JP4689230B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device that fixes an image on a recording material (recording medium) such as a sheet. This fixing device is used in an image forming apparatus such as a copying machine, a printer, or a facsimile machine.

  In recent years, various proposals have been made for a heat fixing device of an image forming apparatus in order to save energy. In particular, there are many things that realize energy saving during standby by lowering the temperature of the heat-fixing device during standby by speeding up the startup time, and many proposals for speeding up the startup time have been made.

  For example, as shown in Patent Document 1, an induction heating type fixing device using high frequency induction as a heating source has been proposed. In this induction heating fixing device, a coil is concentrically disposed inside a hollow fixing roller made of a metal conductor, and an induction eddy current is generated in the fixing roller by a high frequency magnetic field generated by flowing a high frequency current through the coil. The fixing roller itself generates Joule heat by the skin resistance of the fixing roller itself. According to this induction heating type fixing device, since the electric-heat conversion efficiency is greatly improved, the warm-up time can be shortened.

  Regardless of the electromagnetic induction heating type fixing device or the heating type fixing device of another heat source such as a halogen heater, it is effective to further speed up the start-up time. This is to reduce the thickness and heat capacity of a heating medium such as a film. In particular, a thin cylindrical metal fixing roller is effective in speeding up the start-up time in a relatively high-speed image forming apparatus that requires both heat and pressure because it can maintain a constant strength.

  With respect to such a thin cylindrical fixing roller, when it is held rotatably in the fixing device, its thrust restriction (to restrict the movement of the fixing roller in the longitudinal direction) is as shown in FIGS. 6 and 7. A hole is formed in a part of the fixing roller, and a snap ring such as a wire is engaged with the hole. Here, FIGS. 6 and 7 are schematic views for explaining the thrust regulation of the fixing roller in the conventional fixing device.

  In FIG. 6, reference numeral 150 denotes a thin fixing roller, which is fitted to a bearing 151 via a heat insulating bush (not shown) and is rotatably supported on the fixing side plate 152. A fixing gear 153 is engaged with the fixing roller 150 so that the key portion 154 engages with the cutout portion of the thin fixing roller 150 and rotates integrally with the fixing roller 150. A retaining ring 155 formed of a spring wire so as to fix the end face of the fixing gear 153 in the thrust direction is fixed by engaging a part thereof with holes 156a, 156b, and 156c of the fixing roller. .

  By doing so, it is possible to perform thrust regulation with a simple and low-cost configuration even for a thin fixing roller in which a groove cannot be formed over the entire circumference of the roller.

In addition, as a thrust restricting means for the thin fixing roller, a snap fit is used for a thrust restricting means (refer to Patent Documents 2 and 3) that uses the groove and elasticity of the thin roller without using a retaining ring, and a gear and a heat insulating bush. There has been proposed a thrust restricting means (see Patent Document 4).
JP 59-33787 Japanese Patent Laid-Open No. 5-188817 JP 2000-81807 A JP 2003-76191 A

  However, the thrust restricting means as described above has the following problems.

  FIG. 8 is a schematic cross-sectional view showing a conventional fixing device, which shows an induction heating type fixing device.

  For example, in an induction heating type fixing device as shown in FIG. 8, it is necessary to arrange an induction heating coil unit 157 in the vicinity of the fixing roller 150. In addition, for the purpose of preventing temperature rise at the end, a magnetic flux shielding means 158 is inserted between the coil unit 157 and the fixing roller 150 to block the magnetic flux as necessary.

  As described above, in recent fixing devices, other components may be arranged at the edge of the inner peripheral surface of the roller. In this case, in the conventional thrust regulating method as shown in FIGS. The engaging part of the retaining ring 155 protrudes greatly (in a business trip) on the inner surface of the roller 150 and interferes with the components arranged at the very inner surface.

  In order to avoid this, it is necessary to escape the shape of the components such as the coil unit and the magnetic flux shielding means with respect to the position of the retaining ring or to cut the portion protruding from the inner surface of the retaining ring.

  However, in the former case, it is necessary to form these components in a complicated shape in a small space, which is an undesirable shape in terms of cost and strength. In the latter case, the overlap length of the engaging portion between the retaining ring and the fixing roller is shortened, causing a problem that the retaining ring is easily detached. In particular, in the case of such a snap ring made of a spring material wire, the bending shape always has a bending inner radius R. When this R rides on the end of the hole of the fixing roller, a slope force is generated, and a small engaging portion. The overlap is easily removed.

  Also, the thrust restricting means that uses the groove and elasticity of the roller without using the retaining ring described in the background art is unsuitable for strong pressure fixing because the roller strength is reduced in shape, and it is not suitable for gears and heat insulation. Regarding the thrust restricting means using a snap fit for the bush, it is difficult to achieve both the heat insulating property and the elasticity of the resin material, and there is a concern that durability may be problematic as a configuration in which the resin material is repeatedly attached and detached.

  The present invention has been made in view of the circumstances as described above, and it is possible to more reliably perform the thrust regulation of the fixing roller even when the installation space in the vicinity of the fixing roller is limited. The purpose is to provide technology.

In order to achieve the above object, the present invention provides:
A coil unit for generating magnetic flux;
A hollow fixing roller having the coil unit therein and fixing an image formed on the recording material at the nip portion by heat generated by magnetic flux;
A ring-shaped engaging member that engages with a hole provided on one end side in the axial direction of the fixing roller;
A bearing provided on one end side in the axial direction and rotatably supporting the fixing roller;
A regulating member that is provided between the engaging member and the bearing in the axial direction of the fixing roller and that regulates the axial position of the fixing roller by engaging with the engaging member;
A protrusion that protrudes from the restricting member in the axial direction and restricts the restricting member from rotating in the rotational direction relative to the fixing roller by engaging with the engaging member;
In a fixing device having
The engagement play in the rotation direction between the protrusion and the engagement member is smaller than the engagement play in the rotation direction between the hole of the fixing roller and the engagement member.

According to the present invention, it is possible to provide a technique capable of more reliably performing thrust regulation of the fixing roller even when the installation space near the fixing roller is limited.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  FIG. 1 is a schematic sectional view showing an image forming apparatus provided with an electromagnetic induction heating device as a fixing device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of an identification fixing device.

  In the figure, reference numeral 101 denotes an original platen glass. An original O is placed on the original platen glass 101 in accordance with a predetermined placement standard with the image surface facing downward, and the original cover 102 is placed thereon. .

  When the copy start key is pressed, the image photoelectric reading device (reader unit) 103 including the moving optical system operates to photoelectrically read the image information on the downward image surface of the document O on the document table glass 101. An original document feeder (ADF, RDF) may be mounted on the platen glass 101 to automatically feed the document onto the platen glass 101.

  Reference numeral 104 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotationally driven at a predetermined peripheral speed in the clockwise direction of an arrow. The photosensitive drum 104 is uniformly charged with a predetermined polarity and potential by the charging device 105 during the rotation process, and is uniformly charged by receiving image exposure L by the image writing device 106 on the uniformly charged surface. The potential of the exposed bright portion of the surface is attenuated, and an electrostatic latent image corresponding to the exposure pattern is formed on the surface of the photosensitive drum 104. In the present embodiment, a laser scanner is applied as the image writing device 106, and in response to a command from a controller (not shown), the time series electric digital pixel signal of the document image information photoelectrically read by the photoelectric reading device 103 is used. Correspondingly modulated laser light L is output, and the uniformly charged surface of the rotating photosensitive drum 104 is scanned and exposed to form an electrostatic latent image corresponding to the document image information.

  Next, the electrostatic latent image is developed as a toner image by the developing device 107, and at a position of the transfer charging device 108, a predetermined portion is transferred from the feeding mechanism unit side to a transfer portion that is a portion facing the photosensitive drum 104 and the transfer charging device 108. Is electrostatically transferred from the surface of the photosensitive drum 104 to the sheet S fed at the control timing.

  In the image forming apparatus according to the present embodiment, the feeding mechanism unit includes first to fourth cassette feeding units 109 to 112, an MP tray (multipurpose tray) 113, and a reverse refeeding unit 114. From there, the sheet S is selectively fed to the transfer section. Reference numeral 115 denotes a registration roller for timing-feeding the sheet to the transfer unit.

  The sheet S that has received the transfer of the toner image from the surface of the photosensitive drum 104 in the transfer unit is separated from the surface of the photosensitive drum 104 and conveyed to the fixing device 116. In the fixing device 116, the sheet S is subjected to a fixing process by being given thermal energy while being nipped and conveyed at the fixing nip portion N, and an unfixed toner image on the sheet S is fixed. Thereafter, the sheet S is discharged by a paper discharge roller 117 onto a paper discharge tray 118 outside the apparatus.

  On the other hand, the surface of the photosensitive drum 104 after separation of the sheet is cleaned by the cleaning device 119 after removing adhering contaminants such as transfer residual toner, and is repeatedly used for image formation.

  In the double-sided copy mode, the first-side copied sheet that has exited the fixing device 116 is introduced into the reverse refeed unit 114 and is reversely re-fed to the transfer unit so that the toner image on the second side of the sheet is transferred. Then, the sheet is transferred again through the fixing device 116 and discharged onto a discharge tray 118 outside the apparatus by a discharge roller 117 as a double-sided copy.

  In FIG. 2, reference numeral 50 denotes a fixing rotator. In the present embodiment, an iron thin cylindrical fixing roller is used as an induction heating element that generates electromagnetic induction heat. A toner release layer (not shown) is provided on the outer surface of the fixing roller 50. The toner release layer is made of PTFE 30 μm.

  Reference numeral 57 denotes a coil unit for induction heating, which is disposed in the fixing roller 50 as a magnetic flux generating means, and is disposed in the vicinity of the inner peripheral surface of the fixing roller 50.

  Reference numeral 8 denotes an elastic pressure roller as a pressure member arranged below the fixing roller 50 in parallel with the fixing roller. The elastic pressure roller 8 is rotatably held between bearings (not shown) and is fixed to the lower surface of the fixing roller 50. A fixing nip portion N as a heating portion having a predetermined width is formed by pressing with a predetermined pressing force against elasticity by a biasing means (not shown). The pressure roller 8 has a configuration in which a silicone rubber layer and a toner release layer are provided on the outer periphery of an iron core bar in the same manner as the fixing roller 50.

  Between the fixing roller 50 and the coil unit 57, magnetic shielding means 58 as a magnetic flux suppressing member whose rotational phase is controlled by a rotational driving means (not shown) is disposed, and from the coil unit 57 to the fixing roller 50 as necessary. The magnetic field is partially blocked.

  3 is a schematic perspective view for explaining the thrust regulation of the fixing roller 50 according to the present embodiment, FIG. 4 is a schematic sectional view for explaining the thrust regulation of the fixing roller 50 according to the present embodiment, and FIG. 3 is a schematic diagram of a fixing gear 80 used in the fixing device 116 according to the embodiment. FIG.

  When the fixing roller 50 is rotatably held in the fixing device 116, the thrust regulation is performed by forming holes 56a, 56b, and 56c at the longitudinal ends of the thin cylindrical fixing roller 50 as shown in FIGS. Then, the holes 56a, 56b, and 56c are engaged by engaging engaging portions 92a, 92b, and 92c provided on a retaining ring (for example, a ring-shaped wire) 90 as an engaging member. Yes.

  As shown in FIG. 3, the fixing roller 50 is fitted to a bearing 51 via a heat insulating bush (not shown), and is rotatably supported by a fixing side plate 52 that constitutes a frame (housing) of the fixing device 116. .

  Reference numeral 80 denotes a fixing gear as a regulating member having a gear portion that receives a rotational driving force from a driving source (not shown). The fixing gear 80 is fitted to the fixing roller 50 so that a key portion 81 provided on the fixing gear 80 engages with the notch 56 d of the fixing roller 50 and rotates integrally with the fixing roller 50. .

  A retaining ring 90 formed of a spring wire or the like regulates the position of the fixing roller 50 in the fixing device 116, and particularly restricts the position of the fixing roller 50 in the axial direction (longitudinal direction, thrust direction). For this purpose, the engaging portions 92a, 92b, and 92c are engaged and fixed to the holes 56a, 56b, and 56c of the fixing roller 50 so that the end face of the fixing gear 80 is fixed (restricted) in the thrust direction. .

Further, the fixing roller 90 is configured so that the overlap amount between the engaging portions 92a, 92b, and 92c of the retaining ring 90 and the holes 56a, 56b, and 56c of the fixing roller 50 does not protrude greatly toward the inner peripheral surface side of the fixing roller 50. The thickness is appropriately set so as to be a necessary minimum amount of 50 thickness + α. Here, the engaging portions 92a, 92b, and 92c of the retaining ring 90 are engaged with the holes 56a, 56b, and 56c of the fixing roller 50, whereby the end portions on the inner peripheral side of the engaging portions 92a, 92b, and 92c. Is positioned between the fixing roller 50 and the magnetic shielding means 58.

  Further, as shown in FIG. 5, the fixing gear 80 is formed with projections 82a and 82b on a part thereof. The hooks 91a and 91b provided on the retaining ring 90 are engaged with the protrusions 82a and 82b as shown in FIG. 3, thereby restricting the retaining ring 90 from moving in the rotational direction with respect to the fixing roller 50. ing.

  The engagement play (range of relative movement in the rotation direction) between the projections 82a and 82b and the hooks 91a and 91b is the engagement play (engagement in the rotation direction between the retaining ring 90 and the fixing roller 50). The range of relative movement in the rotational direction of the joint portions 92a, 92b, and 92c and the hole portions 56a, 56b, and 56c is set to be smaller.

  Accordingly, the engagement play in the rotation direction of the retaining ring 90 is restricted by the play between the retaining ring 90 and the fixing gear 80 that can sufficiently secure the overlap amount and can be more securely fixed in the rotational direction.

  Therefore, when the retaining ring 90 rotates, the slopes and the bent R portions of the engaging portions 92a, 92b, and 92c of the retaining ring 90 come into contact with the end surfaces of the holes 56a, 56b, and 56c of the fixing roller 50. Is prevented. That is, even when the retaining ring 90 engages with the fixing roller 50 with a minimum overlap amount, it is possible to perform more reliable thrust regulation.

  As described above, according to the present embodiment, a part of the retaining ring 90 engages with the fixing gear 80 that rotates integrally with the fixing roller 50, so that the retaining ring 90 protrudes to the inner surface of the fixing roller. Even if the amount (protrusion on the inner surface of the fixing roller) is reduced, more reliable thrust regulation can be performed.

  That is, in the fixing device according to the present embodiment, even when the space on the inner peripheral surface side of the fixing roller 50 is limited, more reliable thrust regulation of the fixing roller 50 can be realized with a simple configuration. .

  As a result, even when the induction heating method is adopted as the heating means for heating the fixing roller 50, the coil unit, the magnetic shielding means, etc. can be easily arranged at the optimum position. Can be realized.

  In the present embodiment, the retaining ring 90 is applied as the engaging member, the engaging portions 92a, 92b, and 92c have a projecting shape, and the engaging portion of the fixing roller 50 is the hole (56a, 56b, 56c), but is not limited to this as long as the engaging member and the fixing roller 50 are engaged and fixed. The same applies to the engaging relationship between the engaging member (retaining ring 90) and the regulating member (fixing gear 80).

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device according to an embodiment of the present invention. FIG. 4 is a schematic diagram for explaining thrust regulation of the fixing roller in the fixing device according to the embodiment of the present invention. FIG. 4 is a schematic diagram for explaining thrust regulation of the fixing roller in the fixing device according to the embodiment of the present invention. FIG. 3 is a schematic view of a fixing gear used in the fixing device according to the embodiment of the present invention. FIG. 10 is a schematic view for explaining thrust regulation of a fixing roller in a conventional fixing device. FIG. 10 is a schematic view for explaining thrust regulation of a fixing roller in a conventional fixing device. FIG. 10 is a schematic cross-sectional view showing a conventional fixing device.

Explanation of symbols

8 Pressure roller 50 Fixing roller 51 Bearing 52 Fixing side plate 56a, 56b, 56c Hole portion 56d Notch portion 57 Coil unit 58 Magnetic shielding means 80 Fixing gear 81 Key portion 82a, 82b Protrusion portion 90 Retaining ring 91a, 91b Hook portion 92a , 92b, 92c engaging portion 104 photosensitive drum 116 fixing device

Claims (3)

A coil unit for generating magnetic flux;
A hollow fixing roller having the coil unit therein and fixing an image formed on the recording material at the nip portion by heat generated by magnetic flux;
A ring-shaped engaging member that engages with a hole provided on one end side in the axial direction of the fixing roller;
A bearing provided on one end side in the axial direction and rotatably supporting the fixing roller;
A regulating member that is provided between the engaging member and the bearing in the axial direction of the fixing roller and that regulates the axial position of the fixing roller by engaging with the engaging member;
A protrusion that protrudes from the restricting member in the axial direction and restricts the restricting member from rotating in the rotational direction relative to the fixing roller by engaging with the engaging member;
In a fixing device having
The fixing device is characterized in that the engagement backlash in the rotation direction between the protrusion and the engagement member is smaller than the engagement backlash in the rotation direction between the hole of the fixing roller and the engagement member.   The fixing device according to claim 1, wherein the restriction member includes a gear portion that receives a rotational driving force.   The fixing device according to claim 1, further comprising a magnetic flux suppressing member that is movably provided between the inner surface of the fixing roller and the coil unit and suppresses a part of the magnetic flux directed to the fixing roller.

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