Fixing device and image forming apparatus

Abstract

To reduce the likelihood of the generation of abnormal noise.SOLUTION: A fixing device is provided with: a fixing roller 21 (fixing rotating body) that is heated by a heater 25 (heating means) and heats a toner image T to fix the toner image to a surface of a sheet P, and is provided with a shank 21x at the ends in a rotation axis direction; and a pressure roller 31 (pressure rotating body) that is in pressure contact with the fixing roller 21 to form a nip part where the sheet P is conveyed. The fixing device is provided with: a bearing member 50 that has an inner diameter part 50b into which the shank 21x of the fixing roller 21 is inserted, is formed, on the inner diameter part 50b, with projections 50b1 (drive transmission target parts) to which drive is transmitted from groove parts 21x1 (drive transmission parts) of the shank 21x, and rotates together with the fixing roller 21. The fixing device is further provided with a housing 40 that is provided with a circular hole part 40a (holding part) in which the bearing member 50 is rotatably held.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a fixing device that heats a toner image to fix it on the surface of a sheet, and to an image forming apparatus that includes the fixing device, such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] Conventionally, in a fixing device of an image forming apparatus such as a copier or a printer, a technique of rotatably holding a shaft portion of a fixing rotor (fixing roller) via a bearing in a housing thereof has been widely known (see, for example, Patent Document 1).

[0003] Specifically, in the fixing device, a pressure roller (pressure rotating member) is pressed against a fixing roller (fixing rotating member), forming a nip portion (fixing nip) through which a sheet (paper) is transported. The fixing roller is heated by a heating means such as a heater, an electromagnetic induction coil, or a resistance heating element. The toner image on the sheet transported to the nip portion is fixed onto the sheet by the heat received from the fixing roller and the pressure of the nip portion. In such a fixing device, the fixing roller has a shaft portion at an end portion in the rotational axis direction thereof rotatably held in a housing (frame body) of the device via a bearing such as a ball bearing or a sliding bearing. Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional fixing devices, the bearing that holds the shaft of the fixing rotor (fixing roller) was the source of abnormal noise.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a fixing device and an image forming apparatus that are less likely to produce abnormal noise. [Means for solving the problem]

[0006] The fixing device of the present invention includes a fixing rotor that is heated by a heating means to heat a toner image and fix it on the surface of a sheet, the fixing rotor having a shaft portion at an end in the rotational axis direction, a pressure rotor that forms a nip portion through which the sheet is conveyed by being pressed against the fixing rotor, a bearing member into whose inner diameter portion the shaft portion of the fixing rotor is inserted, and a drive-receiving portion to which drive is transmitted from a drive transmission portion of the shaft portion is formed in the inner diameter portion, and which rotates together with the fixing rotor, and a bearing member that rotates the bearing member. directly a housing having a holding portion to be held; The bearing member is a substantially cylindrical member with no gaps in the circumferential direction, and the holding portion of the housing is a circular hole portion into which the outer diameter portion of the bearing member is directly inserted. It is something. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a fixing device and an image forming apparatus that are less likely to produce abnormal noise. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating a configuration of a fixing device. [Figure 3] FIG. 2 is a side view showing an end portion of the fixing device in the direction of the rotation axis. [Figure 4] FIG. 2 is a cross-sectional view showing an end portion of the fixing device in the direction of the rotation axis. [Figure 5] FIG. 10 is a cross-sectional view showing an end portion of a fixing device in the rotation axis direction as a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. In FIG. 1, 1 indicates a tandem color copier as an image forming apparatus, 2 indicates a writing unit that emits laser light based on input image information, 3 indicates a document transport unit that transports a document D to a document reading unit 4, and 4 indicates a document reading unit that reads the image information of the document D. Also, 7 indicates a paper feed section in which sheets P such as paper are stored, 9 indicates a registration roller (timing roller) that adjusts the timing of conveying sheets P, and 11Y, 11M, 11C, and 11BK indicate photosensitive drums on which toner images of each color (yellow, magenta, cyan, and black) are formed.

[0011] Also, 12 denotes a charging unit that charges the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, 13 denotes a developing unit that develops the electrostatic latent image formed on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK, 14 denotes a primary transfer roller that transfers the toner image formed on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK onto the surface of sheet P, and 15 denotes a cleaning unit that collects untransferred toner remaining on the surface of each photosensitive drum 11Y, 11M, 11C, and 11BK. Also, 16 indicates an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 indicates the intermediate transfer belt onto which multiple color toner images are transferred in layers, 18 indicates a secondary transfer roller for transferring the color toner image on the intermediate transfer belt 17 onto the sheet P, and 20 indicates a fixing device that fixes the toner image (unfixed image) on the sheet P.

[0012] Hereinafter, the operation (printing operation) of the image forming apparatus during normal color image formation will be described. First, the document D is transported from the document table by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

[0013] More specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating it with light emitted from an illumination lamp. The light reflected from the document D is then imaged on a color sensor via a group of mirrors and a lens. The color image information of the document D is read by the color sensor in units of RGB (red, green, blue) color separation light, and then converted into electrical image signals. Furthermore, the image processing unit performs color conversion processing, color correction processing, spatial frequency correction processing, etc. based on the RGB color separation image signals, thereby obtaining color image information of yellow, magenta, cyan, and black.

[0014] Then, the image information for each color of yellow, magenta, cyan, and black is sent to the writing unit 2. Then, from the writing unit 2, laser light (exposure light) based on the image information for each color is emitted toward the surfaces of the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

[0015] Meanwhile, the four photoconductor drums 11Y, 11M, 11C, and 11BK each rotate counterclockwise in FIG. 1. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at the portions facing the charging unit 12 (charging process). In this way, a charging potential is formed on the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK. Thereafter, the surfaces of the charged photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams (exposure process). More specifically, in the writing unit 2, four light sources emit laser beams corresponding to the image signals, one for each color. Each laser beam passes through a separate optical path for each color component: yellow, magenta, cyan, and black.

[0016] The laser light corresponding to the yellow component is irradiated onto the surface of the first photoconductor drum 11Y from the left side of the drawing. At this time, the laser light of the yellow component is scanned in the rotational axis direction (main scanning direction, width direction) of the photoconductor drum 11Y by a polygon mirror rotating at high speed. In this way, an electrostatic latent image corresponding to the yellow component is formed on the photoconductor drum 11Y after it has been charged by the charging unit 12.

[0017] Similarly, the laser light corresponding to the magenta component is irradiated onto the surface of the photosensitive drum 11M, which is the second from the left on the paper, and an electrostatic latent image corresponding to the magenta component is formed. The laser light corresponding to the cyan component is irradiated onto the surface of the photosensitive drum 11C, which is the third from the left on the paper, and an electrostatic latent image corresponding to the cyan component is formed. The laser light corresponding to the black component is irradiated onto the surface of the photosensitive drum 11BK, which is the fourth from the left on the paper, and an electrostatic latent image corresponding to the black component is formed.

[0018] Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of each color have been formed reach positions facing the developing units 13. Then, toner of each color is supplied from each developing unit 13 to the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (this is the developing process). Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process each reach a portion facing the intermediate transfer belt 17. Here, a primary transfer roller 14 is installed at each facing portion so as to abut against the inner circumferential surface of the intermediate transfer belt 17. Then, at the position of the primary transfer roller 14, the toner images of each color formed on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred onto the intermediate transfer belt 17 in order, superimposed on top of each other (this is the primary transfer process).

[0019] After the transfer process, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK each reach a position facing the cleaning unit 15. Then, the cleaning unit 15 collects untransferred toner remaining on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK (this is the cleaning process). Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK pass through a charge removal section, and a series of image forming processes on the photosensitive drums 11Y, 11M, 11C, and 11BK are completed.

[0020] Meanwhile, the intermediate transfer belt 17, onto which the toner of each color is transferred (carried) in an overlapping manner on the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK, travels in the clockwise direction in FIG. 1 and reaches a position facing the secondary transfer roller 18. Then, at the position facing the secondary transfer roller 18, the color toner images carried on the intermediate transfer belt 17 are transferred onto the sheet P (secondary transfer process). Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhering to the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and the series of transfer processes on the intermediate transfer belt 17 is completed.

[0021] Here, the sheet P conveyed between the intermediate transfer belt 17 and the secondary transfer roller 18 (secondary transfer nip) is conveyed from the paper feed unit 7 via the registration rollers 9 and the like. Specifically, the sheet P is fed by a paper feed roller 8 from a paper feed unit 7 that stores the sheet P, passes through a conveyance path, and is then guided to a registration roller 9. The sheet P that has reached the registration roller 9 is conveyed in time toward the secondary transfer nip.

[0022] Then, the sheet P onto which the full-color image has been transferred is guided by a conveyor belt to the fixing device 20. In the fixing device 20, the color image (toner image) is fixed to the surface of the sheet P at the nip portion (fixing nip) between a fixing roller and a pressure roller (fixing process). After the fixing process, the sheet P is discharged as an output image to the outside of the apparatus main body 1 by a paper discharge roller, and a series of image forming processes (printing) is completed.

[0023] Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIG. 2 and other figures. As shown in FIG. 2, the fixing device 20 is composed of a fixing roller 21 as a fixing rotor, a heater 25 as a heating means, a pressure roller 31 as a pressure rotor, a temperature sensor 45 (temperature detection means) that detects the temperature (surface temperature) of the central part of the width of the fixing roller 21, and the like.

[0024] Here, the fixing roller 21 (fixing member) as a fixing rotor is a roller member with a multilayer structure in which a coating layer 21b (a laminate of an elastic layer and a release layer) is formed on a hollow core metal 21a made of a metal material such as stainless steel, and is pressed against a pressure roller 31 as a pressure rotor to form a nip portion (fixing nip). The fixing roller 21 is heated by a heater 25 as a heating means to heat the toner image and fix it on the surface of the sheet P. The elastic layer in the covering layer 21b of the fixing roller 21 is made of an elastic material such as fluororubber, silicone rubber, or foamed silicone rubber. The release layer in the covering layer 21b of the fixing roller 21 is made of PFA (tetrafluoroethylene perfluoroalkylvinylether copolymer resin) or the like. By providing the release layer on the surface layer of the fixing roller 21, the releasing property (peelability) of the toner T (toner image) is ensured. The fixing roller 21 is rotated clockwise in FIG. 2 by a drive motor 90.

[0025] A heater 25 serving as a heating means is fixed inside the hollow fixing roller 21 (core metal 21a). The heater 25 is a rod-shaped halogen heater, and both ends thereof are fixed to the side plates (part of the housing 40) of the fixing device 20. When the main switch of the image forming apparatus main body 1 is turned on (power on), power is supplied to the heater 25 from a power supply unit (not shown). The fixing roller 21 is heated by radiant heat from the heater 25, whose output is controlled (PID controlled) by a control unit, and further heat is applied to the toner image T on the sheet P from the surface of the heated fixing roller 21. The output control of the heater 25 is performed based on the detection result of the roller surface temperature by a temperature sensor 45 (e.g., a thermopile or a non-contact thermistor) that faces the surface of the fixing roller 21 without contacting it at the center of the width direction (the direction perpendicular to the plane of FIG. 2, which is the direction of the rotation axis). That is, the heater 25 as a heating means is controlled based on the detection result of the temperature sensor 45. More specifically, an AC voltage is applied to the heater 25 from a power supply unit (not shown) for a current-carrying time determined based on the detection result of the temperature sensor 45. By controlling the output of the heater 25 in this way, the temperature (fixing temperature) of the fixing roller 21 can be adjusted and controlled to a desired temperature (target control temperature).

[0026] The pressure roller 31 (pressure member) as a pressure rotating body is a roller member mainly made up of a core metal 32 and an elastic layer 33 as a coating layer that covers the outer circumferential surface of the core metal 32. The elastic layer 33 (covering layer) of the pressure roller 31 is made of a material such as silicone rubber, foamed silicone rubber, etc. A thin release layer made of PFA or the like may be provided on the surface of the elastic layer 33, and the cover layer may be formed of the elastic layer 33 and the release layer. The pressure roller 31 is then pressed against the fixing roller 21 by a pressure mechanism (not shown). In this way, a desired nip portion is formed between the pressure roller 31 and the fixing roller 21. The pressure mechanism can be configured, for example, with a rotatable lever that contacts shaft portions at both ends of the pressure roller 31, and a spring (biasing member) that biases the lever upward (toward the fixing roller 21). The pressure roller 31 is rotated counterclockwise in FIG. 2 in accordance with the rotation of the fixing roller 21.

[0027] The fixing device 20 configured as described above operates as follows. When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (power is supplied) to the heater 25 from a power supply unit (not shown). When a print command (print request) is input, the driving force of the drive motor 90 (drive mechanism) is transmitted to the fixing gear 55 (FIG. 3), causing the fixing roller 21 to start rotating clockwise. At the same time, the pressure roller 31 starts rotating counterclockwise. Thereafter, a sheet P is fed from the paper feed unit 7, and at the position of the secondary transfer roller 18, the toner image on the intermediate transfer belt 17 is carried on the sheet P as an unfixed image. The sheet P carrying the unfixed image T (toner image) is transported in the direction of the arrow in FIG. 2 and sent into the nip between the fixing roller 21 and the pressure roller 31, which are in a pressure-contact state. The toner image T is then fixed to the surface of the sheet P by the heat of the fixing roller 21 and the pressure force of the fixing roller 21 and the pressure roller 31. After the fixing process, the sheet P is sent out of the nip in the direction of the arrow by the rotating fixing roller 21 and pressure roller 31.

[0028] The following describes in detail the characteristic configuration and operation of the fixing device 20 (image forming apparatus 1) in this embodiment. 3, in this embodiment, fixing roller 21 serving as a fixing rotator has shaft portion 21x at the end in the rotation axis direction (the vertical direction in FIGS. 2 and 4, the left-right direction in FIG. 3). Shaft portion 21x is not provided with coating layer 21b (see FIG. 2) and is a portion that does not come into contact with sheet P (a portion that does not contribute to the fixing process). The shaft portion 21x can be formed integrally with the hollow core metal 21a (see FIG. 2) (the core metal 21a can be extended to form a portion where the coating layer 21b is not provided).

[0029] This shaft portion 21x is provided not only at the drive side end (one end) shown in Fig. 3 but also at the non-drive side end (the other end) on the opposite side. That is, the shaft portion 21x is formed at each end of the fixing roller 21 in the rotation axis direction. 3, a D-shaped cut portion 21x10 is formed on the shaft portion 21x provided at the end (one end) on the driving side to fit into a D-shaped hole (not shown) of the fixing gear 55 to which the driving force from the drive motor 90 (see FIG. 2) is input. A retaining ring 61 is also attached to the shaft portion 21x to prevent the fixing gear 55 attached to the shaft portion 21x from falling off. With this configuration, the fixing roller 21 is rotated by the drive motor 90.

[0030] Here, as shown in Figures 3 and 4, the fixing device 20 in this embodiment is provided with a bearing member 50 that receives the shaft portion 21x of the fixing roller 21 (fixing rotor), and a circular hole portion 40a is formed in the housing 40 as a holding portion that holds the bearing member 50.

[0031] The bearing member 50 is a substantially cylindrical member made of a heat-resistant resin material, and the shaft portion 21x of the fixing roller 21 (fixing rotor) is inserted into the inner diameter portion 50b thereof. The inner diameter portion 50b of the bearing member 50 is formed with a protrusion 50b1 as a driven portion to which drive is transmitted from the groove portion 21x1 as a drive transmitting portion of the shaft portion 21x. This allows the bearing member 50 to rotate together with the fixing roller 21 (fixing rotor). Referring to FIG. 4, the groove 21x1 is formed to be recessed in the radial direction (toward the rotation center), and functions as a drive transmission part for the shaft part 21x. On the other hand, the protrusion 50b1 is formed to protrude in the radial direction (toward the rotation center) so as to be able to fit into the groove 21x1, and functions as the drive-receiving part of the bearing member 50. In this embodiment, as shown in Fig. 4, when viewed in a cross section perpendicular to the rotation axis direction, the groove 21x1 functioning as a drive transmitting portion and the protrusion 50b1 functioning as a drive-receiving portion come into contact with each other during drive transmission, and a parallel wall surface is formed on the opposite side of the wall surface (the wall surface extending in the vertical direction in Fig. 4) to which the drive is transmitted. However, this parallel wall surface is not used for drive transmission. Therefore, the shapes of the groove 21x1 and the protrusion 50b1 are not limited to these, and various shapes are possible as long as drive transmission is possible, such as a substantially triangular shape with no wall surface opposite the wall surface to which the drive is transmitted.

[0032] In this embodiment, a small gap can be formed between the shaft portion 21x and the inner diameter portion 50b of the bearing member 50. The bearing member 50 rotates together with the shaft portion 21x (fixing roller 21) by transmission of a rotational driving force from the groove portion 21x1 to the protrusion portion 50b1. Therefore, the bearing member 50 does not need to be press-fitted into the inner diameter portion 50b of the bearing member 50, and even if it is inserted loosely, it can sufficiently rotate together with the shaft portion 21x. By loosely fitting the shaft portion 21x and the bearing member 50 (inner diameter portion 50b) in this way, the dimensional precision of the two members can be relaxed, which makes it possible to reduce the cost of parts (yield).

[0033] The housing 40 is a frame made of a metal material (or a resin material) that rotatably holds the fixing roller 21 and the pressure roller 31 and covers the main components of the fixing device 20. A cover member made of a heat-resistant resin material that covers the housing 40 can also be provided. The housing 40 is formed with a circular hole 40a as a holding portion that rotatably holds the bearing member 50. The outer diameter portion 50a of the bearing member 50 is inserted into the circular hole 40a so as to fit therein, and functions as a holding portion for the housing 40. In this embodiment, the circular hole 40a is provided with a step (small diameter hole portion) that restricts movement of the bearing member 50 inward in the rotation axis direction, as shown in FIG.

[0034] The circular hole 40a (holding portion) configured in this manner can be said to function as a bearing that rotatably supports the bearing member 50 that rotates together with the fixing roller 21 (shaft portion 21x). Therefore, in order to reduce the sliding resistance between the circular hole portion 40a and the bearing member 50 (outer diameter portion 50a), it is preferable to form at least one of the circular hole portion 40a and the bearing member 50 (outer diameter portion 50a) from a low-friction material. As a specific example, it is preferable to apply a fluorine coating to the circular hole portion 40a and the outer diameter portion 50a of the bearing member 50.

[0035] In this embodiment, a retaining ring 62 is provided on the shaft portion 21x to prevent the bearing member 50 set in the circular hole portion 40a from falling off (falling off to the left in FIG. 3). In this embodiment, the bearing member 50 is positioned in the direction of the rotational axis by the retaining ring 62 and the step portion of the circular hole portion 40a described above, but the method for positioning the bearing member 50 in the direction of the rotational axis is not limited to this. For example, the bearing member 50 can also be positioned in the direction of the rotational axis by forming a rib on the housing 40. In addition, in this embodiment, the end portion of the drive side (one end side) of the fixing device 20 is illustrated in Figure 3, but the end portion of the non-drive side (the other end side) of the fixing device 20 is also configured in almost the same way, except that the fixing gear 55 is not installed and that it is symmetrical on the left and right.

[0036] Hereinafter, the procedure for assembling the fixing roller 21 and the bearing member 50 into the housing 40 will be briefly described with reference to FIG. First, the fixing roller 21 is set in the housing 40 as a single component (without the bearing member 50 installed). Then, the bearing member 50 is attached to the shaft portion 21x of the fuser roller 21 set in the housing 40. At this time, the end face of the roller portion (the portion where the coating layer 21b is provided) of the fuser roller 21 is moved toward the inner wall surface (the end face on the right side in FIG. 3) of the housing 40 so that the groove portion 21x1 is positioned outside the housing 40 (the left side in FIG. 3), which makes it easier to attach the bearing member 50 to the shaft portion 21x. Then, the bearing member 50 is slid and attached from the side of the D-cut portion 21x10 (the left side in FIG. 3) via the D-cut portion 21x10 (connected to the groove portion 21x1) to the position of the groove portion 21x1 so that the protrusion 50b1 fits into the groove portion 21x1. Then, the fuser roller 21 is slid, and the bearing member 50 fitted in the shaft portion 21x (groove portion 21x1) is inserted into the circular hole portion 40a of the housing 40 (as shown in FIG. 3). Then, as shown in FIG. 3, after the retaining ring 62 is installed on the shaft portion 21x, the fuser gear 55 is set at the position of the D-cut portion 21x10, and the retaining ring 61 is installed on the shaft portion 21x. In this way, the assembly of the fuser roller 21 and the bearing member 50 into the housing 40 is completed.

[0037] In this manner, the fixing device 20 in this embodiment has the circular hole 40a (holding portion) in the housing 40 that rotatably holds the bearing member 50 that rotates together with the fixing roller 21. This makes it less likely that abnormal noise originating from the bearing member 50 will occur. In conventional fixing devices, the shaft of the fixing roller at the end in the rotational axis direction is rotatably supported in the housing (frame) of the device via a bearing such as a ball bearing or a sliding bearing. In fixing devices configured in this way, the bearing is fitted into the housing without rotating with the fixing roller. However, the bearing and the shaft of the fixing roller are made of different materials and have different degrees of thermal deformation (thermal expansion and thermal contraction). As a result, the degree of fit between the two components changes depending on the operating conditions (thermal environment) of the device, causing the bearing to rotate irregularly due to sliding resistance, resulting in irregular vibrations, or the bearing vibrating repeatedly at a fixed position, or stick-slip caused by wear on one of the two components, resulting in abnormal noise. In contrast, in the present embodiment, the bearing member 50 is configured to be forcibly rotated together with the fixing roller 21 (shaft portion 21x), thereby reducing problems such as vibration of the bearing member 50 as described above, and making it less likely that abnormal noise will be generated from the bearing member 50.

[0038] Here, in this embodiment, regardless of whether or not thermal deformation occurs between the bearing member 50 and the circular hole portion 40a, the outer diameter of the outer diameter portion 50a of the bearing member 50 is configured not to be equal to or greater than the hole diameter of the circular hole portion 40a. That is, the gap between the bearing member 50 (outer diameter portion 50a) and the circular hole portion 40a is prevented from becoming zero due to thermal expansion, which would otherwise cause a problem in that the bearing member 50 cannot rotate properly. Specifically, the materials of the bearing member 50 and the housing 40 are each selected to prevent such a problem from occurring. In particular, when the bearing member 50 and the housing 40 are made of the same material, the gap between the outer diameter portion 50a and the circular hole portion 40a is set to be zero or greater (a very small gap is preferred). When the bearing member 50 and the housing 40 are made of different materials, the thermal expansion coefficient of the material is an important factor in selecting the material so that the gap between the outer diameter portion 50a and the circular hole portion 40a does not become zero.

[0039] In this embodiment, the bearing members 50 that rotate with the fixing roller 21 are installed at both ends in the direction of the rotation axis, but it is also possible to install the bearing member 50 that rotates with the fixing roller 21 only at one end in the direction of the rotation axis, and install a normal bearing (such as a ball bearing or a sliding bearing) that does not rotate with the fixing roller 21 at the other end in the direction of the rotation. In this case, it is preferable that one end in the rotational axis direction where the bearing member 50 that rotates together with the fixing roller 21 is installed is the drive side (the side to which the driving force of the drive motor 90 is input and where the fixing gear 55 is installed). This is because the drive side tends to vibrate more strongly and generate more heat than the non-drive side, making it more susceptible to abnormal noise. Therefore, by installing the bearing member 50 that actively rotates only on the drive side, it is possible to efficiently reduce the occurrence of abnormal noise.

[0040] <Modification> As a modified example, the fixing device 20 shown in Figure 5(A) has multiple pairs of convex portions 50b1 of the bearing member 50 and groove portions 21x1 of the shaft portion 21x, which are provided at positions spaced apart in the circumferential direction (in the example of Figure 5(A), two pairs are provided). 5(B), a convex portion 21x2 serving as a drive transmitting portion is formed on the shaft portion 21x so as to protrude in the radial direction (the direction away from the rotation center). In contrast, a groove portion 50b2 serving as a drive receiving portion is formed on the bearing member 50 so as to be recessed in the radial direction (the direction away from the rotation center) so as to be able to fit into the convex portion 21x2. Even in such a configuration, the bearing member 50 actively rotates together with the fixing roller 21, so that abnormal noise originating from the bearing member 50 is less likely to occur.

[0041] As described above, the fixing device 20 in this embodiment includes a fixing roller 21 (fixing rotor) that is heated by a heater 25 (heating means) to heat and fix a toner image T on the surface of a sheet P, and that includes a shaft portion 21x at an end in the direction of the rotation axis, and a pressure roller 31 (pressure rotor) that presses against the fixing roller 21 to form a nip portion through which the sheet P is conveyed. The shaft portion 21x of the fixing roller 21 is inserted into an inner diameter portion 50b, and a convex portion 50b1 (drive-receiving portion) to which drive is transmitted from a groove portion 21x1 (drive-transmitting portion) of the shaft portion 21x is formed in the inner diameter portion 50b, thereby providing a bearing member 50 that rotates together with the fixing roller 21. The housing 40 also includes a circular hole 40a (retaining portion) in which the bearing member 50 is rotatably held. This makes it possible to make abnormal noise less likely to occur.

[0042] In this embodiment, the fixing roller 21 is used as the fixing rotor and the pressure roller 31 is used as the pressure rotor, but the fixing rotor and the pressure rotor are not limited to these, and for example, a fixing belt can be used as the fixing rotor, and a pressure belt can be used as the pressure rotor. In addition, in this embodiment, a thermal heater type heating means is used as the heating means for heating the fixing rotor (fixing roller 21), but the heating means is not limited to this, and for example, an electromagnetic induction type (IH type) or a resistance heating element type can also be used. In such cases, the same effect as that of this embodiment can be obtained.

[0043] It is to be noted that the present invention is not limited to the present embodiment, and it is clear that the present embodiment can be appropriately modified within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components can be any number, position, shape, etc. that is suitable for implementing the present invention.

[0044] In this specification, the term "sheet" is defined to include not only paper (sheet of paper), but also all sheet-like recording media such as coated paper, label paper, OHP sheets, and film sheets. [Explanation of symbols]

[0045] 1 Image forming apparatus (image forming apparatus main body), 20 Fixing device, 21 fixing roller (fixing rotor), 21x shaft, 21x1 groove (drive transmission part), 25 heater (heating means), 31 pressure roller (pressure rotating body), 40 Housing (frame), 40a circular hole portion (retaining portion), 50 bearing member, 50a outer diameter, 50b inner diameter, 50b1 protrusion (driven transmission part), P sheet (paper). [Prior art documents] [Patent documents]

[0046] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-148987

Claims

1. a fixing rotor that is heated by a heating means to heat and fix a toner image on a surface of a sheet, and that has a shaft portion at an end in the direction of the rotation axis; a pressure rotating body that forms a nip portion through which a sheet is conveyed by being pressed against the fixing rotating body; a bearing member into which the shaft portion of the fixing rotor is inserted and a driven transmission portion to which drive is transmitted from a drive transmission portion of the shaft portion is formed in the inner diameter portion, the bearing member rotating together with the fixing rotor; a housing having a holding portion on which the bearing member is directly held so as to be rotatable; Equipped with The bearing member is a substantially cylindrical member with no gaps in the circumferential direction, The fixing device is characterized in that the holding portion of the housing is a circular hole into which the outer diameter portion of the bearing member is directly inserted.

2. The drive transmission portion of the shaft portion is a groove portion recessed in a radial direction, 2. The fixing device according to claim 1, wherein the drive-receiving portion of the bearing member is a convex portion that protrudes in the radial direction and is capable of being fitted into the groove.

3. The drive transmission portion of the shaft portion is a convex portion that protrudes in a radial direction, 2. The fixing device according to claim 1, wherein the drive-transmitted portion of the bearing member is a groove recessed in the radial direction so as to be able to fit into the protrusion.

4. 4. The fixing device according to claim 1, wherein a gap is formed between the shaft portion and the inner diameter portion of the bearing member during driving.

5. 5. The fixing device according to claim 4, wherein the outer diameter of the outer diameter portion of the bearing member is configured not to be equal to or greater than the hole diameter of the circular hole portion, regardless of whether or not the bearing member and the circular hole portion are thermally deformed.

6. 6. The fixing device according to claim 1, wherein a plurality of pairs of the drive transmitting portion and the drive receiving portion are provided at positions spaced apart in the circumferential direction.

7. 7. The fixing device according to claim 1, wherein at least one of the outer diameter portion of the bearing member and the circular hole is coated with fluorine.

8. An image forming apparatus comprising the fixing device according to any one of claims 1 to 7.

Images