JP6471711B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes a toner image on a sheet, and an image forming apparatus including the fixing device.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine includes a fixing device that fixes a toner image on a sheet. In a fixing device of a full-color image forming apparatus, an endless fixing belt heated by a heat source, a fixing roller rotatably provided inside the fixing belt, a pressure roller pressed against the fixing roller via the fixing belt, And a fixing nip is formed between the fixing belt and the pressure roller.

  The fixing roller has a metal core formed of aluminum, iron, or the like, and an elastic layer provided on the outer peripheral surface of the metal core. The elastic layer is formed of a material having low thermal conductivity such as silicone rubber or foamed resin, and suppresses heat transfer from the fixing belt. The fixing belt has an elastic layer and a release layer formed in order on the surface of the base material layer formed of nickel or the like, and the fixing belt generates heat when the base material layer generates heat by a heating source such as IH. Is heated.

  In such a fixing device, since a slight clearance is provided between the fixing roller and the fixing belt, the fixing belt may meander depending on the contact state between the fixing belt and the paper. Therefore, Patent Document 1 describes a fixing device in which a detent member is provided outside the both end faces of the fixing belt with a predetermined interval in consideration of thermal expansion and dimensional tolerance of the fixing belt. In this fixing device, when the fixing belt meanders, the end face comes into contact with one of the detent members, and the meandering is regulated.

  On the other hand, the fixing belt may be charged by contact with paper. Therefore, there is a case where the stopper member is formed of a metal or a conductive resin, and the charge of the fixing belt is discharged from the stopper member through the core metal.

JP 2010-169737 A

  However, in the fixing device described in Patent Document 1, the fixing belt is in an electrically floating state until the fixing belt meanders and comes into contact with one of the detent members. Further, when the elastic layer of the fixing roller is heated by the fixing belt, the elastic layer expands and contacts the fixing belt, and the fixing belt may not be able to move in the axial direction due to friction between the elastic layer and the fixing belt. If the fixing belt cannot move in the axial direction before the fixing belt comes into contact with one of the detent members, the fixing belt is maintained in an electrically floating state. If the fixing belt continues to be charged in this way, noise may be generated by discharge, which may affect electrical components such as the thermistor.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fixing device and an image forming apparatus that can reliably remove static electricity from a fixing belt.

  In order to solve the above-described problems, the fixing device of the present invention includes an endless fixing belt heated by a heat source, a fixing roller provided inside the fixing belt so as to be rotatable about a rotation axis, and the fixing belt. A pressure member that rotates in pressure contact with the fixing roller, and forms a fixing nip between the fixing belt and the pressure member, the rotation of the end surface of the fixing belt A conductive detent member facing the end surface on the outer side in the axial direction and slidable in the direction of the rotation axis and grounded, and urging the detent member toward the end surface of the fixing belt And an urging member to be brought into contact with the end face.

  By adopting such a configuration, the detent member is surely brought into contact with the end face of the fixing belt, so that the charged charge of the fixing belt is quickly discharged through the detent member to prevent discharge from the charged fixing belt. be able to.

  In the fixing device according to the aspect of the invention, the fixing device includes a retaining ring that is provided on the outer side in the rotational axis direction so as not to be slidable in the rotational axis direction, and the urging member includes the retaining member and the retaining ring. The detent member may be urged toward the end surface of the fixing belt with respect to the retaining ring so as to contact the end surface.

  By adopting such a configuration, even when the fixing belt is meandering, the detent member can be urged so as to follow the end surface of the fixing belt to be surely brought into contact with the end surface.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, since the conductive detent member always comes into contact with the end face of the fixing belt, the fixing belt can be reliably discharged.

1 is a schematic diagram illustrating an outline of a color printer according to an embodiment of the present invention. 1 is a front sectional view of a fixing device according to an embodiment of the present invention. FIG. 3 is a side sectional view showing the fixing belt during normal running in the fixing device according to the embodiment of the present invention. In the fixing device according to an embodiment of the present invention, FIG.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

  First, the overall configuration of a color printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram showing an outline of a color printer. In the following description, the front-rear direction shown in FIG. 1 is the front-rear direction of the color printer 1, and the left-right direction is based on the direction of the color printer 1 viewed from the front side.

  As shown in FIG. 1, the color printer 1 includes a box-shaped housing 2. A paper discharge port 4 and a paper discharge tray 5 provided below the paper discharge port 4 are formed on the upper surface of the housing 2. A rear opening 2 a is formed on the rear side surface of the housing 2. The rear opening 2a is opened and closed by a rear cover 6 supported so as to be rotatable about the lower end. Further, a transport unit 7 is supported inside the rear opening 2a so as to be rotatable about the lower end.

  A paper feeding cassette 9 that contains paper S is detachably housed in the lower part of the housing 2, and a paper feeding device 10 that feeds the paper S from the paper feeding cassette 9 is located at the upper right of the paper feeding cassette 9. Is provided. An exposure device 12 is provided above the paper feed cassette 9. Above the exposure device 12, an intermediate transfer unit 14 and four image forming units 15 arranged below the intermediate transfer unit 14 in the front-rear direction are provided. The intermediate transfer unit 14 includes an intermediate transfer belt 17 that is rotatably supported, and four primary transfer rollers 18 that are arranged inside the intermediate transfer belt 17 in the front-rear direction.

  The four image forming units 15 include a photosensitive drum 20 that is rotatably provided, a charger 21 that is disposed around the photosensitive drum 20 along the rotation direction of the photosensitive drum 20, a developing device 22, Each has a cleaning device 23 and a charge removal device 24. The photosensitive drum 20 is opposed to the primary transfer roller 18 via the intermediate transfer belt 17 between the developing device 22 and the cleaning device 23, and the primary transfer unit is interposed between the intermediate transfer belt 17 and the photosensitive drum 20. 26 is formed. Each image forming unit 15 is connected to a toner container (not shown) that stores toner of a corresponding color, and the toner is supplied from the toner container to the developing device 22.

  A secondary transfer roller 28 is rotatably supported by the transport unit 7 behind the intermediate transfer unit 14, and a secondary transfer portion 29 is formed between the intermediate transfer belt 17 and the secondary transfer roller 28. Yes. A fixing device 30 is provided above the secondary transfer unit 29, and a paper discharge device 31 facing the paper discharge port 4 is provided above the fixing device 30.

  Further, a main transport path 33 and a double-sided printing path 34 for the paper S are formed inside the housing 2. The main conveyance path 33 is formed inside the conveyance unit 7 so as to go from the sheet feeding device 10 to the discharge device 31 through the secondary transfer unit 29 and the fixing device 30. The duplex printing path 34 branches from the downstream side of the fixing device 30 in the transport direction of the main transport path 33 and joins the main transport path 33 on the downstream side of the sheet feeding device 10. Is formed between.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. First, in each image forming unit 15, after the surface of the photosensitive drum 20 is charged by the charger 21, exposure corresponding to the image data is performed on the photosensitive drum 20 by the laser light from the exposure device 12. An electrostatic latent image is formed on the surface of the photosensitive drum 20. The electrostatic latent image is developed into a toner image by the developing device 22, and the toner image is transferred to the intermediate transfer belt 17 by the primary transfer unit 26. The toner and charge remaining on the photosensitive drum 20 are removed by the cleaning device 23 and the charge eliminating device 24, respectively. The toner images formed by the image forming units 15 are superimposed on the intermediate transfer belt 17, so that a full-color toner image is formed on the intermediate transfer belt 17.

  On the other hand, the sheet S fed from the sheet feeding cassette 9 by the sheet feeding device 10 is transported to the secondary transfer unit 29 along the main transport path 33 in synchronism with the toner image forming operation described above, and is subjected to secondary transfer. The toner image on the intermediate transfer belt 17 is secondarily transferred to the paper S in the portion 29. The sheet S on which the toner image is secondarily transferred is conveyed downstream through the main conveyance path 33 and enters the fixing device 30, and the toner image is fixed on the sheet S in the fixing device 30. The paper S on which the toner image is fixed is discharged from the paper discharge device 31 to the paper discharge tray 5. When duplex printing is performed, the sheet S on which an image is formed on one side branches from the main conveyance path 33 to the duplex printing path 34, is conveyed through the duplex printing path 34, and joins the main conveyance path 33. Thus, image formation is similarly performed on the other surface.

  Next, the fixing device 30 will be described with reference to FIGS. 2 is a front sectional view showing the fixing device, and FIGS. 3 and 4 are side sectional views showing the fixing device. FIG. 3 shows the fixing belt during normal running, and FIG. 4 shows the fixing belt meandering.

  As shown in FIG. 2 and FIG. 3, the fixing device 30 includes a fixing belt 41, an IH heater 42 as a heating source for heating the fixing belt 41, and a fixing roller 43 that is rotatably provided inside the fixing belt 41. A pressure roller 44 that is a pressure member that rotates in pressure contact with the fixing roller 43 via the fixing belt 41, a locking member 45 provided outside both end surfaces of the fixing belt 41, and each locking member 45. A coil spring 46 as a biasing member that biases the fixing belt 41 toward the end face of the fixing belt 41.

  The fixing belt 41 is an endless belt having a predetermined inner diameter and having a width longer than a sheet passing region through which a sheet is passed, a base material layer formed of a magnetic metal such as nickel, silicone rubber, and the like And a release layer such as a PFA tube are laminated in order from the inside.

  The IH heater 42 includes a coil portion 42a, a coil bobbin 42b that holds the coil portion 42a in a winding shape, and an arch core 42c. The IH heater 42 is supported so as to cover the upper half of the fixing belt 41. A magnetic field is generated by applying a high-frequency AC voltage to the coil portion 42a. Due to the action of this magnetic field, an eddy current is generated in the base material layer of the fixing belt 41, the base material layer generates heat, and the fixing belt 41 is heated. The

  The fixing roller 43 includes a cored bar 51 as a rotation shaft and an elastic layer 52 provided on the outer peripheral surface of the cored bar 51. The cored bar 51 includes a central part 51a and outer end parts 51b that are provided on both outer sides of the central part 51a and have a smaller diameter than the central part 51a. The length of the central portion 51 a is shorter than the width of the fixing belt 41. Further, an annular groove 51c is formed in the outer end portions 51b along the outer peripheral surface in the vicinity of the center in the axial direction. The core metal 51 is made of aluminum, iron, or the like.

  The elastic layer 52 is provided around the central portion 51 a of the core bar 51 and has an outer diameter smaller than the inner diameter of the fixing belt 41. Further, on both end faces of the elastic layer 52, stepped portions 52 a that are cut out along the outer periphery are formed. The elastic layer 52 is formed of a material having a low heat transfer coefficient such as silicone rubber or foamed resin.

  The fixing roller 43 is inserted inside the fixing belt 41, and the end portions of both outer end portions 51 b of the cored bar 51 are respectively supported by bearings 56 via conductive bushes 55. The bearing 56 is supported by a conductive frame (not shown) of the housing 2. Accordingly, the cored bar 51 is grounded to the housing 2 via the bush 55 and the bearing 56. Further, a slight clearance is interposed between the fixing belt 41 and the fixing roller 43.

  The pressure roller 44 includes a cylindrical cored bar 44a, an elastic layer 44b provided on the outer peripheral surface of the cored bar 44a, and a release layer (not shown) provided on the outer peripheral surface of the elastic layer 44b. Yes. The pressure roller 44 is supported from below the fixing roller 43 through the fixing belt 41 so as to be in pressure contact with the fixing roller 43 to form a fixing nip 58, and is connected to a driving source (not shown) to rotate. Is done. When the pressure roller 44 is rotated counterclockwise in FIG. 2 by the drive source, the fixing belt 41 and the fixing roller 43 are driven to rotate in the clockwise direction opposite to the rotation direction of the pressure roller 44. As a result, the sheet that has passed through the fixing nip 58 is conveyed.

  When the pressure roller 44 is pressed against the fixing roller 43, the elastic layer 52 of the fixing roller 43 is pressed and deformed as shown in FIG. Along with this deformation, both end portions of the fixing belt 41 are deformed so as to be bent inward within the stepped portion 52 a of the elastic layer 52.

  The detent member 45 is a ring-shaped member having an outer diameter larger than the outer diameter of the fixing belt 41 and an inner diameter slightly larger than the outer diameter of the outer end portion 51 b of the core metal 51 of the fixing roller 43. The stopper member 45 is supported on the inner side of the tubular grooves 51c of both outer end portions 51b of the core metal 51 so as to be rotatable about the core metal 51 and slidable in the axial direction. The stopper member 45 is made of a conductive metal or resin. Accordingly, when the stopper member 45 is supported by the cored bar 51, it is grounded to the conductive frame of the housing 2 through the cored bar 51.

  The coil spring 46 is interposed between the retaining ring 61 that engages with each annular groove 51 c of the cored bar 51 and each detent member 45. By the respective coil springs 46, the respective detent members 45 are urged toward the retaining ring 61 in the axial direction so as to be in contact with both end surfaces of the fixing belt 41.

  Further, as shown in FIG. 2, the fixing device 30 includes a paper entry guide 63 provided on the upstream side in the paper conveyance direction from the fixing nip 58, and a separation member 64 provided on the downstream side in the paper conveyance direction from the fixing nip 58. And a thermistor 65 for detecting the temperature of the fixing belt 41. The sheet entry guide 63 is disposed along the main conveyance path 33 so as to be inclined upward toward the fixing nip 58. The separation member 64 is supported from the counter direction toward the surface of the fixing belt 41 with respect to the rotation direction of the fixing belt 41. The thermistor 65 is supported in a non-contact manner with respect to the fixing belt 41.

  In the fixing device 30 having the above-described configuration, the sheet S on which the toner image is transferred is guided to the sheet entry guide 63 and conveyed to the fixing nip 58. The sheet S is heated by the fixing belt 41 when passing through the fixing nip 58 and is pressed by the pressure roller 44 and the fixing roller 43 to fix the toner image on the sheet S. The sheet S on which the toner is fixed is separated from the fixing belt by the separation member 64 and is conveyed along the main conveyance path 33. Further, the IH heater 42 is controlled based on the temperature of the fixing belt 41 detected by the thermistor 65.

  As shown in FIG. 3, during the normal running of the fixing belt 41, the detent members 45 always come into contact with both end surfaces of the fixing belt 41. That is, the fixing belt 41 is grounded to the conductive frame of the housing 2 via the stopper member 45, the cored bar 51, the bush 55, and the bearing 6. Therefore, even if the sheet S passing through the fixing nip 58 and the fixing belt 41 are frictionally charged, the fixing belt 41 is interposed via the detent member 45, the core metal 51, the bush 55, and the bearing 56. Grounded, the charged charge is quickly eliminated.

  Also, as shown in FIG. 4, when the fixing belt 41 meanders in a direction away from one of the detent members 45 (left side in FIG. 4) (see the arrow in FIG. 4), the detent member 45 is a coil. Since it is urged by the spring 46 and slides along the metal core 51 to follow the fixing belt 41, the detent member 45 always comes into contact with both end faces of the fixing belt 41. However, since each detent member 45 is urged so as to abut against both end faces of the fixing belt 41, a situation in which the fixing belt 41 meanders greatly does not occur. Further, each detent is also prevented when the elastic layer 52 of the fixing roller 43 thermally expands to contact the fixing belt 41 and the fixing belt 41 cannot move in the axial direction due to friction between the elastic layer 52 and the fixing belt 41. Since the member 45 is urged by the coil spring 46 and slides along the metal core 51, the detent member 45 always comes into contact with both end faces of the fixing belt 41.

  As described above, in the fixing device 30 of the present invention, since the conductive detent member 45 is always in contact with both end faces of the fixing belt 41, even when the fixing belt 41 is charged by friction with the paper, It is possible to quickly eliminate the charge via the detent member 45 and prevent the fixing belt 41 from being charged. Accordingly, it is possible to prevent noise from being generated due to discharge from the charged fixing belt 41.

  Further, when the fixing belt 41 meanders, or the elastic layer 52 of the fixing roller 43 is heated and thermally expanded to come into contact with the fixing belt 41, and the fixing belt 41 is axially moved by friction between the elastic layer 52 and the fixing belt 41. Even when it becomes impossible to move to each other, each detent member 45 is urged by the coil spring 46 and slides along the metal core 51 so as to follow the fixing belt 41. The member 45 always comes into contact.

  In the embodiment of the present invention, the case where the configuration of the present invention is applied to the color printer 1 has been described. However, in other different embodiments, the present invention is applied to an image forming apparatus other than the color printer 1 such as a copying machine, a facsimile machine, and a multifunction machine. You may apply the structure of invention.

  Furthermore, since the above description of the embodiments of the present invention describes preferred embodiments of the fixing device and the image forming apparatus according to the present invention, various technically preferable limitations may be imposed. However, the technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the embodiment of the present invention described above does not limit the contents of the invention described in the claims.

1 Color printer (image forming device)
30 fixing device 41 fixing belt 43 fixing roller 44 pressure roller (pressure member)
45 Locking member 46 Coil spring (biasing member)
58 Fixing nip 61 Retaining ring

Claims (3)

An endless fixing belt heated by a heat source, a fixing roller provided inside the fixing belt so as to be rotatable about a rotation axis, and a pressure member that rotates in pressure contact with the fixing roller via the fixing belt A fixing device that forms a fixing nip between the fixing belt and the pressure member,
A conductive detent member which is opposed to the end surface of the end surface of the fixing belt in the axial direction of the rotating shaft , is slidable along the rotating shaft , and is grounded;
A biasing member that biases the detent member in the direction of the end surface of the fixing belt and always abuts against the end surface ;
The rotating shaft is made of metal;
The fixing device according to claim 1, wherein the stopper member is grounded via the rotating shaft . Prior Symbol axially outward than the close stop member, provided with a retaining ring provided so as not to slide before Symbol axial direction,
The urging member is interposed between the detent member and the retaining ring, and urges the detent member toward the end surface of the fixing belt against the retaining ring. The fixing device according to claim 1, wherein the fixing device is contacted.   An image forming apparatus comprising the fixing device according to claim 1.

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