rotating shaft, and a plurality of wires forming a cage shape in parallel between the flange members, (Claim 1).
[0010]
The image forming apparatus of the present invention comprises a fixing device comprising the support roller and the fixing belt, a photoconductor, a developing device, and a transfer means (claim 7).
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a fixing device of the present invention and an image forming apparatus including the fixing device will be described with reference to the drawings.
[0012]
FIG. 1 is a configuration diagram showing a color printer which is an image forming apparatus provided with a fixing device of the present invention.
[0013]
In this color printer, four sets of scorotron chargers (hereinafter referred to as chargers) 2Y, 2M are disposed around a flexible endless belt-like photoreceptor (hereinafter referred to as a photoreceptor) 1 as an image carrier. , 2C, 2K, 4 sets of image exposure devices 3Y, 3M, 3C, 3K, and 4 sets of developing units 4Y, 4M, 4C, 4K, which are arranged in tandem. It is. The illustrated image exposure apparatuses 3Y, 3M, 3C, and 3K use a laser beam scanning optical apparatus.
[0014]
The photosensitive member 1 is stretched around the driving roller 11, the lower roller 12, and the upper roller 13, is in a tension state by the action of the tension roller 14, and is locally in contact with the backup member 15 provided on the inner peripheral surface. It rotates clockwise as shown. The backup member 15 abuts on the inner side of the photosensitive member 1 to develop the developing regions of the developer carriers 41Y, 41M, 41C, and 41K of the developing devices 4Y, 4M, 4C, and 4K and the image exposure devices 3Y, 3M, 3C, and The photosensitive member 1 is restricted to the 3K imaging position.
[0015]
At the start of image recording, a driving motor (not shown) rotates and the photosensitive member 1 rotates clockwise through the driving roller 11, and the charging device 2 </ b> Y charges the photosensitive member 1. Application of a potential is started. After the photoconductor 1 is applied with a potential, exposure by an electric signal corresponding to the first color signal, that is, the yellow (Y) image signal is started in the image exposure device 3Y, and the photoconductor 1 is rotated (sub-scanning). As a result, an electrostatic latent image corresponding to the yellow (Y) image of the developed image is formed on the photosensitive layer on the surface. The latent image is reversibly developed in a non-contact state in the developing area by the developer adhered and transported on the developer carrier 41Y by the developing device 4Y to form a yellow (Y) toner image.
[0016]
Next, the photosensitive member 1 is further applied with a potential on the yellow (Y) toner image by the charging action of the charger 2M, and an electric signal corresponding to the second color signal of the image exposure device 3M, that is, the magenta (M) image signal. Signal exposure is performed, and a magenta (M) toner image is formed on top of the yellow (Y) toner image by non-contact reversal development by the developing device 4M.
[0017]
By the same process, a cyan (C) toner image corresponding to the third color signal is further formed by the charger 2C, the image exposure device 3C, and the developing device 4C. Further, a black (K) toner image corresponding to the fourth color signal is sequentially superimposed by the charger 2K, the image exposure device 3K, and the developing device 4K, and is formed on the peripheral surface within one rotation of the photoreceptor 1. A color toner image is formed.
[0018]
The color toner image formed on the peripheral surface of the photoreceptor 1 reaches the transfer area after the potential of the adhering toner is made uniform by the charger 2F. The transfer material P fed from the paper feed cassette 51 or the manual paper feed tray 53 of the paper feeding device 5 by the paper feeding means 52 and 54 and conveyed to the registration rollers 55 is driven by the registration rollers 55. The toner image is transferred by the transfer means 6 which is fed in synchronization with the passage of the upper toner image area and is arranged opposite to the lower portion of the driving roller 11.
[0019]
The transfer material P onto which the toner image has been transferred is separated from the circumferential surface of the photoreceptor 1 by the curvature, and is then conveyed to the fixing device 7 via the conveyance guide 56. The toner image is melted by the fixing device 7 and fixed to the transfer material P. After completion of the fixing process, the transfer material P is transported by the paper discharge rollers 81, 82, and 83 and discharged to a paper discharge tray 84 provided at the top.
[0020]
On the other hand, the photosensitive member 1 from which the transfer material P has been separated is cleaned by removing residual toner by the cleaning blade 91 of the cleaning device 9. When the toner image of the next document image is subsequently formed, the pre-charge static eliminator 92 exposes the photoconductor surface of the photoconductor 1 and the previous charge is removed.
[0021]
FIG. 2 is a cross-sectional view showing an embodiment of the fixing device of the present invention, and FIG. 3 is a plan view of the fixing device.
[0022]
In these drawings, reference numerals 71 and 72 denote a pair of pressure rollers that can be moved toward and away from each other, and reference numeral 73 denotes an endless belt-like fixing belt. The support rollers 74 and 75 are a pair of support rollers that support and fix the fixing belt 73. 76 is a halogen heater as a heating source, 77 is a reflector, and 78 is a temperature sensor that detects the temperature of the fixing belt 73.
[0023]
At least one of the pair of pressure rollers 71 and 72 has a movable rotational axis position. At the time of non-fixing, as shown in FIG. 2A, the pressure roller 72 moves in the direction of the arrow against the pressure contact force, and is separated from the pressure roller 71 to form a gap. At the time of fixing, as shown in FIG. 2B, the fixing belt 73 and the transfer material P are clamped and conveyed.
[0024]
The fixing belt 73 includes a central metal base, an outer layer on the outer peripheral surface side, an inner layer on the inner peripheral surface side, and the like. The metal substrate of the fixing belt 73 is made of, for example, an endless belt-like nickel metal layer formed by electroforming.
[0025]
On the outer peripheral surface of the metal substrate, an outer layer coated with silicone rubber is formed. The outer layer is moved and heated and pressed in a state where it overlaps with the transfer material P carrying the toner image t at the nip position between the pressure rollers 71 and 72, so that both heat resistance and toner releasability are achieved. ing.
[0026]
The toner image t on the transfer material P is in contact with the outer layer made of silicone rubber of the fixing belt 73. The elasticity of the silicone rubber follows the unevenness of the transfer material P and the toner image t, and makes uniform contact. By the heat of the fixing belt 73 heated by the halogen heater 76 and the pressure applied by the pressure rollers 71 and 72, uniform fixing without uneven gloss is performed.
[0027]
An inner layer is formed on the inner peripheral surface of the metal substrate of the fixing belt 73. The inner layer is formed by applying a silicone rubber in which carbon is dispersed on the inner peripheral surface of the metal substrate. The inner layer absorbs the irradiation light of the halogen heater 76 with high efficiency and emits the irradiation light leaking around the device. Minimized. That is, the inner layer of the fixing belt 73 is coated with a silicone rubber in which carbon, which is an infrared absorbing material, is dispersed, and has a high absorption rate of irradiation light. The temperature rises to 190 ° C.
[0028]
Since the silicone rubber forming the inner layer has flexibility, it does not peel off due to the bending of the fixing belt 73 when the fixing belt 73 is rotated, unlike a normal heat resistant paint.
[0029]
The fixing belt 73 is stretched between the support roller 74 and the support roller 75 with a very weak tension of 0.5 kg / cm or less, more preferably 0.2 kg / cm or less. Alternatively, it may be in a state where the tension is zero.
[0030]
The fixing belt 73 is rotated by the rotation of the support roller at times other than the fixing process. The fixing belt 73 at the time of the fixing process is nipped and rotated by the pressure contact driving of the pressure rollers 71 and 72. The rotation speed of the fixing belt 73 is the same as the conveyance speed of the transfer material P.
[0031]
The support roller 74 includes a rotating shaft 742 driven and rotated by a driving source, fixing members 746 and 747 fixed near both ends of the rotating shaft 742, a flange member 743 fixed to the fixing member 746 and a fixing member 747, It is composed of a flange member 744 fixed integrally, a wire 741 installed between flange members 743 and 744 arranged to face each other, and a gear 745 fixed to one shaft end of the rotating shaft 742 and connected to a drive source. .
[0032]
The support roller 75 has the same shape as the support roller 74, and includes a wire 751, a rotating shaft 752, flange members 753, 754, and the like. Hereinafter, the support roller 74 of the support rollers 74 and 75 will be described as a representative.
[0033]
4A is a cross-sectional view of the support roller 74, FIG. 4B is a cross-sectional view of the support roller 74 taken along line AA, and FIG. 4C is a cross-sectional view of the support roller 74 taken along line BB. FIG. 5 is a perspective view of the support roller 74.
[0034]
The wire 741 is formed of one continuous wire, and is formed in a cage shape by being reciprocally mounted in parallel between the two flange members 743 and 744, and both ends thereof are either of the flange members 743 and 744. It is fixed to.
[0035]
For example, one end of the wire 741 is locked and fixed to a part of the flange member 743. The wire 741 is reciprocally mounted in parallel between the flange members 743 and 744, and the other end of the wire 741 is tightly wound around the outer periphery of the rotating shaft 742, and then locked and fixed by the screw member 748. .
[0036]
By forming a support roller 74 by extending a plurality of wires between flange members 743 and 744 disposed opposite to both ends of the rotating shaft 742, the area of negotiation between the support roller 74 and the fixing belt 73 is made small. At the same time, the heat capacity can be extremely reduced.
[0037]
Even if the wire 741 is a metal wire such as a steel wire, the effect of the present invention can be obtained. However, if a resin fiber material having high strength, high heat resistance, low thermal conductivity, low specific heat, and low elongation is used, a higher effect can be obtained. Is obtained. As the resin fiber material suitable for this, polymer fibers such as aromatic polyamide, polyamideimide, polyimide, and polyarylate are preferable. For example, aromatic polyamide fiber Kevlar (trade name, manufactured by DuPont, USA) and polyarylate Examples include fiber Vectran (trade name, manufactured by Kuraray Co., Ltd.).
[0038]
Since these highly functional fibers have been developed in various ways and are expected to appear newly in the future, the wire 741 of the present invention is not limited to these.
[0039]
The number of wires 741 installed is preferably small in terms of heat, but in order to increase the driving accuracy of the fixing belt 73, a larger number is preferable. The wire 741 is preferably thin in terms of heat, but is preferably thick in terms of mechanical strength. The tension of the wire 741 is preferably large in order to obtain mechanical accuracy. However, if the tension is too large, the strength of the flange member 743 supporting the wire 741 must be increased, and the weight, driving torque, manufacturing cost, etc. There is a rising problem.
[0040]
These numerical values are appropriately selected according to the wire diameter of the wire 741, the tension of the fixing belt 73, the diameter of the support roller 74, the manufacturing cost, and the like.
[0041]
It is appropriate that the number of wires 741 installed is 8 to 30, the thickness of the wire 741 is 100 to 1000 denier, and the tension of the wire 741 is 10 to 50 N (Newton).
[0042]
One wire 741 may be reciprocated as many times as necessary, and a plurality of wires 741 may be individually stretched between the flange members 743 and 744, respectively.
[0043]
An example of the wire 741 is shown below.
A fixing belt 73 having a circumference of 500 mm, a width of 320 mm, and a tension of 30 N or less is fixed by applying a tension of 20 to 30 N to each of 16 wires 741 constructed of 400 denier aromatic polyamide fibers and having a diameter of 50 mm. A corresponding support roller 74 was constructed.
[0044]
The support roller 74 is driven and rotated in a clockwise direction indicated by an arrow by a power device of the image forming apparatus main body. As the support roller 74 is driven to rotate, the fixing belt 73 and the support roller 75 are driven to rotate clockwise. The design value of the driving speed of the fixing belt 73 is the same as the transfer speed of the transfer material P. The peripheral speeds of the pressure rollers 71 and 72 are driven to be the same as the driving speed of the fixing belt 73.
[0045]
A rod-shaped halogen heater 76 is disposed inside the fixing belt 73 between the pressure roller 71 and the support roller 74 on the upstream side in the conveyance direction of the fixing belt 73. The halogen heater 76 irradiates the inside of the closed loop of the fixing belt 73 on the upstream side of the pressure roller 71 and heats it to a predetermined temperature.
[0046]
A reflection plate 77 is disposed inside the closed loop of the fixing belt 73 and in the vicinity of the support roller 74 on the driving side. The reflection plate 77 reflects and blocks the irradiation light reaching the support roller 74 among the irradiation light of the halogen heater 76.
[0047]
The irradiation reflected light reflected by the reflecting plate 77 irradiates the inner surface of the fixing belt 73 and efficiently heats the fixing belt 73 without waste. Further, the reflection plate 77 prevents the wire 741 from being excessively heated by the irradiation light of the halogen heater 76.
[0048]
As the transfer material P carrying the toner image t is conveyed to the fixing region via the guide plate 701, or prior to this, the pressure roller 72 disposed outside the fixing belt 73 is raised, Pressure is applied with the transfer material P and the fixing belt 73 interposed therebetween. The toner image t on the transfer material P is fixed to the transfer material P by heating by the heat of the fixing belt 73 and nipping and pressing by the pressure rollers 71 and 72.
[0049]
A predetermined load acts on the support shafts at both ends of the pressure roller 72 toward the pressure roller 71 when sandwiched by spring members (not shown), and a certain pressure acts on the pressure-bonding portions of the pressure rollers 71 and 72. It has become.
[0050]
Since one or both of the pressure rollers 71 and 72 are connected to a driving unit and driven to rotate, the transfer of the transfer material P and the driving of the pressure rollers 71 and 72 require the driving force of the fixing belt 73. In other words, no load is caused by holding and conveying the fixing belt 73 and the transfer material P.
[0051]
That is, the pressure roller 71 or the pressure roller 72 is driven at a peripheral speed that is the same as the moving speed of the fixing belt 73, so that excessive force is not applied to the fixing belt 73 and the transfer material P. It has become. Further, after the fixing, the pressure rollers 71 and 72 are released from the pressure bonding, so that distortions and deviations caused by a minute speed difference between the fixing belt 73 and the pressure rollers 71 and 72 are eliminated, and the pressure roller 71 from the fixing belt 73. , 72 is prevented from flowing out of heat.
[0052]
The fixed transfer material P is separated by the curvature of the support roller 75 that supports the fixing belt 73. Since the fixed transfer material P is cooled by the outside air when it comes out of the nip portion of the fixing belt 73 by the pressure rollers 71 and 72, an offset and a separation failure during separation are avoided. In order to obtain reliable separation performance, the diameter of the support roller 75 may be reduced, or a small-diameter separation roller may be disposed inside the fixing belt 73 separately from the support roller 75.
[0053]
6A is a cross-sectional view showing another embodiment of the fixing device of the present invention, FIG. 6B is a cross-sectional view of the support roller 74 taken along line AA, and FIG. It is -B sectional drawing. In addition, about the code | symbol used in these drawings, the same code | symbol is attached | subjected to the part which has the same function as embodiment shown in the said FIGS. 4-5. Further, differences from the above embodiment will be described.
[0054]
Since the support roller 75 has the same shape as the support roller 74, the support roller 74 will be described as a representative of the support rollers 74 and 75.
[0055]
A spring member 749 is fixed to the back side (the right side in the figure) of the flange member 744 of the support roller 74 by a screw member 748 via a pressing member 749A.
[0056]
The spring member 749 has a plurality of petal-shaped wire support portions 749B formed around the outer diameter portion. The spring member 749 is made of a plate-like elastic material. One end of the wire 741 is locked to each of the plurality of wire support portions 749B. The other end portion of the wire 741 is locked to a flange member 743 arranged to face the flange member 744.
[0057]
In this way, by making the spring member 749 into a petal shape, tension is reliably applied to each wire 741. When members with a plurality of wires 741 installed are pulled together by a spring, there is a possibility that tension may be too strong or conversely insufficient due to variations in the length of the wire 741.
[0058]
The plurality of wire support portions 749 </ b> B are elastically deformed by stretching the wires 741 between the flange members 743 and apply tension to the wires 741. The plurality of wire support portions 749 </ b> B may be integrally formed spring members 749, or may be configured by a plurality of members and fixed to the flange member 744.
[0059]
The wires 741 that are supported in parallel by a spring member 749 having a plurality of wire support portions 749B are stretched in a straight line without any slack, forming a substantially cylindrical outer periphery, and have a cage shape.
[0060]
The wire 741 comes into contact with the fixing belt 73 heated by the halogen heater 76, rises in temperature, expands, and extends in the length direction. The stretched wire 741 absorbs the stretched amount by the elasticity of the plurality of wire support portions 749B of the spring member 749. Therefore, the wire 741 is always stretched in a straight line without being relaxed regardless of the temperature change.
[0061]
Note that a spring member having the same shape as the spring member 749 having the plurality of wire support portions 749B may be attached to the opposing flange member 743 to apply tension to both ends of the wire 741. Instead of the spring member 749, the end of the wire 741 may be connected to a coiled spring to apply tension.
[0062]
【The invention's effect】
According to the present invention, the following effects can be achieved by the configuration described above.
(1) A fixing device according to the present invention includes a fixing belt and a pressure roller that are rotated by winding a plurality of support rollers. The support roller is fixed to a rotating shaft and both ends of the rotating shaft. Supporting roller having a low heat capacity and low thermal conductivity by minimizing the area in contact with the fixing belt by comprising a plurality of flange members and a plurality of wires laid in parallel in a cage shape between the flange members. Therefore, the heat capacity to escape to the support roller becomes small, and the thermal efficiency is improved.
(2) Highly efficient heat supply is realized by the image forming apparatus provided with the fixing device including the pressure roller, the support roller, the fixing belt, and the heating source according to the present invention. An image forming apparatus excellent in shortening, high-speed fixing, high-quality fixing, stabilization, and long-life maintenance is provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a color printer which is an image forming apparatus provided with a fixing device of the present invention.
FIG. 2 is a cross-sectional view of the fixing device of the present invention.
FIG. 3 is a plan view of the fixing device.
FIG. 4 is a cross-sectional view, AA cross-sectional view, and BB cross-sectional view of a support roller.
FIG. 5 is a perspective view of a support roller.
FIG. 6 is a cross-sectional view, AA cross-sectional view, and BB cross-sectional view showing another embodiment of the support roller.
[Explanation of symbols]
7 Fixing devices 71, 72 Pressure roller 73 Fixing belts 74, 75 Support rollers 741, 751 Wires 742, 752 Rotating shafts 743, 744, 753, 754 Flange members 746, 747 Fixing members 748 Screw members 749 Spring members 749A Pressing members 749B Wire support 76 Halogen heater (heating source)
77 Reflecting plate 78 Temperature sensor 92 Charger before charging P Transfer material t Toner image

Claims (7)

In a fixing device that heats and fixes a toner image formed on a transfer material with a heated fixing belt,
Among the plurality of support rollers that rotatably support the fixing belt, at least one support roller is provided with a rotation shaft, two flange members fixed to both ends of the rotation shaft, and the flange member. A fixing device comprising a plurality of wires that are installed in parallel to form a cage shape. The wire is composed of one continuous wire, is formed in a cylindrical bus bar shape in a reciprocating manner between the two flange members, and both ends are fixed to the flange member. The fixing device according to claim 1. The fixing device according to claim 1, wherein a spring member is provided on at least one of the flange members, and an end of the wire is urged and extended by the spring member. The fixing device according to claim 1, wherein the wire is a resin fiber material. The fixing device according to claim 4, wherein the resin fiber material is made of a polymer fiber selected from aromatic polyamide, polyamideimide, polyimide, and polyarylate. The fixing device according to claim 1, wherein the spring member is configured to independently apply tension to at least two wires. An image forming apparatus comprising: a fixing device comprising the support roller and the fixing belt according to claim 1; and a photosensitive member, a developing device, and a transfer unit.

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