JP5445836B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes an unfixed image on a recording medium to the recording medium, and an image forming apparatus including the fixing device.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine thereof, a fixing device that fixes a toner image transferred onto a recording sheet as a recording medium by heat and pressure is often used. This type of fixing device includes, for example, a fixing rotator that is heated by a heating element and a pressure rotator that pressurizes the fixing rotator, and a fixing nip formed by contacting these rotators with each other. By passing the recording paper, the unfixed toner image on the recording paper is fixed by heat and pressure.

  In recent years, there has been a demand for downsizing, energy saving, and speeding up of image forming apparatuses. Therefore, in the image forming apparatuses described in Patent Documents 1 and 2, for example, a thin cylindrical shape that can be elastically deformed as the fixing rotating body. The roller is used. As described above, the fixing rotating body is a thin cylindrical roller, so that the heat capacity is reduced, and the amount of heat required for warm-up can be reduced and the warm-up time can be shortened. Further, since the thin cylindrical roller is elastically deformed, the width of the fixing nip can be widened, and heat can be efficiently transmitted to the recording paper to increase the fixing speed.

  Further, as shown in FIG. 9, the fixing device described in Patent Documents 1 and 2 supports the roller 100 by attaching rotation support members 200 (rolling bearings) to the outer circumferences on both ends of the thin cylindrical roller 100. Is configured to do. On the other hand, as shown in FIG. 10, the fixing device described in Patent Document 3 disposes the rotation support member by disposing the rotation support members 300 on the inner peripheral surfaces on both ends of the thin cylindrical roller 100. The diameter can be reduced, and the device can be downsized.

  In the fixing devices described in Patent Documents 1 and 2, the pressure roller 400 is formed shorter than the fixing roller 100 in order to avoid interference between the pressure roller 400 and the rotation support member 200, as shown in FIG. ing. In this way, in the configuration in which the pressure roller 400 is shorter than the fixing roller 100, when both ends of the fixing roller 100 are pressed against the pressure roller 400 side by the spring 500, as shown in FIG. A rotational moment (F × L) due to the load F of the spring 500 is generated at the end portion of the fixing roller 100 that is separated from the portion by L in the axial direction. As a result, there is a problem that the fixing roller 100 is bent in the longitudinal direction, the deformation at the end of the fixing roller 100 is increased, the width of the fixing nip and the pressing force are nonuniform, and fixing unevenness occurs.

  In order to solve the above problem, in the fixing device described in Patent Document 2, as shown in FIG. 9, the length L2 of the pressure roller 400 is set to L2 / L1 = the width L1 between the holding member center positions. Setting in the range of 0.9 to 0.99 suppresses bending of the fixing roller in the longitudinal direction. However, even if the relationship between the length of the pressure roller and the width of the position between the holding member centers is set as described above, the above problem cannot be sufficiently solved depending on the rigidity (or diameter) and thickness of the fixing roller. There is.

  In the fixing device described in Patent Document 3 shown in FIG. 10, the rotation support member 300 is disposed on the inner peripheral surface of the end of the thin cylindrical roller 100 (fixing roller). The roller 100 cannot be elastically deformed at the position where is provided. Therefore, in this case, in order to secure a wide fixing nip, the pressure roller must be brought into contact only with the elastically deformable portion of the fixing roller. As a result, the length of the pressure roller is larger than the length of the fixing roller. Will also be shorter. For this reason, the fixing device described in Patent Document 3 also has a problem that the fixing roller bends in the longitudinal direction and fixing unevenness occurs as described above.

  Accordingly, in view of such circumstances, the present invention provides a fixing device that can prevent the occurrence of uneven fixing by suppressing the bending of the fixing nip forming member in the longitudinal direction, and an image forming apparatus including the fixing device. It is what.

According to the first aspect of the present invention, at least one fixing nip forming member of the two fixing nip forming portions is formed of an elastically deformable cylindrical elastic cylindrical body, and the fixing nip forming members are brought into contact with each other. In the fixing device for fixing the unfixed image on the recording medium by passing the recording medium through the fixing nip, the inner peripheral surfaces of both ends of the elastic cylindrical body are supported by supporting means via elastic members, respectively. The other fixing nip forming member is brought into contact with an outer peripheral surface extending from the elastic member disposition region on one end side of the elastic cylindrical body to the elastic member disposition region on the other end side, and the support member is A flange portion that contacts an end surface of the one fixing nip forming member to restrict axial movement of the fixing nip forming member, and positions of both ends of the other fixing nip forming member from the position of the flange portion. Also In which it arranged in inwardly.

  As described above, the other fixing nip forming member is brought into contact with the elastic member on one end of the fixing nip forming member from the region on which the elastic member on the other end is brought into contact. The supporting portions at both ends of the fixing nip forming member can be received by the other fixing nip forming member. Thereby, generation | occurrence | production of the rotational moment in the edge part of one fixing nip formation member can be suppressed, and it can suppress highly that the one fixing nip formation member bends over a longitudinal direction. As described above, according to the first aspect of the present invention, the width and pressure of the fixing nip can be made uniform over the longitudinal direction, and image fixing unevenness can be prevented.

  In addition, since the inner peripheral surfaces of both ends of the elastic cylindrical body are supported by the support means via the elastic members, the elastic cylindrical body can be elastically deformed also at both ends. For this reason, as described above, the other fixing nip forming member is brought into contact with the elastic member disposed on one end side of the one fixing nip forming member over the elastic member disposed on the other end side. However, it is possible to elastically deform one fixing nip forming member over the entire contacted area, and to secure a wide fixing nip in the recording medium conveyance direction.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, a recording medium passage area through which the recording medium passes is set in the area between the elastic members.

  The influence on the fixing of the image is different between the position where the elastic member is disposed in the elastic cylindrical body and the position where the elastic member is not disposed. Therefore, as described above, by setting the recording medium passage area within the area between the elastic members, it is possible to make the fixing conditions uniform and prevent the occurrence of uneven fixing.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the heat generating portion of the heating means for heating the elastic cylindrical body from the inside is larger than the recording medium passage region through which the recording medium passes. The elastic member is disposed in a range smaller than the area between the elastic members.

  By arranging the heat generating portion as described above, it is possible to suppress an excessive temperature rise of the elastic member and to efficiently supply heat to the recording medium.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the elastic member is formed in a ring shape that can be fitted to an inner peripheral surface of the elastic cylindrical body, and the support The means is interposed between the heat insulating member and the boss, a cylindrical heat insulating member that can be fitted to the inner peripheral surface of the elastic member, a boss that is provided on the side plate and that can be inserted into the heat insulating member. It is constituted by a rolling bearing.

  Since the elastic member is interposed between the elastic cylindrical body and the heat insulating member, one fixing nip forming member can be elastically deformed over the entire area where the fixing nip forming members are in contact with each other. Therefore, as described above, it is possible to highly suppress the fixing nip forming member from being bent in the longitudinal direction while ensuring a wide fixing nip. Further, by configuring the support means as described above, the side plate can be reduced in size and secured, and the thickness of the elastic cylindrical body can be easily reduced.

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the elastic member is disposed between the elastic cylindrical body and the heat insulating member in a state in which the elastic member is compressed in the radial direction.

  By arranging the elastic member between the elastic cylindrical body and the heat insulating member in a state compressed in the radial direction, the elastic cylindrical body and the heat insulating member can be assembled together, Replacement work is facilitated.

A sixth aspect of the present invention is the fixing device according to the fourth or fifth aspect, wherein the thermal expansion member has a linear expansion coefficient of 10 ⁻⁶ to 10 ⁻⁴ [/ ° C.].

  By setting the linear expansion coefficient of the heat insulating member as described above, the heat insulating member is thermally expanded during heating, and the fitted state between the heat insulating member and the rolling bearing is stabilized.

  According to a seventh aspect of the present invention, in the fixing device according to any one of the fourth to sixth aspects, the fit between the heat insulating member and the rolling bearing is an intermediate fit or a clearance fit at normal temperature, and during heating, Is an intermediate or interference fit due to thermal expansion of the heat insulating member.

  When the fitting between the heat insulating member and the rolling bearing is an intermediate fit or a clearance fit at normal temperature, the heat insulating member and the rolling bearing can be easily fitted. On the other hand, an intermediate or interference fit is caused by thermal expansion of the heat insulating member during heating, so that the fitted state between the heat insulating member and the rolling bearing is stabilized.

  According to an eighth aspect of the present invention, in the fixing device according to any one of the first to seventh aspects, when only one of the two fixing nip forming members is configured by the elastic cylindrical body, The fixing nip forming member is rotationally driven, and the one fixing nip forming member is driven to rotate with respect to the other fixing nip forming member.

  By rotating the fixing nip forming member formed of an elastic cylindrical body in a driven manner, the fixing nip forming member can receive a driving force over the entire area in contact with the other fixing nip forming member, and torsionally deform. It can rotate stably without doing.

  According to a ninth aspect of the present invention, in the fixing device according to any one of the first to eighth aspects, the unfixed image on the recording medium when viewed from the axial direction at a position where the two fixing nip forming members are in contact with each other. The fixing nip forming member disposed on the side in contact with the forming surface is configured to be deformed into a flat shape or a concave shape.

  By configuring the fixing nip forming member disposed on the side in contact with the unfixed image forming surface to be deformed into a flat shape or a concave shape, it is possible to improve the separation of the recording medium from the fixing nip forming member. . As a result, there is no need to provide separation means such as a separation claw or a separation plate for separating the recording medium from the fixing nip forming member, so that the apparatus can be reduced in size and cost.

  A tenth aspect of the present invention is an image forming apparatus including the fixing device according to any one of the first to ninth aspects.

  Since the image forming apparatus includes the fixing device according to any one of the first to ninth aspects, the above-described effects of these fixing devices can be obtained.

  According to the present invention, even if the fixing nip forming member is formed of an elastically deformable cylindrical elastic tubular body, the fixing nip forming member can be highly suppressed from being bent in the longitudinal direction. it can. Thereby, the width and pressure of the fixing nip can be made uniform in the longitudinal direction, and uneven fixing of the image can be prevented.

1 is a schematic configuration diagram of a color image forming apparatus according to an embodiment of the present invention. It is a schematic sectional view of a fixing device of a reference example . It is sectional drawing of the fixing roller and pressure roller in the arrangement | positioning area | region of an elastic member. It is sectional drawing of the fixing roller and pressure roller in the area | region between elastic members. It is a fitting dimension figure of the component of the fixing device of a reference example . FIG. 6 is an exploded perspective view of components of a fixing device of a reference example . It is a schematic cross-sectional view of a fixing device according to implementation embodiments of the present invention. A fitting dimensional diagram for components of a fixing device according to implementation embodiments of the present invention. It is a schematic block diagram of the conventional fixing device. It is a figure which shows the support structure of the fixing roller with which the other conventional fixing device is provided. FIG. 10 is a diagram for explaining a problem in a conventional fixing device.

FIG. 1 is a schematic configuration diagram showing a color image forming apparatus according to an embodiment of the present invention.
As shown in FIG. 1, an intermediate transfer device 1 is disposed at the center of the color image forming apparatus. Around the intermediate transfer device 1, a photosensitive device 2, a transfer device 3, a sheet peeling means 4, and an intermediate transfer device cleaning means 5 are arranged. Further, a charger 6, a photosensitive member cleaning unit 7, and a residual image removing unit 8 are disposed around the photosensitive device 2. In this embodiment, developing devices 9K, 9Y, 9M, and 9C enclosing toners, which are finely colored powders of four different colors, are arranged in an overlapping manner, below which are exposure means 10 and further below that. A paper holding means 11 for storing recording paper as a recording medium and a paper supply device 12 are arranged. Above the color image forming apparatus, a fixing device 20 and a paper discharge device 13 are arranged.

  In the color image forming apparatus having such a configuration, the charger 6 charges the surface of the photosensitive device 2 uniformly. Next, image and character information by a personal computer, an image scanner or the like is transferred by exposing in dot units by the exposure means 10, and an electrostatic latent image is formed on the surface of the photosensitive device 2. Thereafter, toner is supplied to the electrostatic latent image by the developing devices 9K, 9Y, 9M, and 9C, whereby the electrostatic latent image is visualized (developed) as a toner image and conveyed to the first transfer position T1. At the first transfer position T1, the toner image is transferred to the surface of the intermediate transfer device 1 due to a potential difference between the photosensitive device 2 and the intermediate transfer device 1 supplied from a power source (not shown). After passing through the first transfer position T1, the surface of the photosensitive device 2 is lowered to a certain potential or less by light irradiation by the afterimage removing means 8, and the electrostatic latent image is erased. The remaining toner remaining on the surface that is not transferred at the transfer position T1 is cleaned, and the next toner image can be formed. By performing the above steps in each of the developing devices 9K to 9C, a toner image corresponding to image and character information is formed on the surface of the intermediate transfer device 1. Thereafter, the toner image is transferred to the recording paper supplied from the paper holding means 11 by the paper supply device 12 by the transfer device 3 at the second transfer position T2. The recording paper to which the toner image has been transferred is peeled off from the intermediate transfer device 1 by the paper peeling means 4, carried to the fixing device 20, the toner image is fixed on the recording paper, and discharged by the paper discharge device 13.

  The above description is an image forming operation when a full color image is formed on a recording sheet. A single color toner image is formed by using any one of the four developing devices 9K, 9Y, 9M, and 9C. It is also possible to form a two-color or three-color toner image using two or three developing devices.

Next, a reference example and a fixing device according to an embodiment of the present invention will be described with reference to FIGS. 2-8, the same code | symbol shows the same member or part.

As shown in FIG. 2, the fixing device 20 of the reference example includes a fixing roller 21 as a fixing member, a pressure roller 22 as a pressure member, and a pressure as an urging unit that urges the pressure roller 22. A spring 23 and a heater 24 as heating means for heating the fixing roller 21 are provided.

The fixing roller 21 is formed of a cylindrical elastic cylindrical body that can be elastically deformed. Specifically, the fixing roller 21 is coated with an elastically deformable thin cylindrical core metal 21a (metal base), an elastic layer 21b coated on the outer periphery of the core metal 21a, and an outer periphery of the elastic layer 21b. It is comprised by the mold release layer (illustration omitted). Here, a straight thin stainless steel pipe having an outer diameter of 45.3 mm, a thickness of 150 μm, and a length of 240 mm is used as the core metal 21a. The elastic layer 21b is a silicone elastic layer having a thickness of 0.5 mm and a JIS hardness of 20 degrees, and the release layer is PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) having a thickness of 30 μm. In addition, each said member which forms the metal core 21a, the elastic layer 21b, and a mold release layer is an example, and is not limited to this example .

The pressure roller 22 has a metal core 22a having an outer diameter of φ24 mm. An outer peripheral surface of the cored bar 22a is covered with an elastic layer 22b made of silicone rubber having a rubber hardness of 40 degrees and a thickness of 2 mm. Further, the outer peripheral surface of the elastic layer 22b is covered with a release layer (not shown) made of PFA having a thickness of 30 μm. The configuration of the pressure roller 22 is not limited to the example given here.

  As shown in FIG. 2, both ends of the shaft provided on the pressure roller 22 are rotatably supported by a rolling bearing 25. One end of a pressure spring 23 is attached to the rolling bearing 25, and the pressure roller 22 is urged toward the fixing roller 21 by the pressure spring 23 so that the pressure roller 22 and the fixing roller 21 are at a predetermined pressure. They are in contact with each other. A driving gear 26 is attached to one end of a shaft provided on the pressure roller 22, and a rotational driving force from a motor (not shown) is transmitted to the pressure roller 22 by the driving gear 26.

On the other hand, the fixing roller 21 is configured to be rotated by a rotating pressure roller 22. If the fixing roller 21 is rotated by applying a driving force to one end of the fixing roller 21, the fixing roller 21 formed of a thin elastic cylindrical body may be twisted and deformed to be unstable. Therefore, in this reference example , by rotating the fixing roller 21 with respect to the pressure roller 22, the fixing roller 21 can receive a driving force over the entire area in contact with the pressure roller 22 and twist. It can rotate stably without deformation.

  The heater 24 is disposed inside the fixing roller 21, and the fixing roller 21 is heated from the inner surface by the heater 24. Around the fixing roller 21, a thermistor (not shown) that detects the surface temperature of the fixing roller 21 to control the heat generation of the heater 24, and a thermostat (not shown) for detecting an abnormal temperature of the fixing roller 21. Is arranged.

The fixing roller support means will be described with reference to FIG.
The fixing roller support means includes a double-cylindrical heat insulating member 27 disposed inside both ends of the fixing roller 21, a cylindrical boss 29 formed integrally with the side plate 28, and a rolling bearing 30. And have. The boss 29 is inserted between the outer cylinder and the inner cylinder of the heat insulating member 27. Further, a rolling bearing 30 is interposed between the heat insulating member 27 and the boss 29, whereby the heat insulating member 27 is configured to be rotatable with respect to the boss 29.

Here, the rolling bearing 30 is a single-row deep groove bearing having an outer diameter of the outer ring 30a of 32 mm, an inner diameter of the inner ring 30b of 25 mm, and a nominal symbol 6705. The outer diameter of the boss 29 is formed to be φ25 mm so as to be fitted to the inner ring 30 b of the rolling bearing 30. Further, the side plate 28 is a steel plate having a thickness of 1.2 mm, and is provided in a fixing device main body (not shown). The outer ring 30 a of the rolling bearing 30 is fitted to the inner peripheral surface of the outer cylinder of the heat insulating member 27. The cylinder inside the heat insulating member 27 is inserted into the boss 29, and the end of the heater 24 is inserted into the cylinder inside the heat insulating member 27. In addition, the dimension of each said member is an example, and is not limited to this example .

A ring-shaped elastic body 31 is disposed on the outer peripheral surface of the boss 29. The elastic body 31 is disposed so as to be compressed to some extent in the axial direction of the fixing roller 21 and to contact the inner ring 30 b of the rolling bearing 30 and the side plate 28. That is, the rolling bearing 30 is positioned in the axial direction by the elastic body 31, and further absorbs the thermal expansion in the axial direction of the heat insulating member 27 and the fixing roller 21 by compressive deformation of the heat insulating member 27 and the fixing roller 21 at high temperatures. It is the composition to do. In this reference example , a corrugated ring made of SUS304-WPB is used as the elastic body 31, but a ring made of a heat-resistant rubber material may be used.

In the present reference example , the fixing roller supporting means is configured as described above, so that there is an advantage that the side plate of the fixing device can be downsized and the strength can be ensured. For example, as shown in FIG. 9, when the outer peripheral surface of the fixing roller is configured to be received by the inner ring of the rolling bearing, the diameter of the bearing is increased, and the outer ring of the rolling bearing is fitted to the side plate. A hole of the same size as the outer ring is required. For this reason, there is a limit to downsizing the side plate from the viewpoint of reinforcing the strength of the side plate. On the other hand, in this reference example , as shown in FIG. 2, the side plate 28 may be provided with a boss 29 having the same outer diameter as the inner diameter of the inner ring 30b of the rolling bearing 30 and a hole through which the heater 24 passes. 28 is advantageous in terms of downsizing and ensuring strength. Further, in this reference example , it is easy to reduce the thickness of the cored bar, and as a result, there is an advantage that the warm-up time can be shortened.

Further, in this reference example , a ring-shaped elastic member 40 is interposed between the inner peripheral surface of the fixing roller 21 and the outer peripheral surface of the heat insulating member 27. Here, silicone rubber having a width of 15 mm and a JIS hardness of 20 degrees is used as the elastic member 40, but is not limited thereto. In this reference example , the elastic member 40 is fitted to the inner peripheral surface of the end portion of the fixing roller 21, and the outer peripheral surface of the elastic member 40 and the inner peripheral surface of the fixing roller 21 are bonded. On the other hand, the elastic member 40 and the heat insulating member 27 are merely fitted to each other and are not bonded. In this case, if the elastic member 40 and the heat insulating member 27 move relative to each other in the axial direction and are separated from each other, the fixing roller 21 may fall off the heat insulating member 27. Therefore, a flange portion 27 a that contacts the end surface of the elastic member 40 is provided on the outer peripheral surface of the heat insulating member 27, and the axial movement of the elastic member 40 is restricted to prevent the fixing roller 21 from falling off.

In the fixing roller 21, a region where the elastic members 40 at both ends are disposed is referred to as “elastic member disposition region W”, and a region between the elastic members 40 is referred to as “interelastic member region X”. The pressure roller 22 is in contact with both outer peripheral surfaces of the elastic member arrangement region W of the fixing roller 21 and the region X between the elastic members. In other words, the pressure roller 22 is in contact with the outer peripheral surface of the fixing roller 21 extending from the elastic member arrangement region W on one end side to the elastic member arrangement region W on the other end side. In this reference example , the axial length of the pressure roller 22 is set to be substantially the same as the axial length of the fixing roller 21, and each of the rollers 21 and 22 extends over the entire area in the axial direction. In contact.

3 is a cross-sectional view of the fixing roller 21 and the pressure roller 22 in the elastic member arrangement region W shown in FIG.
As shown in FIG. 3, the pressure roller 22 is in contact with the fixing roller 21 under the urging force of the pressure spring, and a fixing nip h is formed at the contact point. In this reference example , the rigidity of the fixing roller 21 and the rubber hardness of the elastic member 40 are set to be smaller than the rubber hardness of the elastic layer 22 b of the pressure roller 22. Therefore, due to the pressing force F from the pressure roller 22, the fixing roller 21 is elastically deformed into a concave shape with a compression deformation amount δ (in the recording paper conveyance direction) when viewed from the axial direction with respect to the pressure roller 22. The member 40 is similarly compressed and deformed into a concave shape.

4 is a cross-sectional view of the fixing roller 21 and the pressure roller 22 in the region X between the elastic members shown in FIG.
Also in FIG. 4, the pressure roller 22 is in contact with the fixing roller 21 by the pressure spring, and a fixing nip hf is formed at the contact point. Further, the fixing roller 21 is elastically deformed into a concave shape (in the conveyance direction of the recording paper) by a compression deformation amount δ ′ when viewed from the axial direction by receiving the pressing force f from the pressure roller 22.

When performing fixing of images starts heating of the heater 24 in the fixing roller 21, to heat the fixing roller 21. Further, a control means (not shown) is controlled so as to switch on / off the heat generation of the heater 24 based on the surface temperature of the fixing roller 21 detected by the thermistor so that the surface temperature of the fixing roller 21 becomes a predetermined temperature. The Next, as shown in FIG. 3 or FIG. 4, the pressure roller 22 is rotationally driven in the direction of the arrow A in the drawing, and the fixing roller 21 is driven to rotate in the direction of the arrow B in the drawing. Then, the recording paper P on which the unfixed toner image t is transferred is passed through the fixing nip. At this time, the toner on the recording paper P is melted by the heat from the fixing roller 21, and the toner image is fixed on the recording paper P.

  Since the fixing roller 21 is configured to be elastically deformable, it is possible to ensure a wide fixing nip in the recording sheet conveyance direction by contact with the pressure roller 22. Therefore, the heat from the heater 24 can be effectively applied to the recording paper, and the fixing speed can be increased. Further, since the fixing roller 21 is formed thin, the heat capacity is small, and the amount of heat required for warm-up can be reduced and the warm-up time can be shortened.

In this reference example , as shown in FIG. 3 or 4, the fixing roller 21 is elastically deformed so as to be concave with respect to the pressure roller 22, and the recording paper P is moved along the surface of the pressure roller 22. At the same time, it is discharged in the direction of arrow C in the figure. Thereby, the recording paper P is prevented from sticking or winding around the fixing roller 21, and the self-strip property for separating the recording paper P from the fixing roller 21 is ensured. Further, it is not necessary to provide separation means such as a separation claw or a separation plate for separating the recording paper from the fixing roller, so that the apparatus can be reduced in size and cost. In addition to elastically deforming the fixing roller into a concave shape, it is possible to easily separate the recording paper from the fixing roller even when the fixing roller is elastically deformed into a flat shape.

  As shown in FIG. 2, the sheet passing area Lp (recording medium passing area) through which the recording sheet passes is set in the area X between the elastic members. This is because the heat transfer rate from the heater 24 and the pressure when contacting the pressure roller 22 are different between the position where the elastic member 40 is disposed and the position where the elastic member 40 is not disposed on the surface of the fixing roller 21. This is because there is a difference in influence. Therefore, by setting the sheet passing region Lp in the region excluding the elastic member disposition region W (in the region X between the elastic members), the heat of the heater 24 is efficiently and evenly applied to the recording paper. The pressure by the pressure roller 22 can be uniformly applied, and a high-quality image without fixing unevenness can be provided.

  In FIG. 2, the heat generating portion Lh (heat generation length) of the heater 24 is disposed in a range larger than the sheet passing region Lp and smaller than the inter-region X of the elastic member. By setting the arrangement area of the heat generating portion Lh in this way, it is possible to suppress an excessive temperature rise of the heat insulating member 27 and the elastic member 40 and to efficiently supply heat to the recording paper.

Hereinafter, the fitting dimensions of the fixing roller, the heat insulating member, the rolling bearing, and the boss of the side plate according to this reference example will be described with reference to FIG.
FIG. 5 shows inner and outer diameters of the fixing roller 21, the elastic member 40, the heat insulating member 27, the rolling bearing 30, and the boss 29 of the side plate 28. The inner diameter of the cored bar 21 a of the fixing roller 21 is d4 and the fixing roller 21. The inner diameter of the ring-shaped elastic member 40 bonded to the inner peripheral surface of the cylindrical member is D4, the inner and outer diameters of the outer cylinder of the heat insulating member 27 are D3 and d3, the inner and outer diameters of the rolling bearing 30 are D2 and d2, and the outer diameter of the boss 29 is. Is d1.

First, the relationship between the inner diameter D2 of the rolling bearing 30 and the outer diameter d1 of the boss 29 will be described. The materials of the rolling bearing 30 and the boss 29 are high carbon chrome bearing steel SUJ2 (JIS G 4805) and cold rolled steel plate SPCC (JIS G 3141), respectively, and have the same linear expansion coefficient. There is almost no difference due to thermal expansion in time. In this reference example , the rolling bearing 30 has a structure in which the inner ring 30b is fixed to the boss 29 and receives a radial load. Therefore, it is desirable that D2 and d1 be fitted by intermediate or interference fit. In this reference example , an intermediate fit is used in consideration of assembly.

Next, the inner and outer diameters D3 and d3 of the heat insulating member 27 will be described. The heat insulating member 27 must also take into account dimensional changes due to thermal expansion at high temperatures. That is, at a high temperature, the outer diameter d2 of the rolling bearing 30 becomes larger due to the thermal expansion of the heat insulating member 27. Furthermore, it is desirable that the heat insulating member 27 and the rolling bearing 30 be intermediate or tight fit at high temperatures, and at the normal temperature, each should be in the middle or clear fit to facilitate assembly. Is desirable. Therefore, in this reference example , the linear expansion coefficient of the heat insulating member 27 is in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻⁴ [/ ° C.], preferably 5 × 10 ^{−6 to} 5 × 10 ⁻⁵ [/ ° C. ] Is desirable. Therefore, in this reference example , considering the above heat resistance and low thermal conductivity, PPS (polyphenylene sulfide) manufactured by Toray Industries, Inc. whose linear expansion coefficient is 2.3 × 10 ⁻⁵ [/ ° C.] in the resin flow direction. ) Resin, model A504 is adopted.

  Furthermore, the fitting of the inner diameter D4 of the elastic member 40 and the heat insulating member 27 will be described. The inner diameter D4 of the heat insulating member 27 is smaller than the outer diameter d3 of the heat insulating member 27, and the elastic member 40 is compressed and deformed in the outer diameter direction to be fitted to the heat insulating member 27. The heat insulating member 27 has a flange portion 27a set to an outer diameter T3 larger than the outer diameter d3 of the outer cylinder. The flange portion 27a abuts against the end surface of the elastic member 40, so that the fixing roller 21 is prevented from being offset in the axial direction.

The assembly / disassembly property in this reference example will be described. FIG. 6 is an exploded perspective view of this reference example . First, the side plate bumi 42 in which the inner ring of the rolling bearing 30 is fitted and fixed to the outer diameter of the boss 29 of the side plate 28 via the elastic body 31 by an intermediate fit is formed. On the other hand, the elastic member 40 bonded to the inner surface of the fixing roller 21 is compressed and deformed to form the fixing roller bumi 41 in which the heat insulating member 27 is fitted by interference fit. Next, the outer diameter of the rolling bearing 30 in the side plate bumi 42 and the inner diameter of the outer cylinder of the heat insulating member 27 in the fixing roller bumi 41 are fitted by intermediate fitting or clearance fitting to form a fixing device. According to this structure, since the fixing roller bumi 41 fitted with the heat insulating member 27 can be easily disassembled, even if the fixing roller 21 has reached the end of its life due to scratches on the surface or a decrease in releasability from the toner, If only the fixing roller Bumi 41 is replaced without replacing all the fixing devices, other components can be reused.

Figure 7 shows an implementation form of the fixing device according to the present invention.
In the reference example shown in FIG. 2, the elastic members 40 are bonded to the inner peripheral surfaces on both ends of the fixing roller 21, and the heat insulating member 27 is fitted to the elastic members 40, but the embodiment shown in FIG. 7 is used. Then, the elastic member 40 is fitted to the inner peripheral surface of the fixing roller 21 without being bonded, and is bonded to the outer peripheral surface of the heat insulating member 27. In this case, since the elastic member 40 and the fixing roller 21 are not bonded, it is conceivable that the fixing roller 21 falls off when the elastic member 40 moves relative to the fixing roller 21 in the axial direction and separates from each other. . Therefore, in this embodiment, as shown in FIG. 7, the flange portion 27 a provided on the outer peripheral surface of the heat insulating member 27 is disposed to a position where it abuts on the end surface of the fixing roller 21, and the fixing roller 21 is moved in the axial direction. It is regulated and prevented from falling out. Further, as shown in FIG. 7, the pressure roller 22 is formed shorter than the fixing roller 21 by a dimension G. As a result, the fixing roller 21 can be prevented from interfering with the flange portion 27a protruding from the outer peripheral surface of the fixing roller 21, and the fixing roller 21 is driven to rotate stably.

  Based on FIG. 8, the fitting of the inner diameter d4 of the fixing roller 21 and the outer diameter d3 of the elastic member 40 in the embodiment shown in FIG. 7 will be described. The outer diameter d3 of the elastic member 40 is larger than the inner diameter d4 of the fixing roller 21, and the heat insulating member 27 is fitted to the fixing roller 21 by the elastic member 40 being compressed and deformed in the inner diameter direction. Further, the outer diameter T3 of the flange portion 27a provided on the heat insulating member 27 is at least larger than the inner diameter d4 of the fixing roller 21, and the flange portion 27a contacts the end surface of the fixing roller 21 in the axial direction of the fixing roller 21. It has a configuration that prevents displacement.

  The fixing device shown in FIGS. 7 and 8 is the same as the configuration of the fixing device shown in FIGS. 2 to 6 except for the configuration described above.

  As described above, in the fixing device according to the present invention, the pressure roller is brought into contact with the elastic member disposed on one end side of the fixing roller over the elastic member disposed on the other end side. Support points at both ends of the fixing roller can be received by the pressure roller. Thereby, generation | occurrence | production of the rotational moment in the edge part of a fixing roller can be suppressed, and it can suppress highly that a fixing roller bends over a longitudinal direction (or axial direction). As described above, according to the present invention, the width and pressure of the fixing nip can be made uniform in the longitudinal direction, and uneven rotation of the fixing roller and uneven fixing of the image can be prevented.

  Further, since the inner peripheral surfaces of both ends of the fixing roller are supported by the supporting means via the elastic members, the fixing roller can be elastically deformed also at both ends (see FIG. 3). For this reason, as described above, even when the pressure roller is brought into contact with the elastic member on the one end side of the fixing roller from the region on which the elastic member is arranged on the other end side, the entire area where the pressure roller comes into contact. Thus, the fixing roller can be elastically deformed, and the fixing nip can be secured widely in the recording sheet conveyance direction. Accordingly, heat from the heater can be effectively applied to the recording paper, and the fixing speed can be increased.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. In the above-described embodiment, the configuration of the present invention has been described by taking, as an example, the case where the fixing roller is formed of an elastic cylindrical body among the fixing roller and the pressure roller as the fixing nip forming member. The configuration of the present invention is applicable when at least one of the fixing nip forming members is formed of an elastic cylindrical body. For example, when the pressure roller as the fixing nip forming member is formed of an elastic cylindrical body, the inner peripheral surfaces on both ends of the pressure roller can be supported by the support means via the elastic member, respectively. It is. Further, the fixing device of the present invention can be mounted not only on the color image forming apparatus shown in FIG. 1 but also on a monochrome image forming apparatus, other copiers, printers, facsimiles, or complex machines thereof. It is.

20 Fixing device 21 Fixing roller (fixing nip forming member)
22 Pressure roller (fixing nip forming member)
27 Heat insulating member 28 Side plate 29 Boss 30 Rolling bearing 40 Elastic member Lp Paper passing area (recording medium passing area)
W Area of elastic member X Area between elastic members

Japanese Patent No. 3738615 JP 2001-201969 A Japanese Patent No. 4217872

Claims (10)

Of the two fixing nip forming portions, at least one fixing nip forming member is formed of an elastically deformable cylindrical cylindrical body, and a recording medium is placed in the fixing nip formed by bringing the fixing nip forming members into contact with each other. In a fixing device that passes and fixes an unfixed image on the recording medium,
The inner peripheral surfaces on both ends of the elastic cylindrical body are supported by supporting means via elastic members,
The other fixing nip forming member is brought into contact with the outer peripheral surface extending from the elastic member disposition region on one end side of the elastic cylindrical body to the elastic member disposition region on the other end side ,
The support member has a flange portion that abuts against an end surface of the one fixing nip forming member and restricts movement of the fixing nip forming member in the axial direction;
A fixing device characterized in that both end positions of the other fixing nip forming member are arranged inward in the axial direction from the position of the flange portion .   The fixing device according to claim 1, wherein a recording medium passage region through which a recording medium passes is set in a region between the elastic members.   The heating unit of the heating means for heating the elastic cylindrical body from the inside is disposed in a range larger than a recording medium passage region through which a recording medium passes and smaller than a region between the elastic members. 3. The fixing device according to 2. The elastic member is configured in a ring shape that can be fitted to the inner peripheral surface of the elastic cylindrical body,
The support means includes a cylindrical heat insulating member that can be fitted to the inner peripheral surface of the elastic member, a boss that is provided on a side plate and can be inserted into the heat insulating member, and between the heat insulating member and the boss. The fixing device according to claim 1, wherein the fixing device is configured by an interposed rolling bearing.   The fixing device according to claim 4, wherein the fixing member is disposed between the elastic cylindrical body and the heat insulating member in a state where the elastic member is compressed in a radial direction. The fixing device according to claim 4, wherein a linear expansion coefficient of the heat insulating member is 10 ⁻⁶ to 10 ⁻⁴ [/ ° C.].   7. The fit between the heat insulating member and the rolling bearing is an intermediate fit or a clearance fit at normal temperature, and is an intermediate fit or an interference fit due to thermal expansion of the heat insulating member at the time of heating. The fixing device according to Item.   When only one of the two fixing nip forming members is formed of the elastic cylindrical body, the other fixing nip forming member is driven to rotate, and the one fixing nip forming member is used as the other fixing nip forming member. The fixing device according to claim 1, wherein the fixing device is configured to be driven and rotated with respect to the fixing device.   When the two fixing nip forming members are in contact with each other, the fixing nip forming member disposed on the side of the recording medium in contact with the unfixed image forming surface is deformed into a flat shape or a concave shape when viewed from the axial direction. The fixing device according to claim 1, configured as described above.   An image forming apparatus comprising the fixing device according to claim 1.

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