JP2006195324A - Fixing device and image forming device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sensitively detect the abnormal temperature rise of a fixing roller, by reducing the effect of dimensional tolerance of a thermostat, as much as possible and approximating an apical surface of a temperature detection part of a thermostat to an outer surface of a fixing roller. <P>SOLUTION: The fixing device 10 constitutes a part of a housing 18 rotatably supporting the fixing roller 16, and is provided with a thermostat fixing member 22 positioned to the outer surface 16a of the fixing roller 16, and a bracket 27 for fixing and positioning a thermostat 24 to the positioning member 47 of the fixing member 22 of the thermostat. For the bracket 27, a recess 43 is provided that accommodates the temperature detection part 31 of the thermostat 24. At the end part of the recess 43, facing the fixing roller 16, the stoppers 44 for positioning with respect to the outer surface 16a of the fixing roller 16, by abutting the apical surface 32 of the thermostat 24, are formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device configured to heat and press a recording material (sheet copy paper, plastic film, etc.) onto which a toner image has been transferred, and to fix the toner image on the recording material, and the fixing device. The present invention relates to an image forming apparatus such as an electrostatic copying type copying machine, a printer, a facsimile, and a composite machine of these.

  Conventionally, an image forming apparatus such as an electrostatic copying type copying machine transfers a toner image onto a recording material in an image forming unit, and sends the recording material onto which the toner image has been transferred to a fixing device along a conveyance path, In this fixing device, after the toner image is fixed on the recording material, the recording material on which the toner image is fixed is discharged onto a paper discharge tray.

  A fixing device of such an image forming apparatus includes a fixing roller having a built-in heater, and a pressure roller that is pressed by the fixing roller and rotates together with the fixing roller, and a nip between the fixing roller and the pressure roller. The recording material is heated and pressurized at the portion to fix the toner image on the recording material. In order to maintain the temperature of the outer surface of the fixing roller at a predetermined temperature suitable for fixing, the fixing device is provided with a thermistor so as to face the outer surface of the fixing roller, and the temperature of the outer surface of the fixing roller is set by the thermistor. Detection is performed, and energization to the heater of the fixing roller is controlled based on the detection result. The fixing device is fixed by a thermostat arranged so as to face the outer surface of the fixing roller when the fixing roller reaches an abnormal temperature (a predetermined temperature higher than a preset fixing temperature) for some reason. The energization of the heater of the roller is cut off to prevent the fixing roller from being abnormally heated.

  In recent years, in order to shorten the warm-up time of the fixing device, the thickness of the fixing roller is reduced, and the outer surface of the fixing roller is heated to a predetermined temperature in a short time. Therefore, in order to prevent the outer surface of the fixing roller from being abnormally heated, a thermostat is disposed close to the outer surface of the fixing roller (for example, a case where the clearance between the fixing roller and the thermostat is 2 mm is 0 mm). It is necessary to detect the temperature of the outer surface of the fixing roller sensitively.

  Therefore, as in the fixing device 100 shown in FIGS. 8 to 9, terminals 105 and 106 fixed to the end portion 104 on the opposite side of the tip surface (temperature detection surface) 103 on the fixing roller 102 side of the thermostat 101 are provided. The front end surface 103 of the temperature detection unit of the thermostat 101 is positioned against the positioning unit 108 of the housing 107 by abutting against the positioning unit 108 of the housing 107 that fixes the thermostat 101, and the housing 107 in which the thermostat 101 is positioned and fixed is positioned. A technique for positioning and fixing the front end surface 103 of the thermostat 101 with respect to the outer surface 102a of the fixing roller 102 by fixing it at a predetermined position of the positioning plate 110 of the fixing device 100 has been developed (see Patent Document 1). In FIG. 8, the pressure roller 111 is pressed against the fixing roller 102 with a predetermined spring force, and the pressure roller 111 is rotated by the rotation of the fixing roller 102.

JP 2003-15463 A

  However, in general, the fixing device 100 disclosed in Patent Document 1 uses a commercially available thermostat as the thermostat 101, and there is a dimensional tolerance from the terminals 105 and 106 to the tip surface 103 of the temperature detection unit. Since the size variation from the positioning portion 108 of the housing 107 to the front end surface 103 of the thermostat 101 is large, the front end surface 103 of the thermostat 101 cannot be brought too close to the outer surface 102 a of the fixing roller 102. When the thermostat 101 comes into contact with the outer surface 102a of the fixing roller 102, the fixing roller 102 is damaged, resulting in a problem that the life of the fixing roller 102 is shortened, fixing failure is caused, and printing quality is deteriorated. On the other hand, when the thermostat 101 is separated from the outer surface 102 a of the fixing roller 102, a problem arises that the temperature rise of the fixing roller 102 cannot be detected sensitively.

  In the fixing device 100 of Patent Document 1, the spring members 112 and 113 are spot-welded to the terminals 105 and 106 of the thermostat 101, and the terminals 105 and 106 are connected to the positioning portions 108 of the housing 107 by the spring force of the spring members 112 and 113. Therefore, the processing is difficult and the manufacturing cost increases.

  Further, since the fixing device 100 of Patent Document 1 performs spot welding of the spring members 112 and 113 on a portion where the spot welding area of the terminals 105 and 106 of the thermostat 101 is very small, spot welding of the spring members 112 and 113 is performed. The broken portion is easily broken, and there is a possibility that the thermostat 101 does not function normally due to poor conduction due to the breaking of the spring members 112 and 113.

  Therefore, the present invention can minimize the influence of the dimensional tolerance of the thermostat as much as possible, and bring the tip surface of the thermostat temperature detection part closer to the outer surface of the fixing roller, so that an abnormal temperature rise of the fixing roller can be detected sensitively. The purpose is to.

  According to the first aspect of the present invention, a fixing roller having a built-in heater, a pressure roller that rotates together with the fixing roller to press the recording material between the fixing roller, and a position facing the outer surface of the fixing roller. The present invention relates to a fixing device including a thermostat that is disposed and shuts off power to the heater when it detects that the temperature of the outer surface of the fixing roller has reached a predetermined temperature. The fixing device includes (1) a thermostat mounting member that forms a part of a housing that rotatably supports the fixing roller and is positioned with respect to an outer surface of the fixing roller; and (2) the thermostat. A bracket for positioning and fixing the thermostat with respect to the positioning member of the mounting member. And the said bracket is formed with the recessed part which accommodates the temperature detection part of the said thermostat. In addition, a stopper is provided at an end portion of the concave portion located on the fixing roller side so as to abut against a front end surface of the temperature detecting portion of the thermostat so as to be positioned with respect to the outer surface of the fixing roller. An opening is formed to expose the temperature detecting portion toward the outer surface of the fixing roller.

  According to a second aspect of the present invention, in the fixing device according to the first aspect of the present invention, the temperature detecting portion of the thermostat is elastically pressed against the stopper by a pressing means.

  According to a third aspect of the present invention, in the fixing device according to the first aspect of the present invention, a pair of left and right terminals that protrude outward from the concave portion are fixed to an end portion of the thermostat opposite to the fixing roller side. ing. The pair of terminals are fixed to the bracket by fastening means each consisting of a screw and a nut. An elastic deformation means is disposed between the head of the screw and the nut, which is elastically deformed by a tightening force by the screw and the nut and elastically presses the temperature detecting portion of the thermostat against the stopper. Yes.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus, wherein the recording material onto which the toner image has been transferred by the image forming section is heated and pressed by the fixing device according to any one of the first to third aspects, and the toner image is An image forming apparatus, wherein the image forming apparatus is fixed on a recording material.

  According to the present invention configured as described above, the positioning member of the thermostat mounting member is positioned with respect to the outer surface of the fixing roller, and the temperature detection of the thermostat is performed on the bracket that positions the front end surface of the thermostat with respect to the positioning member. Because the stopper for positioning the tip surface of the part is formed, even if a commercially available thermostat is used, the tip surface of the thermostat temperature detector (temperature detection) is not affected by the dimensional accuracy of the thermostat. Surface) can be positioned with high accuracy with respect to the outer surface of the fixing roller.

  As a result, according to the present invention, the gap between the front end surface of the thermostat temperature detection unit and the outer surface of the fixing roller can be reduced, and an abnormal temperature rise on the outer surface of the fixing roller can be sensitively detected. Become.

  Therefore, when the temperature of the outer surface of the fixing roller reaches a predetermined temperature exceeding the normal fixing temperature, the thermostat sensitively detects the temperature of the fixing device of the present invention and the image forming apparatus provided with the fixing roller. Since energization to the heater of the fixing roller can be cut off, it is possible to prevent occurrence of an excessive temperature rise phenomenon of the fixing roller.

  In addition, according to the present invention, since a commercially available thermostat can be used as it is, and it is not necessary to perform a laborious process as in the conventional example on a commercially available thermostat, the fixing device and the product of the image forming apparatus provided with the fixing device are provided. The price can be reduced.

  Further, according to the present invention, since a commercially available thermostat can be used as it is, the spot welded portion of the thermostat terminal as in the conventional example is not broken, and the function of the thermostat is stably exhibited for a long time. Therefore, the reliability of the fixing device and the image forming apparatus including the fixing device is improved.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings.

(Schematic configuration of a copying machine as an image forming apparatus)
FIG. 1 is a diagram showing a schematic configuration of a copying machine 1 as an image forming apparatus according to the present invention. As shown in FIG. 1, a copying machine 1 prints a scanner unit 2 that reads an image of a document and image data read by the scanner unit 2 on a recording material (sheet-like copy paper, plastic film, etc.) P. And a printing unit 3. Among these, the printing unit 3 conveys the recording material P sent out from the paper feed cassettes 4 and 5 or the manual paper feed tray 6 along the conveyance path 7, and first, a toner image is formed on the recording material P in the image forming unit 8. Next, the recording material P onto which the toner image has been transferred is fed into the fixing device 10, the toner image is fixed on the recording material P by the fixing device 10, and the fixed recording material P is placed on the paper discharge tray 11. The recording material P is discharged or sent to the conveyance path 12 for double-sided printing so that printing can be performed on both the front and back surfaces of the recording material P.

  In the duplex printing process of the copying machine 1, the recording material P discharged from the fixing device 10 is not completely discharged onto the paper discharge tray 11, but the rear end of the recording material P is held by the paper discharge roller 13. In this state, the paper discharge roller 13 is rotated in the reverse direction, the recording material P is sent to the duplex printing conveyance path 12, and the conveyance path 7 on the upstream side in the recording material conveyance direction of the image forming unit 8 with the front and back sides of the recording material P reversed. Then, the image forming unit 8 transfers the toner image onto the unprinted surface of the recording material P, the recording material P to which the toner image has been transferred is fixed again by the fixing device 10, and then the fixed recording material. P is discharged to the discharge tray 11 or the recording material P that has been printed on both sides is sent again to the conveyance path 12 for double-sided printing, and the image forming unit 8 and the fixing device 10 are passed through in a state of being reversed. The tray 11 is discharged.

  When the copying machine 1 shown in FIG. 1 is a multifunction machine having a printer function and a facsimile function, the copying machine 1 is connected to various data transmission / reception devices such as other copying machines, facsimiles, and personal computers connected by various communication systems. Data can be transmitted / received between them, and printing on a recording material or image display on a display panel can be performed based on data received from various data transmission / reception devices.

(Fixing device)
As shown in FIGS. 1 and 2, a fixing device 10 according to the present invention includes a fixing roller 16 including heaters 14 and 15 and a pressure roller pressed against the fixing roller 16 by a spring force of a spring (not shown). 17, and both ends of the fixing roller 16 and the pressure roller 17 are rotatably supported by bearing portions 20 and 21 of the housing 18. The fixing roller 16 is connected to a motor (not shown) via a power transmission device such as a gear, and is rotated by a motor (not shown). On the other hand, the pressure roller 17 forms a nip having a predetermined width with the fixing roller 16, and rotates following the rotation of the fixing roller 16. In FIG. 2, the recording material P is conveyed from below to above.

  As shown in FIG. 2, the housing 18 of the fixing device 10 includes a thermostat mounting member 22 so as to face the outer surface 16 a of the fixing roller 16. The thermostat mounting member 22 is formed of a thin plate-like metal or resin, and is positioned with high accuracy with respect to the outer surface 16 a of the fixing roller 16. In particular, as will be described later with reference to FIGS. 4 and 7, the pair of positioning members 47, 47 for positioning the front end surface 27 a of the bracket 27 with respect to the outer surface 16 a of the fixing roller 16 is an outer surface 16 a of the fixing roller 16. Is positioned with high accuracy. The thermostat mounting member 22 extends to the bearing portions 20 and 21 located at both ends of the fixing roller 16.

  As shown in FIGS. 2 to 3, the temperature of the outer surface 16 a of the fixing roller 16 is detected in the vicinity of the substantially central portion of the thermostat mounting member 22 in the sheet passing width direction (direction orthogonal to the conveyance direction of the recording material P). A thermistor 23 and a thermostat 24 that cuts off the power to the heaters 14 and 15 when it is detected that the temperature of the outer surface 16a of the fixing roller 16 has reached a predetermined temperature higher than the normal fixing temperature are arranged in the sheet passing width direction. It is to be installed.

  In FIG. 4, the thermostat mounting member 22 is formed such that a thermostat mounting opening 25 and a thermistor mounting opening 26 are adjacent to each other side by side in the left-right direction. Among these, the thermistor 23 is attached to the thermistor attachment opening 26 as shown in FIGS. Further, the thermostat 24 is attached to the thermostat attachment opening 25 via a bracket 27 as shown in FIGS.

  As shown in FIGS. 4 and 6, the thermostat 24 has a substantially cylindrical temperature composed of a first cylindrical portion 28 having a substantially large diameter and a second cylindrical portion 30 having a slightly smaller diameter than the first cylindrical portion 28. The detection part 31 is exhibited, and the front end surface 32 of the temperature detection part 31 on the first cylindrical part 28 side is a temperature detection surface. A pair of terminals 34 and 35 are formed on the end surface 33 of the second cylindrical portion 30 of the thermostat 24 so as to protrude outward in the radial direction of the second cylindrical portion 30. In the thermostat 24, a terminal 35 on the right side in the figure is connected to a power source (not shown) via a harness 36, and a terminal 34 on the left side in the figure is two harnesses 37 and 38, respectively. , 15 (see FIGS. 2 and 3). The harnesses 36 to 38 are fixed to the terminals 34 and 35 of the thermostat 24 via the metal fittings 40 and 41 with screws 42 and 42.

  The bracket 27 is formed with high accuracy by injection molding of a resin material, and as shown in FIGS. 4 and 6, a recess 43 that accommodates the temperature detection unit 31 of the thermostat 24 is formed at substantially the center thereof. Has been. Then, a tip surface (temperature detection surface) 32 of the temperature detection unit 31 of the thermostat 24 is abutted against an end portion of the recess 43 located on the fixing roller 16 side, and the tip surface 32 of the temperature detection unit 31 of the thermostat 24 is contacted. A plurality of stoppers 44 are positioned in the radial direction inwardly (three at approximately equal intervals in the circumferential direction of the concave portion 43) in a claw shape.

  Here, the front end surface 27 a (the surface of the stopper 44 on the fixing roller 16 side) of the bracket 27 on the fixing roller 16 side is a pair of tongue pieces formed on the lower end edge of the thermostat mounting opening 25 of the thermostat mounting member 22. The stopper 44 is positioned with respect to the outer surface 16a of the fixing roller 16 (see FIGS. 4 and 7 (a)). Further, as shown in FIG. 7A, the stopper 44 is formed by injection molding so that the thickness t thereof is highly accurate. In this way, the positioning member 47 of the thermostat mounting member 22 is positioned with high accuracy with respect to the outer surface 16a of the fixing roller 16, and the stopper 44 is molded with high accuracy, resulting in variations in the wall thickness t (molding error). Since it is small, the tip surface 32 of the thermostat 24 can be positioned with high accuracy with respect to the outer surface 16a of the fixing roller 16 (see FIG. 7A).

  Further, as shown in FIGS. 4 and 7A, the end portion of the recess portion 43 of the bracket 27 located on the fixing roller 16 side is an opening portion 45 other than the stopper 44 described above. The inside and outside communicate with each other. As a result, when the temperature detection unit 31 of the thermostat 24 is accommodated in the recess 43, the tip surface 32 of the temperature detection unit 31 is exposed to the outside of the recess 43 through the opening 45.

  As shown in FIGS. 4 to 6, the bracket 27 has a flange portion 46 attached to the outer surface 22 a of the thermostat attachment member 22. The flange portion 46 of the bracket 27 is formed with a hole 52 through which the shaft portion 51 of the nut 50 that is screwed into the thermostat fixing screw 42 is inserted. Further, as shown in FIGS. 4 and 5, holes 54 through which the shafts of the screws 53 for fixing the bracket 27 to the thermostat mounting member 22 pass are formed at both ends on the lower end side of the flange portion 46 of the bracket 27. Has been. A screw hole 55 is formed in the thermostat mounting member 22 so as to correspond to the hole 54 of the bracket 27, and a screw 53 for fixing the bracket is screwed into the screw hole 55.

  The nut 50, wave washer (elastic deformation means) 56, and screw 42 shown in FIGS. 4 and 6 are pressing means K that elastically press the tip surface 32 of the temperature detection unit 31 of the thermostat 24 against the stopper 44 of the bracket 27. It is composed. Among the pressing means K, the wave washer 56 and the nut 50 are arranged on the thermostat mounting member 22 side (surface side) of the flange portion 46 of the bracket 27 in the order of the wave washer 56 and the nut 50 (the nut 50 and the flange portion). 46, the wave washer 56 is positioned between them. The wave washer 56 is so fitted that the cylindrical shaft portion 51 of the nut 50 is fitted into the hole 56a at the center thereof, and is pressed between the head portion 50a of the nut 50 and the flange portion 46 of the bracket 27. It has become. Further, the shaft portion 51 of the nut 50 passes through the hole 56a of the wave washer 56 and the hole 52 of the bracket 27, and comes into contact with the surface (surface on the fixing roller 16 side) side of the terminals 34 and 35 of the thermostat 24. ing. Further, the wave washer 56 can absorb dimensional errors of the housing 18, the bracket 27, and the thermostat 24 by being elastically deformed. In addition, although the fastening means is comprised with the screw 42 and the nut 50, the nut 50 is not restricted to this embodiment with a square head, You may make it use a nut with a hexagonal head.

  As shown in FIGS. 4 and 6, the pressing means K is configured such that the shaft portion 42 a of the screw 42 disposed on the back side of the flange portion 46 of the bracket 27 is connected to the holes 40 a and 41 a of the metal fittings 40 and 41, the terminals. The wave washer 56 is elastically deformed by passing the holes 34a and 35a of the holes 34a and 35a in this order and screwing the screw 42 into the nut 50 and tightening, and the temperature detecting portion of the thermostat 24 with the elastic deformation force of the wave washer 56 It becomes possible to elastically press the distal end surface 32 of the 31 against the stopper 44. The metal fittings 40 and 41 are also fixed to the terminals 34 and 35 of the thermostat 24 by the elastic deformation force of the wave washer 56. In this way, the bracket 27 and the thermostat 24 are integrated in a state where they are positioned by the pressing means K.

  5 to 6 are views showing a state in which the bracket 27 to which the thermostat 24 is attached is attached to the thermostat attachment member 22, FIG. 5 is a front view showing the attachment state, and FIG. 6 is a line AA in FIG. It is sectional drawing cut | disconnected and shown along.

  As shown in FIGS. 5 to 6, the recess 43 and the thermostat 24 of the bracket 27 are inserted into the thermostat mounting opening 25 of the thermostat mounting member 22, and the projections 57 and 58 formed on the surface side of the bracket 27 are thermostat. Inserted into the positioning holes 60 and 61 of the mounting member 22, the front end surface 27 a of the bracket 27 is abutted against the positioning member 47 of the thermostat mounting member 22, and the flange portion 46 of the bracket 27 is fastened and fixed to the thermostat mounting member 22 with a screw 53. . As shown in FIG. 4, the thermostat mounting opening 25 penetrates from the outer surface 22 a side of the thermostat mounting member 22 to the surface side facing the fixing roller 16, and the thermostat 24 positioned by the bracket 27. The front end surface 32 is exposed toward the outer surface 16a of the fixing roller 16 (see FIG. 7A).

  FIG. 7 is a diagram schematically showing the attachment state of the thermostat 24. As shown in FIG. 7A, the positioning member 47 of the thermostat mounting member 22 for positioning the tip end surface 27a of the bracket 27 is offset by L with respect to a line T1 connecting the rotation center of the fixing roller and the center of the thermostat. The bracket 27 is positioned at this position. Further, as shown in FIG. 7B, the thermostat 24 is positioned with the upper end portion of the distal end surface 32 thereof being offset by L1 with respect to the line T1 by the stopper 44 of the bracket 27. The lower end side is positioned offset by L2 with respect to the line T1 by the stoppers 44, 44 of the bracket 27. As a result, the front end surface 32 of the thermostat 27 can be brought close to the outer surface 16 a of the fixing roller 16 so that the bracket 27 and the thermostat mounting member 22 do not interfere with the fixing roller 16. In addition, as described above, the front end surface 32 of the thermostat 24 can be positioned with high accuracy with respect to the outer surface 16a of the fixing roller 16 (because an error in the mounting position can be reduced). Can be brought closer to the outer surface 16a of the fixing roller 16 than in the conventional example.

  Therefore, according to the present embodiment, the thermostat 24 can detect the temperature sensitively when the outer surface 16a of the fixing roller 16 reaches a predetermined high temperature, and can cut off the energization of the heaters 14 and 15 of the fixing roller 16. As a result, the abnormal temperature rise phenomenon of the fixing roller 16 can be effectively prevented.

(Operation and effect of this embodiment)
According to the present embodiment configured as described above, the front end surface 27a of the bracket 27 is positioned by the positioning member 47 of the thermostat mounting member 22 from the outer surface 16a of the fixing roller 16, and the temperature of the thermostat 24 by the stopper 44 of the bracket 27. Since the front end surface 32 of the detection unit 31 is positioned, even if a commercially available thermostat 24 is used, the front end surface of the temperature detection unit 31 of the thermostat 24 is not affected by the dimensional accuracy of the thermostat 24 ( The temperature detection surface 32) can be positioned with high accuracy with respect to the outer surface 16a of the fixing roller 16.

  As a result, according to the present embodiment, the gap between the tip surface 32 of the temperature detection unit 31 of the thermostat 24 and the outer surface 16a of the fixing roller 16 can be reduced, and the abnormal temperature of the outer surface 16a of the fixing roller 16 can be reduced. The rise can be detected sensitively.

  Therefore, when the temperature of the outer surface 16a of the fixing roller 16 reaches a predetermined temperature exceeding the normal fixing temperature, the thermostat 24 makes the thermostat 24 sensitive to the fixing device 10 of the present embodiment and the copying machine 1 having the same. Thus, since the thermostat 24 can cut off the energization of the heaters 14 and 15 of the fixing roller 16, it is possible to prevent an excessive temperature rise phenomenon of the fixing roller 16.

  In addition, according to the present embodiment, the commercially available thermostat 24 can be used as it is, and it is not necessary to perform the time-consuming processing as in the conventional example on the commercially available thermostat 24. Therefore, the fixing device 10 and a copy provided with the same. The product price of the machine 1 can be reduced.

  Further, according to the present embodiment, since the commercially available thermostat 24 can be used as it is, the spot welded portion of the thermostat terminal as in the conventional example is not broken, and the function of the thermostat 24 is stabilized for a long time. This improves the reliability of the fixing device 10 and the copying machine 1 including the same.

(Modification of the fixing device)
In the above-described embodiment, the wave washer 56 is arranged between the head 50a of the nut 50 and the bracket 27. However, the present invention is not limited to this, and the head of the screws 42 and 42 and the metal fittings are not limited thereto. You may make it arrange | position between 40,41.

  In the above-described embodiment, instead of the wave washer 56, a rubber plate, a rubber tube, a spring washer, or the like may be used as an elastically deformable elastic deformation means.

  Moreover, in the above-mentioned embodiment, the terminals 34 and 35 of the thermostat 24 and the metal fittings 40 and 41 are fixed with screws, the wave washer 56 and the nut 50 are omitted, and the end surface side of the second cylindrical portion 30 of the thermostat 24 is disposed. You may make it press directly toward the stopper 44 side of the bracket 27 with the spring member attached to the thermostat attachment member 22 side.

  In FIG. 7, the stopper 44 may be at least two places in the upper and lower directions.

  The fixing device according to the present invention is not limited to the above-described copying machine, but can be widely applied to printers, facsimiles, composite machines, and the like that transfer a toner image onto a recording material.

1 is a schematic configuration diagram of a copying machine as an image forming apparatus including a fixing device according to the present invention. 1 is an external perspective view of a fixing device according to the present invention. FIG. 3 is an external perspective view showing a part of the fixing device shown in FIG. 2 in an enlarged manner. FIG. 4 is an exploded perspective view showing the fixing device shown in FIG. 3. 1 is a front view of a fixing device according to the present invention. FIG. 6 is a cross-sectional view of the fixing device cut along the line AA in FIG. 5. FIG. 7A is a cross-sectional view schematically showing the mounting state of the thermostat, and FIG. 7B is a view showing the engagement state between the bracket stopper and the thermostat. It is sectional drawing which shows typically the attachment state of the conventional thermostat. It is a perspective view which decomposes | disassembles and shows the conventional thermostat and a housing typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 8 ... Image forming part, 10 ... Fixing device, 14, 15 ... Heater, 16 ... Fixing roller, 16a ... Outer surface, 17 ... Pressure roller, 18 ... Housing, 22 ... Thermostat mounting member, 24 ... Thermostat, 27 ... Bracket, 31 ... Temperature detection part, 32 ... Tip surface, 34,35 ... Terminal, 42 ... Screw (fastening means) , 43... Recess, 44. Stopper, 45. Opening, 47 .. positioning member, 50. Nut (fastening means), 56. Wave washer (elastic deformation means), K. ...... Recording material

Claims (4)

A fixing roller with a built-in heater,
A pressure roller that rotates together with the fixing roller to press the recording material between the fixing roller, and
A thermostat disposed at a position facing the outer surface of the fixing roller, and shutting off the power to the heater when detecting that the temperature of the outer surface of the fixing roller has reached a predetermined temperature;
In the fixing device provided with
A thermostat mounting member that forms part of a housing that rotatably supports the fixing roller and is positioned with respect to an outer surface of the fixing roller;
A bracket for positioning and fixing the thermostat with respect to a positioning member of the thermostat mounting member,
The bracket is formed with a recess for accommodating the temperature detection part of the thermostat,
At the end of the recess located on the fixing roller side, a stopper is formed that is positioned against the outer surface of the fixing roller by abutting the front end surface of the temperature detection unit of the thermostat, and the temperature of the thermostat The fixing device is characterized in that an opening for exposing the detection portion toward the outer surface of the fixing roller is formed.   The fixing device according to claim 1, wherein the temperature detection unit of the thermostat is elastically pressed against the stopper by a pressing unit. A pair of left and right terminals protruding outward from the recess are fixed to the end of the thermostat opposite to the fixing roller.
The pair of terminals are fixed to the bracket by fastening means each consisting of a screw and a nut,
Between the head of the screw and the nut, there is disposed elastic deformation means that is elastically deformed by a tightening force by the screw and nut and elastically presses the temperature detecting portion of the thermostat against the stopper. The fixing device according to claim 1.   The recording material onto which the toner image has been transferred by the image forming unit is heated and pressed by the fixing device according to claim 1 to fix the toner image on the recording material. Forming equipment.

Images