JP2019015880A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can accurately detect a temperature of a fixing member moving relative to a pressure member.SOLUTION: A fixing device 7 of the present invention comprises: a fixing belt 21 that heats toner on a sheet while rotating around an axis; a pressure roller 22 that forms a pressure area N with the fixing belt 21 while rotating around the axis and applies a pressure to the toner on the sheet passing through the pressure area N; a pressure adjustment unit that applies a pressure to the pressure area N by moving the fixing belt 21 in a direction approaching the pressure roller 22 and reduces the pressure on the pressure area N by moving the fixing belt 21 in a direction separating from the pressure roller 22; and an interlocking detection unit 25 that moves following the fixing belt 21 while maintaining an interval with the fixing belt 21 and detects a temperature of the fixing belt 21.SELECTED DRAWING: Figure 3

Description

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

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred onto a medium such as paper.

  For example, the fixing device described in Patent Literature 1 includes a heating roller that is heated by a heat source, a pressure roller that is pressed against the heating roller, and a thermopile that detects heat radiated from the heating roller. The thermopile is mounted on the holder with its detection surface facing the heating roller.

JP 2003-5574 A

  In the fixing device described above, the rotating shaft of the heating roller is fixed, and the pressure roller is pressed against the heating roller. In this configuration, since the distance between the surface of the heating roller and the detection surface of the thermopile is kept constant, the thermopile was able to accurately detect the surface temperature of the heating roller.

  However, when the rotation axis of the pressure roller is fixed and the heating roller is pressed against this pressure roller, the distance between the surface of the heating roller and the detection surface of the thermopile changes, so there is an error in the temperature detected by the thermopile. There was a problem that occurred.

  In order to solve the above problems, the present invention provides a fixing device and an image forming apparatus that can accurately detect the temperature of a fixing member that moves relative to a pressure member.

  In order to achieve the above object, the fixing device of the present invention forms a pressure region between a fixing member that heats toner on a medium while rotating around an axis and the fixing member that rotates around an axis. And pressurizing the pressure area by moving the fixing member in a direction approaching the pressure member and a pressure member that pressurizes the toner on the medium passing through the pressure area. The fixing member is moved so as to follow the fixing member while keeping a distance between the fixing member and a pressure adjusting unit that reduces the pressure area by moving the fixing member in a direction away from the pressure member. And an interlocking detection unit that detects temperature.

  In this case, the apparatus further includes a movable frame that supports the fixing member so as to be rotatable about an axis, and a support frame that rotatably supports the movable frame, and the pressure adjusting unit rotates the movable frame. The fixing member is moved, and the interlocking detection unit is disposed opposite to the fixing member across the movable frame, and is fixed to an apparatus main body that supports the support frame; and the fixing A temperature sensor that detects heat radiated from the member in a non-contact manner, and holds the temperature sensor, is connected to the movable frame, and is supported by the fixed frame in a state of moving in the rotating direction of the movable frame. It is preferable that a holder and a biasing member that biases the holder toward the movable frame are included.

  In this case, the image forming apparatus further includes a heat source that is provided inside the fixing member and heats the fixing member from the inside, and the axial center of the fixing member, the heat source, and the temperature sensor are arranged on the same straight line. It is preferable.

  In order to achieve the above object, an image forming apparatus of the present invention includes any of the fixing devices described above.

  According to the present invention, it is possible to accurately detect the temperature of the fixing member that moves relative to the pressure member.

1 is a schematic view (front view) showing a printer according to an embodiment of the present invention. 1 is a perspective view showing a fixing device (housing) according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present invention. FIG. 2 is a perspective view showing an internal structure of a fixing device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing an internal structure of a fixing device according to an embodiment of the present invention. FIG. 3 is an exploded perspective view showing an interlocking detection unit of the fixing device according to the embodiment of the present invention. FIG. 3 is a perspective view showing an upper part of an interlocking detection unit of the fixing device according to the embodiment of the present invention. FIG. 3 is a perspective view showing a lower portion of an interlocking detection unit of the fixing device according to the embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a procedure for attaching the interlocking detection unit of the fixing device according to the embodiment of the present disclosure to a housing. FIG. 6 is a cross-sectional view illustrating the operation of the interlock detection unit of the fixing device according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, “Fr” indicates “front”, “Rr” indicates “rear”, “L” indicates “left”, “R” indicates “right”, and “U” indicates “Up” indicates “D”, and “D” indicates “Down”.

[Entire printer configuration]
A printer 1 as an example of an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic view (front view) showing the printer 1. In the following description, “conveyance direction” refers to the direction in which the sheet S is conveyed. The terms “upstream” and “downstream” and similar terms refer to “upstream” and “downstream” in the conveying direction of the sheet S and similar concepts.

  The printer 1 includes an apparatus main body 2 that forms a substantially rectangular parallelepiped appearance. In the lower part of the apparatus main body 2, for example, a paper feed cassette 3 that stores a sheet S (medium) such as plain paper is provided. A paper discharge tray 4 is provided on the upper surface of the apparatus main body 2. Note that the sheet S is not limited to paper, and may be made of resin or the like.

  The printer 1 includes a paper feeding device 5, an image forming device 6, and a fixing device 7. The paper feeding device 5 is provided at the upstream end of the conveyance path 8 extending from the paper feeding cassette 3 to the paper discharge tray 4. The image forming device 6 is provided in an intermediate portion of the conveyance path 8, and the fixing device 7 is provided on the downstream side of the conveyance path 8.

  The image forming device 6 includes a toner container 10, a drum unit 11, and an optical scanning device 12. The toner container 10 contains, for example, black toner (developer). The drum unit 11 includes a photosensitive drum 13, a charging device 14, a developing device 15, and a transfer roller 16. The transfer roller 16 is in contact with the photosensitive drum 13 from below to form a transfer nip. The toner may be a two-component developer in which the toner and the carrier are mixed, or may be a one-component developer made of a magnetic toner.

  A control device (not shown) of the printer 1 appropriately controls each device, and executes an image forming process as follows. The charging device 14 charges the surface of the photosensitive drum 13. The photosensitive drum 13 receives the scanning light emitted from the optical scanning device 12 and carries an electrostatic latent image. The developing device 15 uses the toner supplied from the toner container 10 to develop the electrostatic latent image on the photosensitive drum 13 into a toner image. The sheet S is sent from the sheet feeding cassette 3 to the conveyance path 8 by the sheet feeding device 5, and the toner image on the photosensitive drum 13 is transferred to the sheet S passing through the transfer nip. The fixing device 7 fixes the toner image on the sheet S. Thereafter, the sheet S is discharged to the paper discharge tray 4.

[Fixing device]
Next, the fixing device 7 will be described with reference to FIGS. FIG. 2 is a perspective view showing the fixing device 7 (housing 20). FIG. 3 is a cross-sectional view showing the fixing device 7. FIG. 4 is a perspective view showing the internal structure of the fixing device 7. FIG. 5 is an exploded perspective view showing the internal structure of the fixing device 7. FIG. 6 is an exploded perspective view showing the interlock detection unit 25. FIG. 7 is a perspective view showing the upper side of the interlocking detection unit 25. FIG. 8 is a perspective view showing the lower side of the interlocking detection unit 25.

  As shown in FIGS. 2 and 3, the fixing device 7 includes a housing 20, a fixing belt 21, a pressure roller 22, a halogen heater 23, a pressure adjustment unit 24, and an interlocking detection unit 25. It is out. The fixing belt 21 and the pressure roller 22 are provided inside the housing 20. The halogen heater 23 is a heat source for heating the fixing belt 21 by emitting light. The fixing device 7 employs a belt fixing method using a fixing belt 21 having a small heat capacity so as to reach a set temperature in a short time. The pressure adjusting unit 24 is a unit for adjusting the contact pressure of the fixing belt 21 with respect to the pressure roller 22. The interlock detection unit 25 is a unit for detecting the temperature of the fixing belt 21.

<Case>
As shown in FIGS. 2 and 3, the housing 20 includes a support frame 30 and a movable frame 40. The support frame 30 is supported by the apparatus main body 2. As will be described in detail later, the movable frame 40 is provided inside the support frame 30 and supports the fixing belt 21 so as to be rotatable about an axis.

(Support frame)
The support frame 30 is formed in a substantially rectangular parallelepiped that is long in the front-rear direction (see FIG. 2). Openings for inserting the sheet S are formed on both the left and right sides of the support frame 30. An entrance guide 31 for guiding the sheet S to a contact portion (pressure area N) between the fixing belt 21 and the pressure roller 22 is provided at the right side opening of the support frame 30. The left opening of the support frame 30 is provided with a pair of conveying rollers 32 for sending the sheet S downstream (see FIG. 3).

  Further, the upper portion of the support frame 30 (hereinafter also referred to as an upper sheet metal 33) is formed in a substantially plate shape bent in a substantially L shape by a metal material such as iron or aluminum alloy, for example. Specifically, the upper sheet metal 33 includes a horizontal portion 33A that forms an upper surface, a vertical portion 33B that forms a right side surface, and an inclined portion 33C that forms a downward gradient from the horizontal portion 33A toward the vertical portion 33B. It is out. A substantially rectangular outer through hole 34 is opened in the inclined portion 33C. The outer through hole 34 is formed on the right side of the substantially central portion in the front-rear direction of the inclined portion 33C (see FIG. 2). A pair of fulcrum shafts 35 are provided inside the support frame 30 (see FIG. 4). The support frame 30 rotatably supports the movable frame 40 via a pair of fulcrum shafts 35.

(Movable frame)
As shown in FIGS. 3 and 4, the movable frame 40 includes a pair of end holders 41, a construction sheet metal 42, and a positioning member 43. The pair of end holders 41 are attached to both front and rear ends of the fixing belt 21. The construction sheet metal 42 is constructed between the pair of end holders 41. The positioning member 43 is fixed to the upper surface of the construction sheet metal 42 (see FIG. 3). Since the pair of end holders 41 have a symmetrical shape, the front end holder 41 will be described below.

  As shown in FIG. 4, the end holder 41 is formed in a substantially plate shape by a metal material such as iron or aluminum alloy, for example. A holding hole 44 is opened in the central portion of the end holder 41. A fulcrum shaft 35 of the support frame 30 is fitted to the lower left portion of the end holder 41. The end holder 41 is rotatably supported on the fulcrum shaft 35. On the right side of the end holder 41, an arm portion 41A extending in the right direction is formed. The arm portion 41 </ b> A is formed in a substantially U shape that is open upward when viewed from the side. A connecting piece 41B is formed in the axially inner upper part of the arm portion 41A so as to extend inward in the axial direction. A shape holding portion (not shown) that fits inside the axial end portion of the substantially cylindrical fixing belt 21 is fixed on the inner side in the axial direction of the end holder 41. When the shape holding portion is fitted to the axial end portion of the fixing belt 21, the fixing belt 21 is held in a substantially cylindrical shape and is supported rotatably around the axis.

  The installation sheet metal 42 is formed in a substantially plate shape by a metal material such as iron or aluminum alloy, for example. The construction sheet metal 42 is bridged between a pair of end holders 41, and both front and rear ends thereof are fixed to the pair of end holders 41 via connecting screws B1. Further, the connecting piece 41B of the arm portion 41A is also fixed to the front and rear side surfaces of the installation sheet metal 42 via a connecting screw B1. A substantially circular inner through hole 45 is opened in the installation sheet metal 42. The inner through hole 45 is formed at a position (substantially directly below) corresponding to the outer through hole 34 (see FIG. 2) of the support frame 30 (upper sheet metal 33).

  The positioning member 43 is formed in a substantially plate shape by a synthetic resin material having heat resistance, for example. As shown in FIG. 3, the positioning member 43 is fixed to the upper surface of the construction sheet metal 42 and is disposed between the construction sheet metal 42 and the upper sheet metal 33.

  As shown in FIG. 2, the positioning member 43 is provided with a pair of positioning pins 46 and a communication hole 47. The pair of positioning pins 46 and the communication holes 47 are provided at positions exposed from the outer through holes 34 of the support frame 30 (upper sheet metal 33). The pair of positioning pins 46 are spaced apart in the front-rear direction and protrude upward from the upper surface of the positioning member 43. Each positioning pin 46 is formed in a substantially cylindrical shape, and its tip is formed in a tapered shape. The communication hole 47 opens in the positioning member 43 between the pair of positioning pins 46. The communication hole 47 is formed in a substantially U shape with the right side opened as viewed from above, and communicates the outer through hole 34 and the inner through hole 45 (see FIG. 4).

<Fixing belt>
As shown in FIGS. 3 to 5, the fixing belt 21 as an example of the fixing member is an endless belt, and is formed in a substantially cylindrical shape that is long in the front-rear direction. The fixing belt 21 is made of, for example, a synthetic resin material having heat resistance and elasticity such as polyimide resin.

(Pressing structure)
As shown in FIGS. 3 and 5, a pressing structure 26 is provided inside (inside) the fixing belt 21. The pressing structure 26 includes a support member 26A, a reflecting member 26B, and a pressing member 26C.

  The support member 26A is formed, for example, in a substantially rectangular cylindrical shape that is long in the front-rear direction using a metal material, and penetrates the fixing belt 21 in the axial direction. Both ends in the axial direction of the support member 26A are fitted in the holding holes 44 of the end holder 41 (see FIG. 4). The reflecting member 26B is formed in a substantially plate shape that is long in the front-rear direction by, for example, a metal material. The reflection member 26B is fixed to the upper surface of the support member 26A and has a function of reflecting light from the halogen heater 23. The pressing member 26C is formed, for example, in a substantially plate shape that is long in the front-rear direction using a heat-resistant resin or the like. The pressing member 26 </ b> C is fixed to the lower surface of the support member 26 </ b> A and has a function of receiving the fixing belt 21 pressed against the pressure roller 22.

<Pressure roller>
As shown in FIGS. 3 to 5, the pressure roller 22 as an example of a pressure member is formed in a substantially cylindrical shape that is long in the front-rear direction. The pressure roller 22 includes a metal cored bar 22A and an elastic layer 22B such as a silicone sponge laminated on the outer peripheral surface thereof. Both front and rear ends of the pressure roller 22 (core metal 22A) are supported by the housing 20 (support frame 30) so as to rotate around the axis. A driving motor (not shown) is connected to the metal core 22A through a gear train or the like, and the pressure roller 22 is rotationally driven by the driving motor.

<Halogen heater>
As shown in FIG. 3 and FIG. 5, the halogen heater 23 as an example of a heat source is formed in a substantially rod shape (substantially cylindrical shape) long in the front-rear direction and penetrates the fixing belt 21 in the axial direction. The halogen heater 23 is provided inside the fixing belt 21 on the side opposite to the pressure region N with the support member 26A interposed therebetween. The halogen heater 23 includes a substantially cylindrical light emitting portion 23A including a filament, and a pair of electrode portions 23B fixed to both ends in the axial direction. The pair of electrode portions 23B are supported by the end holder 41 in a state of passing through the holding holes 44 of the end holder 41 (see FIG. 4). The halogen heater 23 heats the fixing belt 21 from the inside by using infrared light emitted from the light emitting portion 23A. Specifically, the light emitted from the light emitting portion 23A is reflected directly or by the reflecting member 26B and irradiated on the upper inner surface of the fixing belt 21 to heat the upper side of the fixing belt 21. In the above description, the halogen heater 23 is employed as the heat source. However, instead of this, a heat source such as a carbon heater may be employed.

<Pressure adjustment part>
As shown in FIG. 4, the pressure adjusting unit 24 includes a pair of eccentric cams 50, a pair of operating metal plates 51, and a pair of adjusting springs 52.

  The pair of eccentric cams 50 are so-called disc cams, and are fixed to both ends of a cam coupling shaft 53 extending in the front-rear direction. The cam connection shaft 53 is adjacent to the right side of the pressure roller 22 and is provided substantially parallel to the pressure roller 22. A cam motor 55 is connected to one end (front end) of the cam coupling shaft 53 via a gear train 54. Each actuating sheet metal 51 is formed in a substantially U shape with the lower part opened, and is disposed below the arm part 41 </ b> A of the end holder 41. An operation roller 56 that contacts the outer peripheral surface of the eccentric cam 50 is supported at the lower part of each operation sheet metal 51. An operation rod 57 that passes through a shaft hole opened in the arm portion 41A is fixed to the upper portion of each operation sheet metal 51. Each adjustment spring 52 is, for example, a coil spring, and is installed between the upper end portion of the operating rod 57 and the arm portion 41A. The adjustment spring 52 urges the arm portion 41A downward.

  When the eccentric cam 50 is rotated about the cam coupling shaft 53 by the drive of the cam motor 55, the working sheet metal 51 (working rod 57) reciprocates in the vertical direction. For example, when the eccentric cam 50 pushes the operation roller 56 downward and the operation sheet metal 51 descends, the adjustment spring 52 is compressed and the urging force increases. Then, since the movable frame 40 (end holder 41) rotates downward about the fulcrum shaft 35, the fixing belt 21 is pressed against the pressure roller 22 (pressure state). That is, the pressure region N formed between the fixing belt 21 and the pressure roller 22 is pressurized. On the other hand, when the eccentric cam 50 releases the push-down of the operation roller 56 and the operation sheet metal 51 is raised, the adjustment spring 52 is extended and the urging force is reduced. Then, the movable frame 40 rotates slightly upward about the fulcrum shaft 35, and the pressure in the pressurizing region N decreases (depressurized state).

  As described above, the pressure adjusting unit 24 moves the fixing belt 21 by rotating the movable frame 40. The pressure adjustment unit 24 moves the fixing belt 21 in a direction approaching the pressure roller 22 to pressurize the pressure region N, and moves the fixing belt 21 in a direction away from the pressure roller 22 to pressurize. The area N is depressurized. The pressurization region N refers to a region from an upstream position where the pressure is 0 Pa to a downstream position where the pressure is again 0 Pa via a position where the pressure is maximum.

<Interlock detection unit>
As shown in FIGS. 3 and 6 to 8, the interlocking detection unit 25 includes a fixed frame 60, a temperature sensor 61, a holder 62, and a pair of interlocking springs 63.

(Fixed frame)
As shown in FIGS. 6 to 8, the fixed frame 60 is formed in a substantially plate shape that is long in the front-rear direction, for example, by a metal material such as iron or aluminum alloy. The fixed frame 60 is a sheet metal bent in a substantially L shape when viewed from the front. The fixed frame 60 is disposed to face the opposite side of the fixing belt 21 with the movable frame 40 interposed therebetween. Specifically, the fixed frame 60 is disposed so as to cover the upper sheet metal 33 of the support frame 30 from the upper right side. A plurality of fixed pieces 60 </ b> A are formed at both front and rear ends of the fixed frame 60.

  A recessed portion 60B having a bottom surface that is inclined downward from the left side to the right side is formed at a substantially central portion in the front-rear direction of the fixed frame 60. The bottom surface of the recessed portion 60B is inclined so as to be substantially parallel to the inclined portion 33C in a state where the fixed frame 60 is disposed above the upper sheet metal 33 (see FIG. 3).

  A pair of support pins 64 and a frame detection hole 65 are provided in the recess 60 </ b> B of the fixed frame 60. The pair of support pins 64 are spaced apart in the front-rear direction and project upward from the bottom surface of the recess 60B. The distance between the pair of support pins 64 is wider than the distance between the pair of positioning pins 46 (see FIG. 2). Each support pin 64 is formed in a substantially cylindrical shape. A screw hole 64 </ b> A in which a female screw is cut opens at the upper end surface of each support pin 64. The frame detection hole 65 opens on the bottom surface of the recess 60B between the pair of support pins 64. The frame detection hole 65 is formed in a substantially oblong shape when viewed from the plane. The frame detection hole 65 is formed at a position corresponding to the outer through hole 34 of the upper sheet metal 33 with the fixed frame 60 disposed above the upper sheet metal 33 (see FIG. 3).

(Temperature sensor)
The temperature sensor 61 is a thermopile that detects heat (infrared rays) radiated from the fixing belt 21 in a non-contact manner. The temperature sensor 61 is mounted on a substrate C in which a control circuit is incorporated.

(holder)
For example, the holder 62 is formed in a substantially rectangular parallelepiped shape from a synthetic resin material having heat resistance. The holder 62 includes a holder main body 62A, a pair of holder arms 62B, and a pair of holder projections 62C.

  The holder main body 62A is formed in a substantially tray shape with the upper surface opened. The temperature sensor 61 is mounted on the holder body 62A together with the substrate C. A holder detection hole 66 for exposing the detection surface 61A of the temperature sensor 61 is opened on the bottom surface of the holder main body 62A (see FIG. 8). The pair of holder arms 62B extends outward from both front and rear side surfaces of the holder body 62A. Each holder arm 62B has a substantially circular support through hole 67 opened. Each support through hole 67 has an inner diameter larger than the outer diameter of the support pin 64.

  The pair of holder protrusions 62C extends downward from the lower surface of the holder body 62A. Each holder projection 62C is formed in a substantially cylindrical shape with a fitting hole 68 opened on its lower surface. The pair of holder protrusions 62 </ b> C are spaced apart in the front-rear direction across the holder detection hole 66. The distance between the pair of holder projections 62 </ b> C is set to be approximately the same as the distance between the pair of positioning pins 46.

(Linked spring)
Each of the pair of interlocking springs 63 as an example of the urging member is a coil spring, for example.

<Assembly of interlocking detection unit>
Next, a procedure for assembling the interlocking detection unit 25 will be described with reference to FIG. It is assumed that the holder 62 (holder body 62A) holds the temperature sensor 61 mounted on the substrate C.

  First, the operator aligns the support through holes 67 of the pair of holder arms 62 </ b> B with the pair of support pins 64 of the fixed frame 60, and inserts the pair of support pins 64 into the pair of support through holes 67. Since the inner diameter of the support through hole 67 is larger than the outer diameter of the support pin 64, the support pin 64 is inserted into the support through hole 67 with play. Further, the holder main body 62 </ b> A is disposed in the frame detection hole 65 of the fixed frame 60, and the pair of holder projecting portions 62 </ b> C penetrates the frame detection hole 65. Next, the operator inserts the pair of interlocking springs 63 into the pair of support pins 64 that have passed through the pair of support through holes 67. Subsequently, the operator screws the fixing screw B <b> 2 with the washer W sandwiched in the screw hole 64 </ b> A opened in the upper end surface of the support pin 64.

  Thus, the assembly of the interlock detection unit 25 is completed (see FIG. 7). In this state, the lower end portion of the interlocking spring 63 is fitted into an annular convex portion 67A (see FIG. 6) protruding from the edge portion of the support through hole 67 of the holder arm 62B. The upper end surface of the interlocking spring 63 is in contact with the lower surface of the washer W. The interlocking spring 63 is stretched between the upper surface of the holder arm 62B and the lower surface of the washer W in a compressed state (see FIG. 7). The interlocking spring 63 urges the holder 62 downward with the washer W as a base. In this state, the holder 62 is supported so as to be movable in the vertical direction along the pair of support pins 64. The holder 62 is supported so as to be movable in the front-rear direction and the left-right direction by the gap between the support through hole 67 and the support pin 64.

<Mounting the interlock detection unit>
Next, with reference to FIG. 3 and FIG. 9, the procedure for attaching the interlocking detection unit 25 to the housing 20 will be described. FIG. 9 is a cross-sectional view illustrating a procedure for attaching the interlocking detection unit 25 to the housing 20. In addition, the pressurization area | region N shall be a pressurization state.

  The assembled interlocking detection unit 25 is attached to the upper right side of the housing 20. First, as shown in FIG. 9, the operator places the interlocking detection unit 25 at a position away from the upper right side of the housing 20, and moves the interlocking detection unit 25 leftward so as to cover the upper sheet metal 33. Move (see white arrow in FIG. 9).

  Then, as shown in FIG. 3, the fixed frame 60 is disposed to face the upper sheet metal 33 with a gap therebetween. Further, the holder 62 is disposed above the outer through hole 34 of the support frame 30. The temperature sensor 61 (detection surface 61 </ b> A) held by the holder 62 is disposed to face the communication hole 47 exposed in the outer through hole 34. The pair of positioning pins 46 exposed in the outer through holes 34 are fitted into fitting holes 68 (see FIG. 8) opened at the front end surfaces of the pair of holder projections 62C.

  Next, the operator screws the fixed piece 60 </ b> A of the fixed frame 60 to the main frame (not shown) in the apparatus main body 2. In this state, the fixed frame 60 is fixed to the apparatus main body 2, and the holder 62 is connected to the movable frame 40. The interlocking spring 63 biases the holder 62 toward the movable frame 40 (downward). The detection surface 61 </ b> A of the temperature sensor 61 is disposed to face the surface of the fixing belt 21 through the communication hole 47 and the inner through hole 45. In this state, the axis (rotation center) of the fixing belt 21, the halogen heater 23 (axis), and the temperature sensor 61 are arranged on the same straight line.

  The halogen heater 23, the drive motor, the cam motor 55, the temperature sensor 61 (substrate C), and the like described above are electrically connected to the control device of the printer 1. The control device controls devices connected via various drive circuits.

[Operation of fixing device]
Here, the operation (fixing process) of the fixing device 7 will be described with reference to FIG. Note that when the fixing process is performed, the pressure region N is in a pressurized state.

  First, the control device drives and controls the drive motor and the halogen heater 23. The pressure roller 22 is rotated by receiving the driving force of the drive motor, and the fixing belt 21 is rotated forward by following the pressure roller 22 (refer to the solid thin arrow in FIG. 3). The halogen heater 23 heats the fixing belt 21 from the inside. The temperature sensor 61 detects the surface temperature of the fixing belt 21 and transmits a detection signal to the control device via the input circuit. When the control device receives a detection signal indicating that the set temperature (for example, 150 to 200 ° C.) has been reached from the temperature sensor 61, the control device controls the halogen heater 23 so as to maintain the set temperature, and the already described image formation. Start executing the process. The sheet S to which the toner image has been transferred enters the housing 20, and the fixing belt 21 heats the toner (toner image) on the sheet S that passes through the pressure region N while rotating normally around the axis. The pressure roller 22 pressurizes the toner on the sheet S passing through the pressure region N while rotating around the axis. Then, the toner image is fixed on the sheet S. Then, the sheet S on which the toner image is fixed is sent out of the housing 20 and discharged to the paper discharge tray 4.

  Note that the control device drives and controls the cam motor 55 when the printer 1 (fixing device 7) is stopped or when a conveyance failure (jam) of the sheet S occurs in the housing 20 (pressure area N). The pressurizing region N is set to a reduced pressure state. In this case, the halogen heater 23 is turned off.

  In addition, when the image forming process (fixing process) is performed on a medium that is prone to wrinkles such as an envelope, the control device executes the image forming process with the pressurization region N in a reduced pressure state. In this case, the control device controls the halogen heater 23 so as to maintain the surface of the fixing belt 21 at a set temperature, similarly to the above-described normal fixing process. If the distance between the fixing belt 21 and the temperature sensor 61 changes due to the raising and lowering of the fixing belt 21, the temperature sensor 61 may not be able to detect an accurate temperature. Therefore, in the fixing device 7 according to the present embodiment, the interlock detection unit 25 is configured to maintain the distance between the fixing belt 21 and the temperature sensor 61 substantially constant.

<Operation of interlock detection unit>
With reference to FIGS. 3 and 10, the operation of the interlock detection unit 25 will be described. FIG. 10 is a cross-sectional view for explaining the operation of the interlock detection unit 25. Note that the pressurization region N is in a pressurized state.

  First, when the pressure region N is changed from the pressurized state (see FIG. 3) to the reduced pressure state (see FIG. 10), the eccentric cam 50 receives the driving force of the cam motor 55 and rotates to actuate the operating roller 56 (operating sheet metal). 51) Release the push down. Then, the movable frame 40 is rotated upward about the fulcrum shaft 35 by the biasing force of the adjustment spring 52 (see the upward thick arrows in FIGS. 4 and 10). Thereby, the pressurization area | region N will be in a pressure reduction state from a pressurization state (refer FIG. 10).

  As shown in FIG. 10, when the movable frame 40 (fixing belt 21) is raised, the holder 62 connected thereto is also raised. The holder 62 moves upward along the support pin 64 while compressing the interlocking spring 63. Precisely, the holder 62 moves along an arc-shaped trajectory centered on the fulcrum shaft 35 (see the upward thick arrow in FIG. 10). Since there is a gap (play) between the support through hole 67 of the holder 62 and the support pin 64, the holder 62 can move on a circular path without interfering with the support pin 64.

  Next, when the pressure region N is changed from the reduced pressure state to the pressurized state, the eccentric cam 50 receives the driving force of the cam motor 55 and rotates to push down the operating roller 56 (operating sheet metal 51). Then, the movable frame 40 rotates downward about the fulcrum shaft 35 while compressing the adjustment spring 52 (see FIG. 4). Thereby, the pressurization area | region N will be in a pressurization state from a pressure reduction state (refer FIG. 3).

  As shown in FIG. 3, when the movable frame 40 (fixing belt 21) is lowered, the holder 62 connected thereto is urged by the interlocking spring 63 and moves (rotates) downward along the support pin 64. .

  As described above, when the movable frame 40 is raised, the holder 62 is pushed up together with the movable frame 40 against the biasing force of the interlocking spring 63. On the other hand, when the movable frame 40 is lowered, the holder 62 is pushed by the interlocking spring 63 and is lowered together with the movable frame 40. In this manner, the holder 62 moves integrally with the movable frame 40 that supports the fixing belt 21 in the vertical direction (direction approaching or separating from the pressure roller 22). Accordingly, the temperature sensor 61 (detection surface 61A) held by the holder 62 moves up and down while maintaining a substantially constant distance from the fixing belt 21.

  In the fixing device 7 according to the present embodiment described above, the interlocking detection unit 25 (temperature sensor 61) moves so as to follow the fixing belt 21 while keeping a distance from the fixing belt 21, and the temperature of the fixing belt 21 is increased. It was set as the structure to detect. According to this configuration, the distance between the interlock detection unit 25 and the fixing belt 21 can be maintained substantially constant. Thereby, the temperature of the fixing belt 21 that moves relative to the pressure roller 22 can be accurately detected.

  In the fixing device 7 according to the present embodiment, the holder 62 holds the temperature sensor 61, is connected to the movable frame 40, and is supported by the fixed frame 60 in a state of moving in the rotational direction of the movable frame 40. It was. Further, the holder 62 holding the temperature sensor 61 is supported by the fixed frame 60 so as to be movable up and down, and is pressed against the movable frame 40 by the interlocking spring 63. According to this configuration, the holder 62 can follow the rotation of the movable frame 40, and the distance between the temperature sensor 61 held by the holder 62 and the fixing belt 21 supported by the movable frame 40 is made substantially constant. Can be maintained.

  In the fixing device 7 according to this embodiment, the temperature sensor 61 is provided on the fixed frame 60 separated from the movable frame 40 via the holder 62. According to this configuration, for example, the ambient temperature around the temperature sensor 61 can be lowered as compared with the case where the temperature sensor 61 is fixed to the movable frame 40. Thereby, the excessive temperature rise of the temperature sensor 61 can be suppressed, and the temperature sensor 61 can be protected.

  Further, according to the fixing device 7 according to the present embodiment, the temperature sensor 61 (the detection surface 61 </ b> A thereof) is arranged on the fixing belt 21 by arranging the axis of the fixing belt 21, the halogen heater 23, and the temperature sensor 61 in a straight line. Can be directed. Thereby, it can suppress that an error generate | occur | produces in detection temperature by the shift | offset | difference of the installation position of the temperature sensor 61. FIG. It should be noted that the temperature sensor 61 (interlocking detection unit 25) has a straight line (extension) connecting the axis of the fixing belt 21 and the axis of the halogen heater 23 according to the characteristics such as the size and angle of the detection range of the temperature sensor 61. Line) may be provided at a position slightly deviated from above.

  In the fixing device 7 according to the present embodiment, the pressure roller 22 is driven to rotate and the fixing belt 21 is driven to rotate. However, the present invention is not limited to this, and the fixing belt 21 is driven to rotate so that the pressure roller 22 is rotated. It may be driven and rotated.

  In the fixing device 7 according to the present embodiment, the thermopile is used as the temperature sensor 61. However, the present invention is not limited to this, and a pyroelectric sensor may be used as another example of the temperature sensor 61. Two or more temperature sensors 61 may be provided. Furthermore, it is sufficient that at least one positioning pin 46, holder projection 62C, interlocking spring 63, support pin 64, and the like are provided.

  In the description of the present embodiment, the case where the present invention is applied to the monochrome printer 1 is shown as an example. However, the present invention is not limited thereto, and the present invention is applied to, for example, a color printer, a copying machine, a facsimile machine, or a multifunction machine. You may apply.

  The description of the above embodiment shows one aspect of the fixing device and the image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above embodiment.

1 Printer (image forming device)
2 Device body 7 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (pressure member)
23 Halogen heater (heat source)
24 Pressure adjustment unit 25 Interlocking detection unit 30 Support frame 40 Movable frame 60 Fixed frame 61 Temperature sensor 62 Holder 63 Interlocking spring (biasing member)
N Pressurized area S Sheet (medium)

Claims (4)

A fixing member that heats the toner on the medium while rotating around an axis;
A pressure member that forms a pressure region with the fixing member while rotating around an axis, and pressurizes the toner on the medium passing through the pressure region;
Pressure that moves the fixing member in a direction approaching the pressure member to pressurize the pressure area, and moves the fixing member in a direction away from the pressure member to depressurize the pressure area. An adjustment unit;
A fixing device, comprising: an interlocking detection unit that detects the temperature of the fixing member by moving so as to follow the fixing member while maintaining a distance from the fixing member. A movable frame that rotatably supports the fixing member around an axis;
A support frame that rotatably supports the movable frame;
The pressure adjusting unit moves the fixing member by rotating the movable frame,
The interlock detection unit
A fixed frame that is disposed opposite to the fixing member across the movable frame and is fixed to an apparatus main body that supports the support frame;
A temperature sensor for detecting heat radiated from the fixing member in a non-contact manner;
A holder that holds the temperature sensor, is connected to the movable frame, and is supported by the fixed frame in a state of moving in the rotational direction of the movable frame;
The fixing device according to claim 1, further comprising: an urging member that urges the holder toward the movable frame. A heat source provided inside the fixing member, for heating the fixing member from the inside;
The fixing device according to claim 2, wherein an axis of the fixing member, the heat source, and the temperature sensor are arranged on the same straight line.   An image forming apparatus comprising the fixing device according to claim 1.

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