JP7377453B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to a fixing device and an image forming apparatus.

Conventionally, a first rotary body is provided in an endless shape so as to be rotatable, and the first rotary body is rotatably provided and is configured to take two postures: a pressurizing posture in which the first rotary body is pressurized, and a non-pressurizing posture. a second rotating body, a nip forming member that contacts the second rotating body via the first rotating body and forms a nip portion with the second rotating body, and a nip forming member installed at both ends of the first rotating body. 2. Description of the Related Art A fixing device is known that includes a regulating member that regulates the rotational trajectory of a first rotating body and a heat source disposed on at least one of the first rotating body and the second rotating body.

Patent Document 1 discloses that the above-mentioned fixing device has a guide portion disposed at both ends of a fixing belt serving as a first rotating body in the direction of the rotation axis, regulating the rotation trajectory of the fixing belt, and serving as a regulating member for holding a nip forming member. A type with a flange is described. Each flange is formed with an opening, and one longitudinal end of the nip forming member is inserted into the opening of the flange disposed on one end, and the other longitudinal end of the nip forming member is inserted into the other end. The nip forming member is fixed by being inserted into the opening of the flange located on the end side.

However, in Patent Document 1, there is a risk that fixing failure may occur at both end portions of the image in the direction of the rotation axis.

In order to solve the above-mentioned problems, the present invention provides a first rotating body that is rotatably provided in an endless shape, a pressurizing posture that is rotatably provided and pressurizes the first rotating body, and a non-pressurizing posture that pressurizes the first rotating body. a second rotating body configured to take two postures; and a nip portion formed between the second rotating body and the second rotating body, the second rotating body being in contact with the second rotating body via the first rotating body. a nip forming member; a regulating member installed at both ends of the first rotating body to regulate a rotation trajectory of the first rotating body; and a heat source disposed on at least one of the first rotating body and the second rotating body. In the fixing device, the nip forming member is configured to be movable within a predetermined range with respect to the regulating member, and the nip forming member presses the second rotating body against the first rotating body. The nip forming member has a movement regulating member that regulates the movement of the nip forming member, and when the second rotating body is in the pressurizing posture, the nip forming member is in contact with the movement regulating member and the second rotating body in a non-contact state with respect to the regulating member. When the second rotating body is in the non-pressure position, it is held movably within a predetermined range by the regulating member and the movement regulating member, and the nip forming member is held by its own weight. The second rotating body is configured to move in the direction of the second rotating body, and is characterized in that movement due to its own weight is regulated by contacting the regulating member.

According to the present invention, it is possible to suppress the occurrence of fixing failure at both ends of the image in the axial direction.

FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. FIG. 2 is a schematic explanatory diagram of a fixing device. FIG. 3 is a perspective view showing a belt holding member, a nip forming member, and a reinforcing member. FIG. 4 is a schematic cross-sectional perspective view of the location indicated by the dashed-dotted line in FIG. 3; FIG. 3 is a schematic vertical cross-sectional view of the vicinity of the belt holding member 28. FIG. 3 is a schematic diagram showing a reinforcing member and a nip forming member. (a) is a diagram showing the positional relationship between the nip forming member and the belt holding member when the pressure roller is in the pressing position, and (b) is a diagram showing the nip forming member when the pressure roller is in the pressing position. It is a figure which shows the positional relationship between and a belt holding member. FIG. 7 is a diagram illustrating a case where the nip forming surface of the nip forming member is tilted at a predetermined angle θ with respect to the vertical direction so as to face downward. The figure which shows the structure which does not have an incorrect attachment prevention mechanism.

Hereinafter, one embodiment of an electrophotographic color printer (hereinafter referred to as printer 1) will be described as an image forming apparatus equipped with a fixing device to which the present invention is applied.
FIG. 1 is a schematic configuration diagram of a printer 1 according to this embodiment.
As shown in FIG. 1, printer 1 in this embodiment is a tandem color printer.
Four toner bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, and black) are removably (replaceably) installed in a bottle accommodating section 101 located above the printer main body.

An intermediate transfer unit 85 is arranged below the bottle accommodating section 101. Image forming sections 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, and black) are arranged in parallel to face the intermediate transfer belt 78 of the intermediate transfer unit 85. Each of the image forming units 4Y, 4M, 4C, and 4K is provided with a photosensitive drum 5Y, 5M, 5C, and 5K, respectively. Further, a charging section 75, a developing section 76, a cleaning section 77, a static eliminating section, etc. are arranged around each of the photoconductor drums 5Y, 5M, 5C, and 5K. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on each photoconductor drum 5Y, 5M, 5C, 5K, and each photoconductor drum 5Y, 5M, 5C, Images of each color will be formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotated clockwise in FIG. 1 by a drive motor. Then, at the position of the charging section 75, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K are uniformly charged (this is a charging process). Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser beam L emitted from the exposure section 3, and electrostatic latent images corresponding to each color are formed by exposure scanning at this position. (This is an exposure process.) Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach a position facing the developing section 76, where the electrostatic latent image is developed and a toner image of each color is formed (developing step ). Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and the primary transfer bias rollers 79Y, 79M, 79C, and 79K, and at this position, the surfaces of the photoreceptor drums 5Y, 5M, , 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer step). At this time, a small amount of untransferred toner remains on the photoreceptor drums 5Y, 5M, 5C, and 5K. Thereafter, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning section 77, and at this position, the untransferred toner remaining on the photoreceptor drums 5Y, 5M, 5C, and 5K is transferred to the cleaning section. It is mechanically recovered by a cleaning blade 77 (this is a cleaning process). Finally, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K reach a position facing the static eliminating section, and at this position, the residual potential on the photoreceptor drums 5Y, 5M, 5C, and 5K is removed.

In this way, a series of image forming processes performed on the photoreceptor drums 5Y, 5M, 5C, and 5K are completed. Thereafter, the toner images of each color formed on each photoreceptor drum through a 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, 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning section 80. , etc.

The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is moved endlessly in the direction of the arrow in FIG. 1 by the rotation of one roller 82. The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 between the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, to form primary transfer nips.

A transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 then travels in the direction of the arrow and sequentially passes through the primary transfer nip of each primary transfer bias roller 79Y, 79M, 79C, and 79K. In this way, the toner images of each color on the photoreceptor drums 5Y, 5M, 5C, and 5K are primarily transferred onto the intermediate transfer belt 78 in an overlapping manner. Thereafter, the intermediate transfer belt 78, onto which the toner images of each color have been superimposed and transferred, reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 and the secondary transfer roller 89 sandwich the intermediate transfer belt 78 between them to form a secondary transfer nip.

Then, the four-color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of this 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. After that, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning section 80 . At this position, untransferred toner on the intermediate transfer belt 78 is collected. In this way, the series of transfer processes performed on the intermediate transfer belt 78 is completed. Here, the recording medium P conveyed to the position of the secondary transfer nip is conveyed from the paper feed section 12 disposed below the printer 1 via a paper feed roller 97, a pair of registration rollers 98, etc. It is something.

A plurality of recording media P such as transfer paper are stored in the paper feed section 12 in a stacked manner. Then, when the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed toward between the rollers of the registration roller pair 98. The recording medium P conveyed to the registration roller pair 98 temporarily stops at the roller nip position of the registration roller pair 98 whose rotational drive has been stopped. 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 onto which the color image has been transferred at the secondary transfer nip position is conveyed to the fixing device 20 position.

Then, at this position, the color image transferred to the surface is fixed onto the recording medium P by heat and pressure from the fixing belt 21 and the pressure roller 31. Thereafter, the recording medium P passes between the rollers of the paper ejection roller pair 99 and is ejected out of the apparatus. The recording medium P discharged from the apparatus by the paper discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image. In this way, a series of image forming processes in the image forming apparatus are completed.

Next, referring to FIG. 2, the configuration and operation of the fixing device 20 installed in the printer 1 will be described in detail.
FIG. 2 is a schematic explanatory diagram of the fixing device 20.
As shown in FIG. 2, the fixing device 20 includes a fixing belt 21 which is a first rotating body and a belt member, a nip forming member 26, a heat transfer assisting member 27 which is a heat conducting member, a heating member 22, a reinforcing member 23, It is composed of a heater 25 (heat source), a pressure roller 31 which is a second rotating body and a pressure rotating body, a temperature sensor, a contact/separation mechanism 50, and the like.

The fixing belt 21 is a thin, flexible, endless belt that rotates (travels) in the direction of the arrow (counterclockwise) in FIG. The fixing belt 21 has a base material layer, an elastic layer, and a release layer laminated in this order from the inner peripheral surface side, and the total thickness thereof is set to 1 mm or less.

The base material layer of the fixing belt 21 has a layer thickness of 30 to 100 μm, and is made 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 made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing the elastic layer, minute irregularities are not formed on the surface of the fixing belt 21 at the nip portion, heat is uniformly transmitted to the toner image T on the recording medium P, and the generation of a citron skin image is suppressed.

The release layer of the fixing belt 21 has a layer thickness of 10 to 50 μm and is made of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES ( Polyether sulfide), etc. By providing the release layer, releasability (peelability) for the toner (toner image T) is ensured. Further, the diameter of the fixing belt 21 is set to be 15 to 120 mm. Note that in this embodiment, the diameter of the fixing belt 21 is set to about 30 mm.

Furthermore, guide portions 28a of a belt holding member 28 (FIG. 3) serving as regulating members are inserted into both ends of the fixing belt 21 in the width direction. ) and is rotatably held.

Further, the pressure roller 31 that comes into contact with the outer peripheral surface of the fixing belt 21 at the nip portion has a diameter of about 30 to 40 mm, and has an elastic layer 33 formed on a core bar 32 having a hollow structure. The elastic layer 33 of the pressure roller 31 is made of a material such as foamable silicone rubber, silicone rubber, or fluororubber. Note that a thin mold release layer made of PFA, PTFE, etc. can also be provided on the surface layer of the elastic layer 33. Pressure roller 31 presses against fixing belt 21 to form a desired nip between both members.

The nip forming member 26 is made of a heat-resistant resin material such as a liquid crystal polymer. By providing an elastic member such as silicone rubber or fluororubber between the nip forming member 26 and the fixing belt 21, the belt surface follows minute irregularities on the surface of the recording medium P at the nip portion, and the recording medium Heat is uniformly transmitted to the toner image T on P, which is effective in preventing yuzu skin images.

The nip forming member 26 has a concave cross-sectional shape so that the surface on the pressure roller 31 side follows the curvature of the pressure roller 31. As a result, since the recording medium P is sent out from the nip portion so as to follow the curvature of the pressure roller 31, problems such as the recording medium P being attracted to the fixing belt 21 after the fixing process and not being separated can be prevented. be able to.

In addition, in FIG. 2, the cross-sectional shape of the nip forming member 26 that forms the nip portion is formed into a concave shape, but the shape of the nip forming member 26 that forms the nip portion may be formed into a planar shape or continuous from a planar shape to a concave shape. It can also be formed so as to change depending on the situation. By setting the nip shape to an arbitrary shape, when the shape of the nip portion is substantially parallel to the image plane of the recording medium P, there is an effect of preventing wrinkles from occurring on the recording medium.

Moreover, by making the cross-sectional shape approximate to a concave shape, the adhesion between the fixing belt 21 and the recording medium becomes high, and the fixing performance is improved. Furthermore, since the curvature of the fixing belt 21 on the exit side of the nip section is increased, the recording medium sent out from the nip section can be easily separated from the fixing belt 21.

The heat transfer auxiliary member 27 is made of a member having higher thermal conductivity than the nip forming member 26, and is installed between the nip forming member 26 and the fixing belt 21. As a result, when a temperature deviation occurs in the fixing belt 21, heat transfer occurs by the heat transfer assisting member 27 to reduce the temperature deviation. Thereby, temperature deviation of the fixing belt 21 at the nip portion can be suppressed. Thereby, it is possible to suppress uneven gloss from occurring in the image on the recording medium. The heat transfer assisting member 27 is fixed to the nip forming member 26 and covers the surface of the nip forming member 26 that faces the inner circumferential surface of the fixing belt 21 .

Further, the heat transfer assisting member 27 is preferably made of metal, and is particularly preferably made of copper, aluminum, or silver, which have high thermal conductivity. Aluminum is particularly preferred because of its excellent cost and workability. By using metal as the heat transfer assisting member, it is possible to obtain the effect of reinforcing the strength of the nip forming member.

Furthermore, since the heat transfer auxiliary member 27 slides on the fixing belt 21, it is also possible to coat the surface with a material with good sliding properties such as PTFE in order to reduce torque and prevent wear of the fixing belt 21.

The heating member 22 is a pipe-shaped member with a wall thickness of 0.2 mm or less. As a material for the heating member 22, a metal thermal conductor (a metal with thermal conductivity) such as aluminum, iron, or stainless steel can be used. By setting the thickness of the heating member 22 to 0.2 mm or less, the heating efficiency of the fixing belt 21 (heating member 22) can be improved.

The heating member 22 is formed so as to be close to or in contact with the inner circumferential surface of the fixing belt 21 at a position other than the nip part, and at the nip part there is a recessed part formed internally in a concave shape and having an opening. It is provided.

Here, the gap A between the fixing belt 21 and the heating member 22 at room temperature (the gap at the position excluding the nip portion) is preferably greater than 0 mm and less than or equal to 1 mm (0 mm<A≦1 mm). . This prevents a problem in which the area of sliding contact between the heating member 22 and the fixing belt 21 becomes large and the wear of the fixing belt 21 accelerates, and also prevents the problem that the heating member 22 and the fixing belt 21 are too far apart and the fixing belt 21 is heated. It is possible to prevent problems that reduce efficiency.

Furthermore, by placing the heating member 22 close to the fixing belt 21, the circular posture of the flexible fixing belt 21 is maintained to some extent, so deterioration and damage due to deformation of the fixing belt 21 can be reduced. .

In order to reduce the sliding resistance between the heating member 22 and the fixing belt 21, the sliding surface of the heating member 22 may be formed of a material with a low coefficient of friction, or the inner peripheral surface 21a of the fixing belt 21 may contain fluorine. It is also possible to form a surface layer of the material. In FIG. 2, the heating member 22 is formed to have a substantially circular cross-sectional shape, but the heating member 22 may also be formed to have a polygonal cross-sectional shape.

In addition, if a means for uniformly transmitting heat from a heat source to the fixing belt 21 and ensuring running stability of the fixing belt 21 during driving is provided separately, the heating member 22 is not provided and the belt It is also possible to configure a fixing device that directly heats the image. In this case, since the heat capacity of the heating member 22 is excluded from the heat capacity of the entire fixing device, there is an advantage that the fixing device 20 can be configured with better temperature increase performance and energy saving performance.

Both longitudinal ends of the heating member 22 are fixedly supported by the side plates of the fixing device 20 . The heating member 22 is heated by radiant heat (radiant light) from a heater 25 serving as a heat source, and heats the fixing belt 21 . That is, the heating member 22 is directly heated by the heater 25 (heating means), and the fixing belt 21 is indirectly heated by the heater 25 via the heating member 22.
Note that the output control of the heater 25 is performed based on the detection result of the belt surface temperature by a temperature sensor such as a thermopile or thermistor that faces the surface of the fixing belt 21.

Further, by controlling the output of the heater 25 in this manner, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature. In this way, in the fixing device 20, the fixing belt 21 is heated almost entirely in the circumferential direction by the heating member 22, rather than only a part of the fixing belt 21 being heated locally. Even when the speed of the apparatus is increased, the fixing belt 21 is sufficiently heated and the occurrence of fixing defects can be suppressed.

Although a halogen heater is used as an example of the heater 25 in FIG. 2, the type of heat source is not limited to the halogen heater, and may be a fixing device having an induction heating type heat source, for example.

Further, the reinforcing member 23 is for reinforcing the nip forming member 26 that forms the nip portion, and is fixedly provided on the inner peripheral surface side of the fixing belt 21 . The reinforcing member 23 is formed so that its length in the longitudinal direction is equal to that of the nip forming member 26, and both ends of the reinforcing member 23 in the longitudinal direction are fixedly supported by the side plates of the fixing device 20. Since the reinforcing member 23 comes into contact with the pressure roller 31 via the nip formation member 26 and the fixing belt 21, the problem that the nip formation member 26 is greatly deformed by the pressure of the pressure roller 31 at the nip portion can be avoided. It's suppressed.
Note that, in order to satisfy the above-mentioned functions, the reinforcing member 23 is preferably formed of a metal material with high mechanical strength, such as stainless steel or iron.

If the heater 25 is a heat source that uses radiant heat, such as a halogen heater, a heat insulating member may be provided on part or all of the surface of the reinforcing member 23 that faces the heater 25, or BA treatment may be applied. It is also possible to perform mirror polishing treatment. Since the radiant heat directed from the heater 25 toward the reinforcing member 23 (heat that heats the reinforcing member 23) is used to heat the heating member 22, the heating efficiency of the fixing belt 21 (heating member 22) is further improved. Become.

A gear that meshes with a drive gear of a drive mechanism is installed on the pressure roller 31, and the pressure roller 31 is rotationally driven in the direction of the arrow (clockwise) in FIG. Further, both longitudinal ends of the pressure roller 31 are rotatably supported by the side plates of the fixing device 20 via bearings. Note that a heat source such as a halogen heater may be provided inside the pressure roller 31.

Furthermore, 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, so that the deflection occurring in the nip forming member 26 can be reduced. can be reduced. Furthermore, the heat insulation of the pressure roller 31 is improved, and the heat of the fixing belt 21 is less likely to move toward the pressure roller 31, so that the heating efficiency of the fixing belt 21 is improved.

Further, in FIG. 2, 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 may be formed to be smaller than the diameter of the pressure roller 31. can. In this case, since the curvature of the fixing belt 21 at the nip portion is smaller than the curvature of the pressure roller 31, the recording medium P sent out from the nip portion is likely to be separated from the fixing belt 21.

Further, the diameter of the fixing belt 21 can be formed to be larger than the diameter of the pressure roller 31; however, regardless of the relationship between the diameter of the fixing belt 21 and the diameter of the pressure roller 31, The heating member 22 is configured such that the pressing force does not act on the heating member 22.

Furthermore, the fixing device 20 is provided with a contact/separation mechanism 50 that brings the pressure roller 31 into contact with and separates from the fixing belt 21 . Specifically, the contact/separation mechanism 50 includes a pressure lever 51, an eccentric cam 52, a pressure spring 53, and the like.

The pressure lever 51 is rotatably supported by the side plate of the fixing device 20 around a support shaft 51a provided at one end. The center portion of the pressure lever 51 is in contact with a bearing of the pressure roller 31. The bearing of the pressure roller 31 is movably held in an elongated hole formed in the side plate.

Further, a pressure spring 53 is connected to the other end of the pressure lever 51, and an eccentric cam 52 is engaged with a retaining plate of the pressure spring 53. The eccentric cam 52 is configured to be rotatable by a drive motor.

With this configuration, the rotation of the eccentric cam 52 causes the pressure lever 51 to rotate about the support shaft 51a, and the pressure roller 31 to move in the direction of the broken line arrow in FIG. That is, during the normal fixing process, the eccentric cam 52 takes the position in the rotational direction as shown in FIG. 2, and the pressure roller 31 assumes the pressing position to press the fixing belt 21 to form a desired nip portion.

On the other hand, at times other than the normal fixing process (such as during jam removal or standby), the orientation of the eccentric cam 52 in the rotational direction rotates 180 degrees from the state shown in FIG. The roller 31 separates from the fixing belt 21 (or reduces the pressure on the fixing belt 21) and assumes a non-pressure position.

The normal operation of the fixing device 20 configured as described above will be briefly described below. When the power switch of the printer 1 is turned on, power is supplied to the heater 25 and rotational driving of the pressure roller 31 in the arrow direction in FIG. 2 is started. As a result, the fixing belt 21 is also driven (rotated) in the direction of the arrow in FIG. 2 due to the frictional force with the pressure roller 31.

Thereafter, the recording medium P is fed from the paper feeding section 12, and the unfixed color image is carried (transferred) onto the recording medium P at the position of the secondary transfer roller 89. The recording medium P carrying the unfixed image (toner image T) is guided by a guide plate and conveyed in the direction of arrow Y10 in FIG. sent.

Then, due to the heating by the fixing belt 21 heated by the heating member 22 (heater 25) and the pressing force between the nip forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31, toner is applied to the surface of the recording medium P. Image T is fixed. Thereafter, the recording medium P sent out from the nip portion is conveyed in the direction of arrow Y11.

FIG. 3 is a perspective view showing the belt holding member 28, the nip forming member 26, and the reinforcing member 23, and FIG. 4 is a schematic cross-sectional perspective view of the portion indicated by the dashed line A in FIG. 4(a) shows a state in which the fixing belt 21 is not assembled, and FIG. 4(b) shows a state in which the fixing belt 21 is assembled.
Belt holding members 28 disposed at both ends of the fixing belt 21 in the width direction have the same shape. The belt holding member 28 includes an attachment portion 28b that is attached to the side plate of the fixing device 20, and a guide portion 28a that faces one end of the inner peripheral surface of the fixing belt 21.

The guide portion 28a has a substantially cylindrical shape with a notch on the pressure roller side. The guide portion 28a has an outer diameter that is approximately the same as the inner diameter of the fixing belt 21, and has a length that extends a predetermined amount into the fixing belt 21 from both ends thereof. In other words, the guide portion 28a serves as a circumferential guide convex portion, and by being inserted into the end of the fixing belt 21 and sliding thereon, the guide portion 28a regulates the rotation locus of the fixing belt 21 and changes the cross-sectional shape of the fixing belt 21. maintain a circular shape.

Further, the belt holding member 28 has a flange portion 28c that extends outward from the guide portion 28a, has a linear shape on the pressure roller side, and has a substantially cylindrical shape on the other portion. A through hole 28e is provided at a location corresponding to the inside of the flange portion 28c of the attachment portion 28b, and the reinforcing member 23 and the heater 25 are attached to the side plate of the fixing device 20 by passing through the through hole 28e.

Further, a slip ring 29 that protects the end portion of the fixing belt 21 is rotatably held between the flange portion 28c and the guide portion 28a. The slip ring 29 faces the end of the fixing belt 21 and prevents the end of the fixing belt 21 from coming into direct contact with the end surface of the flange portion 28c when the fixing belt 21 shifts in the axial direction. The slip ring 29 rotates with the fixing belt 21 when the ends of the fixing belt 21 come into contact with each other, thereby suppressing wear and damage of the ends. Note that the slip ring 29 may be made of a material that has a smaller coefficient of friction with the fixing belt 21 than the flange portion 28c, so that the slip ring 29 does not rotate with the fixing belt 21 when it comes into contact with the end portion of the fixing belt 21. Even with such a configuration, it is possible to suppress wear and damage of the end portions of the fixing belt 21.

Further, the inner circumferential surface of the through hole 28e on the pressure roller side (also the inner circumferential surface of the flange portion 28c) has an erroneous attachment prevention protrusion 28d for suppressing erroneous attachment of the nip forming member 26. .

At both ends of the nip forming member 26 in the axial direction, holding portions 126 that are held by the belt holding member are provided. An erroneous attachment prevention groove 126a is formed in the center of the nip forming member 26 in the width direction at the end of the holding portion 126 on the one end side. On the other hand, the end of the holding portion 126 on the other end side is not provided with the erroneous attachment prevention groove 126a. With this configuration, if one axial end and the other end of the nip forming member are mistakenly inserted into the through hole 28e of the belt holding member, the erroneous attachment prevention protrusion 28d will be caught and the insertion will not be possible. On the other hand, when the nip forming member has one end in the axial direction and the other end correct, the erroneous attachment prevention protrusion 28d enters the erroneous attachment prevention groove 126a, and both ends of the nip formation member are inserted into the through holes 28e of the belt holding member. be done. This prevents incorrect assembly of the nip forming member.

In this embodiment, the lateral length of the erroneous attachment prevention groove 126a is sufficiently longer than the lateral length of the erroneous attachment prevention protrusion 28d, and after the nip forming member is assembled, the erroneous attachment prevention protrusion 28d is inserted into the erroneous attachment prevention groove. 126a.

FIG. 5 is a schematic vertical cross-sectional view of the belt holding member 28 and its vicinity.
As shown in FIG. 5, the holding portion 126 of the nip forming member 26 is inserted into the through hole 28e of the belt holding member 28 with a gap α. Thereby, the nip forming member 26 is held by the belt holding member 28 so as to be movable within the gap α in the thickness direction of the nip forming member 26 (also referred to as the pressing direction of the pressure roller).

FIG. 6 is a schematic diagram showing the reinforcing member 23 and the nip forming member 26. As shown in FIG.
As shown in FIG. 6, on the surface of the nip forming member 26 facing the reinforcing member 23, there is a protrusion group consisting of a plurality of protrusions 26a arranged in the longitudinal direction at predetermined intervals. They are arranged in two rows in the vertical direction of the page.

Two positioning members 123a and 123b for positioning the nip forming member 26 in the longitudinal direction are attached to the opposing surface of the reinforcing member 23 facing the nip forming member 26 at a predetermined interval in the longitudinal direction. . Each positioning member 123a, 123b has a positioning hole 124a, 124b through which the protrusion 26a passes.

The positioning member 123a on the left side of the figure is the main reference for positioning, and the shape of the positioning hole 124a is almost the same as the outer shape of the protrusion 26a. On the other hand, the positioning member 123b on the right side of the figure is a secondary reference for positioning, and the length of the positioning hole 124b in the longitudinal direction is longer than the length of the protrusion 26a in the longitudinal direction.

One of the plurality of protrusions 26a of the nip forming member 26 passes through the positioning hole 124a of one positioning member 123a, and the other one passes through the positioning hole 124b of the other positioning member 123b, so that the nip forming member 26 are positioned on the reinforcing member 23 in the longitudinal direction and the lateral direction. Furthermore, when the pressure roller 31 applies pressure, the plurality of protrusions 26a abut against the reinforcing member 23, so that the nip formation member 26 is compressed in the pressure direction of the pressure roller 31 (which is also the thickness direction of the nip formation member). is positioned.

In this way, by positioning the nip forming member 26 in the longitudinal direction and the lateral direction, the erroneous attachment prevention protrusion 28d of the belt holding member 28, which has entered the erroneous attachment prevention groove 126a of the nip formation member, 26 can be prevented from touching.

In this embodiment, as described above, the nip forming member 26 is held movably within a predetermined range (gap α) in the thickness direction. In this embodiment, even if the nip forming member 26 moves in the direction away from the reinforcing member 23 as much as possible, the protrusion 26a does not come out of the positioning hole. Specifically, the relationship of the amount of movement of the nip forming member 26 (gap α)<the amount of fitting of the protrusion into the positioning hole (β in the figure) is satisfied.

FIG. 7A is a diagram showing the positional relationship between the nip forming member 26 (holding portion 126) and the belt holding member 28 (inner circumferential surface of the through hole 28e) when the pressure roller 31 is in the pressing posture. , FIG. 7(b) is a diagram showing the positional relationship between the nip forming member 26 (holding portion 126) and the belt holding member 28 (inner circumferential surface of the through hole 28e) when the pressure roller 31 is in the pressure position. be.

As shown in FIG. 7A, when the pressure roller 31 forms a nip portion in a pressure posture, such as during warming up or during a fixing operation, the nip forming member 26 moves from the pressure roller 31 to the fixing belt 21. , a load is applied in the direction of the arrow in the figure via the heat transfer assisting member 27. As a result, the nip forming member 26 is pushed toward the reinforcing member 23 by the pressure roller 31, and the projection 26a (see FIG. 6) of the nip forming member 26 abuts against the reinforcing member 23, causing the reinforcing member 23 to act as a movement regulating member. This restricts the movement of the nip forming member 26 on the side opposite to the pressure roller side. As a result, when the pressure roller 31 is in the pressure posture, the nip forming member 26 is held between the reinforcing member 23 and the pressure roller 31, that is, the nip forming member 26 is held between the reinforcing member 23 and the pressure roller 31. held.

As is clear from FIG. 7A, the nip forming member 26 is pushed toward the reinforcing member 23 by the pressure roller 31, so that the holding portion 126 is separated from the inner peripheral surface of the through hole 28e of the belt holding member 28. (See gap α in the figure). As a result, the nip forming member 26 is out of contact with the belt holding member 28 during warm-up and fixing operations.

In a configuration in which the nip forming member 26 contacts the belt holding member 28 during warm-up or fixing operation, the heat accumulated in the nip forming member 26 moves to the belt holding member 28, and the temperature at the longitudinal end of the nip forming member 26 increases. may be lower than the center. As a result, there is a possibility that fixing failure may occur at both ends of the image on the recording medium in the width direction. In particular, in this embodiment, a heat transfer assisting member 27 is provided between the nip forming member 26 and the fixing belt 21 to assist in heat transfer in the longitudinal direction. As a result, the heat at the end of the fixing belt 21 is easily transferred to the belt holding member 28 by the heat transfer assisting member 27, and the temperature at the end of the fixing belt is likely to drop. As a result, poor fixing tends to occur at both ends of the image on the recording medium in the width direction.

On the other hand, in the present embodiment, during warming up and fixing operation, the nip forming member 26 is held between the reinforcing member 23 and the pressure roller 31 without contacting the belt holding member 28. . Thereby, it is possible to prevent the heat accumulated in the nip forming member 26 from moving to the belt holding member 28, and it is possible to suppress a decrease in temperature at both longitudinal ends of the nip forming member 26. Thereby, it is possible to suppress fixation failures at both ends in the width direction of the image on the recording medium. In particular, in the configuration in which the heat transfer assisting member 27 is disposed between the nip forming member 26 and the fixing belt 21 as in this embodiment, defective fixing at both widthwise ends of the image on the recording medium is effectively suppressed. can do.

Furthermore, in this embodiment, as described above, the heat transfer assisting member 27 fixed to the nip forming member 26 is made of metal. In this way, by composing the heat transfer assisting member 27 with metal, in addition to its original function of assisting the heat transfer in the width direction of the fixing belt 21 and making the temperature of the fixing belt in the width direction uniform, The forming member 26 can be reinforced. In this way, since the nip forming member 26 is reinforced by the heat transfer assisting member 27, sufficient strength against the load of the pressure roller 31 can be ensured.

On the other hand, as shown in FIG. 7(b), when the pressure roller 31 is in a non-pressing position and does not form a nip portion, such as during jam processing, the pressure roller 31 of the nip forming member 26 and the reinforcing member 23, and the nip forming member 26 is held by the belt holding member 28 and the reinforcing member 23 so as to be movable within a predetermined range in the pressing direction of the pressure roller (thickness direction of the nip forming member).

As described above, when the nip forming member 26 moves toward the pressure roller as shown by the arrow in the figure when the pressure roller 31 is in the non-pressing position, the holding portion 126 of the nip forming member 26 moves toward the belt holding member. It abuts against the inner circumferential surface of the through hole 28e, and its movement is restricted. This prevents the protrusion 26a (see FIG. 6) of the nip forming member 26 from slipping out of the positioning holes 124a, 124b (see FIG. 6) of the reinforcing member, and prevents the nip forming member 26 from falling off. .
Furthermore, in this embodiment, since the heat transfer assisting member 27 is fixed to the nip forming member 26, it is possible to prevent the heat transfer assisting member from falling off from the apparatus when the pressure roller 31 is in the non-pressing position.

FIG. 8 is a diagram illustrating a case where the nip forming surface of the nip forming member is inclined at a predetermined angle θ with respect to the vertical direction so as to face downward.
In the configuration shown in FIG. 8, when the pressure roller 31 is in the non-pressing position, the weight of the nip forming member 26 acts on the pressure roller 31 side. As a result, when the pressure roller is in the non-pressing position, the nip forming member 26 moves toward the pressure roller (in the direction away from the reinforcing member 23) due to its own weight. In particular, in the configuration in which the heat transfer assisting member 27 made of metal is fixed to the nip forming member 26, the nip forming member 26 is further affected by the weight of the heat transfer assisting member 27 in the configuration shown in FIG. Easy to move to the pressure roller side.

In this manner, the configuration of this embodiment described above is effective in the configuration in which the nip forming member 26 moves toward the pressure roller (in the direction away from the reinforcing member 23) due to its own weight when the pressure roller is in the non-pressing position. functions. Specifically, the inner circumferential surface of the through hole 28e, which is a part of the belt holding member 28 of this embodiment, is configured to face the nip forming member 26 (holding portion 126) from the pressure roller side, and the nip The configuration is such that movement of the forming member 26 on the pressure roller side is restricted.

In this way, when the pressure roller is in the non-pressure position, the nip forming member 26 (holding portion 126) that has moved toward the pressure roller due to its own weight is attached to the belt holding member 28 (inner peripheral surface of the through hole 28e). By restricting the movement of its own weight upon abutting, it is possible to reliably prevent the nip forming member 26 from falling off.

In addition, in the above description, the erroneous attachment prevention protrusion 28d is provided on the inner peripheral surface of the through hole 28e of the belt holding member 28, and the erroneous attachment prevention groove 126a is provided at the end of the nip forming member 26 to prevent the erroneous attachment of the nip forming member. However, as shown in FIG. 9, a structure in which the erroneous attachment prevention protrusion 28d and the erroneous attachment prevention groove 126a are not provided may be used.

What has been described above is just an example, and each of the following aspects has its own unique effects.
(Aspect 1)
A first rotating body such as the fixing belt 21 is provided in an endless and rotatable manner, and the first rotating body is rotatably provided so that it can take two postures: a pressurizing posture that pressurizes the first rotating body, and a non-pressurizing posture. a second rotating body such as a pressure roller 31 configured to have a nip forming member 26 that contacts the second rotating body via the first rotating body and forms a nip portion between the second rotating body and the second rotating body; A regulating member such as a belt holding member 28 installed at both ends of the first rotating body to regulate the rotational trajectory of the first rotating body, and a heater 25 or the like disposed on at least one of the first rotating body and the second rotating body. In the fixing device 20 having a heat source, the nip forming member 26 is held without contacting the regulating member when the second rotating body is in the pressurizing position.
In Patent Document 1, both longitudinal ends of the nip forming member are fixed to the regulating member, and both ends of the nip forming member are in contact with the regulating member during the fixing operation. Therefore, during the fixing operation, the heat stored in the nip forming member moves from each longitudinal end of the nip forming member to the regulating member, and the temperature at both ends of the nip forming member becomes lower than the temperature at the center. There is a risk of As a result, there is a possibility that poor fixing may occur at both ends of the image in the axial direction.
On the other hand, in aspect 1, when the second rotating body is in the pressurizing posture to pressurize the first rotating body, the nip forming member is held in a non-contact manner with respect to the regulating member. Thereby, during the fixing operation, it is possible to suppress the heat accumulated in the nip forming member from moving to the regulating member, and it is possible to suppress a decrease in temperature at both longitudinal ends of the nip forming member. Thereby, sufficient heat can be applied to both ends of the image on the recording medium passing through the nip in the axial direction, and it is possible to suppress defective fixing of the image at both ends.

(Aspect 2)
In aspect 1, the nip forming member 26 is configured to be movable within a predetermined range with respect to a regulating member such as the belt holding member 28, and the fixing belt of the second rotating body such as the pressure roller 31 of the nip forming member 26 is movable within a predetermined range. The nip forming member has a movement regulating member such as a reinforcing member 23 that regulates movement in the pressurizing direction with respect to the first rotating body such as 21, and the nip forming member is non-aligned with respect to the regulating member when the second rotating body is in the pressurizing posture. The movement regulating member and the second rotating body are held in contact with each other.
According to this, as described in the embodiment, when the second rotating body such as the pressure roller 31 is in the pressurizing posture, the nip forming member 26 and the regulating member such as the belt holding member 28 are in a non-contact state. can be kept.

(Aspect 3)
In the second aspect, when the second rotating body such as the pressure roller 31 is in the non-pressing position, the nip forming member 26 is moved within a predetermined range by a regulating member such as the belt holding member 28 and a movement regulating member such as the reinforcing member 23. is held movably.
According to this, as described in the embodiment, it is possible to prevent the nip forming member 26 from falling off from the device when the second rotating body is in the non-pressurizing position.

(Aspect 4)
In aspect 3, the nip forming member 26 is configured to move in the direction of the second rotating body such as the pressure roller 31 due to its own weight, and is prevented from moving due to its own weight by coming into contact with a regulating member such as the belt holding member 28. Regulated.
According to this, as explained using FIG. 8, movement of the nip forming member due to its own weight is regulated by the regulating member such as the belt holding member 28, and it is possible to prevent the nip forming member from falling off from the device due to its own weight. can.

(Aspect 5)
In any of the first to fourth embodiments, a heat conductive member such as a heat transfer auxiliary member 27 having higher thermal conductivity than the nip forming member 26 is provided between the nip forming member 26 and the first rotating body such as the fixing belt 21. Ta.
According to this, as described in the embodiment, heat transfer in the rotation axis direction of the first rotating body such as the fixing belt can be promoted by the heat transfer member such as the heat transfer assisting member 27, and the first rotating body The temperature distribution in the direction of the rotation axis can be made uniform.
In addition, in a configuration in which a heat conductive member is provided, as described in the embodiment, when the temperature of the axial end of the nip forming member 26 decreases, the heat conductive member transfers the heat of the axial end of the first rotating body. It is easy to move to the nip forming member, the temperature at the axial end of the first rotating body is likely to drop, and the image on the recording medium is likely to be poorly fixed at the axial end. However, in this embodiment, since the temperature drop at the axial end of the nip forming member 26 can be suppressed, it is possible to effectively prevent the fixing failure of the axial end of the image on the recording medium.

(Aspect 6)
In aspect 5, a heat conductive member such as the heat transfer assisting member 27 is fixed to the nip forming member 26.
According to this, as described in the embodiment, it is possible to prevent the heat transfer members such as the heat transfer assisting member 27 from falling off from the device.

(Aspect 7)
In aspect 5 or 6, the heat conductive member such as the heat transfer auxiliary member 27 is metal.
According to this, as described in the embodiment, the nip forming member 26 can be reinforced with the heat transfer assisting member.

(Aspect 8)
In an image forming apparatus including a toner image forming means such as an image forming section that forms a toner image on a recording medium using toner, and a fixing means that fixes the toner image on the recording medium, the fixing means may be any one of Aspects 1 to 1. 7. Use any of the fixing devices.
According to this, it is possible to form a good image in which fixing defects at the ends in the width direction of the image are suppressed.

20: Fixing device 21: Fixing belt 21a: Inner peripheral surface 22: Heating member 23: Reinforcing member 25: Heater 26: Nip forming member 26a: Protrusion 27: Heat transfer auxiliary member 28: Belt holding member 28a: Guide portion 28b: Attachment part 28c: Flange part 28d: Mis-installation prevention protrusion 28e: Through hole 29: Slip ring 31: Pressure roller 50: Contact/separation mechanism 123a: Positioning member 123b: Positioning member 124a: Positioning hole 124b: Positioning hole 126: Holding part 126a: Misinstallation prevention groove P: Recording medium T: Toner image α: Gap

Patent No. 5747502

Claims (5)

a first rotating body rotatably provided in an endless shape;
a second rotary body that is rotatably provided and configured to take two postures: a pressurizing posture that pressurizes the first rotary body and a non-pressurizing posture;
a nip forming member that abuts the second rotating body via the first rotating body and forms a nip portion with the second rotating body;
A fixing device including regulating members installed at both ends of the first rotating body to regulate a rotational trajectory of the first rotating body, and a heat source disposed on at least one of the first rotating body and the second rotating body. In ,
The nip forming member is configured to be movable within a predetermined range with respect to the regulating member,
a movement regulating member that regulates movement of the nip forming member in a pressing direction of the second rotating body with respect to the first rotating body;
The nip forming member is sandwiched between the movement regulating member and the second rotating body in a non-contact state with respect to the regulating member when the second rotating body is in the pressurizing posture, and When the rotating body is in the non-pressurized position, it is held movably within a predetermined range by the regulating member and the movement regulating member;
The nip forming member is configured to move in the direction of the second rotating body due to its own weight,
The fixing device is characterized in that movement due to its own weight is restricted by contacting the regulating member . The fixing device according to claim 1 ,
A fixing device characterized in that a heat conductive member having higher thermal conductivity than the nip forming member is provided between the nip forming member and the first rotating body. The fixing device according to claim 2 ,
A fixing device, wherein the heat conductive member is fixed to the nip forming member. The fixing device according to claim 2 or 3 ,
A fixing device characterized in that the heat conductive member is metal. a toner image forming means for forming a toner image on a recording medium using toner;
An image forming apparatus including a fixing means for fixing a toner image on a recording medium,
An image forming apparatus characterized in that the fixing device according to any one of claims 1 to 4 is used as a fixing means.

Images