JP2014228706A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus capable of suppressing the occurrence of a reduction in heating performance and the rotation failure of a fixing belt resulting from the relative position between heating means and a pressure member.SOLUTION: A fixing device 12 includes an endless fixing belt 38 that is provided in a rotatable manner, a contact member 30 that is rotatably provided and brought into contact with the outer peripheral surface of the fixing belt to form a nip part with the fixing belt, heating means 56 that is provided in contact with the inner peripheral surface of a part of the fixing belt other than the part forming the nip part to heat the fixing belt, and a pressure member 40 that is provided at a position facing the heating means with the fixing belt interposed therebetween to apply pressure to the fixing belt, and fixes an unfixed image on a recording material having passed through the nip part onto the recording material at least by heat. The fixing device 12 further includes adjustment means 70 for adjusting the relative position between the heating means and the pressure member.

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus including the fixing device.

  Conventionally, in an image forming apparatus, a latent image formed on an image carrier based on image data is developed with toner supplied from a developing device, and a toner image as a visible image is formed on the image carrier. The The toner image on the image carrier is transferred to a recording material by a transfer device and fixed on the recording material by a fixing device.

  In the fixing device described in Patent Document 1, a pressure roller that is rotatably provided and a fixing belt that is a flexible endless belt member provided to face the pressure roller are brought into pressure contact with each other. Thus, a nip portion is formed.

  Further, on the inner peripheral surface side of the fixing belt other than the fixing belt portion forming the nip portion, there is a heating means that contacts the inner peripheral surface of the fixing belt and heats the fixing belt with electric power supplied from a power source. A heating element is provided. Further, a pressing member for pressing the fixing belt toward the heating body and bringing the fixing belt into contact with the heating body is provided at a position facing the heating body via the fixing belt.

  The heating body has a plurality of heat generating portions in the paper width direction orthogonal to the paper transport direction. Then, based on the image data, the heating area by each heating unit is changed corresponding to the unfixed image on the paper, and the fixing belt is attached to the fixing belt by the heating body so as to apply heat only to the portion corresponding to the unfixed image of the fixing belt. Heat. As a result, the unfixed image on the sheet conveyed to the nip portion is fixed on the sheet by heat and pressure.

  Thus, by heating only the portion of the fixing belt corresponding to the unfixed image and heating it to the fixing temperature, energy saving can be achieved as compared with the case where the entire fixing belt is heated to the fixing temperature.

  However, the relative position between the heating body and the pressing member via the fixing belt may deviate from a predetermined desired positional relationship due to part processing accuracy, assembly errors, and the like.

  If the pressing member is located at a position away from the target position with respect to the heating body, the fixing belt cannot be properly pressed against the heating body, resulting in poor contact between the fixing belt and the heating body, and the fixing belt due to the heating body. There is a possibility that the heating performance of this will deteriorate. On the contrary, if the pressing member is positioned closer to the heating body than the target position, the rotational load of the fixing belt sandwiched between the heating body and the pressing member becomes excessively large, leading to poor rotation of the fixing belt. There is a fear.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to fix the deterioration of the heating performance and the rotation failure of the fixing belt caused by the relative position between the heating unit and the pressing member. And an image forming apparatus including the fixing device.

  In order to achieve the above object, an invention according to claim 1 is provided between an endless fixing belt rotatably provided and an outer peripheral surface of the fixing belt rotatably provided between the fixing belt and the fixing belt. A contact member that forms a nip portion, a heating unit that is provided in contact with an inner peripheral surface of the fixing belt other than the fixing belt portion that forms the nip portion, and that heats the fixing belt; A fixing device that is provided at a position facing the heating unit and presses the fixing belt, and fixes the unfixed image on the recording material that has passed through the nip portion to the recording material at least by heat. And the adjusting means for adjusting the relative position of the heating means and the pressing member.

  As described above, according to the present invention, there is an excellent effect that it is possible to suppress the deterioration of the heating performance and the rotation failure of the fixing belt due to the relative position between the heating unit and the pressing member.

FIG. 3 is a schematic diagram of a fixing device including an adjustment mechanism that adjusts a relative position between a heating member and an elastic roller. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram of a fixing device. FIG. The top view which shows an image formation pattern. The graph which shows the relationship between the 1st target temperature with respect to an image area | region and a non-image area | region, and a 2nd target temperature. The top view which shows an image formation pattern. The figure explaining the conventional problem. (A) The figure which shows the state where the contact width of an elastic body roller and a heating body is large, (b) The figure which shows the state which shifted the elastic body roller from the position of Fig.9 (a). Explanatory drawing of the other example of the adjustment mechanism which adjusts the relative position of a heating body and an elastic body roller. Explanatory drawing at the time of using a pad as a pressing member. FIG. 4 is a diagram illustrating cleaning of the fixing belt in the fixing device according to the embodiment. The figure which shows the state through which the comparatively big deposit | attachment adhering to a fixing belt passes the opposing part of a heating body and an elastic body roller. The figure which shows the structure which provided the several temperature detection sensor which detects the temperature of each heater of a heating body. The schematic diagram at the time of arrange | positioning the temperature detection sensor to each on the back surface of a heating body corresponding to the heating area | region of each heater.

FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the present embodiment.
As shown in FIG. 2, a printer as an example of an image forming apparatus according to the present embodiment includes a paper feeding device 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer device 10, It has a fixing device 12 and the like.

  The paper feeding device 4 feeds the paper S as a recording material stored in a stacked state and the paper S stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like.

  The sheet S sent out by the sheet feeding roller 16 is temporarily stopped by the registration roller pair 6 to correct the posture deviation. Thereafter, at the timing synchronized with the rotation of the photosensitive drum 8, that is, at the timing at which the leading edge of the toner image formed on the photosensitive drum 8 coincides with the predetermined position of the leading edge of the sheet S in the transport direction. The pair 6 is sent to the transfer portion N.

  Around the photosensitive drum 8, the charging roller 18, the mirror 20 constituting a part of the exposure unit, the developing device 22 including the developing roller 22a, the transfer device 10, and the cleaning are arranged in order of the photosensitive drum rotation direction. A cleaning device 24 provided with a blade 24a is disposed. Between the charging roller 18 and the developing device 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 through the mirror 20 and scanned.

  The image forming operation in the printer is performed in the same manner as in the past. That is, when the photosensitive drum 8 starts to rotate, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned on the exposure unit 26 based on the image data to create an image to be created. A latent image corresponding to is formed. The latent image is moved to a position facing the developing device 22 by the rotation of the photosensitive drum 8, where toner is supplied from the developing device 22 to the latent image to be visualized to form a toner image.

  The toner image formed on the photosensitive drum 8 is transferred onto the paper S that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer device 10.

  The sheet S on which the toner image has been transferred is conveyed toward the fixing device 12, and after the toner image is fixed on the sheet S by the fixing device 12, the sheet S is discharged to a discharge tray (not shown) and stacked.

  Residual toner remaining on the photosensitive drum 8 without being transferred from the photosensitive drum 8 to the paper S at the transfer portion N reaches the cleaning device 24 as the photosensitive drum 8 rotates, and is scraped off by the cleaning blade 24a. Thus, the surface of the photosensitive drum is cleaned. Thereafter, the residual potential on the photosensitive drum 8 is removed by a neutralizing unit (not shown) and prepared for the next image forming step.

  FIG. 3 is a schematic configuration diagram of the fixing device 12 according to the present embodiment. FIG. 4 is a diagram illustrating a relationship among the pressure roller 30, the fixing belt 38, and the heating body 56 as viewed from above the fixing device.

  3 and 4, the fixing device 12 includes a fixing belt 38, a pressure roller 30 that forms a fixing nip SN between the fixing belt 38, and a sheet heating element such as a thermal heater. A heating body 56 is provided. The pressure roller 30 is a contact member that is rotatably provided and forms a fixing nip portion SN with the fixing belt 38 by contacting the outer peripheral surface of the fixing belt 38. In this embodiment, the pressure roller 30 is urged toward the fixing belt 38 by an urging means (not shown) and is pressed against the fixing belt 38.

  The heating body 56 is attached to the stay-like member 57 and is disposed at a position in contact with the inner peripheral surface of the fixing belt 38. By providing the heating body 56 in contact with the inner surface of the fixing belt 38, it is possible to prevent the outer circumferential surface of the fixing belt 38 that contacts the toner image on the paper S from being scratched by the heating body 56. The life of the fixing belt 38 can be extended.

  The heating element 56 is provided with a resistance heating element 55 so as to occupy the entire image forming area in the sheet width direction orthogonal to the sheet conveyance direction of the sheet S. As shown in FIG. 4, the heating element 56 has a resistance heating element 55 divided into seven parts in the paper width direction, and the heating parts 55a, 55b, 55c, 55d, 55e, 55f, and 55g are independently fixed. The belt 38 can be heated.

  In this embodiment, the resistance heating element 55 of the heating body 56 is divided into seven in the paper width direction (longitudinal direction). However, the present invention is not limited to this. You may divide into 6 or 10 in the width direction.

  Thermistor as temperature detecting means for detecting the surface temperature of the fixing belt 38 in the vicinity of the heating body 56 and downstream of the fixing nip portion SN in the fixing belt rotation direction and upstream of the heating body 56 in the fixing belt rotation direction. 34 is provided.

  A thermistor 36 is provided on the surface of the heating body 56 opposite to the side in contact with the inner peripheral surface of the fixing belt 38 as temperature detecting means for detecting the temperature of the heating body 56.

  A power supply 39 for supplying power to the heating body 56 is provided. When power is supplied from the power supply 39 to the resistance heating body 55 of the heating body 56, the resistance heating body 55 of the heating body 56 generates heat. Further, based on the temperature information detected by the thermistor 34 and the thermistor 36, the power supply 39 is controlled by the control device 37, so that the power supply 39 supplies power to the resistance heating element 55 of the heating body 56. The control device 37 can independently control power supply by the power supply 39 in each of the divided resistance heating elements 55 of the heating body 56. The control device 37 is a microcomputer including a CPU, a ROM, a RAM, an I / O interface, and the like.

  The fixing belt 38 has a stainless steel base 38a having an outer diameter of 40 [mm] and a thickness of 40 [μm], and an elastic layer 38b coated on the surface of the base 38a. The elastic layer 38b is made of silicone rubber and has a thickness of 100 [μm]. Further, on the surface of the elastic layer 38b, in order to enhance the durability of the fixing belt 38 and to ensure the releasability, the release with a fluorine resin such as PFA or PTFE having a thickness of 5 [μm] to 50 [μm]. A layer 38c is formed. The base 38a of the fixing belt 38 may be polyimide.

  Inside the fixing belt 38, besides the heating body 56 and the like, a belt support member 61 that supports the fixing belt 38, and a nip forming member 60 that forms the pressure roller 30 and the fixing nip SN with the fixing belt 38 interposed therebetween. Is provided. These members are connected to and supported by a device side plate (not shown).

  The belt support member 61 is inserted into both end portions in a direction (axial direction) orthogonal to the rotation direction of the fixing belt 38, and both end portions of the fixing belt 38 are rotatably held by the belt support member 61.

  The pressure roller 30 includes an iron core 30a having an outer diameter of 40 [mm] and a thickness of 2 [mm], and an elastic layer 30b covered on the surface of the core 30a. The elastic layer 30b is made of silicone rubber and has a thickness of 5 [mm]. In addition, it is desirable to form a fluororesin layer having a thickness of about 40 [μm] on the surface of the elastic layer 30b in order to improve releasability.

  In the present embodiment, the contact portion of the heating body 56 with the fixing belt 38 is substantially flat. Here, in order for the heating body 56 to be in good contact with the inner peripheral surface of the cylindrical fixing belt 38, it may be formed in a semi-cylindrical shape along the inner peripheral surface of the fixing belt 38. Mounting and forming the heater and wiring with high accuracy is a complicated process. Therefore, it is inferior in accuracy and productivity as compared with a so-called “planar type” in which the heater and the wiring portion are formed on the same plane.

  For this reason, in the present embodiment, a planar heating element excellent in both accuracy and productivity is used as the heating element 56. Since the mounting accuracy is good, the heat generation efficiency can be improved.

  On the other hand, when the fixing belt 38 is used as a fixing member with a low heat capacity or a small size, in order to place the planar heating body 56 in contact with the inner peripheral surface of the cylindrical fixing belt 38, heating is simply performed. It is difficult to secure a flat surface portion of the fixing belt 38 only by arranging the body 56. Therefore, heat transfer due to sufficient contact between the inner peripheral surface of the rotating fixing belt 38 and the heating element 56 becomes a problem.

  If the heating body 56 is provided in the fixing belt portion forming the fixing nip portion SN together with the pressure roller 30, the contact between the fixing belt 38 and the heating body 56 even when the fixing belt 38 is rotating. It becomes possible to keep the state good. However, it takes time to transfer heat from the back surface to the front surface of the fixing belt 38 heated by the heating body 56. Therefore, even if the fixing belt 38 is heated by the heating body 56 at the fixing belt portion that forms the fixing nip portion SN, heat cannot be immediately supplied to the toner on the paper S at the fixing nip portion SN.

  The heat of the fixing belt 38 heated by the heating body 56 is transmitted to the surface of the fixing belt while the fixing belt 38 is rotating. However, heat is released from the surface of the fixing belt until the fixing belt 38 rotates once and the heated portion of the fixing belt 38 reaches the fixing nip SN again. For this reason, it is necessary to supply a large amount of heat from the heating body 56 to the fixing belt 38 so that the fixing temperature can be obtained at the fixing nip portion SN assuming that the temperature is lowered due to heat dissipation, which increases power consumption. End up.

  Therefore, in the fixing device 12 of the present embodiment, as shown in FIGS. 3 and 4, a heating body 56 is provided in addition to the fixing nip SN of the fixing belt 38. In other words, in the present embodiment, the heating body 56 is provided on an extension line connecting the approximate center of the fixing nip SN and the approximate center line of the pressure roller 30.

  As a result, the portion of the fixing belt 38 heated by the heating body 56 is rotated until the fixing belt 38 makes one rotation and reaches the fixing nip portion SN again, compared with the case where the heating body 56 is provided in the fixing nip portion SN. In the meantime, the amount of heat radiated from the surface of the fixing belt can be reduced. Therefore, the amount of heat supplied from the heating body 56 to the fixing belt 38 can be reduced so that the fixing temperature can be obtained at the fixing nip portion SN. You can plan.

  In addition, an elastic roller 40 that is a pressing member that presses the fixing belt 38 that is urged by an urging means (not shown) is provided at a position facing the heating body 56 via the fixing belt 38. Thereby, even when the fixing belt 38 is rotating, the contact state between the heating body 56 and the fixing belt 38 in which the contact portion with the fixing belt 38 is substantially flat can be kept good.

  The elastic roller 40 includes an iron cored bar 40a having an outer diameter of φ15 [mm] to 30 [mm] and an outer diameter of φ8 [mm], and an elastic layer 40b covered on the surface of the cored bar 40a. And have. The elastic layer 40b is made of silicone rubber and has a thickness of 3.5 [mm] to 11 [mm]. It is desirable to form a fluororesin layer having a thickness of about 40 [μm] on the surface of the elastic layer 40b in order to improve the releasability.

  The pressing member that presses the fixing belt 38 at a position facing the heating body 56 via the fixing belt 38 is not limited to the elastic roller 40. For example, a mechanism such as a pressing pad that can maintain a good contact state between the fixing belt 38 and the heating element 56 may be used. In addition, it is desirable to use an elastic roller 40 having an elastic layer or a pressing pad in consideration of the fact that the pressing member has high adhesion and enables stable heat transfer. It may be possible.

  In the fixing device 12 of the present embodiment, the control device 37 controls the power supply from the power source 39 to each heat generating portion of the heating body 56 based on image data for forming an image on the paper S, thereby saving energy. I am trying. An example of this control operation is shown below.

  FIG. 5A shows an image forming pattern in which an image area a, a non-image area b, and an image area a ′ are present on the sheet S in order from the leading end side in the sheet conveyance direction. The image area a and the image area a 'need to be fixed, but the non-image area b does not need to be fixed because there is no toner to be fixed.

  Image data of the image forming pattern is input to the control device 37 from an image processing device (not shown). Then, the control device 37 sets the heating body 56 so that the temperature of the part corresponding to the non-image area b of the fixing belt 38 is lower than the temperature of the part corresponding to the image area a and the image area a ′ of the fixing belt 38. To control. That is, in the portion corresponding to the image region a and the image region a ′, electric power for obtaining a fixing temperature is supplied to the heating body 56, and in the portion corresponding to the non-image region b, the heating body 56 has a temperature lower than the fixing temperature. Supply the resulting power.

  Note that “corresponding to an image region” and “corresponding to a non-image region” mean a position where the fixing belt 38 is in close contact, and hereinafter, it is also expressed as “contact” as appropriate.

  FIG. 5B shows an image forming pattern in which an image area a and a non-image area b exist on the paper S in order from the leading end side in the paper transport direction. Also in this case, as in FIG. 5A, the control device 37 causes the temperature of the portion corresponding to the non-image region b of the fixing belt 38 to be lower than the temperature of the portion corresponding to the image region a of the fixing belt 38. Thus, the heating body 56 is controlled. In other words, in the portion corresponding to the image area a, power that provides a fixing temperature is supplied to the heating body 56, and in the portion corresponding to the non-image area b, power that provides a temperature lower than the fixing temperature is supplied to the heating body 56. To do.

  Here, it is conceivable that the power supply to the heating body 56 is completely stopped (turned off) at a portion corresponding to the non-image area b of the fixing belt 38. If the temperature of the fixing belt 38 is too low, the next image is displayed. The rise to the fixing temperature in the region is not in time. For this reason, in the present embodiment, as shown in FIG. 6, the temperature of the fixing belt 38 is maintained so that the second target temperature is lower than the first target temperature that is the fixing temperature and higher than the room temperature. It is desirable to control. In this way, the temperature of the portion corresponding to the non-image area b of the fixing belt 38 is also maintained at the second target temperature.

  As a result, even the portion corresponding to the non-image area b of the fixing belt 38 is heated by supplying power to the heating body 56. However, the temperature of the portion corresponding to the non-image area b of the fixing belt 38 is changed to the first temperature. Power consumption can be reduced as compared with the case where the target temperature is set to one. That is, since the power supplied in the region P ′ is smaller than the power supplied in the region P shown in FIG. 6, energy saving is possible.

  FIG. 7A shows an image forming pattern in which an image area c and a non-image area d are mixed on the sheet S in the sheet width direction. FIG. 7B shows an image forming pattern in which a mixed area h in which an image area a and an image area c and a non-image area d are mixed in the sheet width direction exists on the sheet S in order from the leading end side in the sheet conveying direction. Is shown.

  Similarly, in this case, the control device 37 causes the temperature of the portion of the fixing belt 38 corresponding to the non-image area d to be lower than the temperature of the portion of the fixing belt 38 corresponding to the image area a and the image area c. The heating body 56 is controlled. That is, in the portion corresponding to the image region a and the image region c, electric power for obtaining a fixing temperature is supplied to the heating body 56, and in the portion corresponding to the non-image region d, a temperature lower than the fixing temperature is obtained for the heating body 56. Supply power.

  When the portion corresponding to the image area a of the fixing belt 38 is heated by the heating body 56, all the heat generating portions 55a, 55b, 55c, 55d, 55e, 55f, and 55g included in the heating body 56 shown in FIG. To supply power. On the other hand, when the portion corresponding to the image region c of the fixing belt 38 is heated by the heating body 56, power is supplied to the heat generating portions 55a, 55b, 55c, and 55d included in the heating region e shown in FIG. Then, power is not supplied to the heat generating portions 55e, 55f, and 55g included in the heating region f.

  Further, in the present embodiment, when power is supplied to the heating body 56, the image area is a portion before entering the fixing nip portion SN in the paper transport direction as indicated by the hatched portion in FIGS. 5 and 7. Electric power is supplied from the power source 39 so as to preheat the preheating region g. The preheating region g is a region that is necessary because the heating length of the heating body 56 in the circumferential direction and the heating body 56 itself require a temperature raising time. The preheating region g is desirably as small as possible from the viewpoint of energy saving.

FIG. 8 is a diagram for explaining a conventional problem.
In order to perform partial heating that eliminates wasteful energy supply to the non-image area, a heating element represented by a thermal head is very effective. In order to improve the energy saving performance of the apparatus, it is preferable to use a cylindrical and small-diameter fixing belt for the fixing member of the fixing apparatus in order to reduce the heat capacity. Further, in order to reduce the size of the fixing device, it is preferable to arrange a heating body inside the fixing belt.

  In order for the heating body to make good contact with the inner peripheral surface of the cylindrical fixing belt, the heating body may be formed in a semi-columnar shape along the inner peripheral surface of the cylindrical fixing belt. However, the process of mounting and forming a resistance heating element and wiring part on a curved surface with high accuracy is complicated, and the accuracy is higher than that of the so-called "planar type" in which the resistance heating element and wiring part are formed on the same plane. In addition, it is widely known that the productivity is inferior. In other words, the flat type is superior in both accuracy and productivity.

  However, when a cylindrical fixing belt is used in order to reduce the heat capacity and the size, it is difficult to secure a flat portion of the fixing belt in order to dispose a flat heater inside the cylindrical fixing belt. It is. Therefore, heat transfer due to sufficient contact between the inner peripheral surface of the fixing belt and the heating element has been a problem.

  Therefore, by providing a pressing member at a position opposite to the heating body via the fixing belt, pressing the fixing belt against the heating body by the pressing member, and maintaining the contact between the fixing belt and the heating body, the fixing belt and the heating body It is necessary to suppress poor contact.

  On the other hand, in order to perform partial heating, heat must be rapidly supplied to the fixing belt that rotates at high speed so that there is a temperature difference between the image area and the non-image area. For this purpose, it is necessary to increase the heat flux from the resistance heating element of the heating element to the fixing belt, and it is effective to narrow the width of the resistance heating element in the fixing belt rotation direction.

  However, if the width of the resistance heating element in the fixing belt rotation direction is narrowed, if the contact failure between the fixing belt and the resistance heating element occurs, the resistance heating element becomes instantaneously hot and easily damaged. It is necessary to make a good contact with the belt. Furthermore, it is necessary that the contact state between the fixing belt and the resistance heating element can be maintained against changes with time.

  Therefore, it is effective to bring the heating element and the pressing member into contact with each other through the fixing belt with a width equal to or larger than the width of the resistance heating element in the rotation direction of the fixing belt. However, if the heating element and the pressing member are brought into contact with each other through the fixing belt more than the width of the resistance heating element in the fixing belt rotation direction, the efficiency of partial heating of the fixing belt by the heating element is reduced, and the energy saving performance is reduced. Furthermore, the heating element is heated.

  Specifically, as shown in FIG. 8, since the temperature difference between the resistance heating element portion and the non-resistance heating element portion of the heating element 56 becomes large, the heat given to the fixing belt 38 by the resistance heating element portion is fixed. A back flow of heat that easily returns to the non-resistance heating element portion immediately downstream of the resistance heating element portion in the belt rotation direction is likely to occur. As a result, in addition to preventing the temperature of the fixing belt 38 from rising, the temperature of the heating body 56 is increased, leading to damage.

  Therefore, in order to suppress the backflow of heat from the fixing belt 38 to the heating body 56, it is necessary to suppress the contact between the fixing belt 38 and the heating body 56 at a portion other than the resistance heating element 55 of the heating body 56. It becomes.

  Further, such a back flow of heat from the fixing belt 38 to the heating element 56 appears significantly due to an increase in the contact width of the order of 1/10 [mm]. Therefore, the influence of the position variation and the component variation caused by the mechanism design. It is easy to receive. In an apparatus configuration that does not have a mechanism for adjusting the contact state between the fixing belt 38 and the heating body 56, the pressing member cannot be pressed only against the resistance heating element portion of the heating body 56 with high accuracy. Therefore, it is insufficient as a fixing device capable of partial heating.

  Next, features of the fixing device 12 provided in the image forming apparatus according to the present exemplary embodiment will be described.

  FIG. 1 is a schematic diagram of the fixing device 12 including an adjustment mechanism 70 that adjusts the relative position between the heating body 56 and the elastic roller 40. Here, as an example, a case where an elastic roller 40 having an elastic layer is used as a pressing member that presses the fixing belt 38 toward the heating body 56 will be described.

  As shown in FIG. 1, the adjustment mechanism 70 has vertical movement mechanism portions 71 for moving the elastic body roller 40 up and down in the apparatus height direction on both sides in the axial direction of the elastic body roller 40. The vertical movement mechanism unit 71 includes a support member 71a, a rack gear member 71b, a spring 71c, a pinion gear 71d, a drive motor (not shown), and the like.

  The support member 71a supports the rotation shaft of the elastic roller 40 in a rotatable manner. The spring 71c is an urging means having one end connected to the support member 71a and urging the elastic roller 40 via the support member 71a. The rack gear member 71b is formed with a rack gear that is connected to the other end of the spring 71c and extends in the apparatus height direction. The pinion gear 71d is provided so as to rotate by a driving force from a driving motor such as a stepping motor (not shown) and to mesh with the rack gear of the rack gear member 71b.

  Then, by rotating the pinion gear 71d by the drive motor and displacing the rack gear member 71b in the apparatus height direction, the support member 71a is pushed or pulled by the spring 71c. As a result, the elastic roller 40 whose rotation shaft is supported by the support member 71a is moved up and down in the apparatus height direction, and the relative position between the heating body 56 and the elastic roller 40 via the fixing belt 38 can be adjusted. it can. Further, by adjusting the relative position of the heating body 56 and the elastic roller 40 in the apparatus height direction, the load applied to the heating body 56 can be adjusted by pressing the fixing belt 38 by the elastic body roller 40. it can.

  The adjustment mechanism 70 has left and right moving mechanisms 72 for moving the elastic roller 40 left and right in the device width direction perpendicular to the axial direction of the elastic roller 40 on both sides in the axial direction of the elastic roller 40. Yes. The left-right movement mechanism 72 is configured by a rack gear member 72a, a pinion gear 72b, a shaft member 72c, a support plate 72d, a drive motor (not shown), and the like.

  The rack gear member 72a is attached to the rack gear member 71b of the vertical movement mechanism portion 71, and is formed with a rack gear extending in the apparatus width direction. The rack gear members 72a on both sides in the axial direction of the elastic roller 40 are attached to both ends in the longitudinal direction of the support plate 72d.

  The pinion gear 72b is provided so as to rotate by a driving force from a driving motor such as a stepping motor (not shown) so as to mesh with the rack gear of the rack gear member 71b. In addition, each of the pinion gears 72b on both sides in the axial direction of the elastic roller 40 is attached to both axial ends of the shaft member 72c.

  Then, by rotating the pinion gear 72b by the drive motor and displacing the rack gear member 72a in the apparatus width direction, the elastic roller 40 is moved left and right in the apparatus width direction via the rack gear member 71b of the vertical movement mechanism portion 71 and the like. Thereby, the contact position of the heating body 56 and the elastic roller 40 via the fixing belt 38 in the apparatus width direction (fixing belt rotation direction) can be adjusted.

  Thus, by providing the adjustment mechanism 70, the heating body 56 via the fixing belt 38 and the elastic body roller 40 are prevented from coming into contact with the portions other than the resistance heating element 55 of the heating body 56 via the fixing belt 38. The contact state with the elastic roller 40 can be adjusted.

  For example, when the desired contact width or load cannot be obtained due to the hardness variation of the elastic layer 40b of the elastic roller 40, the pinion gear 71d that moves the elastic roller 40 up and down in the apparatus height direction is rotated to achieve the desired contact. The width and load can be adjusted. If there is a design misalignment, the pinion gear 72b that moves the elastic roller 40 left and right in the apparatus width direction is rotated, and the elastic roller 40 is pressed against the heating body 56 via the fixing belt 38 at a desired contact position. be able to.

  Furthermore, if the relative position between the heating body 56 and the elastic roller 40 can be adjusted, not only can the position shift and component variations be accommodated, but also the shift due to changes over time can be accommodated.

  The hardness of the elastic layer 40b of the elastic roller 40 has a feature that it decreases with time. Therefore, when the urging force of the spring 71c urging the elastic body roller 40 toward the heating body 56 is the same, as shown in FIG. 9A, the elastic body roller 40 and the heating body via the fixing belt 38 are used. The contact width with 56 becomes large. For this reason, the contact of the elastic roller 40 with the portion of the heating element 56 downstream of the resistance heating element 55 in the rotation direction of the fixing belt increases, and a reverse flow of heat from the fixing belt 38 to the heating element 56 occurs.

  At this time, by reducing the load applied to the elastic roller 40, the contact width between the heating member 56 and the elastic roller 40 via the fixing belt 38 can be reduced. However, if the load applied to the elastic roller 40 is small, contact failure between the fixing belt 38 and the resistance heating element 55 may occur, and the fixing belt 38 may not be heated sufficiently.

  Therefore, as shown in FIG. 9B, by shifting the position of the elastic roller 40 to the upstream side in the fixing belt rotation direction, the contact of the heating body 56 on the downstream side of the resistance heating element 55 is suppressed as much as possible. A decrease in heating efficiency can be minimized.

  The adjustment mechanism 70 needs to be able to adjust the relative position of the heating body 56 and the elastic roller 40 with high accuracy, and therefore preferably has a high-precision mechanism such as a rack and pinion mechanism. However, it is not limited to a rack and pinion mechanism. For example, as shown in FIG. 10, the amount of pushing of the spring 71c by the spring pushing member 71f is changed by turning a screw 71e to change the urging force of the spring 71c. A configuration in which fine adjustments such as adjusting the load with which the elastic roller 40 presses the heating body 56 via the fixing belt 38 may be possible.

  As shown in FIG. 11, the pressing member that presses the fixing belt 38 toward the heating body 56 may be a member such as a resin pad 41 that does not have an elastic layer. In consideration of adhesion and the like, it is desirable to use a pressing member having the elastic body 40 elastic body. However, unlike the elastic body, the load does not change with time. For this reason, the adjustment of the relative position between the heating body 56 and the elastic roller 40 by the adjusting mechanism 70 only needs to be dealt with with respect to the design positional deviation and component variation.

  FIG. 12 is a diagram illustrating cleaning of the fixing belt 38 in the fixing device 12 of the present embodiment.

  A cleaning web device 45 for cleaning the surface of the fixing belt 38 is provided. The cleaning web device 45 includes a cleaning web 45c, a stretching roller 45b, and a stretching roller 45a. The tension rollers 45a and 45b stretch the cleaning web 45c in a rotatable manner. The elastic roller 40 presses the cleaning web 45 c toward the surface of the fixing belt 38. With such a configuration, the cleaning web 45 c is rotated with the rotation of the fixing belt 38 while being pressed against the surface of the fixing belt 38 by the elastic roller 40.

  Deposits such as toner adhere to the surface of the fixing belt 38. If there is any deposit on the surface of the fixing belt 38, the transfer of heat to the unfixed image at the fixing nip SN may be hindered, and the toner may be prevented from being fixed on the paper.

  Further, as shown in FIG. 13, when a relatively large adhering matter adhering to the fixing belt 38 passes through the facing portion between the heating body 56 and the elastic roller 40, the elastic layer 40 b of the elastic roller 40 is deformed. For this reason, the heating body 56 and the fixing belt 38 are in poor contact, leading to a temperature rise of the heating body 56 and possibly being damaged.

  Therefore, by cleaning the surface of the fixing belt 38 with the cleaning web 45c of the cleaning web device 45, it is possible to suppress the occurrence of problems that may occur due to the adhering matter adhering to the surface of the fixing belt 38 as described above. can do.

  On the other hand, by providing the cleaning web device 45 as shown in FIG. 12, the positional relationship between the heating body 56 and the elastic roller 40 is likely to be shifted in mechanical design. It is desirable to provide it.

  In the fixing device according to the present embodiment, as shown in FIGS. 14 and 15, a plurality of thermistors 36 are provided on the back surface of the heating body 56 that is not in contact with the fixing belt 38, and the resistance heating element 55 is provided. The structure which detects the temperature of each heat-emitting part of these may be sufficient. In FIG. 14, the illustration of the adjusting mechanism 70 is simplified, but the adjusting mechanism 70 shown in FIG. 1 can be used.

  A plurality of temperature detection sensors such as the thermistor 36 are provided corresponding to each heat generating portion of the resistance heat generating element 55. Thereby, a change in the contact state between the heating body 56 and the elastic roller 40 via the fixing belt during the fixing operation can be detected, and damage to the resistance heating element 55 of the heating body 56 can be suppressed.

  Specifically, the thermistors 36 a, 36 b, and the thermistors 36 a, 36 b, 55 b, 55 c, 55 f, 55 g, 55 h are respectively provided on the back surface of the heating element 56 in correspondence with the heating regions of the resistance heating elements 55. 36c, 36d, 36e, 36f, 36g, and 36h are arranged. In FIG. 15, the resistance heating element 55 of the heating element 56 is divided into eight in the paper width direction (longitudinal direction). Thereby, abnormal temperature rise of each heat generating portion of the resistance heating element 55 can be detected, and deterioration of the contact state due to a decrease in contact width in the fixing belt rotation direction can be detected. Thereby, damage to the heating body 56 can be prevented beforehand.

  The thermistor 36 that detects the temperature of each heat generating portion of the resistance heating element 55 may be either a contact type or a non-contact type. FIG. 15 shows a case where the thermistor 36 is used as a contact-type temperature detection sensor, and an abnormal temperature rise of each heat generating portion is detected by arranging the thermistor 36 for each heating region of each heat generating portion of the resistance heating element 55. Accuracy can be increased. On the other hand, the thermistor 36 does not have to be arranged for each heating region of each heat generating portion as long as the abnormal temperature rise of each heat generating portion of the resistance heating element 55 can be detected.

  Further, as shown in FIG. 14, the temperature detection sensor 33 detects the fixing belt temperature downstream of the heating body 56 in the rotation direction of the fixing belt, so that the heating body 56 and the elastic roller 40 via the fixing belt 38 are also detected. A change in contact state can be detected. When the surface temperature of the fixing belt 38 is detected by the temperature detection sensor 33 and the first target temperature is not reached, the contact width between the heating body 56 and the elastic roller 40 via the fixing belt 38 is increased. It is possible to detect that the reverse flow of heat has occurred.

  Furthermore, a load detection sensor 90 that detects a load applied to the heating body 56 is provided on the elastic roller 40 side. Then, a load applied to the heating body 56 pressed against the elastic roller 40 via the fixing belt 38 is detected by the load detection sensor 90, whereby the heating body 56 and the elastic roller 40 via the fixing belt 38 are detected. You may comprise so that a contact state may be detected.

  Further, the adjustment mechanism 70 may be automatically controlled by the control device 37 based on detection signals from the thermistor 36, the temperature detection sensor 33, the pressure sensor, and the like. As a result, the relative position between the heating body 56 and the elastic roller 40 can be automatically adjusted via the fixing belt 38, so that the optimal contact state between the fixing belt 38 and the heating body 56 can be maintained over time. The damage of the heating body 56 and the deterioration of the heating performance can be suppressed.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
Contact between a fixing belt such as an endless fixing belt 38 that is rotatably provided and a pressure roller 30 that is in contact with an outer peripheral surface of the fixing belt that is rotatably provided to form a nip portion. A member, a heating means such as a heating member 56 that heats the fixing belt provided in contact with the inner peripheral surface of the fixing belt other than the portion forming the nip portion, and the heating means via the fixing belt. A fixing device provided with a pressing member such as an elastic roller 40 provided at a position to press the fixing belt, and fixing an unfixed image on the recording material such as the sheet S passed through the nip portion to the recording material by at least heat. The fixing device such as 12 has an adjusting means such as an adjusting mechanism 70 for adjusting a relative position between the heating means and the pressing member.
In (Aspect A), the relative position of the heating means and the pressing member can be adjusted by the adjusting means. In this way, even if there are parts processing accuracy, assembly errors, etc., the relative position of each other is adjusted so that the heating means and the pressing member are in an optimal positional relationship without being too close or too far away. Can do. Accordingly, it is possible to suppress the deterioration of the heating performance and the rotation failure of the fixing belt due to the relative position between the heating unit and the pressing member.
(Aspect B)
In (Aspect A), the heating means has a plurality of heat sources in the recording material width direction orthogonal to the recording material conveyance direction, and each heat source is associated with an unfixed image on the recording material based on the image data. The fixing belt is heated by changing the heating area. According to this, as described in the above embodiment, energy saving can be achieved.
(Aspect C)
In (Aspect A) or (Aspect B), the pressing member is an elastic body roller such as the elastic body roller 40 provided to be rotatable with respect to the apparatus main body. According to this, as described in the above embodiment, it is possible to ensure contact between the inner peripheral surface of the fixing belt and the heating unit with little change with time and high adhesion.
(Aspect D)
In (Aspect A) or (Aspect B), the pressing member is an elastic pad. According to this, as described in the above embodiment, the contact area between the inner circumferential surface of the fixing belt and the heating means can be increased compared with the case where a roller member is provided as the pressing member, and the fixing belt can be stably heated. Is possible.
(Aspect E)
In (Aspect C), fixing belt cleaning means such as a cleaning web device 45 having a cleaning web such as a cleaning web 45c which is pressed against the surface of the fixing belt by the elastic roller and cleans the surface of the fixing belt while moving. Provided. According to this, as described in the above embodiment, the fixing belt surface becomes dirty, resulting in poor contact between the fixing belt and the heating unit, and fixing failure or the heating unit is excessively heated and damaged. Can be suppressed.
(Aspect F)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D) or (Aspect E), it has a temperature detection means such as the thermistor 36 for detecting the temperature of the heating means. According to this, as described in the above embodiment, it is possible to detect an abnormal temperature rise of the heating means, detect deterioration of the contact state due to a decrease in contact width or the like, and prevent damage to the heating means in advance. it can.
(Aspect G)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E) or (Aspect F), the temperature at which the belt surface temperature of the portion of the fixing belt that has passed through the heating means is detected. Belt surface temperature detection means such as a detection sensor 33 is provided. According to this, as described in the above embodiment, the surface temperature of the fixing belt is detected by the belt surface temperature detecting unit, and when the first target temperature is not reached, the heat generated by the increase in the contact width is detected. It is possible to detect the occurrence of backflow.
(Aspect H)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), or (Aspect G), a load applied to the heating means is detected by pressing with the pressing member. Load detecting means 90 and the like. According to this, as described in the above embodiment, it is possible to detect a contact state between the heating unit and the pressing member via the fixing belt.
(Aspect I)
In (Aspect A), (Aspect B), (Aspect C), (Aspect D) or (Aspect E), temperature detecting means such as the thermistor 36 for detecting the temperature of the heating means, and the heating means of the fixing belt. Belt surface temperature detection means such as a temperature detection sensor 33 for detecting the belt surface temperature of the portion that has passed through the belt, and load detection means such as a load detection sensor 90 for detecting a load applied to the heating means by pressing by the pressing member. And control means for controlling the adjusting means based on the detection result detected by them. According to this, as described in the above embodiment, it is possible to automatically adjust the relative position of the heating unit and the pressing member via the fixing belt.
(Aspect J)
An image carrier such as the photosensitive drum 8, a toner image forming unit having a developing device 22 that forms a toner image on the image carrier, and a transfer device that transfers the toner image from the image carrier onto a recording medium. In an image forming apparatus, such as a printer, provided with a transfer means such as 10 and a fixing means such as a fixing device 12 for fixing the toner image transferred onto the recording medium to the recording medium, the fixing means (Aspect A The fixing device of (Aspect B), (Aspect C), (Aspect D), (Aspect E), (Aspect F), (Aspect G), (Aspect H) or (Aspect I) is used. According to this, as described in the above embodiment, the deterioration of the heating performance and the rotation failure of the fixing belt due to the relative position between the heating unit and the pressing member are suppressed, and good image formation is achieved. It can be carried out.

DESCRIPTION OF SYMBOLS 4 Paper feeder 6 Registration roller pair 8 Photosensitive drum 10 Transfer device 12 Fixing device 14 Paper feed tray 16 Paper feed roller 18 Charging roller 20 Mirror 22 Developing device 22a Developing roller 24 Cleaning device 24a Cleaning blade 26 Exposure unit 30 Pressure roller 30a Core 30b Elastic layer 33 Temperature sensor 34 Thermistor 36 Thermistor 37 Controller 38 Fixing belt 38a Base 38b Elastic layer 38c Release layer 39 Power supply 40 Elastic roller 40a Core metal 40b Elastic layer 41 Pad 45 Cleaning web device 45a Roller 45b Stretching roller 45c Cleaning web 55 Resistance heating element 56 Heating element 57 Stay-like member 60 Nip forming member 61 Belt support member 70 Adjustment mechanism 71 Vertical movement mechanism portion 71a Support member 71b Rack Gear member 71c spring 71d pinion gear 71e screw 71f spring pushing member 72 left and right moving mechanism 72a rack gear member 72b pinion gear 72c shaft member 72d support plate 90 load detection sensor

JP 2012-42746 A

Claims (10)

An endless fixing belt provided rotatably;
A contact member that is rotatably provided to contact an outer peripheral surface of the fixing belt to form a nip portion with the fixing belt;
A heating unit that is provided in contact with an inner peripheral surface other than a portion forming the nip portion of the fixing belt and heats the fixing belt;
A pressing member provided at a position facing the heating unit via the fixing belt and pressing the fixing belt;
In a fixing device for fixing an unfixed image on a recording material passed through the nip portion to the recording material by at least heat,
A fixing device comprising an adjusting means for adjusting a relative position between the heating means and the pressing member. The fixing device according to claim 1.
The heating means has a plurality of heat sources in the recording material width direction orthogonal to the recording material conveyance direction, and changes the heating area by each heat source in accordance with the unfixed image on the recording material based on the image data. A fixing device that heats the fixing belt. The fixing device according to claim 1 or 2,
The fixing device according to claim 1, wherein the pressing member is an elastic roller provided rotatably with respect to the apparatus main body. The fixing device according to claim 1 or 2,
The fixing device, wherein the pressing member is an elastic pad. The fixing device according to claim 3.
A fixing device comprising a fixing belt cleaning unit having a cleaning web which is pressed against the surface of the fixing belt by the elastic roller and cleans the surface of the fixing belt while moving. The fixing device according to claim 1, 2, 3, 4 or 5.
A fixing device comprising temperature detecting means for detecting the temperature of the heating means. The fixing device according to claim 1, 2, 3, 4, 5 or 6.
A fixing device comprising belt surface temperature detecting means for detecting a belt surface temperature of a portion of the fixing belt that has passed through the heating means. The fixing device according to claim 1, 2, 3, 4, 5, 6 or 7.
A fixing device comprising load detecting means for detecting a load applied to the heating means when pressed by the pressing member. The fixing device according to claim 1, 2, 3, 4 or 5.
A temperature detecting means for detecting the temperature of the heating means, a belt surface temperature detecting means for detecting a belt surface temperature of a portion of the fixing belt that has passed through the heating means, and a pressure applied by the pressing member to the heating means. A fixing device having at least one load detecting means for detecting such a load, and having a control means for controlling the adjusting means based on a detection result detected by the load detecting means. An image carrier;
Toner image forming means for forming a toner image on the image carrier;
Transfer means for transferring the toner image from the image carrier onto a recording medium;
An image forming apparatus comprising: a fixing unit that fixes the toner image transferred onto the recording medium to the recording medium;
An image forming apparatus using the fixing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9 as the fixing unit.

Images