JP2008158482A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus, in which the warm-up time and the first print time are short, longitudinal variation in nip width is reduced and problems, such as fixing failures, will not occur, even when the speed of the apparatus is increased. <P>SOLUTION: The fixing device includes a fixing member 21 to heat and melt a toner image T, a facing member 22 that faces the inner peripheral surface of the fixing member 21, heat the fixing member 21 and form a nip portion, and a reinforcing member 23, which is fixedly provided on an inner peripheral surface side of the fixing member 21 and reinforces the strength of the facing member 22 at the nip potion, by contacting a pressure member 31 via the facing member 22 and the fixing member 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed there.

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine and a printer, a technique using a fixing belt stretched around a plurality of roller members as a fixing member is known (for example, see Patent Document 1).
An apparatus using such a fixing belt is provided in a fixing belt (endless belt) as a fixing member, a plurality of roller members that stretch and support the fixing belt, and one of the plurality of roller members. And a heater, a pressure roller (pressure member), and the like. The heater heats the fixing belt via the roller member. The toner image on the recording medium conveyed toward the nip formed between the fixing belt and the pressure roller is fixed on the recording medium by receiving heat and pressure at the nip.

On the other hand, Patent Document 2 discloses an on-demand fixing device with a short warm-up time.
An on-demand fixing device includes a fixing film (endless film) as a fixing member, a pressure roller (pressure member), a heater such as a ceramic heater, and the like. The heater is installed inside the fixing film, contacts the pressure roller through the fixing film to form a nip portion, and heats the fixing film. The toner image on the recording medium conveyed toward the nip portion is fixed on the recording medium by receiving heat and pressure at the nip portion.

  On the other hand, Patent Document 3 discloses a technique for forming a base layer of a fixing belt with a radiant heat permeable material and forming a surface layer and an intermediate layer with a radiant heat absorbing material for the purpose of efficiently heating the fixing member. ing. In particular, FIG. 9 of Patent Document 3 includes a fixing belt, a belt guide member that guides the fixing belt, and a translucent pressure member that contacts the pressure roller (backup roller) via the fixing belt. A fixing device is disclosed.

Japanese Patent Laid-Open No. 11-2982 JP 2002-6656 A JP 2003-107948 A

  The fixing device described in Patent Document 1 and the like described above is suitable for speeding up the device as compared with a device using a fixing roller, but it has a warm-up time (a time required to reach a printable temperature) and first. There is a limit to shortening the printing time (the time from when a print request is received until the printing operation is performed and the paper discharge is completed).

  On the other hand, in the fixing device disclosed in Patent Document 2, the warm-up time and the first print time can be shortened by reducing the heat capacity, and the size of the device can be reduced. However, in such a fixing device, only the nip portion of the fixing film is locally heated, and the other portions of the fixing film are not sufficiently heated. For this reason, there is a problem that the fixing film is most cooled on the inlet side of the nip portion due to the rotation of the fixing film, and the fixing defect is likely to occur. Such a problem has not been particularly negligible because when the speed of the apparatus is increased, the rotation of the fixing film becomes faster and the heat radiation of the fixing film at positions other than the nip portion increases.

In order to solve such a problem, a pipe-shaped metal heat conductor is installed so as to face the inner peripheral surface of an endless fixing member such as a fixing belt or a fixing film, and the metal heat conductor is directly attached. Alternatively, it is conceivable to heat the entire fixing member sufficiently and uniformly by indirectly heating.
However, in that case, there is a possibility that the pipe-shaped metal heat conductor is bent by the applied pressure received from the pressure member at the nip portion. In particular, since the pipe-shaped metal heat conductor needs to be thinned in order to improve the heating efficiency of the fixing member, there is a high possibility that the problem will occur.

When the metal heat conductor is bent, the inner peripheral surface of the fixing member is strongly rubbed at that position. Therefore, the inner circumferential surface of the fixing member is worn unevenly, and the durability life of the fixing member is shortened, or the driving torque when the fixing member is driven increases and the fixing member slips, causing the recording medium to jam at the nip portion. I do.
Further, when the metal heat conductor is bent, the nip width deviation at the nip portion is increased. That is, the area of contact with the pressure member at the central portion in the width direction decreases, and the nip width at that position becomes smaller than the nip width at both ends in the width direction. In such a state, the amount of heat applied to the recording medium differs between the central portion and both end portions, and a cold offset tends to occur at the central portion in the output image, and hot offset tends to occur at both end portions. Further, the difference in glossiness between the center and both ends of the output image becomes large, and an abnormal image with a large glossiness deviation is output. In addition, when the above-described nip width deviation is extremely large, not only the influence on the output image but also wrinkles may occur on the recording medium.

  Further, the fixing device disclosed in FIG. 9 of Patent Document 3 described above is intended to efficiently heat the fixing member, and does not solve the bending of the metal heat conductor described above. That is, the belt guide member that guides the fixing belt is formed of a light-transmitting material and does not actively heat the fixing belt. The translucent pressure member that contacts the pressure roller via the fixing belt has a function of forming a nip portion between the fixing belt and the pressure roller, but has a plate thickness of about 1 to several mm. Since it is a plate-like member, there is a possibility that bending due to the pressure applied by the pressure roller may occur.

  The present invention has been made to solve the above-mentioned problems. Even when the warm-up time and the first print time are short, the nip width deviation in the width direction is small, and the speed of the apparatus is increased, fixing failure, etc. It is an object of the present invention to provide a fixing device and an image forming apparatus that do not cause the above problem.

  The fixing device according to the first aspect of the present invention heats and melts the toner image and fixes the endless fixing member having flexibility and the inner peripheral surface of the fixing member so as to face each other. A fixing member that heats the fixing member and abuts against the pressure member through the fixing member to form a nip portion; and an opposing member that is fixedly provided on the inner peripheral surface side of the fixing member, and A reinforcing member that abuts against the pressure member via the fixing member and reinforces the strength of the opposing member in the nip portion.

  A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the reinforcing member is a metal thermal conductor.

  The fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect, wherein the reinforcing member is a heat insulating member, the opposing member, and the pressing member via the fixing member. It abuts against.

  The fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein the reinforcing member has a central portion in the width direction compared to both end portions in the width direction. It is formed in a convex shape so as to protrude toward the pressure member.

  According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the facing member is heated by radiant heat of a heat source.

  According to a sixth aspect of the present invention, in the fixing device according to the fifth aspect, the reinforcing member has a part or all of a surface facing the heat source as a mirror surface.

  A fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the facing member is heated by electromagnetic induction.

  According to an eighth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the opposing member is heated by the heat of the resistance heating element.

  A fixing device according to a ninth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the opposing member is a resistance heating element.

  The fixing device according to a tenth aspect of the present invention is the fixing device according to any one of the first to ninth aspects, wherein the opposing member is disposed on the inner peripheral surface of the fixing member at the position of the nip portion. A first opposing member that opposes and a second opposing member that opposes the inner peripheral surface of the fixing member at a position excluding the nip portion, and the reinforcing member is integrated with the first opposing member. Is.

  The fixing device according to an eleventh aspect of the present invention is the fixing device according to the tenth aspect of the present invention, further comprising a heat source that emits radiant heat on the inner peripheral surface side of the fixing member, and the first opposing member is light-transmissive It consists of materials.

  A fixing device according to a twelfth aspect of the present invention is the fixing device according to any one of the first to eleventh aspects, wherein the pressure member includes a sponge-like elastic layer.

  A fixing device according to a thirteenth aspect of the present invention is the fixing device according to any one of the first to twelfth aspects, wherein the fixing member is a fixing belt or a fixing film.

  A fixing device according to a fourteenth aspect of the present invention is the fixing device according to any one of the first to thirteenth aspects, wherein the opposing member is a metal thermal conductor.

  An image forming apparatus according to a fifteenth aspect of the present invention includes the fixing device according to any one of the first to fourteenth aspects.

  The present invention provides a counter member that heats the fixing member opposite to the inner peripheral surface of the fixing member, and further abuts against the pressure member via the counter member and the fixing member to reinforce the strength of the counter member in the nip portion. A reinforcing member is provided. Accordingly, it is possible to provide a fixing device and an image forming apparatus in which the warm-up time and the first print time are short, the nip width deviation in the width direction is small, and even when the apparatus is speeded up, problems such as fixing failure do not occur. Can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an exposure light L based on image information read by the original reading unit 2. Is exposed to the photosensitive drum 5, 4 is an image forming unit for forming a toner image (image) on the photosensitive drum 5, and 7 is a toner image formed on the photosensitive drum 5 on the recording medium P. A transfer unit 10 for transferring, a document transport unit for transporting the set document D to the document reading unit 2, 12 to 14 a paper feed unit storing a recording medium P such as transfer paper, and 20 on the recording medium P A fixing device for fixing an unfixed image, 21 is a fixing belt as a fixing member installed in the fixing device 20, and 31 is a pressure roller as a pressure member installed in the fixing device 20.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, the document D is conveyed from the document table in the direction of the arrow in the drawing by the conveyance roller of the document conveyance unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated in the clockwise direction in the drawing, and image information is transferred onto the photosensitive drum 5 through a predetermined image forming process (charging process, exposure process, development process). An image (toner image) corresponding to is formed.
Thereafter, the image formed on the photosensitive drum 5 is transferred by the transfer unit 7 onto the recording medium P conveyed by the registration roller.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 12, 13, and 14 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 12 is selected). To do.)
Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 12 is transported toward the position of the transport path K.

  Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller. Then, the recording medium P that has reached the position of the registration roller is conveyed toward the transfer unit 7 at the same timing in order to align with the image formed on the photosensitive drum 5.

After the transfer process, the recording medium P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The recording medium P that has reached the fixing device 20 is fed between the fixing belt 21 and the pressure roller 31, and the image is fixed by the heat received from the fixing belt 21 and the pressure received from both members 21, 31. The The recording medium P on which the image is fixed is delivered from between the fixing belt 21 and the pressure roller 31 (a nip portion), and then discharged from the image forming apparatus main body 1.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram showing the fixing device 20. FIG. 3 is a diagram of the fixing device 20 viewed in the width direction.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 as a fixing member, a facing member 22, a reinforcing member 23, a heater 25 as a heat source, a pressure roller 31 as a pressure member, a temperature sensor 40, and a guide plate. 35, 37, etc.

Here, the fixing belt 21 as a fixing member is a thin and flexible endless belt, and rotates in the arrow direction (clockwise) in FIG. The fixing belt 21 is formed by sequentially laminating an elastic layer and a release layer on a base material, and the entire thickness thereof is set to 1 mm or less.
The base material of the fixing belt 21 has a layer thickness of 30 to 50 μm and is formed of a metal material such as nickel or stainless steel or a resin material such as polyimide.
The elastic layer of the fixing belt 21 has a layer thickness of 100 to 300 μm and is formed of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities on the surface of the fixing belt 21 in the nip portion are not formed, and heat is uniformly transmitted to the toner image T on the recording medium P, thereby suppressing the generation of a scum skin image.
The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm, such as PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), and the like. Made of material. By providing the release layer, the releasability (peelability) for the toner T (toner image) is secured.

Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. In the first embodiment, the diameter of the fixing belt 21 is set to 30 mm.
Inside the fixing belt 21 (inner peripheral surface side), a heater 25 (heat source), a facing member 22, a reinforcing member 23, and the like are fixed. The fixing belt 21 is pressed by the facing member 22 reinforced by the reinforcing member 23 to form a nip portion with the pressure roller 31.

The facing member 22 is fixed so as to face the inner peripheral surface of the fixing belt 21, and contacts the pressure roller 31 via the fixing belt 21 to form a nip portion. With reference to FIG. 3, both ends of the facing member 22 in the width direction are fixedly supported by the side plates 43 of the fixing device 20.
Here, the opposing member 22 is formed so that the shape of the nip portion is a substantially rectangular parallelepiped. That is, the facing surface of the facing member 22 in the nip portion (the surface facing the pressure roller 31) is formed to have a planar shape. As a result, the shape of the nip portion is substantially parallel to the image surface of the recording medium P, and the adhesion between the fixing belt 21 and the recording medium P is increased, so that the fixing property is improved. Further, since the curvature of the fixing belt 21 on the exit side of the nip portion is increased, the recording medium P sent from the nip portion can be easily separated from the fixing belt 21.
In the first embodiment, the opposing member 22 is formed to have a substantially circular cross-sectional shape, but the opposing member 22 may be formed to have a polygonal sectional shape. A slit can also be provided on the peripheral surface.

  Here, in the first embodiment, the reinforcing member 23 that reinforces the strength of the facing member 11 in the nip portion is fixed to the inner peripheral surface side of the fixing belt 21. Referring to FIG. 3, the reinforcing member 23 is formed so that the length in the width direction is equal to that of the facing member 22, and both end portions in the width direction are fixedly supported by the side plates 43 of the fixing device 20. . The reinforcing member 23 abuts against the pressure roller 31 via the facing member 22 and the fixing belt 21, thereby preventing a problem that the facing member 22 is greatly deformed by the pressure applied by the pressure roller 31 in the nip portion. ing.

That is, referring to FIG. 4, when the reinforcing member 23 is not provided, the opposing member 22 is bent by receiving pressure from the pressure roller 31 (as shown by arrows in FIG. The central portion in the width direction is greatly bent by the applied pressure. In particular, when the opposing member 22 is thinned in order to improve the heating efficiency of the fixing belt 21, the problem becomes remarkable.
However, in the first embodiment, since the reinforcing member 23 is installed at a position where the deformation of the facing member 22 is restricted, the bending of the facing member 22 is reduced even when the facing member 22 is thinned. can do. As a result, problems such as the opposing member 22 being bent and the inner peripheral surface of the fixing belt 21 being strongly rubbed, and the opposing member 22 being bent and the driving torque of the fixing belt 21 being increased are suppressed.
The reinforcing member 23 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the functions described above. Furthermore, by forming the reinforcing member 23 so as to have a horizontally long cross section along the direction of pressure applied by the pressure roller 31, the section modulus is increased and the mechanical strength of the reinforcing member 23 can be increased.

  The heater 25 as a heat source is a halogen heater or a carbon heater, and both ends thereof are fixed to the side plate 43 of the fixing device 20 (see FIG. 3). Then, the opposing member 22 is heated by the radiant heat of the heater 25 whose output is controlled by the power supply unit of the apparatus main body 1. Further, the fixing belt 21 is entirely heated by the facing member 22, and heat is applied to the toner image T on the recording medium P from the surface of the heated fixing belt 21. The output control of the heater 25 is performed based on the detection result of the belt surface temperature by the temperature sensor 40 such as a thermistor facing the surface of the fixing belt 21. Further, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature by such output control of the heater 25.

Referring to FIG. 2, the facing member 22 is fixed so as to face the entire inner peripheral surface of the fixing belt 21 including the position of the nip portion, and is heated by the radiant heat of the heater 25 to heat the fixing belt 21. Do (convey heat). As the material of the facing member 22, a metal thermal conductor (a metal having thermal conductivity) such as aluminum, iron, and stainless steel can be used.
As described above, in the fixing device 20 according to the first exemplary embodiment, only the part of the fixing belt 21 is not locally heated, and the fixing belt 21 is almost entirely heated in the circumferential direction by the facing member 22. For this reason, even when the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated, and the occurrence of fixing failure can be suppressed. That is, since the fixing belt 21 can be efficiently heated with a relatively simple configuration, the warm-up time and the first print time are shortened, and the size of the apparatus is reduced.

The gap δ between the fixing belt and the opposing member (the gap at the position excluding the nip portion) is preferably greater than 0 mm and 1 mm or less (0 mm <δ ≦ 1 mm). As a result, the area in which the opposing member 22 and the fixing belt 21 are in sliding contact with each other is prevented, and the problem that the wear of the fixing belt 21 is accelerated is suppressed, and the opposing member 22 and the fixing belt 21 are separated from each other excessively. Inconveniences that reduce efficiency can be suppressed. Furthermore, since the opposing member 22 is provided close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained to some extent, so that deterioration and breakage due to deformation of the fixing belt 21 can be reduced. .
Further, the sliding contact surface of the opposing member 22 can be formed of a material having a low friction coefficient so that the wear of the fixing belt 21 is reduced even if the opposing member 22 and the fixing belt 21 are in sliding contact.

  Here, in Embodiment 1, since the reinforcing member 23 is formed of a metal heat conductor such as stainless steel or iron, heat from the heater 25 is stored during the printing operation. Thereby, even when the printing operation is finished and the heater 25 is turned off, the opposing member 22 receives the heat stored in the reinforcing member 23 and the temperature drop of the opposing member 22 slows down, so the printing operation is resumed. It is possible to shorten the warm-up time.

  Referring to FIG. 2, a pressure roller 31 as a pressure member has a diameter of 30 mm and has an elastic layer 33 formed on a hollow cored bar 32. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip portion between both members. Referring to FIG. 3, the pressure roller 31 is provided with a gear 45 that meshes with a drive gear of a drive mechanism (not shown). The pressure roller 31 is in the direction of the arrow (counterclockwise) in FIG. Is driven to rotate. Further, both ends of the pressure roller 31 in the width direction are rotatably supported by the side plates 43 of the fixing device 20 via bearings 42. A heat source such as a halogen heater can be provided inside the pressure roller 31.

Note that when the elastic layer 33 of the pressure roller 31 is formed of a sponge-like material such as foamable silicone rubber, the pressure applied to the nip portion can be reduced. Further reduction can be achieved.
In the first embodiment, the diameter of the fixing belt 21 is formed to be equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 is formed to be smaller than the diameter of the pressure roller 31. You can also In that case, since the curvature of the fixing belt 21 in the nip portion is smaller than the curvature of the pressure roller 31, the recording medium P sent out from the nip portion is easily separated from the fixing belt 21.

  Referring to FIG. 2, a guide plate 35 that guides the recording medium P conveyed toward the nip portion on the entrance side of the contact portion (a nip portion) between the fixing belt 21 and the pressure roller 31. (Inlet guide plate) is provided. Further, a guide plate 37 (exit guide plate) for guiding the recording medium P fed from the nip portion is disposed on the outlet side of the nip portion. Both guide plates 35 and 37 are fixed to the side plate 43 of the fixing device 20.

Hereinafter, the operation of the fixing device 20 configured as described above will be briefly described.
When the power switch of the apparatus main body 1 is turned on, electric power is supplied to the heater 25, and rotation driving of the pressure roller 31 in the direction of the arrow in FIG. Thereby, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG. 2 by the frictional force with the pressure roller 31.
Thereafter, the recording medium P is fed from the paper feeding units 12 to 14, and an unfixed image is carried on the recording medium P by the image forming unit 4. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 while being guided by the guide plate 35, and the nip portion between the fixing belt 21 and the pressure roller 31 in the pressure contact state. To be sent to.
The toner image is formed on the surface of the recording medium P by the heating by the fixing belt 21 heated by the facing member 22 (heater 25) and the pressing force of the facing member 22 reinforced by the reinforcing member 23 and the pressure roller 31. T is fixed. Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

  The inventor of the present application uses the fixing member 20 according to the first embodiment to reinforce the nip width deviation by using an aluminum facing member 22 reinforced by a replenishing member 23 having a width of 2 mm and a wall thickness of 0.4 mm. When measured, the nip width deviation (the nip width deviation between the widthwise center and both ends in the width direction) was 1.5 mm. On the other hand, when the reinforcing member 23 is not installed, it is necessary to set the thickness of the aluminum facing member 22 to 1.5 mm in order to obtain the same nip width deviation. From these measurement results, if the deflection amount of the opposing member 22 is the same, the thickness of the opposing member 22 can be reduced and the heat capacity can be reduced when the reinforcing member 23 is used. Warm-up time is shortened.

  As described above, in the first embodiment, the opposing member 22 that heats the fixing belt 21 is provided opposite to the inner circumferential surface of the fixing belt 21 (fixing member), and the opposing member 22 and the fixing belt 21 are further provided. A reinforcing member 23 is provided to reinforce the strength of the opposing member 22 at the nip portion by abutting against the pressure roller 31 (pressure member). As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

  In the first embodiment, the present invention is applied to the fixing device using the pressure roller 31 as the pressure member, but the fixing device using the pressure belt or the pressure pad as the pressure member. However, the present invention can be applied. In this case, the same effect as that of the first embodiment can be obtained.

  In the first embodiment, the fixing belt 21 having a multilayer structure is used as the fixing member. However, an endless fixing film made of polyimide, polyamide, fluororesin, metal, or the like can be used as the fixing member. In this case, the same effect as that of the first embodiment can be obtained.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a configuration diagram illustrating the fixing device according to the second embodiment, and corresponds to FIG. 2 according to the first embodiment. In the fixing device according to the second embodiment, a heat insulating member 27 is provided between the reinforcing member 23 and the counter member 22, and the point where the counter member 22 is formed so that the shape of the nip portion is concave. This is different from that of the first embodiment.

  As shown in FIG. 5, the fixing device 20 according to the second embodiment also has a fixing belt 21 (fixing member), a facing member 22, a reinforcing member 23, and a heater 25 (heat source) as in the first embodiment. , Pressure roller 31 (pressure member), and the like. In the second embodiment, two heaters 25 are installed inside the fixing belt 21.

Here, in the second embodiment, the reinforcing member 23 is configured to come into contact with the pressure roller 31 via the heat insulating member 27, the facing member 22, and the fixing belt 21. That is, the heat insulating member 27 is installed between the reinforcing member 23 and the opposing member 22. As a material of the heat insulating member 27, silicone rubber, heat resistant resin, heat resistant felt or the like can be used.
Accordingly, it is possible to suppress a problem that the temperature of the fixing belt 21 is increased because the heat of the facing member 22 is transmitted to the reinforcing member 23 at the nip portion during the warm-up. Such an effect is particularly effective when the heat capacity of the reinforcing member 23 is larger than the heat capacity of the opposing member 22.

Further, in the second embodiment, the reinforcing member 23 has a part or all of the surface facing the heater 25 as a mirror surface (mirror finishing is applied).
As a result, the heat from the heater 25 toward the reinforcing member 23 (heat for heating the reinforcing member 23) is used for heating the opposing member 22, so that the heating efficiency of the fixing belt 21 (opposing member 22) is further improved. Will do. At this time, the reinforcing member 23 has a mirror-like surface and the heating rate is reduced, but is heated by the heater 25, so that the effect of heat storage described in the first embodiment is exhibited. .

  In the second embodiment, referring to FIG. 5, the shape of the facing member 22 in the nip portion is formed in a concave shape. That is, the facing member 22 is formed so that the surface facing the pressure roller 31 follows the curvature of the pressure roller 31. Thereby, since the recording medium P is sent out from the nip portion so as to follow the curvature of the pressure roller 31, it is possible to suppress a problem that the recording medium P after the fixing process is not attracted to and separated from the fixing belt 21. it can.

  As described above, in the second embodiment, as in the first embodiment, the opposing member 22 that heats the fixing belt 21 is provided opposite to the inner peripheral surface of the fixing belt 21, and the opposing member is further provided. A reinforcing member 23 is provided that abuts against the pressure roller 31 via the fixing belt 21 and the fixing belt 21 to reinforce the strength of the opposing member 22 at the nip portion. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a configuration diagram illustrating the fixing device according to the third embodiment, and corresponds to FIG. 5 according to the second embodiment. The fixing device according to the third embodiment is different from that according to the second embodiment in that the facing member 22 is heated by electromagnetic induction.

As shown in FIG. 6, the fixing device 20 according to the third embodiment also has a fixing belt 21 (fixing member), a facing member 22, a reinforcing member 23, and a pressure roller 31 (as in the second embodiment). Pressurizing member), heat insulating member 27, and the like.
Here, the fixing device 20 according to the third embodiment is provided with an induction heating unit 50. And the opposing member 22 in this Embodiment 3 is heated by the electromagnetic induction by the induction heating part 50 unlike the thing of the said Embodiment 2 heated by the radiant heat of the heat source 25. FIG.

  The induction heating unit 50 includes an exciting coil, a core, a coil guide, and the like. The exciting coil is formed by extending a litz wire, which is a bundle of thin wires, in the width direction (in the direction perpendicular to the plane of FIG. 6) so as to cover a part of the fixing belt 21. The coil guide is made of a resin material having high heat resistance and holds the exciting coil and the core. The core is a semi-cylindrical member made of a ferromagnetic material such as ferrite (having a relative magnetic permeability of about 1000 to 3000), and in order to form an efficient magnetic flux toward the opposing member 22, A side core is provided. The core is installed so as to face the exciting coil extending in the width direction.

The fixing device 20 configured as described above operates as follows.
When the fixing belt 21 is rotationally driven in the direction of the arrow in FIG. 6, the fixing belt 21 is heated at a position facing the induction heating unit 50. Specifically, the magnetic field lines are formed so as to be alternately switched around the opposing member 22 by flowing a high-frequency alternating current through the exciting coil. At this time, an eddy current is generated on the surface of the opposing member 22, and Joule heat is generated by the electrical resistance of the opposing member 22 itself. Due to this Joule heat, the facing member 22 is heated by electromagnetic induction, and the fixing belt 22 is heated by the heated facing member 22.
In order to efficiently perform electromagnetic induction heating of the facing member 22, the induction heating unit 50 is preferably configured to face the entire circumferential direction of the facing member 22. Further, as the material of the facing member 22, nickel, stainless steel, iron, copper, cobalt, chromium, aluminum, gold, platinum, silver, tin, palladium, an alloy composed of a plurality of these metals, or the like can be used. .

  As described above, also in the third embodiment, as in each of the above embodiments, the opposing member 22 that heats the fixing belt 21 is provided opposite to the inner peripheral surface of the fixing belt 21, and the opposing member is further provided. A reinforcing member 23 is provided that abuts against the pressure roller 31 via the fixing belt 21 and the fixing belt 21 to reinforce the strength of the opposing member 22 at the nip portion. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a configuration diagram illustrating the fixing device according to the fourth embodiment, and corresponds to FIG. 5 according to the second embodiment. In the fixing device according to the fourth embodiment, the opposing member 22 is heated by the heat of the resistance heating element 60, the opposing member is configured by the first opposing member 22B and the second opposing member 22A, Is different from that of the second embodiment.

As shown in FIG. 7, the fixing device 20 according to the fourth embodiment also has a fixing belt 21 (fixing member), a contact member 22, opposing members 22 </ b> A and 22 </ b> B, pressurization, as in the second embodiment. It comprises a roller 31 (pressure member), a heat insulating member 27, and the like.
Here, in the fixing device 20 according to the fourth embodiment, the resistance heating element 60 is installed on the inner peripheral surface side of the fixing belt 21. The opposed member 22A (second opposed member) in the fourth embodiment is heated by the heat generated by the resistance heating element 60, unlike the second embodiment that is heated by the radiant heat of the heat source 25.

Here, the resistance heating element 60 is a planar heating element such as a ceramic heater, and a power supply unit (not shown) is connected to both ends thereof. When a current is passed through the resistance heating element 60, the resistance heating element 60 rises in temperature due to the electric resistance of the resistance heating element 60 itself, and heats the second opposing member 22A in contact therewith. Further, the fixing belt 21 is heated by the heated second facing member 22A.
As described above, by using the resistance heating element 60 as a heating source for heating the facing member 22A, the fixing belt 21 can be efficiently heated relatively inexpensively.

Here, the opposing member in the fourth embodiment is opposed to the first opposing member 22B facing the inner peripheral surface of the fixing belt 21 at the position of the nip portion and the inner peripheral surface of the fixing belt 21 at a position excluding the nip portion. And a second opposing member 22A.
Further, the reinforcing member 23 is integrated with the first opposing member 22B. That is, the reinforcing member 23 configured integrally with the first opposing member 22B functions as a member that directly forms the nip portion.

  In the fourth embodiment, the first opposing member 22B is formed of a heat insulating material and functions as the heat insulating member 27. In contrast, the second facing member 22A actively heats the fixing belt 21 while facing the fixing belt 21 at a position excluding the nip portion. Therefore, in the fourth embodiment, the nip portion becomes the opening of the second opposing member 22A, and the heat capacity in the nip portion is reduced, so that the temperature raising efficiency of the fixing belt 21 can be increased.

  As described above, also in the fourth embodiment, as in each of the above embodiments, the opposing member 22A that heats the fixing belt 21 is provided opposite to the inner peripheral surface of the fixing belt 21, and the opposing member is further provided. A reinforcing member 23 is provided to reinforce the strength of the opposing member 22B in the nip portion by contacting the pressure roller 31 via 22B and the fixing belt 21. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

  In the fourth embodiment, the resistance heating element 60 is used as a heating source for heating the opposing member 22, but the opposing member 22 itself may be a resistance heating element. That is, the opposing member 22 itself can be used as a heat source. In this case, the same effect as in the fourth embodiment can be obtained.

Embodiment 5. FIG.
A fifth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 8 is a configuration diagram illustrating the fixing device according to the fifth embodiment, and corresponds to FIG. 5 according to the second embodiment. The fixing device according to the fifth embodiment is different from that according to the second embodiment in that the opposing member is composed of a first opposing member 22B and a second opposing member 22A made of a light transmissive material. .

  As shown in FIG. 8, the fixing device 20 according to the fifth embodiment also has a fixing belt 21 (fixing member), opposing members 22A and 22B, a reinforcing member 23, a heater 25 (like the one in the second embodiment). Heat source), pressure roller 31 (pressure member), and the like. In addition, the opposing member in this Embodiment 5 is comprised by 22 A of 1st opposing members and 22 A of 2nd opposing members similarly to the thing of the said Embodiment 4. FIG.

  Here, in the fifth embodiment, the first facing member 22 </ b> B is formed of the light transmissive material 28. Thereby, the infrared rays emitted from the heater 25 pass through the first opposing member 22B (light transmissive material 28), and the fixing belt 21 is directly heated by the radiant heat also in the nip portion. Accordingly, the heat supply amount at the nip portion is increased, and the fixability is improved.

  As described above, also in the fifth embodiment, as in each of the above embodiments, the opposing member 22A that heats the fixing belt 21 is provided opposite to the inner peripheral surface of the fixing belt 21, and the opposing member is further provided. A reinforcing member 23 is provided to reinforce the strength of the opposing member 22B in the nip portion by contacting the pressure roller 31 via 22B and the fixing belt 21. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 9 is a view of the fixing device according to the sixth embodiment when viewed in the width direction, and corresponds to FIG. 3 according to the first embodiment. The fixing device according to the sixth embodiment is different from that according to the first embodiment in that the reinforcing member 23 is formed in a convex shape when viewed in the width direction.

As shown in FIG. 9, in the sixth embodiment, the reinforcing member 23 is formed in a convex shape (arch shape) so that the central portion in the width direction protrudes toward the pressure roller 31 as compared to both ends in the width direction. (Reference can be made to region A in FIG. 9).
Thus, even if the bending of the opposing member 22 at the center in the width direction becomes larger than the both ends in the width direction due to the structure of the pressurizing mechanism, the reinforcing member 23 is convex so as to offset the difference in the amount of bending. Since it is formed, the deflection deviation in the width direction of the facing member 22 can be reduced. Accordingly, the nip width deviation in the width direction is also reduced, and uniform and good fixability can be obtained over the entire width direction.

  It should be noted that the inventor of the present application uses a replenishment member 23 having a width of 2 mm in the fixing device 20 according to the sixth embodiment (the central portion in the width direction protrudes in a convex shape by 0.4 mm as compared to both ends in the width direction) When the nip width deviation was measured using the aluminum facing member 22 reinforced by the above and having a wall thickness of 0.4 mm, the nip width deviation was almost 0 mm. On the other hand, when the fixing device 20 according to the first embodiment is used (when the reinforcing member 23 is not formed in a convex shape), the nip width deviation is 1.5 mm. From these measurement results, it can be seen that the nip width deviation in the width direction is also reduced by forming the reinforcing member 23 in a convex shape.

  As described above, also in the sixth embodiment, as in each of the above embodiments, the facing member 2 that heats the fixing belt 21 is provided opposite to the inner peripheral surface of the fixing belt 21, and the facing member is further provided. A reinforcing member 23 is provided that abuts against the pressure roller 31 via the fixing belt 21 and the fixing belt 21 to reinforce the strength of the opposing member 22 at the nip portion. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

Embodiment 7 FIG.
A seventh embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is an overall configuration diagram illustrating an image forming apparatus according to the seventh embodiment. The fixing device according to the seventh embodiment is different from that according to the first embodiment in which the fixing device is installed in the color image forming apparatus.

As shown in FIG. 10, the image forming apparatus 1 according to the seventh embodiment is a tandem color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 10 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).
Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). .)
Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 10, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing unit 20. At this position, the color image transferred on the surface is fixed on the recording medium P by heat and pressure generated by the fixing belt 21 and the pressure roller 31.
Here, the fixing device 20 according to the seventh embodiment is configured and operates in the same manner as in the first embodiment. That is, the fixing device 20 according to the seventh embodiment is provided with a facing member 22 that heats the fixing belt 21 so as to face the inner peripheral surface of the fixing belt 21 as in the first embodiment. A reinforcing member 23 is provided to reinforce the strength of the opposing member 22 at the nip portion by contacting the pressure roller 31 via the opposing member 22 and the fixing belt 21.
Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

  As described above, also in the seventh embodiment, as in each of the above embodiments, the facing member 2 that heats the fixing belt 21 is provided so as to face the inner peripheral surface of the fixing belt 21, and the facing member is further provided. A reinforcing member 23 is provided that abuts against the pressure roller 31 via the fixing belt 21 and the fixing belt 21 to reinforce the strength of the opposing member 22 at the nip portion. As a result, the warm-up time and first print time are short, the nip width deviation in the width direction is small, and it is possible to prevent problems such as poor fixing even when the apparatus is speeded up.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating a fixing device installed in the image forming apparatus of FIG. 1. FIG. 3 is a diagram in which the fixing device of FIG. 2 is viewed in the width direction. It is a figure which shows the state which the opposing member bent. It is a block diagram which shows the fixing device in Embodiment 2 of this invention. It is a block diagram which shows the fixing device in Embodiment 3 of this invention. It is a block diagram which shows the fixing device in Embodiment 4 of this invention. It is a block diagram which shows the fixing device in Embodiment 5 of this invention. It is the figure which looked at the fixing device in Embodiment 6 of this invention in the width direction. It is a whole block diagram which shows the image forming apparatus in Embodiment 7 of this invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (fixing member),
22 counter member,
22A second opposing member, 22B first opposing member,
23 reinforcing members,
25 Heater (heat source),
27 heat insulation member,
28 light transmissive material,
31 Pressure roller (pressure member),
40 temperature sensor,
50 induction heating unit,
60 Resistance heating element, P recording medium.

Claims (15)

An endless fixing member having heat and melting the toner image;
An opposing member fixed to the inner peripheral surface of the fixing member to heat the fixing member and abutting the pressure member via the fixing member to form a nip portion;
A reinforcing member fixed on the inner peripheral surface side of the fixing member and abutting the pressure member via the opposing member and the fixing member to reinforce the strength of the opposing member in the nip portion;
A fixing device comprising:   The fixing device according to claim 1, wherein the reinforcing member is a metal thermal conductor.   The fixing device according to claim 1, wherein the reinforcing member is in contact with the pressure member via a heat insulating member, the facing member, and the fixing member.   The said reinforcing member was formed in convex shape so that the width direction center part may protrude toward the said pressurization member compared with the width direction both ends. The fixing device described.   The fixing device according to claim 1, wherein the facing member is heated by radiant heat of a heat source.   The fixing device according to claim 5, wherein a part or all of a surface of the reinforcing member facing the heat source is a mirror surface.   The fixing device according to claim 1, wherein the facing member is heated by electromagnetic induction.   The fixing device according to claim 1, wherein the facing member is heated by heat of a resistance heating element.   The fixing device according to claim 1, wherein the facing member is a resistance heating element. The opposing member includes a first opposing member that opposes the inner peripheral surface of the fixing member at a position of the nip portion, a second opposing member that opposes the inner peripheral surface of the fixing member at a position excluding the nip portion, and Comprising
The fixing device according to claim 1, wherein the reinforcing member is integrated with the first facing member. A heat source that emits radiant heat on the inner peripheral surface side of the fixing member;
The fixing device according to claim 10, wherein the first facing member is made of a light transmissive material.   The fixing device according to claim 1, wherein the pressure member includes a sponge-like elastic layer.   The fixing device according to claim 1, wherein the fixing member is a fixing belt or a fixing film.   The fixing device according to claim 1, wherein the facing member is a metal thermal conductor.   An image forming apparatus comprising the fixing device according to claim 1.

Images