JP7014077B2 - Fixing device and image forming device - Google Patents

Description

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

Conventionally, in an image forming apparatus such as a printer, a copying machine, a facsimile, or a compound machine, 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 arranged, and the toner image formed in the image forming unit is transferred to the paper by the transfer roller and fixed to the paper in the fixing device.

The fuser 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 with a predetermined nip pressure. A pressing mechanism or the like for forming the nip portion is arranged between the and the pressing mechanism, and an eccentric cam for moving the heating roller to form the nip portion or release the nip portion is arranged in the pressing mechanism. Will be set up. Then, 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, the patent). See Document 1).

Japanese Unexamined Patent Publication No. 2017-227937

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

An object of the present invention is to solve the problems of the conventional fixing device and to provide a fixing device and an image forming device capable of accurately forming a nip portion between the first and second fixing members. do.

Therefore, in the fixing device of the present invention, the frame constituting the housing, the first fixing member, and the second fixing member supported by the frame and arranged so as to face the first fixing member. A member, a support member movably arranged adjacent to the frame and supporting the first fixing member, a shaft rotatably supported by the frame, and a center side of the frame on the shaft. In the nip region for forming the nip portion, the release region for releasing the nip portion, and the nip region and the release region, which are rotatably arranged so as to face the pressed portion formed on the support member. A cam member having a cam surface formed with a transition region between the two, and a cam member that moves the support member with rotation, and between the drive unit, the drive unit, the second fixing member, and the cam member. A rotation transmission mechanism for connecting the cam member, a rotation position detection processing unit for detecting the rotation position of the cam member after the nip region is opposed to the pressed portion as the cam member rotates, and the cam member. It has a drive processing unit that stops the drive unit after the rotation position is detected.

Then, the rotation transmission mechanism is driven by a first rotation transmission element that transmits the rotation of the drive unit to one of the second fixing member and the cam member, outside the frame on the shaft. A second rotation transmission element that transmits the rotation of the portion to the cam member via the shaft, a cover arranged outside the second rotation transmission element on the shaft, and between the cover and the frame. A second urging member that is disposed and urges the second rotation transmitting element toward the frame and suppresses the rotation of the cam member is provided.

According to the present invention, in the fixing device, a frame constituting the housing, a first fixing member, and a second fixing supported by the frame and arranged to face the first fixing member. A member, a support member movably arranged adjacent to the frame and supporting the first fixing member, a shaft rotatably supported by the frame, and a center side of the frame on the shaft. In the nip region for forming the nip portion, the release region for releasing the nip portion, and the nip region and the release region, which are rotatably arranged so as to face the pressed portion formed on the support member. A cam member having a cam surface formed with a transition region between the two, and a cam member that moves the support member with rotation, and between the drive unit, the drive unit, the second fixing member, and the cam member. A rotation transmission mechanism for connecting the cam member, a rotation position detection processing unit for detecting the rotation position of the cam member after the nip region is opposed to the pressed portion as the cam member rotates, and the cam member. It has a drive processing unit that stops the drive unit after the rotation position is detected.

Then, the rotation transmission mechanism is driven by a first rotation transmission element that transmits the rotation of the drive unit to one of the second fixing member and the cam member, outside the frame on the shaft. A second rotation transmission element that transmits the rotation of the portion to the cam member via the shaft, a cover arranged outside the second rotation transmission element on the shaft, and between the cover and the frame. A second urging member that is disposed and urges the second rotation transmitting element toward the frame and suppresses the rotation of the cam member is provided.

In this case, after the nip region is made to face the pressed portion as the cam member rotates, the rotational position of the cam member is detected and the drive portion is stopped, so that the rotational speed of the cam member is stable. The drive unit can be stopped with.

Further, since the rotation of the cam member is suppressed by the second urging member, it is possible to suppress the moment of inertia generated in the rotation transmission mechanism arranged between the drive unit and the cam member. Therefore, since the cam member can be stopped at a predetermined position when the drive unit is stopped, the nip portion can be accurately formed between the first and second fixing members.

It is a main part perspective view of the fuser in embodiment of this invention. It is a perspective view of the fuser in embodiment of this invention. It is a top view of the fuser in embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a cross-sectional view taken along the line BB of FIG. It is a figure for demonstrating operation of the rotation transmission system which transmits rotation to a fuser in embodiment of this invention. It is a perspective view of the pressing mechanism in embodiment of this invention. It is a control block diagram of the printer in embodiment of this invention. It is a figure for demonstrating operation of a pressing mechanism in embodiment of this invention. It is a conceptual diagram of the eccentric cam in embodiment of this invention. It is a figure for demonstrating the operation of the pressing mechanism when the fuser in the embodiment of this invention is put in the nip state. It is a figure for demonstrating the operation of the pressing mechanism when the fuser in the Embodiment of this invention is put in a depressurized state. It is a figure for demonstrating the operation of the pressing mechanism when the fuser in the Embodiment of this invention is put in the released state. It is a figure for demonstrating the operation of the pressing mechanism when the fuser in the embodiment of this invention is put in the 2nd 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 fuser according to the embodiment of the present invention, FIG. 2 is a perspective view of the fuser according to the embodiment of the present invention, and FIG. 3 is a plan view of the fuser according to the embodiment of the present invention. 4 is a sectional view taken along the line AA of FIG. 3, FIG. 5 is a sectional view taken along the line BB of FIG. 3, and FIG. 1 and 7 are perspective views of the pressing mechanism according to the embodiment of the present invention.

In the figure, reference numeral 11 is a fuser, which is arranged in a printer body (not shown), that is, in the device body, downstream of an image forming unit (not shown) in a transport direction of paper (not shown) as a medium. Will be done.

In the image forming unit, a toner image as a developer image is formed on a photoconductor drum as an image carrier, and a toner image is transferred to paper at a transfer portion between the photoconductor drum and a transfer roller. The paper is fed to the fuser 11, where the toner image on the paper is fixed and an image is formed on the paper.

Further, Cs is a housing of the fuser 11, and the housing Cs is a lower plate PL covering the bottom of the fixing device 11, a top plate PT covering the top of the fixing device 11, and downstream from the upstream side in the paper transport direction. The side frame FL, which is arranged on the left side of the fuser 11 when viewed from the side and covers the side portion of the fuser 11, and the right side of the fuser 11 when viewed from the upstream side to the downstream side in the paper transport direction. It is disposed and consists of a side frame FR as a fixing element that covers the side portion of the fuser 11. A plurality of fins fn are formed on the lower plate PL so as to dissipate the heat generated in the fuser 11.

Then, 16 is movable so as to be adjacent to each side frame FL and FR on the top plate PT side between the side frame FL and FR, and in the present embodiment, the axis sh1 is the center of rotation (swing center). The pair of levers 12 as support members rotatably arranged are rotatably (swingable) erected between the levers 16 as a first fixing member and as a heating side member. The belt unit 13 is rotatably on the lower plate PL side between the side frame FL and FR, and serves as a second fixing member erected so as to face the belt unit 12 and on the pressurizing side. It is a pressure roller as a member.

The belt unit 12 is supported by a lever 16, extends between the levers 16, and is a traveling member of the belt 18 as a traveling member. Both ends of the belt 18 are on the lever 16 on the inner peripheral surface side. A fixed nip portion forming member 19 and the like are provided. Each lever 16 is formed with a shaft hole h1 for passing through a shaft sh1 that rotatably supports the lever 16.

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

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

During this time, the fixing motor M1 as a fixing drive unit arranged in the main body of the apparatus is driven, the rotation generated by the fixing motor M1 is transmitted to the pressurizing roller 13, and the belt 18 of the belt unit 12 is transferred. The paper that has been run and sent from the image forming unit is conveyed along the nip portion N in the direction of the arrow TR in FIG.

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

Therefore, in the present embodiment, the fuser 11 is provided with a pressing mechanism 20 for pressing the belt unit 12 against the pressure roller 13 and separating the belt unit 12 from the pressure roller 13. ..

The pressing mechanism 20 is rotatably supported by the shaft 26 rotatably supported by the side frame FL and FR, and the shaft 26 facing the pressed portion 21 formed at the upper end portion of the lever 16. A pair of eccentric cams 23 as cam members, a pair of levers 27 attached to the shaft 26, and a position attached to the tip of the shaft 26 in the rotational direction of the eccentric cam 23, that is, for detecting a rotational position. As a first urging member, which is arranged so as to face the eccentric cam 23 with the reflecting plate 45 as a detected element and the pressed portion 21 interposed therebetween, and urges the belt unit 12 toward the pressurizing roller 13. A spring 28 and the like are provided.

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

Further, the shaft 26 is extended so as to penetrate the side frame FR and the gear cover 39 described later, and the reflector 45 is attached to the tip of the shaft 26 outside the gear cover 39 and arranged in the device main body of the printer. It faces the optical sensor S (FIG. 8) as a detection element described later for detecting the rotational position of the eccentric cam 23 provided.

Then, the spring 28 is brought into contact with the pressed portion 21 at one end (downstream end in the paper transport direction), and the other end (upstream end in the paper transport direction). ), It is brought into contact with a predetermined portion of the housing Cs, in the present embodiment, the back surface 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 placed at a predetermined position and the nip portion N is formed, and the paper is conveyed by rotating the pressurizing roller 13. It is not necessary to convey the paper while the lever 16 is rotated to form or eliminate the nip portion N.

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

That is, the fixing motor M1 is driven in the forward direction and the reverse direction, and when the paper is conveyed, the fixing motor M1 is driven in the forward direction to rotate the pressurizing roller 13 to form or eliminate the nip portion N. Occasionally, it is driven in the opposite direction to rotate the shaft 26 and rotate the eccentric cam 23.

Therefore, the fixing motor M1 and the pressurizing roller 13 and the shaft 26 (eccentric cam 23) are connected by a rotation transmission mechanism 31.

The rotation transmission mechanism 31 is arranged adjacent to the fuser 11 in the apparatus main body of the printer, and is the apparatus in the apparatus main body rotation transmission unit 36 and the fuser 11 that transmits the rotation of the fixing motor M1 to the fuser 11. It has a fixing device rotation transmission unit 38 that transmits the rotation of the main body rotation transmission unit 36 to the shaft 26, a gear cover 39 that is attached to the side frame FR and covers the main part of the fixing device rotation transmission unit 38, and the like.

The device main body rotation transmission unit 36 serves as a second gear that is rotatably arranged by being meshed with an output gear gr1 as a first gear that outputs the rotation of the fixing motor M1 and the output gear gr1. The idle gear gr2, the idle gear gr3 as a third gear that is meshed with the idle gear gr2 and is connected to and rotated by the shaft sh2, is arranged coaxially with the shaft sh2 and transmits rotation in one direction. As the sixth and seventh gears, which are meshed with the one-way gears gr4 and gr5 as the fourth and fifth gears and the one-way gears gr4 and gr5, respectively, and are rotatably arranged with the shaft sh3 as the center of rotation. It has idle gears gr6, gr7 and the like.

The one-way gears gr4 and gr5 are connected between the fixing motor M1 and the pressurizing roller 13 and the eccentric cam 23, and when the fixing motor M1 is driven in the forward direction and the reverse direction, the fixing motor M1 It constitutes a rotation transmission element that transmits rotation to one of the pressure roller 13 and the eccentric cam 23. Further, on the shaft sh2, the one-way gear gr4 is arranged adjacent to the one-way gear gr5 on the center side of the one-way gear gr5, and on the shaft sh3, the idle gear gr6 is arranged on the idle gear gr7 on the center side of the idle gear gr7. It is arranged adjacent to.

The fixing device rotation transmission unit 38 is rotatably arranged around a shaft sh4 attached to the side frame FR as a rotation center, and serves as eighth and ninth gears that are meshed with the idle gears gr6 and gr7, respectively. The idle gear gr10 and the side frame FR as a tenth gear that are rotatably arranged around the axis sh5 attached to the connecting gears gr8 and gr9 and the side frame FR and meshed with the connecting gear gr8. The shaft sh6 is rotatably arranged around the center of rotation, is connected to the pressurizing roller 13, and is attached to the pressurizing roller gear gr11 as the eleventh gear to be meshed with the idle gear gr10, and the side frame FR. A two-stage gear gr12 as a twelfth gear, which is rotatably arranged around the shaft sh7 and is composed of a large-diameter gear ga and a small-diameter gear gb, and the large-diameter gear ga is meshed with the connecting gear gr9. The thirteenth, which is attached to the side frame FR, is rotatably arranged around the shaft 26, is connected to the eccentric cam 23 via the shaft 26, and is meshed with the small diameter gear gb of the two-stage gear gr12. As a gear and as a rotation transmission element of the cam gear gr13, and as a second urging member arranged so as to surround the shaft 26 between the gear cover 39 and the cam gear gr13 of the shaft 26. It has a spring 46 and the like as a rotation suppressing member.

As shown in FIG. 4, one end of the spring 46 is brought into contact with the inner peripheral surface of the gear cover 39, and the other end is brought into contact with the end face of the cam gear gr13, and the cam gear gr13 is directed toward the side frame FR with a predetermined urging force. It is 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, and the rotation of the shaft 26 and the eccentric cam 23 is suppressed. .. Therefore, the cam gear gr13 is disposed between the side frame FR on the shaft 26 and the gear cover 39 so as to be movable in the axial direction and slidable with respect to the shaft 26.

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

In the device main body rotation transmission unit 36, when the fixing motor M1 is driven in the positive direction, in the present embodiment, in the clockwise direction in FIG. 6, that is, in the direction of the arrow A, the idle gear gr3 is driven in the clockwise direction. 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 cannot be rotated.

Then, in the fixing device rotation transmission unit 38, the connecting gear gr8 is rotated in the clockwise direction in FIGS. 1 and 6, that is, in the arrow E direction, the idle gear gr10 is rotated in the counterclockwise direction, and the pressurizing roller gear gr11 is rotated. Is rotated clockwise in FIG. 1, that is, in the direction of arrow G. As a result, the pressurizing roller 13 is rotated in the clockwise direction. At this time, the connecting gear gr9 cannot be rotated, and the eccentric cam 23 cannot be rotated either.

Further, in the device main body rotation transmission unit 36, when the fixing motor M1 is driven in the reverse direction, in the present embodiment, in the counterclockwise direction in FIG. 6, that is, in the arrow B direction, the idle gear gr3 is driven. It is rotated counterclockwise, whereby the rotation is transmitted to the one-way gear gr5, the one-way gear gr5 is rotated counterclockwise, that is, in the arrow D direction, and the idle gear gr7 is rotated clockwise. Be made to. At this time, the rotation is not transmitted to the one-way gear gr4, and the one-way gear gr4 cannot be rotated.

Then, in the fixing device rotation transmission unit 38, the connecting gear gr9 is rotated in the counterclockwise direction in FIGS. 1 and 6, that is, in the arrow F direction, the two-stage gear gr12 is rotated in the clockwise direction, and the cam gear gr13 is rotated. Is rotated in the counterclockwise direction in FIG. 1, that is, in the direction of arrow H. As a result, the eccentric cam 23 is rotated in the counterclockwise direction, and the reflector 45 is rotated in the arrow H direction. At this time, the connecting gear gr8 cannot be rotated, and the pressure roller 13 cannot be rotated either.

In this way, the rotation of the fixing motor M1 is transmitted to one of the one-way gears gr4 and gr5 according to the driving direction of the fixing motor M1. That is, by driving the fixing motor M1 in the direction of arrow A, the pressurizing roller 13 can be rotated and the paper can be conveyed, and by driving the fixing motor M1 in the direction of arrow B, the eccentric cam 23 is driven. It can be rotated to form or eliminate the nip portion N.

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. A conceptual diagram, FIG. 11 is a diagram for explaining the operation of the pressing mechanism when the fuser in the embodiment of the present invention is placed in the nip state, and FIG. 12 is a diagram in which the fuser in the embodiment of the present invention is in a depressurized state. FIG. 13 is a diagram for explaining the operation of the pressing mechanism when the fuser is placed in the released state, and FIG. 13 is a diagram for explaining the operation of the pressing mechanism when the fuser in the embodiment of the present invention is placed in the released state. 14 is a diagram for explaining the operation of the pressing mechanism when the fuser in the embodiment of the present invention is placed in the second transition state.

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

As shown in FIG. 9, the reflector 45 has a predetermined region in the circumferential direction in order to detect the rotational position of the eccentric cam 23 by the optical sensor S, and in the present embodiment, in the circumferential direction. A marker Mk having a fan-shaped shape is formed over a range of approximately 100 [°]. The marker Mk is a first color, in the present embodiment, a predetermined portion of the plate formed of black, for example, a second color by thin-filming aluminum, silver in the present embodiment. It is formed by making.

The optical 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 reflector 45, and irradiates the irradiation unit. The reflected 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 downstream edge portion m1 of the marker Mk is irradiated by the optical sensor S as the reflector 45 rotates, the intensity of the reflected light in the irradiation portion Rd decreases, and then the intensity of the reflected light decreases. When the upstream edge portion m2 of the marker Mk is irradiated by the optical sensor S, the intensity of the reflected light in the irradiation 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 has each edge portion m1 in the marker Mk based on the detection signal SG2 sent from the optical sensor S. , M2 detects whether or not the eccentric cam 23 is irradiated by the optical sensor S, and the drive processing unit Pr2 detects the rotation position of the eccentric cam 23, and the fixing motor M1 is based on the detected rotation position of the eccentric cam 23. To drive or stop.

Next, the eccentric cam 23 will be described.

The eccentric cam 23 includes a cam surface Sc as shown in FIG. 10 so that the force for pressing the pressed portion 21 can be changed with rotation. The cam surface Sc has a plurality of edges formed from the downstream side to the upstream side in the rotation direction (arrow H direction), and in the present embodiment, the cam surface Sc includes five edges eg1 to eg5, and the second edge between the edges eg1 and eg2. In the nip region Ar1 which is a region of 1, a first surface S1 is formed in which the distance from the axis Cn is longer as it is closer to the edges eg1 and eg2 and shorter as it is farther from the edges eg1 and eg2. A second surface S2 having a constant distance from the axis Cn is formed in the decompression region Ar2, which is the second region of the above, and the first region between the edges eg3 and eg4 is the first. A third surface S3 is formed in the transition region Ar3, which is shorter as the distance from the axis Cn is closer to the edge eg3 and longer as the distance is closer to the edge eg4. A fourth surface S4 having a constant value R2 whose distance from the axis Cn is larger than the value R1 is formed in Ar4, and a second transition region Ar5 which is a fifth region between the edges eg5 and eg1 is formed. A fifth surface S5 is formed, which 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 and the eccentric cam 23 is rotated 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 region Ar1 faces the pressed portion 21 as shown in FIG. The eccentric cam 23 is not brought into contact with the pressed portion 21 and is placed in a free state. At this time, the lever 16 is rotated in the direction of arrow I in FIG. 9 with the shaft sh1 as the rotation center by the urging force of the spring 28. The belt unit 12 is pressed against the pressurizing roller 13 with a predetermined nip pressure, and the fuser 11 is placed in the nip state. When the fixing motor M1 is stopped in a state where substantially the center of the nip region Ar1 faces the pressed portion 21, the fixing device 11 keeps the state of being 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 run, and the paper is conveyed.

Then, the fixing motor M1 is driven again in the direction of arrow A, the eccentric cam 23 is further rotated in the direction of arrow H, and the decompression region Ar2 is made to face the pressed portion 21 as shown in FIG. 23 is brought into contact with the pressed portion 21, the lever 16 is rotated in the direction of arrow J with the shaft sh1 as the center of rotation against the urging force of the spring 28, and the belt unit 12 is brought into the pressure roller 13. The pressed nip pressure is lowered and the fuser 11 is placed in a reduced pressure state.

After that, when the fixing motor M1 is driven in the direction of arrow A, the eccentric cam 23 is further rotated in the direction of arrow H, and the first transition region Ar3 is made to face the pressed portion 21, the eccentric cam 23 becomes the pressed portion. In the state of being in contact with the 21, the lever 16 is further rotated in the direction of arrow J with the axis sh1 as the rotation center against the urging force of the spring 28, and the belt unit 12 is pressed against the pressure roller 13. The nip pressure to be applied is further reduced, and the fuser 11 is placed in the first transition state.

Subsequently, the fixing motor M1 is driven in the direction of arrow A, the eccentric cam 23 is further rotated in the direction of arrow H, and the release region Ar4 faces the pressed portion 21 as shown in FIG. With the 23 in contact with the pressed portion 21, the lever 16 is further rotated in the arrow J direction with the axis sh1 as the rotation center against the urging force of the spring 28, and the belt unit 12 is applied. It is separated from the compression roller 13, the nip portion N is eliminated, and the fuser 11 is placed in the released state. When the fixing motor M1 is stopped in a state where the center of the release area Ar4 faces the pressed portion 21, the fixing device 11 keeps the state of being placed in the released state.

Then, the fixing motor M1 is driven in the direction of arrow A, the eccentric cam 23 is further rotated in the direction of arrow H, and the second transition region Ar5 is made to face the pressed portion 21 as shown in FIG. With the eccentric cam 23 in contact with the pressed portion 21, the lever 16 is rotated in the direction of arrow I with the shaft sh1 as the rotation center by the urging force of the spring 28, and the belt unit 12 and the pressurizing roller. The distance from 13 is shortened, and the fuser 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 hits the pressurizing roller 13. Contact.

By the way, in order to place the fuser 11 in the nip state with high accuracy, it is preferable to stop the fixing motor M1 in a state where substantially the center of the nip region Ar1 faces the pressed portion 21, and the fuser 11 is accurately placed. In order to put it in the released state well, it is preferable to stop the fixing motor M1 in a state where the center of the release region Ar4 faces the pressed portion 21.

Therefore, in the present embodiment, after the first and second reference positions are set on the eccentric cam 23 so that the nip region Ar1 faces the pressed portion 21, the eccentric cam 23 becomes the first. When placed at the reference position of, 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 detects the rotation position of the eccentric cam 23. After stopping the fixing motor M1 in a state where the center of the nip region Ar1 faces the pressed portion 21 based on the rotation position, the release region Ar4 comes to face the pressed portion 21. When the eccentric cam 23 is placed at the second reference 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 drives the drive processing unit. Based on the rotation position of the eccentric cam 23, Pr2 stops the fixing motor M1 in a state where substantially the center of the release region Ar4 faces the pressed portion 21.

Therefore, after the nip region Ar1 is opposed to the pressed portion 21 with the rotation of the eccentric cam 23, when the cam member 23 is placed at the first reference position at a set timing, the reflector 45 The cam member 23 is set to the second reference position at a set timing after the edge portion m1 of the marker Mk is irradiated by the optical sensor S and the decompression 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 fuser 11 in the nip state, when the fixing motor M1 is driven and the eccentric cam 23 is rotated, the edge portion 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 timing after the nip region Ar1 is opposed to the pressed portion 21, the drive processing unit Pr2 clocks the timer 82. When it starts and a 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 so that the front half portion on the upstream side of the nip region Ar1 in the rotation direction of the eccentric cam 23 faces the pressed portion 21 and the predetermined time. τ1 is set so that substantially the center of the nip region Ar1 faces the pressed portion 21 when the eccentric cam 23 is rotated at a rotational speed driven by the fixing motor M1. This allows the fuser 11 to be placed in the nip state.

Further, in order to put the fuser 11 in the released state, when the fixing motor M1 is driven and the eccentric cam 23 is rotated, the edge portion m2 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 second rotation position of the eccentric cam 23 at the timing after the decompression region Ar2 is opposed to the pressed portion 21, the drive processing unit Pr2 clocks the timer 82. When the start and the predetermined time τ2 have elapsed, 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 so that the front half portion on the upstream side of the release region Ar4 in the rotation direction of the eccentric cam 23 faces the pressed portion 21 and the predetermined time. τ2 is set so that substantially the center of the release region Ar4 faces the pressed portion 21 when the eccentric cam 23 is rotated at a rotational speed driven by the fixing motor M1. As a result, the fuser 11 can be placed in the released state after passing through the depressurized state and the first transition state.

By the way, when the fuser 11 is placed in the released state, when the fixing motor M1 is driven to rotate the eccentric cam 23 and the fuser 11 is placed in the nip state, the second transition region is described. While the Ar5 is opposed to the pressed portion 21, the lever 16 is rotated in the direction of arrow I as the distance from the axis Cn gradually decreases, pushing the eccentric cam 23 and pushing the eccentric cam 23. A rotational force is applied to 23. As a result, the one-way gear gr5 (FIG. 6) is idled, and the eccentric cam 23 has a rotation speed faster than the rotation speed driven by the fixing motor M1 in a predetermined section while facing the pressed portion 21. It can be rotated with.

In that case, if the fixing motor M1 is stopped and the fixing device 11 is placed in the nip state while the second transition region Ar5 is opposed to the pressed portion 21, the rotation speed of the eccentric cam 23 is increased. Is unstable, so that 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 timing, and when a predetermined time τ1 elapses. , The fixing motor M1 can be stopped.

In this case, after the nip region Ar1 is opposed to the pressed portion 21, the eccentric cam 23 cannot be brought into contact with the pressed portion 21, the lever 16 does not push the eccentric cam 23, and the eccentric cam 23 No rotational force is applied, and the eccentric cam 23 can be rotated at the rotational speed driven by the fixing motor M1. Therefore, the rotational speed of the eccentric cam 23 can be stabilized, and by stopping the fixing motor M1, the fixing device 11 can be placed in the nip state with high accuracy.

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), mounting parts such as gears mounted on each shaft, and the like. If the eccentric cam 23 cannot be stopped accurately due to the moment of inertia, the fuser 11 cannot be accurately placed in the nip state.

Therefore, in the present embodiment, as described above, the spring 46 is arranged 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 A rotational load is applied to the eccentric cam 23 and the eccentric cam 23.

Therefore, the eccentric cam 23 can be reliably stopped by facing the nip region Ar1 with the pressed portion 21, and the fuser 11 can be placed in the nip state with high accuracy.

Further, when the fixing device 11 is placed in the nip state, the fixing motor M1 is driven to rotate the eccentric cam 23, and when the fixing device 11 is placed in the released state, the decompression region Ar2, No. While the transition region Ar3 and the release region Ar4 of 1 are opposed to the pressed portion 21, the distance from the axial center Cn becomes long, the eccentric cam 23 pushes the pressed portion 21, and the lever 16 moves in the arrow J direction. It can be rotated. Therefore, since the eccentric cam 23 is stably rotated at the rotational speed driven by the fixing motor M1, the fixing device 11 can be accurately placed in the released state by stopping the fixing motor M1.

As described above, in the present embodiment, after the nip region 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 used. Since it is stopped, the fixing motor M1 can be stopped in a state where the rotational 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 moment of inertia generated in the rotation transmission mechanism 31 arranged between the fixing motor M1 and the eccentric cam 23. Therefore, since the rotational position of the eccentric cam 23 when the fixing motor M1 is stopped can be accurately positioned, the nip portion N can be accurately formed between the belt unit 12 and the pressure roller 13. can.

Moreover, since it is not necessary to use a gear with a torque limiter or the like in order 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 released state, the fixing device 11 is in the second transition state in a state where the eccentric cam 23 is in contact with the pressed portion 21. The eccentric cam 23 is subsequently placed, and the eccentric cam 23 is separated from the pressed portion 21 and the fuser 11 is placed in the nip state. It can be prevented from occurring.

Further, in the present embodiment, since the eccentric cam 23 and the reflector 45 are arranged on the shaft 26, the rotation position of the eccentric cam 23 can be set without being affected by the backlash of the gear of the rotation transmission mechanism 31. It can be detected directly by the reflector 45. Therefore, the rotational position of the eccentric cam 23 can be accurately positioned.

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

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

The present invention is not limited to the above-described embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

11 Fixer 12 Belt unit 13 Pressurizing roller 16 Lever 21 Pressed part 23 Eccentric cam 31 Rotation transmission mechanism 46 Spring Ar1 Nip area Ar4 Release area Ar5 Second transition area gr4, gr5 One-way gear M1 Fixing motor N Nip part Pr1 Rotation position detection processing unit Pr2 Drive processing unit Sc Cam surface

Claims (10)

(A) The frame that constitutes the housing and
(B) The first fixing member and
(C) A second fixing member supported by the frame and arranged to face the first fixing member.
(D) A support member that is movably arranged adjacent to the frame and supports the first fixing member, and a support member.
(E) A shaft rotatably supported by the frame and
(F) On the center side of the frame on the shaft, the nip region and the nip portion for forming the nip portion are released so as to be rotatably arranged so as to face the pressed portion formed on the support member. A cam member for which a release region for the purpose and a transition region between the nip region and the release region are formed, and a cam member that moves the support member with rotation.
(G) Drive unit and
(H) A rotation transmission mechanism that connects the drive unit to the second fixing member and the cam member.
(I) A rotation position detection processing unit that detects the rotation position of the cam member after the nip region is opposed to the pressed portion as the cam member rotates.
(J) It has a drive processing unit that stops the drive unit after the rotation position of the cam member is detected, and also has a drive processing unit.
(K) The rotation transmission mechanism is a first rotation transmission element that transmits the rotation of the drive unit to one of the second fixing member and the cam member, and the rotation transmission mechanism is located outside the frame on the shaft. A second rotation transmission element that transmits the rotation of the drive unit to the cam member via the shaft, a cover arranged outside the second rotation transmission element on the shaft, and between the cover and the frame. The fixing device is provided with a second urging member that urges the second rotation transmitting element toward the frame and suppresses the rotation of the cam member. The rotation position detection processing unit is the rotation position of the cam member when the cam member is placed at a preset reference position after the nip region is opposed to the pressed portion due to the rotation of the cam member. The fixing device according to claim 1. The fixing device according to claim 2, wherein the cam member is placed at a reference position while the front half portion on the upstream side of the nip region in the rotation direction of the cam member is opposed to the pressed portion. (A) It has a first urging member that urges the first fixing member toward the second fixing member, and also has a first urging member.
(B) Claims 1 to 3 in which the cam member is rotated at a rotation speed higher than the rotation speed driven by the drive unit in a predetermined section while the transition region is opposed to the pressed portion. The fixing device according to any one of the above items. The fixing device according to any one of claims 1 to 4, wherein the cam member is rotated at a rotational speed driven by the driving portion while the nip region is moved so as to face the pressed portion. (A) The detected element is attached to the outside of the second rotation transmitting element on the shaft .
(B) The fixing device according to any one of claims 1 to 5, wherein the rotation position detection processing unit detects the rotation position of the cam member based on a detection signal sent from the detected element. The fixing device according to claim 2 or 3, wherein the drive processing unit stops the drive unit when a predetermined time elapses after the cam member is placed in the reference position. (A) The driving unit is driven in the forward direction and the reverse direction.
(B) The fixing device according to claim 1, wherein the first rotation transmission element transmits rotation according to the driving direction of the drive unit. The fixing device according to claim 1, wherein the second urging member suppresses the rotation of the cam member by a frictional force generated by pressing the second rotation transmitting element against the frame . An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 9.

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