JP5459488B2 - Fixing apparatus 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, and a fixing device installed therein.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, fixing apparatuses that have a short warm-up time and first print time and are less likely to cause poor fixing even when the apparatus is speeded up are known (for example, (See Patent Documents 1 and 2.)

Specifically, the fixing device disclosed in Patent Documents 1 and 2 includes a fixing belt as a fixing member, a substantially cylindrical metal member (facing member) fixed so as to face part or all of the inner peripheral surface of the fixing belt. ), A heater (heating means) provided in the metal member for heating the metal member, a pressure roller as a pressure rotator that presses against the fixing belt to form a nip portion, and the like.
The fixing belt is heated by the metal member heated by the heater, and 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. It will be.

In such a fixing device, the pressure roller is rotationally driven by the driving means, so that the fixing belt pressed against the pressure roller at the position of the nip portion is driven to rotate by frictional resistance.
In such a fixing device, a lubricant is applied between the fixing belt and the metal member in order to reduce wear due to the sliding contact between the fixing belt and the metal member.
Further, in such a fixing device, a toner containing wax is used in order to ensure the releasability of the toner with respect to the fixing belt.

In the fixing devices described in Patent Documents 1 and 2 described above, in order to prevent the fixing belt from slipping by increasing the frictional resistance between the fixing belt and the pressure roller in the nip portion to ensure the driven rotation of the fixing belt. It is conceivable to provide a pressure part made of a material having a higher frictional resistance than the sheet passing area in the non-sheet passing area of the pressure roller.
However, in that case, the lubricant applied between the fixing belt and the metal member flows into and adheres to the pressurization portion formed in the non-sheet passing region, or the wax contained in the toner is attached. There is a possibility that a problem arises in that the frictional resistance decreases due to inflow and adhesion as a foreign object. When such a problem occurs, the pressurizing portion made of the high friction resistance material does not function, and the fixing belt slips (running failure).

  The present invention has been made to solve the above-described problems. The warm-up time and the first print time are short, and the fixing image does not cause fixing defects such as uneven fixing, and the fixing belt slips. It is an object of the present invention to provide a fixing device and an image forming apparatus which are difficult.

According to a first aspect of the present invention, there is provided a fixing device that travels in a predetermined direction to heat and melt a toner image, and has an endless fixing belt having flexibility, and an inner peripheral surface of the fixing belt. A fixing member fixed on the side, and a pressure rotator which is pressed against the fixing member via the fixing belt to form a nip portion where the recording medium is conveyed, and is rotated in a predetermined direction by a driving unit And a pipe-shaped metal member that is fixed so as to oppose the inner peripheral surface of the fixing belt and heats the fixing belt and is heated by a heating means. A first pressure part formed in the paper region and a non-sheet passing region are formed so that the friction coefficient of the outer peripheral surface thereof is larger than the friction coefficient of the outer peripheral surface of the first pressure part. A second pressurizing part, Serial stands up radially outwardly so as to cover the outer circumferential surface of the pressure rotating body except for the nip portion at the boundary portion between the first pressure and the second pressure, the pressure rotating body It further includes a plate-like member that blocks an inflow path of foreign matter from the outer peripheral surface of the first pressurizing unit to the outer peripheral surface of the second pressurizing unit without hindering rotation .

According to a second aspect of the present invention, in the fixing device according to the first aspect, the plate member corresponds to a boundary portion between the first pressure portion and the second pressure portion. The outer peripheral surface of the fixing belt stands up in the outer diameter direction so as to cover the outer peripheral surface of the fixing belt excluding the nip portion.

A fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect, wherein the fixing device is arranged so as to cover an outer peripheral surface excluding the nip portion at an end portion in the width direction of the fixing belt. A second plate-like member standing up in the radial direction and blocking an inflow path of foreign matters from the width direction end portion to the width direction central portion on the outer peripheral surface of the fixing belt without hindering the running of the fixing belt; It is provided.

According to a fourth aspect of the present invention, there is provided the fixing device according to the third aspect , wherein the second plate-shaped member is the second additional member corresponding to an end in the width direction of the pressure rotator. The pressure part stands up in the outer diameter direction so as to cover the outer peripheral surface of the pressure rotating body excluding the nip part at the end in the width direction.

According to a fifth aspect of the present invention, in the fixing device according to the third or fourth aspect, the second plate member is formed of a heat insulating material.

A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the plate-like member is formed of a heat insulating material.

A fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, further comprising a second heating means for heating the second pressure unit. is there.

According to an eighth aspect of the present invention, there is provided a fixing device according to any one of the first to seventh aspects, wherein the fixing belt and / or the pressure rotator are opposed to each other in a non-contact manner. A separation member for guiding a recording medium fed from the nip portion to a conveyance path, wherein the separation member has a region in a width direction opposite to the fixing belt and / or the pressure rotating body; It is configured so as not to overlap with the region in the width direction of the part.

The fixing device according to a ninth aspect of the present invention is the fixing device according to any one of the first to eighth aspects, wherein the metal member is an inner peripheral surface of the fixing belt at a position excluding the nip portion. And a reinforcing member which is fixed to the inner peripheral surface side of the metal member and abuts on the fixing member to reinforce the fixing member.

An image forming apparatus according to a tenth aspect includes the fixing device according to any one of the first to ninth aspects.

In the present application, the “sheet passing area” is defined as a range in the width direction (direction perpendicular to the sheet passing direction) of the maximum size recording medium to be passed by the image forming apparatus. The “non-sheet passing area” is defined as an area outside the range of the “sheet passing area”.
Further, in the present application, the “width direction” is defined as a direction orthogonal to the paper passing direction of the recording medium.

  In the present application, the state in which the fixing member, the metal member, or the reinforcing member is “fixed” is a state in which the fixing member, the metal member, or the reinforcing member is held in a non-rotating manner without being driven to rotate. It is defined as Therefore, for example, even when the fixing member is biased toward the nip portion by a biasing member such as a spring, the fixing member is “fixed” if the fixing member is held non-rotating. It becomes a state.

  The present invention is provided with a pressure rotating body in which a first pressurizing portion is formed in a paper passing area and a second pressurizing portion having a high frictional resistance is formed in a non-paper passing area. Moreover, the interruption | blocking member which interrupts | blocks the inflow path | route of the foreign material to a 2nd pressurization part is further provided. As a result, 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 fixing image does not cause fixing defects such as uneven fixing, and the fixing belt does not easily slip.

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 an expanded sectional view showing the neighborhood of a nip part. FIG. 4 is a perspective view showing width direction end portions of a fixing belt and a pressure roller. It is a side view showing a pressure roller and a blocking member. It is a perspective view which shows a part of fixing device in Embodiment 2 of this invention. It is the figure which looked at the fixing device of another form in the width direction. It is a figure which shows a part of fixing device in Embodiment 3 of this invention. It is sectional drawing which shows the pressure roller installed in the fixing device of another form. It is a block diagram which shows the fixing device in Embodiment 4 of this invention.

  Hereinafter, embodiments 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.
As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment is a tandem type 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. 1 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 the 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 rotationally driven in the counterclockwise direction in FIG. 1, 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.
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.

  Note that the toner used in the first exemplary embodiment contains wax as a release agent in order to ensure the releasability of the toner with respect to the fixing belt 21 in the fixing device 20. As such a wax, carnauba wax, oxidized rice wax, low molecular weight polypropylene wax, or the like can be used.

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.
2 to 4, the fixing device 20 includes a fixing belt 21 (belt member) as a fixing member, a fixing member 26, a metal member 22 (heating member), a reinforcing member 23, and a heater 25 (heating means). A heat source), a pressure roller 31 as a pressure rotator, a blocking member 55, a temperature sensor 40, a heat insulating member 27, a stay member 28, a flange 29, a separation plate 51 as a separation member, and the like.

Here, the fixing belt 21 is a thin and flexible endless belt, and rotates (runs) in an arrow direction (counterclockwise) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer sequentially laminated from the inner peripheral surface 21a (sliding contact surface with the fixing member 26) side, and its total thickness is 1 mm or less. Is set to
The base material layer 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, and includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( Polyether sulfide) and the like. 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 inner diameter of the fixing belt 21 is set to 30 mm.
A fixing member 26, a heater (heating means), a metal member 22, a reinforcing member 23, a heat insulating member 27, a stay member 28, and the like are fixedly provided inside the fixing belt 21 (inner peripheral surface side). Although not shown, a lubricant is applied between the fixing belt 21 and the metal member 22.
Here, the fixing member 26 is fixed so as to be in sliding contact with the inner peripheral surface 21 a of the fixing belt 21. The fixing member 26 is pressed against the pressure roller 31 via the fixing belt 21 to form a nip portion where the recording medium P is conveyed. Referring to FIG. 3, both ends of the fixing member 26 in the width direction are fixedly supported by the side plates 43 of the fixing device 20. The configuration of the fixing member 26 will be described in detail later.

Referring to FIG. 2, the metal member 22 (heating member) is formed so as to face the inner peripheral surface of the fixing belt 21 at a position excluding the nip portion, and the fixing member is interposed via the heat insulating member 27 at the position of the nip portion. 26 is a substantially cylindrical body formed so as to hold 26. Referring to FIG. 3, both ends of the metal member 22 in the width direction are fixedly supported by the side plates 43 of the fixing device 20. In addition, flanges 29 are provided at both ends of the metal member 22 to limit the displacement of the fixing belt 21 (movement in the width direction).
The metal member 22 formed in a substantially pipe shape is heated by the radiant heat of the heater 25 to heat the fixing belt 21 (transmits heat). That is, the metal member 22 is directly heated by the heater 25, and the fixing belt 21 is indirectly heated by the heater 25 through the metal member 22. In order to maintain the heating efficiency of the fixing belt 21 favorably, the thickness of the metal member 22 is preferably set to 0.1 mm or less.
As a material of the metal member 22, a metal heat conductor (a metal having heat conductivity) such as stainless steel, nickel, aluminum, and iron can be used. X Ferrite stainless steel having a relatively small specific heat) is preferred. In the first embodiment, SUS430 that is ferritic stainless steel is used as the material of the metal member 22. Further, the thickness of the metal member 22 is set to 0.1 mm.

  The heater 25 as a heating means is a halogen heater (or carbon heater), and both ends thereof are fixed to the side plate 43 of the fixing device 20 (see FIG. 3). The metal member 22 is heated by the radiant heat of the heater 25 (heating means) whose output is controlled by the power supply unit of the apparatus body 1. Further, the fixing belt 21 is entirely heated by the metal member 22 at a position excluding the nip portion, 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 (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.

  As described above, in the fixing device 20 according to the first embodiment, not only a part of the fixing belt 21 is locally heated, but the fixing belt 21 is almost entirely heated in the circumferential direction by the metal member 22. Therefore, 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.

Here, the substantially pipe-shaped metal member 22 is fixed so as to face the inner peripheral surface (the position excluding the nip portion) of the fixing belt 21 with a clearance. A clearance amount δ (a gap at a position excluding the nip portion) between the fixing belt 21 and the metal member 22 is set to be larger than 0 mm and not larger than 1 mm (0 mm <δ ≦ 1 mm). As a result, the area in which the metal member 22 and the fixing belt 21 are in sliding contact with each other is increased, and the problem that the wear of the fixing belt 21 is accelerated is suppressed. In addition, the metal member 22 and the fixing belt 21 are separated from each other too much. Inconveniences that reduce efficiency can be suppressed. Furthermore, since the metal 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, in order to reduce the wear of the fixing belt 21 even if the metal member 22 and the fixing belt 21 are in sliding contact with each other, the inner circumferential surface of the fixing belt 21 has fluorine grease or the like between both members 21 and 22. A lubricant such as silicone oil is applied.
In the first embodiment, the metal member 22 is formed to have a substantially circular cross-sectional shape, but the metal member 22 may be formed to have a polygonal cross-sectional shape.

  Here, in the first embodiment, the reinforcing member 23 that reinforces the strength of the fixing member 26 that forms 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 fixing member 26, 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 fixing member 26 and the fixing belt 21, thereby preventing a problem that the fixing member 26 is greatly deformed by the pressure applied by the pressure roller 31 in the nip portion. ing. In the first embodiment, the reinforcing member 23 is a plate-like member disposed so as to divide the inside of the metal member 22 into two spaces.

In order to satisfy the above-described function, the reinforcing member 23 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron.
In addition, a heat insulating member can be provided on a part or all of the surface of the reinforcing member 23 facing the heater 25, or a mirror surface treatment can be performed. 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 metal member 22, so that the heating efficiency of the fixing belt 21 (metal member 22) is further improved. Will do.

  2 and 3, a pressure roller 31 as a pressure rotator that abuts the outer peripheral surface of the fixing belt 21 at the position of the nip portion is formed on a hollow cored bar 34 with a first pressure portion. 32 and the 2nd pressurizing part 33 are formed, respectively. In the pressure roller 31, the first pressure unit 32 is formed in the sheet passing region M, and the second pressure unit 33 is formed in the non-sheet passing region N at both ends. As shown in FIG. 3, in the first embodiment, the first pressurizing unit 32 takes a target sheet passing area M in consideration of the sheet passing accuracy of the recording medium P (accuracy of lateral registration). It is widely formed with a margin on the non-sheet passing area N side. In addition, a blocking member 55 is installed between the first pressurizing unit 32 and the second pressurizing unit 33 to prevent inflow of foreign matter from the first pressurizing unit 32 to the second pressurizing unit 33. ing.

The first pressure part 32 of the pressure roller 31 (pressure rotator) is a main part that forms a nip part through which the recording medium P is conveyed, and is made of an elastic material having a diameter of 30 mm (core). It is an elastic layer formed on the gold 34.) The first pressure portion 32 (elastic layer) of the pressure roller 31 is formed of a material such as foamable silicone rubber, silicone rubber, or fluorine rubber. Note that a thin release layer made of PFA, PTFE, or the like may be provided as a surface layer on the first pressure unit 32 (elastic layer). The pressure roller 31 (first pressure unit 32) is in pressure contact with the fixing belt 21 to form a desired nip portion between both members.
In addition, the 2nd pressurization part 33 and the interruption | blocking member 55 provided in the both ends of the pressure roller 31 are demonstrated in detail later.

When the elastic layer 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. Can be reduced. Furthermore, since the heat insulation of the pressure roller 31 is enhanced and the heat of the fixing belt 21 is difficult to move to the pressure roller 31 side, the heating efficiency of the fixing belt 21 is improved.
In the first embodiment, the diameter of the fixing belt 21 is formed so as to be approximately equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 is smaller than the diameter of the pressure roller 31. It can also be formed. 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. 3, the pressure roller 31 is provided with a gear 45 that meshes with a drive gear of a drive means (drive mechanism) (not shown). The pressure roller 31 is driven by the drive means in FIG. It is rotationally driven in the direction of the arrow (clockwise).

Referring to FIG. 4, the fixing member 26 that is in sliding contact with the inner peripheral surface 21a of the fixing belt 21 has a surface layer 26a formed on a base layer 26b. The fixed member 26 is formed in a concave shape so that the surface (sliding contact 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, the problem that the recording medium P after the fixing process is not attracted to the fixing belt 21 and separated is suppressed. be able to.
In the first embodiment, the shape of the fixing member 26 that forms the nip portion is formed in a concave shape, but the shape of the fixing member 26 that forms the nip portion can also be formed in a flat shape. That is, the sliding contact surface of the fixing member 26 (the surface facing the pressure roller 31) can be formed in 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.

Here, with reference to FIG. 2, the fixing device 20 according to the first embodiment includes a separation plate 51 as a separation member for guiding the recording medium P sent from the nip portion to the conveyance path. It is installed so as to face the non-contact. Specifically, the separation plate 51 (separation member) is a plate material disposed so that the front end portion thereof is close to the position in the vicinity of the exit of the nip portion of the fixing belt 21. The side plate 43 is fixedly supported. Further, the separation plate 51 is set so that the width direction region H (the width direction region facing the fixing belt 21) of the leading end thereof does not overlap the width direction region of the second pressure unit 33. Has been. Specifically, the region H in the width direction of the front end portion of the separation plate 51 is set so as not to protrude from the sheet passing region M.
As described above, since the separation plate 55 is provided in the region H that occupies most of the paper passing region M, the recording medium fed from the nip portion is equivalent to the case where the separating plate is provided in a range exceeding the paper passing region M. It is possible to reliably prevent the separation failure that P is adsorbed to the fixing belt 21.
In order to prevent a problem that the recording medium P sent out from the nip portion is attracted to the pressure roller 31 side, a separation member is disposed so as to be close to a position near the nip portion outlet in the pressure roller 31. You can also.

In addition, as a material for forming the base layer 26b of the fixing member 26, a material having a certain degree of rigidity (for example, a high-rigidity metal or ceramic so as not to bend greatly even when applied with pressure by the pressure roller 31). Etc.).
Since the thickness of the substantially pipe-shaped metal member 22 formed by bending a metal plate can be reduced, the warm-up time can be shortened. However, since the rigidity of the metal member 22 itself is small, the metal member 22 may bend or deform without resisting the pressure applied by the pressure roller 31. If the pipe-shaped metal member 22 is deformed, a desired nip width cannot be obtained and the fixing property is deteriorated. On the other hand, in the first embodiment, since the high-rigidity fixing member 26 is installed separately from the thin metal member 22 to form the nip portion, such a problem is caused in advance. Can be prevented.

  Further, the surface layer 26a of the fixing member 26 is formed of a coarse sheet-like low friction material. The surface layer 26a is impregnated with a lubricant in advance. As a result, the fixing member 26 is in a state where the lubricant is held on the surface in contact with the fixing belt 21. Therefore, the problem that both the members 21 and 26 are worn due to the sliding contact between the fixing member 26 and the fixing belt 21 is reduced.

In the first embodiment, the heat insulating member 27 is installed between the fixing member 26 and the heater 25 (heating means). Specifically, the heat insulating member 27 is installed between the fixing member 26 and the metal member 22 so as to cover the surface of the fixing member 26 excluding the sliding contact surface. As a material of the heat insulating member 27, sponge rubber having excellent heat insulating properties, ceramic having an empty package, or the like can be used.
In the first embodiment, since the fixing belt 21 and the metal member 22 are close to each other over almost the entire circumference, the fixing belt 21 can be heated in the circumferential direction without temperature unevenness even when waiting for heating (when waiting for a printing operation). Therefore, after receiving a print request, a print operation can be performed promptly. At this time, in a conventional on-demand type fixing device (see, for example, Japanese Patent No. 2884714), if heat is applied while the pressure roller is deformed during heating standby at the nip portion, the rubber of the pressure roller Depending on the material, heat deterioration may cause the life of the pressure roller to be shortened or compression set to be generated on the pressure roller. Increased by joining.) When compression set is generated in the pressure roller, a part of the pressure roller is indented, and a desired nip width cannot be obtained. Therefore, fixing failure occurs or abnormal noise occurs during rotation. To do.
On the other hand, in the first embodiment, since the heat insulating member 27 is installed between the fixing member 26 and the metal member 22, the heat of the metal member 22 does not easily reach the fixing member 26 during heating standby. . Therefore, the problem of being heated at a high temperature in a state where the pressure roller 31 is deformed at the time of heating standby can be reduced, and the above-described problems can be prevented from occurring.

Further, the lubricant applied between the two members in order to reduce the frictional resistance between the fixing member 26 and the fixing belt 21 is deteriorated by use under a high temperature condition in addition to the high pressure condition in the nip portion. There is a possibility that problems such as slippage may occur.
On the other hand, in Embodiment 1, since the heat insulating member 27 is installed between the fixing member 26 and the metal member 22, the heat of the metal member 22 does not easily reach the lubricant in the nip portion. Therefore, deterioration due to high temperature of the lubricant is reduced, and the above-described problems can be prevented from occurring.

  In the first embodiment, since the heat insulating member 27 is installed between the fixing member 26 and the metal member 22, the fixing member 26 is thermally insulated and the fixing belt 21 is actively heated in the nip portion. Will not be. For this reason, the temperature of the recording medium P fed into the nip portion is lowered when it is sent out from the nip portion. That is, at the exit of the nip portion, the temperature of the toner image fixed on the recording medium P is lowered, the viscosity of the toner is lowered, and the toner adhesive force to the fixing belt 21 is reduced. Separated from the fixing belt 21. Therefore, the problem that the recording medium P immediately after the fixing process is wound around the fixing belt 21 and jamming is prevented, and toner adhesion to the fixing belt 21 is also suppressed.

In the first embodiment, referring to FIG. 4, a stay member 28 that holds the concave portion of the metal member 22 in which the fixing member 26 is inserted from the inner peripheral surface side is provided.
The substantially pipe-shaped metal member 22 is formed by bending a stainless steel plate having a thickness of 0.1 mm. Therefore, even if it is going to process a stainless steel plate into a desired pipe shape by bending, it will open in the direction where a diameter becomes large with a spring back, and a desired pipe shape cannot be formed. If the metal member 22 is opened by the spring back, it contacts the inner peripheral surface of the fixing belt 21 and damages the fixing belt 21 or causes uneven heating of the fixing belt 21 due to uneven contact with the fixing belt 21. Resulting in. In the first embodiment, in order to prevent such a problem from occurring, the recess of the opening of the metal member 22 (bending portion) is fixed by the stay member 28, whereby the spring of the metal member 22 is fixed. Deformation due to back is suppressed. Specifically, the stay member 28 is press-fitted into the recess from the inner peripheral surface side of the metal member 22 while maintaining the shape of the metal member 22 that has been bent so as to resist the springback force.

Here, in order to increase the heating efficiency of the metal member 22, the thickness of the metal member 22 is preferably set to 0.2 mm or less.
As described above, since the thickness of the substantially pipe-shaped metal member 22 formed by bending a metal plate can be reduced, the warm-up time can be shortened. However, since the rigidity of the metal member 22 itself is small, when the pressing force of the pressure roller 31 acts on the metal member 22, the metal member 22 cannot be fully resisted and is bent or deformed. When the pipe-shaped metal member 22 is deformed, a desired nip width cannot be obtained, and a problem that the fixing property is deteriorated occurs. In contrast, in the first embodiment, the thin metal member 22 is provided with a recess (a portion where the fixing member 26 is inserted) so as to be separated from the nip portion, and the pressure roller 31 is added. Since the pressure does not directly act on the metal member 22, it is possible to prevent such a problem from occurring.

The normal operation of the fixing device 20 configured as described above will be briefly described below.
When the power switch of the apparatus main body 1 is turned on, 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 supply unit 12, and an unfixed color image is carried (transferred) on the recording medium P at the position of the secondary transfer roller 89. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by a guide plate (not shown), and the fixing belt 21 and the pressure roller 31 that are in a pressure contact state. It is fed into the nip part.
And by the heating by the fixing belt 21 heated by the metal member 22 (heater 25), and the pressing force of the fixing member 26 reinforced by the reinforcing member 23 and the pressure roller 31 (first pressure part 32), The toner image T is fixed on the surface of the recording medium P. Thereafter, the recording medium P delivered from the nip portion is conveyed in the direction of arrow Y11.

Hereinafter, a characteristic configuration and operation of the fixing device 20 according to the first embodiment will be described in detail.
As described above, with reference to FIGS. 2, 3, and 5, the pressure roller 31 (pressure rotator) of the fixing device 20 according to the first embodiment has a sheet passing region on the cored bar 34. A first pressurizing unit 32 is formed in M, and a second pressurizing unit 33 is formed in the non-sheet passing region N. The first pressurizing unit 32 and the second pressurizing unit 33 are each formed of an elastic material such as foamable silicone rubber, silicone rubber, or fluororubber. In addition, the friction coefficient of the outer peripheral surface of the second pressurizing unit 33 is formed to be larger than the friction coefficient of the outer peripheral surface of the first pressurizing unit 32. Specifically, the elastic material of the 1st pressurization part 32 and the 2nd pressurization part 33 is optimized, or a surface layer is provided in an outer peripheral surface, and it is constituted so that the difference in the above-mentioned friction coefficient may arise. .
With this configuration, the frictional resistance of the pressure roller 31 against the fixing belt 21 at the nip portion can be set to be large as a whole, so that a running failure (slip) of the fixing belt 21 is less likely to occur.
Note that the frictional resistance between the fixing belt 21 and the second pressure unit 33 is larger than the frictional resistance between the fixing belt 21 and the first pressure unit 32, so that the fixing that is in sliding contact with the second pressure unit 33 is performed. The wear deterioration in the area of the belt 21 is accelerated. However, since the area of the fixing belt 21 that is in sliding contact with the second pressure unit 33 is the non-sheet passing area N, the image quality of the fixed image does not deteriorate.

Here, in the first embodiment, as shown in FIGS. 3, 5, and 6 (A), the blocking member 55 that blocks the foreign material inflow path A <b> 1 on the outer peripheral surface of the second pressurizing unit 33 is provided. is set up.
Specifically, referring to FIG. 5, the blocking member 55 is disposed so as to cover the outer peripheral surface of the pressure roller 31 excluding the nip portion at the boundary portion between the first pressure portion 32 and the second pressure portion 33. It is a plate-like member that stands up in the radial direction, and a holding portion 55d is fastened to the side plate 43 by screws, although not shown. More specifically, referring to FIG. 6A, a groove portion (a groove portion having a depth G in the drawing) is formed at a boundary portion between first pressure portion 32 and second pressure portion 33. In addition, the blocking member 55 is installed so that the inner diameter portion of the blocking member 55 enters the groove portion and partitions both the pressure portions 32 and 33.

With such a configuration, even if the wax (foreign matter) contained in the toner is about to flow from the first pressurizing unit 32 into the second pressurizing unit 33, the wax is installed between the pressurizing units 32 and 33. The blocking member 55 blocks the inflow path A1 (path). Therefore, the problem that the wax (foreign matter) adheres to the second pressurizing portion 33 and the surface frictional resistance thereof decreases to cause the fixing belt 21 to slip (running failure) is suppressed.
Here, the wax adhering to the first pressurizing unit 32 evaporates when the wax contained in the toner image formed on the recording medium P is heated at a high temperature at the position of the nip portion during the fixing process and then evaporated. It is formed by being naturally cooled at rest.

  Note that the blocking member 55 in the first embodiment is preferably formed of a heat insulating material (for example, a heat resistant heat insulating resin material). As a result, the movement of heat from the first heating unit 32 to the second heating unit 33 is also limited, and the second heating unit 33 greatly expands and the running of the fixing belt 21 due to the change in the frictional resistance with respect to the fixing belt 21. Defects can be prevented.

In the first embodiment, as described above with reference to FIG. 3, the separation plate 51 is a region H in the width direction at the tip (a region in the width direction facing the fixing belt 21). Is set so as not to overlap with the region N in the width direction of the second pressure member 33.
With such a configuration, even if foreign matter such as wax contained in the toner adheres to the tip of the separation plate 55, the foreign matter is less likely to flow from the separation plate 55 to the second pressure unit 33. It is possible to suppress a decrease in the function of the second pressure unit 33 described above.

In the first embodiment, as shown in FIG. 6A, a groove portion (a groove portion having a depth G in the drawing) is formed at the boundary portion between the first pressure portion 32 and the second pressure portion 33. ) Was formed, and the blocking member 55 was installed so that the inner diameter portion of the blocking member 55 entered into the groove portion to partition both the pressure portions 32 and 33.
On the other hand, the inner diameter portion of the blocking member 55 is changed from the first pressurizing unit 32 to the second pressurizing unit 33 without forming a groove at the boundary between the first pressurizing unit 32 and the second pressurizing unit 33. It can also comprise so that it may contact | abut to the boundary part. In that case, considering the thermal expansion of the second pressurizing unit 33 (or the first pressurizing unit 32), the viscosity of the wax, etc., as shown in FIG. 6B, the second pressurizing unit 33 (or the first pressurizing unit 33). It is preferable that a predetermined gap D (for example, about 0.1 to 1 mm) is provided in advance between the 1 pressurizing portion 32) and the inner diameter portion of the blocking member 55.

  As described above, in the first embodiment, the first pressurizing unit 32 is formed in the sheet passing region M, and the second pressurizing unit 33 having a high frictional resistance is formed in the non-sheet passing region N. A pressure roller 31 (pressure rotator) is provided. Further, a blocking member 55 is further provided to block the inflow path of the foreign matter to the second pressurizing unit 33. As a result, the warm-up time and the first print time are short, and the fixing belt 21 can be prevented from slipping without causing a fixing failure such as uneven fixing in the fixed image.

Embodiment 2. FIG.
7 and 8, the second embodiment of the present invention will be described in detail.
FIG. 7 is a perspective view illustrating a part of the fixing device according to the second embodiment, and corresponds to FIG. 5 according to the first embodiment. FIG. 8 is a view of another embodiment of the fixing device as viewed in the width direction, and corresponds to FIG. 3 in the first embodiment.
The fixing device according to the second embodiment is different from that of the first embodiment in the configuration of the blocking member.

  The fixing device 20 according to the second embodiment also has a fixing belt 21, a fixing member 26, a substantially pipe-shaped metal member 22, a reinforcing member 23, a heat insulating member 27, and a pressure roller 31, as in the first embodiment. (Heating rotator), blocking members 55 and 56, temperature sensor 40, separation plate 51 (separation member), and the like. Further, in the pressure roller 31 in the second embodiment, as in the first embodiment, the first pressure unit 32 is formed in the paper passing area, and the second friction resistance second in the non-paper passing area. A pressurizing part 33 is formed.

Here, as shown in FIG. 7, the fixing device 20 according to the second embodiment is provided with a first blocking member 55 and a second blocking member 56.
The first shielding member 55 is for blocking the inflow paths A <b> 1 and A <b> 2 through which wax (foreign matter) in the toner flows into the second pressure unit 33. On the other hand, the second shielding member 56 blocks the inflow paths B1 and B2 through which the lubricant (foreign matter) interposed between the fixing belt 21 and the metal member 22 flows into the second pressure unit 33. Is for.

  Specifically, the first blocking member 55 stands up in the outer diameter direction so as to cover the outer peripheral surface of the pressure roller 31 excluding the nip portion at the boundary portion between the first pressure unit 32 and the second pressure unit 33. And the outer peripheral surface of the fixing belt 21 corresponding to the boundary portion between the first pressurizing unit 32 and the second pressurizing unit 33 and covering the outer peripheral surface of the fixing belt 21 excluding the nip portion. In this way, the plate-like member stands in the outer diameter direction. That is, the first blocking member 55 includes a first standing portion 55 a that stands at the boundary portion between the first pressure portion 32 and the second pressure portion 33 in the pressure roller 31, and a first standing portion in the fixing belt 21. A second upright portion 55b that rises at a position in the width direction corresponding to 55a is integrally formed in an 8-shape. In addition, the 1st standing part 55a and the 2nd standing part 55b are not connected in the position of the nip part.

With such a configuration, even if the wax contained in the toner is about to flow into the second pressurizing unit 33 from the first pressurizing unit 32 as a foreign substance, the blocking provided between the pressurizing units 32 and 33 is provided. The inflow path A1 is blocked by the first standing portion 55a of the member 55. Further, even if the wax contained in the toner tries to flow into the second pressure unit 33 from the sheet passing area of the fixing belt 21 through the non-sheet passing area as a foreign substance, the wax passing area and the non-sheet passing position of the fixing belt 21 are not affected. The inflow path A2 is blocked by the second standing portion 55b of the blocking member 55 installed between the regions. In this way, the problem that the wax (foreign matter) adheres to the second pressurizing portion 33 and the surface frictional resistance thereof decreases to cause the fixing belt 21 to slip (running failure) is suppressed. .
Here, the wax adhering to the first pressure unit 32 and the sheet passing area of the fixing belt 21 is heated at a high temperature at the position of the nip portion, and the wax contained in the toner image formed on the recording medium P evaporates. Then, it is formed by being naturally cooled thereafter.

  On the other hand, the second blocking member 56 is a plate-like member that stands in the outer diameter direction so as to cover a part of the outer peripheral surface at the end portion in the width direction of the fixing belt 21 (a portion excluding the nip portion). And rises in the outer diameter direction so as to cover the outer peripheral surface of the pressure roller 31 excluding the nip portion at the width direction end portion of the second pressure portion 33 corresponding to the width direction end portion of the pressure roller 31. It is a plate-like member. That is, the second blocking member 56 stands at a position in the width direction corresponding to the first standing portion 56 a in the first standing portion 56 a standing at the width direction end portion of the fixing belt 21 and the second pressurizing portion 33. The second upright portion 56b is integrally formed in an 8-shape. In addition, the 1st standing part 56a and the 2nd standing part 56b are not connected in the position of the nip part.

With such a configuration, the lubricant applied between the fixing belt 21 and the metal member 22 moves from the end of the fixing belt 21 toward the inside of the outer peripheral surface, and then becomes a foreign matter in the second pressure unit 33. Even if it tries to flow in, the inflow path B1 is blocked by the first upright portion 56a of the blocking member 56 installed at the end in the width direction of the fixing belt 21. Further, the lubricant applied between the fixing belt 21 and the metal member 22 moves from the end of the fixing belt 21 to the end of the second pressurizing unit 33, and on the outer peripheral surface of the second pressurizing unit 33. Even if it tries to flow inward as a foreign substance, the inflow path B2 is blocked by the second upright portion 56b of the blocking member 56 installed at the width direction end of the second pressure unit 33. In this way, the problem that the lubricant (foreign matter) adheres to the second pressurizing portion 33 and the surface frictional resistance thereof decreases to cause the fixing belt 21 to slip (running failure) is suppressed. Become.
Here, the lubricant that flows from the end portion of the fixing belt 21 is a lubricant that is applied between the fixing belt 21 and the metal member 22 and leaks from the gap between the end portions of both the members 21 and 22. .

  In the second embodiment, the first standing part 55a and the second standing part 55b are integrally formed in the first blocking member 55, and the first standing part 56a and the second standing part 56b are integrally formed in the second blocking member 56. Although the two standing portions 56b are integrally formed, these standing portions 55a, 55b, 56a, and 56b can be provided separately.

Further, in the second embodiment, the first standing portion 56 a of the second blocking member 56 is covered with a part of the outer peripheral surface (the portion excluding the nip portion) at the width direction end portion of the fixing belt 21. It was configured to stand up in the outer diameter direction.
On the other hand, as shown in FIG. 8, the second blocking member 56 is a plate-like member that stands up in the outer diameter direction so as to cover the entire outer circumferential surface (the entire circumference) at the end in the width direction of the fixing belt 21. It can also be. Specifically, as shown in FIG. 8, the second blocking member 56 rises so as to cover the outer peripheral surface at the end portion in the width direction of the fixing belt 21, and contacts the end surface of the second pressure unit 33. Is formed. Even in such a configuration, the second blocking member 56 allows the lubricant (foreign matter) interposed between the fixing belt 21 and the metal member 22 to flow into the second pressurizing unit 33, the inflow path B <b> 1. Since B2 is cut off, slipping (running failure) of the fixing belt 21 can be suppressed.

  As described above, also in the second embodiment, as in the first embodiment, the first pressurizing unit 32 is formed in the sheet passing area M, and the second friction resistance second in the non-sheet passing area N. A pressure roller 31 (pressure rotator) on which the pressure unit 33 is formed is provided. Further, blocking members 55 and 56 for blocking the inflow path of the foreign matter to the second pressurizing unit 33 are further provided. As a result, the warm-up time and the first print time are short, and the fixing belt 21 can be prevented from slipping without causing a fixing failure such as uneven fixing in the fixed image.

Embodiment 3 FIG.
9 and 10, the third embodiment of the present invention will be described in detail.
FIG. 9 is a diagram illustrating a part of the fixing device according to the third embodiment. FIG. 9A is a front view of the pressure roller 31 viewed in the width direction, and FIG. 9B is a side view showing the pressure roller 31. FIG. 10 is a cross-sectional view showing a pressure roller 31 installed in another type of fixing device.
The fixing device according to the third embodiment is different from that according to the first embodiment in that a second heating unit that heats the second pressure unit 33 of the pressure roller 31 is provided.

  Similarly to the first embodiment, the fixing device 20 according to the third embodiment also has a fixing belt 21, a fixing member 26, a substantially pipe-shaped metal member 22, a reinforcing member 23, a heat insulating member 27, and a pressure roller 31. (Heating rotator), blocking member 55, temperature sensor 40, separation plate 51 (separation member), and the like. Further, in the pressure roller 31 in the third embodiment, as in the first embodiment, the first pressure portion 32 is formed in the paper passing area, and the second friction resistance second in the non-paper passing area. A pressurizing part 33 is formed. Further, a blocking member 55 that blocks inflow of foreign matter (wax or lubricant) to the second pressure unit 33 of the pressure roller 31 is provided.

Here, as shown in FIG. 9, the fixing device 20 according to the third embodiment is provided with an induction heating unit 57 as a second heating unit that directly heats the second pressure unit 33.
Specifically, the induction heating unit 57 (second heating means) includes an exciting coil, a core, a coil guide, and the like. The exciting coil is formed by extending a litz wire bundled with thin wires in the width direction (in the direction perpendicular to the paper surface of FIG. 9) so as to cover a part of the outer peripheral surface of the second pressure unit 33. 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 cored bar 34, A side core is provided. The core is installed so as to face the exciting coil extending in the width direction.

Then, a high frequency alternating current is passed through the exciting coil so that the magnetic lines of force are alternately switched around the second pressurizing unit 33 in both directions. At this time, an eddy current is generated on the surface of the core metal 34 (the core metal surface in the non-sheet-passing region), and Joule heat is generated by the electrical resistance of the core metal 34 itself. Due to this Joule heat, the non-sheet passing region of the cored bar 34 is electromagnetically heated, and the second pressure member 33 is heated by the heated cored bar 34.
In order to efficiently heat the second pressurizing unit 33 by electromagnetic induction, the second pressurizing unit 33 itself can be provided with a metal layer that is heated by electromagnetic induction.

  With such a configuration, the second pressurizing unit 33 is positively heated by the induction heating unit 57 (second heating means), so that wax or lubricant adheres to the second pressurizing unit 33. Even it can be evaporated. Therefore, the problem that the wax or the lubricant adheres to the second pressurizing portion 33 and the surface frictional resistance is reduced to cause the fixing belt 21 to slip (running failure) is suppressed.

  In the third embodiment, the induction heating unit 57 is used as the second heating means for heating the second pressure unit 33. However, as shown in FIG. A heater 58 can also be used as the heating means. Specifically, a halogen heater in which a heater portion 58 is formed only at a position facing the second pressurizing portion 33 is installed inside the hollow cored bar 34. Thereby, since the 2nd pressurization part 33 is positively heated by the heater 58 (2nd heating means), even if wax or a lubricant adheres to the 2nd pressurization part 33, it Can be evaporated. Therefore, the problem that the wax or the lubricant adheres to the second pressurizing portion 33 and the surface frictional resistance is reduced to cause the fixing belt 21 to slip (running failure) is suppressed.

  As described above, also in the third embodiment, as in the first embodiment, the first pressurizing unit 32 is formed in the paper passing area M, and the second high frictional resistance is provided in the non-paper passing area N. A pressure roller 31 (pressure rotator) on which the pressure unit 33 is formed is provided. Further, a blocking member 55 is further provided to block the inflow path of the foreign matter to the second pressurizing unit 33. As a result, the warm-up time and the first print time are short, and the fixing belt 21 can be prevented from slipping without causing a fixing failure such as uneven fixing in the fixed image.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 11 is a configuration diagram illustrating the fixing device according to the fourth embodiment, and corresponds to FIG. 2 according to the first embodiment. The fixing device according to the fourth embodiment is different from that according to the first embodiment in that the metal member 22 is heated by electromagnetic induction.

As shown in FIG. 11, the fixing device 20 according to the fourth embodiment also has a fixing belt 21, a fixing member 26, a substantially pipe-shaped metal member 22, a reinforcing member 23, a heat insulating member, as in the first embodiment. The member 27, the pressure roller 31 (heating rotator), the blocking member 55, the temperature sensor 40, the separation plate 51 (separation member), and the like. Further, in the pressure roller 31 according to the fourth embodiment, similarly to the first embodiment, the first pressure unit 32 is formed in the sheet passing area, and the second friction resistance second is formed in the non-sheet passing area. A pressurizing part 33 is formed. Further, a blocking member 55 that blocks inflow of foreign matter (wax or lubricant) to the second pressure unit 33 of the pressure roller 31 is provided.
Here, in the fixing device 20 according to the fourth embodiment, an induction heating unit 50 is installed as a heating unit instead of the heater 25. And unlike the said Embodiment 1 heated by the radiant heat of the heater 25, the metal member 22 in this Embodiment 4 is heated by the electromagnetic induction by the induction heating part 50. 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. 11) 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 permeability of about 1000 to 3000), and in order to form an efficient magnetic flux toward the metal 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 pressure roller 31 is rotationally driven in the direction of the arrow in FIG. 11, the fixing belt 21 is also driven to rotate in the direction of the arrow. The fixing belt 21 is heated at a position facing the induction heating unit 50. Specifically, the magnetic lines of force are formed alternately around the metal 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 metal member 22, and Joule heat is generated by the electric resistance of the metal member 22 itself. Due to this Joule heat, the metal member 22 is heated by electromagnetic induction, and the fixing belt 21 is heated by the heated metal member 22.
In order to efficiently perform electromagnetic induction heating of the metal member 22, it is preferable that the induction heating unit 50 is configured to face the entire circumferential direction of the metal member 22. Moreover, as a material of the metal 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 fourth embodiment, the first pressurizing unit 32 is formed in the paper passing area M and the second high frictional resistance is formed in the non-paper passing area N in the same manner as the above-described embodiments. A pressure roller 31 (pressure rotator) on which the pressure unit 33 is formed is provided. Further, a blocking member 55 is further provided to block the inflow path of the foreign matter to the second pressurizing unit 33. As a result, the warm-up time and the first print time are short, and the fixing belt 21 can be prevented from slipping without causing a fixing failure such as uneven fixing in the fixed image.

In the fourth embodiment, the metal member 22 is heated by electromagnetic induction heating, but the metal member 22 can also be heated by the heat of the resistance heating element. Specifically, the resistance heating element is brought into contact with part or all of the inner peripheral surface of the metal member 22. The resistance heating element is a planar heating element such as a ceramic heater, and a power supply unit is connected to both ends thereof. When a current is passed through the resistance heating element, the resistance heating element is heated by the electric resistance of the resistance heating element itself, and heats the metal member 22 in contact therewith. Further, the fixing belt 21 is heated by the heated metal member 22.
Even in such a case, the same effect as in the fourth embodiment can be obtained by configuring the pressure roller 31 and the blocking member 55 in the same manner as in the fourth embodiment.

  In each of the above embodiments, the fixing belt 21 having a multilayer structure is used as the fixing belt. However, an endless fixing film made of polyimide, polyamide, fluororesin, metal, or the like may be used as the fixing belt. In this case, the same effects as those of the above embodiments can be obtained.

  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 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing belt (fixing member),
22 metal member (heating member),
23 reinforcing members,
25 heater (heating means),
26 fixing member,
31 Pressure roller (pressure rotating body),
32 1st pressurizing part,
33 second pressure part,
50 induction heating unit (heating means),
51 Separation plate (separation member),
55, 56 blocking member (plate-like member),
57 induction heating unit (second heating means),
58 heater (second heating means),
P recording medium, M paper passing area, N non-paper passing area.

Japanese Patent No. 2008-158482 Japanese Patent No. 2009-3410

Claims (10)

An endless fixing belt having flexibility and running in a predetermined direction to heat and melt the toner image;
A fixing member fixed to the inner peripheral surface side of the fixing belt;
A pressure rotator that is pressed against the fixing member via the fixing belt to form a nip portion on which a recording medium is conveyed, and is rotated in a predetermined direction by a driving unit;
A pipe-shaped metal member fixed to be opposed to the inner peripheral surface of the fixing belt to heat the fixing belt and heated by a heating unit;
With
The pressure rotator is
A first pressure unit formed in the paper passing area;
A second pressure member formed in a non-sheet passing region and having a friction coefficient of the outer peripheral surface thereof larger than a friction coefficient of the outer peripheral surface of the first pressure member;
Comprising
Standing up in the outer diameter direction so as to cover the outer peripheral surface of the pressurizing rotating body excluding the nip portion at the boundary portion between the first pressurizing part and the second pressurizing part , A fixing device, further comprising: a plate-like member that blocks an inflow path of foreign matters from the outer peripheral surface of the first pressure member to the outer peripheral surface of the second pressure member without hindering rotation .   The plate-like member also covers an outer peripheral surface of the fixing belt corresponding to a boundary portion between the first pressurizing unit and the second pressurizing unit and excluding the nip portion. The fixing device according to claim 1, wherein the fixing device stands up in the outer diameter direction. An end portion in the width direction on the outer peripheral surface of the fixing belt stands up in the outer diameter direction so as to cover the outer peripheral surface excluding the nip portion at the end portion in the width direction of the fixing belt, and does not disturb the running of the fixing belt 3. The fixing device according to claim 1, further comprising a second plate-like member that blocks an inflow path of the foreign matter from the first portion to the center portion in the width direction .   The second plate-like member has an outer peripheral surface of the pressure rotator excluding the nip portion at the width direction end of the second pressure portion corresponding to the width direction end of the pressure rotator. The fixing device according to claim 3, wherein the fixing device stands up in an outer diameter direction so as to cover the fixing device.   The fixing device according to claim 3, wherein the second plate-shaped member is formed of a heat insulating material.   The fixing device according to claim 1, wherein the plate-like member is formed of a heat insulating material.   The fixing device according to claim 1, further comprising a second heating unit that heats the second pressure unit. A separation member for guiding the recording medium sent out from the nip portion to the fixing belt or / and the pressure rotator in a non-contact manner and leading to a conveyance path;
The separation member is configured such that a region in a width direction facing the fixing belt and / or the pressure rotator does not overlap a region in the width direction of the second pressure unit. The fixing device according to claim 1. The metal member is fixed so as to face the inner peripheral surface of the fixing belt at a position excluding the nip portion,
The reinforcing member according to any one of claims 1 to 8, further comprising a reinforcing member that is fixed to an inner peripheral surface side of the metal member and abuts on the fixing member to reinforce the fixing member. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

Images