JP2020016734A - Fixing device and image forming apparatus - Google Patents

Abstract

To make it possible to accurately form a nip part between a first fixing member and a second fixing member.SOLUTION: A fixing device comprises: first and second fixing members; a support member that supports the first fixing member; a cam member that is disposed opposite to a part to be pressed of the support member; a driving unit; a rotation transmission mechanism that transmits rotation of the driving unit to one of the second fixing member and cam member; a rotation position detection processing unit that, after a nip area of the cam member is arranged opposite to the part to be pressed, detects the rotation position of the cam member; and a drive processing unit that stops the driving unit. The rotation transmission mechanism includes a rotation prevention member that prevents the rotation of the cam member.SELECTED DRAWING: Figure 1

Description

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

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile, a multifunction machine, and the like, for example, in an electrophotographic printer, an image forming unit, an LED head, a transfer roller, and a fixing device arranged corresponding to the image forming unit. A fixing device or the like as a device is provided, and a toner image formed in the image forming unit is transferred to a sheet by a transfer roller, and is fixed to the sheet in the fixing device.

  The fixing device has a heating roller as a first fixing member, a pressure roller as a second fixing member, and a heating roller and a pressure roller by pressing the heating roller against the pressure roller at a predetermined nip pressure. A pressing mechanism or the like for forming a nip portion is disposed between the eccentric cam and the pressing mechanism. An eccentric cam for moving a heating roller to form a nip portion or releasing the nip portion is provided in the pressing mechanism. Is established. By driving the fixing motor to rotate the eccentric cam and stopping it at a predetermined position, the nip portion is formed and the nip pressure is adjusted (for example, see Patent Reference 1).

JP 2017-227937 A

  However, in the conventional fixing device, if the operation of the pressing mechanism is repeated, even if the driving of the fixing motor is stopped when the nip portion is formed, the fixing device is disposed between the fixing motor and the eccentric cam. The eccentric cam cannot be stopped at a predetermined position due to the inertia moment generated in the rotation transmission mechanism, and the nip cannot be formed with high accuracy.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device and an image forming apparatus which can solve the problems of the conventional fixing device and accurately form a nip portion between the first and second fixing members. I do.

  For this purpose, in the fixing device of the present invention, the first fixing member, the second fixing member disposed to face the first fixing member, and the first fixing member are movably disposed, and A support member for supporting the fixing member, a nip region for forming a nip portion, and a release region for releasing the nip portion, the nip region being rotatably disposed to face a pressed portion formed on the support member; A cam member having a transition area formed between the nip area and the release area, and a cam member for moving the support member with rotation; a driving section; and the driving section and the second fixing member. And a rotation transmission mechanism having a rotation transmission element for transmitting rotation of the driving unit to one of the second fixing member and the cam member, and The nip area is opposed to the pressed part To have a rotation position detection processing unit for detecting the rotational position of the cam member, and a drive unit for rotational position stops the drive unit after detection of said cam member.

  The rotation transmission mechanism includes a rotation suppressing member that suppresses rotation of the cam member.

  According to the present invention, in the fixing device, the first fixing member, the second fixing member disposed to face the first fixing member, and the first fixing member are movably disposed, and A support member for supporting the fixing member, a nip region for forming a nip portion, and a release region for releasing the nip portion, the nip region being rotatably disposed to face a pressed portion formed on the support member; A cam member having a transition area formed between the nip area and the release area, and a cam member for moving the support member with rotation; a driving section; and the driving section and the second fixing member. And a rotation transmission mechanism having a rotation transmission element for transmitting rotation of the driving unit to one of the second fixing member and the cam member, and After the nip area is opposed to the pressed part It has a rotational position detecting unit for detecting the rotational position of the cam member, and a drive unit for rotational position stops the drive unit after detection of said cam member.

  The rotation transmission mechanism includes a rotation suppressing member that suppresses rotation of the cam member.

  In this case, the rotation position of the cam member is detected after the nip region is made to face the pressed portion with the rotation of the cam member, and the driving unit is stopped, so that the rotation speed of the cam member is stable. Can stop the drive unit.

  In addition, since the rotation of the cam member is suppressed by the rotation suppressing member, it is possible to suppress the generation of the moment of inertia in the rotation transmitting mechanism disposed between the driving unit and the cam member. Therefore, the cam member can be stopped at a predetermined position when the driving unit is stopped, so that a nip portion can be formed between the first and second fixing members with high accuracy.

FIG. 2 is a perspective view of a main part of the fixing device according to the embodiment of the present invention. FIG. 2 is a perspective view of the fixing device according to the embodiment of the present invention. FIG. 2 is a plan view of the fixing device according to the embodiment of the present invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. FIG. 5 is a diagram for explaining an operation of a rotation transmission system that transmits rotation to the fixing device according to the embodiment of the present invention. It is a perspective view of a pressing mechanism in an embodiment of the invention. FIG. 2 is a control block diagram of the printer according to the embodiment of the present invention. It is a figure for explaining operation of a pressing mechanism in an embodiment of the invention. It is a key map of an eccentric cam in an embodiment of the invention. FIG. 7 is a diagram for explaining an operation of the pressing mechanism when the fixing device is placed in a nip state according to the embodiment of the present invention. FIG. 5 is a diagram for explaining an operation of the pressing mechanism when the fixing device in the embodiment of the present invention is placed in a reduced pressure state. FIG. 7 is a diagram for explaining an operation of the pressing mechanism when the fixing device according to the embodiment of the present invention is placed in a release state. FIG. 6 is a diagram for explaining an operation of the pressing mechanism when the fixing device according to the embodiment of the present invention is placed in a second transition state.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a fixing device as a fixing device and a printer as an image forming device will be described.

  1 is a perspective view of a main part of the fixing device according to the embodiment of the present invention, FIG. 2 is a perspective view of the fixing device according to the embodiment of the present invention, FIG. 3 is a plan view of the fixing device according to the embodiment of the present invention, 4 is a cross-sectional view taken along the line AA in FIG. 3, FIG. 5 is a cross-sectional view taken along the line BB in FIG. 3, and FIG. FIG. 7 is a perspective view of the pressing mechanism according to the embodiment of the present invention.

  In the figure, reference numeral 11 denotes a fixing device, and the fixing device 11 is provided downstream of an image forming unit (not shown) in a main body of the printer (not shown), that is, in a main body of the apparatus, in a conveying direction of paper (not shown) as a medium. Is done.

  In the image forming unit, a toner image as a developer image is formed on a photosensitive drum as an image carrier, and a toner image is transferred to a sheet at a transfer portion between the photosensitive drum and a transfer roller. Then, the sheet is sent to the fixing device 11, where the toner image on the sheet is fixed, and an image is formed on the sheet.

  Cs is a housing of the fixing device 11, and the housing Cs includes a lower plate PL that covers the bottom of the fixing device 11, a top plate PT that covers the top of the fixing device 11, and a downstream from the upstream side in the sheet conveyance direction. The side frame FL is disposed on the left side of the fixing unit 11 when viewed from the side, and covers the side portion of the fixing unit 11, and the right side of the fixing unit 11 when viewed from the upstream side to the downstream side in the sheet conveyance direction. A side frame FR is provided and serves as a fixing element that covers a side portion of the fixing device 11. On the lower plate PL, a plurality of fins fn are formed so as to project to dissipate heat generated in the fixing device 11.

  The reference numeral 16 denotes a top plate PT side between the side frames FL and FR, which is adjacent to the side frames FL and FR so as to be movable. In the present embodiment, the shaft sh1 is a center of rotation (a swing center). A pair of levers 12 serving as support members rotatably disposed as a first fixing member provided rotatably (swingably) between the levers 16 and as a heating-side member The belt unit 13 is a second fixing member that is rotatably mounted on the lower plate PL side between the side frames FL and FR, and is opposed to the belt unit 12, and is a pressing side. It is a pressure roller as a member.

  The belt unit 12 is supported by levers 16, is extended between the levers 16, and is a belt 18 as a traveling member that is movably disposed. Both ends of the belt 18 on the inner peripheral surface side of the belt 18 are connected to the lever 16. It includes a fixed nip portion forming member 19 and the like. Note that each lever 16 has a shaft hole h1 through which a shaft sh1 that rotatably supports the lever 16 passes.

  The nip portion forming member 19 generates a predetermined nip pressure when the belt unit 12 is pressed against the pressure roller 13, and forms a nip portion N between the belt unit 12 and the pressure roller 13. A heater (not shown) as a heating element for heating the sheet via the belt 18 is provided in the nip portion forming member 19.

  Therefore, when the lever 16 is placed at a predetermined position and the nip portion N is formed between the belt unit 12 and the pressure roller 13, that is, when the fixing device 11 is placed in the nip state, The toner image on the sheet sent from the forming unit is pressed by the pressure roller 13, heated by the heater, melted, and fixed on the sheet.

  During this time, a fixing motor M1 serving as a fixing driving unit disposed in the apparatus main body is driven, and rotation generated by the fixing motor M1 is transmitted to the pressure roller 13, and the belt 18 of the belt unit 12 is moved. The paper is transported, and the paper sent from the image forming unit is transported in the nip portion N in the direction of arrow TR in FIG.

  By the way, in the present embodiment, not only can the fixing unit 11 be placed in the nip state by pressing the belt unit 12 against the pressure roller 13 to form the nip portion N, The fixing device 11 can be placed in a released state by separating the fixing device 11 from the nip portion N and eliminating the nip portion N.

  For this purpose, in the present embodiment, the fixing device 11 is provided with a pressing mechanism 20 for pressing the belt unit 12 against the pressing roller 13 and for separating the belt unit 12 from the pressing roller 13. .

  The pressing mechanism 20 is rotatably supported by the shaft 26 rotatably supported by the side frames FL and FR, and by the shaft 26 opposing the pressed portion 21 formed at the upper end of the lever 16. A pair of eccentric cams 23 as a cam member, a pair of levers 27 attached to the shaft 26, and a position in the rotational direction of the eccentric cam 23 attached to the tip of the shaft 26, that is, for detecting the rotational position. A reflection plate 45 as a detected element is disposed opposite to the eccentric cam 23 with the pressed portion 21 interposed therebetween, and serves as a first urging member for urging the belt unit 12 toward the pressure roller 13. A spring 28 and the like are provided.

  The eccentric cam 23 is disposed on the shaft 26 on the center side of the side frames FL and FR, adjacent to the side frames FL and FR, and moves the lever 16 with rotation. In this embodiment, Rotate. The lever 27 is disposed adjacent to the eccentric cam 23 on the shaft 26 on the center side of each eccentric cam 23.

  The shaft 26 extends through the side frame FR and a gear cover 39 to be described later, and the reflector 45 is attached to the tip of the shaft 26 outside the gear cover 39 and disposed on the apparatus main body of the printer. The optical sensor S (FIG. 8), which is provided as a detection element for detecting the rotational position of the eccentric cam 23, will be described later.

  The spring 28 is brought into contact with the pressed portion 21 at one end (an end on the downstream side in the sheet conveying direction), and the other end (an upstream end in the sheet conveying direction). ), It is brought into contact with a predetermined portion of the housing Cs, in this embodiment, the back portion pr of the top plate PT.

  As shown in FIG. 5, the eccentric cam 23 is attached to the shaft 26 via a knock pin 24 as an engaging member attached to the shaft 26, and is rotated with the rotation of the shaft 26.

  By the way, the fixing motor M1 is driven in a state where the lever 16 is located at a predetermined position and the nip portion N is formed, and conveys the sheet by rotating the pressure roller 13. The paper need not be transported while the nip N is formed or eliminated by rotating the lever 16.

  Therefore, in the present embodiment, the fixing motor M1 is driven not only when the sheet is conveyed, but also when the lever 16 is rotated to form or cancel the nip portion N. I am trying to do it.

  That is, the fixing motor M1 is driven in the forward direction and the reverse direction, and is driven in the forward direction to rotate the pressure roller 13 to form or cancel the nip portion N when conveying the sheet. Sometimes, the shaft 26 is rotated by being driven in the opposite direction, and the eccentric cam 23 is rotated.

  For this purpose, the fixing motor M1 is connected to the pressure roller 13 and the shaft 26 (the eccentric cam 23) by the rotation transmission mechanism 31.

  The rotation transmission mechanism 31 is disposed adjacent to the fixing device 11 in the apparatus main body of the printer, and transmits the rotation of the fixing motor M1 to the fixing device 11. The fixing device rotation transmitting portion 38 for transmitting the rotation of the main body rotation transmitting portion 36 to the shaft 26, a gear cover 39 attached to the side frame FR and covering a main portion of the fixing device rotation transmitting portion 38, and the like.

  The apparatus main body rotation transmission unit 36 includes an output gear gr1 serving as a first gear for outputting the rotation of the fixing motor M1, and a second gear meshed with the output gear gr1 and rotatably disposed. An idle gear gr2, an idle gear gr3 as a third gear meshed with the idle gear gr2 and connected to and rotated by the shaft sh2, disposed coaxially with the shaft sh2, and transmitting rotation in one direction. One-way gears gr4 and gr5 as fourth and fifth gears, and sixth and seventh gears meshed with the one-way gears gr4 and gr5, respectively, and rotatably disposed about a shaft sh3 as a rotation center. It has idle gears gr6 and gr7.

  The one-way gears gr4 and gr5 connect the fixing motor M1 to the pressure roller 13 and the eccentric cam 23. When the fixing motor M1 is driven in the forward and reverse directions, the one-way gears gr4 and gr5 A rotation transmission element that transmits rotation to one of the pressure roller 13 and the eccentric cam 23 is configured. In addition, on the shaft sh2, the one-way gear gr4 is disposed on the center side of the one-way gear gr5 and adjacent to the one-way gear gr5. It is arranged adjacent to.

  The fixing device rotation transmission unit 38 is rotatably disposed about a shaft sh4 attached to the side frame FR, and is rotatable about the shaft sh4. The fixing device rotation transmission unit 38 functions as eighth and ninth gears that mesh with the idle gears gr6 and gr7, respectively. The connection gears gr8, gr9, the idle gear gr10 serving as a tenth gear rotatably disposed about the shaft sh5 attached to the side frame FR and engaged with the connection gear gr8, and attached to the side frame FR. A pressure roller gear gr11 as an eleventh gear, which is rotatably disposed about the shaft sh6 provided as a rotation center, is connected to the pressure roller 13, and meshes with the idle gear gr10, and is attached to the side frame FR. The large-diameter gear ga and the small-diameter gear g A large-diameter gear ga is attached to the side frame FR as a twelfth gear gr12 as a twelfth gear meshed with the coupling gear gr9, and is rotatably disposed around the shaft 26 as a rotation center. A cam gear gr13 as a thirteenth gear and a rotation transmitting element, which is connected to the eccentric cam 23 via the eccentric cam 23 and meshed with the small-diameter gear gb of the two-stage gear gr12, and the gear cover 39 and the cam gear on the shaft 26. A spring 46 and the like as a second urging member and a rotation suppressing member disposed around the shaft 26 with the gr13 are provided.

  As shown in FIG. 4, the spring 46 has one end in contact with the inner peripheral surface of the gear cover 39 and the other end in contact with the end surface of the cam gear gr13, and the cam gear gr13 is directed toward the side frame FR by a predetermined urging force. The shaft 26 and the eccentric cam 23 are urged and pressed against the side frame FR, and a rotational load is applied to the shaft 26 and the eccentric cam 23 by the frictional force generated between the cam gear gr13 and the side frame FR to suppress the rotation of the shaft 26 and the eccentric cam 23. . Therefore, the cam gear gr13 is disposed between the side frame FR and the gear cover 39 on the shaft 26 so as to be movable in the axial direction and slidably with respect to the shaft 26.

  Next, the operation of the rotation transmission mechanism 31 will be described.

  In the apparatus main body rotation transmitting section 36, when the fixing motor M1 is driven in the forward direction, in this embodiment, in the clockwise direction in FIG. Thus, the rotation is transmitted to the one-way gear gr4, the one-way gear gr4 is rotated in the clockwise direction, that is, in the direction of arrow C, and the idle gear gr6 is rotated in the counterclockwise direction. At this time, the rotation is not transmitted to the one-way gear gr5, and the one-way gear gr5 is not rotated.

  In the fixing device rotation transmitting section 38, the connecting gear gr8 is rotated in the clockwise direction in FIGS. 1 and 6, that is, in the direction of arrow E, the idle gear gr10 is rotated in the counterclockwise direction, and the pressing roller gear gr11 is rotated. Are rotated clockwise in FIG. 1, that is, in the direction of arrow G. As a result, the pressure roller 13 is rotated clockwise. At this time, the connection gear gr9 is not rotated, and the eccentric cam 23 is not rotated.

  When the fixing motor M1 is driven in the reverse direction in the apparatus main body rotation transmission unit 36, in this embodiment, in the counterclockwise direction in FIG. The rotation is transmitted to the one-way gear gr5, whereby the one-way gear gr5 is rotated in the counterclockwise direction, that is, the direction of arrow D, and the idle gear gr7 is rotated in the clockwise direction. Let me do. At this time, the rotation is not transmitted to the one-way gear gr4, and the one-way gear gr4 is not rotated.

  In the fixing device rotation transmitting section 38, the connecting gear gr9 is rotated in the counterclockwise direction in FIGS. 1 and 6, that is, in the direction of arrow F, the two-stage gear gr12 is rotated in the clockwise direction, and the cam gear gr13 is rotated. Are rotated in the counterclockwise direction in FIG. As a result, the eccentric cam 23 is rotated in the counterclockwise direction, and the reflection plate 45 is rotated in the arrow H direction. At this time, the connection gear gr8 is not rotated, and the pressure roller 13 is not rotated.

  As described above, the rotation of the fixing motor M1 is transmitted to one of the one-way gears gr4 and gr5 according to the direction in which the fixing motor M1 is driven. In other words, by driving the fixing motor M1 in the direction of arrow A, the pressure roller 13 can be rotated to convey the paper, and by driving the fixing motor M1 in the direction of arrow B, the eccentric cam 23 can be moved. By rotating, the nip portion N can be formed or eliminated.

  By operating the lever 27 to rotate the shaft 26, the nip portion N can be formed or the nip portion N can be eliminated.

  Next, the operation of the pressing mechanism 20 when the eccentric cam 23 is rotated will be described.

  FIG. 8 is a control block diagram of the printer according to the embodiment of the present invention, FIG. 9 is a diagram for explaining the operation of the pressing mechanism according to the embodiment of the present invention, and FIG. 10 is a diagram of the eccentric cam according to the embodiment of the present invention. FIG. 11 is a conceptual diagram, FIG. 11 is a view for explaining the operation of the pressing mechanism when the fixing device in the embodiment of the present invention is placed in a nip state, and FIG. FIG. 13 is a view for explaining the operation of the pressing mechanism when the fixing device is placed in the release state, and FIG. 13 is a view for explaining the operation of the pressing mechanism when the fixing device in the embodiment of the present invention is in the released state. FIG. 14 is a diagram for explaining the operation of the pressing mechanism when the fixing device in the embodiment of the present invention is placed in the second transition state.

  In the figure, 11 is a fixing device, 12 is a belt unit, 13 is a pressure roller, 16 is a lever arranged rotatably in the directions of arrows I and J, 18 is a belt, 20 is a pressing mechanism, and 21 is a pressed part. , 23 is an eccentric cam, 26 is a shaft, 28 is a spring, 45 is a reflection plate, 81 is a control unit, 82 is a timer as a clock unit, M1 is a fixing motor, gr13 is a cam gear, S is an optical sensor, and Rd is a reflection. A portion on the plate 45 irradiated by the optical sensor S, that is, an irradiated portion, h1 is a shaft hole through which the shaft sh1 (FIG. 5) passes. The shaft 26 and the reflection plate 45 are rotated in the direction of arrow H.

  As shown in FIG. 9, the reflecting plate 45 has a predetermined area in the circumferential direction in order to detect the rotational position of the eccentric cam 23 by the optical sensor S. A marker Mk having a fan-like shape is formed over a range of approximately 100 [°]. The marker Mk has a first color, in the present embodiment, a predetermined portion of a plate formed in black, is subjected to, for example, aluminum deposition to form a second color, in this embodiment, a silver color. To be formed.

  The light sensor S includes a light emitting unit Se and a light receiving unit Sr, receives a control signal SG1 sent from the control unit 81, generates light in the light emitting unit Se, irradiates the irradiation unit Rd of the reflection plate 45, and irradiates the irradiation unit Rd. The light reflected by Rd is received by the light receiving unit Sr, and the detection signal SG2 is sent to the control unit 81.

  As shown in FIG. 9, when the edge m1 on the downstream side of the marker Mk is illuminated by the optical sensor S with the rotation of the reflection plate 45, the intensity of the reflected light at the illuminated portion Rd decreases. When the upstream edge m2 of the marker Mk is illuminated by the optical sensor S, the intensity of the reflected light at the illuminated portion Rd increases.

  The control unit 81 includes a rotation position detection processing unit Pr1 and a drive processing unit Pr2, and the rotation position detection processing unit Pr1 determines each edge m1 of the marker Mk based on the detection signal SG2 sent from the optical sensor S. , M2 is detected by the optical sensor S to detect the rotational position of the eccentric cam 23, and the drive processing unit Pr2 determines the fixing motor M1 based on the detected rotational position of the eccentric cam 23. Drive or stop.

  Next, the eccentric cam 23 will be described.

  The eccentric cam 23 has a cam surface Sc as shown in FIG. 10 so that the force for pressing the pressed portion 21 can be changed with the rotation. The cam surface Sc includes a plurality of, in the present embodiment, five edges eg1 to eg5 formed from the downstream side to the upstream side in the rotation direction (the direction of the arrow H). A first surface S1 is formed in the nip area Ar1, which is the area No. 1; the first surface S1 is longer as the distance from the axis Cn is closer to the edges eg1 and eg2 and shorter as the distance from the edges eg1 and eg2 is increased. A second surface S2 having a constant value R1 at a distance from the axis Cn is formed in a decompression region Ar2 which is a second region of the second region, and a first region which is a third region between the edges eg3 and eg4. In the transition region Ar3, a third surface S3 whose distance from the axis Cn is closer to the edge eg3 and which is longer as it is closer to the edge eg4 is formed, and is a fourth region between the edges eg4 and eg5. A fourth surface S4 having a constant value R2 whose distance from the axis Cn is larger than the value R1 is formed in the region Ar4, and a fourth transition region Ar5 that is a fifth region between the edges eg5 and eg1 is formed. A fifth surface S5 is formed that is longer as the distance from the axis Cn is closer to the edge eg5 and shorter as the distance is closer to the edge eg1.

  Next, the operation of the pressing mechanism 20 when the fixing motor M1 is driven to rotate the eccentric cam 23 will be described.

  When the fixing motor M1 is driven in the direction of arrow A in FIG. 6, the eccentric cam 23 is rotated in the direction of arrow H in FIG. 9, and the nip area Ar1 is opposed to the pressed portion 21 as shown in FIG. The eccentric cam 23 is placed in a free state without being brought into contact with the pressed portion 21. At this time, the lever 16 rotates in the direction of arrow I in FIG. Then, the belt unit 12 is pressed against the pressure roller 13 with a predetermined nip pressure, and the fixing device 11 is placed in a nip state. When the fixing motor M1 is stopped in a state where the center of the nip area Ar1 is opposed to the pressed portion 21, the fixing device 11 maintains the state where the fixing device 11 is placed in the nip state. Subsequently, when the fixing motor M1 is driven in the direction of arrow B in FIG. 6, the pressure roller 13 is rotated in the direction of arrow G in FIG. 9, the belt 18 is caused to travel, and the sheet is conveyed.

  Then, the fixing motor M1 is driven again in the direction of arrow A, and the eccentric cam 23 is further rotated in the direction of arrow H, so that the depressurized area Ar2 faces the pressed portion 21 as shown in FIG. 23 is brought into contact with the pressed portion 21, the lever 16 is turned around the axis sh <b> 1 in the direction of the arrow J against the urging force of the spring 28, and the belt unit 12 is The nip pressure to be pressed is reduced, and the fixing device 11 is placed in a reduced pressure state.

  Thereafter, the fixing motor M1 is driven in the direction of arrow A, and the eccentric cam 23 is further rotated in the direction of arrow H, so that the first transition region Ar3 faces the pressed portion 21. In the state where the belt unit 12 is in contact with the pressure roller 21, the lever 16 is further rotated in the direction of the arrow J around the axis sh <b> 1 against the urging force of the spring 28, and the belt unit 12 is pressed against the pressure roller 13. The nip pressure is further reduced, and the fuser 11 is placed in the first transition state.

  Subsequently, when the fixing motor M1 is driven in the direction of arrow A, and the eccentric cam 23 is further rotated in the direction of arrow H, and the release area Ar4 faces the pressed portion 21 as shown in FIG. When the lever 23 is in contact with the pressed portion 21, the lever 16 is further rotated in the arrow J direction about the shaft sh <b> 1 against the urging force of the spring 28, and the belt unit 12 is actuated. The fixing roller 11 is separated from the pressure roller 13, the nip N is eliminated, and the fixing device 11 is placed in a release state. When the fixing motor M1 is stopped in a state where the center of the release area Ar4 is opposed to the pressed portion 21, the fixing device 11 maintains the state where it is in the release state.

  Then, the fixing motor M1 is driven in the direction of arrow A, and the eccentric cam 23 is further rotated in the direction of arrow H so that the second transition region Ar5 faces the pressed portion 21 as shown in FIG. In a state where the eccentric cam 23 is in contact with the pressed portion 21, the lever 16 is rotated in the direction of arrow I about the axis sh1 by the urging force of the spring 28, and the belt unit 12 and the pressure roller are rotated. 13, the fixing device 11 is placed in the second transition state.

  Subsequently, when the fixing motor M1 is driven in the direction of arrow A and the eccentric cam 23 is further rotated in the direction of arrow H, the eccentric cam 23 is separated from the pressed portion 21 and the belt unit 12 contacts the pressure roller 13. Touch

  Incidentally, in order to accurately place the fixing device 11 in the nip state, it is preferable to stop the fixing motor M1 in a state where the substantially center of the nip area Ar1 faces the pressed portion 21. In order to place the fixing motor M1 in the release state, it is preferable to stop the fixing motor M1 in a state where the center of the release area Ar4 is opposed to the pressed portion 21.

  Therefore, in the present embodiment, the first and second reference positions are set on the eccentric cam 23, and after the nip area Ar1 is made to face the pressed portion 21, the eccentric cam 23 is moved to the first position. The rotation position detection processing unit Pr1 detects the rotation position of the eccentric cam 23 based on the detection signal SG2 sent from the optical sensor S, and the drive processing unit Pr2 After the fixing motor M1 is stopped in a state where the center of the nip region Ar1 is opposed to the pressed portion 21 based on the rotational position, and after the release region Ar4 comes to be opposed to the pressed portion 21, When the eccentric cam 23 is placed at the second reference position, the rotational position detection processing unit Pr1 detects the rotational position of the eccentric cam 23 based on the detection signal SG2 sent from the optical sensor S, and performs a driving process. Pr2, based on the rotational position of the eccentric cam 23, substantially in the center of the release area Ar4 is adapted to stop the fixing motor M1 in a state that faces the object to be pressed 21.

  Therefore, when the cam member 23 is placed at the first reference position at a set timing after the nip region Ar1 is made to face the pressed portion 21 with the rotation of the eccentric cam 23, the reflection plate 45 The cam member 23 is moved to the second reference position at a set timing so that the edge m1 of the marker Mk is illuminated by the optical sensor S and after the depressurized region Ar2 is opposed to the pressed portion 21. When placed, the positions of the edges m1 and m2 of the marker Mk are set so that the edge m2 of the marker Mk is irradiated by the optical sensor S.

  Then, in order to place the fixing device 11 in the nip state, the fixing motor M1 is driven, and when the eccentric cam 23 is being rotated, the edge m1 of the marker Mk is irradiated by the optical sensor S, and the rotation is performed. When the position detection processing unit Pr1 detects the first rotation position of the eccentric cam 23 at the above timing after the nip area Ar1 is opposed to the pressed part 21, the drive processing unit Pr2 counts the time of the timer 82. When the predetermined time τ1 elapses, the fixing motor M1 is stopped, and the eccentric cam 23 is stopped.

  In this case, the first reference position of the eccentric cam 23 is set such that the first half on the upstream side of the nip area Ar1 in the rotation direction of the eccentric cam 23 faces the pressed portion 21, and τ1 is set such that substantially the center of the nip area Ar1 faces the pressed portion 21 when the eccentric cam 23 is rotated at a rotation speed driven by the fixing motor M1. Thereby, the fixing device 11 can be placed in the nip state.

  When the fixing motor M1 is driven and the eccentric cam 23 is rotated to put the fixing device 11 in the release state, the edge m2 of the marker Mk is irradiated by the optical sensor S when the eccentric cam 23 is rotated. When the position detection processing unit Pr1 detects the second rotational position of the eccentric cam 23 at the above timing after the depressurized area Ar2 is opposed to the pressed part 21, the drive processing unit Pr2 counts the time of the timer 82. When the predetermined time τ2 elapses, the fixing motor M1 is stopped, and the eccentric cam 23 is stopped.

  In this case, the second reference position of the eccentric cam 23 is set such that the upstream half of the release area Ar4 in the rotation direction of the eccentric cam 23 faces the pressed portion 21 for the predetermined time. τ2 is set such that substantially the center of the release area Ar4 faces the pressed portion 21 when the eccentric cam 23 is rotated at a rotation speed driven by the fixing motor M1. Thus, the fixing device 11 can be placed in the release state after passing through the reduced pressure state and the first transition state.

  By the way, when the fixing motor M1 is driven and the eccentric cam 23 is rotated to place the fixing device 11 in the nip state when the fixing device 11 is in the release state, the second transition area While Ar5 is opposed to the pressed portion 21, as the distance from the axis Cn gradually decreases, the lever 16 is rotated in the direction of arrow I to push the eccentric cam 23, and the eccentric cam 23 is pressed. A rotational force is applied to 23. As a result, the one-way gear gr5 (FIG. 6) is caused to idle, and the eccentric cam 23 rotates at a higher speed than the rotation speed by the driving of the fixing motor M1 in a predetermined section while being opposed to the pressed portion 21. Rotated with.

  In this case, if the fixing motor M1 is stopped and the fixing device 11 is set in the nip state while the second transition area Ar5 is opposed to the pressed portion 21, the rotation speed of the eccentric cam 23 is increased. Is unstable, the eccentric cam 23 cannot be stopped accurately after the nip region Ar1 is opposed to the pressed portion 21.

  Therefore, in the present embodiment, as described above, after the nip region Ar1 is opposed to the pressed portion 21, the timer 82 starts timing at the above timing, and when a predetermined time τ1 has elapsed. , The fixing motor M1 is stopped.

  In this case, after the nip region Ar1 is opposed to the pressed portion 21, the eccentric cam 23 is not brought into contact with the pressed portion 21, the lever 16 does not press the eccentric cam 23, and the eccentric cam 23 The rotational force is not applied, and the eccentric cam 23 is rotated at the rotational speed driven by the fixing motor M1. Accordingly, the rotation speed of the eccentric cam 23 can be stabilized, and the fixing device 11 can be accurately placed in the nip state by stopping the fixing motor M1.

  By the way, when the predetermined time τ1 elapses and the fixing motor M1 is stopped, it is generated by each shaft of the rotation transmission mechanism 31 (FIG. 6), and mounting parts such as gears mounted on each shaft. If the eccentric cam 23 cannot be stopped accurately with the inertia moment, the fixing device 11 cannot be accurately placed in the nip state.

  Therefore, in the present embodiment, as described above, the spring 46 is provided between the gear cover 39 and the cam gear gr13, and the cam gear gr13 is pressed against the side frame FR by the urging force of the spring 46, and the shaft 26 In addition, a rotational load is applied to the eccentric cam 23.

  Therefore, the eccentric cam 23 can be reliably stopped with the nip region Ar1 facing the pressed portion 21, and the fixing device 11 can be accurately placed in the nip state.

  When the fixing device 11 is placed in the nip state, the fixing motor M1 is driven to rotate the eccentric cam 23 to put the fixing device 11 in the release state. While the first transition region Ar3 and the release region Ar4 are opposed to the pressed portion 21, the distance from the axis Cn increases, the eccentric cam 23 presses the pressed portion 21, and the lever 16 moves in the arrow J direction. Rotated. Therefore, the eccentric cam 23 can be stably rotated at the rotation speed by the driving of the fixing motor M1, and the fixing device 11 can be accurately placed in the release state by stopping the fixing motor M1.

  As described above, in the present embodiment, after the nip area Ar1 is made to face the pressed portion 21 with the rotation of the eccentric cam 23, the rotational position of the eccentric cam 23 is detected, and the fixing motor M1 is turned on. Since the rotation is stopped, the fixing motor M1 can be stopped in a state where the rotation speed of the eccentric cam 23 is stable.

  Further, since the rotation of the eccentric cam 23 is suppressed by the spring 46, it is possible to suppress the generation of the moment of inertia in the rotation transmission mechanism 31 disposed between the fixing motor M1 and the eccentric cam 23. Therefore, the rotational position of the eccentric cam 23 when the fixing motor M1 is stopped can be accurately positioned, so that the nip portion N can be accurately formed between the belt unit 12 and the pressure roller 13. it can.

  Moreover, since it is not necessary to use a gear with a torque limiter or the like to suppress the rotation of the eccentric cam 23, the structure of the rotation transmission mechanism 31 can be simplified.

  Further, when the fixing motor M1 is driven while the fixing device 11 is in the release state, the fixing device 11 is brought into the second transition state with the eccentric cam 23 being in contact with the pressed portion 21. After that, the eccentric cam 23 is separated from the pressed portion 21 and the fixing device 11 is placed in the nip state. During this time, the eccentric cam 23 and the pressed portion 21 do not collide with each other, and abnormal noise is generated. This can be prevented from occurring.

  In the present embodiment, since the eccentric cam 23 and the reflection plate 45 are provided on the shaft 26, the rotational position of the eccentric cam 23 can be adjusted without being affected by the gear backlash of the rotation transmission mechanism 31. The light can be directly detected by the reflection plate 45. Therefore, the rotational position of the eccentric cam 23 can be accurately positioned.

  In this embodiment, the one-way gear gr4 is used to transmit the rotation of the fixing motor M1 to one of the pressure roller 13 and the eccentric cam 23 when the fixing motor M1 is driven in the forward and reverse directions. , Gr5 are used, but instead of the one-way gears gr4, gr5, two electromagnetic clutches or a planetary gear device can be used.

  Further, in the present embodiment, a printer is described, but the present invention can be applied to an image forming apparatus such as a copying machine, a facsimile, and a multifunction peripheral.

  It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

Reference Signs List 11 fixing device 12 belt unit 13 pressure roller 16 lever 21 pressed portion 23 eccentric cam 31 rotation transmission mechanism 46 spring Ar1 nip region Ar4 release region Ar5 second transition region gr4, gr5 one-way gear M1 fixing motor N nip portion Pr1 Rotational position detection processing unit Pr2 Drive processing unit Sc Cam surface

Claims (10)

(A) a first fixing member;
(B) a second fixing member disposed to face the first fixing member;
(C) a supporting member movably disposed and supporting the first fixing member;
(D) a nip area for forming a nip, a release area for releasing the nip, a release area for releasing the nip, and a release area for releasing the nip; A cam member having a cam surface on which a transition region between the regions is formed, and a cam member for moving the support member with rotation;
(E) a driving unit;
(F) a rotation transmitting element for connecting the drive section to the second fixing member and the cam member and transmitting rotation of the drive section to one of the second fixing member and the cam member; A rotation transmission mechanism,
(G) a rotation position detection processing unit that detects the rotation position of the cam member after the nip region is made to face the pressed portion with the rotation of the cam member;
(H) a drive processing unit that stops the drive unit after the rotation position of the cam member is detected,
(I) The fixing device, wherein the rotation transmitting mechanism includes a rotation suppressing member that suppresses rotation of the cam member.   The rotation position detection processing unit is configured such that, after the nip region is opposed to the pressed portion with the rotation of the cam member, the rotation position of the cam member is set when the cam member is placed at a preset reference position. The fixing device according to claim 1, wherein the fixing device detects:   3. The fixing device according to claim 2, wherein the cam member is located at a reference position while a front half of the nip region in the rotation direction of the cam member on the upstream side is opposed to the pressed portion. 4. (A) an urging member for urging the first fixing member toward the second fixing member;
(B) The cam member is rotated at a rotation speed higher than a rotation speed driven by the driving unit in a predetermined section while the transition region is opposed to the pressed portion. The fixing device according to claim 1.   5. The fixing device according to claim 1, wherein the cam member is rotated at a rotation speed by driving of the driving unit while moving the nip region in opposition to the pressed portion. 6. (A) an element to be detected is attached to a shaft that is rotatably disposed and supports the cam member;
(B) The fixing device according to any one of claims 1 to 5, wherein the rotation position detection processing unit detects a rotation position of the cam member based on a detection signal sent from the detected element.   The fixing device according to claim 2, wherein the drive processing unit stops the drive unit when a predetermined time has elapsed after the cam member has been placed at the reference position. (A) the driving unit is driven in a forward direction and a reverse direction,
The fixing device according to claim 1, wherein (b) the rotation transmitting element transmits rotation according to a direction in which the driving unit is driven.   The fixing device according to claim 1, wherein the rotation suppressing member suppresses rotation of the cam member by a frictional force generated by pressing a predetermined rotation transmitting element of the rotation transmitting mechanism against a fixed element.   An image forming apparatus comprising the fixing device according to claim 1.

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